title: Multivariate Fuss-Catalan numbers

abstract:
  Catalan numbers $C(n)=\frac{1}{n+1}{2n\choose n}$ enumerate binary trees and
Dyck paths. The distribution of paths with respect to their number $k$ of
factors is given by ballot numbers $B(n,k)=\frac{n-k}{n+k}{n+k\choose n}$.
These integers are known to satisfy simple recurrence, which may be visualised
in a ``Catalan triangle'', a lower-triangular two-dimensional array. It is
surprising that the extension of this construction to 3 dimensions generates
integers $B_3(n,k,l)$ that give a 2-parameter distribution of $C_3(n)=\frac 1
{2n+1} {3n\choose n}$, which may be called order-3 Fuss-Catalan numbers, and
enumerate ternary trees. The aim of this paper is a study of these integers
$B_3(n,k,l)$. We obtain an explicit formula and a description in terms of trees
and paths. Finally, we extend our construction to $p$-dimensional arrays, and
in this case we obtain a $(p-1)$-parameter distribution of $C_p(n)=\frac 1
{(p-1)n+1} {pn\choose n}$, the number of $p$-ary trees.


title: Precise Half-Life Measurement of the Superallowed beta emitter 10C

abstract:
  The half-life of 10C has been measured to be 19.310(4)s, a result with 0.02%
precision, which is a factor of three improvement over the best previous
result. Since 10C is the lightest superallowed 0+ --> 0+ beta emitter, its ft
value has the greatest weight in setting an upper limit on the possible
presence of scalar currents.


title:
Quasi-invariant and super-coinvariant polynomials for the generalized
  symmetric group

abstract:
  The aim of this work is to extend the study of super-coinvariant polynomials,
to the case of the generalized symmetric group $G_{n,m}$, defined as the wreath
product $C_m\wr\S_n$ of the symmetric group by the cyclic group. We define a
quasi-symmetrizing action of $G_{n,m}$ on $\Q[x_1,...,x_n]$, analogous to those
defined by Hivert in the case of $\S_n$. The polynomials invariant under this
action are called quasi-invariant, and we define super-coinvariant polynomials
as polynomials orthogonal, with respect to a given scalar product, to the
quasi-invariant polynomials with no constant term. Our main result is the
description of a Gr\"obner basis for the ideal generated by quasi-invariant
polynomials, from which we dedece that the dimension of the space of
super-coinvariant polynomials is equal to $m^n C_n$ where $C_n$ is the $n$-th
Catalan number.


title:
Polyn\^omes quasi-invariants et super-coinvariants pour le groupe
  sym\'etrique g\'en\'eralis\'e

abstract:
  A classical result of Artin states that the ideal generated by symmetric
polynomials in $n$ variables is of codimension $n!$. The author, F. Bergeron
and N. Bergeron have recently obtained a surprising analogous in the case of
quasi-symmetric polynomials. In this case, the ideal is of codimension given by
$C_n$, the $n$-th Catalan number. Quasi-symmetric polynomials are the
invariants of a certain action of the symmetric group $S_n$ defined by F.
Hivert. The aim of this work is to generalize these results to the wreath
product $S_n\wr \Z_m$, also known as the generalized symmetric group $G\nm$. We
first define a quasi-symmetrizing action of $G\nm$ on $\C[x_1,...,x_n]$, then
obtain a description of the invariants and the codimension of the associated
ideal, which is $m^n C_n$.


title:
Use of resonance Raman spectroscopy to study the phase diagram of
  PbZr0.52Ti0.48O3

abstract:
  Evidence is presented for the first time that the sharp and continuous
spectral changes observed in PbZr0.52Ti0.48O3 (PZT) between 350 and 10 K with
the 647.1 nm wavelength are due to a resonance Raman effect. Such a phenomenon
can be explained by means of a self-trapped exciton emission oxygen deficient
complex (TiTi' - VO-) of PZT powder whose energy is close to the radiation line
of the laser. This kind of approach should also be very useful to distinguish
the phase transition sequence for other related ferro/ piezoelectric systems.


title: A heated vapor cell unit for DAVLL in atomic rubidium

abstract:
  The design and performance of a compact heated vapor cell unit for realizing
a dichroic atomic vapor laser lock (DAVLL) for the D2 transitions in atomic
rubidium is described. A 5 cm-long vapor cell is placed in a double-solenoid
arrangement to produce the required magnetic field; the heat from the solenoid
is used to increase the vapor pressure and correspondingly the DAVLL signal. We
have characterized experimentally the dependence of important features of the
DAVLL signal on magnetic field and cell temperature. For the weaker transitions
both the amplitude and gradient of the signal are increased by an order of
magnitude.


title:
Temperature dependent vibrational spectra in non-crystalline materials:
  application to hydrogenated amorphous silicon

abstract:
  We present a novel approach for parameter-free modeling of the structural,
dynamical and electronic properties of non-crystalline materials based on
ab-initio Molecular Dynamics, improved signal processing technique and computer
visualization. The method have been extensively tested by investigating
hydrogen and silicon dynamics in hydrogenated amorphous silicon (a-Si:H). By
comparing the theoretical and experimental vibrational spectra we demonstrate
how to relate vibrational properties to the structural stability, bonding and
hydrogen diffusion. We extracted microscopic characteristics that cannot be
obtained by other techniques, namely hydrogen migration and related bond
switching, dangling bond passivation, low hydrogen activation energy, and
a-Si:H stability in general, and we show, via the analysis of a test case, that
our method provides a rigorous and realistic description of non-crystalline
materials. We also demonstrate that this method offers the possibility of
accessing other important macroscopic characteristics of amorphous silicon and
can be used to model all the aspects of a-Si:H dynamics, including the
detrimental Staebler-Wronski effect.


title:
Generalizations of two theorems of Ritt on decompositions of polynomial
  maps

abstract:
  Two theorems of J. F. Ritt on decompositions of polynomials maps are
generalized to a more general situation: for, so-called, reduction monoids
($(K[x], \circ)$ and $(K[x^2]x, \circ)$ are examples of reduction monoids). In
particular, analogues of the two theorems of J. F. Ritt hold for the monoid
$(K[x^2]x, \circ)$ of odd polynomials. It is shown that, in general, the two
theorems of J. F. Ritt fail for the cusp $(K+K[x]x^2, \circ)$ but their
analogues are still true for decompositions of maximal length of regular
elements of the cusp.


title: Universal properties of bulk viscosity near the QCD phase transition

abstract:
  We extract the bulk viscosity of hot quark-gluon matter in the presence of
light quarks from the recent lattice data on the QCD equation of state. For
that purpose we extend the sum rule analysis by including the contribution of
light quarks. We also discuss the universal properties of bulk viscosity in the
vicinity of a second order phase transition, as it might occur in the chiral
limit of QCD at fixed strange quark mass and most likely does occur in
two-flavor QCD. We point out that a chiral transition in the O(4) universality
class at zero baryon density as well as the transition at the chiral critical
point which belongs to the Z(2) universality class both lead to the critical
behavior of bulk viscosity. In particular, the latter universality class
implies the divergence of the bulk viscosity, which may be used as a signature
of the critical point. We discuss the physical picture behind the dramatic
increase of bulk viscosity seen in our analysis, and devise possible
experimental tests of related phenomena.


title: The Discrete Fundamental Group of the Order Complex of $B_n$

abstract:
  A few years ago Kramer and Laubenbacher introduced a discrete notion of
homotopy for simplicial complexes. In this paper, we compute the discrete
fundamental group of the order complex of the Boolean lattice. As it turns out,
it is equivalent to computing the discrete homotopy group of the 1-skeleton of
the permutahedron. To compute this group we introduce combinatorial techniques
that we believe will be helpful in computing discrete fundamental groups of
other polytopes. More precisely, we use the language of words, over the
alphabet of simple transpositions, to obtain conditions that are necessary and
sufficient to characterize the equivalence classes of cycles. The proof
requires only simple combinatorial arguments. As a corollary, we also obtain a
combinatorial proof of the fact that the first Betti number of the complement
of the 3-equal arrangement is equal to $2^{n-3}(n^2-5n+8)-1.$ This formula was
originally obtained by Bj\"orner and Welker in 1995.


title:
Monte Carlo simulations of proteins in cages: influence of confinement
  on the stability of intermediate states

abstract:
  We present a theoretical study of the folding of small proteins inside
confining potentials. Proteins are described in the framework of an effective
potential model which contains the Ramachandran angles as degrees of freedom
and does not need any {\it a priori} information about the native state.
Hydrogen bonds, dipole-dipole- and hydrophobic interactions are taken
explicitly into account. An interesting feature displayed by this potential is
the presence of some intermediates between the unfolded and native states. We
consider different types of confining potentials in order to study the
structural properties of proteins folding inside cages with repulsive or
attractive walls. Using the Wang-Landau algorithm we determine the density of
states (DOS) and analyze in detail the thermodynamical properties of the
confined proteins for different sizes of the cages. We show that confinement
dramatically reduces the phase space available to the protein and that the
presence of intermediate states can be controlled by varying the properties of
the confining potential. Cages with strongly attractive walls lead to the
disappearance of the intermediate states and to a two-state folding into a less
stable configuration. However, cages with slightly attractive walls make the
native structure more stable than in the case of pure repulsive potentials, and
the folding process occurs through intermediate configurations. In order to
test the metastable states we analyze the free energy landscapes as a function
of the configurational energy and of the end-to-end distance as an order
parameter.


title: SWI-Prolog and the Web

abstract:
  Where Prolog is commonly seen as a component in a Web application that is
either embedded or communicates using a proprietary protocol, we propose an
architecture where Prolog communicates to other components in a Web application
using the standard HTTP protocol. By avoiding embedding in external Web servers
development and deployment become much easier. To support this architecture, in
addition to the transfer protocol, we must also support parsing, representing
and generating the key Web document types such as HTML, XML and RDF.
  This paper motivates the design decisions in the libraries and extensions to
Prolog for handling Web documents and protocols. The design has been guided by
the requirement to handle large documents efficiently. The described libraries
support a wide range of Web applications ranging from HTML and XML documents to
Semantic Web RDF processing.
  To appear in Theory and Practice of Logic Programming (TPLP)


title:
Renormalization Group Functions for Two-Dimensional Phase Transitions:
  To the Problem of Singular Contributions

abstract:
  According to the available publications, the field theoretical
renormalization group (RG) approach in the two-dimensional case gives the
critical exponents that differ from the known exact values. This fact was
attempted to explain by the existence of nonanalytic contributions in the RG
functions. The situation is analysed in this work using a new algorithm for
summing divergent series that makes it possible to analyse dependence of the
results for the critical exponents on the expansion coefficients for RG
functions. It has been shown that the exact values of all the exponents can be
obtained with a reasonable form of the coefficient functions. These functions
have small nonmonotonities or inflections, which are poorly reproduced in
natural interpolations. It is not necessary to assume the existence of singular
contributions in RG functions.

