title: Toy quantum categories

abstract:
  We show that Rob Spekken's toy quantum theory arises as an instance of our
categorical approach to quantum axiomatics, as a (proper) subcategory of the
dagger compact category FRel of finite sets and relations with the cartesian
product as tensor, where observables correspond to dagger Frobenius algebras.
This in particular implies that the quantum-like properties of the toy model
are in fact very general category-theoretic properties. We also show the
remarkable fact that we can already interpret complementary quantum observables
on the two-element set FRel.


title: A Banach space determined by the Weil height

abstract:
  The absolute logarithmic Weil height is well defined on the group of units of
the algebraic closure of the rational numbers, modulo roots of unity, and
induces a metric topology on this group. We show that the completion of this
metric space is a Banach space over the field of real numbers. We further show
that this Banach space is isometrically isomorphic to a co-dimension one
subspace of L1 of a certain totally disconnected, locally compact space,
equipped with a certain measure satisfying an invariance property with respect
to the absolute Galois group.


title: Gravity action on discontinuous metrics

abstract:
  We consider minisuperspace gravity system described by piecewise flat metric
discontinuous on three-dimensional faces (tetrahedra). There are infinite terms
in the Einstein action. However, starting from proper regularization, these
terms in the exponential of path integral result in pre-exponent factor with
$\delta$-functions requiring vanishing metric discontinuities. Thereby path
integral measure in Regge calculus is related to path integral measure in Regge
calculus where length of an edge is not constrained to be the same for all the
4-tetrahedra containing this edge, i.e. in Regge calculus with independent
4-tetrahedra. The result obtained is in accordance with our previous one
obtained from symmetry considerations.


title:
Gluon density and $F_{2}$ functions from BK equation with local impact
  parameter dependence in DIS on nuclei

abstract:
  The DIS process on nuclei is considered in the framework of LO BK equation
with local impact parameter dependence. Solving BK equation parameters for
initial conditions of GBW type found in \cite{Serg1} were used. Integrated
gluon density function and $F_2$ nucleus structure function for different
nuclei are calculated. Obtained results are compared with the different
parameterizations of integrated gluon density function from
\cite{Flor,Eskola1,Eskola2,Tywon}. The anomalous dimensions and saturation
scales for different nuclei are calculated at different energies. Fitting
obtained results, expressions for the form of saturation scale are obtained for
the proton and different nuclei as functions of impact parameter and energy.


title: Independent 4-tetrahedra connection representation of Regge calculus

abstract:
  We consider simplest piecewise flat manifold consisting of two identical
4-tetrahedra (call it bisimplex). General relativity action for arbitrary
piecewise flat manifold can be expressed in terms of sum of the (half of)
bisimplex actions. We use representation of each bisimplex action in terms of
certain rotation matrices (connections). This gives representation of any
minisuperspace piecewise flat gravity system in terms of connections which do
not connect neighboring 4-tetrahedra (more appropriate would be call these
self-connections). If Regge calculus with independent 4-tetrahedra is
considered, i. e. when the length of an edge is not constrained to be the same
for all the 4-tetrahedra containing this edge, self-connection representation
leaves 4-tetrahedra independent also in connection matrices sector. Action
remains sum of independent 4-tetrahedra terms.


title: Defining some integrals in Regge calculus

abstract:
  Regge calculus minisuperspace action in the connection representation has the
form in which each term is linear over some field variable (scale of area-type
variable with sign). We are interested in the result of performing integration
over connections in the path integral. To find this function, we compute its
moments, i. e. integrals with powers of that variable. Calculation proceeds
through intermediate appearance of $\delta$-functions and integrating them out
and leads to finite result for any power. The function of interest should
therefore be exponentially suppressed at large areas and it really does being
restored from moments. This gives for gravity a way of defining such
nonabsolutely convergent integral as path integral.


title: Backreaction of superhorizon perturbations in scalar field cosmologies

abstract:
  It has been suggested that the acceleration of the Universe may be due to the
backreaction of perturbations to the Friedmann-Robertson-Walker background. For
a Universe dominated by cold dark matter, it is known that the backreaction of
superhorizon perturbations can not drive acceleration. We extend this result to
models with cold dark matter together with a scalar field. We show that the
scalar field can drive acceleration only via the standard mechanism of a
constant or nearly constant piece of its potential (i.e., a cosmological
constant); there is no separate mechanism involving superhorizon backreaction.
This rules out some models which have been proposed in the literature.


title: SL(2,R) matrix model and supersymmetric Yang-Mills integrals

abstract:
  The density of states of Yang-Mills integrals in the supersymmetric case is
characterized by power-law tails whose decay is independent of N, the rank of
the gauge group. It is believed that this has no counterpart in matrix models,
but we construct a matrix model that exactly exhibits this property. In
addition, we show that the eigenfunctions employed to construct the matrix
model are invariant under the collinear subgroup of conformal transformations,
SL(2,R). We also show that the matrix model itself is invariant under a
fractional linear transformation. The wave functions of the model appear in the
trigonometric Rosen-Morse potential and in free relativistic motion on AdS
space.


title: Ultra high energy cosmic rays and neutrinos after Auger

abstract:
  We discuss the main results that were recently published by the Auger
Collaboration and their impact on our knowledge of the ultra high energy cosmic
rays and neutrinos.


title: About the geometry of almost para-quaternionic manifolds

abstract:
  We provide a general criteria for the integrability of the almost
para-quaternionic structure of an almost para-quaternionic manifold (M,P) of
dimension bigger or equal to eight, in terms of the integrability of two or
three sections of the defining rank three vector bundle P. We relate it with
the integrability of the canonical almost complex structure of the twistor
space and to the integrability of the canonical almost para-complex structure
of the reflector space of (M,P). We show that (M, P) has plenty of locally
defined, compatible, complex and para-complex structures, provided that P is
para-quaternionic.


title: Cosmological constant in a quantum fluid model

abstract:
  Possible analogies between vacuum state and quantum fluid provide a model to
study vacuum energy density induced by thermal corrections, space-time
curvature, boundary conditions and quantum back-reaction. We find that vacuum
energy density in this quantum fluid model is not naturally of the order of the
matter energy density. We show how higher-order corrections in quantum
back-reaction can also contribute to vacuum energy density, and how the
cosmological expansion is a manifestation of an universe out of mechanical
equilibrium. This last fact implies that simple thermodynamic arguments are not
enough to explain the cosmological constant problem due to the calculation of
the associated vacuum energy density requires first the knowing of the
underlying microscopic physics of vacuum.


title:
Charge carrier induced barrier height reduction at organic
  heterojunctions

abstract:
  In order to provide an accurate theoretical description of current density
voltage (J-V) characteristics of an organic heterojunction device over a wide
range of electric fields at various temperatures, it is proposed that an
accumulation of charge carriers at the heterojunction will lead to a reduction
in the barrier height across the heterojunction. Two well-known hole
transporting materials, 4,4,4-Tris(N-3-methylphenyl-N-phenyl-amino)
triphenylamine (MTDATA) and
N,N-diphenyl-N,N-bis(1-naphthyl)(1,1-biphenyl)-4,4diamine (NPB) were used to
fabricate unipolar heterojunction devices. It is found that the J-V
characteristics depends strongly on applied bias. The simulated J-V
characteristics of the heterojunction device, with the modified injection
model, are found to be in excellent agreement with the experimental data.


title: Is there Quark Matter in (Low-Mass) Pulsars?

abstract:
  The effect of the QCD phase transition is studied for the mass-radius
relation of compact stars and for hot and dense matter at a given proton
fraction used as input in core-collapse supernova simulations. The phase
transitions to the 2SC and CFL color superconducting phases lead to stable
hybrid star configurations with a pure quark matter core. In supernova
explosions quark matter could be easily produced due to $\beta$-equilibrium,
small proton fractions and nonvanishing temperatures. A low critical density
for the phase transition to quark matter is compatible with present pulsar mass
measurements.


title: Modelling ultra-fine structure in dark matter halos

abstract:
  Various laboratory-based experiments are underway attempting to detect dark
matter directly. The event rates and detailed signals expected in these
experiments depend on the dark matter phase space distribution on
sub-milliparsec scales. These scales are many orders of magnitude smaller than
those that can be resolved by conventional N-body simulations, so one cannot
hope to use such tools to investigate the effect of mergers in the history of
the Milky Way on the detailed phase-space structure probed by the current
experiments. In this paper we present an alternative approach to investigating
the results of such mergers, by studying a simplified model for a merger of a
sub-halo with a larger parent halo. With an appropriate choice of parent halo
potential, the evolution of material from the sub-halo can be expressed
analytically in action-angle variables, so it is possible to obtain its entire
orbit history very rapidly without numerical integration. Furthermore by
evolving backwards in time, we can obtain arbitrarily-high spatial resolution
for the current velocity distribution at a fixed point. Although this model
cannot provide a detailed quantitative comparison with the Milky Way, its
properties are sufficiently generic that it offers qualitative insight into the
expected structure arising from a merger at a resolution that cannot be
approached with full numerical simulations. Preliminary results indicate that
the velocity-space distribution of dark matter particles remains characterized
by discrete and well-defined peaks over an extended period of time, both for
single and multi-merging systems, in contrast to the simple smooth velocity
distributions sometimes assumed in predicting laboratory experiment detection
rates.


title: Exploring Pure Spinor String Theory on AdS_4 x CP^3

abstract:
  In this paper we formulate the pure spinor superstring theory on AdS_4 x
CP^3. By recasting the pure spinor action as a topological A-model on the
fermionic supercoset Osp(6|4)/SO(6)xSp(4) plus a BRST exact term, we prove the
exactness of the sigma-model. We then give a gauged linear sigma-model which
reduces to the superstring in the limit of large volume and we study its branch
geometry in different phases. Moreover, we discuss possible D-brane boundary
conditions and the principal chiral model for the fermionic supercoset.


title:
Structural approximations to positive maps and entanglement breaking
  channels

abstract:
  Structural approximations to positive, but not completely positive maps are
approximate physical realizations of these non-physical maps. They find
applications in the design of direct entanglement detection methods. We show
that many of these approximations, in the relevant case of optimal positive
maps, define an entanglement breaking channel and, consequently, can be
implemented via a measurement and state-preparation protocol. We also show how
our findings can be useful for the design of better and simpler direct
entanglement detection methods.


