title:
Realistic modelling of quantum point contacts subject to high magnetic
  fields and with current bias at out of linear response regime

abstract:
  The electron and current density distributions in the close proximity of
quantum point contacts (QPCs) are investigated. A three dimensional Poisson
equation is solved self-consistently to obtain the electron density and
potential profile in the absence of an external magnetic field for gate and
etching defined devices. We observe the surface charges and their apparent
effect on the confinement potential, when considering the (deeply) etched QPCs.
In the presence of an external magnetic field, we investigate the formation of
the incompressible strips and their influence on the current distribution both
in the linear response and out of linear response regime. A spatial asymmetry
of the current carrying incompressible strips, induced by the large source
drain voltages, is reported for such devices in the non-linear regime.


title:
Anisotropic cosmological models with spinor and scalar fields and
  viscous fluid in presence of a $\Lambda$ term: qualitative solutions

abstract:
  The study of a self-consistent system of interacting spinor and scalar fields
within the scope of a Bianchi type I (BI) gravitational field in presence of a
viscous fluid and $\Lambda$ term has been carried out. The system of equations
defining the evolution of the volume scale of BI universe, energy density and
corresponding Hubble constant has been derived. The system in question has been
thoroughly studied qualitatively. Corresponding solutions are graphically
illustrated. The system in question is also studied from the view point of blow
up. It has been shown that the blow up takes place only in presence of
viscosity.


title: Coherent energy manipulation in single-neutron interferometry

abstract:
  We have observed the stationary interference oscillations of a
triple-entangled neutron state in an interferometric experiment. Time-dependent
interaction with two radio-frequency (rf) fields enables coherent manipulation
of an energy degree of freedom in a single neutron. The system is characterized
by a multiply entangled state governed by a Jaynes-Cummings Hamiltonian. The
experimental results confirm coherence of the manipulation as well as the
validity of the description.


title:
The Horizontal Branch of NGC 1851: Constraints on the Cluster
  Subpopulations

abstract:
  We investigate the distribution of stars along the Horizontal Branch of the
Galactic globular cluster NGC1851, to shed light on the progeny of the two
distinct Subgiant Branch populations harbored by this cluster. On the basis of
detailed synthetic Horizontal Branch modelling, we conclude that the two
subpopulations are distributed in different regions of the observed Horizontal
Branch: the evolved stars belonging to the bright Subgiant branch component are
confined in the red portion of the observed sequence, whereas the ones
belonging to the faint Subgiant branch component are distributed from the blue
to the red, populating also the RR Lyrae instability strip. Our simulations
strongly suggest that it is not possible to reproduce the observations assuming
that the two subpopulations lose the same amount of mass along the Red Giant
Branch. We warmly encourage empirical estimates of mass loss rates in Red Giant
stars belonging to this cluster.


title: Holographic Duals of Long Open Strings

abstract:
  We study the holographic map between long open strings, which stretch between
D-branes separated in the bulk space-time, and operators in the dual boundary
theory. We focus on a generalization of the Sakai-Sugimoto holographic model of
QCD, where the simplest chiral condensate involves an operator of this type.
Its expectation value is dominated by a semi-classical string worldsheet, as
for Wilson loops. We also discuss the deformation of the model by this
operator, and in particular its effect on the meson spectrum. This deformation
can be thought of as a generalization of a quark mass term to strong coupling.
It leads to the first top-down holographic model of QCD with a non-Abelian
chiral symmetry which is both spontaneously and explicitly broken, as in QCD.
Other examples we study include half-supersymmetric open Wilson lines, and
systems of D-branes ending on NS5-branes, which can be analyzed using
worldsheet methods.


title: SDSS 1507+02: A Halo Cataclysmic Variable?

abstract:
  We report a photometric and spectroscopic study of the peculiar cataclysmic
variable SDSS 1507+52. The star shows very deep eclipses on the 67 minute
orbital period, and those eclipses are easily separable into white-dwarf and
hot-spot components. This leads to tight constraints on binary parameters, with
M_1=0.83(8) solar masses, M_2=0.057(8) solar masses, R_1=0.0097(9) solar radii,
R_2=0.097(4) solar radii, q=0.069(2), and i=83.18(13) degrees. Such numbers
suggest possible membership among the WZ Sge stars, a common type of dwarf
nova. The spectroscopic behavior (strong and broad H emission, double-peaked
and showing a classic rotational disturbance during eclipse) is also typical.
But the star's orbital period is shockingly below the "period minimum" of
approximately 77 min which is characteristic of hydrogen-rich CVs; producing
such a strange binary will require some tinkering with the theory of
cataclysmic-variable evolution. The proper motion is also remarkably high for a
star of its distance, which we estimate from photometry and trigonometric
parallax as 230 +- 40 pc. This suggests a transverse velocity of 164 +- 30 km/s
- uncomfortably high if the star belongs to a Galactic-disk population. These
difficulties with understanding its evolution and space velocity can be solved
if the star belongs to a Galactic-halo population.


title:
Multidimensional delta-shock waves and the transportation and
  concentration processes

abstract:
  {\it $\delta$-Shock wave type solutions} in the multidimensional system of
conservation laws $$ \rho_t + \nabla\cdot(\rho F(U))=0, \qquad (\rho U)_t +
\nabla\cdot(\rho N(U))=0, \quad x\in \bR^n, $$ are studied, where $F=(F_j)$ is
a given vector field, $N=(N_{jk})$ is a given tensor field, $F_j, N_{kj}:\bR^n
\to \bR$, $j,k=1,...,n$; $\rho(x,t)\in \bR$, $U(x,t)\in \bR^n$. The well-known
particular cases of this system are zero-pressure gas dynamics in a standard
form $$ \rho_t + \nabla\cdot(\rho U)=0, \quad (\rho U)_t + \nabla\cdot(\rho
U\otimes U)=0, $$ and in the relativistic form $$ \rho_t + \nabla\cdot(\rho
C(U))=0, \quad (\rho U)_t + \nabla\cdot(\rho U\otimes C(U))=0, $$ where
$C(U)=\frac{c_0U}{\sqrt{c_0^2+|U|^2}}$, $c_0$ is the speed of light. We
introduce the integral identities which constitute definition of
$\delta$-shocks for the above systems and using this definition derive the
Rankine--Hugoniot conditions for curvilinear $\delta$-shocks. We show that
$\delta$-shocks are connected with {\em transportation processes and
concentration processes} and derive the $\delta$-shock balance laws describing
mass and momentum transportation between the volume outside the wave front and
the wave front. In the case of zero-pressure gas dynamics the transportation
process is the concentration process. We also prove that energy of the volume
outside the wave front and total energy are {\em nonincreasing quantities}. The
possibility of the {\em effect of kinematic self-gravitation} and the {\em
effect of dimensional bifurcations of $\delta$-shock} in zero-pressure gas
dynamics are discussed.


title: Hochschild homology and global dimension

abstract:
  We prove that for certain classes of graded algebras (Koszul, local,
cellular), infinite global dimension implies that Hochschild homology does not
vanish in high degrees, provided the characteristic of the ground field is
zero. Our proof uses Igusa's formula relating the Euler characteristic of
relative cyclic homology to the graded Cartan determinant.


title:
On convergence of dynamics of hopping particles to a birth-and-death
  process in continuum

abstract:
  We show that some classes of birth-and-death processes in continuum (Glauber
dynamics) may be derived as a scaling limit of a dynamics of interacting
hopping particles (Kawasaki dynamics)


title:
Two-integral distribution functions for axisymmetric stellar systems
  with separable densities

abstract:
  We show different expressions of distribution functions (DFs) which depend
only on the two classical integrals of the energy and the magnitude of the
angular momentum with respect to the axis of symmetry for stellar systems with
known axisymmetric densities. The density of the system is required to be a
product of functions separable in the potential and the radial coordinate,
where the functions of the radial coordinate are powers of a sum of a square of
the radial coordinate and its unit scale. The even part of the two-integral DF
corresponding to this type of density is in turn a sum or an infinite series of
products of functions of the energy and of the magnitude of the angular
momentum about the axis of symmetry. A similar expression of its odd part can
be also obtained under the assumption of the rotation laws. It can be further
shown that these expressions are in fact equivalent to those obtained by using
Hunter and Qian's contour integral formulae for the system. This method is
generally computationally preferable to the contour integral method. Two
examples are given to obtain the even and odd parts of their two-integral DFs.
One is for the prolate Jaffe model and the other for the prolate Plummer model.
  It can be also found that the Hunter-Qian contour integral formulae of the
two-integral even DF for axisymmetric systems can be recovered by use of the
Laplace-Mellin integral transformation originally developed by Dejonghe.


title: New Families of Triple Error Correcting Codes with BCH Parameters

abstract:
  Discovered by Bose, Chaudhuri and Hocquenghem, the BCH family of error
correcting codes are one of the most studied families in coding theory. They
are also among the best performing codes, particularly when the number of
errors being corrected is small relative to the code length. In this article we
consider binary codes with minimum distance of 7. We construct new families of
codes with these BCH parameters via a generalisation of the Kasami-Welch
Theorem.


title: $N=1$ formal genus $0$ Gromov-Witten theories and Givental's formalism

abstract:
  In [Gi3] Givental introduced and studied a space of formal genus zero
Gromov-Witten theories $GW_0$, i.e. functions satisfying string and dilaton
equations and topological recursion relations. A central role in the theory
plays the geometry of certain Lagrangian cones and a twisted symplectic group
of hidden symmetries. In this note we show that the Lagrangian cones
description of the action of this group coincides with the genus zero part of
Givental's quantum Hamiltonian formalism. As an application we identify
explicitly the space of $N=1$ formal genus zero GW theories with
lower-triangular twisted symplectic group modulo the string flow.


title:
Classification of groups generated by 3-state automata over a 2-letter
  alphabet

abstract:
  This article contains most of the known results on the classification of
groups generated by 3-state automata over a 2-letter alphabet, extending the
previous papers 0704.3876 and math/0612178.


title:
On the theory of cavities with point-like perturbations. Part I: General
  theory

abstract:
  The theoretical interpretation of measurements of "wavefunctions" and spectra
in electromagnetic cavities excited by antennas is considered. Assuming that
the characteristic wavelength of the field inside the cavity is much larger
than the radius of the antenna, we describe antennas as "point-like
perturbations". This approach strongly simplifies the problem reducing the
whole information on the antenna to four effective constants. In the framework
of this approach we overcame the divergency of series of the phenomenological
scattering theory and justify assumptions lying at the heart of "wavefunction
measurements". This selfconsistent approach allowed us to go beyond the
one-pole approximation, in particular, to treat the experiments with
degenerated states. The central idea of the approach is to introduce
``renormalized'' Green function, which contains the information on boundary
reflections and has no singularity inside the cavity.