categories: cond-mat.stat-mech cond-mat.other hep-ph hep-th


title: Commensurations and Subgroups of Finite Index of Thompson's Group F

abstract:
  We determine the abstract commensurator com(F) of Thompson's group F and
describe it in terms of piecewise linear homeomorphisms of the real line and in
terms of tree pair diagrams. We show com (F) is not finitely generated and
determine which subgroups of finite index in F are isomorphic to F. We show
that the natural map from the commensurator group to the quasi-isometry group
of F is injective.


title: Revolving rivers in sandpiles: from continuous to intermittent flows

abstract:
  In a previous paper [Phys. Rev. Lett. 91, 014501 (2003)], the mechanism of
"revolving rivers" for sandpile formation is reported: as a steady stream of
dry sand is poured onto a horizontal surface, a pile forms which has a river of
sand on one side owing from the apex of the pile to the edge of the base. For
small piles the river is steady, or continuous. For larger piles, it becomes
intermittent. In this paper we establish experimentally the "dynamical phase
diagram" of the continuous and intermittent regimes, and give further details
of the piles topography, improving the previous kinematic model to describe it
and shedding further light on the mechanisms of river formation. Based on
experiments in Hele-Shaw cells, we also propose that a simple dimensionality
reduction argument can explain the transition between the continuous and
intermittent dynamics.


title: Finite-size correction in many-body electronic structure calculations

abstract:
  Finite-size (FS) effects are a major source of error in many-body (MB)
electronic structure calculations of extended systems. A method is presented to
correct for such errors. We show that MB FS effects can be effectively included
in a modified local density approximation calculation. A parametrization for
the FS exchange-correlation functional is obtained. The method is simple and
gives post-processing corrections that can be applied to any MB results.
Applications to a model insulator (P$_2$ in a supercell), to semiconducting Si,
and to metallic Na show that the method delivers greatly improved FS
corrections.


title:
Genetic algorithms predict formation of exotic ordered configurations
  for two-component dipolar monolayers

abstract:
  We employ genetic algorithms (GA), which allow for an unbiased search for the
global minimum of energy landscapes, to identify the ordered equilibrium
configurations formed by binary dipolar systems confined on a plane. A large
variety of arrangements is identified, the complexity of which grows with
increasing asymmetry between the two components and with growing concentration
of the small particles. The effects of the density are briefly discussed and a
comparison with results obtained via conventional lattice-sum minimization is
presented. Our results can be confirmed by experiments involving Langmuir
monolayers of polystyrene dipolar spheres or super-para-magnetic colloids
confined on the air-water interface and polarized by an external, perpendicular
magnetic field.


title: Thermal noise suppression: how much does it cost?

abstract:
  In order to stabilize the behavior of noisy systems, confining it around a
desirable state, an effort is required to suppress the intrinsic noise. This
noise suppression task entails a cost. For the important case of thermal noise
in an overdamped system, we show that the minimum cost is achieved when the
system control parameters are held constant: any additional deterministic or
random modulation produces an increase of the cost. We discuss the implications
of this phenomenon for those overdamped systems whose control parameters are
intrinsically noisy, presenting a case study based on the example of a Brownian
particle optically trapped in an oscillating potential.


title:
Finiteness and vanishing results on weighted Poincare inequality of
  complete manifolds

abstract:
  We study manifolds satisfying a weighed Poincare inequality, which was first
introduced by Li-Wang. We generalized one of their results by relaxing the
Ricci curvature bound condition only being satisfied outside a compact set and
established a finitely many ends result. We proved a vanishing result for $L^2$
harmonic 1-form provided that the weight function $\rho$ is of sub-quadratic
growth of the distance function.


title: Eight New Millisecond Pulsars in NGC 6440 and NGC 6441

abstract:
  Motivated by the recent discovery of 30 new millisecond pulsars in Terzan 5,
made using the Green Bank Telescope's S-band receiver and the Pulsar Spigot
spectrometer, we have set out to use the same observing system in a systematic
search for pulsars in other globular clusters. Here we report on the discovery
of five new pulsars in NGC 6440 and three in NGC 6441; each cluster previously
had one known pulsar. Using the most recent distance estimates to these
clusters, we conclude that there are as many potentially observable pulsars in
NGC 6440 and NGC 6441 as in Terzan 5. We present timing solutions for all of
the pulsars in these globular clusters. Four of the new discoveries are in
binary systems; one of them, PSR J1748-2021B (NGC 6440B), has a wide (P_b =
20.5 d) and eccentric (e = 0.57) orbit. This allowed a measurement of its rate
of advance of periastron: 0.00391(18) degrees per year. If due to the effects
of general relativity, the total mass of this binary system is 2.92 +/- 0.20
solar masses (1 sigma), implying a median pulsar mass of 2.74 +/- 0.21 solar
masses. There is a 1 % probability that the inclination is low enough that
pulsar mass is below 2 solar masses, and 0.10 % probability that it is between
1.20 and 1.44 solar masses. If confirmed, this anomalously large mass would
strongly constrain the equation of state for dense matter. The other highly
eccentric binary, PSR J1750-37A, has e = 0.71, and periastron advance of
0.0055(3) degrees per year, implying a total system mass of 1.97 +/-0.15 solar
masses and, along with the mass function, maximum and median pulsar masses of
1.65 and 1.26 solar masses respectively.


title: Atomic alignment and Diagnostics of Magnetic Fields in Diffuse Media

abstract:
  We continue our studies of atomic alignment in diffuse media, in
particularly, in interstellar and circumstellar media, with the goal of
developing new diagnostics of magnetic fields in these environments. We
understand atomic alignment as alignment of atoms or ions in their ground
state. Such atoms are sensitive to weak magnetic fields. In particular, we
provide predictions of the polarization that arises from astrophysically
important aligned atoms (ions) with fine structure of the ground level, namely,
OI and SII and Ti II. Unlike our earlier papers which dealt with weak fields
only, a substantial part of our current paper is devoted to the studies of
atomic alignment when magnetic fields get strong enough to affect the emission
from the excited level, i.e. with the regime when the magnetic splitting is
comparable to the line-width. This is a regime of Hanle effect modified by the
atomic alignment. Using an example of emission and absorption lines of SII ion
we demonstrate how polarimetric studies can probe magnetic fields in
circumstellar regions and accretion disks. In addition, we show that atomic
alignment induced by anisotropic radiation can induce substantial variations of
magnetic dipole transitions within the ground state, thus affecting abundance
studies based on this emission. Moreover, the radio emission is polarized,
provides a new way to study magnetic fields, e.g. at the epoch of Universe
reionization.


title:
Plasmon phenomena as origin of DC-current induced resistivity
  oscillations in two-dimensional electron systems

abstract:
  We analyze theoretically the oscillations that the magnetoresistivity of
two-dimensional electron systems present when a high intensity direct current
is applied. In the model presented here we suggest that a plasma wave is
excited in the system producing an oscillating motion of the whole
two-dimensional electron gas at the plasma frequency. This scenario affects
dramatically the way that electrons interact with scatterers giving rise to
oscillations in the longitudinal resistivity. With this theoretical model
experimental results are well reproduced and explained.


title: Infinite Viterbi alignments in the two state hidden Markov models

abstract:
  Since the early days of digital communication, Hidden Markov Models (HMMs)
have now been routinely used in speech recognition, processing of natural
languages, images, and in bioinformatics. An HMM $(X_i,Y_i)_{i\ge 1}$ assumes
observations $X_1,X_2,...$ to be conditionally independent given an
"explanotary" Markov process $Y_1,Y_2,...$, which itself is not observed;
moreover, the conditional distribution of $X_i$ depends solely on $Y_i$.
Central to the theory and applications of HMM is the Viterbi algorithm to find
{\em a maximum a posteriori} estimate $q_{1:n}=(q_1,q_2,...,q_n)$ of $Y_{1:n}$
given the observed data $x_{1:n}$. Maximum {\em a posteriori} paths are also
called Viterbi paths or alignments. Recently, attempts have been made to study
the behavior of Viterbi alignments of HMMs with two hidden states when $n$
tends to infinity. It has indeed been shown that in some special cases a
well-defined limiting Viterbi alignment exists. While innovative, these
attempts have relied on rather strong assumptions. This work proves the
existence of infinite Viterbi alignments for virtually any HMM with two hidden
states.


title: Half quantum vortices and Majorana fermions in triplet superconductors

abstract:
  Half quantum vortices (HQVs) in superfluid $^3He-A$ have been speculated
since 1976. Two years ago, Yamashita et al reported a very unusual NMR
satellite in the rotating superfluid $^3He-A$ in a parallel plate geometry.
Recently this satellite has been interpreted in terms of HQVs. Also, the strong
flux pinnings in the triplet superconductors $UPt_3, Sr_2RuO_4$ and
$U_{1-x}Th_xBe_{13}$ have been discovered by Mota and her colleagues which are
interpreted in terms of HQVs. We shall first review the bound state spectra
around a single vortex in unconventional superconductors, which provides the
necessary background. In particular, we find the zero modes of the Majorana
fermions in some of triplet superconductors $UPt_3, Sr_2RuO_4$ and $CePt_3Sn$.
Armed with these results we analyze the microscopic aspects of HQVs in $UPt_3$
and $Sr_2RuO_4$. We compute the quasiparticle density of states and the local
magnetic field around HQVs, which should be accessible to scanning tunneling
microscopy (STM), micromagnetometry and neutron scattering below 300 mK.


title: Fast Equilibration of Hadrons in an Expanding Fireball

abstract:
  Due to long chemical equilibration times within standard hadronic reactions
during the hadron gas phase in relativistic heavy ion collisions it has been
suggested that the hadrons are "born" into equilibrium after the quark gluon
plasma phase. Here we develop a dynamical scheme in which possible Hagedorn
states contribute to fast chemical equilibration times of baryon anti-baryon
pairs (as well as kaon anti-kaon pairs) inside a hadron gas and just below the
critical temperature. Within this scheme, we use master equations and derive
various analytical estimates for the chemical equilibration times. Applying a
Bjorken picture to the expanding fireball, the kaons and baryons as well as the
bath of pions and Hagedorn resonances can indeed quickly chemically equilibrate
for both an initial overpopulation or underpopulation of Hagedorn resonances.
Moreover, a comparison of our results to $(B+\bar{B})/\pi^{+}$ and $K/\pi^{+}$
ratios at RHIC, indeed, shows a close match.


title: Is there a tower of charges to be discovered?

