title:
Communication Network Design: Balancing Modularity and Mixing via
  Optimal Graph Spectra

abstract:
  By leveraging information technologies, organizations now have the ability to
design their communication networks and crowdsourcing platforms to pursue
various performance goals, but existing research on network design does not
account for the specific features of social networks, such as the notion of
teams. We fill this gap by demonstrating how desirable aspects of
organizational structure can be mapped parsimoniously onto the spectrum of the
graph Laplacian allowing the specification of structural objectives and build
on recent advances in non-convex programming to optimize them. This design
framework is general, but we focus here on the problem of creating graphs that
balance high modularity and low mixing time, and show how "liaisons" rather
than brokers maximize this objective.


title: $D_{s0}^*(2317)$ Meson and $D$-Meson-Kaon Scattering from Lattice QCD

abstract:
  The scalar meson $D_{s0}^*(2317)$ is found 37(17)MeV below DK threshold in a
lattice simulation of the $J^P=0^+$ channel using, for the first time, both DK
as well as $\bar sc$ interpolating fields. The simulation is done on $N_f=2+1$
gauge configurations with $m_\pi\simeq 156 $MeV, and the resulting
$M_{D_{s0}^*}-\tfrac{1}{4}(M_{D_s}+3M_{D_s^*})=266(16)$ MeV is close to the
experimental value 241.5(0.8)MeV. The energy level related to the scalar meson
is accompanied by additional discrete levels due to DK scattering states. The
levels near threshold lead to the negative DK scattering length $a_0=-1.33(20)$
fm that indicates the presence of a state below threshold.


title: Fluctuations and the axial anomaly with three quark flavors

abstract:
  The role of the axial anomaly in the chiral phase transition at finite
temperature and quark chemical potential is investigated within a
non-perturbative functional renormalization group approach. The flow equation
for the grand potential is solved to leading-order in a derivative expansion of
a three flavor quark-meson model truncation. The results are compared with a
standard and an extended mean-field analysis, which facilitates the exploration
of the influence of bosonic and fermionic fluctuations, respectively, on the
phase transition. The influence of U(1)_A-symmetry breaking on the chiral
transition, the location of a possible critical endpoint in the phase diagram
and the quark mass sensitivity is studied in detail.


title: Normalized Google Distance of Multisets with Applications

abstract:
  Normalized Google distance (NGD) is a relative semantic distance based on the
World Wide Web (or any other large electronic database, for instance Wikipedia)
and a search engine that returns aggregate page counts. The earlier NGD between
pairs of search terms (including phrases) is not sufficient for all
applications. We propose an NGD of finite multisets of search terms that is
better for many applications. This gives a relative semantics shared by a
multiset of search terms. We give applications and compare the results with
those obtained using the pairwise NGD. The derivation of NGD method is based on
Kolmogorov complexity.


title: Maximum Number of Minimum Dominating and Minimum Total Dominating Sets

abstract:
  Given a connected graph with domination (or total domination) number
\gamma>=2, we ask for the maximum number m_\gamma and m_{\gamma,T} of
dominating and total dominating sets of size \gamma. An exact answer is
provided for \gamma=2and lower bounds are given for \gamma>=3.


title:
Stable pseudoanalytical computation of electromagnetic fields from
  arbitrarily-oriented dipoles in cylindrically stratified media

abstract:
  Computation of electromagnetic fields due to point sources (Hertzian dipoles)
in cylindrically stratified media is a classical problem for which analytical
expressions of the associated tensor Green's function have been long known.
However, under finite-precision arithmetic, direct numerical computations based
on the application of such analytical (canonical) expressions invariably lead
to underflow and overflow problems related to the poor scaling of the
eigenfunctions (cylindrical Bessel and Hankel functions) for extreme arguments
and/or high-order, as well as convergence problems related to the numerical
integration over the spectral wavenumber and to the truncation of the infinite
series over the azimuth mode number. These problems are exacerbated when a
disparate range of values is to be considered for the layers' thicknesses and
material properties (resistivities, permittivities, and permeabilities), the
transverse and longitudinal distances between source and observation points, as
well as the source frequency. To overcome these challenges in a systematic
fashion, we introduce herein different sets of range-conditioned, modified
cylindrical functions (in lieu of standard cylindrical eigenfunctions), each
associated with non-overlapped subdomains of (numerical) evaluation to allow
for stable computations under any range of physical parameters. In addition
adaptively-chosen integration contours are employed in the complex spectral
wavenumber plane to ensure convergent numerical integration in all cases. We
illustrate the application of the algorithm to problems of geophysical interest
involving layer resistivities ranging from 1000 $\Omega \cdot$m to 10$^{-8}
\Omega \cdot$m, frequencies of operation ranging from 10 MHz down to the low
magnetotelluric range of 0.01 Hz, and for various combinations of layer
thicknesses.


title: On Finite Groups of Symmetries of Surfaces

abstract:
  The genus spectrum of a finite group $G$ is the set of all $g\geq 2$ such
that $G$ acts faithfully and orientation-preserving on a closed compact
orientable surface of genus $g$. This article is an overview of some results
relating the genus spectrum of $G$ to its group theoretical properties. In
particular, the arithmetical properties of genus spectra are discussed, and
explicit results are given on the 2-groups of maximal class, certain sporadic
simple groups and a some of the groups PSL$(2,q)$, where $q$ is a small prime
power. These results are partially new, and obtained through both theoretical
reasoning and application of computational techniques.


title: Isometric embedding of Busemann surfaces into $L_1$

abstract:
  In this paper, we prove that any non-positively curved 2-dimensional surface
(alias, Busemann surface) is isometrically embeddable into $L_1$. As a
corollary, we obtain that all planar graphs which are 1-skeletons of planar
non-positively curved complexes with regular Euclidean polygons as cells are
$L_1$-embeddable with distortion at most $2+\pi/2<4$. Our results significantly
improve and simplify the results of the recent paper {\it A. Sidiropoulos,
Non-positive curvature, and the planar embedding conjecture, FOCS 2013.}}


title: Structural measures for multiplex networks

abstract:
  Many real-world complex systems consist of a set of elementary units
connected by relationships of different kinds. All such systems are better
described in terms of multiplex networks, where the links at each layer
represent a different type of interaction between the same set of nodes, rather
than in terms of (single-layer) networks. In this paper we present a general
framework to describe and study multiplex networks, whose links are either
unweighted or weighted. In particular we propose a series of measures to
characterize the multiplexicity of the systems in terms of: i) basic node and
link properties such as the node degree, and the edge overlap and
reinforcement, ii) local properties such as the clustering coefficient and the
transitivity, iii) global properties related to the navigability of the
multiplex across the different layers. The measures we introduce are validated
on a genuine multiplex data set of Indonesian terrorists, where information
among 78 individuals are recorded with respect to mutual trust, common
operations, exchanged communications and business relationships.


title:
Nuclear shell structure and response toward the limits of mass,
  temperature and isospin

abstract:
  We present a short overview of our recent theoretical developments aiming at
the description of exotic nuclear phenomena to be reached and studied at the
next-generation radioactive beam facilities. Applications to nuclear shell
structure and response of nuclei at the limits of their existence, with a
special focus on the physics cases of astrophysical importance, are discussed.


title: Relativistic two-phonon model for low-energy nuclear response

abstract:
  A two-phonon version of the relativistic quasiparticle time blocking
approximation introduces as a new class of many-body models for nuclear
structure calculations based on the covariant energy density functional. As a
fully consistent extension of the relativistic quasiparticle random phase
approximation, the relativistic two-phonon model implies fragmentation of
nuclear states over two-quasiparticle and two-phonon configurations coupled to
each other. In particular, we show how the lowest two-phonon $1^-$ state,
identified as a member of the $[2^+\otimes 3^-]$ quintuplet, emerges from the
coherent two-quasiparticle pygmy dipole mode in vibrational nuclei. The
inclusion of the two-phonon configurations into the model space allows a
quantitative description of the positions and the reduced transition
probabilities of the lowest 1$^-$ states in tin isotopes $^{112,116,120,124}$Sn
as well as the low-energy fraction of the dipole strength below the giant
dipole resonance without any adjustment procedures. The model is applied to the
low-lying dipole strength in neutron-rich $^{68,70,72}$Ni isotopes. Recent
experimental data for $^{68}$Ni are reproduced fairly well.


title:
To Relay or Not to Relay: Learning Device-to-Device Relaying Strategies
  in Cellular Networks

abstract:
  We consider a cellular network where mobile transceiver devices that are
owned by self-interested users are incentivized to cooperate with each other
using tokens, which they exchange electronically to "buy" and "sell" downlink
relay services, thereby increasing the network's capacity compared to a network
that only supports base station-to-device (B2D) communications. We investigate
how an individual device in the network can learn its optimal cooperation
policy online, which it uses to decide whether or not to provide downlink relay
services for other devices in exchange for tokens. We propose a supervised
learning algorithm that devices can deploy to learn their optimal cooperation
strategies online given their experienced network environment. We then
systematically evaluate the learning algorithm in various deployment scenarios.
Our simulation results suggest that devices have the greatest incentive to
cooperate when the network contains (i) many devices with high energy budgets
for relaying, (ii) many highly mobile users (e.g., users in motor vehicles),
and (iii) neither too few nor too many tokens. Additionally, within the token
system, self-interested devices can effectively learn to cooperate online, and
achieve over 20% higher throughput on average than with B2D communications
alone, all while selfishly maximizing their own utilities.


title: Hubbard Model on the Pyrochlore Lattice: a 3D Quantum Spin Liquid

abstract:
  We demonstrate that the insulating one-band Hubbard model on the pyrochlore
lattice contains, for realistic parameters, an extended quantum spin-liquid
phase. This is a three-dimensional spin liquid formed from a highly degenerate
manifold of dimer-based states, which is a subset of the classical dimer
coverings obeying the ice rules. It possesses spinon excitations, which are
both massive and deconfined, and on doping it exhibits spin-charge separation.
We discuss the realization of this state in effective S = 1/2 pyrochlore
materials with and without spin-orbit coupling.


title: Successive Spectral Sequences

abstract:
  In this paper, we develop a structure theory for generalized spectral
sequences, which are derived from chain complexes that are filtered over
arbitrary partially ordered sets. Also, a more general construction method
reminiscent of exact couples is studied, together with examples where they
arise naturally. As for ordinary spectral sequences we will see differentials
and group extensions, however the real power comes from the appearance of
natural isomorphims between pages of differing indices.
  The constructions reveal finer invariants than ordinary spectral sequences,
and they connect to other fields such as Fary functors and perverse sheaves.
They are based on a natural index scheme, which allows us to obtain new results
even in the standard case of Z-filtered chain complexes, e.g. a useful
criterion for a product structure for Grothendieck's spectral sequences, and
news paths to connect the first or second page to the limit.
  This turns out to yield the right framework for unifying several spectral
sequences that one would usually apply one after another. Examples that we work
out are successive Leray--Serre spectral sequences, the Adams--Novikov spectral
sequence following the chromatic spectral sequence, successive Grothendieck
spectral sequences, and successive Eilenberg--Moore spectral sequences.