title:
Positive Realness of a Transfer Function Neither Implies Nor is Implied
  by the External Positivity of their Associate Realizations

abstract:
  This letter discusses the differences between the properties of positive
realness of transfer functions and external positivity in linear time-invariant
dynamic systems. It is proved that each one of both properties does not imply
to each other.


title: Lecture notes on duality and interpolation spaces

abstract:
  Known or essentially known results about duals of interpolation spaces are
presented, taking a point of view sometimes slightly different from the usual
one. Particular emphasis is placed on Alberto Calderon's theorem describing the
duals of his complex interpolation spaces [A_0,A_1]_\theta. The pace is slow,
since these notes are intended for graduate students who have just begun to
study interpolation spaces. This second version corrects some small misprints.
It also draws attention to a convenient norming subspace of the dual of a
complex interpolation space, and to the slight difference between the spaces
\mathcal{G}(X_0,X_1) introduced by Calderon and by Stafney.


title:
Loop Quantum Cosmology of Diagonal Bianchi Type I model: simplifications
  and scaling problems

abstract:
  A simplified theory of the diagonal Bianchi type I model coupled with a
massless scalar field in loop quantum cosmology is constructed according to the
$\bar{\mu}$ scheme. Kinematical and physical sectors of the theory are under
good analytical control as well as the scalar constraint operator. Although it
is possible to compute numerically the nonsingular evolution of the three
gravitational degrees of freedom, the naive implementation of the $\bar{\mu}$
scheme to the diagonal Bianchi type I model is problematic. The lack of the
full invariance of the theory with respect to the fiducial cell and fiducial
metric scaling causes serious problems in the semiclassical limit of the
theory. Because of this behavior it is very difficult to extract reasonable
physics from the model. The weaknesses of the implementation of the $\bar{\mu}$
scheme to the Bianchi I model do not imply limitations of the $\bar{\mu}$
scheme in the isotropic case.


title: Definably complete and Baire structures and Pfaffian closure

abstract:
  We consider definably complete and Baire expansions of ordered fields: every
definable subset of the domain of the structure has a supremum and the domain
can not be written as the union of a definable increasing family of nowhere
dense sets. Every expansion of the real field is definably complete and Baire.
So is every o-minimal expansion of a field. However, unlike the o-minimal case,
the structures considered form an elementary class. In this context we prove a
version of Kuratowski-Ulam's Theorem and some restricted version of Sard's
Lemma. We use the above results to prove the following version of Wilkie's
Theorem of the Complement: given a definably complete Baire expansion K of an
ordered field with a family of smooth functions, if there are uniform bounds on
the number of definably connected components of quantifier free definable sets,
then K is o-minimal. We further generalize the above result, along the line of
Speissegger's theorem, and prove the o-minimality of the relative Pfaffian
closure of an o-minimal structure inside a definably complete Baire structure.


title:
Complete Michel Parameter Analysis of inclusive semileptonic b \to c
  transition

abstract:
  We perform a complete "Michel parameter" analysis of all possible helicity
structures which can appear in the process $B \to X_c \ell \bar{\nu}_\ell$. We
take into account the full set of operators parametrizing the effective
Hamiltonian and include the complete one-loop QCD corrections as well as the
non-perturbative contributions. The moments of the leptonic energy as well as
the combined moments of the hadronic energy and hadronic invariant mass are
calculated including the non-standard contributions.


title: Exact treatment of exciton-polaron formation by Diagrammatic Monte Carlo

abstract:
  We develop an approximation-free Diagrammatic Monte Carlo technique to study
fermionic particles interacting with each other simultaneously through both an
attractive Coulomb potential and bosonic excitations of the underlying medium.
Exemplarily we apply the method to the long-standing exciton-polaron problem
and present numerically exact results for the wave function, ground-state
energy, binding energy and effective mass of this quasiparticle. Focusing on
the electron-hole pair bound-state formation, we discuss various limiting cases
of a generic exciton-polaron model. The frequently used instantaneous
approximation to the retarded interaction due to the phonon exchange is found
to be of very limited applicability. For the case of a light electron and heavy
hole the system is well approximated by a particle in the field of a static
attractive impurity.


title: The bigger Brauer group and twisted sheaves

abstract:
  Given an algebraic stack with quasiaffine diagonal, we show that each
G_m-gerbe comes from a central separable algebra. In other words, Taylor's
bigger Brauer group equals the etale cohomology in degree two with coefficients
in G_m. This gives new results also for schemes. We use the method of twisted
sheaves explored by de Jong and Lieblich.


title:
Very low 1/f noise at room temperature in fully epitaxial Fe/MgO/Fe
  magnetic tunnel junctions

abstract:
  We report on room temperature 1/f noise in fully epitaxial
Fe(45nm)/MgO(2.6nm)/Fe(10nm) magnetic tunnel junctions (MTJs) with and without
carbon doping of the Fe/MgO bottom interface. We have found that the normalized
noise (Hooge factor) asymmetry between parallel and antiparallel states may
strongly depend on the applied bias and its polarity. Both types of MTJs
exhibit record low Hooge factors being at least one order of magnitude smaller
than previously reported.


title: Individual based model with competition in spatial ecology

abstract:
  We analyze an interacting particle system with a Markov evolution of
birth-and-death type. We have shown that a local competition mechanism
(realized via a density dependent mortality) leads to a globally regular
behavior of the population in course of the stochastic evolution.


title:
Generation of homogeneous granular packings: Contact dynamics method
  with coupling to an external pressure bath

abstract:
  The contact dynamics method (CD) is an efficient simulation technique of
dense granular media where unilateral and frictional contact problems for a
large number of rigid bodies have to be solved. In this paper we present a
modified version of the contact dynamics to generate homogeneous random
packings of rigid grains. CD is coupled to an external pressure bath, which
allows the variation of the size of a periodically repeated cell. We follow the
concept of the Andersen dynamics and show how it can be applied within the
framework of the contact dynamics method. The main challenge here is to handle
the interparticle interactions properly, which are based on constraint forces
in CD. We implement the proposed algorithm, perform test simulations and
investigate the properties of the final packings.


title: Experimental investigation of the freely cooling granular gas

abstract:
  Using diamagnetically levitated particles we investigate the dynamics of the
freely cooling granular gas. At early times we find good agreement with Haff's
law, where the time scale for particle collisions can be determined from
independent measurements. At late times, clustering of particles occurs. This
can be included in a Haff-like description taking into account the decreasing
number of free particles. With this a good description of the data is possible
over the whole time range.


title:
Structural and Magnetic Properties of Pyrochlore Solid Solutions
  (Y,Lu)2Ti2-x(Nb,Ta)xO7+/-y

abstract:
  The synthesis and characterization of the pyrochlore solid solutions,
Y2Ti2-xNbxO7-y, Lu2Ti2-xNbxO7-y, Y2Ti2-xTaxO7-y and Lu2TiTaO7-y (-0.4<y<0.5),
is described. Synthesis at 1600 C, and 10-5 Torr yields oxygen deficiency in
all systems. All compounds are found to be paramagnetic and semiconducting,
with the size of the local moments being less, in some cases substantially
less, than the expected value for the number of nominally unpaired electrons
present. Thermogravimetric analysis (TGA) shows that all compounds can be fully
oxidized while retaining the pyrochlore structure, yielding oxygen rich
pyrochlores as white powders. Powder neutron diffraction of Y2TiNbO7-based
samples was done. Refinement of the data for oxygen deficient Y2TiNbO6.76
indicates the presence of a distribution of oxygen over the 8b and 48f sites.
Refinement of the data for oxygen rich Y2TiNbO7.5 shows these sites to be
completely filled, with an additional half filling of the 8a site. The magnetic
and TGA data strongly suggest a preference for a Ti3+/(Nb,Ta)5+ combination, as
opposed to Ti4+/(Nb,Ta)4+, in this pyrochlore family. In addition, the evidence
clearly points to Ti3+ as the source of the localized moments, with no evidence
for localized Nb4+ moments.


title:
Interplay of chemical pressure and hydrogen insertion effects in $ {\bf
  CeRhSn} $ from first principles

abstract:
  Investigations within the local spin density functional theory (LSDF) of the
intermetallic hydride system $ {\rm CeRhSnH_x} $ were carried out for discrete
model compositions in the range $ 0.33 \leq x_H \leq 1.33 $. The aim of this
study is to assess the change of the cerium valence state in the neighborhood
of the experimental hydride composition, $ {\rm CeRhSnH_{0.8}} $. In agreement
with experiment, the analyses of the electronic and magnetic structures and of
the chemical bonding properties point to trivalent cerium for $ 1 \leq x_H \leq
1.33 $. In contrast, for lower hydrogen amounts the hydride system stays in an
intermediate-valent state for cerium, like in $ {\rm CeRhSn} $. The influence
of the insertion of hydrogen is addressed from both the volume expansion and
chemical bonding effects. The latter are found to have the main influence on
the change of Ce valence character. Spin polarized calculations point to a
finite magnetic moment carried by the Ce $ 4f $ states; its magnitude increases
with $ x_H $ in the range $ 1 \leq x_H \leq 1.33 $.


title: Whittaker Modules for Generalized Weyl Algebras

abstract:
  We investigate Whittaker modules for generalized Weyl algebras, a class of
associative algebras which includes the quantum plane, Weyl algebras, the
universal enveloping algebra of sl_2 and of Heisenberg Lie algebras, Smith's
generalizations of U(sl_2), various quantum analogues of these algebras, and
many others. We show that the Whittaker modules V = Aw of the generalized Weyl
algebra A = R(phi,t) are in bijection with the phi-stable left ideals of R. We
determine the annihilator Ann_A(w) of the cyclic generator w of V. We also
describe the annihilator ideal Ann_A(V) under certain assumptions that hold for
most of the examples mentioned above. As one special case, we recover Kostant's
well-known results on Whittaker modules and their associated annihilators for
U(sl_2).


title: Stellar Collapse in the Time Dependent Hartree-Fock Approximation

abstract:
  We prove blow-up in finite time for radially symmetric solutions to the
pseudo-relativistic Hartree-Fock equation with negative energy. The non-linear
Hartree-Fock equation is commonly used in the physics literature to describe
the dynamics of white dwarfs. We extend thereby recent results by Fr\"ohlich
and Lenzmann, who established in \cite{FL1,FL2} blow-up for solutions to the
pseudo-relativistic Hartree equation. As key ingredient for handling the
exchange term we use the conservation of the expectation of the square of the
angular momentum operator.


title: The stable free rank of symmetry of products of spheres

abstract:
  A well known conjecture in the theory of transformation groups states that if
p is a prime and (Z/p)^r acts freely on a product of k spheres, then r is less
than or equal to k. We prove this assertion if p is large compared to the
dimension of the product of spheres. The argument builds on tame homotopy
theory for non simply connected spaces.


