title: Can we use hadronic tau decay for V_us determination

abstract:
  It is known that the discrepancy in pion spectral functions extracted from
positron-electron annihilation and tau decay leads to different predictions for
the muon anomalous magnetic moment. We will show that this discrepancy effects
also the extraction of the Cabibbo angle from the hadronic tau decays. The
corrections to the tau branching fractions, corresponding to the presence of
new centi-weak tensor interactions, allow us to extract the Cabibbo angle from
tau decays in agreement with its other precision determinations. Thus a more
precise value of |V_us|=0.2246 +/- 0.0012 is obtained and as a consequence
f(0)=0.9645 +/- 0.0055 and F_K/F_pi=1.196 +/- 0.007.


title: Sets of double and triple weights of trees

abstract:
  Let T be a weighted tree with n leaves. Let D_{i,j} be the distance between
the leaves i and j. Let D_{i,j,k}= (D_{i,j} + D_{j,k} +D_{i,k})/2. We will call
such numbers "triple weights" of the tree. In this paper, we give a
characterization, different from the previous ones, for sets indexed by
2-subsets of a $n$-set to be double weights of a tree. By using the same
ideas,we find also necessary and sufficient conditions for a set of real
numbers indexed by 3-subsets of an $n$-set to be the set of the triple weights
of a tree with $n$ leaves. Besides we propose a slight modification of
Saitou-Nei's Neighbour-Joining algorithm to reconstruct trees from the data
D_{i,j}.


title: Simple queueing approach to segregation dynamics in Schelling model

abstract:
  A simple queueing approach for segregation of agents in modified one
dimensional Schelling segregation model is presented. The goal is to arrive at
simple formula for the number of unhappy agents remaining after the
segregation.


title:
A practical guide to Basic Statistical Techniques for Data Analysis in
  Cosmology

abstract:
  This is the summary of 4 Lectures given at the XIX Canary islands winter
school of Astrophysics ''The Cosmic Microwave Background, from Quantum
Fluctuations to the present Universe''. Lectures were intended for
master/beginning PhD students in cosmology.


title:
Approximation of sets defined by polynomials with holomorphic
  coefficients

abstract:
  Let X be an analytic set defined by polynomials whose coefficients
a_1,...,a_s are holomorphic functions. We formulate conditions such that for
all sequences {a_(1,n)},...,{a_(s,n)} of holomorphic functions converging
locally uniformly to a_1,...,a_s respectively the following holds true. If
a_(1,n),...,a_(s,n) satisfy the conditions then the sequence of the sets {X_n}
obtained by replacing a_j by a_(j,n) in the polynomials, converge to X.


title: Nuclear fission with mean-field instantons

abstract:
  We present a description of nuclear spontaneous fission, and generally of
quantum tunneling, in terms of instantons - periodic imaginary-time solutions
to time-dependent mean-field equations - that allows for a comparison with more
familiar and used generator coordinate (GCM) and adiabatic time-dependent
Hartree-Fock (ATDHF) methods. It is shown that the action functional whose
value for the instanton is the quasiclassical estimate of the decay exponent
fulfils the minimum principle when additional constraints are imposed on trial
fission paths. In analogy with mechanics, these are conditions of energy
conservation and the velocity-momentum relations. In the adiabatic limit the
instanton method reduces to the time-odd ATDHF equation, with collective mass
including the time-odd Thouless-Valatin term, while the GCM mass completely
ignores velocity-momentum relations. This implies that GCM inertia generally
overestimates instanton-related decay rate.
  The very existence of the minimum principle offers a hope for a variational
search for instantons. After the inclusion of pairing, the instanton equations
and the variational principle can be expressed in terms of the
imaginary-time-dependent Hartree-Fock- Bogolyubov (TDHFB) theory. The adiabatic
limit of this theory reproduces ATDHFB inertia.


title: Stability of homogeneous bundles on P^3

abstract:
  We study the stability of some homogeneous bundles on P^3 by using their
representations of the quiver associated to the homgeneous bundles on P^3. In
particular we show that homogeneous bundles on P^3 whose support of the quiver
representation is a parallelepiped are stable, for instance the bundles E whose
minimal free resolution is of the kind 0 --> S^{l_1, l_2, l_3} V (t) --> S^{l_1
+s, l_2, l_3} V (t+s) --> E --> 0 are stable.


title:
Power spectrum of large-scale magnetic fields from
  Gravitoelectromagnetic inflation with a decaying cosmological parameter

abstract:
  Introducing a variable cosmological parameter $\Lambda (t)$ in a geometrical
manner from a 5D Riemann-flat metric, we investigate the origin and evolution
of primordial magnetic fields in the early universe, when the expansion is
governed by a cosmological parameter $\Lambda (t)$ that decreases with time.
Using the gravitoelectromagnetic inflationary formalism, but without the
Feynman gauge, we obtain the power of spectrums for large-scale magnetic fields
and the inflaton field fluctuations during inflation. A very important fact is
that our formalism is {\em naturally non-conformally invariant}.


title:
Particle-species dependent modification of jet-induced correlations in
  Au+Au collisions at sqrt(s_NN) = 200 GeV

abstract:
  We report PHENIX measurements of the correlation of a trigger hadron at
intermediate transverse momentum (2.5<p_{T,trig}<4 GeV/c), with associated
mesons or baryons at lower p_{T,assoc}, in Au+Au collisions at sqrt(s_NN) = 200
GeV. The jet correlations for both baryons and mesons show similar shape
alterations as a function of centrality, characteristic of strong modification
of the away-side jet. The ratio of jet-associated baryons to mesons for this
jet increases with centrality and p_{T,assoc} and, in the most central
collisions, reaches a value similar to that for inclusive measurements. This
trend is incompatible with in-vacuum fragmentation, but could be due to
jet-like contributions from correlated soft partons which recombine upon
hadronization.


title: Emergence of Oscillons in an Expanding Background

abstract:
  We consider a (1+1) dimensional scalar field theory that supports oscillons,
which are localized, oscillatory, stable solutions to nonlinear equations of
motion. We study this theory in an expanding background and show that oscillons
now lose energy, but at a rate that is exponentially small when the expansion
rate is slow. We also show numerically that a universe that starts with
(almost) thermal initial conditions will cool to a final state where a
significant fraction of the energy of the universe -- on the order of 50% -- is
stored in oscillons. If this phenomenon persists in realistic models, oscillons
may have cosmological consequences.


title: Identities and Inequalities for Tree Entropy

abstract:
  The notion of tree entropy was introduced by the author as a normalized limit
of the number of spanning trees in finite graphs, but is defined on random
infinite rooted graphs. We give some new expressions for tree entropy; one uses
Fuglede-Kadison determinants, while another uses effective resistance. We use
the latter to prove that tree entropy respects stochastic domination. We also
prove that tree entropy is non-negative in the unweighted case, a special case
of which establishes Lueck's Determinant Conjecture for Cayley-graph
Laplacians. We use techniques from the theory of operators affiliated to von
Neumann algebras.


title: Quenched mesonic spectrum at large N

abstract:
  We compute the masses of the $\pi$ and of the $\rho$ mesons in the quenched
approximation on a lattice with fixed lattice spacing $a \simeq 0.145 \
\mathrm{fm}$ for SU($N$) gauge theory with $N = 2,3,4,6$. We find that a simple
linear expression in $1/N^2$ correctly captures the features of the
lowest-lying meson states at those values of $N$. This enables us to
extrapolate to $N = \infty$ the behaviour of $m_{\pi}$ as a function of the
quark mass and of $m_{\rho}$ as a function of $m_{\pi}$. Our results for the
latter agree within 5% with recent predictions obtained in the AdS/CFT
framework.


title: Comments on "Improved Efficient Remote User Authentication Schemes"

abstract:
  Recently, Tian et al presented an article, in which they discussed some
security weaknesses of Yoon et al's scheme and subsequently proposed two
``improved'' schemes. In this paper, we show that the Tian et al's schemes are
insecure and vulnerable than the Yoon et al's scheme.


title:
Towards observable signatures of other bubble universes II: Exact
  solutions for thin-wall bubble collisions

abstract:
  We assess the effects of a collision between two vacuum bubbles in the
thin-wall limit. After describing the outcome of a generic collision possessing
the expected hyperbolic symmetry, we focus on collisions experienced by a
bubble containing positive vacuum energy, which could in principle contain our
observable universe. We provide criteria governing whether the post-collision
domain wall accelerates towards or away from this "observation" bubble, and
discuss the implications for observers located at various positions inside of
the bubble. Then, we identify the class of solutions which have minimal impact
on the interior of the observation bubble, and derive a simple formula for the
energy density of a shell of radiation emitted from such a collision. In the
context of a universe undergoing false vacuum eternal inflation, these
solutions are perhaps the most promising candidates for collisions that could
exist within our past light cone, and therefore in principle be observable.


title: A note on generalized equivariant homotopy groups

abstract:
  In this paper, we generalize the equivariant homotopy groups or equivalently
the Rhodes groups. We establish a short exact sequence relating the generalized
Rhodes groups and the generalized Fox homotopy groups and we introduce
$\Gamma$-Rhodes groups, where $\Gamma$ admits a certain co-grouplike structure.
Evaluation subgroups of $\Gamma$-Rhodes groups are discussed.


title: Renormalization-scale independence of the physical cosmological constant

abstract:
  Treating the metric as a classical background field, we show that the
cosmological constant does not run with the renormalization scale -- contrary
to some claims in the literature.


title:
The Complexity of the Consistency and N-representability Problems for
  Quantum States

abstract:
  QMA (Quantum Merlin-Arthur) is the quantum analogue of the class NP. There
are a few QMA-complete problems, most notably the ``Local Hamiltonian'' problem
introduced by Kitaev. In this dissertation we show some new QMA-complete
problems.
  The first one is ``Consistency of Local Density Matrices'': given several
density matrices describing different (constant-size) subsets of an n-qubit
system, decide whether these are consistent with a single global state. This
problem was first suggested by Aharonov. We show that it is QMA-complete, via
an oracle reduction from Local Hamiltonian. This uses algorithms for convex
optimization with a membership oracle, due to Yudin and Nemirovskii.
  Next we show that two problems from quantum chemistry, ``Fermionic Local
Hamiltonian'' and ``N-representability,'' are QMA-complete. These problems
arise in calculating the ground state energies of molecular systems.
N-representability is a key component in recently developed numerical methods
using the contracted Schrodinger equation. Although these problems have been
studied since the 1960's, it is only recently that the theory of quantum
computation has allowed us to properly characterize their complexity.
  Finally, we study some special cases of the Consistency problem, pertaining
to 1-dimensional and ``stoquastic'' systems. We also give an alternative proof
of a result due to Jaynes: whenever local density matrices are consistent, they
are consistent with a Gibbs state.


