title:
Spin and pseudospin symmetries of the Dirac equation with confining
  central potentials

abstract:
  We derive the node structure of the radial functions which are solutions of
the Dirac equation with scalar $S$ and vector $V$ confining central potentials,
in the conditions of exact spin or pseudospin symmetry, i.e., when one has
$V=\pm S+C$, where $C$ is a constant. We show that the node structure for exact
spin symmetry is the same as the one for central potentials which go to zero at
infinity but for exact pseudospin symmetry the structure is reversed. We obtain
the important result that it is possible to have positive energy bound
solutions in exact pseudospin symmetry conditions for confining potentials of
any shape, including naturally those used in hadron physics, from nuclear to
quark models. Since this does not happen for potentials going to zero at large
distances, used in nuclear relativistic mean-field potentials or in the atomic
nucleus, this shows the decisive importance of the asymptotic behavior of the
scalar and vector central potentials on the onset of pseudospin symmetry and on
the node structure of the radial functions. Finally, we show that these results
are still valid for negative energy bound solutions for anti-fermions.


title:
Efficiency for Regularization Parameter Selection in Penalized
  Likelihood Estimation of Misspecified Models

abstract:
  It has been shown that AIC-type criteria are asymptotically efficient
selectors of the tuning parameter in non-concave penalized regression methods
under the assumption that the population variance is known or that a consistent
estimator is available. We relax this assumption to prove that AIC itself is
asymptotically efficient and we study its performance in finite samples. In
classical regression, it is known that AIC tends to select overly complex
models when the dimension of the maximum candidate model is large relative to
the sample size. Simulation studies suggest that AIC suffers from the same
shortcomings when used in penalized regression. We therefore propose the use of
the classical corrected AIC (AICc) as an alternative and prove that it
maintains the desired asymptotic properties. To broaden our results, we further
prove the efficiency of AIC for penalized likelihood methods in the context of
generalized linear models with no dispersion parameter. Similar results exist
in the literature but only for a restricted set of candidate models. By
employing results from the classical literature on maximum-likelihood
estimation in misspecified models, we are able to establish this result for a
general set of candidate models. We use simulations to assess the performance
of AIC and AICc, as well as that of other selectors, in finite samples for both
SCAD-penalized and Lasso regressions and a real data example is considered.


title:
Macroscopic superpositions in Bose-Josephson junctions: Controlling
  decoherence due to atom losses

abstract:
  We study how macroscopic superpositions of coherent states produced by the
nondissipative dynamics of binary mixtures of ultracold atoms are affected by
atom losses. We identify different decoherence scenarios for symmetric or
asymmetric loss rates and interaction energies in the two modes. In the
symmetric case the quantum coherence in the superposition is lost after a
single loss event. By tuning appropriately the energies we show that the
superposition can be protected, leading to quantum correlations useful for atom
interferometry even after many loss events.


title:
X-ray diagnostics of chemical composition of the accretion disk and
  donor star in ultra-compact X-ray binaries

abstract:
  Non-solar composition of the donor star in ultra-compact X-ray binaries may
have a pronounced effect on the fluorescent lines appearing in their spectra
due to reprocessing of primary radiation by the accretion disk and the white
dwarf surface. We show that the most dramatic and easily observable consequence
of the anomalous C/O abundance, is the significant, by more than an order of
magnitude, attenuation of the Ka line of iron. It is caused by screening of the
presence of iron by oxygen - in the C/O dominated material the main interaction
process for a E ~ 7keV photon is absorption by oxygen rather than by iron,
contrary to the solar composition case. Ionization of oxygen at high mass
accretion rates adds a luminosity dependence to this behavior - the iron line
is significantly suppressed only at low luminosity, log(LX) less than 37-37.5,
and should recover its nominal strength at higher luminosity. The increase of
the EW of the Ka lines of carbon and oxygen, on the other hand, saturates at
rather moderate values. Screening by He is less important, due to its low
ionization threshold and because in the accretion disk it is mostly ionized.
Consequently, in the case of the He-rich donor, the iron line strength remains
close to its nominal value, determined by the iron abundance in the accretion
disk. This opens the possibility of constraining the nature of donor stars in
UCXBs by means of X-ray spectroscopy with moderate energy resolution.


title:
Reentrant topological phase transitions in a disordered spinless
  superconducting wire

abstract:
  In a one-dimensional spinless p-wave superconductor with coherence length
\xi, disorder induces a phase transition between a topologically nontrivial
phase and a trivial insulating phase at the critical mean free path l=\xi/2.
Here, we show that a multichannel spinless p-wave superconductor goes through
an alternation of topologically trivial and nontrivial phases upon increasing
the disorder strength, the number of phase transitions being equal to the
channel number N. The last phase transition, from a nontrivial phase into the
trivial phase, takes place at a mean free path l = \xi/(N+1), parametrically
smaller than the critical mean free path in one dimension. Our result is valid
in the limit that the wire width W is much smaller than the superconducting
coherence length \xi.


title: Rare beauty and charm decays at LHCb

abstract:
  Rare heavy flavor decays are an ideal place to search for the effects of
potential new particles that modify the decay rates or the Lorentz structure of
the decay vertices. The LHCb experiment, a dedicated heavy flavour experiment
at the LHC at CERN. It has recorded the worlds largest sample of heavy meson
and lepton decays. The status of the rare decay analyses with 1\,fb$^{-1}$ of
$\sqrt s = 7\,$TeV and 1.1\,fb$^{-1}$ of $\sqrt s = 8\,$TeV of $pp$--collisions
collected by the LHCb experiment in 2011 and 2012 is reviewed. The worlds most
precise measurements of the angular structure of $B^0\rightarrow K^{*0} \mu^+
\mu^-$ and $B^+\rightarrow K^{+} \mu^+ \mu^-$ decays is discussed, as well as
the isospin asymmetry measurement in $B\rightarrow K^{(*)} \mu^+ \mu^-}$
decays. The first evidence for the very rare decay $B^0_s \rightarrow \mu^+
\mu^-$ is presented together with the most stringent upper exclusion limits on
the branching fraction of decays of $B^0$, $D^0$ and $K^0_s$ mesons into two
muons. This note finishes with the discussion of searches for lepton number and
lepton flavor violating $\tau$ decays.


title:
pROST : A Smoothed Lp-norm Robust Online Subspace Tracking Method for
  Realtime Background Subtraction in Video

abstract:
  An increasing number of methods for background subtraction use Robust PCA to
identify sparse foreground objects. While many algorithms use the L1-norm as a
convex relaxation of the ideal sparsifying function, we approach the problem
with a smoothed Lp-norm and present pROST, a method for robust online subspace
tracking. The algorithm is based on alternating minimization on manifolds.
Implemented on a graphics processing unit it achieves realtime performance.
Experimental results on a state-of-the-art benchmark for background subtraction
on real-world video data indicate that the method succeeds at a broad variety
of background subtraction scenarios, and it outperforms competing approaches
when video quality is deteriorated by camera jitter.


title: Geometric uncertainty relation for mixed quantum states

abstract:
  In this paper we use symplectic reduction in an Uhlmann bundle to construct a
principal fiber bundle over a general space of unitarily equivalent mixed
quantum states. The bundle, which generalizes the Hopf bundle for pure states,
gives in a canonical way rise to a Riemannian metric and a symplectic structure
on the base space. With these we derive a geometric uncertainty relation for
observables acting on quantum systems in mixed states. We also give a geometric
proof of the classical Robertson-Schr\"{o}dinger uncertainty relation, and we
compare the two. They turn out not to be equivalent, because of the multiple
dimensions of the gauge group for general mixed states. We give examples of
observables for which the geometric relation provides a stronger estimate than
that of Robertson and Schr\"{o}dinger, and vice versa.


title: Matrix-valued Boltzmann equation for the non-integrable Hubbard chain

abstract:
  The standard Fermi-Hubbard chain becomes non-integrable by adding to the
nearest neighbor hopping additional longer range hopping amplitudes. We assume
that the quartic interaction is weak and investigate numerically the dynamics
of the chain on the level of the Boltzmann type kinetic equation. Only the
spatially homogeneous case is considered. We observe that the huge degeneracy
of stationary states in case of nearest neighbor hopping is lost and the
convergence to the thermal Fermi-Dirac distribution is restored. The
convergence to equilibrium is exponentially fast. However for small n.n.n.
hopping amplitudes one has a rapid relaxation towards the manifold of
quasi-stationary states and slow relaxation to the final equilibrium state.

categories: math-ph cond-mat.mes-hall math.MP physics.comp-ph


title: On measures of symmetry and floating bodies

abstract:
  We consider the following measure of symmetry of a convex n-dimensional body
K: $\rho(K)$ is the smallest constant for which there is a point x in K such
that for partitions of K by an n-1-dimensional hyperplane passing through x the
ratio of the volumes of the two parts is at most $\rho(K)$. It is well known
that $\rho(K)=1$ iff K is symmetric. We establish a precise upper bound on
$\rho(K)$; this recovers a 1960 result of Grunbaum. We also provide a
characterization of equality cases (relevant to recent results of Nill and
Paffenholz about toric varieties) and relate these questions to the concept of
convex floating bodies.


title: Motivic height zeta functions

abstract:
  Let $C$ be a projective smooth connected curve over an algebraically closed
field of characteristic zero, let $F$ be its field of functions, let $C_0$ be a
dense open subset of $C$. Let $X$ be a projective flat morphism to $C$ whose
generic fiber $X_F$ is a smooth equivariant compactification of $G$ such that
$D=X_F\setminus G_F$ is a divisor with strict normal crossings, let $U$ be a
surjective and flat model of $G$ over $C_0$. We consider a motivic height zeta
function, a formal power series with coefficients in a suitable Grothendieck
ring of varieties, which takes into account the spaces of sections $s$ of $X\to
C$ of given degree with respect to (a model of) the log-anticanonical divisor
$-K_{X_F}(D)$ such that $s(C_0)$ is contained in $U$. We prove that this power
series is rational, that its "largest pole" is at $\mathbf L^{-1}$, the inverse
of the class of the affine line in the Grothendieck ring, and compute the
"order" of this pole as a sum of dimensions of various Clemens complexes at
places of $ C\setminus C_0$. This is a geometric analogue of a result over
number fields by the first author and Yuri Tschinkel (Duke Math. J., 2012). The
proof relies on the Poisson summation formula in motivic integration,
established by Ehud Hrushovski and David Kazhdan (Moscow Math. J, 2009).


title: Sliding inverse problems for radial Dirac and Schr\"odinger equations

abstract:
  New inverse and half-inverse problems: {\it sliding problems} are introduced.
In this way several physically important equations are recovered from the
quantum defect. In particular, sliding problems are solved for radial
Schr\"odinger equation, radial Dirac system and multidimensional Schr\"odinger
equation. Systems with Coulomb-type potentials are considered as well.


