title:
Magnetic flux noise in the three Josephson junctions superconducting
  ring

abstract:
  We analyze the influence of noise on magnetic properties of a su-
perconducting loop which contains three Josephson junctions. This circuit is a
classical analog of a persistent current (flux) qubit. A loop supercurrent
induced by external magnetic field in the presence of thermal fluctuations is
calculated. In order to get connection with experiment we calculate the
impedance of the low-frequency tank cir- cuit which is inductively coupled with
a loop of interest. We compare obtained results with the results in quantum
mode - when the three junction loop exhibits quantum tunneling of the magnetic
flux. We demonstrate that the tank-loop impedance in the classical and quan-
tum modes have different temperature dependence and can be easily distinguished
experimentally.


title: Counting cluster-tilted algebras of type $A_n$

abstract:
  The purpose of this paper is to give an explicit formula for the number of
non-isomorphic cluster-tilted algebras of type $A_n$, by counting the mutation
class of any quiver with underlying graph $A_n$. It will also follow that if
$T$ and $T'$ are cluster-tilting objects in a cluster category $\mathcal{C}$,
then $\End_{\mathcal{C}}(T)$ is isomorphic to $\End_{\mathcal{C}}(T')$ if and
only if $T=\tau^i T'$.


title:
EPR and magnetization studies on single crystals of a heterometallic
  (Cu^{II}} and Cr^{III}) complex: zero-field splitting determination

abstract:
  Magnetic properties of single crystals of the heterometallic complex
[Cu(bpy)$_3$]$_2$[Cr(C$_2$O$_4$)$_3$]NO$_3\cdot $9H$_2$O (bpy =
2,2'-bipyridine) have been investigated. From the recorded EPR spectra, the
spin-Hamiltonian parameters have been determined. The magnetization
measurements have shown magnetic anisotropy at low temperatures, which has been
analysed as a result of the zero-field splitting of the Cr$^{\mathrm{III}}$
ion. By fitting the exactly derived magnetization expression to the measured
magnetization data, the axial zero-field splitting parameter, D, has been
calculated. Comparing to the EPR measurements, it has been confirmed that $D$
can be determined from the measurements of the macroscopic magnetization on the
single crystals.


title:
Non Markovian Noise mediated through Anamolous Diffusion within Ion
  Channels

abstract:
  It is quite clear from a wide range of experiments that gating phenomena of
ion channels is inherently stochastic. It has been discussed using BD
simulations in a recent paper that memory effects in ion transport is
negligible, unless the barrier height is high. In this brief report we like to
state using Differential Stochastic Methods (DSM's) that the Markovian property
of exponential dwell times do indeed give rise to a high barrier, which in turn
indicates that memory effects need not be ignored. We have thus constructed a
Generalized Langevin Equation which contains a combination of Non Markovian at
different time scales & Markovian processes and develop an algorithm to
describe the scheme of events. We see that the oscillatory function behaviour
with exponential decay is obtained in the Markovian limit and two distinct time
scales corresponding to the processes of diffusion & drift may be obtained from
preliminary simulation results. We propose that the results need much more
inspection and it will be worthwhile to reproduce using MD simulations. The
most important idea which we like to propose in this paper is that the rise of
time scales and memory effects may be inherently related to the differential
behaviour of shear viscosity in the cytoplasm & extracellular matrix.


title: Deformation properties of the BCP energy density functional

abstract:
  We explore the deformation properties of the newly postulated BCP energy
density functional (EDF). The results obtained for three isotope chains of Mg,
Dy and Ra are compared to the available experimental data as well as to the
results of the Gogny-D1S force. Results for the fission barrier of $^{240}$Pu
are also discussed.


title:
On the Well-possedness of the Problem of Reconstruction of Non-separate
  Boundary Conditions

abstract:
  We consider an inverse spectral problem with the third-order differential
equation and the non-separated boundary conditions. Two theorems on the
uniqueness of the solution of this problem are proved, and a method for
establishing the unknown conditions is obtained, using 19 eigenvalues. The
method of approximate calculation of unknown boundary conditions is explained,
with the help of an example.


title:
Accretion discs, coronae and jets in black hole binaries: prospects for
  Simbol-X

abstract:
  The phenomenology of accretion disc, coronnae and jets in X-ray binaries is
rather well established. However the structure of the accretion flow in the
various spectral states is still debated and the connection between the hot
flow and compact jet is far from being understood. Simbol-X should address
these two important questions in several ways. First, it will provide us with
the capability of producing high sensivity, broad band spectra and therefore
constrain simultaneously the shape and luminosity of all spectral components
(iron line, reflection bump, thermal disc and comptonised emission) which in
turn provides information on the geometry of the accretion flow. It will also
determine the exact contribution of jets to the X-ray band both in bright and
quiescent states. Finally it will shed new lights on the underlying mechanisms
triggering spectral state transitions by allowing us to follow in exquisite
details the rapid spectral evolution and its correlation with the radio jet
emission during those transitions.


title: Arrested state of clay-water suspensions: gel or glass?

abstract:
  The aging of a charged colloidal system has been studied by Small Angle
X-rays Scattering, in the exchanged momentum range Q=0.03 - 5 nm-1, and by
Dynamic Light Scattering, at different clay concentrations (Cw =0.6 % - 2.8 %).
The static structure factor, S(Q), has been determined as a function of both
aging time and concentration. This is the first direct experimental evidence of
the existence and evolution with aging time of two different arrested states in
a single system simply obtained only by changing its volume fraction: an
inhomogeneous state is reached at low concentrations, while a homogenous one is
found at high concentrations.


title:
Revisiting the conformal invariance of the scalar field: from Minkowski
  space to de Sitter space

abstract:
  In this article, we clarify the link between the conformal (i.e. Weyl)
correspondence from the Minkowski space to the de Sitter space and the
conformal (i.e. SO(2,$d$)) invariance of the conformal scalar field on both
spaces. We exhibit the realization on de Sitter space of the massless scalar
representation of SO$(2,d)$. It is obtained from the corresponding
representation in Minkowski space through an intertwining operator inherited
from the Weyl relation between the two spaces. The de Sitter representation is
written in a form which allows one to take the point of view of a Minkowskian
observer who sees the effect of curvature through additional terms.


title: Maximal Crossed Product Orders over Discrete Valuation Rings

abstract:
  The problem of determining when a (classical) crossed product $T=S^f*G$ of a
finite group $G$ over a discrete valuation ring $S$ is a maximal order, was
answered in the 1960's for the case where $S$ is tamely ramified over the
subring of invariants $S^G$. The answer was given in terms of the conductor
subgroup (with respect to $f$) of the inertia. In this paper we solve this
problem in general when $S/S^G$ is residually separable. We show that the
maximal order property entails a restrictive structure on the sub-crossed
product graded by the inertia subgroup. In particular, the inertia is abelian.
Using this structure, one is able to extend the notion of the conductor. As in
the tame case, the order of the conductor is equal to the number of maximal two
sided ideals of $T$ and hence to the number of maximal orders containing $T$ in
its quotient ring. Consequently, $T$ is a maximal order if and only if the
conductor subgroup is trivial.


title: Unparticle physics with broken scale invariance

abstract:
  If scale invariance is exact, unparticles are unlikely to be probed in
colliders since there are stringent constraints from astrophysics and
cosmology. However these constraints are inapplicable if scale invariance is
broken at a scale mu >~ 1 GeV. The case 1 GeV <~ mu < M_Z is particularly
interesting since it allows unparticles to be probed at and below the Z pole.
We show that mu can naturally be in this range if only vector unparticles
exist, and briefly remark on implications for Higgs phenomenology. We then
obtain constraints on unparticle parameters from e+ e- -> mu+ mu- cross-section
and forward-backward asymmetry data, and compare with the constraints from
mono-photon production and the Z hadronic width.


title:
Biases on initial mass function determinations. II. Real multiple
  systems and chance superpositions

abstract:
  When calculating IMFs for young clusters, one has to take into account that
(a) most massive stars are born in multiple systems (b) most IMFs are derived
from data that cannot resolve such systems, and (c) multiple chance
superpositions between members are expected to happen if the cluster is too
distant. In this article I use numerical experiments to model the consequences
of those phenomena on the observed color-magnitude diagrams and the IMFs
derived from them. Real multiple systems affect the observed or apparent
massive-star MF slope little but can create a significant population of
apparently ultramassive stars. Chance superpositions produce only small biases
when the number of superimposed stars is low but, once a certain number
threshold is reached, they can affect both the observed slope and the apparent
stellar upper mass limit. I apply those experiments to two well known massive
young clusters in the Local Group, NGC 3603 and R136. In both cases I show that
the observed population of stars with masses above 120 solar masses can be
explained by the effects of unresolved objects, mostly real multiple systems
for NGC 3603 and a combination of real and chance-alignment multiple systems
for R136. Therefore, the case for the reality of a stellar upper mass limit at
solar or near-solar metallicities is strengthened, with a possible value even
lower than 150 solar masses. An IMF slope somewhat flatter than Salpeter or
Kroupa with gamma between -1.6 and -2.0 is derived for the central region of
NGC 3603, with a significant contribution to the uncertainty arising from the
imprecise knowledge of the distance to the cluster. The IMF at the very center
of R136 cannot be measured with the currently available data but the situation
could change with new HST observations. (abridged)


title:
Graph-Based Classification of Self-Dual Additive Codes over Finite
  Fields

abstract:
  Quantum stabilizer states over GF(m) can be represented as self-dual additive
codes over GF(m^2). These codes can be represented as weighted graphs, and
orbits of graphs under the generalized local complementation operation
correspond to equivalence classes of codes. We have previously used this fact
to classify self-dual additive codes over GF(4). In this paper we classify
self-dual additive codes over GF(9), GF(16), and GF(25). Assuming that the
classical MDS conjecture holds, we are able to classify all self-dual additive
MDS codes over GF(9) by using an extension technique. We prove that the minimum
distance of a self-dual additive code is related to the minimum vertex degree
in the associated graph orbit. Circulant graph codes are introduced, and a
computer search reveals that this set contains many strong codes. We show that
some of these codes have highly regular graph representations.


title:
Analyticity of the scattering operator for semilinear dispersive
  equations

abstract:
  We present a general algorithm to show that a scattering operator associated
to a semilinear dispersive equation is real analytic, and to compute the
coefficients of its Taylor series at any point. We illustrate this method in
the case of the Schrodinger equation with power-like nonlinearity or with
Hartree type nonlinearity, and in the case of the wave and Klein-Gordon
equations with power nonlinearity. Finally, we discuss the link of this
approach with inverse scattering, and with complete integrability.


