title: Mass modelling of galaxy clusters via velocity moments

abstract:
  We summarize the method of mass modelling of galaxy clusters based on
reproducing the dispersion and kurtosis of the projected velocity distribution
of galaxies. The models are parametrized within the framework of the NFW
density profile, characterized by the virial mass and concentration, together
with the constant anisotropy of galaxy orbits. The use of velocity dispersion
alone does not allow to constrain all the three parameters from kinematic data
due to the mass-anisotropy degeneracy. The degeneracy is broken by introducing
the fourth velocity moment, the kurtosis. We tested the method based on fitting
both moments on mock data sets drawn from simulated dark matter haloes and
showed it to reproduce reliably the properties of the haloes. The method has
been applied to estimate the mass, concentration and anisotropy of more than 20
clusters which allowed us to confirm, for the first time using kinematic data,
the mass-concentration relation found in N-body simulations.


title: Dynamos and Chemical Mixing in Evolved Stars

abstract:
  In low-mass Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) stars,
anomalous mixing must transport material near the hydrogen-burning shell to the
convective envelope. Recently, it was suggested that buoyant magnetic flux
tubes could supply the necessary transport rate (Busso et al. 2007). The fields
are assumed to originate from a dynamo operating in the stellar interior. Here,
we show what is required of an $\alpha-\Omega$ dynamo in the envelope of an AGB
star to maintain these fields. Differential rotation and rotation drain via
turbulent dissipation and Poynting flux, so if shear can be resupplied by
convection, then large-scale toroidal field strengths of
$\left<B_\phi\right>\simeq3\times10^4$ G can be sustained at the base of the
convection zone.


title:
Lifting to cluster-tilting objects in 2-Calabi-Yau triangulated
  categories

abstract:
  We show that a tilting module over the endomorphism algebra of a
cluster-tilting object in a 2-Calabi-Yau triangulated category lifts to a
cluster-tilting object in this 2-Calabi-Yau triangulated category. This
generalizes a recent work of D. Smith for cluster categories.


title: Maximum-rate, Minimum-Decoding-Complexity STBCs from Clifford Algebras

abstract:
  It is well known that Space-Time Block Codes (STBCs) from orthogonal designs
(ODs) are single-symbol decodable/symbol-by-symbol decodable (SSD) and are
obtainable from unitary matrix representations of Clifford algebras. However,
SSD codes are obtainable from designs that are not orthogonal also. Recently,
two such classes of SSD codes have been studied: (i) Coordinate Interleaved
Orthogonal Designs (CIODs) and (ii) Minimum-Decoding-Complexity (MDC) STBCs
from Quasi-ODs (QODs). Codes from ODs, CIODs and MDC-QODs are mutually
non-intersecting classes of codes. The class of CIODs have {\it non-unitary
weight matrices} when written as a Linear Dispersion Code (LDC) proposed by
Hassibi and Hochwald, whereas several known SSD codes including CODs have {\it
unitary weight matrices}. In this paper, we obtain SSD codes with unitary
weight matrices (that are not CODs) called Clifford Unitary Weight SSDs
(CUW-SSDs) from matrix representations of Clifford algebras. A main result of
this paper is the derivation of an achievable upper bound on the rate of any
unitary weight SSD code as $\frac{a}{2^{a-1}}$ for $2^a$ antennas which is
larger than that of the CODs which is $\frac{a+1}{2^a}$. It is shown that
several known classes of SSD codes are CUW-SSD codes and CUW-SSD codes meet
this upper bound. Also, for the codes of this paper conditions on the signal
sets which ensure full-diversity and expressions for the coding gain are
presented. A large class of SSD codes with non-unitary weight matrices are
obtained which include CIODs as a proper subclass.


title: The effect of unbound stars on the mass modelling of the Fornax dwarf

abstract:
  We discuss how different approaches to selecting member stars in kinematic
samples of dwarf spheroidal galaxies affect the estimates of their mass and
anisotropy of stellar orbits. We demonstrate that the selection of members is
an additional source of error compared to the usual uncertainties due to the
sampling of velocity moments. As an example we use the kinematic data set for
202 stars in the Fornax dwarf galaxy for which we model the velocity dispersion
profile and estimate the mass-to-light ratio and anisotropy assuming that mass
follows light. We also show that stronger constraints on these parameters can
be obtained if kurtosis of the velocity distribution is included in the
analysis. Using the Besancon model of the Milky Way we demonstrate that the
majority of contamination in Fornax probably comes from the Milky Way stars.


title: Simple model for QCD analysis of the proton helicity structure

abstract:
  In this paper we use the experimental data to obtain the polarized parton
distribution functions (PPDFs) in the LO and NLO approximations. The analysis
is based on the Jacobi polynomials expansion of the polarized structure
function (PSF). Our calculations for polarized parton distribution functions
based on the Jacobi polynomials method are in good agreement with the other
theoretical models.


title: Instability in a Network Coevolving with a Particle System

abstract:
  We study a coupled dynamics of a network and a particle system. Particles of
density $\rho$ diffuse freely along edges, each of which is rewired at a rate
given by a decreasing function of particle flux. We find that the coupled
dynamics leads to an instability toward the formation of hubs and that there is
a dynamic phase transition at a threshold particle density $\rho_c$. In the low
density phase, the network evolves into a star-shaped one with the maximum
degree growing linearly in time. In the high density phase, the network
exhibits a fat-tailed degree distribution and an interesting dynamic scaling
behavior. We present an analytic theory explaining mechanism for the
instability and a scaling theory for the dynamic scaling behavior.


title: Missing Baryons and the Warm-Hot Intergalactic Medium

abstract:
  Stars and gas in galaxies, hot intracluster medium, and intergalactic
photo-ionized gas make up at most half of the baryons that are expected to be
present in the universe. The majority of baryons are still missing and are
expected to be hidden in a web of warm-hot intergalactic medium. This matter
was shock-heated during the collapse of density perturbations that led to the
formation of the relaxed structures that we see today. Finding the missing
baryons and thereby producing a complete inventory of possibly the only
detectable component of the energy-mass budget of the universe is crucial to
validate or invalidate our standard cosmological model.


title:
Electron spin relaxation in GaAs quantum dot systems - The role of the
  hyperfine interaction

abstract:
  We present numerical results for electron spin relaxation rates for single
and laterally coupled double GaAs quantum dots in a perpendicular magnetic
field. As source of spin relaxation we consider hyperfine interaction with the
nuclear spins in the GaAs substrate. Due to the differences in the energy
scales of the nuclear and electronic Zeeman energies, the phonon bath system
has to be taken into account for energy dissipation. The corresponding
transition rates of second order show strong dependencies on correlations
between the electrons and the electronic energy differences, and hence on the
magnetic field. For a highly asymmetric double dot we have found a relatively
low second order electron spin relaxation rate for a wide range of magnetic
fields.


title:
High-order perturbative expansions of multi-parameter Phi^4 quantum
  field theories

abstract:
  We present high-order pertubative expansions of multi-parameter Phi^4 quantum
field theories with an N-component fundamental field, containing up to
4th-order polynomials of the field. Multi-parameter Phi^4 theories generalize
the simplest O(N)-symmetric Phi^4 theories, and describe more complicated
symmetry breaking patterns. These notes collect several high-order perturbative
series of physically interesting multi-parameter Phi^4 theories, to five or six
loops. We consider the O(M)XO(N)-symmetric Phi^4 model, the so-called MN model,
and a spin-density-wave Phi^4 model containing five quartic terms.


title: The Wickstead Problem

abstract:
  In 1977 Anthony Wickstead raised the question of the conditions for all band
preserving linear operators to be order bounded in a vector lattice. This
article overviews the main ideas and results on the Wickstead problem and its
variations, focusing primarily on the case of band preserving operators in a
universally complete vector lattice.


title: Gribov copies and anomalous scaling

abstract:
  Nonperturbative and lattice methods indicate that Gribov copies modify the
infrared behavior of gauge theories and cause a suppression of gluon
propagation. We investigate whether this can be implemented in a modified
perturbation theory. The minimal modification proceeds via a nonlocal
generalization of the Fadeev-Popov ghost that automatically decouples from
physical states. The expected scale invariance of the physics associated with
Gribov copies leads to the emergence of a nontrivial infrared fixed point. For
a range of a scaling exponent the gauge bosons exhibit unparticlelike behavior
in the infrared. The confining regime of interest for QCD requires a larger
scaling exponent, but then the severity of ghost dominance upsets naive power
counting for the infrared scaling behavior of amplitudes.


title:
A variational Jastrow coupled-cluster theory of quantum many-body
  systems

abstract:
  We study many-body correlations in the ground states of a general quantum
system of bosons or fermions by including an additional Jastrow function in our
ecently proposed variational coupled-cluster method. Our approach combines the
dvantages of state-dependent correlations in the coupled-cluster theory and of
strong, short-ranged correlations of the Jastrow function. We apply a
generalized linked-cluster expansion for the Jastrow wavefunction and provide
detailed analysis for practical evaluation of Hamiltonian expectation value as
an energy functional of the Jastrow function and the bare density-distribution
functions introduced and calculated in our earlier publications; a simple,
first-order energy functional is derived and detailed formulas for higher-order
contributions are provided. Our energy functional does not suffer the
divergence as in most coupled-cluster calculations when applying to
Hamiltonians with hardcore potentials. We also discuss relations between our
energy functional and the energy functionals from other theories.


title:
A proof of Goldbach's conjecture that all even numbers greater than four
  are the sum of two primes

abstract:
  In this paper I introduce a model which allows one to prove Goldbachs
hypothesis. The model is produced by studying Goldbach partitions as displayed
by an inverted mirror image of all the primes up to some even number equal to
the last prime plus three. The bottom half of the model is then moved to the
right in steps of two which exhibit the Goldbach partitions for the next even
number. As long as the model contains all the primes up to the resulting even
number minus three, then Goldbachs hypothesis can be proven if it can be shown
that each move must produce a Goldbach partition until one reaches the next
prime plus one. I show that this must be the case.


title: Nuclear suppression at RHIC and LHC in Glauber-Gribov approach

abstract:
  The approach to problem of nuclear shadowing based on Gribov Reggeon calculus
is presented. Here the total cross section of $h A$ interaction is found in a
parameter-free description, employing the new data on the gluon density of the
Pomeron, measured with high precision at HERA, as input. The model is then
applied for calculation of $J/\psi$ production in $d Au$ collisions at top RHIC
energy. It is shown that the theoretical estimates are in a very good agreement
with the PHENIX data, and further predictions for the $J/\psi$ suppression in
$p Pb$ collisions at coming soon LHC are made.