title: Dynamic force spectroscopy on multiple bonds: experiments and model

abstract:
  We probe the dynamic strength of multiple biotin-streptavidin adhesion bonds
under linear loading using the biomembrane force probe setup for dynamic force
spectroscopy. Measured rupture force histograms are compared to results from a
master equation model for the stochastic dynamics of bond rupture under load.
This allows us to extract the distribution of the number of initially closed
bonds. We also extract the molecular parameters of the adhesion bonds, in good
agreement with earlier results from single bond experiments. Our analysis shows
that the peaks in the measured histograms are not simple multiples of the
single bond values, but follow from a superposition procedure which generates
different peak positions.


title:
On the correspondence principle: implications from a study of the
  chaotic dynamics of a macroscopic quantum device

abstract:
  The recovery of classical chaotic dynamics from quantum systems has long been
a subject of interest. Furthermore, recent work indicates that quantum chaos
may well be significant in quantum information processing. In this paper we
discuss the quantum to classical crossover of a superconducting quantum
inference device (SQUID) ring. Such devices comprise of thick superconducting
loop enclosing a Josephson weak link. These devices are currently strong
candidates for many applications in quantum technologies. The weak link brings
with it a non-linearity such that semi-classical models of this system can
exhibit chaotic dynamics. For many similar systems an application of the
correspondence principle together with the inclusion of environmental degrees
of freedom through a quantum trajectories approach can be used to effectively
recover classical dynamics. Here we show (i) that the standard expression of
the correspondence principle is incompatible with the ring Hamiltonian and we
present a more pragmatic and general expression which finds application here
and (ii) that practical limitations to circuit parameters of the SQUID ring
prevent arbitrarily accurate recovery of classical chaotic dynamics.

categories: quant-ph cond-mat.mes-hall cond-mat.other cond-mat.supr-con


title: Observation of electromagnon excitations in the BiFe0$_3$ spiral magnet

abstract:
  Recently, oxide multiferroics have attracted much attention due to their
large magnetoelectric effect which allows the tuning of magnetic properties
with electric field and vice versa and open new venues for future spintronic
applications such as multiple-state memory devices with dual magnetic and
electric control. BiFeO$_3$ (BFO) belongs to this new class of materials and
shows both ferroelectric and antiferromagnetic orders at room temperature with
a large electric polarizationassociated with a cycloidal spiral magnetic
ordering. The incommensurate magnetic order induces magnon zone folding and
allows investigations by optical probes of unusual spin waves which couples to
optical phonons, the so called "`electromagnons"'. Here, we unravel for the
first time the electromagnon spectra of BFO by means low energy inelastic light
scattering technique. We show the existence of two species of electromagnons
corresponding to spin wave excitations in and out of the cycloidal plane. The
present observations present an unique opportunity to study the interplay
between ferroelectric and magnetic orders.


title: Physics and the measurement of continuous variables

abstract:
  Wigner had expressed the opinion that the impossibility of exact measurements
of single operators like position operators rendered the notion of geometrical
points somewhat dubious in physics. Using Sewell's recent resolution of the
measurement problem (collapse of the wave packet) in quantum mechanics and
extending it to the measurement of operators with continuous spectra, we are
able to compare the situation in quantum mechanics with that in quantum
mechanics. Our conclusion is that the notion of a geometrical point is as
meaningful in quantum mechanics as it is in classical mechanics.


title: Spectral Flow in AdS(3)/CFT(2)

abstract:
  We study the spectral flowed sectors of the H3 WZW model in the context of
the holographic duality between type IIB string theory in AdS(3)x S^3 x T^4
with NSNS flux and the symmetric product orbifold of T^4. We construct
explicitly the physical vertex operators in the flowed sectors that belong to
short representations of the superalgebra, thus completing the bulk-to-boundary
dictionary for 1/2 BPS states. We perform a partial calculation of the string
three-point functions of these operators. A complete calculation would require
the three-point couplings of non-extremal flowed operators in the H3 WZW model,
which are at present unavailable. In the unflowed sector, perfect agreement has
recently been found between the bulk and boundary three-point functions of 1/2
BPS operators. Assuming that this agreement persists in the flowed sectors, we
determine certain unknown three-point couplings in the H3 WZW model in terms of
three-point couplings of affine descendants in the SU(2) WZW model.


title: High-resolution radio observations of submillimetre galaxies

abstract:
  We have produced sensitive, high-resolution radio maps of 12 SMGs in the
Lockman Hole using combined MERLIN and VLA data at a frequency of 1.4 GHz.
Integrating for 350hr yielded an r.m.s. noise of 6.0 uJy/beam and a resolution
of 0.2-0.5". For the first time, wide-field data from the two arrays have been
combined in the (u,v) plane and the bandwidth smearing response of the VLA data
has been removed. All of the SMGs are detected in our maps as well as sources
comprising a non-submm luminous control sample. We find evidence that SMGs are
more extended than the general uJy radio population and that therefore, unlike
in local ULIRGs, the starburst component of the radio emission is extended and
not confined to the galactic nucleus. For the eight sources with redshifts we
measure linear sizes between 1 and 8 kpc with a median of 5 kpc. Therefore,
they are in general larger than local ULIRGs which may support an early-stage
merger scenario for the starburst trigger. X-rays betray AGN in six of the 33
sources in the combined sample. All but one of these are in the control sample,
suggesting a lower incidence of AGN amongst the submm-luminous galaxies which
is, in turn, consistent with increased X-ray absorption in these dust-obscured
starbursts. Only one of our sources is resolved into multiple, distinct
components with our high-resolution data. Finally, compared to a previous study
of faint radio sources in the GOODS-N field we find systematically smaller
source sizes and no evidence for a tail extending to ~4". Possible reasons for
this are discussed.


title:
Nonlinear Simulations of the Heat Flux Driven Buoyancy Instability and
  its Implications for Galaxy Clusters

abstract:
  In low collisionality plasmas heat flows almost exclusively along magnetic
field lines, and the condition for stability to convection is modified from the
standard Schwarzschild criterion. We present local two and three-dimensional
simulations of a new heat flux driven buoyancy instability (the HBI) that
occurs when the temperature in a plasma decreases in the direction of gravity.
We find that the HBI drives a convective dynamo that amplifies an initially
weak magnetic field by a factor of ~20. In simulations that begin with the
magnetic field aligned with the temperature gradient, the HBI saturates by
rearranging the magnetic field lines to be almost purely perpendicular to the
initial temperature gradient. This magnetic field reorientation results in a
net heat flux through the plasma that is less than 1% of the field-free
(Spitzer) value. We show that the HBI is likely to be present in the cool cores
of clusters of galaxies between ~0.1-100 kpc, where the temperature increases
outwards. The saturated state of the HBI suggests that inward thermal
conduction from large radii in clusters is unlikely to solve the cooling flow
problem. Finally, we also suggest that the HBI may contribute to suppressing
conduction across cold fronts in galaxy clusters.


title: ZOBOV: a parameter-free void-finding algorithm

abstract:
  ZOBOV (ZOnes Bordering On Voidness) is an algorithm that finds density
depressions in a set of points, without any free parameters, or assumptions
about shape. It uses the Voronoi tessellation to estimate densities, which it
uses to find both voids and subvoids. It also measures probabilities that each
void or subvoid arises from Poisson fluctuations. This paper describes the
ZOBOV algorithm, and the results from its application to the dark-matter
particles in a region of the Millennium Simulation. Additionally, the paper
points out an interesting high-density peak in the probability distribution of
dark-matter particle densities.


title: Vector chiral order in frustrated spin chains

abstract:
  By means of a numerical analysis using a non-Abelian symmetry realization of
the density matrix renormalization group, we study the behavior of vector
chirality correlations in isotropic frustrated chains of spin S=1 and S=1/2,
subject to a strong external magnetic field. It is shown that the field induces
a phase with spontaneously broken chiral symmetry, in line with earlier
theoretical predictions. We present results on the field dependence of the
order parameter and the critical exponents.


title:
Ultraviolet, Optical, and Infrared Constraints on Models of Stellar
  Populations and Dust Attenuation

abstract:
  The color of galaxies is a fundamental property, easily measured, that
constrains models of galaxies and their evolution. Dust attenuation and star
formation history (SFH) are the dominant factors affecting the color of
galaxies. Here we explore the empirical relation between SFH, attenuation, and
color for a wide range of galaxies, including early types. These galaxies have
been observed by GALEX, SDSS, and Spitzer, allowing the construction of
measures of dust attenuation from the ratio of infrared (IR) to ultraviolet
(UV) flux and measures of SFH from the strength of the 4000A break. The
empirical relation between these three quantities is compared to models that
separately predict the effects of dust and SFH on color. This comparison
demonstrates the quantitative consistency of these simple models with the data
and hints at the power of multiwavelength data for constraining these models.
The UV color is a strong constraint; we find that a Milky Way extinction curve
is disfavored, and that the UV emission of galaxies with large 4000A break
strengths is likely to arise from evolved populations. We perform fits to the
relation between SFH, attenuation, and color. This relation links the
production of starlight and its absorption by dust to the subsequent reemission
of the absorbed light in the IR. Galaxy models that self-consistently treat
dust absorption and emission as well as stellar populations will need to
reproduce these fitted relations in the low-redshift universe.


title: Variable Low-Mass X-ray Binaries in Early-Type Galaxies

abstract:
  As the Chandra X-ray Observatory mission matures, increasing numbers of
nearby galaxies are being observed multiple times, sampling the variability of
extragalactic X-ray binaries on timescales extending from seconds to years. We
present results on luminous low-mass X-ray binaries from several early-type
galaxies. We show that instantaneous LMXB luminosity functions of early-type
galaxies do not significantly change between observations; a relatively low
fraction of sources are strongly variable on <~ 5 yr timescales. We discuss the
implications that a relatively small number of transient LMXBs are being
discovered in early-type galaxies.


title:
The Kinematics of Molecular Cloud Cores in the Presence of Driven and
  Decaying Turbulence: Comparisons with Observations

abstract:
  In this study we investigate the formation and properties of prestellar and
protostellar cores using hydrodynamic, self-gravitating Adaptive Mesh
Refinement simulations, comparing the cases where turbulence is continually
driven and where it is allowed to decay. We model observations of these cores
in the C$^{18}$O$(2\to 1)$, NH$_3(1,1)$, and N$_2$H$^+(1\to 0)$ lines, and from
the simulated observations we measure the linewidths of individual cores, the
linewidths of the surrounding gas, and the motions of the cores relative to one
another. Some of these distributions are significantly different in the driven
and decaying runs, making them potential diagnostics for determining whether
the turbulence in observed star-forming clouds is driven or decaying. Comparing
our simulations with observed cores in the Perseus and $\rho$ Ophiuchus clouds
shows reasonably good agreement between the observed and simulated core-to-core
velocity dispersions for both the driven and decaying cases. However, we find
that the linewidths through protostellar cores in both simulations are too
large compared to the observations. The disagreement is noticably worse for the
decaying simulation, in which cores show highly supersonic infall signatures in
their centers that decrease toward their edges, a pattern not seen in the
observed regions. This result gives some support to the use of driven
turbulence for modeling regions of star formation, but reaching a firm
conclusion on the relative merits of driven or decaying turbulence will require
more complete data on a larger sample of clouds as well as simulations that
include magnetic fields, outflows, and thermal feedback from the protostars.


