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arxiv_dataset-57001411.0028 | Lattice polytopes in coding theory
cs.IT math.CO math.IT
In this paper we discuss combinatorial questions about lattice polytopes
motivated by recent results on minimum distance estimation for toric codes. We
also prove a new inductive bound for the minimum distance of generalized toric
codes. As an application, we give new formulas for the minimum distance of
generalized toric codes for special lattice point configurations.
| arxiv topic:cs.IT math.CO math.IT |
arxiv_dataset-57011411.0128 | The Evolution of the EM Distribution in the Core of an Active Region
astro-ph.SR
We study the spatial distribution and evolution of the slope of the Emission
Measure between 1 and 3~MK in the core active region NOAA~11193, first when it
appeared near the central meridian and then again when it re-appeared after a
solar rotation. We use observations recorded by the Extreme-ultraviolet Imaging
Spectrometer (EIS) aboard Hinode, with a new radiometric calibration. We also
use observations from the Atmospheric Imaging Assembly (AIA) aboard Solar
Dynamics Observatory (SDO). We present the first spatially resolved maps of the
EM slope in the 1--3~MK range within the core of the AR using several methods,
both approximate and from the Differential Emission Measure (DEM). A
significant variation of the slope is found at different spatial locations
within the active region. We selected two regions that were not affected too
much by any line-of-sight lower temperature emission. We found that the EM had
a power law of the form EM~$\propto T^{b}$, with b = 4.4$\pm0.4$, and
4.6$\pm0.4$, during the first and second appearance of the active region,
respectively. During the second rotation, line-of-sight effects become more
important, although difficult to estimate. We found that the use of the ground
calibration for Hinode/EIS and the approximate method to derive the Emission
Measure, used in previous publications, produce an underestimation of the
slopes. The EM distribution in active region cores is generally found to be
consistent with high frequency heating, and stays more or less the same during
the evolution of the active region.
| arxiv topic:astro-ph.SR |
arxiv_dataset-57021411.0228 | Relay-Selection Improves the Security-Reliability Trade-off in Cognitive
Radio Systems
cs.IT math.IT
We consider a cognitive radio (CR) network consisting of a secondary
transmitter (ST), a secondary destination (SD) and multiple secondary relays
(SRs) in the presence of an eavesdropper. We rely on careful relay selection
for protecting the ST-SD transmission against the eavesdropper with the aid of
both single-relay and multi-relay selection. To be specific, only the "best" SR
is chosen in the single-relay selection for assisting the secondary
transmission, whereas the multi-relay selection invokes multiple SRs for
simultaneously forwarding the ST's transmission to the SD. We analyze both the
intercept probability and outage probability of the proposed single-relay and
multi-relay selection schemes for the secondary transmission relying on
realistic spectrum sensing. We also evaluate the performance of classic direct
transmission and artificial noise based methods for the purpose of comparison
with the proposed relay selection schemes. It is shown that as the intercept
probability requirement is relaxed, the outage performance of the direct
transmission, the artificial noise based and the relay selection schemes
improves, and vice versa. This implies a trade-off between the security and
reliability of the secondary transmission in the presence of eavesdropping
attacks, which is referred to as the security-reliability trade-off (SRT).
Furthermore, we demonstrate that the SRTs of the single-relay and multi-relay
selection schemes are generally better than that of classic direct
transmission. Moreover, as the number of SRs increases, the SRTs of the
proposed single-relay and multi-relay selection approaches significantly
improve. Finally, our numerical results show that as expected, the multi-relay
selection scheme achieves a better SRT performance than the single-relay
selection.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-57031411.0328 | An explicit high-order single-stage single-step positivity-preserving
finite difference WENO method for the compressible Euler equations
math.NA
In this work we construct a high-order, single-stage, single-step
positivity-preserving method for the compressible Euler equations. Space is
discretized with the finite difference weighted essentially non-oscillatory
(WENO) method. Time is discretized through a Lax-Wendroff procedure that is
constructed from the Picard integral formulation (PIF) of the partial
differential equation. The method can be viewed as a modified flux approach,
where a linear combination of a low- and high-order flux defines the numerical
flux used for a single-step update. The coefficients of the linear combination
are constructed by solving a simple optimization problem at each time step. The
high-order flux itself is constructed through the use of Taylor series and the
Cauchy-Kowalewski procedure that incorporates higher-order terms. Numerical
results in one- and two-dimensions are presented.
| arxiv topic:math.NA |
arxiv_dataset-57041411.0428 | Cosmological Perturbation Theory for streams of relativistic particles
astro-ph.CO
Motion equations describing streams of relativistic particles and their
properties are explored in detail in the framework of Cosmological Perturbation
Theory. Those equations, derived in any metric both in the linear and nonlinear
regimes, express the matter and momentum conservation. In this context we
extend the setup of adiabatic initial conditions - that was initially performed
in the Conformal Newtonian gauge - to the Synchronous gauge. The subhorizon
limit of the nonlinear motion equations written in a generic perturbed
Friedmann-Lema\^{i}tre metric is then derived and analyzed. We show in
particular that the momentum field $P_{i}(x)$ is always potential in the linear
regime and remains so at subhorizon scales in the nonlinear regime. Finally the
equivalence principle is exploited to highlight invariance properties satisfied
by such a system of equations, extending that known for streams of
non-relativistic particles, namely the extended Galilean invariance.
| arxiv topic:astro-ph.CO |
arxiv_dataset-57051411.0528 | On the pion distribution amplitude. Derivation, properties, predictions
hep-ph
We provide an in-depth analysis of the $\pi$ distribution amplitude in terms
of two different Gegenbauer representations. Detailed predictions for the
$\pi-\gamma$ transition form factor are presented, obtained with light-cone sum
rules. Various $\pi$ distribution amplitudes are tested and the crucial role of
their endpoint behavior in the form-factor analysis is discussed. Comparison
with the data is given.
| arxiv topic:hep-ph |
arxiv_dataset-57061411.0628 | PH = PSPACE
cs.CC cs.DS math.GM
In this paper we show that PSPACE is equal to 4th level in the polynomial
hierarchy. We also deduce a lot of important consequences.
True quantified Boolean formula is a generalisation of the Boolean
Satisfiability Problem, where determining of interpretation that satisfies a
given Boolean formula is replaced by existence of Boolean functions that makes
a given QBF to be tautology. Such functions are called the Skolem functions.
The essential idea of the proof is to show that for any quantified Boolean
formula $\phi$ we can obtain a formula $\phi'$ which is in the 4th level of the
polynomial hierarchy, no more than polynomial in the size of a given $\phi$,
such that the truth of $\phi$ can be determined from the truth of $\phi'$. The
idea is to skolemize, and then use additional formulas from the 2nd level of
the polynomial hierarchy inside the skolemized prefix to enforce that the
skolem variables indeed depend only on the universally quantified variables
they are supposed to. However, some dependence is lost when the quantification
is reversed. It is called "XOR issue" because the functional dependence can be
expressed by means of an XOR formula. Thus, it is needed to locate these XORs,
but there is no need to locate all chains with XORs: any chain includes a XOR
of only two variables. The last can be done locally in each iteration (keep in
mind the algebraic normal form (ANF)), when all arguments are specified, i.e.
as a polynomial subroutine.
Relativization is defeated due to the well-known fact: PH = PSPACE iff
second-order logic over finite structures gains no additional power from the
addition of a transitive closure operator. The exchange is possible due to
finite possibilities for arguments. So, the theorems with oracles are not
applicable since a random oracle is an arbitrary set. And that's why PH is
infinite relative to a random oracle with probability 1.
| arxiv topic:cs.CC cs.DS math.GM |
arxiv_dataset-57071411.0728 | Approachability in Stackelberg Stochastic Games with Vector Costs
cs.LG cs.GT cs.SY math.OC
The notion of approachability was introduced by Blackwell [1] in the context
of vector-valued repeated games. The famous Blackwell's approachability theorem
prescribes a strategy for approachability, i.e., for `steering' the average
cost of a given agent towards a given target set, irrespective of the
strategies of the other agents. In this paper, motivated by the multi-objective
optimization/decision making problems in dynamically changing environments, we
address the approachability problem in Stackelberg stochastic games with vector
valued cost functions. We make two main contributions. Firstly, we give a
simple and computationally tractable strategy for approachability for
Stackelberg stochastic games along the lines of Blackwell's. Secondly, we give
a reinforcement learning algorithm for learning the approachable strategy when
the transition kernel is unknown. We also recover as a by-product Blackwell's
necessary and sufficient condition for approachability for convex sets in this
set up and thus a complete characterization. We also give sufficient conditions
for non-convex sets.
| arxiv topic:cs.LG cs.GT cs.SY math.OC |
arxiv_dataset-57081411.0828 | Expanding the principle of local distinguishability
quant-ph
The principle of local distinguishability states that an arbitrary physical
state of a bipartite system can be determined by the combined statistics of
local measurements performed on the subsystems. A necessary and sufficient
requirement for the local measurements is that each one must be able to
distinguish between all pairs of states of the respective subsystems. We show
that if the task is changed into the determination of an arbitrary bipartite
pure state, then at least in certain cases it is possible to restrict to local
measurements which can distintinguish all pure states but not all states. This
surprising fact gives evidence that the principle of local distinguishability
may be expanded beyond its usual applicability.
| arxiv topic:quant-ph |
arxiv_dataset-57091411.0928 | Power-law distributions, the h-index, and Google Scholar (GS) citations:
a test of their relationship with economics Nobelists
cs.DL
This paper presents proof that Google Scholar (GS) can construct documentary
sets relevant for evaluating researchers' works. Nobelists in economics were
the researchers under analysis, and two types of tests of the GS cites to their
works were performed: distributional and semantic. Distributional tests found
that the GS cites to the laureates' works conformed to the power-law model with
an asymptote or "tail" conterminous with their h-index demarcating their core
oeuvre, validating both GS and the h-index. Semantic tests revealed that their
works highest in GS cites were on topics for which they were awarded the prize.
| arxiv topic:cs.DL |
arxiv_dataset-57101411.1028 | Braid groups and euclidean simplices
math.GR math.GT
When Daan Krammer and Stephen Bigelow independently proved that braid groups
are linear, they used the Lawrence-Krammer-Bigelow representation for generic
values of its variables q and t. The t variable is closely connected to the
traditional Garside structure of the braid group and plays a major role in
Krammer's algebraic proof. The q variable, associated with the dual Garside
structure of the braid group, has received less attention.
