title:
HR 710 (HD 15144): An ultra-Sr-rich, magnetic Ap star with a close
  companion

abstract:
  The magnetic, chemically peculiar A-star HR 710 (HD 15144, ADS 1849A, AB Cet)
has a close companion in a nearly circular orbit. Its 3-day period is unusually
short for such stars. The system emits moderately hard x-rays, which likely
come from a white dwarf secondary (ADS 1849Ab). The Sr II spectrum is very
strong, and the resonance lines show similar core-nib structure to the stronger
Ca K line. We place only loose constraints on a model. There are indications of
a lower electron/gas pressure than expected from the star's parallax and
brightness. Strong-line profiles and anomalous excitation/ionization indicate
significant deviations from traditional models, fixed by Teff, log{g}, and
abundances. Weak spectral-line profiles and wavelength shifts probably indicate
abundance patches rather than the presence of a secondary (ADS 1849Ab)
spectrum. Our UVES spectra are from only one epoch. Additional low-noise,
high-resolution spectra are needed. We discuss the spectrum within the context
of abundance stratification.


title: Energy Dependence of CP-Violation Reach for Monochromatic Neutrino Beam

abstract:
  The ultimate goal for future neutrino facilities is the determination of CP
violation in neutrino oscillations. Besides $| U(e3) | \ne 0$, this will
require precision experiments with a very intense neutrino source and energy
control. With this objective in mind, the creation of monochromatic neutrino
beams from the electron capture decay of boosted ions by the SPS of CERN has
been proposed. We discuss the capabilities of such a facility as a function of
the energy of the boost and the baseline for the detector. We compare the
physics potential for two different configurations: I) $\gamma=90$ and
$\gamma=195$ (maximum achievable at present SPS) to Frejus; II) $\gamma=195$
and $\gamma=440$ (maximum achievable at upgraded SPS) to Canfranc. We conclude
that the SPS upgrade to 1000 GeV is important to reach a better sensitivity to
CP violation iff it is accompanied by a longer baseline. In both Setups, the
gain in the CP violation sensitivity with a previous knowledge of $| U(e3) |$
is apparent.


title: Nano-Engineering Defect Structures on Graphene

abstract:
  We present a new way of nano-engineering graphene using defect domains. These
regions have ring structures that depart from the usual honeycomb lattice,
though each carbon atom still has three nearest neighbors. A set of stable
domain structures is identified using density functional theory (DFT),
including blisters, ridges, ribbons, and metacrystals. All such structures are
made solely out of carbon; the smallest encompasses just 16 atoms. Blisters,
ridges and metacrystals rise up out of the sheet, while ribbons remain flat. In
the vicinity of vacancies, the reaction barriers to formation are sufficiently
low that such defects could be synthesized through the thermally activated
restructuring of coalesced adatoms.


title:
The lowest-mass stellar black holes: catastrophic death of neutron stars
  in gamma-ray bursts

abstract:
  Mergers of double neutron stars are considered the most likely progenitors
for short gamma-ray bursts. Indeed such a merger can produce a black hole with
a transient accreting torus of nuclear matter (Lee & Ramirez-Ruiz 2007,
Oechslin & Janka 2006), and the conversion of a fraction of the torus
mass-energy to radiation can power a gamma-ray burst (Nakar 2006). Using
available binary pulsar observations supported by our extensive evolutionary
calculations of double neutron star formation, we demonstrate that the fraction
of mergers that can form a black hole -- torus system depends very sensitively
on the (largely unknown) maximum neutron star mass. We show that the available
observations and models put a very stringent constraint on this maximum mass
under the assumption that a black hole formation is required to produce a short
gamma-ray burst in a double neutron star merger. Specifically, we find that the
maximum neutron star mass must be within 2 - 2.5 Msun. Moreover, a single
unambiguous measurement of a neutron star mass above 2.5 Msun would exclude a
black hole -- torus central engine model of short gamma-ray bursts in double
neutron star mergers. Such an observation would also indicate that if in fact
short gamma-ray bursts are connected to neutron star mergers, the gamma-ray
burst engine is best explained by the lesser known model invoking a highly
magnetized massive neutron star (e.g., Usov 1992; Kluzniak & Ruderman 1998; Dai
et al. 2006; Metzger, Quataert & Thompson 2007).


title:
The Importance of Being First: Position Dependent Citation Rates on
  arXiv:astro-ph

abstract:
  We study the dependence of citation counts of e-prints published on the
arXiv:astro-ph server on their position in the daily astro-ph listing. Using
the SPIRES literature database we reconstruct the astro-ph listings from July
2002 to December 2005 and determine citation counts for e-prints from their ADS
entry. We use Zipf plots to analyze the citation distributions for each
astro-ph position. We find that e-prints appearing at or near the top of the
astro-ph mailings receive significantly more citations than those further down
the list. This difference is significant at the 7 sigma level and on average
amounts to two times more citations for papers at the top than those further
down the listing. We propose three possible non-exclusive explanations for this
positional citation effect and try to test them. We conclude that
self-promotion by authors plays a role in the observed effect but cannot
exclude that increased visibility at the top of the daily listings contributes
to higher citation counts as well. We can rule out that the positional
dependence of citations is caused by the coincidence of the submission deadline
with the working hours of a geographically constrained set of intrinsically
higher cited authors. We discuss several ways of mitigating the observed
effect, including splitting astro-ph into several subject classes, randomizing
the order of e-prints, and a novel approach to sorting entries by relevance to
individual readers.


title: Extended Anomalous Foreground Emission in the WMAP 3-Year Data

abstract:
  We study the spectral and morphological characteristics of the diffuse
Galactic emission in the WMAP temperature data using a template-based
multi-linear regression, and obtain the following results. 1. We confirm
previous observations of a bump in the dust-correlated spectrum, consistent
with the Draine & Lazarian spinning dust model. 2. We also confirm the "haze"
signal in the inner Galaxy, and argue that it does not follow a free-free
spectrum as first thought, but instead is synchrotron emission from a hard
electron cosmic-ray population. 3. In a departure from previous work, we allow
the spectrum of Halpha-correlated emission (which is used to trace the
free-free component) to float in the fit, and find that it does not follow the
expected free-free spectrum. Instead there is a bump near 50 GHz, modifying the
spectrum at the 20% level, which we speculate is caused by spinning dust in the
warm ionized medium. 4. The derived cross-correlation spectra are not sensitive
to the map zero points, but are sensitive to the choice of CMB estimator. In
cases where the CMB estimator is derived by minimizing variance of a linear
combination of the WMAP bands, we show that a bias proportional to the
cross-correlation of each template and the true CMB is always present. This
bias can be larger than any of the foreground signals in some bands. 5. Lastly,
we consider the frequency coverage and sensitivity of the Planck mission, and
suggest linear combination coefficients for the CMB template that will reduce
both the statistical and systematic uncertainty in the synchrotron and haze
spectra by more than an order of magnitude.


title: The Corona Theorem on the Complements of Certain Square Cantor Sets

abstract:
  Let $K$ be a square Cantor set, i.e. the Cartesian product $K=E\times E$ of
two linear Cantor sets. Let $\delta_n$ denote the proportion of the intervals
removed in the $n$th stage of the construction of $E$. It is shown that if
$\delta_n=o(\frac1{\log\log n})$ then the corona theorem holds on the domain
$\Omega=\mathbb C^\ast\setminus K$.


title:
How rapidly do neutron stars spin at birth? Constraints from archival
  X-ray observations of extragalactic supernovae

abstract:
  Traditionally, studies aimed at inferring the distribution of birth periods
of neutron stars are based on radio surveys. Here we propose an independent
method to constrain the pulsar spin periods at birth based on their X-ray
luminosities. In particular, the observed luminosity distribution of supernovae
poses a constraint on the initial rotational energy of the embedded pulsars,
via the L_X-dot{E}_{rot} correlation found for radio pulsars, and under the
assumption that this relation continues to hold beyond the observed range. We
have extracted X-ray luminosities (or limits) for a large sample of historical
SNe observed with Chandra, XMM and Swift, that have been firmly classified as
core-collapse supernovae. We have then compared these observational limits with
the results of Monte Carlo simulations of the pulsar X-ray luminosity
distribution, for a range of values of the birth parameters. We find that a
pulsar population dominated by millisecond periods at birth is ruled out by the
data.


title: Supermassive Black Holes in Deep Multiwavelength Surveys

abstract:
  In recent years deep X-ray and infrared surveys have provided an efficient
way to find accreting supermassive black holes, otherwise known as active
galactic nuclei (AGN), in the young universe. Such surveys can, unlike optical
surveys, find AGN obscured by high column densities of gas and dust. In those
cases, deep optical data show only the host galaxy, which can then be studied
in greater detail than in unobscured AGN. Some years ago the hard spectrum of
the X-ray "background" suggested that most AGN were obscured. Now GOODS, MUSYC,
COSMOS and other surveys have confirmed this picture and given important
quantitative constraints on AGN demographics. Specifically, we show that most
AGN are obscured at all redshifts and the amount of obscuration depends on both
luminosity and redshift, at least out to redshift z~2, the epoch of substantial
black holes and galaxy growth. Larger-area deep infrared and hard X-ray surveys
will be needed to reach higher redshifts and to probe fully the co-evolution of
galaxies and black holes.


title:
Nodal $d+id$ pairing and topological phases on the triangular lattice:
  unconventional superconducting state of Na$_x$CoO$_2\cdot y$H$_2$O

abstract:
  We show that finite angular momentum pairing chiral superconductors on the
triangular lattice have point zeroes in the complex gap function. A topological
quantum phase transition takes place through a nodal superconducting state at a
specific carrier density $x_c$ where the normal state Fermi surface crosses the
isolated zeros. For spin singlet pairing, we show that the second nearest
neighbor $d+id$-wave pairing can be the dominant pairing channel. The gapless
critical state at $x_c\simeq0.25$ has six Dirac points and is topologically
nontrivial with a $T^3$ spin relaxation rate below $T_c$. This picture provides
a possible explanation for the unconventional superconducting state of
Na$_x$CoO$_2\cdot y$H$_2$O. Analyzing a pairing model with strong correlation
using the Gutzwiller projection and symmetry arguments, we study these
topological phases and phase transitions as a function of Na doping.


