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arxiv_dataset-54001407.3243 | Learning about the Energy of a Hurricane System through an Estimation
Epistemic Game
physics.ed-ph
As part of a study into students' problem solving behaviors, we asked
upper-division physics students to solve estimation problems in clinical
interviews. We use the Resources Framework and epistemic games to describe
students' problem solving moves. We present a new epistemic game, the
"estimation epistemic game". In the estimation epistemic game, students break
the larger problem into a series of smaller, tractable problems. Within each
sub-problem, they try to remember a method for solving the problem, and use
estimation and reasoning abilities to justify their answers. We demonstrate how
a single case study student plays the game to estimate the total energy in a
hurricane. Finally, we discuss the implications of epistemic game analysis for
other estimation problems.
| arxiv topic:physics.ed-ph |
arxiv_dataset-54011407.3343 | Generalized $q$-Stirling numbers and normal ordering
math.CO
The normal ordering coefficients of strings consisting of $V,U$ which satisfy
$UV=qVU+hV^s$ ($s\in\mathbb N$) are considered. These coefficients are studied
in two contexts: first, as a multiple of a sequence satisfying a generalized
recurrence, and second, as $q$-analogues of rook numbers under the row creation
rule introduced by Goldman and Haglund. A number of properties are derived,
including recurrences, expressions involving other $q$-analogues and explicit
formulas. We also give a Dobinsky-type formula for the associated Bell numbers
and the corresponding extension of Spivey's Bell number formula. The
coefficients, viewed as rook numbers, are extended to the case $s\in\mathbb R$
via a modified rook model.
| arxiv topic:math.CO |
arxiv_dataset-54021407.3443 | Design rules for dislocation filters
cond-mat.mtrl-sci
The efficacy of strained layer threading dislocation filter structures in
single crystal epitaxial layers is evaluated using numerical modeling for (001)
face-centred cubic materials, such as GaAs or Si(1-x)Ge(x), and (0001)
hexagonal materials such as GaN. We find that threading dislocation densities
decay exponentially as a function of the strain relieved, irrespective of the
fraction of threading dislocations that are mobile. Reactions between threading
dislocations tend to produce a population that is a balanced mixture of mobile
and sessile in (001) cubic materials. In contrast, mobile threading
dislocations tend to be lost very rapidly in (0001) GaN, often with little or
no reduction in the immobile dislocation density. The capture radius for
threading dislocation interactions is estimated to be approx. 40nm using cross
section transmission electron microscopy of dislocation filtering structures in
GaAs monolithically grown on Si. We find that the minimum threading dislocation
density that can be obtained in any given structure is likely to be limited by
kinetic effects to approx. 1.0e+04 to 1.0e+05 per square cm.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-54031407.3543 | Intermittent Control in Man and Machine
q-bio.QM cs.SY
Intermittent control has a long history in the physiological literature and
there is strong experimental evidence that some human control systems are
intermittent. Intermittent control has also appeared in various forms in the
engineering literature. This article discusses a particular mathematical model
of Event-driven Intermittent Control which brings together engineering and
physiological insights and builds on and extends previous work in this area.
Illustrative examples of the properties of Intermittent Control in a
physiological context are given together with suggestions for future research
directions in both physiology and engineering.
| arxiv topic:q-bio.QM cs.SY |
arxiv_dataset-54041407.3643 | Measurement of differential production cross-sections for a $Z$ boson in
association with $b$-jets in 7 TeV proton-proton collisions with the ATLAS
detector
hep-ex
Measurements of differential production cross-sections of a $Z$ boson in
association with $b$-jets in $pp$ collisions at $\sqrt{s}=7$ TeV are reported.
The data analysed correspond to an integrated luminosity of 4.6 fb$^{-1}$
recorded with the ATLAS detector at the Large Hadron Collider. Particle-level
cross-sections are determined for events with a $Z$ boson decaying into an
electron or muon pair, and containing $b$-jets. For events with at least one
$b$-jet, the cross-section is presented as a function of the $Z$ boson
transverse momentum and rapidity, together with the inclusive $b$-jet
cross-section as a function of $b$-jet transverse momentum, rapidity and
angular separations between the $b$-jet and the $Z$ boson. For events with at
least two $b$-jets, the cross-section is determined as a function of the
invariant mass and angular separation of the two highest transverse momentum
$b$-jets, and as a function of the $Z$ boson transverse momentum and rapidity.
Results are compared to leading-order and next-to-leading-order perturbative
QCD calculations.
| arxiv topic:hep-ex |
arxiv_dataset-54051407.3743 | Numerical simulation of growth of Escherichia coli in unsaturated porous
media
q-bio.CB
A model for the aerobic and anaerobic growth of Escherichia coli (HB101 K12
pGLO) depending on the concentration of oxygen and DOC as substrate has been
developed based on laboratory batch experiments. Using inverse modelling to
obtain optimal sets of parameters, it could be shown that a model based on a
modified double Contois kinetic can predict cell densities, organic carbon
utilisation, oxygen transfer and utilisation rates for a large number of
experiments under aerobic and anaerobic conditions with a single unique set of
parameters.
The model was extended to describe growth of E. coli in unsaturated porous
media, combining diffusion, phase exchange and microbiological growth.
Experiments in a Hele-Shaw cell, filled with quartz sand, were conducted to
study bacterial growth in the capillary fringe above a saturated porous medium.
Cell density profiles in the Hele-Shaw cell were predicted with the growth
model and the parameters from the batch experiments without any further
calibration. They showed a very good qualitative and quantitative agreement
with cell densities determined from samples taken from the Hele-Shaw cell by
re-suspension and subsequent counting. Thus it could be shown, that it is
possible to successfully transfer growth parameters from batch experiments to
porous media for both aerobic and anaerobic conditions.
| arxiv topic:q-bio.CB |
arxiv_dataset-54061407.3843 | Probing Competing and Intertwined Orders with Resonant Inelastic x-ray
Scattering in the Hole-Doped Cuprates
cond-mat.str-el
We develop a formalism to study indirect resonant inelastic x-ray scattering
(RIXS) in systems with itinerant electrons, accounting for the attraction
between valence electrons and the positively-charged core hole exactly, and
apply this formalism to the hole-doped cuprate superconductors. We focus on the
relationship between RIXS lineshapes and band structure, including broken
symmetries. We show that RIXS is capable of distinguishing between competing
order parameters, establishing it as a useful probe of the pseudogap phase.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-54071407.3943 | A class of L\'evy driven SDEs and their explicit invariant measures
math.PR
We describe a class of explicit invariant measures for both finite and
infinite dimensional Stochastic Differential Equations (SDE) driven by L\'evy
noise. We first discuss in details the finite dimensional case with a linear,
resp. non linear, drift. In particular, we exhibit a class of such SDEs for
which the invariant measures are given in explicit form, coherently in all
dimensions. We then indicate how to relate them to invariant measures for SDEs
on separable Hilbert spaces.
| arxiv topic:math.PR |
arxiv_dataset-54081407.4043 | Lie-point symmetries of the discrete Liouville equation
math-ph math.MP math.NA nlin.SI
The Liouville equation is well known to be linearizable by a point
transformation. It has an infinite dimensional Lie point symmetry algebra
isomorphic to a direct sum of two Virasoro algebras. We show that it is not
possible to discretize the equation keeping the entire symmetry algebra as
point symmetries. We do however construct a difference system approximating the
Liouville equation that is invariant under the maximal finite subalgebra $ SL_x
\lf 2 , \mathbb{R} \rg \otimes SL_y \lf 2 , \mathbb{R} \rg $. The invariant
scheme is an explicit one and provides a much better approximation of exact
solutions than comparable standard (non invariant) schemes.
| arxiv topic:math-ph math.MP math.NA nlin.SI |
arxiv_dataset-54091407.4143 | Strong competition between orbital-ordering and itinerancy in a
frustrated spinel vanadate
cond-mat.str-el
The crossover from localized- to itinerant-electron behavior is associated
with many intriguing phenomena in condensed-matter physics. In this paper, we
investigate the crossover from localized to itinerant regimes in the spinel
system Mn$_{1-x}$Co$_x$V$_2$O$_4$. At low Co doping, orbital order (OO) of the
localized electrons on the V3+ ions suppresses magnetic frustration by
triggering a tetragonal distortion. With Co doping, electronic itinerancy melts
the OO and suppresses the structural phase transition while the reduced
spin-lattice coupling produces magnetic frustration. Neutron scattering
measurements and first-principles-guided spin models reveal that the
non-collinear state at high Co doping is produced by weakened local anisotropy
and enhanced Co-V spin interactions.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-54101407.4243 | Inclusive production of Higgs boson in the two-photon channel at the LHC
within $k_{t}$-factorization approach and with the Standard Model couplings
hep-ph hep-ex
We calculate differential cross sections for Higgs boson and/or two-photon
production from intermediate (virtual) Higgs boson within the formalism of
$k_t$-factorization. The off-shell $g^* g^* \to H$ matrix elements are used. We
compare results obtained with infinite top fermion (quark) mass and with finite
mass taken into account. The latter effect is rather small. We compare results
with different unintegrated gluon distributions from the literature. Two
methods are used. In the first method first Higgs boson is produced in the $2
\to 1$ $g g \to H$ $k_t$-factorization approach and then isotropic decay with
the Standard Model branching fraction is performed. In the second method we
calculate directly two photons coupled to the virtual Higgs boson. The results
of the two methods are compared and differences are discussed. The results for
two photons from the Higgs boson are compared with recent ATLAS collaboration
data. In contrast to a recent calculation the leading order $g g \to H$
contribution is rather small compared to the ATLAS experimental data ($\gamma
\gamma$ transverse momentum and rapidity distributions) for all unintegrated
gluon distributions from the literature. We include also higher-order
contribution $g g \to H (\to \gamma \gamma) g$, $g g \to g H g$ and the
contribution of the $W^+ W^-$ and $Z^0 Z^0$. The $gg\to Hg$ mechanism gives
similar cross section as the $gg\to H$ mechanism. We argue that there is almost
no double counting when adding $gg\to H$ and $gg\to Hg$ contributions due to
different topology of Feynman diagrams. The final sum is comparable with the
ATLAS two-photon data. We discuss uncertainties related to both the theoretical
approach and existing UGDFs.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-54111407.4343 | Quantum Speed Limits for General Physical Processes
quant-ph
Quantum speed limits are relations yielding lower bounds on the evolution
time of quantum systems. These results have been generalized in some ways, in
particular by including evolutions to non-orthogonal states. However, there was
a gap in the literature on this area, for only unitary evolutions -- closed
quantum systems -- had been considered. On this Ph.D. thesis, such limitation
is overcome: our main result is a bound for quantum-system evolutions in
general, whether unitary or not, and correctly recovers the known bounds in the
unitary case. Applications of this bound to several concrete cases of interest
are herein presented. This bound is also used to extend to the non-unitary case
the discussion of the role of entanglement in fast evolutions, leading to
nontrivial results.
For the derivation of the results, a geometric approach has been employed,
which allows a clear interpretation of the bounds and a discussion of the
criteria for their saturation. No previous knowledge of quantum-state geometry
by the reader has been assumed.
| arxiv topic:quant-ph |
arxiv_dataset-54121407.4443 | On the Complexity of Best Arm Identification in Multi-Armed Bandit
Models
stat.ML cs.LG
The stochastic multi-armed bandit model is a simple abstraction that has
proven useful in many different contexts in statistics and machine learning.