title: Optimal simplices and codes in projective spaces

abstract:
  We find many tight codes in compact spaces, i.e., optimal codes whose
optimality follows from linear programming bounds. In particular, we show the
existence (and abundance) of several hitherto unknown families of simplices in
quaternionic projective spaces and the octonionic projective plane. The most
noteworthy cases are 15-point simplices in HP^2 and 27-point simplices in OP^2,
both of which are the largest simplices and the smallest 2-designs possible in
their respective spaces. These codes are all universally optimal, by a theorem
of Cohn and Kumar. We also show the existence of several positive-dimensional
families of simplices in the Grassmannians of subspaces of R^n with n <= 8;
close numerical approximations to these families had been found by Conway,
Hardin, and Sloane, but no proof of existence was known. Our existence proofs
are computer-assisted, and the main tool is a variant of the Newton-Kantorovich
theorem. This effective implicit function theorem shows, in favorable
conditions, that every approximate solution to a set of polynomial equations
has a nearby exact solution. Finally, we also exhibit a few explicit codes,
including a configuration of 39 points in OP^2 that form a maximal system of
mutually unbiased bases. This is the last tight code in OP^2 whose existence
had been previously conjectured but not resolved.


title:
Model-independent search for CP violation in D0 to K-K+pi-pi+ and D0 to
  pi-pi+pi+pi- decays

abstract:
  A search for CP violation in the phase-space structures of D0 and D0bar
decays to the final states K-K+pi-pi+ and pi-pi+pi+pi- is presented. The search
is carried out with a data set corresponding to an integrated luminosity of
1.0fb^-1 collected in 2011 by the LHCb experiment in $pp$ collisions at a
centre-of-mass energy of 7TeV. For the K-K+pi-pi+ final state, the four-body
phase space is divided into 32 bins, each bin with approximately 1800 decays.
The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a
CP asymmetry greater than 6.5% observed. The phase space of the pi-pi+pi+pi-
final state is partitioned into 128 bins, each bin with approximately 2500
decays. The $p$-value under the hypothesis of no CP violation is 41%, and in no
bin is a CP asymmetry greater than 5.5% observed. All results are consistent
with the hypothesis of no CP violation at the current sensitivity.


title:
The number of independent Traces and Supertraces on Symplectic
  Reflection Algebras

abstract:
  It is shown that $A:=H_{1,\eta}(G)$, the Sympectic Reflection Algebra, has
$T_G$ independent traces, where $T_G$ is the number of conjugacy classes of
elements without eigenvalue 1 belonging to the finite group $G$ generated by
the system of symplectic reflections.
  Simultaneously, we show that the algebra $A$, considered as a superalgebra
with a natural parity, has $S_G$ independent supertraces, where $S_G$ is the
number of conjugacy classes of elements without eigenvalue -1 belonging to $G$.
  We consider also $A$ as a Lie algebra $A^L$ and as a Lie superalgebra $A^S$.
  It is shown that if $A$ is a simple associative algebra, then the
supercommutant $[A^{S},A^{S}]$ is a simple Lie superalgebra having at least
$S_G$ independent supersymmetric invariant non-degenerate bilinear forms, and
the quotient $[A^L,A^L]/([A^L,A^L]\cap\mathbb C)$ is a simple Lie algebra
having at least $T_G$ independent symmetric invariant non-degenerate bilinear
forms.


title: Near-field heat transfer between gold nanoparticle arrays

abstract:
  The radiative heat transfer between gold nanoparticle layers is presented
using the coupled dipole method. Gold nanoparticles are modelled as effective
electric and magnetic dipoles interacting via electromagnetic fluctuations. The
effect of higher-order multipoles is implemented in the expression of electric
polarizability to calculate the interactions at short distances. Our findings
show that the near-field radiation reduces as the radius of the nanoparticles
is increased. Also, the magnetic dipole contribution to the heat exchange
becomes more important for larger particles. When one layer is displayed in
parallel with respect to the other layer, the near-field heat transfer exhibits
oscillatory-like features due to the influence of the individual
nanostructures. Further details about the effect of the nanoparticles size are
also discussed.


title: On pairs of finitely generated subgroups in free groups

abstract:
  We prove that for arbitrary two finitely generated subgroups A and B having
infinite index in a free group F, there is a subgroup H of finite index in B
such that the subgroup generated by A and H has infinite index in F. The main
corollary of this theorem says that a noncyclic free group of finite rank
admits a faithful highly transitive action on an infinite set, whereas the
restriction of this action to any finitely generated subgroup of infinite index
in F has no infinite orbits.


title: When does cp-rank equal rank?

abstract:
  The problem of finding completely positive matrices with equal cp-rank and
rank is considered. We give some easy-to-check sufficient conditions on the
entries of a doubly nonnegative matrix for it to be completely positive with
equal cp-rank and rank. An algorithm is also presented to show its efficiency.


title:
Terahertz metamaterials for linear polarization conversion and anomalous
  refraction

abstract:
  Polarization is one of the basic properties of electromagnetic waves
conveying valuable information in signal transmission and sensitive
measurements. Conventional methods for advanced polarization control impose
demanding requirements on material properties and attain only limited
performance. Here, we demonstrate ultrathin, broadband, and highly efficient
metamaterial-based terahertz polarization converters that are capable of
rotating a linear polarization state into its orthogonal one. Based on these
results we create metamaterial structures capable of realizing near-perfect
anomalous refraction. Our work opens new opportunities for creating high
performance photonic devices and enables emergent metamaterial functionalities
for applications in the technologically difficult terahertz frequency regime.


title: Bose Hubbard model far from equilibrium

abstract:
  We study the nonequilibrium steady state of the Bose Hubbard model coupled to
Lindblad reservoirs, using the density matrix renormalization group in operator
space. We observe a transition from a flat particle density profile in the
noninteracting limit to the linear profile with onset of the interparticle
interaction. Analyzing the effect of coherent pumping on the nonequilibrium
steady state we find a subspace which remains unaffected by the pumping in the
noninteracting limit with the protection gradually diminishing due to
interparticle interaction. In the equilibrium situation with one or more
symmetric reservoirs we show analytically that the steady state of the system
is a product state for any interaction strength. We also provide analytical
results in the noninteracting limits, using the method of the third
quantization in operator space.


title: Twistor spaces for hyperkaehler implosions

abstract:
  We study the geometry of the twistor space of the universal hyperkaehler
implosion Q for SU(n). Using the description of Q as a hyperkaehler quiver
variety, we construct a holomorphic map from the twistor space Z_Q of Q to a
complex vector bundle over P^1, and an associated map of Q to the affine space
R of the bundle's holomorphic sections. The map from Q to R is shown to be
injective and equivariant for the action of SU(n) x T^{n-1} x SU(2). Both maps,
from Q and from Z_Q, are described in detail for n=2 and n=3. We explain how
the maps are built from the fundamental irreducible representations of SU(n)
and the hypertoric variety associated to the hyperplane arrangement given by
the root planes in the Lie algebra of the maximal torus. This indicates that
the constructions might extend to universal hyperkaehler implosions for other
compact groups.


title: "Self-absorbed" GeV light-curves of Gamma-Ray Burst afterglows

abstract:
  We investigate the effect that the absorption of high-energy (above 100 MeV)
photons produced in GRB afterglow shocks has on the light-curves and spectra of
Fermi-LAT afterglows. Afterglows produced by the interaction of a relativistic
outflow with a wind-like medium peak when the blast-wave deceleration sets in,
and the afterglow spectrum could be hardening before that peak, as the optical
thickness to pair-formation is decreasing. In contrast, in afterglows produced
in the interaction with a homogeneous medium, the optical thickness to
pair-formation should increase and yield a light-curve peak when it reaches
unity, followed by a fast light-curve decay, accompanied by a spectral
softening. If energy is injected in the blast-wave, then the accelerated
increase of the optical thickness yields a convex afterglow light-curve. Other
features, such as a double-peak light-curve or a broad hump, can arise from the
evolution of the optical thickness to photon-photon absorption. Fast decays and
convex light-curves are seen in a few LAT afterglows, but the expected spectral
softening is rarely seen in (and difficult to measure with) LAT observations.
Furthermore, for the effects of photon-photon attenuation to shape the
high-energy afterglow light-curve without attenuating it too much, the ejecta
initial Lorentz factor must be in a relatively narrow range (50-200), which
reduces the chance of observing those effects.


title: Comparison of mass renormalization schemes for simple model systems

abstract:
  We discuss an alternative method to mass renormalize a quantum field
Hamiltonian based on a requirement that the vacuum and single-particle sectors
are not self-scattering. We illustrate the feasibility of this method for the
concrete example of bosonic quadratic and also quartic interactions. The
results are compared with those obtained by the standard renormalization
technique based on a spectral analysis of the usual field-based propagators. We
also discuss a potential method for renormalizing a quantum field theory in a
non-perturbative way using computational methods.


title: Who Ordered the Anti-de Sitter Tangent Group?

abstract:
  General relativity can be unambiguously formulated with Lorentz, de Sitter
and anti-de Sitter tangent groups, which determine the fermionic
representations. We show that besides of the Lorentz group only anti-de Sitter
tangent group is consistent with all physical requirements.


title: An Upper Bound On the Size of Locally Recoverable Codes

abstract:
  In a {\em locally recoverable} or {\em repairable} code, any symbol of a
codeword can be recovered by reading only a small (constant) number of other
symbols. The notion of local recoverability is important in the area of
distributed storage where a most frequent error-event is a single storage node
failure (erasure). A common objective is to repair the node by downloading data
from as few other storage node as possible. In this paper, we bound the minimum
distance of a code in terms of its length, size and locality. Unlike previous
bounds, our bound follows from a significantly simple analysis and depends on
the size of the alphabet being used. It turns out that the binary Simplex codes
satisfy our bound with equality; hence the Simplex codes are the first example
of a optimal binary locally repairable code family. We also provide
achievability results based on random coding and concatenated codes that are
numerically verified to be close to our bounds.