title:
Bootes II ReBooted: An MMT/MegaCam Study of An Ultra-Faint Milky Way
  Satellite

abstract:
  [abridged] We present MMT/Megacam imaging in Sloan $g$ and $r$ of the
extremely low luminosity Bo\"otes II Milky Way companion. We use a bootstrap
approach to perform robust measurements of, and uncertainties on, Bo\"otes II's
distance, luminosity, size, and morphology. We show that Bo\"otes II's stellar
population is old and metal-poor ([Fe/H] $\lta$ -2). Assuming a stellar
population like that of M92, Bo\"otes II is at a distance of 42 $\pm$ 2 kpc,
closer than the initial published estimate of 60 $\pm$ 10 kpc. This distance
revision, combined with a more robust measurement of Bo\"otes II's structure
with a Plummer model (exponential model) results in a more compact half-light
size of $r_h\simeq 36 (33) \pm 9 (10)$ pc and lower luminosity of
$M_V\simeq-2.4 (-2.2) \pm 0.7 (0.7)$ mag. This revised size and luminosity move
Bo\"otes II into a region of size-luminosity space not previously known to be
occupied by old stellar populations, but also occupied by the recently
discovered Milky Way satellites Willman 1 and SEGUE 1. We show that the
apparently distorted morphology of Bo\"otes II is not statistically significant
given the present data. We use a tidal argument to support a scenario where
Bo\"otes II is a dwarf galaxy (dark matter dominated) rather than a globular
cluster (not dark matter dominated). However, we can not rule out that Bo\"otes
II is a star cluster on the verge of disruption, such as Palomar 5.


title: Landau-deGennes Theory of Biaxial Nematics Re-examined

abstract:
  Recent experiments report that the long looked for thermotropic biaxial
nematic phase has been finally detected in some thermotropic liquid crystalline
systems. Inspired by these experimental observations we concentrate on some
elementary theoretical issues concerned with the classical sixth-order
Landau-deGennes free energy expansion in terms of the symmetric and traceless
tensor order parameter $Q_{\alpha\beta}$. In particular, we fully explore the
stability of the biaxial nematic phase giving analytical solutions for all
distinct classes of the phase diagrams that theory allows. This includes
diagrams with triple- and (tri-)critical points and with multiple (reentrant)
biaxial- and uniaxial phase transitions. A brief comparison with predictions of
existing molecular theories is also given.


title: Gibbs Sampling for a Bayesian Hierarchical General Linear Model

abstract:
  We consider a Bayesian hierarchical version of the normal theory general
linear model which is practically relevant in the sense that it is general
enough to have many applications and it is not straightforward to sample
directly from the corresponding posterior distribution. Thus we study a block
Gibbs sampler that has the posterior as its invariant distribution. In
particular, we establish that the Gibbs sampler converges at a geometric rate.
This allows us to establish conditions for a central limit theorem for the
ergodic averages used to estimate features of the posterior. Geometric
ergodicity is also a key component for using batch means methods to
consistently estimate the variance of the asymptotic normal distribution.
Together, our results give practitioners the tools to be as confident in
inferences based on the observations from the Gibbs sampler as they would be
with inferences based on random samples from the posterior. Our theoretical
results are illustrated with an application to data on the cost of health plans
issued by health maintenance organizations.


title: Top Compositeness at the Tevatron and LHC

abstract:
  We explore the possibility that the right-handed top quark is composite. We
examine the consequences that compositeness would have on $t \bar{t}$
production at the Tevatron, and derive a weak constraint on the scale of
compositeness of order a few hundred GeV from the $t \bar{t}$ inclusive cross
section. More detailed studies of differential properties of $t \bar{t}$
production could potentially improve this limit. We find that a composite top
can result in an enhancement of the $t \bar{t} t \bar{t}$ production rate at
the LHC (of as much as $10^3$ compared to the Standatd Model four top rate). We
explore observables which allow us to extract the four top rate from the
backgrounds, and show that the LHC can either discover or constrain top
compositeness for wide ranges of parameter space.


title: Chiral d-wave superconductivity in the heavy-fermion compound CeIrIn_5

abstract:
  Recent thermal conductivity measurements in the heavy-fermion compound
CeIrIn_5 indicate that its superconducting order parameter is very different
from CeCoIn_5. Here we show that these experiments are consistent with chiral
d-wave symmetry.


title: A note on the universality of the Hagedorn behavior of pp-wave strings

abstract:
  Following on from recent studies of string theory on a one-parameter family
of integrable deformations of $AdS_{5}\times S^{5}$ proposed by Lunin and
Maldacena, we carry out a systematic analysis of the high temperature
properties of type IIB strings on the associated pp-wave geometries. In
particular, through the computation of the thermal partition function and free
energy we find that not only does the theory exhibit a Hagedorn transition in
both the $(J,0,0)$ and $(J,J,J)$ class of pp-waves, but that the Hagedorn
temperature is insensitive to the deformation suggesting an interesting
universality in the high temperature behaviour of the pp-wave string theory. We
comment also on the implications of this universality on the
confinement/deconfinement transition in the dual $\mathcal{N}=1$
Leigh-Strassler deformation of ${\cal N}=4$ Yang-Mills theory.


title: Almost all integer matrices have no integer eigenvalues

abstract:
  For a fixed $n\ge2$, consider an $n\times n$ matrix $M$ whose entries are
random integers bounded by $k$ in absolute value. In this paper, we examine the
probability that $M$ is singular (hence has eigenvalue 0), and the probability
that $M$ has at least one rational eigenvalue. We show that both of these
probabilities tend to 0 as $k$ increases. More precisely, we establish an upper
bound of size $k^{-2+\epsilon}$ for the probability that $M$ is singular, and
size $k^{-1+\epsilon}$ for the probability that $M$ has a rational eigenvalue.
These results generalize earlier work by Kowalsky for the case $n=2$ and answer
a question posed by Hetzel, Liew, and Morrison.


title:
Manifestation of geometric frustration on magnetic and thermodynamic
  properties of pyrochlores $Sm_2X_2O_7$ (X=Ti, Zr)

abstract:
  We present here magnetization, specific heat and Raman studies on
single-crystalline specimens of the first pyrochlore member $Sm_2Ti_2O_7$ of
the rare-earth titanate series. Its analogous compound $Sm_2Zr_2O_7$ in the
rare-earth zirconate series is also investigated in the polycrystalline form.
The Sm spins in $Sm_2Ti_2O_7$ remain unordered down to at least T = 0.5 K. The
absence of magnetic ordering is attributed to very small values of exchange
($\theta_{cw} ~ -0.26 K$) and dipolar interaction ($\mu_{eff} ~ 0.15 \mu_B$)
between the $Sm^{3+}$ spins in this pyrochlore. In contrast, the pyrochlore
$Sm_2Zr_2O_7$ is characterized by a relatively large value of Sm-Sm spin
exchange ($\theta_{cw} ~ - 10 K$); however, long-range ordering of the
$Sm^{3+}$ spins is not established at least down to T = 0.67 K, due to
frustration of the $Sm^{3+}$ spins on the pyrochlore lattice. The ground state
of $Sm^{3+}$ ions in both pyrochlores is a well-isolated Kramer's doublet. The
higher-lying crystal field excitations are observed in the low-frequency region
of the Raman spectra of the two compounds recorded at T = 10 K. At higher
temperatures, the magnetic susceptibility of $Sm_2Ti_2O_7$ shows a broad
maximum at T = 140 K while that of $Sm_2Zr_2O_7$ changes monotonically. Whereas
$Sm_2Ti_2O_7$ is a promising candidate for investigating spin-fluctuations on a
frustrated lattice as indicated by our data, the properties of $Sm_2Zr_2O_7$
seem to conform to a conventional scenario where geometrical frustration of the
spin exclude their long-range ordering.


title: Cosmic acceleration from second order gauge gravity

abstract:
  We construct a phenomenological theory of gravitation based on a second order
gauge formulation for the Lorentz group. The model presents a long-range
modification for the gravitational field leading to a cosmological model
provided with an accelerated expansion at recent times. We estimate the model
parameters using observational data and verify that our estimative for the age
of the Universe is of the same magnitude than the one predicted by the standard
model. The transition from the decelerated expansion regime to the accelerated
one occurs recently (at $\sim9.3\;Gyr$).


title:
A method to search for strong galaxy-galaxy lenses in optical imaging
  surveys

abstract:
  We present a semi-automated method to search for strong galaxy-galaxy lenses
in optical imaging surveys. Our search technique constrains the shape of
strongly lensed galaxies (or arcs) in a multi-parameter space, which includes
the third order (octopole) moments of objects. This method is applied to the
Deep Lens Survey (DLS), a deep ground based weak lensing survey imaging to
$R\sim26$. The parameter space of arcs in the DLS is simulated using real
galaxies extracted from deep HST fields in order to more accurately reproduce
the properties of arcs. Arcs are detected in the DLS using a pixel thresholding
method and candidate arcs are selected within this multi-parameter space.
Examples of strong galaxy-galaxy lens candidates discovered in the DLS F2 field
(4 square degrees) are presented.


title: Hard QCD Processes at Colliders

abstract:
  Recent developments in the study of hard QCD processes at colliders are
reviewed, in the context of the imminent startup of the LHC.


title:
Wavefunction considerations for the central spin decoherence problem in
  a nuclear spin bath

abstract:
  Decoherence of a localized electron spin in a solid state material (the
``central spin'' problem) at low temperature is believed to be dominated by
interactions with nuclear spins in the lattice. This decoherence is partially
suppressed through the application of a large magnetic field that splits the
energy levels of the electron spin and prevents depolarization. However,
dephasing decoherence resulting from a dynamical nuclear spin bath cannot be
removed in this way. Fluctuations of the nuclear field lead to uncertainty of
the electron's precessional frequency in a process known as spectral diffusion.
This article considers the effect of the electron's wavefunction shape upon
spectral diffusion and provides wavefunction dependent decoherence time
formulas for free induction decay as well as spin echoes and concatenated
dynamical decoupling schemes for enhancing coherence. We also discuss dephasing
of a qubit encoded in singlet-triplet states of a double quantum dot. A central
theoretical result of this work is the development of a continuum approximation
for the spectral diffusion problem which we have applied to GaAs and InAs
materials specifically.


title:
Generalized Pairing Wave Functions and Nodal Properties for Electronic
  Structure Quantum Monte Carlo

abstract:
  The quantum Monte Carlo (QMC) is one of the most promising many-body
electronic structure approaches. It employs stochastic techniques for solving
the stationary Schr\" odinger equation and for evaluation of expectation
values. The key advantage of QMC is its capability to use the explicitly
correlated wave functions, which allow the study of many-body effects beyond
the reach of mean-field methods. The most important limit on QMC accuracy is
the fixed-node approximation, which comes from necessity to circumvent the
fermion sign problem. The size of resulting fixed-node errors depends on the
quality of the nodes (the subset of position space where the wave function
vanishes) of a used wave function. In this dissertation, we analyze the nodal
properties of the existing fermionic wave functions and offer new types of
variational wave functions with improved nodal structure.


