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Given two polygonal curves, there are many ways to define a notion of
similarity between them. One popular measure is the Fr\'echet distance which
has many desirable properties but is notoriously expensive to calculate,
especially for non-trivial metrics. In 1994, Eiter and Mannila introduced the
discrete Fr\'echet distance which is much easier to implement and approximates
the continuous Fr\'echet distance with a quadratic runtime overhead. However,
this algorithm relies on recursions and is not well suited for modern hardware.
To that end, we introduce the Fast Fr\'echet Distance algorithm, a
recursion-free algorithm that calculates the discrete Fr\'echet distance with a
linear memory overhead and that can utilize modern hardware more effectively.
We showcase an implementation with only four lines of code and present
benchmarks of our algorithm running fast on modern CPUs and GPGPUs.
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We prove a nonexistence theorem for product type manifolds. In particular we
show that the 4-manifold $\Sigma_g\times\Sigma_h$ does not admit any locally
conformally flat metric arising from discrete and faithful representations for
$g\geq 2$ and $h\geq 1$
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Though objectives of trusted routing and virtual private networks (VPN) data
transfer methods are to guarantee data transfer securely to from senders to
receivers over public networks like Internet yet there are paramount
differences between the two methods. This paper analyses their differences.
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We prove that stable-like non-local Dirichlet forms converge to local
Dirichlet form in the sense of Mosco on metric measure spaces. We prove that
subordinated Dirichlet forms converge to the original Dirichlet form in the
sense of Mosco on metric measure spaces.
|
The FlexRay bus is a modern standard used in the automotive industry.It
offers deterministic message transmission with zero jitter while using
time-triggered scheduling in the static segment. When several vehicle variants
(i.e. different models and their versions) share the same signal, the car
manufacturers require to schedule such signal at the same time in all vehicle
variants. This requirement simplifies the signal traceability and diagnostics
in different vehicle variants using the same platform and simplifies reuse of
components and tools.
In this paper, we propose a first fit based heuristic algorithm which creates
the schedules for several vehicle variants at once, while transmitting a given
signal at the same time in all the schedules. The scheduling algorithm also
takes the time constraints as release dates and deadlines into account.
Finally, different algorithm versions are compared on benchmark sets and low
computational time demands are validated on large instances.
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In the 3SUM-Indexing problem the goal is to preprocess two lists of elements
from $U$, $A=(a_1,a_2,\ldots,a_n)$ and $B=(b_1,b_2,...,b_n)$, such that given
an element $c\in U$ one can quickly determine whether there exists a pair
$(a,b)\in A \times B$ where $a+b=c$. Goldstein et al.~[WADS'2017] conjectured
that there is no algorithm for 3SUM-Indexing which uses $n^{2-\Omega(1)}$ space
and $n^{1-\Omega(1)}$ query time.
We show that the conjecture is false by reducing the 3SUM-Indexing problem to
the problem of inverting functions, and then applying an algorithm of Fiat and
Naor [SICOMP'1999] for inverting functions.
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Saliency methods generating visual explanatory maps representing the
importance of image pixels for model classification is a popular technique for
explaining neural network decisions. Hierarchical dynamic masks (HDM), a novel
explanatory maps generation method, is proposed in this paper to enhance the
granularity and comprehensiveness of saliency maps. First, we suggest the
dynamic masks (DM), which enables multiple small-sized benchmark mask vectors
to roughly learn the critical information in the image through an optimization
method. Then the benchmark mask vectors guide the learning of large-sized
auxiliary mask vectors so that their superimposed mask can accurately learn
fine-grained pixel importance information and reduce the sensitivity to
adversarial perturbations. In addition, we construct the HDM by concatenating
DM modules. These DM modules are used to find and fuse the regions of interest
in the remaining neural network classification decisions in the mask image in a
learning-based way. Since HDM forces DM to perform importance analysis in
different areas, it makes the fused saliency map more comprehensive. The
proposed method outperformed previous approaches significantly in terms of
recognition and localization capabilities when tested on natural and medical
datasets.
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Stepped wedge cluster-randomized trial (CRTs) designs randomize clusters of
individuals to intervention sequences, ensuring that every cluster eventually
transitions from a control period to receive the intervention under study by
the end of the study period. The analysis of stepped wedge CRTs is usually more
complex than parallel-arm CRTs due to potential secular trends that result in
changing intra-cluster and period-cluster correlations over time. A further
challenge in the analysis of closed-cohort stepped wedge CRTs, which follow
groups of individuals enrolled in each period longitudinally, is the occurrence
of dropout. This is particularly problematic in studies of individuals at high
risk for mortality, which causes non-ignorable missing outcomes. If not
appropriately addressed, missing outcomes from death will erode statistical
power, at best, and bias treatment effect estimates, at worst. Joint
longitudinal-survival models can accommodate informative dropout and
missingness patterns in longitudinal studies. Specifically, within this
framework one directly models the dropout process via a time-to-event submodel
together with the longitudinal outcome of interest. The two submodels are then
linked using a variety of possible association structures. This work extends
linear mixed-effects models by jointly modeling the dropout process to
accommodate informative missing outcome data in closed-cohort stepped wedge
CRTs. We focus on constant intervention and general time-on-treatment effect
parametrizations for the longitudinal submodel and study the performance of the
proposed methodology using Monte Carlo simulation under several data-generating
scenarios. We illustrate the joint modeling methodology in practice by
reanalyzing the `Frail Older Adults: Care in Transition' (ACT) trial, a stepped
wedge CRT of a multifaceted geriatric care model versus usual care in the
Netherlands.
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Deep Reinforcement Learning (Deep RL) has had incredible achievements on high
dimensional problems, yet its learning process remains unstable even on the
simplest tasks. Deep RL uses neural networks as function approximators. These
neural models are largely inspired by developments in the (un)supervised
machine learning community. Compared to these learning frameworks, one of the
major difficulties of RL is the absence of i.i.d. data. One way to cope with
this difficulty is to control the rate of change of the policy at every
iteration. In this work, we challenge the common practices of the
(un)supervised learning community of using a fixed neural architecture, by
having a neural model that grows in size at each policy update. This allows a
closed form entropy regularized policy update, which leads to a better control
of the rate of change of the policy at each iteration and help cope with the
non i.i.d. nature of RL. Initial experiments on classical RL benchmarks show
promising results with remarkable convergence on some RL tasks when compared to
other deep RL baselines, while exhibiting limitations on others.
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We investigate properties of the conserved charge in general relativity,
recently proposed by one of the present authors with his collaborators, in the
inflation era, the matter dominated era and the radiation dominated era of the
expanding Universe. We show that the conserved charge in the inflation era
becomes the Bekenstein-Hawking entropy for de Sitter space, and it becomes the
matter entropy and the radiation entropy in the matter and radiation dominated
eras, respectively, while the charge itself is always conserved. These
properties are qualitatively confirmed by a numerical analysis of a model with
a scalar field and radiations. Results in this paper provide more evidences on
the interpretation that the conserved charge in general relativity corresponds
to entropy.
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Nash-Williams proved that every graph has a well-balanced orientation. A key
ingredient in his proof is admissible odd-vertex pairings. We show that for two
slightly different definitions of admissible odd-vertex pairings, deciding
whether a given odd-vertex pairing is admissible is co-NP-complete. This
resolves a question of Frank. We also show that deciding whether a given graph
has an orientation that satisfies arbitrary local arc-connectivity requirements
is NP-complete.
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We carry out an analytical and numerical study of the motion of an isolated
vortex in thermal equilibrium, the vortex being defined as the point
singularity of a complex scalar field $\psi(\r,t)$ obeying a nonlinear
stochastic Schr\"odinger equation. Because hydrodynamic fluctuations are
included in this description, the dynamical picture of the vortex emerges as
that of both a massive particle in contact with a heat bath, and as a passive
scalar advected to a background random flow. We show that the vortex does not
execute a simple random walk and that the probability distribution of vortex
flights has non-Gaussian (exponential) tails.
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A coordinate transformation is found which diagonalizes the axisymmetric
pp-waves. Its effect upon concrete solutions, including impulsive and shock
waves, is discussed.
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We investigate orbital resonances expected to arise when a system of two
planets, with masses in the range 1-4 Earth masses, undergoes convergent
migration while embedded in a section of gaseous disc where the flow is
laminar. We consider surface densities corresponding to 0.5-4 times that
expected for a minimum mass solar nebula at 5.2 AU. Using hydrodynamic
simulations we find that when the configuration is such that convergent
migration occurs the planets can become locked in a first order
commensurability for which the period ratio is (p+1)/p with p being an integer
and migrate together maintaining it for many orbits. Relatively rapid
convergent migration as tends to occur for disparate masses, results in
commensurabilities with p larger than 2. However, in these cases the dynamics
is found to have a stochastic character. When the convergent migration is
slower, such as occurs in the equal mass case, lower p commensurabilities such
as 3:2 are attained which show much greater stability. In one already known
example of a system with nearly equal masses in the several Earth mass range
(planets around pulsar PSR B1257+12) the two largest planets are intriguingly
close to a 3:2 commensurability. A very similar behaviour is obtained when the
systems are modeled using an N body code with simple prescriptions for the disc
planet interaction. Using that, we found that an 8:7 resonance established in a
hydrodynamic simulation run for 10-100 thousand orbits could be maintained for
more than million orbits. Resonant capture leads to a rise in eccentricities
that can be predicted using a simple analytic model constructed in this paper.
