title:
Intuitive understanding of non-gaussianity in ekpyrotic and cyclic
  models

abstract:
  It has been pointed out by several groups that ekpyrotic and cyclic models
generate significant non-gaussianity. In this paper, we present a physically
intuitive, semi-analytic estimate of the bispectrum. We show that, in all such
models, there is an intrinsic contribution to the non-gaussianity parameter
f_{NL} that is determined by the geometric mean of the equation of state w_{ek}
during the ekpyrotic phase and w_{c} during the phase that curvature
perturbations are generated and whose value is O(100) or more times the
intrinsic value predicted by simple slow-roll inflationary models,
f_{NL}^{intrinsic} = O(0.1). Other contributions to f_{NL}, which we also
estimate, can increase |f_{NL}| but are unlikely to decrease it significantly,
making non-gaussianity a useful test of these models. Furthermore, we discuss a
predicted correlation between the non-gaussianity and scalar spectral index
that sharpens the test.


title: Bounds for the minimum oriented diameter

abstract:
  We consider the problem of finding an orientation with minimum diameter of a
connected bridgeless graph. Fomin et. al. discovered a relation between the
minimum oriented diameter an the size of a minimal dominating set. We improve
their upper bound.


title: CMB data analysis and sparsity

abstract:
  The statistical analysis of the soon to come Planck satellite CMB data will
help set tighter bounds on major cosmological parameters. On the way, a number
of practical difficulties need to be tackled, notably that several other
astrophysical sources emit radiation in the frequency range of CMB
observations. Some level of residual contributions, most significantly in the
galactic region and at the locations of strong radio point sources will
unavoidably contaminate the estimated spherical CMB map. Masking out these
regions is common practice but the gaps in the data need proper handling. In
order to restore the stationarity of a partly incomplete CMB map and thus lower
the impact of the gaps on non-local statistical tests, we developed an
inpainting algorithm on the sphere based on a sparse representation of the
data, to fill in and interpolate across the masked regions.


title: Bounds for the minimum diameter of integral point sets

abstract:
  Geometrical objects with integral sides have attracted mathematicians for
ages. For example, the problem to prove or to disprove the existence of a
perfect box, that is, a rectangular parallelepiped with all edges, face
diagonals and space diagonals of integer lengths, remains open. More generally
an integral point set $\mathcal{P}$ is a set of $n$ points in the
$m$-dimensional Euclidean space $\mathbb{E}^m$ with pairwise integral distances
where the largest occurring distance is called its diameter. From the
combinatorial point of view there is a natural interest in the determination of
the smallest possible diameter $d(m,n)$ for given parameters $m$ and $n$. We
give some new upper bounds for the minimum diameter $d(m,n)$ and some exact
values.


title: Local Superfluidity of Parahydrogen Clusters

abstract:
  We study by Quantum Monte Carlo simulations the local superfluid response of
small (up to 27 molecules) parahydrogen clusters, down to temperatures as low
as 0.05 K. We show that at low temperature superfluidity is not confined at the
surface of the clusters, as recently claimed by Khairallah et al. [Phys. Rev.
Lett. 98, 183401 (2007)]. Rather, even clusters with a pronounced shell
structure are essentially uniformly superfluid. Superfluidity occurs as a
result of long exchange cycles involving all molecules.


title:
Valid for Much of "Realistic" Fields: A Non-Generational Conjecture For
  Deriving All First-Class Constraints at Once

abstract:
  We propose a single-step non-generational conjecture of all first class
constraints,(involving only variables compatible with canonical Poisson
brackets), for a realistic gauge singular field theory. We verify our proposal
for the free electromagnetic field, Yang-Mills fields in interaction with
spinor and scalar fields, and we also verify our proposal in the case
gravitational field. We show that the first class constraints which were
reached at using the standard Dirac's multi-generational algorithm will be
reproduced using the proposed conjecture. We make no claim that our conjecture
will be valid for all mathematically plausible Lagrangians; but, nevertheless
the examples we consider here show that this conjecture is valid for wide range
or much of realistic fields of physical interest that are know to exist and are
manifested in nature


title: Integral point sets over $\mathbb{Z}_n^m$

abstract:
  There are many papers studying properties of point sets in the Euclidean
space $\mathbb{E}^m$ or on integer grids $\mathbb{Z}^m$, with pairwise integral
or rational distances. In this article we consider the distances or coordinates
of the point sets which instead of being integers are elements of $\mathbb{Z} /
\mathbb{Z}n$, and study the properties of the resulting combinatorial
structures.


title: Universal star products

abstract:
  One defines the notion of universal deformation quantization: given any
manifold $M$, any Poisson structure $\P$ on $M$ and any torsionfree linear
connection $\nabla$ on $M$, a universal deformation quantization associates to
this data a star product on $(M,\P)$ given by a series of bidifferential
operators whose corresponding tensors are given by universal polynomial
expressions in the Poisson tensor $\P$, the curvature tensor $R$ and their
covariant iterated derivatives. Such universal deformation quantization exist.
We study their unicity at order 3 in the deformation parameter, computing the
appropriate universal Poisson cohomology.


title: Steady-State L\'evy Flights in a Confined Domain

abstract:
  We derive the generalized Fokker-Planck equation associated with a Langevin
equation driven by arbitrary additive white noise. We apply our result to study
the distribution of symmetric and asymmetric L\'{e}vy flights in an infinitely
deep potential well. The fractional Fokker-Planck equation for L\'{e}vy flights
is derived and solved analytically in the steady state. It is shown that
L\'{e}vy flights are distributed according to the beta distribution, whose
probability density becomes singular at the boundaries of the well. The origin
of the preferred concentration of flying objects near the boundaries in
nonequilibrium systems is clarified.


title: Bolasso: model consistent Lasso estimation through the bootstrap

abstract:
  We consider the least-square linear regression problem with regularization by
the l1-norm, a problem usually referred to as the Lasso. In this paper, we
present a detailed asymptotic analysis of model consistency of the Lasso. For
various decays of the regularization parameter, we compute asymptotic
equivalents of the probability of correct model selection (i.e., variable
selection). For a specific rate decay, we show that the Lasso selects all the
variables that should enter the model with probability tending to one
exponentially fast, while it selects all other variables with strictly positive
probability. We show that this property implies that if we run the Lasso for
several bootstrapped replications of a given sample, then intersecting the
supports of the Lasso bootstrap estimates leads to consistent model selection.
This novel variable selection algorithm, referred to as the Bolasso, is
compared favorably to other linear regression methods on synthetic data and
datasets from the UCI machine learning repository.


title:
There are integral heptagons, no three points on a line, no four on a
  circle

abstract:
  We give two configurations of seven points in the plane, no three points in a
line, no four points on a circle with pairwise integral distances. This answers
a famous question of Paul Erd\H{o}s.


title:
Weak approximation of stochastic partial differential equations: the non
  linear case

abstract:
  We study the error of the Euler scheme applied to a stochastic partial
differential equation. We prove that as it is often the case, the weak order of
convergence is twice the strong order. A key ingredient in our proof is
Malliavin calculus which enables us to get rid of the irregular terms of the
error. We apply our method to the case a semilinear stochastic heat equation
driven by a space-time white noise.


title: LERF and the Lubotzky-Sarnak conjecture

abstract:
  We prove that every closed hyperbolic 3-manifold has a family of (possibly
infinite sheeted) coverings with the property that the Cheeger constants in the
family tend to zero. This is used to show that, if in addition the fundamental
group of the manifold is LERF, then it satisfies the Lubotzky-Sarnak
conjecture.


title: Learning in cognitive systems with autonomous dynamics

abstract:
  The activity patterns of highly developed cognitive systems like the human
brain are dominated by autonomous dynamical processes, that is by a
self-sustained activity which would be present even in the absence of external
sensory stimuli.
  During normal operation the continuous influx of external stimuli could
therefore be completely unrelated to the patterns generated internally by the
autonomous dynamical process. Learning of spurious correlations between
external stimuli and autonomously generated internal activity states needs
therefore to be avoided.
  We study this problem within the paradigm of transient state dynamics for the
internal activity, that is for an autonomous activity characterized by a
infinite time-series of transiently stable attractor states. We propose that
external stimuli will be relevant during the sensitive periods, the transition
period between one transient state and the subsequent semi-stable attractor. A
diffusive learning signal is generated unsupervised whenever the stimulus
influences the internal dynamics qualitatively.
  For testing we have presented to the model system stimuli corresponding to
the bar-stripes problem and found it capable to perform the required
independent-component analysis on its own, all the time being continuously and
autonomously active.


title: On the minimum diameter of plane integral point sets

abstract:
  Since ancient times mathematicians consider geometrical objects with integral
side lengths. We consider plane integral point sets $\mathcal{P}$, which are
sets of $n$ points in the plane with pairwise integral distances where not all
the points are collinear.
  The largest occurring distance is called its diameter. Naturally the question
about the minimum possible diameter $d(2,n)$ of a plane integral point set
consisting of $n$ points arises. We give some new exact values and describe
state-of-the-art algorithms to obtain them. It turns out that plane integral
point sets with minimum diameter consist very likely of subsets with many
collinear points. For this special kind of point sets we prove a lower bound
for $d(2,n)$ achieving the known upper bound $n^{c_2\log\log n}$ up to a
constant in the exponent.
  A famous question of Erd\H{o}s asks for plane integral point sets with no 3
points on a line and no 4 points on a circle. Here, we talk of point sets in
general position and denote the corresponding minimum diameter by
$\dot{d}(2,n)$. Recently $\dot{d}(2,7)=22 270$ could be determined via an
exhaustive search.


title:
Transverse nonlinear instability of solitary waves for some Hamiltonian
  PDE's

abstract:
  We present a general result of transverse nonlinear instability of 1-d
solitary waves for Hamiltonian PDE's for both periodic or localized transverse
perturbations. Our main structural assumption is that the linear part of the 1d
model and the transverse perturbation "have the same sign". Our result applies
to the generalized KP-I equation, the Nonlinear Schr\"odinger equation, the
generalized Boussinesq system and the Zakharov-Kuznetsov equation and we hope
that it may be useful in other contexts.


title: Surface subgroups of Kleinian groups with torsion

abstract:
  We prove that every finitely generated Kleinian group that contains a finite,
non-cyclic subgroup either is finite or virtually free or contains a surface
subgroup. Hence, every arithmetic Kleinian group contains a surface subgroup.


title: Enumeration of integral tetrahedra

abstract:
  We determine the numbers of integral tetrahedra with diameter $d$ up to
isomorphism for all $d\le 1000$ via computer enumeration. Therefore we give an
algorithm that enumerates the integral tetrahedra with diameter at most $d$ in
$O(d^5)$ time and an algorithm that can check the canonicity of a given
integral tetrahedron with at most 6 integer comparisons. For the number of
isomorphism classes of integral $4\times 4$ matrices with diameter $d$
fulfilling the triangle inequalities we derive an exact formula.


