title:
Funnel-flow accretion onto highly magnetized neutron stars and shock
  generation

abstract:
  In this paper, we initiate a new study of steady funnel-flow accretion onto
strongly magnetized neutron stars, including a full treatment of shock
generation. As a first step, we adopt a simplified model considering the flow
within Newtonian theory and neglecting radiative pressure and cooling. The flow
is taken to start from an accretion disc and then to follow magnetic field
lines, forming a transonic funnel flow onto the magnetic poles. A standing
shock occurs at a certain point in the flow and beyond this material accretes
subsonically onto the star with high pressure and density. We calculate the
location of the standing shock and all other features of the flow within the
assumptions of our model. Applications to observed X-ray pulsars are discussed.


title: Eigenvalue based Spectrum Sensing Algorithms for Cognitive Radio

abstract:
  Spectrum sensing is a fundamental component is a cognitive radio. In this
paper, we propose new sensing methods based on the eigenvalues of the
covariance matrix of signals received at the secondary users. In particular,
two sensing algorithms are suggested, one is based on the ratio of the maximum
eigenvalue to minimum eigenvalue; the other is based on the ratio of the
average eigenvalue to minimum eigenvalue. Using some latest random matrix
theories (RMT), we quantify the distributions of these ratios and derive the
probabilities of false alarm and probabilities of detection for the proposed
algorithms. We also find the thresholds of the methods for a given probability
of false alarm. The proposed methods overcome the noise uncertainty problem,
and can even perform better than the ideal energy detection when the signals to
be detected are highly correlated. The methods can be used for various signal
detection applications without requiring the knowledge of signal, channel and
noise power. Simulations based on randomly generated signals, wireless
microphone signals and captured ATSC DTV signals are presented to verify the
effectiveness of the proposed methods.


title: Extended BRS symmetry in topological field theories

abstract:
  A class of topological field theories like the $BF$ model and Chern-Simons
theory, when quantized in the Landau gauge, enjoys the property of invariance
under a vector supersymmetry, which is responsible for their finiteness. We
introduce a new type of gauge fixing which makes these theories invariant under
an extended $BRS$ symmetry, containing a new type of field, the ghost of
diffeomorphisms. The presence of such an extension is naturally related to the
vector supersymmetry discussed before.


title:
Comment: Demystifying Double Robustness: A Comparison of Alternative
  Strategies for Estimating a Population Mean from Incomplete Data

abstract:
  Comment on ``Demystifying Double Robustness: A Comparison of Alternative
Strategies for Estimating a Population Mean from Incomplete Data''
[arXiv:0804.2958]


title:
A possible ground state and its electronic structure of a mother
  material (LaOFeAs) of new superconductors

abstract:
  The electronic and magnetic properties of the mother material LaOFeAs of new
superconductors have been carefully studied using first-principles electronic
structure calculations based on the generalized gradient approximation in the
density functional theory. The present calculation predicts that the ground
state of LaOFeAs is antiferromagnetic with a stripe type magnetic moment
alignment leading to orthorhombic symmetry of the crystal. In this particular
magnetic state, the density of states at the Fermi level is very small. On the
other hand, LaOFeP has turned out to be paramagnetic and a good metal.
Implications of the results regarding the experimental observations will also
be presented.


title:
Structural properties and liquid spinodal of water confined in a
  hydrophobic environment

abstract:
  We present the results of a computer simulation study of thermodynamical
properties of TIP4P water confined in a hydrophobic disordered matrix of soft
spheres upon supercooling. The hydrogen bond network of water appears preserved
in this hydrophobic confinement. Nonetheless a reduction in the average number
of hydrogen bonds due to the geometrical constraints is observed. The liquid
branch of the spinodal line is calculated from 350 K down to 210 K. The same
thermodynamic scenario of the bulk is found: the spinodal curve is
monotonically decreasing. The line of maximum density bends avoiding a crossing
of the spinodal. There is however a shift both of the line of maximum density
and of the spinodal toward higher pressures and lower temperatures with respect
to bulk.


title:
Comment: Performance of Double-Robust Estimators When ``Inverse
  Probability'' Weights Are Highly Variable

abstract:
  Comment on ``Performance of Double-Robust Estimators When ``Inverse
Probability'' Weights Are Highly Variable'' [arXiv:0804.2958]


title: Metamagnetism and 1/3 Plateau in the Spin Chain Compound CoV2O6

abstract:
  The pseudo-one dimensional brannerite type compound CoV2O6 has been studied
by magnetisation and heat capacity measurements in the temperature range 1.8 <
T < 300 K and in applied fields of up to 9 T. Our measurements show an unusual
balance of exchange interactions (CW= 2.8(2) K) and a single antiferromagnetic
transition at TN = 7 K. M(H) isotherms recorded below 5 K show a metamagnetic
transition and a 1/3 magnetisation plateau. From 5-7 K, only the metamagnetic
transition is observed. For T < TN < ~ 25 K, our heat capacity and
magnetisation measurements show evidence for strong low dimensional
ferromagnetic fluctuations. We propose a simple phase diagram, discuss the
principle features and emphasise the importance of Ising anisotropy.


title: Quantum modulation of the Kondo resonance of Co adatoms on Cu/Co/Cu(100)

abstract:
  Low-temperature scanning tunneling spectroscopy reveals that the Kondo
temperature T_K of Co atoms adsorbed on Cu/Co/Cu(100) multilayers varies
between 60 K and 134 K as the Cu film thickness decreases from 20 to 5 atomic
layers. The observed change of T_K is attributed to a variation of the density
of states at the Fermi level \rho_F induced by quantum well states confined to
the Cu film. A model calculation based on the quantum oscillations of \rho_F at
the belly and the neck of the Cu Fermi surface reproduces most of the features
in the measured variation of T_K.


title:
Confinement-enhanced spin relaxation for electron ensembles in large
  quantum dots

abstract:
  We present a numerical study of spin relaxation in a semiclassical electron
ensemble in a large ballistic quantum dot. The dot is defined in a GaAs/AlGaAs
heterojunction system with a two-dimensional electron gas, and relaxation
occurs due to Dresselhaus and Rashba spin orbit interaction. We find that
confinement in a micronscale dot can result in strongly enhanced relaxation
with respect to a free two-dimensional electron ensemble, contrary to the
established result that strong confinement or frequent momentum scattering
reduces relaxation. This effect occurs when the size of the system is on the
order of the spin precession length, but smaller than the mean free path.


title: Comment: Understanding OR, PS and DR

abstract: Comment on ``Understanding OR, PS and DR'' [arXiv:0804.2958]


title:
WMAP 5-year constraints on lepton asymmetry and radiation energy
  density: Implications for Planck

abstract:
  In this paper we set bounds on the radiation content of the Universe and
neutrino properties by using the WMAP-5 year CMB measurements complemented with
most of the existing CMB and LSS data (WMAP5+All),imposing also self-consistent
BBN constraints on the primordial helium abundance. We consider lepton
asymmetric cosmological models parametrized by the neutrino degeneracy
parameter and the variation of the relativistic degrees of freedom, due to
possible other physical processes occurred between BBN and structure formation
epochs. We find that WMAP5+All data provides strong bounds on helium mass
fraction and neutrino degeneracy parameter that rivals the similar bounds
obtained from the conservative analysis of the present data on helium
abundance. We also find a strong correlation between the matter energy density
and the redshift of matter-radiation equality, z_re, showing that we observe
non-zero equivalent number of relativistic neutrinos mainly via the change of
the of z_re, rather than via neutrino anisotropic stress claimed by the WMAP
team. We forecast that the CMB temperature and polarization measurements
observed with high angular resolutions and sensitivities by the future Planck
satellite will reduce the errors on these parameters down to values fully
consistent with the BBN bounds.


title:
Monte Carlo simulations of the directional-ordering transition in the
  two-dimensional classical and quantum compass model

abstract:
  A comprehensive study of the two-dimensional (2D) compass model on the square
lattice is performed for classical and quantum spin degrees of freedom using
Monte Carlo and quantum Monte Carlo methods. We employ state-of-the-art
implementations using Metropolis, stochastic series expansion and parallel
tempering techniques to obtain the critical ordering temperatures and critical
exponents. In a pre-investigation we reconsider the classical compass model
where we study and contrast the finite-size scaling behavior of ordinary
periodic boundary conditions against annealed boundary conditions. It is shown
that periodic boundary conditions suffer from extreme finite-size effects which
might be caused by closed loop excitations on the torus. These excitations also
appear to have severe effects on the Binder parameter. On this footing we
report on a systematic Monte Carlo study of the quantum compass model. Our
numerical results are at odds with recent literature on the subject which we
trace back to neglecting the strong finite-size effects on periodic lattices.
The critical temperatures are obtained as $T_\mathrm{c}=0.1464(2)J$ and
$T_\mathrm{c}=0.055(1)J$ for the classical and quantum version, respectively,
and our data support a transition in the 2D Ising universality class for both
cases.


title:
Rejoinder: Demystifying Double Robustness: A Comparison of Alternative
  Strategies for Estimating a Population Mean from Incomplete Data

abstract:
  Rejoinder to ``Demystifying Double Robustness: A Comparison of Alternative
Strategies for Estimating a Population Mean from Incomplete Data''
[arXiv:0804.2958]


title:
Quasiparticle properties of strongly correlated electron systems with
  itinerant metamagnetic behavior

abstract:
  A brief account of the zero temperature magnetic response of a system of
strongly correlated electrons in strong magnetic field is given in terms of its
quasiparticle properties. The scenario is based on the paramagnetic phase of
the half-filled Hubbard model, and the calculations are carried out with the
dynamical mean field theory (DMFT) together with the numerical renormalization
group (NRG). As well known, in a certain parameter regime one finds a magnetic
susceptibility which increases with the field strength. Here, we analyze this
metamagnetic response based on Fermi liquid parameters, which can be calculated
within the DMFT-NRG procedure. The results indicate that the metamagnetic
response can be driven by field-induced effective mass enhancement. However,
also the contribution due to quasiparticle interactions can play a significant
role. We put our results in context with experimental studies of itinerant
metamagnetic materials.


title: J/psi production in association with a charm-quark pair at the Tevatron

abstract:
  I study the direct hadroproduction of J\psi associated with a charm-quark
pair at leading order in alpha_S and v in NRQCD. This process provides an
interesting signature that could be studied at the Tevatron. I consider both
colour-singlet and colour-octet transitions. I compare our results to the
fragmentation approximation and discuss the associated experimental signatures.


