title: Fluid mixing by curved trajectories of microswimmers

abstract:
  We consider the tracer diffusion $D_{rr}$ that arises from the run-and-tumble
motion of low Reynolds number swimmers, such as bacteria. Assuming a dilute
suspension, where the bacteria move in uncorrelated runs of length $\lambda$,
we obtain an exact expression for $D_{rr}$ for dipolar swimmers in three
dimensions, hence explaining the surprising result that this is independent of
$\lambda$. We compare $D_{rr}$ to the contribution to tracer diffusion from
entrainment.

categories: cond-mat.soft nlin.CD physics.bio-ph physics.flu-dyn


title:
Variable neutron star free precession in Hercules X-1 from evolution of
  RXTE X-ray pulse profiles with phase of the 35-day cycle

abstract:
  Accretion of matter onto the surface of a freely precessing NS with a complex
non-dipole magnetic field can explain the change of X-ray pulse profiles of Her
X-1 observed by RXTE with the phase of the 35-day cycle. We demonstrate this
using all available measurements of X-ray pulse profiles in the 9-13 keV energy
range obtained with the RXTE/PCA. The measured profiles guided the elaboration
of a geometrical model and the definition of locations of emitting poles, arcs,
and spots on the NS surface which satisfactorily reproduce the observed pulse
profiles and their dependence on free precession phase. We have found that the
observed trend of the times of the 35-day turn-ons on the O-C diagram, which
can be approximated by a collection of consecutive linear segments around the
mean value, can be described by our model by assuming a variable free
precession period, with a fractional period change of about a few percent. We
propose that the 2.5% changes in the free precession period that occur on time
scales of several to tens of 35-day cycles can be related to wandering of the
principal inertia axis of the NS body due to variations in the patterns of
accretion onto the NS surface. The closeness of periods of the disk precession
and the NS free precession can be explained by the presence of a
synchronization mechanism in the system, which modulates the dynamical
interaction of the gas streams and the accretion disk with the NS free
precession period.


title:
Orbital superexchange and crystal field simultaneously at play in YVO3:
  resonant inelastic x-ray scattering at the V L edge and the O K edge

abstract:
  We report on the observation of orbital excitations in YVO3 by means of
resonant inelastic x-ray scattering (RIXS) at energies across the vanadium L3
and oxygen K absorption edges. Due to the excellent experimental resolution we
are able to resolve the intra-t2g excitations at 0.1-0.2 eV, 1.07 eV, and 1.28
eV, the lowest excitations from the t2g into the eg levels at 1.86 eV, and
further excitations above 2.2 eV. For the intra-t2g excitations at 0.1-0.2 eV,
the RIXS peaks show small shifts of the order of 10-40 meV as a function of
temperature and of about 13-20 meV as a function of the transferred momentum
q||a. We argue that the latter reflects a finite dispersion of the orbital
excitations. For incident energies tuned to the oxygen K edge, RIXS is more
sensitive to intersite excitations. We observe excitations across the
Mott-Hubbard gap and find an additional feature at 0.4 eV which we attribute to
two-orbiton scattering, i.e., an exchange of orbitals between adjacent sites.
Altogether, these results indicate that both superexchange interactions and the
coupling to the lattice are important for a quantitative understanding of the
orbital excitations in YVO3.


title: A hierarchical coding-window model of Parkinson's disease

abstract:
  Parkinson's disease is an ongoing challenge to theoretical neuroscience and
to medical treatment. During the evolution of the disease, neurodegeneration
leads to physiological and anatomical changes that affect the neuronal
discharge of the Basal Ganglia to an extent that impairs normal behavioral
patterns. To investigate this problem, single Globus Pallidus pars interna
(GPi) neurons of the 6-OHDA rat model of Parkinson's disease were
extracellularly recorded at different degrees of alertness and compared to
non-Parkinson control neurons. A structure function analysis of these data
revealed that the temporal range of rate-coded information in GPi was
substantially reduced in the Parkinson animal-model, suggesting that a
dominance of small neighborhood dynamics could be the hallmark of Parkinson's
disease. A mathematical-model of the GPi circuit, where the small neighborhood
coupling is expressed in terms of a diffusion constant, corroborates this
interpretation.


title: A Tight Upper Bound on Acquaintance Time of Graphs

abstract:
  In this note we confirm a conjecture raised by Benjamini et al. \cite{BST} on
the acquaintance time of graphs, proving that for all graphs $G$ with $n$
vertices it holds that $\AC(G) = O(n^{3/2})$, which is tight up to a
multiplicative constant. This is done by proving that for all graphs $G$ with
$n$ vertices and maximal degree $\Delta$ it holds that $\AC(G) \leq 20 \Delta
n$. Combining this with the bound $\AC(G) \leq O(n^2/\Delta)$ from \cite{BST}
gives the foregoing uniform upper bound of all $n$-vertex graphs.
  We also prove that for the $n$-vertex path $P_n$ it holds that
$\AC(P_n)=n-2$. In addition we show that the barbell graph $B_n$ consisting of
two cliques of sizes $\ceil{n/2}$ and $\floor{n/2}$ connected by a single edge
also has $\AC(B_n) = n-2$. This shows that it is possible to add $\Omega(n^2)$
edges to $P_n$ without changing the $\AC$ value of the graph.


title:
Inviscid incompressible limits under mild stratification: A rigorous
  derivation of the Euler-Boussinesq system

abstract:
  We consider the full Navier-Stokes-Fourier system in the singular regime of
small Mach and large Reynolds and Peclet numbers, with ill prepared initial
data on an unbounded domain in the three dimensional Euclidean space with a
compact boundary. We perform the singular limit in the framework of weak
solutions and identify the Euler-Boussinesq system as the target problem.


title:
Toward a New Geometric Distance to the Active Galaxy NGC 4258. III.
  Final Results and the Hubble Constant

abstract:
  We report a new geometric maser distance estimate to the active galaxy NGC
4258. The data for the new model are maser line-of-sight velocities and sky
positions from 18 epochs of Very Long Baseline Interferometry observations, and
line-of-sight accelerations measured from a 10-year monitoring program of the
22 GHz maser emission of NGC 4258. The new model includes both disk warping and
confocal elliptical maser orbits with differential precession. The distance to
NGC 4258 is 7.60 +/- 0.17 +/- 0.15 Mpc, a 3% uncertainty including formal
fitting and systematic terms. The resulting Hubble Constant, based on the use
of the Cepheid Variables in NGC 4258 to recalibrate the Cepheid distance scale
(Riess et al. 2011), is H_0 = 72.0 +/- 3.0 km/s/Mpc.


title: Charge qubit driven via the Josephson nonlinearity

abstract:
  We study the novel nonlinear phenomena that emerge in a charge qubit due to
the interplay between a strong microwave flux drive and a periodic Josephson
potential. We first analyze the system in terms of the linear
Landau-Zener-St\"uckelberg model, and show its inadequacy in a periodic system
with several Landau-Zener crossings within a drive period. Experimentally, we
probe the quasienergy levels of the driven qubit with an LC-cavity, which
requires the use of linear response theory. We also show that our numerical
calculations are in good agreement with the experimental data.


title:
Sparse Reconstruction-based Detection of Spatial Dimension Holes in
  Cognitive Radio Networks

abstract:
  In this paper, we investigate a spectrum sensing algorithm for detecting
spatial dimension holes in Multiple Inputs Multiple Outputs (MIMO)
transmissions for OFDM systems using Compressive Sensing (CS) tools. This
extends the energy detector to allow for detecting transmission opportunities
even if the band is already energy filled. We show that the task described
above is not performed efficiently by regular MIMO decoders (such as MMSE
decoder) due to possible sparsity in the transmit signal. Since CS
reconstruction tools take into account the sparsity order of the signal, they
are more efficient in detecting the activity of the users. Building on
successful activity detection by the CS detector, we show that the use of a
CS-aided MMSE decoders yields better performance rather than using either
CS-based or MMSE decoders separately. Simulations are conducted to verify the
gains from using CS detector for Primary user activity detection and the
performance gain in using CS-aided MMSE decoders for decoding the PU
information for future relaying.


title: Scaling of quantum discord in spin models

abstract:
  We study the scaling of quantum discord (a measure of quantum correlation
beyond entanglement) in spin models analytically and systematically. We find
that at finite temperature the block scaling of quantum discord satisfies an
area law for any two-local Hamiltonian. We show that generically and
heuristically the two-site scaling of quantum discord is similar to that of
correlation functions. In particular, at zero temperature it decays
exponentially and polynomially in gapped and gapless (critical) systems,
respectively; at finite temperature it decays exponentially in both gapped and
gapless systems. We compute the two-site scaling of quantum discord in the XXZ
chain, the XY chain (in a magnetic field), and the transverse field Ising chain
at zero temperature.


title:
Star count density profiles and structural parameters of 26 Galactic
  globular clusters

abstract:
  We used a proper combination of high-resolution HST observations and
wide-field ground based data to derive the radial star density profile of 26
Galactic globular clusters from resolved star counts (which can be all freely
downloaded on-line). With respect to surface brightness (SB) profiles (which
can be biased by the presence of sparse, bright stars), star counts are
considered to be the most robust and reliable tool to derive cluster structural
parameters. For each system a detailed comparison with both King and Wilson
models has been performed and the most relevant best-fit parameters have been
obtained. This is the largest homogeneous catalog collected so far of star
count profiles and structural parameters derived therefrom. The analysis of the
data of our catalog has shown that: (1) the presence of the central cusps
previously detected in the SB profiles of NGC 1851, M13 and M62 is not
confirmed; (2) the majority of clusters in our sample are fitted equally well
by the King and the Wilson models; (3) we confirm the known relationship
between cluster size (as measured by the effective radius) and galactocentric
distances; (4) the ratio between the core and the effective radii shows a
bimodal distribution, with a peak at ~ 0.3 for about 80% of the clusters, and a
secondary peak at ~ 0.6 for the remaining 20%. Interestingly, the main peak
turns out to be in agreement with what expected from simulations of cluster
dynamical evolution and the ratio between these two radii well correlates with
an empirical dynamical age indicator recently defined from the observed shape
of blue straggler star radial distribution, thus suggesting that no exotic
mechanisms of energy generation are needed in the cores of the analyzed
clusters.


