title:
Linear Relations and their Breakdown in High Energy Massive String
  Scatterings in Compact Spaces

abstract:
  We calculate high energy massive scattering amplitudes of closed bosonic
string compactified on the torus. For each fixed mass level with given
quantized and winding momenta ((m/R),(1/2)nR), we obtain infinite linear
relations among high energy scattering amplitudes of different string states.
For some kinematic regimes, we discover that linear relations with N_{R}=N_{L}
break down and, simultaneously, the amplitudes enhance to power-law behavior
instead of the usual expoential fall-off behavior at high energies. It is the
space-time T-duality symmetry that plays a role here. This result is consistent
with the coexistence of the linear relations and the softer exponential
fall-off behavior of high energy string scattering amplitudes as we pointed out
prevously. It is also reminiscent of our previous work on the power-law
behavior of high energy string/domain-wall scatterings.


title: Optical variabilities in Be/X-ray binary system:GRO J2058+42

abstract:
  We present an analysis of long-term optical monitoring observations and
optical spectroscopic observations of the counterpart to CXOU J205847.5+414637
(high mass X-ray binary system). We search for a variability in the light curve
of Be star. We used differential magnitudes in the time series analysis. The
variability search in the optical light curve was made by using different
algorithms. The reduction and analysis of spectra were done by using MIDAS and
its suitable packages. We have performed a frequency search which gave us the
value 2.404 1/day. This value is attributed to the non-radial pulsation of Be
star. H alpha emission line profiles always show double-peaked emissions with a
mean equivalent width of 2.31 \pm 0.19 \AA ~and a peak separation of 516 \pm 45
km/s. This suggests that Be star disk is still present. CXOU J205847.5+414637
is in X-ray quiescent state.


title:
A criterion for transience of multidimensional branching random walk in
  random environment

abstract:
  We develop a criterion for transience for a general model of branching Markov
chains. In the case of multi-dimensional branching random walk in random
environment (BRWRE) this criterion becomes explicit. In particular, we show
that \emph{Condition L} of Comets and Popov is necessary and sufficient for
transience as conjectured. Furthermore, the criterion applies to two important
classes of branching random walks and implies that the critical branching
random walk is transient resp. dies out locally.


title: On Mordell-Weil groups of elliptic curves induced by Diophantine triples

abstract:
  We study the possible structure of the groups of rational points on elliptic
curves of the form y^2=(ax+1)(bx+1)(cx+1), where a,b,c are non-zero rationals
such that the product of any two of them is one less than a square.


title: Scheduling Dags under Uncertainty

abstract:
  This paper introduces a parallel scheduling problem where a directed acyclic
graph modeling $t$ tasks and their dependencies needs to be executed on $n$
unreliable workers. Worker $i$ executes task $j$ correctly with probability
$p_{i,j}$. The goal is to find a regimen $\Sigma$, that dictates how workers
get assigned to tasks (possibly in parallel and redundantly) throughout
execution, so as to minimize the expected completion time. This fundamental
parallel scheduling problem arises in grid computing and project management
fields, and has several applications.
  We show a polynomial time algorithm for the problem restricted to the case
when dag width is at most a constant and the number of workers is also at most
a constant. These two restrictions may appear to be too severe. However, they
are fundamentally required. Specifically, we demonstrate that the problem is
NP-hard with constant number of workers when dag width can grow, and is also
NP-hard with constant dag width when the number of workers can grow. When both
dag width and the number of workers are unconstrained, then the problem is
inapproximable within factor less than 5/4, unless P=NP.


title: The reaction-free trajectories of a classical point charge

abstract:
  It is well-known that a classical point charge in 1+1 D hyperbolic motion in
space and time is reaction-free. But this is a special case of a larger set of
reaction-free trajectories that in general are curved paths through space, i.e.
in 2+1 D. This note catalogs the full family of reaction-free trajectories,
giving a geometrical interpretation by which means the curved path possibility
is easily related to the better known case of hyperbolic motion in 1+1 D.
Motivated by the geometry, it is shown how the catalog of motions can be
naturally extended to include the possibility of lossless reaction-free closed
spatial orbits that turn out to be classical pair creation and destruction
events. The extended theory can accommodate a vacuum plenum of classical
current that could be regarded as a classical version of the Fermionic ZPF of
QFT, reminiscent of the relationship between the Electromagnetic ZPF and the
classical imitation that characterizes `Stochastic Electrodynamics'.


title: Isospin asymmetry in the continuum of the A=14 mirror nuclei

abstract:
  We study the isospin asymmetry in the isoscalar (IS) excitations in the
mirror nuclei $^{14}$O and $^{14}$C by using the Hartree-Fock(HF)+random phase
approximation (RPA) linear response function theory with a Skyrme interaction
to take into account the continuum effect properly. The asymmetry in the IS
monopole, dipole responses is pointed out in the continuum near the particle
threshold with respect to the excitation energy and the sum rule strength. On
the other hand, no clear sign of the asymmetry is found in the giant resonance
(GR) region. In the quadrupole case, the calculated strengths of the mirror
nuclei show almost the same energy dependence from the threshold to the GR
region. It is found that the transition densities of the monopole response show
an extended halo structure near the threshold, while those of GR region show a
typical radial dependence of the compressional collective mode without any halo
effect. Contrary to the transition densities of the monopole response, those of
quadrupole response do not show any sign of the extended feature of wave
functions neither near the threshold nor the GR energy region. Calculated
strength distributions of the IS multipole states are compared with recent
experimental data obtained by the multipole decomposition analysis of $\alpha $
inelastic scattering on $^{14}$O.


title: Lovelock Gravity at the Crossroads of Palatini and Metric Formulations

abstract:
  We consider extensions of the Einstein-Hilbert Lagrangian to a general
functional of metric and Riemann curvature tensor. A given such Lagrangian
describes two different theories depending on considering connection and metric
(Palatini formulation), or only the metric (metric formulation) as independent
dynamical degrees of freedom. Equivalence of the Palatini and metric
formulations at the level of equations of motion, which as we will argue is a
manifestation of the Equivalence Principle, is the physical criterion that
restricts form of the Lagrangians of modified gravity theories. We prove that
within the class of modified gravity theories we consider, only the Lovelock
gravity satisfies this requirement.


title:
Conservation-Law-Induced Quantum Limits for Physical Realizations of the
  Quantum NOT Gate

abstract:
  In recent investigations, it has been found that conservation laws generally
lead to precision limits on quantum computing. Lower bounds of the error
probability have been obtained for various logic operations from the
commutation relation between the noise operator and the conserved quantity or
from the recently developed universal uncertainty principle for the
noise-disturbance trade-off in general measurements. However, the problem of
obtaining the precision limit to realizing the quantum NOT gate has eluded a
solution from these approaches. Here, we develop a new method for this problem
based on analyzing the trace distance between the output state from the
realization under consideration and the one from the ideal gate. Using the
mathematical apparatus of orthogonal polynomials, we obtain a general lower
bound on the error probability for the realization of the quantum NOT gate in
terms of the number of qubits in the control system under the conservation of
the total angular momentum of the computational qubit plus the the control
system along the direction used to encode the computational basis. The lower
bound turns out to be more stringent than one might expect from previous
results. The new method is expected to lead to more accurate estimates for
physical realizations of various types of quantum computations under
conservation laws, and to contribute to related problems such as the accuracy
of programmable quantum processors.


title: Charged hadron R_AA as a function of p_T at the LHC

abstract:
  We compute the nuclear suppression factor R_AA for charged hadrons within a
radiative energy loss picture using a hydrodynamical evolution to describe the
soft medium inducing energy loss. A minijet + saturation picture provides
initial conditions for LHC energies and leading order perturbative QCD (LO
pQCD) is used to compute the parton spectrum before distortion by energy loss.


title: Weyl Projective Curvature Symmetry in FRW k=0 Model

abstract:
  A study of proper Weyl projective curvature collineations in FRW k=0
space-time is given using the rank of Weyl projective curvature matrix and
direct integration techniques. It is shown that a very special class of the
above space-time admits proper Weyl projective curvature collineation.


title: Asymptotic freedom in massive Yang-Mills theory

abstract:
  An effective field theory model of the massive Yang-Mills theory is
considered. Assuming that the renormalized coupling constants of
'non-renormalizable' interactions are suppressed by a large scale parameter it
is shown that in analogy to the non-abelian gauge invariant theory the
dimensionless coupling constant vanishes logarithmically for large values of
the renormalization scale parameter.


title:
Broken spin-Hall accumulation symmetry by magnetic field and coexisted
  Rashba and Dresselhaus interactions

abstract:
  The spin-Hall effect in the two-dimensional electron gas (2DEG) generates
symmetric out-of-plane spin Sz accumulation about the current axis in the
absence of external magnetic field. Here we employ the real space
Landauer-Keldysh formalism [B. K. Nikolic et al., Phys. Rev. Lett. 95, 046601
(2005); Phys. Rev. B 73, 075303 (2006)] by considering a four-terminal setup to
investigate the circumstances in which this symmetry is broken. For the absence
of Dresselhaus interaction, starting from the applied out-of-plane B
corresponding to Zeeman splitting energy 0 - 0.5 times the Rashba hopping
energy tR, the breaking process is clearly seen. The influence of the Rashba
interaction on the magnetization of the 2DEG is studied herein. For coexisted
Rashba tR and Dresselhaus tD spin-orbit couplings in the absence of B,
interchanging tR and tD reverses the entire accumulation pattern.


title: The dipole form of the gluon part of the BFKL kernel

abstract:
  The dipole form of the gluon part of the colour singlet BFKL kernel in the
next-to-leading order (NLO) is obtained in the coordinate representation by
direct transfer from the momentum representation, where the kernel was
calculated before. With this paper the transformation of the NLO BFKL kernel to
the dipole form, started a few months ago with the quark part of the kernel, is
completed.


title:
Ontology-Supported and Ontology-Driven Conceptual Navigation on the
  World Wide Web

abstract:
  This paper presents the principles of ontology-supported and ontology-driven
conceptual navigation. Conceptual navigation realizes the independence between
resources and links to facilitate interoperability and reusability. An engine
builds dynamic links, assembles resources under an argumentative scheme and
allows optimization with a possible constraint, such as the user's available
time. Among several strategies, two are discussed in detail with examples of
applications. On the one hand, conceptual specifications for linking and
assembling are embedded in the resource meta-description with the support of
the ontology of the domain to facilitate meta-communication. Resources are like
agents looking for conceptual acquaintances with intention. On the other hand,
the domain ontology and an argumentative ontology drive the linking and
assembling strategies.