title:
A Suprime-Cam study of the stellar population of Ursa Major I dwarf
  spheroidal galaxy

abstract:
  We present deep and wide V, I CCD photometry of Ursa Major I (UMa I) dwarf
spheroidal galaxy (dSph) in Local Group. The images of the galaxy were taken by
Subaru/Suprime-Cam wide field camera, covering a field of 34\arcmin $\times$
27\arcmin located at the centre of the galaxy. Colour-magnitude diagram (CMD)
of the UMa I dSph shows a steep and narrow red giant branch (RGB), blue and red
horizontal branch (HB), and main sequence (MS) stars. A well-defined main
sequence turn-off (MSTO) is found to be located at V$_{0,MSTO}\sim$23.5 mag.
The distance modulus is derived as $(m-M)_0=19.93\pm0.1$ (corresponding to a
distance D$=96.8\pm4$ kpc) from the V-band magnitude of the horizontal branch
(V$_{0,HB}=20.45\pm0.02$). The mean metallicity of the RGB stars is estimated
by the V$-$I colour to [Fe/H]$\sim-2.0$. The turn-off age estimated by
overlaying the theoretical isochrones reveals that most of stars in the UMa I
dSph are formed at very early epoch ($\sim12$Gyrs ago). The isopleth map of
stellar number density of the UMa I dSph, based upon the resolved star counts
of MS, RGB, HB stars as well as blue stragglers (BS), shows that the morphology
of the UMa I dSph is quite irregular and distorted, suggesting that the galaxy
is in a process of disruption. The very old and metal-poor nature of the
stellar population implies that the star formation history of this newly
discoverd faint dSph may have been different from other well-known `classical'
dSphs, which show significant stellar population of intermediate age. The
stellar population of the UMa I dSph closely resembles that of Galactic old
metal-poor globular cluster, but its size is typical of Galactic dSphs
(r$_{e}$=188 [pc], r$_{1/2}$=300 [pc]), and the shape of its spatial density
contours suggests that it is undergoing tidal disruption.


title:
On some Moduli spaces of stable vector bundles on cubic and quartic
  threefolds

abstract:
  We study certain moduli spaces of stable vector bundles of rank two on cubic
and quartic threefolds. In many cases under consideration, it turns out that
the moduli space is complete and irreducible and a general member has vanishing
intermediate cohomology. In one case, all except one component of the moduli
space has such vector bundles.


title:
Elementary symmetric functions of two solvents of a quadratic matrix
  equation

abstract:
  Quadratic matrix equations occur in a variety of applications. In this paper
we introduce new permutationally invariant functions of two solvents of the n
quadratic matrix equation X^2- L1X - L0 = 0, playing the role of the two
elementary symmetric functions of the two roots of a quadratic scalar equation.
Our results rely on the connection existing between the QME and the theory of
linear second order difference equations with noncommutative coefficients. An
application of our results to a simple physical problem is briefly discussed.


title:
Two-Dimensional Central-Upwind Schemes for Curvilinear Grids and
  Application to Gas Dynamics with Angular Momentum

abstract:
  In this work we present new second order semi-discrete central schemes for
systems of hyperbolic conservation laws on curvilinear grids. Our methods
generalise the two-dimensional central-upwind schemes developed by Kurganov and
Tadmor. In these schemes we account for area and volume changes in the
numerical flux functions due to the non-cartesian geometries. In case of
vectorial conservation laws we introduce a general prescription of the
geometrical source terms valid for various orthogonal curvilinear coordinate
systems. The methods are applied to the two-dimensional Euler equations of
inviscid gas dynamics with and without angular momentum transport. In the
latter case we introduce a new test problem to examine the detailed
conservation of specific angular momentum.


title:
Reconstructing the free energy landscape of a polyprotein by
  single-molecule experiments

abstract:
  The mechanical unfolding of an engineered protein composed of eight domains
of Ig27 is investigated by using atomic force microscopy. Exploiting a
fluctuation relation, the equilibrium free energy as a function of the molecule
elongation is estimated from pulling experiments. Such a free energy exhibits a
regular shape that sets a typical unfolding length at zero force of the order
of 20 nm. This length scale turns out to be much larger than the kinetic
unfolding length that is also estimated by analyzing the typical rupture force
of the molecule under dynamic loading.


title: Quantum estimation for quantum technology

abstract:
  Several quantities of interest in quantum information, including entanglement
and purity, are nonlinear functions of the density matrix and cannot, even in
principle, correspond to proper quantum observables. Any method aimed to
determine the value of these quantities should resort to indirect measurements
and thus corresponds to a parameter estimation problem whose solution, i.e the
determination of the most precise estimator, unavoidably involves an
optimization procedure. We review local quantum estimation theory and present
explicit formulas for the symmetric logarithmic derivative and the quantum
Fisher information of relevant families of quantum states. Estimability of a
parameter is defined in terms of the quantum signal-to-noise ratio and the
number of measurements needed to achieve a given relative error. The
connections between the optmization procedure and the geometry of quantum
statistical models are discussed. Our analysis allows to quantify quantum noise
in the measurements of non observable quantities and provides a tools for the
characterization of signals and devices in quantum technology.


title: Measuring Traffic

abstract:
  A traffic performance measurement system, PeMS, currently functions as a
statewide repository for traffic data gathered by thousands of automatic
sensors. It has integrated data collection, processing and communications
infrastructure with data storage and analytical tools. In this paper, we
discuss statistical issues that have emerged as we attempt to process a data
stream of 2 GB per day of wildly varying quality. In particular, we focus on
detecting sensor malfunction, imputation of missing or bad data, estimation of
velocity and forecasting of travel times on freeway networks.


title:
Optimal network topologies for information transmission in active
  networks

abstract:
  This work clarifies the relation between network circuit (topology) and
behavior (information transmission and synchronization) in active networks,
e.g. neural networks. As an application, we show how to determine a network
topology that is optimal for information transmission. By optimal, we mean that
the network is able to transmit a large amount of information, it possesses a
large number of communication channels, and it is robust under large variations
of the network coupling configuration. This theoretical approach is general and
does not depend on the particular dynamic of the elements forming the network,
since the network topology can be determined by finding a Laplacian matrix (the
matrix that describes the connections and the coupling strengths among the
elements) whose eigenvalues satisfy some special conditions. To illustrate our
ideas and theoretical approaches, we use neural networks of electrically
connected chaotic Hindmarsh-Rose neurons.


title:
Phenomenology of the normal state in-plane transport properties of
  high-$T_c$ cuprates

abstract:
  In this article, I review progress towards an understanding of the normal
state (in-plane) transport properties of high-$T_c$ cuprates in the light of
recent developments in both spectroscopic and transport measurement techniques.
Against a backdrop of mounting evidence for anisotropic single-particle
lifetimes in cuprate superconductors, new results have emerged that advocate
similar momentum dependence in the transport decay rate $\Gamma$({\bf k}). In
addition, enhancement of the energy scale (up to the bare bandwidth) over which
spectroscopic information on the quasiparticle response can be obtained has led
to the discovery of new, unforeseen features that surprisingly, may have a
significant bearing on the transport properties at the dc limit. With these two
key developments in mind, I consider here whether all the ingredients necessary
for a complete phenomenological description of the anomalous normal state
transport properties of high-$T_c$ cuprates are now in place.


title:
Splitting type, global sections and Chern classes for torsion free
  sheaves on P^N

abstract:
  In this paper we compare a torsion free sheaf $\FF$ on $\PP^N$ and the free
vector bundle $\oplus_{i=1}^n\OPN(b_i)$ having same rank and splitting type. We
show that the first one has always "less" global sections, while it has a
higher second Chern class. In both cases bounds for the difference are found in
terms of the maximal free subsheaves of $\FF$. As a consequence we obtain a
direct, easy and more general proof of the "Horrocks' splitting criterion",
also holding for torsion free sheaves, and lower bounds for the Chern classes
$c_i(\FF(t))$ of twists of $\FF$, only depending on some numerical invariants
of $\FF$. Especially, we prove for rank $n$ torsion free sheaves on $\PP^N$,
whose splitting type has no gap (i.e. $b_i\geq b_{i+1}\geq b_i-1$ for every
$i=1, ...,n-1$), the following formula for the discriminant: \[
\Delta(\FF):=2nc_2-(n-1)c_1^2\geq -{1/12}n^2(n^2-1)\] Finally in the case of
rank $n$ reflexive sheaves we obtain polynomial upper bounds for the absolute
value of the higher Chern classes $c_3(\FF(t)), ..., c_n(\FF(t))$, for the
dimension of the cohomology modules $H^i\FF(t)$ and for the Castelnuovo-Mumford
regularity of $\FF$; these polynomial bounds only depend only on $c_1(\FF)$,
$c_2(\FF)$, the splitting type of $\FF$ and $t$.


title: Higher order invariants of Levi degenerate hypersurfaces

abstract:
  The first part of this paper considers higher order CR invariants of three
dimensional hypersurfaces of finite type. Using a full normal form we give a
complete characterization of hypersurfaces with trivial local automorphism
group, and analogous results for finite groups. The second part considers
hypersurfaces of finite Catlin multitype and the Kohn-Nirenberg phenomenon in
higher dimensions. We give a necessary condition for local convexifiability of
a class of pseudoconvex hypersurfaces in $\mathbb C^{n+1}$.


title:
Solar off-limb line widths: Alfven waves, ion-cyclotron waves, and
  preferential heating

abstract:
  Alfven waves and ion-cyclotron absorption of high-frequency waves are
frequently brought into models devoted to coronal heating and fast solar-wind
acceleration. Signatures of ion-cyclotron resonance have already been observed
in situ in the solar wind (HELIOS spacecrafts) and, recently, in the upper
corona (UVCS/SOHO remote-sensing results). We propose a method to constrain
both the Alfven wave amplitude and the preferential heating induced by
ion-cyclotron resonance, above a partially developed polar coronal hole
observed with the SUMER/SOHO spectrometer. The instrumental stray light
contribution is first substracted from the spectra. By supposing that the
non-thermal velocity is related to the Alfven wave amplitude, it is constrained
through a density diagnostic and the gradient of the width of the Mg X 625 A
line. The temperatures of several coronal ions, as functions of the distance
above the limb, are then determined by substracting the non-thermal component
to the observed line widths. The effect of stray light explains the apparent
decrease with height in the width of several spectral lines, this decrease
usually starting about 0.1-0.2 Rs above the limb. This result rules out any
direct evidence of damping of the Alfven waves, often suggested by other
authors. We also find that the ions with the smallest charge-to-mass ratios are
the hottest ones at a fixed altitude and that they are subject to a stronger
heating, as compared to the others, between 57" and 102" above the limb. This
constitutes a serious clue to ion-cyclotron preferential heating.


