title: Massive Dark Matter Halos around Bright Isolated Galaxies in the 2dFGRS

abstract:
  We identify a large sample of isolated bright galaxies and their fainter
satellites in the 2dF Galaxy Redshift Survey (2dFGRS). We analyse the dynamics
of ensembles of these galaxies selected according to luminosity and
morphological type by stacking the positions of their satellites and estimating
the velocity dispersion of the combined set. We test our methodology using
realistic mock catalogues constructed from cosmological simulations. The method
returns an unbiased estimate of the velocity dispersion provided that the
isolation criterion is strict enough to avoid contamination and that the
scatter in halo mass at fixed primary luminosity is small. Using a maximum
likelihood estimator that accounts for interlopers, we determine the satellite
velocity dispersion within a projected radius of 175 kpc/h. The dispersion
increases with the luminosity of the primary and is larger for elliptical
galaxies than for spiral galaxies of similar bJ luminosity. Calibrating the
mass-velocity dispersion relation using our mock catalogues, we find a
dynamical mass within 175 kpc/h of M_175 ~ 4.0^{+2.3}_{-1.5} 10^12 (L_bJ/L_*)
M_sol/h for elliptical galaxies and M_175 ~ 6.3^{+6.3}_{-3.1} 10^11
(L_bJ/L_*)^1.6 Msol/h for spiral galaxies. Finally, we compare our results with
recent studies and investigate their limitations using our mock catalogues.


title: Ultra-Sensitive Hot-Electron Nanobolometers for Terahertz Astrophysics

abstract:
  The background-limited spectral imaging of the early Universe requires
spaceborne terahertz (THz) detectors with the sensitivity 2-3 orders of
magnitude better than that of the state-of-the-art bolometers. To realize this
sensitivity without sacrificing operating speed, novel detector designs should
combine an ultrasmall heat capacity of a sensor with its unique thermal
isolation. Quantum effects in thermal transport at nanoscale put strong
limitations on the further improvement of traditional membrane-supported
bolometers. Here we demonstrate an innovative approach by developing
superconducting hot-electron nanobolometers in which the electrons are cooled
only due to a weak electron-phonon interaction. At T<0.1K, the electron-phonon
thermal conductance in these nanodevices becomes less than one percent of the
quantum of thermal conductance. The hot-electron nanobolometers, sufficiently
sensitive for registering single THz photons, are very promising for
submillimeter astronomy and other applications based on quantum calorimetry and
photon counting.


title:
A sharp upper bound for the first Dirichlet eigenvalue and the growth of
  the isoperimetric constant of convex domains

abstract:
  We show that as the ratio between the first Dirichlet eigenvalues of a convex
domain and of the ball with the same volume becomes large, the same must happen
to the corresponding ratio of isoperimetric constants. The proof is based on
the generalization to arbitrary dimensions of Polya and Szego's 1951 upper
bound for the first eigenvalue of the Dirichlet Laplacian on planar star-shaped
domains which depends on the support function of the domain.
  As a by-product, we also obtain a sharp upper bound for the spectral gap of
convex domains.


title: Ly$\alpha$ Leaks and Reionization

abstract:
  Ly$\alpha$ absorption spectra of QSOs at redshifts $z\simeq6$ show complete
Gunn-Peterson absorption troughs (dark gaps) separated by tiny leaks. The dark
gaps are from the intergalactic medium (IGM) where the density of neutral
hydrogen are high enough to produce almost saturated absorptions, however,
where the transmitted leaks come from is still unclear so far. We demonstrate
that leaking can originate from the lowest density voids in the IGM as well as
the ionized patches around ionizing sources using semi-analytical simulations.
If leaks were produced in lowest density voids, the IGM might already be highly
ionized, and the ionizing background should be almost uniform; in contrast, if
leaks come from ionized patches, the neutral fraction of IGM would be still
high, and the ionizing background is significantly inhomogeneous. Therefore,
the origin of leaking is crucial to determining the epoch of
inhomogeneous-to-uniform transition of the the ionizing photon background. We
show that the origin could be studied with the statistical features of leaks.
Actually, Ly$\alpha$ leaks can be well defined and described by the equivalent
width $W$ and the full width of half area $W_{\rm H}$, both of which are less
contaminated by instrumental resolution and noise. It is found that the
distribution of $W$ and $W_{\rm H}$ of Ly$\alpha$ leaks are sensitive to the
modeling of the ionizing background. We consider four representative
reionization models. It is concluded that the leak statistics provides an
effective tool to probe the evolutionary history of reionization at
$z\simeq5-6.5$. Similar statistics would also be applicable to the reionization
of He II at $z \simeq 3$(Abridged)


title: Thermoelectrical manipulation of nano-magnets

abstract:
  We propose a device that can operate as a magneto-resistive switch or
oscillator. The device is based on a spin-thermo-electronic control of the
exchange coupling of two strong ferromagnets through a weakly ferromagnetic
spacer. We show that the local Joule heating due to a high concentration of
current in a magnetic point contact or a nanopillar can be used to reversibly
drive the weak ferromagnet through its Curie point and thereby
exchange-decouple the strongly ferromagnetic layers, which have an antiparallel
ground state. Such a spin-thermionic parallel-to-antiparallel switching causes
magnetoresistance oscillations where the frequency can be controlled by proper
biasing from essentially DC to GHz.


title: The work of Jesse Douglas on Minimal Surfaces

abstract:
  This paper describes the work of Jesse Douglas on the Plateau problem, work
for which he was awarded a Fields Medal in 1936, and considers the
contributions Tibor Rado made in the 1930s.


