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Let $M$ be an irreducible smooth projective variety, defined over an
algebraically closed field, equipped with an action of a connected reductive
affine algebraic group $G$, and let ${\mathcal L}$ be a $G$--equivariant very
ample line bundle on $M$. Assume that the GIT quotient $M/\!\!/G$ is a nonempty
set. We prove that the homomorphism of algebraic fundamental groups $\pi_1(M)\,
\longrightarrow\, \pi_1(M/\!\!/G)$, induced by the rational map $M\,
\longrightarrow\, M/\!\!/G$, is an isomorphism.
If $k\,=\, \mathbb C$, then we show that the above rational map $M\,
\longrightarrow \, M/\!\!/G$ induces an isomorphism between the topological
fundamental groups.
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The principle of the background-eliminated extinction-parallax (BEEP) method
is examining the extinction difference between on- and off-cloud regions to
reveal the extinction jump caused by molecular clouds, thereby revealing the
distance in complex dust environments. The BEEP method requires high-quality
images of molecular clouds and high-precision stellar parallaxes and extinction
data, which can be provided by the Milky Way Imaging Scroll Painting (MWISP) CO
survey and the Gaia DR2 catalog, as well as supplementary AV extinction data.
In this work, the BEEP method is further improved (BEEP-II) to measure
molecular cloud distances in a global search manner. Applying the BEEP-II
method to three regions mapped by the MWISP CO survey, we collectively measured
238 distances for 234 molecular clouds. Compared with previous BEEP results,
the BEEP-II method measures distances efficiently, particularly for those
molecular clouds with large angular size or in complicated environments, making
it suitable for distance measurements of molecular clouds in large samples.
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Properties of Bosonic linear (quasi-free) channels, in particular, Bosonic
Gaussian channels with two types of degeneracy are considered.
The first type of degeneracy can be interpreted as existence of noise-free
canonical variables (for Gaussian channels it means that $\det\alpha=0$). It is
shown that this degeneracy implies existence of (infinitely many) "direct sum
decompositions" of Bosonic linear channel, which clarifies reversibility
properties of this channel (described in arXiv:1212.2354) and provides explicit
construction of reversing channels.
The second type of degeneracy consists in rank deficiency of the operator
describing transformations of canonical variables. It is shown that this
degeneracy implies existence of (infinitely many) decompositions of input space
into direct sum of orthogonal subspaces such that the restriction of Bosonic
linear channel to each of these subspaces is a discrete classical-quantum
channel.
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In this paper we propagate a large deviations approach for proving limit
theory for (generally) multivariate time series with heavy tails. We make this
notion precise by introducing regularly varying time series. We provide general
large deviation results for functionals acting on a sample path and vanishing
in some neighborhood of the origin. We study a variety of such functionals,
including large deviations of random walks, their suprema, the ruin functional,
and further derive weak limit theory for maxima, point processes, cluster
functionals and the tail empirical process. One of the main results of this
paper concerns bounds for the ruin probability in various heavy-tailed models
including GARCH, stochastic volatility models and solutions to stochastic
recurrence equations. 1. Preliminaries and basic motivation In the last
decades, a lot of efforts has been put into the understanding of limit theory
for dependent sequences, including Markov chains (Meyn and Tweedie [42]),
weakly dependent sequences (Dedecker et al. [21]), long-range dependent
sequences (Doukhan et al. [23], Samorodnitsky [54]), empirical processes
(Dehling et al. [22]) and more general structures (Eberlein and Taqqu [25]), to
name a few references. A smaller part of the theory was devoted to limit theory
under extremal dependence for point processes, maxima, partial sums, tail
empirical processes. Resnick [49, 50] started a systematic study of the
relations between the convergence of point processes, sums and maxima, see also
Resnick [51] for a recent account. He advocated the use of multivariate regular
variation as a flexible tool to describe heavy-tail phenomena combined with
advanced continuous mapping techniques. For example, maxima and sums are
understood as functionals acting on an underlying point process, if the point
process converges these functionals converge as well and their limits are
described in terms of the points of the limiting point process. Davis and Hsing
[13] recognized the power of this approach for limit theory of point processes,
maxima, sums, and large deviations for dependent regularly varying processes,
i.e., stationary sequences whose finite-dimensional distributions are regularly
varying with the same index. Before [13], limit theory for particular regularly
varying stationary sequences was studied for the sample mean, maxima, sample
autocovariance and autocorrelation functions of linear and bilinear processes
with iid regularly varying noise and extreme value theory was considered for
regularly varying ARCH processes and solutions to stochastic recurrence
equation, see Rootz\'en [53], Davis and 1991 Mathematics Subject
Classification. Primary 60F10, 60G70, secondary 60F05. Key words and phrases.
Large deviation principle, regularly varying processes, central limit theorem,
ruin probabilities, GARCH.
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A linear theory of a wakefield excitation in a plasma-dielectric accelerating
structure by a drive electron bunch in the case of an off-axis bunch injection
has been constructed. The structure under investigation is a round
dielectric-loaded metal waveguide with a channel for the charged particles,
filled with homogeneous cold plasma. Derived theory was used to investigate
numerically the spatial distribution of the bunch-excited wakefield components,
which act on both the drive and witness bunches.
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We introduce a minimal set of physically motivated postulates that the
Hamiltonian H of a continuous-time quantum walk should satisfy in order to
properly represent the quantum counterpart of the classical random walk on a
given graph. We found that these conditions are satisfied by infinitely many
quantum Hamiltonians, which provide novel degrees of freedom for quantum
enhanced protocols, In particular, the on-site energies, i.e. the diagonal
elements of H, and the phases of the off-diagonal elements are unconstrained on
the quantum side. The diagonal elements represent a potential energy landscape
for the quantum walk, and may be controlled by the interaction with a classical
scalar field, whereas, for regular lattices in generic dimension, the
off-diagonal phases of H may be tuned by the interaction with a classical gauge
field residing on the edges, e.g., the electro-magnetic vector potential for a
charged walker.
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In this work we present in-network techniques to improve the efficiency of
spatial aggregate queries. Such queries are very common in a sensornet setting,
demanding more targeted techniques for their handling. Our approach constructs
and maintains multi-resolution cube hierarchies inside the network, which can
be constructed in a distributed fashion. In case of failures, recovery can also
be performed with in-network decisions. In this paper we demonstrate how
in-network cube hierarchies can be used to summarize sensor data, and how they
can be exploited to improve the efficiency of spatial aggregate queries. We
show that query plans over our cube summaries can be computed in polynomial
time, and we present a PTIME algorithm that selects the minimum number of data
requests that can compute the answer to a spatial query. We further extend our
algorithm to handle optimization over multiple queries, which can also be done
in polynomial time. We discuss enriching cube hierarchies with extra summary
information, and present an algorithm for distributed cube construction.
Finally we investigate node and area failures, and algorithms to recover query
results.
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In Part VII, we proved that the range of the big J-function in
permutation-equivariant genus-0 quantum K-theory is an overruled cone, and gave
its adelic characterization. Here we show that the ruling spaces are
D_q-modules in Novikov's variables, and moreover, that the whole cone is
invariant under a large group of symmetries defined in terms of q-difference
operators. We employ this for the explicit reconstruction of the cone from one
point on it, and apply the result to toric target spaces, when such a point is
given by the q-hypergeometric function.
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We construct a family of quantum Hall Hamiltonians whose ground states, at
least for small system sizes, give correlators of the S3 conformal field
theories. The ground states are considered as trial wavefunctions for quantum
Hall effect of bosons at filling fraction nu=3/4 interacting either via delta
function interaction or delta function plus dipole interaction. While the S3
theories can be either unitary or nonunitary, we find high overlaps with exact
diagonalizations only for the nonunitary case, suggesting that these
wavefunctions may correspond to critical points, possibly analogous to the
previously studied Gaffnian wavefunction. These wavefunctions give an explicit
example which cannot be fully characterized by their thin-torus limit or by
their pattern of zeros.
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Ensuring the safety of road vehicles at an acceptable level requires the
absence of any unreasonable risk arising from all potential hazards linked to
the intended au-tomated driving function and its implementation. The assurance
that there are no unreasonable risks stemming from hazardous behaviours
associated to functional insufficiencies is denoted as safety of intended
functionality (SOTIF), a concept outlined in the ISO 21448 standard. In this
context, the acquisition of real driving data is considered essential for the
verification and validation. For this purpose, we are currently developing a
method with which data collect-ed representatively from production vehicles can
be modelled into a knowledge-based system in the future. A system that
represents the probabilities of occur-rence of concrete driving scenarios over
the statistical population of road traffic and makes them usable. The method
includes the qualitative and quantitative ab-straction of the drives recorded
by the sensors in the vehicles, the possibility of subsequent wireless
transmission of the abstracted data from the vehicles and the derivation of the
distributions and correlations of scenario parameters. This paper provides a
summary of the research project and outlines its central idea. To this end,
among other things, the needs for statistical information and da-ta from road
traffic are elaborated from ISO 21448, the current state of research is
addressed, and methodical aspects are discussed.
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We start with a short survey of the basic properties of the Mittag-Leffler
functions. Then we focus on the key role of these functions to explain the
after-effects and relaxation phenomena occurring in dielectrics and in
viscoelastic bodies. For this purpose we recall the main aspects that were
formerly discussed by two pioneers in the years 1930's-1940's whom we have
identified with Harold T. Davis and Bernhard Gross.