title:
Friedel phase discontinuity and bound states in the continuum in quantum
  dot systems

abstract:
  n this article we study the Friedel phase of the electron transport in two
different systems of quantum dots which exhibit bound states in the continuum
(BIC). The Friedel phase jumps abruptly in the energies of the BICs, which is
associated to the vanishing width of these states, as shown by Friedrich and
Wintgen in Phys. Rev. A \textbf{31}, 3964 (1985). This odd behavior of the
Friedel phase has consequences in the charge through the Friedel sum rule.
Namely, if the energy of the BIC drops under the Fermi energy the charge
changes abruptly in a unity. We show that this behavior closely relates with
discontinuities in the conductance predicted for interacting quantum dot
systems.


title:
Self-consistent solution for proximity effect and Josephson current in
  ballistic graphene SNS Josephson junctions

abstract:
  We use a tight-binding Bogoliubov-de Gennes (BdG) formalism to
self-consistently calculate the proximity effect, Josephson current, and local
density of states in ballistic graphene SNS Josephson junctions. Both short and
long junctions, with respect to the superconducting coherence length, are
considered, as well as different doping levels of the graphene. We show that
self-consistency does not notably change the current-phase relationship derived
earlier for short junctions using the non-selfconsistent Dirac-BdG formalism
but predict a significantly increased critical current with a stronger junction
length dependence. In addition, we show that in junctions with no Fermi level
mismatch between the N and S regions superconductivity persists even in the
longest junctions we can investigate, indicating a diverging Ginzburg-Landau
superconducting coherence length in the normal region.


title: Harmonic maps from degenerating Riemann surfaces

abstract:
  We study harmonic maps from degenerating Riemann surfaces with uniformly
bounded energy and show the so-called generalized energy identity. We find
conditions that are both necessary and sufficient for the compactness in
$W^{1,2}$ and $C^{0}$ modulo bubbles of sequences of such maps.


title: Long range order for lattice dipoles

abstract:
  We consider a system of classical Heisenberg spins on a cubic lattice in
dimensions three or more, interacting via the dipole-dipole interaction. We
prove that at low enough temperature the system displays orientational long
range order, as expected by spin wave theory. The proof is based on reflection
positivity methods. In particular, we demonstrate a previously unproven
conjecture on the dispersion relation of the spin waves, first proposed by
Froehlich and Spencer, which allows one to apply infrared bounds for estimating
the long distance behavior of the spin-spin correlation functions.


title:
Polarization of spin-1 particles without an anomalous magnetic moment in
  a uniform magnetic field

abstract:
  The polarization operator projections onto four directions remain unchanged
for spin-1 particles without an anomalous magnetic moment in a uniform magnetic
field. The approximate conservation of the polarization operator projections
onto the horizontal axes of the cylindrical coordinate system takes place.


title:
Nucleation and growth of a quasicrystalline monolayer: Bi adsorption on
  the five-fold surface of i-Al70Pd21Mn9

abstract:
  Scanning tunnelling microscopy has been used to study the formation of a Bi
monolayer deposited on the five-fold surface of i-Al70Pd21Mn9. Upon deposition
of low sub-monolayer coverages, the nucleation of pentagonal clusters of Bi
adatoms of edge length 4.9 A is observed. The clusters have a common
orientation leading to a film with five-fold symmetry. By inspection of images
where both the underlying surface and the Bi atoms are resolved, the pentagonal
clusters are found to nucleate on pseudo-Mackay clusters truncated such that a
Mn atom lies centrally in the surface plane. The density of these sites is
sufficient to form a quasiperiodic framework, and subsequent adsorption of Bi
atoms ultimately leads to the formation of a quasicrystalline monolayer. The
initial nucleation site is different to that proposed on the basis of recent
density functional theory calculations.


title:
Spin Dynamics in the Second Subband of a Quasi Two Dimensional System
  Studied in a Single Barrier Heterostructure by Time Resolved Kerr Rotation

abstract:
  By biasing a single barrier heterostructure with a 500nm-thick GaAs layer as
the absorption layer, the spin dynamics for both of the first and second
subband near the AlAs barrier are examined. We find that when simultaneously
scanning the photon energy of both the probe and pump beams, a sign reversal of
the Kerr rotation (KR) takes place as long as the probe photons break away the
first subband and probe the second subband. This novel feature, while stemming
from the exchange interaction, has been used to unambiguously distinguish the
different spin dynamics ($T_2^{1*}$ and $T_2^{2*}$) for the first and second
subbands under the different conditions by their KR signs (negative for
$1^{st}$ and positive for $2^{nd}$). In the zero magnetic field, by scanning
the wavelength towards the short wavelength, $T_2^{1*}$ decreases in accordance
with the D'yakonov-Perel' (DP) spin decoherence mechanism. At 803nm,
$T_2^{2*}$(450ps) becomes ten times longer than $T_2^{1*}$(50ps). However, the
value of $T_2^{2*}$ at 803nm is roughly the same as the value of $T_2^{1*}$ at
815nm. A new feature has been disclosed at the wavelength of 811nm under the
bias of -0.3V (807nm under the bias of -0.6V) that the spin coherence times
($T_2^{1*}$ and $T_2^{2*}$) and the effective $g^*$ factors ($|g^*(E1)|$ and
$|g^*(E2)|$) all display a sudden change, due to the "resonant" spin exchange
coupling between two spin opposite bands.


title: On Morita theory for self-dual modules

abstract:
  Let $G$ be a finite group and let $k$ be a field of characteristic $p$. It is
known that a $kG$-module $V$ carries a non-degenerate $G$-invariant bilinear
form $b$ if and only if $V$ is self-dual. We show that whenever a Morita
bimodule $M$ which induces an equivalence between two blocks $B(kG)$ and
$B(kH)$ of group algebras $kG$ and $kH$ is self-dual then the correspondence
preserves self-duality. Even more, if the bilinear form on $M$ is symmetric
then for $p$ odd the correspondence preserves the geometric type of simple
modules. In characteristic 2 this holds also true for projective modules.


title:
Formation of a quasicrystalline Pb monolayer on the ten-fold surface of
  the decagonal Al-Ni-Co quasicrystal

abstract:
  Lead has been deposited on the ten-fold surface of decagonal Al72Ni11Co17 to
form an epitaxial quasicrystalline single-element monolayer. The overlayer
grows through nucleation of nanometer-sized irregular islands and the coverage
saturates at 1 ML. The overlayer is well-ordered quasiperiodically as evidenced
by LEED and Fourier transforms of STM images. Annealing the film to 600 K
improves the structural quality, but causes the evaporation of some material
such that the film develops pores. Electronic structure measurements using
X-ray photoemission spectroscopy indicate that the chemical interaction of the
Pb atoms with the substrate is weak.


title:
Nonzero U_{e3}, CP violation and leptogenesis in a see-saw type softly
  broken A_4 symmetric model

abstract:
  We have shown that non-zero U_{e3} is generated in a see-saw type softly
broken A_4 symmetric model through a single parameter perturbation in m_D in a
single element. We have explored all possible 9 cases to study the neutrino
mixing angles considering the best fitted values of \Delta m_{\odot}^2 and
\Delta m_{atm}^2 with all parameters real. We have extended our analysis for
the complex case and demonstrated large low energy CP violation (J_{CP}\simeq
10^{-2}) and m_{ee} in addition to mixing and mass pattern. We have also
investigated leptogenesis and for a reasonable choice of model parameters
compatible with low energy data, WMAP value of baryon asymmetry 6\times
10^{-10} is obtained for right handed neutrino mass scale M_0\simeq 10^{13}
GeV. We have obtained a relation among the phases responsible for leptogenesis
and have shown that these phases also have correlations with low energy CP
violating phases.


title:
Dissection of the protostellar envelope surrounding IRAS 05173-0555 in
  L1634

abstract:
  Context. The youngest protostars that power energetic outflows are surrounded
by infalling and rotating envelopes that contain most of the mass of the
system. Aims. To study the properties and kinematics of the protostellar
envelope surrounding the embedded source IRAS 05173-0555 in L1634. Methods. We
carried out VLA ammonia observations at 1.3 cm with the VLA in the D
configuration to map the gas towards the core of L1634. Results. The NH3
emission towards IRAS 05173-0555 is resolved and shows two components clearly
distinguishable morphologically: a cross-like structure, roughly elongated in
the direction of the HH 240/241 outflow and associated with IRAS 05173-0555,
plus an arc-like stream elongated towards the north. The properties and
kinematics of the gas suggest that the origin of the cross-like morphology
could be the interaction between the outflow and the envelope. A more compact
and flattened structure, which could be undergoing rotation about the axis of
the outflow, has been detected towards the center of the cross-like envelope.
The northern stream, which has properties and velocity different from those of
the cross-like envelope, is likely part of the original cloud envelope, and
could be either a quiescent core that would never form stars, or be in a
prestellar phase.


title:
Pre-recombinational energy release and narrow features in the CMB
  spectrum

abstract:
  Energy release in the early Universe (z<~ 2x10^6) should lead to some broad
spectral distortion of the cosmic microwave background (CMB) radiation field,
which can be characterized as y-type distortion when the injection process
started at redshifts z<~ 5x10^4. Here we demonstrate that if energy was
released before the beginning of cosmological hydrogen recombination (z~1400),
closed loops of bound-bound and free-bound transitions in HI and HeII lead to
the appearance of (i) characteristic multiple narrow spectral features at dm
and cm wavelengths, and (ii) a prominent sub-millimeter feature consisting of
absorption and emission parts in the far Wien tail of CMB spectrum. The
additional spectral features are generated in the pre-recombinational epoch of
HI (z>~1800) and HeII (z>~7000), and therefore differ from those arising due to
normal cosmological recombination in the undisturbed CMB blackbody radiation
field. We present the results of numerical computations including 25 atomic
shells for both HI and HeII, and discuss the contributions of several
individual transitions in detail. As examples, we consider the case of
instantaneous energy release (e.g. due to phase transitions) and exponential
energy release because of long-lived decaying particles. Our computations show
that due to possible pre-recombinational atomic transitions the variability of
the CMB spectral distortion increases when comparing with the distortions
arising in the normal recombination epoch. The existence of these narrow
spectral features would open an unique way to separate y-distortions due to
pre-recombinational ($1400<~ z <~5x10^4) energy release from those arising in
the post-recombinational era at redshifts z<~800. (abridged)


title:
The solar photospheric abundance of hafnium and thorium. Results from
  CO5BOLD 3D hydrodynamic model atmospheres

abstract:
  Context: The stable element hafnium (Hf) and the radioactive element thorium
(Th) were recently suggested as a suitable pair for radioactive dating of
stars. The applicability of this elemental pair needs to be established for
stellar spectroscopy. Aims: We aim at a spectroscopic determination of the
abundance of Hf and Th in the solar photosphere based on a \cobold 3D
hydrodynamical model atmosphere. We put this into a wider context by
investigating 3D abundance corrections for a set of G- and F-type dwarfs.
Method: High-resolution, high signal-to-noise solar spectra were compared to
line synthesis calculations performed on a solar CO5BOLD model. For the other
atmospheres, we compared synthetic spectra of CO5BOLD 3D and associated 1D
models. Results: For Hf we find a photospheric abundance A(Hf)=0.87+-0.04, in
good agreement with a previous analysis, based on 1D model atmospheres. The
weak Th ii 401.9 nm line constitutes the only Th abundance indicator available
in the solar spectrum. It lies in the red wing of an Ni-Fe blend exhibiting a
non-negligible convective asymmetry. Accounting for the asymmetry-related
additional absorption, we obtain A(Th)=0.09+-0.03, consistent with the
meteoritic abundance, and about 0.1 dex lower than obtained in previous
photospheric abundance determinations. Conclusions: Only for the second time,
to our knowledge, has am non-negligible effect of convective line asymmetries
on an abundance derivation been highlighted. Three-dimensional hydrodynamical
simulations should be employed to measure Th abundances in dwarfs if similar
blending is present, as in the solar case. In contrast, 3D effects on Hf
abundances are small in G- to mid F-type dwarfs and sub-giants, and 1D model
atmospheres can be conveniently used.