title: A Weyl function approach to matter-wave coherence and Talbot-Lau effects

abstract:
  Weyl functions conveniently describe the evolution of wave coherences in
periodic or quadratic potentials. In this work we use Weyl functions to study
the ``Talbot-Lau effect'' in a time-domain matter-wave interferometer. A
``displacement diagram'' is introduced to analyze and calculate the matter-wave
interference for an atomic cloud in a quadratic potential that interacts with a
sequence of short optical standing wave pulses producing an atomic grating
echo. Unlike previous treatments, this new approach allows the atomic ensemble
to have an arbitrary initial phase-space distribution, and the standing wave
grating vectors to span three dimensions. Several examples are discussed to
illustrate the convenience of the diagrammatic technique including the
following: a two-dimensional Talbot-Lau effect, the shift in the echo time and
the recoil phase for the interferometer perturbed by a quadratic potential; and
the realization of a time-domain ``Lau effect'' using a pulsed harmonic
potential. The diagrammatic technique is applicable to diffraction gratings
with arbitrary grating transmission functions. We conclude the paper with a
general discussion on the Weyl function representations of matter-wave
coherence, and relate the conservation of matter-wave coherence with the
conservation of purity that distinguishes decoherence effects from dephasing
effects.


title: Eikonal Methods in AdS/CFT: Regge Theory and Multi-Reggeon Exchange

abstract:
  We analyze conformal field theory 4-point functions of the form A ~ O_1(x_1)
O_2(x_2) O_1(x_3) O_2(x_4), where the operators O_i are scalar primaries. We
show that, in the Lorentzian regime, the limit x_1 -> x_3 is dominated by the
exchange of conformal partial waves of highest spin. When partial waves of
arbitrary spin contribute to A, the behavior of the Lorentzian amplitude for
x_1 -> x_3 must be analyzed using complex-spin techniques, leading to a
generalized Regge theory for CFT's. Whenever the CFT is dual to a string
theory, the string tree-level contribution A_tree to the amplitude A presents a
Regge pole corresponding the a gravi-reggeon exchange. In this case, we apply
the impact parameter representation for CFT amplitudes, previously developed,
to analyze multiple reggeon exchanges in the eikonal limit. As an example, we
apply these general techniques to N=4 super-Yang-Mills theory in d=4 in the
limit of large 't Hooft coupling, including the leading string corrections to
pure graviton exchange.


title: Bose-Einstein condensates of atoms with arbitrary spin

abstract:
  We show that the ground state of a Bose-Einstein condensate of atoms with
hyperfine spin f = 2 can be either spin aligned, condensed into pairs of atoms
coupled to F = 0, or condensed into triplets of atoms coupled to F = 0. The
complete phase diagram is constructed for f = 2 and the generic properties of
the phase diagram are obtained for f > 2.


title: The Effects of Charged Charm Mesons on the Line Shapes of the X(3872)

abstract:
  The quantum numbers J^PC = 1++ of the X(3872) and the proximity of its mass
to the D*0 anti-D0 threshold imply that it is either a loosely-bound hadronic
molecule whose constituents are a superposition of D*0 anti-D0 and D0 anti-D*0
or it is a virtual state of charm mesons. The line shapes of the X(3872) can
discriminate between these two possibilities. At energies within a few MeV of
the D*0 anti-D0 threshold, the lines shapes of the X produced in B -> K
transitions are determined by its binding energy and its width. Their
normalizations are determined by a short-distance constant that is different
for B+ -> K+ and B0 -> K0. At energies comparable to the 8 MeV splitting
between the D*0 anti-D0 and D*+ D- thresholds, the charged meson channels D*+
D- and D+ D*- have a significant effect on the line shapes of the X. We
calculate the line shapes taking into account the resonant coupling between the
charged and neutral 1++ channels. The line shapes and their normalizations
depend on one additional scattering parameter and two additional short-distance
constants associated with the B -> K transitions. The line shapes of the X
resonance depend on its decay channel; they are different for J/psi pi+ pi-,
J/psi pi+ pi- pi0, and D0 anti-D0 pi0. The line shapes are also different for X
produced in B+ decays and in B0 decays. Some conceptual errors in previous work
on this problem are pointed out.


title: Holographic Entanglement Entropy at Finite Temperature

abstract:
  Using a holographic proposal for the entanglement entropy we study its
behavior in various supergravity backgrounds. We are particularly interested in
the possibility of using the entanglement entropy as way to detect transitions
induced by the presence horizons. We consider several geometries with horizons:
the black hole in $AdS_3$, nonextremal Dp-branes, dyonic black holes
asymptotically to $AdS_4$ and also Schwarzschild black holes in global $AdS_p$
coordinates. Generically, we find that the entanglement entropy does not
exhibit a transition, that is, one of the two possible configurations always
dominates.


title:
Exploring Exotic Superfluidity of Polarized Ultracold Fermions in
  Optical Lattices

abstract:
  We explore theoretically the novel superfluidity of harmonically-trapped
polarized ultracold fermionic atoms in a two-dimensional (2D) optical lattice
by solving the Bogoliubov-de Gennes equations. The pairing amplitude is found
to oscillate along the radial direction at low particle density and along the
angular direction at high density. The former is consistent with the existing
experiments and the latter is a newly predicted
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, which can be tested in
experiments.