title: A Benchmark Approach to Risk-Minimization under Partial Information

abstract:
  In this paper we study a risk-minimizing hedging problem for a semimartingale
incomplete financial market where d+1 assets are traded continuously and whose
price is expressed in units of the num\'{e}raire portfolio. According to the
so-called benchmark approach, we investigate the (benchmarked) risk-minimizing
strategy in the case where there are restrictions on the available information.
More precisely, we characterize the optimal strategy as the integrand appearing
in the Galtchouk-Kunita-Watanabe decomposition of the benchmarked claim under
partial information and provide its description in terms of the integrands in
the classical Galtchouk-Kunita-Watanabe decomposition under full information
via dual predictable projections. Finally, we apply the results in the case of
a Markovian jump-diffusion driven market model where the assets prices dynamics
depend on a stochastic factor which is not observable by investors.


title: A Note on State Decomposition Independent Local Invariants

abstract:
  We derive a set of invariants under local unitary transformations for
arbitrary dimensional quantum systems. These invariants are given by
hyperdeterminants and independent from the detailed pure state decompositions
of a given quantum state. They also give rise to necessary conditions for the
equivalence of quantum states under local unitary transformations.


title:
Superstable cycles for antiferromagnetic Q-state Potts and three-site
  interaction Ising models on recursive lattices

abstract:
  We consider the superstable cycles of the Q-state Potts (QSP) and the
three-site interaction antiferromagnetic Ising (TSAI) models on recursive
lattices. The rational mappings describing the models' statistical properties
are obtained via the recurrence relation technique. We provide analytical
solutions for the superstable cycles of the second order for both models. A
particular attention is devoted to the period three window. Here we present an
exact result for the third order superstable orbit for the QSP and a numerical
solution for the TSAI model. Additionally, we point out a non-trivial
connection between bifurcations and superstability: in some regions of
parameters a superstable cycle is not followed by a doubling bifurcation.
Furthermore, we use symbolic dynamics to understand the changes taking place at
points of superstability and to distinguish areas between two consecutive
superstable orbits.


title:
On simultaneous identification of the shape and generalized impedance
  boundary condition in obstacle scattering

abstract:
  We consider the inverse obstacle scattering problem of determining both the
shape and the "equivalent impedance" from far field measurements at a fixed
frequency. In this work, the surface impedance is represented by a second order
surface differential operator (refer to as generalized impedance boundary
condition) as opposed to a scalar function. The generalized impedance boundary
condition can be seen as a more accurate model for effective impedances and is
widely used in the scattering problem for thin coatings. Our approach is based
on a least square optimization technique. A major part of our analysis is to
characterize the derivative of the cost function with respect to the boundary
and this complex surface impedance configuration. In particular, we provide an
extension of the notion of shape derivative to the case where the involved
impedance parameters do not need to be surface traces of given functions, which
leads (in general) to a non-vanishing tangential boundary perturbation. The
efficiency of considering this type of derivative is illustrated by several 2D
numerical experiments based on a (classical) steepest descent method. The
feasibility of retrieving both the shape and the impedance parameters is also
discussed in our numerical experiments.


title: Height functions on compact symmetric spaces

abstract:
  We consider height functions on symmetric spaces $M\cong G/K$ embedded in the
associated matrix Lie group $G$. In particular we study the relationship
between the critical sets of the height function on $G$ and its restriction to
$M$. Also we prove that the gradient flow on $M$ can be integrated by means of
a generalized Cayley transform. This allows to obtain explicit local charts for
the critical submanifolds. Finally, we discuss how to reduce the generic case
to a height function whose ground hyperplane is orhogonal to a real diagonal
matrix. This result requires to prove the existence of a polar decomposition
adapted to the automorphism defining $M$. Detailed examples are given.


title: Quantum Optical Realization of Classical Linear Stochastic Systems

abstract:
  The purpose of this paper is to show how a class of classical linear
stochastic systems can be physically implemented using quantum optical
components. Quantum optical systems typically have much higher bandwidth than
electronic devices, meaning faster response and processing times, and hence has
the potential for providing better performance than classical systems. A
procedure is provided for constructing the quantum optical realization. The
paper also describes the use of the quantum optical realization in a
measurement feedback loop. Some examples are given to illustrate the
application of the main results.


title: Pseudo-Lattice Treatment for Subspace Aligned Interference Signals

abstract:
  For multi-input multi-output (MIMO) K-user interference networks, we propose
the use of a channel transformation technique for joint detection of the useful
and interference signals in an interference alignment scenario. We coin our
detection technique as "pseudo-lattice treatment" and show that applying our
technique, we can alleviate limitations facing Lattice Interference Alignment
(L-IA). We show that for a 3-user interference network, two of the users can
have their interference aligned in lattice structure through precoding. For the
remaining user, performance gains in decoding subspace interference aligned
signals at the receiver are achieved using our channel transformation
technique. Our "pseudo-lattice" technique can also be applied at all users in
case of Subspace Interference Alignment (S-IA). We investigate different
solutions for applying channel transformation at the third receiver and
evaluate performance for these techniques. Simulations are conducted to show
the performance gain in using our pseudo-lattice method over other decoding
techniques using different modulation schemes.


title: New outcomes in mutation rates analysis

abstract:
  The GC-content is very variable in different genome regions and species but
although many hypothesis we still do not know the reason why. Here we show that
a relationship exists with the mutation rate, in particular we noticed a new
recurrence in the amino acids coding table. Moreover we analyze recombination
frequency taking into account Single Nucleotide Polymorphisms hourglass
distribution.


title:
Self-normalized Cram\'{e}r type moderate deviations for the maximum of
  sums

abstract:
  Let $X_1,X_2,...$ be independent random variables with zero means and finite
variances, and let $S_n=\sum_{i=1}^nX_i$ and $V^2_n=\sum_{i=1}^nX^2_i$. A
Cram\'{e}r type moderate deviation for the maximum of the self-normalized sums
$\max_{1\leq k\leq n}S_k/V_n$ is obtained. In particular, for identically
distributed $X_1,X_2,...,$ it is proved that $P(\max_{1\leq k\leq n}S_k\geq
xV_n)/(1-\Phi (x))\rightarrow2$ uniformly for $0<x\leq\mathrm{o}(n^{1/6})$
under the optimal finite third moment of $X_1$.


title: Combination prevention for the elimination of HIV

abstract:
  The development of potent drugs for the control of viraemia in people living
with HIV means that infected people may live a normal, healthy life and offers
the prospect of eliminating HIV transmission in the short term and HIV
infection in the long term. Other interventions, including the use of condoms,
pre-exposure prophylaxis, treatment of sexually transmitted infections and
behaviour change programmes, may also be effective in reducing HIV transmission
to varying degrees.
  Here we examine recommendations for when to start treatment with
anti-retroviral drugs, estimate the impact that treatment may have on HIV
transmission in the short and in the long term, and compare the impact and cost
of treatment with that of other methods of control. We focus on generalized HIV
epidemics in sub-Saharan Africa. We show that universal access to ART combined
with early treatment is the most effective and, in the long term, the most
cost-effective intervention. Elimination will require effective coverage of
about 80% or more but treatment is effective and cost effective even at low
levels of coverage.
  Other interventions may provide important support to a programme of early
treatment in particular groups. Condoms provide protection for both men and
women and should be readily available whenever they are needed. Medical male
circumcision will provide a degree of immediate protection for men and
microbicides will do the same for women. Behaviour change programmes in
themselves are unlikely to have a significant impact on overall transmission
but may play a critical role in supporting early treatment through helping to
avoid stigma and discrimination, ensuring the acceptability of testing and
early treatment as well as compliance.


title: Mixed-correlated ARFIMA processes for power-law cross-correlations

abstract:
  We introduce a general framework of the Mixed-correlated ARFIMA (MC-ARFIMA)
processes which allows for various specifications of univariate and bivariate
long-term memory. Apart from a standard case when $H_{xy}={1}{2}(H_x+H_y)$,
MC-ARFIMA also allows for processes with $H_{xy}<{1}{2}(H_x+H_y)$ but also for
long-range correlated processes which are either short-range cross-correlated
or simply correlated. The major contribution of MC-ARFIMA lays in the fact that
the processes have well-defined asymptotic properties for $H_x$, $H_y$ and
$H_{xy}$, which are derived in the paper, so that the processes can be used in
simulation studies comparing various estimators of the bivariate Hurst exponent
$H_{xy}$. Moreover, the framework allows for modeling of processes which are
found to have $H_{xy}<{1}{2}(H_x+H_y)$.


title: PT-Symmetric Dimer of Coupled Nonlinear Oscillators

abstract:
  We provide a systematic analysis of a prototypical nonlinear oscillator
system respecting PT-symmetry i.e., one of them has gain and the other an equal
and opposite amount of loss. Starting from the linear limit of the system, we
extend considerations to the nonlinear case for both soft and hard cubic
nonlinearities identifying symmetric and anti-symmetric breather solutions, as
well as symmetry breaking variants thereof. We propose a reduction of the
system to a Schr\"odinger type PT-symmetric dimer, whose detailed earlier
understanding can explain many of the phenomena observed herein, including the
PT phase transition. Nevertheless, there are also significant parametric as
well as phenomenological potential differences between the two models and we
discuss where these arise and where they are most pronounced. Finally, we also
provide examples of the evolution dynamics of the different states in their
regimes of instability.


title: The dynamics and excitation of torsional waves in geodynamo simulations

abstract:
  The predominant force balance in rapidly rotating planetary cores is between
Coriolis, pressure, buoyancy and Lorentz forces. This magnetostrophic balance
leads to a Taylor state where the spatially averaged azimuthal Lorentz force is
compelled to vanish on cylinders aligned with the rotation axis. Any deviation
from this state leads to a torsional oscillation, signatures of which have been
observed in the Earth's secular variation and are thought to influence length
of day variations via angular momentum conservation. In order to investigate
the dynamics of torsional oscillations, we perform several three-dimensional
dynamo simulations in a spherical shell. We find torsional oscillations,
identified by their propagation at the correct Alfv\'{e}n speed, in many of our
simulations. We find that the frequency, location and direction of propagation
of the waves are influenced by the choice of parameters. Torsional waves are
observed within the tangent cylinder and also have the ability to pass through
it. Several of our simulations display waves with core travel times of 4 to 6
years. We calculate the driving terms for these waves and find that both the
Reynolds force and ageostrophic convection acting through the Lorentz force are
important in driving torsional oscillations.


title:
A proper understanding of the Davisson and Germer experiments for
  undergraduate modern physics course

abstract:
  The physical interpretation for the Davisson-Germer experiments on nickel
(Ni) single crystals [(111), (100), and (110) surfaces] is presented in terms
of two-dimensional (2D) Bragg scattering. The Ni surface acts as a reflective
diffraction grating when the incident electron beams hits the surface. The 2D
Bragg reflection occurs when the Ewald sphere intersects the Bragg rods arising
from the two-dimension character of the system. Such a concept is essential to
proper understanding of the Davisson-Germer experiment for undergraduate modern
physics course.


