title:
Calculation Of The Elastic P6He And P8He Scattering In Glauber
  Approximation

abstract:
  The series of calculations of differential cross sections and analyzing
powers (Ay) of the elastic proton scattering on isotopes 6He and 8He was
presented in the framework of the theory of Glauber multiple diffraction
scattering. The three-body {\alpha}-n-n and harmonic oscillator wave functions
were used for 6He, for 8He - the function of density distribution in LSSM. For
p6He scattering the expansion of the Glauber operator into a series of multiple
scattering is written in the form consistent with the picture of weakly bound
clusters in halo-nuclei, for p8He scattering the members of single- and double
collisions are included in the operator. We have done the comparison of our
results with available experimental data (including new data of Ay for p6He
scattering at the E = 71 MeV/nucleon) and with the calculations results in the
other approaches (high-energy, optical model, RMF). Also, the comparison of the
characteristics of two isotopes 6He and 8He was made, which showed that they
correlate quite well with each other.


title: Optimal Prediction in an Additive Functional Model

abstract:
  The functional generalized additive model (FGAM) provides a more flexible
nonlinear functional regression model than the well-studied functional linear
regression model. This paper restricts attention to the FGAM with identity link
and additive errors, which we will call the additive functional model, a
generalization of the functional linear model. This paper studies the minimax
rate of convergence of predictions from the additive functional model in the
framework of reproducing kernel Hilbert space. It is shown that the optimal
rate is determined by the decay rate of the eigenvalues of a specific kernel
function, which in turn is determined by the reproducing kernel and the joint
distribution of any two points in the random predictor function. For the
special case of the functional linear model, this kernel function is jointly
determined by the covariance function of the predictor function and the
reproducing kernel. The easily implementable roughness-regularized predictor is
shown to achieve the optimal rate of convergence. Numerical studies are carried
out to illustrate the merits of the predictor. Our simulations and real data
examples demonstrate a competitive performance against the existing approach.


title: Pr\"ufer codes for hypertrees

abstract: We describe a new Pr\"ufer code which works also for infinite trees.


title: How Fast Can Quantum Annealers Count?

abstract:
  We outline an algorithm for the Quantum Counting problem using Adiabatic
Quantum Computation (AQC). We show that using local adiabatic evolution, a
process in which the adiabatic procedure is performed at a variable rate, the
problem is solved with the same complexity as the analogous circuit-based
algorithm, i.e., quadratically faster than the corresponding classical
algorithm. The above algorithm provides further evidence for the potentially
powerful capabilities of AQC as a paradigm for more efficient problem solving
on a quantum computer, and may be used as the basis for solving more
sophisticated problems.


title: On automorphisms of blowups of projective manifolds

abstract:
  In this paper we mainly study the following question: For what projective
manifold $X$ of dimension $\geq 3$ that any $f\in Aut(X)$ has zero topological
entropy? Using some non-vanishing conditions on nef cohomology classes, we
study the case where $X\rightarrow X_0$ is a finite blowup along smooth
centers, here $X_0$ is a projective manifold of interest. Here we allow $X_0$
to be either one of the following manifolds: it has Picard number 1, or a Fano
manifold, or it is a projective hyper-K\"ahler manifold. We also allow the
centers of blowups to have large dimensions relative to that of $X_0$ (may be
upto $dim(X_0)-2$). Explicit constructions are given in Section
\ref{SectionBlowupsAndNonVanishingConditions}, where we also show that the
assumptions in the results in that section are necessary (see Example 6 in
Section \ref{SectionBlowupsAndNonVanishingConditions}).
  As a consequence, we obtain new examples of manifolds $X$, whose any
automorphism is either of zero topological entropy or is cohomologically
hyperbolic.


title:
Improved algorithms and analysis for the laminar matroid secretary
  problem

abstract:
  In a matroid secretary problem, one is presented with a sequence of objects
of various weights in a random order, and must choose irrevocably to accept or
reject each item. There is a further constraint that the set of items selected
must form an independent set of an associated matroid. Constant-competitive
algorithms (algorithms whose expected solution weight is within a constant
factor of the optimal) are known for many types of matroid secretary problems.
We examine the laminar matroid and show an algorithm achieving provably 0.053
competitive ratio.


title:
Realizing non-Abelian gauge potentials in optical square lattices:
  Application to atomic Chern insulators

abstract:
  We describe a scheme to engineer non-Abelian gauge potentials on a square
optical lattice using laser-induced transitions. We emphasize the case of
two-electron atoms, where the electronic ground state g is laser coupled to a
metastable state e within a state-dependent optical lattice. In this scheme,
the alternating pattern of lattice sites hosting g and e states depict a
checkerboard structure, allowing for laser-assisted tunneling along both
spatial directions. In this configuration, the nuclear spin of the atoms can be
viewed as a "flavor" quantum number undergoing non-Abelian tunneling along
nearest-neighbor links. We show that this technique can be useful to simulate
the equivalent of the Haldane quantum Hall model using cold atoms trapped in
square optical lattices, offering an interesting route to realize Chern
insulators. The emblematic Haldane model is particularly suited to investigate
the physics of topological insulators, but requires, in its original form,
complex hopping terms beyond nearest-neighboring sites. In general, this
drawback inhibits a direct realization with cold atoms, using standard
laser-induced tunneling techniques. We demonstrate that a simple mapping allows
to express this model in terms of matrix hopping operators, that are defined on
a standard square lattice. This mapping is investigated for two models that
lead to anomalous quantum Hall phases. We discuss the practical implementation
of such models, exploiting laser-induced tunneling methods applied to the
checkerboard optical lattice.


title: Dirac-Schrodinger transformations in contacted graphene structures

abstract:
  At an interface between contacts and graphene, the mathematical equation that
governs the propagation of electrons transforms from the Schrodinger to the
Dirac equation. The condition of current probability conservation at such an
interface does not determine uniquely the boundary conditions for the quantum
wavefunction. We discuss the possible form of boundary conditions, determine
its influence on the transmission coefficient of a contacted graphene structure
and suggest that optical experiments on photonic crystals with Dirac points can
help identifying, under certain circumstances, the proper boundary condition at
graphene- electrode interfaces.


title: A method for testing the cosmic homogeneity with Shannon entropy

abstract:
  We propose a method for testing cosmic homogeneity based on the Shannon
entropy in Information theory and test the potentials and limitations of the
method on Monte Carlo simulations of some homogeneous and inhomogeneous 3D
point process in a finite region of space. We analyze a set of N-body
simulations to investigate the prospect of determining the scale of homogeneity
with the proposed method and show that the method could serve as an efficient
tool for the study of homogeneity.


title:
Wahlquist's metric versus an approximate solution with the same equation
  of state

abstract:
  We compare an approximation of the singularity-free Wahlquist exact solution
with a stationary and axisymmetric metric for a rigidly rotating perfect fluid
with the equation of state $\mu + 3p= \mu_0$, a sub-case of a global
approximate metric obtained recently by some of us. We see that to have a fluid
with vanishing twist vector everywhere in Wahlquist's metric the only option is
to let its parameter $r_0\rightarrow0$ and using this in the comparison allows
us in particular to determine the approximate relation between the angular
velocity of the fluid in a set of harmonic coordinates and $r_0$. Through some
coordinate changes we manage to make every component of both approximate
metrics equal. In this situation, the free constants of our metric take values
that happen to be those needed for it to be of Petrov type D, the last
condition that this fluid must verify to give rise to the Wahlquist solution.


title: Average Error for Spectral Asymptotics on Surfaces

abstract:
  Let $N(t)$ denote the eigenvalue counting funtion of the Laplacian on a
compact surface of constant nonnegative curvature, with or without boundary. We
define a refined asymptotic formula $\tilde{N}(t)=At+Bt^{1/2}+C$, where the
constants are expressed in terms of the geometry of the surface and its
boundary, and consider the average error $A(t) = \frac{1}{t} \int_0^{t}D(s)ds$
for $D(t) = N(t) - \tilde{N}(t)$. We present a conjecture for the asymptotic
behavior of $A(t)$, and study some examples that support the conjecture.


title:
Dynamical canonical heights for Jordan blocks, arithmetic degrees of
  orbits, and nef canonical heights on abelian varieties

abstract:
  Let f : X --> X be an endomorphism of a normal projective variety defined
over a global field K, and let D_0,D_1,D_2,... be divisor classes that form a
Jordan block with eigenvalue b for the action of f^* on Pic(X) tensored with C.
We construct appropriately normalized canonical heights h_0,h_1,h_2,...
associated to D_0,D_1,D_2,... and satisfying Jordan transformation formulas
h_k(f(x)) = b h_k(x) + h_{k-1}(x). As an application, we prove that for every x
in X, the arithmetic degree a_f(x) exists, is an algebraic integer, and takes
on only finitely many values as x varies over X. Further, if X is an abelian
variety defined over a number field and D is a nonzero nef divisor, we
characterize points satisfying h_D(x)=0, and we use this characterization to
prove that if the f-orbit of x is Zariski dense in X, then a_f(x) is equal to
the dynamical degree of f.


title:
Probing the spin-parity of the Higgs boson via jet kinematics in vector
  boson fusion

abstract:
  Determining the spin and the parity quantum numbers of the recently
discovered Higgs-like boson at the LHC is a matter of great importance. In this
paper, we consider the possibility of using the kinematics of the tagging jets
in Higgs production via the vector boson fusion (VBF) process to test the
tensor structure of the Higgs-vector boson ($HVV$) interaction and to determine
the spin and CP properties of the observed resonance. We show that an anomalous
$HVV$ vertex, in particular its explicit momentum dependence, drastically
affects the rapidity between the two scattered quarks and their transverse
momenta and, hence, the acceptance of the kinematical cuts that allow to select
the VBF topology. The sensitivity of these observables to different spin-parity
assignments, including the dependence on the LHC center of mass energy, are
evaluated. In addition, we show that in associated Higgs production with a
vector boson some kinematical variables, such as the invariant mass of the
system and the transverse momenta of the two bosons and their separation in
rapidity, are also sensitive to the spin--parity assignments of the Higgs--like
boson.