abstract:
  We investigate higher loop integrability for a q-deformation of the
su(2)-sector of N=4 SYM theory. First we construct a generalisation of the long
range spin chain, which for the lowest orders describes the non-deformed
dilatation operator. This generalised model is built up from Temperley-Lieb
algebra generators and describes the deformed theory to at least two loops.
When constructing the model we have demanded the existence of one commuting
charge, which puts strong constraints on the parameters to three loop orders.
We also write down the five first charges for this model at two loops order.
Our main goal is to obtain an explicit expression for an infinite number of
commuting charges, all commuting with the dilatation operator. This would imply
integrability. As a step towards this goal we present in this paper an
expression for a generic local charge of the one-loop dilatation operator,
which happens to be a generator of the Temperley-Lieb algebra.


title:
FDTD Computation of Human Eye Exposure to Ultra-wideband Electromagnetic
  Pulses

abstract:
  With an increase in the application of ultra-wideband (UWB) electromagnetic
pulses in the communications industry, radar, biotechnology and medicine, comes
an interest in UWB exposure safety standards. Despite an increase of the
scientific research on bioeffects of exposure to non-ionizing UWB pulses,
characterization of those effects is far from complete. A numerical
computational approach, such as a finite-difference time domain (FDTD) method,
is required to visualize and understand the complexity of broadband
electromagnetic interactions. The FDTD method has almost no limits in the
description of the geometrical and dispersive properties of the simulated
material, it is numerically robust and appropriate for current computer
technology. In this paper, a complete calculation of exposure of the human eye
to UWB electromagnetic pulses in the frequency range of 3.1-10.6, 22-29, and
57-64 GHz is performed. Computation in this frequency range required a
geometrical resolution of the eye of $\rm 0.1 \: mm$ and an arbitrary precision
in the description of its dielectric properties in terms of the Debye model.
New results show that the interaction of UWB pulses with the eye tissues
exhibits the same properties as the interaction of the continuous
electromagnetic waves (CW) with the frequencies from the pulse's frequency
spectrum. It is also shown that under the same exposure conditions the exposure
to UWB pulses is from one to many orders of magnitude safer than the exposure
to CW.


title:
86-km optical link with a resolution of 2.10-18 for RF frequency
  transfer

abstract:
  RF frequency transfer over an urban 86 km fibre has been demonstrated with a
resolution of 2.10-18 at one day measuring time using an optical compensator.
This result is obtained with a reference carrier frequency of 1 GHz, and a
rapid scrambling of the polarisation state of the input light in order to
reduce the sensitivity to the polarisation mode dispersion in the fibre. The
limitation due to the fibre chromatic dispersion associated with the laser
frequency fluctuations is highlighted and analyzed. A preliminary test of an
extended compensated link over 186 km using optical amplifiers gives a
resolution below 10-17 at 1 day.


title: Time-Depentent Hartree-Fock description of heavy ions fusion

abstract:
  A microscopic mean-field description of heavy ions fusion is performed in the
framework of the Time-Dependent Hartree-Fock (TDHF) theory using a Skyrme
interaction with the SLy4d parametrization. A good agreement with experiments
is obtained on the position of the fusion barriers for various total masses,
mass asymmetries and deformations. The excitation function of the 16O+208Pb is
overestimated by about 16% above the barrier. The restriction to an independent
particles state in the mean-field dynamics prevents the description of
sub-barrier fusion. Effect of transfer on fusion is discussed.


title: CP violation and the H-A lineshape

abstract:
  In two-Higgs doublet models (and particularly in the MSSM) the CP-even (H)
and CP-odd (A) neutral scalars are nearly degenerate in mass, and their
s-channel production would lead to nearly overlapping resonances. CP-violating
effects may connect these two Higgs bosons, giving origin to one-loop particle
mixing, which, due to their mass proximity, can be resonantly enhanced,
altering their lineshape significantly. We show that, in general, the effect of
such a CP-violating mixing cannot be mimicked by (or be re-absorbed into) a
simple redefinition of the H and A masses in the context of a CP-conserving
model. Specifically, the effects of the CP-mixing are such that, either the
mass-splitting of the H and A bosons lies outside the range allowed by the
theory in the absence of CP-mixing, and/or the detailed energy dependence of
the produced lineshape is clearly different from the one obtained by redefining
the masses, but not allowing any mixing.


title: Gluon mass and freezing of the QCD coupling

abstract:
  Infrared finite solutions for the gluon propagator of pure QCD are obtained
from the gauge-invariant non-linear Schwinger-Dyson equation formulated in the
Feynman gauge of the background field method. These solutions may be fitted
using a massive propagator, with the special characteristic that the effective
mass employed drops asymptotically as the inverse square of the momentum
transfer, in agreement with general operator-product expansion arguments. Due
to the presence of the dynamical gluon mass the strong effective charge
extracted from these solutions freezes at a finite value, giving rise to an
infrared fixed point for QCD.


title:
Fractal Fluctuations and Quantum-Like Chaos in the Brain by Analysis of
  Variability of Brain Waves: A New Method Based on a Fractal Variance Function
  and Random Matrix Theory

abstract:
  We developed a new method for analysis of fundamental brain waves as recorded
by EEG. To this purpose we introduce a Fractal Variance Function that is based
on the calculation of the variogram. The method is completed by using Random
Matrix Theory. Some examples are given.


title: Commissioning of the ATLAS Level-1 Trigger with Cosmic Rays

abstract:
  The ATLAS detector at CERN's Large Hadron Collider will be exposed to
proton-proton collisions from beams crossing at 40 MHz. A three-level trigger
system was designed to select potentially interesting events and reduce the
incoming rate to 100-200 Hz. The first trigger level (LVL1) is implemented in
custom-built electronics, the second and third trigger levels are realized in
software. Based on calorimeter information and hits in dedicated muon-trigger
detectors, the LVL1 decision is made by the central-trigger processor yielding
an output rate of less than 100 kHz. The allowed latency for the trigger
decision at this stage is less than 2.5 microseconds. Installation of the final
LVL1 trigger system at the ATLAS site is in full swing, to be completed later
this year. We present a status report of the main components of the first-level
trigger and the in-situ commissioning of the full trigger chain with cosmic-ray
muons.


title: Neutrino mixing, flavor states and dark energy

abstract:
  We shortly summarize the quantum field theory formalism for the neutrino
mixing and report on recent results showing that the vacuum condensate induced
by neutrino mixing can be interpreted as a dark energy component of the
Universe.


title:
Quenching of quantum Hall effect and the role of undoped planes in
  multilayered epitaxial graphene

abstract:
  We propose a mechanism for the quenching of the Shubnikov de Haas
oscillations and the quantum Hall effect observed in epitaxial graphene.
Experimental data show that the scattering time of the conduction electron is
magnetic field dependent and of the order of the cyclotron orbit period,
\textit{i.e.} can be much smaller than the zero field scattering time. Our
scenario involves the extraordinary graphene $n=0$ Landau level of the
uncharged layers that produces a high density of states at the Fermi level. We
find that the coupling between this $n=0$ Landau level and the conducting
states of the doped plane leads to a scattering mechanism having the right
magnitude to explain the experimental data.


title: Stationary states of spinless particles in square potentials

abstract:
  The one-dimensional Klein-Gordon equation is investigated with the most
general Lorentz structure for the external potentials. The analysis and
calculation of the reflection and transmission coefficients for the scattering
of particles in a square potential, with an arbitrary mixing of vector and
scalar couplings, reveal circumstances which conflict with the predictions from
nonrelativistic quantum mechanics. It is shown that such anomalous scatterings
are mediated by antiparticle bound states, even if the incident particles have
low energies. The analysis of bound states also reveals surprising results,
remarkable is the inhibition of the Schiff-Snyder-Weinberg effect due to the
presence of a scalar coupling.


title: Entanglement in the Bose-Einstein condensate phase transition

abstract:
  We determine the behaviour of entanglement between regions of space in a Bose
gas of fixed particle number around the critical temperature condensation.
Long-range correlations develop in the Bose-Einstein condensate (BEC) phase
transition and the aim here is to find out whether spatial coherence alone
implies entanglement. We use a purity measure of entanglement to derive an
entanglement witness that detects entanglement between two regions of space in
the BEC. It is shown that spatial coherence between the two regions is
necessary for entanglement with coherence and entanglement becoming equivalent
only when the regions occupy the entire confining volume of the gas. The
probabilities for Bosons to occupy the regions is the only other parameter that
influences the amount of entanglement. We calculate explicitly the amount of
entanglement between two regions for a cigar-shaped harmonic potential and find
that it increases with decreasing temperature. A second entanglement witness is
derived for entanglement between three regions of space, where again spatial
coherence between each pair of regions is precursor to entanglement. It is
shown that the state with the maximum amount of entanglement occurs when the
probabilities for the Bosons to occupy the three regions are equal.


title: Quantum measurements without macroscopic superpositions

abstract:
  We study a class of quantum measurement models. A microscopic object is
entangled with a macroscopic pointer such that each eigenvalue of the measured
object observable is tied up with a specific pointer deflection. Different
pointer positions mutually decohere under the influence of a bath.
Object-pointer entanglement and decoherence of distinct pointer readouts
proceed simultaneously. Mixtures of macroscopically distinct object-pointer
states may then arise without intervening macroscopic superpositions.
Initially, object and apparatus are statistically independent while the latter
has pointer and bath correlated according to a metastable local thermal
equilibrium. We obtain explicit results for the object-pointer dynamics with
temporal coherence decay in general neither exponential nor Gaussian. The
decoherence time does not depend on details of the pointer-bath coupling if it
is smaller than the bath correlation time, whereas in the opposite Markov
regime the decay depends strongly on whether that coupling is Ohmic or
super-Ohmic.


title: The space of tropically collinear points is shellable

abstract:
  The space T_{d,n} of n tropically collinear points in a fixed tropical
projective space TP^{d-1} is equivalent to the tropicalization of the
determinantal variety of matrices of rank at most 2, which consists of real d x
n matrices of tropical or Kapranov rank at most 2, modulo projective
equivalence of columns. We show that it is equal to the image of the moduli
space M_{0,n}(TP^{d-1},1) of n-marked tropical lines in TP^{d-1} under the
evaluation map. Thus we derive a natural simplicial fan structure for T_{d,n}
using a simplicial fan structure of M_{0,n}(TP^{d-1},1) which coincides with
that of the space of phylogenetic trees on d+n taxa. The space of phylogenetic
trees has been shown to be shellable by Trappmann and Ziegler. Using a similar
method, we show that T_{d,n} is shellable with our simplicial fan structure and
compute the homology of the link of the origin. The shellability of T_{d,n} has
been conjectured by Develin in 2005.