title: Limit theorems for excursion sets of stationary random fields

abstract:
  We give an overview of the recent asymptotic results on the geometry of
excursion sets of stationary random fields. Namely, we cover a number of limit
theorems of central type for the volume of excursions of stationary (quasi--,
positively or negatively) associated random fields with stochastically
continuous realizations for a fixed excursion level. This class includes in
particular Gaussian, Poisson shot noise, certain infinitely divisible,
$\alpha$--stable and max--stable random fields satisfying some extra dependence
conditions. Functional limit theorems (with the excursion level being an
argument of the limiting Gaussian process) are reviewed as well. For stationary
isotropic $C^1$--smooth Gaussian random fields similar results are available
also for the surface area of the excursion set.
  Statistical tests of Gaussianity of a random field which are of importance to
real data analysis as well as results for an increasing excursion level round
up the paper.


title: Path-memory induced quantization of classical orbits

abstract:
  A droplet bouncing on a liquid bath can self-propel due to its interaction
with the waves it generates. The resulting "walker" is a dynamical association
where, at a macroscopic scale, a particle (the droplet) is driven by a
pilot-wave field. A specificity of this system is that the wave field itself
results from the superposition of the waves generated at the points of space
recently visited by the particle. It thus contains a memory of the past
trajectory of the particle. Here, we investigate the response of this object to
forces orthogonal to its motion. We find that the resulting closed orbits
present a spontaneous quantization. This is observed only when the memory of
the system is long enough for the particle to interact with the wave sources
distributed along the whole orbit. An additional force then limits the possible
orbits to a discrete set. The wave-sustained path memory is thus demonstrated
to generate a quantization of angular momentum. Because a quantum-like
uncertainty was also observed recently in these systems, the nonlocality
generated by path memory opens new perspectives.


title: Excited Mob

abstract:
  We show that for an i.i.d. bounded and weakly elliptic cookie environment,
one dimensional excited random walk on the $k$-time leftover environment is
right transient if and only if $\delta > k+1$ and has positive speed if and
only if $\delta > k+2$, where $\delta$ is the expected drift per site. This
gives, to the best of our knowledge, the first example of an environment with
positive speed that has stationary and ergodic properties but does not follow
by trivial comparison to an i.i.d. environment. In another formulation, we show
that on such environments an excited mob of $k$ walkers is right transient if
and only if $\delta > k$ and moves with positive speed if and only if
$\delta>k+1$. We show that for stationary and erogodic cookie environments, a
law of large numbers for the walkers on leftover environments holds. Whenever
the environments are also elliptic, a zero-one law for directional transience
is also proven.


title:
A frustrated spin-1/2 Heisenberg antiferromagnet on a chevron-square
  lattice

abstract:
  The coupled cluster method (CCM) is used to study the zero-temperature
properties of a frustrated spin-half ($s={1}{2}$) $J_{1}$--$J_{2}$ Heisenberg
antiferromagnet (HAF) on a 2D chevron-square lattice. Each site on an
underlying square lattice has 4 nearest-neighbor exchange bonds of strength
$J_{1}>0$ and 2 next-nearest-neighbor (diagonal) bonds of strength $J_{2}
\equiv x J_{1}>0$, with each square plaquette having only one diagonal bond.
The diagonal bonds form a chevron pattern, and the model thus interpolates
smoothly between 2D HAFs on the square ($x=0$) and triangular ($x=1$) lattices,
and also extrapolates to disconnected 1D HAF chains ($x \to \infty$). The
classical ($s \to \infty$) version of the model has N\'{e}el order for $0 < x <
x_{{\rm cl}}$ and a form of spiral order for $x_{{\rm cl}} < x < \infty$, where
$x_{{\rm cl}} = {1}{2}$. For the $s={1}{2}$ model we use both these classical
states, as well as other collinear states not realized as classical
ground-state (GS) phases, as CCM reference states, on top of which the
multispin-flip configurations resulting from quantum fluctuations are
incorporated in a systematic truncation scheme, which we carry out to high
orders and extrapolate to the physical limit. We calculate the GS energy, GS
magnetic order parameter, and the susceptibilities of the states to various
forms of valence-bond crystalline (VBC) order, including plaquette and two
different dimer forms. We find that the $s={1}{2}$ model has two quantum
critical points, at $x_{c_{1}} \approx 0.72(1)$ and $x_{c_{2}} \approx 1.5(1)$,
with N\'{e}el order for $0 < x < x_{c_{1}}$, a form of spiral order for
$x_{c_{1}} < x < x_{c_{2}}$ that includes the correct three-sublattice
$120^{\circ}$ spin ordering for the triangular-lattice HAF at $x=1$, and
parallel-dimer VBC order for $x_{c_{2}} < x < \infty$.


title: Expanding actions: minimality and ergodicity

abstract:
  We prove that every expanding minimal semigroup action of $C^1$
diffeomorphisms of a compact manifold (resp. $C^{1+\alpha}$ conformal) is
robustly minimal (resp. ergodic with respect to Lebesgue measure). We also show
how, locally, a blending region yields the robustness of the minimality and
implies ergodicity.


title:
Quantum graphs whose spectra mimic the zeros of the Riemann zeta
  function

abstract:
  One of the most famous problems in mathematics is the Riemann hypothesis:
that the non-trivial zeros of the Riemann zeta function lie on a line in the
complex plane. One way to prove the hypothesis would be to identify the zeros
as eigenvalues of a Hermitian operator, many of whose properties can be derived
through the analogy to quantum chaos. Using this, we construct a set of quantum
graphs that have the same oscillating part of the density of states as the
Riemann zeros, offering an explanation of the overall minus sign. The smooth
part is completely different, and hence also the spectrum, but the graphs pick
out the low-lying zeros.


title:
Review on the inclusion of isospin breaking effects in lattice
  calculations

abstract:
  Isospin symmetry is explicitly broken in the Standard Model by the non-zero
differences of mass and electric charge between the up and down quarks. Both of
these corrections are expected to have a comparable size of the order of one
percent relatively to hadronic energies. Although these contributions are
small, they play a crucial role in hadronic and nuclear physics. In this review
we explain how to properly define QCD and QED on a finite and discrete
space-time so that isospin corrections to hadronic observables can be computed
ab-initio. We then consider the different approaches to compute lattice
correlation functions of QCD and QED observables. Finally we summarise the
actual lattice results concerning the isospin corrections to the light hadron
spectrum.


title:
Goos-H\"anchen and Imbert-Fedorov shifts from a quantum-mechanical
  perspective

abstract:
  We study the classical optics effects known as Goos-H\"anchen (GH) and
Imbert-Fedorov (IF) shifts, occurring when reflecting a bounded light beam from
a planar surface, by using a quantum-mechanical formalism. This new approach
allows us to naturally separate the spatial shift into two parts, one
independent on orbital angular momentum (OAM) and the other one showing
OAM-induced spatial-vs-angular shift mixing. In addition, within this
quantum-mechanical-like formalism, it becomes apparent that the angular shift
is proportional to the beams angular spread, namely to the variance of the
transverse components of the wave vector. Moreover, we extent our treatment to
the enhancement of beam shifts via weak measurements and relate our results to
recent experiments.


title: Properties of $D_{s2}^*(2573)$ charmed-strange tensor meson

abstract:
  The mass and current coupling constant of the $D_{s2}^* (2573)$
charmed-strange meson is calculated in the framework of two-point QCD sum rule
approach. Although the quantum numbers of this meson is not exactly known, its
width and decay modes are consistent with $I(J^P)=0(2^+)$, which we consider to
write the interpolating current used in our calculations. Replacing the light
strange quark with up or down quark we also compare the results with those of
$D_{2}^*$ charmed tensor meson and estimate the order of SU(3) flavor symmetry
violation.


title: Entropy of Closure Operators

abstract:
  The entropy of a closure operator has been recently proposed for the study of
network coding and secret sharing. In this paper, we study closure operators in
relation to their entropy. We first introduce four different kinds of rank
functions for a given closure operator, which determine bounds on the entropy
of that operator. This yields new axioms for matroids based on their closure
operators. We also determine necessary conditions for a large class of closure
operators to be solvable. We then define the Shannon entropy of a closure
operator, and use it to prove that the set of closure entropies is dense.
Finally, we justify why we focus on the solvability of closure operators only.


title: Diffusion and Coulomb separation of ions in dense matter

abstract:
  We analyze diffusion equations in strongly coupled Coulomb mixtures of ions
in dense stellar matter. Strong coupling of ions in the presence of
gravitational forces and electric fields (induced by plasma polarization in the
presence of gravity) produces a specific diffusion current which can separate
ions with the same A/Z (mass to charge number) ratios but different Z. This
Coulomb separation of ions can be important for the evolution of white dwarfs
and neutron stars.


title: Geometrical theory of diffracted rays, orbiting and complex rays

abstract:
  In this article, the ray tracing method is studied beyond the classical
geometrical theory. The trajectories are here regarded as geodesics in a
Riemannian manifold, whose metric and topological properties are those induced
by the refractive index (or, equivalently, by the potential). First, we derive
the geometrical quantization rule, which is relevant to describe the orbiting
bound-states observed in molecular physics. Next, we derive properties of the
diffracted rays, regarded here as geodesics in a Riemannian manifold with
boundary. A particular attention is devoted to the following problems: (i)
modification of the classical stationary phase method suited to a neighborhood
of a caustic; (ii) derivation of the connection formulae which enable one to
obtain the uniformization of the classical eikonal approximation by patching up
geodesic segments crossing the axial caustic; (iii) extension of the eikonal
equation to mixed hyperbolic-elliptic systems, and generation of complex-valued
rays in the shadow of the caustic. By these methods, we can study the creeping
waves in diffractive scattering, describe the orbiting resonances present in
molecular scattering beside the orbiting bound-states, and, finally, describe
the generation of the evanescent waves, which are relevant in the nuclear
rainbow.


title:
Fidelity of optically induced single-spin rotations in semiconductor
  quantum dots in the presence of nuclear spins

abstract:
  We examine the influence of nuclear spins on the performance of optically
induced rotations of single electron spins in semiconductor quantum dots. We
consider Raman type optical transitions between electron spin states and take
into account the additional effect of the Overhauser field. We calculate
average fidelities of rotations around characteristic axes in the presence of
nuclear spins analytically with perturbation theory up to second order in the
Overhauser field. Moreover, we calculate the fidelity using numerical averaging
over the nuclear field distribution, including arbitrary orders of the
hyperfine interaction.


