title: Asymptotic enumeration of sparse multigraphs with given degrees

abstract:
  Let J and J* be subsets of Z+ such that 0,1\in J and 0\in J*. For infinitely
many n, let k=(k_1,..., k_n) be a vector of nonnegative integers whose sum M is
even. We find an asymptotic expression for the number of multigraphs on the
vertex set {1,..., n} with degree sequence given by k, such that every loop has
multiplicity in J* and every non-loop edge has multiplicity in J. Equivalently,
these are symmetric integer matrices with values J* allowed on the diagonal and
J off the diagonal. Our expression holds when the maximum degree K satisfies K
= o(M^(1/3)). We prove this result using the switching method, building on an
asymptotic enumeration of simple graphs with given degrees (McKay and Wormald,
1991). Our application of the switching method introduces a novel way of
combining several different switching operations into a single computation.


title: LHCb Results on Semileptonic B/B$_s$/$\Lambda_b$ Decays

abstract:
  Studies of semileptonic decays of b hadrons with the LHCb experiment are
reported. In particular, measurements of the b hadron production fractions at
the LHC and Bs semileptonic decays in P-wave charmed mesons are presented. An
outlook of the LHCb potential in measuring the CKM matrix elements Vub and Vcb,
as well as decays involving taus, is given.


title: Hyperelliptic curves covering an elliptic curve twice

abstract:
  We show that for any elliptic curve (with j invariant not 0 or 1728) over any
field of characteristic different from 2 and 3, there exists an hyperelliptic
curve H of genus 5 with two independent maps to the given elliptic curve. We
also show that, if we want such a curve to be just geometrically hyperelliptic,
so having a degree two map to a conic, then there are some with genus 3.


title: Regarding a uniqueness property of singly-periodic Scherk surfaces

abstract:
  Inspired by an argument of Ros [15] -- we use the L\'{o}pez-Ros deformation
to give another proof of the fact -- due to Meeks and Wolf [13] -- that the
only smooth, connected, singly-periodic minimal surfaces in $\Real^3$ with the
area growth of two planes are the singly-periodic Scherk surfaces.


title: Isoperimetric domains of large volume in homogeneous three-manifolds

abstract:
  Given a non-compact, simply connected homogeneous three-manifold $X$ and a
sequence $\{\Omega_n\}_n$ of isoperimetric domains in $X$ with volumes tending
to infinity, we prove that as $n\to \infty $: 1. The radii of the $\Omega_n$
tend to infinity. 2. The ratios $\{Area} (\partial \Omega_n)/\{Vol}(\Omega_n)$
converge to the Cheeger constant Ch$(X)$, which we also prove to be equal to
$2H(X)$ where $H(X)$ is the critical mean curvature of $X$. 3. The values of
the constant mean curvatures $H_n$ of the boundary surfaces $\partial \Omega_n$
converge to $\frac{1}{2}\{Ch}(X)$. Furthermore, when Ch$(X)$ is positive, we
prove that for $n$ large, $\partial \Omega_n$ is well-approximated in a natural
sense by the leaves of a certain foliation of $X$, where every leaf of the
foliation is a surface of constant mean curvature $H(X)$.


title: Continuous Weak Approximation for Stochastic Differential Equations

abstract:
  A convergence theorem for the continuous weak approximation of the solution
of stochastic differential equations by general one step methods is proved,
which is an extension of a theorem due to Milstein. As an application, uniform
second order conditions for a class of continuous stochastic Runge-Kutta
methods containing the continuous extension of the second order stochastic
Runge-Kutta scheme due to Platen are derived. Further, some coefficients for
optimal continuous schemes applicable to It\^o stochastic differential
equations with respect to a multi-dimensional Wiener process are presented.


title:
Generalized parallel concatenated block codes based on BCH and RS codes,
  construction and Iterative decoding

abstract:
  In this paper, a generalization of parallel concatenated block GPCB codes
based on BCH and RS codes is presented.


title:
Blowup of classical solutions for a class of 3-D quasilinear wave
  equations with small initial data

abstract:
  This paper is concerned with the small smooth data problem for the 3-D
nonlinear wave equation $\partial_t^2u-\left (1+u+\p_t u\right)\Delta u=0$.
This equation is prototypical of the more general equation
$\dsize\sum_{i,j=0}^3g_{ij}(u, \nabla u)\partial_{ij}u=0$, where $x_0=t$ and
$g_{ij}(u, \nabla
u)=c_{ij}+d_{ij}u+\dsize\sum_{k=0}^3e_{ij}^k\partial_ku+O(|u|^2+|\nabla u|^2)$
are smooth functions of their arguments, with $c_{ij}, d_{ij}$ and $e_{ij}^k$
being constants, and $d_{ij}\neq0$ for some $(i,j)$; moreover,
$\dsize\sum_{i,j,k=0}^3e_{ij}^k(\partial_ku)\p_{ij} u$ does not fulfill the
null condition. For the 3-D nonlinear wave equations $\partial_t^2u-\left
(1+u\right)\Delta u=0$ and $\partial_t^2u-\left (1+\partial_t u\right)\Delta
u=0$, H. Lindblad, S. Alinhac, and F. John proved and disproved, respectively,
the global existence of small smooth data solutions. For radial initial data,
we show that the small smooth data solution of
$\partial_t^2u-\left(1+u+\partial_t u\right)\Delta u=0$ blows up in finite
time. The explicit expression of the asymptotic lifespan $T_{\varepsilon}$ as
$\varepsilon\to0^+$ is also given.


title: A search for cosmic topology in the final WMAP data

abstract:
  A search for matched circle pairs of similar temperature fluctuations in the
final WMAP 9yr data is carried out. Such a signature is expected if the space
of the Universe is multiply connected. We investigate the relation between the
pixel resolution of cosmic microwave background (CMB) maps and a Gaussian
smoothing in order to lower the probability for missing matched circle pairs.
CMB maps having the 3-torus topology are generated with the characteristics of
the WMAP satellite in order to determine how large the smoothing should be
chosen in CMB maps disturbed by detector noise. The V- and W-band data are
analysed with respect to matched circle pairs and a tentatively signal is found
for a circle pair, which lies, however, close to the plane of the Galaxy. It
is, however, inconclusive whether this signal is generated by chance, is due to
residual foregrounds contained in the V- and W-band maps, or is due to a
genuine topology.


title:
Genetic algorithms for finding the weight enumerator of binary linear
  block codes

abstract:
  In this paper we present a new method for finding the weight enumerator of
binary linear block codes by using genetic algorithms. This method consists in
finding the binary weight enumerator of the code and its dual and to create
from the famous MacWilliams identity a linear system (S) of integer variables
for which we add all known information obtained from the structure of the code.
The knowledge of some subgroups of the automorphism group, under which the code
remains invariant, permits to give powerful restrictions on the solutions of
(S) and to approximate the weight enumerator. By applying this method and by
using the stability of the Extended Quadratic Residue codes (ERQ) by the
Projective Special Linear group PSL2, we find a list of all possible values of
the weight enumerators for the two ERQ codes of lengths 192 and 200. We also
made a good approximation of the true value for these two enumerators.


title:
Symmetrical laws of structure of helicoidally-like biopolymers in the
  framework of algebraic topology. III. Nature of the double and relations
  between the alpha helix and the various forms of DNA structures

abstract:
  In the frameworks of algebraic topology {\alpha}-helix and different
DNA-conformations are determined as the local latticed packing, confined by
peculiar minimal surfaces which are similar to helicoids. These structures are
defined by Weierstrass representation and satisfy to a zero condition for the
instability index of the surface and availability of bifurcation points for
these surfaces. The topological stability of such structures corresponds to
removing of the configuration degeneracy and to existence of bifurcation points
for these surfaces. The considered ordered non-crystalline structures are
determined by homogeneous manifolds - algebraic polytopes, corresponding to the
definite substructures the 8-dimensional lattice E8.The joining of two
semi-turns of two spirals into the turn of a single two-spiral (helical) system
is effected by the topological operation of a connected sum. The applied
apparatus permits to determine a priori the symmetry parameters of the double
spirals in A, B and Z forms DNA structures.


title:
Lognormality and oscillations in the coverage of high-throughput
  transcriptomic data towards gene ends

abstract:
  High-throughput transcriptomics experiments have reached the stage where the
count of the number of reads alignable to a given position can be treated as an
almost-continuous signal. This allows to ask questions of
biophysical/biotechnical nature, but which may still have biological
implications. Here we show that when sequencing RNA fragments from one end, as
it is the case on most platforms, an oscillation in the read count is observed
at the other end. We further show that these oscillations can be well described
by Kolmogorov's 1941 broken stick model. We investigate how the model can be
used to improve predictions of gene ends (3' transcript ends) but conclude that
with present data the improvement is only marginal. The results highlight
subtle effects in high-throughput transcriptomics experiments which do not have
a biological origin, but which may still be used to obtain biological
information.


title: The Aharonov--Bohm effect in scattering theory

abstract:
  The Aharonov--Bohm effect is considered as a scattering event with
nonrelativistic charged particles of the wavelength which is less than the
transverse size of an impenetrable magnetic vortex. The quasiclassical WKB
method is shown to be efficient in solving this scattering problem. We find
that the scattering cross section consists of two terms, one describing the
classical phenomenon of elastic reflection and another one describing the
quantum phenomenon of diffraction; the Aharonov--Bohm effect is manifested as a
fringe shift in the diffraction pattern. Both the classical and the quantum
phenomena are independent of the choice of a boundary condition at the vortex
edge, providing that probability is conserved. We show that a propagation of
charged particles can be controlled by altering the flux of a magnetic vortex
placed on their way.

categories: quant-ph cond-mat.mes-hall hep-th math-ph math.MP


title:
Towards a model of the human society: A theoretical solution of the
  cooperation problem

abstract:
  In this paper we address the cooperation problem in structured populations by
considering the prisoner's dilemma game as metaphor of the social interactions
between individuals with imitation capacity. We present a new strategy update
rule called democratic weighted update where the individuals behavior is
socially influenced by each one of their neighbors. In particular, the capacity
of an individual to socially influence other ones is proportional to its wisdom
which is defined by its successful in the game. When in a neighborhood there
are cooperators and defectors, the focal player is contradictorily influenced
by them and, therefore, the effective social influence is given by the
difference of the total wisdom of each strategy in its neighborhood. First, by
considering the growing process of the network and neglecting mutations we show
the evolution of highly cooperative systems. Then, we broadly shown that the
social influence allows to overcome the emergence of mutants into highly
cooperative systems. In this way, we are able to conclude that considering the
growing process of the system, individuals with imitation capacity and the
social influence the cooperation evolves. Therefore, here we present a
theoretical solution of the cooperation problem among unrelated individuals
with imitiation capacity.