title: Low Mass X-ray Binaries and Black Holes in Globular Clusters

abstract:
  Studies of nearby galaxies reveal that roughly half of their low mass X-ray
binary (LMXB) populations are associated with globular clusters (GCs). We have
established that the LMXB hosting frequency is correlated to various GC
properties such as mass and metallicity. While the X-ray luminosities of a few
of the brightest LMXBs in GCs are consistent with the accreting object being a
black hole (BH), the only definitive way to distinguish between a black hole
and multiple superposed sources in a GC is to detect variability. We have
discovered just such a variable 4x10^39 erg/s black hole X-ray binary in a low
metallicity globular cluster in the halo of NGC 4472. The change in the X-ray
spectrum between the bright and faint epochs suggests that the luminosity
variation is due to eclipsing by a warped accretion disk. The optical spectrum
of this source also reveals strong, broad, [O III] lambda 5007 and [O III]
lambda 4959 emission. An analysis of the X-ray spectrum suggests that the [O
III] lines are produced by the photoionization of a wind driven by a stellar
mass black hole accreting mass at or above its Eddington luminosity. As it is
dynamically implausible to form an accreting stellar mass BH system in a GC
with an intermediate mass BH it appears that this massive globular cluster does
not harbor an intermediate mass BH. The inferred mass of this BH falls well
below the extrapolation of the well known M_BH-sigma and M_BH-M_Stellar
relations to this GC. Therefore our analysis suggests that not all old, metal
poor stellar systems form black holes consistent with these relations, which
have been established for much more massive stellar systems.


title: Three-Loop Leading Singularities and BDS Ansatz for Five Particles

abstract:
  We use the leading singularity technique to determine the planar three-loop
five-particle amplitude in N=4 super Yang-Mills in terms of a simple basis of
integrals. We analytically compute the integral coefficients for both the
parity-even and the parity-odd parts of the amplitude. The parity-even part
involves only dual conformally invariant integrals. Using the method of
obstructions we numerically evaluate two previously unfixed coefficients which
appear in the three-loop BDS ansatz.


title: Perturbative description of inclusive single hadron production at HERA

abstract:
  Light charged hadron production data in the current fragmentation region at
HERA are calculated using next-to-leading order perturbative calculations and
fragmentation functions obtained from similar data from e+ e- reactions.
General good agreement is found at large photon virtuality Q^2 and intermediate
momentum fraction x_p, consistent with fragmentation function universality. The
description of the small x_p and Q^2 region is improved by incorporating hadron
mass effects.


title:
Effects of Beta-Decays of Excited-State Nuclei on the Astrophysical
  r-Process

abstract:
  A rudimentary calculation is employed to evaluate the possible effects of
beta- decays of excited-state nuclei on the astrophysical r-process.
Single-particle levels calculated with the FRDM are adapted to the calculation
of beta-decay rates of these excited-state nuclei. Quantum numbers are
determined based on proximity to Nilson model levels. The resulting rates are
used in an r-process network calculation in which a supernova hot-bubble model
is coupled to an extensive network calculation including all nuclei between the
valley of stability and the neutron drip line and with masses A<284. Beta-decay
rates are included as functional forms of the environmental temperature. While
the decay rate model used is simple and phenomenological, it is consistent
across all 3700 nuclei involved in the r-process network calculation. This
represents an approximate first estimate to gauge the possible effects of
excited-state beta-decays on r-process freeze-out abundances.


title: Quarkyonic Matter and the Phase Diagram of QCD

abstract:
  Quarkyonic matter is a new phase of QCD at finite temperature and density
which is distinct from the confined and de-confined phases. Its existence is
unambiguously argued in the large number of colors limit in QCD. Hints of its
existence for 3 color QCD are shown in lattice Monte-Carlo data and heavy ion
experiments.


title: The Laurent norm

abstract:
  We generalize a semi-norm for the Alexander polynomial of a connected,
compact, oriented 3-manifold on its first cohomology group to a semi-norm for
an arbitrary Laurent polynomial f on the dual vector space to the space of
exponents of f. We determine a decomposition formula for this Laurent norm; an
expression for the Laurent norm for f in terms of the Laurent norms for each of
the irreducible factors of f. For an n-variable polynomial f, we introduce a
space of m \leq n essential variables which determine the reduced Laurent norm
unit ball; a convex polyhedron of the same dimension m as the Newton polyhedron
of f. In the space spanned by the essential variables, the Laurent semi-norm
for polynomials with at least two terms is shown to be a norm.


title:
Precise measurement of Br(tau^- -> K^*0(892) K^- nu_tau) and the mass
  and width of the K^*0(892) meson

abstract:
  Using the high statistics tau data sample recorded in the Belle experiment at
KEKB, we have greatly improved the precision of the branching fraction
  Br(tau^- -> K^*0(892) K^- nu_tau) = (1.56+-0.02+-0.09)x10^-3, while the mass
and width of the K^*0(892) meson are measured to be (895.10+-0.27+-0.31)
MeV/c^2 and (47.23+-0.49+-0.79) MeV/c^2, respectively, with better accuracy
than the PDG world average values. The first measurement of the decay tau^- ->
K^*0(892) K^- pi^0 nu_tau is also reported with a branching fraction of
Br(tau^- -> K^*0(892) K^- pi^0 nu_tau)=(2.39+-0.46+-0.26)x10^-5.


title: Brascamp-Lieb Inequalities for Non-Commutative Integration

abstract:
  We formulate a non-commutative analog of the Brascamp-Lieb inequality, and
prove it in several concrete settings.


title: Arithmetic of K3 surfaces

abstract:
  We review recent developments in the arithmetic of K3 surfaces. Our focus
lies on aspects of modularity, Picard number and rational points. Throughout we
emphasise connections to geometry.


title:
Optimization of Location Management for PCS Networks with CTRW Mobility
  Model

abstract:
  This paper considers the design of the optimal locationupdate area (LA) of
the distance-based scheme for personal communication service (PCS) networks. We
focus on the optimization of two design parameters associated with the LA: 1)
initial position upon LA update; 2) distance threshold for triggering of LA
update. Based on the popular continuous-time random walk (CTRW) mobility model,
we propose a novel analytical framework that uses a diffusion equation to
minimize the location management cost. In this framework, a number of
measurable physical parameters, such as length of road section, angle between
road sections, and road section crossing time, can be integrated into the
system design. This framework allows us to easily evaluate the total cost under
general call arrival distributions and LA of different shapes. For the
particular case of circular LA and small Poisson call-arrival rate, we prove
the following: (1) When the drift is weak, the optimal initial position
approaches the center of the LA; when the drift is strong, it approaches the
boundary of the LA. (2) Comparing the optimal initial-position and
center-initial-position solutions (which is assumed in most prior work), when
the drift is weak, the optimal distance threshold and the minimum total cost
are roughly equal; when the drift is strong, the optimal distance threshold in
the later is about 1.260 times that in the former, and the minimum total cost
in the later is about 1.587 times that in the former. That is, optimizing on
initial position, which previous work did not consider, has the potential of
reducing the cost measure by 37%.


title:
Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-based
  Oxypnictide Superconductors NdFeAs0.85

abstract:
  Photoemission spectroscopy with low-energy tunable photons on
oxygen-deficient iron-based oxypnictide superconductors NdFeAsO0.85 (Tc=52K)
reveals a distinct photon-energy dependence of the electronic structure near
the Fermi level (EF). A clear shift of the leading-edge can be observed in the
superconducting states with 9.5 eV photons, while a clear Fermi cutoff with
little leading-edge shift can be observed with 6.0 eV photons. The results are
indicative of the superconducting gap opening not on the hole-like ones around
Gamma (0,0) point but on the electron-like sheets around M(pi,pi) point.


title:
On Strong Convergence to Equilibrium for the Boltzmann Equation with
  Soft Potentials

abstract:
  The paper concerns $L^1$- convergence to equilibrium for weak solutions of
the spatially homogeneous Boltzmann Equation for soft potentials $(-4\le
\gm<0$), with and without angular cutoff. We prove the time-averaged
$L^1$-convergence to equilibrium for all weak solutions whose initial data have
finite entropy and finite moments up to order greater than $2+|\gm|$. For the
usual $L^1$-convergence we prove that the convergence rate can be controlled
from below by the initial energy tails, and hence, for initial data with long
energy tails, the convergence can be arbitrarily slow. We also show that under
the integrable angular cutoff on the collision kernel with $-1\le \gm<0$, there
are algebraic upper and lower bounds on the rate of $L^1$-convergence to
equilibrium. Our methods of proof are based on entropy inequalities and moment
estimates.


title: Infinite log-concavity: developments and conjectures

abstract:
  Given a sequence (a_k) = a_0, a_1, a_2,... of real numbers, define a new
sequence L(a_k) = (b_k) where b_k = a_k^2 - a_{k-1} a_{k+1}. So (a_k) is
log-concave if and only if (b_k) is a nonnegative sequence. Call (a_k)
"infinitely log-concave" if L^i(a_k) is nonnegative for all i >= 1. Boros and
Moll conjectured that the rows of Pascal's triangle are infinitely log-concave.
Using a computer and a stronger version of log-concavity, we prove their
conjecture for the nth row for all n <= 1450. We also use our methods to give a
simple proof of a recent result of Uminsky and Yeats about regions of infinite
log-concavity. We investigate related questions about the columns of Pascal's
triangle, q-analogues, symmetric functions, real-rooted polynomials, and
Toeplitz matrices. In addition, we offer several conjectures.


title: Alexander and Thurston norms of graph links

abstract:
  We show that the Alexander and Thurston norms are the same for all
irreducible Eisenbud-Neumann graph links in homology 3-spheres. These are the
links obtained by splicing Seifert links in homology 3-spheres together along
tori. By combining this result with previous results, we prove that the two
norms coincide for all links in S^3 if either of the following two conditions
are met; the link is a graph link, so that the JSJ decomposition of its
complement in S^3 is made up of pieces which are all Seifert-fibered, or the
link is alternating and not a (2,n)-torus link, so that the JSJ decomposition
of its complement in S^3 is made up of pieces which are all hyperbolic. We use
the E-N obstructions to fibrations for graph links together with the Thurston
cone theorem on link fibrations to deduce that every facet of the reduced
Thurston norm unit ball of a graph link is a fibered facet.