title: Mild Solutions for a Class of Fractional SPDEs and Their Sample Paths

abstract:
  In this article we introduce and analyze a notion of mild solution for a
class of non-autonomous parabolic stochastic partial differential equations
defined on a bounded open subset $D\subset\mathbb{R}^{d}$ and driven by an
infinite-dimensional fractional noise. The noise is derived from an
$L^{2}(D)$-valued fractional Wiener process $W^{H}$ whose covariance operator
satisfies appropriate restrictions; moreover, the Hurst parameter $H$ is
subjected to constraints formulated in terms of $d$ and the H\"{o}lder exponent
of the derivative $h^\prime$ of the noise nonlinearity in the equations. We
prove the existence of such solution, establish its relation with the
variational solution introduced in \cite{nuavu} and also prove the H\"{o}lder
continuity of its sample paths when we consider it as an $L^{2}(D)$--valued
stochastic processes. When $h$ is an affine function, we also prove uniqueness.
The proofs are based on a relation between the notions of mild and variational
solution established in Sanz-Sol\'e and Vuillermot 2003, and adapted to our
problem, and on a fine analysis of the singularities of Green's function
associated with the class of parabolic problems we investigate. An immediate
consequence of our results is the indistinguishability of mild and variational
solutions in the case of uniqueness.


title: Double-detonation supernovae of sub-Chandrasekhar mass white dwarfs

abstract:
  In the "double-detonation sub-Chandrasekhar" model for type Ia supernovae, a
carbon-oxygen (C + O) white dwarf accumulates sufficient amounts of helium such
that a detonation ignites in that layer before the Chandrasekhar mass is
reached. This detonation is thought to trigger a secondary detonation in the C
+ O core. By means of one- and two-dimensional hydrodynamic simulations, we
investigate the robustness of this explosion mechanism for generic 1-M_sun
models and analyze its observable predictions. Also a resolution dependence in
numerical simulations is analyzed. The propagation of thermonuclear detonation
fronts, both in helium and in the carbon-oxygen mixture, is computed by means
of both a level-set function and a simplified description for nuclear
reactions. The decision whether a secondary detonation is triggered in the
white dwarf's core or not is made based on criteria given in the literature. In
a parameter study involving different initial flame geometries for He-shell
masses of 0.2 and 0.1 M_sun, we find that a secondary detonation ignition is a
very robust process. Converging shock waves originating from the detonation in
the He shell generate the conditions for a detonation near the center of the
white dwarf in most of the cases considered. Finally, we follow the complete
evolution of three selected models with 0.2 M_sun of He through the
C/O-detonation phase and obtain nickel-masses of about 0.40 to 0.45 M_sun.
Although we have not done a complete scan of the possible parameter space, our
results show that sub-Chandrasekhar models are not good candidates for normal
or sub-luminous type Ia supernovae. The chemical composition of the ejecta
features significant amounts of nickel in the outer layers at high expansion
velocities, which is inconsistent with near-maximum spectra. (abbreviated)


title: Ricci Yang-Mills flow on surfaces

abstract:
  We study the behaviour of the Ricci Yang-Mills flow for U(1) bundles on
surfaces. We show that existence for the flow reduces to a bound on the
isoperimetric constant. In the presence of such a bound, we show that on $S^2$,
if the bundle is nontrivial, the flow exists for all time. For higher genus
surfaces the flow always exists for all time. The volume normalized flow always
exists for all time and converges to a constant scalar curvature metric with
the bundle curvature $F$ parallel. Finally, in an appendix we classify all
gradient solitons of this flow on surfaces.


title:
Spitzer, Near-Infrared, and Submillimeter Imaging of the Relatively
  Sparse Young Cluster, Lynds 988e

abstract:
  We present {\it Spitzer} images of the relatively sparse, low luminosity
young cluster L988e, as well as complementary near-infrared (NIR) and
submillimeter images of the region. The cluster is asymmetric, with the western
region of the cluster embedded within the molecular cloud, and the slightly
less dense eastern region to the east of, and on the edge of, the molecular
cloud. With these data, as well as with extant H$\alpha$ data of stars
primarily found in the eastern region of the cluster, and a molecular $^{13}$CO
gas emission map of the entire region, we investigate the distribution of
forming young stars with respect to the cloud material, concentrating
particularly on the differences and similarities between the exposed and
embedded regions of the cluster. We also compare star formation in this region
to that in denser, more luminous and more massive clusters already investigated
in our comprehensive multi-wavelength study of young clusters within 1 kpc of
the Sun.


title: Non-Markovian continuous quantum measurement of retarded observables

abstract:
  We reconsider the non-Markovian time-continuous measurement of a Heisenberg
observable x and show for the first time that it can be realized by an infinite
set of entangled von Neumann detectors. The concept of continuous read-out is
introduced and used to re-derive the non-Markovian stochastic Schrodinger
equation. We can prove that, contrary to recent doubts, the resulting
non-Markovian quantum trajectories are true single system trajectories and
correspond to the continuous measurement of a retarded functional of x.
However, the generic non-Markovian trajectories are mixed state trajectories.
  This version merges an Erratum [PRL, in print] with my Letter [PRL 100,
080401 (2008)], some corrections follow directly from the recent criticism by
Wiseman and Gambetta, further corrections restore the validity of my Letter.
Contrary to my suggestion there, the given continuous measurement schemes
cannot yield pure state trajectories but mixed-state ones. Yet, it is possible
to retain my claim that the non-Markovian stochastic Schrodinger equation
describes true time-continuous measurement - with delay and retrodiction.


title: Supersymmetry versus black holes at the LHC

abstract:
  Supersymmetry and extra dimensions are the two most promising candidates for
new physics at the TeV scale. Supersymmetric particles or extra-dimensional
effects could soon be observed at the Large Hadron Collider. We propose a
simple but powerful method to discriminate the two models: the analysis of
isolated leptons with high transverse momentum. Black hole events are simulated
with the CATFISH black hole generator. Supersymmetry simulations use a
combination of PYTHIA and ISAJET, the latter providing the mass spectrum. Our
results show the measure of the dilepton invariant mass provides a strong
signature to differentiate supersymmetry and black hole events at the Large
Hadron Collider. Analysis of event-shape variables and multilepton events
complement and strengthen this conclusion.


