title: A note on the Hamiltonian constraint in canonical GR

abstract:
  The Hamiltonian constraint of the coupled Einstein-Yang-Mills-Higgs system
with a cosmological constant is shown to be a pure Poisson bracket of a
dimensionless functional on the phase space and the volume of the three-space.
One of its potential consequences, a restriction on the eigenstates of the
volume operator in a class of canonical quantum gravity theories, is also
pointed out.


title:
Optical and X-ray variability of two Small Magellanic Cloud X-ray binary
  pulsars - SXP46.6 and SXP6.85

abstract:
  We present long-term optical and RXTE data of two X-ray binary pulsars in the
Small Magellanic Cloud, SXP46.6 and SXP6.85. The optical light curves of both
sources show substantial (~0.5-0.8 mag) changes over the time span of the
observations. While the optical data for SXP6.85 do not reveal any periodic
behaviour, by detrending the optical measurements for SXP46.6 we find an
orbital period of ~137 days, consistent with results from the X-ray data. The
detection of Type I X-ray outbursts from SXP46.6, combined with the fact that
we also see optical outbursts at these times, implies that SXP46.6 is a high
orbital eccentricity system. Using contemporaneous optical spectra of SXP46.6
we find that the equivalent width of the H_alpha emission line changes over
time indicating that the size of the circumstellar disc varies. By studying the
history of the colour variations for SXP6.85 we find that the source gets
redder as it brightens which can also be attributed to changes in the
circumstellar disc. We do not find any correlation between the X-ray and
optical data for SXP6.85. The results for SXP6.85 suggest that it is a low
eccentricity binary and that the optical modulations are due to the Be
phenomenon.


title:
On the detectability of different forms of interaction in regression
  models

abstract:
  We derive an asymptotic power function for a likelihood-based test for
interaction in a regression model, with possibly misspecified alternative
distribution. This allows a general investigation of types of interactions
which are poorly or well detected via data. Principally we contrast
pairwise-interaction models with `diffuse interaction models' as introduced in
Gustafson, Kazi, and Levy (2005).


title:
Why the Pennington-Wilson expansion with real coefficients is of little
  use in the analysis of production processes

abstract:
  We critically analyse and comment on the claims of M. R. Pennington and D. J.
Wilson [arxiv:0711.3521]. Although we generally agree with their obvious
algebra, it is clearly not applicable to our equations. Moreover, we argue that
the corresponding proposal is not useful for production-data analysis. The
advantages of our approach, which involves complex yet purely kinematical
coefficients, are summarised.


title:
Holographic dark energy: quantum correlations against thermodynamical
  description

abstract:
  Classical and quantum entropic properties of holographic dark energy (HDE)
are considered in view of the fact that its entropy is far more restrictive
than the entropy of a black hole of the same size. In cosmological settings (in
which HDE is promoted to a plausible candidate for being the dark energy of the
universe), HDE should be viewed as a combined state composed of the event
horizon and the stuff inside the horizon. By any interaction of the subsystems,
the horizon and the interior become entangled, raising thereby a possibility
that their quantum correlations be responsible for the almost purity of the
combined state. Under this circumstances, the entanglement entropy is almost
the same for both subsystems, being also of the same order as the thermal
(coarse grained) entropy of the interior or the horizon. In the context of
thermodynamics, however, only additive coarse grained entropies matter, so we
use these entropies to test the generalized second law (GSL) of gravitational
thermodynamics in this framework. While we find that the original Li's model
passes the GSL test for a special choice of parameters, in a saturated model
with the choice for the IR cutoff in the form of the Hubble parameter, the GSL
always breaks down.


title: Light-Cone Distribution Amplitudes for Non-Relativistic Bound States

abstract:
  We calculate light-cone distribution amplitudes for non-relativistic bound
states, including radiative corrections from relativistic gluon exchange to
first order in the strong coupling constant. Our results apply to hard
exclusive reactions with non-relativistic bound states in the QCD factorization
approach like, for instance, [B_c -> eta_c l nu] or [e+ e- -> J/psi eta_c].
They also serve as a toy model for light-cone distribution amplitudes of light
mesons or heavy B and D mesons.


title: Twisted spin Sutherland models from quantum Hamiltonian reduction

abstract:
  Recent general results on Hamiltonian reductions under polar group actions
are applied to study some reductions of the free particle governed by the
Laplace-Beltrami operator of a compact, connected, simple Lie group. The
reduced systems associated with arbitrary finite dimensional irreducible
representations of the group by using the symmetry induced by twisted
conjugations are described in detail. These systems generically yield
integrable Sutherland type many-body models with spin, which are called twisted
spin Sutherland models if the underlying twisted conjugations are built on
non-trivial Dynkin diagram automorphisms. The spectra of these models can be
calculated, in principle, by solving certain Clebsch-Gordan problems, and the
result is presented for the models associated with the symmetric tensorial
powers of the defining representation of SU(N).


title:
Quantum interference phenomena in four-wave mixing processes in a cavity
  driven by quantized fields

abstract: This paper has been withdrawn by the author due to some problems.


title:
A general theory for the van der Waals interactions in colloidal systems
  based on fluctuational electrodynamics

abstract:
  A rigourous theory for the determination of the van der Waals interactions in
colloidal systems is presented. The method is based on fluctuational
electrodynamics and a multiple-scattering method which provides the
electromagnetic Green's tensor. In particular, expressions for the Green's
tensor are presented for arbitrary, finite, collections of colloidal particles,
for infinitely periodic or defected crystals as well as for finite slabs of
crystals. The presented formalism allows for {\it ab initio} calculations of
the vdW interactions is colloidal systems since it takes fully into account
retardation, many-body, multipolar and near-fields effects.


title: Discovery of the Spin Frequency of 4U 0614+09 with SWIFT/BAT

abstract:
  We report the discovery of burst oscillations at 414.7 Hz during a
thermonuclear X-ray burst from the low mass X-ray binary (LMXB) 4U 0614+091
with the Burst Alert Telescope (BAT) onboard SWIFT. In a search of the BAT
archive, we found two burst triggers consistent with the position of 4U
0614+091. We searched both bursts for high frequency timing signatures, and
found a significant detection at 414.7 Hz during a 5 s interval in the cooling
tail of the brighter burst. This result establishes the spin frequency of the
neutron star in 4U 0614+091 as 415 Hz. The oscillation had an average amplitude
(rms) of 14%, These results are consistent with those known for burst
oscillations seen in other LMXBs. The inferred ratio of the frequency
difference between the twin kHz QPOs, and the spin frequency in this source is
strongly inconsistent with either 0.5 or 1, and tends to support the recent
suggestions by Yin et al., and Mendez & Belloni, that the kHz QPO frequency
difference may not have a strong connection to the neutron star spin frequency.


title:
Subwavelength imaging of light by arrays of metal-coated semiconductor
  nanoparticles: a theoretical study

abstract:
  Rigourous calculations of the imaging properties of metamaterials consisting
of metal-coated semiconductor nanoparticles are presented. In particular, it is
shown that under proper choice of geometric and materials parameters, arrays of
such particles exhibit negative refractive index within the region of the
excitonic resonance of the semiconductor. The occurrence of negative refractive
index is predicted by the extended Maxwell-Garnett theory and confirmed by a
layer-multiple scattering method for electromagnetic waves. By using the same
method it is shown that within the negative refractive-index band, arrays of
such nanoparticles amplify the transmitted near-field emitted while
simultaneously narrow down its spatial profile leading to subwavelength
resolution. The effect of material losses to the imaging properties of the
arrays is also addressed.


title: Modeling snow crystal growth III: three-dimensional snowfakes

abstract:
  We introduce a three-dimensional, computationally feasible, mesoscopic model
for snow crystal growth, based on diffusion of vapor, anisotropic attachment,
and a semi-liquid boundary layer. Several case studies are presented that
faithfully emulate a wide variety of physical snowflakes.


title: How many CNOT gates does it take to generate a three-qubit state ?

abstract:
  The number of two-qubit gates required to transform deterministically a
three-qubit pure quantum state into another is discussed. We show that any
state can be prepared from a product state using at most three CNOT gates, and
that, starting from the GHZ state, only two suffice. As a consequence, any
three-qubit state can be transformed into any other using at most four CNOT
gates. Generalizations to other two-qubit gates are also discussed.


title: A precision constraint on multi-Higgs-doublet models

abstract:
  We derive a general expression for Delta rho (or, equivalently, for the
oblique parameter T) in the SU(2) x U(1) electroweak model with an arbitrary
number of scalar SU(2) doublets, with hypercharge +-1/2, and an arbitrary
number of scalar SU(2) singlets. The experimental bound on Delta rho
constitutes a strong constraint on the masses and mixings of the scalar
particles in that model.


title:
^{59}Co NMR evidence for charge ordering below T_{CO}\sim 51 K in
  Na_{0.5}CoO_2

abstract:
  The CoO$_{2}$ layers in sodium-cobaltates Na$_{x}$CoO$_{2}$ may be viewed as
a spin $S=1/2$ triangular-lattice doped with charge carriers. The underlying
physics of the cobaltates is very similar to that of the high $T_{c}$ cuprates.
We will present unequivocal $^{59}$Co NMR evidence that below $T_{CO}\sim51 K$,
the insulating ground state of the itinerant antiferromagnet
Na$_{0.5}$CoO$_{2}$ ($T_{N}\sim 86 K$) is induced by charge ordering.


title:
Rate Dependence and Role of Disorder in Linearly Sheared Two-Dimensional
  Foams

abstract:
  The shear flow of two dimensional foams is probed as a function of shear rate
and disorder. Disordered foams exhibit strongly rate dependent velocity
profiles, whereas ordered foams show rate independence. Both behaviors are
captured quantitatively in a simple model based on the balance of the
time-averaged drag forces in the foam, which are found to exhibit power-law
scaling with the foam velocity and strain rate. Disorder modifies the scaling
of the averaged inter-bubble drag forces, which in turn causes the observed
rate dependence in disordered foams.


title: Harmonic generation of gravitational wave induced Alfven waves

abstract:
  Here we consider the nonlinear evolution of Alfven waves that have been
excited by gravitational waves from merging binary pulsars. We derive a wave
equation for strongly nonlinear and dispersive Alfven waves. Due to the weak
dispersion of the Alfven waves, significant wave steepening can occur, which in
turn implies strong harmonic generation. We find that the harmonic generation
is saturated due to dispersive effects, and use this to estimate the resulting
spectrum. Finally we discuss the possibility of observing the above process.


