title:
Large deviations of lattice Hamiltonian dynamics coupled to stochastic
  thermostats

abstract:
  We discuss the Donsker-Varadhan theory of large deviations in the framework
of Hamiltonian systems thermostated by a Gaussian stochastic coupling. We
derive a general formula for the Donsker-Varadhan large deviation functional
for dynamics which satisfy natural properties under time reversal. Next, we
discuss the characterization of the stationary state as the solution of a
variational principle and its relation to the minimum entropy production
principle. Finally, we compute the large deviation functional of the current in
the case of a harmonic chain thermostated by a Gaussian stochastic coupling.

categories: math-ph cond-mat.stat-mech math.MP math.PR


title:
Noise-dependent stability of the synchronized state in a coupled system
  of active rotators

abstract:
  We consider a Kuramoto model for the dynamics of an excitable system
consisting of two coupled active rotators. Depending on both the coupling
strength and the noise, the two rotators can be in a synchronized or
desynchronized state. The synchronized state of the system is most stable for
intermediate noise intensity in the sense that the coupling strength required
to desynchronize the system is maximal at this noise level. We evaluate the
phase boundary between synchronized and desynchronized states through numerical
and analytical calculations.


title: Extremal orders of compositions of certain arithmetical functions

abstract:
  We study the exact extremal orders of compositions $f(g(n))$ of certain
arithmetical functions, including the functions $\sigma(n)$, $\phi(n)$,
$\sigma^*(n)$ and $\phi^*(n)$, representing the sum of divisors of $n$, Euler's
function and their unitary analogues, respectively. Our results complete,
generalize and refine known results.


title:
Quantized current blockade and hydrodynamic correlations in biopolymer
  translocation through nanopores: evidence from multiscale simulations

abstract:
  We present a detailed description of biopolymer translocation through a
nanopore in the presence of a solvent, using an innovative multi-scale
methodology which treats the biopolymer at the microscopic scale as combined
with a self-consistent mesoscopic description for the solvent fluid dynamics.
We report evidence for quantized current blockade depending on the folding
configuration and offer detailed information on the role of hydrodynamic
correlations in speeding-up the translocation process.


title: Fractional periodicity and magnetism of extended quantum rings

abstract:
  The magnetic properties and nature of the persistent current in small
flux-penetrated $t-t'-U$ rings are investigated. An effective rigid-rotator
description is formulated for this system, which coincides with a transition to
a ferromagnetic state in the model. The criteria for the onset of effective
rigid rotation is given. The model is used to understand continuum model
ground-state solutions for a 2D few-particle hard-wall quantum dot, where
ferromagnetic solutions are found even without the Zeeman coupling to spin.
After the onset of effective rigid rotation, a 97--98% correspondence can be
determined between the lattice model and continuum model eigenstate results.


abstract:
  A projectional skeleton in a Banach space is a sigma-directed family of
projections onto separable subspaces, covering the entire space. The class of
Banach spaces with projectional skeletons is strictly larger than the class of
Plichko spaces (i.e. Banach spaces with a countably norming Markushevich
basis). We show that every space with a projectional skeleton has a
projectional resolution of the identity and has a norming space with similar
properties to Sigma-spaces. We characterize the existence of a projectional
skeleton in terms of elementary substructures, providing simple proofs of known
results concerning weakly compactly generated spaces and Plichko spaces.
  We prove a preservation result for Plichko Banach spaces, involving
transfinite sequences of projections. As a corollary, we show that a Banach
space is Plichko if and only if it has a commutative projectional skeleton.


title: Kaon-condensed hypernuclei as highly dense self-bound objects

abstract:
  The structure of $K^-$-condensed hypernuclei, which may be produced in the
laboratory in strangeness-conserving processes, is investigated using an
effective chiral Lagrangian for the kaon-baryon interaction, combined with a
nonrelativistic baryon-baryon interaction model. It is shown that a large
number of negative strangeness is needed for the formation of highly dense and
deeply bound state with kaon condensates and that part of the strangeness
should be carried by hyperons mixed in the nucleus. The properties of
kaon-condensed hypernuclei such as the ground state energy and particle
composition are discussed. Such a self-bound object has a long lifetime and may
decay only through weak interaction processes. Comparison with other possible
nuclear states is also made, such as kaon-condensed nuclei without mixing of
hyperons and noncondensed multistrange hypernuclei. Implications of
kaon-condensed hypernuclei for experiments are mentioned.


title:
Exponential decay phenomenon of the principal eigenvalue of an elliptic
  operator with a large drift term of gradient type

abstract:
  We study an asymptotic behaviour of the principal eigenvalue for an elliptic
operator with large advection which is given by a gradient of a potential
function. It is shown that the principal eigenvalue decays exponentially under
the velocity potential well condition as the parameter tends to infinity.


title:
Bornes pour la r\'egularit\'e de Castelnuovo-Mumford des sch\'emas non
  lisses

abstract:
  We show that bounds on the Castelnuovo-Mumford regularity of singular
schemes, as a function of the degrees of the equations defining the shceme, of
its dimension and of the dimension of their singular space. In the case where
the singularities are isolated, we improve the bound given by Chardin and
Ulrich, and in the general case we establish a bound doubly exponential in the
dimension of the singular space.
  --
  Nous montrons dans cet article des bornes pour la regularite de
Castelnuovo-Mumford d'un schema admettant des singularites, en fonction des
degres des equations definissant le schema, de sa dimension et de la dimension
de son lieu singulier. Dans le cas ou les singularites sont isolees, nous
ameliorons la borne fournie par Chardin et Ulrich et dans le cas general, nous
etablissons une borne doublement exponentielle en la dimension du lieu
singulier.


title: Multi-Use Unidirectional Proxy Re-Signatures

abstract:
  In 1998, Blaze, Bleumer, and Strauss suggested a cryptographic primitive
named proxy re-signatures where a proxy turns a signature computed under
Alice's secret key into one from Bob on the same message. The semi-trusted
proxy does not learn either party's signing key and cannot sign arbitrary
messages on behalf of Alice or Bob. At CCS 2005, Ateniese and Hohenberger
revisited the primitive by providing appropriate security definitions and
efficient constructions in the random oracle model. Nonetheless, they left open
the problem of designing a multi-use unidirectional scheme where the proxy is
able to translate in only one direction and signatures can be re-translated
several times.
  This paper solves this problem, suggested for the first time 10 years ago,
and shows the first multi-hop unidirectional proxy re-signature schemes. We
describe a random-oracle-using system that is secure in the
Ateniese-Hohenberger model. The same technique also yields a similar
construction in the standard model (i.e. without relying on random oracles).
Both schemes are efficient and require newly defined -- but falsifiable --
Diffie-Hellman-like assumptions in bilinear groups.


title:
Toward a Deterministic Model of Planetary Formation V. Accumulation Near
  the Ice Line

abstract:
  We address two outstanding issues in the sequential accretion scenario for
gas giant planet formation, the retention of dust grains in the presence of gas
drag and that of cores despite type I migration. The efficiency of these
processes is determined by the disk structure. Theoretical models suggest that
planets form in protostellar disk regions with an inactive neutral ``dead
zone'' near the mid plane, sandwiched together by partially ionized surface
layers where magnetorotational instability is active. Due to a transition in
the abundance of dust grains, the active layer's thickness decreases abruptly
near the ice line. Over a range of modest accretion rates ($\sim
10^{-9}-10^{-8} M_\odot$ yr$^{-1}$), the change in the angular momentum
transfer rate leads to local surface density and pressure distribution maxima
near the ice line. The azimuthal velocity becomes super-Keplerian and the
grains accumulate in this transition zone. This barrier locally retains
protoplanetary cores and enhances the heavy element surface density to the
critical value needed to initiate efficient gas accretion. It leads to a
preferred location and epoch of gas giant formation. We simulate and reproduce
the observed frequency and mass-period distribution of gas giants around solar
type stars without having to greatly reduce the type I migration strength. The
mass function of the short-period planets can be utilized to calibrate the
efficiency of type I migration and to extrapolate the fraction of stars with
habitable terrestrial planets.


title:
Determination of the barycentric velocity of an astrometric satellite
  using its own observational data

abstract:
  The problem of determination of the orbital velocity of an astrometric
satellite from its own observational data is studied. It is well known that
data processing of microarcsecond-level astrometric observations imposes very
stringent requirements on the accuracy of the orbital velocity of the satellite
(a velocity correction of 1.45 mm/s implies an aberrational correction of 1
$\mu$as). Because of a number of degeneracies the orbital velocity cannot be
fully restored from observations provided by the satellite. Seven constraints
that must be applied on a velocity parameterization are discussed and
formulated mathematically. It is shown what part of velocity can be recovered
from astrometric data by a combined fit of both velocity parameters and
astrometric parameters of the sources. Numerical simulations show that, with
the seven constraints applied, the velocity and astrometric parameters can be
reliably estimated from observational data. It is also argued that the idea to
improve the velocity of an astrometric satellite from its own observational
data is only useful if the a priori information on the orbital velocity
justifies the applicability of the velocity constraints. The proposed model
takes into account only translational motion of the satellite and ignores any
satellite-specific parameters. Therefore, the results of this study are equally
applicable to both scanning missions similar to Gaia, and pointing ones like
SIM, provided that enough sources were observed sufficiently uniformly.


title:
The He-McKellar-Wilkens effect for spin one particles in non-commutative
  quantum mechanics

abstract:
  The He-McKellar-Wilkens(HMW) effect for spin one neutral particle in
non-commutative quantum mechanics is studied. By solving the Kemmer like
equations on non-commutative (NC) space and non-commutative phase space, we
obtain topological He-McKellar-Wilkens phase on NC space and NC phase space
respectively, where the additional terms related to the space-space and
momentum-momentum non-commutativity are given explicitly.


title: Degeneracy and size consistency in electronic density functional theory

abstract:
  The electronic structure calculations based upon energy density functionals
are highly successful and widely used both in solid state physics and quantum
chemistry. Moreover, the Hohenberg-Kohn theorems and the Kohn-Sham method
provide them with a firm basis. However, several basic issues are not solved,
and hamper the progress to achieve high accuracy. In this paper we focus on the
conceptual problem of size consistency, basing our analysis on the
non-intensive character of the (spin) electronic density in the presence of
degeneracy. We also briefly discuss some of the issues concerning fractional
electron numbers from the same point of view, analyzing the behavior of the
exact functionals for the He and the Hooke's atom series when the number of
electrons fluctuates between one and two.


