title: Witt groups of Grassmann varieties

abstract:
  We compute the total Witt groups of (split) Grassmann varieties, over any
regular base X. The answer is a free module over the total Witt ring of X. We
provide an explicit basis for this free module, which is indexed by a special
class of Young diagrams, that we call even Young diagrams.


title:
Could the GSI Oscillations be Observed in a Standard Electron Capture
  Decay Experiment?

abstract:
  The electron-capture decay of 180Re has been investigated to search for
oscillations in the decay probability as reported from a recent measurement at
GSI, Darmstadt. The production period was kept short compared to the reported
oscillation period. No such oscillation was observed, indicating that the
reported oscillations would not have been observable in a conventional
experiment with radioactive atoms in a solid environment but must have to do
with the unique conditions in the GSI experiment where hydrogen-like ions are
moving independently in a storage ring and decaying directly by a true two-body
decay to a long-lived (ground-) state. Our finding could restrict possible
theoretical interpretations of the oscillations.


title: Remarks on shrinking target properties

abstract:
  This paper defines and describes a few (related) notions of shrinking target
property. We show that simultaneous expanding circle maps have a certain
shrinking target property, but that circle homeomorphisms and isometries of
complete, separable metric spaces do not have any shrinking target property.


title: w-Divisoriality in Polynomial Rings

abstract:
  We extend the Bass-Matlis characterization of local Noetherian divisorial
domains to the non-Noetherian case. This result is then used to study the
following question: If a domain D is w-divisorial, that is, if each w-ideal of
D is divisorial, then is D[X] automatically w-divisorial? We show that the
answer is yes if D is either integrally closed or Mori.


title:
Correlation between nucleotide composition and folding energy of coding
  sequences with special attention to wobble bases

abstract:
  Background: The secondary structure and complexity of mRNA influences its
accessibility to regulatory molecules (proteins, micro-RNAs), its stability and
its level of expression. The mobile elements of the RNA sequence, the wobble
bases, are expected to regulate the formation of structures encompassing coding
sequences.
  Results: The sequence/folding energy (FE) relationship was studied by
statistical, bioinformatic methods in 90 CDS containing 26,370 codons. I found
that the FE (dG) associated with coding sequences is significant and negative
(407 kcal/1000 bases, mean +/- S.E.M.) indicating that these sequences are able
to form structures. However, the FE has only a small free component, less than
10% of the total. The contribution of the 1st and 3rd codon bases to the FE is
larger than the contribution of the 2nd (central) bases. It is possible to
achieve a ~ 4-fold change in FE by altering the wobble bases in synonymous
codons. The sequence/FE relationship can be described with a simple algorithm,
and the total FE can be predicted solely from the sequence composition of the
nucleic acid. The contributions of different synonymous codons to the FE are
additive and one codon cannot replace another. The accumulated contributions of
synonymous codons of an amino acid to the total folding energy of an mRNA is
strongly correlated to the relative amount of that amino acid in the translated
protein.
  Conclusion: Synonymous codons are not interchangable with regard to their
role in determining the mRNA FE and the relative amounts of amino acids in the
translated protein, even if they are indistinguishable in respect of amino acid
coding.


title:
Calculations of static dipole polarizabilities of alkali dimers.
  Prospects for alignment of ultracold molecules

abstract:
  The rapid development of experimental techniques to produce ultracold alkali
molecules opens the ways to manipulate them and to control their dynamics using
external electric fields. A prerequisite quantity for such studies is the
knowledge of their static dipole polarizabilities. In this paper, we computed
the variations with internuclear distance and with vibrational index of the
static dipole polarizability components of all homonuclear alkali dimers
including Fr$_2$, and of all heteronuclear alkali dimers involving Li to Cs, in
their electronic ground state and in their lowest triplet state. We use the
same quantum chemistry approach than in our work on dipole moments (M. Aymar
and O. Dulieu, J. Chem. Phys. 122, 204302 (2005)), based on pseudopotentials
for atomic core representation, Gaussian basis sets, and effective potentials
for core polarization. Polarizabilities are extracted from electronic energies
using the finite-field method. For the heaviest species Rb$_2$, Cs$_2$ and
Fr$_2$ and for all heteronuclear alkali dimers, such results are presented for
the first time. The accuracy of our results on atomic and molecular static
dipole polarizabilities is discussed by comparing our values with the few
available experimental data and elaborate calculations. We found that for all
alkali pairs, the parallel and perpendicular components of the ground state
polarizabilities at the equilibrium distance $R_e$ scale as $(R_e)^3$, which
can be related to a simple electrostatic model of an ellipsoidal charge
distribution. Prospects for possible alignment and orientation effects with
these molecules in forthcoming experiments are discussed.


title: Exploring the potential of antihyperons in nuclei with antiprotons

abstract:
  A simple method to explore the interaction of antihyperons in nuclei by
exclusive hyperon-antihyperon pair production close to threshold in antiproton
nucleus interactions is proposed. Due to energy and momentum conservation
event-by-event transverse momentum correlations of the produced hyperons and
antihyperons contain information on the difference between their potentials. A
schematic Monte Carlo simulation is used to illustrate the sensitivities of the
proposed method for the reaction 1.66GeV/c antiproton+$^{12}$C $\to
{\Lambda\bar{\Lambda}}$. For produced D-meson pairs at 6.7GeV/c the sensitivity
of the transverse momenta correlation will probably be to small to deduce
differences between the potentials for D$^+$ and D$^-$ mesons. However, for
$\Xi\bar{\Xi}$ pairs produced at 2.9GeV/c the asymmetry is sufficiently
sensitive to predicted differences between the $\Xi$ and $\bar{\Xi}$
potentials.


title:
Reply to "Comment on 'Critique of the foundations od time-dependent
  density functional theory'"

abstract:
  The Comment by Holas et al. [A. Holas, M. Cinal, and N. H. March, Phys. Rev.
A 78, 016501 (2008)] on our recent paper [J. Schirmer and A. Dreuw, Phys. Rev.
A 75, 022513 (2007)]. is an appropriate and valuable contribution. As a small
addendum we briefly comment on the relationship between the radical Kohn-Sham
(rKS) form of density-functional theory and previous one-electron (particle)
potential (OPP) developments.


title: On Nonlinear Gauge Theories

abstract:
  In this note, we study non-linear gauge theories for principal bundles, where
the structure group is replaced by a Lie groupoid. We follow the approach of
Moerdijk-Mrcun and establish its relation with the existing physics literature.
In particular, we derive a new formula for the gauge transformation which
closely resembles and generalizes the classical formulas found in Yang Mills
gauge theories.


title: Isometries of Half Supersymmetric Time-Like Solutions In Five Dimensions

abstract:
  Spinorial geometry techniques have recently been used to classify all half
supersymmetric solutions in gauged five dimensional supergravity with vector
multiplets. In this paper we consider solutions for which at least one of the
Killing spinors generates a timelike Killing vector. We obtain coordinate
transformations which considerably simplify the solutions, and in a number of
cases, we obtain explicitly some additional Killing vectors which were hidden
in the original analysis.


title:
Observation of an Efimov-like resonance in ultracold atom-dimer
  scattering

abstract:
  The field of few-body physics has originally been motivated by understanding
nuclear matter. New model systems to experimentally explore few-body quantum
systems can now be realized in ultracold gases with tunable interactions.
Albeit the vastly different energy regimes of ultracold and nuclear matter (peV
as compared to MeV), few-body phenomena are universal for near-resonant
two-body interactions. Efimov states represent a paradigm for universal
three-body states, and evidence for their existence has been obtained in
measurements of three-body recombination in an ultracold gas of caesium atoms.
Interacting samples of halo dimers can provide further information on universal
few-body phenomena. Here we study interactions in an optically trapped mixture
of such halo dimers with atoms, realized in a caesium gas at nanokelvin
temperatures. We observe an atom-dimer scattering resonance, which we interpret
as being due to a trimer state hitting the atom-dimer threshold. We discuss the
close relation of this observation to Efimov's scenario, and in particular to
atom-dimer Efimov resonances.


title: Gravity effects in inclined air showers induced by cosmic neutrino

abstract:
  The Randall-Sundrum model with a small curvature is considered in which
five-dimensional Planck scale lies in the TeV region, and a spectrum of
Kaluza-Klein gravitons reminds that in one flat extra dimension. The cross
sections for interactions of ultra-high energy cosmic neutrinos with nucleons
are calculated. It is shown that effects related with massive graviton
excitations can be detected in deeply penetrating inclined air showers induced
by these neutrinos. The expected number of air showers at the Auger Observatory
is estimated as a function of two parameters of the model.


title: Visibility to infinity in the hyperbolic plane, despite obstacles

abstract:
  Suppose that $Z$ is a random closed subset of the hyperbolic plane $\H^2$,
whose law is invariant under isometries of $\H^2$. We prove that if the
probability that $Z$ contains a fixed ball of radius 1 is larger than some
universal constant $p<1$, then there is positive probability that $Z$ contains
(bi-infinite) lines.
  We then consider a family of random sets in $\H^2$ that satisfy some
additional natural assumptions. An example of such a set is the covered region
in the Poisson Boolean model. Let $f(r)$ be the probability that a line segment
of length $r$ is contained in such a set $Z$. We show that if $f(r)$ decays
fast enough, then there are almost surely no lines in $Z$. We also show that if
the decay of $f(r)$ is not too fast, then there are almost surely lines in $Z$.
In the case of the Poisson Boolean model with balls of fixed radius $R$ we
characterize the critical intensity for the almost sure existence of lines in
the covered region by an integral equation.
  We also determine when there are lines in the complement of a Poisson process
on the Grassmannian of lines in $\H^2$.


title: Local Approach to Hawking Radiation

abstract:
  We consider an approach to the Hawking effect which is free of the asymptotic
behavior of the metric or matter fields, and which is not confined to one
specific metric configuration. As a result, we find that for a wide class of
spacetime horizons there exists an emission of particles out of the horizon. As
expected, the energy distribution of the radiating particles turns out to be
thermal.


title: On Parametrization of Compact Wavelet Matrices

abstract:
  It is given an efficient complete parametrization of wavelet matrices of rank
$m$, genus $g+1$, and degree $g$, which are naturally identified with
corresponding polynomial paraunitary matrix-functions. The parametrization
depends on Wiener-Hopf factorization of unitary matrix-functions with constant
determinant given in the unit circle. This method allows us to construct in
real time the coefficients of wavelet matrices from the above class.