title:
Confidence Sets Based on Thresholding Estimators in High-Dimensional
  Gaussian Regression Models

abstract:
  We study confidence intervals based on hard-thresholding, soft-thresholding,
and adaptive soft-thresholding in a linear regression model where the number of
regressors $k$ may depend on and diverge with sample size $n$. In addition to
the case of known error variance, we define and study versions of the
estimators when the error variance is unknown. In the known variance case, we
provide an exact analysis of the coverage properties of such intervals in
finite samples. We show that these intervals are always larger than the
standard interval based on the least-squares estimator. Asymptotically, the
intervals based on the thresholding estimators are larger even by an order of
magnitude when the estimators are tuned to perform consistent variable
selection. For the unknown-variance case, we provide non-trivial lower bounds
for the coverage probabilities in finite samples and conduct an asymptotic
analysis where the results from the known-variance case can be shown to carry
over asymptotically if the number of degrees of freedom $n-k$ tends to infinity
fast enough in relation to the thresholding parameter.


title:
Study of the muon content of very high-energy EAS measured with the
  KASCADE-Grande observatory

abstract:
  The KASCADE-Grande detector is an air-shower array devoted to the study of
primary cosmic rays with very high-energies (E = 10^{16} - 10^{18} eV). The
instrument is composed of different particle detector systems suitable for the
detailed study of the properties of Extensive Air Showers (EAS) developed by
cosmic rays in the atmosphere. Among the EAS observables studied with the
detector, the charged number of particles, the muon content (at different
energy thresholds), and the number of electrons are found. By comparing the
measurements of these air-shower parameters with the expectations from MC
simulations, different hadronic interaction models can be tested at the
high-energy regime with the KASCADE-Grande experiment. In this work, the
results of a study on the evolution of the muon content of EAS with zenith
angle, performed with the KASCADE-Grande instrument, is presented. Measurements
are compared with predictions from MC simulations based on the QGSJET II,
QGSJET II-04, SIBYLL 2.1 and EPOS 1.99 hadronic interaction models. A mismatch
between experiment and simulations is observed. A similar problem is found for
the evolution of the lateral distribution function of muons in the atmosphere.


title: Detecting Data Races on OpenCL Kernels with Symbolic Execution

abstract:
  We present an automatic analysis technique for checking data races on OpenCL
kernels. Our method defines symbolic execution techniques based on separation
logic with suitable abstractions to automatically detect non-benign racy
behaviours on kernel


title:
Optically enhanced coherent transport in YBa2Cu3O6.5 by ultrafast
  redistribution of interlayer coupling

abstract:
  Nonlinear optical excitation of infrared active lattice vibrations has been
shown to melt magnetic or orbital orders and to transform insulators into
metals. In cuprates, this technique has been used to remove charge stripes and
promote superconductivity, acting in a way opposite to static magnetic fields.
Here, we show that excitation of large-amplitude apical oxygen distortions in
the cuprate superconductor YBa2Cu3O6.5 promotes highly unconventional
electronic properties. Below the superconducting transition temperature (Tc =
50 K), interbilayer coherence is transiently enhanced at the expense of
intra-bilayer coupling. Strikingly, even above Tc a qualitatively similar
effect is observed up to room temperature, with transient inter-bilayer
coherence emerging from the incoherent ground state and similar transfer of
spectral weight from high to low frequency. These observations are compatible
with previous reports of an inhomogeneous normal state that retains important
properties of a superconductor, in which light may be melting competing orders
or dynamically synchronizing the interlayer phase. The transient redistribution
of coherence discussed here could lead to new strategies to enhance
superconductivity in steady state.


title: How to compute the Hilbert depth of a graded ideal

abstract:
  We give two algorithms for computing the Hilbert depth of a \emph{graded
ideal} in the polynomial ring. These algorithms work efficiently for
(squarefree) lex ideals. As a consequence, we construct counterexamples to some
conjectures made by Shen in \cite{B:Sh2}.


title: Wormhole solutions supported by interacting dark matter and dark energy

abstract:
  We show that the presence of a nonminimal interaction between dark matter and
dark energy may lead to a violation of the null energy condition and to the
formation of a configuration with nontrivial topology (a wormhole). In this it
is assumed that both dark matter and dark energy satisfy the null energy
condition, a violation of which takes place only in the inner high-density
regions of the configuration. This is achieved by assuming that, in a
high-density environment, a nonminimal coupling function changes its sign in
comparison with the case where dark matter and dark energy have relatively low
densities which are typical for a cosmological background. For this case, we
find regular static, spherically symmetric solutions describing wormholes
supported by dark matter nonminimally coupled to dark energy in the form of a
quintessence scalar field.


title:
Curved walls: Grain growth, settling, and composition patterns in T
  Tauri disk dust sublimation fronts

abstract:
  The dust sublimation walls of disks around T Tauri stars represent a directly
observable cross-section through the disk atmosphere and midplane. Their
emission properties can probe the grain size distribution and composition of
the innermost regions of the disk, where terrestrial planets form. Here we
calculate the inner dust sublimation wall properties for four classical T Tauri
stars with a narrow range of spectral types and inclination angles and a wide
range of mass accretion rates to determine the extent to which the walls are
radially curved. Best-fits to the near- and mid-IR excesses are found for
curved, 2-layer walls in which the lower layer contains larger, hotter,
amorphous pyroxene grains with Mg/(Mg+Fe)=0.6 and the upper layer contains
submicron, cooler, mixed amorphous olivine and forsterite grains. As the mass
accretion rates decrease from 10^(-8) to 10^(-10) Msol/yr, the maximum grain
size in the lower layer decreases from 3 to 0.5 microns. We attribute this to a
decrease in fragmentation and turbulent support for micron-sized grains with
decreasing viscous heating. The atmosphere of these disks is depleted of dust
with dust-gas mass ratios 1x10^(-4) of the ISM value, while the midplane is
enhanced to 8 times the ISM value. For all accretion rates, the wall
contributes at least half of the flux in the optically thin 10 micron silicate
feature. Finally, we find evidence for an iron gradient in the disk, suggestive
of that found in our solar system.


title: SU(3) orbital Kondo effect with ultracold atoms

abstract:
  We propose a simple but novel scheme to realize the Kondo effect with
ultracold atoms. Our system consists of a Fermi sea of spinless fermions
interacting with an impurity atom of different species which is confined by an
isotropic potential. The interspecies attraction can be tuned with an $s$-wave
Feshbach resonance so that the impurity atom and a spinless fermion form a
bound dimer that occupies a threefold-degenerate $p$ orbital of the confinement
potential. Many-body scatterings of this dimer and surrounding spinless
fermions occur with exchanging their angular momenta and thus exhibit the SU(3)
orbital Kondo effect. The associated Kondo temperature has a universal leading
exponent given by $T_K\propto\exp[-\pi/(3a_p k_F^3)]$ that depends only on an
effective $p$-wave scattering volume $a_p$ and a Fermi wave vector $k_F$. We
also elucidate a Kondo singlet formation at zero temperature and an anisotropic
interdimer interaction mediated by surrounding spinless fermions. The Kondo
effect thus realized in ultracold atom experiments may be observed as an
increasing atom loss by lowering the temperature or with radio-frequency
spectroscopy. Our scheme and its extension to a dense Kondo lattice will be
useful to develop new insights into yet unresolved aspects of Kondo physics.


title:
High-energy neutrino production from photo-hadronic interactions of
  gamma rays from Active Galactic Nuclei at source

abstract:
  Recent astronomical observations reveal that Active Galactic Nuclei (AGN) are
sources of high-energy radiation. For example, the Fermi-LAT and Hess
telescopes have detected gamma-ray emissions from the cores of several types of
AGN's. Even more, the Pierre Auger observatory has found a correlation of
ultra-high energy cosmic ray events with the position of Active Galactic
Nuclei, such as Centaurus A. In this way, according to particle physics, a flux
of high-energy neutrinos should be expected from the interactions of cosmic and
gamma-rays with the ambient matter and radiation at the source. In this work,
estimations of the diffuse neutrino flux from AGN's arising from interactions
of the gamma radiation with the gas and dust of the sources will be presented.


title: Bounds on the Maximum Number of Minimum Dominating Sets

abstract:
  We use probabilistic methods to find lower bounds on the maximum number, in a
graph with domination number \gamma, of dominating sets of size \gamma. We find
that we can randomly generate a graph that, w.h.p., is dominated by almost all
sets of size \gamma. At the same time, we use a modified adjacency matrix to
obtain lower bounds on the number of sets of a given size that do not dominate
a graph on n vertices


title: On Schwarz Methods for Nonsymmetric and Indefinite Problems

abstract:
  In this paper we introduce a new Schwarz framework and theory, based on the
well-known idea of space decomposition, for nonsymmetric and indefinite linear
systems arising from continuous and discontinuous Galerkin approximations of
general nonsymmetric and indefinite elliptic partial differential equations.
The proposed Schwarz framework and theory are presented in a variational
setting in Banach spaces instead of Hilbert spaces which is the case for the
well-known symmetric and positive definite (SPD) Schwarz framework and theory.
Condition number estimates for the additive and hybrid Schwarz preconditioners
are established. The main idea of our nonsymmetric and indefinite Schwarz
framework and theory is to use weak coercivity (satisfied by the nonsymmetric
and indefinite bilinear form) induced norms to replace the standard bilinear
form induced norm in the SPD Schwarz framework and theory. Applications of the
proposed nonsymmetric and indefinite Schwarz framework and theory. Applications
of the proposed nonsymmetric and indefinite Schwarz framework to solutions of
discontinuous Galerkin approximations of convection-diffusion problems are also
discussed. Extensive 1-D numerical experiments are also provided to gauge the
performance of the proposed Schwarz methods.


title: Thickness Dependent Carrier Density at the Surface of SrTiO3 (111) Slabs

abstract:
  We investigate the surface electronic structure and thermodynamic stability
of the SrTiO3 (111) slabs using density functional theory. We observe that, for
Ti-terminated slabs it is indeed possible to create a two-dimensional electron
gas (2DEG). However, the carrier density of the 2DEG displays a strong
thickness dependence due to the competition between electronic reconstruction
and polar distortions. As expected, having a surface oxygen atom at the Ti
termination can stabilize the system, eliminating any electronic
reconstruction, thereby making the system insulating. An analysis of the
surface thermodynamic stability suggests that the Ti terminated (111) surface
should be experimentally realizable. This surface may be useful for exploring
the behavior of electrons in oxide (111) interfaces and may have implications
for modern device applications.


title: Torsion-balance probes of fundamental physics

abstract:
  This white paper is submitted as part of Snowmass2013 (subgroup CF2). The
extraordinary sensitivity of torsion-balances can be used to search for the
ultra-feeble forces suggested by attempts to unify gravity with the other
fundamental interactions. The motivation, the results and their implications as
well as the future prospects of this work are summarized. The experiments
include tests of the universality of free fall (weak equivalence principle),
probes of the short-distance behavior of gravity (inverse-square law tests for
extra dimensions and exchange forces from new meV scale bosons), and
Planck-scale tests of Lorentz invariance (preferred-frame effects,
non-commutative geometries).