title:
Combined CDF and Dzero Upper Limits on Standard Model Higgs-Boson
  Production

abstract:
  We combine results from CDF and D0 searches for a standard model Higgs boson
(H) in ppbar collisions at the Fermilab Tevatron at sqrt{s}=1.96 TeV. With
1.0-1.9 fb-1 of data collected at CDF, and 0.9-1.7 fb-1 at D0, the 95% C.L.
upper limits on Higgs production are a factor of 6.2 (1.4) higher than the SM
cross section for a Higgs mass of m_Higgs = 115 (160) GeV/c^2. Based on
simulation, the median expected upper limit is 4.3 (1.9). These results extend
significantly the individual limits of each experiment.


title:
Multi-group ML Decodable Collocated and Distributed Space Time Block
  Codes

abstract:
  In this paper, collocated and distributed space-time block codes (DSTBCs)
which admit multi-group maximum likelihood (ML) decoding are studied. First the
collocated case is considered and the problem of constructing space-time block
codes (STBCs) which optimally tradeoff rate and ML decoding complexity is
posed. Recently, sufficient conditions for multi-group ML decodability have
been provided in the literature and codes meeting these sufficient conditions
were called Clifford Unitary Weight (CUW) STBCs. An algebraic framework based
on extended Clifford algebras is proposed to study CUW STBCs and using this
framework, the optimal tradeoff between rate and ML decoding complexity of CUW
STBCs is obtained for few specific cases. Code constructions meeting this
tradeoff optimally are also provided. The paper then focuses on multi-group ML
decodable DSTBCs for application in synchronous wireless relay networks and
three constructions of four-group ML decodable DSTBCs are provided. Finally,
the OFDM based Alamouti space-time coded scheme proposed by Li-Xia for a 2
relay asynchronous relay network is extended to a more general transmission
scheme that can achieve full asynchronous cooperative diversity for arbitrary
number of relays. It is then shown how differential encoding at the source can
be combined with the proposed transmission scheme to arrive at a new
transmission scheme that can achieve full cooperative diversity in asynchronous
wireless relay networks with no channel information and also no timing error
knowledge at the destination node. Four-group decodable DSTBCs applicable in
the proposed OFDM based transmission scheme are also given.


title: Time-dependent embedding

abstract:
  A method of solving the time-dependent Schr\"odinger equation is presented,
in which a finite region of space is treated explicitly, with the boundary
conditions for matching the wave-functions on to the rest of the system
replaced by an embedding term added on to the Hamiltonian. This time-dependent
embedding term is derived from the Fourier transform of the energy-dependent
embedding potential, which embeds the time-independent Schr\"odinger equation.
Results are presented for a one-dimensional model of an atom in a time-varying
electric field, the surface excitation of this model atom at a jellium surface
in an external electric field, and the surface excitation of a bulk state.


title: Method of invariant grid for model reduction of hydrogen combustion

abstract:
  The Method of Invariant Grid (MIG) is a model reduction technique based on
the concept of slow invariant manifold (SIM), which approximates the SIM by a
set of nodes in the concentration space (invariant grid). In the present work,
the MIG is applied to a realistic combustion system: An adiabatic constant
volume reactor with H2-air at stoichiometric proportions. By considering the
thermodynamic Lyapunov function of the detailed kinetic system, the notion of
the quasi-equilibrium manifold (QEM) is adopted as an initial approximation to
the SIM. One- and two-dimensional discrete approximations of the QEM
(quasi-equilibrium grids) are constructed and refined via the MIG to obtain the
corresponding invariant grids. The invariant grids are tabulated and used to
integrate the reduced system. Excellent agreements between the reduced and
detailed kinetics is demonstrated.


title: Particle Approximation of the Wasserstein Diffusion

abstract:
  We construct a system of interacting two-sided Bessel processes on the unit
interval and show that the associated empirical measure process converges to
the Wasserstein Diffusion, assuming that Markov uniqueness holds for the
generating Wasserstein Dirichlet form. The proof is based on the variational
convergence of an associated sequence of Dirichlet forms in the generalized
Mosco sense of Kuwae and Shioya.


title:
Theory of electronic transport in random alloys with short-range order:
  Korringa-Kohn-Rostoker non-local coherent potential approximation

abstract:
  We present an ab-initio formalism for the calculation of transport properties
in compositionally disordered systems within the framework of the
Korringa-Kohn-Rostoker non-local coherent potential approximation. Our
formalism is based upon the single-particle Kubo-Greenwood linear response and
provides a natural means of incorporating the effects of short-range order upon
the transport properties. We demonstrate the efficacy of the formalism by
examining the effects of short-range order and clustering upon the transport
properties of disordered $AgPd$ and $CuZn$ alloys.


title: Decomposition During Search for Propagation-Based Constraint Solvers

abstract:
  We describe decomposition during search (DDS), an integration of And/Or tree
search into propagation-based constraint solvers. The presented search
algorithm dynamically decomposes sub-problems of a constraint satisfaction
problem into independent partial problems, avoiding redundant work.
  The paper discusses how DDS interacts with key features that make
propagation-based solvers successful: constraint propagation, especially for
global constraints, and dynamic search heuristics.
  We have implemented DDS for the Gecode constraint programming library. Two
applications, solution counting in graph coloring and protein structure
prediction, exemplify the benefits of DDS in practice.


title: General runner removal and the Mullineux map

abstract:
  We prove a new `runner removal theorem' for $q$-decomposition numbers of the
level 1 Fock space of type $A^{(1)}_{e-1}$, generalising earlier theorems of
James--Mathas and the author. By combining this with another theorem relating
to the Mullineux map, we show that the problem of finding all $q$-decomposition
numbers indexed by partitions of a given weight is a finite computation.


title: IPHAS and the symbiotic stars. I. Selection method and first discoveries

abstract:
  The study of symbiotic stars is essential to understand important aspects of
stellar evolution in interacting binaries. Their observed population in the
Galaxy is however poorly known, and is one to three orders of magnitudes
smaller than the predicted population size. IPHAS, the INT Photometric Halpha
survey of the Northern Galactic plane, gives us the opportunity to make a
systematic, complete search for symbiotic stars in a magnitude-limited volume,
and discover a significant number of new systems.
  A method of selecting candidate symbiotic stars by combining IPHAS and
near-IR (2MASS) colours is presented. It allows us to distinguish symbiotic
binaries from normal stars and most of the other types of Halpha emission line
stars in the Galaxy. The only exception are T Tauri stars, which can however be
recognized because of their concentration in star forming regions. Using these
selection criteria, we discuss the classification of a list of 4338 IPHAS stars
with Halpha in emission. 1500 to 2000 of them are likely to be Be stars. Among
the remaining objects, 1183 fulfill our photometric constraints to be
considered candidate symbiotic stars. The spectroscopic confirmation of three
of these objects, which are the first new symbiotic stars discovered by IPHAS,
proves the potential of the survey and selection method.


title:
Optical conductivity and the correlation strength of high temperature
  copper-oxide superconductors

abstract:
  High temperature copper-oxide-based superconductivity is obtained by adding
carriers to insulating "parent compounds". It is widely believed the parent
compounds are "Mott" insulators, in which the lack of conduction arises from
anomalously strong electron-electron repulsion, and that the unusual properties
of Mott insulators are responsible for high temperature superconductivity. This
paper presents a comparison of optical conductivity measurements and
theoretical calculations which challenges this belief. The analysis indicates
that the correlation strength in the cuprates is not as strong as previously
believed, that the materials are not properly regarded as Mott insulators, that
antiferromagnetism is essential to obtain the insulating state and, by
implication, that antiferromagnetism is essential to the properties of the
doped metallic and superconducting state as well.


title: Local Ramsey theory. An abstract approach

abstract:
  It is shown that the known notion of selective coideal can be extended to a
family $\mathcal{H}$ of subsets of $\mathcal{R}$, where $(\mathcal{R},\leq,r)$
is a topological Ramsey space in the sense of Todorcevic (see \cite{todo}).
Then it is proven that, if $\mathcal{H}$ selective, the $\mathcal{H}$-Ramsey
and $\mathcal{H}$-Baire subsets of $\mathcal{R}$ are equivalent. This extends
the results of Farah in \cite{farah} for semiselective coideals of
$\mathbb{N}$. Also, it is proven that the family of ${\cal H}$--Ramsey subsets
of ${\cal R}$ is closed under the Souslin operation.


title: Moduli evolution in the presence of thermal corrections

abstract:
  We study the effect of thermal corrections on the evolution of moduli in
effective Supergravity models. This is motivated by previous results in the
literature suggesting that these corrections could alter and, even, erase the
presence of a minimum in the zero temperature potential, something that would
have disastrous consequences in these particular models. We show that, in a
representative sample of flux compactification constructions, this need not be
the case, although we find that the inclusion of thermal corrections can
dramatically decrease the region of initial conditions for which the moduli are
stabilised. Moreover, the bounds on the reheating temperature coming from
demanding that the full, finite temperature potential, has a minimum can be
considerably relaxed given the slow pace at which the evolution proceeds.


title: Imaging the oxygen-rich disk toward the silicate carbon star EU And

abstract:
  We present multi-epoch high-angular resolution observations of 22 GHz H2O
masers toward the silicate carbon star EU And to probe the spatio-kinematic
distribution of oxygen-rich material. EU And was observed at three epochs
(maximum time interval of 14 months) with the Very Long Baseline Array (VLBA).
Our VLBA observations of the 22 GHz H2O masers have revealed that the maser
spots are distributed along a straight line across ~20 mas, with a slight hint
of an S-shaped structure. The observed spectra show three prominent velocity
components at V_LSR = -42, -38, and -34 km s^-1, with the masers in SW
redshifted and those in NE blueshifted. The maser spots located in the middle
of the overall distribution correspond to the component at V_LSR = -38 km s^-1,
which approximately coincides with the systemic velocity. These observations
can be interpreted as either an emerging helical jet or a disk viewed almost
edge-on (a circumbinary or circum-companion disk). However, the outward motion
measured in the VLBA images taken 14 months apart is much smaller than that
expected from the jet scenario. Furthermore, the mid-infrared spectrum obtained
with the Spitzer Space Telescope indicates that the 10 micron silicate emission
is optically thin and the silicate grains are of sub-micron size. This lends
support to the presence of a circum-companion disk, because an optically thin
circumbinary disk consisting of such small grains would be blown away by the
intense radiation pressure of the primary (carbon-rich) star. If we assume
Keplerian rotation for the circum-companion disk, the mass of the companion is
estimated to be 0.5--0.8 M_sun. We also identify CO2 emission features at
13--16 micron in the Spitzer spectrum of EU And--the first unambiguous
detection of CO2 in silicate carbon stars.


title: Strains and Jets in Black Hole Fields

abstract:
  We study the behaviour of an initially spherical bunch of particles emitted
along trajectories parallel to the symmetry axis of a Kerr black hole. We show
that, under suitable conditions, curvature and inertial strains compete to
generate jet-like structures.