title: CP Violation in the Neutrino Sector

abstract:
  This talk will address how various experiments will address the following
issues: the $\nu_e$ flavor content of the 3rd neutrino mass eigenstates,
$\sin^2 \theta_{13}$, the mass ordering of the neutrinos, ${\rm sign}(\delta
m^2_{31})$ and whether CP is violated in the neutrino sector, $\sin \delta \neq
0$.


title:
Existence, covolumes and infinite generation of lattices for Davis
  complexes

abstract:
  Let $\Sigma$ be the Davis complex for a Coxeter system (W,S). The
automorphism group G of $\Sigma$ is naturally a locally compact group, and a
simple combinatorial condition due to Haglund--Paulin determines when G is
nondiscrete. The Coxeter group W may be regarded as a uniform lattice in G. We
show that many such G also admit a nonuniform lattice $\Gamma$, and an infinite
family of uniform lattices with covolumes converging to that of $\Gamma$. It
follows that the set of covolumes of lattices in G is nondiscrete. We also show
that the nonuniform lattice $\Gamma$ is not finitely generated. Examples of
$\Sigma$ to which our results apply include buildings and non-buildings, and
many complexes of dimension greater than 2. To prove these results, we
introduce a new tool, that of "group actions on complexes of groups", and use
this to construct our lattices as fundamental groups of complexes of groups
with universal cover $\Sigma$.


title: Space-Time Current Process for Independent Random Walks in One Dimension

abstract:
  In a system made up of independent random walks, fluctuations of order
$n^{1/4}$ from the hydrodynamic limit come from particle current across
characteristics. We show that a two-parameter space-time particle current
process converges to a two-parameter Gaussian process. These Gaussian processes
also appear as the limit for the one-dimensional random average process. The
final section of this paper looks at large deviations of the current process.


title: An Offset Seyfert 2 Nucleus in the Minor Merger System NGC 3341

abstract:
  We present the discovery of a triplet of emission-line nuclei in the
disturbed disk galaxy NGC 3341, based on archival data from the Sloan Digital
Sky Survey and new observations from the Keck Observatory. This galaxy contains
two offset nuclei within or projected against its disk, at projected distances
of 5.1 and 8.4 kpc from its primary nucleus and at radial velocity separation
of less than 200 km/s from the primary. These appear to be either dwarf
ellipticals or the bulges of low-mass spirals whose disks have already been
stripped off while merging into the primary galaxy. The inner offset nucleus
has a Seyfert 2 spectrum and a stellar velocity dispersion of 70+/-7 km/s. The
outer offset nucleus has very weak emission lines consistent with a LINER
classification, and the primary nucleus has an emission-line spectrum close to
the boundary between LINER/HII composite systems and HII nuclei; both may
contain accreting massive black holes, but the optical classifications alone
are ambiguous. The detection of an offset active nucleus in NGC 3341 provides a
strong suggestion that black hole accretion episodes during minor mergers can
be triggered in the nuclei of dwarf secondary galaxies as well as in the
primary.


title: On representations of Bol algebras

abstract:
  In this paper, we introduce the notion of representation of Bol algebra. We
prove an analogue of the classical Engel's theorem and the ex- tension of
Ado-Iwasawa theorem for Bol Algebras. We study the category of representations
of Bol algebras and show that it is a tensor category. In the case of regular
representations of Bol algebras, we give a complete classification of them for
all two-dimensional Bol algebras.


title: Low-Mass Seyfert 2 Galaxies in the Sloan Digital Sky Survey

abstract:
  (Abridged) We describe a sample of low-mass Seyfert 2 galaxies selected from
the Sloan Digital Sky Survey, having a median absolute magnitude of M_g = -19.0
mag. These galaxies are Type 2 counterparts to the Seyfert 1 galaxies with
intermediate-mass black holes identified by Greene & Ho (2004). Spectra
obtained with the Echellette Spectrograph and Imager at the Keck Observatory
are used to determine the central stellar velocity dispersions and to examine
the emission-line properties. Overall, the stellar velocity dispersions are low
(40-90 km/s), and we find 12 objects having sigma < 60 km/s, a range where very
few Seyfert 2 galaxies were previously known. The sample follows the
correlation between stellar velocity dispersion and FWHM([OIII]) seen in more
massive Seyfert galaxies, indicating that the narrow-line FWHM values are
largely determined by virial motion of gas in the central regions of the host
galaxies. Using estimates of the black hole masses and AGN bolometric
luminosities, we find that these galaxies are typically radiating at a high
fraction of their Eddington rate, with a median L_bol/L_Edd = 0.4. We identify
one galaxy, SDSS J110912.40+612346.7, as a Type 2 analog of the nearby dwarf
Seyfert 1 galaxy NGC 4395, with a nearly identical narrow-line spectrum and a
dwarf spiral host of only M_g = -16.8 mag. Forthcoming observations of this
sample, including X-ray and mid-infrared spectroscopy, can provide new tests of
the obscuring torus model for active galaxies at low luminosities.


title: The topology of moduli spaces of free group representations

abstract:
  For any complex affine reductive group G and a fixed choice of maximal
compact subgroup K, we show that the G-character variety of a free group
strongly deformation retracts to the corresponding K-character space, which is
a real semi-algebraic set. Combining this with constructive invariant theory
and classical topological methods, we show that the SL(3,C)-character variety
of a rank 2 free group is homotopic to an 8 sphere and the SL(2,C)-character
variety of a rank 3 free group is homotopic to a 6 sphere.


title:
What is the ground-state structure of intermediate-sized carbon
  clusters?

abstract:
  A comprehensive study on the relative structural stability of various
nanostructures of carbon clusters (including fullerenes, cages, onions,
icosahedral clusters, bucky-diamond clusters, spherically bulk terminated
clusters, and clusters with faceted termination) in the range of d < 5 nm has
been carried out using a semi-empirical method based on a self-consistent and
environment-dependent/linear combination of atomic orbital (SCED-LCAO)
Hamiltonian. It was found that among these nanostructures with the same
diameter, fullerenes are still the most stable structure, in contrast to the
icosahedral cluster being the ground state structure for a series of discrete n
values for other tetravalent clusters. The transformations from a bucky-diamond
structure to an onion structure, or to a cage structure, or from an onion
structure to a cage structure have been observed using a finite temperature
molecular dynamics scheme based on the SCED-LCAO Hamiltonian. It was also found
that the size-dependence of the HOMO-LUMO gap of fullerene shows an oscillation
as a function of its diameter (d). Such oscillation is associated with the
symmetry of the fullerene, and the magnitude of oscillation appears to decrease
as its size increases.


title: Two Higgs Pair Heterotic Vacua and Flavor-Changing Neutral Currents

abstract:
  We present a vacuum of heterotic M-theory whose observable sector has the
MSSM spectrum with the addition of one extra pair of Higgs-Higgs conjugate
superfields. The quarks/leptons have a realistic mass hierarchy with a
naturally light first family. The double elliptic structure of the Calabi-Yau
compactification threefold leads to two ``stringy'' selection rules. These
classically disallow Yukawa couplings to the second Higgs pair and, hence,
Higgs mediated flavor-changing neutral currents. Such currents are induced in
higher-dimensional interactions, but are naturally suppressed. We show that our
results fit comfortably below the observed upper bounds on neutral
flavor-changing processes.


title: Gluonic correlation length from spin-dependent potentials

abstract:
  The vacuum gluonic correlation length is extracted from recent lattice data
on spin-dependent interquark potentials in heavy quarkonia. It is shown that
the data are consistent with extremely small values of the correlation length,
Tg<0.1 fm.


title:
Boundary of the Rauzy fractal sets in $\RR \times \CC$ generated by
  $P(x)=x^4-x^3-x^2-x-1$

abstract:
  We study the boundary of the 3-dimensional Rauzy fractal ${\mathcal E}
\subset \RR \times \CC$ generated by the polynomial $P(x) = x^4-x^3-x^2-x-1$.
The finite automaton characterizing the boundary of ${\mathcal E}$ is given
explicitly. As a consequence we prove that the set ${\mathcal E}$ has 18
neighborhoods where 6 of them intersect the central tile ${\mathcal E}$ in a
point. Our construction shows that the boundary is generated by an iterated
function system starting with 2 compact sets.


title: A characterization of substitutive sequences using return words

abstract:
  We prove that a sequence is primitive substitutive if and only if the set of
its derived sequences is finite; we defined these sequences here.


title: Spontaneous vortices in the formation of Bose-Einstein condensates

abstract:
  Phase transitions are ubiquitous in nature, ranging from protein folding and
denaturisation, to the superconductor-insulator quantum phase transition, to
the decoupling of forces in the early universe. Remarkably, phase transitions
can be arranged into universality classes, where systems having unrelated
microscopic physics exhibit identical scaling behaviour near the critical
point. Here we present an experimental and theoretical study of the
Bose-Einstein condensation phase transition of an atomic gas, focusing on one
prominent universal element of phase transition dynamics: the spontaneous
formation of topological defects during a quench through the transition. While
the microscopic dynamics of defect formation in phase transitions are generally
difficult to investigate, particularly for superfluid phase transitions,
Bose-Einstein condensates (BECs) offer unique experimental and theoretical
opportunities for probing such details. Although spontaneously formed vortices
in the condensation transition have been previously predicted to occur, our
results encompass the first experimental observations and statistical
characterisation of spontaneous vortex formation in the condensation
transition. Using microscopic theories that incorporate atomic interactions and
quantum and thermal fluctuations of a finite-temperature Bose gas, we simulate
condensation and observe vortex formation in close quantitative agreement with
our experimental results. Our studies provide further understanding of the
development of coherence in superfluids, and may allow for direct investigation
of universal phase-transition dynamics.


title: Precision holography for non-conformal branes

abstract:
  We set up precision holography for the non-conformal branes preserving 16
supersymmetries. The near-horizon limit of all such p-brane solutions with p
\leq 4, including the case of fundamental string solutions, is conformal to
AdS_{p+2} x S^{8-p} with a linear dilaton. We develop holographic
renormalization for all these cases. In particular, we obtain the most general
asymptotic solutions with appropriate Dirichlet boundary conditions, find the
corresponding counterterms and compute the holographic 1-point functions, all
in complete generality and at the full non-linear level. The result for the
stress energy tensor properly defines the notion of mass for backgrounds with
such asymptotics. The analysis is done both in the original formulation of the
method and also using a radial Hamiltonian analysis. The latter formulation
exhibits most clearly the existence of an underlying generalized conformal
structure. In the cases of Dp-branes, the corresponding dual boundary theory,
the maximally supersymmetric Yang-Mills theory SYM_{p+1}, indeed exhibits the
generalized conformal structure found at strong coupling. We compute the
holographic 2-point functions of the stress energy tensor and gluon operator
and show they satisfy the expected Ward identities and the constraints of
generalized conformal structure. The holographic results are also manifestly
compatible with the M-theory uplift, with the asymptotic solutions,
counterterms, one and two point functions etc of the IIA F1 and D4
appropriately descending from those of M2 and M5 branes, respectively. We
present a few applications including the computation of condensates in Witten's
model of holographic YM_4 theory.