title: Scaling behavior of self-avoiding walks on percolation clusters

abstract:
  The scaling behavior of self-avoiding walks (SAWs) on the backbone of
percolation clusters in two, three and four dimensions is studied by Monte
Carlo simulations. We apply the pruned-enriched Rosenbluth chain-growth method
(PERM). Our numerical results bring about the estimates of critical exponents,
governing the scaling laws of disorder averages of the end-to-end distance of
SAW configurations. The effects of finite-size scaling are discussed as well.


title: A New Look at the Higgs-Kibble Model

abstract:
  An elementary perturbative method of handling the Higgs-Kibble models and
deriving their relevant properties, is described. It is based on Wightman field
theory and avoids some of the mathematical weaknesses of the standard
treatments.


title: Collapse of a Bose gas: kinetic approach

abstract:
  We have analytically explored temperature dependence of critical number of
particles for the collapse of a harmonically trapped attractively interacting
Bose gas below the condensation point by introducing a kinetic approach within
the Hartree-Fock approximation. The temperature dependence obtained by this
easy approach is consisted with that obtained from the scaling theory.


title: Low-Complexity LDPC Codes with Near-Optimum Performance over the BEC

abstract:
  Recent works showed how low-density parity-check (LDPC) erasure correcting
codes, under maximum likelihood (ML) decoding, are capable of tightly
approaching the performance of an ideal maximum-distance-separable code on the
binary erasure channel. Such result is achievable down to low error rates, even
for small and moderate block sizes, while keeping the decoding complexity low,
thanks to a class of decoding algorithms which exploits the sparseness of the
parity-check matrix to reduce the complexity of Gaussian elimination (GE). In
this paper the main concepts underlying ML decoding of LDPC codes are recalled.
A performance analysis among various LDPC code classes is then carried out,
including a comparison with fixed-rate Raptor codes. The results show that LDPC
and Raptor codes provide almost identical performance in terms of decoding
failure probability vs. overhead.


title:
"E pluribus unum" or How to Derive Single-equation Descriptions for
  Output-quantities in Nonlinear Circuits using Differential Algebra

abstract:
  In this paper we describe by a number of examples how to deduce one single
characterizing higher order differential equation for output quantities of an
analog circuit.
  In the linear case, we apply basic "symbolic" methods from linear algebra to
the system of differential equations which is used to model the analog circuit.
For nonlinear circuits and their corresponding nonlinear differential
equations, we show how to employ computer algebra tools implemented in Maple,
which are based on differential algebra.


title:
Molecular spin resonance in the geometrically frustrated MgCr2O4 magnet
  by inelastic neutron scattering

abstract:
  We measured two magnetic modes with finite and discrete energies in an
antiferromagnetic ordered phase of a geometrically frustrated magnet MgCr2O4 by
single-crystal inelastic neutron scattering, and clarified the spatial spin
correlations of the two levels: one is an antiferromagnetic hexamer and the
other is an antiferromagnetic heptamer. Since these correlation types are
emblematic of quasielastic scattering with geometric frustration, our results
indicate instantaneous suppression of lattice distortion in an ordered phase by
spin-lattice coupling, probably also supported by orbital and charge. The
common features in the two levels, intermolecular independence and discreteness
of energy, suggest that the spin molecules are interpreted as quasiparticles
(elementary excitations with energy quantum) of highly frustrated spins, in
analogy with the Fermi liquid approximation.


title:
Observation of Coherent Precession of Magnetization in Superfluid 3He
  A-phase

abstract:
  We report the first observation of coherent quantum precession of
magnetization (CQP) in superfluid 3He-A in aerogel. The coherent precession in
bulk 3He A-phase is unstable due to the positive feedback of spin supercurrent
to the gradient of phase of precession. It was predicted that the homogeneous
precession will be stable if the orbital momentum of 3He-A could be oriented
along the magnetic field. We have succeeded to prepare this configuration by
emerging 3He in uniaxially-deformed anisotropic aerogel. The dissipation rate
of coherent precession states in aerogel is much larger then one in bulk 3He-B.
We propose a mechanism of this dissipation.


title:
The Convenient Setting for non-Quasianalytic Denjoy--Carleman
  Differentiable Mappings

abstract:
  For Denjoy--Carleman differential function classes $C^M$ where the weight
sequence $M=(M_k)$ is logarithmically convex, stable under derivations, and
non-quasianalytic of moderate growth, we prove the following: A mapping is
$C^M$ if it maps $C^M$-curves to $C^M$-curves. The category of $C^M$-mappings
is cartesian closed in the sense that $C^M(E,C^M(F,G))\cong C^M(E\x F, G)$ for
convenient vector spaces. Applications to manifolds of mappings are given: The
group of $C^M$-diffeomorphisms is a $C^M$-Lie group but not better.


title: The Epic Story of Maximum Likelihood

abstract:
  At a superficial level, the idea of maximum likelihood must be prehistoric:
early hunters and gatherers may not have used the words ``method of maximum
likelihood'' to describe their choice of where and how to hunt and gather, but
it is hard to believe they would have been surprised if their method had been
described in those terms. It seems a simple, even unassailable idea: Who would
rise to argue in favor of a method of minimum likelihood, or even mediocre
likelihood? And yet the mathematical history of the topic shows this ``simple
idea'' is really anything but simple. Joseph Louis Lagrange, Daniel Bernoulli,
Leonard Euler, Pierre Simon Laplace and Carl Friedrich Gauss are only some of
those who explored the topic, not always in ways we would sanction today. In
this article, that history is reviewed from back well before Fisher to the time
of Lucien Le Cam's dissertation. In the process Fisher's unpublished 1930
characterization of conditions for the consistency and efficiency of maximum
likelihood estimates is presented, and the mathematical basis of his three
proofs discussed. In particular, Fisher's derivation of the information
inequality is seen to be derived from his work on the analysis of variance, and
his later approach via estimating functions was derived from Euler's Relation
for homogeneous functions. The reaction to Fisher's work is reviewed, and some
lessons drawn.


title: Helicity correlations of vector bosons

abstract:
  We calculate the helicity and polarization correlation functions in the
Einstein-Podolsky-Rosen-type experiments with relativistic vector bosons. We
show that the linear polarization correlation function in the appriopriately
chosen state in the massless limit is the same as the correlation function in
the scalar two-photon state. We show also that the polarization correlation
function violate the Clauser-Horne-Shimony-Holt inequality and that the degree
of this violation can increase with the particle momentum.


title: OFDM based Distributed Space Time Coding for Asynchronous Relay Networks

abstract:
  Recently Li and Xia have proposed a transmission scheme for wireless relay
networks based on the Alamouti space time code and orthogonal frequency
division multiplexing to combat the effect of timing errors at the relay nodes.
This transmission scheme is amazingly simple and achieves a diversity order of
two for any number of relays. Motivated by its simplicity, this scheme is
extended to a more general transmission scheme that can achieve full
cooperative diversity for any number of relays. The conditions on the
distributed space time block code (DSTBC) structure that admit its application
in the proposed transmission scheme are identified and it is pointed out that
the recently proposed full diversity four group decodable DSTBCs from precoded
co-ordinate interleaved orthogonal designs and extended Clifford algebras
satisfy these conditions. It is then shown how differential encoding at the
source can be combined with the proposed transmission scheme to arrive at a new
transmission scheme that can achieve full cooperative diversity in asynchronous
wireless relay networks with no channel information and also no timing error
knowledge at the destination node. Finally, four group decodable distributed
differential space time block codes applicable in this new transmission scheme
for power of two number of relays are also provided.


title:
Combining The Tunneling And Anomaly Phenomena In Deriving the
  Gravitational Anomaly

abstract:
  In this Letter we have derived the gravitational anomaly leading to the
Hawking radiation from a fundamentally different perspective: it emerges due to
the {\it{complimentary}} roles played by tunneling and (gravitational) anomaly.
We have used the analogy of an early idea \cite{niel1} of visualizing chiral
gauge anomaly as an effect of {\it{spectral flow}} of the energy levels, from
the negative energy Dirac sea, across zero energy level in presence of gauge
interactions. This was extended to conformal anomaly in \cite{fumita}. In the
present work, we exploit the latter formalism in black hole physics where we
interpret crossing the horizon of black hole (the zero energy level) as a
spectral flow since it is also accompanied by a change of sign in the energy of
the particle. Hence in our formulation the negative energy states below horizon
play a similar role as the Dirac sea. We successfully recover the gravitational
anomaly.


title: On the Carleson measure criterion in linear systems theory

abstract:
  In Ho, Russell, and Weiss, a Carleson measure criterion for admissibility of
one-dimensional input elements with respect to diagonal semigroups is given. We
extend their results from the Hilbert space situation $X=\ell_2$ and
$L^2$--admissibility to the more general situation of $L^p$--admissibility on
$\ell_q$--spaces. In case of analytic diagonal semigroups we present a new
result that does not rely on Laplace transform methods. A comparison of both
criteria leads to result of $L^p$--admissibility for reciprocal systems in the
sense of Curtain.


title: Rank four vector bundles without theta divisor over a curve of genus two

abstract:
  We show that the locus of stable rank four vector bundles without theta
divisor over a smooth projective curve of genus two is in canonical bijection
with the set of theta-characteristics. We give several descriptions of these
bundles and compute the degree of the rational theta map.


title: Theoretical study of kinks on screw dislocation in silicon

abstract:
  Theoretical calculations of the structure, formation and migration of kinks
on a non-dissociated screw dislocation in silicon have been carried out using
density functional theory calculations as well as calculations based on
interatomic potential functions. The results show that the structure of a
single kink is characterized by a narrow core and highly stretched bonds
between some of the atoms. The formation energy of a single kink ranges from
0.9 to 1.36 eV, and is of the same order as that for kinks on partial
dislocations. However, the kinks migrate almost freely along the line of an
undissociated dislocation unlike what is found for partial dislocations. The
effect of stress has also been investigated in order to compare with previous
silicon deformation experiments which have been carried out at low temperature
and high stress. The energy barrier associated with the formation of a stable
kink pair becomes as low as 0.65 eV for an applied stress on the order of 1
GPa, indicating that displacements of screw dislocations likely occur via
thermally activated formation of kink pairs at room temperature.


title: Group Classification of Burgers' Equations

abstract:
  In this work we carry out a complete group classification of Burgers'
equations.