title:
Stability analysis of rotating beams rubbing on an elastic circular
  structure

abstract:
  This paper presents the stability analysis of a system composed of rotating
beams on a flexible, circular fixed ring, using the Routh-Hurwitz criterion.
The model displayed has been fully developed within the rotating frame by use
of an energy approach. The beams considered possess two degrees of freedom
(dofs), a flexural motion as well as a traction/compression motion. In-plane
deformations of the ring will be considered. Divergences and mode couplings
have thus been underscored within the rotating frame and in order to simplify
understanding of all these phenomena, the dofs of the beams will first be
treated separately and then together. The dynamics of radial rotating loads on
an elastic ring can create divergence instabilities as well as post-critical
mode couplings. Moreover, the flexural motion of beam rubbing on the ring can
also lead to mode couplings and to the locus-veering phenomenon. The presence
of rubbing seems to make the system unstable as soon as the rotational speed of
the beams is greater than zero. Lastly, the influence of an angle between the
beams and the normal to the ring's inner surface will be studied with respect
to system stability, thus highlighting a shift frequency phenomenon.


title: Cosmological constant and time delay

abstract:
  The effect of the cosmological constant on the time delay caused by an
isolated spherical mass is calculated without using the lens equation and
compared to a recent observational bound on the time delay of the lensed quasar
SDSS J1004+4112.


title: Prospects for B-Decay Studies at the LHC

abstract:
  In this decade, there are huge efforts to explore B-meson decays, which offer
interesting probes to test the quark-flavour structure of the Standard Model
and to search for signals of new physics. Exciting new perspectives for these
studies will soon arise at the LHC, where decays of $B^0_s$ mesons will be a
key target of the B-physics programme. We will discuss theoretical aspects of
various benchmark channels and address the question of how much space for
new-physics effects in their observables is left by the recent experimental
results from the B factories and the Tevatron.


title: IMF biases created by binning and unresolved systems

abstract:
  I discuss two of the possible sources of biases in the determination of the
IMF: binning and the existence of unresolved components. The first source is
important for clusters with a small number of stars detected in a given mass
bin while the second one is relevant for all clusters located beyond the
immediate solar neighborhood. For both cases I will present results of
numerical simulations and I will discuss strategies to correct for their
effects. I also present a brief description of a third unrelated bias source.


title:
Bipolaronic proximity and other unconventional effects in cuprate
  superconductors

abstract:
  There is compelling evidence for a strong electron-phonon interaction (EPI)
in cuprate superconductors from the isotope effects on the supercarrier mass,
high resolution angle resolved photoemission spectroscopies (ARPES), a number
of optical and neutron-scattering measurements in accordance with our
prediction of high-temperature superconductivity in polaronic liquids. A number
of observations point to the possibility that high-Tc cuprate superconductors
may not be conventional Bardeen-Cooper-Schrieffer (BCS) superconductors, but
rather derive from the Bose-Einstein condensation (BEC) of real-space pairs,
which are mobile small bipolarons. Here I review the bipolaron theory of
unconventional proximity effects, the symmetry and checkerboard modulations of
the order parameter and quantum magneto-oscillations discovered recently in
cuprates.


title: Stable laws and products of positive random matrices

abstract:
  Let $S$ be the multiplicative semigroup of $q\times q$ matrices with positive
entries such that every row and every column contains a strictly positive
element. Denote by $(X_n)_{n\geq1}$ a sequence of independent identically
distributed random variables in $S$ and by $X^{(n)} = X_n ... X_1$, $ n\geq 1$,
the associated left random walk on $S$. We assume that $(X_n)_{n\geq1}$
verifies the contraction property
  $\P(\bigcup_{n\geq1}[X^{(n)} \in S^\circ])>0$,
  where $S^\circ $ is the subset of all matrices which have strictly positive
entries. We state conditions on the distribution of the random matrix $X_1$
which ensure that the logarithms of the entries, of the norm, and of the
spectral radius of the products $X^{(n)}$, $n\ge 1$, are in the domain of
attraction of a stable law.


title: Higher dimensional cosmological model with a phantom field

abstract:
  We consider a higher dimensional gravity theory with a negative kinetic
energy scalar field and a cosmological constant. We find that the theory admits
an exact cosmological solution for the scale factor of our universe. It has the
feature that the universe undergoes a continuous transition from deceleration
to acceleration at some finite time. This transition time can be interpreted as
that of recent acceleration of our universe.


title:
IRAC Photometric Analysis and the Mid-IR Photometric Properties of Lyman
  Break Galaxies

abstract:
  We present photometric analysis of deep mid-infrared observations obtained by
Spitzer/IRAC covering the fields Q1422+2309, Q2233+1341, DSF2237a,b, HDFN,
SSA22a,b and B20902+34, giving the number counts and the depths for each field.
In a sample of 751 LBGs lying in those fields, 443, 448, 137 and 152 are
identified at 3.6microns, 4.5microns, 5.8microns, 8.0microns IRAC bands
respectively, expanding their spectral energy distribution to
rest-near-infrared and revealing that LBGs display a variety of colours. Their
rest-near-infrared properties are rather inhomogeneous, ranging from those that
are bright in IRAC bands and exhibit [R]-[3.6] > 1.5 colours to those that are
faint or not detected at all in IRAC bands with [R]-[3.6] < 1.5 colours and
these two groups of LBGs are investigated. We compare the mid-IR colours of the
LBGs with the colours of star-forming galaxies and we find that LBGs have
colours consistent with star-foming galaxies at z~3. The properties of the LBGs
detected in the 8microns IRAC band (rest frame K-band) are examined separately,
showing that they exhibit redder [R]-[3.6] colours than the rest of the
population and that IRAC 8microns band can be used as a diagnostic tool, to
separate AGN dominated objects from normal star-forming galaxies at z~3


title: Non-linear response of molecular junctions: The polaron model revisited

abstract:
  A polaron model proposed as a possible mechanism for nonlinear conductance
[Galperin M, Ratner M A, and Nitzan A 2005 Nano Lett. 5 125-30] is revisited
with focus on the differences between the weak and strong molecule-lead
coupling cases. Within the one-molecular level model we present an approximate
expression for the electronic Green function corresponding to inelastic
transport case, which in the appropriate limits reduces to expressions
presented previously for the isolated molecule and for molecular junction
coupled to a slow vibration (static limit). The relevance of considerations
based on the isolated molecule limit to understanding properties of molecular
junctions is discussed.


title: Response of Boolean networks to perturbations

abstract:
  We evaluate the probability that a Boolean network returns to an attractor
after perturbing h nodes. We find that the return probability as function of h
can display a variety of different behaviours, which yields insights into the
state-space structure. In addition to performing computer simulations, we
derive analytical results for several types of Boolean networks, in particular
for Random Boolean Networks. We also apply our method to networks that have
been evolved for robustness to small perturbations, and to a biological
example.


title: Asymmetric simple exclusion process describing conflicting traffic flows

abstract:
  We use the asymmetric simple exclusion process for describing vehicular
traffic flow at the intersection of two streets. No traffic lights control the
traffic flow. The approaching cars to the intersection point yield to each
other to avoid collision. This yielding dynamics is model by implementing
exclusion process to the intersection point of the two streets. Closed boundary
condition is applied to the streets. We utilize both mean-field approach and
extensive simulations to find the model characteristics. In particular, we
obtain the fundamental diagrams and show that the effect of interaction between
chains can be regarded as a dynamic impurity at the intersection point.


title: Particle Acceleration by Fast Modes in Solar Flares

abstract:
  We address the problem of particle acceleration in solar flares by fast modes
which may be excited during the reconnection and undergo cascade and are
subjected to damping. We extend the calculations beyond quasilinear
approximation and compare the acceleration and scattering by transit time
damping and gyroresonance interactions. We find that the acceleration is
dominated by the so called transit time damping mechanism. We estimate the
total energy transferred into particles, and show that our approach provides
sufficiently accurate results We compare this rate with energy loss rate.
Scattering by fast modes appears to be sufficient to prevent the protons from
escaping the system during the acceleration. Confinement of electrons, on the
other hand, requires the existence of plasma waves. Electrons can be
accelerated to GeV energies through the process described here for solar flare
conditions.


title: Reduced Density Matrix Functional for Many-Electron Systems

abstract:
  Reduced density matrix functional theory for the case of solids is presented
and a new exchange correlation functional based on a fractional power of the
density matrix is introduced. We show that compared to other functionals, this
produces more accurate results for both finite systems. Moreover, it captures
the correct band gap behavior for conventional semiconductors as well as
strongly correlated Mott insulators, where a gap is obtained in absence of any
magnetic ordering.


title:
Hilbert's Nullstellensatz and an Algorithm for Proving Combinatorial
  Infeasibility

abstract:
  Systems of polynomial equations over an algebraically-closed field K can be
used to concisely model many combinatorial problems. In this way, a
combinatorial problem is feasible (e.g., a graph is 3-colorable, hamiltonian,
etc.) if and only if a related system of polynomial equations has a solution
over K. In this paper, we investigate an algorithm aimed at proving
combinatorial infeasibility based on the observed low degree of Hilbert's
Nullstellensatz certificates for polynomial systems arising in combinatorics
and on large-scale linear-algebra computations over K. We report on experiments
based on the problem of proving the non-3-colorability of graphs. We
successfully solved graph problem instances having thousands of nodes and tens
of thousands of edges.


title: Anomalous transport and relaxation in classical one-dimensional models

abstract:
  After reviewing the main features of anomalous energy transport in 1D
systems, we report simulations performed with chains of noisy anharmonic
oscillators. The stochastic terms are added in such a way to conserve total
energy and momentum, thus keeping the basic hydrodynamic features of these
models. The addition of this "conservative noise" allows to obtain a more
efficient estimate of the power-law divergence of heat conductivity kappa(L) ~
L^alpha in the limit of small noise and large system size L. By comparing the
numerical results with rigorous predictions obtained for the harmonic chain, we
show how finite--size and --time effects can be effectively controlled. For low
noise amplitudes, the alpha values are close to 1/3 for asymmetric potentials
and to 0.4 for symmetric ones. These results support the previously conjectured
two-universality-classes scenario.


title:
Characterization of the Vertices and Extreme Directions of the Negative
  Cycles Polyhedron and Hardness of Generating Vertices of 0/1-Polyhedra

abstract:
  Given a graph $G=(V,E)$ and a weight function on the edges $w:E\mapsto\RR$,
we consider the polyhedron $P(G,w)$ of negative-weight flows on $G$, and get a
complete characterization of the vertices and extreme directions of $P(G,w)$.
As a corollary, we show that, unless $P=NP$, there is no output polynomial-time
algorithm to generate all the vertices of a 0/1-polyhedron. This strengthens
the NP-hardness result of Khachiyan et al. (2006) for non 0/1-polyhedra, and
comes in contrast with the polynomiality of vertex enumeration for
0/1-polytopes \cite{BL98} [Bussieck and L\"ubbecke (1998)].