title:
Effects of the Regularization on the Restoration of Chiral and Axial
  Symmetries

abstract:
  The effects of a type of regularization for finite temperatures on the
estoration of chiral and axial symmetries are investigated within the SU(3)
Nambu-Jona-Lasinio model. The regularization consists in using an infinite
cutoff in the integrals that are convergent at finite temperature, a procedure
that allows one to take into account the effects of high momentum quarks at
high temperatures. It is found that the critical temperature for the phase
transition is closer to lattice results than the one obtained with the
conventional regularization, and the restoration of chiral and axial
symmetries, signaled by the behavior of several observables, occurs
simultaneously and at a higher temperature. The restoration of the axial
symmetry appears as a natural consequence of the full recovering of the chiral
symmetry that was dynamically broken. By using an additional ansatz that
simulates instanton suppression effects, by means of a convenient temperature
dependence of the anomaly coefficient, we found that the restoration of U(2)
symmetry is shifted to lower values, but the dominant effect at high
temperatures comes from the new regularization that enhances the decrease of
quark condensates, especially in the strange sector.


title: Koszul Equivalences in $A_\infty$-Algebras

abstract:
  We prove a version of Koszul duality and the induced derived equivalence for
Adams connected $A_\infty$-algebras that generalizes the classical
Beilinson-Ginzburg-Soergel Koszul duality. As an immediate consequence, we give
a version of the Bern\v{s}te{\u\i}n-Gel'fand-Gel'fand correspondence for Adams
connected $A_\infty$-algebras.
  We give various applications. For example, a connected graded algebra $A$ is
Artin-Schelter regular if and only if its Ext-algebra $\Ext^\ast_A(k,k)$ is
Frobenius. This generalizes a result of Smith in the Koszul case. If $A$ is
Koszul and if both $A$ and its Koszul dual $A^!$ are noetherian satisfying a
polynomial identity, then $A$ is Gorenstein if and only if $A^!$ is. The last
statement implies that a certain Calabi-Yau property is preserved under Koszul
duality.


title: Report on workshop A1: Exact solutions and their interpretation

abstract:
  I report on the communications and posters presented on exact solutions and
their interpretation at the GRG18 Conference, Sydney.


title: Transport Networks Revisited: Why Dual Graphs?

abstract:
  Deterministic equilibrium flows in transport networks can be investigated by
means of Markov's processes defined on the dual graph representations of the
network. Sustained movement patterns are generated by a subset of automorphisms
of the graph spanning the spatial network of a city naturally interpreted as
random walks. Random walks assign absolute scores to all nodes of a graph and
embed space syntax into Euclidean space.


title: Statistical Physics of Group Testing

abstract:
  This paper provides a short introduction to the group testing problem, and
reviews various aspects of its statistical physics formulation. Two main issues
are discussed: the optimal design of pools used in a two-stage testing
experiment, like the one often used in medical or biological applications, and
the inference problem of detecting defective items based on pool diagnosis. The
paper is largely based on: M. M\'ezard and C. Toninelli, arXiv:0706.3104, and
M. M\'ezard and M. Tarzia {\it Phys. Rev. E} {\bf 76}, 041124 (2007).


title: Mesoscopic density-operator in a uniform magnetic field

abstract:
  A self-consistent linear-response theory for a two-lead mesoscopic structure
in Landauer's viewpoint for transport is developed. A density operator relevant
in this viewpoint, in a uniform magnetic field is derived. It is shown that
this operator differs from the one given in Kubo's viewpoint by a term that
represents the self-consistent effects. Hence, a special emphasis is devoted to
the diagonal master equation where an exact solution is obtained in the
framework of elastic scattering theory.


title: Multifractality in the Random Parameters Model

abstract:
  The Random Parameters model was proposed to explain the structure of the
covariance matrix in problems where most, but not all, of the eigenvalues of
the covariance matrix can be explained by Random Matrix Theory. In this
article, we explore other properties of the model, like the scaling of its PDF
as one take larger scales. Special attention is given to the multifractal
structure of the model time series, which revealed a scaling structure
compatible with the known stylized facts for a reasonable choice of the
parameter values.


title: Debris disks around Sun-like stars

abstract:
  We have observed nearly 200 FGK stars at 24 and 70 microns with the Spitzer
Space Telescope. We identify excess infrared emission, including a number of
cases where the observed flux is more than 10 times brighter than the predicted
photospheric flux, and interpret these signatures as evidence of debris disks
in those systems. We combine this sample of FGK stars with similar published
results to produce a sample of more than 350 main sequence AFGKM stars. The
incidence of debris disks is 4.2% (+2.0/-1.1) at 24 microns for a sample of 213
Sun-like (FG) stars and 16.4% (+2.8/-2.9) at 70 microns for 225 Sun-like (FG)
stars. We find that the excess rates for A, F, G, and K stars are statistically
indistinguishable, but with a suggestion of decreasing excess rate toward the
later spectral types; this may be an age effect. The lack of strong trend among
FGK stars of comparable ages is surprising, given the factor of 50 change in
stellar luminosity across this spectral range. We also find that the incidence
of debris disks declines very slowly beyond ages of 1 billion years.


title:
Multiple scattering approach to low-energy electron collisions with the
  water dimer

abstract:
  Multiple scattering theory is applied to low-energy electron collisions with
a complex target formed of two molecular scatterers. The total T-matrix is
expressed in terms of the T-matrix for each isolated molecule. We apply the
approach to elastic electron-(H2O)2 collisions. Following the method developed
in our previous work on crystalline ice, we impose a cut-off on the dipole
outside the R-matrix sphere and an energy dependent cut-off on the angular
momentum components of the monomer T-matrix. An R-matrix calculation of
electron-dimer collisions is performed in order to evaluate the accuracy of the
multiple scattering approach. The agreement between the two calculations is
very good.


