title:
Cosmic Reionization and the 21-cm signal: Comparison between an
  analytical model and a simulation

abstract:
  We measure several properties of the reionization process and the
corresponding low-frequency 21-cm signal associated with the neutral hydrogen
distribution, using a large volume, high resolution simulation of cosmic
reionization. The brightness temperature of the 21-cm signal is derived by
post-processing this numerical simulation with a semi-analytical prescription.
Our study extends to high redshifts (z ~ 25) where, in addition to collisional
coupling, our post-processed simulations take into account the inhomogeneities
in the heating of the neutral gas by X-rays and the effect of an inhomogeneous
Lya radiation field. Unlike the well-studied case where spin temperature is
assumed to be significantly greater than the temperature of the cosmic
microwave background due to uniform heating of the gas by X-rays, spatial
fluctuations in both the Lya radiation field and X-ray intensity impact
predictions related to the brightness temperature at z > 10, during the early
stages of reionization and gas heating. The statistics of the 21-cm signal from
our simulation are then compared to existing analytical models in the
literature and we find that these analytical models provide a reasonably
accurate description of the 21-cm power spectrum at z < 10. Such an agreement
is useful since analytical models are better suited to quickly explore the full
astrophysical and cosmological parameter space relevant for future 21-cm
surveys. We find, nevertheless, non-negligible differences that can be
attributed to differences in the inhomogeneous X-ray heating and Lya coupling
at z > 10 and, with upcoming interferometric data, these differences in return
can provide a way to better understand the astrophysical processes during
reionization.


title: Cosmological HII Bubble Growth During Reionization

abstract:
  We present general properties of ionized hydrogen (HII) bubbles and their
growth based on a state-of-the-art large-scale (100 Mpc/h) cosmological
radiative transfer simulation. The simulation resolves all halos with atomic
cooling at the relevant redshifts and simultaneously performs radiative
transfer and dynamical evolution of structure formation. Our major conclusions
include: (1) for significant HII bubbles, the number distribution is peaked at
a volume of $\sim 0.6 {\rm Mpc^{3}/h^{3}}$ at all redshifts. But, at $z\le 10$,
one large, connected network of bubbles dominates the entire HII volume. (2)
HII bubbles are highly non-spherical. (3) The HII regions are highly biased
with respect to the underlying matter distribution with the bias decreasing
with time. (4) The non-gaussianity of the HII region is small when the universe
becomes 50% ionized. The non-gaussianity reaches its maximal near the end of
the reionization epoch $z\sim 6$. But at all redshifts of interest there is a
significant non-gaussianity in the HII field. (5) Population III galaxies may
play a significant role in the reionization process. Small bubbles are
initially largely produced by Pop III stars. At $z\ge 10$ even the largest HII
bubbles have a balanced ionizing photon contribution from Pop II and Pop III
stars, while at $z\le 8$ Pop II stars start to dominate the overall ionizing
photon production for large bubbles, although Pop III stars continue to make a
non-negligible contribution. (6) The relationship between halo number density
and bubble size is complicated but a strong correlation is found between halo
number density and bubble size for large bubbles.


title: Emergent Gravity from Noncommutative Gauge Theory

abstract:
  We show that the matrix-model action for noncommutative U(n) gauge theory
actually describes SU(n) gauge theory coupled to gravity. This is elaborated in
the 4-dimensional case. The SU(n) gauge fields as well as additional scalar
fields couple to an effective metric G_{ab}, which is determined by a dynamical
Poisson structure. The emergent gravity is intimately related to
noncommutativity, encoding those degrees of freedom which are usually
interpreted as U(1) gauge fields. This leads to a class of metrics which
contains the physical degrees of freedom of gravitational waves, and allows to
recover e.g. the Newtonian limit with arbitrary mass distribution. It also
suggests a consistent picture of UV/IR mixing in terms of an induced gravity
action. This should provide a suitable framework for quantizing gravity.


title:
Non-universal gaugino masses: a signal-based analysis for the Large
  Hadron Collider

abstract:
  We discuss the signals at the Large Hadron Collider (LHC) for scenarios with
non-universal gaugino masses in supersymmetric (SUSY) theories. We perform a
multichannel analysis, and consider the ratios of event rates in different
channels such as $jets + {E}_T/ $, $same$ - and $opposite$-$sign dileptons$
$+jets+ {E}_T/ $, as well as $single-lepton$ and $trilepton$ final states
together with $jets + {E}_T/ $ . Low-energy SUSY spectra corresponding to
high-scale gaugino non-universality arising from different breaking schemes of
SU(5) as well as SO(10) Grand Unified (GUT) SUSY models are considered, with
both degenerate low-energy sfermion masses and those arising from a
supergravity scenario. We present the numerical predictions over a wide range
of the parameter space using the event generator {\tt Pythia}, specifying the
event selection criteria and pointing out regions where signals are likely to
be beset with backgrounds. Certain broad features emerge from the study, which
may be useful in identifying the signatures of different GUT breaking schemes
and distinguishing them from a situation with a universal gaugino mass at high
scale. The absolute values of the predicted event rates for different scenarios
are presented together with the various event ratios, so that these can also be
used whenever necessary.


title: A macroscopic test of the Aharonov-Bohm effect

abstract:
  The Aharonov-Bohm (AB) effect is a purely quantum mechanical effect. The
original (classified as Type-I) AB-phase shift exists in experimental
conditions where the electromagnetic fields and forces are zero. It is the
absence of forces that makes the AB-effect entirely quantum mechanical.
Although the AB-phase shift has been demonstrated unambiguously, the absence of
forces in Type-I AB-effects has never been shown. Here, we report the
observation of the absence of time delays associated with forces of the
magnitude needed to explain the AB-phase shift for a macroscopic system.


title: Dynamics of trion formation in GaAs quantum wells

abstract:
  We propose a double channel mechanism for the formation of charged excitons
(trions); they are formed through bi- and tri-molecular processes. This
directly implies that both negatively and positively charged excitons coexist
in a quantum well, even in the absence of excess carriers. The model is applied
to a time-resolved photoluminescence experiment performed on a very high
quality InGaAs quantum well sample, in which the photoluminescence
contributions at the energy of the trion, exciton and at the band edge can be
clearly separated and traced over a broad range of times and densities. The
unresolved discrepancy between the theoretical and experimental radiative decay
time of the exciton in a doped semiconductor is explained.


title:
Schwinger Mechanism for Gluon Pair Production in the Presence of
  Arbitrary Time Dependent Chromo-Electric Field

abstract:
  We study Schwinger mechanism for gluon pair production in the presence of
arbitrary time-dependent chromo-electric background field $E^a(t)$ with
arbitrary color index $a$=1,2,...8 in SU(3) by directly evaluating the path
integral. We obtain an exact expression for the probability of non-perturbative
gluon pair production per unit time per unit volume and per unit transverse
momentum $\frac{dW}{d^4x d^2p_T}$ from arbitrary $E^a(t)$. We show that the
tadpole (or single gluon) effective action does not contribute to the
non-perturbative gluon pair production rate $\frac{dW}{d^4x d^2p_T}$. We find
that the exact result for non-perturbative gluon pair production is independent
of all the time derivatives $\frac{d^nE^a(t)}{dt^n}$ where $n=1,2,....\infty$
and has the same functional dependence on two casimir invariants
$[E^a(t)E^a(t)]$ and $[d_{abc}E^a(t)E^b(t)E^c(t)]^2$ as the constant
chromo-electric field $E^a$ result with the replacement: $E^a \to E^a(t)$. This
result may be relevant to study the production of a non-perturbative
quark-gluon plasma at RHIC and LHC.


title: The Topology of Cosmological Reionization

abstract:
  Using the largest cosmological reionization simulation to-date (~24 billion
particles), we use the genus curve to quantify the topology of neutral hydrogen
distribution on scales > 1 Mpc as it evolves during cosmological reionization.
We find that the reionization process proceeds primarily in an inside-out
fashion, where higher density regions become ionized earlier than lower density
regions. There are four distinct topological phases: (1) Pre-reionization at z
~ 15, when the genus curve is consistent with a Gaussian density distribution.
(2) Pre-overlap at 10 < z < 15, during which the number of HII bubbles
increases gradually with time, until percolation of HII bubbles starts to take
effect, characterized by a very flat genus curve at high volume fractions. (3)
Overlap at 8 < z < 10, when large HII bubbles rapidly merge, manifested by a
precipitous drop in the amplitude of the genus curve. (4) Post-overlap at 6 < z
< 8, when HII bubbles have mostly overlapped and the genus curve is consistent
with a diminishing number of isolated neutral islands. After the end of
reionization (z < 6), the genus of neutral hydrogen is consistent with Gaussian
random phase, in agreement with observations.


title: A structure from motion inequality

abstract:
  We state an elementary inequality for the structure from motion problem for m
cameras and n points. This structure from motion inequality relates space
dimension, camera parameter dimension, the number of cameras and number points
and global symmetry properties and provides a rigorous criterion for which
reconstruction is not possible with probability 1. Mathematically the
inequality is based on Frobenius theorem which is a geometric incarnation of
the fundamental theorem of linear algebra. The paper also provides a general
mathematical formalism for the structure from motion problem. It includes the
situation the points can move while the camera takes the pictures.


title: Relativistic hydrodynamics for heavy-ion collisions

abstract:
  Relativistic hydrodynamics is essential to our current understanding of
nucleus-nucleus collisions at ultrarelativistic energies (current experiments
at the Relativistic Heavy Ion Collider, forthcoming experiments at the CERN
Large Hadron Collider). This is an introduction to relativistic hydrodynamics
for graduate students. It includes a detailed derivation of the equations, and
a description of the hydrodynamical evolution of a heavy-ion collisions. Some
knowledge of thermodynamics and special relativity is assumed.


title: Graded infinite order jet manifolds

abstract:
  The relevant material on differential calculus on graded infinite order jet
manifolds and its cohomology is summarized. This mathematics provides the
adequate formulation of Lagrangian theories of even and odd variables on smooth
manifolds in terms of the Grassmann-graded variational bicomplex.


title: The Two Dimensional Kondo Model with Rashba Spin-Orbit Coupling

abstract:
  We investigate the effect that Rashba spin-orbit coupling has on the low
energy behaviour of a two dimensional magnetic impurity system. It is shown
that the Kondo effect, the screening of the magnetic impurity at temperatures T
< T_K, is robust against such spin-orbit coupling, despite the fact that the
spin of the conduction electrons is no longer a conserved quantity. A proposal
is made for how the spin-orbit coupling may change the value of the Kondo
temperature T_K in such systems and the prospects of measuring this change are
discussed. We conclude that many of the assumptions made in our analysis
invalidate our results as applied to recent experiments in semi-conductor
quantum dots but may apply to measurements made with magnetic atoms placed on
metallic surfaces.