title: Hypernuclear Physics for Neutron Stars

abstract:
  The role of hypernuclear physics for the physics of neutron stars is
delineated. Hypernuclear potentials in dense matter control the hyperon
composition of dense neutron star matter. The three-body interactions of
nucleons and hyperons determine the stiffness of the neutron star equation of
state and thereby the maximum neutron star mass. Two-body hyperon-nucleon and
hyperon-hyperon interactions give rise to hyperon pairing which exponentially
suppresses cooling of neutron stars via the direct hyperon URCA processes.
Non-mesonic weak reactions with hyperons in dense neutron star matter govern
the gravitational wave emissions due to the r-mode instability of rotating
neutron stars.


title: Inverse Zero-Sum Problems III

abstract:
  Let $G$ be a finite abeilian group. A sequence $S$ with terms from $G$ is
zero-sum if the sum of terms in $S$ equals zero. It is a minimal zero-sum
sequence if no proper, nontrivial subsequence is zero-sum. The maximal length
of a minimal zero-sum subsequence in $G$ is the Davenport constant, denoted
$D(G)$. For a rank 2 group $G=C_n \oplus C_n$, it is known that $D(G)=2n-1$.
However, the structure of all maximal length minimal zero-sum sequences remains
open. If every such sequence contains a term with multiplicity $n-1$, then $C_n
\oplus C_n$ is said to have Property B, and it is conjectured that this is true
for all rank 2 groups $C_n \oplus C_n$.
  In this paper, we show that Property B is multiplicative, namely, if $G=C_n
\oplus C_n$ and $G=C_m \oplus C_m$ both satisfy Property B, with $m, n\geq 3$
odd and $mn>9$, then $C_{mn}\oplus C_{mn}$ satisfies Property B also. Combined
with previous work in the literature, this reduces the question of establishing
Property B to the prime cases, and in such case the complete structural
description of the sequence follows.


title: Second order contributions to the absorption of massive particles

abstract:
  Recently, in analogy with multiphoton ionization, it has been suggested that
multiparticle ionization can also be induced by massive systems. We explore in
this paper the possibility that multiparticle absorption processes can also
take place for massive particles. To study it we consider, in a perturbative
way, a model of absorption which illustrates the analogies with Glauber's
scheme for photons and previous analysis on matter-waves coherence. A major
advantage of this approach is that the dependence of the absorption rates on
the wavefunction of the incident system can be analyzed in an explicit way. The
calculations confirm the form of the second order (two-particle) contributions.


title:
Resonant Energy Transfer from Organics to Quantum Dots and Carrier
  Multiplication

abstract:
  It was shown in the recent experiments that the hybrid organic/inorganic
resonant structures can provide a flexible materials platform aimed at the
design of novel light emitting devices. The applications of hybrid structures
for photovoltaic solar cell can also be useful. We pay attention in this note
that the resonant energy transfer in hybrid structure from the organic thin
layer to the semiconductor nanostructures can drastically increase the
intensity of the free carrier generation. To demonstrate this idea we use the
results of recently published paper by Zhang et al., Nature Nanotechnology 2,
555 (2007), demonstrating the highly efficient resonance energy transfer from
J-aggregates layer to semiconductor nanocrystals. It is known that the
semiconductor nanocrystals with small energy gap represent a promising route to
increased solar conversion in single--junction photovoltaic cells. We argue
that the using of nanocrystals with small energy gap in the hybrid
organic/inorganic structures similar to created by Zhang et al. can increase
tens times the total intensity of carrier multiplication. The organic part in
such hybrid structures will play a role of the peculiar organic concentrator of
the light energy.


title: Trapped p-wave superfluids: a local density approach

abstract:
  The local density approximation is used to study the ground state superfluid
properties of harmonically trapped p-wave Fermi gases as a function of
fermion-fermion attraction strength. While the density distribution is bimodal
on the weakly attracting BCS side, it becomes unimodal with increasing
attraction and saturates towards the BEC side. This non-monotonic evolution is
related to the topological gapless to gapped phase transition, and may be
observed via radio-frequency spectroscopy since quasi-particle transfer current
requires a finite threshold only on the BEC side.


title: A Quantum Optical Spring

abstract:
  We study the dynamics of the quantum optical spring, i.e., a spring whose
spring constant undergoes discreet jumps depending on the quantum state of
another system. We show the existence of revivals and fractional revivals in
the quantum dynamics reminiscent of similar dynamical features in cavity QED.
We recover in the semi classical limit the results for an oscillator whose
frequency undergoes a sudden change. The quantum optical spring is conceivable
for example by a micromirror under the influence of radiation pressure by a
field which is strictly quantum. Our work suggests that driven systems would in
general exhibit a very different dynamics if the drive is replaced by a quantum
source.


title: Novel Bounds on Marginal Probabilities

abstract:
  We derive two related novel bounds on single-variable marginal probability
distributions in factor graphs with discrete variables. The first method
propagates bounds over a subtree of the factor graph rooted in the variable,
and the second method propagates bounds over the self-avoiding walk tree
starting at the variable. By construction, both methods not only bound the
exact marginal probability distribution of a variable, but also its approximate
Belief Propagation marginal (``belief''). Thus, apart from providing a
practical means to calculate bounds on marginals, our contribution also lies in
an increased understanding of the error made by Belief Propagation.
Empirically, we show that our bounds often outperform existing bounds in terms
of accuracy and/or computation time. We also show that our bounds can yield
nontrivial results for medical diagnosis inference problems.


title:
Isotope shift in the dielectronic recombination of three-electron
  ^{A}Nd^{57+}

abstract:
  Isotope shifts in dielectronic recombination spectra were studied for Li-like
^{A}Nd^{57+} ions with A=142 and A=150. From the displacement of resonance
positions energy shifts \delta E^{142,150}(2s-2p_1/2)= 40.2(3)(6) meV
(stat)(sys)) and \delta E^{142,150}(2s-2p_3/2) = 42.3(12)(20) meV of 2s-2p_j
transitions were deduced. An evaluation of these values within a full QED
treatment yields a change in the mean-square charge radius of ^{142,150}\delta
<r^2> = -1.36(1)(3) fm^2. The approach is conceptually new and combines the
advantage of a simple atomic structure with high sensitivity to nuclear size.


title:
Early SUSY discovery at LHC without missing E_T: the role of
  multi-leptons

abstract:
  Traditional searches for SUSY at hadron colliders rely heavily on the
presence of large missing transverse energy (ME_T) to reject background
compared to signal. On the other hand, initial searches for new physics at the
LHC may not be able to rely on ME_T due to a variety of detector calibration
issues. We show that much of SUSY parameter space is accessible to discovery
even {\it without} using ME_T, and with rather low integrated luminosities
0.1-1 fb^{-1}. A key role is played by isolated lepton multiplicity which
arises from gluino and squark cascade decays. Requiring \ge 3 isolated leptons
plus jets yields a high rate of background rejection compared to signal. We
find an LHC reach in m(gluino) of about 700-750 GeV for just 0.1 fb^{-1} of
integrated luminosity by requiring events with \ge 4 jets plus \ge 3 isolated
leptons but {\it without} using ME_T. If a large enough event sample is
assembled, then kinematic reconstruction of sparticle mass properties should be
possible just as in the case where large ME_T is required. SUSY without ME_T
can also be seen in opposite-sign/same flavor {\it dilepton plus jets} events
when a characteristic invariant mass edge stands out against background.


title:
Non-perturbative k-body to two-body commuting conversion Hamiltonians
  and embedding problem instances into Ising spins

abstract:
  An algebraic method has been developed which allows one to engineer several
energy levels including the low-energy subspace of interacting spin systems. By
introducing ancillary qubits, this approach allows k-body interactions to be
captured exactly using 2-body Hamiltonians. Our method works when all terms in
the Hamiltonian share the same basis and has no dependence on perturbation
theory or the associated large spectral gap. Our methods allow problem instance
solutions to be embedded into the ground energy state of Ising spin systems.
Adiabatic evolution might then be used to place a computational system into
it's ground state.


title:
A Cross-correlation method to search for gravitational wave bursts with
  AURIGA and Virgo

abstract:
  We present a method to search for transient GWs using a network of detectors
with different spectral and directional sensitivities: the interferometer Virgo
and the bar detector AURIGA. The data analysis method is based on the
measurements of the correlated energy in the network by means of a weighted
cross-correlation. To limit the computational load, this coherent analysis step
is performed around time-frequency coincident triggers selected by an excess
power event trigger generator tuned at low thresholds. The final selection of
GW candidates is performed by a combined cut on the correlated energy and on
the significance as measured by the event trigger generator. The method has
been tested on one day of data of AURIGA and Virgo during September 2005. The
outcomes are compared to the results of a stand-alone time-frequency
coincidence search. We discuss the advantages and the limits of this approach,
in view of a possible future joint search between AURIGA and one
interferometric detector.


title:
Dichotomy Results for Fixed-Point Existence Problems for Boolean
  Dynamical Systems

abstract:
  A complete classification of the computational complexity of the fixed-point
existence problem for boolean dynamical systems, i.e., finite discrete
dynamical systems over the domain {0, 1}, is presented. For function classes F
and graph classes G, an (F, G)-system is a boolean dynamical system such that
all local transition functions lie in F and the underlying graph lies in G. Let
F be a class of boolean functions which is closed under composition and let G
be a class of graphs which is closed under taking minors. The following
dichotomy theorems are shown: (1) If F contains the self-dual functions and G
contains the planar graphs then the fixed-point existence problem for (F,
G)-systems with local transition function given by truth-tables is NP-complete;
otherwise, it is decidable in polynomial time. (2) If F contains the self-dual
functions and G contains the graphs having vertex covers of size one then the
fixed-point existence problem for (F, G)-systems with local transition function
given by formulas or circuits is NP-complete; otherwise, it is decidable in
polynomial time.

