title: Continuous Wave Photonic Crystal Laser in Ultraviolet Range

abstract:
  Great potential of photonic band-gap (PBG) structures for the development of
continuous wave ultraviolet all-solid-state laser, including UV femtosecond
pulse source, as well as for increase of output laser power at short-wave
optical range is shown. The basic idea is a decrease of the laser threshold via
suppression of the spontaneous emission in the active medium by means of
embedding it into 2D or 3D PBG structure having the midgap frequency close to
the frequency of the laser transition. Different schemes of 2D and 3D photonic
crystal laser for ultraviolet range are proposed.


title:
An algorithm to determine the Heegaard genus of simple 3-manifolds with
  non-empty boundary

abstract:
  We provide an algorithm to determine the Heegaard genus of simple 3-manifolds
with non-empty boundary. More generally, we supply an algorithm to determine
(up to ambient isotopy) all the Heegaard splittings of any given genus for the
manifold. As a consequence, the tunnel number of a hyperbolic link is
algorithmically computable. Our techniques rely on Rubinstein's work on almost
normal surfaces, and also a new structure called a partially flat angled ideal
triangulation.


title:
Signatures of star streams in the phase space distribution of nearby
  halo stars

abstract:
  We have analyzed the phase space distribution of a sample of about 900
non--kinematically selected low metallicity stars in the solar vicinity. The
stars primarily represent the thick disk and halo populations of the Milky Way.
We aim to identify overdensely populated regions in phase space, which we
interpret as signatures of star streams passing close to the Sun. The search
was conducted in a space constructed from the angular momenta and
eccentricities of the stellar orbits. Besides recovering all well known star
streams in the thick disk, we isolated four statistically significant phase
space overdensities amongst halo stars. One of them is associated with a
previously known halo star stream, but three of them are novel features, which
we propose be also considered as genuine halo streams.


title: Spiral Model: a cellular automaton with a discontinuous glass transition

abstract:
  We introduce a new class of two-dimensional cellular automata with a
bootstrap percolation-like dynamics. Each site can be either empty or occupied
by a single particle and the dynamics follows a deterministic updating rule at
discrete times which allows only emptying sites. We prove that the threshold
density $\rho_c$ for convergence to a completely empty configuration is non
trivial, $0<\rho_c<1$, contrary to standard bootstrap percolation. Furthermore
we prove that in the subcritical regime, $\rho<\rho_c$, emptying always occurs
exponentially fast and that $\rho_c$ coincides with the critical density for
two-dimensional oriented site percolation on $\bZ^2$. This is known to occur
also for some cellular automata with oriented rules for which the transition is
continuous in the value of the asymptotic density and the crossover length
determining finite size effects diverges as a power law when the critical
density is approached from below. Instead for our model we prove that the
transition is {\it discontinuous} and at the same time the crossover length
diverges {\it faster than any power law}. The proofs of the discontinuity and
the lower bound on the crossover length use a conjecture on the critical
behaviour for oriented percolation. The latter is supported by several
numerical simulations and by analytical (though non rigorous) works through
renormalization techniques. Finally, we will discuss why, due to the peculiar
{\it mixed critical/first order character} of this transition, the model is
particularly relevant to study glassy and jamming transitions. Indeed, we will
show that it leads to a dynamical glass transition for a Kinetically
Constrained Spin Model. Most of the results that we present are the rigorous
proofs of physical arguments developed in a joint work with D.S.Fisher.


title: Prediction of polar ordered oxynitride perovskites

abstract:
  Using a materials by design approach, the authors find a class of ordered
oxynitride piezoelectrics with perovskite structure. They predict that ordered
YSiO2N and YGeO2N are characterized by large nonlinear optic responses and by
some of the largest polarizations known to date.


title: Predictive protocol of flocks with small-world connection pattern

abstract:
  By introducing a predictive mechanism with small-world connections, we
propose a new motion protocol for self-driven flocks. The small-world
connections are implemented by randomly adding long-range interactions from the
leader to a few distant agents, namely pseudo-leaders. The leader can directly
affect the pseudo-leaders, thereby influencing all the other agents through
them efficiently. Moreover, these pseudo-leaders are able to predict the
leader's motion several steps ahead and use this information in decision making
towards coherent flocking with more stable formation. It is shown that drastic
improvement can be achieved in terms of both the consensus performance and the
communication cost. From the industrial engineering point of view, the current
protocol allows for a significant improvement in the cohesion and rigidity of
the formation at a fairly low cost of adding a few long-range links embedded
with predictive capabilities. Significantly, this work uncovers an important
feature of flocks that predictive capability and long-range links can
compensate for the insufficiency of each other. These conclusions are valid for
both the attractive/repulsive swarm model and the Vicsek model.


title: An Unexpectedly Swift Rise in the Gamma-ray Burst Rate

abstract:
  The association of long gamma-ray bursts with supernovae naturally suggests
that the cosmic GRB rate should trace the star formation history. Finding
otherwise would provide important clues concerning these rare, curious
phenomena. Using a new estimate of Swift GRB energetics to construct a sample
of 36 luminous GRBs with redshifts in the range z=0-4, we find evidence of
enhanced evolution in the GRB rate, with ~4 times as many GRBs observed at z~4
than expected from star formation measurements. This direct and empirical
demonstration of needed additional evolution is a new result. It is consistent
with theoretical expectations from metallicity effects, but other causes remain
possible, and we consider them systematically.


title:
Synthetic NLTE accretion disc spectra for the dwarf nova SS Cyg during
  an outburst cycle

abstract:
  Dwarf nova outbursts result from enhanced mass transport through the
accretion disc of a cataclysmic variable system.
  We assess the question of whether these outbursts are caused by an enhanced
mass transfer from the late-type main sequence star onto the white dwarf
(so-called mass transfer instability model, MTI) or by a thermal instability in
the accretion disc (disc instability model, DIM).
  We compute non-LTE models and spectra of accretion discs in quiescence and
outburst and construct spectral time sequences for discs over a complete
outburst cycle. We then compare our spectra to published optical spectroscopy
of the dwarf nova SS Cygni. In particular, we investigate the hydrogen and
helium line profiles that are turning from emission into absorption during the
rise to outburst.
  The evolution of the hydrogen and helium line profiles during the rise to
outburst and decline clearly favour the disc-instability model. Our spectral
model sequences allow us to distinguish inside-out and outside-in moving
heating waves in the disc of SS Cygni, which can be related to symmetric and
asymmetric outburst light curves, respectively.


title: Signatures of heavy sterile neutrinos at long baseline experiments

abstract:
  Sterile neutrinos with masses $\sim 0.1$ eV or higher would play an important
role in astrophysics and cosmology. We explore possible signatures of such
sterile neutrinos at long baseline experiments. We determine the neutrino
conversion probabilities analytically in a 4-neutrino framework, including
matter effects, treating the sterile mixing angles $\theta_{14}, \theta_{24},
\theta_{34}$, the deviation of $\theta_{23}$ from maximality,as well as
$\theta_{13}$ and the ratio $\Delta m^2_\odot/\Delta m^2_{atm}$ as small
parameters for a perturbative expansion. This gives rise to analytically
tractable expressions for flavor conversion probabilities from which effects of
these parameters can be clearly understood. We numerically calculate the
signals at a neutrino factory with near and far detectors that can identify the
lepton charge, and point out observables that can discern the sterile mixing
signals. We find that clean identification of sterile mixing would be possible
for $\theta_{24}\theta_{34} \gsim 0.005$ and $\theta_{14} \gsim 0.06$ rad with
the current bound of $\theta_{13} < 0.2$ rad; a better $\theta_{13}$ bound
would allow probing smaller values of sterile mixing. We also generalize the
formalism for any number of sterile neutrinos, and demonstrate that only
certain combinations of sterile mixing parameters are relevant irrespective of
the number of sterile neutrinos. This also leads to a stringent test of the
scenario with multiple sterile neutrinos that currently is able to describe all
the data from the short baseline experiments, including LSND and MiniBOONE.


title: Thermophoresis of charged colloidal particles

abstract:
  Thermally induced particle flow in a charged colloidal suspension is studied
in a fluid-mechanical approach. The force density acting on the charged
boundary layer is derived in detail. From Stokes' equation with no-slip
boundary conditions at the particle surface, we obtain the particle drift
velocity and the thermophoretic transport coefficients. The results are
discussed in view of previous work and available experimental data.


title:
Interpretation of recent JLab results on quasi elastic (e,e'p) reactions
  off few-nucleon systems

abstract:
  Recent JLab experimental data on quasi elastic 3He(e,e'p)2H(pn) and
4He(e,e'p)3H processes are interpreted using an approach based upon realistic
wave functions and Glauber multiple scattering theory within a generalized
eikonal approximation (GEA). The results of a non factorized calculation of the
left-right asymmetry A_{TL} of the process 3He(e,e'p)2H, obtained using the
full covariant form of the electromagnetic operator, are also presented.


title: The rotation of polarization by gravitational waves

abstract:
  There are conflicting statements in the literature about the gravitational
Faraday rotation of the plane of polarization of polarized electromagnetic
radiation travelling through a gravitational wave. This issue is reconsidered
using a simple formalism describing the rotation of the plane of polarization
in a gravitational field, in the geometric optics approximation. It is shown
that, to first order in the gravitational wave amplitude, the rotation angle is
a boundary effect which vanishes for localized (astrophysically generated)
gravitational waves and is non-zero, but nevertheless negligible, for
cosmological gravitational waves.


title: A Multitrace Matrix Model from Fuzzy Scalar Field Theory

abstract:
  We present the analytical approach to scalar field theory on the fuzzy sphere
which has been developed in arXiv:0706.2493 [hep-th]. This approach is based on
considering a perturbative expansion of the kinetic term in the partition
function. After truncating this expansion at second order, one arrives at a
multitrace matrix model, which allows for an application of the saddle-point
method. The results are in agreement with the numerical findings in the
literature.


title:
Effects of a Fluctuating Interface between a Superfluid and a Polarized
  Fermi Gas

abstract:
  Motivated by recent experiments in trapped Fermi gas with spin population
imbalance, we discuss the effects of the quantum and thermal fluctuations of
the interface between a fully paired superfluid core and a fully polarized
Fermi gas. We demonstrate that even if there is no true partially polarized
thermodynamic phase in bulk, the interface fluctuation can give rise to a
partially polarized transition regime in trap. Our theory yields a definite
prediction for the functional forms of the spatial profile of spin polarization
and pairing gap, and we show that the spin-resolved density profiles measured
by both the MIT and Rice groups obey this function form. We also show that
sufficient large fluctuation will lead to a visibly unequal density even at the
center of the cloud. We hope this picture can shed lights on the controversial
discrepancies in recent experiments.


