title:
High-Temperature Activated AB2 Nanopowders for Metal Hydride Hydrogen
  Compression

abstract:
  A reliable process for compressing hydrogen and for removing all contaminants
is that of the metal hydride thermal compression. The use of metal hydride
technology in hydrogen compression applications though, requires thorough
structural characterization of the alloys and investigation of their sorption
properties. The samples have been synthesized by induction - levitation melting
and characterized by Rietveld analysis of the X-Ray diffraction (XRD) patterns.
Volumetric PCI (Pressure-Composition Isotherm) measurements have been conducted
at 20, 60 and 90 oC, in order to investigate the maximum pressure that can be
reached from the selected alloys using water of 90oC. Experimental evidence
shows that the maximum hydrogen uptake is low since all the alloys are
consisted of Laves phases, but it is of minor importance if they have fast
kinetics, given a constant volumetric hydrogen flow. Hysteresis is almost
absent while all the alloys release nearly all the absorbed hydrogen during
desorption. Due to hardware restrictions, the maximum hydrogen pressure for the
measurements was limited at 100 bars. Practically, the maximum pressure that
can be reached from the last alloy is more than 150 bars.


title: Introducing many-body physics using atomic spectroscopy

abstract:
  Atoms constitute relatively simple many-body systems, making them suitable
objects for developing an understanding of basic aspects of many-body physics.
Photoabsorption spectroscopy is a prominent method to study the electronic
structure of atoms and the inherent many-body interactions. In this article the
impact of many-body effects on well-known spectroscopic features such as
Rydberg series, Fano resonances, Cooper minima, and giant resonances is
studied, and related many-body phenomena in other fields are outlined. To
calculate photoabsorption cross sections the time-dependent configuration
interaction singles (TDCIS) model is employed. The conceptual clearness of
TDCIS in combination with the compactness of atomic systems allows for a
pedagogical introduction to many-body phenomena.


title: On the Geometry of Sculpting-like Gauging Processes

abstract:
  Recently, a new gauging procedure called Sculpting mechanism was proposed to
obtain the M-theory origin of type II gauged Supergravity theories in 9D. We
study this procedurein detail and give a better understanding of the different
deformations and changes in fiber bundles, that are able to generate new
relevant physical gauge symmetries in the theory. We discuss the geometry
involved in the standard approach (Noether-like) and in the new Scultping-like
one and comment on possible new applications.


title:
Stochastic processes and feedback-linearisation for online
  identification and Bayesian adaptive control of fully-actuated mechanical
  systems

abstract:
  This work proposes a new method for simultaneous probabilistic identification
and control of an observable, fully-actuated mechanical system. Identification
is achieved by conditioning stochastic process priors on observations of
configurations and noisy estimates of configuration derivatives. In contrast to
previous work that has used stochastic processes for identification, we
leverage the structural knowledge afforded by Lagrangian mechanics and learn
the drift and control input matrix functions of the control-affine system
separately. We utilise feedback-linearisation to reduce, in expectation, the
uncertain nonlinear control problem to one that is easy to regulate in a
desired manner. Thereby, our method combines the flexibility of nonparametric
Bayesian learning with epistemological guarantees on the expected closed-loop
trajectory. We illustrate our method in the context of torque-actuated pendula
where the dynamics are learned with a combination of normal and log-normal
processes.


title: Genetic diversity in introduced populations with Allee effect

abstract:
  A phenomenon that strongly influences the demography of small introduced
populations and thereby potentially their genetic diversity is the Allee
effect, a reduction in population growth rates at small population sizes. We
take a stochastic modeling approach to investigate levels of genetic diversity
in populations that successfully overcame a strong demographic Allee effect, a
scenario in which populations smaller than a certain critical size are expected
to decline. Our results indicate that compared to successful populations
without Allee effect, successful Allee-effect populations tend to 1) derive
from larger founder population sizes and thus have a higher initial amount of
genetic variation, 2) spend fewer generations at small population sizes where
genetic drift is particularly strong, and 3) spend more time around the
critical population size and thus experience more drift there. Altogether, the
Allee effect can either increase or decrease genetic diversity, depending on
the average founder population size. In the case of multiple introduction
events, there is an additional increase in diversity because Allee-effect
populations tend to derive from a larger number of introduction events than
other populations. Finally, we show that given genetic data from sufficiently
many populations, we can statistically infer the critical population size.


title: Coherent caloritronics in Josephson-based nanocircuits

abstract:
  We describe here the first experimental realization of a heat interferometer,
thermal counterpart of the well-known superconducting quantum interference
device (SQUID). These findings demonstrate, on the first place, the existence
of phase-dependent heat transport in Josephson-based superconducting circuits
and, on the second place, open the way to novel ways of mastering heat at the
nanoscale. Combining the use of external magnetic fields for phase biasing and
different Josephson junction architectures we show here that a number of heat
interference patterns can be obtained. The experimental realization of these
architectures, besides being relevant from a fundamental physics point of view,
might find important technological application as building blocks of
phase-coherent quantum thermal circuits. In particular, the performance of two
different heat rectifying devices is analyzed.


title:
Glassy clusters: Relations between their dynamics and characteristic
  features of their energy landscape

abstract:
  Based on a recently introduced metric for measuring distances between
configurations, we in- troduce distance-energy (DE) plots to characterize the
potential energy surface (PES) of clusters. Producing such plots is
computationally feasible on the density functional (DFT) level since it re-
quires only a set of a few hundred stable low energy configurations including
the global minimum. By comparison with standard criteria based on
disconnectivity graphs and on the dynamics of Lennard- Jones clusters we show
that the DE plots convey the necessary information about the character of the
potential energy surface and allow to distinguish between glassy and non-glassy
systems. We then apply this analysis to real systems on the DFT level and show
that both glassy and non-glassy clusters can be found in simulations. It
however turns out that among our investigated clusters only those can be
synthesized experimentally which exhibit a non-glassy landscape.


title: A Component Lasso

abstract:
  We propose a new sparse regression method called the component lasso, based
on a simple idea. The method uses the connected-components structure of the
sample covariance matrix to split the problem into smaller ones. It then solves
the subproblems separately, obtaining a coefficient vector for each one. Then,
it uses non-negative least squares to recombine the different vectors into a
single solution. This step is useful in selecting and reweighting components
that are correlated with the response. Simulated and real data examples show
that the component lasso can outperform standard regression methods such as the
lasso and elastic net, achieving a lower mean squared error as well as better
support recovery.


title:
On Localization for Quantum Hamiltonian Reductions in Arbitrary
  Characteristic

abstract:
  For quantum Hamiltonian reductions in arbitrary characteristics, it is known
that derived localization holds if and only if the algebra of global sections
has finite global dimension. In this paper we provide an alternative
characterization of when derived localization holds: Derived localization holds
if and only if it holds for an explicit finite set of (quantized) line bundles.
As an application, we prove a new result that there are integral weights for
which localization holds on in the positive characteristic hypertoric case for
$p$ larger than an explicit bound. We also discuss how derived localization is
a consequence of a finite number of Morita equivalences.


title:
Sizing up entanglement in mutually unbiased bases with Fisher
  information

abstract:
  An efficient method for assessing the quality of quantum state tomography is
developed. Special attention is paid to the tomography of multipartite systems
in terms of unbiased measurements. Although the overall reconstruction errors
of different sets of mutually unbiased bases are the same, differences appear
when particular aspects of the measured system are contemplated. This point is
illustrated by estimating the fidelities of genuinely tripartite entangled
states.


title: Counting results for thin Butson matrices

abstract:
  A partial Butson matrix is a matrix $H\in M_{M\times N}(\mathbb Z_q)$ having
its rows pairwise orthogonal, where $\mathbb Z_q\subset\mathbb C^\times$ is the
group of $q$-th roots of unity. We investigate here the counting problem for
these matrices in the "thin" regime, where $M=2,3,\ldots$ is small, and where
$N\to\infty$ (subject to the condition $N\in p\mathbb N$ when $q=p^k>2$). The
proofs are inspired from the de Launey-Levin and Richmond-Shallit counting
results.


title: Critical properties on Roman domination graphs

abstract:
  A Roman domination function on a graph G is a function $r:V(G)\to \{0,1,2\}$
satisfying the condition that every vertex $u$ for which $r(u)=0$ is adjacent
to at least one vertex $v$ for which $r(v)=2$. The weight of a Roman function
is the value $r(V(G))=\sum_{u\in V(G)}r(u)$. The Roman domination number
$\gamma_R(G)$ of $G$ is the minimum weight of a Roman domination function on
$G$. "Roman Criticality" has been defined in general as the study of graphs
where the Roman domination number decreases when removing an edge or a vertex
of the graph. In this paper we give further results in this topic as well as
the complete characterization of critical graphs that have Toman Domination
number $\gamma_R(G)=4$.


title: The size of quadratic $p$-adic linearization disks

abstract:
  We find the exact radius of linearization disks at indifferent fixed points
of quadratic maps in $\mathbb{C}_p$. We also show that the radius is invariant
under power series perturbations. Localizing all periodic orbits of these
quadratic-like maps we then show that periodic points are not the only
obstruction for linearization. In so doing, we provide the first known examples
in the dynamics of polynomials over $\mathbb{C}_p$ where the boundary of the
linearization disk does not contain any periodic point.


title:
Optimal cycles in ultrametric dynamics and minimally ramified power
  series

abstract:
  We study ultrametric germs in one variable having an irrationally indifferent
fixed point at the origin with a prescribed multiplier. We show that for many
values of the multiplier, the cycles in the unit disk of the corresponding
monic quadratic polynomial are "optimal" in the following sense: They minimize
the distance to the origin among cycles of the same minimal period of
normalized germs having an irrationally indifferent fixed point at the origin
with the same multiplier. We also give examples of multipliers for which the
corresponding quadratic polynomial does not have optimal cycles. In those cases
we exhibit a higher degree polynomial such that all of its cycles are optimal.
The proof of these results reveals a connection between the geometric location
of periodic points of ultrametric power series and the lower ramification
numbers of wildly ramified field automorphisms. We also give an extension of
Sen's theorem on wildly ramified field automorphisms, and a characterization of
minimally ramified power series in terms of the iterative residue.