title:
The Monitor project: tracking the evolution of low mass and pre-main
  sequence stars

abstract:
  The Monitor project is a large-scale program of photometric and spectroscopic
monitoring of young open clusters using telescopes at ESO and other
observatories. Its primary goal is to detect and characterise new low-mass
eclipsing binaries, and the first three detected systems are discussed here. We
derive the masses and radii of the components of each system directly from the
light and radial velocity curves, and compare them to the predictions of
commonly used theoretical evolutionary models of low-mass stars.


title:
Engineering the phase speed of surface-plasmon wave at the planar
  interface of a metal and a chiral sculptured thin film

abstract:
  The solution of a boundary-value problem formulated for a modified
Kretschmann configuration shows that the phase speed of a surface-plasmon wave
guided by the planar interface of a sufficiently thin metal film and a chiral
sculptured thin film (STF) depends on the vapor incidence angle used while
fabricating the chiral STF by physical vapor depoistion. Therefore, it may be
possible to engineer the phase speed quite simply by selecting an appropriate
value of the vapor deposition angle (in addition to the metal and the evaporant
species).


title: Rings whose modules are weakly supplemented are perfect

abstract:
  In this note we show that a ring R is left perfect if and only if every left
R-module is weakly supplemented if and only if R is semilocal and the radical
of the countably infinite free left R-module has a weak supplement.


title:
Reflectionless measures with a point mass and singular continuous
  component

abstract:
  We construct mesures supported on a compact subset E of the real line having
zero principal value of their Cauchy integral a.e. on E with respect to
Lebesgue measure and having singular components. E is sufficiently regular
(Widom property is satisfied) but not homogeneous as for homogeneous spectrum
such construction is impossible. This impossibility played an important role in
characterizing almost periodic Jacobi matrices with homogeneous spectrum
(Sodin-Yuditskii).


title:
Formation of Subgap States in Carbon Nanotubes Due to a Local Transverse
  Electric Field

abstract:
  We introduce two simple models to study the effect of a spatially localized
transverse electric field on the low-energy electronic structure of
semiconducting carbon nanotubes. Starting from the Dirac Hamiltonian for the
low energy states of a carbon nanotube, we use scattering theory to show that
an arbitrarily weak field leads to the formation of localized electronic states
inside the free nanotube band gap. We study the binding energy of these subgap
states as a function of the range and strength of the electrostatic potential.
When the range of the potential is held constant and the strength is varied,
the binding energy shows crossover behavior: the states lie close to the free
nanotube band edge until the potential exceeds a threshold value, after which
the binding energy increases rapidly. When the potential strength is held
constant and the range is varied, we find resonant behavior: the binding energy
passes through a maximum as the range of the potential is increased. Large
electric fields confined to a small region of the nanotube are required to
create localized states far from the band edge.


title:
The effects of topological charge change in heavy ion collisions: "Event
  by event P and CP violation"

abstract:
  Quantum chromodynamics (QCD) contains field configurations which can be
characterized by a topological invariant, the winding number Q_w.
Configurations with nonzero Q_w break the charge-parity CP symmetry of QCD. We
consider a novel mechanism by which these configurations can separate charge in
the presence of a background magnetic field - the "Chiral Magnetic Effect". We
argue that sufficiently large magnetic fields are created in heavy ion
collisions so that the Chiral Magnetic Effect causes preferential emission of
charged particles along the direction of angular momentum. Since separation of
charge is CP-odd, any observation of the Chiral Magnetic Effect could provide a
clear demonstration of the topological nature of the QCD vacuum. We give an
estimate of the effect and conclude that it might be observed experimentally.


title:
Left-invariant Stochastic Evolution Equations on SE(2) and its
  Applications to Contour Enhancement and Contour Completion via Invertible
  Orientation Scores

abstract:
  We provide the explicit solutions of linear, left-invariant,
(convection)-diffusion equations and the corresponding resolvent equations on
the 2D-Euclidean motion group SE(2). These diffusion equations are forward
Kolmogorov equations for stochastic processes for contour enhancement and
completion. The solutions are group-convolutions with the corresponding Green's
function, which we derive in explicit form. We mainly focus on the Kolmogorov
equations for contour enhancement processes which, in contrast to the
Kolmogorov equations for contour completion, do not include convection. The
Green's functions of these left-invariant partial differential equations
coincide with the heat-kernels on SE(2), which we explicitly derive. Then we
compute completion distributions on SE(2) which are the product of a forward
and a backward resolvent evolved from resp. source and sink distribution on
SE(2). On the one hand, the modes of Mumford's direction process for contour
completion coincide with elastica curves minimizing $\int \kappa^{2} + \epsilon
ds$, related to zero-crossings of 2 left-invariant derivatives of the
completion distribution. On the other hand, the completion measure for the
contour enhancement concentrates on geodesics minimizing $\int \sqrt{\kappa^{2}
+ \epsilon} ds$. This motivates a comparison between geodesics and elastica,
which are quite similar. However, we derive more practical analytic solutions
for the geodesics. The theory is motivated by medical image analysis
applications where enhancement of elongated structures in noisy images is
required. We use left-invariant (non)-linear evolution processes for automated
contour enhancement on invertible orientation scores, obtained from an image by
means of a special type of unitary wavelet transform.


title:
On the Luttinger theorem concerning number of particles in the ground
  states of systems of interacting fermions

abstract:
  We analyze the original proof by Luttinger and Ward of the Luttinger theorem,
according to which for uniform ground states of systems of (interacting)
fermions, which may be metallic or insulating, the number of k points
corresponding to non-negative values of G_s(k;mu) is equal to the total number
of particles with spin index s in these ground states. Here G_s(k;mu) is the
single-particle Green function of particles with spin index s at the chemical
potential mu. For the cases where the two-body interaction potential is
short-range, and in particular for lattice models, we explicitly demonstrate
that this theorem is unconditionally valid, irrespective of the strength of the
bare interaction potential. We arrive at this conclusion by amongst other
things demonstrating that the perturbation series expansion for self-energy in
terms of skeleton diagrams, as encountered in the proof of the Luttinger-Ward
identity, is uniformly convergent for almost all momenta and energies. We
further investigate the mechanisms underlying some reported instances of
failure of the Luttinger theorem. With one exception, for all the cases
considered in this paper, we show that the apparent failures of the Luttinger
theorem can be attributed either to shortcomings of the employed
single-particle Green functions or to misapplication of this theorem. The one
exceptional case brings to light the possibility of a genuine failure of the
Luttinger theorem for insulating ground states, which we show to be brought
about by a false limit that in principle can be reached on taking the
zero-temperature limit without the value of mu coinciding with the
zero-temperature limit of the chemical potential satisfying the equation of
state at finite temperatures; no such ambiguity can arise for metallic states.

categories: cond-mat.str-el cond-mat.mtrl-sci cond-mat.supr-con math-ph math.MP


title:
Isolated vibrational wavepackets in D2+: Defining superposition
  conditions and wavepacket distinguishability

abstract:
  Tunnel ionization of room-temperature D$_2$ in an ultrashort (12 femtosecond)
near infra-red (800 nm) pump laser pulse excites a vibrational wavepacket in
the D2+ ions; a rotational wavepacket is also excited in residual D2 molecules.
Both wavepacket types are collapsed a variable time later by an ultrashort
probe pulse. We isolate the vibrational wavepacket and quantify its evolution
dynamics through theoretical comparison. Requirements for quantum computation
(initial coherence and quantum state retrieval) are studied using this
well-defined (small number of initial states at room temperature, initial
wavepacket spatially localized) single-electron molecular prototype by
temporally stretching the pump and probe pulses.


title:
Effects of Neutron Emission on Fragment Mass and Kinetic Energy
  Distribution from Thermal Neutron-Induced Fission of $^{235}U$

abstract:
  The mass and kinetic energy distribution of nuclear fragments from thermal
neutron-induced fission of 235U have been studied using a Monte-Carlo
simulation. Besides reproducing the pronounced broadening in the standard
deviation of the kinetic energy at the final fragment mass number around m =
109, our simulation also produces a second broadening around m = 125. These
results are in good agreement with the experimental data obtained by Belhafaf
et al. and other results on yield of mass. We conclude that the obtained
results are a consequence of the characteristics of the neutron emission, the
sharp variation in the primary fragment kinetic energy and mass yield curves.
We show that because neutron emission is hazardous to make any conclusion on
primary quantities distribution of fragments from experimental results on final
quantities distributions.


title: Gauge Symmetry and Supersymmetry of Multiple M2-Branes

abstract:
  In previous work we proposed a field theory model for multiple M2-branes
based on an algebra with a totally antisymmetric triple product. In this paper
we gauge a symmetry that arises from the algebra's triple product. We then
construct a supersymmetric theory that is consistent with all the symmetries
expected of a multiple M2-brane theory: 16 supersymmetries, conformal
invariance, and an SO(8) R-symmetry that acts on the eight transverse scalars.
The gauge field is not dynamical. The result is a new type of maximally
supersymmetric gauge theory in three dimensions.


title: Supersymmetry Breaking by Type II Seesaw Assisted Anomaly Mediation

abstract:
  Anomaly mediated supersymmetry breaking (AMSB), when implemented in MSSM is
known to suffer from the problem of negative slepton mass squared leading to
breakdown of electric charge conservation. We show however that when MSSM is
extended to explain small neutrino masses by including a pair of superheavy
Higgs triplet superfields (the type II seesaw mechanism), the slepton masses
can be deflected from the pure AMSB trajectory and become positive. In a simple
model we present in this paper, the seesaw scale is about $10^{13}-10^{14}{\rm
GeV}$. Gauge coupling unification can be maintained by embedding the triplet to
SU(5) {\bf 15}-multiplet. In this scenario, bino is the LSP and its mass is
nearly degenerate with NLSP slepton when the triplet mass is right around the
seesaw scale.


title: Zero dimensional area law in a gapless fermion system

abstract:
  The entanglement entropy of a gapless fermion subsystem coupled to a gapless
bulk by a "weak link" is considered. It is demonstrated numerically that each
independent weak link contributes an entropy proportional to lnL, where L is
linear dimension of the subsystem.