title: Neutrino masses from the GSI anomaly

abstract:
  We investigate the influence of the strong Coulomb field of a heavy nucleus
on massive neutrinos, produced in the K-shell electron capture (EC) decays of
the H-like 140Pr58+ and 142Pm60+ ions. The corrections to the neutrino masses
due to virtually produced charged lepton W-boson pairs in the strong Coulomb
field of a nucleus with charge Ze are calculated and discussed with respect to
their influence on the period of the time-modulation of the number of daughter
ions, observed recently in the EC-decays of the H-like 140Pr58+ and 142Pm60+
ions at GSI in Darmstadt. These corrections explain the 2.9 times higher
difference of the squared neutrino masses obtained from the time-modulation of
the EC-decays with respect to the value deduced from the
antineutrino-oscillation experiments of KamLAND.


title:
Microscopic Work Distribution of Small System in Quantum Isothermal
  Process

abstract:
  For a two-level quantum mechanical system, we derive microscopically the
exact expression for the fluctuation of microscopic work in a multi-step
non-equilibrium process, and we rigorously prove that in an isothermal process,
the fluctuation is vanishingly small, and the most probabilistic work just
equals to the difference of the free energy. Our study demonstrates that the
convergence of the microscopic work in the isothermal process is due to the
nature of isothermal process rather than usual thermodynamic limit condition.
Our investigation justifies the validity of "minimum work principle"
formulation of the second law even for a small system far from thermodynamic
limit.


title: Tilting modules arising from ring epimorphisms

abstract:
  Given a ring R, we investigate tilting modules of the form S \oplus S/R for
some injective ring epimorphism R \to S. In particular, we are interested in
tilting modules arising from Schofield's universal localization. For some
rings, in this way one obtains a classification of all tilting modules.


title: Milky Way Mass Models and MOND

abstract:
  Using the Tuorla-Heidelberg model for the mass distribution of the Milky Way,
I determine the rotation curve predicted by MOND. The result is in good
agreement with the observed terminal velocities interior to the solar radius
and with estimates of the Galaxy's rotation curve exterior thereto. There are
no fit parameters: given the mass distribution, MOND provides a good match to
the rotation curve. The Tuorla-Heidelberg model does allow for a variety of
exponential scale lengths; MOND prefers short scale lengths in the range 2.0 to
2.5 kpc. The favored value of scale length depends somewhat on the choice of
interpolation function. There is some preference for the `simple' interpolation
function as found by Famaey & Binney. I introduce an interpolation function
that shares the advantages of the simple function on galaxy scales while having
a much smaller impact in the solar system. I also solve the inverse problem,
inferring the surface mass density distribution of the Milky Way from the
terminal velocities. The result is a Galaxy with `bumps and wiggles' in both
its luminosity profile and rotation curve that are reminiscent of those
frequently observed in external galaxies.


title: The six-photon amplitude

abstract:
  Thanks to the absence of tree order, the six-photon processes is a good
laboratory to study multi-leg one-loop diagrams. Particularly, there are enough
on-shell external legs to observe a special Landau singularity: the double
parton scattering.


title: Plurisubharmonicity in a General Geometric Context

abstract:
  Recently the authors have explored new concepts of plurisubharmonicity and
pseudoconvexity, with much of the attendant analysis, in the context of
calibrated manifolds. Here a much broader extension is made. This development
covers a wide variety of geometric situations, including, for example,
Lagrangian plurisubhamonicity and convexity. It also applies in a number of
non-geometric situations. Results include: fundamental properties of
$P^+$-plurisubharmonic functions, plurisubharmonic distributions and
regularity, $P^+$-convex domains and $P^+$-convex boundaries, topological
restrictions on and construction of such domains, continuity of upper
envelopes, and solutions of the Dirichlet problem for related Monge-Ampere-type
equations.
  Many results in this paper have been generalized in recent work of the
authors. However, this article covers many cases of geometric interest, and
certain convexity assumptions here allow the use of classical analytic methods,
making the exposition more accessible.


title: Error analysis in unconditionally stable coarsening algorithms

abstract:
  In order to quantitatively study the accuracy of the unconditionally stable
coarsening algorithms, we calculate the Fourier space multi step error on the
order parameter field by explicitly distinguishing the analytic time $\tau$ and
the algorithmic time $t$. The calculation determines the error in the order
parameter and the scaled correlations. This error contributes a correction term
in the analytic time step, which is crucial in understanding the accuracy in
unconditionally stable coarsening algorithms.


title:
Magneto-thermal evidence of a partial gap at the Fermi surface of
  UPt_2Si_2

abstract:
  Motivated by the observation of a giant Nernst effect in URu_2Si_2, the
thermoelectric response of the related system UPt_2Si_2 was investigated using
thermal and electric transport properties such as the Nernst and Seebeck
effects, thermal conductivity, Hall effect and electrical resitivity. Unlike
URu_2Si_2, UPt_2Si_2 is neither superconducting nor exhibits a ``hidden-order''
state. Nevertheless a pronounced Nernst effect anomaly is found to coincide
with the onset of the antiferromagnetic order in UPt_2Si_2. Although the
absolute values are substantially lower, its appearance and characteristics can
favorably be compared to the giant Nernst effect in URu_2Si_2 indicating the
common feature of a partial Fermi surface gap.


title:
Fully Symmetrized VB Based Technique for Solving Exchange Hamiltonians
  of Molecular Magnets

abstract:
  Generally, the first step in modeling molecular magnets involves obtaining
the low-lying eigenstates of a Heisenberg exchange Hamiltonian which conserves
total spin and belongs usually to a non-Abelian point group. In quantum
chemistry, it has been a long standing problem to target a state which has
definite total spin and also belongs to a definite irreducible representation
of the point group. Many attempts have been made over years, but unfortunately
these have not resulted in methods that are easy to implement, or even
applicable to all point groups. Here we present a general technique which is a
hybrid method based on VB basis and constant Ms basis, which is applicable to
all types of point groups, easy to implement on computer. We illustrate the
power of the method by applying it to the molecular magnetic system, Cu6Fe8,
with cubic symmetry. We emphasize that our method is applicable to spin
clusters with arbitrary site spins and is easily extended to Fermionic systems.


title: Stability estimates in stationary inverse transport

abstract:
  We study the stability of the reconstruction of the scattering and absorption
coefficients in a stationary linear transport equation from knowledge of the
full albedo operator in dimension $n\geq3$. The albedo operator is defined as
the mapping from the incoming boundary conditions to the outgoing transport
solution at the boundary of a compact and convex domain. The uniqueness of the
reconstruction was proved in [M. Choulli-P. Stefanov, 1996 and 1999] and
partial stability estimates were obtained in [J.-N. Wang, 1999] for spatially
independent scattering coefficients. We generalize these results and prove an
$L^1$-stability estimate for spatially dependent scattering coefficients.


title:
High resolution spectroscopy for Cepheids distance determination. I.
  Line asymmetry

abstract:
  The ratio of pulsation to radial velocity (the projection factor) is
currently limiting the accuracy of the interferometric Baade-Wesselink method.
This work aims at establishing a link between the line asymmetry evolution over
the Cepheids' pulsation cycles and their projection factor, with the final
objective to improve the accuracy of the Baade-Wesselink method for distance
determinations. We present HARPS high spectral resolution observations of nine
galactic Cepheids having a good period sampling. We fit spectral line profiles
by an asymmetric bi-Gaussian to derive radial velocity, Full-Width at
Half-Maximum in the line (FWHM) and line asymmetry for all stars. We then
extract correlations curves between radial velocity and asymmetry. A geometric
model providing synthetic spectral lines, including limb-darkening, a constant
FWHM (hereafter sigma_c) and the rotation velocity is used to interpret these
correlations curves. For all stars, comparison between observations and
modelling is satisfactory, and we were able to determine the projected rotation
velocities and sigma_c for all stars. We also find a correlation between the
rotation velocity (Vrot sin i) and the period of the star: Vrot sin i = (11.5
+- 0.9) log(P) + (19.8 +- 1.0) [km/s]. Moreover, we observe a systematic shift
in observational asymmetry curves (noted gamma_O), related to the period of the
star, which is not explained by our static model: gamma_O = (10.7+-0.1) log(P)
+ (9.7+-0.2) [in %] . For long-period Cepheids, in which velocity gradients,
compression or shock waves seem to be large compared to short- or medium period
Cepheids we observe indeed a greater systematic shift in asymmetry curves.
(abridged)


title:
Current conservation, screening and the magnetic moment of the $\Delta$
  resonance. -- 1. Formulation without quark degrees of freedom

abstract:
  The pion-nucleon bremsstrahlung $\pi+N\Longrightarrow\gamma'+\pi'+N'$ is
studied in a new form of current conservation. According to this condition, the
internal and external particle radiation parts of the $\pi N$ radiation
amplitude have opposite signs, i.e., they contain terms which must cancel each
other.
  Therefore, one has a screening of the internal and external particle
radiation in the $\pi N$ bremsstrahlung. In particular, it is shown that the
double $\Delta$ exchange diagram with the $\Delta-\gamma' \Delta'$ vertex
cancel against the appropriate longitudinal part of the external particle
radiation diagrams. Consequently, a model independent relation between the
magnetic dipole moments of the $\Delta^+$ and $\Delta^{++}$ resonances and the
anomalous magnetic moment of the proton $\mu_p$ is obtained, where
$\mu_{\Delta}$ is expressed by $\mu_p$ as $\mu_{\Delta^+}={{M_{\Delta}}\over
{m_p}} \mu_p$ and $\mu_{\Delta^{++}}={3\over 2}\mu_{\Delta^+}$ in agreement
with the values extracted from the fit for the experimental cross section of
the $\pi^+ p\to\gamma'\pi^+ p$ reaction.


title:
Non-thermal emission from relativistic MHD simulations of PWNe: from
  synchrotron to inverse Compton

abstract:
  In this paper we complete the set of diagnostic tools for synchrotron
emitting sources presented by Del Zanna et al. (Astron. Astrophys. 453, 621,
2006) with the computation of inverse Compton radiation from the same
relativistic particles. Moreover we investigate, for the first time, the
gamma-ray emission properties of Pulsar Wind Nebulae in the light of the
axisymmetric jet-torus scenario. The method consists in evolving the
relativistic MHD equations and the maximum energy of the emitting particles.
The particle energy distribution function is split in two components: the radio
one connected to a relic population born at the outburst of the supernova and
the other associated to the wind population continuously accelerated at the
termination shock and emitting up to the gamma-ray band. We consider the
general Klein-Nishina cross section and three different photon targets: the
nebular synchrotron photons, far-infrared thermal ones and the cosmic microwave
background. The overall synchrotron spectrum is fitted assuming an excess of
injected particles and a steeper power law with respect to previous models. The
TeV emission has the correct shape but is in excess of the data. This is due to
the nebular magnetic field structure as obtained by the simulations. The
jet-torus morphology is visible in high-resolution gamma-ray synthetic maps
too. We present a preliminary exploration of time variability in the X and
gamma-ray bands.


