text
stringlengths 135
9.96k
| idx
int64 0
162k
|
|---|---|
title: Study of the dependence of direct soft photon production on the jet characteristics in hadronic Z (0) decays; abstract: An analysis of the direct soft photon production rate as a function of the parent jet characteristics is presented, based on hadronic events collected by the DELPHI experiment at LEP1. The dependences of the photon rates on the jet kinematic characteristics (momentum, mass, etc.) and on the jet charged, neutral and total hadron multiplicities are reported. Up to a scale factor of about four, which characterizes the overall value of the soft photon excess, a similarity of the observed soft photon behavior to that of the inner hadronic bremsstrahlung predictions is found for the momentum, mass, and jet charged multiplicity dependences. However for the dependence of the soft photon rate on the jet neutral and total hadron multiplicities a prominent difference is found for the observed soft photon signal as compared to the expected bremsstrahlung from final state hadrons. The observed linear increase of the soft photon production rate with the jet total hadron multiplicity and its strong dependence on the jet neutral multiplicity suggest that the rate is proportional to the number of quark pairs produced in the fragmentation process, with the neutral pairs being more effectively radiating than the charged ones. | 162,200 |
title: Experimental analysis of flow structures and forces on a 3D-bluff-body in constant cross-wind; abstract: The effect of cross-wind on a bluff-body in ground proximity is analysed experimentally. A recently introduced wind-tunnel model is used to analyse the effect of flow structures on the global forces and global moments. This study aims at creating a large database of the flow produced in the proximity of this bluff-body and giving some new insight into the physical mechanisms responsible for the increase in force in cross-wind situations. The importance of the model\u0027s lee side to the global yawing moment is put forward. Two vortices are identified and changes in the slope of the yawing moment versus yaw angle are attributed to their presence. | 162,201 |
title: Fully resolved simulation of a gas-fluidized bed: A critical test of DEM models; abstract: Abstract We performed Direct Numerical Simulation (DNS) of a gas-fluidized bed using the Immersed Boundary method combined with traditional Computational Fluid Dynamics. We have compared the individual fluid–particle force with the force as evaluated in an unresolved Discrete Element Model (DEM) simulation using closures for the gas–solid force for one fluidisation condition. We find that the average DEM gas–solid force is about 33% smaller than the “true” value which follows from the DNS model. For more realistic DEM simulations, a modification of the gas–solid force calculation is required, for instance by adding fluctuations or including the effect of the granular temperature. | 162,202 |
title: Parity-Violating in e − e + Scattering at Finite Temperature; abstract: Parity violation implies that physics laws are not invariant under spatial coordinate reversal. Electron-positron scattering is a process that displays parity violation. Using the Thermo Field Dynamics formalism this scattering at finite temperature is analyzed. The transition amplitude is calculated as a function of temperature. The parity violation at very high temperatures tend to go to zero. | 162,203 |
title: Self-Gravitating Gas Spheres in a Box and Relativistic Clusters: Relation between Dynamical and Thermodynamical Stability; abstract: We derive a variational principle for the dynamical stability of a cluster as a gas sphere in a box. Newtonian clusters are always dynamically stable, and for relativistic clusters, the relation between dynamical and thermodynamical instabilities is analyzed. The boundaries between dynamically and thermodynamically stable and unstable models are found numerically for relativistic stellar systems with different cutoff parameters. A criterion based on the binding energy curve is used for determination of the boundary of dynamical stability. | 162,204 |
title: A Color Analysis of the NICMOS Parallel Image Archive; abstract: We present a photometric analysis of all high Galactic latitude (|b| \u003e 20°) broadband parallel images taken by the Near-Infrared Camera and Multi-Object Spectrometer instrument of the Hubble Space Telescope during its initial lifetime in HST Cycle 7. These images, taken through the F110W and F160W filters, reach a mean 3 σ limiting magnitude of approximately 22 in both bands, and cover a total area of approximately 92 arcmin2. The reddest of the 358 galaxies detected have F110W-F160W colors and F160W magnitudes consistent with being a combination of both dusty star-forming and evolved early-type galaxies at 1 z 2. The surface density of these galaxies is comparable to that of the population of extremely red objects (EROs) discovered in ground-based surveys (~100 deg-2), suggesting that EROs also represent a combination of both galaxy types in this redshift range. Roughly 10% of the detected galaxies appear to be blue compact dwarf galaxies at z 1, a result consistent with studies of the HST Medium Deep Survey fields. The surface density of these objects down to a magnitude of 22 in F160W is ~300 deg-2. None of the 631 point sources detected have F110W-F160W colors matching those expected for quasi-stellar objects (QSOs) whose continua have been significantly reddened by internal dust. Our data limit the surface density of such QSOs to be 50 deg-2 down to the mean limiting magnitudes of the sample images. Since the surface density of QSOs detected on the basis of ultraviolet excess in optical surveys to comparable depth is ~100 deg-2, this argues against the suggestion that dust-reddened QSOs compose the undetected majority of the QSO population. The F110W-F160W color can also be used to identify unreddened QSOs at z 8, but we find no such candidates. This is consistent with the evidence that QSO space density declines sharply at z 5. | 162,205 |
title: Single top quarks at the Fermilab Tevatron; abstract: We present a calculation of the single top quark cross section for proton-antiproton interactions with {radical}(s)=1.8TeV at the Fermilab Tevatron collider. We examine the effects of the top quark mass, parton distribution functions, QCD scale, and collision energy, on each of the component production mechanisms, and study the kinematic distributions for standard model electroweak production. At the upgraded Tevatron with {radical}(s)=2.0TeV and high luminosity, it will be possible to test the nature of the Wtb coupling using single top quark production. We estimate the sensitivity to measure the single top quark cross section, and thus to directly measure V{sub tb} and the top quark partial width. We show what happens to the V{sub tb} measurement when an anomalous (V+A) component is added to the Wtb coupling, and how the top quark polarization affects the kinematic distributions. {copyright} {ital 1997} {ital The American Physical Society} | 162,206 |
title: Atomic Interferometry Test of Dark Energy; abstract: Atomic interferometry can be used to probe dark energy models coupled to matter. We consider the constraints coming from recent experimental results on models generalising the inverse power law chameleons such as $f(R)$ gravity in the large curvature regime, the environmentally dependent dilaton and symmetrons. Using the tomographic description of these models, we find that only symmetrons with masses smaller than the dark energy scale can be efficiently tested. In this regime, the resulting constraints complement the bounds from the E\\\"otwash experiment and exclude small values of the symmetron self-coupling. | 162,207 |
title: Correlation among oxygen vacancies in bismuth titanate ferroelectric ceramics; abstract: Pure Bi4Ti3O12 ceramics were prepared using the conventional solid-state reaction method and their dielectric properties were investigated. A dielectric loss peak with the relaxation-type characteristic was observed at about 370K at 100Hz frequency. This peak was confirmed to be associated with the migration of oxygen vacancies inside ceramics. The Cole–Cole fitting to this peak reveals a strong correlation among oxygen vacancies and this strong correlation is considered to commonly exist among oxygen vacancies in ferroelectrics. Therefore, the migration of oxygen vacancies in ferroelectric materials would demonstrate a collective behavior instead of an individual one due to this strong correlation. Furthermore, this correlation is in proportion to the concentration and in inverse proportion to the activation energy of oxygen vacancies. These results could be helpful to the understanding of the fatigue mechanisms in ferroelectric materials. | 162,208 |
title: Analytical Characterization and Production of an Isothermal Surface for Biological and Electronic Applications; abstract: Characterization and regulation of isothermal surfaces are key issues in a number of thermal management devices. The surface temperature uniformity can be controlled utilizing a variable area channel heat exchanger filled with a porous medium. A comprehensive analytical investigation of forced convection through a generic variable area channel is carried out to design a compact heat exchanger in producing an isothermal surface subject to a constant heat flux, which may be required in the biological, electronics, optical, laser, manufacturing, and solidification applications. Exact solutions for the fluid and solid phases and the wall surface temperature distributions as well as the Nusselt number correlations are established while incorporating local thermal nonequilibrium and transverse conduction contributions. The channel temperature field is adjusted utilizing either an adiabatic or a constant temperature on the inclined surface. The effects of the pertinent physical parameters, such as channel inlet/outlet thickness, inclination angle, Biot number, ratio of fluid and matrix thermal conductivities, working fluid properties, and imposed heat flux, on the fluid and solid temperature fields and the isothermal surface are thoroughly investigated. The results indicate that utilizing proper pertinent parameters, an isothermal surface is achieved. The validity of the utilization of the local thermal equilibrium model is also investigated and error maps are presented. | 162,209 |
title: Vortex-induced vibrations of a diamond cross-section: Sensitivity to corner sharpness; abstract: Abstract This paper studies the fluid–structure interaction of an elastically mounted square cross-section cylinder immersed in a free stream. The cross-section is mounted such that its sides are at 45° to the free stream direction, in a “diamond” configuration, and its motion is constrained to the transverse direction relative to the flow direction. Apart from the cross-section, this setup is the same as the majority of single-degree-of-freedom vortex-induced vibration studies of cylinders. Two-dimensional direct numerical simulations of this system have been performed. The Reynolds number based on the point-to-point distance of the cross-section has been fixed at Re=200). Simulations at this Reynolds number allow a direct comparison with previous results from circular cylinders, and therefore focus directly on the impact of the geometry. The sensitivity of the flow, and therefore the motion of the cylinder, to geometrical effects is considered. This is done by rounding the two side corners (those pointing across the flow) at a given radius. For well-rounded corners, the flow behaviour resembles that of a circular cylinder undergoing vortex-induced vibration. However, below a critical radius, the dynamics are considerably altered. Highly disordered and irregular wakes and body motions are observed, as well as a synchronized, periodic P+S wake mode ( Williamson and Roshko, 1988 ), which consists of a pair of vortices on one side, and a single vortex on the other side, shed per oscillation cycle, which results in a non-zero mean lift force. A period-doubled version of this P+S wake is also presented. The spatial structure, and the spatio-temporal symmetries of each of these modes is reported. The results show that even though the spatio-temporal symmetry of the flow is unaffected by the geometry when the body is rigidly mounted (the flow always saturating to a Karman vortex street) geometric features such as sharp corners can induce a number of spontaneous symmetry breaking bifurcations when the body is elastically mounted. Which of these various modes is observed is shown to be a function of both the corner radius and the spring stiffness, expressed through the reduced velocity. | 162,210 |
title: Free-electron lasers in Europe; abstract: The principles of a free-electron laser are outlined, and a brief history of its development is given. The main experimental results obtained to date are described with emphasis on results obtained by European workers. | 162,211 |