title: Flow instabilities of magnetic flux tubes -- III. Toroidal flux tubes

abstract:
  In addition to buoyancy- and magnetic tension-driven instabilities, magnetic
flux rings are also susceptible to an instability induced by the hydrodynamic
drag force. We investigate the influence of the toroidal shape and equilibrium
condition on the thresholds of the friction-induced instability and on their
relevance for emerging magnetic flux in solar-like stars. Analytical
instability criteria are derived for axial symmetric perturbations and for flux
rings in the equatorial plane by analysing the sequence of principal minors of
the coefficient matrices of dispersion polynomials. The general case of
non-equatorial flux rings is investigated numerically by considering flux tubes
in the solar overshoot region. The friction-induced instability occurs when an
eigenmode reverses its direction of propagation due to advection, typically
from the retrograde to the prograde direction. Since the reversal requires a
certain relative velocity difference between plasma inside the flux tube and
the environment, the instability criterion depends on the location and field
strength of the flux ring. The friction-induced instability sets in at lower
field strengths than buoyancy- and tension-driven instabilities. Its threshold
is independent of the strength of friction, but the growth rates depend on the
strength of the frictional coupling between flux tube and environment. The
friction-induced instability lowers the critical magnetic field strength beyond
which flux tubes are subject to growing perturbations. Whereas buoyancy- and
tension-driven instabilities depend on the magnetic field strength alone, the
dependence of hydrodynamic drag on the tube diameter gives rise to an
additional dependence of growth times on the magnetic flux.


title: Establishing EPR-channels between Nanomechanics and Atomic Ensembles

abstract:
  We suggest to interface nanomechanical systems via an optical quantum bus to
atomic ensembles, for which means of high precision state preparation,
manipulation and measurement are available. This allows in particular for a
Quantum Non-Demolition Bell measurement, projecting the coupled system, atomic
ensemble - nanomechanical resonator, into an entangled EPR-state. The
entanglement is observable even for nanoresonators initially well above their
ground states and can be utilized for teleportation of states from an atomic
ensemble to the mechanical system.


title:
Theory of near-field matter wave interference beyond the eikonal
  approximation

abstract:
  A generalized description of Talbot-Lau interference with matter waves is
presented, which accounts for arbitrary grating interactions and realistic beam
characteristics. The dispersion interaction between the beam particles and the
optical elements strongly influences the interference pattern in this
near-field effect, and it is known to dominate the fringe visibility if
increasingly massive and complex particles are used. We provide a general
description of the grating interaction process by combining semiclassical
scattering theory with a phase space formulation. It serves to systematically
improve the eikonal approximation used so far, and to assess its regime of
validity.


title:
Exceptional Sensitivity to Neutrino Parameters with a Two Baseline
  Beta-Beam Set-up

abstract:
  We examine the reach of a Beta-beam experiment with two detectors at
carefully chosen baselines for exploring neutrino mass parameters. Locating the
source at CERN, the two detectors and baselines are: (a) a 50 kton iron
calorimeter (ICAL) at a baseline of around 7150 km which is roughly the magic
baseline, e.g., ICAL@INO, and (b) a 50 kton Totally Active Scintillator
Detector at a distance of 730 km, e.g., at Gran Sasso. We choose 8B/8Li source
ions with a boost factor \gamma of 650 for the magic baseline while for the
closer detector we consider 18Ne/6He ions with a range of Lorentz boosts. We
find that the locations of the two detectors complement each other leading to
an exceptional high sensitivity. With \gamma=650 for 8B/8Li and \gamma=575 for
18Ne/6He and total luminosity corresponding to 5\times (1.1 \times 10^{18}) and
5\times (2.9\times 10^{18}) useful ion decays in neutrino and antineutrino
modes respectively, we find that our two detector set-up can probe maximal CP
violation and establish the neutrino mass ordering if \sin^22\theta_{13} is
1.4\times 10^{-4} and 2.7\times 10^{-4}, respectively, or more. The sensitivity
reach for \sin^22\theta_{13} itself is 5.5 \times 10^{-4}. With a factor of 10
higher luminosity, the corresponding \sin^22\theta_{13} reach of this set-up
would be 1.8\times 10^{-5}, 4.6\times 10^{-5} and 5.3\times 10^{-5}
respectively for the above three performance indicators. CP violation can be
discovered for 64% of the possible \delta_{CP} values for \sin^22\theta_{13}
\geq 10^{-3} (\geq 8\times 10^{-5}), for the standard luminosity (10 times
enhanced luminosity). Comparable physics performance can be achieved in a
set-up where data from CERN to INO@ICAL is combined with that from CERN to the
Boulby mine in United Kingdom, a baseline of 1050 km.


title:
Group structure of the integration-by-part identities and its
  application to the reduction of multiloop integrals

abstract:
  The excessiveness of integration-by-part (IBP) identities is discussed. The
Lie-algebraic structure of the IBP identities is used to reduce the number of
the IBP equations to be considered. It is shown that Lorentz-invariance (LI)
identities do not bring any information additional to that contained in the IBP
identities, and therefore, can be discarded.


title: Crossovers from parity conserving to directed percolation universality

abstract:
  The crossover behavior of various models exhibiting phase transition to
absorbing phase with parity conserving class has been investigated by numerical
simulations and cluster mean-field method. In case of models exhibiting Z_2
symmetric absorbing phases (the NEKIMCA and Grassberger's A stochastic cellular
automaton) the introduction of an external symmetry breaking field causes a
crossover to kink parity conserving models characterized by dynamical scaling
of the directed percolation (DP) and the crossover exponent: 1/\phi ~ 0.53(2).
In case an even offspringed branching and annihilating random walk model (dual
to NEKIMCA) the introduction of spontaneous particle decay destroys the parity
conservation and results in a crossover to the DP class characterized by the
crossover exponent: 1/\phi\simeq 0.205(5). The two different kinds of crossover
operators can't be mapped onto each other and the resulting models show a
diversity within the DP universality class in one dimension. These
'sub-classes' differ in cluster scaling exponents.


title:
Generalized SURE for Exponential Families: Applications to
  Regularization

abstract:
  Stein's unbiased risk estimate (SURE) was proposed by Stein for the
independent, identically distributed (iid) Gaussian model in order to derive
estimates that dominate least-squares (LS). In recent years, the SURE criterion
has been employed in a variety of denoising problems for choosing
regularization parameters that minimize an estimate of the mean-squared error
(MSE). However, its use has been limited to the iid case which precludes many
important applications. In this paper we begin by deriving a SURE counterpart
for general, not necessarily iid distributions from the exponential family.
This enables extending the SURE design technique to a much broader class of
problems. Based on this generalization we suggest a new method for choosing
regularization parameters in penalized LS estimators. We then demonstrate its
superior performance over the conventional generalized cross validation
approach and the discrepancy method in the context of image deblurring and
deconvolution. The SURE technique can also be used to design estimates without
predefining their structure. However, allowing for too many free parameters
impairs the performance of the resulting estimates. To address this inherent
tradeoff we propose a regularized SURE objective. Based on this design
criterion, we derive a wavelet denoising strategy that is similar in sprit to
the standard soft-threshold approach but can lead to improved MSE performance.


title:
Cross-Molecular Coupling in Combined Photoassociation and Feshbach
  Resonances

abstract:
  We model combined photoassociation and Feshbach resonances in a Bose-Einstein
condensate. When the magnetic field is far-off resonance, cross coupling
between the two target molecules--enabled by the shared dissociation
continuum--leads to an anomalous dispersive shift in the position of laser
resonance, as well as unprecedented elimination and enhancement of resonant
photoassociation via quantum interference. For off-resonant lasers, a
dispersive shift and quantum interference appear similarly in resonant
three-body Feshbach losses, except that the Feshbach node is tunable with
intensity.


title: Geodesics in large planar maps and in the Brownian map

abstract:
  We study geodesics in the random metric space called the Brownian map, which
appears as the scaling limit of large planar maps. In particular, we completely
describe geodesics starting from the distinguished point called the root, and
we characterize the set S of all points that are connected to the root by more
than one geodesic. The set S is dense in the Brownian map and homeomorphic to a
non-compact real tree. Furthermore, for every x in S, the number of distinct
geodesics from x to the root is equal to the number of connected components of
the complement of {x} in S. In particular, points of the Brownian map can be
connected to the root by at most three distinct geodesics. Our results have
applications to the behavior of geodesics in large planar maps.


title:
Comparison of Geant4 hadron generation with data from the interactions
  with beryllium nuclei of +8.9 GeV/c protons and pions, and of -8 GeV/c pions

abstract:
  Hadron generation in the Geant4 simulation tool kit is compared with
inclusive spectra of secondary protons and pions from the interactions with
beryllium nuclei of +8.9 GeV/c protons and pions, and of -8.0 GeV/c pions. The
data were taken in 2002 at the CERN Proton Synchrotron with the HARP
spectrometer. We report on significant disagreements between data and simulated
data especially in the polar-angle distributions of secondary protons and
pions.


title: Real Paley-Wiener theorems and local spectral radius formulas

abstract:
  We systematically develop real Paley-Wiener theory for the Fourier transform
on R^d for Schwartz functions, L^p-functions and distributions, in an
elementary treatment based on the inversion theorem. As an application, we show
how versions of classical Paley-Wiener theorems can be derived from the real
ones via an approach which does not involve domain shifting and which may be
put to good use for other transforms of Fourier type as well. An explanation is
also given why the easily applied classical Paley-Wiener theorems are unlikely
to be able to yield information about the support of a function or distribution
which is more precise than giving its convex hull, whereas real Paley-Wiener
theorems can be used to reconstruct the support precisely, albeit at the cost
of combinatorial complexity. We indicate a possible application of real
Paley-Wiener theory to partial differential equations in this vein and
furthermore we give evidence that a number of real Paley-Wiener results can be
expected to have an interpretation as local spectral radius formulas. A
comprehensive overview of the literature on real Paley-Wiener theory is
included.


title: Gauge-invariant ground state for canonically quantized Yang-Mills theory

abstract:
  We use Hamilton-Jacobi theory to construct a gauge-invariant zero-energy
candidate ground state for canonically quantized Yang-Mills theory with a
"nonlinear normal" factor ordering, generalizing an analogous ordering
introduced by Moncrief and Ryan for problems with finitely many degrees of
freedom. Invariance under spatial rotations and translations is immediate;
boost invariance remains under investigation. The motivation is to find a model
for constructing a candidate ground state in general relativity, canonically
quantized a la the Ashtekar variables. We seek to avoid replicating some of the
more troublesome features of the Kodama state, inherited from the Chern-Simons
state.


