title: A 6 dimensional $(Z_{2})^3$ symmetric model with warped physical space

abstract:
  The Randall-Sundrum model is studied in 6 dimension with AdS$_4$ or dS$_4$
metric in the physical 4 dimensional space. Two solutions are found, one with
induced 5-dimensional gravity terms added to the induced cosmological constant
terms. We study the graviton modes in both solutions by transforming the mass
eigenvalue equation to a Schrodinger equation with a volcano potential. The
spectrum of gravitational excitations depends on the input parameters of the
theory, the six dimensional and the effective four-dimensional cosmological
constants. The model gives a physically acceptable spectrum if the 4
dimensional cosmological constant is sufficiently small.


title: The role of microscopic fluctuations in transition prediction

abstract:
  The commonly accepted description of transition to turbulence in shear flows
requires the presence of an external source of disturbances that get amplified
by an essentially linear mechanism up to the point where breakdown to
turbulence occurs. Microscopic fluctuations are shown here to provide just the
right amount of initial disturbances to match the predictions of linear
stability theory.


title:
Self-trapping of Bose-Einstein condensates expanding into shallow
  optical lattices

abstract:
  We observe a sudden breakdown of the transport of a strongly repulsive
Bose-Einstein condensate through a shallow optical lattice of finite width. We
are able to attribute this behavior to the development of a self-trapped state
by using accurate numerical methods and an analytical description in terms of
nonlinear Bloch waves. The dependence of the breakdown on the lattice depth and
the interaction strength is investigated. We show that it is possible to
prohibit the self-trapping by applying a constant offset potential to the
lattice region. Furthermore, we observe the disappearance of the self-trapped
state after a finite time as a result of the revived expansion of the
condensate through the lattice. This revived expansion is due to the finite
width of the lattice.


title: Induced scattering of short radio pulses

abstract:
  Effect of the induced Compton and Raman scattering on short, bright radio
pulses is investigated. It is shown that when a single pulse propagates through
the scattering medium, the effective optical depth is determined by the
duration of the pulse but not by the scale of the medium. The induced
scattering could hinder propagation of the radio pulse only if close enough to
the source a dense enough plasma is presented. The induced scattering within
the relativistically moving source places lower limits on the Lorentz factor of
the source. The results are applied to the recently discovered short
extragalactic radio pulse.


title: Strategies for Optimize Off-Lattice Aggregate Simulations

abstract:
  We review some computer algorithms for the simulation of off-lattice clusters
grown from a seed, with emphasis on the diffusion-limited aggregation,
ballistic aggregation and Eden models. Only those methods which can be
immediately extended to distinct off-lattice aggregation processes are
discussed. The computer efficiencies of the distinct algorithms are compared.


title: Automorphisms of elliptic Poisson algebras

abstract:
  We describe the automorphism groups of elliptic Poisson algebras on
polynomial algebras in three variables and give an explicit set of generators
and defining relations for this group.


title:
Extended Zee model for Neutrino Mass, Leptogenesis and Sterile Neutrino
  like Dark Matter

abstract:
  We propose an extension of the standard model with a $U(1)_{\rm B-L}$ global
symmetry that accommodates radiative neutrino masses along with dark matter and
leptogenesis. The observed matter antimatter asymmetry of the universe is
generated through the leptogenesis route keeping the $U(1)_{\rm B-L}$ symmetry
intact. The $B-L$ global symmetry is then softly broken, providing the sub-eV
neutrino masses. The model then incorporates a MeV scale sterile neutrino like
dark matter.


title: Examples of relative deformation spaces that are not locally connected

abstract:
  We provide an infinite family of pared manifolds whose relative deformation
spaces of hyperbolic structures on these manifolds are not locally connected.
This is a natural extension of the recent result of Bromberg that shows the
space of Kleinian punctured torus groups is not locally connected.


title: Bohdan's Impact on Our Understanding of Gamma-ray Bursts

abstract:
  Bohdan Paczy'nski was one of the pioneers of the cosmological GRB model. His
ideas on how GRBs operate and what are their progenitors have dominated the
field of GRBs in the hectic nineties during which the distances and the origin
of GRBs were revealed. I discuss here Bohdan's contributions in some historical
perspective.


title: Kreps-Yan theorem for Banach ideal spaces

abstract:
  Let $C$ be a closed convex cone in a Banach ideal space $X$ on a measurable
space with a $\sigma$-finite measure. We prove that conditions $C\cap
X_+=\{0\}$ and $C\supset -X_+$ imply the existence of a strictly positive
continuous functional on $X$, whose restriction to $C$ is non-positive.


title: Spin and Charge Shot Noise in Mesoscopic Spin Hall Systems

abstract:
  Injection of unpolarized charge current through the longitudinal leads of a
four-terminal two-dimensional electron gas with the Rashba spin-orbit (SO)
coupling and/or SO scattering off extrinsic impurities is responsible not only
for the pure spin Hall current in the transverse leads, but also for random
time-dependent current fluctuations. We employ the scattering approach to
current-current correlations in multiterminal nanoscale conductors to analyze
the shot noise of transverse pure spin Hall and zero charge current, or
transverse spin current and non-zero charge Hall current, driven by unpolarized
or spin-polarized longitudinal current, respectively. Since any spin-flip acts
as an additional source of noise, we argue that these shot noises offer a
unique tool to differentiate between intrinsic and extrinsic SO mechanisms
underlying the spin Hall effect in paramagnetic devices.


title:
Nonlinear dynamics in an alternating gradient guide for neutral
  particles

abstract:
  Neutral particles can be guided and focussed using electric field gradients
that focus in one transverse direction and defocus in the other, alternating
between the two directions. Such a guide is suitable for transporting particles
that are attracted to strong electric fields, which cannot be guided using
static fields. Particles are only transmitted if their initial positions and
transverse speeds lie within the guide's phase space acceptance. Nonlinear
forces are always present in the guide and can severely reduce this acceptance.
We consider the effects of the two most important nonlinear forces, a term in
the force that is cubic in the off-axis displacement, and a nonlinear term
which couples together the two transverse motions. We use approximate
analytical techniques, along with numerical methods, to calculate the influence
of these nonlinear forces on the particle trajectories and on the phase space
acceptance. The cubic term alters the focussing and defocussing powers, leading
either to an increase or a decrease of the acceptance depending on its sign. We
find an approximate analytical result for the phase space acceptance including
this cubic term. Using a perturbation method we show how the coupling term
leads to slow changes in the amplitudes of the transverse oscillations. This
term reduces the acceptance when it reduces the focussing power, but has little
influence when it increases that power. It is not possible to eliminate both
nonlinear terms, but one can be made small at the expense of the other. We show
how to choose the guide parameters so that the acceptance is optimized.


title:
Continuous Families of Rational Surface Automorphisms with Positive
  Entropy

abstract:
  We construct k-parameter families of rational surface automorphisms for any
k. These are automorphisms of surfaces X, which are constructed from iterated
blowups over the projective plane. In certain cases: we are able to determine
the exact automorphism group of X, as well as when two of the surfaces X are
inequivalent.


title: On the Stress Tensor for Asymptotically Flat Gravity

abstract:
  The recent introduction of a boundary stress tensor for asymptotically flat
spacetimes enabled a new construction of energy, momentum, and Lorentz charges.
These charges are known to generate the asymptotic symmetries of the theory,
but their explicit formulas are not identical to previous constructions in the
literature. This paper corrects an earlier comparison with other approaches,
including terms in the definition of the stress tensor charges that were
previously overlooked. We show that these terms either vanish identically (for
d > 4) or take a form that does not contribute to the conserved charges (for
d=4). This verifies the earlier claim that boundary stress tensor methods for
asymptotically flat spacetimes yield the same conserved charges as other
approaches. We also derive some additional connections between the boundary
stress tensor and the electric part of the Weyl tensor.


title: A diagrammatic approach to categorification of quantum groups II

abstract:
  We categorify one-half of the quantum group associated to an arbitrary Cartan
datum.


title: Conductance of p-n-p graphene structures with 'air-bridge' top gates

abstract:
  We have fabricated graphene devices with a top gate separated from the
graphene layer by an air gap--a design which does not decrease the mobility of
charge carriers under the gate. This gate is used to realise p-n-p structures
where the conducting properties of chiral carriers are studied. The band
profile of the structures is calculated taking into account the specifics of
the graphene density of states and is used to find the resistance of the p-n
junctions expected for chiral carriers. We show that ballistic p-n junctions
have larger resistance than diffusive ones. This is caused by suppressed
transmission of chiral carriers at angles away from the normal to the junction.


title: BTZ Black Hole Entropy: A spin foam model description

abstract:
  We present a microscopical explanation of the entropy of the BTZ black hole
using discrete spin foam models of quantum gravity. The entropy of a black hole
is given in geometrical terms which lead us to think that its statistical
description must be given in terms of a quantum geometry. In this paper we
present it in terms of spin foam geometrical observables at the horizon of the
black hole.


title:
Quantum corrections and bound-state effects in the energy relaxation of
  hot dense Hydrogen

abstract:
  Simple analytic formulae for energy relaxation (ER) in electron-ion systems,
with quantum corrections, ion dynamics and RPA-type screening are presented. ER
in the presence of bound electrons is examined in view of of recent simulations
for ER in hydrogen in the range 10^{20}-10^{24} electrons/cc.

categories: physics.plasm-ph astro-ph cond-mat.stat-mech physics.gen-ph


title: A and B branes from N=2 superspace

abstract:
  We present a manifestly supersymmetric description of A and B branes on
Kaehler manifolds using a completely local N=2 superspace formulation of the
world-sheet nonlinear sigma-model in the presence of a boundary. In particular,
we show that an N=2 superspace description of type A boundaries is possible.
This leads to a concrete realization of the still poorly understood coisotropic
A branes. We also discuss briefly how the superspace description of a B brane
provides an efficient way to compute higher loop beta-functions. In particular,
we sketch how one obtains the fourth order derivative correction to the
Born-Infeld action by using a beta-function method.


title:
On regularity in codimension one of irreducible components of module
  varieties

abstract:
  Let A be a tame quasi-tilted algebra and d the dimension vector of an
indecomposable A-module. In the paper we prove that each irreducible component
of the variety of A-modules of dimension vector d is regular in codimension
one.