Whereas the achievable limit in terms of regret minimization is now well known,
our aim is to contribute to a better understanding of the performance in terms
of identifying the m best arms. We introduce generic notions of complexity for
the two dominant frameworks considered in the literature: fixed-budget and
fixed-confidence settings. In the fixed-confidence setting, we provide the
first known distribution-dependent lower bound on the complexity that involves
information-theoretic quantities and holds when m is larger than 1 under
general assumptions. In the specific case of two armed-bandits, we derive
refined lower bounds in both the fixed-confidence and fixed-budget settings,
along with matching algorithms for Gaussian and Bernoulli bandit models. These
results show in particular that the complexity of the fixed-budget setting may
be smaller than the complexity of the fixed-confidence setting, contradicting
the familiar behavior observed when testing fully specified alternatives. In
addition, we also provide improved sequential stopping rules that have
guaranteed error probabilities and shorter average running times. The proofs
rely on two technical results that are of independent interest : a deviation
lemma for self-normalized sums (Lemma 19) and a novel change of measure
inequality for bandit models (Lemma 1).
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-54131407.4543 | Sparse Quadratic Discriminant Analysis and Community Bayes
stat.ML stat.CO
We develop a class of rules spanning the range between quadratic discriminant
analysis and naive Bayes, through a path of sparse graphical models. A group
lasso penalty is used to introduce shrinkage and encourage a similar pattern of
sparsity across precision matrices. It gives sparse estimates of interactions
and produces interpretable models. Inspired by the connected-components
structure of the estimated precision matrices, we propose the community Bayes
model, which partitions features into several conditional independent
communities and splits the classification problem into separate smaller ones.
The community Bayes idea is quite general and can be applied to non-Gaussian
data and likelihood-based classifiers.
| arxiv topic:stat.ML stat.CO |
arxiv_dataset-54141407.4643 | Deriving physical parameters of unresolved star clusters. II. The
degeneracies of age, mass, extinction, and metallicity
astro-ph.SR astro-ph.GA
This paper is the second of a series that investigates the stochasticity and
degeneracy problems that hinder the derivation of the age, mass, extinction,
and metallicity of unresolved star clusters in external galaxies when
broad-band photometry is used. While Paper I concentrated on deriving age,
mass, and extinction of star clusters for one fixed metallicity, we here derive
these parameters in case when metallicity is let free to vary. The results were
obtained using several different filter systems ($UBVRI$, $UBVRIJHK$,
GALEX+$UBVRI$), which allowed to optimally reduce the different degeneracies
between the cluster physical parameters. The age, mass, and extinction of a
sample of artificial star clusters were derived by comparing their broad-band
integrated magnitudes with the magnitudes of a large grid of cluster models
with various metallicities. A large collection of artificial clusters was
studied to model the different degeneracies in the age, mass, extinction, and
metallicity parameter space when stochasticity is taken into account in the
cluster models. We show that, without prior knowledge on the metallicity, the
optical bands ($UBVRI$) fail to allow a correct derivation of the age, mass,
and extinction because of the strong degeneracies between models of different
metallicities. Adding near-infrared information ($UBVRI$+$JHK$) slightly helps
in improving the parameter derivation, except for the metallicity. Adding
ultraviolet data (GALEX+$UBVRI$) helps significantly in deriving these
parameters and allows constraining the metallicity when the photometric errors
have a Gaussian distribution with standard deviations 0.05 mag for $UBVRI$ and
0.15 mag for the GALEX bands.
| arxiv topic:astro-ph.SR astro-ph.GA |
arxiv_dataset-54151407.4743 | Limit theorems for linear eigenvalue statistics of overlapping matrices
math.PR
The paper proves several limit theorems for linear eigenvalue statistics of
overlapping Wigner and sample covariance matrices. It is shown that the
covariance of the limiting multivariate Gaussian distribution is diagonalized
by choosing the Chebyshev polynomials of the first kind as the basis for the
test function space. The covariance of linear statistics for the Chebyshev
polynomials of sufficiently high degree depends only on the first two moments
of the matrix entries. Proofs are based on a graph-theoretic interpretation of
the Chebyshev linear statistics as sums over non-backtracking cyclic paths
| arxiv topic:math.PR |
arxiv_dataset-54161407.4843 | Noncommutative quantum mechanics in a time-dependent background
quant-ph hep-th math-ph math.MP
We investigate a quantum mechanical system on a noncommutative space for
which the structure constant is explicitly time-dependent. Any autonomous
Hamiltonian on such a space acquires a time-dependent form in terms of the
conventional canonical variables. We employ the Lewis-Riesenfeld method of
invariants to construct explicit analytical solutions for the corresponding
time-dependent Schroedinger equation. The eigenfunctions are expressed in terms
of the solutions of variants of the nonlinear Ermakov-Pinney equation and
discussed in detail for various types of background fields. We utilize the
solutions to verify a generalized version of Heisenberg's uncertainty relations
for which the lower bound becomes a time-dependent function of the background
fields. We study the variance for various states including standard Glauber
coherent states with their squeezed versions and Gaussian Klauder coherent
states resembling a quasi-classical behaviour. No type of coherent states
appears to be optimal in general with regard to achieving minimal
uncertainties, as this feature turns out to be background field dependent.
| arxiv topic:quant-ph hep-th math-ph math.MP |
arxiv_dataset-54171407.4943 | Renormalization, Hopf algebras and Mellin transforms
hep-th math-ph math.MP
This article aims to give a short introduction into Hopf-algebraic aspects of
renormalization, enjoying growing attention for more than a decade by now. As
most available literature is concerned with the minimal subtraction scheme, we
like to point out properties of the kinematic subtraction scheme which is also
widely used in physics (under the names of MOM or BPHZ).
In particular we relate renormalized Feynman rules $\phi_R$ in this scheme to
the universal property of the Hopf algebra $H_R$ of rooted trees, exhibiting a
refined renormalization group equation which is equivalent to $\phi_R: H_R
\rightarrow K[x]$ being a morphism of Hopf algebras to the polynomials in one
indeterminate.
Upon introduction of analytic regularization this results in efficient
combinatorial recursions to calculate $\phi_R$ in terms of the Mellin
transform. We find that different Feynman rules are related by a distinguished
class of Hopf algebra automorphisms of $H_R$ that arise naturally from
Hochschild cohomology.
Also we recall the known results for the minimal subtraction scheme and shed
light on the interrelationship of both schemes.
Finally we incorporate combinatorial Dyson-Schwinger equations to study the
effects of renormalization on the physical meaningful correlation functions.
This yields a precise formulation of the equivalence of the two different
renormalization prescriptions mentioned before and allows for non-perturbative
definitions of quantum field theories in special cases.
| arxiv topic:hep-th math-ph math.MP |
arxiv_dataset-54181407.5043 | Fluctuation Theorems for Synchronization of Interacting Polya's urns
math.PR
We consider a model of N two-colors urns in which the reinforcement of each
urn depends also on the content of all the other urns. This interaction is of
mean-field type and it is tuned by a parameter $\alpha$ in [0,1]; in
particular, for $\alpha=0$ the N urns behave as N independent Polya's urns. As
shown in [9], for $\alpha>0$ urns synchronize, in the sense that the fraction
of balls of a given color converges a.s. to the same (random) limit in all
urns. In this paper we study fluctuations around this synchronized regime. The
scaling of these fluctuations depends on the parameter $\alpha$. In particular
the standard scaling $t^{-1/2}$ appears only for $\alpha>1/2$. For $\alpha\geq
1/2$ we also determine the limit distribution of the rescaled fluctuations. We
use the notion of stable convergence, which is stronger than convergence in
distribution.
| arxiv topic:math.PR |
arxiv_dataset-54191407.5143 | The double-slit quantum eraser experiments and Hardy's paradox in the
quantum linguistic interpretation
quant-ph
Recently we proposed the linguistic interpretation of quantum mechanics
(called quantum and classical measurement theory), which was characterized as a
kind of metaphysical and linguistic turn of the Copenhagen interpretation. This
turn from physics to language does not only extend quantum theory to classical
systems but also yield the quantum mechanical world view (i.e., quantum
philosophy or quantum language). The purpose of this paper is to formulate the
double-slit experiment, the quantum eraser experiment, Wheeler's delayed choice
experiment, Hardy's paradox and the three boxes paradox (the weak value
associated with a weak measurement due to Aharonov, et al.) in the linguistic
interpretation of quantum mechanics. Through these arguments, we assert that
the linguistic interpretation is just the final version of so called Copenhagen
interpretation. And therefore, we conclude that the Copenhagen interpretation
does not belong to physics (i.e., the realistic world view) but the linguistic
world view.
| arxiv topic:quant-ph |
arxiv_dataset-54201407.5243 | Small Oscillations via Conservation of Energy in a Simple Static
Equilibrium Problem
physics.ed-ph physics.class-ph
The work describes an analogy-based small oscillations analysis of a standard
static equilibrium lab problem. In addition to force analysis, a potential
energy function for the system is developed, and by drawing out mathematical
similarities to the simple harmonic oscillator, we are able to describe (and
verify) the period of small oscillations about the static equilibrium state.
The problem was developed and implemented in a standard University Physics
course at Winona State University.
| arxiv topic:physics.ed-ph physics.class-ph |
arxiv_dataset-54211407.5343 | Efficiency of Monte Carlo Sampling in Chaotic Systems
nlin.CD cond-mat.stat-mech physics.comp-ph
In this paper we investigate how the complexity of chaotic phase spaces
affect the efficiency of importance sampling Monte Carlo simulations. We focus
on a flat-histogram simulation of the distribution of finite-time Lyapunov
exponent in a simple chaotic system and obtain analytically that the
computational effort of the simulation: (i) scales polynomially with the
finite-time, a tremendous improvement over the exponential scaling obtained in
usual uniform sampling simulations; and (ii) the polynomial scaling is
sub-optimal, a phenomenon known as critical slowing down. We show that critical
slowing down appears because of the limited possibilities to issue a local
proposal on the Monte Carlo procedure in chaotic systems. These results remain
valid in other methods and show how generic properties of chaotic systems limit
the efficiency of Monte Carlo simulations.
| arxiv topic:nlin.CD cond-mat.stat-mech physics.comp-ph |
arxiv_dataset-54221407.5443 | Vector bundles on proper toric 3-folds and certain other schemes
math.AG
We show that a proper algebraic n-dimensional scheme Y admits nontrivial
vector bundles of rank n, even if Y is non-projective, provided that there is a
modification containing a projective Cartier divisor that intersects the
exceptional locus in only finitely many points. Moreover, there are such vector
bundles with arbitrarily large top Chern number. Applying this to toric
varieties, we infer that every proper toric threefold admits such vector
bundles of rank three. Furthermore, we describe a class of higher-dimensional
toric varieties for which the result applies, in terms of convexity properties
around rays.
| arxiv topic:math.AG |
arxiv_dataset-54231407.5543 | Spin pumping efficiency in room-temperature CdSe nanocrystal quantum
dots
cond-mat.mes-hall
To understand and optimize optical spin initialization in room temperature
CdSe nanocrystal quantum dots (NCQDs) we studied the dependence of the
time-resolved Faraday rotation signal on pump energy $E_p$ in a series of NCQD
samples with different sizes. In larger NCQDs, we observe two peaks in the spin
signal vs. $E_p$, whereas in smaller NQCDs, only a single peak is observed
before the signal falls to a low, broad plateau at higher energies. We
calculate the spin-dependent oscillator strengths of optical transitions using
a simple effective mass model to understand these results. The observed $E_p$
dependence of the spin pumping efficiency (SPE) arises from the competition
between the heavy hole (hh), light hole (lh) and split-off (so) band
contributions to transitions to the conduction band. The two latter
contributions lead to an electron spin polarization in the opposite direction
from the former. At lower $E_p$ the transitions are dominated by the hh band,
giving rise to the low energy peaks. At higher $E_p$, the increasing
contributions from the lh and so bands lead to a reduction in SPE. The
different number of peaks in larger and smaller NCQDs is attributed to
size-dependence of the ordering of the valence band states.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-54241407.5643 | A note on colored HOMFLY polynomials for hyperbolic knots from WZW
models
hep-th math.GT
Using the correspondence between Chern-Simons theories and Wess-Zumino-Witten
models we present the necessary tools to calculate colored HOMFLY polynomials
for hyperbolic knots. For two-bridge hyperbolic knots we derive the colored
HOMFLY invariants in terms of crossing matrices of the underlying
Wess-Zumino-Witten model. Our analysis extends previous works by incorporating
non-trivial multiplicities for the primaries appearing in the crossing
matrices, so as to describe colorings of HOMFLY invariants beyond the totally
symmetric or anti-symmetric representations of SU(N). The crossing matrices
directly relate to 6j-symbols of the quantum group U_q(su(N)). We present
powerful methods to calculate such quantum 6j-symbols for general N. This
allows us to determine previously unknown colored HOMFLY polynomials for
two-bridge hyperbolic knots. We give explicitly the HOMFLY polynomials colored
by the representation {2,1} for two-bridge hyperbolic knots with up to eight
crossings. Yet, the scope of application of our techniques goes beyond knot
theory; e.g., our findings can be used to study correlators in
Wess-Zumino-Witten conformal field theories or -- in the limit to classical
groups -- to determine color factors for Yang Mills amplitudes.
