title:
Role of transverse displacements for a quantized-velocity state of the
  lubricant

abstract:
  Within the idealized scheme of a 1-dimensional Frenkel-Kontorova-like model,
a special "quantized" sliding state was found for a solid lubricant confined
between two periodic layers [PRL 97, 056101 (2006)]. This state, characterized
by a nontrivial geometrically fixed ratio of the mean lubricant drift velocity
<v_cm> and the externally imposed translational velocity v_ext, was understood
as due to the kinks (or solitons), formed by the lubricant due to
incommensuracy with one of the substrates, pinning to the other sliding
substrate. A quantized sliding state of the same nature is demonstrated here
for a substantially less idealized 2-dimensional model, where atoms are allowed
to move perpendicularly to the sliding direction and interact via Lennard-Jones
potentials. Clear evidence for quantized sliding at finite temperature is
provided, even with a confined solid lubricant composed of multiple (up to 6)
lubricant layers. Characteristic backward lubricant motion produced by the
presence of "anti-kinks" is also shown in this more realistic context.


title:
The stellar content of the Hamburg/ESO survey. IV. Selection of
  candidate metal-poor stars

abstract:
  We present the quantitative methods used for selecting candidate metal-poor
stars in the Hamburg/ESO objective-prism survey (HES). The selection is based
on the strength of the Ca II K line, B-V colors (both measured directly from
the digital HES spectra), as well as J-K colors from the 2 Micron All Sky
Survey. The KP index for Ca II K can be measured from the HES spectra with an
accuracy of 1.0 Angstrom, and a calibration of the HES B-V colors, using CCD
photometry, yields a 1-sigma uncertainty of 0.07 mag for stars in the color
range 0.3 < B-V < 1.4. These accuracies make it possible to reliably reject
stars with [Fe/H] > -2.0 without sacrificing completeness at the lowest
metallicities. A test of the selection using 1121 stars of the HK survey of
Beers, Preston, and Shectman present on HES plates suggests that the
completeness at [Fe/H] < -3.5 is close to 100% and that, at the same time, the
contamination of the candidate sample with false positives is low: 50% of all
stars with [Fe/H] > -2.5 and 97% of all stars with [Fe/H] > -2.0 are rejected.
The selection was applied to 379 HES fields, covering a nominal area of 8853
square degrees of the southern high Galactic latitude sky. The candidate sample
consists of 20,271 stars in the magnitude range 10 < B < 18. A comparison of
the magnitude distribution with that of the HK survey shows that the magnitude
limit of the HES sample is about 2 mag fainter. Taking the overlap of the sky
areas covered by both surveys into account, it follows that the survey volume
for metal-poor stars has been increased by the HES by about a factor of 10 with
respect to the HK survey. We have already identified several very rare objects
with the HES, including, e.g., the three most heavy-element deficient stars
currently known.


title: Tri-bimaximal neutrino mixing and neutrinoless double beta decay

abstract:
  We present a tri-bimaximal lepton mixing scheme where the neutrinoless double
beta decay rate (bb0v) has a lower bound which correlates with the ratio alpha
= Dmsol/Dmatm well determined by current data, as well as with the unknown
Majorana CP phase phi12 characterizing the solar neutrino sub-system. For the
special value phi12 = pi/2 (opposite CP-sign neutrinos) the bb0v rate vanishes
at tree level when Dmsol/Dmatm = 3/80, only allowed at 3 sigma. For all other
cases the rate is nonzero, and lies within current and projected experimental
sensitivities close to phi12=0. We suggest two model realizations of this
scheme in terms of an A4xZ2 and A4xZ4 flavour symmetries.


title: The supersingular locus of the Shimura variety of GU(1,n-1) II

abstract:
  We complete the study of the supersingular locus in the fiber at $p$ of a
Shimura variety attached to a unitary similitude group $\GU(1,n-1)$ over $\QQ$
in the case that $p$ is inert. This was started by the first author in
\cite{Vo_Uni} where complete results were obtained for $n =2,3$. The
supersingular locus is uniformized by a formal scheme $\Ncal$ which is a moduli
space of so-called unitary $p$-divisible groups. It depends on the choice of a
unitary isocrystal $\Nbf$. We define a stratification of $\Ncal$ indexed by
vertices of the Bruhat-Tits building attached to the reductive group of
automorphisms of $\Nbf$. We show that the combinatorial behaviour of this
stratification is given by the simplicial structure of the building. The
closures of the strata (and in particular the reduced irreducible components of
$\Ncal$) are identified with (generalized) Deligne-Lusztig varieties. We show
that the Bruhat-Tits stratification is a refinement of the Ekedahl-Oort
stratification and also relate the Ekedahl-Oort strata to Deligne-Lusztig
varieties. We deduce that the supersingular locus is locally a complete
intersection, that its irreducible components and each Ekedahl-Oort stratum in
every irreducible component is isomorphic to a Deligne-Lusztig variety, and
give formulas for the number of irreducible components of every Ekedahl-Oort
stratum of the supersingular locus.


title: On the S-Matrix of the Faddeev-Reshetikhin Model

abstract:
  The Faddeev-Reshetikhin model arises as a truncation of strings in AdS_5XS^5.
Its two particle S-matrix should be obtained by diagonalizing its Hamiltonian.
However this does not happen in a straightforward way. There is a Lorentz
violating term in the Hamiltonian which prevents its plain diagonalization. We
then find out the most general quartic Hamiltonian that can be diagonalized. It
includes the bosonic Thirring model as well as another model which shares the
same two particle S-matrix as the Faddeev-Reshetikhin model. We also find a one
parameter family of interactions which lead to non-Hermitian Hamiltonians which
have unitary S-matrices and are PT symmetric.


title:
Magnetic-Field Variations of the Pair-Breaking Effects of
  Superconductivity in (TMTSF)2ClO4

abstract:
  We have studied the onset temperature of the superconductivity Tc_onset of
the organic superconductor (TMTSF)2ClO4, by precisely controlling the direction
of the magnetic field H. We compare the results of two samples with nearly the
same onset temperature but with different scattering relaxation time tau. We
revealed a complicated interplay of a variety of pair-breaking effects and
mechanisms that overcome these pair-breaking effects. In low fields, the linear
temperature dependences of the onset curves in the H-T phase diagrams are
governed by the orbital pair-breaking effect. The dips in the in-plane
field-angle phi dependence of Tc_onset, which were only observed in the
long-tau sample, provides definitive evidence that the field-induced
dimensional crossover enhances the superconductivity if the field direction is
more than about 19-degrees away from the a axis. In the high-field regime for
H//a, the upturn of the onset curve for the long-tau sample indicates a new
superconducting state that overcomes the Pauli pair-breaking effect but is
easily suppressed by impurity scatterings. The Pauli effect is also overcome
for H//b' by a realization of another state for which the maximum of
Tc_onset(phi) occurs in a direction different from the crystalline axes. The
effect on Tc_onset of tilting the applied field out of the conductive plane
suggests that the Pauli effect plays a significant role in determining
Tc_onset. The most plausible explanation of these results is that (TMTSF)2ClO4
is a singlet superconductor and exhibits Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) states in high fields.


title: Bound entanglement in the magic simplex of two--qutrits

abstract:
  We investigate the entanglement properties of a three--parameter family of
states that are part of the magic simplex of two qutrits, which is a simplex of
states that are mixtures of maximally entangled two--qutrit Bell states. Using
entanglement witnesses we reveal large regions of bound entangled and separable
states.


title:
Nonempirical Density Functionals Investigated for Jellium:
  Spin-Polarized Surfaces, Spherical Clusters, and Bulk Linear Response

abstract:
  Earlier tests show that the Tao-Perdew-Staroverov-Scuseria (TPSS)
nonempirical meta-generalized gradient approximation (meta-GGA) for the
exchange-correlation energy yields more accurate surface energies than the
local spin density (LSD) approximation for spin-unpolarized jellium. In this
study, work functions and surface energies of a jellium metal in the presence
of ``internal'' and external magnetic fields are calculated with LSD,
Perdew-Burke-Ernzerhof (PBE) GGA, and TPSS meta-GGA and its predecessor, the
nearly nonempirical Perdew-Kurth-Zupan-Blaha (PKZB) meta-GGA, using
self-consistent LSD orbitals and densities. The results show that: (i) For
normal bulk densities, the surface correlation energy is the same in TPSS as in
PBE, as it should be since TPSS strives to represent a self-correlation
correction to PBE; (ii) Normal surface density profiles can be scaled uniformly
to the low-density or strong-interaction limit, and TPSS provides an estimate
for that limit that is consistent with (but probably more accurate than) other
estimates; (iii) For both normal and low densities, TPSS provides the same
description of surface magnetism as PBE, suggesting that these approximations
may be generally equivalent for magnetism. The energies of jellium spheres with
up to 106 electrons are calculated using density functionals and compared to
those obtained with Diffusion Quantum Monte Carlo data, including our estimate
for the fixed-node correction. Finally we calculate the linear response of bulk
jellium using these density functionals, and find that not only LSD but also
PBE GGA and TPSS meta-GGA yield a linear-response in good agreement with that
of the Quantum Monte Carlo method, for wavevectors of the perturbing external
potential up to twice the Fermi wavevector.


title: Subluminous O Stars - Origin and Evolutionary Links

abstract:
  Hot subluminous stars can be roughly divided into B- and O-types. Unlike the
latter many sdBs are found in close binaries, indicating that binary evolution
plays a vital role. Recent NLTE spectral analyses revealed that an evolutionary
link between sdB stars and sdO stars is plausible only for the helium-deficient
sdO stars, i.e. they are the likely successors to sdB stars. The atmospheric
properties of helium-enriched sdO stars can be explained by the late hot
flasher as well as by the white-dwarf merger scenarios, although both models do
not match the observed properties of helium-enriched sdO stars in detail. The
white dwarf merger scenario is favoured because it naturally explains the
scarcity of close binaries amongst helium-enriched sdO stars. A hyper-velocity
sdO star moving so fast that it is unbound to the Galaxy has probably been
ejected by the super-massive black hole in the Galactic centre.


title:
Review of Applications of YFS-Style Resummation in Quantum Field Theory
  via Monte Carlo Methods

abstract:
  We review the application of exact, amplitude-based, YFS-syle resummation in
quantum field theory via Monte Carlo methods.


title: A realization of the quantum Lorentz group

abstract:
  A realization of a deformed Lorentz algebra is considered and its irreducible
representations are found; in the limit $q\to 1$, these are precisely the
irreducible representations of the classical Lorentz group.