title:
Nonequilibrium-induced metal-superconductor quantum phase transition in
  graphene

abstract:
  We study the effects of dissipation and time-independent nonequilibrium drive
on an open superconducting graphene. In particular, we investigate how
dissipation and nonequilibrium effects modify the semi-metal-BCS quantum phase
transition that occurs at half-filling in equilibrium graphene with attractive
interactions. Our system consists of a graphene sheet sandwiched by two
semi-infinite three-dimensional Fermi liquid reservoirs, which act both as a
particle pump/sink and a source of decoherence. A steady-state charge current
is established in the system by equilibrating the two reservoirs at different,
but constant, chemical potentials. The nonequilibrium BCS superconductivity in
graphene is formulated using the Keldysh path integral formalism, and we obtain
generalized gap and number density equations valid for both zero and finite
voltages. The behaviour of the gap is discussed as a function of both
attractive interaction strength and electron densities for various
graphene-reservoir couplings and voltages. We discuss how tracing out the
dissipative environment (with or without voltage) leads to decoherence of
Cooper pairs in the graphene sheet, hence to a general suppression of the gap
order parameter at all densities. For weak enough attractive interactions we
show that the gap vanishes even for electron densities away from half-filling,
and illustrate the possibility of a dissipation-induced metal-superconductor
quantum phase transition. We find that the application of small voltages does
not alter the essential features of the gap as compared to the case when the
system is subject to dissipation alone (i.e. zero voltage).


title: Finding Extreme Subdwarfs

abstract:
  I develop a new technique to identify M-type extreme subdwarfs (esdMs) and
demonstrate that it is substantially more efficient than previous methods. I
begin by obtaining spectroscopy and improved photometry of a sample of 54
late-type halo candidates using the rNLTT reduced proper motion (RPM) diagram.
  From spectroscopy, I find that four of these are esdMs, three of which were
previously unknown. From the improved photometry, I show that all four lie in a
narrow RPM corridor that contains only 4 non-esdMs. Hence, with good photometry
(i.e., without spectroscopy), it appears possible to select esdM candidates
with a 50% esdM yield. This is more than an order of magnitude more efficient
than previous methods.


title: Optical Link of the Atlas Pixel Detector

abstract:
  The on-detector optical link of the ATLAS pixel detector contains
radiation-hard receiver chips to decode bi-phase marked signals received on PIN
arrays and data transmitter chips to drive VCSEL arrays. The components are
mounted on hybrid boards (opto-boards). We present results from the irradiation
studies with 24 GeV protons up to 32 Mrad (1.2 x 10^15 p/cm^2) and the
experience from the production.


title:
Polylogarithms, hyperfunctions and generalized Lipschitz summation
  formulae

abstract:
  A generalization of the classical Lipschitz summation formula is proposed. It
involves new polylogarithmic rational functions constructed via the Fourier
expansion of certain sequences of Bernoulli--type polynomials. Related families
of one--dimensional hyperfunctions are also constructed.


title: The sorting order on a Coxeter group

abstract:
  Let $(W,S)$ be an arbitrary Coxeter system. For each word $\omega$ in the
generators we define a partial order--called the {\sf $\omega$-sorting
order}--on the set of group elements $W_\omega\subseteq W$ that occur as
subwords of $\omega$. We show that the $\omega$-sorting order is a
supersolvable join-distributive lattice and that it is strictly between the
weak and Bruhat orders on the group. Moreover, the $\omega$-sorting order is a
"maximal lattice" in the sense that the addition of any collection of Bruhat
covers results in a nonlattice. Along the way we define a class of structures
called {\sf supersolvable antimatroids} and we show that these are equivalent
to the class of supersolvable join-distributive lattices.


title: Lasing of donor-bound excitons in ZnSe microdisks

abstract:
  Excitons bound to flourine atoms in ZnSe have the potential for several
quantum optical applications. Examples include optically accessible quantum
memories for quantum information processing and lasing without inversion. These
applications require the bound-exciton transitions to be coupled to cavities
with high cooperativity factors, which results in the experimental observation
of low-threshold lasing. We report such lasing from fluorine-doped ZnSe quantum
wells in 3 and 6 micron microdisk cavities. Photoluminescence and selective
photoluminescence spectroscopy confirm that the lasing is due to bound-exciton
transitions.


title:
Interplay of Higgs and Sparticle Masses in the CMSSM with updated SUSY
  constraints

abstract:
  We estimate the bounds on Higgs and sparticle masses and discuss their
correlations in the constrained minimal supersymmetric standard model (CMSSM).
In our analysis we have applied the present constraints from collider and low
energy experiments, as well as the experimental bound on cold dark matter from
WMAP. For a given lightest Higgs boson mass, which is expected to be measured
with good precision at the LHC, we find important correlations between the
Higgs and sparticle masses which allows one to delineate the MSSM model
parameters and particle spectra. We have also demonstrated an important
complementarity between the LHC and direct dark matter detection experiments
emphasizing that by including the experimental input both from collider physics
and from dark matter detection experiments, one would significantly improve the
measurement of the SUSY spectrum and the underlying parameter space.


title:
Quantitative analysis of resolved X-ray emission line profiles of O
  stars

abstract:
  By quantitatively fitting simple emission line profile models that include
both atomic opacity and porosity to the Chandra X-ray spectrum of $\zeta$ Pup,
we are able to explore the trade-offs between reduced mass-loss rates and wind
porosity. We find that reducing the mass-loss rate of $\zeta$ Pup by roughly a
factor of four, to 1.5 \times 10^{-6} M_sun/yr, enables simple non-porous wind
models to provide good fits to the data. If, on the other hand, we take the
literature mass-loss rate of 6 \times 10^{-6} M_sun/yr, then to produce X-ray
line profiles that fit the data, extreme porosity lengths -- of $h_{\infty}
\approx 3$ Rstar -- are required. Moreover, these porous models do not provide
better fits to the data than the non-porous, low optical depth models.
Additionally, such huge porosity lengths do not seem realistic in light of 2-D
numerical simulations of the wind instability.


title: The world underground scientific facilities. A compendium

abstract:
  Underground laboratories provide the low radioactive background environment
necessary to explore the highest energy scales that cannot be reached with
accelerators, by searching for extremely rare phenomena. I have requested to
the Directors of the Laboratories a standard set of questions on the principal
characteristics of their laboratory and collected them in this compendium. I
included the ideas and plans for short-range developments. However,
next-generation structures, such as those for megaton-size detectors, are not
discussed. A short version of this work will be published in the Proccedings of
TAUP 2007.


title: Ground-based variability surveys towards Centaurus A: worthwhile or not?

abstract:
  Context: Difference imaging has proven to be a powerful technique for
detecting and monitoring the variability of unresolved stellar sources in M 31.
Using this technique in surveys of galaxies outside the Local Group could have
many interesting applications. Aims: The goal of this paper is to test
difference imaging photometry on Centaurus A, the nearest giant elliptical
galaxy, at a distance of 4 Mpc. Methods: We obtained deep photometric data with
the Wide Field Imager at the ESO/MPG 2.2m at La Silla spread over almost two
months. Applying the difference imaging photometry package DIFIMPHOT, we
produced high-quality difference images and detected variable sources. The
sensitivity of the current observational setup was determined through
artificial residual tests. Results: In the resulting high-quality difference
images, we detect 271 variable stars. We find a difference flux detection limit
corresponding to m_R~24.5. Based on a simple model of the halo of Centaurus A,
we estimate that a ground-based microlensing survey would detect in the order
of 4 microlensing events per year due to lenses in the halo. Conclusions:
Difference imaging photometry works very well at the distance of Centaurus A
and promises to be a useful tool for detecting and studying variable stars in
galaxies outside the local group. For microlensing surveys, a higher
sensitivity is needed than achieved here, which would be possible with a large
ground-based telescope or space observatory with wide-field imaging
capabilities.


title:
Near Zone Navier-Stokes Analysis of Heavy Quark Jet Quenching in an
  $\mathcal{N}$ =4 SYM Plasma

abstract:
  The near zone energy-momentum tensor of a supersonic heavy quark jet moving
through a strongly-coupled $\mathcal{N}=4$ SYM plasma is analyzed in terms of
first-order Navier-Stokes hydrodynamics. It is shown that the hydrodynamical
description of the near quark region worsens with increasing quark velocities.
For realistic quark velocities, $v=0.99$, the non-hydrodynamical region is
located at a narrow band surrounding the quark with a width of approximately
$3/\pi T$ in the direction parallel to the quark's motion and with a length of
roughly $10/\pi T$ in the perpendicular direction. Our results can be
interpreted as an indication of the presence of coherent Yang-Mills fields
where deviation from hydrodynamics is at its maximum. In the region where
hydrodynamics does provide a good description of the system's dynamics, the
flow velocity is so small that all the nonlinear terms can be dropped. Our
results, which are compatible with the thermalization timescales extracted from
elliptic flow measurements, suggest that if AdS/CFT provides a good description
of the RHIC system, the bulk of the quenched jet energy has more than enough
time to locally thermalize and become encoded in the collective flow. The
resulting flow pattern close to the quark, however, is shown to be considerably
different than the superposition of Mach cones and diffusion wakes observed at
large distances.


title: A Spectro-photometric Search for Galaxy Clusters in SDSS

abstract:
  Recent large-scale galaxy spectroscopic surveys, such as the Sloan Digital
Sky Survey (SDSS), enable us to execute a systematic, relatively-unbiased
search for galaxy clusters. Such surveys make it possible to measure the 3-d
distribution of galaxies but are hampered by the incompleteness problem due to
fiber collisions. In this study we aim to develop a density measuring technique
that alleviates the problem and derives densities more accurately by adding
additional cluster member galaxies that follow optical color-magnitude
relations for the given redshift. The new density measured with both
spectroscopic and photometric data shows a good agreement with apparent
information on cluster images and is supported by follow-up observations. By
adopting this new method, a total of 924 $robust$ galaxy clusters are found
from the SDSS DR5 database in the redshift range $0.05<z<0.1$, of which 212 are
new. Local maximum-density galaxies successfully represent cluster centers. We
provide the cluster catalogue including a number of cluster parameters.


title: Interaction correction to the conductance of a ballistic conductor

abstract:
  In disordered metals, electron-electron interactions are the origin of a
small correction to the conductivity, the "Altshuler-Aronov correction". Here
we investigate the Altshuler-Aronov correction of a conductor in which the
electron motion is ballistic and chaotic. We consider the case of a double
quantum dot, which is the simplest example of a ballistic conductor in which
the Altshuler-Aronov correction is nonzero. The fact that the electron motion
is ballistic leads to an exponential suppression of the correction if the
Ehrenfest time is larger than the mean dwell time or the inverse temperature.


title:
Can the tidal quality factors of terrestrial planets and moons scale as
  positive powers of the tidal frequency?