title:
Nernst effect of the new iron-based superconductor
  LaO$_{1-x}$F$_{x}$FeAs

abstract:
  We report the first Nernst effect measurement on the new iron-based
superconductor LaO$_{1-x}$F$_{x}$FeAs $(x=0.1)$. In the normal state, the
Nernst signal is negative and very small. Below $T_{c}$ a large positive peak
caused by vortex motion is observed. The flux flowing regime is quite large
compared to conventional type-II superconductors. However, a clear deviation of
the Nernst signal from normal state background and an anomalous depression of
off-diagonal thermoelectric current in the normal state between $T_{c}$ and 50
K are observed. We propose that this anomaly in the normal state Nernst effect
could correlate with the SDW fluctuations.


title:
On the underestimation of model uncertainty by Bayesian K-nearest
  neighbors

abstract:
  When using the K-nearest neighbors method, one often ignores uncertainty in
the choice of K. To account for such uncertainty, Holmes and Adams (2002)
proposed a Bayesian framework for K-nearest neighbors (KNN). Their Bayesian KNN
(BKNN) approach uses a pseudo-likelihood function, and standard Markov chain
Monte Carlo (MCMC) techniques to draw posterior samples. Holmes and Adams
(2002) focused on the performance of BKNN in terms of misclassification error
but did not assess its ability to quantify uncertainty. We present some
evidence to show that BKNN still significantly underestimates model
uncertainty.


title: Holographic Monopole Catalysis of Baryon Decay

abstract:
  We study how monopole catalysis of baryon decay is realized in holographic
QCD. Physics of monopole catalysis becomes much simpler in holographic
description as it occurs due to the violation of the Bianchi identity for the
5D gauge symmetry when magnetic monopole is present. In holographic QCD we find
a unified picture of the baryon number violation under magnetic monopole or
electroweak sphaleron, giving a new mechanism of baryon number violation. We
also embed our set-up in the string theory model by Sakai and Sugimoto.


title: Asymptotic behavior of growth functions of D0L-systems

abstract:
  A D0L-system is a triple (A, f, w) where A is a finite alphabet, f is an
endomorphism of the free monoid over A, and w is a word over A. The
D0L-sequence generated by (A, f, w) is the sequence of words (w, f(w), f(f(w)),
f(f(f(w))), ...). The corresponding sequence of lengths, that is the function
mapping each non-negative integer n to |f^n(w)|, is called the growth function
of (A, f, w). In 1978, Salomaa and Soittola deduced the following result from
their thorough study of the theory of rational power series: if the
D0L-sequence generated by (A, f, w) is not eventually the empty word then there
exist a non-negative integer d and a real number b greater than or equal to one
such that |f^n(w)| behaves like n^d b^n as n tends to infinity. The aim of the
present paper is to present a short, direct, elementary proof of this theorem.


title: Quantum Cosmology and Tachyons

abstract:
  We discuss the relevance of the classical and quantum rolling tachyons
inflation in the frame of the standard, p-adic and adelic minisuperspace
quantum cosmology. The field theory of tachyon matter proposed by Sen in a
zero-dimensional version suggested by Kar leads to a model of a particle moving
in a constant external field with quadratic damping. We calculate the exact
quantum propagator of the model, as well as, the vacuum states and conditions
necessary to construct an adelic generalization.


title: Planar Graphs On The World Sheet: The Hamiltonian Approach

abstract:
  The present work continues the program of summing planar Feynman graphs on
the world sheet. Although it is based on the same classical action introduced
in the earlier work, there are important new features: Instead of the path
integral used in the earlier work, the model is quantized using the canonical
algebra and the Hamiltonian picture. The new approach has an important
advantage over the old one: The ultraviolet divergence that plagued the earlier
work is absent. Using a family of projection operators, we are able to give an
exact representation on the world sheet of the planar graphs of both the phi^3
theory, on which most of the previous work was based, and also of the phi^4
theory. We then apply the mean field approximation to determine the structure
of the ground state. In agreement with the earlier work, we find that the
graphs of phi^3 theory form a dense network (condensate) on the world sheet. In
the case of the phi^4 theory, graphs condense for the unphysical (attractive)
sign of the coupling, whereas there is no condensation for the physical
(repulsive) sign.


title:
High resolution spectroscopy for Cepheids distance determination. II. A
  period- projection factor relation

abstract:
  The projection factor is a key quantity for the interferometric
Baade-Wesselink (hereafter IBW) and surface-brightness (hereafter SB) methods
of determining the distance of Cepheids. Indeed, it allows a consistent
combination of angular and linear diameters of the star. We aim to determine
consistent projection factors that include the dynamical structure of the
Cepheids' atmosphere. Methods. Hydrodynamical models of delta Cep and l Car
have been used to validate a spectroscopic method of determining the projection
factor. This method, based on the amplitude of the radial velocity curve, is
applied to eight stars observed with the HARPS spectrometer. The projection
factor is divided into three sub-concepts : (1) a geometrical effect, (2) the
velocity gradient within the atmosphere, and (3) the relative motion of the
"optical" pulsating photosphere compared to the corresponding mass elements
(hereafter fo-g). Both, (1) and (3) are deduced from geometrical and
hydrodynamical models, respectively, while (2) is derived directly from
observations. The Fe I 4896.439 A line is found to be the best one to use in
the context of IBW and SB methods. A coherent and consistent period-projection
factor relation (hereafter Pp relation) is derived for this specific spectral
line: p = [0.064 +- 0.020] log P + [1.376 +- 0.023]. This procedure is then
extended to derive dynamic projection factors for any spectral line of any
Cepheid. This Pp relation is an important tool for removing bias in the
calibration of the period-luminosity relation of Cepheids. Moreover, it reveals
a new physical quantity fo-g to investigate in the near future.


title:
High resolution spectroscopy for Cepheids distance determination. III. A
  relation between gamma-velocities and gamma-asymmetries

abstract:
  Galactic Cepheids in the vicinity of the Sun have a residual line-of-sight
velocity, or gamma-velocity, which shows a systematic blueshift of about 2 km/s
compared to an axisymmetric rotation model of the Milky Way. This term is
either related to the space motion of the star and, consequently, to the
kinematic structure of our Galaxy, or it is the result of the dynamical
structure of the Cepheids' atmosphere. We aim to show that these residual
gamma-velocities are an intrinsic property of Cepheids. We observed nine
galactic Cepheids with the HARPS spectroscope, focusing specifically on 17
spectral lines. For each spectral line of each star, we computed the
gamma-velocity (resp. gamma-asymmetry) as an average value of the interpolated
radial velocity (resp. line asymmetry) curve. For each Cepheid in our sample, a
linear relation is found between the gamma-velocities of the various spectral
lines and their corresponding gamma-asymmetries, showing that residual
gamma-velocities stem from the intrinsic properties of Cepheids. We also
provide a physical reference to the stellar gamma-velocity: it should be zero
when the gamma-asymmetry is zero. Following this definition, we provide very
precise and physically calibrated estimates of the gamma-velocities for all
stars of our sample. To understand this very subtle gamma-asymmetry effect,
further numerical studies are needed. Cepheids' atmosphere are strongly
affected by pulsational dynamics, convective flows, nonlinear physics, and
complex radiative transport. Hence, all of these effects have to be
incorporated simultaneously and consistently into the numerical models to
reproduce the observed line profiles in detail.


title: Order in 2D nodal superconductors

abstract:
  A topological theory of d-wave superconductors is derived in this thesis.
Ginzburg-Landau theory describes superconductivity by defining a complex order
parameter and applying Landau's theory for phase transitions. However, there is
no local, gauge invariant order parameter for a superconductor and classical
order is no appropriate description. Topological order has proven to be a
powerful tool for describing the Quantum Hall effect and it gives also an
appropriate description of s-wave superconductors. For d-wave superconductors
there are gapless excitations at four points on the Fermi surface. The
topological theory for superconductors exhibits a similar structure for the
ground state as found in the s-wave case. However, the gapless excitations
destroy the topological degeneracy of the ground state and introduce an
additional degeneracy in one of the flux sectors. In search for regularities
which reflect the topological order, I include a magnetic point impurity and
focus on the effects it has on the Casimir energy. Indeed, it is shown that the
energy shift reflects the topology to some extend. However, this is work in
progress and further computations will be done.


title: Packing index of subsets in Polish groups

abstract:
  For a subset $A$ of a Polish group $G$, we study the (almost) packing index
$\ind_P(A)$ (resp. $\Ind_P(A)$) of $A$, equal to the supremum of cardinalities
$|S|$ of subsets $S\subset G$ such that the family of shifts $\{xA\}_{x\in S}$
is (almost) disjoint (in the sense that $|xA\cap yA|<|A|$ for any distinct
points $x,y\in S$). Subsets $A\subset G$ with small (almost) packing index are
small in a geometric sense. We show that $\ind_P(A)\in \IN\cup\{\aleph_0,\cc\}$
for any $\sigma$-compact subset $A$ of a Polish group. If $A\subset G$ is
Borel, then the packing indices $\ind_P(A)$ and $\Ind_P(A)$ cannot take values
in the half-interval $[\sq(\Pi^1_1),\cc)$ where $\sq(\Pi^1_1)$ is a certain
uncountable cardinal that is smaller than $\cc$ in some models of ZFC. In each
non-discrete Polish Abelian group $G$ we construct two closed subsets
$A,B\subset G$ with $\ind_P(A)=\ind_P(B)=\cc$ and $\Ind_P(A\cup B)=1$ and then
apply this result to show that $G$ contains a nowhere dense Haar null subset
$C\subset G$ with $\ind_P(C)=\Ind_P(C)=\kappa$ for any given cardinal number
$\kappa\in[4,\cc]$.


title: A cosmological AMR MHD module for Enzo

abstract:
  Magnetic fields play an important role in almost all astrophysical phenomena
including star formation. But due to the difficulty in analytic modeling and
observation, magnetic fields are still poorly studied and numerical simulation
has become a major tool. We have implemented a cosmological
magnetohydrodynamics package for Enzo which is an AMR hydrodynamics code
designed to simulate structure formation. We use the TVD solver developed by S.
Li as the base solver. In addition, we employ the constrained transport(CT)
algorithm as described by D. Balsara. For interpolation magnetic fields to fine
grids we used a divergence free quadratic reconstruction, also described by
Balsara. We present results from several test problems including MHD caustics,
MHD pancake and galaxy cluster formation with magnetic fields. We also discuss
possible applications of our AMR MHD code to first star research.


title: Symmetric monochromatic subsets in colorings of the Lobachevsky plane

abstract:
  We prove that for each partition of the Lobachevsky plane into finitely many
Borel pieces one of the cells of the partition contains an unbounded centrally
symmetric subset.