title:
Interatomic potentials, electric properties, and spectroscopy of the
  ground and excited states of the Rb_2 molecule: Ab initio calculations and
  effect of a non-resonant field

abstract:
  We formulate the theory for a diatomic molecule in a spatially degenerate
electronic state interacting with a non-resonant laser field and investigate
its rovibrational structure in the presence of the field. We report on
\textit{ab initio} calculations employing the double electron attachment
intermediate Hamiltonian Fock space coupled cluster method restricted to single
and double excitations for all electronic states of the Rb$_2$ molecule up to
$5s+5d$ dissociation limit of about 26.000$\,$cm$^{-1}$. In order to correctly
predict the spectroscopic behavior of Rb$_2$, we have also calculated the
electric transition dipole moments, non-adiabatic coupling and spin-orbit
coupling matrix elements, and static dipole polarizabilities, using the
multireference configuration interaction method. When a molecule is exposed to
strong non-resonant light, its rovibrational levels get hybridized. We study
the spectroscopic signatures of this effect for transitions between the
X$^1\Sigma_g^+$ electronic ground state and the A$^1\Sigma_u^+$ and b$^3\Pi_u$
excited state manifold. The latter is characterized by strong perturbations due
to the spin-orbit interaction. We find that for non-resonant field strengths of
the order $10^9$W/cm$^2$, the spin-orbit interaction and coupling to the
non-resonant field become comparable. The non-resonant field can then be used
to control the singlet-triplet character of a rovibrational level.


title: Finiteness of the polyhedral Q-codegree spectrum

abstract:
  In this paper we show that the spectrum of the Q-codegree of a d-dimensional
lattice polytope is finite above any positive threshold in the class of lattice
polytopes with \alpha-canonical normal fan for any fixed \alpha>0. For
\alpha=1/r this includes lattice polytopes with Q-Gorenstein normal fan of
index r. In particular, this proves Fujita's Spectrum Conjecture for polarized
varieties in the case of Q-Gorenstein toric varieties of index r.


title: On the estimators of autocorrelation model parameters

abstract:
  Estimation of autocorrelations and spectral densities is of fundamental
importance in many fields of science, from identifying pulsar signals in
astronomy to measuring heart beats in medicine. In circumstances where one is
interested in specific autocorrelation functions that do not fit into any
simple families of models, such as auto-regressive moving average (ARMA),
estimating model parameters is generally approached in one of two ways: by
fitting the model autocorrelation function to a non-parameteric autocorrelation
estimate via regression analysis or by fitting the model autocorrelation
function directly to the data via maximum likelihood. Prior literature suggests
that variogram regression yields parameter estimates of comparable quality to
maximum likelihood. In this letter we demonstrate that, as sample size is
increases, the accuracy of the maximum-likelihood estimates (MLE) ultimately
improves by orders of magnitude beyond that of variogram regression. For
relatively continuous and Gaussian processes, this improvement can occur for
sample sizes of less than 100. Moreover, even where the accuracy of these
methods is comparable, the MLE remains almost universally better and, more
critically, variogram regression does not provide reliable confidence
intervals. Inaccurate regression parameter estimates are typically accompanied
by underestimated standard errors, whereas likelihood provides reliable
confidence intervals.


title:
On the Ordering of Spectral Radius Product r(A) r(AD) Versus r(A^2 D)
  and Related Applications

abstract:
  For a nonnegative matrix A and real diagonal matrix D, two known inequalities
on the spectral radius, r(A^2 D^2) >= r(AD)^2 and r(A) r(A D^2) >= r(AD)^2,
leave open the question of what determines the order of r(A^2 D^2) with respect
to r(A) r(A D^2). This is a special case of a broad class of problems that
arise repeatedly in ecological and evolutionary dynamics. Here, sufficient
conditions are found on A that determine orders in either direction. For a
diagonally symmetrizable nonnegative matrix A with all positive eigenvalues and
nonnegative D, r(A^2 D) <= r(A) r(AD). The reverse holds if all of the
eigenvalues of A are negative besides the Perron root. This is a particular
case of the more general result that r(A [(1-m) r(B) I + m B] D) is monotonic
in m when all non-Perron eigenvalues of A have the same sign --- decreasing for
positive signs and increasing for negative signs, for symmetrizable nonnegative
A and B that commute. Commuting matrices include the Kronecker products A, B in
{\otimes_{i=1}^L M_i^{t_i}}, t_i in {0, 1, 2, ...}, which comprise a class of
application for these results. This machinery allows analysis of the sign of
d/d m_j r({\otimes_{i=1}^L[(1-m_i) r(A_i) I_i + m_i A_i]}D). The eigenvalue
sign conditions also provide lower or upper bounds to the harmonic mean of the
expected sojourn times of Markov chains. These inequalities appear in the
asymptotic growth rates of viral quasispecies, models for the evolution of
dispersal in random environments, and the evolution of site-specific mutation
rates over the entire genome.


title:
New derived autoequivalences of Hilbert schemes and generalised Kummer
  varieties

abstract:
  We show that for every smooth projective surface X and every $n\ge 2$ the
push-forward along the diagonal embedding gives a $P^{n-1}$-functor into the
$S_n$-equivariant derived category of X^n. Using the
Bridgeland--King--Reid--Haiman equivalence this yields a new autoequivalence of
the derived category of the Hilbert scheme of n points on X. In the case that
the canonical bundle of X is trivial and n=2 this autoequivalence coincides
with the known EZ-spherical twist induced by the boundary of the Hilbert
scheme. We also generalise the 16 spherical objects on the Kummer surface given
by the exceptional curves to n^4 orthogonal $P^{n-1}$-Objects on the
generalised Kummer variety.


title:
On extraction of the total photoabsorption cross section on the neutron
  from data on the deuteron

abstract:
  An improved procedure is suggested for finding the total photoabsorption
cross section on the neutron from data on the deuteron at energies < 1.5 GeV.
It includes unfolding of smearing effects caused by Fermi motion of nucleons in
the deuteron and also takes into account non-additive contributions to the
deuteron cross section due to final-state interactions of particles in single
and double pion photoproduction. This procedure is applied to analysis of
existing data.


title: Extremal words in morphic subshifts

abstract:
  Given an infinite word X over an alphabet A a letter b occurring in X, and a
total order \sigma on A, we call the smallest word with respect to \sigma
starting with b in the shift orbit closure of X an extremal word of X. In this
paper we consider the extremal words of morphic words. If X = g(f^{\omega}(a))
for some morphisms f and g, we give two simple conditions on f and g that
guarantees that all extremal words are morphic. This happens, in particular,
when X is a primitive morphic or a binary pure morphic word. Our techniques
provide characterizations of the extremal words of the Period-doubling word and
the Chacon word and give a new proof of the form of the lexicographically least
word in the shift orbit closure of the Rudin-Shapiro word.


title:
Disjunctive Interpolants for Horn-Clause Verification (Extended
  Technical Report)

abstract:
  One of the main challenges in software verification is efficient and precise
compositional analysis of programs with procedures and loops. Interpolation
methods remain one of the most promising techniques for such verification, and
are closely related to solving Horn clause constraints. We introduce a new
notion of interpolation, disjunctive interpolation, which solve a more general
class of problems in one step compared to previous notions of interpolants,
such as tree interpolants or inductive sequences of interpolants. We present
algorithms and complexity for construction of disjunctive interpolants, as well
as their use within an abstraction-refinement loop. We have implemented Horn
clause verification algorithms that use disjunctive interpolants and evaluate
them on benchmarks expressed as Horn clauses over the theory of integer linear
arithmetic.


title: Spin-Polarized Electrons in Bilayer Graphene Flakes

abstract:
  We show that a bilayer graphene flake deposited above a ferromagnetic
insulator can behave as a spin-filtering device. The ferromagnetic material
induces exchange splitting in the graphene flake, and due to the Fano
antiresonances occurring in the transmission of the graphene flake as a
function of flake length and energy, it is possible to obtain a net spin
current. This happens when an antiresonance for one spin channel coincides with
a maximum transmission for the opposite spin. We propose these structures as a
means to obtain spin-polarized currents and spin filters in graphene-based
systems.


title:
A counter-example to Martino's conjecture about generic Calogero-Moser
  families

abstract:
  The Calogero-Moser families are partitions of the irreducible characters of a
complex reflection group derived from the block structure of the corresponding
restricted rational Cherednik algebra. It was conjectured by Martino in 2009
that the generic Calogero-Moser families coincide with the generic Rouquier
families, which are derived from the corresponding Hecke algebra. This
conjecture is already proven for the whole infinite series G(m,p,n) and for the
exceptional group G4. A combination of theoretical facts with explicit
computations enables us to determine the generic Calogero-Moser families for
the nine exceptional groups G4, G5, G6, G8, G10, G23=H3, G24, G25, and G26. We
show that the conjecture holds for all these groups - except surprisingly for
the group G25, thus being the first and only-known counter-example so far.


title: Supervised Classification Using Sparse Fisher's LDA

abstract:
  It is well known that in a supervised classification setting when the number
of features is smaller than the number of observations, Fisher's linear
discriminant rule is asymptotically Bayes. However, there are numerous modern
applications where classification is needed in the high-dimensional setting.
Naive implementation of Fisher's rule in this case fails to provide good
results because the sample covariance matrix is singular. Moreover, by
constructing a classifier that relies on all features the interpretation of the
results is challenging. Our goal is to provide robust classification that
relies only on a small subset of important features and accounts for the
underlying correlation structure. We apply a lasso-type penalty to the
discriminant vector to ensure sparsity of the solution and use a shrinkage type
estimator for the covariance matrix. The resulting optimization problem is
solved using an iterative coordinate ascent algorithm. Furthermore, we analyze
the effect of nonconvexity on the sparsity level of the solution and highlight
the difference between the penalized and the constrained versions of the
problem. The simulation results show that the proposed method performs
favorably in comparison to alternatives. The method is used to classify
leukemia patients based on DNA methylation features.


title: Effective Polyakov line action from the relative weights method

abstract:
  We apply the relative weights method (arXiv:1209.5697) to determine the
effective Polyakov line action for SU(2) lattice gauge theory in the confined
phase, at lattice coupling beta=2.2 and N_t=4 lattice spacings in the time
direction. The effective action turns out to be bilinear in the fundamental
representation Polyakov line variables, with a rather simple expression for the
finite range kernel. The validity of this action is tested by computing
Polyakov line correlators, via Monte Carlo simulation, in both the effective
action and the underlying lattice theory. It is found that the correlators in
each theory are in very close agreement.


title:
Homotopy groups of spheres and Lipschitz homotopy groups of Heisenberg
  groups

abstract:
  We provide a sufficient condition for the nontriviality of the Lipschitz
homotopy group of the Heisenberg group, $\pi_m^{Lip}(H_n)$, in terms of
properties of the classical homotopy group of the sphere, $\pi_m(S^n)$. As an
application we provide a new simplified proof of the fact that
$\pi_n^{Lip}(H_n)\neq 0$, $n=1,2,...$, and we prove a new result that
$\pi_{4n-1}^{Lip}(H_{2n})\neq 0$ for $n=1,2,...$ The last result is based on a
new generalization of the Hopf invariant. We also prove that Lipschitz mappings
are not dense in the Sobolev space $W^{1,p}(M,H_{2n})$ when $dim M\geq 4n$ and
$4n-1\leq p<4n$.