title: Classification of Swift's gamma-ray bursts

abstract:
  Two classes of gamma-ray bursts have been identified in the BATSE catalogs
characterized by durations shorter and longer than about 2 seconds. There are,
however, some indications for the existence of a third class. Swift satellite
detectors have different spectral sensitivity than pre-Swift ones for gamma-ray
bursts. Therefore, it is worth to reanalyze the durations and their
distribution. We analyze, the maximum likelihood estimation, the bursts
duration distribution, published in The First BAT Catalog, whether it contains
two, three or more groups. The three log-normal fit is significantly (99.54%
probability) better than the two for the duration distribution. Monte-Carlo
simulations also confirm this probability (99.2%). Similarly, in previous
results we found that the fourth component is not needed. The relative
frequencies of the distribution of the groups are 7% short 35% intermediate and
58% long. Although the relative frequencies of the groups are different than in
the BATSE GRB sample, the difference in the instrument spectral sensitivities
can explain this bias on a natural way. This means theoretical models may be
needed to explain three different type of gamma-ray bursts.


title: Symplectic approach to quantum constraints

abstract:
  A general prescription for the treatment of constrained quantum motion is
outlined. We consider in particular constraints defined by algebraic
submanifolds of the quantum state space. The resulting formalism is applied to
obtain solutions to the constrained dynamics of systems of multiple spin-1/2
particles. When the motion is constrained to a certain product space containing
all of the energy eigenstates, the dynamics thus obtained are quasi-unitary in
the sense that the equations of motion take a form identical to that of unitary
motion, but with different boundary conditions. When the constrained subspace
is a product space of disentangled states, the associated motion is more
intricate. Nevertheless, the equations of motion satisfied by the dynamical
variables are obtained in closed form.


title: The unusual pre-main-sequence star V718 Per (HMW 15)

abstract:
  The remarkable pre-main-sequence object V718 Per (HMW 15, H187) in the young
cluster IC 348 periodically undergoes long-lasting eclipses caused by variable
amounts of circumstellar dust in the line-of-sight to the star. It has been
speculated that the star is a close binary and similar to another unusual
eclipsing object, KH 15D. We have submitted V718 Per to a detailed photometric
and spectroscopic study to find out more about the properties of the stellar
object and the occulting circumstellar material, and to look for signatures of
a possible binary component. Our photometric data show that the eclipses are
very symmetric and persistent, and that the extinction deviates only little
from what is expected for normal interstellar material. The spectroscopic data,
obtained at minimum as well as at maximum brightness, indicate a primordial
abundance of Li and a surface effective temperature of about 5200 K.
Remarkably, the in-eclipse spectrum shows a significant broadening of the
photospheric absorption lines, as well as a weak increase in emission
components of H-alpha and the Ca II IR triplet. We did not detect any atomic or
molecular features from to the occulting body in the in-eclipse spectrum. We
also found no evidence of radial velocity changes in V718 Per to within about
+/- 80 m/s, which for an edge-on system corresponds to a maximum companion mass
of 6 Jupiter masses. Our observations suggest that V718 Per is a single star,
and thus very different from KH 15D. We conclude that V718 Per is surrounded by
an edge-on circumstellar disk with an irregular mass distribution orbiting at a
distance of 3.3 AU from the star, presumably at the inner disk edge. We ascribe
the broadening of photospheric absorption lines during the eclipse to forward
scattering of stellar light in the circumstellar dust feature.


title:
Hopf algebras and the combinatorics of connected graphs in quantum field
  theory

abstract:
  In this talk, we are concerned with the formulation and understanding of the
combinatorics of time-ordered n-point functions in terms of the Hopf algebra of
field operators. Mathematically, this problem can be formulated as one in
combinatorics or graph theory. It consists in finding a recursive algorithm
that generates all connected graphs in their Hopf algebraic representation.
This representation can be used directly and efficiently in evaluating Feynman
graphs as contributions to the n-point functions.


title: On the equilibrium rotation of Earth-like extra-solar planets

abstract:
  The equilibrium rotation of tidally evolved "Earth-like" extra-solar planets
is often assumed to be synchronous with their orbital mean motion. The same
assumption persisted for Mercury and Venus until radar observations revealed
their true spin rates. As many of these planets follow eccentric orbits and are
believed to host dense atmospheres, we expect the equilibrium rotation to
differ from the synchronous motion. Here we provide a general description of
the allowed final equilibrium rotation states of these planets, and apply this
to already discovered cases in which the mass is lower than twelve
Earth-masses. At low obliquity and moderate eccentricity, it is shown that
there are at most four distinct equilibrium possibilities, one of which can be
retrograde. Because most presently known "Earth-like" planets present eccentric
orbits, their equilibrium rotation is unlikely to be synchronous.


title:
Mass-loss and diffusion in subdwarf B stars and hot white dwarfs: do
  weak winds exist?

abstract:
  The effect of diffusion on the chemical composition of subdwarf B (sdB) stars
and of hot white dwarfs strongly depends on the presence of weak winds. In the
paper, for stars with half a solar mass, for various effective temperatures
between 25000 K and 50000 K, and for various metallicities between solar and
1/100 solar, the mass loss rates are predicted as a function of the surface
gravity. With assumptions similar to the original theory of radiatively driven
winds, the method of solution of the momentum equation has been modified,
because the usual parametrization of the line force multiplier leads to
complications in the case of weak winds. According to the results, weak winds
with mass-loss rates of the order E-11 solar masses per year may exist only for
the most luminous sdB stars. For the more compact ones, the decoupling of the
metals from the bulk matter (hydrogen and helium) is expected in the wind
region, because the momentum exchange via Coulomb collisions is not effective
enough. Thus multicomponent effects are of great importance. For the case of
white dwarfs no wind solution exists at all, if multicomponent effects are
neglected.


title: Entropy flow of a perfect fluid in (1+1) hydrodynamics

abstract:
  Using the formalism of the Khalatnikov potential, we derive exact general
formulae for the entropy flow dS/dy, where y is the rapidity, as a function of
temperature for the (1+1) relativistic hydrodynamics of a perfect fluid. We
study in particular flows dominated by a sufficiently long hydrodynamic
evolution, and provide an explicit analytical solution for dS/dy. We discuss
the theoretical implications of our general formulae and some phenomenological
applications for heavy-ion collisions.


title: Three-dimensional models of metal-poor stars

abstract:
  I present here the main results of recent realistic, 3D, hydrodynamical
simulations of convection at the surface of metal-poor red giant stars. I
discuss the application of these convection simulations as time-dependent, 3D,
hydrodynamical model atmospheres to spectral line formation calculations and
abundance analyses. The impact of 3D models on derived elemental abundances is
investigated by means of a differential comparison of the line strengths
predicted in 3D under the assumption of local thermodynamic equilibrium (LTE)
with the results of analogous line formation calculations performed with
classical, 1D, hydrostatic model atmospheres. The low surface temperatures
encountered in the upper photospheric layers of 3D model atmospheres of very
metal-poor stars cause spectral lines of neutral metals and molecules to appear
stronger in 3D than in 1D calculations. Hence, 3D elemental abundances derived
from such lines are significantly lower than estimated by analyses with 1D
models. In particular, differential 3D$-$1D LTE abundances for C, N, and O
derived from CH, NH, and OH lines are found to be in the range -0.5 to -1 dex.
Large negative differential 3D-1D corrections to the Fe abundance are also
computed for weak low-excitation neutral Fe lines. The application of
metal-poor 3D models to the spectroscopic analysis of extremely iron-poor halo
stars is discussed.


title: Statistical physics of cerebral embolization leading to stroke

abstract:
  We discuss the physics of embolic stroke using a minimal model of emboli
moving through the cerebral arteries. Our model of the blood flow network
consists of a bifurcating tree, into which we introduce particles (emboli) that
halt flow on reaching a node of similar size. Flow is weighted away from
blocked arteries, inducing an effective interaction between emboli. We justify
the form of the flow weighting using a steady flow (Poiseuille) analysis and a
more complicated nonlinear analysis. We discuss free flowing and heavily
congested limits and examine the transition from free flow to congestion using
numerics. The correlation time is found to increase significantly at a critical
value, and a finite size scaling is carried out. An order parameter for
non-equilibrium critical behavior is identified as the overlap of blockages'
flow shadows. Our work shows embolic stroke to be a feature of the cerebral
blood flow network on the verge of a phase transition.

categories: cond-mat.soft cond-mat.stat-mech physics.bio-ph q-bio.TO


title: Power-law scaling in protein synthesis of a stochastic regulon

abstract:
  We investigate the protein expression pattern of the lamB gene in Escherichia
coli LE392. The gene product LamB is an important membrane protein for maltose
transport into cells but it is also exploited by bacteriophage lambda for
infection. Although our bacterial population is clonal, stochastic gene
expression leads to a majority population with a large receptor number and a
minority population with a small receptor number. We find that the LamB
receptor distribution p(n) of the small-n population is scale invariant with
the exponent depending on growth conditions. A heuristic model is proposed that
relates the observed exponent to the protein production rate.


title: Bottomonium masses, decay rates and scalar charge radii

abstract:
  The masses of bottomonium s and p-states, decay constants, leptonic as well
as radiative decay widths are computed in the framework of extended harmonic
confinement model without any additional parameters.


title: Rapid Molecular Cloud and Star Formation: Mechanisms and Movies

abstract:
  We demonstrate that the observationally inferred rapid onset of star
formation after parental molecular clouds have assembled can be achieved by
flow-driven cloud formation of atomic gas, using our previous three-dimensional
numerical simulations. We post-process these simulations to approximate CO
formation, which allows us to investigate the times at which CO becomes
abundant relative to the onset of cloud collapse. We find that global gravity
in a finite cloud has two crucial effects on cloud evolution. (a) Lateral
collapse (perpendicular to the flows sweeping up the cloud) leads to rapidly
increasing column densities above the accumulation from the one-dimensional
flow. This in turn allows fast formation of CO, allowing the molecular cloud to
``appear'' rapidly. (b) Global gravity is required to drive the dense gas to
the high pressures necessary to form solar-mass cores, in support of recent
analytical models of cloud fragmentation. While the clouds still appear
``supersonically turbulent'', this turbulence is relegated to playing a
secondary role, in that it is to some extent a consequence of gravitational
forces.


title:
Chern-Simons theory, exactly solvable models and free fermions at finite
  temperature

abstract:
  We show that matrix models in Chern-Simons theory admit an interpretation as
1D exactly solvable models, paralleling the relationship between the Gaussian
matrix model and the Calogero model. We compute the corresponding Hamiltonians,
ground-state wavefunctions and ground-state energies and point out that the
models can be interpreted as quasi-1D Coulomb plasmas. We also study the
relationship between Chern-Simons theory on $S^3$ and a system of N
one-dimensional fermions at finite temperature with harmonic confinement. In
particular we show that the Chern-Simons partition function can be described by
the density matrix of the free fermions in a very particular, crystalline,
configuration. For this, we both use the Brownian motion and the matrix model
description of Chern-Simons theory and find several common features with c=1
theory at finite temperature. Finally, using the exactly solvable model result,
we show that the finite temperature effect can be described with a specific
two-body interaction term in the Hamiltonian, with 1D Coulombic behavior at
large separations.