title:
Perturbations In A Non-Uniform Dark Energy Fluid: Equations Reveal
  Effects of Modified Gravity and Dark Matter

abstract:
  We propose a unified single-field description of the galactic Dark Matter and
various uniform scalar fields for the inflation and cosmological constant. The
two types of effects could originate from a fluid of both spatially and
temporally varying Vacuum Energy if the vacuum has an uneven pressure caused by
a photon-like vector field (of perhaps an unstable massive boson). We propose a
most general Lagrangian with a {\bf N}on-{\bf u}niform Cosmological Constant
for this vacuum fluid (dubbed as a Nu-Lambda fluid), working within the
framework of Einsteinian gravity. This theory includes a continuous spectrum of
plausible dark energy theories and gravity theories, e.g., inflation,
quintessence, k-essence, f(R), Generalized Einstein-Aether f(K), MOND, TeVeS,
BSTV etc. theories. It also suggests new models such as a certain f(K+R) model,
which suggests intriguing corrections to MOND depending of redshift and
density. Some specific constructions of the Nu-Lambda fluid (e.g., Zhao's
V-$\Lambda$ model) closely resemble the $\Lambda$CDM cosmology on large scale,
but fit galaxy rotation curves as good as MOND. Perturbed Einstein Equations in
a simple $f(K_4)$ model are solvable and show effects of a DM coupled to DE.
Incorporating the perturbation equations here into standard simulations for
cosmological structure growth offers a chance to falsify examples of the
Nu-Lambda theories.


title:
Boltzmann limit and quasifreeness for a homogenous Fermi gas in a weakly
  disordered random medium

abstract:
  We discuss some basic aspects of the dynamics of a homogenous Fermi gas in a
weak random potential, under negligence of the particle pair interactions. We
derive the kinetic scaling limit for the momentum distribution function with a
translation invariant initial state and prove that it is determined by a linear
Boltzmann equation. Moreover, we prove that if the initial state is quasifree,
then the time evolved state, averaged over the randomness, has a quasifree
kinetic limit. We show that the momentum distributions determined by the Gibbs
states of a free fermion field are stationary solutions of the linear Boltzmann
equation; this includes the limit of zero temperature.


title: Late-time Kerr tails revisited

abstract:
  The decay rate of late time tails in the Kerr spacetime have been the cause
of numerous conflicting results, both analytical and numerical. In particular,
there is much disagreement on whether the decay rate of an initially pure
multipole moment ${\ell}$ is according to $t^{-(2{\bar\ell}+3)}$, where
${\bar\ell}$ is the least multipole moment whose excitation is not disallowed,
or whether the decay rate is according to $t^{-n}$, where $n=n({\ell})$. We do
careful 2+1D numerical simulations, and explain the various results. In
particular, we show that pure multipole outgoing initial data in either
Boyer--Lindquist on ingoing Kerr coordinates on the corresponding slices lead
to the same late time tail behavior. We also show that similar initial data
specified in terms of the Poisson spherical coordinates lead to the simpler
$t^{-(2{\bar\ell}+3)}$ late time tail. We generalize the rule $n=n({\ell})$ to
subdominant modes, and also study the behavior of non--axisymmetric initial
data. We discuss some of the causes for possible errors in 2+1D simulations,
demonstrate that our simulations are free of those errors, and argue that some
conflicting past results may be attributed to them.


title:
Perturbative QCD Calculations of Elliptic Flow and Shear Viscosity in
  Au+Au Collisions at $\sqrt{s_{NN}}=200$ GeV

abstract:
  The elliptic flow $v_2$ and the ratio of the shear viscosity over the entropy
density, $\eta/s$, of gluon matter are calculated from the perturbative QCD
(pQCD) based parton cascade Boltzmann approach of multiparton scatterings. For
Au+Au collisions at $\sqrt{s}=200$A GeV the gluon plasma generates large $v_2$
values measured at the BNL Relativistic Heavy Ion Collider. Standard pQCD
yields $\eta/s\approx 0.08-0.15$ as small as the lower bound found from the
anti-de Sitter/conformal field theory conjecture.


title: Photometric Redshift Error Estimators

abstract:
  Photometric redshift (photo-z) estimates are playing an increasingly
important role in extragalactic astronomy and cosmology. Crucial to many
photo-z applications is the accurate quantification of photometric redshift
errors and their distributions, including identification of likely catastrophic
failures in photo-z estimates. We consider several methods of estimating
photo-z errors and propose new training-set based error estimators based on
spectroscopic training set data. Using data from the Sloan Digital Sky Survey
and simulations of the Dark Energy Survey as examples, we show that this method
provides a robust, relatively unbiased estimate of photo-z errors. We show that
culling objects with large, accurately estimated photo-z errors from a sample
can reduce the incidence of catastrophic photo-z failures.


title: Density functional theory for self-bound systems

abstract:
  The density functional theory is extended to account for self-bound systems.
To this end the Hohenberg-Kohn theorem is formulated for the intrinsic density
and a Kohn-Sham like procedure for an $N$--body system is derived using the
adiabatic approximation to account for the center of mass motion.


title: Singularities of admissible normal functions

abstract:
  In a recent paper, M. Green and P. Griffiths used R. Thomas' works on nodal
hypersurfaces to establish the equivalence of the Hodge conjecture and the
existence of certain singular admissible normal functions. Inspired by their
work, we study normal functions using M. Saito's mixed Hodge modules and prove
that the existence of singularities of the type considered by Griffiths and
Green is equivalent to the Hodge conjecture. Several of the intermediate
results, including a relative version of the weak Lefschetz theorem for
perverse sheaves, are of independent interest.


title: On a question of Landis and Oleinik

abstract:
  We answer in the affirmative a question posed by Landis and Oleinik on unique
continuation of variable coefficients parabolic equations.


title: Observable Properties of Double-Barred Galaxies in N-Body Simulations

abstract:
  Although at least one quarter of early-type barred galaxies host secondary
stellar bars embedded in their large-scale primary counterparts, the dynamics
of such double barred galaxies are still not well understood. Recently we
reported success at simulating such systems in a repeatable way in
collisionless systems. In order to further our understanding of double-barred
galaxies, here we characterize the density and kinematics of the N-body
simulations of these galaxies. This will facilitate comparison with
observations and lead to a better understanding of the observed double-barred
galaxies. We find the shape and size of our simulated secondary bars are quite
reasonable compared to the observed ones. We demonstrate that an authentic
decoupled secondary bar may produce only a weak twist of the kinematic minor
axis in the stellar velocity field, due to the relatively large random motion
of stars in the central region. We also find that the edge-on nuclear bars are
probably not related to boxy peanut-shaped bulges which are most likely to be
edge-on primary large-scale bars. Finally we demonstrate that the non-rigid
rotation of the secondary bar causes its pattern speed not to be derived with
great accuracy using the Tremaine-Weinberg method. We also compare with
observations of NGC 2950, a prototypical double-barred early-type galaxy, which
suggest that the nuclear bar may be rotating in the opposite sense as the
primary.


title: Simulating the Bullet Cluster

abstract:
  We present high resolution N-body/SPH simulations of the interacting cluster
1E0657-56. The main and the sub-cluster are modeled using extended cuspy LCDM
dark matter halos and isothermal beta-profiles for the collisional component.
The hot gas is initially in hydrostatic equilibrium inside the global potential
of the clusters. We investigate the X-ray morphology and derive the most likely
impact parameters, mass ratios and initial relative velocities. We find that
the observed displacement between the X-ray peaks and the associated mass
distribution, the morphology of the bow shock, the surface brightness and
projected temperature profiles across the shock discontinuity can be well
reproduced by offset 1:6 encounters where the sub-cluster has initial velocity
(in the rest frame of the main cluster) close to 2 times the virial velocity of
the main cluster dark matter halo. A model with the same mass ratio and lower
velocity (1.5 times the main cluster virial velocity) matches quite well most
of the observations. However, it does not reproduce the morphology of the main
cluster peak. Dynamical friction strongly affects the kinematics of the
sub-cluster so that the low velocity bullet is actually bound to the main
system at the end of the simulation. We find that a relatively high
concentration (c=6) of the main cluster dark matter halo is necessary in order
to prevent the disruption of the associated X-ray peak. For a selected
sub-sample of runs we perform a detailed three dimensional analysis following
the past, present and future evolution of the interacting systems. In
particular, we investigate the kinematics of the gas and dark matter components
as well as the changes in the density profiles and the motion of the system in
the L_X-T diagram.


title:
Quantum Monte Carlo study of the visibility of one-dimensional
  Bose-Fermi mixtures

abstract:
  The study of ultracold optically trapped atoms has opened new vistas in the
physics of correlated quantum systems. Much attention has now turned to
mixtures of bosonic and fermionic atoms. A central puzzle is the disagreement
between the experimental observation of a reduced bosonic visibility ${\cal
V}_b$, and quantum Monte Carlo (QMC) calculations which show ${\cal V}_b$
increasing. In this paper, we present QMC simulations which evaluate the
density profiles and ${\cal V}_b$ of mixtures of bosons and fermions in
one-dimensional optical lattices. We resolve the discrepancy between theory and
experiment by identifying parameter regimes where ${\cal V}_b$ is reduced, and
where it is increased. We present a simple qualitative picture of the different
response to the fermion admixture in terms of the superfluid and
Mott-insulating domains before and after the fermions are included. Finally, we
show that ${\cal V}_b$ exhibits kinks which are tied to the domain evolution
present in the pure case, and also additional structure arising from the
formation of boson-fermion molecules, a prediction for future experiments.


title: 2D Toda chain and associated commutator identity

abstract:
  Developing observation made in \cite{commut} we show that simple identity of
the commutator type on an associative algebra is in one-to-one correspondence
to 2D (infinite) Toda chain. We introduce representation of elements of
associative algebra that, under some generic conditions, enables derivation of
the Toda chain equation and its Lax pair from the given commutator identity.


title:
An introduction to Cosmic Rays and Gamma-Ray Bursts, and to their simple
  understanding

abstract:
  I review the subjects of non-solar cosmic rays (CRs) and long-duration
gamma-ray bursts (GRBs). Of the various interpretations of these phenomena, the
one best supported by the data is the following. Accreting compact objects,
such as black holes, are seen to emit relativistic puffs of plasma:
`cannonballs' (CBs). The inner domain of a rotating star whose core has
collapsed resembles such an accreting system. This suggests that core-collapse
supernovae (SNe) emit CBs, as SN1987A did. The fate of a CB as it exits a SN
and travels in space can be studied as a function of the CB's mass and energy,
and of `ambient' properties: the encountered matter- and light- distributions,
the composition of the former, and the location of intelligent observers. The
latter may conclude that the interactions of CBs with ambient matter and light
generate CRs and GRBs, all of whose properties can be described by this `CB
model' with few parameters and simple physics. GRB data are still being taken
in unscrutinized domains of energy and timing. They agree accurately with the
model's predictions. CR data are centenary. Their precision will improve, but
new striking predictions are unlikely. Yet, a one-free-parameter description of
all CR data works very well. This is a bit as if one discovered QED today and
only needed to fit $\alpha$.