title:
Three-Nucleon Bound State in a Spin-Isospin Dependent Three Dimensional
  Approach

abstract:
  A spin-isospin dependent Three-Dimensional approach based on momentum vectors
for formulation of the three-nucleon bound state is presented in this paper.
The three-nucleon Faddeev equations with two-nucleon interactions are
formulated as a function of vector Jacobi momenta, specifically the magnitudes
of the momenta and the angle between them with the inclusion of the
spin-isospin quantum numbers, without employing a partial wave decomposition.
As an application the spin-isospin dependent Faddeev integral equations are
solved with Bonn-B potential. Our result for the Triton binding energy with the
value of -8.152 MeV is in good agreement with the achievements of the other
partial wave based methods.


title:
CCD Photometry of the globular cluster NGC 5466. RR Lyrae light curve
  decomposition and the distance scale

abstract:
  We report the results of CCD V and r photometry of the globular cluster NGC
5466. The difference image analysis technique adopted in this work has resulted
in accurate time series photometry even in crowded regions of the cluster
enabling us to discover five probably semi-regular variables. We present new
photometry of three previously known eclipsing binaries and six SX Phe stars.
The light curves of the RR Lyrae stars have been decomposed in their Fourier
harmonics and their fundamental physical parameters have been estimated using
semi-empirical calibrations. The zero points of the metallicity, luminosity and
temperature scales are discussed and our Fourier results are transformed
accordingly. The average iron abundance and distance to the Sun derived from
individual RR Lyrae stars, indicate values of [Fe/H]=-1.91 +- 0.19 and D = 16.0
+- 0.6 kpc, or a true distance modulus of 16.02 +- 0.09 mag, for the parent
cluster. These values are respectively in the Zinn & West metallicity scale and
in agreement with recent luminosity determinations for the RR Lyrae stars in
the LMC. The M_V-[Fe/H] relation has been recalibrated as
M_V=+(0.18+-0.03)[Fe/H]+(0.85+-0.05) using the mean values derived by the
Fourier technique on RR Lyrae stars in a family of clusters. This equation
predicts M_V=0.58 mag for [Fe/H]=-1.5, in agreement with the average absolute
magnitude of RR Lyrae stars calculated from several independent methods. The
M_V-[Fe/H] relationship and the value of [Fe/H] have implications on the age of
the globular clusters when determined from the magnitude difference between the
horizontal branch and the turn off point (HB-TO method). The above results
however would not imply a change in the age of NGC 5466, of 12.5+-0.9 Gyr,
estimated from recent isochrone fitting.


title:
Towards effective payoffs in the prisoner's dilemma game on scale-free
  networks

abstract:
  We study the transition towards effective payoffs in the prisoner's dilemma
game on scale-free networks by introducing a normalization parameter guiding
the system from accumulated payoffs to payoffs normalized with the connectivity
of each agent. We show that during this transition the heterogeneity-based
ability of scale-free networks to facilitate cooperative behavior deteriorates
continuously, eventually collapsing with the results obtained on regular
graphs. The strategy donations and adaptation probabilities of agents with
different connectivities are studied. Results reveal that strategies generally
spread from agents with larger towards agents with smaller degree. However,
this strategy adoption flow reverses sharply in the fully normalized payoff
limit. Surprisingly, cooperators occupy the hubs even if the averaged
cooperation level due to partly normalized payoffs is moderate.


title:
Experimental investigation on the microscopic structure of intrinsic
  paramagnetic point defects in amorphous silicon dioxide

abstract:
  In the present Ph.D. Thesis we report an experimental investigation on the
effects of gamma- and beta-ray irradiation and of subsequent thermal treatment
on many types of a-SiO2 materials, differing in the production methods, OH- and
Al-content, and oxygen deficiencies. Our main objective is to gain further
insight on the microscopic structures of the E'_gamma, E'_delta, E'_alpha and
triplet paramagnetic centers, which are among the most important and studied
class of radiation induced intrinsic point defects in a-SiO2. To pursue this
objective, we use prevalently the EPR spectroscopy. In particular, our work is
focused on the properties of the unpaired electrons wave functions involved in
the defects, and this aspect is mainly investigated through the study of the
EPR signals originating from the interaction of the unpaired electrons with
29Si magnetic nuclei (with nuclear spin I=1/2 and natural abundance 4.7 %). In
addition, in some cases of interest, OA measurements are also performed with
the aim to further characterize the electronic properties of the defects.
Furthermore, due to its relevance for electronics application, the charge state
of the defects is investigated by looking at the processes responsible for the
generation of the defects of interest. Once these information were gained, the
possible sites that can serve as precursors for defects formation are deduced,
with the definitive purpose to obtain in the future more radiation resistant
a-SiO2 materials in which the deleterious effects connected with the point
defects are significantly reduced.


title:
Pauli Pascal Pyramids, Pauli Fibonacci Numbers, and Pauli Jacobsthal
  Numbers

abstract:
  The three anti-commutative two-dimensional Pauli Pascal triangles can be
generalized into multi-dimensional Pauli Pascal hyperpyramids. Fibonacci and
Jacobsthal numbers are then generalized into Pauli Fibonacci numbers, Pauli
Jacobsthal numbers, and Pauli Fibonacci numbers of higher order. And the
question is: are Pauli rabbits killer rabbits?


title:
Equations aux q-differences et fibres vectoriels holomorphes sur la
  courbe elliptique C^*/q^Z

abstract:
  Nous presentons diverses applications des fibres vectoriels aux equations aux
q-differences, dans la lignee de la correspondance de Weil.
  (We present some applications of vector bundles to $q$-difference equtions,
in continuation of Weil's correspondance.)


title: Increasing the power of the verifier in Quantum Zero Knowledge

abstract:
  In quantum zero knowledge, the assumption was made that the verifier is only
using unitary operations. Under this assumption, many nice properties have been
shown about quantum zero knowledge, including the fact that Honest-Verifier
Quantum Statistical Zero Knowledge (HVQSZK) is equal to Cheating-Verifier
Quantum Statistical Zero Knowledge (QSZK) (see [Wat02,Wat06]).
  In this paper, we study what happens when we allow an honest verifier to flip
some coins in addition to using unitary operations. Flipping a coin is a
non-unitary operation but doesn't seem at first to enhance the cheating
possibilities of the verifier since a classical honest verifier can flip coins.
In this setting, we show an unexpected result: any classical Interactive Proof
has an Honest-Verifier Quantum Statistical Zero Knowledge proof with coins.
Note that in the classical case, honest verifier SZK is no more powerful than
SZK and hence it is not believed to contain even NP. On the other hand, in the
case of cheating verifiers, we show that Quantum Statistical Zero Knowledge
where the verifier applies any non-unitary operation is equal to Quantum
Zero-Knowledge where the verifier uses only unitaries.
  One can think of our results in two complementary ways. If we would like to
use the honest verifier model as a means to study the general model by taking
advantage of their equivalence, then it is imperative to use the unitary
definition without coins, since with the general one this equivalence is most
probably not true. On the other hand, if we would like to use quantum zero
knowledge protocols in a cryptographic scenario where the honest-but-curious
model is sufficient, then adding the unitary constraint severely decreases the
power of quantum zero knowledge protocols.


title:
Phonon-assisted and magnetic field induced Kondo tunneling in single
  molecular devices

abstract:
  We consider the Kondo tunneling induced by multiphonon emission/absorption
processes in magnetic molecular complexes with low-energy singlet-triplet spin
gap and show that the number of assisting phonons may be changed by varying the
Zeeman splitting of excited triplet state. As a result, the structure of
multiphonon Kondo resonances may be scanned by means of magnetic field tuning.


title: The q-analogue of the wild fundamental group (II)

abstract:
  In [RS1], we defined q-analogues of alien derivations and stated their basic
properties. In this paper, we prove the density theorem and the freeness
theorem announced in loc. cit.
  [RS1] Ramis J.-P. and Sauloy J., 2007. The q-analogue of the wild fundamental
group (I)


title:
Decay bounds on eigenfunctions and the singular spectrum of unbounded
  Jacobi matrices

abstract:
  Bounds on the exponential decay of generalized eigenfunctions of bounded and
unbounded selfadjoint Jacobi matrices are established. Two cases are considered
separately: (i) the case in which the spectral parameter lies in a general gap
of the spectrum of the Jacobi matrix and (ii) the case of a lower semi-bounded
Jacobi matrix with values of the spectral parameter below the spectrum. It is
demonstrated by examples that both results are sharp.
  We apply these results to obtain a "many barriers-type" criterion for the
existence of square-summable generalized eigenfunctions of an unbounded Jacobi
matrix at almost every value of the spectral parameter in suitable open sets.
As an application, we provide examples of unbounded Jacobi matrices with a
spectral mobility edge.


title: A Realistic Three-Dimensional Calculation of 3H Binding Energy

abstract:
  A recently developed three-dimensional Faddeev integral equations for
three-nucleon bound state with two-nucleon interactions have been solved in
momentum space for Bonn-B potential.


title:
Nonlinear Effects in Pulse Propagation through Doppler-Broadened
  Closed-Loop Atomic Media

abstract:
  Nonlinear effects in pulse propagation through a medium consisting of
four-level double-$\Lambda$-type systems are studied theoretically. We apply
three continous-wave driving fields and a pulsed probe field such that they
form a closed interaction loop. Due to the closed loop and the finite frequency
width of the probe pulses the multiphoton resonance condition cannot be
fulfilled, such that a time-dependent analysis is required. By identifying the
different underlying physical processes we determine the parts of the solution
relevant to calculate the linear and nonlinear response of the system. We find
that the system can exhibit a strong intensity dependent refractive index with
small absorption over a range of several natural linewidths. For a realistic
example we include Doppler and pressure broadening and calculate the nonlinear
selfphase modulation in a gas cell with Sodium vapor and Argon buffer gas. We
find that a selfphase modulation of $\pi$ is achieved after a propagation of
few centimeters through the medium while the absorption in the corresponding
spectral range is small.


title: Spitzer IRS Spectra and Envelope Models of Class I Protostars in Taurus

abstract:
  We present Spitzer Infrared Spectrograph spectra of 28 Class I protostars in
the Taurus star-forming region. The 5 to 36 micron spectra reveal excess
emission from the inner regions of the envelope and accretion disk surrounding
these predecessors of low-mass stars, as well as absorption features due to
silicates and ices. Together with shorter- and longer-wavelength data from the
literature, we construct spectral energy distributions and fit envelope models
to 22 protostars of our sample, most of which are well-constrained due to the
availability of the IRS spectra. We infer that the envelopes of the Class I
objects in our sample cover a wide range in parameter space, particularly in
density and centrifugal radius, implying different initial conditions for the
collapse of protostellar cores.