In this article we give a geometric interpretation of the q portion of the
LKB representation in terms of an action of the braid group on the space of
non-degenerate euclidean simplices. In our interpretation, braid group elements
act by systematically reshaping (and relabeling) euclidean simplices. The
reshapings associated to the simple elements in the dual Garside structure of
the braid group are of an especially elementary type that we call relabeling
and rescaling.
| arxiv topic:math.GR math.GT |
arxiv_dataset-57111411.1128 | Non-renormalization theorem and cyclic Leibniz rule in lattice
supersymmetry
hep-lat hep-th
We propose a lattice model of supersymmetric complex quantum mechanics which
realizes the non-renormalization theorem on a lattice. In our lattice model,
the Leibniz rule in the continuum, which cannot hold on a lattice due to a
no-go theorem, is replaced by the cyclic Leibniz rule (CLR) for difference
operators. It is shown that CLR allows two of four supercharges of the
continuum theory to preserve while a naive lattice model can realize one
supercharge at the most. A striking feature of our lattice model is that there
are no quantum corrections to potential terms in any finite order of
perturbation theory. This is one of characteristic properties of supersymmetric
theories in the continuum. It turns out that CLR plays a crucial role in the
proof of the non-renormalization theorem. This result suggests that CLR grasps
an essence of supersymmetry on a lattice.
| arxiv topic:hep-lat hep-th |
arxiv_dataset-57121411.1228 | Extracting surface rotation periods of solar-like Kepler targets
astro-ph.SR
We use various method to extract surface rotation periods of Kepler targets
exhibiting solar-like oscillations and compare their results.
| arxiv topic:astro-ph.SR |
arxiv_dataset-57131411.1328 | Discrete-Time Models Resulting From Dynamic Continuous-Time
Perturbations In Phase-Amplitude Modulation-Demodulation Schemes
cs.SY math.OC
We consider discrete-time (DT) systems S in which a DT input is first
tranformed to a continuous-time (CT) format by phase-amplitude modulation, then
modified by a non-linear CT dynamical transformation F, and finally converted
back to DT output using an ideal de-modulation scheme. Assuming that F belongs
to a special class of CT Volterra series models with fixed degree and memory
depth, we provide a complete characterization of S as a series connection of a
DT Volterra series model of fixed degree and memory depth, and an LTI system
with special properties. The result suggests a new, non-obvious, analytically
motivated structure of digital compensation of analog nonlinear distortions
(for example, those caused by power amplifiers) in digital communication
systems. Results from a MATLAB simulation are used to demonstrate effectiveness
of the new compensation scheme, as compared to the standard Volterra series
approach.
| arxiv topic:cs.SY math.OC |
arxiv_dataset-57141411.1428 | The JCMT Legacy Survey of the Gould Belt: a molecular line study of the
Ophiuchus molecular cloud
astro-ph.GA
CO, $^{13}$CO and C$^{18}$O ${\it J}$ = 3--2 observations are presented of
the Ophiuchus molecular cloud. The $^{13}$CO and C$^{18}$O emission is
dominated by the Oph A clump, and the Oph B1, B2, C, E, F and J regions. The
optically thin(ner) C$^{18}$O line is used as a column density tracer, from
which the gravitational binding energy is estimated to be $4.5 \times 10^{39}$
J (2282 $M_\odot$ km$^2$ s$^{-2}$). The turbulent kinetic energy is $6.3 \times
10^{38}$ J (320 $M_\odot$ km$^2$ s$^{-2}$), or 7 times less than this, and
therefore the Oph cloud as a whole is gravitationally bound. Thirty protostars
were searched for high velocity gas, with eight showing outflows, and twenty
more having evidence of high velocity gas along their lines-of-sight. The total
outflow kinetic energy is $1.3 \times 10^{38}$ J (67 $M_\odot$ km$^2$
s$^{-2}$), corresponding to 21$\%$ of the cloud's turbulent kinetic energy.
Although turbulent injection by outflows is significant, but does ${\it not}$
appear to be the dominant source of turbulence in the cloud. 105 dense
molecular clumplets were identified, which had radii $\sim$ 0.01--0.05 pc,
virial masses $\sim$ 0.1--12 $M_\odot$, luminosities $\sim$ 0.001--0.1 K~km
s$^{-1}$ pc$^{-2}$, and excitation temperatures $\sim$ 10--50K. These are
consistent with the standard GMC based size-line width relationships, showing
that the scaling laws extend down to size scales of hundredths of a parsec, and
to sub solar-mass condensations. There is however no compelling evidence that
the majority of clumplets are undergoing free-fall collapse, nor that they are
pressure confined.
| arxiv topic:astro-ph.GA |
arxiv_dataset-57151411.1528 | A network inference method for large-scale unsupervised identification
of novel drug-drug interactions
q-bio.MN cond-mat.dis-nn physics.bio-ph physics.data-an
Characterizing interactions between drugs is important to avoid potentially
harmful combinations, to reduce off-target effects of treatments and to fight
antibiotic resistant pathogens, among others. Here we present a network
inference algorithm to predict uncharacterized drug-drug interactions. Our
algorithm takes, as its only input, sets of previously reported interactions,
and does not require any pharmacological or biochemical information about the
drugs, their targets or their mechanisms of action. Because the models we use
are abstract, our approach can deal with adverse interactions,
synergistic/antagonistic/suppressing interactions, or any other type of drug
interaction. We show that our method is able to accurately predict
interactions, both in exhaustive pairwise interaction data between small sets
of drugs, and in large-scale databases. We also demonstrate that our algorithm
can be used efficiently to discover interactions of new drugs as part of the
drug discovery process.
| arxiv topic:q-bio.MN cond-mat.dis-nn physics.bio-ph physics.data-an |
arxiv_dataset-57161411.1628 | Successive Radii and Ball Operators in Generalized Minkowski Spaces
math.MG
We investigate elementary properties of successive radii in generalized
Minkowski spaces (that is, with respect to gauges), i.e., we measure the "size"
of a given convex set in a finite-dimensional real vector space with respect to
another convex set. This is done via formulating some kind of minimal
containment problems, where intersections or Minkowski sums of the latter set
and affine flats of a certain dimension are incorporated. Since this is
strongly related to minimax location problems and to the notions of diametrical
completeness and constant width, we also have a look at ball intersections and
ball hulls.
| arxiv topic:math.MG |
arxiv_dataset-57171411.1728 | On the Geometry of Spacetime I: baby steps in quantum ring theory
math-ph gr-qc hep-th math.MP quant-ph
Vierbeins provide a bridge between the curved space of general relativity and
the flat tangent space of special relativity. Both spaces should be causal and
spin. We posit intertwining the two symmetries of spacetime bundles
asymmetrically; disentangling the non-trivial Id between the base, curved space
as a locally ringed space and its Zariski (co-)tangent space. This involves the
introduction of a "two-sided vector space" as a section of the smooth,
stratified diffeomorphism bundle of spacetime. A change of paradigm from the
fiber bundle approach ensues where the bundle space takes an active role and
the group actions are implemented through asymmetric "scalar multiplication" by
elements of a skewed K-algebra on a free K-bimodule. Accordingly, the left
action is augmented from that on the right algebraically by a left-sided
algebra automorphism via a left alpha-derivation as a non-central Ore extension
of a Weyl algebra. Curiously, summoning the left $\alpha$-derivation in the
context of spacetime symmetries may constitute the key to an asymmetric
quantization of the theory. Furthermore, it is conjectured that causal and spin
structure may be endowed upon the spacetime itself, independently of the
tangent space structure.
| arxiv topic:math-ph gr-qc hep-th math.MP quant-ph |
arxiv_dataset-57181411.1828 | Molecular Gas and Star Formation in Voids
astro-ph.GA astro-ph.CO
We present the detection of molecular gas using CO(1-0) line emission and
follow up Halpha imaging observations of galaxies located in nearby voids. The
CO(1-0) observations were done using the 45m telescope of the Nobeyama Radio
Observatory (NRO) and the optical observations were done using the Himalayan
Chandra Telescope (HCT). Although void galaxies lie in the most under dense
parts of our universe, a significant fraction of them are gas rich, spiral
galaxies that show signatures of ongoing star formation. Not much is known
about their cold gas content or star formation properties. In this study we
searched for molecular gas in five void galaxies using the NRO. The galaxies
were selected based on their relatively higher IRAS fluxes or Halpha line
luminosities. CO(1--0) emission was detected in four galaxies and the derived
molecular gas masses lie between (1 - 8)E+9 Msun. The H$\alpha$ imaging
observations of three galaxies detected in CO emission indicates ongoing star
formation and the derived star formation rates vary between from 0.2 - 1.0
Msun/yr, which is similar to that observed in local galaxies. Our study shows
that although void galaxies reside in under dense regions, their disks may
contain molecular gas and have star formation rates similar to galaxies in
denser environments.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-57191411.1928 | A remark on the Laplacian operator which acts on symmetric tensors
math.DG
More than forty years ago J. H. Samson has defined the Laplacian
$\Delta_{sym}$ acting on the space of symmetric covariant $p$-tensors on an
$n$-dimensional Riemannian manifold $(M, g)$. This operator is an analogue of
the well known Hodge-de Rham Laplacian $\Delta$ which acts on the space of
exterior differential $p$-forms ($1 \le p \le n$) on $(M, g)$. In the present
paper we will prove that for $n > p = 1$ the operator $\Delta_{sym}$ is the
Yano rough Laplacian and show its spectrum properties on a compact Riemannian
manifold.
| arxiv topic:math.DG |
arxiv_dataset-57201411.2028 | The triggering of local AGN and their role in regulating star formation
astro-ph.GA
We explore the processes that trigger local AGN and the role of these AGN in
regulating star formation, using ~350 nearby galaxies observed by the mJy
Imaging VLBA Exploration at 20cm (mJIVE) survey. The >10^7 K brightness
temperature required for an mJIVE detection cannot be achieved via star
formation alone, allowing us to unambiguously detect nearby radio AGN and study
their role in galaxy evolution. Radio AGN are an order of magnitude more common
in early-type galaxies (ETGs) than in their late-type counterparts. The
VLBI-detected ETGs in this study have a similar stellar mass distribution to
their undetected counterparts, are typically not the central galaxies of
clusters and exhibit merger fractions that are significantly higher than in the
average ETG. This suggests that these radio AGN (which have VLBI luminosities
>10^22 W Hz^-1) are primarily fuelled by mergers, and not by internal stellar
mass loss or cooling flows. Our radio AGN are a factor of ~3 times more likely
to reside in the UV-optical red sequence than the average ETG. Furthermore,
typical AGN lifetimes (a few 10^7 yr) are much shorter than the transit times
from blue cloud to red sequence (~1.5 Gyr). This indicates that the AGN are not
triggered promptly and appear several dynamical timescales into the associated
star formation episode, implying that they typically couple only to residual
gas, at a point where star formation has already declined significantly. While
evidence for AGN feedback is strong in systems where the black hole is fed by
the cooling of hot gas, AGN triggered by mergers appear not to strongly
regulate the associated star formation. The inability of the AGN to rapidly
quench merger-driven star formation is likely to make merging the dominant mode
of star formation in nearby ETGs, in line with evidence for minor mergers being
the primary driver of stellar mass growth in these systems.
| arxiv topic:astro-ph.GA |
arxiv_dataset-57211411.2128 | Complementarity of direct and indirect searches in the pMSSM
hep-ph
We explore the pMSSM parameter space in view of the constraints from SUSY and
monojet searches at the LHC, from Higgs data and flavour physics observables,
as well as from dark matter searches. We show that whilst the simplest SUSY
scenarios are already ruled out, there are still many possibilities left over
in the pMSSM. We discuss the complementarity between different searches and
consistency checks which are essential in probing the pMSSM and will be even
more important in the near future with the next round of data becoming
available.
| arxiv topic:hep-ph |
arxiv_dataset-57221411.2228 | Classification of the automorphism and isometry groups of Higgs bundle
moduli spaces
math.DG math.AG
Let $\mathcal{M}_{n,d}$ be the moduli space of semi-stable rank $n$,
trace-free Higgs bundles with fixed determinant of degree $d$ on a Riemann
surface of genus at least $3$. We determine the following automorphism groups
of $\mathcal{M}_{n,d}$: (i) the group of automorphisms as a complex analytic
variety, (ii) the group of holomorphic symplectomorphisms, (iii) the group of
K\"ahler isomorphisms, (iv) the group of automorphisms of the quaternionic
structure, (v) the group of hyper-K\"ahler isomorphisms. When $n$ and $d$ are
coprime we show that $\mathcal{M}_{n,d}$ admits an anti-holomorphic isomorphism
if and only if the corresponding Riemann surface admits such a map. We then use
this to determine the isometry group of $\mathcal{M}_{n,d}$.
| arxiv topic:math.DG math.AG |
arxiv_dataset-57231411.2328 | Modeling Word Relatedness in Latent Dirichlet Allocation
cs.CL cs.AI
Standard LDA model suffers the problem that the topic assignment of each word
is independent and word correlation hence is neglected. To address this
problem, in this paper, we propose a model called Word Related Latent Dirichlet
Allocation (WR-LDA) by incorporating word correlation into LDA topic models.