title:
Transforming nonlocality into frequency dependence: a shortcut to
  spectroscopy

abstract:
  Measurable spectra are theoretically very often derived from complicated
many-body Green's functions. In this way, one calculates much more information
than actually needed. Here we present an in principle exact approach to
construct effective potentials and kernels for the direct calculation of
electronic spectra. In particular, the potential that yields the spectral
function needed to describe photoemission turns out to be dynamical but {\it
local} and {\it real}. As example we illustrate this ``photoemission
potential'' for sodium and aluminium, modelled as homogeneous electron gas, and
discuss in particular its frequency dependence stemming from the nonlocality of
the corresponding self-energy. We also show that our approach leads to a very
short derivation of a kernel that is known to well describe absorption and
energy-loss spectra of a wide range of materials.


title:
Quantum Phases of Ultracold Bosonic Atoms in a Two-Dimensional Optical
  Superlattice

abstract:
  We study quantum phases of ultracold bosonic atoms in a two-dimensional
optical superlattice. The extended Bose-Hubbard model derived from the system
of ultracold bosonic atoms in an optical superlattice is solved numerically
with Gutzwiller approach. We find that the modulated superfluid(MS),
Mott-insulator (MI) and density-wave(DW) phases appear in some regimes of
parameters. The experimental detection of the first order correlations and the
second order correlations of different quantum phases with time-of-flight and
noise-correlation techniques is proposed.


title:
The dynamical response to the node defect in thermally activated
  remagnetization of magnetic dot array

abstract:
  The influence of nonmagnetic central node defect on dynamical properties of
regular square-shaped 5 x 5 segment of magnetic dot array under the thermal
activation is investigated via computer simulations. Using stochastic
Landau-Lifshitz-Gilbert equation we simulate hysteresis and relaxation
processes. The remarkable quantitative and qualitative differences between
magnetic dot arrays with nonmagnetic central node defect and magnetic dot
arrays without defects have been found.


title:
Microscopic analysis of the superconducting quantum critical point:
  Finite temperature crossovers in transport near a pair-breaking quantum phase
  transition

abstract:
  A microscopic analysis of the superconducting quantum critical point realized
via a pair-breaking quantum phase transition is presented. Finite temperature
crossovers are derived for the electrical conductivity, which is a key probe of
superconducting fluctuations. By using the diagrammatic formalism for
disordered systems, we are able to incorporate the interplay between
fluctuating Cooper pairs and electrons, that is outside the scope of a
time-dependent Ginzburg Landau or effective bosonic action formalism. It is
essential to go beyond the standard approximation in order to capture the zero
temperature correction which results purely from the (dynamic) quantum
fluctuations and dictates the behavior of the conductivity in an entire low
temperature quantum regime. All dynamic contributions are of the same order and
conspire to add up to a negative total, thereby inhibiting the conductivity as
a result of superconducting fluctuations. On the contrary, the classical and
the intermediate regimes are dominated by the positive bosonic channel. Our
theory is applicable in one, two and three dimensions and is relevant for
experiments on superconducting nanowires, doubly-connected cylinders, thin
films and bulk in the presence of magnetic impurities, magnetic field or other
pair-breakers. A window of non-monotonic behavior is predicted to exist as
either the temperature or the pair-breaking parameter is swept.


title: The influence of AGN nuclear parameters on the FRI/FRII dichotomy

abstract:
  We have investigated the influence of nuclear parameters such as black hole
(BH) mass and photoionizing luminosity on the FRI/FRII transition in a sample
of nearby (z<0.2) 3CR radio galaxies. The sample was observed with
medium-resolution, optical spectroscopy and contains some galaxies with
unpublished velocity dispersion measurements and emission-line fluxes. Measured
velocity dispersions are 130-340 km/s with a mean of 216 km/s. Converting to BH
mass, we find that the BH mass distribution is identical for FRIs and FRIIs,
with a mean of approximately 2.5x10^8 Msun. We convert [OII] and [OIII]
emission-line luminosities to photoionizing luminosity under the assumption
that the gas is ionized by the nuclear UV continuum. Most of the galaxies with
FRI morphology and/or low-excitation emission-line spectra have progressively
lower BH masses at lower photoionizing (and jet) luminosities. This agrees with
the Ledlow-Owen relation which states that the radio luminosity at the FRI/FRII
transition depends on the optical luminosity of the host, L_radio ~
L_optical^1.8, because both L_radio and L_optical relate to AGN nuclear
parameters. When recasting the Ledlow-Owen relation into BH mass versus
photoionizing and jet luminosity, we find that the recasted relation describes
the sample quite well. The FRI/FRII transition occurs at approximately an order
of magnitude lower luminosity relative to the Eddington luminosity than the
soft-to-hard transition in X-ray binaries. This difference is consistent with
the Ledlow-Owen relation, which predicts a weak BH mass dependence in the
transition luminosity. We conclude that the FRI/FRII dichotomy is caused by a
combination of external and nuclear factors, with the latter dominating.


title: Optoacoustic solitons in Bragg gratings

abstract:
  Optical gap solitons, which exist due to a balance of nonlinearity and
dispersion due to a Bragg grating, can couple to acoustic waves through
electrostriction. This gives rise to a new species of ``gap-acoustic'' solitons
(GASs), for which we find exact analytic solutions. The GAS consists of an
optical pulse similar to the optical gap soliton, dressed by an accompanying
phonon pulse. Close to the speed of sound, the phonon component is large. In
subsonic (supersonic) solitons, the phonon pulse is a positive (negative)
density variation. Coupling to the acoustic field damps the solitons'
oscillatory instability, and gives rise to a distinct instability for
supersonic solitons, which may make the GAS decelerate and change direction,
ultimately making the soliton subsonic.


title: On Possibilities of Studying of Supernova Neutrinos at BAKSAN

abstract:
  We consider the possibilities of studying a supernova collapse neutrino burst
at Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy
of Sciences) using the prposed 5-kt target-mass liquid scintillation
spectrometer. Attention is given to the influence of mixing angle
${\theta}_{13}$ on the expected rates and spectra of neutrino events.


title:
Set theoretic solutions of the Yang-Baxter equation, graphs and
  computations

abstract:
  We extend our recent work on set-theoretic solutions of the Yang-Baxter or
braid relations with new results about their automorphism groups, strong
twisted unions of solutions and multipermutation solutions. We introduce and
study graphs of solutions and use our graphical methods for the computation of
solutions of finite order and their automorphisms. Results include a detailed
study of solutions of multipermutation level 2.


title: CIV 1549 as an Eigenvector 1 Parameter for Active Galactic Nuclei

abstract:
  [Abridged] We have been exploring a spectroscopic unification for all known
types of broad line emitting AGN. The 4D Eigenvector 1 (4DE1) parameter space
shows promise as a unification capable of organizing quasar diversity on a
sequence primarily governed by Eddington ratio. This paper considers the role
of CIV 1549 measures with special emphasis on the CIV 1549 line shift as a
principal 4DE1 diagnostic. We use HST archival spectra for 130 sources with S/N
high enough to permit reliable CIV 1549 broad component (BC) measures. We find
a CIV 1549 BC profile blueshift that is strongly concentrated among (largely
radio-quiet: RQ) sources with FWHM(H beta BC) < 4000 km/s (which we call
Population A). Narrow line Seyfert 1 (NLSy1, with FWHM H beta < 2000 km/s)
sources belong to this population but do not emerge as a distinct class. The
systematic blueshift, widely interpreted as arising in a disk wind/outflow, is
not observed in broader lined AGN which we call Population B. We find new
correlations between FWHM(CIV 1549 BC) and CIV 1549 line shift as well as the
equivalent width of CIV 1549. They are seen only in Pop. A sources. CIV 1549
measures enhance the apparent dichotomy at FWHM(Hbeta BC) approx. 4000 \kms\
(Sulentic et al. 2000) suggesting that it has more significance in the context
of Broad Line Region structure than the more commonly discussed RL vs. RQ
dichotomy. Black hole masses computed from FWHM CIV 1549 BC for about 80 AGN
indicate that the CIV 1549 width is a poor virial estimator. Comparison of mass
estimates derived from Hbeta BC and CIV 1549 reveals that the latter show
different and nonlinear offsets for population A and B sources. A significant
number of sources also show narrow line CIV 1549 emission. We present a recipe
for CIV 1549 narrow component extraction.


title: Chiral Properties of Baryon Interpolating Fields

abstract:
  We study the chiral transformation properties of all possible local
(non-derivative) interpolating field operators for baryons consisting of three
quarks with two flavors, assuming good isospin symmetry. We derive and use the
relations/identities among the baryon operators with identical quantum numbers
that follow from the combined colour, Dirac and isospin Fierz transformations.
These relations reduce the number of independent baryon operators with any
given spin and isospin. The Fierz identities also effectively restrict allowed
baryon chiral multiplets. It turns out that the chiral multiplets of the
baryons are equivalent to their Lorentz representation. For the two independent
nucleon operators the only permissible chiral multiplet is the fundamental one
$(\frac12,0)\oplus(0,\frac12)$. For the $\Delta$, admissible Lorentz
representations are $(1,\frac12)\oplus (\frac12,1)$ and
$(\frac32,0)\oplus(0,\frac32)$. In the case of the $(1,\frac12)\oplus
(\frac12,1)$ chiral multiplet the $I(J)=\frac32(\frac32)$ $\Delta$ field has
one $I(J)=\frac12(\frac32)$ chiral partner; otherwise it has none. We also
consider the Abelian ($U_A(1)$) chiral transformation properties of fields and
show that each baryon comes in two varieties: 1) with Abelian axial charge +3;
and 2) with Abelian axial charge -1. In case of the nucleon these are the two
Ioffe's fields; in case of the $\Delta$, the $(1,\frac12)\oplus (\frac12,1)$
multiplet has Abelian axial charge -1 and the $(\frac32,0)\oplus(0,\frac32)$
multiplet has Abelian axial charge +3.


title:
Neutrino telescope modelling of Lorentz invariance violation in
  oscillations of atmospheric neutrinos

abstract:
  One possible feature of quantum gravity may be the violation of Lorentz
invariance. In this paper we consider one particular manifestation of the
violation of Lorentz invariance, namely modified dispersion relations for
massive neutrinos. We show how such modified dispersion relations may affect
atmospheric neutrino oscillations. We then consider how neutrino telescopes,
such as ANTARES, may be able to place bounds on the magnitude of this type of
Lorentz invariance violation.


title: Experimental test of the no signaling theorem

abstract:
  In 1981 N. Herbert proposed a gedanken experiment in order to achieve by the
''First Laser Amplified Superluminal Hookup'' (FLASH) a faster than light
communication (FTL) by quantum nonlocality. The present work reports the first
experimental realization of that proposal by the optical parametric
amplification of a single photon belonging to an entangled EPR pair into an
output field involving 5 x 10^3 photons. A thorough theoretical and
experimental analysis explains in general and conclusive terms the precise
reasons for the failure of the FLASH program as well as of any similar FTL
proposals.