title:
A Proposal of Multigrid Methods for Hermitian Positive Definite Linear
  Systems enjoying an order relation

abstract:
  Given a multigrid procedure for linear systems with coefficient matrices
$A_n$, we discuss the optimality of a related multigrid procedure with the same
smoother and the same projector, when applied to properly related algebraic
problems with coefficient matrices $B_n$: we assume that both $A_n$ and $B_n$
are positive definite with $A_n\le \vartheta B_n$, for some positive
$\vartheta$ independent of $n$. In this context we prove the Two-Grid method
optimality. We apply this elementary strategy for designing a multigrid
solution for modifications of multilevel structured (Toeplitz, circulants,
Hartley, sine ($\tau$ class) and cosine algebras) linear systems, in which the
coefficient matrix is banded in a multilevel sense and Hermitian positive
definite. In such a way, several linear systems arising from the approximation
of integro-differential equations with various boundary conditions can be
efficiently solved in linear time (with respect to the size of the algebraic
problem). Some numerical experiments are presented and discussed, both with
respect to Two-Grid and multigrid procedures.


title: Gamma Rays from Centaurus A

abstract:
  Centaurus A, the cosmic ray accelerator a few Mpc away from us is possibly
one of the nearest sources of extremely high energy cosmic rays. We investigate
whether the gamma ray data currently available from Centaurus A in the GeV-TeV
energy band can be explained with only proton proton interactions. We show that
for a single power law proton spectrum, mechanisms of $\gamma$-ray production
other than proton proton interactions are needed inside this radio-galaxy to
explain the gamma ray flux observed by EGRET, upper limits by
H.E.S.S./CANGAROO-III and the correlated extremely energetic cosmic ray events
observed by the Pierre Auger experiment. In future with better $\gamma$-ray
data, simultaneous observation with $\gamma$-ray and cosmic ray detectors, it
would be possible to carry out such studies on different sources in more
detail.


title:
Scaling limits of a tagged particle in the exclusion process with
  variable diffusion coefficient

abstract:
  We prove a law of large numbers and a central limit theorem for a tagged
particle in a symmetric simple exclusion process in the one-dimensional lattice
with variable diffusion coefficient. The scaling limits are obtained from a
similar result for the current through -1/2 for a zero-range process with bond
disorder. For the CLT, we prove convergence to a fractional Brownian motion of
Hurst exponent 1/4.


title: Three Dimensional Corners: A Box Norm Proof

abstract:
  In an additive group (G,+), a three-dimensional corner is the four points g,
g+d(1,0,0), g+d(0,1,0), g+d(0,0,1), where g is in G^3, and d is a non-zero
element of G. The Ramsey number of interest is R_3(G) the maximal cardinality
of a subset of G^3 that does not contain a three-dimensional corner.
Furstenberg and Katznelson have shown R_3(Z_N) is little-o of N^3, and in fact
the corresponding result holds in all dimensions, a result that is a far
reaching extension of the Szemeredi Theorem. We give a new proof of the finite
field version of this fact, a proof that is a common generalization of the
Gowers proof of Szemeredi's Theorem for four term progressions, and the result
of Shkredov on two-dimensional corners. The principal tool are the Gowers Box
Norms.


title: Torsion Invariants for Families

abstract:
  We give an overview over the higher torsion invariants of Bismut-Lott,
Igusa-Klein and Dwyer-Weiss-Williams, including some more or less recent
developments.


title:
A narrow-linewidth external cavity quantum dot laser for high-resolution
  spectroscopy in the near-infrared and yellow spectral ranges

abstract:
  We demonstrate a diode laser system which is suitable for high-resolution
spectroscopy in the 1200 nm and yellow spectral ranges. It is based on a
two-facet quantum dot chip in a Littrow-type external cavity configuration. The
laser is tunable in the range 1125 -1280 nm, with an output power of more than
200 mW and exhibits a free-running linewidth of 200 kHz. Amplitude and
frequency noise were characterized, including the dependence of frequency noise
on the cavity length. Frequency stabilization to a high-finesse reference
cavity is demonstrated reducing the linewidth to about 20 - 30 kHz. Yellow
light (> 3 mW) at 578 nm was generated by frequency doubling in an enhancement
cavity containing a PPLN crystal. The source has potential application for
precision spectroscopy of ultra-cold Yb atoms and molecular hydrogen ions.


title: Quantum reflection: The invisible quantum barrier

abstract:
  We construct the invisible quantum barrier which represents the phenomenon of
quantum reflection using the available data. We use the Abel equation to invert
the data. The resulting invisible quantum barrier is double-valued in both
axes. We study this invisible barrier in the case of atom and Bose-Einstein
Condensate reflection from a solid silicon surface. A time-dependent,
one-spatial dimension Gross-Pitaevskii equation is solved for the BEC case. We
found that the BEC behaves very similarly to the single atom except for size
effects, which manifest themselves in a maximum in the reflectivity at small
distances from the wall. The effect of the atom-atom interaction on the BEC
reflection and correspondingly on the invisible barrier is found to be
appreciable at low velocities and comparable to the finite size effect. The
trapping of ultracold atom or BEC between two walls is discussed.


title: Experiments in Model-Checking Optimistic Replication Algorithms

abstract:
  This paper describes a series of model-checking experiments to verify
optimistic replication algorithms based on Operational Transformation (OT)
approach used for supporting collaborative edition. We formally define, using
tool UPPAAL, the behavior and the main consistency requirement (i.e.
convergence property) of the collaborative editing systems, as well as the
abstract behavior of the environment where these systems are supposed to
operate. Due to data replication and the unpredictable nature of user
interactions, such systems have infinitely many states. So, we show how to
exploit some features of the UPPAAL specification language to attenuate the
severe state explosion problem. Two models are proposed. The first one, called
concrete model, is very close to the system implementation but runs up against
a severe explosion of states. The second model, called symbolic model, aims to
overcome the limitation of the concrete model by delaying the effective
selection and execution of editing operations until the construction of
symbolic execution traces of all sites is completed. Experimental results have
shown that the symbolic model allows a significant gain in both space and time.
Using the symbolic model, we have been able to show that if the number of sites
exceeds 2 then the convergence property is not satisfied for all OT algorithms
considered here. A counterexample is provided for every algorithm.


title:
A systematic phenomenological study of the $\cos 2 \phi$ asymmetry in
  unpolarized semi--inclusive DIS

abstract:
  We study the $\cos 2 \phi$ azimuthal asymmetry in unpolarized semi-inclusive
DIS, taking into account both the perturbative contribution (gluon emission and
splitting) and the non perturbative effects arising from intrinsic transverse
motion and transverse spin of quarks. In particular we explore the possibility
to extract from $<\cos 2 \phi>$ some information about the Boer--Mulders
function $h_1^{\perp}$, which represents a transverse--polarization asymmetry
of quarks inside an unpolarized hadron. Predictions are presented for the
HERMES, COMPASS and JLab kinematics, where $<\cos 2 \phi>$ is dominated by the
kinematical higher--twist contribution, and turns to be of order of few
percent. We show that a larger asymmetry in $\pi^-$ production, compared to
$\pi^+$ production, would represent a signature of the Boer--Mulders effect.


title: A Model of Heat Conduction

abstract:
  We define a deterministic ``scattering'' model for heat conduction which is
continuous in space, and which has a Boltzmann type flavor, obtained by a
closure based on memory loss between collisions. We prove that this model has,
for stochastic driving forces at the boundary, close to Maxwellians, a unique
non-equilibrium steady state.

categories: math-ph cond-mat.stat-mech math.MP nlin.CD


title: Quantum Dynamics in the Thermodynamic Limit

abstract:
  The description of spontaneous symmetry breaking that underlies the
connection between classically ordered objects in the thermodynamic limit and
their individual quantum mechanical building blocks is one of the cornerstones
of modern condensed matter theory and has found applications in many different
areas of physics. The theory of spontaneous symmetry breaking however, is
inherently an equilibrium theory, which does not address the dynamics of
quantum systems in the thermodynamic limit. Here, we will use the example of a
particular antiferromagnetic model system to show that the presence of a
so-called thin spectrum of collective excitations with vanishing energy -one of
the well-known characteristic properties shared by all symmetry-breaking
objects- can allow these objects to also spontaneously break time-translation
symmetry in the thermodynamic limit. As a result, that limit is found to be
able, not only to reduce quantum mechanical equilibrium averages to their
classical counterparts, but also to turn individual-state quantum dynamics into
classical physics. In the process, we find that the dynamical description of
spontaneous symmetry breaking can also be used to shed some light on the
possible origins of Born's rule. We conclude by describing an experiment on a
condensate of exciton polaritons which could potentially be used to
experimentally test the proposed mechanism.


title:
Quark-meson coupling model for antikaon condensation in neutron star
  matter with strong magnetic fields

abstract:
  We study the effects of strong magnetic fields on antikaon condensation in
neutron star matter using the quark-meson coupling (QMC) model. The QMC model
describes a nuclear many-body system as nonoverlapping MIT bags in which quarks
interact through the self-consistent exchange of scalar and vector mesons in
the mean-field approximation. It is found that the presence of strong magnetic
fields alters the threshold density of antikaon condensation significantly. The
onset of $K^-$ condensation stronger depends on the magnetic field strength,
and it even shifts beyond the threshold of $\bar K^0$ condensation for
sufficiently strong magnetic fields. In the presence of strong magnetic fields,
the equation of state (EOS) becomes stiffer in comparison with the field-free
case. The softening of the EOS by antikaon condensation also depends on the
magnetic field strength, and it becomes less pronounced with increasing
magnetic field strength. The results of the QMC model are compared with those
obtained in a relativistic mean-field (RMF) model, and we find there are
quantitative differences between the results of the QMC and RMF models.


title:
Parameterized Low-distortion Embeddings - Graph metrics into lines and
  trees

abstract:
  We revisit the issue of low-distortion embedding of metric spaces into the
line, and more generally, into the shortest path metric of trees, from the
parameterized complexity perspective.Let $M=M(G)$ be the shortest path metric
of an edge weighted graph $G=(V,E)$ on $n$ vertices. We describe algorithms for
the problem of finding a low distortion non-contracting embedding of $M$ into
line and tree metrics.
  We give an $O(nd^4(2d+1)^{2d})$ time algorithm that for an unweighted graph
metric $M$ and integer $d$ either constructs an embedding of $M$ into the line
with distortion at most $d$, or concludes that no such embedding exists. We
find the result surprising, because the considered problem bears a strong
resemblance to the notoriously hard Bandwidth Minimization problem which does
not admit any FPT algorithm unless an unlikely collapse of parameterized
complexity classes occurs.
  We show that our algorithm can also be applied to construct small distortion
embeddings of weighted graph metrics. The running time of our algorithm is
$O(n(dW)^4(2d+1)^{2dW})$ where $W$ is the largest edge weight of the input
graph. We also show that deciding whether a weighted graph metric $M(G)$ with
maximum weight $W < |V(G)|$ can be embedded into the line with distortion at
most $d$ is NP-Complete for every fixed rational $d \geq 2$. This rules out any
possibility of an algorithm with running time $O((nW)^{h(d)})$ where $h$ is a
function of $d$ alone.
  We generalize the result on embedding into the line by proving that for any
tree $T$ with maximum degree $\Delta$, embedding of $M$ into a shortest path
metric of $T$ is FPT, parameterized by $(\Delta,d)$.