title:
Luminosity distance in "Swiss cheese" cosmology with randomized voids:
  I. Single void size

abstract:
  Recently there have been suggestions that the Type Ia supernova data can be
explained using only general relativity and cold dark matter with no dark
energy. In "Swiss cheese" models of the Universe, the standard
Friedmann-Robertson-Walker picture is modified by the introduction of mass
compensating spherical inhomogeneities, typically described by the
Lemaitre-Tolman-Bondi metric. If these inhomogeneities correspond to underdense
cores surrounded by mass-compensating overdense shells, then they can modify
the luminosity distance-redshift relation in a way that can mimic accelerated
expansion. It has been argued that this effect could be large enough to explain
the supernova data without introducing dark energy or modified gravity. We show
that the large apparent acceleration seen in some models can be explained in
terms of standard weak field gravitational lensing together with insufficient
randomization of void locations. The underdense regions focus the light less
than the homogeneous background, thus dimming supernovae in a way that can
mimic the effects of acceleration. With insufficient randomization of the
spatial location of the voids and of the lines of sight, coherent defocusing
can lead to anomalously large demagnification effects. We show that a proper
randomization of the voids and lines of sight reduces the effect to the point
that it can no longer explain the supernova data.


title: The kinematic origin of the cosmological redshift

abstract:
  A common belief about big-bang cosmology is that the cosmological redshift
cannot be properly viewed as a Doppler shift (that is, as evidence for a
recession velocity), but must be viewed in terms of the stretching of space. We
argue that, contrary to this view, the most natural interpretation of the
redshift is as a Doppler shift, or rather as the accumulation of many
infinitesimal Doppler shifts. The stretching-of-space interpretation obscures a
central idea of relativity, namely that it is always valid to choose a
coordinate system that is locally Minkowskian. We show that an observed
frequency shift in any spacetime can be interpreted either as a kinematic
(Doppler) shift or a gravitational shift by imagining a suitable family of
observers along the photon's path. In the context of the expanding universe the
kinematic interpretation corresponds to a family of comoving observers and
hence is more natural.

categories: physics.pop-ph astro-ph gr-qc physics.ed-ph


title:
Spin Waves and Quantum Criticality in the Frustrated XY Pyrochlore
  Antiferromagnet Er2Ti2O7

abstract:
  We report detailed measurements of the low temperature magnetic phase diagram
of Er$_2$Ti$_2$O$_7$. Heat capacity and time-of-flight neutron scattering
studies of single crystals, subject to magnetic fields applied along the
crystallographic [110] direction, reveal unconventional low energy states.
Er$^{3+}$ magnetic ions reside on a pyrochlore lattice in Er$_2$Ti$_2$O$_7$,
where local XY anisotropy and antiferromagnetic interactions give rise to a
unique frustrated system. In zero field, the ground state exhibits coexisting
short and long range order, accompanied by soft collective spin excitations
previously believed to be absent. The application of finite magnetic fields
tunes the ground state continuously through a landscape of non-collinear
phases, divided by a zero temperature phase transition at $\mu_0 H_c \sim$ 1.5
T. The characteristic energy scale for spin fluctuations is seen to vanish at
the critical point, as expected for a second order quantum phase transition
driven by quantum fluctuations.


title: The general relativistic Poynting-Robertson effect

abstract:
  The general relativistic version is developed for Robertson's discussion of
the Poynting-Robertson effect that he based on special relativity and Newtonian
gravity for point radiation sources like stars. The general relativistic model
uses a test radiation field of photons in outward radial motion with zero
angular momentum in the equatorial plane of the exterior Schwarzschild or Kerr
spacetime.


title:
Homogenization procedure for a metamaterial and local violation of the
  second principle of thermodynamics

abstract:
  Classical theory of crystals states that a medium to be considered
homogeneous must satisfy the following requirements: a) the dimension of the
elementary cell must be much smaller than the incident wavelength; b) the
sample must contain a large number of elementary cells, i.e. it must be
macroscopic with respect to wavelength. Under these conditions, macroscopic
quantities can be introduced in order to describe the optical response of the
medium. We analytically demonstrate that for a symmetric elementary cell those
requirements can be relaxed, and it is possible to assign a permittivity and a
permeability to a composite structure, even if the metamaterial cannot be
considered homogeneous under the requirements stated above. However, the
effective permittivity and permeability in some cases may give rise to
unphysical, effective behaviors inside the medium, notwithstanding the fact
that they satisfy requirements like being Kramers-Kronig pairs, for example,
and are consistent with all the linear properties outside the structure (i.e.
reflection, transmission, and absorption at all frequencies). In some
situations the medium is assigned a magnetic response even though the medium is
not magnetically active. In particular, we demonstrate that the homogenization
procedure can lead to a medium that locally violates the second principle of
thermodynamics. We also show that, in the non-homogeneous regime, it is not
possible to describe the nonlinear behavior of the structure using an effective
parameters approach, despite the possibility to assign an effective linear
refractive index.


title:
An intermediate regime for exit phenomena driven by non-Gaussian Levy
  noises

abstract:
  A dynamical system driven by non-Gaussian L\'evy noises of small intensity is
considered. The first exit time of solution orbits from a bounded neighborhood
of an attracting equilibrium state is estimated. For a class of non-Gaussian
L\'evy noises, it is shown that the mean exit time is asymptotically faster
than exponential (the well-known Gaussian Brownian noise case) but slower than
polynomial (the stable L\'evy noise case), in terms of the reciprocal of the
small noise intensity.


title:
Electron-phonon Interaction in Non-polar Quantum Dots Induced by the
  Amorphous Polar Environment

abstract:
  We propose a mechanism of energy relaxation for carriers confined in a
non-polar quantum dot surrounded by an amorphous polar environment. The carrier
transitions are due to their interaction with the oscillating electric field
induced by the local vibrations in the surrounding amorphous medium. We
demonstrate that this mechanism controls energy relaxation for electrons in Si
nanocrystals embedded in a SiO$_2$ matrix, where conventional mechanisms of
electron-phonon interaction are not efficient.


title:
Extending Soft-Collinear-Effective-Theory to describe hard jets in dense
  QCD media

abstract:
  An extension to the Soft-Collinear-Effective Theory (SCET) description of
hard jets is motivated to include the leading contributions between the
propagating partons within the jet with partons radiated from a dense extended
medium. The resulting effective Lagrangian, containing both a leading and a
power suppressed (in the hard scale $Q^2$) contribution, arises primarily from
interactions between the hard collinear modes in the jet with Glauber modes
from the medium. In this first attempt, the interactions between the hard jet
and soft and collinear partonic modes have been ignored, in an effort to focus
solely on the interactions with the Glauber modes. While the effect of such
modes on vacuum cross sections are suppressed by powers of the hard scale
compared to the terms from the SCET Lagrangian, such sub-leading contributions
are enhanced by the extent of the medium and result in measurable corrections.
The veracity of the derived Lagrangian is checked by direct comparison with
known results from full QCD calculations of two physical observables: the
transverse momentum broadening of hard jets in dense media and a reanalysis of
the transverse momentum dependent parton distribution function (TMDPDF).


title: Nonlinear resonances in \delta-kicked Bose-Einstein Condensates

abstract:
  We investigate the Quantum Resonance (QR) regime of a periodically kicked
atomic Bose-Einstein condensate. We find that the clearest indicator of the
nonlinear dynamics is a surprisingly abrupt cut-off which appears on the main
"Talbot time" QR. We show that this is due and excitation path combining both
Beliaev and Landau processes, with some analogies to nonlinear self-trapping.
Investigation of dynamical instability reveals further symptoms of nonlinearity
such as a regime of exponential oscillations.


title: Combination of CDF and D0 Results on the Mass of the Top Quark

abstract:
  We summarize the top-quark mass measurements from the CDF and D0 experiments
at Fermilab. We combine published Run-I (1992-1996) measurements with the most
recent preliminary Run-II (2001-present) measurements using up to 2.8 fb^-1 of
data. Taking correlated uncertainties properly into account the resulting
preliminary world average mass of the top quark is M_t = 172.4 +/- 0.7 (stat.)
+/- 1.0 (syst.) GeV/c^2, assuming Gaussian systematic uncertainties. Adding in
quadrature yields a total uncertainty of 1.2 GeV/c^2, corresponding to a
relative precision of 0.7% on the top-quark mass.


title: Changes in the Distribution of Income Volatility

abstract:
  Recent research has documented a significant rise in the volatility (e.g.,
expected squared change) of individual incomes in the U.S. since the 1970s.
Existing measures of this trend abstract from individual heterogeneity,
effectively estimating an increase in average volatility. We decompose this
increase in average volatility and find that it is far from representative of
the experience of most people: there has been no systematic rise in volatility
for the vast majority of individuals. The rise in average volatility has been
driven almost entirely by a sharp rise in the income volatility of those
expected to have the most volatile incomes, identified ex-ante by large income
changes in the past. We document that the self-employed and those who
self-identify as risk-tolerant are much more likely to have such volatile
incomes; these groups have experienced much larger increases in income
volatility than the population at large. These results color the policy
implications one might draw from the rise in average volatility. While the
basic results are apparent from PSID summary statistics, providing a complete
characterization of the dynamics of the volatility distribution is a
methodological challenge. We resolve these difficulties with a Markovian
hierarchical Dirichlet process that builds on work from the non-parametric
Bayesian statistics literature.


title: Explosive Events and the Evolution of the Photospheric Magnetic Field

abstract:
  Transition region explosive events have long been suggested as direct
signatures of magnetic reconnection in the solar atmosphere. In seeking further
observational evidence to support this interpretation, we study the relation
between explosive events and the evolution of the solar magnetic field as seen
in line-of-sight photospheric magnetograms. We find that about 38% of events
show changes of the magnetic structure in the photosphere at the location of an
explosive event over a time period of 1 h. We also discuss potential
ambiguities in the analysis of high sensitivity magnetograms.