title:
Phase separation of an asymmetric binary fluid mixture confined in a
  nanoscopic slit pore: Molecular-dynamics simulations

abstract:
  As a generic model system of an asymmetric binary fluid mixture, hexadecane
dissolved in carbon dioxide is considered, using a coarse-grained bead-spring
model for the short polymer, and a simple spherical particle with Lennard-Jones
interactions for the carbon dioxide molecules. In previous work, it has been
shown that this model reproduces the real phase diagram reasonable well, and
also the initial stages of spinodal decomposition in the bulk following a
sudden expansion of the system could be studied. Using the parallelized
simulation package ESPResSo on a multiprocessor supercomputer, phase separation
of thin fluid films confined between parallel walls that are repulsive for both
types of molecules are simulated in a rather large system (1356 x 1356 x 67.8
A^3, corresponding to about 3.2 million atoms). Following the sudden system
expansion, a complicated interplay between phase separation in the directions
perpendicular and parallel to the walls is found: in the early stages the
hexadecane molecules accumulate mostly in the center of the slit pore, but as
the coarsening of the structure in the parallel direction proceeds, the
inhomogeneity in the perpendicular direction gets much reduced. Studying then
the structure factors and correlation functions at fixed distances from the
wall, the densities are essentially not conserved at these distances, and hence
the behavior differs strongly from spinodal decomposition in the bulk. Some of
the characteristic lengths show a nonmonotonic variation with time, and simple
coarsening described by power-law growth is only observed if the domain sizes
are much larger than the film thickness.


title:
Test of isospin symmetry via low energy $^1$H($\pi^-$,$\pi^o$)$n$ charge
  exchange

abstract:
  We report measurements of the $\pi^- p \to \pi^o n$ differential cross
sections at six momenta (104-143 MeV/c) and four angles (0-40 deg) by detection
of $\gamma$-ray pairs from $\pi^o \to \gamma \gamma$ decays using the TRIUMF
RMC spectrometer. This region exhibits a vanishing zero-degree cross section
from destructive interference between s-- and p--waves, thus yielding special
sensitivity to pion-nucleon dynamics and isospin symmetry breaking. Our data
and previous data do not agree, with important implications for earlier claims
of large isospin violating effects in low energy pion-nucleon interactions.


title:
A maximum likelihood method for bidimensional experimental
  distributions, and its application to the galaxy merger fraction

abstract:
  The determination of galaxy merger fraction of field galaxies using automatic
morphological indices and photometric redshifts is affected by several biases
if observational errors are not properly treated. Here, we correct these biases
using maximum likelihood techniques. The method takes into account the
observational errors to statistically recover the real shape of the
bidimensional distribution of galaxies in redshift - asymmetry space, needed to
infer the redshift evolution of galaxy merger fraction. We test the method with
synthetic catalogs and show its applicability limits. The accuracy of the
method depends on catalog characteristics such as the number of sources or the
experimental error sizes. We show that the maximum likelihood method recovers
the real distribution of galaxies in redshift and asymmetry space even when
binning is such that bin sizes approach the size of the observational errors.
We provide a step-by-step guide to applying maximum likelihood techniques to
recover any one- or bidimensional distribution subject to observational errors.


title:
Estimating a cosmic ray detector exposure sky map under the hypothesis
  of seasonal and diurnal effects factorization

abstract:
  The measurement of large scale patterns or anisotropies in the arrival
direction of high energy cosmic rays is an important step towards the
understanding of their origin. Such measurements rely on an accurate estimation
of the detector relative exposure in each direction on the sky : the coverage
map. To reach an accuracy on the determination of this map below the one
percent level one must properly identify and correct for all the environmental
effects that may induce variations in the detector exposure as a function of
time. In an approach, similar to the one used in anti-sidereal time analysis,
we propose a method to empirically estimate and correct for those effects under
the hypothesis that seasonal and diurnal variations can be factorized. We
tested this method using a model ground detector of cosmic ray air showers,
whose aperture varies due to the dependence of the air shower development on
the atmospheric conditions.


title:
Fractionally charged Wilson loops as a probe of $\theta$-dependence in
  $CP^{N-1}$ sigma models: Instantons vs. large N

abstract:
  The behavior of Wilson loops with fractional charge is used to study the
$\theta$-dependence of the free energy density $\epsilon(\theta)$ for the
$CP^1$, $CP^5$, and $CP^9$ sigma models in two spacetime dimensions. The
function $\epsilon(\theta)$ is extracted from the area law for a Wilson loop of
charge $q=\theta/2\pi$. For $CP^1$, $\epsilon(\theta)$ is smooth in the region
$\theta\approx\pi$ and well-described by a dilute instanton gas throughout the
range $0<\theta<2\pi$. For $CP^5$ and $CP^9$ the energy exhibits a clear cusp
and evidence for discrete, degenerate vacua at $\theta = \pi$, as expected from
large $N$ arguments. For $CP^9$ the $\theta$-dependence is in good quantitative
agreement with the leading order large $N$ prediction
$\epsilon(\theta)={1/2}\chi_t\theta^2$ throughout the range $0<\theta<\pi$.


title: Rooted induced trees in triangle-free graphs

abstract:
  For a graph $G$, let $t(G)$ denote the maximum number of vertices in an
induced subgraph of $G$ that is a tree. Further, for a vertex $v\in V(G)$, let
$t^v(G)$ denote the maximum number of vertices in an induced subgraph of $G$
that is a tree, with the extra condition that the tree must contain $v$. The
minimum of $t(G)$ ($t^v(G)$, respectively) over all connected triangle-free
graphs $G$ (and vertices $v\in V(G)$) on $n$ vertices is denoted by $t_3(n)$
($t_3^v(n)$). Clearly, $t^v(G)\le t(G)$ for all $v\in V(G)$. In this note, we
solve the extremal problem of maximizing $|G|$ for given $t^v(G)$, given that
$G$ is connected and triangle-free. We show that $|G|\le
1+\frac{(t_v(G)-1)t_v(G)}{2}$ and determine the unique extremal graphs. Thus,
we get as corollary that $t_3(n)\ge t_3^v(n)=\lceil
{1/2}(1+\sqrt{8n-7})\rceil$, improving a recent result by Fox, Loh and Sudakov.


title:
The Large Scale Structure in the Universe: From Power-Laws to Acoustic
  Peaks

abstract:
  The most popular tools for analysing the large scale distribution of galaxies
are second-order spatial statistics such as the two-point correlation function
or its Fourier transform, the power spectrum. In this review, we explain how
our knowledge of cosmic structures, encapsulated by these statistical
descriptors, has evolved since their first use when applied on the early galaxy
catalogues to the present generation of wide and deep redshift surveys,
incorporating the most challenging discovery in the study of the galaxy
distribution: the detection of Baryon Acoustic Oscillations.


title: Quenching Spin Decoherence in Diamond through Spin Bath Polarization

abstract:
  We experimentally demonstrate that the decoherence of a spin by a spin bath
can be completely eliminated by fully polarizing the spin bath. We use electron
paramagnetic resonance at 240 gigahertz and 8 Tesla to study the spin coherence
time $T_2$ of nitrogen-vacancy centers and nitrogen impurities in diamond from
room temperature down to 1.3 K. A sharp increase of $T_2$ is observed below the
Zeeman energy (11.5 K). The data are well described by a suppression of the
flip-flop induced spin bath fluctuations due to thermal spin polarization.
$T_2$ saturates at $\sim 250 \mu s$ below 2 K, where the spin bath polarization
is 99.4 %.


title: More Efficient Purifying scheme via Controlled- Controlled NOT Gate

abstract:
  A new modified version of the Oxford purification protocol is proposed. This
version is based on the controlled-controlled NOT gate instead of controlled
NOT in the original one. Comparisons between the results of the new version and
the original and an earlier modification are given. It is found that the new
version converges faster and consumes fewer initial qubit pairs of low fidelity
per final qubit pair of high fidelity.


title: Multiferroic materials for spin-based logic devices

abstract:
  Logical devices based on spin waves offer the potential to avoid dissipation
mechanisms that limit devices based on either the charge or spin of mobile
electrons. Multiferroic magnetoelectrics, which are materials that combine
ferroelectric and magnetic order, allow direct switching of magnetic order and
thence of spin-wave properties using an applied electric field. The intrinsic
coupling between polarization and magnetic moments, generated by strong
electronic correlations in these multiferroic materials, is argued to provide
new approaches to spin-wave injection and spin-wave switching using applied
voltages with no external magnetic field. These effects are shown to arise in a
phenomenological Landau theory of coupled electronic and magnetic orders in
multiferroic BiFeO3, and found to depend subtly on differences between the
crystalline and film states of this material.


title:
Rich polymorphism of a rod-like liquid crystal (8CB) confined in two
  types of unidirectional nanopores

abstract:
  We present a neutron and X-rays scattering study of the phase transitions of
4-n-octyl-4'-cyanobiphenyl (8CB) confined in unidirectional nanopores of porous
alumina and porous silicon (PSi) membranes with an average diameter of 30 nm.
Spatial confinement reveals a rich polymorphism, with at least four different
low temperature phases in addition to the smectic A phase. The structural study
as a function of thermal treatments and conditions of spatial confinement
allows us to get insights into the formation of these phases and their relative
stability. It gives the first description of the complete phase behavior of 8CB
confined in PSi and provides a direct comparison with results obtained in bulk
conditions and in similar geometric conditions of confinement but with reduced
quenched disorder effects using alumina anopore membranes


title:
Gauge Invariant Overlaps for Classical Solutions in Open String Field
  Theory

abstract:
  We calculate gauge invariant observables for Schnabl's solution with analytic
method and with the level truncation approximation. We also compute them for
the numerical solution initially obtained by Sen and Zwiebach in the level
truncation approximation to compare with the one for Schnabl's solution. The
results are consistent with the expectation that they may be gauge equivalent.
We briefly discuss the gauge invariant observables and the action for a
marginal solution with a nonsingular current.


title: Symmetric links and Conway sums: volume and Jones polynomial

abstract:
  We obtain bounds on hyperbolic volume for periodic links and Conway sums of
alternating tangles. For links that are Conway sums we also bound the
hyperbolic volume in terms of the coefficients of the Jones polynomial.


title:
Explanation of 100-fold reduction of spectral shifts for hydrogen on
  helium films

abstract:
  We show that helium film-mediated hydrogen-hydrogen interactions account for
a two orders of magnitude discrepancy between previous theory and recent
experiments on cold collision shifts in spin-polarized hydrogen adsorbed on a
helium film. These attractive interactions also explain the anomalous
dependence of the cold collision frequency shifts on the $^3$He covering of the
film. Our findings suggest that the gas will become mechanically unstable
before reaching the Kosterlitz-Thouless transition unless the experiment is
performed in a drastically different regime, for example with a much different
helium film geometry.