title:
Chromospheric magnetic reconnection: Two-fluid simulations of coalescing
  current loops

abstract:
  Aims: To investigate magnetic reconnection rates during the coalescence of
two current loops in the solar chromosphere, by altering the neutral-hydrogen
to proton density ratio, ioniziation/recombination coefficients, collision
frequency and relative helicity of the loops. Methods: 2.5D numerical
simulations of the chromosphere were conducted using a newly developed
two-fluid (ion-neutral) numerical code. Developed from the Artificial Wind
scheme, the numerical code includes the effects of ion-neutral collisions,
ionization/recombination, thermal/resistive diffusivity and
collisional/resistive heating. Results: It was found that the rates of magnetic
reconnection strongly depend on the neutral-hydrogen to proton density ratio;
increasing the density ratio by a thousand-fold decreased the rate of magnetic
reconnection by twenty-fold. This result implies that magnetic reconnection
proceeds significantly faster in the upper chromosphere, where the density of
ions (protons) and neutral-hydrogen is comparable, than in the lower
chromosphere where the density of neutral-hydrogen is over a thousand times the
ion density. The inclusion of ionization/recombination, an important physics
effect in the chromosphere, increases the total reconnected magnetic flux, but
does not alter the rate of magnetic reconnection. Reductions in the ion-neutral
collision frequency, result in small increases to the rates of magnetic
reconnection. The relative helicity of the two current loops was not observed
to have any significant effect on the rates of magnetic reconnection.
Conclusions: The magnetic reconnection rates of coalescing current loops are
strongly affected by the inclusion of neutral-hydrogen particles.


title:
Phase transitions on the edge of the \nu=5/2 Pfaffian and anti-Pfaffian
  quantum Hall state

abstract:
  Starting from the edge reconstructed Pfaffian state and the anti-Pfaffian
state for the filling fraction $\nu={5/2}$ fractional quantum Hall (FQH) state
with the filled Landau levels included, we find that interactions between
counterpropagating edge modes can induce phase transitions on the edge. In the
new `Majorana-gapped' phases, a pair of counter propagating neutral Majorana
modes becomes gapped. The quasiparticle tunneling exponent changes from $g=1/4$
to $g=1/2$ for the edge reconstructed Pfaffian state, and changes from $g=1/2$
to $g=0.55-0.75$ for the anti-Pfaffian state, in the new Majorana-gapped
phases. The new phases are candidate states for the observed $\nu={5/2}$ state.
Furthermore, Majorana-gapped phases provide examples that non-trivial quantum
phase transitions can happen on the edge of a FQH state without any change in
bulk topological order.


title: More about neutron - mirror neutron oscillation

abstract:
  It was pointed out recently that oscillation of the neutron $n$ into mirror
neutron $n'$, a sterile twin of the neutron with exactly the same mass, could
be a very fast process with the the baryon number violation, even faster than
the neutron decay itself. This process is sensitive to the magnetic fields and
it could be observed by comparing the neutron lose rates in the UCN storage
chambers for different magnetic backgrounds. We calculate the probability of
$n-n'$ oscillation in the case when a mirror magnetic field $\vec{B}'$ is
non-zero and show that in this case it can be suppressed or resonantly enhanced
by applying the ordinary magnetic field $\vec{B}$, depending on its strength
and on its orientation with respect to $\vec{B}'$. The recent experimental
data, under this hypothesis, still allow the $n-n'$ oscillation time order 1 s
or even smaller. Moreover, they indicate that the neutron losses are sensitive
to the orientation of the magnetic field. %at about $3\sigma$ level. If these
hints will be confirmed in the future experiments, this would point to the
presence of the mirror magnetic field on the Earth of the order of 0.1 G, or
some equivalent spin-dependent force of the other origin that makes a
difference between the neutron and mirror neutron states.


title:
Improved measurement of the CKM angle gamma in B^-+ -> D^(*) K^(*)-+
  decays with a Dalitz plot analysis of D decays to K_S^0 pi^+ pi^- and K_S^0
  K^+ K^-

abstract:
  We report on an improved measurement of the Cabibbo-Kobayashi-Maskawa {\it
CP}-violating phase $\gamma$ through a Dalitz plot analysis of neutral $D$
meson decays to $K_S^0 \pi^+ \pi^-$ and $K_S^0 K^+ K^-$ in the processes $B^\mp
\to D K^\mp$, $B^\mp \to D^* K^\mp$ with $D^* \to D\pi^0,D\gamma$, and $B^\mp
\to D K^{*\mp}$ with $K^{*\mp} \to K_S^0 \pi^\mp$. Using a sample of 383
million $B\bar{B}$ pairs collected by the BABAR detector, we measure
$\gamma=(76 \pm 22 \pm 5 \pm 5)^\circ$ (mod $180^\circ$), where the first error
is statistical, the second is the experimental systematic uncertainty and the
third reflects the uncertainty on the description of the Dalitz plot
distributions. The corresponding two standard deviation region is $29^\circ <
\gamma < 122^\circ$. This result has a significance of direct {\it CP}
violation ($\gamma \ne 0$) of 3.0 standard deviations.


title:
The hexaquark-flavoured antiK-N-N state computed microscopically with a
  clusterized octoquark

abstract:
  The possible production processes of the antiK-NN are explored. We derive
microscopically, with the RGM, the microscopic derivation of the K-N and
antiK-N interactions. We discuss the binding or not binding of the different
antiK-N and antiK-NN systems. When binding occurs, the respective decay widths
are also discussed.


title:
Stability analysis of twist grain boundaries in lamellar phases of block
  copolymers

abstract:
  Twist grain boundaries are widely observed in lamellar phases of block
copolymers. A mesoscopic model of the copolymer is used to obtain stationary
configurations that include a twist grain boundary, and to analyze their
stability against long wavelength perturbations. The analysis presented is
valid in the weak segregation regime, and includes direct numerical solution of
the governing equations as well as a multiple scale analysis. We find that a
twist boundary configuration with arbitrary misorientation angle can be well
described by two modes, and obtain the equations for their slowly varying
amplitudes. The width of the boundary region is seen to scale as
$\epsilon^{-1/4}$, with $\epsilon$ being the dimensionless distance to the
order-disorder transition. We finally present the results of the linear
stability analysis of the planar boundary.


title:
Canonical Electromagnetic Observables for Systematic Characterization of
  Electric and Magnetic Wave Field Data on board Spacecraft

abstract:
  We present a new characterization of partially coherent electric and magnetic
wave vector fields.This characterization is based on the 36 auto/cross
correlations of the 3+3 complex Cartesian components of the electric and
magnetic wave fields and is particularly suited for analyzing electromagnetic
wave data on board spacecraft. Data from spacecraft based electromagnetic wave
instruments are usually processed as data arrays. These data arrays however do
not have a physical interpretation in themselves; they are simply a convenient
storage format. In contrast, the characterization proposed here contains
exactly the same information but are in the form of manifestly covariant
space-time tensors. We call this data format the Canonical Electromagnetic
Observables (CEO) since they correspond to unique physical observables. Some of
them are already known, such as energy density, Poynting flux, stress tensor,
etc, while others should be relevant in future space research. As an example we
use this formalism to analyze data from a chorus emission in the mid-latitude
magnetosphere, as recorded by the STAFF-SA instrument on board the Cluster-II
spacecraft.


title:
Large deviations for quantum Markov semigroups on the 2 x 2 matrix
  algebra

abstract:
  Let $({\mathcal{T}}_{*t})$ be a predual quantum Markov semigroup acting on
the full 2 x 2 matrix algebra and having an absorbing pure state. We prove that
for any initial state $\omega$, the net of orthogonal measures representing the
net of states $({\mathcal{T}}_{*t}(\omega))$ satisfies a large deviation
principle in the pure state space, with a rate function given in terms of the
generator, and which does not depend on $\omega$. This implies that
$({\mathcal{T}}_{*t}(\omega))$ is faithful for all $t$ large enough. Examples
arising in weak coupling limit are studied.


title: A Catalog of Diffuse Interstellar Bands in the Spectrum of HD 204827

abstract:
  Echelle spectra of the double-lined spectroscopic binary HD 204827 were
obtained on five nights, at a resolving power R = 38,000 and with a S/N ratio =
750 near 6000 A in the final, combined spectrum. The stars show E(B-V) = 1.11
and spectral types near O9.5V and B0.5III. A catalog is presented of 380
diffuse interstellar bands (DIBs) measured between 3900 and 8100 A in the
stars' spectrum. The central wavelengths, the widths (FWHM), and the equivalent
widths of nearly all of the bands are tabulated, along with the minimum
uncertainties in the latter. The reliable removal of very weak stellar lines
from the catalog, and of some stellar lines from the less severe blends with
DIBs, is made generally easy by the highly variable radial velocities of both
stars. The principal result of this investigation is that the great majority of
the bands in the catalog are very weak and relatively narrow. Typical
equivalent widths amount to a few mA, and the band widths (FWHM) are most often
near 0.55 A. Therefore, most of these DIBs can be detected only in spectra
obtained at a resolving power and a S/N ratio at least comparable to those used
here. In addition, the anomalous interstellar reddening and the very high value
of the ratio N(C2)/E(B-V) seen toward HD 204827 indicate that the physical
conditions in one or more of the several interstellar clouds seen in this
direction differ significantly from those found toward the prototypical DIB
target HD 183143, for example. Probably primarily for these reasons, 113 of the
380 bands, or 30%, were not detected in four previous, modern surveys of the
DIBs seen in the spectra of stars other than HD 204827. Both the tabulated data
for the DIBs and a plot of our spectrum of HD 204827 are available online at
http://dibdata.org


title: A Logic Programming Framework for Combinational Circuit Synthesis

abstract:
  Logic Programming languages and combinational circuit synthesis tools share a
common "combinatorial search over logic formulae" background. This paper
attempts to reconnect the two fields with a fresh look at Prolog encodings for
the combinatorial objects involved in circuit synthesis. While benefiting from
Prolog's fast unification algorithm and built-in backtracking mechanism,
efficiency of our search algorithm is ensured by using parallel bitstring
operations together with logic variable equality propagation, as a mapping
mechanism from primary inputs to the leaves of candidate Leaf-DAGs implementing
a combinational circuit specification. After an exhaustive expressiveness
comparison of various minimal libraries, a surprising first-runner, Strict
Boolean Inequality "<" together with constant function "1" also turns out to
have small transistor-count implementations, competitive to NAND-only or
NOR-only libraries. As a practical outcome, a more realistic circuit
synthesizer is implemented that combines rewriting-based simplification of
(<,1) circuits with exhaustive Leaf-DAG circuit search.
  Keywords: logic programming and circuit design, combinatorial object
generation, exact combinational circuit synthesis, universal boolean logic
libraries, symbolic rewriting, minimal transistor-count circuit synthesis


title: On heterotic model constraints

abstract:
  The constraints imposed on heterotic compactifications by global consistency
and phenomenology seem to be very finely balanced. We show that weakening these
constraints, as was proposed in some recent works, is likely to lead to
frivolous results. In particular, we construct an infinite set of such
frivolous models having precisely the massless spectrum of the MSSM and other
quasi-realistic features. Only one model in this infinite collection (the one
constructed in arXiv:hep-th/0512149) is globally consistent and supersymmetric.
The others might be interpreted as being anomalous, or as non-supersymmetric
models, or as local models that cannot be embedded in a global one. We also
show that the strongly coupled model of arXiv:hep-th/0512149 can be modified to
a perturbative solution with stable SU(4) or SU(5) bundles in the hidden
sector. We finally propose a detailed exploration of heterotic vacua involving
bundles on Calabi-Yau threefolds with Z_6 Wilson lines; we obtain many more
frivolous solutions, but none that are globally consistent and supersymmetric
at the string scale.