title:
Mechanical energy dissipation induced by sloshing and wave breaking in a
  fully coupled angular motion system. Part II: Experimental Investigation

abstract:
  In Part I of this paper series, a theoretical and numerical model for a a
driven pendulum filled with liquid was developed. The system was analyzed in
the framework of tuned liquid dampers (TLD) and hybrid mass liquid dampers
(HMLD) theory. In this Part II, in order to measure the energy dissipation
resulting from shallow water sloshing, an experimental investigation is
conducted. Accurate evaluations of energy transfers are obtained through the
recorded kinematics of the system. A set of experiments is conducted with three
different liquids: water, sunflower oil and glycerine. Coherently with the
results of Part I, the energy dissipation obtained when the tank is filled with
water can mainly be explained by the breaking waves. For all three liquids, the
effects of varying the external excitation amplitude are discussed.


title:
Mechanical energy dissipation induced by sloshing and wave breaking in a
  fully coupled angular motion system. Part I: Theoretical formulation and
  Numerical Investigation

abstract:
  A dynamical system involving a driven pendulum filled with liquid, is
analyzed in the present paper series. The study of such a system is conducted
in order to understand energy dissipation resulting from the shallow water
sloshing and induced wave breaking. This analysis is relevant for the design of
Tuned Liquid Damper devices. The complexity and violence of the flow generated
by the roll motion results in the impossibility of using an analytical
approach, requiring in turn the use of a suitable numerical solver. In Part I,
the coupled dynamical system is thoroughly described, revealing its nonlinear
features associated with the large amplitude of the forcing, both in terms of
mechanical and fluid dynamical aspects. A smoothed particle hydrodynamics (SPH)
model, largely validated in literature, is used to calculate the frequency
behavior of the whole system. For small rotation angles, a semi-analytical
model of the energy dissipated by the fluid, based on a hydraulic jump
solution, is developed; the energy transfer is numerically calculated in order
to extend the analysis to large oscillation angles. The experimental part of
the investigation is carried out in Part II of this work.


title:
Efficient approach to two-centre exponential integrals with applications
  to excited states of molecular hydrogen

abstract:
  A general approach to evaluation of two-centre two-electron exponential
integrals with arbitrary parameters is presented. The results for the
Born-Oppenheimer potential for various excited states of molecular hydrogen
with Ko{\l} os-Wolniewicz functions are obtained with precision exceeding
previous values by about 3 orders of magnitude.


title:
Continuous Double Auction Mechanism and Bidding Strategies in Cloud
  Computing Markets

abstract:
  Cloud computing has been an emerging model which aims at allowing customers
to utilize computing resources hosted by Cloud Service Providers (CSPs). More
and more consumers rely on CSPs to supply computing and storage service on the
one hand, and CSPs try to attract consumers on favorable terms on the other. In
such competitive cloud computing markets, pricing policies are critical to
market efficiency. While CSPs often publish their prices and charge users
according to the amount of resources they consume, auction mechanism is rarely
applied. In fact a feasible auction mechanism is the most effective method for
allocation of resources, especially double auction is more efficient and
flexible for it enables buyers and sellers to enter bids and offers
simultaneously. In this paper we bring up an electronic auction platform for
cloud, and a cloud Continuous Double Auction (CDA) mechanism is formulated to
match orders and facilitate trading based on the platform. Some evaluating
criteria are defined to analyze the efficiency of markets and strategies.
Furthermore, the selection of bidding strategies for the auction plays a very
important role for each player to maximize its own profit, so we developed a
novel bidding strategy for cloud CDA, BH-strategy, which is a two-stage game
bidding strategy. At last we designed three simulation scenarios to compare the
performance of our strategy with other dominating bidding strategies and proved
that BH-strategy has better performance on surpluses, successful transactions
and market efficiency. In addition, we discussed that our cloud CDA mechanism
is feasible for cloud computing resource allocation.


title:
Charge tuning of non-resonant magneto-exciton phonon interactions in
  graphene

abstract:
  Far from resonance, the coupling of the G-band phonon to magneto-excitons in
single layer graphene displays kinks and splittings versus filling factor that
are well described by Pauli blocking and unblocking of inter- and intra- Landau
level transitions. We explore the non-resonant electron-phonon coupling by
high-magnetic field Raman scattering while electrostatic tuning of the carrier
density controls the filling factor. We show qualitative and quantitative
agreement between spectra and a linearized model of electron-phonon
interactions in magnetic fields. The splitting is caused by dichroism of left
and right handed circular polarized light due to lifting of the G-band phonon
degeneracy, and the piecewise linear slopes are caused by the linear occupancy
of sequential Landau levels versus $\nu$.


title:
Constraints on axion-like particles with H.E.S.S. from observations of
  PKS 2155-304

abstract:
  Axion-like particles are hypothetical new light (sub-eV) bosons predicted in
some extensions of the Standard Model of particle physics. In astrophysical
environments comprising high-energy gamma rays and turbulent magnetic fields,
the existence of axion-like particles can modify the energy spectrum of the
gamma rays. This modification would take the form of an irregular behavior of
the energy spectrum in a limited energy range. Data from the H.E.S.S.
observations of the distant BL Lac PKS 2155-304 are used to derive conservative
upper limits on the strength of the axion-like particle coupling to photons.
This study gives rise to the first exclusions on axion-like particles from
gamma-ray astronomy. The derived constraints apply to both light pseudo-scalar
and scalar bosons that couple to the electromagnetic field.


title: The small scale power asymmetry in the cosmic microwave background

abstract:
  We investigate the hemispherical power asymmetry in the cosmic microwave
background on small angular scales. We find an anomalously high asymmetry in
the multipole range l=601-2048, with a naive statistical significance of 6.5
sigma. However, we show that this extreme anomaly is simply a coincidence of
three other effects, relativistic power modulation, edge effects from the mask
applied, and inter-scale correlations. After correcting for all of these
effects, the significance level drops to ~1 sigma, i.e., there is no anomalous
intrinsic asymmetry in the small angular scales. Using this null result, we
derive a constraint on a potential dipolar modulation amplitude, A(k)<0.0045 on
the ~10 Mpc-scale, at 95% C.L. This new constraint must be satisfied by any
theoretical model attempting to explain the hemispherical asymmetry at large
angular scales.


title:
Measurement of the prompt J/psi and psi(2S) polarizations in pp
  collisions at sqrt(s) = 7 TeV

abstract:
  The polarizations of prompt J/psi and psi(2S) mesons are measured in
proton-proton collisions at sqrt(s) = 7 TeV, using a dimuon data sample
collected by the CMS experiment at the LHC, corresponding to an integrated
luminosity of 4.9 inverse femtobarns. The prompt J/psi and psi(2S) polarization
parameters lambda[theta], lambda[phi], and lambda[theta,phi], as well as the
frame-invariant quantity lambda(tilde), are measured from the dimuon decay
angular distributions in three different polarization frames. The J/psi results
are obtained in the transverse momentum range 14 < pt < 70 GeV, in the rapidity
intervals abs(y) < 0.6 and 0.6 < abs(y) < 1.2. The corresponding psi(2S)
results cover 14 < pt < 50 GeV and include a third rapidity bin, 1.2 < abs(y) <
1.5. No evidence of large transverse or longitudinal polarizations is seen in
these kinematic regions, which extend much beyond those previously explored.


title: Bacterial chemotaxis without gradient-sensing

abstract:
  Models for chemotaxis are based on gradient sensing of individual organisms.
The key contribution of Keller and Segel is showing that erratic movements of
individuals may result in an accurate chemotaxis phenomenon as a group. In this
paper we provide another option to understand chemotactic behavior when
individuals do not sense the gradient of chemical concentration by any means.
We show that, if individuals increase their motility to find food when they are
hungry, an accurate chemotactic behavior may obtained without sensing the
gradient. Such a random dispersal has been suggested by Cho and Kim and is
called starvation driven diffusion. This model is surprisingly similar to the
original derivation of Keller-Segel model. A comprehensive picture of traveling
band and front solutions is provided with numerical simulations.


title:
Near field of an oscillating electric dipole and cross-polarization of a
  collimated beam of light: two sides of the same coin

abstract:
  We address the question of whether there exists a hidden relationship between
the near-field distribution generated by an oscillating electric dipole and the
so-called cross polarization of a collimated beam of light. We find that the
answer is affirmative by showing that the complex field distributions occurring
in both cases have a common physical origin: the requirement that the
electromagnetic fields must be transverse.


title:
The asymmetric drift, the local standard of rest, and implications from
  RAVE data

abstract:
  The determination of the LSR is still a matter of debate. The classical value
of the tangential peculiar motion of the Sun with respect to the LSR was
challenged in recent years, claiming a significantly larger value. We show that
the RAdial Velocity Experiment (RAVE) sample of dwarf stars is an excellent
data set to derive tighter boundary conditions to chemodynamical evolution
models of the extended solar neighbourhood. We present an improved Jeans
analysis, which allows a better interpretation of the measured kinematics of
stellar populations in the Milky Way disc. We propose an improved version of
the Str\"omberg relation with the radial scalelengths as the only unknown.
Binning RAVE stars in metallicity reveals a bigger asymmetric drift
(corresponding to a smaller radial scalelength) for more metal-rich
populations. With the standard assumption of velocity-dispersion independent
radial scalelengths in each metallicity bin, we redetermine the LSR. The new
Str\"omberg equation yields a joint LSR value of V_\sun=3.06 \pm 0.68 km/s,
which is even smaller than the classical value based on Hipparcos data. The
corresponding radial scalelength increases from 1.6 kpc for the metal-rich bin
to 2.9 kpc for the metal-poor bin, with a trend of an even larger scalelength
for young metal-poor stars. When adopting the recent Sch\"onrich value of
V_\sun=12.24 km/s for the LSR, the new Str\"omberg equation yields much larger
individual radial scalelengths of the RAVE subpopulations, which seem
unphysical in part. The new Str\"omberg equation allows a cleaner
interpretation of the kinematic data of disc stars in terms of radial
scalelengths. Lifting the LSR value by a few km/s compared to the classical
value results in strongly increased radial scalelengths with a trend of smaller
values for larger velocity dispersions.


title: Multiwavelength study of the region around the ANTARES neutrino excess

abstract:
  The ANTARES collaboration reported the results of a search for point-like
neutrino sources using data taken in the period 2007-2010. An unbinned maximum
likelihood based all-sky search yielded a cluster of 9 (5) events within a cone
of 3 (1) degrees around (R.A., Dec) = (-46.5deg, -65.0deg). The trial factor
corrected p-value of 2.6% (2.2 sigma) is not significant enough to claim the
observation of an astrophysical point source. However, it currently constitutes
the most significant localized neutrino excess observed by ANTARES. Here we
present a multi-wavelength analysis including optical to X-ray archival data
and a dedicated analysis of gamma-ray data from Fermi-LAT. In order to cover
the TeV domain, dedicated observations with the H.E.S.S. telescope array were
carried out. We present these data and discuss implications of the results in
terms of signatures for a cosmic-ray acceleration site.