title: A mixed method for Dirichlet problems with radial basis functions

abstract:
  We present a simple discretization by radial basis functions for the Poisson
equation with Dirichlet boundary condition. A Lagrangian multiplier using
piecewise polynomials is used to accommodate the boundary condition. This
simplifies previous attempts to use radial basis functions in the interior
domain to approximate the solution and on the boundary to approximate the
multiplier, which technically requires that the mesh norm in the interior
domain is significantly smaller than that on the boundary. Numerical
experiments confirm theoretical results.


title:
Classical Limit of Relativistic Quantum Mechanical Equations in the
  Foldy-Wouthuysen Representation

abstract:
  It is shown that, under the Wentzel-Kramers-Brillouin approximation
conditions, using the Foldy-Wouthuysen representation allows the problem of
finding a classical limit of relativistic quantum mechanical equations to be
reduced to the replacement of operators in the Hamiltonian and quantum
mechanical equations of motion by the respective classical quantities.


title: Propagation and spectral properties of quantum walks in electric fields

abstract:
  We study one-dimensional quantum walks in a homogeneous electric field. The
field is given by a phase which depends linearly on position and is applied
after each step. The long time propagation properties of this system, such as
revivals, ballistic expansion and Anderson localization, depend very
sensitively on the value of the electric field $\Phi$, e.g., on whether
$\Phi/(2\pi)$ is rational or irrational. We relate these properties to the
continued fraction expansion of the field. When the field is given only with
finite accuracy, the beginning of the expansion allows analogous conclusions
about the behavior on finite time scales.


title: Sequences with Minimal Time-Frequency Uncertainty

abstract:
  A central problem in signal processing and communications is to design
signals that are compact both in time and frequency. Heisenberg's uncertainty
principle states that a given function cannot be arbitrarily compact both in
time and frequency, defining an "uncertainty" lower bound. Taking the variance
as a measure of localization in time and frequency, Gaussian functions reach
this bound for continuous-time signals. For sequences, however, this is not
true; it is known that Heisenberg's bound is generally unachievable. For a
chosen frequency variance, we formulate the search for "maximally compact
sequences" as an exactly and efficiently solved convex optimization problem,
thus providing a sharp uncertainty principle for sequences. Interestingly, the
optimization formulation also reveals that maximally compact sequences are
derived from Mathieu's harmonic cosine function of order zero. We further
provide rational asymptotic expansions of this sharp uncertainty bound. We use
the derived bounds as a benchmark to compare the compactness of well-known
window functions with that of the optimal Mathieu's functions.


title: Linear and circular polarimetry observations of GRB afterglows

abstract:
  Follow-up observations of large numbers of gamma-ray burst (GRB) afterglows,
facilitated by the Swift satellite, have produced a large sample of spectral
energy distributions and light curves, from which the basic micro- and
macrophysical parameters of afterglows may be derived. However, a number of
phenomena have been observed that defy explanation by simple versions of the
standard fireball model, leading to a variety of new models. Polarimetry has
shown great promise as a diagnosis of afterglow physics, probing the magnetic
field properties of the afterglow and geometrical effects (e.g. jet breaks).
Unfortunately, high quality polarimetry of a significant sample of afterglows
is difficult to acquire, requiring specialised instrumentation and observing
modes. In this paper I will review the recent successes in late-time afterglow
polarimetry, also showing first results of new instruments and observing
campaigns. I will particularly focus on jet breaks.


title:
Einstein and Boltzmann: Determinism and Probability or The Virial
  Expansion Revisited

abstract:
  Boltzmann's Principle S = k ln W was repeatedly criticized by Einstein since
it lacked a proper dynamical foundation in view of the thermal motion of the
particles, out of which a physical system consists. This suggests, in
particular, that the statistical mechanics of a system in thermal equilibrium
should be based on dynamics. As an example, a dynamical derivation of the
density expansions of the two-particle distribution function, as well as of the
thermodynamic properties of a moderately dense gas in thermal equilibrium, is
outlined here. This is a different derivation than the usual one based on
Gibbs' probabilistic canonical ensemble, where dynamics is eliminated at the
beginning and equilibrium statistical mechanics is reduced to statics. It is
argued that the present derivation in this paper could, in principle, also be
applied to other equilibrium properties and perhaps also to other fields.


title:
Analysis of the Forward-Backward Trajectory Solution for the Mixed
  Quantum-Classical Liouville Equation

abstract:
  Mixed quantum-classical methods provide powerful algorithms for the
simulation of quantum processes in large and complex systems. The
forward-backward trajectory solution of the mixed quantum-classical Liouville
equation in the mapping basis [J. Chem. Phys. 137, 22A507 (2012)] is one such
scheme. It simulates the dynamics via the propagation of forward and backward
trajectories of quantum coherent state variables, and the propagation of bath
trajectories on a mean-field potential determined jointly by the forward and
backward trajectories. An analysis of the properties of this solution,
numerical tests of its validity and an investigation of its utility for the
study of nonadiabtic quantum processes are given. In addition, we present an
extension of this approximate solution that allows one to systematically
improve the results. This extension, termed the jump forward-backward
trajectory solution, is analyzed and tested in detail and its various
implementations are discussed.


title: Ultra-high-ohmic microstripline resistors for Coulomb blockade devices

abstract:
  In this paper, we report on the fabrication and the low-temperature
characterization of extremely high-ohmic microstrip resistors made of a thin
film of weakly oxidized titanium. Nearly linear voltage-current characteristics
were measured at temperatures down to $T \sim \unit[20]{mK}$ for films with
sheet resistivity up to as high as $\sim \unit[7]{k\Omega}$, i.e. about an
order of magnitude higher than our previous findings for weakly oxidized Cr.
Our analysis indicates that such an improvement can help to create an
advantageous high-impedance environment for different Coulomb blockade devices.
Further properties of the Ti film addressed in this work show a promise of
low-noise behavior of the resistors when applied in different realizations of
the quantum standard of current.


title: MHD modeling on geodesic grids

abstract:
  This report describes a new magnetohydrodynamic numerical model based on a
hexagonal spherical geodesic grid. The model is designed to simulate
astrophysical flows of partially ionized plasmas around a central compact
object, such as a star or a planet with a magnetic field. The geodesic grid,
produced by a recursive subdivision of a base platonic solid (an icosahedron),
is free from control volume singularities inherent in spherical polar grids.
Multiple populations of plasma and neutral particles, coupled via
charge-exchange interactions, can be simulated simultaneously with this model.
Our numerical scheme uses piecewise linear reconstruction on a surface of a
sphere in a local two-dimensional "Cartesian" frame. The code employs HLL-type
approximate Riemann solvers and includes facilities to control the divergence
of magnetic field and maintain pressure positivity. Several test solutions are
discussed, including a problem of an interaction between the solar wind and the
local interstellar medium, and a simulation of Earth's magnetosphere.


title:
Spin-dependent observables and the D_2 parameter in breakup of deuteron
  and 3He

abstract:
  We analyze the momentum distributions of constituents in 3He, as well as the
spin-dependent observables for (3He,d), (3He,p), and (d,p) breakup reactions.
Special attention is paid to the region of small relative momenta of the
helium-3 and the deuteron constituents, where a single parameter, D_2, has
determining role for the spin-dependent observables. We extract also this
parameter for the deuteron, basing on existing data for the tensor analyzing
power of this reaction.


title:
Properties of trapped neutrons interacting with realistic nuclear
  Hamiltonians

abstract:
  We calculate properties of neutron drops in external potentials using both
quantum Monte Carlo and no-core full configuration techniques. The properties
of the external wells are varied to examine different density profiles. We
compare neutron drop results given by a selection of nuclear Hamiltonians,
including realistic two-body interactions as well as several three-body forces.
We compute a range of properties for the neutron drops: ground-state energies,
spin-orbit splittings, excitation energies, radial densities and rms radii. We
compare the equations of state for neutron matter for several of these
Hamiltonians. Our results can be used as benchmarks to test other many-body
techniques, and to constrain properties of energy-density functionals.


title: On the physical meaning of the 2.1 keV absorption feature in 4U 1538-52

abstract:
  The improvement of the capabilities of nowadays X-ray observatories, like
Chandra or XMM-Newton, offers the possibility to detect both absorption and
emission lines and to study the nature of the matter surrounding the neutron
star in X-ray binaries and the phenomena that produce these lines. The aim of
this work is to discuss the different physical scenarios in order to explain
the meaning of the significant absorption feature present in the X-ray spectrum
of 4U 1538-52. Using the last available calibrations, we discard the
possibility that this feature is due to calibration, gain effects or be
produced by the X-ray background or a dust region. Giving the energy resolution
of the XMM-Newton telescope we could not establish if the line is formed in the
atmosphere of the neutron star or by the dispersion of the stellar wind of the
optical counterpart.


title:
The high-pressure high-temperature phase diagram of calcium fluoride
  from classical atomistic simulations

abstract:
  We study the phase diagram of calcium fluoride (CaF2) under pressure using
classical molecular dynamic simulations performed with a simple pairwise
interatomic potential of the Born-Mayer-Huggings form. Our results obtained
under conditions 0 < P < 20 GPa and 0 < T < 4000 K reveal a rich variety of
multi-phase boundaries involving different crystal, superionic and liquid
phases, for all which we provide an accurate parametrization. Interestingly, we
predict the existence of three special triple points (i.e.
solid-solid-superionic, solid-superionic-superionic and
superionic-superionic-liquid coexisting states) within a narrow and
experimentally accessible thermodynamic range of 6 < P < 8 GPa and 1500 < T <
2750 K. Also, we examine the role of short-ranged repulsive (SR) and
long-ranged attractive (LA) atomic interactions in the prediction of melting
lines with the finding that SR Ca-F and LA F-F contributions are most decisive.


title:
Polarization Effects in Two-Photon Free-Free Transitions in
  Laser-Assisted Electron-Hydrogen Collisions

abstract:
  Two-photon free-free transitions in elastic laser-assisted electron-hydrogen
collisions are studied in the domain of high scattering energies and low or
moderate field intensities, in the third order of perturbation theory, taking
into account all the involved Feynman diagrams. Based on the analytical
expressions of the transition amplitudes, the differential cross sections for
two-photon absorption/emission are computed at impact energy $E_i=100$ eV. The
effect of field polarizations on the angular distribution and on the frequency
dependence of the differential cross section is analyzed.