| arxiv topic:hep-th math.GT |
arxiv_dataset-54251407.5743 | Equiconnected spaces and Baire classification of separately continuous
functions and their analogs
math.GN
We investigate the Baire classification of mappings $f:X\times Y\to Z$, where
$X$ belongs to a wide class of spaces, which includes all metrizable spaces,
$Y$ is a topological space, $Z$ is an equiconnected space, which are continuous
in the first variable and for a dense set in $X$ these mappings are functions
of a Baire class $\alpha$ in the second variable.
| arxiv topic:math.GN |
arxiv_dataset-54261407.5843 | Explicit Orbifold Riemann-Roch for quasismooth varieties
math.AG
Considering quasismooth varieities as global $\CC^*$ quotients, we present a
Riemann-Roch formula via general Riemann-Roch formula for quotient stacks.
Furthermore, we give a parcing formula for Hilbert series associated to a
polarized quasismooth projectively Gorenstein algebraic varieties with orbifold
curves and dissident points, which is an extension of the result in \cite{BRZ}.
| arxiv topic:math.AG |
arxiv_dataset-54271407.5943 | Convergence of a crystalline algorithm for the motion of a simple closed
convex curve by weighted curvature
math.NA
Motion by weighted mean curvature is a geometric evolution law for surfaces
and represents steepest descent with respect to anisotropic surface energy. It
has been proposed that this motion could be computed numerically by using a
"crystalline" approximation to the surface energy in the evolution law. In this
paper we prove the convergence of this numerical method for the case of simple
closed convex curves in the plane.
| arxiv topic:math.NA |
arxiv_dataset-54281407.6043 | The filtering equations revisited
math.PR
The problem of nonlinear filtering has engendered a surprising number of
mathematical techniques for its treatment. A notable example is the
change-of--probability-measure method originally introduced by Kallianpur and
Striebel to derive the filtering equations and the Bayes-like formula that
bears their names. More recent work, however, has generally preferred other
methods. In this paper, we reconsider the change-of-measure approach to the
derivation of the filtering equations and show that many of the technical
conditions present in previous work can be relaxed. The filtering equations are
established for general Markov signal processes that can be described by a
martingale-problem formulation. Two specific applications are treated.
| arxiv topic:math.PR |
arxiv_dataset-54291407.6143 | A six-part collisional model of the main asteroid belt
astro-ph.EP
In this work, we construct a new model for the collisional evolution of the
main asteroid belt. Our goals are to test the scaling law of Benz and Asphaug
(1999) and ascertain if it can be used for the whole belt. We want to find
initial size-frequency distributions (SFDs) for the considered six parts of the
belt (inner, middle, 'pristine', outer, Cybele zone, high-inclination region)
and to verify if the number of synthetic asteroid families created during the
simulation matches the number of observed families as well. We used new
observational data from the WISE satellite (Masiero et al., 2011) to construct
the observed SFDs. We simulate mutual collisions of asteroids with a modified
version of the Boulder code (Morbidelli et al., 2009), where the results of
hydrodynamic (SPH) simulations of Durda et al. (2007) and Benavidez et al.
(2012) are included. Because material characteristics can significantly affect
breakups, we created two models - for monolithic asteroids and for
rubble-piles. To explain the observed SFDs in the size range D = 1 to 10 km we
have to also account for dynamical depletion due to the Yarkovsky effect. The
assumption of (purely) rubble-pile asteroids leads to a significantly worse fit
to the observed data, so that we can conclude that majority of main-belt
asteroids are rather monolithic. Our work may also serve as a motivation for
further SPH simulations of disruptions of smaller targets (with a parent body
size of the order of 1 km).
| arxiv topic:astro-ph.EP |
arxiv_dataset-54301407.6243 | Influence of autocorrelation on the topology of the climate network
physics.ao-ph physics.data-an physics.soc-ph
Different definitions of links in climate networks may lead to considerably
different network topologies. We construct a network from climate records of
surface level atmospheric temperature in different geographical sites around
the globe using two commonly used definitions of links. Utilizing detrended
fluctuation analysis, shuffled surrogates and separation analysis of maritime
and continental records, we find that one of the major influences on the
structure of climate networks is due to the auto-correlation in the records,
that may introduce spurious links. This may explain why different methods could
lead to different climate network topologies.
| arxiv topic:physics.ao-ph physics.data-an physics.soc-ph |
arxiv_dataset-54311407.6343 | Pull-based load distribution in large-scale heterogeneous service
systems
math.PR
The model is motivated by the problem of load distribution in large-scale
cloud-based data processing systems. We consider a heterogeneous service
system, consisting of multiple large server pools. The pools are different in
that their servers may have different processing speed and/or different buffer
sizes (which may be finite or infinite). We study an asymptotic regime in which
the customer arrival rate and pool sizes scale to infinity simultaneously, in
proportion to some scaling parameter $n$.
Arriving customers are assigned to the servers by a "router", according to a
{\em pull-based} algorithm, called PULL. Under the algorithm, each server sends
a "pull-message" to the router, when it becomes idle; the router assigns an
arriving customer to a server according to a randomly chosen available
pull-message, if there are any, or to a random server, otherwise.
Assuming sub-critical system load, we prove asymptotic optimality of PULL.
Namely, as system scale $n\to\infty$, the steady-state probability of an
arriving customer experiencing blocking or waiting, vanishes. We also describe
some generalizations of the model and PULL algorithm, for which the asymptotic
optimality still holds.
| arxiv topic:math.PR |
arxiv_dataset-54321407.6443 | A theorem about Cremona maps and symbolic Rees algebras
math.AC
This work is about the structure of the symbolic Rees algebra of the base
ideal of a Cremona map. We give sufficient conditions under which this algebra
has the "expected form" in some sense. The main theorem in this regard
seemingly covers all previous results on the subject so far. The proof relies
heavily on a criterion of birationality and the use of the so-called inversion
factor of a Cremona map. One adds a pretty long selection of examples of plane
and space Cremona maps tested against the conditions of the theorem, with
special emphasis on Cohen--Macaulay base ideals.
| arxiv topic:math.AC |
arxiv_dataset-54331407.6543 | A discretised projection theorem in the plane
math.CA
The main result of this paper is that for any $1/2 \leq s < 2 - \sqrt{2}
\approx 0.5858$, there is a number $\sigma = \sigma(s) < s$ with the following
property. Let $\delta > 0$ be small, assume that $A \subset [0,1]$ is a
$(\delta,1/2)$-set, and that $E \subset [0,1]$ contains $\gtrsim
\delta^{-\sigma}$ roughly $\delta^{s}$-separated points. Then there exists a
number $t \in E$ such that $A + tA$ contains $\gtrsim \delta^{-s}$
$\delta$-separated points.
For $\sigma = s$, this is essentially a consequence of Kaufman's well-known
bound for exceptional sets of projections. Our proof consists of a structural
observation concerning sets, for which Kaufman's bound is near-optimal,
combined with (an adaptation of) Solymosi's argument for his "$4/3$"
sum-product theorem.
| arxiv topic:math.CA |
arxiv_dataset-54341407.6643 | Measurement of the ttbar production cross section in pp collisions at
sqrt(s) = 8 TeV in dilepton final states containing one tau lepton
hep-ex
The top-quark pair production cross section is measured in final states with
one electron or muon and one hadronically decaying tau lepton from the process
ttbar to (l nu[l]) (tau nu[tau]) bbbar, where l = e, mu. The data sample
corresponds to an integrated luminosity of 19.6 inverse femtobarns collected
with the CMS detector in proton-proton collisions at sqrt(s) = 8 TeV. The
measured cross section sigma[ttbar] = 257 +/- 3 (stat) +/- 24 (syst) +/- 7
(lumi) pb, assuming a top-quark mass of 172.5 GeV, is consistent with the
standard model prediction.
| arxiv topic:hep-ex |
arxiv_dataset-54351407.6743 | The role of particle shape in active depletion
cond-mat.soft cond-mat.mes-hall cond-mat.mtrl-sci physics.chem-ph
Using numerical simulations, we study how a solution of small active disks,
acting as depletants, induces effective interactions on large passive colloids.
Specifically, we analyze how the range, strength, and sign of these
interactions are crucially dependent on the shape of the colloids. Our findings
indicate that while colloidal rods experience a long-ranged predominantly
attractive interaction, colloidal disks feel a purely repulsive force that is
short-ranged in nature and grows in strength with the size ratio between the
colloids and active depletants. For colloidal rods, simple scaling arguments
are proposed to characterize the strength of these induced interactions.
| arxiv topic:cond-mat.soft cond-mat.mes-hall cond-mat.mtrl-sci physics.chem-ph |
arxiv_dataset-54361407.6843 | On canonical-type connections on almost contact complex Riemannian
manifolds
math.DG
We consider a pair of smooth manifolds, which are the counterparts in the
even-dimensional and odd-dimensional cases. They are separately an almost
complex manifold with Norden metric and an almost contact manifolds with
B-metric, respectively. They can be combined as the so-called almost contact
complex Riemannian manifold. This paper is a survey with additions of results
on differential geometry of canonical-type connections (i.e. metric connections
with torsion satisfying a certain algebraic identity) on the considered
manifolds.
| arxiv topic:math.DG |
arxiv_dataset-54371407.6943 | Overstability of acoustic waves in strongly magnetized anisotropic MHD
shear flows
astro-ph.SR physics.plasm-ph
We present a linear stability analysis of the perturbation modes in
anisotropic MHD flows with velocity shear and strong magnetic field.
Collisionless or weakly collisional plasma is described within the 16-momentum
MHD fluid closure model, that takes into account not only the effect of
pressure anisotropy, but also the effect of anisotropic heat fluxes. In this
model the low frequency acoustic wave is revealed into a standard acoustic mode
and higher frequency fast thermo-acoustic and lower frequency slow
thermo-acoustic waves. It is shown that thermo-acoustic waves become unstable
and grow exponentially when the heat flux parameter exceeds some critical
value. It seems that velocity shear makes thermo-acoustic waves overstable even
at subcritical heat flux parameters. Thus, when the effect of heat fluxes is
not profound acoustic waves will grow due to the velocity shear, while at
supercritical heat fluxes the flow reveals compressible thermal instability.
