title: Protodiscs around Hot Magnetic Rotator Stars

abstract:
  We develop equations and obtain solutions for the structure and evolution of
a protodisc region that is initially formed with no radial motion and
super-Keplerian rotation speed when wind material from a hot rotating star is
channelled towards its equatorial plane by a dipole-type magnetic field. Its
temperature is around $10^7$K because of shock heating and the inflow of wind
material causes its equatorial density to increase with time. The centrifugal
force and thermal pressure increase relative to the magnetic force and material
escapes at its outer edge. The protodisc region of a uniformly rotating star
has almost uniform rotation and will shrink radially unless some instability
intervenes. In a star with angular velocity increasing along its surface
towards the equator, the angular velocity of the protodisc region decreases
radially outwards and magnetorotational instability (MRI) can occur within a
few hours or days. Viscosity resulting from MRI will readjust the angular
velocity distribution of the protodisc material and may assist in the formation
of a quasi-steady disc. Thus, the centrifugal breakout found in numerical
simulations for uniformly rotating stars does not imply that quasi-steady discs
with slow outflow cannot form around magnetic rotator stars with solar-type
differential rotation.


title:
Further Improvements of Lower Bounds for the Least Common Multiples of
  Arithmetic Progressions

abstract:
  For relatively prime positive integers u_0 and r, we consider the arithmetic
progression {u_k := u_0+k*r} (0 <= k <= n). Define L_n := lcm{u_0,u_1,...,u_n}
and let a >= 2 be any integer. In this paper, we show that, for integers
alpha,r >= a and n >= 2*alpha*r, we have L_n >= u_0*r^{alpha+a-2}*(r+1)^n. In
particular, letting a = 2 yields an improvement to the best previous lower
bound on L_n (obtained by Hong and Yang) for all but three choices of alpha,r
>= 2.


title: Some equivariant constructions in noncommutative algebraic geometry

abstract:
  We here present rudiments of an approach to geometric actions in
noncommutative algebraic geometry, based on geometrically admissible actions of
monoidal categories. This generalizes the usual (co)module algebras over Hopf
algebras which provide affine examples. We introduce a compatibility of
monoidal actions and localizations which is a distributive law. There are
satisfactory notions of equivariant objects, noncommutative fiber bundles and
quotients in this setup.


title:
Low temperature resonances in the electron heat capacity and its
  spectral distribution in finite systems

abstract:
  Temperature variations of the heat capacity (C) are studied in a low
temperature regime for 2D-, and 3D-systems with N~100-10000 treated as a
canonical ensemble of N-noninteracting fermions. The analysis of C is performed
by introducing function q, the spectral distribution of C, that gives the
contribution of each single-particle state to C. This function has two peaks
divided by the energy interval ~(2-5)T. If at some temperature Tres there takes
place a resonance i.e. the positions of these peaks coincide with energies of
two levels nearest to Fermi enrgy then C vs T can show a local maximum at Tres.
This gives possibility to assess the single-particle level spacings near the
Fermi level.


title:
Metastable states influence on the magnetic behavior of the triangular
  lattice: Application to the spin-chain compound Ca3Co2O6

abstract:
  It is known that the spin-chain compound Ca3Co2O6 exhibits very interesting
plateaus in the magnetization as a function of the magnetic field at low
temperatures. The origin of them is still controversial. In this paper we study
the thermal behavior of this compound with a single-flip Monte Carlo simulation
on a triangular lattice and demonstrate the decisive influence of metastable
states in the splitting of the ferrimagnetic 1/3 plateau below 10 K. We
consider the [Co2O6]n chains as giant magnetic moments described by large Ising
spins on planar clusters with open boundary conditions. With this simple
frozen-moment model we obtain stepped magnetization curves which agree quite
well with the experimental results for different sweeping rates. We describe
particularly the out-of-equilibrium states that split the low-temperature 1/3
plateau into three steps. They relax thermally to the 1/3 plateau, which has
long-range order at the equilibrium. Such states are further analyzed with
snapshots unveiling a domain-wall structure that is responsible for the
observed behavior of the 1/3 plateau. A comparison is also given of the exact
results in small triangular clusters with our Monte Carlo results, providing
further support for our thermal description of this compound.


title: Two-way source coding with a helper

abstract:
  Consider the two-way rate-distortion problem in which a helper sends a common
limited-rate message to both users based on side information at its disposal.
We characterize the region of achievable rates and distortions where a Markov
form (Helper)-(User 1)-(User 2) holds. The main insight of the result is that
in order to achieve the optimal rate, the helper may use a binning scheme, as
in Wyner-Ziv, where the side information at the decoder is the "further" user,
namely, User 2. We derive these regions explicitly for the Gaussian sources
with square error distortion, analyze a trade-off between the rate from the
helper and the rate from the source, and examine a special case where the
helper has the freedom to send different messages, at different rates, to the
encoder and the decoder.


title: ABJM models in N=3 harmonic superspace

abstract:
  We construct the classical action of the Aharony-Bergman-Jafferis-Maldacena
(ABJM) model in the N=3, d=3 harmonic superspace. In such a formulation three
out of six supersymmetries are realized off shell while the other three mix the
superfields and close on shell. The superfield action involves two
hypermultiplet superfields in the bifundamental representation of the gauge
group and two Chern-Simons gauge superfields corresponding to the left and
right gauge groups. The N=3 superconformal invariance allows only for a minimal
gauge interaction of the hypermultiplets. Amazingly, the correct sextic scalar
potential of ABJM emerges after the elimination of auxiliary fields. Besides
the original U(N)xU(N) ABJM model, we also construct N=3 superfield
formulations of some generalizations. For the SU(2)xSU(2) case we give a simple
superfield proof of its enhanced N=8 supersymmetry and SO(8) R-symmetry.


title: Nonperturbative m_X cut effects in B -> Xs l+ l- observables

abstract:
  Recently, it was shown that in inclusive B -> Xs l+ l- decay, an angular
decomposition provides three independent (q^2 dependent) observables. A
strategy was formulated to extract all measurable Wilson coefficients in B ->
Xs l+ l- from a few simple integrals of these observables in the low q^2
region. The experimental measurements in the low q^2 region require a cut on
the hadronic invariant mass, which introduces a dependence on nonperturbative b
quark distribution functions. The associated hadronic uncertainties could
potentially limit the sensitivity of these decays to new physics. We compute
the nonperturbative corrections to all three observables at leading and
subleading order in the power expansion in \Lambda_QCD/m_b. We find that the
subleading power corrections give sizeable corrections, of order -5% to -10%
depending on the observable and the precise value of the hadronic mass cut.
They cause a shift of order -0.05 GeV^2 to -0.1 GeV^2 in the zero of the
forward-backward asymmetry.


title:
A step towards testing general relativity using weak gravitational
  lensing and redshift surveys

abstract:
  Using the linear theory of perturbations in General Relativity, we express a
set of consistency relations that can be observationally tested with current
and future large scale structure surveys. We then outline a stringent
model-independent program to test gravity on cosmological scales. We illustrate
the feasibility of such a program by jointly using several observables like
peculiar velocities, galaxy clustering and weak gravitational lensing. After
addressing possible observational or astrophysical caveats like galaxy bias and
redshift uncertainties, we forecast in particular how well one can predict the
lensing signal from a cosmic shear survey using an over-lapping galaxy survey.
We finally discuss the specific physics probed this way and illustrate how
$f(R)$ gravity models would fail such a test.


title:
Modeling the cosmological co-evolution of supermassive black holes and
  galaxies: II. The clustering of quasars and their dark environment

abstract:
  We use semi-analytic modeling on top of the Millennium simulation to study
the joint formation of galaxies and their embedded supermassive black holes.
  Our goal is to test scenarios in which black hole accretion and quasar
activity are triggered by galaxy mergers, and to constrain different models for
the lightcurves associated with individual quasar events. In the present work
we focus on studying the spatial distribution of simulated quasars. At all
luminosities, we find that the simulated quasar two-point correlation function
is fit well by a single power-law in the range 0.5 < r < 20 h^{-1} Mpc, but its
normalization is a strong function of redshift. When we select only quasars
with luminosities within the range typically accessible by today's quasar
surveys, their clustering strength depends only weakly on luminosity, in
agreement with observations. This holds independently of the assumed lightcurve
model, since bright quasars are black holes accreting close to the Eddington
limit, and are hosted by dark matter haloes with a narrow mass range of a few
10^12 h^{-1} M_sun. Therefore the clustering of bright quasars cannot be used
to disentangle lightcurve models, but such a discrimination would become
possible if the observational samples can be pushed to significantly fainter
limits.
  Overall, our clustering results for the simulated quasar population agree
rather well with observations, lending support to the conjecture that galaxy
mergers could be the main physical process responsible for triggering black
hole accretion and quasar activity.


title: Ultracold gases far from equilibrium

abstract:
  Ultracold atomic quantum gases belong to the most exciting challenges of
modern physics. Their theoretical description has drawn much from classical
field equations. These mean-field approximations are in general reliable for
dilute gases in which the atoms collide only rarely with each other, and for
situations where the gas is not too far from thermal equilibrium. With
present-day technology it is, however, possible to drive and observe a system
far away from equilibrium. Functional quantum field theory provides powerful
tools to achieve both, analytical understanding and numerical computability,
also in higher dimensions, of far-from-equilibrium quantum many-body dynamics.
In the article, an outline of these approaches is given, including methods
based on the two-particle irreducible effective action as well as on
renormalisation-group theory. Their relation to near-equilibrium kinetic theory
is discussed, and the distinction between quantum and classical statistical
fluctuations is shown to naturally emerge from the functional-integral
description. Example applications to the evolution of an ultracold atomic Bose
gas in one spatial dimension underline the power of the methods. The article is
compiled from the notes for lectures held at 46. Internationale
Universitaetswochen fuer Theoretische Physik 2008 in Schladming, Austria.


title: Stationary Measure in the Multiverse

abstract:
  We study the recently proposed "stationary measure" in the context of the
string landscape scenario. We show that it suffers neither from the "Boltzmann
brain" problem nor from the "youngness" paradox that makes some other measures
predict a high CMB temperature at present. We also demonstrate a satisfactory
performance of this measure in predicting the results of local experiments,
such as proton decay.


title: Scaling of entanglement entropy and superselection rules

abstract:
  Particle number conservation in fermionic systems restricts the allowed local
operations on bi-partite systems. We show how this restriction is related to
measurement entropy of particle fluctuations and compute it for several regimes
of practical relevance. The accessible entanglement entropy restricted by
particle number conservation is equal, to leading order, to the full
entanglement entropy. The correction is bounded by the log of the variance of
particle number fluctuations. The results are applied to generic Fermi systems
in dimension d>1 as well as to several critical systems in d=1.