title:
First Flavor-Tagged Determination of Bounds on Mixing-Induced CP
  Violation in Bs -> J/psi phi Decays

abstract:
  This Letter describes the first determination of bounds on the CP-violation
parameter 2*beta_s using Bs decays in which the flavor of the bottom meson at
production is identified. The result is based on approximately 2,000 Bs ->
J/psi phi decays reconstructed in a 1.35 fb-1 data sample collected with the
CDF II detector using p-bar p collisions produced at the Fermilab Tevatron. We
report confidence regions in the two-dimensional space of 2*beta_s and the
decay-width difference Delta-Gamma. Assuming the standard model predictions of
2*beta_s and Delta-Gamma, the probability of a deviation as large as the level
of the observed data is 15%, corresponding to 1.5 Gaussian standard deviations.
  Dedicated to the memory of our dear friend and colleague, Michael P. Schmidt.


title: Structural motifs of biomolecules

abstract:
  Biomolecular structures are assemblies of emergent anisotropic building
modules such as uniaxial helices or biaxial strands. We provide an approach to
understanding a marginally compact phase of matter that is occupied by proteins
and DNA. This phase, which is in some respects analogous to the liquid crystal
phase for chain molecules, stabilizes a range of shapes that can be obtained by
sequence-independent interactions occurring intra- and intermolecularly between
polymeric molecules. We present a singularityfree self-interaction for a tube
in the continuum limit and show that this results in the tube being positioned
in the marginally compact phase. Our work provides a unified framework for
understanding the building blocks of biomolecules.


title:
Parity nonconserving two-pion exchange in elastic proton-proton
  scattering

abstract:
  Parity nonconserving two-pion exchange in elastic pp scattering is
investigated in the presence of phenomenological strong distortions in various
models. Parity violation is included in the nucleon-pion vertex considering NN
and N Delta(1232) intermediate states in box and crossed box diagrams. Using
the derived parity nonconserving two-pion exchange potential we calculate the
longitudinal analyzing power A_L in elastic $pp$ scattering. The predicted
effect is of the same order as vector meson exchanges.


title: Continuous variable versus EIT-based quantum memories

abstract:
  We discuss a general model of a quantum memory for a single light mode in a
collective mode of atomic oscillators. The model includes interaction
Hamiltonians that are of second order in the canonical position and momentum
operators of the light- and atomic oscillator modes. We also consider the
possibility of measurement and feedback. We identify an interaction Hamiltonian
that leads to an ideal mapping by pure unitary evolution and compare several
schemes which realize this mapping using a common continuous-variable
description. In particular we discuss schemes based on the off-resonant Faraday
effect supplemented by measurement and feedback and proper preparation of the
atoms in a squeezed state and schemes based on off-resonant Raman coupling as
well as electromagnetically induced transparency (EIT).


title: Large Deviations for Riesz Potentials of Additive Processes

abstract:
  We study functionals of the form \[\zeta_{t}=\int_0^{t}...\int_0^{t} |
X_1(s_1)+...+ X_p(s_p)|^{-\sigma}ds_1... ds_p\] where $X_1(t),..., X_p(t)$ are
i.i.d. $d$-dimensional symmetric stable processes of index $0<\bb\le 2$. We
obtain results about the large deviations and laws of the iterated logarithm
for $\zeta_{t}$.


title: MHD mode coupling in the neighbourhood of a 2D null point

abstract:
  At this time there does not exist a robust set of rules connecting low and
high $\beta$ waves across the $\beta \approx 1$ layer. The work here
contributes specifically to what happens when a low $\beta$ fast wave crosses
the $\beta \approx 1$ layer and transforms into high $\beta$ fast and slow
waves. The nature of fast and slow magnetoacoustic waves is investigated in a
finite $\beta$ plasma in the neighbourhood of a two-dimensional null point. The
linearised equations are solved in both polar and cartesian forms with a
two-step Lax-Wendroff numerical scheme. Analytical work (e.g. small $\beta$
expansion and WKB approximation) also complement the work. It is found that
when a finite gas pressure is included in magnetic equilibrium containing an
X-type null point, a fast wave is attracted towards the null by a refraction
effect and that a slow wave is generated as the wave crosses the $\beta \approx
1$ layer. Current accumulation occurs close to the null and along nearby
separatrices. The fast wave can now \emph{pass through the origin} due to the
non-zero sound speed, an effect not previously seen in related papers but clear
seen for larger values of $\beta$. Some of the energy can now leave the region
of the null point and there is again generation of a slow wave component (we
find that the fraction of the incident wave converted to a slow wave is
proportional to $\beta$). We conclude that there are two competing phenomena;
the refraction effect (due to the variable Alfv\'en speed) and the contribution
from the non-zero sound speed. These experiments illustrate the importance of
the magnetic topology and of the location of the $\beta \approx 1$ layer in the
system.


title: Degree k Linear Recursions Mod(p)

abstract:
  Linear recursions of degree $k$ are determined by evaluating the sequence of
Generalized Fibonacci Polynomials, $\{F_{k,n}(t_1,...,t_k)\}$ (isobaric
reflects of the complete symmetric polynomials) at the integer vectors
$(t_1,...,t_k)$. If $F_{k,n}(t_1,...,t_k) = f_n$, then
  $$f_n - \sum_{j=1}^k t_j f_{n-j} = 0,$$ and $\{f_n\}$ is a linear recursion
of degree $k$. On the one hand, the periodic properties of such sequences
modulo a prime $p$ are discussed, and are shown to be rela ted to the prime
structure of certain algebraic number fields; for example, the arithmetic
properties of the period ar e shown to characterize ramification of primes in
an extension field. On the other hand, the structure of the semiloca l rings
associated with the number field is shown to be completely determined by
Schur-hook polynomials.


title:
Multipartite Continuous Variable Solution for the Byzantine Agreement
  Problem

abstract:
  We demonstrate that the Byzantine Agreement (detectable broadcast) is also
solvable in the continuous-variable scenario with multipartite entangled
Gaussian states and Gaussian operations (homodyne detection). Within this
scheme we find that Byzantine Agreement requires a minimum amount of
entanglement in the multipartite states used in order to achieve a solution. We
discuss realistic implementations of the protocol, which consider the
possibility of having inefficient homodyne detectors, not perfectly correlated
outcomes, and noise in the preparation of the resource states. The proposed
protocol is proven to be robust and efficiently applicable under such non-ideal
conditions.


title:
Identification of DNA-binding protein target sequences by physical
  effective energy functions. Free energy analysis of lambda repressor-DNA
  complexes

abstract:
  Specific binding of proteins to DNA is one of the most common ways in which
gene expression is controlled. Although general rules for the DNA-protein
recognition can be derived, the ambiguous and complex nature of this mechanism
precludes a simple recognition code, therefore the prediction of DNA target
sequences is not straightforward. DNA-protein interactions can be studied using
computational methods which can complement the current experimental methods and
offer some advantages. In the present work we use physical effective potentials
to evaluate the DNA-protein binding affinities for the lambda repressor-DNA
complex for which structural and thermodynamic experimental data are available.
The effect of conformational sampling by Molecular Dynamics simulations on the
computed binding energy is assessed; results show that this effect is in
general negative and the reproducibility of the experimental values decreases
with the increase of simulation time considered. The free energy of binding for
non-specific complexes agrees with earlier theoretical suggestions. Moreover,
as a results of these analyses, we propose a protocol for the prediction of
DNA-binding target sequences. The possibility of searching regulatory elements
within the bacteriophage-lambda genome using this protocol is explored. Our
analysis shows good prediction capabilities, even in the absence of any
thermodynamic data and information on the naturally recognized sequence. This
study supports the conclusion that physics-based methods can offer a completely
complementary methodology to sequence-based methods for the identification of
DNA-binding protein target sequences.


title:
Uniqueness of a pre-generator for $C_0$-semigroup on a general locally
  convex vector space

abstract:
  The main purpose is to generalize a theorem of Arendt about uniqueness of
$C_0$-semigroups from Banach space setting to the general locally convex vector
spaces, more precisely, we show that cores are the only domains of uniqueness
for $C_0$-semigroups on locally convex spaces. As an application, we find a
necessary and sufficient condition for that the mass transport equation has one
unique $L^1(\R^d,dx)$ weak solution.


title: Transverse Momentum Spectra of J/\psi in Heavy-Ion Collisions

abstract:
  We investigate J/\psi transverse-momentum (p_t) distributions and their
centrality dependence in heavy-ion collisions at SPS and RHIC within the
framework of a two-component model, which includes (i) primordial production
coupled with various phases of dissociation, (ii) statistical coalescence of c
and \bar{c} quarks at the hadronization transition. The suppression of the
direct component (i) is calculated by solving a transport equation for J/\psi,
\chi_c and \psi' in an expanding fireball using momentum dependent dissociation
rates in the Quark-Gluon Plasma (QGP). The coalescence component is inferred
from a kinetic rate equation with a momentum dependence following from a blast
wave approach. At SPS energies, where the direct component dominates, the
interplay of Cronin effect and QGP suppression results in fair agreement with
NA50 p_t spectra. At RHIC energies, the p_t spectra in central Au+Au collisions
are characterized by a transition from regeneration at low p_t to direct
production above. At lower centralities, the latter dominates at all p_t.


title: A polynomial parametrization of torus knots

abstract:
  For every odd integer $N$ we give an explicit construction of a polynomial
curve $\cC(t) = (x(t), y (t))$, where $\deg x = 3$, $\deg y = N + 1 + 2\pent
N4$ that has exactly $N$ crossing points $\cC(t_i)= \cC(s_i)$ whose parameters
satisfy $s_1 < ... < s_{N} < t_1 < ... < t_{N}$. Our proof makes use of the
theory of Stieltjes series and Pad\'e approximants. This allows us an explicit
polynomial parametrization of the torus knot $K_{2,N}$.


title:
On the possible nature of Bp-Ap Stars: an application to HD101065 and
  HR465

abstract:
  We have proposed the new explanation of some magnetic chemically peculiar
(MCP) stars anomalies, which is based on assumption that such stars can be the
close binary systems with a secondary component being neutron star. Within this
hypothesis one can naturally explain the main anomalous features of MCP stars:
first of all, an existence of the short-lived radioactive isotopes detected in
some stars (like Przybylski's star and HR465), and some others peculiarities
(e.g. the behavior of CU Vir in radio range, the phenomenon of the roAp stars).


title: Magnetic properties of HO2 thin films

abstract:
  We report on the magnetic and transport studies of hafnium oxide thin films
grown by pulsed-laser deposition on sapphire substrates under different oxygen
pressures, ranging from 10-7 to 10-1 mbar. Some physical properties of these
thin films appear to depend on the oxygen pressure during growth: the film
grown at low oxygen pressure (P ~= 10-7 mbar) has a metallic aspect and is
conducting, with a positive Hall signal, while those grown under higher oxygen
pressures (7 x 10-5 <= P <= 0.4 mbar) are insulating. However, no intrinsic
ferromagnetic signal could be attributed to the HfO2 films, irrespective of the
oxygen pressure during the deposition.