Anisotropic thermal instability should be also important in astrophysical
environments, where it will limit the maximal value of magnetic field that a
low density ionized anisotropic flow can sustain.
| arxiv topic:astro-ph.SR physics.plasm-ph |
arxiv_dataset-54381407.7043 | Torsion, Parity-odd Response and Anomalies in Topological States
cond-mat.mes-hall hep-th
We study the response of a class of topological systems to electromagnetic
and gravitational sources, including torsion and curvature. By using the
technology of anomaly polynomials, we derive the parity-odd response of a
massive Dirac fermion in $d=2+1$ and $d=4+1$, which provides a simple model for
a topological insulator. We discuss the covariant anomalies of the
corresponding edge states, from a Callan-Harvey anomaly-inflow, as well as a
Hamiltonian spectral flow point of view. We also discuss the applicability of
our results to other systems such as Weyl semi-metals. Finally, using
dimensional reduction from $d=4+1$, we derive the effective action for a
$d=3+1$ time-reversal invariant topological insulator in the presence of
torsion and curvature, and discuss its various physical consequences.
| arxiv topic:cond-mat.mes-hall hep-th |
arxiv_dataset-54391407.7143 | "Your click decides your fate": Leveraging clickstream patterns from
MOOC videos to infer students' information processing & attrition behavior
cs.HC cs.CY
With an expansive and ubiquitously available gold mine of educational data,
Massive Open Online courses (MOOCs) have become the an important foci of
learning analytics research. The hope is that this new surge of development
will bring the vision of equitable access to lifelong learning opportunities
within practical reach. MOOCs offer many valuable learning experiences to
students, from video lectures, readings, assignments and exams, to
opportunities to connect and collaborate with others through threaded
discussion forums and other Web 2.0 technologies. Nevertheless, despite all
this potential, MOOCs have so far failed to produce evidence that this
potential is being realized in the current instantiation of MOOCs. In this
work, we primarily explore video lecture interaction in Massive Open Online
Courses (MOOCs), which is central to student learning experience on these
educational platforms. As a research contribution, we operationalize video
lecture clickstreams of students into behavioral actions, and construct a
quantitative information processing index, that can aid instructors to better
understand MOOC hurdles and reason about unsatisfactory learning outcomes. Our
results illuminate the effectiveness of developing such a metric inspired by
cognitive psychology, towards answering critical questions regarding students'
engagement, their future click interactions and participation trajectories that
lead to in-video dropouts. We leverage recurring click behaviors to
differentiate distinct video watching profiles for students in MOOCs.
Additionally, we discuss about prediction of complete course dropouts,
incorporating diverse perspectives from statistics and machine learning, to
offer a more nuanced view into how the second generation of MOOCs be benefited,
if course instructors were to better comprehend factors that lead to student
attrition.
| arxiv topic:cs.HC cs.CY |
arxiv_dataset-54401407.7243 | The Evolving Block Universe and the Meshing Together of Times
gr-qc hep-th
It is proposed that spacetime should be regarded as an evolving block
universe, bounded to the future by the present time, which continually extends
to the future. This future boundary is defined at each time by measuring proper
time along Ricci eigenlines from the start of the universe. A key point is that
physical reality can be represented at many different scales: hence the passage
of times may be seen as different at different scales, with quantum gravity
determining the evolution of space time itself but quantum field theory
determining the evolution of events within spacetime .The fundamental issue
then arises as to how the effective times at different scales mesh together,
leading to the concept so global and local times.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-54411407.7343 | A Systematic Approach to the Reconstruction of Saturated SDO/AIA Images
astro-ph.SR
EUV images of solar flares provided by the Atmospheric Imaging Assembly
onboard the Solar Dynamics Observatory (SDO/AIA) are often affected by
saturation effects in their core, physically most interesting region. We
introduce an image reconstruction procedure that allows recovering information
in the primary saturation domain using the secondary images produced by the
diffraction fringes as input data. Such a procedure is based on standard
image-processing tools like correlation, convolution, and back-projection. Its
effectiveness is tested in the case of SDO/AIA observations of the July 8 2013
flaring event.
| arxiv topic:astro-ph.SR |
arxiv_dataset-54421407.7443 | Property-Driven Fence Insertion using Reorder Bounded Model Checking
cs.SE
Modern architectures provide weaker memory consistency guarantees than
sequential consistency. These weaker guarantees allow programs to exhibit
behaviours where the program statements appear to have executed out of program
order. Fortunately, modern architectures provide memory barriers (fences) to
enforce the program order between a pair of statements if needed. Due to the
intricate semantics of weak memory models, the placement of fences is
challenging even for experienced programmers. Too few fences lead to bugs
whereas overuse of fences results in performance degradation. This motivates
automated placement of fences. Tools that restore sequential consistency in the
program may insert more fences than necessary for the program to be correct.
Therefore, we propose a property-driven technique that introduces
"reorder-bounded exploration" to identify the smallest number of program
locations for fence placement. We implemented our technique on top of CBMC;
however, in principle, our technique is generic enough to be used with any
model checker. Our experimental results show that our technique is faster and
solves more instances of relevant benchmarks as compared to earlier approaches.
| arxiv topic:cs.SE |
arxiv_dataset-54431407.7543 | Deep Chandra Observations of HCG 16 - I. Active Nuclei, Star formation
and Galactic Winds
astro-ph.GA
We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope
610~MHz observations of the spiral-galaxy-rich compact group HCG 16, which we
use to examine nuclear activity, star formation and the high luminosity X-ray
binary populations in the major galaxies. We confirm the presence of obscured
active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized
nuclear source in NGC 838. All three nuclei are variable on timescales of
months to years, and for NGC 833 and NGC 835 this is most likely caused by
changes in accretion rate. The deep Chandra observations allow us to detect for
the first time an Fe-K$\alpha$ emission line in the spectrum of the Seyfert 2
nucleus of NGC 835. We find that NGC 838 and NGC 839 are both
starburst-dominated systems, with only weak nuclear activity, in agreement with
previous optical studies. We estimate the star formation rates in the two
galaxies from their X-ray and radio emission, and compare these results with
estimates from the infra-red and ultra-violet bands to confirm that star
formation in both galaxies is probably declining after galaxy-wide starbursts
were triggered ~400-500 Myr ago. We examine the physical properties of their
galactic superwinds, and find that both have temperatures of ~0.8 keV. We also
examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in
the group, and show that it is dominated by emission from its starburst.
| arxiv topic:astro-ph.GA |
arxiv_dataset-54441407.7643 | HI in the Arp 202 system and its tidal dwarf candidate
astro-ph.GA
We present results from our Giant Metrewave Radio Telescope (GMRT) HI
observations of the interacting pair Arp 202 (NGC 2719 and NGC 2719A). Earlier
deep UV(GALEX) observations of this system revealed a tidal tail like extension
with a diffuse object towards its end, proposed as a tidal dwarf galaxy (TDG)
candidate. We detect HI emission from the Arp 202 system, including HI
counterparts for the tidal tail and the TDG candidate. Our GMRT HI
morphological and kinematic results clearly link the HI tidal tail and the HI
TDG counterparts to the interaction between NGC 2719 and NGC 2719A, thus
strengthening the case for the TDG. The Arp 202 TDG candidate belongs to a
small group of TDG candidates with extremely blue colours. In order to gain a
better understanding of this group we carried out a comparative study of their
properties from the available data. We find that HI (and probably stellar)
masses of this extremely blue group are similar to the lowest HI mass TDGs in
the literature. However the number of such blue TDG candidates examined so far
is too small to conclude whether or not their properties justify them to be
considered as a subgroup of TDGs.
| arxiv topic:astro-ph.GA |
arxiv_dataset-54451407.7743 | Multisolitonic solutions from a B\"acklund transformation for a
parametric coupled Korteweg-de Vries system
math-ph hep-th math.MP nlin.SI
We introduce a parametric coupled KdV system which contains, for particular
values of the parameter, the complex extension of the KdV equation and one of
the Hirota-Satsuma integrable systems. We obtain a generalized Gardner
transformation and from the associated $\varepsilon$- deformed system we get
the infinite sequence of conserved quantities for the parametric coupled
system. We also obtain a B\"{a}cklund transformation for the system. We prove
the associated permutability theorem corresponding to such transformation and
we generate new multi-solitonic and periodic solutions for the system depending
on several parameters. We show that for a wide range of the parameters the
solutions obtained from the permutability theorem are regular solutions.
Finally we found new multisolitonic solutions propagating on a non-trivial
regular static background.
| arxiv topic:math-ph hep-th math.MP nlin.SI |
arxiv_dataset-54461407.7843 | Alternate Forms of the T-Matrix in Quantum State Tomography
quant-ph
In this paper, we focus on alternate forms of the T-matrix used in the
Maximum Likelihood Estimate (MLE) procedure for fitting the experimental data
collected in quantum state tomography experiments. In particular, we analyze
the single quantum state tomography case, deriving in the process three new
valid alternate forms for achieving optimality. These alternative forms then
serve as a consistency check, thus enhancing the robustness of the MLE fitting
process. One form, in particular, serves as a useful compliment to the standard
form normally employed. We subsequently provide a generalization of these forms
to the case of multiqubit state tomography.
| arxiv topic:quant-ph |
arxiv_dataset-54471407.7943 | Second random-phase approximation, Thouless' theorem and the stability
condition reexamined and clarified
nucl-th cond-mat.other cond-mat.str-el
It has been revealed through numerical calculations that the Second Random
Phase Approximation (SRPA) with the Hartree-Fock solution as its reference
state results in 1) spurious states at genuinely finite energy, contrary to
common expectation, and 2) unstable solutions, which within the first-order
Random Phase Approximation correspond to real low-energy collective vibrations.
In the present work, these shortcomings of SRPA are shown to not contradict
Thouless' theorem about the energy-weighted sum rule, and their origin is
traced to the violation of the stability condition. A more general theorem is
proven. Formal arguments are elucidated through numerical examples.
Implications for the validity of SRPA are discussed.
| arxiv topic:nucl-th cond-mat.other cond-mat.str-el |
arxiv_dataset-54481407.8043 | Persistence of the Thomas-Fermi approximation for ground states
supported by the nonlinear confinement
nlin.PS math.AP
We justify the Thomas--Fermi approximation for the elliptic problem with the
repulsive nonlinear confinement used in the recent physical literature. The
method is based on the resolvent estimates and the fixed-point iterations.
| arxiv topic:nlin.PS math.AP |
arxiv_dataset-54491407.8143 | Realization of DSR-relativistic symmetries in Finsler geometries
gr-qc hep-th
Finsler geometry is a well known generalization of Riemannian geometry which
allows to account for a possibly non trivial structure of the space of
configurations of relativistic particles. We here establish a link between
Finsler geometry and the sort of models with curved momentum space and
DSR-relativistic symmetries which have been recently of interest in the
quantum-gravity literature. We use as case study the much-studied scenario
which is inspired by the $\kappa$-Poincar\'e quantum group, and show that the
relevant deformation of relativistic symmetries can be implemented within a
Finsler geometry.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-54501407.8243 | Universal critical behavior of the two-magnon-bound-state mass gap for
the (2+1)-dimensional Ising model
cond-mat.stat-mech
The two-magnon-bound-state mass gap m_2 for the two-dimensional quantum Ising
model was investigated by means of the numerical diagonalization method; the
low-lying spectrum is directly accessible via the numerical diagonalization
method. It has been claimed that the ratio m_2/m_1 (m_1: one-magnon mass gap)
is a universal constant in the vicinity of the critical point. Aiming to
suppress corrections to scaling (lattice artifact), we consider the spin-S=1
Ising model with finely-adjusted extended interactions. The simulation result
for the finite-size cluster with N \le 20 spins indicates the mass-gap ratio
m_2/m_1=1.84(1).
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-54511407.8343 | Direct topological factorization for topological flows
math.DS
This paper considers the general question of when a topological action of a
countable group can be factored into a direct product of a nontrivial actions.
In the early 1980's D. Lind considered such questions for $\mathbb{Z}$-shifts
of finite type. We study in particular direct factorizations of subshifts of
finite type over $\mathbb{Z}^d$ and other groups, and $\mathbb{Z}$-subshifts
which are not of finite type. The main results concern direct factors of the
multidimensional full $n$-shift, the multidimensional $3$-colored chessboard
and the Dyck shift over a prime alphabet.