title:
Hubble Space Telescope detection of oxygen in the atmosphere of
  exoplanet HD189733b

abstract:
  Detecting heavy atoms in the inflated atmospheres of giant exoplanets that
orbit close to their parent stars is a key factor for understanding their bulk
composition, and the processes that drive their expansion and interaction with
the impinging stellar wind. Here, we use archive data obtained with the Cosmic
Origins Spectrograph onboard the Hubble Space Telescope to report an absorption
of ~6.4+/-1.8% by neutral oxygen during the HD 189733b transit. Scaling
published HI results from a simple hydrodynamic model of HD 189733b, a vertical
OI column density of ~8x10^15/cm2 produces only a 3.5% attenuation, implying
that non-thermal line broadening or super-solar abundances are required. We
also report evidence of short-time variability in the measured stellar flux, a
variability that we analyze and compare to solar flaring activity. In that
frame, we find that non-statistical uncertainties in the measured fluxes are
not negligible, which calls for caution when reporting transit absorptions.
Despite these uncertainties, we also show a possible detection for both a
transit and early-ingress absorption in the ion CII 133.5nm lines. If
confirmed, this would be the second exoplanet for which an early-ingress
absorption is reported. Assuming the HD 189733b magnetosphere to be at the
origin of the early absorption, we use the Parker model for the stellar wind
and a particle-in-cell code for the magnetosphere to show that its orientation
should be deflected ~10-30{\deg} from the planet-star line, while its nose's
position should be at least ~16.7 Rp upstream of the exoplanet in order to fit
the CII transit light curve. The derived stand-off distance is consistent with
a surface magnetic field strength of ~5.3 Gauss for the exoplanet, and a
supersonic stellar wind impinging at ~250 km/s, with a temperature of 1.2x10^5K
and a density ~6.3x10^6/cm^3 at the planetary orbit, yet the fit is not unique.


title: Friction forces on phase transition fronts

abstract:
  In cosmological first-order phase transitions, the microscopic interaction of
the phase transition fronts with non-equilibrium plasma particles manifests
itself macroscopically as friction forces. In general, it is a nontrivial
problem to compute these forces, and only two limits have been studied, namely,
that of very slow walls and, more recently, ultra-relativistic walls which run
away. In this paper we consider ultra-relativistic velocities and show that
stationary solutions still exist when the parameters allow the existence of
runaway walls. Hence, we discuss the necessary and sufficient conditions for
the fronts to actually run away. We also propose a phenomenological model for
the friction, which interpolates between the non-relativistic and
ultra-relativistic values. Thus, the friction depends on two friction
coefficients which can be calculated for specific models. We then study the
velocity of phase transition fronts as a function of the friction parameters,
the thermodynamic parameters, and the amount of supercooling.


title: Algebraic properties of classes of path ideals

abstract:
  We consider path ideals associated to special classes of posets such as tree
posets and cycles. We express their property of being sequentially
Cohen-Macaulay in terms of the underlying poset. Moreover, monomial ideals,
which arise from the Luce-decomposable model in algebraic statistics, can be
viewed as path ideals of certain posets. We study invariants of these so-called
\emph{Luce-decomposable} monomial ideals for diamond posets and products of
chains. In particular, for these classes of posets, we explicitly compute their
Krull dimension, their projective dimension, their regularity and their Betti
numbers.


title:
Superconductivity From Repulsive Electronic Correlations on Alternant
  Cuprate and Iron-based Lattices

abstract:
  A key question in the theory of high-temperature superconductivity is whether
Off-diagonal Long-Range Order (ODLRO) can be induced wholly or in large part by
repulsive electronic correlations. Electron pairs on Cuprate and the iron-based
pnictide and chalcogenide alternant lattices may interact with a strong
short-range Coulomb repulsion and much weaker longer range attractive tail.
Here we show that such interacting electrons can cooperate to produce a
superconducting state in which time-reversed electron pairs effectively avoid
the repulsive part but reside predominantly in the attractive region of the
potential. The alternant lattice structure is a key feature of such a
stabilization mechanism leading to the occurrence of high temperature
superconductivity with dx2 -y2 or sign alternating s-wave or s plus/minus
condensate symmetries.


title: Thermodynamics of two-component log-gases with alternating charges

abstract:
  We consider a one-dimensional gas of positive and negative unit charges
interacting via a logarithmic potential, which is in thermal equilibrium at the
(dimensionless) inverse temperature $\beta$. In a previous paper [Samaj, L.: J.
Stat. Phys. 105, 173-191 (2001)], the exact thermodynamics of the unrestricted
log-gas of pointlike charges was obtained using an equivalence with a
(1+1)-dimensional boundary sine-Gordon model. The present aim is to extend the
exact study of the thermodynamics to the log-gas on a line with alternating
$\pm$ charges. The formula for the ordered grand partition function is obtained
by using the exact results of the Thermodynamic Bethe ansatz. The complete
thermodynamics of the ordered log-gas with pointlike charges is checked by a
small-$\beta$ expansion and at the collapse point $\beta_c=1$. The inclusion of
a small hard core around particles permits us to go beyond the collapse point.
The differences between the unconstrained and ordered versions of the log-gas
are pointed out.


title:
On Integrable Structure and Geometric Transition in Supersymmetric Gauge
  Theories

abstract:
  We generalize the exact field theoretic correspondence proposed in
arXiv:1103.5726 and embed it into the context of refined topological string.
The correspondence originally proposed from the common integrable structures in
different field theories can be recast as a special limit of the refined
geometric transition relating open and closed topological string partition
functions. We realize the simplest examples of the correspondence explicitly in
terms of open-closed geometric transition.


title: On the Skitovich-Darmois theorem for a-adic solenoids

abstract:
  Let $X$ be a compact connected Abelian group. It is well-known that then
there exist topological automorphisms $\alpha_j, \beta_j $ of $X$ and
independent random variables $\xi_1$ and $\xi_2$ with values in $X$ and
distributions $\mu_1, \mu_2$ such that the linear forms $L_1 = \alpha_1\xi_1 +
\alpha_2\xi_2$ and $L_2 = \beta_1\xi_1 + \beta_2\xi_2$ are independent, whereas
$\mu_1$ and $\mu_2$ are not represented as convolutions of Gaussian and
idempotent distributions. This means that the Skitovich--Darmois theorem fails
for such groups. We prove that if we consider three linear forms of three
independent random variables taking values in $X$, where $X$ is an
${\boldsymbol a}$-adic solenoid, then the independence of the linear forms
implies that at least one of the distributions is idempotent. We describe all
such solenoids.


title: On the Genus number of Algebraic groups

abstract:
  We compute the number of orbit types for simply connected simple algebraic
groups over algebraically closed fields as well as for compact simply connected
simple Lie groups. We also compute the number of orbit types for the adjoint
action of these groups on their Lie algebras. We also prove that the genus
number of a connected reductive algebraic group coincides with the genus number
of its semisimple part.


title:
X-ray exploration of the outskirts of the nearby Centaurus cluster using
  Suzaku and Chandra

abstract:
  We present Suzaku observations of the Centaurus cluster out to 0.95r200,
taken along a strip to the north west. We have also used congruent Chandra
observations of the outskirts to resolve point sources down to a threshold flux
around 7 times lower than that achievable with just Suzaku data, considerably
reducing the systematic uncertainties in the cosmic X-ray background emission
in the outskirts. We find that the temperature decreases by a factor of 2 from
the peak temperature to the outskirts. The entropy profile demonstrates a
central excess (within 0.5r200) over the baseline entropy profile predicted by
simulations of purely gravitational hierarchical structure formation. In the
outskirts the entropy profile is in reasonable agreement with the baseline
entropy profile from Voit et al., but lies slightly below it. We find that the
pressure profile agrees with the universal pressure profile of Arnaud et al.
but lies slightly above it in the outskirts. The excess pressure and decrement
in entropy in the outskirts appear to be the result of an excess in the
measured gas density, possible due to gas clumping biasing the density
measurements high. The gas mass fraction rises and reaches the mean cosmic
baryon fraction at the largest radius studied. The clumping corrected gas mass
fraction agrees with the expected hot gas fraction and with the simulations of
Young et al. We further the analysis of Walker et al. which studied the shapes
of the entropy profiles of the clusters so far explored in the outskirts with
Suzaku. When scaled by the self similar entropy the Suzaku entropy profiles
demonstrate a central excess over the baseline entropy profile, and are
consistent with it at around r500 . However outside r500 the entropy profiles
tend to lie below the baseline entropy profile.


title: Low Dimensional Test Sets for Nonnegativity of Even Symmetric Forms

abstract:
  An important theorem by Timofte states that nonnegativity of real $n$-variate
symmetric polynomials of degree $d$ can be decided at test sets given by all
points with at most $\lfloor\frac{d}{2}\rfloor$ distinct components. However,
if the degree is sufficiently larger than the number of variables, then the
theorem obviously does not provide nontrivial information. Our approach is to
look at $(m + 1)$-dimensional subspaces of even symmetric forms of degree 4d,
at which nonnegativity can be checked at $(m - 1)$-points, i.e., points with at
most $m - 1 \in \N$ distinct components, where $m$ is independent of the degree
of the forms and better than Timofte's bound. Furthermore, for fixed $k \in
\N$, we tackle problems concerning the maximum dimension of such subspaces, at
which nonnegativity can be checked at all $k$-points, as well as the
geometrical and topological structure of the set of all forms whose
nonnegativity can be decided at all $k$-points.


title:
A candidate circumbinary Keplerian disk in G35.20-0.74 N: A study with
  ALMA

abstract:
  We report on ALMA observations of continuum and molecular line emission with
0.4" resolution towards the high-mass star forming region G35.20-0.74 N. Two
dense cores are detected in typical hot-core tracers, such as CH3CN, which
reveal velocity gradients. In one of these cores, the velocity field can be
fitted with an almost edge-on Keplerian disk rotating about a central mass of
18 Msun. This finding is consistent with the results of a recent study of the
CO first overtone bandhead emission at 2.3mum towards G35.20-0.74 N. The disk
radius and mass are >2500 au and 3 Msun. To reconcile the observed bolometric
luminosity (3x10^4 Lsun) with the estimated stellar mass of 18 Msun, we propose
that the latter is the total mass of a binary system.