title: Relativistic hydrodynamics in the presence of puncture black holes

abstract:
  Many of the recent numerical simulations of binary black holes in vacuum
adopt the moving puncture approach. This successful approach avoids the need to
impose numerical excision of the black hole interior and is easy to implement.
Here we wish to explore how well the same approach can be applied to moving
black hole punctures in the presence of relativistic hydrodynamic matter.
First, we evolve single black hole punctures in vacuum to calibrate our BSSN
(Baumgarte-Shapiro-Shibata-Nakamura) implementation and to confirm that the
numerical solution for the exterior spacetime is invariant to any ``junk''
(i.e., constraint-violating) initial data employed in the black hole interior.
Then we focus on relativistic Bondi accretion onto a moving puncture
Schwarzschild black hole as a numerical testbed for our high-resolution
shock-capturing relativistic hydrodynamics scheme. We find that the
hydrodynamical equations can be evolved successfully in the interior without
imposing numerical excision. These results help motivate the adoption of the
moving puncture approach to treat the binary black hole-neutron star problem
using conformal thin-sandwich initial data.


title: Fluctuation relations and coarse-graining

abstract:
  We consider the application of fluctuation relations to the dynamics of
coarse-grained systems, as might arise in a hypothetical experiment in which a
system is monitored with a low-resolution measuring apparatus. We analyze a
stochastic, Markovian jump process with a specific structure that lends itself
naturally to coarse-graining. A perturbative analysis yields a reduced
stochastic jump process that approximates the coarse-grained dynamics of the
original system. This leads to a non-trivial fluctuation relation that is
approximately satisfied by the coarse-grained dynamics. We illustrate our
results by computing the large deviations of a particular stochastic jump
process. Our results highlight the possibility that observed deviations from
fluctuation relations might be due to the presence of unobserved degrees of
freedom.


title: On Ullman's theorem in computer vision

abstract:
  Both in the plane and in space, we invert the nonlinear Ullman transformation
for 3 points and 3 orthographic cameras. While Ullman's theorem assures a
unique reconstruction modulo a reflection for 3 cameras and 4 points, we find a
locally unique reconstruction for 3 cameras and 3 points. Explicit
reconstruction formulas allow to decide whether picture data of three cameras
seeing three points can be realized as a point-camera configuration.


title: An extension of Boyd's $p$-adic algorithm for the harmonic series

abstract:
  In this paper we will extend a $p$-adic algorithm of Boyd in order to study
the size of the set: \[J_p(y)=\left\{n :\sum_{j=1}^{n}\frac{y^j}{j}\equiv
0(\mod p)\right\}.\] Suppose that $p$ is one of the first 100 odd primes and
$y\in\{1,2,...,p-1\}$, then our calculations prove that $|J_p(y)|<\infty$ in
24240 out of 24578 possible cases. Among other results we show that
$|J_{13}(9)|=18763$. The paper concludes by discussing some possible
applications of our method to sums involving Fibonacci numbers.


title:
Spitzer Observations of Gamma-Ray Burst Host Galaxies: A Unique Window
  into High Redshift Chemical Evolution and Star-formation

abstract:
  We present deep Spitzer 3.6 micron observations of three z~5 GRB host
galaxies. Our observations reveal that z~5 GRB hosts are a factor of 3 less
luminous than the median rest-frame V-band luminosity of spectroscopically
confirmed z~5 galaxies in the GOODS fields and the UDF. The strong connection
between GRBs and massive star formation implies that not all star-forming
galaxies at these redshifts are currently being accounted for in deep surveys
and GRBs provide a unique way to measure the contribution to the star-formation
rate density from galaxies at the faint end of the galaxy luminosity function.
By correlating the co-moving star-formation rate density with co-moving GRB
rates at lower redshifts, we estimate a lower limit to the star-formation rate
density of 0.12+/-0.09 and 0.09+/-0.05 M_sun/yr/Mpc^3 at z~4.5 and z~6,
respectively. Finally, we provide evidence that the average metallicity of
star-forming galaxies evolves as (stellar mass density)^(0.69+/-0.17) between
$z\sim5$ and $z\sim0$, probably indicative of the loss of a significant
fraction of metals to the intergalactic medium, particularly in low-mass
galaxies.


title: Compactifications of Moduli Spaces and Cellular Decompositions

abstract:
  This paper studies compactifications of moduli spaces involving closed
Riemann surfaces. The first main result identifies the homeomorphism types of
these compactifications. The second main result introduces orbicell
decompositions on these spaces using semistable ribbon graphs extending the
earlier work of Looijenga.


title: Space and camera path reconstruction for omni-directional vision

abstract:
  In this paper, we address the inverse problem of reconstructing a scene as
well as the camera motion from the image sequence taken by an omni-directional
camera. Our structure from motion results give sharp conditions under which the
reconstruction is unique. For example, if there are three points in general
position and three omni-directional cameras in general position, a unique
reconstruction is possible up to a similarity. We then look at the
reconstruction problem with m cameras and n points, where n and m can be large
and the over-determined system is solved by least square methods. The
reconstruction is robust and generalizes to the case of a dynamic environment
where landmarks can move during the movie capture. Possible applications of the
result are computer assisted scene reconstruction, 3D scanning, autonomous
robot navigation, medical tomography and city reconstructions.


title:
HypExp 2, Expanding Hypergeometric Functions about Half-Integer
  Parameters

abstract:
  In this article, we describe a new algorithm for the expansion of
hypergeometric functions about half-integer parameters. The implementation of
this algorithm for certain classes of hypergeometric functions in the already
existing Mathematica package HypExp is described. Examples of applications in
Feynman diagrams with up to four loops are given.


title: Ionization Front Instabilities in Primordial H II Regions

abstract:
  Radiative cooling by metals in shocked gas mediates the formation of
ionization front instabilities in the galaxy today that are responsible for a
variety of phenomena in the interstellar medium, from the morphologies of
nebulae to triggered star formation in molecular clouds. An important question
in early reionization and chemical enrichment of the intergalactic medium is
whether such instabilities arose in the H II regions of the first stars and
primeval galaxies, which were devoid of metals. We present three-dimensional
numerical simulations that reveal both shadow and thin-shell instabilities
readily formed in primordial gas. We find that the hard UV spectra of
Population III stars broadened primordial ionization fronts, causing H2
formation capable of inciting violent thin- shell instabilities in D-type
fronts, even in the presence of intense Lyman-Werner flux. The high post- front
gas temperatures associated with He ionization sustained and exacerbated shadow
instabilities, unaided by molecular hydrogen cooling. Our models indicate that
metals eclipsed H2 cooling in I-front instabilities at modest concentrations,
from 0.001- 0.01 solar. We conclude that ionization front instabilities were
prominent in the H II regions of the first stars and galaxies, influencing the
escape of ionizing radiation and metals into the early universe.


title: Horizontal Branch Stars and the Ultraviolet Universe

abstract:
  Extremely hot horizontal branch (HB) stars and their progeny are widely
considered to be responsible for the "ultraviolet upturn" (or UVX) phenomenon
observed in elliptical galaxies and the bulges of spirals. Yet, the precise
evolutionary channels that lead to the production of these stars remain the
source of much debate. In this review, we discuss two key physical ingredients
that are required in order for reliable quantitative models of the UV output of
stellar populations to be computed, namely, the mass loss rates of red giant
branch stars and the helium enrichment "law" at high metallicities. In
particular, the recent evidence pointing towards a strong enhancement in the
abundances of the alpha-elements in the Galactic bulge (compared to the disk),
and also the available indications of a similar overabundance in (massive)
elliptical galaxies, strongly suggest that the helium abundance Y may be higher
in ellipticals and bulges than it is in spiral disks by an amount that may
reach up to 0.15 at [Fe/H] ~ +0.5. If so, this would strongly favor the
production of hot HB stars at high metallicity in galactic spheroids. We also
discuss the existence of mass loss recipes beyond the commonly adopted Reimers
"law" that are not only more consistent with the available empirical data, but
also much more favorable to the production of extended HB stars at high
metallicity. Finally, we discuss new empirical evidence that suggests that
different evolutionary channels may be responsible for the production of EHB
stars in the field and in clusters.


title: Neutrino Experiments

abstract:
  This article is a summary of four introductory lectures on ``Neutrino
Experiments,'' given at the 2006 TASI summer school. The purposes were to
sketch out the present questions in neutrino physics and to discuss the
experimental challenges in addressing them. This article concentrates on
specific, illustrative examples rather than providing a complete overview of
the field of neutrino physics. These lectures were meant to lay the ground-work
for the talks which followed on specific, selected topics in neutrino physics.


title:
Electromagnetic pulse reflection at self-generated plasma mirrors: laser
  pulse shaping and high order harmonic generation

abstract:
  A thin layer of overdense plasma is created when an electromagnetic pulse
interacts with a rapidly ionizing thin foil. This layer will reflect the
incoming pulse, forming a so-called plasma mirror. A simple realistic model
based on paired kinetic and wave equations is used to describe analytically the
process of mirror formation and the reflection and transmission of the incident
pulse. The model incorporates the exact description of the ionization process
in the foil and the polarization and conduction currents that follow. The
analytical description of the reflected and transmitted pulses as well as their
dependence on foil parameters, and initial pulse amplitude and form are
presented. Possible application and effectiveness of this process to improve
laser pulse contrast are discussed. In the case of the linearly polarized
incident pulse, there harmonic generation occurs, that is absent in the case of
the circular polarization. The spectra of the reflected pulses for different
initial forms and amplitudes are studied.


title: Aharonov-Bohm-Like Oscillations in Quantum Hall Corrals

abstract:
  Experimental study of quantum Hall corrals reveals Aharonov-Bohm-Like (ABL)
oscillations. Unlike the Aharonov-Bohm effect which has a period of one flux
quantum, $\Phi_{0}$, the ABL oscillations possess a flux period of
$\Phi_{0}/f$, where $f$ is the integer number of fully filled Landau levels in
the constrictions. Detection of the ABL oscillations is limited to the low
magnetic field side of the $\nu_{c}$ = 1, 2, 4, 6... integer quantum Hall
plateaus. These oscillations can be understood within the Coulomb blockade
model of quantum Hall interferometers as forward tunneling and backscattering,
respectively, through the center island of the corral from the bulk and the
edge states. The evidence for quantum interference is weak and circumstantial.


title: The Local Velocity Anomaly

abstract:
  There is a velocity discontinuity at about 7 Mpc between the galaxies of the
Local Sheet that are moving together with low internal velocity dispersion and
the adjacent structures. The Local Sheet bounds the Local Void. The Local Sheet
is determined to have a peculiar velocity of 260 km/s away from the center of
the void. In order for this large velocity to be generated by an absence of
gravity, the Local Void must be at least 45 Mpc in diameter and be very empty.