abstract:
  In geophysics and seismology, it is a common knowledge that the quality
factors Q of the mantle and crust materials scale as the tidal frequency to a
positive fractional power (Karato 2007, Efroimsky and Lainey 2007). In
astronomy, there exists an equally common belief that such rheological models
introduce discontinuities into the equations and thus are unrealistic at low
frequencies. We demonstrate that, while such models indeed make the
conventional expressions for the tidal torque diverge for vanishing
frequencies, the emerging infinities reveal not the impossible nature of one or
another rheology, but a subtle flaw in the underlying mathematical model of
friction. Flawed is the common misassumption that the tidal force and torque
are inversely proportional to the quality factor. In reality, they are
proportional to the sine of the tidal phase lag, while the inverse quality
factor is commonly identified with the tangent of the lag. The sine and tangent
of the lag are close everywhere {\it{except in the vicinity of the zero
frequency}}. Reinstating of this detail tames the fake infinities and
rehabilitates the "impossible" scaling law (which happens to be the actual law
the mantles obey). This preprint is a pilot paper. A more comprehensive
treatise on tidal torques is to be published (Efroimsky and Williams 2009).


title:
Evolution of Mid-IR Excess Around Sun-like Stars: Constraints on Models
  of Terrestrial Planet Formation

abstract:
  We report observations from the Spitzer Space Telescope (SST) regarding the
frequency of 24 micron excess emission toward sun-like stars. Our unbiased
sample is comprised of 309 stars with masses 0.7-2.2 Msun and ages from <3 Myr
to >3 Gyr that lack excess emission at wavelengths <=8 microns. We identify 30
stars that exhibit clear evidence of excess emission from the observed 24/8
micron flux ratio. The implied 24 micron excesses of these candidate debris
disk systems range from 13 % (the minimum detectable) to more than 100 %
compared to the expected photospheric emission. The frequency of systems with
evidence for dust debris emitting at 24 micron ranges from 8.5-19 % at ages
<300 Myr to < 4 % for older stars. The results suggest that many, perhaps most,
sun-like stars might form terrestrial planets.


title: Half-Twisted (0,2) Landau-Ginzburg Models

abstract:
  We compute correlators of chiral operators in (0,2) supersymmetric
Landau-Ginzburg theories. The class of theories and the correlators we study
are relevant for extending and testing mirror symmetry away from the (2,2)
locus. More generally, these methods provide alpha'-exact results about certain
superpotential couplings in compactifications of the heterotic string.


title: Jets in coronal holes: Hinode observations and 3D computer modelling

abstract:
  Recent observations of coronal hole areas with the XRT and EIS instruments
onboard the Hinode satellite have shown with unprecedented detail the launching
of fast, hot jets away from the solar surface. In some cases these events
coincide with episodes of flux emergence from beneath the photosphere. In this
letter we show results of a 3D numerical experiment of flux emergence from the
solar interior into a coronal hole and compare them with simultaneous XRT and
EIS observations of a jet-launching event that accompanied the appearance of a
bipolar region in MDI magnetograms. The magnetic skeleton and topology that
result in the experiment bear a strong resemblance to linear force-fee
extrapolations of the SOHO/MDI magnetograms. A thin current sheet is formed at
the boundary of the emerging plasma. A jet is launched upward along the open
reconnected field lines with values of temperature, density and velocity in
agreement with the XRT and EIS observations. Below the jet, a split-vault
structure results with two chambers: a shrinking one containing the emerged
field loops and a growing one with loops produced by the reconnection. The
ongoing reconnection leads to a horizontal drift of the vault-and-jet
structure. The timescales, velocities, and other plasma properties in the
experiment are consistent with recent statistical studies of this type of
events made with Hinode data.


title:
The Effect of Poloidal Magnetic Field on Type I Planetary Migration:
  Significance of Magnetic Resonance

abstract:
  We study the effect of poloidal magnetic field on type I planetary migration
by linear perturbation analysis in the shearing-sheet approximation and the
analytic results are compared with numerical calculations. In contrast to the
unmagnetized case, the basic equations that describe the wake due to the planet
in the disk allow magnetic resonances at which density perturbation diverges.
In order to simplify the problem, we consider the case without
magneto-rotational instability. We perform two sets of analyses:
two-dimensional and three-dimensional. In two-dimensional analysis, we find the
generalization of the torque formula previously known in unmagnetized case. In
three-dimensional calculations, we focus on the disk with very strong magnetic
field and derive a new analytic formula for the torque exerted on the planet.
We find that when Alfven velocity is much larger than sound speed,
two-dimensional torque is suppressed and three-dimensional modes dominate, in
contrast to the unmagnetized case.


title:
Non-perturbative renormalization of quark bilinear operators and B_K
  using domain wall fermions

abstract:
  We present a calculation of the renormalization coefficients of the quark
bilinear operators and the K-Kbar mixing parameter B_K. The coefficients
relating the bare lattice operators to those in the RI/MOM scheme are computed
non-perturbatively and then matched perturbatively to the MSbar scheme. The
coefficients are calculated on the RBC/UKQCD 2+1 flavor dynamical lattice
configurations. Specifically we use a 16^3 x 32 lattice volume, the Iwasaki
gauge action at beta=2.13 and domain wall fermions with L_s=16.


title:
Solutions with Vortices of a Semi-Stiff Boundary Value Problem for the
  Ginzburg-Landau Equation

abstract:
  We study solutions of the 2D Ginzburg-Landau equation -\Delta
u+\frac{1}{\ve^2}u(|u|^2-1)=0 subject to "semi-stiff" boundary conditions: the
Dirichlet condition for the modulus, |u|=1, and the homogeneous Neumann
condition for the phase. The principal result of this work shows there are
stable solutions of this problem with zeros (vortices), which are located near
the boundary and have bounded energy in the limit of small epsilon. For the
Dirichlet bondary condition ("stiff" problem), the existence of stable
solutions with vortices, whose energy blows up as epsilon goes to 0, is well
known. By contrast, stable solutions with vortices are not established in the
case of the homogeneous Neumann ("soft") boundary condition. (nonexistence is
proved for simply connected domains).
  In this work, we develop a variational method which allows one to construct
local minimizers of the corresponding Ginzburg-Landau energy functional. We
introduce an approximate bulk degree as the key ingredient of this method, and,
unlike the standard degree over the curve, it is preserved in the weak
H^1-limit.


title: Nucleosome Switching

abstract:
  We present a statistical-mechanical analysis of the positioning of
nucleosomes along one of the chromosomes of yeast DNA as a function of the
strength of the binding potential and of the chemical potential of the
nucleosomes. We find a significant density of two-level nucleosome switching
regions where, as a function of the chemical potential, the nucleosome
distribution undergoes a "micro" first-order transition. The location of these
nucleosome switches shows a strong correlation with the location of
transcription-factor binding sites.


title:
Environmentally-Induced Rabi Oscillations and Decoherence in Phase
  Qubits

abstract:
  We study decoherence effects in a dc SQUID phase qubit caused by an isolation
circuit with a resonant frequency. The coupling between the SQUID phase qubit
and its environment is modeled via the Caldeira-Leggett formulation of quantum
dissipation/coherence, where the spectral density of the environment is related
to the admittance of the isolation circuit. When the frequency of the qubit is
at least two times larger than the resonance frequency of the isolation
circuit, we find that the decoherence time of the qubit is two orders of
magnitude larger than the typical ohmic regime, where the frequency of the
qubit is much smaller than the resonance frequency of the isolation circuit.
Lastly, we show that when the qubit frequency is on resonance with the
isolation circuit, an oscillatory non-Markovian decay emerges, as the dc SQUID
phase qubit and its environment self-generate Rabi oscillations of
characteristic time scales shorter than the decoherence time.


title: Essential optical states in $\pi$-conjugated polymer thin films

abstract:
  We develop a theory of the electronic structure and photophysics of
interacting chains of $\pi$-conjugated polymers to understand the differences
between solutions and films. While photoexcitation generates only the exciton
in solutions, the optical exciton as well as weakly allowed excimers are
generated in films. Photoinduced absorption in films is primarily from the
lowest excimer. We are also able to explain peculiarities associated with
photoluminescence, including delayed photoluminescence and its quenching by
electric field.


title:
Realizable response matrices of multiterminal electrical, acoustic, and
  elastodynamic networks at a given frequency

abstract:
  We give a complete characterization of the possible response matrices at a
fixed frequency of n-terminal electrical networks of inductors, capacitors,
resistors and grounds, and of n-terminal discrete linear elastodynamic networks
of springs and point masses, both in the three-dimensional case and in the
two-dimensional case. Specifically we construct networks which realize any
response matrix which is compatible with the known symmetry properties and
thermodynamic constraints of response matrices. Due to a mathematical
equivalence we also obtain a characterization of the response matrices of
discrete acoustic networks.


title: A Compact Extreme Scattering Event Cloud Towards AO 0235+164

abstract:
  We present observations of a rare, rapid, high amplitude Extreme Scattering
Event toward the compact BL-Lac AO 0235+164 at 6.65 GHz. The ESE cloud is
compact; we estimate its diameter between 0.09 and 0.9 AU, and is at a distance
of less than 3.6 kpc. Limits on the angular extent of the ESE cloud imply a
minimum cloud electron density of ~ 4 x 10^3 cm^-3. Based on the amplitude and
timescale of the ESE observed here, we suggest that at least one of the
transients reported by Bower et al. (2007) may be attributed to ESEs.


title:
Exchange effects in elastic collisions of spin-polarized electrons with
  open-shell molecules with $^3\Sigma_g^-$ symmetry

abstract:
  The spin-exchange effect in spin-polarized electron collisions with
unpolarized open-shell molecules, O$_2$, B$_2$, S$_2$ and Si$_2$, has been
studied by the R-matrix method with the fixed-bond approximation. All of these
molecules have ${}^3 \Sigma_{g}^{-}$ symmetry in their ground states. Usual
integrated cross sections with unpolarized electrons has also been studied. We
used the complete active space self consistent field orbitals and put more than
10 target electronic states in the R-matrix models. In electron O$_2$ elastic
collisions, calculated polarization fractions agree well with the experimental
results, especially around the ${}^4 \Sigma_u^-$ resonance. In e-B$_2$, S$_2$
and Si$_2$ elastic collisions, larger spin-exchange effect is observed compared
to the e-O$_2$ elastic collisions. In all four cases, spin-exchange effect
becomes prominent near resonances. This association of resonance and magnitude
of the spin-exchange effect was studied by explicitly removing the resonance
configurations from the R-matrix calculations. In general, spin-exchange effect
is larger in e-B$_2$ collisions than in e-S$_2$ and Si$_2$ collisions, and is
smallest in e-O$_2$ collisions.


title: Strongly minimal PD4-complexes

abstract:
  We consider the homotopy types of $PD_4$-complexes $X$ with fundamental group
$\pi$ such that $c.d.\pi=2$ and $\pi$ has one end. Let $\beta=\beta_2(\pi;F_2)$
and $w=w_1(X)$. Our main result is that (modulo two technical conditions on
$(\pi,w)$) there are at most $2^\beta$ orbits of $k$-invariants determining
"strongly minimal" complexes (i.e., those with homotopy intersection pairing
$\lambda_X$ trivial). The homotopy type of a $PD_4$-complex $X$ with $\pi$ a
$PD_2$-group is determined by $\pi$, $w$, $\lambda_X$ and the $v_2$-type of
$X$. Our result also implies that Fox's 2-knot with metabelian group is
determined up to TOP isotopy and reflection by its group.