title: Eigenvalue estimates for Schroedinger operators on metric trees

abstract:
  We consider Schroedinger operators on regular metric trees and prove
Lieb-Thirring and Cwikel-Lieb-Rozenblum inequalities for their negative
eigenvalues. The validity of these inequalities depends on the volume growth of
the tree. We show that the bounds are valid in the endpoint case and reflect
the correct order in the weak or strong coupling limit.


title: Discriminated Belief Propagation

abstract:
  Near optimal decoding of good error control codes is generally a difficult
task. However, for a certain type of (sufficiently) good codes an efficient
decoding algorithm with near optimal performance exists. These codes are
defined via a combination of constituent codes with low complexity trellis
representations. Their decoding algorithm is an instance of (loopy) belief
propagation and is based on an iterative transfer of constituent beliefs. The
beliefs are thereby given by the symbol probabilities computed in the
constituent trellises. Even though weak constituent codes are employed close to
optimal performance is obtained, i.e., the encoder/decoder pair (almost)
achieves the information theoretic capacity. However, (loopy) belief
propagation only performs well for a rather specific set of codes, which limits
its applicability.
  In this paper a generalisation of iterative decoding is presented. It is
proposed to transfer more values than just the constituent beliefs. This is
achieved by the transfer of beliefs obtained by independently investigating
parts of the code space. This leads to the concept of discriminators, which are
used to improve the decoder resolution within certain areas and defines
discriminated symbol beliefs. It is shown that these beliefs approximate the
overall symbol probabilities. This leads to an iteration rule that (below
channel capacity) typically only admits the solution of the overall decoding
problem. Via a Gauss approximation a low complexity version of this algorithm
is derived. Moreover, the approach may then be applied to a wide range of
channel maps without significant complexity increase.


title: Piecewise adiabatic population transfer in a molecule via a wave packet

abstract:
  We propose a class of schemes for robust population transfer between quantum
states that utilize trains of coherent pulses and represent a generalized
adiabatic passage via a wave packet. We study piecewise Stimulated Raman
Adiabatic Passage with pulse-to-pulse amplitude variation, and piecewise
chirped Raman passage with pulse-to-pulse phase variation, implemented with an
optical frequency comb. In the context of production of ultracold ground-state
molecules, we show that with almost no knowledge of the excited potential,
robust high-efficiency transfer is possible


title:
High-ionization mid-infrared lines as black hole mass and bolometric
  luminosity indicators in active galactic nuclei

abstract:
  We present relations of the black hole mass and the optical luminosity with
the velocity dispersion and the luminosity of the [Ne V] and the [O IV]
high-ionization lines in the mid-infrared (MIR) for 28 reverberation-mapped
active galactic nuclei. We used high-resolution Spitzer Infrared Spectrograph
and Infrared Space Observatory Short Wavelength Spectrometer data to fit the
profiles of these MIR emission lines that originate from the narrow-line region
of the nucleus. We find that the lines are often resolved and that the velocity
dispersion of [Ne V] and [O IV] follows a relation similar to that between the
black hole mass and the bulge stellar velocity dispersion found for local
galaxies. The luminosity of the [Ne V] and the [O IV] lines in these sources is
correlated with that of the optical 5100A continuum and with the black hole
mass. Our results provide a means to derive black hole properties in various
types of active galactic nuclei, including highly obscured systems.


title: Geometric derivation of quantum uncertainty

abstract:
  Quantum observables can be identified with vector fields on the sphere of
normalized states. Consequently, the uncertainty relations for quantum
observables become geometric statements. In the Letter the familiar uncertainty
relation follows from the following stronger statement: Of all parallelograms
with given sides the rectangle has the largest area.


title: Light-cone averages in a swiss-cheese universe

abstract:
  We analyze a toy swiss-cheese cosmological model to study the averaging
problem. In our model, the cheese is the EdS model and the holes are
constructed from a LTB solution. We study the propagation of photons in the
swiss-cheese model, and find a phenomenological homogeneous model to describe
observables. Following a fitting procedure based on light-cone averages, we
find that the the expansion scalar is unaffected by the inhomogeneities. This
is because of spherical symmetry. However, the light-cone average of the
density as a function of redshift is affected by inhomogeneities. The effect
arises because, as the universe evolves, a photon spends more and more time in
the (large) voids than in the (thin) high-density structures. The
phenomenological homogeneous model describing the light-cone average of the
density is similar to the concordance model. Although the sole source in the
swiss-cheese model is matter, the phenomenological homogeneous model behaves as
if it has a dark-energy component. Finally, we study how the equation of state
of the phenomenological model depends on the size of the inhomogeneities, and
find that the equation-of-state parameters w_0 and w_a follow a power-law
dependence with a scaling exponent equal to unity. That is, the equation of
state depends linearly on the distance the photon travels through voids. We
conclude that within our toy model, the holes must have a present size of about
250 Mpc to be able to mimic the concordance model.


title: An Atom Laser is not monochromatic

abstract:
  We study both numerically and analytically the possibility of using an
adiabatic passage control method to construct a Mach-Zehnder interferometer
(MZI) for Bose-Einstein condensates (BECs) in the time domain, in exact
one-to-one correspondence with the traditional optical MZI that involves two
beam splitters and two mirrors. The interference fringes one obtains from such
a minimum-disturbance set up clearly demonstrates that, fundamentally, an atom
laser is not monochromatic due to interatomic interactions. We also consider
how the amount of entanglement in the system correlates to the interference
fringes.