title:
Corrections to the Friedmann Equations from LQG for a Universe with a
  Free Scalar Field

abstract:
  In loop quantum cosmology the quantum dynamics is well understood. We
approximate the full quantum dynamics in the infinite dimensional Hilbert space
by projecting it on a finite dimensional submanifold thereof, spanned by
suitably chosen semiclassical states. This submanifold is isomorphic with the
classical phase space and the projected dynamical flow provides effective
equations incorporating the leading quantum corrections to the classical
equations of motion. Numerical work has been done using quantum states which
are semiclassical at late times. These states follow the classical trajectory
until the density is on the order of 1% of the Planck density then deviate
strongly from the classical trajectory. The effective equations we obtain
reproduce this behavior to surprising accuracy.


title:
An $O(\log n)$-approximation for the Set Cover Problem with Set
  Ownership

abstract:
  In highly distributed Internet measurement systems distributed agents
periodically measure the Internet using a tool called {\tt traceroute}, which
discovers a path in the network graph. Each agent performs many traceroute
measurement to a set of destinations in the network, and thus reveals a portion
of the Internet graph as it is seen from the agent locations. In every period
we need to check whether previously discovered edges still exist in this
period, a process termed {\em validation}. For this end we maintain a database
of all the different measurements performed by each agent. Our aim is to be
able to {\em validate} the existence of all previously discovered edges in the
minimum possible time. In this work we formulate the validation problem as a
generalization of the well know set cover problem. We reduce the set cover
problem to the validation problem, thus proving that the validation problem is
${\cal NP}$-hard. We present a $O(\log n)$-approximation algorithm to the
validation problem, where $n$ in the number of edges that need to be validated.
We also show that unless ${\cal P = NP}$ the approximation ratio of the
validation problem is $\Omega(\log n)$.


title: A version of Lomonosov's theorem for collections of positive operators

abstract:
  It is known that for every Banach space X and every proper WOT-closed
subalgebra A of L(X), if A contains a compact operator then it is not
transitive. That is, there exist non-zero x in X and f in X* such that f(Tx)=0
for all T in A. In the case of algebras of adjoint operators on a dual Banach
space, V.Lomonosov extended this as follows: without having a compact operator
in the algebra, |f(Tx)| is less than or equal to the essential norm of the
pre-adjoint operator T_* for all T in A. In this paper, we prove a similar
extension (in case of adjoint operators) of a result of R.Drnovsek. Namely, we
prove that if C is a collection of positive adjoint operators on a Banach
lattice X satisfying certain conditions, then there exist non-zero positive x
in X and f in X* such that f(Tx) is less than or equal to the essential norm of
T_* for all T in C.


title: Color Gradients Detected in the HD 15115 Circumstellar Disk

abstract:
  We report HST/NICMOS coronagraphic images of the HD 15115 circumstellar disk
at 1.1\micron. We find a similar morphology to that seen in the visible and at
H band--an edge-on disk that is asymmetric in surface brightness. Several
aspects of the 1.1\micron data are different, highlighting the need for
multi-wavelength images of each circumstellar disk. We find a flattening to the
western surface brightness profile at 1.1\micron interior to 2\arcsec (90 AU)
and a warp in the western half of the disk. We measure the surface brightness
profiles of the two disk lobes and create a measure of the dust scattering
efficiency between 0.55-1.65\micron at 1\arcsec, 2\arcsec, and 3\arcsec. At
2\arcsec the western lobe has a neutral spectrum up to 1.1\micron and a strong
absorption or blue spectrum $>$1.1\micron, while a blue trend is seen in the
eastern lobe. At 1\arcsec the disk has a red F110W-H color in both lobes.


title:
Formation of Nuclear Disks and Supermassive Black Hole Binaries in
  Multi-Scale Hydrodynamical Galaxy Mergers

abstract:
  (Abridged) We review the results of the first multi-scale, hydrodynamical
simulations of mergers between galaxies with central supermassive black holes
(SMBHs) to investigate the formation of SMBH binaries in galactic nuclei. We
demonstrate that strong gas inflows produce nuclear disks at the centers of
merger remnants whose properties depend sensitively on the details of gas
thermodynamics. In numerical simulations with parsec-scale spatial resolution
in the gas component and an effective equation of state appropriate for a
starburst galaxy, we show that a SMBH binary forms very rapidly, less than a
million years after the merger of the two galaxies. Binary formation is
significantly suppressed in the presence of a strong heating source such as
radiative feedback by the accreting SMBHs. We also present preliminary results
of numerical simulations with ultra-high spatial resolution of 0.1 pc in the
gas component. These simulations resolve the internal structure of the
resulting nuclear disk down to parsec scales and demonstrate the formation of a
central massive object (~ 10^8 Mo) by efficient angular momentum transport.
This is the first time that a radial gas inflow is shown to extend to parsec
scales as a result of the dynamics and hydrodynamics involved in a galaxy
merger, and has important implications for the fueling of SMBHs. Due to the
rapid formation of the central clump, the density of the nuclear disk decreases
significantly in its outer region, reducing dramatically the effect of
dynamical friction and leading to the stalling of the two SMBHs at a separation
of ~1 pc. We discuss how the orbital decay of the black holes might continue in
a more realistic model which incorporates star formation and the multi-phase
nature of the ISM.


title:
Wilson loop correlators at strong coupling: from matrices to bubbling
  geometries

abstract:
  We compute at strong coupling the large N correlation functions of
supersymmetric Wilson loops in large representations of the gauge group with
local operators of N=4 super Yang-Mills. The gauge theory computation of these
correlators is performed using matrix model techniques. We show that the strong
coupling correlator of the Wilson loop with the stress tensor computed using
the matrix model exactly matches the semiclassical computation of the
correlator of the 't Hooft loop with the stress tensor, providing a non-trivial
quantitative test of electric-magnetic duality of N=4 super Yang-Mills. We then
perform these calculations using the dual bulk gravitational picture, where the
Wilson loop is described by a "bubbling" geometry. By applying holographic
methods to these backgrounds we calculate the Wilson loop correlation
functions, finding perfect agreement with our gauge theory results.


title: The impact of type Ia supernovae on main sequence binary companions

abstract:
  The nature of Type Ia supernova progenitors is still unclear. The outstanding
characteristic of the single-degenerate scenario is that it contains hydrogen
in the binary companion of the exploding white dwarf star, which, if mixed into
the ejecta of the supernova in large amounts may lead to conflicts with the
observations thus ruling out the scenario. We investigate the effect of the
impact of Type Ia supernova ejecta on a main sequence companion star of the
progenitor system. With a series of simulations we investigate how different
parameters of this system affect the amount of hydrogen stripped from the
companion by the impact. The stellar evolution code GARSTEC is used to set up
the structure of the companion stars mimicking the effect of a binary evolution
phase. The impact itself is simulated with the smoothed particle hydrodynamics
code GADGET2. We reproduce and confirm the results of earlier grid-based
hydrodynamical simulation. Parameter studies of the progenitor system are
extended to include the results of recent binary evolution studies. The more
compact structure of the companion star found here significantly reduces the
stripped hydrogen mass. The low hydrogen masses resulting from a more realistic
companion structure are consistent with current observational constraints.
Therefore, the single-degenerate scenario remains a valid possibility for Type
Ia supernova progenitors. These new results are not a numerical effect, but the
outcome of different initial conditions.


title:
Energy-efficient Scheduling of Delay Constrained Traffic over Fading
  Channels

abstract:
  A delay-constrained scheduling problem for point-to-point communication is
considered: a packet of $B$ bits must be transmitted by a hard deadline of $T$
slots over a time-varying channel. The transmitter/scheduler must determine how
many bits to transmit, or equivalently how much energy to transmit with, during
each time slot based on the current channel quality and the number of unserved
bits, with the objective of minimizing expected total energy. In order to focus
on the fundamental scheduling problem, it is assumed that no other packets are
scheduled during this time period and no outage is allowed. Assuming
transmission at capacity of the underlying Gaussian noise channel, a
closed-form expression for the optimal scheduling policy is obtained for the
case T=2 via dynamic programming; for $T>2$, the optimal policy can only be
numerically determined. Thus, the focus of the work is on derivation of simple,
near-optimal policies based on intuition from the T=2 solution and the
structure of the general problem. The proposed bit-allocation policies consist
of a linear combination of a delay-associated term and an opportunistic
(channel-aware) term. In addition, a variation of the problem in which the
entire packet must be transmitted in a single slot is studied, and a
channel-threshold policy is shown to be optimal.


title: The LHC String Hunter's Companion

abstract:
  The mass scale of fundamental strings can be as low as few TeV/c^2 provided
that spacetime extends into large extra dimensions. We discuss the
phenomenological aspects of weakly coupled low mass string theory related to
experimental searches for physics beyond the Standard Model at the Large Hadron
Collider (LHC). We consider the extensions of the Standard Model based on open
strings ending on D-branes, with gauge bosons due to strings attached to stacks
of D-branes and chiral matter due to strings stretching between intersecting
D-branes. We focus on the model-independent, universal features of low mass
string theory. We compute, collect and tabulate the full-fledged string
amplitudes describing all 2->2 parton scattering subprocesses at the leading
order of string perturbation theory. We cast our results in a form suitable for
the implementation of stringy partonic cross sections in the LHC data analysis.
The amplitudes involving four gluons as well as those with two gluons plus two
quarks do not depend on the compactification details and are completely
model-independent. They exhibit resonant behavior at the parton center of mass
energies equal to the masses of Regge resonances. The existence of these
resonances is the primary signal of string physics and should be easy to
detect. On the other hand, the four-fermion processes like quark-antiquark
scattering include also the exchanges of heavy Kaluza-Klein and winding states,
whose details depend on the form of internal geometry. They could be used as
``precision tests'' in order to distinguish between various compactification
scenarios.


title: Is a step in the primordial spectral index favored by CMB data ?