title: Landau Problem in Noncommutative Quantum Mechanics

abstract:
  The Landau problem in non-commutative quantum mechanics (NCQM) is studied.
First by solving the Schr$\ddot{o}$dinger equations on noncommutative(NC) space
we obtain the Landau energy levels and the energy correction that is caused by
space-space noncommutativity. Then we discuss the noncommutative phase space
case, namely, space-space and momentum-momentum non-commutative case, and we
get the explicit expression of the Hamiltonian as well as the corresponding
eigenfunctions and eigenvalues.


title:
Tau energy losses at ultra-high energy: continuous versus stochastic
  treatment

abstract:
  We study the energy losses of the tau lepton in matter through
electromagnetic processes at ultra-high energy (UHE). We use both a stochastic
and a continuous framework to treat these interactions and compare the flux of
tau leptons propagated after some amount of matter. We discuss the accuracy of
the approximation of continuous energy losses by studying the propagation in
standard rock of taus with both mono-energetic and power law injection spectra.


title: Hyperbolic Models of Homogeneous Two-Fluid Mixtures

abstract:
  One derives the governing equations and the Rankine - Hugoniot conditions for
a mixture of two miscible fluids using an extended form of Hamilton's principle
of least action. The Lagrangian is constructed as the difference between the
kinetic energy and a potential depending on the relative velocity of
components. To obtain the governing equations and the jump conditions one uses
two reference frames related with the Lagrangian coordinates of each component.
Under some hypotheses on flow properties one proves the hyperbolicity of the
governing system for small relative velocity of phases.


title: Representation of the penalty term of dynamic concave utilities

abstract:
  In this paper we will provide a representation of the penalty term of general
dynamic concave utilities (hence of dynamic convex risk measures) by applying
the theory of g-expectations.


title: Dynamical friction in modified Newtonian dynamics

abstract:
  We have tested a previous analytical estimate of the dynamical friction
timescale in Modified Newtonian Dynamics (MOND) with fully non-linear N-body
simulations. The simulations confirm that the dynamical friction timescale is
significantly shorter in MOND than in equivalent Newtonian systems, i.e.
systems with the same phase-space distribution of baryons and additional dark
matter. An apparent conflict between this result and the long timescales
determined for bars to slow and mergers to be completed in previous N-body
simulations of MOND systems is explained. The confirmation of the short
dynamical-friction timescale in MOND underlines the challenge that the Fornax
dwarf spheroidal poses to the viability of MOND.


title: Snap-Stabilization in Message-Passing Systems

abstract:
  In this paper, we tackle the open problem of snap-stabilization in
message-passing systems. Snap-stabilization is a nice approach to design
protocols that withstand transient faults. Compared to the well-known
self-stabilizing approach, snap-stabilization guarantees that the effect of
faults is contained immediately after faults cease to occur. Our contribution
is twofold: we show that (1) snap-stabilization is impossible for a wide class
of problems if we consider networks with finite yet unbounded channel capacity;
(2) snap-stabilization becomes possible in the same setting if we assume
bounded-capacity channels. We propose three snap-stabilizing protocols working
in fully-connected networks. Our work opens exciting new research perspectives,
as it enables the snap-stabilizing paradigm to be implemented in actual
networks.


title: Nucleosynthesis in slowly evolving Cosmologies

abstract:
  We explore aspects of Cosmological Nucleosynthesis in an FRW universe in
which the scale factor evolves linearly with time: $a(t) \sim t$. A high Lepton
number density during the period when significant nucleosynthesis takes place
would lead to a dominant screening of the Coulomb potential of colliding
nucleii. This would lead to a significant enhancement of nucleosynthesis rates.
We demonstrate how adequate amount of $^4He$ and a collataral metallicity,
close to the lowest metallicity observed in metal poor Pop II stars and clouds,
can be produced with such an evolution.


title: Quantitative vectorial spin analysis in ARPES: Bi/Ag(111) and Pb/Ag(111)

abstract:
  The concept of vectorial spin analysis in spin and angle resolved
photoemission is illustrated in this report. Two prototypical systems,
Bi/Ag(111)(sqrt3 x sqrt3)R30 and Pb/Ag(111)(sqrt3 x sqrt3)R30, which show a
large Rashba type spin-orbit splitting, were investigated by means of spin and
angle resolved photoemission. The spin polarization vectors of individual bands
are determined by a two-step fitting routine. First, the measured intensities
are fitted with an appropriate number of suitable peaks to quantify the
contributions of the individual bands, then the measured spin polarization
curves are fitted by varying for each band the polarization direction and its
magnitude. We confirm that the surface states experience a large spin
splitting. Moreover, we find that all surface state bands are 100 percent spin
polarized, and that for some states spin polarization vectors rotate out of the
surface plane.


title: Earthquake Prediction: Probabilistic Aspect

abstract:
  A theoretical analysis of the earthquake prediction problem in space-time is
presented. We find an explicit structure of the optimal strategy and its
relation to the generalized error diagram. This study is a generalization of
the theoretical results for time prediction. The possibility and simplicity of
this extension is due to the choice of the class of goal functions. We also
discuss issues in forecasting versus prediction, scaling laws versus
predictability, and measure of prediction efficiency at the research stage.


title:
A Directly-Written Monolithic Waveguide-Laser Incorporating a DFB
  Waveguide-Bragg Grating

abstract:
  We report the fabrication and performance of the first C-band
directly-written monolithic waveguide-laser. The waveguide-laser device was
created in an Erbium and Ytterbium doped phosphate glass host and consisted of
an optical waveguide that included a distributed feedback Bragg grating
structure. The femtosecond laser direct-write technique was used to create both
the waveguide and the waveguide-Bragg grating simultaneously and in a single
processing step. The waveguide-laser was optically pumped at approximately 980
nm and lased at 1537nm with a bandwidth of less than 4 pm.


title: Nuclear effects in neutrino induced reactions

abstract:
  We discuss the relevance of nuclear medium effects in the analysis of some
low and medium energy neutrino reactions of current interest. In particular, we
study the Quasi-Elastic (QE) process, where RPA correlations and Final State
Interactions (FSI) are shown to play a crucial role. We have also investigated
the neutrino induced coherent pion production. We find a strong reduction of
the cross section due to the distortion of the pion wave function and the
modification of the production mechanisms in the nucleus. The sensitivity of
the results to the axial $N\Delta$ coupling $C_5^A(0)$ has been also
investigated.


title: Doubly special relativity in de Sitter spacetime

abstract:
  We discuss the generalization of Doubly Special Relativity to a curved de
Sitter background. The model has three observer-independent scales, the
velocity of light $c$, the radius of curvature of the geometry $\alpha$, and
the Planck energy $\kappa$, and can be realized in a noncommutative position
space. It is possible to construct a model exhibiting a duality for the
interchange of positions and momenta together with the exchange of $\alpha$ and
$\kappa$.


title: On Riemannian almost product manifolds with nonintegrable structure

abstract:
  The class of the Riemannian almost product manifolds with nonintegrable
structure is considered. Some identities for curvature tensor as certain
invariant tensors and quantities are obtained.


title: Rheology of colloidal microphases in a model with competing interactions

abstract:
  We study the rheological properties of colloidal microphases in two
dimensions simulating a model of colloidal particles with competing
interactions. Due to the competition between short-range attraction and
long-range repulsion, as a function of the density the model exhibits a variety
of microphases such as clusters, stripes or crystals with bubbles. We prepare
the system in a confined microphase employing Monte-Carlo simulations and then
quench the system at T=0. The resulting configurations are then sheared by
applying a drag force profile. We integrate numerically the equation of motion
for the particles and analyze the dynamics as a function of the density and the
applied strain rate. We measure the stress-strain curves and characterize the
yielding of the colloidal microphases. The results depend on the type of
microphase: (i) clusters are easily sheared along layers and the relative
motion is assisted by rotations. (ii) Stripes shear easily when they are
parallel to the flow and tend to jam when are perpendicular to it. Under a
sufficiently strong shear rate perpendicular stripes orient in the flow
direction. (iii) Crystals with bubbles yield by fracturing along the bubbles
and eventually forming stripes. We discuss the role of dislocations, emitted by
the bubbles, in the yielding process.


title: Expansion of a plasma cloud into the solar wind

abstract:
  Three-dimensional (3D) hybrid particle-in-cell (PIC) simulations, with
kinetic ions and fluid electrons, of a plasma cloud expansion in the solar wind
are presented, revealing the dynamics of the expansion, with shock formation,
magnetic field compression, and the solar wind ions deflection around the
plasma bubble. The similarities of this system with a magnetosphere are also
pointed out.


title: The algorithm for simulating of phase transition in Ising magnetic

abstract:
  Simple algorithm of dynamics of Ising magnetic is described. The algorithm
can be implemented on conventional digital computer and can be used for
construction of specialized processor for simulation of ferromagnetic systems.
The algorithm gives a simple way to calculate 1D correlation functions for 1D
Ising magnetic.


title: On the interaction of microquasar jets with stellar winds

abstract:
  Strong interactions between jets and stellar winds at binary system spatial
scales could occur in high-mass microquasars. We study here, mainly from a
dynamical but also a radiative point of view, the collision between a dense
stellar wind and a mildly relativistic hydrodynamical jet of supersonic
nature.}{We have performed numerical 2-dimensional simulations of jets, with
cylindrical and planar (slab) symmetry, crossing the stellar wind material.
  From the results of the simulations, we derive estimates of the particle
acceleration efficiency, using first order Fermi acceleration theory, and give
some insight on the possible radiative outcomes. We find that, during jet
launching, the jet head generates a strong shock in the wind. During and after
this process, strong recollimation shocks can occur due to the initial
overpressure of the jet with its environment. The conditions in all these
shocks are convenient to accelerate particles up to $\sim$ TeV energies, which
can lead to leptonic (synchrotron and inverse Compton) and hadronic
(proton-proton) radiation. In principle, the cylindrical jet simulations show
that the jet is stable, and can escape from the system even for relatively low
power. However, when accounting for the wind ram pressure, the jet can be bent
and disrupted for power $\la 10^{36}$ erg s$^{-1}$.


title: Spectra of weighted algebras of holomorphic functions

abstract:
  We consider weighted algebras of holomorphic functions on a Banach space. We
determine conditions on a family of weights that assure that the corresponding
weighted space is an algebra or has polynomial Schauder decompositions. We
study the spectra of weighted algebras and endow them with an analytic
structure. We also deal with composition operators and algebra homomorphisms,
in particular to investigate how their induced mappings act on the analytic
structure of the spectrum. Moreover, a Banach-Stone type question is addressed.