title:
Femtosecond study of the effects of ions on the reorientation dynamics
  of water

abstract:
  We study the effects of ions on the reorientation dynamics of liquid water
with polarization-resolved femtosecond mid-infared spectroscopy. We probe the
anisotropy of the excitation of the O-D stretch vibration of HDO molecules in
solutions of NaCl, NaI and tetra-alkylammonium bromide salts in 8 percent
HDO:H2O. We find that the reorientation O-D groups of HDO molecules hydrating
the Cl- and I- anions occurs on two different time scales with time constants
of 2pm0.3 ps and 9pm2 ps. The fast component is due to a wobbling motion of the
O-D group that keeps the hydrogen bond with the halogenic anion intact. For
solutions of tetra-alkylammonium bromide salts we observe a very strong slowing
down of the reorientation of water that is associated with the hydration of the
hydrophobic alkyl groups of the tetra-alkylammonium ions.


title: Equidistribution of points via energy

abstract:
  We study the asymptotic equidistribution of points with discrete energy close
to Robin's constant of a compact set in the plane. Our main tools are the
energy estimates from potential theory. We also consider the quantitative
aspects of this equidistribution. Applications include estimates of growth for
the Fekete and Leja polynomials associated with large classes of compact sets,
convergence rates of the discrete energy approximations to Robin's constant,
and problems on the means of zeros of polynomials with integer coefficients.


title: Linear response of tripartite entanglement to infinitesimal noise

abstract:
  Recent experimental progress in prolonging the coherence time of a quantum
system prompts us to explore the behavior of quantum entanglement at the
beginning of the decoherence process. The response of the entanglement under an
infinitesimal noise can serve as a signature of the robustness of entangled
states. A crucial problem of this topic in multipartite systems is to compute
the degree of entanglement in a mixed state. We find a family of global noise
in three-qubit systems, which is composed of four W states. Under its
influence, the linear response of the tripartite entanglement of a symmetrical
three-qubit pure state is studied. A lower bound of the linear response is
found to depend completely on the initial tripartite and bipartite
entanglement. This result shows that the decay of tripartite entanglement is
hastened by the bipartite one.


title:
Resonator Power to Frequency Conversion in a Cryogenic Sapphire
  Oscillator

abstract:
  We report on the measurement and characterization of power to frequency
conversion in the resonant mode of a cryogenic sapphire loaded cavity
resonator, which is used as the frequency discriminating element of a loop
oscillator circuit. Fluctuations of power incident on the resonator leads to
changes in radiation pressure and temperature in the sapphire dielectric, both
of which contribute to a shift in the resonance frequency. We measure a
modulation and temperature independent radiation pressure induced power to
frequency sensitivity of -0.15 Hz/mW and find that this is the primary factor
limiting the stability of the resonator frequency.


title: Fuzzy Conifold $Y_F^6$ and Monopoles on $S_F^2\times S_F^2$

abstract:
  In this article, we construct the fuzzy (finite dimensional) analogues of the
conifold $Y^6$ and its base $X^5$. We show that fuzzy $X^5$ is (the analogue
of) a principal U(1) bundle over fuzzy spheres $S^2_F \times S^2_F$ and
explicitly construct the associated monopole bundles. In particular our
construction provides an explicit discretization of the spaces
$T^{\kappa,\kappa}$ and $T^{\kappa,0}$.


title: Timely crawling of high-quality ephemeral new content

abstract:
  Nowadays, more and more people use the Web as their primary source of
up-to-date information. In this context, fast crawling and indexing of newly
created Web pages has become crucial for search engines, especially because
user traffic to a significant fraction of these new pages (like news, blog and
forum posts) grows really quickly right after they appear, but lasts only for
several days.
  In this paper, we study the problem of timely finding and crawling of such
ephemeral new pages (in terms of user interest). Traditional crawling policies
do not give any particular priority to such pages and may thus crawl them not
quickly enough, and even crawl already obsolete content. We thus propose a new
metric, well thought out for this task, which takes into account the decrease
of user interest for ephemeral pages over time.
  We show that most ephemeral new pages can be found at a relatively small set
of content sources and present a procedure for finding such a set. Our idea is
to periodically recrawl content sources and crawl newly created pages linked
from them, focusing on high-quality (in terms of user interest) content. One of
the main difficulties here is to divide resources between these two activities
in an efficient way. We find the adaptive balance between crawls and recrawls
by maximizing the proposed metric. Further, we incorporate search engine click
logs to give our crawler an insight about the current user demands. Efficiency
of our approach is finally demonstrated experimentally on real-world data.


title:
Bankruptcy Prediction of Small and Medium Enterprises Using a Flexible
  Binary Generalized Extreme Value Model

abstract:
  We introduce a binary regression accounting-based model for bankruptcy
prediction of small and medium enterprises (SMEs). The main advantage of the
model lies in its predictive performance in identifying defaulted SMEs. Another
advantage, which is especially relevant for banks, is that the relationship
between the accounting characteristics of SMEs and response is not assumed a
priori (e.g., linear, quadratic or cubic) and can be determined from the data.
The proposed approach uses the quantile function of the generalized extreme
value distribution as link function as well as smooth functions of accounting
characteristics to flexibly model covariate effects. Therefore, the usual
assumptions in scoring models of symmetric link function and linear or
pre-specied covariate-response relationships are relaxed. Out-of-sample and
out-of-time validation on Italian data shows that our proposal outperforms the
commonly used (logistic) scoring model for different default horizons.


title:
A Case of Collusion: A Study of the Interface Between Ad Libraries and
  their Apps

abstract:
  A growing concern with advertisement libraries on Android is their ability to
exfiltrate personal information from their host applications. While previous
work has looked at the libraries' abilities to measure private information on
their own, advertising libraries also include APIs through which a host
application can deliberately leak private information about the user. This
study considers a corpus of 114,000 apps. We reconstruct the APIs for 103 ad
libraries used in the corpus, and study how the privacy leaking APIs from the
top 20 ad libraries are used by the applications. Notably, we have found that
app popularity correlates with privacy leakage; the marginal increase in
advertising revenue, multiplied over a larger user base, seems to incentivize
these app vendors to violate their users' privacy.


title: Ontological aspects of the Casimir Effect

abstract:
  The role of the vacuum, in the Casimir Effect, is a matter of some dispute:
the Casimir force has been variously described as a phenomenon resulting "from
the alteration, by the boundaries, of the zero-point electromagnetic energy",
or a "Van der Waals force between the metal plates" that can be "computed
without reference to zero point energies". Neither of these descriptions are
grounded in a consistently quantum mechanical treatment of matter interacting
with the electromagnetic field. However, the Casimir Effect has been
canonically described within the framework of macroscopic quantum
electrodynamics. On this account, the force is seen to arise due to the
coupling of fluctuating currents to the zero-point radiation, and it is in this
restricted sense that the phenomenon requires the existence of zero-point
fields. The conflicting descriptions of the Casimir Effect, on the other hand,
appear to arise from inadequate ontologies in which an unwarranted metaphysical
priority is assigned either to the matter or the fields. Such ontological
errors may have a direct bearing on the problem of the cosmological constant
and the correct prediction of the Casimir force in a state of thermal
equilibrium.


title: An algorithm to compute the Hilbert depth

abstract:
  We present an algorithm which computes the Hilbert depth of a graded module
based on a theorem of Uliczka. Connected to a Herzog's question we see that the
Hilbert depth of a direct sum of modules can be strictly bigger than the
Hilbert depth of all the summands.


title: Additive Structures on Cubic Hypersurfaces

abstract:
  By an additive structure on a hypersurface S in projective space we mean an
effective action of commutative unipotent group on projective space which
leaves S invariant and acts on S with an open orbit. It is known that these
structures correspond to pairs (R,H) of local finite-dimensional algebra R and
a hyperplane H in the maximal ideal of R. We show when a projective
hypersurface of degree 3 has an additive structure and when structure is
unique.


title: Outbreak Patterns of the Novel Avian Influenza (H7N9)

abstract:
  The attack of novel avian influenza (H7N9) in east China caused a serious
health crisis and public panic. In this paper, we empirically analyze the onset
patterns of human cases of the novel avian influenza and observe several
spatial and temporal properties that are similar to other infective diseases.
More deeply, using the empirical analysis and modeling studies, we find that
the spatio-temporal network that connects the cities with human cases along the
order of outbreak timing emerges two-section-power-law edge-length
distribution, indicating the picture that several islands with higher and
heterogeneous risk straggle in east China. The proposed method is applicable to
the analysis on the spreading situation in early stage of disease outbreak
using quite limited dataset.


title: On Perfectly Clean Rings

abstract:
  An element $a$ of a ring $R$ is called perfectly clean if there exists an
idempotent $e\in comm^2(a)$ such that $a-e\in U(R)$. A ring $R$ is perfectly
clean in case every element in $R$ is perfectly clean. In this paper, we
investigate conditions on a local ring $R$ that imply that $2\times 2$ matrix
rings and triangular matrix rings are perfectly clean. We shall show that for
these rings perfect cleanness and strong cleanness coincide with each other,
and enhance many known results. We also obtain several criteria for such a
triangular matrix ring to be perfectly $J$-clean. For instance, it is proved
that for a commutative ring $R$, $T_n(R)$ is perfectly $J$-clean if and only if
$R$ is strongly $J$-clean.


title:
Thermodynamic properties of strongly coupled plasma in presence of
  external magnetic field

abstract:
  Thermodynamic properties of a Yukawa system consisting of dust particles in
plasma are studied in presence of an external magnetic field. It is assumed
that dust particles interact with each other by modified potential in presence
of magnetic field. Accordingly, a modified expression for internal energy has
been obtained. A molecular dynamics code is developed to calculate this
internal energy for the entire system. Based on the values of internal energy
given by the code Helmholtz free energy and pressure are calculated for the
system. Our study shows novel kind of behaviour for internal energy in presence
of magnetic field. Thermodynamic properties are affected significantly by
magnetic field. The study helps to express internal energy as a function of
Coulomb coupling parameter and magnetic field.


title: Efficient hybrid entanglement concentration for quantum communications

abstract:
  We present two groups of practical entanglement concentration protocols
(ECPs) for optical hybrid entangled state (HES). In the first group, it
contains two ECPs and both ECPs do not need to know the initial coefficients of
the less-entangled state. The second group contains three ECPs and they need to
know the initial coefficients. It is shown that the yield of the entanglement
concentration in the second group is greater than the first group. Moreover,
some protocols are based on the linear optics and can be easily realized under
current experiment condition. These protocols may be useful in current hybrid
quantum communication.