title:
An Evidence Based Time-Frequency Search Method for Gravitational Waves
  from Pulsar Glitches

abstract:
  We review and expand on a Bayesian model selection technique for the
detection of gravitational waves from neutron star ring-downs associated with
pulsar glitches. The algorithm works with power spectral densities constructed
from overlapping time segments of gravitational wave data. Consequently, the
original approach was at risk of falsely identifying multiple signals where
only one signal was present in the data. We introduce an extension to the
algorithm which uses posterior information on the frequency content of detected
signals to cluster events together. The requirement that we have just one
detection per signal is now met with the additional bonus that the belief in
the presence of a signal is boosted by incorporating information from adjacent
time segments.


title: Borovik-Poizat rank and stability

abstract:
  There is an axiomatic treatment of Morley rank in groups, due to Borovik and
Poizat. These axioms form the basis of the algebraic treatment of groups of
finite Morley rank which is common today. There are, however, ranked
structures, i.e. structures on which a Borovik-Poizat rank function is defined,
which are not $\aleph_0$-stable. Poizat raised the issue of the relationship
between this notion of rank and stability theory in the following terms: ``un
groupe de Borovik est une structure stable, alors qu'un univers rang\'e n'a
aucune raison de l'\^etre ...''. Nonetheless, we show that a ranked structure
is superstable.


title: Absorption suppression in photonic crystals

abstract:
  We study electromagnetic properties of periodic composite structures, such as
photonic crystals, involving lossy components. We show that in many cases a
properly designed periodic structure can dramatically suppress the losses
associated with the absorptive component, while preserving or even enhancing
its useful functionality. As an example, we consider magnetic photonic
crystals, in which the lossy magnetic component provides nonreciprocal Faraday
rotation. We show that the electromagnetic losses in the composite structure
can be reduced by up to two orders of magnitude, compared to those of the
uniform magnetic sample made of the same lossy magnetic material. Importantly,
the dramatic absorption reduction is not a resonance effect and occurs over a
broad frequency range covering a significant portion of photonic frequency
band.


title: Resonances in chiral unitary approaches

abstract:
  The extension of chiral theories to the description of resonances, via the
incorporation of unitarity in coupled channels, has provided us with a new
theoretical perspective on the nature of some of the observed excited hadrons.
In this contribution some of the early achievements in the field of baryonic
resonances are reviewed, the recent evidence of the two-pole nature of the
Lambda(1405) is discussed and results on charmed baryon resonances are
presented.


title: An introduction to upper half plane polynomials

abstract:
  This is a straightforward introduction to the properties of polynomials in
many variables that do not vanish in the open upper half plane. Such
polynomials generalize many of the well-known properties of polynomials with
all real roots.


title:
Measurement of the cross section for W-boson production in association
  with jets in ppbar collisions at sqrt(s)=1.96 TeV

abstract:
  We present a measurement of the cross section for W-boson production in
association with jets in pbar-p collisions at sqrt(s)=1.96 TeV. The analysis
uses a data sample corresponding to an integrated luminosity of 320 pb^-1
collected with the CDF II detector. W bosons are identified in their electron
decay channel and jets are reconstructed using a cone algorithm. For each W+>=
n-jet sample (n= 1 - 4) we measure dsigma(ppbar =>W+>=n-jet)/dE_T^(nth-jet) x
BR(W => e nu) with respect to the transverse energy E_T of the n^th-highest E_T
jet above 20 GeV, and the total cross section sigma(ppbar =>W+>=n-jet;
E_T^(nth-jet)>25 GeV) x BR(W => e nu), for a restricted W => e nu decay phase
space. The cross sections, corrected for all detector effects, can be directly
compared to particle level W+ jet(s) predictions. We present here comparisons
to leading order and next-to-leading order predictions.


title: Fiducial Stellar Population Sequences for the u'g'r'i'z' System

abstract:
  We describe an extensive observational project that has obtained high-quality
and homogeneous photometry for a number of different Galactic star clusters
(including M 92, M 13, M 3, M 71, and NGC 6791) spanning a wide range in
metallicity (-2.3<[Fe/H]<+0.4), as observed in the u'g'r'i'z' passbands with
the MegaCam wide-field imager on the Canada-France-Hawaii Telescope. By
employing these purest of stellar populations, fiducial sequences have been
defined from color-magnitude diagrams that extend from the tip of the red-giant
branch down to approximately 4 magnitudes below the turnoff: these sequences
have been accurately calibrated to the standard u'g'r'i'z' system via a set of
secondary photometric standards located within these same clusters.
Consequently, they can serve as a valuable set of empirical fiducials for the
interpretation of stellar populations data in the u'g'r'i'z' system.


title:
Arguments against a dominantly hadronic origin of the VHE radiation from
  the supernova remnant RX J1713-3946

abstract:
  The flux of photons with energies above 1 TeV from the direction of the
centre and a cloud in the western part of the nearby southern supernova remnant
(SNR) RX J1713.7-3946 is calculated in the ``hadronic scenario'' that aims to
explain the intense VHE radiation from this remnant with the decay of \pi_0
pions produced in nuclear collisions. The expected flux from its centre is
found to fall short by about factor 40 from the one observed by the HESS
collaboration. This discrepancy presents a serious obstacle to the ``hadronic
scenario''. The theoretically expected flux from the molecular cloud exceeds
the one observed by HESS by at least a factor 3. While the size of this
discrepancy might still seem acceptable in the face of various theoretical
uncertainties, the result strongly suggests a strict spatial correlation of the
cloud with an excess of TeV \gamma radiation. The observational lack of such
correlations in the remnant reported by HESS is another counter argument
against the hadronic scenario. In combination these arguments cannot be refuted
by choosing certain parameters for the total energy or acceleration efficiency
of the SNR.


title:
Feedback Processes [in Massive Star Formation]: A Theoretical
  Perspective

abstract:
  I review the evidence for the importance of feedback from massive stars at
small and large scales. The feedback mechanisms include accretion luminosity,
ionizing radiation, collimated outflows, and stellar winds. The good news is
that feedback doesn't entirely prevent the formation of massive stars, while
the bad news is that we don't know what does limit their masses. Feedback from
massive stars also influences their surroundings. I argue that this does not
produce a triggering efficiency above unity, nor does it prevent lots of prompt
star formation in GMCs, though it may preserve massive remnants of the clouds
for many dynamical times.


title:
Annihilating States in Close-Coupling Method for Collisions between
  Hadronic and Ordinary Atoms

abstract:
  Traditional close-coupling methods suppose an expansion of the total wave
function in terms of inner stationary states of colliding subsystems. In the
case of hadronic atoms, a similar expansion has to involve, \emph{inter alia},
low angular momentum states (ns, np) with large annihilation or nuclear
absorbtion widths. The life times of these states are small as compared with
the collision time and mean time between subsequent collisions, therefore the
close-coupling approach has to be modified for the similar problems.
  In this paper we propose a generalization of the close-coupling method with
annihilating states included in the basis. The correct asymptotic behaviour of
the wave function in the annihilating channels suppose that the annihilating
states can not be presented in the incoming channels whereas the corresponding
components of the wave function of relative motion in outgoing channels have to
damp out at large distances. The S-matrix of the transitions in the subspace of
all other (non-annihilating) states is not unitary, because the hamiltonian of
the problem is non-hermitian. The unitary defect gives the cross section of
induced annihilation. The scheme of the numerical solving of the generalized
close-coupling equations is proposed. It includes the calculations of two types
of solution, from the origin to an intermediate sewing point R=a and from a
large R to the point a.


title: New Bisoltion Solutions in Dispersion Managed Systems

abstract:
  In this paper we propose a method which provides a full description of
solitary wave solutions of the Schroedinger equation with periodically varying
dispersion. This method is based on analysis and polynomial deformation of the
spectrum of an iterative map. Using this method we discover a new family of
antisymmetric bisoliton solutions. In addition to the fact that these solutions
are of interest for nonlinear fiber optics and the theory of nonlinear
Schroedinger equations with periodic coefficients, they have potential
applications for increasing of bit-rate in high speed optical fiber
communications.


title:
Space and time as containers, Space divisibility, and Unrepeatability of
  events

abstract:
  Our main purpose here is to study some qualitative aspects of space and time.
These include the notion of space and time regarded as the containers of
respectively bodies and events, the divisibility of space, and the
unrepeatability of events. We thereof argue that the ideas of an empty space,
portions of empty space and a homogenous space are misleading when they are
applied to realized space, and that they are therefore not suitable for space
as a condition of corporeal world (as it is often assumed). We also show that
smallest (indivisible) and "final" ("ultimate") parts of space and bodies have,
at most, a conventional character, and not a "fundamental" one (as it is
usually claimed). With respect to time and events, analogous conclusions
follow. However, we claim that between space and time there exist rather big
qualitative differences, which make time's nature much more difficult to grasp
than that of space. In this sense, we discuss the impossibility of repetition
of events and some of its applications in modern science, notably,
probabilistic and statistical science. Some other implications of this study in
conceptual ("philosophical") aspects of modern physics are briefly discussed,
such as the "timeless" interpretation of general relativity, the notion of
space-time, among others. Finally, some considerations about the usual
conception and the scope of modern science in general, and modern physics in
particular, are addressed throughout the article.


title: Formation of cold filaments in cooling flow clusters

abstract:
  Emission-lines in the form of filamentary structures is common in bright
clusters characterized by short cooling times. In the Perseus cluster, cold
molecular gas, tightly linked to the H$\alpha$ filaments, has been recently
revealed by CO observations. In order to understand the origin of these
filamentary structures, we have investigated the evolution of the hot ICM gas
perturbed by the AGN central activity in a Perseus like cluster. Using
very-high resolution TreeSPH simulations combined with a multiphase model and a
model of plasma bubbles, we have been able to follow the density and
temperature evolution of the disturbed ICM gas around the bubbles. Our
simulations show that a fraction of the $1-2 \rm{keV}$ gas present at the
center of clusters is trapped and entrained by the rising buoyant bubble to
higher radius where the AGN heating is less efficient. The radiative cooling
makes it cool in a few tens of Myr below $10^4 \rm{K}$, forming cold
filamentary structures in the wake and in the rim of the bubbles.


title: An FPT Algorithm for Directed Spanning k-Leaf

abstract:
  An out-branching of a directed graph is a rooted spanning tree with all arcs
directed outwards from the root. We consider the problem of deciding whether a
given directed graph D has an out-branching with at least k leaves (Directed
Spanning k-Leaf). We prove that this problem is fixed parameter tractable, when
k is chosen as the parameter. Previously this was only known for restricted
classes of directed graphs.
  The main new ingredient in our approach is a lemma that shows that given a
locally optimal out-branching of a directed graph in which every arc is part of
at least one out-branching, either an out-branching with at least k leaves
exists, or a path decomposition with width O(k^3) can be found. This enables a
dynamic programming based algorithm of running time 2^{O(k^3 \log k)} n^{O(1)},
where n=|V(D)|.