title:
Piezo-control of magnetic anisotropy in GaMnAs: Reversible manipulation
  of magnetization orientation and irreversible magnetization switching

abstract:
  We have investigated the magnetic properties of a piezoelectric
actuator/ferromagnetic semiconductor hybrid structure. Using a GaMnAs epilayer
as the ferromagnetic semiconductor and applying the piezo-stress along its
[110] direction, we quantify the magnetic anisotropy as a function of the
voltage V_p applied to the piezoelectric actuator using anisotropic
magnetoresistance techniques. We find that the easy axis of the strain-induced
uniaxial magnetic anisotropy contribution can be inverted from the [110] to the
[1-10] direction via the application of appropriate voltages V_p. At T=5K the
magnetoelastic term is a minor contribution to the magnetic anisotropy.
Nevertheless, we show that the switching fields of rho(H) loops are shifted as
a function of V_p at this temperature. At 50K - where the magnetoelastic term
dominates the magnetic anisotropy - we are able to tune the magnetization
orientation by about 70 degree solely by means of the electrical voltage V_p
applied. Furthermore, we derive the magnetostrictive constant lambda_111 as a
function of temperature and find values consistent with earlier results. We
argue that the piezo-voltage control of magnetization orientation is directly
transferable to other ferromagnetic/piezoelectric hybrid structures, paving the
way to innovative multifunctional device concepts. As an example, we
demonstrate piezo-voltage induced irreversible magnetization switching at
T=40K, which constitutes the basic principle of a nonvolatile memory element.


title:
Coupled radio and X-ray emission and evidence for discrete ejecta in the
  jets of SS 433

abstract:
  We present five epochs of simultaneous radio (VLA) and X-ray (Chandra)
observations of SS 433, to study the relation between the radio and X-ray
emission in the arcsecond-scale jets of the source. We detected X-ray emission
from the extended jets in only one of the five epochs of observation,
indicating that the X-ray reheating mechanism is transient. The reheating does
not correlate with the total flux in the core or in the extended radio jets.
However, the radio emission in the X-ray reheating regions is enhanced when
X-ray emission is present. Deep images of the jets in linear polarization show
that outside of the core, the magnetic field in the jets is aligned parallel to
the local velocity vector, strengthening the case for the jets to be composed
of discrete bullets rather than being continuous flux tubes. We also observed
anomalous regions of polarized emission well away from the kinematic trace,
confirming the large-scale anisotropy of the magnetic field in the ambient
medium surrounding the jets.


title: Parity realization in Vector-like theories from Fermion Bilinears

abstract:
  We reconsider in this paper the old aim of trying to understand if the
observed realization of discrete symmetries as Parity or CP in the QCD vacuum
can be satisfied from first principles. We show how under the appropriate
assumptions implicitely done by Vafa and Witten in their old paper on parity
realization in vector-like theories, all parity and CP odd operators
constructed from fermion bilinears of the form $\bar\psi\tilde O\psi$ should
take a vanishing vacuum expectation value in a vector-like theory with N
degenerate flavours (N>1). In our analysis the Vafa-Witten theorem on the
impossibility to break spontaneously the flavour symmetry in a vector-like
theory plays a fundamental role.


title: The expansion for the overlap function

abstract:
  In this work, it is proved the complete expansion for the second moment of
the overlap function for the Sherrington-Kirkpatrick model. It is a technical
result which takes advantage of the cavity method and other induction
arguments.


title: A little noticed right triangle

abstract:
  Given a right triangle ABC, with the ninety degree angle at A; consider the
triangle O1OO2.Where the point O is the midpoint of the hypotenuseBC(and so the
center of the triangle ABC's circumcircle), the point O1 being the triangle
AOB's circumcenter, and the point O2 being the triangle AOC circumcenter. The
triangle O1OO2 is actually a right triangle similar to ABC. In the early part
of this work, some geometrical formulas are derived, including some lengths of
segments from a nearby trapezoid. After that, the focus changes. We examine the
case when ABC is a Pythagorean triangle, and find the precise conditions under
which the triangle O1OO2 is also Pythagorean. A numerical table of values is
also offered at the end of the paper.


title: Quantum String Liquid State in LaOFeAs and Superconductivity

abstract:
  Superconducting LaOFeAs family of even electron metallic systems have
striking resemblance to odd electron cuprates. We suggest that this resemblance
is caused by presence of two coupled 2D resonating valence bond systems in
LaOFeAs . Bond charge repulsion and Hund coupling fuse the 2 species of valence
bonds into closed strings with a Haldane gap, resulting in a quantum string
liquid. A pair of doped holes (electrons) creates an open string and remain at
the ends as holon(doublon). Charge -2e spin singlet strings condense to produce
high Tc superconductivity. Higher Tc's are likely in our string route to High
Tc superconductivity, when competing orders are taken care of.


title:
Ising spin glass under continuous-distribution random magnetic fields:
  Tricritical points and instability lines

abstract:
  The effects of random magnetic fields are considered in an Ising spin-glass
model defined in the limit of infinite-range interactions. The probability
distribution for the random magnetic fields is a double Gaussian, which
consists of two Gaussian distributions centered respectively, at $+H_{0}$ and
$-H_{0}$, presenting the same width $\sigma$. It is argued that such a
distribution is more appropriate for a theoretical description of real systems
than its simpler particular two well-known limits, namely the single Gaussian
distribution ($\sigma \gg H_{0}$), and the bimodal one ($\sigma = 0$). The
model is investigated by means of the replica method, and phase diagrams are
obtained within the replica-symmetric solution. Critical frontiers exhibiting
tricritical points occur for different values of $\sigma$, with the possibility
of two tricritical points along the same critical frontier. To our knowledge,
it is the first time that such a behavior is verified for a spin-glass model in
the presence of a continuous-distribution random field, which represents a
typical situation of a real system. The stability of the replica-symmetric
solution is analyzed, and the usual Almeida-Thouless instability is verified
for low temperatures. It is verified that, the higher-temperature tricritical
point always appears in the region of stability of the replica-symmetric
solution; a condition involving the parameters $H_{0}$ and $\sigma$, for the
occurrence of this tricritical point only, is obtained analytically. Some of
our results are discussed in view of experimental measurements available in the
literature.


title: On the exact solution of the accelerating string in $AdS_5$ space

abstract:
  In this letter, the exact accelerating string solution of a heavy
quark-antiquark pair is found in $AdS_5$ space. On the accelerating string,
there is a particular scale which separates the radiation and the heavy quark.
This scale is explicitly shown to be an event horizon in the proper frame of
the heavy quark. Furthermore, we find a new correspondence, which relates the
horizon in $AdS_5$ space on the gravity theory side to the Unruh temperature in
Minkowski space on the field theory side of the AdS/CFT correspondence.
$p_{\perp}$-broadening and $p_{L}$-broadening of the heavy quark due to
radiation are computed using the AdS/CFT correspondence.


title: Groebner-Shirshov Bases: Some New Results

abstract:
  In this survey article, we report some new results of Groebner-Shirshov
bases, including new Composition-Diamond lemmas, applications of some known
Composition-Diamond lemmas and content of some expository papers.


title:
Long-time stability of large-amplitude noncharacteristic boundary layers
  for hyperbolic--parabolic systems

abstract:
  Extending investigations of Yarahmadian and Zumbrun in the strictly parabolic
case, we study time-asymptotic stability of arbitrary (possibly large)
amplitude noncharacteristic boundary layers of a class of hyperbolic-parabolic
systems including the Navier--Stokes equations of compressible gas- and
magnetohydrodynamics, establishing that linear and nonlinear stability are both
equivalent to an Evans function, or generalized spectral stability, condition.
The latter is readily checkable numerically, and analytically verifiable in
certain favorable cases; in particular, it has been shown by Costanzino,
Humpherys, Nguyen, and Zumbrun to hold for sufficiently large-amplitude layers
for isentropic ideal gas dynamics, with general adiabiatic index $\gamma \ge
1$. Together with these previous results, our results thus give nonlinear
stability of large-amplitude isentropic boundary layers, the first such result
for compressive (``shock-type'') layers in other than the nearly-constant case.
The analysis, as in the strictly parabolic case, proceeds by derivation of
detailed pointwise Green function bounds, with substantial new technical
difficulties associated with the more singular, hyperbolic behavior in the
high-frequency/short time regime.


title:
On the phenomenon of emergent spacetimes: An instruction guide for
  experimental cosmology

abstract:
  We present a toy model where spacetime is emergent from a more fundamental
microscopic system, and investigate the gray area interpolating between the
collective and free-particle regimes. For a period of rapid exponential growth
in the analogue universe, we argue that the intermediate regime is best
described by a coloured potpourri of geometries -- a "rainbow geometry". This
can be viewed as an alternative approach towards understanding quantum field
theories in the presence of Lorentz-symmetry breaking at ultraviolet scales.
Firstly, it is pointed out that cosmological particle production in our
emergent FRW-type analogue universe, when compared to conventional
semi-classical quantum gravity, is only temporarily robust against
model-specific deviations from Lorentz invariance. Secondly, it is possible to
carry out a straightforward quantitative analysis to estimate a suitable
parameter regime for experimental (analogue) cosmology.


title:
Conformation of single-stranded RNA in a virus capsid: implications of
  dimensional reduction

abstract:
  The statistical mechanics of a treelike polymer in a confining volume is
relevant to the packaging of the genome in RNA viruses. Making use of the
mapping of the grand partition function of this system onto the statistical
mechanics of a hard-core gas in two fewer spatial dimensions and of techniques
developed for the evaluation of the equilibrium properties of a one-dimensional
hard rod gas, we show how it is possible to determine the density and other key
properties of a collection of rooted excluded-volume tress confined between two
walls, both in the absence and in the presence of a one-dimensional external
potential. We find, somewhat surprisingly, that in the case of key quantities,
the statistical mechanics of the excluded volume, randomly branched polymer map
exactly into corresponding problems for an unrestricted linear polymer.


title:
GALEX, Optical and IR Light Curves of MQ Dra: UV Excesses at Low
  Accretion Rates

abstract:
  Ultraviolet light curves constructed from NUV and FUV detectors on GALEX
reveal large amplitude variations during the orbital period of the Low
Accretion Rate Polar MQ Dra (SDSSJ1553+55). This unexpected variation from a UV
source is similar to that seen and discussed in the Polar EF Eri during its low
state of accretion, even though the accretion rate in MQ Dra is an order of
magnitude lower than even the low state of EF Eri. The similarity in phasing of
the UV and optical light curves in MQ Dra imply a similar location for the
source of light. We explore the possibilities of hot spots and cyclotron
emission with simple models fit to the UV, optical and IR light curves of MQ
Dra. To match the GALEX light curves with a single temperature circular hot
spot requires different sizes of spots for the NUV and FUV, while a cyclotron
model that can produce the optical harmonics with a magnetic field near 60 MG
requires multipoles with fields > 200 MG to match the UV fluxes.