abstract:
  A sudden small change in the second derivative of the inflaton potential can
result in a universal local feature in the spectrum of primordial perturbations
generated during inflation. The exact solution describing this feature
\cite{minu} is characterized by a step in the spectral index modulated by
characteristic oscillations and results in a large running of the spectral
index localized over a few e-folds of scale. In this paper we confront this
step-like feature with the 5 year WMAP results and demonstrate that it provides
a better fit to this data than a featureless initial spectrum. If such a
feature exists at all, then it should lie at sufficiently large scales $k_0
\lesssim 0.003 {\rm Mpc}^{-1}$ corresponding to $l \lesssim 40$. The sign of
the effect is shown to correspond to the negative running of $n_s$ localized
near this scale. This feature could arise as a result of a
`mini-waterfall'-type fast second order phase transition experienced by an
auxiliary heavy field during inflation, in a model similar to hybrid inflation
(though for a different choice of parameters). If this is the case, then the
auxiliary field should be positively coupled to the inflaton.


title: Extremely massive young clusters in NGC1365

abstract:
  In a previous work, three bright MIR/radio sources were discovered in the
nuclear region of NGC1365. We here confirm that these sources are young and
massive ``embedded'' clusters, and derive their parameters, such as extinction,
age and mass. Using ISAAC and VISIR at the VLT we obtained NIR and MIR maps and
LR spectra. The dataset is first interpreted by comparing the observations with
images and spectra of the close-by young cluster R136 in the LMC and then by
using model predictions for both the nebular emission lines and the spectral
energy distribution of the sources. We produce maps of the region containing
the three sources in the R, J, Ks, L' bands and at 12.8micro. We also provide
spectra in K, L and N. The spectral energy distribution of the three sources
rises with wavelength. Emission lines from ionised hydrogen and molecular
hydrogen are detected, as well as PAH emission. Conspicuous [NeII]12.8 line is
also present, while neither the [ArIII] 8.9 nor the [SIV] 10.4 lines are
detected. This provides a stringent constraint on the age of the sources: they
are relatively evolved young clusters (6-8 Myr). Owing to their ionising photon
rates and ages, they must be extremely massive clusters (around 10^7 solar
masses). Their MIR spectral energy distribution suggests the presence of two
components: (1) an optically thin component, with a continuum comparable to
that of R136, and (2) an optically thick component which might be related to
subsequent or on-going episodes of star formation. These sources are good
candidates for evolving according to a bi-modal hydrodynamical regime, in which
matter is trapped at the centre of a compact and massive cluster.


title: Modified scalar and tensor spectra in spinor driven inflation

abstract:
  One of the firm predictions of the single-scalar field inflationary cosmology
is the consistency relation between the scalar and tensor perturbations. It has
been argued that such a relation, if observationally verified, would offer
strong support for the idea of inflation. In this letter, we critically analyze
the validity of the consistency relation in the context of spinflation.
Spinflaton -- a scalar condensate of the Elko field -- has a single scalar
degree of freedom and leads to the identical acceleration equation as the
single canonical scalar field. We obtain the perturbation equations for the
Einstein-Elko system and show that (i) The scalar perturbations are purely
adiabatic and speed of the perturbations is identically one. (ii) In the
slow-roll limit, the scalar and tensor perturbations are nearly scale-invariant
and (iii) Obtain the consistency relations for the scalar and tensor spectra.


title: Algebraic constructions of LDPC codes with no short cycles

abstract:
  An algebraic group ring method for constructing codes with no short cycles in
the check matrix is derived. It is shown that the matrix of a group ring
element has no short cycles if and only if the collection of group differences
of this element has no repeats. When applied to elements in the group ring with
small support this gives a general method for constructing and analysing low
density parity check (LDPC) codes with no short cycles from group rings.
Examples of LDPC codes with no short cycles are constructed from group ring
elements and these are simulated and compared with known LDPC codes, including
those adopted for wireless standards.


title:
In-depth Chandra study of the AGN feedback in Virgo elliptical galaxy
  M84

abstract:
  Using deep Chandra observations of M84 we study the energetics of the
interaction between the black hole and the interstellar medium of this
early-type galaxy. We perform a detailed two dimensional reconstruction of the
properties of the X-ray emitting gas using a constrained Voronoi tessellation
method, identifying the mean trends and carrying out the fluctuation analysis
of the thermodynamical properties of the hot ISM. In addition to the PV work
associated with the bubble expansion, we identify and measure the wave energy
associated with the mildly supersonic bubble expansion. We show that, depending
on the age of the cavity and the associated wave, the waves can have a
substantial contribution to the total energy release from the AGN. The energy
dissipated in the waves tends to be concentrated near the center of M84 and in
the direction perpendicular to the bubble outflow, possibly due to the
interference of the waves generated by the expansion of northern and southern
bubbles. We also find direct evidence for the escape of radio plasma from the
ISM of the host galaxy into the intergalactic medium.


title: HI holes and high-velocity clouds in the spiral galaxy NGC 6946

abstract:
  We present a study of the distribution and kinematics of the neutral gas in
the low-inclination Scd galaxy NGC 6946. The galaxy has been observed for 192
hours at 21-cm with the Westerbork Synthesis Radio Telescope. These are among
the deepest observations ever obtained for a nearby galaxy. We detect
widespread high-velocity HI (up to about 100 km/s) and find 121 HI holes, most
of which are located in the inner regions where the gas density and the star
formation rate are higher. Much of the high-velocity gas appears to be related
to star formation and to be, in some cases, associated with HI holes. The
overall kinematics of the high-velocity gas is characterized by a slower
rotation as compared with the regular disk rotation. We conclude that the
high-velocity gas in NGC 6946 is extra-planar and has the same properties as
the gaseous halos observed in other spiral galaxies including the Milky Way.
Stellar feedback (galactic fountain) is probably at the origin of most of the
high-velocity gas and of the HI holes. There are also indications, especially
in the outer regions, -an extended HI plume, velocity anomalies, sharp edges,
and large-scale asymmmetries- pointing to tidal encounters and recent gas
accretion.


title: From AGS-SPS and Onwards to the LHC

abstract:
  I review the history of the efforts using heavy ion collisions to make new
forms of matter. I discuss both the development of the theoretical ideas about
such new forms of matter, as well the past, present and planned experimental
efforts. I also highlight the development of this activity in both India and
China.


title:
Thermopower as a Probe of Non-Abelian Quasiparticle Statistics in
  Fractional Quantum Hall States

abstract:
  This paper has been superseded by a new preprint: Kun Yang and Bertrand I.
Halperin, arXiv:0901.1429.


title:
Asymmetric silicate dust distribution toward the silicate carbon star BM
  Gem

abstract:
  Silicate carbon stars show the 10 micron silicate emission, despite their
carbon-rich photospheres. They are considered to have circumbinary or
circum-companion disks, which serve as a reservoir of oxygen-rich material shed
by mass loss in the past. We present N-band spectro-interferometric
observations of the silicate carbon star BM Gem using MIDI at the Very Large
Telescope Interferometer (VLTI). Our aim is to probe the spatial distribution
of oxygen-rich dust with high spatial resolution. BM Gem was observed with
VLTI/MIDI at 44--62 m baselines using the UT2-UT3 and UT3-UT4 baseline
configurations. The N-band visibilities observed for BM Gem show a steep
decrease from 8 to ~10 micron and a gradual increase longward of ~10 micron,
reflecting the optically thin silicate emission feature emanating from
sub-micron-sized amorphous silicate grains. The differential phases obtained at
baselines of ~44--46 m show significant non-zero values (~ -70 degrees) in the
central part of the silicate emission feature between ~9 and 11 micron,
revealing a photocenter shift and the asymmetric nature of the silicate
emitting region. The observed N-band visibilities and differential phases can
be fairly explained by a simple geometrical model in which the unresolved star
is surrounded by a ring with azimuthal brightness modulation. The best-fit
model is characterized by a broad ring (~70 mas across at 10 micron) with a
bright region which is offset from the unresolved star by ~20 mas at a position
angle of ~280 degrees. This model can be interpreted as a system with a
circum-companion disk and is consistent with the spectroscopic signatures of an
accretion disk around an unseen companion recently discovered in the violet
spectrum of BM Gem.


title:
Parameterizing the Effect of Dark Energy Perturbations on the Growth of
  Structures

abstract:
  We present an analytical fit to the growth function of the dark matter
perturbations when dark energy perturbations are present. The growth index
depends upon the dark energy equation of state w, the speed of sound of the
dark energy fluctuations, the dark matter abundance and the observed comoving
scale. The growth index changes by ~5% for small speed of sound and large
deviations of w from -1 with respect to its value in the limit of no dark
energy perturbations.


title: An Index for Non-relativistic Superconformal Field Theories

abstract:
  We study the highest-weight representation of N=2 supersymmetric Schrodinger
algebra which appears in non-relativistic superconformal field theories in
(1+2) dimension. We define the index for the non-relativistic superconformal
field theories and study its properties. As a concrete example, we compute the
index for the non-relativistic limit of N=6 superconformal Chern-Simons-matter
theory recently proposed by Aharony et al.


title:
The Invisibles: A Detection Algorithm to Trace the Faintest Milky Way
  Satellites

abstract:
  [Abridged] A specialized data mining algorithm has been developed using
wide-field photometry catalogues, enabling systematic and efficient searches
for resolved, extremely low surface brightness satellite galaxies in the halo
of the Milky Way (MW). Tested and calibrated with the Sloan Digital Sky Survey
Data Release 6 (SDSS-DR6) we recover all fifteen MW satellites recently
detected in SDSS, six known MW/Local Group dSphs in the SDSS footprint, and 19
previously known globular and open clusters. In addition, 30 point source
overdensities have been found that correspond to no cataloged objects. The
detection efficiencies of the algorithm have been carefully quantified by
simulating more than three million model satellites embedded in star fields
typical of those observed in SDSS, covering a wide range of parameters
including galaxy distance, scale-length, luminosity, and Galactic latitude.