title:
The Magueijo-Smolin model of Deformed Special Relativity from five
  dimensions

abstract:
  It is known that the space of momenta of DSR can be identified with de Sitter
space. In this paper, we discuss the relation of the noncanonical phase space
of the Magueijo-Smolin model of DSR with the canonical 5-dimensional phase
space in which the de Sitter space of momenta is embedded. We suggest that in
analogy with the momentum variables, also the position variables should be
constrained to lie on a null hypersurface of the five-dimensional space


title:
Quantum fluctuations in high field magnetization of 2D square lattice
  J1-J2 antiferromagnets

abstract:
  The J1-J2 square lattice Heisenberg model with spin S=1/2 has three phases
with long-range magnetic order and two unconventionally ordered phases
depending on the ratio of exchange constants. It describes a number of recently
found layered vanadium oxide compounds. A simple means of investigating the
ground state is the study of the magnetization curve and high-field
susceptibility. We discuss these quantities by using the spin-wave theory and
the exact diagonalization in the whole J1-J2 plane. We compare both results and
find good overall agreement in the sectors of the phase diagram with magnetic
order. Close to the disordered regions the magnetization curve shows strong
deviations from the classical linear behaviour caused by large quantum
fluctuations and spin-wave approximation breaks down. On the FM side (J1<0)
where one approaches the quantum gapless spin nematic ground state this region
is surprisingly large. We find that inclusion of second order spin-wave
corrections does not lead to fundamental improvement. Quantum corrections to
the tilting angle of the ordered moments are also calculated. They may have
both signs, contrary to the always negative first order quantum corrections to
the magnetization. Finally we investigate the effect of the interlayer coupling
and find that the quasi-2D picture remains valid up to |J_\perp/J1| ~ 0.3.


title: Phase transition in the fine structure constant

abstract:
  Within the context of mass-varying neutrinos, we construct a cosmological
model that has a phase transition in the electromagnetic fine structure
constant \alpha at a redshift of 0.5. The model accommodates hints of a time
variable \alpha in quasar spectra and the nonobservance of such an effect at
very low redshifts. It is consistent with limits from the recombination and
primordial nucleosynthesis eras and is free of instabilities.


title: Physics at ELSA

abstract:
  Recent experimental results of the Crystal-Barrel/TAPS collaboration at ELSA
are presented. The experiments used a tagged photon beam incident on proton and
neutron targets. Multiple photon final states were detected in the hermetically
closed Crystal-Barrel/TAPS detector setup, enabling the reconstruction of
various neutral meson production channels. In addition to cross sections also
photon beam asymmetries and, in the $K^0_s\Sigma^+$ channel, recoil
polarisations were determined.


title: Stellar Collisions in Young Clusters: Formation of (Very) Massive Stars?

abstract:
  In young star clusters, the density can be high enough and the velocity
dispersion low enough for stars to collide and merge with a significant
probability. This has been suggested as a possible way to build up the
high-mass portion of the stellar mass function and as a mechanism leading to
the formation of one or two very massive stars (M > 150 Msun) through a
collisional runaway. I quickly review the standard theory of stellar
collisions, covering both the stellar dynamics of dense clusters and the
hydrodynamics of encounters between stars. The conditions for collisions to
take place at a significant rate are relatively well understood for idealised
spherical cluster models without initial mass segregation, devoid of gas and
composed of main-sequence (MS) stars. In this simplified situation, 2-body
relaxation drives core collapse through mass segregation and a collisional
phase ensues if the core collapse time is shorter than the MS lifetime of the
most massive stars initially present. The outcome of this phase is still highly
uncertain. A more realistic situation is that of a cluster still containing
large amounts of interstellar gas from which stars are accreting. As stellar
masses increase, the central regions of the cluster contracts. This
little-explored mechanism can potentially lead to very high stellar densities
but it is likely that, except for very rich systems, the contraction is halted
by few-body interactions before collisions set in. A complete picture,
combining both scenarios, will need to address many uncertainties, including
the role of cluster sub-structure, the dynamical effect of interstellar gas,
non-MS stars and the structure and evolution of merged stars.


title:
Creep of current-driven domain-wall lines: intrinsic versus extrinsic
  pinning

abstract:
  We present a model for current-driven motion of a magnetic domain-wall line,
in which the dynamics of the domain wall is equivalent to that of an overdamped
vortex line in an anisotropic pinning potential. This potential has both
extrinsic contributions due to, e.g., sample inhomogeneities, and an intrinsic
contribution due to magnetic anisotropy. We obtain results for the domain-wall
velocity as a function of current for various regimes of pinning. In
particular, we find that the exponent characterizing the creep regime depends
strongly on the presence of a dissipative spin transfer torque. We discuss our
results in the light of recent experiments on current-driven domain-wall creep
in ferromagnetic semiconductors, and suggest further experiments to corroborate
our model.


title: Planets in the Galactic Bulge: Results from the SWEEPS Project

abstract:
  The exoplanets discovered so far have been mostly around relatively nearby
and bright stars. As a result, the host stars are mostly (i) in the Galactic
disk, (ii) relatively massive, and (iii) relatively metal rich. The aim of the
SWEEPS project is to extend our knowledge to stars which (i) are in a different
part of the Galaxy, (ii) have lower masses, and (iii) have a large range of
metallicities. To achieve this goal, we used the Hubble Space Telescope to
search for transiting planets around F, G, K, and M dwarfs in the Galactic
bulge. We photometrically monitored 180,000 stars in a dense bulge field
continuously for 7 days. We discovered 16 candidate transiting extrasolar
planets with periods of 0.6 to 4.2 days, including a new class of ultra-short
period planets (USPPs) with P < 1.2 days. Radial-velocity observations of the
two brightest candidates support their planetary nature. These results suggest
that planets are as abundant in the Galactic bulge as they are in the solar
neighborhood, and they are equally abundant around low-mass stars (within a
factor 2). The planet frequency increases with metallicity even for the stars
in the Galactic bulge. All the USPP hosts are low-mass stars, suggesting either
that close-in planets around higher-mass stars are irradiatively evaporated, or
that the planets can migrate to close-in orbits only around such old and
low-mass stars.


title:
Comment on "Correlation of the Highest-Energy Cosmic Rays with Nearby
  Extragalactic Objects"

abstract:
  We argue that the data published by the Pierre Auger Collaboration
(arXiv:0711.2256) disfavor at 99% confidence level their hypothesis that most
of the highest-energy cosmic rays are protons from nearby astrophysical
sources, either Active Galactic Nuclei or other objects with a similar spatial
distribution.


title: Parking on a Random Tree

abstract:
  Consider an infinite tree with random degrees, i.i.d. over the sites, with a
prescribed probability distribution with generating function G(s). We consider
the following variation of Renyi's parking problem, alternatively called
blocking RSA: at every vertex of the tree a particle (or car) arrives with rate
one. The particle sticks to the vertex whenever the vertex and all of its
nearest neighbors are not occupied yet. We provide an explicit expression for
the so-called parking constant in terms of the generating function.


title: Lifetime measurements of first excited states in 16,18C

abstract:
  The electric quadrupole transition from the first 2+ state to the ground 0+
state in 18C was studied through lifetime measurement by an upgraded recoil
shadow method applied to inelastically scattered radioactive 18C nuclei. The
measured mean lifetime is 18.9 +/- 0.9 (stat) +/- 4.4 (syst) ps, corresponding
to a B(E2;2+ -> 0+) value of 4.3 +/- 0.2 +/- 1.0 e2fm4, or about 1.5 Weisskopf
units. The mean lifetime of the first 2+ state in 16C was remeasured to be 18.0
+/- 1.6 +/- 4.7 ps, about four times shorter than the value reported
previously. The discrepancy between the two results was resolved by
incorporating the gamma-ray angular distribution measured in this work into the
previous measurement. These transition strengths are hindered compared to the
empirical transition strengths, indicating that the anomalous hindrance
observed in 16C persists in 18C.


title: Dimensional reduction and the long-time behavior of Ricci flow

abstract:
  If g(t) is a three-dimensional Ricci flow solution, with sectional curvatures
that decay like the inverse of t and diameter that increases at most like the
square root of t, then the pullback Ricci flow solution on the universal cover
approaches a homogeneous expanding soliton.


title: A primer on elliptic functions with applications in classical mechanics

abstract:
  The Jacobi and Weierstrass elliptic functions used to be part of the standard
mathematical arsenal of physics students. They appear as solutions of many
important problems in classical mechanics: the motion of a planar pendulum
(Jacobi), the motion of a force-free asymmetric top (Jacobi), the motion of a
spherical pendulum (Weierstrass), and the motion of a heavy symmetric top with
one fixed point (Weierstrass). The problem of the planar pendulum, in fact, can
be used to construct the general connection between the Jacobi and Weierstrass
elliptic functions. The easy access to mathematical software by physics
students suggests that they might reappear as useful tools in the undergraduate
curriculum.


title:
FFLO state in 1, 2, and 3 dimensional optical lattices combined with a
  non-uniform background potential

abstract:
  We study the phase diagram of an imbalanced two-component Fermi gas in
optical lattices of 1-3 dimensions, considering the possibilities of the FFLO,
Sarma/breached pair, BCS and normal states as well as phase separation, at
finite and zero temperatures. In particular, phase diagrams with respect to
average chemical potential and the chemical potential difference of the two
components are considered, because this gives the essential information about
the shell structures of phases that will occur in presence of an additional
(harmonic) confinement. These phase diagrams in 1, 2 and 3 dimensions show in a
striking way the effect of Van Hove singularities on the FFLO state. Although
we focus on population imbalanced gases, the results are relevant also for the
(effective) mass imbalanced case. We demonstrate by LDA calculations that
various shell structures such as normal-FFLO-BCS-FFLO-normal, or FFLO-normal,
are possible in presence of a background harmonic trap. The phases are
reflected in noise correlations: especially in 1D the unpaired atoms leave a
clear signature of the FFLO state as a zero-correlation area (``breach'')
within the Fermi sea. This strong signature occurs both for a 1D lattice as
well as for a 1D continuum. We also discuss the effect of Hartree energies and
the Gorkov correction on the phase diagrams.