title: Optimal Mechansim Design and Money Burning

abstract:
  Mechanism design is now a standard tool in computer science for aligning the
incentives of self-interested agents with the objectives of a system designer.
There is, however, a fundamental disconnect between the traditional application
domains of mechanism design (such as auctions) and those arising in computer
science (such as networks): while monetary transfers (i.e., payments) are
essential for most of the known positive results in mechanism design, they are
undesirable or even technologically infeasible in many computer systems.
Classical impossibility results imply that the reach of mechanisms without
transfers is severely limited.
  Computer systems typically do have the ability to reduce service
quality--routing systems can drop or delay traffic, scheduling protocols can
delay the release of jobs, and computational payment schemes can require
computational payments from users (e.g., in spam-fighting systems). Service
degradation is tantamount to requiring that users burn money}, and such
``payments'' can be used to influence the preferences of the agents at a cost
of degrading the social surplus.
  We develop a framework for the design and analysis of money-burning
mechanisms to maximize the residual surplus--the total value of the chosen
outcome minus the payments required.


title:
A Microfluidic Pore Network Approach to Investigate Water Transport in
  Fuel Cell Porous Transport Layers

abstract:
  Pore network modelling has traditionally been used to study displacement
processes in idealized porous media related to geological flows, with
applications ranging from groundwater hydrology to enhanced oil recovery. Very
recently, pore network modelling has been applied to model the gas diffusion
layer (GDL) of a polymer electrolyte membrane (PEM) fuel cell. Discrete pore
network models have the potential to elucidate transport phenomena in the GDL
with high computational efficiency, in contrast to continuum or molecular
dynamics modelling that require extensive computational resources. However, the
challenge in studying the GDL with pore network modelling lies in defining the
network parameters that accurately describe the porous media as well as the
conditions of fluid invasion that represent realistic transport processes. In
this work, we discuss the first stage of developing and validating a
GDL-representative pore network model. We begin with a two-dimensional pore
network model with a single mobile phase invading a hydrophobic media, whereby
the slow capillary dominated flow process follows invasion percolation. Pore
network geometries are designed, and transparent hydrophobic microfluidic
networks are fabricated from silicon elastomer PDMS using a soft lithography
technique. These microfluidic networks are designed to have channel size
distributions and wettability properties of typical GDL materials. Comparisons
between the numerical and experimental flow patterns show reasonable agreement.
Furthermore, the fractal dimension and saturation are measured during invasion,
revealing different operating regimes that can be applied to GDL operation.
Future work for model development will also be discussed.


title: Josephson junction transmission lines as tunable artificial crystals

abstract:
  We investigate one-dimensional Josephson junction arrays with generalized
unit cells as a circuit approach to engineer microwave band gaps. An array
described by a lattice with a basis can be designed to have a gap in the
electromagnetic spectrum, in full analogy to electronic band gaps in diatomic
or many-atomic crystals. We derive the dependence of this gap on the array
parameters in the linear regime, and suggest experimentally feasible designs to
bring the gap below the single junction plasma frequency. The gap can be tuned
in a wide frequency range by applying external flux, and it persists in the
presence of small imperfections.


title: Self pinning protein-laden drops

abstract:
  Proteins dissolved in a drop induce and enhance the pinning of the drop
contact line. This effect dramatically increases volume of drops that are
vertically pinned on a flat siliconized substrate. The drop pinning behavior
exhibits two regimes: for low protein content in a drop the pinning increases
as the contact angle hysteresis increases, and for high protein content the
pinning decreases as the surface tension of the protein solution decreases.


title:
Effects of dilution on magnetic and transport properties of
  La0.7Ca0.3Mn1-xM'xO3

abstract:
  Magnetic and transport properties of La0.7Ca0.3Mn1-xM'xO3 (M'=Al,Ti) are
studied. The dilution of the Mn lattice results in a weakening of the
ferromagnetism, a deterioration of the metallic conductivity, and a strong
enhancement of the magnetoresistance. Although Tc linearly decreases with x in
the low substitution ranges for both M' series, the scaling behavior Tc(np)
previously observed for La0.7Sr0.3Mn1-xM'xO3 [Phys. Rev. B 73, 184403 (2006)]
is no longer obtained. Extrapolations of the Tc(np) linear curves to Tc=0 give
np values much smaller than 1. These results suggest that, according to a
molecular-field approximation, antiferromagnetic superexchange between Mn ions
is significant in La0.7Ca0.3MnO3, in contrast to what observed in
La0.7Sr0.3MnO3. Additionally, structural data of the Al-substituted samples
suggest that variations of the eg-electron bandwidth W cannot explain the
decrease of Tc in magnetically diluted manganites.


title: The Standard Model via Dirac-Kahler spinors

abstract: This paper has been withdrawn by the author.


title: Minimizing the kinematical effects on LISA's performance

abstract:
  Proper tuning of the orbital characteristics of the three spacecrafts that
constitute the usual triangular configuration of the space-borne
gravitational-wave detector LISA, could minimize the breathing mode of its
arm-lengths. Since the three spacecrafts form three pairs of interferometric
arms, we have the freedom to minimize whichever combination of arm-length
variations that might be useful in signal analysis. Thus for any kind of time
delay interferometry (TDI), that is chosen to be used in analysing the data,
the optimal orbital characteristics could be chosen accordingly, so as to
enhance the performance of the gravitational wave detector.


title:
Polarization properties of laser-diode-pumped micro-grained Nd:YAG
  ceramic lasers

abstract:
  Detailed polarization properties have been examined in laser-diode-pumped
(LD-pumped) micro-grained ceramic Nd:YAG lasers in different microchip cavity
configurations. Stable linearly-polarized single-frequency oscillations, whose
polarization direction coincide with that of an LD pump light, were observed in
an external cavity scheme. While, in the case of a thin-slice laser scheme with
coated reflective ends, elliptically-polarized single-frequency operations took
place in the low pump-power regime and dynamic instabilities appeared,
featuring self-induced antiphase modulations among counter-rotating
circularly-polarized components having slightly different lasing frequencies,
with increasing the pump power.


title:
Phase Diagram and Quantum Critical Point in Newly Discovered
  Superconductors: SmO_{1-x}F_xFeAs

abstract:
  The magnetic fluctuations associated with a quantum critical point (QCP) are
widely believed to cause the non-Fermi liquid behaviors and unconventional
superconductivities, for example, in heavy fermion systems and high temperature
cuprate superconductors. Recently, superconductivity has been discovered in
iron-based layered compound $LaO_{1-x}F_xFeAs$ with $T_c$=26 K\cite{yoichi},
and it competes with spin-density-wave (SDW) order\cite{dong}. Neutron
diffraction shows a long-rang SDW-type antiferromagnetic (AF) order at $\sim
134$ K in LaOFeAs\cite{cruz,mcguire}. Therefore, a possible QCP and its role in
this system are of great interests. Here we report the detailed phase diagram
and anomalous transport properties of the new high-Tc superconductors
$SmO_{1-x}F_xFeAs$ discovered by us\cite{chenxh}. It is found that
superconductivity emerges at $x\sim$0.07, and optimal doping takes place in the
$x\sim$0.20 sample with highest $T_c \sim $54 K. While $T_c$ increases
monotonically with doping, the SDW order is rapidly suppressed, suggesting a
QCP around $x \sim$0.14. As manifestations, a linear temperature dependence of
the resistivity shows up at high temperatures in the $x<0.14$ regime, but at
low temperatures just above $T_c$ in the $x>0.14$ regime; a drop in carrier
density evidenced by a pronounced rise in Hall coefficient are observed, which
mimic the high-$T_c$ cuprates. The simultaneous occurrence of order, carrier
density change and criticality makes a compelling case for a quantum critical
point in this system.


title: First VLBI observations of methanol maser polarisation, in G339.88-1.2

abstract:
  We investigate class II methanol masers and the environment in which they
form with the Long Baseline Array (LBA).
  Using full polarisation VLBI, we're able to measure the magnetic field
directions so as to distinguish between the two main models of the environment
in which methanol masers form: disks or shocks.
  We present polarised images of the methanol maser source G339.88-1.2, made
with the LBA at 6.7-GHz. With these first polarisation maps made with the LBA,
which successfully reproduce observations with the ATCA confirming the new AIPS
code, a new technique for Southern VLBI is opened. The magnetic field
directions found are inconstant with methanol masers arising in disks for the
majority of the emission.


title: Mass Matrix Model Broken From A4 To 2 $\leftrightarrow$ 3 Symmetry

abstract:
  2$\leftrightarrow$3 symmetry is realized by the breaking from alterating
group of degree 4 ($A4$) symmetry. $A4$ explains why the generation number is
three. However the mass matrices are realized in the form of the breaking to
$2\leftrightarrow 3$ symmetry $\times Z_3$, which leads us to $2\leftrightarrow
3$ symmetric mass matrix with vanishing (1,1) component. Thus the $3\times 3$
mass matrix model with $2\leftrightarrow 3$ symmetry and vanishing (1,1)
component has the group theoretical background as the symmetry in GUT model.


title:
On the determination of $\sigma$ from experimental data on the $\pi\pi$
  isoscalar $S$-wave at low energies

abstract:
  We investigate the determination of the pole associated to $\sigma$ from
$\pi\pi$ scattering data below the $K\bar{K}$ threshold, including the new
precise data from $K_{e4}$ decay reported recently by the NA48/2 Collaboration.
Using a large class of analytic parametrizations based on expansions in powers
of conformal variables, we obtain for the mass and width of $\sigma$ values
which are consistent with those calculated recently using ChPT and Roy
equations, but have larger theoretical uncertainties.


title:
A new proof for the multiplicative property of the boolean cumulants
  with applications to operator-valued case

abstract:
  The paper presents several combinatorial properties of the boolean cumulants.
A corollary is a new proof of the multiplicative property of the boolean
cumulant series that can be easily adapted for the case of boolean independence
with amalgamation over an algebra.


title: Lie 3-Algebra and Multiple M2-branes

abstract:
  Motivated by the recent proposal of an N=8 supersymmetric action for multiple
M2-branes, we study the Lie 3-algebra in detail. In particular, we focus on the
fundamental identity and the relation with Nambu-Poisson bracket. Some new
algebras not known in the literature are found. Next we consider cubic matrix
representations of Lie 3-algebras. We show how to obtain higher dimensional
representations by tensor products for a generic 3-algebra. A criterion of
reducibility is presented. We also discuss the application of Lie 3-algebra to
the membrane physics, including the Basu-Harvey equation and the Bagger-Lambert
model.