We find that the system with the 8:7 commensurability is fully consistent with
this prediction.
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Multi-label classification deals with the problem where each instance is
associated with multiple class labels. Because evaluation in multi-label
classification is more complicated than single-label setting, a number of
performance measures have been proposed. It is noticed that an algorithm
usually performs differently on different measures. Therefore, it is important
to understand which algorithms perform well on which measure(s) and why. In
this paper, we propose a unified margin view to revisit eleven performance
measures in multi-label classification. In particular, we define label-wise
margin and instance-wise margin, and prove that through maximizing these
margins, different corresponding performance measures will be optimized. Based
on the defined margins, a max-margin approach called LIMO is designed and
empirical results verify our theoretical findings.
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We investigate soliton collisions a one-parameter family of scalar field
theories in 1+1 dimensions which was first discussed by Christ and Lee. The
models have a sextic potential with three local minima, and for suitably small
values of the parameter its kinks have an internal structure in the form of two
weakly-bound subkinks. We show that for these values of the parameter kink
collisions are best understood as an independent sequence of collisions of
these subkinks, and that a static mode analysis is not enough to explain
resonant structures emerging in this model. We also emphasise the role of
radiation and oscillon formation in the collision process.
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We collect a number of striking recent results in a study of dimers on
infinite regular bipartite lattices and also on regular bipartite graphs. We
clearly separate rigorously proven results from conjectures. A primary goal is
to show people: here is a field which is ripe for further interesting research.
We separate four classes of endeavor, of which we here extract two items to
whet one's appetite. Primo,for hyper-rectangular lattices of every dimension
the first 20 virial coefficients are positive. (One has no understanding of
this yet!) Secondo, all regular bipartite graphs with less than $14$ vertices
satisfy graph positivity, defined below. (Here there is some understanding.)
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This paper considers an unsignalized intersection used by two traffic
streams. A stream of cars is using a primary road, and has priority over the
other stream. Cars belonging to the latter stream cross the primary road if the
gaps between two subsequent cars on the primary road are larger than their
critical headways. A question that naturally arises relates to the capacity of
the secondary road: given the arrival pattern of cars on the primary road, what
is the maximum arrival rate of low-priority cars that can be sustained? This
paper addresses this issue by considering a compact model that sheds light on
the dynamics of the considered unsignalized intersection. The model, which is
of a queueing-theoretic nature, reveals interesting insights into the impact of
the user behavior on stability.
The contributions of this paper are threefold. First, we obtain new results
for the aforementioned model that includes driver impatience. Secondly, we
reveal some surprising aspects that have remained unobserved in the existing
literature so far, many of which are caused by the fact that the capacity of
the minor road cannot be expressed in terms of the \emph{mean} gap size;
instead more detailed characteristics of the critical headway distribution play
a crucial role. The third contribution is the introduction of a new form of
bunching on the main road, called Markov platooning. The tractability of this
model allows us to study the impact of various platoon formations on the main
road on the capacity of the minor road.
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In this paper, we consider an online distributed composite optimization
problem over a time-varying multi-agent network that consists of multiple
interacting nodes, where the objective function of each node consists of two
parts: a loss function that changes over time and a regularization function.
This problem naturally arises in many real-world applications ranging from
wireless sensor networks to signal processing. We propose a class of online
distributed optimization algorithms that are based on approximate mirror
descent, which utilize the Bregman divergence as distance-measuring function
that includes the Euclidean distances as a special case. We consider two
standard information feedback models when designing the algorithms, that is,
full-information feedback and bandit feedback. For the full-information
feedback model, the first algorithm attains an average regularized regret of
order $\mathcal{O}(1/\sqrt{T})$ with the total number of rounds $T$. The second
algorithm, which only requires the information of the values of the loss
function at two predicted points instead of the gradient information, achieves
the same average regularized regret as that of the first algorithm. Simulation
results of a distributed online regularized linear regression problem are
provided to illustrate the performance of the proposed algorithms.
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A study of the relation between the electrostatic charge density at a point
on a conducting surface and the curvature of the surface (at that point) is
presented. Two major scientific literature on this topic are reviewed and the
apparent discrepancy between them is resolved. Hence, a step is taken towards
obtaining a general analytic formula for relating the charge density with
surface curvature of conductors. The merit of this formula and its limitations
are discussed.
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The charge density wave phase transition of 1T-TiSe2 is studied by
angle-resolved photoemission over a wide temperature range. An important
chemical potential shift which strongly evolves with temperature is evidenced.
In the framework of the exciton condensate phase, the detailed temperature
dependence of the associated order parameter is extracted. Having a
mean-field-like behaviour at low temperature, it exhibits a non-zero value
above the transition, interpreted as the signature of strong excitonic
fluctuations, reminiscent of the pseudo-gap phase of high temperature
superconductors. Integrated intensity around the Fermi level is found to
display a trend similar to the measured resistivity and is discussed within the
model.
|
Coherent superposition is a key feature of quantum mechanics that underlies
the advantage of quantum technologies over their classical counterparts.
Recently, coherence has been recast as a resource theory in an attempt to
identify and quantify it in an operationally well-defined manner. Here we study
how the coherence present in a state can be used to implement a quantum channel
via incoherent operations and, in turn, to assess its degree of coherence. We
introduce the robustness of coherence of a quantum channel---which reduces to
the homonymous measure for states when computed on constant-output
channels---and prove that: i) it quantifies the minimal rank of a maximally
coherent state required to implement the channel; ii) its logarithm quantifies
the amortized cost of implementing the channel provided some coherence is
recovered at the output; iii) its logarithm also quantifies the zero-error
asymptotic cost of implementation of many independent copies of a channel. We
also consider the generalized problem of imperfect implementation with
arbitrary resource states. Using the robustness of coherence, we find that in
general a quantum channel can be implemented without employing a maximally
coherent resource state. In fact, we prove that \textit{every} pure coherent
state in dimension larger than $2$, however weakly so, turns out to be a
valuable resource to implement \textit{some} coherent unitary channel. We
illustrate our findings for the case of single-qubit unitary channels.
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We characterize a semiconductor external cavity diode laser whose optical
feedback is provided by a guided mode resonance filter (GMRF). We focus on the
spectral properties. The wavelength of operation falls in the telecom range
(1506 nm). The GMRF acting both as a wavelength intracavity filter and feedback
mirror allows for a compact laser design. The single-mode operation is verified
in a wide range of driving currents. We finely tune the cavity length to adjust
the frequency by 14 GHz without mode-hops in agreement with the expected
free-spectral range of the resonator $\sim$20 GHz. The compactness of the
cavity allows fast frequency sweeps when modulating the current (90 MHz/mA at
100 kHz, the modulation bandwidth). The frequency noise (366 kHz white-noise
contribution) is also analysed to evaluate the potential of our design for
high-resolution applications.
|
We revisit the Lichnerowicz-York method, and an alternative method of York,
in order to obtain some conformally covariant systems. This type of
parameterization is certainly more natural for non constant mean curvature
initial data.
|
We review origins and main properties of the most important bracket
operations appearing canonically in differential geometry and mathematical
physics in the classical, as well as the supergeometric setting. The review is
supplemented by a few new concepts and examples.
|
We address the stability of superfluid currents in a system of interacting
lattice bosons. We consider various Gutzwiller trial states for the quantum
phase model which provides a good approximation for the Bose-Hubbard model in
the limit of large interactions and boson populations. We thoroughly analyze
the current-carrying stationary states of the dynamics ensuing from a Gaussian
ansatz, and derive analytical results for the critical lines signaling their
modulational and energetic instability, as well as the maximum of the carried
current. We show that these analytical results are in good qualitative
agreement with those obtained numerically in previous works on the Bose-Hubbard
model, and in the present work for the quantum phase model.
|
Isochronous mass spectrometry (IMS) in storage rings is a successful
technique for accurate mass measurements of short-lived nuclides with relative
precision of about $10^{-5}-10^{-7}$. Instabilities of the magnetic fields in
storage rings are one of the major contributions limiting the achievable mass
resolving power, which is directly related to the precision of the obtained
mass values. A new data analysis method is proposed allowing one to minimise
the effect of such instabilities. The masses of the previously measured at the
CSRe $^{41}$Ti, $^{43}$V, $^{47}$Mn, $^{49}$Fe, $^{53}$Ni and $^{55}$Cu
nuclides were re-determined with this method. An improvement of the mass
precision by a factor of $\sim 1.7$ has been achieved for $^{41}$Ti and
$^{43}$V. The method can be applied to any isochronous mass experiment
irrespective of the accelerator facility. Furthermore, the method can be used
as an on-line tool for checking the isochronous conditions of the storage ring.
|
In the framework of a Skyrme-Hartree-Fock approach combined with BCS method,
the role of the tensor force on the pseudospin energy splitting for tin isotope
chain is investigated. The tensor force turns out to obviously affect the
pseudospin energy splitting of the spin-unsaturated nuclei. Since the tensor
force shifts the single-particle levels, it modifies the single-particle level
density and the shell correction energy thereof. The influence of the tensor
interaction on shell correction energy is considerable according to our
analysis taking a magic nucleus $^{132}$Sn as well as a superheavy nucleus
$^{298}114$ as examples. This modification of the shell correction energy due
to the tensor component affects the stability of the superheavy nuclei.
|
We calculated the effects of spin-orbit interaction (SOI) on the energy
bands, ballistic conductance and the electron-diffusion thermoelectric power of
a nanowire by varying the temperature, electron density and width of the wire.