title: Magnetodielectric coupling in a triangular Ising lattice

abstract:
  Dielectric constant measurement under magnetic field is an efficient
technique to study the coupling between charges and spins in insulating
materials. For magnetic oxides, the geometric frustration is known to be a key
ingredient to observe such a coupling. Measurements for the triangular
Ising-like cobaltite Ca3Co2O6 have been made. Single crystals of Ca3Co2O6 are
found to exhibit a magnetodielectric effect below TN=25K with a peak in the
e(H) curve at the ferri to ferromagnetic transition. This relation between e
and magnetization has been modelized by using two order parameters in an energy
expansion derived from the Landau formalism and the fluctuation-dissipation
theorem. This result emphasizes the great potential of insulating transition
metal oxides for the search of magnetodielectric effect.


title: Mirage Pattern from the Heterotic String

abstract:
  We provide a simple example of dilaton stabilization in the framework of
heterotic string theory. It requires a gaugino condensate and an up-lifting
sector similar to the one postulated in type IIB string theory. Its signature
is a hybrid mediation of supersymmetry breakdown with a variant of a mirage
pattern for the soft breaking terms. The set-up is suited for the discussion of
heterotic MSSM candidates.


title: A closer look at time averages of the logistic map at the edge of chaos

abstract:
  The probability distribution of sums of iterates of the logistic map at the
edge of chaos has been recently shown [see U. Tirnakli, C. Beck and C. Tsallis,
Phys. Rev. E 75, 040106(R) (2007)] to be numerically consistent with a
q-Gaussian, the distribution which, under appropriate constraints, maximizes
the nonadditive entropy S_q, the basis of nonextensive statistical mechanics.
This analysis was based on a study of the tails of the distribution. We now
check the entire distribution, in particular its central part. This is
important in view of a recent q-generalization of the Central Limit Theorem,
which states that for certain classes of strongly correlated random variables
the rescaled sum approaches a q-Gaussian limit distribution. We numerically
investigate for the logistic map with a parameter in a small vicinity of the
critical point under which conditions there is convergence to a q-Gaussian both
in the central region and in the tail region, and find a scaling law involving
the Feigenbaum constant delta. Our results are consistent with a large number
of already available analytical and numerical evidences that the edge of chaos
is well described in terms of the entropy S_q and its associated concepts.


title:
Exact number conserving phase-space dynamics of the M-site Bose-Hubbard
  model

abstract:
  The dynamics of M-site, N-particle Bose-Hubbard systems is described in
quantum phase space constructed in terms of generalized SU(M) coherent states.
These states have a special significance for these systems as they describe
fully condensed states. Based on the differential algebra developed by Gilmore,
we derive an explicit evolution equation for the (generalized) Husimi-(Q)- and
Glauber-Sudarshan-(P)-distributions. Most remarkably, these evolution equations
turn out to be second order differential equations where the second order terms
scale as 1/N with the particle number. For large N the evolution reduces to a
(classical) Liouvillian dynamics. The phase space approach thus provides a
distinguished instrument to explore the mean-field many-particle crossover. In
addition, the thermodynamic Bloch equation is analyzed using similar
techniques.


title:
Non maximal cyclically monotone graphs and construction of a bipotential
  for the Coulomb's dry friction law

abstract:
  We show a surprising connexion between a property of the inf convolution of a
family of convex lower semicontinuous functions and the fact that the
intersection of maximal cyclically monotone graphs is the critical set of a
bipotential.
  We then extend the results from arXiv:math/0608424v4 to bipotentials convex
covers, generalizing the notion of a bi-implicitly convex lagrangian cover.
  As an application we prove that the bipotential related to Coulomb's friction
law is related to a specific bipotential convex cover with the property that
any graph of the cover is non maximal cyclically monotone.


title: Newman Tamburino solutions with an aligned Maxwell field

abstract:
  We prove that there exists no aligned Einstein Maxwell generalization of the
spherical class of Newman Tamburino solutions. The presence of an aligned
Maxwell field automatically leads to the cylindrical class.


title:
Beyond mean-field dynamics of small Bose-Hubbard systems based on the
  number-conserving phase space approach

abstract:
  The number-conserving quantum phase space description of the Bose-Hubbard
model is discussed for the illustrative case of two and three modes, as well as
the generalization of the two-mode case to an open quantum system. The
phase-space description based on generalized SU(M) coherent states yields a
Liouvillian flow in the macroscopic limit, which can be efficiently simulated
using Monte Carlo methods even for large systems. We show that this description
clearly goes beyond the common mean-field limit. In particular it resolves
well-known problems where the common mean-field approach fails, like the
description of dynamical instabilities and chaotic dynamics. Moreover, it
provides a valuable tool for a semi-classical approximation of many interesting
quantities, which depend on higher moments of the quantum state and are
therefore not accessible within the common approach. As a prominent example, we
analyse the depletion and heating of the condensate. A comparison to methods
ignoring the fixed particle number shows that in this case artificial number
fluctuations lead to ambiguities and large deviations even for quite simple
examples.


title:
On the scaling of the damping time for resonantly damped oscillations in
  coronal loops

abstract:
  There is not as yet full agreement on the mechanism that causes the rapid
damping of the oscillations observed by TRACE in coronal loops. It has been
suggested that the variation of the observed values of the damping time as
function of the corresponding observed values of the period contains
information on the possible damping mechanism. The aim of this Letter is to
show that, for resonant absorption, this is definitely not the case unless
detailed a priori information on the individual loops is available.


title: Constraints on coupling constant between dark energy and dark matter

abstract:
  We have investigated constraints on the coupling between dark matter and the
interacting Chaplygin gas. Our results indicate that the coupling constant $c$
between these two entities can take arbitrary values, which can be either
positive or negative, thus giving arbitrary freedom to the inter-conversion
between Chaplygin gas and dark matter. Thus our results indicate that the
restriction $0<c<1$ on the coupling constant occurs as a very special case. Our
analysis also supports the existence of phantom energy under certain conditions
on the coupling constant.


title:
Constraints of the $B_{\mu}/\mu$ solution due to the hidden sector
  renormalization

abstract:
  We investigate the validity of an idea that the $B_{\mu}$ problem is solvable
via the renormalization effect in the strongly interacting hidden sector within
the gauge mediated supersymmetry breaking scenario. Our analysis starts with a
naive boundary condition, which is that the squared scalar masses experience
$16\pi^2$ suppression. We use \texttt{softsusy} to get the low energy spectra
of superparticles with the boundary condition at the scale ($\Lambda_{CFT}$)
where the hidden sector is integrated out. We visit the low energy spectra and
return to $\Lambda_{CFT}$ where the boundary conditions are given. We find that
there is a sign problem, which seems to be generic.


title: Interacting Modified Variable Chaplygin Gas in Non-flat Universe

abstract:
  A unified model of dark energy and matter is presented using the modified
variable Chaplygin gas for interacting dark energy in a non-flat universe. The
two entities interact with each other non-gravitationally which involves a
coupling constant. Due to dynamic interaction, the variation in this constant
arises that henceforth changes the equations of state of these quantities. We
have derived the effective equations of state corresponding to matter and dark
energy in this interacting model. Moreover, the case of phantom energy is
deduced by putting constraints on the parameters involved.


title: On Hunting for Taxicab Numbers

abstract:
  In this article, we make use of some known method to investigate some
properties of the numbers represented as sums of two equal odd powers, i.e.,
the equation $x^n+y^n=N$ for $n\ge3$. It was originated in developing
algorithms to search new taxicab numbers (i.e., naturals that can be
represented as a sum of positive cubes in many different ways) and to verify
their minimality. We discuss properties of diophantine equations that can be
used for our investigations. This techniques is applied to develop an algorithm
allowing us to compute new taxicab numbers (i.e., numbers represented as sums
of two positive cubes in $k$ different ways), for $k=7...14$.


title:
Comments on "Charged particle dynamics in the field of slowly rotating
  compact star"

abstract:
  B.M. Mirza \cite{1} presented a solution of coupled Einstein-Maxwell
equations for a slowly rotating neutron star; however his derivations had some
errors and implicit assumptions that rendered the solution invalid. We point
out the errors and present a mathematically consistent solution. The resulting
solution is also physically consistent as it remains finite in the no rotation
limit, whereas Mirza's solution diverges for zero rotation.


title:
Theory of reduced singlet pairing without the underlying state of charge
  stripes in the high-temperature superconductor YBa_2Cu_3O_6.45

abstract:
  Recently, a strongly enhanced xy anisotropy of magnetic excitations was
observed in YBa_2Cu_3O_y (YBCO_y) with y=6.45 and Tc=35 K [Science 319, 597
(2008)]. Unlike the observation in YBCO_6.6 and YBCO_6.85, the anisotropy grows
to be pronounced at lower temperature and at lower energy, and is not
suppressed by the onset of superconductivity. We propose that the effect of
singlet pairing is substantially reduced in YBCO_6.45. This reduction
concomitantly enhances an order competing with singlet pairing, a strong
tendency of the so-called d-wave Pomeranchuk instability, leading to the
magnetic excitations observed experimentally.


title: Cellular neural networks for NP-hard optimization problems

abstract:
  Nowadays, Cellular Neural Networks (CNN) are practically implemented in
parallel, analog computers, showing a fast developing trend. Physicist must be
aware that such computers are appropriate for solving in an elegant manner
practically important problems, which are extremely slow on the classical
digital architecture. Here, CNN is used for solving NP-hard optimization
problems on lattices. It is proved, that a CNN in which the parameters of all
cells can be separately controlled, is the analog correspondent of a
two-dimensional Ising type (Edwards-Anderson) spin-glass system. Using the
properties of CNN computers a fast optimization method can be built for such
problems. Estimating the simulation time needed for solving such NP-hard
optimization problems on CNN based computers, and comparing it with the time
needed on normal digital computers using the simulated annealing algorithm, the
results are astonishing: CNN computers would be faster than digital computers
already at 10*10 lattice sizes. Hardwares realized nowadays are of 176*144
size. Also, there seems to be no technical difficulties adapting CNN chips for
such problems and the needed local control is expected to be fully developed in
the near future.


title: The eta decay constant in `resummed' chiral perturbation theory

abstract:
  The recently developed 'Resummed' ChPT is illustrated on the case of
pseudoscalar meson decay constants. We try to get an estimate of the eta decay
constant, which is not well known from experiments, while using several ways
including the Generalized ChPT Lagrangian to gather information beyond Standard
next-to-leading order. We compare the results to published ChPT predictions,
our own Standard ChPT calculations and available phenomenological estimates.