categories: cs.CC cond-mat.dis-nn cs.DM nlin.AO nlin.CG


title:
INTEGRAL, XMM-Newton and ESO/NTT identification of AX J1749.1-2733: an
  obscured and probably distant Be/X-ray binary

abstract:
  AX J1749.1-2733 is an unclassified transient X-ray source discovered during
surveys by ASCA in 1993-1999. A multi-wavelength study in NIR, optical, X-rays
and hard X-rays is undertaken in order to determine its nature. AX J1749.1-2733
is a new high-mass X-ray binary pulsar with an orbital period of 185.5+/-1.1 d
(or 185.5/f with f=2,3 or 4) and a spin period of ~66 s, parameters typical of
a Be/X-ray binary. The outbursts last ~12 d. A spin-down of 0.08+/-0.02 s/yr is
also observed, very likely due to the propeller effect. The most accurate X-ray
position is R.A. (2000) =17h49m06.8s and Dec. = -27deg32'32".5 (unc. 2"). The
high-energy broad-band spectrum is well-fitted with an absorbed powerlaw and a
high-energy cutoff with values NH=(20+/-1)e22 cm-2, Gamma=1.0+/-0.1, and
Ecut=21+/-3 keV. The only optical/NIR candidate counterpart within the X-ray
error circle has magnitudes of R=21.9+/-0.1, I=20.92+/-0.09, J=17.42+/-0.03,
H=16.71+/-0.02, and Ks=15.75+/-0.07, which points towards a Be star located far
away (> 8.5 kpc) and highly absorbed (NH~1.7e22 cm-2). The average 22-50 keV
luminosity is (0.4-0.9)e36 erg/s during the long outbursts and 3e36 erg/s
during the bright flare that occurred on MJD 52891 for an assumed distance of
8.5 kpc.


title: On the corresponding states law of the Yukawa fluid

abstract:
  We have analyzed the currently available simulation results, as well as
performed some additional Monte Carlo simulation for the hard-core attractive
Yukawa fluid in order to study its corresponding state behavior. We show that
the values of reduced surface tension map onto the master curve, and a
universal equation of state can be obtained in the wide range of the attractive
Yukawa tail length after a certain re-scaling of the number density. Some
comparisons with other nonconformal potentials are presented and discussed.


title:
Scattering and absorption of gravitational plane waves by rotating black
  holes

abstract:
  This is a study of the scattering and absorption of planar gravitational
waves by a Kerr black hole in vacuum. We apply the partial wave method to
compute cross sections for the special case of radiation incident along the
rotation axis. A catalogue of numerically-accurate cross sections is presented,
for a range of incident wavelengths $M\omega \le 4$ and rotation rates $a \le
0.999M$. Three effects are studied in detail: polarization, helicity-reversal
and glory scattering. First, a new approximation to the polarization in the
long-wavelength limit is derived. We show that black hole rotation
distinguishes between co- and counter-rotating wave helicities, leading to a
term in the cross section proportional to $a\omega$. Second, we confirm that
helicity is not conserved by the scattering process, and show that
superradiance amplifies the effect. For certain wavelengths, the back-scattered
flux is enhanced by as much as $\sim 35$ times for a rapidly-rotating hole
(e.g. for $a = 0.999M$ at $M\omega = 0.945$). Third, we observe regular glory
and spiral scattering peaks in the numerically-determined cross sections. We
show that the angular width and intensity of the peaks may be estimated via a
semi-classical approximation. We conclude with a discussion of the observable
implications of our results.


title:
Minimum requirements for laser-induced symmetry breaking in quantum and
  classical mechanics

abstract:
  Necessary conditions for generating phase controllable asymmetry in spatially
symmetric systems using lasers are identified and are shown to be identical in
quantum and classical mechanics. First, by studying the exact dynamics of
harmonic systems in the presence of an arbitrary radiation field, it is
demonstrated that anharmonicities in the system's potential are a necessary
requirement for phase controllability. Then, by analyzing the space-time
symmetries of the laser-driven Liouville dynamics for classical and quantum
systems, a common set of temporal symmetries for the driving field that need to
be violated to induce transport are identified. The conditions apply to
continuous wave lasers and to symmetry breaking effects that do not rely on the
control of the absolute phase of the field. Known examples of laser fields that
can induce transport in symmetric systems are seen to be particular cases of
these symmetry constraints.


title:
Solar Mass Loss, the Astronomical Unit, and the Scale of the Solar
  System

abstract:
  The radiative and particulate loss of mass by the Sun, -9.13*10^-14 Solar
masses per year or more causes the orbits of the planets to expand at the same
rate, and their periods to lengthen at twice this rate. Unfortunately, under
the present definition of the Astronomical Unit (AU) based on the fixed
Gaussian gravity constant kGS = 0.01720209895 (AU)^1.5/day, the value AUmet of
the AU in meters must decrease at 1/3 this rate, all these rates being
expressed logarithmically. The progress of the planets along their orbits slows
quadratically with time. For example, in one century Mercury would lag behind
the position predicted using constant solar mass by almost 1.4 km, in two
centuries 5.5 km. The value of AUmet can be made constant by redefining it,
based on a reference solar mass unit, such as the solar mass at J2000; else,
the solar Gaussian gravity constant kGS used in defining the AU could be
redefined proportional to the square root of the solar mass. Improved accuracy
of the ephemerides would impose useful bounds on losses due to axion emission
(Sikivie 2005). With no axion emission the Earth's semi-major axis grows 1.37
m/cy; with the maximum allowable such emission the result is 1.57 m/cy. Under
reasonable assumptions about alternate gravity theories, radar delay data are
used to show that the effect of a changing Newtonian gravity constant is
negligible.


title:
Creating semiclassical black holes in collider experiments and keeping
  them on a string

abstract:
  We argue that a simple modification of the TeV scale quantum gravity scenario
allows production of semiclassical black holes in particle collisions at the
LHC. The key idea is that in models with large extra dimensions the strength of
gravity in the bulk can be higher than on the brane where we live. A well-known
example of this situation is the case of warped extra dimensions. Even if the
energy of the collision is not sufficient to create a black hole on the brane,
it may be enough to produce a particle which accelerates into the bulk up to
trans-Planckian energy and creates a large black hole there. In a concrete
model we consider, the black hole is formed in a collision of the particle with
its own image at an orbifold plane. When the particle in question carries some
Standard Model gauge charges the created black hole gets attached to our brane
by a string of the gauge flux. For a 4-dimensional observer such system looks
as a long-lived charged state with the mass continuously decreasing due to
Hawking evaporation of the black hole. This provides a distinctive signature of
black hole formation in our scenario.


title: An existence result for the sandpile problem on flat tables with walls

abstract:
  We derive an existence result for solutions of a differential system which
characterizes the equilibria of a particular model in granular matter theory,
the so-called partially open table problem for growing sandpiles. Such result
generalizes a recent theorem of Cannarsa and Cardaliaguet established for the
totally open table problem. Here, due to the presence of walls at the boundary,
the surface flow density at the equilibrium may result no more continuous nor
bounded, and its explicit mathematical characterization is obtained by domain
decomposition techniques. At the same time we show how these solutions can be
numerically computed as stationary solutions of a dynamical two-layer model for
growing sandpiles and we present the results of some simulations.


title: Electron mass shift in nonthermal systems

abstract:
  The electron mass is known to be sensitive to local fluctuations in the
electromagnetic field, and undergoes a small shift in a thermal field. It was
claimed recently that a very large electron mass shift should be expected near
the surface of a metal hydride [{\it Eur. Phys. J. C}, {\bf 46} 107 (2006)]. We
examine the shift using a formulation based on the Coulomb gauge, which leads
to a much smaller shift. The maximization of the electron mass shift under
nonequilibrium conditions seems nonetheless to be an interesting problem. We
consider a scheme in which a current in a hollow wire produces a large vector
potential in the wire center. Fluctuations in an LC circuit with nearly matched
loss and gain can produce large current fluctuations; and these can increase
the electron mass shift by orders of magnitude over its room temperature value.


title: Vari\'et\'es homog\`enes sous $\PGL_n$

abstract:
  Let $A$ be an Azumaya algebra over a field. If $G$ is the group of
automorphisms of $A$ and $X$ denotes a projective homogeneous variety under
$G$, we construct in a very explicit way and under suitable hypotheses a bundle
$\mathcal{V}$ on $S$, where $S$ is a (generalized) Severi-Brauer variety
associated to $A$, and a canonical isomorphism between $X$ and a flag bundle on
$\mathcal{V}$. This allows to explicitely compute Chow groups of $X$ in terms
of the Chow groups of $S$.


title:
Melvin Twists of global AdS_5 \times S_5 and their Non-Commutative Field
  Theory Dual

abstract:
  We consider the Melvin Twist of AdS_5 \times S_5 under U(1) \times U(1)
isometry of the boundary S_3 of the global AdS_5 geometry and identify its
field theory dual. We also study the thermodynamics of the Melvin deformed
theory.


title: Frame potential and finite abelian groups

abstract:
  This article continues a prior investigation of the authors with the goal of
extending characterization results of convolutional tight frames from the
context of cyclic groups to general finite abelian groups. The collections
studied are formed by translating a number of \emph{generators} by elements of
a fixed subgroup and it is shown, under certain norm conditions, that tight
frames with this structure are characterized as local minimizers of the frame
potential. Natural analogs to the downsampling and upsampling operators of
finite cyclic groups are studied for arbitrary subgroups of finite abelian
groups. Directions of further study are also proposed.


title: Non thermal emission in clusters of galaxies

abstract:
  I briefly review our current knowledge of the non thermal emission from
galaxy clusters and discuss future prospect with Simbol-X. Simbol-X will map
the hard X-ray emission in clusters, determine its origin and disentangle the
thermal and non-thermal components. Correlated with radio observations, the
observation of the non-thermal X-ray emission, when confirmed, will allow to
map both the magnetic field and the relativistic electron properties, key
information to understand the origin and acceleration of relativistic particles
in clusters and its impact on cluster evolution.


title: On cusps and flat tops

abstract:
  We develop non-invertible Pesin theory for a new class of maps called cusp
maps. These maps may have unbounded derivative, but nevertheless verify a
property analogous to $C^{1+\epsilon}$. We do not require the critical points
to verify a non-flatness condition, so the results are applicable to
$C^{1+\epsilon}$ maps with flat critical points. If the critical points are too
flat, then no absolutely continuous invariant probability measure can exist.
This generalises a result of Benedicks and Misiurewicz.


title:
Algorithm for solving optimization problems with Interval Valued
  Probability Measure

abstract:
  We are concerned with three types of uncertainties: probabilistic,
possibilitistic and interval. By using possibility and necessity measures as an
Interval Valued Probability Measure (IVPM), we present IVPM's interval expected
values whose possibility distributions are in the form of polynomials. By
working with interval expected values of independent uncertainty coefficients
in a linear optimization problem together with operations suggested in Lodwick
and Jamison (2007), the problem after applying these operations becomes a
linear programming problem with constant coefficients. This is achieved by the
application of two functions. The first is applied to the interval
coefficients, v: I -> R^k, where I= {[a,b] | a <= b}. The second is u: R^k ->
R, applied to the product we got from a previous function. Similar concepts
hold for any types of optimization problems with linear constraints. Moreover,
it implied that optimization problems containing all three types of
uncertainties in one problem can be solved as ordinary optimization problems.