title:
Higher order A-stable schemes for the wave equation using a recursive
  convolution approach

abstract:
  In several recent works \cite{Causley2013a}, \cite{Causley2013}, we developed
a new second order, A-stable approach to wave propagation problems based on the
method of lines transpose (MOL$^T$) formulation combined with alternating
direction implicit (ADI) schemes. In this work, we present several important
modifications to our work, and thus obtain a family of wave solvers which are
unconditionally stable, accurate of order 2P, and require $O(P^d N)$ operations
per time step, where $N$ is the number of spatial points, and $d$ the number of
spatial dimensions. We obtain these schemes by including higher derivatives of
the solution, rather than increasing the number of time levels. The novel
aspect of our approach is that the higher derivatives are constructed using
successive applications of the convolution operator.
  We develop these schemes in one spatial dimension, and then extend the
results to higher dimensions, by reformulating the ADI scheme to include
recursive convolution. Thus, we retain a fast, unconditionally stable scheme,
which does not suffer from the large dispersion errors characteristic to the
ADI method. We demonstrate the utility of the method by applying it to a host
of wave propagation problems. This method holds great promise for developing
higher order, parallelizable algorithms for solving hyperbolic PDEs, and can
also be extended to parabolic PDEs.


title: Parseval frames with n+1 vectors in R^n

abstract:
  We construct a Parseval frame with $n+1$ vectors in $\R^n$ that contains a
given vector. We also provide a characterization of unit-norm frames that can
be scaled to a Parseval frame.


title: One more neighbor: The first brown dwarf in the VVV survey

abstract:
  Context. The discovery of brown dwarfs (BDs) in the solar neighborhood and
young star clusters has helped to constraint the low-mass end of the stellar
mass function and the initial mass function. We use data of the Vista Variables
in the V\'ia L\'actea (VVV), a near-infrared (NIR) multiwavelength (Z Y J H Ks)
multi-epoch (Ks) ESO Public Survey mapping the Milky Way bulge and southern
Galactic plane to search for nearby BDs.
  Aims. The ultimate aim of the project is to improve the completeness of the
census of nearby stellar and substellar objects towards the Galactic bulge and
inner disk regions.
  Methods. Taking advantage of the homogeneous sample of VVV multi-epoch data,
we identified stars with high proper motion (> 0.1"/yr), and then selected
low-mass objects using NIR colors. We searched for a possible parallax
signature using the all available Ks band epochs. We set some constraints on
the month-to-year scale Ks band variability of our candidates, and even
searched for possible transiting companions. We obtained NIR spectra to
properly classify spectral type and then the physical properties of the final
list of candidates.
  Results. We report the discovery of VVV BD001, a new member of the local
volume-limited sample (within 20pc from the sun) with well defined proper
motion, distance, and luminosity. The spectral type of this new object is an
L5+-1, unusually blue dwarf. The proper motion for this BD is
PM(\alpha)=-0.5455+-0.004 "/yr, PM(\delta)=-0.3255+-0.004 "/yr, and it has a
parallax of 57+-4 mas which translates into a distance of 17.5 +- 1.1 pc. VVV
BD001 shows no evidence of variability (\Delta Ks <0.05mag) over two years,
especially constrained on a six month scale during the year 2012.


title: Can Visible Light Communications Provide Gb/s Service?

abstract:
  Visible light communications (VLC) that use the infrastructure of the indoor
illumination system have been envisioned as a compact, safe, and green
alternative to WiFi for the downlink of an indoor wireless mobile communication
system. Although the optical spectrum is typically well-suited to high
throughput applications, combining communications with indoor lighting in a
commercially viable system imposes severe limitations both in bandwidth and
received power. Clever techniques are needed to achieve Gb/s transmission, and
to do it in a cost effective manner so as to successfully compete with other
high-capacity alternatives for indoor access, such as millimeter-wave
radio-frequency (RF). This article presents modulation schemes that have the
potential to overcome the many challenges faced by VLC in providing multi Gb/s
indoor wireless connectivity.


title: Knots with many minimal genus Seifert surfaces

abstract:
  Roberts proved that a family of alternating, arborescent, prime knots each
have at least $2^{2n-1}$ distinct minimal genus Seifert surfaces, where $n$ is
the genus of the knot in question. We give a subfamily of these knots that have
exactly this many minimal genus Seifert surfaces.


title: A unifying perspective: the relaxed linear micromorphic continuum

abstract:
  We formulate a relaxed linear elastic micromorphic continuum model with
symmetric Cauchy force-stresses and curvature contribution depending only on
the micro-dislocation tensor. Our relaxed model is still able to fully describe
rotation of the microstructure and to predict non-polar size-effects. It is
intended for the homogenized description of highly heterogeneous, but non polar
materials with microstructure liable to slip and fracture. In contrast to
classical linear micromorphic models our free energy is not uniformly pointwise
positive definite in the control of the independent constitutive variables. The
new relaxed micromorphic model supports well-posedness results for the dynamic
and static case. There, decisive use is made of new coercive inequalities
recently proved by Neff, Pauly and Witsch and by Bauer, Neff, Pauly and Starke.
The new relaxed micromorphic formulation can be related to dislocation
dynamics, gradient plasticity and seismic processes of earthquakes. It unifies
and simplifies the understanding of the linear micromorphic models.


title: Domain walls and their experimental signatures in s+is superconductors

abstract:
  Arguments were recently advanced that hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$
exhibits $s+is$ state at certain doping. Spontaneous breaking of time reversal
symmetry in $s+is$ state, dictates that it possess domain wall excitations.
Here, we discuss what are the experimentally detectable signatures of domain
walls in $s+is$ state. We find that in this state the domain walls can have
dipole-like magnetic signature (in contrast to the uniform magnetic signature
of domain walls $p+ip$ superconductors). We propose experiments where
quench-induced domain walls can be stabilized by geometric barriers and be
observed via their magnetic signature or their influence on the magnetization
process, thereby providing an experimental tool to confirm $s+is$ state.


title: Large Eddy Simulation, Turbulent Transport And The Renormalization Group

abstract:
  In large eddy simulations, the Reynolds averages of nonlinear terms are not
directly computable in terms of the resolved variables and require a closure
hypothesis or model, known as a subgrid scale term. Inspired by the
renormalization group (RNG),we introduce an expansion for the unclosed terms,
carried out explicitly to all orders. In leading order, this expansion defines
subgrid scale unclosed terms, which we relate to the dynamic subgrid scale
closure models. The expansion, which generalizes the Leonard stress for closure
analysis, suggests a systematic higher order determination of the model
coefficients.
  The RNG point of view sheds light on the nonuniqueness of the infinite
Reynolds number limit. For the mixing of N species, we see an N+1 parameter
family of infinite Reynolds number solutions labeled by dimensionless
parameters of the limiting Euler equations, in a manner intrinsic to the RNG
itself. Large eddy simulations, with their Leonard stress and dynamic subgrid
models, break this nonuniqueness and predict unique model coefficients on the
basis of theory. In this sense large eddy simulations go beyond the RNG
methodology, which does not in general predict model coefficients.


title: The Dark Side of Neutron Stars

abstract:
  We review severe constraints on asymmetric bosonic dark matter based on
observations of old neutron stars. Under certain conditions, dark matter
particles in the form of asymmetric bosonic WIMPs can be effectively trapped
onto nearby neutron stars, where they can rapidly thermalize and concentrate in
the core of the star. If some conditions are met, the WIMP population can
collapse gravitationally and form a black hole that can eventually destroy the
star. Based on the existence of old nearby neutron stars, we can exclude
certain classes of dark matter candidates.


title: Modular operads and the quantum open-closed homotopy algebra

abstract:
  We verify that certain algebras appearing in string field theory are algebras
over Feynman transform of modular operads which we describe explicitly.
Equivalent description in terms of solutions of generalized BV master equations
are explained from the operadic point of view.


title: Quasi-morphisms on contactomorphism groups and contact rigidity

abstract:
  We build homogeneous quasi-morphisms on the universal cover of the
contactomorphism group for certain prequantizations of monotone symplectic
toric manifolds. This is done using Givental's nonlinear Maslov index and a
contact reduction technique for quasi-morphisms. We show how these
quasi-morphisms lead to a hierarchy of rigid subsets of contact manifolds. We
also show that the nonlinear Maslov index has a vanishing property, which plays
a key role in our proofs. Finally we present applications to orderability of
contact manifolds and Sandon-type metrics on contactomorphism groups.


title:
An interactive engine for multilingual video browsing using semantic
  content

abstract:
  The amount of audio-visual information has increased dramatically with the
advent of High Speed Internet. Furthermore, technological advances in recent
years in the field of information technology, have simplified the use of video
data in various fields by the general public. This made it possible to store
large collections of video documents into computer systems. To enable efficient
use of these collections, it is necessary to develop tools to facilitate access
to these documents and handling them. In this paper we propose a method for
indexing and retrieval of video sequences in a video database of large
dimension, based on a weighting technique to calculate the degree of membership
of a concept in a video also a structuring of the data of the audio-visual
(context / concept / video) and a relevance feedback mechanism.


title: Flavoured searches for type-III seesaw at the LHC

abstract:
  We present a reinterpretation of CMS searches for type-III seesaw lepton
triplets at the LHC, both for the normal and the inverse seesaw. We find that,
in contrast with previous expectations, these searches in the trilepton final
state have a good sensitivity to triplets with predominant coupling to the tau
lepton. We also show that the limits resulting from direct searches can be
neatly presented for arbitrary masses and general flavour mixings. Thus, it
turns out that the common (and often unrealistic) simplifying assumptions about
the flavour couplings of the triplets used by experimental collaborations to
present their results are unnecessary and should be dropped.


title: Double-mode Cepheids in M31

abstract:
  Until now, double mode Cepheids (or beat Cepheids) were known in the Galaxy,
Magellanic Clouds and M33. Curiously, none of more than 2000 Cepheids in M31
was claimed to show two pulsation modes. We conducted a systematic search for
double mode Cepheids in the archival data and discovered four such objects. We
identify one of the stars as a first and second overtone pulsator even though
its secondary period is subject to strong aliasing. Two stars turn out to
pulsate in the fundamental mode and the first overtone. Their fundamental
periods are 9.392 d and 9.163 d. This makes them the first candidates for the
fundamental mode and the first overtone Cepheids, which double mode pulsations
are caused by the 1:2 resonance of the fundamental mode and the second
overtone.