title: Evolving Communities with Individual Preferences

abstract:
  The goal of this paper is to provide mathematically rigorous tools for
modelling the evolution of a community of interacting individuals. We model the
population by a measure space where the measure determines the abundance of
individual preferences. The preferences of an individual are described by a
measurable choice of a rough path. We focus on the case of weakly interacting
systems, where we are able to exhibit the existence and uniqueness of
consistent solutions. In general, solutions are continuum of interacting
threads analogous to the huge number of individual atomic trajectories that
together make up the motion of a fluid. The evolution of the population need
not be governed by any over-arching PDE. Although one can match the standard
nonlinear parabolic PDEs of McKean-Vlasov type with specific examples of
communities in this case. The bulk behaviour of the evolving population
provides a solution to the PDE. An important technical result is continuity of
the behaviour of the system with respect to changes in the measure assigning
weight to individuals. Replacing the deterministic measure with the empirical
distribution of an i.i.d. sample from it leads to many standard models, and
applying the continuity result allows easy proofs for propagation of chaos. The
rigorous underpinning presented here leads to uncomplicated models which have
wide applicability in both the physical and social sciences. We make no
presumption that the macroscopic dynamics are modelled by a PDE. This work
builds on the fine probability literature considering the limit behaviour for
systems where a large no of particles are interacting with independent
preferences; there is also work on continuum models with preferences described
by a semi-martingale measure. We mention some of the key papers.


title:
An analytic approach to the asymptotic variance of trie statistics and
  related structures

abstract:
  We develop analytic tools for the asymptotics of general trie statistics,
which are particularly advantageous for clarifying the asymptotic variance.
Many concrete examples are discussed for which new Fourier expansions are
given. The tools are also useful for other splitting processes with an
underlying binomial distribution. We specially highlight Philippe Flajolet's
contribution in the analysis of these random structures.


title: Cyclicity in families of circle maps

abstract:
  In this paper we will study families of circle maps of the form $x\mapsto
x+2\pi r + a f(x) \pmod{2\pi}$ and investigate how many periodic trajectories
maps from this family can have for a "typical" function $f$ provided the
parameter $a$ is small.


title:
On decay and blow-up of solutions for a singular nonlocal viscoelastic
  problem with a nonlinear source term

abstract:
  In this paper we consider a singular nonlocal viscoelastic problem with a
nonlinear source term and a possible damping term. We proved that if the
initial data enter into the stable set, the solution exists globally and decays
to zero with a more general rate, and if the initial data enter into the
unstable set, the solution with non-positive initial energy as well as positive
initial energy blows up in finite time. These are achieved by using the
potential well theory, the modified convexity method and the perturbed energy
method.


title:
On the efficiency of the new Italian Senate and the role of 5 Stars
  Movement: Comparison among different possible scenarios by means of a virtual
  Parliament model

abstract:
  The recent 2013 Italian elections are over and the situation that President
Napolitano will have to settle soon for the formation of the new government is
not the simplest one. After twenty years of bipolarism (more or less
effective), where we were accustomed to a tight battle between two great
political coalitions, the center-right and center-left, now, in the new
Parliament, we have four political formations. But is it really this result, as
it would seem to suggest our common sense, the prelude to an inevitable phase
of ungovernability? Can a Parliament with changing majorities in Senate to be
as efficient as a Parliament with a large majority in both the Houses? In this
short note we will try to answer these questions going beyond common sense and
analyzing the current political situation by means of a scientific, original
and innovative instrument, i.e. an "agent-based simulation". We show that the
situation is not so dramatic as it sounds, but it contains within itself
potential positive aspects, as long as one makes the most appropriate choices.


title: Periodic attractors of perturbed one dimensional maps

abstract:
  In this paper we investigate how many periodic attractors maps in a small
neighbourhood of a given map can have. For this purpose we develop new tools
which help to make uniform cross-ratio distortion estimates in a neighbourhood
of a map with degenerate critical points.


title:
Discrete flow mapping: transport of phase space densities on
  triangulated surfaces

abstract:
  Energy distributions of high frequency linear wave fields are often modelled
in terms of flow or transport equations with ray dynamics given by a
Hamiltonian vector field in phase space. Applications arise in underwater and
room acoustics, vibro-acoustics, seismology, electromagnetics, and quantum
mechanics. Related flow problems based on general conservation laws are used,
for example, in weather forecasting or molecular dynamics simulations.
Solutions to these flow equations are often large scale, complex and
high-dimensional, leading to formidable challenges for numerical approximation
methods. This paper presents an efficient and widely applicable method, called
discrete flow mapping, for solving such problems on triangulated surfaces. An
application in structural dynamics - determining the vibro-acoustic response of
a cast aluminium car body component - is presented.


title: Embeddings of locally compact hyperbolic groups into Lp-spaces

abstract:
  In the last years, there has been a large amount of research on embeddability
properties of finitely generated hyperbolic groups. In this paper, we elaborate
on the more general class of locally compact hyperbolic groups. We compute the
equivariant $L_p$-compression in a number of locally compact examples, such as
the groups $SO(n,1)$: by proving that the equivariant $L_p$-compression of a
locally compact compactly generated group is minimal for $p=2$, we calculate
all equivariant $L_p$-compressions of $SO(n,1)$. Next, we show that although
there are locally compact, non-discrete hyperbolic groups $G$ with Kazhdan's
property ($T$), it is true that any locally compact hyperbolic group admits a
proper affine isometric action on an $L_p$-space for $p$ larger than the
Ahlfors regular conformal dimension of $\partial G$. This answers a question
asked by Yves de Cornulier. Finally, we elaborate on the locally compact
version of property $(A)$ and show that, as in the discrete case, a locally
compact second countable group has property (A) if its non-equivariant
compression is greater than 1/2.


title: An Approximation Inequality for Continued Radicals and Power Forms

abstract:
  In this article we derive an approximation inequality for continued radicals,
generalizing an inequality of Herschfeld for continued square roots to
arbitrary radicals, which is useful in exploring convergence issues and
obtaining convergence rates. In fact, we generalize this inequality further to
encompass the more general continued power forms. We demonstrate the use of
this inequality by obtaining estimates for the convergence rates of several
continued radicals including the famous Ramanujan radical.


title: Electromagnetic Decay of Molecular States

abstract:
  Electromagnetic transitions from deformed structures based on $\alpha$
configurations or on heavier clusters are discussed, drawing the link between
multiparticle-multihole excited bands and cluster structures. Enhanced E2 and
E1 transitions are reviewed in the light nuclei, $^8$Be, $^{10}$Be, $^{12}$C,
$^{16}$O, $^{18}$O and heavier ones like $^{212}$Po. Connections between
cluster structures and superdeformed configurations in $^{36}$Ar and $^{40}$Ca
are discussed. What the cluster states based on heavier substructures like
$^{12}$C and $^{16}$O are concerned, recent results on the resonant radiative
capture reaction $^{12}$C($^{16}$O,$\gamma$)$^{28}$Si are presented, in
particular the strong decay mode involving the feeding of low-lying $^{28}$Si
1$^+$ and 2$^+$ T=1 states by enhanced M1 isovector transitions.


title:
Renormalization flow towards gravitational catalysis in the 3d
  Gross-Neveu model

abstract:
  Catalyzed symmetry breaking arises from a parametric enhancement of critical
fluctuations independently of the coupling strength. Symmetry-breaking
fermionic long-range fluctuations exhibit such an enhancement on negatively
curved spaces, as is known from mean-field studies. We study gravitational
catalysis from the viewpoint of the functional renormalization group using the
3d Gross-Neveu model as a specific example. We observe gravitational catalysis
towards a phase of broken discrete chiral symmetry both on a maximally
symmetric (AdS) and on a purely spatially curved manifold for constant negative
curvature (Lobachevsky plane). The resulting picture for gravitational
catalysis obtained from the renormalization flow is closely related to that of
magnetic catalysis. As an application, we estimate the curvature required for
subcritical systems of finite length to acquire a gravitionally catalyzed gap.


title:
Inhomogeneities in type Ib/c supernovae: An inverse Compton scattering
  origin of the X-ray emission

abstract:
  Inhomogeneities in a synchrotron source can severely affect the conclusions
drawn from observations regarding the source properties. However, their
presence is not always easy to establish, since several other effects can give
rise to similar observed characteristics. It is argued that the recently
observed broadening of the radio spectra and/or light curves in some of the
type Ib/c supernovae is a direct indication of inhomogeneities. As compared to
a homogeneous source, this increases the deduced velocity of the forward shock
and the observed correlation between total energy and shock velocity could in
part be due to a varying covering factor. The X-ray emission from at least some
type Ib/c supernovae is unlikely to be synchrotron radiation from an electron
distribution accelerated in a non-linear shock. Instead it is shown that the
observed correlation during the first few hundred days between the radio, X-ray
and bolometric luminosities indicates that the X-ray emission is inverse
Compton scattering of the photospheric photons. Inhomogeneities are consistent
with equipartition between electrons and magnetic fields in the optically thin
synchrotron emitting regions.


title:
Resolution enhancement in digital holography by self-extrapolation of
  holograms

abstract:
  It is generally believed that the resolution in digital holography is limited
by the size of the captured holographic record. Here, we present a method to
circumvent this limit by self-extrapolating experimental holograms beyond the
area that is actually captured. This is done by first padding the surroundings
of the hologram and then conducting an iterative reconstruction procedure. The
wavefront beyond the experimentally detected area is thus retrieved and the
hologram reconstruction shows enhanced resolution. To demonstrate the power of
this concept, we apply it to simulated as well as experimental holograms.


title: Muon g-2 vs LHC in Supersymmetric Models

abstract:
  There is more than 3 sigma deviation between the experimental and theoretical
results of the muon g-2. This suggests that some of the SUSY particles have a
mass of order 100 GeV. We study searches for those particles at the LHC with
particular attention to the muon g-2. In particular, the recent results on the
searches for the non-colored SUSY particles are investigated in the parameter
region where the muon g-2 is explained. The analysis is independent of details
of the SUSY models. Future prospects of the collider searches are also
discussed.