title:
Time delay for dispersive systems in quantum scattering theory. I. The
  Friedrichs model

abstract:
  We present a method for proving the existence of time delay (defined in terms
of sojourn times) as well as its identity with Eisenbud-Wigner time delay in
the case of the Friedrichs model. We show that this method applies to
scattering by finite rank potentials.


title:
Splitting the spectral flow and the SU(3) Casson invariant for spliced
  sums

abstract:
  We show that the SU(3) Casson invariant for spliced sums along certain torus
knots equals 16 times the product of their SU(2) Casson knot invariants. The
key step is a splitting formula for su(n) spectral flow for closed 3-manifolds
split along a torus.


title:
Band Alignment in Molecular Devices: Influence of Anchoring Group and
  Metal Work Function

abstract:
  We present periodic Density Functional Theory calculations of the electronic
properties of molecular junctions formed by amine-, and thiol-terminated alkane
chains attached to two metal (Au, Ag) electrodes. Based on extensive analysis
that includes molecular monolayers of varying densities, we establish a
relationship between the alignment of the molecular energy levels and the
interface dipoles, which shows that the band alignment (BA) in the limit of
long, isolated chains is independent of the link group and can be computed from
a reference system of non interacting molecule + metal electrodes. The main
difference between the amine and thiol linkers is the effective dipole moment
at the contact. This is very large, about 4.5 D, for amine linkers, leading to
a strong dependence of the BA on the monolayer density and a slow convergence
to the isolated molecule limit. Instead, this convergence is fast for S anchors
due to the very small, ~ 0.2 D, effective dipoles at the contacts.


title: Probing the symmetry energy from the nuclear isoscaling

abstract:
  Using different parameterizations of the nuclear mass formula, we study the
sensitivity of the isoscaling parameters to the mass formula employed in
grand-canonical calculations. Previous works on isoscaling have suggested that
the symmetry energy implied in such calculations is anomalously smaller than
that suggested by fits to nuclear masses. We show that surface corrections to
the symmetry energy naturally broadens the isotopic distribution thus allowing
for values of the symmetry energy which more closely match those obtained from
nuclear masses.


title: Spherical Accretion with Anisotropic Thermal Conduction

abstract:
  We study the effects of anisotropic thermal conduction on magnetized
spherical accretion flows using global axisymmetric MHD simulations. In low
collisionality plasmas, the Bondi spherical accretion solution is unstable to
the magnetothermal instability (MTI). The MTI grows rapidly at large radii
where the inflow is subsonic. For a weak initial field, the MTI saturates by
creating a primarily radial magnetic field, i.e., by aligning the field lines
with the background temperature gradient. The saturation is quasilinear in the
sense that the magnetic field is amplified by a factor of $\sim 10-30$
independent of the initial field strength (for weak fields). In the saturated
state, the conductive heat flux is much larger than the convective heat flux,
and is comparable to the field-free (Spitzer) value (since the field lines are
largely radial). The MTI by itself does not appreciably change the accretion
rate $\dot M$ relative to the Bondi rate $\dot M_B$. However, the radial field
lines created by the MTI are amplified by flux freezing as the plasma flows in
to small radii. Oppositely directed field lines are brought together by the
converging inflow, leading to significant resistive heating. When the magnetic
energy density is comparable to the gravitational potential energy density, the
plasma is heated to roughly the virial temperature; the mean inflow is highly
subsonic; most of the energy released by accretion is transported to large
radii by thermal conduction; and the accretion rate $\dot M \ll \dot M_B$. The
predominantly radial magnetic field created by the MTI at large radii in
spherical accretion flows may account for the stable Faraday rotation measure
towards Sgr A* in the Galactic Center.


title: OGLE-2005-BLG-071Lb, the Most Massive M-Dwarf Planetary Companion?

abstract:
  We combine all available information to constrain the nature of
OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first
in a high-magnification event. These include photometric and astrometric
measurements from Hubble Space Telescope, as well as constraints from higher
order effects extracted from the ground-based light curve, such as microlens
parallax, planetary orbital motion and finite-source effects. Our primary
analysis leads to the conclusion that the host of Jovian planet
OGLE-2005-BLG-071Lb is an M dwarf in the foreground disk with mass M= 0.46 +/-
0.04 Msun, distance D_l = 3.3 +/- 0.4 kpc, and thick-disk kinematics v_LSR ~
103 km/s. From the best-fit model, the planet has mass M_p = 3.8 +/- 0.4 M_Jup,
lies at a projected separation r_perp = 3.6 +/- 0.2 AU from its host and so has
an equilibrium temperature of T ~ 55 K, i.e., similar to Neptune. A degenerate
model less favored by \Delta\chi^2 = 2.1 (or 2.2, depending on the sign of the
impact parameter) gives similar planetary mass M_p = 3.4 +/- 0.4 M_Jup with a
smaller projected separation, r_\perp = 2.1 +/- 0.1 AU, and higher equilibrium
temperature T ~ 71 K. These results from the primary analysis suggest that
OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that
is hosted by an M dwarf. However, the formation of such high-mass planetary
companions in the outer regions of M-dwarf planetary systems is predicted to be
unlikely within the core-accretion scenario. There are a number of caveats to
this primary analysis, which assumes (based on real but limited evidence) that
the unlensed light coincident with the source is actually due to the lens, that
is, the planetary host. However, these caveats could mostly be resolved by a
single astrometric measurement a few years after the event.


title:
Metabelian representations, twisted Alexander polynomials, knot slicing,
  and mutation

abstract:
  Given a knot complement X and its p-fold cyclic cover X_p, we identify
twisted polynomials associated to 1-dimensional linear representations of the
fundamental group of X_p with twisted polynomials associated to related
p-dimensional linear representations of the fundamental group of X. This
provides a simpler and faster algorithm to compute these twisted polynomials,
allowing us to prove that 16 (of 18 previously unknown) algebraically slice
knots of 12 or fewer crossings are not slice. We also use this improved
algorithm to prove that the 24 mutants of the pretzel knot P(3,7,9,11,15),
corresponding to permutations of (7,9,11,15), represent distinct concordance
classes.


title: Doubly Lopsided Mass Matrices from Unitary Unification

abstract:
  It is shown that the stratified or "doubly lopsided" mass matrix structure
that is known to reproduce well the qualitative features of the quark and
lepton masses and mixings can arise quite naturally in the context of grand
unification based on the groups SU(N) with N > 5. An SU(8) example is
constructed with the minimal anomaly-free, three-family set of fermions, in
which a realistic flavor structure results without flavor symmetry.


title: Stationary ring solitons in field theory - knots and vortons

abstract:
  We review the current status of the problem of constructing classical field
theory solutions describing stationary vortex rings in Minkowski space in 3+1
dimensions. We describe the known up to date solutions of this type, such as
the static knot solitons stabilized by the topological Hopf charge, the
attempts to gauge them, the anomalous solitons stabilized by the Chern-Simons
number, as well as the non-Abelian monopole and sphaleron rings. Passing to the
rotating solutions, we first discuss the conditions insuring that they do not
radiate, and then describe the spinning $Q$-balls, their twisted and gauged
generalizations reported here for the first time, spinning skyrmions, and
rotating monopole-antimonopole pairs. We then present the first explicit
construction of global vortons as solutions of the elliptic boundary value
problem, which demonstrates their non-radiating character. Finally, we describe
the analogs of vortons in the Bose-Einstein condensates, analogs of spinning
$Q$-balls in the non-linear optics, and also moving vortex rings in superfluid
helium and in ferromagnetics.

categories: hep-th cond-mat.other gr-qc hep-ph nlin.PS


title: On the triple nature of the X-ray source 4U2129+47 (= V1727 Cyg)

abstract:
  Context. In quiescence, the proposed optical counterpart to the neutron star
low mass X-ray binary 4U 2129+47 (V1727 Cyg) shows a spectrum consistent with a
late F-type subgiant and no radial velocity variations on the 5.24 hour binary
period. This could imply that V1727 Cyg is a chance line of sight interloper.
Radial velocity measurements, however, showed evidence for a longer term ~40
km/s shift, which suggested that 4U 2129+47 could be a hierarchical triple
system, with the F-type star in a wide orbit about the inner low mass X-ray
binary. Aims. In order to confirm the long-term radial velocity shift reported
in Garcia et al. (1989) and its amplitude, we obtained spectroscopic
observations of V1727 Cyg during 1996 and 1998 with the William Herschel
Telescope using the ISIS spectrograph. Methods. We determined radial velocities
from the ISIS spectra by means of the cross-correlation technique with a
template spectrum. Results. The resulting radial velocities show variations
with a maximum amplitude of ~40 km/s, confirming previous results and
supporting the F-type star as being the third body in a hierarchical triple
system. The odds that this star could be an interloper are ~3e-6


title: Doped Kagome System as Exotic Superconductor

abstract:
  A Chern--Simons theory for the doped spin-1/2 kagom\'e system is constructed,
from which it is shown that the system is an exotic superconductor that breaks
time-reversal symmetry. It is also shown that the system carries minimal
vortices of flux $hc/4e$ (as opposed to the usual $hc/2e$ in conventional
superconductors) and contains fractional quasiparticles (including fermionic
quasiparticles with \emph{semionic} mutual statistics and spin-1/2
quasiparticles with \emph{bosonic} self-statistics) in addition to the usual
spin-1/2 fermionic Bougoliubov quasiparticle. Two Chern--Simons theories--one
with an auxiliary gauge field kept and one with the auxiliary field and a
redundant matter field directly eliminated--are presented and shown to be
consistent with each other.


title:
Brownian Motion in Robertson-Walker Space-Times from electromagnetic
  Vacuum Fluctuations

abstract:
  We consider classical particles coupled to the quantized electromagnetic
field in the background of a spatially flat Robertson-Walker universe. We find
that these particles typically undergo Brownian motion and acquire a non-zero
mean squared velocity which depends upon the scale factor of the universe. This
Brownian motion can be interpreted as due to non-cancellation of
anti-correlated vacuum fluctuations in the time dependent background
space-time. We consider several types of coupling to the electromagnetic field,
including particles with net electric charge, a magnetic dipole moment, and
electric polarizability. We also investigate several different model scale
factors.


title: Carath\'eodory, Helly and the others in the max-plus world

abstract:
  Carath\'eodory's, Helly's and Radon's theorems are three basic results in
discrete geometry. Their max-plus counterparts have been proved by various
authors. In this paper, more advanced results in discrete geometry are shown to
have also their max-plus counterparts: namely, the colorful Carath\'eodory
theorem and the Tverberg theorem. A conjecture connected to the Tverberg
theorem -- Sierksma's conjecture --, although still open for the usual
convexity, is shown to be true in the max-plus settings.