title: Desingularization of G_2 manifolds with isolated conical singularities

abstract:
  We present a method to desingularize a compact G_2 manifold with isolated
conical singularities by cutting out a neighbourhood of each singular point and
glueing in an asymptotically conical G_2 manifold. Controlling the error on the
overlap glueing region enables us to use a result of Joyce to conclude that the
resulting compact smooth 7-manifold admits a torsion-free G_2 structure, with
full G_2 holonomy.
  There are topological obstructions for this procedure to work, which arise
from the degree 3 and degree 4 cohomology of the asymptotically conical G_2
manifolds which are glued in at each conical singularity. When a certain
necessary topological condition on the manifold with isolated conical
singularities is satisfied, we can introduce correction terms to the glueing
procedure to ensure that it still works. In the case of degree 4 obstructions,
these correction terms are trivial to construct, but in the case of degree 3
obstructions we need to solve an elliptic equation on a non-compact manifold.
For this we use the Lockhart-McOwen theory of weighted Sobolev spaces on
manifolds with ends. This theory is also used to obtain a good asymptotic
expansion of the G_2 structure on an asymptotically conical G_2 manifold under
an appropriate gauge-fixing condition, which is required to make the glueing
procedure work.


title: Strong magnetic fields in normal galaxies at high redshifts

abstract:
  The origin and growth of magnetic fields in galaxies is still something of an
enigma. It is generally assumed that seed fields are amplified over time
through the dynamo effect, but there are few constraints on the timescale. It
has recently been demonstrated that field strengths as traced by rotation
measures of distant quasars are comparable to those seen today, but it was
unclear whether the high fields were in the exotic environments of the quasars
themselves or distributed along the line of sight. Here we demonstrate that the
quasars with strong MgII absorption lines are unambiguously associated with
larger rotation measures. Since MgII absorption occurs in the haloes of normal
galaxies along the sightline to the quasars, this association requires that
organized fields of surprisingly high strength are associated with normal
galaxies when the Universe was only about one-third of its present age.


title: Electronic properties of a biased graphene bilayer

abstract:
  We study, within the tight-binding approximation, the electronic properties
of a graphene bilayer in the presence of an external electric field applied
perpendicular to the system -- \emph{biased bilayer}. The effect of the
perpendicular electric field is included through a parallel plate capacitor
model, with screening correction at the Hartree level. The full tight-binding
description is compared with its 4-band and 2-band continuum approximations,
and the 4-band model is shown to be always a suitable approximation for the
conditions realized in experiments. The model is applied to real biased bilayer
devices, either made out of SiC or exfoliated graphene, and good agreement with
experimental results is found, indicating that the model is capturing the key
ingredients, and that a finite gap is effectively being controlled externally.
Analysis of experimental results regarding the electrical noise and cyclotron
resonance further suggests that the model can be seen as a good starting point
to understand the electronic properties of graphene bilayer. Also, we study the
effect of electron-hole asymmetry terms, as the second-nearest-neighbor hopping
energies $t'$ (in-plane) and $\gamma_{4}$ (inter-layer), and the on-site energy
$\Delta$.


title: Exclusion of black hole disaster scenarios at the LHC

abstract:
  The upcoming high energy experiments at the LHC are one of the most
outstanding efforts for a better understanding of nature. It is associated with
great hopes in the physics community. But there is also some fear in the
public, that the conjectured production of mini black holes might lead to a
dangerous chain reaction. In this paper we summarize the most straight forward
arguments that are necessary to rule out such doomsday scenarios.


title:
Evaluating Intraspecific Variation and Interspecific Diversity:
  comparing humans and fish species

abstract:
  The analysis of eight molecular datasets involving human and teleost examples
along with morphological samples from several groups of Neotropical electric
fish (Order: Gymnotiformes) were used in this thesis to test the dynamics of
both intraspecific variation and interspecific diversity. In terms of
investigating molecular interspecific diversity among humans, two experimental
exercises were performed. A cladistic exchange experiment tested for the extent
of discontinuity and interbreeding between H. sapiens and neanderthal
populations. As part of the same question, another experimental exercise tested
the amount of molecular variance resulting from simulations which treated
neanderthals as being either a local population of modern humans or as a
distinct subspecies. Finally, comparisons of hominid populations over time with
fish species helped to define what constitutes taxonomically relevant
differences between morphological populations as expressed among both trait
size ranges and through growth patterns that begin during ontogeny. Compared to
the subdivision found within selected teleost species, H. sapiens molecular
data exhibited little variation and discontinuity between geographical regions.
Results of the two experimental exercises concluded that neanderthals exhibit
taxonomic distance from modern H. sapiens. However, this distance was not so
great as to exclude the possibility of interbreeding between the two
subspecific groups. Finally, a series of characters were analyzed among species
of Neotropical electric fish. These analyses were compared with hominid
examples to determine what constituted taxonomically relevant differences
between populations as expressed among specific morphometric traits that
develop during the juvenile phase.


title:
Transmission in the vicinity of the Dirac point in hexagonal Photonic
  Crystals

abstract:
  We use a scattering matrix approach to simulate the transmission through a
hexagonal Photonic Crystal in the vicinity of the Dirac point. If the crystal
is oriented so that the propagation direction perpendicular to the surface
corresponds to the Gamma-K direction, no oblique transmission is possible for a
very long (infinite) structure. For a finite structure with width, W, and
length, L, the length dependence of the transmission is given by T_total =
Gamma_0 W/L. For T_total all waves with a wavevector parallel to the surface,
k_||=n 2pi/W, described by a channel number, n, must be considered. We show the
transmission at the Dirac point follows the given scaling law and this scaling
law is related to the behavior of the individual channels. This leads to the
establishment of a criterion for the maximum length for this scaling behavior
when the total transmission reaches a constant value. We also compare this
scaling behavior to the results in other frequency regions.


title: Where can we really find the First Stars' Remnants today?

abstract:
  A number of recent numerical investigations concluded that the remnants of
rare structures formed at very high redshift, such as the very first stars and
bright redshift z~6 QSOs, are preferentially located at the center of the most
massive galaxy clusters at redshift z=0. In this paper we readdress this
question using a combination of cosmological simulations of structure formation
and extended Press-Schechter formalism and we show that the typical remnants of
Population III stars are instead more likely to be found in a group
environment, that is in dark matter halos of mass ~2x10^{13} h^{-1}M_sun.
Similarly, the descendants of the brightest z~6 QSOs are expected to be in
medium-sized clusters (mass of a few 10^{14} h^{-1}M_sun), rather than in the
most massive superclusters (M>10^{15} h^{-1}M_sun) found within the typical 1
Gpc^3 cosmic volume where a bright z~6 QSO lives. The origin of past claims
that the most massive clusters preferentially host these remnants is rooted in
the numerical method used to initialize their numerical simulations: Only a
small region of the cosmological volume of interest was simulated with
sufficient resolution to identify low-mass halos at early times, and this
region was chosen to host the most massive halo in the cosmological volume at
late times. The conclusion that the earliest structures formed in the entire
cosmological volume evolve into the most massive halo at late times was thus
arrived at by construction. We demonstrate that, to the contrary, the first
structures to form in a cosmological region evolve into relatively typical
objects at later times. We propose alternative numerical methods for simulating
the earliest structures in cosmological volumes.


title:
Towards a core genome: pairwise similarity searches on interspecific
  genomic data

abstract:
  The phenomenon of gene conservation is an interesting evolutionary problem
related to speciation and adaptation. Conserved genes are acted upon in
evolution in a way that preserves their function despite other structural and
functional changes going on around them. The recent availability of
whole-genomic data from closely related species allows us to test the
hypothesis that a core genome present in a hypothetical common ancestor is
inherited by all sister taxa. Furthermore, this core genome should serve
essential functions such as genetic regulation and cellular repair.
Whole-genome sequences from three strains of bacteria (Shewanella sp.) were
used in this analysis. The open reading frames (ORFs) for each identified and
putative gene were used for each genome. Reciprocal Blast searches were
conducted on all three genomes, which distilled a list of thousands of genes to
68 genes that were identical across taxa. Based on functional annotation, these
genes were identified as housekeeping genes, which confirmed the original
hypothesis. This method could be used in eukaryotes as well, in particular the
relationship between humans, chimps, and macaques.


title: On extended homogenization formalisms for nanocomposites

abstract:
  In a long wavelength regime, the effective properties of particulate
composites, including nanocomposites, may be estimated using one of various
homogenization formalisms, such as the Bruggeman and Maxwell Garnett
formalisms, and the approach of the strong--property--fluctuation theory
(SPFT). In the conventional implementations of these formalisms, the
constituent particles are treated as point--like scattering centres. However,
extended formalisms have been established--which involve integral
formulations--that take account of the spatial extent of the constituent
particles. In particular, the extended second--order SPFT takes account of both
the size of the constituent particles and their statistical distributions. We
derive explicit representations of the extended second--order SPFT appropriate
to isotropic chiral and uniaxial dielectric homogenized composite mediums.
These results may also be employed in extended versions of the Bruggeman and
Maxwell Garnett formalisms.


title: Parallel Approximation and Integer Programming Reformulation

abstract:
  We show that in a knapsack feasibility problem an integral vector $p$, which
is short, and near parallel to the constraint vector gives a branching
direction with small integer width.
  We use this result to analyze two computationally efficient reformulation
techniques on low density knapsack problems. Both reformulations have a
constraint matrix with columns reduced in the sense of Lenstra, Lenstra, and
Lov\'asz. We prove an upper bound on the integer width along the last variable,
which becomes 1, when the density is sufficiently small.
  In the proof we extract from the transformation matrices a vector which is
near parallel to the constraint vector $a.$ The near parallel vector is a good
branching direction in the original knapsack problem, and this transfers to the
last variable in the reformulations.


title: Cardy algebras and sewing constraints, I

abstract:
  This is part one of a two-part work that relates two different approaches to
two-dimensional open-closed rational conformal field theory. In part one we
review the definition of a Cardy algebra, which captures the necessary
consistency conditions of the theory at genus 0 and 1. We investigate the
properties of these algebras and prove uniqueness and existence theorems. One
implication is that under certain natural assumptions, every rational closed
CFT is extendable to an open-closed CFT. The relation of Cardy algebras to the
solutions of the sewing constraints is the topic of part two.


title: Equivariant CW-Complexes and the Orbit Category

abstract:
  We give a general framework for studying G-CW complexes via the orbit
category. As an application we show that the symmetric group G=S_5 admits a
finite G-CW complex X homotopy equivalent to a sphere, with cyclic isotropy
subgroups.


title: Quantum interface between light and atomic ensembles

abstract:
  During the past decade the interaction of light with multi-atom ensembles has
attracted a lot of attention as a basic building block for quantum information
processing and quantum state engineering. The field started with the
realization that optically thick free space ensembles can be efficiently
interfaced with quantum optical fields. By now the atomic ensemble - light
interfaces have become a powerful alternative to the cavity-enhanced
interaction of light with single atoms. We discuss various mechanisms used for
the quantum interface, including quantum nondemolition or Faraday interaction,
quantum measurement and feedback, Raman interaction and electromagnetically
induced transparency. The paper provides a common theoretical frame for these
processes, describes basic experimental techniques and media used for quantum
interfaces, and reviews several key experiments on quantum memory for light,
quantum entanglement between atomic ensembles and light, and quantum
teleportation with atomic ensembles. We discuss the two types of quantum
measurements which are most important for the interface: homodyne detection and
photon counting. The paper concludes with an outlook on the future of atomic
ensembles as an enabling technology in quantum information processing.