title: CERES for First-Order Schemata

abstract:
  The cut-elimination method CERES (for first- and higher-order classical
logic) is based on the notion of a characteristic clause set, which is
extracted from an LK-proof and is always unsatisfiable. A resolution refutation
of this clause set can be used as a skeleton for a proof with atomic cuts only
(atomic cut normal form). This is achieved by replacing clauses from the
resolution refutation by the corresponding projections of the original proof.
  We present a generalization of CERES (called CERESs) to first-order proof
schemata and define a schematic version of the sequent calculus called LKS, and
a notion of proof schema based on primitive recursive definitions. A method is
developed to extract schematic characteristic clause sets and schematic
projections from these proof schemata. We also define a schematic resolution
calculus for refutation of schemata of clause sets, which can be applied to
refute the schematic characteristic clause sets. Finally the projection
schemata and resolution schemata are plugged together and a schematic
representation of the atomic cut normal forms is obtained. A major benefit of
CERESs is the extension of cut-elimination to inductively defined proofs: we
compare CERESs with standard calculi using induction rules and demonstrate that
CERESs is capable of performing cut-elimination where traditional methods fail.
The algorithmic handling of CERESs is supported by a recent extension of the
CERES system.


title: Computing with Non-equilibrium Ratchets

abstract:
  Electronic ratchets transduce local spatial asymmetries into directed
currents in the absence of a global drain bias, by rectifying temporal signals
that reside far from thermal equilibrium. We show that the absence of a drain
bias can provide distinct energy advantages for computation, specifically,
reducing static dissipation in a logic circuit. Since the ratchet functions as
a gate voltage-controlled current source, it also potentially reduces the
dynamic dissipation associated with charging/discharging capacitors. In
addition, the unique charging mechanism eliminates timing related constraints
on logic inputs, in principle allowing for adiabatic charging. We calculate the
ratchet currents in classical and quantum limits, and show how a sequence of
ratchets can be cascaded to realize universal Boolean logic.


title:
Quantum Monte Carlo studies of edge magnetism in chiral graphene
  nanoribbons

abstract:
  We investigate chiral graphene nanoribbons using projective quantum Monte
Carlo simulations within the local Hubbard model description and study the
effects of electron-electron interactions on the electronic and magnetic
properties at the ribbon edges. Static and dynamical properties are analyzed
for nanoribbons of varying width and edge chirality, and compared to a
self-consistent Hartee-Fock mean-field approximation. Our results show that for
chiral ribbons of sufficient width, the spin correlations exhibit exceedingly
long correlation lengths, even between zigzag segments that are well separated
by periodic armchair regions. Characteristic enhancements in the magnetic
correlations for distinct ribbon widths and chiralities are associated with
energy gaps in the tight-binding limit of such ribbons. We identify specific
signatures in the local density of states and low- energy modes in the local
spectral function which directly relate to enhanced electronic correlations
along graphene nanoribbons and which can be accessed scanning tunneling
spectroscopy.


title: MHD Simulation of the Inner-Heliospheric Magnetic Field

abstract:
  Maps of the radial magnetic field at a heliocentric distance of ten solar
radii are used as boundary conditions in the MHD code CRONOS to simulate a 3D
inner-heliospheric solar wind emanating from the rotating Sun out to 1 AU. The
input data for the magnetic field are the result of solar surface flux
transport modelling using observational data of sunspot groups coupled with a
current sheet source surface model. Amongst several advancements, this allows
for higher angular resolution than that of comparable observational data from
synoptic magnetograms. The required initial conditions for the other MHD
quantities are obtained following an empirical approach using an inverse
relation between flux tube expansion and radial solar wind speed. The
computations are performed for representative solar minimum and maximum
conditions, and the corresponding state of the solar wind up to the Earths
orbit is obtained. After a successful comparison of the latter with
observational data, they can be used to drive outer-heliospheric models.


title:
Ultra-relativistic, neutrino driven flows in GRBs: A double transonic
  flow solution in Schwarzschild spacetime

abstract:
  The structure of a hydrodynamic, double transonic flow driven by neutrino
annihilation in the polar region of a Schwarzschild black hole is computed for
different energy deposition profiles. The requirement that both, the inflow
into the black hole and the outflow to infinity pass smoothly through their
sonic points fixes the stagnation radius and stagnation pressure. The
asymptotic power of the outflow is shown to be the integral of the energy
deposition rate above the stagnation radius. The outflow production efficiency
depends on the energy deposition profile, and is generally higher for shallower
profiles. Using recent calculations of the neutrino annihilation rate, we
estimate that over 50 percents of the total energy deposited above the horizon
can emerge in the form of a relativistic outflow at infinity. The continuous
creation of plasma during the expansion of the outflow leads to generation of a
large specific entropy. This has important implications for the prompt
photospheric emission in GRBs.


title: On the Use of Key Assignment Schemes in Authentication Protocols

abstract:
  Key Assignment Schemes (KASs) have been extensively studied in the context of
cryptographically-enforced access control, where derived keys are used to
decrypt protected resources. In this paper, we explore the use of KASs in
entity authentication protocols, where we use derived keys to encrypt
challenges. This novel use of KASs permits the efficient authentication of an
entity in accordance with an authentication policy by associating entities with
security labels representing specific services. Cryptographic keys are
associated with each security label and demonstrating knowledge of an
appropriate key is used as the basis for authentication. Thus, by controlling
the distribution of such keys, restrictions may be efficiently placed upon the
circumstances under which an entity may be authenticated and the services to
which they may gain access.
  In this work, we explore how both standardized protocols and novel
constructions may be developed to authenticate entities as members of a group
associated to a particular security label, whilst protecting the long-term
secrets in the system. We also see that such constructions may allow for
authentication whilst preserving anonymity, and that by including a trusted
third party we can achieve the authentication of individual identities and
authentication based on timestamps without the need for synchronized clocks.


title:
Commuting ordinary differential operators of arbitrary genus and
  arbitrary rank with polynomial coefficients

abstract:
  In this paper we construct examples of commuting ordinary scalar differential
operators with polynomial coefficients that are related to a spectral curve of
an arbitrary genus g>0 and to an arbitrary rank r>1 of the vector bundle of
common eigenfunctions of the commuting operators over the spectral curve. This
solves completely the well-known existence problem for commuting operators of
arbitrary genus and arbitrary rank with polynomial coefficients. The
constructed commuting operators of arbitrary rank r>1 and arbitrary genus g>0
are given explicitly, they are generated by the Chebyshev polynomials T_r (x).

categories: math.CA math-ph math.AG math.MP math.RA nlin.SI


title: StegTorrent: a Steganographic Method for the P2P File Sharing Service

abstract:
  The paper proposes StegTorrent a new network steganographic method for the
popular P2P file transfer service-BitTorrent. It is based on modifying the
order of data packets in the peer-peer data exchange protocol. Unlike other
existing steganographic methods that modify the packets' order it does not
require any synchronization. Experimental results acquired from prototype
implementation proved that it provides high steganographic bandwidth of up to
270 b/s while introducing little transmission distortion and providing
difficult detectability.


title:
The improvement about convergence properties for pairwise NQD random
  sequences

abstract:
  In this paper, the improvement about the generalized Kolmogorov-type three
series theorem, in the case of NQD random variables, is obtained by different
method. Furthermore, the generalized Kolmogorov-type three series theorem is
simplified. From the simplified theorem, related results in Wu (Acta. Math.
Sinica. 45(3), 617-624, 2002) and some main results in Shi (Acta. Math. Appl.
Sin., 34(1), 122-130, 2011) and Li et al. (J. Math. Anal. Appl., 344, 741-747,
2008) are also discussed or improved in the article.


title: Statistical Mechanics Approach to Sparse Noise Denoising

abstract:
  Reconstruction fidelity of sparse signals contaminated by sparse noise is
considered. Statistical mechanics inspired tools are used to show that the
l1-norm based convex optimization algorithm exhibits a phase transition between
the possibility of perfect and imperfect reconstruction. Conditions
characterizing this threshold are derived and the mean square error of the
estimate is obtained for the case when perfect reconstruction is not possible.
Detailed calculations are provided to expose the mathematical tools to a wide
audience.


title:
Sensitivity analysis of a time-delayed thermo-acoustic system via an
  adjoint-based approach

abstract:
  We apply adjoint-based sensitivity analysis to a time-delayed thermo-acoustic
system: a Rijke tube containing a hot wire. We calculate how the growth rate
and frequency of small oscillations about a base state are affected either by a
generic passive control element in the system (the structural sensitivity
analysis) or by a generic change to its base state (the base-state sensitivity
analysis). We illustrate the structural sensitivity by calculating the effect
of a second hot wire with a small heat release parameter. In a single
calculation, this shows how the second hot wire changes the growth rate and
frequency of the small oscillations, as a function of its position in the tube.
We then examine the components of the structural sensitivity in order to
determine the passive control mechanism that has the strongest influence on the
growth rate. We find that a force applied to the acoustic momentum equation in
the opposite direction to the instantaneous velocity is the most stabilizing
feedback mechanism. We also find that its effect is maximized when it is placed
at the downstream end of the tube. This feedback mechanism could be supplied,
for example, by an adiabatic mesh. We illustrate the base-state sensitivity by
calculating the effects of small variations in the damping factor, the
heat-release time-delay coefficient, the heat-release parameter, and the hot
wire location. The successful application of sensitivity analysis to
thermo-acoustics opens up new possibilities for the passive control of
thermo-acoustic oscillations by providing gradient information that can be
combined with constrained optimization algorithms in order to reduce linear
growth rates.


title: The Small-Maturity Heston Forward Smile

abstract:
  In this paper we investigate the asymptotics of forward-start options and the
forward implied volatility smile in the Heston model as the maturity approaches
zero. We prove that the forward smile for out-of-the-money options explodes and
compute a closed-form high-order expansion detailing the rate of the explosion.
Furthermore the result shows that the square-root behaviour of the variance
process induces a singularity such that for certain parameter configurations
one cannot obtain high-order out-of-the-money forward smile asymptotics. In the
at-the-money case a separate model-independent analysis shows that the
small-maturity limit is well defined for any Ito diffusion. The proofs rely on
the theory of sharp large deviations (and refinements) and incidentally we
provide an example of degenerate large deviations behaviour.


title: Cohesion-decohesion asymmetry in geckos

abstract:
  Lizards and insects can strongly attach to walls and then detach applying
negligible additional forces. We propose a simple mechanical model of this
phenomenon which implies active muscle control. We show that the detachment
force may depend not only on the properties of the adhesive units, but also on
the elastic interaction among these units. By regulating the scale of such
cooperative interaction, the organism can actively switch between two modes of
adhesion: delocalized (pull off) and localized (peeling).