title: Anomalous Hydrodynamics of Two-Dimensional Vortex Fluid

abstract:
  Turbulent flows of incompressible liquid in two dimensions are comprised of
dense systems of vortices. Such system of vortices can be treated as a fluid
and itself could be described in terms of hydrodynamics. We develop the
hydrodynamics of the vortex fluid. This hydrodynamics captures characteristics
of fluid flows averaged over fast circulations in the inter-vortex space. The
hydrodynamics of the vortex fluid features the anomalous stress absent in
Euler's hydrodynamics. The anomalous stress yields a number of interesting
effects. Some of them are: a deflection of stream lines, a correction to the
Bernoulli law, accumulation of vortices in regions with high curvature in the
curved space. The origin of the anomalous stresses is a divergence of
inter-vortex interactions at the micro-scale which manifest at the macro-scale.
We obtain the hydrodynamics of the vortex fluid from the Kirchhoff equations
for dynamics of point-like vortices

categories: physics.flu-dyn cond-mat.quant-gas cond-mat.str-el hep-th math-ph math.MP


title:
Zeilberger's KOH theorem and the strict unimodality of q-binomial
  coefficients

abstract:
  A recent nice result due to I. Pak and G. Panova is the strict unimodality of
the $q$-binomial coefficients $\binom{a+b}{b}_q$ (see \cite{PP} and also
\cite{PP2} for a slightly revised version of their theorem). Since their proof
used representation theory and Kronecker coefficients, the authors also asked
for an argument that would employ Zeilberger's KOH theorem. In this note, we
give such a proof. Then, as a further application of our method, we also
provide a short proof of their conjecture that the difference between
consecutive coefficients of $\binom{a+b}{b}_q$ can get arbitrarily large, when
we assume that $b$ is fixed and $a$ is large enough.


title:
Cosmological signature change in Cartan Gravity with dynamical symmetry
  breaking

abstract:
  We investigate the possibility for classical metric signature change in a
straightforward generalization of the first order formulation of gravity,
dubbed "Cartan gravity". The mathematical structure of this theory mimics the
electroweak theory in that the basic ingredients are an $SO(1,4)$ Yang-Mills
gauge field $A^{ab}_{\phantom{ab}\mu}$ and a symmetry breaking Higgs field
$V^{a}$, with no metric or affine structure of spacetime presupposed. However,
these structures can be recovered, with the predictions of General Relativity
exactly reproduced, whenever the Higgs field breaking the symmetry to $SO(1,3)$
is forced to have a constant (positive) norm $V^aV_a$. This restriction is
usually imposed "by hand", but in analogy with the electroweak theory we
promote the gravitational Higgs field $V^a$ to a genuine dynamical field,
subject to non-trivial equations of motion. Even though we limit ourselves to
actions polynomial in these variables, we discover a rich phenomenology. Most
notably we derive classical cosmological solutions exhibiting a smooth
transition between Euclidean and Lorentzian signature in the four-metric. These
solutions are non-singular and arise whenever the $SO(1,4)$ norm of the Higgs
field changes sign i.e. the signature of the metric of spacetime is determined
dynamically by the gravitational Higgs field. It is possible to find a plethora
of such solutions and in some of them this dramatic behaviour is confined to
the early universe, with the theory asymptotically tending to Einstein gravity
at late times. Curiously the theory can also naturally embody a well-known dark
energy model: Peebles-Ratra quintessence.


title:
A Bayesian Nonparametric Causal Model for Regression Discontinuity
  Designs

abstract:
  For non-randomized studies, the regression discontinuity design (RDD) can be
used to identify and estimate causal effects from a "locally-randomized"
subgroup of subjects, under relatively mild conditions. However, current models
focus causal inferences on the impact of the treatment (versus non-treatment)
variable on the mean of the dependent variable, via linear regression. For
RDDs, we propose a flexible Bayesian nonparametric regression model that can
provide accurate estimates of causal effects, in terms of the predictive mean,
variance, quantile, probability density, distribution function, or any other
chosen function of the outcome variable. We illustrate the model through the
analysis of two real educational data sets, involving (resp.) a sharp RDD and a
fuzzy RDD.


title: Stacking boundaries and transport in bilayer graphene

abstract:
  Pristine bilayer graphene behaves in some instances as an insulator with a
transport gap of a few meV. This behaviour has been interpreted as the result
of an intrinsic electronic instability induced by many-body correlations.
Intriguingly, however, some samples of similar mobility exhibit good metallic
properties, with a minimal conductivity of the order of $2e^2/h$. Here we
propose an explanation for this dichotomy, which is unrelated to electron
interactions and based instead on the reversible formation of boundaries
between stacking domains (`solitons'). We argue, using a numerical analysis,
that the hallmark features of the previously inferred many-body insulating
state can be explained by scattering on boundaries between domains with
different stacking order (AB and BA). We furthermore present experimental
evidence, reinforcing our interpretation, of reversible switching between a
metallic and an insulating regime in suspended bilayers when subjected to
thermal cycling or high current annealing.


title: Weak lensing with 21cm intensity mapping at $z \sim 2-3$

abstract:
  We study how 21 cm intensity mapping can be used to measure gravitational
lensing over a wide range of redshift. This can extend weak lensing
measurements to higher redshifts than are accessible with conventional galaxy
surveys. We construct a convergence estimator taking into account the
discreteness of galaxies and calculate the expected noise level as a function
of redshift and telescope parameters. At $z \sim 2-3$ we find that a telescope
array with a collecting area $\sim 0.2 \, {\rm km}^2$ spread over a region with
diameter $\sim 2 \, {\rm km}$ would be sufficient to measure the convergence
power spectrum to high accuracy for multipoles between 10 and 1,000. We show
that these measurements can be used to constrain interacting dark energy
models.


title: An extension theorem for K\"ahler currents

abstract:
  We prove an extension theorem for Kahler currents with analytic singularities
in a Kahler class on a complex submanifold of a compact Kahler manifold.


title: Discriminative Density-ratio Estimation

abstract:
  The covariate shift is a challenging problem in supervised learning that
results from the discrepancy between the training and test distributions. An
effective approach which recently drew a considerable attention in the research
community is to reweight the training samples to minimize that discrepancy. In
specific, many methods are based on developing Density-ratio (DR) estimation
techniques that apply to both regression and classification problems. Although
these methods work well for regression problems, their performance on
classification problems is not satisfactory. This is due to a key observation
that these methods focus on matching the sample marginal distributions without
paying attention to preserving the separation between classes in the reweighted
space. In this paper, we propose a novel method for Discriminative
Density-ratio (DDR) estimation that addresses the aforementioned problem and
aims at estimating the density-ratio of joint distributions in a class-wise
manner. The proposed algorithm is an iterative procedure that alternates
between estimating the class information for the test data and estimating new
density ratio for each class. To incorporate the estimated class information of
the test data, a soft matching technique is proposed. In addition, we employ an
effective criterion which adopts mutual information as an indicator to stop the
iterative procedure while resulting in a decision boundary that lies in a
sparse region. Experiments on synthetic and benchmark datasets demonstrate the
superiority of the proposed method in terms of both accuracy and robustness.


title: Spontaneous supersymmetry breaking probed by geometric invariants

abstract:
  The presence of the Aharonov-Anandan invariant in phenomena in which vacuum
condensates are physically relevant can help to reveal the spontaneous
supersymmetry breaking induced by condensates. The analysis is presented in the
case of the Wess--Zumino model. The manifestation of the Aharonov-Anandan
invariant of atoms and their superpartners, generated at non-zero temperature,
could reveal the signature of SUSY violation in a recently proposed
experimental setup based on an optical lattice in which SUSY is broken at
non-zero temperature.


title: A New Loophole in Recent Bell Test Experiments

abstract:
  Recent experiments have reached detection efficiencies sufficient to close
the detection loophole with photons. Both experiments ran multiple successive
trials in fixed measurement configurations, rather than randomly re-setting the
measurement configurations before each measurement trial. This opens a new
potential loophole for a local hidden variable theory. The loophole invalidates
one proposed method of statistical analysis of the experimental results, as
demonstrated in this note. Therefore a different analysis will be necessary to
definitively assert that these experiments are subject only to the locality
loophole.


title: Local Detection of Quantum Correlations with a Single Trapped Ion

abstract:
  As one of the most striking features of quantum mechanics, quantum
correlations are at the heart of quantum information science. Detection of
correlations usually requires access to all the correlated subsystems. However,
in many realistic scenarios this is not feasible since only some of the
subsystems can be controlled and measured. Such cases can be treated as open
quantum systems interacting with an inaccessible environment. Initial
system-environment correlations play a fundamental role for the dynamics of
open quantum systems. Following a recent proposal, we exploit the impact of the
correlations on the open-system dynamics to detect system-environment quantum
correlations without accessing the environment. We use two degrees of freedom
of a trapped ion to model an open system and its environment. The present
method does not require any assumptions about the environment, the interaction
or the initial state and therefore provides a versatile tool for the study of
quantum systems.


title: $Out(F_3)$ Index Realization

abstract:
  By proving precisely which singularity index lists arise from the pair of
invariant foliations for a pseudo-Anosov surface homeomorphism, Masur and
Smillie determined a Teichmueller flow invariant stratification of the space of
quadratic differentials. In this paper we determine an analog to the theorem
for $Out(F_3)$. That is, we determine which index lists permitted by the
Gaboriau-Jaeger-Levitt-Lustig index sum inequality are achieved by fully
irreducible outer automorphisms of the rank-$3$ free group.


title:
Geometric invariants as detector of Hawking and Unruh effects and
  quantum field theory in curved space

abstract:
  We report on the recent results revealing the presence of geometric
invariants in all the phenomena in which vacuum condensates appear and we show
that Aharonov--Anandan phase can be used to provide the evidence of phenomena
like Hawking and Unruh effects and to test some behavior of quantum field
theory in curved space. A very precise quantum thermometer can be also built by
using geometric invariants.


title: Two-phase model for Black Hole feeding and feedback

abstract:
  We study effects of AGN feedback outflows on multi-phase inter stellar medium
(ISM) of the host galaxy. We argue that SMBH growth is dominated by accretion
of dense cold clumps and filaments. AGN feedback outflows overtake the cold
medium, compress it, and trigger a powerful starburst -- a positive AGN
feedback. This predicts a statistical correlation between AGN luminosity and
star formation rate at high luminosities. Most of the outflow's kinetic energy
escapes from the bulge via low density voids. The cold phase is pushed outward
only by the ram pressure (momentum) of the outflow. The combination of the
negative and positive forms of AGN feedback leads to an $M-\sigma$ relation
similar to the result of King (2003). Due to porosity of cold ISM in the bulge,
SMBH influence on the low density medium of the host galaxy is significant even
for SMBH well below the $M-\sigma$ mass. The role of SMBH feedback in our model
evolves in space and time with the ISM structure. In the early gas rich phase,
SMBH accelerates star formation in the bulge. During later gas poor
(red-and-dead) phases, SMBH feedback is mostly negative everywhere due to
scarcity of the cold ISM.