title:
On the zeros of certain modular functions for the normalizers of
  congruence subgroups of low levels II

abstract:
  We research the location of the zeros of the Eisenstein series and the
modular functions from the Hecke type Faber polynomials associated with the
normalizers of congruence subgroups which are of genus zero and of level at
most twelve.
  In Part II, we will observe the location of the zeros of the above functions
by numerical calculation.


title:
Einstein's unified field theory predicts the equilibrium positions of n
  wires run by steady electric currents

abstract:
  A particular exact solution of Einstein's Hermitian theory of relativity is
examined, after recalling that there is merit in adding phenomenological
sources to the theory, and in choosing the metric like it was done long ago by
Kursunoglu and Hely. It is shown by intrinsic arguments, relying on the
properties of the chosen metric manifold, that the solution describes in
Einstein's theory the field of n thin parallel wires at rest, run by steady
electric currents, and predicts their equilibrium positions through the
injunction that the metric must display cylindrical symmetry in the
infinitesimal neighbourhood of each wire. In the weak field limit the
equilibrium positions coincide with the ones prescribed by Maxwell's
electrodynamics.


title:
Enhanced phase sensitivity and soliton formation in an integrated BEC
  interferometer

abstract:
  We study the dynamics of Bose-Einstein condensates in time-dependent
microtraps for the purpose of understanding the influence of the mean field
interaction on the performance of interferometers. We identify conditions where
the non-linearity due to atom interactions increases the sensitivity of
interferometers to a phase shift. This feature is connected with the adiabatic
generation of a dark soliton. We analyze the robustness of this phenomenon with
respect to thermal fluctuations, due to excited near fields in an
electromagnetic surface trap.


title: Universality in Globally Coupled Maps and Flows

abstract:
  We show that universality in chaotic elements can be lifted to that in
complex systems. We construct a globally coupled Flow lattice (GCFL), an analog
of a globally coupled Map lattice (GCML). We find that Duffing GCFL shows the
same behavior with GCML; population ratio between synchronizing clusters acts
as a bifurcation parameter. Lorenz GCFL exhibits interesting two quasi-clusters
in an opposite phase motion. Each of them looks like Will o' the wisp; they
dance around in opposite phase.


title: Escaping the Brownian stalkers

abstract:
  We propose a simple model for the behaviour of longterm investors on a stock
market, consisting of three particles, which represent the current price of the
stock and the opinion of the buyers, respectively sellers, about the right
trading price. As time evolves, both groups of traders update their opinions
with respect to the current price. The update speed is controled by a parameter
$\gamma$, the price process is described by a geometric Brownian motion. We
consider the stability of the market in terms of the distance between the
buyers' and sellers' opinion, and prove that the distance process is
recurrent/transient in dependence on $\gamma$.


title:
Persistent Cell Motion in the Absence of External Signals: A Search
  Strategy for Eukaryotic Cells

abstract:
  Eukaryotic cells are large enough to detect signals and then orient to them
by differentiating the signal strength across the length and breadth of the
cell. Amoebae, fibroblasts, neutrophils and growth cones all behave in this
way. Little is known however about cell motion and searching behavior in the
absence of a signal. Is individual cell motion best characterized as a random
walk? Do individual cells have a search strategy when they are beyond the range
of the signal they would otherwise move toward? Here we ask if single,
isolated, Dictyostelium and Polysphondylium amoebae bias their motion in the
absence of external cues. We placed single well-isolated Dictyostelium and
Polysphondylium cells on a nutrient-free agar surface and followed them at 10
sec intervals for ~10 hr, then analyzed their motion with respect to velocity,
turning angle, persistence length, and persistence time, comparing the results
to the expectation for a variety of different types of random motion. We find
that amoeboid behavior is well described by a special kind of random motion:
Amoebae show a long persistence time (~10 min) beyond which they start to lose
their direction; they move forward in a zig-zag manner; and they make turns
every 1-2 min on average. They bias their motion by remembering the last turn
and turning away from it. Interpreting the motion as consisting of runs and
turns, the duration of a run and the amplitude of a turn are both found to be
exponentially distributed. We show that this behavior greatly improves their
chances of finding a target relative to performing a random walk. We believe
that other eukaryotic cells may employ a strategy similar to Dictyostelium when
seeking conditions or signal sources not yet within range of their detection
system.


title: Differentiating polynomials, and zeta(2)

abstract:
  We study the derivatives of polynomials with equally spaced zeros and find
connections to the values of the Riemann zeta-function at the positive even
integers.


title:
Structural phase transitions in geometrically frustrated
  antiferromagnets

abstract:
  We study geometrically frustrated antiferromagnets with magnetoelastic
coupling. Frustration in these systems may be relieved by a structural
transition to a low temperature phase with reduced lattice symmetry. We examine
the statistical mechanics of this transition and the effects on it of quenched
disorder, using Monte Carlo simulations of the classical Heisenberg model on
the pyrochlore lattice with coupling to uniform lattice distortions. The model
has a transition between a cubic, paramagnetic high-temperature phase and a
tetragonal, Neel ordered low-temperature phase. It does not support the
spin-Peierls phase, which is predicted as an additional possibility within
Landau theory, and the transition is first-order for reasons unconnected with
the symmetry analysis of Landau theory. Quenched disorder stabilises the cubic
phase, and we find a phase diagram as a function of temperature and disorder
strength similar to that observed in ZnCdCrO.


title: Algebras of higher operads as enriched categories

abstract:
  We decribe the correspondence between normalised $\omega$-operads and certain
lax monoidal structures on the category of globular sets. As with ordinary
monoidal categories, one has a notion of category enriched in a lax monoidal
category. Within the aforementioned correspondence, we provide also an
equivalence between the algebras of a given normalised $\omega$-operad, and
categories enriched in globular sets for the induced lax monoidal structure.


title: Evidence for Non-Hydrostatic Gas Motions in the Hot ISM of Centaurus A

abstract:
  We present preliminary results from a deep (600 ks) {\em Chandra} observation
of the hot interstellar medium of the nearby early-type galaxy Centaurus A (Cen
A). We find a surface brightness discontinuity in the gas $\sim$3.5 kpc from
the nucleus spanning a 120$^\circ$ arc. The temperature of the gas is
0.60$\pm$0.05 and 0.68$\pm$0.10 keV, interior and exterior to the
discontinuity, respectively. The elemental abundance is poorly constrained by
the spectral fits, but if the abundance is constant across the discontinuity,
there is a factor of 2.3$\pm$0.4 pressure jump across the discontinuity. This
would imply that the gas is moving at 470$\pm$100 km s$^{-1}$, or Mach
1.0$\pm$0.2 (1.2$\pm$0.2) relative to the sound speed of the gas external
(internal) to the discontinuity. Alternatively, pressure balance could be
maintained if there is a large (factor of $\sim$7) discontinuity in the
elemental abundance. We suggest that the observed discontinuity is the result
of non-hydrostatic motion of the gas core (i.e. sloshing) due to the recent
merger. In this situation, both gas motions and abundance gradients are
important in the visibility of the discontinuity. Cen A is in the late stages
of merging with a small late-type galaxy, and a large discontinuity in density
and abundance across a short distance demonstrates that the gas of the two
galaxies remains poorly mixed even several hundred million years after the
merger. The pressure discontinuity may have had a profound influence on the
temporal evolution of the kpc-scale jet. The jet could have decollimated
crossing the discontinuity and thereby forming the northeast radio lobe.


title: Supernova Shock Breakout from a Red Supergiant

abstract:
  Massive stars undergo a violent death when the supply of nuclear fuel in
their cores is exhausted, resulting in a catastrophic "core-collapse"
supernova. Such events are usually only detected at least a few days after the
star has exploded. Observations of the supernova SNLS-04D2dc with the Galaxy
Evolution Explorer space telescope reveal a radiative precursor from the
supernova shock before the shock reached the surface of the star and show the
initial expansion of the star at the beginning of the explosion. Theoretical
models of the ultraviolet light curve confirm that the progenitor was a red
supergiant, as expected for this type of supernova. These observations provide
a way to probe the physics of core-collapse supernovae and the internal
structures of their progenitor stars


title:
Carrier-wave steepened pulses and gradient-gated high-order harmonic
  generation using linear ramp waveforms

abstract:
  We show how to optimize the process of high-harmonic generation (HHG) by
gating the interaction using the field gradient of a driving pulse with a
linear ramp waveform. Since maximized field gradients are efficiently generated
by self-steepening processes, we first present a generalized theory of optical
carrier-wave self-steepened (CSS) pulses. This goes beyond existing treatments,
which only consider third-order nonlinearity, and has the advantage of
describing pulses whose wave forms have a range of symmetry properties.
Although a fertile field for theoretical work, CSS pulses are difficult to
realize experimentally because of the deleterious effect of dispersion. We
therefore consider synthesizing CSS-like profiles using a suitably phased
sub-set of the harmonics present in a true CSS wave form. Using standard
theoretical models of HHG, we show that the presence of gradient-maximized
regions on the wave forms can raise the spectral cut-off and so yield shorter
attosecond pulses. We study how the quality of the attosecond bursts created by
spectral filtering depends on the number of harmonics included in the driving
pulse.