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We study the quasi-stationary evolution of systems where an energetic
confinement is unable to completely retain their constituents. It is performed
an extensive numerical study of a gas whose dynamics is driven by binary
encounters and its particles are able to escape from the container when their
kinetic energies overcome a given cutou Uc .We use a parametric family of
differential cross sections in order to modify the effectiveness of this
equilibration mechanism. It is verified that when the binary encounters favor
an effective exploration of all accessible velocities, the quasi-stationary
evolution is reached when the detailed balance is imposed for all those binary
collisions which do not provoke particle evaporation. However, the weakening of
this effectiveness leads to energy distribution functions which could be very
well fitted by using a Michie-King-like profile. We perform a theoretical
analysis, in the context of Hamiltonian systems driven by a strong chaotic
dynamics and particle evaporation, in order to take into account the effect of
the nonhomogeneous character of the confining potential.
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As the success of deep learning reaches more grounds, one would like to also
envision the potential limits of deep learning. This paper gives a first set of
results proving that certain deep learning algorithms fail at learning certain
efficiently learnable functions. The results put forward a notion of
cross-predictability that characterizes when such failures take place. Parity
functions provide an extreme example with a cross-predictability that decays
exponentially, while a mere super-polynomial decay of the cross-predictability
is shown to be sufficient to obtain failures. Examples in community detection
and arithmetic learning are also discussed.
Recall that it is known that the class of neural networks (NNs) with
polynomial network size can express any function that can be implemented in
polynomial time, and that their sample complexity scales polynomially with the
network size. The challenge is with the optimization error (the ERM is
NP-hard), and the success behind deep learning is to train deep NNs with
descent algorithms. The failures shown in this paper apply to training
poly-size NNs on function distributions of low cross-predictability with a
descent algorithm that is either run with limited memory per sample or that is
initialized and run with enough randomness. We further claim that such types of
constraints are necessary to obtain failures, in that exact SGD with careful
non-random initialization can be shown to learn parities. The
cross-predictability in our results plays a similar role the statistical
dimension in statistical query (SQ) algorithms, with distinctions explained in
the paper. The proof techniques are based on exhibiting algorithmic constraints
that imply a statistical indistinguishability between the algorithm's output on
the test model v.s.\ a null model, using information measures to bound the
total variation distance.
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We study a question which can be roughly stated as follows: Given a (unital
or nonunital) algebra $A$ together with a Gr\"obner-Shirshov basis $G$,
consider the free operated algebra $B$ over $A$, such that the operator
satisfies some polynomial identities $\Phi$ which are Gr\"obner-Shirshov in the
sense of Guo et al., when doesthe union $\Phi\cup G$ will be an operated
Gr\"obner-Shirshov basis for $B$? We answer this question in the affirmative
under a mild condition in our previous work with Wang. When this condition is
satisfied, $\Phi\cup G$ is an operated Gr\"obner-Shirshov basis for $ B$ and as
a consequence, we also get a linear basis of $B$. However, the condition could
not be applied directly to differential type algebras introduced by Guo, Sit
and Zhang, including usual differential algebras.
This paper solves completely this problem for differential type algebras.Some
new monomial orders are introduced which, together with some known ones, permit
the application of the previous result to most of differential type algebras,
thus providing new operated GS bases and linear bases for these differential
type algebras.Versions are presented both for unital and nonunital algebras.
However, a class of examples are also presented, for which the natural
expectation in the question is wrong and these examples are dealt with by
direct inspection.
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We give completely combinatorial proofs of the main results of [3] using
polygons. Namely, we prove that the mapping class group of a surface with
boundary acts faithfully on a finitely-generated linear category. Along the way
we prove some foundational results regarding the relevant objects from bordered
Heegaard Floer homology,
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We consider $\mathcal{PT}$-symmetric ring-like arrays of optical waveguides
with purely nonlinear gain and loss. Regardless of the value of the gain-loss
coefficient, these systems are protected from spontaneous
$\mathcal{PT}$-symmetry breaking. If the nonhermitian part of the array matrix
has cross-compensating structure, the total power in such a system remains
bounded -- or even constant -- at all times. We identify two-, three-, and
four-waveguide arrays with cross-compensatory nonlinear gain and loss that
constitute completely integrable Hamiltonian systems.
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Spin insulatronics covers efforts to generate, detect, control, and utilize
high-fidelity pure spin currents and excitations inside magnetic insulators.
Ultimately, the new findings may open doors for pure spin-based information and
communication technologies. The aim is to replace moving charges with dynamical
entities that utilize low-dissipation coherent and incoherent spin excitations
in antiferromagnetic and ferromagnetic insulators. The ambition is that the new
pure spin-based system will suffer reduced energy losses and operate at high
frequencies. In magnetic insulators, there are no mobile charge carriers that
can dissipate energy. Integration with conventional electronics is possible via
interface exchange interactions and spin-orbit couplings. In this way, the free
electrons in the metals couple to the localized spins in the magnetic
insulators. In turn, these links facilitate spin-transfer torques and
spin-orbit torques across metal-insulator interfaces and the associated
phenomena of spin-pumping and charge-pumping. The interface couplings also
connect the electron motion inside the metals with the spin fluctuations inside
the magnetic insulators. These features imply that the system can enable
unprecedented control of correlations resulting from the electron-magnon
interactions. We review recent developments to realize electric and thermal
generation, manipulation, detection, and control of pure spin information in
insulators.
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Quantum walks are a promising framework for developing quantum algorithms and
quantum simulations. They represent an important test case for the application
of quantum computers. Here we present different forms of discrete-time quantum
walks (DTQWs) and show their equivalence for physical realizations. Using an
appropriate digital mapping of the position space on which a walker evolves to
the multiqubit states of a quantum processor, we present different
configurations of quantum circuits for the implementation of DTQWs in
one-dimensional position space. We provide example circuits for a five-qubit
processor and address scalability to higher dimensions as well as larger
quantum processors.
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Enhanced global non-abelian symmetries at zero coupling in Yang Mills theory
play an important role in diagonalising the two-point functions of multi-matrix
operators. Generalised Casimirs constructed from the iterated commutator action
of these enhanced symmetries resolve all the multiplicity labels of the bases
of matrix operators which diagonalise the two-point function. For the case of U
(N) gauge theory with a single complex matrix in the adjoint of the gauge group
we have a U(N)^{\times 4} global symmetry of the scaling operator at zero
coupling. Different choices of commuting sets of Casimirs, for the case of a
complex matrix, lead to the restricted Schur basis previously studied in
connection with string excitations of giant gravitons and the Brauer basis
studied in connection with brane-anti-brane systems. More generally these
remarks can be extended to the diagonalisation for any global symmetry group G.
Schur-Weyl duality plays a central role in connecting the enhanced symmetries
and the diagonal bases.
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The explicit semiclassical treatment of the logarithmic perturbation theory
for the bound-state problem of the radial Shrodinger equation with the screened
Coulomb potential is developed. Based upon h-expansions and new quantization
conditions a novel procedure for deriving perturbation expansions is offered.
Avoiding disadvantages of the standard approach, new handy recursion formulae
with the same simple form both for ground and excited states have been
obtained.
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In this article we propose a novel method to accelerate adiabatic passage in
a two-level system with only longitudinal field (detuning) control, while the
transverse field is kept constant. The suggested method is a modification of
the Roland-Cerf protocol, during which the parameter quantifying local
adiabaticity is held constant. Here, we show that with a simple ``on-off"
modulation of this local adiabaticity parameter, a perfect adiabatic passage
can be obtained for every duration larger than the lower bound $\pi/\Omega$,
where $\Omega$ is the constant transverse field. For a fixed maximum amplitude
of the local adiabaticity parameter, the timings of the ``on-off"
pulse-sequence which achieves perfect fidelity in minimum time are obtained
using optimal control theory. The corresponding detuning control is continuous
and monotonic, a significant advantage compared to the detuning variation at
the quantum speed limit which includes non-monotonic jumps. The proposed
methodology can be applied in several important core tasks in quantum
computing, for example to the design of a high fidelity controlled-phase gate,
which can be mapped to the adiabatic quantum control of such a qubit.
Additionally, it is expected to find applications across all Physics
disciplines which exploit the adiabatic control of such a two-level system.
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In the frames of the DLVO theory the root mean square amplitude and
correlation length of capillary waves in thin liquid films are calculated.
Their dependencies on some important physical parameters are studied. Two
models are considered: films with classical interfaces and films between lipid
bilayers. The performed numerical analysis demonstrates essential difference in
their behavior, which is due to the different elastic properties of the film
surfaces in the models.
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We study the conditions imposed on matter to produce a regular (non-singular)
interior of a class of spherically symmetric black holes in the $f(T)$
extension of teleparallel gravity. The class of black holes studied is
necessarily singular in general relativity. We derive a tetrad which is
compatible with the black hole interior and utilize this tetrad in the
gravitational equations of motion to study the black hole interior. It is shown
that in the case where the gravitational Lagrangian is expandable in a power
series $f(T)=T+\underset{n\neq 1}{\sum} b_{n}T^{n}$ that black holes can be
non-singular while respecting certain energy conditions in the matter fields.
Thus the black hole singularity may be removed and the gravitational equations
of motion can remain valid throughout the manifold. This is true as long as $n$
is positive, but is not true in the negative sector of the theory. Hence,
gravitational $f(T)$ Lagrangians which are Taylor expandable in powers of $T$
may yield regular black holes of this type. Although it is found that these
black holes can be rendered non-singular in $f(T)$ theory, we conjecture that a
mild singularity theorem holds in that the dominant energy condition is
violated in an arbitrarily small neighborhood of the general relativity
singular point if the corresponding $f(T)$ black hole is regular. The analytic
techniques here can also be applied to gravitational Lagrangians which are not
Laurent or Taylor expandable.