title: The Role of Cold Flows in the Assembly of Galaxy Disks

abstract:
  We use high resolution cosmological hydrodynamical simulations to demonstrate
that cold flow gas accretion, particularly along filaments, modifies the
standard picture of gas accretion and cooling onto galaxy disks. In the
standard picture, all gas is initially heated to the virial temperature of the
galaxy as it enters the virial radius. Low mass galaxies are instead dominated
by accretion of gas that stays well below the virial temperature, and even when
a hot halo is able to develop in more massive galaxies there exist dense
filaments that penetrate inside of the virial radius and deliver cold gas to
the central galaxy. For galaxies up to ~L*, this cold accretion gas is
responsible for the star formation in the disk at all times to the present.
Even for galaxies at higher masses, cold flows dominate the growth of the disk
at early times. Within this modified picture, galaxies are able to accrete a
large mass of cold gas, with lower initial gas temperatures leading to shorter
cooling times to reach the disk. Although star formation in the disk is
mitigated by supernovae feedback, the short cooling times allow for the growth
of stellar disks at higher redshifts than predicted by the standard model.


title: On the Yang-Mills two-loop effective action with wordline methods

abstract:
  We derive the two-loop effective action for covariantly constant field
strength of pure Yang-Mills theory in the presence of an infrared scale. The
computation is done in the framework of the worldline formalism, based on a
generalization procedure of constructing multiloop effective actions in terms
of the bosonic worldline path integral. The two-loop beta-function is correctly
reproduced. This is the first derivation in the worldline formulation, and
serves as a nontrivial check on the consistency of the multiloop generalization
procedure in the worldline formalism.


title: The dynamics of satellite disruption in cold dark matter haloes

abstract:
  We investigate the physical mechanisms of tidal heating and satellite
disruption in cold dark matter host haloes using N-body simulations based on
cosmological initial conditions. We show the importance of resonant shocks and
resonant torques with the host halo to satellite heating. A resonant shock
(torque) couples the radial (tangential) motion of a satellite in its orbit to
its phase space. For a satellite on a circular orbit, an ILR-like resonance
dominates the heating and this heating results in continuous satellite mass
loss. We estimate the requirements for simulations to achieve these dynamics
using perturbation theory. Both resonant shocks and resonant torques affect
satellites on eccentric orbits. We demonstrate that satellite mass loss is an
outside-in process in energy space; a satellite's stars and gas are thus
protected by their own halo against tidal stripping. We simulate the evolution
of a halo similar to the Large Magellanic Cloud (LMC) in our Galactic dark
matter halo and conclude that the LMC stars have not yet been stripped.
Finally, we present a simple algorithm for estimating the evolution of
satellite mass that includes both shock heating and resonant torques.


title: Lyman-alpha constraints on warm and on warm-plus-cold dark matter models

abstract:
  We revisit Lyman-alpha bounds on the dark matter mass in Lambda Warm Dark
Matter (Lambda-WDM) models, and derive new bounds in the case of mixed Cold
plus Warm models (Lambda-CWDM), using a set up which is a good approximation
for several theoretically well-motivated dark matter models. We combine WMAP5
results with two different Lyman-alpha data sets, including observations from
the Sloan Digital Sky Survey. We pay a special attention to systematics, test
various possible sources of error, and compare the results of different
statistical approaches. Expressed in terms of the mass of a non-resonantly
produced sterile neutrino, our bounds read m_NRP > 8 keV (frequentist 99.7%
confidence limit) or m_NRP > 12.1 keV (Bayesian 95% credible interval) in the
pure Lambda-WDM limit. For the mixed model, we obtain limits on the mass as a
function of the warm dark matter fraction F_WDM. Within the mass range studied
here (5 keV < m_NRP < infinity), we find that any mass value is allowed when
F_WDM < 0.6 (frequentist 99.7% confidence limit); similarly, the Bayesian joint
probability on (F_WDM, 1/m_NRP) allows any value of the mass at the 95%
confidence level, provided that F_WDM < 0.35.


title:
Stability of the directly imaged multiplanet system HR 8799: resonance
  and masses

abstract:
  A new era of directly imaged extrasolar planets has produced a three-planet
system (Marois et al. 2008), where the masses of the planets have been
estimated by untested cooling models. We point out that the nominal circular,
face-on orbits of the planets lead to a dynamical instability in ~10^5 yr, a
factor of at least 100 shorter than the estimated age of the star. Reduced
planetary masses produce stability only for unreasonably small planets (<~2 M_
Jup). Relaxing the face-on assumption, but still requiring circular orbits
while fitting the observed positions, makes the instability time even shorter.
A promising solution is that the inner two planets have a 2:1 commensurability
between their periods, and they avoid close encounters with each other through
this resonance. That the inner resonance has lasted until now, in spite of the
perturbations of the outer planet, leads to a limit <~10 M_Jup on the masses
unless the outer two planets are also engaged in a 2:1 mean-motion resonance.
In a double resonance, which is consistent with the current data, the system
could survive until now even if the planets have masses of ~20 M_Jup. Apsidal
alignment can further enhance the stability of a mean-motion resonant system. A
completely different dynamical configuration, with large eccentricities and
large mutual inclinations among the planets, is possible but finely tuned.


title:
The n-body problem in General Relativity up to the second post-Newtonian
  order from perturbative field theory

abstract:
  Motivated by experimental probes of general relativity, we adopt methods from
perturbative (quantum) field theory to compute, up to certain integrals, the
effective lagrangian for its n-body problem. Perturbation theory is performed
about a background Minkowski spacetime to O[(v/c)^4] beyond Newtonian gravity,
where v is the typical speed of these n particles in their center of energy
frame. For the specific case of the 2 body problem, the major efforts underway
to measure gravitational waves produced by in-spiraling compact astrophysical
binaries require their gravitational interactions to be computed beyond the
currently known O[(v/c)^7]. We argue that such higher order post-Newtonian
calculations must be automated for these field theoretic methods to be applied
successfully to achieve this goal. In view of this, we outline an algorithm
that would in principle generate the relevant Feynman diagrams to an arbitrary
order in v/c and take steps to develop the necessary software. The Feynman
diagrams contributing to the n-body effective action at O[(v/c)^6] beyond
Newton are derived.


title: Three-Point Correlations in f(R) Models of Gravity

abstract:
  Modifications of general relativity provide an alternative explanation to
dark energy for the observed acceleration of the universe. We calculate
quasilinear effects in the growth of structure in f(R) models of gravity using
perturbation theory. We find significant deviations in the bispectrum that
depend on cosmic time, length scale and triangle shape. However the deviations
in the reduced bispectrum Q for f(R) models are at the percent level, much
smaller than the deviations in the bispectrum itself. This implies that
three-point correlations can be predicted to a good approximation simply by
using the modified linear growth factor in the standard gravity formalism. Our
results suggest that gravitational clustering in the weakly nonlinear regime is
not fundamentally altered, at least for a class of gravity theories that are
well described in the Newtonian regime by the parameters G_eff and Phi/Psi.
This approximate universality was also seen in the N-body simulation
measurements of the power spectrum by Stabenau and Jain (2006), and in other
recent studies based on simulations. Thus predictions for such modified gravity
models in the regime relevant to large-scale structure observations may be less
daunting than expected on first principles. We discuss the caveats that apply
to such predictions.


title:
XMM-Newton discovery of 2.6 s pulsations in the soft gamma-ray repeater
  SGR 1627-41

abstract:
  After nearly a decade of quiescence, the soft gamma-ray repeater SGR 1627-41
reactivated on 2008 May 28 with a bursting episode followed by a slowly
decaying enhancement of its persistent emission. To search for the still
unknown spin period of this SGR taking advantage of its high flux state, we
performed on 2008 September 27-28 a 120 ks long X-ray observation with the
XMM-Newton satellite. Pulsations with P = 2.594578(6) s were detected at a
higher than 6-sigma confidence level, with a double-peaked pulse profile. The
pulsed fraction in the 2-12 keV range is 19% +/- 3% and 24% +/- 3% for the
fundamental and the second harmonic, respectively. The observed 2-10 keV flux
is 3.4E-13 erg/cm^2/s, still a factor of ~ 5 above the quiescent
pre-burst-activation level, and the spectrum is well fitted by an absorbed
power law plus blackbody model (photon index Gamma = 0.6, blackbody temperature
kT = 0.5 keV, and absorption nH = 1.2E+23 cm^-2). We also detected a shell of
diffuse soft X-ray emission which is likely associated with the young supernova
remnant G337.0-0.1.


title:
Andreev Bound states as a phase sensitive probe of the pairing symmetry
  of the iron pnictide superconductors

abstract:
  A leading contender for the pairing symmetry in the Fe-pnictide high
temperature superconductors is extended s-wave $s_\pm$, a nodeless state in
which the pairing changes sign between Fermi surfaces. Verifying such a pairing
symmetry requires a special phase sensitive probe that is also momentum
selective. We show that the sign structure of $s_\pm$ pairing leads to surface
Andreev bound states at the sample edge. In the clean limit they only occur
when the edge is along the nearest neighbor Fe-Fe bond, but not for a diagonal
edge or a surface orthogonal to the c-axis. In contrast to d-wave Andreev bound
states, they are not at zero energy and, in general, do not produce a zero bias
tunneling peak. Consequences for tunneling measurements are derived, within a
simplified two band model and also for a more realistic five band model.


title:
Global Phase Diagram for Magnetism and Lattice Distortion of Fe-pnictide
  Materials

abstract:
  We study the global phase diagram of magnetic orders and lattice structure in
the Fe-pnictide materials at zero temperature within one unified theory, tuned
by both doping and pressure. On the low doping and high pressure side of the
phase diagram, there is one single transition, which is described by a $z=2$
mean field theory with very weak run-away flows; on the high doping and low
pressure side the transition is expected to split to two transitions, with one
O(3) spin density wave transition followed by a z = 3 quantum Ising transition
at larger doping. The fluctuation of the strain field fluctuation of the
lattice will not affect the spin density wave transition, but will likely drive
the Ising nematic transition more mean field like through a linear coupling, as
observed experimentally in BaFe_2-xCo_xAs_2.


title:
A note on the abelianizations of finite-index subgroups of the mapping
  class group

abstract:
  For some $g \geq 3$, let $\Gamma$ be a finite index subgroup of the mapping
class group of a genus $g$ surface (possibly with boundary components and
punctures). An old conjecture of Ivanov says that the abelianization of
$\Gamma$ should be finite. In this note, we prove two theorems supporting this
conjecture. For the first, let $T_x$ denote the Dehn twist about a simple
closed curve $x$. For some $n \geq 1$, we have $T_x^n \in \Gamma$. We prove
that $T_x^n$ is torsion in the abelianization of $\Gamma$. Our second result
shows that the abelianization of $\Gamma$ is finite if $\Gamma$ contains a
"large chunk" (in a certain technical sense) of the Johnson kernel, that is,
the subgroup of the mapping class group generated by twists about separating
curves. This generalizes work of Hain and Boggi.