title:
Differential Forms on Riemannian (Lorentzian) and Riemann-Cartan
  Structures and Some Applications to Physics

abstract:
  In this paper after recalling some essential tools concerning the theory of
differential forms in the Cartan, Hodge and Clifford bundles over a Riemannian
or Riemann-Cartan space or a Lorentzian or Riemann-Cartan spacetime we solve
with details several exercises involving different grades of difficult. One of
the problems is to show that a recent formula appearing in the literature for
the exterior covariant derivative of the Hodge dual of the torsion 2-forms is
simply wrong. We believe that the paper will be useful for students (and
eventually for some experts) on applications of differential geometry on
physical problems. A detailed account of the issues discussed in the paper
appears in the table of contents.


title:
Effect of Edge Roughness on Electronic Transport in Graphene Nanoribbon
  Channel Metal Oxide Semiconductor Field-Effect Transistors

abstract:
  Results of quantum mechanical simulations of the influence of edge disorder
on transport in graphene nanoribbon metal oxide semiconductor field-effect
transistors (MOSFETs) are reported. The addition of edge disorder significantly
reduces ON-state currents and increases OFF-state currents, and introduces wide
variability across devices. These effects decrease as ribbon widths increase
and as edges become smoother. However the bandgap decreases with increasing
width, thereby increasing the band-to-band tunneling mediated subthreshold
leakage current even with perfect nanoribbons. These results suggest that
without atomically precise edge control during fabrication, MOSFET performance
gains through use of graphene will be difficult to achieve.


title: Complete semi-conjugacies for psuedo-Anosov homeomorphisms

abstract:
  Suppose $S$ is a surface of genus $\ge 2 $, $f: S \to S$ is a surface
homeomorphism isotopic to a pseudo-Anosov map $\alpha$ and suppose $\ti S$ is
the universal cover of $S$ and $F$ and $A$ are lifts of $f$ and $\alpha$
respectively. We show there is a semiconjugacy $\Theta : \ti S \to \bar \L^s
\times \bar \L^u$ from $F$ to $\bar A$, where $\bar \L^s$ ($\bar \L^u$) is the
completion of the $R$-tree of leaves of the stable (resp. unstable) foliation
for $A$ and $\bar A$ is the map induced by $A$.
  We also generalize a result of Markovich and show that for any $g \in
Homeo(S)$ which commutes with $f$ and has identity lift $G : \ti S \to \ti S$
and for any $(c,w)$ in the image of $\Theta$ each component of
$\Theta^{-1}(c,w)$ is $G$-invariant.


title: Supernova explosions and the birth of neutron stars

abstract:
  We report here on recent progress in understanding the birth conditions of
neutron stars and the way how supernovae explode. More sophisticated numerical
models have led to the discovery of new phenomena in the supernova core, for
example a generic hydrodynamic instability of the stagnant supernova shock
against low-mode nonradial deformation and the excitation of gravity-wave
activity in the surface and core of the nascent neutron star. Both can have
supportive or decisive influence on the inauguration of the explosion, the
former by improving the conditions for energy deposition by neutrino heating in
the postshock gas, the latter by supplying the developing blast with a flux of
acoustic power that adds to the energy transfer by neutrinos. While recent
two-dimensional models suggest that the neutrino-driven mechanism may be viable
for stars from about 8 solar masses to at least 15 solar masses, acoustic
energy input has been advocated as an alternative if neutrino heating fails.
Magnetohydrodynamic effects constitute another way to trigger explosions in
connection with the collapse of sufficiently rapidly rotating stellar cores,
perhaps linked to the birth of magnetars. The global explosion asymmetries seen
in the recent simulations offer an explanation of even the highest measured
kick velocities of young neutron stars.


title:
Estimates for the quenching time of a parabolic equation modeling
  electrostatic MEMS

abstract:
  The singular parabolic problem $u_t=\Delta u -\frac{\lambda f(x)}{(1+u)^2}$
on a bounded domain $\Omega$ of $R^N$ with Dirichlet boundary conditions,
models the dynamic deflection of an elastic membrane in a simple electrostatic
Micro-Electromechanical System (MEMS) device. In this paper, we analyze and
estimate the quenching time of the elastic membrane in terms of the applied
voltage --represented here by $\lambda$. As a byproduct, we prove that for
sufficiently large $\lambda$, finite-time quenching must occur near the maximum
point of the varying dielectric permittivity profile $f(x)$.


title: Luminosity Dependent X-ray AGN Clustering ?

abstract:
  We have analysed the angular clustering of X-ray selected active galactic
nuclei (AGN) in different flux-limited sub-samples of the Chandra Deep Field
North (CDF-N) and South (CDF-S) surveys. We find a strong dependence of the
clustering strength on the sub-sample flux-limit, a fact which explains most of
the disparate clustering results of different XMM and Chandra surveys. Using
Limber's equation, we find that the inverted CDF-N and CDF-S spatial clustering
lengths are consistent with direct spatial clustering measures found in the
literature, while at higher flux-limits the clustering length increases
considerably; for example, at $fx,limit ~ 10^{-15} erg/s/cm^{-2} we obtain r_0~
17 +- 5 and 18+- 3 h^{-1} Mpc, for the CDF-N and CDF-S, respectively. We show
that the observed flux-limit clustering trend hints towards an X-ray luminosity
dependent clustering of X-ray selected, $z\sim 1$, AGNs.


title: C*-algebras associated to product systems of Hilbert bimodules

abstract:
  Let (G,P) be a quasi-lattice ordered group and let X be a compactly aligned
product system over P of Hilbert bimodules. Under mild hypotheses we associate
to X a C*-algebra which we call the Cuntz-Nica-Pimsner algebra of X. Our
construction generalises a number of others: a sub-class of Fowler's
Cuntz-Pimsner algebras for product systems of Hilbert bimodules; Katsura's
formulation of Cuntz-Pimsner algebras of Hilbert bimodules; the C*-algebras of
finitely aligned higher-rank graphs; and Crisp and Laca's boundary quotients of
Toeplitz algebras. We show that for a large class of product systems X, the
universal representation of X in its Cuntz-Nica-Pimsner algebra is isometric.


title:
Lattice Actions for Yang-Mills Quantum Mechanics with Exact
  Supersymmetry

abstract:
  We derive lattice actions for Yang-Mills quantum mechanics for models with
$\cQ=4, 8$ and 16 supercharges which possess an exact supersymmetry at non-zero
lattice spacing. These are obtained by dimensional reduction of twisted
versions of the corresponding super Yang-Mills theories in $D=2, 3$ and 4
dimensions.


title: SSC scenario for TeV emission from non-blazar AGNs

abstract:
  M87 is the first extragalactic source detected in the TeV gamma-ray domain
that is not a blazar, its large scale jet not being aligned to the line of
sight. We present here a multi-blob synchrotron self-Compton model accounting
explicitly for large viewing angles and moderate Lorentz factors as inferred
from magnetohydrodynamic simulations of jet formation, motivated by the
detection of M87 at very high energies (VHE; E > 100GeV). Predictions are
presented for the very high-energy emission of active galactic nuclei with
extended optical or X-ray jet, which could be misaligned blazars but still show
some moderate beaming. We include predictions for 3C273, Cen A and PKS 0521-36.


title:
How winding is the coast of Britain ? Conformal invariance of rocky
  shorelines

abstract:
  We show that rocky shorelines with fractal dimension 4/3 are conformally
invariant curves by measuring the statistics of their winding angles from
global high-resolution data. Such coastlines are thus statistically equivalent
to the outer boundary of the random walk and of percolation clusters. A simple
model of coastal erosion gives an explanation for these results. Conformal
invariance allows also to predict the highly intermittent spatial distribution
of the flux of pollutant diffusing ashore.


title:
Continuity, curvature, and the general covariance of optimal
  transportation

abstract:
  Let M and \bar M be n-dimensional manifolds equipped with suitable Borel
probability measures \rho and \bar\rho. Ma, Trudinger & Wang gave sufficient
conditions on a transportation cost c \in C^4(M \times \bar M) to guarantee
smoothness of the optimal map pushing \rho forward to \bar\rho; the necessity
of these conditions was deduced by Loeper. The present manuscript shows the
form of these conditions to be largely dictated by the covariance of the
question; it expresses them via non-negativity of the sectional curvature of
certain null-planes in a novel but natural pseudo-Riemannian geometry which the
cost c induces on the product space M \times \bar M.
  H\"older continuity of optimal maps was established for rougher mass
distributions by Loeper, still relying on a key result of Trudinger & Wang
which required certain structure on the domains and the cost. We go on to
develop this theory for mass distributions on differentiable manifolds --
recovering Loeper's Riemannian examples such as the round sphere as particular
cases -- give a direct proof of the key result mentioned above, and revise
Loeper's H\"older continuity argument to make it logically independent of all
earlier works, while extending it to less restricted geometries and cost
functions even for subdomains M and \bar M of R^n. We also give new examples of
geometries satisfying the hypotheses -- obtained using submersions and tensor
products -- and some connections to spacelike Lagrangian submanifolds in
symplectic geometry.


title: Two-dimensional elastic turbulence

abstract:
  We investigate the effect of polymer additives on a two-dimensional
Kolmogorov flow at very low Reynolds numbers by direct numerical simulations of
the Oldroyd-B viscoelastic model. We find that above the elastic instability
threshold the flow develops the elastic turbulence regime recently observed in
experiments. We observe that both the turbulent drag and the Lyapunov exponent
increase with Weissenberg, indicating the presence of a disordered,
turbulent-like mixing flow. The energy spectrum develops a power-law scaling
range with an exponent close to the experimental and theoretical expectations.


title: Block-diagonal semidefinite programming hierarchies for 0/1 programming

abstract:
  Lovasz and Schrijver, and later Lasserre, proposed hierarchies of
semidefinite programming relaxations for general 0/1 linear programming
problems. In this paper these two constructions are revisited and two new,
block-diagonal hierarchies are proposed. They have the advantage of being
computationally less costly while being at least as strong as the
Lovasz-Schrijver hierarchy. Our construction is applied to the stable set
problem and experimental results for Paley graphs are reported.


title:
Superconducting nanowire photon number resolving detector at telecom
  wavelength

abstract:
  The optical-to-electrical conversion, which is the basis of optical
detectors, can be linear or nonlinear. When high sensitivities are needed
single-photon detectors (SPDs) are used, which operate in a strongly nonlinear
mode, their response being independent of the photon number. Nevertheless,
photon-number resolving (PNR) detectors are needed, particularly in quantum
optics, where n-photon states are routinely produced. In quantum communication,
the PNR functionality is key to many protocols for establishing, swapping and
measuring entanglement, and can be used to detect photon-number-splitting
attacks. A linear detector with single-photon sensitivity can also be used for
measuring a temporal waveform at extremely low light levels, e.g. in
long-distance optical communications, fluorescence spectroscopy, optical
time-domain reflectometry. We demonstrate here a PNR detector based on parallel
superconducting nanowires and capable of counting up to 4 photons at
telecommunication wavelengths, with ultralow dark count rate and high counting
frequency.