title:
Exact entropy of dimer coverings for a class of lattices in three or
  more dimensions

abstract:
  We construct a class of lattices in three and higher dimensions for which the
number of dimer coverings can be determined exactly using elementary arguments.
These lattices are a generalization of the two-dimensional kagome lattice, and
the method also works for graphs without translational symmetry. The partition
function for dimer coverings on these lattices can be determined also for a
class of assignments of different activities to different edges.


title: Proton Electromagnetic Form Factor Ratios at Low Q^2

abstract:
  We study the ratio $R\equiv\mu G_E(Q^2)/G_M(Q^2)$ of the proton at very small
values of $Q^2$. Radii commonly associated with these form factors are not
moments of charge or magnetization densities. We show that the form factor
$F_2$ is correctly interpretable as the two-dimensional Fourier transformation
of a magnetization density. A relationship between the measurable ratio and
moments of true charge and magnetization densities is derived. We find that
existing measurements show that the magnetization density extends further than
the charge density, in contrast with expectations based on the measured
reduction of $R$ as $Q^2$ increases.


title: Magnetic dynamo action in helical turbulence

abstract:
  We investigate magnetic field amplification in a turbulent velocity field
with nonzero helicity, in the framework of the kinematic Kazantsev-Kraichnan
model. We present the numerical solution of the model for the practically
important case of Kolmogorov distribution of velocity fluctuations, with a
large magnetic Reynolds number. We find that in contrast to the nonhelical case
where growing magnetic fields are described by a few bound eigenmodes
concentrated inside the inertial interval of the velocity field, in the helical
case the number of bound eigenmodes considerably increases; moreover, new
unbound eigenmodes appear. Both bound and unbound eigenmodes contribute to the
large-scale magnetic field. This indicates a limited applicability of the
conventional alpha model of a large-scale dynamo action, which captures only
unbound modes.


abstract:
  This writeup is a compilation of the predictions for the forthcoming Heavy
Ion Program at the Large Hadron Collider, as presented at the CERN Theory
Institute 'Heavy Ion Collisions at the LHC - Last Call for Predictions', held
from May 14th to June 10th 2007.


title: Anisotropic Pressures in Very Dense Magnetized Matter

abstract:
  The problem of anisotropic pressures arising as a consequence of the spatial
symmetry breaking introduced by an external magnetic field in quantum systems
is discussed. The role of the conservation of energy and momentum of external
fields as well as of systems providing boundary conditions in quantum
statistics is considered. The vanishing of the average transverse momentum for
an electron-positron system in its Landau ground state is shown, which means
the vanishing of its transverse pressure. The situation for neutron case and
Strange Quark Matter (SQM) in $\beta$-equilibrium is also briefly discussed.
Thermodynamical relations in external fields as well as the form of the stress
tensor in a quantum relativistic medium are also discussed. The ferromagnetic
symmetry breaking is briefly discussed.


title:
Bose-Einstein condensation and superfluidity of magnetobiexcitons in
  quantum wells' and graphene superlattices

abstract:
  We propose the Bose-Einstein condensation (BEC) and superfluidity of
quasi-two-dimensional (2D) spatially indirect magnetobiexcitons in a slab of
superlattice with alternating electron and hole layers consisting from the
semiconducting quantum wells (QWs) and graphene superlattice in high magnetic
field. The two different Hamiltonians of a dilute gas of magnetoexcitons with a
dipole-dipole repulsion in superlattices consisting of both QWs and graphene
layers in the limit of high magnetic field have been reduced to one effective
Hamiltonian a dilute gas of two-dimensional excitons without magnetic field.
Moreover, for $N$ excitons we have reduced the problem of $2N\times 2$
dimensional space onto the problem of $N\times 2$ dimensional space by
integrating over the coordinates of the relative motion of an electron (e) and
a hole (h). The instability of the ground state of the system of interacting
two-dimensional indirect magnetoexcitons in a slab of superlattice with
alternating electron and hole layers in high magnetic field is established. The
stable system of indirect quasi-two-dimensional magnetobiexcitons, consisting
of pair of indirect excitons with opposite dipole moments is considered. The
density of superfluid component $n_{s}(T)$ and the temperature of the
Kosterlitz-Thouless phase transition to the superfluid state in the system of
two-dimensional indirect magnetobiexcitons, interacting as electrical
quadrupoles, are obtained for both QW and graphene realizations.


title: Affine Hermitian-Einstein Metrics

abstract:
  We develop a theory of stable bundles and affine Hermitian-Einstein metrics
for flat vector bundles over a special affine manifold (a manifold admitting an
atlas whose gluing maps are all locally constant volume-preserving affine
maps). Our paper presents a parallel to Donaldson-Uhlenbeck-Yau's proof of the
existence of Hermitian-Einstein metrics on K\"ahler manifolds, and the
extension of this theorem by Li-Yau to the non-K\"ahler complex case of
Gauduchon metrics. Our definition of stability involves only flat vector
subbundles (and not singular subsheaves), and so is simpler than the complex
case in some places.


title: Construction of SU(3) irreps in canonical SO(3)-coupled bases

abstract:
  Alternative canonical methods for defining canonical SO(3)-coupled bases for
SU(3) irreps are considered and compared. It is shown that a basis that
diagonalizes a particular linear combination of SO(3) invariants in the SU(3)
universal enveloping algebra gives basis states that have good $K$ quantum
numbers in the asymptotic rotor-model limit.


title: Minimal Homeomorphisms on Low-Dimension Tori

abstract:
  In this article we study minimal homeomorphisms(all orbits are dense) of the
tori $T^{n},$ $n<5.$ The linear part of a homeomorphism $\phi $ of $T^{n}$ is
the linear mapping $L$ induced by $\phi $ on the first homology group of
$T^{n}$. It follows from the Lefschetz fixed point theorem that 1 is an
eigenvalue of $L$ if $\phi $ minimal. We show that if $\phi $ is minimal and
$n<5$ then $L$ is quasi-unipontent, i.e., all the eigenvalues of $L$ are roots
of unity and conversely if $L\in GL(n,\Z)$ is quasi-unipotent and 1 is an
eigenvalue of $L$ then there exists a $ C^{\infty}$ minimal skew-product
diffeomorphism $\phi $ of $T^{n}$ whose linear part is precisely $L.$ We do not
know if these results are true for $n>4$. We give a sufficient condition for a
smooth skew-product diffeomorphism of a torus of arbitrary dimension to be
smoothly conjugate to an affine transformation.


title:
Search for Lepton Flavor Violating Decays \tau^\pm \to l^\pm\omega (l =
  e, \mu)

abstract:
  We have searched for lepton flavor violating decays of a $\tau$ to a
lighter-mass charged lepton and an $\omega$ vector mesonusing 384.1 $fb^{-}$ of
$e^+e^- $ annihilation data collected with the BABAR detector at the Stanford
Linear Accelerator Center PEP-II storage ring. No signal is found, and the
upper limits on the branching ratios are determined to be ${\cal B}(\tau^{\pm}
\to \mathrm{e}^{\pm} \omega) < 1.1\times10^{-7}$ and ${\cal B}(\tau^{\pm} \to
\mu^{\pm} \omega) < 1.0\times10^{-7}$ at 90% confidence level.


title: From RHIC to LHC

abstract:
  Measurements of the nuclear modification factor of inclusive yields of
$\pi^0$, $p\bar{p}$, non-phtonic electrons and prompt photon measured at RHIC
are reviewed. Some of the difficulties arising from interpretation of these
measurements such as similarity of the suppression pattern of light and heavy
quarks, quarks and gluons, light quarks and prompt photon are discussed. The
potential of two-particle and promt photon correlation technique to unravel
some of these open questions is presented. An emphasis is given to the
influence of partonic transverse momentum on the prompt-photon correlations.
The smearing between the trigger photon and back-to-back jet at LHC energy is
discussed.


title:
First exit times for L\'evy-driven diffusions with exponentially light
  jumps

abstract:
  We consider a dynamical system described by the differential equation
$\dot{Y}_t=-U'(Y_t)$ with a unique stable point at the origin. We perturb the
system by the L\'evy noise of intensity $\varepsilon$ to obtain the stochastic
differential equation $dX^{\varepsilon}_t=-U'(X^{\varepsilon}_{t-})
dt+\varepsilon dL_t.$ The process $L$ is a symmetric L\'evy process whose jump
measure $\nu$ has exponentially light tails,
$\nu([u,\infty))\sim\exp(-u^{\alpha})$, $\alpha>0$, $u\to \infty$. We study the
first exit problem for the trajectories of the solutions of the stochastic
differential equation from the interval $(-1,1)$. In the small noise limit
$\varepsilon\to0$, the law of the first exit time $\sigma_x$, $x\in(-1,1)$, has
exponential tail and the mean value exhibiting an intriguing phase transition
at the critical index $\alpha=1$, namely,
$\ln\mathbf{E}\sigma\sim\varepsilon^{-\alpha}$ for $0<\alpha<1$, whereas
$\ln\mathbf{E}\sigma\sim\varepsilon^{- 1}|\ln\varepsilon|^{1-{1}/{\alpha}}$ for
$\alpha>1$.


title: Positivity in the cohomology of flag bundles (after Graham)

abstract:
  We give a short, geometric proof of Graham's theorem on positivity in the
equivariant cohomology of a flag variety, based on a transversality argument.


title: Secular Evolution of Planetary Systems in Binaries

abstract:
  The orbital eccentricity of a single planet around a component of a stellar
binary system with a sufficiently large mutual inclination angle is known to
oscillate on a secular timescale through the Kozai mechanism. We have
investigated the effects of the Kozai mechanism on double-planet systems in
binaries. The evolutionary sequence of a pair of planets under the influence of
a binary companion is fairly complex. Various dynamical outcomes are seen in
numerical simulations. One interesting outcome is the rigid rotation of the
planetary orbits in which the planetary orbital planes secularly precess in
concert, while the orbital eccentricities oscillate synchronously. In such
cases the outer planet acts as a propagator of the perturbation from the binary
companion to the inner planet and drives the inner planetary orbit to precess
at a rate faster than what is predicted by the Kozai mechanism.


title:
Associated production of the scalars and new gauge bosons from a little
  Higgs model at the LHC

abstract:
  The littlest Higgs model with T-parity ($LHT$ model) predicts the existence
of the T-odd scalars ($\phi^{\pm}$, $\phi^{0}$, and $\phi^{p}$). We consider
production of these new particles associated with T-odd gauge bosons at the
$LHC$. We find that the partonic process $q\bar{q'}\to\phi^{+}B_{H}$ can
generate a number of the characteristic signal events with a charged lepton and
large missing energy at the $LHC$.