title: A Turbulent Model of Gamma-Ray Burst Variability

abstract:
  A popular paradigm to explain the rapid temporal variability observed in
gamma-ray burst (GRB) lightcurves is the internal shock model. We propose an
alternative model in which the radiating fluid in the GRB shell is
relativistically turbulent with a typical eddy Lorentz factor $\gamma_t$. In
this model, all pulses in the gamma-ray lightcurve are produced at roughly the
same distance $R$ from the center of the explosion. The burst duration is $\sim
R/c\Gamma^2$, where $\Gamma$ is the bulk Lorentz factor of the expanding shell,
and the duration of individual pulses in the lightcurve is $\sim
R/c\Gamma^2\gamma_t^2$. The model naturally produces highly variable
lightcurves with $\sim\gamma_t^2$ individual pulses. Even though the model
assumes highly inhomogeneous conditions, nevertheless the efficiency for
converting jet energy to radiation is high.


title: Hessenberg Pairs of Linear Transformations

abstract:
  Let $\fld$ denote a field and $V$ denote a nonzero finite-dimensional vector
space over $\fld$. We consider an ordered pair of linear transformations $A: V
\to V$ and $A^*: V \to V$ that satisfy (i)--(iii) below. Each of $A, A^*$ is
diagonalizable on $V$. There exists an ordering $\lbrace V_i \rbrace_{i=0}^d$
of the eigenspaces of $A$ such that A^* V_i \subseteq V_0 + V_1 + ... + V_{i+1}
\qquad \qquad (0 \leq i \leq d), where $V_{-1} = 0$, $V_{d+1}= 0$. There exists
an ordering $\lbrace V^*_i \rbrace_{i=0}^{\delta}$ of the eigenspaces of $A^*$
such that A V^*_i \subseteq V^*_0 + V^*_1 + ... +V^*_{i+1} \qquad \qquad (0
\leq i \leq \delta), where $V^*_{-1} = 0$, $V^*_{\delta+1}= 0$. We call such a
pair a {\it Hessenberg pair} on $V$. In this paper we obtain some
characterizations of Hessenberg pairs. We also explain how Hessenberg pairs are
related to tridiagonal pairs.


title: Trace operators of modulation, alpha modulation and Besov spaces

abstract:
  In this paper, we consider the trace theorem for modulation spaces, alpha
modulation spaces and Besov spaces. For the modulation space, we obtain the
sharp results.


title:
Gamma-ray Burst 080319B: Evidence for Relativistic Turbulence, Not
  Internal Shocks

abstract:
  We show that the excellent optical and gamma-ray data available for GRB
080319B rule out the internal shock model for the prompt emission. The data
instead point to a model in which the observed radiation was produced close to
the deceleration radius ($\sim10^{17}$ cm) by a turbulent source with random
Lorentz factors $\sim10$ in the comoving frame. The optical radiation was
produced by synchrotron emission from relativistic electrons, and the
gamma-rays by inverse Compton scattering of the synchrotron photons. The
gamma-ray emission originated both in eddies and in an inter-eddy medium,
whereas the optical radiation was mostly from the latter. Therefore, the
gamma-ray emission was highly variable whereas the optical was much less
variable. The model explains all the observed features in the prompt optical
and gamma-ray data of GRB 080319B. We are unable to determine with confidence
whether the energy of the explosion was carried outward primarily by particles
(kinetic energy) or magnetic fields. Consequently, we cannot tell whether the
turbulent medium was located in the reverse shock (we can rule out the forward
shock) or in a Poynting-dominated jet.


title: Some Examples of Dynamics for Gelfand Tsetlin Patterns

abstract:
  We give examples of stochastic processes in the Gelfand Tsetlin cone in which
each component evolves independently apart from a blocking and pushing
interaction. The processes give couplings to certain conditioned Markov
processes, last passage times and asymetric exclusion processes. An example of
a cone valued process whose components cannot escape past a wall at the origin
is also considered.


title:
The WFC3 Galactic Bulge Treasury Program: A First Look at Resolved
  Stellar Population Tools

abstract:
  [Abridged] When WFC3 is installed on HST, the community will have powerful
new tools for investigating resolved stellar populations. The WFC3 Galactic
Bulge Treasury program will obtain deep imaging on 4 low-extinction fields.
These non-proprietary data will enable a variety of science investigations not
possible with previous data sets. To aid in planning for the use of these data
and for future proposals, we provide an introduction to the program, its
photometric system, and the associated calibration effort.
  The observing strategy is based upon a new 5-band photometric system spanning
the UV, optical, and near-infrared. With these broad bands, one can construct
reddening-free indices of Teff and [Fe/H]. Besides the 4 bulge fields, the
program will target 6 fields in well-studied star clusters, spanning a wide
range of [Fe/H]. The cluster data serve to calibrate the indices, provide
population templates, and correct the transformation of isochrones into the
WFC3 photometric system. The bulge data will shed light on the bulge formation
history, and will also serve as population templates for other studies. One of
the fields includes 12 candidate hosts of extrasolar planets.
  CMDs are the most popular tool for analyzing resolved stellar populations.
However, due to degeneracies among Teff, [Fe/H], and reddening in traditional
CMDs, it can be difficult to draw robust conclusions from the data. The 5-band
system used for the bulge Treasury observations will provide indices that are
roughly orthogonal in Teff and [Fe/H], and we argue that model fitting in an
index-index diagram will make better use of the information than fitting
separate CMDs. We provide simulations to show the expected data quality and the
potential for differentiating between different star-formation histories.


title: Electronic Transport at Low Temperatures: Diagrammatic Approach

abstract:
  We prove that a diagrammatic evaluation of the Kubo formula for the
electronic transport conductivity due the exchange of bosonic excitations, in
the usual conserving ladder approximation, yields a result consistent with the
Boltzmann equation. In particular, we show that an uncontrolled approximation
that has been used to solve the integral equation for the vertex function is
unnecessary. An exact solution of the integral equation yields the same
asymptotic low-temperature behavior as the approximate one, albeit with a
different prefactor, and agrees with the temperature dependence of the
Boltzmann solution. Examples considered are electron scattering from acoustic
phonons, and from helimagnons in helimagnets.


title: Small RNAs Establish Delays and Temporal Thresholds in Gene Expression

abstract:
  Non-coding RNAs are crucial regulators of gene expression in prokaryotes and
eukaryotes, but it remains poorly understood how they affect the dynamics of
transcriptional networks. We analyzed the temporal characteristics of the
cyanobacterial iron stress response by mathematical modeling and quantitative
experimental analyses, and focused on the role of a recently discovered small
non-coding RNA, IsrR. We found that IsrR is responsible for a pronounced delay
in the accumulation of isiA mRNA encoding the late-phase stress protein, IsiA,
and that it ensures a rapid decline in isiA levels once external stress
triggers are removed. These kinetic properties allow the system to selectively
respond to sustained (as opposed to transient) stimuli, and thus establish a
temporal threshold, which prevents energetically costly IsiA accumulation under
short-term stress conditions. Biological information is frequently encoded in
the quantitative aspects of intracellular signals (e.g., amplitude and
duration). Our simulations reveal that competitive inhibition and regulated
degradation allow intracellular regulatory networks to efficiently discriminate
between transient and sustained inputs.


title:
Temperature dependent Raman and x-ray studies of spin-ice pyrochlore
  $Dy_2Ti_2O_7$ and non-magnetic pyrochlore $Lu_2Ti_2O_7$

abstract:
  We present here temperature-dependent Raman, x-ray diffraction and specific
heat studies between room temperature and 12 K on single crystals of spin-ice
pyrochlore compound $Dy_2Ti_2O_7$ and its non-magnetic analogue $Lu_2Ti_2O_7$.
Raman data show a "new" band not predicted by factor group analysis of
Raman-active modes for the pyrochlore structure in $Dy_2Ti_2O_7$, appearing
below a temperature of $T_c=$110 K with a concomitant contraction of the cubic
unit cell volume as determined from the powder x-ray diffraction analysis. Low
temperature Raman experiments on O$^{18}$-isotope substituted $Dy_2Ti_2O_7$
confirm the phonon origin of the "new" mode. These findings, absent in
$Lu_2Ti_2O_7$, suggest that the room temperature cubic lattice of the
pyrochlore $Dy_2Ti_2O_7$ undergoes a "subtle" structural transformation near
$T_c$. We find anomalous \textit{red-shift} of some of the phonon modes in both
the $Dy_2Ti_2O_7$ and the $Lu_2Ti_2O_7$ as the temperature decreases, which is
attributed to strong phonon-phonon anharmonic interactions.


title: A Wreath Product Approach to Classical Subgroup Theorems

abstract:
  We provide elementary proofs of the Nielsen-Schreier Theorem and the Kurosh
Subgroup Theorem via wreath products. Our proofs are diagrammatic in nature and
work simultaneously in the abstract and profinite categories. A new proof that
open subgroups of quasifree profinite groups are quasifree is also given.


title:
Anomalies in electrostatic calibrations for the measurement of the
  Casimir force in a sphere-plane geometry

abstract:
  We have performed precision electrostatic calibrations in the sphere-plane
geometry and observed anomalous behavior. Namely, the scaling exponent of the
electrostatic signal with distance was found to be smaller than expected on the
basis of the pure Coulombian contribution and the residual potential found to
be distance dependent. We argue that these findings affect the accuracy of the
electrostatic calibrations and invite reanalysis of previous determinations of
the Casimir force.


title: A Smaller Radius for the Transiting Exoplanet WASP-10b

abstract:
  We present photometry of WASP-10 during the transit of its short-period
Jovian planet. We employed the novel PSF-shaping capabilities the OPTIC camera
mounted on the UH 2.2m telescope to achieve a photometric precision of 4.7e-4
per 1.3 min sample. With this new light curve, in conjunction with stellar
evolutionary models, we improve on existing measurements of the planetary,
stellar and orbital parameters. We find a stellar radius Rstar = 0.698 +/-
0.012 Rsun and a planetary radius Rp = 1.080 +/- 0.020 Rjup. The quoted errors
do not include any possible systematic errors in the stellar evolutionary
models. Our measurement improves the precision of the planet's radius by a
factor of 4, and revises the previous estimate downward by 16% (2.5sigma, where
sigma is the quadrature sum of the respective confidence limits). Our measured
radius of WASP-10b is consistent with previously published theoretical radii
for irradiated Jovian planets.