The potential barriers at the edges of the wire are assumed to be very high. A
consequence of the boundary conditions used in this model is determined by the
energy band structure, resulting in wider plateaus when the electron density is
increased due to larger energy-level separation as the higher subbands are
occupied by electrons. The nonlinear dependence of the transverse confinement
on position with respect to the well center excludes the "pole-like feature" in
the conductance which is obtained when a harmonic potential is employed for
confinement. At low temperature, the electron diffusion thermoelectric power
increases linearly with T but deviates from the linear behavior for large
values of T.
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Suppose L is any finite algebraic extension of either the ordinary rational
numbers or the p-adic rational numbers. Also let g_1,...,g_k be polynomials in
n variables, with coefficients in L, such that the total number of monomial
terms appearing in at least one g_i is exactly m. We prove that the maximum
number of isolated roots of G:=(g_1,...,g_k) in L^n is finite and depends
solely on (m,n,L), i.e., is independent of the degrees of the g_i. We thus
obtain an arithmetic analogue of Khovanski's Theorem on Fewnomials, extending
earlier work of Denef, Van den Dries, Lipshitz, and Lenstra.
|
We analyze the cooling of a mechanical resonator coupled to an ensemble of
interacting two-level systems via an open quantum systems approach. Using an
exact analytical result, we find optimal cooling occurs when the phonon mode is
critically coupled ($\gamma \sim g$) to the two-level system ensemble. Typical
systems operate in sub-optimal cooling regimes due to the intrinsic parameter
mismatch ($\gamma \gg g$) between the dissipative decay rate $\gamma$ and the
coupling factor $g$. To overcome this obstacle, we show that carefully
engineering the coupling parameters through the strain profile of the
mechanical resonator allows phonon cooling to proceed through the dark
(subradiant) entangled states of an \emph{interacting} ensemble, thereby
resulting in optimal phonon cooling. Our results provide a new avenue for
ground-state cooling and should be accessible for experimental demonstrations.
|
This paper addresses the problem of sparse recovery with graph constraints in
the sense that we can take additive measurements over nodes only if they induce
a connected subgraph. We provide explicit measurement constructions for several
special graphs. A general measurement construction algorithm is also proposed
and evaluated. For any given graph $G$ with $n$ nodes, we derive order optimal
upper bounds of the minimum number of measurements needed to recover any
$k$-sparse vector over $G$ ($M^G_{k,n}$). Our study suggests that $M^G_{k,n}$
may serve as a graph connectivity metric.
|
The first fully-documented study into the quantitative impact of errors in
operational spreadsheets identified an interesting anomaly. One of the five
participating organisations involved in the study contributed a set of five
spreadsheets of such quality that they set the organisation apart in a
statistical sense. This virtuoso performance gave rise to a simple sampling
test - The Clean Sheet Test - which can be used to objectively evaluate if an
organisation is in control of the spreadsheets it is using in important
processes such as financial reporting.
|
We demonstrate a nonlinear metamaterial in microwave frequency regime with
hysteresis effect and bistable states, which can be utilized as a remotely
controllable micro second switching device. A varactor loaded split-ring
resonator (SRR) design which exhibits power and frequency dependent broadband
tunability of the resonance frequency for an external control signal is used.
More importantly, the SRR shows bistability with distinct transmission levels.
The transition between bi-states is controlled by impulses of an external pump
signal. Furthermore, we experimentally demonstrate that transition rate is in
the order of microseconds by using a varactor loaded double split-ring
resonator (DSRR) design composed of two concentric rings.
|
The increase in distributed energy resources and flexible electricity
consumers has turned TSO-DSO coordination strategies into a challenging
problem. Existing decomposition/decentralized methods apply divide-and-conquer
strategies to trim down the computational burden of this complex problem, but
rely on access to proprietary information or fail-safe real-time communication
infrastructures. To overcome these drawbacks, we propose in this paper a
TSO-DSO coordination strategy that only needs a series of observations of the
nodal price and the power intake at the substations connecting the transmission
and distribution networks. Using this information, we learn the price response
of active distribution networks (DN) using a decreasing step-wise function that
can also adapt to some contextual information. The learning task can be carried
out in a computationally efficient manner and the curve it produces can be
interpreted as a market bid, thus averting the need to revise the current
operational procedures for the transmission network. Inaccuracies derived from
the learning task may lead to suboptimal decisions. However, results from a
realistic case study show that the proposed methodology yields operating
decisions very close to those obtained by a fully centralized coordination of
transmission and distribution.
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We study the eigenvalue problem for the $p$-Laplacian on K\"ahler manifolds.
Our first result is a lower bound for the first nonzero eigenvalue of the
$p$-Laplacian on compact K\"ahler manifolds in terms of dimension, diameter,
and lower bounds of holomorphic sectional curvature and orthogonal Ricci
curvature for $p\in (1, 2]$. Our second result is a sharp lower bound for the
first Dirichlet eigenvalue of the $p$-Laplacian on compact K\"ahler manifolds
with smooth boundary for $p\in (1, \infty)$. Our results generalize
corresponding results for the Laplace eigenvalues on K\"ahler manifolds proved
in [14].
|
Adaptive indexing is a concept that considers index creation in databases as
a by-product of query processing; as opposed to traditional full index creation
where the indexing effort is performed up front before answering any queries.
Adaptive indexing has received a considerable amount of attention, and several
algorithms have been proposed over the past few years; including a recent
experimental study comparing a large number of existing methods. Until now,
however, most adaptive indexing algorithms have been designed single-threaded,
yet with multi-core systems already well established, the idea of designing
parallel algorithms for adaptive indexing is very natural. In this regard only
one parallel algorithm for adaptive indexing has recently appeared in the
literature: The parallel version of standard cracking. In this paper we
describe three alternative parallel algorithms for adaptive indexing, including
a second variant of a parallel standard cracking algorithm. Additionally, we
describe a hybrid parallel sorting algorithm, and a NUMA-aware method based on
sorting. We then thoroughly compare all these algorithms experimentally; along
a variant of a recently published parallel version of radix sort. Parallel
sorting algorithms serve as a realistic baseline for multi-threaded adaptive
indexing techniques. In total we experimentally compare seven parallel
algorithms. Additionally, we extensively profile all considered algorithms. The
initial set of experiments considered in this paper indicates that our parallel
algorithms significantly improve over previously known ones. Our results
suggest that, although adaptive indexing algorithms are a good design choice in
single-threaded environments, the rules change considerably in the parallel
case. That is, in future highly-parallel environments, sorting algorithms could
be serious alternatives to adaptive indexing.
|
The Cherenkov Telescope Array is expected to lead to the detection of many
new supernova remnants in the TeV and multi-TeV range. In addition to the
individual study of each SNR, the study of these objects as a population can
help constraining the parameters describing the acceleration of particles and
increasing our understanding of the mechanisms involved. We present Monte Carlo
simulations of the population of Galactic SNRs emitting TeV gamma rays. We also
discuss how the simulated population can be confronted with future observations
to provide a novel test for the SNR hypothesis of cosmic ray origins.
|
We consider federated edge learning (FEEL) among mobile devices that harvest
the required energy from their surroundings, and share their updates with the
parameter server (PS) through a shared wireless channel. In particular, we
consider energy harvesting FL with over-the-air (OTA) aggregation, where the
participating devices perform local computations and wireless transmission only
when they have the required energy available, and transmit the local updates
simultaneously over the same channel bandwidth. In order to prevent bias among
heterogeneous devices, we utilize a weighted averaging with respect to their
latest energy arrivals and data cardinalities. We provide a convergence
analysis and carry out numerical experiments with different energy arrival
profiles, which show that even though the proposed scheme is robust against
devices with heterogeneous energy arrivals in error-free scenarios, we observe
a 5-10% performance loss in energy harvesting OTA FL.