title: Self-duality of Selmer groups

abstract:
  The first part of the paper gives a new proof of self-duality for Selmer
groups: if A is an abelian variety over a number field K, and F/K is a Galois
extension with Galois group G, then the Q_pG-representation naturally
associated to the p-infinity Selmer group of A/F is self-dual. The second part
describes a method for obtaining information about parities of Selmer ranks
from the local Tamagawa numbers of A in intermediate extensions of F/K.


title: Dynamics of coupled non-identical systems with period-doubling cascade

abstract:
  Structure of bifurcation diagram in the plane of parameters controlling
period-doublings for the system of coupled logistic maps is discussed. The
analysis is carried out by computing the charts of dynamical regimes and charts
of Lyapunov exponents giving showy and effective illustrations. The critical
point of codimension two at the border of chaos is found. It is a terminal
point for the Feigenbaum critical line. The bifurcation analysis in the
vicinity of this point is presented.


title: Hall drift of axisymmetric magnetic fields in solid neutron-star matter

abstract:
  Hall drift, i. e., transport of magnetic flux by the moving electrons giving
rise to the electrical current, may be the dominant effect causing the
evolution of the magnetic field in the solid crust of neutron stars. It is a
nonlinear process that, despite a number of efforts, is still not fully
understood. We use the Hall induction equation in axial symmetry to obtain some
general properties of nonevolving fields, as well as analyzing the evolution of
purely toroidal fields, their poloidal perturbations, and current-free, purely
poloidal fields. We also analyze energy conservation in Hall instabilities and
write down a variational principle for Hall equilibria. We show that the
evolution of any toroidal magnetic field can be described by Burgers' equation,
as previously found in plane-parallel geometry. It leads to sharp current
sheets that dissipate on the Hall time scale, yielding a stationary field
configuration that depends on a single, suitably defined coordinate. This
field, however, is unstable to poloidal perturbations, which grow as their
field lines are stretched by the background electron flow, as in instabilities
earlier found numerically. On the other hand, current-free poloidal
configurations are stable and could represent a long-lived crustal field
supported by currents in the fluid stellar core.

categories: astro-ph math-ph math.MP nlin.SI physics.plasm-ph


title: Pion form factor in the Kroll-Lee-Zumino model

abstract:
  The renormalizable Abelian quantum field theory model of Kroll, Lee, and
Zumino is used to compute the one-loop vertex corrections to the tree-level,
Vector Meson Dominance (VMD) pion form factor. These corrections, together with
the known one-loop vacuum polarization contribution, lead to a substantial
improvement over VMD. The resulting pion form factor in the space-like region
is in excellent agreement with data in the whole range of accessible momentum
transfers. The time-like form factor, known to reproduce the Gounaris-Sakurai
formula at and near the rho-meson peak, is unaffected by the vertex correction
at order $\cal{O}$$(g_\rpp^2)$.


title: Searching for integrable lattice maps using factorization

abstract:
  We analyze the factorization process for lattice maps, searching for
integrable cases. The maps were assumed to be at most quadratic in the
dependent variables, and we required minimal factorization (one linear factor)
after 2 steps of iteration. The results were then classified using algebraic
entropy. Some new models with polynomial growth (strongly associated with
integrability) were found. One of them is a nonsymmetric generalization of the
homogeneous quadratic maps associated with KdV (modified and Schwarzian), for
this new model we have also verified the "consistency around a cube".


title:
Loss Tolerant Linear Optical Quantum Memory By Measurement Based Quantum
  Computing

abstract:
  We give a scheme for loss tolerantly building a linear optical quantum memory
which itself is tolerant to qubit loss. We use the encoding recently introduced
in [Phys. Rev. Lett. 97, 120501, (2006)] and give a method for efficiently
achieving this. The entire approach resides within the "One-way" model for
quantum computing. Our results suggest that it is possible to build a loss
tolerant quantum memory, such that if the requirement is to keep the data
stored over arbitrarily long times then this is possible with only polynomially
increasing resources and logarithmically increasing individual photon life
times.


title: Multipartite omnidirectional generalized Bell inequality

abstract:
  We derive a multipartite generalized Bell inequality which involves the
entire range of settings for each of the local observers. Especially, it is
applied to show non-local behavior of a six-qubit mixture of
Greenberger-Horne-Zeilinger correlations stronger than previous Bell
inequalities. For certain noise admixture to the correlations an explicit local
realistic model exists in the case of a standard Bell experiment. Bell
experiments with many local settings reveal the non-locality of the state. It
turns out that the new inequality is more stringent than many other Bell
inequalities in the specific quantum state.


title:
The tension of cosmological magnetic fields as a contribution to dark
  energy

abstract:
  We propose that cosmological magnetic fields generated in regions of finite
spatial dimensions may manifest themselves in the global dynamics of the
Universe as `dark energy'. We test our model in the context of spatially flat
cosmological models by assuming that the Universe contains non-relativistic
matter $\rho_m\propto \alpha^{-3}$, dark energy $\rho_{Q}\propto
\alpha^{-3(1+w)}$, and an extra fluid with $\rho_{B} \propto \alpha^{n-3}$ that
corresponds to the magnetic field. We place constraints on the main
cosmological parameters of our model by combining the recent supernovae type Ia
data and the differential ages of passively evolving galaxies. In particular,
we find that the model which best reproduces the observational data when
$\Omega_m=0.26$ is one with $\Omega_{B}\simeq 0.03$, $n\simeq 7.68$,
$\Omega_{Q}\simeq 0.71$ and $w\simeq -0.8$.


title:
Electron-positron pair creation by Coulomb and laser fields in the
  tunneling regime

abstract:
  Electron-positron pair creation due to combined nuclear Coulomb and strong
laser fields is investigated for the tunneling regime. The energy spectra and
angular distributions of the pair are found analytically for the first time.
The energy spectrum for each lepton exhibits a sharp maximum located well above
the threshold for any polarization of the laser field. The angular
distributions of leptons depend on the polarization: for the linear
polarization both leptons move predominantly along the laser beam direction;
for the circular polarization leptons are emitted in a thin-walled cone
centered on the laser beam. The spectral and angular distributions found are
governed by the intensity and frequency of the field, and the frequency
independent total pair creation rates comply with the previously known results.
A new method of calculation - the vicinal approximation - which uses the fact
that the pair production takes place in the close vicinity of the nucleus, is
suggested.


title: Self-similarity for V-shaped field potentials - further examples

abstract:
  Three new models with V-shaped field potentials $U$ are considered: a complex
scalar field $X$ in 1+1 dimensions with $U(X)= |X|$, a real scalar field $\Phi$
in 2+1 dimensions with $U(\Phi) = |\Phi|$, and a real scalar field $\phi$ in
1+1 dimensions with $U{\phi) = \phi \Theta(\phi)$ where $\Theta$ is the step
function. Several explicit, self-similar solutions are found. They describe
interesting dynamical processes, for example, `freezing' a string in a static
configuration.


title:
On the Enhanced Reverse Beta Processes in Graphene-Iron Composite
  Nanostructures at High Temperatures in Strong Magnetic Field

abstract:
  Strong dense many-spin interactions have been proposed to organize novel
orbital dynamics (the Little Effect) for novel chemical and catalytic
phenomena. The recent determinations of the relativistic and quantum Hall
effects of carriers in graphene under strong magnetic confinement have
substantiated the Little Effect. Moreover such nonclassical phenomena under the
stronger magnetic confinement of ferro-nanocatalysts are here shown to organize
reverse beta processes and possibly pycnonuclear reactions under high
temperature and high-pressure conditions. Such processes have implications for
reverse beta reactions and nuclear reactions within the interior of the earth
and new technologies for carbon nanotube-ferrometal and nanographene-ferrometal
composites.


title: Conductivity of a superlattice with parabolic miniband

abstract:
  The static and high-frequency differential conductivity of a one-dimensional
superlattice with parabolic miniband, in which the dispersion law is assumed to
be parabolic up to the Brillouin zone edge, are investigated theoretically.
Unlike the earlier published works, devoted to this problem, the novel formula
for the static current density contains temperature dependence, which leads to
the current maximum shift to the low field side with increasing temperature.
The high-frequency differential conductivity response properties including the
temperature dependence is examined and opportunities of creating a terahertz
oscillator on Bloch electron oscillations in such superlattices are discussed.
Analysis shows that superlattices with parabolic miniband dispersion law may be
used for generation and amplification of terahertz fields only at very low
temperatures.


title:
On the invertibility of "rectangular" bi-infinite matrices and
  applications in time--frequency analysis

abstract:
  Finite dimensional matrices having more columns than rows have no left
inverses while those having more rows than columns have no right inverses. We
give generalizations of these simple facts to bi--infinite matrices and use
those to obtain density results for $p$--frames of time--frequency molecules in
modulation spaces and identifiability results for operators with bandlimited
Kohn--Nirenberg symbols.


title: Necessary Conditions for Geometric Realizability of Simplicial Complexes

abstract:
  We associate with any simplicial complex $\K$ and any integer $m$ a system of
linear equations and inequalities. If $\K$ has a simplicial embedding in $\R^m$
then the system has an integer solution. This result extends the work of I.
Novik (2000).


title: Self-overlap as a method of analysis in Ising models

abstract:
  The damage spreading method (DS) provided a useful tool to obtain analytical
results of the thermodynamics and stability of the 2D Ising model --amongst
many others--, but it suffered both from ambiguities in its results and from
large computational costs. In this paper we propose an alternative method, the
so called self-overlap method, based on the study of correlation functions
measured at subsequent time steps as the system evolves towards its
equilibrium. Applying markovian and mean field approximations to a 2D Ising
system we obtain both analytical and numerical results on the thermodynamics
that agree with the expected behavior. We also provide some analytical results
on the stability of the system. Since only a single replica of the system needs
to be studied, this method would seem to be free from the ambiguities that
afflicted DS. It also seems to be numerically more efficient and analytically
simpler.


title: Measurement of time--varying Multiple--Input Multiple--Output Channels

abstract:
  We derive a criterion on the measurability / identifiability of
Multiple--Input Multiple--Output (MIMO) channels based on the size of the
so-called spreading support of its subchannels. Novel MIMO transmission
techniques provide high-capacity communication channels in time-varying
environments and exact knowledge of the transmission channel operator is of key
importance when trying to transmit information at a rate close to channel
capacity.


