title: On the BCS-BEC crossover in the 2D Asymmetric Attractive Hubbard Model

abstract:
  We analyze the evolution from the weak coupling (BCS-like limit) to the
strong coupling limit of tightly bound local pairs (LP's) in the 2D asymmetric
attractive Hubbard model, in the presence of the Zeeman magnetic field ($h$).
The broken symmetry Hartree approximation is used. We also apply the
Kosterlitz-Thouless (KT) scenario to determine the phase coherence
temperatures. We obtain that for the spin dependent hopping integrals
($t^{\uparrow}\neq t^{\downarrow}$) the homogeneous polarized superfluid
(SC$_M$) phase in the ground state for the strong attraction and lower filling
can be stabilized. We find a topological quantum phase transition (Lifshitz
type) from the unpolarized superfluid phase (SC$_0$) to SC$_M$ and tricritical
point in the ($h-\mu$) and spin polarization ($P$) vs. attraction ($U<0$)
ground state phase diagrams. The finite temperatures phase diagrams for
$t^{\uparrow}\neq t^{\downarrow}$ are constructed.


title:
Heat transport in the geostrophic regime of rotating Rayleigh-B{\'e}nard
  convection

abstract:
  We report experimental measurements of heat transport in rotating
Rayleigh-B{\'e}nard convection in a cylindrical convection cell with aspect
ratio $\Gamma = 1/2$. The fluid was helium gas with Prandtl number Pr = 0.7.
The range of control parameters was Rayleigh number $4 \times 10^9 < {\rm Ra} <
4 \times 10^{11}$ and Ekman number $2 \times 10^{-7} < {\rm Ek} < 3 \times
10^{-5}$(corresponding to Taylor number $4 \times 10^9 < {\rm Ta} < 1 \times
10^{14}$ and convective Rossby number $0.07 < {\rm Ro} < 5$). We determine the
crossover from weakly rotating turbulent convection to rotation dominated
geostrophic convection through experimental measurements of the normalized heat
transport Nu. The heat transport for the rotating state in the geostrophic
regime, normalized by the zero-rotation heat transport, is consistent with
scaling of $({\rm RaEk}^{-7/4})^\beta$ with $\beta \approx 1$. A phase diagram
is presented that encapsulates measurements on the potential geostrophic
turbulence regime of rotating thermal convection.


title:
On the Imbalanced d-wave Superfluids within the Spin Polarized Extended
  Hubbard Model: Weak Coupling Limit

abstract:
  We investigate the superfluid properties of d-wave pairing symmetry within
the Extended Hubbard Model (EHM) in a magnetic field. We analyze the
temperature and magnetic field dependencies of the order parameter. We find
that in the two-dimensional case, the spatially homogeneous spin polarized
superfluidity ($SC(P\neq0)$) is stable in the weak coupling limit, at T=0, as
opposed to the s-wave pairing symmetry case in 2D. We construct the ground
state phase diagrams both for fixed chemical potential ($\mu$) and electron
concentration ($n$). Furthermore, we obtain the temperature vs. magnetic field
and temperature vs. spin polarization phase diagrams.


title: X-ray Variability Study of Polar Scattered Seyfert 1 Galaxies

abstract:
  We study 12 Seyfert 1 galaxies with a high level of optical polarization.
Optical light emerging from the innermost regions is predominantly scattered in
a polar region above the central engine directly in our line of sight. These
sources show characteristics of Seyfert 2 galaxies such as, e.g., polarized
broad lines. The polarization signatures suggest a viewing angle of 45 degrees
classifying them as intermediate Seyfert 1/2 types. The unified model predicts
this line of sight to pass through the outer layer of the torus resulting in
significant soft X-ray variability due to a strongly varying column density.
The aim is to find evidence for this geometrical assumption in the spectral
variability of all available historical observations of these sources by
XMM-Newton and Swift.


title: Miniature Dilatometer Based upon an AFM Piezocantilever

abstract:
  We report on the development of a sensitive dilatometer based upon a AFM
piezocantilever. This dilatometer has been tested at temperatures down to 25 mK
and in magnetic fields up to 16 T. The layered heavy fermion superconductor
$CeCoIn_5$ and its non-magnetic analog $LaRhIn_5$ have been measured to
demonstrate its use in detecting phase transitions and quantum oscillations. In
addition, using this dilatometer, a simultaneous multi-axis dilation
measurement has been done. This compact dilatometer has many advantages such as
its ability to measure very small samples with lengths at sub-mm levels, low
temperature and field dependence, ability to rotate, and works well
irrespective of being in a changing liquid or gas environment (i.e. within a
flow cryostat or mixing chamber).


title:
Fully gapped topological surface states in Bi$_2$Se$_3$ films induced by
  a d-wave high-temperature superconductor

abstract:
  Topological insulators are a new class of materials, that exhibit robust
gapless surface states protected by time-reversal symmetry. The interplay
between such symmetry-protected topological surface states and symmetry-broken
states (e.g. superconductivity) provides a platform for exploring novel quantum
phenomena and new functionalities, such as 1D chiral or helical gapless
Majorana fermions, and Majorana zero modes which may find application in
fault-tolerant quantum computation. Inducing superconductivity on topological
surface states is a prerequisite for their experimental realization. Here by
growing high quality topological insulator Bi$_2$Se$_3$ films on a d-wave
superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ using molecular beam epitaxy,
we are able to induce high temperature superconductivity on the surface states
of Bi$_2$Se$_3$ films with a large pairing gap up to 15 meV. Interestingly,
distinct from the d-wave pairing of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, the
proximity-induced gap on the surface states is nearly isotropic and consistent
with predominant s-wave pairing as revealed by angle-resolved photoemission
spectroscopy. Our work could provide a critical step toward the realization of
the long sought-after Majorana zero modes.


title: On involutivity of p-support

abstract:
  The p-support of a holonomic D-module was introduced by Kontsevich. Thomas
Bitoun in his PhD thesis proved several properties of p-support conjectured by
Kontsevich. In this note we give an alternative proof for involutivity by
reducing it to a slight extension of Gabber's theorem on the integrability of
the characteristic variety. For the benefit of the reader we review how this
extension follows from Kaledin's proof of Gabber's theorem.


title: Stability of D-brane embeddings in nontrivial backgrounds

abstract:
  We propose a new analytical method for determining whether nonsupersymmetric
probe branes embedded in nontrivial backgrounds are perturbatively stable or
not. The method is based on a relationship between zero mass solutions of the
relevant DBI equations of motion and tachyonic solutions. Furthermore, due to
the above relation, the question, of whether a classical solution is stable or
not, can be answered simply by studying the derivatives of that solution with
respect to its integration constants. Finally, we illustrate the efficiency of
this method by applying it to several interesting examples.


title:
A Systematic Retrieval Analysis of Secondary Eclipse Spectra III:
  Diagnosing Chemical Disequilibrium in Planetary Atmospheres

abstract:
  Chemical disequilibrium has recently become a relevant topic in the study of
the atmospheres of of transiting extrasolar planets, brown dwarfs, and directly
imaged exoplanets. We present a new way of assessing whether or not a
Jovian-like atmosphere is in chemical disequilibrium from observations of
detectable or inferred gases such as H$_2$O, CH$_4$, CO, and H$_2$. Our
hypothesis, based on previous kinetic modeling studies, is that cooler
atmospheres will show stronger signs of disequilibrium than hotter atmospheres.
We verify this with chemistry-transport models and show that planets with
temperatures less than $\sim$1200 K are likely to show the strongest signs of
disequilibrium due to the vertical quenching of CO, and that our new approach
is able to capture this process. We also find that in certain instances a
planetary composition may appear in equilibrium when it actually is not due to
the degeneracy in the shape of the vertical mixing ratio profiles. We determine
the state of disequilibrium in eight exoplanets using the results from
secondary eclipse temperature and abundance retrievals. We find that all of the
planets in our sample are consistent with thermochemical equilibrium to within
3-sigma. Future observations are needed to further constrain the abundances in
order to definitively identify disequilibrium in exoplanet atmospheres.


title:
The influence of magnetic field on the superconducting properties and
  the BCS-BEC crossover in systems with local fermion pairing

abstract:
  The aim of this Ph.D. thesis was to investigate superconducting properties in
the presence of Zeeman magnetic field in systems with local fermion pairing on
the lattice. The study also concerned the evolution from the weak coupling
(BCS-like) limit to the strong coupling limit of tightly bound local pairs
(BEC) with increasing attraction, both in the ground state and at finite
temperatures, within the spin-polarized extended Hubbard model. The analysis
was also extended to the case of spin dependent hopping integrals (mass
imbalance), with special attention paid to the BCS-BEC crossover physics in the
ground state. The methods used included: the mean field approximation
(BCS-Stoner type) and the estimation of the phase coherence temperature within
the Kosterlitz-Thouless (KT) scenario in two dimensions. The BCS-BEC crossover
was also analyzed in three dimensions, at finite temperatures, within the spin
polarized Attractive Hubbard Model (AHM), going beyond the mean field
approximation. In this case, the critical temperatures of the superconducting
transition were determined within the self-consistent T-matrix method. The
strong coupling expansion was applied to map the spin polarized AHM onto the
model of hard-core bosons on the lattice.

categories: cond-mat.str-el cond-mat.quant-gas cond-mat.supr-con hep-lat


title: Study of the $\bar K N$ system and coupled channels in a finite volume

abstract:
  We investigate the $\bar KN$ and coupled channels system in a finite volume
and study the properties of the $\Lambda(1405)$ resonance. We calculate the
energy levels in a finite volume and solve the inverse problem of determining
the resonance position in the infinite volume. We devise the best strategy of
analysis to obtain the two poles of the $\Lambda(1405)$ in the infinite volume
case, with sufficient precision to distinguish them.


title: Some Implications of Two Forms of the Generalized Uncertainty Principle

abstract:
  Various theories of quantum gravity predict the existence of a minimum length
scale, which leads to the modification of the standard uncertainty principle to
the Generalized Uncertainty Principle (GUP). In this paper, we study two forms
of the GUP and calculate their implications on the energy of the harmonic
oscillator and the Hydrogen atom more accurately than previous studies. In
addition, we show how the GUP modifies the Lorentz force law and the
time-energy uncertainty principle.