title: Hiding a drift

abstract:
  In this article we consider a Brownian motion with drift of the form
\[dS_t=\mu_t dt+dB_t\qquadfor t\ge0,\] with a specific nontrivial
$(\mu_t)_{t\geq0}$, predictable with respect to $\mathbb{F}^B$, the natural
filtration of the Brownian motion $B=(B_t)_{t\ge0}$. We construct a process
$H=(H_t)_{t\ge0}$, also predictable with respect to $\mathbb{F}^B$, such that
$((H\cdot S)_t)_{t\ge 0}$ is a Brownian motion in its own filtration.
Furthermore, for any $\delta>0$, we refine this construction such that the
drift $(\mu_t)_{t\ge0}$ only takes values in $]\mu-\delta,\mu+\delta[$, for
fixed $\mu>0$.


title: Sums of Hermitian Squares as an Approach to the BMV Conjecture

abstract:
  Lieb and Seiringer stated in their reformulation of the Bessis-Moussa-Villani
(BMV) conjecture that all coefficients of the polynomial p(t)=Tr[(A+tB)^m],
where A and B are positive semidefinite matrices of the same size and m an
arbitrary integer, are nonnegative. The coefficient of t^k is the trace of
S_{m,k}(A,B), which is the sum of all words of length m in the letters A and B
in which B appears exactly k times. We consider the case k=4 and show that
S_{m,4}(A,B) is a sum of hermitian squares and commutators. In particular, the
trace of S_{m,4}(A,B) is nonnegative.


title: Phase diagram of the Holstein polaron in one dimension

abstract:
  The behavior of the 1D Holstein polaron is described, with emphasis on
lattice coarsening effects, by distinguishing between adiabatic and
nonadiabatic contributions to the local correlations and dispersion properties.
The original and unifying systematization of the crossovers between the
different polaron behaviors, usually considered in the literature, is obtained
in terms of quantum to classical, weak coupling to strong coupling, adiabatic
to nonadiabatic, itinerant to self-trapped polarons and large to small
polarons. It is argued that the relationship between various aspects of polaron
states can be specified by five regimes: the weak-coupling regime, the regime
of large adiabatic polarons, the regime of small adiabatic polarons, the regime
of small nonadiabatic (Lang-Firsov) polarons, and the transitory regime of
small pinned polarons for which the adiabatic and nonadiabatic contributions
are inextricably mixed in the polaron dispersion properties. The crossovers
between these five regimes are positioned in the parameter space of the
Holstein Hamiltonian.


title: Mass of Neutron Star in SdS space-time

abstract:
  In this work we present a modified TOV equation which incorporates the
cosmological constant with regard to the recent astronomical observations that
the Universe is in a phase of accelerated expansion. Using this modified TOV
equation we considered the structure of a neutron star in SdS space-time and
calculated maximum mass limit for neutron stars.


title:
Efficiently contractable quantum circuits cannot produce much
  entanglement

abstract:
  We show a similarity between two different classical simulation methods for
measurement based quantum computation -- one relying on a low entanglement
(tree tensor network) representation of the computer's state, and the other a
tensor contraction method based on the topology of the graph state. We use this
similarity to show that any quantum circuit that can be efficiently simulated
via tensor contraction cannot produce much entanglement.


title: Effective thermostat induced by coarse-graining of SPC water

abstract:
  We investigate how the transport properties of a united atoms fluid with a
dissipative particle dynamics thermostat depend on the functional form and
magnitude of both the conservative and the stochastic interactions. We
demonstrate how the thermostat strongly affects the hydrodynamics, especially
diffusion, viscosity, and local escape times. As model system we use SPC water,
from which projected trajectories are used to determine the effective
interactions in the united atoms model. The simulation results support our
argument that the thermostat should be viewed as an integral part of the
coarse-grained dynamics, rather than a tool for approaching thermal
equilibrium. As our main result we show that the united atoms model with the
adjusted effective interactions approximately reproduce the diffusion constant
and the viscosity of the underlying detailed SPC water model.


title:
A Combined EIS-NVSS Survey Of Radio Sources (CENSORS) III: Spectroscopic
  observations

abstract:
  The Combined EIS-NVSS Survey Of Radio Sources (CENSORS) is a 1.4GHz radio
survey selected from the NRAO VLA Sky Survey (NVSS) and complete to a
flux-density of 7.2mJy. It targets the ESO Imaging Survey (EIS) Patch D, which
is a 3 by 2 square degree field centred on 09 51 36.0, -21 00 00 (J2000). This
paper presents the results of spectroscopic observations of 143 of the 150
CENSORS sources. The primary motivation for these observations is to achieve
sufficient spectroscopic completeness so that the sample may be used to
investigate the evolution of radio sources.
  The observations result in secure spectroscopic redshifts for 63% of the
sample and likely redshifts (based on a single emission line, for example) for
a further 8%. Following the identification of the quasars and star-forming
galaxies in the CENSORS sample, estimated redshifts are calculated for the
remainder of the sample via the K-z relation for radio galaxies. Comparison of
the redshift distribution of the CENSORS radio sources to distributions
predicted by the various radio luminosity function evolution models of Dunlop &
Peacock 1990, results in no good match. This demonstrates that this sample can
be used to expand upon previous work in that field.


title:
Hamilton's Principle and Rankine-Hugoniot Conditions for General Motions
  of Mixtures

abstract:
  In previous papers, we have presented hyperbolic governing equations and jump
conditions for barotropic fluid mixtures. Now we extend our results to the most
general case of two-fluid conservative mixtures taking into account the
entropies of components. We obtain governing equations for each component of
the medium. This is not a system of conservation laws. Nevertheless, using
Hamilton's principle we are able to obtain a complete set of Rankine-Hugoniot
conditions. In particular, for the gas dynamics they coincide with classical
jump conditions of conservation of momentum and energy. For the two-fluid case,
the jump relations do not involve the conservation of the total momentum and
the total energy.


title: Variability of the proton-to-electron mass ratio on cosmological scales

abstract:
  So far the only seemingly significant indication of a cosmological variation
exists for the proton-to-electron mass ratio as stated by Reinhold et al.
(2006). The measured indication of variation is based on the combined analysis
of H2 absorption systems in the spectra of Q0405-443 and Q0347-383 at z=2.595
and z=3.025, respectively. The high resolution data of the latter is reanalyzed
in this work to examine the influence of different fitting procedures and
further potential nonconformities. This analysis cannot reproduce the
significance achieved by the previous detection.


title:
Direct Numerical Simulation of Turbulent Heat Transfer Modulation in
  Micro-Dispersed Channel Flow

abstract:
  The object of this paper is to study the influence of dispersed micrometer
size particles on turbulent heat transfer mechanisms in wall-bounded flows. The
strategic target of the current research is to set up a methodology to size and
design new-concept heat transfer fluids with properties given by those of the
base fluid modulated by the presence of dynamically-interacting,
suitably-chosen, discrete micro- and nano- particles. We run Direct Numerical
Simulation (DNS) for hydrodynamically fully-developed, thermally-developing
turbulent channel flow at shear Reynolds number Re=150 and Prandtl number Pr=3,
and we tracked two large swarms of particles, characterized by different
inertia and thermal inertia. Preliminary results on velocity and temperature
statistics for both phases show that, with respect to single-phase flow, heat
transfer fluxes at the walls increase by roughly 2% when the flow is laden with
the smaller particles, which exhibit a rather persistent stability against
non-homogeneous distribution and near-wall concentration. An opposite trend
(slight heat transfer flux decrease) is observed when the larger particles are
dispersed into the flow. These results are consistent with previous
experimental findings and are discussed in the frame of the current research
activities in the field. Future developments are also outlined.


title: Approximate substitutions and the normal ordering problem

abstract:
  In this paper, we show that the infinite generalised Stirling matrices
associated with boson strings with one annihilation operator are projective
limits of approximate substitutions, the latter being characterised by a finite
set of algebraic equations.


title: Dark matter millilensing and VSOP-2

abstract:
  According to the cold dark matter scenario, a large number of dark subhalos
should be located within the halo of each Milky-way sized galaxy. One promising
possibility for detecting such subhalos is to try to observe their
gravitational lensing effects on background sources. Dark matter subhalos in
the 10^6 - 10^10 M_solar mass range should cause strong gravitational lensing
on the (sub)milliarcsecond scales, which can be observed only using space VLBI.
We study the feasibility of a strong-lensing detection of dark subhalos by
deriving the image separations expected for density profiles favoured by
current simulations and comparing it to the angular resolution of both existing
and upcoming observational facilities. We show that the detection of subhalos
is likely much more difficult than suggested in previous studies, due to the
smaller image separations predicted for subhalo density profiles more realistic
than the singular isothermal sphere models often adopted.


title: Edge Channel Interference Controlled by Landau Level Filling

abstract:
  We study the visibility of Aharonov-Bohm interference in an electronic
Mach-Zehnder interferometer (MZI) in the integer quantum Hall regime. The
visibility is controlled by the filling factor $\nu$ and is observed only
between $\nu \approx 2.0$ and 1.0, with an unexpected maximum near $\nu=1.5$.
Three energy scales extracted from the temperature and voltage dependences of
the visibility change in a very similar way with the filling factor, indicating
that the different aspects of the interference depend sensitively on the local
structure of the compressible and incompressible strips forming the quantum
Hall edge channels.


title:
The Extended Fe distribution in the intracluster medium and the
  implications regarding AGN Heating

abstract:
  We present a systematic analysis of XMM-Newton observations of 8 cool-core
clusters of galaxies and determine the Fe distribution in the intracluster
medium relative to the stellar distribution in the central dominant galaxy
(CDG). Our analysis shows that the Fe is significantly more extended than the
stellar mass in the CDG in all of the clusters in our sample, with a slight
trend of increasing extent with increasing central cooling time. The excess Fe
within the central 100 kpc in these clusters can be produced by Type Ia
supernovae from the CDG over the past 3-7 Gyr. Since the excess Fe primarily
originates from the CDG, it is a useful probe for determining the motion of the
gas and the mechanical energy deposited by AGN outbursts over the past $\sim$ 5
Gyr in the centers of clusters. We explore two possible mechanisms for
producing the greater extent of the Fe relative to the stars in the CDG,
including: bulk expansion of the gas and turbulent diffusion of Fe. Assuming
the gas and Fe expand together, we find that a total energy of $10^{60} -
10^{61}$~erg~s$^{-1}$ must have been deposited into the central 100 kpc of
these clusters to produce the presently observed Fe distributions. Since the
required enrichment time for the excess Fe is approximately 5 Gyr in these
clusters, this gives an average AGN mechanical power over this time of $10^{43}
- 10^{44}$~erg~s$^{-1}$. The extended Fe distribution in cluster cores can also
arise from turbulent diffusion. Assuming steady-state (i.e., the outward mass
flux of Fe across a given surface is equal to the mass injection rate of Fe
within that surface) we find that diffusion coefficients of $10^{29} - 10^{30}$
cm$^2$~s$^{-1}$ are required to maintain the presently observed Fe profiles
(abridged).