title:
An improved upper limit to the CMB circular polarization at large
  angular scales

abstract:
  Circular polarization of the Cosmic Microwave Background (CMB) offers the
possibility of detecting rotations of the universe and magnetic fields in the
primeval universe or in distant clusters of galaxies. We used the Milano
Polarimeter (MIPOL) installed at the Testa Grigia Observatory, on the italian
Alps, to improve the existing upper limits to the CMB circular polarization at
large angular scales. We obtain 95% confidence level upper limits to the degree
of the CMB circular polarization ranging between 5.0x10^{-4} and 0.7x10^{-4} at
angular scales between 8 and 24 deg, improving by one order of magnitude
preexisting upper limits at large angular scales. Our results are still far
from the nK region where today expectations place the amplitude of the V Stokes
parameter used to characterize circular polarization of the CMB but improve the
preexisting limit at similar angular scales. Our observations offered also the
opportunity of characterizing the atmospheric emission at 33 GHz at the Testa
Grigia Observatory.


title: A small survey of the magnetic fields of planet-host stars

abstract:
  Using spectropolarimetry, we investigate the large-scale magnetic topologies
of stars hosting close-in exoplanets. A small survey of ten stars has been done
with the twin instruments TBL/NARVAL and CFHT/ESPaDOnS between 2006 and 2011.
Each target consists of circular-polarization observations covering 7 to 22
days. For each of the 7 targets in which a magnetic field was detected, we
reconstructed the magnetic field topology using Zeeman-Doppler imaging.
Otherwise, a detection limit has been estimated. Three new epochs of
observations of Tau Boo are presented, which confirm magnetic polarity
reversal. We estimate that the cycle period is 2 years, but recall that a
shorter period of 240 days can not still be ruled out. The result of our survey
is compared to the global picture of stellar magnetic field properties in the
mass-rotation diagram. The comparison shows that these giant planet-host stars
tend to have similar magnetic field topologies to stars without detected
hot-Jupiters. This needs to be confirmed with a larger sample of stars.


title:
Role of Mutual Information in Entropy Production under Information
  Exchanges

abstract:
  We relate the information exchange between two stochastic systems to the
nonequilibrium entropy production in the whole system. By deriving a general
formula that decomposes the total entropy production into the thermodynamic and
informational parts, we obtain nonequilibrium equalities such as the
fluctuation theorem in the presence of information processing. Our results
apply not only to situations under measurement and feedback control, but also
to those under multiple information exchanges between two systems, giving the
fundamental energy cost for information processing and elucidating the
thermodynamic and informational roles of a memory in information processing. We
clarify a dual relationship between measurement and feedback.


title: Noise reduction in muon tomography for detecting high density objects

abstract:
  The muon tomography technique, based on multiple Coulomb scattering of cosmic
ray muons, has been proposed as a tool to detect the presence of high density
objects inside closed volumes. In this paper a new and innovative method is
presented to handle the density fluctuations (noise) of reconstructed images, a
well known problem of this technique. The effectiveness of our method is
evaluated using experimental data obtained with a muon tomography prototype
located at the Legnaro National Laboratories (LNL) of the Istituto Nazionale di
Fisica Nucleare (INFN). The results reported in this paper, obtained with real
cosmic ray data, show that with appropriate image filtering and muon momentum
classification, the muon tomography technique can detect high density
materials, such as lead, albeit surrounded by light or medium density material,
in short times. A comparison with algorithms published in literature is also
presented.


title:
The numbers of z~2 star-forming and passive galaxies in 2.5 square
  degrees of deep CFHT imaging

abstract:
  We use an adaptation of the BzKs technique to select ~40,000 z~2 galaxies (to
K(AB) = 24), including ~5,000 passively evolving (PE) objects (to K(AB) = 23),
from 2.5 deg^2 of deep CFTH imaging. The passive galaxy luminosity function
exhibits a clear peak at R = 22 and a declining faint-end slope ({\alpha} = -
0.12 [+0.16 -0.14]),while that of star-forming galaxies is characterized by a
steep faint-end slope ({\alpha} = -1.43 +- [0.02] (systematic) [+0.05 -0.04]
(random)). The details of the LFs are somewhat sensitive (at <25% level) to
cosmic variance even in these large(~0.5 deg^2) fields, with the D2 field
(located in the COSMOS field) most discrepant from the mean. The shape of the z
~ 2 stellar mass function of passive galaxies is remarkably similar to that at
z ~ 0.9, save for a factor of ~4 lower number density. This similarity suggests
that the same mechanism may be responsible for the formation of passive
galaxies seen at both these epochs. This same formation mechanism may also
operate down to z ~ 0 if the local PE galaxy mass function, known to be
two-component, contains two distinct galaxy populations. This scenario is
qualitatively in agreement with recent phenomenological mass-quenching models
and extends them to span more than three quarters of the history of the
Universe.


title:
Universal quantum computation by the unitary control of ancilla qubits
  and using a fixed ancilla-register interaction

abstract:
  We characterise a model of universal quantum computation where the register
(computational) qubits are controlled by ancillary qubits, using only a single
fixed interaction between register and ancillary qubits. No additional access
is required to the computational register and the dynamics of both the register
and ancilla are unitary. This scheme is inspired by the measurement-based
ancilla-driven quantum computation of Anders et al. [PRA 82, 020301(R), 2010],
but does not require measurements of the ancillas, and in this respect is
similar to the original gate based model of quantum computation. We consider
what possible forms this ancilla-register interaction can take, with a proof
that the interaction is necessarily locally equivalent to SWAP combined with an
entangling controlled gate. We further show which Hamiltonians can create such
interactions and discuss two examples; the two-qubit XY Hamiltonian and a
particular case of the XXZ Hamiltonian. We then give an example of a simple,
finite and fault tolerant gate set for universal quantum computation in this
model.


title:
Inherent fluctuation-mediated equivalent force drives directional
  motions of nanoscale asymmetric particles -- Surf-riding of asymmetric
  molecules in thermal fluctuations

abstract:
  Using a simple theoretical model of a nanoscale asymmetric particle/molecule
with asymmetric structure or/and asymmetric charge distribution, here using a
charge dipole as an example, we show that there is unidirectional
transportation mediated by non-white fluctuations if the asymmetric orientation
of the particle/molecule is constrained. This indicates the existence of an
inherent equivalent force, which drives the particle/molecule itself along the
orientation of the asymmetric particle in the environment of fluctuations. In
practical systems, equivalent force also exist in the asymmetric molecules,
such as water and ethanol, at the ambient condition since thermal fluctuations
are not white anymore at nanoscale [Wan, R., J. Hu, and H. Fang, Sci. China
Phys. Mech. Astron. 2012, 55, 751]. Molecular dynamic simulations show that
there is unidirectional transportation of an ultrathin water layer on solid
surface at room temperature when the orientations of water molecules have a
preference. The finding will play an essential role in the understanding of the
world from a molecular view and the developing of novel technology for various
nanoscale and bulk applications, such as chemical separation, water treatment,
sensing and drug delivery.


title:
The Electronic Structure of CdSe/CdS Core/Shell Seeded Nanorods: Type-I
  or Quasi-Type-II?

abstract:
  The electronic structure of CdSe/CdS core/shell seeded nanorods of
experimentally relevant size is studied using a combination of molecular
dynamics and semiempirical pseudopotential techniques, with the aim to address
the transition from type-I to a quasi-type-II band alignment. The hole is found
to be localized in the core region regardless of its size. The overlap of the
electron density with the core region depends markedly on the size of the CdSe
core: For small cores, we observe little overlap, consistent with type-II
behavior. For large cores, significant core-overlap of a number of excitonic
states can lead to type-I behavior. When electron-hole interactions are taken
into account, the core-overlap is further increased. Our calculations indicate
that the observed transition from type-II to type-I is largely due to simple
volume effects, and not to band alignment.

categories: cond-mat.mtrl-sci cond-mat.mes-hall physics.chem-ph physics.comp-ph


title:
Diffraction, Refraction, and Reflection of An Extreme-Ultraviolet Wave
  Observed during Its Interactions with Remote Active Regions

abstract:
  We present observations of the diffraction, refraction, and reflection of a
global extreme-ultraviolet (EUV) wave propagating in the solar corona. These
intriguing phenomena are observed when the wave interacts with two remote
active regions, and they together exhibit the wave property of this EUV wave.
When the wave approached AR11465, it became weaker and finally disappeared in
the active region, but a few minutes latter a new wavefront appeared behind the
active region, and it was not concentric with the incoming wave. In addition, a
reflected wave was also observed simultaneously on the wave incoming side. When
the wave approached AR11459, it transmitted through the active region directly
and without reflection. The formation of the new wavefront and the transmission
could be explained with diffraction and refraction effects, respectively. We
propose that the different behaviors observed during the interactions may
caused by different speed gradients at the boundaries of the two active
regions. For the origin of the EUV wave, we find that it formed ahead of a
group of expanding loops a few minutes after the start of the loops' expansion,
which represents the initiation of the associated coronal mass ejection (CME).
Based on these results, we conclude that the EUV wave should be a nonlinear
magnetosonic wave or shock driven by the associated CME, which propagated
faster than the ambient fast-mode speed and gradually slowed down to an
ordinary linear wave. Our observations support the hybrid model that includes
both fast wave and slow non-wave components.


title:
Observations of a Quasi-Periodic Fast Propagating Magnetosonic Wave in
  Multi-Wavelength and Its Interaction with Other Magnetic Structures

abstract:
  We present an observational study of a quasi-periodic fast propagating (QFP)
magnetosonic wave on 2012, April 23. The multiple wave trains were observed
along an active region open loop system which has a divergence geometry. The
wave trains were first observed in 171 A observations at a distance of 150 Mm
from the footpoint of the guiding loop system and with a speed of 689 km/s,
then they appeared in 193 A observations after their interaction with a
perpendicular underlaying loop system on the path, in the meantime, the wave
speed decelerated to 343 km/s quickly within a short timescale. The sudden
deceleration of the wave trains and their appearance in 193 A observations
caused by the interaction are interpreted through geometric effect and the
density increase of the guiding loop system, respectively. On the other hand,
with Wavelet and Fourier analysis methods we find that the wave trains has a
common period of 80 s with the associated flare. In addition, a few low
frequencies are also identified in the QFP wave. We propose that the generation
of the period of 80 s was caused by the periodic releasing of energy busts
through some nonlinear processes in magnetic reconnection or the so-called
oscillatory reconnection mechanism, while the low frequencies detected in the
QFP wave were possibly the manifestations of the leakage of pressure-driven
oscillations from the photosphere or chromosphere, which could be an important
source for driving QFP waves in the low corona. Our observational results also
indicate that the properties of the guiding magnetic structure such as the
distributions of magnetic field and density as well as geometry are crucial for
modulating the propagation behaviors of QFP waves. Therefore, QFP waves could
be used for remote diagnostics of the local physical properties of the solar
corona.