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Oxygen-defect control has long been considered an influential tuning knob for
producing various property responses in complex oxide films. In addition to
physical property changes, modification to the lattice structure, specifically
lattice expansion, with increasing oxygen vacancy concentrations has been
reported often and has become the convention for oxide materials. However, the
current understanding of the lattice behavior in oxygen-deficient films becomes
disputable when considering compounds containing different bonding environments
or atomic layering. Moreover, tensile strain has recently been discovered to
stabilize oxygen vacancies in epitaxial films, which further complicates the
interpretation of lattice behavior resulting from their appearance. Here, we
report on the selective strain control of oxygen vacancy formation and
resulting lattice responses in the layered, Ruddlesden-Popper phases,
La1.85Sr0.15CuO4. We found that a drastically reduced Gibbs free energy for
oxygen vacancy formation near the typical growth temperature for
tensile-strained epitaxial LSCO accounts for the large oxygen
non-stoichiometry. Additionally, oxygen vacancies form preferentially in the
equatorial position of the CuO2 plane, leading to a lattice contraction, rather
than the expected expansion, observed with apical oxygen vacancies. Since
oxygen stoichiometry plays a key role in determining the physical properties of
many complex oxides, the strong strain coupling of oxygen nonstoichiometry and
the unusual structural response reported here can provide new perspectives and
understanding to the structure and property relationships of many other
functional oxide materials.
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We use sequences of t-induced T-nets and p-induced P-nets to convert
free-choice nets into T-nets and P-nets while preserving properties such as
well-formedness, liveness, lucency, pc-safety, and perpetuality. The approach
is general and can be applied to different properties. This allows for more
systematic proofs that "peel off" non-trivial parts while retaining the essence
of the problem (e.g., lifting properties from T-net and P-net to free-choice
nets).
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We consider that the price of a firm follows a non linear stochastic delay
differential equation. We also assume that any claim value whose value depends
on firm value and time follows a non linear stochastic delay differential
equation. Using self-financed strategy and replication we are able to derive a
Random Partial Differential Equation (RPDE) satisfied by any corporate claim
whose value is a function of firm value and time. Under specific final and
boundary conditions, we solve the RPDE for the debt value and loan guarantees
within a single period and homogeneous class of debt.
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We have measured the rf magnetoconductivity of unidirectional lateral
superlattices (ULSLs) by detecting the attenuation of microwave through a
coplanar waveguide placed on the surface. ULSL samples with the principal axis
of the modulation perpendicular (S_perp) and parallel (S_||) to the microwave
electric field are examined. For low microwave power, we observe expected
anisotropic behavior of the commensurability oscillations (CO), with CO in
samples S_perp and S_|| dominated by the diffusion and the collisional
contributions, respectively. Amplitude modulation of the Shubnikov-de Haas
oscillations is observed to be more prominent in sample S_||. The difference
between the two samples is washed out with the increase of the microwave power,
letting the diffusion contribution govern the CO in both samples. The failure
of the intended directional selectivity in the conductivity measured with high
microwave power is interpreted in terms of large-angle electron-phonon
scattering.
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(Abridged) A simple quantitative model is presented for the history of
galaxies to explain galaxy number counts, redshift distributions and some other
related observations. We first infer that irregular galaxies and the disks of
spiral galaxies are young, probably formed at $z\approx 0.5-2$ from a
simultaneous consideration of colours and gas content under a moderate
assumption on the star formation history. Assuming that elliptical galaxies and
bulges of spiral galaxies, both called spheroids in the discussion, had formed
early in the universe, the resulting scenario is that spiral galaxies formed as
intergalactic gas accreting onto pre-existing bulges mostly at $z\approx 1-2$;
irregular galaxies as seen today formed by aggregation of clouds at $z\approx
0.5-1.5$. Taking the formation epochs thus estimated into account, we construct
a model for the history of galaxies employing a stellar population synthesis
model. We assume that the number of galaxies does not change except that some
of them (irregulars) were newly born, and use a morphology-dependent local
luminosity function to constrain the number of galaxies. The predictions of the
model are compared with the observation of galaxy number counts and redshift
distributions for the $B$, $I$ and $K$ colour bands. It is shown that young
irregular galaxies cause the steep slope of the $B$-band counts. The fraction
of irregular galaxies increases with decreasing brightness: at $B=24$ mag, they
contribute as much as spiral galaxies. Thus, ``the faint blue galaxy problem''
is solved by invoking young galaxies. This interpretation is corroborated by a
comparison of our prediction with the morphologically-classified galaxy counts
in the $I$ band.
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Command and Control (C2) communication is a key component of any structured
cyber-attack. As such, security operations actively try to detect this type of
communication in their networks. This poses a problem for legitimate pentesters
that try to remain undetected, since commonly used pentesting tools, such as
Metasploit, generate constant traffic patterns that are easily distinguishable
from regular web traffic. In this paper we start with these identifiable
patterns in Metasploit's C2 traffic and show that a machine learning-based
detector is able to detect the presence of such traffic with high accuracy,
even when encrypted. We then outline and implement a set of modifications to
the Metasploit framework in order to decrease the detection rates of such
classifier. To evaluate the performance of these modifications, we use two
threat models with increasing awareness of these modifications. We look at the
detection evasion performance and at the byte count and runtime overhead of the
modifications. Our results show that for the second, increased-awareness threat
model the framework-side traffic modifications yield a better detection
avoidance rate (90%) than payload-side only modifications (50%). We also show
that although the modifications use up to 3 times more TLS payload bytes than
the original, the runtime does not significantly change and the total number of
bytes (including TLS payload) reduces.
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The Generative Adversarial Network (GAN) has achieved great success in
generating realistic (real-valued) synthetic data. However, convergence issues
and difficulties dealing with discrete data hinder the applicability of GAN to
text. We propose a framework for generating realistic text via adversarial
training. We employ a long short-term memory network as generator, and a
convolutional network as discriminator. Instead of using the standard objective
of GAN, we propose matching the high-dimensional latent feature distributions
of real and synthetic sentences, via a kernelized discrepancy metric. This
eases adversarial training by alleviating the mode-collapsing problem. Our
experiments show superior performance in quantitative evaluation, and
demonstrate that our model can generate realistic-looking sentences.
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Today, the Internet of Things (IoT) is one of the emerging technologies that
enable the connection and transfer of information through communication
networks. The main idea of the IoT is the widespread presence of objects such
as mobile devices, sensors, and RFID. With the increase in traffic volume in
urban areas, the existing intelligent urban traffic management system based on
IoT can be vital. Therefore, this paper focused on security in urban traffic
based on using RFID. In our scheme, RFID tags chose as the purpose of this
article. We, in this paper, present a mutual authentication protocol that leads
to privacy based on hybrid cryptography. Also, an authentication process with
RFID tags is proposed that can be read at high speed. The protocol has
attempted to reduce the complexity of computing. At the same time, the proposed
method can withstand attacks such as spoofing of tag and reader, tag tracking,
and replay attack.
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In this article, we investigate the formation and disruption of a coronal
sigmoid from the active region (AR) NOAA 11909 on 07 December 2013, by
analyzing multi-wavelength and multi-instrument observations. Our analysis
suggests that the formation of `transient' sigmoid initiated $\approx$1 hour
before its eruption through a coupling between two twisted coronal loop
systems. A comparison between coronal and photospheric images suggests that the
coronal sigmoid was formed over a simple $\beta$-type AR which also possessed
dispersed magnetic field structure in the photosphere. The line-of-sight
photospheric magnetograms also reveal moving magnetic features, small-scale
flux cancellation events near the PIL, and overall flux cancellation during the
extended pre-eruption phase which suggest the role of tether-cutting
reconnection toward the build-up of the flux rope. The disruption of the
sigmoid proceeded with a two-ribbon eruptive M1.2 flare (SOL2013-12-07T07:29).
In radio frequencies, we observe type III and type II bursts in meter
wavelengths during the impulsive phase of the flare. The successful eruption of
the flux rope leads to a fast coronal mass ejection (with a linear speed of
$\approx$1085 km s -1 ) in SOHO/LASCO field-of-view. During the evolution of
the flare, we clearly observe typical "sigmoid-to-arcade" transformation. Prior
to the onset of the impulsive phase of the flare, flux rope undergoes a slow
rise ($\approx$15 km s -1 ) which subsequently transitions into a fast eruption
($\approx$110 km s -1 ). The two-phase evolution of the flux rope shows
temporal associations with the soft X-ray precursor and impulsive phase
emissions of the M-class flare, respectively, thus pointing toward a feedback
relationship between magnetic reconnection and early CME dynamics.
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Deduction modulo is a way to express a theory using computation rules instead
of axioms. We present in this paper an extension of deduction modulo, called
Polarized deduction modulo, where some rules can only be used at positive
occurrences, while others can only be used at negative ones. We show that all
theories in propositional calculus can be expressed in this framework and that
cuts can always be eliminated with such theories.
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In the past decade, HCI surveys provided new insights about the frequency and
properties of substellar companions at separation larger than 5 au. In this
context, our study aims to detect and characterise potential exoplanets and
brown dwarfs within debris disks, by considering the SHARDDS survey, which
gathers 55 Main Sequence stars with known bright debris disk. We rely on the
AutoRSM framework to perform an in-depth analysis of the targets, via the
computation of detection maps and contrast curves. A clustering approach is
used to divide the set of targets in multiple subsets, in order to reduce the
computation time by estimating a single optimal parametrisation for each
considered subset. The use of Auto-RSM allows to reach high contrast at short
separations, with a median contrast of 10-5 at 300 mas, for a completeness
level of 95%. Detection maps generated with different approaches are used along
with contrast curves, to identify potential planetary companions. A new
planetary characterisation algorithm, based on the RSM framework, is developed
and tested successfully, showing a higher astrometric and photometric precision
for faint sources compared to standard approaches. Apart from the already known
companion of HD206893 and two point-like sources around HD114082 which are most
likely background stars, we did not detect any new companion around other
stars. A correlation study between achievable contrasts and parameters
characterising HCI sequences highlights the importance of the strehl, wind
speed and wind driven halo to define the quality of high contrast images.