|
Relative $t$-designs in the $n$-dimensional hypercube $\mathcal{Q}_n$ are
equivalent to weighted regular $t$-wise balanced designs, which generalize
combinatorial $t$-$(n,k,\lambda)$ designs by allowing multiple block sizes as
well as weights. Partly motivated by the recent study on tight Euclidean
$t$-designs on two concentric spheres, in this paper we discuss tight relative
$t$-designs in $\mathcal{Q}_n$ supported on two shells. We show under a mild
condition that such a relative $t$-design induces the structure of a coherent
configuration with two fibers. Moreover, from this structure we deduce that a
polynomial from the family of the Hahn hypergeometric orthogonal polynomials
must have only integral simple zeros. The Terwilliger algebra is the main tool
to establish these results. By explicitly evaluating the behavior of the zeros
of the Hahn polynomials when they degenerate to the Hermite polynomials under
an appropriate limit process, we prove a theorem which gives a partial evidence
that the non-trivial tight relative $t$-designs in $\mathcal{Q}_n$ supported on
two shells are rare for large $t$.
|
The ages and masses of neutron stars (NSs) are two fundamental threads that
make pulsars accessible to other sub-disciplines of astronomy and physics. A
realistic and accurate determination of these two derived parameters play an
important role in understanding of advanced stages of stellar evolution and the
physics that govern relevant processes. Here I summarize new constraints on the
ages and masses of NSs with an evolutionary perspective. I show that the
observed P-Pdot demographics is more diverse than what is theoretically
predicted for the standard evolutionary channel. In particular, standard
recycling followed by dipole spin-down fails to reproduce the population of
millisecond pulsars with higher magnetic fields (B > 4 x 10^{8} G) at rates
deduced from observations. A proper inclusion of constraints arising from
binary evolution and mass accretion offers a more realistic insight into the
age distribution. By analytically implementing these constraints, I propose a
"modified" spin-down age for millisecond pulsars that gives estimates closer to
the true age. Finally, I independently analyze the peak, skewness and cutoff
values of the underlying mass distribution from a comprehensive list of radio
pulsars for which secure mass measurements are available. The inferred mass
distribution shows clear peaks at 1.35 Msun and 1.50 Msun for NSs in double
neutron star (DNS) and neutron star-white dwarf (NS-WD) systems respectively. I
find a mass cutoff at 2 Msun for NSs with WD companions, which establishes a
firm lower bound for the maximum mass of NSs.
|
In 2009, the BESIII experiment has collected about 225M $\jpsi$ and 106M
$\psip$ samples, both of which are the world largest on-peak charmonium
production. Based on these dataset, BESIII has made great effort on the study
of the charmonium decays, some important of which have been reviewed in this
proceeding. In addition, a searching for new physics through the $CP/P$
violation process is reported.
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The three-dimensional structures of individual trees are important pieces of
information necessary to understand the effect of trees on urban environments.
In this study, we demonstrate a method for estimating the leaf area density
(LAD) distribution of individual trees using high-resolution airborne LiDAR.
This method improves upon the previously proposed method, which calculates LAD
based on the contact frequency between the laser beams and leaves by tracing
the paths of the laser beams. The proposed method in this study exploits the
last and intermediate pulses in addition to the first and single pulses to
capture the foliage distribution in the inner part of the crown. Each laser
beam is traced from a point derived by the last pulse to the point derived by
the first or intermediate pulse that is recorded immediately before the last
pulse. The laser beam interceptions and intersections can thus be accurately
reproduced while considering the last and intermediate pulses. We verify the
estimation accuracy of the three-dimensional LAD distribution using terrestrial
LiDAR data from a single tree (Z. serrata). The appropriate voxel size for
representing the LAD distribution from the airborne LiDAR is first determined
by comparing the distribution of voxels containing one or more airborne LiDAR
points with that containing one or more terrestrial LiDAR points. The estimated
LAD distribution with a voxel size of 1 m by 1 m by 0.5 m is subsequently
compared to the terrestrial LiDAR-derived LAD distribution. When only the first
and single pulses are used, the LAD is overestimated and underestimated in the
upper and lower part of the crown, respectively. We confirmed that using the
last and intermediate pulses improves the estimation accuracy of the entire
crown area.
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Quantum Computing promises accelerated simulation of certain classes of
problems, in particular in plasma physics. Given the nascent interest in
applying quantum computing techniques to study plasma systems, a compendium of
the relevant literature would be most useful. As a novel field, new results are
common, and it is important for researchers to stay up-to-date on the latest
developments. With this in mind, the goal of this document is to provide a
regularly up-to-date and thorough list of citations for those developing and
applying these quantum computing approaches to experimental or theoretical work
in plasma physics. As a living document, it will be updated as often as
possible to incorporate the latest developments. References are grouped by
topic, both in itemized format and through the use of tags. We provide
instructions on how to participate, and suggestions are welcome.
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Covering from photography to depth and spectral estimation, diverse
computational imaging (CI) applications benefit from the versatile modulation
of coded apertures (CAs). The light wave fields as space, time, or spectral can
be modulated to obtain projected encoded information at the sensor that is then
decoded by efficient methods, such as the modern deep learning decoders.
Despite the CA can be fabricated to produce an analog modulation, a binary CA
is mostly preferred since easier calibration, higher speed, and lower storage
are achieved. As the performance of the decoder mainly depends on the structure
of the CA, several works optimize the CA ensembles by customizing regularizers
for a particular application without considering critical physical constraints
of the CAs. This work presents an end-to-end (E2E) deep learning-based
optimization of CAs for CI tasks. The CA design method aims to cover a wide
range of CI problems easily changing the loss function of the deep approach.
The designed loss function includes regularizers to fulfill the widely used
sensing requirements of the CI applications. Mainly, the regularizers can be
selected to optimize the transmittance, the compression ratio, and the
correlation between measurements, while a binary CA solution is encouraged, and
the performance of the CI task is maximized in applications such as
restoration, classification, and semantic segmentation.
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The mechanisms and properties of synchronization of oscillating ecological
populations attract attention because it is a fairly common phenomenon and
because spatial synchrony may elevate a risk of extinction and may lead to
other environmental impacts. Conditions for stable synchronization in a system
of linearly coupled predator-prey oscillators have been considered in the past.
However, the spatial dispersion coupling may be relatively weak and may not
necessarily lead to a stable, complete synchrony. If the coupling between
oscillators is too weak to induce a stable synchrony, oscillators may be
engaged into intermittent synchrony, when episodes of synchronized dynamics are
interspersed with the episodes of desynchronized dynamics. In the present study
we consider the temporal patterning of this kind of intermittent synchronized
dynamics in a system of two dispersal-coupled Rosenzweig-MacArthur
predator-prey oscillators. We consider the properties of the distributions of
durations of desynchronized intervals and their dependence on the model
parameters. We show that the temporal patterning of synchronous dynamics (an
ecological network phenomenon) may depend on the properties of individual
predator-prey patch (individual oscillator) and may vary independently of the
strength of dispersal. We also show that if the dynamics of predator is slow
relative to the dynamics of the prey (a situation that may promote brief but
large outbreaks), dispersal-coupled predator-prey oscillating populations
exhibit numerous short desynchronizations (as opposed to few long
desynchronizations) and may require weaker dispersal in order to reach strong
synchrony.
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The Z Cam stars IW And and V513 Cas are unusual in having outbursts following
their standstills in contrast to the usual Z Cam behavior of quiescence
following standstills. In order to gain further understanding of these
little-studied systems, we obtained spectra correlated with photometry from the
AAVSO throughout a 3-4 month interval in 2011. In addition, time-resolved
spectra were obtained in 2012 that provided orbital periods of 3.7 hrs for IW
And and 5.2 hrs for V513 Cas. The photometry of V513 Cas revealed a regular
pattern of standstills and outbursts with little time at quiescence, while IW
And underwent many excursions from quiescence to outburst to short standstills.
The spectra of IW And are similar to normal dwarf novae, with strong Balmer
emission at quiescence and absorption at outburst. In contrast, V513 Cas shows
a much flatter/redder spectrum near outburst with strong HeII emission and
prominent emission cores in the Balmer lines. Part of this continuum difference
may be due to reddening effects. While our attempts to model the outburst and
standstill states of IW And indicate a mass accretion rate near 3E-9 solar
masses per year, we could find no obvious reason why these systems behave
differently following standstill compared to normal Z Cam stars.
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This paper aims to quantitatively explain rationales of each prediction that
is made by a pre-trained convolutional neural network (CNN). We propose to
learn a decision tree, which clarifies the specific reason for each prediction
made by the CNN at the semantic level. I.e., the decision tree decomposes
feature representations in high conv-layers of the CNN into elementary concepts
of object parts. In this way, the decision tree tells people which object parts
activate which filters for the prediction and how much they contribute to the
prediction score. Such semantic and quantitative explanations for CNN
predictions have specific values beyond the traditional pixel-level analysis of
CNNs. More specifically, our method mines all potential decision modes of the
CNN, where each mode represents a common case of how the CNN uses object parts
for prediction. The decision tree organizes all potential decision modes in a
coarse-to-fine manner to explain CNN predictions at different fine-grained
levels. Experiments have demonstrated the effectiveness of the proposed method.
|
We report Molecular Dynamics (MD) simulations of a generic hydrophobic
nanopore connecting two reservoirs which are initially at different Na+
concentrations, as in a biological cell. The nanopore is impermeable to water
under equilibrium conditions, but the strong electric field caused by the ionic
concentration gradient drives water molecules in. The density and structure of
water in the pore are highly field dependent. In a typical simulation run, we
observe a succession of cation passages through the pore, characterized by
approximately bulk mobility. These ion passages reduce the electric field,
until the pore empties of water and closes to further ion transport, thus
providing a possible mechanism for biological ion channel gating.