title:
Non-Abelian Supercurrents and de Sitter Ground State in Electroweak
  Theory

abstract:
  We show that gauge symmetry breaking in the Weinberg-Salam model can be
implemented by a mere change of variables and without any explicit gauge
fixing. The change of variables entails the concept of supercurrent which has
been widely employed in the study of superconductivity. It also introduces a
separation between the isospin and the hypercharge, suggesting that our new
variables describe a strongly coupled regime of the electroweak theory. We
discuss the description of various embedded topological defects in terms of
these variables. We also propose that in terms of our variables the
Weinberg-Salam model can be interpreted in terms of a gravity theory with the
modulus of Higgs field as dilaton and the de Sitter space as the ground state.


title: The Evolution of Late-time Optical Emission from SN 1986J

abstract:
  We present late-time optical images and spectra of the Type IIn supernova SN
1986J. HST ACS/WFC images obtained in February 2003 show it to be still
relatively bright with m(F606W) = 21.4 and m(F814W) = 20.0 mag. Compared
against December 1994 HST WFPC2 images, SN 1986J shows a decline of only <1 mag
in brightness over eight years. Ground-based spectra taken in 1989, 1991 and
2007 show a 50% decline in Halpha emission between 1989-1991 and an order of
magnitude drop between 1991-2007, along with the disappearance of He I line
emissions during the period 1991-2007. The object's [O I] 6300, 6364, [O II]
7319, 7330 and [O III] 4959, 5007 emission lines show two prominent peaks near
-1000 km/s and -3500 km/s, with the more blueshifted component declining
significantly in strength between 1991 and 2007. The observed spectral
evolution suggests two different origins for SN 1986J's late-time optical
emission: dense, shock-heated circumstellar material which gave rise to the
initially bright Halpha, He I, and [N II] 5755 lines, and reverse-shock heated
O-rich ejecta on the facing expanding hemisphere dominated by two large clumps
generating two blueshifted emission peaks of [O I], [O II], and [O III] lines.


title:
Entangled maximal mixings in U_PMNS=U_l^dagger U_nu, and a connection to
  complex mass textures

abstract:
  We discuss two different configurations of U_PMNS=U_l^dagger U_nu with
maximal mixings in both U_l and U_nu. The non-maximal mixing angles are assumed
to be small, which means that they can be expanded in. Since we are
particularly interested in the implications for CP violation, we fully take
into account complex phases. We demonstrate that one possibility leads to
intrinsically large theta_13 and strong deviations from maximal mixings. The
other possibility is generically close to tri-bimaximal mixing, and allows for
large CP violation. We demonstrate how the determination of the theta_23 octant
and the precision measurement of delta_CP could discriminate among different
qualitative sub-cases. In order to constrain the unphysical and observable
phases even further, we relate our configurations to complex mass matrix
textures. In particular, we focus on phase patterns which could be generated by
powers of a single complex quantity eta=theta_C exp(i Phi), which can be
motivated by Froggatt-Nielsen-like models. For example, it turns out that in
all of the discussed cases, one of the Majorana phases is proportional to Phi
to leading order. In the entire study, we encounter three different classes of
sum rules, which we systematically classify.


title: Supersolid state of ultracold fermions in an optical lattice

abstract:
  We study ultracold fermionic atoms trapped in an optical lattice with
harmonic confinement by means of the dynamical mean-field approximation. It is
demonstrated that a supersolid state, where an s-wave superfluid coexists with
a density-wave state with a checkerboard pattern, is stabilized by attractive
onsite interactions on a square lattice. Our new finding here is that a
confining potential plays an invaluable role in stabilizing the supersolid
state. We establish a rich phase diagram at low temperatures, which clearly
shows how the insulator, the density wave and the superfluid compete with each
other to produce an intriguing domain structure. Our results shed light on the
possibility of the supersolid state in fermionic optical lattice systems.


title:
Deep near-IR variability survey of pre-main-sequence stars in Rho
  Ophiuchi

abstract:
  Variability is a common characteristic of pre-main-sequence stars (PMS).
Near-IR variability surveys of young stellar objects (YSOs) can probe stellar
and circumstellar environments and provide information about the dynamics of
the on going magnetic and accretion processes. Furthermore, variability can be
used as a tool to uncover new cluster members in star formation regions. We
hope to achieve the deepest near-IR variability study of YSOs targeting the Rho
Ophiuchi cluster. Fourteen epochs of observations were obtained with the Wide
Field Camera (WFCAM) at the UKIRT telescope scheduled in a manner that allowed
the study of variability on timescales of days, months, and years. Statistical
tools, such as the multi-band cross correlation index and the reduced
chi-square, were used to disentangle signals of variability from noise.
Variability characteristics are compared to existing models of YSOs in order to
relate them to physical processes, and then used to select new candidate
members of this star-forming region. Variability in the near-IR is found to be
present in 41% of the known population of Rho Ophiuchi recovered in our sample.
The behaviours shown are several and can be associated with the existence of
spots on the stellar surface, variations in circumstellar extinction, or
changes in the geometry of an accretion disc. Using variability, a new
population of objects has been uncovered that is believed to be part of the Rho
Ophiuchi cluster.


title:
Blow up of smooth highly decreasing at infinity solutions to the
  compressible Navier-Stokes equations

abstract:
  We prove that the smooth solutions to the Cauchy problem for the
Navier-Stokes equations with conserved mass, total energy and finite momentum
of inertia loses the initial smoothness within a finite time in the case of
space of dimension 3 or greater even if the initial data are not compactly
supported.


title:
The IRCAL Polarimeter: Design, Calibration, and Data Reduction for an
  Adaptive Optics Imaging Polarimeter

abstract:
  We have upgraded IRCAL, the near-infrared science camera of the Lick
Observatory adaptive optics system, to add a dual-channel imaging polarimetry
mode. This mode uses an optically contacted YLF (LiYF_4) Wollaston prism to
provide simultaneous images in perpendicular linear polarizations, providing
high resolution, high dynamic range polarimetry in the near infrared. We
describe the design and construction of the polarimeter, discuss in detail the
data reduction algorithms adopted, and evaluate the instrument's on-the-sky
performance. The IRCAL polarimeter is capable of reducing the stellar PSF halo
by about two orders of magnitude, thereby increasing contrast for studies of
faint circumstellar dust-scattered light. We discuss the various factors that
limit the achieved contrast, and present lessons applicable to future high
contrast imaging polarimeters.


title:
Bouncing ball orbits and symmetry breaking effects in a
  three-dimensional chaotic billiard

abstract:
  We study the classical and quantum mechanics of a three-dimensional stadium
billiard. It consists of two quarter cylinders that are rotated with respect to
each other by 90 degrees, and it is classically chaotic. The billiard exhibits
only a few families of nongeneric periodic orbits. We introduce an analytic
method for their treatment. The length spectrum can be understood in terms of
the nongeneric and unstable periodic orbits. For unequal radii of the quarter
cylinders the level statistics agree well with predictions from random matrix
theory. For equal radii the billiard exhibits an additional symmetry. We
investigated the effects of symmetry breaking on spectral properties. Moreover,
for equal radii, we observe a small deviation of the level statistics from
random matrix theory. This led to the discovery of stable and marginally stable
orbits, which are absent for un equal radii.


title:
The impact of mergers on relaxed X-ray clusters - III. Effects on
  compact cool cores

abstract:
  (Abridged) We use the simulations presented in Poole et al. 2006 to examine
the effects of mergers on compact cool cores in X-ray clusters. We propose a
scheme for classifying the morphology of clusters based on their surface
brightness and entropy profiles. Three dominant morphologies emerge: two
hosting compact cores and central temperatures which are cool (CCC systems) or
warm (CWC systems) and one hosting extended cores which are warm (EWC systems).
We find that CCC states are disrupted only after direct collisions between
cluster cores in head-on collisions or during second pericentric passage in
off-axis mergers. By the time they relax, our remnant cores have generally been
heated to warm core (CWC or EWC) states but subsequently recover CCC states.
The only case resulting in a long-lived EWC state is a slightly off-axis 3:1
merger for which the majority of shock heating occurs during the accretion of a
low-entropy stream formed from the disruption of the secondary's core.
Compression prevents core temperatures from falling until after relaxation thus
explaining the observed population of relaxed CWC systems with no need to
invoke AGN feedback. The morphological segregation observed in the L_x-T_x and
beta-r_c scaling relations is reflected in our simulations as well. However,
none of the cases we have studied produce sufficiently high remnant central
entropies to account for the most under-luminous EWC systems observed. Lastly,
systems which initially host central metallicity gradients do not yield merger
remnants with flat metallicity profiles. Taken together, these results suggest
that once formed, compact core systems are remarkably stable against disruption
from mergers. It remains to be demonstrated exactly how the sizable observed
population of extended core systems was formed.


title:
Suppression of unbounded gradients in a SDE associated with the Burgers
  equation

abstract:
  We consider the Langevin equation describing a stochastically perturbed by
uniform noise non-viscous Burgers fluid and introduce a deterministic function
that corresponds to the mean of the velocity when we keep the value of position
fixed. We study interrelations between this function and the solution of the
non-perturbed Burgers equation. Especially we are interested in the property of
the solution of the latter equation to develop unbounded gradients within a
finite time. We study the question how the initial distribution of particles
for the Langevin equation influences this blowup phenomenon. It is shown that
for a wide class of initial data and initial distributions of particles the
unbounded gradients are eliminated. The case of a linear initial velocity is
particular. We show that if the initial distribution of particles is uniform,
then the mean of the velocity for a given position coincides with the solution
of the Burgers equation and in particular does not depend on the constant
variance of the stochastic perturbation. Further, for a one space space
variable we get the following result: if the decay rate of the power-behaved
initial particles distribution at infinity is greater or equal $|x|^{-2},$ then
the blowup is suppressed, otherwise, the blowup takes place at the same moment
of time as in the case of the non-perturbed Burgers equation.


title: Inseparable local uniformization

abstract:
  It is known since the works of Zariski in early 40ies that desingularization
of varieties along valuations (called local uniformization of valuations) can
be considered as the local part of the desingularization problem. It is still
an open problem if local uniformization exists in positive characteristic and
dimension larger than three. In this paper, we prove that Zariski local
uniformization of algebraic varieties is always possible after a purely
inseparable extension of the field of rational functions, i.e. any valuation
can be uniformized by a purely inseparable alteration.


title: Theory of a continuous Mott transition in two dimensions

abstract:
  We study theoretically the zero temperature phase transition in two
dimensions from a Fermi liquid to a paramagnetic Mott insulator with a spinon
Fermi surface. We show that the approach to the bandwidth controlled Mott
transition from the metallic side is accompanied by a vanishing quasiparticle
residue and a diverging effective mass. The Landau parameters $F^0_s, F^0_a$
also diverge. Right at the quantum critical point there is a sharply defined
`critical Fermi surface' but no Landau quasiparticle. The critical point has a
$Tln\frac{1}{T}$ specific heat and a non-zero $T = 0$ resistivity. We predict
an interesting {\em universal resistivity jump} in the residual resistivity at
the critical point as the transition is approached from the metallic side. The
crossovers out of the critical region are also studied. Remarkably the initial
crossover out of criticality on the metallic side is to a Marginal Fermi Liquid
metal. At much lower temperatures there is a further crossover into the Landau
Fermi liquid. The ratio of the two crossover scales vanishes on approaching the
critical point. Similar phenomena are found in the insulating side. The filling
controlled Mott transition is also studied. Implications for experiments on the
layered triangular lattice organic material $\kappa-(ET)_2Cu_2(CN)_3$ are
discussed.