title: The space density of magnetic cataclysmic variables

abstract:
  We use the complete, X-ray flux-limited ROSAT Bright Survey (RBS) to measure
the space density of magnetic cataclysmic variables (mCVs). The survey provides
complete optical identification of all sources with count rate >0.2/s over half
the sky ($|b|>30^\circ$), and detected 6 intermediate polars (IPs) and 24
polars. If we assume that the 30 mCVs included in the RBS are representative of
the intrinsic population, the space density of mCVs is $8^{+4}_{-2} \times
10^{-7}\,{\rmpc^{-3}}$. Considering polars and IPs separately, we find
$\rho_{polar}=5^{+3}_{-2} \times 10^{-7}\,{\rm pc^{-3}}$ and
$\rho_{IP}=3^{+2}_{-1} \times 10^{-7}\,{\rm pc^{-3}}$. Allowing for a 50%
high-state duty cycle for polars (and assuming that these systems are below the
RBS detection limit during their low states) doubles our estimate of
$\rho_{polar}$ and brings the total space density of mCVs to $1.3^{+0.6}_{-0.4}
\times 10^{-6}\,{\rm pc^{-3}}$. We also place upper limits on the sizes of
faint (but persistent) mCV populations that might have escaped detection in the
RBS. Although the large uncertainties in the $\rho$ estimates prevent us from
drawing strong conclusions, we discuss the implications of our results for the
evolutionary relationship between IPs and polars, the fraction of CVs with
strongly magnetic white dwarfs (WDs), and for the contribution of mCVs to
Galactic populations of hard X-ray sources at $L_X \ga 10^{31} {\rm erg/s}$.
Our space density estimates are consistent with the very simple model where
long-period IPs evolve into polars and account for the whole short-period polar
population. We find that the fraction of WDs that are strongly magnetic is not
significantly higher for CV primaries than for isolated WDs. Finally, the space
density of IPs is sufficiently high to explain the bright, hard X-ray source
population in the Galactic Centre.


title:
Comparison of solar horizontal velocity fields from SDO/HMI and Hinode
  data

abstract:
  The measurement of the Sun's surface motions with a high spatial and temporal
resolution is still a challenge. We wish to validate horizontal velocity
measurements all over the visible disk of the Sun from Solar Dynamics
Observatory/ Helioseismic and Magnetic Imager (SDO/HMI) data. Horizontal
velocity fields are measured by following the proper motions of solar granules
using a newly developed version of the Coherent Structure Tracking (CST) code.
The comparison of the surface flows measured at high spatial resolution
(Hinode, 0.1 arcsec) and low resolution (SDO/HMI, 0.5 arcsec) allows us to
determine corrections to be applied to the horizontal velocity measured from
HMI white light data. We derive horizontal velocity maps with spatial and
temporal resolutions of respectively 2.5 Mm and 30 min. From the two components
of the horizontal velocity Vx and Vy measured in the sky plane and the
simultaneous line of sight component from SDO/HMI dopplergrams v_D, we derive
the spherical velocity components (Vr, Vtheta, Vphi). The azimuthal component
Vphi gives the solar differential rotation with a high precision (+-0.037km/s)
from a temporal sequence of only three hours. By following the proper motions
of the solar granules, we can revisit the dynamics of the solar surface at high
spatial and temporal resolutions from hours to months and years with the SDO
data.


title:
The IMACS Cluster Building Survey: II. Spectral Evolution of Galaxies in
  the Epoch of Cluster Assembly

abstract:
  The IMACS Cluster Building Survey (ICBS) provides spectra of ~2200 galaxies
0.31<z<0.54 in 5 rich clusters (R <= 5 Mpc) and the field. Infalling,
dynamically cold groups with tens of members account for approximately half of
the supercluster population, contributing to a growth in cluster mass of ~100%
by today. The ICBS spectra distinguish non-starforming (PAS) and poststarburst
(PSB) from starforming galaxies -- continuously starforming (CSF) or
starbursts, (SBH or SBO), identified by anomalously strong H-delta absorption
or [O II] emission. For the infalling cluster groups and similar field groups,
we find a correlation between PAS+PSB fraction and group mass, indicating
substantial "preprocessing" through quenching mechanisms that can turn
starforming galaxies into passive galaxies without the unique environment of
rich clusters. SBH + SBO starburst galaxies are common, and they maintain an
approximately constant ratio (SBH+SBO)/CSF ~ 25% in all environments -- from
field, to groups, to rich clusters. Similarly, while PSB galaxies strongly
favor denser environments, PSB/PAS ~ 10-20% for all environments. This result,
and their timescale tau < 500 Myr, indicates that starbursts are not signatures
of a quenching mechanism that produces the majority of passive galaxies. We
suggest instead that starbursts and poststarbursts signal minor mergers and
accretions, in starforming and passive galaxies, respectively, and that the
principal mechanisms for producing passive systems are (1) early major mergers,
for elliptical galaxies, and (2) later, less violent processes -- such as
starvation and tidal stripping, for S0 galaxies.


title:
Optimal least-squares estimators of the diffusion constant from a single
  Brownian trajectory

abstract:
  Modern developments in microscopy and image processing are revolutionising
areas of physics, chemistry, and biology as nanoscale objects can be tracked
with unprecedented accuracy. However, the price paid for having a direct
visualisation of a single particle trajectory with high temporal and spatial
resolution is a consequent lack of statistics. This naturally calls for
reliable analytical tools which will allow one to extract the properties
specific to a statistical ensemble from just a single trajectory. In this
article we briefly survey different analytical methods currently used to
determine the ensemble average diffusion coefficient from single particle data
and then focus specifically on weighted least-squares estimators, seeking the
weight functions for which such estimators are ergodic. Finally, we address the
question of the effects of disorder on such estimators.


title: A note on pricing of contingent claims under G-expectation

abstract:
  In this paper, we study the pricing of contingent claims under G-expectation.
In order to accomodate volatility uncertainty, the price of the risky security
is supposed to governed by a general linear stochastic differential equation
(SDE) driven by G-Brownian motion. Utilizing the recently developed results of
Backward SDE driven by G-Brownian motion, we obtain the superhedging and
suberhedging prices of a given contingent claim. Explicit results in the
Markovian case are also derived.


title: Tame and Wild Scoring Play Games

abstract:
  In this paper, we will be proving mathematically that scoring play
combinatorial game theory covers all combinatorial games. That is, there is a
sub-set of scoring play games that are identical to the set of normal play
games, and a different sub-set that is identical to the set of mis\`ere play
games.
  This proves conclusively, that scoring play combinatorial game theory is a
complete theory for combinatorial games, and that every combinatorial game,
regardless of the rule-set, can be analysed using scoring play combinatorial
game theory.


title: Positive Topological Quantum Field Theories

abstract:
  We propose a new notion of positivity for topological field theories (TFTs),
based on S. Eilenberg's concept of completeness for semirings. We show that a
complete ground semiring, a system of fields on manifolds and a system of
action functionals on these fields determine a positive TFT. The main feature
of such a theory is a semiring-valued topologically invariant state sum that
satisfies a gluing formula. The abstract framework has been carefully designed
to cover a wide range of phenomena. For instance, we derive Polya's counting
theory in combinatorics from state sum identities in a suitable positive TFT.
Several other concrete examples are discussed, among them Novikov signatures of
fiber bundles over spacetimes and arithmetic functions in number theory. In the
future, we will employ the framework presented here in constructing a new
differential topological invariant that detects exotic smooth structures on
spheres.


title: Simple Schemas for Unordered XML

abstract:
  We consider unordered XML, where the relative order among siblings is
ignored, and propose two simple yet practical schema formalisms: disjunctive
multiplicity schemas (DMS), and its restriction, disjunction-free multiplicity
schemas (MS). We investigate their computational properties and characterize
the complexity of the following static analysis problems: schema
satisfiability, membership of a tree to the language of a schema, schema
containment, twig query satisfiability, implication, and containment in the
presence of schema. Our research indicates that the proposed formalisms retain
much of the expressiveness of DTDs without an increase in computational
complexity.


title:
On the symmetric equiaffine hyperspheres and the minimal symmetric
  Lagrangian submanifolds

abstract:
  In this paper, a correspondence via duality is established between the set of
locally strongly convex symmetric equiaffine hyperspheres and the set of
minimal symmetric Lagrangian submanifolds in a certain complex space form. By
using this correspondence theorem, we are able to provide an alternative proof
of the classification theorem for the locally strongly convex equiaffine
hypersurfaces with parallel Fubini-Pick forms, which has been established
recently by Z.J. Hu etc in a totally different way.


title: Biharmonic surfaces with parallel mean curvature in complex space forms

abstract:
  We classify complete biharmonic surfaces with parallel mean curvature vector
field and non-negative Gaussian curvature in complex space forms.


title:
Singlet Portal Extensions of the Standard Seesaw Models to a Dark Sector
  with Local Dark Symmetry

abstract:
  Assuming ({\it i}) the seesaw mechanism works for neutrino masses and
mixings, ({\it ii}) dark matter is absolutely stable due to unbroken $U(1)_X$
dark gauge symmetry, and ({\it iii}) the singlet fields ($H^\dagger H$ and
$N_R$) are portal to the dark sector, we construct a simple model which is
consistent with all the cosmological observations as well as terrestrial
experiments available as of now, including leptogenesis, extra dark radiation
of $\sim 8 %$ (resulting in $N_{\rm eff} = 3.130$ the effective number of
neutrino species), Higgs inflation, small and large scale structure formation,
and current relic density of scalar dark matter ($X$). The electroweak vacuum
of this model is stable up to Planck scale for $m_H = 125$ GeV without any
other new physics. The Higgs signal strength is equal to one as in the standard
model for unbroken $U(1)_X$ case with a scalar dark matter, but it could be
less than one independent of decay channels if the dark matter is a dark sector
fermion or if $U(1)_X$ is spontaneously broken, because of a mixing with a new
neutral scalar boson in the models. Detailed study of Higgs properties at the
LHC would shed light on the models described in this work.


title:
On representation of boundary integrals involving the mean curvature for
  mean-convex domains

abstract:
  Given a mean-convex domain $\Omega\subset \R^n$ with boundary of class
$C^{2,1}$, we provide a representation formula for a boundary integral of the
type \[ \int_{\partial \Omega} f(k(x)) \, d\mathcal{H}^{n-1} \] where $k\geq 0$
is the mean curvature of $\partial \Omega$ and $f$ is non-increasing and
sufficiently regular, in terms of volume integrals and defect measure on the
ridge set.