title: Quantum reflection and dwell times of metastable states

abstract:
  The concept of phase and dwell times used in tunneling is extended to quantum
collisions to derive a relation between the phase and dwell time delays in
scattering. This relation can be used to remove the near threshold s-wave
singularities in the Wigner-Eisenbud delay times and amounts to an extension of
the concept of quantum reflection to strong interactions. Dwell time delay
emerges as the quantity which gives the correct behaviour of the density of
states of a metastable state at all energies. This fact is demonstrated by
investigating some recently found metastable states of mesic-nuclei.


title: Two new Weyl-type bounds for the Dirichlet Laplacian

abstract:
  In this paper, we prove two new Weyl-type upper estimates for the eigenvalues
of the Dirichlet Laplacian. As a consequence, we obtain the following {\em
lower} bounds for its counting function. For $\la\ge \la_1$, one has
  N(\la) > \dfrac{2}{n+2} \dfrac{1}{H_n} (\la-\la_1)^{n/2} \la_1^{-n/2},
  and
  N(\la) > (\dfrac{n+2}{n+4})^{n/2} \dfrac{1}{H_n} (\la-(1+4/n) \la_1)^{n/2}
\la_1^{-n/2},
  where
  H_n=\dfrac{2 n}{j_{n/2-1,1}^2 J_{n/2}^2(j_{n/2-1,1})}
  is a constant which depends on $n$, the dimension of the underlying space,
and Bessel functions and their zeros.


title:
Kondo temperature and crystal field levels of Ce systems within a finite
  U Non-Crossing Approximation

abstract:
  We calculate the Kondo temperature ($T_K$) and crystal-field levels of
strongly correlated multiorbital systems solving the Anderson Impurity Model
with the finite U Non-Crossing Approximation (UNCA) in its simplest scheme,
that is, considering the self energies at lowest order in the 1/N diagrammatic
expansion. We introduced an approximation to the vertex function that includes
the double energy dependence and investigate its effect on the values of $T_K$
for simple electronic models. We also analyze the competition between the two
spin flip mechanisms, involving virtual transitions to empty and doubly
occupied states, in the determination of the ground state symmetry by including
an extra diagram of higher order in $1/N.$ We finally combine the resulting
simple formalism with {\it ab initio} calculated electronic structures to
obtain $T_K$'s, ground states, and crystal field splittings in excellent
agreement with experimental results for two particular Ce compounds, namely
CeIn$_3$ and CeSn$_3$.


title: Negative-weight percolation

abstract:
  We describe a percolation problem on lattices (graphs, networks), with edge
weights drawn from disorder distributions that allow for weights (or distances)
of either sign, i.e. including negative weights. We are interested whether
there are spanning paths or loops of total negative weight. This kind of
percolation problem is fundamentally different from conventional percolation
problems, e.g. it does not exhibit transitivity, hence no simple definition of
clusters, and several spanning paths/loops might coexist in the percolation
regime at the same time. Furthermore, to study this percolation problem
numerically, one has to perform a non-trivial transformation of the original
graph and apply sophisticated matching algorithms.
  Using this approach, we study the corresponding percolation transitions on
large square, hexagonal and cubic lattices for two types of disorder
distributions and determine the critical exponents. The results show that
negative-weight percolation is in a different universality class compared to
conventional bond/site percolation. On the other hand, negative-weight
percolation seems to be related to the ferromagnet/spin-glass transition of
random-bond Ising systems, at least in two dimensions.


title: Hausdorff dimension of the SLE curve intersected with the real line

abstract:
  We establish an upper bound on the asymptotic probability of an SLE(kappa)
curve hitting two small intervals on the real line as the interval width goes
to zero, for the range 4 < kappa < 8. As a consequence we are able to prove
that the SLE curve intersected with the real line has Hausdorff dimension
2-8/kappa, almost surely.


title: Observational semantics of the Prolog Resolution Box Model

abstract:
  This paper specifies an observational semantics and gives an original
presentation of the Byrd box model. The approach accounts for the semantics of
Prolog tracers independently of a particular Prolog implementation. Prolog
traces are, in general, considered as rather obscure and difficult to use. The
proposed formal presentation of its trace constitutes a simple and pedagogical
approach for teaching Prolog or for implementing Prolog tracers. It is a form
of declarative specification for the tracers. The trace model introduced here
is only one example to illustrate general problems relating to tracers and
observing processes. Observing processes know, from observed processes, only
their traces. The issue is then to be able to reconstitute, by the sole
analysis of the trace, part of the behaviour of the observed process, and if
possible, without any loss of information. As a matter of fact, our approach
highlights qualities of the Prolog resolution box model which made its success,
but also its insufficiencies.


title: The Spectral Structure of Correlator Matrices

abstract:
  In lattice QCD spectrum calculations, it is desirable to obtain multiple
excited state energies in each symmetry channel. Typically, one constructs
several interpolating operators for the symmetry channel of interest, forms the
`correlator matrix' of all possible two-point functions, and uses the
variational method to obtain as many energy levels as possible. We present a
detailed look at this last step, starting from a discussion of the symmetry
properties and spectral structure of the correlator matrix. We continue by
motivating and describing the variational method, before discussing some
conceptual and practical challenges concerning the light baryon sector. We
conclude by mentioning some alternate spectrum extraction methods currently
under study. Throughout, we attempt to quantify all approximations and
assumptions, and we illustrate our points using a nucleon correlator matrix
estimated on dynamical two-flavor lattice data.


title:
On the solution of the Heaviside - Klein - Gordon thermal equation for
  heat transport in graphene

abstract:
  We report studies of the solution of the Heaviside - Klein - Gordon thermal
equation. As the result it is shown that the solution consists of two
components: the fast thermal wave and slow diffusion for very large (compared
to relaxation time) time period. We argue that the fast thermal wave can be
recognized as the indication of the ballistic heat transport. As an example we
consider the ballistic heat transport in graphene.


title: A weighted generalization of Gao's n+D-1 Theorem

abstract:
  Let $G$ denotes a finite abelian group of order $n$ and Davenport constant
$D$, and put $m= n+D-1$.
  Let $x=(x_1, ..., x_m)\in G^m$ be a sequence with a maximal repetition $\ell$
attained by $x_m$ and put $r=\min(D,\ell)$. Let $w=(w_1, ..., w_{m-r})\in
\Z^{m-r}.$ Then there are an $n$-subset $I\subset [1,m-r]$ and an injection $f:
I\mapsto [1,m]$, such that $m\in f(I)$ and $$\sum_{i\in
I}w_{i}x_{f({i})}=(\sum_{i\in I}w_{i})x_{m}.$$


title:
Evaluating the Impact of Information Distortion on Normalized
  Compression Distance

abstract:
  In this paper we apply different techniques of information distortion on a
set of classical books written in English. We study the impact that these
distortions have upon the Kolmogorov complexity and the clustering by
compression technique (the latter based on Normalized Compression Distance,
NCD). We show how to decrease the complexity of the considered books
introducing several modifications in them. We measure how the information
contained in each book is maintained using a clustering error measure. We find
experimentally that the best way to keep the clustering error is by means of
modifications in the most frequent words. We explain the details of these
information distortions and we compare with other kinds of modifications like
random word distortions and unfrequent word distortions. Finally, some
phenomenological explanations from the different empirical results that have
been carried out are presented.


title: Dynamic Nuclear Polarization in Silicon Microparticles

abstract:
  We report record high Si-29 spin polarization obtained using dynamic nuclear
polarization in microcrystalline silicon powder. Unpaired electrons in this
silicon powder are due to dangling bonds in the amorphous region of this
intrinsically heterogeneous sample. Si-29 nuclei in the amorphous region become
polarized by forced electron-nuclear spin flips driven by off-resonant
microwave radiation while nuclei in the crystalline region are polarized by
spin diffusion across crystalline boundaries. Hyperpolarized silicon
microparticles have long T1 relaxation times and could be used as tracers for
magnetic resonance imaging.


title: The dark matter halo of NGC 1399 - CDM or MOND?

abstract:
  Central galaxies in galaxy clusters may be key discriminants in the
competition between the cold dark matter (CDM) paradigm and modified Newtonian
dynamics (MOND). We investigate the dark halo of NGC 1399, the central galaxy
of the Fornax cluster, out to a galactocentric distance of 80 kpc. The data
base consists of 656 radial velocities of globular clusters obtained with
MXU/VLT and GMOS/Gemini, which is the largest sample so far for any galaxy. We
performed a Jeans analysis for a non-rotating isotropic model. An NFW halo with
the parameters r_s = 50 kpc and rho_s = 0.0065 M_sun/pc^3 provides a good
description of our data, fitting well to the X-ray mass. More massive halos are
also permitted that agree with the mass of the Fornax cluster as derived from
galaxy velocities. We compare this halo with the expected MOND models under
isotropy and find that additional dark matter on the order of the stellar mass
is needed to get agreement. A fully radial infinite globular cluster system
would be needed to change this conclusion. Regarding CDM, we cannot draw firm
conclusions. To really constrain a cluster wide halo, more data covering a
larger radius are necessary. The MOND result appears as a small-scale variant
of the finding that MOND in galaxy clusters still needs dark matter.


title: Quasistars: Accreting black holes inside massive envelopes

abstract:
  We study the structure and evolution of "quasistars", accreting black holes
embedded within massive hydrostatic gaseous envelopes. These configurations may
model the early growth of supermassive black hole seeds. The accretion rate
onto the black hole adjusts so that the luminosity carried by the convective
envelope equals the Eddington limit for the total mass. This greatly exceeds
the Eddington limit for the black hole mass alone, leading to rapid growth of
the black hole. We use analytic models and numerical stellar structure
calculations to study the structure and evolution of quasistars. We derive
analytically the scaling of the photospheric temperature with the black hole
mass and envelope mass, and show that it decreases with time as the black hole
mass increases. Once the photospheric temperature becomes lower than 10,000 K,
the photospheric opacity drops precipitously and the photospheric temperature
hits a limiting value, analogous to the Hayashi track for red giants and
protostars, below which no hydrostatic solution for the convective envelope
exists. For metal-free (Population III) opacities this limiting temperature is
approximately 4000 K. After a quasistar reaches this limiting temperature, the
envelope is rapidly dispersed by radiation pressure. We find that black hole
seeds with masses between 1000 and 10000 solar masses could form via this
mechanism in less than a few Myr.


title: Schubert calculus and representations of general linear group

abstract:
  We construct a canonical isomorphism between the Bethe algebra acting on a
multiplicity space of a tensor product of evaluation gl_N[t]-modules and the
scheme-theoretic intersection of suitable Schubert varieties. Moreover, we
prove that the multiplicity space as a module over the Bethe algebra is
isomorphic to the coregular representation of the scheme-theoretic
intersection.
  In particular, this result implies the simplicity of the spectrum of the
Bethe algebra for real values of evaluation parameters and the transversality
of the intersection of the corresponding Schubert varieties.