title:
The Spectrum of the Fractional Laplacian and First Passage Time
  Statistics

abstract:
  We present exact results for the spectrum of the fractional Laplacian in a
bounded domain and apply them to First Passage Time (FPT) Statistics of L\'evy
flights. We specifically show that the average is insufficient to describe the
distribution of FPT, although it is the only quantity available in the existing
literature. In particular, we show that the FPT distribution is not peaked
around the average, and that knowledge of the whole distribution is necessary
to describe this phenomenon. For this purpose, we provide an efficient method
to calculate higher order cumulants and the whole distribution.


title: Non-gaussianity from the trispectrum in general single field inflation

abstract:
  We compute the fourth order action in perturbation theory for scalar and
second order tensor perturbations for a minimally coupled single field
inflationary model, where the inflaton's lagrangian is a general function of
the field's value and its kinetic energy. We obtain the fourth order action in
two gauges, the comoving gauge and the uniform curvature gauge. Using the
comoving gauge action we calculate the trispectrum at leading order in
slow-roll, finding agreement with a previously known result in the literature.
We point out that in general to obtain the correct leading order trispectrum
one cannot ignore second order tensor perturbations as previously done by
others. The next-to-leading order corrections may become detectable depending
on the shape and we provide the necessary formalism to calculate them.


title: INTEGRAL observations of Her X-1

abstract:
  Aims: We investigate the X-ray spectral and timing properties of the
accreting X-ray pulsar Her X-1 observed with the INTEGRAL satellite in
July-August 2005. Methods: The data analyzed in this work cover a substantial
part of one main-on state of the source. The short-time scale pulse period
development is measured. X-ray pulse profiles for different energy ranges and
time intervals are constructed. Pulse-averaged and pulse-phase resolved broad
band X-ray spectra are studied. Spectral changes during X-ray dips are
explored. Results: The X-ray pulse profiles are found to change significantly
during the period of observations. For the first time a strong spinup is
measured within one 35 d cycle. Spectral characteristics observed during the
X-ray dips are consistent with their interpretaion as due to partial covering
as has been reported by several authors. The fundamental cyclotron absorption
line is firmly observed in both pulse-averaged and pulse-phase resolved X-ray
spectra. The energy, width, and the depth of the line are found to vary
significantly with pulse phase.


title: Reentrant magnetic ordering and percolation in a spin-crossover system

abstract:
  Spin-crossover compounds, which are characterized by magnetic ions showing
low-spin and high-spin states at thermally accessible energies, are ubiquitous
in nature. We here focus on the effect of an exchange interaction on the
collective properties for the case of non-magnetic low-spin ions, which applies
to Fe(II) compounds. Monte Carlo simulations are used to study a
three-dimensional spin-crossover model for the full parameter range from
essentially pure high spin to essentially pure low spin. We find that as the
low-spin state becomes more favorable, the Curie temperature drops, the
universality class deviates from the three-dimensional Heisenberg class, and
the transition eventually changes to first order. A heat-bath algorithm that
grows or shrinks low-spin and high-spin domains is developed to handle the
first-order transition. When the ground state has low spin, a reentrant
magnetic transition is found in a broad parameter range. We also observe a
percolation transition of the high spins, which branches off the first-order
magnetic transition.


title: Scalar-tensor cosmological simulations

abstract:
  We present $N$-body cosmlogical simulations in the framework of the Newtonian
limit of scalar-tensor theories of gravity. The scalar field is described by a
modified Helmholtz equation with a source that is coupled to the standard
Poisson equation of Newtonian gravity. The effective gravitational force is
given by two contributions: the standard Newtonian potential plus a Yukawa
potential stemming from massive scalar fields. In particular, we consider
simulations of $\Lambda$CDM models and compute the density and velocity
profiles of the most massive groups found at z=0.


title:
Attractor Bifurcation and Final Patterns of the N-Dimensional and
  Generalized Swift-Hohenberg Equations

abstract:
  In this paper I will investigate the bifurcation and asymptotic behavior of
solutions of the Swift-Hohenberg equation and the generalized Swift-Hohenberg
equation with the Dirichlet boundary condition on a one- dimensional domain
$(0,L)$. I will also study the bifurcation and stability of patterns in the
n-dimensional Swift-Hohenberg equation with the odd-periodic and periodic
boundary conditions. It is shown that each equation bifurcates from the trivial
solution to an attractor, when the control parameter crosses the principal
eigenvalue of the linearized equation. The local behavior of solutions and
their bifurcation to an invariant set near higher eigenvalues are analyzed as
well.


title: Pfister's Theorem for orthogonal involutions of degree 12

abstract:
  We use the fact that a projective half-spin representation of $Spin_{12}$ has
an open orbit to generalize Pfister's result on quadratic forms of dimension 12
in $I^3$ to orthogonal involutions.


title: Finite type coarse expanding conformal dynamics

abstract:
  We continue the study of non-invertible topological dynamical systems with
expanding behavior. We introduce the class of {\em finite type} systems which
are characterized by the condition that, up to rescaling and uniformly bounded
distortion, there are only finitely many iterates. We show that subhyperbolic
rational maps and finite subdivision rules (in the sense of Cannon, Floyd,
Kenyon, and Parry) with bounded valence and mesh going to zero are of finite
type. In addition, we show that the limit dynamical system associated to a
selfsimilar, contracting, recurrent, level-transitive group action (in the
sense of V. Nekrashevych) is of finite type. The proof makes essential use of
an analog of the finiteness of cone types property enjoyed by hyperbolic
groups.


title:
A compact pulsar wind nebula model of the gamma-ray loud binary LS I +61
  303

abstract:
  We study a model of of LS I +61 303 in which its radio to TeV emission is due
to interaction of a relativistic wind from a young pulsar with the wind from
its companion Be star. We assume the fast polar wind is clumpy, which is
typical for radiatively-driven winds. The clumpiness cause the two winds to
mix. The relativistic electrons from the pulsar wind are retained in the moving
clumps by inhomogeneities of the magnetic field, which explains the X-ray
variability observed on time scales much shorter than the orbital period. We
calculate detailed inhomogeneous spectral models reproducing the average
broad-band spectrum from radio to TeVs. Given the uncertainties the form of the
distribution of relativistic electrons, the X-ray spectrum could be dominated
by either Compton or synchrotron emission. The recent Fermi observations
constrain the high-energy cut-off in the electron distribution to be at the
Lorentz factor of 2 10^4 or 10^8 in the former and latter model, respectively.
We provide formulae comparing the losses of the relativistic electrons due to
Compton, synchrotron and Coulomb processes vs. the distance from the Be star.
We calculate the optical depth of the wind to free-free absorption, showing
that it will suppress most of the radio emission within the orbit. We point out
the importance of Compton and Coulomb heating of the stellar wind within and
around the gamma-ray emitting region. Then, we find the most likely mechanism
explaining the orbital modulation at TeV energies is anisotropy of emission.


title: The B-->pi K Puzzle and Supersymmetry

abstract:
  At present, there are discrepancies between the measurements of several
observables in B-->pi K decays and the predictions of the standard model (the
``B-->pi K puzzle''). Although the effect is not yet statistically significant
-- it is at the level of $\gsim 3\sigma$ -- it does hint at the presence of new
physics. In this paper, we explore whether supersymmetry (SUSY) can explain the
B-->pi K puzzle. In particular, we consider the SUSY model of Grossman, Neubert
and Kagan (GNK). We find that it is extremely unlikely that GNK explains the
B-->pi K data. We also find a similar conclusion in many other models of SUSY.
And there are serious criticisms of the two SUSY models that do reproduce the
B-->pi K data. If the B-->pi K puzzle remains, it could pose a problem for SUSY
models.


title: Note sur les temps de service r\'esiduels dans les syst\`emes type M/G/c

abstract:
  Approximations for the mean performance indices for the M/G/c queue rely on
the approximate computation of the probability that an arriving request has to
wait for service and of the minimum of residual service times if all servers
are found busy. Using numerical examples, we investigate properties of these
two quantities. In particular, we show that the minimum of residual service
times depends on higher order properties, beyond the first two moments, of the
service time distribution. Improved knowledge of the properties of the two
quantities studied in this paper provides insight into avenues for improving
the accuracy of approximations for the M/G/c queue.


title:
Learning more about what can be concluded from the observation of
  neutrinos from a galactic supernova

abstract:
  We investigate what one can hope to learn about the parameters that describe
the neutrino fluxes emitted by the explosion of a galactic supernova using the
observations of a megaton-size Water-Cherenkov detector. We calculate the
allowed regions that can be obtained by fitting these parameters to a simulated
observation of events by such a detector. All four available detection channels
(inverse beta decay, charge and neutral current on oxygen and elastic
scattering on electrons) are included in the fit and we use a ten dimensional
parameters space. Nine parameters describe the initial neutrino fluxes and are
referred to as the supernova parameters. Furthermore, we include the dependence
on the Chooz mixing angle $\theta_{13}$, which controls the matter effects that
the neutrino undergoes in the outer-parts of the supernova. If we do not make
any extra assumption on these parameters, we show that one can hope to
determine $\theta_{13}$ quite well whereas, except for the parameters
describing the $\bar\nu_e$ flux, most of the supernova parameters are rather
difficult to constrain, even if the four detection channels could be completely
separated.


title: Hadron structure for x << 1 and upcoming collider measurements

abstract:
  We discuss theoretical aspects of parton distribution functions for very high
energy scattering in relation with upcoming measurements in DIS and
hadron-hadron collisions.


title:
Superconducting Transition in the $\beta$-Pyrochlore AOs$_2$O$_6$ (A=Cs,
  Rb, K) under Pressure

abstract:
  Pressure dependence of superconducting transition temperature $T_{\rm c}$ has
been determined through the DC magnetic measurements under pressure up to
$P$=10 GPa for $\beta$-pyrochlore oxides AOs$_2$O$_6$ with A=Cs ($T_{\rm
c}$=3.3 K), Rb (6.3 K) and K (9.6 K). Both for A=Rb and Cs, $T_{\rm c}$
increases with increasing $P$ and shows a saturation at $T_{\rm cm}$$\sim$8.8
K, which is considered as the upper limit of $T_{\rm c}$ inherent in
AOs$_2$O$_6$. In contrast, the $T_{\rm c}-P$ curve for KOs$_2$O$_6$ shows a
sharp maximum of $\sim$10 K at $P$$\sim$0.5 GPa, and $T_{\rm c}$ is higher than
$T_{\rm cm}$ for 0$\leq$$P$$\leq$1.5GPa, suggesting the enhanced
superconductivity due to the rattling of K ions.