title: Asymptotic parabolicity for strongly damped wave equations

abstract:
  For $S$ a positive selfadjoint operator on a Hilbert space, \[
\frac{d^2u}{dt}(t) + 2 F(S)\frac{du}{dt}(t) + S^2u(t)=0 \] describes a class of
wave equations with strong friction or damping if $F$ is a positive Borel
function. Under suitable hypotheses, it is shown that \[ u(t)=v(t)+ w(t) \]
where $v$ satisfies \[ 2F(S)\frac{dv}{dt}(t)+ S^2v(t)=0 \] and \[
\frac{w(t)}{\|v(t)\|} \rightarrow 0, \; \text{as} \; t \rightarrow +\infty. \]
The required initial condition $v(0)$ is given in a canonical way in terms of
$u(0)$, $u'(0)$.


title: Numerical Exploration of Soliton Creation

abstract:
  We explore the classical production of solitons in the easy axis O(3) model
in 1+1 dimensions, for a wide range of initial conditions that correspond to
the scattering of small breathers. We characterize the fractal nature of the
region in parameter space that leads to soliton production and find certain
trends in the data. We identify a tension in the initial conditions required
for soliton production - low velocity incoming breathers are more likely to
produce solitons, while high velocity incoming breathers provide momentum to
the final solitons and enable them to separate. We find new "counter-spinning"
initial conditions that can alleviate some of this tension.


title: The genus of regular languages

abstract:
  The article defines and studies the genus of finite state deterministic
automata (FSA) and regular languages. Indeed, a FSA can be seen as a graph for
which the notion of genus arises. At the same time, a FSA has a semantics via
its underlying language. It is then natural to make a connection between the
languages and the notion of genus. After we introduce and justify the the
notion of the genus for regular languages, the following questions are
addressed. First, depending on the size of the alphabet, we provide upper and
lower bounds on the genus of regular languages : we show that under a
relatively generic condition on the alphabet and the geometry of the automata,
the genus grows at least linearly in terms of the size of the automata. Second,
we show that the topological cost of the powerset determinization procedure is
exponential. Third, we prove that the notion of minimization is orthogonal to
the notion of genus. Fourth, we build regular languages of arbitrary large
genus: the notion of genus defines a proper hierarchy of regular languages.


title: Low-temperature spin dynamics of a valence bond glass in Ba2YMoO6

abstract:
  We carried out AC magnetic susceptibility measurements and muon spin
relaxation spectroscopy on the cubic double perovskite Ba2YMoO6, down to 50 mK.
Below ~1 K the muon relaxation is typical of a magnetic insulator with a
spin-liquid type ground state, i.e. without broken symmetries or frozen
moments. However, the AC susceptibility revealed a dilute-spin-glass like
transition below ~ 1 K. Antiferromagnetically coupled Mo5+ 4d1 electrons in
triply degenerate t2g orbitals are in this material arranged in a geometrically
frustrated fcc lattice. Bulk magnetic susceptibility data has previously been
interpreted in terms of a freezing to a heterogeneous state with non-magnetic
sites where 4d^1 electrons have paired in spin-singlets dimers, and residual
unpaired Mo5+ 4d1 electrons. Based on the magnetic heat capacity data it has
been suggested that this heterogeneity is the result of kinetic constraints
intrinsic to the physics of the pure system (possibly due to topological
overprotection), leading to a self-induced glass of valence bonds between
neighbouring 4d1 electrons. The muSR relaxation unambiguously points to a
static heterogeneous state with a static arrangement of unpaired electrons
isolated by spin-singlet (valence bond) dimers between the majority of Mo5+ 4d
electrons. The AC susceptibility data indicate that the residual magnetic
moments freeze into a dilute-spin-glass-like state. This is in apparent
contradiction with the muon-spin decoupling at 50 mK in fields up to 200 mT,
which indicates that, remarkably, the time scale of the field fluctuations from
the residual moments is ~ 5 ns. Comparable behaviour has been observed in other
geometrically frustrated magnets with spin-liquid-like behaviour and the
implications of our observations on Ba2YMoO6 are discussed in this context.


title:
Closed form solutions of linear difference equations in terms of
  symmetric products

abstract:
  In this paper we show how to find a closed form solution for third order
difference operators in terms of solutions of second order operators. This work
is an extension of previous results on finding closed form solutions of
recurrence equations and a counterpart to existing results on differential
equations. As motivation and application for this work, we discuss the problem
of proving positivity of sequences given merely in terms of their defining
recurrence relation. The main advantage of the present approach to earlier
methods attacking the same problem is that our algorithm provides
human-readable and verifiable, i.e., certified proofs.


title:
Constraints on primordial black holes as dark matter candidates from
  capture by neutron stars

abstract:
  We investigate constraints on primordial black holes (PBHs) as dark matter
candidates that arise from their capture by neutron stars (NSs). If a PBH is
captured by a NS, the star is accreted onto the PBH and gets destroyed in a
very short time. Thus, mere observations of NSs put limits on the abundance of
PBHs. High DM densities and low velocities are required to constrain the
fraction of PBHs in DM. Such conditions may be realized in the cores of
globular clusters if the latter are of a primordial origin. Assuming that cores
of globular clusters possess the DM densities exceeding several hundred
GeV/cm$^3$ would imply that PBHs are excluded as comprising all of the dark
matter in the mass range $3\times 10^{18} \text{g} \lesssim m_\text{BH}\lesssim
10^{24} \text{g}$. At the DM density of $2\times 10^3$ GeV/cm$^3$ that has been
found in simulations in the corresponding models, less than 5% of the DM may
consist of PBH for these PBH masses.


title: Tunable Infrared Phonon Anomalies in Trilayer Graphene

abstract:
  Trilayer graphene in both ABA (Bernal) and ABC (rhombohedral) stacking
sequences is shown to exhibit intense infrared absorption from in-plane optical
phonons. The feature, lying at ~1580 cm-1, changes strongly with electrostatic
gating. For ABC-stacked graphene trilayers, we observed a large enhancement in
phonon absorption amplitude, as well as softening of the phonon mode, as the
Fermi level is tuned away from charge neutrality. A similar, but substantially
weaker effect is seen in samples with the more common ABA stacking order. The
strong infrared response of the optical phonons and the pronounced variation
with electrostatic gating and stacking-order reflect the interactions of the
phonons and electronic excitations in the two systems. The key experimental
findings can be reproduced within a simplified charged-phonon model that
considers the influence of charging through Pauli blocking of the electronic
transitions.


title:
On some sharp spectral inequalities for Schr\"odinger operators on
  semi-axis

abstract:
  In this paper we obtain sharp Lieb-Thirring inequalities for a Schr\"odinger
operator on semi-axis with a matrix potential and show how they can be used to
other related problems. Among them are spectral inequalities on star graphs and
spectral inequalities for Schr\"odinger operators on half-spaces with Robin
boundary conditions.


title:
Strong Coupling between a Topological Qubit and a Nanomechanical
  Resonator

abstract:
  We describe a scheme that enables a strong coherent coupling between a
topological qubit and the quantized motion of a magnetized nanomechanical
resonator. This coupling is achieved by attaching an array of magnetic tips to
a namomechanical resonator under a quantum phase controller which coherently
controls the energy gap of a topological qubit. Combined with single-qubit
rotations the strong coupling enables arbitrary unitary transformations on the
hybrid system of topological and mechanical qubits and may pave the way for the
quantum information transfer between topological and optical qubits. Numerical
simulations show that quantum state transfer and entanglement distributing
between the topological and mechanical qubits may be accomplished with high
fidelity.


title: Centralized Lifetime Maximizing Tree For Wireless Sensor Networks

abstract:
  To enable data aggregation among the event sources in wireless sensor
networks and to reduce the communication cost there is a need to establish a
coveraged tree structure inside any given event region to allow data reports to
be aggregated at a single processing point prior to transmission to the
network. In this paper we propose a novel technique to create one such tree
which maximizes the lifetime of the event sources while they are constantly
transmitting for data aggregation. We use the term Centralized Lifetime
Maximizing Tree (CLMT) to denote this tree. CLMT features with identification
of bottleneck node among the given set of nodes. This node collects the data
from every other node via routes with the highest branch energy subject to
condition loop is not created. By constructing tree in such a way, protocol is
able to reduce the frequency of tree reconstruction, minimize the delay and
maximize the functional lifetime of source nodes by minimizing the additional
energy involved in tree reconstruction.


title:
Solutions of the matrix inequalities $BXB^* <=^- A$ in the minus partial
  ordering and $BXB^* <=^L A$ in the L\"owner partial ordering

abstract:
  Two matrices $A$ and $B$ of the same size are said to satisfy the minus
partial ordering, denoted by $B\leqslant^{-}A$, iff the rank subtractivity
equality ${\rm rank}(\, A - B\,) = {\rm rank}(A) -{\rm rank}(B)$ holds; two
complex Hermitian matrices $A$ and $B$ of the same size are said to satisfy the
L\"owner partial ordering, denoted by $B\leqslant^{\rm L} A$, iff the
difference $A - B$ is nonnegative definite. In this note, we establish general
solution of the inequality $BXB^{*} \leqslant^{-}A$ induced from the minus
partial ordering, and general solution of the inequality $BXB^{*}
\leqslant^{\rm L} A$ induced from the L\"owner partial ordering, respectively,
where $(\cdot)^{*}$ denotes the conjugate transpose of a complex matrix. As
consequences, we give closed-form expressions for the shorted matrices of $A$
relative to the range of $B$ in the minus and L\"owner partial orderings,
respectively, and show that these two types of shorted matrices in fact are the
same.


title:
Can an interacting varying Chaplygin gas and tachyonic matter accelerate
  Universe?

abstract:
  In this paper a possibility to accelerated the expansion of the large scale
universe due to interacting varying Chaplygin gas of a specific form and a
tachyonic matter is considered. A specific form of the potential and
appropriate values of the parameters allow to obtain early tachyonic dark
matter with $\omega_{T} \approx 0$ in recent Universe as well. On the other
hand, related to the structure of the field equations describing the dynamics
of the background we assumed the form of non-gravitational interaction to be
given in advance. A sing changeable interaction between dark energy and dark
matter is also included due to a huge interest towards it in recent literature.
Possible future finite time singularities for cansidered models have been
determined to finalize the paper. The study shows that in case of
non-interacting model, the fate of the Universe will be either Type II~(The
Sudden Singularity), or Type IV~(Generalized Sudden Singularity) singularity.
On the other hand, the consideration of $Q=3 b H \rho_{de}$ non-gravitational
interaction in addition to Type II and Type IV singularities will induce also
Type V~($\omega$-singularity) singularity. Whilst in the model with $Q=3 b q H
\rho_{de}$ non-gravitational interaction only Type IV singularity will be
observed. Moreover, $2$ forms of the scale factor has been considered
separately allowing analytically obtain the behavior of the cosmological
parameters without specifying an explicit form of the potential for tachyonic
matter.