title:
Counterexamples to Rational Dilation on Symmetric Multiply Connected
  Domains

abstract:
  We show that if R is a compact domain in the complex plane with two or more
holes and an anticonformal involution onto itself (or equivalently a
hyperelliptic Schottky double), then there is an operator T which has R as a
spectral set, but does not dilate to a normal operator with spectrum on the
boundary of R.


title: Ideal boundary of 7-systolic complexes and groups

abstract:
  We prove that ideal boundary of a 7-systolic group is strongly hereditarily
aspherical. For some class of 7-systolic groups we show their boundaries are
connected and without local cut points, thus getting some results concerning
splittings of those groups.


title: Peakons and Cauchy Biorthogonal Polynomials

abstract:
  The contents of the paper is now covered in two separate papers
arXiv:0904.2188 and arXiv:0904.2602. Please refer to those. Note that you can
still access the original version arXiv:0711.4082v1.


title:
Quantum transport in a resonant tunnel junction coupled to a
  nanomechanical oscillator

abstract:
  We discuss the quantum transport of electrons through a resonant tunnel
junction coupled to a nanomechanical oscillator at zero temperature. By using
the Green's function technique we calculate the transport properties of
electrons through a single dot strongly coupled to a single oscillator. We
consider a finite chemical potential difference between the right and left
leads. In addition to the main resonant peak of electrons on the dot, we find
satellite peaks due to the creation of phonons. These satellite peaks become
sharper and more significant with increasing coupling strength between the
electrons and the oscillator. We also consider the energy transferred from the
electrons to the oscillator.


title:
Systematic Study of the Boundary Composition in Poisson Boltzmann
  Calculations

abstract:
  We describe a three-stage procedure to analyze the dependence of Poisson
Boltzmann calculations on the shape, size and geometry of the boundary between
solute and solvent. Our study is carried out within the boundary element
formalism, but our results are also of interest to finite difference techniques
of Poisson Boltzmann calculations. At first, we identify the critical size of
the geometrical elements for discretizing the boundary, and thus the necessary
resolution required to establish numerical convergence. In the following two
steps we perform reference calculations on a set of dipeptides in different
conformations using the Polarizable Continuum Model and a high-level Density
Functional as well as a high-quality basis set. Afterwards, we propose a
mechanism for defining appropriate boundary geometries. Finally, we compare the
classic Poisson Boltzmann description with the Quantum Chemical description,
and aim at finding appropriate fitting parameters to get a close match to the
reference data. Surprisingly, when using default AMBER partial charges and the
rigorous geometric parameters derived in the initial two stages, no scaling of
the partial charges is necessary and the best fit against the reference set is
obtained automatically


title:
Functional integration and gauge ambiguities in generalized abelian
  gauge theories

abstract:
  We consider the covariant quantization of generalized abelian gauge theories
on a closed and compact n-dimensional manifold whose space of gauge invariant
fields is the abelian group of Cheeger-Simons differential characters. The
space of gauge fields is shown to be a non-trivial bundle over the orbits of
the subgroup of smooth Cheeger-Simons differential characters. Furthermore each
orbit itself has the structure of a bundle over a multi-dimensional torus. As a
consequence there is a topological obstruction to the existence of a global
gauge fixing condition. A functional integral measure is proposed on the space
of gauge fields which takes this problem into account and provides a
regularization of the gauge degrees of freedom. For the generalized p-form
Maxwell theory closed expressions for all physical observables are obtained.
The Greens functions are shown to be affected by the non-trivial bundle
structure. Finally the vacuum expectation values of circle-valued
homomorphisms, including the Wilson operator for singular p-cycles of the
manifold, are computed and selection rules are derived.


title: Loops in the Hamiltonian group: a survey

abstract:
  This note describes some recent results about the homotopy properties of
Hamiltonian loops in various manifolds, including toric manifolds and one point
blow ups. We describe conditions under which a circle action does not contract
in the Hamiltonian group, and construct an example of a loop $\ga$ of
diffeomorphisms of a symplectic manifold M with the property that none of the
loops smoothly isotopic to $\ga$ preserve any symplectic form on M. We also
discuss some new conditions under which the Hamiltonian group has infinite
Hofer diameter. Some of the methods used are classical (Weinstein's action
homomorphism and volume calculations), while others use quantum methods (the
Seidel representation and spectral invariants).


title: On the Helix-coil Transition in Alanine-based Polypeptides in Gas Phase

abstract:
  Using multicanonical simulations, the authors study the effect of charged end
groups on helix formation in alanine based polypeptides. They confirm earlier
reports that neutral polyalanine exhibits a pronounced helix-coil transition in
gas phase simulations. Introducing a charged Lys+ at the C terminal stabilizes
the helix and leads to a higher transition temperature. On the other hand,
adding the Lys+ at the N terminal inhibits helix formation. Instead, a more
globular structure was found. These results are in agreement with recent
experiments on alanine based polypeptides in gas phase. They indicate that
present force fields describe accurately the intramolecular interactions in
proteins.


title: Side chain and backbone ordering in a polypeptide

abstract:
  We report results from multicanonical simulations of polyglutamic acid chains
of length of ten residues. For this simple polypeptide we observe a decoupling
of backbone and side-chain ordering in the folding process. While the details
of the two transitions vary between the peptide in gas phase and in an implicit
solvent, our results indicate that, independent of the specific surroundings,
upon continuously lowering the temperature side-chain ordering occurs only
after the backbone topology is completely formed.


title:
Complex microwave conductivity of Pr$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$
  thin films using a cavity perturbation method

abstract:
  We report a study of the microwave conductivity of electron-doped
Pr$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$ superconducting thin films using a
cavity perturbation technique. The relative frequency shifts obtained for the
samples placed at a maximum electric field location in the cavity are treated
using the high conductivity limit presented recently by Peligrad $\textit{et}$
$\textit{al.}$ Using two resonance modes, TE$_{102}$ (16.5 GHz) and TE$_{101}$
(13 GHz) of the same cavity, only one adjustable parameter $\Gamma$ is needed
to link the frequency shifts of an empty cavity to the ones of a cavity loaded
with a perfect conductor. Moreover, by studying different sample
configurations, we can relate the substrate effects on the frequency shifts to
a scaling factor. These procedures allow us to extract the temperature
dependence of the complex penetration depth and the complex microwave
conductivity of two films with different quality. Our data confirm that all the
physical properties of the superconducting state are consistent with an order
parameter with lines of nodes. Moreover, we demonstrate the high sensitivity of
these properties on the quality of the films.


title: Backbone and Sidechain Ordering in a small Protein

abstract:
  We investigate the relation between backbone and side-chain ordering in a
small protein. For this purpos e we have performed multicanonical simulations
of the villin headpiece subdomain HP-36, an often used to y model in protein
studies. Concepts of circular statistics are introduced to analyze side-chain
fluctuations. In contrast to earlier studies on homopolypeptides (Wei et al.,
J. Phys. Chem. B, 111 (2007) 4244) we do not find collective effects leading to
a separate transition. Rather, side-chain ordering is spread over a wide
temperature range. Our results indicate a thermal hierarchy of ordering events,
with side-chain ordering appearing at temperatures below the helix-coil
transition but above the folding transition. We conjecture that this thermal
hierarchy reflects an underlying temporal order, and that side-chain ordering
facilitates the search for the correct backbone topology.


title: Symmetries in noncommutative field theories: Hopf versus Lie

abstract:
  I discuss motivations for introducing Hopf algebra symmetries in
noncommutative field theories and briefly describe twisting of main symmetry
transformations. New results include an extended list of twisted gauge
invariants (which may help to overcome the problem of inconsistency of
equations of motion) and a gauge-covariant twist operator (leading to a
gauge-covariant star product).


title:
Computational assesment of the entropy of solvation of small-sized
  hydrophobic entities

abstract:
  A high level polarizable force field is used to study the temperature
dependence of hydrophobic hydration of small-sized molecules from computer
simulations. Molecular dynamics (MD) simulations of liquid water at various
temperatures form the basis of free energy perturbation calculations that
consider the onset and growth of a repulsive sphere. This repulsive sphere acts
as a model construct for the hydrophobic species. In the present study, an
extension is pursued for seven independent target temperatures, ranging from
close to the freezing point almost up to the boiling point of liquid water
under standard conditions. Care is taken to maintain proper physico-chemical
model descriptions by cross-checking with experimental water densities at the
selected target temperatures. The polarizable force field description of
molecular water turns out to be suitable throughout the entire temperature
domain considered. Derivatives of the computed free energies of hydrophobic
hydration with respect to the temperature give access to the changes in
entropy. In practice the entropy differential is determined from the negative
of the slope of tangential lines formed at a certain target temperature in the
free energy profile. The obtained changes in entropy are negative for
small-sized cavities, and hence reconfirm the basic ideas of the Lum Chandler
Weeks theory on hydrophobic hydration of small-sized solutes.


title: Connectedness at infinity of systolic complexes and groups

abstract:
  By studying connectedness at infinity of systolic groups we distinguish them
from some other classes of groups, in particular from the fundamental groups of
manifolds covered by euclidean space of dimension at least three. We also study
semistability at infinity for some systolic groups.


title:
Quasi-universal finite-$T$ scaling in gapped one-dimensional quantum
  magnets

abstract:
  Temperature dependencies of gap energies and magnon lifetimes are measured in
the quasi-1-dimensional S=1/2 gapped quantum magnets IPA-CuCl3 and Sul-Cu2Cl4
using inelastic neutron scattering. The results are compared to those found in
literature for S=1 Haldane spin chain materials and to theoretical calculations
for the O(3)- and O(N)- quantum non-linear sigma-models. It is found that when
the T=0 energy gap Delta is used as the temperature scale, all experimental and
theoretical curves are identical to within system-dependent but
temperature-independent scaling factors of the order of unity. This
quasi-universality extends over a surprising broad T range, at least up to
kappa T ~ 1.5 Delta.


title:
Potential for Precision Measurement of Solar Neutrino Luminosity by
  HERON

abstract:
  Results are presented for a simulation carried out to test the precision with
which a detector design (HERON) based on a superfluid helium target material
should be able to measure the solar pp and Be7 fluxes. It is found that
precisions of +/- 1.68% and +/- 2.97% for pp and Be7 fluxes, respectively,
should be achievable in a 5-year data sample. The physics motivation to aim for
these precisions is outlined as are the detector design, the methods used in
the simulation and sensitivity to solar orbit eccentricity.