This leads to new capabilities that standard LDA model does not have such as
estimating infrequently occurring words or multi-language topic modeling.
Experimental results demonstrate the effectiveness of our model compared with
standard LDA.
| arxiv topic:cs.CL cs.AI |
arxiv_dataset-57241411.2428 | A solvable two-dimensional singular stochastic control problem with non
convex costs
math.OC
In this paper we provide a complete theoretical analysis of a two-dimensional
degenerate non convex singular stochastic control problem. The optimisation is
motivated by a storage-consumption model in an electricity market, and features
a stochastic real-valued spot price modelled by Brownian motion. We find
analytical expressions for the value function, the optimal control and the
boundaries of the action and inaction regions. The optimal policy is
characterised in terms of two monotone and discontinuous repelling free
boundaries, although part of one boundary is constant and the smooth fit
condition holds there.
| arxiv topic:math.OC |
arxiv_dataset-57251411.2528 | Hybrid Ant Colony Algorithm Clonal Selection in the Application of the
Cloud's Resource Scheduling
cs.DC
In this paper, thinking over characteristics of ant colony optimization
Algorithm, taking into account the characteristics of cloud computing, combined
with clonal selection algorithm (CSA) global optimum advantage of the
convergence of the clonal selection algorithm (CSA) into every ACO iteration,
speeding up the convergence rate, and the introduction of reverse mutation
strategy, ant colony optimization algorithm avoids local optimum. Depth study
of the cloud environment ant colony clonal selection algorithm resource
scheduling policy, clonal selection algorithm converges to solve optimization
problems when sufficient condition for global optimal solution based on clonal
selection algorithm for various applications such as BCA and CLONALG algorithm,
using these sufficient condition to meet and simulation platform CloudSim
achieve a simulation by extending the cloud. Experimental results show that
this task can be shortened fusion algorithm running time cloud environment,
improve resource utilization. Demonstrate the effectiveness of the method.
| arxiv topic:cs.DC |
arxiv_dataset-57261411.2628 | Exact solution of a generalized version of the Black-Scholes equation
q-fin.CP
We analyze a generalized version of the Black-Scholes equation depending on a
parameter $a\!\in \!(-\infty,0)$. It satisfies the martingale condition and
coincides with the Black-Scholes equation in the limit case $a\nearrow 0$. We
show that the generalized equation is exactly solvable in terms of Hermite
polynomials and numerically compare its solution with the solution of the
Black-Scholes equation.
| arxiv topic:q-fin.CP |
arxiv_dataset-57271411.2728 | Boundary elements method for microfluidic two-phase flows in shallow
channels
physics.flu-dyn
In the following work we apply the boundary element method to two-phase flows
in shallow microchannels, where one phase is dispersed and does not wet the
channel walls. These kinds of flows are often encountered in microfluidic
Lab-on-a-Chip devices and characterized by low Reynolds and low capillary
numbers.
Assuming that these channels are homogeneous in height and have a large
aspect ratio, we use depth-averaged equations to describe these two-phase flows
using the Brinkman equation, which constitutes a refinement of Darcy's law.
These partial differential equations are discretized and solved numerically
using the boundary element method, where a stabilization scheme is applied to
the surface tension terms, allowing for a less restrictive time step at low
capillary numbers. The convergence of the numerical algorithm is checked
against a static analytical solution and on a dynamic test case. Finally the
algorithm is applied to the non-linear development of the Saffman-Taylor
instability and compared to experimental studies of droplet deformation in
expanding flows.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-57281411.2828 | Spin chiral current induced by curvature of space-time
physics.gen-ph
Klein-Gordon equation is derived for a particle in the brane model of
Universe. It is compared with squared Dirac-Fock-Ivanenko equation and
expression for a chiral current is obtained by this comparison. This expression
defines chiral current through variation of spin connection gauge field that
arises due to the symmetry in respect to local Lorenz transformations. So, the
second derivative of gravitational gauge field determines variation of chiral
current responsible for variation of mass. The role of these processes on the
early stages of Universe evolution is discussed.
| arxiv topic:physics.gen-ph |
arxiv_dataset-57291411.2928 | Homothetic Polygons and Beyond: Intersection Graphs, Recognition, and
Maximum Clique
cs.DM
We study the {\sc Clique} problem in classes of intersection graphs of convex
sets in the plane. The problem is known to be NP-complete in convex-set
intersection graphs and straight-line-segment intersection graphs, but solvable
in polynomial time in intersection graphs of homothetic triangles. We extend
the latter result by showing that for every convex polygon $P$ with sides
parallel to $k$ directions, every $n$-vertex graph which is an intersection
graph of homothetic copies of $P$ contains at most $n^{k}$ inclusion-wise
maximal cliques. We actually prove this result for a more general class of
graphs, the so called $k_{\text{DIR}}-\text{CONV}$, which are intersection
graphs of convex polygons whose sides are parallel to some fixed $k$
directions. Moreover, we provide some lower bounds on the numbers of maximal
cliques, discuss the complexity of recognizing these classes of graphs and
present a relationship with other classes of convex-set intersection graphs.
Finally, we generalize the upper bound on the number of maximal cliques to
intersection graphs of higher-dimensional convex polytopes in Euclidean space.
| arxiv topic:cs.DM |
arxiv_dataset-57301411.3028 | A fast fault-tolerant decoder for qubit and qudit surface codes
quant-ph
The surface code is one of the most promising candidates for combating errors
in large scale fault-tolerant quantum computation. A fault-tolerant decoder is
a vital part of the error correction process---it is the algorithm which
computes the operations needed to correct or compensate for the errors
according to the measured syndrome, even when the measurement itself is error
prone. Previously decoders based on minimum-weight perfect matching have been
studied. However, these are not immediately generalizable from qubit to qudit
codes. In this work, we develop a fault-tolerant decoder for the surface code,
capable of efficient operation for qubits and qudits of any dimension,
generalizing the decoder first introduced by Bravyi and Haah [Phys. Rev. Lett.
111, 200501 (2013)]. We study its performance when both the physical qudits and
the syndromes measurements are subject to generalized uncorrelated bit-flip
noise (and the higher dimensional equivalent). We show that, with appropriate
enhancements to the decoder and a high enough qudit dimension, a threshold at
an error rate of more than 8% can be achieved.
| arxiv topic:quant-ph |
arxiv_dataset-57311411.3128 | Deep Multi-Instance Transfer Learning
cs.LG stat.ML
We present a new approach for transferring knowledge from groups to
individuals that comprise them. We evaluate our method in text, by inferring
the ratings of individual sentences using full-review ratings. This approach,
which combines ideas from transfer learning, deep learning and multi-instance
learning, reduces the need for laborious human labelling of fine-grained data
when abundant labels are available at the group level.
| arxiv topic:cs.LG stat.ML |
arxiv_dataset-57321411.3228 | Rigidity of Circle Packings with Crosscuts
math.CV math.MG
Circle packings with specified patterns of tangencies form a discrete
counterpart of analytic functions. In this paper we study univalent packings
(with a combinatorial closed disk as tangent graph) which are embedded in (or
fill) a bounded, simply connected domain. We introduce the concept of crosscuts
and investigate the rigidity of circle packings with respect to maximal
crosscuts. The main result is a discrete version of an indentity theorem for
analytic functions (in the spirit of Schwarz' Lemma), which has implications to
uniqueness statements for discrete conformal mappings.
| arxiv topic:math.CV math.MG |
arxiv_dataset-57331411.3328 | Cosmology on a cosmic ring
gr-qc astro-ph.CO hep-th
We derive the modified Friedmann equations for a generalization of the
Dvali-Gabadadze-Porrati (DGP) model in which the brane has one additional
compact dimension. The main new feature is the emission of gravitational waves
into the bulk. We study two classes of solutions: First, if the compact
dimension is stabilized, the waves vanish and one exactly recovers DGP
cosmology. However, a stabilization by means of physical matter is not possible
for a tension-dominated brane, thus implying a late time modification of 4D
cosmology different from DGP. Second, for a freely expanding compact direction,
we find exact attractor solutions with zero 4D Hubble parameter despite the
presence of a 4D cosmological constant. The model hence constitutes an explicit
example of dynamical degravitation at the full non-linear level. Without
stabilization, however, there is no 4D regime and the model is ruled out
observationally, as we demonstrate explicitly by comparing to supernova data.
| arxiv topic:gr-qc astro-ph.CO hep-th |
arxiv_dataset-57341411.3428 | Some of semileptonic and nonleptonic decays of $B_c$ meson in a
Bethe-Salpeter relativistic quark model
hep-ph hep-ex
The semileptonic decays $B_c^+\rightarrow P(V) +\ell^++\bar{\nu}_\ell$ and
the nonleptonic decays $B_c^+\rightarrow P(V)+L$, where $P(V)$ denotes a
pseudoscalar (vector) charmonium or ($\bar{b}s$)-meson, and $L$ denotes a light
meson, are studied in the framework of improved instantaneous Bethe-Salpeter
(BS) equation and the Mandelstam formula. The numerical results (width and
branching ratio of the decays) are presented in tables, and in order to compare
conveniently, those obtained by other approaches are also put in the relevant
tables. Based on the fact that the ratio
$\frac{\mathcal{BR}(B_c^+\rightarrow\psi(2S)\pi^+)}{\mathcal{BR}(B_c^+\rightarrow
J/\psi \pi^+)}=0.24^{+0.023}_{-0.040}$ estimated here is in good agreement with
the observation by the LHCb $\frac{\mathcal{BR}(B_c^+\rightarrow
\psi(2S)\pi^+)}{\mathcal{BR}(B_c^+\rightarrow J/\psi
\pi^+)}=0.250\pm0.068(\mathrm{stat})\pm0.014(\mathrm{syst})\pm0.006(\mathcal{B})$,
one may conclude that with respect to the decays the present framework works
quite well.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-57351411.3528 | Reverberation measurement of the inner radius of the dust torus in NGC
4151 during 2008-2013
astro-ph.GA astro-ph.HE
We investigate the correlation between infrared (JHKL) and optical (B) fluxes
of the variable nucleus of the Seyfert galaxy NGC 4151 using partially
published data for the last 6 years (2008-2013.). Here we are using the same
data as in Oknyansky et al. (2014), but include also optical (B) data from Guo
et al. We find that the lag of flux in all the infrared bands is the same, 40
+- 6 days, to within the measurement accuracy. Variability in the J and K bands
is not quite simultaneous, perhaps due to the differing contributions of the
accretion disk in these bands. The lag found for the K band compared with the B
band is not significantly different from earlier values obtained for the period
2000-2007. However, finding approximately the same lags in all IR bands for
2008-2013 differs from previous results at earlier epochs when the lag
increased with increasing wavelength. Examples of almost the same lag in
different IR bands are known for some other active nuclei. In the case of NGC
4151 it appears that the relative lags between the IR bands may be different in
different years. The available data, unfortunately, do not allow us to
investigate a possible change in the lags during the test interval. We discuss
our results in the framework of the standard model where the variable infrared
radiation is mainly due to thermal re-emission from the part of the dusty torus
closest to the central source. There is also a contribution of some IR emission
from the accretion disk, and this contribution increases with decreasing
wavelength. Some cosmological applications of obtained results are discussed.