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We study the equational theory of the Weihrauch lattice with multiplication,
meaning the collection of equations between terms built from variables, the
lattice operations $\sqcup$, $\sqcap$, the product $\times$, and the finite
parallelization $(-)^*$ which are true however we substitute Weihrauch degrees
for the variables. We provide a combinatorial description of these in terms of
a reducibility between finite graphs, and moreover, show that deciding which
equations are true in this sense is complete for the third level of the
polynomial hierarchy.
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The gravitational production of superheavy dark matter, in the
Peebles-Vilenkin quintessential inflation model, is studied in two different
scenarios: When the particles, whose decay products reheat the universe after
the end of the inflationary period, are created gravitationally, and when are
produced via instant preheating. We show that the viability of both scenarios
requires that the mass of the superheavy dark matter to be approximately
between 10^{16} and 10^{17} GeV.
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Solar flares are some of the most energetic events in the solar system and
can be studied to investigate the physics of plasmas and stellar processes. One
interesting aspect of solar flares is the presence of accelerated (nonthermal)
particles, whose signatures appear in solar flare hard X-ray emissions. Debate
has been ongoing since the early days of the space age as to how these
particles are accelerated, and one way to probe relevant acceleration
mechanisms is by investigating short-timescale (tens of milliseconds)
variations in solar flare hard X-ray flux. The Impulsive Phase Rapid Energetic
Solar Spectrometer (IMPRESS) CubeSat mission aims to measure these fast hard
X-ray variations. In order to produce the best possible science data from this
mission, we characterize the IMPRESS scintillator detectors using Geant4 Monte
Carlo models. We show that the Geant4 Monte Carlo detector model is consistent
with an analytical model. We find that Geant4 simulations of X-ray and optical
interactions explain observed features in experimental data, but do not
completely account for our measured energy resolution. We further show that
nonuniform light collection leads to double-peak behavior at the 662 keV
$^{137}$Cs photopeak and can be corrected in Geant4 models and likely in the
lab.
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Computing in-memory (CiM) has emerged as an attractive technique to mitigate
the von-Neumann bottleneck. Current digital CiM approaches for in-memory
operands are based on multi-wordline assertion for computing bit-wise Boolean
functions and arithmetic functions such as addition. However, most of these
techniques, due to the many-to-one mapping of input vectors to bitline
voltages, are limited to CiM of commutative functions, leaving out an important
class of computations such as subtraction. In this paper, we propose a CiM
approach, which solves the mapping problem through an asymmetric wordline
biasing scheme, enabling (a) simultaneous single-cycle memory read and CiM of
primitive Boolean functions (b) computation of any Boolean function and (c) CiM
of non-commutative functions such as subtraction and comparison. While the
proposed technique is technology-agnostic, we show its utility for
ferroelectric transistor (FeFET)-based non-volatile memory. Compared to the
standard near-memory methods (which require two full memory accesses per
operation), we show that our method can achieve a full scale two-operand
digital CiM using just one memory access, leading to a 23.2% - 72.6% decrease
in energy-delay product (EDP).
|
The proliferation of social media platforms has fueled the rapid
dissemination of fake news, posing threats to our real-life society. Existing
methods use multimodal data or contextual information to enhance the detection
of fake news by analyzing news content and/or its social context. However,
these methods often overlook essential textual news content (articles) and
heavily rely on sequential modeling and global attention to extract semantic
information. These existing methods fail to handle the complex, subtle twists
in news articles, such as syntax-semantics mismatches and prior biases, leading
to lower performance and potential failure when modalities or social context
are missing. To bridge these significant gaps, we propose a novel multi-hop
syntax aware fake news detection (MSynFD) method, which incorporates
complementary syntax information to deal with subtle twists in fake news.
Specifically, we introduce a syntactical dependency graph and design a
multi-hop subgraph aggregation mechanism to capture multi-hop syntax. It
extends the effect of word perception, leading to effective noise filtering and
adjacent relation enhancement. Subsequently, a sequential relative
position-aware Transformer is designed to capture the sequential information,
together with an elaborate keyword debiasing module to mitigate the prior bias.
Extensive experimental results on two public benchmark datasets verify the
effectiveness and superior performance of our proposed MSynFD over
state-of-the-art detection models.
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In this paper, we prove a theorem on the rate of convergence for the optimal
cost computed using PS methods. It is a first proved convergence rate in the
literature of PS optimal control. In addition to the high-order convergence
rate, two theorems are proved for the existence and convergence of the
approximate solutions. This paper contains several essential differences from
existing papers on PS optimal control as well as some other direct
computational methods. The proofs do not use necessary conditions of optimal
control. Furthermore, we do not make coercivity type of assumptions. As a
result, the theory does not require the local uniqueness of optimal solutions.
In addition, a restrictive assumption on the cluster points of discrete
solutions made in existing convergence theorems are removed.
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We obtain existence, uniqueness, and stability results for the modified
1-homogeneous infinity Laplace equation \[ -\Delta_\infty u - \beta |Du| = f,
\] subject to Dirichlet or mixed Dirichlet-Neumann boundary conditions. Our
arguments rely on comparing solutions of the PDE to subsolutions and
supersolutions of a certain finite difference approximation.
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Pseudo-Goldstone bosons in 4D strongly coupled theories have a dual
description in terms of 5D gauge theories in warped backgrounds. We introduce
systematic methods of computing the pseudo-Goldstone potential for an arbitrary
warp factor in 5D. When applied to electroweak symmetry breaking, our approach
clarifies the relation of physical observables to geometrical quantities in
five dimensions.
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In this paper we determine the radius of convexity for three kind of
normalized Bessel functions of the first kind. In the mentioned cases the
normalized Bessel functions are starlike-univalent and convex-univalent,
respectively, on the determined disks. The key tools in the proofs of the main
results are some new Mittag-Leffler expansions for quotients of Bessel
functions of the first kind, special properties of the zeros of Bessel
functions of the first kind and their derivative, and the fact that the
smallest positive zeros of some Dini functions are less than the first positive
zero of the Bessel function of the first kind. Moreover, we find the optimal
parameters for which these normalized Bessel functions are convex in the open
unit disk. In addition, we disprove a conjecture of Baricz and Ponnusamy
concerning the convexity of the Bessel function of the first kind.
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Persistent homology and persistent entropy have recently become useful tools
for patter recognition. In this paper, we find requirements under which
persistent entropy is stable to small perturbations in the input data and scale
invariant. In addition, we describe two new stable summary functions combining
persistent entropy and the Betti curve. Finally, we use the previously defined
summary functions in a material classification task to show their usefulness in
machine learning and pattern recognition.
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I discuss some theoretical aspects of how to observe leptonic CP violation.
It is divided into two parts, one for CP violation due to Majorana, and the
other more conventional leptonic Kobayashi-Maskawa (KM) phases. In the first
part, I estimate the effect of Majorana phase to observable of neutrinoless
double beta decay experiments by paying a careful attention to the definition
of the atmospheric scale Delta m^2. In the second part, I discuss
Tokai-to-Kamioka-Korea two detector complex which receives neutrino superbeam
from J-PARC as a concrete setting for discovering CP violation due to the KM
phase, as well as resolving mass hierarchy and the theta_{23} octant
degeneracy. A cautionary remark is also given on comparison between various
projects aiming at exploring CP violation and the mass hierarchy.
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Automated Program Repair (APR) is defined as the process of fixing a
bug/defect in the source code, by an automated tool. APR tools have recently
experienced promising results by leveraging state-of-the-art Neural Language
Processing (NLP) techniques. APR tools such as TFix and CodeXGLUE combine
text-to-text transformers with software-specific techniques are outperforming
alternatives, these days. However, in most APR studies the train and test sets
are chosen from the same set of projects. In reality, however, APR models are
meant to be generalizable to new and different projects. Therefore, there is a
potential threat that reported APR models with high effectiveness perform
poorly when the characteristics of the new project or its bugs are different
than the training set's(Domain Shift).
In this study, we first define and measure the domain shift problem in
automated program repair. Then, we then propose a domain adaptation framework
that can adapt an APR model for a given target project. We conduct an empirical
study with three domain adaptation methods FullFineTuning,
TuningWithLightWeightAdapterLayers, and CurriculumLearning using two
state-of-the-art domain adaptation tools (TFix and CodeXGLUE) and two APR
models on 611 bugs from 19 projects. The results show that our proposed
framework can improve the effectiveness of TFix by 13.05% and CodeXGLUE by
23.4%. Another contribution of this study is the proposal of a data synthesis
method to address the lack of labelled data in APR. We leverage transformers to
create a bug generator model. We use the generated synthetic data to domain
adapt TFix and CodeXGLUE on the projects with no data (Zero-shot learning),
which results in an average improvement of 5.76% and 24.42% for TFix and
CodeXGLUE, respectively.