title: The homotopy fixed point spectra of profinite Galois extensions

abstract:
  Let E be a k-local profinite G-Galois extension of an E_infty-ring spectrum A
(in the sense of Rognes). We show that E may be regarded as producing a
discrete G-spectrum. Also, we prove that if E is a profaithful k-local
profinite extension which satisfies certain extra conditions, then the forward
direction of Rognes's Galois correspondence extends to the profinite setting.
We show the function spectrum F_A((E^hH)_k, (E^hK)_k) is equivalent to the
homotopy fixed point spectrum ((E[[G/H]])^hK)_k where H and K are closed
subgroups of G. Applications to Morava E-theory are given, including showing
that the homotopy fixed points defined by Devinatz and Hopkins for closed
subgroups of the extended Morava stabilizer group agree with those defined with
respect to a continuous action and in terms of the derived functor of fixed
points.


title:
Quantum interference and spin-charge separation in a disordered
  Luttinger liquid

abstract:
  We study the influence of spin on the quantum interference of interacting
electrons in a single-channel disordered quantum wire within the framework of
the Luttinger liquid (LL) model. The nature of the electron interference in a
spinful LL is particularly nontrivial because the elementary bosonic
excitations that carry charge and spin propagate with different velocities. We
extend the functional bosonization approach to treat the fermionic and bosonic
degrees of freedom in a disordered spinful LL on an equal footing. We analyze
the effect of spin-charge separation at finite temperature both on the spectral
properties of single-particle fermionic excitations and on the conductivity of
a disordered quantum wire. We demonstrate that the notion of weak localization,
related to the interference of multiple-scattered electron waves and their
decoherence due to electron-electron scattering, remains applicable to the
spin-charge separated system. The relevant dephasing length, governed by the
interplay of electron-electron interaction and spin-charge separation, is found
to be parametrically shorter than in a spinless LL. We calculate both the
quantum (weak localization) and classical (memory effect) corrections to the
conductivity of a disordered spinful LL. The classical correction is shown to
dominate in the limit of high temperature.


title: Handling jets + missing E_T channel using inclusive mT2

abstract:
  The ATLAS and CMS experiments at the Large Hadron Collider (LHC) may discover
the squarks (\tilde{q}) and gluino (\tilde{g}) of the minimal supersymmetric
standard model (MSSM) in the early stage of the experiments if their masses are
lighter than 1.5 TeV. In this paper we propose the sub-system m_{T2} variable,
which is sensitive to the gluino mass when m_{\tilde{q}}>m_{\tilde{g}}. Using
it with the inclusive m_{T2} distribution proposed earlier, \tilde{q} and
\tilde{g} masses can be determined simultaneously in the early stage of the
experiments. Results of Monte Carlo simulations at sample MSSM model points are
presented both for signal and background.


title: On finite and elementary generation of SL_2(R)

abstract:
  Motivated by a question of A. Rapinchuk concerning general reductive groups,
we are investigating the following question: Given a finitely generated
integral domain $R$ with field of fractions $F$, is there a \emph{finitely
generated subgroup} $\Gamma$ of $SL_2(F)$ containing $SL_2(R)$? We shall show
in this paper that the answer to this question is negative for any polynomial
ring $R$ of the form $R = R_0[s,t]$, where $R_0$ is a finitely generated
integral domain with infinitely many (non--associate) prime elements. The proof
applies Bass--Serre theory and reduces to analyzing which elements of $SL_2(R)$
can be generated by elementary matrices with entries in a given finitely
generated $R$--subalgbra of $F$. Using Bass--Serre theory, we can also exhibit
new classes of rings which do not have the $GE_2$ property introduced by P.M.
Cohn.


title:
The chiral critical point of Nf=3 QCD at finite density to the order
  (mu/T)^4

abstract:
  QCD with three degenerate quark flavours at zero baryon density exhibits a
first order thermal phase transition for small quark masses, which changes to a
smooth crossover for some critical quark mass m^c_0, i.e. the chiral critical
point. It is generally believed that as an (even) function of quark chemical
potential, m_c(mu), the critical point moves to larger quark masses,
constituting the critical endpoint of a first order phase transition in
theories with m\geq m^c_0. To test this, we consider a Taylor expansion of
m_c(mu) around mu=0 and determine the first two coefficients from lattice
simulations with staggered fermions on N_t=4 lattices. We employ two different
techniques: a) calculating the coefficients directly from a mu=0 ensemble using
a novel finite difference method, and b) fitting them to simulation data
obtained for imaginary chemical potentials. The mu^2 and mu^4 coefficients are
found to be negative by both methods, with consistent absolute values.
Combining both methods gives evidence that also the mu^6 coefficient is
negative. Hence, on coarse N_t=4 lattices a three-flavour theory with m > m^c_0
does not possess a chiral critical endpoint for quark chemical potentials
mu\lsim T. Simulations on finer lattices are required for reliable continuum
physics. Possible implications for the QCD phase diagram are discussed.


title: Sequestering the Gravitino: Neutralino Dark Matter in Gauge Mediation

abstract:
  In conventional models of gauge-mediated supersymmetry breaking, the lightest
supersymmetric particle (LSP) is invariably the gravitino. However, if the
supersymmetry breaking sector is strongly coupled, conformal sequestering may
raise the mass of the gravitino relative to the remaining soft
supersymmetry-breaking masses. In this letter, we demonstrate that such
conformal dynamics in gauge-mediated theories may give rise to satisfactory
neutralino dark matter while simultaneously solving the flavor and mu/ B mu
problems.


title: Edward Teller and Nuclei: Along the Trail to the Neutrino

abstract:
  I discuss two of Edward Teller's contributions to nuclear physics, the
introduction of the Gamow-Teller operator in beta decay and the formulation of
the Goldhaber-Teller model for electric dipole transitions, in the context of
efforts to understand the weak interaction and the nature of the neutrino.


title: The TEXES Survey For H2 Emission From Protoplanetary Disks

abstract:
  We report the results of a search for pure rotational molecular hydrogen
emission from the circumstellar environments of young stellar objects with
disks using the Texas Echelon Cross Echelle Spectrograph (TEXES) on the NASA
Infrared Telescope Facility and the Gemini North Observatory. We searched for
mid-infrared H2 emission in the S(1), S(2), and S(4) transitions. Keck/NIRSPEC
observations of the H2 S(9) transition were included for some sources as an
additional constraint on the gas temperature. We detected H2 emission from 6 of
29 sources observed: AB Aur, DoAr 21, Elias 29, GSS 30 IRS 1, GV Tau N, and HL
Tau. Four of the six targets with detected emission are class I sources that
show evidence for surrounding material in an envelope in addition to a
circumstellar disk. In these cases, we show that accretion shock heating is a
plausible excitation mechanism. The detected emission lines are narrow (~10
km/s), centered at the stellar velocity, and spatially unresolved at scales of
0.4 arcsec, which is consistent with origin from a disk at radii 10-50 AU from
the star. In cases where we detect multiple emission lines, we derive
temperatures > 500 K from ~1 M_earth of gas. Our upper limits for the
non-detections place upper limits on the amount of H2 gas with T > 500 K of
less than a few Earth masses. Such warm gas temperatures are significantly
higher than the equilibrium dust temperatures at these radii, suggesting that
the gas is decoupled from the dust in the regions we are studying and that
processes such as UV, X-ray, and accretion heating may be important.


title: High-Redshift Galaxy Kinematics: Constraints on Models of Disk Formation

abstract:
  Integral field spectroscopy of galaxies at redshift z~2 has revealed a
population of early-forming, rotationally-supported disks. These high-redshift
systems provide a potentially important clue to the formation processes that
build disk galaxies in the universe. A particularly well-studied example is the
z=2.38 galaxy BzK-15504, which was shown by Genzel et al. (2006) to be a
rotationally supported disk despite the fact that its high star formation rate
and short gas consumption timescale require a very rapid acquisition of mass.
Previous kinematical analyses have suggested that z~2 disk galaxies like
BzK-15504 did not form through mergers because their line-of-sight velocity
fields display low levels of asymmetry. We perform the same kinematical
analysis on a set of simulated disk galaxies formed in gas-rich mergers of the
type that may be common at high redshift, and show that the remnant disks
display low velocity field asymmetry and satisfy the criteria that have been
used to classify high-redshift galaxies as disks observationally. Further, we
compare one of our remnants to the bulk properties of BzK-15504 and show that
it has a star formation rate, gas surface density, and a circular
velocity-to-velocity dispersion ratio that matches BzK-15504 remarkably well.
We suggest that observations of high-redshift disk galaxies like BzK-15504 are
consistent with the hypothesis that gas-rich mergers play an important role in
disk formation at high redshift.


title:
Scale Dependent Galaxy Bias in the SDSS as a function of Luminosity and
  Colour

abstract:
  It has been known for a long time that the clustering of galaxies changes as
a function of galaxy type. This galaxy bias acts as a hindrance to the
extraction of cosmological information from the galaxy power spectrum or
correlation function. Theoretical arguments show that a change in the amplitude
of the clustering between galaxies and mass on large-scales is unavoidable, but
cosmological information can be easily extracted from the shape of the power
spectrum or correlation function if this bias is independent of scale.
Scale-dependent bias is generally small on large scales, k<0.1 h.Mpc^{-1}, but
on smaller scales can affect the recovery of \Omega_m.h from the measured shape
of the clustering signal, and have a small effect on the Baryon Acoustic
Oscillations. In this paper we investigate the transition from
scale-independent to scale-dependent galaxy bias as a function of galaxy
population. We use the Sloan Digital Sky Survey DR5 sample to fit various
models, which attempt to parametrise the turn-off from scale-independent
behaviour. For blue galaxies, we find that the strength of the turn-off is
strongly dependent on galaxy luminosity, with stronger scale-dependent bias on
larger scales for more luminous galaxies. For red galaxies, the
scale-dependence is a weaker function of luminosity. Such trends need to be
modelled in order to optimally extract the information available in future
surveys, and can help with the design of such surveys.


title:
Quantum Feedback Control: How to use Verification Theorems and Viscosity
  Solutions to Find Optimal Protocols

abstract:
  While feedback control has many applications in quantum systems, finding
optimal control protocols for this task is generally challenging. So-called
"verification theorems" and "viscosity solutions" provide two useful tools for
this purpose: together they give a simple method to check whether any given
protocol is optimal, and provide a numerical method for finding optimal
protocols. While treatments of verification theorems usually use sophisticated
mathematical language, this is not necessary. In this article we give a simple
introduction to feedback control in quantum systems, and then describe
verification theorems and viscosity solutions in simple language. We also
illustrate their use with a concrete example of current interest.