title: Dynamic Structural Equation Models for Social Network Topology Inference

abstract:
  Many real-world processes evolve in cascades over complex networks, whose
topologies are often unobservable and change over time. However, the so-termed
adoption times when blogs mention popular news items, individuals in a
community catch an infectious disease, or consumers adopt a trendy electronics
product are typically known, and are implicitly dependent on the underlying
network. To infer the network topology, a \textit{dynamic} structural equation
model is adopted to capture the relationship between observed adoption times
and the unknown edge weights. Assuming a slowly time-varying topology and
leveraging the sparse connectivity inherent to social networks, edge weights
are estimated by minimizing a sparsity-regularized exponentially-weighted
least-squares criterion. To this end, solvers with complementary strengths are
developed by leveraging (pseudo) real-time sparsity-promoting proximal gradient
iterations, the improved convergence rate of accelerated variants, or reduced
computational complexity of stochastic gradient descent. Numerical tests with
both synthetic and real data demonstrate the effectiveness of the novel
algorithms in unveiling sparse dynamically-evolving topologies, while
accounting for external influences in the adoption times. Key events in the
recent succession of political leadership in North Korea, explain connectivity
changes observed in the associated network inferred from global cascades of
online media.


title: Three-body hadron systems with strangeness

abstract:
  Recently, many efforts are being put in studying three-hadron systems made of
mesons and baryons and interesting results are being found. In this talk, I
summarize the main features of the formalism used to study such three hadron
systems with strangeness $S=-1,0$ within a framework built on the basis of
unitary chiral theories and solution of the Faddeev equations. In particular, I
present the results obtained for the $\pi\bar{K}N$, $K\bar{K}N$ and $KK\bar{K}$
systems and their respective coupled channels. In the first case, we find four
$\Sigma$'s and two $\Lambda$'s with spin-parity $J^P=1/2^+$, in the 1500-1800
MeV region, as two meson-one baryon s-wave resonances. In the second case, a
$1/2^+$ $N^*$ around 1900 MeV is found. For the last one a kaon close to 1420
MeV is formed, which can be identified with K(1460).


title: Fundamental Groups of Spaces with Bakry-Emery Ricci Tensor Bounded Below

abstract:
  We first extend Cheeger-Colding Almost Splitting Theorem to smooth metric
measure spaces. Arguments utilizing this extension of the Almost Splitting
Theorem show that if a smooth metric measure space has almost nonnegative
Bakry-Emery Ricci curvature and a lower bound on volume, then its fundamental
group is almost abelian. Second, if the smooth metric measure space has
Bakry-Emery Ricci curvature bounded from below then the number of generators of
the fundamental group is uniformly bounded. These results are extensions of
theorems which hold for Riemannian manifolds with Ricci curvature bounded from
below.


title: Packing Posets in the Boolean Lattice

abstract:
  We are interested in maximizing the number of pairwise unrelated copies of a
poset $P$ in the family of all subsets of $[n]$. We prove that for any $P$ the
maximum number of unrelated copies of $P$ is asymptotic to a constant times the
largest binomial coefficient. Moreover, the constant has the form
$\frac{1}{c(P)}$, where $c(P)$ is the size of the smallest convex closure over
all embeddings of $P$ into the Boolean lattice.


title: Removal of Data Incest in Multi-agent Social Learning in Social Networks

abstract:
  Motivated by online reputation systems, we investigate social learning in a
network where agents interact on a time dependent graph to estimate an
underlying state of nature. Agents record their own private observations, then
update their private beliefs about the state of nature using Bayes' rule. Based
on their belief, each agent then chooses an action (rating) from a finite set
and transmits this action over the social network. An important consequence of
such social learning over a network is the ruinous multiple re-use of
information known as data incest (or mis-information propagation). In this
paper, the data incest management problem in social learning context is
formulated on a directed acyclic graph. We give necessary and sufficient
conditions on the graph topology of social interactions to eliminate data
incest. A data incest removal algorithm is proposed such that the public belief
of social learning (and hence the actions of agents) is not affected by data
incest propagation. This results in an online reputation system with a higher
trust rating. Numerical examples are provided to illustrate the performance of
the proposed optimal data incest removal algorithm.


title: Non-Perturbative Nekrasov Partition Function from String Theory

abstract:
  We calculate gauge instanton corrections to a class of higher derivative
string effective couplings introduced in [1]. We work in Type I string theory
compactified on K3xT2 and realise gauge instantons in terms of D5-branes
wrapping the internal space. In the field theory limit we reproduce the
deformed ADHM action on a general {\Omega}-background from which one can
compute the non-perturbative gauge theory partition function using
localisation. This is a non-perturbative extension of [1] and provides further
evidence for our proposal of a string theory realisation of the
{\Omega}-background.


title: On the Connectivity Preserving Minimum Cut Problem

abstract:
  In this paper, we study a generalization of the classical minimum cut prob-
lem, called Connectivity Preserving Minimum Cut (CPMC) problem, which seeks a
minimum cut to separate a pair (or pairs) of source and destination nodes and
meanwhile ensure the connectivity between the source and its partner node(s).
The CPMC problem is a rather powerful formulation for a set of problems and
finds applications in many other areas, such as network security, image
processing, data mining, pattern recognition, and machine learning. For this
important problem, we consider two variants, connectiv- ity preserving minimum
node cut (CPMNC) and connectivity preserving minimum edge cut (CPMEC). For
CPMNC, we show that it cannot be ap- proximated within {\alpha}logn for some
constant {\alpha} unless P=NP, and cannot be approximated within any poly(logn)
unless NP has quasi-polynomial time algorithms. The hardness results hold even
for graphs with unit weight and bipartite graphs. Particularly, we show that
polynomial time solutions exist for CPMEC in planar graphs and for CPMNC in
some special planar graphs. The hardness of CPMEC in general graphs remains
open, but the polynomial time algorithm in planar graphs still has important
practical applications.


title:
Training-Based Synchronization and Channel Estimation in AF Two-Way
  Relaying Networks

abstract:
  Two-way relaying networks (TWRNs) allow for more bandwidth efficient use of
the available spectrum since they allow for simultaneous information exchange
between two users with the assistance of an intermediate relay node. However,
due to superposition of signals at the relay node, the received signal at the
user terminals is affected by \emph{multiple impairments}, i.e., channel gains,
timing offsets, and carrier frequency offsets, that need to be jointly
estimated and compensated. This paper presents a training-based system model
for amplify-and-forward (AF) TWRNs in the presence of multiple impairments and
proposes maximum likelihood and differential evolution based algorithms for
joint estimation of these impairments. The Cramer-Rao lower bounds (CRLBs) for
the joint estimation of multiple impairments are derived. A minimum mean-square
error based receiver is then proposed to compensate the effect of multiple
impairments and decode each user's signal. Simulation results show that the
performance of the proposed estimators is very close to the derived CRLBs at
moderate-to-high signal-to-noise-ratios. It is also shown that the bit-error
rate performance of the overall AF TWRN is close to a TWRN that is based on
assumption of perfect knowledge of the synchronization parameters.


title: Characterness: An Indicator of Text in the Wild

abstract:
  Text in an image provides vital information for interpreting its contents,
and text in a scene can aide with a variety of tasks from navigation, to
obstacle avoidance, and odometry. Despite its value, however, identifying
general text in images remains a challenging research problem. Motivated by the
need to consider the widely varying forms of natural text, we propose a
bottom-up approach to the problem which reflects the `characterness' of an
image region. In this sense our approach mirrors the move from saliency
detection methods to measures of `objectness'. In order to measure the
characterness we develop three novel cues that are tailored for character
detection, and a Bayesian method for their integration. Because text is made up
of sets of characters, we then design a Markov random field (MRF) model so as
to exploit the inherent dependencies between characters.
  We experimentally demonstrate the effectiveness of our characterness cues as
well as the advantage of Bayesian multi-cue integration. The proposed text
detector outperforms state-of-the-art methods on a few benchmark scene text
detection datasets. We also show that our measurement of `characterness' is
superior than state-of-the-art saliency detection models when applied to the
same task.


title: Signal transduction and directional sensing in eukaryotes

abstract:
  Control of the cytoskeleton and mechanical contacts with the extracellular
environment are essential component of motility in eukaryotic cells. In the
absence of signals, cells continuously rebuild the cytoskeleton and
periodically extend pseudopods or other protrusions at random membrane
locations. Extracellular signals bias the direction of movement by biasing the
extension of protrusions, but this involves another layer of biochemical
networks for signal detection, transduction, and control of the rebuilding of
the cytoskeleton. Here we develop a model for the latter processes that centers
on a Ras-based module that adapts to constant extracellular signals and
controls the downstream PI3K-PIP3-based module responsible for amplifying a
spatial gradient of the signal. The resulting spatial gradient can lead to
polarization, which enables cells to move in the preferred direction (up
gradient for attractants and down-gradient for repellents). We show that the
model can replicate many of the observed characteristics of the responses to
cAMP stimulation for Dictyostelium, and analyze how cell geometry and signaling
interact to produce the observed localization of some of the key components of
the amplification module. We show how polarization can emerge without
directional cues, and how it interacts with directional signals and leads to
directional persistence. Since other cells such as neutrophils use similar
pathways, the model is a generic one for a large class of eukaryotic cells.


title:
Improving Transient Performance of Adaptive Control Architectures using
  Frequency-Limited System Error Dynamics

abstract:
  We develop an adaptive control architecture to achieve stabilization and
command following of uncertain dynamical systems with improved transient
performance. Our framework consists of a new reference system and an adaptive
controller. The proposed reference system captures a desired closed-loop
dynamical system behavior modified by a mismatch term representing the
high-frequency content between the uncertain dynamical system and this
reference system, i.e., the system error. In particular, this mismatch term
allows to limit the frequency content of the system error dynamics, which is
used to drive the adaptive controller. It is shown that this key feature of our
framework yields fast adaptation with- out incurring high-frequency
oscillations in the transient performance. We further show the effects of
design parameters on the system performance, analyze closeness of the uncertain
dynamical system to the unmodified (ideal) reference system, discuss robustness
of the proposed approach with respect to time-varying uncertainties and
disturbances, and make connections to gradient minimization and classical
control theory.


title: The theory of ordinal length

abstract:
  We generalize the notion of length to an ordinal-valued invariant defined on
the class of finitely generated modules over a Noetherian ring. A key property
of this invariant is its semi-additivity on short exact sequences. We show how
to calculate this combinatorial invariant by means of the fundamental cycle of
the module, thus linking the lattice of submodules to homological properties of
the module. Using this, we equip each module with its canonical topology.


title: Compactness and finite forcibility of graphons

abstract:
  Graphons are analytic objects associated with convergent sequences of graphs.
Problems from extremal combinatorics and theoretical computer science led to a
study of graphons determined by finitely many subgraph densities, which are
referred to as finitely forcible. Following the intuition that such graphons
should have finitary structure, Lovasz and Szegedy conjectured that the
topological space of typical vertices of a finitely forcible graphon is always
compact. We disprove the conjecture by constructing a finitely forcible graphon
such that the associated space is not compact. The construction method gives a
general framework for constructing finitely forcible graphons with non-trivial
properties.