title: Quantum Energy Inequalities for the Non-Minimally Coupled Scalar Field

abstract:
  In this paper we discuss local averages of the energy density for the
non-minimally coupled scalar quantum field, extending a previous investigation
of the classical field. By an explicit example, we show that such averages are
unbounded from below on the class of Hadamard states. This contrasts with the
minimally coupled field, which obeys a state-independent lower bound known as a
Quantum Energy Inequality (QEI). Nonetheless, we derive a generalised QEI for
the non-minimally coupled scalar field, in which the lower bound is permitted
to be state-dependent. This result applies to general globally hyperbolic
curved spacetimes for coupling constants in the range $0<\xi\leq 1/4$. We
analyse the state-dependence of our QEI in four-dimensional Minkowski space and
show that it is a nontrivial restriction on the averaged energy density in the
sense that the lower bound is of lower order, in energetic terms, than the
averaged energy density itself.


title: Nearly Ordinary Galois Deformations over Arbitrary Number Fields

abstract:
  Let K be an arbitrary number field, and let rho: Gal(Kbar/K) -> GL_2(E) be a
nearly ordinary irreducible geometric Galois representation. In this paper, we
study the nearly ordinary deformations of rho. When K is totally real and rho
is modular, results of Hida imply that the nearly ordinary deformation space
associated to rho contains a Zariski dense set of points corresponding to
"automorphic" Galois representations. We conjecture that if K is_not_ totally
real, then this is never the case, except in three exceptional cases,
corresponding to (1) "base change", (2) "CM" forms, and (3) "Even"
representations. The latter case conjecturally can only occur if the image of
rho is finite. Our results come in two flavours. First, we prove a general
result for Artin representations, conditional on a strengthening of Leopoldt's
conjecture. Second, when K is an imaginary quadratic field, we prove an
unconditional result that implies the existence of "many" positive dimensional
components (of certain deformation spaces) that do not contain infinitely many
classical points. Also included are some speculative remarks about "p-adic
functorality", as well as some remarks on how our methods should apply to
n-dimensional representations of Gal(Qbar/Q) when n > 2.


title: Kinetic limitations of cooperativity based drug delivery systems

abstract:
  We study theoretically a novel drug delivery system that utilizes the
overexpression of certain proteins in cancerous cells for cell specific
chemotherapy. The system consists of dendrimers conjugated with "keys" (ex:
folic acid) which "key-lock" bind to particular cell membrane proteins (ex:
folate receptor). The increased concentration of "locks" on the surface leads
to a longer residence time for the dendrimer and greater incorporation into the
cell. Cooperative binding of the nanocomplexes leads to an enhancement of cell
specificity. However, both our theory and detailed analysis of in-vitro
experiments indicate that the degree of cooperativity is kinetically limited.
We demonstrate that cooperativity and hence the specificity to particular cell
type can be increased by making the strength of individual bonds weaker, and
suggest a particular implementation of this idea. The implications of the work
for optimizing the design of drug delivery vehicles are discussed.


title: A note on Talagrand's positivity principle

abstract:
  Talagrand's positivity principle states that one can slightly perturb a
Hamiltonian in the Sherrington-Kirkpatrick model in such a way that the overlap
of two configurations under the perturbed Gibbs' measure will become typically
nonnegative. In this note we observe that abstracting from the setting of the
SK model only improves the result and does not require any modifications in
Talagrand's argument. In this version, for example, positivity principle
immediately applies to the setting of Aizenman-Sims-Starr interpolation. Also,
abstracting from the SK model improves the conditions in the Ghirlanda-Guerra
identities and as a consequence results in a perturbation of smaller order
necessary to ensure positivity of the overlap.


title:
Ab Initio Method for Obtaining Exactly Solvable Quantum Mechanical
  Potentials

abstract:
  The shape invariance condition is the integrability condition in
supersymmetric quantum mechanics (SUSYQM). It is a difference-differential
equation connecting the superpotential W and its derivative at two different
values of parameters. We show that this difference equation is equivalent to a
non-linear partial differential equation whose solutions are translational
shape invariant superpotentials. In lieu of trial and error, this method
provides the first ab initio technique for generating shape invariant
superpotentials.


title: Shape invariance and the exactness of quantum Hamilton-Jacobi formalism

abstract:
  Quantum Hamilton-Jacobi Theory and supersymmetric quantum mechanics (SUSYQM)
are two parallel methods to determine the spectra of a quantum mechanical
systems without solving the Schr\"odinger equation. It was recently shown that
the shape invariance, which is an integrability condition in SUSYQM formalism,
can be utilized to develop an iterative algorithm to determine the quantum
momentum functions. In this paper, we show that shape invariance also suffices
to determine the eigenvalues in Quantum Hamilton-Jacobi Theory.


title: On the subset sum problem over finite fields

abstract:
  The subset sum problem over finite fields is a well-known {\bf NP}-complete
problem. It arises naturally from decoding generalized Reed-Solomon codes. In
this paper, we study the number of solutions of the subset sum problem from a
mathematical point of view. In several interesting cases, we obtain explicit or
asymptotic formulas for the solution number. As a consequence, we obtain some
results on the decoding problem of Reed-Solomon codes.


title: The relative growth rate for partial quotients

abstract:
  We look at the rate of growth of the partial quotients of the infinite
continued fraction expansion of an irrational number relative to the rate of
approximation of the number by its convergents. In non-generic cases the
Hausdorff dimension of some exceptional sets is computed.


title: Chkareuli-Froggatt-Nielsen Theorem and Photon Mass

abstract:
  We analyze there is a relation between fossil charge and the mass of photon
based on Chkareuli-Froggatt-Nielsen Theorem and Proca Lagrangian. As generally
known, massive photon will lead to Lorentz non-invariance field theory.


title:
Carbon nanotube, graphene, nanowire, and molecule-based electron and
  spin transport phenomena using the non-equilibrium Green function method at
  the level of first principles theory

abstract:
  Based on density functional theory (DFT), we have developed algorithms and a
program code to investigate the electron transport characteristics for a
variety of nanometer scaled devices in the presence of an external bias
voltage. We employed basis sets comprised of linear combinations of numerical
type atomic orbitals and k-point sampling for the realistic modeling of the
bulk electrode. The scheme coupled with the matrix version of the
non-equilibrium Green function method enables determination of the transmission
coefficients at a given energy and voltage in a self-consistent manner, as well
as the corresponding current-voltage (I-V) characteristics. This scheme has
advantages because it is applicable to large systems, easily transportable to
different types of quantum chemistry packages, and extendable to describe
time-dependent phenomena or inelastic scatterings. It has been applied to
diverse types of practical electronic devices such as carbon nanotubes,
graphene nano-ribbons, metallic nanowires, and molecular electronic devices.
The quantum conductance phenomena for systems involving quantum point contacts
and I-V curves are described for the dithiol-benzene molecule in contact with
two Au electrodes using the k-point sampling method.


title: Synchronization in coupled phase oscillators

abstract:
  We make a short review about the synchronization in coupled phase oscillator
models. Next, we study the common-noise-induced synchronization among active
rotators. At an intermediate noise strength, the noise-induced synchronization
takes place most effectively, which is analogous to the stochastic resonance.
Finally, we study the synchronization of coupled phase oscillators with
nonvariational interaction on scale-free networks. We find a sharp transition
and a weak hysteresis in the nonvariational systems. The sharp transition is
found also in the mean-field approximation.


title:
The $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$, 2(\pi^+\pi^-)\eta$, $K^+
  K^-\pi^+\pi^-\pi^0$ and $K^+ K^-\pi^+\pi^-\eta$ Cross Sections Measured with
  Initial-State Radiation

abstract:
  We study the processes $e^+ e^-\to 2(\pi^+\pi^-)\pi^0\gamma$,
$2(\pi^+\pi^-)\eta\gamma$, $K^+ K^-\pi^+\pi^-\pi^0\gamma$ and $K^+
K^-\pi^+\pi^-\eta\gamma$ with the hard photon radiated from the initial state.
About 20000, 4300, 5500 and 375 fully reconstructed events, respectively, are
selected from 232 fb$^{-1}$ of BaBar data. The invariant mass of the hadronic
final state defines the effective $e^+ e^-$ center-of-mass energy, so that the
obtained cross sections from the threshold to about 5 GeV can be compared with
corresponding direct \epem measurements, currently available only for the
$\eta\pi^+\pi^-$ and $\omega\pi^+\pi^-$ submodes of the $e^+ e^-\to
2(\pi^+\pi^-)\pi^0$ channel. Studying the structure of these events, we find
contributions from a number of intermediate states, and we extract their cross
sections where possible. In particular, we isolate the contribution from $e^+
e^-\to\omega(782)\pi^+\pi^-$ and study the $\omega(1420)$ and $\omega(1650)$
resonances. In the charmonium region, we observe the $J/\psi$ in all these
final states and several intermediate states, as well as the $\psi(2S)$ in some
modes, and we measure the corresponding branching fractions.


title: Eigenvalue bounds on the pseudocodeword weight of expander codes

abstract:
  Four different ways of obtaining low-density parity-check codes from expander
graphs are considered. For each case, lower bounds on the minimum stopping set
size and the minimum pseudocodeword weight of expander (LDPC) codes are
derived. These bounds are compared with the known eigenvalue-based lower bounds
on the minimum distance of expander codes. Furthermore, Tanner's
parity-oriented eigenvalue lower bound on the minimum distance is generalized
to yield a new lower bound on the minimum pseudocodeword weight. These bounds
are useful in predicting the performance of LDPC codes under graph-based
iterative decoding and linear programming decoding.


title: Some Implications of Perturbative Approach to AdS/CFT Correspondence

abstract:
  We show some implications of the approach to AdS/CFT correspondence based on
Type IIB string in the flat space-time with D3-branes proposed in our previous
paper. We discuss a correspondence for high energy scattering amplitudes of N=4
super-Yang-Mills proposed recently. We also discuss AdS/CFT correspondence at
finite temperature. Our approach provides clear understanding of these issues.


title: z-Scaling at RHIC and Tevatron

abstract:
  The experimental data on inclusive cross sections of jet, direct photon and
hadron production in pp/antipp and AA collisions at RHIC and Tevatron are
analyzed in the framework of z-scaling. Results of analysis are compared with
data obtained at ISR, SppS and Tevatron. The properties of z-presentation of
experimental data are verified. Physical interpretation of the scaling function
and variable z is discussed. The locality, self-similarity and fractality are
argued to reflect the general structure of the colliding objects, interaction
of their constituents and particle formation at small scales. The obtained
results suggest that the z-scaling may be used as a tool for searching for new
physics phenomena beyond Standard Model in hadron and nucleus collisions at
high transverse momentum and high multiplicity at U70, RHIC, Tevatron and LHC.