title:
First-principles Calculation of Atomic Forces and Structural Distortions
  in Strongly Correlated Materials

abstract:
  We introduce a novel computational approach for the investigation of complex
correlated electron materials which makes it possible to evaluate interatomic
forces and thereby determine atomic displacements and structural
transformations induced by electronic correlations. It combines \textit{ab
initio} band structure and dynamical mean-field theory and is implemented with
the linear-response formalism regarding atomic displacements. We apply this new
technique to explore structural transitions of prototypical correlated systems
such as elemental hydrogen, SrVO$_3$, and KCuF$_3$.


title:
Probability distribution for the relative velocity of colliding
  particles in a relativistic classical gas

abstract:
  We find the probability density function $\mathcal{P}(V_{\texttt{r}})$ of the
relativistic relative velocity for two colliding particles in a non-degenerate
relativistic gas. The distribution reduces to Maxwell distribution for the
relative velocity in the non-relativistic limit. We find an exact formula for
the mean value $\langle V_{\texttt{r}}\rangle$. The mean velocity tends to the
Maxwell's value in the non-relativistic limit and to the velocity of light in
the ultra-relativistic limit. At a given temperature $T$, when at least for one
of the two particles the ratio of the rest energy over the thermal energy $m
c^2/k_B T$ is smaller than 40 the Maxwell distribution is inadequate.

categories: astro-ph.CO hep-ph math-ph math.MP nucl-th


title: On the Cauchy Problem for Energy Critical Self-Gravitating Wave Maps

abstract:
  This work is on the Cauchy problem for critical wave maps coupled to
Einstein's equations of general relativity. The main result of this work is the
proof that the energy of the Einstein-equivariant wave map system does not
concentrate during the Cauchy evolution. A key ingredient in the proof is the
use of the fact that geometric mass at infinity of the Einstein-equivariant
wave map system is conserved during the evolution. However, this observation
has some subtle local implications which have been used to estimate the energy
locally. For instance, we construct a divergence-free vector field which gives
monotonicity of energy in the past null cone of any point. In addition, this
vector has also been used to prove that the energy does not concentrate away
from the axis of the domain manifold. Later, estimating the divergence of a
Morawetz vector on a truncated past null cone, we prove that the kinetic energy
does not concentrate. Finally, assuming that the target manifold satisfies the
Grillakis condition, we proceed to prove the non-concentration of energy for
the critical Einstein-equivariant wave map system. Keeping track of various
quantities of wave map relative to the evolving null geometry of the background
manifold is a recurring theme throughout the course of this work.
  Apart from a purely mathematical interest, the motivation to study critical
self-gravitating wave maps is that they occur naturally in 3+1 Einstein's
equations of general relativity. Therefore, studying critical self-gravitating
wave maps could be a fruitful way of understanding the ever elusive global
behaviour of Einstein's equations. This work is a step in this endeavour.


title: Connecting Leptonic Unitarity Triangle to Neutrino Oscillation

abstract:
  Leptonic unitarity triangle (LUT) provides a geometric description of CP
violations in the lepton-neutrino sector and is directly measurable in
principle. In this work, we reveal that the angles in the LUT have definite
physical meaning, and demonstrate the exact connection of the LUT to neutrino
oscillations. For the first time, we prove that these leptonic angles act as
phase shifts in neutrino oscillations, by shifting \Delta m^{2}L/2E to \Delta
m^{2}L/2E + \alpha, where (L, E, \alpha) denote the baseline length, neutrino
energy and corresponding angle of the LUT. Each LUT has three independent
parameters and contains only partial information of the PMNS matrix. We
demonstrate that the partial information in each LUT can describe the
corresponding neutrino oscillation. Hence, for the first time, we uncover that
any given kind of neutrino oscillations contain at most three (rather than
four) independent degrees of freedom from the PMNS matrix. This may provide a
cleaner way for fitting the corresponding oscillation data.


title:
The structure and dynamics of self-assembling colloidal monolayers in
  oscillating magnetic fields

abstract:
  Many fascinating phenomena such as large-scale collective flows, enhanced
fluid mixing and pattern formation have been observed in so-called active
fluids, which are composed of particles that can absorb energy and dissipate it
into the fluid medium. For active particles immersed in liquids, fluid-mediated
viscous stresses can play an important role on the emergence of collective
behavior. Here, we experimentally investigate their role in the dynamics of
self-assembling magnetically-driven colloidal particles which can rapidly form
organized hexagonal structures. We find that viscous stresses reduce hexagonal
ordering, generate smaller clusters, and significantly decrease the rate of
cluster formation, all while holding the system at constant number density.
Furthermore, we show that time and length scales of cluster formation depend on
the Mason number (Mn), or ratio of viscous to magnetic forces, scaling as t /
Mn and L / Mn^(1/2). Our results suggest that viscous stresses hinder
collective behavior in a self-assembling colloidal system.


title: Classification of Isomonodromy Problems on Elliptic Curves

abstract:
  We consider the isomonodromy problems for flat $G$-bundles over punctured
elliptic curves $\Sigma_\tau$ with regular singularities of connections at
marked points. The bundles are classified by their characteristic classes.
These classes are elements of the second cohomology group
$H^2(\Sigma_\tau,{\mathcal Z}(G))$, where ${\mathcal Z}(G)$ is the center of
$G$. For any complex simple Lie group $G$ and arbitrary class we define the
moduli space of flat bundles, and in this way construct the monodromy
preserving equations in the Hamiltonian form and their Lax representations. In
particular, they include the Painlev\'e VI equation, its multicomponent
generalizations and elliptic Schlesinger equations. The general construction is
described for punctured curves of arbitrary genus. We extend the
Drinfeld-Simpson (double coset) description of the moduli space of Higgs
bundles to the case of flat connections. This local description allows us to
establish the Symplectic Hecke Correspondence for a wide class of the monodromy
preserving equations classified by characteristic classes of underlying
bundles. In particular, the Painlev\'e VI equation can be described in terms of
${\rm SL}(2, {\mathbb C})$-bundles. Since ${\mathcal Z}({\rm SL}(2, {\mathbb
C}))= {\mathbb Z}_2$, the Painlev\'e VI has two representations related by the
Hecke transformation: 1) as the well-known elliptic form of the Painlev\'e
VI(for trivial bundles); 2) as the non-autonomous Zhukovsky-Volterra gyrostat
(for non-trivial bundles).


title: Unified description for kappa-deformations of orthogonal groups

abstract:
  In this paper we provide universal formulas describing Drinfeld-type
quantization of inhomogeneous orthogonal groups determined by a metric tensor
of an arbitrary signature living in a spacetime of arbitrary dimension. The
metric tensor does not need to be in diagonal form and kappa-deformed
coproducts are presented in terms of classical generators. It opens the
possibility for future applications in deformed general relativity. The
formulas depend on the choice of an additional vector field which parameterizes
classical r-matrices. Non-equivalent deformations are then labeled by the
corresponding type of stability subgroups. For the Lorentzian signature it
covers three (non-equivalent) Hopf-algebraic deformations: time-like,
space-like (a.k.a. tachyonic) and light-like (a.k.a. light-cone) quantizations
of the Poincare algebra. Finally the existence of the so-called Majid-Ruegg
(non-classical) basis is reconsidered.


title:
Time series prediction via aggregation : an oracle bound including
  numerical cost

abstract:
  We address the problem of forecasting a time series meeting the Causal
Bernoulli Shift model, using a parametric set of predictors. The aggregation
technique provides a predictor with well established and quite satisfying
theoretical properties expressed by an oracle inequality for the prediction
risk. The numerical computation of the aggregated predictor usually relies on a
Markov chain Monte Carlo method whose convergence should be evaluated. In
particular, it is crucial to bound the number of simulations needed to achieve
a numerical precision of the same order as the prediction risk. In this
direction we present a fairly general result which can be seen as an oracle
inequality including the numerical cost of the predictor computation. The
numerical cost appears by letting the oracle inequality depend on the number of
simulations required in the Monte Carlo approximation. Some numerical
experiments are then carried out to support our findings.


title: A note on vortices from Lorentz-violating models

abstract:
  We consider two self-dual abelian Higgs systems obtained from Lorentz
breaking symmetry models by dimensional reduction. For the first model, we show
that the self-dual equations are identical to those of Nielsen-Olesen vortices.
Also, we show that our vortices have electric charge. In the second case we
show that self-dual Chern-Simons-Higgs vortices without electric charge are
possible.


title: Multiplicate inverse forms of terminating hypergeometric series

abstract:
  The multiplicate form of Gould--Hsu's inverse series relations enables to
investigate the dual relations of the Chu-Vandermonde-Gau{\ss}'s, the
Pfaff-Saalsch\"utz's summation theorems and the binomial convolution formula
due to Hagen and Rothe. Several identitity and reciprocal relations are thus
established for terminating hypergeometric series. By virtue of the duplicate
inversions, we establish several dual formulae of Chu-Vandermonde-Gau{\ss}'s
and Pfaff-Saalsch\"utz's summation theorems in Section (3)\cite{ChuVanGauss}
and (4)\cite{PfaffSaalsch}, respectively. Finally, the last section is devoted
to deriving several identities and reciprocal relations for terminating
balanced hypergeometric series from Hagen-Rothe's convolution identity in
accordance with the duplicate, triplicate and multiplicate inversions.


title:
A numerical algorithm for fully nonlinear HJB equations: an approach by
  control randomization

abstract:
  We propose a probabilistic numerical algorithm to solve Backward Stochastic
Differential Equations (BSDEs) with nonnegative jumps, a class of BSDEs
introduced in [9] for representing fully nonlinear HJB equations. In
particular, this allows us to numerically solve stochastic control problems
with controlled volatility, possibly degenerate. Our backward scheme, based on
least-squares regressions, takes advantage of high-dimensional properties of
Monte-Carlo methods, and also provides a parametric estimate in feedback form
for the optimal control. A partial analysis of the error of the scheme is
provided, as well as numerical tests on the problem of superreplication of
option with uncertain volatilities and/or correlations, including a detailed
comparison with the numerical results from the alternative scheme proposed in
[7].


title: Constrain on superconductivity of potassium intercalated phenanthrene

abstract:
  Raman-scattering measurements are performed in K${_x}$phenanthrene with the
nominal value ${x}$ ranging from 0 to 6.0 at room temperature. Based on the
Raman spectra, two phases (${x}$ = 3.0 and 4.0) are observed among the
K${_x}$phenanthrene, and the immediate phase (${x}$ = 3.5) is produced. Only
the ${x}$ = 3.0 phase is found to exhibit the superconducting transition at 5
K. The C-C stretching mods are observed to broaden and become disorder in
K${_x}$phenanthrene (nominal value ${x}$ =2.0, 2.5, 6.0), indicating some
molecular disorder in the metal intercalation process. This disorder is
expected to influence the nonmetallic nature of these materials. The absence of
metallic characteristics in those nonsuperconducting phases is provided from
the calculated electronic structures based on the local density approximation.