title:
On the justification of the Foldy-Lax approximation for the acoustic
  scattering by small rigid bodies of arbitrary shapes

abstract:
  We are concerned with the acoustic scattering problem by many small rigid
obstacles of arbitrary shapes.
  We give a sufficient condition on the number $M$ and the diameter $a$ of the
obstacles as well as the minimum distance $d$ between them under which the
Foldy-Lax approximation is valid.
  Precisely, if we use single layer potentials for the representation of the
scattered fields, as it is done sometimes in the literature, then this
condition is $(M-1)\frac{a}{d^2} <c$, with an appropriate constant $c$, while
if we use double layer potentials then a weaker condition of the form
$\sqrt{M-1}\frac{a}{d} <c$ is enough.
  In addition, we derive the error in this approximation explicitly in terms of
the parameters $M, a$ and $d$. The analysis is based, in particular, on the
precise scalings of the boundary integral operators between the corresponding
  Sobolev spaces. As an application, we study the inverse scattering by the
small obstacles in the presence of multiple scattering.


title: The Quest for Sustainable Smart Grids

abstract:
  This letter is my comment about the opinion paper: Transdisciplinary electric
power grid science (PNAS, 2013 -
http://www.pnas.org/content/110/30/12159.full). [arXiv:1307.7305].


title: Singlet-Triplet Superconducting Quantum Magnetometer

abstract:
  Motivated by the recent experimental realization of a quantum interference
transistor based on the superconducting proximity effect, we here demonstrate
that the inclusion of a textured ferromagnet both strongly enhances the flux
sensitivity of such a device and additionally allows for singlet-triplet
switching by tuning a bias voltage. This functionality makes explicit use of
the induced spin-triplet correlations due to the magnetic texture. Whereas the
existence of such triplet correlations is well-known, our finding demonstrates
how spin-triplet superconductivity may be utilized for concrete technology,
namely to improve the functionality of ultra-sensitive magnetometers.


title:
Three Dimensional Hydrodynamic Simulations of Multiphase Galactic Disks
  with Star Formation Feedback: I. Regulation of Star Formation Rates

abstract:
  The energy and momentum feedback from young stars has a profound impact on
the interstellar medium (ISM), including heating and driving turbulence in the
neutral gas that fuels future star formation. Recent theory has argued that
this leads to a quasi-equilibrium self-regulated state, and for outer
atomic-dominated disks results in the surface density of star formation
$\Sigma_{SFR}$ varying approximately linearly with the weight of the ISM (or
midplane turbulent + thermal pressure). We use three-dimensional numerical
hydrodynamic simulations to test the theoretical predictions for thermal,
turbulent, and vertical dynamical equilibrium, and the implied functional
dependence of $\Sigma_{SFR}$ on local disk properties. Our models demonstrate
that all equilibria are established rapidly, and that the expected
proportionalities between mean thermal and turbulent pressures and
$\Sigma_{SFR}$ apply. For outer disk regions, this results in $\Sigma_{SFR}
\propto \Sigma \sqrt{\rho_{sd}}$, where $\Sigma$ is the total gas surface
density and $\rho_{sd}$ is the midplane density of the stellar disk (plus dark
matter). This scaling law arises because $\rho_{sd}$ sets the vertical
dynamical time in our models (and outer disk regions generally). The
coefficient in the star formation law varies inversely with the specific energy
and momentum yield from massive stars. We find proportions of warm and cold
atomic gas, turbulent-to-thermal pressure, and mean velocity dispersions that
are consistent with Solar-neighborhood and other outer-disk observations. This
study confirms the conclusions of a previous set of simulations, which
incorporated the same physics treatment but was restricted to radial-vertical
slices through the ISM.


title: Using Cumulative Number Densities to Compare Galaxies across Cosmic Time

abstract:
  Comparing galaxies across redshifts at fixed cumulative number density is a
popular way to estimate the evolution of specific galaxy populations. This
method ignores scatter in mass accretion histories and galaxy-galaxy mergers,
which can lead to errors when comparing galaxies over large redshift ranges
(Delta z > 1). We use abundance matching in the LCDM paradigm to estimate the
median change in number density with redshift and provide a simple fit (+0.16
dex per unit Delta z) for progenitors of z = 0 galaxies. We find that galaxy
descendants do not evolve in the same way as galaxy progenitors, largely due to
scatter in mass accretion histories. We also provide estimates for the 1-sigma
range of number densities corresponding to galaxy progenitors and descendants.
Finally, we discuss some limits on number density comparisons, which arise due
to difficulties measuring physical quantities (e.g., stellar mass) consistently
across redshifts. A public tool to calculate number density evolution for
galaxies, as well as approximate halo masses, is available online.


title: A Healthy Electron/Neutron EDM in D3/D7 mu-Split-Like SUSY

abstract:
  Within the framework of N=1 gauged supergravity, using a phenomenological
model which can be obtained locally as a Swiss-Cheese Calabi-Yau
string-theoretic compactification with a mobile D3-brane localized on a nearly
sLag three-cycle in the Calabi-Yau and fluxed stacks of wrapped D7-branes, and
which provides a natural realization of mu-Split SUSY, we show that in addition
to getting a significant value of electron/neutron EDM d_{e,n}/e at two-loop
level, one can obtain a sizable contribution of d_{e,n}/e even at one-loop
level. We obtain d_{e}/e ~ O(10^{-29}) cm from two-loop diagrams involving
heavy sfermions and a light Higgs, and d_{e}/e ~ O(10^{-32}) cm from one-loop
diagram involving heavy chargino and a light Higgs. Also, d_{n}/e ~ O(10^{-33})
cm from one-loop diagram involving SM-like quarks and Higgs. Next, by
considering a Barr-Zee diagram involving W bosons and Higgs, and conjecturing
that the CP-violating phase can appear from a linear combination of Higgs
doublet obtained in the context of mu-split SUSY, we obtain d_{e,n}/e ~
O(10^{-27}) cm at two-loop level .


title:
Entanglement entropy of compressible holographic matter: loop
  corrections from bulk fermions

abstract:
  Entanglement entropy is a useful probe of compressible quantum matter because
it can detect the existence of Fermi surfaces, both of microscopic fermionic
degrees of freedom and of "hidden" gauge charged fermions. Much recent
attention has focused on holographic efforts to model strongly interacting
compressible matter of interest for condensed matter physics. We complete the
entanglement analysis initiated in Huijse {\em et al.}, Phys. Rev. B 85, 035121
(2012) (arXiv:1112.0573) and Ogawa {\em et al.}, JHEP 1, 125 (2012)
(arXiv:1111.1023) using the recent proposal of Faulkner {\em et al.}
(arXiv:1307.2892) to analyze the entanglement entropy of the visible fermions
which arises from bulk loop corrections. We find perfect agreement between
holographic and field theoretic calculations.


title:
The Discovery of a New Instability in a Hyperaccretion Flow and its
  Implication for Gamma-ray Bursts

abstract:
  A hyperaccretion flow around a stellar mass black hole is thought to be the
most plausible engine that powers gamma-ray bursts (GRBs). The flow efficiently
cools via neutrino emission at >~ 0.003-0.01 M_sun s^{-1} (corresponding to a
luminosity of ~10^50 erg s^{-1}), while neither neutrino nor photon emission is
efficient below this rate, so the flow should be advection dominated. We
carefully solve how a transition occurs from the advection-dominated to the
neutrino-dominated branches, and find that the slope of the thermal equilibrium
curve is negative in the surface density - accretion rate (Sigma-Mdot) plane, a
condition for viscous instability, at radii smaller than ~12R_g (with R_g being
the gravitational radius). We also confirm that the flow is thermally stable.
The consequence of this instability is the formation of a clumpy structure in
the flow. This is because the larger (respectively smaller) surface density is,
the smaller (respectively larger) the mass accretion rate from the region in
question becomes, leading to growth of the density contrast. The timescale for
clump formation is estimated to be shorter than 0.1s. The observational
implication is discussed in the context of GRBs. We suggest that this might
explain the origin of the large variability observed in the prompt emission of
GRBs.


title: Jet Luminosity from Neutrino-Dominated Accretion Flows in GRBs

abstract:
  A hyperaccretion disk around a stellar-mass black hole is a plausible model
for the central engine that powers gamma-ray bursts (GRBs). We estimate the
luminosity of a jet driven by magnetohydrodynamic processes such as the
Blandford-Znajek (BZ) mechanism as a function of mass accretion rate, the black
hole mass, and other accretion parameters. We show that the jet is most
efficient when the accretion flow is cooled via optically-thin neutrino
emission, and that its luminosity is much larger than the energy deposition
rate through neutrino annihilation provided that the black hole is spinning
rapidly enough. Also, we find a significant jump in the jet luminosity at the
transition mass accretion rate between the advection dominated accretion flow
(ADAF) regime and the neutrino-dominated accretion flow (NDAF) regime. This may
cause the large variability observed in the prompt emission of GRBs.


title: Chiral Bosonic Mott Insulator on the Frustrated Triangular Lattice

abstract:
  We study the superfluid and insulating phases of interacting bosons on the
triangular lattice with an inverted dispersion, corresponding to frustrated
hopping between sites. The resulting single-particle dispersion has multiple
minima at nonzero wavevectors in momentum space, in contrast to the unique
zero-wavevector minimum of the unfrustrated problem. As a consequence, the
superfluid phase is unstable against developing additonal chiral order that
breaks time reversal (T) and parity (P) symmetries by forming a condensate at
nonzero wavevector. We demonstrate that the loss of superfluidity can lead to
an even more exotic phase, the chiral Mott insulator, with nontrivial current
order that breaks T, P. These results are obtained via variational estimates,
as well as a combination of bosonization and DMRG of triangular ladders, which
taken together permit a fairly complete characterization of the phase diagram.
We discuss the relevance of these phases to optical lattice experiments, as
well as signatures of chiral symmetry breaking in time-of-flight images.


title: RCW36: characterizing the outcome of massive star formation

abstract:
  Massive stars play a dominant role in the process of clustered star
formation, with their feedback into the molecular cloud through ionizing
radiation, stellar winds and outflows. The formation process of massive stars
is poorly constrained because of their scarcity, the short formation timescale
and obscuration. By obtaining a census of the newly formed stellar population,
the star formation history of the young cluster and the role of the massive
stars within it can be unraveled. We aim to reconstruct the formation history
of the young stellar population of the massive star-forming region RCW 36. We
study several dozens of individual objects, both photometrically and
spectroscopically, look for signs of multiple generations of young stars and
investigate the role of the massive stars in this process. We obtain a census
of the physical parameters and evolutionary status of the young stellar
population. Using a combination of near-infrared photometry and spectroscopy we
estimate ages and masses of individual objects. We identify the population of
embedded young stellar objects (YSO) by their infrared colors and emission line
spectra. RCW 36 harbors a stellar population of massive and intermediate-mass
stars located around the center of the cluster. Class 0/I and II sources are
found throughout the cluster. The central population has a median age of 1.1
+/- 0.6 Myr. Of the stars which could be classified, the most massive ones are
situated in the center of the cluster. The central cluster is surrounded by
filamentary cloud structures; within these, some embedded and accreting YSOs
are found. Our age determination is consistent with the filamentary structures
having been shaped by the ionizing radiation and stellar winds of the central
massive stars. The formation of a new generation of stars is ongoing, as
demonstrated by the presence of embedded protostellar clumps, and two exposed
jets.