title: Jets in pp collisions at RHIC and Monte Carlo study of z-scaling

abstract:
  Impact of the cone algorithm parameters Ecut, Eseed, R on the efficiency and
characteristics of the reconstructed jets in p-p collisions at the energy sqrt
s = 200 GeV is studied. The PYTHIA Monte Carlo generator is used for event
generation. The dependence of dijet production fraction on the parton
transverse momentum at different algorithm parameters is analyzed. The
dependence of reconstruction efficiency of parton energy in dijet events and
two leading jets in N-jet events on Ecut, Eseed, R is studied. Monte Carlo
results are compared with predictions made in the framework of z-scaling and
experimental data obtained at RHIC. The independence of the slope parameter
beta of the scaling function, on the algorithm parameters over the energy range
ETJet=25-60 GeV is found. The strong dependence of the invariant cross section
and the slope parameter on the algorithm parameters with decreasing of ETJet
for ETJet<25 GeV is observed.


title: Probing electroweak physics using B -> XM decays in the endpoint region

abstract:
  Using soft-collinear effective theory we describe at leading order in 1/m_b
all the semi-inclusive hadronic B -> XM decays near the endpoint, where an
energetic light meson M recoils against an inclusive jet X. We also include the
decays involving eta, eta' mesons that receive additional contributions from
gluonic operators. The predicted branching ratios and CP asymmetries depend on
fewer hadronic parameters than the corresponding two-body B decays. This makes
semi-inclusive hadronic B -> XM decays a powerful probe of the potential
nonperturbative nature of charming penguins as well as a useful probe of new
physics effects in electroweak flavor changing transitions. A comparison with B
-> KX data from BaBar points to an enhanced charming penguin, albeit with large
experimental errors.


title:
Non-Riemannian geometrical asymmetrical damping stresses on the Lagrange
  instability of shear flows

abstract:
  It is shown that the physical interpretation of Elie Cartan three-dimensional
space torsion as couple asymmetric stress, has the effect of damping,
previously Riemannian unstable Couette planar shear flow, leading to stability
of the flow in the Lagrangean sense. Actually, since the flow speed is
inversely proportional to torsion, it has the effect of causing a damping in
the planar flow atenuating the instability effect. In this sense we may say
that Cartan torsion induces shear viscous asymmetric stresses in the fluid,
which are able to damp the instability of the flow. The stability of the flow
is computed from the sectional curvature in non-Riemannian three-dimensional
manifold. Marginal stability is asssumed by making the sectional non-Riemannian
curvature zero, which allows us to determine the speeds of flows able to induce
this stability. The ideas discussed here show that torsion plays the
geometrical role of magnetic field in hydromagnetic instability of Couette
flows recently investigated by Bonnano and Urpin (PRE, (2007,in press) can be
extended and applied to plastic flows with microstructure defects. Recently
Riemannian asymmetric stresses in magnetohydrodynamics (MHD) have been
considered by Billig (2004).


title: Categorical Foundations for Physics - I: Program at a Glance

abstract:
  Measures in the context of Category Theory lead to various relations, even
differential relations, of categories that are independent of the mathematical
structure forming objects of a category. Such relations, which are independent
of mathematical structure that we may represent a physical body or a system of
reference with, are, precisely, demanded to be the Laws of Physics by the
General Principle of Relativity. This framework leads to a theory for the
physical entirety.


title: Extraordinary vacuum black string solutions

abstract:
  In addition to the boosted static solution there are two other classes of
stationary string-like solutions of the vacuum Einstein equation in
(4+1)-dimensions. Each class is characterized by three parameters of mass,
tension, and momentum flow along the fifth coordinate. We analyze the metric
properties of one of the two classes, which was previously assumed to be naked
singular, and show that the solution spectrum contains black string and
wormhole in addition to the known naked singularity as the momentum flow to
mass ratio increases. Interestingly, there does not exist new zero momentum
solution in these cases.


title:
Nanopillar Arrays on Semiconductor Membranes as Electron Emission
  Amplifiers

abstract:
  A new transmission-type electron multiplier was fabricated from
silicon-on-insulator (SOI) material by integrating an array of one dimensional
(1D) silicon nanopillars onto a two dimensional (2D) silicon membrane. Primary
electrons are injected into the nanopillar-membrane system from the flat
surface of the membrane, while electron emission from the other side is probed
by an anode. The secondary electron yield (SEY) from nanopillars is found to be
about 1.8 times that of plane silicon membrane. This gain in electron number is
slightly enhanced by the electric field applied from the anode. Further
optimization of the dimensions of nanopillars and membrane and application of
field emission promise an even higher gain for detector applications and allow
for probing of electronic/mechanical excitations in nanopillar-membrane system
excited by incident particles or radiation.


title: Noncommutative Induced Gauge Theories on Moyal Spaces

abstract:
  Noncommutative field theories on Moyal spaces can be conveniently handled
within a framework of noncommutative geometry. Several renormalisable matter
field theories that are now identified are briefly reviewed. The construction
of renormalisable gauge theories on these noncommutative Moyal spaces, which
remains so far a challenging problem, is then closely examined. The computation
in 4-D of the one-loop effective gauge theory generated from the integration
over a scalar field appearing in a renormalisable theory minimally coupled to
an external gauge potential is presented. The gauge invariant effective action
is found to involve, beyond the expected noncommutative version of the pure
Yang-Mills action, additional terms that may be interpreted as the gauge theory
counterpart of the harmonic term, which for the noncommutative $\phi^4$-theory
on Moyal space ensures renormalisability. A class of possible candidates for
renormalisable gauge theory actions defined on Moyal space is presented and
discussed.


title: Spectral Hardening of Large Solar Flares

abstract:
  RHESSI observations are used to quantitatively study the hard X-ray evolution
in 5 large solar flares selected for spectral hardening in the course of the
event. The X-ray bremsstrahlung emission from non-thermal electrons is
characterized by two spectroscopically distinct phases: impulsive and gradual.
The impulsive phase usually consists of several emission spikes following a
soft-hard-soft spectral pattern, whereas the gradual stage manifests itself as
spectral hardening while the flux slowly decreases. Both the soft-hard-soft
(impulsive) phase and the hardening (gradual) phase are well described by
piecewise linear dependence of the photon spectral index on the logarithm of
the hard X-ray flux. The different linear parts of this relation correspond to
different rise and decay phases of emission spikes. The temporal evolution of
the spectra is compared with the configuration and motion of the hard X-ray
sources in RHESSI images. These observations reveal that the two stages of
electron acceleration causing these two different behaviors are closely related
in space and time. The transition between the impulsive and gradual phase is
found to be smooth and progressive rather than abrupt. This suggests that they
arise because of a slow change in a common accelerator rather than being caused
by two independent and distinct acceleration processes. We propose that the
hardening during the decay phase is caused by continuing particle acceleration
with longer trapping in the accelerator before escape.


title: Radio-frequency point-contact electrometer

abstract:
  We fabricate and characterize a radio-frequency semiconductor point-contact
electrometer (RF-PC) analogous to radio-frequency single-electron transistors
[RF-SETs, see Science {\bf 280}, 1238 (1998)]. The point contact is formed by
surface Schottky gates in a two-dimensional electron gas (2DEG) in an
AlGaAs/GaAs heterostructure. In the present setup, the PC is operating as a
simple voltage-controlled resistor rather than a quantum point contact (QPC)
and demonstrates a charge-sensitivity about $2\times 10^{-1}
\mathrm{e/\sqrt{Hz}}$ at a bandwidth of $30 \mathrm{kHz}$ without the use of a
cryogenic RF preamplifier. Since the impedance of a typical point-contact
device is much lower than the impedance of the typical SET, a
semiconductor-based RF-PC, equipped with practical cryogenic RF preamplifiers,
could realize an ultra-fast and ultra-sensitive electrometer.


title:
Tame Functions with strongly isolated singularities at infinity: a tame
  version of a Parusinski's Theorem

abstract:
  Let f be a definable function, enough differentiable. Under the condition of
having strongly isolated singularities at infinity at a regular value c we give
a sufficient condition expressed in terms of the total absolute curvature
function to ensure the local triviality of the function f over a neighbourhood
of c and doing so providing the tame version of Parusinski's Theorem on complex
polynomials with isolated singularities at infinity.


title: Descent for quasi-coherent sheaves on stacks

abstract:
  We give a homotopy theoretic characterization of sheaves on a stack and, more
generally, a presheaf of groupoids on an arbitary small site C. We use this to
prove homotopy invariance and generalized descent statements for categories of
sheaves and quasi-coherent sheaves. As a corollary we obtain an alternate proof
of a generalized change of rings theorem of Hovey.


title:
Origin of ferromagnetism in (Zn,Co)O from magnetization and
  spin-dependent magnetoresistance

abstract:
  In order to elucidate the nature of ferromagnetic signatures observed in
(Zn,Co)O we have examined experimentally and theoretically magnetic properties
and spin-dependent quantum localization effects that control low-temperature
magnetoresistance. Our findings, together with a through structural
characterization, substantiate the model assigning spontaneous magnetization of
(Zn,Co)O to uncompensated spins at the surface of antiferromagnetic nanocrystal
of Co-rich wurtzite (Zn,Co)O. The model explains a large anisotropy observed in
both magnetization and magnetoresistance in terms of spin hamiltonian of Co
ions in the crystal field of the wurtzite lattice.


title:
Peculiar Features of the Interaction Potential between Hydrogen and
  Antihydrogen at Intermediate Separations

abstract:
  We evaluate the interaction potential between a hydrogen and an antihydrogen
using the second-order perturbation theory within the framework of the
four-body system in a separable two-body basis. We find that the H-Hbar
interaction potential possesses the peculiar features of a shallow local
minimum located around interatomic separations of r ~ 6 a.u. and a barrier
rising at r~5 a.u. Additional theoretical and experimental investigations on
the nature of these peculiar features will be of great interest.


title: The Multidimensional Cube Recurrence

abstract:
  We introduce a recurrence which we term the multidimensional cube recurrence,
generalizing the octahedron recurrence studied by Propp, Fomin and Zelevinsky,
Speyer, and Fock and Goncharov and the three-dimensional cube recurrence
studied by Fomin and Zelevinsky, and Carroll and Speyer. The states of this
recurrence are indexed by tilings of a polygon with rhombi, and the variables
in the recurrence are indexed by vertices of these tilings. We travel from one
state of the recurrence to another by performing elementary flips. We show that
the values of the recurrence are independent of the order in which we perform
the flips; this proof involves nontrivial combinatorial results about rhombus
tilings which may be of independent interest. We then show that the
multidimensional cube recurrence exhibits the Laurent phenomenon -- any
variable is given by a Laurent polynomial in the other variables. We recognize
a special case of the multidimensional cube recurrence as giving explicit
equations for the isotropic Grassmannians IG(n-1,2n). Finally, we describe a
tropical version of the multidimensional cube recurrence and show that, like
the tropical octahedron recurrence, it propagates certain linear inequalities.