title: State transition of a non-Ohmic damping system in a corrugated plane

abstract:
  Anomalous transport of a particle subjected to non-Ohmic damping of the power
$\delta$ in a tilted periodic potential is investigated via Monte Carlo
simulation of generalized Langevin equation. It is found that the system
exhibits two relative motion modes: the locking state and the running state.
Under the surrounding of sub-Ohmic damping ($0<\delta<1$), the particle should
transfer into a running state from a locking state only when local minima of
the potential vanish; hence the particle occurs a synchronization oscillation
in its mean displacement and mean square displacement (MSD). In particular, the
two motion modes are allowed to coexist in the case of super-Ohmic damping
($1<\delta<2$) for moderate driving forces, namely, where exists double centers
in the velocity distribution. This induces the particle having faster
diffusion, i.e., its MSD reads $<\Delta x^2(t)> = 2D^{(\delta)}_{eff}
t^{\delta_{eff}}$. Our result shows that the effective power index
$\delta_{\textmd{eff}}$ can be enhanced and is a nonmonotonic function of the
temperature and the driving force. The mixture effect of the two motion modes
also leads to a breakdown of hysteresis loop of the mobility.


title:
High spatial resolution X-ray spectroscopy of SNR Cassiopeia A with {\sl
  Chandra}

abstract:
  We present high spatial resolution X-ray spectroscopy of supernova remnant
Cassiopeia A with the {\sl Chandra} observations. The X-ray emitting region of
this remnant was divided into 38 $\times$ 34 pixels with a scale of 10$\arcsec$
$\times$ 10$\arcsec$ each. Spectra of 960 pixels were created and fitted with
an absorbed two component non-equilibrium ionization model. With the spectral
analysis results we obtained maps of absorbing column density, temperatures,
ionization ages, and the abundances for Ne, Mg, Si, S, Ca and Fe. The Si, S and
possibly Ca abundance maps show obviously jet structures, while Fe doesn't
follow the jet but seems to be distributed perpendicular to it. In the range of
about two orders of magnitude, the abundances of Si, S and Ca show tight
correlations between each other, suggesting them to be ejecta from explosive
O-burning and incomplete Si-burning. Meanwhile, Ne abundance is well correlated
with that of Mg, indicating them to be the ashes of explosive C/Ne burning. The
Fe abundance is positively correlated with that of Si when Si abundance is
lower than 3 solar abundances, but a negative correlation appears when the Si
abundance is higher. We suggest that such a two phase correlation is the
results of different ways in which Fe is synthesized.


title: Generalised morphisms of k-graphs: k-morphs

abstract:
  In a number of recent papers, (k+l)-graphs have been constructed from
k-graphs by inserting new edges in the last l dimensions. These constructions
have been motivated by C*-algebraic considerations, so they have not been
treated systematically at the level of higher-rank graphs themselves. Here we
introduce k-morphs, which provide a systematic unifying framework for these
various constructions. We think of k-morphs as the analogue, at the level of
k-graphs, of C*-correspondences between C*-algebras. To make this analogy
explicit, we introduce a category whose objects are k-graphs and whose
morphisms are isomorphism classes of k-morphs. We show how to extend the
assignment \Lambda \mapsto C*(\Lambda) to a functor from this category to the
category whose objects are C*-algebras and whose morphisms are isomorphism
classes of C*-correspondences.


title: A characterisation of the Calabi product of hyperbolic affine spheres

abstract:
  There exists a well known construction which allows to associate with two
hyperbolic affine spheres $f_i: M_i^{n_i} \to \mathbb R^{n_i+1}$ a new
hyperbolic affine sphere immersion of $I \times M_1 \times M_2$ into $\mathbb
R^{n_1+n_2+3}$. In this paper we deal with the inverse problem: how to
determine from properties of the difference tensor whether a given hyperbolic
affine sphere immersion of a manifold $M^n \to \mathbb R^{n+1}$ can be
decomposed in such a way.


title: On sumsets of dissociated sets

abstract:
  In the paper we are studying some properties of subsets Q of sums of
dissociated sets. The exact upper bound for the number of solutions of the
following equation
  (1) q_1 + ... + q_p = q_{p+1} + ... + q_{2p}, q_i \in Q
  in groups F_2^n is found. Using our approach, we easily prove a recent result
of J. Bourgain on sets of large exponential sums and obtain a tiny improvement
of his theorem. Besides an inverse problem is considered in the article. Let Q
be a set belonging a sumset of two dissociated sets such that equation (1) has
many solutions. We prove that in the case the large proportion of Q is highly
structured.


title: The Jacobian as a measure of planar dose congruence

abstract:
  We propose a new starting point for comparing dose distributions in
therapeutic radiation physics using a Jacobian-based measure. The measure is
normalization independent, free of tunable parameters, bounded and converges to
a unique value when comparing unrelated dose distributions. We present a
preliminary demonstration of the sensitivity and general characteristics of
this measure.


title:
Field Tuned Superconductor to Insulator Transitions in an Amorphous Film
  with an Imposed Multiply Connected Geometry

abstract:
  We have observed multiple magnetic field driven superconductor to insulator
transitions (SIT) in amorphous Bi films perforated with a nano-honeycomb (NHC)
array of holes. The period of the magneto-resistance, H=H_M=h/2eS where S is
the area of a unit cell of holes, indicates the field driven transitions are
boson dominated. The field-dependent resistance follows
R(T)=R_0(H)exp(T_0(H)/T) on both sides of the transition so that the evolution
between these states is controlled by the vanishing of T_0 to0. We compare our
results to the thickness driven transition in NHC films and the field driven
transitions in unpatterned Bi films, other materials, and Josephson junction
arrays. Our results suggest a structural source for similar behavior found in
some materials and that despite the clear bosonic nature of the SITs,
quasiparticle degrees of freedom likely also play an important part in the
evolution of the SIT.


title: Level Structure of 103Ag at high spins

abstract:
  High spin states in $^{103}$Ag were investigated with the Gammasphere array,
using the $^{72}$Ge($^{35}$Cl,$2p2n$)$^{103}$Ag reaction at an incident beam
energy of 135 MeV. A $\Delta J$=1 sequence with predominantly magnetic
transitions and two nearly-degenerate $\Delta J=1$ doublet bands have been
observed. The dipole band shows a decreasing trend in the $B(M1)$ strength as
function of spin, a well established feature of magnetic bands. The
nearly-degenerate band structures satisfy the three experimental signatures of
chirality in the nuclei; however microscopic calculations are indicative of a
magnetic phenomenon


title: Representation theory of liftings of quantum planes

abstract:
  We systematically determine the regular representations, quivers and
representation type of all liftings of two-dimensional quantum linear spaces.


title: Orbit closures in the enhanced nilpotent cone

abstract:
  We study the orbits of $G=\mathrm{GL}(V)$ in the enhanced nilpotent cone
$V\times\mathcal{N}$, where $\mathcal{N}$ is the variety of nilpotent
endomorphisms of $V$. These orbits are parametrized by bipartitions of $n=\dim
V$, and we prove that the closure ordering corresponds to a natural partial
order on bipartitions. Moreover, we prove that the local intersection
cohomology of the orbit closures is given by certain bipartition analogues of
Kostka polynomials, defined by Shoji. Finally, we make a connection with Kato's
exotic nilpotent cone in type C, proving that the closure ordering is the same,
and conjecturing that the intersection cohomology is the same but with degrees
doubled.


title: On the Distribution of Pseudopowers

abstract:
  An $x$-pseudopower to base $g$ is a positive integer which is not a power of
$g$ yet is so modulo $p$ for all primes $p\le x$. We improve an upper bound for
the least such number due to E. Bach, R. Lukes, J. Shallit, and H. C. Williams.
The method is based on a combination of some bounds of exponential sums with
new results about the average behaviour of the multiplicative order of $g$
modulo prime numbers.


title: On Pseudosquares and Pseudopowers

abstract:
  Introduced by Kraitchik and Lehmer, an $x$-pseudosquare is a positive integer
$n\equiv1\pmod 8$ that is a quadratic residue for each odd prime $p\le x$, yet
is not a square. We use bounds of character sums to prove that pseudosquares
are equidistributed in fairly short intervals. An $x$-pseudopower to base $g$
is a positive integer which is not a power of $g$ yet is so modulo $p$ for all
primes $p\le x$. It is conjectured by Bach, Lukes, Shallit, and Williams that
the least such number is at most $\exp(a_g x/\log x)$ for a suitable constant
$a_g$. A bound of $\exp(a_g x\log\log x/\log x)$ is proved conditionally on the
Riemann Hypothesis for Dedekind zeta functions, thus improving on a recent
conditional exponential bound of Konyagin and the present authors. We also give
a GRH-conditional equidistribution result for pseudopowers that is analogous to
our unconditional result for pseudosquares.


title: Invariant properties for finding distance in space of elasticity tensors

abstract:
  Using orthogonal projections, we investigate distance of a given elasticity
tensor to classes of elasticity tensors exhibiting particular material
symmetries. These projections depend on the orientation of the elasticity
tensor, hence the distance is obtained as the minimization of corresponding
expressions with respect to the action of the orthogonal group. These
expressions are stated in terms of the eigenvalues of both the given tensor and
the projected one. The process of minimization is facilitated by the fact that,
as we prove, the traces of the corresponding Voigt and dilatation tensors are
invariant under these orthogonal projections. For isotropy, cubic symmetry and
transverse isotropy, we formulate algorithms to find both the orientation and
the eigenvalues of the elasticity tensor that is endowed with a particular
symmetry and is closest to the given elasticity tensor.


title: Polynomial Bridgeland stability conditions and the large volume limit

abstract:
  We introduce the notion of a polynomial stability condition, generalizing
Bridgeland stability conditions on triangulated categories. We construct and
study a family of polynomial stability conditions for any normal projective
variety. This family includes both Simpson-stability, and large volume limits
of Bridgeland stability conditions.
  We show that the PT/DT-correspondence relating stable pairs to
Donaldson-Thomas invariants (conjectured by Pandharipande and Thomas) can be
understood as a wall-crossing in our family of polynomial stability conditions.
Similarly, we show that the relation between stable pairs and invariants of
one-dimensional torsion sheaves (proven recently by the same authors) is a
wall-crossing formula.