title:
Random walk local time approximated by a Wiener sheet combined with an
  independent Brownian motion

abstract:
  Let $\xi(k,n)$ be the local time of a simple symmetric random walk on the
line. We give a strong approximation of the centered local time process
$\xi(k,n)-\xi(0,n)$ in terms of a Wiener sheet and an independent Wiener
process, time changed by an independent Brownian local time. Some related
results and consequences are also established.


title: Entanglement, EPR-correlations, Bell-nonlocality, and Steering

abstract:
  In a recent work [Phys. Rev. Lett. {\bf 98}, 140402 (2007)] we defined
``steering'', a type of quantum nonlocality that is logically distinct from
both nonseparability and Bell-nonlocality. In the bipartite setting, it hinges
on the question of whether Alice can affect Bob's state at a distance through
her choice of measurement. More precisely and operationally, it hinges on the
question of whether Alice, with classical communication, can convince Bob that
they share an entangled state, under the circumstances that Bob trusts nothing
that Alice says. We argue that if she can, then this demonstrates the nonlocal
effect first identified in the famous EPR paper [Phys. Rev. {\bf 47}, 777
(1935)] as a universal effect for pure entangled states. This ability of Alice
to remotely prepare Bob's state was subsequently called steering by
Schr\"odinger, whose terminology we adopt. The phenomenon of steering has been
largely overlooked, and prior to our work had not even been given a rigorous
definition that is applicable to mixed states as well as pure states. Armed
with our rigorous definition, we proved that steerable states are a strict
subset of the entangled states, and a strict superset of the states that can
exhibit Bell-nonlocality. In this work we expand on these results and provide
further examples of steerable states. We also elaborate on the connection with
the original EPR paradox.


title:
Sobolev spaces and mappings with bounded (P,Q)-distortion on Carnot
  groups

abstract:
  We study mappings with bounded (p,q)-distortion associated to Sobolev spaces
on Carnot groups. Mappings of such type have applications to the Sobolev type
embedding theory and classification of manifolds. For this class of mappings,
we obtain estimates of linear distortion, and a geometrical description. We
prove also Liouville type theorems and give some sufficient conditions for
removability of sets.


title: The impact of reduced mass loss rates on the evolution of massive stars

abstract:
  Mass loss is a very important aspect of the life of massive stars. After
briefly reviewing its importance, we discuss the impact of the recently
proposed downward revision of mass loss rates due to clumping (difficulty to
form Wolf-Rayet stars and production of critically rotating stars). Although a
small reduction might be allowed, large reduction factors around ten are
disfavoured.
  We then discuss the possibility of significant mass loss at very low
metallicity due to stars reaching break-up velocities and especially due to the
metal enrichment of the surface of the star via rotational and convective
mixing. This significant mass loss may help the first very massive stars avoid
the fate of pair-creation supernova, the chemical signature of which is not
observed in extremely metal poor stars. The chemical composition of the very
low metallicity winds is very similar to that of the most metal poor star known
to date, HE1327-2326 and offer an interesting explanation for the origin of the
metals in this star.
  We also discuss the importance of mass loss in the context of long and soft
gamma-ray bursts and pair-creation supernovae. Finally, we would like to stress
that mass loss in cooler parts of the HR-diagram (luminous blue variable and
yellow and red supergiant stages) are much more uncertain than in the hot part.
More work needs to be done in these areas to better constrain the evolution of
the most massive stars.


title: Finite area and volume of pointed $k$-surfaces

abstract:
  We define the ``volume'' contained by pointed $k$-surfaces, first studied by
the author in [9], and we show that this volume is always finite. Likewise, we
show that the surface area of a pointed $k$-surface is always finite.


title: Spatial variation of total column ozone on a global scale

abstract:
  The spatial dependence of total column ozone varies strongly with latitude,
so that homogeneous models (invariant to all rotations) are clearly unsuitable.
However, an assumption of axial symmetry, which means that the process model is
invariant to rotations about the Earth's axis, is much more plausible and
considerably simplifies the modeling. Using TOMS (Total Ozone Mapping
Spectrometer) measurements of total column ozone over a six-day period, this
work investigates the modeling of axially symmetric processes on the sphere
using expansions in spherical harmonics. It turns out that one can capture many
of the large scale features of the spatial covariance structure using a
relatively small number of terms in such an expansion, but the resulting fitted
model provides a horrible fit to the data when evaluated via its likelihood
because of its inability to describe accurately the process's local behavior.
Thus, there remains the challenge of developing computationally tractable
models that capture both the large and small scale structure of these data.


title: The total cross section at the LHC

abstract:
  We do not have the ability to perform precise calculations of long-range
strong interaction effects, because the effective QCD coupling is not small and
so we cannot use perturbation theory. Nevertheless, I show that we know a lot,
though not nearly enough. As a measure of our lack of knowledge, the best
prediction for the total cross section at LHC energy is 125 +/- 25 mb.


title:
Observation and Modeling of Coronal "Moss" With the EUV Imaging
  Spectrometer on Hinode

abstract:
  Observations of transition region emission in solar active regions represent
a powerful tool for determining the properties of hot coronal loops. In this
Letter we present the analysis of new observations of active region moss taken
with the Extreme Ultraviolet Imaging Spectrometer (EIS) on the \textit{Hinode}
mission. We find that the intensities predicted by steady, uniformly heated
loop models are too intense relative to the observations, consistent with
previous work. To bring the model into agreement with the observations a
filling factor of about 16% is required. Furthermore, our analysis indicates
that the filling factor in the moss is nonuniform and varies inversely with the
loop pressure.


title: Charmed ${\bf (70,1^-)}$ baryon multiplet

abstract:
  The masses of negative parity $(70,1^-)$ charmed nonstrange baryons are
calculated in the relativistic quark model. The relativistic three-quark
equations of the $(70,1^-)$ charmed baryon multiplet are found in the framework
of the dispersion relation technique. The approximate solutions of these
equations using the method based on the extraction of leading singularities of
the amplitude are obtained. The calculated mass values of the $(70,1^-)$
charmed baryons are in good agreement with the experimental data.


title: N=2 Supersymmetric Black Attractors in Six and Seven Dimensions

abstract:
  Using a quaternionic formulation of the moduli space $\boldsymbol{M}({\small
IIA/K3}) $ of 10D type IIA superstring on a generic K3 complex surface with
volume $\boldsymbol{V}_{0}$, we study extremal $\mathcal{N}=2$ black attractors
in 6D space-time and their uplifting to 7D. For the 6D theory, we exhibit the
role played by 6D $\mathcal{N}=1$ hypermultiplets and the $Z^{m}$ central
charges isotriplet of the 6D $\mathcal{N}=2$ superalgebra. We construct
explicitly the special hyperKahler geometry of $% \boldsymbol{M}({\small
IIA/K3}) $ and show that the $SO(4) \times SO(20) $ invariant hyperKahler
potential is given by $\mathcal{H}=\mathcal{H}_{0}+\mathrm{Tr}[ \ln (1-%
\boldsymbol{V}_{0}^{-1}\boldsymbol{S}) ] $ with Kahler leading term
$\mathcal{H}_{0}=\mathrm{Tr}[ \ln \boldsymbol{V}_{0}] $ plus an extra term
which can be expanded as a power series in $\boldsymbol{V}%_{0}^{-1}$ and the
traceless and symmetric 3$\times $3 matrix $\boldsymbol{S} $. We also derive
the holomorphic matrix prepotential $\mathcal{G}$ and the flux potential
$\mathcal{G}_{BH}$ of the 6D black objects induced by the topology of the RR
field strengths $\mathcal{F}_{2}=d\mathcal{A}_{1}$ and $%
\mathcal{F}_{4}=d\mathcal{A}_{3}$ on the K3 surface and show that $\mathcal{G%
}_{BH}$ reads as $Q_{0}+\sum_{m=1}^{3}q^{m}Z^{m}$. Moreover, we reveal that $%
Z^{m}=\sum_{I=1}^{20}Q_{I}(\int_{C_{2}^{I}}J^{m}) $ where the isotriplet
$J^{m}$ is the hyperKahler 2- form on the K3 surface. It is found as well that
the uplifting to seven dimensions is quite similar to 4D/5D correspondence for
back hole potential considered in arXiv 0707.0964 [hep-th].


title: The quantum harmonic oscillator on the sphere and the hyperbolic plane

abstract:
  A nonlinear model of the quantum harmonic oscillator on two-dimensional
spaces of constant curvature is exactly solved. This model depends of a
parameter $\la$ that is related with the curvature of the space. Firstly the
relation with other approaches is discussed and then the classical system is
quantized by analyzing the symmetries of the metric (Killing vectors),
obtaining a $\la$-dependent invariant measure $d\mu_\la$ and expressing the
Hamiltonian as a function of the Noether momenta. In the second part the
quantum superintegrability of the Hamiltonian and the multiple separability of
the Schr\"odinger equation is studied. Two $\la$-dependent Sturm-Liouville
problems, related with two different $\la$-deformations of the Hermite
equation, are obtained. This leads to the study of two $\la$-dependent families
of orthogonal polynomials both related with the Hermite polynomials. Finally
the wave functions $\Psi_{m,n}$ and the energies $E_{m,n}$ of the bound states
are exactly obtained in both the sphere $S^2$ and the hyperbolic plane $H^2$.


title: Noether's Theorem on Time Scales

abstract:
  We show that for any variational symmetry of the problem of the calculus of
variations on time scales there exists a conserved quantity along the
respective Euler-Lagrange extremals.


title: Multicolor photometry of the Type II Cepheid prototype W Virginis

abstract:
  We present the results of recent long-term BVRcIc photometric monitoring of
the type II Cepheid prototype W Virginis. These new observations, made during
the 2006 and 2007 observing season, represent the longest homogeneous,
multicolor light curve of W Vir to date. The BVRcIc light and color curves show
conclusively that W Vir exhibits modest but detectable cycle-to-cycle
variations, the cause of which appears to be multiperiodicity rather than
nonlinearity. We combined our V-band data with the five available years of
ASAS-3 V-band photometry to obtain a 6.5-year light curve that we then analyzed
to obtain the pulsation spectrum of W Vir. We find a best-fit period P(0) =
17.27134 d; along with this period and its integer harmonics, we clearly detect
two additional periods, P(1) and P(low), that are close to but not exactly
2P(0)/3 and 2P(0), respectively. The former, P(1) = 11.52562 d, we interpret to
be the first overtone mode; the latter, P(low) = 34.59760 d is close to the
beat period of P(0) and P(1), as well as to the value of 2P(0). We interpret
the previously reported but thus far unconfirmed descriptions of alternating
minima as manifestations of this multiperiodicity. Finally, we use the period
derived from the V-band light curve to define a new ephemeris: HJD(max) =
2452758.172 + 17.27134E. The resulting (O-C) diagram using 75 years of data
from 1932 to 2007 yields a period change term for the ephemeris of -9.9 times
10(-7) E^(2), indicating a period decrease.