title:
Orthogonality and Cooperation in Collaborative Spectrum Sensing through
  MIMO Decision Fusion

abstract:
  This paper deals with spectrum sensing for cognitive radio scenarios where
the decision fusion center (DFC) exploits array processing. More specifically,
we explore the impact of user cooperation and orthogonal transmissions among
secondary users (SUs) on the reporting channel. To this aim four protocols are
considered: (i) non-orthogonal and non-cooperative; (ii) orthogonal and
non-cooperative; (iii) non-orthogonal and cooperative; (iv) orthogonal and
cooperative. The DFC employs maximum ratio combining (MRC) rule and performance
are evaluated in terms of complementary receiver operating characteristic
(CROC). Analytical results, coupled with Monte Carlo simulations, are
presented.


title: Precision measures of the primordial abundance of deuterium

abstract:
  We report the discovery of deuterium absorption in the very metal-poor
([Fe/H] = -2.88) damped Lyman-alpha system at z_abs = 3.06726 toward the QSO
SDSS J1358+6522. On the basis of 13 resolved D I absorption lines and the
damping wings of the H I Lyman alpha transition, we have obtained a new,
precise measure of the primordial abundance of deuterium. Furthermore, to
bolster the present statistics of precision D/H measures, we have reanalyzed
all of the known deuterium absorption-line systems that satisfy a set of strict
criteria. We have adopted a blind analysis strategy (to remove human bias), and
developed a software package that is specifically designed for precision D/H
abundance measurements. For this reanalyzed sample of systems, we obtain a
weighted mean of (D/H)_p = (2.53 +/- 0.04) x 10^-5, corresponding to a
Universal baryon density100 Omega_b h^2 = 2.202 +/- 0.046 for the standard
model of Big Bang Nucleosynthesis. By combining our measure of (D/H)_p with
observations of the cosmic microwave background, we derive the effective number
of light fermion species, N_eff = 3.28 +/- 0.28. We therefore rule out the
existence of an additional (sterile) neutrino (i.e. N_eff = 4.046) at 99.3
percent confidence (2.7 sigma), provided that N_eff and the baryon-to-photon
ratio (eta_10) did not change between BBN and recombination. We also place a
strong bound on the neutrino degeneracy parameter, xi_D = +0.05 +/- 0.13 based
only on the CMB+(D/H)_p observations. Combining xi_D with the current best
literature measure of Y_p, we find |xi| <= +0.062. In future, improved
measurements of several key reaction rates, in particular d(p,gamma)3He, and
further measures of (D/H)_p with a precision comparable to those considered
here, should allow even more stringent limits to be placed on new physics
beyond the standard model.


title:
Experimental reconstruction of work distribution and verification of
  fluctuation relations at the full quantum level

abstract:
  Research on the out-of-equilibrium dynamics of quantum systems has so far
produced important statements on the thermodynamics of small systems undergoing
quantum mechanical evolutions. Key examples are provided by the Crooks and
Jarzynski relations: taking into account fluctuations in non-equilibrium
dynamics, such relations connect equilibrium properties of thermodynamical
relevance with explicit non-equilibrium features. Although the experimental
verification of such fundamental relations in the classical domain has
encountered some success, their quantum mechanical version requires the
assessment of the statistics of work performed by or onto an evolving quantum
system, a step that has so far encountered considerable difficulties in its
implementation due to the practical difficulty to perform reliable projective
measurements of instantaneous energy states. In this paper, by exploiting a
radical change in the characterization of the work distribution at the quantum
level, we report the first experimental verification of the quantum Jarzynski
identity and the Tasaki-Crooks relation following a quantum process implemented
in a Nuclear Magnetic Resonance (NMR) system. Our experimental approach has
enabled the full characterisation of the out-of-equilibrium dynamics of a
quantum spin in a statistically significant way, thus embodying a key step
towards the grounding of quantum-systems thermodynamics.


title:
A new method for enumerating independent sets of a fixed size in general
  graphs

abstract:
  We develop a new method for enumerating independent sets of a fixed size in
general graphs, and we use this method to show that a conjecture of Engbers and
Galvin holds for all but finitely many graphs. We also use our method to prove
special cases of a conjecture of Kahn. In addition, we show that our method is
particularly useful for computing the number of independent sets of small sizes
in general regular graphs and Moore graphs, and we argue that it can be used in
many other cases when dealing with graphs that have numerous structural
restrictions.


title: Arabic Text Recognition in Video Sequences

abstract:
  In this paper, we propose a robust approach for text extraction and
recognition from Arabic news video sequence. The text included in video
sequences is an important needful for indexing and searching system. However,
this text is difficult to detect and recognize because of the variability of
its size, their low resolution characters and the complexity of the
backgrounds. To solve these problems, we propose a system performing in two
main tasks: extraction and recognition of text. Our system is tested on a
varied database composed of different Arabic news programs and the obtained
results are encouraging and show the merits of our approach.


title: Superdiffusion of Cosmic Rays: Implications for Cosmic Ray Acceleration

abstract:
  Diffusion of cosmic rays (CRs) is the key process of understanding their
propagation and acceleration. We employ the description of spatial separation
of magnetic field lines in MHD turbulence in Lazarian & Vishniac (1999) to
quantify the divergence of magnetic field on scales less than the injection
scale of turbulence and show this divergence induces superdiffusion of CR in
the direction perpendicular to the mean magnetic field. The perpendicular
displacement squared increases, not as distance $x$ along magnetic field, which
is the case for a regular diffusion, but as the $x^{3}$ for freely streaming
CRs. The dependence changes to $x^{3/2}$ for the CRs propagating diffusively
along magnetic field. In the latter case we show that it is important to
distinguish the perpendicular displacement in respect to the mean field and to
the local magnetic field. We consider how superdiffusion changes the
acceleration of CRs in shocks and show how it decreases efficiency of the CRs
acceleration in perpendicular shocks. We also demonstrate that in the case when
small-scale magnetic field is being generated in the pre-shock region, an
efficient acceleration can take place for the CRs streaming without collisions
along magnetic loops.


title:
Quasi-energies, parametric resonances, and stability limits in ac-driven
  $\mathcal{PT}$-symmetric systems

abstract:
  We introduce a simple model for implementing the concepts of quasi-energy and
parametric resonances (PRs) in systems with the $\mathcal{PT}$ symmetry, i.e.,
a pair of coupled and mutually balanced gain and loss elements. The parametric
(ac) forcing is applied through periodic modulation of the coefficient
accounting for the coupling of the two degrees of freedom. The system may be
realized in optics as a dual-core waveguide with the gain and loss applied to
different cores, and the thickness of the gap between them subject to a
periodic modulation. The onset and development of the parametric instability
for a small forcing amplitude ($V_{1}$) is studied in an analytical form. The
full dynamical chart of the system is generated by systematic simulations. At
sufficiently large values of the forcing frequency, $\omega $, tongues of the
parametric instability originate, with the increase of $V_{1}$, as predicted by
the analysis. However, the tongues following further increase of $V_{1}$
feature a pattern drastically different from that in usual
(non-$\mathcal{PT}$)\ parametrically driven systems: instead of bending down to
larger values of the dc coupling constant, $V_{0}$, they maintain a direction
parallel to the $V_{1}$ axis. The system of the parallel tongues gets dense
with the decrease of $\omega $, merging into a complex small-scale structure of
alternating regions of stability and instability. The cases of $\omega
\rightarrow 0$ and $\omega \rightarrow \infty $ are studied analytically by
means of the adiabatic and averaging approximation, respectively. The cubic
nonlinearity, if added to the system, alters the picture, destabilizing many
originally robust dynamical regimes, and stabilizing some which were unstable.


title:
Brightest cluster galaxies in cosmological simulations: achievements and
  limitations of AGN feedback models

abstract:
  We analyze the basic properties of Brightest Cluster Galaxies (BCGs) produced
by state of the art cosmological zoom-in hydrodynamical simulations. These
simulations have been run with different sub-grid physics included. Here we
focus on the results obtained with and without the inclusion of the
prescriptions for supermassive black hole (SMBH) growth and of the ensuing
Active Galactic Nuclei (AGN) feedback. The latter process goes in the right
direction of decreasing significantly the overall formation of stars. However,
BCGs end up still containing too much stellar mass, a problem that increases
with halo mass, and having an unsatisfactory structure. This is in the sense
that their effective radii are too large, and that their density profiles
feature a flattening on scales much larger than observed. We also find that our
model of thermal AGN feedback has very little effect on the stellar velocity
dispersions, which turn out to be very large. Taken together, these problems,
which to some extent can be recognized also in other numerical studies
typically dealing with smaller halo masses, indicate that on one hand present
day sub-resolution models of AGN feedback are not effective enough in
diminishing the global formation of stars in the most massive galaxies, but on
the other hand they are relatively too effective in their centers. It is likely
that a form of feedback generating large scale gas outflows from BCGs
precursors, and a more widespread effect over the galaxy volume, can alleviate
these difficulties.


title:
Hardness of Finding Independent Sets in 2-Colorable and Almost
  2-Colorable Hypergraphs

abstract:
  This work studies the hardness of finding independent sets in hypergraphs
which are either 2-colorable or are almost 2-colorable, i.e. can be 2-colored
after removing a small fraction of vertices and the incident hyperedges. To be
precise, say that a hypergraph is (1-eps)-almost 2-colorable if removing an eps
fraction of its vertices and all hyperedges incident on them makes the
remaining hypergraph 2-colorable. In particular we prove the following results.
  For an arbitrarily small constant gamma > 0, there is a constant xi > 0, such
that, given a 4-uniform hypergraph on n vertices which is (1 - eps)-almost
2-colorable for eps = 2^{-(log n)^xi}, it is quasi-NP-hard to find an
independent set of n/(2^{(log n)^{1-gamma}}) vertices.
  For any constants eps, delta > 0, given as input a 3-uniform hypergraph on
$n$ vertices which is (1-eps)-almost 2-colorable, it is NP-hard to find an
independent set of delta n vertices. Assuming the d-to-1 Games Conjecture the
following holds.
  For any constant delta > 0, given a 2-colorable 3-uniform hypergraph on n
vertices, it is NP-hard to find an independent set of delta n vertices.
  The hardness result on independent set in almost 2-colorable 3-uniform
hypergraphs was earlier known only assuming the Unique Games Conjecture. In
this work we prove the result unconditionally. For independent sets in
2-colorable 3-uniform hypergaphs we prove the first strong hardness result,
albeit assuming the d-to-1 Games Conjecture. Our result on almost 2-colorable
4-uniform hypergraphs gives the first nearly polynomial hardness factor for
independent set in hypergraphs which are (almost) colorable with constantly
many colors. It partially bridges the gap between the previous best lower bound
of poly(log n) and the algorithmic upper bounds of n^{Omega(1)}.