title: M-theory, exceptional generalised geometry and superpotentials

abstract:
  We discuss the structure of "exceptional generalised geometry" (EGG), an
extension of Hitchin's generalised geometry that provides a unified geometrical
description of backgrounds in eleven-dimensional supergravity. On a
d-dimensional background, as first described by Hull, the action of the
generalised geometrical O(d,d) symmetry group is replaced in EGG by the
exceptional U-duality group E_d(d). The metric and form-field degrees of
freedom combine into a single geometrical object, so that EGG naturally
describes generic backgrounds with flux, and there is an EGG analogue of the
Courant bracket which encodes the differential geometry. Our focus is on the
case of seven-dimensional backgrounds with N=1 four-dimensional supersymmetry.
The corresponding EGG is the generalisation of a G_2-structure manifold. We
show it is characterised by an element \phi in a particular orbit of the 912
representation of E_7(7), which defines an SU(7) (subset of E_7(7)) structure.
As an application, we derive the generic form of the four-dimensional effective
superpotential, and show that it can be written in a universal form, as a
homogeneous E_7(7)-invariant functional of \phi.


title:
The Accuracy of Morphological Decomposition of Active Galactic Nucleus
  Host Galaxies

abstract:
  In order to assess the accuracy with which we can determine the morphologies
of AGN host galaxies, we have simulated more than 50,000 ACS images of galaxies
with z < 1.25, using image and noise properties appropriate for the GOODS
survey. We test the effect of central point-source brightness on host galaxy
parameter recovery with a set of simulated AGN host galaxies made by adding
point sources to the centers of normal galaxies. We extend this analysis and
also quantify the recovery of intrinsic morphological parameters of AGN host
galaxies with a set of fully simulated inactive and AGN host galaxies.
  We can reliably separate good from poor fit results using a combination of
reasonable error cuts, in the regime where L_{host}:L_{PS} > 1:4. We give
quantitative estimates of parameter errors as a function of
host-to-point-source ratio. In general, we separate host and point-source
magnitudes reliably at all redshifts; point sources are well recovered more
than 90% of the time, although spurious detection of central point sources can
be as high as 25% for bulge-dominated sources. We find a general correlation
between Sersic index and intrinsic bulge-to-total ratio, such that a host
galaxy with Sersic n < 1.5 generally has at least 80% of its light from a disk
component. Likewise, "bulge-dominated" galaxies with n > 4 typically derive at
least 70% of their total host galaxy light from a bulge, but this number can be
as low as 55%. Single-component Sersic fits to an AGN host galaxy are
statistically very reliable to z < 1.25 (for ACS survey data like ours). In
contrast, two-component fits involving separate bulge and disk components tend
to over-estimate the bulge fraction by ~10%, with uncertainty of order 50%.


title: A Spectroscopic Binary at the M/L Transition

abstract:
  We report the discovery of a single-lined spectroscopic binary with an Ultra
Cool Dwarf (UCD) primary with a spectral type between M8 and L0.5. This system
was discovered during the course of an ongoing survey to monitor L dwarfs for
radial velocity variations and is the first known small separation (a<1 AU)
spectroscopic binary among dwarfs at the M/L transition. Based on
radial-velocity measurements with a typical precision of 300 m/s we estimate
the orbital parameters of this system to be P=246.73+/-0.49 d, a1
sin(i)=0.159+/-0.003 AU, M2 sin(i)=0.2062 (M1+M2)^(2/3)+/-0.0034 M_{\sun}.
Assuming a primary mass of M1=0.08M_{\sun} (based on spectral type), we
estimate the secondary minimum mass to be M2 sin(i)=0.054 M_{\sun}. With future
photometric, spectroscopic, and interferometric observations it may be possible
to determine the dynamical masses of both components directly, making this
system one of the best characterized UCD binaries known.


title: The Enigmatic Young Object: Walker 90/V590 Monocerotis

abstract:
  We assess the evolutionary status of the intriguing object Walker 90/V590
Mon, which is located about 20 arcminutes northwest of the Cone Nebula near the
center of the open cluster NGC 2264. This object, according to its most recent
optical spectral type determination (B7), which we confirmed, is at least 3
magnitudes too faint in V for the cluster distance, but it shows the classical
signs of a young pre-main sequence object, such as highly variable Halpha
emission, Mg II emission, IR excess, UV continuum, and optical variability. We
analyzed a collection of archival and original data on Walker 90, covering 45
years including photometry, imaging, and spectroscopic data ranging from
ultraviolet to near-infrared wavelengths. According to star formation
processes, it is expected that, as this object clears its primordial
surroundings, it should become optically brighter, show a weakening of its IR
excess and present decreasing line emissions. This behavior is supported by our
observations and analysis, but timescales are expected to be longer than the
one observed here. Based on photometric data secured in 2007, we find Walker 90
at its brightest recorded optical magnitude. We document an evolution in
spectral type over the past five decades (from A2/A3 to currently B7 and as
early as B4), along with a decrease in the near-infrared K fluxes. From
near-infrared images secured in 2004, Walker 90 appears as a point source
placing an upper limit of 0.1 arcsec for its diameter. We conclude that many
observational features are explained if W90 is a flared disk system, surrounded
by an inclined optically thick accretion disk.


title:
Scale-free networks as preasymptotic regimes of superlinear preferential
  attachment

abstract:
  We study the following paradox associated with networks growing according to
superlinear preferential attachment: superlinear preference cannot produce
scale-free networks in the thermodynamic limit, but there are superlinearly
growing network models that perfectly match the structure of some real
scale-free networks, such as the Internet. We obtain an analytic solution,
supported by extensive simulations, for the degree distribution in
superlinearly growing networks with arbitrary average degree, and confirm that
in the true thermodynamic limit these networks are indeed degenerate, i.e.,
almost all nodes have low degrees. We then show that superlinear growth has
vast preasymptotic regimes whose depths depend both on the average degree in
the network and on how superlinear the preference kernel is. We demonstrate
that a superlinearly growing network model can reproduce, in its preasymptotic
regime, the structure of a real network, if the model captures some
sufficiently strong structural constraints -- rich-club connectivity, for
example. These findings suggest that real scale-free networks of finite size
may exist in preasymptotic regimes of network evolution processes that lead to
degenerate network formations in the thermodynamic limit.

categories: cond-mat.stat-mech cond-mat.dis-nn cs.NI physics.soc-ph


title:
Influence of the Radio-Frequency source properties on RF-based atom
  traps

abstract:
  We discuss the quality required for the RF source used to trap neutral atoms
in RF-dressed potentials. We illustrate this discussion with experimental
results obtained on a Bose-Einstein condensation experiment with different RF
sources.


title: Quark-Gluon Plasma: Present and Future

abstract:
  We review a sample of the experimental results from AGS to SPS and RHIC and
their interpretations towards understanding of the Quark-Gluon Plasma. We
discuss extrapolations of these results to the upcoming LHC experiments.
Finally, we present the plans to probe the QCD critical point with an energy
scan at RHIC and FAIR facilities.


title:
Primitively divergent diagrams in $\kappa$-deformed scalar field with
  quartic self-interaction

abstract:
  We obtain the primitively divergent diagrams in $\kappa$-deformed scalar
field in four-dimensional spacetime with quartic self-interaction in order to
investigate the effect of the fundamental length $q=1/(2\kappa)$ on such
diagrams. Thanks to $\kappa$-deformation, we find that the dimensionally
regularized forms of the diagrams lead to finite results in the limit of
space-time dimension four. The effect of the deformation appears as a
displacement of the poles in the complex plane.


title:
Detailed Abundances for 28 Metal-poor Stars: Stellar Relics in the Milky
  Way

abstract:
  We present the results of an abundance analysis for a sample of stars with
$-4<$[Fe/H]$<-2$. The data were obtained with the HIRES spectrograph at Keck
Observatory. The set includes 28 stars, with effective temperature ranging from
4800 to 6600 K. For 13 stars with [Fe/H]$<-2.6$, including nine with
[Fe/H]$<-3.0$ and one with [Fe/H]$=-4.0$, these are the first reported detailed
abundances. For the most metal-poor star in our sample, CS 30336-049, we
measure an abundance pattern that is very similar to stars in the range
[Fe/H]$\sim-3.5$, including a normal C+N abundance. We also find that it has
very low but measurable Sr and Ba, indicating some neutron-capture activity
even at this low of a metallicity. We explore this issue further by examining
other very neutron-capture-deficient stars, and find that at the lowest levels,
[Ba/Sr] exhibits the ratio of the main r-process. We also report on a new
r-process-enhanced star, CS 31078-018. This star has [Fe/H]$=-2.85$,
[Eu/Fe]$=1.23$, and [Ba/Eu]$=-0.51$. CS 31078-018 exhibits an ``actinide
boost'', i.e. much higher [Th/Eu] than expected and at a similar level to CS
31082-001. Our spectra allow us to further constrain the abundance scatter at
low metallicities, which we then use to fit to the zero-metallicity Type II
supernova yields of Heger & Woosley (2008). We find that supernovae with
progenitor masses between 10 and 20 M$_{\odot}$ provide the best matches to our
abundances.


title: Seiberg-Witten Floer homology and symplectic forms on S^1 X M^3

abstract:
  Let M be a closed, connected, orientable 3-manifold. The purpose of this
paper is to study the Seiberg-Witten Floer homology of M given that S^1 X M
admits a symplectic form. In particular, we prove that M fibers over the circle
if M has first Betti number 1 and S^1 X M admits a symplectic form with
non-torsion canonical class.


title:
Bond stretching phonon softening and angle-resolved photoemission kinks
  in optimally doped Bi2Sr1.6La0.4Cu2O6 superconductors

abstract:
  We report the first measurement of the optical phonon dispersion in optimally
doped single layer Bi2Sr1.6La0.4Cu2O6+delta using inelastic x-ray scattering.
We found a strong softening of the Cu-O bond stretching phonon at about
q=(0.25,0,0) from 76 to 60 meV, similar to the one reported in other cuprates.
A direct comparison with angle-resolved photoemission spectroscopy measurements
taken on the same sample, revealed an excellent agreement in terms of energy
and momentum between the ARPES nodal kink and the soft part of the bond
stretching phonon. Indeed, we find that the momentum space where a 63 meV kink
is observed can be connected with a vector q=(xi,0,0) with xi~0.22, which
corresponds exactly to the soft part of the bond stretching phonon mode. This
result supports an interpretation of the ARPES kink in terms of electron-phonon
coupling.


title: Quark-Gluon Plasma - New Frontiers

abstract:
  As implied by organizers, this talk is not a conference summary but rather an
outline of progress/challenges/``frontiers'' of the theory. Some fundamental
questions addressed are:
  Why is sQGP such a good liquid? Do we understand (de)confinement and what do
we know about ``magnetic'' objects creating it? Can we understand the AdS/CFT
predictions, from the gauge theory side? Can they be tested experimentally? Can
AdS/CFT duality help us understand rapid equilibration/entropy production? Can
we work out a complete dynamical ``gravity dual'' to heavy ion collisions?