title: Constructing processes with prescribed mixing coefficients

abstract:
  The rate at which dependencies between future and past observations decay in
a random process may be quantified in terms of mixing coefficients. The latter
in turn appear in strong laws of large numbers and concentration of measure
results for dependent random variables. Questions regarding what rates are
possible for various notions of mixing have been posed since the 1960's, and
have important implications for some open problems in the theory of strong
mixing conditions.
  This paper deals with $\eta$-mixing, a notion defined in [Kontorovich and
Ramanan], which is closely related to $\phi$-mixing. We show that there exist
measures on finite sequences with essentially arbitrary $\eta$-mixing
coefficients, as well as processes with arbitrarily slow mixing rates.


title: Obtaining Measure Concentration from Markov Contraction

abstract:
  Concentration bounds for non-product, non-Haar measures are fairly recent:
the first such result was obtained for contracting Markov chains by Marton in
1996 via the coupling method. The work that followed, with few exceptions, also
used coupling. Although this technique is of unquestionable utility as a
theoretical tool, it is not always simple to apply. As an alternative to
coupling, we use the elementary Markov contraction lemma to obtain simple,
useful, and apparently novel concentration results for various Markov-type
processes. Our technique consists of expressing probabilities as matrix
products and applying Markov contraction to these expressions; thus it is
fairly general and holds the potential to yield further results in this vein.


title:
A Search for New Galactic Magnetars in Archival Chandra and XMM-Newton
  Observations

abstract:
  We present constraints on the number of Galactic magnetars, which we have
established by searching for sources with periodic variability in 506 archival
Chandra observations and 441 archival XMM-Newton observations of the Galactic
plane (|b|<5 degree). Our search revealed four sources with periodic
variability on time scales of 200-5000 s, all of which are probably accreting
white dwarfs. We identify 7 of 12 known Galactic magnetars, but find no new
examples with periods between 5 and 20 s. We convert this non-detection into
limits on the total number of Galactic magnetars by computing the fraction of
the young Galactic stellar population that was included in our survey. We find
that easily-detectable magnetars, modeled after persistent anomalous X-ray
pulsars, could have been identified in 5% of the Galactic spiral arms by mass.
If we assume there are 3 previously-known examples within our random survey,
then there are 59 (+92,-32) in the Galaxy. Transient magnetars in quiescence
could have been identified throughout 0.4% of the spiral arms, and the lack of
new examples implies that <540 exist in the Galaxy (90% confidence). Similar
constraints are found by considering the detectability of transient magnetars
in outburst by current and past X-ray missions. For assumed lifetimes of 1e4
yr, we find that the birth rate of magnetars could range between 0.003 and 0.06
per year. Therefore, the birth rate of magnetars is at least 10% of that for
normal radio pulsars. The magnetar birth rate could exceed that of radio
pulsars, unless the lifetimes of transient magnetars are >1e5 yr. Obtaining
better constraints will require wide-field X-ray or radio searches for
transient X-ray pulsars similar to XTE J1810--197, AX J1845.0--0250, CXOU
J164710.2--455216, and 1E 1547.0-5408.


title: Color Dependence in the Spatial Distribution of Satellite Galaxies

abstract:
  We explore the color dependence of the radial profile of satellite galaxies
around isolated parent galaxies. Samples of potential satellites selected from
large galaxy redshift surveys are significantly contaminated by interlopers --
objects not bound to the parent galaxy. We use the Sloan Digital Sky Survey to
estimate the interloper fraction in samples of candidate satellite galaxies. We
show that samples of red and blue satellites have different interloper
populations: a larger fraction of blue galaxies are likely to be interlopers
compared to red galaxies. Both with and without interloper subtraction, the
radial profile of blue satellites is significantly shallower than that of red
satellites. In addition, while red and blue primaries have different interloper
fractions, the slope of the corrected radial profiles are consistent after
interloper correction. We discuss the implications of these results for galaxy
formation models.


title:
A combinatorial formula for Earle's twisted 1-cocycle on the mapping
  class group \mathcal{M}_{g,*}

abstract:
  We present a formula expressing Earle's twisted 1-cocycle on the mapping
class group of a closed oriented surface of genus >=2 relative to a fixed base
point, with coefficients in the first homology group of the surface. For this
purpose we compare it with Morita's twisted 1-cocycle which is combinatorial.
The key is the computation of these cocycles on a particular element of the
mapping class group, which is topologically a hyperelliptic involution.


title: Low mass stellar evolution with WIMP capture and annihilation

abstract:
  Recent work has indicated that WIMP annihilation in stellar cores has the
potential to contribute significantly to a star's total energy production. We
report on progress in simulating the effects of WIMP capture and annihilation
upon stellar structure and evolution near supermassive black holes, using the
new DarkStars code. Preliminary results indicate that low-mass stars are the
most influenced by WIMP annihilation, which could have consequences for
upcoming observational programs.


title: Photon-graviton mixing in an electromagnetic field

abstract:
  Einstein-Maxwell theory implies the mixing of photons with gravitons in an
external electromagnetic field. This process and its possible observable
consequences have been studied at tree level for many years. We use the
worldline formalism for obtaining an exact integral representation for the
one-loop corrections to this amplitude due to scalars and fermions. We study
the structure of this amplitude, and obtain exact expressions for various
limiting cases.


title:
Upper bounds on the minimum coverage probability of confidence intervals
  in regression after variable selection

abstract:
  We consider a linear regression model, with the parameter of interest a
specified linear combination of the regression parameter vector. We suppose
that, as a first step, a data-based model selection (e.g. by preliminary
hypothesis tests or minimizing AIC) is used to select a model. It is common
statistical practice to then construct a confidence interval for the parameter
of interest based on the assumption that the selected model had been given to
us a priori. This assumption is false and it can lead to a confidence interval
with poor coverage properties. We provide an easily-computed finite sample
upper bound (calculated by repeated numerical evaluation of a double integral)
to the minimum coverage probability of this confidence interval. This bound
applies for model selection by any of the following methods: minimum AIC,
minimum BIC, maximum adjusted R-squared, minimum Mallows' Cp and t-tests. The
importance of this upper bound is that it delineates general categories of
design matrices and model selection procedures for which this confidence
interval has poor coverage properties. This upper bound is shown to be a finite
sample analogue of an earlier large sample upper bound due to Kabaila and Leeb.


title: Cosmic String Loops, Large and Small

abstract:
  We extend our earlier model of the small scale structure of cosmic string
networks through an improved treatment of the separation of long and short
scales. We find that the production of small loops (at the gravitational
radiation scale) is a robust feature of string networks, in addition to a
population of loops near the horizon scale. We obtain quantitative agreement
with the scaling of loop production functions as found in simulations by two
groups.


title: The Quadratic Spin Squeezing Operators

abstract:
  We discuss generic spin squeezing operators (quadratic in angular momentum
operators) capable of squeezing out quantum mechanical noise from a system of
two-level atoms (spins) in a coherent state. Such systems have been considered
by Kitagawa and Ueda (Refs. 2) in this context and a Hamiltonian of this nature
governs the Lipkin model (Ref. 14) which is relevant to nuclear physics.


title:
"Gauge" in General Relativity: Second-order general relativistic
  gauge-invariant perturbation theory

abstract:
  As in the case of the other gauge field theories, there is so called
``gauge'' also in general relativity. This ``gauge'' is unphysical degree of
freedom. There are two kinds of ``gauges'' in general relativity. These are
called the first- and the second-kind of gauges, respectively. The gauge of the
first kind is just coordinate system on a single manifold. On the other hand,
the gauge of the second kind arises in the general relativistic perturbations.
Through the precise distinction of these two concepts of ``gauges'', we develop
second-order gauge-invariant general relativistic perturbation theory.


title: Keck spectroscopy of globular clusters in the spiral galaxy NGC 2683

abstract:
  We analyse Keck spectra of 24 candidate globular clusters (GCs) associated
with the spiral galaxy NGC 2683. We identify 19 bona fide GCs based on their
recession velocities, of which 15 were suitable for stellar population
analysis. Age and metallicity determinations reveal old ages in 14 out of 15
GCs. These old GCs exhibit age and metallicity distributions similar to that of
the Milky Way GC system. One GC in NGC 2683 was found to exhibit an age of ~3
Gyr. The age, metallicity and alpha-element abundance of this centrally located
GC are remarkably similar to the values found for the galactic centre itself,
providing further evidence for a recent star formation event in NGC 2683.


title: Stellar models with Schwarzschild and non-Schwarzschild vacuum exteriors

abstract:
  A striking characteristic of non-Schwarzschild vacuum exteriors is that they
contain not only the total gravitational mass of the source, but also an {\it
arbitrary} constant. In this work, we show that the constants appearing in the
"temporal Schwarzschild", "spatial Schwarzschild" and
"Reissner-Nordstr{\"o}m-like" exteriors are not arbitrary but are completely
determined by star's parameters, like the equation of state and the
gravitational potential. Consequently, in the braneworld scenario the
gravitational field outside of a star is no longer determined by the total mass
alone, but also depends on the details of the internal structure of the source.
We show that the general relativistic upper bound on the gravitational
potential $M/R < 4/9$, for perfect fluid stars, is significantly increased in
these exteriors. Namely, $M/R < 1/2$, $M/R < 2/3$ and $M/R < 1$ for the
temporal Schwarzschild, spatial Schwarzschild and Reissner-Nordstr{\"o}m-like
exteriors, respectively. Regarding the surface gravitational redshift, we find
that the general relativistic Schwarzschild exterior as well as the braneworld
spatial Schwarzschild exterior lead to the same upper bound, viz., $Z < 2$.
However, when the external spacetime is the temporal Schwarzschild metric or
the Reissner-Nordstr{\"o}m-like exterior there is no such constraint: $Z <
\infty$. This infinite difference in the limiting value of $Z$ is because for
these exteriors the effective pressure at the surface is negative. The results
of our work are potentially observable and can be used to test the theory.


title: Quenching Bloch oscillations in a strongly correlated material

abstract:
  Dynamical mean-field theory is generalized to solve the nonequilibrium
Keldysh boundary problem: a system is started in equilibrium at a temperature
T=0.1, a uniform electric field is turned on at t=0, and the system is
monitored as it approaches the steady state. The focus here is on the Bloch
oscillations of the current and how they decay after their initial appearance
near t=0. The system is evolved out to the longest time allowed by our
computational resources--in most cases we are unable to reach the steady state.
The strongly correlated material is modeled by the spinless Falicov-Kimball
model at half-filling on a hypercubic lattice in d=oo dimensions, which has a
Mott-like metal-insulator transition at U=sqrt{2}. The computational algorithm
employed is highly efficient, parallelizes well, and scales to thousands of
processors. For strong fields, we find beats develop with a period of 2 pi/U,
while for strong interactions, the Bloch oscillations are sharply damped and
become quite irregular in time.