title: On continuous fields of JB-algebras

abstract:
  We introduce and study continuous fields of JB-algebras (which are real
non-associate analogues of C*-algebras). In particular, we show that for the
universal enveloping C*-algebra C*sub-u(B) for the JB-algebra B defined by a
continuous field of JB-algebras A-sub-t, t belongs to T, on a locally compact
space T, there exists a decomposition of C*-sub-u(B) into a continuous field of
C*-algebras C*u(A-sub-t), t belongs to T, on the same space T, composed
entirely of the universal enveloping C*-algebras of the corresponding
JB-algebras from the aforementioned decomposition of the algebra B.


title:
A solution in 3 dimensions for current in a semiconductor under high
  level injection from a point contact

abstract:
  The standard equations for semiconductor device analysis were solved by
specifying the electron and hole current injected at a small contact, assuming
high-level injection. Calculated current-voltage characteristics were fit to
measurements of a single point breakdown in an ultrathin dielectric. It was
found that the minority carrier injection level was about 70%.


title:
On Intrinsic Characterization of Real Locally C*- and Locally
  JB-Algebras

abstract:
  In the present paper we obtain an intrinsic characterization of real locally
C*-algebras (projective limits of projective families of real C*-algebras)
among complete real lmc *-algebras, and of locally JB-algebras (projective
limits of projective families of JB-algebras) among complete fine Jordan
locally multiplicatively-convex topological algebras.


title: Braid group B_3 irreducibles, a DIY guide

abstract:
  This note tells you how to construct a k(n)-dimensional family of
(isomorphism classes of) irreducible representations of dimension n for the
three string braid group B_3, where k(n) is an admissible function of your
choosing; for example take k(n) = [ n/2 ] +1 as in arXiv:0803.2778 and
arXiv:0803.2785.


title: Ettore Majorana and his heritage seventy years later

abstract:
  The physicists working in several areas of research know quite well the name
of Ettore Majorana, since it is currently associated to fundamental concepts
like {\it Majorana neutrinos} in particle physics and cosmology or {\it
Majorana fermions} in condensed matter physics. But, probably, very few is
known about other substantial contributions of that ingenious scholar, and even
less about his personal background. For non specialists, instead, the name of
Ettore Majorana is usually intimately related to the fact that he disappeared
rather mysteriously on March 26, 1938, just seventy years ago, and was never
seen again. The life and the work of this Italian scientist is the object of
the present review, which will also offer a summary of the main results
achieved in recent times by the historical and scientific researches on his
work.

categories: physics.hist-ph hep-ph hep-th physics.pop-ph


title: Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAsO_{1-x}F_x$

abstract:
  Since the discovery of high-transition temperature ($T_c$) superconductivity
in layered copper oxides, extensive efforts have been devoted to explore the
higher $T_c$ superconductivity. However, the $T_c$ higher than 40 K can be
obtained only in the copper oxide superconductors so far. The highest reported
value of $T_c$ for non-copper-oxide bulk superconductivity is 39 K in
$MgB_2$.\cite{jun} The $T_c$ of about 40 K is close to or above the theoretical
value predicted from BCS theory.\cite{mcmillan} Therefore, it is very
significant to search for non-copper oxide superconductor with the transition
temperature higher than 40 K to understand the mechanism of high-$T_c$
superconductivity. Here we report the discovery of bulk superconductivity in
samarium-arsenide oxides $SmFeAsO_{1-x}F_x$ with ZrCuAiAs type structure.
Resistivity and magnetization measurements show strong evidences for transition
temperature as high as 43 K. $SmFeAsO_{1-x}F_x$ is the first non-copper oxide
superconductor with $T_c$ higher than 40 K. The $T_c$ higher than 40 K may be a
strong argument to consider $SmFeAsO_{1-x}F_x$ as an unconventional
superconductor.


title: Was There A Big Bang?

abstract:
  The big bang hypothesis is widely accepted despite numerous physics
conflicts. It rests upon two experimental supports, galactic red shift and the
cosmic microwave background. Both are produced by dark matter, shown here to be
hydrogen dominated aggregates with a few percent of helium nodules. Scattering
from these non-radiating intergalactic masses produce a red shift that normally
correlates with distance. Warmed by our galaxy to an Eigenvalue of 2.735 K,
drawn near the Earth, these bodies, kept cold by ablation, resonance radiate
the Planckian microwave signal. Several tests are proposed that will
distinguish between this model and the big bang.


title:
Certain Properties of Pythagorean Triangles involving the interior
  diameter, and the exterior diameters

abstract:
  There are four characteristic circles for each triangle on a plane. All for
are tangential to the three straight lines containing the triangles' three
sides. Three are exterior circles, the fourth is the in-circle. When the
triangle is Pythagorean, the four diameters are integers. Consider a
Pythagorean triangle with the property that one leglength is a perfect(or
integer)square, and with one of the four diameters also a integer square.Of the
eight resulting combinations, we prove that only six are possible or can occur.
We then completely parametrically describe the six families; each corresponding
to one of the six combinations.


title: Gas and dust in the inner disk of the Herbig Ae star MWC 758

abstract:
  In this Letter we investigate the origin of the near-infrared emission of the
Herbig Ae star MWC 758 on sub-astronomical unit (AU) scales using spectrally
dispersed low resolution (R=35) AMBER/VLTI interferometric observations both in
the H ($1.7 \mu$m) and K ($2.2 \mu$m) bands. We find that the K band
visibilities and closure phases are consistent with the presence of a dusty
disk inner rim located at the dust evaporation distance (0.4 AU) while the bulk
of the H band emission arises within 0.1 AU from the central star. Comparing
the observational results with theoretical model predictions, we suggest that
the H band emission is dominated by an hot gaseous accretion disk.


title: Detailed Atmosphere Model Fits to Disk-Dominated ULX Spectra

abstract:
  We have chosen 6 Ultra-Luminous X-ray sources from the {\it XMM-Newton}
archive whose spectra have high signal-to-noise and can be fitted solely with a
disk model without requiring any power-law component. To estimate systematic
errors in the inferred parameters, we fit every spectrum to two different disk
models, one based on local blackbody emission (KERRBB) and one based on
detailed atmosphere modelling (BHSPEC). Both incorporate full general
relativistic treatment of the disk surface brightness profile, photon Doppler
shifts, and photon trajectories. We found in every case that they give almost
identical fits and similar acceptable parameters. The best-fit value of the
most interesting parameter, the mass of the central object, is between 23 and
73 M$_\sun$ in 5 of the 6 examples. In every case, the best-fit inclination
angle and mass are correlated, in the sense that large mass corresponds to high
inclination. Even after allowing for this degeneracy, we find that, with
$\gtrsim 99.9%$ formal statistical confidence, 3 of the 6 objects have mass
$\gtrsim 25 M_\sun$; for the other 3, these data are consistent with a wide
range of masses. A mass greater than several hundred $M_\sun$ is unlikely for
the 3 best-constrained objects. These fits also suggest comparatively rapid
black hole spin in the 3 objects whose masses are relatively well-determined,
but our estimate of the spin is subject to significant systematic error having
to do with uncertainty in the underlying surface brightness profile.


title: The Category-Theoretic Arithmetic of Information

abstract:
  We highlight the underlying category-theoretic structure of measures of
information flow. We present an axiomatic framework in which communication
systems are represented as morphisms, and information flow is characterized by
its behavior when communication systems are combined. Our framework includes a
variety of discrete, continuous, and, conjecturally, quantum information
measures. It also includes some familiar mathematical constructs not normally
associated with information, such as vector space dimension. We discuss these
examples and prove basic results from the axioms.


title: Quarkonia potential

abstract:
  Using the quark-antiquark interactions obtained in the framework of the
bootstrap method we construct a potential model, investigate the possibility of
describing of heavy quarkonia and calculate the bottomonium spectrum. The
potential of the interaction was obtained as a nonrelativistic limit of the
relativistic quark-antiquark amplitudes Q{\bar Q} -> Q\bar Q.


title:
Finite-size scaling of the entanglement entropy of the quantum Ising
  chain with homogeneous, periodically modulated and random couplings

abstract:
  Using free-fermionic techniques we study the entanglement entropy of a block
of contiguous spins in a large finite quantum Ising chain in a transverse
field, with couplings of different types: homogeneous, periodically modulated
and random. We carry out a systematic study of finite-size effects at the
quantum critical point, and evaluate subleading corrections both for open and
for periodic boundary conditions. For a block corresponding to a half of a
finite chain, the position of the maximum of the entropy as a function of the
control parameter (e.g. the transverse field) can define the effective critical
point in the finite sample. On the basis of homogeneous chains, we demonstrate
that the scaling behavior of the entropy near the quantum phase transition is
in agreement with the universality hypothesis, and calculate the shift of the
effective critical point, which has different scaling behaviors for open and
for periodic boundary conditions.


title: Aspects of Multiple Membranes

abstract:
  This paper examines various aspects of the recently proposed theory of
coincident membranes by Bagger and Lambert. These include the properties of
open membranes and the resulting boundary theory with an interpretation in
terms of the fivebrane and marginal supersymmetric deformations of the
interactions with the relation to the holographic dual.


title: Is Planck's Constant h a "Quantum" Constant?

abstract:
  One should not confuse a physical constant with a theory which incorporates
the constant. Planck's constant h can appear in classical or quantum theories.


title: An Arc of Young Stars in the Halo of M82

abstract:
  The properties of the brightest resolved stars in an arc that was originally
identified by Sun et al. (2005) and is located in the extraplanar regions of
M82 are discussed. The stars form an elongated structure that is traced over a
projected area of 3.0 x 0.8 kpc. The integrated brightness is M_V ~ -11, while
the total stellar mass is between 3 x 10^5 and 2 x 10^6 solar masses. If there
is only foreground extinction then the youngest stars have a metallicity Z >
0.008 and an age log(tyears) ~ 7.75; thus, the youngest stars formed at roughly
the same time as stars in tidal features that are associated with other M81
Group galaxies. If the arc is dispersing then it will deposit young, chemically
enriched stars into the M82 halo.


title: Topological Superconductivity and Superfluidity

abstract:
  We construct time reversal invariant topological superconductors and
superfluids in two and three dimensions which are analogous to the recently
discovered quantum spin Hall and three-d $Z_2$ topological insulators
respectively. These states have a full pairing gap in the bulk, gapless
counter-propagating Majorana states at the boundary, and a pair of Majorana
zero modes associated with each vortex. We show that the time reversal symmetry
naturally emerges as a supersymmetry, which changes the parity of the fermion
number associated with each time-reversal invariant vortex. In the presence of
external T-breaking fields, non-local topological correlation is established
among these fields, which is an experimentally observable manifestation of the
emergent supersymmetry.