title:
Knowledge Base Approach for 3D Objects Detection in Point Clouds Using
  3D Processing and Specialists Knowledge

abstract:
  This paper presents a knowledge-based detection of objects approach using the
OWL ontology language, the Semantic Web Rule Language, and 3D processing
built-ins aiming at combining geometrical analysis of 3D point clouds and
specialist's knowledge. Here, we share our experience regarding the creation of
3D semantic facility model out of unorganized 3D point clouds. Thus, a
knowledge-based detection approach of objects using the OWL ontology language
is presented. This knowledge is used to define SWRL detection rules. In
addition, the combination of 3D processing built-ins and topological Built-Ins
in SWRL rules allows a more flexible and intelligent detection, and the
annotation of objects contained in 3D point clouds. The created WiDOP prototype
takes a set of 3D point clouds as input, and produces as output a populated
ontology corresponding to an indexed scene visualized within VRML language. The
context of the study is the detection of railway objects materialized within
the Deutsche Bahn scene such as signals, technical cupboards, electric poles,
etc. Thus, the resulting enriched and populated ontology, that contains the
annotations of objects in the point clouds, is used to feed a GIS system or an
IFC file for architecture purposes.


title:
From 9-IM Topological Operators to Qualitative Spatial Relations using
  3D Selective Nef Complexes and Logic Rules for bodies

abstract:
  This paper presents a method to compute automatically topological relations
using SWRL rules. The calculation of these rules is based on the definition of
a Selective Nef Complexes Nef Polyhedra structure generated from standard
Polyhedron. The Selective Nef Complexes is a data model providing a set of
binary Boolean operators such as Union, Difference, Intersection and Symmetric
difference, and unary operators such as Interior, Closure and Boundary. In this
work, these operators are used to compute topological relations between objects
defined by the constraints of the 9 Intersection Model (9-IM) from Egenhofer.
With the help of these constraints, we defined a procedure to compute the
topological relations on Nef polyhedra. These topological relationships are
Disjoint, Meets, Contains, Inside, Covers, CoveredBy, Equals and Overlaps, and
defined in a top-level ontology with a specific semantic definition on relation
such as Transitive, Symmetric, Asymmetric, Functional, Reflexive, and
Irreflexive. The results of the computation of topological relationships are
stored in an OWL-DL ontology allowing after what to infer on these new
relationships between objects. In addition, logic rules based on the Semantic
Web Rule Language allows the definition of logic programs that define which
topological relationships have to be computed on which kind of objects with
specific attributes. For instance, a "Building" that overlaps a "Railway" is a
"RailStation".


title: Cosmologies of extended massive gravity

abstract:
  We study the background cosmology of two extensions of dRGT massive gravity.
The first is variable mass massive gravity, where the fixed graviton mass of
dRGT is replaced by the expectation value of a scalar field. We ask whether
self-inflation can be driven by the self-accelerated branch of this theory, and
we find that, while such solutions can exist for a short period, they cannot be
sustained for a cosmologically useful time. Furthermore, we demonstrate that
there generally exist future curvature singularities of the "big brake" form in
cosmological solutions to these theories. The second extension is the covariant
coupling of galileons to massive gravity. We find that, as in pure dRGT
gravity, flat FRW solutions do not exist. Open FRW solutions do exist -- they
consist of a branch of self-accelerating solutions that are identical to those
of dRGT, and a new second branch of solutions which do not appear in dRGT.


title: Detecting bio-markers in habitable-zone earths transiting white dwarfs

abstract:
  The characterization of the atmospheres of habitable-zone Earth-mass
exoplanets that transit across main-sequence stars, let alone the detection of
bio-markers in their atmospheres, will be challenging even with future
facilities. It has been noted that white dwarfs (WDs) have long-lived habitable
zones and that a large fraction of WDs may host planets. We point out that
during a transit of an Earth-mass planet across a WD, the planet's atmospheric
transmission spectrum obtains a much higher contrast over the stellar
background compared to a main-sequence host, because of the small surface area
of the WD. The most prominent bio-marker in the present-day terrestrial
atmosphere, molecular oxygen, is readily detectable in a WD transit via its
A-band absorption at ~0.76 micron. A potentially life-sustaining Earth-like
planet transiting a WD can be found by assembling a suitable sample of ~500 WDs
and then surveying them for transits using small telescopes. If and when such a
transiting case is found, the O_2 absorption in the planetary atmospheric
transmission spectrum would be detectable with the James Webb Space Telescope
(JWST) in about 5 hours of total exposure time, integrated over 160 2-minute
transits. Characterization of the planet atmosphere using other tracers such as
water vapour and CO_2 will be considerably easier. We demonstrate this future
discovery space by simulating a possible transmission spectrum that would be
obtained with JWST.


title: Time Dependence of Hawking Radiation Entropy

abstract:
  If a black hole starts in a pure quantum state and evaporates completely by a
unitary process, the von Neumann entropy of the Hawking radiation initially
increases and then decreases back to zero when the black hole has disappeared.
Here numerical results are given for an approximation to the time dependence of
the radiation entropy under an assumption of fast scrambling, for large
nonrotating black holes that emit essentially only photons and gravitons. The
maximum of the von Neumann entropy then occurs after about 53.81% of the
evaporation time, when the black hole has lost about 40.25% of its original
Bekenstein-Hawking (BH) entropy (an upper bound for its von Neumann entropy)
and then has a BH entropy that equals the entropy in the radiation, which is
about 59.75% of the original BH entropy 4 pi M_0^2, or about 7.509 M_0^2
\approx 6.268 x 10^{76}(M_0/M_sun)^2, using my 1976 calculations that the
photon and graviton emission process into empty space gives about 1.4847 times
the BH entropy loss of the black hole. Results are also given for black holes
in initially impure states. If the black hole starts in a maximally mixed
state, the von Neumann entropy of the Hawking radiation increases from zero up
to a maximum of about 119.51% of the original BH entropy, or about 15.018 M_0^2
\approx 1.254 x 10^{77}(M_0/M_sun)^2, and then decreases back down to 4 pi
M_0^2 = 1.049 x 10^{77}(M_0/M_sun)^2.


title: The sub-stellar birth rate from UKIDSS

abstract:
  We present a new sample of mid L to mid T dwarfs with effective temperatures
of 1100 to 1700K selected from the UKIDSS Large Area Survey and confirmed with
infrared spectra from X-Shooter/VLT. This effective temperature range is
especially sensitive to the formation history of Galactic brown dwarfs and
allows us to constrain the form of the sub-stellar birth rate, with sensitivity
to differentiate between a flat (stellar like) birth rate, and an exponentially
declining form. We present the discovery of 63 new L and T dwarfs from the
UKIDSS LAS DR7, including the identification of 12 likely unresolved binaries,
which form the first complete sub-set from our program, covering 495 sq degrees
of sky, complete to J=18.1. We compare our results for this sub-sample with
simulations of differing birth rates for objects of mass 0.10-0.03Msol and ages
1-10Gyrs. We find that the more extreme birth rates (e.g. a halo type form) can
likely be excluded as the true form of the birth rate. In addition we find that
although there is substantial scatter we find a preference for a mass function,
with a power-law index, alpha in the range -1 < alpha < 0 that is consistent
(within the errors) with the studies of late T dwarfs.


title: Tackling the soft X-ray excess in AGN with variability studies

abstract:
  The origin of the soft X-ray excess in AGN has been a mystery ever since its
discovery. We present how the time variability of this spectral component can
point towards its origin. Using the powerful technique of multi-epoch fitting,
we study how the soft excess in a given object depends on other parameters of
the continuum and the accretion disk possibly hinting at its nature. As an
example, we present results from this technique applied to the Seyfert galaxy
Mrk 841. We study all (3) XMM and some of the Suzaku pointings available and
find that the source displays an impressive variability in the soft X-ray band
on the timescale of years. We study several common soft excess models and their
ability to physically consistently explain this spectral variability. Mrk 841
is found to show a distinct variability pattern that can be best explained by
the soft excess originating mostly from a thermal Comptonization component. The
variability timescale can be constrained to be on the order of a few days.


title:
Ionized absorbers as evidence for supernova-driven cooling of the lower
  Galactic corona

abstract:
  We show that the ultraviolet absorption features, newly discovered in HST
spectra, are consistent with being formed in a layer that extends a few kpc
above the disk of the Milky Way. In this interface between the disk and the
Galactic corona, high-metallicity gas ejected from the disk by supernova
feedback can mix efficiently with the virial-temperature coronal material. The
mixing process triggers the cooling of the lower corona down to temperatures
encompassing the characteristic range of the observed absorption features,
producing a net supernova-driven gas accretion onto the disk at a rate of a few
Msun/yr. We speculate that this mechanism explains how the hot-mode of
cosmological accretion feeds star formation in galactic disks.


title:
Prediction of unexpected behavior of the mean inner potential of
  superconductors

abstract:
  Off-axis electron holography can measure the mean inner electric potential of
materials. The theory of hole superconductivity predicts that when a material
is cooled into the superconducting state it expels electrons from its interior
to the surface, giving rise to a mean inner potential that increases with
sample thickness. Instead, in a normal metal and in a conventional BCS
superconductor the mean inner potential is expected to be independent of sample
thickness and temperature. Thus, this experiment can provide a definitive test
of the validity of the theory of hole superconductivity.


title:
Measurement of the Sigma pi photoproduction line shapes near the
  Lambda(1405)

abstract:
  The reaction gamma + p -> K+ + Sigma + pi was used to determine the invariant
mass distributions or "line shapes" of the Sigma+ pi-, Sigma- pi+ and Sigma0
pi0 final states, from threshold at 1328 MeV/c^2 through the mass range of the
Lambda(1405) and the Lambda(1520). The measurements were made with the CLAS
system at Jefferson Lab using tagged real photons, for center-of-mass energies
1.95 < W < 2.85 GeV. The three mass distributions differ strongly in the
vicinity of the I=0 \Lambda(1405), indicating the presence of substantial I=1
strength in the reaction. Background contributions to the data from the
Sigma0(1385) and from K^* Sigma production were studied and shown to have
negligible influence. To separate the isospin amplitudes, Breit-Wigner model
fits were made that included channel-coupling distortions due to the NKbar
threshold. A best fit to all the data was obtained after including a
phenomenological I=1, J^P = 1/2^- amplitude with a centroid at 1394\pm20
MeV/c^2 and a second I=1 amplitude at 1413\pm10 MeV/c^2. The centroid of the
I=0 Lambda(1405) strength was found at the Sigma pi threshold, with the
observed shape determined largely by channel-coupling, leading to an apparent
overall peak near 1405 MeV/c^2.