title:
$L^\infty$-uniqueness of Schr\"odinger operators restricted in an open
  domain

abstract:
  Consider the Schr\"odinger operator ${\cal A}=-\frac{\Delta}{2}+V$ acting on
space $C_0^\infty(D)$, where $D$ is an open domain in $\R^d$. The main purpose
of this paper is to present the $L^\infty(D,dx)$-uniqueness for Schr\"odinger
operators which is equivalent to the $L^1(D,dx)$-uniqueness of weak solutions
of the heat diffusion equation associated to the operator $\cal A$.


title: Generalized Parton Distributions and Hadronic Observables

abstract:
  Following a previous detailed study of unpolarized generalized parton
distribution functions in the non-singlet sector, and at zero values of the
skewness variable, $\zeta$, we propose a physically motivated parametrization
that is valid at $\zeta \neq 0$. Our method makes use of information from the
nucleon form factor data, from deep inelastuc scattering parton distribution
functions, and from lattice results on the Mellin moments of generalized parton
distributions. It provides, therefore, a step towards a model independent
extraction of generalized distributions from the data, alternative to the
mathematical ansatz of double distributions. Comparisons with recent
experimental data on the proton are shown.


title: Heralded generation of entanglement with coupled cavities

abstract:
  We propose a scheme to generate two-photon, two-atom, or atom-photon
entangledstates with a coupled system of two cavities. In our scheme, two
cavity photonsare exchanged by the direct inter-cavity coupling, while atoms in
the cavitiessimply play the role of generating and probing them. By virtue of
the highefficiency of atomic state measurement, this method enables the
realization ofefficient heralded entanglement generation robust against photon
loss, whichgreatly facilitates applications in quantum information processing.


title:
Compensation of the Kondo effect in quantum dots coupled to
  ferromagnetic leads within equation of motion approach

abstract:
  We propose a new approximation scheme within equation of motion approach
(EOM) to spin polarized transport through a quantum dot coupled to
ferromagnetic leads. It has some advantages over a widely used in the
literature standard EOM technique, in particular when we are interested in spin
polarized quantities. Namely, it gives the values of the dot spin polarization
which are closer to the ones obtained within numerical renormalization group
(NRG), than the standard EOM approach. While restoring the Kondo effect, the
spin polarization vanishes and the transport becomes unpolarized, in agreement
with NRG and a real time diagrammatic calculations. The standard EOM procedure
gives nonzero values of the spin polarization, and the transport is still spin
polarized. Both approximations give the same correct splitting of the Kondo
peaks due to ferromagnetism in the electrodes.


title:
On the integrability of stellar motion in an accelerated logarithmic
  potential

abstract:
  An accelerated logarithmic potential models the mean motion of stars in a
flat rotation curve galaxy that sustains a wind system. For stars outside the
galactic wind launching region, the asymmetric removal of linear momentum by
the wind is seen as a perturbing acceleration superimposed onto the galactic
potential. We study the integrability of stellar motion in an accelerated
logarithmic potential. We use surfaces of section of the dynamical system to
probe the integrability of motion. We provide numerical evidence that motion in
an accelerated logarithmic potential is non-integrable. Large scale chaotic
diffusion occurs for lower values of the projected angular momentum along the
direction of acceleration and persists at all values of the angular momentum in
the outer part of the galaxy inside the truncation radius where the galactic
acceleration balances the wind-induced acceleration.


title: Image Effects on the Transport of Intense Nonaxisymmetric Charged Beams

abstract:
  The effect of conducting pipes on the equilibrium of intense nonaxisymmetric
continuous beams of charged particles is investigated. For a cylindrical pipe
and an elliptical beam, we obtain an exact closed form analytical expression
for the electrostatic potential. Using a variational principle, we then explore
the distortions that equilibrium beams suffer due to the conducting channel.
Finally, we present an exact proof that despite the nonlinear forces acting on
beams of arbitrary cross section inside conducting pipes of arbitrary shape,
the density of these beams remains homogeneous and their cross sectional area
remains the sa me as the one in free-space.


title: $\pi^o$ Electroproduction and Transversity

abstract:
  Exclusive $\pi^o$ electroproduction and related processes are suggested to
investigate the chiral odd transversity distributions of quarks in the
transversely polarized nucleon, $h_1(x)$, and its first moment, the tensor
charge. The connection between a description based on partonic degrees of
freedom, given in terms of generalized parton distributions, and Regge
phenomenology is explored.


title: The general quadruple point formula

abstract:
  Maps between manifolds $M^m\to N^{m+\ell}$ ($\ell>0$) have multiple points,
and more generally, multisingularities. The closure of the set of points where
the map has a particular multisingularity is called the multisingularity locus.
There are universal relations among the cohomology classes represented by
multisingularity loci, and the characteristic classes of the manifolds. These
relations include the celebrated Thom polynomials of monosingularities. For
multisingularities, however, only the form of these relations is clear in
general (due to Kazarian), the concrete polynomials occurring in the relations
are much less known. In the present paper we prove the first general such
relation outside the region of Morin-maps: the general quadruple point formula.
We apply this formula in enumerative geometry by computing the number of
4-secant linear spaces to smooth projective varieties. Some other
multisingularity formulas are also studied, namely 5, 6, 7 tuple point
formulas, and one corresponding to $\Sigma^2\Sigma^0$ multisingularities.


title: Concepts of Electroweak Symmetry Breaking and Higgs Physics

abstract:
  We present an introduction to the basic concepts of electroweak symmetry
breaking and Higgs physics within the Standard Model and its supersymmetric
extensions. A brief overview will also be given on alternative mechanisms of
electroweak symmetry breaking. In addition to the theoretical basis, the
present experimental status of Higgs physics and prospects at the Tevatron, the
LHC and e+e- linear colliders are discussed.


title: Multi-linear multipliers associated to simplexes of arbitrary length

abstract:
  In this article we prove that the $n$-linear operator whose symbol is the
characteristic function of the simplex $\Delta_n = \xi_1 < ... < \xi_n$ is
bounded from $L^2 \times ... \times L^2$ into $L^{2/n}$, generalizing in this
way our previous work on the "bi-est" operator (which corresponds to the case
$n=3$) as well as Lacey-Thiele theorem on the bi-linear Hilbert transform
(which corresponds to the case $n=2$).


title: The ground-based solar observations database BASS 2000

abstract:
  BASS 2000 is the French solar database for ground-based instruments. We
describe hereafter our organization, our tasks and the products we can deliver
to the international community. Our prospects cover data mining into the THeMIS
archive, a participation to the EST endeavour and the creation and curation of
the ESPaDOnS/NARVAL stellar spectra database.


title:
Reconstructing Bottom mesons using displaced vertices from semi-leptonic
  decays

abstract:
  Precise determination of heavy flavor production cross-sections at LHC
energies will be of primary importance. The produced heavy quarks are expected
to be sensitive probes of parton energy loss in the medium formed in heavy-ion
collisions. Through the measurement of charm and bottom suppression in Pb + Pb
with respect to p + p, we hope to obtain insight into the color-charge and
quark mass dependence of the energy loss mechanism. The ALICE experiment with
its large acceptance is well suited to investigate the intermediate transverse
momentum spectrum of heavy flavor mesons where these energy loss effects are
expected to be visible. ALICE has very good electron PID capabilities over a
large kinematic range using Time Projection Chamber (TPC), Transition Radiation
Detector (TRD) and the Electromagnetic Calorimeter (EMCal). In addition the
EMCal, to be installed for the Pb + Pb runs, is planned to allow efficient
triggering on high-pT jets. We first introduce the EMCal project and an
overview of detector specifications. Then we introduce a method developed to
select preferentially electrons from heavy flavor decays by reconstructing
displaced secondary vertices. The strategy is to reconstruct displaced vertices
from semi-leptonic heavy flavor meson decays using the excellent spatial
resolution of the Inner Tracking System (ITS). We show preliminary results of
an efficiency study from charm vs. bottom vertices.


title: Towards BAD conjecture

abstract:
  For $\alpha, \beta, \delta \in [0,1], \alpha +\beta = 1 $ we consider sets $$
{\rm BAD}^* (\alpha, \beta ;\delta) = \left\{\xi = (\xi_1,\xi_2) \in [0,1]^2:
,\inf_{p\in \mathbb{N}} \max \{(p\log(p+1))^\alpha ||p\xi_1||,
  (p\log (p+1))^\beta ||p\xi_2||\} \ge \delta \right\}. $$ We prove that for
different $(\alpha_1,\beta_1), (\alpha_2,\beta_2), \alpha_1 +\beta_1 = \alpha_2
+\beta_2 = 1 $ and $\delta $ small enough $$ {\rm BAD}^* (\alpha_1, \beta_1
;\delta) \bigcap {\rm BAD}^* (\alpha_2, \beta_2 ;\delta) \neq \varnothing . $$
  Our result is based on A. Khintchine's construction and an original method
due to Y. Peres and W. Schlag.


title: Positivity results on ribbon Schur function differences

abstract:
  There is considerable current interest in determining when the difference of
two skew Schur functions is Schur positive. We consider the posets that result
from ordering skew diagrams according to Schur positivity, before focussing on
the convex subposets corresponding to ribbons. While the general solution for
ribbon Schur functions seems out of reach at present, we determine necessary
and sufficient conditions for multiplicity-free ribbons, i.e. those whose
expansion as a linear combination of Schur functions has all coefficients
either zero or one. In particular, we show that the poset that results from
ordering such ribbons according to Schur-positivity is essentially a product of
two chains.


title: Bicycling Black Rings

abstract:
  We present detailed physics analyses of two different 4+1-dimensional
asymptotically flat vacuum black hole solutions with spin in two independent
planes: the doubly spinning black ring and the bicycling black ring system
("bi-rings"). The latter is a new solution describing two concentric orthogonal
rotating black rings which we construct using the inverse scattering technique.
We focus particularly on extremal zero-temperature limits of the solutions. We
construct the phase diagram of currently known zero-temperature vacuum black
hole solutions with a single event horizon, and discuss the non-uniqueness
introduced by more exotic black hole configurations such as bi-rings and
multi-ring saturns.


title:
The Spin Reorientation Transition and Phase Diagram of Ultrathin
  Ferromagnetic Films

abstract:
  We show results from Monte Carlo simulations of a two dimensional Heisenberg
model for ultrathin films with perpendicular anisotropy. A complete phase
diagram is obtained as a function of anisotropy and temperature, spanning a
wide range of behavior. We discuss our results in relation with experimental
findings in different ultrathin films. We observe and characterize a line of
Spin Reorientation Transitions . This transition from out of plane stripe order
to in plane ferromagnetic order presents a paramagnetic gap in between in a
finite region in parameter space, as reported in experiments. For large
anisotropies direct transitions from a low temperature stripe phase to a
paramagnetic or tetragonal phase with dominant perpendicular magnetization is
observed, also in agreement with experiments.
  We also show the phase diagram for a system without exchange, i.e. with pure
dipolar and anisotropy interactions. It shows a similar behavior to the
ferromagnetic case with antiferromagnetic instead of stripe phases at low
temperatures. A Spin Reorientation Transition is also found in this case.