title:
Accretion variability of Herbig Ae/Be stars observed by X-Shooter. HD
  31648 and HD 163296

abstract:
  This work presents X-Shooter/VLT spectra of the prototypical, isolated Herbig
Ae stars HD 31648 (MWC 480) and HD 163296 over five epochs separated by
timescales ranging from days to months. Each spectrum spans over a wide
wavelength range covering from 310 to 2475 nm. We have monitored the continuum
excess in the Balmer region of the spectra and the luminosity of twelve
ultraviolet, optical and near infrared spectral lines that are commonly used as
accretion tracers for T Tauri stars. The observed strengths of the Balmer
excesses have been reproduced from a magnetospheric accretion shock model,
providing a mean mass accretion rate of 1.11 x 10^-7 and 4.50 x 10^-7 Msun
yr^-1 for HD 31648 and HD 163296, respectively. Accretion rate variations are
observed, being more pronounced for HD 31648 (up to 0.5 dex). However, from the
comparison with previous results it is found that the accretion rate of HD
163296 has increased by more than 1 dex, on a timescale of ~ 15 years. Averaged
accretion luminosities derived from the Balmer excess are consistent with the
ones inferred from the empirical calibrations with the emission line
luminosities, indicating that those can be extrapolated to HAe stars. In spite
of that, the accretion rate variations do not generally coincide with those
estimated from the line luminosities, suggesting that the empirical
calibrations are not useful to accurately quantify accretion rate variability.


title:
Galactic abundance gradients from Cepheids: alpha and heavy elements in
  the outer disk

abstract:
  Context: Galactic abundance gradients set strong constraints to
chemo-dynamical evolutionary models of the Milky Way. Given the PL relations
that provide accurate distances and the large number of spectral lines,
Cepheids are excellent tracers of the present-day abundance gradients. Aims: We
want to measure the Galactic abundance gradient of several chemical elements.
While the slope of the Cepheid iron gradient did not vary much from the very
first studies, the gradients of the other elements are not that well
constrained. In this paper we focus on the inner and outer regions of the
Galactic thin disk. Methods: We use HR spectra (FEROS, ESPADONS, NARVAL) to
measure the abundances of several light (Na, Al), alpha (Mg, Si, S, Ca), and
heavy elements (Y, Zr, La, Ce, Nd, Eu) in a sample of 65 Milky Way Cepheids.
Combining these results with accurate distances from period-Wesenheit relations
in the NIR enables us to determine the abundance gradients in the Milky Way.
Results: Our results are in good agreement with previous studies on either
Cepheids or other tracers. In particular, we confirm an upward shift of
approximatively 0.2 dex for the Mg abundances, as has recently been reported.
We also confirm the existence of a gradient for all the heavy elements studied
in the context of a LTE analysis. However, for Y, Nd, and especially La, we
find lower abundances for Cepheids in the outer disk than reported in previous
studies, leading to steeper gradients. This effect can be explained by the
differences in the line lists used by different groups. Conclusions: Our data
do not support a flattening of the gradients in the outer disk, in agreement
with recent Cepheid studies and chemo-dynamical simulations. This is in
contrast to the open cluster observations but remains compatible with a picture
where the transition zone between the inner disk and the outer disk would move
outward with time.


title:
On integrability of zero-range chipping models with factorized steady
  state

abstract:
  Conditions of integrability of general zero range chipping models with
factorized steady state, which were proposed in [Evans, Majumdar, Zia 2004 J.
Phys. A 37 L275], are examined. We find a three-parametric family of hopping
probabilities for the models solvable by the Bethe ansatz, which includes most
of known integrable stochastic particle models as limiting cases. The solution
is based on the quantum binomial formula for two elements of an associative
algebra obeying generic homogeneous quadratic relations, which is proved as a
byproduct. We use the Bethe ansatz to solve an eigenproblem for the transition
matrix of the Markov process. On its basis we conjecture an integral formula
for the Green function of evolution operator for the model on an infinite
lattice and derive the Bethe equations for the spectrum of the model on a ring.


title: Hypersurfaces Invariant by Pfaff Equations

abstract:
  We present results expressing conditions for the existence of meromorphic
first integrals for Pfaff equations of arbitrary codimension, integrable or
not, on complex manifolds. These results are in the same vein as previous ones
by J-P. Jouanolou and E. Ghys. We also prove an enumerative result counting the
number of hypersurfaces invariant by a projective holomorphic foliation with
split tangent sheaf.


title: Testing MONDian Dark Matter with Galactic Rotation Curves

abstract:
  MONDian dark matter (MDM) is a new form of dark matter quantum that naturally
accounts for Milgrom's scaling, usually associated with modified Newtonian
dynamics (MOND), and theoretically behaves like cold dark matter (CDM) at
cluster and cosmic scales. In this paper, we provide the first observational
test of MDM by fitting rotation curves to a sample of 30 local spiral galaxies
(z approximately 0.003). For comparison, we also fit the galactic rotation
curves using MOND, and CDM. We find that all three models fit the data well.
The rotation curves predicted by MDM and MOND are virtually indistinguishable
over the range of observed radii (~1 to 30 kpc). The best-fit MDM and CDM
density profiles are compared. We also compare with MDM the dark matter density
profiles arising from MOND if Milgrom's formula is interpreted as Newtonian
gravity with an extra source term instead of as a modification of inertia. We
find that discrepancies between MDM and MOND will occur near the center of a
typical spiral galaxy. In these regions, instead of continuing to rise sharply,
the MDM mass density turns over and drops as we approach the center of the
galaxy. Our results show that MDM, which restricts the nature of the dark
matter quantum by accounting for Milgrom's scaling, accurately reproduces
observed rotation curves.


title:
\nu-production in Centaurus A and M87 from \gamma-ray interactions with
  the gas and dust at the sources

abstract:
  Centaurus A and M87 are the closest galaxies with active galactic nuclei and
TeV gamma-ray emission. The existence of such TeV radiation suggests the
production of a neutrino flux from the photo- hadronic interactions of the
gamma-photons of the active galaxies and their own gas and dust content. Using
a simple model of Centaurus A and M87, the corresponding neutrino luminosities
at source and their fluxes at Earth were calculated. The neutrino fluxes
associated with the aforementioned process resulted to be $E^2 \Phi_{\nu +
\bar{\nu}} < 10^{-13} s^{-1} GeV cm^{-2}$, more than 6 orders of magnitude
below the modern upper limits from neutrino telescopes. It will be shown that,
at high-energies relevant for neutrino astronomy, these neutrino fluxes are not
competitive with those fluxes which could be produced from astrophysical
scenarios involving cosmic ray acceleration.


title: Optimal processing of reversible quantum channels

abstract:
  We consider the general problem of the optimal transformation of N uses of
(possibly different) unitary channels to a single use of another unitary
channel in any finite dimension. We show how the optimal transformation can be
fully parallelized, consisting in a preprocessing channel followed by a
parallel action of all the N unitaries and a final postprocessing channel. Our
techniques allow to achieve an exponential reduction in the number of the free
parameters of the optimization problem making it amenable to an efficient
numerical treatment. Finally, we apply our general results to find the
analytical solution for special cases of interest like the cloning of qubit
phase gates.


title:
A new life for sterile neutrinos: resolving inconsistencies using hot
  dark matter

abstract:
  Within the standard LCDM model of cosmology, the recent Planck measurements
have shown discrepancies with other observations, e.g., measurements of the
current expansion rate H_0, the galaxy shear power spectrum and counts of
galaxy clusters. We show that if LCDM is extended by a hot dark matter
component, which could be interpreted as a sterile neutrino, the data sets can
be combined consistently. A combination of Planck data, WMAP-9 polarisation
data, measurements of the BAO scale, the HST measurement of H_0, Planck galaxy
cluster counts and galaxy shear data from the CFHTLens survey yields Delta
N_eff = 0.61 pm 0.30 and m_s^eff = (0.41 pm 0.13) eV at 1 sigma. The former is
driven mainly by the large H_0 of the HST measurement, while the latter is
driven by cluster data. CFHTLens galaxy shear data prefer Delta N_eff >0 and a
non-zero mass. Taken together, we find hints for the presence of a hot dark
matter component at 3 sigma. A sterile neutrino motivated by the reactor and
gallium anomalies appears rejected at even higher significance and an
accelerator anomaly sterile neutrino is found in tension at 2 sigma.


title:
Interpretation of experimental results on Kondo systems with crystal
  field

abstract:
  We present a simple approach to calculate the thermodynamic properties of
single Kondo impurities including orbital degeneracy and crystal field effects
(CFE) by extending a previous proposal by K. D. Schotte and U. Schotte [Physics
Lett. A 55, 38 (1975)]. Comparison with exact solutions for the specific heat
of a quartet ground state split into two doublets shows deviations below $10\%$
in absence of CFE and a quantitative agreement for moderate or large CFE. As an
application, we fit the measured specific heat of the compounds CeCu$_2$Ge$_2$,
CePd$_{3}$Si$_{0.3}$, CePdAl, CePt, Yb$_2$Pd$_2$Sn and YbCo$_2$Zn$_{20}$. The
agreement between theory and experiment is very good or excellent depending on
the compound, except at very low temperatures due to the presence of magnetic
correlations (not accounted in the model).


title:
Three-dimensional pure deflagration models with nucleosynthesis and
  synthetic observables for Type Ia supernovae

abstract:
  We investigate whether pure deflagration models of Chandrasekhar-mass
carbon-oxygen white dwarf stars can account for one or more subclass of the
observed population of Type Ia supernova (SN Ia) explosions. We compute a set
of 3D full-star hydrodynamic explosion models, in which the deflagration
strength is parametrized using the multispot ignition approach. For each model,
we calculate detailed nucleosynthesis yields in a post-processing step with a
384 nuclide nuclear network. We also compute synthetic observables with our 3D
Monte Carlo radiative transfer code for comparison with observations. For weak
and intermediate deflagration strengths (energy release E_nuc <~ 1.1 x 10^51
erg), we find that the explosion leaves behind a bound remnant enriched with 3
to 10 per cent (by mass) of deflagration ashes. However, we do not obtain the
large kick velocities recently reported in the literature. We find that weak
deflagrations with E_nuc ~ 0.5 x 10^51 erg fit well both the light curves and
spectra of 2002cx-like SNe Ia, and models with even lower explosion energies
could explain some of the fainter members of this subclass. By comparing our
synthetic observables with the properties of SNe Ia, we can exclude the
brightest, most vigorously ignited models as candidates for any observed class
of SN Ia: their B - V colours deviate significantly from both normal and
2002cx-like SNe Ia and they are too bright to be candidates for other
subclasses.