title:
Effect of strong correlations on the high energy anomaly in hole- and
  electron-doped high-Tc superconductors

abstract:
  Recently, angle-resolved photoemission spectroscopy (ARPES) has been used to
highlight an anomalously large band renormalization at high binding energies in
cuprate superconductors: the high energy 'waterfall' or high energy anomaly
(HEA). This paper demonstrates, using a combination of new ARPES measurements
and quantum Monte Carlo simulations, that the HEA is not simply the by-product
of matrix element effects, but rather represents a cross-over from a
quasiparticle band at low binding energies near the Fermi level to valence
bands at higher binding energy, assumed to be of strong oxygen character, in
both hole- and electron-doped cuprates. While photoemission matrix elements
clearly play a role in changing the aesthetic appearance of the band
dispersion, i.e. the 'waterfall'-like behavior, they provide an inadequate
description for the physics that underlies the strong band renormalization
giving rise to the HEA. Model calculations of the single-band Hubbard
Hamiltonian showcase the role played by correlations in the formation of the
HEA and uncover significant differences in the HEA energy scale for hole- and
electron-doped cuprates. In addition, this approach properly captures the
transfer of spectral weight accompanying both hole and electron doping in a
correlated material and provides a unifying description of the HEA across both
sides of the cuprate phase diagram.


title: Inclusions between parabolic geometries

abstract:
  Some of the well known Fefferman like constructions of parabolic geometries
end up with a new structure on the same manifold. In this paper, we classify
all such cases with the help of the classical Onishchik's lists \cite{onish1}
and we treat in detail the only new series of inclusions providing the
spinorial structures on the manifolds with generic free distributions. Our
technique relies on the cohomological understanding of the canonical normal
Cartan connections for parabolic geometries and the classical computations with
exterior forms. Apart of the complete discussion of the distributions from the
geometrical point of view and the new functorial construction of the inclusion
into the spinorial geometry, we also discuss the normality problem of the
resulting spinorial connections. In particular, there is a non--trivial
subclass of distributions providing normal spinorial connections directly by
the construction.


title:
Measurement of the in-medium K0 inclusive cross section in pi- -induced
  reactions at 1.15 GeV/c

abstract:
  The K0 meson production by pi- mesons of 1.15 GeV/c momentum on C, Al, Cu, Sn
and Pb nuclear targets was measured with the FOPI spectrometer at the SIS
accelerator of GSI. Inclusive production cross-sections and the momentum
distributions of K0 mesons are compared to scaled elementary production
cross-sections and to predictions of theoretical models describing the
in-medium production of kaons. The data represent a new reference for those
models, which are widely used for interpretation of the strangeness-production
in heavy-ion collisions. The presented results demonstrate the sensitivity of
the kaon production to the reaction amplitudes inside nuclei and point to the
existence of a repulsive KN-potential of 20+-5 MeV at normal nuclear matter
density.


title: Statistical Model of Heavy-Ion Fusion-Fission Reactions

abstract:
  Cross-section and neutron-emission data from heavy-ion fusion-fission
reactions are consistent with the fission of fully equilibrated systems with
fission lifetime estimates obtained via a Kramers-modified statistical model
which takes into account the collective motion of the system about the ground
state, the temperature dependence of the location and height of fission
transition points, and the orientation degree of freedom. If the standard
techniques for calculating fission lifetimes are used, then the calculated
excitation-energy dependence of fission lifetimes is incorrect. We see no
evidence to suggest that the nuclear viscosity has a temperature dependence.
The strong increase in the nuclear viscosity above a temperature of
approximately 1.3 MeV deduced by others is an artifact generated by an
inadequate fission model.


title:
Combinatorial bases of Feigin-Stoyanovsky's type subspaces of level 1
  standard modules for $\tilde{\mathfrak sl}(\ell+1,\C)$

abstract:
  Let $\tilde{\mathfrak g}$ be an affine Lie algebra of type $A_\ell^{(1)}$.
Suppose we're given a $\mathbb Z$-gradation of the corresponding simple
finite-dimensional Lie algebra ${\mathfrak g}={\mathfrak
g}_{-1}\oplus{\mathfrak g}_0 \oplus {\mathfrak g}_1$; then we also have the
induced $\mathbb Z$-gradation of the affine Lie algebra $$\tilde{\mathfrak
g}=\tilde{\mathfrak g}_{-1} \oplus \tilde{\mathfrak g}_0 \oplus
\tilde{\mathfrak g}_1.$$
  Let $L(\Lambda)$ be a standard module of level 1. Feigin-Stoyanovsky's type
subspace $W(\Lambda)$ is the $\tilde{\mathfrak g}_1$-submodule of $L(\Lambda)$
generated by the highest-weight vector $v_\Lambda$,
$$W(\Lambda)=U(\tilde{\mathfrak g}_1)\cdot v_\Lambda\subset L(\Lambda).$$ We
find a combinatorial basis of $W(\Lambda)$ given in terms of difference and
initial conditions. Linear independence of the generating set is proved
inductively by using coefficients of intertwining operators. A basis of
$L(\Lambda)$ is obtained as an ``inductive limit'' of the basis of
$W(\Lambda)$.


title: Discrete piecewise linear functions

abstract:
  The concept of permutograph is introduced and properties of integral
functions on permutographs are established. The central result characterizes
the class of integral functions that are representable as lattice polynomials.
This result is used to establish lattice polynomial representations of
piecewise linear functions on convex domains and continuous selectors on linear
orders.


title: New evidence for halo gas accretion onto disk galaxies

abstract:
  Studies of the halo gas in the Milky Way and in nearby spiral galaxies show
the presence of gas complexes that cannot be reconciled with an internal
(galactic fountain) origin and are direct evidence of gas accretion. Estimating
gas accretion rates from these features consistently gives values, which are
one order of magnitude lower than what is needed to feed the star formation. I
show that this problem can be overcome if most of the accretion is in fact
"hidden" as it mixes with the galactic fountain material coming from the disk.
This model not only provides an explanation for the missing gas accretion but
also reproduces the peculiar kinematics of the halo gas in particular the
vertical rotation gradient. In this view this gradient becomes indirect
evidence for gas accretion.


title:
Motion of an impurity particle in an ultracold quasi-one-dimensional gas
  of hard-core bosons

abstract:
  The low-lying eigenstates of a one-dimensional (1D) system of many
impenetrable point bosons and one moving impurity particle with repulsive
zero-range impurity-boson interaction are found for all values of the
impurity-boson mass ratio and coupling constant. The moving entity is a
polaron-like composite object consisting of the impurity clothed by a co-moving
gray soliton. The special case with impurity-boson interaction of point
hard-core form and impurity-boson mass ratio $m_i/m$ unity is first solved
exactly as a special case of a previous Fermi-Bose (FB) mapping treatment of
soluble 1D Bose-Fermi mixture problems. Then a more general treatment is given
using second quantization for the bosons and the second-quantized form of the
FB mapping, eliminating the impurity degrees of freedom by a Lee-Low-Pines
canonical transformation. This yields the exact solution for arbitrary $m_i/m$
and impurity-boson interaction strength.


title:
Measurement of the electron charge asymmetry in ppbar->W+X->enu+X events
  at sqrt{s}=1.96 TeV

abstract:
  We present a measurement of the electron charge asymmetry in
ppbar->W+X->enu+X events at a center of mass energy of 1.96 TeV using 0.75 fb-1
of data collected with the D0 detector at the Fermilab Tevatron Collider. The
asymmetry is measured as a function of the electron transverse momentum and
pseudorapidity in the interval (-3.2, 3.2) and is compared with expectations
from next-to-leading order calculations in perturbative quantum chromodynamics.
These measurements will allow more accurate determinations of the proton parton
distribution functions.


title: Field theory in 4D N=2 conformally flat superspace

abstract:
  Building on the superspace formulation for four-dimensional N=2
matter-coupled supergravity developed in arXiv:0805.4683, we elaborate upon a
general setting for field theory in N=2 conformally flat superspaces, and
concentrate specifically on the case of anti-de Sitter (AdS) superspace. We
demonstrate, in particular, that associated with the N=2 AdS supergeometry is a
unique vector multiplet such that the corresponding covariantly chiral field
strength W_0 is constant, W_0=1. This multiplet proves to be intrinsic in the
sense that it encodes all the information about the N=2 AdS supergeometry in a
conformally flat frame. Moreover, it emerges as a building block in the
construction of various supersymmetric actions. Such a vector multiplet, which
can be identified with one of the two compensators of N=2 supergravity, also
naturally occurs for arbitrary conformally flat superspaces. An explicit
superspace reduction N=2 to N=1 is performed for the action principle in
general conformally flat N=2 backgrounds, and examples of such reduction are
given.


title: A new look at Bell's inequalities and Nelson's theorem

abstract:
  In 1985, Edward Nelson, who formulated the theory of stochastic mechanics,
made an interesting remark on Bell's theorem. Nelson analysed the latter in the
light of classical fields that behave randomly. He found that if a stochastic
hidden variable theory fulfils certain conditions, the inequality of Bell can
be violated. Moreover, Nelson was able to prove that this may happen without
any instantaneous communication between the two spatially separated measurement
stations. Since Nelson's article got almost overlooked by physicists, we try to
review his comments on Bell's theorem. We argue that a modification of
stochastic mechanics published recently by Fritsche and Haugk can be extended
to a theory which fulfils the requirements of Nelson's analysis. The article
proceeds to derive the quantum mechanical formalism of spinning particles and
the Pauli equation from this version of stochastic mechanics. Then, we
investigate Bohm's version of the EPR experiment. Additionally, other setups,
like entanglement swapping or time and position correlations, are shortly
explained from the viewpoint of our local hidden-variable model. Finally, we
mention that this theory could perhaps be relativistically extended.


title: Phonon Density of States of LaFeAsO1-xFx

abstract:
  We have studied the phonon density of states (PDOS) in LaFeAsO1-xFx with
inelastic neutron scattering methods. The PDOS of the parent compound(x=0) is
very similar to the PDOS of samples optimally doped with fluorine to achieve
the maximum Tc (x~0.1). Good agreement is found between the experimental PDOS
and first-principle calculations with the exception of a small difference in Fe
mode frequencies. The PDOS reported here is not consistent with conventional
electron-phonon mediated superconductivity.