title: Climate Networks around the Globe are Significantly Effected by El Nino

abstract:
  The temperatures in different zones in the world do not show significant
changes due to El-Nino except when measured in a restricted area in the Pacific
Ocean. We find, in contrast, that the dynamics of a climate network based on
the same temperature records in various geographical zones in the world is
significantly influenced by El-Nino. During El-Nino many links of the network
are broken, and the number of surviving links comprises a specific and
sensitive measure for El-Nino events. While during non El-Nino periods these
links which represent correlations between temperatures in different sites are
more stable, fast fluctuations of the correlations observed during El-Nino
periods cause the links to break.


title: Outbursts Large and Small from EXO 2030+375

abstract:
  During the summer of 2006, the accreting X-ray pulsar EXO 2030+375 underwent
its first giant outburst since its discovery in 1985. Our observations include
the first ever of the rise of a giant outburst of EXO 2030+375. EXO 2030+375
was monitored daily with the Rossi X-ray Timing Explorer (RXTE) from 2006 June
through 2007 May. During the giant outburst, we discovered evidence for a
cyclotron feature at ~11 keV. This feature was confidently detected for about
90 days, during the brighter portion of the outburst. Daily observations of the
next five EXO 2030+375 orbits detected pulsations at all orbital phases and
normal outbursts shifted to a later orbital phase than before the giant
outburst. An accretion disk appears to be present in both the normal and giant
outbursts, suggesting that the long-term behavior is a product of the state of
the Be star disk and the accretion disk. Here we will present flux and
frequency histories from our detailed RXTE observations of the giant outburst
and the normal outbursts that surrounded it. A new orbital analysis is
presented that includes observations from 1991 through 2007 August.


title:
Construction of density operator for a general mean-field Hamiltonian
  and its application to the models of correlated fermions

abstract:
  We analyze a class of mean-field (MF) lattice-fermion Hamiltonians and
construct the corresponding grand-canonical density operator for such system.
New terms are introduced, which may be interpreted as local fugacities,
molecular fields, etc. The presence of such terms is an unavoidable consequence
of a consistent statistical description. Although in some cases (e.g. in the
Hartree or the Hartree-Fock-type approximation) the presented formalism is
redundant, in general (e.g. for a renormalized t-J model) it leads to
nontrivial modifications of the thermodynamic properties.


title: Quantum Noise as an Entanglement Meter

abstract:
  Entanglement entropy, which is a measure of quantum correlations between
separate parts of a many-body system, has emerged recently as a fundamental
quantity in broad areas of theoretical physics, from cosmology and field theory
to condensed matter theory and quantum information. The universal appeal of the
entanglement entropy concept is related, in part, to the fact that it is
defined solely in terms of the many-body density matrix of the system, with no
relation to any particular observables. However, for the same reason, it has
not been clear how to access this quantity experimentally. Here we derive a
universal relation between entanglement entropy and the fluctuations of current
flowing through a quantum point contact (QPC) which opens a way to perform a
direct measurement of entanglement entropy. In particular, by utilizing
space-time duality of 1d systems, we relate electric noise generated by opening
and closing the QPC periodically in time with the seminal S = 1/3 log L
prediction of conformal field theory.

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


title:
Hard Electron Energy Distribution in the Relativistic Shocks of GRB
  Afterglows

abstract:
  Particle acceleration in relativistic shocks is not a very well understood
subject. Owing to that difficulty, radiation spectra from relativistic shocks,
such as those in GRB afterglows, have been often modelled by making assumptions
about the underlying electron distribution. One such assumption is a relatively
soft distribution of the particle energy, which need not be true always, as is
obvious from observations of several GRB afterglows. In this paper, we describe
modifications to the afterglow standard model to accommodate energy spectra
which are `hard'. We calculate the overall evolution of the synchrotron and
compton flux arising from such a distribution. We also model two afterglows,
GRB010222 and GRB020813, under this assumption and estimate the physical
parameters.


title: A Fredholm Determinant Representation in ASEP

abstract:
  In previous work the authors found integral formulas for probabilities in the
asymmetric simple exclusion process (ASEP) on the integer lattice. The dynamics
are uniquely determined once the initial state is specified. In this note we
restrict our attention to the case of step initial condition with particles at
the positive integers, and consider the distribution function for the m'th
particle from the left. In the previous work an infinite series of multiple
integrals was derived for this distribution. In this note we show that the
series can be summed to give a single integral whose integrand involves a
Fredholm determinant. We use this determinant representation to derive
(non-rigorously, at this writing) a scaling limit.


title:
A bijection on core partitions and a parabolic quotient of the affine
  symmetric group

abstract:
  Let $\ell,k$ be fixed positive integers. In an earlier work, the first and
third authors established a bijection between $\ell$-cores with first part
equal to $k$ and $(\ell-1)$-cores with first part less than or equal to $k$.
This paper gives several new interpretations of that bijection. The
$\ell$-cores index minimal length coset representatives for
$\widetilde{S_{\ell}} / S_{\ell}$ where $\widetilde{S_{\ell}}$ denotes the
affine symmetric group and $S_{\ell}$ denotes the finite symmetric group. In
this setting, the bijection has a beautiful geometric interpretation in terms
of the root lattice of type $A_{\ell-1}$. We also show that the bijection has a
natural description in terms of another correspondence due to Lapointe and
Morse.


title:
Long-Term Variability in the Optical Spectrum of the Seyfert Galaxy NGC
  2992

abstract:
  New spectra of NGC 2992 from the Cerro Tololo Inter-American Observatory show
that this nearby AGN has changed its type classification to a Seyfert 2 in
2006. It was originally classified as a Seyfert 1.9, and has been previously
seen as a Seyfert 1.5 with strong broad Halpha emission. A comparison of the
reddening and equivalent hydrogen column density derived for the narrow-line
region from these new data with those previously calculated for different
regions closer to the nucleus shows them to be very similar, and suggests that
these different regions are all being absorbed by the same opacity source, a
large 100-pc scale dust lane running across the nucleus. However, obscuration
by dust in this lane is probably not responsible for classification changes
which occur in only a few years. It is more likely that NGC 2992's observed
variations are due to a highly variable ionizing continuum. We therefore
conclude that, although NGC 2992 was originally identified as a Seyfert 1.9,
this was not because of an oblique viewing angle through the atmosphere of a
central dusty torus, but because its active nucleus was identified when it was
in a low continuum state.


title: Interference-Assisted Secret Communication

abstract:
  Wireless communication is susceptible to adversarial eavesdropping due to the
broadcast nature of the wireless medium. In this paper it is shown how
eavesdropping can be alleviated by exploiting the superposition property of the
wireless medium. A wiretap channel with a helping interferer (WT-HI), in which
a transmitter sends a confidential message to its intended receiver in the
presence of a passive eavesdropper, and with the help of an independent
interferer, is considered. The interferer, which does not know the confidential
message, helps in ensuring the secrecy of the message by sending independent
signals. An achievable secrecy rate for the WT-HI is given. The results show
that interference can be exploited to assist secrecy in wireless
communications. An important example of the Gaussian case, in which the
interferer has a better channel to the intended receiver than to the
eavesdropper, is considered. In this situation, the interferer can send a
(random) codeword at a rate that ensures that it can be decoded and subtracted
from the received signal by the intended receiver but cannot be decoded by the
eavesdropper. Hence, only the eavesdropper is interfered with and the secrecy
level of the confidential message is increased.


title: Main Belt Binary Asteroidal Systems With Circular Mutual Orbits

abstract:
  In 2003, we initiated a long-term adaptive optics campaign to study the orbit
of various main-belt asteroidal systems. Here we present a consistent solution
for the mutual orbits of four binary systems: 22 Kalliope, 45 Eugenia, 107
Camilla and 762 Pulcova. With the exception of 45 Eugenia, we did not detect
any additional satellites around these systems although we have the capability
of detecting a loosely-bound fragment (located at 1/4 x RHill) that is ~40
times smaller in diameter than the primary. The common characteristic of these
mutual orbits is that they are roughly circular. Three of these binary systems
belong to a C-"group" taxonomic class. Our estimates of their bulk densities
are consistently lower (~1 g/cm3) than their associated meteorite analogs,
suggesting an interior porosity of 30-50% (taking CI-CO meteorites as analogs).
22 Kalliope, a W-type asteroid, has a significantly higher bulk density of ~3
g/cm3, derived based on IRAS radiometric size measurement. We compare the
characteristics of these orbits in the light of tidal-effect evolution.


title:
Quantum interference and weak localisation effects in the interlayer
  magnetoresistance of layered metals

abstract:
  Studies of angle-dependent magnetoresistance oscillations (AMRO) in the
interlayer conductivity of layered metals have generally considered
semi-classical electron transport. We consider a quantum correction to the
semi-classical conductivity that arises from what can be described as an
interlayer Cooperon. This depends on both the disorder potential within a layer
and the correlations of the disorder potential between layers. We compare our
results with existing experimental data on organic charge transfer salts that
are not explained within the standard semi-classical transport picture. In
particular, our results may be applicable to effects that have been seen when
the applied magnetic field is almost parallel to the conducting layers. We
predict the presence of a peak in the resistivity as the field direction
approaches the plane of the layers. The peak can occur even when there is
weakly incoherent transport between layers.


title: Main Belt Binary Asteroidal Systems With Eccentric Mutual Orbits

abstract:
  Using 8m-10m class telescopes and their Adaptive Optics (AO) systems, we
conducted a long-term adaptive optics campaign initiated in 2003 focusing on
four binary asteroid systems: (130) Elektra, (283) Emma, (379) Huenna, and
(3749) Balam. The analysis of these data confirms the presence of their
asteroidal satellite. We did not detect any additional satellite around these
systems even though we have the capability of detecting a loosely-bound
fragment (located at 1/4 x RHill) ~40 times smaller in diameter than the
primary. The orbits derived for their satellites display significant
eccentricity, ranging from 0.1 to 0.9, suggesting a different origin. Based on
AO size estimate, we show that (130) Elektra and (283) Emma, G-type and P-type
asteroids respectively, have a significant porosity (30-60% considering CI-CO
meteorites as analogs) and their satellite's eccentricities (e~0.1) are
possibly due to excitation by tidal effects. (379) Huenna and (3749) Balam, two
loosely bound binary systems, are most likely formed by mutual capture. (3749)
Balam's possible high bulk density is similar to (433) Eros, another S-type
asteroid, and should be poorly fractured as well. (379) Huenna seems to display
both characteristics: the moonlet orbits far away from the primary in term of
stability (20% x RHill), but the primary's porosity is significant (30-60%).