title: Nonlinear Stability of Riemann Ellipsoids with Symmetric Configurations

abstract:
  We apply geometric techniques to obtain the necessary and sufficient
conditions on the existence and nonlinear stability of self-gravitating Riemann
ellipsoids having at least two equal axes.


title: Dynamic Phase Transitions for Ferromagnetic Systems

abstract:
  This article presents a phenomenological dynamic phase transition theory for
ferromagnetism, leading to a precise description of the dynamic transitions,
and to a physical predication on the spontaneous magnetization. The analysis
also suggests asymmetry of fluctuations in both the ferromagnetism and the PVT
systems.


title: Coherent and Incoherent States of Electron-doped SrTiO3

abstract:
  Resonant photoemission at the Ti 2p and O 1s edges on a Nb-doped SrTiO3 thin
film revealed that the coherent state (CS) at the Fermi level (EF) had mainly
Ti 3d character whereas the incoherent in-gap state (IGS) positioned ~1.5 eV
below EF had mixed character of Ti 3d and O 2p states. This indicates that the
IGS is formed by a spectral-weight transfer from the CS and subsequent
spectral-weight redistribution through d-p hybridization. We discuss the
evolution of the excitation spectrum with 3d band filling and rationalize the
IGS through a mechanism similar to that proposed by Haldane and Anderson.


title: Proxy Signature Scheme with Effective Revocation Using Bilinear Pairings

abstract:
  We present a proxy signature scheme using bilinear pairings that provides
effective proxy revocation. The scheme uses a binding-blinding technique to
avoid secure channel requirements in the key issuance stage. With this
technique, the signer receives a partial private key from a trusted authority
and unblinds it to get his private key, in turn, overcomes the key escrow
problem which is a constraint in most of the pairing-based proxy signature
schemes. The scheme fulfills the necessary security requirements of proxy
signature and resists other possible threats.


title:
Disappearance of the metal-like behavior in GaAs two-dimensional holes
  below 30 mK

abstract:
  The zero-field temperature-dependence of the resistivity of two-dimensional
holes are observed to exhibit two qualitatively different characteristics for a
fixed carrier density for which only the metallic behavior of the so-called
metal-insulator transition is anticipated. As $T$ is lowered from 150 mK to 0.5
mK, the sign of the derivative of the resistivity with respect to $T$ changes
from being positive to negative when the temperature is lowered below $\sim$30
mK and the resistivity continuously rises with cooling down to 0.5 mK,
suggesting a crossover from being metal-like to insulator-like.


title: Superfluid Transition in a Chiron Gas

abstract:
  Low temperature measurements of the magnetic susceptibility of LSCO suggest
that the superconducting transition is associated with the disappearance of a
vortex liquid. In this note we wish to draw attention to the fact that
spin-orbit-like interactions in a poorly conducting layered material can lead
to a new type of quantum ground state with spin polarized soliton-like charge
carriers as the important quantum degree of freedom. In 2-dimensions these
solitons are vortex-like, while in 3-dimensional systems they are
monopole-like. In either case there is a natural mechanism for the pairing of
spin up and spin down solitons, and we find that at low temperatures there is a
cross-over transition as a function of carrier density between a state where
the solitons are free and a condensate state where the spin up and spin down
solitons in neighboring layers are paired.


title: Real stabilization method for nuclear single particle resonances

abstract:
  We develop the real stabilization method within the framework of the
relativistic mean field (RMF) model. With the self-consistent nuclear
potentials from the RMF model, the real stabilization method is used to study
single-particle resonant states in spherical nuclei. As examples, the energies,
widths and wave functions of low-lying neutron resonant states in $^{120}$Sn
are obtained. These results are compared with those from the scattering phase
shift method and the analytic continuation in the coupling constant approach
and satisfactory agreements are found.


title: Clones and Genoids in Lambda Calculus and First Order Logic

abstract:
  A genoid is a category of two objects such that one is the product of itself
with the other. A genoid may be viewed as an abstract substitution algebra. It
is a remarkable fact that such a simple concept can be applied to present a
unified algebraic approach to lambda calculus and first order logic.


title: Charm Production in DPMJET

abstract:
  In this work, charm production in the {\sc dpmjet} hadronic jet simulation is
compared to experimental data. Since the major application of {\sc dpmjet} is
the simulation of cosmic ray-induced air showers, the version of the code
integrated in the CORSIKA simulation package has been used for the comparison.
Wherever necessary, adjustments have been made to improve agreement between
simulation and data. With the availability of new muon/neutrino detectors that
combine a large fiducial volume with large amounts of shielding, investigation
of prompt muons and neutrinos from cosmic ray interactions will be feasible for
the first time. Furthermore, above $\gtrsim 100$ TeV charmed particle decay
becomes the dominant background for diffuse extraterrestrial neutrino flux
searches. A reliable method to simulate charm production in high-energy
proton-nucleon interactions is therefore required.


title: Regularity of Leray-Hopf solutions to Navier-Stokes equations

abstract:
  Limit behaviors of blow up solutions for impressible Navier-Stokes equations
are obtained.


title:
Orthogonal polynomials and partial differential equations on the unit
  ball

abstract:
  Orthogonal polynomials of degree $n$ with respect to the weight function
$W_\mu(x) = (1-\|x\|^2)^\mu$ on the unit ball in $\RR^d$ are known to satisfy
the partial differential equation $$
  [ \Delta - \la x, \nabla \ra^2 -
  (2 \mu +d) \la x, \nabla \ra \right ] P = -n(n+2 \mu+d) P $$ for $\mu > -1$.
The singular case of $\mu = -1,-2, ...$ is studied in this paper. Explicit
polynomial solutions are constructed and the equation for $\nu = -2,-3,...$ is
shown to have complete polynomial solutions if the dimension $d$ is odd. The
orthogonality of the solution is also discussed.


title: On splitting polynomials with noncommutative coefficients

abstract:
  It is shown that for every splitting of a polynomial with noncommutative
coefficients into linear factors $(X-a_{k})$ with $a_{k}$'s commuting with
coefficients, any cyclic permutation of linear factors gives the same result
and all $a_{k}$ are roots of that polynomial. Examples are given and analyzed
from Galois theory point of view.


title:
Discrete Fourier analysis, Cubature and Interpolation on a Hexagon and a
  Triangle

abstract:
  Several problems of trigonometric approximation on a hexagon and a triangle
are studied using the discrete Fourier transform and orthogonal polynomials of
two variables. A discrete Fourier analysis on the regular hexagon is developed
in detail, from which the analysis on the triangle is deduced. The results
include cubature formulas and interpolation on these domains. In particular, a
trigonometric Lagrange interpolation on a triangle is shown to satisfy an
explicit compact formula, which is equivalent to the polynomial interpolation
on a planer region bounded by Steiner's hypocycloid. The Lebesgue constant of
the interpolation is shown to be in the order of $(\log n)^2$. Furthermore, a
Gauss cubature is established on the hypocycloid.


title: CANGAROO-III Observations of the 2006 Outburst of PKS2155-304

abstract:
  We have used the CANGAROO-III imaging atmospheric Cherenkov telescopes to
observe the high-frequency-peaked BL Lacertae (HBL) object PKS 2155-304 between
2006 July 28 (MJD 53944) and August 2, triggered by the H.E.S.S. report that
the source was in a high state of TeV gamma-ray emission. A signal was detected
at the 4.8 sigma level in an effective live time of 25.1 hours during the
outburst period. The flux of Very High Energy gammarays from the CANGAROO-III
observations shows the variability on the time scale of less than a few hours.
The averaged integral flux above 660 GeV is (1.6 +/- 0.3_stat +/- 0.5_syst) x
10^-11 cm^-2 sec^-1 which corresponds to ~45% of the flux observed from the
Crab nebula. Follow-up observations between August 17 (MJD 53964) and 25
indicate the source activity had decreased.


title:
Hawking radiation in GHS blackhole, Effective action and Covariant
  Boundary condition

abstract:
  We exploit the expression for the anomalous (chiral) effective action to
obtain the Hawking radiation from the GHS (stringy) blackhole falling in the
class of the most general spherically symmetric blackholes $(\sqrt{-g}\neq1)$,
using only covariant boundary condition at the event horizon. The connection
between the anomalous and the normal energy-momentum tensors is also
established from the effective action approach.


title: Photocatalytic Activity of Pulsed Laser Deposited TiO2 Thin Films

abstract:
  Nanostructured TiO2 thin films were prepared by pulsed laser deposition (PLD)
on indium doped tin oxide (ITO) substrates. Results from X-ray photoelectron
spectroscopy (XPS) show that Ti 2p core level peaks shift toward the lower
binding energy with decrease in the buffer gas pressure (O2:Ar = 1:1). This
suggests that oxygen vacancies are created under insufficient oxygen
conditions. Anatase to rutile ratio is also found to be system pressure
dependent. Under deposition pressure of 750 mTorr only anatase phase was
observed even at 1073 K substrate temperature which is much higher that the
bulk anatase to rutile phase transformation temperature. The deposited TiO2
thin films were fabricated as photoanodes for photoelectrochemical (PEC)
studies. PEC measurements on TiO2 photoanodes show that the flatband potential
(Vfb) increases by 0.088 eV on absolute vacuum energy scale (AVS) with decrease
in the deposition pressure, from 750 to 250 mTorr at 873K. The highest incident
photon to current conversion efficiency [IPCE(lambda)] of 2.5 to 6 % was
obtained from the thin films prepared at substrate temperature of 873K.
Combining the results from XPS and PEC studies, we conclude that the deposition
pressure affects the concentration of the oxygen vacancies which changes the
electronic structure of the TiO2. With reference to photoelectrochemical
catalytic performance, our results suggest that it is possible to adjust the
Fermi energy level and structure of TiO2 thin films by controlling the buffer
gas pressure and temperature to align the energy of the flatband potential
(Vfb) with respect to specific redox species in the electrolyte.


title: Madelung Energy of the Valence Skipping Compound BaBiO$_3$

abstract:
  Several elements show valence skip fluctuation, for instance, Tl forms the
compounds in valence states +1 and +3, and Bi forms in +3 and +5 states. This
kind of fluctuation gives rise to a negative effective attractive interaction
and the Kondo effect. In the compounds of valence skipping elements, the
carrier doping will induce superconductivity with high critical temperature.
For example, Ba$_{1-x}$K$_x$BiO$_3$ shows high $T_c$ which is unlikely from the
conventional electron-phonon mechanism. The reason for the missing of some
valence states in such valence skip compounds remains a mystery. We have
performed the evaluation of the Madelung potential for BaBiO$_3$, and have
shown for the first time that charge-ordered state is stabilized if we take
into account the polarization of the oxygen charge. We argue that the effective
Coulomb interaction energy $U$ may be negative evaluating the local excitation
energy.