Finally, planet detection and occurrence frequency maps are generated and show,
for the SHARDDS survey, a high detection rate between 10 and 100 au for
substellar companions with mass >10MJ.
|
This paper simplifies and further develops various aspects of Tasho Kaletha's
construction of regular supercuspidal representations. Moreover, Kaletha's
construction is connected with the author's revision of Yu's construction of
tame supercuspidal representations. This allows for a more direct construction
of regular supercuspidal representations that is more amenable to applications.
|
We report on a study of the density response in doped Weyl semimetals or Weyl
metals in the presence of an external magnetic field. We show that the applied
field leads to a contribution to the density response, which is topological in
nature and is closely related to the phenomenon of chiral anomaly. This
contribution manifests in a nonanalytic nonclassical correction to the
electronic compressibility and the plasmon frequency, proportional to the
magnitude of the magnetic field. Such a nonanalytic correction to the
electronic compressibility is a smoking-gun feature of Weyl metals, which
clearly distinguishes them from ordinary ferromagnetic metals.
|
Pre-training a model and then fine-tuning it on downstream tasks has
demonstrated significant success in the 2D image and NLP domains. However, due
to the unordered and non-uniform density characteristics of point clouds, it is
non-trivial to explore the prior knowledge of point clouds and pre-train a
point cloud backbone. In this paper, we propose a novel pre-training method
called Point cloud Diffusion pre-training (PointDif). We consider the point
cloud pre-training task as a conditional point-to-point generation problem and
introduce a conditional point generator. This generator aggregates the features
extracted by the backbone and employs them as the condition to guide the
point-to-point recovery from the noisy point cloud, thereby assisting the
backbone in capturing both local and global geometric priors as well as the
global point density distribution of the object. We also present a recurrent
uniform sampling optimization strategy, which enables the model to uniformly
recover from various noise levels and learn from balanced supervision. Our
PointDif achieves substantial improvement across various real-world datasets
for diverse downstream tasks such as classification, segmentation and
detection. Specifically, PointDif attains 70.0% mIoU on S3DIS Area 5 for the
segmentation task and achieves an average improvement of 2.4% on ScanObjectNN
for the classification task compared to TAP. Furthermore, our pre-training
framework can be flexibly applied to diverse point cloud backbones and bring
considerable gains.
|
Federated learning has quickly gained popularity with its promises of
increased user privacy and efficiency. Previous works have shown that federated
gradient updates contain information that can be used to approximately recover
user data in some situations. These previous attacks on user privacy have been
limited in scope and do not scale to gradient updates aggregated over even a
handful of data points, leaving some to conclude that data privacy is still
intact for realistic training regimes. In this work, we introduce a new threat
model based on minimal but malicious modifications of the shared model
architecture which enable the server to directly obtain a verbatim copy of user
data from gradient updates without solving difficult inverse problems. Even
user data aggregated over large batches -- where previous methods fail to
extract meaningful content -- can be reconstructed by these minimally modified
models.
|
In this work, we obtain bound states for a nonrelativistic spin-half neutral
particle under the influence of a Coulomb-like potential induced by the Lorentz
symmetry breaking effects. We present a new possible scenario of studying the
Lorentz symmetry breaking effects on a nonrelativistic quantum system defined
by a fixed space-like vector field parallel to the radial direction interacting
with a uniform magnetic field along the z-axis. Furthermore, we also discuss
the influence of a Coulomb-like potential induced by Lorentz symmetry violation
effects on the two-dimensional harmonic oscillator.
|
In commutative algebra, E. Miller and B. Sturmfels defined the notion of
multidegree for multigraded modules over a multigraded polynomial ring. We
apply this theory to bifiltered modules over the Weyl algebra D. The
bifiltration is a combination of the standard filtration by the order of
differential operators and of the so-called V-filtration along a coordinate
subvariety of the ambient space defined by M. Kashiwara. The multidegree we
define provides a new invariant for D-modules. We investigate its relation with
the L-characteristic cycles considered by Y. Laurent. We give examples from the
theory of A-hypergeometric systems defined by I. M. Gelfand, M. M. Kapranov and
A. V. Zelevinsky. We consider the V-filtration along the origin. When the toric
projective variety defined from the matrix A is Cohen-Macaulay, we have an
explicit formula for the multidegree of the hypergeometric system.
|
We study the extent to which knot and link states (that is, states in 3d
Chern-Simons theory prepared by path integration on knot and link complements)
can or cannot be described by stabilizer states. States which are not classical
mixtures of stabilizer states are known as "magic states" and play a key role
in quantum resource theory. By implementing a particular magic monotone known
as the "mana" we quantify the magic of knot and link states. In particular, for
$SU(2)_k$ Chern-Simons theory we show that knot and link states are generically
magical. For link states, we further investigate the mana associated to
correlations between separate boundaries which characterizes the state's
long-range magic. Our numerical results suggest that the magic of a majority of
link states is entirely long-range. We make these statements sharper for torus
links.
|
The paper presents status of three studies involving the $\omega$ meson using
data collected by the KLOE detector. The first two projects are feasibility
studies performed on simulated data concerning an upper limit measure ment of
BR($\Phi \to \omega \gamma$) and the form factor measurement in the
$\omega\to\pi^0l^+l^-$ dalitz decay. The third study shows the effect $\pi^0 -
\pi^0$ interference has in the $\omega\to\pi^+\pi^-\pi^0$ Dalitz plot when
$\omega$ is produced through the $e^+e^-\to\omega\pi^0$ channel.
|
Gas-giant planets, such as Jupiter, Saturn and massive exoplanets, were
formed via the gas accretion onto the solid cores each with a mass of roughly
ten Earth masses. However, rapid radial migration due to disk-planet
interaction prevents the formation of such massive cores via planetesimal
accretion. Comparably rapid core growth via pebble accretion requires very
massive protoplanetary disks because most pebbles fall into the central star.
Although planetesimal formation, planetary migration, and gas-giant core
formation have been studied with much effort, the full evolution path from dust
to planets are still uncertain. Here we report the result of full simulations
for collisional evolution from dust to planets in a whole disk. Dust growth
with realistic porosity allows the formation of icy planetesimals in the inner
disk (> 10 au), while pebbles formed in the outer disk drift to the inner disk
and there grow to planetesimals. The growth of those pebbles to planetesimals
suppresses their radial drift and supplies small planetesimals sustainably in
the vicinity of cores. This enables rapid formation of sufficiently massive
planetary cores within 0.2-0.4 million years, prior to the planetary migration.
Our models shows first gas giants form at 2-7 au in rather common
protoplanetary disks, in agreement with the exoplanet and solar systems.
|
We argue that the proton charge radius conundrum can be resolved by weakening
the assumption of perturbative formulation of quantum electrodynamics within
the proton
|
The concept "centre of mass" is analyzed in spaces with torsion free flat
linear connection. It is shown that under sufficiently general conditions it is
almost uniquely defined, the corresponding arbitrariness in its definition
being explicitly described.
|
We prove that the nilpotent commuting variety of a reductive Lie algebra over
an algebraically closed field of good characteristic is equidimensional. In
characteristic zero, this confirms a conjecture of Vladimir Baranovsky. As a
by-product, we obtain tat the punctual (local) Hilbert scheme parametrising the
ideals of colength $n$ in $k[[X,Y]]$ is irreducible over any algebraically
closed field $k$.
|
We consider the effects of vacuum polarization and proton cyclotron
resonances on the propagation of radiation through a strongly magnetized
plasma. We analyze the conditions under which the photons evolve adiabatically
through the resonant density and find that the adibaticity condition is
satisfied for most photon energies of interest, allowing for a normal-mode
treatment of the photon propagation. We then construct radiative equilibrium
atmosphere models of strongly magnetized neutron stars that includes these
effects, employing a new numerical method that resolves accurately the sharp
changes of the absorption and mode-coupling cross sections at the resonant
densities. We show that the resulting spectra are modified by both resonances
and are harder at all field strengths than a blackbody at the effective
temperature. We also show that the narrow absorption features introduced by the
proton cyclotron resonance have small equivalent widths. We discuss the
implications of our results for properties of thermal emission from the
surfaces of young neutron stars.
|
Many things will have to go right for quantum computation to become a reality
in the lab. For any of the presently-proposed approaches involving spin states
in solids, an essential requirement is that these spins should be measured at
the single-Bohr-magneton level. Fortunately, quantum computing provides a
suggestion for a new approach to this seemingly almost impossible task: convert
the magnetization into a charge, and measure the charge. I show how this might
be done by exploiting the spin filter effect provided by ferromagnetic tunnel
barriers, used in conjunction with one-electron quantum dots.
|
Interconnected embedded devices are increasingly used invarious scenarios,
including industrial control, building automation, or emergency communication.
As these systems commonly process sensitive information or perform safety
critical tasks, they become appealing targets for cyber attacks. A promising
technique to remotely verify the safe and secure operation of networked
embedded devices is remote attestation. However, existing attestation protocols
only protect against software attacks or show very limited scalability. In this
paper, we present the first scalable attestation protocol for interconnected
embedded devices that is resilient to physical attacks. Based on the assumption
that physical attacks require an adversary to capture and disable devices for
some time, our protocol identifies devices with compromised hardware and
software. Compared to existing solutions, our protocol reduces ommunication
complexity and runtimes by orders of magnitude, precisely identifies
compromised devices, supports highly dynamic and partitioned network
topologies, and is robust against failures. We show the security of our
protocol and evaluate it in static as well as dynamic network topologies. Our
results demonstrate that our protocol is highly efficient in well-connected
networks and robust to network disruptions.
|
We present a new supervised image classification method applicable to a broad
class of image deformation models. The method makes use of the previously
described Radon Cumulative Distribution Transform (R-CDT) for image data, whose
mathematical properties are exploited to express the image data in a form that
is more suitable for machine learning. While certain operations such as
translation, scaling, and higher-order transformations are challenging to model
in native image space, we show the R-CDT can capture some of these variations
and thus render the associated image classification problems easier to solve.