title:
Discrete time approximation of fully nonlinear HJB equations via BSDEs
  with nonpositive jumps

abstract:
  We propose a new probabilistic numerical scheme for fully nonlinear equation
of Hamilton-Jacobi-Bellman (HJB) type associated to stochastic control problem,
which is based on the Feynman-Kac representation in [12] by means of control
randomization and backward stochastic differential equation with nonpositive
jumps. We study a discrete time approximation for the minimal solution to this
class of BSDE when the time step goes to zero, which provides both an
approximation for the value function and for an optimal control in feedback
form. We obtained a convergence rate without any ellipticity condition on the
controlled diffusion coefficient. Explicit implementable scheme based on
Monte-Carlo simulations and empirical regressions, associated error analysis,
and numerical experiments are performed in the companion paper [13].


title:
Neutrino-nucleus interaction models and their impact on oscillation
  analyses

abstract:
  In neutrino oscillation experiments, neutrino interactions at the detector
are simulated using event generators which attempt to reflect our understanding
of nuclear physics. We study the impact of different neutrino interactions and
nuclear models on the determination of neutrino oscillation parameters. We use
two independent neutrino event generators, GENIE and GiBUU, and apply them to a
setup with a conventional neutrino beam aiming at a water \v{C}erenkov
detector, for which only the QE-like sample is selected. Subsequently, we
perform a fit to the oscillation parameters in the $\nu_\mu$ disappearance
channel.


title: Theory of G2 Cloud Multi-Wavelength Emission

abstract:
  An object called G2 was recently discovered moving towards the supermassive
black hole in the Galactic Center. G2 emits infrared (IR) lines and continuum,
which allows constraining its properties. The question is still unresolved
whether G2 has a central windy star or it is a coreless cloud. Assuming the
object is a cloud originating near the apocenter I perform line/continuum IR
diagnostics, revisit estimates of non-thermal emission from pericenter passage,
and speculate about future observational prospects. This work is partially
reported in arXiv:1309.2282 and partially consists of new ideas discussed at
the conference.


title:
Relativistic $<\sigma v_\text{rel}>$ in the calculation of relics
  abundances: a closer look

abstract:
  In this paper we clarify the relation between the invariant relativistic
relative velocity $V_\text{r}$, the M\o{}ller velocity $\bar{v}$, and the
non-relativistic relative velocity $v_r$. Adopting $V_{\text{r}}$ as the true
physical relative velocity for pair-collisions in a non-degenerate relativistic
gas, we show that in the frame co-moving with the gas (i) the thermally
averaged cross section times relative velocity $<\sigma v_\text{rel}>$ that
appears in the density evolution equation for thermal relics is reformulated
only in terms of $V_\text{r}$ and $\mathcal{P}(V_{\text{r}})$ in a manifestly
Lorentz invariant form; (ii) the frame-dependent issues of the standard
formulation in terms of the M\o{}ller velocity, as well as "superluminal"
relative velocities, are not present in this formulation. Furthermore,
considering the annihilation of dark matter into a particle-antiparticle pair
$f\bar{f}$, in the cases $m_f=0$, $m_f=m$ and $m_f \gg m$, we find that the
coefficients of the low velocity expansion of $<\sigma V_{\text{r}}>$ admit an
exact analytical representation in terms of the Meijer $G$ functions that can
be reduced to combinations of modified Bessel functions of the second kind.


title: On the Riemann problem for the simplified Bouchut-Boyaval system

abstract:
  In this paper we study the one-dimensional Riemann problem for a new
hyperbolic system of three conservation laws of Temple class. This systems it
is a simplification of a recently propose system of five conservations laws by
Bouchut and Boyaval that model viscoelastic fluids. An important issues is that
the considered $3 \times 3$ system is such that every characteristic field is
linearly degenerate. Then, in despite of the fact that it is of Temple class,
the analysis of the Cauchy problem is more involved since general results for
such a systems are not yet available. We show a explicit solution for the
Cauchy problem with initial data in $L^\infty$. We also study the Riemann
problem for this system. Under suitable generalized Rankine-Hugoniot relation
and entropy condition, both existence and uniqueness of particular delta-shock
type solutions are established.


title:
On the quasi-invariance of the Wiener measure on path spaces and the
  anticipative integrals over a Riemannian manifold

abstract:
  Some parts of stochastic analysis on curved spaces are revisted. A concise
proof of the quasi-invariance of the Wiener measure on the path spaces over a
Riemannian manifold is presented. The shifts are allowed to be in the
Cameron-Martin space and random. The second part of the paper presents some
remarks on the anticipative integrals on Riemannian manifolds.


title: A light readout system for gas TPCs

abstract:
  A novel light detection scheme has been tested for use in medium-pressure gas
TPCs, in view of rare events searches in low energy particle physics. It has
the advantage of minimal interference with the ionization collection system,
used for track imaging. It provides an absolute time reference, which allows an
absolute determination of the Z coordinate of events, along the direction of
the drift field. This makes possible a fiducial cut along the Z-axis, allowing
to reduce the background from the ends of the drift volume.


title:
Magnetic-film atom chip with 10 $\mu$m period lattices of microtraps for
  quantum information science with Rydberg atoms

abstract:
  We describe the fabrication and construction of a setup for creating lattices
of magnetic microtraps for ultracold atoms on an atom chip. The lattice is
defined by lithographic patterning of a permanent magnetic film. Patterned
magnetic-film atom chips enable a large variety of trapping geometries over a
wide range of length scales. We demonstrate an atom chip with a lattice
constant of 10 $\mu$m, suitable for experiments in quantum information science
employing the interaction between atoms in highly-excited Rydberg energy
levels. The active trapping region contains lattice regions with square and
hexagonal symmetry, with the two regions joined at an interface. A structure of
macroscopic wires, cut out of a silver foil, was mounted under the atom chip in
order to load ultracold $^{87}$Rb atoms into the microtraps. We demonstrate
loading of atoms into the square and hexagonal lattice sections simultaneously
and show resolved imaging of individual lattice sites. Magnetic-film lattices
on atom chips provide a versatile platform for experiments with ultracold
atoms, in particular for quantum information science and quantum simulation.


title: Character rigidity for lattices and commensurators

abstract:
  We prove an operator algebraic superrigidity statement for homomorphisms of
irreducible lattices, and also their commensurators, in certain higher-rank
groups into unitary groups of finite factors. This extends the authors'
previous work regarding non-free measure-preserving actions, and also answers a
question of Connes for such groups.


title: The importance of crowding in signaling, genetic, and metabolic networks

abstract:
  It is now well established that the cell is a highly crowded environment.
Yet, the effects of crowding on the dynamics of signaling pathways, gene
regulation networks and metabolic networks are still largely unknown. Crowding
can alter both molecular diffusion and the equilibria of biomolecular
reactions. In this review, we first discuss how diffusion can affect
biochemical networks. Diffusion of transcription factors can increase noise in
gene expression, while diffusion of proteins between intracellular compartments
or between cells can reduce concentration fluctuations. In push-pull networks
diffusion can impede information transmission, while in multi-site protein
modification networks diffusion can qualitatively change the macroscopic
response of the system, such as the loss or emergence of bistability. Moreover,
diffusion can directly change the metabolic flux. We describe how crowding
affects diffusion, and thus how all these phenomena are influenced by crowding.
Yet, a potentially more important effect of crowding on biochemical networks is
mediated via the shift in the equilibria of bimolecular reactions, and we
provide computational evidence that supports this idea. Finally, we discuss how
the effects of crowding can be incorporated in models of biochemical networks.


title:
Some rigidity results for noncompact gradient steady Ricci solitons and
  Ricci-flat manifolds

abstract:
  Gradient steady Ricci solitons are natural generalizations of Ricci-flat
manifolds. In this article, we prove a curvature gap theorem for gradient
steady Ricci solitons with nonconstant potential functions; and a curvature gap
theorem for Ricci-flat manifolds, removing the volume growth assumptions in
known results.


title: Constructing Space From Entanglement Entropy

abstract:
  We explicitly reconstruct the metric of a gravity dual to field theories
using known entanglement entropies using the Ryu-Takayanagi formula. We use for
examples CFT's in $d = 1$, 2 and 3 as well as CFT on a circle of length $L$ and
a thermal CFT at temperature $\beta^{-1}$. We also give the first several
coefficients in the Taylor series of the metric for a general entanglement
entropy in 1+1 dimensions as well as some examples (Appendix B). The beginnings
of a dictionary between the dual theories appears naturally and does not need
to be inserted by hand. For example, the dictionary entries $c=3R/2G_N$ for 1+1
dimensional CFT and $N^2 = \pi R^3/2G_N$ for $\mathcal{N}=4$ SYM in 3+1
dimensions are forced upon us. After uploading this paper I was made aware of
(arXiv:1012.1812) which solves the same problem in a similar way.


title: Multi-Shell Ankylography

abstract:
  Three-dimensional (3D) imaging techniques appeal to a broad range of
scientific and industrial applications. Typically, projection slice theorem
enables multiple two-dimensional (2D) projections of an object to be combined
in the Fourier domain to yield a 3D image. However, traditional techniques
require a significant number of projections. The significant number of views
required in conventional tomography not only complicates such imaging
modalities, but also limits their ability to image samples that are sensitive
to radiation dose or are otherwise unstable in time. In this work, we
demonstrate through numerical simulations and an eigenvalue analysis that a
recently developed technique called ankylography enables 3D image
reconstruction using much fewer views than conventional tomography. Such a
technique with the ability to obtain the 3D structure information from a few
views is expected to find applications in both optical and x-ray imaging
fields.


title: Linear response theory for superradiant lasers

abstract:
  We theoretically study a superradiant laser, deriving both the steady-state
behaviors and small-amplitude responses of the laser's atomic inversion, atomic
polarization, and light field amplitude. Our minimum model for a three-level
laser includes atomic population accumulating outside of the lasing transition
and dynamics of the atomic population distribution causing cavity frequency
tuning, as can occur in realistic experimental systems. We show that the
population dynamics can act as real-time feedback to stabilize or de-stabilize
the laser's output power, and we derive the cavity frequency tuning for a Raman
laser. We extend the minimal model to describe a cold-atom Raman laser using
$^{87}$Rb, showing that the minimal model qualitatively captures the essential
features of the more complex system. This work informs our understanding of the
stability of proposed millihertz linewidth lasers based on ultranarrow optical
atomic transitions and will guide the design and development of these
next-generation optical frequency references.