title:
Approximation via regularization of the local time of semimartingales
  and Brownian motion

abstract:
  Through a regularization procedure, few approximation schemes of the local
time of a large class of one dimensional processes are given. We mainly
consider the local time of continuous semimartingales and reversible
diffusions, and the convergence holds in ucp sense. In the case of standard
Brownian motion, we have been able to determine a rate of convergence in $L^2$,
and a.s. convergence of some of our schemes.


title: Unstable g-modes in Proto-Neutron Stars

abstract:
  In this article we study the possibility that, due to non-linear couplings,
unstable g-modes associated to convective motions excite stable oscillating
g-modes. This problem is of particular interest, since gravitational waves
emitted by a newly born proto-neutron star pulsating in its stable g-modes
would be in the bandwidth of VIRGO and LIGO. Our results indicate that
nonlinear saturation of unstable modes occurs at relatively low amplitudes, and
therefore, even if there exists a coupling between stable and unstable modes,
it does not seem to be sufficiently effective to explain, alone, the excitation
of the oscillating g-modes found in hydrodynamical simulations.


title:
Observation of enhanced X-ray emission from the CTTS AA Tau during a
  transit of an accretion funnel

abstract:
  AA Tau was observed for about 5h per XMM orbit (2 days) over 8 successive
orbits, which covers two optical eclipse periods (8.2 days). The XMM optical/UV
monitor simultaneously provided UV photometry with a ~15 min sampling rate.
Some V-band photometry was also obtained from the ground during this period in
order to determine the dates of the eclipses. Two X-ray and UV measurements
were secured close to the center of the eclipse. The UV flux is the highest
just before the eclipse starts and the lowest towards the end of it. We model
the UV flux variations with a weekly modulation (inner disk eclipse), plus a
daily modulation, which suggests a non-steady accretion. No eclipses are
detected in X-rays. For one measurement, the X-ray count rate was nearly 50
times stronger than the minimum observed level, and the plasma temperature
reached 60 MK, i.e., a factor of 2-3 higher than in the other observations.
This X-ray event, observed close to the center of the optical eclipse, is
interpreted as an X-ray flare. We identify the variable column density with the
low-density accretion funnel flows blanketing the magnetosphere. The lack of
X-ray eclipses indicates that X-ray emitting regions are located at high
latitudes. Furthermore, the occurrence of a strong X-ray flare near the center
of the optical eclipse suggests that the magnetically active areas are closely
associated with the base of the high-density accretion funnel flow. We
speculate that the impact of this free falling accretion flow onto the strong
magnetic field of the stellar corona may boost the X-ray emission (abridged).


title: Metastability of persistent currents in trapped gases of atoms

abstract:
  We examine the conditions that give rise to metastable, persistent currents
in a trapped Bose-Einstein condensate. A necessary condition for the stability
of persistent currents is that the trapping potential is not a monotonically
increasing function of the distance from the trap center. Persistent currents
also require that the interatomic interactions are sufficiently strong and
repulsive. Finally, any off-center vortex state is shown to be unstable, while
a driven gas shows hysteresis.


title:
A resampling-based test to detect person-to-person transmission of
  infectious disease

abstract:
  Early detection of person-to-person transmission of emerging infectious
diseases such as avian influenza is crucial for containing pandemics. We
developed a simple permutation test and its refined version for this purpose. A
simulation study shows that the refined permutation test is as powerful as or
outcompetes the conventional test built on asymptotic theory, especially when
the sample size is small. In addition, our resampling methods can be applied to
a broad range of problems where an asymptotic test is not available or fails.
We also found that decent statistical power could be attained with just a small
number of cases, if the disease is moderately transmissible between humans.


title: Another proof of the positive energy theorem in gravity

abstract:
  We show that gravitational energy expression simplifies when a new set of
coordinates that satisfies a certain asymptotic gauge condition is used.
Compared to the ADM formula, positivity of the energy is more transparent in
this new construction. Our proof relies on the asymptotic symmetries
(specifically supertranslations) of the asymptotically flat spacetimes at
spatial infinity in four dimensions.


title: Scalar theory of gravity as a pressure force

abstract:
  The theory starts from a tentative interpretation of gravity as Archimedes'
thrust exerted on matter at the scale of elementary particles by an imagined
perfect fluid ("ether"): the gravity acceleration is expressed by a formula in
which the "ether pressure" p_e plays the role of the Newtonian potential. The
instantaneous propagation of Newtonian gravity is obtained with an
incompressible ether, giving a field equation for p_e. For a compressible
ether, this equation holds in the static case. The extension to non-static
situations follows the lines of acoustics and leads to gravitational (pressure)
waves. To account for metric effects, the modern version of the
Lorentz-Poincare interpretation of special relativity is used. Einstein's
equivalence principle (EP) is seen as a correspondence between the metric
effects of gravity and those of uniform motion with respect to the ether: a
gravitational contraction (dilation) of space (time) standards is assumed. This
implies geodesic motion for test particles in a static field. The scalar field
equation is now expressed in terms of the physical space and time metrics in
the frame of ether. Since both metrics depend on p_e due to the EP, it becomes
non-linear in p_e. In the spherical static situation, Schwarzschild's exterior
metric is predicted, but the interior metric differs from GR. Since pressure
produces gravitation also in the investigated theory, no equilibrium is
possible for very massive objects. But the gravitational collapse in free fall
does not lead to any singularity. Moreover, gravitational waves, and even shock
ones, can exist in vacuo also with spherical symmetry.


title:
A DH-parameter based condition for 3R orthogonal manipulators to have 4
  distinct inverse kinematic solutions

abstract:
  Positioning 3R manipulators may have two or four inverse kinematic solutions
(IKS). This paper derives a necessary and sufficient condition for 3R
positioning manipulators with orthogonal joint axes to have four distinct IKS.
We show that the transition between manipulators with 2 and 4 IKS is defined by
the set of manipulators with a quadruple root of their inverse kinematics. The
resulting condition is explicit and states that the last link length of the
manipulator must be greater than a quantity that depends on three of its
remaining DH-parameters. This result is of interest for the design of new
manipulators.


title:
Transition from diffusive to ballistic dynamics for a class of finite
  quantum models

abstract:
  The transport of excitation probabilities amongst weakly coupled subunits is
investigated for a class of finite quantum systems. It is demonstrated that the
dynamical behavior of the transported quantity depends on the considered length
scale, e. g., the introduced distinction between diffusive and ballistic
transport appears to be a scale-dependent concept, especially since a
transition from diffusive to ballistic behavior is found in the limit of small
as well as in the limit of large length scales. All these results are derived
by an application of the time-convolutionless projection operator technique and
are verified by the numerical solution of the full time-dependent Schroedinger
equation which is obtained by exact diagonalization for a range of model
parameters.


title: Distant galaxy clusters in the COSMOS field found by HIROCS

abstract:
  We present the first high-redshift galaxy cluster candidate sample from the
HIROCS survey found in the COSMOS field. It results from a combination of
public COSMOS with proprietary H-band data on a 0.66 square degree part of the
COSMOS field and comprises 12 candidates in the redshift range 1.23 < z < 1.55.
We find an increasing fraction of blue cluster members with increasing
redshift. Many of the blue and even some of the reddest member galaxies exhibit
disturbed morphologies as well as signs of interaction.


title:
Energy and equations of motion in a tentative theory of gravity with a
  privileged reference frame

abstract:
  Based on a tentative interpretation of gravity as a pressure force, a scalar
theory of gravity was previously investigated. It assumes gravitational
contraction (dilation) of space (time) standards. In the static case, the same
Newton law as in special relativity was expressed in terms of these distorted
local standards, and was found to imply geodesic motion. Here, the formulation
of motion is reexamined in the most general situation. A consistent Newton law
can still be defined, which accounts for the time variation of the space
metric, but it is not compatible with geodesic motion for a time-dependent
field. The energy of a test particle is defined: it is constant in the static
case. Starting from 'dust', a balance equation is then derived for the energy
of matter. If the Newton law is assumed, the field equation of the theory
allows to rewrite this as a true conservation equation, including the
gravitational energy. The latter contains a Newtonian term, plus the square of
the relative rate of the local velocity of gravitation waves (or that of
light), the velocity being expressed in terms of absolute standards.


title: Effects of Lightest Neutrino Mass in Leptogenesis

abstract:
  The effects of the lightest neutrino mass in ``flavoured'' leptogenesis are
investigated in the case when the CP-violation necessary for the generation of
the baryon asymmetry of the Universe is due exclusively to the Dirac and/or
Majorana phases in the neutrino mixing matrix U. The type I see-saw scenario
with three heavy right-handed Majorana neutrinos having hierarchical spectrum
is considered. The ``orthogonal'' parametrisation of the matrix of neutrino
Yukawa couplings, which involves a complex orthogonal matrix R, is employed.
Results for light neutrino mass spectrum with normal and inverted ordering
(hierarchy) are obtained. It is shown, in particular, that if the matrix R is
real and CP-conserving and the lightest neutrino mass m_3 in the case of
inverted hierarchical spectrum lies the interval 5 \times 10^{-4} eV < m_3 < 7
\times 10^{-3} eV, the predicted baryon asymmetry can be larger by a factor of
\sim 100 than the asymmetry corresponding to negligible m_3 \cong 0. As
consequence, we can have successful thermal leptogenesis for 5 \times 10^{-6}
eV < m_3 < 5 \times 10^{-2} eV even if R is real and the only source of
CP-violation in leptogenesis is the Majorana and/or Dirac phase(s) in U.