title: The field of definition for dynamical systems on P^N

abstract:
  Let Hom^N_d be the set of morphisms of degree d from P^N to itself. For f an
element of PGL_{N+1}, let phi^f represent the conjugation action f^{-1} phi f.
Let M^N_d = Hom_d^N/PGL_{N+1} be the moduli space of degree d morphisms of P^N.
A field of definition for class of morphisms is a field over which at least one
morphism in the class is defined. The field of moduli for a class of morphisms
is the fixed field of the set of Galois elements fixing that class. Every field
of definition contains the field of moduli. In this article, we give a
sufficient condition for the field of moduli to be a field of definition for
morphisms whose stabilizer group is trivial.


title:
Variable selection in functional data classification: a maxima-hunting
  proposal

abstract:
  Variable selection is considered in the setting of supervised binary
classification with functional data $\{X(t),\ t\in[0,1]\}$. By "variable
selection" we mean any dimension-reduction method which leads to replace the
whole trajectory
  $\{X(t),\ t\in[0,1]\}$, with a low-dimensional vector
$(X(t_1),\ldots,X(t_k))$ still keeping a similar classification error. Our
proposal for variable selection is based on the idea of selecting the local
maxima $(t_1,\ldots,t_k)$ of the function ${\mathcal V}_X^2(t)={\mathcal
V}^2(X(t),Y)$, where ${\mathcal V}$ denotes the "distance covariance"
association measure for random variables due to Sz\'ekely, Rizzo and Bakirov
(2007). This method provides a simple natural way to deal with the relevance
vs. redundancy trade-off which typically appears in variable selection. This
paper includes
  (a) Some theoretical motivation: a result of consistent estimation on the
maxima of ${\mathcal V}_X^2$ is shown. We also show different theoretical
models for the underlying process $X(t)$ under which the relevant information
in concentrated in the maxima of ${\mathcal V}_X^2$.
  (b) An extensive empirical study, including about 400 simulated models and
real data examples, aimed at comparing our variable selection method with other
standard proposals for dimension reduction.


title:
Lateral distribution of radio signal measured in showers with energy
  5*10^16-10^18 eV at the Yakutsk EAS array

abstract:
  We present of measurements of radio emission from EAS at the frequency 32 MHz
performed in 2008-2012. Showers were selected by zenith and azimuth directions,
sampled by energy. A mean lateral distribution function was fitted to the data
each interval. The paper presents unied approximation formula for all three
energy intervals of lateral distribution, using connection between equation (1)
and (2) coefficients with energy and geomagnetic angle. Here we analyze the
connection between the shape of lateral distribution and the depth of the
maximum shower development Xmax too.


title: Finite Sample Properties of Adaptive Markov Chains via Curvature

abstract:
  Adaptive Markov chains are an important class of Monte Carlo methods for
sampling from probability distributions. The time evolution of adaptive
algorithms depends on past samples, and thus these algorithms are
non-Markovian. Although there has been previous work establishing conditions
for their ergodicity, not much is known theoretically about their finite sample
properties. In this paper, using a notion of discrete Ricci curvature for
Markov kernels introduced by Ollivier, we establish concentration inequalities
and finite sample bounds for a class of adaptive Markov chains. After
establishing some general results, we give quantitative bounds for
`multi-level' adaptive algorithms such as the equi-energy sampler. We also
provide the first rigorous proofs that the finite sample properties of an
equi-energy sampler are superior to those of related parallel tempering and
Metropolis-Hastings samplers after a learning period comparable to their mixing
times.


title:
Spectral conditions for the existence of specified paths and cycles in
  graphs

abstract:
  Let $G$ be a graph with $n$ vertices and $\lambda_n(G)$ be the least
eigenvalue of its adjacency matrix of $G$. In this paper, we give sharp bounds
on the least eigenvalue of graphs without given pathes or cycles and determine
the extremal graphs. This result gives spectral conditions for the existence of
specified paths and cycles in graphs.


title: Generalization of Rashmi-Shah-Kumar Minimum-Storage-Regenerating Codes

abstract:
  In this paper, we propose a generalized version of the Rashmi-Shah-Kumar
Minimum-Storage-Regenerating(RSK-MSR) codes based on the product-matrix
framework. For any $(n,k,d)$ such that $d \geq 2k-2$ and $d \leq n-1$, we can
directly construct an $(n,k,d)$ MSR code without constructing a larger MSR code
and shortening of the larger MSR code. As a result, the size of a finite field
over which the proposed code is defined is smaller than or equal to the size of
a finite field over which the RSK-MSR code is defined. In addition, the
$\{\ell,\ell'\}$ secure codes based on the generalized RSK-MSR codes can be
obtained by applying the construction method of $\{\ell,\ell'\}$ secure codes
proposed by Shah, Rashmi and Kumar. Furthermore, the message matrix of the
$(n,k,d)$ generalized RSK-MSR code is derived from that of the RSK-MSR code by
using the construction method of the $\{\ell=k,\ell'=0\}$ secure code.


title: Statistical paleoclimate reconstructions via Markov random fields

abstract:
  Understanding centennial scale climate variability requires data sets that
are accurate, long, continuous and of broad spatial coverage. Since
instrumental measurements are generally only available after 1850, temperature
fields must be reconstructed using paleoclimate archives, known as proxies.
Various climate field reconstructions (CFR) methods have been proposed to
relate past temperature to such proxy networks. In this work, we propose a new
CFR method, called GraphEM, based on Gaussian Markov random fields embedded
within an EM algorithm. Gaussian Markov random fields provide a natural and
flexible framework for modeling high-dimensional spatial fields. At the same
time, they provide the parameter reduction necessary for obtaining precise and
well-conditioned estimates of the covariance structure, even in the
sample-starved setting common in paleoclimate applications. In this paper, we
propose and compare the performance of different methods to estimate the
graphical structure of climate fields, and demonstrate how the GraphEM
algorithm can be used to reconstruct past climate variations. The performance
of GraphEM is compared to the widely used CFR method RegEM with regularization
via truncated total least squares, using synthetic data. Our results show that
GraphEM can yield significant improvements, with uniform gains over space, and
far better risk properties. We demonstrate that the spatial structure of
temperature fields can be well estimated by graphs where each neighbor is only
connected to a few geographically close neighbors, and that the increase in
performance is directly related to recovering the underlying sparsity in the
covariance of the spatial field. Our work demonstrates how significant
improvements can be made in climate reconstruction methods by better modeling
the covariance structure of the climate field.


title:
Efficient spectral hole-burning and atomic frequency comb storage in
  Nd3+:YLiF4

abstract:
  We present spectral hole-burning measurements of the
$^{4}I_{9/2}\rightarrow{}^4F_{3/2}$ transition in Nd$^{3+}$:YLiF$_4$. The
isotope shifts of Nd$^{3+}$ can be directly resolved in the optical absorption
spectrum. We report atomic frequency comb storage with an echo efficiency of up
to 35% and a memory bandwidth of 60 MHz in this material. The interesting
properties show the potential of this material for use in both quantum and
classical information processing.


title: Intensity Frontier Instrumentation

abstract:
  This report summarizes findings of the 2013 Snowmass Community Summer Study
Instrumentation Frontier's subgroup on the Intensity Frontier. This report is
directed at identifying instrumentation R&D needed to support particle physics
research over the coming decades at the Intensity Frontier.


title:
Leading slow roll corrections to the volume of the universe and the
  entropy bound

abstract:
  We make an extension to recent calculations of the probability density
\rho(V) for the volume of the universe after inflation. Previous results have
been accurate to leading order in the slow roll parameters \epsilon=\dot{H}/H^2
and \eta=\ddot{\phi}/(\dot{\phi} H), and 1/N_c, where H is the Hubble parameter
and N_c is the classical number of e-foldings. Here, we present a modification
which captures effects of order \epsilon N_c, which amounts to letting the
parameters of inflation H and \dot{\phi} depend on the value of the inflaton
\phi. The phase of slow roll eternal inflation can be defined as when the
probability to have an infinite volume is greater than zero. Using this
definition, we study the Laplace transform of \rho(V) numerically to determine
the condition that triggers the transition to eternal inflation. We also study
the average volume <V> analytically and show that it satisfies the universal
volume bound. This bound states that, in any realization of inflation which
ends with a finite volume, an initial volume must grow by less than a factor of
exp(S_{dS}/2), where S_{dS} is the de Sitter (dS) entropy.


title:
Single-shot readout of a superconducting flux qubit with a flux-driven
  Josephson parametric amplifier

abstract:
  We report single-shot readout of a superconducting flux qubit by using a
flux-driven Josephson parametric amplifier (JPA). After optimizing the readout
power, gain of the JPA and timing of the data acquisition, we observe the Rabi
oscillations with a contrast of 74% which is mainly limited by the bandwidth of
the JPA and the energy relaxation of the qubit. The observation of quantum
jumps between the qubit eigenstates under continuous monitoring indicates the
nondestructiveness of the readout scheme.


title: Distributed Online Learning in Social Recommender Systems

abstract:
  In this paper, we consider decentralized sequential decision making in
distributed online recommender systems, where items are recommended to users
based on their search query as well as their specific background including
history of bought items, gender and age, all of which comprise the context
information of the user. In contrast to centralized recommender systems, in
which there is a single centralized seller who has access to the complete
inventory of items as well as the complete record of sales and user
information, in decentralized recommender systems each seller/learner only has
access to the inventory of items and user information for its own products and
not the products and user information of other sellers, but can get commission
if it sells an item of another seller. Therefore the sellers must distributedly
find out for an incoming user which items to recommend (from the set of own
items or items of another seller), in order to maximize the revenue from own
sales and commissions. We formulate this problem as a cooperative contextual
bandit problem, analytically bound the performance of the sellers compared to
the best recommendation strategy given the complete realization of user
arrivals and the inventory of items, as well as the context-dependent purchase
probabilities of each item, and verify our results via numerical examples on a
distributed data set adapted based on Amazon data. We evaluate the dependence
of the performance of a seller on the inventory of items the seller has, the
number of connections it has with the other sellers, and the commissions which
the seller gets by selling items of other sellers to its users.