title: K-Shell Photoabsorption of Magnesium Ions

abstract:
  X-ray photoabsorption cross sections have been computed for all magnesium
ions using the $R$-matrix method. A comparison with the other available data
for Mg II-Mg X shows good qualitative agreement in the resultant resonance
shapes. However, for the lower ionization stages, and for singly-ionized Mg II
in particular, the previous $R$-matrix results (Witthoeft et al.2009; Witthoeft
et al. 2011) overestimate the K-edge position due to the neglect of important
orbital relaxation effects, and a global shift downward in photon energy of
those cross sections is therefore warranted. We have found that the cross
sections for Mg I and Mg II are further complicated by the M-shell ($n=3$)
occupancy. As a result, the treatment of spectator Auger decay of
$1s\rightarrow np$ resonances using a method based on multichannel quantum
defect theory and an optical potential becomes problematic, making it necessary
to implement an alternative, approximate treatment of Auger decay for neutral
Mg. The new cross sections are used to fit the Mg K edge in XMM-Newton spectra
of the low-mass X-ray binary GS 1826-238, where most of the interstellar Mg is
found to be in ionized form.


title: Zirconium, Barium, Lanthanum and Europium Abundances in Open Clusters

abstract:
  We present an analysis of the s-process elements Zr, Ba, and La and the
r-process element Eu in a sample of 50 stars in 19 open clusters. Stellar
abundances of each element are based on measures of a minimum of two lines per
species via both equivalent width and spectrum synthesis techniques. We
investigate cluster mean neutron-capture abundance trends as a function of
cluster age and location in the Milky Way disk and compare them to results
found in other studies in the literature. We find a statistically significant
trend of increasing cluster [Ba/Fe] as a function of decreasing cluster age, in
agreement with recent findings for other open cluster samples, supporting the
increased importance of low-mass asymptotic giant branch stars to the
generation of s-process elements. However, the other s-process elements,
[La/Fe] and [Zr/Fe], do not show similar dependences, in contrast to
theoretical expectations and the limited observational data from other studies.
Conversely, cluster [Eu/Fe] ratios show a slight increase with increasing
cluster age, although with marginal statistical significance. Ratios of
[s/r]-process abundances, [Ba/Eu] and [La/Eu], however, show more clearly the
increasing efficiency of s-process relative to r-process enrichment in open
cluster chemical evolution, with significant increases among younger clusters.
Last, cluster neutron-capture element abundances appear to be independent of
Galactocentric distance. We conclude that a homogeneous analysis of a larger
sample of open clusters is needed to resolve the apparent discrepant
conclusions between different studies regarding s-process element abundance
trends with age to better inform models of galactic chemical evolution.


title: On the uniqueness of the equation for state-vector collapse

abstract:
  The linearity of quantum mechanics leads, under the assumption that the wave
function offers a complete description of reality, to grotesque situations
famously known as Schroedinger's cat. Ways out are either adding elements of
reality or replacing the linear evolution by a nonlinear one. Models of
spontaneous wave function collapses took the latter path. The way such models
are constructed leaves the question, whether such models are in some sense
unique, i.e. whether the nonlinear equations replacing Schroedinger's equation,
are uniquely determined as collapse equations. Various people worked on
identifying the class of nonlinear modifications of the Schroedinger equation,
compatible with general physical requirements. Here we identify the most
general class of continuous wavefunction evolutions under the assumption of
no-faster-than-light signalling.


title: Charge Order Breaks Magnetic Symmetry in Molecular Quantum Spin Chains

abstract:
  Charge order affects most of the electronic properties but is believed not to
alter the spin arrangement since the magnetic susceptibility remains unchanged.
We present electron-spin-resonance experiments on quasi-one-dimensional
(TMTTF)2X salts (X= PF6, AsF6 and SbF6), which reveal that the magnetic
properties are modified below TCO when electronic ferroelectricity sets in. The
coupling of anions and organic molecules rotates the g-tensor out of the
molecular plane creating magnetically non-equivalent sites on neighboring
chains at domain walls. Due to anisotropic Zeeman interaction a novel magnetic
interaction mechanism in the charge-ordered state is observed as a doubling of
the rotational periodicity of Delta H.


title: Non-Abelian Gauge Fields in Photonic Cavities and Photonic Superfluids

abstract:
  We show that the interplay between the structure anisotropy and the energy
splitting between the TE and TM modes of a microcavity leads to the appearance
of a gauge field for a propagating polariton condensate. This field is analog
with a spin-orbit coupling and the field texture can be tuned by rotating the
sample and ranges continuously from a Rashba to a monopolar field. In the
linear regime, the monopolar field leads to a remarkable focusing effect. In
the interacting regime, the effective spin-orbit coupling induces a breakdown
of superfluidity. The spatially homogeneous flows become unstable and
dynamically evolve into textured ground states such as stripes and domain
walls.


title:
Search for heavy resonances, and resonant diboson production with the
  ATLAS detector

abstract:
  Heavy resonances decaying into a pair of fundamental particles such as $jj$,
$\ell^+\ell^-$, $\gamma\gamma$, and $\ell\nu$, are among the most common
features to search for phenomena beyond the standard model (SM). Electroweak
boson pair production, such as $WW$ or $ZZ$ with subsequent decays to
$\ell\nu\ell'\nu'$ and $\ell\ell jj$ respectively, is a powerful test of the
spontaneously broken gauge symmetry of the SM and can be also used to search
for phenomena beyond the SM. There is a wide spectrum of theoretical models
predicting these kinds of resonant signatures. This note covers several
searches for these new phenomena conducted within ATLAS in 2011 and 2012 for
the LHC 7 and 8 TeV center of mass energies respectively. No significant
deviations from the SM have been observed and therefore, limits are set on the
characteristic parameters of several new physics models. These benchmark models
include new heavy $Z'/W'$ gauge bosons, chiral excitation of the SM weak gauge
bosons, $Z^*/W^*$ Randal-Sundrum and ADD gravitons, Composite models for
quarks, e.g. $q^*$ with substructure scale $\Lambda$, Quantum black holes,
TeV$^{-1}$ Kaluza-Klein excitation of $\gamma/Z$ and more.


title: Iterative Isotonic Regression

abstract:
  This article introduces a new nonparametric method for estimating a
univariate regression function of bounded variation. The method exploits the
Jordan decomposition which states that a function of bounded variation can be
decomposed as the sum of a non-decreasing function and a non-increasing
function. This suggests combining the backfitting algorithm for estimating
additive functions with isotonic regression for estimating monotone functions.
The resulting iterative algorithm is called Iterative Isotonic Regression
(I.I.R.). The main technical result in this paper is the consistency of the
proposed estimator when the number of iterations $k_n$ grows appropriately with
the sample size $n$. The proof requires two auxiliary results that are of
interest in and by themselves: firstly, we generalize the well-known
consistency property of isotonic regression to the framework of a non-monotone
regression function, and secondly, we relate the backfitting algorithm to Von
Neumann's algorithm in convex analysis.


title:
On the Design of Channel Estimators for given Signal Estimators and
  Detectors

abstract:
  The fundamental task of a digital receiver is to decide the transmitted
symbols in the best possible way, i.e., with respect to an appropriately
defined performance metric. Examples of usual performance metrics are the
probability of error and the Mean Square Error (MSE) of a symbol estimator. In
a coherent receiver, the symbol decisions are made based on the use of a
channel estimate. This paper focuses on examining the optimality of usual
estimators such as the minimum variance unbiased (MVU) and the minimum mean
square error (MMSE) estimators for these metrics and on proposing better
estimators whenever it is necessary. For illustration purposes, this study is
performed on a toy channel model, namely a single input single output (SISO)
flat fading channel with additive white Gaussian noise (AWGN). In this way,
this paper highlights the design dependencies of channel estimators on target
performance metrics.


title:
Anyonic quantum spin chains: Spin-1 generalizations and topological
  stability

abstract:
  There are many interesting parallels between systems of interacting
non-Abelian anyons and quantum magnetism, occuring in ordinary SU(2) quantum
magnets. Here we consider theories of so-called su(2)_k anyons, well-known
deformations of SU(2), in which only the first k+1 angular momenta of SU(2)
occur. In this manuscript, we discuss in particular anyonic generalizations of
ordinary SU(2) spin chains with an emphasis on anyonic spin S=1 chains. We find
that the overall phase diagrams for these anyonic spin-1 chains closely mirror
the phase diagram of the ordinary bilinear-biquadratic spin-1 chain including
anyonic generalizations of the Haldane phase, the AKLT construction, and
supersymmetric quantum critical points. A novel feature of the anyonic spin-1
chains is an additional topological symmetry that protects the gapless phases.
Distinctions further arise in the form of an even/odd effect in the deformation
parameter k when considering su(2)_k anyonic theories with k>4, as well as for
the special case of the su(2)_4 theory for which the spin-1 representation
plays a special role. We also address anyonic generalizations of spin-1/2
chains with a focus on the topological protection provided for their gapless
ground states. Finally, we put our results into context of earlier
generalizations of SU(2) quantum spin chains, in particular so-called (fused)
Temperley-Lieb chains.


title: Non-Fault Tolerant T-Gates for the [7,1,3] Quantum Error Correction Code

abstract:
  We simulate the implementation of a T-gate, or $\frac{\pi}{8}$-gate, for a
[7,1,3] encoded logical qubit in a non-equiprobable error environment. We
demonstrate that the use of certain non-fault tolerant methods in the
implementation may nevertheless enable reliable quantum computation while
reducing basic resource consumption. Reliability is determined by calculating
gate fidelities for the one-qubit logical gate. Specifically, we show that
despite using a non-fault tolerant procedures in constructing a logical zero
ancilla to implement the T-gate the gate fidelity of the logical gate, after
perfect error correction, has no first order error terms. Meaning, any errors
that may have occurred during implementation are `correctable' and fault
tolerance may still be achieved.


title:
A massive parsec-scale dust ring nebula around the yellow hypergiant
  Hen3-1379

abstract:
  On the basis of far-infrared images obtained by the Herschel Space
Observatory, we report the discovery of a large and massive dust shell around
the yellow hypergiant Hen3-1379 . The nebula appears as a detached ring of 1 pc
diameter which contains 0.17 Msun of dust. We estimate the total gas mass to be
7 Msun, ejected some 16000 years ago. The ring nebula is very similar to
nebulae found around luminous blue variables (LBVs) except it is not
photoionized. We argued that Hen3-1379 is in a pre-LBV stage, providing direct
evidence that massive LBV ring nebulae can be ejected during the red supergiant
phase.