title: The cosmological information of shear peaks: beyond the abundance

abstract:
  We study the cosmological information of weak lensing (WL) peaks, focusing on
two other statistics besides their abundance: the stacked tangential-shear
profiles and the peak-peak correlation function. We use a large ensemble of
simulated WL maps with survey specifications relevant to future missions like
Euclid and LSST, to explore the three peak probes. We find that the correlation
function of peaks with high signal-to-noise (S/N) measured from fields of size
144 sq. deg. has a maximum of ~0.3 at an angular scale ~10 arcmin. For peaks
with smaller S/N, the amplitude of the correlation function decreases, and its
maximum occurs on smaller angular scales. We compare the peak observables
measured with and without shape noise and find that for S/N~3 only ~5% of the
peaks are due to large-scale structures, the rest being generated by shape
noise. The covariance matrix of the probes is examined: the correlation
function is only weakly covariant on scales < 30 arcmin, and slightly more on
larger scales; the shear profiles are very correlated for theta > 2 arcmin,
with a correlation coefficient as high as 0.7. Using the Fisher-matrix
formalism, we compute the cosmological constraints for {Om_m, sig_8, w, n_s}
considering each probe separately, as well as in combination. We find that the
correlation function of peaks and shear profiles yield marginalized errors
which are larger by a factor of 2-4 for {Om_m, sig_8} than the errors yielded
by the peak abundance alone, while the errors for {w, n_s} are similar. By
combining the three probes, the marginalized constraints are tightened by a
factor of ~2 compared to the peak abundance alone, the least contributor to the
error reduction being the correlation function. This work therefore recommends
that future WL surveys use shear peaks beyond their abundance in order to
constrain the cosmological model.


title: Stress Tensors from Trace Anomalies in Conformal Field Theories

abstract:
  Using trace anomalies, we determine the vacuum stress tensors of arbitrary
even dimensional conformal field theories in Weyl flat backgrounds. We
demonstrate a simple relation between the Casimir energy on the real line times
a sphere and the type A anomaly coefficient. This relation generalizes earlier
results in two and four dimensions. These field theory results for the Casimir
are shown to be consistent with holographic predictions in two, four, and six
dimensions.


title:
Adaptive Interference Suppression for CDMA Systems using Interpolated
  FIR Filters with Adaptive Interpolators in Multipath Channels

abstract:
  In this work we propose an adaptive linear receiver structure based on
interpolated finite impulse response (FIR) filters with adaptive interpolators
for direct sequence code division multiple access (DS-CDMA) systems in
multipath channels. The interpolated minimum mean-squared error (MMSE) and the
interpolated constrained minimum variance (CMV) solutions are described for a
novel scheme where the interpolator is rendered time-varying in order to
mitigate multiple access interference (MAI) and multiple-path propagation
effects. Based upon the interpolated MMSE and CMV solutions we present
computationally efficient stochastic gradient (SG) and exponentially weighted
recursive least squares type (RLS) algorithms for both receiver and
interpolator filters in the supervised and blind modes of operation. A
convergence analysis of the algorithms and a discussion of the convergence
properties of the method are carried out for both modes of operation.
Simulation experiments for a downlink scenario show that the proposed
structures achieve a superior BER convergence and steady-state performance to
previously reported reduced-rank receivers at lower complexity.


title: Planar functions and perfect nonlinear monomials over finite fields

abstract:
  The study of finite projective planes involves planar functions, namely,
functions f : F_q --> F_q such that, for each nonzero a in F_q, the function c
--> f(c+a) - f(c) is a bijection on F_q. Planar functions are also used in the
construction of DES-like cryptosystems, where they are called perfect nonlinear
functions. We determine all planar functions on F_q of the form c --> c^t,
under the assumption that q >= (t-1)^4. This implies two conjectures of
Hernando, McGuire and Monserrat. Our arguments also yield a new proof of a
conjecture of Segre and Bartocci from 1971 about monomial hyperovals in finite
Desarguesian projective planes.


title:
Evolution of M82-like starburst winds revisited: 3D radiative cooling
  hydrodynamical simulations

abstract:
  In this study we present three-dimensional radiative cooling hydrodynamical
simulations of galactic winds generated particularly in M82-like starburst
galaxies. We have considered intermittent winds induced by SNe explosions
within super star clusters randomly distributed in the central region of the
galaxy and were able to reproduce the observed M82 wind conditions with its
complex morphological outflow structure. We have found that the environmental
conditions in the disk in nearly recent past are crucial to determine whether
the wind will develop a large scale rich filamentary structure, as in M82 wind,
or not. Also, the numerical evolution of the SN ejecta have allowed us to
obtain the abundance distribution over the first 3 kpc extension of the wind
and we have found that the SNe explosions change significantly the metallicity
only of the hot, low-density wind component. Moreover, we have found that the
SN-driven wind transports to outside the disk large amounts of energy, momentum
and gas, but the more massive high-density component reaches only intermediate
altitudes smaller than 1.5 kpc. Therefore, no significant amounts of gas mass
are lost to the IGM and the mass evolution of the galaxy is not much affected
by the starburst events occurring in the nuclear region.


title:
Blind Adaptive Algorithms for Decision Feedback DS-CDMA Receivers in
  Multipath Channels

abstract:
  In this work we examine blind adaptive and iterative decision feedback (DF)
receivers for direct sequence code division multiple access (DS-CDMA) systems
in frequency selective channels. Code-constrained minimum variance (CMV) and
constant modulus (CCM) design criteria for DF receivers based on constrained
optimization techniques are investigated for scenarios subject to multipath.
Computationally efficient blind adaptive stochastic gradient (SG) and recursive
least squares (RLS) algorithms are developed for estimating the parameters of
DF detectors along with successive, parallel and iterative DF structures. A
novel successive parallel arbitrated DF scheme is presented and combined with
iterative techniques for use with cascaded DF stages in order to mitigate the
deleterious effects of error propagation. Simulation results for an uplink
scenario assess the algorithms, the blind adaptive DF detectors against linear
receivers and evaluate the effects of error propagation of the new
cancellations techniques against previously reported approaches.


title:
Ergodicity and scaling limit of a constrained multivariate Hawkes
  process

abstract:
  We introduce a multivariate Hawkes process with constraints on its
conditional density. It is a multivariate point process with conditional
intensity similar to that of a multivariate Hawkes process but certain events
are forbidden with respect to boundary conditions on a multidimensional
constraint variable, whose evolution is driven by the point process. We study
this process in the special case where the fertility function is exponential so
that the process is entirely described by an underlying Markov chain, which
includes the constraint variable. Some conditions on the parameters are
established to ensure the ergodicity of the chain. Moreover, scaling limits are
derived for the integrated point process. This study is primarily motivated by
the stochastic modelling of a limit order book for high frequency financial
data analysis.


title:
Phenomenological Z_2 lattice gauge theory of the spin-liquid state of
  the kagome Heisenberg antiferromagnet

abstract:
  We construct a phenomenological Z_2 lattice gauge theory to describe the
spin-liquid state of the S=1/2 kagome Heisenberg antiferromagnet in the sector
with zero total spin. The model is a natural generalization of the
Misguich-Serban-Pasquier Hamiltonian with added interactions that are strongly
constrained by lattice symmetries. We are able to reproduce qualitatively many
of the characteristic features observed in recent numerical studies. We also
make connections to the previous works along similar lines.


title:
The Structure of the X-ray and Optical Emitting Regions of the Lensed
  Quasar Q 2237+0305

abstract:
  We use gravitational microlensing to determine the size of the X-ray and
optical emission regions of the quadruple lens system Q 2237+0305. The optical
half-light radius, log(R_{1/2,V}/cm)=16.41\pm0.18 (at lambda_{rest}=2018 \AA),
is significantly larger than the observed soft,
log(R_{1/2,soft}/cm)=15.76^{+0.41}_{-0.34} (1.1-3.5 keV in the rest frame), and
hard, log(R_{1/2,hard}/cm)=15.46^{+0.34}_{-0.29} (3.5-21.5 keV in the rest
frame), band X-ray emission. There is a weak evidence that the hard component
is more compact than the soft, with log(R_{1/2,soft}/R_{1/2,hard}) \sim
0.30^{+0.53}_{-0.45}. This wavelength-dependent structure agrees with recent
results found in other lens systems using microlensing techniques, and favors
geometries in which the corona is concentrated near the inner edge of the
accretion disk. While the available measurements are limited, the size of the
X-ray emission region appears to be roughly proportional to the mass of the
central black hole.


title: Mass segregation in the diffuse outer-halo globular cluster Palomar 14

abstract:
  We present an analysis of the radial dependence of the stellar mass function
in the diffuse outer-halo globular cluster Palomar 14. Using archival HST/WFPC2
data of the cluster's central 39 pc (corresponding to ~0.85*r_h) we find that
the mass function in the mass range of 0.55 to 0.85 solar masses is well
approximated by a power-law at all radii. The mass function steepens with
increasing radius, from a shallow power-law slope of 0.66+/-0.32 in the
cluster's centre to a slope of 1.61+/-0.33 beyond the core radius, showing that
the cluster is mass-segregated. This is seemingly in conflict with its long
present-day half-mass relaxation time of ~20 Gyr, and with the recent finding
by Beccari et al. (2011), who interpret the cluster's non-concentrated
population of blue straggler stars as evidence that dynamical segregation has
not affected the cluster yet. We discuss this apparent conflict and argue that
the cluster must have either formed with primordial mass segregation, or that
its relaxation time scale must have been much smaller in the past, i.e. that
the cluster must have undergone a significant expansion.