title: First derivatives estimates for finite-difference schemes

abstract:
  We give sufficient conditions under which solutions of discretized in space
second-order parabolic and elliptic equations, perhaps degenerate, admit
estimates of the first derivatives in the space variables independent of the
mesh size.


title: Estimation of n non-identical unitary channels

abstract:
  We investigate the simultaneous estimation of $n$ not necessarily identical
unitary channels using multi-partite entanglement. We examine whether it is
possible for the rate at which the mean square error decreases to be greater
than that using the channels individually. For a reasonably general situation,
in which there is no functional dependence between the channels, we show that
this is not possible. We look at a case in which the channels are not
necessarily identical but depend on a common variable. In this case, the mean
square error decreases more rapidly using multi-partite entanglement.


title:
Evidence of Fragmenting Dust Particles from Near-Simultaneous Optical
  and Near-IR Photometry and Polarimetry of Comet 73P/Schwassmann-Wachmann 3

abstract:
  We report imaging polarimetry of segments B and C of the Jupiter-family Comet
73P/Schwassmann-Wachmann 3 in the I and H bandpasses at solar phase angles of
approximately 35 and 85deg. The level of polarization was typical for active
comets, but larger than expected for a Jupiter-family comet. The polarimetric
color was slightly red (dP/dL = +1.2 +/- 0.4) at a phase angle of ~ 35deg and
either neutral or slightly blue at a phase angle of ~ 85deg. Observations
during the closest approach from 2006 May 11-13 achieved a resolution of 35 km
at the nucleus. Both segments clearly depart from a 1/rho surface brightness
for the first 50 - 200 km from the nucleus. Simulations of radiation driven
dust dynamics can reproduce some of the observed coma morphology, but only with
a wide distribution of initial dust velocities (at least a factor of 10) for a
given grain radius. Grain aggregate breakup and fragmentation are able to
reproduce the observed profile perpendicular to the Sun-Comet axis, but fit the
observations less well along this axis (into the tail). The required
fragmentation is significant, with a reduction in the mean grain aggregate size
by about a factor of 10. A combination of the two processes could possibly
explain the surface brightness profile of the comet.


title: Infrared behavior of the running coupling in scalar field theory

abstract:
  We compute the Green function of the massless scalar field theory in the
infrared till the next-to-leading order, providing a fully covariant strong
coupling expansion. Applying Callan-Symanzik equation we obtain the exact
running coupling for this case by computing the beta function. This result is
applied using a recently proved mapping theorem between a massless scalar field
theory and Yang-Mills theory. This beta function gives a running coupling going
to zero as $p^4$ in agreement with lattice results presented in Boucaud et al.
[JHEP 0304 (2003) 005] and showing that the right definition of the running
coupling for a Yang-Mills theory in the infrared is given in a MOM scheme. The
emerging scenario is supporting a quantum field theory based on instantons.


title: Glimm's Method for Relativistic Hydrodynamics

abstract:
  We present the results of standard one-dimensional test problems in
relativistic hydrodynamics using Glimm's (random choice) method, and compare
them to results obtained using finite differencing methods. For problems
containing profiles with sharp edges, such as shocks, we find Glimm's method
yields global errors ~1-3 orders of magnitude smaller than the traditional
techniques. The strongest differences are seen for problems in which a shear
field is superposed. For smooth flows, Glimm's method is inferior to standard
methods. The location of specific features can be off by up to two grid points
with respect to an exact solution in Glimm's method, and furthermore curved
states are not modeled optimally since the method idealizes solutions as being
composed of piecewise constant states. Thus although Glimm's method is superior
at correctly resolving sharp features, especially in the presence of shear, for
realistic applications in which one typically finds smooth flows plus strong
gradients or discontinuities, standard FD methods yield smaller global errors.
Glimm's method may prove useful in certain applications such as GRB afterglow
shock propagation into a uniform medium.


title:
Extra cancellation of even Calderon-Zygmund operators and quasiconformal
  mappings

abstract:
  We discuss a special class of Beltrami coefficients whose associated
quasiconformal mapping is bilipschitz. These are of the form the characteristic
function of a planar bounded domain with smooth boundary of class C 1+epsilon
times a density of class Lip epsilon on the domain. The crucial fact in the
argument is the special extracancellation property of even Calderon-Zygmund
kernels, namely that they have zero integral on half the unit ball. This
property is expressed in a particularly suggestive way and is shown to have
far-reaching consequences. The main result may also be viewed as a Lipschitz
regularity result for the Beltrami equation, and so for certain planar second
order elliptic equations in divergence form.


title: LOFAR-UK White Paper: A Science case for UK involvement in LOFAR

abstract:
  LOFAR, the Low-Frequency Array, is a next-generation software-driven radio
telescope operating between 30 and 240MHz, currently under construction by
ASTRON in the Netherlands. This low frequency radio band is one of the few
largely unexplored regions of the electromagnetic spectrum. The sensitivity and
angular resolution offered by LOFAR will be two to three orders of magnitude
better than existing telescopes, and as such it will open up this new window on
the Universe. LOFAR will impact on a broad range of astrophysics, from
cosmology to solar system studies.
  There is growing European involvement in LOFAR, driven by the need to add
stations far from the main core in order to improve angular resolution.
LOFAR-UK is a project aimed at cementing UK participation in LOFAR via the
operation of four stations within the UK. LOFAR-UK ground stations will allow
LOFAR observations to reach sub-arcsecond scales at the highest frequencies,
and as a result will also improve the (confusion-limited) sensitivity limit of
the telescope for deep surveys.
  LOFAR-UK will achieve involvement for UK astronomers in a world-leading
science facility operating in the immediate future. It will allow the UK to
build up important scientific and technical expertise in `next generation'
radio astronomy in preparation for the Square Kilometre Array (SKA), and will
play an important role in broadening the UK community that has an interest in
radio astronomy. This White Paper outlines the strategic importance to the UK
astronomy community of gaining involvement in the LOFAR project, the scientific
interests of UK researchers in using the telescope, and the technical
challenges that will need to be overcome [abridged].


title:
Fast switching NMR system for measurements of ground-state quadrupole
  moments of short-lived nuclei

abstract:
  A beta-ray detecting nuclear quadrupole resonance system has been developed
at NSCL/MSU to measure ground-state electric quadrupole moments of short-lived
nuclei produced as fast rare isotope beams. This system enables quick and
sequential application of multiple transition frequencies over a wide range.
Fast switching between variable capacitors in resonance circuits ensures
sufficient power delivery to the coil in the beta-ray detecting nuclear
magnetic resonance technique. The fast switching technique enhances detection
efficiency of resonance signals and is especially useful when the polarization
and/or production rate of the nucleus of interest are small and when the
nuclear spin is large.


title: The Catchment Area of Jets

abstract:
  The area of a jet is a measure of its susceptibility to radiation, like
pileup or underlying event (UE), that on average, in the jet's neighbourhood,
is uniform in rapidity and azimuth. In this article we establish a theoretical
grounding for the discussion of jet areas, introducing two main definitions,
passive and active areas, which respectively characterise the sensitivity to
pointlike or diffuse pileup and UE radiation. We investigate the properties of
jet areas for three standard jet algorithms, k_t, Cambridge/Aachen and SISCone.
Passive areas for single-particle jets are equal to the naive geometrical
expectation \pi R^2, but acquire an anomalous dimension at higher orders in the
coupling, calculated here at leading order. The more physically relevant active
areas differ from \pi R^2 even for single-particle jets, substantially so in
the case of the cone algorithms like SISCone with a Tevatron Run-II
split--merge procedure. We compare our results with direct measures of areas in
parton-shower Monte Carlo simulations and find good agreement with the main
features of the analytical predictions. We furthermore justify the use of jet
areas to subtract the contamination from pileup.


title: The anti-k_t jet clustering algorithm

abstract:
  The k_t and Cambridge/Aachen inclusive jet finding algorithms for
hadron-hadron collisions can be seen as belonging to a broader class of
sequential recombination jet algorithms, parametrised by the power of the
energy scale in the distance measure. We examine some properties of a new
member of this class, for which the power is negative. This ``anti-k_t''
algorithm essentially behaves like an idealised cone algorithm, in that jets
with only soft fragmentation are conical, active and passive areas are equal,
the area anomalous dimensions are zero, the non-global logarithms are those of
a rigid boundary and the Milan factor is universal. None of these properties
hold for existing sequential recombination algorithms, nor for cone algorithms
with split--merge steps, such as SISCone. They are however the identifying
characteristics of the collinear unsafe plain ``iterative cone'' algorithm, for
which the anti-k_t algorithm provides a natural, fast, infrared and collinear
safe replacement.


title: Note on spin-orbit interactions in nuclei and hypernuclei

abstract:
  A detailed comparison is made between the spin-orbit interactions in
$\Lambda$ hypernuclei and ordinary nuclei. We argue that there are three major
contributions to the spin-orbit interaction: 1) a short-range component
involving scalar and vector mean fields; 2) a ''wrong-sign'' spin-orbit term
generated by the pion exchange tensor force in second order; and 3) a
three-body term induced by two-pion exchange with excitation of virtual
$\Delta(1232)$-isobars (a la Fujita-Miyazawa). For nucleons in nuclei the
long-range pieces related to the pion-exchange dynamics tend to cancel, leaving
room dominantly for spin-orbit mechanisms of short-range origin (parametrized
e.g. in terms of relativistic scalar and vector mean fields terms). In
contrast, the absence of an analogous $2\pi$-exchange three-body contribution
for $\Lambda$ hyperons in hypernuclei leads to an almost complete cancellation
between the short-range (relativistic mean-field) component and the
''wrong-sign'' spin-orbit interaction generated by second order $\pi$-exchange
with an intermediate $\Sigma$ hyperon. These different balancing mechanisms
between short- and long-range components are able to explain simultaneously the
very strong spin-orbit interaction in ordinary nuclei and the remarkably weak
spin-orbit splitting in $\Lambda$ hypernuclei.