title: Parton content of the nucleon from distribution amplitudes and transition distribution amplitudes; abstract: The nucleon distribution amplitudes and the nucleon-to-pion transition distribution amplitudes are investigated at leading twist within the frame of a light-cone quark model. The distribution amplitudes probe the three-quark component of the nucleon light-cone wave function, while higher order components in the Fock-space expansion of the nucleon state are essential to describe the nucleon-to-pion transition distribution amplitudes. Adopting a meson-cloud model of the nucleon the nucleon-to-pion transition distribution amplitudes are calculated for the first time. | 162,212 |
title: Off-Shell Longitudinal Photon Light-Cone Wavefunction in the Low-Energy Effective Theory of QCD; abstract: Within the framework of the low-energy effective theory arising from the instanton vacuum model of QCD, the longitudinal virtual photon light-cone wavefunction, γ∥(u,P2), corresponding to the nonlocal quark–antiquark vector current is calculated at the low-energy scale. The coupling constant, Fγ(P2) or equivalently fγ(P2), of the quark–antiquark vector current to the virtual photon state is also obtained by imposing the normalization condition to the photon wavefunction. The behaviour of the coupling constant as well as the obtained photon wavefunction is discussed. | 162,213 |
title: Numerical simulation of head-on droplet collision : Effect of viscosity on maximum deformation; abstract: Numerical simulation of head-on collision of two equal-size droplets is conducted to observe the effect of viscosity on the maximum deformation amplitude using a moving-mesh finite-volume method. Recent experimental results by Willis and Orme [Exp. Fluids 34, 28 (2003)] have shown that the maximum deformation amplitude depends on the viscosity coefficient, and thus the percentage of energy that is dissipated until the instant of maximum deformation increases with the increasing fluid viscosity. This observation contradicts previous results by Jiang, Umemura, and Law [J. Fluid Mech. 234, 171 (1992)]. The numerical results in this Letter show that the dissipated energy and the maximum deformation depend on the collision Reynolds number, which is consistent with Willis and Orme (2003). However, this dependence decreases with increasing Reynolds number, which suggests that the effect caused by viscosity on maximum deformation becomes insignificant at sufficiently high Reynolds number. | 162,214 |
title: Exact solutions of the generalized Kuramoto-Sivashinsky equation; abstract: Abstract Transformations for the solutions obtained by the Weiss-Tabor-Carnevale method are used for investigation of several classes of analytical solutions of the generalised Kuramoto-Sivashinsky equation which is nonintegrable by means of the usual inverse scattering transform method. | 162,215 |
title: A VUV undulator for MAX; abstract: Abstract An undulator operating at radiation wavelengths between 250 and 2000 A has been constructed at the Technical Research Centre of Finland and recently installed at the MAX storage ring in Lund. The undulator utilizes ferrite permanent magnets in the hybrid configuration. The magnetic and mechanical design, calculated performance and influence on the electron beam of the undulator are discussed. | 162,216 |
title: Application of a modified pseudopotential lattice Boltzmann model for simulation of splashing phenomenon; abstract: Abstract In this study, a two dimensional modified pseudopotential single-component multiphase lattice Boltzmann model is utilized to simulate impingement of single and double droplets on both stationary and moving liquid films. The model is confirmed to be accurate according to the power law in terms of crown spreading. In addition, coexistence densities at both liquid and gas phases are compared with densities, obtained by Maxwell analytical solution. The effects of the Reynolds number, Weber number, Bond number, liquid film thickness, and wall interactions with liquid film for the case of single droplet are individually investigated. The results prove that the enhancement of liquid film thickness postpones the droplet break-up on the crown’s free edge. It is also found that, the hydrophobic surface abates the splashing mechanism due to the existing repulsive force between wall and liquid film. Simulation of splashing phenomenon inside a slit indicates that the crown formation follows the rectangular and curvature shape of the slit. The simulation is also carried out for two droplets with horizontal and vertical arrangements. For the horizontal arrangement, the crown is divided into central and lateral regions. In comparison with lateral jets, crown’s central jet is higher. Furthermore, droplets’ vertical arrangement elevated the cross section of the crown’s free edge, therefore the secondary droplets do not form in this condition. Up to the end of this study, the effect of the bottom moving wall on the binary droplet impact is examined, and it is found that by increasing the moving wall’s velocity, the crown height at the central region and the downstream side abates. Moreover, the effect of moving wall at the upstream side is different, and the splashing mechanism can be either suppressed or enhanced at this side. In fact, the moving wall performance at the upstream depends on the impact conditions and the governing non-dimensional numbers. | 162,217 |
title: Universality of Delta I=1 meson mixing and charge symmetry breaking.; abstract: The Coleman-Glashow scheme for {Delta}{ital I}{sub {ital z}}=1 charge symmetry breaking (CSB) applied to meson and baryon SU(2) mass splittings suggests a universal scale. This scale can be extended to {Delta}{ital I}=1 nonstrange CSB transitions {l_angle}{rho}{sup 0}{vert_bar}{ital H}{sub em}{vert_bar}{omega}{r_angle} and {l_angle}{pi}{sup 0}{vert_bar}{ital H}{sub em}{vert_bar}{eta}{sub {ital N}{ital S}}{r_angle} of size {minus}0.005 GeV{sup 2} in the energy region 760--780 MeV. The resulting nucleon-nucleon vector meson exchange CSB potential then predicts {Delta}{ital I}=1 effects which are in approximate agreement with recent data characterizing nuclear charge asymmetry. | 162,218 |
title: Development of Surface Morphology of Epitaxial Al2O3 on Silicon by Controlling Reaction between Oxygen and Silicon Surface; abstract: Epitaxial growth of Al2O3 on Si has been investigated using ultrahigh-vacuum chemical vapor deposition (UHV-CVD). The uniformity of Al2O3 growth in a wafer was improved by UHV-CVD with a hot-wall heating system, but the surface morphology of grown films was degraded compared with that of films grown by low-pressure chemical vapor deposition (LP-CVD) with a cold-wall heating system. Using oxygen for Al2O3 growth instead of N2O, crystalline quality and electrical properties of Al2O3 films were improved, but microroughness still exist at the Al2O3 surface. A new Al2O3 growth method is proposed taking into account thermochemical considerations. The growth temperature of Al2O3 was lowered at a temperature below 780°C to improve the surface morphology. Although the surface morphology of Al2O3 film was improved, its crystalline structure was degraded by the low-temperature growth. Then, a high-temperature growth was performed on the Al2O3 layer grown at the low temperature, to recover the crystalline structure of the grown films. Using two complementary growth steps with different temperatures, the surface morphology and electrical properties of epitaxial Al2O3 films on Si substrates were improved. | 162,219 |
title: Axions and high-energy cosmic rays: Can the relic axion density be measured?; abstract: In a previous work we investigated the propagation of fast moving charged particles in a spatially constant but slowly time dependent pseudoscalar background, such as the one provided by cold relic axions. The background induces cosmic rays to radiate in the low-energy spectrum. While the energy loss caused by this mechanism on the primary cosmic rays is negligible, we investigate the hypothetical detection of the photons radiated and how they could provide an indirect way of verifying the cosmological relevance of axions. Assuming that the cosmic ray flux is of the form J(E)~ E^-g we find that the energy radiated follows a distribution k^-((g-1)/2) for proton primaries, identical to the Galaxy synchrotron radiation that is the main background, and k^-(g/2) for electron primaries, which in spite of this sharper decay provide the dominant contribution in the low-energy spectrum. We discuss possible ways to detect this small diffuse contribution. Local detection in the vicinity of powerful cosmic rays emitters might also be possible. | 162,220 |
title: EXO 0748-676 AS A QUARK STAR; abstract: This work shows results for the EXO 0748-676 neutron star structure obtained with the use of a phenomenological quark matter description by taking into account a quark interaction, and observing the asymptotic freedom and the confinement characteristics of the fundamental theory. An appropriated choice of model parameters permit to reach the stability of compact dense stellar objects compatible with the observational data to the neutron star EXO 0748-676. It is assumed a color-flavor locked (CFL) superconducting phase to the ground state of the quark–gluon plasma formed in the object interior. We also discuss the surface properties of these objects, introducing a crust composed by a lattice of neutron-rich nucleus close to the neutron drip line, imbedded in an electron gas. | 162,221 |
title: How and why silicon sensors are becoming more and more intelligent; abstract: This paper describes the historical evolution of silicon detectors from simple strip configurations to hybrid pixel detectors for high energy physics applications. This development has been critical to maintain the necessary physics performance in the high-rate and highdensity environment of the LHC. The importance of pixel detectors and their evolution for future projects and other fields is also described. | 162,222 |
title: Chiral-invariant CP-violating effective interactions in Z decays to three jets; abstract: Abstract Tests of CP violation by appropriate momentum correlations in Z → 3 jets and in particular in Z → b b X probe CP-violating effective couplings — that manifest themselves as form factors — which conserve the quark chirality and quark flavour. By giving two examples we show that such couplings can be induced at one-loop order in extensions of the Standard Model with CP violation beyond the Kobayashi-Maskawa phase. In one of the models we compute the chirality-conserving part of the CP-violating Zb b -gluon amplitude for massless b quarks, determine the resulting effective dimension d = 6 couplings in the local limit, and discuss the possible size of the effects. Finally we show that in models with excited quarks the chiral-invariant CP-violating effective interactions could be quite large if appropriate couplings are of a size characteristic of a strong interaction. | 162,223 |
title: SS 433, X-ray binaries and stellar evolution; abstract: Abstract It is argued from the stationary optical and I.R. spectrum, absolute luminosity and the optical light- and radial-velocity curves, that the SS 433 system consists of a luminous early-type star which is overflowing its Roche lobe ( R \u003e 20 R ⊚) , together with a large luminous accretion disk. Both components have roughly similar luminosities. The star transfers mass to the disk at a rate of some 10−4 M⊚/yr. The entire system is embedded in a dense spherically symmetric outflowing atmosphere, resembling that of a Wolf-Rayet star; the outflow velocities are ∼ 1 − 2 × 103 km/sec and the wind mass loss rate is ∼ 10 −5 − 10 −4 M ⊚/ yr . The presence of the beams suggests that the object at the center of the disk is a neutron star or a black hole. Various possibilities for the evolutionary state of the system are examined. Although the possibility that the compact object is young (∼ 104 yr) cannot be excluded (in which case the progenitor should have been a binary with initial mass ratio very close to unity), it appears more likely that the system is a later evolutionary state of a massive X-ray binary. This would imply that W50 was entirely produced by the beams. | 162,224 |
title: Susskind Fermions on a Euclidean Lattice; abstract: A version of euclidean lattice QCD obtained by introducing the fermions using Susskind\u0027s method is described and certain properties discussed. A U(1) axial current having the correct axial anomaly in the continuum limit is identified. We find ΛminΛL,Suss = 28.78 for SU(3) with 4 flavors. | 162,225 |
title: Viscoelastic drop falling through a viscous medium; abstract: Deformation and sedimentation velocities of a viscoelastic drop falling through a Newtonian medium are numerically investigated using a front-tracking finite difference method. In contrast to a viscous drop, viscoelasticity deforms an initially spherical drop into an oblate shape and decreases its sedimentation velocity. Further increase of elasticity results in a dimple at the rear end, as the viscoelastic stress at the trailing end of the drop pulls the drop interface inward. The dimple becomes more prominent with increasing Deborah number, amount of polymeric viscosity, and capillary number. An approximate analysis is performed to model the stress development along the axis of symmetry, specifically its increase at the rear end that governs the dimple formation. For even higher values of Deborah number, the interfacial tension cannot balance the viscoelastic stresses leading to an unstable situation toward a toroidal shape. We numerically find the critical Deborah number for the transition. It shows an... | 162,226 |