| arxiv topic:astro-ph.GA astro-ph.HE |
arxiv_dataset-57361411.3628 | An improved source-subtracted and destriped 408 MHz all-sky map
astro-ph.IM astro-ph.CO astro-ph.GA
The all-sky 408 MHz map of Haslam et al. is one the most important
total-power radio surveys. It has been widely used to study diffuse synchrotron
radiation from our Galaxy and as a template to remove foregrounds in cosmic
microwave background data. However, there are a number of issues associated
with it that must be dealt with, including large-scale striations and
contamination from extragalactic radio sources. We have re-evaluated and
re-processed the rawest data available to produce a new and improved 408 MHz
all-sky map. We first quantify the positional accuracy ($\approx 7$ arcmin) and
effective beam ($56.0\pm1.0$ arcmin) of the four individual surveys from which
it was assembled. Large-scale striations associated with $1/f$ noise in the
scan direction are reduced to a level $\ll 1$ K using a Fourier-based filtering
technique. The most important improvement results from the removal of
extragalactic sources. We have used an iterative combination of two techniques
-- two-dimensional Gaussian fitting and minimum curvature spline surface
inpainting -- to remove the brightest sources ($\gtrsim 2$ Jy), which provides
a significant improvement over previous versions of the map. We quantify the
impact with power spectra and a template fitting analysis of foregrounds to the
WMAP data. The new map is publicly available and is recommended as the template
of choice for large-scale diffuse Galactic synchrotron emission. We also
provide a higher resolution map with small-scale fluctuations added, assuming a
power-law angular power spectrum down to the pixel scale (1.7 arcmin). This
should prove useful in simulations used for studying the feasibility of
detecting HI fluctuations from the Epoch of Reionization.
| arxiv topic:astro-ph.IM astro-ph.CO astro-ph.GA |
arxiv_dataset-57371411.3728 | Flat space (higher spin) gravity with chemical potentials
hep-th gr-qc
We introduce flat space spin-3 gravity in the presence of chemical potentials
and discuss some applications to flat space cosmology solutions, their entropy,
free energy and flat space orbifold singularity resolution. Our results include
flat space Einstein gravity with chemical potentials as special case. We
discover novel types of phase transitions between flat space cosmologies with
spin-3 hair and show that the branch that continuously connects to spin-2
gravity becomes thermodynamically unstable for sufficiently large temperature
or spin-3 chemical potential.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-57381411.3828 | Quantum star-graph analogues of PT-symmetric square wells. II: Spectra
quant-ph math.SP
For non-Hermitian equilateral q-pointed star-shaped quantum graphs of paper I
[Can. J. Phys. 90, 1287 (2012), arXiv 1205.5211] we show that due to certain
dynamical aspects of the model as controlled by the external,
rotation-symmetric complex Robin boundary conditions, the spectrum is
obtainable in a closed asymptotic-expansion form, in principle at least.
Explicit formulae up to the second order are derived for illustration, and a
few comments on their consequences are added.
| arxiv topic:quant-ph math.SP |
arxiv_dataset-57391411.3928 | Dark Bogolon-Excitons in a Linear Atomic Super-Lattice
quant-ph cond-mat.mes-hall
Dark and bright excitons are shown to appear naturally in a linear atomic
super-lattice with two atoms per unit cell. In bringing the super-lattice into
a strong coupling regime with a one-dimensional nanophotonic waveguide, bright
excitons and photons are coherently mixed to form polaritons. Treating excitons
as bosons implies a mechanism that forbids two excitations from being at the
same atomic state, which is included here through a bosonization procedure with
kinematic interactions. Interestingly these interactions couple dark and bright
excitons, and which we exploit as a new tool for exciting dark states in a
controllable way. We suggest a pump-probe experiment where two polaritons
scatter into two dark excitons that found to be correlated and are represented
as dark bogolon-excitons. The results can be adapted for any super-lattice of
active materials, e.g., of organic molecules.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-57401411.4028 | A Quantum Approximate Optimization Algorithm
quant-ph
We introduce a quantum algorithm that produces approximate solutions for
combinatorial optimization problems. The algorithm depends on a positive
integer p and the quality of the approximation improves as p is increased. The
quantum circuit that implements the algorithm consists of unitary gates whose
locality is at most the locality of the objective function whose optimum is
sought. The depth of the circuit grows linearly with p times (at worst) the
number of constraints. If p is fixed, that is, independent of the input size,
the algorithm makes use of efficient classical preprocessing. If p grows with
the input size a different strategy is proposed. We study the algorithm as
applied to MaxCut on regular graphs and analyze its performance on 2-regular
and 3-regular graphs for fixed p. For p = 1, on 3-regular graphs the quantum
algorithm always finds a cut that is at least 0.6924 times the size of the
optimal cut.
| arxiv topic:quant-ph |
arxiv_dataset-57411411.4128 | Exploiting Fine Block Triangularization and Quasilinearity in
Differential-Algebraic Equation Systems
math.NA
The $\Sigma$-method for structural analysis of a differential-algebraic
equation (DAE) system produces offset vectors from which the sparsity pattern
of DAE's system Jacobian is derived; this pattern implies a fine
block-triangular form (BTF).
This article derives a simple method for quasilinearity analysis of a DAE and
combines it with its fine BTF to construct a method for finding the minimal set
of initial values needed for consistent initialization and a method for a
block-wise computation of derivatives for the solution to the DAE.
| arxiv topic:math.NA |
arxiv_dataset-57421411.4228 | Towards Cross-Project Defect Prediction with Imbalanced Feature Sets
cs.SE
Cross-project defect prediction (CPDP) has been deemed as an emerging
technology of software quality assurance, especially in new or inactive
projects, and a few improved methods have been proposed to support better
defect prediction. However, the regular CPDP always assumes that the features
of training and test data are all identical. Hence, very little is known about
whether the method for CPDP with imbalanced feature sets (CPDP-IFS) works well.
Considering the diversity of defect data sets available on the Internet as well
as the high cost of labeling data, to address the issue, in this paper we
proposed a simple approach according to a distribution characteristic-based
instance (object class) mapping, and demonstrated the validity of our method
based on three public defect data sets (i.e., PROMISE, ReLink and AEEEM).
Besides, the empirical results indicate that the hybrid model composed of CPDP
and CPDP-IFS does improve the prediction performance of the regular CPDP to
some extent.
| arxiv topic:cs.SE |
arxiv_dataset-57431411.4328 | Opinion Dynamics with Confirmation Bias
physics.soc-ph cs.SI
Background: Confirmation bias is the tendency to acquire or evaluate new
information in a way that is consistent with one's preexisting beliefs. It is
omnipresent in psychology, economics, and even scientific practices. Prior
theoretical research of this phenomenon has mainly focused on its economic
implications possibly missing its potential connections with broader notions of
cognitive science. Methodology/Principal Findings: We formulate a
(non-Bayesian) model for revising subjective probabilistic opinion of a
confirmationally-biased agent in the light of a persuasive opinion. The
revision rule ensures that the agent does not react to persuasion that is
either far from his current opinion or coincides with it. We demonstrate that
the model accounts for the basic phenomenology of the social judgment theory,
and allows to study various phenomena such as cognitive dissonance and
boomerang effect. The model also displays the order of presentation effect|when
consecutively exposed to two opinions, the preference is given to the last
opinion (recency) or the first opinion (primacy)|and relates recency to
confirmation bias. Finally, we study the model in the case of repeated
persuasion and analyze its convergence properties. Conclusions: The standard
Bayesian approach to probabilistic opinion revision is inadequate for
describing the observed phenomenology of persuasion process. The simple
non-Bayesian model proposed here does agree with this phenomenology and is
capable of reproducing a spectrum of effects observed in psychology:
primacy-recency phenomenon, boomerang effect and cognitive dissonance. We point
out several limitations of the model that should motivate its future
development.
| arxiv topic:physics.soc-ph cs.SI |
arxiv_dataset-57441411.4428 | Cloning in nonlinear Hamiltonian quantum and hybrid mechanics
quant-ph
Possibility of state cloning is analyzed in two types of generalizations of
quantum mechanics with nonlinear evolution. It is first shown that nonlinear
Hamiltonian quantum mechanics does not admit cloning without the cloning
machine. It is then demonstrated that the addition of the cloning machine,
treated as a quantum or as a classical system, makes the cloning possible by
nonlinear Hamiltonian evolution. However, a special type of quantum-classical
theory, known as the mean-field Hamiltonian hybrid mechanics, does not admit
cloning by natural evolution. The latter represents an example of a theory
where it appears to be possible to communicate between two quantum systems at
super-luminal speed, but at the same time it is impossible to clone quantum
pure states.
| arxiv topic:quant-ph |
arxiv_dataset-57451411.4528 | A multilayered plate theory with transverse shear and normal warping
functions
physics.class-ph
A multilayered plate theory which takes into account transverse shear and
normal stretching is presented. The theory is based on a seven-unknowns
kinematic field with five warping functions. Four warping functions are related
to the transverse shear behaviour, the fifth is related to the normal
stretching. The warping functions are issued from exact three-dimensional
solutions. They are related to the variations of transverse shear and normal
stresses computed at specific points for a simply supported bending problem.
Reddy, Cho-Parmerter and (a modified version of) Beakou-Touratier theories have
been retained for comparisons. Extended versions of these theories, able to
manage the normal stretching, are also considered. All these theories can be
emulated by the kinematic field of the present model thanks to the adaptation
of the five warping functions. Results of all these theories are confronted and
compared to analytical solutions, for the bending of simply supported plates.
Various plates are considered, with special focus on very low
length-to-thickness ratios: an isotropic plate, two homogeneous orthotropic
plates with ply orientation of $0$ and $5$ degrees, a $[0/c/0]$ sandwich panel
and a $[-45/0/45/90]_s$ composite plate. Results show that models are more
accurate if their kinematic fields (i) depend on all material properties (not
only the transverse shear stiffnesses) (ii) depend on the length-to-thickness
ratio (iii) present a coupling between the $x$ and $y$ directions.
| arxiv topic:physics.class-ph |
arxiv_dataset-57461411.4628 | Entanglement dynamics and Mollow nonuplets between two coupled quantum
dots in a nanowire photonic crystal system
cond-mat.mes-hall
We introduce a nanowire-based photonic crystal waveguide system capable of
controllably mediating the photon coupling between two quantum dots which are
macroscopically separated. Using a rigorous Green-function-based master
equation approach, our two-dot system is shown to provide a wide range of
interesting quantum regimes. In particular, we demonstrate the formation of
long-lived entangled states and study the resonance fluorescence spectrum which
contains clear signatures of the coupled quantum dot pair. Depending upon the
operating frequency, one can obtain a modified Mollow triplet spectrum or a
Mollow nonuplet, namely a spectrum with nine spectral peaks. These multiple
peaks are explained in the context of photon-exchange-mediated dressed states.
Results are robust with respect to scattering loss, and spatial filtering via
propagation allows for each quantum dot's emission to be observed individually.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-57471411.4728 | Genus Periods, Genus Points and Congruent Number Problem
math.NT
In this paper, based on an ideal of Tian, we establish a new sufficient
condition for a positive integer to be a congruent number in terms of Legendre
symbols of prime factors of the positive integer. Our criterion generalizes
previous criterions of Heegner, and Birch--Stephens, Monsky, and Tian, and
conjecturally provides a list of positive density of congruent numbers. Our
method of proving our criterion is to give formulae for the analytic
Tate--Shafarevich number in terms of the so-called genus periods and genus
points. These formulae are derived from the Waldspurger formula and the
generalized Gross--Zagier formula of Yuan-Zhang-Zhang.
| arxiv topic:math.NT |
arxiv_dataset-57481411.4828 | Deformed compact extra space as dark matter candidate
gr-qc astro-ph.CO hep-th
We elaborate the possibility for a deformed extra space to be considered as
the dark matter candidate. To perform calculations a class of two-dimensional
extra metrics was considered in the framework of the multidimensional gravity.