title:
Adaptive Space-Time Decision Feedback Neural Detectors with Data
  Selection for High-Data Rate Users in DS-CDMA Systems

abstract:
  A space-time adaptive decision feedback (DF) receiver using recurrent neural
networks (RNN) is proposed for joint equalization and interference suppression
in direct-sequence code-division-multiple-access (DS-CDMA) systems equipped
with antenna arrays. The proposed receiver structure employs dynamically driven
RNNs in the feedforward section for equalization and multi-access interference
suppression and a finite impulse response (FIR) linear filter in the feedback
section for performing interference cancellation. A data selective gradient
algorithm, based upon the set-membership design framework, is proposed for the
estimation of the coefficients of RNN structures and is applied to the
estimation of the parameters of the proposed neural receiver structure.
Simulation results show that the proposed techniques achieve significant
performance gains over existing schemes.


title:
Frustration and Packing in Curved-Filament Assemblies: From Isometric to
  Isomorphic Bundles

abstract:
  Densely-packed bundles of biological filaments (filamentous proteins) are
common and critical structural elements in range of biological materials. While
most bundles form from intrinsically straight filaments, there are notable
examples of protein filaments possessing a natural, or intrinsic, curvature,
such as the helical bacterial flagellum. We study the non-linear interplay
between thermodynamic preference for dense and regular inter-filament packing
and the mechanical preference for uniform filament shape in bundles of
helically-curved filaments. Geometric constraints in bundles make perfect
inter-filament (constant spacing, or isometric) packing incompatible with
perfect intra-filament (constant shape, or isomorphic) packing. As a
consequence, we predict that bundle packing exhibits a strong sensitivity to
bundle size, evolving from the isometric packing at small radii to an
isomorphic packing at large radii. The nature of the transition between these
extremal states depends on thermodynamic costs of packing distortion, with
packing in elastically-constrained bundles evolving smoothly with size, while
packing in osmotically-compressed bundles may exhibit a singular transition
from the isometric packing at a finite bundle radius. We consider the
equilibrium assembly of bundles in a saturated solution of filaments and show
that mechanical cost of isomorphic packing leads to self-limited equilibrium
bundle diameters, whose size and range of thermodynamic stability depend both
on condensation mechanism, as well as the helical geometry of filaments.


title:
Mass-metallicity relation from z=5 to the present: Evidence for a
  transition in the mode of galaxy growth at z=2.6 due to the end of sustained
  primordial gas infall

abstract:
  We analyze the redshift evolution of the mass-metallicity relation in a
sample of 110 Damped Ly$\alpha$ absorbers spanning the redshift range
$z=0.11-5.06$ and find that the zero-point of the correlation changes
significantly with redshift. The evolution is such that the zero-point is
constant at the early phases of galaxy growth (i.e. no evolution) but then
features a sharp break at $z=2.6\pm 0.2$ with a rapid incline towards lower
redshifts such that damped absorbers of identical masses are more metal rich at
later times than earlier. The slope of this mass metallicity correlation
evolution is $0.35 \pm 0.07$ dex per unit redshift.
  We compare this result to similar studies of the redshift evolution of
emission selected galaxy samples and find a remarkable agreement with the slope
of the evolution of galaxies of stellar mass log$(M_{*}/M_\odot) \approx 8.5$.
This allows us to form an observational tie between damped absorbers and
galaxies seen in emission.
  We use results from simulations to infer the virial mass of the dark matter
halo of a typical DLA galaxy and find a ratio $(M_{vir}/M_{*}) \approx 30$.
  We compare our results to those of several other studies that have reported
strong transition-like events at redshifts around $z=2.5-2.6$ and argue that
all those observations can be understood as the consequence of a transition
from a situation where galaxies were fed more unprocessed infalling gas than
they could easily consume to one where they suddenly become infall starved and
turn to mainly processing, or re-processing, of previously acquired gas.


title: Quantum Key Distribution with Qubit Pairs

abstract:
  We propose a new Quantum Key Distribution method in which Alice sends pairs
of qubits to Bob, each in one of four possible states. Bob uses one qubit to
generate a secure key and the other to generate an auxiliary key. For each pair
he randomly decides which qubit to use for which key. The auxiliary key has to
be added to Bob's secure key in order to match Alice's secure key. This scheme
provides an additional layer of security over the standard BB84 protocol.


title: Master Key Secured Quantum Key Distribution

abstract:
  A new scheme of Quantum Key Distribution is proposed using three entangled
particles in a GHZ state. Alice holds a 3-particle source and sends two
particles to Bob, keeping one with herself. Bob uses one particle to generate a
secure key, and the other to generate a master-key. This scheme should prove to
be harder to break in non-ideal situations as compared to the standard
protocols BB84 and Eckert. The scheme uses the concept of Quantum
Disentanglement Eraser. Extension to multi-partite scheme has also been
investigated.


title:
The role of massive stars in the turbulent infancy of Galactic globular
  clusters: Feedback on the intracluster medium, and detailed timeline

abstract:
  A major paradigm shift has recently revolutionized our picture of globular
clusters (GC) that were long thought to be simple systems of coeval stars born
out of homogeneous material. Indeed, detailed abundance studies of GC
long-lived low-mass stars performed with 8-10m class telescopes, together with
high-precision photometry of Galactic GCs obtained with HST,have brought
compelling clues on the presence of multiple stellar populations in individual
GCs. These stellar subgroups can be recognized thanks to their different
chemical properties (more precisely by abundance differences in light elements
from carbon to aluminium; see Bragaglia, this volume) and by the appearance of
multimodal sequences in the colour-magnitude diagrams (see Piotto, this
volume). This has a severe impact on our understanding of the early evolution
of GCs, and in particular of the possible role that massive stars played in
shaping the intra-cluster medium (ICM) and in inducing secondary star
formation. Here we summarize the detailed timeline we have recently proposed
for the first 40 Myrs in the lifetime of a typical GC following the general
ideas of our so-called "Fast Rotating Massive stars scenario" (FRMS, Decressin
et al. 2007b) and taking into account the dynamics of interstellar bubbles
produced by stellar winds and supernovae. More details can be found in Krause
et al. (2012, 2013).


title: Every z-linear maps is a functional p-convex

abstract:
  The main result of the paper is the following: Every $z$-linear maps is a
functional p-convex. We will prove this statement using lemma developed by
Kalton and Peck [6] and theorem developed by Aoki and Rolewicz.Based on the
definition of functional and using the tool of the triangle inequality prove
the following theorem.


title:
Gr\"obner-Shirshov Bases for Commutative Algebras with Multiple
  Operators and Free Commutative Rota-Baxter Algebras

abstract:
  In this paper, the Composition-Diamond lemma for commutative algebras with
multiple operators is established. As applications, the Gr\"obner-Shirshov
bases and linear bases of free commutative Rota-Baxter algebra, free
commutative $\lambda$-differential algebra and free commutative
$\lambda$-differential Rota-Baxter algebra are given, respectively.
Consequently, these three free algebras are constructed directly by commutative
$\Omega$-words.


title: Unsteady laminar pipe flow of a Carbopol gel. Part I: experiment

abstract:
  A experimental study of low Reynolds numbers unsteady pipe flows of a yield
stress shear thinning fluid (Carbopol- 980) is presented. The investigation of
the solid-fluid transition in a rheometric flow in the presence and in the ab-
sence of the wall slip reveals a coupling between the irreversible deformation
states and the wall slip phenomenon. Particularly, the presence of wall slip
nearly suppresses the scaling of the deformation power deficit associated to
the rheological hysteresis with the rate at which the material is forced. The
irreversible solid-fluid transition and the wall slip behaviour emerge in the
same range of the applied stresses and thus, the two phenomena appear to be
coupled to each other. In-situ measurements of the flow fields performed during
an increasing/decreasing stepped pressure ramp reveal three distinct flow
regimes: solid (pluglike), solid-fluid and fluid. The deformation power deficit
associated with the hysteresis observed during the increasing/decreasing
branches of the pressure ramps reveals a dependence on the rate at which the
unsteady flow is driven consistent with that observed during the rheological
measurements in the presence of slip. The dependence of the slip velocity on
the wall shear stresses reveals a Navier-type slip behaviour only within the
fluid flow regime, which indicates that the wall slip phenomenon is directly
coupled to the solid-fluid transition. A universal scaling of the slip velocity
with the wall velocity gradients is found and the slip length is independent on
the characteristic time of forcing t0. The paper closes with a discussion of
the main findings, their possible impact on our current understanding of the
yielding and slip behaviour of Carbopol gels. Several steps worth being pursued
by future experimental/theoretical studies are proposed.


title: Generalized cover ideals and the persistence property

abstract:
  Let $I$ be a square-free monomial ideal in $R = k[x_1,\ldots,x_n]$, and
consider the sets of associated primes ${\rm Ass}(I^s)$ for all integers $s
\geq 1$. Although it is known that the sets of associated primes of powers of
$I$ eventually stabilize, there are few results about the power at which this
stabilization occurs (known as the index of stability). We introduce a family
of square-free monomial ideals that can be associated to a finite simple graph
$G$ that generalizes the cover ideal construction. When $G$ is a tree, we
explicitly determine ${\rm Ass}(I^s)$ for all $s \geq 1$. As consequences, not
only can we compute the index of stability, we can also show that this family
of ideals has the persistence property.


title:
Light curve analysis and orbital period change of the extreme mass-ratio
  overcontact binary AW CrB

abstract:
  Extreme mass-ratio contact binaries with a high degree of overcontact may be
in the late evolutionary stages of the contact phase. Detailed photometric
analyses and orbital period studies of those systems can provide invaluable
information for the coalescence scenario of close binary systems, as recently
observed in V1309 Sco. In this paper the first light curve analysis and period
study for the totally eclipsing contact binary AW CrB is presented. The VRcIc
CCD photometric light curves are analysed by means of the WD code. The
asymmetry of the light curves is modelled by a cool star spot on the primary
component. It is shown that AW CrB has a high degree of overcontact f=75% and
an extreme mass-ratio of q=0.10, placing it among the few contact binaries with
the lowest known mass-ratios. The mean density of the primary component suggest
that it has evolved away from the ZAMS. Eighty-four times of minimum light are
reported, derived from observations available in public archives, the
literature, and the observations presented in this paper. The orbital period
study shows a continuously increasing period, at a rate of dP/dt=3.58x10^-7 d
yr^-1, suggesting a mass transfer from the secondary component to the primary
one, implying a further decreasing mass-ratio.


title:
A formalization of re-identification in terms of compatible
  probabilities

abstract:
  Re-identification algorithms are used in data privacy to measure disclosure
risk. They model the situation in which an adversary attacks a published
database by means of linking the information of this adversary with the
database.
  In this paper we formalize this type of algorithm in terms of true
probabilities and compatible belief functions. The purpose of this work is to
leave aside as re-identification algorithms those algorithms that do not
satisfy a minimum requirement.