title:
Light Echoes in Kerr Geometry: A Source of High Frequency QPOs from
  Random X-ray Bursts

abstract:
  We propose that high frequency quasi-periodic oscillations (HFQPOs) can be
produced from randomly-formed X-ray bursts (flashes) by plasma interior to the
ergosphere of a rapidly-rotating black hole. We show by direct computation of
their orbits that the photons comprising the observed X-ray light curves, if
due to a multitude of such flashes, are affected significantly by the black
hole's dragging of inertial frames; the photons of each such burst arrive to an
observer at infinity in multiple (double or triple), distinct "bunches"
separated by a roughly constant time lag of t/M~14, regardless of the bursts'
azimuthal position. We argue that every other such "bunch" represents photons
that follow trajectories with an additional orbit around the black hole at the
photon circular orbit radius (a photon "echo"). The presence of this constant
lag in the response function of the system leads to a QPO feature in its power
density spectra, even though the corresponding light curve consists of a
totally stochastic signal. This effect is by and large due to the black hole
spin and is shown to gradually diminish as the spin parameter a decreases or
the radial position of the burst moves outside the static limit surface
(ergosphere). Our calculations indicate that for a black hole with Kerr
parameter of a/M=0.99 and mass of M=10*Msun the QPO is expected at a frequency
of ~ 1.3-1.4 kHz. We discuss the plausibility and observational implications of
our model/results as well as its limitations.


title: Cost-driven weighted networks evolution

abstract:
  Inspired by studies on airline networks we propose a general model for
weighted networks in which topological growth and weight dynamics are both
determined by cost adversarial mechanism. Since transportation networks are
designed and operated with objectives to reduce cost, the theory of cost in
micro-economics plays a critical role in the evolution. We assume vertices and
edges are given cost functions according to economics of scale and diseconomics
of scale (congestion effect). With different cost functions the model produces
broad distribution of networks. The model reproduces key properties of real
airline networks: truncated degree distributions, nonlinear strength degree
correlations, hierarchy structures, and particulary the disassortative and
assortative behavior observed in different airline networks. The result
suggests that the interplay between economics of scale and diseconomics of
scale is a key ingredient in order to understand the underlying driving factor
of the real-world weighted networks.


title:
Airy kernel with two sets of parameters in directed percolation and
  random matrix theory

abstract:
  We introduce a generalization of the extended Airy kernel with two sets of
real parameters. We show that this kernel arises in the edge scaling limit of
correlation kernels of determinantal processes related to a directed
percolation model and to an ensemble of random matrices.


title: Short-time critical dynamics at perfect and non-perfect surface

abstract:
  We report Monte Carlo simulations of critical dynamics far from equilibrium
on a perfect and non-perfect surface in the 3d Ising model. For an ordered
initial state, the dynamic relaxation of the surface magnetization, the line
magnetization of the defect line, and the corresponding susceptibilities and
appropriate cumulant is carefully examined at the ordinary, special and surface
phase transitions. The universal dynamic scaling behavior including a dynamic
crossover scaling form is identified. The exponent $\beta_1$ of the surface
magnetization and $\beta_2$ of the line magnetization are extracted. The impact
of the defect line on the surface universality classes is investigated.


title: Asymmetry of Endofullerenes with Silver Atoms

abstract:
  A series of endofullerenes Ag@C60 with different symmetry are calculated at
ab initio level. The lowest energy structure is completely asymmetrical one
(C1), in which the endo-atom has noticeably off-centre position. The
symmetrical structures are less stable. Silver atom in the Ag@C60 (C1)
endofullerene has the low negative charge and high spin density.


title:
Second-Order Approximate Symmetries of the Geodesic Equations for the
  Reissner-Nordstr\"om Metric and Re-Scaling of Energy of a Test Particle

abstract:
  Following the use of approximate symmetries for the Schwarzschild spacetime
by A.H. Kara, F.M. Mahomed and A. Qadir (Nonlinear Dynam., to appear), we have
investigated the exact and approximate symmetries of the system of geodesic
equations for the Reissner-Nordstr\"om spacetime (RN). For this purpose we are
forced to use second order approximate symmetries. It is shown that in the
second-order approximation, energy must be rescaled for the RN metric. The
implications of this rescaling are discussed.


title:
A maximum principle for the Muskat problem for fluids with different
  densities

abstract:
  We consider the fluid interface problem given by two incompressible fluids
with different densities evolving by Darcy's law. This scenario is known as the
Muskat problem for fluids with the same viscosities, being in two dimensions
mathematically analogous to the two-phase Hele-Shaw cell. We prove in the
stable case (the denser fluid is below) a maximum principle for the $L^\infty$
norm of the free boundary.


title: Two-dimensional imaging of the spin-orbit effective magnetic field

abstract:
  We report on spatially resolved measurements of the spin-orbit effective
magnetic field in a GaAs/InGaAs quantum-well. Biased gate electrodes lead to an
electric-field distribution in which the quantum-well electrons move according
to the local orientation and magnitude of the electric field. This motion
induces Rashba and Dresselhaus effective magnetic fields. The projection of the
sum of these fields onto an external magnetic field is monitored locally by
measuring the electron spin-precession frequency using time-resolved Faraday
rotation. A comparison with simulations shows good agreement with the
experimental data.


title:
Comment on "Exposed-Key Weakness of Alpha-Eta" [Phys. Lett. A 370 (2007)
  131]

abstract:
  We show that the insecurity claim of the AlphaEta cryptosystem made by C. Ahn
and K. Birnbaum in Phys. Lett. A 370 (2007) 131-135 under heterodyne attack is
based on invalid extrapolations of Shannon's random cipher analysis and on an
invalid statistical independence assumption. We show, both for standard ciphers
and AlphaEta, that expressions of the kind given by Ahn and Birnbaum can at
best be interpreted as security lower bounds.


title: The derivatives of Asian call option prices

abstract:
  The distribution of a time integral of geometric Brownian motion is not well
understood. To price an Asian option and to obtain measures of its dependence
on the parameters of time, strike price, and underlying market price, it is
essential to have the distribution of time integral of geometric Brownian
motion and it is also required to have a way to manipulate its distribution. We
present integral forms for key quantities in the price of Asian option and its
derivatives ({\it{delta, gamma,theta, and vega}}). For example for any $a>0$
$\mathbb{E} [ (A_t -a)^+] = t -a + a^{2} \mathbb{E} [ (a+A_t)^{-1} \exp
(\frac{2M_t}{a+ A_t} - \frac{2}{a}) ]$, where $A_t = \int^t_0 \exp (B_s -s/2)
ds$ and $M_t =\exp (B_t -t/2).$


title:
Atomic clusters of various sizes irradiated with short intense pulses of
  VUV radiation

abstract:
  Non-equilibrium processes following the irradiation of atomic clusters with
short pulses of vacuum ultraviolet radiation are modelled using kinetic
Boltzmann equations. The dependence of the ionization dynamics on the cluster
size is investigated. The predictions on: (i) the maximal and average ion
charge created, (ii) ion charge state distribution, (iii) average energy
absorbed per atom, (iv) spatial charge distribution, and (v) thermalization
scales are obtained for spherical xenon clusters containing: 20, 70, 2500 and
90000 atoms. These clusters were exposed to single rectangular pulses of vacuum
ultraviolet radiation of various pulse intensities, I ~ 10^{12}-10^{14} W/cm^2
and durations < 50 fs, at a fixed integrated radiation flux of F=0.4 J/cm^2.
The results obtained are found to be in good agreement with the available
experimental data, especially the dependence on the cluster size, if it is
assumed that the ions from the positively charged outer layer of the cluster
constitute the dominant contribution to the experimentally measured ion charge
state distribution.


title: Magnetocaloric effect in R2Ti3Ge4 (R = Gd, Tb and Er) Compounds

abstract:
  Heat capacity of polycrystalline R2Ti3Ge4 (R = Gd, Tb and Er) compounds
(Orthorhombic, Sm5Ge4-type, Space group Pnma) has been studied in the
temperature range of 1.8 K to 300 K in various applied magnetic fields. The
compounds with magnetic lanthanide elements show interesting low field
magnetism intrigued by possible presence of competing antiferromagnetic and
ferromagnetic interactions. The magnetocaloric effect in these compounds is
estimated from the field dependent heat capacity data. The magnetic entropy
change and the adiabatic temperature change in the vicinity of the magnetic
transition are found to be significant.


title:
A FDR-preserving field theory for interacting Brownian particles:
  one-loop theory and MCT

abstract:
  We develop a field theoretical treatment of a model of interacting Brownian
particles. We pay particular attention to the requirement of the time reversal
invariance and the fluctuation-dissipation relationship (FDR). The method used
is a modified version of the auxiliary field method due originally to
Andreanov, Biroli and Lefevre [J. Stat. Mech. P07008 (2006)]. We recover the
correct diffusion law when the interaction is dropped as well as the standard
mode coupling equation in the one-loop order calculation for interacting
Brownian particle systems.


title: On Using Unsatisfiability for Solving Maximum Satisfiability

abstract:
  Maximum Satisfiability (MaxSAT) is a well-known optimization pro- blem, with
several practical applications. The most widely known MAXS AT algorithms are
ineffective at solving hard problems instances from practical application
domains. Recent work proposed using efficient Boolean Satisfiability (SAT)
solvers for solving the MaxSAT problem, based on identifying and eliminating
unsatisfiable subformulas. However, these algorithms do not scale in practice.
This paper analyzes existing MaxSAT algorithms based on unsatisfiable
subformula identification. Moreover, the paper proposes a number of key
optimizations to these MaxSAT algorithms and a new alternative algorithm. The
proposed optimizations and the new algorithm provide significant performance
improvements on MaxSAT instances from practical applications. Moreover, the
efficiency of the new generation of unsatisfiability-based MaxSAT solvers
becomes effectively indexed to the ability of modern SAT solvers to proving
unsatisfiability and identifying unsatisfiable subformulas.


title: Quantum Computations: Fundamentals And Algorithms

abstract:
  Basic concepts of quantum theory of information, principles of quantum
calculations and the possibility of creation on this basis unique on
calculation power and functioning principle device, named quantum computer, are
briefly reviewed. The main blocks of quantum logic, schemes of implementation
of quantum calculations, as well as some known today effective quantum
algorithms, called to realize advantages of quantum calculations upon
classical, are concerned. Among them special place is taken by Shor's algorithm
of number factorization, Grover's algorithm of unsorted database search and,
finally, the most promising in application methods of quantum phenomena
simulation, particularly quantum chaos. The most perspective methods of
experimental realization of quantum computer, namely nuclear-magnetic resonance
and trapped ions realizations, are discussed. Phenomena of decoherence, its
influence on quantum computer stability and methods of quantum error correction
are described.