It was shown that there exists a family of stationary metrics of the extra
space possessing point-like defect. Estimation of cross section of scattering
of a particle of the ordinary matter on a spatial domain with deformed extra
space is in agreement with the observational constraints.
| arxiv topic:gr-qc astro-ph.CO hep-th |
arxiv_dataset-57491411.4928 | Dynamics of self-gravitating systems : Variations on a theme by Michel
Henon
astro-ph.GA
In this contribution to the volume in memoriam of Michel Henon, we thought
appropriate to look at his early scientific work devoted to the dynamics of
large assemblies of interacting masses. He predicted in his PhD thesis that, in
such a system, first a collapse of mass occurs at the center and that later
binaries stars are formed there. Henceforth, the negative energy of binding of
pairs becomes a source of positive energy for the rest of the cluster which
evaporate because of that. We examine under what conditions such a singularity
can occur, and what could happen afterwards. We hope to show that this
fascinating problem of evolution of self-gravitating clusters keeps its
interest after the many years passed since Henon thesis, and is still worth
discussing now.
| arxiv topic:astro-ph.GA |
arxiv_dataset-57501411.5028 | Central charges from the $\mathcal{N} = 1$ superconformal index
hep-th
We present prescriptions for obtaining the central charges, $a$ and $c$, of a
four dimensional superconformal quantum field theory from the superconformal
index. At infinite $N$, for holographic theories dual to Sasaki-Einstein
5-manifolds the prescriptions give the $\mathcal{O}(1)$ parts of the central
charges. This allows us, among other things, to show the exact AdS/CFT matching
of $a$ and $c$ for arbitrary toric quiver CFTs without adjoint matter that are
dual to smooth Sasaki-Einstein 5-manifolds. In addition, we include evidence
from non-holographic theories for the applicability of these results outside of
a holographic setting and away from the large-$N$ limit.
| arxiv topic:hep-th |
arxiv_dataset-57511411.5128 | Elastic, electronic and magnetic properties of new oxide perovskite
BaVO3: a first-principles study
cond-mat.mtrl-sci
The structural, elastic, magnetic properties, as well as electronic structure
and chemical bonding picture of new oxide 3d1-perovskite BaVO3, recently
synthesized, were systematically investigated involving the first-principles
FLAPW-GGA calculations. The obtained results are discussed in comparison with
available experimental data, as well as with those obtained before for
isostructural and isoelectronic SrVO3 perovskite.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-57521411.5228 | Hostile Intent Enumeration using Soft Computing Techniques
cs.OH
In any tactical scenario, the successful quantification and triangulation of
potential hostile elements is instrumental to minimize any casualties which
might be incurred. The most commonly deployed infrastructures to cater to this
have mostly been surveillance systems which only extract some data pertaining
to the targets of interest in the area of observation and convey the
information to the human operators. Accordingly, with the ever increasing rate
at which warfare tactics are evolving, there has been a growing need for
smarter solutions to this problem of hostile intent enumeration. Recently, a
number of developments have been made to ameliorate the efficacy and the
certitude with which this task is performed. This paper discusses two of the
most prominent approaches which address this problem and posits the outline of
a novel solution which seeks to address the shortcomings faced by the existing
approaches.
| arxiv topic:cs.OH |
arxiv_dataset-57531411.5328 | ConceptLearner: Discovering Visual Concepts from Weakly Labeled Image
Collections
cs.CV cs.AI cs.LG
Discovering visual knowledge from weakly labeled data is crucial to scale up
computer vision recognition system, since it is expensive to obtain fully
labeled data for a large number of concept categories. In this paper, we
propose ConceptLearner, which is a scalable approach to discover visual
concepts from weakly labeled image collections. Thousands of visual concept
detectors are learned automatically, without human in the loop for additional
annotation. We show that these learned detectors could be applied to recognize
concepts at image-level and to detect concepts at image region-level
accurately. Under domain-specific supervision, we further evaluate the learned
concepts for scene recognition on SUN database and for object detection on
Pascal VOC 2007. ConceptLearner shows promising performance compared to fully
supervised and weakly supervised methods.
| arxiv topic:cs.CV cs.AI cs.LG |
arxiv_dataset-57541411.5428 | Differentially Private Algorithms for Empirical Machine Learning
cs.LG
An important use of private data is to build machine learning classifiers.
While there is a burgeoning literature on differentially private classification
algorithms, we find that they are not practical in real applications due to two
reasons. First, existing differentially private classifiers provide poor
accuracy on real world datasets. Second, there is no known differentially
private algorithm for empirically evaluating the private classifier on a
private test dataset.
In this paper, we develop differentially private algorithms that mirror real
world empirical machine learning workflows. We consider the private classifier
training algorithm as a blackbox. We present private algorithms for selecting
features that are input to the classifier. Though adding a preprocessing step
takes away some of the privacy budget from the actual classification process
(thus potentially making it noisier and less accurate), we show that our novel
preprocessing techniques significantly increase classifier accuracy on three
real-world datasets. We also present the first private algorithms for
empirically constructing receiver operating characteristic (ROC) curves on a
private test set.
| arxiv topic:cs.LG |
arxiv_dataset-57551411.5528 | Kernel density estimation of a multidimensional efficiency profile
physics.data-an hep-ex
Kernel density estimation is a convenient way to estimate the probability
density of a distribution given the sample of data points. However, it has
certain drawbacks: proper description of the density using narrow kernels needs
large data samples, whereas if the kernel width is large, boundaries and narrow
structures tend to be smeared. Here, an approach to correct for such effects,
is proposed that uses an approximate density to describe narrow structures and
boundaries. The approach is shown to be well suited for the description of the
efficiency shape over a multidimensional phase space in a typical particle
physics analysis. An example is given for the five-dimensional phase space of
the $\Lambda_b^0\to D^0p\pi$ decay.
| arxiv topic:physics.data-an hep-ex |
arxiv_dataset-57561411.5628 | First-principles calculations of phonon frequencies, lifetimes and
spectral functions from weak to strong anharmonicity: the example of
palladium hydrides
cond-mat.mtrl-sci
The variational stochastic self-consistent harmonic approximation is combined
with the calculation of third-order anharmonic coefficients within
density-functional perturbation theory and the "$2n+1$" theorem to calculate
anharmonic properties of crystals. It is demonstrated that in the perturbative
limit the combination of these two methods yields the perturbative phonon
linewidth and frequency shift in a very efficient way, avoiding the explicit
calculation of fourth-order anharmonic coefficients. Moreover, it also allows
calculating phonon lifetimes and inelastic neutron scattering spectra in solids
where the harmonic approximation breaks down and a non-perturbative approach is
required to deal with anharmonicity. To validate our approach, we calculate the
anharmonic phonon linewidth in the strongly anharmonic palladium hydrides. We
show that due to the large anharmonicity of hydrogen optical modes the
inelastic neutron scattering spectra are not characterized by a Lorentzian
line-shape, but by a complex structure including satellite peaks.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-57571411.5728 | Conserved currents for Mobius Domain Wall Fermions
hep-lat
We derive the exactly conserved vector, and almost conserved axial currents
for rational approximations to the overlap operator with a general Mobius
kernel. The approach maintains manifest Hermiticity, and allows matrix elements
of the currents to be constructed at no extra cost after solution of the usual
5d system of equations, similar to the original approach of Furman and Shamir
for domain wall Fermions.
| arxiv topic:hep-lat |
arxiv_dataset-57581411.5828 | Nucleon axial form factors from two-flavour Lattice QCD
hep-lat
We present preliminary results on the axial form factor $G_A(Q^2)$ and the
induced pseudoscalar form factor $G_P(Q^2)$ of the nucleon. A systematic
analysis of the excited-state contributions to form factors is performed on the
CLS ensemble `N6' with $m_\pi = 340 \ \text{MeV}$ and lattice spacing $a \sim
0.05 \ \text{fm}$. The relevant three-point functions were computed with
source-sink separations ranging from $t_s \sim 0.6 \ \text{fm}$ to $t_s \sim \
1.4 \ \text{fm}$. We observe that the form factors suffer from non-trivial
excited-state contributions at the source-sink separations available to us. It
is noted that naive plateau fits underestimate the excited-state contributions
and that the method of summed operator insertions correctly accounts for these
effects.
| arxiv topic:hep-lat |
arxiv_dataset-57591411.5928 | Learning to Generate Chairs, Tables and Cars with Convolutional Networks
cs.CV cs.LG cs.NE
We train generative 'up-convolutional' neural networks which are able to
generate images of objects given object style, viewpoint, and color. We train
the networks on rendered 3D models of chairs, tables, and cars. Our experiments
show that the networks do not merely learn all images by heart, but rather find
a meaningful representation of 3D models allowing them to assess the similarity
of different models, interpolate between given views to generate the missing
ones, extrapolate views, and invent new objects not present in the training set
by recombining training instances, or even two different object classes.
Moreover, we show that such generative networks can be used to find
correspondences between different objects from the dataset, outperforming
existing approaches on this task.
| arxiv topic:cs.CV cs.LG cs.NE |
arxiv_dataset-57601411.6028 | Quantifying an Adherence Path-Specific Effect of Antiretroviral Therapy
in the Nigeria PEPFAR Program
stat.AP
Since the early 2000s, evidence has accumulated for a significant
differential effect of first-line antiretroviral therapy (ART) regimens on
human immunodeficiency virus (HIV) viral load suppression. This finding was
replicated in our data from the Harvard President's Emergency Plan for AIDS
Relief (PEPFAR) program in Nigeria. Investigators were interested in finding
the source of these differences, i.e., understanding the mechanisms through
which one regimen outperforms another, particularly via adherence. This
question can be naturally formulated via mediation analysis with adherence
playing the role of a mediator. Existing mediation analysis results, however,
have relied on an assumption of no exposure-induced confounding of the
intermediate variable, and generally require an assumption of no unmeasured
confounding for nonparametric identification. Both assumptions are violated by
the presence of drug toxicity. In this paper, we relax these assumptions and
show that certain path-specific effects remain identified under weaker
conditions. We focus on the path-specific effect solely mediated by adherence
and not by toxicity and propose an estimator for this effect. We illustrate
with simulations and present results from a study applying the methodology to
the Harvard PEPFAR data. Supplementary materials are available online.
| arxiv topic:stat.AP |
arxiv_dataset-57611411.6128 | Testing the quasi-static approximation in $f(R)$ gravity simulations
astro-ph.CO
Numerical simulations in modified gravity have commonly been performed under
the quasi-static approximation -- that is, by neglecting the effect of time
derivatives in the equation of motion of the scalar field that governs the
fifth force in a given modified gravity theory. To test the validity of this
approximation, we analyse the case of $f(R)$ gravity beyond this quasi-static
limit, by considering effects, if any, these terms have in the matter and
velocity divergence cosmic fields. To this end, we use the adaptive mesh
refinement code ECOSMOG to study three variants ($|f_{R}|= 10^{-4}[$F4$],
10^{-5}[$F5$]$ and $10^{-6}[$F6$]$) of the Hu-Sawicki $f(R)$ gravity model,
each of which refers to a different magnitude for the scalar field that
generates the fifth force. We find that for F4 and F5, which show stronger
deviations from standard gravity, a low-resolution simulation is enough to
conclude that time derivatives make a negligible contribution to the matter
distribution. The F6 model shows a larger deviation from the quasi-static
approximation, but one that diminishes when re-simulated at higher resolution.