title: A RELATIVISTIC EFFECTIVE MODEL WITH PARAMETERIZED COUPLINGS FOR NEUTRON STARS; abstract: We present a relativistic effective model with derivative couplings which includes genuine many-body forces simulated by nonlinear interaction terms involving scalar-isoscalar (σ, σ*), vector-isoscalar (ω, ɸ), vector-isovector (ϱ), scalar-isovector (δ) mesons. The effective model presented in this work has a philosophy quite similar to the original version of the model with parameterized couplings. But unlike that, in which the parametrization is directly inserted in the coupling constants of the Glendenning model, we present here a method for the derivation of the parametric dependence of the coupling terms, in a way that allows in one side to consistently justify this parametrization and in the other to extend in a coherent way the range of possibilities of parameterizations in effective models with derivative couplings. The extended model is then applied to the description of the mass of neutron stars. | 162,227 |
title: Theoretical backgrounds for interpretation of spectroscopic observations; abstract: The advantage of analysis of observed data using their fit with theoretical model of the directly observed quantities is shown as well as the need for simultaneous solution of all available data. Some particular problems of disentangling of stellar spectra and model atmospheres of component stars of multiple systems are discussed. | 162,228 |
title: Electronic and crystal structure of Cu2-xS: Full-potential electronic structure calculations; abstract: Electronic structure calculations are presented for Cu2�xS using the full-potential linearized muffin-tin orbital method. In the simple cubic antifluorite structure, Cu2S is found to be semimetallic both in the local density approximation LDA and using the quasiparticle self-consistent GW QSGW method. This is because the Cu d bands comprising the valence band maximum are degenerate at the point and the fact that the Cu s band, which can be considered to be the lowest conduction band, lies slightly below it at . Small deviations from the ideal antifluorite positions for the Cu atoms, however, open a small gap between the Cu d valence and Cu s-like conduction bands because the symmetry breaking allows the Cu s and Cu d bands to hybridize. Supercell models are constructed for cubic and hexagonal chalcocite Cu2S as well as cubic digenite Cu1.8 Sb y means of a weighted random number structure generating algorithm. This approach generates models with Wyckoff site occupancies adjusted to those obtained from experimental x-ray diffraction results and with the constraint that atoms should stay within reasonable distance from each other. The band structures of these models as well as of the low-chalcocite monoclinic structure Cu96S48 are calculated in LDA with an additional Cu s shift obtained from the QSGW-LDA difference for the antifluorite structure. Even with this correction, smaller band gaps of about 0.4– 0.6 eV increasing from cubic to hexagonal to monoclinic than experimentally observed 1.1– 1.2 eV are obtained for the Cu2S composition. Decreasing the Cu content of Cu2�xS in the range 0.06x 0.2 is found to essentially dope the p-type material by placing the Fermi level 0.2– 0.3 eV below the valence band maximum but also to increase the gap between highest partially filled valence band and lowest conduction bands to about 0.7– 1.0 eV. This results from a reduced Cu d-band width. Thus, the optical band gap or onset of optical absorption increases in part but not exclusively due to the Moss-Burstein effect. The total energies of the structures are found to increase from monoclinic to hexagonal to cubic to antifluorite. This is consistent with the fact that the simple antifluorite structure is not observed and that the systems change from monoclinic to hexagonal to cubic with increasing temperature, under the assumption that the electronic energy of the system dominates the free energy. We find that Cu2S is unstable toward the formation of Cu vacancies even in thermodynamic equilibrium with bulk Cu metal. The experimental data on the band gaps and optical absorption are discussed. We find no evidence for indirect band gaps in the hexagonal materials and argue that the experimental results are consistent with this in spite of previous reports to the contrary. The presence of a second onset of absorption located about 0.5 eV higher than the minimum band gap observed in experiment is explained by a rise in conduction band density of states at this energy in our calculations. The calculated increase in gap with decreasing Cu concentration is in agreement with experimental observations. | 162,229 |
title: The impact of flavour changing neutral gauge bosons on \bar{B} \to {X_s}\gamma; abstract: The branching ratio of the rare decay \\( \\bar{B} \\to {X_s}\\gamma \\) provides potentially strong constraints on models beyond the Standard Model. Considering a general scenario with new heavy neutral gauge bosons, present in particular in Z′ and gauge flavour models, we point out two new contributions to the \\( \\bar{B} \\to {X_s}\\gamma \\) decay. The first one originates from one-loop diagrams mediated by gauge bosons and heavy exotic quarks with electric charge −1/3. The second contribution stems from the QCD mixing of neutral current-current operators generated by heavy neutral gauge bosons and the dipole operators responsible for the \\( \\bar{B} \\to {X_s}\\gamma \\) decay. The latter mixing is calculated here for the first time. We discuss general sum rules which have to be satisfied in any model of this type. We emphasise that the neutral gauge bosons in question could also significantly affect other fermion radiative decays as well as non-leptonic two-body B decays, ϵ′/ϵ, anomalous (g − 2) μ and electric dipole moments. | 162,230 |
title: Constraints on a massive Dirac neutrino model.; abstract: We examine constraints on a simple neutrino model in which there are three massless and three massive Dirac neutrinos and in which the left-handed neutrinos are linear combinations of doublet and singlet neutrinos. We examine constraints from direct decays into heavy neutrinos, indirect effects on electroweak parameters, and flavor-changing processes. We combine these constraints to examine the allowed mass range for the heavy neutrinos of each of the three generations. | 162,231 |
title: Coexistence of magnetic phases in La(Mn0.70Ga0.30)O3 under high pressure: A neutron powder diffraction investigation; abstract: Abstract Neutron powder diffraction was used to analyse the La(Mn 0.70 Ga 0.30 )O 3 compound under pressures of up to 6.1 GPa and temperatures down to 1.3 K. At ambient pressure, the magnetic ground state corresponds to a canted antiferromagnetic A x F y -type spin ordering. As the pressure increases, the F y component is suppressed and a novel A y -type ordering takes place coexisting with the A x -type. The simultaneous occurrence of these spin orderings can be ascribed to a demixing of the pristine nuclear phase into a Jahn-Teller distorted phase (where the A x -ordering takes place) and an undistorted nuclear phase which grows under pressure (where the A y -ordering develops). | 162,232 |
title: OXYGEN METALLICITY DETERMINATIONS FROM OPTICAL EMISSION LINES IN EARLY-TYPE GALAXIES; abstract: We measured the oxygen abundances of the warm (T {approx} 10{sup 4} K) phase of gas in seven early-type galaxies through long-slit observations. A template spectra was constructed from galaxies void of warm gas and subtracted from the emission-line galaxies, allowing for a clean measurement of the nebular lines. The ratios of the emission lines are consistent with photoionization, which likely originates from the ultraviolet flux of postasymototic giant branch stars. We employ H II region photoionization models to determine a mean oxygen metallicity of 1.01 {+-} 0.50 solar for the warm interstellar medium (ISM) in this sample. This warm ISM 0.5-1.5 solar metallicity is consistent with modern determinations of the metallicity in the hot (T {approx} 10{sup 6}-10{sup 7} K) ISM and the upper range of this warm ISM metallicity is consistent with stellar population metallicity determinations. A solar metallicity of the warm ISM favors an internal origin for the warm ISM such as asymptotic giant branch mass loss within the galaxy. | 162,233 |
title: Large eddy simulation of turbulent forced gas flows in vertical pipes with high heat transfer rates; abstract: Abstract Large eddy simulation (LES) of vertical turbulent pipe flows with significant property variations has been performed to investigate the effects of high heat fluxes on the turbulent structures and transport. The Cartesian-based, compressible filtered Navier–Stokes equations were solved using a second-order accurate finite volume method. Low Mach number preconditioning was used to enable the compressible code to perform efficiently at low Mach numbers. A dynamic subgrid-scale stress model accounted for the subgrid-scale turbulence. In this study, the simulations were designed to simulate the experiments of Shehata and McEligot with three different near-constant heat fluxes. Step-periodic boundary conditions based on a quasi-developed assumption were used. The predicted integral parameters and mean velocity and temperature profiles agreed well with the experimental data. The fluid structures have been distorted due to high heat fluxes leading to significant property variations in the near wall region. The results showed that strong heating resulted in remarkable reductions of turbulent intensities, shear stresses, and turbulent heat flux. Apparent “laminarization” of the flow has been observed. | 162,234 |
title: VAMOS: A variable mode high acceptance spectrometer for identifying reaction products induced by SPIRAL beams; abstract: The study of reactions induced by the SPIRAL beams at GANIL requires new techniques: the low intensity of secondary beams implies the need of a very high efficiency detection system; the study of nearly or completely unknown nuclei, over a wide range of masses and energies, needs a very efficient method for attributing a reaction product to a nucleus. The variable mode high acceptance spectrometer VAMOS is being designed and built especially for this purpose. | 162,235 |
title: Das Elektronenkontinuum in der Säule des Hochstromkohlebogens und in anderen Bögen; abstract: Aus derKramersschen Theorie ergibt sich fur die kontinuierliche Strahlung eines Plasmas ein frequenzunabhangiger Verlauf bis zu einer Grenzfrequenzvg, die dem Termabstand von der wahren Ionisierungsgrenze bis zu dem Term entspricht, bis zu welchem die Folge der Terme als hinreichend dicht angesehen werden kann. Von dieser Grenze aus fallt die Kontinuumsintensitat nach groseren Frequenzen hin mit exp(-hv/k T) ab. Dieser Abfall wird im Spektrum der Hochstrombogensaule nach eigenen Messungen und im Ar-, Kr-, Xe- und Hg-Bogen auf Grund anderer Messungen nachgewiesen. Beim Vergleich zwischen Theorie und Messung des Kontinuums stimmt die Absolutintensitat einigermasen (bis auf etwa Faktor 2) uberein, dagegen ist die Forderung der Frequenzunabhangigkeit nicht immer voll erfullt. Der Verlauf des Kontinuums in der Umgebung der Grenzfrequenz (ohne Rucksicht auf die Absolutwerte) last sich mehr oder weniger gut durch eineKirchhoff-Planck-Funktion approximieren. Die so bestimmte Farbtemperatur liegt wesentlich unter der wahren Temperatur der Entladung. Man darf daher derartige Lichtquellen nicht als Graustrahler bezeichnen. Wegen der Abhangigkeit der Kontinuumsintensitat vonN e 2 ergibt eine Absolutmessung des Kontinuums die ElektronenkonzentrationNe und uber dieSaha-Gleichung recht genau die wahre Temperatur. | 162,236 |
title: Chern-Simons Theory with Vector Fermion Matter; abstract: We study three dimensional conformal field theories described by U(N) Chern-Simons theory at level k coupled to massless fermions in the fundamental representation. By solving a Schwinger-Dyson equation in lightcone gauge, we compute the exact planar free energy of the theory at finite temperature on R^2 as a function of the \u0027t Hooft coupling lambda=N/k. Employing a dimensional reduction regularization scheme, we find that the free energy vanishes at |lambda|=1; the conformal theory does not exist for |lambda|\u003e1. We analyze the operator spectrum via the anomalous conservation relation for higher spin currents, and in particular show that the higher spin currents do not develop anomalous dimensions at leading order in 1/N. We present an integral equation whose solution in principle determines all correlators of these currents at leading order in 1/N and present explicit perturbative results for all three point functions up to two loops. We also discuss a lightcone Hamiltonian formulation of this theory where a W-infinity algebra arises. The maximally supersymmetric version of our theory is ABJ model with one gauge group taken to be U(1), demonstrating that a pure higher spin gauge theory arises as a limit of string theory. | 162,237 |