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We investigated the representation thoery of an Ariki-Koike algebra whose
Poincare polynomial associated with the "bottom", i.e., the subgroup on which
the symmetric group acts, is non-zero in the base field. We proved that the
module category of such an Ariki-Koike algebra is Morita equivalent to the
module category of a direct sum of tensor products of Hecke algebras associated
with certain symmetric groups. We also generalized this Morita equivalence
theorem to give a Morita equivalenve between a $q$-Schur$^m$ algebra and a
direct sum of tensor products of certain $q$-Schur algebras.
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Short pulse lasers are used to characterize the nonlinear response of
amplified photodetectors. Two widely used balanced detectors are characterized
in terms of amplitude, area, broadening, and balancing the mismatch of their
impulse response. The dynamic impact of pulses on the detector is also
discussed. It is demonstrated that using photodetectors with short pulses
triggers nonlinearities even when the source average power is well below the
detector continuous power saturation threshold.
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We investigate the lifetime of macroscopic entanglement under the influence
of decoherence. For GHZ-type superposition states we find that the lifetime
decreases with the size of the system (i.e. the number of independent degrees
of freedom) and the effective number of subsystems that remain entangled
decreases with time. For a class of other states (e.g. cluster states),
however, we show that the lifetime of entanglement is independent of the size
of the system.
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Electronic structure across the metal-insulator (MI) transition of
electron-doped V1-xWxO2 epitaxial films (x = 0-0.06) grown on alfa-Al2O3
substrates was studied by means of thermopower (S) measurements. Significant
increase of |S|-values accompanied by MI transition was observed, and the
transition temperatures of S (TS) decreased with x in good linear relation with
MI transition temperatures. |S| values of V1-xWxO2 films at T > TS were
constant at low values of 23 microV K-1 independently of x, which reflects a
metallic electronic structure, whereas, those at T < TS almost linearly
decreased with logarithmic W-concentrations. The gradient of -213 microV K-1
agrees well with -kB/e*ln10 (-198 microV K-1), suggesting that V1-xWxO2 films
have insulating electronic structures with a parabolic density of state around
the conduction band bottom.
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It is shown that the internal stationary state of the Schwarzschild black
hole can be represented by a maximally entangled two-mode squeezed state of
collapsing matter and infalling Hawking radiation. The final boundary condition
at the singularity is then described by the random unitary transformation
acting on the collapsing matter field. The outgoing Hawking radiation is
obtained by the final state projection on the total wave function, which looks
like a quantum teleportation process without the classical information
transmitted. The black hole evaporation process as seen by the observer outside
the black hole is now a unitary process but non-local physics is required to
transmit the information outside the black hole. It is also shown that the
final state projection by the evaporation process is strongly affected by the
quantum state outside the event horizon, which clearly violates the locality
principle.
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The relative partition function and the relative zeta function of the
perturbation of the Laplace operator by a Coulomb potential plus a point
interaction centered in the origin is discussed. Applications to the study of
the Casimir effect are indicated.
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We present here a relationship among massive self-dual models for spin-3
particles in $D=2+1$ via the master action procedure. Starting with a first
order model (in derivatives) $S_{SD(1)}$ we have constructed a master action
which interpolates among a sequence of four self-dual models $S_{SD(i)}$ where
$i=1,2,3,4$. By analyzing the particle content of mixing terms, we give
additional arguments that explain why it is apparently impossible to jump from
the fourth order model to a higher order model. We have also analyzed
similarities and differences between the fourth order $K$-term in the spin-2
case and the analogous fourth order term in the spin-3 context.
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Several aspects of classical and quantum mechanics applied to a class of
strongly chaotic systems are studied. These consist of single particles moving
without external forces on surfaces of constant negative Gaussian curvature
whose corresponding fundamental groups are supplied with an arithmetic
structure. It is shown that the arithmetic features of the considered systems
lead to exceptional properties of the corresponding spectra of lengths of
periodic orbits. The most significant one is an exponential growth of
degeneracies in these length spectra. Furthermore, the arithmetical systems are
distinguished by a structure that appears as a generalization of geometric
symmetries. These pseudosymmetries occur in the quantization of the classical
arithmetic systems as Hecke operators, which form an infinite algebra of
self-adjoint operators commuting with the Hamiltonian. The statistical
properties of quantum energies in the arithmetical have previously been
identified as exceptional. They do not fit into the general scheme of random
matrix theory. It is shown with the help of a simplified model for the spectral
form factor how the spectral statistics in arithmetic quantum chaos can be
understood by the properties of the corresponding classical length spectra. A
decisive is played by the exponentially increasing multiplicities of lengths.
The model developed for the level spacings distribution and for the number
variance is compared to the corresponding quantities obtained from quantum
energies for a specific arithmetical system.
|
We obtain Margulis-type asymptotic estimates for the number of free homotopy
classes of closed geodesics on certain manifolds without conjugate points. Our
results cover all compact surfaces of genus at least 2 without conjugate
points.
|
Production of strange quarks in neutron stars is investigated in this work.
Three cases, one in which the energy and neutrinos produced in the strangeness
production reactions are retained in the reaction region, second in which the
neutrinos are allowed to escape the reaction region but the energy is retained
and the third in which both the energy and neutrinos escape the reaction region
are considered. It is shown that the nonleptonic weak process dominates strange
quark production while semileptonic weak processes, which produce neutrinos,
lead to the cooling if the neutrinos escape the reaction region. It is found
that the time required for the saturation of the strangeness fraction is
between $10^{-7}$ and $10^{-5}$ sec, with the shorter time corresponding to the
first two cases. About 0.2 neutrinos/baryon are emitted during the process in
the first two cases where as the neutrino emission is somewhat suppressed in
the last case. The average energy of the neutrinos produced in all the three
cases is found to be several hundred $MeV$. We also find that a large amount of
energy is released during the strangeness production in the first two cases and
this leads to the heating of the reaction region. Implications of the neutrino
production are investigated.
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In this dissertation we study the coefficients spaces (SAYD modules) of
Hopf-cyclic cohomology theory over a certain family of bicrossed product Hopf
algebras, and we compute the Hopf-cyclic cohomology of such Hopf algebras with
coefficients. We associate a Hopf algebra, what we call a Lie-Hopf algebra, to
any matched pair of Lie groups, Lie algebras and affine algebraic groups via
the semi-dualization procedure of Majid. We then identify the SAYD modules over
Lie-Hopf algebras with the representations and corepresentations of the total
Lie group, Lie algebra or the affine algebraic group of the matched pair. First
we classify the SAYD modules that correspond only to the representations of a
total Lie group (algebra). We call them induced SAYD modules. We then
generalize this identification, focusing on the matched pair of Lie algebras.
We establish a one-to-one correspondence between the SAYD modules over the
Lie-Hopf algebra associated to a matched pair of Lie algebras and certain SAYD
modules over the total Lie algebra. Once the SAYD modules are associated to the
representations and the corepresentations of Lie algebras, nontrivial examples
can be constructed. This way, we illustrate a highly nontrivial 4-dimensional
SAYD module over the Schwarzian Hopf algebra H_{1S}. In addition, we discuss
the periodic cyclic cohomology of Lie-Hopf algebras with nontrivial SAYD
coefficients. We obtain a general van Est isomorphism identifying the periodic
cyclic cohomology of a Lie-Hopf algebra with the (relative) Lie algebra
cohomology of the corresponding total Lie algebra.
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Blue noise error patterns are well suited to human perception, and when
applied to stochastic rendering techniques, blue noise masks (blue noise
textures) minimize unwanted low-frequency noise in the final image. Current
methods of applying blue noise masks at each frame independently produce white
noise frequency spectra temporally. This white noise results in slower
integration convergence over time and unstable results when filtered
temporally. Unfortunately, achieving temporally stable blue noise distributions
is non-trivial since 3D blue noise does not exhibit the desired 2D blue noise
properties, and alternative approaches degrade the spatial blue noise
qualities.
We propose novel blue noise patterns that, when animated, produce values at a
pixel that are well distributed over time, converge rapidly for Monte Carlo
integration, and are more stable under TAA, while still retaining spatial blue
noise properties. To do so, we propose an extension to the well-known void and
cluster algorithm that reformulates the underlying energy function to produce
spatiotemporal blue noise masks.
These masks exhibit blue noise frequency spectra in both the spatial and
temporal domains, resulting in visually pleasing error patterns, rapid
convergence speeds, and increased stability when filtered temporally. We
demonstrate these improvements on a variety of applications, including
dithering, stochastic transparency, ambient occlusion, and volumetric
rendering.
By extending spatial blue noise to spatiotemporal blue noise, we overcome the
convergence limitations of prior blue noise works, enabling new applications
for blue noise distributions.