A direct factorization of an expansive $\mathbb{G}$-action must be finite,
but a example is provided of a non-expansive $\mathbb{Z}$-action for which
there is no finite direct prime factorization. The question about existence of
direct prime factorization of expansive actions remains open, even for
$\mathbb{G}=\mathbb{Z}$.
| arxiv topic:math.DS |
arxiv_dataset-54521407.8443 | The 2-adic valuations of differences of Stirling numbers of the second
kind
math.NT
Let $m, n, k$ and $c$ be positive integers. Let $\nu_2(k)$ be the 2-adic
valuation of $k$. By $S(n,k)$ we denote the Stirling numbers of the second
kind. In this paper, we first establish a convolution identity of the Stirling
numbers of the second kind and provide a detailed 2-adic analysis to the
Stirling numbers of the second kind. Consequently, we show that if $2\le m\le
n$ and $c$ is odd, then $\nu_2(S(c2^{n+1},2^m-1)-S(c2^n, 2^m-1))=n+1$ except
when $n=m=2$ and $c=1$, in which case $\nu_2(S(8,3)-S(4,3))=6$. This solves a
conjecture of Lengyel proposed in 2009.
| arxiv topic:math.NT |
arxiv_dataset-54531407.8543 | Grossberg-Karshon twisted cubes and hesitant walk avoidance
math.CO math.RT
Let $G$ be a complex semisimple simply connected linear algebraic group. Let
$\lambda$ be a dominant weight for $G$ and $\mathcal{I} = (i_1, i_2, \ldots,
i_n)$ a word decomposition for an element $w = s_{i_1} s_{i_2} \cdots s_{i_n}$
of the Weyl group of $G$, where the $s_i$ are the simple reflections. In the
1990s, Grossberg and Karshon introduced a virtual lattice polytope associated
to $\lambda$ and $\mathcal{I}$, which they called a twisted cube, whose lattice
points encode (counted with sign according to a density function) characters of
representations of $G$. In recent work, the first author and Jihyeon Yang prove
that the Grossberg-Karshon twisted cube is untwisted (so the support of the
density function is a closed convex polytope) precisely when a certain
torus-invariant divisor on a toric variety, constructed from the data of
$\lambda$ and $\mathcal{I}$, is basepoint-free. This corresponds to the
situation in which the Grossberg-Karshon character formula is a true
combinatorial formula in the sense that there are no terms appearing with a
minus sign. In this note, we translate this toric-geometric condition to the
combinatorics of $\mathcal{I}$ and $\lambda$. More precisely, we introduce the
notion of hesitant $\lambda$-walks and then prove that the associated
Grossberg-Karshon twisted cube is untwisted precisely when $\mathcal{I}$ is
hesitant-$\lambda$-walk-avoiding.
| arxiv topic:math.CO math.RT |
arxiv_dataset-54541408.0094 | Constraining non--BPS interactions from counterterms in three loop
maximal supergravity
hep-th
The structure of one, two and three loop counterterms imposes strong
constraints on several non--BPS interactions in the low momentum expansion of
the three loop four graviton amplitude in maximal supergravity. The constraints
are imposed by demanding consistency with string amplitudes. We analyze these
constraints imposed on the D^8 R^4 interaction in 11 dimensional supergravity
compactified on T^2. We also discuss partial contributions from counterterms to
interactions at higher orders in the momentum expansion.
| arxiv topic:hep-th |
arxiv_dataset-54551408.0194 | Critical current oscillation by magnetic field in semiconductor nanowire
Josephson junction
cond-mat.mes-hall cond-mat.supr-con
We study theoretically the critical current in semiconductor nanowire
Josephson junction with strong spin-orbit interaction. The critical current
oscillates by an external magnetic field. We reveal that the oscillation of
critical current depends on the orientation of magnetic field in the presence
of spin-orbit interaction. We perform a numerical simulation for the nanowire
by using a tight-binding model. The Andreev levels are calculated as a function
of phase difference $\varphi$ between two superconductors. The DC Josephson
current is evaluated from the Andreev levels in the case of short junctions.
The spin-orbit interaction induces the effective magnetic field. When the
external field is parallel with the effective one, the critical current
oscillates accompanying the $0$-$\pi$ like transition. The period of
oscillation is longer as the angle between the external and effective fields is
larger.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con |
arxiv_dataset-54561408.0294 | Large deviation upper bounds for sums of positively associated
indicators
math.PR
We give exponential upper bounds for $P(S \le k)$, in particular $P(S=0)$,
where $S$ is a sum of indicator random variables that are positively
associated. These bounds allow, in particular, a comparison with the
independent case. We give examples in which we compare with a famous
exponential inequality for sums of correlated indicators, the Janson
inequality. Here our bound sometimes proves to be superior to Janson's bound.
| arxiv topic:math.PR |
arxiv_dataset-54571408.0394 | Destroyed quantum Hall effect in graphene with [0001] tilt grain
boundaries
cond-mat.mes-hall
The reason why the half-integer quantum Hall effect (QHE) is suppressed in
graphene grown by chemical vapor deposition (CVD) is unclear. We propose that
it might be connected to extended defects in the material and present results
for the quantum Hall effect in graphene with [0001] tilt grain boundaries
connecting opposite sides of Hall bar devices. Such grain boundaries contain
5-7 ring complexes that host defect states that hybridize to form bands with
varying degree of metallicity depending on grain boundary defect density. In a
magnetic field, edge states on opposite sides of the Hall bar can be connected
by the defect states along the grain boundary. This destroys Hall resistance
quantization and leads to non-zero longitudinal resistance. Anderson disorder
can partly recover quantization, where current instead flows along returning
paths along the grain boundary depending on defect density in the grain
boundary and on disorder strength. Since grain sizes in graphene made by
chemical vapor deposition are usually small, this may help explain why the
quantum Hall effect is usually poorly developed in devices made of this
material.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-54581408.0494 | A note on the existence of traveling-wave solutions to a Boussinesq
system
math.AP
We obtain a one-parameter family $$(u_{\mu}(x,t),\eta_{\mu}(x,t))_{\mu\geq
\mu_0}=(\phi_{\mu}(x-\omega_{\mu} t),\psi_{\mu}(x-\omega_{\mu} t))_{\mu\geq
\mu_0}$$ of traveling-wave solutions to the Boussinesq system
$$u_t+\eta_x+uu_x+c\eta_{xxx}=0,\eta_t+u_x+(\eta u)_x+au_{xxx}=0$$ in the
case $a,c<0$, with non-null speeds $\omega_{\mu}$ arbitrarily close to $0$
($\omega_{\mu}\xrightarrow[\mu\to+\infty]{} 0$). We show that the $L^2$-size of
such traveling-waves satisfies the uniform (in $\mu$) estimate
$\|\phi_{\mu}\|_2^2+\|\psi_{\mu}\|_2^2\leq C\sqrt{|a|+|c|},$ where $C$ is a
positive constant. Furthermore, $\phi_{\mu}$ and $-\psi_{\mu}$ are smooth,
non-negative, radially decreasing functions which decay exponentially at
infinity.
| arxiv topic:math.AP |
arxiv_dataset-54591408.0594 | Crack Propagation in Bone on the Scale of Mineralized Collagen Fibrils :
Role of Polymers with Sacrificial Bonds and Hidden Length
cond-mat.soft
Sacrificial bonds and hidden length (SBHL) in structural molecules provide a
mechanism for energy dissipation at the nanoscale. It is hypothesized that
their presence leads to greater fracture toughness than what is observed in
materials without such features. Here, we investigate this hypothesis using a
simplified model of a mineralized collagen fibril sliding on a polymeric
interface with SBHL systems. A 1D coarse-grained nonlinear spring-mass system
is used to model the fibril. Rate-and-displacement constitutive equations are
used to describe the mechanical properties of the polymeric system. The model
quantifies how the interface toughness increases as a function of polymer
density and number of sacrificial bonds. Other characteristics of the SBHL
system, such as the length of hidden loops and the strength of the bonds, are
found to influence the results. The model also gives insight into the
variations in the mechanical behavior in response to physiological changes,
such as the degree of mineralization of the collagen fibril and polymer density
in the interfibrillar matrix. The model results provide constraints relevant
for bio-mimetic material design and multiscale modeling of fracture in human
bone.
| arxiv topic:cond-mat.soft |
arxiv_dataset-54601408.0694 | The Dynamics of Offensive Messages in the World of Social Media: the
Control of Cyberbullying on Twitter
cs.SI cs.CY physics.soc-ph
The 21st century has redefined the way we communicate, our concept of
individual and group privacy, and the dynamics of acceptable behavioral norms.
The messaging dynamics on Twitter, an internet social network, has opened new
ways/modes of spreading information. As a result cyberbullying or in general,
the spread of offensive messages, is a prevalent problem. The aim of this
report is to identify and evaluate conditions that would dampen the role of
cyberbullying dynamics on Twitter. We present a discrete-time non-linear
compartmental model to explore how the introduction of a Quarantine class may
help to hinder the spread of offensive messages. We based the parameters of
this model on recent Twitter data related to a topic that communities would
deem most offensive, and found that for Twitter a level of quarantine can
always be achieved that will immediately suppress the spread of offensive
messages, and that this level of quarantine is independent of the number of
offenders spreading the message. We hope that the analysis of this dynamic
model will shed some insights into the viability of new models of methods for
reducing cyberbullying in public social networks.
| arxiv topic:cs.SI cs.CY physics.soc-ph |
arxiv_dataset-54611408.0794 | An Enigmatic Pointlike Feature within the HD 169142 Transitional Disk
astro-ph.EP astro-ph.SR
We report the detection of a faint pointlike feature possibly related to
ongoing planet-formation in the disk of the transition disk star HD 169142. The
pointlike feature has a $\Delta$mag(L)$\sim$6.4, at a separation of $\sim$0.11"
and PA$\sim$0$^{\circ}$. Given its lack of an H or K$_{S}$ counterpart despite
its relative brightness, this candidate cannot be explained by purely
photospheric emission and must be a disk feature heated by an as yet unknown
source. Its extremely red colors make it highly unlikely to be a background
object, but future multi-wavelength followup is necessary for confirmation and
characterization of this feature.
| arxiv topic:astro-ph.EP astro-ph.SR |
arxiv_dataset-54621408.0894 | Properties and significance of the surface dipole mode
nucl-th nucl-ex
A strong isoscalar dipole resonance is known to be excited in a variety of
nuclei, including isospin symmetric ones, at approximately 6-7 MeV. A series of
theoretical studies and accumulating experimental evidence support an
interpretation of the above dipole resonance as an elementary surface
vibration. Obviously, such a mode is potentially as interesting as any
collective excitation for a variety of reasons. In addition, though, it is
found to account for the observed isoscalar segment of pygmy dipole strength.