title: Review of Flicker Noise Spectroscopy in Electrochemistry

abstract:
  This review presents the fundamentals of Flicker-Noise Spectroscopy (FNS), a
general phenomenological methodology in which the dynamics and structure of
complex systems, characterized by nonlinear interactions, dissipation, and
inertia, are analyzed by extracting information from various signals with
stochastically varying components generated by the systems. The basic idea of
FNS is to treat the correlation links present in sequences of different
irregularities, such as spikes, "jumps", and discontinuities in derivatives of
different orders, on all levels of the spatiotemporal hierarchy of the system
under study as main information carriers. The tools to extract and analyze the
information are power spectra and difference moments (structural functions) of
various orders. Presently, FNS can be applied to three types of problems: (1)
determination of parameters or patterns that characterize the dynamics or
structural features of complex systems; (2) finding precursors of abrupt
changes in the state of various complex systems based on a priori information
about the dynamics of the systems; and (3) determination of flow dynamics in
distributed systems based on the analysis of dynamic correlations in stochastic
signals that are simultaneously measured at different points in space. Examples
of FNS applications to such problems as parameterization of the images produced
with atomic force microscopy (AFM), determination of precursors for electric
breakdowns and major earthquakes, and analysis of electric potential
fluctuations in electromembrane systems, as well as to some other problems in
electrochemistry and medicine are discussed.


title: Probing Quark-Gluon Interactions with Transverse Polarized Scattering

abstract:
  We have extracted QCD matrix elements from our data on double polarized
inelastic scattering of electrons on nuclei. We find the higher twist matrix
element \tilde{d_2}, which arises strictly from quark- gluon interactions, to
be unambiguously non zero. The data also reveal an isospin dependence of higher
twist effects if we assume that the Burkhardt-Cottingham Sum rule is valid. The
fundamental Bjorken sum rule obtained from the a0 matrix element is satisfied
at our low momentum transfer.


title: Homogeneous interpolation on ten points

abstract:
  In this paper we prove that for all pairs $(d,m)$ with $d/m \geq 174/55$, the
linear system of plane curves of degree $d$ with ten general base points of
multiplicity $m$ has the expected dimension.


title:
Multiplicative approximation of wealth processes involving no-short-sale
  strategies via simple trading

abstract:
  A financial market model with general semimartingale asset-price processes
and where agents can only trade using no-short-sales strategies is considered.
We show that wealth processes using continuous trading can be approximated very
closely by wealth processes using simple combinations of buy-and-hold trading.
This approximation is based on controlling the proportions of wealth invested
in the assets. As an application, the utility maximization problem is
considered and it is shown that optimal expected utilities and wealth processes
resulting from continuous trading can be approximated arbitrarily well by the
use of simple combinations of buy-and-hold strategies.


title: Inertia and gravitation in teleparallel gravity

abstract:
  Using the fact that teleparallel gravity allows a separation between
gravitation and inertia, explicit expressions for the gravitational and the
inertial energy-momentum densities are obtained. It is shown that, like all
other fields of nature, gravitation alone has a tensorial energy-momentum
density which in a general frame is conserved in the covariant sense. Together
with the inertial energy-momentum density, they form a pseudotensor which is
conserved in the ordinary sense. An analysis of the role played by the
gravitational and the inertial densities in the computation of the total energy
and momentum of gravity is presented.


title: The central value of the Rankin-Selberg $L$-functions

abstract:
  Let $f$ be a Maass form for $SL(3, \mathbb{Z})$ which is fixed and $u_j$ be
an orthonormal basis of even Maass forms for $SL(2, \mathbb{Z}),$ we prove an
asymptotic formula for the average of the product of the Rankin-Selberg
$L$-function of $f$ and $u_j$ and the $L$-function of $u_j$ at the central
value 1/2. This implies simultaneous nonvanishing results of these
$L$-functions at $1/2.$


title: Bounds for $GL(3)\times GL(2)$ $L$-functions and GL(3) $L$-functions

abstract:
  In this paper, we will give the subconvexity bounds for self dual GL(3)
$L-$functions in the $t$ aspect as well as subconvexity bounds for self dual
$GL(3)\times GL(2)$ $L-$functions in the GL(2) spectral aspect.


title: New Presentations of Thompson's Groups and Applications

abstract:
  We find new presentations for the Thompson's groups $F$, the derived group
$F^{'}$ and the intermediate group $D$. These presentations have a common
ground in that their relators are the same and only the generating sets differ.
As an application of these presentations we extract the following consequences:
the cost of the group $F^{'}$ is 1 hence the cost cannot decide the
(non)amenability question of $F$; the $II_1$ factor $L(F^{'})$ is inner
asymptotically abelian and the reduced $C^*$-algebra of $F$ is not residually
finite dimensional.


title: Omnidirectional Relay in Wireless Networks

abstract:
  For wireless networks with multiple sources, an omnidirectional relay scheme
is developed, where each node can simultaneously relay different messages in
different directions. This is accomplished by the decode-and-forward relay
strategy, with each relay binning the multiple messages to be transmitted, in
the same spirit of network coding. Specially for the all-source all-cast
problem, where each node is an independent source to be transmitted to all the
other nodes, this scheme completely eliminates interference in the whole
network, and the signal transmitted by any node can be used by any other node.
For networks with some kind of symmetry, assuming no beamforming is to be
performed, this omnidirectional relay scheme is capable of achieving the
maximum achievable rate.


title:
On the average indices of closed geodesics on positively curved Finsler
  spheres

abstract:
  In this paper, we prove that on every Finsler $n$-sphere $(S^n, F)$ for $n\ge
6$ with reversibility $\lambda$ and flag curvature $K$ satisfying
$(\frac{\lambda}{\lambda+1})^2<K\le 1$, either there exist infinitely many
prime closed geodesics or there exist $[\frac{n}{2}]-2$ closed geodesics
possessing irrational average indices. If in addition the metric is bumpy, then
there exist $n-3$ closed geodesics possessing irrational average indices
provided the number of closed geodesics is finite.


title: Simulations of waves in sunspots

abstract:
  Magnetic field modifies the properties of waves in a complex way. Significant
advances has been made recently in our understanding of the physics of waves in
solar active regions with the help of analytical theories, numerical
simulations, as well as hi-resolution observations. In this contribution we
review the current ideas in the field, with the emphasis on theoretical models
of waves in sunspots.


title:
Stability of closed characteristics on symmetric compact convex
  hypersurfaces in $\R^{2n}$

abstract:
  In this article, let $\Sigma\subset\R^{2n}$ be a compact convex hypersurface
which is symmetric with respect to the origin. We prove that if $\Sg$ carries
finitely many geometrically distinct closed characteristics, then at least
$n-1$ of them must be non-hyperbolic; if $\Sg$ carries exactly $n$
geometrically distinct closed characteristics, then at least two of them must
be elliptic.


title: Magnetic fingerprints of solar and stellar oscillations

abstract:
  Waves connect all the layers of the Sun, from its interior to the upper
atmosphere. It is becoming clear now the important role of magnetic field on
the wave propagation. Magnetic field modifies propagation speed of waves, thus
affecting the conclusions of helioseismological studies. It can change the
direction of the wave propagation, help channeling them straight up to the
corona, extending the dynamic and magnetic couplings between all the layers.
Modern instruments provide measurements of complex patterns of oscillations in
solar active regions and of tiny effects such as temporal oscillations of the
magnetic field. The physics of oscillations in a variety of magnetic structures
of the Sun is similar to that of pulsations of stars that posses strong
magnetic fields, such as roAp stars. All these arguments point toward a need of
systematic self-consistent modeling of waves in magnetic structures that is
able to take into account the complexity of the magnetic field configurations.
In this paper, we describe simulations of this kind, summarize our recent
findings and bring together results from the theory and observations.


title: The Narcowich-Wigner spectrum of a pure state

abstract:
  We completely characterize the Narcowich-Wigner spectrum of Wigner functions
associated with pure states.


title:
All path-symmetric pure states achieve their maximal phase sensitivity
  in conventional two-path interferometry

abstract:
  It is shown that the condition for achieving the quantum Cramer-Rao bound of
phase estimation in conventional two-path interferometers is that the state is
symmetric with regard to an (unphysical) exchange of the two paths. Since path
symmetry is conserved under phase shifts, the maximal phase sensitivity can be
achieved at arbitrary bias phases, indicating that path symmetric states can
achieve their quantum Cramer-Rao bound in Bayesian estimates of a completely
unknown phase.


title: On the Burns-Epstein invariants of spherical CR 3-manifolds

abstract:
  In this paper we develop a method to compute the Burns-Epstein invariant of a
spherical CR homology sphere, up to an integer, from its holonomy
representation. As application, we give a formula for the Burns-Epstein
invariant, modulo an integer, of a spherical CR structure on a Seifert fibered
homology sphere in terms of its holonomy representation.


title: Overview of the Orion Complex

abstract:
  The Orion star formation complex is the nearest region of on-going star
formation that continues to produce both low and high mass stars. Orion is
discussed in the larger context of star formation in the Solar vicinity over
the last 100 Myr. The Orion complex is located on the far side of the Gould's
Belt system of clouds and young stars throughwhich our Solar systemis drifting.
A review is given of the overall structure and properties of the Orion star
forming complex, the best studied OB association. Over the last 12 Myr, Orion
has given birth to at least ten thousand stars contained in a half dozen
sub-groups and short-lived clusters. The Orion OB association has been the
source of several massive, high-velocity run-away stars, including mu-Columbae
and AE Aurigae. Some of Orion's most massive members died in supernova
explosions that created the 300 pc diameter Orion / Eridanus super-bubble whose
near wall may be as close as 180 pc. The combined effects of UV radiation,
stellar winds, and supernovae have impacted surviving molecular clouds in
Orion. The large Orion A, IC 2118 molecular clouds and dozens of smaller clouds
strewn throughout the interior of the superbubble have cometary shapes pointing
back towards the center of the Orion OB association. Most are forming stars in
the compressed layers facing the bubble interior.


title: On a generalization of P(3,n)

abstract:
  By using techniques of poset representation theory, we present a formula for
the number of partitions of a positive integer into three polygonal numbers.


title:
Fabrication of graphene nanoribbon by local anodic oxidation lithography
  using atomic force microscope

abstract:
  We conducted local anodic oxidation (LAO) lithography in single-layer,
bilayer, and multilayer graphene using tapping-mode atomic force microscope.
The width of insulating oxidized area depends systematically on the number of
graphene layers. An 800-nm-wide bar-shaped device fabricated in single-layer
graphene exhibits the half-integer quantum Hall effect. We also fabricated a
55-nm-wide graphene nanoribbon (GNR). The conductance of the GNR at the charge
neutrality point was suppressed at low temperature, which suggests the opening
of an energy gap due to lateral confinement of charge carriers. These results
show that LAO lithography is an effective technique for the fabrication of
graphene nanodevices.