title:
A Possible Future Long Baseline Neutrino and Nucleon Decay Experiment
  with a 100 kton Liquid Argon TPC at Okinoshima using the J-PARC Neutrino
  Facility

abstract:
  In this paper, we consider the physics performance of a single far detector
composed of a 100 kton next generation Liquid Argon Time Projection Chamber
(LAr TPC) possibly located at shallow depth, coupled to the J-PARC neutrino
beam facility with a realistic 1.66 MW operation of the Main Ring. The new far
detector could be located in the region of Okinoshima islands (baseline $L\sim
658$ km). Our emphasis is based on the measurement of the $\theta_{13}$ and
$\delta_{CP}$ parameters, possibly following indications for a non-vanishing
$\theta_{13}$ in T2K, and relies on the opportunity offered by the LAr TPC to
reconstruct the incoming neutrino energy with high precision compared to other
large detector technologies. We mention other possible baselines like for
example J-PARC-Kamioka (baseline $L\sim 295$ km), or J-PARC-Eastern Korean
coast (baseline $L\sim 1025$ km). Such a detector would also further explore
the existence of proton decays.


title: Truthful Unsplittable Flow for Large Capacity Networks

abstract:
  In this paper, we focus our attention on the large capacities unsplittable
flow problem in a game theoretic setting. In this setting, there are selfish
agents, which control some of the requests characteristics, and may be
dishonest about them. It is worth noting that in game theoretic settings many
standard techniques, such as randomized rounding, violate certain monotonicity
properties, which are imperative for truthfulness, and therefore cannot be
employed. In light of this state of affairs, we design a monotone deterministic
algorithm, which is based on a primal-dual machinery, which attains an
approximation ratio of $\frac{e}{e-1}$, up to a disparity of $\epsilon$ away.
This implies an improvement on the current best truthful mechanism, as well as
an improvement on the current best combinatorial algorithm for the problem
under consideration. Surprisingly, we demonstrate that any algorithm in the
family of reasonable iterative path minimizing algorithms, cannot yield a
better approximation ratio. Consequently, it follows that in order to achieve a
monotone PTAS, if exists, one would have to exert different techniques. We also
consider the large capacities \textit{single-minded multi-unit combinatorial
auction problem}. This problem is closely related to the unsplittable flow
problem since one can formulate it as a special case of the integer linear
program of the unsplittable flow problem. Accordingly, we obtain a comparable
performance guarantee by refining the algorithm suggested for the unsplittable
flow problem.


title:
Cold gas in the Perseus cluster core: Excitation of molecular gas in
  filaments

abstract:
  We have recently detected CO lines in the well-known filaments around NGC
1275, the galaxy at the centre of the Perseus cluster of galaxies. These
previous observations, with the HERA multi-beam array at the IRAM 30m telescope
enabled us to make a large map of the CO(2-1) line and to see hints of
molecular gas far away from the cluster centre. To confirm the presence of CO
emission lines in the outer filaments and to study the CO(2-1)/CO(1-0) line
ratio, we observed seven regions of interest again with the 30m telescope in
both CO(1-0) and CO(2-1). The regions we observed were: the eastern filament,
the horseshoe, the northern filament and a southern extension, all selected
from Halpha emission line mapping. Molecular gas is detected in all the
observed regions. This result confirms the large extent of the cold molecular
gas filaments. We discuss the CO(2-1)/CO(1-0) ratios in the filaments. The
eastern filament has optically thick gas, whereas further away, the line ratio
increases close to values expected for a warmer optically thin medium. We also
show CO(1-0) and CO(2-1) lines in 9 regions closer to the centre. The
kinematics of the CO is studied here in more detail and confirms that it
follows the motions of the warm H_2 gas found in the near-infrared. Finally, we
searched for dense gas tracers around 3C84 and claim here the first detection
of HCN(3-2).


title:
Isospectral Deformations of Eguchi-Hanson Spaces as Nonunital Spectral
  Triples

abstract:
  We study the isospectral deformations of the Eguchi-Hanson spaces along a
torus isometric action in the noncompact noncommutative geometry. We
concentrate on locality, smoothness and summability conditions of the nonunital
spectral triples, and relate them to the geometric conditions to be
noncommutative spin manifolds.


title: Composition-Diamond Lemma for Tensor Product of Free Algebras

abstract:
  In this paper, we establish Composition-Diamond lemma for tensor product $k<
X> \otimes k< Y>$ of two free algebras over a field. As an application, we
construct a Groebner-Shirshov basis in $k< X> \otimes k< Y>$ by lifting a
Groebner-Shirshov basis in $k[X] \otimes k< Y>$, where $k[X]$ is a commutative
algebra.


title:
On Universality of Bulk Local Regime of the Deformed Gaussian Unitary
  Ensemble

abstract:
  We consider the deformed Gaussian Ensemble $H_n=M_n+H^{(0)}_n$ in which
$H_n^{(0)}$ is a diagonal Hermitian matrix and $M_n$ is the Gaussian Unitary
Ensemble (GUE) random matrix. Assuming that the Normalized Counting Measure of
$H_n^{(0)}$ (both non-random and random) converges weakly to a measure
$N^{(0)}$ with a bounded support we prove universality of the local eigenvalue
statistics in the bulk of the limiting spectrum of $H_n$.


title:
Retrograde resonances in compact multi-planetary systems: a feasible
  stabilizing mechanism

abstract:
  Multi-planet systems detected until now are in most cases characterized by
hot-Jupiters close to their central star as well as high eccentricities. As a
consequence, from a dynamical point of view, compact multi-planetary systems
form a variety of the general N-body problem (with N >= 3), whose solutions are
not necessarily known. Extrasolar planets are up to now found in prograde (i.e.
direct) orbital motions about their host star and often in mean-motion
resonances (MMR). In the present paper, we investigate a theoretical
alternative suitable for the stability of compact multi-planetary systems. When
the outer planet moves on a retrograde orbit in MMR with respect to the inner
planet, we find that the so-called retrograde resonances present fine and
characteristic structures particularly relevant for dynamical stability. We
show that retrograde resonances and their resources open a family of
stabilizing mechanisms involving specific behaviors of apsidal precessions. We
also point up that for particular orbital data, retrograde MMRs may provide
more robust stability compared to the corresponding prograde MMRs.


title:
Direct construction of the effective action of chiral gauge fermions in
  the anomalous sector

abstract:
  The anomaly implies an obstruction to a fully chiral covariant calculation of
the effective action in the abnormal parity sector of chiral theories. The
standard approach then is to reconstruct the anomalous effective action from
its covariant current. In this work we use a recently introduced formulation
which allows to directly construct the non trivial chiral invariant part of the
effective action within a fully covariant formalism. To this end we develop an
appropriate version of Chan's approach to carry out the calculation within the
derivative expansion. The result to four derivatives, i.e., to leading order in
two and four dimensions and next-to-leading order in two dimensions, is
explicitly worked out. Fairly compact expressions are found for these terms.


title:
Micromagnetics of single and double point contact spin torque
  oscillators

abstract:
  In this paper we numerically conduct micromagnetic modelling to optimize
computational boundaries of magnetic thin-film elements applicable to single
and double point contact spin torque nano-oscillators. Different boundary
conditions have been introduced to compensate spin waves reflections at
boundaries that are based on extended layers, absorbing boundaries, and focal
point methods and are compared with a technique based on scattering theory. A
surface roughness boundary model is presented which is modelled according to
the Rayleigh criterion to minimize specular reflections at computational
boundaries. It is shown that the surface roughness model disperses the
reflected spin waves and improves the signal to background noise ratio. The
model is tested in comparison to conventional approaches such as extended layer
systems, variable damping constant and focal point methods for double point
contacts. The surface roughness model gives solutions that are stable in time,
in qualitative agreement with experiments and capable to reproduce phenomena
such as phase locking in double point contacts.


title:
The One-Dimenshional Inverse Wave Spectral Problem with Discontinuous
  Wave Speed

abstract:
  The inverse problem for the Sturm- Liouville operator with complex periodic
potential and positive discontinuous coefficients on the axis is studied. Main
characteristics of the fundamental solutions are investigated, the spectrum of
the operator is studied. We give formulation of the inverse problem, prove a
uniqueness theorem and provide a constructive procedure for the solution of the
inverse problem


title: Self-properties of codimension-2 braneworlds

abstract:
  We consider four-dimensional de Sitter, flat and anti de Sitter branes
embedded in a six-dimensional bulk spacetime whose dynamics is dictated by
Lovelock theory. We find, applying a generalised version of Birkhoff's theorem,
that all possible maximally symmetric braneworld solutions are embedded in
Wick-rotated black hole spacetimes of Lovelock theory. These are warped
solitonic spaces, where the horizons of the black hole geometries correspond to
the possible positions of codimension-2 branes. The horizon temperature is
related via conical singularities to the tension or vacuum energy of the
branes. We classify the braneworld solutions for certain combinations of bulk
parameters, according to their induced curvature, their vacuum energy and their
effective compactness in the extra dimensions. The bulk Lovelock theory gives
an induced gravity term on the brane, which, we argue, generates
four-dimensional gravity up to some distance scale.
  As a result, some simple solutions, such as the Lovelock corrected
Schwarzschild black hole in six dimensions, are shown to give rise to
self-accelerating braneworlds. We also find that several other solutions have
self-tuning properties. Finally, we present regular gravitational instantons of
Lovelock gravity and comment on their significance.


title:
Nonexistence of holomorphic submersions between complex unit balls
  equivariant with respect to a lattice and their generalizations

abstract:
  In this article we prove first of all the nonexistence of holomorphic
submersions other than covering maps between compact quotients of complex unit
balls, with a proof that works equally well in a more general equivariant
setting. For a non-equidimensional surjective holomorphic map between compact
ball quotients, our method applies to show that the set of critical values must
be nonempty and of codimension 1. In the equivariant setting the line of
arguments extend to holomorphic mappings of maximal rank into the complex
projective space or the complex Euclidean space, yielding in the latter case a
lower estimate on the dimension of the singular locus of certain holomorphic
maps defined by integrating holomorphic 1-forms. In another direction, we
extend the nonexistence statement on holomorphic submersions to the case of
ball quotients of finite volume, provided that the target complex unit ball is
of dimension m>=2, giving in particular a new proof that a local biholomorphism
between noncompact m-ball quotients of finite volume must be a covering map
whenever m>=2. Finally, combining our results with Hermitian metric rigidity,
we show that any holomorphic submersion from a bounded symmetric domain into a
complex unit ball equivariant with respect to a lattice must factor through a
canonical projection to yield an automorphism of the complex unit ball,
provided that either the lattice is cocompact or the ball is of dimension at
least 2.