title:
Search for contact interactions using the inclusive jet pT spectrum in
  pp collisions at sqrt(s) = 7 TeV

abstract:
  Results are reported of a search for a deviation in the jet production cross
section from the prediction of perturbative quantum chromodynamics at
next-to-leading order. The search is conducted using a 7 TeV proton-proton data
sample corresponding to an integrated luminosity of 5.0 inverse femtobarns,
collected with the Compact Muon Solenoid detector at the Large Hadron Collider.
A deviation could arise from interactions characterized by a mass scale Lambda
too high to be probed directly at the LHC. Such phenomena can be modeled as
contact interactions. No evidence of a deviation is found. Using the CLs
criterion, lower limits are set on Lambda of 9.9 TeV and 14.3 TeV at 95%
confidence level for models with destructive and constructive interference,
respectively. Limits obtained with a Bayesian method are also reported.


title: Gate-Tunable Exchange Coupling Between Cobalt Clusters on Graphene

abstract:
  We use spin-density-functional theory (SDFT) ab initio calculations to
theoretically explore the possibility of achieving useful gate control over
exchange coupling between cobalt clusters placed on a graphene sheet. By
applying an electric field across supercells we demonstrate that the exchange
interaction is strongly dependent on gate voltage, but find that it is also
sensitive to the relative sublattice registration of the cobalt clusters. We
use our results to discuss strategies for achieving strong and reproducible
magneto-electric effects in graphene/transition-metal hybrid systems.


title:
On the Evolution of the Bi-Modal Distribution of Galaxies in the Plane
  of Specific Star Formation Rate versus Stellar Mass

abstract:
  We have compared the observed distribution of galaxies in the plane of
specific star formation rate versus stellar mass with the predictions of the
Garching semi-analytic model at redshifts 0, 1 and 2. The goal is to test
whether the implementation of radio mode AGN feedback, which is responsible for
terminating the formation of stars in high mass galaxies, provides an adequate
match to current high-redshift observations. The fraction of quenched galaxies
as a function of stellar mass in the models is in good agreement with data at
z=0 and z=1. By z=2, there are too few quenched galaxies with low stellar
masses in the models. At z=2, the population of galaxies with no ongoing star
formation is clearly separated from the `main sequence' of star-forming
galaxies in the data. This is not found in the models, because z=2 galaxies
with stellar masses less than 10^11 solar masses are predicted to host black
holes with relatively low masses (less than 10^8 solar masses). The current
implementation of radio mode feedback from such black holes reduces the cooling
rates from the surrounding halo, but does not generate sufficient energy to
stop star formation entirely. We suggest that the models may be brought into
better agreement with the data if black hole growth is triggered by disc
instabilities in addition to major mergers, and if feedback mechanisms
associated with the formation of galactic bulges act to quench star formation
in galaxies.


title: The Crossover from a Bad Metal to a Frustrated Mott Insulator

abstract:
  We use a novel Monte Carlo method to study the Mott transition in an
anisotropic triangular lattice. The real space approach, retaining extended
spatial correlations, allows an accurate treatment of non trivial magnetic
fluctuations in this frustrated structure. Choosing the degree of anisotropy to
mimic the situation in the quasi-two dimensional organics,
$\kappa-$(BEDT-TTF)$_2$Cu[N(CN)$_2$]-X, we detect a wide pseudogap phase, with
anomalous spectral and transport properties, between the `ungapped' metal and
the `hard gap' Mott insulator. The magnetic fluctuations also lead to
pronounced momentum dependence of quasiparticle damping and pseudogap formation
on the Fermi surface as the Mott transition is approached. Our predictions
about the `bad metal' state have a direct bearing on the organics where they
can be tested via tunneling, angle resolved photoemission, and magnetic
structure factor measurement.


title: Thinking like Archimedes with a 3D printer

abstract:
  We illustrate Archimedes' method using models produced with 3D printers. This
approach allowed us to create physical proofs of results known to Archimedes
and illustrate ideas of a mathematician who is known both for his for his
mechanical inventions as well as his breakthroughs in geometry and calculus. We
use technology from the 21st century to trace intellectual achievements from
the 3rd century BC. While we celebrate the 2300th birthday of Archimedes
(287-212 BC) in 2013, we also live in an exciting time, where 3D printing is
becoming popular and affordable.


title: Markoff-Rosenberger triples in geometric progression

abstract:
  Solutions of the Markoff-Rosenberger equation ax^2+by^2+cz^2 = dxyz such that
their coordinates belong to the ring of integers of a number field and form a
geometric progression are studied.


title: Markoff-Rosenberger triples in arithmetic progression

abstract:
  We study the solutions of the Rosenberg--Markoff equation ax^2+by^2+cz^2 =
dxyz (a generalization of the well--known Markoff equation). We specifically
focus on looking for solutions in arithmetic progression that lie in the ring
of integers of a number field. With the help of previous work by Alvanos and
Poulakis, we give a complete decision algorithm, which allows us to prove
finiteness results concerning these particular solutions. Finally, some
extensive computations are presented regarding two particular cases: the
generalized Markoff equation x^2+y^2+z^2 = dxyz over quadratic fields and the
classic Markoff equation x^2+y^2+z^2 = 3xyz over an arbitrary number field.


title: A simple C*-algebra with finite nuclear dimension which is not Z-stable

abstract:
  We construct a simple C*-algebra with nuclear dimension zero that is not
isomorphic to its tensor product with the Jiang-Su algebra Z, and a hyperfinite
II_1 factor not isomorphic to its tensor product with the separable hyperfinite
II_1 factor R. The proofs use a weakening of the Continuum Hypothesis.


title: Enhanced supersymmetry from vanishing Euler number

abstract:
  We argue that compactifications on Calabi-Yau threefolds with vanishing Euler
number yield effective four dimensional theories exhibiting (spontaneously
broken) N=4 supersymmetry. To this end, we derive the low-energy effective
action for general SU(2) structure manifolds in type IIA string theory and show
its consistency with gauged N=4 supergravity. Focusing on the special case of
Calabi-Yau manifolds with vanishing Euler number, we explain the absence of
perturbative corrections at the two-derivative level. In addition, we
conjecture that all non-perturbative corrections are governed and constrained
by the couplings of N=4 massive gravitino multiplets.


title:
Stability estimates for the lowest eigenvalue of a Schr\"odinger
  operator

abstract:
  There is a family of potentials that minimize the lowest eigenvalue of a
Schr\"odinger eigenvalue under the constraint of a given L^p norm of the
potential. We give effective estimates for the amount by which the eigenvalue
increases when the potential is not one of these optimal potentials. Our
results are analogous to those for the isoperimetric problem and the Sobolev
inequality. We also prove a stability estimate for H\"older's inequality, which
we believe to be new.


title:
On the Distribution of MIMO Mutual Information: An In-Depth Painlev\'{e}
  Based Characterization

abstract:
  This paper builds upon our recent work which computed the moment generating
function of the MIMO mutual information exactly in terms of a Painlev\'{e} V
differential equation. By exploiting this key analytical tool, we provide an
in-depth characterization of the mutual information distribution for
sufficiently large (but finite) antenna numbers. In particular, we derive
systematic closed-form expansions for the high order cumulants. These results
yield considerable new insight, such as providing a technical explanation as to
why the well known Gaussian approximation is quite robust to large SNR for the
case of unequal antenna arrays, whilst it deviates strongly for equal antenna
arrays. In addition, by drawing upon our high order cumulant expansions, we
employ the Edgeworth expansion technique to propose a refined Gaussian
approximation which is shown to give a very accurate closed-form
characterization of the mutual information distribution, both around the mean
and for moderate deviations into the tails (where the Gaussian approximation
fails remarkably). For stronger deviations where the Edgeworth expansion
becomes unwieldy, we employ the saddle point method and asymptotic integration
tools to establish new analytical characterizations which are shown to be very
simple and accurate. Based on these results we also recover key well
established properties of the tail distribution, including the
diversity-multiplexing-tradeoff.


title:
Downlink MIMO HetNets: Modeling, Ordering Results and Performance
  Analysis

abstract:
  We develop a general downlink model for multi-antenna heterogeneous cellular
networks (HetNets), where base stations (BSs) across tiers may differ in terms
of transmit power, target signal-to-interference-ratio (SIR), deployment
density, number of transmit antennas and the type of multi-antenna
transmission. In particular, we consider and compare space division multiple
access (SDMA), single user beamforming (SU-BF), and baseline single-input
single-output (SISO) transmission. For this general model, the main
contributions are: (i) ordering results for both coverage probability and per
user rate in closed form for any BS distribution for the three considered
techniques, using novel tools from stochastic orders, (ii) upper bounds on the
coverage probability assuming a Poisson BS distribution, and (iii) a comparison
of the area spectral efficiency (ASE). The analysis concretely demonstrates,
for example, that for a given total number of transmit antennas in the network,
it is preferable to spread them across many single-antenna BSs vs. fewer
multi-antenna BSs. Another observation is that SU-BF provides higher coverage
and per user data rate than SDMA, but SDMA is in some cases better in terms of
ASE.


title:
Computing Robust Leverage Diagnostics when the Design Matrix Contains
  Coded Categorical Variables

abstract:
  For a robust leverage diagnostic in linear regression, Rousseeuw and van
Zomeren [1990] proposed using robust distance (Mahalanobis distance computed
using robust estimates of location and covariance). However, a design matrix X
that contains coded categorical predictor variables is often sufficiently
sparse that robust estimates of location and covariance cannot be computed.
Specifically, matrices formed by taking subsets of the rows of X are likely to
be singular, causing algorithms that rely on subsampling to fail. Following the
spirit of Maronna and Yohai [2000], we observe that extreme leverage points are
extreme in the continuous predictor variables. We therefore propose a robust
leverage diagnostic that combines a robust analysis of the continuous predictor
variables and the classical definition of leverage.


title: A Kine-Chemical Investigation of the AB Dor Moving Group "Stream"

abstract:
  The AB Dor Moving Group consists of a "nucleus" of ~10 stars at d ~ 20 pc,
along with dozens of purported "stream" members distributed across the sky. We
perform a chemical and kinematic analysis of a subsample of AB Dor stream stars
to test whether they constitute a physical stellar group. We use the NEMO
Galactic kinematic code to investigate the orbits of the stream members, and
perform a chemical abundance analysis using high resolution spectra taken with
the Magellan Clay 6.5-m telescope. Using a chi^2 test with the measured
abundances for 10 different elements, we find that only half of the purported
AB Dor stream members could possibly constitute a statistically chemically
homogeneous sample. Some stream members with 3D velocities were hundreds of
parsecs from the AB Dor nucleus ~10^8 yr ago, and hence were unlikely to share
a common origin. We conclude that the published lists of AB Dor moving group
stream members are unlikely to represent the dispersed remnant of a single star
formation episode. A subsample of the stream stars appears to be both
statistically chemically homogeneous and in the vicinity of the AB Dor nucleus
at birth. Their mean metallicity is [Fe/H] = 0.02 +/- 0.02 dex, which we
consider representative for the AB Dor group. Finally, we report a strong lower
limit on the age of the AB Dor nucleus of >110 Myr based on the pre-MS
contraction times for K-type members which have reached the main sequence.