title: A Technical Report On Grid Benchmarking using ATLAS V.O

abstract:
  Grids include heterogeneous resources, which are based on different hardware
and software architectures or components. In correspondence with this diversity
of the infrastructure, the execution time of any single job, as well as the
total grid performance can both be affected substantially, which can be
demonstrated by measurements. Running a simple benchmarking suite can show this
heterogeneity and give us results about the differences over the grid sites.


title: Disk Partition Function and Oscillatory Rolling Tachyons

abstract:
  An exact cubic open string field theory rolling tachyon solution was recently
found by Kiermaier et. al. and Schnabl. This oscillatory solution has been
argued to be related by a field redefinition to the simple exponential rolling
tachyon deformation of boundary conformal theory. In the latter approach, the
disk partition function takes a simple form. Out of curiosity, we compute the
disk partition function for an oscillatory tachyon profile, and find that the
result is nevertheless almost the same.


title:
Teleportation and Superdense coding with Genuine quadripartite entangled
  states

abstract:
  We investigate the usefulness of different classes of genuine quadripartite
entangled states as quantum resources for teleportation and superdense coding.
We examine the possibility of teleporting unknown one, two and three qubit
states. We show that one can use the teleportation protocol to send any general
one and two qubit states. A restricted class of three qubit states can also be
faithfully teleported. We also explore superdense coding protocol in
single-receiver and multi-receiver scenarios. We show that there exist genuine
quadripartite entangled states that can be used to transmit four cbits by
sending two qubits. We also discuss some interesting features of multi-receiver
scenario under LOCC paradigm.


title:
Massive CP$^1$ theory from a microscopic model for doped
  antiferromagnets

abstract:
  A path-integral for the t-J model in two dimensions is constructed based on
Dirac quantization, with an action found originally by Wiegmann (Phys. Rev.
Lett. {\bf 60}, 821 (1988); Nucl. Phys. B323, 311 (1989)). Concentrating on the
low doping limit, we assume short range antiferromagnetic order of the spin
degrees of freedom. Going over to a local spin quantization axis of the dopant
fermions, that follows the spin degree of freedom, staggered CP$^1$ fields
result and the constraint against double occupancy can be resolved. The
staggered CP$^1$ fields are split into slow and fast modes, such that after a
gradient expansion, and after integrating out the fast modes and the dopant
fermions, a CP$^1$ field-theory with a massive gauge field is obtained that
describes generically incommensurate coplanar magnetic structures, as discussed
previously in the context of frustrated quantum antiferromagnets. Hence, the
possibility of deconfined spinons is opened by doping a colinear
antiferromagnet.


title:
Optimal Watermark Embedding and Detection Strategies Under Limited
  Detection Resources

abstract:
  An information-theoretic approach is proposed to watermark embedding and
detection under limited detector resources. First, we consider the attack-free
scenario under which asymptotically optimal decision regions in the
Neyman-Pearson sense are proposed, along with the optimal embedding rule.
Later, we explore the case of zero-mean i.i.d. Gaussian covertext distribution
with unknown variance under the attack-free scenario. For this case, we propose
a lower bound on the exponential decay rate of the false-negative probability
and prove that the optimal embedding and detecting strategy is superior to the
customary linear, additive embedding strategy in the exponential sense.
Finally, these results are extended to the case of memoryless attacks and
general worst case attacks. Optimal decision regions and embedding rules are
offered, and the worst attack channel is identified.


title: Leptogenesis, Dark Matter and Higgs Phenomenology at TeV

abstract:
  We propose an interesting model of neutrino masses to realize leptogenesis
and dark matter at the TeV scale. A real scalar is introduced to naturally
realize the Majorana masses of the right-handed neutrinos. We also include a
new Higgs doublet that contributes to the dark matter of the universe. The
neutrino masses come from the vacuum expectation value of the triplet Higgs
scalar. The right-handed neutrinos are not constrained by the neutrino masses
and hence they could generate leptogenesis at the TeV scale without subscribing
to resonant leptogenesis. In our model, all new particles could be observable
at the forthcoming Large Hardon Collider or the proposed future International
Linear Collider.


title: Chemical enrichment of galaxy clusters from hydrodynamical simulations

abstract:
  We present cosmological hydrodynamical simulations of galaxy clusters aimed
at studying the process of metal enrichment of the intra--cluster medium (ICM).
These simulations have been performed by implementing a detailed model of
chemical evolution in the Tree-SPH \gd code. This model allows us to follow the
metal release from SNII, SNIa and AGB stars, by properly accounting for the
lifetimes of stars of different mass, as well as to change the stellar initial
mass function (IMF), the lifetime function and the stellar yields. As such, our
implementation of chemical evolution represents a powerful instrument to follow
the cosmic history of metal production. The simulations presented here have
been performed with the twofold aim of checking numerical effects, as well as
the impact of changing the model of chemical evolution and the efficiency of
stellar feedback.


title: Crystallization in large wireless networks

abstract:
  We analyze fading interference relay networks where M single-antenna
source-destination terminal pairs communicate concurrently and in the same
frequency band through a set of K single-antenna relays using half-duplex
two-hop relaying. Assuming that the relays have channel state information
(CSI), it is shown that in the large-M limit, provided K grows fast enough as a
function of M, the network "decouples" in the sense that the individual
source-destination terminal pair capacities are strictly positive. The
corresponding required rate of growth of K as a function of M is found to be
sufficient to also make the individual source-destination fading links converge
to nonfading links. We say that the network "crystallizes" as it breaks up into
a set of effectively isolated "wires in the air". A large-deviations analysis
is performed to characterize the "crystallization" rate, i.e., the rate (as a
function of M,K) at which the decoupled links converge to nonfading links. In
the course of this analysis, we develop a new technique for characterizing the
large-deviations behavior of certain sums of dependent random variables. For
the case of no CSI at the relay level, assuming amplify-and-forward relaying,
we compute the per source-destination terminal pair capacity for M,K converging
to infinity, with K/M staying fixed, using tools from large random matrix
theory.


title:
Spontaneous Symmetry Breaking in the Bulk as a Localization Mechanism of
  Fields on the Brane

abstract:
  We consider real and complex scalar fields non-minimally coupled to gravity
in the bulk spacetime and study their impact on the brane upon acquiring a
non-vanishing vacuum expectation value. When examining the case of the complex
scalar field, a minimally coupled U(1) gauge field is also considered so that
spontaneous symmetry breaking can take place. Particular attention is paid to
the terms arising from the junction conditions, which act towards reinforcing
the mechanism of spontaneous symmetry breaking. We find that the embedding of a
braneworld universe in a bulk spacetime endowed with matter fields can induce
this mechanism at very high energies, which implies the localization on the
brane of the bulk fields.


title:
Matching of Wilson loop eigenvalue densities in 1+1, 2+1 and 3+1
  dimensions

abstract:
  We investigate the matching of eigenvalue densities of Wilson loops in SU(N)
lattice gauge theory: the eigenvalue densities in 1+1, 2+1 and 3+1 dimensions
are nearly identical when the traces of the loops are equal. We show that the
matching is present to at least second order in the strong-coupling expansion,
and also to second order in perturbation theory. We find that in the continuum
limit there is matching at all values of the trace for bare Wilson loops. We
confirm numerically that there is matching in these limits and find there are
small violations away from them. We discuss the implications for the bulk
transitions and for non-analytic gap formation at N = infinity in 2+1 and 3+1
dimensions.


title: Double Sided Watermark Embedding and Detection with Perceptual Analysis

abstract:
  In our previous work, we introduced a double-sided technique that utilizes
but not reject the host interference. Due to its nice property of utilizing but
not rejecting the host interference, it has a big advantage over the host
interference schemes in that the perceptual analysis can be easily implemented
for our scheme to achieve the locally bounded maximum embedding strength. Thus,
in this work, we detail how to implement the perceptual analysis in our
double-sided schemes since the perceptual analysis is very important for
improving the fidelity of watermarked contents. Through the extensive
performance comparisons, we can further validate the performance advantage of
our double-sided schemes.


title:
The Dirichlet problem in the plane with semianalytic raw data,
  quasianalyticity and o-minimal structures

abstract:
  We investigate the Dirichlet solution for a semianalytic continuous function
on the boundary of a semianalytic bounded domain in the plane. We show that the
germ of the Dirichlet solution at a boundary point with angle greater than 0
lies in a certain quasianalytic class used by Ilyashenko in his work on
Hilbert's 16th problem. With this result we can prove that the Dirichlet
solution is definable in an o-minimal structure if the angle at a singular
boundary point of the domain is an irrational multiple of $\pi$.


title:
Linear Prediction of Long-Memory Processes: Asymptotic Results on
  Mean-squared Errors

abstract:
  We present two approaches for linear prediction of long-memory time series.
The first approach consists in truncating the Wiener-Kolmogorov predictor by
restricting the observations to the last $k$ terms, which are the only
available values in practice. We derive the asymptotic behaviour of the
mean-squared error as $k$ tends to $ + \infty$. By contrast, the second
approach is non-parametric. An AR($k$) model is fitted to the long-memory time
series and we study the error that arises in this misspecified model.


title: Quantum computation algorithm for many-body studies

abstract:
  We show in detail how the Jordan-Wigner transformation can be used to
simulate any fermionic many-body Hamiltonian on a quantum computer. We develop
an algorithm based on appropriate qubit gates that takes a general fermionic
Hamiltonian, written as products of a given number of creation and annihilation
operators, as input. To demonstrate the applicability of the algorithm, we
calculate eigenvalues and eigenvectors of two model Hamiltonians, the
well-known Hubbard model and a generalized pairing Hamiltonian. Extensions to
other systems are discussed.

categories: quant-ph math-ph math.MP nucl-th physics.comp-ph


title: Cargese Lectures on Brane Induced Gravity

abstract:
  A brief introduction is given to the subject of brane induced gravity. The 5D
example is discussed in detail. The 4D laws of gravity are obtained on a brane
embedded in an infinite volume extra space, where the problem of stabilization
of the volume modulus is absent. The theory has two classically disjoint
branches of solutions -- the conventional and self-accelerated one. The
conventional branch gives a perturbatively stable model of a metastable
graviton, with potentially testable predictions within the Solar system. The
self-accelerated branch, on the other hand, provides an existence proof for an
idea that the accelerated expansion of the Universe could be due to modified
gravity. The issue of perturbative stability of the self-accelerated branch is
obscured by a breakdown of the conventional perturbative expansion. However, a
certain exact non-perturbative solution found in hep-th/0612016 exhibits a net
negative gravitational mass, while this mass is positive on the conventional
branch. This suggest that the self-accelerated solution must be
non-perturbatively unstable. A proposal to overcome this problem in an
extension of the original model, that also allows for the quantum gravity scale
to be unrestricted, is briefly discussed.