title: On black hole thermodynamics and the entropy function formalism

abstract:
  From the black hole thermodynamics point of view, we show that the entropy
function $\mathbf{f}$ and the free energy $F$ are related via
$\mathbf{f}=e_{I}q_{I}+\Omega_Hq_I{A_{\phi}^I}'-\frac{\partial F}{\partial r}
|_{r_{H}}$. Assuming the entropy function is known for extremal black holes, we
propose an approach to calculate the entropy of non-extremal cases by slightly
moving the extremal black hole geometry from extremality. The entropy of
non-extremal $D1D5$- and $D1D5p$-branes in the presence of higher derivative
corrections are computed as concrete examples. An attempt has also been made to
explain why the entropy function method can calculate the corrected entropy
without knowing the exact form of black hole solution in higher derivative
gravity theories.


title: Hyperbolic lattice-point counting and modular symbols

abstract:
  For a cocompact group $\G$ of $\slr$ we fix a real non-zero harmonic 1-form
$\alpha$. We study the asymptotics of the hyperbolic lattice-counting problem
for $\G$ under restrictions imposed by the modular symbols
$\modsym{\gamma}{\a}$. We prove that the normalized values of the modular
symbols, when ordered according to this counting, have a Gaussian distribution.


title: "Pair production of scalar top quarks in e+e- collisions at ILC."

abstract:
  We study the pair production of scalar top quarks in e+e- collisions with the
subsequent decay of the top squarks into b-quarks and charginos. We simulate
this process using PYTHIA6.4 for beam energies 2E_beam = 350, 400, 500, 800,
1000 GeV. Proposing a set of criteria we obtain a good separation of the signal
stop events from top quark pair production which is the main background. The
number of stop production events obtained with the proposed cuts for different
energies is calculated for an integrated luminosity of 1000 1/fb. We propose a
method to reconstruct the mass of the top squark, provided the mass of the
lightest neutralino is known, and estimate the error of the mass determination
for the case sqrt{s} = 500 GeV.


title:
Shot-noise detection of ultrasound-tagged photons in
  ultrasound-modulated optical imaging

abstract:
  We propose a new detection method for ultrasound-modulated optical tomography
that allows us to perform parallel speckle detection with optimum shot-noise
sensitivity, using a CCD camera. Moreover, we show that making use of a spatial
filter system allows us to fully filter out speckle decorrelation noise. This
method is confirmed by a test experiment


title: Conservation Properties in the Time-Dependent Hartree Fock Theory

abstract:
  We discuss the conservation of angular momentum in nuclear time-dependent
Hartree-Fock calculations for a numerical representation of wave functions and
potentials on a three-dimensional cartesian grid. Free rotation of a deformed
nucleus performs extremely well even for relatively coarse spatial grids. Heavy
ion collisions produce a highly excited compound system associated with
substantial nucleon emission. These emitted nucleons reach the bounds of the
numerical box which leads to a decrease of angular momentum. We discuss
strategies to distinguish the physically justified loss from numerical
artifacts.


title: Group Actions as Stroboscopic Maps of Ordinary Differential Equations

abstract:
  Discrete-time dynamical systems can be derived from group actions. In the
present work possibility of application of this method to systems of ordinary
differential equations is studied. Invertible group actions are considered as
possible candidates for stroboscopic maps of ordinary differential equations.
It is shown that flow of the Bloch equation is a unique suspension of an
invertible map on the SU(2) group.


title:
Effect of the Photon's Brownian Doppler Shift on the Weak-Localization
  Coherent-Backscattering Cone

abstract:
  We report the first observation of the dependence of the
coherent-backscattering (CBS) enhanced cone with the frequency of the
backscattered photon. The experiment is performed on a diffusing liquid
suspension and the Doppler broadening of light is induced by the Brownian
motion of the scatterers. Heterodyne detection on a CCD camera is used to
measure the complex field (i.e., the hologram) of the light that is
backscattered at a given frequency. The analysis of the holograms yield the
frequency and the propagation direction of the backscattered photons. We
observe that the angular CBS cone becomes more narrow in the tail of the
Brownian spectrum. The experimental results are in good agreement with a simple
theoretical model.


title:
The Dynamics of Silica Melts under High Pressure: Mode-Coupling Theory
  Results

abstract:
  The high-pressure dynamics of a computer-modeled silica melt is studied in
the framework of the mode-coupling theory of the glass transition (MCT) using
static-structure input from molecular-dynamics (MD) computer simulation. The
theory reproduces the experimentally known viscosity minimum (diffusivity
maximum) as a function of density or pressure and explains it in terms of a
corresponding minimum in its critical temperature. This minimum arises from a
gradual change in the equilibrium static structure which shifts from being
dominated by tetrahedral ordering to showing the cageing known from
high-density liquids. The theory is in qualitative agreement with computer
simulation results.


title: $G_2$-Holonomy Metrics Connected with a 3-Sasakian Manifold

abstract:
  We construct complete noncompact Riemannian metrics with $G_2$-holonomy on
noncompact orbifolds that are $\Bbb R^3$-bundles with the twistor space
$\mathcal{Z}$ as a spherical fiber.


title: Geometry of neutral metrics in dimesnion four

abstract:
  The purpose of this article is to review some recent results on the geometry
of neutral signature metrics in dimension four and their twistor spaces. The
following topics are considered: Neutral K\"ahler and hyperk\"ahler surfaces,
Walker metrics, Neutral anti-self-dual 4-manifolds and projective structures,
Twistor spaces of neutral metrics.


title: Noise and aliases in off-axis and phase-shifting holography

abstract:
  We have compared the respective efficiencies of off-axis and phase-shifting
holography in terms of noise and aliases removal. The comparison is made by
analyzing holograms of an USAF target backlit with laser illumination, recorded
with a charge-coupled device camera. We show that it is essential to remove the
LO beam noise, especially at low illumination levels.


title:
Representing elementary semi-algebraic sets by a few polynomial
  inequalities: A constructive approach

abstract:
  Let P be an elementary closed semi-algebraic set in R^d, i.e., there exist
real polynomials p_1,...,p_s such that P= \{x \in R^d : p_1(x) \ge 0, >...,
p_s(x) \ge 0 \}; in this case p_1,...,p_s are said to represent P. Denote by
$n$ the maximal number of the polynomials from \{p_1,...,p_s\} that vanish in a
point of P. If P is non-empty and bounded, we show that it is possible to
construct n+1 polynomials representing P. Furthermore, the number n+1 can be
reduced to n in the case when the set of points of P in which n polynomials
from \{p_1,...,p_s\} vanish is finite. Analogous statements are also obtained
for elementary open semi-algebraic sets.


title: Sagnac-loop phase shifter with polarization-independent operation

abstract:
  A bulk-optics, polarization-independent phase shifter for photonic quantum
information applications is demonstrated. A transverse mode electro-optic
modulator using lithium niobate is placed in a Sagnac-like loop containing
Faraday rotators. This direction-dependent polarization rotation in the loop is
combined with a Mach-Zehnder interferometer to form an optical switch with an
on/off contrast of 96% and a switching time of 1.6 ns.


title:
Controlling instabilities along a 3DVar analysis cycle by assimilating
  in the unstable subspace: a comparison with the EnKF

abstract:
  A hybrid scheme obtained by combining 3DVar with the Assimilation in the
Unstable Subspace (3DVar-AUS) is tested in a QG model, under perfect model
conditions, with a fixed observational network, with and without observational
noise. The AUS scheme, originally formulated to assimilate adaptive
observations, is used here to assimilate the fixed observations that are found
in the region of local maxima of BDAS vectors (Bred vectors subject to
assimilation), while the remaining observations are assimilated by 3DVar.
  The performance of the hybrid scheme is compared with that of 3DVar and of an
EnKF. The improvement gained by 3DVar-AUS and the EnKF with respect to 3DVar
alone is similar in the present model and observational configuration, while
3DVar-AUS outperforms the EnKF during the forecast stage. The 3DVar-AUS
algorithm is easy to implement and the results obtained in the idealized
conditions of this study encourage further investigation toward an
implementation in more realistic contexts.


title: Kinetic-growth self-avoiding walks on small-world networks

abstract:
  Kinetically-grown self-avoiding walks have been studied on Watts-Strogatz
small-world networks, rewired from a two-dimensional square lattice. The
maximum length L of this kind of walks is limited in regular lattices by an
attrition effect, which gives finite values for its mean value < L >. For
random networks, this mean attrition length < L > scales as a power of the
network size, and diverges in the thermodynamic limit (large system size N).
For small-world networks, we find a behavior that interpolates between those
corresponding to regular lattices and randon networks, for rewiring probability
p ranging from 0 to 1. For p < 1, the mean self-intersection and attrition
length of kinetically-grown walks are finite. For p = 1, < L > grows with
system size as N^{1/2}, diverging in the thermodynamic limit. In this limit and
close to p = 1, the mean attrition length diverges as (1-p)^{-4}. Results of
approximate probabilistic calculations agree well with those derived from
numerical simulations.


title: A constructive proof of the existence of Viterbi processes

abstract:
  Since the early days of digital communication, hidden Markov models (HMMs)
have now been also routinely used in speech recognition, processing of natural
languages, images, and in bioinformatics. In an HMM $(X_i,Y_i)_{i\ge 1}$,
observations $X_1,X_2,...$ are assumed to be conditionally independent given an
``explanatory'' Markov process $Y_1,Y_2,...$, which itself is not observed;
moreover, the conditional distribution of $X_i$ depends solely on $Y_i$.
Central to the theory and applications of HMM is the Viterbi algorithm to find
{\em a maximum a posteriori} (MAP) estimate $q_{1:n}=(q_1,q_2,...,q_n)$ of
$Y_{1:n}$ given observed data $x_{1:n}$. Maximum {\em a posteriori} paths are
also known as Viterbi paths or alignments. Recently, attempts have been made to
study the behavior of Viterbi alignments when $n\to \infty$. Thus, it has been
shown that in some special cases a well-defined limiting Viterbi alignment
exists. While innovative, these attempts have relied on rather strong
assumptions and involved proofs which are existential. This work proves the
existence of infinite Viterbi alignments in a more constructive manner and for
a very general class of HMMs.