title: Robustness Evaluation of Two CCG, a PCFG and a Link Grammar Parsers

abstract:
  Robustness in a parser refers to an ability to deal with exceptional
phenomena. A parser is robust if it deals with phenomena outside its normal
range of inputs. This paper reports on a series of robustness evaluations of
state-of-the-art parsers in which we concentrated on one aspect of robustness:
its ability to parse sentences containing misspelled words. We propose two
measures for robustness evaluation based on a comparison of a parser's output
for grammatical input sentences and their noisy counterparts. In this paper, we
use these measures to compare the overall robustness of the four evaluated
parsers, and we present an analysis of the decline in parser performance with
increasing error levels. Our results indicate that performance typically
declines tens of percentage units when parsers are presented with texts
containing misspellings. When it was tested on our purpose-built test set of
443 sentences, the best parser in the experiment (C&C parser) was able to
return exactly the same parse tree for the grammatical and ungrammatical
sentences for 60.8%, 34.0% and 14.9% of the sentences with one, two or three
misspelled words respectively.


title: Multiwavelength Studies of X-ray Binaries

abstract:
  Simultaneous multiwavelength studies of X-ray binaries have been remarkably
successful and resulted in improved physical constraints, a new understanding
of the dependence of mass accretion rate on X-ray state, as well as insights on
the time-dependent relationship between disk structure and mass-transfer rate.
I will give some examples of the tremendous gains we have obtained in our
understanding of XRBs by using multiwavelength observations. I will end with an
appeal that while Spitzer cryogens are still available a special effort be put
forth to obtaining coordinated observations including the mid-infrared: Whereas
the optical and near-IR originate as superpositions of the secondary star and
of accretion processes, the mid-IR crucially detects jet synchrotron emission
from NSs that is virtually immeasurable at other wavelengths. A further benefit
of Spitzer observations is that mid-infrared wavelengths can easily penetrate
regions that are heavily obscured. Many X-ray binaries lie in the Galactic
plane and as such are often heavily obscured in the optical by interstellar
extinction. The infrared component of the SED, vital to the study of jets and
dust, can be provided {\it only} by Spitzer; in the X-rays we currently have an
unprecedented six satellites available and in the optical and radio dozens of
ground-based facilities to complement the Spitzer observations.


title:
Symmetry of Reidemeister torsion on $SU_2$-representation spaces of
  knots

abstract:
  We study two sorts of actions on the space of conjugacy classes of
irreducible $SU_2$-representations of a knot group. One of them is an
involution which comes from the algebraic structure of $SU_2$ and the other is
the action by the outer automorphism group of the knot group. In particular, we
consider them on an 1-dimensional smooth part of the space, which is
canonically oriented and metrized via a Reidemeister torsion volume form. As an
application we show that the Reidemeister torsion function on the 1-dimensional
subspace has symmetry about the metrization.


title:
Time evolution of a superposition of dressed oscillator states in a
  cavity

abstract:
  Using the formalism of {\it renormalized} coordinates and \textit{dressed}
states introduced in previous publications, we perform a nonperturbative study
of the time evolution of a superposition of two states, the ground state and
the first excited level of a harmonic oscillator, the system being confined in
a perfectly reflecting cavity of radius $R$. For $R\to\infty$, we find
dissipation with dominance of the interference terms of the density matrix, in
both weak- and strong-coupling regimes. For small values of $R$ all elements of
the density matrix present an oscillatory behavior as times goes on and the
system is not dissipative. In both cases, we obtain improved theoretical
results with respect to those coming from perturbation theory.

categories: quant-ph cond-mat.other hep-th math-ph math.MP


title: On the radiative decays of light vector and axial-vector mesons

abstract:
  We study the light vector and axial-vector mesons. According to the
hadrogenesis conjecture the nature of the two types of states is distinct. The
axial-vector mesons are generated dynamically by coupled-channel interactions
based on the chiral Lagrangian written down in terms of the Goldstone bosons
and the light vector mesons. We propose a novel counting scheme that arises if
the chiral Lagrangian is supplemented by constraints from large-N_c QCD in the
context of the hadrogenesis conjecture. The counting scheme is successfully
tested by a systematic study of the properties of vector mesons. The spectrum
of light axial-vector mesons is derived relying on the leading order
interaction of the Goldstone bosons with the vector mesons supplemented by a
phenomenology for correction terms. The f_1(1282), b_1(1230), h_1(1386),
a_1(1230) and K_1(1272) mesons are recovered as molecular states. Based on
those results the one-loop contributions to the electromagnetic decay
amplitudes of axial-vector molecules into pseudo-scalar or vector mesons are
evaluated systematically. In order to arrive at gauge invariant results in a
transparent manner we choose to represent the vector particles by
anti-symmetric tensor fields. It is emphasized that there are no tree-level
contributions to a radiative decay amplitude of a given state if that state is
generated by coupled-channel dynamics. The inclusion of the latter would be
double counting. At present we restrict ourselves to loops where a vector and a
pseudo-scalar meson couple to the axial-vector molecule. We argue that final
and predictive results require further computations involving intermediate
states with two vector mesons. The relevance of the latter is predicted by our
counting rules.


title: Estimating the Redshift Distribution of Faint Galaxy Samples

abstract:
  We present an empirical method for estimating the underlying redshift
distribution N(z) of galaxy photometric samples from photometric observables.
The method does not rely on photometric redshift (photo-z) estimates for
individual galaxies, which typically suffer from biases. Instead, it assigns
weights to galaxies in a spectroscopic subsample such that the weighted
distributions of photometric observables (e.g., multi-band magnitudes) match
the corresponding distributions for the photometric sample. The weights are
estimated using a nearest-neighbor technique that ensures stability in sparsely
populated regions of color-magnitude space. The derived weights are then summed
in redshift bins to create the redshift distribution. We apply this weighting
technique to data from the Sloan Digital Sky Survey as well as to mock catalogs
for the Dark Energy Survey, and compare the results to those from the
estimation of photo-z's derived by a neural network algorithm. We find that the
weighting method accurately recovers the underlying redshift distribution,
typically better than the photo-z reconstruction, provided the spectroscopic
subsample spans the range of photometric observables covered by the photometric
sample.


title:
Role of the $\sigma$-resonance in determining the convergence of chiral
  perturbation theory

abstract:
  The dimensionless parameter $\xi = M_\pi^2/(16 \pi^2 F_\pi^2)$, where $F_\pi$
is the pion decay constant and $M_\pi$ is the pion mass, is expected to control
the convergence of chiral perturbation theory applicable to QCD. Here we
demonstrate that a strongly coupled lattice gauge theory model with the same
symmetries as two-flavor QCD but with a much lighter $\sigma$-resonance is
different. Our model allows us to study efficiently the convergence of chiral
perturbation theory as a function of $\xi$. We first confirm that the leading
low energy constants appearing in the chiral Lagrangian are the same when
calculated from the $p$-regime and the $\epsilon$-regime as expected. However,
$\xi \lesssim 0.002$ is necessary before 1-loop chiral perturbation theory
predicts the data within 1%. For $\xi > 0.0035$ the data begin to deviate
dramatically from 1-loop chiral perturbation theory predictions. We argue that
this qualitative change is due to the presence of a light $\sigma$-resonance in
our model. Our findings may be useful for lattice QCD studies.


title: Junctions of three quantum wires for spin 1/2 electrons

abstract:
  We study the effects of electron-electron interactions on the transport
properties of a junction of three quantum wires enclosing a magnetic flux. The
wires are modeled as single channel spin-1/2 Tomonaga-Luttinger liquids. The
system exhibits a rich phase diagram as a function of the electronic
interaction strength, which includes a chiral fixed point with an asymmetric
current flow highly sensitive to the sign of the flux, and another fixed point
where pair tunneling dominates, similarly to the case of spinless electrons.
While in the case of spinless electrons the perturbations that correspond to
unequal couplings between the three wires are always irrelevant, we find that,
when the electron spin is included, there are small regions in the phase
diagram where a current flows only between two of the wires and the third wire
is decoupled.


title: NICMOS Measurements of the Near Infrared Background

abstract:
  This paper addresses the nature of the near infrared background. We
investigate whether there is an excess background at 1.4 microns, what is the
source of the near infrared background and whether that background after the
subtraction of all known sources contains the signature of high redshift
objects (Z > 10). Based on NICMOS observations in the Hubble Ultra Deep Field
and the Northern Hubble Deep Field we find that there is no excess in the
background at 1.4 microns and that the claimed excess is due to inaccurate
models of the zodiacal background. We find that the near infrared background is
now spatially resolved and is dominated by galaxies in the redshift range
between 0.5 and 1.5. We find no signature than can be attributed to high
redshift sources after subtraction of all known sources either in the residual
background or in the fluctuations of the residual background. We show that the
color of the fluctuations from both NICMOS and Spitzer observations are
consistent with low redshift objects and inconsistent with objects at redshifts
greater than 10. It is most likely that the residual fluctuation power after
source subtraction is due to the outer regions of low redshift galaxies that
are below the source detection limit and therefore not removed during the
source subtraction.


title: Normal Toric Ideals of Low Codimension

abstract:
  Every normal toric ideal of codimension two is minimally generated by a
Grobner basis with squarefree initial monomials. A polynomial time algorithm is
presented for checking whether a toric ideal of fixed codimension is normal.


title: Discovery of Localized Regions of Excess 10-TeV Cosmic Rays

abstract:
  An analysis of 7 years of Milagro data performed on a 10-degree angular scale
has found two localized regions of excess of unknown origin with greater than
12 sigma significance. Both regions are inconsistent with gamma-ray emission
with high confidence. One of the regions has a different energy spectrum than
the isotropic cosmic-ray flux at a level of 4.6 sigma, and it is consistent
with hard spectrum protons with an exponential cutoff, with the most
significant excess at ~10 TeV. Potential causes of these excesses are explored,
but no compelling explanations are found.


title:
Rheological study of polymer flow past rough surfaces with slip boundary
  conditions

abstract:
  The slip phenomena in thin polymer films confined by either flat or
periodically corrugated surfaces are investigated by molecular dynamics and
continuum simulations. For atomically flat surfaces and weak wall-fluid
interactions, the shear rate dependence of the slip length has a distinct local
minimum which is followed by a rapid increase at higher shear rates. For
corrugated surfaces with wavelength larger than the radius of gyration of
polymer chains, the effective slip length decays monotonically with increasing
corrugation amplitude. At small amplitudes, this decay is reproduced accurately
by the numerical solution of the Stokes equation with constant and
rate-dependent local slip length. When the corrugation wavelength is comparable
to the radius of gyration, the continuum predictions overestimate the effective
slip length obtained from molecular dynamics simulations. The analysis of the
conformational properties indicates that polymer chains tend to stretch in the
direction of shear flow above the crests of the wavy surface.