title: Phases of QCD: Summary of the Rutgers Long Range Plan Town Meeting

abstract:
  This White Paper summarizes the outcome of the Town Meeting on Phases of QCD
that took place January 12-14, 2007 at Rutgers University, as part of the NSAC
2007 Long Range Planning process.


title:
Multijet production at low $x_{\rm Bj}$ in deep inelastic scattering at
  HERA

abstract:
  Inclusive dijet and trijet production in deep inelastic $ep$ scattering has
been measured for $10<Q^2<100$ GeV$^2$ and low Bjorken $x$, $10^{-4}<x_{\rm
Bj}<10^{-2}$. The data were taken at the HERA $ep$ collider with centre-of-mass
energy $\sqrt{s} = 318 \gev$ using the ZEUS detector and correspond to an
integrated luminosity of $82 {\rm pb}^{-1}$. Jets were identified in the
hadronic centre-of-mass (HCM) frame using the $k_{T}$ cluster algorithm in the
longitudinally invariant inclusive mode. Measurements of dijet and trijet
differential cross sections are presented as functions of $Q^2$, $x_{\rm Bj}$,
jet transverse energy, and jet pseudorapidity. As a further examination of
low-$x_{\rm Bj}$ dynamics, multi-differential cross sections as functions of
the jet correlations in transverse momenta, azimuthal angles, and
pseudorapidity are also presented. Calculations at $\mathcal{O}(\alpha_{s}^3)$
generally describe the trijet data well and improve the description of the
dijet data compared to the calculation at $\mathcal{O}(\alpha_{s}^2)$.


title:
Spin Effects in Quantum Chromodynamics and Recurrence Lattices with
  Multi-Site Exchanges

abstract:
  In this thesis, we consider some spin effects in QCD and recurrence lattices
with multi-site exchanges. Main topic of our manuscript are critical phenomena
in spin systems defined on the recurrence lattices. Main tool of our approach
is the method of recursive (hierarchical) lattices. We apply the method of
dynamical mapping (or recursive lattices) for investigation of magnetic
properties of the fluid and solid $^3$He, phase transitions in crystals and
macromolecules. First, we analyze the helix-coil phase transition for
polypeptides and proteins, and describe an quasi unfolding transition (like the
cold denaturation process) for the degree of helicity (the order parameter for
macromolecules). Next we consider the recurrent models of $^3$He defined on the
square, Husimi and hexagon lattices. Using the method of dynamical mapping, the
magnetization curves with plateaus, bifurcation point and one period doubling
are obtained. Then we investigate the model with cubic symmetry defined on the
Bethe lattice and containing both linear and quadratic spin-spin interactions.
The magnetization of the system is calculated, and a complex structure of the
phase transitions between the disordered, partially ordered and completely
ordered states is observed. In the framework of QCD, we consider the azimuthal
asymmetries in heavy flavor production in the lepton-nucleon deep inelastic
scattering (DIS). We calculate the azimuthal (or $\phi$-) dependence of the
next-to-leading order heavy-quark-initiated contributions to DIS. It is shown
that, contrary to the basic gluon-initiated component, the photon-quark
scattering mechanism is practically $\cos2\phi$-independent. We investigate the
possibility of measuring both nonperturbative (intrinsic) and perturbative
(CTEQ, MRST) charm distributions using the $\cos2\phi$ asymmetry.


title: Percolation Crossing Formulas and Conformal Field Theory

abstract:
  Using conformal field theory, we derive several new crossing formulas at the
two-dimensional percolation point. High-precision simulation confirms these
results. Integrating them gives a unified derivation of Cardy's formula for the
horizontal crossing probability $\Pi_h(r)$, Watts' formula for the
horizontal-vertical crossing probability $\Pi_{hv}(r)$, and Cardy's formula for
the expected number of clusters crossing horizontally $\mathcal{N}_h(r)$. The
main step in our approach implies the identification of the derivative of one
primary operator with another. We present operator identities that support this
idea and suggest the presence of additional symmetry in $c=0$ conformal field
theories.

categories: cond-mat.stat-mech cond-mat.dis-nn hep-th math-ph math.MP math.PR


title: Reentrant Kondo effect in Landau quantized graphene

abstract:
  We have studied the interplay of an Anderson impurity in Landau quantized
graphene, with special emphasis on the influence of the chemical potential.
Within the slave-boson mean-field theory, we found reentrant Kondo behaviour by
varying the chemical potential or gate voltage. Between Landau levels, the
density of states is suppressed, and by changing the graphene's Fermi energy,
we cross from metallic to semiconducting regions. Hence, the corresponding
Kondo behaviour is also influenced. The f-level spectral function reveals both
the presence of Landau levels in the conduction band and the Kondo resonance.


title:
Field induced tricritical behavior in the S=1/2 quasi one-dimensional
  frustrated Ising antiferromagnet

abstract:
  The results of extensive histogram cluster heat-bath Monte Carlo simulations
on the critical behavior of the quasi-one dimensional Ising antiferromagnet on
a stacked triangular lattice are presented. A small applied field is shown to
induce a crossover from XY universality to mean-field tricritical behavior.
Experimental estimates of critical exponents suggest that these two types of
phase transitions are observed in S=1 CsNiCl$_3$ and $S=1/2$ CsCoBr$_3$,
respectively. The present results demonstrate that this difference can be
explained by an unusual staggered magnetic field arising from quantum exchange
mixing previously proposed to account for spin excitations in $S=1/2$
quasi-one-dimensional Ising antiferromagnets.


title:
Interaction of Lamb modes with two-level systems in amorphous nanoscopic
  membranes

abstract:
  Using a generalized model of interaction between a two-level system (TLS) and
an arbitrary deformation of the material, we calculate the interaction of Lamb
modes with TLSs in amorphous nanoscopic membranes. We compare the mean free
paths of the Lamb modes with different symmetries and calculate the heat
conductivity $\kappa$. In the limit of an infinitely wide membrane, the heat
conductivity is divergent. Nevertheless, the finite size of the membrane
imposes a lower cut-off for the phonons frequencies, which leads to the
temperature dependence $\kappa\propto T(a+b\ln T)$. This temperature dependence
is a hallmark of the TLS-limited heat conductance at low temperature.


title: Accurate predictions for heavy quark jets

abstract:
  Heavy-flavour jets enter many of today's collider studies, yet NLO
predictions for these quantities are subject to large uncertainties, larger
than the corresponding experimental errors. We propose a new, infrared safe
definition of heavy-quark jets which allows one to reduce theoretical
uncertainties by a factor of three.


title: The extraordinary LBV/WR system HD 5980

abstract:
  The LBV/WR system HD 5980 contains a short-period, eccentric binary system
with interacting stellar winds. In this paper we summarize results from model
calculations of the tidal flows on the LBV component showing that energy
dissipation rates, E-dot, associated with turbulent viscosity are orbital-phase
dependent as well as variable over the stellar surface. We speculate that if
E-dot contributes towards driving mass-loss, the strongest wind-wind
interaction effects may occur after periastron passage. In addition, the model
suggests the presence of stronger outflows localized at polar angles theta~30
--50 degrees during part of the orbital cycle. Thus, the analysis of wind-wind
interactions in this system requires that models be revised to incorporate
non-stationary and asymmetric wind structures.


title: Towards Informative Statistical Flow Inversion

abstract:
  A problem which has recently attracted research attention is that of
estimating the distribution of flow sizes in internet traffic. On high traffic
links it is sometimes impossible to record every packet. Researchers have
approached the problem of estimating flow lengths from sampled packet data in
two separate ways. Firstly, different sampling methodologies can be tried to
more accurately measure the desired system parameters. One such method is the
sample-and-hold method where, if a packet is sampled, all subsequent packets in
that flow are sampled. Secondly, statistical methods can be used to ``invert''
the sampled data and produce an estimate of flow lengths from a sample.
  In this paper we propose, implement and test two variants on the
sample-and-hold method. In addition we show how the sample-and-hold method can
be inverted to get an estimation of the genuine distribution of flow sizes.
Experiments are carried out on real network traces to compare standard packet
sampling with three variants of sample-and-hold. The methods are compared for
their ability to reconstruct the genuine distribution of flow sizes in the
traffic.


title: Charge-Ordering Phenomena in One-Dimensional Solids

abstract:
  As the dimensionality is reduced, the world becomes more and more
interesting; novel and fascinating phenomena show up which call for
understanding. Physics in one dimension is a fascinating topic for theory and
experiment: for the former often a simplification, for the latter always a
challenge. Various ways will be demonstrated how one-dimensional structures can
be achieved in reality. In particular organic conductors could establish
themselves as model systems for the investigation of the physics in reduced
dimensions.
  In the metallic state of a one-dimensional solid, Fermi-liquid theory breaks
down and spin and charge degrees of freedom become separated. But the metallic
phase is not stable in one dimension: as the temperature is reduced, the
electronic charge and spin tend to arrange themselves in an ordered fashion due
to strong correlations. The competition of the different interactions is
responsible for which broken-symmetry ground state is eventually realized in a
specific compound and which drives the system towards an insulating state.
  Here we review the various ordering phenomena and how they can be identified
by dielectric and optic measurements.


title: Cross-Kerr interaction in a four-level atomic system

abstract:
  We derive the form of the cross-Kerr interaction in a four-level atomic
system in the N-configuration. We use time-independent perturbation theory to
calculate the eigenenergies and eigenstates of the Schrodinger equation for the
system. The system is considered as a perturbation of a Raman resonant
three-level lambda scheme for which exact solutions are known. We show that
within the strong control field limit the cross-Kerr interaction can arise
between two weak probe fields. The strength of this nonlinear coupling is
several orders of magnitude larger than that achievable using optical fibres.


title: Ideals of varieties parameterized by certain symmetric tensors

abstract:
  The ideal of a Segre variety is generated by the 2-minors of a generic
hypermatrix of indeterminates. We extend this result to the case of
Segre-Veronese varieties. The main tool is the concept of weak generic
hypermatrix which allows us to treat also the case of projection of Veronese
surfaces from a set of generic points and of Veronese varieties from a
Cohen-Macaulay subvariety of codimension 2.