title: Quantum decoherence and classical correlations in open systems

abstract:
  In the framework of the Lindblad theory for open quantum systems we determine
the degree of quantum decoherence and classical correlations of a harmonic
oscillator interacting with a thermal bath. The transition from quantum to
classical behaviour of the considered system is analyzed and it is shown that
the classicality takes place during a finite interval of time. We calculate
also the decoherence time and show that it has the same scale as the time after
which thermal fluctuations become comparable with quantum fluctuations.


title: Limits Of One Dimensional Diffusions

abstract:
  In this paper we look at the properties of limits of a sequence of real
valued time inhomogeneous diffusions. When convergence is only in the sense of
finite-dimensional distributions then the limit does not have to be a
diffusion. However, we show that as long as the drift terms satisfy a Lipschitz
condition and the limit is continuous in probability, then it will lie in a
class of processes that we refer to as almost-continuous diffusions. These
processes are strong Markov and satisfy an `almost-continuity' condition. We
also give a simple condition for the limit to be a continuous diffusion. These
results contrast with the multidimensional case where, as we show with an
example, a sequence of two dimensional martingale diffusions can converge to a
process that is both discontinuous and non-Markov.


title:
Non-perturbative renormalisation of Delta F=2 four-fermion operators in
  two-flavour QCD

abstract:
  Using Schroedinger Functional methods, we compute the non-perturbative
renormalisation and renormalisation group running of several four-fermion
operators, in the framework of lattice simulations with two dynamical Wilson
quarks. Two classes of operators have been targeted: (i) those with left-left
current structure and four propagating quark fields; (ii) all operators
containing two static quarks. In both cases, only the parity-odd contributions
have been considered, being the ones that renormalise multiplicatively. Our
results, once combined with future simulations of the corresponding lattice
hadronic matrix elements, may be used for the computation of phenomenological
quantities of interest, such as B_K and B_B (the latter also in the static
limit).


title: Limits to consistent on-line forecasting for ergodic time series

abstract:
  This study concerns problems of time-series forecasting under the weakest of
assumptions. Related results are surveyed and are points of departure for the
developments here, some of which are new and others are new derivations of
previous findings. The contributions in this study are all negative, showing
that various plausible prediction problems are unsolvable, or in other cases,
are not solvable by predictors which are known to be consistent when mixing
conditions hold.


title: An equivariant index formula for elliptic actions on contact manifolds

abstract:
  Given an elliptic action of a compact Lie group $G$ on a co-oriented contact
manifold $(M,E)$ one obtains two naturally associated objects: A
$G$-transversally elliptic operator $\dirac$, and an equivariant differential
form with generalised coefficients $\mathcal{J}(E,X)$ defined in terms of a
choice of contact form on $M$. We explain how the form $\mathcal{J}(E,X)$ is
natural with respect to the contact structure, and give a formula for the
equivariant index of $\dirac$ involving $\mathcal{J}(E,X)$. A key tool is the
Chern character with compact support developed by Paradan-Vergne \cite{PV1,PV}.


title: Morse Inequalities for Orbifold Cohomology

abstract:
  This paper begins the study of Morse theory for orbifolds, or more precisely
for differentiable Deligne-Mumford stacks. The main result is an analogue of
the Morse inequalities that relates the orbifold Betti numbers of an
almost-complex orbifold to the critical points of a Morse function on the
orbifold. We also show that a generic function on an orbifold is Morse. In
obtaining these results we develop for differentiable Deligne-Mumford stacks
those tools of differential geometry and topology -- flows of vector fields,
the strong topology -- that are essential to the development of Morse theory on
manifolds.


title: C*-Algebras Generated by Partial Isometries

abstract:
  In this paper, we characterize the C*-Algebra generated by partial
isometries.


title: Typicality, Black Hole Microstates and Superconformal Field Theories

abstract:
  We analyze the structure of heavy multitrace BPS operators in N = 1
superconformal quiver gauge theories that arise on the worldvolume of D3-branes
on an affine toric cone. We exhibit a geometric procedure for counting heavy
mesonic operators with given U(1) charges. We show that for any fixed linear
combination of the U(1) charges, the entropy is maximized when the charges are
in certain ratios. This selects preferred directions in the charge space that
can be determined with the help of a piece of string. We show that almost all
heavy mesonic operators of fixed U(1) charges share a universal structure. This
universality reflects the properties of the dual extremal black holes whose
microstates they create. We also interpret our results in terms of typical
configurations of dual giant gravitons in AdS space.


title: Linking electroweak and gravitational generators

abstract:
  Using complexified quaternions, an intriguing link between generators of two
different and surprisingly commuting four-dimensional representations of the
SU(2)xU(1) Lie group, and generators of two four-dimensional spin 1/2
representations of the Spin(3,1) Lie group is established: the former
generators completely determine the latter ones, and cross-combined they
constitute two different, but closely related, four-dimensional representations
of Spin(3,1)xSU(2)xU(1). These representations are used to construct a
Spin(3,1)xSU(2)xU(1) gauge invariant Lagrangian, containing two four-spinors
consisting not as usual of Weyl two-spinors of opposite helicity and equal weak
isospin, but instead of Weyl two-spinors of opposite weak isospin and equal
helicity, a construction which arises naturally from the mathematical formalism
itself. A possible future generalization, using complexified octonions, is
discussed.


title:
Comparative Direct Analysis of Type Ia Supernova Spectra. IV.
  Postmaximum

abstract:
  A comparative study of optical spectra of Type Ia supernovae (SNe Ia)
obtained near 1 week, 3 weeks, and 3 months after maximum light is presented.
Most members of the four groups that were defined on the basis of maximum light
spectra in Paper II (core normal, broad line, cool, and shallow silicon)
develop highly homogeneous postmaximum spectra, although there are interesting
exceptions. Comparisons with SYNOW synthetic spectra show that most of the
spectral features can be accounted for in a plausible way. The fits show that 3
months after maximum light, when SN Ia spectra are often said to be in the
nebular phase and to consist of forbidden emission lines, the spectra actually
remain dominated by resonance scattering features of permitted lines, primarily
those of Fe II. Even in SN 1991bg, which is said to have made a very early
transition to the nebular phase, there is no need to appeal to forbidden lines
at 3 weeks postmaximum, and at 3 months postmaximum the only clear
identification of a forbidden line is [Ca II] 7291, 7324. Recent studies of SN
Ia rates indicate that most of the SNe Ia that have ever occurred have been
"prompt" SNe Ia, produced by young (100,000,000 yr) stellar populations, while
most of the SNe Ia that occur at low redshift today are "tardy", produced by an
older (several Gyrs) population. We suggest that the shallow silicon SNe Ia
tend to be the prompt ones.


title: Faster solutions of the inverse pairwise Ising problem

abstract:
  Recent work has shown that probabilistic models based on pairwise
interactions-in the simplest case, the Ising model-provide surprisingly
accurate descriptions of experiments on real biological networks ranging from
neurons to genes. Finding these models requires us to solve an inverse problem:
given experimentally measured expectation values, what are the parameters of
the underlying Hamiltonian? This problem sits at the intersection of
statistical physics and machine learning, and we suggest that more efficient
solutions are possible by merging ideas from the two fields. We use a
combination of recent coordinate descent algorithms with an adaptation of the
histogram Monte Carlo method, and implement these techniques to take advantage
of the sparseness found in data on real neurons. The resulting algorithm learns
the parameters of an Ising model describing a network of forty neurons within a
few minutes. This opens the possibility of analyzing much larger data sets now
emerging, and thus testing hypotheses about the collective behaviors of these
networks.


title:
Ratios of 15N/12C and 4He/12C inclusive electroproduction cross sections
  in the nucleon resonance region

abstract:
  The (W,Q2)-dependence of the ratio of inclusive electron scattering cross
sections for 15N/12C was determined in the kinematic range 0.8<W<2 GeV and
0.2<Q2<1 GeV2 using 2.285 GeV electrons and the CLAS detector at Jefferson Lab.
The ratios exhibit only slight resonance structure, in agreement with a simple
phenomenological model and an extrapolation of DIS ratios to low Q2. Ratios of
4He/12C using 1.6 to 2.5 GeV electrons were measured with very high statistical
precision, and were used to correct for He in the N and C targets. The (W,Q2)
dependence of the 4He/12C ratios is in good agreement with the phenomenological
model, and exhibit significant resonance structure centered at W=0.94, 1.23 and
1.5 GeV.


title: Electron fractionalization for two-dimensional Dirac fermions

abstract:
  Fermion-number fractionalization without breaking of time-reversal symmetry
was recently demonstrated for a field theory in $(2+1)$-dimensional space and
time that describes the couplings between massive Dirac fermions, a
complex-valued Higgs field carrying an axial gauge charge of 2, and a U(1)
axial gauge field. Charge fractionalization occurs whenever the Higgs field
either supports vortices by itself, or when these vortices are accompanied by
half-vortices in the axial gauge field. The fractional charge is computed by
three different techniques. A formula for the fractional charge is given as a
function of a parameter in the Dirac Hamiltonian that breaks the spectral
energy-reflection symmetry. In the presence of a charge $\pm1$ vortex in the
Higgs field only, the fractional charge varies continuously and thus can take
irrational values. The simultaneous presence of a half-vortex in the axial
gauge field and a charge $\pm1$ vortex in the Higgs field re-rationalizes the
fractional charge to the value 1/2.

categories: hep-th cond-mat.str-el physics.atom-ph quant-ph


title: Refinements of Milnor's Fibration Theorem for Complex Singularities

abstract:
  Let $X$ be an analytic subset of an open neighbourhood $U$ of the origin
$\underline{0}$ in $\mathbb{C}^n$. Let $f\colon (X,\underline{0}) \to
(\mathbb{C},0)$ be holomorphic and set $V =f^{-1}(0)$. Let $\B_\epsilon$ be a
ball in $U$ of sufficiently small radius $\epsilon>0$, centred at
$\underline{0}\in\mathbb{C}^n$. We show that $f$ has an associated canonical
pencil of real analytic hypersurfaces $X_\theta$, with axis $V$, which leads to
a fibration $\Phi$ of the whole space $(X \cap \mathbb{B}_\epsilon) \setminus
V$ over $\mathbb{S}^1 $. Its restriction to $(X \cap \mathbb{S}_\epsilon)
\setminus V$ is the usual Milnor fibration $\phi = \frac{f}{|f|}$, while its
restriction to the Milnor tube $f^{-1}(\partial \D_\eta) \cap
\mathbb{B}_\epsilon$ is the Milnor-L\^e fibration of $f$. Each element of the
pencil $X_\theta$ meets transversally the boundary sphere $\mathbb{S}_\epsilon
= \partial \B_\epsilon$, and the intersection is the union of the link of $f$
and two homeomorphic fibers of $\phi$ over antipodal points in the circle.
Furthermore, the space ${\tilde X}$ obtained by the real blow up of the ideal
$(Re(f), Im(f))$ is a fibre bundle over $\mathbb{R} \mathbb{P}^1$ with the
$X_\theta$ as fibres. These constructions work also, to some extent, for real
analytic map-germs, and give us a clear picture of the differences, concerning
Milnor fibrations, between real and complex analytic singularities.