title: Ferromagnet proximity effects and magnetoresistance of bilayer graphene

abstract:
  A drastic modification of electronic band structure is predicted in bilayer
graphene when it is placed between two ferromagnetic insulators. Due to the
exchange interaction with the proximate ferromagnet, the electronic energy
dispersion in the graphene channel strongly depends on the magnetization
orientation of two ferromagnetic layers, $\mathbf{M_{1}}$ and $\mathbf{M_{2}}
$. While the parallel configuration $\mathbf{M_{1}}= \mathbf{M_{2}}$ leads to
simple spin splitting of both conduction and valence bands, an energy gap is
induced as soon as the angle $\theta$ between $\mathbf{M_{1}}$ and $%
\mathbf{M_{2}}$ becomes non-zero with the maximum achieved at $\theta=\pi$
(i.e., antiparallel alignment). Consequently, bilayer graphene may exhibit a
sizable magnetoresistive effect in the current-in-plane configuration. A rough
estimate suggests the resistance changes on the order of tens of percent at
room temperature. This effect is expected to become more pronounced as the
temperatures decreases.


title: Climate Stability and Policy: A Synthesis

abstract:
  During most of the Phanerozoic eon, which began about a half-billion years
ago, there were few glacial intervals until the late Pliocene 2.75 million
years ago. Beginning at that time, the Earth's climate entered a period of
instability with the onset of cyclical ice ages. At first these had a 41,000
year cycle, and about 1 million years ago the period lengthened to 100,000
years, which has continued to the present. Over this period of instability the
climate has been extraordinarily sensitive to small forcings, whether due to
Milankovitch cycles, solar variations, aerosols, or albedo variations driven by
cosmic rays. The current interglacial has lasted for some ten thousand
years-about the duration of past interglacials-and serious policy
considerations arise as it nears its likely end. It is extremely unlikely that
the current rise in carbon dioxide concentration-some 30% since 1750, and
projected further increase over the next few decades-will significantly
postpone the next glaciation.


title: Experimental Quantum Process Discrimination

abstract:
  Discrimination between unknown processes chosen from a finite set is
experimentally shown to be possible even in the case of non-orthogonal
processes. We demonstrate unambiguous deterministic quantum process
discrimination (QPD) of non-orthogonal processes using properties of
entanglement, additional known unitaries, or higher dimensional systems. Single
qubit measurement and unitary processes and multipartite unitaries (where the
unitary acts non-separably across two distant locations) acting on photons are
discriminated with a confidence of $\geq97%$ in all cases.


title: Pinwheel stability, pattern selection and the geometry of visual space

abstract:
  It has been proposed that the dynamical stability of topological defects in
the visual cortex reflects the Euclidean symmetry of the visual world. We
analyze defect stability and pattern selection in a generalized Swift-Hohenberg
model of visual cortical development symmetric under the Euclidean group E(2).
Euclidean symmetry strongly influences the geometry and multistability of model
solutions but does not directly impact on defect stability.


title:
The Effects of Doubly Ionized Chemistry on SH+ and S^+2 Abundances in
  X-ray Dominated Regions

abstract:
  Recent laboratory measurements for the S^+2 + H2 reaction find a total rate
coefficient significantly larger than previously used in theoretical models of
X-ray dominated regions (XDRs). While the branching ratio of the products is
unknown, one energetically possible route leads to the SH+ molecule, a known
XDR diagnostic. In this work, we study the effects of S^+2 on the formation of
SH+ and the destruction of S^+2 in XDRs. We find the predicted SH+ column
density for molecular gas surrounding an Active Galactic Nucleus (AGN)
increases by as much as 2 dex. As long as the branching ratio for S^+2 + H2 ->
SH+ + H+ exceeds a few percent, doubly ionized chemistry will be the dominant
pathway to SH+, which then initiates the formation of other sulfur-bearing
molecules. We also find that the high rate of S^+2 + H2 efficiently destroys
S^+2 once H2 forms, while the S^+2 abundance remains high in the atomic
hydrogen region. We discuss the possible consequences of S^+2 in the atomic
hydrogen region on mid-infrared diagnostics. The enhanced SH+ abundance has
important implications in the study of XDRs, while our conclusions for S^+2
could potentially impact the interpretation of Spitzer and SOFIA observations.


title:
Large p-groups actions with a p-elementary abelian second ramification
  group

abstract:
  Let $k$ be an algebraically closed field of characteristic $p>0$ and $C$ a
connected nonsingular projective curve over $k$ with genus $g \geq 2$. Let
$(C,G)$ be a "big action", i.e. a pair $(C,G)$ where $G$ is a $p$-subgroup of
the $k$-automorphism group of $C$ such that$\frac{|G|}{g} >\frac{2 p}{p-1}$. We
denote by $G_2$ the second ramification group of $G$ at the unique ramification
point of the cover $C \to C/G$. The aim of this paper is to describe the big
actions whose $G_2$ is $p$-elementary abelian. In particular, we obtain a
structure theorem by considering the $k$-algebra generated by the additive
polynomials. We more specifically explore the case where there is a maximal
number of jumps in the ramification filtration of $G_2$. In this case, we
display some universal families.


title: Computing Arakelov class groups

abstract:
  Shanks's infrastructure algorithm and Buchmann's algorithm for computing
class groups and unit groups of rings of integers of algebraic number fields
are most naturally viewed as computations inside Arakelov class groups. In this
paper we discuss the basic properties of Arakelov class groups and of the set
of reduced Arakelov divisors. As an application we describe Buchmann's
algorithm in this context.


title: A-twisted Landau-Ginzburg models

abstract:
  In this paper we discuss correlation functions in certain A-twisted
Landau-Ginzburg models. Although B-twisted Landau-Ginzburg models have been
discussed extensively in the literature, virtually no work has been done on
A-twisted theories. In particular, we study examples of Landau-Ginzburg models
over topologically nontrivial spaces - not just vector spaces - away from
large-radius limits, so that one expects nontrivial curve corrections. By
studying examples of Landau-Ginzburg models in the same universality class as
nonlinear sigma models on nontrivial Calabi-Yaus, we obtain nontrivial tests of
our methods as well as a physical realization of some simple examples of
virtual fundamental class computations.


title: Universal Fingerprinting: Capacity and Random-Coding Exponents

abstract:
  This paper studies fingerprinting (traitor tracing) games in which the number
of colluders and the collusion channel are unknown. The fingerprints are
embedded into host sequences representing signals to be protected and provide
the receiver with the capability to trace back pirated copies to the colluders.
The colluders and the fingerprint embedder are subject to signal fidelity
constraints. Our problem setup unifies the signal-distortion and Boneh-Shaw
formulations of fingerprinting. The fundamental tradeoffs between fingerprint
codelength, number of users, number of colluders, fidelity constraints, and
decoding reliability are then determined. Several bounds on fingerprinting
capacity have been presented in recent literature. This paper derives exact
capacity formulas and presents a new randomized fingerprinting scheme with the
following properties: (1) the encoder and receiver assume a nominal coalition
size but do not need to know the actual coalition size and the collusion
channel; (2) a tunable parameter $\Delta$ trades off false-positive and
false-negative error exponents; (3) the receiver provides a reliability metric
for its decision; and (4) the scheme is capacity-achieving when the
false-positive exponent $\Delta$ tends to zero and the nominal coalition size
coincides with the actual coalition size.
  A fundamental component of the new scheme is the use of a "time-sharing"
randomized sequence. The decoder is a maximum penalized mutual information
decoder, where the significance of each candidate coalition is assessed
relative to a threshold, and the penalty is proportional to the coalition size.
A much simpler {\em threshold decoder} that satisfies properties (1)---(3)
above but not (4) is also given.


title:
Pseudodifferential multi-product representation of the solution operator
  of a parabolic equation

abstract:
  By using a time slicing procedure, we represent the solution operator of a
second-order parabolic pseudodifferential equation on $\R^n$ as an infinite
product of zero-order pseudodifferential operators. A similar representation
formula is proven for parabolic differential equations on a compact Riemannian
manifold. Each operator in the multi-product is given by a simple explicit
Ansatz. The proof is based on an effective use of the Weyl calculus and the
Fefferman-Phong inequality.


title: Gravitational Form Factors of Vector Mesons in an AdS/QCD Model

abstract:
  We calculate gravitational form factors of vector mesons using a holographic
model of QCD. These provide restrictions on the generalized parton
distributions of vector mesons, via the sum rules connecting stress tensor form
factors to GPDs. We concentrate on the traceless part of the stress tensor,
which suffices to fix the momentum and angular momentum sum rules. The vector
mesons appear noticeably more compact measured by the gravitational form
factors than by the charge form factor.


title: Four primality testing algorithms

abstract:
  In this expository paper we describe four primality tests. The first test is
very efficient, but is only capable of proving that a given number is either
composite or 'very probably' prime. The second test is a deterministic
polynomial time algorithm to prove that a given numer is either prime or
composite. The third and fourth primality tests are at present most widely used
in practice. Both tests are capable of proving that a given number is prime or
composite, but neither algorithm is deterministic. The third algorithm exploits
the arithmetic of cyclotomic fields. Its running time is almost, but not quite
polynomial time. The fourth algorithm exploits elliptic curves. Its running
time is difficult to estimate, but it behaves well in practice.


title: Analysis of Prime Reciprocal Sequences in Base 10

abstract:
  Prime reciprocals have applications in coding and cryptography and for
generation of random sequences. This paper investigates the structural
redundancy of prime reciprocals in base 10 in a manner that parallels an
earlier study for binary prime reciprocals. Several different kinds of
structural relationships amongst the digits in reciprocal sequences are
classified with respect to the digit in the least significant place of the
prime. It is also shown that the frequency of digit 0 exceeds that of every
other digit when the entire set of prime reciprocal sequences is considered.


title: Long-living Bloch oscillations of matter waves in optical lattices

abstract:
  It is shown that by properly designing the spatial dependence of the
nonlinearity it is possible to induce long-living Bloch oscillations of a
localized wavepacket in a periodic potential. The results are supported both by
analytical and numerical investigations and are interpreted in terms of matter
wave dynamics displaying dozens of oscillation periods without any visible
distortion of the wave packet.


title: The Classifying Space of a Topological 2-Group

abstract:
  Categorifying the concept of topological group, one obtains the notion of a
'topological 2-group'. This in turn allows a theory of 'principal 2-bundles'
generalizing the usual theory of principal bundles. It is well-known that under
mild conditions on a topological group G and a space M, principal G-bundles
over M are classified by either the first Cech cohomology of M with
coefficients in G, or the set of homotopy classes [M,BG], where BG is the
classifying space of G. Here we review work by Bartels, Jurco,
Baas-Bokstedt-Kro, and others generalizing this result to topological 2-groups
and even topological 2-categories. We explain various viewpoints on topological
2-groups and Cech cohomology with coefficients in a topological 2-group C, also
known as 'nonabelian cohomology'. Then we give an elementary proof that under
mild conditions on M and C there is a bijection between the first Cech
cohomology of M with coefficients in C and [M,B|C|] where B|C| is the
classifying space of the geometric realization of the nerve of C. Applying this
result to the 'string 2-group' String(G) of a simply-connected compact simple
Lie group G, it follows that principal String(G)-2-bundles have rational
characteristic classes coming from elements of the rational cohomology of BG
modulo the ideal generated by c, where c is any nonzero element in the 4th
cohomology of BG.