categories: math.ST cs.IT math.IT math.PR stat.CO stat.ML stat.TH


title:
Robust adiabatic approach to optical spin entangling in coupled quantum
  dots

abstract:
  Excitonic transitions offer a possible route to ultrafast optical spin
manipulation in coupled nanostructures. We perform here a detailed study of the
three principal exciton-mediated decoherence channels for optically-controlled
electron spin qubits in coupled quantum dots: radiative decay of the excitonic
state, exciton-phonon interactions, and Landau-Zener transitions between
laser-dressed states. We consider a scheme to produce an entangling
controlled-phase gate on a pair of coupled spins which, in its simplest dynamic
form, renders the system subject to fast decoherence rates associated with
exciton creation during the gating operation. In contrast, we show that an
adiabatic approach employing off-resonant laser excitation allows us to
suppress all sources of decoherence simultaneously, significantly increasing
the fidelity of operations at only a relatively small gating time cost. We find
that controlled-phase gates accurate to one part in 10^2 can realistically be
achieved with the adiabatic approach, whereas the conventional dynamic approach
does not appear to support a fidelity suitable for scalable quantum
computation. Our predictions could be demonstrated experimentally in the near
future.


title:
Universal Charge-Radius Relation for Subatomic and Astrophysical Compact
  Objects

abstract:
  Electron-positron pair creation in supercritical electric fields limits the
net charge of any static, spherical object, such as superheavy nuclei,
strangelets, and Q-balls, or compact stars like neutron stars, quark stars, and
black holes. For radii between $4\times10^2$ fm and $10^4$ fm the upper bound
on the net charge is given by the universal relation $Z=0.71R_{fm}$, and for
larger radii (measured in fm or km) $Z = 7 \times 10^{-5} R_{fm}^2 = 7 \times
10^{31} R_{km}^2$. For objects with nuclear density the relation corresponds to
$Z \approx 0.7 A^{1/3}$ ($10^{8} < A < 10^{12}$) and $Z \approx 7\times10^{-5}
A^{2/3}$ ($A > 10^{12}$), where $A$ is the baryon number. For some systems this
universal upper bound improves existing charge limits in the literature.


title:
The prompt, high resolution spectroscopic view of the "naked-eye"
  GRB080319B

abstract:
  GRB080319B reached 5th optical magnitude during the burst prompt emission.
Thanks to the VLT/UVES rapid response mode, we observed its afterglow just
8m:30s after the GRB onset when the magnitude was R ~ 12. This allowed us to
obtain the best signal-to-noise, high resolution spectrum of a GRB afterglow
ever (S/N per resolution element ~ 50). The spectrum is rich of absorption
features belonging to the main system at z=0.937, divided in at least six
components spanning a total velocity range of 100 km/s. The VLT/UVES
observations caught the absorbing gas in a highly excited state, producing the
strongest Fe II fine structure lines ever observed in a GRB. A few hours later
the optical depth of these lines was reduced by a factor of 4-20, and the
optical/UV flux by a factor of ~ 60. This proves that the excitation of the
observed fine structure lines is due to "pumping" by the GRB UV photons. A
comparison of the observed ratio between the number of photons absorbed by the
excited state and those in the Fe II ground state suggests that the six
absorbers are ~ 2-6 kpc from the GRB site, with component I ~ 3 times closer to
the GRB site than components III to VI. Component I is characterized also by
the lack of Mg I absorption, unlike all other components. This may be due both
to a closer distance and a lower density, suggesting a structured ISM in this
galaxy complex.


title: A General Reciprocity Law on arbitrary Vector Spaces

abstract:
  The paper contained a preliminary version of a general theory of reciprocity
laws on vector spaces.


title:
The candidate filament close to the 3C295 galaxy cluster: optical and
  X-ray spectroscopy

abstract:
  We present a detailed analysis of the overdensity of X-ray sources colse to
the 3C 295 galaxy cluster (z=0.46) to assess whether it is associated with a
filament of the large-scale structure of the Universe. We obtained optical
spectra of the optical counterparts of eleven sources associated with the
filament, finding that one is at z=0.474. This is a type 1 AGN at 1.5 arcmin
from the cluster center. We found three more sources with a redshift in the
range 0.37 - 0.53. We extracted the stacked X-ray spectrum of 47 X-ray sources
belonging to the putative filament. We found a significant narrow (at the
resolution of the Chandra ACIS-I) line at E ~ 4.4 keV, the energy of the iron
Kalpha line at the redshift of the cluster. The detection of this line is
confirmed at a confidence level of better than 3sigma and its energy is
constrained to be in the range 6.2--6.47 (at a 90% confidence level), excluding
an identification with the 6.7 helium-like iron line from the hot cluster ICM
at better than 4 sigma. We conclude that the detection of the redshifted line
is a strong indication that at least several of the excess sources lie at z ~
0.46 and that AGNs are efficient tracers of the ``filament'' connected with the
central cluster of galaxies.


title: Thorough analysis of input physics in CESAM and CLES codes

abstract:
  This contribution is not about the quality of the agreement between stellar
models computed by CESAM and CLES codes, but more interesting, on what
ESTA-Task~1 run has taught us about these codes and about the input physics
they use. We also quantify the effects of different implementations of the same
physics on the seismic properties of the stellar models, that in fact is the
main aim of ESTA experiments.


title: A classification of mahonian maj-inv statistics

abstract:
  Two well known mahonian statistics on words are the inversion number and the
major index. In 1996, Foata and Zeilberger introduced generalizations,
parameterized by relations, of these statistics. In this paper, we study the
statistics which can be written as a sum of these generalized statistics. This
leads to generalizations of some classical results. In particular, we
characterize all such statistics which are mahonian.


title:
The Chebotarev-Gregoratti Hamiltonian as singular perturbation of a
  nonsemibounded operator

abstract:
  We derive the Hamiltonian associated to a quantum stochastic flow by
extending the Albeverio-Kurasov construction of self-adjoint extensions to
finite rank perturbations of nonsemibounded operators to Fock space.


title: Thermonuclear Supernovae

abstract:
  The application of Type Ia supernovae (SNe Ia) as distance indicators in
cosmology calls for a sound understanding of these objects. Recent years have
seen a brisk development of astrophysical models which explain SNe Ia as
thermonuclear explosions of white dwarf stars. While the evolution of the
progenitor is still uncertain, the explosion mechanism certainly involves the
propagation of a thermonuclear flame through the white dwarf star.
Three-dimensional hydrodynamical simulations allowed to study a wide variety of
possibilities involving subsonic flame propagation (deflagrations), flames
accelerated by turbulence, and supersonic detonations. These possibilities lead
to a variety of scenarios. I review the currently discussed approaches and
present some recent results from simulations of the turbulent deflagration
model and the delayed detonation model.


title: The Baltimore and Utrecht models for cluster dissolution

abstract:
  The analysis of the age distributions of star cluster samples of different
galaxies has resulted in two very different empirical models for the
dissolution of star clusters: the Baltimore model and the Utrecht model. I
describe these two models and their differences. The Baltimore model implies
that the dissolution of star clusters is mass independent and that about 90% of
the clusters are destroyed each age dex, up to an age of about a Gyr, after
which point mass-dependent dissolution from two-body relaxation becomes the
dominant mechanism. In the Utrecht model, cluster dissolution occurs in three
stages: (i) mass-independent infant mortality due to the expulsion of gas up to
about 10 Myr; (ii) a phase of slow dynamical evolution with strong evolutionary
fading of the clusters lasting up to about a Gyr; and (iii) a phase dominated
by mass dependent-dissolution, as predicted by dynamical models. I describe the
cluster age distributions for mass-limited and magnitude-limited cluster
samples for both models. I refrain from judging the correctness of these
models.


title: Classical and quantum scattering by a Coulomb potential

abstract:
  For relativistic energies the small angle classical cross section for
scattering on a Coulomb potential agrees with the first Born approximation for
quantum cross section for scalar particle only in the leading term. The
disagreement in other terms can be avoided if the sum of all corrections to the
first Born approximation for large enough Coulomb charge contain the classical
terms which are independent of that charge. A small part of the difference in
classical and quantum cross sections may be attributed to the fact that the
relativistic quantum particle can rush through the field without interaction.
We expect that smaller impact parameters and spin facilitate this affect.


title:
Combinatorial representations of Coxeter groups over a field of two
  elements

abstract:
  Let $W$ denote a simply-laced Coxeter group with $n$ generators. We construct
an $n$-dimensional representation $\phi$ of $W$ over the finite field $F_2$ of
two elements. The action of $\phi(W)$ on $F_2^n$ by left multiplication is
corresponding to a combinatorial structure extracted and generalized from Vogan
diagrams. In each case W of types A, D and E, we determine the orbits of
$F_2^n$ under the action of $\phi(W)$, and find that the kernel of $\phi$ is
the center $Z(W)$ of $W.$


title: The orbital and physical parameters of the eclipsing binary OW Gemiorum

abstract:
  We present our multicolour photometric data of the primary and secondary
eclipses of OW Gem that took place in 1995, 2002, and 2006, as well as the new
radial-velocity data collected since 1993 by R. F. Griffin and A. Duquennoy.
The Wilson-Devinney code was used for the simultaneous solution of both
photometric and spectroscopic data. A complete set of orbital and physical
parameters of the components was obtained. The pair of values, eccentricity
e=0.5286 and argument of periastron omega=140.73 degree, give better
compatibility of the moment of the secondary minimum with the observations
compared to previous estimates.


title:
The evolution of the brightest cluster galaxies since z~1 from the ESO
  Distant Cluster Survey (EDisCS)

abstract:
  [Abridged] We present K-band data for the brightest cluster galaxies (BCGs)
from the ESO Distant Cluster Survey. These data are combined with photometry
from Aragon-Salamanca et al. (1998) and a low-redshift comparison sample from
von der Linden et al. (2007). The K-band Hubble diagram for BCGs exhibits very
low scatter (~0.35mag) since z=1. The colour and $K$-band luminosity evolution
of the BCGs are in good agreement with passively-evolving stellar populations
formed at z>2. We do not detect any significant change in the stellar mass of
the BCG since z~1. These results do not seem to depend on the velocity
dispersion of the parent cluster. There is a correlation between the 1D
velocity dispersion of the clusters and the K-band luminosity of the BCGs
(after correcting for passive evolution). The clusters with large velocity
dispersions tend to have brighter BCGs, i.e., BCGs with larger stellar masses.
This dependency, although significant, is relatively weak: the stellar mass of
the BCGs changes only by ~70% over a two-order-of-magnitude range in cluster
mass. This dependency doesn't change significantly with redshift. The models of
De Lucia & Blaizot (2007) predict colours which are in reasonable agreement
with the observations because the growth in stellar mass is dominated by the
accretion of old stars. However, the stellar mass in the model BCGs grows by a
factor of 3-4 since z=1, a growth rate which seems to be ruled out by the
observations. The models predict a dependency between the BCG's stellar mass
and the velocity dispersion of the parent cluster in the same sense as the
data, but the dependency is significantly stronger than observed. However, one
major difficulty in this comparison is that we have measured fixed metric
aperture magnitudes while the models compute total luminosities.