title:
Stability of closed characteristics on compact hypersurfaces in
  $\R^{2n}$ under pinching condition

abstract:
  In this article, let $\Sigma\subset\R^{2n}$ be a compact convex hypersurface
which is $(r, R)$-pinched with $\frac{R}{r}<\sqrt{{3/2}}$. Then $\Sg$ carries
at least two strictly elliptic closed characteristics; moreover, $\Sg$ carries
at least $2[\frac{n+2}{4}]$ non-hyperbolic closed characteristics.


title: Intersecting Attractors

abstract:
  We apply the entropy formalism to the study of the near-horizon geometry of
extremal black p-brane intersections in D>5 dimensional supergravities. The
scalar flow towards the horizon is described in terms an effective potential
given by the superposition of the kinetic energies of all the forms under which
the brane is charged. At the horizon active scalars get fixed to the minima of
the effective potential and the entropy function is given in terms of U-duality
invariants built entirely out of the black p-brane charges. The resulting
entropy function reproduces the central charges of the dual boundary CFT and
gives rise to a Bekenstein-Hawking like area law. The results are illustrated
in the case of black holes and black string intersections in D=6, 7, 8
supergravities where the effective potentials, attractor equations, moduli
spaces and entropy/central charges are worked out in full detail.


title: Indirect Cross-validation for Density Estimation

abstract:
  A new method of bandwidth selection for kernel density estimators is
proposed. The method, termed indirect cross-validation, or ICV, makes use of
so-called selection kernels. Least squares cross-validation (LSCV) is used to
select the bandwidth of a selection-kernel estimator, and this bandwidth is
appropriately rescaled for use in a Gaussian kernel estimator. The proposed
selection kernels are linear combinations of two Gaussian kernels, and need not
be unimodal or positive. Theory is developed showing that the relative error of
ICV bandwidths can converge to 0 at a rate of $n^{-1/4}$, which is
substantially better than the $n^{-1/10}$ rate of LSCV. Interestingly, the
selection kernels that are best for purposes of bandwidth selection are very
poor if used to actually estimate the density function. This property appears
to be part of the larger and well-documented paradox to the effect that "the
harder the estimation problem, the better cross-validation performs." The ICV
method uniformly outperforms LSCV in a simulation study, a real data example,
and a simulated example in which bandwidths are chosen locally.


title: Empirical study of indirect cross-validation

abstract:
  In this paper we provide insight into the empirical properties of indirect
cross-validation (ICV), a new method of bandwidth selection for kernel density
estimators. First, we describe the method and report on the theoretical results
used to develop a practical-purpose model for certain ICV parameters. Next, we
provide a detailed description of a numerical study which shows that the ICV
method usually outperforms least squares cross-validation (LSCV) in finite
samples. One of the major advantages of ICV is its increased stability compared
to LSCV. Two real data examples show the benefit of using both ICV and a local
version of ICV.


title: On the total mean curvature of non-rigid surfaces

abstract:
  Using Green's theorem we reduce the variation of the total mean curvature of
a smooth surface in the Euclidean 3-space to a line integral of a special
vector field and obtain the following well-known theorem as an immediate
consequence: the total mean curvature of a closed smooth surface in the
Euclidean 3-space is stationary under an infinitesimal flex.


title: Multi-pronged events from Coulomb fission of nuclei at very low energies

abstract:
  Multi-pronged tracks have been recorded in the polyethylene terephthalate
(C$_{10}$H$_8$O$_4$)$_n$ solid state nuclear track detector by exposure to a
$^{252}$Cf fission source. After chemical etching, two-prong to six-pronged
tracks along with single tracks have been observed under the optical
microscope. We carried out a systematic study to understand the origin of the
prongs. The track detectors were coated with metals (Cu, Ag and Pb) and were
exposed to $^{252}$Cf source. After chemical etching two-prong to four pronged
tracks were observed in each plate. We believe that at this very low energy of
the order of 1 MeV/A, Coulomb fission is the only plausible explanation for the
origin of such multi-pronged tracks.


title: Membrane simulation models from nm to $\mu$m scale

abstract:
  Recent developments in lipid membrane models for simulations are reviewed. To
reduce computational costs, various coarse-grained molecular models have been
proposed. Among them, implicit solvent (solvent-free) molecular models are
relatively more coarse-grained and efficient for simulating large bilayer
membranes. On a $\mu$m scale, the molecular details are typically negligible
and the membrane can be described as a continuous curved surface. The
theoretical models for fluid and elastic membranes with mesh or meshless
discretizations are presented. As examples of applications, the dynamics of
vesicles in flows, vesicle formation, and membrane fusion are presented.


title:
Phenomenological theory of phase transitions in epitaxial BaxSr(1-x)TiO3
  thin films

abstract:
  A phenomenological thermodynamic theory of BaxSr(1-x)TiO3 (BST-x) thin films
epitaxially grown on cubic substrates is developed using the Landau-Devonshire
approach. The eighth-order thermodynamic potential for BT single crystal and
modified fourth-order potential for ST single crystal were used as starting
potentials for the end-members of the solid solution with the aim to develop
potential of BST-$x$ solid solution valid at high temperatures. Several
coefficients of these potentials for BT were changed to obtain reasonable
agreement between theory and experimental phase diagram for BST-x (x > 0.2)
solid solutions. For low Ba content we constructed the specific phase diagram
where five phases converge at the multiphase point (T_N2 = 47 K, x = 0.028) and
all transitions are of the second order. The "concentration-misfit strain"
phase diagrams for BST-x thin films at room temperature and "temperature-misfit
strain" phase diagrams for particular concentrations are constructed and
discussed. Near T_N2 coupling between polarization and structural order
parameter in the epitaxial film is modified considerably and large number of
new phases not present in the bulk materials appear on the phase diagram.


title:
A model for unsteady mixed flows in non uniform closed water pipes and a
  well-balanced finite volume scheme

abstract:
  We present the derivation of a new unidirectional model for We present the
derivation of a new unidirectional model for unsteady mixed flows in non
uniform closed water pipes. We introduce a local reference frame to take into
account the local perturbation caused by the changes of section and slope. Then
an asymptotic analysis is performed to obtain a model for free surface flows
and another one for pressurized flows. By coupling these models through the
transition points by the use of a common set of variables and a suitable
pressure law, we obtain a simple formulation called PFS-model close to the
shallow water equations with source terms. It takes into account the changes of
section and the slope variation in a continuous way through transition points.
Transition point between the two types of flows is treated as a free boundary
associated to a discontinuity of the gradient of pressure. The numerical
simulation is performed by making use of a Roe-like finite volume scheme that
we adapted to take into account geometrical source terms in the convection
matrix. Finally some numerical tests are presented.


title:
Equivalence of Control Systems with Linear Systems on Lie Groups and
  Homogeneous Spaces

abstract:
  The aim of this paper is to prove that a control affine system on a manifold
is equivalent by diffeomorphism to a linear system on a Lie group or a
homogeneous space if and only the vector fields of the system are complete and
generate a finite dimensional Lie algebra. A vector field on a connected Lie
group is linear if its flow is a one parameter group of automorphisms. An
affine vector field is obtained by adding a left invariant one. Its projection
on a homogeneous space, whenever it exists, is still called affine. Affine
vector fields on homogeneous spaces can be characterized by their Lie brackets
with the projections of right invariant vector fields. A linear system on a
homogeneous space is a system whose drift part is affine and whose controlled
part is invariant. The main result is based on a general theorem on finite
dimensional algebras generated by complete vector fields, closely related to a
theorem of Palais, and which have its own interest. The present proof makes use
of geometric control theory arguments.


title: Multiplicities of the discrete series

abstract:
  The purpose of this paper is to show that the multiplicities of a discrete
series representation relatively to a compact subgroup can be "computed"
geometrically, in the way predicted by the "qantization commutes with
reduction" principle of Guillemin-Sternberg.


title: Cutoff phenomena for random walks on random regular graphs

abstract:
  The cutoff phenomenon describes a sharp transition in the convergence of a
family of ergodic finite Markov chains to equilibrium. Many natural families of
chains are believed to exhibit cutoff, and yet establishing this fact is often
extremely challenging. An important such family of chains is the random walk on
$\G(n,d)$, a random $d$-regular graph on $n$ vertices. It is well known that
almost every such graph for $d\geq 3$ is an expander, and even essentially
Ramanujan, implying a mixing-time of $O(\log n)$. According to a conjecture of
Peres, the simple random walk on $\G(n,d)$ for such $d$ should then exhibit
cutoff with high probability. As a special case of this, Durrett conjectured
that the mixing time of the lazy random walk on a random 3-regular graph is
w.h.p. $(6+o(1))\log_2 n$.
  In this work we confirm the above conjectures, and establish cutoff in
total-variation, its location and its optimal window, both for simple and for
non-backtracking random walks on $\G(n,d)$. Namely, for any fixed $d\geq3$, the
simple random walk on $\G(n,d)$ w.h.p. has cutoff at $\frac{d}{d-2}\log_{d-1}
n$ with window order $\sqrt{\log n}$. Surprisingly, the non-backtracking random
walk on $\G(n,d)$ w.h.p. has cutoff already at $\log_{d-1} n$ with constant
window order. We further extend these results to $\G(n,d)$ for any $d=n^{o(1)}$
that grows with $n$ (beyond which the mixing time is O(1)), where we establish
concentration of the mixing time on one of two consecutive integers.


title: Hyperoctahedral Chen calculus for effective Hamiltonians

abstract:
  The algebraic structure of iterated integrals has been encoded by Chen.
Formally, it identifies with the shuffle and Lie calculus of Lyndon, Ree and
Sch\"utzenberger. It is mostly incorporated in the modern theory of free Lie
algebras. Here, we tackle the problem of unraveling the algebraic structure of
computations of effective Hamiltonians. This is an important subject in view of
applications to chemistry, solid state physics, quantum field theory or
engineering. We show, among others, that the correct framework for these
computations is provided by the hyperoctahedral group algebras. We define
several structures on these algebras and give various applications. For
example, we show that the adiabatic evolution operator (in the time-dependent
interaction representation of an effective Hamiltonian) can be written
naturally as a Picard-type series and has a natural exponential expansion.


title: Configurations of infinitely near points

abstract:
  We present a survey of some aspects and new results on configurations, i.e.
disjoint unions of constellations of infinitely near points, local and global
theory, with some applications and results on generalized Enriques diagrams,
singular foliations, and linear systems defined by clusters.


title: Some Orthogonal Polynomials in Four Variables

abstract:
  The symmetric group on 4 letters has the reflection group $D_{3}$ as an
isomorphic image. This fact follows from the coincidence of the root systems
$A_{3}$ and $D_{3}$. The isomorphism is used to construct an orthogonal basis
of polynomials of 4 variables with 2 parameters. There is an associated quantum
Calogero-Sutherland model of 4 identical particles on the line.