title:
Gain/loss induced localization in one-dimensional PT-symmetric
  tight-binding models

abstract:
  We investigate the properties of PT-symmetric tight-binding models by
considering both bounded and unbounded models. For the bounded case, we obtain
closed form expressions for the corresponding energy spectra and we analyze the
structure of eigenstates as well as their dependence on the gain/loss contrast
parameter. For unbounded PT-lattices, we explore their scattering properties
through the development of analytical models. Based on our approach we identify
a mechanism that is responsible to the emergence of localized states that are
entirely due to the presence of gain and loss. The derived expressions for the
transmission and reflection coefficients allow one to better understand the
role of PT-symmetry in energy transport problems occurring in such PT-symmetric
tight-binding settings. Our analytical results are further exemplified via
pertinent examples.


title:
A new transfer-matrix algorithm for exact enumerations: self-avoiding
  walks on the square lattice

abstract:
  We recently published [J. Phys A: Math. Theor. {\bf 45} 115202 (2012)] a new
and more efficient implementation of a transfer-matrix algorithm for exact
enumerations of self-avoiding polygons. Here we extend this work to the
enumeration of self-avoiding walks on the square lattice. A detailed comparison
with our previous best algorithm shows very significant improvement in the
running time of the new algorithm. The new algorithm is used to extend the
enumeration of self-avoiding walks to length 79 from the previous record of 71
and for metric properties, such as the average end-to-end distance, from 59 to
71.


title: On the number of spanning trees in random regular graphs

abstract:
  Let $d \geq 3$ be a fixed integer. We give an asympotic formula for the
expected number of spanning trees in a uniformly random $d$-regular graph with
$n$ vertices. (The asymptotics are as $n\to\infty$, restricted to even $n$ if
$d$ is odd.) We also obtain the asymptotic distribution of the number of
spanning trees in a uniformly random cubic graph, and conjecture that the
corresponding result holds for arbitrary (fixed) $d$. Numerical evidence is
presented which supports our conjecture.


title:
A Spin-Light Polarimeter for Multi-GeV Longitudinally Polarized Electron
  Beams

abstract:
  The physics program at the upgraded Jefferson Lab (JLab) and the physics
program envisioned for the proposed electron-ion collider (EIC) include large
efforts to search for interactions beyond the Standard Model (SM) using parity
violation in electroweak interactions. These experiments require precision
electron polarimetry with an uncertainty of $<$ 0.5 %. The spin dependent
Synchrotron radiation, called "spin-light," can be used to monitor the electron
beam polarization. In this article we develop a conceptual design for a
"spin-light" polarimeter that can be used at a high intensity, multi-GeV
electron accelerator. We have also built a Geant4 based simulation for a
prototype device and report some of the results from these simulations.


title: The order of principal congruences of a bounded lattice

abstract:
  We characterize the order of principal congruences of a bounded lattice as a
bounded ordered set. We also state a number of open problems in this new field.


title: Decoupling MSSM Higgs Sector and Heavy Higgs Decay

abstract:
  The decoupling limit in the MSSM Higgs sector is the most likely scenario in
light of the Higgs discovery. This scenario is further constrained by MSSM
Higgs search bounds and flavor observables. We perform a comprehensive scan of
MSSM parameters and update the constraints on the decoupling MSSM Higgs sector
in terms of 8 TeV LHC data. We highlight the effect of light SUSY spectrum in
the heavy neutral Higgs decay in the decoupling limit. We find that the
chargino and neutralino decay mode can reach at most 40% and 20% branching
ratio, respectively. In particular, the invisible decay mode BR(H^0(A^0) ->
\tilde{\chi}^0_1\tilde{\chi}^0_1) increases with increasing Bino LSP mass and
is between 10%-15% (20%) for 30<m_{\tilde{\chi}^0_1}<100 GeV. The leading
branching fraction of heavy Higgses decay into sfermions can be as large as 80%
for H^0 -> \tilde{t}_1\tilde{t}_1^\ast and 60% for H^0/A^0 ->
\tilde{\tau}_1\tilde{\tau}_2^\ast+\tilde{\tau}_1^\ast\tilde{\tau}_2. The
branching fractions are less than 10% for H^0 -> h^0h^0 and 1% for A^0 -> h^0Z
for m_A>400 GeV. The charged Higgs decays to neutralino plus chargino and
sfermions with branching ratio as large as 40% and 60%, respectively. Moreover,
the exclusion limit of leading MSSM Higgs search channel, namely gg,b\bar{b} ->
H^0, A^0 -> tau^+ tau^-, is extrapolated to 14 TeV LHC with high luminosities.
It turns out that the tau tau mode can essentially exclude regime with
tan\beta>20 for L=300 fb^{-1} and tan\beta>15 for L=3000 fb^{-1}.


title: Berry phase and the unconventional quantum Hall effect in graphene

abstract:
  The Berry phase of \pi\ in graphene is derived in a pedagogical way. The
ambiguity of how to calculate this value properly is clarified. Its connection
with the unconventional quantum Hall effect in graphene is discussed.


title:
Games on graphs: A minor modification of payoff scheme makes a big
  difference

abstract:
  Various social dilemma games that follow different strategy updating rules
have been studied on many networks.The reported results span the entire
spectrum, from significantly boosting,to marginally affecting,to seriously
decreasing the level of cooperation.Experimental results that are qualitatively
different from theoretical prediction have also been reported.It is widely
believed that the results are largely determined by three elements,including
payoff matrices of the underlying 2*2 games,the way that the strategic states
of the players are updated and the structure of the networks.Here we discuss
the impact of a seemly non-essential mechanism -- what we refer to as a "payoff
scheme". Specifically, in each round after the states of all of the players are
determined,the payoff scheme is how each player's payoff is calculated.In
addition to the two conventions in which either the accumulated or the averaged
payoff is calculated from playing with all of the neighboring players,we here
study the effects of calculating the payoff from pairing up with one random
player from among the neighboring players. Based on probability theory, in a
situation of uncorrelated events, the average payoff that involves all of the
neighbors should,in principal,be equivalent to the payoff from pairing up with
one neighbor.However,our simulation of games on graphs shows that, in many
cases,the two payoff schemes lead to qualitatively different levels of
cooperation.This finding appears to provide a possible explanation for a wide
spectrum of observed behaviors in the literature.We have also observed that
results from the randomly-pairing-one mechanism are more robust than the
involving-all-neighbours mechanism because,in the former case, neither the
other three main elements nor the initial states of the players have a large
impact on the final level of cooperation compared with in the latter case.


title: Multidimensional quadratic and subquadratic BSDEs with special structure

abstract:
  We study multidimensional BSDEs of the form $$ Y_t = \xi + \int_t^T
f(s,Y_s,Z_s)ds - \int_t^T Z_s dW_s $$ with bounded terminal conditions $\xi$
and drivers $f$ that grow at most quadratically in $Z_s$. We consider three
different cases. In the first one the BSDE is Markovian, and a solution can be
obtained from a solution to a related FBSDE. In the second case, the BSDE
becomes a one-dimensional quadratic BSDE when projected to a one-dimensional
subspace, and a solution can be derived from a solution of the one-dimensional
equation. In the third case, the growth of the driver $f$ in $Z_s$ is strictly
subquadratic, and the existence and uniqueness of a solution can be shown by
first solving the BSDE on a short time interval and then extending the solution
recursively.


title:
Geometric Stabilization of Quadrotor UAV with a Payload Connected by
  Flexible Cable

abstract:
  Equations of motion and dynamics of a quadrotor transporting a load with a
flexible cable modeled as a chain pendulum is obtained using Euler-Lagrange
equations by taking variations on manifolds. An arbitrary number of links
considered in a series models the flexible cable connecting the load to the
quadrotor while the whole system can undergo complex motion in 3D. Geometric
nonlinear control asymptotically stabilizes the load and cable bellow the
quadrotor. A linearization about the equilibrium and the corresponding lyapunov
stability analysis is provided. We produced numerical simulations and validated
our work experimentally using a quadrotor UAV.


title:
Understanding Y(4274) and X(4320) in the $J/\psi \phi$ invariant mass
  spectrum

abstract:
  In this work we study the structures near 4.3 GeV in the $J/\psi \phi$
invariant mass spectra in B meson decay process $B^+\to J/\psi \phi K^+$ and
two photon fusion process $\gamma\gamma\to J/\psi \phi$. The Y(4274) as a
$D_sD_{s0}$ $(2317)$ molecular is studied in the Bethe-Salpeter equation
approach with quasipotential approximation. The absence of Y(4274) in
$\gamma\gamma\to J/\psi \phi$ channel can be well explained by the decay widths
of Y(4274) decaying to $\gamma\gamma$ and $J/\psi\phi$. The distribution of
mass difference released by CMS collaboration is reproduced by two resonances
near 4.3 GeV, Y(4274) and X(4320). The different production mechanism suggests
X(4320) observed in the B decay should be the missing $3^3P_1$ charmonium state
$\chi''_{c1}$ and different from X(4350) observed in two photon fusion which
can be assigned as $\chi''_{c2}$.


title: Differential OTF Wavefront Sensing

abstract:
  An image-based technique for measuring the complex field in the pupil of an
imaging system is presented. Two point source images, one with a small
modification introduced in the pupil, are combined using a simple and
non-iterative algorithm. The non-interferometric method is based on the change
in the optical transfer function (OTF), giving a differential OTF (dOTF). The
dOTF includes two images of the complex pupil field, conjugated and reflected
about the position of the pupil modification, leaving an overlap that obscures
some the the pupil. The overlap can be minimized by introducing the
modification near the edge of the pupil. The overlap region can be eliminated
altogether by using a second modification and a third point source image. The
pupil field is convolved by the change in the pupil field, so smaller
modification areas are preferred. The non-monochromatic light, but the result
incurs a proportional radial blurring determined by the fractional bandwidth.
We include some simple demonstration experiments, including using a pupil
blockage and moving a single deformable mirror actuator as the pupil
modification. In each case the complex wavefront is easily recovered, even when
the pupil mask is unknown and the wavefront aberrations are large.


title: A simple proof for the number of tilings of quartered Aztec diamonds

abstract:
  We get four quartered Aztec diamonds by dividing an Aztec diamond region by
two zigzag cuts passing its center. W. Jockusch and J. Propp (in an unpublished
work) found that the number of tilings of quartered Aztec diamonds is given by
simple product formulas. In this paper we present a simple proof for this
result.


title: Comparison theorems and some of their applications

abstract:
  Analogues of Kolmogorov comparison theorems and some of their applications
were established.