title:
Fully self-consistent ion-drag force calculations for dust in
  collisional plasmas with external electric field

abstract:
  The ion-drag force on a spherical dust particle immersed in a flowing plasma
with external electric field is self-consistently calculated using the Particle
In Cell code SCEPTIC in the entire range of charge-exchange collisionality. Our
results, not based on questionable approximations, extend prior analytic
calculations valid only in a few limiting regimes. Particular attention is
given to the force direction, shown never to be directed opposite to the flow
except in the continuum limit, where other forces are of much stronger
magnitude.


title: Four Fermion Operator Matching with NRQCD Heavy and AsqTad Light Quarks

abstract:
  We present one-loop matching coefficients between continuum and lattice QCD
for the heavy-light four-fermion operators relevant for neutral B meson mixing
both within and beyond the Standard Model. For the lattice theory we use
nonrelativistic QCD (NRQCD) to describe b quarks and improved staggered
fermions (AsqTad) for light quarks. The gauge action is the tree-level Symanzik
improved gauge action. Matching to full QCD is carried out through order
alpha_s, Lambda_{QCD}/M_b, and alpha_s/(aM_b).


title: K3 surfaces with Picard rank 20

abstract:
  We determine all complex K3 surfaces with Picard rank 20 over Q. Here the
Neron-Severi group has rank 20 and is generated by divisors which are defined
over Q. Our proof uses modularity, the Artin-Tate conjecture and class group
theory. With different techniques, the result has been established by Elkies to
show that Mordell-Weil rank 18 over Q is impossible for an elliptic K3 surface.
We then apply our methods to general singular K3 surfaces, i.e. with
Neron-Severi group of rank 20, but not necessarily generated by divisors over
Q.


title: Contact Geometry of Hyperbolic Equations of Generic Type

abstract:
  We study the contact geometry of scalar second order hyperbolic equations in
the plane of generic type. Following a derivation of parametrized
contact-invariants to distinguish Monge-Ampere (class 6-6), Goursat (class 6-7)
and generic (class 7-7) hyperbolic equations, we use Cartan's equivalence
method to study the generic case. An intriguing feature of this class of
equations is that every generic hyperbolic equation admits at most a
nine-dimensional contact symmetry algebra. The nine-dimensional bound is sharp:
normal forms for the contact-equivalence classes of these maximally symmetric
generic hyperbolic equations are derived and explicit symmetry algebras are
presented. Moreover, these maximally symmetric equations are Darboux
integrable. An enumeration of several submaximally symmetric (eight and
seven-dimensional) generic hyperbolic structures is also given.


title:
Ab Initio Many-Body Calculations of n-3H, n-4He, p-{3,4}He, and n-10Be
  Scattering

abstract:
  We develop a new ab initio many-body approach capable of describing
simultaneously both bound and scattering states in light nuclei, by combining
the resonating-group method with the use of realistic interactions, and a
microscopic and consistent description of the nucleon clusters. This approach
preserves translational symmetry and Pauli principle. We present phase shifts
for neutron scattering on 3H, 4He and 10Be and proton scattering on {3,4}He,
using realistic nucleon-nucleon potentials. Our A=4 scattering results are
compared to earlier ab initio calculations. We demonstrate that a proper
treatment of the coupling to the n-10Be continuum is essential to explain the
parity-inverted ground state in 11Be.


title: Rigid Surface Operators

abstract:
  Surface operators in gauge theory are analogous to Wilson and 't Hooft line
operators except that they are supported on a two-dimensional surface rather
than a one-dimensional curve. In a previous paper, we constructed a certain
class of half-BPS surface operators in N=4 super Yang-Mills theory, and
determined how they transform under S-duality. Those surface operators depend
on a relatively large number of freely adjustable parameters. In the present
paper, we consider the opposite case of half-BPS surface operators that are
``rigid'' in the sense that they do not depend on any parameters at all. We
present some simple constructions of rigid half-BPS surface operators and
attempt to determine how they transform under duality. This attempt is only
partially successful, suggesting that our constructions are not the whole
story. The partial match suggests interesting connections with quantization. We
discuss some possible refinements and some string theory constructions which
might lead to a more complete picture.


title: Saturation in Deep Inelastic Scattering from AdS/CFT

abstract:
  We analyze deep inelastic scattering at small Bjorken x, using the
approximate conformal invariance of QCD at high energies. Hard pomeron
exchanges are resummed eikonally, restoring unitarity at large values of the
phase shift in the dual AdS geometry. At weak coupling this phase is imaginary,
corresponding to a black disk in AdS. In this saturated regime, cross sections
exhibit geometric scaling and have a simple universal form, which we test
against available experimental data for the proton structure function
F_2(x,Q^2). We predict, in particular, the dependence of the cross section on
the scaling variable (Q/Q_s)^2 in the deeply saturated region, where Q_s is the
usual saturation scale. We find agreement with current data on F_2 in the
kinematical region 0.5 < Q^2 < 10 GeV^2, x < 10^-2, with an average 6%
accuracy. We conclude by discussing the relation of our approach with the
commonly used dipole formalism.


title:
Generalized Navier Boundary Condition and Geometric Conservation Law for
  surface tension

abstract:
  We consider two-fluid flow problems in an Arbitrary Lagrangian Eulerian (ALE)
framework. The purpose of this work is twofold. First, we address the problem
of the moving contact line, namely the line common to the two fluids and the
wall. Second, we perform a stability analysis in the energy norm for various
numerical schemes, taking into account the gravity and surface tension effects.
The problem of the moving contact line is treated with the so-called
Generalized Navier Boundary Conditions. Owing to these boundary conditions, it
is possible to circumvent the incompatibility between the classical no-slip
boundary condition and the fact that the contact line of the interface on the
wall is actually moving. The energy stability analysis is based in particular
on an extension of the Geometry Conservation Law (GCL) concept to the case of
moving surfaces. This extension is useful to study the contribution of the
surface tension. The theoretical and computational results presented in this
paper allow us to propose a strategy which offers a good compromise between
efficiency, stability and artificial diffusion.


title:
X-ray Properties of the GigaHertz-Peaked and Compact Steep Spectrum
  Sources

abstract:
  We present {\it Chandra} X-ray Observatory observations of Giga-Hertz Peaked
Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources. The {\it
Chandra} sample contains 13 quasars and 3 galaxies with measured 2-10 keV X-ray
luminosity within $10^{42} - 10^{46}$ erg s$^{-1}$. We detect all of the
sources, five of which are observed in X-ray for the first time. We study the
X-ray spectral properties of the sample. The measured absorption columns in the
quasars are different than those in the galaxies in the sense that the quasars
show no absorption (with limits $\sim 10^{21} \rm cm^{-2}$) while the galaxies
have large absorption columns ($> 10^{22} \rm cm^{-2}$) consistent with
previous findings. The median photon index of the sources with high S/N is
$\Gamma=1.84 \pm0.24$ and it is larger than the typical index of radio loud
quasars. The arcsec resolution of {\it Chandra} telescope allows us to
investigate X-ray extended emission, and look for diffuse components and X-ray
jets. We found X-ray jets in two quasars (PKS 1127-145, B2 0738+32), an X-ray
cluster surrounding a CSS quasar (z=1.1, 3C 186), detected a possible binary
structure in 0941-080 galaxy and an extended diffuse emission in galaxy PKS B2
1345+12. We discuss our results in the context of X-ray emission processes and
radio source evolution. We conclude that the X-ray emission in these sources is
most likely unrelated to a relativistic jet, while the sources' radio-loudness
may suggest a high radiative efficiency of the jet power in these sources.


title: Modular polynomials for genus 2

abstract:
  Modular polynomials are an important tool in many algorithms involving
elliptic curves. In this article we investigate their generalization to the
genus 2 case following pioneering work by Gaudry and Dupont. We prove various
properties of these genus 2 modular polynomials and give an improved way to
explicitly compute them.


title: Nilpotent noncommutativity and renormalization

abstract:
  We analyze renormalizability properties of noncommutative (NC) theories with
a bifermionic NC parameter. We introduce a new 4-dimensional scalar field model
which is renormalizable at all orders of the loop expansion. We show that this
model has an infrared stable fixed point (at the one-loop level). We check that
the NC QED (which is one-loop renormalizable with usual NC parameter) remains
renormalizable when the NC parameter is bifermionic, at least to the extent of
one-loop diagrams with external photon legs. Our general conclusion is that
bifermionic noncommutativity improves renormalizablility properties of NC
theories.


title: Electron-phonon interaction in a superconductor with Kondo scattering

abstract:
  In a superconductor with magnetic impurities, Kondo scattering results in the
formation of localized states inside the superconducting gap. We show that
inelastic electronic transitions involving quasiparticle scattering into and
out of the localized states may result in significant changes in the non
equilibrium properties of the superconductor. Using the model of
Muller-Hartmann and Zittartz for the extreme dilute limit, and including both
deformation potential and spin-lattice coupling we have calculated the rates of
such inelastic transitions between continuum and discrete states, and shown
that they may greatly modify quasiparticle interactions. The individual
processes are: quasiparticle trapping into discrete states, enhanced
recombination with localized quasiparticles, and pair breaking and detrapping
of localized quasiparticles by sub-gap phonons. We find that all these
processes give rise to clearly distinguishable temperature dependences of the
kinetic parameters.


title: Giroux torsion and twisted coefficients

abstract:
  We explain the effect of applying a full Lutz twist along a pre-Lagrangian
torus in a contact 3-manifold, on the contact invariant in Heegaard Floer
homology with twisted coefficients.


title: The Weyl group of type $A_1$ root systems extended by an abelian group

abstract:
  We investigate the class of root systems $R$ obtained by extending an
$A_1$-type irreducible root system by a free abelian group $G$. In this context
there is a Weyl group $W$ and a group $U$ with the presentation by conjugation.
Both groups are reflection groups with respect to a discrete symmetric space
$T$ associated to $R$. We show that the natural homomorphism $U\to W$ is an
isomorphism if and only if an associated subset $T^{ab}\setminus\{0\}$ of
$G_2=G/2G$ is 2-independent, i.e. its image under the map $G_2\to G_2\otimes
G_2, g\mapsto g\otimes g$ is linearly independent over the Galois field $F_2$.