title:
A distributed accelerated gradient algorithm for distributed model
  predictive control of a hydro power valley

abstract:
  A distributed model predictive control (DMPC) approach based on distributed
optimization is applied to the power reference tracking problem of a hydro
power valley (HPV) system. The applied optimization algorithm is based on
accelerated gradient methods and achieves a convergence rate of O(1/k^2), where
k is the iteration number. Major challenges in the control of the HPV include a
nonlinear and large-scale model, nonsmoothness in the power-production
functions, and a globally coupled cost function that prevents distributed
schemes to be applied directly. We propose a linearization and approximation
approach that accommodates the proposed the DMPC framework and provides very
similar performance compared to a centralized solution in simulations. The
provided numerical studies also suggest that for the sparsely interconnected
system at hand, the distributed algorithm we propose is faster than a
centralized state-of-the-art solver such as CPLEX.


title: Electric quantum walks with individual atoms

abstract:
  We report on the experimental realization of electric quantum walks, which
mimic the effect of an electric field on a charged particle in a lattice.
Starting from a textbook implementation of discrete-time quantum walks, we
introduce an extra operation in each step to implement the effect of the field.
The recorded dynamics of such a quantum particle exhibits features closely
related to Bloch oscillations and interband tunneling. In particular, we
explore the regime of strong fields, demonstrating contrasting quantum
behaviors: quantum resonances vs. dynamical localization depending on whether
the accumulated Bloch phase is a rational or irrational fraction of 2\pi.


title: Spinon and eta-spinon correlation functions

abstract:
  We calculate real-space static correlation functions related to basic
entities of the one-dimensional Hubbard model, which emerge from the exact
Bethe-ansatz solution. These entities involve complex rearrangements of the
original electrons. Basic ingredients are operators related to unoccupied,
singly occupied with spin up or spin down and doubly occupied sites. The
spatial decay of their correlation functions is determined using an approximate
mean-field-like approach based on the Zou-Anderson transformation and DMRG
results for the half-filled case. The nature and spatial extent of the
correlations between two sites on the Hubbard chain is studied using the
eigenstates and eigenvalues of the two-site reduced density matrix.


title:
Electrical transport across Au/Nb:SrTiO3 Schottky interface with
  different Nb doping

abstract:
  We have investigated electron transport in Nb doped SrTiO$_3$ single crystals
for two doping densities. We find that the resistivity and mobility are
temperature dependent in both whereas the carrier concentration is almost
temperature invariant. We rationalize this using the hydrogenic theory for
shallow donors. Further, we probe electrical transport across Schottky
interfaces of Au on TiO$_2$ terminated n-type SrTiO$_3$. Quantitative analysis
of macroscopic I-V measurements reveal thermionic emission dominated transport
for the low doped substrate whereas it deviates from such behavior for the high
doped substrate. This work is relevant for designing devices to study
electronic transport using oxide-semiconductors.


title: Flow-Induced Draping

abstract:
  Crumpled paper or drapery patterns are everyday examples of how elastic
sheets can respond to external forcing. In this Letter, we study experimentally
a novel sort of forcing. We consider a circular flexible plate clamped at its
center and subject to a uniform flow normal to its initial surface. As the flow
velocity is gradually increased, the plate exhibits a rich variety of bending
deformations: from a cylindrical taco-like shape, to isometric developable
cones with azimuthal periodicity two or three, to eventually a rolled-up
period-three cone. We show that this sequence of flow-induced deformations can
be qualitatively predicted by a linear analysis based on the balance between
elastic energy and pressure force work.


title: Summary of Physics Results from the TOTEM Experiment

abstract:
  The TOTEM experiment has performed several measurements related to its
physics program in dedicated (high \beta*, low L) LHC fills at $\sqrt{s}$ = 7
TeV. Under various beam and background conditions, the differential elastic (as
a function of |t|), elastic, inelastic and total pp cross-sections have been
measured. A measurement of the forward charged particle \eta density has also
been performed. A summary of these measurements is here reported, as well as
the first results from runs at the LHC energy of $\sqrt{s}$ = 8 TeV.


title:
Vibrationally Excited HCN around AFGL 2591: A Probe of Protostellar
  Structure

abstract:
  Vibrationally excited molecules with sub-mm rotational transitions are
potentially excellent probes of physical conditions near protostars. This study
uses observations of the v=1 and v=2 ro-vibrational modes of HCN (4-3) to probe
this environment. The presence or absence and relative strengths of these
ro-vibrational lines probe the gas excitation mechanism and physical conditions
in warm, dense material associated with protostellar disks. We present pilot
observations from the Heinrich Hertz Submillimeter Telescope (HHSMT) and
followup observations from the Submillimeter Array (SMA). All vibrationally
excited HCN (4-3) v=0, v=1, and v=2 lines were observed. The existence of the
three v=2 lines at approximately equal intensity imply collisional excitation
with a density of greater than (10^10 cm^-3) and a temperature of >1000 K for
the emitting gas. This warm, high density material should directly trace
structures formed in the protostellar envelope and disk environment. Further,
the line shapes of the v=2 emission may suggest a Keplerian disk. This letter
demonstrates the utility of this technique which is of particular interest due
to the recent inauguration of the Atacama Large Millimeter Array (ALMA).


title: Short note on the convolution of binomial coefficients

abstract:
  We know [Rui Duarte and Ant\'onio Guedes de Oliveira, New developments of an
old identity, manuscript arXiv:1203.5424, submitted.] that, for every
non-negative integer numbers $n,i,j$ and for every real number $\ell$, $$
\sum_{i+j=n} \binom{2i-\ell}{i} \binom{2j+\ell}{j} = \sum_{i+j=n}\binom{2i}{i}
\binom{2j}{j}, $$ which is well-known to be $4^n$. We extend this result by
proving that, indeed, $$ \sum_{i+j=n} \binom{ai+k-\ell}{i} \binom{aj+\ell}{j} =
\sum_{i+j=n} \binom{ai+k}{i} \binom{aj}{j} $$ for every integer $a$ and for
every real $k$, and present new expressions for this value.


title: Total wave based fast direct solver for volume scattering problems

abstract:
  We present a fast direct solver for the volume scattering problem of the
Helmholtz equation. The algorithm is faster than existing methods. Moreover,
discretization for our method is much simpler and more accurate than that for
finite difference, finite elements, and integral equations.


title: Estimating Common Principal Components in High Dimensions

abstract:
  We consider the problem of minimizing an objective function that depends on
an orthonormal matrix. This situation is encountered when looking for common
principal components, for example, and the Flury method is a popular approach.
However, the Flury method is not effective for higher dimensional problems. We
obtain several simple majorization-minizmation (MM) algorithms that provide
solutions to this problem and are effective in higher dimensions. We then use
simulated data to compare them with other approaches in terms of convergence
and computational time.


title: The Orlik-Solomon model for hypersurface arrangements

abstract:
  We develop a model for the cohomology of the complement of a hypersurface
arrangement inside a smooth projective complex variety. This generalizes the
case of normal crossing divisors, discovered by P. Deligne in the context of
the mixed Hodge theory of smooth complex varieties. Our model is a global
version of the Orlik-Solomon algebra, which computes the cohomology of the
complement of a union of hyperplanes in an affine space. The main tool is the
complex of logarithmic forms along a hypersurface arrangement, and its weight
filtration. Connections with wonderful compactifications and the configuration
spaces of points on curves are also studied.


title:
Construction of exact travelling waves for the Benjamin-Bona-Mahony
  equation on networks

abstract:
  We are interested in the existence of travelling waves for the
Benjamin-Bona-Mahony equation on a network. First we construct an explicit
wave, defined in $\mathbb{R}$. Then, we use this wave to derive some conditions
on the coefficients appearing in the equations and on the geometry of the
network to ensure the existence of travelling waves on the network.


title: An alternative IIB embedding of F(4) gauged supergravity

abstract:
  Through the construction of a complete non-linear Kaluza-Klein reduction
ansatz from type IIB supergravity to Romans' F(4) gauged supergravity, we
identify a recently discovered supersymmetric AdS_6 solution as the IIB uplift
of the supersymmetric vacuum of Romans' theory. We present new IIB uplifts of a
number of known solutions of Romans' theory and comment on supersymmetry in
higher-dimensions where it is expected.


title:
Calculation of the connective constant for self-avoiding walks via the
  pivot algorithm

abstract:
  We calculate the connective constant for self-avoiding walks on the simple
cubic lattice to unprecedented accuracy, using a novel application of the pivot
algorithm. We estimate that \mu = 4.684 039 931(27). Our method also provides
accurate estimates of the number of self-avoiding walks, even for walks with
millions of steps.

categories: cond-mat.stat-mech math-ph math.CO math.MP


title:
Impact of sequential disorder on the scaling behavior of airplane
  boarding time

abstract:
  Airplane boarding process is an example where disorder properties of the
system are relevant to the emergence of universality classes. Based on a simple
model, we present a systematic analysis of finite-size effects in boarding
time, and propose a comprehensive view of the role of sequential disorder in
the scaling behavior of boarding time against the plane size. Using numerical
simulations and mathematical arguments, we find how the scaling behavior
depends on the number of seat columns and the range of sequential disorder. Our
results show that new scaling exponents can arise as disorder is localized to
varying extents.


title:
Gutzwiller Variational Method for Intersite Coulomb Interactions: The
  Spinless Fermion Model in One Dimension

abstract:
  We study the Gutzwiller method for the spinless fermion model in one
dimension, which is one of the simplest models that incorporates the intersite
Coulomb interaction. The Gutzwiller solution of this model has been studied in
the literature but with differing results. We obtain the Gutzwiller solution of
the problem by a careful enumeration of the many-particle configurations and
explain the origin of the discrepancy in the literature to be due to the
neglect of the correlation between the neighbouring bond occupancies. The
correct implementation of the Gutzwiller approach yields results different from
the slave-boson mean-field theory, unlike for the Hubbard model with on-site
interaction, where both methods are known to be equivalent. The slave-boson and
the Gutzwiller results are compared to the exact solution, available for the
half-filled case, and to the numerical exact diagonalization results for the
case of general filling.


title:
On the Damping-Induced Self-Recovery Phenomenon in Mechanical Systems
  with Several Unactuated Cyclic Variables

abstract:
  The damping-induced self-recovery phenomenon refers to the fundamental
property of underactuated mechanical systems: if an unactuated cyclic variable
is under a viscous damping-like force and the system starts from rest, then the
cyclic variable will always move back to its initial condition as the actuated
variables come to stop. The regular momentum conservation phenomenon can be
viewed as the limit of the damping-induced self-recovery phenomenon in the
sense that the self-recovery phenomenon disappears as the damping goes to zero.
This paper generalizes the past result on damping-induced self-recovery for the
case of a single unactuated cyclic variable to the case of multiple unactuated
cyclic variables. We characterize a class of external forces that induce new
conserved quantities, which we call the damping-induced momenta. The
damping-induced momenta yield first-order asymptotically stable dynamics for
the unactuated cyclic variables under some conditions, thereby inducing the
self-recovery phenomenon. It is also shown that the viscous damping-like forces
impose bounds on the range of trajectories of the unactuated cyclic variables.
Two examples are presented to demonstrate the analytical discoveries: the
planar pendulum with gimbal actuators and the three-link planar manipulator on
a horizontal plane.