title: Quantum Tachyon Dynamics

abstract:
  It is suggested that charged tachyons of extremely large mass M could not
only contribute to the dark matter needed to fit astrophysical observations,
but could also provide an explanation for gamma ray bursts and ulta high energy
cosmic rays. The present paper defines a quantum field theory of tachyons,
particles similar to ordinary leptons, but with momenta larger than energy. The
theory is invariant under the full CPT transformation, but separately violates
P and T invariance. Micro causality is broken for space-time intervals smaller
than 1/M, but is effectively preserved for larger separations. Charged
fermionic, rather than charged scalar tachyons are considered in order to
minimize the probability of Cerenkov-like radiation by the tachyon, thereby
permitting a high energy tachyon to retain its energy over galactic distances.
Topics treated include the choice and Schwinger Action Principle variations of
an appropriate Lagrangian, spinorial wave functions, relevant Green's
functions, a functional description of an S-Matrix and generating functional,
and a variety of interesting kinematical processes, including photon emission
and reabsorption, and relevant annihilation and scattering effects. A version
of Ehrenfest's theorem is developed, in order to provide a foundation for a
classical description of charged tachyons in an external electromagnetic field.
Applications are then made to three outstanding astrophysical puzzles : dark
matter, gamma ray bursts and ultra high energy cosmic rays.


title:
Existence of Positive Solutions for Non Local p-Laplacian Thermistor
  Problems on Time Scales

abstract:
  We make use of the Guo-Krasnoselskii fixed point theorem on cones to prove
existence of positive solutions to a non local p-Laplacian boundary value
problem on time scales arising in many applications.


title:
Freiheitss\"{a}tze for one-relator quotients of surface groups and of
  limit groups

abstract:
  Three versions of the Freiheitssatz are proved in the context of one-relator
quotients of limit groups, where the latter are equipped with 1-acylindrical
splittings over cyclic subgroups. These are natural extensions of previously
published corresponding statements for one-relator quotients of orientable
surface groups. Two of the proofs are new even in that restricted context.


title: Nucleosynthesis in the Early Galaxy

abstract:
  Recent observations of r-process-enriched metal-poor star abundances reveal a
non-uniform abundance pattern for elements $Z\leq47$. Based on non-correlation
trends between elemental abundances as a function of Eu-richness in a large
sample of metal-poor stars, it is shown that the mixing of a consistent and
robust light element primary process (LEPP) and the r-process pattern found in
r-II metal-poor stars explains such apparent non-uniformity. Furthermore, we
derive the abundance pattern of the LEPP from observation and show that it is
consistent with a missing component in the solar abundances when using a recent
s-process model. As the astrophysical site of the LEPP is not known, we explore
the possibility of a neutron capture process within a site-independent
approach. It is suggested that scenarios with neutron densities
$n_{n}\leq10^{13}$ $cm^{-3}$ or in the range $n_{n}\geq10^{24}$ $cm^{-3}$ best
explain the observations.


title:
Role of electrostatic interactions in the assembly of empty spherical
  viral capsids

abstract:
  We examine the role of electrostatic interactions in the assembly of empty
spherical viral capsids. The charges on the protein subunits that make the
viral capsid mutually interact and are expected to yield electrostatic
repulsion acting against the assembly of capsids. Thus, attractive
protein-protein interactions of non-electrostatic origin must act to enable the
capsid formation. We investigate whether the interplay of repulsive
electrostatic and attractive interactions between the protein subunits can
result in the formation of spherical viral capsids of a preferred radius. For
this to be the case, we find that the attractive interactions must depend on
the angle between the neighboring protein subunits (i.e. on the mean curvature
of the viral capsid) so that a particular angle(s) is (are) preferred
energywise. Our results for the electrostatic contributions to energetics of
viral capsids nicely correlate with recent experimental determinations of the
energetics of protein-protein contacts in Hepatitis B virus [P. Ceres and A.
Zlotnick, Biochemistry {\bf 41}, 11525 (2002).


title: Operator approach to analytical evaluation of Feynman diagrams

abstract:
  The operator approach to analytical evaluation of multi-loop Feynman diagrams
is proposed. We show that the known analytical methods of evaluation of
massless Feynman integrals, such as the integration by parts method and the
method of "uniqueness" (which is based on the star-triangle relation), can be
drastically simplified by using this operator approach. To demonstrate the
advantages of the operator method of analytical evaluation of multi-loop
Feynman diagrams, we calculate ladder diagrams for the massless $\phi^3$ theory
(analytical results for these diagrams are expressed in terms of multiple
polylogarithms). It is shown how operator formalism can be applied to
calculation of certain massive Feynman diagrams and investigation of Lipatov
integrable chain model.


title: SPM Bulletin 22

abstract:
  Contents:
  2. Invited contribution: Ultrafilters and small sets 3. Research
announcements 3.1. Inverse Systems and I-Favorable Spaces 3.2. Combinatorial
and hybrid principles for sigma-directed families of countable sets modulo
finite 3.3. A dichotomy characterizing analytic digraphs of uncountable Borel
chromatic number in any dimension 3.4. A dichotomy characterizing analytic
digraphs of uncountable Borel chromatic number in any dimension 3.5. Large
continuum, oracles 3.6. Borel hierarchies in infinite products of Polish spaces
3.7. A game for the Borel functions 3.8. On some problems in general topology
4. Problem of the Issue


title: Probabilistic projections of HIV prevalence using Bayesian melding

abstract:
  The Joint United Nations Programme on HIV/AIDS (UNAIDS) has developed the
Estimation and Projection Package (EPP) for making national estimates and
short-term projections of HIV prevalence based on observed prevalence trends at
antenatal clinics. Assessing the uncertainty about its estimates and
projections is important for informed policy decision making, and we propose
the use of Bayesian melding for this purpose. Prevalence data and other
information about the EPP model's input parameters are used to derive a
probabilistic HIV prevalence projection, namely a probability distribution over
a set of future prevalence trajectories. We relate antenatal clinic prevalence
to population prevalence and account for variability between clinics using a
random effects model. Predictive intervals for clinic prevalence are derived
for checking the model. We discuss predictions given by the EPP model and the
results of the Bayesian melding procedure for Uganda, where prevalence peaked
at around 28% in 1990; the 95% prediction interval for 2010 ranges from 2% to
7%.


title: Lepton pair production in muon scattering by nucleus

abstract:
  Coherent production of lepton pair in muon scattering by nucleus is
considered. With the help of different approaches (equivalent photon
approximation, direct numerical and analytical calculations) we obtain total
cross section of this reaction and distributions over invariant masses of final
leptons. Special attention is paid to influence of final lepton identity on
total and differential cross sections. We also study the role of coherence
condition. Total cross sections of charmonia production in muon interaction
with electromagnetic field of nucleus are also presented.


title: Invariant characterization of Liouville metrics and polynomial integrals

abstract:
  A criterion in terms of differential invariants for a metric on a surface to
be Liouville is established. Moreover, in this paper we completely solve in
invariant terms the local mobility problem of a 2D metric, considered by
Darboux: How many quadratic in momenta integrals does the geodesic flow of a
given metric possess? The method is also applied to recognition of other
polynomial integrals of geodesic flows.


title:
Asymptotics of eigenvalues of Sturm--Liouville problem with discrete
  self-similar weight

abstract:
  The Sturm--Liouville problem $-y''-\lambda\rho y=0$, $y(0)=y(1)=0$, where
$\rho$ is a generalized derivative of self-similar function $P\in L_2[0,1]$
with spectral degree D=0, is studied. Asymptotic formulas for eigenvalues are
obtained.


title: Two Color Matter in the Quenched Approximation

abstract:
  We study a quenched SU(2) lattice gauge theory in 4d in which the spatial
gauge ensemble $\{U_i\}$ is generated from a 3d gauge-Higgs model and the
timelike link variables are ``reconstructed'' from the Higgs fields. The
resulting ensemble is used to study quenched quark propagation with non-zero
chemical potential $\mu$. While it proves possible to alter the strength of the
inter-quark interaction by changing the parameters of the dimensionally reduced
model, there is no evidence for any region of parameter space where quarks
exhibit deconfined behaviour or thermodynamic observables scale as if there
were a Fermi surface.


title: Do oral messages help visual search?

abstract:
  A preliminary experimental study is presented, that aims at eliciting the
contribution of oral messages to facilitating visual search tasks on crowded
visual displays. Results of quantitative and qualitative analyses suggest that
appropriate verbal messages can improve both target selection time and
accuracy. In particular, multimodal messages including a visual presentation of
the isolated target together with absolute spatial oral information on its
location in the displayed scene seem most effective. These messages also got
top-ranking ratings from most subjects.


title:
A multivariate semiparametric Bayesian spatial modeling framework for
  hurricane surface wind fields

abstract:
  Storm surge, the onshore rush of sea water caused by the high winds and low
pressure associated with a hurricane, can compound the effects of inland
flooding caused by rainfall, leading to loss of property and loss of life for
residents of coastal areas. Numerical ocean models are essential for creating
storm surge forecasts for coastal areas. These models are driven primarily by
the surface wind forcings. Currently, the gridded wind fields used by ocean
models are specified by deterministic formulas that are based on the central
pressure and location of the storm center. While these equations incorporate
important physical knowledge about the structure of hurricane surface wind
fields, they cannot always capture the asymmetric and dynamic nature of a
hurricane. A new Bayesian multivariate spatial statistical modeling framework
is introduced combining data with physical knowledge about the wind fields to
improve the estimation of the wind vectors. Many spatial models assume the data
follow a Gaussian distribution. However, this may be overly-restrictive for
wind fields data which often display erratic behavior, such as sudden changes
in time or space. In this paper we develop a semiparametric multivariate
spatial model for these data. Our model builds on the stick-breaking prior,
which is frequently used in Bayesian modeling to capture uncertainty in the
parametric form of an outcome. The stick-breaking prior is extended to the
spatial setting by assigning each location a different, unknown distribution,
and smoothing the distributions in space with a series of kernel functions.
This semiparametric spatial model is shown to improve prediction compared to
usual Bayesian Kriging methods for the wind field of Hurricane Ivan.


title: Oral messages improve visual search

abstract:
  Input multimodality combining speech and hand gestures has motivated numerous
usability studies. Contrastingly, issues relating to the design and ergonomic
evaluation of multimodal output messages combining speech with visual
modalities have not yet been addressed extensively. The experimental study
presented here addresses one of these issues. Its aim is to assess the actual
efficiency and usability of oral system messages including brief spatial
information for helping users to locate objects on crowded displays rapidly.
Target presentation mode, scene spatial structure and task difficulty were
chosen as independent variables. Two conditions were defined: the visual target
presentation mode (VP condition) and the multimodal target presentation mode
(MP condition). Each participant carried out two blocks of visual search tasks
(120 tasks per block, and one block per condition). Scene target presentation
mode, scene structure and task difficulty were found to be significant factors.
Multimodal target presentation proved to be more efficient than visual target
presentation. In addition, participants expressed very positive judgments on
multimodal target presentations which were preferred to visual presentations by
a majority of participants. Besides, the contribution of spatial messages to
visual search speed and accuracy was influenced by scene spatial structure and
task difficulty: (i) messages improved search efficiency to a lesser extent for
2D array layouts than for some other symmetrical layouts, although the use of
2D arrays for displaying pictures is currently prevailing; (ii) message
usefulness increased with task difficulty. Most of these results are
statistically significant.