title: Simple Method for Solving Transport Equations Describing the Propagation of Cosmic-Ray Nucleons in the Atmosphere; abstract: A simple and efficient method is proposed for solving transport equations that describe the propagation of cosmic-ray protons and neutrons in the atmosphere at high energies. It is shown that, upon taking into account a non-power-law character of the primary spectrum, a growth of total cross sections for inelastic nucleon-nucleus interactions, and violation of scaling in such interactions, the effective absorption ranges of nucleons come to be dependent not only on energy but also on the depth in the atmosphere. The results of the calculations are compared with available experimental data. | 162,238 |
title: Gravitational collapse of dust fluid and dark energy in the presence of curvature: Black hole formation; abstract: Study of gravitational collapse and black hole formation has got much interest in recent years after gravitational waves detection from mergers of black hole binaries. Here, we studied the gravitat... | 162,239 |
title: Numerical Modeling of Micromechanical Devices Using the Direct Simulation Monte Carlo Method; abstract: A direct simulation Monte Carlo (DSMC) investigation of flows related to microelectromechanical systems (MEMS) is detailed. This effort is intended to provide tools to facilitate the design and optimization of micro-devices as well as to probe the effects of rarefaction, especially in regimes not amenable to other means of analysis. The code written for this purpose employs an unstructured grid, a trajectory-tracing particle movement scheme, and an infinite channel boundary formulation. Its results for slip-flow and transition regime micro-channels and a micro-nozzle are presented to demonstrate its capabilities. | 162,240 |
title: GRMHD simulations of magnetized advection‐dominated accretion on a non‐spinning black hole: role of outflows; abstract: We present results from two long-duration general relativistic magneto-hydrodynamic (GRMHD) simulations of advection-dominated accretion around a non-spinning black hole. The first simulation was designed to avoid significant accumulation of magnetic flux around the black hole. This simulation was run for a time of 200 000 GM/c3 and achieved inflow equilibrium out to a radius ∼90 GM/c2. Even at this relatively large radius, the mass outflow rate is found to be only 60 per cent of the net mass inflow rate into the black hole. The second simulation was designed to achieve substantial magnetic flux accumulation around the black hole in a magnetically arrested disc. This simulation was run for a shorter time of 100 000 GM/c3. Nevertheless, because the mean radial velocity was several times larger than in the first simulation, it reached inflow equilibrium out to a radius ∼170 GM/c2. Here, becomes equal to at r ∼ 160 GM/c2. Since the mass outflow rates in the two simulations do not show robust convergence with time, it is likely that the true outflow rates are lower than our estimates. The effect of black hole spin on mass outflow remains to be explored. Neither simulation shows strong evidence for convection, though a complete analysis including the effect of magnetic fields is left for the future. | 162,241 |
title: Measurement of transverse energy-energy correlations in multi-jet events in pp collisions at √s = 7 TeV using the ATLAS detector and determination of the strong coupling constant αs(mZ); abstract: High transverse momentum jets produced in pp collisions at a centre of mass energy of 7 TeV are used to measure the transverse energy–energy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of 158 pb−1. The selection criteria demand the average transverse momentum of the two leading jets in an event to be larger than 250 GeV. The data at detector level are well described by Monte Carlo event generators. They are unfolded to the particle level and compared with theoretical calculations at next-to-leading-order accuracy. The agreement between data and theory is good and provides a precision test of perturbative Quantum Chromodynamics at large momentum transfers. From this comparison, the strong coupling constant given at the Z boson mass is determined to be αs(mZ)=0.1173±0.0010 (exp.) −0.0026+0.0065 (theo.). | 162,242 |
title: Control of an interfacial MoSe2 layer in Cu2ZnSnSe4 thin film solar cells: 8.9% power conversion efficiency with a TiN diffusion barrier; abstract: We have examined Cu2ZnSnSe4 (CZTSe) solar cells prepared by thermal co-evaporation on Mo-coated glass substrates followed by post-deposition annealing under Se ambient. We show that the control of an interfacial MoSe2 layer thickness and the introduction of an adequate Se partial pressure (PSe) during annealing are essential to achieve high efficiency CZTSe solar cells—a reverse correlation between device performance and MoSe2 thickness is observed, and insufficient PSe leads to the formation of defects within the bandgap as revealed by photoluminescence measurements. Using a TiN diffusion barrier, we demonstrate 8.9% efficiency CZTSe devices with a long lifetime of photo-generated carriers. | 162,243 |
title: Vortex generation and inhomogeneous Faraday rotation of a nonparaxial Gaussian beam in isotropic magneto-optic crystals; abstract: We study the propagation of a nonparaxial Gaussian beam in the isotropic Bi4Ge3O12 crystal under an external magnetic field. The analytical solutions in the paraxial limit are derived, which show that a vortex with topological charge m=2 (m=1) generates in the E− (Ez) component. Numerical calculations in the nonparaxial regime confirm that, with the assistance of an external magnetic field, the spin-to-orbital angular momentum coupling effect can occur even in the isotropic crystal. We also study the Faraday rotation of the nonparaxial Gaussian beam. At the center of the transverse plane, the rotation of the plane of polarization is linearly proportional to the magnetic field. However, the rotation is not uniform on the whole transverse plane, manifesting the nonparaxial effect. | 162,244 |
title: Orbital variability of the PSR J2051-0827 Binary System; abstract: We have carried out high-precision timing measurements of the binary millisecond pulsar PSR J2051$-$0827 with the Effelsberg 100-m radio telescope of the Max-Planck-Institut f\\\"ur Radioastronomie and with the Lovell 76-m radio telescope at Jodrell Bank. The 6.5-yrs radio timing measurements have revealed a significant secular variation of the projected semi-major axis of the pulsar at a rate of $\\dot x\\equiv d(a_{\\rm 1} \\sin i)/dt = (-0.23\\pm 0.03)\\times 10^{-12}$, which is probably caused by the Newtonian spin-orbit coupling in this binary system leading to a precession of the orbital plane. The required misalignment of the spin and orbital angular momenta of the companion are evidence for an asymmetric supernova explosion. We have also confirmed that the orbital period is currently decreasing at a rate of $\\dot P_{\\rm b}=(-15.5 \\pm 0.8)\\times 10^{-12}$s s$^{-1}$ and have measured second and third orbital period derivatives $d^2P_{\\rm b}/dt^2=(+2.1 \\pm 0.3)\\times 10^{-20} {\\rm s^{-1}}$ and $d^3P_{\\rm b}/dt^3 =(3.6 \\pm 0.6)\\times 10^{-28} {\\rm s^{-2}}$, which indicate a quasi-cyclic orbital period variation similar to those found in another eclipsing pulsar system, PSR B1957+20. The observed variation of the orbital parameters constrains the maximal value of the companion radius to $R_{\\rm c max} \\sim 0.06 R_{\\odot}$ and implies that the companion is underfilling its Roche lobe by 50 %. The derived variation in the quadrupole moment of the companion is probably caused by tidal dissipation similar to the mechanism proposed for PSR B1957+20. We conclude that the companion is at least partially non-degenerate, convective and magnetically active. | 162,245 |
title: Self-consistent Hartree–Fock RPA calculations in 208 Pb; abstract: The nuclear structure of 208Pb is studied in the framework of the self-consistent random phase approximation (SCRPA). The Hartree–Fock mean field and single particle states are used to implement a completely SCRPA with Skyrme-type interactions. The Hamiltonian is diagonalised within a model space using five Skyrme parameter sets, namely LNS, SkI3, SkO, SkP and SLy4. In view of the huge number of the existing Skyrme-force parameterizations, the question remains which of them provide the best description of data. The approach attempts to accurately describe the structure of the spherical even–even nucleus 208Pb. To illustrate our approach, we compared the binding energy, charge density distribution, excitation energy levels scheme with the available experimental data. Moreover, we calculated isoscalar and isovector monopole, dipole, and quadrupole transition densities and strength functions. | 162,246 |
title: Cosmological lepton asymmetry, primordial nucleosynthesis and sterile neutrinos; abstract: We study post weak decoupling coherent active-sterile and active-active matter-enhanced neutrino flavor transformation in the early Universe. We show that flavor conversion efficiency at Mikheyev-Smirnov-Wolfenstein resonances is likely to be high (adiabatic evolution) for relevant neutrino parameters and energies. However, we point out that these resonances cannot sweep smoothly and continuously with the expansion of the Universe. We show how neutrino flavor conversion in this way can leave both the active and sterile neutrinos with nonthermal energy spectra, and how, in turn, these distorted energy spectra can affect the neutron-to-proton ratio, primordial nucleosynthesis, and cosmological mass/closure constraints on sterile neutrinos. We demonstrate that the existence of a light sterile neutrino which mixes with active neutrinos can change fundamentally the relationship between the cosmological lepton numbers and the primordial nucleosynthesis 4He yield. | 162,247 |
title: Heavy elements Ba, La, Ce, Nd, and Eu in 56 Galactic bulge red giants; abstract: Aims. The aim of this work is the study of abundances of the heavy elements Ba, La, Ce, Nd, and Eu in 56 bulge giants (red giant branch and red clump) with metallicities ranging from -1.3 dex to 0.5 dex. Methods. We obtained high-resolution spectra of our giant stars using the FLAMES-UVES spectrograph on the Very Large Telescope. We inspected four bulge fields along the minor axis. Results. We measure the chemical evolution of heavy elements, as a function of metallicity, in the Galactic bulge. Conclusions. The [Ba, La, Ce, Nd/Fe] vs. [Fe/H] ratios decrease with increasing metallicity, in which aspect they differ from disc stars. In our metal-poor bulge stars, La and Ba are enhanced relative to their thick disc counterpart, while in our metal-rich bulge stars La and Ba are underabundant relative to their disc counterpart. Therefore, this contrast between bulge and discs trends indicates that bulge and (solar neighbourhood) thick disc stars could behave differently. An increase in [La, Nd/Eu] with increasing metallicity, for metal-rich stars with [Fe/H] \u003e 0 dex, may indicate that the s-process from AGB stars starts to operate at a metallicity around solar. Finally, [Eu/Fe] follows the [{\\alpha}/Fe] behaviour, as expected, since these elements are produced by SNe type II. | 162,248 |
title: Two-tone frequency modulation saturation spectroscopy for tunable frequency offset locking of a single laser; abstract: Abstract The two-tone frequency modulation spectroscopy (TTFMS) is widely used for gas trace detection with its low noise absorption signal. In this paper we propose and implement the TTFMS scheme for frequency offset locking a single diode laser to an atomic resonance line by using its dispersion signal. The TTFMS theory is first discussed under the assumption that the intermediate modulation frequency is comparable to the linewidth of the absorption feature, and the dependence of the TTFMS absorption and dispersion features on the intermediate modulation frequency and modulation index are investigated theoretically. Based on a fiber-coupled electro-optic modulator (EOM) with two-tone modulation, we experimentally demonstrated the performance of the frequency offset locking method. The result shows a short-term frequency stability of the frequency offset locked laser reached around 1.1 × 10−11, with an averaging time of 2 s. This method can find wide applications in fields requiring widely tunable frequency offset locking a single laser to the atomic resonance line, like precision spectroscopy and Raman optics for atom interferometers. | 162,249 |
title: NEXTCALIBUR – A four-fermion generator for electron–positron collisions; abstract: Abstract A fully massive Monte Carlo program to compute all four-fermion processes in e + e − collisions, including Higgs boson production, is presented. Leading higher order effects are discussed and included. | 162,250 |
title: The origin of ferromagnetism in LaMnO3+δ; abstract: Studies on different LaMnO3+δ samples have revealed that there is no correlation between the magnetic properties and large values of δ (Mn4+ content) or the rhombohedral structure of the material. From powder x-ray diffraction studies, it was found that those LaMnO3+δ samples showing well defined ferromagnetic transitions are of mixed-phase character: an La1-xMnO3+δ phase and minor amounts of an La-rich phase. The results give sufficient evidence to conclude that the self-doped, La-deficient, phases formed are responsible for ferromagnetism in LaMnO3+δ. | 162,251 |