title:
Atomic oxygen adsorption and incipient oxidation of the Pb(111) surface:
  A density-functional theory study

abstract:
  We study the atomic oxygen adsorption on Pb(111) surface by using
density-functional theory within the generalized gradient approximation and a
supercell approach. The atomic and energetic properties of purely on-surface
and subsurface oxygen structures at the Pb(111) surface are systematically
investigated for a wide range of coverages and adsorption sites. The fcc and
tetra-II sites (see the text for definition) are found to be energetically
preferred for the on-surface and subsurface adsorption, respectively, in the
whole range of coverage considered. The on-surface and subsurface oxygen
binding energies monotonically increase with the coverage, and the latter is
always higher than the former, thus indicating the tendency to the formation of
oxygen islands (clusters) and the higher stability of subsurface adsorption.
The on-surface and subsurface diffusion-path energetics of atomic oxygen, and
the activation barriers for the O penetration from the on-surface to the
subsurface sites are presented at low and high coverages. In particular, it is
shown that the penetration barrier from the on-surface hcp to the subsurface
tetra-I site is as small as 65 meV at low coverage ($\Theta $=0.25). The other
properties of the O/Pb(111) system, including the charge distribution, the
lattice relaxation, the work function, and the electronic density of states,
are also studied and discussed in detail, which consistently show the gradually
stabilizing ionic O-Pb bond with increase of the oxygen coverage.


title: Quantum heat engines and information

abstract:
  Recently, Zhang {\em et al.} [PRA, {\bf 75}, 062102 (2007)] extended Kieu's
interesting work on the quantum Otto engine [PRL, {\bf 93}, 140403 (2004)] by
considering as working substance a bipartite quantum system $AB$ composed of
subsystems $A$ and $B$. In this paper, we express the net work done $W_{AB}$ by
such an engine explicitly in terms of the macroscopic bath temperatures and
information theoretic quantities associated with the microscopic quantum states
of the working substance. This allows us to gain insights into the dependence
of positive $W_{AB}$ on the quantum properties of the states. We illustrate
with a two-qubit XY chain as the working substance. Inspired by the expression,
we propose a plausible formula for the work derivable from the subsystems. We
show that there is a critical entanglement beyond which it is impossible to
draw positive work locally from the individual subsystems while $W_{AB}$ is
positive. This could be another interesting manifestation of quantum
nonlocality.


title:
Comment on "Are the spectra of geometrical operators in Loop Quantum
  Gravity really discrete?" by B. Dittrich and T. Thiemann

abstract:
  I argue that the prediction of physical discreteness at the Planck scale in
loop gravity is a reasonable conclusion that derives from a sensible ensemble
of hypotheses, in spite of some contrary arguments considered in an interesting
recent paper by Dittrich and Thiemann. The counter-example presented by
Dittrich and Thiemann illustrates a pathology which does not seem to be present
in gravity. I also point out a common confusion between two distinct frameworks
for the interpretation of general-covariant quantum theory, and observe that
within one of these, the derivation of physical discreteness is immediate, and
not in contradiction with gauge invariance.


title: Pulsar slow glitches in a solid quark star model

abstract:
  A series of five unusual slow glitches of the radio pulsar B1822-09 (PSR
J1825-0935) were observed over the 1995-2005 interval. This phenomenon is
understood in a solid quark star model, where the reasonable parameters for
slow glitches are presented in the paper. It is proposed that, because of
increasing shear stress as a pulsar spins down, a slow glitch may occur,
beginning with a collapse of a superficial layer of the quark star. This layer
of material turns equivalently to viscous fluid at first, the viscosity of
which helps deplete the energy released from both the accumulated elastic
energy and the gravitation potential. This performs then a process of slow
glitch. Numerical calculations show that the observed slow glitches could be
reproduced if the effective coefficient of viscosity is ~10^2 cm^{2}/s and the
initial velocity of the superficial layer is order of 10^{-10} cm/s in the
coordinate rotating frame of the star.


title: Visualizing curved spacetime

abstract:
  I present a way to visualize the concept of curved spacetime. The result is a
curved surface with local coordinate systems (Minkowski Systems) living on it,
giving the local directions of space and time. Relative to these systems,
special relativity holds. The method can be used to visualize gravitational
time dilation, the horizon of black holes, and cosmological models. The idea
underlying the illustrations is first to specify a field of timelike
four-velocities. Then, at every point, one performs a coordinate transformation
to a local Minkowski system comoving with the given four-velocity. In the local
system, the sign of the spatial part of the metric is flipped to create a new
metric of Euclidean signature. The new positive definite metric, called the
absolute metric, can be covariantly related to the original Lorentzian metric.
For the special case of a 2-dimensional original metric, the absolute metric
may be embedded in 3-dimensional Euclidean space as a curved surface.


title:
High-resolution radio continuum survey of M33 II. Thermal and nonthermal
  emission

abstract:
  We determine the variation in the nonthermal radio spectral index in the
nearby spiral galaxy M33 at a linear resolution of 360 pc. We separate the
thermal and nonthermal components of the radio continuum emission without the
assumption of a constant nonthermal spectral index. Using the Spitzer FIR data
at 70 and 160 $\mu$m and a standard dust model, we deredden the H$\alpha$
emission. The extinction corrected H$\alpha$ emission serves as a template for
the thermal free-free radio emission. Subtracting from the observed 3.6 cm and
20 cm emission (Effelsberg and the VLA) this free-free emission, we obtain the
nonthermal maps. A constant electron temperature used to obtain the thermal
radio intensity seems appropriate for M~33 which, unlike the Milky Way, has a
shallow metallicity gradient. For the first time, we derive the distribution of
the nonthermal spectral index across a galaxy, M33. We detect strong nonthermal
emission from the spiral arms and star-forming regions. Wavelet analysis shows
that at 3.6 cm the nonthermal emission is dominated by contributions from
star-forming regions, while it is smoothly distributed at 20 cm. For the whole
galaxy, we obtain thermal fractions of 51% and 18% at 3.6 cm and 20 cm,
respectively. The thermal emission is slightly stronger in the southern than in
the northern half of the galaxy. We find a clear radial gradient of mean
extinction in the galactic plane. The nonthermal spectral index map indicates
that the relativistic electrons suffer energy-loss when diffusing from their
origin in star-forming regions towards interarm regions and the outer parts of
the galaxy. We also conclude that the radio emission is mostly nonthermal at R
$>$ 5 kpc in M33.


title:
Analytical Analysis of Single-Photon Correlations Emitted by Disordered
  Semiconductor Heterostructures

abstract:
  In a recent publication [Phys. Rev. Lett. 97, 227402 (2006),
cond-mat/0611411], it has been demonstrated numerically that a long-range
disorder potential in semiconductor quantum wells can be reconstructed reliably
via single-photon interferometry of spontaneously emitted light.
  In the present paper, a simplified analytical model of independent two-level
systems is presented in order to study the reconstruction procedure in more
detail. With the help of this model, the measured photon correlations can be
calculated analytically and the influence of parameters such as the disorder
length scale, the wavelength of the used light, or the spotsize can be
investigated systematically. Furthermore, the relation between the proposed
angle-resolved single-photon correlations and the disorder potential can be
understood and the measured signal is expected to be closely related to the
characteristic strength and length scale of the disorder.


title: Microlensing under Shear

abstract:
  We investigate the distortions due to this shear in the microlensing light
curves and in the astrometric microlensing centroid shift trajectories. As
expected, the light curve deviation increases as the shear increases and the
impact parameter decreases. Although the light curve in the presence of a small
shear is similar to the simple Paczynski curve with a slightly smaller impact
parameter, the detailed difference between the light curve with and without
shear reflects the direction and the magnitude of the shear. The centroid shift
trajectory also deviates from a simple ellipse in the presence of shear. The
distortion of the centroid shift trajectory increases as the impact parameter
decreases, and the shape of the trajectory becomes complicated when the impact
parameter becomes small enough. The magnitude of the maximum distortion depends
on the magnitude and the direction of the shear. For a source trajectory in a
given direction, the time of the maximum distortion depends mostly on the
impact parameter and hardly on the shear. It is possible to determine the
magnitude of the shear and its direction if both the time and the magnitude of
the maximum astrometric distortion are measured. The magnitude of the shear
produced by the Galactic bulge or a globular cluster falls in the range
10^{-6}--10^{-4} in normalized units. Although the actual determination of the
shear from the Galactic sub-structures will not be easy due to complications
such as binary companion, future large scale microlensing experiments may
enable us to determine the shear in some high amplification events, leading
eventually to mapping the Galactic mass distribution.


title:
Thermal correction to the Casimir force, radiative heat transfer, and an
  experiment

abstract:
  The low-temperature asymptotic expressions for the Casimir interaction
between two real metals described by Leontovich surface impedance are obtained
in the framework of thermal quantum field theory. It is shown that the Casimir
entropy computed using the impedance of infrared optics vanishes in the limit
of zero temperature. By contrast, the Casimir entropy computed using the
impedance of the Drude model attains at zero temperature a positive value which
depends on the parameters of a system, i.e., the Nernst heat theorem is
violated. Thus, the impedance of infrared optics withstands the thermodynamic
test, whereas the impedance of the Drude model does not. We also perform a
phenomenological analysis of the thermal Casimir force and of the radiative
heat transfer through a vacuum gap between real metal plates. The
characterization of a metal by means of the Leontovich impedance of the Drude
model is shown to be inconsistent with experiment at separations of a few
hundred nanometers. A modification of the impedance of infrared optics is
suggested taking into account relaxation processes. The power of radiative heat
transfer predicted from this impedance is several times less than previous
predictions due to different contributions from the transverse electric
evanescent waves. The physical meaning of low frequencies in the Lifshitz
formula is discussed. It is concluded that new measurements of radiative heat
transfer are required to find out the adequate description of a metal in the
theory of electromagnetic fluctuations.


title:
An intuitive approach to inertial forces and the centrifugal force
  paradox in general relativity

abstract:
  As the velocity of a rocket in a circular orbit near a black hole increases,
the outwardly directed rocket thrust must increase to keep the rocket in its
orbit. This feature might appear paradoxical from a Newtonian viewpoint, but we
show that it follows naturally from the equivalence principle together with
special relativity and a few general features of black holes. We also derive a
general relativistic formalism of inertial forces for reference frames with
acceleration and rotation. The resulting equation relates the real experienced
forces to the time derivative of the speed and the spatial curvature of the
particle trajectory relative to the reference frame. We show that an observer
who follows the path taken by a free (geodesic) photon will experience a force
perpendicular to the direction of motion that is independent of the observers
velocity. We apply our approach to resolve the submarine paradox, which regards
whether a submerged submarine in a balanced state of rest will sink or float
when given a horizontal velocity if we take relativistic effects into account.
We extend earlier treatments of this topic to include spherical oceans and show
that for the case of the Earth the submarine floats upward if we take the
curvature of the ocean into account.