title:
Influence of static Jahn-Teller distortion on the magnetic excitation
  spectrum of PrO2: A synchrotron x-ray and neutron inelastic scattering study

abstract:
  A synchrotron x-ray diffraction study of the crystallographic structure of
PrO2 in the Jahn-Teller distorted phase is reported. The distortion of the
oxygen sublattice, which was previously ambiguous, is shown to be a chiral
structure in which neighbouring oxygen chains have opposite chiralities. A
temperature dependent study of the magnetic excitation spectrum, probed by
neutron inelastic scattering, is also reported. Changes in the energies and
relative intensities of the crystal field transitions provide an insight into
the interplay between the static and dynamic Jahn-Teller effects.


title:
Muon content of ultra-high-energy air showers: Yakutsk data versus
  simulations

abstract:
  We analyse a sample of 33 extensive air showers (EAS) with estimated primary
energies above 2\cdot 10^{19} eV and high-quality muon data recorded by the
Yakutsk EAS array. We compare, event-by-event, the observed muon density to
that expected from CORSIKA simulations for primary protons and iron, using
SIBYLL and EPOS hadronic interaction models. The study suggests the presence of
two distinct hadronic components, ``light'' and ``heavy''. Simulations with
EPOS are in a good agreement with the expected composition in which the light
component corresponds to protons and the heavy component to iron-like nuclei.
With SYBILL, simulated muon densities for iron primaries are a factor of \sim
1.5 less than those observed for the heavy component, for the same
electromagnetic signal. Assuming two-component proton-iron composition and the
EPOS model, the fraction of protons with energies E>10^{19} eV is
0.52^{+0.19}_{-0.20} at 95% confidence level.


title:
Fingerprinting Soft Materials: A Framework for Characterizing Nonlinear
  Viscoelasticity

abstract:
  We introduce a comprehensive scheme to physically quantify both viscous and
elastic rheological nonlinearities simultaneously, using an imposed large
amplitude oscillatory shear (LAOS) strain. The new framework naturally lends a
physical interpretation to commonly reported Fourier coefficients of the
nonlinear stress response. Additionally, we address the ambiguities inherent in
the standard definitions of viscoelastic moduli when extended into the
nonlinear regime, and define new measures which reveal behavior that is
obscured by conventional techniques.


title:
Renormalization of the one-loop theory of fluctuations in polymer blends
  and diblock copolymer melts

abstract:
  Attempts to use coarse-grained molecular theories to calculate corrections to
the random-phase approximation (RPA) for correlations in polymer mixtures have
been plagued by an unwanted sensitivity to the value of an arbitrary cutoff
length, {\it i.e.}, by an ultraviolet (UV) divergence. We analyze the UV
divergence of the inverse structure factor $S^{-1}(k)$ predicted by a
`one-loop' approximation similar to that used in several previous studies. We
consider both miscible homopolymer blends and disordered diblock copolymer
melts. We show, in both cases, that all UV divergent contributions can be
absorbed into a renormalization of the values of the phenomenological
parameters of a generalized self-consistent field theory (SCFT). This
observation allows the construction of a UV convergent theory of corrections to
SCFT phenomenology. The UV-divergent one-loop contribution to $S^{-1}(k)$ are
shown to be the sum of: (i) a $k$-independent contribution that arises from a
renormalization of the effective $\chi$ parameter, (ii) a $k$-dependent
contribution that arises from a renormalization of monomer statistical segment
lengths, (iii) a contribution proportional to $k^{2}$ that arises from a
square-gradient contribution to the one-loop fluctuation free energy, and (iv)
a $k$-dependent contribution that is inversely proportional to the degree of
polymerization, which arises from local perturbations in fluid structure near
chain ends and near junctions between blocks in block copolymers.


title:
GHOSTS | Bulges, Halos, and the Resolved Stellar Outskirts of Massive
  Disk Galaxies

abstract:
  In hierarchical galaxy formation the stellar halos of galaxies are formed by
the accretion of minor satellites and therefore contain valuable information
about the (early) assembly process of galaxies. Our GHOSTS survey measures the
stellar envelope properties of 14 nearby disk galaxies by imaging their
resolved stellar populations with HST/ACS&WFPC2. Most of the massive galaxies
in the sample (Vrot>200 km/s) have very extended stellar envelopes with mu(r) ~
r^{-2.5} power law profiles in the outer regions. For these massive galaxies
there is some evidence that the stellar surface density of the profiles
correlates with Hubble type and bulge-to-disk ratio, begging the question
whether these envelopes are more related to bulges than to a Milky Way-type
stellar halo. Smaller galaxies (Vrot 100 km/s) have much smaller stellar
envelopes, but depending on geometry, they could still be more luminous than
expected from satellite remnants in hierarchical galaxy formation models.
Alternatively, they could be created by disk heating through the bombardment of
small dark matter sub-halos. We find that galaxies show varying amounts of halo
substructure.


title:
Risk Minimization and Optimal Derivative Design in a Principal Agent
  Game

abstract:
  We consider the problem of Adverse Selection and optimal derivative design
within a Principal-Agent framework. The principal's income is exposed to
non-hedgeable risk factors arising, for instance, from weather or climate
phenomena. She evaluates her risk using a coherent and law invariant risk
measure and tries minimize her exposure by selling derivative securities on her
income to individual agents. The agents have mean-variance preferences with
heterogeneous risk aversion coefficients. An agent's degree of risk aversion is
private information and hidden to the principal who only knows the overall
distribution. We show that the principal's risk minimization problem has a
solution and illustrate the effects of risk transfer on her income by means of
two specific examples. Our model extends earlier work of Barrieu and El Karoui
(2005) and Carlier, Ekeland and Touzi (2007).