title:
Inversion of marine heat flow measurements by expansion of the
  temperature decay function

abstract:
  Marine heat flow data, obtained with a Lister-type probe, consists of two
temperature decay curves, frictional and heat pulse decay. Both follow the same
physical model of a cooling cylinder. The mathematical model describing the
decays is non-linear as to the thermal sediment parameters thus a direct
inversion is not possible. To overcome this difficulty, the model equations are
expanded using a first-orderTaylor series. The linearised model equations are
used in an iterative scheme to invert the temperature decay for undisturbed
temperature and thermal conductivity of the sediment. The inversion scheme is
tested first for its theoretical limitations using synthetic data. Inversion of
heat flow measurements obtained during a cruise of R/V SONNE in 1996 and needle
probe measurements in material of known thermal conductivity show that the
algorithm is robust and gives reliable results. The programme can be obtained
from the authors.


title: Unipolar Induction

abstract:
  The phenomenon of unipolar induction consists in generating electric field by
uniformly rotating permanent magnets made of either conducting or dielectric
substance. The origin of the field around conducting magnets is explained and
calculated in Sect. 1. Dielectrics are considered in Sect. 2, where the role of
the electric moment due to moving magnetic dipole moment is clarified. Sect. 3
is devoted to the description of the effect in the corotating frame of
reference. In Sect. 4 the theory is applied to the Earth core and it is shown
that the calculated electric field falls precisely into the range of the
ambient electric field observed in the Tethered Satellite System mission of
NASA. In the last paragraph I reflect on whether flyby anomaly might be
attributed to an electric effect.


title:
Lunar dust characterization by polarimetric signature. I. Negative
  polarization branch of sphere aggregates of various porosities

abstract:
  Context. In support of NASA's exploration program and the return to the Moon,
the polarimetric signature of dispersed individual Lunar regolith dust grains
is studied to enable the characterization of the dust exopsheric environment by
remote, in-situ, and standoff sensing. Aims. We explore the value of the
negative polarization branch (NPB) as a signature for characterizing individual
grains to determine if it can be used in the same way as for surfaces of
planets and atmosphereless bodies. Results. Calculations show that polarization
phase curves for spherical grains exhibit a sharp transition over a narrow
range of size parameter between two distinct regimes, one typical of Rayleigh
scattering and another dominated by a large NPB. The linear polarimetric
signature observed for aggregates is a composite of a) the polarization induced
by individual grains composing the aggregate and b) the polarization due to the
aggregate as a whole dust grain. The weight of each component varies depending
on the porosity of the aggregate. An NPB similar to the one observed for
atmosphereless astronomical bodies is present for different ranges of the size
parameter depending on the value of the porosity. It appears as a remnant of
the negative branch exhibited by the single spherical grains. The sharper,
narrow negative branch that is measured for some granular surfaces in the
laboratory or seen in astronomical observations is not observed here.


title: Stochastically Induced Gamma-Ray Burst Wakefield Processes

abstract:
  We present a numerical study of Gamma-Ray Burst - Circumburst Medium
interaction and plasma preconditioning via Compton scattering. The simulation
tool employed is a unique hybrid model; it combines a highly parallelized
(Vlasov) particle-in-cell approach with continuous weighting of particles and a
sub-Debye Monte-Carlo binary particle interaction framework. These first
results from 3D simulations with this new simulation tool, the PhotonPlasma
code, suggests that magnetic fields and plasma density filaments are created in
the wakefield of prompt gamma-ray bursts, and that the photon flux density
gradient has a significant impact on particle acceleration in the burst head
and wakefield. We discuss some possible implications of the circumburst medium
preconditioning for the trailing afterglow, and also discuss which additional
processes will be needed to improve future studies within this unique and
powerful simulation framework.


title: Solar rotation rate and its gradients during cycle 23

abstract:
  Available helioseismic data now span almost the entire solar activity cycle
23 making it possible to study solar-cycle related changes of the solar
rotation rate in detail. In this paper we study how the solar rotation rate, in
particular, the zonal flows change with time. In addition to the zonal flows
that show a well known pattern in the solar convection zone, we also study
changes in the radial and latitudinal gradients of the rotation rate,
particularly in the shear layer that is present in the immediate sub-surface
layers of the Sun. In the case of the zonal-flow pattern, we find that the band
indicating fast rotating region close to the equator seems to have bifurcated
around 2005. Our investigation of the rotation-rate gradients show that the
relative variation in the rotation-rate gradients is about 20% or more of their
average values, which is much larger than the relative variation in the
rotation rate itself. These results can be used to test predictions of various
solar dynamo models.


title:
Tracing the Mass-Dependent Star Formation History of Late-Type Galaxies
  using X-ray Emission: Results from the Chandra Deep Fields

abstract:
  We report on the X-ray evolution over the last ~9 Gyr of cosmic history
(i.e., since z = 1.4) of late-type galaxy populations in the Chandra Deep
Field-North and Extended Chandra Deep Field-South (CDF-N and E-CDF-S,
respectively; jointly CDFs) survey fields. Our late-type galaxy sample consists
of 2568 galaxies, which were identified using rest-frame optical colors and HST
morphologies. We utilized X-ray stacking analyses to investigate the X-ray
emission from these galaxies, emphasizing the contributions from normal
galaxies that are not dominated by active galactic nuclei (AGNs). Over this
redshift range, we find significant increases (factors of ~5--10) in the
X-ray--to--optical mean luminosity ratio (L_X/L_B) and the
X-ray--to--stellar-mass mean ratio (L_X/M*) for galaxy populations selected by
L_B and M*, respectively. When analyzing galaxy samples selected via SFR, we
find that the mean X-ray--to--SFR ratio (L_X/SFR) is consistent with being
constant over the entire redshift range for galaxies with SFR = 1--100 Msol
yr^-1, thus demonstrating that X-ray emission can be used as a robust indicator
of star-formation activity out to z = 1.4. We find that the star-formation
activity (as traced by X-ray luminosity) per unit stellar mass in a given
redshift bin increases with decreasing stellar mass over the redshift range z =
0.2--1, which is consistent with previous studies of how star-formation
activity depends on stellar mass. Finally, we extend our X-ray analyses to
Lyman break galaxies at z ~ 3 and estimate that L_X/L_B at z ~ 3 is similar to
its value at z = 1.4.


title: Central Charge for AdS_2 Quantum Gravity

abstract:
  Two-dimensional Maxwell-dilaton quantum gravity on AdS_2 with radius $\ell$
and a constant electric field E is studied. In conformal gauge, this is
equivalent to a CFT on a strip. In order to maintain consistent boundary
conditions, the usual conformal diffeomorphisms must be accompanied by a
certain U(1) gauge transformation. The resulting conformal transformations are
generated by a twisted stress tensor, which has a central charge $c={3k E^2
\ell^4/4}$ where k is the level of the U(1) current. This is an AdS_2 analog of
the Brown-Henneaux formula $c = 3\ell/2G$ for the central charge of quantum
gravity on AdS_3.


title: Inverting Phase Functions to Map Exoplanets

abstract:
  We describe how to generate a longitudinal brightness map for a tidally
locked exoplanet from its phase function light curve. We operate under a number
of simplifying assumptions, neglecting limb darkening/brightening, star spots,
detector ramps, as well as time-variability over a single planetary rotation.
We develop the transformation from a planetary brightness map to a phase
function light curve and simplify the expression for the case of an edge-on
system. We introduce two models--composed of longitudinal slices of uniform
brightness, and sinusoidally varying maps, respectively--which greatly simplify
the transformation from map to light curve. We discuss numerical approaches to
extracting a longitudinal map from a phase function light curve, explaining how
to estimate the uncertainty in a computed map and how to choose an appropriate
number of fit parameters. We demonstrate these techniques on a simulated map
and discuss the uses and limitations of longitudinal maps. The sinusoidal model
provides a better fit to the planet's underlying brightness map, although the
slice model is more appropriate for light curves which only span a fraction of
the planet's orbit. Regardless of which model is used, we find that there is a
maximum of ~5 free parameters which can be meaningfully fit based on a full
phase function light curve, due to the insensitivity of the latter to certain
modes of the map.


title:
Nature and strength of bonding in a crystal of semiconducting nanotubes:
  van der Waals density functional calculations and analytical results

abstract:
  The dispersive interaction between nanotubes is investigated through ab
initio theory calculations and in an analytical approximation. A van der Waals
density functional (vdW-DF) [Phys. Rev. Lett. 92, 246401 (2004)] is used to
determine and compare the binding of a pair of nanotubes as well as in a
nanotube crystal. To analyze the interaction and determine the importance of
morphology, we furthermore compare results of our ab initio calculations with a
simple analytical result that we obtain for a pair of well-separated nanotubes.
In contrast to traditional density functional theory calculations, the vdW-DF
study predicts an intertube vdW bonding with a strength that is consistent with
recent observations for the interlayer binding in graphitics. It also produce a
nanotube wall-to-wall separation which is in very good agreement with
experiments. Moreover, we find that the vdW-DF result for the nanotube-crystal
binding energy can be approximated by a sum of nanotube-pair interactions when
these are calculated in vdW-DF. This observation suggests a framework for an
efficient implementation of quantum-physical modeling of the CNT bundling in
more general nanotube bundles, including nanotube yarn and rope structures.


title: The Structure of Halos: Implications for Group and Cluster Cosmology

abstract:
  The dark matter halo mass function is a key repository of cosmological
information over a wide range of mass scales, from individual galaxies to
galaxy clusters. N-body simulations have established that the
friends-of-friends (FOF) mass function has a universal form to a surprising
level of accuracy (< 10%). The high-mass tail of the mass function is
exponentially sensitive to the amplitude of the initial density perturbations,
the mean matter density parameter, Omega_m, and to the dark energy controlled
late-time evolution of the density field. Observed group and cluster masses,
however, are usually stated in terms of a spherical overdensity (SO) mass which
does not map simply to the FOF mass. Additionally, the widely used halo models
of structure formation -- and halo occupancy distribution descriptions of
galaxies within halos -- are often constructed exploiting the universal form of
the FOF mass function. This again raises the question of whether FOF halos can
be simply related to the notion of a spherical overdensity mass. By employing
results from Monte Carlo realizations of ideal Navarro-Frenk-White (NFW) halos
and N-body simulations, we study the relationship between the two definitions
of halo mass. We find that the vast majority of halos (80-85%) in the
mass-range 10^{12.5}-10^{15.5} M_sun/h indeed allow for an accurate mapping
between the two definitions (~ 5%), but only if the halo concentrations are
known. Nonisolated halos fall into two broad classes: those with complex
substructure that are poor fits to NFW profiles and those ``bridged'' by the
(isodensity-based)FOF algorithm. A closer investigation of the bridged halos
reveals that the fraction of these halos and their satellite mass distribution
is cosmology dependent. (abridged)


title: 1/N_c and 1/n preasymptotic corrections to Current-Current correlators

abstract:
  We obtain the corrections in $1/n$ and in $1/\ln n$ ($n$ is the principal
quantum number of the bound state) of the decay constants of scalar and
pseudoscalar currents in two and four dimensions in the large $N_c$. We obtain
them from the operator product expansion provided a model for the large $n$
mass spectrum is given. In the two-dimensional case the spectrum is known and
the corrections obtained in this paper are model independent. We confirm these
results by confronting them with the numerical solution of the 't Hooft model.
We also consider a model at finite $N_c$ and obtain the associated decay
constants that are consistent with perturbation theory. This example shows that
that the inclusion of perturbative corrections, or finite $N_c$ effects, to the
OPE does not constrain the slope of the Regge trajectories, which remain a free
parameter for each different channel.