categories: math.DS math-ph math.MP math.OC physics.class-ph


title: Metal nanoparticle field-effect transistor

abstract:
  We demonstrate that by means of a local top-gate current oscillations can be
observed in extended, monolayered films assembled from monodisperse metal
nanocrystals -- realizing transistor function. The oscillations in this
metal-based system are due to the occurrence of a Coulomb energy gap in the
nanocrystals which is tunable via the nanocrystal size. The nanocrystal
assembly by the Langmuir-Blodgett method yields homogeneous monolayered films
over vast areas. The dielectric oxide layer protects the metal nanocrystal
field-effect transistors from oxidation and leads to stable function for
months. The transistor function can be reached due to the high monodispersity
of the nanocrystals and the high super-crystallinity of the assembled films.
Due to the fact that the film consists of only one monolayer of nanocrystals
and all nanocrystals are simultaneously in the state of Coulomb blockade the
energy levels can be influenced efficiently (limited screening).


title: X-ray Irradiation of the LkCa 15 Protoplanetary Disk

abstract:
  LkCa 15 in the Taurus star-forming region has recently gained attention as
the first accreting T Tauri star likely to host a young protoplanet. High
spatial resolution infrared observations have detected the suspected
protoplanet within a dust-depleted inner gap of the LkCa 15 transition disk at
a distance of 15 AU from the star. If this object's status as a protoplanet is
confirmed, LkCa 15 will serve as a unique laboratory for constraining physical
conditions within a planet-forming disk. Previous models of the LkCa 15 disk
have accounted for disk heating by the stellar photosphere but have ignored the
potential importance of X-ray ionization and heating. We report here the
detection of LkCa 15 as a bright X-ray source with Chandra. The X-ray emission
is characterized by a cool heavily-absorbed plasma component at kT_cool ~0.3
keV and a harder component at kT_hot ~5 keV. We use the observed X-ray
properties to provide initial estimates of the X-ray ionization and heating
rates within the tenuous inner disk. These estimates and the observed X-ray
properties of LkCa 15 can be used as a starting point for developing more
realistic disk models of this benchmark system.


title: Cryptanalysis and Improvement of Akleylek et al.'s cryptosystem

abstract:
  Akleylek et al. [S. Akleylek, L. Emmungil and U. Nuriyev, A mod ified
algorithm for peer-to-peer security, journal of Appl. Comput. Math., vol. 6(2),
pp.258-264, 2007.], introduced a modified public-key encryption scheme with
steganographic approach for security in peer-to-peer (P2P) networks. In this
cryptosystem, Akleylek et al. attempt to increase security of the P2P networks
by mixing ElGamal cryptosystem with knapsack problem. In this paper, we present
a ciphertext-only attack against their system to recover message. In addition,
we show that for their scheme completeness property is not holds, and
therefore, the receiver cannot uniquely decrypts messages. Furthermore, we also
show that this system is not chosen-ciphertext secure, thus the proposed scheme
is vulnerable to man-in-the-middle-attack, one of the most pernicious attacks
against P2P networks. Therefore, this scheme is not suitable to implement in
the P2P networks.
  We modify this cryptosystem in order to increase its security and efficiency.
Our construction is the efficient CCA2-secure variant of the Akleylek et al.'s
encryption scheme in the standard model, the de facto security notion for
public-key encryption schemes.


title:
Signatures of Majorana Fermions in Topological Insulator Josephson
  Junction Devices

abstract:
  We study theoretically the electrical current and low-frequency noise for a
linear Josephson junction structure on a topological insulator, in which the
superconductor forms a closed ring and currents are injected from normal
regions inside and outside the ring. We find that this geometry offers a
signature for the presence of gapless 1D Majorana fermion modes that are
predicted in the channel when the phase difference \phi, controlled by the
magnetic flux through the ring, is \pi. We show that for low temperature the
linear conductance jumps when \phi\ passes through \pi, accompanied by
non-local correlations between the currents from the inside and outside of the
ring. We compute the dependence of these features on temperature, voltage and
linear dimensions, and discuss the implications for experiments.


title:
Long-term variability of extragalactic radio sources in the Planck Early
  Release Compact Source Catalogue

abstract:
  Combining measurements taken using the Wilkinson Microwave Anisotropy Probe
(WMAP) from 2001 to 2008 with measurements taken using Planck from 2009 to
2010, we investigate the long-term flux density variability of extragalactic
radio sources selected from the Planck Early Release Compact Source Catalogue.
The single-year, single-frequency WMAP maps are used to estimate
yearly-averaged flux densities of the sources in the four WMAP bands: Ka (33
GHz), Q (41 GHz), V (61 GHz), and W (94 GHz). We identify 82, 67, 32, and 15
sources respectively as variable at greater than 99% confidence level in these
four bands. The amplitudes of variation are comparable between bands, and are
not correlated with either the flux densities or the spectral indices of the
sources. The number counts of WMAP Ka-band sources are stable from year to year
despite the fluctuation caused by individual source variability. Most of our
sources show strong correlation in variability between bands. Almost all the
sources that show variability are blazars. We have attempted to fit two simple,
four-parameter models to the time-series of 32 sources showing correlated
variability at multiple frequencies - a long-term flaring model and a
rotating-jet model. We find that 19 sources (60%) can be fit with the simple
rotating-jet model, and ten of these also fit the simple long-term flaring
model. The remaining 13 sources (40%) show more complex variability behaviour
that is not consistent with either model. Extended radio galaxies in our sample
show no sign of variability, as expected, with the exception of Pictor A for
which we report evidence for a millimetre flare lasting between 2002 and 2010.


title: On the structure of some modules over generalized soluble groups

abstract:
  Let R be a ring and G a group. An R-module A is said to be
artinian-by-(finite rank) if TorR(A) is artinian and A/TorR(A) has finite
R-rank. The authors study ZG-modules A such that A/CA(H) is artinian-by-(finite
rank) (as a Z-module) for every proper subgroup H.


title: Exchangeable random measures

abstract:
  Let A be a standard Borel space, and consider the space A^{\bbN^{(k)}} of
A-valued arrays indexed by all size-k subsets of \bbN. This paper concerns
random measures on such a space whose laws are invariant under the natural
action of permutations of \bbN. The main result is a representation theorem for
such `exchangeable' random measures, obtained using the classical
representation theorems for exchangeable arrays due to de Finetti, Hoover,
Aldous and Kallenberg.
  After proving this representation, two applications of exchangeable random
measures are given. The first is a short new proof of the Dovbysh-Sudakov
Representation Theorem for exchangeable PSD matrices. The second is in the
formulation of a natural class of limit objects for dilute mean-field spin
glass models, retaining more information than just the limiting Gram-de Finetti
matrix used in the study of the Sherrington-Kirkpatrick model.


title: Photoinduced inverse spin Hall effect in Pt/Ge(001) at room temperature

abstract:
  We performed photoinduced inverse spin Hall effect (ISHE) measurements on a
Pt/Ge(001) junction at room temperature. The spin-oriented electrons,
photogenerated at the direct gap of Ge using circularly polarized light,
provide a net spin current which yields an electromotive field E_ISHE in the Pt
layer. Such a signal is clearly detected at room temperature despite the strong
{\Gamma} to L scattering which electrons undergo in the Ge conduction band. The
ISHE signal dependence on the exciting photon energy is in good agreement with
the electron spin polarization expected for optical orientation at the direct
gap of Ge.


title: Hyperquarks and generation number

abstract:
  In a model in which quarks and leptons are built up from two spin 1/2 preons
as fundamental entities, a new class of fermionic bound states (hyperquarks)
arises. It turns out that these hyperquarks are necessary to fulfill the 't
Hooft anomaly constraint, which then links the number of fermionic generations
to the number of colors and hypercolors.


title:
Three-point functions of semiclassical string states and conserved
  currents in AdS_4 x CP^3

abstract:
  In this paper we study the three-point correlation functions of two scalar
operators with large conformal dimensions and the R-current or stress-energy
tensor at strong coupling with the help of the AdS_4/CFT_3 correspondence. The
scalar operators are dual to semiclassical strings in AdS_4 x CP^3, which are
point-like in AdS. We establish thorough concordance between string theory
results at large coupling constant and general predictions coming from Ward
identities in the dual three-dimensional superconformal gauge theory.


title:
Continued fraction analysis of dressed systems: application to
  periodically driven optical lattices

abstract:
  Radio-frequency quantum engineering of spins is based on the dressing by a
non resonant electromagnetic field. Radio-frequency dressing occurs also for
the motion of particles, electrons or ultracold atoms, within a periodic
spatial potential. The dressing, producing a renormalisation and also a freeze
of the system energy, is described by different approaches, dressed atom,
magnetic resonance semiclassical treatment, continued fraction solution of the
Schr\"odinger equation. A comparison between those solutions points out that
the semiclassical treatment, to be denoted as the $S$-solution, represents the
most convenient tool to evaluate the tunneling renormalization of ultracold
atoms.


title: Spin dynamics of cold fermions with synthetic spin-orbit coupling

abstract:
  We consider spin relaxation dynamics in cold Fermi gases with a pure-gauge
spin-orbit coupling corresponding to recent experiments. We show that such
experiments can give a direct access to the collisional spin drag rate, and
establish conditions for the observation of spin drag effects. In the recent
experiments the dynamics is found to be mainly ballistic leading to new regimes
of reversible spin relaxation-like processes.


title: From Mobius to Gyrogroups

abstract:
  The evolution from Mobius to gyrogroups began in 1988, and is still ongoing
in [14, 15]. Gyrogroups, a natural generalization of groups, lay a fruitful
bridge between nonassociative algebra and hyperbolic geometry, just as groups
lay a fruitful bridge between associative algebra and Euclidean geometry. More
than 150 years have passed since the German mathematician August Ferdinand
Mobius first studied the transformations that now bear his name. Yet, the rich
structure he thereby exposed is still far from being exhausted, as the
evolution from Mobius to gyrogroups demonstrates.


title: Belief Semantics of Authorization Logic

abstract:
  Authorization logics have been used in the theory of computer security to
reason about access control decisions. In this work, a formal belief semantics
for authorization logics is given. The belief semantics is proved to subsume a
standard Kripke semantics. The belief semantics yields a direct representation
of principals' beliefs, without resorting to the technical machinery used in
Kripke semantics. A proof system is given for the logic; that system is proved
sound with respect to the belief and Kripke semantics. The soundness proof for
the belief semantics, and for a variant of the Kripke semantics, is mechanized
in Coq.