title:
Chandra X-ray Observations of the 0.6 < z < 1.1 Red-Sequence Cluster
  Survey Sample

abstract:
  We present the results of Chandra observations of 13 optically-selected
clusters with 0.6<z< 1.1, discovered via the Red-sequence Cluster Survey (RCS).
All but one are detected at S/N>3; though 3 were not observed long enough to
support detailed analysis. Surface brightness profiles are fit to beta-models.
Integrated spectra are extracted within R(2500), and Tx and Lx information is
obtained. We derive gas and total masses within R(2500) and R(500).
Cosmologically corrected scaling relations are investigated, and we find the
RCS clusters to be consistent with self-similar scaling expectations. However
discrepancies exist between the RCS sample and lower-z X-ray selected samples
for relationships involving Lx, with the higher-z RCS clusters having lower Lx
for a given Tx. In addition, we find that gas mass fractions within R(2500) for
the high-z RCS sample are lower than expected by a factor of ~2. This suggests
that the central entropy of these high-z objects has been elevated by processes
such as pre-heating, mergers, and/or AGN outbursts, that their gas is still
infalling, or that they contain comparatively more baryonic matter in the form
of stars. Finally, relationships between red-sequence optical richness (Bgc)
and X-ray properties are fit to the data. For systems with measured Tx, we find
that optical richness correlates with both Tx and mass, having a scatter of
~30% with mass for both X-ray and optically-selected clusters. However we also
find that X-ray luminosity is not well correlated with richness, and that
several of our sample appear to be significantly X-ray faint.


title: Dust Properties and Star-Formation Rates in Star-Forming Dwarf Galaxies

abstract:
  We have used the Spitzer Space Telescope to study the dust properties of a
sample of star-forming dwarf galaxies. The differences in the mid-infrared
spectral energy distributions for these galaxies which, in general, are low
metallicity systems, indicate differences in the physical properties, heating,
and/or distribution of the dust. Specifically, these galaxies have more hot
dust and/or very small grains and less PAH emission than either spiral or
higher luminosity starburst galaxies. As has been shown in previous studies,
there is a gradual decrease in PAH emission as a function of metallicity.
Because much of the energy from star formation in galaxies is re-radiated in
the mid-infrared, star-formation rate indicators based on both line and
continuum measurements in this wavelength range are coming into more common
usage. We show that the variations in the interstellar medium properties of
galaxies in our sample, as measured in the mid-infrared, result in over an
order of magnitude spread in the computed star-formation rates.


title: Magnetic Monopoles in Spin Ice

abstract:
  Electrically charged particles, such as the electron, are ubiquitous. By
contrast, no elementary particles with a net magnetic charge have ever been
observed, despite intensive and prolonged searches. We pursue an alternative
strategy, namely that of realising them not as elementary but rather as
emergent particles, i.e., as manifestations of the correlations present in a
strongly interacting many-body system. The most prominent examples of emergent
quasiparticles are the ones with fractional electric charge e/3 in quantum Hall
physics. Here we show that magnetic monopoles do emerge in a class of exotic
magnets known collectively as spin ice: the dipole moment of the underlying
electronic degrees of freedom fractionalises into monopoles. This enables us to
account for a mysterious phase transition observed experimentally in spin ice
in a magnetic field, which is a liquid-gas transition of the magnetic
monopoles. These monopoles can also be detected by other means, e.g., in an
experiment modelled after the celebrated Stanford magnetic monopole search.


title: Looking for rational curves on cubic hypersurfaces

abstract:
  These are the substantially expanded notes of the lectures of JK at the
summer school "Higher-Dimensional Geometry over Finite Fields" in G\"ottingen,
June 2007. The first part gives an overview of the methods. The main new result
is the construction of rational curves passing through a given collection of
points on smooth cubic hypersurfaces over finite fields.


title: Relativistic dark matter at the Galactic center

abstract:
  In a large region of the supersymmetry parameter space, the annihilation
cross section for neutralino dark matter is strongly dependent on the relative
velocity of the incoming particles. We explore the consequences of this
velocity dependence in the context of indirect detection of dark matter from
the galactic center. We find that the increase in the annihilation cross
section at high velocities leads to a flattening of the halo density profile
near the galactic center and an enhancement of the annihilation signal.


title: Metric properties of the braided Thompson's groups

abstract:
  Braided Thompson's groups are finitely presented groups introduced by Brin
and Dehornoy which contain the ordinary braid groups $B_n$, the finitary braid
group $B_{\infty}$ and Thompson's group $F$ as subgroups. We describe some of
the metric properties of braided Thompson's groups and give upper and lower
bounds for word length in terms of the number of strands and the number of
crossings in the diagrams used to represent elements.


title: On the Geometry of Metastable Supersymmetry Breaking

abstract:
  We give a concise geometric recipe for constructing D-brane gauge theories
that exhibit metastable SUSY breaking. We present two simple examples in terms
of branes at deformed CY singularities.


title: The virialized mass of dark matter haloes

abstract:
  (Abridged) Virial mass is used as an estimator for the mass of a dark matter
halo. However, the commonly used constant overdensity criterion does not
reflect the dynamical structure of haloes. Here we analyze dark matter
cosmological simulations in order to obtain properties of haloes of different
masses focusing on the size of the region with zero mean radial velocity. Dark
matter inside this region is stationary, and thus the mass of this region is a
much better approximation for the virial mass. We call this mass the static
mass to distinguish from the commonly used constant overdensity mass. We also
study the relation of this static mass with the traditional virial mass, and we
find that the matter inside galaxy-size haloes is underestimated by the virial
mass by nearly a factor of two. At redshift zero the virial mass is close to
the static mass for cluster-size haloes. The same pattern - large haloes having
M_vir > M_static - exists at all redshifts, but the transition mass M_0 = M_vir
= M_static decreases dramatically with increasing redshift. When rescaled to
the same M_0 haloes clearly demonstrate a self-similar behaviour, which in a
statistical sense gives a relation between the static and virial mass. To our
surprise we find that the abundance of haloes with a given static mass, i.e.
the static mass function, is very accurately fitted by the Press & Schechter
approximation at z=0, but this approximation breaks at higher redshifts.
Instead, the virial mass function is well fitted as usual by the Sheth & Tormen
approximation. We find an explanation why the static radius can be 2-3 times
larger as compared with the constant overdensity estimate. Applying the
non-stationary Jeans equation we find that the role of the pressure gradients
is significantly larger for small haloes.