title: The micro-glitch in PSR B1821−24: a case for a strange pulsar?; abstract: The single glitch observed in PSR B1821-24, a millisecond pulsar in M28, is unusual on two counts. First, the magnitude of this glitch is at least an order of magnitude smaller (Δν/ν∼10 -11 ) than the smallest glitch observed to date. Secondly, all other glitching pulsars have strong magnetic fields with B ≳ 10 11 G and are young, whereas PSR B1821-24 is an old recycled pulsar with a field strength of 2.25 x 10 9 G. We have earlier suggested that some of the recycled pulsars could actually be strange quark stars. In this work, we argue that the crustal properties of such a strange pulsar are just right to give rise to a glitch of this magnitude, explaining the scarcity of larger glitches in millisecond pulsars. | 162,252 |
title: Anomalous microstructure and magnetocaloric properties in off-stoichiometric La-Fe-Si and its hydride; abstract: In the present work we reported the phase formation, microstructure, magnetocaloric effect and hydrogenation behavior of La-rich La1.7Fe11.6Si1.4 alloy. In this off-stoichiometric La(Fe,Si)13 alloy, the NaZn13-type La(Fe,Si)13 matrix phase shows faceted grains, with the Cr5B3-type La5Si3 used as the secondary phase distributed intergranularly. Such a peculiar morphology quickly forms upon one day annealing. In La1.7Fe11.6Si1.4 alloy, we have observed a significant field dependence of magnetostructural transition temperature (~ 6.3 K/T), resulting in a large and table-like entropy change (ΔS ~ 18 J/kgK in 2 T) over a broad temperature range (~ 10 K). Upon hydrogenation, the maximum value of ΔS keeps almost unchanged, while the Curie temperature increases up to 350 K. These results indicate that the investigated off-stoichiometric La(Fe,Si)13 alloy is a promising magnetic material for magnetic refrigerators. | 162,253 |
title: Mixed QCD-electroweak O(α s α) corrections to Drell-Yan processes in the resonance region: Pole approximation and non-factorizable corrections; abstract: Abstract Drell–Yan-like W-boson and Z-boson production in the resonance region allows for high-precision measurements that are crucial to carry experimental tests of the Standard Model to the extremes, such as the determination of the W-boson mass and the effective weak mixing angle. In this article, we establish a framework for the calculation of the mixed QCD–electroweak O ( α s α ) corrections to Drell–Yan processes in the resonance region, which are one of the main remaining theoretical uncertainties. We describe how the Standard Model prediction can be successfully performed in terms of a consistent expansion about the resonance poles, which classifies the corrections in terms of factorizable and non-factorizable contributions. The former can be attributed to the W / Z production and decay subprocesses individually, while the latter link production and decay by soft-photon exchange. At next-to-leading order we compare the full electroweak corrections with the pole-expanded approximations, confirming the validity of the approximation. At O ( α s α ) , we describe the concept of the expansion and explicitly give results on the non-factorizable contributions, which turn out to be phenomenologically negligible. Our results, thus, demonstrate that for phenomenological purposes the O ( α s α ) corrections can be factorized into terms associated with initial-state and/or final-state corrections. Moreover, we argue that the factorization properties of the non-factorizable corrections at O ( α s α ) from lower-order O ( α s ) graphs generalize to any order in O ( α s n α ) . | 162,254 |
title: Hypercritical Accretion, Induced Gravitational Collapse, and Binary-Driven Hypernovae; abstract: The induced gravitational collapse (IGC) paradigm has been successfully applied to the explanation of the concomitance of gamma-ray bursts (GRBs) with supernovae (SNe) Ic. The progenitor is a tight binary system composed by a carbon-oxygen (CO) core and a neutron star (NS) companion. The explosion of the SN leads to hypercritical accretion onto the NS companion which reaches the critical mass, hence inducing its gravitational collapse to a black hole (BH) with consequent emission of the GRB. The first estimates of this process were based on a simplified model of the binary parameters and the Bondi-Hoyle-Lyttleton accretion rate. We present here the first full numerical simulations of the IGC phenomenon. We simulate the core-collapse and SN explosion of CO stars to obtain the density and ejection velocity of the SN ejecta. We follow the hydrodynamic evolution of the accreting material falling into the Bondi-Hoyle surface of the NS all the way up to its incorporation to the NS surface. The simulations go up to BH formation when the NS reaches the critical mass. For appropriate binary parameters the IGC occurs in short timescales (100-1000s) owing to the combined effective action of the photon trapping and the neutrino cooling near the NS surface. We also show that the IGC scenario leads to a natural explanation for why GRBs are associated only to SN Ic with totally absent or very little helium. | 162,255 |
title: Power corrections in the dispersive model for a determination of the strong coupling constant from the thrust distribution; abstract: In the context of the dispersive model for non-perturbative corrections, we extend the leading renormalon subtraction to NNLO for the thrust distribution in e + e − annihilation. Within this framework, using a NNLL+NNLO perturbative description and including bottom-quark mass effects to NLO, we analyse data in the centre-of-mass energy range \\(\\sqrt{s}=14\\mbox{--}206~\\mbox{GeV}\\) in view of a simultaneous determination of the strong coupling constant and the non-perturbative parameter α 0. The fits are performed by matching the resummed and fixed-order predictions both in the R and the log-R matching schemes. The final values in the R scheme are \\(\\alpha_{s}(M_{Z}) = 0.1131^{+0.0028}_{-0.0022}\\), \\(\\alpha_{0}(2~\\mathrm{GeV}) = 0.538^{+0.102}_{-0.047}\\). | 162,256 |
title: Sensitive Probe for Symmetry Potential; abstract: Based on both very obvious isospin effect of the neutron–proton number ratio of nucleon emissions (n/p)nucl on symmetry potential and (n/p)nucl\u0027s sensitive dependence on symmetry potential in the nuclear reactions induced by halo-neutron projectiles, compared to the same mass stable projectile, probing symmetry potential is investigated within the isospin-dependent quantum molecular dynamics with isospin and momentum-dependent interactions for different symmetry potentials U1sym and U2sym. It is found that the neutron-halo projectile induces very obvious increase of (n/p)nucl and strengthens the dependence of (n/p)nucl on the symmetry potential for all the beam energies and impact parameters, compared to the same mass stable projectile under the same incident channel condition. Therefore (n/p)nucl induced by the neutron-halo projectile is a more favourable probe than the normal neutron-rich and neutron-poor projectiles for extracting the symmetry potential. | 162,257 |
title: Extending the trapping lifetime of single atom in a microscopic far-off-resonance optical dipole trap; abstract: In our experiment, a single cesium atom prepared in a large-magnetic-gradient magneto-optical trap (MOT) can be efficiently transferred into a 1064-nm far-off-resonance microscopic optical dipole trap (FORT). The efficient transfer of the single atom between the two traps is used to determine the trapping lifetime and the effective temperature of the single atom in FORT. The typical trapping lifetime has been improved from ∼ 6.9 s to ∼ 130 s by decreasing the background pressure from ∼ 1 × 10−10 Torr to ∼ 2 × 10−11 Torr and applying one-shot 10-ms laser cooling phase. We also theoretically investigate the dependence of trapping lifetimes of a single atom in a FORT on trap parameters based on the FORT beam’s intensity noise induced heating. Numerical simulations show that the heating depends on the FORT beam’s waist size and the trap depth. The trapping time can be predicted based on effective temperature measurement of a single atom in the FORT and the intensity noise spectra of the FORT beam. These experimental results are found to be in agreement with the predictions of the heating model. | 162,258 |
title: On the Saturation of the Magnetorotational Instability via Parasitic Modes; abstract: We investigate the stability of incompressible, exact, non-ideal magnetorotational (MRI) modes against parasitic instabilities. Both Kelvin-Helmholtz and tearing-mode parasitic instabilities may occur in the dissipative regimes accessible to current numerical simulations. We suppose that a primary MRI mode saturates at an amplitude such that its fastest parasite has a growth rate comparable to its own. The predicted alpha parameter then depends critically on whether the fastest primary and parasitic modes fit within the computational domain and whether non-axisymmetric parasitic modes are allowed. Hence even simulations that resolve viscous and resistive scales may not saturate properly unless the numerical domain is large enough to allow the free evolution of both MRI and parasitic modes. To minimally satisfy these requirements in simulations with vertical background fields, the vertical extent of the domain should accommodate the fastest growing MRI mode while the radial and azimuthal extents must be twice as large. The fastest parasites have horizontal wavelengths roughly twice as long as the vertical wavelength of the primary. | 162,259 |
title: Acceleration of rain initiation by cloud turbulence; abstract: Vapour condensation in cloud cores produces small droplets that are close to one another in size. Droplets are believed to grow to raindrop size by coalescence due to collision. Air turbulence is thought to be the main cause for collisions of similar-sized droplets exceeding radii of a few micrometres, and therefore rain prediction requires a quantitative description of droplet collision in turbulence. Turbulent vortices act as small centrifuges that spin heavy droplets out, creating concentration inhomogeneities and jets of droplets, both of which increase the mean collision rate. Here we derive a formula for the collision rate of small heavy particles in a turbulent flow, using a recently developed formalism for tracing random trajectories. We describe an enhancement of inertial effects by turbulence intermittency and an interplay between turbulence and gravity that determines the collision rate. We present a new mechanism, the \u0027sling effect\u0027, for collisions due to jets of droplets that become detached from the air flow. We conclude that air turbulence can substantially accelerate the appearance of large droplets that trigger rain. | 162,260 |
title: Ultra-weak sector, Higgs boson mass, and the dilaton; abstract: The Higgs boson mass may arise from a portal coupling to a singlet field $$\\sigma$$ which has a very large VEV $$f \\gg m_\\text{Higgs}$$. This requires a sector of \"ultra-weak\" couplings $$\\zeta_i$$, where $$\\zeta_i \\lesssim m_\\text{Higgs}^2 / f^2$$. Ultra-weak couplings are technically naturally small due to a custodial shift symmetry of $$\\sigma$$ in the $$\\zeta_i \\rightarrow 0$$ limit. The singlet field $$\\sigma$$ has properties similar to a pseudo-dilaton. We engineer explicit breaking of scale invariance in the ultra-weak sector via a Coleman-Weinberg potential, which requires hierarchies amongst the ultra-weak couplings. | 162,261 |
title: Decoration–iteration transformation and Monte Carlo simulation for mixed ferrimagnetic ternary alloy; abstract: Abstract The spin fluctuation effect on the appearance of plural compensation temperatures in ferrimagnet is studied for a simple mixed ferro-ferrimagnetic ternary alloy model of the type AX ( X = B p C 1 - p ) on a decorated lattice consisting of three kinds of magnetic ions A , B and C . The combination of molecular field approximation, decorated–iteration transformation and the Monte Carlo simulation enabled us to discuss systematically the effect of inclusion of spin fluctuation and also showed a possibility to discuss the effect of spin fluctuation and that of concentration distribution separately. | 162,262 |
title: Gravito-electromagnetic analogies; abstract: We reexamine and further develop dierent gravito-electromagnetic (GEM) analogies found in the literature, and clarify the connection between them. Special emphasis is placed in two exact physical analogies: the analogy based on inertial elds from the so-called \\1+3 formalism\", and the analogy based on tidal tensors. Both are reformulated, extended and generalized. We write in both formalisms the Maxwell and the full exact Einstein eld equations with sources, plus the algebraic Bianchi identities, which are cast as the source-free equations for the gravitational eld. New results within each approach are unveiled. The well known analogy between linearized gravity and electromagnetism in Lorentz frames is obtained as a limiting case of the exact ones. The formal analogies between the Maxwell and Weyl tensors are also discussed, and, together with insight from the other approaches, used to physically interpret gravitational radiation. The precise conditions under which a similarity between gravity and electromagnetism occurs are discussed, and we conclude by summarizing the main outcome of each approach. | 162,263 |