title: The rarity of DNA profiles

abstract:
  It is now widely accepted that forensic DNA profiles are rare, so it was a
surprise to some people that different people represented in offender databases
are being found to have the same profile. In the first place this is just an
illustration of the birthday problem, but a deeper analysis must take into
account dependencies among profiles caused by family or population membership.


title: Primordial Nucleosynthesis in the Precision Cosmology Era

abstract:
  Primordial nucleosynthesis provides a probe of the Universe during its early
evolution. Given the progress exploring the constituents, structure, and recent
evolution of the Universe, it is timely to review the status of Big Bang
Nucleosynthesis (BBN) and to confront its predictions, along with the
constraints which emerge from them, with those derived from independent
observations of the Universe at much later epochs in its evolution. Following
an overview of the key physics controlling element synthesis in the early
Universe, the predictions of BBN in the standard models of cosmology and
particle physics are presented, along with those from some non-standard models.
The observational data used to infer the primordial abundances are described,
with an emphasis on the distinction between precision and accuracy. The
observationally inferred relic abundances are compared with the predicted
abundances, testing the internal consistency of BBN and enabling a comparison
of the BBN-inferred constraints with those derived from the Cosmic Background
Radiation and Large Scale Structure data. Emerging from these comparisons is
confirmation of a successful standard model along with constraints on (or hints
of) physics beyond the standard models of particle physics and of cosmology.


title:
Scattering of Spin-Zero and Spin-Half Particles in Momentum-Helicity
  Basis

abstract:
  Scattering of 2 particles of spin 0 and 1/2 is evaluated based on a basis
constructed from the momentum and the helicity states (the momentum-helicity
basis). This shortly called three-dimensional (3D) technique is a good
alternative to the standard partial wave (PW) technique especially for higher
energies, where PW calculations may become not feasible. Taking as input a
simple spin-orbit potential model we calculate as an example the spin averaged
differential cross section and polarization.


title:
Quantum Dimer Model on the triangular lattice: Semiclassical and
  variational approaches to vison dispersion and condensation

abstract:
  After reviewing the concept of vison excitations in Z_2 dimer liquids, we
study the liquid-crystal transition of the Quantum Dimer Model on the
triangular lattice by means of a semiclassical spin-wave approximation to the
dispersion of visons in the context of a "soft-dimer" version of the model.
This approach captures some important qualitative features of the transition:
continuous nature of the transition, linear dispersion at the critical point,
and \sqrt{12}x\sqrt{12} symmetry-breaking pattern. In a second part, we present
a variational calculation of the vison dispersion relation at the RK point
which reproduces the qualitative shape of the dispersion relation and the order
of magnitude of the gap. This approach provides a simple but reliable
approximation of the vison wave functions at the RK point.


title: Solitons for the nonlinear Klein-Gordon equation

abstract:
  In this paper we study existence and orbital stability for solitary waves of
the nonlinear Klein-Gordon equation. The energy of these solutions travels as a
localized packet, hence they are a particular type of solitons. In particular
we are interested in sufficient conditions on the potential for the existence
of solitons. Our proof is based on the study of the ratio energy/charge of a
function, which turns out to be a useful approach for many field equations.


title:
Two-Particle Correlations in the Wave Function and Covariant Current
  Approaches

abstract:
  We consider two-particle correlations, which appear in relativistic nuclear
collisions due to the quantum statistics of identical particles, in the frame
of two formalisms: wave-function and current. The first one is based on
solution of the Cauchy problem, whereas the second one is a so-called current
parametrization of the source of secondary particles. We argue that these two
parameterizations of the source coincide when the wave function at freeze-out
times is put in a specific correspondence with a current. Then, the
single-particle Wigner density evaluated in both approaches gives the same
result.


title:
Externally Occulted Terrestrial Planet Finder Coronagraph: Simulations
  and Sensitivities

abstract:
  A multitude of coronagraphic techniques for the space-based direct detection
and characterization of exo-solar terrestrial planets are actively being
pursued by the astronomical community. Typical coronagraphs have internal
shaped focal plane and/or pupil plane occulting masks which block and/or
diffract starlight thereby increasing the planet's contrast with respect to its
parent star. Past studies have shown that any internal technique is limited by
the ability to sense and control amplitude, phase (wavefront) and polarization
to exquisite levels - necessitating stressing optical requirements. An
alternative and promising technique is to place a starshade, i.e. external
occulter, at some distance in front of the telescope. This starshade suppresses
most of the starlight before entering the telescope - relaxing optical
requirements to that of a more conventional telescope. While an old technique
it has been recently been advanced by the recognition that circularly symmetric
graded apodizers can be well approximated by shaped binary occulting masks.
Indeed optimal shapes have been designed that can achieve smaller inner working
angles than conventional coronagraphs and yet have high effective throughput
allowing smaller aperture telescopes to achieve the same coronagraphic
resolution and similar sensitivity as larger ones.
  Herein we report on our ongoing modeling, simulation and optimization of
external occulters and show sensitivity results with respect to number and
shape errors of petals, spectral passband, accuracy of Fresnel propagation, and
show results for both filled and segmented aperture telescopes and discuss
acquisition and sensing of the occulter's location relative to the telescope.


title: Interpretation of interaction: A review

abstract:
  Several different types of statistical interaction are defined and
distinguished, primarily on the basis of the nature of the factors defining the
interaction. Illustrative examples, mostly epidemiological, are given. The
emphasis is primarily on interpretation rather than on methods for detecting
interactions.


title:
Self-Localized Quasi-Particle Excitation in Quantum Electrodynamics and
  Its Physical Interpretation

abstract:
  The self-localized quasi-particle excitation of the electron-positron field
(EPF) is found for the first time in the framework of a standard form of the
quantum electrodynamics. This state is interpreted as the ``physical'' electron
(positron) and it allows one to solve the following problems: i) to express the
``primary'' charge $e_0$ and the mass $m_0$ of the ``bare'' electron in terms
of the observed values of $e$ and $m$ of the ``physical'' electron without any
infinite parameters and by essentially nonperturbative way; ii) to consider
$\mu$-meson as another self-localized EPF state and to estimate the ratio
$m_{\mu}/m$; iii) to prove that the self-localized state is Lorentz-invariant
and its energy spectrum corresponds to the relativistic free particle with the
observed mass $m$; iv) to show that the expansion in a power of the observed
charge $e \ll 1$ corresponds to the strong coupling expansion in a power of the
``primary'' charge $e^{-1}_0 \sim e $ when the interaction between the
``physical'' electron and the transverse electromagnetic field is considered by
means of the perturbation theory and all terms of this series are free from the
ultraviolet divergence.


title:
The color excess of quasars with intervening DLA systems- Analysis of
  the SDSS data release five

abstract:
  We analyzed the spectroscopic and photometric database of the 5th data
release of the Sloan Digital Sky Survey (SDSS) to search for evidence of the
quasar reddening produced by dust embedded in intervening damped Ly alpha (DLA)
systems. From a list of 5164 quasars in the interval of emission redshift 2.25
</= z_e </= 3.5 and SDSS spectra with signal-to-noise ratio SNR >/= 4, we built
up an "absorption sample" of 248 QSOs with a single DLA system in the interval
of absorption redshift 2.2 < z_a </= 3.5 and a "pool" of 1959 control QSOs
without DLA systems or strong metal systems. For each QSO of the absorption
sample we extracted from the pool a subset of control QSOs that are closest in
redshift and magnitude. The mean color of this subset was used as a zero point
to measure the "deviation from the mean color" of individual DLA-QSOs, Delta_i.
The colors were measured using "BEST" ugriz SDSS imaging data. The mean color
excess of the absorption sample, <E>, was estimated by averaging the individual
color deviations Delta_i. We find <E(r-z)> = 27 +/- 9 x 10**(-3) mag and
<E(g-z)> = 54 +/- 12 x 10**(-3) mag. These values are representative of the
reddening of DLA systems at z_a ~ 2.7 in SDSS QSOs with limiting magnitude r
=/~ 20.2. The detection of the mean reddening is confirmed by several
statistical tests. Analysis of the results suggests an origin of the reddening
in dust embedded in the DLA systems, with an SMC-type extinction curve. By
converting the reddening into rest-frame extinction, we derive a mean
dust-to-gas ratio <A_V/N(HI)> ~ 2 to 4 x 10**(-23) mag cm^2. This value is ~
-1.25 dex lower than the mean dust-to-gas ratio of the Milky Way, in line with
the lower level of metallicity in the present DLA sample.


title: Massive Star Formation: The Power of Interferometry

abstract:
  This article presents recent work to constrain the physical and chemical
properties in high-mass star formation based largely on interferometric
high-spatial-resolution continuum and spectral line studies at (sub)mm
wavelengths. After outlining the concepts, potential observational tests, a
proposed evolutionary sequence and different possible definitions for massive
protostars, four particular topics are highlighted: (a) What are the physical
conditions at the onset of massive star formation? (b) What are the
characteristics of potential massive accretion disks and what do they tell us
about massive star formation in general? (c) How do massive clumps fragment,
and what does it imply to high-mass star formation? (d) What do we learn from
imaging spectral line surveys with respect to the chemistry itself as well as
for utilizing molecules as tools for astrophysical investigations?


title:
Vacuum Modified Gravity as an explanation for flat galaxy rotation
  curves

abstract:
  A theory is proposed which allows explaining the observed flat galaxy
rotation curves, without needing to invoke dark matter. Whereas other theories
have been proposed in the past which realize the same, the present theory rests
on basic physical principles, in contrast to for instance the MOND theory. The
key to arrive at this new theory is to consider from the start the energy
density of the vacuum. The way to calculate the effect of the corresponding
vacuum pressure on a mass has previously been laid down by Van Nieuwenhove
(1992). We obtain a modification of Newton's law of gravitation with some
peculiar properties such as the occurrence of regions of repulsive gravity.
Based on a newly derived equation of state of the vacuum, the Tully-Fisher
relation is derived. The theory can make detailed predictions about galaxy
rotation curves and is also able to explain to the Pioneer anomaly, the foamy
distribution of galaxies and the observed accelerated expansion of the
universe. A relativistic extension of the theory is included as well.


title: The pigeonhole bootstrap

abstract:
  Recently there has been much interest in data that, in statistical language,
may be described as having a large crossed and severely unbalanced random
effects structure. Such data sets arise for recommender engines and information
retrieval problems. Many large bipartite weighted graphs have this structure
too. We would like to assess the stability of algorithms fit to such data. Even
for linear statistics, a naive form of bootstrap sampling can be seriously
misleading and McCullagh [Bernoulli 6 (2000) 285--301] has shown that no
bootstrap method is exact. We show that an alternative bootstrap separately
resampling rows and columns of the data matrix satisfies a mean consistency
property even in heteroscedastic crossed unbalanced random effects models. This
alternative does not require the user to fit a crossed random effects model to
the data.