title: Electrostatic Climber for Space Elevator and Launcher

abstract:
  Author details research on the new, very prospective, electrostatic Space
Elevator climber based on a new electrostatic linear engine previously offered
at the 42nd Joint Propulsion Conference (AIAA-2006-5229) and published in AEAT,
Vol.78, No.6, 2006, pp. 502-508. The electrostatic climber discussed can have
any speed (and braking), the energy for climber movement is delivered by a
lightweight high-voltage line into a Space Elevator-holding cable from Earth
electric generator. This electric line also can be used for delivery electric
energy to a Geosynchronous Space Station. At present, the best solution of the
climber problem (announced by NASA as one important awarding problem of Space
Elevator) is problematic.
  Author also shows the linear electrostatic engine may be used as realistic
power space launcher at the present time. Two projects illustrate these new
devices.
  Key words: Space elevator, Electrostatic climber for space elevator,
Electrostatic space launcher, Electrostatic accelerator.
  This work is presented as paper AIAA-2007-5838 for 43 Joint Propulsion
Conference, Cincinnati, Ohio, USA, 9-11 July, 2007,


title: Polaronic features in the optical properties of the Holstein-t-J model

abstract:
  We derive the exact solution for the optical conductivity $\sigma(\omega)$ of
one hole in the Holstein-t-J model in the framework of dynamical mean-field
theory (DMFT). We investigate the magnetic and phonon features associated with
polaron formation as a function of the exchange coupling $J$, of the
electron-phonon interaction $\lambda$ and of the temperature. Our solution
directly relates the features of the optical conductivity to the excitations in
the single-particle spectral function, revealing two distinct mechanisms of
closing and filling of the optical pseudogap that take place upon varying the
microscopic parameters. We show that the optical absorption at the polaron
crossover is characterized by a coexistence of a magnon peak at low frequency
and a broad polaronic band at higher frequency. An analytical expression for
$\sigma(\omega)$ valid in the polaronic regime is presented.


title:
The non-equilibrium work relation. Thermodynamic analysis and
  microscopic foundations

abstract:
  We discuss the conditions for which the non-equilibrium work relation is
valid by means of thermodynamic and microscopic arguments.


title:
Novel Josephson Effects in d-wave Superconductor Junctions with
  Antiferromagnetic Interlayers

abstract:
  We calculate the dc supercurrent through a Josephson tunnel junction
consisting of an antiferromagnetic (AF) interlayer sandwiched between two
d-wave superconductors (d). Such d/AF/d junctions exhibit a rich dependence of
the Josephson current on the interlayer parameters, including the possibility
of 0-pi transitions with varying temperature or interlayer thickness.
Furthermore, we study d/I/d junctions when the dSC leads include subdominant
magnetic correlations. In this case induced magnetism near the interface can
strongly diminish the critical current for 110 oriented junctions whereas no
suppression is obtained for the 100 orientation. This may help resolve a
long-standing puzzle of the critical current versus grain boundary angle in
high-T_c superconductors.


title: Riesz and Szeg\"o type factorizations for noncommutative Hardy spaces

abstract:
  Let $\A$ be a finite subdiagonal algebra in Arveson's sense. Let $H^p(\A)$ be
the associated noncommutative Hardy spaces, $0<p\le\8$. We extend to the case
of all positive indices most recent results about these spaces, which include
notably the Riesz, Szeg\"o and inner-outer type factorizations. One new tool of
the paper is the contractivity of the underlying conditional expectation on
$H^p(\A)$ for $p<1$.


title:
BMO functions and Carleson measures with values in uniformly convex
  spaces

abstract:
  This paper studies the relationship between vector-valued BMO functions and
the Carleson measures defined by their gradients. Let $dA$ and $dm$ denote
Lebesgue measures on the unit disc $D$ and the unit circle $\mathbb T$,
respectively. For $1< q<\infty$ and a Banach space $B$ we prove that there
exists a positive constant $c$ such that
  $$\sup_{z_0\in D}\int_{D}(1-|z|)^{q-1}\|\nabla f(z)\|^q
  P_{z_0}(z) dA(z)
  \le c^q\sup_{z_0\in D}\int_{\T}\|f(z)-f(z_0)\|^qP_{z_0}(z) dm(z)$$ holds for
all trigonometric polynomials $f$ with coefficients in $B$ iff $B$ admits an
equivalent norm which is $q$-uniformly convex, where
  $$P_{z_0}(z)=\frac{1-|z_0|^2}{|1-\bar{z_0}z|^2} .$$ The validity of the
converse inequality is equivalent to the existence of an equivalent
$q$-uniformly smooth norm.


title: Correlated multi-asset portfolio optimisation with transaction cost

abstract:
  We employ perturbation analysis technique to study multi-asset portfolio
optimisation with transaction cost. We allow for correlations in risky assets
and obtain optimal trading methods for general utility functions. Our
analytical results are supported by numerical simulations in the context of the
Long Term Growth Model.


title: Sums of lens spaces bounding rational balls

abstract:
  We classify connected sums of three-dimensional lens spaces which smoothly
bound rational homology balls. We use this result to determine the order of
each lens space in the group of rational homology 3-spheres up to rational
homology cobordisms, and to determine the concordance order of each 2-bridge
knot.


title: Brownian Motion, "Diverse and Undulating"

abstract:
  We describe in detail the history of Brownian motion, as well as the
contributions of Einstein, Sutherland, Smoluchowski, Bachelier, Perrin and
Langevin to its theory. The always topical importance in physics of the theory
of Brownian motion is illustrated by recent biophysical experiments, where it
serves, for instance, for the measurement of the pulling force on a single DNA
molecule.
  In a second part, we stress the mathematical importance of the theory of
Brownian motion, illustrated by two chosen examples. The by-now classic
representation of the Newtonian potential by Brownian motion is explained in an
elementary way. We conclude with the description of recent progress seen in the
geometry of the planar Brownian curve. At its heart lie the concepts of
conformal invariance and multifractality, associated with the potential theory
of the Brownian curve itself.

categories: cond-mat.stat-mech cond-mat.soft math-ph math.HO math.MP math.PR physics.chem-ph physics.hist-ph


title: Noncommutative Burkholder/Rosenthal inequalities II: applications

abstract:
  We show norm estimates for the sum of independent random variables in
noncommutative $L_p$-spaces for $1<p<\infty$ following our previous work. These
estimates generalize the classical Rosenthal inequality in the commutative
case. Among applications, we derive an equivalence for the $p$-norm of the
singular values of a random matrix with independent entries, and characterize
those symmetric subspaces and unitary ideals which can be realized as subspaces
of a noncommutative $L_p$ for $2<p<\infty$.


title:
Z boson decay to photon plus Kaluza-Klein graviton in large extra
  dimensions

abstract:
  In the large extra dimensional ADD scenario, Z bosons undergo a one-loop
decay into a photon and Kaluza-Klein towers of gravitons/gravi-scalars. We
calculate such a decay width, extending previous arguments about the general
form of the four-dimensional on-shell amplitude. The amplitudes calculated are
relevant to processes in other extra dimensional models where the Standard
Model fields are confined to a 4-brane.


title:
Intersections of polynomial orbits, and a dynamical Mordell-Lang
  conjecture

abstract:
  We prove that if nonlinear complex polynomials of the same degree have orbits
with infinite intersection, then the polynomials have a common iterate. We also
prove a special case of a conjectured dynamical analogue of the Mordell-Lang
conjecture.


title:
Can we ever distinguish between quintessence and a cosmological
  constant?

abstract:
  Many ambitious experiments have been proposed to constrain dark energy and
detect its evolution. At present, observational constraints are consistent with
a cosmological constant and there is no firm evidence for any evolution in the
dark energy equation of state w. In this paper, we pose the following question:
suppose that future dark energy surveys constrain w at low redshift to be
consistent with -1 to a percent level accuracy, what are the implications for
models of dynamical dark energy? We investigate this problem in a
model-independent way by following quintessence field trajectories in `energy'
phase-space. Attractor dynamics in this phase-space leads to two classes of
acceptable models: 1) models with flat potentials, i.e. an effective
cosmological constant, and 2) models with potentials that suddenly flatten with
a characteristic kink. The prospect of further constraining the second class of
models from distance measurements and fluctuation growth rates at low redshift
(z<3) seems poor. However, in some models of this second class, the dark energy
makes a significant contribution to the total energy density at high redshift.
Such models can be further constrained from observation of the cosmic microwave
background anisotropies and from primordial nucleosynthesis. It is possible,
therefore, to construct models in which the dark energy at high redshift causes
observable effects, even if future dark energy surveys constrain w at low
redshift to be consistent with -1 to high precision.


title: A Branch and Cut Algorithm for the Halfspace Depth Problem

abstract:
  The concept of data depth in non-parametric multivariate descriptive
statistics is the generalization of the univariate rank method to multivariate
data. Halfspace depth is a measure of data depth. Given a set S of points and a
point p, the halfspace depth (or rank) k of p is defined as the minimum number
of points of S contained in any closed halfspace with p on its boundary.
Computing halfspace depth is NP-hard, and it is equivalent to the Maximum
Feasible Subsystem problem. In this thesis a mixed integer program is
formulated with the big-M method for the halfspace depth problem. We suggest a
branch and cut algorithm. In this algorithm, Chinneck's heuristic algorithm is
used to find an upper bound and a related technique based on sensitivity
analysis is used for branching. Irreducible Infeasible Subsystem (IIS) hitting
set cuts are applied. We also suggest a binary search algorithm which may be
more stable numerically. The algorithms are implemented with the BCP framework
from the COIN-OR project.


title:
Wandering breathers and self-trapping in weakly coupled nonlinear
  chains: classical counterpart of macroscopic tunneling quantum dynamics

abstract:
  We present analytical and numerical studies of phase-coherent dynamics of
intrinsically localized excitations (breathers) in a system of two weakly
coupled nonlinear oscillator chains. We show that there are two qualitatively
different dynamical regimes of the coupled breathers, either immovable or
slowly-moving: the periodic transverse translation (wandering) of low-amplitude
breather between the chains, and the one-chain-localization of high-amplitude
breather. These two modes of coupled nonlinear excitations, which involve large
number of anharmonic oscillators, can be mapped onto two solutions of a single
pendulum equation, detached by a separatrix mode. We also study two-chain
breathers, which can be considered as bound states of discrete breathers with
different symmetry and center locations in the coupled chains, and bifurcation
of the anti-phase two-chain breather into the one-chain one. Delocalizing
transition of 1D breather in 2D system of a large number of parallel coupled
nonlinear chains is described, in which the breather, initially excited in a
given chain, abruptly spreads its vibration energy in the whole 2D system upon
decreasing breather frequency or amplitude below the threshold one. The
threshold breather frequency is above the cut off phonon frequency in 2D
system, and the threshold breather amplitude scales as square root of the
inter-chain coupling constant. Delocalizing transition of discrete vibrational
breather in 2D and 3D systems of coupled nonlinear chains has an analogy with
delocalizing transition for Bose-Einstein condensates in 2D and 3D optical
lattices.