We therefore come to the conclusion that the quasi-static approximation is
valid for the most practical applications in $f(R)$ cosmologies.
| arxiv topic:astro-ph.CO |
arxiv_dataset-57621411.6228 | From Image-level to Pixel-level Labeling with Convolutional Networks
cs.CV
We are interested in inferring object segmentation by leveraging only object
class information, and by considering only minimal priors on the object
segmentation task. This problem could be viewed as a kind of weakly supervised
segmentation task, and naturally fits the Multiple Instance Learning (MIL)
framework: every training image is known to have (or not) at least one pixel
corresponding to the image class label, and the segmentation task can be
rewritten as inferring the pixels belonging to the class of the object (given
one image, and its object class). We propose a Convolutional Neural
Network-based model, which is constrained during training to put more weight on
pixels which are important for classifying the image. We show that at test
time, the model has learned to discriminate the right pixels well enough, such
that it performs very well on an existing segmentation benchmark, by adding
only few smoothing priors. Our system is trained using a subset of the Imagenet
dataset and the segmentation experiments are performed on the challenging
Pascal VOC dataset (with no fine-tuning of the model on Pascal VOC). Our model
beats the state of the art results in weakly supervised object segmentation
task by a large margin. We also compare the performance of our model with state
of the art fully-supervised segmentation approaches.
| arxiv topic:cs.CV |
arxiv_dataset-57631411.6328 | Explicit MDS Codes for Optimal Repair Bandwidth
cs.IT math.IT
MDS codes are erasure-correcting codes that can correct the maximum number of
erasures for a given number of redundancy or parity symbols. If an MDS code has
$r$ parities and no more than $r$ erasures occur, then by transmitting all the
remaining data in the code, the original information can be recovered. However,
it was shown that in order to recover a single symbol erasure, only a fraction
of $1/r$ of the information needs to be transmitted. This fraction is called
the repair bandwidth (fraction). Explicit code constructions were given in
previous works. If we view each symbol in the code as a vector or a column over
some field, then the code forms a 2D array and such codes are especially widely
used in storage systems. In this paper, we address the following question:
given the length of the column $l$, number of parities $r$, can we construct
high-rate MDS array codes with optimal repair bandwidth of $1/r$, whose code
length is as long as possible? In this paper, we give code constructions such
that the code length is $(r+1)\log_r l$.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-57641411.6428 | An extended Generalised Variance, with Applications
math.ST stat.TH
We consider a measure $\psi$ k of dispersion which extends the notion of
Wilk's generalised variance, or entropy, for a d-dimensional distribution, and
is based on the mean squared volume of simplices of dimension k $\le$ d formed
by k + 1 independent copies. We show how $\psi$ k can be expressed in terms of
the eigenvalues of the covariance matrix of the distribution, also when a
n-point sample is used for its estimation, and prove its concavity when raised
at a suitable power. Some properties of entropy-maximising distributions are
derived, including a necessary and sufficient condition for optimality.
Finally, we show how this measure of dispersion can be used for the design of
optimal experiments, with equivalence to A and D-optimal design for k = 1 and k
= d respectively. Simple illustrative examples are presented.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-57651411.6528 | Structural Changes in Thermoelectric SnSe at High Pressures
cond-mat.mtrl-sci
The crystal structure of the thermoelectric material tin selenide has been
investigated with angle-dispersive synchrotron x-ray powder diffraction under
hydrostatic pressure up to 27 GPa. With increasing pressure, a continuous
evolution of the crystal structure from the GeS type to the higher-symmetry TlI
type was observed, with a critical pressure of 10.5(3) GPa. The orthorhombic
high-pressure modification, beta'-SnSe, is closely related to the
pseudo-tetragonal high-temperature modification at ambient pressure. The
similarity between the changes of the crystal structure at elevated
temperatures and at high pressures suggests the possibility that strained thin
films of SnSe may provide a route to overcoming the problem of the limited
thermal stability of beta-SnSe at high temperatures.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-57661411.6628 | Primordial star clusters at extreme magnification
astro-ph.CO
Gravitationally lensed galaxies with magnification ~10-100 are routinely
detected at high redshifts, but magnifications significantly higher than this
are hampered by a combination of low probability and large source sizes.
Magnifications of ~1000 may nonetheless be relevant in the case of
intrinsically small, high-redshift objects with very high number densities.
Here, we explore the prospects of detecting compact (< 10 pc), high-redshift (z
> 7) Population III star clusters at such extreme magnifications in large-area
surveys with planned telescopes like Euclid, WFIRST and WISH. We find that the
planned WISH 100 sq. deg ultradeep survey may be able to detect a small number
of such objects, provided that the total stellar mass of these star clusters is
> 10000 solar masses. If candidates for such lensed Population III star
clusters are found, follow-up spectroscopy of the surrounding nebula with the
James Webb Space Telescope or groundbased Extremely Large Telescopes should be
able to confirm the Population III nature of these objects. Multiband
photometry of these objects with the James Webb Space Telescope also has the
potential to confirm that the stellar initial mass function in these Population
III star clusters is top-heavy, as supported by current simulations.
| arxiv topic:astro-ph.CO |
arxiv_dataset-57671411.6728 | Boundedness of anti-canonical volumes of singular log Fano threefolds
math.AG
We prove Weak Borisov--Alexeev--Borisov Conjecture in dimension three which
states that the anti-canonical volume of an $\epsilon$-klt log Fano pair of
dimension three is bounded from above.
| arxiv topic:math.AG |
arxiv_dataset-57681411.6828 | Gravitational Collapse and Disk Formation in Magnetized Cores
astro-ph.GA astro-ph.SR
We discuss the effects of the magnetic field observed in molecular clouds on
the process of star formation, concentrating on the phase of gravitational
collapse of low-mass dense cores, cradles of sunlike stars. We summarize recent
analytic work and numerical simulations showing that a substantial level of
magnetic field diffusion at high densities has to occur in order to form
rotationally supported disks. Furthermore, newly formed accretion disks are
threaded by the magnetic field dragged from the parent core during the
gravitational collapse. These disks are expected to rotate with a sub-Keplerian
speed because they are partially supported by magnetic tension against the
gravity of the central star. We discuss how sub-Keplerian rotation makes it
difficult to eject disk winds and accelerates the process of planet migration.
Moreover, magnetic fields modify the Toomre criterion for gravitational
instability via two opposing effects: magnetic tension and pressure increase
the disk local stability, but sub-Keplerian rotation makes the disk more
unstable. In general, magnetized disks are more stable than their nonmagnetic
counterparts; thus, they can be more massive and less prone to the formation of
giant planets by gravitational instability.
| arxiv topic:astro-ph.GA astro-ph.SR |
arxiv_dataset-57691411.6928 | A Tag Identification Approach Based On Fragile Watermark
cs.MM
This paper proposes a tag identify approach based on fragile Watermark that
based on Least significant bit of the replacement that we first use a special
way to initialize the cover to ensure that we can use random positions to embed
the information of tag. Using this way enhance the security of other to get the
right information of this tag. Finally as long as the covered information can
be decoded, the completeness and accuracy of the tag information can be
guaranteed. the result of simulation experiment show that this approach has
high sensitivity and security .
| arxiv topic:cs.MM |
arxiv_dataset-57701411.7028 | The Possible Moon of Kepler-90g is a False Positive
astro-ph.EP
The discovery of an exomoon would provide deep insights into planet formation
and the habitability of planetary systems, with transiting examples being
particularly sought after. Of the hundreds of Kepler planets now discovered,
the seven-planet system Kepler-90 is unusual for exhibiting an unidentified
transit-like signal in close proximity to one of the transits of the
long-period gas-giant Kepler-90g, as noted by Cabrera et. al. (2014). As part
of the 'Hunt for Exomoons with Kepler' (HEK) project, we investigate this
possible exomoon signal and find it passes all conventional photometric,
dynamical and centroid diagnostic tests. However, pixel-level light curves
indicate that the moon-like signal occurs on nearly all of the target's pixels,
which we confirm using a novel way of examining pixel-level data which we dub
the 'transit centroid'. This test reveals that the possible exomoon to
Kepler-90g is likely a false positive, perhaps due to a cosmic ray induced
Sudden Pixel Sensitivity Dropout (SPSD). This work highlights the extreme care
required for seeking non-periodic low-amplitude transit signals, such as
exomoons.
| arxiv topic:astro-ph.EP |
arxiv_dataset-57711411.7128 | Electrical manipulation of orbital occupancy and magnetic anisotropy in
manganites
cond-mat.mtrl-sci
Electrical manipulation of lattice, charge, and spin has been realized
respectively by the piezoelectric effect, field-effect transistor, and electric
field control of ferromagnetism, bringing about dramatic promotions both in
fundamental research and industrial production. However, it is generally
accepted that the orbital of materials are impossible to be altered once they
have been made. Here we use electric-field to dynamically tune the electronic
phase transition in (La,Sr)MnO3 films with different Mn^4+/(Mn^3+ + Mn^4+)
ratios. The orbital occupancy and corresponding magnetic anisotropy of these
thin films are manipulated by gate voltage in a reversible and quantitative
manner. Positive gate voltage increases the proportion of occupancy of the
orbital and magnetic anisotropy that were initially favored by strain
(irrespective of tensile and compressive), while negative gate voltage reduces
the concomitant preferential orbital occupancy and magnetic anisotropy. Besides
its fundamental significance in orbital physics, our findings might advance the
process towards practical oxide-electronics based on orbital.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-57721411.7228 | Efficient SimRank Computation via Linearization
cs.DS
SimRank, proposed by Jeh and Widom, provides a good similarity measure that
has been successfully used in numerous applications. While there are many
algorithms proposed for computing SimRank, their computational costs are very
high. In this paper, we propose a new computational technique, "SimRank
linearization," for computing SimRank, which converts the SimRank problem to a
linear equation problem. By using this technique, we can solve many SimRank
problems, such as single-pair compuation, single-source computation, all-pairs
computation, top k searching, and similarity join problems, efficiently.
| arxiv topic:cs.DS |
arxiv_dataset-57731411.7328 | Characterization of the nitrogen split interstitial defect in wurtzite
aluminum nitride using density functional theory
cond-mat.mtrl-sci
We carried out Heyd-Scuseria-Ernzerhof hybrid density functional theory plane
wave supercell calculations in wurtzite aluminum nitride in order to
characterize the geometry, formation energies, transition levels and hyperfine
tensors of the nitrogen split interstitial defect. The calculated hyperfine
tensors may provide useful fingerprint of this defect for electron paramagnetic
resonance measurement.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-57741411.7428 | How a charge conserving alternative to Maxwells displacement current
entails a Darwin like approximation to the solutions of Maxwells equations
physics.class-ph
Though sufficient for local conservation of charge, Maxwells displacement
current is not necessary. An alternative to the Ampere-Maxwell equation is
exhibited and the alternatives electric and magnetic fields and scalar and
vector potentials are expressed in terms of the charge and current densities.
The magnetic field is shown to satisfy the Biot_Savart Law. The electric field
is shown to be the sum of the gradient of a scalar potential and the time
derivative of a vector potential which is different from but just as tractable
as the simplest vector potential that yields the Biot_Savart Law The
alternative describes a theory in which action is instantaneous and so may
provide a good approximation to Maxwells equations where and when the finite
speed of light can be neglected. The result recalls the Darwin approximation
which arose from the study classical charged point particles to order (v/c)2 in
the Lagrangian. Unlike Darwin, this approach does not depend on the
constitution of the electric current. Instead, this approach grows from a
straightforward revision of the Ampere Equation that enforces the local
conservation of charge.
| arxiv topic:physics.class-ph |
arxiv_dataset-57751411.7528 | Can Baryon Chiral Perturbation Theory be used to extrapolate lattice
data for the moment $\langle x\rangle_{u-d}$ of the nucleon?
hep-lat hep-ph
We discuss the question in the title employing manifestly covariant Baryon
Chiral Perturbation Theory and recent high-statistics lattice results published
in [1].
| arxiv topic:hep-lat hep-ph |
arxiv_dataset-57761411.7628 | Efficient production of an 87Rb F = 2, mF = 2 Bose-Einstein condensate
in a hybrid trap
cond-mat.quant-gas physics.atom-ph quant-ph
We have realized Bose-Einstein condensation (BEC) of 87Rb in the F=2, m_F=2
hyperfine substate in a hybrid trap, consisting of a quadrupole magnetic field
and a single optical dipole beam. The symmetry axis of the quadrupole magnetic
trap coincides with the optical beam axis, which gives stronger axial
confinement than previous hybrid traps. After loading 2x10^6 atoms at 14 muK
from a quadrupole magnetic trap into the hybrid trap, we perform efficient
forced evaporation and reach the onset of BEC at a temperature of 0.5 muK and
with 4x10^5 atoms. We also obtain thermal clouds of 1x10^6 atoms below 1 muK in
a pure single beam optical dipole trap, by ramping down the magnetic field
gradient after evaporative cooling in the hybrid trap.