The method -- utilizing a nearest-subspace algorithm in R-CDT space -- is
simple to implement, non-iterative, has no hyper-parameters to tune, is
computationally efficient, label efficient, and provides competitive accuracies
to state-of-the-art neural networks for many types of classification problems.
In addition to the test accuracy performances, we show improvements (with
respect to neural network-based methods) in terms of computational efficiency
(it can be implemented without the use of GPUs), number of training samples
needed for training, as well as out-of-distribution generalization. The Python
code for reproducing our results is available at
https://github.com/rohdelab/rcdt_ns_classifier.
|
We predict energy spectra and angular distributions of nucleons above
10**(19) eV that originate from sources distributed in the Local Supercluster,
which is also supposed to contain a large scale magnetic field of strength
between 0.05 and 0.5 micro Gauss. We show that this model can explain all
present-day features of ultra-high energy cosmic rays, at least for field
strengths close to 0.5 micro Gauss. The large-scale anisotropy and the
clustering predicted by this scenario will allow strong discrimination against
other models with next generation experiments.
|
We study heuristic algorithms for job shop scheduling problems.
We compare classical approaches, such as the shifting bottleneck heuristic
with novel strategies using decision diagrams. Balas' local refinement is used
to improve feasible solutions. Heuristic approaches are combined with Mixed
Integer Programming and Constraint Programming approaches. We discuss our
results via computational experiments.
|
For a given second-order linear elliptic operator $L$ which admits a positive
minimal Green function, and a given positive weight function $W$, we introduce
a family of weighted Lebesgue spaces $L^p(\phi_p)$ with their dual spaces,
where $1\leq p\leq \infty$. We study some fundamental properties of the
corresponding (weighted) Green operators on these spaces. In particular, we
prove that these Green operators are bounded on $L^p(\phi_p)$ for any $1\leq
p\leq \infty$ with a uniform bound. We study the existence of a principal
eigenfunction for these operators in these spaces, and the simplicity of the
corresponding principal eigenvalue. We also show that such a Green operator is
a resolvent of a densely defined closed operator which is equal to $(-W^{-1})L$
on $C_0^\infty$, and that this closed operator generates a strongly continuous
contraction semigroup. Finally, we prove that if $W$ is a (semi)small
perturbation of $L$, then for any $1\leq p\leq \infty$, the associated Green
operator is compact on $L^p(\phi_p)$, and the corresponding spectrum is
$p$-independent.
|
This study presents a methodology for surrogate optimization of cyclic
adsorption processes, focusing on enhancing Pressure Swing Adsorption units for
carbon dioxide ($CO_{2}$) capture. We developed and implemented a
multiple-input, single-output (MISO) framework comprising two deep neural
network (DNN) models, predicting key process performance indicators. These
models were then integrated into an optimization framework, leveraging particle
swarm optimization (PSO) and statistical analysis to generate a comprehensive
Pareto front representation. This approach delineated feasible operational
regions (FORs) and highlighted the spectrum of optimal decision-making
scenarios. A key aspect of our methodology was the evaluation of optimization
effectiveness. This was accomplished by testing decision variables derived from
the Pareto front against a phenomenological model, affirming the surrogate
models reliability. Subsequently, the study delved into analyzing the feasible
operational domains of these decision variables. A detailed correlation map was
constructed to elucidate the interplay between these variables, thereby
uncovering the most impactful factors influencing process behavior. The study
offers a practical, insightful operational map that aids operators in
pinpointing the optimal process location and prioritizing specific operational
goals.
|
We study a combinatorial object, which we call a GRRS (generalized reflection
root system); the classical root systems and GRSs introduced by V. Serganova
are examples of finite GRRSs. A GRRS is finite if it contains a finite number
of vectors and is called affine if it is infinite and has a finite minimal
quotient. We prove that an irreducible GRRS containing an isotropic root is
either finite or affine; we describe all finite and affine GRRSs and classify
them in most of the cases.
|
By using the optical design software Zemax, on the basis of geometric optics
and primary aberration theory, the optimal design method of collimating mirror
is discussed and proposed, which eliminates the influence of conical concave
acoustic lens on beam transmission. The lens system imaging before and after
the optimization of the calibration lens is simulated by numerical simulation:
from the simulation results, after the calibration mirror is optimized, the
spherical aberration of the system is greatly reduced,. The root mean square
radius of the spot under the 0 degree field of view changes from 993.842
micrometers to 8.091 micrometers, and the geometric radius changes from 1000.98
micrometers to 11.087 micrometers; the MTF curve is obviously improved, the
cut-off frequency is increased by nearly 15 times, and the MTF value of the
meridian direction and sagittal direction under the 0 degree field of view are
between 0.9 and 1; The proposed optimization method of the collimating mirror
has important theoretical guiding significance for the study of the large depth
of field photoacoustic microscopy imaging system.
|
We propose a matrix model description of extended D-branes in 2D noncritical
string
|
In the framework of theory of open quantum systems, we derive quantum master
equations for the ultrastrong system-bath coupling regime and, more generally,
the strong-decoherence regime. In this regime, the strong decoherence is
complemented by slow relaxation processes. We use a generalization of the
Foerster and modified Redfield peturbation theories known in theory of
excitation energy transfer. Also, we show that the mean force Gibbs state in
the corresponding limits are stationary for the derived master equations.
|
For the class of attractive potentials V(r) <= 0 which vanish at infinity, we
prove that the ground-state energy E of the semirelativistic Hamiltonian
H = \sqrt{m^2 + p^2} + V(r) is bounded below by the ground-state energy e of
the corresponding Klein--Gordon problem
(p^2 + m^2)\phi = (V(r) -e)^2\phi. Detailed results are presented for the
exponential and Woods--Saxon potentials.
|
In this paper, we show that when policy-motivated parties can commit to a
particular platform during a uni-dimensional electoral contest where valence
issues do not arise there must be a positive association between the policies
preferred by candidates and the policies adopted in expectation in the lowest
and the highest equilibria of the electoral contest. We also show that this
need not be so if the parties cannot commit to a particular policy. The
implication is that evidence of a negative relationship between enacted and
preferred policies is suggestive of parties that hold positions from which they
would like to move from yet are unable to do so.
|
First results on the production of Xi and AntiXi hyperons in Pb+Pb
interactions at 40 AGeV are presented. The AntiXi/Xi ratio at midrapidity is
studied as a function of collision centrality. The ratio shows no significant
centrality dependence within statistical errors; it ranges from 0.07 to 0.15.
The AntiXi/Xi ratio for central Pb+Pb collisions increases strongly with the
collision energy.
|
We present a partial upgrade of the Monte Carlo event generator TAUOLA with
the two and three hadron decay modes using the theoretical models based on
Resonance Chiral Theory. These modes account for 88% of total hadronic width of
the tau meson. First results of the model parameters have been obtained using
BaBar data for three pion mode.
|
We consider the normalized Ricci flow $\del_t g = (\rho - R)g$ with initial
condition a complete metric $g_0$ on an open surface $M$ where $M$ is conformal
to a punctured compact Riemann surface and $g_0$ has ends which are asymptotic
to hyperbolic cusps. We prove that when $\chi(M) < 0$ and $\rho < 0$, the flow
$g(t)$ converges exponentially to the unique complete metric of constant Gauss
curvature $\rho$ in the conformal class.
|
We discuss an interferometric scheme employing interference of bright
solitons formed as specific bound states of attracting bosons on a lattice. We
revisit the proposal of Castin and Weiss [Phys. Rev. Lett. vol. 102, 010403
(2009)] for using the scattering of a quantum matter-wave soliton on a barrier
in order to create a coherent superposition state of the soliton being entirely
to the left of the barrier and being entirely to the right of the barrier. In
that proposal, it was assumed that the scattering is perfectly elastic, i.e.\
that the center-of-mass kinetic energy of the soliton is lower than the
chemical potential of the soliton. Here we relax this assumption: By employing
a combination of Bethe ansatz and DMRG based analysis of the dynamics of the
appropriate many-body system, we find that the interferometric fringes persist
even when the center-of-mass kinetic energy of the soliton is above the energy
needed for its complete dissociation into constituent atoms.
|
We show that all meromorphic solutions of the stationary reduction of the
real cubic Swift-Hohenberg equation are elliptic or degenerate elliptic. We
then obtain them all explicitly by the subequation method, and one of them
appears to be a new elliptic solution.
|
Hardness magnification reduces major complexity separations (such as
$\mathsf{\mathsf{EXP}} \nsubseteq \mathsf{NC}^1$) to proving lower bounds for
some natural problem $Q$ against weak circuit models. Several recent works
[OS18, MMW19, CT19, OPS19, CMMW19, Oli19, CJW19a] have established results of
this form. In the most intriguing cases, the required lower bound is known for
problems that appear to be significantly easier than $Q$, while $Q$ itself is
susceptible to lower bounds but these are not yet sufficient for magnification.
In this work, we provide more examples of this phenomenon, and investigate
the prospects of proving new lower bounds using this approach. In particular,
we consider the following essential questions associated with the hardness
magnification program:
Does hardness magnification avoid the natural proofs barrier of Razborov and
Rudich [RR97]?