title: Fueling QSOs: The Relevance of Mergers

abstract:
  To study the relevance of mergers for the fueling of QSOs, we are currently
conducting an HST imaging campaign of a sample of QSO host galaxies classified
as ellipticals in the literature. Here, we present results from a study of the
first five QSO host galaxies imaged with HST/ACS. For the majority of objects,
strong signs of interactions such as tidal tails, shells, and other fine
structure are revealed. We estimate the nature and age of the merger by
comparing the images with numerical simulations. The merger ages range between
a few hundred Myr up to a Gyr. These timescales are comparable to starburst
ages in the QSO hosts previously inferred from Keck spectroscopy, but longer
than theoretical estimates of AGN duty cycles. A possible scenario emerging
from our results is that most QSO host galaxies experienced mergers with
accompanying starbursts but that the activity is triggered with a delay of
several hundreds Myr after the merger. To probe whether there is indeed a
causal connection between the merger and the QSO activity, we study a control
sample of inactive ellipticals. Our preliminary results do not reveal
comparable fine structure.


title: Conductivity and Spin Susceptibility for the Disordered 2D Hubbard Model

abstract:
  The effect of disorder on a class of transition metal oxides described by a
single orbital Hubbard model at half filling is investigated. The phases are
characterized by the nature of the electronic and spin excitations. The
frequency and temperature-dependent conductivity and spin susceptibility as
functions of disorder are calculated. The interplay of disorder and
electron-electron interaction produces unusual behavior in this system. For
example, the dc conductivity, which is vanishingly small at low disorder in the
Mott phase and at high disorder in the localized phase, gets surprisingly
enhanced at intermediate disorder in a "metallic" phase. Moreover, the spin
susceptibility in this "metallic" phase is not the expected Pauli-behavior but
Curie-$1/T$ due to the presence of local moments.


title: Statistical Mechanics of Steiner trees

abstract:
  The Minimum Weight Steiner Tree (MST) is an important combinatorial
optimization problem over networks that has applications in a wide range of
fields. Here we discuss a general technique to translate the imposed global
connectivity constrain into many local ones that can be analyzed with cavity
equation techniques. This approach leads to a new optimization algorithm for
MST and allows to analyze the statistical mechanics properties of MST on random
graphs of various types.


title:
The Dynamics of Internet Traffic: Self-Similarity, Self-Organization,
  and Complex Phenomena

abstract:
  The Internet is the most complex system ever created in human history.
Therefore, its dynamics and traffic unsurprisingly take on a rich variety of
complex dynamics, self-organization, and other phenomena that have been
researched for years. This paper is a review of the complex dynamics of
Internet traffic. Departing from normal treatises, we will take a view from
both the network engineering and physics perspectives showing the strengths and
weaknesses as well as insights of both. In addition, many less covered
phenomena such as traffic oscillations, large-scale effects of worm traffic,
and comparisons of the Internet and biological models will be covered.


title: A simple circuit realization of the tent map

abstract:
  We present a very simple electronic implementation of the tent map, one of
the best-known discrete dynamical systems. This is achieved by using integrated
circuits and passive elements only. The experimental behavior of the tent map
electronic circuit is compared with its numerical simulation counterpart. We
find that the electronic circuit presents fixed points, periodicity, period
doubling, chaos and intermittency that match with high accuracy the
corresponding theoretical values


title: Decoherence and the (non)emergence of classicality

abstract:
  We consider the claim that decoherence explains the emergence of classicality
in quantum systems, and conclude that it does not. We show that, given a
randomly chosen universe composed of a variety of subsystems, some of which are
macroscopic and subject to decoherence-inducing interactions, and some of which
are microscopic, the macroscopic subsystems will not display any distinctively
classical behavior. Therefore, a universe in which macroscopic and microscopic
do display distinct behavior must be in a very special, highly nongeneric
quantum state.


title: The geodesic problem in quasimetric spaces

abstract:
  In this article, we study the geodesic problem in a generalized metric space,
in which the distance function satisfies a relaxed triangle inequality
$d(x,y)\leq \sigma (d(x,z)+d(z,y))$ for some constant $\sigma \geq 1$, rather
than the usual triangle inequality. Such a space is called a quasimetric space.
We show that many well-known results in metric spaces (e.g. Ascoli-Arzel\`{a}
theorem) still hold in quasimetric spaces. Moreover, we explore conditions
under which a quasimetric will induce an intrinsic metric. As an example, we
introduce a family of quasimetrics on the space of atomic probability measures.
The associated intrinsic metrics induced by these quasimetrics coincide with
the $d_{\alpha}$ metric studied early in the study of branching structures
arisen in ramified optimal transportation. An optimal transport path between
two atomic probability measures typically has a "tree shaped" branching
structure. Here, we show that these optimal transport paths turn out to be
geodesics in these intrinsic metric spaces.


title: Controlling transistor threshold voltages using molecular dipoles

abstract:
  We develop a theoretical model for how organic molecules can control the
electronic and transport properties of an underlying transistor channel to
whose surface they are chemically bonded. The influence arises from a
combination of long-ranged dipolar electrostatics due to the molecular
head-groups, as well as short-ranged charge transfer and interfacial dipole
driven by equilibrium band-alignment between the molecular backbone and the
reconstructed semiconductor surface atoms.


title: Accelerating Cold Dark Matter Cosmology ($\Omega_{\Lambda}\equiv 0$)

abstract:
  A new kind of accelerating flat model with no dark energy that is fully
dominated by cold dark matter (CDM) is investigated. The number of CDM
particles is not conserved and the present accelerating stage is a consequence
of the negative pressure describing the irreversible process of gravitational
particle creation. A related work involving accelerating CDM cosmology has been
discussed before the SNe observations [Lima, Abramo & Germano, Phys. Rev. D53,
4287 (1996)]. However, in order to have a transition from a decelerating to an
accelerating regime at low redshifts, the matter creation rate proposed here
includes a constant term of the order of the Hubble parameter. In this case,
$H_0$ does not need to be small in order to solve the age problem and the
transition happens even if the matter creation is negligible during the
radiation and part of the matter dominated phase. Therefore, instead of the
vacuum dominance at redshifts of the order of a few, the present accelerating
stage in this sort of Einstein-de Sitter CDM cosmology is a consequence of the
gravitational particle creation process. As an extra bonus, in the present
scenario does not exist the coincidence problem that plagues models with
dominance of dark energy. The model is able to harmonize a CDM picture with the
present age of the universe, the latest measurements of the Hubble parameter
and the Supernovae observations.


title:
\mu SR-detection of the soft-mode toward the exotic magnetic ground
  state in bond-disordered quantum spin system
  IPA-Cu(Cl$_{0.35}$Br$_{0.65}$)$_3$

abstract:
  The spin-gap system with a bond-disorder (CH3)2CHNH3-Cu(ClxBr1-x)3 is
reported by experiments on macroscopic quantities of the uniform susceptibility
and the specific heat to show a magnetic order at low temperatures when the
value of x is within the limited region between 0.44 and 0.87, and otherwise a
gapped behavior. We have investigated microscopically the ground state of the
sample with x=0.35 by muon spin relaxation (mSR) to observe that the frequency
spectrum of the spin fluctuation tends to concentrate around zero energy as
lowering temperatures. This behavior was interpreted as the soft-mode toward
the possible magnetic phase transition at absolute zero.


title: On N = 2 supergravity and projective superspace: Dual formulations

abstract:
  The superspace formulation for four-dimensional N = 2 matter-coupled
supergravity recently developed in arXiv:0805.4683 makes use of a new type of
conformal compensator with infinitely many off-shell degrees of freedom: the
so-called covariant weight-one polar hypermultiplet. In the present note we
prove the duality of this formulation to the known minimal (40+40) off-shell
realization for N = 2 Poincare supergravity involving the improved tensor
compensator. Within the latter formulation, we present new off-shell matter
couplings realized in terms of covariant weight-zero polar hypermultiplets. We
also elaborate upon the projective superspace description of vector multiplets
in N = 2 conformal supergravity. An alternative superspace representation for
locally supersymmetric chiral actions is given. We present a model for massive
improved tensor multiplet with both ``electric'' and ``magnetic'' types. of
mass terms.


title: Conservative Force Fields in Non-Gaussian Statistics

abstract:
  In this letter, we determine the $\kappa$-distribution function for a gas in
the presence of an external field of force described by a potential U(${\bf
r}$). In the case of a dilute gas, we show that the $\kappa$-power law
distribution including the potential energy factor term can rigorously be
deduced in the framework of kinetic theory with basis on the Vlasov equation.
Such a result is significant as a preliminary to the discussion on the role of
long range interactions in the Kaniadakis thermostatistics and the underlying
kinetic theory.


title: Recover plaintext attack to block ciphers

abstract:
  we will present an estimation for the upper-bound of the amount of 16-bytes
plaintexts for English texts, which indicates that the block ciphers with block
length no more than 16-bytes will be subject to recover plaintext attacks in
the occasions of plaintext -known or plaintext-chosen attacks.


title: Prospect of Rapidity Asymmetry and Nuclear Modifications

abstract:
  In asymmetric heavy ion collisions like dA or pA, particle production yields
are different in the forward (d- or p-side) and backward (A-side) rapidity
directions. The rapidity distribution reflects the geometry and phase-space
distribution of nuclear matter. These properties may depend on the time
evolution of the collision. Due to the smallness of the backward-forward
differences, the rapidity asymmetry factor can be useful to quantify nuclear
modification effects, like e.g. shadowing and the EMC effect. Our work is a
survey of the nuclear modification factor and the rapidity asymmetries at RHIC
energies. We analyze the rapidity dependence and the strength of the nuclear
effects. We focus on the high transverse momentum region, and make predictions
for the role of nuclear modifications and rapidity asymmetries for future
experimental measurements at increasing absolute values of rapidity.


title:
Tests of flavor universality for neutrino-Z couplings in future neutrino
  experiments

abstract:
  We investigate the physics potential of NuSOnG experiment to probe new
physics contributions to Z-neutrino-neutrino couplings in muon-neutrino
electron elastic and neutral-current deep-inelastic scattering processes. We
employ an effective Lagrangian approach and do not a priori assume universality
of the coupling of neutrinos to Z. We obtain 95% C.L. limits on possible
universality violating couplings.