title: Fourth Generation Leptons and Muon $g-2$

abstract:
  We consider the contributions to $g_\mu-2$ from fourth generation heavy
neutral and charged leptons, $N$ and $E$, at the one-loop level.
Diagrammatically, there are two types of contributions: boson-boson-$N$, and
$E$-$E$-boson in the loop diagram. In general, the effect from $N$ is
suppressed by off-diagonal lepton mixing matrix elements. For $E$, we consider
flavor changing neutral couplings arising from various New Physics models,
which are stringently constrained by $\mu\to e\gamma$. We assess how the
existence of a fourth generation would affect these New Physics models.


title: Morphogenesis and dynamics of quantum state

abstract:
  New construction of 4D dynamical space-time (DST) has been proposed in the
framework of unification of relativity and quantum theory. Such unification is
based solely on the fundamental notion of generalized coherent state (GCS) of
N-level system and the geometry of unitary group SU(N) acting in state space
$C^N$. Neither contradictable notion of quantum particle, nor space-time
coordinates (that cannot be a priori attached to nothing) are used in this
construction. Morphogenesis of the "field shell"-lump of GCS and its dynamics
have been studied for N=2 in DST. The main technical problem is to find
non-Abelian gauge field arising from conservation law of the local Hailtonian
vector field. The last one may be expressed as parallel transport of local
Hamiltonian in projective Hilbert space $CP(N-1)$. Co-movable local "Lorentz
frame" being attached to GCS is used for qubit encoding result of comparison of
the parallel transported local Hamiltonian in infinitesimally close points.
This leads to quasi-linear relativistic field equations with soliton-like
solutions for "field shell" in emerged DST. The terms "comparison" and
"encoding" resemble human's procedure, but here they have objective content
realized in invariant quantum dynamics. The dynamical motion of the lump in DST
may be associated with "kinesis" time whereas the evolution parameter
describing morphogenesis of GCS evolving in $CP(N-1)$, may be naturally
identified with "metabole" time.


title: Potential functions via toric degenerations

abstract:
  This is a short companion paper to arXiv:0810.3470. We construct an
integrable system on an open subset of a Fano manifold equipped with a toric
degeneration, and compute the potential function for its Lagrangian torus
fibers if the central fiber is a toric Fano variety admitting a small
resolution.


title: Stable normal forms for polynomial system solving

abstract:
  This paper describes and analyzes a method for computing border bases of a
zero-dimensional ideal $I$. The criterion used in the computation involves
specific commutation polynomials and leads to an algorithm and an
implementation extending the one provided in [MT'05]. This general border basis
algorithm weakens the monomial ordering requirement for \grob bases
computations. It is up to date the most general setting for representing
quotient algebras, embedding into a single formalism Gr\"obner bases, Macaulay
bases and new representation that do not fit into the previous categories. With
this formalism we show how the syzygies of the border basis are generated by
commutation relations. We also show that our construction of normal form is
stable under small perturbations of the ideal, if the number of solutions
remains constant. This new feature for a symbolic algorithm has a huge impact
on the practical efficiency as it is illustrated by the experiments on
classical benchmark polynomial systems, at the end of the paper.


title: Centrifugal deformations of the gravitational kink

abstract:
  The Kaluza-Klein reduction of 4d conformally flat spacetimes is reconsidered.
The corresponding 3d equations are shown to be equivalent to 2d gravitational
kink equations augmented by a centrifugal term. For space-like gauge fields and
non-trivial values of the centrifugal term the gravitational kink solutions
describe a spacetime that is divided in two disconnected regions.


title:
Post-Newtonian corrections to the gravitational-wave memory for
  quasicircular, inspiralling compact binaries

abstract:
  The Christodoulou memory is a nonlinear contribution to the
gravitational-wave field that is sourced by the gravitational-wave
stress-energy tensor. For quasicircular, inspiralling binaries, the
Christodoulou memory produces a growing, nonoscillatory change in the
gravitational-wave "plus" polarization, resulting in the permanent displacement
of a pair of freely-falling test masses after the wave has passed. In addition
to its nonoscillatory behavior, the Christodoulou memory is interesting because
even though it originates from 2.5 post-Newtonian (PN) order multipole
interactions, it affects the waveform at leading (Newtonian/quadrupole) order.
The memory is also potentially detectable in binary black-hole mergers. While
the oscillatory pieces of the gravitational-wave polarizations for
quasicircular, inspiralling compact binaries have been computed to 3PN order,
the memory contribution to the polarizations has only been calculated to
leading order (the next-to-leading order 0.5PN term has previously been shown
to vanish). Here the calculation of the memory for quasicircular, inspiralling
binaries is extended to 3PN order. While the angular dependence of the memory
remains qualitatively unchanged, the PN correction terms tend to reduce the
memory's magnitude. Explicit expressions are given for the memory contributions
to the plus polarization and the spin-weighted spherical-harmonic modes of the
metric and curvature perturbations. Combined with the recent results of
Blanchet et al.(2008), this completes the waveform to 3PN order. This paper
also discusses: (i) the difficulties in extracting the memory from numerical
simulations, (ii) other nonoscillatory effects that enter the waveform at high
PN orders, and (iii) issues concerning the observability of the memory.


title:
An Integrated Software-based Solution for Modular and Self-independent
  Networked Robot

abstract:
  An integrated software-based solution for a modular and self-independent
networked robot is introduced. The wirelessly operatable robot has been
developed mainly for autonomous monitoring works with full control over web.
The integrated software solution covers three components : a) the digital
signal processing unit for data retrieval and monitoring system; b) the
externally executable codes for control system; and c) the web programming for
interfacing the end-users with the robot. It is argued that this integrated
software-based approach is crucial to realize a flexible, modular and low
development cost mobile monitoring apparatus.


title:
Bifurcation and Secondary Bifurcation of Heavy Periodic Hydroelastic
  Travelling Waves

abstract:
  The paper deals with a problem of interaction between hydrodynamics and
mechanics of nonlinear elastic bodies. The existence question for
two-dimensional symmetric steady waves travelling on the surface of a deep
ocean beneath a heavy elastic membrane is analyzed as a problem in bifurcation
theory. The behaviour of the two-dimensional cross-section of the membrane is
modelled as a thin (unshearable), heavy, hyperelastic Cosserat rod, following
Antman's elasticity theory, and the fluid beneath is supposed to be in steady
2D irrotational motion under gravity. Assuming that gravity and the density of
the undeformed membrane are prescribed, the free parameters of the problem are
the speed of the wave and drift velocity of the membrane.
  The analysis relies upon a conformal formulation of the hydro-elastic problem
developed in previous papers; the basic tool for the study of the bifurcation
picture is the implicit function theorem, under some non-resonance assumptions.
  The most interesting part of the final result is the existence of a
symmetry-breaking 'third sheet' of solutions, which bifurcates from primary
sheets, and is a hydro-elastic analogue of the phenomenon known as 'Wilton
ripples' in the surface tension case.


title: Breit-Wigner Enhancement of Dark Matter Annihilation

abstract:
  We point out that annihilation of dark matter in the galactic halo can be
enhanced relative to that in the early universe due to a Breit-Wigner tail, if
the dark matter annihilates through a pole just below the threshold. This
provides a new explanation to the "boost factor" which is suggested by the
recent data of the PAMELA, ATIC and PPB-BETS cosmic-ray experiments.


title: Brownian Brownian Motion-1

abstract:
  A classical model of Brownian motion consists of a heavy molecule submerged
into a gas of light atoms in a closed container. In this work we study a 2D
version of this model, where the molecule is a heavy disk of mass M and the gas
is represented by just one point particle of mass m = 1, which interacts with
the disk and the walls of the container via elastic collisions. Chaotic
behavior of the particles is ensured by convex (scattering) walls of the
container. We prove that the position and velocity of the disk, in an
appropriate time scale, converge, as M tends to infinity, to a Brownian motion
(possibly, inhomogeneous); the scaling regime and the structure of the limit
process depend on the initial conditions. Our proofs are based on strong
hyperbolicity of the underlying dynamics, fast decay of correlations in systems
with elastic collisions (billiards), and methods of averaging theory.


title: Relative entropy of entanglement of rotationally invariant states

abstract:
  We calculate the relative entropy of entanglement for rotationally invariant
states of spin-1/2 and arbitrary spin-$j$ particles or of spin-1 particle and
spin-$j$ particle with integer $j$. A lower bound of relative entropy of
entanglement and an upper bound of distillable entanglement are presented for
rotationally invariant states of spin-1 particle and spin-$j$ particle with
half-integer $j$.


title: Nearly-optimal estimates for the stability problem in Hardy spaces

abstract:
  We continue the work of \cite{TLNT}. Let $E$ be a non-Blaschke subset of the
unit disc $\mathbb{D}$ of the complex plane $\mathbb{C}$. Fixed $1\leq p\leq
\infty$, let $H^p(\mathbb{D})$ be the Hardy space of holomorphic functions in
the disk whose boundary value function is in $L^p(\partial \mathbb{D})$. Fixed
$0<R<1$. For $\epsilon >0$ define C_p(\varepsilon, R) = \sup \{\sup_{|z| \leq
R}|g(z)|: g\in H^p, \|g\|_p\leq 1, |g(\zeta)| \leq \varepsilon \forall \zeta\in
E\}. In this paper we find upper and lower bounds for $C_p(\epsilon, R)$ when
$\epsilon$ is small for any non-Blaschke set $E$. The bounds are nearly-optimal
for many such sets $E$, including sets contained in a compact subset of
$\mathbb{D}$ and sets contained in a finite union of Stolz angles.


title: Note on potential theory for functions in Hardy classes

abstract:
  The purpose of this note is to show that the set functions defined in
\cite{trong-tuyen} can be suitably extended to all subsets $E$ of the unit disk
$\mathbb{D}$. In particular we obtain uniform nearly-optimal estimates for the
following quantity D_p(E,\epsilon, R) = \sup \{\sup_{|z| \leq R}|g(z)|: g\in
H^p, ||g||_{H^p}\leq 1, (1-|\zeta |)|g(\zeta)| \leq \epsilon \forall \zeta\in
E\}.


title: The Powers Sum of spatial CPD-semigroups and CP-semigroups

abstract:
  We define spatial CPD-semigroup and construct their Powers sum. We construct
the Powers sum for general spatial CP-semigroups. In both cases, we show that
the product system of that Powers sum is the product of the spatial product
systems of its factors. We show that on the domain of intersection, pointwise
bounded CPD-semigroups on the one side and Schur CP-semigroups on the other,
the constructions coincide. This summarizes all known results about Powers sums
and generalizes them considerably.


title:
Plane Gravitational Radiation from Neutrinos Source with Kalb-Ramond
  Coupling

abstract:
  In this work, we propose a model based on a non-minimal coupling of neutrinos
to a Kalb-Ramond field. The latter is taken as a possible source for
gravitational radiation. As an immediate illustration of this system, we have
studied the case where gravitational (plane) wave solutions behave as damped
harmonic oscillators.