title: HN Peg B: A Test of Models of the L to T Dwarf Transition

abstract:
  Luhman and collaborators recently discovered an early-T dwarf companion to
the G0 dwarf star HN Peg, using Spitzer Infrared Array Camera (IRAC) images.
Companionship was established on the basis of the common proper motion inferred
from 1998 Two Micron All Sky Survey images and the 2004 IRAC images. In this
paper we present new near-infrared imaging data which confirms the common
proper motion of the system. We also present new 3 - 4 um spectroscopy of HN
Peg B, which provides tighter constraints on both the bolometric luminosity
determination and the comparison to synthetic spectra. New adaptive optics
imaging data are also presented, which shows the T dwarf to be unresolved,
providing limits on the multiplicity of the object. We use the age, distance
and luminosity of the solar-metallicity T dwarf to determine its effective
temperature and gravity, and compare synthetic spectra with these values, and a
range of grain properties and vertical mixing, to the observed 0.8 - 4.0 um
spectra and mid-infrared photometry. We find that models with temperature and
gravity appropriate for the older end of the age range of the system (0.5 Gyr)
can do a reasonable job of fitting the data, but only if the photospheric
condensate cloud deck is thin, and if there is significant vertical mixing in
the atmosphere. Dwarfs such as HN Peg B, with well-determined metallicity,
radius, gravity and temperature will allow development of dynamical atmosphere
models, leading to the solution of the puzzle of the L to T dwarf transition.


title: A Note on Approximate Liftings

abstract:
  In this paper, we prove approximate lifting results in the C$^{\ast}$-algebra
and von Neumann algebra settings. In the C$^{\ast}$-algebra setting, we show
that two (weakly) semiprojective unital C*-algebras, each generated by $n$
projections, can be glued together with partial isometries to define a larger
(weakly) semiprojective algebra. In the von Neumann algebra setting, we prove
lifting theorems for trace-preserving *-homomorphisms from abelian von Neumann
algebras or hyperfinite von Neumann algebras into ultraproducts. We also extend
a classical result of S. Sakai \cite{sakai} by showing that a tracial
ultraproduct of C*-algebras is a von Neumann algebra, which yields a
generalization of Lin's theorem \cite{Lin} on almost commuting selfadjoint
operators with respect to $\Vert\cdot\Vert_{p}$ on any unital C*-algebra with
trace.


title: Topological Stable Rank of Nest Algebras

abstract:
  We establish a general result about extending a right invertible row over a
Banach algebra to an invertible matrix. This is applied to the computation of
right topological stable rank of a split exact sequence. We also introduce a
quantitative measure of stable rank. These results are applied to compute the
right (left) topological stable rank for all nest algebras. This value is
either 2 or infinity, and rtsr(T(N)) = 2 occurs only when N is of ordinal type
less than omega^2 and the dimensions of the atoms grows sufficiently quickly.
We introduce general results on `partial matrix algebras' over a Banach
algebra. This is used to obtain an inequality akin to Rieffel's formula for
matrix algebras over a Banach algebra. This is used to give further insight
into the nest case.


title: Switching Energy of Ferromagnetic Logic Bits

abstract:
  Power dissipation in switching devices is believed to be the single most
important roadblock to the continued down scaling of electronic circuits. There
is a lot of experimental effort at this time to implement switching circuits
based on magnets and it is important to establish power requirements for such
circuits and their dependence on various parameters. This paper analyzes
switching energy which is dissipated in the switching process of single domain
Ferromagnets used as cascadable logic bits. We obtain generic results that can
be used for comparison with alternative technologies or guide the design of
magnet based switching circuits. Two central results are established. One is
that the switching energy drops significantly if the ramp time of an external
pulse exceeds a critical time. This drop occurs more rapidly than what is
normally expected of adiabatic switching for a capacitor. The other result is
that under the switching scheme that allows for logic operations, the switching
energy can be described by a single equation in both fast and slow limits.
Furthermore, these generic results are used to quantitatively examine the
possible operation frequencies and integration densities of these logic bits
which show that nanomagnets can have scaling laws similar to CMOS technology.


title: Combustion of biomass as a global carbon sink

abstract:
  This note is intended to highlight the important role of black carbon
produced from biomass burning in the global carbon cycle, and encourage further
research in this area. Consideration of the fundamental physical chemistry of
cellulose thermal decomposition suggests that suppression of biomass burning or
biasing burning practices to produce soot-free flames must inevitably transfer
more carbon to the atmosphere. A simple order-of-magnitude quantitative
analysis indicates that black carbon may be a significant carbon reservoir that
persists over geological time scales.


title:
A Height Gap Theorem For Finite Subsets Of GL_d(\bar{Q}) and Non
  Amenable Subgroups

abstract:
  We show a global adelic analog of the classical Margulis Lemma from
hyperbolic geometry. We introduce a conjugation invariant normalized height
$\hat{h}(F)$ of a finite set of matrices $F$ in $GL_{n}(\bar{\Bbb{Q}})$ which
is the adelic analog of the minimal displacement on a symmetric space. We then
show, making use of theorems of Bilu and Zhang on the equidistribution of
Galois orbits of small points, that $\hat{h}(F)>\epsilon $ as soon as $F$
generates a non-virtually solvable subgroup of $SL_{n}(\bar{\Bbb{Q}}),$ where
$\epsilon =\epsilon (n)>0$ is an absolute constant.


title: Coverage Probability of Wald Interval for Binomial Parameters

abstract:
  In this paper, we develop an exact method for computing the minimum coverage
probability of Wald interval for estimation of binomial parameters. Similar
approach can be used for other type of confidence intervals.


title:
Optimal Explicit Binomial Confidence Interval with Guaranteed Coverage
  Probability

abstract:
  In this paper, we develop an approach for optimizing the explicit binomial
confidence interval recently derived by Chen et al. The optimization reduces
conservativeness while guaranteeing prescribed coverage probability.


title: The RAGE radiation-hydrodynamic code

abstract:
  We describe RAGE, the ``Radiation Adaptive Grid Eulerian''
radiation-hydrodynamics code, including its data structures, its
parallelization strategy and performance, its hydrodynamic algorithm(s), its
(gray) radiation diffusion algorithm, and some of the considerable amount of
verification and validation efforts. The hydrodynamics is a basic Godunov
solver, to which we have made significant improvements to increase the
advection algorithm's robustness and to converge stiffnesses in the equation of
state. Similarly, the radiation transport is a basic gray diffusion, but our
treatment of the radiation-material coupling, wherein we converge
nonlinearities in a novel manner to allow larger timesteps and more robust
behavior, can be applied to any multi-group transport algorithm.


title: A Strong Tits Alternative

abstract:
  We show that for every integer $d$, there is a constant $N(d)$ such that if
$K$ is any field and $F$ is a finite subset of $GL_d(K)$, which generates a non
amenable subgroup, then $F^{N(d)}$ contains two elements, which freely generate
a non abelian free subgroup. This improves the original statement of the Tits
alternative. It also implies a growth gap and a co-growth gap for non-amenable
linear groups, and has consequences about the girth and uniform expansion of
small sets in finite subgroups of $GL_d(\Bbb{F}_q)$ as well as other
diophantine properties of non-discrete subgroups of Lie groups.


title: Presentations of finite simple groups: a computational approach

abstract:
  All nonabelian finite simple groups of rank $n$ over a field of size $q$,
with the possible exception of the Ree groups $^2G_2(3^{2e+1})$, have
presentations with at most $80 $ relations and bit-length $O(\log n +\log q)$.
Moreover, $A_n$ and $S_n$ have presentations with 3 generators$,$ 7 relations
and bit-length $O(\log n)$, while $\SL(n,q)$ has a presentation with 7
generators, $2 5$ relations and bit-length $O(\log n +\log q)$.


title:
Order of current variance and diffusivity in the rate one totally
  asymmetric zero range process

abstract:
  We prove that the variance of the current across a characteristic is of order
t^{2/3} in a stationary constant rate totally asymmetric zero range process,
and that the diffusivity has order t^{1/3}. This is a step towards proving
universality of this scaling behavior in the class of one-dimensional
interacting systems with one conserved quantity and concave hydrodynamic flux.
The proof proceeds via couplings to show the corresponding moment bounds for a
second class particle. We build on the methods developed by Balazs-Seppalainen
for asymmetric simple exclusion. However, some modifications were needed to
handle the larger state space. Our results translate into t^{2/3}-order of
variance of the tagged particle on the characteristics of totally asymmetric
simple exclusion.


title:
Electronic structure and Fermi surface character of LaONiP from first
  principles

abstract:
  Based on First-principles calculation, we have investigated electronic
structure of a ZrCuSiAs structured superconductor LaNiPO. The density of
states, band structures and Fermi surfaces have been given in detail. Our
results indicate that the bonding of the La-O and Ni-P is strongly covalent
whereas binding property between the LaO and NiP blocks is mostly ionic. It's
also found that four bands are across the Fermi level and the corresponding
Fermi surfaces all have a two-dimensional character. In addition, we also give
the band decomposed charge density, which suggests that orbital components of
Fermi surfaces are more complicated than cuprate superconductors.


title: On Estimation and Optimization of Mean Values of Bounded Variables

abstract:
  In this paper, we develop a general approach for probabilistic estimation and
optimization. An explicit formula and a computational approach are established
for controlling the reliability of probabilistic estimation based on a mixed
criterion of absolute and relative errors. By employing the Chernoff-Hoeffding
bound and the concept of sampling, the minimization of a probabilistic function
is transformed into an optimization problem amenable for gradient descendent
algorithms.


title: Nonequilibrium spin transport on Au(111) surfaces

abstract:
  The well-known experimentally observed \textit{sp}-derived Au(111) Shockley
surface states with Rashba spin splitting are perfectly fit by an effective
tight-binding model, considering a two-dimensional hexagonal lattice with
$p_{z}$-orbital and nearest neighbor hopping only. The extracted realistic band
parameters are then imported to perform the Landauer-Keldysh formalism to
calculate nonequilibrium spin transport in a two-terminal setup sandwiching a
Au(111) surface channel. Obtained results show strong spin density on the
Au(111) surface and demonstrate (i) intrinsic spin-Hall effect, (ii)
current-induced spin polarization, and (iii) Rashba spin precession, all of
which have been experimentally observed in semiconductor heterostructures, but
not in metallic surface states. We therefore urge experiments in the latter for
these spin phenomena.


title: The generalized Lefschetz number of homeomorphisms on punctured disks

abstract:
  We compute the generalized Lefschetz number of orientation-preserving
self-homeomorphisms of a compact punctured disk, using the fact that homotopy
classes of these homeomorphisms can be identified with braids. This result is
applied to study Nielsen-Thurston canonical homeomorphisms on a punctured disk.
We determine, for a certain class of braids, the rotation number of the
corresponding canonical homeomorphisms on the outer boundary circle. Also,it is
shown that the canonical homeomorphisms corresponding to some braids are
pseudo-Anosov.