title: How to detect level crossings without looking at the spectrum

abstract:
  We remind the reader that it is possible to tell if two or more eigenvalues
of a matrix are equal, without calculating the eigenvalues. We then use this
property to detect (avoided) crossings in the spectra of quantum Hamiltonians
representable by matrices. This approach provides a pedagogical introduction to
(avoided) crossings, is capable of handling realistic Hamiltonians
analytically, and offers a way to visualize crossings which is sometimes
superior to that provided by the spectrum. We illustrate the method using the
Breit-Rabi Hamiltonian to describe the hyperfine-Zeeman structure of the ground
state hydrogen atom in a uniform magnetic field.


title:
R-symmetry breaking, runaway directions and global symmetries in
  O'Raifeartaigh models

abstract:
  We discuss O'Raifeartaigh models with general R-charge assignments,
introduced by Shih to break R-symmetry spontaneously. We argue that most of
these models have runaway directions related to the R-symmetry. In addition, we
study the simplest model with a U(N) global symmetry and show that in a range
of parameters R-symmetry is spontaneously broken in a metastable vacuum.


title: Field Theory of Yang-Mills Quantum Mechanics for D Particles

abstract:
  We propose a new field-theoretic framework for formulating the
non-relativistic quantum mechanics of D particles in a Fock space of U(N)
Yang-Mills theories with all different N in a unified way. D-particle field
operators, creating and annihilating a D particle and hence changing N one by
one, are defined. The base space of these D-particle fields is a (complex)
vector space of infinite dimensions. The gauge invariance of Yang-Mills quantum
mechanics is reinterpreted as a quantum-statistical symmetry, which is taken
into account by setting up a novel algebraic and projective structure in the
formalism. Ordinary physical observables of Yang-Mills theory, obeying the
standard algebra, are expressed as bilinear forms of the D-particle fields.
Together with the open-closed string duality, our new formulation suggests a
trinity of three different but mutually dual viewpoints in string theory.


title: $C^*$-alg\`ebres gradu\'ees par un semi-treillis

abstract:
  Graded $C^*$-algebras by a semi lattice were introduced and studied by Anne
Boutet de Monvel, Vladimir Georgescu and their collaborators in relation with
the quantum N body problem. This thesis is devoted to a systematic study of
these algebras and their properties. In particular, we show that they are
completely described by their homogenous subalgebras and that they are
invariant under several operations such as tensor products, crossed products
(by actions of locally compact groups that respect the graduation). We give the
$K$-theory of graded $C^*$-algebras and finally, we study some examples of such
algebras.


title:
Transport properties of microstructured ultrathin films of
  La0.67Ca0.33MnO3 on SrTiO3

abstract:
  We have investigated the electrical transport properties of 8 nm thick
La0.67Ca0.33MnO3 films, sputter-deposited on SrTiO3 (STO), and etched into 5
micrometer-wide bridges by Ar-ion etching. We find that even slight overetching
of the film leads to conductance of the STO substrate, and asymmetric and
non-linear current-voltage (I-V) characteristics. However, a brief oxygen
plasma etch allows full recovery of the insulating character of the substrate.
The I-V characteristics of the bridges are then fully linear over a large range
of current densities. We find colossal magnetoresistance properties typical for
strained LCMO on STO but no signature of non-linear effects (so-called
electroresistance) connected to electronic inhomogeneites. In the metallic
state below 150 K, the highest current densities lead to heating effects and
non-linear I-V characteristics.


title:
Electron-muon heat conduction in neutron star cores via the exchange of
  transverse plasmons

abstract:
  We calculate the thermal conductivity of electrons and muons kappa_{e-mu}
produced owing to electromagnetic interactions of charged particles in neutron
star cores and show that these interactions are dominated by the exchange of
transverse plasmons (via the Landau damping of these plasmons in
nonsuperconducting matter and via a specific plasma screening in the presence
of proton superconductivity). For normal protons, the Landau damping strongly
reduces kappa_{e-mu} and makes it temperature independent. Proton
superconductivity suppresses the reduction and restores the Fermi-liquid
behavior kappa_{e-mu} ~ 1/T. Comparing with the thermal conductivity of
neutrons kappa_n, we obtain kappa_{e-mu}> kappa_n for T>2 GK in normal matter
and for any T in superconducting matter with proton critical temperatures
T_c>3e9 K. The results are described by simple analytic formulae.


title: Cooling Torsional Nanomechanical Vibration by Spin-Orbit Interactions

abstract:
  We propose and study a spin-orbit interaction based mechanism to actively
cool down the torsional vibration of a nanomechanical resonator made by
semiconductor materials. We show that the spin-orbit interactions of electrons
can induce a coherent coupling between the electron spins and the torsional
modes of nanomechanical vibration. This coherent coupling leads to an active
cooling for the torsional modes via the dynamical thermalization of the
resonator and the spin ensemble.


title:
An Explicit Computation of the Bures Metric Over the Space of
  $N$-Dimensional Density Matrices

abstract:
  The aim of this paper is to provide a method for explicit computation of the
Bures metric over the space of $N$-level quantum system, based on the coset
parametrization of density matrices.


title: All-order consistency of 5d sugra vacua

abstract:
  We show that the maximally supersymmetric vacua of d=5 N=1 sugra remain
maximally supersymmetric solutions when taking into account higher order
corrections.


title:
Supercritical series expansion for the contact process in heterogeneous
  and disordered environments

abstract:
  The supercritical series expansion of the survival probability for the
one-dimensional contact process in heterogeneous and disordered lattices is
used for the evaluation of the loci of critical points and critical exponents
$\beta$. The heterogeneity and disorder are modeled by considering binary
regular and irregular lattices of nodes characterized by different recovery
rates and identical transmission rates. Two analytical approaches based on
Nested Pad\'e approximants and Partial Differential approximants were used in
the case of expansions with respect to two variables (two recovery rates) for
the evaluation of the critical values and critical exponents. The critical
exponents in heterogeneous systems are very close to those for the homogeneous
contact process thus confirming that the contact process in periodic
heterogeneous environment belongs to the directed percolation universality
class. The disordered systems, in contrast, seem to have continuously varying
critical exponents.


title:
Are collisions with neutral hydrogen important for modelling the Second
  Solar Spectrum of Ti I and Ca II ?

abstract:
  The physical interpretation of scattering line polarization offers a novel
diagnostic window for exploring the thermal and magnetic structure of the quiet
regions of the solar atmosphere. Here we evaluate the impact of isotropic
collisions with neutral hydrogen atoms on the scattering polarization signals
of the 13 lines of multiplet 42 of Ti I and on those of the K line and of the
IR triplet of Ca II, with emphasis on the collisional transfer rates between
nearby J-levels. To this end, we calculate the linear polarization produced by
scattering processes considering realistic multilevel models and solving the
statistical equilibrium equations for the multipolar components of the atomic
density matrix. We confirm that the lower levels of the 13 lines of multiplet
42 of Ti I are completely depolarized by elastic collisions. We find that
upper-level collisional depolarization turns out to have an unnoticeable impact
on the emergent linear polarization amplitudes, except for the ${\lambda 4536$
line for which it is possible to notice a rather small depolarization caused by
the collisional transfer rates. Concerning the Ca II lines, we show that the
collisional rates play no role on the polarization of the upper level of the K
line, while they have a rather small depolarizing effect on the atomic
polarization of the metastable lower levels of the Ca II IR triplet.


title: Quantum Correlation Without Classical Correlations

abstract:
  We show that genuine multiparty quantum correlations can exist on its own,
without a supporting background of genuine multiparty classical correlations,
even in macroscopic systems. Such possibilities can have important implications
in the physics of quantum information and phase transitions.


title:
A Closed-Form Method for LRU Replacement under Generalized Power-Law
  Demand

abstract:
  We consider the well known \emph{Least Recently Used} (LRU) replacement
algorithm and analyze it under the independent reference model and generalized
power-law demand. For this extensive family of demand distributions we derive a
closed-form expression for the per object steady-state hit ratio. To the best
of our knowledge, this is the first analytic derivation of the per object hit
ratio of LRU that can be obtained in constant time without requiring laborious
numeric computations or simulation. Since most applications of replacement
algorithms include (at least) some scenarios under i.i.d. requests, our method
has substantial practical value, especially when having to analyze multiple
caches, where existing numeric methods and simulation become too time
consuming.


title:
Realizing Kasparov's KK-theory groups as the homotopy classes of maps of
  a Quillen model category

abstract:
  In this article we build a Quillen model category structure on the category
of sequentially complete l.m.c.-C*-algebras such that the corresponding
homotopy classes of maps Ho(A,B) for separable C*-algebras A and B coincide
with the Kasparov groups KK(A,B). This answers an open question posed by Mark
Hovey about the possibility of describing KK-theory for C*-algebras using the
language of Quillen model categories.


title:
Numerical propagation of high energy cosmic rays in the Galaxy I:
  technical issues

abstract:
  We present the results of a numerical simulation of propagation of cosmic
rays with energy above $10^{15}$ eV in a complex magnetic field, made in
general of a large scale component and a turbulent component. Several
configurations are investigated that may represent specific aspects of a
realistic magnetic field of the Galaxy, though the main purpose of this
investigation is not to achieve a realistic description of the propagation in
the Galaxy, but rather to assess the role of several effects that define the
complex problem of propagation. Our simulations of Cosmic Rays in the Galaxy
will be presented in Paper II. We identified several effects that are difficult
to interpret in a purely diffusive approach and that play a crucial role in the
propagation of cosmic rays in the complex magnetic field of the Galaxy. We
discuss at length the problem of the extrapolation of our results to much lower
energies where data are available on the confinement time of cosmic rays in the
Galaxy. The confinement time and its dependence on particles' rigidity are
crucial ingredients for 1) relating the source spectrum to the observed cosmic
ray spectrum; 2) quantifying the production of light elements by spallation; 3)
predicting the anisotropy as a function of energy.


title:
Years of RXTE Monitoring of Anomalous X-ray Pulsar 4U 0142+61: Long-Term
  Variability

abstract:
  We report on 10 years of monitoring of the 8.7-s Anomalous X-ray Pulsar 4U
0142+61 using the Rossi X-Ray Timing Explorer (RXTE). This pulsar exhibited
stable rotation from 2000 March until 2006 February: the RMS phase residual for
a spin-down model which includes nu, nudot, and nuddot is 2.3%. We report a
possible phase-coherent timing solution valid over a 10-yr span extending back
to March 1996. A glitch may have occured between 1998 and 2000, but is not
required by the existing timing data. The pulse profile has been evolving since
2000. In particular, the dip of emission between its two peaks got shallower
between 2002 and 2006, as if the profile were evolving back to its pre-2000
morphology, following an earlier event, which possibly also included the glitch
suggested by the timing data. These profile variations are seen in the 2-4 keV
band but not in 6-8 keV. We also detect a slow increase in the pulsed flux
between 2002 May and 2004 December, such that it has risen by 36+/-3% over 2.6
years in the 2-10 keV band. The pulsed flux variability and the narrow-band
pulse profile changes present interesting challenges to aspects of the magnetar
model.