title:
A Nearby Old Halo White Dwarf Candidate from the Sloan Digital Sky
  Survey

abstract:
  We report the discovery of a nearby, old, halo white dwarf candidate from the
Sloan Digital Sky Survey. SDSS J110217.48+411315.4 has a proper motion of 1.75
arcsec/year and redder optical colors than all other known featureless (type
DC) white dwarfs. We present SDSS imaging and spectroscopy of this object,
along with near-infrared photometry obtained at the United Kingdom Infra-Red
Telescope. Fitting its photometry with up-to-date model atmospheres, we find
that its overall spectral energy distribution is fit reasonably well with a
pure hydrogen composition and T_eff~3800 K (assuming log g=8). That temperature
and gravity would place this white dwarf at 35 pc from the Sun with a
tangential velocity of 290 km/s and space velocities consistent with halo
membership; furthermore, its combined main sequence and white dwarf cooling age
would be ~11 Gyr. However, if this object is a massive white dwarf, it could be
a younger object with a thick disk origin. Whatever its origin, the optical
colors of this object are redder than predicted by any current pure hydrogen,
pure helium or mixed hydrogen-helium atmospheric model, indicating that there
remain problems in our understanding of the complicated physics of the dense
atmospheres of cool white dwarfs.


title: Quantum Simulations of Classical Annealing Processes

abstract:
  We describe a quantum algorithm that solves combinatorial optimization
problems by quantum simulation of a classical simulated annealing process. Our
algorithm exploits quantum walks and the quantum Zeno effect induced by
evolution randomization. It requires order $1/\sqrt{\delta}$ steps to find an
optimal solution with bounded error probability, where $\delta$ is the minimum
spectral gap of the stochastic matrices used in the classical annealing
process. This is a quadratic improvement over the order $1/\delta$ steps
required by the latter.


title: Radiative $\phi$ decays with derivative interactions

abstract:
  We study the line shapes of radiative $\phi$-decays involving virtual
$f_{0}(980)$ and $a_{0}(980)$ mesons which decay, via derivative couplings, to
$\pi^{0}\pi^{0}$ and $\pi^{0}\eta$ respectively. After developing the formalism
for derivative interactions at one-loop level, we show that they can reproduce
the measured peaked line shapes of $\phi$-decays without including kaon loops.


title: Coarse differentiation and multi-flows in planar graphs

abstract:
  We show that the multi-commodity max-flow/min-cut gap for series-parallel
graphs can be as bad as 2, matching a recent upper bound Chakrabarti, Jaffe,
Lee, and Vincent for this class, and resolving one side of a conjecture of
Gupta, Newman, Rabinovich, and Sinclair.
  This also improves the largest known gap for planar graphs from 3/2 to 2,
yielding the first lower bound that doesn't follow from elementary
calculations. Our approach uses the {\em coarse differentiation} method of
Eskin, Fisher, and Whyte in order to lower bound the distortion for embedding a
particular family of shortest-path metrics into $L_1$.


title: Spitzer Space Telescope Observations of Low Mass X-ray Binaries

abstract:
  We present preliminary results from our archival Spitzer Space Telescope
program aimed at characterizing the mid-IR properties of compact objects, both
isolated and in binary systems, i.e. white dwarfs, X-ray binaries, cataclysmic
variables, and magnetars. Most of these sources are too faint at mid-IR
wavelengths to be observable from the ground, so this study provides the very
first comprehensive look at the mid-IR emission of these objects. Here we
present our results for the low mass X-ray binaries. We considered all of the
systems listed in the most recent catalog of Liu et al. (2007) that have known
optical counterparts. The particular goals of our projects encompass: to
establish the mid-IR spectral energy distribution, to search for the signatures
of jets, circumbinary disks, low mass or planetary companions and debris disks,
and to study the local environment of these sources.


title: The Quark Model and $b$ Baryons

abstract:
  The recent observation at the Tevatron of $\Sigma_b^{\pm}$ ($uub$ and $ddb$)
baryons within 2 MeV of the predicted $\Sigma_b - \Lambda_b$ splitting and of
$\Xi_b^-$ $(dsb)$ baryons at the Tevatron within a few MeV of predictions has
provided strong confirmation for a theoretical approach based on modeling the
color hyperfine interaction. The prediction of $M(\Xi^-_b) = 5790$ to 5800 MeV
is reviewed and similar methods used to predict the masses of the excited
states $\Xi_b^\prime$ and $\Xi_b^*$. The main source of uncertainty is the
method used to estimate the mass difference $m_b - m_c$ from known hadrons. We
verify that corrections due to the details of the interquark potential and to
$\Xi_b$--$\Xi_b^\prime$ mixing are small. For S-wave $qqb$ states we predict
$M(\Omega_b) = 6052.1 \pm 5.6$ MeV, $M(\Omega^*_b) = 6082.8 \pm 5.6$ MeV, and
$M(\Xi_b^0) = 5786.7 \pm 3.0$ MeV. For states with one unit of orbital angular
momentum between the $b$ quark and the two light quarks we predict
$M(\Lambda_{b[1/2]}) = 5929 \pm 2$ MeV, $M(\Lambda_{b[3/2]}) = 5940 \pm 2$ MeV,
$M(\Xi_{b[1/2]}) = 6106 \pm 4$ MeV, and $M(\Xi_{b[3/2]}) = 6115 \pm 4$ MeV.
Results are compared with those of other recent approaches.


title: D-particle Field Category

abstract:
  We formulate the homotopy associative (A_\infty) category of D-particle field
states via gauged S-duality. By invoking the minimal model theorem of this
D-particle field category, we investigate the equivalence principle and the
A_\infty covariance principle in the theory of gauged S-duality considered as
D-particle field theory.


title: Heat conduction in low-dimensional quantum magnets

abstract:
  Transport properties provide important information about the mobility,
elastic and inelastic of scattering of excitations in solids. Heat transport is
well understood for phonons and electrons, but little is known about heat
transport by magnetic excitations. Very recently, large and unusual magnetic
heat conductivities were discovered in low-dimensional quantum magnets. This
article summarizes experimental results for the magnetic thermal conductivity
$\kappa_\mathrm{mag}$ of several compounds which are good representations of
different low-dimensional quantum spin models, i.e. arrangements of S=1/2 spins
in the form of two-dimensional (2D) square lattices and one-dimensional (1D)
structures such as chains and two-leg ladders. Remarkable properties of
$\kappa_\mathrm{mag}$ have been discovered: It often dwarfs the usual phonon
thermal conductivity and allows the identification and analysis of different
scattering mechanisms of the relevant magnetic excitations.


title:
Curie point singularity in the temperature derivative of resistivity in
  (Ga,Mn)As

abstract:
  We observe a singularity in the temperature derivative $d\rho/dT$ of
resistivity at the Curie point of high-quality (Ga,Mn)As ferromagnetic
semiconductors with $T_c$'s ranging from approximately 80 to 185 K. The
character of the anomaly is sharply distinct from the critical contribution to
transport in conventional dense-moment magnetic semiconductors and is
reminiscent of the $d\rho/dT$ singularity in transition metal ferromagnets.
Within the critical region accessible in our experiments, the temperature
dependence on the ferromagnetic side can be explained by dominant scattering
from uncorrelated spin fluctuations. The singular behavior of $d\rho/dT$ on the
paramagnetic side points to the important role of short-range correlated spin
fluctuations.


title:
Oscillatory Integral Decay, Sublevel Set Growth, and the Newton
  Polyhedron

abstract:
  Using some resolution of singularities methods of the author, a
generalization of a well-known theorem of Varchenko relating decay of
oscillatory integrals to the Newton polyhedron is proven. They are derived from
analogous results for sublevel integrals, proven here.
  Varchenko's theorem requires a certain nondegeneracy condition on the faces
of the Newton polyhedron on the phase. In this paper, it is shown that the
estimates of Varchenko's theorem also hold for a significant class of phase
functions for which this nondegeneracy condition does not hold. Thus in
problems where one wants to switch coordinates to a coordinate system where
Varchenko's estimates are valid, one has greater flexibility.
  Some additional estimates are also proven for more degenerate situations,
including some too degenerate for the Newton polyhedron to give the optimal
decay in the sense of Varchenko.


title: Improved Measurement of Inclusive Radiative B-meson decays

abstract:
  We report a fully inclusive measurement of the flavor changing neutral
current decay $B\to X_s\gamma$ in the energy range $1.7 \GeV\le
E^\mathrm{c.m.s}_\gamma\le 2.8 \GeV$, covering 97% of the total spectrum, where
c.m.s is the center of mass system. Using $605\ifb$ of data, we obtain in the
rest frame of the $B$-meson ${\mathcal B}(B\to X_s\gamma : E^B_\gamma>1.7
\mathrm{GeV})= (3.31 \pm 0.19 \pm 0.37 \pm 0.01)\times 10^{-4}$, where the
errors are statistical, systematic and from the boost correction needed to
transform from the rest frame of the $\Upsilon(4S)$ (c.m.s) to that of the
$B$-meson, respectively. We also measure the first and second moments of the
photon energy spectrum as functions of various energy thresholds, which extend
down to $1.7 \GeV$. The results are preliminary.


title:
New Light Windows for Sparticle Masses and Higgs Decays in the R Parity
  Violating MSSM

abstract:
  In supersymmetric models with R parity violation, constraints on superpartner
masses are significantly weaker than in models which conserve R parity. We find
in regions of parameter space where a neutral gaugino or third generation
scalar is decoupled from the Z and/or traditional gaugino mass relationships do
not hold allow some particles to be light enough to allow them to be the decay
products of the Higgs. For example, surprisingly a stau could be lighter than
30 GeV if it decays hadronically. We estimate the Higgs bounds when one of
these decays dominates and find allowed Higgs masses well below the current LEP
bound on the standard model Higgs. We also survey the rich variety of final
states in Higgs production.


title:
Pressure Effects on the Superconducting and Spin-Density-Wave States of
  the Newly Discovered Sm(O1-xFx)FeAs

abstract:
  High temperature superconductors with a Tc above 40 K have been found to be
strongly correlated electron systems and to have a layered structure. Guided by
these rules, Kamihara et al. discovered a Tc up to 26 K in the layered
La(O1-xFx)FeAs. By replacing La with tri-valence rare-earth elements RE of
smaller ionic radii, Tc has subsequently been raised to 41-52 K. Many
theoretical models have been proposed emphasizing the important magnetic origin
of superconductivity in this compound system and a possible further
Tc-enhancement in RE(O1-xFx)FeAs by compression. This later prediction appears
to be supported by the pressure-induced Tc-increase in La(O0.89F0.11)FeAs
observed. Here we show that, in contrast to previous expectations, pressure can
either suppress or enhance Tc, depending on the doping level, suggesting that a
Tc exceeding 50's K may be found only in the yet-to-be discovered compound
systems related to but different from R(O1-xFx)FeAs and that the Tc of
La(O1-xFx)FeAs and Sm(O1-xFx)FeAs may be further raised to 50's K.