| arxiv topic:cond-mat.quant-gas physics.atom-ph quant-ph |
arxiv_dataset-57771411.7728 | A uniqueness of periodic maps on surfaces
math.GT
Kulkarni showed that, if g is greater than 3, a periodic map on an oriented
surface S_g of genus g with order more than or equal to 4g is uniquely
determined by its order, up to conjugation and power. In this paper, we show
that, if g is greater than 30, the same phenomenon happens for periodic maps on
the surfaces with orders more than 8g/3 and, for any integer N, there is g > N
such that there are periodic maps of S_g of order 8g/3 which are not conjugate
up to power each other. Moreover, as a byproduct of our argument, we provide a
short proof of Wiman's classical theorem: the maximal order of periodic maps of
S_g is 4g+2.
| arxiv topic:math.GT |
arxiv_dataset-57781411.7828 | Hidden charm and bottom molecular states
hep-ph
We investigate heavy quark symmetries for heavy light meson-antimeson systems
in a contact-range effective field theory. In the SU(3) light flavor limit, the
leading order Lagrangian respecting heavy quark spin symmetry contains four
independent counter-terms. Neglecting $1/m_Q$ corrections, three of these low
energy constants can be determ1ined by theorizing a molecular description of
the $X(3872)$ and $Z_b(10610)$ states. Thus, we can predict new hadronic
molecules, in particular the isovector charmonium partners of the $Z_b(10610)$
and the $Z_b(10650)$ states. We also discuss hadron molecules composed of a
heavy meson and a doubly-heavy baryon, which would be related to the heavy
meson-antimeson molecules thanks to the heavy antiquark-diquark symmetry.
Finally, we also study the $X(3872) \to D^0\bar D^0\pi^0$ decay, which is not
only sensitive to the short distance part of the $X(3872)$ molecular wave
function, as the $J/\psi\pi\pi$ and $J/\psi3\pi$ $X(3872)$ decay modes are, but
it is also affected by the long-distance structure of the resonance.
Furthermore, this decay might provide some information on the interaction
between the $D\bar D$ charm mesons.
| arxiv topic:hep-ph |
arxiv_dataset-57791411.7928 | New methods to constrain the radio transient rate: results from a survey
of four fields with LOFAR
astro-ph.IM astro-ph.HE
We report on the results of a search for radio transients between 115 and
190\,MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored
with cadences between 15 minutes and several months. A total of 151 images were
obtained, giving a total survey area of 2275 deg$^2$. We analysed our data
using standard LOFAR tools and searched for radio transients using the LOFAR
Transients Pipeline (TraP). No credible radio transient candidate has been
detected; however, we are able to set upper limits on the surface density of
radio transient sources at low radio frequencies. We also show that
low-frequency radio surveys are more sensitive to steep-spectrum coherent
transient sources than GHz radio surveys. We used two new statistical methods
to determine the upper limits on the transient surface density. One is free of
assumptions on the flux distribution of the sources, while the other assumes a
power-law distribution in flux and sets more stringent constraints on the
transient surface density. Both of these methods provide better constraints
than the approach used in previous works. The best value for the upper limit we
can set for the transient surface density, using the method assuming a
power-law flux distribution, is 1.3$\cdot$10$^{-3}$ deg$^{-2}$ for transients
brighter than 0.3 Jy with a time-scale of 15 min, at a frequency of 150 MHz. We
also calculated for the first time upper limits for the transient surface
density for transients of different time-scales. We find that the results can
differ by orders of magnitude from previously reported, simplified estimates.
| arxiv topic:astro-ph.IM astro-ph.HE |
arxiv_dataset-57801412.0022 | Galaxy triplets in Sloan Digital Sky Survey Data Release 7 - III.
Analysis of Configuration and Dynamics
astro-ph.GA
We analyse the spatial configuration and the dynamical properties of a sample
of 92 galaxy triplets obtained from the SDSS-DR7 (SDSS-triplets) restricted to
have members with spectroscopic redshifts in the range $0.01\le z \le 0.14 $
and absolute r-band luminosities brighter than $M_r=-20.5$. The configuration
analysis was performed through Agekyan & Anosova map (AA-map). We estimated
dynamical parameters, namely the radius of the system, the velocity dispersion,
a dimensionless crossing-time and the virial mass. We compared our results with
those obtained for a sample of triplets from the catalogue "Isolated Triplets
of Galaxies" (K-triplets) and a sample of Compact Groups. We have also studied
a mock catalogue in order to compare real and projected configurations, and to
estimate the three dimensional dynamical parameters of the triple systems. We
found that the SDSS-triplets prefer alignment configurations while K-triplets
present an uniform distribution in the AA-map. From the dynamical analysis we
conclude that the SDSS-triplets, K-triplets and Compact Groups present a
similar behaviour comprising compact systems with low crossing-time values,
with velocity dispersions and virial masses similar to those of low mass loose
groups. Moreover, we found that observed and simulated triplets present similar
dynamical parameters. We also performed an analysis of the dark matter content
of galaxy triplets finding that member galaxies of mock triplets belong to the
same dark matter halo, showing a dynamical co-evolution of the system. These
results suggest that the configuration and dynamics of triple systems favour
galaxy interactions and mergers.
| arxiv topic:astro-ph.GA |
arxiv_dataset-57811412.0122 | Triple Root Systems, Quasi-determinantal Quivers and Linear Free
Divisors
math.AG
We start by constructing a new root system for rational triple singularities
and determine the number of roots for each rational triple singularity. Then we
show that, for each root, we obtain a linear free divisor. So we obtain a new
family of linear free divisors. This gives the converse part of an existing
theorem which says, by using the quiver representation, that linear free
divisors come from a tree. We prove that our construction is independent of the
orientation on the rational triple trees. Furthermore, we deduce that linear
free divisors defined by rational triple quivers satisfy the logarithmic
comparison theorem. In last section, we generalize the results of these results
to rational quasi-determinantal singularities.
| arxiv topic:math.AG |
arxiv_dataset-57821412.0222 | The non-commutative Khintchine inequalities for p<1
math.OA math.FA
We give a proof of the Khintchine inequalities in non-commutative
$L_p$-spaces for all $0< p<1$. These new inequalities are valid for the
Rademacher functions or Gaussian random variables, but also for more general
sequences, e.g. for the analogues of such random variables in free probability.
We also prove a factorization for operators from a Hilbert space to a non
commutative $L_p$-space, which is new for $0<p<1$. We end by showing that Mazur
maps are H\"older on semifinite von Neumann algebras. The main tool is a new
form of H\"older inequality for non commutative Lp spaces with weights.
| arxiv topic:math.OA math.FA |
arxiv_dataset-57831412.0322 | Quantum Monte Carlo calculations in solids with downfolded Hamiltonians
cond-mat.mtrl-sci cond-mat.str-el
We present a systematic downfolding many-body approach for extended systems.
Many-body calculations operate on a simpler Hamiltonian which retains
material-specific properties. The Hamiltonian is systematically improvable and
allows one to dial, in principle, between the simplest model and the original
Hamiltonian. As a by-product, pseudopotential errors are essentially eliminated
using a frozen-core treatment. The computational cost of the many-body
calculation is dramatically reduced without sacrificing accuracy. We use the
auxiliary-field quantum Monte Carlo (AFQMC) method to solve the downfolded
Hamiltonian. Excellent accuracy is achieved for a range of solids, including
semiconductors, ionic insulators, and metals. We further test the method by
determining the spin gap in NiO, a challenging prototypical material with
strong electron correlation effects. This approach greatly extends the reach of
general, ab initio many-body calculations in materials.
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-57841412.0422 | Parameter Space Design of Repetitive Controllers for Satisfying a Robust
Performance Requirement
cs.SY
A parameter space procedure for designing chosen parameters of a repetitive
controller to satisfy a robust performance criterion is presented. Using this
method, low order robust repetitive controllers can be designed and implemented
for plants that possibly include time delay, poles on the imaginary axis and
discontinuous weights. A design and simulation study based on a high speed
atomic force microscope position control example is utilized to illustrate the
method presented in this paper.
| arxiv topic:cs.SY |
arxiv_dataset-57851412.0522 | Bell and steering scenarios in terms of operator systems
math.OA math.FA quant-ph
The aim of this paper is to indicate possible applications of operator
systems in qualitative description of varoius scenarios while studying
non-locality. To this end we study in details the notion of generalized
non-commuting cube. Following ideas of Fritz and
Farenick-Kavruk-Paulsen-Todorov we show in systematic way that various classes
of Tsirelson's correlation boxes as well as NPA hierarchies can be described by
using various operator system tensor products of generalized non-commuting
cubes. Moreover, we show also that noncommuting cubes can be applied for the
description of steering assemblages. Next we study some aproximation properties
of noncommuting cubes by finite dimensional models. Finaly, we indicate
possibility to use the framework operator systems for studying Bell and
steering inequalities.
| arxiv topic:math.OA math.FA quant-ph |
arxiv_dataset-57861412.0622 | Thermoelectric transport properties of a T-shaped double quantum dot
system in the Coulomb blockade regime
cond-mat.mes-hall
We investigate the thermoelectric properties of a T-shaped double quantum dot
system described by a generalized Anderson Hamiltonian. The system's electrical
conduction (G) and the fundamental thermoelectric parameters such as the
Seebeck coefficient ($S$) and the thermal conductivity ($\kappa$), along with
the system's thermoelectric figure of merit (ZT) are numerically estimated
based on a Green's function formalism that includes contributions up to the
Hartree-Fock level. Our results account for finite onsite Coulomb interaction
terms in both component quantum dots and discuss various ways leading to an
enhanced thermoelectric figure of merit for the system. We demonstrate that the
presence of Fano resonances in the Coulomb blockade regime is responsible for a
strong violation of the Wiedemann-Franz law and a considerable enhancement of
the system's figure of merit ($ZT$).
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-57871412.0722 | Creation of a high spatiotemporal resolution global database of
continuous mangrove forest cover for the 21st Century (CGMFC-21)
physics.geo-ph physics.ao-ph
The goal of this research is to provide high resolution local, regional,
national and global estimates of annual mangrove forest area from 2000 through
to 2012. To achieve this we synthesize the Global Forest Change database, the
Terrestrial Ecosystems of the World database, and the Mangrove Forests of the
World database to extract mangrove forest cover at high spatial and temporal
resolutions. We then use the new database to monitor mangrove cover at the
global, national and protected area scales. Countries showing relatively high
amounts of mangrove loss include Myanmar, Malaysia, Cambodia, Indonesia, and
Guatemala. Indonesia remains by far the largest mangrove-holding nation,
containing between 26 percent and 29 percent of the global mangrove inventory
with a deforestation rate of between 0.26 percent and 0.66 percent annually.