title: On heavy–light meson resonances and chiral symmetry; abstract: Abstract We study heavy–light meson resonances with quantum numbers J P =0 + and J P =1 + in terms of the non-linear chiral SU(3) Lagrangian. At leading order a parameter-free prediction is obtained for the scattering of Goldstone bosons off heavy–light pseudo-scalar and vector mesons. The recently announced narrow open-charm states observed by the BABAR and CLEO Collaborations are reproduced. We suggest the existence of states that form an anti-triplet and a sextet representation of the SU(3) group. In particular, so far unobserved narrow isospin-singlet states with negative strangeness are predicted. The open-beauty states with ( I , S )=(0,−1) are anticipated at 5761 MeV ( J P =0 + ) and 5807 MeV ( J P =1 + ). For the anti-triplet states our results differ most significantly from predictions that are based on the chiral quark model in the open-beauty sector. Strongly bound 0 + - and 1 + -states with ( I , S )=(0,1) at 5643 and 5690 MeV are predicted. | 162,264 |
title: NuSTAR and Suzaku Observations of the Hard State in Cygnus X-1: Locating the Inner Accretion Disk; abstract: We present simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR ) and Suzaku observations of the X-ray binary Cygnus X-1 in the hard state. This is the first time this state has been observed in Cyg X-1 with NuSTAR, which enables us to study the reflection and broadband spectra in unprecedented detail. We confirm that the iron line cannot be fit with a combination of narrow lines and absorption features, instead requiring a relativistically blurred profile in combination with a narrow line and absorption from the companion wind. We use the reflection models of Garcia et al. to simultaneously measure the black hole spin, disk inner radius, and coronal height in a self-consistent manner. Detailed fits to the iron line profile indicate a high level of relativistic blurring, indicative of reflection from the inner accretion disk. We find a high spin, a small inner disk radius, and a low source height and rule out truncation to greater than three gravitational radii at the 3σ confidence level. In addition, we find that the line profile has not changed greatly in the switch from soft to hard states, and that the differences are consistent with changes in the underlying reflection spectrum rather than the relativistic blurring. We find that the blurring parameters are consistent when fitting either just the iron line or the entire broadband spectrum, which is well modeled with a Comptonized continuum plus reflection model. | 162,265 |
title: Neutral pions and η mesons as probes of the hadronic fireball in nucleus-nucleus collisions around 1A GeV; abstract: Chemical and thermal freeze-out of the hadronic fireball formed in symmetric collisions of light, intermediate-mass, and heavy nuclei at beam energies between $0.8A$ GeV and $2.0A$ GeV are discussed in terms of an equilibrated, isospin-symmetric ideal hadron gas with grand-canonical baryon-number conservation. For each collision system the baryochemical potential ${\\ensuremath{\\mu}}_{B}$ and the chemical freeze-out temperature ${T}_{c}$ are deduced from the inclusive ${\\ensuremath{\\pi}}^{0}$ and \\ensuremath{\\eta} yields which are augmented by interpolated data on deuteron production. With increasing beam energy ${\\ensuremath{\\mu}}_{B}$ drops from 800 MeV to 650 MeV, while ${T}_{c}$ rises from 55 MeV to 90 MeV. For given beam energy ${\\ensuremath{\\mu}}_{B}$ grows with system size, whereas ${T}_{c}$ remains constant. The centrality dependence of the freeze-out parameters is weak as exemplified by the system Au+Au at 0.8A GeV. For the highest beam energies the fraction of nucleons excited to resonance states reaches freeze-out values of nearly 15%, suggesting resonance densities close to normal nuclear density at maximum compression. In contrast to the particle yields, which convey the status at chemical freeze-out, the shapes of the related transverse-mass spectra do reflect thermal freeze-out. The observed thermal freeze-out temperatures ${T}_{\\mathrm{th}}$ are equal to or slightly lower than ${T}_{c},$ indicative of nearly simultaneous chemical and thermal freeze-out. | 162,266 |
title: The Quiescent Optical and Infrared Counterpart to EXO 0748-676 = UY Vol; abstract: We present optical and infrared photometry of the low-mass X-ray binary EXO 0748-676 in quiescence for the first time in 24 years since it became X-ray active in 1985. We find the counterpart at average magnitudes of R = 22.4 and J = 21.3. We monitored the source approximately nightly from 2008 November to 2009 January. During this time there was considerable night-to-night optical variability but no long-term trends were apparent. The night-to-night variability reveals a periodicity of P = 0.159331 ± 0.000012 d, consistent with the X-ray orbital period to within 0.01%. This indicates that the quiescent optical modulation is indeed orbital in nature rather than a superhump. Interestingly, the modulation remains single-peaked with a deep minimum coincident with the times of X-ray eclipse, and there is no indication of a double-peaked ellipsoidal modulation. This indicates that even in \"quiescence,\" emission from the accretion disk and/or X-ray heated inner face of the companion star dominate the optical emission, and implies that obtaining an accurate dynamical mass estimate in quiescence will be challenging. | 162,267 |
title: Baryons as Three Flavor Solitons; abstract: The description of baryons as soliton solutions of effective meson theories for three flavor (up, down, strange) degrees of freedom is reviewed and the phenomenological implications are illuminated. In the collective approach the soliton configuration is equipped with baryon quantum numbers by canonical quantization of the coordinates describing the flavor orientation. The baryon spectrum resulting from exact diagonalization of the collective Hamiltonian is discussed. The prediction of static properties such as the baryon magnetic moments and the Cabibbo matrix elements for semi--leptonic hyperon decays are explored with regard to the influence of flavor symmetry breaking. In particular, the role of strange degrees of freedom in the nucleon is investigated for both the vector and axial--vector current matrix elements. The latter are discussed extensively within in the context of the {\\it proton spin puzzle}. The influence of flavor symmetry breaking on the shape of the soliton is examined and observed to cause significant deviations from flavor covariant predictions on the baryon magnetic moments. Short range effects are incorporated by a chiral invariant inclusion of vector meson fields. These extensions are necessary to properly describe the singlet axial--vector current and the neutron proton mass difference. The effects of the vector meson excitations on baryon properties are also considered. The bound state description of hyperons and its generalization to baryons containing a heavy quark are illustrated. In the case of the Skyrme model a comparison is performed between the collective quantization scheme and bound state approach. Finally, the Nambu--Jona--Lasinio model is employed to demonstrate that hyperons can be described as solitons in a microscopic theory of the quark | 162,268 |
title: Several-MeV γ-ray generation at NewSUBARU by laser Compton backscattering; abstract: Abstract A new laser Compton gamma ray source in the energy range of several-MeV was developed using a CO 2 laser at the NewSUBARU electron storage ring. When the electron energies were 974, 1220 and 1460 MeV, the maximum gamma ray energies were measured to be 1.72, 2.72, and 3.91 MeV. The luminosity of the gamma rays was 7300 photon/mA/W/s and a flux of 5.8×10 6 photon/s was achieved. A gamma beam divergence of 0.5 mrad and its pattern were also measured. These performances agreed with calculations. This generation of gamma rays is in a no-loss mode for the storage electrons, and the maximum flux was limited only by the power of the laser. A flux of up to 10 11 photon/s will be achieved using a 30 kW class CO 2 laser. Several-MeV gamma ray sources at NewSUBARU are capable of generating such high power. | 162,269 |
title: Determination of the Michel parameters and the τ neutrino helicity in τ decay; abstract: Using the CLEO II detector at the e{sup +}e{sup -} storage ring CESR, we have determined the Michel parameters {rho}, {zeta}, and {delta} in {tau}{sup {-+}}{nu}{bar {nu}} decay as well as the {tau} neutrino helicity parameter H{sub {nu}{sub {tau}}} in {tau}{sup {-+}}{pi}{sup 0}{nu} decay. From a data sample of 3.02 x 10{sup 6} {tau} pairs produced at {radical}s = 10.6 GeV, using events of the topology e{sup +}e{sup -} {yields} {tau}{sup +}{tau}{sup -} {yields} (l{sup {+-}}{nu}{bar {nu}})({pi}{sup {-+}}{pi}{sup 0}{nu}) and e{sup +}e{sup -} {yields} {tau}{sup +}{tau}{sup -} {yields} ({pi}{sup {+-}}{pi}{sup 0}{bar {nu}})({pi}{sup {-+}}{pi}{sup 0}{nu}), and the determined sign of h{sub {nu}{sub {tau}}} the combined result of the three samples is: {rho} = 0.747 {+-} 0.010 {+-} 0.006, {zeta} = 1.007 {+-} 0.040 {+-} 0.015, {zeta}{delta} = 0.745 {+-}0.026 {+-}0.009, and h{sub {nu}{sub {tau}}} = -0.995 {+-} 0.010 {+-} 0.003. The results are in agreement with the Standard Model V-A interaction. | 162,270 |
title: High coercivity in mechanically alloyed Sm‐Fe‐V magnets with a ThMn12 crystal structure; abstract: Microcrystalline Sm‐Fe‐V magnets with a ThMn12 crystal structure were prepared by mechanical alloying and a subsequent reaction heat treatment. In Sm15Fe70V15 a coercivity of 11.7 kOe is obtained. This is the best value reported so far for 1:12 magnets. As expected from their high anisotropy fields, the 1:12 magnets, therefore, show coercivities which are common in the Nd‐Fe‐B system. | 162,271 |
title: Improved fabrication techniques for infrared bolometers; abstract: Techniques are described for producing improved infrared bolometers from doped germanium. Ion implantation and sputter metalization have been used to make ohmic electrical contacts to Ge:Ga chips. This method results in a high yield of small monolithic bolometers with very little lowfrequency noise. When one of these chips is used as the thermometric element of a composite bolometer, it must be bonded to a dielectric substrate. The thermal resistance of the conventional epoxy bond has been measured and found to be undesirably large. A procedure for soldering the chip to a metalized portion of the substrate is described which reduced this resistance. The contribution of the metal film absorber to the heat capacity of a composite bolometer has been measured. The heat capacity of a NiCr absorber at 1.3K can dominate the bolometer performance. A Bi absorber has significantly lower heat capacity. A low-temperature blackbody calibrator has been built to measure the optical responsivity of bolometers. A composite bolometer system with a throughput of ∼0.1 sr cm2 has been constructed using our new techniques. In negligible background, it has an optical NEP of\\(3.6 \\cdot 10^{ - 15} W/\\sqrt {Hz}\\) at 1.0K with a time constant of 20 ms. The noise in this bolometer is white above 2.5 Hz and is somewhat below the value predicted by thermodynamic equilibrium theory. It is in agreement with calculations based on a recent nonequilibrium theory. | 162,272 |
title: Response of streamer tubes to highly ionizing particles; abstract: Abstract The charge response of streamer tubes has been measured as a function of ionization power by exposure to relativistic ions. The results are discussed in view of the use of streamer tubes in the search for magnetic monopoles. | 162,273 |
title: HIGH-SPIN 1P-1H CONFIGURATIONS IN SN-116 AND THEIR FRAGMENTATION AS SEEN IN THE REACTIONS SN-116(-]P,P'), SN-116(E,E'), IN-115(3HE,D) AND IN-115(ALPHA, T); abstract: Stretched spin configurations in 116Sn have been studied via the reactions 116Sn(p, p′), 116Sn(e, e′), 115In(3He, d) and 115In(α, t). The high-spin negative parity two-neutron quasiparticle states within the N = 51 − 82 major shell appear to be little fragmented. The most prominent examples are the Iπ = 9- state at Ex = 3.522 MeV and two 7− states at 2.909 and 3.120 MeV. It is found that in contrast the proton configurations (g−192, h112) and (g−192 g72) are strongly fragmented. Large-basis BCS shell model calculation, using a SkE-force have been made and DWBA analyses of the (e, e′) data and of the (p, p′) data are presented. | 162,274 |
title: Lattice Boltzmann model with nearly constant density.; abstract: An improved lattice Boltzmann model is developed to simulate fluid flow with nearly constant fluid density. The ingredient is to incorporate an extra relaxation for fluid density, which is realized by introducing a feedback equation in the equilibrium distribution functions. The pressure is dominated by the moving particles at a node, while the fluid density is kept nearly constant and explicit mass conservation is retained as well. Numerical simulation based on the present model for the (steady) plane Poiseuille flow and the (unsteady) two-dimensional Womersley flow shows a great improvement in simulation results over the previous models. In particular, the density fluctuation has been reduced effectively while achieving a relatively large pressure gradient. | 162,275 |