title:
Velocity Statistics Distinguish Quantum Turbulence from Classical
  Turbulence

abstract:
  By analyzing trajectories of solid hydrogen tracers, we find that the
distributions of velocity in decaying quantum turbulence in superfluid $^4$He
are strongly non-Gaussian with $1/v^3$ power-law tails. These features differ
from the near-Gaussian statistics of homogenous and isotropic turbulence of
classical fluids. We examine the dynamics of many events of reconnection
between quantized vortices and show by simple scaling arguments that they
produce the observed power-law tails.


title:
Flavour Violation in Gauge-Mediated Supersymmetry Breaking Models:
  Experimental Constraints and Phenomenology at the LHC

abstract:
  We present an extensive analysis of gauge-mediated supersymmetry breaking
models with minimal and non-minimal flavour violation. We first demonstrate
that low-energy, precision electroweak, and cosmological constraints exclude
large "collider-friendly" regions of the minimal parameter space. We then
discuss various possibilities how flavour violation, although naturally
suppressed, may still occur in gauge-mediation models. The introduction of
non-minimal flavour violation at the electroweak scale is shown to relax the
stringent experimental constraints, so that benchmark points, that are also
cosmologically viable, can be defined and their phenomenology, i.e. squark and
gaugino production cross sections with flavour violation, at the LHC can be
studied.


title: Constraining Interactions in Cosmology's Dark Sector

abstract:
  We consider the cosmological constraints on theories in which there exists a
nontrivial coupling between the dark matter sector and the sector responsible
for the acceleration of the universe, in light of the most recent supernovae,
large scale structure and cosmic microwave background data. For a variety of
models, we show that the strength of the coupling of dark matter to a
quintessence field is constrained to be less than 7% of the coupling to
gravity. We also show that long range interactions between fermionic dark
matter particles mediated by a light scalar with a Yukawa coupling are
constrained to be less than 5% of the strength of gravity at a distance scale
of 10 Mpc. We show that all of the models we consider are quantum mechanically
weakly coupled, and argue that some other models in the literature are ruled
out by quantum mechanical strong coupling.


title: Rotation and Turbulence of the Hot ICM in Galaxy Clusters

abstract:
  Cosmological simulations of galaxy clusters typically find that the weight of
a cluster at a given radius is not balanced entirely by the thermal gas
pressure of the hot ICM, with theoretical studies emphasizing the role of
random turbulent motions to provide the necessary additional pressure support.
Using a set of high-resolution, hydrodynamical simulations of galaxy clusters
that include radiative cooling and star formation, we find instead that in the
most relaxed clusters rotational support exceeds that from random turbulent
motions for radii 0.1 - 0.5 r_500, and that the observed clusters are much
rounder than the simulated, relaxed clusters within ~ 0.4 r_500. Moreover,
while the observed clusters display an average ellipticity profile that does
not vary significantly with radius, the ellipticity of the relaxed CDM clusters
declines markedly with increasing radius, suggesting that the ICM of the
observed clusters rotates less rapidly than that of the relaxed CDM clusters
out to ~ 0.6 r_500. We also find the ellipticity profile of a simulated cluster
without radiative cooling is in much better agreement with the observations,
implying that over-cooling has a substantial impact on the gas dynamics and
morphology out to larger radii than previously recognized. It also suggests
that the 10%-20% systematic errors from non-thermal gas pressure support
reported for simulated cluster masses, obtained from fitting simulated X-ray
data over large radial ranges within r_500, may need to be revised downward.
These results demonstrate the utility of X-ray ellipticity profiles as a probe
of ICM rotation and over-cooling which should be used to constrain future
cosmological cluster simulations.


title: Semiclassical regime of Regge calculus and spin foams

abstract:
  Recent attempts to recover the graviton propagator from spin foam models
involve the use of a boundary quantum state peaked on a classical geometry. The
question arises whether beyond the case of a single simplex this suffices for
peaking the interior geometry in a semiclassical configuration. In this paper
we explore this issue in the context of quantum Regge calculus with a general
triangulation. Via a stationary phase approximation, we show that the boundary
state succeeds in peaking the interior in the appropriate configuration, and
that boundary correlations can be computed order by order in an asymptotic
expansion. Further, we show that if we replace at each simplex the exponential
of the Regge action by its cosine -- as expected from the semiclassical limit
of spin foam models -- then the contribution from the sign-reversed terms is
suppressed in the semiclassical regime and the results match those of
conventional Regge calculus.


title:
Cache oblivious storage and access heuristics for blocked matrix-matrix
  multiplication

abstract:
  We investigate effects of ordering in blocked matrix--matrix multiplication.
We find that submatrices do not have to be stored contiguously in memory to
achieve near optimal performance. Instead it is the choice of execution order
of the submatrix multiplications that leads to a speedup of up to four times
for small block sizes. This is in contrast to results for single matrix
elements showing that contiguous memory allocation quickly becomes irrelevant
as the blocksize increases.


title:
Simulating High-Redshift Disk Galaxies: Applications to Long Duration
  Gamma-Ray Burst Hosts

abstract:
  The efficiency of star formation governs many observable properties of the
cosmological galaxy population, yet many current models of galaxy formation
largely ignore the important physics of star formation and the interstellar
medium (ISM). Using hydrodynamical simulations of disk galaxies that include a
treatment of the molecular ISM and star formation in molecular clouds
(Robertson & Kravtsov 2008), we study the influence of star formation
efficiency and molecular hydrogen abundance on the properties of high-redshift
galaxy populations. In this work, we focus on a model of low-mass, star forming
galaxies at 1<~z<~2 that may host long duration gamma-ray bursts (GRBs).
Observations of GRB hosts have revealed a population of faint systems with star
formation properties that often differ from Lyman-break galaxies (LBGs) and
more luminous high-redshift field galaxies. Observed GRB sightlines are
deficient in molecular hydrogen, but it is unclear to what degree this
deficiency owes to intrinsic properties of the galaxy or the impact the GRB has
on its environment. We find that hydrodynamical simulations of low-stellar mass
systems at high-redshifts can reproduce the observed star formation rates and
efficiencies of GRB host galaxies at redshifts 1<~z<~2. We show that the
compact structure of low-mass high-redshift GRB hosts may lead to a molecular
ISM fraction of a few tenths, well above that observed in individual GRB
sightlines. However, the star formation rates of observed GRB host galaxies
imply molecular gas masses of 10^8 - 10^9 M_sun similar to those produced in
the simulations, and may therefore imply fairly large average H_2 fractions in
their ISM.


title:
Bogoliubov transformations and fermion condensates in lattice field
  theories

abstract:
  We apply generalized Bogoliubov transformations to the transfer matrix of
relativistic field theories regularized on a lattice. We derive the conditions
these transformations must satisfy to factorize the transfer matrix into two
terms which propagate fermions and antifermions separately, and we solve the
relative equations under some conditions. We relate these equations to the
saddle point approximation of a recent bosonization method and to the
Foldy-Wouthuysen transformations which separate positive from negative energy
states in the Dirac Hamiltonian.


title: Total mass biases in X-ray galaxy clusters

abstract:
  The exploitation of clusters of galaxies as cosmological probes relies on
accurate measurements of their total gravitating mass. X-ray observations
provide a powerful means of probing the total mass distribution in galaxy
clusters, but might be affected by observational biases and rely on simplistic
assumptions originating from our limited understanding of the intracluster
medium physics. This paper is aimed at elucidating the reliability of X-ray
total mass estimates in clusters of galaxies by properly disentangling various
biases of both observational and physical origin. We use N-body/SPH simulation
of a large sample of ~100 galaxy clusters and investigate total mass biases by
comparing the mass reconstructed adopting an observational-like approach with
the true mass in the simulations. X-ray surface brightness and temperature
profiles extracted from the simulations are fitted with different models and
adopting different radial fitting ranges in order to investigate modeling and
extrapolation biases. Different theoretical definitions of gas temperature are
used to investigate the effect of spectroscopic temperatures and a power ratio
analysis of the surface brightness maps allows us to assess the dependence of
the mass bias on cluster dynamical state. Moreover, we perform a study on the
reliability of hydrostatic and hydrodynamical equilibrium mass estimates using
the full three-dimensional information in the simulation.[abridged]


title:
General Matrix-Valued Inhomogeneous Linear Stochastic Differential
  Equations and Applications

abstract:
  The expressions of solutions for general $n\times m$ matrix-valued
inhomogeneous linear stochastic differential equations are derived. This
generalizes a result of Jaschke (2003) for scalar inhomogeneous linear
stochastic differential equations. As an application, some $\R^n$ vector-valued
inhomogeneous nonlinear stochastic differential equations are reduced to random
differential equations, facilitating pathwise study of the solutions.


title:
A constructive mean field analysis of multi population neural networks
  with random synaptic weights and stochastic inputs

abstract:
  We deal with the problem of bridging the gap between two scales in neuronal
modeling. At the first (microscopic) scale, neurons are considered individually
and their behavior described by stochastic differential equations that govern
the time variations of their membrane potentials. They are coupled by synaptic
connections acting on their resulting activity, a nonlinear function of their
membrane potential. At the second (mesoscopic) scale, interacting populations
of neurons are described individually by similar equations. The equations
describing the dynamical and the stationary mean field behaviors are considered
as functional equations on a set of stochastic processes. Using this new point
of view allows us to prove that these equations are well-posed on any finite
time interval and to provide a constructive method for effectively computing
their unique solution. This method is proved to converge to the unique solution
and we characterize its complexity and convergence rate. We also provide
partial results for the stationary problem on infinite time intervals. These
results shed some new light on such neural mass models as the one of Jansen and
Rit \cite{jansen-rit:95}: their dynamics appears as a coarse approximation of
the much richer dynamics that emerges from our analysis. Our numerical
experiments confirm that the framework we propose and the numerical methods we
derive from it provide a new and powerful tool for the exploration of neural
behaviors at different scales.

categories: physics.bio-ph cond-mat.dis-nn math-ph math.MP q-bio.NC


title: Holographic quark gluon plasma with flavor

abstract:
  In this work I explore theoretical and phenomenological implications of
chemical potentials and charge densities inside a strongly coupled thermal
plasma, using the gauge/gravity correspondence. Strong coupling effects
discovered in this model theory are interpreted geometrically and may be taken
as qualitative predictions for heavy ion collisions at RHIC and LHC. In
particular I examine the thermodynamics, spectral functions, transport
coefficients and the phase diagram of the strongly coupled plasma. For example
stable mesons, which are the analogs of the QCD Rho-mesons, are found to
survive beyond the deconfinement transition. This paper is based on partly
unpublished work performed in the context of my PhD thesis. New results and
ideas extending significantly beyond those published until now are stressed.