title: Tunable All Electric Spin Polarizer

abstract:
  We propose a new device to create a tunable all-electric spin polarizer: a
quantum point contact (QPC) with four gates -- two in-plane side gates in
series. The first pair of gates, near the source, is asymmetrically biased to
create spin polarization in the QPC channel. The second set of gates, near the
drain, is symmetrically biased and that bias is varied to maximize the amount
of spin polarization in the channel. The range of common mode bias on the first
set of gates over which maximum spin polarization can be achieved is much
broader for the four gate structure compared with the case of a single pair of
in-plane side gates.


title: Chiral Plasma Instabilities

abstract:
  We study the collective modes in relativistic electromagnetic or quark-gluon
plasmas with an asymmetry between left- and right-handed chiral fermions, based
on the recently formulated kinetic theory with Berry curvature corrections. We
find that there exists an unstable mode, signaling the presence of a plasma
instability. We argue the fate of this "chiral plasma instability" including
the effect of collisions, and briefly discuss its relevance in heavy ion
collisions and compact stars.


title:
Nonparametric Estimation of Means on Hilbert Manifolds and Extrinsic
  Analysis of Mean Shapes of Contours

abstract:
  Motivated by the problem of nonparametric inference in high level digital
image analysis, we introduce a general extrinsic approach for data analysis on
Hilbert manifolds with a focus on means of probability distributions on such
sample spaces. To perform inference on these means, we appeal to the concept of
neighborhood hypotheses from functional data analysis and derive a one-sample
test. We then consider analysis of shapes of contours lying in the plane. By
embedding the corresponding sample space of such shapes, which is a Hilbert
manifold, into a space of Hilbert-Schmidt operators, we can define extrinsic
mean shapes of planar contours and their sample analogues. We apply the general
methods to this problem while considering the computational restrictions faced
when utilizing digital imaging data. Comparisons of computational cost are
provided to another method for analyzing shapes of contours.


title:
An LMP O(log n)-Approximation Algorithm for Node Weighted Prize
  Collecting Steiner Tree

abstract:
  In the node-weighted prize-collecting Steiner tree problem (NW-PCST) we are
given an undirected graph $G=(V,E)$, non-negative costs $c(v)$ and penalties
$\pi(v)$ for each $v \in V$. The goal is to find a tree $T$ that minimizes the
total cost of the vertices spanned by $T$ plus the total penalty of vertices
not in $T$. This problem is well-known to be set-cover hard to approximate.
Moss and Rabani (STOC'01) presented a primal-dual
Lagrangean-multiplier-preserving $O(\ln |V|)$-approximation algorithm for this
problem. We show a serious problem with the algorithm, and present a new,
fundamentally different primal-dual method achieving the same performance
guarantee. Our algorithm introduces several novel features to the primal-dual
method that may be of independent interest.


title: Modulus Computational Entropy

abstract:
  The so-called {\em leakage-chain rule} is a very important tool used in many
security proofs. It gives an upper bound on the entropy loss of a random
variable $X$ in case the adversary who having already learned some random
variables $Z_{1},\ldots,Z_{\ell}$ correlated with $X$, obtains some further
information $Z_{\ell+1}$ about $X$. Analogously to the information-theoretic
case, one might expect that also for the \emph{computational} variants of
entropy the loss depends only on the actual leakage, i.e. on $Z_{\ell+1}$.
Surprisingly, Krenn et al.\ have shown recently that for the most commonly used
definitions of computational entropy this holds only if the computational
quality of the entropy deteriorates exponentially in
$|(Z_{1},\ldots,Z_{\ell})|$. This means that the current standard definitions
of computational entropy do not allow to fully capture leakage that occurred
"in the past", which severely limits the applicability of this notion.
  As a remedy for this problem we propose a slightly stronger definition of the
computational entropy, which we call the \emph{modulus computational entropy},
and use it as a technical tool that allows us to prove a desired chain rule
that depends only on the actual leakage and not on its history. Moreover, we
show that the modulus computational entropy unifies other,sometimes seemingly
unrelated, notions already studied in the literature in the context of
information leakage and chain rules. Our results indicate that the modulus
entropy is, up to now, the weakest restriction that guarantees that the chain
rule for the computational entropy works. As an example of application we
demonstrate a few interesting cases where our restricted definition is
fulfilled and the chain rule holds.


title:
Non-Asymptotic Analysis of an Optimal Algorithm for Network-Constrained
  Averaging with Noisy Links

abstract:
  The problem of network-constrained averaging is to compute the average of a
set of values distributed throughout a graph G using an algorithm that can pass
messages only along graph edges. We study this problem in the noisy setting, in
which the communication along each link is modeled by an additive white
Gaussian noise channel. We propose a two-phase decentralized algorithm, and we
use stochastic approximation methods in conjunction with the spectral graph
theory to provide concrete (non-asymptotic) bounds on the mean-squared error.
Having found such bounds, we analyze how the number of iterations T_G(n;
\delta) required to achieve mean-squared error \delta\ scales as a function of
the graph topology and the number of nodes n. Previous work provided guarantees
with the number of iterations scaling inversely with the second smallest
eigenvalue of the Laplacian. This paper gives an algorithm that reduces this
graph dependence to the graph diameter, which is the best scaling possible.


title:
Constraints from de Sitter metastability in heterotic string
  compactifications

abstract:
  We study the possibility of obtaining metastable de Sitter vacua of heterotic
string theory compactified on a Calabi-Yau threefold which are classical and
simple in the K\"ahler moduli sector of the theory. For this, we exploit a
known necessary condition on the K\"ahler potential in N=1-supergravity, which
we, under the assumption that only moduli fields contribute to supersymmetry
breaking, express in terms of a tensorial eigenvalue problem for the Calabi-Yau
triple intersection tensor. For three-dimensional moduli spaces we are able to
identify the discriminant of the Calabi-Yau intersection tensor in the
analysis, generalizing a known result for two-dimensional moduli spaces. We
also discuss explicit examples and possible generalizations.


title: Data Mining of the Concept "End of the World" in Twitter Microblogs

abstract:
  This paper describes the analysis of quantitative characteristics of frequent
sets and association rules in the posts of Twitter microblogs, related to the
discussion of "end of the world", which was allegedly predicted on December 21,
2012 due to the Mayan calendar. Discovered frequent sets and association rules
characterize semantic relations between the concepts of analyzed subjects.The
support for some fequent sets reaches the global maximum before the expected
event with some time delay. Such frequent sets may be considered as predictive
markers that characterize the significance of expected events for blogosphere
users. It was shown that time dynamics of confidence of some revealed
association rules can also have predictive characteristics. Exceeding a certain
threshold, it may be a signal for the corresponding reaction in the society
during the time interval between the maximum and probable coming of an event.


title: A Gas-Kinetic Scheme For The Simulation Of Compressible Turbulent Flows

abstract:
  The kinetic theory of gases has suggested the idea of viscosity to model the
effect of thermal fluctuations on the resolved flow. Supported by the assumed
analogy between molecules and the eddies in a turbulent flows, the idea of an
eddy viscosity has been put forward in the pioneering work by Lord Kelvin and
Osborne Reynolds. In over hundred years of turbulence modeling, the numerical
schemes adopted to simulate turbulent flow - with the exception of the Lattice
Boltzmann methods - have never exploited this analogy in any other way. In this
work, a gas-kinetic scheme is modified to simulate turbulent flow; the
turbulent relaxation time is deduced from assumed turbulent quantities. The new
scheme does not adopt an eddy viscosity, yet it relies even more strongly on
the analogy between thermal and turbulent fluctuations, as turbulence dynamics
is mathematically modeled by the Boltzmann equation. In the gas-kinetic scheme,
a measure of the degree of rarefaction is introduced, as the ratio between
unresolved and resolved time scales of motion. At low rarefaction, the
turbulent gas-kinetic scheme deviates negligibly from a conventional
Navier-Stokes scheme. However, as the degree of rarefaction increases, the
kinetic effects become evident. This phenomenon is evident in the mathematical
description of the turbulent stress tensor and also in numerical experiments.
This study does not propose an innovative turbulence model or technique. It
addresses the fact that the traditional coupling numerical scheme and
turbulence modeling might improve the physical consistence of numerical
simulations.


title: Cubulated moves and discrete knots

abstract:
  In this paper, we prove than given two cubic knots $K_1$, $K_2$ in
$\mathbb{R}^3$, they are isotopic if and only if one can pass from one to the
other by a finite sequence of cubulated moves. These moves are analogous to the
Reidemeister moves for classical tame knots. We use the fact that a cubic knot
is determined by a cyclic permutation of contiguous vertices of the
$\mathbb{Z}^3$-lattice (with some restrictions), to describe some of the
classic invariants and properties of the knots in terms of such cyclic
permutations, by projecting onto a plane such that it is injective when
restricted to the $\mathbb{Z}^3$-lattice and the image of the
$\mathbb{Z}^3$-lattice is dense.


title: Long-term polarimetric observations of OH127.8+0.0

abstract:
  OH 1612 and 1667 MHz masers from the well known object OH127.8+0.0 were mon-
itored in full-polarization mode over a period of 6.5 years and mapped with
MERLIN at one epoch. The OH variability pattern of the star is typical of
extremely long- period AGB stars. The distance determined from the 1612 MHz
light curve and a new measurement of the angular radius is 3.87 (0.28) kpc. At
both frequencies, the flux of polarized emission tightly follows the total flux
variations while, the degrees of circu- lar and linear polarization are
constant within measurement accuracy.. There is net polarization at both lines.
The magnetic field strength estimated from a likely Zeeman pair is -0.6 mG at
the distance of 5400 au from the star.At the near and far sides of the
envelope, the polarization vectors are well aligned implying a regular
structure of the magnetic field. The polarization characteristics of the OH
maser emission suggest a radial magnetic field which is frozen in the stellar
wind.


title:
Fluctuations of recentered maxima of discrete Gaussian Free Fields on a
  class of recurrent graphs

abstract:
  We provide conditions that ensure that the recentered maximum of the Gaussian
free field on a sequence of graphs fluctuates at the same order as the field at
the point of maximal variance. In particular, on a sequence of such graphs the
recentered maximum is not tight, similarly to the situation in Z but in
contrast with the situation in Z^2. We show that our conditions cover a large
class of "fractal" graphs.