title: Anti-screening ferromagnetic superconductivity

abstract:
  We consider the Ginzburg-Landau mean field theory of ferromagnetic
superconductors with complex order parameter $\psi_i, i=1,2,3$. Below the
critical temperature superconductivity is generated by means of a tachyonic
term in the free energy $-\alpha |\psi_i|^2$ $(\alpha>0)$, stabilized by a
$\psi^4$-term. However, we show that when $\alpha$ becomes negative
superconductivity can also be generated spontaneously by the magnetic field
through the Zeeman like coupling between the field and the spin of the order
parameter, in analogy with what happens in W-meson condensation. We also show
that this mechanism leads to a vortex lattice which has anti-screening
currents, enhancing the magnetic field instead of counteracting it. The lattice
of vortices is a collective phenomenon where the individual elements do not
exist in isolated form. If the parameter $\alpha$ vanishes it is possible to
obtain an explicit form of the vortex lattice in terms of Weierstrass'
p-function.

categories: hep-th cond-mat.supr-con math-ph math.MP


title: D-Brane Probes in the Matrix Model

abstract:
  Recently, a new approach to large N gauge theories, based on a generalization
of the concept of D-brane probes to any gauge field theory, was proposed. In
the present note, we compute the probe action in the one matrix model with a
quartic potential. This allows to illustrate several non-trivial aspects of the
construction in an exactly solvable set-up. One of our main goal is to test the
bare bubble approximation. The approximate free energy found in this
approximation, which can be derived from a back-of-an-envelope calculation,
matches the exact result for all values of the 't Hooft coupling with a
surprising accuracy. Another goal is to illustrate the remarkable properties of
the equivariant partial gauge-fixing procedure, which is at the heart of the
formalism. For this we use a general xi-gauge to compute the brane action. The
action depends on xi in a very non-trivial way, yet we show explicitly that its
critical value does not and coincide with twice the free energy, as required by
general consistency. This is made possible by a phenomenon of ghost
condensation and the spontaneous breaking of the equivariant BRST symmetry.


title: Experiences with OpenMP in tmLQCD

abstract:
  An overview is given of the lessons learned from the introduction of
multi-threading using OpenMP in tmLQCD. In particular, programming style,
performance measurements, cache misses, scaling, thread distribution for hybrid
codes, race conditions, the overlapping of communication and computation and
the measurement and reduction of certain overheads are discussed. Performance
measurements and sampling profiles are given for different implementations of
the hopping matrix computational kernel.


title:
A first look at maximally twisted mass lattice QCD calculations at the
  physical point

abstract:
  In this contribution, a first look at simulations using maximally twisted
mass Wilson fermions at the physical point is presented. A lattice action
including clover and twisted mass terms is presented and the Monte Carlo
histories of one run with two mass-degenerate flavours at a single lattice
spacing are shown. Measurements from the light and heavy-light pseudoscalar
sectors are compared to previous $N_f = 2$ results and their phenomenological
values. Finally, the strategy for extending simulations to $N_f = 2 + 1 + 1$ is
outlined.


title: Investigating Unitarity in Presence of Anomalous Couplings

abstract:
  We perform a model independent analysis of the helicity amplitudes at high
energy for all the $2\to2$ scattering processes involving gauge and Higgs
bosons in the presence of anomalous $WWV$, $WWVV$, $VVH$, $VVHH$ ($V\equiv
Z,\gamma$ and $W^\pm$), $HHHH$ and $HHH$ interactions. We obtain the
perturbative unitarity constraints on anomalous couplings by demanding the
vanishing of terms proportional to $s^2$ and $s^{3/2}$ in the helicity
amplitudes. Using these constraints, we also compute the upper bound on all the
anomalous couplings from terms linear in $s$.
  Further, assuming all anomalous couplings to have arisen only from dimension
six operators, we show that the perturbative unitarity violation can be evaded
up to $\sim$ 9 TeV corresponding to the best fit values of $f_{WW}/\Lambda^2$
and $f_{BB}/\Lambda^2$ from the combined analysis of Tevatron and LHC data.


title: Chacon's Type Ergodic Transformations with Unbounded Arithmetic Spacers

abstract:
  The following generalizations of the Chacon map are proposed: instead of
classical constant spacer sequence $(0,1,0)$ let a sequence $(0,s_j,0)$ be one
with unbounded $s_j$. (We mention also an analogue of the historical Chacon map
with spacer sequences in the form $(0,s_j)$.) This narrow class of rank-one
transformations may be abundant source of open questions. All such
constructions have partial rigidity, but some other properties could be
different. For root sequence, $ s_j= [\sqrt{j}]$, (or $ s_j= [\ln{j}]$) the
corresponding action is rigid, moreover it possesses all polynomials in its
weak closure. In the linear case $s_j={j}$ we get (as well as for the classical
Chacon transformation) the property of minimal self-joinings (MSJ). We present
some observations about MSJ, mild mixing, partial mixing, $\ae$-mixing, absence
of factors, triviality of centralizer and spectral primality, state several
problems, and mention exponential "self-similar" Chacon transformations and
flows on infinite measure spaces.


title:
Optical and Near-IR Observations of the Faint and Fast 2008ha-like
  Supernova 2010ae

abstract:
  A comprehensive set of optical and near-infrared (NIR) photometry and
spectroscopy is presented for the faint and fast 2008ha-like supernova (SN)
2010ae. Contingent on the adopted value of host extinction, SN 2010ae reached a
peak brightness of -13.8 > M_V > -15.3 mag, while modeling of the UVOIR light
curve suggests it produced 0.003--0.007 M_sun of (56)Ni, ejected 0.30--0.60
M_sun of material, and had an explosion energy of 0.04--0.30x10^51 erg. The
values of these explosion parameters are similar to the peculiar SN 2008ha
--for which we also present previously unpublished early phase optical and NIR
light curves-- and places these two transients at the faint end of the
2002cx-like SN population. Detailed inspection of the post maximum NIR
spectroscopic sequence indicates the presence of a multitude of spectral
features, which are identified through SYNAPPS modeling to be mainly attributed
to Co II. Comparison with a collection of published and unpublished NIR spectra
of other 2002cx-like SNe, reveals that a Co II footprint is ubiquitous to this
subclass of transients, providing a link to Type Ia SNe. A visual-wavelength
spectrum of SN 2010ae obtained at +252 days past maximum shows a striking
resemblance to a similar epoch spectrum of SN 2002cx. However, subtle
differences in the strength and ratio of calcium emission features, as well as
diversity among similar epoch spectra of other 2002cx-like SNe indicates a
range of physical conditions of the ejecta, highlighting the heterogeneous
nature of this peculiar class of transients.


title: Triangular antiferromagnet with nonmagnetic impurities

abstract:
  The effect of nonmagnetic impurities on the phase diagram of the classical
Heisenberg antiferromagnet on a triangular lattice is investigated. We present
analytical arguments confirmed by numerical calculations that at zero
temperature vacancies stabilize a conical state providing an example of "order
by quenched disorder" effect. Competition between thermal fluctuations and the
site disorder leads to a complicated H-T phase diagram, which is deduced from
the classical Monte Carlo simulations for a representative vacancy
concentration. For the XY triangular-lattice antiferromagnet with in-plane
external field nonmagnetic impurities stabilize the fan-like spin structure. We
also briefly discuss the effect of quantum fluctuations.


title: A message-passing algorithm for multi-agent trajectory planning

abstract:
  We describe a novel approach for computing collision-free \emph{global}
trajectories for $p$ agents with specified initial and final configurations,
based on an improved version of the alternating direction method of multipliers
(ADMM). Compared with existing methods, our approach is naturally
parallelizable and allows for incorporating different cost functionals with
only minor adjustments. We apply our method to classical challenging instances
and observe that its computational requirements scale well with $p$ for several
cost functionals. We also show that a specialization of our algorithm can be
used for {\em local} motion planning by solving the problem of joint
optimization in velocity space.


title:
MARS spectral molecular imaging of lamb tissue: data collection and
  image analysis

abstract:
  Spectral molecular imaging is a new imaging technique able to discriminate
and quantify different components of tissue simultaneously at high spatial and
high energy resolution. Our MARS scanner is an x-ray based small animal CT
system designed to be used in the diagnostic energy range (20 to 140 keV). In
this paper, we demonstrate the use of the MARS scanner, equipped with the
Medipix3RX spectroscopic photon-processing detector, to discriminate fat,
calcium, and water in tissue. We present data collected from a sample of lamb
meat including bone as an illustrative example of human tissue imaging. The
data is analyzed using our 3D Algebraic Reconstruction Algorithm (MARS-ART) and
by material decomposition based on a constrained linear least squares
algorithm. The results presented here clearly show the quantification of
lipid-like, water-like and bone-like components of tissue. However, it is also
clear to us that better algorithms could extract more information of clinical
interest from our data. Because we are one of the first to present data from
multi-energy photon-processing small animal CT systems, we make the raw,
partial and fully processed data available with the intention that others can
analyze it using their familiar routines. The raw, partially processed and
fully processed data of lamb tissue along with the phantom calibration data can
be found at [http://hdl.handle.net/10092/8531].


title: Incremental Discovery of Prominent Situational Facts

abstract:
  We study the novel problem of finding new, prominent situational facts, which
are emerging statements about objects that stand out within certain contexts.
Many such facts are newsworthy---e.g., an athlete's outstanding performance in
a game, or a viral video's impressive popularity. Effective and efficient
identification of these facts assists journalists in reporting, one of the main
goals of computational journalism. Technically, we consider an ever-growing
table of objects with dimension and measure attributes. A situational fact is a
"contextual" skyline tuple that stands out against historical tuples in a
context, specified by a conjunctive constraint involving dimension attributes,
when a set of measure attributes are compared. New tuples are constantly added
to the table, reflecting events happening in the real world. Our goal is to
discover constraint-measure pairs that qualify a new tuple as a contextual
skyline tuple, and discover them quickly before the event becomes yesterday's
news. A brute-force approach requires exhaustive comparison with every tuple,
under every constraint, and in every measure subspace. We design algorithms in
response to these challenges using three corresponding ideas---tuple reduction,
constraint pruning, and sharing computation across measure subspaces. We also
adopt a simple prominence measure to rank the discovered facts when they are
numerous. Experiments over two real datasets validate the effectiveness and
efficiency of our techniques.


title: Exceptional orthogonal polynomials and generalized Schur polynomials

abstract:
  We show that the exceptional orthogonal polynomials can be viewed as
confluent limits of the generalized Schur polynomials introduced by Sergeev and
Veselov.