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The established microalgae growth models are semi-empirical or considerable
fitting coefficients exist currently. Therefore, the ability of the model
prediction is reduced by the numerous fitting coefficients. Furthermore, the
predicted results of the established models are dependent on the size of the
photobioreactor (PBR), light intensity, flow and concentration field. The
growth mechanism of microalgae has not clearly understood in PBR cultivation.
It is difficult to predict the microalgae growth by theoretical methods, owing
to the aforementioned factors. We developed an exploratory bridging microalgae
growth model to predict the microalgae growth rate in PBRs by using the
nondimensional method which is effectively in fluid dynamics and heat transfer.
The analytical solution of the growth rate was obtained for the parallel flow.
The nondimensional growth rate expressed as function of Reynolds number and
Schmidt number, which can be used for arbitrary parallel flow due to the
solution was expressed as nondimensional quantities. The theoretically
predicted growth rate is compared with the experimentally measured microalgae
growth rate on the order of magnitude. The nondimensional method successfully
applied to the microalgae growth problem for the first time. The general
nondimensional solution can unify the numerous experimental data for different
laboratory conditions, and give a direction for the disorder of the microalgae
growth problem. The nondimensional solution may be useful to explain the growth
mechanism of microalgae and design large-scale PBRs for microalgae biofuel
production. The significance of the work is to give a theoretical foundation
and methodology of biological theory of microalgae growth.
|
As Clouds are complex, large-scale, and heterogeneous distributed systems,
management of their resources is a challenging task. They need automated and
integrated intelligent strategies for provisioning of resources to offer
services that are secure, reliable, and cost-efficient. Hence, effective
management of services becomes fundamental in software platforms that
constitute the fabric of computing Clouds. In this direction, this paper
identifies open issues in autonomic resource provisioning and presents
innovative management techniques for supporting SaaS applications hosted on
Clouds. We present a conceptual architecture and early results evidencing the
benefits of autonomic management of Clouds.
|
In a Palatini $f(\mathcal{R})$-model, we define chonodynamical effects due to
the choice of atomic clocks as standard reference clocks and we develop a
formalism able to quantitatively separate them from the usual effective dark
sources one has in extended theories. We apply the formalism to Hubble drift
and briefly discuss the issue about the physical frame. In particular, we argue
that there is no physical frame in the sense one does different things in
different frames and that, in a sense, is the physical characteristic of
extended gravity. As an example, we discuss how Jordan frame may be well suited
to discuss cosmology, though it fails within the solar system.
|
The relations between quantum coherence and quantum interference are
discussed. A general method for generation of quantum coherence through
interference-induced state selection is introduced and then applied to `simple'
atomic systems under two-photon transitions, with applications in quantum
optics and laser cooling.
|
In this paper we develop some new variational principles for the exit time of
non-symmetric diffusions from a domain. As applications, we give some
comparison theorems and monotonicity law between different diffusions.
|
Flow signatures in experimental data from relativistic ion collisions are
usually interpreted as a fingerprint of the presence of a hydrodynamic phase
during the evolution of these systems. In this work, flow signatures arising
from event-by-event viscous hydrodynamics are compared to those arising from
event-by-event non-interacting particle dynamics (free-streaming), both
followed by a late-stage hadronic cascade, in d+Au, 3He+Au at sqrt(s)=200 GeV
and p+Pb collisions at sqrt(s)=5 TeV, respectively. For comparison, also Pb+Pb
collisions at sqrt(s)=2.76 TeV are simulated. It is found that non-hydrodynamic
evolution can give rise to equal or larger radial flow than hydrodynamics with
eta/s=0.08 in all simulated collision systems. In light-on-heavy-ion
collisions, free-streaming gives rise to triangular and quadrupolar flow
comparable to or larger than that from hydrodynamics, but it generally leads to
considerably smaller elliptic flow. As expected, free-streaming leads to
considerably less elliptic, triangular and quadrupolar flow than hydrodynamics
in nucleus-nucleus collisions, such as event-by-event Pb+Pb collisions at
sqrt(s)=2.76 TeV.
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We briefly review the covariant formulation of the Green-Schwarz superstring
by Berkovits, and describe how a detailed tree-level and one-loop analysis of
this model leads, for the first time, to a derivation of the low-energy
effective action of the heterotic superstring while keeping target-space
supersymmetry manifest. The resulting low-energy theory is old-minimal
supergravity coupled to tensor multiplet. The dilaton is part of the
compensator multiplet.
|
We continue the study initiated in [F. Albiac and P. Wojtaszczyk,
Characterization of $1$-greedy bases, J. Approx. Theory 138 (2006), no. 1,
65-86] of properties related to greedy bases in the case when the constants
involved are sharp, i.e., in the case when they are equal to $1$. Our main goal
here is to provide an example of a Banach space with a basis that satisfies
Property (A) but fails to be $1$-suppression unconditional, thus settling
Problem 4.4 from [F. Albiac and J.L. Ansorena, Characterization of $1$-almost
greedy bases, Rev. Mat. Complut. 30 (2017), no. 1, 13-24]. In particular, our
construction demonstrates that bases with Property (A) need not be $1$-greedy
even with the additional assumption that they are unconditional and symmetric.
We also exhibit a finite-dimensional counterpart of this example and show that,
at least in the finite-dimensional setting, Property (A) does not pass to the
dual. As a by-product of our arguments, we prove that a symmetric basis is
unconditional if and only if it is total, thus generalizing the well-known
result that symmetric Schauder bases are unconditional.
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We consider the incompressible Euler equations in $R^2$ when the initial
vorticity is bounded, radially symmetric and non-increasing in the radial
direction. Such a radial distribution is stationary, and we show that the
monotonicity produces stability in some weighted norm related to the angular
impulse. For instance, it covers the cases of circular vortex patches and
Gaussian distributions. Our stability does not depend on $L^\infty$-bound or
support size of perturbations. The proof is based on the fact that such a
radial monotone distribution minimizes the impulse of functions having the same
level set measure.
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In the present paper, we will show that a $(p,q,r)$-pretzel knot has the
representativity 3 if and only if $(p,q,r)$ is either $\pm(-2,3,3)$ or
$\pm(-2,3,5)$. We also show that a large algebraic knot has the
representativity less than or equal to 3.
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We discuss what is light-cone quantization on a curved spacetime also without
a null Killing vector. Then we consider as an example the light-cone
quantization of a scalar field on a background with a Killing vector and the
connection with the second quantization of the particle in the same background.
It turns out that the proper way to define the light-cone quantization is to
require that the constant light-cone time hypersurface is null or,
equivalently, that the particle Hamiltonian is free of square roots. Moreover,
in order to quantize the scalar theory it is necessary to use not the original
scalar rather a scalar field density, i.e. the Schr\"odinger wave functional
depends on a scalar density and not on the original field. Finally we recover
this result as the second quantization of a particle on the same background,
where it is necessary to add as input the fact that we are dealing with a
scalar density.
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A $\lambda$-translating soliton with density vector $\vec{v}$ is a surface
$\Sigma$ in Euclidean space ${\mathbb R}^3$ whose mean curvature $H$ satisfies
$2H=2\lambda+\langle N,\vec{v}\rangle$, where $N$ is the Gauss map of $\Sigma$.
In this article we study the shape of a compact $\lambda$-translating soliton
in terms of its boundary. If $\Gamma$ is a given closed curve, we deduce under
what conditions on $\lambda$ there exists a compact $\lambda$-translating
soliton $\Sigma$ with boundary $\Gamma$ and we provide estimates of the surface
area in relation with the height of $\Sigma$. Finally we study the shape of
$\Sigma$ related with the one of $\Gamma$, in particular, we give conditions
that assert that $\Sigma$ inherits the symmetries of its boundary $\Gamma$.
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Human identification is one of the most common and critical tasks for
condition monitoring, human-machine interaction, and providing assistive
services in smart environments. Recently, human gait has gained new attention
as a biometric for identification to achieve contactless identification from a
distance robust to physical appearances. However, an important aspect of gait
identification through wearables and image-based systems alike is accurate
identification when limited information is available, for example, when only a
fraction of the whole gait cycle or only a part of the subject body is visible.
In this paper, we present a gait identification technique based on temporal and
descriptive statistic parameters of different gait phases as the features and
we investigate the performance of using only single gait phases for the
identification task using a minimum number of sensors. It was shown that it is
possible to achieve high accuracy of over 95.5 percent by monitoring a single
phase of the whole gait cycle through only a single sensor. It was also shown
that the proposed methodology could be used to achieve 100 percent
identification accuracy when the whole gait cycle was monitored through pelvis
and foot sensors combined. The ANN was found to be more robust to fewer data
features compared to SVM and was concluded as the best machine algorithm for
the purpose.
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Massive multiple-input multiple-output (MIMO) enjoys great advantage in 5G
wireless communication systems owing to its spectrum and energy efficiency.
However, hundreds of antennas require large volumes of pilot overhead to
guarantee reliable channel estimation in FDD massive MIMO system. Compressive
sensing (CS) has been applied for channel estimation by exploiting the inherent
sparse structure of massive MIMO channel but suffer from high complexity. To
overcome this challenge, this paper develops a hybrid channel estimation scheme
by integrating the model-driven CS and data-driven deep unrolling technique.