As discussed here, this has important implications for pygmy-strength
interpretations and searches for genuine neutron-skin oscillations.
| arxiv topic:nucl-th nucl-ex |
arxiv_dataset-54631408.0994 | A Lower-Upper-Lower Block Triangular Decomposition with Minimal
Off-Diagonal Ranks
math.RA
We propose a novel factorization of a non-singular matrix $P$, viewed as a
$2\times 2$-blocked matrix. The factorization decomposes $P$ into a product of
three matrices that are lower block-unitriangular, upper block-triangular, and
lower block-unitriangular, respectively. Our goal is to make this factorization
"as block-diagonal as possible" by minimizing the ranks of the off-diagonal
blocks. We give lower bounds on these ranks and show that they are sharp by
providing an algorithm that computes an optimal solution. The proposed
decomposition can be viewed as a generalization of the well-known Block LU
factorization using the Schur complement.
| arxiv topic:math.RA |
arxiv_dataset-54641408.1094 | Boundary-law scaling of entanglement entropy in diffusive metals
cond-mat.str-el cond-mat.dis-nn quant-ph
Entanglement structure serves as a powerful way to characterize quantum
many-body phases. This is particularly so for gapless quantum liquids, where
entanglement-based tools provide one of the only means to systematically
characterize these complicated phases. For example, the Fermi-surface structure
of Fermi-liquids is revealed in entanglement entropy by a log-correction to the
typical boundary-law scaling of simpler quantum ground-states. In this paper, I
analyze the entanglement structure of a disordered, but delocalized diffusive
metal. Using a combination of analytic arguments and numerical calculations, I
show that, despite having the same number of extended gapless excitations as a
clean Fermi-liquid, the diffusive metal exhibits only boundary-law entanglement
scaling. This result pinpoints the sharp Fermi-surface structure, rather than
the finite density of gapless excitations, as the origin of the log-correction
in the Fermi-liquid entanglement scaling.
| arxiv topic:cond-mat.str-el cond-mat.dis-nn quant-ph |
arxiv_dataset-54651408.1194 | A comparison between models of gravity induced decoherence
quant-ph gr-qc
It has been suggested in the literature that spatial coherence of the wave
function can be dynamically suppressed by fluctuations in the spacetime
geometry. These fluctuations represent the minimal uncertainty that is present
when one probes spacetime geometry with a quantum probe. Two similar models
have been proposed, one by Di\'osi [D-model] and one by Karolyhazy and
collaborators [K-model], based on apparently unrelated minimal spacetime
bounds. The two models arrive at somewhat different expressions for the
dependence of the localization coherence length on the mass and size of the
quantum object. In the present article we compare and contrast the two models
from three aspects: (i) comparison of the spacetime bounds, (ii) method of
calculating decoherence time, (iii) comparison of noise correlation. We show
that under certain conditions the minimal spacetime bounds in the two models
can be derived one from the other. We argue that the methods of calculating the
decoherence time are equivalent. We re-derive the two-point correlation for the
fluctuation potential in the K-model, and confirm the earlier result of Di\'osi
and Luk\'acs that it is non-white noise, unlike in the D-model, where the
corresponding correlation is white noise in time. This seems to be the origin
of the different results in the two models. We derive the non-Markovian master
equation for the K-model. We argue that the minimal spacetime bound cannot
predict the noise correlation uniquely, and additional criteria are necessary
to accurately determine the effects of gravitationally induced decoherence.
| arxiv topic:quant-ph gr-qc |
arxiv_dataset-54661408.1294 | Network cloning unfolds the effect of clustering on dynamical processes
physics.soc-ph cond-mat.dis-nn cs.SI
We introduce network $L$-cloning, a technique for creating ensembles of
random networks from any given real-world or artificial network. Each member of
the ensemble is an $L$-cloned network constructed from $L$ copies of the
original network. The degree distribution of an $L$-cloned network and, more
importantly, the degree-degree correlation between and beyond nearest neighbors
are identical to those of the original network. The density of triangles in an
\LC network, and hence its clustering coefficient, is reduced by a factor of
$L$ compared to those of the original network. Furthermore, the density of
loops of any fixed length approaches zero for sufficiently large values of $L$.
Other variants of $L$-cloning allow us to keep intact the short loops of
certain lengths. As an application, we employ these network cloning methods to
investigate the effect of short loops on dynamical processes running on
networks and to inspect the accuracy of corresponding tree-based theories. We
demonstrate that dynamics on $L$-cloned networks (with sufficiently large $L$)
are accurately described by the so-called adjacency tree-based theories,
examples of which include the message passing technique, some pair
approximation methods, and the belief propagation algorithm used respectively
to study bond percolation, SI epidemics, and the Ising model.
| arxiv topic:physics.soc-ph cond-mat.dis-nn cs.SI |
arxiv_dataset-54671408.1394 | The stripping of a galaxy group diving into the massive cluster A2142
astro-ph.CO astro-ph.GA astro-ph.HE
Structure formation in the current Universe operates through the accretion of
group-scale systems onto massive clusters. The detection and study of such
accreting systems is crucial to understand the build-up of the most massive
virialized structures we see today. We report the discovery with XMM-Newton of
an irregular X-ray substructure in the outskirts of the massive galaxy cluster
Abell 2142. The tip of the X-ray emission coincides with a concentration of
galaxies. The bulk of the X-ray emission of this substructure appears to be
lagging behind the galaxies and extends over a projected scale of at least 800
kpc. The temperature of the gas in this region is 1.4 keV, which is a factor of
~4 lower than the surrounding medium and is typical of the virialized plasma of
a galaxy group with a mass of a few 10^13M_sun. For this reason, we interpret
this structure as a galaxy group in the process of being accreted onto the main
dark-matter halo. The X-ray structure trailing behind the group is due to gas
stripped from its original dark-matter halo as it moves through the
intracluster medium (ICM). This is the longest X-ray trail reported to date.
For an infall velocity of ~1,200 km s-1 we estimate that the stripped gas has
been surviving in the presence of the hot ICM for at least 600 Myr, which
exceeds the Spitzer conduction timescale in the medium by a factor of >~400.
Such a strong suppression of conductivity is likely related to a tangled
magnetic field with small coherence length and to plasma microinstabilities.
The long survival time of the low-entropy intragroup medium suggests that the
infalling material can eventually settle within the core of the main cluster.
| arxiv topic:astro-ph.CO astro-ph.GA astro-ph.HE |
arxiv_dataset-54681408.1494 | The digital traces of bubbles: feedback cycles between socio-economic
signals in the Bitcoin economy
physics.soc-ph cs.SI nlin.AO q-fin.ST
What is the role of social interactions in the creation of price bubbles?
Answering this question requires obtaining collective behavioural traces
generated by the activity of a large number of actors. Digital currencies offer
a unique possibility to measure socio-economic signals from such digital
traces. Here, we focus on Bitcoin, the most popular cryptocurrency. Bitcoin has
experienced periods of rapid increase in exchange rates (price) followed by
sharp decline; we hypothesise that these fluctuations are largely driven by the
interplay between different social phenomena. We thus quantify four
socio-economic signals about Bitcoin from large data sets: price on on-line
exchanges, volume of word-of-mouth communication in on-line social media,
volume of information search, and user base growth. By using vector
autoregression, we identify two positive feedback loops that lead to price
bubbles in the absence of exogenous stimuli: one driven by word of mouth, and
the other by new Bitcoin adopters. We also observe that spikes in information
search, presumably linked to external events, precede drastic price declines.
Understanding the interplay between the socio-economic signals we measured can
lead to applications beyond cryptocurrencies to other phenomena which leave
digital footprints, such as on-line social network usage.
| arxiv topic:physics.soc-ph cs.SI nlin.AO q-fin.ST |
arxiv_dataset-54691408.1594 | Ferromagnetic resonance of a magnetic dimer with dipolar coupling
cond-mat.mtrl-sci cond-mat.mes-hall
We develop a general formalism for analyzing the ferromagnetic resonance
characteristics of a magnetic dimer consisting of two magnetic elements (in a
horizontal or vertical configuration) coupled by dipolar interaction, taking
account of their finite-size and aspect ratio. We study the effect on the
resonance frequency and resonance field of the applied magnetic field (in
amplitude and direction), the inter-element coupling, and the uniaxial
anisotropy in various configurations. We obtain analytical expressions for the
resonance frequency in various regimes of the interlayer coupling. We
(numerically) investigate the behavior of the resonance field in the
corresponding regimes. The critical value of the applied magnetic field at
which the resonance frequency vanishes may be an increasing or a decreasing
function of the dimer's coupling, depending on the anisotropy configuration. It
is also a function of the nanomagnets aspect ratio in the case of in-plane
anisotropy. This and several other results of this work, when compared with
experiments using the standard ferromagnetic resonance with fixed frequency, or
the network analyzer with varying frequency and applied magnetic field, provide
a useful means for characterizing the effective anisotropy and coupling within
systems of stacked or assembled nanomagnets.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-54701408.1694 | A 24-Hour Global Campaign To Assess Precision Timing of the Millisecond
Pulsar J1713+0747
astro-ph.HE astro-ph.IM
The radio millisecond pulsar J1713+0747 is regarded as one of the
highest-precision clocks in the sky, and is regularly timed for the purpose of
detecting gravitational waves. The International Pulsar Timing Array
collaboration undertook a 24-hour global observation of PSR J1713+0747 in an
effort to better quantify sources of timing noise in this pulsar, particularly
on intermediate (1 - 24 hr) timescales. We observed the pulsar continuously
over 24 hr with the Arecibo, Effelsberg, GMRT, Green Bank, LOFAR, Lovell,
Nancay, Parkes, and WSRT radio telescopes. The combined pulse times-of-arrival
presented here provide an estimate of what sources of timing noise, excluding
DM variations, would be present as compared to an idealized root-N improvement
in timing precision, where N is the number of pulses analyzed. In the case of
this particular pulsar, we find that intrinsic pulse phase jitter dominates
arrival time precision when the S/N of single pulses exceeds unity, as measured
using the eight telescopes that observed at L-band/1.4 GHz. We present first
results of specific phenomena probed on the unusually long timescale (for a
single continuous observing session) of tens of hours, in particular
interstellar scintillation, and discuss the degree to which scintillation and
profile evolution affect precision timing. This paper presents the data set as
a basis for future, deeper studies.
| arxiv topic:astro-ph.HE astro-ph.IM |
arxiv_dataset-54711408.1794 | All-optical production and trapping of metastable noble gas atoms down
to the single atom regime
physics.atom-ph
The determination of isotope ratios of noble gas atoms has many applications
e.g. in physics, nuclear arms control, and earth sciences. For several
applications, the concentration of specific noble gas isotopes (e.g. Kr and Ar)
is so low that single atom detection is highly desirable for a precise
determination of the concentration. As an important step in this direction, we
demonstrate operation of a krypton Atom Trap Trace Analysis (ATTA) setup based
on a magneto-optical trap (MOT) for metastable Kr atoms excited by all-optical
means. Compared to other state-of-the-art techniques for preparing metastable
noble gas atoms, all-optical production is capable of overcoming limitations
regarding minimal probe volume and avoiding cross-contamination of the samples.
In addition, it allows for a compact and reliable setup. We identify optimal
parameters of our experimental setup by employing the most abundant isotope
Kr-84, and demonstrate single atom detection within a 3D MOT.
| arxiv topic:physics.atom-ph |
arxiv_dataset-54721408.1894 | In-plane conductivity of a layered large-bipolaron liquid
cond-mat.supr-con
Distinctive normal-state properties of cuprate superconductors follow from
their charge carriers forming a large-bipolaron liquid. The very weak
scattering of the slow-moving heavy-massed excitations of the liquid by
acoustic phonons yields a scattering rate that is less than the Debye
frequency. The moderate liquid mobility, greater than 1 cm2/V-sec at 300 K,
results as the weak scattering of the liquid compensates for its large mass. In
resolution of a long-standing dilemma, the dc resistivity resulting from
scattering by acoustic phonons remains nearly proportional to temperature to
well below the Debye temperature. Above the Debye frequency the
frequency-dependent conductivity is dominated by excitation and
photo-ionization of the self-trapped electronic carriers of the
large-bipolarons. Below the Debye frequency the frequency-dependent
conductivity is dominated by the Drude-like collective motion of the
large-bipolaron liquid. The gap between these two domains sharpens with
decreasing temperature as phonon scattering of the liquid diminishes. The
high-frequency electronic excitations survive in the superconducting state.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-54731408.1994 | Gauge theory of gravity and matter
hep-th
It is shown how to write the first order action for gravity in a gauge
theoretic formalism where the spin connection and frame field degrees of
freedom are assimilated together into a gauge connection. It is then shown how
to couple the theory to spin-0, 1/2, 1 and 3/2 fields in a gauge invariant
fashion. The results hold in any number of spacetime dimensions.
| arxiv topic:hep-th |
arxiv_dataset-54741408.2094 | Une nouvelle d\'emonstration d'irrationalit\'e de racine carr\'ee de 2
d'apr\`es les Analytiques d'Aristote
math.HO
To account for the first proof of existence of an irrational magnitude,
historians of science as well as commentators of Aristotle refer to the texts
on the incommensurability of the diagonal in Prior Analytics, since they are
the most ancient on the subject. The usual proofs suggested by the historians
of science derive from a proposition found at the end of Book X of Euclid's
Elements. But its conclusions, using the representation of fractions as a ratio
of two integers relatively prime i.e. the proposition VII.22 of the Elements,
do not match the Aristotelian texts. In this article, we propose a new
demonstration conformed to these texts. They are based on very old results of
the odd/even theory. Since they use neither the proposition VII.22, nor any
other result proved by a reductio ad absurdum, it seems to be the first result
which was impossible to prove in another way. The significance of this result,
revealing a complete new territory in Mathematics, the field of irrational
magnitudes, accounts for the centrality gained afterwards by this kind of
reasoning, firstly in Mathematics, then in all forms of rational discourse.