title: Measurement of the charged kaon lifetime with the KLOE detector

abstract:
  We have measured the charged kaon lifetime using a sample of 15 \times 10^6
tagged kaon decays. Charged kaons were produced in pairs at the DA\PhiNE
\phi-factory, e^+e^- \to \phi \to K^+ K^-. The decay of a K^+ was tagged by the
production of a K^- and viceversa. The lifetime was obtained, for both charges,
from independent measurements of the decay time and decay lenght distributions.
  From fits to the four distributions we find \tau = (12.347\pm0.030) ns.


title: Structure of A=3 Nuclear Systems Using Realistic Hamiltonians

abstract:
  The structure of A=3 low-energy scattering states is described using the
hyperspherical harmonics method with realistic Hamiltonian models, consisting
of two- and three-nucleon interactions. Both coordinate and momentum space
two-nucleon potential models are considered.


title: How to construct entanglement witnesses

abstract:
  We present very simple method for constructing indecomposable entanglement
witnesses out of a given pair -- an entanglement witness W and the
corresponding state detected by W. This method may be used to produce new
classes of atomic witnesses which are able to detect the `weakest' quantum
entanglement. Actually, it works perfectly in the multipartite case, too.
Moreover, this method provides a powerful tool for constructing new examples of
bound entangled states.


title:
Law of the exponential functional of a new family of one-sided Levy
  processes via self-similar continuous state branching processes with
  immigration and the Wright hypergeometric functions

abstract:
  We first introduce and derive some basic properties of a two-parameters
family of one-sided Levy processes. Their Laplace exponents are given in terms
of the Pochhammer symbol. This family includes, in a limit case, the family of
Brownian motion with drifts. Then, we proceed by computing the density of the
law of the exponential functional associated to some elements of this family
(and their dual) and some transformations of these elements. These densities
are expressed in terms of the Wright hypergeometric functions. By means of
probabilistic arguments, we derive some interesting properties enjoyed by these
functions. On the way we also characterize explicitly the density of the
semi-groups of the family of self-similar continuous state branching processes
with immigration.


title:
Topics in noncommutative integrable theories and holographic brane-world
  cosmology

abstract:
  This thesis follows two main lines of research, both related to relevant
aspects of string theory and its phenomenological/cosmological applications. We
study two different generalizations of the integrable SG model to NC geometry,
after discussing general properties and issues of integrable theories and NC
field theories, mentioning their role in string theory. The question is whether
we can obtain an integrable NC SG with factorized S matrix. Of the two models
we study, the second NC SG -- derived by dimensional reduction from the stringy
NC self-dual YM in (2+2) dimensions -- exhibits the good properties of S matrix
required by integrability in 2D, while the first one does not. As a second
topic, a particular brane-world model is analyzed both from the cosmological
point of view and in the spirit of holography, after introducing conventional
cosmology, brane-worlds and AdS/CFT. The 7D RS set-up with brane-bulk energy
exchange we propose leads to a non conventional cosmological evolution where
all fixed points have positive acceleration and are found to be stable for a
wide range of choices for the parameters. We construct the holographic dual
theory, represented by a renormalized 6D CFT coupled to 6D gravity. The
matching of parameters on the two sides of the duality is then achieved in
specific approximations.


title: The ALICE Forward Multiplicity Detector

abstract:
  The ALICE Forward Multiplicity Detector (FMD) is a silicon strip detector
with 51,200 strips arranged in 5 rings, covering the range $-3.4 < \eta < 5.1$.
It is placed around the beam pipe at small angles to extend the charged
particle acceptance of ALICE into the forward regions, not covered by the
central barrel detectors.


title: Understanding the WMAP Cold Spot mystery

abstract:
  The first and third year data releases from the WMAP provide evidence of an
anomalous Cold Spot (CS) at galactic latitude b=-57deg and longitude l=209deg.
We have examined the properties of the CS in some detail in order to assess its
cosmological significance. We have performed a cluster analysis of the local
extrema in the CMB signal to show that the CS is actually associated with a
large group of extrema rather than just one. In the light of this we have
re-examined the properties of the WMAP ILC and co-added "cleaned" WCM maps,
which have previously been used for the analysis of the properties of the
signal in the vicinity of the CS. These two maps have remarkably similar
properties on equal latitude rings for |b|>30deg, as well as in the vicinity of
the CS. We have also checked the idea that the CMB signal has a non-Gaussian
tail, localized in the low multipole components of the signal. For each ring we
apply a linear filter with characteristic scale R, dividing the CMB signal in
two parts: the filtered part, with characteristic scale above that of the
filter R, and the difference between the initial and filtered signal. Using the
filter scale as a variable, we can maximize the skewness and kurtosis of the
smoothed signal and minimize these statistics for the difference between
initial and filtered signal. We have discovered that the shape of the CS is
formed primarily by the components of the CMB signal represented by multipoles
between 10<=L<=20, with a corresponding angular scale about 5-10 degs. This
signal leads to modulation of the whole CMB sky, clearly seen at |b|>30deg in
both the ILC and WCM maps, rather than a single localized feature. After
subtraction of this modulation, the remaining part of the CMB signal appears to
be consistent with statistical homogeneity and Gaussianity.


title:
Equilibria of culture contact derived from ingroup and outgroup
  attitudes

abstract:
  Modern societies feature an increasing contact between cultures, yet we have
a poor understanding of what the outcomes might be. Here we consider a
mathematical model of contact between social groups, grounded in social
psychology and analyzed using tools from statistical physics. We use the model
to study how a culture might be affected by immigration. We find that in some
cases residents' culture is relatively unchanged, but in other cases residents
may adopt the opinions and beliefs of immigrants. The decisive factors are each
group's cultural legacy and its attitudes towards in- and out-groups. The model
can also predict how social policies may influence the outcome of culture
contact.

categories: physics.soc-ph cond-mat.stat-mech math-ph math.MP


title: Thermal effects on slow-roll dynamics

abstract:
  A description of the transition from the inflationary epoch to radiation
domination requires the understanding of quantum fields out of thermal
equilibrium, particle creation and thermalisation. This can be studied from
first principles by solving a set of truncated real-time Schwinger-Dyson
equations, written in terms of the mean field (inflaton) and the field
propagators, derived from the two-particle irreducible effective action. We
investigate some aspects of this problem by considering the dynamics of a
slow-rolling mean field coupled to a second quantum field, using a \phi^2\chi^2
interaction. We focus on thermal effects. It is found that interactions lead to
an earlier end of slow-roll and that the evolution afterwards depends on
details of the heatbath.


title: Duality Symmetric Strings, Dilatons and O(d,d) Effective Actions

abstract:
  We calculate the background field equations for the T-duality symmetric
string building on previous work by including the effect of the Dilaton up to
two-loops. Inclusion of the Dilaton allows us to obtain the full beta
functionals of the duality symmetric sigma model. We are able to interpret the
result in terms of a dimensionally reduced O(d,d) invariant target space
effective action.


title:
Variation in the primary and reprocessed radiation from an orbiting spot
  around a black hole

abstract:
  We study light curves and spectra (equivalent widths of the iron line and
some other spectral characteristics) which arise by reflection on the surface
of an accretion disc, following its illumination by a primary off-axis source -
an X-ray 'flare', assumed to be a point-like source just above the accretion
disc resulting in a spot with radius dr/r<1. We consider General Relativity
effects (energy shifts, light bending, time delays) near a rotating black hole,
and we find them all important, including the light bending and delay
amplification due to the spot motion. For some sets of parameters the reflected
flux exceeds the flux from the primary component. We show that the
orbit-induced variations of the equivalent width with respect to its mean value
can be as high as 30% for the observer's inclination of 30 degrees, and much
more at higher inclinations. We calculate the ratio of the reflected flux to
the primary flux and the hardness ratio which we find to vary significantly
with the spot phase mainly for small orbital radii. This offers the chance to
estimate the lower limit of the black hole spin if the flare arises close to
the black hole.


title: Period doubling in the Rossler system - a computer assisted proof

abstract:
  The goal of this paper is to show how to produce a piece of rigorous
bifurcation diagram of periodic orbits for an ODE. We study the Rossler system,
one of the textbook examples of ODEs generating nontrivial dynamics, for the
parameter range containing two period doubling bifurcations.


title:
A statistical analysis of memory CD8 T cell differentiation: An
  application of a hierarchical state space model to a short time course
  microarray experiment

abstract:
  CD8 T cells are specialized immune cells that play an important role in the
regulation of antiviral immune response and the generation of protective
immunity. In this paper we investigate the differentiation of memory CD8 T
cells in the immune response using a short time course microarray experiment.
Structurally, this experiment is similar to many in that it involves
measurements taken on independent samples, in one biological group, at a small
number of irregularly spaced time points, and exhibiting patterns of temporal
nonstationarity. To analyze this CD8 T-cell experiment, we develop a
hierarchical state space model so that we can: (1) detect temporally
differentially expressed genes, (2) identify the direction of successive
changes over time, and (3) assess the magnitude of successive changes over
time. We incorporate hidden Markov models into our model to utilize the
information embedded in the time series and set up the proposed hierarchical
state space model in an empirical Bayes framework to utilize the population
information from the large-scale data. Analysis of the CD8 T-cell experiment
using the proposed model results in biologically meaningful findings. Temporal
patterns involved in the differentiation of memory CD8 T cells are summarized
separately and performance of the proposed model is illustrated in a simulation
study.


title:
Variation of the primary and reprocessed radiation in the flare-spot
  model

abstract:
  We study light curves and spectra (equivalent widths of the iron line and
some other spectral characteristics) which arise by reprocessing on the surface
of an accretion disc, following its illumination by a primary off-axis source -
an X-ray 'flare', assumed to be a point-like source just above the accretion
disc. We consider all general relativity effects (energy shifts, light bending,
time delays, delay amplification due to the spot motion) near a rotating black
hole. For some sets of parameters the reflected flux exceeds the flux from the
primary component. We show that the orbit-induced variations of the equivalent
width with respect to its mean value can be as high as 30% for an observer's
inclination of 30 degrees, and much more at higher inclinations. We calculate
the ratio of the reflected flux to the primary flux and the hardness ratio
which we find to vary significantly with the spot phase mainly for small
orbital radii. This offers the chance to estimate the lower limit of the black
hole spin if the flare arises close to the black hole. We show the results for
different values of the flare orbital radius.


title: Consciousness, brains and the replica problem

abstract:
  Although the conscious state is considered an emergent property of the
underlying brain activity and thus somehow resides on brain hardware, there is
a non-univocal mapping between both. Given a neural hardware, multiple
conscious patterns are consistent with it. Here we show, by means of a simple
{\em gedankenexperiment} that this has an important logic consequence: any
scenario involving the transient shutdown of brain activity leads to the
irreversible death of the conscious experience. In a fundamental way, unless
the continuous stream of consciousness is guaranteed, the previous self
vanishes and is replaced by a new one.