title:
Mass hierarchy, mass gap and corrections to Newton's law on thick branes
  with Poincare symmetry

abstract:
  We consider a scalar thick brane configuration arising in a 5D theory of
gravity coupled to a self-interacting scalar field in a Riemannian manifold. We
start from known classical solutions of the corresponding field equations and
elaborate on the physics of the transverse traceless modes of linear
fluctuations of the classical background, which obey a Schroedinger-like
equation. We further consider two special cases in which this equation can be
solved analytically for any massive mode with m^2>0, in contrast with numerical
approaches, allowing us to study in closed form the massive spectrum of
Kaluza-Klein (KK) excitations and to compute the corrections to Newton's law in
the thin brane limit. In the first case we consider a solution with a mass gap
in the spectrum of KK fluctuations with two bound states - the massless 4D
graviton free of tachyonic instabilities and a massive KK excitation - as well
as a tower of continuous massive KK modes which obey a Legendre equation. The
mass gap is defined by the inverse of the brane thickness, allowing us to get
rid of the potentially dangerous multiplicity of arbitrarily light KK modes. It
is shown that due to this lucky circumstance, the solution of the mass
hierarchy problem is much simpler and transparent than in the (thin)
Randall-Sundrum (RS) two-brane configuration. In the second case we present a
smooth version of the RS model with a single massless bound state, which
accounts for the 4D graviton, and a sector of continuous fluctuation modes with
no mass gap, which obey a confluent Heun equation in the Ince limit. (The
latter seems to have physical applications for the first time within braneworld
models). For this solution the mass hierarchy problem is solved as in the
Lykken-Randall model and the model is completely free of naked singularities.


title: Dark-Energy Dynamics Required to Solve the Cosmic Coincidence

abstract:
  Dynamic dark energy (DDE) models are often designed to solve the cosmic
coincidence (why, just now, is the dark energy density $\rho_{de}$, the same
order of magnitude as the matter density $\rho_m$?) by guaranteeing $\rho_{de}
\sim \rho_m$ for significant fractions of the age of the universe. This
typically entails ad-hoc tracking or oscillatory behaviour in the model.
However, such behaviour is neither sufficient nor necessary to solve the
coincidence problem. What must be shown is that a significant fraction of
observers see $\rho_{de} \sim \rho_m$. Precisely when, and for how long, must a
DDE model have $\rho_{de} \sim \rho_{m}$ in order to solve the coincidence? We
explore the coincidence problem in dynamic dark energy models using the
temporal distribution of terrestrial-planet-bound observers. We find that any
dark energy model fitting current observational constraints on $\rho_{de}$ and
the equation of state parameters $w_0$ and $w_a$, does have $\rho_{de} \sim
\rho_m$ for a large fraction of observers in the universe. This demotivates DDE
models specifically designed to solve the coincidence using long or repeated
periods of $\rho_{de} \sim \rho_m$.


title:
Coulomb correlation in presence of spin-orbit coupling: application to
  plutonium

abstract:
  Attempts to go beyond the local density approximation (LDA) of Density
Functional Theory (DFT) have been increasingly based on the incorporation of
more realistic Coulomb interactions. In their earliest implementations, methods
like LDA+$U$, LDA + DMFT (Dynamical Mean Field Theory), and LDA+Gutzwiller used
a simple model interaction $U$. In this article we generalize the solution of
the full Coulomb matrix involving $F^{(0)}$ to $F^{(6)}$ parameters, which is
usually presented in terms of an $\ell m_\ell$ basis, into a $jm_{j}$ basis of
the total angular momentum, where we also include spin-orbit coupling; this
type of theory is needed for a reliable description of $f$-state elements like
plutonium, which we use as an example of our theory. Close attention will be
paid to spin-flip terms, which are important in multiplet theory but that have
been usually neglected in these kinds of studies. We find that, in a
density-density approximation, the $jm_j$ basis results provide a very good
approximation to the full Coulomb matrix result, in contrast to the much less
accurate results for the more conventional $\ell m_\ell$ basis.


title:
Design of three dimensional isotropic microstructures for maximized
  stiffness and conductivity

abstract:
  The level-set method of topology optimization is used to design isotropic
two-phase periodic multifunctional composites in three dimensions. One phase is
stiff and insulating whereas the other is conductive and mechanically
compliant. The optimization objective is to maximize a linear combination of
the effective bulk modulus and conductivity of the composite. Composites with
the Schwartz primitive and diamond minimal surfaces as the phase interface have
been shown to have maximal bulk modulus and conductivity. Since these
composites are not elastically isotropic their stiffness under uniaxial loading
varies with the direction of the load. An isotropic composite is presented with
similar conductivity which is at least 23% stiffer under uniaxial loading than
the Schwartz structures when loaded uniaxially along their weakest direction.
Other new near-optimal isotropic composites are presented, proving the
capablities of the level-set method for microstructure design.


title: 5D Supergravity and Projective Superspace

abstract:
  This paper is a companion to our earlier work arXiv:0710.3440 in which the
projective superspace formulation for matter-coupled simple supergravity in
five dimensions was presented. For the minimal multiplet of 5D N=1 supergravity
introduced by Howe in 1981, we give a complete solution of the Bianchi
identities. The geometry of curved superspace is shown to allow the existence
of a large family of off-shell supermultiplets that can be used to describe
supersymmetric matter, including vector multiplets and hypermultiplets. We
formulate a manifestly locally supersymmetric action principle. Its natural
property turns out to be the invariance under so-called projective
transformations of the auxiliary isotwistor variables. We then demonstrate that
the projective invariance allows one to uniquely restore the action functional
in a Wess-Zumino gauge. The latter action is well-suited for reducing the
supergravity-matter systems to components.


title:
Stationary solutions of the Schr\"{o}dinger-Newton model - An ODE
  approach

abstract:
  We prove the existence and uniqueness of stationary spherically symmetric
positive solutions for the Schr\"{o}dinger-Newton model in any space dimension
$d$. Our result is based on an analysis of the corresponding system of second
order differential equations. It turns out that $d=6$ is critical for the
existence of finite energy solutions and the equations for positive spherically
symmetric solutions reduce to a Lane-Emden equation for all $d\geq 6$. Our
result implies in particular the existence of stationary solutions for
two-dimensional self-gravitating particles and closes the gap between the
variational proofs in $d=1$ and $d=3$.


title:
Orbit decidability and the conjugacy problem for some extensions of
  groups

abstract:
  Given a short exact sequence of groups with certain conditions, $1\to F\to
G\to H\to 1$, we prove that $G$ has solvable conjugacy problem if and only if
the corresponding action subgroup $A\leqslant Aut(F)$ is orbit decidable. From
this, we deduce that the conjugacy problem is solvable, among others, for all
groups of the form $\mathbb{Z}^2\rtimes F_m$, $F_2\rtimes F_m$, $F_n \rtimes
\mathbb{Z}$, and $\mathbb{Z}^n \rtimes_A F_m$ with virtually solvable action
group $A\leqslant GL_n(\mathbb{Z})$. Also, we give an easy way of constructing
groups of the form $\mathbb{Z}^4\rtimes F_n$ and $F_3\rtimes F_n$ with
unsolvable conjugacy problem. On the way, we solve the twisted conjugacy
problem for virtually surface and virtually polycyclic groups, and give an
example of a group with solvable conjugacy problem but unsolvable twisted
conjugacy problem. As an application, an alternative solution to the conjugacy
problem in $Aut(F_2)$ is given.


title:
Generalized Hasimoto Transform of One-Dimensional Dispersive Flows into
  Compact Riemann Surfaces

abstract:
  We study the structure of differential equations of one-dimensional
dispersive flows into compact Riemann surfaces. These equations geometrically
generalize two-sphere valued systems modeling the motion of vortex filament. We
define a generalized Hasimoto transform by constructing a good moving frame,
and reduce the equation with values in the induced bundle to a complex valued
equation which is easy to handle. We also discuss the relationship between our
reduction and the theory of linear dispersive partial differential equations.


title:
The Subaru/XMM-Newton Deep Survey (SXDS) - VI. Properties of Active
  Galactic Nuclei Selected by Optical Variability

abstract:
  We present the properties of active galactic nuclei (AGN) selected by optical
variability in the Subaru/XMM-Newton Deep Field (SXDF). Based on the locations
of variable components and light curves, 211 optically variable AGN were
reliably selected. We made three AGN samples; X-ray detected optically
non-variable AGN (XA), X-ray detected optically variable AGN (XVA), and X-ray
undetected optically variable AGN (VA). In the VA sample, we found a bimodal
distribution of the ratio between the variable component flux and the host
flux. One of these two components in the distribution, a class of AGN with a
faint variable component $i'_{\rm{vari}}\sim25$ mag in bright host galaxies
$i'\sim21$ mag, is not seen in the XVA sample. These AGN are expected to have
low Eddington ratios if we naively consider a correlation between bulge
luminosity and black hole mass. These galaxies have photometric redshifts
$z_{\rm{photo}}\sim0.5$ and we infer that they are low-luminosity AGN with
radiatively inefficient accretion flows (RIAFs). The properties of the XVA and
VA objects and the differences from those of the XA objects can be explained
within the unified scheme for AGN. Optical variability selection for AGN is an
independent method and could provide a complementary AGN sample which even deep
X-ray surveys have not found.


title: Acceleration of the Universe in Presence of Tachyonic field

abstract:
  In this letter, we have assumed that the Universe is filled in tachyonic
field with potential, which gives the acceleration of the Universe. For certain
choice of potential, we have found the exact solutions of the field equations.
We have shown the decaying nature of potential. From recently developed
statefinder parameters, we have investigated the role of tachyonic field in
different stages of the evolution of the Universe.


title:
The Subaru/XMM-Newton Deep Survey (SXDS) - V. Optically Faint Variable
  Object Survey

abstract:
  We present our survey for optically faint variable objects using multi-epoch
(8-10 epochs over 2-4 years) $i'$-band imaging data obtained with Subaru
Suprime-Cam over 0.918 deg$^2$ in the Subaru/XMM-Newton Deep Field (SXDF). We
found 1040 optically variable objects by image subtraction for all the
combinations of images at different epochs. This is the first statistical
sample of variable objects at depths achieved with 8-10m class telescopes or
HST. The detection limit for variable components is $i'_{\rm{vari}}\sim25.5$
mag. These variable objects were classified into variable stars, supernovae
(SNe), and active galactic nuclei (AGN), based on the optical morphologies,
magnitudes, colors, and optical-mid-infrared colors of the host objects,
spatial offsets of variable components from the host objects, and light curves.
Detection completeness was examined by simulating light curves for periodic and
irregular variability. We detected optical variability for $36\pm2%$ ($51\pm3%$
for a bright sample with $i'<24.4$ mag) of X-ray sources in the field. Number
densities of variable obejcts as functions of time intervals $\Delta{t}$ and
variable component magnitudes $i'_{\rm{vari}}$ are obtained. Number densities
of variable stars, SNe, and AGN are 120, 489, and 579 objects deg$^{-2}$,
respectively. Bimodal distributions of variable stars in the color-magnitude
diagrams indicate that the variable star sample consists of bright ($V\sim22$
mag) blue variable stars of the halo population and faint ($V\sim23.5$ mag) red
variable stars of the disk population. There are a few candidates of RR Lyrae
providing a possible number density of $\sim10^{-2}$ kpc$^{-3}$ at a distance
of $>150$ kpc from the Galactic center.