title:
Experimental investigation to influence of pump phase fluctuation on
  phase-correlation of output optical fields from a non-degenerate parametric
  oscillator

abstract:
  The influence of the phase fluctuation of the pump laser on the
phase-correlation between the signal and idler modes of the output fields from
as non-degenerate optical parametric oscillator operating above oscillation
threshold was experimentally investigated. The noise spectra of the
intensity-difference and the phase-sum of the entangled optical beams were
measured with a pair of unbalanced fiber Match-Zehnder interferometers
specifically designed. The experimental results proved the previously
theoretical prediction and are in reasonable agreement with the calculation
based on semiclassical theory involving the phase fluctuation of pump laser.


title:
Enumeration of paths and cycles and e-coefficients of incomparability
  graphs

abstract:
  We prove that the number of Hamiltonian paths on the complement of an acyclic
digraph is equal to the number of cycle covers. As an application, we obtain a
new expansion of the chromatic symmetric function of incomparability graphs in
terms of elementary symmetric functions. Analysis of some of the combinatorial
implications of this expansion leads to three bijections involving acyclic
orientations.


title:
The innermost region of AGN tori: implications from the HST/NICMOS Type
  1 point sources and near-IR reverberation

abstract:
  Spatially resolving the innermost torus in AGN is one of the main goals of
its high-spatial-resolution studies. This could be done in the near-IR
observations of Type 1 AGNs where we see directly the hottest dust grains in
the torus. We discuss two critical issues in such studies. Firstly, we examine
the nuclear point sources in the HST/NICMOS images of nearby Type 1 AGNs, to
evaluate the possible contribution from the central putative accretion disk.
After a careful subtraction of host bulge flux, we show that near-IR colors of
the point sources appear quite interpretable simply as a composite of a
black-body-like spectrum and a relatively blue distinct component as expected
for a torus and an accretion disk, respectively. Our radiative transfer models
for clumpy tori also support this simple two-component interpretation. The
observed near-IR colors suggest a fractional accretion disk contribution of
~25% or less at 2.2 micron. Secondly, we show that the innermost torus radii as
indicated by the recent near-IR reverberation measurements are systematically
smaller by a factor of ~3 than the predicted dust sublimation radius with a
reasonable assumption for graphite grains of sublimation temperature 1500 K and
size 0.05 micron in radius. The discrepancy might indicate a much higher
sublimation temperature or a typical grain size being much larger in the
innermost tori, though the former case appears to be disfavored by the observed
colors of the HST point sources studied above. The near-IR interferometry with
a baseline of ~100 m should be able to provide the important, independent size
measurements, based on the low accretion disk contribution obtained above.


title: Instanton Counting and Matrix Model

abstract:
  We construct an Imbimbo-Mukhi type matrix model, which reproduces exactly the
partition function of ${\mathbb{CP}^1}$ topological strings in the small phase
space, Nekrasov's instanton counting in ${\cal{N}}=2$ gauge theory and the
large $N$ limit of the partition function in 2-dimensional Yang-Mills theory on
a sphere. In addition, we propose a dual Stieltjes-Wigert type matrix model,
which emerges when all-genus topological string amplitudes on certain simple
toric Calabi-Yau manifolds are compared with the Imbimbo-Mukhi type model.


title: Counterexamples for the convexity of certain matricial inequalities

abstract: This paper is withdrawn. We found a mistake in Lemma 4.1


title: Relaxed Dark Matter Halos

abstract:
  In this paper we reconsider a series expansion for a dark matter distribution
function in the spherically symmetric anisotropic limit. We show here that the
expansion may be renormalized so that the series does converge in time to an
estimate of the steady state distribution function in the central regions.
Subsequently we use this distribution function to discuss the nature of the
central equilibrium and, by invoking stationarity of Boltzmann's H function as
a measure of (thermodynamic) relaxation, we calculate the adiabatic variation
in the local logarithmic slope of the mass density. Similarly the pseudo
(phase-space) density variation with radius is calculated. These are compared
to empirical fitting functions. There is general agreement on the inner part of
the logarithmic slope of the density and of the inner profile of the
pseudo-density power law, but coincident continuity with the outer power-laws
is not yet achieved. Finally some suggestions are made regarding the actual
microphysics acting during the non-equilibrium approach to relaxation. In
particular a cascade regime is identified.


title: A Generic Approach to Coalition Formation

abstract:
  We propose an abstract approach to coalition formation that focuses on simple
merge and split rules transforming partitions of a group of players. We
identify conditions under which every iteration of these rules yields a unique
partition. The main conceptual tool is a specific notion of a stable partition.
The results are parametrized by a preference relation between partitions of a
group of players and naturally apply to coalitional TU-games, hedonic games and
exchange economy games.


title:
Jacobi operators along the structure flow on real hypersurfaces in a
  nonflat complex space form

abstract:
  Let $M$ be a real hypersurface of a complex space form with almost contact
metric structure $(\phi, \xi, \eta, g)$. In this paper, we study real
hypersurfaces in a complex space form whose structure Jacobi operator
$R_\xi=R(\cdot,\xi)\xi$ is $\xi$-parallel. In particular, we prove that the
condition $\nabla_{\xi} R_{\xi}=0$ characterizes the homogeneous real
hypersurfaces of type $A$ in a complex projective space or a complex hyperbolic
space when $R_{\xi} \phi S=S \phi R_{\xi}$ holds on $M$, where $S$ denotes the
Ricci tensor of type (1,1) on $M$.


title:
Assembly Maps for Group Extensions in $K$-Theory and $L$-Theory with
  Twisted Coefficients

abstract:
  In this paper we show that the Farrell-Jones isomorphism conjectures are
inherited in group extensions for assembly maps in algebraic $K$-theory and
$L$-theory with twisted coefficients.


title:
Log Minimal Model Program for the Kontsevich Space of Stable Maps
  $\bar{\mathcal M}_{0,0}(\mathbb P^{3}, 3)$

abstract:
  This work is inspired by conversations with Izzet Coskun and Joe Harris. We
run the log minimal model program for the Kontsevich space of stable maps
$\bar{\mathcal M}_{0,0}(\mathbb P^{3}, 3)$ and give modular interpretations to
all the intermediate spaces appearing in the process. In particular, we show
that one component of the Hilbert scheme $\mathcal H_{3,0,3}$ is the flip of
$\bar{\mathcal M}_{0,0}(\mathbb P^{3}, 3)$ over the Chow variety. Finally as an
easy corollary we obtain that $\bar{\mathcal M}_{0,0}(\mathbb P^{3}, 3)$ is a
Mori dream space.


title:
Cluster Model for Near-barrier Fusion Induced by Weakly Bound and Halo
  Nuclei

abstract:
  The influence on the fusion process of coupling transfer/breakup channels is
investigated for the medium weight $^{6,7}$Li+$^{59}$Co systems in the vicinity
of the Coulomb barrier. Coupling effects are discussed within a comparison of
predictions of the Continuum Discretized Coupled-Channels model. Applications
to $^{6}$He+$^{59}$Co induced by the borromean halo nucleus $^{6}$He are also
proposed.


title: Are volatility estimators robust with respect to modeling assumptions?

abstract:
  We consider microstructure as an arbitrary contamination of the underlying
latent securities price, through a Markov kernel $Q$. Special cases include
additive error, rounding and combinations thereof. Our main result is that,
subject to smoothness conditions, the two scales realized volatility is robust
to the form of contamination $Q$. To push the limits of our result, we show
what happens for some models that involve rounding (which is not, of course,
smooth) and see in this situation how the robustness deteriorates with
decreasing smoothness. Our conclusion is that under reasonable smoothness, one
does not need to consider too closely how the microstructure is formed, while
if severe non-smoothness is suspected, one needs to pay attention to the
precise structure and also the use to which the estimator of volatility will be
put.


title: Progress and challenges in the theory of nuclei

abstract:
  Nuclear theory today aims for a comprehensive theoretical framework that can
describe all nuclei. I discuss recent progress in this pursuit and the
associated challenges as we move forward.


title: Thermal diagnostic of the Optical Window on board LISA Pathfinder

abstract:
  Vacuum conditions inside the LTP Gravitational Reference Sensor must comply
with rather demanding requirements. The Optical Window (OW) is an interface
which seals the vacuum enclosure and, at the same time, lets the laser beam go
through for interferometric Metrology with the test masses. The OW is a
plane-parallel plate clamped in a Titanium flange, and is considerably
sensitive to thermal and stress fluctuations. It is critical for the required
precision measurements, hence its temperature will be carefully monitored in
flight. This paper reports on the results of a series of OW characterisation
laboratory runs, intended to study its response to selected thermal signals, as
well as their fit to numerical models, and the meaning of the latter. We find
that a single pole ARMA transfer function provides a consistent approximation
to the OW response to thermal excitations, and derive a relationship with the
physical processes taking place in the OW. We also show how system noise
reduction can be accomplished by means of that transfer function.


title:
Similar self-organizing scale-invariant properties characterize early
  cancer invasion and long range species spread

abstract:
  Occupancy of new habitats through dispersion is a central process in nature.
In particular, long range dispersal is involved in the spread of species and
epidemics, although it has not been previously related with cancer invasion, a
process that involves spread to new tissues. We show that the early spread of
cancer cells is similar to the species individuals spread and that both
processes are represented by a common spatio-temporal signature, characterized
by a particular fractal geometry of the boundaries of patches generated, and a
power law-scaled, disrupted patch size distribution. We show that both
properties are a direct result of long-distance dispersal, and that they
reflect homologous ecological processes of population self-organization. Our
results are significant for processes involving long-range dispersal like
biological invasions, epidemics and cancer metastasis.


title: Vortices in the two-dimensional Simple Exclusion Process

abstract:
  We show that the fluctuations of the partial current in two dimensional
diffusive systems are dominated by vortices leading to a different scaling from
the one predicted by the hydrodynamic large deviation theory. This is supported
by exact computations of the variance of partial current fluctuations for the
symmetric simple exclusion process on general graphs. On a two-dimensional
torus, our exact expressions are compared to the results of numerical
simulations. They confirm the logarithmic dependence on the system size of the
fluctuations of the partialflux. The impact of the vortices on the validity of
the fluctuation relation for partial currents is also discussed.