title: On the size of identifying codes in binary hypercubes

abstract:
  We consider identifying codes in binary Hamming spaces F^n, i.e., in binary
hypercubes. The concept of identifying codes was introduced by Karpovsky,
Chakrabarty and Levitin in 1998. Currently, the subject forms a topic of its
own with several possible applications, for example, to sensor networks.
  Let C be a subset of F^n. For any subset X of F^n, denote by I_r(X)=I_r(C;X)
the set of elements of C within distance r from at least one x in X. Now C is
called an (r,<= l)-identifying code if the sets I_r(X) are distinct for all
subsets X of size at most l. We estimate the smallest size of such codes with
fixed l and r/n converging to some number rho in (0,1). We further show the
existence of such a code of size O(n^{3/2}) for every fixed l and r slightly
less than n/2, and give for l=2 an explicit construction of small such codes
for r the integer part of n/2-1 (the largest possible value).


title: Limits to the planet candidate GJ 436c

abstract:
  We report on H-band, ground-based observations of a transit of the hot
Neptune GJ 436b. Once combined to achieve sampling equivalent to archived
observations taken with Spitzer, our measurements reach comparable precision
levels. We analyze both sets of observations in a consistent way, and measure
the rate of orbital inclination change to be of 0.02+/-0.04 degrees in the time
span between the two observations (253.8 d, corresponding to 0.03+/-0.05
degrees/yr if extrapolated). This rate allows us to put limits on the relative
inclination between the two planets by performing simulations of planetary
systems, including a second planet, GJ 436c, whose presence has been recently
suggested (Ribas et al. 2008). The allowed inclinations for a 5 M_E super-Earth
GJ 436c in a 5.2 d orbit are within ~7 degrees of the one of GJ 436b; for
larger differences the observed inclination change can be reproduced only
during short sections (<50%) of the orbital evolution of the system. The
measured times of three transit centers of the system do not show any departure
from linear ephemeris, a result that is only reproduced in <1% of the simulated
orbits. Put together, these results argue against the proposed planet candidate
GJ 436c.


title: Torsion dans un produit de courbes elliptiques

abstract:
  Let $A$ be an abelian variety defined over a number field $K$, the number of
torsion points rational over a finite extension $L$ is bounded polynomially in
terms of the degree $[L:K]$. We formulate a question suggesting the optimal
exponent for this bound in terms of the dimension of the Mumford-Tate groups of
the abelian subvarieties of $A$; we study the behaviour under product and then
give a positive answer to our question when $A$ is the product of elliptic
curves.


title: The Clustering Coefficient of a Scale-Free Random Graph

abstract:
  We consider a random graph process in which, at each time step, a new vertex
is added with m out-neighbours, chosen with probabilities proportional to their
degree plus a strictly positive constant. We show that the expectation of the
clustering coefficient of the graph process is asymptotically proportional to
log n/n. Bollob\'as and Riordan have previously shown that when the constant is
zero, the same expectation is asymptotically proportional to ((log n)^2)/n.


title:
A Simple Sample Size Formula for Estimating Means of Poisson Random
  Variables

abstract:
  In this paper, we derive an explicit sample size formula based a mixed
criterion of absolute and relative errors for estimating means of Poisson
random variables.


title:
The initial-final mass relationship of white dwarfs revisited: effect on
  the luminosity function and mass distribution

abstract:
  The initial-final mass relationship connects the mass of a white dwarf with
the mass of its progenitor in the main-sequence. Although this function is of
fundamental importance to several fields in modern astrophysics, it is not well
constrained either from the theoretical or the observational points of view. In
this work we revise the present semi-empirical initial-final mass relationship
by re-evaluating the available data. The distribution obtained from grouping
all our results presents a considerable dispersion, which is larger than the
uncertainties. We have carried out a weighted least-squares linear fit of these
data and a careful analysis to give some clues on the dependence of this
relationship on some parameters such as metallicity or rotation. The
semi-empirical initial-final mass relationship arising from our study covers
the range of initial masses from 1.0 to 6.5 M_sun, including in this way the
low-mass domain, poorly studied until recently. Finally, we have also performed
a test of the initial-final mass relationship by studying its effect on the
luminosity function and on the mass distribution of white dwarfs. This was done
by using different initial-final mass relationships from the literature,
including the expression derived in this work, and comparing the results
obtained with the observational data from the Palomar Green Survey and the
Sloan Digital Sky Survey (SDSS). We find that the semi-empirical initial-final
mass relationship derived here gives results in good agreement with the
observational data, especially in the case of the white dwarf mass
distribution.


title: Anisotropic growth of random surfaces in 2+1 dimensions

abstract:
  We construct a family of stochastic growth models in 2+1 dimensions, that
belong to the anisotropic KPZ class. Appropriate projections of these models
yield 1+1 dimensional growth models in the KPZ class and random tiling models.
We show that correlation functions associated to our models have determinantal
structure, and we study large time asymptotics for one of the models.
  The main asymptotic results are: (1) The growing surface has a limit shape
that consists of facets interpolated by a curved piece. (2) The one-point
fluctuations of the height function in the curved part are asymptotically
normal with variance of order ln(t) for time t>>1. (3) There is a map of the
(2+1)-dimensional space-time to the upper half-plane H such that on space-like
submanifolds the multi-point fluctuations of the height function are
asymptotically equal to those of the pullback of the Gaussian free (massless)
field on H.

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


title:
Distance graphs in vector spaces over finite fields, coloring and
  pseudo-randomness

abstract:
  In this paper we systematically study various properties of the distance
graph in ${\Bbb F}_q^d$, the $d$-dimensional vector space over the finite field
${\Bbb F}_q$ with $q$ elements. In the process we compute the diameter of
distance graphs and show that sufficiently large subsets of $d$-dimensional
vector spaces over finite fields contain every possible finite configurations.


title: Absolute continuity for some one-dimensional processes

abstract:
  We introduce an elementary method for proving the absolute continuity of the
time marginals of one-dimensional processes. It is based on a comparison
between the Fourier transform of such time marginals with those of the one-step
Euler approximation of the underlying process. We obtain some absolute
continuity results for stochastic differential equations with H\"{o}lder
continuous coefficients. Furthermore, we allow such coefficients to be random
and to depend on the whole path of the solution. We also show how it can be
extended to some stochastic partial differential equations and to some
L\'{e}vy-driven stochastic differential equations. In the cases under study,
the Malliavin calculus cannot be used, because the solution in generally not
Malliavin differentiable.


title:
High p_T Triggered Delta-eta,Delta-phi Correlations over a Broad Range
  in Delta-eta

abstract:
  The first measurement of pseudorapidity (Delta-eta) and azimuthal angle
(Delta-phi) correlations between high transverse momentum charged hadrons (p_T
> 2.5 GeV/c) and all associated particles is presented at both short- (small
Delta-eta) and long-range (large Delta-eta) over a continuous pseudorapidity
acceptance (-4<Delta-eta<2). In these proceedings, the various near- and
away-side features of the correlation structure are discussed as a function of
centrality in Au+Au collisions measured by PHOBOS at sqrt(s_NN)=200 GeV. In
particular, this measurement allows a much more complete determination of the
longitudinal extent of the ridge structure, first observed by the STAR
collaboration over a limited eta range. In central collisions the ridge
persists to at least Delta-eta=4, diminishing in magnitude as collisions become
more peripheral until it disappears around Npart=80.


title: Order Parameters and Phase Diagrams of Multiferroics

abstract:
  The symmetry properties, order parameters, and magnetoelectric phase diagrams
of multiferroics are discussed. After brief reviews of Ni$_3$V$_2$O$_8$,
TbMnO$_3$, and RbFe(MoO$_4$)$_2$, we present a detailed analysis of
RMn$_2$O$_5$ (with R=Y, Ho, Dy, Er, Tb, Tm).


title:
Effect of anisotropic hopping on the Bose Hubbard model phase diagram:
  strong-coupling perturbation theory on a square lattice

abstract:
  There has been a recent resurgence of experimental efforts to quantitatively
determine the phase diagram of the Bose Hubbard model by carefully analyzing
experiments with ultracold bosonic atoms on an optical lattice. In many
realizations of these experiments, the hopping amplitudes are not homogeneous
throughout the lattice, but instead, the lattice has an anisotropy where
hopping along one direction is not exactly equal to hopping along a
perpendicular direction. In this contribution, we examine how an anisotropy in
the hopping matrix elements affects the Mott lobes of the Bose Hubbard model.
For weak anisotropy, we find the phase diagram is only slightly modified when
expressed in terms of the average hopping, while for strong anisotropy, one
expects to ultimately see dimensional crossover effects.


title:
Hidden quantum spin gap state in the static stripe phase of
  La$_{2-x}$Sr$_{x}$CuO$_{4}$

abstract:
  Low energy spin excitations were investigated in the static stripe phase of
La_{2-x}Sr_xCuO_4 using elastic and inelastic neutron scattering on single
crystals. For x = 1/8 in which long-range static stripe order exists, an energy
gap of E_g = 4 meV exists in the excitation spectrum in addition to strong
quasi-elastic, incommensurate spin fluctuations associated with the static
stripes. When x increases, the spectral weight of the spin fluctuations shifts
from the quasi-elastic continuum to the excitation spectrum above E_g. The
dynamic correlation length as a function of energy and the temperature
evolution of the energy spectrum suggest a phase separation of two distinct
magnetic phases in real space.


title:
The quark-gluon vertex in Landau gauge QCD: Its role in dynamical chiral
  symmetry breaking and quark confinement

abstract:
  The infrared behavior of the quark-gluon vertex of quenched Landau gauge QCD
is studied by analyzing its Dyson-Schwinger equation. Building on previously
obtained results for Green functions in the Yang-Mills sector we analytically
derive the existence of power-law infrared singularities for this vertex. We
establish that dynamical chiral symmetry breaking leads to the self-consistent
generation of components of the quark-gluon vertex forbidden when chiral
symmetry is forced to stay in the Wigner-Weyl mode. In the latter case the
running strong coupling assumes an infrared fixed point. If chiral symmetry is
broken, either dynamically or explicitely, the running coupling is infrared
divergent. Based on a truncation for the quark-gluon vertex Dyson-Schwinger
equation which respects the analytically determined infrared behavior numerical
results for the coupled system of the quark propagator and vertex
Dyson-Schwinger equation are presented. The resulting quark mass function as
well as the vertex function show only a very weak dependence on the current
quark mass in the deep infrared. From this we infer by an analysis of the
quark-quark scattering kernel a linearly rising quark potential with an almost
mass independent string tension in the case of broken chiral symmetry.
Enforcing chiral symmetry does lead to a Coulomb type potential. Therefore we
conclude that chiral symmetry breaking and confinement are closely related.
Furthermore we discuss aspects of confinement as the absence of long-range
van-der-Waals forces and Casimir scaling. An examination of experimental data
for quarkonia provides further evidence for the viability of the presented
mechanism for quark confinement in the Landau gauge.