title: AB Levitrons and their Applications to Earth's Motionless Satellites

abstract:
  Author offers the new and distinctly revolutionary method of levitation in
artificial magnetic field. It is shown that a very big space station and small
satellites may be suspended over the Earth's surface and used as motionless
radio-TV translators, telecommunication boosters, absolute geographic position
locators, personal and mass entertainment and as planet-observation platforms.
Presented here is the theory of big AB artificial magnetic field and levitation
in it is generally developed. Computation of three macro-projects: space
station at altitude 100 km, TV-communication antenna at height 500 m, and
multi-path magnetic highway.
  Key words: levitation, AB Levitrons, motionless space satellite.


title:
Gyroscope precession in special and general relativity from basic
  principles

abstract:
  In special relativity a gyroscope that is suspended in a torque-free manner
will precess as it is moved along a curved path relative to an inertial frame
S. We explain this effect, which is known as Thomas precession, by considering
a real grid that moves along with the gyroscope, and that by definition is not
rotating as observed from its own momentary inertial rest frame. From the basic
properties of the Lorentz transformation we deduce how the form and rotation of
the grid (and hence the gyroscope) will evolve relative to S. As an
intermediate step we consider how the grid would appear if it were not length
contracted along the direction of motion. We show that the uncontracted grid
obeys a simple law of rotation. This law simplifies the analysis of spin
precession compared to more traditional approaches based on Fermi transport. We
also consider gyroscope precession relative to an accelerated reference frame
and show that there are extra precession effects that can be explained in a way
analogous to the Thomas precession. Although fully relativistically correct,
the entire analysis is carried out using three-vectors. By using the
equivalence principle the formalism can also be applied to static spacetimes in
general relativity. As an example, we calculate the precession of a gyroscope
orbiting a static black hole. In an addendum the general reasoning is extended
to include also rotating reference frames.


title:
On a general solution of the one-dimensional stationary Schrodinger
  equation

abstract:
  The general solution of the one-dimensional stationary Schroedinger equation
in the form of a formal power series is considered. Its efficiency for
numerical analysis of initial value and boundary value problems is discussed.


title: Quasitriviality of the Forms of Segre Varieties

abstract:
  We prove the rationality of a $\k$-form $X$ of the product $S$ of projective
spaces provided the existence of a $\k$-point on $X$. The method of the proof
is to find a Galois-invariant birational projection of $S$ to the projective
space. This method also allows to prove the quasitriviality of the forms of the
hyperplane sections of some Segre varieties.


title: Inertial forces and the foundations of optical geometry

abstract:
  Assuming a general timelike congruence of worldlines as a reference frame, we
derive a covariant general formalism of inertial forces in General Relativity.
Inspired by the works of Abramowicz et. al. (see e.g. Abramowicz and Lasota,
Class. Quantum Grav. 14 (1997) A23), we also study conformal rescalings of
spacetime and investigate how these affect the inertial force formalism. While
many ways of describing spatial curvature of a trajectory has been discussed in
papers prior to this, one particular prescription (which differs from the
standard projected curvature when the reference is shearing) appears novel. For
the particular case of a hypersurface-forming congruence, using a suitable
rescaling of spacetime, we show that a geodesic photon is always following a
line that is spatially straight with respect to the new curvature measure. This
fact is intimately connected to Fermat's principle, and allows for a certain
generalization of the optical geometry as will be further pursued in a
companion paper (Jonsson and Westman, Class. Quantum Grav. 23 (2006) 61). For
the particular case when the shear-tensor vanishes, we present the inertial
force equation in three-dimensional form (using the bold face vector notation),
and note how similar it is to its Newtonian counterpart. From the spatial
curvature measures that we introduce, we derive corresponding covariant
differentiations of a vector defined along a spacetime trajectory. This allows
us to connect the formalism of this paper to that of Jantzen et. al. (see e.g.
Bini et. al., Int. J. Mod. Phys. D 6 (1997) 143).


title: A formula for the normal subgroup growth of Baumslag-Solitar groups

abstract:
  We give an exact formula for the number of normal subgroups of each finite
index in the Baumslag-Solitar group BS(p,q) when p and q are coprime. Unlike
the formula for all finite index subgroups, this one distinguishes different
Baumslag-Solitar groups and is not multiplicative. This allows us to give an
example of a finitely generated profinite group which is not virtually
pronilpotent but whose zeta function has an Euler product.


title: On Unirationality of Quartics over non Algebraically Closed Fields

abstract:
  We give examples of smooth $\k$-unirational line-free quartic hypersurfaces
over a non algebraically closed field $\k$. Unlike other methods of proving
unirationality, our method does not rely on existence of linear spaces on
quartics.


title:
Contributions from cognitive research to mathematics and science
  education

abstract:
  An invited plenary given at the founding meeting of the Southern African
Association for Research in Mathematics and Science Education in 1992.


title: Duality and semi-group property for backward parabolic Ito equations

abstract:
  We study existence, uniqueness, semi-group property, and a priori estimates
for solutions for backward parabolic Ito equations in domains with boundary. We
study also duality between forward and backward equations. The semi-group for
backward equations is established in the form of some anti-causality. The
novelty is that the semi-group property involves the diffusion term that is a
part of the solution.


title: Computation in Classical Mechanics

abstract:
  There is a growing consensus that physics majors need to learn computational
skills, but many departments are still devoid of computation in their physics
curriculum. Some departments may lack the resources or commitment to create a
dedicated course or program in computational physics. One way around this
difficulty is to include computation in a standard upper-level physics course.
An intermediate classical mechanics course is particularly well suited for
including computation. We discuss the ways we have used computation in our
classical mechanics courses, focusing on how computational work can improve
students' understanding of physics as well as their computational skills. We
present examples of computational problems that serve these two purposes. In
addition, we provide information about resources for instructors who would like
to include computation in their courses.


title:
Theoretical spectroscopic studies of the atomic transitions and
  lifetimes of low-lying states in Ti IV

abstract:
  The astrophysically important electric quadrupole (E2) and magnetic dipole
(M1) transitions for the low-lying states of triply ionized titanium (Ti IV)
are calculated very accurately using a state-of-art all-order many-body theory
called Coupled Cluster (CC) theory in the relativistic frame-work. Different
many-body correlations of the CC theory has been estimated by studying the core
and valence electron excitations to the unoccupied states. The calculated
excitation energies of different states are in very good agreement with the
measurements. Also we compare our calculated electric dipole (E1) transition
amplitudes of few transitions with recent many-body calculations by different
groups. We have also carried out the calculations for the lifetimes of the
low-lying states of Ti IV. A long lifetime is found for the first excited
3d$^{2}D_{5/2}$ state, which suggested that Ti IV may be one of the useful
candidates for many important studies. Most of the results reported here are
not available in the literature, to the best of our knowledge.


title:
Variation of the unit roots along the Dwork family of Calabi-Yau
  varieties

abstract:
  We study the variation of unit roots of the Dwork families of Calabi-Yau
varieties over a finite field by the method of Dwork-Katz and also from the
point of view of formal group laws. A p-adic analytic formula for the unit
roots away from the Hasse locus is obtained.


title:
Higher dimensional operators and their effects in (non)supersymmetric
  models

abstract:
  It is shown that a 4D N=1 softly broken supersymmetric theory with higher
derivative operators in the Kahler or the superpotential part of the Lagrangian
and with an otherwise arbitrary superpotential, can be re-formulated as a
theory without higher derivatives but with additional (ghost) superfields and
modified interactions. The importance of the analytical continuation
Minkowski-Euclidean space-time for the UV behaviour of such theories is
discussed in detail. In particular it is shown that power counting for
divergences in Minkowski space-time does not always work in models with higher
derivative operators.


title: Hoeffding's inequality in game-theoretic probability

abstract:
  This note makes the obvious observation that Hoeffding's original proof of
his inequality remains valid in the game-theoretic framework. All details are
spelled out for the convenience of future reference.


title: Window For Higgs Boson Mass From Gauge-Higgs Unification

abstract:
  We consider six dimensional gauge models compactified on the orbifold T^2/Z_N
(N=2,3,4,6) such that the Standard Model (SM) Higgs doublet arises from the
extra-dimensional components of the gauge field. For \Lambda \leq 10^{19} GeV,
where \Lambda denotes the compactification scale, we obtain 114.4 GeV \leq m_H
\leq 164 GeV for the SM Higgs boson mass. We also consider gauge-Higgs-top and
gauge-Higgs-bottom Yukawa unification which respectively yield m_H =
131^{+4}_{-5} GeV and m_H = 150^{+2}_{-2} GeV for a top quark pole mass M_t
=170.9^{+1.8}_{-1.8} GeV. As a special case we recover the result m_H \leq 132
GeV previously obtained for five dimensional models.


title:
Obscured clusters.I. GLIMPSE30 - Young Milky Way Star Cluster Hosting
  Wolf-Rayet Stars

abstract:
  Young massive clusters are perfect astrophysical laboratories for study of
massive stars. Clusters with Wolf-Rayet (WR) stars are of special importance,
since this enables us to study a coeval WR population at a uniform metallicity
and known age. GLIMPSE30 (G30) is one of them. The cluster is situated near the
Galactic plane (l=298.756deg, b=-0.408deg) and we aimed to determine its
physical parameters and to investigate its high-mass stellar content and
especially WR stars. Our analysis is based on SOFI/NTT JsHKs imaging and low
resolution (R~2000) spectroscopy of the brightest cluster members in the K
atmospheric window. For the age determination we applied isochrone fits for MS
and Pre-MS stars. We derived stellar parameters of the WR stars candidates
using a full nonLTE modeling of the observed spectra. Using a variety of
techniques we found that G30 is very young cluster, with age t~4Myr. The
cluster is located in Carina spiral arm, it is deeply embedded in dust and
suffers reddening of Av~10.5+-1.1mag. The distance to the object is
d=7.2+-0.9kpc. The mass of the cluster members down to 2.35Msol is ~1600Msol.
Cluster's MF for the mass range of 5.6 to 31.6Msol shows a slope of
Gamma=-1.01+-0.03. The total mass of the cluster obtained by this MF down to
1Msol is about 3x10^3Msol. The spectral analysis and the models allow us to
conclude that in G30 are at least one Ofpe/WN and two WR stars. The WR stars
are of WN6-7 hydrogen rich type with progenitor masses more than 60Msol. G30 is
a new member of the exquisite family of young Galactic clusters, hosting WR
stars. It is a factor of two to three less massive than some of the youngest
super-massive star clusters like Arches, Quintuplet and Central cluster and is
their smaller analog.