title: Cosmological Constant as a Manifestation of the Hierarchy

abstract:
  There has been the suggestion that the cosmological constant as implied by
the dark energy is related to the well-known hierarchy between the Planck
scale, $M_{\rm Pl}$, and the Standard Model scale, $M_{\rm SM}$. Here we
further propose that the same framework that addresses this hierarchy problem
must also address the smallness problem of the cosmological constant.
Specifically, we investigate the minimal supersymmetric (SUSY) extension of the
Randall-Sundrum model where SUSY-breaking is induced on the TeV brane and
transmitted into the bulk. We show that the Casimir energy density of the
system indeed conforms with the observed dark energy scale.


title: Measurement of the Proton Asymmetry Parameter C in Neutron Beta Decay

abstract:
  The proton asymmetry parameter C in neutron decay describes the correlation
between neutron spin and proton momentum. In this Letter, the first measurement
of this quantity is presented. The result C=-0.2377(26) agrees with the
Standard Model expectation. The coefficient C provides an additional parameter
for new and improved Standard Model tests. From a differential analysis of the
same data (assuming the Standard Model), we obtain lambda=-1.275(16) as ratio
of axial-vector and vector coupling constant.


title:
The model of interacting spatial permutations and its relation to the
  Bose gas

abstract:
  The model of spatial permutations is related to the Feynman-Kac
representation of the Bose gas. The transition to infinite cycles corresponds
to Bose-Einstein condensation. We review the general setting and some results,
and we derive a multi-body interaction between permutation jumps, that is due
to the original interactions between quantum particles.


title:
A priori bounds for some infinitely renormalizable quadratics: III.
  Molecules

abstract:
  In this paper we prove {\it a priori bounds} for infinitely renormalizable
quadratic polynomials satisfying a ``molecule condition''. Roughly speaking,
this condition ensures that the renormalization combinatorics stay away from
the satellite types. These {\it a priori bounds} imply local connectivity of
the corresponding Julia sets and the Mandelbrot set at the corresponding
parameter values.


title: An orientable time of flight detector for cosmic rays

abstract:
  Cosmic ray studies, in particular UHECR, can be in general supported by a
directional, easy deployable, simple and robust detector. The design of this
detector is based on the time of flight between two parallel tiles of
scintillator, to distinguish particle passing through in opposite directions;
by fine time resolution and pretty adjustable acceptance it is possible to
select upward(left)/downward(right) cosmic rays. It has been developed for an
array of detectors to measure upward $\tau$ from Earth-Skimming neutrino events
with energy above $10^8 GeV$. The properties and performances of the detector
are discussed. Test results from a high noise environment are presented.


title:
Thin-thick coexistence behavior of 8CB liquid crystalline films on
  silicon

abstract:
  The wetting behavior of thin films of 4'-n-octyl-4-cyanobiphenyl (8CB) on Si
is investigated via optical and x-ray reflectivity measurement. An experimental
phase diagram is obtained showing a broad thick-thin coexistence region
spanning the bulk isotropic-to-nematic ($T_{IN}$) and the nematic-to-smectic-A
($T_{NA}$) temperatures. For Si surfaces with coverages between 47 and $72\pm3$
nm, reentrant wetting behavior is observed twice as we increase the
temperature, with separate coexistence behaviors near $T_{IN}$ and $T_{NA}$.
For coverages less than 47 nm, however, the two coexistence behaviors merge
into a single coexistence region. The observed thin-thick coexistence near the
second-order NA transition is not anticipated by any previous theory or
experiment. Nevertheless, the behavior of the thin and thick phases within the
coexistence regions is consistent with this being an equilibrium phenomenon.


title: Jets in Hadron-Hadron Collisions

abstract:
  In this article, we review some of the complexities of jet algorithms and of
the resultant comparisons of data to theory. We review the extensive experience
with jet measurements at the Tevatron, the extrapolation of this acquired
wisdom to the LHC and the differences between the Tevatron and LHC
environments. We also describe a framework (SpartyJet) for the convenient
comparison of results using different jet algorithms.


title: Gluing of Surfaces with Polygonal Boundaries

abstract:
  By pairwise gluing of edges of a polygon, one produces two-dimensional
surfaces with handles and boundaries. In this paper, we count the number ${\cal
N}_{g,L}(n_1, n_2, ..., n_L)$ of different ways to produce a surface of given
genus $g$ with $L$ polygonal boundaries with given numbers of edges $n_1, n_2,
>..., n_L$. Using combinatorial relations between graphs on real
two-dimensional surfaces, we derive recursive relations between ${\cal
N}_{g,L}$. We show that Harer-Zagier numbers appear as a particular case of
${\cal N}_{g,L}$ and derive a new explicit expression for them.


title:
Reducing semantic complexity in distributed Digital Libraries: treatment
  of term vagueness and document re-ranking

abstract:
  The purpose of the paper is to propose models to reduce the semantic
complexity in heterogeneous DLs. The aim is to introduce value-added services
(treatment of term vagueness and document re-ranking) that gain a certain
quality in DLs if they are combined with heterogeneity components established
in the project "Competence Center Modeling and Treatment of Semantic
Heterogeneity". Empirical observations show that freely formulated user terms
and terms from controlled vocabularies are often not the same or match just by
coincidence. Therefore, a value-added service will be developed which rephrases
the natural language searcher terms into suggestions from the controlled
vocabulary, the Search Term Recommender (STR). Two methods, which are derived
from scientometrics and network analysis, will be implemented with the
objective to re-rank result sets by the following structural properties: the
ranking of the results by core journals (so-called Bradfordizing) and ranking
by centrality of authors in co-authorship networks.


title: Possible Equilibria of Interacting Dark Energy Models

abstract:
  Interacting dark energy and the holographic principle offer a possible way of
addressing the cosmic coincidence problem as well as accounting for the size of
the dark energy component. The equilibrium points of the Friedmann equations
which govern the evolution behavior of dark energy, matter, and curvature
components can determine the qualitative behavior of the cosmological models.
These possible equilibria and their behavior are examined in a general
framework, and some illustrative examples are presented.


title: Relativistic viscous hydrodynamics, conformal invariance, and holography

abstract:
  We consider second-order viscous hydrodynamics in conformal field theories at
finite temperature. We show that conformal invariance imposes powerful
constraints on the form of the second-order corrections. By matching to the
AdS/CFT calculations of correlators, and to recent results for Bjorken flow
obtained by Heller and Janik, we find three (out of five) second-order
transport coefficients in the strongly coupled N=4 supersymmetric Yang-Mills
theory. We also discuss how these new coefficents can arise within the kinetic
theory of weakly coupled conformal plasmas. We point out that the
Mueller-Israel-Stewart theory, often used in numerical simulations, does not
contain all allowed second-order terms and, frequently, terms required by
conformal invariance.


title:
Tracing the gas at redshift 1.7-3.5 with the Lyman-alpha forest: the FLO
  approach

abstract:
  [Abridged] We present FLO (From Lines to Over-densities), a new technique to
reconstruct the hydrogen density field for the Lya forest lines observed in
high resolution QSO spectra. The method is based on the hypothesis that the Lya
lines arise in the low to intermediate density intergalactic gas and that the
Jeans length is the typical size of the Lya absorbers. The reliability of FLO
is tested against mock spectra obtained from cosmological simulations. The
recovering algorithm gives satisfactory results in the range from the mean
density to over-densities of ~30 and reproduces correctly the correlation
function of the density field and the 1D power spectrum on scales between ~20
and 60 comoving Mpc. A sample of Lya forests from 22 high resolution QSO
spectra is analysed, covering the redshift range 1.7<z<3.5. For each line of
sight, we fit Voigt profiles to the lines of the Lya forest, providing the
largest, homogeneous sample of fitted Lya lines ever studied. The line number
density evolution with redshift follows a power-law relation: dn/dz=(166 +/- 4)
[(1+z)/3.5]^{(2.8 +/- 0.2)} (1 sigma errors). The two-point correlation
function of lines shows a signal up to separations of ~2 comoving Mpc; weak
lines (log N(HI)<13.8) also show a significant clustering but on smaller scales
(r<1.5 comoving Mpc). We estimate with FLO the hydrogen density field toward
the 22 observed lines of sight. The redshift distribution of the average
densities computed for each QSO is consistent with the cosmic mean hydrogen
density in the analysed redshift range. The two-point correlation function and
the 1D power spectrum of the delta field are estimated. The correlation
function shows clustering signal up to ~4 comoving Mpc.


title: Sunyaev-Zeldovich profiles for clusters and groups of galaxies

abstract:
  The Sunyaev-Zeldovich (SZ) effect gives a measure of the thermal energy and
electron pressure in groups and clusters of galaxies. In the near future SZ
surveys will map hundreds of systems, shedding light on the pressure
distribution in the systems. The thermal energy is related to the total mass of
a system of galaxies, but it is only a projection that is observed through the
SZ effect. A model for the 3D distribution of pressure is needed to link the SZ
signal to the total mass of the system. In this work we construct an empirical
model for the 2D and 3D SZ profile, and compare it to a set of realistic high
resolution SPH simulations of galaxy clusters and groups, and to a stacked SZ
profile for massive clusters derived from WMAP data. Furthermore, we combine
observed temperature profiles with dark matter potentials to yield an
additional constraint, under the assumption of hydrostatic equilibrium. We find
a very tight correlation between the characteristic scale in the model, the
integrated SZ signal, and the total mass in the systems with a scatter of only
4%. The model only contains two free parameters, making it readily applicable
even to low resolution SZ observations of galaxy clusters. A fitting routine
for the model that can be applied to observed or simulated data can be found at
http://www.phys.au.dk/~haugboel/software.shtml


title: Evidence for the Multiverse in the Standard Model and Beyond

abstract:
  In any theory it is unnatural if the observed parameters lie very close to
special values that determine the existence of complex structures necessary for
observers. A naturalness probability, P, is introduced to numerically evaluate
the unnaturalness. If P is small in all known theories, there is an observer
naturalness problem. In addition to the well-known case of the cosmological
constant, we argue that nuclear stability and electroweak symmetry breaking
(EWSB) represent significant observer naturalness problems. The naturalness
probability associated with nuclear stability is conservatively estimated as
P_nuc < 10^{-(3-2)}, and for simple EWSB theories P_EWSB < 10^{-(2-1)}. This
pattern of unnaturalness in three different arenas, cosmology, nuclear physics,
and EWSB, provides evidence for the multiverse. In the nuclear case the problem
is largely solved even with a flat multiverse distribution, and with nontrivial
distributions it is possible to understand both the proximity to neutron
stability and the values of m_e and m_d - m_u in terms of the electromagnetic
contribution to the proton mass. It is reasonable that multiverse distributions
are strong functions of Lagrangian parameters due to their dependence on
various factors. In any EWSB theory, strongly varying distributions typically
lead to a little or large hierarchy, and in certain multiverses the size of the
little hierarchy is enhanced by a loop factor. Since the correct theory of EWSB
is unknown, our estimate for P_EWSB is theoretical. The LHC will determine
P_EWSB more robustly, which may remove or strengthen the observer naturalness
problem of EWSB. For each of the three arenas, the discovery of a natural
theory would eliminate the evidence for the multiverse; but in the absence of
such a theory, the multiverse provides a provisional understanding of the data.