title: Lattice susceptibility for 2D Hubbard Model within dual fermion method

abstract:
  In this paper, we present details of the dual fermion (DF) method to study
the non-local correction to single site DMFT. The DMFT two-particle Green's
function is calculated using continuous time quantum monte carlo (CT-QMC)
method. The momentum dependence of the vertex function is analyzed and its
renormalization based on the Bethe-Salpeter equation is performed in
particle-hole channel. We found a magnetic instability in both the dual and the
lattice fermions. The lattice fermion susceptibility is calculated at finite
temperature in this method and also in another recently proposed method, namely
dynamical vertex approximation (D$\Gamma$A). The comparison between these two
methods are presented in both weak and strong coupling region. Compared to the
susceptibility from quantum monte carlo (QMC) simulation, both of them gave
satisfied results.


title: Estimating Third-Order Moments for an Absorber Catalog

abstract:
  Thanks to the recent availability of large surveys, there has been renewed
interest in third-order correlation statistics. Measures of third-order
clustering are sensitive to the structure of filaments and voids in the
universe and are useful for studying large-scale structure. Thus, statistics of
these third-order measures can be used to test and constrain parameters in
cosmological models. Third-order measures such as the three-point correlation
function are now commonly estimated for galaxy surveys. Studies of third-order
clustering of absorption systems will complement these analyses. We define a
statistic, which we denote K, that measures third-order clustering of a data
set of point observations and focus on estimating this statistic for an
absorber catalog. The statistic K can be considered a third-order version of
the second-order Ripley K-function and allows one to study the abundance of
various configurations of point triplets. In particular, configurations
consisting of point triplets that lie close to a straight line can be examined.
Studying third-order clustering of absorbers requires consideration of the
absorbers as a three-dimensional process, observed on QSO lines of sight that
extend radially in three-dimensional space from Earth. Since most of this
three-dimensional space is not probed by the lines of sight, edge corrections
become important. We use an analytical form of edge correction weights and
construct an estimator of the statistic K for use with an absorber catalog. We
show that with these weights, ratio-unbiased estimates of K can be obtained.
Results from a simulation study also verify unbiasedness and provide
information on the decrease of standard errors with increasing number of lines
of sight.


title:
Evolution with hole doping of the electronic excitation spectrum in the
  cuprate superconductors

abstract:
  The recent scanning tunnelling results of Alldredge et al on Bi-2212 and of
Hanaguri et al on Na-CCOC are examined from the perspective of the BCS/BEC
boson-fermion resonant crossover model for the mixed-valent HTSC cuprates. The
model specifies the two energy scales controlling the development of HTSC
behaviour and the dichotomy often now alluded to between nodal and antinodal
phenomena in the HTSC cuprates. Indication is extracted from the data as to how
the choice of the particular HTSC system sees these two basic energy scales
(cursive-U, the local pair binding energy and, Delta-sc, the nodal BCS-like gap
parameter) evolve with doping and change in degree of metallization of the
structurally and electronically perturbed mixed-valent environment.


title: Galois extensions for coquasi-Hopf algebras

abstract:
  The notions of Galois and cleft extensions are generalized for coquasi-Hopf
algebras. It is shown that such an extension over a coquasi-Hopf algebra is
cleft if and only if it is Galois and has the normal basis property. A
Schneider type theorem is proven for coquasi-Hopf algebras with bijective
antipode. As an application, we generalize Schauenburg's bialgebroid
construction for coquasi-Hopf algebras.


title:
Single Spin Asymmetry in Inclusive Hadron Production in pp Scattering
  from Collins Mechanism

abstract:
  We study the Collins mechanism contribution to the single transverse spin
asymmetry in inclusive hadron production in pp scattering p^{\uparrow}p\to \pi
X from the leading jet fragmentation. The azimuthal asymmetric distribution of
hadron in the jet leads to a single spin asymmetry for the produced hadron in
the Lab frame. The effect is evaluated in a transverse momentum dependent model
that takes into account the transverse momentum dependence in the fragmentation
process. We find the asymmetry is comparable in size to the experimental
observation at RHIC at \sqrt{s}=200 GeV.


title: Grid Diagrams and Legendrian Lens Space Links

abstract:
  Grid diagrams encode useful geometric information about knots in S^3. In
particular, they can be used to combinatorially define the knot Floer homology
of a knot K in S^3, and they have a straightforward connection to Legendrian
representatives of K in (S^3, \xi_\st), where \xi_\st is the standard, tight
contact structure. The definition of a grid diagram was extended to include a
description for links in all lens spaces, resulting in a combinatorial
description of the knot Floer homology of a knot K in L(p, q) for all p > 0. In
the present article, we explore the connection between lens space grid diagrams
and the contact topology of a lens space. Our hope is that an understanding of
grid diagrams from this point of view will lead to new approaches to the Berge
conjecture, which claims to classify all knots in S^3 upon which surgery yields
a lens space.


title:
Multivariate $p$-adic formal congruences and integrality of Taylor
  coefficients of mirror maps

abstract:
  We generalise Dwork's theory of $p$-adic formal congruences from the
univariate to a multi-variate setting. We apply our results to prove
integrality assertions on the Taylor coefficients of (multi-variable) mirror
maps. More precisely, with $\mathbf z=(z_1,z_2,...,z_d)$, we show that the
Taylor coefficients of the multi-variable series $q(\mathbf
z)=z_i\exp(G(\mathbf z)/F(\mathbf z))$ are integers, where $F(\mathbf z)$ and
$G(\mathbf z)+\log(z_i) F(\mathbf z)$, $i=1,2,...,d$, are specific solutions of
certain GKZ systems. This result implies the integrality of the Taylor
coefficients of numerous families of multi-variable mirror maps of Calabi-Yau
complete intersections in weighted projective spaces, as well as of many
one-variable mirror maps in the "Tables of Calabi-Yau equations"
[arXiv:math/0507430] of Almkvist, van Enckevort, van Straten and Zudilin. In
particular, our results prove a conjecture of Batyrev and van Straten in [Comm.
Math. Phys. 168 (1995), 493-533] on the integrality of the Taylor coefficients
of canonical coordinates for a large family of such coordinates in several
variables.


title:
Higgs Boson Exempt No-Scale Supersymmetry with a Neutrino Seesaw:
  Implications for Lepton Flavor Violation and Leptogenesis

abstract:
  Motivated by the observation of neutrino oscillations, we extend the Higgs
boson exempt no-scale supersymmetry model (HENS) by adding three heavy
right-handed neutrino chiral supermultiplets to generate the light neutrino
masses and mixings. The neutrino Yukawa couplings can induce new lepton flavor
violating couplings among the soft terms in the course of renormalization group
running down from the boundary scale. We study the effects this has on the
predictions for low-energy probes of lepton flavor violation(LFV). Heavy
right-handed neutrinos also provide a way to generate the baryon asymmetry
through leptogenesis. We find that consistency with LFV and leptogenesis puts
strong requirements on either the form of the Yukawa mass matrix or the
smallness of the Higgs up soft mass. In all cases, we generically expect that
new physics LFV is non-zero and can be found in a future experiment.


title:
Conductor inequalities and criteria for Sobolev-Lorentz two-weight
  inequalities

abstract:
  In this paper we present integral conductor inequalities connecting the
Lorentz p,q-(quasi)norm of a gradient of a function to a one-dimensional
integral of the p,q-capacitance of the conductor between two level surfaces of
the same function. These inequalities generalize an inequality obtained by the
second author in the case of the Sobolev norm. Such conductor inequalities lead
to necessary and sufficient conditions for Sobolev-Lorentz type inequalities
involving two arbitrary measures.


title: Small parts in the Bernoulli sieve

abstract:
  Sampling from a random discrete distribution induced by a `stick-breaking'
process is considered. Under a moment condition, it is shown that the
asymptotics of the sequence of occupancy numbers, and of the small-parts counts
(singletons, doubletons, etc) can be read off from a limiting model involving a
unit Poisson point process and a self-similar renewal process on the halfline.


title: Herwig++ 2.2 Release Note

abstract:
  A new release of the Monte Carlo program Herwig++ (version 2.2) is now
available. This version includes a number of improvements including: matrix
elements for the production of an electroweak gauge boson, W and Z, in
association with a jet; several new processes for Higgs production in
association with an electroweak gauge boson; and the matrix element correction
for QCD radiation in Higgs production via gluon fusion.


title: Gravitation as a Casimir interaction

abstract:
  Gravitation is considered to be one of the four fundamental interactions in
nature. However, one has so far failed to observe the graviton, the quantum
particle that is believed to transmit the gravitational force at a distance -
the analogue to the photon in electromagnetism. Maybe it is now time to
re-evaluate the status of the gravitation as a fundamental interaction. Here,
we propose a completely new interpretation of gravitation. In this description
the gravitational force is no longer a fundamental force. It is an induced
force, a dispersion force, and the analogue to the Casimir force in
electromagnetism. The fundamental force is in our description a force between
particles with a parabolic interaction potential. In our model the nucleons are
made up from these particles. We find the retarded dispersion force between
these composite particles has the correct distance dependence, 1/r. If this
interpretation is correct it has a broad range of implications. Our view on the
fundamental concept mass is altered; our view on the expansion of the Universe
may change.


title:
Escorted Free Energy Simulations: Improving Convergence by Reducing
  Dissipation

abstract:
  Nonequilibrium, ``fast switching'' estimates of equilibrium free energy
differences, Delta F, are often plagued by poor convergence due to dissipation.
We propose a method to improve these estimates by generating trajectories with
reduced dissipation. Introducing an artificial flow field that couples the
system coordinates to the external parameter driving the simulation, we derive
an identity for Delta F in terms of the resulting trajectories. When the flow
field effectively escorts the system along a near-equilibrium path, the free
energy estimate converges efficiently and accurately. We illustrate our method
on a model system, and discuss the general applicability of our approach.