title: Magnetic Braking and Protostellar Disk Formation: The Ideal MHD Limit

abstract:
  Magnetic fields are usually considered dynamically important in star
formation when the dimensionless mass-to-flux ratio is close to, or less than,
unity (lambda<~1). We show that, in disk formation, the requirement is far less
stringent. This conclusion is drawn from a set of 2D (axisymmetric) simulations
of the collapse of rotating, magnetized, singular isothermal cores. We find
that a weak field corresponding to 1ambda~100 can begin to disrupt the
rotationally supported disk through magnetic braking, by creating regions of
rapid, supersonic collapse in the disk. These regions are separated by one or
more centrifugal barriers, where the rapid infall is temporarily halted. The
number of centrifugal barriers increases with lambda. When lambda>~100, they
merge together to form a more or less contiguous, rotationally supported disk.
Even though the magnetic field in such a case is extremely weak on the scale of
dense cores, it is amplified by collapse and differential rotation, to the
extent that its pressure dominates the thermal pressure in both the disk and
its surrounding region. For relatively strongly magnetized cores with
lambda<~10, the disk formation is suppressed completely, as found previously. A
new feature is that the mass accretion is highly episodic, due to reconnection
of the accumulated magnetic field lines. For rotationally supported disks to
appear during the protostellar mass accretion phase of star formation in dense
cores with realistic field strengths, the powerful magnetic brake must be
weakened, perhaps through nonideal MHD effects and/or protostellar winds. We
discuss the possibility of observing a generic product of the magnetic braking,
an extended circumstellar region that is supported by a combination of toroidal
magnetic field and rotation - a "magnetogyrosphere".


title: Logic Column 19: Symbolic Model Checking for Temporal-Epistemic Logics

abstract:
  This article surveys some of the recent work in verification of temporal
epistemic logic via symbolic model checking, focusing on OBDD-based and
SAT-based approaches for epistemic logics built on discrete and real-time
branching time temporal logics.


title: Local mixture models of exponential families

abstract:
  Exponential families are the workhorses of parametric modelling theory. One
reason for their popularity is their associated inference theory, which is very
clean, both from a theoretical and a computational point of view. One way in
which this set of tools can be enriched in a natural and interpretable way is
through mixing. This paper develops and applies the idea of local mixture
modelling to exponential families. It shows that the highly interpretable and
flexible models which result have enough structure to retain the attractive
inferential properties of exponential families. In particular, results on
identification, parameter orthogonality and log-concavity of the likelihood are
proved.


title: When is Eaton's Markov chain irreducible?

abstract:
  Consider a parametric statistical model $P(\mathrm{d}x|\theta)$ and an
improper prior distribution $\nu(\mathrm{d}\theta)$ that together yield a
(proper) formal posterior distribution $Q(\mathrm{d}\theta|x)$. The prior is
called strongly admissible if the generalized Bayes estimator of every bounded
function of $\theta$ is admissible under squared error loss. Eaton [Ann.
Statist. 20 (1992) 1147--1179] has shown that a sufficient condition for strong
admissibility of $\nu$ is the local recurrence of the Markov chain whose
transition function is $R(\theta,\mathrm{d}\eta)=\int
Q(\mathrm{d}\eta|x)P(\mathrm {d}x|\theta)$. Applications of this result and its
extensions are often greatly simplified when the Markov chain associated with
$R$ is irreducible. However, establishing irreducibility can be difficult. In
this paper, we provide a characterization of irreducibility for general state
space Markov chains and use this characterization to develop an easily checked,
necessary and sufficient condition for irreducibility of Eaton's Markov chain.
All that is required to check this condition is a simple examination of $P$ and
$\nu$. Application of the main result is illustrated using two examples.


title:
Comment on "Ab Initio study of 40-Ca with an importance-truncated
  no-core shell model"

abstract:
  In a recent Letter [Phys. Rev. Lett. 99, 092501 (2007)], Roth and Navratil
present an importance-truncation scheme for the no-core shell model. The
authors claim that their truncation scheme leads to converged results for the
ground state of 40-Ca. We believe that this conclusion cannot be drawn from the
results presented in the Letter. Furthermore, the claimed convergence is at
variance with expectations of many-body theory. In particular, coupled-cluster
calculations indicate that a significant fraction of the correlation energy is
missing.


title: Deeply Virtual Compton Scattering off the neutron

abstract:
  The present experiment exploits the interference between the Deeply Virtual
Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the
imaginary part of DVCS amplitudes on the neutron and on the deuteron from the
helicity-dependent D$({\vec e},e'\gamma)X$ cross section measured at $Q^2$=1.9
GeV$^2$ and $x_B$=0.36. We extract a linear combination of generalized parton
distributions (GPDs) particularly sensitive to $E_q$, the least constrained
GPD. A model dependent constraint on the contribution of the up and down quarks
to the nucleon spin is deduced.


title:
SuperB: A High-Luminosity Asymmetric e+ e- Super Flavor Factory.
  Conceptual Design Report

abstract:
  The physics objectives of SuperB, an asymmetric electron-positron collider
with a luminosity above 10^36/cm^2/s are described, together with the
conceptual design of a novel low emittance design that achieves this
performance with wallplug power comparable to that of the current B Factories,
and an upgraded detector capable of doing the physics in the SuperB
environment.


title: The Magnetic Rayleigh-Taylor Instability in Three Dimensions

abstract:
  We study the magnetic Rayleigh-Taylor instability in three dimensions, with
focus on the nonlinear structure and evolution that results from different
initial field configurations. We study strong fields in the sense that the
critical wavelength l_c at which perturbations along the field are stable is a
large fraction of the size of the computational domain. We consider magnetic
fields which are initially parallel to the interface, but have a variety of
configurations, including uniform everywhere, uniform in the light fluid only,
and fields which change direction at the interface. Strong magnetic fields do
not suppress instability, in fact by inhibiting secondary shear instabilities,
they reduce mixing between the heavy and light fluid, and cause the rate of
growth of bubbles and fingers to increase in comparison to hydrodynamics.
Fields parallel to, but whose direction changes at, the interface produce long,
isolated fingers separated by the critical wavelength l_c, which may be
relevant to the morphology of the optical filaments in the Crab nebula.


title:
Powerful nanosecond light sources based on LEDs for astroparticle
  physics experiments

abstract:
  Powerful nanosecond light sources based on LEDs have been developed for use
in astroparticle physics experiments. The light sources use either matrixes of
ultra bright blue LEDs or a new generation high power blue LEDs. It's shown
that such light sources have light yield of up to 10**10 - 10**12 photons per
pulse with very fast light emission kinetics. The described light sources are
important for use in calibration systems of Cherenkov and scintillator
detectors. The developed light sources are currently used successfully in a
number of astroparticle experiments, namely: the TUNKA EAS experiment, the
Baikal neutrino experiment etc.


title: Conformal dual of a quadruplet of points

abstract:
  Let $\{P_1, P_2, P_3, P_4\}$ be a quadruplet of points in $S^3$ . We define a
``dual'' quadruplet of it in a conformal geometric way. We show that the dual
of a dual quadruplet coincides with the original one. We also show that the
cross ratio of the dual quadruplet is equal to the complex conjugate of that of
the original one.


title: On the Origin of Early-type Galaxies Nuclei

abstract:
  The ACS Virgo cluster survey by Cote' and collaborators shows the presence of
compact nuclei at the photocenters of many early-type galaxies. It is argued
that they are the low-mass counterparts of nuclei hosting Super Massive Black
Holes (SBHs) detected in the bright galaxies. If this view is correct, then one
should think in terms of central massive objects, either SBHs or Compact
Stellar Clusters (CSCs), that accompany the formation of almost all early-type
galaxies. In this observational frame, the hypothesis that galactic nuclei may
be the remains of globular clusters driven inward to the galactic center by
dynamical friction and there merged, finds an exciting possible confirm. In
this short paper we report of our recent results on globular cluster mergers
obtained by mean of detailed N-body simulations.


title:
An Improbable Solution to the Underluminosity of 2M1207B: A Hot
  Protoplanet Collision Afterglow

abstract:
  We introduce an alternative hypothesis to explain the very low luminosity of
the cool (L-type) companion to the ~25 M_Jup ~8 Myr-old brown dwarf 2M1207A.
Recently, Mohanty et al. (2007) found that effective temperature estimates for
2M1207B (1600 +- 100 K) are grossly inconsistent with its lying on the same
isochrone as the primary, being a factor of ~10 underluminous at all bands
between I (0.8 um) and L' (3.6 um). Mohanty et al. explain this discrepency by
suggesting that 2M1207B is an 8 M_Jup object surrounded by an edge-on disk
comprised of large dust grains producing 2.5^m of achromatic extinction. We
offer an alternative explanation: the apparent flux reflects the actual source
luminosity. Given the temperature, we infer a small radius (~49,000 km), and
for a range of plausible densities, we estimate a mass < M_Jup. We suggest that
2M1207B is a hot protoplanet collision afterglow and show that the radiative
timescale for such an object is >~1% the age of the system. If our hypothesis
is correct, the surface gravity of 2M1207B should be an order of magnitude
lower than predicted by Mohanty et al. (2007).


title:
Computed Coupling Efficiencies of Kolmogorov Phase Screens into
  Single-Mode Optical Fibers

abstract:
  Coupling efficiencies of an electromagnetic field with a Kolmogorov phase
statistics into a step-index fiber in its monomode regime of wavelengths are
computed from the overlap integral between the phase screens and the far-field
of the monomode at infrared wavelengths. The phase screens are composed from
Karhunen-Loeve basis functions, optionally cutting off some of the eigenmodes
of largest eigenvalue as if Adaptive Optics had corrected for some of the
perturbations. The examples are given for telescope diameters of 1 and 1.8 m,
and Fried parameters of 10 and 20 cm. The wavelength of the stellar light is in
the J, H, or K band of atmospheric transmission, where the fiber core diameter
is tailored to move the cutoff wavelength of the monomode regime to the edges
of these bands.


title: A LED Flasher for TUNKA experiment

abstract:
  A LED flasher has been developed for TUNKA-133 EAS Cherenkov detector. A blue
ultra bright InGaN LED is used as a light source in the flasher. The flasher's
driver is based on a fast discharge of a small capacitor via a complementary
pair of fast RF transistors. The light yield of the flasher is adjusted in the
wide range of from 0 to up to 10**9 photons per pulse. The results of studies
of the flasher's amplitude and timing parameters and their stability are
presented.