title: Hobby-Eberly Telescope Observations of the Dark Halo in NGC 821

abstract:
  We present line-of-sight stellar velocity distributions of elliptical galaxy
NGC 821 obtained to approximately 100 arcsec (over 2 effective radii) with
long-slit spectroscopy from the Hobby-Eberly Telescope. Our measured stellar
line-of-sight velocity distributions are larger than the planetary nebulae
measurements at similar radii. We fit axisymmetric orbit-superposition models
with a range of dark halo density profiles, including two-dimensional
kinematics at smaller radii from SAURON data. Within our assumptions, the
best-fitted model gives a total enclosed mass of 2.0x10^11 M_sun within 100
arcsec, with an accuracy of 2%; this mass is equally divided between halo and
stars. At 1R_e the best-fitted dark matter halo accounts for 13% of the total
mass in the galaxy. This dark halo is inconsistent with previous claims of
little to no dark matter halo in this galaxy from planetary nebula
measurements. We find that a power-law dark halo with a slope 0.1 is the
best-fitted model; both the no dark halo and NFW models are worse fits at a
greater than 99% confidence level. NGC 821 does not appear to have the expected
dark halo density profile. The internal moments of the stellar velocity
distribution show that the model with no dark halo is radially anisotropic at
small radii and tangentially isotropic at large radii, while the best-fitted
halo models are slightly radially anisotropic at all radii. We test the
potential effects of model smoothing and find that there are no effects on our
results within the errors. Finally, we run models using the planetary nebula
kinematics and assuming our best-fitted halos and find that the planetary
nebulae require radial orbits throughout the galaxy.


title: Cosmological Physics with Black Holes (and Possibly White Dwarfs)

abstract:
  The notion that microparsec-scale black holes can be used to probe
gigaparsec-scale physics may seem counterintuitive, at first. Yet, the
gravitational observatory LISA will detect cosmologically-distant coalescing
pairs of massive black holes, accurately measure their luminosity distance and
help identify an electromagnetic counterpart or a host galaxy. A wide variety
of new black hole studies and a gravitational version of Hubble's diagram
become possible if host galaxies are successfully identified. Furthermore, if
dark energy is a manifestation of large-scale modified gravity, deviations from
general relativistic expectations could become apparent in a gravitational
signal propagated over cosmological scales, especially when compared to the
electromagnetic signal from a same source. Finally, since inspirals of white
dwarfs into massive black holes at cosmological distances may permit pre-merger
localizations, we suggest that careful monitoring of these events and any
associated electromagnetic counterpart could lead to high-precision
cosmological measurements with LISA.


title: Band touching from real space topology in frustrated hopping models

abstract:
  We study ``frustrated'' hopping models, in which at least one energy band, at
the maximum or minimum of the spectrum, is dispersionless. The states of the
flat band(s) can be represented in a basis which is fully localized, having
support on a vanishing fraction of the system in the thermodynamic limit. In
the majority of examples, a dispersive band touches the flat band(s) at a
number of discrete points in momentum space. We demonstrate that this band
touching is related to states which exhibit non-trivial topology in real space.
Specifically, these states have support on one-dimensional loops which wind
around the entire system (with periodic boundary conditions). A counting
argument is given that determines, in each case, whether there is band touching
or not, in precise correspondence to the result of straightforward
diagonalization. When they are present, the topological structure protects the
band touchings in the sense that they can only be removed by perturbations
which {\sl also} split the degeneracy of the flat band.


title: The Solar-System-Scale Disk Around AB Aurigae

abstract:
  The young star AB Aurigae is surrounded by a complex combination of gas-rich
and dust dominated structures. The inner disk which has not been studied
previously at sufficient resolution and imaging dynamic range seems to contain
very little gas inside a radius of least 130 astronomical units (AU) from the
star. Using adaptive-optics coronagraphy and polarimetry we have imaged the
dust in an annulus between 43 and 302 AU from the star, a region never seen
before. An azimuthal gap in an annulus of dust at a radius of 102 AU, along
with a clearing at closer radii inside this annulus, suggests the formation of
at least one small body at an orbital distance of about 100 AU. This structure
seems consistent with crude models of mean motion resonances, or accumulation
of material at two of the Lagrange points relative to the putative object and
the star. We also report a low significance detection of a point source in this
outer annulus of dust. This source may be an overdensity in the disk due to
dust accreting onto an unseen companion. An alternate interpretation suggests
that the object's mass is between 5 and 37 times the mass of Jupiter. The
results have implications for circumstellar disk dynamics and planet formation.


title:
M-functions for closed extensions of adjoint pairs of operators with
  applications to elliptic boundary problems

abstract:
  In this paper, we combine results on extensions of operators with recent
results on the relation between the M-function and the spectrum, to examine the
spectral behaviour of boundary value problems. M-functions are defined for
general closed extensions, and associated with realisations of elliptic
operators. In particular, we consider both ODE and PDE examples where it is
possible for the operator to possess spectral points that can not be detected
by the M-function.


title: Neutral Hydrogen Clouds in the M81/M82 Group

abstract:
  We have observed a 3 degree x 3 degree area centered on the M81/M82 group of
galaxies using the Robert C. Byrd Green Bank Telescope (GBT) in a search for
analogs to the High Velocity Clouds (HVCs) of neutral hydrogen found around our
galaxy. The velocity range from -605 to -85 km/s and 25 to 1970 km/s was
searched for HI clouds. Over the inner 2 degrees x 2 degrees the 7-sigma
detection threshold was 9.6 x 10^5 M_sun. We detect 5 previously unknown HI
clouds associated with the group, as well as numerous associated filamentary HI
structures, all lying in the range -105 < V_helio < +280 km/s. From the small
angular distance of the clouds to group members, and the small velocity
difference between group members and clouds, we conclude that the clouds are
most likely relics of ongoing interactions between galaxies in the group.


title: Void Traversal for Guaranteed Delivery in Geometric Routing

abstract:
  Geometric routing algorithms like GFG (GPSR) are lightweight, scalable
algorithms that can be used to route in resource-constrained ad hoc wireless
networks. However, such algorithms run on planar graphs only. To efficiently
construct a planar graph, they require a unit-disk graph. To make the topology
unit-disk, the maximum link length in the network has to be selected
conservatively. In practical setting this leads to the designs where the node
density is rather high. Moreover, the network diameter of a planar subgraph is
greater than the original graph, which leads to longer routes. To remedy this
problem, we propose a void traversal algorithm that works on arbitrary
geometric graphs. We describe how to use this algorithm for geometric routing
with guaranteed delivery and compare its performance with GFG.


title: Simulation of multiple partonic interactions in Herwig++

abstract:
  In this paper we describe a new model of multiple partonic interactions that
has been implemented in Herwig++. Tuning its two free parameters we find a good
description of CDF underlying event data. We show extrapolations to the LHC.


title: Comparison of models and lattice-gas simulations for Liesegang patterns

abstract:
  For more than a century Liesegang patterns -- self-organized, quasi-periodic
structures occurring in diffusion-limited chemical reactions with two
components -- have been attracting scientists. The pattern formation can be
described by four basic empirical laws. In addition to many experiments,
several models have been devised to understand the formation of the bands and
rings. Here we review the most important models and complement them with
detailed three-dimensional lattice-gas simulations. We show how the mean-field
predictions can be reconciled with experimental data by a redefinition of the
distances suggested by our lattice-gas simulations.


title: Nuclear quantum effects in water

abstract:
  In this work, a path integral Car-Parrinello molecular dynamics simulation of
liquid water is performed. It is found that the inclusion of nuclear quantum
effects systematically improves the agreement of first principles simulations
of liquid water with experiment. In addition, the proton momentum distribution
is computed utilizing a recently developed open path integral molecular
dynamics methodology. It is shown that these results are in good agreement with
neutron Compton scattering data for liquid water and ice.


title: Pure Nuclear Fusion Bomb Propulsion

abstract:
  Recent progress towards the non-fission ignition of thermonuclear
micro-explosions raises the prospect for a revival of the nuclear bomb
propulsion idea, both for the fast transport of large payloads within the solar
system and the launch into earth orbit without the release of fission products
into the atmosphere. To reach this goal three areas of research are of
importance: 1)Compact thermonuclear ignition drivers. 2)Fast ignition and
deuterium burn. 3)Space-craft architecture involving magnetic insulation and
GeV electrostatic potentials


title: Complex networks renormalization: flows and fixed points

abstract:
  Recently, it has been claimed that some complex networks are self-similar
under a convenient renormalization procedure. We present a general method to
study renormalization flows in graphs. We find that the behavior of some
variables under renormalization, such as the maximum number of connections of a
node, obeys simple scaling laws, characterized by critical exponents. This is
true for any class of graphs, from random to scale-free networks, from lattices
to hierarchical graphs. Therefore, renormalization flows for graphs are similar
as in the renormalization of spin systems. An analysis of classic
renormalization for percolation and the Ising model on the lattice confirms
this analogy. Critical exponents and scaling functions can be used to classify
graphs in universality classes, and to uncover similarities between graphs that
are inaccessible to a standard analysis.


title:
Distances from Stellar Kinematics for Peculiar Virgo Cluster Spiral
  Galaxies

abstract:
  We present distance estimates for eleven peculiar Virgo cluster spiral
galaxies based on measurements of the stellar kinematics of their central 2
kpc. Stellar circular velocities were obtained using two-integral dynamical
models. Distances were obtained by comparing, at each radius, the stellar
circular velocities with synthetic H_alpha rotation curves derived from NIR
Tully-Fisher relations.The results show that most of our galaxies are located
within 4 Mpc of the core of the cluster. Three of these galaxies, previously
classified as "low rotator galaxies" or with "Truncated/Compact" H_alpha radial
distributions, have stellar kinematics-based distances that are discrepant with
HI-based distances by at least 60%, and are likely to be located within the
virial radius of the cluster. These discrepancies appear due to very truncated
gas distributions plus non-circular gas motions or gas motions not in the plane
of the stellar disk, perhaps as the result of gravitational interactions. Our
results show that environmental effects can significantly reduce the measured
HI linewidths for some disturbed cluster galaxies, thus affecting the accurate
determination of distances based on gas kinematics methods.