Can we adapt known lower bound techniques to establish the desired lower
bound for $Q$?
|
A de Bruijn covering code is a q-ary string S so that every q-ary string is
at most R symbol changes from some n-word appearing consecutively in S. We
introduce these codes and prove that they can have length close to the smallest
possible covering code. The proof employs tools from field theory, probability,
and linear algebra. We also prove a number of ``spectral'' results on de Bruijn
covering codes. Included is a table of the best known bounds on the lengths of
small binary de Bruijn covering codes, up to R=11 and n=13, followed by several
open questions in this area.
|
A Lissajous knot is one that can be parameterized by a single cosine function
in each coordinate. Lissajous knots are highly symmetric, and for this reason,
not all knots are Lissajous. We prove several theorems which allow us to place
bounds on the number of Lissajous knot types with given frequencies and to
efficiently sample all possible Lissajous knots with a given set of
frequencies. In particular, we systematically tabulate all Lissajous knots with
small frequencies and as a result substantially enlarge the tables of known
Lissajous knots.
A Fourier (i, j, k) knot is similar to a Lissajous knot except that each
coordinate is now described by a finite sum of i, j, and k cosine functions
respectively. According to Lamm, every knot is a Fourier-(1,1,k) knot for some
k. By randomly searching the set of Fourier-(1,1,2) knots we find that all
2-bridge knots up to 14 crossings are either Lissajous or Fourier-(1,1,2)
knots. We show that all twist knots are Fourier-(1,1,2) knots and give evidence
suggesting that all torus knots are Fourier-(1,1,2) knots.
As a result of our computer search, several knots with relatively small
crossing numbers are identified as potential counterexamples to interesting
conjectures.
|
We introduce an alternative approach for the analysis and numerical
approximation of the optimal feedback control mapping. It consists in looking
at a typical optimal control problem in such a way that feasible controls are
mappings depending both in time and space. In this way, the feedback form of
the problem is built-in from the very beginning. Optimality conditions are
derived for one such optimal mapping, which by construction is the optimal
feedback mapping of the problem. In formulating optimality conditions, costates
in feedback form are solutions of linear, first-order transport systems, while
optimal descent directions are solutions of appropriate obstacle problems. We
treat situations with no constraint-sets for control and state, as well as the
more general case where a constraint-set is considered for the control
variable. Constraints for the state variable are deferred to a coming
contribution.
|
This article investigates the qualitative aspects of dark solitons of
one-dimensional Gross-Pitaevskii equations with general nonlocal interactions,
which correspond to traveling waves with subsonic speeds. Under general
conditions on the potential interaction term, we provide uniform bounds,
demonstrate the existence of symmetric solitons, and identify conditions under
which monotonicity is lost. Additionally, we present new properties of black
solitons. Moreover, we establish the nonlocal-to-local convergence, i.e. the
convergence of the soliton of the nonlocal model toward the explicit dark
solitons of the local Gross-Pitaevskii equation.
|
In a variety of scientific applications we wish to characterize a physical
system using measurements or observations. This often requires us to solve an
inverse problem, which usually has non-unique solutions so uncertainty must be
quantified in order to define the family of all possible solutions. Bayesian
inference provides a powerful theoretical framework which defines the set of
solutions to inverse problems, and variational inference is a method to solve
Bayesian inference problems using optimization while still producing fully
probabilistic solutions. This chapter provides an introduction to variational
inference, and reviews its applications to a range of geophysical problems,
including petrophysical inversion, travel time tomography and full-waveform
inversion. We demonstrate that variational inference is an efficient and
scalable method which can be deployed in many practical scenarios.
|
Particle induced X-ray emission (PIXE) is an important physical effect that
is not yet adequately modelled in Geant4. This paper provides a critical
analysis of the problem domain associated with PIXE simulation and describes a
set of software developments to improve PIXE simulation with Geant4. The
capabilities of the developed software prototype are illustrated and applied to
a study of the passive shielding of the X-ray detectors of the German eROSITA
telescope on the upcoming Russian Spectrum-X-Gamma space mission.
|
It is shown that any function $G(q_{i}, p_{i}, t)$, defined on the extended
phase space, defines a one-parameter group of canonical transformations which
act on any function $f(q_{i}, t)$, in such a way that if $G$ is a constant of
motion then from a solution of the Hamilton-Jacobi (HJ) equation one obtains a
one-parameter family of solutions of the same HJ equation. It is also shown
that any complete solution of the HJ equation can be obtained in this manner by
means of the transformations generated by $n$ constants of motion in
involution.
|
Sharjah-Sat-1 is a 3U cubesat with a CdZnTe based hard X-ray detector, called
iXRD (improved X-ray Detector) as a scientific payload with the primary
objective of monitoring bright X-ray sources in the galaxy. We investigated the
effects of the in-orbit background radiation on the iXRD based on Geant4
simulations. Several background components were included in the simulations
such as the cosmic diffuse gamma-rays, galactic cosmic rays (protons and alpha
particles), trapped protons and electrons, and albedo radiation arising from
the upper layer of the atmosphere. The most dominant component is the albedo
photon radiation which contributes at low and high energies alike in the
instrument energy range of 20 keV - 200 keV. On the other hand, the cosmic
diffuse gamma-ray contribution is the strongest between 20 keV and 60 keV in
which most of the astrophysics source flux is expected. The third effective
component is the galactic cosmic protons. The radiation due to the trapped
particles, the albedo neutrons, and the cosmic alpha particles are negligible
when the polar regions and the South Atlantic Anomaly region are excluded in
the analysis. The total background count rates are ~0.36 and ~0.85 counts/s for
the energy bands of 20 - 60 keV and 20 - 200 keV, respectively. We performed
charge transportation simulations to determine the spectral response of the
iXRD and used it in sensitivity calculations as well. The simulation framework
was validated with experimental studies. The estimated sensitivity of 180 mCrab
between the energy band of 20 keV - 100 keV indicates that the iXRD could
achieve its scientific goals.
|
Haramaty and Sudan considered the problem of transmitting a message between
two people, Alice and Bob, when Alice's and Bob's priors on the message are
allowed to differ by at most a given factor. To find a deterministic
compression scheme for this problem, they showed that it is sufficient to
obtain an upper bound on the chromatic number of a graph, denoted $U(N,s,k)$
for parameters $N,s,k$, whose vertices are nested sequences of subsets and
whose edges are between vertices that have similar sequences of sets. In turn,
there is a close relationship between the problem of determining the chromatic
number of $U(N,s,k)$ and a local graph coloring problem considered by Erd\H{o}s
et al. We generalize the results of Erd\H{o}s et al. by finding bounds on the
chromatic numbers of graphs $H$ and $G$ when there is a homomorphism $\phi
:H\rightarrow G$ that satisfies a nice property. We then use these results to
improve upper and lower bounds on $\chi(U(N,s,k))$.
|
The distribution of visible matter in the universe, such as galaxies and
galaxy clusters, has its origin in the week fluctuations of density that
existed at the epoch of recombination. The hierarchical distribution of the
universe, with its galaxies, clusters and super-clusters of galaxies indicates
the absence of a natural length scale. In the Newtonian formulation, numerical
simulations of a one-dimensional system permit us to precisely follow the
evolution of an ensemble of particles starting with an initial perturbation in
the Hubble flow. The limitation of the investigation to one dimension removes
the necessity to make approximations in calculating the gravitational field
and, on the whole, the system dynamics. It is then possible to accurately
follow the trajectories of particles for a long time. The simulations show the
emergence of a self-similar hierarchical structure in both the phase space and
the configuration space and invites the implementation of a multifractal
analysis. Here, after showing that symmetry considerations leads to the
construction of a family of equations of motion of the one-dimensional
gravitational system, we apply four different methods for computing generalized
dimensions $D_q$ of the distribution of particles in configuration space. We
first employ the conventional box counting and correlation integral methods
based on partitions of equal size and then the less familiar nearest-neighbor
and k-neighbor methods based on partitions of equal mass. We show that the
latter are superior for computing generalized dimensions for indices $q<-1$
which characterize regions of low density.
|
Homologically fibered knots are knots whose exteriors satisfy the same
homological conditions as fibered knots. In our previous paper, we observed
that for such a knot, higher-order Alexander invariants defined by Cochran,
Harvey and Friedl are generally factorized into the part of the Magnus matrix
and that of a certain Reidemeister torsion, both of which are known as
invariants of homology cylinders over a surface. In this paper, we study more
details of the invariants and give some concrete calculations by restricting to
the case of the invariants associated with metabelian quotients of their knot
groups. We provide examples of explicit calculations of the invariants for all
the 12 crossings non-fibered homologically fibered knots.
|
The Crab pulsar has striking radio emission properties, with the two dominant
pulse components -- the main pulse and the interpulse -- consisting entirely of
giant pulses. The emission is scattered in both the Crab nebula and the
interstellar medium, causing multi-path propagation and thus scintillation. We
study the scintillation of the Crab's giant pulses using phased Westerbork
Synthesis Radio Telescope data at 1668\,MHz. We find that giant pulse spectra
correlate at only $\sim 2 \%$, much lower than the $1/3$ correlation expected
from a randomized signal imparted with the same impulse response function. In
addition, we find that the main pulse and the interpulse appear to scintillate
differently; the 2D cross-correlation of scintillation between the interpulse
and main pulse has a lower amplitude, and is wider in time and frequency delay
than the 2D autocorrelation of main pulses. These lines of evidence suggest
that the giant pulse emission regions are extended, and that the main pulse and
interpulse arise in physically distinct regions which are resolved by the
scattering screen. Assuming the scattering takes place in the nebular
filaments, the emission regions are of order a light cylinder radius, as
projected on the sky. With further VLBI and multi-frequency data, it may be
possible to measure the distance to the scattering screens, the size of giant
pulse emission regions, and the physical separation between the pulse
components.