title: KK Parity in Warped Extra Dimension

abstract:
  We construct models with a Kaluza-Klein (KK) parity in a five- dimensional
warped geometry, in an attempt to address the little hierarchy problem present
in setups with bulk Standard Model fields. The lightest KK particle (LKP) is
stable and can play the role of dark matter. We consider the possibilities of
gluing two identical slices of 5D AdS in either the UV (IR-UV-IR model) or the
IR region (UV-IR-UV model) and discuss the model-building issues as well as
phenomenological properties in both cases. In particular, we find that the
UV-IR-UV model is not gravitationally stable and that additional mechanisms
might be required in the IR-UV-IR model in order to address flavor issues.
Collider signals of the warped KK parity are different from either the
conventional warped extra dimension without KK parity, in which the new
particles are not necessarily pair-produced, or the KK parity in flat universal
extra dimensions, where each KK level is nearly degenerate in mass. Dark matter
and collider properties of a TeV mass KK Z gauge boson as the LKP are
discussed.


title: Nonlinear Fluid Dynamics from Gravity

abstract:
  Black branes in AdS5 appear in a four parameter family labeled by their
velocity and temperature. Promoting these parameters to Goldstone modes or
collective coordinate fields -- arbitrary functions of the coordinates on the
boundary of AdS5 -- we use Einstein's equations together with regularity
requirements and boundary conditions to determine their dynamics. The resultant
equations turn out to be those of boundary fluid dynamics, with specific values
for fluid parameters. Our analysis is perturbative in the boundary derivative
expansion but is valid for arbitrary amplitudes. Our work may be regarded as a
derivation of the nonlinear equations of boundary fluid dynamics from gravity.
As a concrete application we find an explicit expression for the expansion of
this fluid stress tensor including terms up to second order in the derivative
expansion.


title: On Contamination and Completeness in z>5 Lyman Break Galaxy Surveys

abstract:
  A large population of z>5 Lyman break galaxies has been identified in recent
years. However, the high redshift galaxies selected by different surveys are
subject to a variety of selection effects - some overt, others more subtle. We
present an analysis of sample completeness and contamination issues in high
redshift surveys, focusing on surveys at z=5 and using a
spectroscopically-confirmed low redshift sample from the DEEP2 survey in order
to characterise contaminant galaxies. We find that most surveys underestimate
their contamination from highly clustered galaxies at z=1 and stars. We
consider the consequences of this for both the rest-frame ultraviolet
luminosity function and the clustering signal from z=5 galaxies. We also find
that sources with moderate strength Lyman-alpha emission lines can be omitted
from dropout surveys due to their blue colours, again effecting the derived
luminosity functions. We discuss the points of comparison between different
samples, and the applicability of survey-specific results to the population at
z>5 in general.


title:
Spitzer IRS Observations of Class I/II Objects in Taurus: Composition
  and Thermal History of the Circumstellar Ices

abstract:
  We present observations of Taurus-Auriga Class I/II protostars obtained with
the Spitzer InfraRed Spectrograph. Detailed spectral fits to the 6 and 15
micron features are made, using publicly-available laboratory data, to
constrain the molecular composition, abundances, and levels of thermal
processing along the lines of sight. We provide an inventory of the molecular
environments observed, which have an average composition dominated by water ice
with ~12% CO_2 (abundance relative to H_2O), >~2-9% CH_3OH, <~14% NH_3, ~4%
CH_4, ~2% H_2CO, ~0.6% HCOOH, and ~0.5% SO_2. We find CO_2/H_2O ratios nearly
equivalent to those observed in cold clouds and lines of sight toward the
galactic center. The unidentified 6.8 micron profiles vary from source to
source, and it is shown to be likely that even combinations of the most common
candidates (NH_4+ and CH_3OH) are inadequate to explain the feature fully. We
discuss correlations among SED spectral indices, abundance ratios, and
thermally-processed ice fractions and their implications for CO_2 formation and
evolution. Comparison of our spectral fits with cold molecular cloud
sight-lines indicates abundant prestellar ice environments made even richer by
the radiative effects of protostars. Our results add additional constraints and
a finer level of detail to current full-scale models of protostellar and
protoplanetary systems.


title: A Metallicity Map of M33

abstract:
  We present initial results from the M33 Metallicity Project. Out of the
thousands of cataloged HII regions in M33, only ~30 have electron-temperature
based abundances in the literature. We have obtained Keck spectroscopy of a
sample of ~200 HII regions in M33, with 61 detections of the [O III] 4363 A
line that can be used for determining electron temperatures, including
measurements at small galactocentric radii where auroral lines are generally
difficult to detect. We find an oxygen abundance gradient of -0.027 +/- 0.012
dex/kpc, in agreement with infrared measurements of the neon abundance gradient
but much shallower than most previous oxygen gradient measurements. There is
substantial intrinsic scatter of 0.11 dex in the metallicity at any given
radius in M33, which imposes a fundamental limit on the accuracy of gradient
measurements that rely on small samples of objects. Finally, we present a
two-dimensional map of oxygen abundances across the southern half of M33 and
discuss the evidence for deviations from axisymmetry.


title:
Fully General Relativistic Simulations of Black Hole-Neutron Star
  Mergers

abstract:
  Black hole-neutron star (BHNS) binaries are expected to be among the leading
sources of gravitational waves observable by ground-based detectors, and may be
the progenitors of short-hard gamma ray bursts (SGRBs) as well. Here, we
discuss our new fully general relativistic calculations of merging BHNS
binaries, which use high-accuracy, low-eccentricity, conformal thin-sandwich
configurations as initial data. Our evolutions are performed using the moving
puncture method and include a fully relativistic, high-resolution
shock-capturing hydrodynamics treatment. Focusing on systems in which the
neutron star is irrotational and the black hole is nonspinning with a 3:1 mass
ratio, we investigate the inspiral, merger, and disk formation in the system.
We find that the vast majority of material is promptly accreted and no more
than 3% of the neutron star's rest mass is ejected into a tenuous,
gravitationally bound disk. We find similar results for mass ratios of 2:1 and
1:1, even when we reduce the NS compaction in the 2:1 mass ratio case. These
ambient disks reach temperatures suitable for triggering SGRBs, but their
masses may be too small to produce the required total energy output. We measure
gravitational waveforms and compute the effective strain in frequency space,
finding measurable differences between our waveforms and those produced by
binary black hole mergers within the advanced LIGO band. These differences
appear at frequencies corresponding to the emission that occurs when the NS is
tidally disrupted and accreted by the black hole. The resulting information
about the radius of the neutron star may be used to constrain the neutron star
equation of state.


title: The First Mid-Infrared Spectra of Cool White Dwarfs

abstract:
  We present the first mid-infrared spectra of two cool white dwarfs obtained
with the Spitzer Space Telescope. We also present 3.5-8 micron photometry for
19 cool white dwarfs with 5000K < Teff < 9000K. We perform a detailed model
atmosphere analysis of these white dwarfs by fitting their UBVRIJHK and Spitzer
photometry with state-of-the-art model atmospheres, and demonstrate that the
optical and infrared spectral energy distributions of cool white dwarfs are
well reproduced by our grid of models. Our mid-IR photometry and 7.5-14.5
micron spectrum of WD0018-267 are consistent with a Teff = 5720K, pure hydrogen
white dwarf model atmosphere. On the other hand, LHS 1126 remains peculiar with
significant mid-IR flux deficits in all IRAC bands and a featureless spectrum
in the 5.2-7.5 micron range. Even though this deficit is attributed to
collision induced absorption (CIA) due to molecular hydrogen, the shape of the
deficit cannot be explained with current CIA opacity calculations. The infrared
portion of the LHS 1126 spectral energy distribution is best-fit with a power
law index of -1.99; identical to a Rayleigh-Jeans spectrum. This argues that
the deficit may be due to an unrecognized grey-like opacity source in the
infrared.


title: Determining the mass for an ultralight gravitino at LHC

abstract:
  In supersymmetric (SUSY) models with the gravitino being the lightest SUSY
particle (LSP), the SUSY breaking scale (i.e., the gravitino mass) could be
determined by measuring the lifetime of the next-to-lightest SUSY particle
(NLSP). However, for an ultralight gravitino of mass of O(1) eV, which is
favored cosmologically, the determination of the SUSY breaking scale, or the
gravitino mass, is difficult because the NLSP decay length is too short to be
measured directly. Recently we proposed a new determination of the gravitino
mass by measuring a branching fraction of two decay modes of sleptons. In this
paper, we investigate the prospects for determining the gravitino mass at LHC.
For demonstration we take some explicit gauge-mediation models and show that
the gravitino mass can be determined with an accuracy of a few 10% for an
integrated luminosity 10-100 fb^{-1}.


title: Exteneded Longitudinal Scaling and the Thermal Model

abstract:
  The property of extended longitudinal scaling of rapidity distributions was
noticed recently over a broad range of beam energies. It is shown here that
this property is consistent with predictions of the statistical thermal model
up to the highest RHIC beam energies, however, we expect that at LHC energies
the rapidity distribution of produced particles will violate extended
longitudinal scaling.


title: Derivation of the residence time for kinetic Monte Carlo simulations

abstract:
  The kinetic Monte Carlo method is a standard approach for simulating physical
systems whose dynamics are stochastic or that evolve in a probabilistic manner.
Here we show how to calculate the system time for such simulations.


title:
Quantum Spin Excitations through the metal-to-insulator crossover in $Y
  Ba_2 Cu_3 O_{6+y}$

abstract:
  We use inelastic neutron scattering to study the temperature dependence of
the spin excitations of a detwinned superconducting YBa$_2$Cu$_3$O$_{6.45}$
($T_c=48$ K). In contrast to earlier work on YBa$_2$Cu$_3$O$_{6.5}$ ($T_c=58$
K), where the prominent features in the magnetic spectra consist of a sharp
collective magnetic excitation termed ``resonance'' and a large
($\hbar\omega\approx 15$ meV) superconducting spin gap, we find that the spin
excitations in YBa$_2$Cu$_3$O$_{6.45}$ are gapless and have a much broader
resonance. Our detailed mapping of magnetic scattering along the
$a^\ast$/$b^\ast$-axis directions at different energies reveals that spin
excitations are unisotropic and consistent with the ``hourglass''-like
dispersion along the $a^\ast$-axis direction near the resonance, but they are
isotropic at lower energies. Since a fundamental change in the low-temperature
normal state of YBa$_2$Cu$_3$O$_{6+y}$ when superconductivity is suppressed
takes place at $y\sim0.5$ with a metal-to-insulator crossover (MIC), where the
ground state transforms from a metallic to an insulating-like phase, our
results suggest a clear connection between the large change in spin excitations
and the MIC. The resonance therefore is a fundamental feature of metallic
ground state superconductors and a consequence of high-$T_c$ superconductivity.