title:
Fixed point-free isometric actions of topological groups on Banach
  spaces

abstract:
  We show that every non-precompact topological group admits a fixed point-free
continuous action by affine isometries on a suitable Banach space. Thus,
precompact groups are defined by the fixed point property for affine isometric
actions on Banach spaces. For separable topological groups, in the above
statements it is enough to consider affine actions on one particular Banach
space: the unique Banach space envelope of the universal Urysohn metric space,
known as the Holmes space. At the same time, we show that Polish groups need
not admit topologically proper (in particular, free) affine isometric actions
on Banach spaces (nor even on complete metric spaces): this is the case for the
unitary group of the separable infinite dimensional Hilbert space with strong
operator topology, the infinite symmetric group, etc.


title:
Adaptive nonparametric estimation in heteroscedastic regression models.
  Part 2: Asymptotic efficiency

abstract:
  The paper deals with asymptotic properties of the adaptive procedure proposed
in the author paper (2007) for estimation of unknown nonparametric regression.
We prove that this procedure is asymptotically efficient for a quadratic risk.
It means that the asymptotic quadratic risk for this procedure coincides with a
sharp lower bound.


title: Gravity in 2T-Physics

abstract:
  The field theoretic action for gravitational interactions in d+2 dimensions
is constructed in the formalism of 2T-physics. General Relativity in d
dimensions emerges as a shadow of this theory with one less time and one less
space dimensions. The gravitational constant turns out to be a shadow of a
dilaton field in d+2 dimensions that appears as a constant to observers stuck
in d dimensions. If elementary scalar fields play a role in the fundamental
theory (such as Higgs fields in the Standard Model coupled to gravity), then
their shadows in d dimensions must necessarily be conformal scalars. This has
the physical consequence that the gravitational constant changes at each phase
transition (inflation, grand unification, electro-weak, etc.), implying
interesting new scenarios in cosmological applications. The fundamental action
for pure gravity, which includes the spacetime metric, the dilaton and an
additional auxiliary scalar field all in d+2 dimensions with two times, has a
mix of gauge symmetries to produce appropriate constraints that remove all
ghosts or redundant degrees of freedom. The action produces on-shell classical
field equations of motion in d+2 dimensions, with enough constraints for the
theory to be in agreement with classical General Relativity in d dimensions.
Therefore this action describes the correct classical gravitational physics
directly in d+2 dimensions. Taken together with previous similar work on the
Standard Model of particles and forces, the present paper shows that 2T-physics
is a general consistent framework for a physical theory.


title:
Bound-state energy of the d=3 Ising model in the broken-symmetry phase:
  Suppressed finite-size corrections

abstract:
  The low-lying spectrum of the three-dimensional Ising model is investigated
numerically; we made use of an equivalence between the excitation gap and the
reciprocal correlation length. In the broken-symmetry phase, the magnetic
excitations are attractive, forming a bound state with an excitation gap
m_2(<2m_1) (m_1: elementary excitation gap). It is expected that the ratio
m_2/m_1 is a universal constant in the vicinity of the critical point. In order
to estimate m_2/m_1, we perform the numerical diagonalization for finite
clusters with N \le 15 spins. In order to reduce the finite-size errors, we
incorporated the extended (next-nearest-neighbor and four-spin) interactions.
As a result, we estimate the mass-gap ratio as m_2/m_1=1.84(3).


title:
A combinatorial realization of Schur-Weyl duality via crystal graphs and
  dual equivalence graphs

abstract:
  For any polynomial representation of the special linear group, the nodes of
the corresponding crystal may be indexed by semi-standard Young tableaux. Under
certain conditions, the standard Young tableaux occur, and do so with weight 0.
Standard Young tableaux also parametrize the vertices of dual equivalence
graphs. Motivated by the underlying representation theory, in this paper, we
explainthis connection by giving a combinatorial manifestation of Schur-Weyl
duality. In particular, we put a dual equivalence graph structure on the
0-weight space of certain crystal graphs, producing edges combinatorially from
the crystal edges. The construction can be expressed in terms of the local
characterizations given by Stembridge for crystal graphs and the author for
dual equivalence graphs.


title:
Dark Fluid: Towards a unification of empirical theories of galaxy
  rotation, Inflation and Dark Energy

abstract:
  Empirical theories of Dark Matter like MOND gravity and of Dark Energy like
f(R) gravity were motivated by astronomical data. But could these theories be
branches rooted from a more general hence natural framework? Here we propose
the natural Lagrangian of such a framework based on simple dimensional analysis
and co-variant symmetry requirements, and explore various outcomes in a
top-down fashion. Our framework preserves the co-variant formulation of GR, but
allows the expanding physical metric be bent by a single new species of Dark
Fluid flowing in space-time. Its non-uniform stress tensor and current vector
are simply functions of a vector field of variable norm, resembling the
4-vector electromagnetic potential description for the photon fluid, but is
dark (e.g., by very early decoupling from the baryon-radiation fluid). The Dark
Fluid framework naturally branches into a continuous spectrum of theories with
Dark Energy and Dark Matter effects, including the $f(R)$ gravity, TeVeS-like
theories, Einstein-Aether and $\nu\Lambda$ theories as limiting cases. When the
vector field degenerates into a pure Higgs-like scalar field, we obtain the
physics for inflaton and quintessence. In this broad setting we emphasize the
non-constant dynamical field behind the cosmological constant effect, and
highlight plausible corrections beyond the classical MOND predictions. Choices
of parameters can be made to pass BBN, PPN, and causality constraints. The Dark
Fluid is inspired to unify/simplify the astronomically successful ingredients
of previous constructions: the desired effects of inflaton plus quintessence
plus Cold DM particle fields or MOND-like scalar field(s) are shown largely
achievable by one vector field only.


title: Comparison of secondary invariants of algebraic K-theory

abstract:
  In this paper we prove that the multiplicative character of A. Connes and M.
Karoubi and the determinant invariant of L. G. Brown, J. W. Helton and R. E.
Howe agree up to a canonical homomorphism.


title: Interstitial Electronic Localization

abstract:
  We investigate the ground-state properties of a collection of \textit{N}
non-interacting electrons in a macroscopic volume $\Omega$ also containing a
crystalline array of \textit{N} spheres of radius $r_c$ each taken as largely
impenetrable to electrons and with proximity of neighboring excluding regions
playing a key physical role. The sole parameter of this quantum system is the
ratio $r_c/r_s$, where $r_s$ is the Wigner- Seitz radius. Two lattices (FCC and
BCC) are selected to illustrate the behavior of the system as a function of
$r_c/r_s$. As this ratio increases valence electrons localize in the
interstitial regions and the relative band-width $\epsilon_F/\epsilon_F^0$ is
found to decrease monotonically for both. The system is motivated by the
behavior of the alkali metals at significant compression. It accounts for band
narrowing, leads to electronic densities with interstitially centered maxima,
and can be taken as a model which clearly may be improved upon by perturbation
and other methods.


title: Bloch-Nordsieck Estimates of High-Temperature QED

abstract:
  In anticipation of a subsequent application to QCD, we consider the case of
QED at high temperature. We introduce a Fradkin representation into the exact,
Schwingerian, functional expression of a fermion propagator, as well as a new
and relevant version of the Bloch-Nordsieck (BN) model, which extracts the soft
contributions of every perturbative graph, in contradistinction to the assumed
separation of energy scales of previous semi-perturbative treatments. Our
results are applicable to the absorption of a fast particle which enters a heat
bath, as well as to the propagation of a symmetric pulse within the thermal
medium due to the appearance of an instantaneous, shock-wave-like source acting
in the medium. An exponentially-decreasing time dependence of the incident
particle's initial momentum combines with a stronger decrease in the particle's
energy, estimated by a sum over all Matsubara frequencies, to model an initial
"fireball", which subsequently decays in a Gaussian fashion. When extended to
QCD, qualitative applications could be made to RHIC scattering, in which a
fireball appears, expands and is damped away.


title:
The cyclotron spectrum of anisotropic ultrarelativistic electrons:
  interpretation of X-ray pulsar spectra

abstract:
  The spectrum of cyclotron radiation produced by electrons with a strongly
anisotropic velocity distribution is calculated taking into account higher
harmonics. The motion of the electrons is assumed to be ultrarelativistic along
the magnetic field and nonrelativistic across the field. One characteristic
feature of the resulting spectrum is that harmonics of various orders are not
equally spaced. The physical properties and observed spectra of four X-ray
pulsars displaying higher cyclotron harmonics are analyzed. The cyclotron
features in the spectra of all four pulsars can be interpreted only as emission
lines. Moreover, the observed harmonics are not equidistant, and display
certain other properties characteristic of emission by strongly anisotropic
ultrarelativistic electrons. In addition, there are indirect theoretical
arguments that the electrons giving rise to cyclotron features in the spectra
of X-ray pulsars are ultrarelativistic and characterized by strongly
anisotropic distributions. As a result, estimates of the magnetic fields of
X-ray pulsars (which are usually derived from the energies of cyclotron lines)
and certain other physical parameters require substantial revision.


title:
Structural Ramsey theory of metric spaces and topological dynamics of
  isometry groups

abstract:
  In 2003, Kechris, Pestov and Todorcevic showed that the structure of certain
separable metric spaces - called ultrahomogeneous - is closely related to the
combinatorial behavior of the class of their finite metric spaces. The purpose
of the present paper is to explore the different aspects of this connection.


title:
The spin exchange interaction effect on Tc equation of anisotropic
  impure superconductors

abstract:
  We study the influence of spin exchange interaction of impurity scattering on
critical temperature of anisotropic impure superconductors. The model of random
nonmagnetic and magnetic impurity are revised to cover the effect of spin
exchange interaction . The sign of magnitude of the second-order Born
scattering have been changed after consideration the spin exchange interaction
effect that also effect to form of Tc equation. We can get the general Tc
equation that can be described anisotropic impure superconductors well and
cover all model done before.


title: Near-Zero Moment Ferromagnetism in the Semiconductor SmN

abstract:
  The magnetic behaviour of SmN has been investigated in stoichiometric
polycrystalline films. All samples show ferromagnetic order with Curie
temperature (T_c) of 27 +/- 3 K, evidenced by the occurrence of hysteresis
below T_c. The ferromagnetic state is characterised by a very small moment and
a large coercive field, exceeding even the maximum applied field of 6 T below
about 15 K. The residual magnetisation at 2 K, measured after cooling in the
maximum field, is 0.035 mu_B per Sm. Such a remarkably small moment results
from a near cancellation of the spin and orbital contributions for Sm3+ in SmN.
Coupling to an applied field is therefore weak, explaining the huge coercive
field . The susceptibility in the paramagnetic phase shows
temperature-independent Van Vleck and Curie-Weiss contributions. The Van Vleck
contribution is in quantitative agreement with the field-induced admixture of
the J=7/2 excited state and the 5/2 ground state. The Curie-Weiss contribution
returns a Curie temperature that agrees with the onset of ferromagnetic
hysteresis, and a conventional paramagnetic moment with an effective moment of
0.4 mu_B per Sm ion, in agreement with expectations for the crystal-field
modified effective moment on the Sm3+ ions.