title: Finite width of quasi-static shear bands

abstract:
  I study the average deformation rate of an amorphous material submitted to an
external uniform shear strain rate, in the geometry known as the split-bottom
configuration. The material is described using a stochastic model of plasticity
at a mesoscopic scale. A shear band is observed to start at the split point at
the bottom, and widen progressively towards the surface. In a two-dimensional
geometry the average statistical properties of the shear band look similar to
those of the directed polymer model. In particular, the surface width of the
shear band is found to scale with the system height H as H^q with q=0.68 +/-
0.02. In more realistic three dimensional simulations the exponent changes to
q=0.60 +/- 0.02 and the bulk profile of the width of the shear band is closer
to a quarter of circle, as it was observed to be the case in recent simulations
of granular materials.


title: Beyond Chaos

abstract:
  The first part of this paper defines recursive interactions by means of
logistic functions and derives a general result on the way interacting systems
evolve in attractors. It also defines the notion of coevolution trajectory and
presents a new family of attractors: orbital attractors (including single,
irregular, folded, complex and discontinuous orbits). The second part
summarizes the results of a first experimental analysis of recursive
interactions in both binary and multiple interactions. Among other results,
this analysis reveals that interacting systems may easily evolve from chaos to
order.


title:
On Competing Models of Coronal Heating and Solar Wind Acceleration: The
  Debate in '08

abstract:
  In preparation for lively debate at the May 2008 SPD/AGU Meeting in Fort
Lauderdale, this document attempts to briefly lay out my own view of the
evolving controversy over how the solar wind is accelerated. It is still
unknown to what extent the solar wind is fed by flux tubes that remain open
(and are energized by footpoint-driven wavelike fluctuations), and to what
extent much of the mass and energy is input more intermittently from closed
loops into the open-field regions. It may turn out that a combination of the
two ideas is needed to explain the full range of observed solar wind phenomena.


title: Spin-state polaron in lightly hole-doped LaCoO_3

abstract:
  Inelastic neutron scattering (INS), electron spin (ESR) and nuclear magnetic
resonance (NMR) measurements were employed to establish the origin of the
strong magnetic signal in lightly hole-doped La_{1-x}Sr_xCoO_3, x=0.002. Both,
INS and ESR low temperature spectra show intense excitations with large
effective g-factors ~10-18. NMR data indicate the creation of extended magnetic
clusters. From the Q-dependence of the INS magnetic intensity we conclude that
the observed anomalies are caused by the formation of octahedrally shaped
spin-state polarons comprising seven Co ions.


title:
The growth of human settlements during the Neolithic, clustering and
  food crisis

abstract:
  We present a stochastic two-population model that describes the migration and
growth of semi-sedentary foragers and sedentary farmers along a river valley
during the Neolithic transition. The main idea of this paper is that random
migration and transition from sedentary to foraging way of life and backward is
strongly coupled with the local crop production and the associated degradation
of land. We derive a non-linear integral equation for the population density
coupled with the equations for the density of soil nutrients and crop
production. Our model provides an explanation for the formation of human
settlements along a river valley. The numerical results show that the
individual farmers have a tendency for aggregation and clustering. We show that
the large-scale pattern is a transient phenomenon which eventually disappears
due to land degradation.


title:
Noncommutative Yang-Mills-Higgs actions from derivation-based
  differential calculus

abstract:
  Derivations of a noncommutative algebra can be used to construct differential
calculi, the so-called derivation-based differential calculi. We apply this
framework to a version of the Moyal algebra ${\cal{M}}$. We show that the
differential calculus, generated by the maximal subalgebra of the derivation
algebra of ${\cal{M}}$ that can be related to infinitesimal symplectomorphisms,
gives rise to a natural construction of Yang-Mills-Higgs models on ${\cal{M}}$
and a natural interpretation of the covariant coordinates as Higgs fields. We
also compare in detail the main mathematical properties characterizing the
present situation to those specific of two other noncommutative geometries,
namely the finite dimensional matrix algebra $M_n({\mathbb{C}})$ and the
algebra of matrix valued functions $C^\infty(M)\otimes M_n({\mathbb{C}})$. The
UV/IR mixing problem of the resulting Yang-Mills-Higgs models is also
discussed.


title:
Supersymmetric moduli of the SU(2) x R linear dilaton background and
  NS5-branes

abstract:
  We study several classes of marginal deformations of the conformal field
theory SU(2) x R. This theory describes the near-horizon region of a stack of
parallel and coincident NS5-branes and is related holographically to little
string theory. We investigate the supersymmetry properties of these
deformations and we elucidate their role in the context of holography. The
conformal field theory moduli space contains "non-holographic" operators that
do not seem to have a simple interpretation in little string theory.
Subsequently, we analyze several NS5-brane configurations in terms of SU(2) x R
deformations. We discuss in detail interesting phenomena, like the excision of
the strong coupling region associated with the linear dilaton and the
manifestation of the symmetries of an NS5-brane setup in the deforming
operators. Finally, we present a class of conformally hyperkaehler geometries
that arise as "non-holographic" deformations of SU(2) x R.


title:
N=4 superparticle and super Yang-Mills theory in USp(4) harmonic
  superspace

abstract:
  We study the N=4 harmonic superparticle model, both with and without central
charge and quantize it. Since the central charge breaks the U(4) R-symmetry
group of the N=4 superalgebra down to USp(4), we consider the superparticle
dynamics in N=4 harmonic superspace with USp(4)/(U(1)xU(1)) harmonic variables.
We show that the quantization of a massive superparticle with central charge
leads to a superfield realization of the N=4 massive vector multiplet in N=4
harmonic superspace. In the massless case without central charge the
superparticle quantization reproduces three different multiplets: the N=4 SYM
multiplet, the N=4 gravitino multiplet and N=4 supergravity multiplet. The SYM
multiplet is described by six analytic superfield strengths with different
types of analyticity. We show that these strengths solve the N=4 SYM
constraints and can be used for the construction of actions in N=4 harmonic
superspace.


title: Intelligence gathering by capturing the social processes within prisons

abstract:
  We present a prototype system that can be used to capture longitudinal
socialising processes by recording people's encounters in space. We argue that
such a system can usefully be deployed in prisons and other detention
facilities in order help intelligence analysts assess the behaviour or
terrorist and organised crime groups, and their potential relationships. Here
we present the results of a longitudinal study, carried out with civilians,
which demonstrates the capabilities of our system.


title: Visibly Tree Automata with Memory and Constraints

abstract:
  Tree automata with one memory have been introduced in 2001. They generalize
both pushdown (word) automata and the tree automata with constraints of
equality between brothers of Bogaert and Tison. Though it has a decidable
emptiness problem, the main weakness of this model is its lack of good closure
properties.
  We propose a generalization of the visibly pushdown automata of Alur and
Madhusudan to a family of tree recognizers which carry along their (bottom-up)
computation an auxiliary unbounded memory with a tree structure (instead of a
symbol stack). In other words, these recognizers, called Visibly Tree Automata
with Memory (VTAM) define a subclass of tree automata with one memory enjoying
Boolean closure properties. We show in particular that they can be determinized
and the problems like emptiness, membership, inclusion and universality are
decidable for VTAM. Moreover, we propose several extensions of VTAM whose
transitions may be constrained by different kinds of tests between memories and
also constraints a la Bogaert and Tison comparing brother subtrees in the tree
in input. We show that some of these classes of constrained VTAM keep the good
closure and decidability properties, and we demonstrate their expressiveness
with relevant examples of tree languages.


title: Particle phenomenology and Maldacena

abstract:
  A brief review is offered of employing Maldacena's AdS/CFT correspondence in
attempting to identify a model which extends to higher energy the standard
model of particle phenomenology.


title: Degeneracy loci of families of Dirac operators

abstract:
  Generalizing some results from R. Leung's thesis, we compute, in rational
cohomology, the Poincare dual of the degeneracy locus of the family of Dirac
operators parameterized by the moduli space of projectively anti-self-dual
$\SO(3)$ connections. This is the first step in a program to derive a relation
between the Donaldson and spin invariants.


title: From Deterministic Chaos to Anomalous Diffusion

abstract:
  This is an easy-to-read introduction to foundations of deterministic chaos,
deterministic diffusion and anomalous diffusion. The first part introduces to
deterministic chaos in one-dimensional maps in form of Ljapunov exponents and
dynamical entropies. The second part outlines the concept of deterministic
diffusion. Then the escape rate formalism for deterministic diffusion, which
expresses the diffusion coefficient in terms of the above two chaos quantities,
is worked out for a simple map. Part three explains basics of anomalous
diffusion by demonstrating the stochastic approach of continuous time random
walk theory for an intermittent map. As an example of experimental
applications, the anomalous dynamics of biological cell migration is discussed.


title:
Integral equalities for functions of unbounded spectral operators in
  Banach spaces

abstract:
  We investigate a limiting procedure for extending local integral operator
equalities to the global ones and to applying it to obtaining generalizations
of the Newton-Leibnitz formula for operator-valued maps for a wide class of
unbounded operators.


title: On Exchangeable Continuous Variable Systems

abstract:
  We investigate permutation-invariant continuous variable quantum states and
their covariance matrices. We provide a complete characterization of the latter
with respect to permutation-invariance, exchangeability and representing convex
combinations of tensor power states. On the level of the respective density
operators this leads to necessary criteria for all these properties which
become necessary and sufficient for Gaussian states. For these we use the
derived results to provide de Finetti-type theorems for various distance
measures.


title: Shuffling algorithm for boxed plane partitions

abstract:
  We introduce discrete time Markov chains that preserve uniform measures on
boxed plane partitions. Elementary Markov steps change the size of the box from
(a x b x c) to ((a-1) x (b+1) x c) or ((a+1) x (b-1) x c). Algorithmic
realization of each step involves O((a+b)c) operations. One application is an
efficient perfect random sampling algorithm for uniformly distributed boxed
plane partitions.
  Trajectories of our Markov chains can be viewed as random point
configurations in the three-dimensional lattice. We compute the bulk limits of
the correlation functions of the resulting random point process on suitable
two-dimensional sections. The limiting correlation functions define a
two-dimensional determinantal point processes with certain Gibbs properties.


title: Generalized kappa-deformed spaces, star-products, and their realizations

abstract:
  In this work we investigate generalized kappa-deformed spaces. We develop a
systematic method for constructing realizations of noncommutative (NC)
coordinates as formal power series in the Weyl algebra. All realizations are
related by a group of similarity transformations, and to each realization we
associate a unique ordering prescription. Generalized derivatives, the Leibniz
rule and coproduct, as well as the star-product are found in all realizations.
The star-product and Drinfel'd twist operator are given in terms of the
coproduct, and the twist operator is derived explicitly in special
realizations. The theory is applied to a Nappi-Witten type of NC space.