title:
"Orphan" afterglows in the Universal Structured Jet Model for gamma-ray
  bursts

abstract:
  The paucity of reliable achromatic breaks in Gamma-Ray Burst afterglow light
curves motivates independent measurements of the jet aperture. Serendipitous
searches of afterglows, especially at radio wavelengths, have long been the
classic alternative. These survey data have been interpreted assuming a
uniformly emitting jet with sharp edges (``top-hat'' jet), in which case the
ratio of weakly relativistically beamed afterglows to GRBs scales with the jet
solid angle. In this paper, we consider, instead, a very wide outflow with a
luminosity that decreases across the emitting surface. In particular, we adopt
the universal structured jet (USJ) model, that is an alternative to the top-hat
model for the structure of the jet. However, the interpretation of the survey
data is very different: in the USJ model we only observe the emission within
the jet aperture and the observed ratio of prompt emission rate to afterglow
rate should solely depend on selection effects. We compute the number and rate
of afterglows expected in all-sky snapshot observations as a function of the
survey sensitivity. We find that the current (negative) results for OA searches
are in agreement with our expectations. In radio and X-ray bands this was
mainly due to the low sensitivity of the surveys, while in the optical band the
sky-coverage was not sufficient. In general we find that X-ray surveys are poor
tools for OA searches, if the jet is structured. On the other hand, the FIRST
radio survey and future instruments like the Allen Telescope Array (in the
radio band) and especially GAIA, Pan-Starrs and LSST (in the optical band) will
have chances to detect afterglows.


title: New Insights Into the Nature of the Eclipsing System V609 Aquilae

abstract:
  A photometric study of the Near Contact Binary (NCB) system V609 Aql reveals
it to be the westernmost star of a close double, with brightness variations and
implied parameters more extreme than those derived in an earlier photographic
study, in which images of the variable and companion were almost certainly
blended. The system's brightness variations exhibit deep primary eclipses
($\delta$ V = 1.04) and secondary eclipses ($\delta$ V = 0.44) matched to a
model fit with a derived orbital inclination of i = 84.8$\pm$0.2 degrees and
estimated component spectral types of F8-F9 and K2-K3. The primary overfills
its Roche lobe in the optimum eclipse solution, inconsistent with the
definition of NCBs. Period changes in the system are studied from 23 published
times of light minimum and 21 newly-established values: 18 from examination of
archival Harvard plates, and 3 from ASAS data and new CCD observations. O-C
variations from 1891 to 2007 exhibit a long-term parabolic trend indicative of
a period decrease, dP/dt = -(7.75$\pm$1.39) x 10^-8 d/yr, corresponding to mass
transfer to the secondary of (6.5$pm$1.2) x 10^-8 SM/yr. Superposed variations
may indicate fluctuations in the mass flow. The system is estimated to be ~513
pc distant.


title: Cluster algebras and preprojective algebras : the non simply-laced case

abstract:
  We generalize to the non simply-laced case results of Gei\ss, Leclerc and
Schr\"oer about the cluster structure of the coordinate ring of the maximal
unipotent subgroups of simple Lie groups. In this way, cluster structures in
the non simply-laced case can be seen as projections of cluster structures in
the simply-laced case. This allows us to prove that cluster monomials are
linearly independent in the non simply-laced case.


title:
Contribution to Unresolved Infrared Fluctuations from Dwarf Galaxies at
  Redshifts of 2-3

abstract:
  In order to understand the origin of clustered anisotropies detected in
Spitzer images between 3.6 and 8 microns, we stack the Spitzer IRAC/Great
Observatories Origins Deep Survey (GOODS) images at pixel locations
corresponding to faint, z_{AB}~27 mag, optical sources with no obvious IR
counterparts. We obtain a strong detection of the sources with a stacked median
flux at 3.6 microns of 130+/-5 nJy above the background. The wealth of
multi-wavelength imaging data in GOODS enables a similar stacking analysis to
be undertaken at various wavelengths between the ultraviolet and near-infrared
bands. We obtain strong stacked detections of these optically faint sources
over the entire wavelength range which places constraints on the average
properties of these sources. We find that the flux spectrum of the median,
stacked source is consistent with a L<0.03 L_{*,UV} galaxy with a 90%
confidence interval for the redshift of 1.9-2.7. These sources produce a 3.6
micron absolute background intensity between 0.1 and 0.35 nW/m^2/sr and the
clustered IR light could account for ~30-50% of fluctuation power in the IR
background at 4 arcminute angular scales. Although the exact redshift
distribution of these sources is unknown, these galaxies appear to contain
5-20% of the co-moving stellar mass density at z~2.5.


title: On the Convex Closure of the Graph of Modular Inversions

abstract:
  In this paper we give upper and lower bounds as well as a heuristic estimate
on the number of vertices of the convex closure of the set $$ G_n=\left\{(a,b)
: a,b\in \Z, ab \equiv 1 \pmod{n}, 1\leq a,b\leq n-1\right\}. $$ The heuristic
is based on an asymptotic formula of R\'{e}nyi and Sulanke. After describing
two algorithms to determine the convex closure, we compare the numeric results
with the heuristic estimate. The numeric results do not agree with the
heuristic estimate -- there are some interesting peculiarities for which we
provide a heuristic explanation. We then describe some numerical work on the
convex closure of the graph of random quadratic and cubic polynomials over
$\mathbb{Z}_n$. In this case the numeric results are in much closer agreement
with the heuristic, which strongly suggests that the the curve $xy=1\pmod{n}$
is ``atypical''.


title: NLIE of Dirichlet sine-Gordon Model for Boundary Bound States

abstract:
  We investigate boundary bound states of sine-Gordon model on the finite-size
strip with Dirichlet boundary conditions. For the purpose we derive the
nonlinear integral equation (NLIE) for the boundary excited states from the
Bethe ansatz equation of the inhomogeneous XXZ spin 1/2 chain with boundary
imaginary roots discovered by Saleur and Skorik. Taking a large volume (IR)
limit we calculate boundary energies, boundary reflection factors and boundary
Luscher corrections and compare with the excited boundary states of the
Dirichlet sine-Gordon model first considered by Dorey and Mattsson. We also
consider the short distance limit and relate the IR scattering data with that
of the UV conformal field theory.


title: Twisted Homology of Quantum SL(2) - Part II

abstract:
  We complete the calculation of the twisted cyclic homology of the quantised
coordinate ring of SL(2) that we began in math.QA/0405249. In particular, a
nontrivial cyclic 3-cocycle is constructed which also has a nontrivial class in
Hochschild cohomology and thus should be viewed as a noncommutative geometry
analogue of a volume form.


title: Wave scattering by many small particles embedded in a medium

abstract:
  Theory of scattering by many small bodies is developed under various
assumptions concerning the ratio $\frac{a}{d}$, where $a$ is the characteristic
dimension of a small body and $d$ is the distance between neighboring bodies $d
= O(a^{\ka_1})$, $0 < \ka_1 < 1$. On the boundary $S_m$ of every small body an
impedance-type condition is assumed $u_N = \zeta_m u$ on $S_m$, $1 \leq m \leq
M$, $\zeta_m = h_m a^{-\ka}$, $0 < \ka$, $h_m$ are constants independent of
$a$. The behavior of the field in the region in which $M = M(a)\gg 1$ small
particles are embedded is studied as $a\ra 0$ and $m(a)\ra \ue$. Formulas for
the refraction coefficient of the limiting medium are derived under the
assumptions: a) $ \ka_1=(2-\ka)/3$, $0<\ka\leq 1$, and b) $\ka_1=1/3$, $\ka>1$.


title: Tests of the Radial Tremaine-Weinberg Method

abstract:
  At the intersection of galactic dynamics, evolution and global structure,
issues such as the relation between bars and spirals and the persistence of
spiral patterns can be addressed through the characterization of the angular
speeds of the patterns and their possible radial variation. The Radial
Tremaine-Weinberg (TWR) Method, a generalized version of the Tremaine-Weinberg
method for observationally determining a single, constant pattern speed, allows
the pattern speed to vary arbitrarily with radius. Here, we perform tests of
the TWR method with regularization on several simulated galaxy data sets. The
regularization is employed as a means of smoothing intrinsically noisy
solutions, as well as for testing model solutions of different radial
dependence (e.g. constant, linear or quadratic). We test these facilities in
studies of individual simulations, and demonstrate successful measurement of
both bar and spiral pattern speeds in a single disk, secondary bar pattern
speeds, and spiral winding (in the first application of a TW calculation to a
spiral simulation). We also explore the major sources of error in the
calculation and find uncertainty in the major axis position angle most
dominant. In all cases, the method is able to extract pattern speed solutions
where discernible patterns exist to within 20% of the known values, suggesting
that the TWR method should be a valuable tool in the area of galactic dynamics.
For utility, we also discuss the caveats in, and compile a prescription for,
applications to real galaxies.


title:
Directed motion and useful work from an isotropic nonequilibrium
  distribution

abstract:
  We demonstrate that a gas of classical particles trapped in an external
asymmetric potential undergoes a quasiperiodic motion, if the temperature of
its initial velocity distribution $T_{ne}$ differs from the equilibrium
temperature, $T_{eq}$. The magnitude of the effect is determined by the value
of $T_{ne}-T_{eq}$, and the direction of the motion is determined by the sign
of this expression. The "loading'' and "unloading'' of the gas particles change
directions of their motion, thereby creating a possibility of shuttle-like
motion. The system works as a Carnot engine where the heat flow between kinetic
and potential parts of the nonequilibrium distribution produces the useful
work.


title: Characteristic classes associated to Q-bundles

abstract:
  A Q-manifold is a graded manifold endowed with a vector field of degree one
squaring to zero. We consider the notion of a Q-bundle, that is, a fiber bundle
in the category of Q-manifolds. To each homotopy class of ``gauge fields''
(sections in the category of graded manifolds) and each cohomology class of a
certain subcomplex of forms on the fiber we associate a cohomology class on the
base. Any principal bundle yielding canonically a Q-bundle, this construction
generalizes Chern-Weil classes. Novel examples include cohomology classes that
are locally the de Rham differential of the integrands of topological sigma
models obtained by the AKSZ-formalism in arbitrary dimensions. For Hamiltonian
Poisson fibrations one obtains a characteristic 3-class in this manner. We also
relate to equivariant cohomology and Lecomte's characteristic classes of exact
sequences of Lie algebras.