title: Higgs Signal for h to aa at Hadron Colliders

abstract:
  We assess the prospect of observing a neutral Higgs boson at hadron colliders
in its decay to two spin-zero states, a, for a Higgs mass of 90-130 GeV, when
produced in association with a W or Z boson. Such a decay is allowed in
extensions of the MSSM with CP-violating interactions and in the NMSSM, and can
dominate Higgs boson final states, thereby evading the LEP constraints on
standard Higgs boson production. The light spin-zero state decays primarily via
a to bb and tau+tau-, so this signal channel retains features distinct from the
main backgrounds. Our study shows that at the Tevatron, there may be potential
to observe a few events in the bb tau+tau- or bbbb channels with relatively
small background, although this observation would be statistically limited. At
the LHC, the background problem is more severe, but with cross sections and
integrated luminosities orders of magnitude larger than at the Tevatron, the
observation of a Higgs boson in this decay mode would be possible. The channel
h to aa to bbbb would provide a large statistical significance, with a
signal-to-background ratio on the order of 1:2. In these searches, the main
challenge would be to retain the adequate tagging efficiency of b's and tau's
in the low p_T region.


title: Rethinking Information Theory for Mobile Ad Hoc Networks

abstract:
  The subject of this paper is the long-standing open problem of developing a
general capacity theory for wireless networks, particularly a theory capable of
describing the fundamental performance limits of mobile ad hoc networks
(MANETs). A MANET is a peer-to-peer network with no pre-existing
infrastructure. MANETs are the most general wireless networks, with single-hop,
relay, interference, mesh, and star networks comprising special cases. The lack
of a MANET capacity theory has stunted the development and commercialization of
many types of wireless networks, including emergency, military, sensor, and
community mesh networks. Information theory, which has been vital for links and
centralized networks, has not been successfully applied to decentralized
wireless networks. Even if this was accomplished, for such a theory to truly
characterize the limits of deployed MANETs it must overcome three key
roadblocks. First, most current capacity results rely on the allowance of
unbounded delay and reliability. Second, spatial and timescale decompositions
have not yet been developed for optimally modeling the spatial and temporal
dynamics of wireless networks. Third, a useful network capacity theory must
integrate rather than ignore the important role of overhead messaging and
feedback. This paper describes some of the shifts in thinking that may be
needed to overcome these roadblocks and develop a more general theory that we
refer to as non-equilibrium information theory.


title:
Inflation and Quintessence: Theoretical Approach of Cosmological
  Reconstruction

abstract:
  In the first part of this paper, we outline the construction of an
inflationary cosmology in the framework where inflation is described by a
universally evolving scalar field, with the Lagrangian ${\cal
L}_\phi=-{1/2}(\partial\phi)^2 -V(\phi)$. By considering a generic situation
that inflaton attains a nearly constant velocity, during inflation, $m_P^{-1}
(d\phi/dN)\equiv \alpha$ (where $N\equiv \ln a$ is the e-folding time), we find
the conditions that have to satisfied by the (reconstructed) scalar potential
to be consistent with the WMAP inflationary data. In the second part of this
paper, we introduce a novel approach of constructing dark energy within the
context of the standard scalar-tensor gravity. The assumption that a scalar
field might roll with a nearly constant velocity, during inflation, can also be
applied to {\it quintessence} or dark energy models. For the minimally coupled
quintessence, $\alpha_Q\equiv dA(Q)/d(\kappa Q)=0$ (where $A(Q)$ is the
standard matter-quintessence coupling), the dark energy equation of state in
the range $-1\le w_{DE} < -0.82$ can be obtained for $0\le \alpha < 0.63$. For
$\alpha<0.1$, the model allows for only modest evolution of dark energy density
with redshift. The effect of the matter-quintessence coupling can be
significant only if $|\alpha_Q| \gtrsim 0.1$, while a small coupling
$|\alpha_Q|< 0.1$ will have almost no effect on cosmological parameters. The
best fit value of $\alpha_Q$ in our model is found to be $\alpha_Q \simeq
0.06$, but it may contain significant numerical errors, viz $\alpha_Q=0.06\pm
0.35$, which thereby implies the consistency of our model with general
relativity (for which $\alpha_Q=0$) at $1\sigma$ level.


title: Directed Percolation in Wireless Networks with Interference and Noise

abstract:
  Previous studies of connectivity in wireless networks have focused on
undirected geometric graphs. More sophisticated models such as
Signal-to-Interference-and-Noise-Ratio (SINR) model, however, usually leads to
directed graphs. In this paper, we study percolation processes in wireless
networks modelled by directed SINR graphs. We first investigate
interference-free networks, where we define four types of phase transitions and
show that they take place at the same time. By coupling the directed SINR graph
with two other undirected SINR graphs, we further obtain analytical upper and
lower bounds on the critical density. Then, we show that with interference,
percolation in directed SINR graphs depends not only on the density but also on
the inverse system processing gain. We also provide bounds on the critical
value of the inverse system processing gain.


title: A Model of Nuclear Recoil Scintillation Efficiency in Noble Liquids

abstract:
  Scintillation efficiency of low-energy nuclear recoils in noble liquids plays
a crucial role in interpreting results from some direct searches for Weakly
Interacting Massive Particle (WIMP) dark matter. However, the cause of a
reduced scintillation efficiency relative to electronic recoils in noble
liquids remains unclear at the moment. We attribute such a reduction of
scintillation efficiency to two major mechanisms: 1) energy loss and 2)
scintillation quenching. The former is commonly described by Lindhard's theory
and the latter by Birk's saturation law. We propose to combine these two to
explain the observed reduction of scintillation yield for nuclear recoils in
noble liquids. Birk's constants $kB$ for argon, neon and xenon determined from
existing data are used to predict noble liquid scintillator's response to
low-energy nuclear recoils and low-energy electrons. We find that energy loss
due to nuclear stopping power that contributes little to ionization and
excitation is the dominant reduction mechanism in scintillation efficiency for
nuclear recoils, but that significant additional quenching results from the
nonlinear response of scintillation to the ionization density.


title: Additive Extensions of a Quantum Channel

abstract:
  We study extensions of a quantum channel whose one-way capacities are
described by a single-letter formula. This provides a simple technique for
generating powerful upper bounds on the capacities of a general quantum
channel. We apply this technique to two qubit channels of particular
interest--the depolarizing channel and the channel with independent phase and
amplitude noise. Our study of the latter demonstrates that the key rate of BB84
with one-way post-processing and quantum bit error rate q cannot exceed
H(1/2-2q(1-q)) - H(2q(1-q)).


title:
High accuracy simulations of Kerr tails: coordinate dependence and
  higher multipoles

abstract:
  We investigate the late time behavior of a scalar field on a fixed Kerr
background using a 2+1 dimensional pseudospectral evolution code. We compare
evolutions of pure axisymmetric multipoles in both Kerr-Schild and
Boyer-Lindquist coordinates. We find that the late-time power-law decay rate
depends upon the slicing of the background, confirming previous theoretical
predictions for those decay rates. The accuracy of the numerical evolutions is
sufficient to decide unambiguously between competing claims in the literature.


title: Europium, Samarium, and Neodymium Isotopic Fractions in Metal-Poor Stars

abstract:
  We have derived isotopic fractions of europium, samarium, and neodymium in
two metal-poor giants with differing neutron-capture nucleosynthetic histories.
These isotopic fractions were measured from new high resolution (R ~ 120,000),
high signal-to-noise (S/N ~ 160-1000) spectra obtained with the 2dCoude
spectrograph of McDonald Observatory's 2.7m Smith telescope. Synthetic spectra
were generated using recent high-precision laboratory measurements of hyperfine
and isotopic subcomponents of several transitions of these elements and matched
quantitatively to the observed spectra. We interpret our isotopic fractions by
the nucleosynthesis predictions of the stellar model, which reproduces
s-process nucleosynthesis from the physical conditions expected in low-mass,
thermally-pulsing stars on the AGB, and the classical method, which
approximates s-process nucleosynthesis by a steady neutron flux impinging upon
Fe-peak seed nuclei. Our Eu isotopic fraction in HD 175305 is consistent with
an r-process origin by the classical method and is consistent with either an r-
or an s-process origin by the stellar model. Our Sm isotopic fraction in HD
175305 suggests a predominantly r-process origin, and our Sm isotopic fraction
in HD 196944 is consistent with an s-process origin. The Nd isotopic fractions,
while consistent with either r-process or s-process origins, have very little
ability to distinguish between any physical values for the isotopic fraction in
either star. This study for the first time extends the n-capture origin of
multiple rare earths in metal-poor stars from elemental abundances to the
isotopic level, strengthening the r-process interpretation for HD 175305 and
the s-process interpretation for HD196944.


title:
AGN Environments in the Sloan Digital Sky Survey I: Dependence on Type,
  Redshift, and Luminosity

abstract:
  We explore how the local environment is related to the redshift, type, and
luminosity of active galactic nuclei (AGN). Recent simulations and observations
are converging on the view that the extreme luminosity of quasars is fueled in
major mergers of gas-rich galaxies. In such a picture, quasars are expected to
be located in regions with a higher density of galaxies on small scales where
mergers are more likely to take place. However, in this picture, the activity
observed in low-luminosity AGN is due to secular processes that are less
dependent on the local galaxy density. To test this hypothesis, we compare the
local photometric galaxy density on kiloparsec scales around spectroscopic Type
I and Type II quasars to the local density around lower luminosity
spectroscopic Type I and Type II AGN. To minimize projection effects and
evolution in the photometric galaxy sample we use to characterize AGN
environments, we place our random control sample at the same redshift as our
AGN and impose a narrow redshift window around both the AGN and control
targets. We find that higher luminosity AGN have more overdense environments
compared to lower luminosity AGN on all scales out to our $2\Mpchseventy$
limit. Additionally, in the range $0.3\leqslant z\leqslant 0.6$, Type II
quasars have similarly overdense environments to those of bright Type I quasars
on all scales out to our $2\Mpchseventy$ limit, while the environment of dimmer
Type I quasars appears to be less overdense than the environment of Type II
quasars. We see increased overdensity for Type II AGN compared to Type I AGN on
scales out to our limit of $2\Mpchseventy$ in overlapping redshift ranges. We
also detect marginal evidence for evolution in the number of galaxies within
$2\Mpchseventy$ of a quasar with redshift.