title: AEGIS: Radio and Mid-Infrared Selection of Obscured AGN Candidates

abstract:
  The application of multi-wavelength selection techniques is crucial for
discovering a complete and unbiased set of Active Galactic Nuclei (AGNs). Here,
we select a sample of 72 AGN candidates in the Extended Groth Strip (EGS) using
deep radio and mid-infrared data from the Very Large Array (VLA) and the
Spitzer Space Telescope, and analyze their properties across other wavelengths.
Only 30% of these sources are detected in deep 200 ks Chandra X-ray Observatory
pointings. The X-ray detected sources demonstrate moderate obscuration with
column densities of N_H > 10^22 cm^-2. A stacked image of sources undetected by
Chandra shows low levels of X-ray activity, suggesting they may be faint or
obscured AGNs. Less than 40% of our sample are selected as AGNs with optical
broad lines, mid-infrared power laws, or X-ray detections. Thus, if our
candidates are indeed AGNs, the radio/mid-infrared selection criteria we use
provide a powerful tool for identifying sources missed by other surveys.


title:
Limit Theorems for Hybridization Reactions on Oligonucleotide
  Microarrays

abstract:
  We derive herein the limiting laws for certain stationary distributions of
birth-and-death processes related to the classical model of chemical
adsorption-desorption reactions due to Langmuir. The model has been recently
considered in the context of a hybridization reaction on an oligonucleotide DNA
microarray. Our results imply that the truncated gamma- and beta- type
distributions can be used as approximations to the observed distributions of
the fluorescence readings of the oligo-probes on a microarray. These findings
might be useful in developing new model-based, probe-specific methods of
extracting target concentrations from array fluorescence readings.


title:
Induced deformation of the canonical structure and UV/IR duality in
  $(1+1)D$

abstract:
  The purpose of this work is two fold. Working in the framework of $(1+1)D$
Lorentz violating field theories we will investigate in the first place the
general claim that fermionic interactions may be equivalent to a deformation of
the canonical structure of the theory. Second the deformed theory will be
studied using duality reasoning to address the behavior of the Infra-Red and
Ultra-Violet regimes.


title:
Electron loss to the Continuum in the Projectile ionization for
  Positronium - Helium atom collision

abstract:
  The dynamics of the electron loss to the continuum (ELC) from the light
neutral projectile positronium (Ps) atom in collision with the He atom is
studied in the framework of the post collisional Coulomb Distorted Eikonal
Approximation (CDEA). Both the fully differential (TDCS) and the double
differential (DDCS) cross sections are investigated in the intermediate and
high incident energies. Results are compared with the existing experiment and
other theories, where possible.


title: Numerical Solution of the Beltrami Equation

abstract:
  An effective algorithm is presented for solving the Beltrami equation fzbar =
mu fz in a planar disk. The algorithm involves no evaluation of singular
integrals. The strategy, working in concentric rings, is to construct a
piecewise linear mu-conformal mapping and then correct the image using a known
algorithm for conformal mappings. Numerical examples are provided and the
computational complexity is analyzed.


title: A classical bounce: constraints and consequences

abstract:
  We perform a detailed investigation of the simplest possible cosmological
model in which a bounce can occur, namely that where the dynamics is led by a
simple massive scalar field in a general self-interacting potential and a
background spacetime with positively curved spatial sections. By means of a
phase space analysis, we give the conditions under which an initially
contracting phase can be followed by a bounce and an inflationary phase lasting
long enough (i.e., at least 60-70 e-folds) to suppress spatial curvature in
today's observable universe. We find that, quite generically, this realization
requires some amount of fine-tuning of the initial conditions. We study the
effect of this background evolution on scalar perturbations by propagating an
initial power-law power spectrum through the contracting phase, the bounce and
the inflationary phase. We find that it is drastically modified, both
spectrally (k-mode mixing) and in amplitude. It also acquires, at leading
order, an oscillatory component, which, once evolved through the radiation and
matter dominated eras, happens to be compatible with the WMAP data.


title:
Laser-assisted multiphoton ionization of a hydrogen atom by electron
  impact

abstract:
  The dynamics of the electron impact multiphoton ionization of a hydrogen atom
in the presence of an intense laser field has been studied theoretically, with
a view to comparing (qualitatively) the results with the recent kinematically
complete experiments of Horr et al [ Phys. Rev. Lett., vol. 94, 153201, (2005)
] for the He target. Significant laser modifications are noted in the present
doubly (DDCS) and the fully differential cross sections (TDCS). For most of the
explored kinematics (chosen in accordance with the experiment), the present
binary peak intensity of the laser-assisted TDCS is significantly enhanced with
respect to the field free ones, in agreement with the experiment but in
contradiction with the existing first order theories. Importance of the
multiphoton effects are also studied.


title: Socle theory for Leavitt path algebras of arbitrary graphs

abstract:
  The main aim of the paper is to give a socle theory for Leavitt path algebras
of arbitrary graphs. We use both the desingularization process and
combinatorial methods to study Morita invariant properties concerning the socle
and to characterize it, respectively. Leavitt path algebras with nonzero socle
are described as those which have line points, and it is shown that the line
points generate the socle of a Leavitt path algebra, extending so the results
for row-finite graphs in the previous paper [12] (but with different methods).
A concrete description of the socle of a Leavitt path algebra is obtained: it
is a direct sum of matrix rings (of finite or infinite size) over the base
field. New proofs of the Graded Uniqueness and of the Cuntz-Krieger Uniqueness
Theorems are given, shorthening significantly the original ones.


title: Dissipation control in cavity QED with oscillating mode-structures

abstract:
  We demonstrate how a time-dependent dissipative environment may be used as a
tool for controlling the quantum state of a two-level atom. In our model system
the frequency and coupling strength associated with microscopic reservoir modes
are modulated, while the principal features of the reservoir structure remain
fixed in time. Physically, this may be achieved by containing a static
atom-cavity system inside an oscillating external bath. We show that it is
possible to dynamically decouple the atom from its environment, despite the
fact that the two remain resonant at all times. This can lead to Markovian
dynamics, even for a strong atom-bath coupling, as the atomic decay becomes
inhibited into all but a few channels; the reservoir occupation spectrum
consequently acquires a sideband structure, with peaks separated by the
frequency of the environmental modulation. The reduction in the rate of
spontaneous emission using this approach can be significantly greater than
could be achieved with an oscillatory atom-bath detuning using the same
parameters.


title: Statistical properties of SZ and X-ray cluster detections

abstract:
  Aims. We calibrate the number density, completeness, reliability and the
lower mass limit of galaxy-cluster detections through their thermal SZ signal,
and compare them to X-ray cluster detections.
  Methods. We simulate maps of the thermal SZ effect and the X-ray emission
from light cones constructed in a large, hydrodynamical, cosmological
simulation volume, including realistic noise contributions. The maps are
convolved with linear, optimised, single- and multi-band filters to identify
local peaks and their signal-to-noise ratios. The resulting peak catalogues are
then compared to the halo population in the simulation volume to identify true
and spurious detections.
  Results. Multi-band filtering improves the statistics of SZ cluster
detections considerably compared to single-band filtering. Observations with
the characteristics of ACT detect clusters with masses M>6-9e13 M_o/h, quite
independent of redshift, reach 50% completeness at ~1e14 M_o/h and 100%
completeness at ~2e14 M_o/h. Samples are contaminated by only a few per cent
spurious detections. This is broadly comparable to X-ray cluster detections
with XMM-Newton with 100 ks exposure time in the soft band, except that the
mass limit for X-ray detections increases much more steeply with redshift than
for SZ detections. A comparison of true and filtered signals in the SZ and
X-ray maps confirms that the filters introduce at most a negligible bias.


title: Tensorial Structure of the LQG graviton propagator

abstract:
  We review the construction of the tensorial structure of the graviton
propagator in the context of loop quantum gravity and spinfoam formalism. The
main result of this analysis is that applying the same strategy used to compute
the diagonal terms, the Barrett-Crane vertex is unable to yield the correct
propagator in the long distance limit. The problem is in the
intertwiner-independence of the Barrett-Crane vertex. We also review the
asymptotic behavior of an alternative vertex that is able to give the correct
propagator.


title:
Arecibo Multi-frequency Time-Aligned Pulsar Average-Profile and
  Polarization Database

abstract:
  We present Arecibo time-aligned, total intensity profiles for 46 pulsars over
an unusually wide range of radio frequencies and multi-frequency,
polarization-angle density diagrams and/or polarization profiles for 58 pulsars
pulsars at some or all of the frequencies 50, 111/130, 430 and 1400 MHz. The
frequency-dependent dispersion delay has been removed In order to align the
profiles for study of their spectral evolution and wherever possible the
profiles of each pulsar are displayed on the same longitude scale. Most of the
pulsars within Arecibo's declination range that are sufficiently bright for
such spectral or single pulse analysis are included in this survey--and the
calibrated pulse sequences are available by web download for further study.


title:
Chemical consequences of low star formation rates: stochastically
  sampling the IMF

abstract:
  When estimating the abundances which result from a given star formation
event, it is customary to treat the IMF as a series of weight factors to be
applied to the stellar yields, as a function of mass, implicitly assuming one
is dealing with an infinite population. However, when the stellar population is
small, the standard procedure would imply the inclusion of fractional numbers
of stars at certain masses. We study the effects of small number statistics on
the resulting abundances by performing an statistical sampling of the IMF to
form a stellar population out of discrete numbers of stars. A chemical
evolution code then follows the evolution of the population, and traces the
resulting abundances. The process is repeated to obtain an statistical
distribution of the resulting abundances and their evolution. We explore the
manner in which different elements are affected, and how different abundances
converge to the infinite population limit as the total mass increases. We
include a discussion of our results in the context of dwarf spheroidal galaxies
and show the recently reported internal dispersions in abundance ratios for
dSph galaxies might be partly explained through the stochastic effects
introduced by a low star formation rate, which can account for dispersions of
over 2 dex in [C/O], [N/O], [C/Fe], [N/Fe] and [O/Fe].


title:
High-Velocity Interstellar Bullets in IRAS05506+2414: A Very Young
  Protostar

abstract:
  We have made a serendipitous discovery of an enigmatic outflow source, IRAS
05506+2414 (hereafter IRAS 05506), as part of a multi-wavelength survey of
pre-planetary nebulae (PPNs). The HST optical and near-infrared images show a
bright compact central source with a jet-like extension, and a fan-like spray
of high-velocity (with radial velocities upto 350 kms/s) elongated knots which
appear to emanate from it. These structures are possibly analogous to the
near-IR "bullets" seen in the Orion nebula. Interferometric observations at 2.6
mm show the presence of a high-velocity CO outflow and a continuum source also
with a faint extension, both of which are aligned with the optical jet
structure. IRAS 05506 is most likely not a PPN. We find extended NH3 (1,1)
emission towards IRAS 05506; these data together with the combined presence of
far-IR emission, H2O and OH masers, and CO and CS J=2-1 emission, strongly
argue for a dense, dusty star-forming core associated with IRAS 05506. IRAS
05506 is probably an intermediate-mass or massive protostar, and the very short
time-scale (200 yr) of its outflows indicates that it is very young. If IRAS
05506 is a massive star, then the lack of radio continuum and the late G --
early K spectral type we find from our optical spectra implies that in this
object we are witnessing the earliest stages of its life, while its temperature
is still too low to provide sufficient UV flux for ionisation.