Global mangrove deforestation continues but at a much reduced rate of between
0.16 percent and 0.39 percent annually. Southeast Asia is a region of concern
with mangrove deforestation rates between 3.58 percent and 8.08 percent during
the analysis period, this in a region containing half of the entire global
mangrove forest inventory. The global mangrove deforestation pattern from 2000
to 2012 is one of decreasing rates of deforestation, with many nations
essentially stable, with the exception of the largest mangrove-holding region
of Southeast Asia. We provide a standardized global spatial dataset that
monitors mangrove deforestation globally at high spatiotemporal resolutions,
covering 99 percent of all mangrove forests. These data can be used to drive
the mangrove research agenda particularly as it pertains to improved monitoring
of mangrove carbon stocks and the establishment of baseline local mangrove
forest inventories required for payment for ecosystem service initiatives.
| arxiv topic:physics.geo-ph physics.ao-ph |
arxiv_dataset-57881412.0822 | Micro-metric electronic patterning of a topological band structure using
a photon beam
cond-mat.mtrl-sci
In an ideal 3D topological insulator (TI), the bulk is insulating and the
surface conducting due to the existence of metallic states that are localized
on the surface; these are the topological surface states. Quaternary Bi-based
compounds of Bi$_{2-x}$Sb$_{x}$Te$_{3-y}$Se$_{y}$ with finely-tuned bulk
stoichiometries are good candidates for realizing ideal 3D TI behavior due to
their bulk insulating character. However, despite its insulating bulk in
transport experiments, the surface region of
Bi$_{2-x}$Sb$_{x}$Te$_{3-y}$Se$_{y}$ crystals cleaved in ultrahigh vacuum also
exhibits occupied states originating from the bulk conduction band. This is due
to adsorbate-induced downward band-bending, a phenomenon known from other
Bi-based 3D TIs. Here we show, using angle-resolved photoemission, how an EUV
light beam of moderate flux can be used to exclude these topologically trivial
states from the Fermi level of Bi$_{1.46}$Sb$_{0.54}$Te$_{1.7}$Se$_{1.3}$
single crystals, thereby re-establishing the purely topological character of
the low lying electronic states of the system. We furthermore prove that this
process is highly local in nature in this bulk-insulating TI, and are thus able
to imprint structures in the spatial energy landscape at the surface. We
illustrate this by `writing' micron-sized letters in the Dirac point energy of
the system.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-57891412.0922 | Dispersion Corrected DFT Study of Pentacene Thin Films on Flat and
Vicinal Au Surfaces
cond-mat.mtrl-sci
Here we a present a density functional theory study of pentacene ultra-thin
films on flat [(111)] and vicinal [(455)] Au surfaces. We have performed
crystal and electronic structure calculations by using PBE and optB86b-vdW
functionals and investigated the effects of long range Van der Waals
interactions for different coverages starting from a single isolated molecule
up to 4 monolayers of coverage. For an isolated molecule both functionals yield
the hollow site as the most stable one with bridge-60 site being very close in
energy in case of optB86b-vdW. Binding strength of an isolated pentacene on the
step edge was found to be much larger than that on the terrace sites. Different
experimentally reported monolayer structures were compared and the (6 x 3) unit
cell was found to be energetically more stable than the (2 x 2 $\sqrt{7}$) and
(2 x $\sqrt{31}$) ones. For one monolayer films while dispersion corrected
calculations favored flat pentacene molecules on terraces, standard (PBE)
calculations either found tilted and flat configurations to be energetically
similar (on (111) surface) or favored the tilted configuration (on (455)
surface). PDOS calculations performed with optB86b-vdW functional showed larger
dispersion of molecular orbitals over the Au states for the (455) surface when
compared with the (111) surface, indicating an enhanced charge carrier
transport at the pentacene-gold interface in favor of the vicinal surface.
Starting with the second monolayer, both functionals favored tilted
configurations for both surfaces. Our results underline the importance of the
dispersion corrections for the loosely bound systems like pentacene on gold and
the role played by step edges in determining the multilayer film structure and
charge transfer at the organic molecule-metal interface.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-57901412.1022 | Perfect quantum state transfer of hard-core bosons on weighted path
graphs
quant-ph cond-mat.quant-gas
The ability to accurately transfer quantum information through networks is an
important primitive in distributed quantum systems. While perfect quantum state
transfer (PST) can be effected by a single particle undergoing continuous-time
quantum walks on a variety of graphs, it is not known if PST persists for many
particles in the presence of interactions. We show that if single-particle PST
occurs on one-dimensional weighted path graphs, then systems of hard-core
bosons undergoing quantum walks on these paths also undergo PST. The analysis
extends the Tonks-Girardeau ansatz to weighted graphs using techniques in
algebraic graph theory. The results suggest that hard-core bosons do not
generically undergo PST, even on graphs which exhibit single-particle PST.
| arxiv topic:quant-ph cond-mat.quant-gas |
arxiv_dataset-57911412.1122 | A nonextensive statistical model of multiple particle breakage
cond-mat.stat-mech
A time-dependent statistical description of multiple particle breakage is
presented. The approach combines the Tsallis non-extensive entropy with a
fractal kinetic equation for the time variation of the number of fragments. The
obtained fragment size distribution function is tested by fitting some
experimental reports.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-57921412.1222 | M.A. Krasnoselskii theorem and iteration methods of solving ill-posed
linear problems with a self-adjoint operator
math.FA
The article deals with iterative methods of solving linear operator equations
$x = Bx + f$ and $Ax = f$ with self-adjoint operators in Hilbert space $X$ in
critical case when $\rho(B) = 1$ and $0 \in {\rm Sp}\, A$. The main results are
based on the use of M.A. Krasnosel'ski\u{i} theorem about the convergence of
the successive approximations and some its modifications and refinements.
| arxiv topic:math.FA |
arxiv_dataset-57931412.1322 | Aggregation of theta-polymers in spherical confinement
cond-mat.soft
We investigate the aggregation transition of theta polymers in spherical
confinement with multicanonical simulations. This allows for a systematic study
of the effect of density on the aggregation transition temperature for up to 24
monodisperse polymers. Our results for solutions in the dilute regime show that
polymers can be considered isolated for all temperatures larger than the
aggregation temperature, which is shown to be a function of the density. The
resulting competition between single-polymer collapse and aggregation yields
the lower temperature bound of the isolated chain approximation. We provide
entropic and energetic arguments to describe the density dependence and
finite-size effects of the aggregation transition for monodisperse solutions in
finite systems. This allows us to estimate the aggregation transition
temperature of dilute systems in a spherical cavity, using a few simulations of
small, sufficiently dilute polymer systems.
| arxiv topic:cond-mat.soft |
arxiv_dataset-57941412.1422 | Ambipolar surface state transport in non-metallic stoichiometric
Bi$_2$Se$_3$ crystals
cond-mat.mtrl-sci cond-mat.mes-hall cond-mat.str-el
Achieving true bulk insulating behavior in Bi$_2$Se$_3$, the archetypal
topological insulator with a simplistic one-band electronic structure and
sizable band gap, has been prohibited by a well-known self-doping effect caused
by selenium vacancies, whose extra electrons shift the chemical potential into
the bulk conduction band. We report a new synthesis method for achieving
stoichiometric Bi$_2$Se$_3$ crystals that exhibit nonmetallic behavior in
electrical transport down to low temperatures. Hall effect measurements
indicate the presence of both electron- and hole-like carriers, with the latter
identified with surface state conduction and the achievement of ambipolar
transport in bulk Bi$_2$Se$_3$ crystals without gating techniques. With carrier
mobilities surpassing the highest values yet reported for topological surface
states in this material, the achievement of ambipolar transport via upward band
bending is found to provide a key method to advancing the potential of this
material for future study and applications.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall cond-mat.str-el |
arxiv_dataset-57951412.1522 | When Does Linear Stability Not Exclude Nonlinear Instability ?
nlin.PS cond-mat.quant-gas physics.optics
We describe a mechanism that results in the nonlinear instability of
stationary states even in the case where the stationary states are linearly
stable. This instability is due to the nonlinearity-induced coupling of the
linearization's internal modes of negative energy with the wave continuum. In a
broad class of nonlinear Schr{\"o}dinger (NLS) equations considered, the
presence of such internal modes guarantees the nonlinear instability of the
stationary states in the evolution dynamics. To corroborate this idea, we
explore three prototypical case examples: (a) an anti-symmetric soliton in a
double-well potential, (b) a twisted localized mode in a one-dimensional
lattice with cubic nonlinearity, and (c) a discrete vortex in a two-dimensional
saturable lattice. In all cases, we observe a weak nonlinear instability,
despite the linear stability of the respective states.
| arxiv topic:nlin.PS cond-mat.quant-gas physics.optics |
arxiv_dataset-57961412.1622 | Cleft and Galois extensions associated to a weak Hopf quasigroup
math.QA
In this paper we introduce the notions of cleft and Galois (with normal
basis) extension associated to a weak Hopf quasigroup. We show that, under
suitable conditions, both notions are equivalent. As a particular instance we
recover the classical results for (weak) Hopf algebras. Moreover, taking into
account that weak Hopf quasigroups generalize the notion of Hopf quasigroup, we
obtain the definitions of cleft and Galois (with normal basis) extension
associated to a Hopf quasigroup and we get the equivalence betwen these
extensions in this setting.
| arxiv topic:math.QA |
arxiv_dataset-57971412.1722 | Fast quantum algorithm for EC3 problem with trapped ions
quant-ph
Adiabatic quantum computing~(AQC) is based on the adiabatic principle, where
a quantum system remains in an instantaneous eigenstate of the driving
Hamiltonian. The final state of the Hamiltonian encodes solution to the problem
of interest. While AQC has distinct advantages, recent researches have shown
that quantumness such as quantum coherence in adiabatic processes may be lost
entirely due to the system-bath interaction when the evolution time is long,
and consequently the expected quantum speedup dose not show up. Here we propose
a fast-signal assisted adiabatic quantum algorithm. We find that by applying a
sequence of fast random or regular signals during the evolution process, the
runtime can be reduced greatly, yet advantages of the adiabatic algorithm
remain intact. Significantly, we present a \emph{randomized} Trotter formula
and show that the driving Hamiltonian and the sequence of fast signals can be
implemented simultaneously. We apply the algorithm for solving the $3$-bit
exact cover problem~(EC$3$) and put forward an approach for implementing the
problem with trapped ions.
| arxiv topic:quant-ph |
arxiv_dataset-57981412.1822 | Meson-exchange currents and quasielastic predictions for charged-current
neutrino-12C scattering in the superscaling approach
nucl-th
We evaluate and discuss the impact of meson-exchange currents (MECs) on
charged-current quasielastic neutrino cross sections. We consider the nuclear
transverse response arising from two-particle two-hole states excited by the
action of electromagnetic, purely isovector meson-exchange currents in a fully
relativistic framework based on the work by the Torino Collaboration [A. D.
Pace, M. Nardi, W. M. Alberico, T. W. Donnelly, and A. Molinari, Nucl. Phys.
A726, 303 (2003)]. An accurate parametrization of this MEC response as a
function of the momentum and energy transfers involved is presented. Results of
neutrino-nucleus cross sections using this MEC parametrization together with a
recent scaling approach for the one-particle one-hole contributions (named
SuSAv2) are compared with experimental data (MiniBooNE, MINERvA, NOMAD and T2K
Collaborations).
| arxiv topic:nucl-th |
arxiv_dataset-57991412.1922 | Nonstationary ETAS models for nonstandard earthquakes
stat.AP
The conditional intensity function of a point process is a useful tool for
generating probability forecasts of earthquakes. The epidemic-type aftershock
sequence (ETAS) model is defined by a conditional intensity function, and the
corresponding point process is equivalent to a branching process, assuming that
an earthquake generates a cluster of offspring earthquakes (triggered
earthquakes or so-called aftershocks). Further, the size of the
first-generation cluster depends on the magnitude of the triggering (parent)
earthquake. The ETAS model provides a good fit to standard earthquake
occurrences. However, there are nonstandard earthquake series that appear under
transient stress changes caused by aseismic forces such as volcanic magma or
fluid intrusions. These events trigger transient nonstandard earthquake swarms,
and they are poorly fitted by the stationary ETAS model. In this study, we
examine nonstationary extensions of the ETAS model that cover nonstandard
cases. These models allow the parameters to be time-dependent and can be
estimated by the empirical Bayes method. The best model is selected among the
competing models to provide the inversion solutions of nonstationary changes.
To address issues of the uniqueness and robustness of the inversion procedure,
this method is demonstrated on an inland swarm activity induced by the 2011
Tohoku-Oki, Japan earthquake of magnitude 9.0.
| arxiv topic:stat.AP |
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