title: Timing observations of RRAT J1819-1458 at Urumqi Observatory

abstract:
  We report the timing-analysis results obtained for RRAT J1819-1458 from
regular timing observations at 1.54 GHz using the Urumqi 25 m radio telescope
between 2007 April to 2008 March. RRAT J1819-1458 is a relatively young and
highly magnetized neutron star discovered by its sporadic short bursts in the
Parkes Multibeam Pulsar Survey data. In 94 hrs of observation data, we detected
a total of 162 dispersed bursts of RRAT J1819-1458 with the signal-to-noise
ratios (S/Ns) above 5-$\sigma$ threshold. Among them, 5 bursts clearly show
two-component structure. The S/N of the strongest burst is 13.3. The source's
DM measured through our data is 196.0 $\pm$0.4 pc cm$^{-3}$. The timing
position, frequency and its first derivative were determined using standard
pulsar timing techniques on the arrival times of these individual bursts. The
accuracy of the solved rotating parameters are improved comparing with that in
previous publication. Our timing position with 2-$\sigma$ error is consistent
with the position of its X-ray counterpart CXOU J181934.1-145804. The effect of
timing noise and the phase fluctuation of the individual short bursts on the
timing residuals is briefly discussed. The distribution of the timing residuals
is bimodal, which cannot be explained readily by timing irregularity.


title: Phylogenetic estimation with partial likelihood tensors

abstract:
  We present an alternative method for calculating likelihoods in molecular
phylogenetics. Our method is based on partial likelihood tensors, which are
generalizations of partial likelihood vectors, as used in Felsenstein's
approach. Exploiting a lexicographic sorting and partial likelihood tensors, it
is possible to obtain significant computational savings. We show this on a
range of simulated data by enumerating all numerical calculations that are
required by our method and the standard approach.


title:
Observations of Spontaneous Raman Scattering in Silicon Slow-light
  Photonic Crystal Waveguides

abstract:
  We report the observations of spontaneous Raman scattering in silicon
photonic crystal waveguides. Continuous-wave measurements of Stokes emission
for both wavelength and power dependence is reported in single line-defect
waveguides in hexagonal lattice photonic crystal silicon membranes. By
utilizing the Bragg gap edge dispersion of the TM-like mode for pump
enhancement and the TE-like fundamental mode-onset for Stokes enhancement, the
Stokes emission was observed to increase by up to five times in the region of
slow group velocity. The results show explicit nonlinear enhancement in a
silicon photonic crystal slow-light waveguide device.


title: Spinning fluid cosmology

abstract:
  The dynamics of a spinning fluid in a flat cosmological model is
investigated. The space-time is itself generated by the spinning fluid which is
characterized by an energy-momentum tensor consisting a sum of the usual
perfect-fluid energy-momentum tensor and some Belinfante-Rosenfeld tensors. It
is shown that the equations of motion admit a solution for which the fluid
four-velocity and four-momentum are not co-linear in general. The momentum and
spin densities of the fluid are expressed in terms of the scale factor.


title:
Design, theory, and measurement of a polarization insensitive absorber
  for terahertz imaging

abstract:
  We present the theory, design, and realization of a polarization-insensitive
metamaterial absorber for terahertz frequencies. We derive
geometrical-independent conditions for effective medium absorbers in general,
and for resonant metamaterials specically. Our fabricated design reaches and
absorptivity of 78% at 1.145 Thz


title: GZK Horizons and the Anisotropy of Highest-energy Cosmic Ray Sources

abstract:
  Motivated by recent Pierre Auger result on the correlation of the
highest-energy cosmic rays with the nearby active galactic nuclei, we explore
possible ultrahigh energy cosmic ray (UHECR) source distributions and their
effects on GZK horizons. Effects on GZK horizons by local over-density of UHECR
sources are examined carefully with constraints on the degree of local
over-density inferred from the measured UHECR spectrum. We include the energy
calibration effect on the Pierre Auger data in our studies. We propose possible
local over-densities of UHECR sources which are testable in the future cosmic
ray astronomy.


title:
The converse to Curtiss' theorem for one-sided moment generating
  functions

abstract:
  A set of necessary and sufficient conditions for a sequence of moment
generating functions to converge to a moment generating function on an interval
(a,b) not necessarily containing 0, is given. The result is derived using
recent results by Mukherjea, et al. (2006) and Chareka (2007).


title:
Theoretical investigation of the dynamic electronic response of a
  quantum dot driven by time-dependent voltage

abstract:
  We present a comprehensive theoretical investigation on the dynamic
electronic response of a noninteracting quantum dot system to various forms of
time-dependent voltage applied to the single contact lead. Numerical
simulations are carried out by implementing a recently developed hierarchical
equations of motion formalism [J. Chem. Phys. 128, 234703 (2008)], which is
formally exact for a fermionic system interacting with grand canonical
fermionic reservoirs, in the presence of arbitrary time-dependent applied
chemical potentials. The dynamical characteristics of the transient transport
current evaluated in both linear and nonlinear response regimes are analyzed,
and the equivalent classic circuit corresponding to the coupled dot-lead system
is also discussed.


title: Advanced action in classical electrodynamics

abstract:
  The time evolution of a charged point particle is governed by a second-order
integro-differential equation that exhibits advanced effects, in which the
particle responds to an external force before the force is applied. In this
paper we give a simple physical argument that clarifies the origin and physical
meaning of these advanced effects, and we compare ordinary electrodynamics with
a toy model of electrodynamics in which advanced effects do not occur.


title: Schroedinger flow into almost Hermitian manifolds

abstract:
  We present a short-time existence theorem of solutions to the initial value
problem for Schroedinger maps of a closed Riemannian manifold to a compact
almost Hermitian manifold. The classical energy method cannot work for this
problem since the almost complex structure of the target manifold is not
supposed to be parallel with respect to the Levi-Civita connection. In other
words, a loss of one derivative arises from the covariant derivative of the
almost complex structure. To overcome this difficulty, we introduce a bounded
pseudodifferential operator acting on sections of the pullback bundle, and
essentially eliminate the loss of one derivative from the partial differential
equation of the Schroedinger map.


title: Universal Denoising of Discrete-time Continuous-Amplitude Signals

abstract:
  We consider the problem of reconstructing a discrete-time signal (sequence)
with continuous-valued components corrupted by a known memoryless channel. When
performance is measured using a per-symbol loss function satisfying mild
regularity conditions, we develop a sequence of denoisers that, although
independent of the distribution of the underlying `clean' sequence, is
universally optimal in the limit of large sequence length. This sequence of
denoisers is universal in the sense of performing as well as any sliding window
denoising scheme which may be optimized for the underlying clean signal. Our
results are initially developed in a ``semi-stochastic'' setting, where the
noiseless signal is an unknown individual sequence, and the only source of
randomness is due to the channel noise. It is subsequently shown that in the
fully stochastic setting, where the noiseless sequence is a stationary
stochastic process, our schemes universally attain optimum performance. The
proposed schemes draw from nonparametric density estimation techniques and are
practically implementable. We demonstrate efficacy of the proposed schemes in
denoising gray-scale images in the conventional additive white Gaussian noise
setting, with additional promising results for less conventional noise
distributions.


title: What Did Fisher Mean by An Estimate?

abstract:
  Fisher's Method of Maximum Likelihood is shown to be a procedure for the
construction of likelihood intervals or regions, instead of a procedure of
point estimation. Based on Fisher's articles and books it is justified that by
estimation Fisher meant the construction of likelihood intervals or regions
from appropriate likelihood function and that an estimate is a statistic, that
is, a function from a sample space to a parameter space such that the
likelihood function obtained from the sampling distribution of the statistic at
the observed value of the statistic is used to construct likelihood intervals
or regions. Thus Problem of Estimation is how to choose the 'best' estimate.
Fisher's solution for the problem of estimation is Maximum Likelihood Estimate
(MLE). Fisher's Theory of Statistical Estimation is a chain of ideas used to
justify MLE as the solution of the problem of estimation. The construction of
confidence intervals by the delta method from the asymptotic normal
distribution of MLE is based on Fisher's ideas, but is against his 'logic of
statistical inference'. Instead the construction of confidence intervals from
the profile likelihood function of a given interest function of the parameter
vector is considered as a solution more in line with Fisher's 'ideology'. A new
method of calculation of profile likelihood-based confidence intervals for
general smooth interest functions in general statistical models is considered.


title: Torsion-induced spin precession

abstract:
  We investigate the motion of a spinning test particle in a spatially-flat
FRW-type space-time in the framework of the Einstein-Cartan theory. The
space-time has a torsion arising from a spinning fluid filling the space-time.
We show that for spinning particles with nonzero transverse spin components,
the torsion induces a precession of particle spin around the direction of the
fluid spin. We also show that a charged spinning particle moving in a
torsion-less spatially-flat FRW space-time in the presence of a uniform
magnetic field undergoes a precession of a different character.


title: Tunable Up-Conversion Photon Detector

abstract:
  We introduce a simple approach for a tunable up-conversion detector. This
scheme is relevant for both single photon detection or anywhere where low light
levels at telecom wavelengths need to be detected with a high degree of
temporal resolution or where high count rates are desired. A system combining a
periodically poled Lithium niobate waveguide for the nonlinear wavelength
conversion and a low jitter Silicon avalanche photodiode are used in
conjunction with a tunable pump source. We report more than a ten-fold increase
in the detectable bandwidth using this tuning scheme.


title:
Low regularity global well-posedness for the two-dimensional Zakharov
  system

abstract:
  The two-dimensional Zakharov system is shown to have a unique global solution
for data without finite energy if the L^2 - norm of the Schr\"odinger part is
small enough. The proof uses a refined I-method originally initiated by
Colliander, Keel, Staffilani, Takaoka and Tao. A polynomial growth bound for
the solution is also given.


title: The Heisenberg-Lorentz quantum group

abstract:
  In this article we present a new C*-algebraic deformation of the Lorentz
group. It is obtained by means of the Rieffel deformation applied to SL(2,C).
We give a detailed description of the resulting quantum group in terms of
generators - the quantum counterparts of the matrix coefficients of the
fundamental representation of SL(2,C). In order to construct the most involved
of four generators, we first define it on the quantum Borel subgroup, then on
the quantum complement of the Borel subgroup and finally we perform the gluing
procedure. In order to classify representations of the C*-algebra of the
Heisenberg-Lorentz quantum group and to analyze the action of the
comultiplication on the generators we employ the duality in the theory of
locally compact quantum groups.