title: Quantum decoherence reduction by increasing the thermal bath temperature

abstract:
  The well-known increase of the decoherence rate with the temperature, for a
quantum system coupled to a linear thermal bath, holds no longer for a
different bath dynamics. This is shown by means of a simple classical
non-linear bath, as well as a quantum spin-boson model. The anomalous effect is
due to the temperature dependence of the bath spectral profile. The decoherence
reduction via the temperature increase can be relevant for the design of
quantum computers.


title: The formation of disk galaxies in computer simulations

abstract:
  The formation of disk galaxies is one of the most outstanding problems in
modern astrophysics and cosmology. We review the progress made by numerical
simulations carried out on large parallel supercomputers. Recent progress stems
from a combination of increased resolution and improved treatment of the
astrophysical processes modeled in the simulations, such as the
phenomenological description of the interstellar medium and of the process of
star formation. High mass and spatial resolution is a necessary condition in
order to obtain large disks comparable with observed spiral galaxies avoiding
spurious dissipation of angular momentum. A realistic model of the star
formation history. gas-to-stars ratio and the morphology of the stellar and
gaseous component is instead controlled by the phenomenological description of
the non-gravitational energy budget in the galaxy. We show that simulations of
gas collapse within cold dark matter halos including a phenomenological
description of supernovae blast-waves allow to obtain stellar disks with nearly
exponential surface density profiles as those observed in real disk galaxies,
counteracting the tendency of gas collapsing in such halos to form cuspy
baryonic profiles. However, the ab-initio formation of a realistic rotationally
supported disk galaxy with a pure exponential disk in a fully cosmological
simulation is still an open problem. We argue that the suppression of bulge
formation is related to the physics of galaxy formation during the merger of
the most massive protogalactic lumps at high redshift, where the reionization
of the Universe likely plays a key role. A sufficiently high resolution during
this early phase of galaxy formation is also crucial to avoid artificial
angular momentum loss (Abridged).


title: An Autonomous Adaptive Scheduling Agent for Period Searching

abstract:
  We describe the design and implementation of an autonomous adaptive software
agent that addresses the practical problem of observing undersampled, periodic,
time-varying phenomena using a network of HTN-compliant robotic telescopes. The
algorithm governing the behaviour of the agent uses an optimal geometric
sampling technique to cover the period range of interest, but additionally
implements proactive behaviour that maximises the optimality of the dataset in
the face of an uncertain and changing operating environment.


title: Non-parametric Dark Energy Degeneracies

abstract:
  We study the degeneracies between dark energy dynamics, dark matter and
curvature using a non-parametric and non-perturbative approach. This allows us
to examine the knock-on bias induced in the reconstructed dark energy equation
of state, w(z), when there is a bias in the cosmic curvature or dark matter
content, without relying on any specific parameterisation of w. Even assuming
perfect Hubble, distance and volume measurements, we show that for z > 1, the
bias in w(z) is up to two orders of magnitude larger than the corresponding
errors in Omega_k or Omega_m. This highlights the importance of obtaining
unbiased estimators of all cosmic parameters in the hunt for dark energy
dynamics.


title: Self-gravitating accretion discs

abstract:
  I review recent progresses in the dynamics and the evolution of
self-gravitating accretion discs. Accretion discs are a fundamental component
of several astrophysical systems on very diverse scales, and can be found
around supermassive black holes in Active Galactic Nuclei (AGN), and also in
our Galaxy around stellar mass compact objects and around young stars.
Notwithstanding the specific differences arising from such diversity in
physical extent, all these systems share a common feature where a central
object is fed from the accretion disc, due to the effect of turbulence and disc
instabilities, which are able to remove the angular momentum from the gas and
allow its accretion. In recent years, it has become increasingly apparent that
the gravitational field produced by the disc itself (the disc's self-gravity)
is an important ingredient in the models, especially in the context of
protostellar discs and of AGN discs. Indeed, it appears that in many cases (and
especially in the colder outer parts of the disc) the development of
gravitational instabilities can be one of the main agents in the redistribution
of angular momentum. In some cases, the instability can be strong enough to
lead to the formation of gravitationally bound clumps within the disc, and thus
to determine the disc fragmentation. As a result, progress in our understanding
of the dynamics of self-gravitating discs is essential to understand the
processes that lead to the feeding of both young stars and of supermassive
black holes in AGN. At the same time, understanding the fragmentation
conditions is important to determine under which conditions AGN discs would
fragment and form stars and whether protostellar discs might form giant gaseous
planets through disc fragmentation.


title:
Measuring the Fraction of Obscured Quasars by the Infrared Luminosity of
  Unobscured Quasars

abstract:
  Recent work has suggested that the fraction of obscured AGN declines with
increasing luminosity, but it has been difficult to quantify this trend. Here,
we attempt to measure this fraction as a function of luminosity by studying the
ratio of mid-infrared to intrinsic nuclear bolometric luminosity in unobscured
AGN. Because the mid-infrared is created by dust reprocessing of shorter
wavelength nuclear light, this ratio is a diagnostic of f_obsc, the fraction of
solid angle around the nucleus covered by obscuring matter. In order to
eliminate possible redshift-dependences while also achieving a large dynamic
range in luminosity, we have collected archival 24 micron MIPS photometry from
objects with z~1 in the Sloan Digital Sky Survey (SDSS), the Great
Observatories Origins Deep Survey (GOODS) and the Cosmic Evolution Survey
(COSMOS). To measure the bolometric luminosity for each object, we used
archival optical data supplemented by GALEX data. We find that the mean ratio
of 24 microns to bolometric luminosity decreases by a factor of ~3 in the
L_bol=10^44-3x10^47 ergs s^-1 range, but there is also a large scatter at
constant L_bol. Using radiation transfer solutions for model geometries, we
show how the IR/bolometric ratio relates to f_obsc and compare these values
with those obtained obtained from samples of X-ray selected AGN. Although we
find approximate agreement, our method indicates somewhat higher values of
f_obsc, particularly in the middle range of luminosities, suggesting that there
may be a significant number of heavily obscured AGN missed by X-ray surveys.


title: Graphic Bernstein Results in Curved Pseudo-Riemannian Manifolds

abstract:
  We generalize a Bernstein-type result due to Albujer and Al\'ias, for maximal
surfaces in a curved Lorentzian product 3-manifold of the form $\Sigma_1\times
\mathbb{R}$, to higher dimension and codimension. We consider $M$ a complete
spacelike graphic submanifold with parallel mean curvature, defined by a map
$f: \Sigma_1\to \Sigma_2$ between two Riemannian manifolds $(\Sigma_1^m, g_1)$
and $(\Sigma^n_2, g_2)$ of sectional curvatures $K_1$ and $K_2$, respectively.
We take on $\Sigma_1\times \Sigma_2$ the pseudo-Riemannian product metric
$g_1-g_2$. Under the curvature conditions, $\mathrm{Ricci}_1 \geq 0$ and
$K_1\geq K_2$, we prove that, if the second fundamental form of $M$ satisfies
an integrability condition, then $M$ is totally geodesic, and it is a slice if
$\mathrm{Ricci}_1(p)>0$ at some point. For bounded $K_1$, $K_2$ and hyperbolic
angle $\theta$, we conclude $M$ must be maximal. If $M$ is a maximal surface
and $K_1\geq K_2^+$, we show $M$ is totally geodesic with no need for further
assumptions. Furthermore, $M$ is a slice if at some point $p\in \Sigma_1$,
$K_1(p)> 0$, and if $\Sigma_1$ is flat and $K_2<0$ at some point $f(p)$, then
the image of $f$ lies on a geodesic of $\Sigma_2$.


title:
Commutativity of Substitution and Variation in Actions of Quantum Field
  Theory

abstract:
  There exists a paradox in quantum field theory: substituting a field
configuration which solves a subset of the field equations into the action and
varying it is not necessarily equivalent to substituting that configuration
into the remaining field equations. We take the $S^4$ and Freund-Rubin-like
instantons as two examples to clarify the paradox. One must match the
specialized configuration field variables with the corresponding boundary
conditions by adding appropriate Legendre terms to the action. Some comments
are made regarding exceptional degenerate cases.


title: On the expansion of the resolvent for elliptic boundary contact problems

abstract:
  Let $A$ be an elliptic operator on a compact manifold with boundary $M$, and
let $\wp : \partial\M \to Y$ be a covering map, where $Y$ is a closed manifold.
Let $A_C$ be a realization of $A$ subject to a coupling condition $C$ that is
elliptic with parameter in the sector $\Lambda$. By a coupling condition we
mean a nonlocal boundary condition that respects the covering structure of the
boundary.
  We prove that the resolvent trace $\Tr_{L^2} (A_C-\lambda)^{-N}$ for $N$
sufficiently large has a complete asymptotic expansion as $|\lambda| \to
\infty$, $\lambda \in \Lambda$. In particular, the heat trace
$\Tr_{L^2}e^{-tA_C}$ has a complete asymptotic expansion as $t \to 0^+$, and
the $\zeta$-function has a meromorphic extension to $\C$.


title:
Comparison of Spreadsheets with other Development Tools (limitations,
  solutions, workarounds and alternatives)

abstract:
  The spreadsheet paradigm has some unique risks and challenges that are not
present in more traditional development technologies. Many of the recent
advances in other branches of software development have bypassed spreadsheets
and spreadsheet developers. This paper compares spreadsheets and spreadsheet
development to more traditional platforms such as databases and procedural
languages. It also considers the fundamental danger introduced in the
transition from paper spreadsheets to electronic. Suggestions are made to
manage the risks and work around the limitations.


title: Long cycles in fullerene graphs

abstract:
  It is conjectured that every fullerene graph is hamiltonian. Jendrol' and
Owens proved [J. Math. Chem. 18 (1995), pp. 83--90] that every fullerene graph
on n vertices has a cycle of length at least 4n/5. In this paper, we improve
this bound to 5n/6-2/3.