title:
Experimentally efficient methods for estimating the performance of
  quantum measurements

abstract:
  Efficient methods for characterizing the performance of quantum measurements
are important in the experimental quantum sciences. Ideally, one requires both
a physically relevant distinguishability measure between measurement operations
and a well-defined experimental procedure for estimating the distinguishability
measure. Here, we propose the average measurement fidelity and error between
quantum measurements as distinguishability measures. We present protocols for
obtaining bounds on these quantities that are both estimable using
experimentally accessible quantities and scalable in the size of the quantum
system. We explain why the bounds should be valid in large generality and
illustrate the method via numerical examples.


title:
Hermite Reduction and Creative Telescoping for Hyperexponential
  Functions

abstract:
  We present a reduction algorithm that simultaneously extends Hermite's
reduction for rational functions and the Hermite-like reduction for
hyperexponential functions. It yields a unique additive decomposition and
allows to decide hyperexponential integrability. Based on this reduction
algorithm, we design a new method to compute minimal telescopers for bivariate
hyperexponential functions. One of its main features is that it can avoid the
costly computation of certificates. Its implementation outperforms Maple's
function DEtools[Zeilberger]. Moreover, we derive an order bound on minimal
telescopers, which is more general and tighter than the known one.


title: Metric approach for sound propagation in nematic liquid crystals

abstract:
  In the eikonal approach, we describe sound propagation near to topological
defects of nematic liquid crystal as geodesics of a non-euclidian manifold
endowed with an effective metric tensor. The relation between the acoustics of
the medium and this geometrical description is given by Fermat's principle. We
calculate the ray trajectories and propose a diffraction experiment to retrieve
informations about the elastic constants.


title: About possible extensions of quantum theory

abstract:
  Recently it has been claimed that no extension of quantum theory can have
improved predictive power, the statement following, according to the authors,
from the assumptions of free will and of the correctness of quantum predictions
concerning the correlations of measurement outcomes. Here we prove that the
argument is basically awed by an inappropriate use of the assumption of free
will. In particular, among other implications, the claim, if correct, would
imply that Bohmian Mechanics is incompatible with free will. This statement,
appearing in the paper, derives from the unjustified identification of free
will with the no-signaling constraint and of a purely formal and not physical
use of such a constraint.


title: Multiscale Decompositions and Optimization

abstract:
  In this paper, the following type Tikhonov regularization problem will be
systematically studied: [(u_t,v_t):=\argmin_{u+v=f} {|v|_X+t|u|_Y},] where $Y$
is a smooth space such as a $\BV$ space or a Sobolev space and $X$ is the pace
in which we measure distortion. Examples of the above problem occur in
denoising in image processing, in numerically treating inverse problems, and in
the sparse recovery problem of compressed sensing. It is also at the heart of
interpolation of linear operators by the real method of interpolation. We shall
characterize of the minimizing pair $(u_t,v_t)$ for
$(X,Y)=(L_2(\Omega),\BV(\Omega))$ as a primary example and generalize Yves
Meyer's result in [11] and Antonin Chambolle's result in [6]. After that, the
following multiscale decomposition scheme will be studied:
[u_{k+1}:=\argmin_{u\in \BV(\Omega)\cap L_2(\Omega)}
{1/2|f-u|^2_{L_2}+t_{k}|u-u_k|_{\BV}},] where $u_0=0$ and $\Omega$ is a bounded
Lipschitz domain in $\R^d$. This method was introduced by Eitan Tadmor et al.
and we will improve the $L_2$ convergence result in \cite{Tadmor}. Other pairs
such as $(X,Y)=(L_p,W^{1}(L_\tau))$ and $(X,Y)=(\ell_2,\ell_p)$ will also be
mentioned. In the end, the numerical implementation for
$(X,Y)=(L_2(\Omega),\BV(\Omega))$ and the corresponding convergence results
will be given.


title:
Massive gravity, the elasticity of space-time and perturbations in the
  dark sector

abstract:
  We consider a class of modified gravity models where the terms added to the
standard Einstein-Hilbert Lagrangian are just a function of the metric only.
For linearized perturbations around an isotropic space-time, this class of
models is entirely specified by a rank 4 tensor that encodes possibly
time-dependent masses for the gravitons. This tensor has the same symmetries as
an elasticity tensor, suggesting an interpretation of massive gravity as an
effective rigidity of space-time. If we choose a form for this tensor which is
compatible with the symmetries of FRW and enforce full reparameterization
invariance, then the only theory possible is a cosmological constant. However,
in the case where the theory is only time translation invariant, the ghost-free
massive gravity theory is equivalent to the elastic dark energy scenario with
the extra Lorentz violating vector giving rise to 2 transverse and 1
longitudinal degrees of freedom, whereas when one demands spatial translation
invariance one is left with scalar field theory with a non-standard kinetic
term.


title: Enriques moonshine

abstract:
  We propose a new moonshine phenomenon associated with the elliptic genus of
the Enriques surface (1/2 of the elliptic genus of K3) with the symmetry group
given by the Mathieu group M12.


title:
Performance Analysis of Heterogeneous Feedback Design in an OFDMA
  Downlink with Partial and Imperfect Feedback

abstract:
  Current OFDMA systems group resource blocks into subband to form the basic
feedback unit. Homogeneous feedback design with a common subband size is not
aware of the heterogeneous channel statistics among users. Under a general
correlated channel model, we demonstrate the gain of matching the subband size
to the underlying channel statistics motivating heterogeneous feedback design
with different subband sizes and feedback resources across clusters of users.
Employing the best-M partial feedback strategy, users with smaller subband size
would convey more partial feedback to match the frequency selectivity. In order
to develop an analytical framework to investigate the impact of partial
feedback and potential imperfections, we leverage the multi-cluster subband
fading model. The perfect feedback scenario is thoroughly analyzed, and the
closed form expression for the average sum rate is derived for the
heterogeneous partial feedback system. We proceed to examine the effect of
imperfections due to channel estimation error and feedback delay, which leads
to additional consideration of system outage. Two transmission strategies: the
fix rate and the variable rate, are considered for the outage analysis. We also
investigate how to adapt to the imperfections in order to maximize the average
goodput under heterogeneous partial feedback.


title: Complexity of Creative Telescoping for Bivariate Rational Functions

abstract:
  The long-term goal initiated in this work is to obtain fast algorithms and
implementations for definite integration in Almkvist and Zeilberger's framework
of (differential) creative telescoping. Our complexity-driven approach is to
obtain tight degree bounds on the various expressions involved in the method.
To make the problem more tractable, we restrict to bivariate rational
functions. By considering this constrained class of inputs, we are able to
blend the general method of creative telescoping with the well-known Hermite
reduction. We then use our new method to compute diagonals of rational power
series arising from combinatorics.


title: On the Structure of Compatible Rational Functions

abstract:
  A finite number of rational functions are compatible if they satisfy the
compatibility conditions of a first-order linear functional system involving
differential, shift and q-shift operators. We present a theorem that describes
the structure of compatible rational functions. The theorem enables us to
decompose a solution of such a system as a product of a rational function,
several symbolic powers, a hyperexponential function, a hypergeometric term,
and a q-hypergeometric term. We outline an algorithm for computing this
product, and present an application.


title:
Asymptotically Efficient Distributed Estimation With Exponential Family
  Statistics

abstract:
  The paper studies the problem of distributed parameter estimation in
multi-agent networks with exponential family observation statistics. A
certainty-equivalence type distributed estimator of the consensus + innovations
form is proposed in which, at each each observation sampling epoch agents
update their local parameter estimates by appropriately combining the data
received from their neighbors and the locally sensed new information
(innovation). Under global observability of the networked sensing model, i.e.,
the ability to distinguish between different instances of the parameter value
based on the joint observation statistics, and mean connectivity of the
inter-agent communication network, the proposed estimator is shown to yield
consistent parameter estimates at each network agent. Further, it is shown that
the distributed estimator is asymptotically efficient, in that, the asymptotic
covariances of the agent estimates coincide with that of the optimal
centralized estimator, i.e., the inverse of the centralized Fisher information
rate. From a technical viewpoint, the proposed distributed estimator leads to
non-Markovian mixed timescale stochastic recursions and the analytical methods
developed in the paper contribute to the general theory of distributed
stochastic approximation.


title: Continuous rational functions on real and $p$-adic varieties II

abstract:
  This note replaces two earlier preprints (1101.3737 by Koll\'ar) and
(1211.6681 by Nowak). It studies, and partially solves, 3 elementary questions
about continuous rational functions on real (and p-adic) algebraic varieties:
Can one restrict such a function to a subvariety? Can one extend such a
function from a subvariety? Which linear equations can be solved using such
functions? v.2: Section 3 simplified and typos corrected.


title:
Slow dynamics of spin pairs in random hyperfine field: Role of
  inequivalence of electrons and holes in organic magnetoresistance

abstract:
  In an external magnetic field B, the spins of the electron and hole will
precess in effective fields b_e + B and b_h + B, where b_e and b_h are random
hyperfine fields acting on the electron and hole, respectively. For sparse
"soft" pairs the magnitudes of these effective fields coincide. The dynamics of
precession for these pairs acquires a slow component, which leads to a slowing
down of recombination. We study the effect of soft pairs on organic
magnetoresistance, where slow recombination translates into blocking of the
passage of current. It appears that when b_e and b_h have identical gaussian
distributions the contribution of soft pairs to the current does not depend on
B. Amazingly, small inequivalence in the rms values of b_e and b_h gives rise
to a magnetic field response, and it becomes progressively stronger as the
inequivalence increases. We find the expression for this response by performing
the averaging over b_e, b_h analytically. Another source of magnetic field
response in the regime when current is dominated by soft pairs is inequivalence
of the g-factors of the pair partners. Our analytical calculation indicates
that for this mechanism the response has an opposite sign.


title: On a Fixed Point Theorem for a Cyclical Kannan-type Mapping

abstract:
  This paper deals with an extension of a recent result by the authors
generalizing Kannan's fixed point theorem based on a theorem of Vittorino Pata.
The generalization takes place via a cyclical condition.