title:
Soft x-ray magnetic circular dichroism study of Ca_1-xSr_xRuO_3 across
  the ferromagnetic quantum phase transition

abstract:
  Ca_1-xSr_xRuO_3, which is ferromagnetic for Sr concentration x > 0.3, has
been studied by x-ray magnetic circular dichroism (XMCD) in Ru 3p and O 1s
core-level x-ray absorption. XMCD signals appear at x ~ 0.3 and monotonically
increases with x in the ferromagnetic phase. While the monotonic increase of
the XMCD signals with x is of a typical Stoner-type, the absence of appreciable
change in the spectral line shapes of both the Ru 3p and O 1s XMCD spectra
indicate that the itinerant-electron ferromagnetism in Ca_1-xSr_xRuO_3 is
influenced by strong electron correlation.


title: Leptogenesis in a seesaw model with Fritzsch type lepton mass matrices

abstract:
  We investigate how the baryon asymmetry of our universe via leptogenesis can
be achieved within the framework of the seesaw model with Fritzsch type lepton
mass matrices proposed by Fukugita $et. al$. We study the cases with
CP-violating phases in charged lepton Yukawa matrix, however, with and without
Dirac neutrino Yukawa phases. We consider both flavor independent and flavor
dependent leptogenesis, and demonstrate how they lead to different amounts of
lepton asymmetries in detail. In particular, it is shown that flavor dependent
leptogenesis in this model can be worked out only when the CP phases in Dirac
neutrino Yukawa matrix become zero at the GUT scale. In addition to the CP
phases, for successful leptogenesis in the model it is required that the
degeneracy of the heavy Majorana neutrino mass spectrum should be broken and we
also show that the breakdown of the degeneracy can be radiatively induced.


title: Recent Progress in Studies of Pulsar Wind Nebulae

abstract:
  The synchrotron-emitting nebulae formed by energetic winds from young pulsars
provide information on a wide range phenomena that contribute to their
structure. High resolution X-ray observations reveal jets and toroidal
structures in many systems, along with knot-like structures whose emission is
observed to be time-variable. Large-scale filaments seen in optical and radio
images mark instability regions where the expanding nebulae interact with the
surrounding ejecta, and spectral studies reveal the presence of these ejecta in
the form of thermal X-ray emission. Infrared studies probe the frequency region
where evolutionary and magnetic field effects conspire to change the broadband
synchrotron spectrum dramatically, and studies of the innermost regions of the
nebulae provide constraints on the spectra of particles entering the nebula. At
the highest energies, TeV gamma-ray observations provide a probe of the
spectral region that, for low magnetic fields, corresponds to particles with
energies just below the X-ray-emitting regime.
  Here I summarize the structure of pulsar wind nebulae and review several new
observations that have helped drive a recent resurgence in theoretical modeling
of these systems.


title: The $\Sigma\Sigma$ interactions in finite-density QCD sum rules

abstract:
  The properties of $\Sigma$-hyperons in pure $\Sigma$ matter are studied with
the finite-density quantum chromo-dynamics sum rule (QCDSR) approach. The
$\Sigma\Sigma$ nuclear potential $U_\Sigma$ is most likely strongly attractive,
it could be about -50 MeV or even more attractive at normal nuclear density. If
this prediction is the case, the interactions between $\Sigma$-hyperons should
play crucial roles in the strange nuclear matter, when there are multi-$\Sigma$
hyperons. The bound state of double-$\Sigma$ maybe exist.


title:
The principle of least action for test particles in a four-dimensional
  spacetime embedded in 5D

abstract:
  It is well known that, in the five-dimensional scenario of braneworld and
space-time-mass theories, geodesic motion in 5D is observed to be non-geodesic
in 4D. Usually, the discussion is purely geometric and based on the dimensional
reduction of the geodesic equation in 5D, without any reference to the test
particle whatsoever. In this work we obtain the equation of motion in 4D
directly from the principle of least action. So our main thrust is not the
geometry but the particle observed in 4D. A clear physical picture emerges from
our work. Specifically, that the deviation from the geodesic motion in 4D is
due to the variation of the rest mass of a particle, which is induced by the
scalar field in the 5D metric and the explicit dependence of the spacetime
metric on the extra coordinate. Thus, the principle of least action not only
leads to the correct equations of motion, but also provides a concrete physical
meaning for a number of algebraic quantities appearing in the geometrical
reduction of the geodesic equation.


title: Universal quantized spin-Hall conductance fluctuation in graphene

abstract:
  We report a theoretical investigation of quantized spin-Hall conductance
fluctuation of graphene devices in the diffusive regime. Two graphene models
that exhibit quantized spin-Hall effect (QSHE) are analyzed. Model-I is with
unitary symmetry under an external magnetic field $B\ne 0$ but with zero
spin-orbit interaction, $t_{SO}=0$. Model-II is with symplectic symmetry where
B=0 but $t_{SO} \ne 0$. Extensive numerical calculations indicate that the two
models have exactly the same universal QSHE conductance fluctuation value
$0.285 e/4\pi$ regardless of the symmetry. Qualitatively different from the
conventional charge and spin universal conductance distributions, in the
presence of edge states the spin-Hall conductance shows an one-sided log-normal
distribution rather than a Gaussian distribution. Our results strongly suggest
that the quantized spin-Hall conductance fluctuation belongs to a new
universality class.


title: Continuous extension of a densely parameterized semigroup

abstract:
  Let S be a dense sub-semigroup of the positive real numbers, and let X be a
separable, reflexive Banach space. This note contains a proof that every weakly
continuous contractive semigroup of operators on X over S can be extended to a
weakly continuous semigroup over the positive real numbers. We obtain similar
results for non-linear, non-expansive semigroups as well. As a corollary we
characterize all densely parametrized semigroups which are extendable to
semigroups over the positive real numbers.


title: Light Scalar Mesons in the QCD Sum Rule

abstract:
  We study the light scalar mesons in the QCD sum rule. We find that there are
five independent scalar tetraquark currents in the local form, and we perform
QCD sum rule analysis using both these currents and their combinations.
Compared with the sum rules by conventional \bar{q} q currents, our result
supports a tetraquark structure for low-lying scalar mesons.


title:
Corner-Impact Bifurcations: a novel class of discontinuity-induced
  bifurcations in Cam-Follower Systems

abstract:
  This paper is concerned with the analysis of a class of impacting systems of
relevance in applications: cam-follower systems. We show that these systems,
which can be modelled as discontinuously forced impact oscillators, can exhibit
complex behaviour due to the detachment at high rotational speeds between the
follower and the cam. We propose that the observed phenomena can be explained
in terms of a novel type of discontinuity-induced bifurcation, termed as
corner-impact. We present a complete analysis of this bifurcation in the case
of non-autonomous impact oscillator and explain the transition to chaos
observed in a representative cam-follower example. The theoretical findings are
validated numerically.


title: On the Casimir Effect in the High Tc Cuprates

abstract:
  High temperature superconductors have in common that they consist of parallel
planes of copper oxide separated by layers whose composition can vary. Being
ceramics, the cuprate superconductors are poor conductors above the transition
temperature, T_c. Below T_c, the parallel Cu-O planes in those materials become
superconducting while the layers in between stay poor conductors. Here, we ask
to what extent the change in the Casimir energy that arises when the parallel
Cu-O layers become superconducting could contribute to the superconducting
condensation energy. Our aim here is merely to obtain an order of magnitude
estimate. To this end, the material is modelled as consisting below T_c of
parallel plasma sheets separated by vacuum and as without a significant Casimir
effect above T_c. Due to the close proximity of the Cu-O planes the system is
in the regime where the Casimir effect becomes a van der Waals type effect,
dominated by contributions from TM surface plasmons propagating along the ab
planes. Within this model, the Casimir energy is found to be of the same order
of magnitude as the superconducting condensation energy.


title:
Nature of protein family signatures: Insights from singular value
  analysis of position-specific scoring matrices

abstract:
  Position-specific scoring matrices (PSSMs) are useful for detecting weak
homology in protein sequence analysis, and they are thought to contain some
essential signatures of the protein families. In order to elucidate what kind
of ingredients constitute such family-specific signatures, we apply singular
value decomposition to a set of PSSMs and examine the properties of dominant
right and left singular vectors. The first right singular vectors were
correlated with various amino acid indices including relative mutability, amino
acid composition in protein interior, hydropathy, or turn propensity, depending
on proteins. A significant correlation between the first left singular vector
and a measure of site conservation was observed. It is shown that the
contribution of the first singular component to the PSSMs act to disfavor
potentially but falsely functionally important residues at conserved sites. The
second right singular vectors were highly correlated with hydrophobicity
scales, and the corresponding left singular vectors with contact numbers of
protein structures. It is suggested that sequence alignment with a PSSM is
essentially equivalent to threading supplemented with functional information.
The presented method may be used to separate functionally important sites from
structurally important ones, and thus it may be a useful tool for predicting
protein functions.


title:
Super- and subradiant emission of two-level systems in the near-Dicke
  limit

abstract:
  We analyze the stability of super- and subradiant states in a system of
identical two-level atoms in the near-Dicke limit, i.e., when the atoms are
very close to each other compared to the wavelength of resonant light. The
dynamics of the system are studied using a renormalized master equation, both
with multipolar and minimal-coupling interaction schemes. We show that both
models lead to the same result and, in contrast to unrenormalized models,
predict that the relative orientation of the (co-aligned) dipoles is
unimportant in the Dicke limit. Our master equation is of relevance to any
system of dipole-coupled two-level atoms, and gives bounds on the strength of
the dipole-dipole interaction for closely spaced atoms. Exact calculations for
small atom systems in the near-Dicke limit show the increased emission times
resulting from the evolution generated by the strong dipole-dipole interaction.
However, for large numbers of atoms in the near-Dicke limit, it is shown that
as the number of atoms increases, the effect of the dipole-dipole interaction
on collective emission is reduced.


title:
Similarity search for local protein structures at atomic resolution by
  exploiting a database management system

abstract:
  A method to search for local structural similarities in proteins at atomic
resolution is presented. It is demonstrated that a huge amount of structural
data can be handled within a reasonable CPU time by using a conventional
relational database management system with appropriate indexing of geometric
data. This method, which we call geometric indexing, can enumerate ligand
binding sites that are structurally similar to sub-structures of a query
protein among more than 160,000 possible candidates within a few hours of CPU
time on an ordinary desktop computer. After detecting a set of high scoring
ligand binding sites by the geometric indexing search, structural alignments at
atomic resolution are constructed by iteratively applying the Hungarian
algorithm, and the statistical significance of the final score is estimated
from an empirical model based on a gamma distribution. Applications of this
method to several protein structures clearly shows that significant
similarities can be detected between local structures of non-homologous as well
as homologous proteins.