title:
Typical atmospheric aerosol behavior at the Cherenkov Telescope Array
  candidate sites in Argentina

abstract:
  Aerosols from natural and antropogenic sources are one of the atmospheric
components that have the largest spacial-temporal variability, depending on the
type (land or ocean) surface, human activity and climatic conditions (mainly
temperature and wind). Since Cherenkov photons generated by the incidence of a
primary ultraenergetic cosmic gamma photon have a spectral intensity
distribution concentrated in the UV and visible ranges [Hillas AM. Space
Science Reviews, 75, 17-30, 1996], it is important to know the aerosol
concentration and its contribution to atmospheric radiative transfer. We
present results of this concentration measured in typical rather calm (not
windy) days at San Antonio de los Cobres (SAC) and El Leoncito/CASLEO proposed
Argentinean Andes range sites for the placement of the Cherenkov Telescope
Array (CTA). In both places, the aerosol concentration has a peak in the
2.5-5.0$\mu$m range of the mean aerosol diameter and a very low mean total
concentration of 0.097$\mu$g/m$^3$ (0.365$\mu$g/m$^3$) for SAC(CASLEO). The
data were collected the days 15/Dec/2012 (27-28/Dec/2012) for the first
(second) place with a GRIMM aerosol spectrometer, who determines the aerosol
concentration at a given diameter (0.22-32 $\mu$m range) with a laser
technique. We also present AOD values for each CTA proposed place, derived with
the improved Deep Blue algorithm, from data measured by SEAWiFS instrument on
board of SeaStar/NASA satellite. They have very low mean values, determined for
the 1998-2010 period, AOD$_{550nm, SAC}$ = 0.026 $\pm$ 0.011 and AOD$_{550nm,
CASLEO}$ = 0.030 $\pm$ 0.014. Also, we introduce the spectral (380 nm) solar
irradiance as a test in these sites of the tropospheric UV atmospheric
transmittance.


title:
An adaptive aggregation based domain decomposition multilevel method for
  the lattice wilson dirac operator: multilevel results

abstract:
  In lattice QCD computations a substantial amount of work is spent in solving
linear systems arising in Wilson's discretization of the Dirac equations. We
show first numerical results of the extension of the two-level DD-\alpha AMG
method to a true multilevel method based on our parallel MPI-C implementation.
Using additional levels pays off, allowing to cut down the core minutes spent
on one system solve by a factor of approximately 700 compared to standard
Krylov subspace methods and yielding another speed-up of a factor of 1.7 over
the two-level approach.


title: Forecasting Intermittent Demand by Hyperbolic-Exponential Smoothing

abstract:
  Croston's method is generally viewed as superior to exponential smoothing
when demand is intermittent, but it has the drawbacks of bias and an inability
to deal with obsolescence, in which an item's demand ceases altogether. Several
variants have been reported, some of which are unbiased on certain types of
demand, but only one recent variant addresses the problem of obsolescence. We
describe a new hybrid of Croston's method and Bayesian inference called
Hyperbolic-Exponential Smoothing, which is unbiased on non-intermittent and
stochastic intermittent demand, decays hyperbolically when obsolescence occurs
and performs well in experiments.


title:
Investigation of a universal behavior between N\'eel temperature and
  staggered magnetization density for a three-dimensional quantum
  antiferromagnet

abstract:
  We simulate the three-dimensional quantum Heisenberg model with a spatially
anisotropic ladder pattern using the first principles Monte Carlo method. Our
motivation is to investigate quantitatively the newly established universal
relation $T_N/\sqrt{c^3}$ $\propto$ ${\cal M}_s$ near the quantum critical
point (QCP) associated with dimerization. Here $T_N$, $c$, and ${\cal M}_s$ are
the N\'eel temperature, the spinwave velocity, and the staggered magnetization
density, respectively. For all the physical quantities considered here, such as
$T_N$ and ${\cal M}_s$, our Monte Carlo results agree nicely with the
corresponding results determined by the series expansion method. In addition,
we find it is likely that the effect of a logarithmic correction, which should
be present in (3+1)-dimensions, to the relation $T_N/\sqrt{c^3}$ $\propto$
${\cal M}_s$ near the investigated QCP only sets in significantly in the region
with strong spatial anisotropy.


title:
Monte Carlo determination of the critical exponents for a quantum phase
  transition of a dimerized spin-1/2 Heisenberg model

abstract:
  We simulate the spin-1/2 Heisenberg model with a spatially staggered
anisotropy using first principles Monte Carlo method. In particular, the
critical exponents $\beta/\nu$ and $\omega$ associated with the quantum phase
transition induced by dimerization are determined with high precision. Here
$\beta$ and $\nu$ are the exponents related to the magnetization and the
correlation length, respectively. In addition, $\omega$ is the confluent
exponent. With very accurate data of the relevant observables, we first obtain
a value of $\omega$ compatible with the known result in the O(3) universality
class. Further, using either the value of $\omega$ determined here or the
established one in the literature, the exponent $\beta/\nu$ calculated from our
data is in quantitative agreement with the known result $\beta/\nu = 0.519(1)$
as well. Our investigation suggests that the quantum phase transition studied
here is fully consistent with the O(3) universality class.


title:
The QED vacuum polarization function at four loops and the anomalous
  magnetic moment at five loops

abstract:
  The anomalous magnetic moment of the muon is one of the most fundamental
observables. It has been measured experimentally with a very high precision and
on theory side the contributions from perturbative QED have been calculated up
to five-loop level by numerical methods. Contributions to the muon anomalous
magnetic moment from certain diagram classes are also accessible by alternative
methods. In this paper we present the evaluation of contributions to the QED
corrections due to insertions of the vacuum polarization function at five-loop
level.


title: A novel Bayesian approach to spectral function reconstruction

abstract:
  We present a novel approach to the inference of spectral functions from
Euclidean time correlator data that makes close contact with modern Bayesian
concepts. Our method differs significantly from the maximum entropy method
(MEM). A new set of axioms is postulated for the prior probability, leading to
an improved expression, which is devoid of the asymptotically flat directions
present in the Shanon-Jaynes entropy. Hyperparameters are integrated out
explicitly, liberating us from the Gaussian approximations underlying the
evidence approach of the MEM. We present a realistic test of our method in the
context of the non-perturbative extraction of the heavy quark potential. Based
on hard-thermal-loop correlator mock data, we establish firm requirements in
the number of data points and their accuracy for a successful extraction of the
potential from lattice QCD. An improved potential estimation from previously
investigated quenched lattice QCD correlators is provided.


title: Linear Algebra Estimates

abstract:
  In this paper we give a generalization of a linear algebra estimate that
occurs in the paper \cite{RS}, by Michael Rosen and Joseph H. Silverman. In
\cite{RS} authors give a bound for the size of a submodule of $(\mathbb{Z}/n
\mathbb{Z})^2$ in terms of a power of the index of any subgroup of automorphism
group of $(\mathbb{Z}/n \mathbb{Z})^2$ which is acting in an abelian way on
that submodule, meaning that given $A$ and $B$ as any two elements in the
automorphism group $AB-BA$ annihilates all elements of the submodule. We will
give a similar estimate for finite submodules of arbitrary dimension $m$ and
subgroups of general linear group acting on them. Later we will derive the
analog of this result for the case of subgroups of the symplectic group acting
on finite submodules in an abelian fashion.


title: Perceptions of the Schrodinger Equation

abstract:
  The Schrodinger equation has been considered to be a postulate of quantum
physics, but it is also perceived and derived heuristically as the quantum
equivalent of the classical energy relation. We indicate that the Schrodinger
equation cannot be a physical postulate, and we show that the heuristic
derivations wrongly consider that the particle kinetic energy is proportional
to the square of the momentum operator acting on the wavefunction. The correct
term is proportional to the square of the momentum. Analyzing particle
interactions, we realize that particles have multiple virtual motions and that
each motion is accompanied by a wave that has constant amplitude. Accordingly,
we define the wavefunction as the superposition of the virtual waves of the
particle. As a result, quantum mechanics becomes a local and global theory,
while in the traditional formulation it is a local theory. In several
interaction settings we can tell what particle motions arise and explain the
outcomes in simple and tangible terms. Most importantly, the mathematical
foundation of quantum mechanics becomes clear and justified, and we derive the
Schrodinger, Dirac, etc. equations as the conditions the wavefunction must
satisfy at each space-time point in order to fulfill the respective total
energy equation.


title:
Visualization and comparison of classical structures and quantum states
  of 4D maps

abstract:
  For generic 4D symplectic maps we propose the use of 3D phase-space slices
which allow for the global visualization of the geometrical organization and
coexistence of regular and chaotic motion. As an example we consider two
coupled standard maps. The advantages of the 3D phase-space slices are
presented in comparison to standard methods like 3D projections of orbits, the
frequency analysis, and a chaos indicator. Quantum mechanically, the 3D
phase-space slices allow for the first comparison of Husimi functions of
eigenstates of 4D maps with classical phase space structures. This confirms the
semi-classical eigenfunction hypothesis for 4D maps.


title: Secrecy Wireless Information and Power Transfer with MISO Beamforming

abstract:
  The dual use of radio signals for simultaneous wireless information and power
transfer (SWIPT) has recently drawn significant attention. To meet the
practical requirement that energy receivers (ERs) operate with significantly
higher received power as compared to information receivers (IRs), ERs need to
be deployed in more proximity to the transmitter than IRs. However, due to the
broadcast nature of wireless channels, one critical issue arises that the
messages sent to IRs can be eavesdropped by ERs, which possess better channels
from the transmitter. In this paper, we address this new secrecy communication
problem in a multiuser multiple-input single-output (MISO) SWIPT system where
one multi-antenna transmitter sends information and energy simultaneously to an
IR and multiple ERs, each with one single antenna. To optimally design transmit
beamforming vectors and their power allocation, two problems are investigated
with different aims: the first problem maximizes the secrecy rate for IR
subject to individual harvested energy constraints of ERs, while the second
problem maximizes the weighted sum-energy transferred to ERs subject to a
secrecy rate constraint for IR. We solve these two non-convex problems
optimally by reformulating each of them into a two-stage problem. First, by
fixing the signal-to-interference-plus-noise ratio (SINR) target for ERs (for
the first problem) or IR (for the second problem), we obtain the optimal
beamforming and power allocation solution by applying the technique of
semidefinite relaxation (SDR). Then, the original problems are solved by a
one-dimension search over the optimal SINR target for ERs or IR. Furthermore,
for each of the two studied problems, suboptimal solutions of lower complexity
are also proposed in which the information and energy beamforming vectors are
separately designed with their power allocation.