title: Sur les fonctions \`a singularit\'e de dimension 1

abstract:
  In this article we show that all results proved for a large class of
holomorphic germs $f : (\mathbb{C}^{n+1}, 0) \to (\mathbb{C}, 0)$ with a
1-dimension singularity in [B.II] are valid for an arbitrary such germ.


title: Tidal tails around globular clusters

abstract:
  We present the results of detailed N-body simulations of clusters moving in a
realistic Milky Way (MW) potential. The strong interaction with the bulge and
the disk of the Galaxy leads to the formation of tidal tails, emanating from
opposite sides of the cluster. Their orientation and morphology may be
interpreted easily in terms of a comoving frame of coordinates.


title: Simulations of astronomical imaging phased arrays

abstract:
  We describe a theoretical procedure for analyzing astronomical phased arrays
with overlapping beams, and apply the procedure to simulate a simple example.
We demonstrate the effect of overlapping beams on the number of degrees of
freedom of the array, and on the ability of the array to recover a source. We
show that the best images are obtained using overlapping beams, contrary to
common practise, and show how the dynamic range of a phased array directly
affects the image quality.


title: Self-consistent models of triaxial cuspy galaxies with dark matter halos

abstract:
  We have constructed realistic, self-consistent models of triaxial elliptical
galaxies embedded in triaxial dark matter halos. Self-consistent solutions by
means of the standard orbital superposition technique introduced by
Schwarzschild were found in each of the three cases studied. Chaotic orbits
were found to be important in all of the models, and their presence was shown
to imply a possible slow evolution of the shapes of the halos. The equilibrium
velocity distribution is reproduced by a Lorentzian function better than by a
Gaussian. Our results demonstrate for the first time that triaxial dark matter
halos can co-exist with triaxial galaxies.


title: Vortices on a superconducting nanoshell: phase diagram and dynamics

abstract:
  In superconductors, the search for special vortex states such as giant
vortices focuses on laterally confined or nanopatterned thin superconducting
films, disks, rings, or polygons. We examine the possibility to realize giant
vortex states and states with non-uniform vorticity on a superconducting
spherical nanoshell, due to the interplay of the topology and the applied
magnetic field. We derive the phase diagram and identify where, as a function
of the applied magnetic field, the shell thickness and the shell radius, these
different vortex phases occur. Moreover, the curved geometry allows these
states (or a vortex lattice) to coexist with a Meissner state, on the same
curved film. We have examined the dynamics of the decay of giant vortices or
states with non-uniform vorticity into a vortex lattice, when the magnetic
field is adapted so that a phase boundary is crossed.


title: Beltrami States for Plasma Dynamics Models

abstract:
  The various plasma models - incompressible magnetohydrodynamic (MHD) model,
compressible MHD model, incompressible Hall MHD model, compressible Hall MHD
model, electron MHD model, compressible Hall MHD with electron inertia model -
notwithstanding the diversity of the underlying physics, are shown to exhibit
some common features in the Beltrami states like certain robustness with
respect to the plasma compressibility effects (albeit in the barotropy
assumption) and the {\it Bernoulli} condition. The Beltrami states for these
models are deduced by minimizing the appropriate total energy while keeping the
appropriate total helicity constant. A Hamiltonian formulation framework is
used to carry out these variational problems.


title:
Orbital periods of cataclysmic variables identified by the SDSS. II.
  Measurements for six objects, including two eclipsing systems

abstract:
  Continuing our work from Paper I (Southworth et al., 2006) we present
medium-resolution spectroscopy and broad-band photometry of seven cataclysmic
variables (CVs) discovered by the SDSS. For six of these objects we derive
accurate orbital periods, all which are measured for the first time. For SDSS
J013132.39+090122.2, which contains a non-radially pulsating white dwarf, we
find an orbital period of 81.54 +/- 0.13 min and a low radial velocity
variation amplitude indicative of an extreme mass ratio. For SDSS
J205914.87+061220.4, we find a period of 107.52 +/- 0.14 min. This object is a
dwarf nova and was fading from its first recorded outburst throughout our
observations. INT photometry of SDSS J155531.99-001055.0 shows that this system
undergoes total eclipses which are 1.5 mag deep and occur on a period of 113.54
+/- 0.03 min. A NOT light curve of SDSS J075443.01+500729.2 shows that this
system is also eclipsing, on a period of 205.965 +/- 0.014 min, but here the
eclipses are V-shaped and only 0.5 mag deep. Its low emission-line strengths,
orbital period and V-shaped eclipse unambiguously mark it as a novalike object.
WHT photometry of SDSS J005050.88+000912.6 and SDSS J210449.94+010545.8 yields
periods of 80.3 +/- 2.2 and 103.62 +/- 0.12 min, respectively. Photometry of
the seventh and final system, SDSS J165658.12+212139.3, shows only flickering.
Our results strengthen the conclusion that the faint magnitude limit of the
SDSS spectroscopic database implies that the sample of CVs contained in it has
quite different characteristics to previously studied samples of these objects.
Five of the six orbital periods measured here are shorter than the observed 2-3
hr CV period gap. Two systems have periods very close to the minimum orbital
period for hydrogen-rich CVs.


title:
Comment on "Relativistic Aharonov-Bohm effect in the presence of planar
  Coulomb potentials"

abstract:
  It is shown that the principal results of a recent work by Khalilov are
incorrect. These errors are attributable to the author's insistence that wave
functions must be regular at the origin even when the relevant potential is
singular at that point.


title: Lie-algebra Dolbeault cohomology and small deformations of nilmanifolds

abstract:
  We consider nilmanifolds with left-invariant complex structure and prove that
small deformations of such structures are again left invariant if the
Dolbeault-cohomology of the nilmanifold can be calculated using left-invariant
forms. By a result of Console and Fino this is generically the case. Our main
tool is an analog of Dolbeault-cohomology for Lie-algebras with complex
structure.


title: High-j single-particle neutron states outside the N=82 core

abstract:
  The behaviour of the i13/2 and h9/2 single-neutron strength was studied with
the (4He,3He) reaction on 138Ba, 140Ce, 142Nd and 144Sm targets at a beam
energy of 51 MeV. The separation between the single-neutron states i13/2 and
h9/2 was measured in N =83 nuclei with changing proton number. To this end
spectroscopic factors for states populated in high-l transfer were extracted
from the data. Some mixing of l=5 and 6 strength was observed with states that
are formed by coupling the f7/2 state to the 2+ and 3- vibrational states and
the mixing matrix elements were found to be remarkably constant. The centroids
of the strength indicate a systematic change in the energies of the i13/2 and
h9/2 single-neutron states with increasing proton number that is in
quantitative agreement with the effects expected from the tensor interaction.


title: Decoherence bypass of macroscopic superpositions in quantum measurement

abstract:
  We study a class of quantum measurement models. A microscopic object is
entangled with a macroscopic pointer such that a distinct pointer position is
tied to each eigenvalue of the measured object observable. Those different
pointer positions mutually decohere under the influence of an environment.
Overcoming limitations of previous approaches we (i) cope with initial
correlations between pointer and environment by considering them initially in a
metastable local thermal equilibrium, (ii) allow for object-pointer
entanglement and environment-induced decoherence of distinct pointer readouts
to proceed simultaneously, such that mixtures of macroscopically distinct
object-pointer product states arise without intervening macroscopic
superpositions, and (iii) go beyond the Markovian treatment of decoherence.


title: Hidden Dirac Monopoles

abstract:
  Dirac showed that the existence of one magnetic pole in the universe could
offer an explanation of the discrete nature of the electric charge. Magnetic
poles appear naturally in most grand unified theories. Their discovery would be
of greatest importance for particle physics and cosmology. The intense
experimental search carried thus far has not met with success. I proposed a
universe with magnetic poles which are not observed free because they hide in
deeply bound monopole--anti-monopole states named monopolium. I discuss the
realization of this proposal and its consistency with known cosmological
features. I furthermore analyze its implications and the experimental
signatures that confirm the scenario.


title: Space-time filling branes in non critical (super) string theories

abstract:
  We consider solutions of (super) gravities associated to non-critical (super)
string theories in arbitrary space-time dimension D=p+3, that describe
generically non extremal black p-branes charged under NSNS or RR gauge fields,
embedded in some non critical vacuum. In the case of vacuum (uncharged)
backgrounds, we solve completely the problem obtaining all the possible
solutions, that consist of the (p+1)-dimensional Minkowski space times a linear
dilaton times a S^1, and a three parameter family of solutions that include
(p+1)-dimensional Minkowski space times the cigar, and its T-dual
(p+1)-dimensional Minkowski space times the trumpet. For NSNS charged
solutions, we also solve in closed form the problem, obtaining several families
of solutions, that include in particular the fundamental non-critical string
solution embedded in the cigar vacuum, recently found in hep-th/0604202, a
solution that we interpret as a fundamental non-critical string embedded in the
linear dilaton vacuum, and a two-parameter family of regular curvature
solutions asymptotic to AdS_{1,2}\times S^1. In the case of RR charged
Dp-branes solutions, an ansatz allows us to find a non conformal, constant
curvature, asymptotically AdS_{1,p+1} space, T-dual to AdS_{1,p+2}, together
with a two-parameter family of solutions that includes the non conformal, AdS
black hole like solution associated with the earlier space. The solutions
obtained by T-duality are Einstein spaces consisting of a two-parameter family
of conformal, constant dilaton solutions, that include, in particular, the AdS
black hole of hep-th/0403254. We speculate about the possible applications of
some of them in the framework of the gauge-gravity correspondence.


title: Extended N=1 super Yang-Mills theory

abstract:
  We solve a generalization of ordinary N=1 super Yang-Mills theory with gauge
group U(N) and an adjoint chiral multiplet X for which we turn on both an
arbitrary tree-level superpotential term \int d^{2}\theta Tr W(X) and an
arbitrary field-dependent gauge kinetic term \int d^{2}\theta Tr
V(X)W^{\alpha}W_{\alpha}. When W=0, the model reduces to the extended
Seiberg-Witten theory recently studied by Marshakov and Nekrasov. We use two
different points of view: a ''macroscopic'' approach, using generalized anomaly
equations, the Dijkgraaf-Vafa matrix model and the glueball superpotential; and
the recently proposed ''microscopic'' approach, using Nekrasov's sum over
colored partitions and the quantum microscopic superpotential. The two
formalisms are based on completely different sets of variables and statistical
ensembles. Yet it is shown that they yield precisely the same gauge theory
correlators. This beautiful mathematical equivalence is a facet of the
open/closed string duality. A full microscopic derivation of the
non-perturbative N=1 gauge dynamics follows.