title: Holographic Thermodynamics and Transport of Flavor Fields

abstract:
  We use gauge-gravity duality to study a strongly-coupled non-Abelian gauge
theory with flavor fields, i.e. fields transforming in the fundamental
representation of the gauge group. We first study the thermodynamics of the
flavor fields. In the grand canonical ensemble at zero temperature, we find a
second-order transition when the mass of the flavor fields equals the chemical
potential. We then study the transport properties of the flavor fields at
finite temperature and density. We introduce external electric and magnetic
fields and compute the resulting current of flavor charge. From this current we
extract the conductivity, using Ohm's law. In addition, we compute the drag
force on the flavor fields at large mass, in the presence of a finite baryon
density and external electric and magnetic fields.


title: Mott Transition in the Hubbard Model on Checkerboard Lattice

abstract:
  We investigate the bandwidth-controlled Mott transition in the Hubbard model
on the checkerboard lattice at half filling using the path-integral
renormalization group (PIRG) method. It is demonstrated that the system
undergoes a first-order phase transition to the plaquette-singlet insulating
phase at a finite Hubbard interaction. This conclusion is drawn via a detailed
analysis of the spin and charge correlations around the phase transition point
by means of the PIRG method aided with a new iteration scheme introduced in
this paper.


title: Is Detection of Fitzgerald-Lorentz Contraction Possible?

abstract:
  Visual perception of Fitzgerald-Lorentz contraction is known to be
theoretically impossible, and this can be demonstrated pedagogically with the
aid of simple spacetime diagrams of one spatial dimension. Such diagrams also
demonstrate, simply and directly, that the apparent length of a moving meter
stick changes as it passes by and can even look elongated. In addition,
measurement of a moving meter stick with instruments, as opposed to visual
perception, must be inherently ambiguous, as the length measured depends on
clock synchronization, which is widely considered to be conventional. In fact,
for some synchronization choices, a moving meter stick would be measured as
greater than one meter. Thus, the well known Fitzgerald-Lorentz contraction
factor $\sqrt {1-v^2/c^2} $ would generally not be seen visually, and would
only be measured in a system employing one particular (Einstein)
synchronization convention.


title: Magnetic Fields In Astrophysical Objects

abstract:
  Magnetic fields are known to reside in many astrophysical objects and are now
believed to be crucially important for the creation of phenomena on a wide
variety of scales. However, the role of the magnetic field in the bodies that
we observe has not always been clear. In certain situations, the importance of
a magnetic field has been over looked on the grounds that the large-scale
magnetic field was believed to be too weak to play and important role in the
dynamics.
  In this article I discuss some of the recent developments concerning magnetic
fields in stars, planets and accretion discs. I choose to emphasise some of the
situations where it has been suggested that weak magnetic fields may play a
more significant role than previously thought. At the end of the article I list
some of the questions to be answered in the future.


title: Graham's Schedules and the Number Partition Problem

abstract:
  We show the equivalence of the Number Partition Problem and the two processor
scheduling problem. We establish a priori bounds on the completion times for
the scheduling problem which are tighter than Graham's but almost on par with a
posteriori bounds of Coffman and Sethi. We conclude the paper with a
characterization of the asymptotic behavior of the scheduling problem which
relates to the spread of the processing times and the number of jobs.


title: Lattice analysis for the energy scale of QCD phenomena

abstract:
  We formulate a new framework in lattice QCD to study the relevant energy
scale of QCD phenomena. By considering the Fourier transformation of link
variable, we can investigate the intrinsic energy scale of a physical quantity
nonperturbatively. This framework is broadly available for all lattice QCD
calculations. We apply this framework for the quark-antiquark potential and
meson masses in quenched lattice QCD. The gluonic energy scale relevant for the
confinement is found to be less than 1 GeV in the Landau or Coulomb gauge.


title:
Measurement of the branching fraction B(tau- --> K0 pi- nu) using the
  BaBar detector

abstract:
  A preliminary measurement of the branching fraction B(tau- --> K0 pi- nu) is
made using 384.6 fb-1 of e+e- collision data provided by the PEP-II collider,
operating primarily at sqrt(s)=10.58 GeV, and recorded using the BaBar
detector. From this we measure: B(tau- --> K0 pi- nu) = (0.840 +/- 0.004 (stat)
+/- 0.023 (syst)) %. This result is the most precise measurement to date and is
consistent with the world average.


title: When Clusters Collide: Constraints On Antimatter On The Largest Scales

abstract:
  Observations have ruled out the presence of significant amounts of antimatter
in the Universe on scales ranging from the solar system, to the Galaxy, to
groups and clusters of galaxies, and even to distances comparable to the scale
of the present horizon. Except for the model-dependent constraints on the
largest scales, the most significant upper limits to diffuse antimatter in the
Universe are those on the Mpc scale of clusters of galaxies provided by the
EGRET upper bounds to annihilation gamma-rays from galaxy clusters whose
intra-cluster gas is revealed through its x-ray emission. On the scale of
individual clusters of galaxies the upper bounds to the fraction of mixed
matter and antimatter for the 55 clusters from a flux-limited x-ray survey
range from < 5 x 10^(-9) to < 1 x 10^(-6), strongly suggesting that individual
clusters of galaxies are made entirely of matter or, of antimatter. X-ray and
gamma-ray observations of colliding clusters of galaxies, such as the Bullet
Cluster, permit these constraints to be extended to even larger scales. If the
observations of the Bullet Cluster, where the upper bound to the antimatter
fraction is found to be < 3 x 10^-6, can be generalized to other colliding
clusters of galaxies, cosmologically significant amounts of antimatter will be
excluded on scales of order 20 Mpc (5 x 10^(15)M_Sun).


title:
Ferromagnetism and spin polarized charge carriers in In$_{2}$O$_{3}$
  thin films

abstract:
  We present evidence for spin polarized charge carriers in In$_2$O$_3$ films.
Both In$_2$O$_3$ and Cr doped In$_2$O$_3$ films exhibit room temperature
ferromagnetism after vacuum annealing, with a saturation moment of
approximately 0.5 emu/cm$^3$. We used Point Contact Andreev Reflection
measurements to directly determine the spin polarization, which was found to be
approximately 50$\pm$5% for both compositions. These results are consistent
with suggestions that the ferromagnetism observed in certain oxide
semiconductors may be carrier mediated.


title:
Top-Antitop cross section measurement in the di-lepton decay channel
  with ATLAS

abstract:
  We present simulations of the production cross-section measurement of
top-antitop pairs in the di-leptonic decay channel with the ATLAS detector.
This study uses the Commissioning Service Challenge (CSC) data, which is the
latest and centrally produced Monte-Carlo data set to validate the detector
simulation before the actual data taking. The signal process was generated with
MC@NLO and important background processes were studied. A cut and count method
and two likelihood methods were employed to measure the cross section and
important systematic effects were investigated. The expected statistical and
systematic errors for a luminosity of 100 $\ipb$ are also given.


title: Verified Null-Move Pruning

abstract:
  In this article we review standard null-move pruning and introduce our
extended version of it, which we call verified null-move pruning. In verified
null-move pruning, whenever the shallow null-move search indicates a fail-high,
instead of cutting off the search from the current node, the search is
continued with reduced depth.
  Our experiments with verified null-move pruning show that on average, it
constructs a smaller search tree with greater tactical strength in comparison
to standard null-move pruning. Moreover, unlike standard null-move pruning,
which fails badly in zugzwang positions, verified null-move pruning manages to
detect most zugzwangs and in such cases conducts a re-search to obtain the
correct result. In addition, verified null-move pruning is very easy to
implement, and any standard null-move pruning program can use verified
null-move pruning by modifying only a few lines of code.


title: F-term SUSY Breaking and Moduli

abstract:
  We discuss the coupling of heavy moduli fields to light fields when the
dynamics of the latter, absent such couplings, yields metastable vacua. We show
that the survival of the vacuum structure of the local model depends
nontrivially on the cross-couplings of the two sectors. In particular we find
that for "local" models (such as those realized by D-branes in type II string
theories) with metastable vacua breaking supersymmetry via F-terms,
cross-coupling of the two sectors at an intermediate scale can push the
metastable vacuum outside of the regime of the effective field theory. We
parametrize the region in which the metastable vacua are safe. We the show that
sufficiently small cross-couplings can be made natural. Finally, we briefly
discuss the role of moduli in stringy realizations of "retrofitted"
SUSY-breaking sectors.


title:
Correlation functions of the energy-momentum tensor in SU(2) gauge
  theory at finite temperature

abstract:
  We calculate correlation functions of the energy-momentum tensor in the
vicinity of the deconfinement phase transition of (3+1)-dimensional SU(2) gauge
theory and discuss their critical behavior in the vicinity of the second order
deconfinement transition. We show that correlation functions of the trace of
the energy momentum tensor diverge uniformly at the critical point in
proportion to the specific heat singularity. Correlation functions of the
pressure, on the other hand, stay finite at the critical point. We discuss the
consequences of these findings for the analysis of transport coefficients, in
particular the bulk viscosity, in the vicinity of a second order phase
transition point.


title: Dynamic Connectivity: Connecting to Networks and Geometry

abstract:
  Dynamic connectivity is a well-studied problem, but so far the most
compelling progress has been confined to the edge-update model: maintain an
understanding of connectivity in an undirected graph, subject to edge
insertions and deletions. In this paper, we study two more challenging, yet
equally fundamental problems.
  Subgraph connectivity asks to maintain an understanding of connectivity under
vertex updates: updates can turn vertices on and off, and queries refer to the
subgraph induced by "on" vertices. (For instance, this is closer to
applications in networks of routers, where node faults may occur.)
  We describe a data structure supporting vertex updates in O (m^{2/3})
amortized time, where m denotes the number of edges in the graph. This greatly
improves over the previous result [Chan, STOC'02], which required fast matrix
multiplication and had an update time of O(m^0.94). The new data structure is
also simpler.
  Geometric connectivity asks to maintain a dynamic set of n geometric objects,
and query connectivity in their intersection graph. (For instance, the
intersection graph of balls describes connectivity in a network of sensors with
bounded transmission radius.)
  Previously, nontrivial fully dynamic results were known only for special
cases like axis-parallel line segments and rectangles. We provide similarly
improved update times, O (n^{2/3}), for these special cases. Moreover, we show
how to obtain sublinear update bounds for virtually all families of geometric
objects which allow sublinear-time range queries, such as arbitrary 2D line
segments, d-dimensional simplices, and d-dimensional balls.