title: Variational Principle in Langevin Processes

abstract:
  The recent work, Nemoto and Sasa [Phys. Rev. E, 83: 030105(R) (2011)], has
shown that large deviations of the current characterizing a nonequilibrium
system are obtained by observing the typical current for a modified system
specified by a variational principle. In the present study, we will give a
generalized version of the Nemoto-Sasa study by extracting a hidden
mathematical structure from the fluctuation-response relation which is
well-known in statistical mechanics. Here, the minimization of the
Kullback-Leibler divergence plays an essential role.


title: Updates on the Pulsating SdB Star Feige 48 through Spectroscopy

abstract:
  As part of a concentrated effort to understand and exploit better the seismic
properties of Feige 48, we reestimated its atmospheric parameters using, for
the first time, a self-consistent approach based on the detailed metal
abundances that have been determined in previous studies of both its UV and
optical spectrum. We computed a small 3D grid of 150 fully line-blanketed, NLTE
model atmospheres incorporating the 8 most abundant metals found in the
atmosphere of that star. We next compared quantitatively the synthetic spectra
that we calculated from these models with three observed spectra having
different resolutions (1 A, 6 A, and 8.7 A) and wavelength ranges. Our findings
are Teff = 29,890 K, log g = 5.46, and log N(He)/N(H) = -2.88, with very small
formal fitting errors. These estimates are in good agreement with those of
previous studies, thus showing that the presence of metals do not affect
significantly the bulk atmospheric properties of Feige 48. We also modeled the
He II line at 1640 A from the STIS spectrum of the star and we found with this
line an effective temperature and a surface gravity that match well the values
obtained with the optical data. We also present a radial velocity curve based
on several years of observing Feige 48 at the MMT. This curve indicates a
precise orbital period of 8.25 h. Coupled to our discovery of a weak but very
real periodicity of 8.25 h in the light curve of Feige 48, that was gathered
during a recent extensive photometric campaign at the Mount Bigelow 1.55 m
Kuiper Telescope, we conclude that there is a reflection effect in the system,
and that the unseen companion is a low mass MS star and not a white dwarf as
has been previously suggested.


title:
Untangling the role of oxide in Ga-assisted growth of GaAs nanowires on
  Si substrates

abstract:
  The influence of the oxide in Ga-assisted growth of GaAs nanowires on Si
substrates is investigated. Three different types of oxides with different
structure and chemistry are considered. We observe that the critical oxide
thicknesses needed for achieving nanowire growth depends on the nature of oxide
and how it is processed. Additionally, we find that different growth conditions
such as temperature and Ga rate are needed for successful nanowire growth on
different oxides. We generalize the results in terms of the characteristics of
the oxides such as surface roughness, stoichiometry and thickness. These
results constitute a step further towards the integration of GaAs technology on
the Si platform.


title: Semileptonic Mixing Asymmetry Measurements of Adsl and Assl

abstract:
  Standard Model predictions of the CP violation in the mixing of B0d and B0s
mesons are beyond the present experimental sensitivity, any observation would
be therefore a hint of new physics. The D0 collaboration measures a value of
the semileptonic mixing asymmetry for a mixture of B0d and B0s mesons, AbSL,
which misses the Standard Model expectation by 3.9 standard deviations. The
world averages of the flavor specific measurements of the semileptonic
asymmetries for B0d and B0s mesons, AdSL and AsSL, are instead in agreement
with the Standard Model. The combination of the various AqSL (q=d, s)
measurements and the recent LHCb results on B0s -> J/psi phi have placed tight
bounds on the hypothesis of new physics which can explain the D0 result.


title:
Nonlocal resistance and its fluctuations in microstructures of
  band-inverted HgTe/(Hg,Cd)Te quantum wells

abstract:
  We investigate experimentally transport in gated microsctructures containing
a band-inverted HgTe/Hg_{0.3}Cd_{0.7}Te quantum well. Measurements of nonlocal
resistances using many contacts prove that in the depletion regime the current
is carried by the edge channels, as expected for a two-dimensional topological
insulator. However, high and non-quantized values of channel resistances show
that the topological protection length (i.e. the distance on which the carriers
in helical edge channels propagate without backscattering) is much shorter than
the channel length, which is ~100 micrometers. The weak temperature dependence
of the resistance and the presence of temperature dependent reproducible
quasi-periodic resistance fluctuations can be qualitatively explained by the
presence of charge puddles in the well, to which the electrons from the edge
channels are tunnel-coupled.


title: FACT - Long-term stability and observations during strong Moon light

abstract:
  The First G-APD Cherenkov Telescope (FACT) is the first Cherenkov telescope
equipped with a camera made of silicon photon detectors (G-APD aka. SiPM).
Since October 2011, it is regularly taking data on the Canary Island of La
Palma. G-APDs are ideal detectors for Cherenkov telescopes as they are robust
and stable. Furthermore, the insensitivity of G-APDs towards strong ambient
light allows to conduct observations during bright Moon and twilight. This gain
in observation time is essential for the long-term monitoring of bright TeV
blazars. During the commissioning phase, hundreds of hours of data (including
data from the the Crab Nebula) were taken in order to understand the
performance and sensitivity of the instrument. The data cover a wide range of
observation conditions including different weather conditions, different zenith
angles and different light conditions (ranging from dark night to direct full
Moon). We use a new parmetrisation of the Moon light background to enhance our
scheduling and to monitor the atmosphere. With the data from 1.5 years, the
long-term stability and the performance of the camera during Moon light is
studied and compared to that achieved with photomultiplier tubes so far.


title: Complex Gaussian multiplicative chaos

abstract:
  In this article, we study complex Gaussian multiplicative chaos. More
precisely, we study the renormalization theory and the limit of the exponential
of a complex log-correlated Gaussian field in all dimensions (including
Gaussian Free Fields in dimension 2). Our main working assumption is that the
real part and the imaginary part are independent. We also discuss applications
in 2D string theory; in particular we give a rigorous mathematical definition
of the so-called Tachyon fields, the conformally invariant operators in
critical Liouville Quantum Gravity with a c=1 central charge, and derive the
original KPZ formula for these fields.


title: On extendibility and decomposability of certain *-linear maps into C (X)

abstract:
  We consider *-linear maps into a commutative C*-algebra C (X) of continuous
functions on a locally compact Hausdorff space X with certain specified
properties and prove two results: (1) an extension result for a class of
*-linear maps Y --> C (X) which may be called of locally compact type (locally
finite) with respect to an inclusion Y < X of normed vector spaces, and (2) a
minimal decomposition for certain *-linear maps into C (X) (absolutely
continuous) as a difference of two positive maps.


title:
S-wave Superconductivity due to Orbital and Spin fluctuations in
  Fe-pnictides: Self-Consistent Vertex Correction with Self-Energy
  (SC-VC\Sigma) Analysis

abstract:
  To understand the amazing variety of the superconducting states of Fe-based
superconductors, we analyze the multiorbital Hubbard models for LaFeAsO and
LiFeAs going beyond the random-phase approximation (RPA), by calculating the
vertex correction (VC) and self-energy correction. Due to the spin+orbital mode
coupling described by the VC, both orbital and spin fluctuations mutually
develop, consistently with the experimental phase diagram with the orbital and
magnetic orders. Due to both fluctuations, the s-wave gap function with
sign-reversal ($s_{\pm}$-wave), without sign-reversal ($s_{++}$-wave), and
nodal s-wave states are obtained, compatible with the experimental wide variety
of the gap structure. Thus, the present theory provides a microscopic
explanation of the normal and superconducting phase diagram based on the
realistic Hubbard model.


title:
Dual lattice simulation of the U(1) gauge-Higgs model at finite density
  - an exploratory proof-of-concept study

abstract:
  The U(1) gauge-Higgs model with two flavors of opposite charge and a chemical
potential is mapped exactly to a dual representation where matter fields
correspond to loops of flux and the gauge fields are represented by surfaces.
The complex action problem of the conventional formulation at finite chemical
potential mu is overcome in the dual representation and the partition sum has
only real and non-zero contributions. We simulate the model in the dual
representation using a generalized worm algorithm, explore the phase diagram
and study condensation phenomena at finite mu.


title:
Phase diagram and physical properties of NaFe$_{1-x}$Cu$_x$As single
  crystals

abstract:
  A series of high quality NaFe$_{1-x}$Cu$_x$As single crystals has been grown
by a self-flux technique, which were systematically characterized via
structural, transport, thermodynamic, and high pressure measurements. Both the
structural and magnetic transitions are suppressed by Cu doping, and bulk
superconductivity is induced by Cu doping. Superconducting transition
temperature ($T_c$) is initially enhanced from 9.6 to 11.5 K by Cu doping, and
then suppressed with further doping. A phase diagram similar to
NaFe$_{1-x}$Co$_x$As is obtained except that insulating instead of metallic
behavior is observed in extremely overdoped samples. $T_c$'s of underdoped,
optimally doped, and overdoped samples are all notably enhanced by applying
pressure. Although a universal maximum transition temperature ($T_c^{max}$) of
about 31 K under external pressure is observed in underdoped and optimally
doped NaFe$_{1-x}$Co$_x$As, $T_c^{max}$ of NaFe$_{1-x}$Cu$_x$As is monotonously
suppressed by Cu doping, suggesting that impurity potential of Cu is stronger
than Co in NaFeAs. The comparison between Cu and Co doping effect in NaFeAs
indicates that Cu serves as an effective electron dopant with strong impurity
potential, but part of the doped electrons are localized and do not fill the
energy bands as predicted by the rigid-band model.


title: Black-hole entropy and minimal diffusion

abstract:
  The density of states reproducing the Bekenstein-Hawking entropy-area scaling
can be modeled via a nonlocal field theory. We define a diffusion process based
on the kinematics of this theory and find a spectral dimension whose flow
exhibits surprising properties. While it asymptotes four from above in the
infrared, in the ultraviolet the spectral dimension diverges at a finite
(Planckian) value of the diffusion length, signaling a breakdown of the notion
of diffusion on a continuum spacetime below that scale. We comment on the
implications of this minimal diffusion scale for the entropy bound in a
holographic and field-theoretic context.