title: The N-Leg spin-S Heisenberg ladders: A DMRG study

abstract:
  We investigate the N-leg spin-S Heisenberg Ladders by using the density
matrix renormalization group method. We present estimates of the spin gap
$\Delta_{s}$ and of the ground state energy per site $e_{\infty}^{N}$ in the
thermodynamic limit for ladders with widths up to six legs and spin
$S\leq\frac{5}{2}$. We also estimate the ground state energy per site
$e_{\infty}^{2D}$ for the infinite two-dimensional spin-S Heisenberg model. Our
results support that for ladders with semi-integer spins the spin excitation is
gapless for $N$ odd and gapped for N even. Whereas for integer spin ladders the
spin gap is nonzero, independent of the number of legs. Those results agree
with the well known conjectures of Haldane and S\'en\'echal-Sierra for chains
and ladders, respectively. We also observe edge states for ladders with $N$
odd, similar to what happens in the integer spin chains.


title:
Nonlinear and additive white noise perturbations of linear delay
  differential equations at the verge of instability: an averaging approach

abstract:
  The characteristic equation for a linear delay differential equation (DDE)
has countably infinite roots on the complex plane. We deal with linear DDEs
that are on the verge of instability, i.e. a pair of roots of the
characteristic equation (eigenvalues) lie on the imaginary axis of the complex
plane, and all other roots have negative real parts. We show that, when the
system is perturbed by small noise, under an appropriate change of time scale,
the law of the amplitude of projection onto the critical eigenspace is close to
the law of a certain one-dimensional stochastic differential equation (SDE)
without delay. Further, we show that the projection onto the stable eigenspace
is small. These results allow us to give an approximate description of the
delay-system using an SDE (without delay) of just one dimension. The proof is
based on the martingale problem technique.


title:
A Study of Speed of the Boundary Element Method as applied to the
  Realtime Computational Simulation of Biological Organs

abstract:
  In this work, possibility of simulating biological organs in realtime using
the Boundary Element Method (BEM) is investigated. Biological organs are
assumed to follow linear elastostatic material behavior, and constant boundary
element is the element type used. First, a Graphics Processing Unit (GPU) is
used to speed up the BEM computations to achieve the realtime performance.
Next, instead of the GPU, a computer cluster is used. Results indicate that BEM
is fast enough to provide for realtime graphics if biological organs are
assumed to follow linear elastostatic material behavior. Although the present
work does not conduct any simulation using nonlinear material models, results
from using the linear elastostatic material model imply that it would be
difficult to obtain realtime performance if highly nonlinear material models
that properly characterize biological organs are used. Although the use of BEM
for the simulation of biological organs is not new, the results presented in
the present study are not found elsewhere in the literature.

categories: cs.CE cs.DC cs.MS physics.comp-ph physics.med-ph


title: Kinematic Constraints on Absorption of Ultraintense Laser Light

abstract:
  We derive upper and lower bounds on the absorption of ultraintense laser
light by solids as a function of fundamental laser and plasma parameters. These
limits emerge naturally from constrained optimization techniques applied to a
generalization of the laser-solid interaction as a strongly-driven,
relativistic, two degree of freedom Maxwell-Vlasov system. We demonstrate that
the extrema and the phase-space-averaged absorption must always increase with
intensity, and increase most rapidly when $10^{18} < I_L \ \lambda_L^2 <
10^{20}$ W $\mu$m$^2/$cm$^{2}$. Our results indicate that the fundamental
empirical trend towards increasing fractional absorption with irradiance
therefore reflects the underlying phase space constraints.


title: On Type 0 Open String Amplitudes and the Tensionless Limit

abstract:
  The sum over planar multi-loop diagrams in the NS+ sector of type 0 open
strings in flat spacetime has been proposed by Thorn as a candidate to resolve
non-perturbative issues of gauge theories in the large $N$ limit. With $SU (N)$
Chan-Paton factors, the sum over planar open string multi-loop diagrams
describes the 't Hooft limit $N\to \infty$ with $Ng_s^2$ held fixed. By
including only planar diagrams in the sum the usual mechanism for the
cancellation of loop divergences (which occurs, for example, among the planar
and M\"obius strip diagrams by choosing a specific gauge group) is not
available and a renormalization procedure is needed. In this article the
renormalization is achieved by suspending total momentum conservation by an
amount $p\equiv \sum_i^n k_i\neq 0$ at the level of the integrands in the
integrals over the moduli and analytically continuing them to $p=0$ at the very
end. This procedure has been successfully tested for the 2 and 3 gluon planar
loop amplitudes by Thorn. Gauge invariance is respected and the correct running
of the coupling in the limiting gauge field theory was also correctly obtained.
In this article we extend those results in two directions. First, we generalize
the renormalization method to an arbitrary $n$-gluon planar loop amplitude
giving full details for the 4-point case. One of our main results is to provide
a fully renormalized amplitude which is free of both UV and the usual spurious
divergences leaving only the physical singularities in it. Second, using the
complete renormalized amplitude, we extract the high-energy scattering regime
at fixed angle (tensionless limit). Apart from obtaining the usual exponential
falloff at high energies, we compute the full dependence on the scattering
angle which shows the existence of a smooth connection between the Regge and
hard scattering regimes.


title:
A note on the gaps in the support of discretely infinitely divisible
  laws

abstract:
  In this note we discuss the nature of gaps in the support of a discretely
infinitely divisible distribution from the angle of compound Poisson
laws/processes. The discussion is extended to infinitely divisible
distributions on the non-negative real line.


title:
Constraints on Massive Star Formation: Cygnus OB2 was always an
  Association

abstract:
  We examine substructure and mass segregation in the massive OB association
Cygnus OB2 to better understand its initial conditions. Using a well understood
Chandra X-ray selected sample of young stars we find that Cyg OB2 exhibits
considerable physical substructure and has no evidence for mass segregation,
both indications that the association is not dynamically evolved. Combined with
previous kinematical studies we conclude that Cyg OB2 is dynamically very
young, and what we observe now is very close to its initial conditions: Cyg OB2
formed as a highly substructured, unbound association with a low volume density
(< 100 stars/pc^3). This is inconsistent with the idea that all stars form in
dense, compact clusters. The massive stars in Cyg OB2 show no evidence for
having formed particularly close to one another, nor in regions of higher than
average density. Since Cyg OB2 contains stars as massive as ~100 Mo this result
suggests that very massive stars can be born in relatively low-density
environments. This would imply that the massive stars in Cyg OB2 did not form
by competitive accretion, or by mergers.


title: Resolving the Structure of Black Holes: Philosophizing with a Hammer

abstract:
  We give a broad conceptual review of what we have learned about black holes
and their microstate structure from the study of microstate geometries and
their string theory limits. We draw upon general relativity, supergravity,
string theory and holographic field theory to extract universal ideas and
structural features that we expect to be important in resolving the information
problem and understanding the microstate structure of Schwarzschild and Kerr
black holes. In particular, we emphasize two conceptually and physically
distinct ideas, with different underlying energy scales: a) the transition that
supports the microstate structure and prevents the formation of a horizon and
b) the representation of the detailed microstate structure itself in terms of
fluctuations around the transitioned state. We also show that the supergravity
mechanism that supports microstate geometries becomes, in the string theory
limit, either brane polarization or the excitation of non-Abelian degrees of
freedom. We thus argue that if any mechanism for supporting structure at the
horizon scale is to be given substance within string theory then it must be
some manifestation of microstate geometries.


title: On the Marginally Relevant Operator in z=2 Lifshitz Holography

abstract:
  We study holographic renormalization and RG flow in a strongly-coupled
Lifshitz-type theory in 2+1 dimensions with dynamical exponent z=2. The
bottom-up gravity dual we use is 3+1 dimensional Einstein gravity coupled to a
massive vector field. This model contains a marginally relevant operator around
the Lifshitz fixed point. We show how holographic renormalization works in the
presence of this marginally relevant operator without the need to introduce
explicitly cutoff-dependent counterterms. A simple closed-form expression is
found for the renormalized on-shell action. We also discuss how asymptotically
Lifshitz geometries flow to AdS in the interior due to the marginally relevant
operator. We study the behavior of the renormalized entanglement entropy and
confirm that it decreases monotonically along the Lifshitz-to-AdS RG flow.


title: Higher-derivative N=4 superparticle in three-dimensional spacetime

abstract:
  Using the coset approach (nonlinear realization) we construct component
actions for a superparticle in three-dimensional spacetime with N=4
supersymmetry partially broken to N=2. These actions may contain an anyonic
term and the square of the first extrinsic worldline curvature. We present the
supercharges for the unbroken and broken supersymmetries as well as the
Hamiltonian for the supersymmetric anyon. In terms of the nonlinear realization
superfields, the superspace actions take a simple form in all cases.


title:
Competition Between Kondo Screening and Magnetism at the
  LaAlO$_3$/SrTiO$_3$ Interface

abstract:
  We present a theory of magnetic and magneto-transport phenomena at
LaAlO$_3$/SrTiO$_3$ interfaces, which as a central ingredient includes coupling
between the conduction bands and local magnetic moments originating from charge
traps at the interface. Tuning the itinerant electron density in the model
drives transitions between a heavy Fermi liquid phase with screened moments and
various magnetic states. The dependence of the magnetic phenomena on the
electron density or gate voltage stems from competing magnetic interactions
between the local moments and the different conduction bands. At low densities
only the lowest conduction band, composed of the $d_{xy}$ orbitals of Ti, is
occupied. Its antiferromagnetic interaction with the local moments leads to
screening of the moments at a Kondo scale that increases with density. However,
above a critical density, measured in experiments to be $n_c\approx 1.7\times
10^{13} cm^{-2}$, the $d_{xz}$ and $d_{yz}$ bands begin to populate. Their
ferromagnetic interaction with the local moments competes with the
antiferromagnetic interaction of the $d_{xy}$ band leading to eventual
reduction of the Kondo scale with density. We explain the distinct magneto
transport regimes seen in experiments as manifestations of the magnetic phase
diagram computed from the model. We present new data showing a relation between
the anomalous Hall effect and the resistivity in the system. The data strongly
suggests that the concentration of local magnetic moments affecting the
transport in the system is much lower than the carrier density, in accord with
the theoretical model.


title: Angular Distributions as Lifetime Probes

abstract:
  If new TeV scale particles are discovered, it will be important to determine
their width. There is, however, a problematic region, where the width is too
small to be determined directly, and too large to generate a secondary vertex.
For a collection of colored, spin polarized particles, hadronization
depolarizes the particles prior to their decay. The amount of depolarization
can be used to probe the lifetime in the problematic region. In this paper we
apply this method to a realistic scenario of a top-like particle that can be
produced at the LHC. We study how depolarization affects the angular
distributions of the decay products and derive an equation for the
distributions that is sensitive to the lifetime.