title:
A Multilingual Semantic Wiki Based on Attempto Controlled English and
  Grammatical Framework

abstract:
  We describe a semantic wiki system with an underlying controlled natural
language grammar implemented in Grammatical Framework (GF). The grammar
restricts the wiki content to a well-defined subset of Attempto Controlled
English (ACE), and facilitates a precise bidirectional automatic translation
between ACE and language fragments of a number of other natural languages,
making the wiki content accessible multilingually. Additionally, our approach
allows for automatic translation into the Web Ontology Language (OWL), which
enables automatic reasoning over the wiki content. The developed wiki
environment thus allows users to build, query and view OWL knowledge bases via
a user-friendly multilingual natural language interface. As a further feature,
the underlying multilingual grammar is integrated into the wiki and can be
collaboratively edited to extend the vocabulary of the wiki or even customize
its sentence structures. This work demonstrates the combination of the existing
technologies of Attempto Controlled English and Grammatical Framework, and is
implemented as an extension of the existing semantic wiki engine AceWiki.


title: Constraint analysis for variational discrete systems

abstract:
  A canonical formalism and constraint analysis for discrete systems subject to
a variational action principle are devised. The formalism is equivalent to the
covariant formulation, encompasses global and local discrete time evolution
moves and naturally incorporates both constant and evolving phase spaces, the
latter of which is necessary for a time varying discretization. The different
roles of constraints in the discrete and the conditions under which they are
first or second class and/or symmetry generators are clarified. The (non-)
preservation of constraints and the symplectic structure is discussed; on
evolving phase spaces the number of constraints at a fixed time step depends on
the initial and final time step of evolution. Moreover, the definition of
observables and a reduced phase space is provided; again, on evolving phase
spaces the notion of an observable as a propagating degree of freedom requires
specification of an initial and final step and crucially depends on this
choice, in contrast to the continuum. However, upon restriction to translation
invariant systems, one regains the usual time step independence of canonical
concepts. This analysis applies, e.g., to discrete mechanics, lattice field
theory, quantum gravity models and numerical analysis.


title: On integrable generalizations of the pentagram map

abstract:
  In this paper we prove that the generalization to $\mathbb{RP}^n$ of the
pentagram map defined in \cite{KS} is invariant under certain scalings for any
$n$. This property allows the definition of a Lax representation for the map,
to be used to establish its integrability.


title:
Dealing with Run-Time Variability in Service Robotics: Towards a DSL for
  Non-Functional Properties

abstract:
  Service robots act in open-ended, natural environments. Therefore, due to
combinatorial explosion of potential situations, it is not possible to foresee
all eventualities in advance during robot design. In addition, due to limited
resources on a mobile robot, it is not feasible to plan any action on demand.
Hence, it is necessary to provide a mechanism to express variability at
design-time that can be efficiently resolved on the robot at run-time based on
the then available information. In this paper, we introduce a DSL to express
run- time variability focused on the execution quality of the robot (in terms
of non-functional properties like safety and task efficiency) under changing
situations and limited resources. We underpin the applicability of our approach
by an example integrated into an overall robotics architecture.


title: Alfven waves in a partially ionized two-fluid plasma

abstract:
  Alfv\'en waves are a particular class of magnetohydrodynamic waves relevant
in many astrophysical and laboratory plasmas. In partially ionized plasmas the
dynamics of Alfv\'en waves is affected by the interaction between ionized and
neutral species. Here we study Alfv\'en waves in a partially ionized plasma
from the theoretical point of view using the two-fluid description. We consider
that the plasma is composed of an ion-electron fluid and a neutral fluid, which
interact by means of particle collisions. To keep our investigation as general
as possible we take the neutral-ion collision frequency and the ionization
degree as free parameters. First, we perform a normal mode analysis. We find
the modification due to neutral-ion collisions of the wave frequencies and
study the temporal and spatial attenuation of the waves. In addition, we
discuss the presence of cut-off values of the wavelength that constrain the
existence of oscillatory standing waves in weakly ionized plasmas. Later, we go
beyond the normal mode approach and solve the initial-value problem in order to
study the time-dependent evolution of the wave perturbations in the two fluids.
An application to Alfv\'en waves in the low solar atmospheric plasma is
performed and the implication of partial ionization for the energy flux is
discussed.


title:
A possible evolutionary scenario of highly magnetized
  super-Chandrasekhar white dwarfs: progenitors of peculiar type Ia supernovae

abstract:
  Several recently discovered peculiar type Ia supernovae seem to demand an
altogether new formation theory that might help explain the puzzling
dissimilarities between them and the standard type Ia supernovae. The most
striking aspect of the observational analysis is the necessity of invoking
super-Chandrasekhar white dwarfs having masses ~ 2.1-2.8M_sun, M_sun being the
mass of Sun, as their most probable progenitors. Strongly magnetized white
dwarfs having super-Chandrasekhar masses were already established to be
potential candidates for the progenitors of peculiar type Ia supernovae. Owing
to the Landau quantization of the underlying electron degenerate gas,
theoretical results yielded the observationally inferred mass range. Here we
sketch a possible evolutionary scenario by which super-Chandrasekhar white
dwarfs could be formed by accretion on to a commonly observed magnetized white
dwarf, invoking the phenomenon of flux freezing. This opens the multiple
possible evolutions ending in supernova explosions of super-Chandrasekhar white
dwarfs having masses within the range stated above. We point out that our
proposal has observational support, like, the recent discovery of a large
number of magnetized white dwarfs by SDSS.


title: Variational views of stokeslets and stresslets

abstract:
  In this paper we present a self-contained variational theory of the layer
potentials for the Stokes problem on Lipschitz boundaries. We use these weak
definitions to show how to prove the main theorems about the associated
Calder\'on projector. Finally, we relate these variational definitions to the
integral forms. Instead of working these relations from scratch, we show some
formulas parametrizing the Stokes layer potentials in terms of those for the
Lam\'e and Laplace operators. While all the results in this paper are well
known for smooth domains, and most might be known for non-smooth domains, the
approach is novel a gives a solid structure to the theory of Stokes layer
potentials.


title: Helical glasses near ferromagnetic quantum criticality

abstract:
  We study the effects of quenched charge disorder on the phase reconstruction
near itinerant ferromagnetic quantum critical points in three spatial
dimensions. Combining a replica disorder average with a fermionic version of
the quantum order-by-disorder mechanism, we show that weak disorder
destabilizes the ferromagnetic state and enhances the susceptibility towards
incommensurate, spiral magnetic ordering. The Goldstone modes of the spiral
phase are governed by a 3d-XY model. The induced disorder in the pitch of the
spiral generates a random anisotropy for the Goldstone modes, inducing vortex
lines in the phase of the helical order and rendering the magnetic correlations
short ranged with a strongly anisotropic correlation length.


title: Symmetry protected topological phases from decorated domain walls

abstract:
  Symmetry protected topological (SPT) phases with unusual edge excitations can
emerge in strongly interacting bosonic systems and are classified in terms of
the cohomology of their symmetry groups. Here we provide a physical picture
that leads to an intuitive understanding and wavefunctions for several SPT
phases in d=1,2,3 dimensions. We consider symmetries which include a Z_2
subgroup, that allows us to define domain walls. While the usual disordered
phase is obtained by proliferating domain walls, we show that SPT phases are
realized when these proliferated domain walls are `decorated', i.e. are
themselves SPT phases in one lower dimension. For example a d=2 SPT phase with
Z_2 and time reversal symmetry is realized when the domain walls that
proliferate are themselves in a d=1 Haldane/AKLT state. Similarly, d=3 SPT
phases with Z_2 * Z_2 symmetry emerges when domain walls in a d=2 SPT with Z_2
symmetry are proliferated. The resulting ground states are shown to be
equivalent to that obtained from group cohomology and field theoretical
techniques. The result of gauging the Z_2 symmetry in these phases is also
discussed. An extension of this construction where time reversal plays the role
of Z_2 symmetry allows for a discussion of several d=3 SPT phases. This
construction also leads to a new perspective on some well known d=1 SPT phases,
from which exactly soluble parent Hamiltonians may be derived.


title:
The SDSS-III Baryonic Oscillation Spectroscopic Survey: Constraints on
  the Integrated Sachs Wolfe effect

abstract:
  In the context of the study of the Integrated Sachs Wolfe effect (ISW), we
construct a template of the projected density distribution up to $z\simeq 0.7$
by using the Luminous Galaxies (LGs) from the Sloan Digital Sky Survey DR8. We
use a photo-z catalogue trained with more than a hundred thousand galaxies from
BOSS in the SDSS DR8 imaging area. We consider two different LG samples whose
selection matches that of SDSS-III/BOSS: the LOWZ sample ($z\in [0.15,0.5]$)
and the CMASS sample ($z\in[0.4,0.7]$). When building the LG density maps we
use the information from star density, survey footprint, seeing conditions, sky
emission, dust extinction and airmass to explore the impact of these artifacts
on the two LG samples. In agreement with previous studies, we find that the
CMASS sample is particularly sensitive to Galactic stars, which dominate the
contribution to the auto-angular power spectrum below $\ell=7$. Other potential
systematics affect mostly the low multipole range ($\ell\in[2,7]$), but leave
fluctuations on smaller scales practically unchanged. The resulting power
spectra in the multipole range $\ell\in[2,100]$ for the LOWZ, CMASS and
LOWZ+CMASS samples are compatible with linear $\Lambda$CDM expectations and
constant bias values of $b=1.98 \pm 0.11$, $2.08\pm0.14$ and $1.88\pm 0.11$,
respectively, with no traces of non-Gaussianity: $f_{\rm NL}^{\rm local}=59\pm
75$ at 95% confidence level for the full LOWZ+CMASS sample in the range
$\ell\in[4,100]$. After cross-correlating WMAP-9yr data with the LOWZ+CMASS LG
density field, the ISW signal is detected at the level of 1.62--1.69$\,\sigma$.
While this result is in close agreement with predictions from Monte Carlo
simulations in the concordance $\Lambda$CDM model, it cannot rule out by itself
an Einstein-de Sitter scenario, and has a moderately low signal compared to
previous studies conducted on subsets of this LG sample.


title: Dynamic Ising Model: Reconstruction of Evolutionary Trees

abstract:
  An evolutionary tree is a cascade of bifurcations starting from a single
common root, generating a growing set of daughter species as time goes by.
Species here is a general denomination for biological species, spoken languages
or any other entity evolving through heredity. From the N currently alive
species within a clade, distances are measured through pairwise comparisons
made by geneticists, linguists, etc. The larger is such a distance for a pair
of species, the older is their last common ancestor. The aim is to reconstruct
the past unknown bifurcations, i.e. the whole clade, from the knowledge of the
N(N-1)/2 quoted distances taken for granted. A mechanical method is presented,
and its applicability discussed.