title:
Domain-Specific Sentiment Word Extraction by Seed Expansion and Pattern
  Generation

abstract:
  This paper focuses on the automatic extraction of domain-specific sentiment
word (DSSW), which is a fundamental subtask of sentiment analysis. Most
previous work utilizes manual patterns for this task. However, the performance
of those methods highly relies on the labelled patterns or selected seeds. In
order to overcome the above problem, this paper presents an automatic framework
to detect large-scale domain-specific patterns for DSSW extraction. To this
end, sentiment seeds are extracted from massive dataset of user comments.
Subsequently, these sentiment seeds are expanded by synonyms using a
bootstrapping mechanism. Simultaneously, a synonymy graph is built and the
graph propagation algorithm is applied on the built synonymy graph. Afterwards,
syntactic and sequential relations between target words and high-ranked
sentiment words are extracted automatically to construct large-scale patterns,
which are further used to extracte DSSWs. The experimental results in three
domains reveal the effectiveness of our method.


title: A Comparative Study of Replication Techniques in Grid Computing Systems

abstract:
  Grid Computing is a type of parallel and distributed systems that is designed
to provide reliable access to data and computational resources in wide area
networks. These resources are distributed in different geographical locations,
however are organized to provide an integrated service. Effective data
management in today`s enterprise environment is an important issue. Also,
Performance is one of the challenges of using these environments. For improving
the performance of file access and easing the sharing amongst distributed
systems, replication techniques are used. Data replication is a common method
used in distributed environments, where essential data is stored in multiple
locations, so that a user can access the data from a site in his area. In this
paper, we present a survey on basic and new replication techniques that have
been proposed by other researchers. After that, we have a full comparative
study on these replication strategies. Also, at the end of the paper, we
summarize the results and points of these replication techniques.


title:
Coexistence and efficiency of normal and anomalous transport by
  molecular motors in living cells

abstract:
  Recent experiments reveal both passive subdiffusion of various nanoparticles
and anomalous active transport of such particles by molecular motors in the
molecularly crowded environment of living biological cells. Passive and active
microrheology reveals that the origin of this anomalous dynamics is due to the
viscoelasticity of the intracellular fluid. How do molecular motors perform in
such a highly viscous, dissipative environment? Can we explain the observed
co-existence of the anomalous transport of relatively large particles of 100 to
500 nm in size by kinesin motors with the normal transport of smaller particles
by the same molecular motors? What is the efficiency of molecular motors in the
anomalous transport regime? Here we answer these seemingly conflicting
questions and consistently explain experimental findings in a generalization of
the well-known continuous diffusion model for molecular motors with two
conformational states in which viscoelastic effects are included.


title:
Optimal Execution Trajectories. Linear Market Impact with Exponential
  Decay

abstract:
  Optimal execution of portfolio transactions is the essential part of
algorithmic trading. In this paper we present in simple analytical form the
optimal trajectory for risk-averse trader with the assumption of exponential
market recovery and short-time investment horizon.


title:
Lattice Boltzmann simulation of the surface growth effects for the
  infiltration of molten Si in carbon preforms

abstract:
  The infiltration of molten silicon into carbon preforms is a widespread
technique employed in the industry in order to enhance the thermal and
mechanical properties of the final ceramic products. A proper understanding of
this phenomenon is quite challenging since it stems from the reciprocal action
and reaction between fluid flow, the transition to wetting, mass transport,
precipitation, surface growth as well as heat transfer. As a result, the
exhaustive modeling of such problem is an involved task. Lattice Boltzmann
simulations in 2D for capillary infiltration are carried out in the isothermal
regime taking into account surface reaction and subsequent surface growth.
Precisely, for a single capillary in the linear Washburn regime, special
attention is paid to the retardation for the infiltration process induced by
the thickening of the surface behind the contact line of the invading front.
Interestingly, it turns out that the process of surface growth leading to pore
closure marginally depends on the infiltration velocity. We conclude that
porous matrices with straight and wide pathways represent the optimal case for
impregnation. Our analysis includes also a comparison between the radii
characterizing the infiltration process (i.e., minimum, hydraulic, average and
effective radii).


title:
Genie Tree and Degrees of Freedom of the Symmetric MIMO Interfering
  Broadcast Channel

abstract:
  In this paper, we study the information theoretic maximal degrees of freedom
(DoF) for the symmetric multi-input-multi-output (MIMO) interfering broadcast
channel (IBC) with arbitrary antenna configurations. For the G-cell K-user MXN
MIMO-IBC network, we find that the information theoretic maximal DoF per user
are related to three DoF bounds: 1) the decomposition DoF bound
d^{Decom}=MN/(M+KN), a lower-bound of linear interference alignment (IA) with
infinite time/frequency extensions (called asymptotic IA); 2) the proper DoF
bound d^{Proper}=(M+N)/(GK+1), an upper-bound of linear IA without
time/frequency extensions (called linear IA); and 3) the quantity DoF bound
d^{Quan}, a zigzag piecewise linear function of M and N. The whole region of
M/N can be divided into two regions, Region I and Region II. Specifically, for
most configurations in Region I, the information theoretic maximal DoF are the
decomposition DoF bound and can be achieved by the asymptotic IA. For all
configurations in Region II, the information theoretic maximal DoF are the
quantity DoF bound and can be achieved by the linear IA. To obtain the tight
upper-bound, we propose a unified way to construct genies, where the genies
help each base station or user resolve the maximal number of interference.
According to the feature that the designed genies with the same dimension can
derive identical DoF upper-bound, we convert the information theoretic DoF
upper-bound problem into a linear algebra problem and obtain the closed-form
DoF upper-bound expression. Moreover, we develop a non-iterative linear IA
transceiver to achieve the DoF upper-bound for the networks with antenna
configurations in Region II, which means that the derived DoF upper-bound is
tightest. The basic principles to derive the DoF upper-bound and design the
linear IA transceiver to achieve the DoF upper-bound can be extended into
general asymmetric networks.


title:
Uniform boundedness of derivatives of meromorphic inner functions on the
  real line

abstract:
  Inner functions are an important and popular object of study in the field of
complex function theory. We look at meromorphic inner functions with a given
spectrum and provide sufficient conditions for them to have uniformly bounded
derivatives on the real line. This question was first studied by Louis de
Brange in 1968 and was later revived by Anton Baranov in 2011.


title:
Transport properties of double quantum dots with electron-phonon
  coupling

abstract:
  We study transport through a double quantum dot system in which each quantum
dot is coupled to a phonon mode. Such a system can be realized, e.g., using a
suspended carbon nanotube. We find that the interplay between strong
electron-phonon coupling and inter-dot tunneling can lead to a negative
differential conductance at bias voltages exceeding the phonon frequency.
Various transport properties are discussed, and we explain the physics of the
occurrence of negative differential conductance in this system.


title:
$\mu$-Limit Sets of Cellular Automata from a Computational Complexity
  Perspective

abstract:
  This paper concerns $\mu$-limit sets of cellular automata: sets of
configurations made of words whose probability to appear does not vanish with
time, starting from an initial $\mu$-random configuration. More precisely, we
investigate the computational complexity of these sets and of related decision
problems. Main results: first, $\mu$-limit sets can have a $\Sigma\_3^0$-hard
language, second, they can contain only $\alpha$-complex configurations, third,
any non-trivial property concerning them is at least $\Pi\_3^0$-hard. We prove
complexity upper bounds, study restrictions of these questions to particular
classes of CA, and different types of (non-)convergence of the measure of a
word during the evolution.


title: Search Problems in Vector Spaces

abstract:
  We consider the following $q$-analog of the basic combinatorial search
problem: let $q$ be a prime power and $\GF(q)$ the finite field of $q$
elements. Let $V$ denote an $n$-dimensional vector space over $\GF(q)$ and let
$\mathbf{v}$ be an unknown 1-dimensional subspace of $V$. We will be interested
in determining the minimum number of queries that is needed to find
$\mathbf{v}$ provided all queries are subspaces of $V$ and the answer to a
query $U$ is YES if $\mathbf{v} \leqslant U$ and NO if $\mathbf{v}
\not\leqslant U$. This number will be denoted by $A(n,q)$ in the adaptive case
(when for each queries answers are obtained immediately and later queries might
depend on previous answers) and $M(n,q)$ in the non-adaptive case (when all
queries must be made in advance).
  In the case $n=3$ we prove $2q-1=A(3,q)<M(3,q)$ if $q$ is large enough. While
for general values of $n$ and $q$ we establish the bounds \[ n\log q \le A(n,q)
\le (1+o(1))nq \] and \[ (1-o(1))nq \le M(n,q) \le 2nq, \] provided $q$ tends
to infinity.


title: Outage Capacity of Opportunistic Beamforming with Random User Locations

abstract:
  This paper studies the outage capacity of a network consisting of a multitude
of heterogenous mobile users, and operating according to the classical
opportunistic beamforming framework. The base station is located at the center
of the cell, which is modeled as a disk of finite radius. The random user
locations are modeled using a homogenous spatial Poisson point process. The
received signals are impaired by both fading and location dependent path loss.
For this system, we first derive an expression for the beam outage probability.
This expression holds for all path loss models that satisfy some mild
conditions. Then, we focus on two specific path loss models (i.e., an unbounded
model and a more realistic bounded one) to illustrate the applications of our
results. In the large system limit where the cell radius tends to infinity, the
beam outage capacity and its scaling behavior are derived for the selected
specific path loss models. It is shown that the beam outage capacity scales
logarithmically for the unbounded model. On the other hand, this scaling
behavior becomes double logarithmic for the bounded model. Intuitive
explanations are provided as to why we observe different scaling behavior for
different path loss models. Numerical evaluations are performed to give further
insights, and to illustrate the applicability of the outage capacity results
even to a cell having a small finite radius.


title: Constraints on a second planet in the WASP-3 system

abstract:
  There have been previous hints that the transiting planet WASP-3 b is
accompanied by a second planet in a nearby orbit, based on small deviations
from strict periodicity of the observed transits. Here we present 17 precise
radial velocity measurements and 32 transit light curves that were acquired
between 2009 and 2011. These data were used to refine the parameters of the
host star and transiting planet. This has resulted in reduced uncertainties for
the radii and masses of the star and planet. The radial-velocity data and the
transit times show no evidence for an additional planet in the system.
Therefore, we have determined the upper limit on the mass of any hypothetical
second planet, as a function of its orbital period.