title: Radio Emission Signatures in the Crab Pulsar

abstract:
  Our high time resolution observations of individual pulses from the Crab
pulsar show that both the time and frequency signatures of the interpulse are
distinctly different from those of the main pulse. Main pulses can occasionally
be resolved into short-lived, relatively narrow-band nanoshots. We believe
these nanoshots are produced by soliton collapse in strong plasma turbulence.
Interpulses at centimeter wavelengths are very different. Their dynamic
spectrum contains regular, microsecond-long emission bands. We have detected
these bands, proportionately spaced in frequency, from 4.5 to 10.5 GHz. The
bands cannot easily be explained by any current theory of pulsar radio
emission; we speculate on possible new models.


title:
A Characterization of the Angle Defect and the Euler Characteristic in
  Dimension 2 -- Preliminary Draft

abstract:
  The angle defect, which is the standard way to measure curvature at the
vertices of polyhedral surfaces, goes back at least as far as Descartes.
Although the angle defect has been widely studied, there does not appear to be
in the literature an axiomatic characterization of the angle defect. We give a
characterization of the angle defect for simplicial surfaces, and we show that
variants of the same characterization work for two known approaches to
generalizing the angle defect to arbitrary 2-dimensional simplicial complexes.
Simultaneously, we give a characterization of the Euler characteristic on
2-dimensional simplicial complexes in terms of being geometrically locally
determined.


title:
Feasibility of Searches for a Higgs Boson using H->WW->ll+MET and High
  PT Jets at the Tevatron

abstract:
  The sensitivity of Standard Model Higgs boson searches at the Tevatron
experiments with a mass 135<MH<190 GeV using the channel H->WW->ll+MET (l=e,mu)
is discussed. Three new event selections involving Higgs in association with
one or two high PT hadronic jets are discussed. Using Leading Order Matrix
Elements and a conservative cut-based analysis a 95% confidence level exclusion
on sigmaxBR(H->WW), 1.6 times larger than that predicted by the Standard Model
for MH=165 GeV, may be achieved with 5fb-1 of integrated luminosity. By
combining these three event selections with the existing analysis, the
sensitivity of CDF and D0 could improve significantly.


title:
On Killing vector fields of a homogeneous and isotropic universe in
  closed model

abstract:
  Killing vector fields of a closed homogeneous and isotropic universe are
studied. It is shown that in general case there is no time-like Killing vector
fields in such a universe. Two exceptional cases are revealed.


title: Invariants of Knot Diagrams

abstract:
  We construct a new order 1 invariant for knot diagrams. We use it to
determine the minimal number of Reidemeister moves needed to pass between
certain pairs of knot diagrams.


title: Abstract kinetic equations with positive collision operators

abstract:
  We consider "forward-backward" parabolic equations in the abstract form $Jd
\psi / d x + L \psi = 0$, $ 0< x < \tau \leq \infty$, where $J$ and $L$ are
operators in a Hilbert space $H$ such that $J=J^*=J^{-1}$, $L=L^* \geq 0$, and
$\ker L = 0$. The following theorem is proved: if the operator $B=JL$ is
similar to a self-adjoint operator, then associated half-range boundary
problems have unique solutions. We apply this theorem to corresponding
nonhomogeneous equations, to the time-independent Fokker-Plank equation $ \mu
\frac {\partial \psi}{\partial x} (x,\mu) = b(\mu) \frac {\partial^2
\psi}{\partial \mu^2} (x, \mu)$, $ 0<x<\tau$, $ \mu \in \R$, as well as to
other parabolic equations of the "forward-backward" type. The abstract kinetic
equation $ T d \psi/dx = - A \psi (x) + f(x)$, where $T=T^*$ is injective and
$A$ satisfies a certain positivity assumption, is considered also.


title:
The Globular Cluster Luminosity Function and Specific Frequency in Dwarf
  Elliptical Galaxies

abstract:
  The globular cluster luminosity function, specific globular cluster
frequency, S_N, specific globular cluster mass, T_MP, and globular cluster mass
fraction in dwarf elliptical galaxies are explored using the full 69 galaxy
sample of the HST WFPC2 Dwarf Elliptical Galaxy Snapshot Survey. The GCLFs of
the dEs are well-represented with a t_5 function with a peak at
M_{V,Z}^0(dE,HST) = -7.3 +/- 0.1. This is ~0.3 magnitudes fainter than the GCLF
peaks in giant spiral and elliptical galaxies, but the results are consistent
within the uncertainties. The bright-end slope of the luminosity distribution
has a power-law form with slope alpha = -1.9 +/- 0.1. The trend of increasing
S_N or T_MP with decreasing host galaxy luminosity is confirmed. The mean value
for T_MP in dE,N galaxies is about a factor of two higher than the mean value
for non-nucleated galaxies and the distributions of T_MP in dE,N and dE,noN
galaxies are statistically different. These data are combined with results from
the literature for a wide range of galaxy types and environments. At low host
galaxy masses the distribution of T_MP for dE,noN and dI galaxies are similar.
This supports the idea that one pathway for forming dE,noN galaxies is by the
stripping of dIs. The formation of nuclei and the larger values of T_MP in dE,N
galaxies may be due to higher star formation rates and star cluster formation
efficiencies due to interactions in galaxy cluster environments.


title: The Moduli Space of Polynomial Maps and Their Fixed-Point Multipliers

abstract:
  We consider the family $\mathrm{MP}_d$ of affine conjugacy classes of
polynomial maps of one complex variable with degree $d \geq 2$, and study the
map $\Phi_d:\mathrm{MP}_d\to \widetilde{\Lambda}_d \subset \mathbb{C}^d /
\mathfrak{S}_d$ which maps each $f \in \mathrm{MP}_d$ to the set of fixed-point
multipliers of $f$. We show that the local fiber structure of the map $\Phi_d$
around $\bar{\lambda} \in \widetilde{\Lambda}_d$ is completely determined by
certain two sets $\mathcal{I}(\lambda)$ and $\mathcal{K}(\lambda)$ which are
subsets of the power set of $\{1,2,\ldots,d \}$. Moreover for any
$\bar{\lambda} \in \widetilde{\Lambda}_d$, we give an algorithm for counting
the number of elements of each fiber $\Phi_d^{-1}\left(\bar{\lambda}\right)$
only by using $\mathcal{I}(\lambda)$ and $\mathcal{K}(\lambda)$. It can be
carried out in finitely many steps, and often by hand.


title: Pointwise Estimates for Marginals of Convex Bodies

abstract:
  We prove a pointwise version of the multi-dimensional central limit theorem
for convex bodies. Namely, let X be an isotropic random vector in R^n with a
log-concave density. For a typical subspace E in R^n of dimension n^c, consider
the probability density of the projection of X onto E. We show that the ratio
between this probability density and the standard gaussian density in E is very
close to 1 in large parts of E. Here c > 0 is a universal constant. This
complements a recent result by the second named author, where the
total-variation metric between the densities was considered.


title: Minimum Cost Homomorphisms to Reflexive Digraphs

abstract:
  For digraphs $G$ and $H$, a homomorphism of $G$ to $H$ is a mapping $f:\
V(G)\dom V(H)$ such that $uv\in A(G)$ implies $f(u)f(v)\in A(H)$. If moreover
each vertex $u \in V(G)$ is associated with costs $c_i(u), i \in V(H)$, then
the cost of a homomorphism $f$ is $\sum_{u\in V(G)}c_{f(u)}(u)$. For each fixed
digraph $H$, the {\em minimum cost homomorphism problem} for $H$, denoted
MinHOM($H$), is the following problem. Given an input digraph $G$, together
with costs $c_i(u)$, $u\in V(G)$, $i\in V(H)$, and an integer $k$, decide if
$G$ admits a homomorphism to $H$ of cost not exceeding $k$. We focus on the
minimum cost homomorphism problem for {\em reflexive} digraphs $H$ (every
vertex of $H$ has a loop). It is known that the problem MinHOM($H$) is
polynomial time solvable if the digraph $H$ has a {\em Min-Max ordering}, i.e.,
if its vertices can be linearly ordered by $<$ so that $i<j, s<r$ and $ir, js
\in A(H)$ imply that $is \in A(H)$ and $jr \in A(H)$. We give a forbidden
induced subgraph characterization of reflexive digraphs with a Min-Max
ordering; our characterization implies a polynomial time test for the existence
of a Min-Max ordering. Using this characterization, we show that for a
reflexive digraph $H$ which does not admit a Min-Max ordering, the minimum cost
homomorphism problem is NP-complete. Thus we obtain a full dichotomy
classification of the complexity of minimum cost homomorphism problems for
reflexive digraphs.


title:
Verschraenkung versus Stosszahlansatz: Disappearance of the
  Thermodynamic Arrow in a High-Correlation Environment

abstract:
  The crucial role of ambient correlations in determining thermodynamic
behavior is established. A class of entangled states of two macroscopic systems
is constructed such that each component is in a state of thermal equilibrium at
a given temperature, and when the two are allowed to interact heat can flow
from the colder to the hotter system. A dilute gas model exhibiting this
behavior is presented. This reversal of the thermodynamic arrow is a
consequence of the entanglement between the two systems, a condition that is
opposite to molecular chaos and shown to be unlikely in a low-entropy
environment. By contrast, the second law is established by proving Clausius'
inequality in a low-entropy environment. These general results strongly support
the expectation, first expressed by Boltzmann and subsequently elaborated by
others, that the second law is an emergent phenomenon that requires a
low-entropy cosmological environment, one that can effectively function as an
ideal information sink.


title: Superconductor-insulator transition in Coulomb disorder

abstract:
  Superconductor-insulator transition driven by the decreasing concentration of
electrons $n$ is studied in the case of the disorder potential created by
randomly positioned charged impurities. Electrons and Cooper pairs (formed by
an non-Coulomb attraction) nonlinearly screen the random potential of
impurities. Both electrons and Cooper pairs can be delocalized or localized in
the resulting self-consistent potential. The border separating the
superconductor and insulator phases in the plane of the concentration of
electrons and the length of the Cooper pair is found. For a strong disorder the
central segment of this border follows the BEC-BCS crossover line defined for a
clean sample.


title:
Implementing controlled-NOT gate based on free spin qubits with
  semiconductor quantum-dot array

abstract:
  Based on electron spins in semiconductor quantum dots as qubits, a new
quantum controlled-NOT(CNOT) gate is constructed in solid nanostructure without
resorting to spin-spin interactions. Single electron tunneling technology and
coherent quantum-dot cellular automata architecture are used to generate an
ancillary charge entangled state. Using the ancillary charge entangled state as
an intermediate state, we obtain a spin entangled state and design a CNOT gate
by using only single spin rotations.