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Consider a simple algebraic group G of adjoint type, and its wonderful
compactification X. We show that X admits a unique family of minimal rational
curves, and we explicitly describe the subfamily consisting of curves through a
general point. As an application, we show that X has the target rigidity
property when G is not of type A_1 or C.
|
The general prediction that more than half of all CVs have evolved past the
period minimum is in strong disagreement with observational surveys, which show
that the relative number of these objects is just a few per cent. Here, we
investigate whether a large number of post-period minimum CVs could detach
because of the appearance of a strong white dwarf magnetic field potentially
generated by a rotation- and crystallization-driven dynamo. We used the MESA
code to calculate evolutionary tracks of CVs incorporating the spin evolution
and cooling as well as compressional heating of the white dwarf. If the
conditions for the dynamo were met, we assumed that the emerging magnetic field
of the white dwarf connects to that of the companion star and incorporated the
corresponding synchronization torque, which transfers spin angular momentum to
the orbit. We find that for CVs with donor masses exceeding 0.04 Msun, magnetic
fields are generated mostly if the white dwarfs start to crystallize before the
onset of mass transfer. It is possible that a few white dwarf magnetic fields
are generated in the period gap. For the remaining CVs, the conditions for the
dynamo to work are met beyond the period minimum, when the accretion rate
decreased significantly. Synchronization torques cause these systems to detach
for several Gyrs even if the magnetic field strength of the white dwarf is just
one MG. If the rotation- and crystallization-driven dynamo - which is currently
the only mechanism that can explain several observational facts related to
magnetism in CVs and their progenitors - or a similar temperature-dependent
mechanism is responsible for the generation of magnetic field in white dwarfs,
most CVs that have evolved beyond the period minimum must detach for several
Gyrs at some point. This reduces the predicted number of semi-detached period
bouncers by up to 60-80 per cent.
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The $T$-matrix formally describes the solution of any electromagnetic
scattering problem by a given particle in a given medium at a given wavelength.
As such it is commonly used in a number of contexts, for example to predict the
orientation-averaged optical properties of non-spherical particles. The
$T$-matrix for electromagnetic scattering can be divided into four blocks
corresponding physically to coupling between either magnetic or electric
multipolar fields. Analytic expressions were recently derived for the
electrostatic limit of the electric-electric $T$-matrix block $\mathbf T^{22}$,
of prolate spheroids. In such an electrostatic approximation, all the other
blocks were zero. We here analyse the long-wavelength limit for the other
blocks ($\mathbf T^{21}$, $\mathbf T^{12}$, $\mathbf T^{11}$) corresponding to
electric-magnetic, magnetic-electric, and magnetic-magnetic coupling
respectively. Analytic expressions (finite sums) are obtained in the case of
spheroidal particles by expressing the fields with solutions to Laplace's
equation, expanding the fields in terms of spheroidal harmonics and applying
the boundary conditions. Similar expressions are also presented for the
auxiliary matrices in the extended boundary condition method, often used in
conjunction with the $T$-matrix formalism.
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The cross section of pair double heavy diquark production process
$pp\to(bc)+(\bar b \bar c)+X$ is calculated in the leading order of gluonic
fusion channel with all four possible color and spin combinations
$[^1S_0]_{\bar3}$, $[^1S_0]_{6}$, $[^3S_1]_{\bar3}$, and $[^3S_1]_{6}$ for each
of the two final diquarks taken into account. Several sources of relativistic
corrections to the cross section are handled in the framework of relativistic
quark model. Perturbative $\mathcal O(v^2)$ corrections originating from the
production amplitude expansions in heavy quark relative velocity~$v$ depend on
the color and spin states of the final particles, but can be generally
considered as unimportant ones giving maximally 12\% improvement in numerically
significant cases. Modifications of the quark--quark and antiquark--antiquark
bound state wave functions caused by the appropriate generalization of the
Breit interaction potential have rather severe impact on the cross section
suppressing it almost three times. Under assumption of antitriplets and
sextuplets' nonperturbative parameters having the same order of magnitude, it
is shown that the color-sextet mechanism strongly dominates pair diquark
production in both nonrelativistic and relativistic approximations.
|
We give a complete invariant for shift equivalence for Boolean matrices
(equivalently finite relations), in terms of the period, the induced partial
order on recurrent components, and the cohomology class of the relation on
those components.
|
Human-annotated attributes serve as powerful semantic embeddings in zero-shot
learning. However, their annotation process is labor-intensive and needs expert
supervision. Current unsupervised semantic embeddings, i.e., word embeddings,
enable knowledge transfer between classes. However, word embeddings do not
always reflect visual similarities and result in inferior zero-shot
performance. We propose to discover semantic embeddings containing
discriminative visual properties for zero-shot learning, without requiring any
human annotation. Our model visually divides a set of images from seen classes
into clusters of local image regions according to their visual similarity, and
further imposes their class discrimination and semantic relatedness. To
associate these clusters with previously unseen classes, we use external
knowledge, e.g., word embeddings and propose a novel class relation discovery
module. Through quantitative and qualitative evaluation, we demonstrate that
our model discovers semantic embeddings that model the visual properties of
both seen and unseen classes. Furthermore, we demonstrate on three benchmarks
that our visually-grounded semantic embeddings further improve performance over
word embeddings across various ZSL models by a large margin.
|
Automatic evaluation metrics have been facilitating the rapid development of
automatic summarization methods by providing instant and fair assessments of
the quality of summaries. Most metrics have been developed for the general
domain, especially news and meeting notes, or other language-generation tasks.
However, these metrics are applied to evaluate summarization systems in
different domains, such as biomedical question summarization. To better
understand whether commonly used evaluation metrics are capable of evaluating
automatic summarization in the biomedical domain, we conduct human evaluations
of summarization quality from four different aspects of a biomedical question
summarization task. Based on human judgments, we identify different noteworthy
features for current automatic metrics and summarization systems as well. We
also release a dataset of our human annotations to aid the research of
summarization evaluation metrics in the biomedical domain.
|
Reversible logic can provide lower switching energy costs relative to all
irreversible logic, including those developed by industry in semiconductor
circuits, however, more research is needed to understand what is possible.
Superconducting logic, an exemplary platform for both irreversible and
reversible logic, uses flux quanta to represent bits, and the reversible
implementation may switch state with low energy dissipation relative to the
energy of a flux quantum. Here we simulate reversible shift register gates that
are ballistic: their operation is powered by the input bits alone. A storage
loop is added relative to previous gates as a key innovation, which bestows an
asynchronous property to the gate such that input bits can arrive at different
times as long as their order is clearly preserved. The shift register
represents bit states by flux polarity, both in the stored bit as well as the
ballistic input and output bits. Its operation consists of the elastic swapping
of flux between the stored and the moving bit. This is related to a famous
irreversible shift register, developed prior to the advent of superconducting
flux quanta logic (which used irreversible gates). In the base design of our
ballistic shift register (BSR) there is one 1-input and 1-output port, but we
find that we can make other asynchronous ballistic gates by extension. The gate
constitutes the first asynchronous reversible 2-input gate. Finally, for a
better insight into the dynamics, we introduce a collective coordinate model.
We find that the gate can be described as motion in two coordinates subject to
a potential determined by the input bit and initial stored flux quantum. Aside
from the favorable asynchronous feature, the gate is considered practical in
the context of energy efficiency, parameter margins, logical depth, and speed.
|
The yield of $\Upsilon$ associated with open charm has been estimated with
different approaches. The crucial differences between SPS and DPS predictions
are discussed.
|
If H is a flat group of automorphisms of finite rank n of a totally
disconnected, locally compact group G, then each orbit of H in the metric space
B(G) of compact, open subgroups of G is quasi-isometric to n-dimensional
euclidean space. In this note we prove the following partial converse: Assume
that G is a totally disconnected, locally compact group such that B(G) is a
proper metric space and let H be a group of automorphisms of G such that some
(equivalently every) orbit of H in B(G) is quasi-isometric to n-dimensional
euclidean space, then H has a finite index subgroup which is flat of rank n. We
can draw this conclusion under weaker assumptions. We also single out a
naturally defined flat subgroup of such groups of automorphisms.
|
We design the imaging data calibration and reduction software for MICADO, the
First Light near-IR instrument on the Extremely Large Telescope. In this
process we have hit the limit of what can be achieved with a detailed software
design that is primarily captured in pdf/word documents.
Trade-offs between hardware and calibration software are required to meet
stringent science requirements. To support such trade-offs, more software needs
to be developed in the early phases of the project: simulators, archives,
prototype recipes and pipelines. This requires continuous and efficient
exchange of evolving designs between the software and hardware groups, which is
hard to achieve with manually maintained documents. This, and maintaining the
consistency between the design documents and various software components is
possible with a machine readable version of the design.
We construct a detailed design that is readable by both software and humans.