title:
Abundance Profiling of Extremely Metal-Poor Stars and Supernova
  Properties in the Early Universe

abstract:
  After the Big Bang nucleosynthesis, the first heavy element enrichment in the
Universe was made by a supernova (SN) explosion of a population (Pop) III star
(Pop III SN). The abundance ratios of elements produced from Pop III SNe are
recorded in abundance patterns of extremely metal-poor (EMP) stars. The
observations of the increasing number of EMP stars have made it possible to
statistically constrain the explosion properties of Pop III SNe. We present Pop
III SN models whose nucleosynthesis yields well-reproduce individually the
abundance patterns of 48 such metal-poor stars as [Fe/H] $\mathrel{\rlap{\lower
4pt \hbox{$\sim$}}\raise 1pt \hbox {$<$}}-3.5$. We then derive relations
between the abundance ratios of EMP stars and certain explosion properties of
Pop III SNe: the higher [(C+N)/Fe] and [(C+N)/Mg] ratios correspond to the
smaller ejected Fe mass and the larger compact remnant mass, respectively.
Using these relations, the distributions of the abundance ratios of EMP stars
are converted to those of the explosion properties of Pop III SNe. Such
distributions are compared with those of the explosion properties of present
day SNe: The distribution of the ejected Fe mass of Pop III SNe has the same
peak as that of the resent day SNe but shows an extended tail down to
$\sim10^{-2}-10^{-5}M_\odot$, and the distribution of the mass of the compact
remnant of Pop III SNe is as wide as that of the present day stellar-mass black
holes. Our results demonstrate the importance of large samples of EMP stars
obtained by ongoing and future EMP star surveys and subsequent high-dispersion
spectroscopic observations in clarifying the nature of Pop III SNe in the early
Universe.


title:
Relics of Minijets amid Anisotropic Flows in High-energy Heavy-ion
  Collisions

abstract:
  Two dimensional low-$p_T$ dihadron correlations in azimuthal angle $\phi$ and
pseudo-rapidity $\eta$ in high-energy heavy-ion collisions are investigated
within both the HIJING Monte Carlo model and an event-by-event (3+1)D ideal
hydrodynamic model. Without final-state interaction and collective expansion,
dihadron correlations from HIJING simulations have a typical structure from
minijets that contains a near-side two-dimensional peak and an away-side ridge
along the $\eta$-direction. In contrast, event-by-event (3+1)D ideal
hydrodynamic simulations with fluctuating initial conditions from the
HIJING+AMPT model produce a strong dihadron correlation that has an away-side
as well as a near-side ridge. Relics of intrinsic dihadron correlation from
minijets in the initial conditions still remain as superimposed on the two
ridges. By varying initial conditions from HIJING+AMPT, we study effects of
minijets, non-vanishing initial flow and longitudinal fluctuation on the final
state dihadron correlations. With a large rapidity gap, one can exclude
near-side correlations from minijet relics and dihadron correlations can be
described by the superposition of harmonic flows up to the 6th order. When
long-range correlations with a large rapidity gap are subtracted from
short-range correlations with a small rapidity gap, the remaining near-side
dihadron correlations result solely from relics of minijets. Low transverse
momentum hadron yields per trigger ($p_T^{\rm trig} <4$ GeV/$c$, $p_T^{\rm
asso}<2$ GeV/$c$) in central heavy-ion collisions are significantly enhanced
over that in p+p collisions while widths in azimuthal angle remain the same, in
qualitative agreement with experimental data.


title: Programmable quantum simulation by dynamic Hamiltonian engineering

abstract:
  Quantum simulation is a promising near term application for mesoscale quantum
information processors, with the potential to solve computationally intractable
problems at the scale of just a few dozen interacting quantum systems. Recent
experiments in a range of technical platforms have demonstrated the basic
functionality of quantum simulation applied to quantum magnetism, quantum phase
transitions, and relativistic quantum mechanics. In all cases, the underlying
hardware platforms restrict the achievable inter-particle interaction, forming
a serious constraint on the ability to realize a versatile, programmable
quantum simulator. In this work, we address this problem by developing novel
sequences of unitary operations that engineer desired effective Hamiltonians in
the time-domain. The result is a hybrid programmable analog simulator
permitting a broad class of interacting spin-lattice models to be generated
starting only with an arbitrary long-range native inter-particle interaction
and single-qubit addressing. Specifically, our approach permits the generation
of all symmetrically coupled translation-invariant two-body Hamiltonians with
homogeneous on-site terms, a class which includes all spin-1/2 XYZ chains, but
generalized to include long-range couplings. Building on previous work proving
that universal simulation is possible using both entangling gates and
single-qubit unitaries, we show that determining the "program" of unitary
pulses to implement an arbitrary spin Hamiltonian can be formulated as a linear
program that runs in polynomial time and scales efficiently in hardware
resources. Our analysis extends from circuit model quantum information to
adiabatic quantum evolutions, where our approach allows for the creation of
non-native ground state solutions to a computation.


title: Rocking Subdiffusive Ratchets: Origin, Optimization and Efficiency

abstract:
  We study origin, parameter optimization, and thermodynamic efficiency of
isothermal rocking ratchets based on fractional subdiffusion within a
generalized non-Markovian Langevin equation approach. A corresponding
multi-dimensional Markovian embedding dynamics is realized using a set of
auxiliary Brownian particles elastically coupled to the central Brownian
particle (see video on the journal web site). We show that anomalous
subdiffusive transport emerges due to an interplay of nonlinear response and
viscoelastic effects for fractional Brownian motion in periodic potentials with
broken space-inversion symmetry and driven by a time-periodic field. The
anomalous transport becomes optimal for a subthreshold driving when the driving
period matches a characteristic time scale of interwell transitions. It can
also be optimized by varying temperature, amplitude of periodic potential and
driving strength. The useful work done against a load shows a parabolic
dependence on the load strength. It grows sublinearly with time and the
corresponding thermodynamic efficiency decays algebraically in time because the
energy supplied by the driving field scales with time linearly. However, it
compares well with the efficiency of normal diffusion rocking ratchets on an
appreciably long time scale.


title:
Bulk effects on topological conduction on the surface of 3-D topological
  insulators

abstract:
  The surface states of a topological insulator in a fine-tuned magnetic field
are ideal candidates for realizing a topological metal which is protected
against disorder. Its signatures are (1) a conductance plateau in long wires in
a finely tuned longitudinal magnetic field and (2) a conductivity which always
increases with sample size, and both are independent of disorder strength. We
numerically study how these experimental transport signatures are affected by
bulk physics in the interior of the topological insulator sample. We show that
both signatures of the topological metal are robust against bulk effects.
However the bulk does substantially accelerate the metal's decay in a magnetic
field and alter its response to surface disorder. When the disorder strength is
tuned to resonance with the bulk band the conductivity follows the predictions
of scaling theory, indicating that conduction is diffusive. At other disorder
strengths the bulk reduces the effects of surface disorder and scaling theory
is systematically violated, signaling that conduction is not fully diffusive.
These effects will change the magnitude of the surface conductivity and the
magnetoconductivity.


title:
Probing electron acceleration and X-ray emission in laser-plasma
  accelerator

abstract:
  While laser-plasma accelerators have demonstrated a strong potential in the
acceleration of electrons up to giga-electronvolt energies, few experimental
tools for studying the acceleration physics have been developed. In this paper,
we demonstrate a method for probing the acceleration process. A second laser
beam, propagating perpendicular to the main beam is focused in the gas jet few
nanosecond before the main beam creates the accelerating plasma wave. This
second beam is intense enough to ionize the gas and form a density depletion
which will locally inhibit the acceleration. The position of the density
depletion is scanned along the interaction length to probe the electron
injection and acceleration, and the betatron X-ray emission. To illustrate the
potential of the method, the variation of the injection position with the
plasma density is studied.


title:
Detection of the elite structure in a virtual multiplex social system by
  means of a generalized $K$-core

abstract:
  Elites are subgroups of individuals within a society that have the ability
and means to influence, lead, govern, and shape societies. Members of elites
are often well connected individuals, which enables them to impose their
influence to many and to quickly gather, process, and spread information. Here
we argue that elites are not only composed of highly connected individuals, but
also of intermediaries connecting hubs to form a cohesive and structured
elite-subgroup at the core of a social network. For this purpose we present a
generalization of the $K$-core algorithm that allows to identify a social core
that is composed of well-connected hubs together with their `connectors'. We
show the validity of the idea in the framework of a virtual world defined by a
massive multiplayer online game, on which we have complete information of
various social networks. Exploiting this multiplex structure, we find that the
hubs of the generalized $K$-core identify those individuals that are high
social performers in terms of a series of indicators that are available in the
game. In addition, using a combined strategy which involves the generalized
$K$-core and the recently introduced $M$-core, the elites of the different
'nations' present in the game are perfectly identified as modules of the
generalized $K$-core. Interesting sudden shifts in the composition of the elite
cores are observed at deep levels. We show that elite detection with the
traditional $K$-core is not possible in a reliable way. The proposed method
might be useful in a series of more general applications, such as community
detection.


title:
Tuning the metamagnetic transition in the (Co,Fe)MnP system for
  magnetocaloric purposes

abstract:
  The inverse magnetocaloric effect taking place at the
antiferro-to-ferromagnetic transition of (Co,Fe)MnP phosphides has been
characterized by magnetic and direct {\Delta}Tad measurements. In
Co0.53Fe0.47MnP, entropy change of 1.5 Jkg-1K-1 and adiabatic temperature
change of 0.6 K are found at room temperature for an intermediate field change
({\Delta}B= 1 T). Several methods were used to control the metamagnetic
transition properties, in each case a peculiar splitting of the
antiferro-to-ferromagnetic transition is observed.


title: Quark contribution for center domain in heavy ion collisions

abstract:
  The center domain structure is revisited with introduction of quark
contribution to understand phenomenology in high-energy heavy ion collisions.
We show the quark contribution may allow metastable states that would lead to a
natural and consistent explanation for the temperature dependences of color
opacity and viscosity. We also argue the possibility of indirect observations
of the center domain structure in experiments due to a topological critical
temperature.


title: Witten's mechanism in the flipped SU(5) unification

abstract:
  We argue that the Witten's loop mechanism for the right-handed Majorana
neutrino mass generation identified originally in the SO(10) grand unification
context can be successfully adopted to the class of the simplest flipped SU(5)
models. In such a framework, the main drawback of the SO(10) prototype, in
particular, the generic tension among the gauge unification constraints and the
absolute neutrino mass scale is alleviated and a simple yet potentially
realistic and testable scenario emerges.


title:
Extraction of dihadron-jet correlations with rigorous flow-background
  subtraction in a multiphase transport model

abstract:
  Dihadron azimuthal correlations in Au+Au collisions at $\sqrt{S_{NN}}$=200
GeV have been explored by using a multi-phase transport (AMPT) model. In order
to obtain the contributions from jet-medium interactions, the combined harmonic
flow background is subtracted from the raw dihadron correlation functions. The
signals are compared in three associated transverse momentum ($p_{T}^{assoc}$)
bins: 0.2-0.8 GeV/c, 0.8-1.4 GeV/c and 1.4-2.0 GeV/c from central to
semi-peripheral geometries. The medium modifications are observed from changes
in the signal shape and the relative jet contribution has been obtained within
the change in the centrality from peripheral to central one. A strong
$p_{T}^{assoc}$ dependence of the RMS width of jet correlation function is
observed within the central geometry bin, i.e. 0-10$%$.