The proposed scheme consists of a coarse estimation part and a fine correction
part to respectively exploit the inter- and intraframe sparsities of channels
to greatly reduce the pilot overhead. Theoretical result is provided to
indicate the convergence of the fine correction and coarse estimation net.
Simulation results are provided to verify that our scheme can estimate MIMO
channels with low pilot overhead while guaranteeing estimation accuracy with
relatively low complexity.
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In this paper we consider $\rho$-Einstein solitons of type $M= \left(B^n,
g^{*}\right) \times (F^m,g_F)$, where $\left(B^n,g^{*}\right)$ is conformal to
a pseudo-Euclidean space and invariant under the action of the
pseudo-orthogonal group, and $\left(F^m,g_{F}\right)$ is an Einstein manifold.
We provide all the solutions for the gradient Schouten soliton case. Moreover,
in the Riemannian case, we prove that if
$M= \left(B^n, g^{*}\right) \times (F^m,g_F)$ is a complete gradient Schouten
soliton then $\left(B^{n},g^{*}\right)$ is isometric to $\mathbb{S}^{n-1}\times
\mathbb{R}$ and $F^m$ is a compact Einstein manifold.
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Cross-contrast image translation is an important task for completing missing
contrasts in clinical diagnosis. However, most existing methods learn separate
translator for each pair of contrasts, which is inefficient due to many
possible contrast pairs in real scenarios. In this work, we propose a unified
Hyper-GAN model for effectively and efficiently translating between different
contrast pairs. Hyper-GAN consists of a pair of hyper-encoder and hyper-decoder
to first map from the source contrast to a common feature space, and then
further map to the target contrast image. To facilitate the translation between
different contrast pairs, contrast-modulators are designed to tune the
hyper-encoder and hyper-decoder adaptive to different contrasts. We also design
a common space loss to enforce that multi-contrast images of a subject share a
common feature space, implicitly modeling the shared underlying anatomical
structures. Experiments on two datasets of IXI and BraTS 2019 show that our
Hyper-GAN achieves state-of-the-art results in both accuracy and efficiency,
e.g., improving more than 1.47 and 1.09 dB in PSNR on two datasets with less
than half the amount of parameters.
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While teaching a course on integral equations, I noticed that a
straightforward combination of Neumann series and Fourier series for the
resolvent (or the solution) of an integral equation has good approximation
qualities. This short article presents and investigates this combination of
approximating series.
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Non-relativistic charged open strings coupled with Abelian gauge fields are
quantized in a geometric representation that generalizes the Loop
Representation. The model comprises open-strings interacting through a
Kalb-Ramond field in four dimensions. It is shown that a consistent
geometric-representation can be built using a scheme of ``surfaces and lines of
Faraday'', provided that the coupling constant (the ``charge'' of the string)
is quantized.
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Nonlinear damping of parallel propagating Alfv\'en waves in high-$\beta$
plasma is considered. Trapping of thermal ions and Coulomb collisions are taken
into account. Saturated damping rate is calculated. Applications are made for
cosmic ray propagation in the Galaxy.
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An action for a string and a particle with two timelike dimensions is
proposed and analyzed. Due to new gauge symmetries and associated constraints,
the motion of each system in the background of the other is equivalent to
effective motion with a single timelike dimension. The quantum constraints are
consistent only in critical dimensions. For the bosonic system in flat
spacetime the critical dimension is 27 or 28, with signature (25,2) or (26,2),
depending on whether the particle is massive or massless respectively. For the
supersymmetric case the critical dimensions are 11 or 12, with signature (9,2)
or (10,2), under the same circumstances. Generalizations to multiparticles,
strings and p-branes are outlined.
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Given R groups of numerical variables X1, ... XR, we assume that each group
is the result of one underlying latent variable, and that all latent variables
are bound together through a linear equation system. Moreover, we assume that
some explanatory latent variables may interact pairwise in one or more
equations. We basically consider PLS Path Modelling's algorithm to estimate
both latent variables and the model's coefficients. New "external" estimation
schemes are proposed that draw latent variables towards strong group structures
in a more flexible way. New "internal" estimation schemes are proposed to
enable PLSPM to make good use of variable group complementarity and to deal
with interactions. Application examples are given.
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We show that $3$-dimensional AdS spacetime can be semiclassically unstable
due to strongly interacting quantum field effects. In our previous paper, we
have pointed out the possibility of such an instability of AdS$_3$ by
inspecting linear perturbations of the (covering space of) static BTZ black
hole with AdS${}_4$ gravity dual in the context of holographic semiclassical
problems. In the present paper, we further study this issue from thermodynamic
viewpoint by constructing asymptotically AdS$_3$ semiclassical solutions and
computing free energies of the solutions. We find two asymptotically AdS${}_3$
solutions to the semiclassical Einstein equations with non-vanishing source
term: the one whose free energy is smaller than that of the BTZ with vanishing
source term and the other whose free energy is smaller than that of the global
AdS$_3$ with no horizon (thus manifestly zero-temperature background). The
instability found in this paper implies the breakdown of the maximal symmetries
of AdS$_3$, and its origin is different from the well-known semiclassical
linear instability since our holographic semiclassical Einstein equations in
$3$-dimensions do not involve higher order derivative terms.
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Linear Support Vector Machines trained on HOG features are now a de facto
standard across many visual perception tasks. Their popularisation can largely
be attributed to the step-change in performance they brought to pedestrian
detection, and their subsequent successes in deformable parts models. This
paper explores the interactions that make the HOG-SVM symbiosis perform so
well. By connecting the feature extraction and learning processes rather than
treating them as disparate plugins, we show that HOG features can be viewed as
doing two things: (i) inducing capacity in, and (ii) adding prior to a linear
SVM trained on pixels. From this perspective, preserving second-order
statistics and locality of interactions are key to good performance. We
demonstrate surprising accuracy on expression recognition and pedestrian
detection tasks, by assuming only the importance of preserving such local
second-order interactions.
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We show that the topological complexity of a finitely generated torsion free
hyperbolic group $\pi$ with $\cd\pi=n$ equals $2n$.
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An arbitrary initial state of an optical or microwave field in a lossy driven
nonlinear cavity can be changed, in the steady-state limit, into a partially
incoherent superposition of only the vacuum and the single-photon states. This
effect is known as single-photon blockade, which is usually analyzed for a
Kerr-type nonlinear cavity parametrically driven by a single-photon process
assuming single-photon loss mechanisms. We study photon blockade engineering
via a squeezed reservoir, i.e., a quantum reservoir, where only two-photon
absorption is allowed. Namely, we analyze a lossy nonlinear cavity
parametrically driven by a two-photon process and allowing two-photon loss
mechanisms, as described by the master equation derived for a two-photon
absorbing reservoir. The nonlinear cavity engineering can be realized by a
linear cavity with a tunable two-level system via the Jaynes-Cummings
interaction in the dispersive limit. We show that by tuning properly the
frequencies of the driving field and the two-level system, the steady state of
the cavity field can be the single-photon Fock state or a partially incoherent
superposition of several Fock states with photon numbers, e.g., (0,2), (1,3),
(0,1,2), or (0,2,4). We observe that an arbitrary initial coherent or
incoherent superposition of Fock states with an even (odd) number of photons
can be changed into a partially incoherent superposition of a few Fock states
of the same photon-number parity. A general solution for an arbitrary initial
state is a weighted mixture of the above two solutions with even and odd photon
numbers, where the weights are given by the probabilities of measuring the even
and odd numbers of photons of the initial cavity field, respectively. Thus, in
contrast to the standard photon blockade, we prove that the steady state in the
engineered photon blockade, can depend on its initial state.
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The effect of quenched disorder in a many-body system is experimentally
investigated in a controlled fashion. It is done by measuring the phase
synchronization (i.e. mutual coherence) of 400 coupled lasers as a function of
tunable disorder and coupling strengths. The results reveal that correlated
disorder has a non-trivial effect on the decrease of phase synchronization,
which depends on the ratio of the disorder correlation length over the average
number of synchronized lasers. The experimental results are supported by
numerical simulations and analytic derivations.
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The structure of the $\Delta J = 1$ doublet bands in $^{128}Cs$ is
investigated within the framework of the Interacting Vector Boson Fermion Model
(IVBFM). A new, purely collective interpretation of these bands is given on the
basis of the used boson-fermion dynamical symmetry of the model. The energy
levels of the doublet bands as well as the absolute $B(E2)$ and $B(M1)$
transition probabilities between the states of both yrast and yrare bands are
described quite well. The observed odd-even staggering of both $B(M1)$ and
$B(E2)$ values is reproduced by the introduction of an appropriate interaction
term of quadrupole type, which produces such a staggering effect in the
transition strengths. The calculations show that the appearance of doublet
bands in certain odd-odd nuclei could be a consequence of the realization of a
larger dynamical symmetry based on the non-compact supersymmetry group
$OSp(2\Omega /12, R)$.
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