From this the design documentation, prototype pipelines and data archives are
generated automatically. We present the implementation of such an approach for
the calibration software detailed design for the ELT MICADO imager which is
based on expertise and lessons learned in earlier projects (e.g. OmegaCAM,
MUSE, Euclid).
|
Any local relativistic quantum field theory of Dirac-Weyl fermions conserves
CPT. Here we examine whether a simple nonlocal field theory can violate CPT. We
construct a new relativistic field theory of fermions, which we call
``homeotic'', which is nonlocal but causal and Lorentz invariant. The free
homeotic theory is in fact equivalent to free Dirac theory. We show that a
homeotic theory with a suitable nonlocal four-fermion interaction is causal and
as a result has a well-defined perturbative S-matrix. By coupling a
right-handed homeotic fermion to a left-handed Dirac-Weyl fermion, we obtain a
causal theory of CPT-violating neutrino oscillations.
|
Molecular dynamics simulations using empirical force fields (EFFs) are
crucial for gaining fundamental insights into atomic structure and long
timescale dynamics of Au nanoclusters with far-reaching applications in energy
and devices. This approach is thwarted by the failure of currently available
EFFs in describing the size-dependent dimensionality and diverse geometries
exhibited by Au clusters (e.g., planar, hollow cages, pyramids). Owing to their
ability to account for bond directionality, bond-order based EFFs, such as the
Tersoff-type Bond Order Potential (BOP), are well suited for such a
description. Nevertheless, the predictive power of existing BOP parameters is
severely limited in the nm length scale owing to the predominance of bulk Au
properties used to train them. Here, we mitigate this issue by introducing a
new hybrid bond order potential (HyBOP), which account for (a) short-range
interactions via Tersoff-type BOP terms and (b) long-range effects by a scaled
LJ term whose contribution depends on the local atomic density. We optimized
the independent parameters for our HyBOP using a global optimization scheme
driven by genetic algorithms. Moreover, to ensure good transferability of these
parameters across different length scales, we used an extensive training
dataset encompasses structural and energetic properties of a thousand 13-atom
Au clusters, surface energies, as well as bulk polymorphs, obtained from
density functional theory (DFT) calculations. Our newly developed HyBOP has
been found to accurately describe (a) global minimum energy configurations at
different clusters sizes, (b) critical size of transition from planar to
globular clusters, (c) evolution of structural motifs with cluster size, and
(d) thermodynamics, structure, elastic properties of bulk polymorphs as well as
surfaces, in excellent agreement with DFT calculations and spectroscopic
experiments.
|
The diametral dimension, $\Delta(E)$, and the approximate diametral
dimension, $\delta(E)$ of an element $E$ of a large class of nuclear Fr\'echet
spaces are set theoretically between the corresponding invariant of power
series spaces $\Lambda_{1}(\varepsilon)$ and $\Lambda_{\infty}(\varepsilon)$
for some exponent sequence $\varepsilon$. Aytuna et al., \cite{AKT2}, proved
that $E$ contains a complemented subspace which is isomorphic to
$\Lambda_{\infty}(\varepsilon)$ provided $\Delta(E)=\Delta(
\Lambda_{\infty}(\varepsilon))$ and $\varepsilon$ is stable. In this article,
we will consider the other extreme case and we proved that in this large
family, there exist nuclear Fr\'echet spaces, even regular nuclear K\"othe
spaces, satisfying $\Delta(E)=\Delta(\Lambda_{1}(\varepsilon))$ such that there
is no subspace of $E$ which is isomorphic to $\Lambda_{1}(\varepsilon)$.
|
Motivated by the problem of characterizing KMS states on the reduced
C$^*$-algebras of \'etale groupoids, we show that the reduced norm on these
algebras induces a C$^*$-norm on the group algebras of the isotropy groups.
This C$^*$-norm coincides with the reduced norm for the transformation
groupoids, but, as follows from examples of Higson-Lafforgue-Skandalis, it can
be exotic already for groupoids of germs associated with group actions. We show
that the norm is still the reduced one for some classes of graded groupoids, in
particular, for the groupoids associated with partial actions of groups and the
semidirect products of exact groups and groupoids with amenable isotropy
groups.
|
This paper gives a new deterministic algorithm for the dynamic Minimum
Spanning Forest (MSF) problem in the EREW PRAM model, where the goal is to
maintain a MSF of a weighted graph with $n$ vertices and $m$ edges while
supporting edge insertions and deletions. We show that one can solve the
dynamic MSF problem using $O(\sqrt n)$ processors and $O(\log n)$ worst-case
update time, for a total of $O(\sqrt n \log n)$ work. This improves on the work
of Ferragina [IPPS 1995] which costs $O(\log n)$ worst-case update time and
$O(n^{2/3} \log{\frac{m}{n}})$ work.
|
To construct a quantum group gauge theory one needs an algebra which is
invariant under gauge transformations. The existence of this invariant algebra
is closely related with the existence of a differential algebra $\delta _{{\cal
H}} G_{q}$ compatible with the Hopf algebra structure. It is shown that $\delta
_{{\cal H}} G_{q}$ exists only for the quantum group $U_{q}(N)$ and that the
quantum group $SU_q(N)$ as a quantum gauge group is not allowed. The
representations of the algebra $\delta _{{\cal H}} G_{q}$ are con- structed.
The operators corresponding to the differentials are realized via derivations
on the space of all irreducible *-representations of $U_q(2)$. With the help of
this construction infinitesimal gauge transformations in two-dimensional
classical space-time are described.
|
In gravitational lensing, the magnification effect changes the luminosity and
size of a background galaxy. If the image sizes are not small compared to the
scale over which the magnification and shear vary, higher-order distortions
occur which are termed differential magnification. We give an approximation of
the magnification gradient for several halo models. Assuming a symmetric
distribution of source brightness, estimates for the differential magnification
are obtained and then tested with simulations. One of the main uncertainties of
our estimators comes from the finite resolution of the image. We study the
strength of our method with the resolution of current and future telescopes. We
point out that out method is a potential approach to estimate the first
flexion, and can be used to study galaxy and cluster mass profiles.
|
We elaborate on anomaly induced actions of the Wess-Zumino (WZ) form and
their relation to the renormalized effective action, which is defined by an
ordinary path integral over a conformal sector, in an external gravitational
background. In anomaly-induced actions, the issue of scale breaking is usually
not addressed, since these actions are obtained only by solving the trace
anomaly constraint and are determined by scale invariant functionals. We
investigate the changes induced in the structure of such actions once
identified in dimensional renormalization (DR) when the $\epsilon = d-4 \to 0$
limit is accompanied by the dimensional reduction (DRed) of the field
dependencies. We show that operatorial nonlocal modifications
$(\sim\Box^\epsilon)$ of the counterterms are unnecessary to justify a scale
anomaly. In this case, only the ordinary finite subtractions play a critical
role in the determination of the scale breaking. This is illustrated for the WZ
form of the effective action and its WZ consistency condition, as seen from a
renormalization procedure. Logarithmic corrections from finite subtractions are
also illustrated in a pure $d=4$ (cutoff) scheme. The interplay between two
renormalization schemes, one based on dimensional regularization (DR) and the
second on a cutoff in $d=4$, illustrates the ambiguities of DR in handling the
quantum corrections in a curved background. Therefore, using DR in a curved
background, the scale and trace anomalies can both be obtained by counterterms
that are Weyl invariant only at $d=4$.
|
A two-parametric non-standard (Jordanian) deformation of the Lie algebra
$gl(2)$ is constructed, and then, exploited to obtain a new, triangular
R-matrix solution of the coloured Yang-Baxter equation. The corresponding
coloured quantum group is presented explicitly.
|
The algebras of the symmetry operators for the Hamilton-Jacobi and
Klein-Gordon-Fock equations are found for a charged test particle moving in an
external electromagnetic field in a spacetime manifold, on the isotropic (null)
hypersurface of which a three-parameter groups of motions act transitively.on
the isotropic (null) hypersurface of which a three-parameter groups of motions
act transitively. We have found all admissible electromagnetic fields for which
such algebras exist. We have proved that an admissible field does not deform
the algebra of symmetry operators for the free Hamilton-Jacobi and
Klein-Gordon-Fock equations. The results complete the classification of
admissible electromagnetic fields in which the Hamilton-Jacobi and
Klein-Gordon-Fock equations admit algebras of motion integrals that are
isomorphic to the algebras of operators of $r$-parametric groups of motions of
spacetime manifolds if $(r \leq 4)$.
|
Cerium-134 is an isotope desired for applications as a chemical analogue to
the promising therapeutic radionuclide $^{225}$Ac, for use in bio-distribution
assays as an in vivo generator of the short-lived positron-emitting isotope
$^{134}$La. In the 50-100 MeV energy range relevant to the production of
$^{134}$Ce by means of high-energy proton bombardment of lanthanum, existing
cross section data are discrepant and have gaps at important energies. To
address these deficiencies, a series of 17 $^{139}$La foils (99.919% natural
abundance) were irradiated in two stacked-target experiments: one at the LANL's
Isotope Production Facility with an incident proton energy of 100 MeV, and a
second at BNL's Brookhaven Linac Isotope Producer with an incident proton
energy of 200 MeV - a complete energy range spanning approximately 55-200 MeV.
Cross sections are reported for 30 products of $^{139}$La(p,x) reactions
(representing up to 55% of the total non-elastic cross section), in addition to
24 residual products measured in the $^{nat}$Cu and $^{nat}$Ti foils that were
used as proton flux monitors. The measured production cross sections for
$^{139}$La reactions were compared to literature data as well as default
calculations from the nuclear reaction modeling codes TALYS, EMPIRE and ALICE,
as well as the TENDL-2023 library. The default calculations typically exhibited
poor predictive capability, due to the complexity of multiple interacting
physics models in this energy range, and deficiencies in preequilibrium
reaction modeling. Building upon previous efforts to evaluate proton-induced
reactions in this energy range, a parameter adjustment procedure was performed
upon the optical model and the two-component exciton model using the TALYS-2.0
code. This resulted in an improvement in $^{139}$La(p,x) cross sections for
applications including isotope production, over default predictions.
|
Subsets and Splits
Filtered Text Samples
Retrieves 100 samples of text containing the specific phrase "You are a helpful assistant", providing limited insight into the dataset.
Helpful Assistant Text Samples
Returns a limited set of rows containing the phrase 'helpful assistant' in the text, providing basic filtering of relevant entries.