title: Particle Efficient Importance Sampling

abstract:
  The efficient importance sampling (EIS) method is a general principle for the
numerical evaluation of high-dimensional integrals that uses the sequential
structure of target integrands to build variance minimising importance
samplers. Despite a number of successful applications in high dimensions, it is
well known that importance sampling strategies are subject to an exponential
growth in variance as the dimension of the integration increases. We solve this
problem by recognising that the EIS framework has an offline sequential Monte
Carlo interpretation. The particle EIS method is based on non-standard
resampling weights that take into account the look-ahead construction of the
importance sampler. We apply the method for a range of univariate and bivariate
stochastic volatility specifications. We also develop a new application of the
EIS approach to state space models with Student's t state innovations. Our
results show that the particle EIS method strongly outperforms both the
standard EIS method and particle filters for likelihood evaluation in high
dimensions. Moreover, the ratio between the variances of the particle EIS and
particle filter methods remains stable as the time series dimension increases.
We illustrate the efficiency of the method for Bayesian inference using the
particle marginal Metropolis-Hastings and importance sampling squared
algorithms.


title:
Transition states and thermal collapse of dipolar Bose-Einstein
  condensates

abstract:
  We investigate thermally excited, dipolar Bose-Einstein condensates.
Quasi-particle excitations of the atomic cloud cause density fluctuations which
can induce the collapse of the condensate if the inter-particle interaction is
attractive. Within a variational approach, we identify the collectively excited
stationary states of the gas which form transition states on the way to the
BEC's collapse. We analyze transition states with different $m$-fold rotational
symmetry and identify the one which mediates the collapse. The latter's
symmetry depends on the trap aspect ratio of the external trapping potential
which determines the shape of the BEC. Moreover, we present the collapse
dynamics of the BEC and calculate the corresponding decay rate using transition
state theory. We observe that the thermally induced collapse mechanism is
important near the critical scattering length, where the lifetime of the
condensate can be significantly reduced. Our results are valid for an arbitrary
strength of the dipole-dipole interaction. Specific applications are discussed
for the elements $^{52}$Cr, $^{164}$Dy and $^{168}$Er with which dipolar BECs
have been experimentally realized.


title: Challenges for QCD theory - some personal reflections -

abstract:
  At the LHC all processes are QCD ones, whether "signal" or "background". In
this review the frontiers of current QCD research are addressed, towards
increased understanding, improved calculational precision, and role in
potential future discoveries. Issues raised include the limits of perturbative
QCD calculations and parton distribution usage, the nature of multiparton
interactions, the impact of colour reconnection on physical observables, the
need for progress on hadronization modelling, the improvements of parton
showers and their combination with the matrix-element description, the use of
QCD concepts in Beyond-the-Standard-Model scenarios, and the key position of
event generators and other software in the successful exploration of LHC
physics. On the way, several questions are posed, where further studies are
needed.


title: On a H\"older constant in the theory of quasiconformal mappings

abstract:
  A K-quasiconformal selfmap of the unit disk with identity boundary values
satisfies the H\"older estimate $|f(z)-f(w)| \leq 4^{1-1/K} |z-w|^{1/K}$. The
constant $4^{1-\frac{1}{K}}$ is sharp.


title:
Subdiffusive rocking ratchets in viscoelastic media: transport
  optimization and thermodynamic efficiency in overdamped regime

abstract:
  We study subdiffusive overdamped Brownian ratchets periodically rocked by an
external zero-mean force in viscoelastic media within the framework of
non-Markovian Generalized Langevin equation (GLE) approach and associated
multi-dimensional Markovian embedding dynamics. Viscoelastic deformations of
the medium caused by the transport particle are modeled by a set of auxiliary
Brownian quasi-particles elastically coupled to the transport particle and
characterized by a hierarchy of relaxation times which obey a fractal scaling.
The most slowly relaxing deformations which cannot immediately follow to the
moving particle imprint long-range memory about its previous positions and
cause subdiffusion and anomalous transport on a sufficiently long time scale.
This anomalous behavior is combined with normal diffusion and transport on an
initial time scale of overdamped motion. Anomalously slow directed transport in
a periodic ratchet potential with broken space inversion symmetry emerges due
to a violation of the thermal detailed balance by a zero-mean periodic driving
and is optimized with frequency of driving, its amplitude, and temperature.
Such optimized anomalous transport can be low dispersive and characterized by a
large generalized Peclet number. Moreover, we show that overdamped subdiffusive
ratchets can sustain a substantial load and do a useful work. The corresponding
thermodynamic efficiency decays algebraically in time since the useful work
done against a load scales sublinearly with time following to the transport
particle position, but the energy pumped by an external force scales with time
linearly. Nevertheless, it can be transiently appreciably high and compare well
with the thermodynamical efficiency of the normal diffusion overdamped ratchets
on sufficiently long temporal and spatial scales.


title: Conservation laws for colliding branes with induced gravity

abstract:
  We derive conservation laws for collisions of self-gravitating $n$-branes (or
$n$-dimensional shells) in an $(n+2)$ dimensional spacetime including induced
gravity on the brane. Previous work has shown how geometrical identities in
general relativity enforce conservation of energy-momentum at collisions. The
inclusion of induced gravity terms introduces a gravitational self-energy on
the brane which permits energy-momentum conservation of matter fields on the
brane to be broken, so long as the total energy-momentum, including induced
gravity terms, is conserved. We give simple examples with two branes (one
ingoing and one outgoing) and three branes.


title: Kelvin wake pattern at large Froude numbers

abstract:
  Gravity waves generated by an object moving at constant speed at the water
surface form a specific pattern commonly known as the Kelvin wake. It was
proved by Lord Kelvin that such a wake is delimited by a constant angle $\simeq
19.47^\circ$. However a recent study by Rabaud and Moisy based on the
observation of airborne images showed that the wake angle seems to decrease as
the Froude number $Fr$ increases, scaling as $Fr^{-1}$ for large Froude
numbers. To explain such observations the authors make the strong hypothesis
that an object of size $b$ cannot generate wavelengths larger than $b$. With no
need of such an assumption and modelling the moving object by an axisymmetric
pressure field, we analytically show that the angle corresponding to the
maximum amplitude of the waves scales as $Fr^{-1}$ for large Froude numbers,
whereas the angle delimiting the wake region outside which the surface is
essentially flat remains constant and equal to the Kelvin angle for all $Fr$.

categories: physics.flu-dyn math-ph math.MP physics.pop-ph


title:
Anisotropy test of the axion-like particle Universe opacity effect: a
  case for the Cherenkov Telescope Array

abstract:
  The Universe opacity to gamma rays is still an open question, in particular
anomalies may have been observed. Assuming that such anomalies find their
origin in conventional physics like intrinsic source spectra or the density of
the extragalactic background light, they would be evenly distributed over the
sky. If they exist, axion-like particles (ALPs) would have a potential effect
on the opacity of the Universe to gamma rays, possibly related to the anomalies
in the spectral indices of distant gamma-ray sources. In the scenario where
ALPs from distant sources convert back to photons in the Galactic magnetic
field, their effect on the opacity is expected to depend on the position of the
sources. In that case the anomaly is expected to exhibit peculiar correlations
on the sky. We propose a method to test the origin of the opacity anomaly,
based on angular correlations of spectral softening anomalies. Such a diagnosis
requires a wide-field survey of high-energy gamma-ray sources over a broad
range of energy. The future Cherenkov Telescope Array (CTA) is perfectly suited
to perform such a study. It is shown that while the current sample of sources
is not large enough to base conclusions on, with this method CTA will be
sensitive to ALP couplings to gamma rays of the order of 3e-11 GeV^-1 for ALP
masses below 1e-8 eV.


title:
Semiclassical and Quantum Analysis of a Focussing Free Particle Hermite
  Wavefunction

abstract:
  In this paper we discuss a solution of the free particle Schrodinger
equation in which the time and space dependence are not separable. The
wavefunction is written as a product of exponential terms, Hermite polynomials
and a phase. The peaks in the wavefunction decelerate and then accelerate
around t = 0. We analyse this behaviour within both a quantum and a
semi-classical regime. We show that the acceleration does not represent true
acceleration of the particle but can be related to the envelope function of the
allowed classical paths. Comparison with other "accelerating" wavefunctions is
also made. The analysis provides considerable insight into the meaning of the
quantum wavefunction.


title: Hybridization gap and Fano resonance in SmB${_6}$

abstract:
  We present results of Scanning Tunneling Microscopy and Spectroscopy (STS)
measurements on the "Kondo insulator" SmB$_6$. The vast majority of surface
areas investigated was reconstructed but, infrequently, also patches of varying
size of non-reconstructed, Sm- or B-terminated surfaces were found. On the
smallest patches, clear indications for the hybridization gap and
inter-multiplet transitions were observed. On non-reconstructed surface areas
large enough for coherent co-tunneling we were able to observe clear-cut Fano
resonances. Our locally resolved STS indicated considerable finite conductance
on all surfaces independent of their structure.


title:
The Scattering amplitude for Rationally extended shape invariant Eckart
  potentials

abstract:
  We consider the rationally extended exactly solvable Eckart potentials which
exhibit extended shape invariance property. These potentials are isospectral to
the conventional Eckart potential. The scattering amplitude for these
rationally ex- tended potentials is calculated analytically for the generalized
mth (m = 1, 2, 3, ...) case by considering the asymptotic behavior of the
scattering state wave functions which are written in terms of some new
polynomials related to the Jacobi polyno- mials. As expected, in the m = 0
limit, this scattering amplitude goes over to the scattering amplitude for the
conventional Eckart potential.


title:
The universe dominated by oscillating scalar with non-minimal derivative
  coupling to gravity

abstract:
  We study the expansion law of the universe dominated by the oscillating
scalar field with non-minimal derivative coupling to gravity as G^{\mu \nu}
\partial_{\mu} \phi \partial_{\nu} \phi. In this system the Hubble parameter
oscillates with a frequency of the effective mass of the scalar field, which
formerly caused a difficulty in analyzing how the universe expands. We find an
analytical solution for power law potentials and interpret the solution in an
intuitive way by using a new invariant of the system. As a result, we find
marginally accelerated expansion for the quadratic potential and no accelerated
expansion for the potential with higher power.