From the consequences of this new proof, we can construe very simply the
lecture on the irrationals in the mathematical text in Plato's Theaetetus
(147d-148b). It will be done in an article to appear in a forthcoming volume.
| arxiv topic:math.HO |
arxiv_dataset-54751408.2194 | Assortative mixing enhances the irreversible nature of explosive
synchronization in growing scale-free networks
nlin.AO
We discuss the behavior of large ensembles of phase oscillators networking
via scale-free topologies in the presence of a positive correlation between the
oscillators' natural frequencies and network's degrees. In particular, we show
that the further presence of degree-degree correlation in the network structure
has important consequences on the nature of the phase transition characterizing
the passage from the phase-incoherent to the phase-coherent network's state.
While high levels of positive and negative mixing consistently induce a
second-order phase transition, moderate values of assortative mixing, such as
those ubiquitously characterizing social networks in the real world, greatly
enhance the irreversible nature of explosive synchronization in growing
scale-free networks. This latter effect corresponds to a maximization of the
area and of the width of the hysteretic loop that differentiates the forward
and backward transitions to synchronization.
| arxiv topic:nlin.AO |
arxiv_dataset-54761408.2294 | Digital Filter Designs for Recursive Frequency Analysis
cs.SY cs.SD
Digital filters for recursively computing the discrete Fourier transform
(DFT) and estimating the frequency spectrum of sampled signals are examined,
with an emphasis on magnitude-response and numerical stability. In this
tutorial-style treatment, existing recursive techniques are reviewed, explained
and compared within a coherent framework; some fresh insights are provided and
new enhancements/modifications are proposed. It is shown that the replacement
of resonators by (non-recursive) modulators in sliding DFT (SDFT) analyzers
with either a finite impulse response (FIR), or an infinite impulse response
(IIR), does improve performance somewhat; however stability is not guaranteed,
as the cancellation of marginally stable poles by zeros is still involved. The
FIR deadbeat observer is shown to be more reliable than the SDFT methods, an
IIR variant is presented, and ways of fine-tuning its response are discussed. A
novel technique for stabilizing IIR SDFT analyzers with a fading memory, so
that all poles are inside the unit circle, is also derived. Slepian and
sum-of-cosine windows are adapted to improve the frequency responses for the
various FIR and IIR DFT methods.
| arxiv topic:cs.SY cs.SD |
arxiv_dataset-54771408.2394 | Theory of Optical Rectification Effect in Metallic Thin Film with
Periodic Modulation
physics.optics
We conducted theoretical and numerical investigations of the optical
rectification (OR) effect in metallic structures with periodic modulation. A
new formulation of the OR effect is presented, and the mechanism by which the
OR effect is generated, which has been a controversial issue in previous
studies, is clarified. We reveal that the OR effect is strongly enhanced by a
combination of spatial variation of the metallic structure and local electric
field enhancement. Our theory was numerically evaluated and agreed fairly well
with experiment.
| arxiv topic:physics.optics |
arxiv_dataset-54781408.2494 | GeV electrons due to a transition from laser wakefield acceleration to
plasma wakefield acceleration
physics.plasm-ph hep-ex
We show through experiments that a transition from laser wakefield
acceleration (LWFA) regime to a plasma wakefield acceleration (PWFA) regime can
drive electrons up to energies close to the GeV level. Initially, the
acceleration mechanism is dominated by the bubble created by the laser in the
nonlinear regime of LWFA, leading to an injection of a large number of
electrons. After propagation beyond the depletion length, leading to a
depletion of the laser pulse, whose transverse ponderomotive force is not able
to sustain the bubble anymore, the high energy dense bunch of electrons
propagating inside bubble will drive its own wakefield by a PWFA regime. This
wakefield will be able to trap and accelerate a population of electrons up to
the GeV level during this second stage. Three dimensional (3D) particle-in-cell
(PIC) simulations support this analysis, and confirm the scenario.
| arxiv topic:physics.plasm-ph hep-ex |
arxiv_dataset-54791408.2594 | Two charges on plane in a magnetic field: III. $He^+$ ion
physics.atom-ph quant-ph
The $He^+$ ion on a plane subject to a constant magnetic field $B$
perpendicular to the plane is considered taking into account the finite nuclear
mass. Factorization of eigenfunctions permits to reduce the four-dimensional
problem to three-dimensional one. The ground state energy of the composite
system is calculated in a wide range of magnetic fields from $B=0.01$ up to
$B=100$ a.u. and center-of-mass Pseudomomentum $K$ from $0$ to $1000$ a.u.
using a variational approach. The accuracy of calculations for $B = 0.1 $ a.u.
is cross-checked in Lagrange-mesh method and not less than five significant
figures are reproduced in energy. Similarly to the case of moving neutral
system on the plane a phenomenon of a sharp change of energy behavior as a
function of $K$ for a certain critical $K_c$ but a fixed magnetic field occurs.
| arxiv topic:physics.atom-ph quant-ph |
arxiv_dataset-54801408.2694 | The Mixed Phase of Charged AdS Black holes
hep-th
We study the mixed phase of charged AdS black hole and radiation when the
total energy is fixed below the threshold to produce a stable charged black
hole branch. The coexistence conditions for the charged AdS black hole and
radiation are derived for the generic case when radiation particles carry
charge. The phase diagram of the mixed phase is demonstrated for both fixed
potential and charge ensemble. In the dual gauge picture, they correspond to
the mixed phase of quark-gluon plasma~(QGP) and hadron gas in the fixed
chemical potential and density ensemble respectively. In the nuclei and heavy
ion collisions at intermediate energies, the mixed phase of exotic QGP and
hadron gas could be produced. The mixed phase will condensate and evaporate
into the hadron gas as the fireball expands.
| arxiv topic:hep-th |
arxiv_dataset-54811408.2794 | Sector-Based Factor Models for Asset Returns
q-fin.ST stat.AP
Factor analysis is a statistical technique employed to evaluate how observed
variables correlate through common factors and unique variables. While it is
often used to analyze price movement in the unstable stock market, it does not
always yield easily interpretable results. In this study, we develop improved
factor models by explicitly incorporating sector information on our studied
stocks. We add eleven sectors of stocks as defined by the IBES, represented by
respective sector-specific factors, to non-specific market factors to revise
the factor model. We then develop an expectation maximization (EM) algorithm to
compute our revised model with 15 years' worth of S&P 500 stocks' daily close
prices. Our results in most sectors show that nearly all of these factor
components have the same sign, consistent with the intuitive idea that stocks
in the same sector tend to rise and fall in coordination over time. Results
obtained by the classic factor model, in contrast, had a homogeneous blend of
positive and negative components. We conclude that results produced by our
sector-based factor model are more interpretable than those produced by the
classic non-sector-based model for at least some stock sectors.
| arxiv topic:q-fin.ST stat.AP |
arxiv_dataset-54821408.2894 | On the dynamics of traveling phase-oscillators with positive and
negative couplings
nlin.AO nlin.CD
We investigate numerically the dynamics of traveling clusters in systems of
phase oscillators, some of which possess positive couplings and others negative
couplings. The phase distribution, speed of traveling, and average separation
between clusters as well as order parameters for positive and negative
oscillators are computed, as the ratio of the two coupling constants and/or the
fraction of positive oscillators are varied. The traveling speed depending on
these parameters is obtained and observed to fit well with the numerical data
of the systems. With the help of this, we describe the conditions for the
traveling state to appear in the systems with or without periodic driving.
| arxiv topic:nlin.AO nlin.CD |
arxiv_dataset-54831408.2994 | Properties of the CO and H$_2$O MOLsphere of the red supergiant
Betelgeuse from VLTI/AMBER observations
astro-ph.SR
Context. Betelgeuse is the closest red supergiant (RSG); therefore, it is
well suited for studying the complex processes in its atmosphere that lead to
the chemical enrichment of the interstellar medium. Aims. We intend to
investigate the shape and composition of the close molecular layer (also known
as the MOLsphere) that surrounds the star. This analysis is part of a wider
program that aims at understanding the dynamics of the circumstellar envelope
of Betelgeuse. Methods. On January and February 2011, Betelgeuse was observed
using the Astronomical Multi-BEam combineR (AMBER) instrument of the Very Large
Telescope Interferometer (VLTI) in the H and K bands. Using the medium spectral
resolution of the instrument (R $\sim$ 1500), we were able to investigate the
carbon monoxide band heads and the water-vapor bands. We used two different
approaches to analyse our data: a model fit in both the continuum and
absorption lines and then a fit with a Radiative HydroDynamics (RHD)
simulation. Results. Using the continuum data, we derive a uniform disk
diameter of $41.01 \pm 0.41$~mas, a power law type limb-darkened disk diameter
of $42.28 \pm 0.43$~mas and a limb-darkening exponent of $0.155 \pm 0.009$.
Within the absorption lines, using a single layer model, we obtain parameters
of the MOLsphere. Using a RHD simulation, we unveil the convection pattern in
the visibilities. Conclusions. We derived a new value of the angular diameter
of Betelgeuse in the K band continuum. Our observations in the absorption lines
are well reproduced by a molecular layer at 1.2 stellar radii containing both
CO and H$_2$O. The visibilities at higher spatial frequencies are matching a
convection pattern in a RHD simulation.
| arxiv topic:astro-ph.SR |
arxiv_dataset-54841408.3094 | Large Deflections of Beam Subject to Three-points Bending
physics.class-ph math.NA
In the paper a solution for equilibrium configurations of an elastic beam
subject to three points bending is given in terms of Jacobi elliptical
functions. General equations are derived and the domain of solution is
established. Several examples that illustrate a use of the solution are
discussed. The obtained numerical results are compared with results of other
authors. Approximation formula by which the beam load is given as polynomial
function of beam deflection is also derived. The range of applicability of the
approximation is illustrated by numerical example.
| arxiv topic:physics.class-ph math.NA |
arxiv_dataset-54851408.3194 | Quantum coherence and correlations in quantum system
quant-ph
Criteria of measure quantifying quantum coherence, a unique property of
quantum system, are proposed recently. In this paper, we first give an
uncertainty-like expression relating the coherence and the entropy of quantum
system. This finding allows us to discuss the relations between the
entanglement and the coherence. Further, we discuss in detail the relations
among the coherence, the discord and the deficit in the bipartite quantum
system. We show that, the one-way quantum deficit is equal to the sum between
quantum discord and the relative entropy of coherence of measured subsystem.
| arxiv topic:quant-ph |
arxiv_dataset-54861408.3294 | The $(p,q)$-Analogues of Some Inequalities for the Digamma Function
math.CA
In this paper, we present the (p; q)-analogues of some inequalities
concerning the digamma function. Our results generalize some earlier results.
| arxiv topic:math.CA |
arxiv_dataset-54871408.3394 | Mean-Value of Product of Shifted Multiplicative Functions and Average
Number of Points on Elliptic Curves
math.NT
In this paper, we consider the mean value of the product of two real valued
multiplicative functions with shifted arguments. The functions $F$ and $G$
under consideration are close to two nicely behaved functions $A$ and $B$, such
that the average value of $A(n-h)B(n)$ over any arithmetic progression is only
dependent on the common difference of the progression. We use this method on
the problem of finding mean value of $K(N)$, where $K(N)/\log N$ is the
expected number of primes such that a random elliptic curve over rationals has
$N$ points when reduced over those primes.
| arxiv topic:math.NT |
arxiv_dataset-54881408.3494 | The singularities and birational geometry of the universal compactified
Jacobian
math.AG
In this paper we establish that the singularities of the universal
compactified Jacobian are canonical if the genus is at least four. As a
corollary we determine the Kodaira dimension and the Iitaka fibration of the
universal compactified Jacobian for every degree and genus. We also determine
the birational automorphism group for every degree if the genus is at least
twelve. This extends work of G. Farkas and A. Verra, as well as that of G.