title: Anti-Coordination Games and Stable Graph Colorings

abstract:
  Motivated by understanding non-strict and strict pure strategy equilibria in
network anti-coordination games, we define notions of stable and, respectively,
strictly stable colorings in graphs. We characterize the cases when such
colorings exist and when the decision problem is NP-hard. These correspond to
finding pure strategy equilibria in the anti-coordination games, whose price of
anarchy we also analyze. We further consider the directed case, a
generalization that captures both coordination and anti-coordination. We prove
the decision problem for non-strict equilibria in directed graphs is NP-hard.
Our notions also have multiple connections to other combinatorial questions,
and our results resolve some open problems in these areas, most notably the
complexity of the strictly unfriendly partition problem.


title: Ising models on the Regularized Apollonian Network

abstract:
  We investigate the critical properties of Ising models on a Regularized
Apollonian Network (RAN), here defined as a kind of Apollonian Network (AN) in
which the connectivity asymmetry associated to its corners is removed.
Different choices for the coupling constants between nearest neighbors are
considered, and two different order parameters are used to detect the critical
behaviour. While ordinary ferromagnetic and anti-ferromagnetic models on RAN do
not undergo a phase transition, some anti-ferrimagnetic models show an
interesting infinite order transition. All results are obtained by an exact
analytical approach based on iterative partial tracing of the Boltzmann factor
as intermediate steps for the calculation of the partition function and the
order parameters.


title:
On the Relation between Perfect Tunneling and Band Gaps for SNG
  Metamaterial Structures

abstract:
  In this article, we have proposed a compact classification of isotropic and
homogeneous single negative (SNG) electromagnetic metamaterial based perfect
tunneling unit cells. This unified classification has been made by means of the
band gap theories and properties of the arrays made up of these unit cells.
Based on their reported characteristics, we have proposed new structures that
simultaneously show perfect tunneling band and complete band gap (CBG-omni
directional stop band for both polarizations). Besides, we have identified a
kind of perfect tunneling which can be considered as "phase shifted perfect
tunneling". Several interesting and new phenomena like Complete Perfect
Tunneling (CPT-omni directional perfect tunneling for both polarizations), Band
Gap Shifting,CBG in Double Positive (DPS) material range, etc. have been
reported with proper physical and mathematical explanations.


title:
Functional plasmonic nano-circuits with low insertion and propagation
  losses

abstract:
  We experimentally demonstrate plasmonic nano-circuits operating as
sub-diffraction directional couplers optically excited with high efficiency
from free-space using optical Yagi-Uda style antennas at \lambda = 1550 nm. The
optical Yagi-Uda style antennas are designed to feed channel plasmon waveguides
with high efficiency (45 % in coupling, 60 % total emission), narrow angular
directivity (< 40{\deg}) and low insertion loss. SPP gap waveguides exhibit
propagation lengths as large as 34 {\mu}m with adiabatically tuned confinement,
and are integrated with ultra-compact (5 \mu m x 10 \mu m), highly dispersive
directional couplers, which enable 30 dB discrimination over {\Delta}{\lambda}
= 200 nm with only 0.3 dB device loss.


title: Isomorphisms between pattern classes

abstract:
  Isomorphisms p between pattern classes A and B are considered. It is shown
that, if p is not a symmetry of the entire set of permutations, then, to within
symmetry, A is a subset of one a small set of pattern classes whose structure,
including their enumeration, is determined.


title: A short proof of the Arendt-Chernoff-Kato theorem

abstract:
  We give a short new proof of the Arendt-Chernoff-Kato theorem, which
characterizes generators of positive C0 semigroups in order unit spaces. The
proof avoids half-norms and subdifferentials, and is based on a sufficient
condition for an operator to have positive inverse, which is new even for
matrices.


title:
Spin-orbit interaction induced singularity of the charge density
  relaxation propagator

abstract:
  The charge density relaxation propagator of a two dimensional electron
system, which is the slope of the imaginary part of the polarization function,
exhibits singularities for bosonic momenta having the order of the spin-orbit
momentum and depending on the momentum orientation. We have provided an
intuitive understanding for this non-analytic behavior in terms of the inter
chirality subband electronic transitions, induced by the combined action of
Bychkov-Rashba (BR) and Dresselhaus (D) spin-orbit coupling. It is shown that
the regular behavior of the relaxation propagator is recovered in the presence
of only one BR or D spin-orbit field or for spin-orbit interaction with equal
BR and D coupling strengths. This creates a new possibility to influence
carrier relaxation properties by means of an applied electric field.


title: The High Resolution X-Ray Imaging Detector Planes for the MIRAX Mission

abstract:
  The MIRAX X-ray observatory, the first Brazilian-led astrophysics space
mission, is designed to perform an unprecedented wide-field, wide-band hard
X-ray (5-200 keV) survey of Galactic X-ray transient sources. In the current
configuration, MIRAX will carry a set of four coded-mask telescopes with high
spatial resolution Cadmium Zinc Telluride (CZT) detector planes, each one
consisting of an array of 64 closely tiled CZT pixelated detectors. Taken
together, the four telescopes will have a total detection area of 959 cm^2, a
large field of view (60x60 degrees FWHM), high angular resolution for this
energy range (6 arcmin) and very good spectral resolution (~2 keV @ 60 keV). A
stratospheric balloon-borne prototype of one of the MIRAX telescopes has been
developed, tested and flown by the Harvard-Smithsonian Center for Astrophysics
(CfA) as part of the ProtoEXIST program. In this paper we show results of
validation and calibration tests with individual CZT detectors of the
ProtoEXIST second generation experiment (P2). Each one of 64 detector units of
the P2 detector plane consists of an ASIC, developed by Caltech for the NuSTAR
telescope, hybridized to a CZT crystal with 0.6 mm pixel size. The performance
of each detector was evaluated using radioactive sources in the laboratory. The
calibration results show that the P2 detectors have average energy resolution
of ~2.1 keV @ 60 keV and ~2.3 keV @ 122 keV. P2 was also successfully tested on
near-space environment on a balloon flight, demonstrating the detector unit
readiness for integration on a space mission telescope, as well as satisfying
all MIRAX mission requirements.


title:
Framed graphs and the non-local ideal in the knot Floer cube of
  resolutions

abstract:
  This article addresses the two significant aspects of Ozsv\'ath and Szab\'o's
knot Floer cube of resolutions that differentiate it from Khovanov and
Rozansky's HOMFLY-PT chain complex: (1) the use of twisted coefficients and (2)
the appearance of a mysterious non-local ideal. Our goal is to facilitate
progress on Rasmussen's conjecture that a spectral sequence relates the two
knot homologies. We replace the language of twisted coefficients with the more
quantum topological language of framings on trivalent graphs. We define a
homology theory for framed trivalent graphs with boundary that -- for a
particular non-blackboard framing -- specializes to the homology of singular
knots underlying the knot Floer cube of resolutions. For blackboard framed
graphs, our theory conjecturally recovers the graph homology underlying the
HOMFLY-PT chain complex. We explain the appearance of the non-local ideal by
expressing it as an ideal quotient of an ideal that appears in both the
HOMFLY-PT and knot Floer cubes of resolutions. This result is a corollary of
our main theorem, which is that closing a strand in a braid graph corresponds
to taking an ideal quotient of its non-local ideal. The proof is a Gr\"obner
basis argument that connects the combinatorics of the non-local ideal to those
of Buchberger's Algorithm.


title: On quadratic points of classical modular curves

abstract:
  Classical modular curves are of deep interest in arithmetic geometry. In this
survey we show how the work of Fumiyuki Momose is involved in order to list the
classical modular curves which satisfy that the set of quadratic points over
$\mathbb{Q}$ is infinite. In particular we recall results of Momose on
hyperelliptic modular curves and on automorphisms groups of modular curves.
Moreover, we fix some inaccuracies of the existing literature in few statements
concerning automorphism groups of modular curves and we make available
different results that are difficult to find a precise reference, for example:
arithmetical results on hyperelliptic and bielliptic curves (like the
arithmetical statement of a Harris and Silverman theorem (or the case $d=2$ of
a Abramovich and Harris theorem)) and on the conductor of elliptic curves over
$\mathbb{Q}$ parametrized by X(N).


title: Equivariant bifurcation in geometric variational problems

abstract:
  We prove an extension of a celebrated equivariant bifurcation result of J.
Smoller and A. Wasserman, in an abstract framework for geometric variational
problems. With this purpose, we prove a slice theorem for continuous affine
actions of a (finite-dimensional) Lie group on Banach manifolds. As an
application, we discuss equivariant bifurcation of constant mean curvature
hypersurfaces, providing a few concrete examples and counter-examples.


title: Improved Callaway model for Lattice Thermal Conductivity

abstract:
  In developing the phonon quasiparticle picture, Peierls discovered that, in a
perfect crystal, without Umklapp (U) events, a current-carrying distribution
can never relax to a zero-current distribution. Callaway introduced a
simplified approximate model version of the Peierls-Boltzmann equation,
retaining its the ability to deal separately with Normal (N) and U events. This
paper clarifies and improves the Callaway model, and shows that Callaway
underestimated the suppression of N-processes in relaxing thermal current. The
new result should improve computations of thermal conductivity from
relaxation-time studies.


title: BRST technique for the cosmological density matrix

abstract:
  The microcanonical density matrix in closed cosmology has a natural
definition as a projector on the space of solutions of Wheeler-DeWitt
equations, which is motivated by the absence of global non-vanishing charges
and energy in spatially closed gravitational systems. Using the BRST/BFV
formalism in relativistic phase space of gauge and ghost variables we derive
the path integral representation for this projector and the relevant
statistical sum. This derivation circumvents the difficulties associated with
the open algebra of noncommutative quantum Dirac constraints and the
construction/regularization of the physical inner product in the subspace of
BRS singlets. This inner product is achieved via the Batalin-Marnelius gauge
fixing in the space of BRS-invariant states, which in its turn is shown to be a
result of truncation of the BRST/BFV formalism to the "matter" sector of
relativistic phase space.