title:
Comment to "Multipolar expansion of the electrostatic interaction
  between charged colloids at interfaces"

abstract:
  We present a comment to a recent paper by Dominguez et. al. They claimed that
the electrostatic interaction between charged colloids trapped at an interface
formed by a dielectric and a screening phase is always isotropic to order
$d^-3$. Base on this result, they claimed that in-plane dipolar attraction of
order $d^-3$ between colloids cannot exist, in contrast to previous proposals.
We point out that their analysis is not completed and anisotropic (dipolar)
interaction between colloids can exist up to order $d^-3$.


title:
Incommensurate Spin Ordering and Fluctuations in underdoped
  La_{2-x}Ba_{x}CuO_{4}

abstract:
  Using neutron scattering techniques, we have studied incommensurate spin
ordering as well as low energy spin dynamics in single crystal underdoped \LBCO
with x$\sim$0.095 and 0.08; high temperature superconductors with T$_C \sim$ 27
K and 29 K respectively. Static two dimensional incommensurate magnetic order
appears below T$_N$=39.5 $\pm$ 0.3 K in \LBCO (x=0.095) and a similar
temperature for x=0.08 within the low temperature tetragonal phase. The spin
order is unaffected by either the onset of superconductivity or the application
of magnetic fields of up to 7 Tesla applied along the c-axis in the x=0.095
sample. Such magnetic field {\it independent} behaviour is in marked contrast
with the field induced enhancement of the staggered magnetisation observed in
the related \LSCO system, indicating this phenomenon is not a universal
property of cuprate superconductors. Surprisingly, we find that
incommensurability $\delta $ is only weakly dependent on doping relative to
\LSCO. Dispersive excitations in \LBCO (x=0.095) at the same incommensurate
wavevector persist up to at least 60 K. The dynamical spin susceptibility of
the low energy spin excitations saturates below \tc, in a similar manner to
that seen in the superconducting state of La$_2$CuO$_{4+y}$.


title:
Comparing tamed and compatible symplectic cones and cohomological
  properties of almost complex manifolds

abstract:
  We introduce certain homology and cohomology subgroups for any almost complex
structure and study their pureness, fullness and duality properties. Motivated
by a question of Donaldson, we use these groups to relate J-tamed symplectic
cones and J-compatible symplectic cones over a large class of almost complex
manifolds, including all Kahler manifolds, almost Kahler 4-manifolds and
complex surfaces.


title: Trigonometric quark confinement potential of QCD traits

abstract:
  We make the case that the Coulomb- plus linear quark confinement potential
predicted by lattice QCD is an approximation to the exactly solvable
trigonometric Rosen-Morse potential that has the property to interpolate
between the Coulomb- and the infinite wells. We test the predictive power of
this potential in the description of the nucleon (considered as a quark-diquark
system) and provide analytic expressions for its mass spectrum and the proton
electric form factor. We compare the results obtained in this fashion to data
and find quite good agreement. We obtain an effective gluon propagator in
closed form as the Fourier transform of the potential under investigation.


title: Higher Spin Alternating Sign Matrices

abstract:
  We define a higher spin alternating sign matrix to be an integer-entry square
matrix in which, for a nonnegative integer r, all complete row and column sums
are r, and all partial row and column sums extending from each end of the row
or column are nonnegative. Such matrices correspond to configurations of spin
r/2 statistical mechanical vertex models with domain-wall boundary conditions.
The case r=1 gives standard alternating sign matrices, while the case in which
all matrix entries are nonnegative gives semimagic squares. We show that the
higher spin alternating sign matrices of size n are the integer points of the
r-th dilate of an integral convex polytope of dimension (n-1)^2 whose vertices
are the standard alternating sign matrices of size n. It then follows that, for
fixed n, these matrices are enumerated by an Ehrhart polynomial in r.


title:
Lattice Calculation of Thermal Properties of Low-Density Neutron Matter
  with Pionless NN Effective Field Theory

abstract:
  Thermal properties of low-density neutron matter are investigated by
determinantal quantum Monte Carlo lattice calculations on 3+1 dimensional cubic
lattices. Nuclear effective field theory (EFT) is applied using the pionless
single- and two-parameter neutron-neutron interactions, determined from the
$^1S_0$ scattering length and effective range. The determination of the
interactions and the calculations of neutron matter are carried out
consistently by applying EFT power counting rules. The thermodynamic limit is
taken by the method of finite-size scaling, and the continuum limit is examined
in the vanishing lattice filling limit. The $^1S_0$ pairing gap at $T \approx
0$ is computed directly from the off-diagonal long-range order of the spin
pair-pair correlation function, and is found to be approximately 30% smaller
than BCS calculations with the conventional nucleon-nucleon potentials. The
critical temperature $T_c$ of the normal-to-superfluid phase transition and the
pairing temperature scale $T^\ast$ are determined, and the temperature-density
phase diagram is constructed. The physics of low-density neutron matter is
clearly identified as being a BCS-Bose-Einstein condensation crossover.


title: From Low-Density Neutron Matter to the Unitary Limit

abstract:
  Various quantities of an attractively interacting fermion system at the
unitary limit are determined by extrapolating Monte Carlo results of
low-density neutron matter. Smooth extrapolation in terms of $1/(k_F a_0)$
($k_F$ is the Fermi momentum, and $a_0$ is the ${}^1S_0$ scattering length) is
found with the quantities examined: the ground-state energy, the pairing gap at
$T \approx 0$, and the critical temperature of the normal-to-superfluid phase
transition. We emphasize proximity of the physics of low-density neutron matter
to that at the unitary limit. The extrapolated quantities are in a reasonable
agreement with those in the literature.


title:
Quantum $\frak {gl}_\infty$, infinite $q$-Schur algebras and their
  representations

abstract:
  In this paper, we investigate the structure and representations of the
quantum group ${\mathbf{U}(\infty)}=\mathbf U_\upsilon(\frak{gl}_\infty)$. We
will present a realization for $\mathbf{U}(\infty)$, following
Beilinson--Lusztig--MacPherson (BLM) \cite{BLM}, and show that the natural
algebra homomorphism $\zeta_r$ from $\mathbf{U}(\infty)$ to the infinite
$q$-Schur algebra ${\boldsymbol{\mathcal S}}(\infty,r)$ is not surjective for
any $r\geq 1$. We will give a BLM type realization for the image
$\mathbf{U}(\infty,r):=\zeta_r(\mathbf{U}(\infty))$ and discuss its
presentation in terms of generators and relations. We further construct a
certain completion algebra $\hat{\boldsymbol{\mathcal K}}^\dagger(\infty)$ so
that $\zeta_r$ can be extended to an algebra epimorphism
$\tilde\zeta_r:\hat{\boldsymbol{\mathcal
K}}^\dagger(\infty)\to{\boldsymbol{\mathcal S}}(\infty,r)$. Finally we will
investigate the representation theory of ${\bf U}(\infty)$, especially the
polynomial representations of ${\bf U}(\infty)$.


title:
Kinetic theory of point vortex systems from the
  Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy

abstract:
  Kinetic equations are derived from the Bogoliubov-Born-Green-Kirkwood-Yvon
(BBGKY) hierarchy for point vortex systems in an infinite plane. As the level
of approximation for the Landau equation, the collision term of the kinetic
equation derived coincides with that by Chavanis ({\it Phys. Rev. E} {\bf 64},
026309 (2001)). Furthermore, we derive a kinetic equation corresponding to the
Balescu-Lenard equation for plasmas, using the theory of the Fredholm integral
equation. For large $N$, this kinetic equation is reduced to the Landau
equation above.


title: Model for processive nucleotide and repeat additions by the telomerase

abstract:
  A model is presented to describe the nucleotide and repeat addition
processivity by the telomerase. In the model, the processive nucleotide
addition is implemented on the basis of two requirements: One is that stem IV
loop stimulates the chemical reaction of nucleotide incorporation, and the
other one is the existence of an ssRNA-binding site adjacent to the polymerase
site that has a high affinity for the unpaired base of the template. The
unpairing of DNA:RNA hybrid after the incorporation of the nucleotide paired
with the last base on the template, which is the prerequisite for repeat
addition processivity, is caused by a force acting on the primer. The force is
resulted from the unfolding of stem III pseudoknot that is induced by the
swinging of stem IV loop towards the nucleotide-bound polymerase site. Based on
the model, the dynamics of processive nucleotide and repeat additions by
Tetrahymena telomerase are quantitatively studied, which give good explanations
to the previous experimental results. Moreover, some predictions are presented.
In particular, it is predicted that the repeat addition processivity is mainly
determined by the difference between the free energy required to disrupt the
DNA:RNA hybrid and that required to unfold the stem III pseudoknot, with the
large difference corresponding to a low repeat addition processivity while the
small one corresponding to a high repeat addition processivity.


title:
Synthesis and properties of CoO2, the x = 0 end member of the LixCoO2
  and NaxCoO2 systems

abstract:
  We report here the synthesis of single-phase bulk samples of CoO2, the x = 0
end member of the AxCoO2 systems (A = Li, Na), from a pristine LiCoO2 sample
using an electrochemical technique to completely de-intercalate lithium. Thus,
synthesized CoO2 samples were found to be oxygen-stoichiometric and possess a
crystal structure consisting of stacked triangular-lattice CoO2 layers only.
The magnetic susceptibility of the CoO2 sample was revealed to be relatively
large in its initial value and then level off as the temperature increases,
suggesting that CoO2 is a Pauli-paramagnetic metal with itinerant electrons.


title:
Molecular dynamics simulation of nanocolloidal amorphous silica
  particles: Part I

abstract:
  Explicit molecular dynamics simulations were applied to a pair of amorphous
silica nanoparticles in aqueous solution, of diameter 4.4 nm with four
different background electrolyte concentrations, to extract the mean force
acting between the pair of silica nanoparticles. Dependences of the
interparticle forces with separation and the background electrolyte
concentration were demonstrated. The nature of the interaction of the
counter-ions with charged silica surface sites (deprotonated silanols) was
investigated. A 'patchy' double layer of adsorbed sodium counter-ions. was
observed. Dependences of the interparticle potential of mean force with
separation and the background electrolyte concentration were demonstrated.
Direct evidence of the solvation forces is presented in terms of changes of the
water ordering at the surfaces of the isolated and double nanoparticles. The
nature of the interaction of the counter-ions with charged silica surface sites
(deprotonated silanols) was investigated in terms of quantifying the effects of
the number of water molecules separately inside each of the pair of
nanoparticles by defining an impermeability measure. A direct correlation was
found between impermeability (related to the silica surface 'hairiness') and
the disruption of water ordering. Differences in the impermeability between the
two nanoparticles are attributed to differences in the calculated electric
dipole moment.