title:
Asymmetric coupling in two-lane simple exclusion process with Langmuir
  kinetics: phase diagrams and boundary layers

abstract:
  We study an open system composed of two parallel totally asymmetric simple
exclusion processes with particle attachment and detachment in the bulk. The
particles are allowed to change their lane from lane-A to lane-B, but not
conversely. We investigate the steady-state behavior of the system using
boundary layer analysis on continuum mean-field equations to provide the phase
diagram. The structure of the phase diagram is quite complex and provides a
complete insight about the steady-state dynamics. We examine two kinds of
transitions in the phase plane: bulk transitions and surface transitions,
qualitatively as well as quantitatively. The dynamics of shock formation,
localization and their dependence on the system parameters and boundary rates
have been investigated. We also justify the non-existence of downward shock in
both the lanes using fixed point theory. Further, we examine the effect of
increasing lane-changing rate on the steady-state dynamics and observe that the
number of steady-state phases reduces with increase in lane-changing rate. Our
theoretical results are supported with extensive Monte-Carlo simulation
results.


title:
Jacob's ladders and $|\zeta|^{-2}$-representation of some functionals
  generated by a new class of transcendental integrals

abstract:
  In this paper we introduce a new infinite set of transcendental integrals.
Each of them is expressed by corresponding value of the function $|\zf|^{-2}$.
Such a property is another argument about universality of the Riemann
zeta-function $\zf$ in the field of pure mathematics.


title:
Enhancing entanglement trapping by weak measurement and quantum
  measurement reversal

abstract:
  In this paper, we propose a scheme to enhance trapping of entanglement of two
qubits in the environment of a photonic band gap material. Our entanglement
trapping promotion scheme makes use of combined weak measurements and quantum
measurement reversals. The optimal promotion of entanglement trapping can be
acquired with a reasonable finite success probability by adjusting measurement
strengths.


title: Geometric quantization and families of inner products

abstract:
  We formulate a quantization commutes with reduction principle in the setting
where the Lie group $G$, the symplectic manifold it acts on, and the orbit
space of the action may all be noncompact. It is assumed that the action is
proper, and the zero set of a deformation vector field, associated to the
momentum map and an equivariant family of inner products on the Lie algebra
$\mathfrak{g}$ of $G$, is $G$-cocompact. The central result establishes an
asymptotic version of this quantization commutes with reduction principle.
Using an equivariant family of inner products on $\mathfrak{g}$ instead of a
single one makes it possible to handle both noncompact groups and manifolds, by
extending Tian and Zhang's Witten deformation approach to the noncompact case.

categories: math.DG hep-th math-ph math.MP math.OA math.SG


title: Quantization of the QCD string with a helical structure

abstract:
  The quantum properties of a helix-like shaped QCD string are studied in the
context of the semi-classical Lund fragmentation model. It is shown how simple
quantization rules combined with the causality considerations in the string
fragmentation process describe the mass hierarchy of light pseudoscalar mesons.
The quantized helix string model predicts observable quantum effects related to
the threshold behaviour of the intrinsic transverse momentum of hadrons, and of
the minimal transverse momentum difference between adjacent hadrons. The
numerical fit of the properties of the QCD field breaking into ground state
hadrons agree with astonishing precision with values obtained recently in the
theory of knotted chromoelectric flux tubes.


title: Magnetic frustration in BaCuSi2O6 released

abstract:
  Han Purple (BaCuSi2O6) is not only an ancient pigment, but also a valuable
model material for studying Bose-Einstein condensation (BEC) of magnons in high
magnetic fields. Using precise low-temperature structural data and extensive
density-functional calculations, we elucidate magnetic couplings in this
compound. The resulting magnetic model comprises two types of nonequivalent
spin dimers, in excellent agreement with the (63,65)Cu nuclear magnetic
resonance data. We further argue that leading interdimer couplings connect the
upper site of one dimer to the bottom site of the contiguous dimer, and not the
upper-to-upper and bottom-to-bottom sites, as assumed previously. This finding
is verified by inelastic neutron scattering data and implies the lack of
magnetic frustration in BaCuSi2O6, thus challenging existing theories of the
magnon BEC in this compound.


title:
Nonstatistical dynamics on potentials exhibiting reaction path
  bifurcations and valley-ridge inflection points

abstract:
  We study reaction dynamics on a model potential energy surface exhibiting
post-transition state bifurcation in the vicinity of a valley ridge inflection
point. We compute fractional yields of products reached after the VRI region is
traversed, both with and without dissipation. It is found that apparently minor
variations in the potential lead to significant changes in the reaction
dynamics. Moreover, when dissipative effects are incorporated, the product
ratio depends in a complicated and highly non-monotonic fashion on the
dissipation parameter. Dynamics in the vicinity of the VRI point itself play
essentially no role in determining the product ratio, except in the highly
dissipative regime.

categories: physics.chem-ph cond-mat.stat-mech math.DS nlin.CD


title:
Dielectric Investigation, Piezoelectric Measurement and Structural
  Studies of Strontium-doped, modified PMS-PZT Piezoelectric Ceramics

abstract:
  The structure and dielectric properties of 6% $\rm{Sr}^{2+}$-substituted,
modified Lead Zirconium Titanate (PZT) piezoelectric ceramic, with composition
$[\rm{Pb}_{0.94}\rm{Sr}_{0.06}][(\rm{Mn}_{1/3}\rm{Sb}_{2/3})_{0.05}(\rm{Zr}_{0.54}\rm{Ti}_{0.46})_{0.95}]O_3$
and lead manganese antimonite as an additional dopant, synthesized by ceramic
route have been investigated in a frequency range from 50Hz to 1MHz and in a
temperature range between room temperature and 633K. The scanning electron
micrograph of the sample taken at the room temperature confirms the formation
of a fairly homogenous structure and well-formed grains with sharp boundaries.
From the Rietveld analysis, it was found that the structure of the material is
tetragonal with space group P4mm. The scaling behavior of imaginary part of the
electric modulus suggests that the relaxation is described by the same
mechanism at various temperatures. The values of the electromechanical coupling
factor ($\rm{k_p}$), the high mechanical quality factor ($\rm{Q_m}$) and the
piezoelectric coefficient ($\rm{d}_{33}$) of the synthesized sintered & poled
ceramics gives a good set of values for the piezoelectric properties when
compared with related materials, useful for various interesting piezoelectric
device applications.


title: Thermolubricity of Xe monolayers on graphene

abstract:
  The nanofriction of Xe monolayers deposited on graphene was explored with a
quartz crystal microbalance (QCM) at temperatures between 25 and 50 K. Graphene
was grown by chemical vapor deposition and transferred to the QCM electrodes
with a polymer stamp. At low temperatures, the Xe monolayers are fully pinned
to the graphene surface. Above 30 K, the Xe film slides and the depinning onset
coverage beyond which the film starts sliding decreases with temperature.
Similar measurements repeated on bare gold show an enhanced slippage of the Xe
films and a decrease of the depinning temperature below 25 K. Nanofriction
measurements of krypton and nitrogen confirm this scenario.This thermolubric
behavior is explained in terms of a recent theory of the size dependence of
static friction between adsorbed islands and crystalline substrates.


title: Interacting particle systems as stochastic social dynamics

abstract:
  The style of mathematical models known to probabilists as Interacting
Particle Systems and exemplified by the Voter, Exclusion and Contact processes
have found use in many academic disciplines. In many such disciplines the
underlying conceptual picture is of a social network, where individuals meet
pairwise and update their "state" (opinion, activity etc) in a way depending on
the two previous states. This picture motivates a precise general setup we call
Finite Markov Information Exchange (FMIE) processes. We briefly describe a few
less familiar models (Averaging, Compulsive Gambler, Deference, Fashionista)
suggested by the social network picture, as well as a few familiar ones.


title: Simultaneous Integer Values of Pairs of Quadratic Forms

abstract:
  We prove that a pair of integral quadratic forms in 5 or more variables will
simultaneously represent "almost all" pairs of integers that satisfy the
necessary local conditions, provided that the forms satisfy a suitable
nonsingularity condition. In particular such forms simultaneously attain prime
values if the obvious local conditions hold. The proof uses the circle method,
and in particular pioneers a two-dimensional version of a Kloosterman
refinement.


title:
Probing the Circumgalactic Medium at High-Redshift Using Composite BOSS
  Spectra of Strong Lyman-alpha Forest Absorbers

abstract:
  We present composite spectra constructed from a sample of 242,150 Lyman-alpha
(Lya) forest absorbers at redshifts 2.4<z<3.1 identified in quasar spectra from
the Baryon Oscillation Spectroscopic Survey (BOSS) as part of Data Release 9 of
the Sloan Digital Sky Survey III. We select forest absorbers by their flux in
bins 138 km/s wide (approximately the size of the BOSS resolution element). We
split these absorbers into five samples spanning the range of flux -0.05 <
F<0.45. Tests on a smaller sample of high-resolution spectra show that our
three strongest absorption bins would probe circumgalactic regions (projected
separation < 300 proper kpc and |Delta v| < 300km/s) in about 60% of cases for
very high signal-to-noise ratio. Within this subset, weakening Lya absorption
is associated with decreasing purity of circumgalactic selection once BOSS
noise is included. Our weaker two Lya absorption samples are dominated by the
intergalactic medium.
  We present composite spectra of these samples and a catalogue of measured
absorption features from HI and 13 metal ionization species, all of which we
make available to the community. We compare measurements of seven Lyman series
transitions in our composite spectra to single line models and obtain further
constraints from their associated excess Lyman limit opacity. This analysis
provides results consistent with column densities over the range 14.4 <~ Log
(N_HI) <~ 16.45. We compare our measurements of metal absorption to a variety
of simple single-line, single-phase models for a preliminary interpretation.
Our results imply clumping on scales down to ~30 pc and near-solar
metallicities in the circumgalactic samples, while high-ionization metal
absorption consistent with typical IGM densities and metallicities is visible
in all samples.


title: Entropy for A-coupled-expanding Maps and Chaos

abstract:
  The concept of "$A$-coupled-expanding" map for a transition matrix $A$ has
been studied as one of the most important criteria of chaos in the past years.
In this paper, the lower bound of the topological entropy for strictly
$A$-coupled-expanding maps is studied as a criterion for chaos in the sense of
Li-Yorke, which is less conservative and more generalized than the latest
result is presented. Furthermore, some conditions for $A$-coupled-expanding
maps excluding the strictness to be factors of subshifts of finite type are
derived. In addition, the topological entropy of
partition-$A$-coupled-expanding map, which is put forward in this paper, is
further estimated on compact metric spaces. Particularly, the topological
entropy for partition-$A$-coupled-expanding circle maps is given, with that for
the Kasner map being calculated for illustration and verification.