title:
Stability and existence analysis of static black holes in pure Lovelock
  theories

abstract:
  In this paper, we study existence and stability of static black holes in
Lovelock theories with a particular focus on pure Lovelock black holes. We
derive the equation of stability from action without using S-deformation
approach. It turns out that though pure-Lovelock black hole in even dimension
is always unstable, however introduction of $\Lambda$ stablizes it by
prescribing a lower threshold mass while there also exists an upper bound on
mass which is given by existence of horizon. We also study stability of
dimensionally continued black holes as well as of pure Lovelock analogue of BTZ
black hole in all odd dimensions.


title:
An Environmental Study of the Ultraluminous X-ray Source Population in
  Early-type Galaxies

abstract:
  Ultraluminous X-ray sources (ULXs) are some of the brightest phenomena found
outside of a galaxy's nucleus, and their explanation typically invokes
accretion of material onto a black hole. Here, we perform the largest
population study to date of ULXs in early-type galaxies, focusing on whether a
galaxy's large scale environment can affect its ULX content. Using the AMUSE
survey, which includes homogeneous X-ray coverage of 100 elliptical galaxies in
the Virgo cluster and a similar number of elliptical galaxies in the field
(spanning stellar masses of 1e8-1e12 M_sun), we identify 37.9 +/- 10.1 ULXs in
Virgo and 28.1 +/- 8.7 ULXs in the field. Across both samples, we constrain the
number of ULXs per unit stellar mass, i.e., the ULX specific frequency, to be
0.062 +/- 0.013 ULXs per 10^10 M_sun (or about 1 ULX per 1.6e11 M_sun of galaxy
stellar mass). We find that the number of ULXs, the specific frequency of ULXs,
and the average ULX spectral properties are all similar in both cluster and
field environments. Contrary to late-type galaxies, we do not see any trend
between specific ULX frequency and host galaxy stellar mass, and we show that
dwarf ellipticals host fewer ULXs than later-type dwarf galaxies at a
statistically meaningful level. Our results are consistent with ULXs in
early-type galaxies probing the luminous tail of the low-mass X-ray binary
population, and are briefly discussed in context of the influence of
gravitational interactions on the long-term evolution of a galaxy's (older)
stellar population.


title: Modeling small dark energy scale with quintessential pseudoscalar boson

abstract:
  Democracy among the same type of particles is a useful paradigm in studying
masses and interactions of particles with supersymmetry(SUSY) or without SUSY.
This simple idea predicts the presence of massless particles. We attempt to use
one of these massless pseudoscalar particles as generating the cosmological
dark energy(DE) potential. To achieve the extremely shallow potential of DE,
the pseudoscalar boson is required not to couple to the QCD anomaly. So, we
consider two pseudoscalars, one coupling to the QCD anomaly (i.e. QCD axion)
and the other not coupling to the QCD anomaly. To obtain these two
pseudoscalars, we introduce two approximate global U(1) symmetries to realize
them as the pseudo-Goldstone bosons of the spontaneously broken U(1)'s. These
global symmetries are dictated by a gravity respected discrete symmetry.
Specifically, we consider an S2(L) X S2(R) X Z(10R) example, and attempt to
obtain the DE scale in terms of two observed fundamental mass scales, the grand
unification scale M(G) and the electroweak scale v(ew).


title: On the four-point function of the stress-energy tensors in a CFT

abstract:
  We discuss to what extent the full set of Ward Identities constrain the
four-point function of the stress-energy tensors or conserved currents in a
conformal field theory. We calculate the number of kinematically unrestricted
functional degrees of freedom governing the corresponding correlators and find
that it matches the number of functional degrees of freedom governing
scattering amplitudes of some "dual" massless particles in the auxiliary
Minkowski space. We also formulate the conformal bootstrap constraints for the
correlators in question in terms of only unrestricted degrees of freedom. As a
by-product we find interesting parallels between solving Ward Identities in
coordinate and momentum space.


title: True randomness from realistic quantum devices

abstract:
  Even if the output of a Random Number Generator (RNG) is perfectly uniformly
distributed, it may be correlated to pre-existing information and therefore be
predictable. Statistical tests are thus not sufficient to guarantee that an RNG
is usable for applications, e.g., in cryptography or gambling, where
unpredictability is important. To enable such applications a stronger notion of
randomness, termed "true randomness", is required, which includes independence
from prior information.
  Quantum systems are particularly suitable for true randomness generation, as
their unpredictability can be proved based on physical principles. Practical
implementations of Quantum RNGs (QRNGs) are however always subject to noise,
i.e., influences which are not fully controlled. This reduces the quality of
the raw randomness generated by the device, making it necessary to post-process
it. Here we provide a framework to analyse realistic QRNGs and to determine the
post-processing that is necessary to turn their raw output into true
randomness.


title:
Estimating Functions of Distributions Defined over Spaces of Unknown
  Size

abstract:
  We consider Bayesian estimation of information-theoretic quantities from
data, using a Dirichlet prior. Acknowledging the uncertainty of the event space
size $m$ and the Dirichlet prior's concentration parameter $c$, we treat both
as random variables set by a hyperprior. We show that the associated
hyperprior, $P(c, m)$, obeys a simple "Irrelevance of Unseen Variables" (IUV)
desideratum iff $P(c, m) = P(c) P(m)$. Thus, requiring IUV greatly reduces the
number of degrees of freedom of the hyperprior. Some information-theoretic
quantities can be expressed multiple ways, in terms of different event spaces,
e.g., mutual information. With all hyperpriors (implicitly) used in earlier
work, different choices of this event space lead to different posterior
expected values of these information-theoretic quantities. We show that there
is no such dependence on the choice of event space for a hyperprior that obeys
IUV. We also derive a result that allows us to exploit IUV to greatly simplify
calculations, like the posterior expected mutual information or posterior
expected multi-information. We also use computer experiments to favorably
compare an IUV-based estimator of entropy to three alternative methods in
common use. We end by discussing how seemingly innocuous changes to the
formalization of an estimation problem can substantially affect the resultant
estimates of posterior expectations.

categories: math.ST physics.data-an q-bio.QM stat.TH


title: Chemodynamics of the Milky Way. I. The first year of APOGEE data

abstract:
  We investigate the chemo-kinematic properties of the Milky Way disc by
exploring the first year of data from the Apache Point Observatory Galactic
Evolution Experiment (APOGEE), and compare our results to smaller optical
high-resolution samples in the literature, as well as results from lower
resolution surveys such as GCS, SEGUE and RAVE. We start by selecting a
high-quality sample in terms of chemistry ($\sim$ 20.000 stars) and, after
computing distances and orbital parameters for this sample, we employ a number
of useful subsets to formulate constraints on Galactic chemical and
chemodynamical evolution processes in the Solar neighbourhood and beyond (e.g.,
metallicity distributions -- MDFs, [$\alpha$/Fe] vs. [Fe/H] diagrams, and
abundance gradients). Our red giant sample spans distances as large as 10 kpc
from the Sun.
  We find remarkable agreement between the recently published local (d $<$ 100
pc) high-resolution high-S/N HARPS sample and our local HQ sample (d $<$ 1
kpc). The local MDF peaks slightly below solar metallicity, and exhibits an
extended tail towards [Fe/H] $= -$1, whereas a sharper cut-off is seen at
larger metallicities. The APOGEE data also confirm the existence of a gap in
the [$\alpha$/Fe] vs. [Fe/H] abundance diagram. When expanding our sample to
cover three different Galactocentric distance bins, we find the
high-[$\alpha$/Fe] stars to be rare towards the outer zones, as previously
suggested in the literature. For the gradients in [Fe/H] and [$\alpha$/Fe],
measured over a range of 6 $ < $ R $ <$ 11 kpc in Galactocentric distance, we
find a good agreement with the gradients traced by the GCS and RAVE dwarf
samples. For stars with 1.5 $<$ z $<$ 3 kpc, we find a positive metallicity
gradient and a negative gradient in [$\alpha$/Fe].


title: The shortened KK spectrum of IIB supergravity on Y^{p,q}

abstract:
  We examine the shortened KK spectrum of IIB supergravity compactified on
Y^{p,q} and conjecture that the spectrum we have obtained is complete. The
(untwisted) shortened spectrum on S^5/Z_{2p} and T^{1,1}/Z_p are obtained as
special cases when p=q and q=0, respectively. Knowledge of the shortened
spectrum allows us to compute the superconformal index of these theories and to
find agreement with earlier calculations from the dual field theories. We also
employ the shortened spectrum to perform a 1/N^2 test of AdS/CFT by
holographically reproducing the difference of the central charges, c-a=p/8, of
the dual CFTs.


title:
Spurious Velocities in Dynamically-Cold Systems Due to the Gravitational
  Redshifts of their Constituent Stars

abstract:
  The Doppler effect is commonly used to infer the velocity difference between
stars based on the relative shifts in the rest-frame wavelengths of their
spectral features. In dynamically-cold systems with a low velocity dispersion,
such as wide binaries, loose star clusters, cold stellar streams or
cosmological mini-halos, the scatter in the gravitational redshift from the
surface of the constituent stars needs to be taken into account as well.
Gravitational redshifts could be important for wide binaries composed of main
sequence stars with separations >0.01 pc or in mini-halos with velocity
dispersions <1 km/s. Variable redshift could also lead to a spurious
"detection" of low-mass planets around a star with periodic photospheric radius
variations.


title:
Efficient algorithms for the longest common subsequence in $k$-length
  substrings

abstract:
  Finding the longest common subsequence in $k$-length substrings (LCS$k$) is a
recently proposed problem motivated by computational biology. This is a
generalization of the well-known LCS problem in which matching symbols from two
sequences $A$ and $B$ are replaced with matching non-overlapping substrings of
length $k$ from $A$ and $B$. We propose several algorithms for LCS$k$, being
non-trivial incarnations of the major concepts known from LCS research (dynamic
programming, sparse dynamic programming, tabulation). Our algorithms make use
of a linear-time and linear-space preprocessing finding the occurrences of all
the substrings of length $k$ from one sequence in the other sequence.


title: Majorana Physics Through the Cabibbo Haze

abstract:
  We present a model in which the Supersymmetric Standard Model is augmented by
the family symmetry $\bs{\m Z_7 \rtimes \m Z_3}$. Motivated by $SO(10)$, where
the charge two-thirds and neutral Dirac Yukawa matrices are related, we
propose, using family symmetry, a special form for the seesaw Majorana matrix;
it contains a squared correlated hierarchy, allowing it to mitigate the severe
hierarchy of the quark sector. It is reproduced naturally by the invariant
operators of $\bs{\m Z_7 \rtimes \m Z_3}$, with the hierarchy carried by
familon fields. In addition to relating the hierarchy of the $\Delta I_{\rm
w}=1/2$ to the $\Delta I_{\rm w}=0$ sector, it contains a Gatto-Sartori-Tonin
like relation, predicts a normal hierarchy for Tri-bimaximal and Golden Ratio
mixings, and gives specific values for the light neutrino masses.