title: Experimental realisation of quantum illumination

abstract:
  We present the first experimental realisation of the quantum illumination
protocol proposed in Ref.s [S. Lloyd, Science 321, 1463 (2008); S. Tan et al.,
Phys. Rev. Lett. 101, 253601 (2008)], achieved in a simple feasible
experimental scheme based on photon-number correlations. A main achievement of
our result is the demonstration of a strong robustness of the quantum protocol
to noise and losses, that challenges some widespread wisdom about quantum
technologies.


title: Winds, Clumps, and Interacting Cosmic Rays in M82

abstract:
  We construct a family of models for the evolution of energetic particles in
the starburst galaxy M82 and compare them to observations to test the
calorimeter assumption that all cosmic ray energy is radiated in the starburst
region. Assuming constant cosmic ray acceleration efficiency with Milky Way
parameters, we calculate the cosmic-ray proton and primary and secondary
electron/positron populations as a function of energy. Cosmic rays are injected
with Galactic energy distributions and electron-to-proton ratio via type II
supernovae at the observed rate of 0.07/yr. From the cosmic ray spectra, we
predict the radio synchrotron and \gamma-ray spectra. To more accurately model
the radio spectrum, we incorporate a multiphase interstellar medium in the
starburst region of M82. Our model interstellar medium is highly fragmented
with compact dense molecular clouds and dense photoionized gas, both embedded
in a hot, low density medium in overall pressure equilibrium. The spectra
predicted by this one-zone model are compared to the observed radio and
\gamma-ray spectra of M82. Chi-squared tests are used with radio and \gamma-ray
observations and a range of model predictions to find the best-fit parameters.
The best-fit model yields constraints on key parameters in the starburst zone
of M82, including a magnetic field strength of ~250 \mu G and a wind advection
speed in the range of 300-700 km/s. We find that M82 is a good electron
calorimeter but not an ideal cosmic-ray proton calorimeter and discuss the
implications of our results for the astrophysics of the far infrared-radio
correlation in starburst galaxies.


title:
X-ray source population study of the starburst galaxy M83 with
  XMM-Newton

abstract:
  We present the results obtained from the analysis of three XMM-Newton
observations of M83. The aims of the paper are studying the X-ray source
populations in M83 and calculating the X-ray luminosity functions of X-ray
binaries for different regions of the galaxy. We detected 189 sources in the
XMM-Newton field of view in the energy range of 0.2-12 keV. We constrained
their nature by means of spectral analysis, hardness ratios, studies of the
X-ray variability, and cross-correlations with catalogues in X-ray, optical,
infrared, and radio wavelengths. We identified and classified 12 background
objects, five foreground stars, two X-ray binaries, one supernova remnant
candidate, one super-soft source candidate and one ultra-luminous X-ray source.
Among these sources, we classified for the first time three active galactic
nuclei (AGN) candidates. We derived X-ray luminosity functions of the X-ray
sources in M83 in the 2-10 keV energy range, within and outside the D_25
ellipse, correcting the total X-ray luminosity function for incompleteness and
subtracting the AGN contribution. The X-ray luminosity function inside the D_25
ellipse is consistent with that previously observed by Chandra. The
Kolmogorov-Smirnov test shows that the X-ray luminosity function of the outer
disc and the AGN luminosity distribution are uncorrelated with a probability of
about 99.3%. We also found that the X-ray sources detected outside the D_25
ellipse and the uniform spatial distribution of AGNs are spatially uncorrelated
with a significance of 99.5%. We interpret these results as an indication that
part of the observed X-ray sources are X-ray binaries in the outer disc of M83.


title: The cold gas content of post-starburst galaxies

abstract:
  Post-starburst galaxies, or E+A galaxies, are characterized by optical
spectra showing strong Balmer absorption lines, indicating a young stellar
population, and little or no emission lines, implying no active star formation.
These galaxies are interpreted as a transitional population between
star-forming, disk-dominated galaxies and spheroidal quiescent, non-star
forming galaxies. Here, we present single dish HI 21-cm emission line
measurements of a sample of eleven of these galaxies at redshifts z<0.05. We
detect H I emission in six of the E+A galaxies. In combination with earlier
studies, the total number of E+A galaxies with measured cold gas components is
now eleven. Roughly half of the E+As studied so far have detectable HI. The gas
fractions of these galaxies, measured with respect to their stellar mass, are
between 1 and 10 percent and are at the high end of the gas fractions measured
in gas-bearing early type galaxies and typically lower than seen in late-type
galaxies with comparable stellar masses. This finding is consistent with the
idea that E+As are currently evolving from the blue cloud to the red sequence.
However, the question of why the star formation has ceased in these galaxies
while a significant gas reservoir is still present can only be answered by
higher spatial resolution observations of the cold gas.


title:
MCNP6 Fission Cross Section Calculations at Intermediate and High
  Energies

abstract:
  MCNP6 has been Validated and Verified (V&V) against intermediate- and
high-energy fission cross-section experimental data. An error in the
calculation of fission cross sections of 181Ta and a few nearby target nuclei
by the CEM03.03 event generator in MCNP6 and a "bug: in the calculation of
fission cross sections with the GENXS option of MCNP6 while using the
LAQGSM03.03 event generator were detected during our V&V work. After fixing
both problems, we find that MCNP6 using CEM03.03 and LAQGSM03.03 calculates
fission cross sections in good agreement with available experimental data for
reactions induced by nucleons, pions, and photons on both subactinide and
actinide nuclei at incident energies from several tens of MeV to about 1 TeV.


title:
The hard X-ray spectrum of NGC 1365: scattered light, not black hole
  spin

abstract:
  Active Galactic Nuclei (AGN) show excess X-ray emission above 10 keV compared
with extrapolation of spectra from lower energies. Risaliti et al. have
recently attempted to model the hard X-ray excess in the type 1.8 AGN NGC 1365,
concluding that the hard excess most likely arises from Compton-scattered
reflection of X-rays from an inner accretion disk close to the black hole.
Their analysis disfavored a model in which the hard excess arises from a high
column density of circumnuclear gas partially covering a primary X-ray source,
despite such components being required in the NGC 1365 data below 10 keV. Using
a Monte Carlo radiative transfer approach, we demonstrate that this conclusion
is invalidated by (i) use of slab absorption models, which have unrealistic
transmission spectra for partial covering gas, (ii) neglect of the effect of
Compton scattering on transmitted spectra and (iii) inadequate modeling of the
spectrum of scattered X-rays. The scattered spectrum is geometry dependent and,
for high global covering factors, may dominate above 10 keV. We further show
that, in models of circumnuclear gas, the suppression of the observed hard
X-ray flux by reprocessing may be no larger than required by the `light
bending' model invoked for inner disk reflection, and the expected emission
line strengths lie within the observed range. We conclude that the
time-invariant `red wing' in AGN X-ray spectra is probably caused by continuum
transmitted through and scattered from circumnuclear gas, not by highly
redshifted line emission, and that measurement of black hole spin is not
possible.


title: Logarithmic conformal invariance in the Abelian sandpile model

abstract:
  We review the status of the two-dimensional Abelian sandpile model as a
strong candidate to provide a lattice realization of logarithmic conformal
invariance with central charge c=-2. Evidence supporting this view is collected
from various aspects of the model. These include the study of some conformally
invariant boundary conditions, and the corresponding boundary condition
changing fields, the calculation of correlations of certain bulk and boundary
observables (the height variables) as well as a proper account of the necessary
dissipation, which allows for a physical understanding of some of the strange
but generic features of logarithmic theories.

categories: hep-th cond-mat.stat-mech math-ph math.MP


title: Preequilibrium Emission of Light Fragments in Spallation Reactions

abstract:
  The ability to describe production of light fragments (LF) is important for
many applications, such as cosmic-ray-induced single event upsets (SEUs),
radiation protection, and cancer therapy with proton and heavy-ion beams. The
Cascade-Exciton Model (CEM) and the Los Alamos version of the Quark-Gluon
String Model (LAQGSM) event generators in the LANL transport code MCNP6,
describe quite well the spectra of fragments with sizes up to 4He across a
broad range of target masses and incident energies (up to ~ 5 GeV for CEM and
up to ~ 1 TeV/A for LAQGSM). However, they do not predict the high-energy tails
of LF spectra heavier than 4He well. Most LF with energies above several tens
of MeV are emitted during the precompound stage of a reaction. The current
versions of our event generators do not account for precompound emission of LF
larger than 4He. The aim of our work is to generalize the precompound model to
include such processes, leading to increased predictive power of LF production.
Extending the model in this way provides preliminary results that have much
better agreement with experimental data.


title: Perfectly load-balanced, optimal, stable, parallel merge

abstract:
  We present a simple, work-optimal and synchronization-free solution to the
problem of stably merging in parallel two given, ordered arrays of m and n
elements into an ordered array of m+n elements. The main contribution is a new,
simple, fast and direct algorithm that determines, for any prefix of the stably
merged output sequence, the exact prefixes of each of the two input sequences
needed to produce this output prefix. More precisely, for any given index
(rank) in the resulting, but not yet constructed output array representing an
output prefix, the algorithm computes the indices (co-ranks) in each of the two
input arrays representing the required input prefixes without having to merge
the input arrays. The co-ranking algorithm takes O(log min(m,n)) time steps.
The algorithm is used to devise a perfectly load-balanced, stable, parallel
merge algorithm where each of p processing elements has exactly the same number
of input elements to merge. Compared to other approaches to the parallel merge
problem, our algorithm is considerably simpler and can be faster up to a factor
of two. Compared to previous algorithms for solving the co-ranking problem, the
algorithm given here is direct and maintains stability in the presence of
repeated elements at no extra space or time cost. When the number of processing
elements p does not exceed (m+n)/log min(m,n), the parallel merge algorithm has
optimal speedup. It is easy to implement on both shared and distributed memory
parallel systems.


title: Partial isomorphisms over finite fields

abstract:
  In this paper, we construct a combinatorial algebra of partial isomorphisms
that gives rise to a "projective limit" of the centers of the group algebras
C[GL(n,Fq)]. It allows us to prove a GL(n,Fq)-analogue of an old theorem of
Farahat and Higman regarding products of conjugacy classes of permutations.