title:
On Walkup's class ${\cal K}(d)$ and a minimal triangulation of $(S^3
  \times \rotatebox{90}{\ltimes} S^1)^{\#3}$

abstract:
  For $d \geq 2$, Walkup's class ${\cal K}(d)$ consists of the $d$-dimensional
simplicial complexes all whose vertex-links are stacked $(d-1)$-spheres. Kalai
showed that for $d \geq 4$, all connected members of ${\cal K}(d)$ are obtained
from stacked $d$-spheres by finitely many elementary handle additions.
According to a result of Walkup, the face vector of any triangulated 4-manifold
$X$ with Euler characteristic $\chi$ satisfies $f_1 \geq 5f_0 - {15/2} \chi$,
with equality only for $X \in {\cal K}(4)$. K\"{u}hnel observed that this
implies $f_0(f_0 - 11) \geq -15\chi$, with equality only for 2-neighborly
members of ${\cal K}(4)$. K\"{u}hnel also asked if there is a triangulated
4-manifold with $f_0 = 15$, $\chi = -4$ (attaining equality in his lower
bound). In this paper, guided by Kalai's theorem, we show that indeed there is
such a triangulation. It triangulates the connected sum of three copies of the
twisted sphere product $S^3 \times {-2.8mm}_{-} S^1$. Because of K\"{u}hnel's
inequality, the given triangulation of this manifold is a vertex-minimal
triangulation. By a recent result of Effenberger, the triangulation constructed
here is tight. Apart from the neighborly 2-manifolds and the infinite family of
$(2d+ 3)$-vertex sphere products $S^{d-1} \times S^1$ (twisted for $d$ odd),
only fourteen tight triangulated manifolds were known so far. The present
construction yields a new member of this sporadic family. We also present a
self-contained proof of Kalai's result.


title: Simplicial Descent Categories

abstract:
  Much of the homotopical and homological structure of the categories of chain
complexes and topological spaces can be deduced from the existence and
properties of the 'simple' functors Tot : {double chain complexes} -> {chain
complexes} and geometric realization : {sSets} -> {Top}, or similarly, Tot :
{simplicial chain complexes} -> {chain complexes} and | | : {sTop} -> {Top}.
The purpose of this thesis is to abstract this situation, and to this end we
introduce the notion of '(co)simplicial descent category'. It is inspired by
Guillen-Navarros's '(cubical) descent categories'. The key ingredients in a
(co)simplicial descent category D are a class E of morphisms in D, called
equivalences, and a 'simple' functor s : {(co)simplicial objects in D} -> D.
They must satisfy axioms like 'Eilenberg-Zilber', 'exactness' and 'acyclicity'.
This notion covers a wide class of examples, as chain complexes, sSets,
topological spaces, filtered cochain complexes (where E = filtered
quasi-isomorphisms or E = E_2-isomorphisms), commutative differential graded
algebras (with s = Navarro's Thom-Whitney simple), DG-modules over a
DG-category and mixed Hodge complexes, where s = Deligne's simple. From the
simplicial descent structure we obtain homotopical structure on D, as cone and
cylinder objects. We use them to i) explicitly describe the morphisms of
HoD=D[E^{-1}] similarly to the case of calculus of fractions; ii) endow HoD
with a non-additive pre-triangulated structure, that becomes triangulated in
the stable additive case. These results use the properties of a 'total
functor', which associates to any biaugmented bisimplicial object a simplicial
object. It is the simplicial analogue of the total chain complex of a double
complex, and it is left adjoint to Illusie's 'decalage' functor.


title:
From Qualitative to Quantitative Proofs of Security Properties Using
  First-Order Conditional Logic

abstract:
  A first-order conditional logic is considered, with semantics given by a
variant of epsilon-semantics, where p -> q means that Pr(q | p) approaches 1
super-polynomially --faster than any inverse polynomial. This type of
convergence is needed for reasoning about security protocols. A complete
axiomatization is provided for this semantics, and it is shown how a
qualitative proof of the correctness of a security protocol can be
automatically converted to a quantitative proof appropriate for reasoning about
concrete security.


title:
Size dependence of multipolar plasmon resonance frequencies and damping
  rates in simple metal spherical nanoparticles

abstract:
  Multipolar plasmon oscillation frequencies and corresponding damping rates
for nanospheres formed of the simplest free-electron metals are studied. The
possibility of controlling plasmon features by choosing the size and dielectric
properties of the sphere surroundings is discussed. Optical properties of the
studied metals are described within the Drude-Sommerfeld model of the
dielectric function with effective parameters acounting for the contribution of
conduction electrons and of interband transitions. No approximation is made in
respect of the size of a particle; plasmon size characteristics are described
rigorously. The results of our experiment on sodium nanodroplets [1] are
compared with the oscillation frequency size dependence of dipole and
quadrupole plasmon.


title: A Characterization of Semisimple Plane Polynomial Automorphisms

abstract:
  It is well-known that an element of the linear group ${\rm GL}_n(\C)$ is
semisimple if and only if its conjugacy class is Zariski closed. The aim of
this paper is to show that the same result holds for the group of complex plane
polynomial automorphisms.


title: Local conditions for global representations of quadratic forms

abstract:
  We show that the theorem of Ellenberg and Venkatesh on representation of
integral quadratic forms by integral positive definite quadratic forms is valid
under weaker conditions on the represented form.


title: Energy Realpolitik: Towards a Sustainable Energy Strategy

abstract:
  A long-term strategy based on existing technological, ecological, economical,
and geopolitical realities is urgently needed to develop a sustainable energy
economy, which should be designed with adaptability to unpredicted changes in
any of these aspects. While only a highly diverse energy portfolio and
conservation can ultimately guarantee optimum sustainability, based on a
comparison of current primary energy generation methods, it is argued that
future energy strategy has to rely heavily on expanded coal and nuclear energy
sectors. A comparison of relative potentials, merits and risks associated with
fossil-fuel, renewable, and nuclear technologies suggests that the balance of
technologies should be shifted in favor of new-generation, safe nuclear methods
to produce electricity, while clean-coal plants should be assigned to
transportation fuel. Novel nuclear technologies exploit fission of uranium and
thorium as primary energy sources with fast-spectrum and transmutation (burner)
reactors. A closed fuel cycle and waste transmutation resolve the strategic
issues associated with nuclear power. Innovative reactor designs utilize
spallation of heavy metals in subcritical accelerator driven systems or
molten-salt reactors. Importation and reconstruction of technical expertise
already lost and aversion of further erosion are preconditions to any
successful energy strategy. Research opportunities to perfect innovative
nuclear, coal, and renewable energy technologies should be pursued.


title: Direct-decay properties of Giant Resonances

abstract:
  A semi-microscopic approach based on the continuum-RPA method and a
phenomenological treatment of the spreading effect is developed and applied to
describe direct-decay properties of a few isovector giant resonances.
Capabilities of the approach to describe giant-resonance gross properties are
also checked.


title: Fermionic quantum criticality and the fractal nodal surface

abstract:
  The complete lack of theoretical understanding of the quantum critical states
found in the heavy fermion metals and the normal states of the high-T$_c$
superconductors is routed in deep fundamental problem of condensed matter
physics: the infamous minus signs associated with Fermi-Dirac statistics render
the path integral non-probabilistic and do not allow to establish a connection
with critical phenomena in classical systems. Using Ceperley's constrained
path-integral formalism we demonstrate that the workings of scale invariance
and Fermi-Dirac statistics can be reconciled. The latter is self-consistently
translated into a geometrical constraint structure. We prove that this "nodal
hypersurface" encodes the scales of the Fermi liquid and turns fractal when the
system becomes quantum critical. To illustrate this we calculate nodal surfaces
and electron momentum distributions of Feynman backflow wave functions and
indeed find that with increasing backflow strength the quasiparticle mass
gradually increases, to diverge when the nodal structure becomes fractal. Such
a collapse of a Fermi liquid at a critical point has been observed in the
heavy-fermion intermetallics in a spectacular fashion.


title: The secret world of shrimps: polarisation vision at its best

abstract:
  Animal vision spans a great range of complexity, with systems evolving to
detect variations in optical intensity, distribution, colour, and polarisation.
Polarisation vision systems studied to date detect one to four channels of
linear polarisation, combining them in opponent pairs to provide
intensity-independent operation. Circular polarisation vision has never been
seen, and is widely believed to play no part in animal vision. Polarisation is
fully measured via Stokes' parameters--obtained by combined linear and circular
polarisation measurements. Optimal polarisation vision is the ability to see
Stokes' parameters: here we show that the crustacean \emph{Gonodactylus
smithii} measures the exact components required. This vision provides optimal
contrast-enhancement, and precise determination of polarisation with no
confusion-states or neutral-points--significant advantages. We emphasise that
linear and circular polarisation vision are not different modalities--both are
necessary for optimal polarisation vision, regardless of the presence of
strongly linear or circularly polarised features in the animal's environment.

categories: physics.bio-ph physics.optics q-bio.NC quant-ph


title: f(R) cosmology by Noether's symmetry

abstract:
  A general approach to find out exact cosmological solutions in f(R)-gravity
is discussed. Instead of taking into account phenomenological models, we
assume, as a physical criterium, the existence of Noether symmetries in the
cosmological f(R) Lagrangian. As a result, the presence of such symmetries
selects viable models and allow to solve the equations of motion. We discuss
also the case in which no Noether charge is present but general criteria can be
used to achieve solutions.


title:
Single electron tunneling as a possible conduction mechanism in diamond
  like carbon film

abstract:
  Nonlinear current voltage characteristics and in some cases also step like
characteristics were observed in diamond like carbon films. We suggest that the
transport mechanism is tunneling between conducting nanoparticles in the films
and the observation of step like structures is a manifestation of Coulomb
blockade found for the first time in these films. We point out that the origin
of similar current voltage characteristics observed in other carbon structures
can be also Coulomb blockade phenomenon.


title: A first principles study on organic molecules encapsulated BN nanotubes

abstract:
  The electronic structures of boron nitride nanotubes (BNNTs) doped by organic
molecules are investigated with density functional theory. Electrophilic
molecule introduces acceptor states in the wide gap of BNNT close to the
valence band edge, which makes the doped system a $p$-type semiconductor.
However, with typical nucleophilic organic molecules encapsulation, only deep
occupied molecular states but no shallow donor states are observed. There is a
significant electron transfer from BNNT to electrophilic molecule, while the
charge transfer between nucleophilic molecule and BNNT is neglectable. When
both electrophilic and nucleophilic molecules are encapsulated in the same
BNNT, large charge transfer between the two kinds of molecules occurs. The
resulted small energy gap can strongly modify the transport and optical
properties of the system.