title: A unified operator splitting approach for multi-scale fluid–particle coupling in the lattice Boltzmann method; abstract: Abstract A unified framework to derive discrete time-marching schemes for the coupling of immersed solid and elastic objects to the lattice Boltzmann method is presented. Based on operator splitting for the discrete Boltzmann equation, second-order time-accurate schemes for the immersed boundary method, viscous force coupling and external boundary force are derived. Furthermore, a modified formulation of the external boundary force is introduced that leads to a more accurate no-slip boundary condition. The derivation also reveals that the coupling methods can be cast into a unified form, and that the immersed boundary method can be interpreted as the limit of force coupling for vanishing particle mass. In practice, the ratio between fluid and particle mass determines the strength of the force transfer in the coupling. The integration schemes formally improve the accuracy of first-order algorithms that are commonly employed when coupling immersed objects to a lattice Boltzmann fluid. It is anticipated that they will also lead to superior long-time stability in simulations of complex fluids with multiple scales. | 162,276 |
title: Galaxy morphology, luminosity, and environment in the SDSS DR7; abstract: Aims. We study the influence of the environment on the evolution of galaxies by investigating the luminosity function (LF) of galaxies of different morphological types and colours at different environmental density levels. Methods. We construct the LFs separately for galaxies of different morphology (spiral and elliptical) and of different colours (red and blue) using data from the Sloan Digital Sky Survey (SDSS), correcting the luminosities for the intrinsic absorption. We use the global luminosity density field to define different environments, and analyse the environmental dependence of galaxy morphology and colour. The smoothed bootstrap method is used to calculate confidence regions of the derived luminosity functions. Results. We find a strong environmental dependency for the LF of elliptical galaxies. The LF of spiral galaxies is almost environment independent, suggesting that spiral galaxy formation mechanisms are similar in different environments. Absorption by the intrinsic dust influences the bright-end of the LF of spiral galaxies. After attenuation correction, the brightest spiral galaxies are still about 0.5 mag less luminous than the brightest elliptical galaxies, except in the least dense environment, where spiral galaxies dominate the LF at every luminosity. Despite the extent of the SDSS survey, the influence of single rich superclusters is present in the galactic LF of the densest environment. | 162,277 |
title: Domains and defects in nuclear "pasta"; abstract: Nuclear pasta topology is an essential ingredient to determine transport properties in the inner crust of neutron stars. We perform semi-classical molecular dynamics simulations of nuclear pasta for proton fractions $Y_p=0.30$ and $Y_p=0.40$ near one third of nuclear saturation density, $n=0.05\\,\\mathrm{fm}^{-3}$, at a temperature $T=1.0\\,\\mathrm{MeV}$. Our simulations are, to our knowledge, the largest nuclear pasta simulations to date and contain up to $3\\,276\\,800$ nucleons in the $Y_p=0.30$ and $819\\,200$ nucleons in the $Y_p=0.40$ case. An algorithm to determine which nucleons are part of a given sub-domain in the system is presented. By comparing runs of different sizes we study finite size effects, equilibration time, the formation of multiple domains and defects in the pasta structures, as well as the structure factor dependence on simulation size. Although we find qualitative agreement between the topological structure and the structure factors of runs with $51\\,200$ nucleons and those with $819\\,200$ nucleons or more, we show that simulations with hundreds of thousands of nucleons may be necessary to accurately predict pasta transport properties. | 162,278 |
title: Electrical transport properties and magnetoresistance of polycrystalline Fe3O4/p-Si heterostructures; abstract: Polycrystalline Fe3O4 films were deposited on the p-Si wafers using reactive sputtering to form the polycrystalline Fe3O4/p-Si heterostructures. A rectifying behavior was observed in the polycrystalline Fe3O4/p-Si heterostructures due to the formation of p-n junction between Fe3O4 and p-Si. The metal-insulator transition was observed, and the transition temperature decreases from 250 K at 100 mA to 110 K at 1 mA in the reverse range, but it keeps at 100 K in the forward range. The current-dependent magnetoresistance (MR) crossovers from negative to positive with different manners for the forward and reverse currents. The characteristic MR is thought to be caused by the rectifying effect and band structure of the Fe3O4 near the interface of the heterostructures. | 162,279 |
title: An active Sun throughout the Maunder Minimum; abstract: Measurements of 10Be concentration in the Dye 3 ice core show that magnetic cycles persisted throughout the Maunder Minimum, although the Sun\u0027s overall activity was drastically reduced and sunspots virtually disappeared. Thus the dates of maxima and minima can now be reliably estimated. Similar behaviour is shown by a nonlinear dynamo model, which predicts that, after a grand minimum, the Sun\u0027s toroidal field may switch from being antisymmetric to being symmetric about the equator. The presence of cyclic activity during the Maunder Minimum limits estimates of the solar contribution to climatic change. | 162,280 |
title: Onset of Benard-Marangoni convection in a rotating liquid layer with nonuniform volumetric energy sources; abstract: The criteria for the onset of natural convection in a rotating liquid layer with nonuniform volumetric energy sources from absorbed thermal radiation are determined via linear stability analysis. The linearized perturbation equations are solved by using a numerical technique to obtain the eigenvalues that governs the onset of convection in a microgravity environment. The stability criteria are obtained in terms of the Marangoni number as function of the optical thickness. The influences of the Rayleigh number, Taylor number, Bond number, Crispation number, and Biot number on convection are examined in detail. These parameters provide a relationship between the critical Marangoni number and the Coriolis force, the buoyancy force, the interfacial tension, and the heat transport mechanisms. | 162,281 |
title: Lyα-EMITTING GALAXIES AT z = 2.1 IN ECDF-S: BUILDING BLOCKS OF TYPICAL PRESENT-DAY GALAXIES?*; abstract: We discovered a sample of 250 Ly{alpha} emitting (LAE) galaxies at z {approx_equal} 2.1 in an ultra-deep 3727 A narrow-band MUSYC image of the Extended Chandra Deep Field-South. The LAEs were selected to have rest-frame equivalent widths (EWs) \u003e20 A and emission-line fluxes F{sub Ly{alpha}\u003e}2.0 x 10{sup -17} erg cm{sup -2} s{sup -1}, after carefully subtracting the continuum contributions from narrow-band photometry. The median emission-line flux of our sample is F{sub Ly{alpha}} = 4.2 x 10{sup -17} erg cm{sup -2} s{sup -1}, corresponding to a median Ly{alpha} luminosity L{sub Ly{alpha}} = 1.3 x 10{sup 42} erg s{sup -1} at z {approx_equal} 2.1. At this flux, our sample is {\u003e=}90% complete. Approximately 4% of the original NB-selected candidates were detected in X-rays by Chandra, and 7% were detected in the rest-frame far-UV by the Galaxy Evolution Explorer; these objects were eliminated to minimize contamination by active galactic nuclei and low-redshift galaxies. At L{sub Ly{alpha} {\u003e=}} 1.3 x 10{sup 42} erg s{sup -1}, the EW distribution is unbiased and is represented by an exponential with scale-length 83 {+-}10 A. Above this same luminosity threshold, we find a number density of 1.5 {+-} 0.5 x 10{sup -3} Mpc{sup -3}. Neither the number densitymore » of LAEs nor the scale-length of their EW distribution show significant evolution from z {approx_equal} 3 to z {approx_equal} 2. We used the rest-frame UV luminosity to estimate a median star formation rate of 4 M{sub sun} yr{sup -1}. The median rest-frame UV slope, parameterized by the color B - R, is typical of dust-free, 0.5-1 Gyr old or moderately dusty, 300-500 Myr old population. Approximately 30% of our sample is consistent with being very young (age \u003c100 Myr) galaxies without dust. Approximately 40% of the sample occupies the z {approx} 2 star-forming galaxy locus in the UVR two-color diagram, but the true percentage could be significantly higher taking into account photometric errors. Clustering analysis reveals that LAEs at z {approx_equal} 2.1 have r{sub 0} = 4.8 {+-} 0.9 Mpc, corresponding to a bias factor b = 1.8 {+-} 0.3. This implies that z {approx_equal} 2.1 LAEs reside in dark matter halos with median masses log(M/M{sub sun}) = 11.5{sup +0.4}{sub -0.5}, which are among the lowest mass halos yet probed at this redshift. We used the Sheth and Tormen conditional mass function to study the descendants of these LAEs and found that their typical present-day descendants are local galaxies with L* properties, like the Milky Way.« less | 162,282 |
title: High mass x-ray binaries as a star formation rate indicator in distant galaxies; abstract: Based on Chandra and ASCA observations of nearby starburst galaxies and RXTE/ASM, ASCA and MIR-KVANT/TTM studies of high-mass X-ray binary (HMXB) populations in the Milky Way and Magellanic Clouds, we propose that the number and/or the collective X-ray luminosity of HMXBs can be used to measure the star formation rate (SFR) of a galaxy. We show that, within the accuracy of the presently available data, a linear relation between HMXB number and star formation rate exists. The relation between SFR and collective luminosity of HMXBs is non-linear in the low-SFR regime, L X ∝ SFR ∼1.7 , and becomes linear only for a sufficiently | 162,283 |
title: Chiral phase transition in an extended NJL model with higher-order multi-quark interactions; abstract: Abstract The chiral phase transition is studied in an extended Nambu–Jona-Lasinio model with eight-quark interactions. Equations for scalar and vector quark densities, derived in the mean field approximation, are nonlinear and mutually coupled. The scalar type nonlinear term hastens the restoration of chiral symmetry, while the scalar–vector mixing term makes the transition sharper. The scalar type nonlinear term shifts the critical endpoint toward the values predicted by lattice QCD simulations and the QCD-like theory. | 162,284 |
title: On the validity of the Landau-Lifshitz method of deriving a higher order gravitational potential; abstract: Abstract The Landau-Lifshitz test particle method of deriving a higher order gravitational potential for many-particle systems is not valid in general coordinate systems. This is shown in the most simple case of the post-newtonian two-particle potential. | 162,285 |
title: S-wave QQqq state in the constituent quark model; abstract: Many proposals have been put forward to explore four-quark states QQqq (Q = s, c, b; q = u, d) by experiment, so a systematic study of QQqq spectrum with different constituent quark models by a high precision, few-body method, the Gaussian expression method, is useful. Three quark models: the Bhaduri, Cohler, Nogami quark model, the chiral quark model (ChQM), and the quark delocalization color screening model are all employed for a systematic calculation of the S-wave QQqq spectrum with different color structures, using the Gaussian expression method. The results show that only the bbqq state with (I, J) = (0, 1) is bound in different color structures within the different quark models. The binding energy varies from several MeV for a di-meson structure to over 100 MeV for a diquark-antidiquark structure. For the ccqq system, the state with (I, J) = (0, 1) is bound in a di-meson structure, and also bound in a diquark-antidiquark structure if pseudoscalar meson exchanges are accounted for. All are weakly bound states. The mixture of diquark-antidiquark and molecular structures is discussed in the framework of quark models for the first time; ccqq with (I, J) = (0, 1) is below the threshold in addition to bbqq in both the ChQM and the Bhaduri, Cohler, Nogami quark model. In the same channel, ssqq is also a possible bound state with mass around 1.4 GeV in ChQM. | 162,286 |
title: High birth velocities of radio pulsars; abstract: NEUTRON stars are usually born during the supernova explosion of a massive star. Any small asymmetry during the explosion can result in a substantial ‘kick’ velocity1 to the neutron star. Pulsars (rapidly rotating, magnetized neutron stars) have long been known to have high space velocities2,3, but new measurements of proper motion4–6, adoption of a new distance scale for the pulsars7 and the realization that some previous velocities were systematically low by a factor of 2 (ref. 8) have prompted us to reassess these velocities. Here, taking into account a strong selection effect that makes the observed velocities unrepresentative of those acquired at birth9, we arrive at a mean pulsar birth velocity of 450 ± 90 km s–1 This exceeds the escape velocity from binary systems, globular clusters and the Galaxy, and so will affect our understanding of the retention of neutron stars in these systems. Those neutron stars that are retained by the Milky Way will be distributed more isotropically than has been thought10–12, which may result in a distribution like that of the γ-ray burst sources. | 162,287 |