title: Discontinuous Galerkin Methods for the Vlasov-Maxwell Equations

abstract:
  Discontinuous Galerkin methods are developed for solving the Vlasov-Maxwell
system, methods that are designed to be systematically as accurate as one wants
with provable conservation of mass and possibly total energy. Such properties
in general are hard to achieve within other numerical method frameworks for
simulating the Vlasov-Maxwell system. The proposed scheme employs discontinuous
Galerkin discretizations for both the Vlasov and the Maxwell equations,
resulting in a consistent description of the distribution function and
electromagnetic fields. It is proven, up to some boundary effects, that charge
is conserved and the total energy can be preserved with suitable choices of the
numerical flux for the Maxwell equations and the underlying approximation
spaces. Error estimates are established for several flux choices. The scheme is
tested on the streaming Weibel instability: the order of accuracy and
conservation properties of the proposed method are verified.


title: On the Tradeoff between Stability and Fit

abstract:
  In computing, as in many aspects of life, changes incur cost. Many
optimization problems are formulated as a one-time instance starting from
scratch. However, a common case that arises is when we already have a set of
prior assignments, and must decide how to respond to a new set of constraints,
given that each change from the current assignment comes at a price. That is,
we would like to maximize the fitness or efficiency of our system, but we need
to balance it with the changeout cost from the previous state.
  We provide a precise formulation for this tradeoff and analyze the resulting
{\em stable extensions} of some fundamental problems in measurement and
analytics. Our main technical contribution is a stable extension of PPS
(probability proportional to size) weighted random sampling, with applications
to monitoring and anomaly detection problems. We also provide a general
framework that applies to top-$k$, minimum spanning tree, and assignment. In
both cases, we are able to provide exact solutions, and discuss efficient
incremental algorithms that can find new solutions as the input changes.


title: Aharonov-Bohm quantum rings in high-Q microcavities

abstract:
  A single-mode microcavity with an embedded Aharonov-Bohm quantum ring, which
is pierced by a magnetic flux and subjected to a lateral electric field, is
studied theoretically. It is shown that external electric and magnetic fields
provide additional means of control of the emission spectrum of the system. In
particular, when the magnetic flux through the quantum ring is equal to a
half-integer number of the magnetic flux quantum, a small change in the lateral
electric field allows tuning of the energy levels of the quantum ring into
resonance with the microcavity mode providing an efficient way to control the
quantum ring-microcavity coupling strength. Emission spectra of the system are
calculated for several combinations of the applied magnetic and electric
fields.


title: On locally phi-semisymmetric Sasakian manifolds

abstract:
  Generalizing the notion of local $\phi$-symmetry of Takahashi, in the present
paper, we introduce the notion of local $\phi$-semisymmetry of a Sasakian
manifold along with its proper existence and characterization. We also study
the notion of local Ricci (resp., projective, conformal) $\phi$-semisymmetry of
a Sasakian manifold and obtain its characterization. It is shown that the local
$\phi$-semisymmetry, local projective $\phi$-semisymmetry and local concircular
$\phi$-semisymmetry are equivalent. It is also shown that local conformal
$\phi$-semisymmetry and local conharmonical $\phi$-semisymmetry are equivalent.


title: Stable analytic bounce in non-local Einstein-Gauss-Bonnet cosmology

abstract:
  We consider the most general quadratic in curvature stringy motivated
non-local action for the modified Einstein's gravity. We present exact analytic
cosmological solutions including the bouncing ones and develop the relevant
techniques for the further study of this type of models. We also elaborate on
the perturbation formalism and argue that the found bouncing solution is stable
during the bounce phase.


title: Polarizabilities, Stark shifts, and lifetimes of In atom

abstract:
  We evaluate the polarizabilities of the 5p_{1/2}, 6s, 6p_{1/2}, and 6p_{3/2}
states of In using two different high-precision relativistic methods:
linearized coupled-cluster approach where single, double and partial triple
excitations of the Dirac-Fock wave function are included to all orders of
perturbation theory and an approach that combines the configuration interaction
and the coupled-cluster method. Extensive comparison of the accuracy of these
methods is carried out. The uncertainties of all recommended values are
evaluated. Our result for the 6s-5p_{1/2} Stark shift is in excellent agreement
with the recent measurement [Ranjit et al., arXiv:1302.0821v1]. Combining our
calculation with this precision measurement allows us to infer the values of
the 6p_{1/2} and 6p_{3/2} lifetimes in In with 0.8% accuracy. Our predictions
for the 6p_{3/2} scalar and tensor polarizabilities may be combined with the
future measurement of the 6s-6p_{3/2} Stark shift to accurately determine the
lifetimes of the 5d_j states.


title: Simulation-efficient shortest probability intervals

abstract:
  Bayesian highest posterior density (HPD) intervals can be estimated directly
from simulations via empirical shortest intervals. Unfortunately, these can be
noisy (that is, have a high Monte Carlo error). We derive an optimal weighting
strategy using bootstrap and quadratic programming to obtain a more compu-
tationally stable HPD, or in general, shortest probability interval (Spin). We
prove the consistency of our method. Simulation studies on a range of theoret-
ical and real-data examples, some with symmetric and some with asymmetric
posterior densities, show that intervals constructed using Spin have better
cov- erage (relative to the posterior distribution) and lower Monte Carlo error
than empirical shortest intervals. We implement the new method in an R package
(SPIn) so it can be routinely used in post-processing of Bayesian simulations.


title:
Dark radiation and dark matter in supersymmetric axion models with high
  reheating temperature

abstract:
  Recent studies of the cosmic microwave background, large scale structure, and
big bang nucleosynthesis (BBN) show trends towards extra radiation. Within the
framework of supersymmetric hadronic axion models, we explore two
high-reheating-temperature scenarios that can explain consistently extra
radiation and cold dark matter (CDM), with the latter residing either in
gravitinos or in axions. In the gravitino CDM case, axions from decays of
thermal saxions provide extra radiation already prior to BBN and decays of
axinos with a cosmologically required TeV-scale mass can produce extra entropy.
In the axion CDM case, cosmological constraints are respected with light
eV-scale axinos and weak-scale gravitinos that decay into axions and axinos.
These decays lead to late extra radiation which can coexist with the early
contributions from saxion decays. Recent results of the Planck satellite probe
extra radiation at late times and thereby both scenarios. Further tests are the
searches for axions at ADMX and for supersymmetric particles at the LHC.


title:
Comparative study of the electronic structure, phonon spectra and
  electron-phonon interaction of ZrB2 and TiB2

abstract:
  The electronic structure, optical and x-ray absorption spectra, angle
dependence of the cyclotron masses and extremal cross sections of the Fermi
surface, phonon spectra, electron-phonon Eliashberg and transport spectral
functions, temperature dependence of electrical resistivity of the MB2 (M=Ti
and Zr) diborides were investigated from first principles using the full
potential linear muffin-tin orbital method. The calculations of the dynamic
matrix were carried out within the framework of the linear response theory. A
good agreement with experimental data of optical and x-ray absorption spectra,
phonon spectra, electron-phonon spectral functions, electrical resistivity,
cyclotron masses and extremal cross sections of the Fermi surface was achieved.


title:
Mapping the Clumpy Structures within Submillimeter Galaxies using
  Laser-Guide Star Adaptive Optics Spectroscopy

abstract:
  We present the first integral-field spectroscopic observations of
high-redshift submillimeter-selected galaxies (SMGs) using Laser Guide Star
Adaptive Optics (LGS-AO). We target H-alpha emission of three SMGs at redshifts
z~1.4-2.4 with the OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) on
Keck. The spatially-resolved spectroscopy of these galaxies reveals unresolved
broad H-alpha line regions (FWHM>1000 km/s) likely associated with an AGN and
regions of diffuse star formation traced by narrow-line H-alpha emission
(FWHM<500 km/s) dominated by multiple Halpha-bright stellar clumps, each
contributing 1-30% of the total clump-integrated H-alpha emission. We find that
these SMGs host high star-formation rate surface densities, similar to local
extreme sources, such as circumnuclear starbursts and luminous infrared
galaxies. However, in contrast to these local environments, SMGs appear to be
undergoing such intense activity on significantly larger spatial scales as
revealed by extended H-alpha emission over 4-16 kpc. H-alpha kinematics show no
evidence of ordered global motion as would be found in a disk, but rather large
velocity offsets (~few x 100 km/s) between the distinct stellar clumps.
Together with the asymmetric distribution of the stellar clumps around the AGN
in these objects, it is unlikely that we are unveiling a clumpy disk structure
as has been suggested in other high-redshift populations of star-forming
galaxies. The SMG clumps in this sample may correspond to remnants of
originally independent gas-rich systems that are in the process of merging,
hence triggering the ultraluminous SMG phase.


title: The Same-Sign Dilepton Signature of RPV/MFV SUSY

abstract:
  The lack of observation of superpartners at the Large Hadron Collider so far
has led to a renewed interest in supersymmetric models with R-parity violation
(RPV). In particular, imposing the Minimal Flavor Violation (MFV) hypothesis on
a general RPV model leads to a realistic and predictive framework. Naturalness
suggests that stops and gluinos should appear at or below the TeV mass scale.
We consider a simplified model with these two particles and MFV couplings. The
model predicts a significant rate of events with same-sign dileptons and
b-jets. We re-analyze a recent CMS search in this channel and show that the
current lower bound on the gluino mass is about 800 GeV at 95% confidence
level, with only a weak dependence on the stop mass as long as the gluino can
decay to an on-shell top-stop pair. We also discuss how this search can be
further optimized for the RPV/MFV scenario, using the fact that MFV stop decays
often result in jets with large invariant mass. With the proposed improvements,
we estimate that gluino masses of up to about 1.4 TeV can be probed at the 14
TeV LHC with a 100 fb^-1 data set.


title: Catastrophic Evaporation of Rocky Planets

abstract:
  Short-period exoplanets can have dayside surface temperatures surpassing 2000
K, hot enough to vaporize rock and drive a thermal wind. Small enough planets
evaporate completely. We construct a radiative-hydrodynamic model of
atmospheric escape from strongly irradiated, low-mass rocky planets, accounting
for dust-gas energy exchange in the wind. Rocky planets with masses < 0.1
M_Earth (less than twice the mass of Mercury) and surface temperatures > 2000 K
are found to disintegrate entirely in < 10 Gyr. When our model is applied to
Kepler planet candidate KIC 12557548b --- which is believed to be a rocky body
evaporating at a rate of dM/dt > 0.1 M_Earth/Gyr --- our model yields a
present-day planet mass of < 0.02 M_Earth or less than about twice the mass of
the Moon. Mass loss rates depend so strongly on planet mass that bodies can
reside on close-in orbits for Gyrs with initial masses comparable to or less
than that of Mercury, before entering a final short-lived phase of catastrophic
mass loss (which KIC 12557548b has entered). Because this catastrophic stage
lasts only up to a few percent of the planet's life, we estimate that for every
object like KIC 12557548b, there should be 10--100 close-in quiescent
progenitors with sub-day periods whose hard-surface transits may be detectable
by Kepler --- if the progenitors are as large as their maximal, Mercury-like
sizes (alternatively, the progenitors could be smaller and more numerous).
According to our calculations, KIC 12557548b may have lost ~70% of its
formation mass; today we may be observing its naked iron core.