title:
Near Fermi level Electronic Structure of Pr$_{1-x}$Sr$_x$MnO$_3$:
  Photoemission Study

abstract:
  In this study, we report the observation of a pseudogap associated with the
insulator-metal transition in compositions of Pr$_{1-x}$Sr$_x$MnO$_3$ system
with no charge ordering. Our valence band photoemission study shows that the
observed shifts in the near Fermi level density of states are abrupt at the
Curie transtion and occur over an energy scale of $\sim$ 1 eV, strongly
suggesting that the charge-ordering gap observed earlier in other manganites
and the pseudogap observed here may indeed have same origin. These results
could be understood within the framework of models based on electronic phase
separation where it has been shown that the pseudogap is a generic feature of
the mixed-phase compositions. Also, our band structure calculations on
Pr$_{0.75}$Sr$_{0.25}$MnO$_3$ show the possible existence of half-metallicity
in this system.


title:
Universal lifts of chain complexes over non-commutative parameter
  algebras

abstract:
  We define the notion of universal lift of a projective complex based on
non-commutative parameter algebras, and prove its existence and uniqueness. We
investigate the properties of parameter algebras for universal lifts.


title: Scattering Processes of Excited Exotic Atoms: Close-Coupling Approach

abstract:
  The scattering processes of exotic atoms in excited states from hydrogen such
as elastic scattering, Stark transitions and Coulomb de-excitation are studied
within a close coupling approach. The vacuum polarization and the strong
interaction shifts of $ns$-states (in case of hadronic atoms) are taken into
account. The differential and integral cross sections of the above processes
are calculated to use them as the input in cascade calculations. The effect of
closed channels on the scattering processes is investigated.


title: A most general edge elimination graph polynomial

abstract:
  We look for graph polynomials which satisfy recurrence relations on three
kinds of edge elimination: edge deletion, edge contraction and deletion of
edges together with their end points. Like in the case of deletion and
contraction only (W. Tutte, 1954), it turns out that there is a most general
polynomial satisfying such recurrence relations, which we call $\xi(G,x,y,z)$.
We show that the new polynomial simultaneously generalizes the Tutte
polynomial, the matching polynomial, and the recent generalization of the
chromatic polynomial proposed by K.Dohmen, A.P\"{o}nitz and P.Tittman (2003),
including also the independent set polynomial of I. Gutman and F. Harary,
(1983) and the vertex-cover polynomial of F,M. Dong, M.D. Hendy, K.T. Teo and
C.H.C. Little (2002). We establish two definitions of the new polynomial:
first, the most general confluent recursive definition, and then an explicit
one, using a set expansion formula, and prove their identity. We further expand
this result to edge-labeled graphs as was done for the Tutte polynomial by T.
Zaslavsky (1992) and B. Bollob\'as and O. Riordan (1999). The edge labeled
polynomial $\xi_{lab}(G,x,y,z, \bar{t})$ also generalizes the chain polynomial
of R.C. Read and E.G. Whitehead Jr. (1999). Finally, we discuss the complexity
of computing $\xi(G,x,y,z)$.


title: Optimizing Queries in a Logic-based Information Integration System

abstract:
  The SINTAGMA information integration system is an infrastructure for
accessing several different information sources together. Besides providing a
uniform interface to the information sources (databases, web services, web
sites, RDF resources, XML files), semantic integration is also needed. Semantic
integration is carried out by providing a high-level model and the mappings to
the models of the sources. When executing a query of the high level model, a
query is transformed to a low-level query plan, which is a piece of Prolog code
that answers the high-level query. This transformation is done in two phases.
First, the Query Planner produces a plan as a logic formula expressing the
low-level query. Next, the Query Optimizer transforms this formula to
executable Prolog code and optimizes it according to structural and statistical
information about the information sources.
  This article discusses the main ideas of the optimization algorithm and its
implementation.


title: New Abstract Hardy Spaces

abstract:
  The aim of this paper is to propose an abstract construction of spaces which
keep the main properties of the (already known) Hardy spaces H^1. We construct
spaces through an atomic (or molecular) decomposition. We prove some results
about continuity from these spaces into L^1 and some results about
interpolation between these spaces and the Lebesgue spaces. We also obtain some
results on weighted norm inequalities. Then we apply this abstract theory to
the L^p maximal regularity. Finally we present partial results in order to
understand a characterization of the duals of Hardy spaces.


title:
Software (Re-)Engineering with PSF II: from architecture to
  implementation

abstract:
  This paper presents ongoing research on the application of PSF in the field
of software engineering and reengineering. We build a new implementation for
the simulator of the PSF Toolkit starting from the specification in PSF of the
architecture of a simple simulator and extend it with features to obtain the
architecture of a full simulator. We apply refining and constraining techniques
on the specification of the architecture to obtain a specification low enough
to build an implementation from.


title:
Proceedings of the 17th Workshop on Logic-based methods in Programming
  Environments (WLPE 2007)

abstract:
  This volume contains the papers presented at WLPE 2007: the 17th Workshop on
Logic-based Methods in Programming Environments on 13th September, 2007 in
Porto, Portugal. It was held as a satellite workshop of ICLP 2007, the 23th
International Conference on Logic Programming.


title: A new approach to Kostant's problem

abstract:
  For every involution $\mathbf{w}$ of the symmetric group $S_n$ we establish,
in terms ofa special canonical quotient of the dominant Verma module associated
with $\mathbf{w}$, an effective criterion, which allows us to verify whether
the universal enveloping algebra $U(\mathfrak{sl}_n)$ surjects onto the space
of all ad-finite linear transformations of the simple highest weight module
$L(\mathbf{w})$. An easy sufficient condition derived from this criterion
admits a straightforward computational check for example using a computer. All
this is applied to get some old and many new results, which answer the
classical question of Kostant in special cases, in particular we give a
complete answer for simple highest weight modules in the regular block of
$\mathfrak{sl}_n$, $n\leq 5$.


title:
Measurement of dispersive forces between evaporated metal surfaces in
  the range below 100 nm

abstract:
  In this work we describe dispersion force (van der Waals/Casimir)
measurements between gold surfaces at separations as close as 12 nm. The force
measurements were performed in the plane-sphere configuration by Atomic Force
Microscopy at distances ranging between 12 and 200 nm. This was accomplished by
using evaporated smooth metal surfaces for both sphere and plane, and stiff
cantilevers to minimize jump-to-contact problems. Finally, it is shown that
below separations of 100 nm experiment and theory are found in agreement within
10 % by including in the theory the measured optical properties of gold and
contribution from surface roughness.


title:
Space-time uncertainty relation from quantum and gravitational
  principles

abstract:
  By collecting both quantum and gravitational principles, a space-time
uncertainty relation $(\delta t)(\delta r)^{3}\geqslant\pi r^{2}l_{p}^{2}$ is
derived. It can be used to facilitate the discussion of several profound
questions, such as computational capacity and thermodynamic properties of the
universe and the origin of holographic dark energy. The universality and
validity of the proposed relation are illustrated via these examples.


title: Trace formulae for dissipative and coupled scattering systems

abstract:
  For scattering systems consisting of a (family of) maximal dissipative
extension(s) and a selfadjoint extension of a symmetric operator with finite
deficiency indices, the spectral shift function is expressed in terms of an
abstract Titchmarsh-Weyl function and a variant of the Birman-Krein formula is
proved.


title: The Host Galaxies and Black Holes of Typical z~0.5-1.4 AGN

abstract:
  We study the stellar and star formation (SF) properties of the host galaxies
of 58 X-ray selected AGN in the GOODS portion of the Chandra Deep Field South
(CDF-S) region at z~0.5-1.4. The AGN are selected such that their rest-frame UV
to near-IR SEDs are dominated by stellar emission, i.e., they show a prominent
1.6micron bump, thus minimizing the AGN emission 'contamination'. This AGN
population comprises approximately 50% of the X-ray selected AGN at these
redshifts. Using models of stellar and dust emission we model their SEDs to
derive stellar masses (M*) and total (UV+IR) star formation rates (SFR). AGN
reside in the most massive galaxies at the redshifts probed here. Their
characteristic stellar masses (M*~7.8x10^10 Msun and M*~1.2x10^11 Msun at
median z of 0.67 and 1.07, respectively) appear to be representative of the
X-ray selected AGN population at these redshifts, and are intermediate between
those of local type 2 AGN and high redshift (z~2) AGN. The inferred black hole
masses (MBH~ 2x10^8 Msun) of typical AGN are similar to those of optically
identified quasars at similar redshifts. Since the AGN in our sample are much
less luminous (L(2-10keV)<10^44 erg/s) than quasars, typical AGN have low
Eddington ratios (eta~0.01-0.001). This suggests that, at least at intermediate
z, the cosmic AGN 'downsizing' is due to both a decrease in the characteristic
stellar mass of typical host galaxies, and less efficient accretion. Finally
there is no strong evidence in AGN host galaxies for either highly suppressed
SF (expected if AGN played a role in quenching SF) or elevated SF when compared
to mass selected (i.e., IRAC-selected) galaxies of similar stellar masses and
redshifts. This may be explained by the fact that galaxies with M*~5x 10^10 -
5x10^11 Msun are still being assembled at the redshifts probed here.


title: Temperature-induced reversal of magnetic interlayer exchange coupling

abstract:
  For epitaxial trilayers of the magnetic rare-earth metals Gd and Tb, exchange
coupled through a non-magnetic Y spacer layer, element-specific hysteresis
loops were recorded by the x-ray magneto-optical Kerr effect at the rare-earth
$M_5$ thresholds. This allowed us to quantitatively determine the strength of
interlayer exchange coupling (IEC). In addition to the expected oscillatory
behavior as a function of spacer-layer thickness $d_Y$, a temperature-induced
sign reversal of IEC was observed for constant $d_Y$, arising from
magnetization-dependent electron reflectivities at the magnetic interfaces.


title: Equivariant stable stems for prime order groups

abstract:
  For groups of prime order, equivariant stable maps between equivariant
representation spheres are investigated using the Borel cohomology Adams
spectral sequence. Features of the equivariant stable homotopy category, such
as stability and duality, are shown to lift to the category of modules over the
associated Steenrod algebra. The dependence on the dimension functions of the
representations is clarified.