title:
Non-simple abelian varieties in a family: geometric and analytic
  approaches

abstract:
  Let $A_t$ be a family of abelian varieties over a number field $k$
parametrized by a rational coordinate $t$, and suppose the generic fiber of
$A_t$ is geometrically simple. For example, we may take $A_t$ to be the
Jacobian of the hyperelliptic curve $y^2 = f(x)(x-t)$ for some polynomial $f$.
We give two upper bounds for the number of $t \in k$ of height at most $B$ such
that the fiber $A_t$ is geometrically non-simple. One bound comes from
arithmetic geometry, and shows that there are only finitely many such $t$; but
one has very little control over how this finite number varies as $f$ changes.
Another bound, from analytic number theory, shows that the number of
geometrically non-simple fibers grows quite slowly with $B$; this bound, by
contrast with the arithmetic one, is effective, and is uniform in the
coefficients of $f$. We hope that the paper, besides proving the particular
theorems we address, will serve as a good example of the strengths and
weaknesses of the two complementary approaches.


title:
The H alpha Galaxy Survey V. The star formation history of late-type
  galaxies

abstract:
  This study of 117 low-redshift Im and Sm galaxies investigates the star
formation rates of late-type galaxies, to determine whether they are
quasi-continuous or dominated by bursts with quiescent interludes. We analyse
the distribution of star formation timescales (stellar masses/star formation
rates) for the entire sample, and of gas depletion timescales for those
galaxies with gas mass measurements. We find that, on average, the late-type
galaxies studied could have produced their total stellar masses by an
extrapolation of their current star formation activity over a period of just
under a Hubble time. This is not the case for a comparison sample of
earlier-type galaxies, even those with disk-dominated morphologies and similar
total stellar masses to the late-type galaxies. The earlier-type galaxies are
on average forming their stars more slowly at present than the average rate
over their past histories. No totally quiescent Im or Sm galaxies are found,
and although some evidence of intrinsic variation in the star formation rate
with time is found, this is typically less than a factor of 2 increase or
decrease relative to the mean level. The Im and Sm galaxies have extensive gas
reservoirs and can maintain star formation at the current rate for more than
another Hubble time. The average spatial distribution of star formation in the
Im galaxies, and to a lesser extent the Sm galaxies, is very similar to that of
the older stellar population traced by the red light.


title: The fast life of holographic mesons

abstract:
  We use holographic techniques to study meson quasiparticles moving through a
thermal plasma in N=2 super-Yang-Mills theory, with gauge group SU(N_c) and
coupled to N_f flavours of fundamental matter. This holographic approach
reliably describes the system at large N_c, large 't Hooft coupling and
N_f/N_c<<1. The meson states are destabilized by introducing a small quark
density n_q. Spectral functions are used to examine the dispersion relations of
these quasiparticles. In a low-momentum regime, the quasiparticles approach a
limiting velocity which can be significantly less than the speed of light. In
this regime, the widths of the quasiparticles also rise dramatically as their
momentum approaches a critical value q_crit. While the spectral functions do
not display isolated resonances for q>q_crit, the dispersion relations can be
extended into this high-momentum regime by studying the dual quasinormal modes.
A preliminary qualitative analysis of these modes suggests that the group
velocity rises to the speed of light for q>>q_crit.


title: Subsystems of Fock Need Not Be Fock: Spatial CP-Semigroups

abstract:
  We show that a product subsystem of a time ordered system (that is, a product
system of time ordered Fock modules), though type I, need not be isomorphic to
a time ordered product system. In that way, we answer an open problem in the
classification of CP-semigroups by product systems. We define spatial strongly
continuous CP-semigroups on a unital C*-algebra and characterize them as those
that have a Christensen-Evans generator.


title:
Quantum critical dynamics of a S = 1/2 antiferromagnetic Heisenberg
  chain studied by 13C-NMR spectroscopy

abstract:
  We present a 13C-NMR study of the magnetic field driven transition to
complete polarization of the S=1/2 antiferromagnetic Heisenberg chain system
copper pyrazine dinitrate Cu(C_4H_4N_2)(NO_3)_2 (CuPzN). The static local
magnetization as well as the low-frequency spin dynamics, probed via the
nuclear spin-lattice relaxation rate 1/T_1, were explored from the low to the
high field limit and at temperatures from the quantum regime (k_B T << J) up to
the classical regime (k_B T >> J). The experimental data show very good
agreement with quantum Monte Carlo calculations over the complete range of
parameters investigated. Close to the critical field, as derived from static
experiments, a pronounced maximum in 1/T_1 is found which we interpret as the
finite-temperature manifestation of a diverging density of zero-energy magnetic
excitations at the field-driven quantum critical point.


title:
Electronic structures of defective BN nanotubes under transverse
  electric fields

abstract:
  We investigate the electronic structures of some defective boron nitride
nanotubes (BNNTs) under transverse electric fields within density-functional
theory. (16,0) BNNTs with antisite, carbon substitution, single vacancy, and
Stone-Wales 5775 defects are studied. Under transverse electric fields, the
band gaps of the defective BNNTs are reduced, similar to the pristine ones. The
energy levels of the defect states vary with the transverse electric field
directions, due to the different electrostatic potential shift at the defect
sites induced by the electric fields. Therefore, besides electronic structure
and optical property engineering, the transverse electric field can be used to
identify the defect positions in BNNTs.


title:
The $e^+e^-\to J/\psi D \bar D$, $J/\psi D\bar D^*$ reactions with
  dynamically generated resonances

abstract:
  In two recent reactions by Belle producing $D\bar D$ and $D\bar D^*$ meson
pairs, peaks above threshold have been measured in the differential cross
sections, possibly indicating new resonances in these channels. We want to
study such reactions from the point of view that the $D$ meson pairs are
produced from already known or predicted resonances below threshold. Our study
shows that the peak in the $D\bar D^*$ production is not likely to be caused by
the X(3872) resonance, but the peak seen in $D\bar D$ invariant mass can be
well described if the $D\bar D$ pair comes from the already predicted scalar
X(3700) resonance.


title:
Quantum electrodynamics and photon-assisted tunnelling in long Josephson
  junctions

abstract:
  We describe the interaction between an electromagnetic field and a long
Josephson junction (JJ) driven by a dc current. We calculate the amplitudes of
emission and absorption of light via the creation and annihilation of quantized
Josephson plasma waves (JPWs). Both, the energies of JPW quanta and the
amplitudes of light absorption and emission, strongly depend on the junction's
length and can be tuned by an applied dc current. Moreover, photon-assisted
macroscopic quantum tunnelling in long Josephson junctions show resonances when
the frequency of the outside radiation coincides with the current-driven
eigenfrequencies of the quantized JPWs.


title:
On the security of a new image encryption scheme based on chaotic map
  lattices

abstract:
  This paper reports a detailed cryptanalysis of a recently proposed encryption
scheme based on the logistic map. Some problems are emphasized concerning the
key space definition and the implementation of the cryptosystem using
floating-point operations. It is also shown how it is possible to reduce
considerably the key space through a ciphertext-only attack. Moreover, a timing
attack allows the estimation of part of the key due to the existent
relationship between this part of the key and the encryption/decryption time.
As a result, the main features of the cryptosystem do not satisfy the demands
of secure communications. Some hints are offered to improve the cryptosystem
under study according to those requirements.


title:
The full curvature effect expected in early X-ray afterglow emission of
  gamma-ray bursts

abstract:
  We explore the influence of the full curvature effect on the flux of early
X-ray afterglow of gamma-ray bursts (GRBs) in cases when the spectrum of the
intrinsic emission is a power-law. We find that the well-known $t^{-(2+\beta)}$
curve is present only when the intrinsic emission is extremely short or the
emission arises from an exponential cooling. The time scale of this curve is
independent of the Lorentz factor. The resulting light curve would contain two
phases when the intrinsic emission has a power-law spectrum and a temporal
power-law profile with infinite duration. The first phase is a rapid decay one
where the light curve well follows the $t^{-(2+\beta)}$ curve. The second is a
shallow decay phase where the power-law index of the light curve is obviously
smaller than that in the first phase. The start of the shallow phase is
strictly constrained by the fireball radius, which in turn, can put a lower
limit to the latter. In the case when the temporal power-law emission lasts a
limited interval of time, there will be a third phase after the
$t^{-(2+\beta)}$ curve and the shallow decay phase, which is much steeper than
the shallow phase. As an example of application, we fit the XRT data of GRB
050219A with our model and show that the curvature effect alone can roughly
account for this burst. Although fitting parameters can not be uniquely
determined due to various choices of fitting, a lower limit of the fireball
radius of this burst can be estimated, which is $\sim 10^{14}cm$.


title: Polarization and SEDs from Microlensing of Circumstellar Envelopes

abstract:
  Microlensing surveys have proven to be tremendously fruitful in providing
valuable data products for many fields of astrophysics, from eclipse
lightcurves for substellar candidates to limb darkening in stellar atmospheres.
We report on a program of modeling observables from microlensing of
circumstellar envelopes, particularly those of red giant stars that are the
most likely to show finite source effects. We will summarize work for how
polarization light curves can be used to infer envelope properties and will
describe recent modeling of the time dependent spectral energy distributions
(SEDs) for microlensing of dusty winds. One of the most exciting developments
is the possibility of measuring variable polarization from microlensing in a
suitable source using the RINGO polarimeter at La Palma. Also quite interesting
is the possibility of probing a dusty wind using IRAC data for a suitable
source in the event that Spitzer has a ``warm'' cycle.


title: Observations of Very Metal-Poor Stars in the Galaxy

abstract:
  I report on recent results from observations of stars with metallicities
[Fe/H] <= -2.0. These include a substantial new sample of objects with
high-resolution observations obtained as part of a follow-up of the HK Survey,
The Hamburg/ESO Survey, and the ongoing survey SEGUE: Sloan Extension for
Galactic Understanding and Exploration. Perspectives on the next directions are
also provided.


title: Thermodynamical Control by Frequent Quantum Measurements

abstract:
  Heat flow between a large ``bath'' and a smaller system brings them
progressively closer to thermal equilibrium while increasing their entropy.
Deviations from this trend are fluctuations involving a small fraction of a
statistical ensemble of systems interacting with the bath: in this respect,
quantum and classical thermodynamics are in agreement. Can there be drastic
differences between them? Here we address a distinctly quantum mechanical
setting that displays such differences: disturbances of thermal equilibrium
between two-level systems (TLS) and a bath by frequent and brief quantum
(non-demolishing) measurements of the TLS energy-states. If the measurements
are frequent enough to induce either the Zeno or the anti-Zeno regime, namely,
the slowdown or speedup of the TLS relaxation, then the resulting entropy and
temperature of both the system and the bath are found to be completely
unrelated to what is expected by standard thermodynamical rules that hold for
memoryless baths. The practical advantage of these anomalies is the possibility
of very fast control of heat and entropy, allowing cooling and
state-purification of quantum systems much sooner than their thermal
equilibration time.