title: Photon Feedback: Screening and the Eddington Limit

abstract:
  Bright star-forming galaxies radiate well below their Eddington Limit. The
value of the flux-mean opacity that mediates the radiation force onto matter is
orders of magnitude smaller than the UV or optical dust opacity. On empirical
grounds, it is shown that high-redshift ULIRGs radiate at two orders of
magnitude below their Eddington Limit, while the local starbursters M82 and Arp
220 radiate at a few percent of their Eddington Limit. A simple model for the
radiative transfer of UV and optical light in dust-rich environments is
considered. Radiation pressure on dust does not greatly affect the large-scale
gas dynamics of star-forming galaxies.


title:
High resolution study of the cluster complexes in a lensed spiral at
  redshift ~1.5; constraints on the bulge formation and disk evolution

abstract:
  We analyse the clump population of the spiral galaxy Sp 1149 at redshift 1.5.
Located behind the galaxy cluster MACS J1149.5+2223, Sp 1149 has been
significantly magnified allowing us to study the galaxy on physical scales down
to ~100 pc. We have used the publicly available multi-band imaging dataset
(CLASH) to reconstruct the spectral energy distributions (SEDs) of the clumps
in Sp 1149, and derive, by means of stellar evolutionary models, their physical
properties. We found that 40% of the clumps observed in Sp 1149 are older than
30 Myr and can be as old as 300 Myr. These are also the more massive (luminous)
clumps in the galaxy. Among the complexes in the local reference sample, the
star-forming knots in luminous blue compact galaxies could be considered
progenitor analogs of these long-lived clumps. The remaining 60% of clumps have
colors comparable to local cluster complexes, suggesting a similar young age.
We observe that the Sp 1149 clumps follow the M ~ R^2 relation similar to local
cluster complexes, suggesting similar formation mechanisms although they may
have different initial conditions (e.g. higher gas surface densities). We
suggest that the galaxy is experiencing a slow decline in star formation rate
and a likely transitional phase toward a more quiescent star-formation mode.
The older clumps have survived between 6 and 20 dynamical times and are all
located at projected distances smaller than 4 kpc from the centre. Their
current location suggests migration toward the centre and the possibility to be
the building blocks of the bulge. On the other hand, the dynamical timescale of
the younger clumps are significantly shorter, meaning that they are quite close
to their birthplace. We show that the clumps of Sp 1149 may account for the
expected metal-rich globular cluster population usually associated with the
bulge and thick disk components of local spirals.


title:
Acceleration of cosmic rays and gamma-ray emission from supernova
  remnants in the Galaxy

abstract:
  Galactic cosmic rays are believed to be accelerated at supernova remnant
shocks. Though very popular and robust, this conjecture still needs a
conclusive proof. The strongest support to this idea is probably the fact that
supernova remnants are observed in gamma-rays, which are indeed expected as the
result of the hadronic interactions between the cosmic rays accelerated at the
shock and the ambient gas. However, also leptonic processes can, in most cases,
explain the observed gamma-ray emission. This implies that the detections in
gamma rays do not necessarily mean that supernova remnants accelerate cosmic
ray protons. To overcome this degeneracy, the multi-wavelength emission (from
radio to gamma rays) from individual supernova remnants has been studied and in
a few cases it has been possible to ascribe the gamma-ray emission to one of
the two processes (hadronic or leptonic). Here we adopt a different approach
and, instead of a case-by-case study we aim for a population study and we
compute the number of supernova remnants which are expected to be seen in TeV
gamma rays above a given flux under the assumption that these objects indeed
are the sources of cosmic rays. The predictions found here match well with
current observational results, thus providing a novel consistency check for the
supernova remnant paradigm for the origin of galactic cosmic rays. Moreover,
hints are presented for the fact that particle spectra significantly steeper
than E^-2 are produced at supernova remnants. Finally, we expect that several
of the supernova remnants detected by H.E.S.S. in the survey of the galactic
plane should exhibit a gamma-ray emission dominated by hadronic processes (i.e.
neutral pion decay). The fraction of the detected remnants for which the
leptonic emission dominates over the hadronic one depends on the assumed values
of the physical parameters and can be as high as roughly a half.


title: Lanczos-Lovelock models of gravity

abstract:
  Lanczos-Lovelock models of gravity represent a natural and elegant
generalization of Einstein's theory of gravity to higher dimensions. They are
characterized by the fact that the field equations only contain up to second
derivatives of the metric even though the action functional can be a quadratic
or higher degree polynomial in the curvature tensor. Because these models share
several key properties of Einstein's theory they serve as a useful set of
candidate models for testing the emergent paradigm for gravity. This review
highlights several geometrical and thermodynamical aspects of Lanczos-Lovelock
models which have attracted recent attention.


title: No Energy Equipartition in Globular Clusters

abstract:
  It is widely believed that globular clusters evolve over many two-body
relaxation times toward a state of energy equipartition, so that velocity
dispersion scales with stellar mass as \sigma ~ m^{-\eta} with \eta = 0.5. We
show that this is incorrect, using direct N-body simulations with a variety of
realistic IMFs and initial conditions. No simulated system ever reaches a state
close to equipartition. Near the center, the luminous main-sequence stars reach
a maximum \eta_{max} ~ 0.15 \pm 0.03. At large times, all radial bins
convergence on an asymptotic value \eta_{\infty} ~ 0.08 \pm 0.02. The
development of this "partial equipartition" is strikingly similar across our
simulations, despite the range of initial conditions employed. Compact remnants
tend to have higher \eta than main-sequence stars (but still \eta < 0.5), due
to their steeper (evolved) mass function. The presence of an intermediate-mass
black hole (IMBH) decreases \eta, consistent with our previous findings of a
quenching of mass segregation under these conditions. All these results can be
understood as a consequence of the Spitzer instability for two-component
systems, extended by Vishniac to a continuous mass spectrum. Mass segregation
(the tendency of heavier stars to sink toward the core) has often been studied
observationally, but energy equipartition has not. Due to the advent of
high-quality proper motion datasets from the Hubble Space Telescope, it is now
possible to measure \eta. Detailed data-model comparisons open up a new
observational window on globular cluster dynamics and evolution. Comparison of
our simulations to Omega Cen observations yields good agreement, confirming
that globular clusters are not generally in energy equipartition. Modeling
techniques that assume equipartition by construction (e.g., multi-mass
Michie-King models) are approximate at best.


title: Imaging topological edge states in silicon photonics

abstract:
  Topological features - global properties not discernible locally - emerge in
systems from liquid crystals to magnets to fractional quantum Hall systems.
Deeper understanding of the role of topology in physics has led to a new class
of matter: topologically - ordered systems. The best known examples are quantum
Hall effects, where insensitivity to local properties manifests itself as
conductance through edge states that is insensitive to defects and disorder.
Current research in engineering topological order primarily focuses on
analogies to quantum Hall systems, where the required magnetic field is
synthesized in non-magnetic systems. Here, we realize synthetic magnetic fields
for photons at room temperature, using linear Silicon photonics. We observe,
for the first time, topological edge states of light in a two - dimensional
system and show their robustness against intrinsic and introduced disorder. Our
experiment demonstrates the feasibility of using photonics to realize
topological order in both the non-interacting and many-body regimes.


title:
Quenching nitrogen-vacancy center photoluminescence with infrared pulsed
  laser

abstract:
  Diamond nanocrystals containing Nitrogen-Vacancy (NV) color centers have been
used in recent years as fluorescent probes for near-field and cellular imaging.
In this work we report that an infrared (IR) pulsed excitation beam can quench
the photoluminescence of NV color center in a diamond nanocrystal (size < 50
nm) with an extinction ratio as high as ~90%. We attribute this effect to the
heating of the nanocrystal consecutive to multi-photon absorption by the
diamond matrix. This quenching is reversible: the photoluminescence intensity
goes back to its original value when the IR laser beam is turned off, with a
typical response time of hundred picoseconds, allowing for a fast control of NV
color center photoluminescence. We used this effect to achieve sub-diffraction
limited imaging of fluorescent diamond nanocrystals on a coverglass. For that,
as in Ground State Depletion super-resolution technique, we combined the green
excitation laser beam with the control IR depleting one after shaping its
intensity profile in a doughnut form, so that the emission comes only from the
sub-wavelength size central part.


title: Kinematic Discovery of a Stellar Stream located in Pisces

abstract:
  We report the kinematic discovery of the Pisces Stellar Stream (PSS), at
Galactic longitude of roughly l=135 degrees and longitude between -39 < b < -36
deg. We originally identified this halo substructure from velocities of red
giant branch stars in Sloan Digital Sky Survey (SDSS) Data Release 8, and
confirmed its presence in turnoff stars from SDSS photometric data. The PSS is
a narrow, kinematically cold tidal stream, with a velocity dispersion of 8
km/s. Its metallicity is [Fe/H]=-2.2, with ~0.3 dex dispersion. The
color-magnitude signature of the stream turnoff, combined with our measured
metallicity, places the PSS at a distance of 35+/-3 kpc. The Pisces Stellar
Stream is the same as the previously announced "Triangulum stream" and part of
the proposed "stream a". We rule out an association of the PSS with other
previously known Milky Way substructures in the same region of the sky.


title: Full counting statistics of photons interacting with emitter

abstract:
  A complete characterization of quantum fluctuations in many-body systems is
accessible through the full counting statistics. We present an exact
computation of statistical properties of light in a basic model of light-matter
interaction: a multimode photonic field coupled to a single two-level emitter.
We mostly consider an initial coherent state in a given mode and demonstrate
how the original Poissonian statistics gets modified because of quantum
many-body scattering effects leading to non-Poissonian distributions. We argue
that measuring this statistics in a simple quantum optical setup provides an
insight into many-body correlation effects with photons.


title: Passive Learning with Target Risk

abstract:
  In this paper we consider learning in passive setting but with a slight
modification. We assume that the target expected loss, also referred to as
target risk, is provided in advance for learner as prior knowledge. Unlike most
studies in the learning theory that only incorporate the prior knowledge into
the generalization bounds, we are able to explicitly utilize the target risk in
the learning process. Our analysis reveals a surprising result on the sample
complexity of learning: by exploiting the target risk in the learning
algorithm, we show that when the loss function is both strongly convex and
smooth, the sample complexity reduces to $\O(\log (\frac{1}{\epsilon}))$, an
exponential improvement compared to the sample complexity
$\O(\frac{1}{\epsilon})$ for learning with strongly convex loss functions.
Furthermore, our proof is constructive and is based on a computationally
efficient stochastic optimization algorithm for such settings which demonstrate
that the proposed algorithm is practically useful.