title: A solvable model for small-x physics in D > 4 dimensions

abstract:
  I present a simplified model for the gluon Green's function governing
high-energy QCD dynamics, in arbitrary space-time dimensions. The BFKL integral
equation (either with or without running coupling) reduces to a second order
differential equation that can be solved in terms of Bessel and hypergeometric
functions. Explicit expressions for the gluon density and its anomalous
dimension are derived in MS and Q_0 factorization schemes. This analysis
illustrates the qualitative features of the QCD gluon density in both
factorization schemes. In addition, it clarifies the mathematical properties
and validates the results of the ``gamma-representation'' method proposed by
M.Ciafaloni and myself for extracting resummed next-to-leading-log x anomalous
dimensions of phenomenological relevance in the two schemes.


title: Compact mid-IR sources east of galactic center source IRS5

abstract:
  There are four less prominent compact sources east of IRS5, the natures of
which were unclear until now. We present near-infrared K-band long slit
spectroscopy of the four sources east of IRS5 obtained with the ISAAC
spectrograph at the ESO VLT in July 2005. We interpret the data in combination
with high angular resolution NIR and MIR images obtained with ISAAC and NACO at
the ESO VLT.


title: Diffusion-limited unbinding of small peptides from PDZ domains

abstract:
  PDZ domains are typical examples of binding motifs mediating the formation of
protein-protein assemblies in many different cells. A quantitative
characterization of the mechanisms intertwining structure, chemistry and
dynamics with the PDZ function represent a challenge in molecular biology. Here
we investigated the influence of native state topology on the thermodynamics
and the dissociation kinetics for a complex PDZ-peptide via Molecular Dynamics
simulations based on a coarse-grained description of PDZ domains. Our
native-centric approach neglects chemical details but incorporates the basic
structural information to reproduce the protein functional dynamics as it
couples to the binding. We found that at physiological temperatures the
unbinding of a peptide from the PDZ domain becomes increasingly diffusive
rather than thermally activated, as a consequence of the significant reduction
of the free energy barrier with temperature. In turn, this results in a
significant slowing down of the process of two orders of magnitude with respect
to the conventional Arrhenius extrapolation from low temperature calculations.
Finally, a detailed analysis of a typical unbinding event based on the rupture
times of single peptide-PDZ contacts allows to shed further light on the
dissociation mechanism and to elaborate a coherent picture of the relation
between function and dynamics in PDZ domains.


title:
Optimal eigenvalue estimate for the Dirac-Witten operator on bounded
  domains with smooth boundary

abstract:
  Eigenvalue estimate for the Dirac-Witten operator is given on bounded domains
(with smooth boundary) of spacelike hypersurfaces satisfying the dominant
energy condition, under four natural boundary conditions (MIT, APS, modified
APS, and chiral conditions). This result is a generalisation of Friedrich's
inequality for the usual Dirac operator. The limiting cases are also
investigated.


title: Software (Re-)Engineering with PSF III: an IDE for PSF

abstract:
  We describe the design of an integrated development environment (IDE) for
PSF. In the software engineering process we used process algebra in the form of
PSF for the specification of the architecture of the IDE. This specification is
refined to a PSF specification of the IDE system as a ToolBus application, by
applying vertical and horizontal implementation techniques. We implemented the
various tools as specified and connected them with a ToolBus script extracted
from the system specification.


title:
Density Fluctuations in the Oscillatory Phase of Nonclassical Inflaton
  in FRW Universe

abstract:
  Using coherent and squeezed state formalisms of quantum optics for a
minimally coupled non-classical inflaton in the FRW mertic is studied, in
semiclassical theory of gravity. The leading order solution for the
semiclassical Einstein equations in the coherent, squeezed and squeezed vacuum
states are obtained perturbatively and are exhibit powerlaw expansion
behaviour. The validity of the semiclassical theory is examined in the squeezed
vacuum state in the oscillatory phase of the inflaton. The semiclassical theory
in the oscillatory phase of the non-classical inflaton holds only if the
associated squeezing parameter is much less compared to unity. Quantum
fluctuations of the inflaton is also examined in coherent and squeezed state
formalisms.


title: Notes on Formal Deformations of Hom-associative and Hom-Lie Algebras

abstract:
  The aim of this paper is to extend to Hom-algebra structures the theory of
formal deformations of algebras which was introduced by Gerstenhaber for
associative algebras and extended to Lie algebras by Nijenhuis-Richardson. We
deal with Hom-associative and Hom-Lie algebras. We construct the first groups
of a deformation cohomology and give several examples of deformations. We
provide families of Hom-Lie algebras deforming Lie algebra $sl_2$ and describe
as formal deformations the q-deformed Witt algebra and Jackson $sl_2$.


title:
Affine symmetries of the equivariant quantum cohomology ring of rational
  homogeneous spaces

abstract:
  Let $X$ be a rational homogeneous space and let $QH^*(X)_{loc}^\times$ be the
group of invertible elements in the small quantum cohomology ring of $X$
localised in the quantum parameters. We generalise results of
arXiv:math/0609796 and realise explicitly the map $\pi_1({\rm Aut}(X))\to
QH^*(X)_{loc}^\times$ described in arXiv:dg-ga/9511011. We even prove that this
map is an embedding and realise it in the equivariant quantum cohomology ring
$QH^*_T(X)_{loc}^\times$. We give explicit formulas for the product by these
elements.
  The proof relies on a generalisation, to a quotient of the equivariant
homology ring of the affine Grassmannian, of a formula proved by Peter Magyar
arXiv:0705.3826. It also uses Peterson's unpublished result -- recently proved
by Lam and Shimozono in arXiv:0705.1386 -- on the comparison between the
equivariant homology ring of the affine Grassmannian and the equivariant
quantum cohomology ring.


title: On the electromagnetic properties of active media

abstract:
  Several results concerning active media or metamaterials are proved and
discussed. In particular, we consider the permittivity, permeability, wave
vector, and refractive index, and discuss stability, refraction, gain, and
fundamental limitations resulting from causality.


title: Molecular gas in NUclei of GAlaxies (NUGA): VIII The Seyfert 2 NGC6574

abstract:
  Within the frame of the NUclei of GAlaxies (NUGA) project, we have determined
the distribution and kinematics of the molecular gas within the central kpc
with high spatial resolution (100-150pc), for a sample of active galaxies. The
goal is to study the gas-fueling mechanisms in AGN. We present interferometric
observations of 12CO(1-0) and 12CO(2-1) line emission from the Seyfert2 galaxy
NGC6574, obtained with the IRAM Plateau de Bure Interferometer (PdBI). These
data have been combined with 30m mapping data in these lines to correct for the
flux resolved by the interferometer. At an angular resolution of 0.7'' (about
110pc), the 12CO(2-1) emission is resolved into an inner disk with a radius of
300pc.


title:
Strong Correlations and Fickian Water Diffusion in Narrow Carbon
  Nanotubes

abstract:
  We have used atomistic molecular dynamics (MD) simulations to study the
structure and dynamics of water molecules inside an open ended carbon nanotube
placed in a bath of water molecules. The size of the nanotube allows only a
single file of water molecules inside the nanotube. The water molecules inside
the nanotube show solid-like ordering at room temperature, which we quantify by
calculating the pair correlation function. It is shown that even for the
longest observation times, the mode of diffusion of the water molecules inside
the nanotube is Fickian and not sub-diffusive. We also propose a
one-dimensional random walk model for the diffusion of the water molecules
inside the nanotube. We find good agreement between the mean-square
displacements calculated from the random walk model and from MD simulations,
thereby confirming that the water molecules undergo normal-mode diffusion
inside the nanotube. We attribute this behavior to strong positional
correlations that cause all the water molecules inside the nanotube to move
collectively as a single object. The average residence time of the water
molecules inside the nanotube is shown to scale quadratically with the nanotube
length.


title: On the spectrum of lamplighter groups and percolation clusters

abstract:
  Let $G$ be a finitely generated group and $X$ its Cayley graph with respect
to a finite, symmetric generating set $S$. Furthermore, let $H$ be a finite
group and $H \wr G$ the lamplighter group (wreath product) over $G$ with group
of "lamps" $H$. We show that the spectral measure (Plancherel measure) of any
symmetric "switch--walk--switch" random walk on $H \wr G$ coincides with the
expected spectral measure (integrated density of states) of the random walk
with absorbing boundary on the cluster of the group identity for Bernoulli site
percolation on $X$ with parameter $p = 1/|H|$. The return probabilities of the
lamplighter random walk coincide with the expected (annealed) return
probabilites on the percolation cluster. In particular, if the clusters of
percolation with parameter $p$ are almost surely finite then the spectrum of
the lamplighter group is pure point. This generalizes results of Grigorchuk and
Zuk, resp. Dicks and Schick regarding the case when $G$ is infinite cyclic.
Analogous results relate bond percolation with another lamplighter random walk.
In general, the integrated density of states of site (or bond) percolation with
arbitrary parameter $p$ is always related with the Plancherel measure of a
convolution operator by a signed measure on $H \wr G$, where $H = Z$ or another
suitable group.


title:
Harnack Inequality and Strong Feller Property for Stochastic
  Fast-Diffusion Equations

abstract:
  This paper presents analogous results for stochastic fast-diffusion
equations. Since the fast-diffusion equation possesses weaker dissipativity
than the porous medium one does, some technical difficulties appear in the
study. As a compensation to the weaker dissipativity condition, a Sobolev-Nash
inequality is assumed for the underlying self-adjoint operator in applications.
Some concrete examples are constructed to illustrate the main results.


title:
Phase transition and computational complexity in a stochastic prime
  number generator

abstract:
  We introduce a prime number generator in the form of a stochastic algorithm.
The character of such algorithm gives rise to a continuous phase transition
which distinguishes a phase where the algorithm is able to reduce the whole
system of numbers into primes and a phase where the system reaches a frozen
state with low prime density. In this paper we firstly pretend to give a broad
characterization of this phase transition, both in terms of analytical and
numerical analysis. Critical exponents are calculated, and data collapse is
provided. Further on we redefine the model as a search problem, fitting it in
the hallmark of computational complexity theory. We suggest that the system
belongs to the class NP. The computational cost is maximal around the
threshold, as common in many algorithmic phase transitions, revealing the
presence of an easy-hard-easy pattern. We finally relate the nature of the
phase transition to an average-case classification of the problem.


title:
Formation and transformation of the 3:1 mean-motion resonance in 55
  Cancri System

abstract:
  We report in this paper the numerical simulations of the capture into the 3:1
mean-motion resonance between the planet b and c in the 55 Cancri system. The
results show that this resonance can be obtained by a differential planetary
migration. The moderate initial eccentricities, relatively slower migration and
suitable eccentricity damping rate increase significantly the probability of
being trapped in this resonance. Otherwise, the system crosses the 3:1
commensurability avoiding resonance capture, to be eventually captured into a
2:1 resonance or some other higher-order resonances. After the resonance
capture, the system could jump from one orbital configuration to another one if
the migration continues, making a large region of the configuration space
accessible for a resonance system. These investigations help us understand the
diversity of resonance configurations and put some constrains on the early
dynamical evolution of orbits in the extra-solar planetary systems.