title:
Holomorphic Representation of Constant Mean Curvature Surfaces in
  Minkowski Space: Consequences of Non-Compactness in Loop Group Methods

abstract:
  We give an infinite dimensional generalized Weierstrass representation for
spacelike constant mean curvature (CMC) surfaces in Minkowski 3-space
$\real^{2,1}$. The formulation is analogous to that given by Dorfmeister, Pedit
and Wu for CMC surfaces in Euclidean space, replacing the group $SU_2$ with
$SU_{1,1}$. The non-compactness of the latter group, however, means that the
Iwasawa decomposition of the loop group, used to construct the surfaces, is not
global. We prove that it is defined on an open dense subset, after doubling the
size of the real form $SU_{1,1}$, and prove several results concerning the
behavior of the surface as the boundary of this open set is encountered. We
then use the generalized Weierstrass representation to create and classify new
examples of spacelike CMC surfaces in $\real^{2,1}$. In particular, we classify
surfaces of revolution and surfaces with screw motion symmetry, as well as
studying another class of surfaces for which the metric is rotationally
invariant.


title: Invariance of a Shift-Invariant Space

abstract:
  A shift-invariant space is a space of functions that is invariant under
integer translations. Such spaces are often used as models for spaces of
signals and images in mathematical and engineering applications. This paper
characterizes those shift-invariant subspaces S that are also invariant under
additional (non-integer) translations. For the case of finitely generated
spaces, these spaces are characterized in terms of the generators of the space.
As a consequence, it is shown that principal shift-invariant spaces with a
compactly supported generator cannot be invariant under any non-integer
translations.


title:
Testing the AGB Scenario as the Origin of the Extreme-Helium Population
  in omega Centauri

abstract:
  The most massive Galactic globular cluster, Omega centauri, appears to have
multiple populations. Its bluest main sequence and extended horizontal branch
stars are suggested to have the common origin, that is, an extremely high
helium abundance of Y ~ 0.4. The high helium abundance is most often attributed
to asymptotic giant branch (AGB) stars. In this study we test the AGB
hypothesis. We simulate the maximum-AGB models where the impact of AGB stars is
maximised by assuming that supernova explosions do not affect the chemical
evolution of the proto cloud. We compare the enrichment history of helium,
metals, carbon and nitrogen to the observed values. Even under the most
generous condition, the maximum-AGB models fail to reproduce the large values
of helium Y ~ 0.4 and helium enrichment parameter Delta Y / Delta Z ~ 70 which
were deduced from the colour-magnitude diagram fits. They also fail to
reproduce the C and N contents of the blue population spectroscopically
determined. We conclude that the AGB scenario with the canonical stellar
evolution theory cannot explain the observational constraints and that the self
chemical enrichment does not provide a viable solution. Alternative processes
are desperately called for.


title: Automorphisms of curves fixing the order two points of the Jacobian

abstract:
  Let X be an irreducible smooth projective curve, of genus at least two,
defined over an algebraically closed field of characteristic different from
two. If X admits a nontrivial automorphism \sigma that fixes pointwise all the
order two points of Pic}^0(X), then we prove that X is hyperelliptic with
\sigma being the unique hyperelliptic involution. As a corollary, if a
nontrivial automorphisms \sigma' of X fixes pointwise all the theta
characteristics on X, then X is hyperelliptic with \sigma' being its
hyperelliptic involution.


title:
Multipartite entanglement of three trapped ions in a cavity and W- State
  generation

abstract:
  A scheme to generate three qubit maximally entangled W-states, using three
trapped ions interacting with red sideband tuned single mode field of a high
finesse cavity, is proposed. For the cavity field initially prepared in a
number state, the probability of generating three ion W-state is calculated. By
using the ion-cavity coupling strengths achieved in experimental realizations,
the interaction time needed for W-state generation is found to be of the order
of 10 $\mu $ sec. It is found that for a fixed number of photons in the cavity
the nature of entanglement of ionic internal states can be manipulated by
appropriate choice of initial state phonon number.
  The ionic qubits in W-like state are found to be entangled to cavity photons.
Analytical expressions for global negativity and partial $K-$way negativities
(K=2 to 4) are obtained to study the evolution of entanglement distribution as
a function of interaction parameter. Reversible entanglement exchange between
different entanglement modes is observed. For specific values of interaction
parameter, the three ions and photon-phonon system are found to have four
partite entanglement, generated by 2-way and 3-way correlations.


title:
On the Fundamental Equation of Nonequilibrium Statistical Physics --
  Nonequilibrium Entropy Evolution Equation and the Formula for Entropy
  Production Rate

abstract:
  In this paper we presented an overview on our works. More than ten years ago,
we proposed a new fundamental equation of nonequilibrium statistical physics in
place of the present Liouville equation. That is the stochastic velocity type's
Langevin equation in 6N dimensional phase space or its equivalent Liouville
diffusion equation. This equation is time-reversed asymmetrical. It shows that
the form of motion of particles in statistical thermodynamic systems has the
drift-diffusion duality, and the law of motion of statistical thermodynamics is
expressed by a superposition of both the law of dynamics and stochastic
velocity and possesses both determinism and probability. Hence it is different
with the law of motion of particles in dynamical systems. Starting from this
fundamental equation the BBGKY diffusion equation hierarchy, the Boltzmann
collision diffusion equation, the hydrodynamic equations such as the mass
drift-diffusion equation, the Navier-Stokes equation and the thermal
conductivity equation have been derived and presented here. What is more
important, we first constructed a nonlinear evolution equation of
nonequilibrium entropy density in 6N, 6 and 3 dimensional phase space,
predicted the existence of entropy diffusion. This evolution equation reveals
that the time rate of change of nonequilibrium entropy density originates
together from its drift, diffusion and production in space. Furthermore, we
presented a formula for entropy production rate (i.e. the law of entropy
increase), proved that internal attractive force in nonequilibrium system can
result in entropy decrease while internal repulsive force leads to another
entropy increase, obtained an unified theoretical expression for thermodynamic
degradation and self-organizing evolution, and revealed that the entropy
diffusion mechanism caused the system to approach to equilibrium.


title: Multiterminal source coding with complementary delivery

abstract:
  A coding problem for correlated information sources is investigated. Messages
emitted from two correlated sources are jointly encoded, and delivered to two
decoders. Each decoder has access to one of the two messages to enable it to
reproduce the other message. The rate-distortion function for the coding
problem and its interesting properties are clarified.


title:
Linear Optimization over a Polymatroid with Side Constraints --
  Scheduling Queues and Minimizing Submodular Functions

abstract:
  Two seemingly unrelated problems, scheduling a multiclass queueing system and
minimizing a submodular function, share a rather deep connection via the
polymatroid that is characterized by a submodular set function on the one hand
and represents the performance polytope of the queueing system on the other
hand. We first develop what we call a {\it grouping} algorithm that solves the
queueing scheduling problem under side constraints, with a computational effort
of $O(n^3LP(n))$, $n$ being the number of job classes, and LP(n) being the
computational efforts of solving a linear program with no more than $n$
variables and $n$ constraints. The algorithm organizes the job classes into
groups, and identifies the optimal policy to be a priority rule across the
groups and a randomized rule within each group (to enforce the side
constraints). We then apply the grouping algorithm to the submodular function
minimization, mapping the latter to a queueing scheduling problem with side
constraints. %Each time the algorithm is applied, it identifies a subset; and
We show the minimizing subset can be identified by applying the grouping
algorithm $n$ times. Hence, this results in a algorithm that minimizes a
submodular function with an effort of $O(n^4LP(n))$.


title: Pair Analysis of Field Galaxies from the Red-Sequence Cluster Survey

abstract:
  We study the evolution of the number of close companions of similar
luminosities per galaxy (Nc) by choosing a volume-limited subset of the
photometric redshift catalog from the Red-Sequence Cluster Survey (RCS-1). The
sample contains over 157,000 objects with a moderate redshift range of 0.25 < z
< 0.8 and absolute magnitude in Rc (M_Rc) < -20. This is the largest sample
used for pair evolution analysis, providing data over 9 redshift bins with
about 17,500 galaxies in each. After applying incompleteness and projection
corrections, Nc shows a clear evolution with redshift. The Nc value for the
whole sample grows with redshift as (1+z)^m, where m = 2.83 +/- 0.33 in good
agreement with N-body simulations in a LCDM cosmology. We also separate the
sample into two different absolute magnitude bins: -25 < M_Rc < -21 and -21 <
M_Rc < -20, and find that the brighter the absolute magnitude, the smaller the
m value. Furthermore, we study the evolution of the pair fraction for different
projected separation bins and different luminosities. We find that the m value
becomes smaller for larger separation, and the pair fraction for the fainter
luminosity bin has stronger evolution. We derive the major merger remnant
fraction f_rem = 0.06, which implies that about 6% of galaxies with -25 < M_Rc
< -20 have undergone major mergers since z = 0.8.


title: The Phase Diagram of the Quantum Curie-Weiss Model

abstract:
  This paper studies a generalization of the Curie-Weiss model (the Ising model
on a complete graph) to quantum mechanics. Using a natural probabilistic
representation of this model, we give a complete picture of the phase diagram
of the model in the parameters of inverse temperature and transverse field
strength. Further analysis computes the critical exponent for the decay of the
order parameter in the approach to the critical curve and gives useful
stability properties of a variational problem associated with the
representation.


title:
Existence of global solutions to the Cauchy problem for the inelastic
  Boltzmann equation with near-vacuum data

abstract:
  The Cauchy problem for the inelastic Boltzmann equation is studied for small
data. Existence and uniqueness of mild and weak solutions is obtained for
sufficiently small data that lies in the space of functions bounded by
Maxwellians. The technique used to derive the result is the well known
iteration process of Kaniel and Shinbrot.


title:
Distributed and Recursive Parameter Estimation in Parametrized Linear
  State-Space Models

abstract:
  We consider a network of sensors deployed to sense a spatio-temporal field
and estimate a parameter of interest. We are interested in the case where the
temporal process sensed by each sensor can be modeled as a state-space process
that is perturbed by random noise and parametrized by an unknown parameter. To
estimate the unknown parameter from the measurements that the sensors
sequentially collect, we propose a distributed and recursive estimation
algorithm, which we refer to as the incremental recursive prediction error
algorithm. This algorithm has the distributed property of incremental gradient
algorithms and the on-line property of recursive prediction error algorithms.
We study the convergence behavior of the algorithm and provide sufficient
conditions for its convergence. Our convergence result is rather general and
contains as special cases the known convergence results for the incremental
versions of the least-mean square algorithm. Finally, we use the algorithm
developed in this paper to identify the source of a gas-leak (diffusing source)
in a closed warehouse and also report numerical simulations to verify
convergence.