Bini, C. Fontanari and the third author.
| arxiv topic:math.AG |
arxiv_dataset-54891408.3594 | Self-Consistent, Self-Coupled Scalar Gravity
gr-qc physics.class-ph
A scalar theory of gravity extending Newtonian gravity to include field
energy as its source is developed. The physical implications of the theory are
probed through its spherically symmetric (source) solutions. The aim is to
demonstrate rational physical model building, together with physical and
experimental checks of correctness. The theory discussed here was originally
considered by Einstein prior to his introduction of general relativity.
| arxiv topic:gr-qc physics.class-ph |
arxiv_dataset-54901408.3694 | Representation stability and finite linear groups
math.AT math.GR math.GT math.RT
We construct analogues of FI-modules where the role of the symmetric group is
played by the general linear groups and the symplectic groups over finite rings
and prove basic structural properties such as Noetherianity. Applications
include a proof of the Lannes--Schwartz Artinian conjecture in the generic
representation theory of finite fields, very general homological stability
theorems with twisted coefficients for the general linear and symplectic groups
over finite rings, and representation-theoretic versions of homological
stability for congruence subgroups of the general linear group, the
automorphism group of a free group, the symplectic group, and the mapping class
group.
| arxiv topic:math.AT math.GR math.GT math.RT |
arxiv_dataset-54911408.3794 | Wave Function of the Universe from a Matrix Valued First-Order Formalism
physics.gen-ph gr-qc hep-th
In this paper, the Wheeler-DeWitt equation in full superspace formalism will
be written in a matrix valued first-order formalism. We will also analyse the
Wheeler-DeWitt equation in minisuperspace approximation using this matrix
valued first-order formalism.
We will note that this Wheeler-DeWitt equation, in this minisuperspace
approximation, can be expressed as an eigenvalue equation. We will use this
fact to analyse the spacetime foam in this formalism. This will be done by
constructing a statistical mechanical partition function for the Wheeler-DeWitt
equation in this matrix valued first-order formalism. This will lead to a
possible solution for the cosmological constant problem.
| arxiv topic:physics.gen-ph gr-qc hep-th |
arxiv_dataset-54921408.3894 | Anomalous magnetoresistance in the spinel superconductor LiTi2O4
cond-mat.supr-con cond-mat.mtrl-sci
Transition-metal oxides offer an opportunity to explore unconventional
superconductors, where the superconductivity (SC) is often interrelated with
novel phenomena such as spin/charge order, fluctuations, and Fermi surface
instability (1-3). LiTi2O4 (LTO) is a unique compound in that it is the only
known spinel oxide superconductor. In addition to electron-phonon coupling,
electron-electron and spin fluctuation contributions have been suggested as
playing important roles in the microscopic mechanism for its superconductivity
(4-8). However, the lack of high quality single crystals has thus far prevented
systematic investigation of their transport properties (9). Here, we report a
careful study of transport and tunneling spectroscopy in epitaxial LTO thin
films. In the superconducting state, the energy gap was found to decrease as a
quadratic function of magnetic field. In the normal state, an unusual
magnetoresistance (MR) was observed where it changes from anisotropic positive
to isotropic negative as the temperature is increased. A constant charge
carrier concentration without any abrupt change in lattice parameters as a
function of temperature suggests that the isotropic MR stems from the
suppression of spin scattering/fluctuations, while the anisotropic term
originates from an orbital contribution. These observations point to an
important role strong correlations play in this unique superconductor.
| arxiv topic:cond-mat.supr-con cond-mat.mtrl-sci |
arxiv_dataset-54931408.3994 | Exciton-Polariton Oscillations in Real Space
cond-mat.mes-hall
We introduce and model spin-Rabi oscillations based on exciton-polaritons in
semiconductor microcavities. The phase and polarization of oscillations can be
controlled by resonant coherent pulses and the propagation of oscillating
domains gives rise to phase-dependent interference patterns in real space. We
show that interbranch polariton-polariton scattering controls the propagation
of oscillating domains, which can be used to realize logic gates based on an
analogue variable phase.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-54941408.4094 | Extracting molecular potentials from insufficient spectroscopic
information
quant-ph physics.chem-ph physics.optics
We extend our recently developed inversion method to extract excited state
potentials from fluorescence line positions and line strengths. We consider a
previous limitation of the method arising due to insufficient input data in
cases where the relatively weaker emission data are not experimentally
available. We develop a solution to this problem by "regenerating" these weak
transition lines via applying a model potential, e.g. a Morse potential. The
result of this procedure, illustrated for the Q-branch emission from the lowest
three vibrational levels of the B($^1 \Pi)$ state of LiRb, is shown to have an
error of $0.29$ cm$^{-1}$ in the classically allowed region and a global error
of $5.67$ cm$^{-1}$ for $V\le E(\nu'=10)$. The robustness of this procedure is
also demonstrated by considering the statistical error in the measured line
intensities.
| arxiv topic:quant-ph physics.chem-ph physics.optics |
arxiv_dataset-54951408.4194 | The Hidden Cost of Accommodating Crowdfunder Privacy Preferences: A
Randomized Field Experiment
cs.SI cs.CY
Online crowdfunding has received a great deal of attention from entrepreneurs
and policymakers as a promising avenue to fostering entrepreneurship and
innovation. A notable aspect of this shift from an offline to an online setting
is that it brings increased visibility and traceability of transactions. Many
crowdfunding platforms therefore provide mechanisms that enable a campaign
contributor to conceal his or her identity or contribution amount from peers.
We study the impact of these information (privacy) control mechanisms on
crowdfunder behavior. Employing a randomized experiment at one of the largest
online crowdfunding platforms, we find evidence of both positive (e.g.,
comfort) and negative (e.g., privacy priming) causal effects. We find that
reducing access to information controls induces a net increase in fundraising,
yet this outcome results from two competing influences: treatment increases
willingness to engage with the platform (a 4.9% increase in the probability of
contribution) and simultaneously decreases the average contribution (a $5.81
decline). This decline derives from a publicity effect, wherein contributors
respond to a lack of privacy by tempering extreme contributions. We unravel the
causal mechanisms that drive the results and discuss the implications of our
findings for the design of online platforms.
| arxiv topic:cs.SI cs.CY |
arxiv_dataset-54961408.4294 | Gaps in the spectrum of the Laplacian on $3N$-Gaskets
math-ph math.FA math.MG math.MP math.PR math.SP
This article develops analysis on fractal $3N$-gaskets, a class of
post-critically finite fractals which include the Sierpinski triangle for
$N=1$, specifically properties of the Laplacian $\Delta$ on these gaskets. We
first prove the existence of a self-similar geodesic metric on these gaskets,
and prove heat kernel estimates for this Laplacian with respect to the geodesic
metric. We also compute the elements of the method of spectral decimation, a
technique used to determine the spectrum of post-critically finite fractals.
Spectral decimation on these gaskets arises from more complicated dynamics than
in previous examples, i.e. the functions involved are rational rather than
polynomial. Due to the nature of these dynamics, we are able to show that there
are gaps in the spectrum.
| arxiv topic:math-ph math.FA math.MG math.MP math.PR math.SP |
arxiv_dataset-54971408.4394 | Symmetry examples in open quantum dynamics
quant-ph
Dependent symmetries, symmetries that depend on the situation of the
subsystem in a larger closed system, are explored by looking at simple
examples. This is a new kind of symmetry in the open quantum dynamics of a
subsystem
Each symmetry implies a particular form for the results of the open dynamics.
The forms exhibit the symmetries very simply. It is shown directly, without
assuming anything about the symmetry, that the dynamics produces the form, but
knowing the symmetry and the form it implies can reduce what needs to be done
to work out the dynamics; pieces can be deduced from the symmetry rather that
calculated from the dynamics.
Symmetries can be related to constants of the motion in new ways. A quantity
might be a dependent constant of the motion, constant only for particular
situations of the subsystem in the larger system. In particular, a generator of
dependent symmetries could represent a quantity that is a dependent constant of
the motion for the same situations as for the symmetries. The examples present
a variety of possibilities. Sometimes a generator of dependent symmetries does
represent a dependent constant of the motion. Sometimes it does not. Sometimes
no quantity is a dependent constant of the motion. Sometimes every quantity is.
| arxiv topic:quant-ph |
arxiv_dataset-54981408.4494 | Bipolar switching in an orthogonal spin transfer spin valve device
cond-mat.mes-hall cond-mat.mtrl-sci
We demonstrate current-induced bipolar switching in in-plane magnetized
spin-valve devices that incorporate a perpendicularly magnetized spin
polarizing layer. Further, hysteretic transitions into a state with
intermediate resistance occur at high currents, again for both current
polarities. These transitions are shown to be consistent with a macrospin model
that considers a spin-polarized current that is tilted with respect to the free
layer plane, due to the presence of spin-transfer torque from the polarizing
layer. These unique switching characteristics, which have their origin in the
noncollinear layer magnetizations, are of interest for magnetic random access
memory and spin-torque oscillator devices.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-54991408.4594 | Sound waves and modulational instabilities on continuous wave solutions
in spinor Bose-Einstein condensates
cond-mat.quant-gas nlin.CD nlin.PS
We analyze sound waves (phonons, Bogoliubov excitations) propagating on
continuous wave (cw) solutions of repulsive $F=1$ spinor Bose-Einstein
condensates (BECs), such as $^{23}$Na (which is antiferromagnetic or polar) and
$^{87}$Rb (which is ferromagnetic). Zeeman splitting by a uniform magnetic
field is included. All cw solutions to ferromagnetic BECs with vanishing
$M_F=0$ particle density and non-zero components in both $M_F=\pm 1$ fields are
subject to modulational instability (MI). MI increases with increasing particle
density. MI also increases with differences in the components' wavenumbers;
this effect is larger at lower densities but becomes insignificant at higher
particle densities. CW solutions to antiferromagnetic (polar) BECS with
vanishing $M_F=0$ particle density and non-zero components in both $M_F=\pm 1$
fields do not suffer MI if the wavenumbers of the components are the same. If
there is a wavenumber difference, MI initially increases with increasing
particle density, then peaks before dropping to zero beyond a given particle
density. The cw solutions with particles in both $M_F=\pm 1$ components and
nonvanishing $M_F=0$ components do not have MI if the wavenumbers of the
components are the same, but do exhibit MI when the wavenumbers are different.
Direct numerical simulations of a cw with weak white noise confirm that weak
noise grows fastest at wavenumbers with the largest MI, and shows some of the
results beyond small amplitude perturbations. Phonon dispersion curves are
computed numerically; we find analytic solutions for the phonon dispersion in a
variety of limiting cases.
| arxiv topic:cond-mat.quant-gas nlin.CD nlin.PS |
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