title: Essentialit\'e dans les bases additives

abstract:
  In this article we study the notion of essential subset of an additive basis,
that is to say the minimal finite subsets $P$ of a basis $A$ such that $A
\setminus P$ doesn't remains a basis. The existence of an essential subset for
a basis is equivalent for this basis to be included, for almost all elements,
in an arithmetic non-trivial progression. We show that for every basis $A$
there exists an arithmetic progression with a biggest common difference
containing $A$. Having this common difference $a$ we are able to give an upper
bound to the number of essential subsets of $A$: this is the radical's length
of $a$ (in particular there is always many finite essential subsets in a
basis).
  In the case of essential subsets of cardinality 1 (essential elements) we
introduce a way to "dessentialize" a basis. As an application, we definitively
improve the earlier result of Deschamps and Grekos giving an upper bound of the
number of the essential elements of a basis. More precisely, we show that for
all basis $A$ of order $h$, the number $s$ of essential elements of $A$ satisfy
$s\leq c\sqrt{\frac{h}{\log h}}$ where $c=30\sqrt{\frac{\log 1564}{1564}}\simeq
2,05728$, and we show that this inequality is best possible.


title:
Extinction imaging of a single quantum emitter in its bright and dark
  states

abstract:
  Room temperature detection of single quantum emitters has had a broad impact
in fields ranging from biophysics to material science, photophysics, or even
quantum optics. These experiments have exclusively relied on the efficient
detection of fluorescence. An attractive alternative would be to employ direct
absorption, or more correctly expressed "extinction" measurements. Indeed,
small nanoparticles have been successfully detected using this scheme in
reflection and transmission. Coherent extinction detection of single emitters
has also been reported at cryogenic temperatures, but their room temperature
implementation has remained a great laboratory challenge owing to the expected
weak signal-to-noise ratio. Here we report the first extinction study of a
single quantum emitter at ambient condition. We obtain a direct measure for the
extinction cross section of a single semiconductor nanocrystal both during and
in the absence of fluorescence, for example in the photobleached state or
during blinking off-times. Our measurements pave the way for the detection and
absorption spectroscopy of single molecules or clusters of atoms even in the
quenched state.


title: Universal quantum walks and adiabatic algorithms by 1D Hamiltonians

abstract:
  We construct a family of time-independent nearest-neighbor Hamiltonians
coupling eight-state systems on a 1D ring that enables universal quantum
computation. Hamiltonians in this family can achieve universality either by
driving a continuous-time quantum walk or by terminating an adiabatic
algorithm. In either case, the universality property can be understood as
arising from an efficient simulation of a programmable quantum circuit. Using
gadget perturbation theory, one can demonstrate the same kind of universality
for related Hamiltonian families acting on qubits in 2D. Our results
demonstrate that simulating 1D chains of spin-7/2 particles is BQP-hard, and
indeed BQP-complete because the outputs of decision problems can be encoded in
the outputs of such simulations.


title: Seesaw Extended MSSM and Anomaly Mediation without Tachyonic Sleptons

abstract:
  Superconformal anomalies provide an elegant and economical way to understand
the soft breaking parameters in SUSY models; however, implementing them leads
to the several undesirable features including: tachyonic sleptons and
electroweak symmetry breaking problems in both the MSSM and the NMSSM. Since
these two theories also have the additonal problem of massless neutrinos, we
have reconsidered the AMSB problems in a class of models that extends the NMSSM
to explain small neutrino masses via the seesaw mechanism. In a recent paper,
we showed that for a class of minimal left-right extensions, a built-in
mechanism exists which naturally solves the tachyonic slepton problem and
provides new alternatives to the MSSM that also have automatic R-parity
conservation. In this paper, we discuss how electroweak symmetry breaking
arises in this model through an NMSSM-like low energy theory with a singlet
VEV, induced by the structure of the left-right extension and of the right
magnitude. We then study the phenomenological issues and find: the LSP is an
Higgsino-wino mix, new phenomenology for chargino decays to the LSP, degenerate
same generation sleptons and a potential for a mild squark-slepton degeneracy.
We also discuss possible collider signatures and the feasibility of dark matter
in this model.


title: Low Lying Scalar Resonances and Chiral Symmetry

abstract:
  Current theoretical studies on the $\sigma$ and $\kappa$ resonances are
reviewed. It is emphasized that all evidences accumulated so far are consistent
with the picture that the $\sigma$ meson is the chiral partner of the
Nambu--Goldstone bosons in a linear realization of chiral symmetry.


title: X-Ray and Optical Microlensing in the Lensed Quasar PG 1115+080

abstract:
  We analyzed the microlensing of the X-ray and optical emission of the lensed
quasar PG 1115+080. We find that the effective radius of the X-ray emission is
1.3(+1.1 -0.5) dex smaller than that of the optical emission. Viewed as a thin
disk observed at inclination angle i, the optical accretion disk has a scale
length, defined by the point where the disk temperature matches the rest frame
energy of the monitoring band (kT=hc/lambda_rest with lambda_rest=0.3 micron),
of log[(r_{s,opt}/cm)(cos(i) / 0.5)^{1/2}] = 16.6 \pm 0.4. The X-ray emission
region (1.4-21.8 keV in the rest frame) has an effective half-light radius of
log[r_{1/2,X}/cm] = 15.6 (+0.6-0.9}. Given an estimated black hole mass of 1.2
* 10^9 M_sun, corresponding to a gravitational radius of log[r_g/cm] = 14.3,
the X-ray emission is generated near the inner edge of the disk while the
optical emission comes from scales slightly larger than those expected for an
Eddington-limited thin disk. We find a weak trend supporting models with low
stellar mass fractions near the lensed images, in mild contradiction to
inferences from the stellar velocity dispersion and the time delays.


title: Renormalization algorithm with graph enhancement

abstract:
  We introduce a class of variational states to describe quantum many-body
systems. This class generalizes matrix product states which underly the
density-matrix renormalization group approach by combining them with weighted
graph states. States within this class may (i) possess arbitrarily long-ranged
two-point correlations, (ii) exhibit an arbitrary degree of block entanglement
entropy up to a volume law, (iii) may be taken translationally invariant, while
at the same time (iv) local properties and two-point correlations can be
computed efficiently. This new variational class of states can be thought of as
being prepared from matrix product states, followed by commuting unitaries on
arbitrary constituents, hence truly generalizing both matrix product and
weighted graph states. We use this class of states to formulate a
renormalization algorithm with graph enhancement (RAGE) and present numerical
examples demonstrating that improvements over density-matrix renormalization
group simulations can be achieved in the simulation of ground states and
quantum algorithms. Further generalizations, e.g., to higher spatial
dimensions, are outlined.


title: Rough edges in quantum transport of Dirac particles

abstract:
  We consider Dirac particles confined to a thin strip, e.g., graphene
nanoribbon, with rough edges. The confinement is implemented by a large mass in
the Hamiltonian or by imposing boundary conditions directly on the graphene
wave-functions. The scattering of a rough edge leads to a transverse
channel-mixing and provides crucial limitation to the quantum transport in
narrow ribbons. We solve the problem perturbatively and find the edge
scattering contribution to the conductivity, which can be measured
experimentally. The case of Schroedinger particles in a strip is also
addressed, and the comparison between Schroedinger and Dirac transport is made.
Anomalies associated with quasi-one dimensionality, such as Van Hove
singularities and localization, are discussed. The violation of the Matthiessen
rule is pointed out.


title: Cold atom confinement in an all-optical dark ring trap

abstract:
  We demonstrate confinement of $^{85}$Rb atoms in a dark, toroidal optical
trap. We use a spatial light modulator to convert a single blue-detuned
Gaussian laser beam to a superposition of Laguerre-Gaussian modes that forms a
ring-shaped intensity null bounded harmonically in all directions. We measure a
1/e spin-relaxation lifetime of ~1.5 seconds for a trap detuning of 4.0 nm. For
smaller detunings, a time-dependent relaxation rate is observed. We use these
relaxation rate measurements and imaging diagnostics to optimize trap alignment
in a programmable manner with the modulator. The results are compared with
numerical simulations.


title:
Handbook for the GREAT08 Challenge: An image analysis competition for
  cosmological lensing

abstract:
  The GRavitational lEnsing Accuracy Testing 2008 (GREAT08) Challenge focuses
on a problem that is of crucial importance for future observations in
cosmology. The shapes of distant galaxies can be used to determine the
properties of dark energy and the nature of gravity, because light from those
galaxies is bent by gravity from the intervening dark matter. The observed
galaxy images appear distorted, although only slightly, and their shapes must
be precisely disentangled from the effects of pixelisation, convolution and
noise. The worldwide gravitational lensing community has made significant
progress in techniques to measure these distortions via the Shear TEsting
Program (STEP). Via STEP, we have run challenges within our own community, and
come to recognise that this particular image analysis problem is ideally
matched to experts in statistical inference, inverse problems and computational
learning. Thus, in order to continue the progress seen in recent years, we are
seeking an infusion of new ideas from these communities. This document details
the GREAT08 Challenge for potential participants. Please visit
http://www.great08challenge.info for the latest information.


title: TeVeS gets caught on caustics

abstract:
  TeVeS uses a dynamical vector field with timelike unit norm constraint to
specify a preferred local frame. When matter moves slowly in this frame - the
so-called quasi-static regime - Modified Newtonian Dynamics (MoND) results.
Theories with such vectors (such as Einstein-aether) are prone to the vector
dynamics forming singularities which render their classical evolution
problematic. Here we analyse the dynamics of the vector in TeVeS in various
situations. We find that, quite generically, the vector field develops caustic
singularities on time scales of order the gravitational in-fall time. Having
shown singularity formation is generic with or without matter, Bekenstein's
original formulation of TeVeS appears dynamically problematic. We argue that by
modifying the vector field kinetic terms to the more general form used by
Einstein-Aether this problem may be avoided.


title: High temperature superconductivity: from complexity to simplicity

abstract:
  I discuss the recent quantum oscillation experiments in the underdoped high
temperature superconductors.