title: Colliding solitons for the nonlinear Schrodinger equation

abstract:
  We study the collision of two fast solitons for the nonlinear Schr\"odinger
equation in the presence of a spatially adiabatic external potential. For a
high initial relative speed $\|v\|$ of the solitons, we show that, up to times
of order $\log\|v\|$ after the collision, the solitons preserve their shape (in
$L^2$-norm), and the dynamics of the centers of mass of the solitons is
approximately determined by the external potential, plus error terms due to
radiation damping and the extended nature of the solitons. We remark on how to
obtain longer time scales under stronger assumptions on the initial condition
and the external potential.


title:
The quantum-to-classical transition: Bohr's doctrine of classical
  concepts, emergent classicality, and decoherence

abstract:
  It is now widely accepted that environmental entanglement and the resulting
decoherence processes play a crucial role in the quantum-to-classical
transition and the emergence of "classicality" from quantum mechanics. To this
extent, decoherence is often understood as signifying a break with the
Copenhagen interpretation, and in particular with Bohr's view of the
indispensability of classical concepts. This paper analyzes the relationship
between Bohr's understanding of the quantum-classical divide and his doctrine
of classical concepts and the decoherence-based program of emergent
classicality. By drawing on Howard's reconstruction of Bohr's doctrine of
classical concepts, and by paying careful attention to a hitherto overlooked
disagreement between Heisenberg and Bohr in the 1930s about the placement of
the quantum-classical "cut," we show that Bohr's view of the quantum-classical
divide can be physically justified by appealing to decoherence. We also discuss
early anticipations of the role of the environment in the quantum-classical
problem in Heisenberg's writings. Finally, we distinguish four different
formulations of the doctrine of classical concepts in an effort to present a
more nuanced assessment of the relationship between Bohr's views and
decoherence that challenges oversimplified statements frequently found in the
literature.


title:
Automorphisms and Verma modules for Generalized Schr\"{o}dinger-Virasoro
  algebras

abstract:
  Let $\mathbb{F}$ be a field of characteristic 0, $G$ an additive subgroup of
$\mathbb{F}$, $\alpha\in \mathbb{F}$ satisfying $\alpha\notin G, 2\alpha\in G$.
We define a class of infinite-dimensional Lie algebras which are called
generalized Schr\"{o}dinger-Virasoro algebras and use
$\mathfrak{gsv}[G,\alpha]$ to denote the one corresponding to $G$ and $\alpha$.
In this paper the automorphism group and irreducibility of Verma modules for
$\mathfrak{gsv}[G,\alpha]$ are completely determined.


title:
Existence of Large Room Temperature Ferroelectricity in Chemical
  Solution Grown PbTiO3 Buffered (BiFeO3)1-x-(PbTiO3)x Films on Pt/Si
  Substrates

abstract:
  Here, we report the existence of large remnant polarization and dielectric
constant in PbTiO3 buffered polycrystalline (BiFeO_3)_{1-x} (PbTiO_3)_x thin
films of composition x = 0.25, 0.30 and 0.35 around the morphotropic phase
boundary. The films were deposited by chemical solution deposition on
platinized silicon substrates. Films reveal a perovskite structure with a
tendency to retain rhombohedral structure even at higher PbTiO_3 content than
that reported in bulk. We observe very large remnant polarization, ~75
microC/cm^2, and high dielectric constant, ~2400 at 1 kHz for x = 0.3, which
lies in the MPB composition range. The unbuffered films show less than 1
microC/cm^2 for the same composition.


title:
Electrical transport and ferromagnetism in Ga1-xMnxAs synthesized by ion
  implantation and pulsed-laser melting

abstract:
  We present a detailed investigation of the magnetic and magnetotransport
properties of thin films of ferromagnetic Ga1-xMnxAs synthesized using ion
implantation and pulsed-laser melting (II-PLM). The field and
temperature-dependent magnetization, magnetic anisotropy, temperature-dependent
resistivity, magnetoresistance, and Hall effect of II-PLM Ga1-xMnxAs films have
all of the characteristic signatures of the strong p-d interaction of holes and
Mn ions observed in the dilute hole-mediated ferromagnetic phase. The
ferromagnetic and electrical transport properties of II-PLM films correspond to
the peak substitutional Mn concentration meaning that the non-uniform Mn depth
distribution is unimportant in determining the film properties. Good
quantitative agreement is found with films grown by low temperature molecular
beam epitaxy (LT-MBE) and having the similar substitutional Mn_Ga composition.
Additionally, we demonstrate that II-PLM Ga1-xMnxAs films are free from
interstitial Mn_I because of the high temperature processing. At high Mn
implantation doses the kinetics of solute redistribution during solidification
alone determine the maximum resulting Mn_Ga concentration. Uniaxial anisotropy
between in-plane [-110]and [110] directions is present in II-PLM Ga1-xMnxAs
giving evidence for this being an intrinsic property of the carrier-mediated
ferromagnetic phase.


title:
The impact of the dark matter-gas interaction on the collapse behaviour
  of spherical symmetric systems

abstract:
  If the gas in the evolving cosmic halos is dissipating energy (cooling) then
due to the variation of the gravitational potential the dark matter halo also
undergoes a compactification. This is well-known as Adiabatic contraction (AC).
Complementary to the AC we investigate the resulting dynamical behaviour of the
whole system if the backreaction of the AC of DM onto the gas is taken into
account. In order to achieve sufficient high resolution also within the central
halo region, we use a crude fluid approximation for the DM obeying the
adiabatic contraction behaviour. Further, we restrict ourself to spherical
symmetry and vanishing angular momentum of the studied matter configurations.
The computations are done using a first-order Godunov type scheme. Our results
show that the dynamical interaction between gas and DM may lead to significant
shorter collapse times. If the gas cools the dynamical behaviour of the whole
system depends strongly on the shape of the initial density profile. Our
findings indicate that for a certain mass range of halo configurations the
dynamical interaction between gas and DM might be important for the halo
evolution and must be taken into account.


title:
Long term flux variations in Cen X-3: clues from flux dependent orbital
  modulation and pulsed fraction

abstract:
  We have investigated the long term flux variation in Cen X-3 using orbital
modulation and pulsed fraction in different flux states using observations made
with the All Sky Monitor and the Proportional Counter Array on board the Rossi
X-ray Timing Explorer. In the high state, the eclipse ingress and egress are
found to be sharp whereas in the intermediate state the transitions are more
gradual. In the low state, instead of eclipse ingress and egress, the
lightcurve shows a smooth flux variation with orbital phase. The orbital
modulation of the X-ray lightcurve in the low state shows that the X-ray
emission observed in this state is from an extended object. The flux dependent
orbital modulations indicate that the different flux states of Cen X-3 are
primarily due to varying degree of obscuration. Measurement of the pulsed
fraction in different flux states is consistent with the X-ray emission of Cen
X-3 having one highly varying component with a constant pulsed fraction and an
unpulsed component and in the low state, the unpulsed component becomes
dominant. The observed X-ray emission in the low state is likely to be due to
scattering of X-rays from the stellar wind of the companion star. Though we can
not ascertain the origin and nature of the obscuring material that causes the
aperiodic long term flux variation, we point out that a precessing accretion
disk driven by radiative forces is a distinct possibility.


title: A unified theory of superconductivity

abstract:
  In this paper, we study the reliability of BCS theory as a scientific
explanation of the mystery of superconductivity. It is shown clearly that the
phonon-mediated BCS theory is fundamentally incorrect. Two kinds of glues,
pairing (pseudogap) glue and superconducting glue, are suggested based on a
real space Coulomb confinement effect. The scenarios provide a unified
explanation of the pairing symmetry, pseudogap and superconducting states,
charge stripe order, spin density wave (SDW), checkerboard-type charge-ordered
phase, magic doping fractions and vortex structures in conventional and
unconventional (the high-Tc cuprates and MgB2) superconductors. The theory
agrees with the existence of a pseudogap in high-temperature superconductors,
while no pseudogap feature could be observed in MgB2 and most of the
conventional superconductors. Our results indicate that the superconducting
phase can coexist with a inclined hexagonal vortex lattice in pure MgB2 single
crystal with a charge carrier density ps=1.49*10^{22}/cm^{3}. Finally, the
physical reasons why the good conductors (for example, Ag, Au, and Cu) and the
overdoped high-Tc superconductors are non-superconducting are also explored.


title: DMRG Numerical Study of the Kagom\'{e} Antiferromagnet

abstract:
  We numerically study the spin-1/2 antiferromagnetic Heisenberg model on the
kagom\'{e} lattice using the density-matrix renormalization group (DMRG)
method. We find that the ground state is a magnetically disordered spin liquid,
characterized by an exponential decay of spin-spin correlation function in real
space and a magnetic structure factor showing system-size independent peaks at
commersurate antiferromangetic wavevectors. We obtain a spin triplet excitation
gap $\Delta E(S=1)=0.055\pm 0.005$ by extrapolation based on the large size
results, and confirm the presence of gapless singlet excitations. The physical
nature of such an exotic spin liquid is also discussed.


title:
Optimal Power Control over Fading Cognitive Radio Channels by Exploiting
  Primary User CSI

abstract:
  This paper is concerned with spectrum sharing cognitive radio networks, where
a secondary user (SU) or cognitive radio link communicates simultaneously over
the same frequency band with an existing primary user (PU) link. It is assumed
that the SU transmitter has the perfect channel state information (CSI) on the
fading channels from SU transmitter to both PU and SU receivers (as usually
assumed in the literature), as well as the fading channel from PU transmitter
to PU receiver (a new assumption). With the additional PU CSI, we study the
optimal power control for the SU over different fading states to maximize the
SU ergodic capacity subject to a new proposed constraint to protect the PU
transmission, which limits the maximum ergodic capacity loss of the PU resulted
from the SU transmission. It is shown that the proposed SU power-control policy
is superior over the conventional policy under the constraint on the maximum
tolerable interference power/interperferecne temperature at the PU receiver, in
terms of the achievable ergodic capacities of both PU and SU.


title: Symmetry of the Riemann Operator

abstract:
  Chaos quantization conditions, which relate the eigenvalues of a Hermitian
operator (the Riemann operator) with the non-trivial zeros of the Riemann zeta
function are considered, and their geometrical interpretation is discussed.


title: Hilbert domains quasi-isometric to normed vector spaces

abstract:
  We prove that a Hilbert domain which is quasi-isometric to a normed vector
space is actually a convex polytope.


title: Hilbert geometry for convex polygonal domains

abstract:
  We prove in this paper that the Hilbert geometry associated with an open
convex polygonal set is Lipschitz equivalent to Euclidean plane.