title: Flexocoupling impact on the generalized susceptibility and soft phonon modes in the ordered phase of ferroics; abstract: The impact of the flexoelectric effect on the generalized susceptibility and soft phonon dispersion is not well known in the long-range-ordered phases of ferroics. Within the Landau-Ginzburg-Devonshire approach we obtained analytical expressions for the generalized susceptibility and phonon dispersion relations in the ferroelectric phase. The joint action of the static and dynamic flexoelectric effects induces nondiagonal components of the generalized susceptibility, whose amplitude is proportional to the convolution of the spontaneous polarization with the flexocoupling constants. The flexocoupling essentially broadens the k spectrum of the generalized susceptibility and leads to an additional “pushing away” of the optical and acoustic soft mode phonon branches. The degeneracy of the transverse optical and acoustic modes disappears in the ferroelectric phase in comparison with the paraelectric phase due to the joint action of flexoelectric coupling and ferroelectric nonlinearity. Lastly, the results obtained might be mainly important for theoretical analyses of a broad spectrum of experimental data, including neutron and Brillouin scattering. | 162,288 |
title: Atomic clocks and inertial sensors; abstract: We show that the language of atom interferometry provides a unified picture for microwave and optical atomic clocks as well as for gravito-inertial sensors. The sensitivity and accuracy of these devices is now such that a new theoretical framework common to all these interferometers is required that includes: (a) a fully quantum mechanical treatment of the atomic motion in free space and in the presence of a gravitational field (most cold-atom interferometric devices use atoms in ``free fall\u0027\u0027 in a fountain geometry); (b) an account of simultaneous actions of gravitational and electromagnetic fields in the interaction zones; (c) a second quantization of the matter fields to take into account their fermionic or bosonic character in order to discuss the role of coherent sources and their noise properties; (d) a covariant treatment including spin to evaluate general relativistic effects. A theoretical description of atomic clocks revisited along these lines is presented, using both an exact propagator of atom waves in gravito-inertial fields and a covariant Dirac equation in the presence of weak gravitational fields. Using this framework, recoil effects, spin-related effects, beam curvature effects, the sensitivity to gravito-inertial fields and the influence of the coherence of the atom source are discussed in the context of present and future atomic clocks and gravito-inertial sensors. | 162,289 |
title: Quasinormal modes of dilatonic Reissner-Nordstr\"om black holes; abstract: We calculate the quasinormal modes of static spherically symmetric dilatonic Reissner-Nordstr\\\"om black holes for general values of the electric charge and of the dilaton coupling constant. The spectrum of quasinormal modes is composed of five families of modes: polar and axial gravitational-led modes, polar and axial electromagnetic-led modes, and polar scalar-led modes. We make a quantitative analysis of the spectrum, revealing its dependence on the electric charge and on the dilaton coupling constant. For large electric charge and large dilaton coupling, strong deviations from the Reissner-Nordstr\\\"om modes arise. In particular, isospectrality is strongly broken, both for the electromagnetic-led and the gravitational-led modes, for large values of the charge. | 162,290 |
title: Total hadronic cross-section for photon-photon interactions at LEP; abstract: Abstract The total hadronic cross-section σ γγ for the interaction of real photons, γγ → hadrons, is extracted from a measurement of the cross-section of the process e + e − → e + e − γ ∗ γ ∗ → ( e + e − + hadrons ) using a luminosity function for the photon flux and form factors for extrapolating to Q 2 = 0. The data was taken with the OPAL detector at LEP at e + e − centre-of-mass energies √ s ee = 161 GeV and 172 GeV. In the energy range 10 ≤ W ≤ 110 GeV the total hadronic γγ cross-section σ γγ is consistent with the Regge behaviour of the total cross-section observed in γp and hadron-hadron interactions. | 162,291 |
title: Application of the multi distribution function lattice Boltzmann approach to thermal flows; abstract: Numerical methods able to model high Rayleigh (Ra) and high Prandtl (Pr) number thermal convection are important to study large-scale geophysical phenomena occuring in very viscous fluids such as magma chamber dynamics (104 \u003c Pr \u003c 107 and 107 \u003c Ra \u003c 1011). The important variable to quantify the thermal state of a convective fluid is a generalized dimensionless heat transfer coefficient (the Nusselt number) whose measure indicates the relative efficiency of the thermal convection. In this paper we test the ability of Multi-distribution Function approach (MDF) Thermal Lattice Boltzmann method to study the well-established scaling result for the Nusselt number (Nu ∝ Ra 1/3) in Rayleigh Benard convection for 104 ≤ Ra ≤ 109 and 101 ≤ Pr ≤ 104. We explore its main drawbacks in the range of Pr and Ra number under investigation: (1) high computational time N c required for the algorithm to converge and (2) high spatial accuracy needed to resolve the thickness of thermal plumes and both thermal and velocity boundary layer. We try to decrease the computational demands of the method using a multiscale approach based on the implicit dependence of the Pr number on the relaxation time, the spatial and temporal resolution characteristic of the MDF thermal model. | 162,292 |
title: Formation of high pressure phases in rapidly quenched Fe‐Nd alloys; abstract: Fe100−xNdx amorphous ribbons were obtained for compositions with 25\u003cx\u003c50, and partially amorphous ribbons for all other compositions.The amorphous phases were magnetically ordered with Curie temperatures ranging from 421 to 493 K. During crystallization, three metastable phases (M1, M2, and M3) were formed. X‐ray structural studies together with Mossbauer and thermomagnetic measurements suggest that the M1 phase is Fe23Nd6 (Mn23Th6 structure) with lattice parameter 1.152 nm and a Curie temperature of 515 K. The M2 phase is identified as Fe2Nd(Cu2Mg structure) with a lattice parameter of 0.745 nm and a Curie temperature of 567 K. The M1 and M2 phases transform to α‐Fe and Nd2Fe17 at high temperatures (≥1000 K). The M3 phase is present in the as‐quenched ribbons with x≥60 as well as in all crystallized ribbons. Structural data show that it is γ‐Nd, an fcc form of Nd. All three nonequilibrium structures are high pressure phases which are often formed during rapid solidification and/or crystallization of amor... | 162,293 |
title: Waveform systematics for binary neutron star gravitational wave signals: Effects of spin, precession, and the observation of electromagnetic counterparts; abstract: Extracting the properties of a binary system emitting gravitational waves relies on models describing the last stages of the compact binary coalescence. In this article, we study potential biases inherent to current tidal waveform approximants for spinning and precessing systems. We perform a Bayesian study to estimate intrinsic parameters of highly spinning binary neutron star systems. Our analysis shows that one has to include the quadrupolar deformation of the neutron stars due to their rotation once dimensionless spins above $\\chi \\sim 0.20$ are reached, otherwise the extracted intrinsic parameters are systematically biased. We find that at design sensitivity of Advanced LIGO and Virgo, it seems unlikely that for GW170817-like sources a clear imprint of precession will be visible in the analysis of the signal employing current waveform models. However, precession effects might be detectable for unequal mass configurations with spins larger than $\\chi\u003e0.2$. We finalize our study by investigating possible benefits of a combined gravitational wave and electromagnetic detection. The presence of electromagnetic counterparts help in reducing the dimensionality of the parameter space with constraints on the sky location, source distance, and inclination. However, we note that although a small improvement in the estimation of the tidal deformability parameter is seen in these cases, changes in the intrinsic parameters are overall very small. | 162,294 |
title: Improvement of (Pb1−xLax)(ZryTi1−y)1−x/4O3 ferroelectric thin films by use of SrRuO3/Ru/Pt/Ti bottom electrodes; abstract: This work deposits (Pb1−xLax)(ZryTi1−y)1−x/4O3 (PLZT) thin films, possessing good ferroelectric properties (Pr=14.4 μC/cm2), on Pt/Ti/SiO2/Si substrates, using SrRuO3 perovskite as bottom electrodes. Precoating a metallic Ru layer on Pt/Ti/SiO2/Si substrates prior to depositing SrRuO3 bottom electrode further improves the film electrical properties. The optimum ferroelectric properties achieved are Pr=25.6 μC/cm2, Ec=47.1 kV/cm, and er=1204. Analyzing the elemental depth profiles using secondary ions mass spectroscopy reveals that the presence of the metallic Ru layer effectively suppresses the outward diffusion of Ti and Si species. The interdiffusion between the SrRuO3 layer and the subsequently deposited PLZT is also substantially reduced, an effect that is presumed to be the primary factor in improving ferroelectric properties for PLZT thin films. | 162,295 |
title: Linear instability of a corrugated vortex sheet - a model for streak instability; abstract: The linear inviscid instability of an infinitely thin vortex sheet, periodically corrugated with finite amplitude along the spanwise direction, is investigated analytically. Two types of corrugations are studied, one of which includes the presence of an impermeable wall. Exact eigensolutions are found in the limits of very long and of very short wavelengths. The intermediate-wavenumber range is explored by means of a second-order asymptotic series and by limited numerical integration. The sheets are unstable to both sinuous and varicose disturbances. The former are generally found to be more unstable, although the difference only appears for finite wavelengths. The effect of the corrugation is shown to be stabilizing, although in the wall-bounded sheet the effect is partly compensated by the increase in the distance from the wall. The controlling parameter in that case appears to be the minimum separation from the sheet valley to the wall. The instability is traced to a pair of oblique Kelvin–Helmholtz waves in the flat-sheet limit, but the eigenfunctions change character both as the corrugation is made sharper and as the wall is approached, becoming localized near the crests and valleys of the corrugation. The study is motivated by the desire to understand the behaviour of lifted low-speed streaks in wall-bounded flows, and it is shown that the spatial structure of the fundamental sinuous eigenmode is remarkably similar to previously known three-dimensional nonlinear equilibrium solutions in both plane Couette and Poiseuille flows. | 162,296 |
title: Estimating the quantum effects from molecular vibrations of water under high pressures and temperatures; abstract: We present a simple model which estimates the influence of quantum effects from molecular vibrations on the equation of state of water under high pressures and temperatures. This model is combined with an ab initio equation of state of water generated by quantum molecular dynamics (QMD) simulations employing density functional theory for the electrons and a classical algorithm for the ions. We calculate the specific heat capacity as well as the principal Hugoniot curve, especially the Hugoniot temperature, in accordance with experiments. | 162,297 |
title: Gravitational wave energy emission and detection rates of Primordial Black Hole hyperbolic encounters.; abstract: We describe in detail gravitational wave bursts from Primordial Black Hole (PBH) hyperbolic encounters. The bursts are one-time events, with the bulk of the released energy happening during the closest approach, which can be emitted in frequencies that could be within the range of both LIGO (10-1000Hz) and LISA ($10^{-6}-1$ Hz). Furthermore, we correct the results for the power spectrum of hyperbolic encounters found in the literature and present new exact and approximate expressions for the peak frequency of the emission. Note that these GW bursts from hyperbolic encounters between PBH are complementary to the GW emission from the bounded orbits of BHB mergers detected by LIGO, and help breaking degeneracies in the determination of the PBH mass, spin and spatial distributions. | 162,298 |
title: Design and construction of precision heat fluxmeters; abstract: In this paper we discuss the design and construction of thermopiles for use as heat flux measurers. Compact structure, mechanical consistency, and a wide range of dimensions and sensitivities are possible. We can thus reach thermocouple densities up to 100 cm−2 and sensitivities of approximately 1 V W−1. | 162,299 |
Subsets and Splits