title:
Magnetic order in coupled spin-half and spin-one Heisenberg chains in
  anisotropic triangular-lattice geometry

abstract:
  We study spin-half and spin-one Heisenberg models in the limit where one
dimensional (1-D) linear chains, with exchange constant J1, are weakly coupled
in an anisotropic triangular lattice geometry. Results are obtained by means of
linked-cluster series expansions at zero temperature around different
magnetically ordered phases. We study the non-colinear spiral phases that arise
classically in the model and the colinear antiferromagnet that has been
recently proposed for the spin-half model by Starykh and Balents using a
Renormalization Group approach. We find that such phases can be stabilized in
the spin-half model for arbitrarily small coupling between the chains. For
vanishing coupling between the chains the energy of each phase must approach
that of decoupled linear chains. With increasing inter-chain coupling, the
non-colinear phase appears to have a lower energy in our calculations. For the
spin-one chain, we find that there is a critical interchain coupling needed to
overcome the Haldane gap. When spin-one chains are coupled in an unfrustrated
manner, the critical coupling is very small (~0.01J1) and agrees well with
previous chain mean-field studies. When they are coupled in the frustrated
triangular-lattice geometry, the critical coupling required to develop magnetic
order is substantially larger (> 0.3J1). The colinear phase is not obtained for
the spin-one Heisenberg model.


title:
The Eclipsing Cataclysmic Variable Lanning 386: Dwarf Nova, SW Sextantis
  Star, or Both?

abstract:
  We present photometry and spectroscopy of the suspected cataclysmic variable
(CV) Lanning 386. We confirm that it is a CV, and observe deep eclipses, from
which we determine the orbital period Porb to be 0.1640517 +- 0.0000001 d (=
3.94 h). Photometric monitoring over two observing seasons shows a very active
system with frequent outbursts of variable amplitude, up to approx. 2 mag. The
spectrum in quiescence is typical of dwarf novae, but in its high state the
system shows strong HeII emission and a broad CIV Wolf-Rayet feature. This is
unusual for dwarf novae in outburst and indicates a high excitation. In its
high state the system shows some features reminiscent of an SW Sextantis-type
CV, but lacks others. We discuss the classification of this puzzling object.


title: Geometry Diagnostics of a Stellar Flare from Fluorescent X-rays

abstract:
  We present evidence of Fe fluorescent emission in the Chandra HETGS spectrum
of the single G-type giant HR 9024 during a large flare. In analogy to solar
X-ray observations, we interpret the observed Fe K$\alpha$ line as being
produced by illumination of the photosphere by ionizing coronal X-rays, in
which case, for a given Fe photospheric abundance, its intensity depends on the
height of the X-ray source. The HETGS observations, together with 3D Monte
Carlo calculations to model the fluorescence emission, are used to obtain a
direct geometric constraint on the scale height of the flaring coronal plasma.
We compute the Fe fluorescent emission induced by the emission of a single
flaring coronal loop which well reproduces the observed X-ray temporal and
spectral properties according to a detailed hydrodynamic modeling. The
predicted Fe fluorescent emission is in good agreement with the observed value
within observational uncertainties, pointing to a scale height $\lesssim
0.3$\rstar. Comparison of the HR 9024 flare with that recently observed on II
Peg by Swift indicates the latter is consistent with excitation by X-ray
photoionization.


title:
The Range of Approximate Unitary Equivalence Classes of Homomorphisms
  from AH-algebras

abstract:
  Let $C$ be a unital AH-algebra and $A$ be a unital simple C*-algebra with
tracial rank zero. It has been shown that two unital monomorphisms $\phi, \psi:
C\to A$ are approximately unitarily equivalent if and only if $$ [\phi]=[\psi]
{\rm in} KL(C,A) and \tau\circ \phi=\tau\circ \psi \tforal \tau\in T(A), $$
where $T(A)$ is the tracial state space of $A.$ In this paper we prove the
following: Given $\kappa\in KL(C,A)$ with $\kappa(K_0(C)_+\setminus
\{0\})\subset K_0(A)_+\setminus \{0\}$ and with $\kappa([1_C])=[1_A]$ and a
continuous affine map $\lambda: T(A)\to T_{\mathtt{f}}(C)$ which is compatible
with $\kappa,$ where $T_{\mathtt{f}}(C)$ is the convex set of all faithful
tracial states, there exists a unital monomorphism $\phi: C\to A$ such that $$
[\phi]=\kappa\andeqn \tau\circ \phi(c)=\lambda(\tau)(c) $$ for all $c\in
C_{s.a.}$ and $\tau\in T(A).$ Denote by ${\rm Mon}_{au}^e(C,A)$ the set of
approximate unitary equivalence classes of unital monomorphisms. We provide a
bijective map $$ \Lambda: {\rm Mon}_{au}^e (C,A)\to KLT(C,A)^{++}, $$ where
$KLT(C,A)^{++}$ is the set of compatible pairs of elements in $KL(C,A)^{++}$
and continuous affine maps from $T(A)$ to $T_{\mathtt{f}}(C).$ Moreover, we
realized that there are compact metric spaces $X$, unital simple AF-algebras
$A$ and $\kappa\in KL(C(X), A)$ with $\kappa(K_0(C(X))_+\setminus\{0\})\subset
K_0(A)_+\setminus \{0\}$ for which there is no \hm $h: C(X)\to A$ so that
$[h]=\kappa.$


title: Determining the Dimensionality of Spacetime by Gravitational Lensing

abstract:
  The physics associated with spherically symmetric charged black holes is
analyzed from the point of view of using weak gravitational lensing as a means
for determining the dimensionality of spacetime. In particular, for exact
solutions of electro-vac black holes in four and five spacetime dimensions the
motion of photons is studied using the equations for the null geodesics and
deriving the weak limit bending angles and delays in photon arrival times.


title: Multi-Modal Properties and Dynamics of the Gradient Echo Quantum Memory

abstract:
  We investigate the properties of a recently proposed Gradient Echo Memory
(GEM) scheme for information mapping between optical and atomic systems. We
show that GEM can be described by the dynamic formation of polaritons in
k-space. This picture highlights the flexibility and robustness with regards to
the external control of the storage process. Our results also show that, as GEM
is a frequency-encoding memory, it can accurately preserve the shape of signals
that have large time-bandwidth products, even at moderate optical depths. At
higher optical depths, we show that GEM is a high fidelity multi-mode quantum
memory.


title:
Effects of medium-induced $\rho-\omega$ meson mixing on the equation of
  state in isospin-asymmetric nuclear matter

abstract:
  We reexamine effects of the $\rho-\omega$ meson mixing mediated by nucleon
polarizations on the symmetry energy in isospin-asymmetric nuclear matter.
Taking into account the rearrangement term neglected in previous studies by
others, we evaluate the $\rho-\omega$ mixing angle in a novel way within the
Relativistic Mean-Field Models with and without chiral limits. It is found that
the symmetry energy is significantly softened at high densities contrary to the
finding in earlier studies. As the first step of going beyond the lowest-order
calculations, we also solve the RPA equation for the $\rho-\omega$ mixing. In
this case, it is found that the symmetry energy is not only significantly
softened by the $\rho-\omega$ mixing at supra-saturation densities, similar to
the lowest-order $\rho-\omega$ mixing, but interestingly also softened at
subsaturation densities. In addition, the softening of the symmetry energy at
subsaturation densities can be partly suppressed by the nonlinear
self-interaction of the $\sigma$ meson.


title: Departure from the conical dispersion in epitaxial graphene

abstract:
  The pi bands of epitaxially grown graphene are studied by using high
resolution angle resolved photoemission spectroscopy. Clear deviations from the
conical dispersion expected for massless Dirac fermions and an anomalous
increase of the scattering rate are observed in the vicinity of the Dirac point
energy. Possible explanations for such anomalies are discussed in terms of
many-body interactions and the opening of a gap. We present detailed
experimental evidences in support of the gap scenario. This finding reveals a
fundamental intrinsic property of epitaxial graphene and demonstrates the
possibility of engineering the band gap in epitaxial graphene.


title: Supergiant Fast X-ray Transients and Other Wind Accretors

abstract:
  Supergiant Fast X-ray Transients are obviously related to persistent
Supergiant X-ray Binaries. Any convincing explanation for their behaviour must
consistently take into account all types of X-ray sources powered by wind
accretion. Here we present a common framework for wind accreting sources,
within the context of clumpy wind models, that allows a coherent interpretation
of their different behaviours as an immediate consequence of diverse orbital
geometries.


title:
Between conjecture and memento: shaping a collective emotional
  perception of the future

abstract:
  Large scale surveys of public mood are costly and often impractical to
perform. However, the web is awash with material indicative of public mood such
as blogs, emails, and web queries. Inexpensive content analysis on such
extensive corpora can be used to assess public mood fluctuations. The work
presented here is concerned with the analysis of the public mood towards the
future. Using an extension of the Profile of Mood States questionnaire, we have
extracted mood indicators from 10,741 emails submitted in 2006 to futureme.org,
a web service that allows its users to send themselves emails to be delivered
at a later date. Our results indicate long-term optimism toward the future, but
medium-term apprehension and confusion.


title:
Simultaneous preconditioning and symmetrization of non-symmetric linear
  systems

abstract:
  Motivated by the theory of self-duality which provides a variational
formulation and resolution for non self-adjoint partial differential equations
\cite{G1, G2}, we propose new templates for solving large non-symmetric linear
systems. The method consists of combining a new scheme that simultaneously
preconditions and symmetrizes the problem, with various well known iterative
methods for solving linear and symmetric problems. The approach seems to be
efficient when dealing with certain ill-conditioned, and highly non-symmetric
systems.


title:
Infinite Dimensional Multiplicity Free Spaces II: Limits of Commutative
  Nilmanifolds

abstract:
  We study direct limits $(G,K) = \varinjlim (G_n,K_n)$ of Gelfand pairs of the
form $G_n = N_n\rtimes K_n$ with $N_n$ nilpotent, in other words pairs
$(G_n,K_n)$ for which $G_n/K_n$ is a commutative nilmanifold. First, we extend
the criterion of \cite{W3} for a direct limit representation to be multiplicity
free. Then we study direct limits $G/K = \varinjlim G_n/K_n$ of commutative
nilmanifolds and look to see when the regular representation of $G = \varinjlim
G_n$ on an appropriate Hilbert space $\varinjlim L^2(G_n/K_n)$ is multiplicity
free. One knows that the $N_n$ are commutative or 2--step nilpotent. In many
cases where the derived algebras $[\gn_n,\gn_n]$ are of bounded dimension we
construct $G_n$--equivariant isometric maps $\zeta_n : L^2(G_n/K_n) \to
L^2(G_{n+1}/K_{n+1})$ and prove that the left regular representation of $G$ on
the Hilbert space $L^2(G/K) := \varinjlim \{L^2(G_n/K_n),\zeta_n\}$ is a
multiplicity free direct integral of irreducible unitary representations. The
direct integral and its irreducible constituents are described explicitly. One
constituent of our argument is an extension of the classical Peter--Weyl
Theorem to parabolic direct limits of compact groups.