title:
Resolving the Multiple Outflows in the Egg Nebula with Keck II Laser
  Guide Star Adaptive Optics

abstract:
  The Egg Nebula has been regarded as the archetype of bipolar proto-planetary
nebulae, yet we lack a coherent model that can explain the morphology and
kinematics of the nebular and dusty components observed at high-spatial and
spectral resolution. Here, we report on two sets of observations obtained with
the Keck Adaptive Optics Laser Guide Star: H to M-band NIRC2 imaging, and
narrow bandpath K-band OSIRIS 3-D imaging-spectroscopy (through the H2
2.121micron emission line). While the central star or engine remains
un-detected at all bands, we clearly resolve the dusty components in the
central region and confirm that peak A is not a companion star. The
spatially-resolved spectral analysis provide kinematic information of the H_2
emission regions in the eastern and central parts of the nebula and show
projected velocities for the H_2 emission higher than 100 km/s. We discuss
these observations against a possible formation scenario for the nebular
components.


title: Disordered Systems, Spanning Trees and SLE

abstract:
  We define a minimization problem for paths on planar graphs that, on the
honeycomb lattice, is equivalent to the exploration path of the critical site
percolation and than has the same scaling limit of SLE_6. We numerically study
this model (testing several SLE properties on other lattices and with different
boundary conditions) and state it in terms of spanning trees. This statement of
the problem allows the definition of a random growth process for trees on two
dimensional graphs such that SLE is recovered as a special choice of boundary
conditions.


title:
Exact Green's functions and Bosonization of a Luttinger liquid coupled
  to impedances

abstract:
  The exact Green's functions of a finite-size Luttinger Liquid (LL) connected
to impedances are computed at zero and finite temperature. Bosonization for a
LL with Impedance boundary conditions (IBC) is proven to hold. The LL with open
boundary conditions (for both Neumann and Dirichlet cases) is explicitly
recovered as a special limit when one has infinite impedances. Additionally
when the impedances are equal to the characteristic impedance of the Luttinger
liquid then the finite Luttinger liquid is shown to be effectively equivalent
to an infinite Luttinger liquid.


title: Eikonal but not: a complementary view of high energy evolution

abstract:
  The high energy evolution equations that describe the evolution of hadronic
amplitudes with energy are derived assuming eikonal interaction of the evolved
hadronic wave function with the target. In this note we remark that this
derivation allows a different interpretation, whereby the hadronic wave
function is not evolved, but instead the evolution acts on the S - matrix
operator. In this approach, analogous to the Heisenberg picture of Quantum
mechanics, the scattering is not eikonal and additional boost provides for
radiation of more gluons in the final state.


title:
A practical model of convective dynamics for stellar evolution
  calculations

abstract:
  Turbulent motions in the interior of a star play an important role in its
evolution, since they transport chemical species, thermal energy and angular
momentum. Our overall goal is to construct a practical turbulent closure model
for convective transport that can be used in a multi-dimensional stellar
evolution calculation including the effects of rotation, shear and magnetic
fields. Here, we focus on the first step of this task: capturing the well-known
transition from radiative heat transport to turbulent convection with and
without rotation, as well as the asymptotic relationship between turbulent and
radiative transport in the limit of large Rayleigh number. We extend the
closure model developed by Ogilvie (2003) and Garaud and Ogilvie (2005) to
include heat transport and compare it with experimental results of
Rayleigh-Benard convection.


title: Soliton interaction with slowly varying potentials

abstract:
  We study the Gross-Pitaevskii equation with a slowly varying smooth
potential, $V(x) = W(hx)$. We show that up to time $\log(1/h)/h $ and errors of
size $h^2$ in $H^1$, the solution is a soliton evolving according to the
classical dynamics of a natural effective Hamiltonian, $ (\xi^2 + \sech^2 * V
(x))/2 $. This provides an improvement ($ h \to h^2 $) compared to previous
works, and is strikingly confirmed by numerical simulations.


title: Granular Fluids

abstract:
  The terminology granular matter refers to systems with a large number of hard
objects (grains) of mesoscopic size ranging from millimeters to meters.
Geological examples include desert sand and the rocks of a landslide. But the
scope of such systems is much broader, including powders and snow, edible
products such a seeds and salt, medical products like pills, and
extraterrestrial systems such as the surface regolith of Mars and the rings of
Saturn. The importance of a fundamental understanding for granular matter
properties can hardly be overestimated. Practical issues of current concern
range from disaster mitigation of avalanches and explosions of grain silos to
immense economic consequences within the pharmaceutical industry. In addition,
they are of academic and conceptual importance as well as examples of systems
far from equilibrium. Under many conditions of interest, granular matter flows
like a normal fluid. In the latter case such flows are accurately described by
the equations of hydrodynamics. Attention is focused here on the possibility
for a corresponding hydrodynamic description of granular flows. The tools of
nonequilibrium statistical mechanics, developed over the past fifty years for
fluids composed of atoms and molecules, are applied here to a system of grains
for a fundamental approach to both qualitative questions and practical
quantitative predictions. The nonlinear Navier-Stokes equations and expressions
for the associated transport coefficients are obtained.


title:
Orbital circularisation of white dwarfs and the formation of
  gravitational radiation sources in star clusters containing an intermediate
  mass black hole

abstract:
  (abbreviated) We consider how tight binaries consisting of a super-massive
black hole of mass $M=10^{3}-10^{4}M_{\odot}$ and a white dwarf can be formed
in a globular cluster. We point out that a major fraction of white dwarfs
tidally captured by the black hole may be destroyed by tidal inflation during
ongoing circularisation, and the formation of tight binaries is inhibited.
However, some stars may survive being spun up to high rotation rates. Then the
energy loss through gravitational wave emission induced by tidally excited
pulsation modes and dissipation through non linear effects may compete with the
increase of pulsation energy due to dynamic tides. The semi-major axes of these
stars can be decreased below a 'critical' value where dynamic tides are not
effective because pulsation modes retain phase coherence between successive
pericentre passages. The rate of formation of such circularising stars is
estimated assuming that they can be modelled as $n=1.5$ polytropes and that
results of the tidal theory for slow rotators can be extrapolated to fast
rotators. We estimate the total capture rate as $\sim \dot N\sim 2.5\cdot
10^{-8}M_{4}^{1.3}r_{0.1}^{-2.1}yr^{-1}$, where $M_{4}=M/10^4M_{\odot}$ and
$r_{0.1}$ is the radius of influence of the black hole in units $0.1pc$. We
find that the formation rate of tight pairs is approximately 10 times smaller
than the total capture rate. It is used to estimate the probability of
detection of gravitational waves coming from such tight binaries by LISA. We
conclude that LISA may detect such binaries provided that the fraction of
globular clusters with black holes in the mass range of interest is substantial
and that the dispersion velocity of the cluster stars near the radius of
influence of the black hole exceeds $\sim 20km/s$.


title: The Fr\"olicher spectral sequence can be arbitrarily non degenerate

abstract:
  The Fr\"olicher spectral sequence of a compact complex manifold $X$ measures
the difference between Dolbeault cohomology and de Rham cohomology.
  We construct for $n\geq 2$ nilmanifolds with left-invariant complex structure
$X_n$ such that the $n$-th differential $d_n$ does not vanish. This replaces an
earlier incorrect example by the second author.


title: Springer correspondences for dihedral groups

abstract:
  Recent work by a number of people has shown that complex reflection groups
give rise to many representation-theoretic structures (e.g., generic degrees
and families of characters), as though they were Weyl groups of algebraic
groups. Conjecturally, these structures are actually describing the
representation theory of as-yet undescribed objects called ''spetses'', of
which reductive algebraic groups ought to be a special case.
  In this paper, we carry out the Lusztig--Shoji algorithm for calculating
Green functions for the dihedral groups. With a suitable set-up, the output of
this algorithm turns out to satisfy all the integrality and positivity
conditions that hold in the Weyl group case, so we may think of it as
describing the geometry of the ''unipotent variety'' associated to a spets.
  From this, we determine the possible ''Springer correspondences'', and we
show that, as is true for algebraic groups, each special piece is rationally
smooth, as is the full unipotent variety.


title:
The PT-symmetric brachistochrone problem, Lorentz boosts and non-unitary
  operator equivalence classes

abstract:
  The PT-symmetric (PTS) quantum brachistochrone problem is reanalyzed as
quantum system consisting of a non-Hermitian PTS component and a purely
Hermitian component simultaneously. Interpreting this specific setup as
subsystem of a larger Hermitian system, we find non-unitary operator
equivalence classes (conjugacy classes) as natural ingredient which contain at
least one Dirac-Hermitian representative. With the help of a geometric analysis
the compatibility of the vanishing passage time solution of a PTS
brachistochrone with the Anandan-Aharonov lower bound for passage times of
Hermitian brachistochrones is demonstrated.


title:
Determination of F_pi from Distributions of Dirac Operator Eigenvalues
  with Imaginary Density

abstract:
  In the epsilon-regime of lattice QCD one can get an accurate measurement of
the pion decay constant F_pi by monitoring how just one single Dirac operator
eigenvalue splits into two when subjected to two different external vector
sources. Because we choose imaginary chemical potentials our Dirac eigenvalues
remain real. Based on the relevant chiral Random Two-Matrix Theory we derive
individual eigenvalue distributions in terms of density correlations functions
to leading order in the finite-volume epsilon-expansion. As a simple byproduct
we also show how the associated individual Dirac eigenvalue distributions and
their correlations can be computed directly from the effective chiral
Lagrangian.


title: The distance to the Orion Nebula

abstract:
  We have used the Very Long Baseline Array to measure the trigonometric
parallax of several member stars of the Orion Nebula Cluster showing
non-thermal radio emission. We have determined the distance to the cluster to
be 414 +/- 7 pc. Our distance determination allows for an improved calibration
of luminosities and ages of young stars. We have also measured the proper
motions of four cluster stars which, when accurate radial velocities are
measured, will put strong constraints on the origin of the cluster.


title:
Enhancement of Intermediate-Field Two-Photon Absorption by
  Rationally-Shaped Femtosecond Pulses

abstract:
  We extend the powerful frequency-domain analysis of femtosecond two-photon
absorption to the intermediate-field regime, which involves both two- and
four-photon transitions. Consequently, we find a broad family of shaped pulses
that enhance the absorption over the transform-limited pulse. It includes any
spectral phase that is anti-symmetric around half the transition frequency. The
spectrum is asymmetric around it. The theoretical framework and results for Na
are verified experimentally. This work opens the door for rational femtosecond
coherent control in a regime of considerable absorption yields.