title: Impurity crystal in a Bose-Einstein condensate

abstract:
  We investigate the behavior of impurity fields immersed in a larger
condensate field in 1, 2, and 3 dimensions. We discuss the localization of a
single impurity field within a condensate and note the effects of surface
energy. We derive the functional form of the attractive interaction between two
impurities due to mediation from the condensate. Generalizing the analysis to
$N$ impurity fields, we show that within various parameter regimes a crystal of
impurity fields can form spontaneously in the condensate. Finally, the system
of condensate and crystallized impurity structure is shown to have nonclassical
rotational inertia, which is characteristic of superfluidity, i.e. the system
can be seen to exhibit supersolid behavior.


title: $\omega$-Lie algebras

abstract:
  We study a certain generalization of Lie algebras where the Jacobian of three
elements does not vanish but is equal to an expression depending on a
skew-symmetric bilinear form.


title: Sprouts game on compact surfaces

abstract:
  Sprouts is a two-player topological game, invented in 1967 by Michael
Paterson and John Conway. The game starts with p spots drawn on a sheet of
paper, and lasts at most 3p-1 moves: the player who makes the last move wins.
  Sprouts is a very intricate game and the best known manual analysis only
achieved to find a winning strategy up to p=7 spots. Recent computer analysis
reached up to p=32.
  The standard game is played on a plane, or equivalently on a sphere. In this
article, we generalize and study the game on any compact surface.
  First, we describe the possible moves on a compact surface, and the way to
implement them in a program. Then, we show that we only need to consider a
finite number of surfaces to analyze the game with p spots on any compact
surface: if we take a surface with a genus greater than some limit genus, then
the game on this surface is equivalent to the game on some smaller surface.
Finally, with computer calculation, we observe that the winning player on
orientable surfaces seems to be always the same one as on a plane, whereas
there are significant differences on non-orientable surfaces.


title: QCD Corrections to the Radiative Decay B -> X_s gamma

abstract:
  In this short review, the calculation of the next-to-next-to-leading order
QCD corrections to the inclusive radiative decay B -> X_s gamma is described. I
summarize the salient features of the calculational framework adopted, discuss
the results obtained in the last few years, and indicate the technical tools
that made the NNLO calculations possible. I conclude by comparing the current
NNLO theoretical estimate for the branching ratio with the experimental
measurement and by briefly discussing the size and origin of the residual
theoretical uncertainty.


title:
On convergence of the optimization process in Radiotherapy treatment
  planning

abstract:
  The Radiotherapy treatment planning optimization process based on a
quasi-Newton algorithm with an object function containing dose-volume
constraints is not guaranteed to converge when the dose value in the
dose-volume constraint is a critical value of the dose distribution. This is
caused by finite differentiability of the dose-volume histogram at such values.
A closer look near such values reveals that convergence is most likely not at
stake, but it might be slowed down.


title:
Neutrino masses and mixing, lightest neutralino decays and a solution to
  the $\mu$ problem in supersymmetry

abstract:
  We examine in detail the neutrino masses and mixing patterns in an extension
of the minimal supersymmetric standard model with three gauge-singlet neutrinos
and R-parity violation. The Majorana masses for the gauge-singlet neutrinos as
well as the usual $\mu$-term for the Higgs superfields are generated at the
electroweak scale through the vacuum expectation values of the singlet
sneutrinos. The resulting effective mass matrix for the three light neutrinos
have contributions from the seesaw mechanism involving the singlet neutrinos as
well as due to the mixing with the heavy neutralinos. This model is popularly
known in the literature as the "$\mu$ from $\nu$ supersymmetric standard model"
($\mu\nu$SSM). We show that even with flavour diagonal neutrino Yukawa
couplings, the global data on three-flavour neutrinos can be well accounted for
in this scenario, at the tree level. We also analyze the mixing in the chargino
and the Higgs sector and calculate the decays of the lightest supersymmetric
particle in this model. The decay branching ratios show certain correlations
with the neutrino mixing angles, which can be tested at the LHC. Some other
phenomenological implications of such a model have been discussed.


title: Large N

abstract:
  I review some of the things we have learned about large N gauge theories (and
QCD at N=oo) from lattice calculations in recent years. I point to some open
problems.


title:
Isotope effect on the E2g phonon and mesoscopic phase separation near
  the electronic topological transition in Mg1-xAlxB2

abstract:
  We report the boron isotope effect on the E2g phonon mode by micro-Raman
spectroscopy on the ternary Mg1-xAlxB2 system, synthesized with pure isotopes
10B and 11B. The isotope coefficient on the phonon frequency is near 0.5 in the
full range decreasing near x = 0. The intraband electron-phonon (e-ph)
coupling, for the electrons in the sigma band, has been extracted from the E2g
line-width and frequency softening. Tuning the Fermi energy near the electronic
topological transition (ETT), where the sigma Fermi surface changes from 2D to
3D topology the E2g mode, shows the known Kohn anomaly on the 2D side of the
ETT and a splitting of the E2g phonon frequency into a hard and soft component
from x = 0 to x = 0.28. The results suggest a minor role of the intraband
phonon mediated pairing in the control of the high critical temperature in
Mg1-xAlxB2. The common physical features of diborides with the novel multigap
FeAs-based superconductors and cuprates is discussed.


title:
Consequences of a unified, anarchical model of fermion masses and
  mixings

abstract:
  We show that most features of the mass and mixing pattern of the second and
third SM fermion families can be accounted for without making use of flavour
symmetries or other types of flavour dynamics. We discuss the implications for
flavour phenomenology, in particular for the $\tau\to\mu\gamma$ decay rate, and
comment on LFV effects at colliders. We show that the model can be embedded in
a full SO(10) supersymmetric GUT in 5 dimensions that preserves the successful
MSSM gauge coupling unification prediction for $\alpha_s$. Interesting features
of this embedding are i) the connection of one of the hierarchy parameters with
the strong coupling assumption, ii) the absence of KK threshold effects on the
$\alpha_s$ prediction at one loop, and iii) the shift of the GUT scale up to
about $10^{17}\GeV$. Proton decay is under control, also due to the larger GUT
scale. A large atmospheric angle for normal hierarchical neutrinos is obtained
in an unusual way.


title: Moment matrices, trace matrices and the radical of ideals

abstract:
  Let $f_1,...,f_s \in \mathbb{K}[x_1,...,x_m]$ be a system of polynomials
generating a zero-dimensional ideal $\I$, where $\mathbb{K}$ is an arbitrary
algebraically closed field. Assume that the factor algebra
$\A=\mathbb{K}[x_1,...,x_m]/\I$ is Gorenstein and that we have a bound
$\delta>0$ such that a basis for $\A$ can be computed from multiples of
$f_1,...,f_s$ of degrees at most $\delta$. We propose a method using Sylvester
or Macaulay type resultant matrices of $f_1,...,f_s$ and $J$, where $J$ is a
polynomial of degree $\delta$ generalizing the Jacobian, to compute moment
matrices, and in particular matrices of traces for $\A$. These matrices of
traces in turn allow us to compute a system of multiplication matrices
$\{M_{x_i}|i=1,...,m\}$ of the radical $\sqrt{\I}$, following the approach in
the previous work by Janovitz-Freireich, R\'{o}nyai and Sz\'ant\'o.
Additionally, we give bounds for $\delta$ for the case when $\I$ has finitely
many projective roots in $\mathbb{P}^m_\CC$.


title: Extending the Set of Quadratic Exponential Vectors

abstract:
  We extend the square of white noise algebra over the step functions on R to
the test function space of bounded square-integrable functions on R^d, and we
show that in the Fock representation the exponential vectors exist for all test
functions bounded by 1/2.


title: All-optical 3D atomic loops generated with Bessel light fields

abstract:
  The propagation invariance of Bessel beams as well as their transversal
structure are used to perform a comparative analysis of their effect on cold
atoms for four different configurations and combinations thereof. We show that,
even at temperatures for which the classical description of the atom center of
mass motion is valid, the interchange of momentum, energy and orbital angular
momentum between light and atoms yields efficient tools for all-optical
trapping, transporting and, in general, manipulating the state of motion of
cold atoms.


title: AGATA: Gamma-ray tracking in segmented HPGe detectors

abstract:
  The next generation of radioactive ion beam facilities, which will give
experimental access to many exotic nuclei, are presently being developed. At
the same time the next generation of high resolution gamma-ray spectrometers,
based on gamma-ray tracking, for studying the structure of these exotic nuclei
are being developed. One of the main differences in tracking of $\gamma$ rays
versus charged particles is that the gamma rays do not deposit their energy
"continuously" in the detector, but in a few discrete steps. Also, in the field
of nuclear spectroscopy, the location of the source is mostly well known while
the exact interaction position in the detector is the unknown quantity. This
makes the challenges of gamma-ray tracking in germanium somewhat different
compared to vertexing in silicon detectors. In these proceedings we present the
methods for determining the 3D interaction positions in the detector and how
these are used to reconstruct the gamma-ray tracks in the AGATA detector array.
We also present preliminary simulation results of a proposed in-beam method to
measure the interaction position resolution in the germanium detectors.


title: Minimally Doubled Fermion Revival

abstract:
  In this paper, we present the recent progress on minimally doubled lattice
actions. In particular, we discuss the proposal of Creutz and its variations on
an orthogonal lattice. A preliminary computation of the pion mass on an SU(3)
background field shows the expected behaviour as predicted form the chiral
perturbation theory.


title: Preferred basis without decoherence

abstract:
  The aim of this paper is to argue that the "preferred basis problem" is not a
real problem in measurement. We will show that, given an apparatus, among the
infinite corrrelations that can be established in the final state by means of a
change of basis, one and only one makes physical sense. It is the apparatus,
through its interaction Hamiltonian, what selects a single basis and determines
the observable to be measured, even without decoherence.


title: A rank inequality for the Tate Conjecture over global function fields

abstract:
  Following D. Ramakrishnan, we explain how L. Lafforgue's modularity theorem
and an analytic theorem of H. Jacquet and J. Shalika can be applied to prove
the following result related to the Tate Conjecture: for a smooth, projective,
geometrically-connected variety defined over a global function field, the
algebraic rank is less than or equal to the analytic rank.
  Also discussed is the analogous (open) question for number fields and an easy
extension of Lafforgue's theorem to remove the "finite-order character"
assumption. All results are likely "known to the experts", but don't appear to
be written down.