title: Local Galois Symbols on E x E

abstract:
  This article is the first part of a two-part work on the Albanese kernel
T_F(E x E), for an elliptic curve E over F. The main result furnishes
information, for any odd prime p, about the kernel and image of the Galois
symbol map from T_F(E \times E)/p to the Galois cohomology group H^2(F, E[p]
(x) E[p]), for F a p-adic field and E/F ordinary, without requiring that the
p-torsion points are F-rational. A key step is to show that the image is zero
when the Galois module E[p] is non-semisimple. The forthcoming second part will
deal with global questions.


title:
Large-wavelength instabilities in free-surface Hartmann flow at low
  magnetic Prandtl numbers

abstract:
  We study the linear stability of the flow of a viscous electrically
conducting capillary fluid on a planar fixed plate in the presence of gravity
and a uniform magnetic field. We first confirm that the Squire transformation
for MHD is compatible with the stress and insulating boundary conditions at the
free surface, but argue that unless the flow is driven at fixed Galilei and
capillary numbers, the critical mode is not necessarily two-dimensional. We
then investigate numerically how a flow-normal magnetic field, and the
associated Hartmann steady state, affect the soft and hard instability modes of
free surface flow, working in the low magnetic Prandtl number regime of
laboratory fluids. Because it is a critical layer instability, the hard mode is
found to exhibit similar behaviour to the even unstable mode in channel
Hartmann flow, in terms of both the weak influence of Pm on its neutral
stability curve, and the dependence of its critical Reynolds number Re_c on the
Hartmann number Ha. In contrast, the structure of the soft mode's growth rate
contours in the (Re, alpha) plane, where alpha is the wavenumber, differs
markedly between problems with small, but nonzero, Pm, and their counterparts
in the inductionless limit. As derived from large wavelength approximations,
and confirmed numerically, the soft mode's critical Reynolds number grows
exponentially with Ha in inductionless problems. However, when Pm is nonzero
the Lorentz force originating from the steady state current leads to a
modification of Re_c(Ha) to either a sublinearly increasing, or decreasing
function of Ha, respectively for problems with insulating and conducting walls.
In the former, we also observe pairs of Alfven waves, the upstream propagating
wave undergoing an instability at large Alfven numbers.


title:
Correlated pressure effects on structure and superconductivity in
  LaFeAsO0.9F0.1

abstract:
  We have studied the structural and superconductivity properties of the
compound LaFeAsO0.9F0.1 under pressures up to 32GPa using synchrotron radiation
and diamond anvil cells. We obtain an ambient pressure bulk modulus K_0 =
78(2)GPa, compressibility comparable to some cuprates. At high pressures, the
sample is in the overdoped region, with a linear decrease with pressure
variation of the superconducting transition temperature.


title: Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei

abstract:
  We evaluate the coincidence spectra in the nonmesonic weak decay (NMWD)
$\Lambda N\go nN$ of $\Lambda$ hypernuclei $^{4}_\Lambda$He, $^{5}_\Lambda$He,
$^{12}_\Lambda$C, $^{16}_\Lambda$O, and $^{28}_\Lambda$Si, as a function of the
sum of kinetic energies $E_{nN}=E_n+E_N$ for $N=n,p$. The strangeness-changing
transition potential is described by the one-meson-exchange model, with
commonly used parameterization. Two versions of the Independent-Particle Shell
Model (IPSM) are employed to account for the nuclear structure of the final
residual nuclei. They are: (a) IPSM-a, where no correlation, except for the
Pauli principle, is taken into account, and (b) IPSM-b, where the highly
excited hole states are considered to be quasi-stationary and are described by
Breit-Wigner distributions, whose widths are estimated from the experimental
data. All $np$ and $nn$ spectra exhibit a series of peaks in the energy
interval 110 MeV $<E_{nN}<170$ MeV, one for each occupied shell-model state.
The IPSM-a could be a pretty fair approximation for the light $^{4}_\Lambda$He
and $^{5}_\Lambda$He hypernuclei. For the remaining, heavier, hypernuclei it is
very important, however, to take into account the spreading in strength of the
deep-hole states, and bring into play the IPSM-b approach. Notwithstanding the
nuclear model that is employed the results depend only very weakly on the
details of the dynamics involved in the decay process proper. We propose that
the IPSM is the appropriate lowest-order approximation for the theoretical
calculations of the of kinetic energy sum spectra in the NMWD. It is in
comparison to this picture that one should appraise the effects of the final
state interactions and of the two-nucleon-induced decay mode.


title:
Universal bounds and semiclassical estimates for eigenvalues of abstract
  Schroedinger operators

abstract:
  We prove trace inequalities for a self-adjoint operator on an abstract
Hilbert space. These inequalities lead to universal bounds on spectral gaps and
on moments of eigenvalues lambda_k that are analogous to those known for
Schroedinger operators and the Dirichlet Laplacian, on which the operators of
interest are modeled. In addition we produce inequalities that are new even in
the model case. These include a family of differential inequalities for
generalized Riesz means and theorems stating that arithmetic means of
lambda_k^p for p <= 3 are universally bounded from above by multiples of the
geometric mean of the lambda_k. For Schroedinger operators and the Dirichlet
Laplacian these bounds are Weyl-sharp, i.e., saturated by the standard
semiclassical estimates for lambda_k at large k.


title: A biophysical model of prokaryotic diversity in geothermal hot springs

abstract:
  Recent field investigations of photosynthetic bacteria living in geothermal
hot spring environments have revealed surprisingly complex ecosystems, with an
unexpected level of genetic diversity. One case of particular interest involves
the distribution along hot spring thermal gradients of genetically distinct
bacterial strains that differ in their preferred temperatures for reproduction
and photosynthesis. In such systems, a single variable, temperature, defines
the relevant environmental variation. In spite of this, each region along the
thermal gradient exhibits multiple strains of photosynthetic bacteria adapted
to several distinct thermal optima, rather than the expected single thermal
strain adapted to the local environmental temperature. Here we analyze
microbiology data from several ecological studies to show that the thermal
distribution field data exhibit several universal features independent of
location and specific bacterial strain. These include the distribution of
optimal temperatures of different thermal strains and the functional dependence
of the net population density on temperature. Further, we present a simple
population dynamics model of these systems that is highly constrained by
biophysical data and by physical features of the environment. This model can
explain in detail the observed diversity of different strains of the
photosynthetic bacteria. It also reproduces the observed thermal population
distributions, as well as certain features of population dynamics observed in
laboratory studies of the same organisms.


title:
Functional gradients through the cortex, multisensory integration and
  scaling laws in brain dynamics

abstract:
  In the context of the increasing number of works on multisensory and
cross-modal effects in cerebral processing, a review is made on the functional
model of human brain proposed by Justo Gonzalo (1910-1986), in relation to what
he called central syndrome (caused by unilateral lesion in the
parieto-occipital cortex, equidistant from the visual, tactile and auditory
projection areas). The syndrome is featured by a bilateral, symmetric and
multisensory involvement, and by a functional depression with dynamic effects
dependent on the neural mass lost and related to physiological laws of nervous
excitability. Inverted or tilted vision as well as tactile and auditive
inversion, under minimum stimulus, appears as a stage of incomplete
integration, being almost corrected under higher stimulus or facilitation by
multisensory integration. The syndrome reveals aspects of the brain dynamics
that suggest a functional continuity and unity of the cortex. A functional
gradients scheme was proposed in which the specificity of the cortex is
distributed with a continuous variation. This syndrome is interpreted as a
scale reduction in the nervous excitability of the system, the different
sensory qualities being affected allometricaly according to scaling laws. A
continuity from lower to higher sensory functions was proposed. The sensory
growth by an increase of the stimulus or by multisensory facilitation is found
to follow approximately power laws, that would reflect basic laws of biological
neural networks. We restrict the analysis to the visual system.


title:
Thermal strain-induced enhancement of electromagnetic properties in
  SiC-MgB2 composites

abstract:
  Strain engineering has been used to modify materials properties in
ferroelectric, superconducting, and ferromagnetic thin films. The advantage of
strain engineering is that it can achieve unexpected enhancement in certain
properties, such as an increase in ferroelectric critical temperature, Tc, by
300 to 500K, with a minimum detrimental effect on the intrinsic properties of
the material. The strain engineering has been largely applied to the materials
in thin film form, where the strain is generated as a result of lattice
mismatch between the substrate and component film or between layers in
multilayer structures. Here, we report the observation of residual thermal
stress/strain in dense SiC-MgB2 superconductor composites prepared by a
diffusion method. We demonstrate that the thermal strain caused by the
different thermal expansion coefficients between the MgB2 and SiC phases is
responsible for the significant improvement in the critical current density,
Jc, the irreversibility field, Hirr, and the upper critical field, Hc2, in the
SiC-MgB2 composite where the carbon substitution level is low. In contrast to
the common practice of improving the Jc and Hc2 of MgB2 through chemical
substitution, by taking advantage of residual thermal strains we are able to
design a composite, which shows only a small drop in Tc and little increase in
resistivity, but a significant improvement over the Jc and Hc2 of MgB2. The
present findings open up a new direction for manipulation of materials
properties through strain engineering for materials in various forms.


title:
Lawson Method for Obtaining Wave Functions and $g$ Factors of Ar
  Isotopes

abstract:
  Lawson has shown that one can obtain sensible wave functions even in the weak
deformation limit of the Nilsson model as long as one projects out states of
good total angular momentum. We apply this method to obtain wave functions and
magnetic $g$ factors of excited states of select even-even Ar isotopes.


title:
A Complete Grammar for Decomposing a Family of Graphs into 3-connected
  Components

abstract:
  Tutte has described in the book "Connectivity in graphs" a canonical
decomposition of any graph into 3-connected components. In this article we
translate (using the language of symbolic combinatorics)
  Tutte's decomposition into a general grammar expressing any family of graphs
(with some stability conditions) in terms of the 3-connected subfamily. A key
ingredient we use is an extension of the so-called dissymmetry theorem, which
yields negative signs in the grammar.
  As a main application we recover in a purely combinatorial way the analytic
expression found by Gim\'enez and Noy for the series counting labelled planar
graphs (such an expression is crucial to do asymptotic enumeration and to
obtain limit laws of various parameters on random planar graphs). Besides the
grammar, an important ingredient of our method is a recent bijective
construction of planar maps by Bouttier, Di Francesco and Guitter.


title: Quantum Destructive Interference

abstract:
  An apparent paradox for unitarity non-conservation is investigated for the
case of destructive quantum interference.