title:
Three-coloring triangle-free graphs on surfaces II. 4-critical graphs in
  a disk

abstract:
  Let G be a plane graph of girth at least five. We show that if there exists a
3-coloring phi of a cycle C of G that does not extend to a 3-coloring of G,
then G has a subgraph H on O(|C|) vertices that also has no 3-coloring
extending phi. This is asymptotically best possible and improves a previous
bound of Thomassen. In the next paper of the series we will use this result and
the attendant theory to prove a generalization to graphs on surfaces with
several precolored cycles.


title: Calculation of the decay ${\bm H\bm\to\bm e\bar{\bm e}\bm\ga}$

abstract:
  We revisit an earlier calculation of the decay $H\to e\,\bar{e}\ga$ using the
recently reported mass value of the Higgs boson candidate observed in the ATLAS
and CMS experiments together with cuts that are appropriate for experimental
analyzes.


title:
Superconducting Transition Temperatures for Spin-Fluctuation Promoted
  Superconductivity in Heavy Fermion Compounds

abstract:
  The quantum critical Antiferromagnetic (AFM) fluctuation spectra measured by
inelastic neutron scattering recently in two heavy fermion superconductors are
used together with their other measured properties to calculate their D-wave
superconducting transition temperatures $T_{\rm c}$. To this end, the
linearized Eliashberg equations for D-wave superconductivity induced by AFM
fluctuations are solved in models of fermions with various levels of nesting.
The results for the ratio of $T_{\rm c}$ to the characteristic spin-fluctuation
energy are well parametrized by a dimensionless coupling constant and the AFM
correlation length. Comparing the results with experiments suggests that one
may reasonably conclude that superconductivity in these compounds is indeed
caused by AFM fluctuations. This conclusion is strengthened by a calculation
with the same parameters of the measured coefficient of the normal state
quantum-critical resistivity $\propto T^{3/2}$ characteristic of {\it gaussian}
AFM quantum-critical fluctuations. The calculations give details of the
superconducting coupling as a function of the correlation length and the
integrated fluctuation spectra useful in other compounds.


title:
Anomalous thermodynamic power laws near topological transitions in nodal
  superconductors

abstract:
  Unconventional superconductors are most frequently identified by the
observation of power-law behaviour on low-temperature thermodynamic or
transport properties, such as specific heat. Here we show that, in addition to
the usual point and line nodes, a much wider class of different nodal types can
occur. These new types of nodes typically occur when there are transitions
between different types of gap node topology, for example when point or line
nodes first appear as a function of some physical parameter. We identify
anomalous, non-integer thermodynamic power laws associated with these new nodal
types, and give physical examples of superconductors in which they might be
observed experimentally, including the noncentrosymmetric superconductor
Li$_2$Pd$_{3-x}$Pt$_x$B.


title:
The hybrid lattice of KxFe2-ySe2: why superconductivity and magnetism
  can coexist

abstract:
  Much remains unknown of the microscopic origin of superconductivity when it
materializes in atomically disordered systems as in amorphous alloys (1) or in
crystals riddled with defects(2). A manifestation of this conundrum is
envisaged in the highly defective iron chalcogenide superconductors of
KxFe2-ySe2 (3-6). How can superconductivity survive under such crude conditions
that call for strong electron localization (7)? With vacancies present both at
the K and Fe sites, superconductivity is bordering a semi-metallic region below
x ~ 0.7 and an insulating and antiferromagnetic region above x ~ 0.85 (8,9).
Here, we report on the bulk local atomic structure and show that the Fe
sublattice is locally distorted in a way that it accommodates two kinds of Fe
valence environments giving rise to a bimodal bond distribution. While the bond
length distribution is driven by K and Fe contents, the superconducting state
is characterized by the coexistence of both short (metallic) and long
(insulating) Fe bond environments and is not phase separated. In contrast to
other Fe-based materials in which only one kind of Fe to Fe bond is present,
the dual nature of the Fe correlations explains why superconductivity is
intertwined with magnetic order. Such a hybrid state is most likely present in
cuprate superconductors as well (10,11) while our results point to the
importance of the local atomic symmetry by which the exchange interactions
between local moments can materialize (12).


title: The triangulated category of K-motives DK_(k)

abstract:
  For any perfect field k a triangulated category of K-motives DK_(k) is
constructed in the style of Voevodsky's construction of the category DM_(k). To
each smooth k-variety X the K-motive is associated in the category DK_(k).
Also, it is shown that K_n(X)=DK_(k)(M_K(X)[n],M_K(pt)), where K(X) is
Quillen's K-theory of X.


title: Wilson loops in supersymmetric Chern-Simons-matter theories and duality

abstract:
  We study the algebra of BPS Wilson loops in 3d gauge theories with N=2
supersymmetry and Chern-Simons terms. We argue that new relations appear on the
quantum level, and that in many cases this makes the algebra
finite-dimensional. We use our results to propose the mapping of Wilson loops
under Seiberg-like dualities and verify that the proposed map agrees with the
exact results for expectation values of circular Wilson loops. In some cases we
also relate the algebra of Wilson loops to the equivariant quantum K-ring of
certain quasi projective varieties. This generalizes the connection between the
Verlinde algebra and the quantum cohomology of the Grassmannian found by
Witten.


title:
About intrinsic Finsler connections for the homogeneous lift to the
  Osculator Bundle of a Finsler metric

abstract:
  In this article we present a study of the subspaces of the manifold OscM, the
total space of the osculator bundle of a real manifold M. We obtain the induced
connections of the canonical metrical N-linear connection determined by the
homogeneous prolongation of a Finsler metric to the manifold OscM. We present
the relation between the induced and intrinsic geometric objects of the
associated osculator submanifold.


Reply to the Comment on "Unified Formulism of Andreev Reflection at a
  Ferromagnetic/Superconductor Interface" by Eschrig et al


title: Information, Estimation, and Lookahead in the Gaussian channel

abstract:
  We consider mean squared estimation with lookahead of a continuous-time
signal corrupted by additive white Gaussian noise. We show that the mutual
information rate function, i.e., the mutual information rate as function of the
signal-to-noise ratio (SNR), does not, in general, determine the minimum mean
squared error (MMSE) with fixed finite lookahead, in contrast to the special
cases with 0 and infinite lookahead (filtering and smoothing errors),
respectively, which were previously established in the literature. We also
establish a new expectation identity under a generalized observation model
where the Gaussian channel has an SNR jump at $t=0$, capturing the tradeoff
between lookahead and SNR.
  Further, we study the class of continuous-time stationary Gauss-Markov
processes (Ornstein-Uhlenbeck processes) as channel inputs, and explicitly
characterize the behavior of the minimum mean squared error (MMSE) with finite
lookahead and signal-to-noise ratio (SNR). The MMSE with lookahead is shown to
converge exponentially rapidly to the non-causal error, with the exponent being
the reciprocal of the non-causal error. We extend our results to mixtures of
Ornstein-Uhlenbeck processes, and use the insight gained to present lower and
upper bounds on the MMSE with lookahead for a class of stationary Gaussian
input processes, whose spectrum can be expressed as a mixture of
Ornstein-Uhlenbeck spectra.


title: Optimal Throughput-Outage Trade-off in Wireless One-Hop Caching Networks

abstract:
  We consider a wireless device-to-device (D2D) network where the nodes have
cached information from a library of possible files. Inspired by the current
trend in the standardization of the D2D mode for 4th generation wireless
networks, we restrict to one-hop communication: each node place a request to a
file in the library, and downloads from some other node which has the requested
file in its cache through a direct communication link, without going through a
base station. We describe the physical layer communication through a simple
"protocol-model", based on interference avoidance (independent set scheduling).
For this network we define the outage-throughput tradeoff problem and
characterize the optimal scaling laws for various regimes where both the number
of nodes and the files in the library grow to infinity.


title:
Representation, simplification and display of fractional powers of
  rational numbers in computer algebra

abstract:
  Simplification of fractional powers of positive rational numbers and of sums,
products and powers of such numbers is taught in beginning algebra. Such
numbers can often be expressed in many ways, as this article discusses in some
detail. Since they are such a restricted subset of algebraic numbers, it might
seem that good simplification of them must already be implemented in all widely
used computer algebra systems. However, the algorithm taught in beginning
algebra uses integer factorization, which can consume unacceptable time for the
large numbers that often arise within computer algebra. Therefore some systems
apparently use various ad hoc techniques that can return an incorrect result
because of not simplifying to 0 the difference between two equivalent such
expressions. Even systems that avoid this flaw often do not return the same
result for all equivalent such input forms, or return an unnecessarily bulky
result that does not have any other compensating useful property. This article
identifies some of these deficiencies, then describes the advantages and
disadvantages of various alternative forms and how to overcome the deficiencies
without costly integer factorization.


title: Vanishing of Tor, and why we care about it

abstract:
  Given finitely generated modules $M$ and $N$ over a local ring $R$, the
tensor product $M\otimes_RN$ typically has nonzero torsion. Indeed, the
assumption that the tensor product is torsion-free influences the structure and
vanishing of the modules $\Tor^R_i(M,N)$ for all $i\geq 1$. In turn, the
vanishing of $\Tor^R_i(M,N)$ imposes restrictions on the depth properties of
the modules $M$ and $N$. These connections made their first appearance in
Auslander's 1961 paper "Modules over unramified regular local rings". We will
survey the literature on these topics, with emphasis on progress during the
past twenty years.


title: Search For New Physics at BABAR

abstract:
  Using a full BABAR data sample of 426 $fb^{-1}$, we present improved
measurements of the ratio ${\cal{R}}(D^{(*)}) = {\cal{B}} (\bar{B} \to
D^{(*)}\tau^{-}\bar{\nu}_{\tau})/$ ${\cal{B}} (\bar{B} \to
D^{(*)}\ell_{\ell}^{-}\bar{\nu}_{\ell})$, where $\ell$ is either electron or
muon. We measure ${\cal{R}}(D) = 0.440 \pm 0.058 \pm 0.042$ and ${\cal{R}}(D^*)
= 0.332 \pm 0.024 \pm 0.018$. These ratios exceed the Standard Model
predictions by $2.0\sigma$ and $2.7\sigma$, respectively. The results disagree
with the Standard Model predictions at the level of $3.4\sigma$. The ratios are
sensitive to new physics contributions in the form of a charged Higgs boson.
However, the access cannot be explained by a charged Higgs boson in the type II
two-Higgs-doublet model.