title:
Parabolic induction and restriction functors for rational Cherednik
  algebras

abstract:
  We introduce parabolic induction and restriction functors for rational
Cherednik algebras, and study their basic properties. Then we discuss
applications of these functors to representation theory of rational Cherednik
algebras. In particular, we prove the Gordon-Stafford theorem about Morita
equivalence of the rational Cherednik algebra for type A and its spherical
subalgebra, without the assumption that c is not a half-integer, which was
required up to now. Also, we classify representations from category O over the
rational Cherednik algebras of type A which do not contain an S_n-invariant
vector, and confirm a conjecture of Okounkov and the first author on the number
of such representations. In the second version we have added a result on the
simplicity of the spherical Cherednik algebra of type A for -1<c<0, and a
strengthened version of the main result of arXiv:math/0312474, as well as an
appendix by the second author containing arXiv:0706.4308, on the reducibility
of the polynomial representation of the trigonometric Cherednik algebra.


title: Electrical control of spin coherence in ZnO

abstract:
  Electric field enhanced electron spin coherence is characterized using
time-resolved Faraday rotation spectroscopy in n-type ZnO epilayers grown by
molecular beam epitaxy. An in-plane dc electric field E almost doubles the
transverse spin lifetime at 20 K, without affecting the effective g-factor.
This effect persists till high temperatures, but decreases with increasing
carrier concentration. Comparisons of the variations in the spin lifetime, the
carrier recombination lifetime and photoluminescence lifetimes indicate that
the applied E enhances the radiative recombination rate. All observed effects
are independent of crystal directionality and are performed at low magnetic
fields (B < 0.2 T).


title:
Pseudo-Newtonian gravitational potential for Schwarzschild-de Sitter
  spacetimes

abstract:
  Pseudo-Newtonian gravitational potential describing the gravitational field
of static and spherically symmetric black holes in the universe with a
repulsive cosmological constant is introduced. In order to demonstrate the
accuracy of the pseudo-Newtonian approach, the related effective potential for
test-particle motion is constructed and compared with its general relativistic
counterpart given by the Schwarzschild-de Sitter geometry. The results indicate
that such an approach could be useful in applications of developed Newtonian
theories of accretion discs in astrophysically interesting situations in large
galactic structures for the Schwarzschild-de Sitter spacetimes with the
cosmological parameter y=(1/3)\Lambda M^2<10^{-6}.


title: Distributed Averaging in the presence of a Sparse Cut

abstract:
  We consider the question of averaging on a graph that has one sparse cut
separating two subgraphs that are internally well connected.
  While there has been a large body of work devoted to algorithms for
distributed averaging, nearly all algorithms involve only {\it convex} updates.
In this paper, we suggest that {\it non-convex} updates can lead to significant
improvements. We do so by exhibiting a decentralized algorithm for graphs with
one sparse cut that uses non-convex averages and has an averaging time that can
be significantly smaller than the averaging time of known distributed
algorithms, such as those of \cite{tsitsiklis, Boyd}. We use stochastic
dominance to prove this result in a way that may be of independent interest.


title:
Robust quantum cryptography with a heralded single-photon source based
  on the decoy-state method

abstract:
  In this paper, we describe a robust quantum cryptography scheme with a
heralded single photon source based on the decoy-state method, which has been
shown by numerical simulations to be advantageous compared with many other
practical schemes not only with respect to the secure key generation rate but
also to secure transmission distance. We have experimentally tested this
scheme, and the results support the conclusions from numerical simulations
well. Although there still exist many deficiencies in our present systems, it's
still sufficient to demonstrate the advantages of the scheme. Besides, even
when cost and technological feasibility are taken into account, our scheme is
still quite promising in the implementation of tomorrow's quantum cryptography.


title: Theoretical study on the possibility of bipolar doping of ScN

abstract:
  Scandium nitride (ScN) is a semiconducting transition metal nitride for which
there are not identified dopants. We present local density functional
calculations, in supercell approach, for ScN doped with O and C in N-sites and
Ca and Ti in Sc-sites. Small additions of these atoms have the effect of
shifting the Fermi level within the electronic band structure. O and Ti bring
occupied states in bottom of conduction band, while C and Ca produces holes in
top of valence band. Based on the theory we propose that bipolar doping is
possible to scandium nitride.


title:
A New Sphere-Packing Bound for Maximal Error Exponent for
  Multiple-Access Channels

abstract:
  In this work, a new lower bound for the maximal error probability of a
two-user discrete memoryless (DM) multiple-access channel (MAC) is derived.
This is the first bound of this type that explicitly imposes independence of
the users' input distributions (conditioned on the time-sharing auxiliary
variable) and thus results in a tighter sphere-packing exponent when compared
to the tightest known exponent derived by Haroutunian.


title:
Characterizing Hilbert spaces using Fourier transform over the field of
  p-adic numbers

abstract:
  We characterize Hilbert spaces in the class of all Banach spaces using
Fourier transform of vector-valued functions over the field $Q_p$ of $p$-adic
numbers. Precisely, Banach space $X$ is isomorphic to a Hilbert one if and only
if Fourier transform $F: L_2(Q_p,X)\to L_2(Q_p,X)$ in space of functions, which
are square-integrable in Bochner sense and take value in $X$, is a bounded
operator.


title: Affine partitions and affine Grassmannians

abstract:
  We give a bijection between certain colored partitions and the elements in
the quotient of an affine Weyl group modulo its Weyl group. By Bott's formula
these colored partitions give rise to some partition identities. In certain
types, these identities have previously appeared in the work of
Bousquet-Melou-Eriksson, Eriksson-Eriksson and Reiner. In other types the
identities appear to be new. For type $A_{n}$, the affine colored partitions
form another family of combinatorial objects in bijection with $n+1$-core
partitions and $n$-bounded partitions. Our main application is to characterize
the rationally smooth Schubert varieties in the affine Grassmannians in terms
of affine partitions and a generalization of Young's lattice which refines weak
order and is a subposet of Bruhat order. Several of the proofs are computer
assisted.


title: Monte Carlo simulation of metal deposition on foreign substrates

abstract:
  The deposition of a metal on a foreign substrate is studied by means of grand
canonical Monte Carlo simulations and a lattice-gas model with pair potential
interactions between nearest neighbors. The influence of temperature and
surface defects on adsorption isotherms and differential heat of adsorption is
considered. The general trends can be explained in terms of the relative
interactions between adsorbate atoms and substrate atoms. The systems
Ag/Au(100), Ag/Pt(100), Au/Ag(100) and Pt/Ag(100) are analyzed as examples.


title: Quasi-Two-Dimensional Extraordinary Hall Effect

abstract:
  Quasi-two-dimensional transport is investigated in a system consisting of one
ferromagnetic layer placed between two insulating layers. Using the mechanism
of skew-scattering to describe the Extraordinary Hall Effect (EHE) and
calculating the conductivity tensor, we compare the quasi- two-dimensional Hall
resistance with the resistance of a massive sample. In this study a new
mechanism of EHE (geometric mechanism of EHE) due to non-ideal interfaces and
volume defects is also proposed.


title: Simulating nonlinear neutrino flavor evolution

abstract:
  We discuss a new kind of astrophysical transport problem: the coherent
evolution of neutrino flavor in core collapse supernovae. Solution of this
problem requires a numerical approach which can simulate accurately the quantum
mechanical coupling of intersecting neutrino trajectories and the associated
nonlinearity which characterizes neutrino flavor conversion. We describe here
the two codes developed to attack this problem. We also describe the surprising
phenomena revealed by these numerical calculations. Chief among these is that
the nonlinearities in the problem can engineer neutrino flavor transformation
which is dramatically different than in standard Mikheyev-Smirnov-Wolfenstein
treatments. This happens even though the neutrino mass-squared differences are
measured to be small, and even when neutrino self-coupling is sub-dominant. Our
numerical work has revealed potential signatures which, if detected in the
neutrino burst from a Galactic core collapse event, could reveal heretofore
unmeasurable properties of the neutrinos, such as the mass hierarchy and vacuum
mixing angle theta_13.


title:
On the Canonical Structure of First Order Einstein-Hilbert Action
  Coupled to Bosonic Matter

abstract:
  A Dirac Hamiltonian formulation of d-dimensional Einstein-Hilbert action in
first order form, has shown that as well as secondary first class constraints,
tertiary first class constraints also arise, with an unusual nonlocal Poisson
bracket (PB) algebra among first class constraints [8 ]. This approach is
different from that of ADM in that of the equations of motion which are
independent of the time derivative of fields only those which correspond to
second class constraints (in the sense of the Dirac constraint formalism) are
used to eliminate fields from the action. In this paper, we consider coupling
of a cosmological term, massive scalar fields, Maxwell gauge fields and
Yang-Mills fields to the first order EH action in this formalism, and show that
in spite of the apparent differences with the ADM results in the Hamiltonian
formulation of the first order EH action and its constraint structure, the
generic properties of the ADM Hamiltonian formulation of the first order EH
action in the presence of Bosonic matter are derivable from this novel
Hamiltonian formulation. Addition of a massive scalar field to the EH action
leaves the PB algebra of constraints unaltered, and when the Yang-Mills fields
or Maxwell gauge fields are coupled to the EH action, the PB algebra of the
constraints pertaining to the EH action receives linear contributions from the
generator of the gauge transformations of the action for matter fields, and
those generators form a closed algebra amongst themselves. Moreover, it is
found that for closed spaces, the Hamiltonian of the EH action coupled to
Bosonic matter is weakly zero on the constraint surface defined by the first
class constraints, including the constraints arising from the matter fields.


title: A categorification of quantum sl(2)

abstract:
  We categorify Lusztig's version of the quantized enveloping algebra for
sl(2). Using a graphical calculus a 2-category is constructed whose split
Grothendieck ring is isomorphic to Lusztig's algebra. The indecomposable
morphisms of this 2-category lift Lusztig's canonical basis, and the Homs
between 1-morphisms are graded lifts of a semilinear form defined on quantum
sl(2). Graded lifts of various homomorphisms and antihomomorphisms of Lusztig's
algebra arise naturally in the context of our graphical calculus. Using
iterated flag varieties, a representation of the 2-category is constructed for
each positive integer N. This representation categorifies the irreducible
(N+1)-dimensional representation of quantum sl(2).