title:
Atomistic modeling of the electrostatic and transport properties of a
  simplified nanoscale field effect transistor

abstract:
  A first-principle model is proposed to study the electrostatic properties of
a double-gated silicon slab of nano scale in the framework of density
functional theory. The applied gate voltage is approximated as a variation of
the electrostatic potential on the boundary of the supercell enclosing the
system. With the electron density estimated by the real space Green's
functions, efficient multigrid and fast Fourier Poisson solvers are employed to
calculate the electrostatic potential from the charge density. In the
representation of localized SIESTA linear combination of atomic orbitals, the
Kohn-Sham equation is established and solved self-consistently for the
wavefunction of the system in the local density approximation. The transmission
for ballistic transport across the atomic silicon slab at small bias is
calculated. The charge distribution and electrostatic potential profile in the
silicon slab versus the gate voltage are then analyzed with the help of the
equivalent capacitive model. Quantum confinement and short gate effects are
observed and discussed.


title: C*-envelopes of tensor algebras for multivariable dynamics

abstract:
  We give a new very concrete description of the C*-envelope of the tensor
algebra associated to multivariable dynamical system. In the surjective case,
this C*-envelope is described as a crossed product by an endomorphism, and as a
groupoid C*-algebra. In the non-surjective case, it is a full corner of a such
an algebra. We also show that when the space is compact, then the C*-envelope
is simple if and only if the system is minimal.


title: Fano hypersurfaces and Calabi-Yau supermanifolds

abstract:
  In this paper, we study the geometrical interpretations associated with
Sethi's proposed general correspondence between N = 2 Landau-Ginzburg orbifolds
with integral \hat{c} and N = 2 nonlinear sigma models. We focus on the
supervarieties associated with \hat{c} = 3 Gepner models. In the process, we
test a conjecture regarding the superdimension of the singular locus of these
supervarieties. The supervarieties are defined by a hypersurface \widetilde{W}
= 0 in a weighted superprojective space and have vanishing super-first Chern
class. Here, \widetilde{W} is the modified superpotential obtained by adding as
necessary to the Gepner superpotential a boson mass term and/or fermion
bilinears so that the superdimension of the supervariety is equal to \hat{c}.
When Sethi's proposal calls for adding fermion bilinears, setting the bosonic
part of \widetilde{W} (denoted by \widetilde{W}_{bos}) equal to zero defines a
Fano hypersurface embedded in a weighted projective space. In this case, if the
Newton polytope of \widetilde{W}_{bos} admits a nef partition, then the
Landau-Ginzburg orbifold can be given a geometrical interpretation as a
nonlinear sigma model on a complete intersection Calabi-Yau manifold. The
complete intersection Calabi-Yau manifold should be equivalent to the
Calabi-Yau supermanifold prescribed by Sethi's proposal.


title: Coupled-channel effects in kaon pair production

abstract:
  Two coupled channel effects connected with kaon pair production in
proton-proton collisions are discussed. (1) Although there is ample evidence
that the antikaon is strongly attracted to the recoil protons in pp -> K+pK-p,
residual effects of the K+K- interaction are seen, including a possible cusp at
the K0\bar{K}0 threshold. This is investigated within a simple K-matrix
approach. (2) The production rates and invariant mass distributions for pp ->
K+p{K-p} and pp -> K+p{pi0 Sigma0} are related using a separable potential
description of the coupled K-p/pi0 Sigma0 channels. It can be plausibly argued
that this pair of reactions is driven through the production of the
Lambda(1405).


title: The Zero Temperature Phase Diagram of the Kitaev Model

abstract:
  We show that the zero temperature phase diagram of the vortex free sector of
the Kitaev model is in one to one correspondence with that of the classical
dimer model on the same lattice. We find that the model generically has three
distinct phases. On a honeycomb lattice with a $3\times3$ fundamental domain
all three phases are accessible. As the couplings are varied there are two
distinct transitions. The new transition is one to a gapped phase that opens up
in the interior of the $B$ phase.


title:
The open cluster Pismis 11 and the very luminous blue supergiant HD
  80077

abstract:
  (Abridged) The very luminous blue supergiant HD 80077 has been claimed to be
a member of the young open cluster Pismis 11, and hence a hypergiant. We
obtained UBVRI photometry of the cluster field and low-resolution spectroscopy
of a number of putative members. We derive spectral types from the spectra and
determine that the reddening in this direction is standard. We then carry out a
careful photometric analysis that allows us to determine individual reddening
values, deriving unreddened parameters that are used for the main sequence fit.
We identify 43 likely members of Pismis 11. We study the variation of
extinction across the face of the cluster and find some dispersion, with a
trend to higher values in the immediate neighbourhood of HD 80077. We estimate
a distance of 3.6 kpc for the cluster. If HD 80077 is a member, it has
M_bol<-10.5 and it is one of the three visually brightest stars in the Galaxy.
Several early type stars in the vicinity of Pismis~11 fit well the cluster
sequence and are likely to represent an extended population at the same
distance. About 18 arcmin to the North of Pismis 11, we find a small
concentration of stars, which form a clear sequence. We identify this group as
a previously uncatalogued open cluster, which we provisionally call Alicante 5.
The distance to Alicante 5 is also 3.6 kpc, suggesting that these two clusters
and neighbouring early-type stars form a small association. Based on its proper
motion, HD 80077 is not a runaway star and may be a member of the cluster. If
this is the case, it would be one of the brightest stars in the Galaxy.


title:
Graphene in the Quantum Hall Regime: Effects of Vacancies, Sublattice
  Polarization and Disorder

abstract:
  We investigate the effects of vacancies, disorder and sublattice polarization
on the electronic properties of a monolayer graphene in the quantum Hall
regime. Energy spectra as a function of magnetic field and the localization
properties of the states within the graphene Landau levels (LLs) are calculated
through a tight-binding model. We first discuss our results considering
vacancies in the lattice, where we show that vacancies introduce extra levels
(or well-defined bands) between consecutive LLs. An striking consequence here
is that extra Hall resistance plateaus are expected to emerge when an organized
vacancy superlattice is considered. Secondly, we discuss the anomalous
localization properties we have found for the lowest LL, where an increasing
disorder is shown to enhance the wave functions delocalization (instead of
inducing localization). This unexpected effect is shown to be directly related
to the way disorder increasingly destroys the sublattice (valley) polarization
of the states in the lowest LL. The reason why this anomalous disorder effect
occurs only for the zero-energy LL is that, in absence of disorder, only for
this level all the states are sublattice polarized, i.e., their wave functions
have amplitudes in only one of the sublattices.


title:
Chiral effective field theory calculations of neutrino processes in
  dense matter

abstract:
  We calculate neutrino processes involving two nucleons at subnuclear
densities using chiral effective field theory. Shorter-range noncentral forces
reduce the neutrino rates significantly compared with the one-pion exchange
approximation currently used in supernova simulations. For densities rho <
10^{14} g cm^{-3}, we find that neutrino rates are well constrained by nuclear
interactions and nucleon-nucleon scattering data. As an application, we
calculate the mean-square energy transfer in scattering of a neutrino from
nucleons and find that collision processes and spin-dependent mean-field
effects dominate over the energy transfer due to nucleon recoil.


title:
Modeling the isotropic/smectic-C tilted lamellar liquid crystalline
  transition

abstract:
  Extensions of a previously presented Landau-de Gennes type liquid crystalline
phase transition model for the direct isotropic/smectic-A (lamellar) a phase
transition to the direct isotropic/smectic-C (tilted lamellar) transition are
studied. Two different proposed extensions to the model are studied both in the
context of ideal ordering (point volume) and full three-dimensional uniaxial
scalar/vector decomposition. Recommendations based upon the inclusion of
essential physics and computational feasibility are made, distinguishing each
of the two proposed extensions based upon these criteria. Additionally, it is
found that the approach used for the isotropic/smectic-A model to
deterministically compute phase diagram data is not possible for either of the
two proposed isotropic/smectic-C models.


title: Fixation Probability for Competing Selective Sweeps

abstract:
  We consider a biological population in which a beneficial mutation is
undergoing a selective sweep when a second beneficial mutation arises at a
linked locus and we investigate the probability that both mutations will
eventually fix in the population. Previous work has dealt with the case where
the second mutation to arise confers a smaller benefit than the first. In that
case population size plays almost no role. Here we consider the opposite case
and observe that, by contrast, the probability of both mutations fixing can be
heavily dependent on population size. Indeed the key parameter is $\rho N$, the
product of the population size and the recombination rate between the two
selected loci. If $\rho N$ is small, the probability that both mutations fix
can be reduced through interference to almost zero while for large $\rho N$ the
mutations barely influence one another. The main rigorous result is a method
for calculating the fixation probability of a double mutant in the large
population limit.


title: A kinetic scheme for pressurized flows in non uniform pipes

abstract:
  The aim of this paper is to present a kinetic numerical scheme for the
computations of transient pressurised flows in closed water pipes with variable
sections. Firstly, we detail the derivation of the mathematical model in
curvilinear coordinates under some hypothesis and we performe a formal
asymptotic analysis. Then the obtained system is written as a conservative
hyperbolic partial differential system of equations, and we recall how to
obtain the corresponding kinetic formulation based on an upwinding of the
source term due to the "pseudo topography" performed in a close manner
described by Perthame and al.


title: A kinetic scheme for unsteady pressurised flows in closed water pipes

abstract:
  The aim of this paper is to present a kinetic numerical scheme for the
computations of transient pressurised flows in closed water pipes. Firstly, we
detail the mathematical model written as a conservative hyperbolic partial
differentiel system of equations, and the we recall how to obtain the
corresponding kinetic formulation. Then we build the kinetic scheme ensuring an
upwinding of the source term due to the topography performed in a close manner
described by Perthame et al. using an energetic balance at microscopic level
for the Shallow Water equations. The validation is lastly performed in the case
of a water hammer in a uniform pipe: we compare the numerical results provided
by an industrial code used at EDF-CIH (France), which solves the Allievi
equation (the commonly used equation for pressurised flows in pipes) by the
method of characteristics, with those of the kinetic scheme. It appears that
they are in a very good agreement.


title: Consistency of regularization for scalar fields

abstract:
  In two dimensional constructive quantum field theory for scalar fields, it is
necessary to regularize both the action and the total (Gaussian) volume. In
this note we consider the compatibility of these regularizations.


title:
Dark energy as the source of the time dependend Einstein cosmological
  constant

abstract:
  In this paper we calculate the Einstein cosmological constant.Following our
results presented in monograph: From quark to bulk matter, we obtain the new
formula for the time dependent cosmological constant, lambda. Following the
general formula for time dependent lambda, we can describe the history of the
cosmological constant


title: Path integral analysis of Jarzynski's equality: Analytical results

abstract:
  We apply path integrals to study nonequilibrium work theorems in the context
of Brownian dynamics, deriving in particular the equations of motion governing
the most typical and most dominant trajectories. For the analytically soluble
cases of a moving harmonic potential and a harmonic oscillator with
time-dependent natural frequency, we find such trajectories, evaluate the
work-weighted propagators, and validate Jarzynski's equality.