title: Risk perception in epidemic modeling

abstract:
  We investigate the effects of risk perception in a simple model of epidemic
spreading. We assume that the perception of the risk of being infected depends
on the fraction of neighbors that are ill. The effect of this factor is to
decrease the infectivity, that therefore becomes a dynamical component of the
model. We study the problem in the mean-field approximation and by numerical
simulations for regular, random and scale-free networks.
  We show that for homogeneous and random networks, there is always a value of
perception that stops the epidemics. In the ``worst-case'' scenario of a
scale-free network with diverging input connectivity, a linear perception
cannot stop the epidemics; however we show that a non-linear increase of the
perception risk may lead to the extinction of the disease. This transition is
discontinuous, and is not predicted by the mean-field analysis.


title: Heavy-quark production in massless quark scattering at two loops in QCD

abstract:
  We present the two-loop virtual QCD corrections to the production of heavy
quarks in the quark--anti-quark--annihilation channel in the limit when all
kinematical invariants are large compared to the mass of the heavy quark. Our
result is exact up to terms suppressed by powers of the heavy-quark mass. The
derivation is based on a simple relation between massless and massive
scattering amplitudes in gauge theories proposed recently by two of the authors
as well as a direct calculation of the massive amplitude at two loops. The
results presented here form an important part of the next-to-next-to-leading
order QCD contributions to heavy-quark production in hadron-hadron collisions.


title: Critical behavior in an evolutionary Ultimatum Game

abstract:
  Experimental studies have shown the ubiquity of altruistic behavior in human
societies. The social structure is a fundamental ingredient to understand the
degree of altruism displayed by the members of a society, in contrast to
individual-based features, like for example age or gender, which have been
shown not to be relevant to determine the level of altruistic behavior. We
explore an evolutionary model aiming to delve how altruistic behavior is
affected by social structure. We investigate the dynamics of interacting
individuals playing the Ultimatum Game with their neighbors given by a social
network of interaction. We show that a population self-organizes in a critical
state where the degree of altruism depends on the topology characterizing the
social structure. In general, individuals offering large shares but in turn
accepting large shares, are removed from the population. In heterogeneous
social networks, individuals offering intermediate shares are strongly selected
in contrast to random homogeneous networks where a broad range of offers, below
a critical one, is similarly present in the population.


title: Correlations with Photons in Heavy-Ion Collisions

abstract:
  We present a study of two-particle correlation functions involving photons
and neutral pions in proton-proton and lead-lead collisions at the LHC energy.
The aim is to use these correlation functions to quantify the effects of the
medium on the jet decay properties.


title: A Radio Nebula Surrounding the Ultra-luminous X-ray Source in NGC 5408

abstract:
  New radio observations of the counterpart of the ultraluminous X-ray source
in NGC 5408 show for the first time that the radio emission is resolved with an
angular size of 1.5 to 2.0 arcseconds. This corresponds to a physical size of
35-46 pc, and rules out interpretation of the radio emission as beamed emission
from a relativistic jet. In addition, the radio spectral index of the
counterpart is well determined from three frequencies and found to be
alpha=-0.8 pm 0.2. The radio emission is likely to be optically-thin
synchrotron emission from a nebula surrounding the X-ray source. The radio
luminosity of the counterpart is 3.8 x 10^34 erg/s and the minimum energy
required to power the nebula is ~1 x 10^49 erg. These values are two orders of
magnitude larger than in any Galactic nebula powered by an accreting compact
object.


title: Complex chaos in conditional qubit dynamics and purification protocols

abstract:
  Selection of an ensemble of equally prepared quantum systems, based on
measurements on it, is a basic step in quantum state purification. For an
ensemble of single qubits, iterative application of selective dynamics has been
shown to lead to complex chaos, which is a novel form of quantum chaos with
true sensitivity to the initial conditions. The Julia set of initial valuse
with no convergence shows a complicated structre on the complex plane. The
shape of the Julia set varies with the parameter of the dynamics. We present
here results for the two qubit case demonstrating how a purification process
can be destroyed with chaotic oscillations.


title:
Amenable groups and Hadamard spaces with a totally disconnected isometry
  group

abstract:
  Let $X$ be a locally compact Hadamard space and $G$ be a totally disconnected
group acting continuously, properly and cocompactly on $X$. We show that a
closed subgroup of $G$ is amenable if and only if it is (topologically locally
finite)-by-(virtually abelian). We are led to consider a set $\bdfine X$ which
is a refinement of the visual boundary $\bd X$. For each $x \in \bdfine X$, the
stabilizer $G_x$ is amenable.


title:
Schiff Screening of Relativistic Nucleon Electric-Dipole Moments by
  Electrons

abstract:
  We show, at leading-order in the multipole expansion of the electron-nucleus
interaction, that nucleon electric-dipole moments are completely shielded by
electrons so that they contribute nothing to atomic electric-dipole moments,
even when relativity in the nucleus is taken into account. It is well known
that relativistic electron motion, by contrast, leads to dipole moments that
are not screened; we discuss the reasons for the difference.


title: Bigravity and Lorentz-violating Massive Gravity

abstract:
  Bigravity is a natural arena where a non-linear theory of massive gravity can
be formulated. If the interaction between the metrics $f$ and $g$ is
non-derivative, spherically symmetric exact solutions can be found. At large
distances from the origin, these are generically Lorentz-breaking bi-flat
solutions (provided that the corresponding vacuum energies are adjusted
appropriately). The spectrum of linearized perturbations around such
backgrounds contains a massless as well as a massive graviton, with {\em two}
physical polarizations each. There are no propagating vectors or scalars, and
the theory is ghost free (as happens with certain massive gravities with
explicit breaking of Lorentz invariance). At the linearized level, corrections
to GR are proportional to the square of the graviton mass, and so there is no
vDVZ discontinuity. Surprisingly, the solution of linear theory for a static
spherically symmetric source does {\em not} agree with the linearization of any
of the known exact solutions. The latter coincide with the standard
Schwarzschild-(A)dS solutions of General Relativity, with no corrections at
all. Another interesting class of solutions is obtained where $f$ and $g$ are
proportional to each other. The case of bi-de Sitter solutions is analyzed in
some detail.


title: On the N=1 super Liouville four-point functions

abstract:
  We construct the four-point correlation functions containing the top
component of the supermultiplet in the Neveu-Schwarz sector of the N=1 SUSY
Liouville field theory. The construction is based on the recursive
representation for the NS conformal blocks. We test our results in the case
where one of the fields is degenerate with a singular vector on the level 3/2.
In this case, the correlation function satisfies a third-order ordinary
differential equation, which we derive. We numerically verify the crossing
symmetry relations for the constructed correlation functions in the
nondegenerate case.


title: Reconstruction from Radon projections and orthogonal expansion on a ball

abstract:
  The relation between Radon transform and orthogonal expansions of a function
on the unit ball in $\RR^d$ is exploited. A compact formula for the partial
sums of the expansion is given in terms of the Radon transform, which leads to
algorithms for image reconstruction from Radon data. The relation between
orthogonal expansion and the singular value decomposition of the Radon
transform is also exploited.


title: The meeting problem in the quantum random walk

abstract:
  We study the motion of two non-interacting quantum particles performing a
random walk on a line and analyze the probability that the two particles are
detected at a particular position after a certain number of steps (meeting
problem). The results are compared to the corresponding classical problem and
differences are pointed out. Analytic formulas for the meeting probability and
its asymptotic behavior are derived. The decay of the meeting probability for
distinguishable particles is faster then in the classical case, but not
quadratically faster. Entangled initial states and the bosonic or fermionic
nature of the walkers are considered.


title: On the Hopcroft's minimization algorithm

abstract:
  We show that the absolute worst case time complexity for Hopcroft's
minimization algorithm applied to unary languages is reached only for de Bruijn
words. A previous paper by Berstel and Carton gave the example of de Bruijn
words as a language that requires O(n log n) steps by carefully choosing the
splitting sets and processing these sets in a FIFO mode. We refine the previous
result by showing that the Berstel/Carton example is actually the absolute
worst case time complexity in the case of unary languages. We also show that a
LIFO implementation will not achieve the same worst time complexity for the
case of unary languages. Lastly, we show that the same result is valid also for
the cover automata and a modification of the Hopcroft's algorithm, modification
used in minimization of cover automata.


title: Lifetime measurements of Triaxial Strongly Deformed bands in $^{163}$Tm

abstract:
  With the Doppler Shift Attenuation Method, quadrupole transition moments,
$Q_t$, were determined for the two recently proposed Triaxial Strongly Deformed
(TSD) bands in $^{163}$Tm. The measured $Q_t$ moments indicate that the
deformation of these bands is larger than that of the yrast, signature
partners. However, the measured values are smaller than those predicted by
theory. This observation appears to be valid for TSD bands in several nuclei of
the region


title: The Resolvent Algebra: A New Approach to Canonical Quantum Systems

abstract:
  The standard C*-algebraic version of the algebra of canonical commutation
relations, the Weyl algebra, frequently causes difficulties in applications
since it neither admits the formulation of physically interesting dynamical
laws nor does it incorporate pertinent physical observables such as (bounded
functions of) the Hamiltonian. Here a novel C*-algebra of the canonical
commutation relations is presented which does not suffer from such problems. It
is based on the resolvents of the canonical operators and their algebraic
relations. The resulting C*-algebra, the resolvent algebra, is shown to have
many desirable analytic properties and the regularity structure of its
representations is surprisingly simple. Moreover, the resolvent algebra is a
convenient framework for applications to interacting and to constrained quantum
systems, as we demonstrate by several examples.


title:
Simulation of Cosmogenic Neutrino Spectra with the GZKFast Event
  Generator

abstract:
  GZKFast is a low-cost astrophysical event generator designed to simulate
photohadron processes resulting from ultra high energy cosmic ray fluxes.
GZKFast is an easy to use event generator which specifically addresses issues
relevant to cosmogenic neutrinos and the ultra high energy (UHE) neutrino
spectrum. GZKFast injects UHE particles into a simulated cosmic microwave
background (CMB) using a Monte Carlo approach. The interaction of each particle
is simulated and the resulting detectable events are spooled to log files.
Although GZKFast uses a simplified particle physics model and limited
accelerator data it generates event distributions which are comparable with
more thorough simulations such as the event generator SOPHIA