title:
Electromagnetic splitting of quark and pseudoscalar meson masses from
  dynamical QCD + QED

abstract:
  Lattice QCD simulations are now reaching a precision where electromagnetic
corrections from QED become important. In investigating the effects of SU(3)
breaking due to quark mass differences within QCD, a group-theoretical analysis
of the mass dependence greatly helped us organize our results. We now do the
same with electromagnetic charge effects by extending the calculations to
dynamical 1+1+1 flavor QCD + QED.


title:
Confidence Intervals for Random Forests: The Jackknife and the
  Infinitesimal Jackknife

abstract:
  We study the variability of predictions made by bagged learners and random
forests, and show how to estimate standard errors for these methods. Our work
builds on variance estimates for bagging proposed by Efron (1992, 2012) that
are based on the jackknife and the infinitesimal jackknife (IJ). In practice,
bagged predictors are computed using a finite number B of bootstrap replicates,
and working with a large B can be computationally expensive. Direct
applications of jackknife and IJ estimators to bagging require B on the order
of n^{1.5} bootstrap replicates to converge, where n is the size of the
training set. We propose improved versions that only require B on the order of
n replicates. Moreover, we show that the IJ estimator requires 1.7 times less
bootstrap replicates than the jackknife to achieve a given accuracy. Finally,
we study the sampling distributions of the jackknife and IJ variance estimates
themselves. We illustrate our findings with multiple experiments and simulation
studies.


title: Evolution of dwarf galaxies: a dynamical perspective

abstract:
  For a rotating galaxy, the inner circular-velocity gradient d_{R}V(0)
provides a direct estimate of the central dynamical mass density, including
gas, stars, and dark matter. We consider 60 low-mass galaxies with high-quality
HI and/or stellar rotation curves (including starbursting dwarfs, irregulars,
and spheroidals), and estimate d_{R}V(0) as V(R_d)/R_d, where R_d is the galaxy
scale-length. For gas-rich dwarfs, we find that V(R_d)/R_d correlates with the
central surface brightness mu(0), the mean atomic gas surface density
Sigma_gas, and the star formation rate surface density Sigma_SFR. Starbursting
galaxies, such as blue compact dwarfs (BCDs), generally have higher values of
V(R_d)/R_d than dwarf irregulars, suggesting that the starburst is closely
related to the inner shape of the potential well. There are, however, some
"compact" irregulars with values of V(R_d)/R_d similar to BCDs. Unless a
redistribution of mass takes place, BCDs must evolve into compact irregulars.
Rotating spheroidals in the Virgo cluster follow the same correlation between
V(R_d)/R_d and mu(0) as gas-rich dwarfs. They have values of V(R_d)/R_d
comparable to those of BCDs and compact irregulars, pointing at evolutionary
links between these types of dwarfs. Finally, we find that, similarly to spiral
galaxies and massive starbursts, the star-formation activity in dwarfs can be
parametrized as Sigma_SFR = epsilon*Sigma_gas/t_orb, where t_orb is the orbital
time and epsilon = 0.02.


title: Quench Dynamics in a Model with Tuneable Integrability Breaking

abstract:
  We consider quantum quenches in an integrable quantum chain with
tuneable-integrability-breaking interactions. In the case where these
interactions are weak, we demonstrate that at intermediate times after the
quench local observables relax to a prethermalized regime, which can be
described by a density matrix that can be viewed as a deformation of a
generalized Gibbs ensemble. We present explicit expressions for the
approximately conserved charges characterizing this ensemble. We do not find
evidence for a crossover from the prethermalized to a thermalized regime on the
time scales accessible to us. Increasing the integrability-breaking
interactions leads to a behaviour that is compatible with eventual
thermalization.


title: A noise inequality for classical forces

abstract:
  Lorentz invariance requires local interactions, with force laws such as the
Coulomb interaction arising via virtual exchange of force carriers such as
photons. Many have considered the possibility that, at long distances or large
mass scales, this process changes in some way to lead to classical behavior.
Here we hypothesize that classical behavior could be due to an inability of
some force carriers to convey entanglement, a characteristic measure of
nonlocal, quantum behavior. We then prove that there exists a local test that
allows one to verify entanglement generation, falsifying our hypothesis.
Crucially, we show that noise measurements can directly verify entanglement
generation. This provides a step forward for a wide variety of experimental
systems where traditional entanglement tests are challenging, including
entanglement generation by gravity alone between macroscopic torsional
oscillators.


title:
A Deep Search for Faint Galaxies Associated with Very Low-Redshift C IV
  Absorbers: A Case with Cold-Accretion Characteristics

abstract:
  Studies of QSO absorber-galaxy connections are often hindered by inadequate
information on whether faint/dwarf galaxies are located near the QSO sight
lines. To investigate the contribution of faint galaxies to QSO absorber
populations, we are conducting a deep galaxy redshift survey near low-z C IV
absorbers. Here we report a blindly-detected C IV absorption system (z(abs) =
0.00348) in the spectrum of PG1148+549 that appears to be associated either
with an edge-on dwarf galaxy with an obvious disk (UGC 6894, z(gal) = 0.00283)
at an impact parameter of rho = 190 kpc or with a very faint dwarf irregular
galaxy at rho = 23 kpc, which is closer to the sightline but has a larger
redshift difference (z(gal) = 0.00107, i.e., dv = 724 km/s). We consider
various gas/galaxy associations, including infall and outflows. Based on
current theoretical models, we conclude that the absorber is most likely
tracing (1) the remnants of an outflow from a previous epoch, a so-called
'ancient outflow', or (2) intergalactic gas accreting onto UGC 6894, 'cold
mode' accretion. The latter scenario is supported by H I synthesis imaging data
that shows the rotation curve of the disk being codirectional with the velocity
offset between UGC 6894 and the absorber, which is located almost directly
along the major axis of the edge-on disk.


title: A remark on an endpoint Kato-Ponce inequality

abstract:
  This note introduces bilinear estimates intended as a step towards an
$L^\infty$-endpoint Kato-Ponce inequality. In particular, a bilinear version of
the classical Gagliardo-Nirenberg interpolation inequalities for a product of
functions is proved.


title:
Pionic and Hidden-Color, Six-Quark Contributions to the Deuteron b1
  Structure Function

abstract:
  The b1 structure function is an observable feature of a spin-1 system
sensitive to non-nucleonic components of the target nuclear wave function. The
contributions of exchanged pions in the deuteron are estimated and found to be
of measurable size for small values of x. A simple model for a hidden-color,
six-quark configurations (with~ 0.15% probability to exist in the deuteron) is
proposed and found to give substantial contributions for values of x>0.2. Good
agreement with Hermes data is obtained. Predictions are made for an upcoming
JLab experiment. The Close & Kumano sum rule is investigated and found to be a
useful guide to understanding various possible effects that may contribute.


title: Large-scale alignments from WMAP and Planck

abstract:
  We revisit the alignments of the largest structures observed in the cosmic
microwave background (CMB) using the seven and nine-year WMAP and first-year
Planck data releases. The observed alignments -- the quadrupole with the
octopole and their joint alignment with the direction of our motion with
respect to the CMB (the dipole direction) and the geometry of the Solar System
(defined by the Ecliptic plane) -- are generally in good agreement with results
from the previous WMAP data releases. However, a closer look at full-sky data
on the largest scales reveals discrepancies between the earlier WMAP data
releases (three to seven-year) and the final nine-year release. There are also
discrepancies between all the WMAP data releases and the first-year Planck
release. Nevertheless, both the WMAP and Planck data confirm the alignments of
the largest observable CMB modes in the Universe. In particular, the p-values
for the mutual alignment between the quadrupole and octopole, and the alignment
of the plane defined by the two with the dipole direction, are both at the
greater than 3-sigma level for all three Planck maps studied. We also calculate
conditional statistics on the various alignments and find that it is currently
difficult to unambiguously identify a leading anomaly that causes the others or
even to distinguish correlation from causation.


title:
Approximation Algorithms for the Incremental Knapsack Problem via
  Disjunctive Programming

abstract:
  In the incremental knapsack problem ($\IK$), we are given a knapsack whose
capacity grows weakly as a function of time. There is a time horizon of $T$
periods and the capacity of the knapsack is $B_t$ in period $t$ for $t = 1,
\ldots, T$. We are also given a set $S$ of $N$ items to be placed in the
knapsack. Item $i$ has a value of $v_i$ and a weight of $w_i$ that is
independent of the time period. At any time period $t$, the sum of the weights
of the items in the knapsack cannot exceed the knapsack capacity $B_t$.
Moreover, once an item is placed in the knapsack, it cannot be removed from the
knapsack at a later time period. We seek to maximize the sum of (discounted)
knapsack values over time subject to the capacity constraints. We first give a
constant factor approximation algorithm for $\IK$, under mild restrictions on
the growth rate of $B_t$ (the constant factor depends on the growth rate). We
then give a PTAS for $\IIK$, the special case of $\IK$ with no discounting,
when $T = O(\sqrt{\log N})$.


title: Planning by case-based reasoning based on fuzzy logic

abstract:
  The treatment of complex systems often requires the manipulation of vague,
imprecise and uncertain information. Indeed, the human being is competent in
handling of such systems in a natural way. Instead of thinking in mathematical
terms, humans describes the behavior of the system by language proposals. In
order to represent this type of information, Zadeh proposed to model the
mechanism of human thought by approximate reasoning based on linguistic
variables. He introduced the theory of fuzzy sets in 1965, which provides an
interface between language and digital worlds. In this paper, we propose a
Boolean modeling of the fuzzy reasoning that we baptized Fuzzy-BML and uses the
characteristics of induction graph classification. Fuzzy-BML is the process by
which the retrieval phase of a CBR is modelled not in the conventional form of
mathematical equations, but in the form of a database with membership functions
of fuzzy rules.


title:
Quarkonium correlation functions at finite temperature in the charm to
  bottom region

abstract:
  Quarkonium correlation functions at finite temperature were studied in a
region of the quark mass for charmonia to bottomonia in quenched lattice QCD
with $O(a)$-improved Wilson quarks. Our simulations were performed on large
isotropic lattices at temperatures in the range from about 0.80$T_c$ to
1.61$T_c$. We investigated quarkonium behavior in terms of temperature
dependence as well as quark mass dependence of the quarkonium correlation
functions and related quantities at both vanishing and finite momenta.