title: The Distance of the SNR Kes 75 and PWN PSR J1846-0258 System

abstract:
  The supernova remnant (SNR) Kes 75/PSR J1846-0258 association can be regarded
as certain due to the accurate location of young PSR J1846-0258 at the center
of Kes 75 and the detected bright radio/X-ray synchrotron nebula surrounding
the pulsar. We provide a new distance estimate to the SNR/pulsar system by
analyzing the HI and $^{13}$CO maps, the HI emission and absorption spectra,
and the $^{13}$CO emission spectrum of Kes 75. No absorption features at
negative velocities strongly argue against the widely-used large distance of 19
to 21 kpc for Kes 75, and show that Kes 75 is within the Solar circle, i.e. a
distance $d<$13.2 kpc. Kes 75 is likely at distance of 5.1 to 7.5 kpc because
the highest HI absorption velocity is at 95 km/s and no absorption is
associated with a nearby HI emission peak at 102 km/s in the direction of Kes
75. This distance to Kes 75 gives a reasonable luminosity of PSR J1846-0258 and
its PWN, and also leads to a much smaller radius for Kes 75. So the age of the
SNR is consistent with the spin-down age of PSR J1846-0258, confirming this
pulsar as the second-youngest in the Galaxy.


title: Tachyon-Free Non-Supersymmetric Strings on Orbifolds

abstract:
  We discuss tachyon-free examples of (Type IIB on) non-compact
non-supersymmetric orbifolds. Tachyons are projected out by discrete torsion
between orbifold twists, while supersymmetry is broken by a Scherk-Schwarz
phase (+1/-1 when acting on space-time bosons/fermions) accompanying some even
order twists. The absence of tachyons is encouraging for constructing
non-supersymmetric D3-brane gauge theories with stable infrared fixed points.
The D3-brane gauge theories in our orbifold backgrounds have chiral N = 1
supersymmetric spectra, but non-supersymmetric interactions.


title:
Constraints on the correlation between QSO luminosity and host halo mass
  from high-redshift quasar clustering

abstract:
  Recent measurements of high-redshift QSO clustering from the Sloan Digital
Sky Survey indicate that QSOs at z~4 have a bias b~14. We find that this
extremely high clustering amplitude, combined with the corresponding space
density, constrains the dispersion in the L-Mhalo relation to be less than 50%
at 99% confidence for the most conservative case of a 100% duty cycle. This
upper limit to the intrinsic dispersion provides as strong a constraint as
current upper limits to the intrinsic dispersion in the local M_BH-sigma
relation and the ratio of bolometric to Eddington luminosity of luminous QSOs.


title: Width of X-ray lines in cooling flows

abstract:
  The dissipation of turbulent gas motions is one of the likely mechanisms that
has been proposed to heat the intracluster medium (ICM) in the cores of
clusters and groups of galaxies. We consider the impact of gas motions on the
width of the most prominent X-ray emission lines. For heavy elements (like
iron) the expected linewidth is much larger than the width due to pure thermal
broadening and the contribution due to turbulent gas motions should be easily
detected with the new generation of X-ray micro-calorimeters, such as the
Spektr-RG calorimeter (SXC). For instance in the Perseus cluster the turbulent
velocity required to balance radiative cooling (as derived by Rebusco et al.
2006), would imply a width of the 6.7 keV Fe line of 10-20 eV, while the pure
thermal broadening is ~4 eV. The radial dependence of the linewidth is
sensitive to i) the radial dependence of the velocity amplitude and ii) the
"directionality" of the stochastic motions (e.g. isotropic turbulence or
predominantly radial gas motions). If the width of several lines,
characteristic for different gas temperatures, can be measured, then it should
be possible to probe both the "directionality" and the amplitude of the gas
motions. Moreover a measurement of the width would put a lower limit on the
amount of the kinetic energy available for dissipation, giving a constraint on
the ICM models.


title:
The Very Low Albedo of an Extrasolar Planet: MOST Spacebased Photometry
  of HD 209458

abstract:
  Measuring the albedo of an extrasolar planet provides insights into its
atmospheric composition and its global thermal properties, including heat
dissipation and weather patterns. Such a measurement requires very precise
photometry of a transiting system sampling fully many phases of the secondary
eclipse. Spacebased optical photometry of the transiting system HD 209458 from
the MOST (Microvariablity and Oscillations of STars) satellite, spanning 14 and
44 days in 2004 and 2005 respectively, allows us to set a sensitive limit on
the optical eclipse of the hot exosolar giant planet in this system. Our best
fit to the observations yields a flux ratio of the planet and star of 7 $\pm$ 9
ppm (parts per million), which corresponds to a geometric albedo through the
MOST bandpass (400-700 nm) of $A_g$ = 0.038 $\pm$ 0.045. This gives a 1$\sigma$
upper limit of 0.08 for the geometric albedo and a 3$\sigma$ upper limit of
0.17. HD 209458b is significantly less reflective than Jupiter (for which $A_g$
would be about 0.5). This low geometric albedo rules out the presence of bright
reflective clouds in this exoplanet's atmosphere. We determine refined
parameters for the star and exoplanet in the HD 209458 system based on a model
fit to the MOST light curve.


title: The power of blazar jets

abstract:
  We estimate the power of relativistic, extragalactic jets by modelling the
spectral energy distribution of a large number of blazars. We adopt a simple
one-zone, homogeneous, leptonic synchrotron and inverse Compton model, taking
into account seed photons originating both locally in the jet and externally.
The blazars under study have an often dominant high energy component, which, if
interpreted as due to inverse Compton radiation, limits the value of the
magnetic field within the emission region. As a consequence, the corresponding
Poynting flux cannot be energetically dominant. Also the bulk kinetic power in
relativistic leptons is often smaller than the dissipated luminosity. This
suggests that the typical jet should comprise an energetically dominant proton
component. If there is one proton per relativistic electrons, jets radiate
around 2-10 per cent of their power in high power blazars and 3-30 per cent in
less powerful BL Lacs.


title:
Detection of the Transverse Proximity Effect: Radiative Feedback from
  Bright QSOs

abstract:
  Measuring the response of the intergalactic medium to a blast of ionizing
radiation allows one to infer the physical properties of the medium and, in
principle, the lifetime and isotropy of the radiating source. The most
sensitive such measurements can be made if the source of radiation is near the
line of sight to a bright background QSO. We present results based on deep
Keck/HIRES observations of the QSO triplet KP76, KP77 and KP78 at z ~2.5, with
separations of 2-3 arcmin on the plane of the sky. Using accurate systemic
redshifts of the QSOs from near-IR spectroscopy, we quantify the state of the
IGM gas in the proximity regions where the expected ionizing flux from the
foreground QSOs exceeds that of the metagalactic background by factors of
10-200, assuming constant and isotropic emission. Based on the unusual
ionization properties of the absorption systems with detected HI, CIV, and OVI,
we conclude that the gas has been significantly affected by the UV radiation
from the nearby QSOs. Aided by observations of the galaxy density near the
foreground QSOs, we discuss several effects that may explain why the transverse
proximity effect has eluded most previous attempts to detect it. Our
observations suggest that the luminosities of KP76 and KP77 have remained
comparable to current values over timescales of, respectively, Delta t > 25 Myr
and 16 Myr < Delta t < 33 Myr - consistent with typical QSO lifetimes estimated
from independent, less-direct methods. There is no evidence that the UV
radiation from either QSO was significantly anisotropic during these intervals.


title: Quantum weak coin flipping with arbitrarily small bias

abstract:
  "God does not play dice. He flips coins instead." And though for some reason
He has denied us quantum bit commitment. And though for some reason he has even
denied us strong coin flipping. He has, in His infinite mercy, granted us
quantum weak coin flipping so that we too may flip coins.
  Instructions for the flipping of coins are contained herein. But be warned!
Only those who have mastered Kitaev's formalism relating coin flipping and
operator monotone functions may succeed. For those foolhardy enough to even
try, a complete tutorial is included.


title:
Path integral for half-binding potentials as quantum mechanical analog
  for black hole partition functions

abstract:
  The semi-classical approximation to black hole partition functions is not
well-defined, because the classical action is unbounded and the first variation
of the uncorrected action does not vanish for all variations preserving the
boundary conditions. Both problems can be solved by adding a Hamilton-Jacobi
counterterm. I show that the same problem and solution arises in quantum
mechanics for half-binding potentials.


title: Star Formation at Zero and Very Low Metallicities

abstract:
  We describe how star formation is expected to proceed in the early metal-free
Universe, focusing on the very first generations of stars. We then discuss how
the star formation process may change as the effects of metallicity, external
radiative feedback, and magnetic and turbulent support of the gas become more
important. The very first stars (Pop III.1) have relatively simple initial
conditions set by cosmology and the cooling properties of primordial gas. We
describe the evolution of these stars as they grow in mass by accretion from
their surrounding gas cores and how the accretion process is affected and
eventually terminated by radiative feedback processes, especially HII region
expansion and disk photoevaporation. The ability of the protostar and its disk
to generate dynamically important magnetic fields is reviewed and their effects
discussed. Pop III.1 star formation is likely to produce massive (~100-200Msun)
stars that then influence their surroundings via ionization, stellar winds, and
supernovae. These processes heat, ionize and metal-enrich the gas, thus
altering the initial conditions for the next generation of star formation.
Stars formed from gas that has been altered significantly by radiative and/or
mechanical feedback, but not by metal enrichment (Pop III.2) are expected to
have significantly smaller masses than Pop III.1 stars because of more
efficient cooling from enhanced HD production. Stars formed from gas that is
metal-enriched to levels that affect the dynamics of the collapse (the first
Pop II stars) are also expected to have relatively low masses. We briefly
compare the above star formation scenarios to what is known about present-day
star formation.


title:
A Simplified Calculation for the Fundamental Solution to the Heat
  Equation on the Heisenberg Group

abstract:
  Let $L = -1/4 (\sum_{j=1}^n(X_j^2+Y_j^2)+i\gamma T)$ where $\gamma$ is a
complex number, $X_j$, $Y_j$, and $T$ are the left invariant vector fields of
the Heisenberg group structure for $R^n \times R^n \times R$. We explicitly
compute the Fourier transform (in the spatial variables) of the fundamental
solution of the Heat Equation $\partial_s\rho = -L\rho$. As a consequence, we
have a simplified computation of the Fourier transform of the fundamental
solution of the $\Box_b$-heat equation on the Heisenberg group and an explicit
kernel of the heat equation associated to the weighted dbar-operator in $C^n$
with weight $\exp(-\tau P(z_1,...,z_n))$ where $P(z_1,...,z_n) = 1/2(x_1^2 +
>... x_n^2)$, $z_j=x_j+iy_j$, and $\tau\in R$.


title: Holographic entanglement entropy for disconnected regions

abstract:
  We present a simple derivation of the entanglement entropy for a region made
up of a union of disjoint intervals in 1+1 dimensional quantum field theories
using holographic techniques. This generalizes the results for 1+1 dimensional
conformal field theories derived previously by exploiting the uniformization
map. We further comment on the generalization of our result to higher
dimensional field theories.