title: Study of ATLAS sensitivity to FCNC top decays

abstract:
  The ATLAS experiment sensitivity to top quark Flavour Changing Neutral
Current (FCNC) decays was studied at LHC using ttbar events. While one of the
top quarks is expected to follow the dominant Standard Model decay t->bW, the
other decays through a FCNC channel, i.e. t-> Z u(c), t-> gamma u(c) or t-> g
u(c). Different types of analyses, applied to each FCNC decay mode, were
compared. The FCNC branching ratio sensitivity (assuming a 5sigma signal
significance) and 95% confidence level limits on the branching ratios (in the
hypothesis of signal absence) were obtained.


title: On operations and characteristic classes

abstract:
  In this paper exterior products are used to define operations and
characteristic classes with values in the K-theory of an abelian category with
tensor and exterior products. We apply the general construction to define Chern
and Segre classes with values in algebraic K-theory and the K-theory of
connections.


title: Relativistic kinematics for reactions involving massless particles

abstract:
  Some useful kinematical relations for the absorption of a photon by a nucleus
and its recoil are derived for the relativistic incident energies. These
expressions provided for the relativistic kinematics of photoabsorption
reactions, though simple, will be immensely useful for experimentalists as well
as theoreticians.


title: Fate of gravitational collapse in semiclassical gravity

abstract:
  While the outcome of gravitational collapse in classical general relativity
is unquestionably a black hole, up to now no full and complete semiclassical
description of black hole formation has been thoroughly investigated. Here we
revisit the standard scenario for this process. By analyzing how semiclassical
collapse proceeds we show that the very formation of a trapping horizon can be
seriously questioned for a large set of, possibly realistic, scenarios. We
emphasise that in principle the theoretical framework of semiclassical gravity
certainly allows the formation of trapping horizons. What we are questioning
here is the more subtle point of whether or not the standard black hole picture
is appropriate for describing the end point of realistic collapse. Indeed if
semiclassical physics were in some cases to prevent formation of the trapping
horizon, then this suggests the possibility of new collapsed objects which can
be much less problematic, making it unnecessary to confront the information
paradox or the run-away end point problem.


title:
On some mathematical identities resulting from evaluation of the
  partition function for an electron moving in a periodic lattice

abstract:
  We consider a simple model of the dynamics of a single electron in a crystal
lattice. Although this is a standard problem in condensed matter physics,
alternative ways of evaluating a partition function for such a system lead to
equalities, that may be interesting from the point of view of mathematical
analysis, combinatorics and graph theory.


title: Development status of a Laue lens project for gamma-ray astronomy

abstract:
  We report the status of the HAXTEL project, devoted to perform a design study
and the development of a Laue lens prototype. After a summary of the major
results of the design study, the approach adopted to develop a Demonstration
Model of a Laue lens is discussed, the set up described, and some results
presented.


title: Homogeneous quasimorphisms on the symplectic linear group

abstract:
  In this note, we show a uniqueness result of homogeneous quasimorphisms
defined on the universal cover of the symplectic linear group.


title: The globular cluster NGC 6388: $XMM$-Newton and $Chandra$ observations

abstract:
  By studying the optical brightness surface density of the globular cluster
NGC 6388, it has been recently proposed that it harbors a central
intermediate-mass black hole with mass $\simeq 5.7\times 10^3$ M$_{\odot}$. We
expect that the compact object in the center of NGC 6388 emits radiation in the
$X$-ray band as a consequence of the accretion from the surrounding matter. We
searched for $XMM$-Newton and $Chandra$ observations towards NGC 6388 to test
this hypothesis. The $Chandra$ satellite disentangles several point-like
$X$-ray sources, probably low mass $X$-ray binaries, well within the core
radius of the globular cluster. However, three of them, coinciding with the
cluster center of gravity, remain unresolved. Their total luminosity is
$L_X^{Obs}\simeq 2.7\times 10^{33}$ erg s$^{-1}$. If one of these sources is
the $X$-ray counterpart of the intermediate-mass black hole in NGC 6388, the
corresponding upper limit on the accretion efficiency, with respect to the
Eddington luminosity, is $3\times 10^{-9}$. This measurement could be tightened
if moderately deep radio observations of the field were performed.


title: Interpolation with a function parameter and refined scale of spaces

abstract:
  The interpolation of couples of separable Hilbert spaces with a function
parameter is studied. The main properties of the classic interpolation are
proved. Some applications to the interpolation of isotropic H\"ormander spaces
over a closed manifold are given.


title:
On Existence of Self-Tuning Solutions in Static Braneworlds without
  Singularities

abstract:
  A static self-tuning SO(3)xZ_2 symmetric and translation invariant braneworld
setup with flat brane is considered. We discuss the null energy conditions
(NEC) for matter on the brane and in the bulk and prove that for the static
regular background with broken Lorentz invariance the NEC and positiveness of
the total energy density on the brane and NEC in the bulk cannot be satisfied
simultaneously. Then we give some examples and elaborate some special cases.
For instance, we provide a macroscopic solution for a background with Lifshitz
scaling.


title:
Mu-tau neutrino refraction and collective three-flavor transformations
  in supernovae

abstract:
  We study three-flavor collective neutrino transformations in the
dense-neutrino region above the neutrino sphere of a supernova core. We find
that two-flavor conversions driven by the atmospheric mass difference and the
13-mixing angle capture the full effect if one neglects the second-order
difference between the muon and tau neutrino refractive index. Including this
"mu-tau matter term" provides a resonance at a density of approximately 3 x
10^7 g cm^-3 that typically causes significant modifications of the overall
electron neutrino and antineutrino survival probabilities. This effect is
surprisingly sensitive to deviations from maximal 23-mixing, being different
for each octant.


title: IMAGES: a unique view of the galaxy mass assembly since z=1

abstract:
  The Large Program IMAGES is near 2/3 of its completion. It provides us with
kinematics (GIRAFFE deployable IFUs), gas chemistry (FORS2), detailed
morphologies (HST/ACS) and IR photometry (Spitzer) for a set of 70 galaxies
representative of intermediate mass galaxies (MJ<=-20.3 or 1.5e10 Mo) at
z=0.4-0.75. We discover that, 6 Gyr ago, a significant fraction of galaxies
(>40%) had anomalous kinematics, i.e. kinematics significantly discrepant from
those of rotational or dispersion supported galaxies. The anomalous kinematics
cause the observed large dispersion of the Tully-Fisher relation at large
distances. IMAGES will soon allow us to study distant galaxies at a level of
detail almost comparable to that of nearby galaxies.


title:
Dynamical replica analysis of processes on finitely connected random
  graphs I: vertex covering

abstract:
  We study the stochastic dynamics of Ising spin models with random bonds,
interacting on finitely connected Poissonnian random graphs. We use the
dynamical replica method to derive closed dynamical equations for the joint
spin-field probability distribution, and solve these within the replica
symmetry ansatz. Although the theory is developed in a general setting, with a
view to future applications in various other fields, in this paper we apply it
mainly to the dynamics of the Glauber algorithm (extended with cooling
schedules) when running on the so-called vertex cover optimization problem. Our
theoretical predictions are tested against both Monte Carlo simulations and
known results from equilibrium studies. In contrast to previous dynamical
analyses based on deriving closed equations for only a small numbers of scalar
order parameters, the agreement between theory and experiment in the present
study is nearly perfect.


title: Benefits of Diversity, Communication Costs, and Public Opinion Dynamics

abstract:
  We study the dynamics of public opinion in a model in which agents change
their opinions as a result of random binary encounters if the opinion
difference is below their individual thresholds that evolve over time. We
ground these thresholds in a simple individual cost-benefit analysis with
linear benefits of diversity and quadratic communication costs. We clarify and
deepen the results of earlier continuous-opinion dynamics models (Deffuant et
al., Adv Complex Systems 2000; Weisbuch et al., Complexity 2002) and establish
several new results regarding the patterns of opinions in the asymptotic state
and the cluster formation time.


title:
Curvature singularities, tidal forces and the viability of Palatini f(R)
  gravity

abstract:
  In a previous paper we showed that static spherically symmetric objects
which, in the vicinity of their surface, are well-described by a polytropic
equation of state with 3/2<Gamma<2 exhibit a curvature singularity in Palatini
f(R) gravity. We argued that this casts serious doubt on the validity of
Palatini f(R) gravity as a viable alternative to General Relativity. In the
present paper we further investigate this characteristic of Palatini f(R)
gravity in order to clarify its physical interpretation and consequences.


title: A Generic Framework for Diamond Lemmas

abstract:
  This paper gives a generic form of the diamond lemma, which includes support
for additive and topological structures of the base set, and which does not
require any further structure (e.g. an associative multiplication operation) to
be present. This result is intended to be used as the core of diamond lemmas
for particular algebraic structures, taking care of all the common
technicalities. With this generic diamond lemma, the main steps needed to prove
a specialised diamond lemma is to define the reduction maps and analyse the
structure of critical ambiguities.
  The abstract machinery is backed up with concrete suggestions for how one
should set things up in order to reproduce traditional results in the general
setting. Several instances of the fundamental theorem of Groebner basis theory
are derived as corollaries of the main result.


title: Observation of Y(2175) in $J/\psi\to \eta\phi f_0(980)$

abstract:
  The decays of $J/\psi\to \eta\phi f_0(980) (\eta\to \gamma\gamma, \phi \to
K^+K^-, f_0(980)\to\pi^+\pi^-)$ are analyzed using a sample of $5.8 \times
10^{7}$ $J/\psi$ events collected with the BESII detector at the Beijing
Electron-Positron Collider (BEPC). A structure at around $2.18 $GeV/$c^2$ with
about $5\sigma$ significance is observed in the $\phi f_0(980)$ invariant mass
spectrum. A fit with a Breit-Wigner function gives the peak mass and width of
$m=2.186\pm 0.010 (stat)\pm 0.006 (syst) $GeV/$c^2$ and $\Gamma=0.065\pm 0.023
(stat)\pm 0.017 (syst) $GeV/$c^2$, respectively, that are consistent with those
of Y(2175), observed by the BABAR collaboration in the initial-state radiation
(ISR) process $e^+e^-\to\gamma_{ISR}\phi f_0(980)$. The production branching
ratio is determined to be $Br(J/\psi\to\eta Y(2175))\cdot Br(Y(2175)\to\phi
f_0(980))\cdot Br(f_0(980)\to\pi^+\pi^-)=(3.23\pm 0.75 (stat)\pm0.73
(syst))\times 10^{-4}$, assuming that the Y(2175) is a $1^{--}$ state.