title: Buoyancy Instabilities in Weakly Magnetized Low Collisionality Plasmas

abstract:
  I calculate the linear stability of a stratified low collisionality plasma in
the presence of a weak magnetic field. Heat is assumed to flow only along
magnetic field lines. In the absence of a heat flux in the background plasma,
Balbus (2000) demonstrated that plasmas in which the temperature increases in
the direction of gravity are buoyantly unstable to convective-like motions (the
``magnetothermal instability''). I show that in the presence of a background
heat flux, an analogous instability is present when the temperature decreases
in the direction of gravity. The instability is driven by the background heat
flux and the fastest growing mode has a growth time of order the local
dynamical time. Thus, independent of the sign of the temperature gradient,
weakly magnetized low collisionality plasmas are unstable on a dynamical time
to magnetically-mediated buoyancy instabilities. The instability described in
this paper is predicted to be present in clusters of galaxies at radii from ~
0.1-100 kpc, where the observed temperature increases outwards. Possible
consequences for the origin of cluster magnetic fields, ``cooling flows,'' and
the thermodynamics of the intercluster medium are briefly discussed.


title: Algebraic series and valuation rings over nonclosed fields

abstract:
  Suppose that $k$ is an arbitrary field. Consider the field
$k((x_1,...,x_n))$, which is the quotient field of the ring $k[[x_1,...,x_n]]$
of formal power series in the variables $x_1,...,x_n$, with coefficients in
$k$. Suppose that $\sigma$ is a formal power series in $x_1,...,x_n$ with
coefficints in the algebraic closure of $k$. We give a very simple necessary
and sufficient condition for $\sigma$ to be algebraic over $k((x_1,...,x_n))$.
  As an application of our methods, we give a characterization of valuation
rings $V$ which dominate an excellent, Noetherian local domain $R$ of dimension
two, and such that the rank increases after passing to the completion of a
birational extension of $R$.


title: Beyond Inside-Out Growth: Formation and Evolution of Disk Outskirts

abstract:
  We have performed a high mass and force resolution simulation of an idealized
galaxy forming from dissipational collapse of gas embedded in a spherical dark
matter halo. The simulation includes star formation and effects of stellar
feedback. In our simulation a stellar disk forms with a surface density profile
consisting of an inner exponential breaking to a steeper outer exponential. The
break forms early on and persists throughout the evolution, moving outward as
more gas is able to cool and add mass to the disk. The parameters of the break
are in excellent agreement with observations. The break corresponds with a
rapid drop in the star formation rate associated with a drop in the cooled gas
surface density, but the outer exponential is populated by stars that were
scattered outward on nearly circular orbits from the inner disk by spiral arms.
The resulting profile and its associated break are therefore a consequence of
the interplay between a radial star formation cutoff and redistribution of
stellar mass by secular processes. A consequence of such evolution is a sharp
change in the radial mean stellar age profile at the break radius.


title: Curvaton field and intermediate inflationary universe model

abstract:
  The curvaton in an intermediate inflationary universe model is studied. This
study has allowed us to find some interesting constraints on different
parameters that appear in the model.


title: Constraining neutrino masses with the ISW-galaxy correlation function

abstract:
  Temperature anisotropies in the Cosmic Microwave Background (CMB) are
affected by the late Integrated Sachs-Wolfe (lISW) effect caused by any
time-variation of the gravitational potential on linear scales. Dark energy is
not the only source of lISW, since massive neutrinos induce a small decay of
the potential on small scales during both matter and dark energy domination. In
this work, we study the prospect of using the cross-correlation between CMB and
galaxy density maps as a tool for constraining the neutrino mass. On the one
hand massive neutrinos reduce the cross-correlation spectrum because
free-streaming slows down structure formation; on the other hand, they enhance
it through their change in the effective linear growth. We show that in the
observable range of scales and redshifts, the first effect dominates, but the
second one is not negligible. We carry out an error forecast analysis by
fitting some mock data inspired by the Planck satellite, Dark Energy Survey
(DES) and Large Synoptic Survey Telescope (LSST). The inclusion of the
cross-correlation data from Planck and LSST increases the sensitivity to the
neutrino mass m_nu by 38% (and to the dark energy equation of state w by 83%)
with respect to Planck alone. The correlation between Planck and DES brings a
far less significant improvement. This method is not potentially as good for
detecting m_nu as the measurement of galaxy, cluster or cosmic shear power
spectra, but since it is independent and affected by different systematics, it
remains potentially interesting if the total neutrino mass is of the order of
0.2 eV; if instead it is close to the lower bound from atmospheric
oscillations, m_nu ~ 0.05 eV, we do not expect the ISW-galaxy correlation to be
ever sensitive to m_nu.


title: Six New Galactic Orbits of Globular Clusters in a Milky-Way-Like Galaxy

abstract:
  Absolute proper motions for six new globular clusters have recently been
determined. This motivated us to obtain the Galactic orbits of these six
clusters both in an axisymmetric Galactic potential and in a barred potential,
such as the one of our Galaxy. Orbits are also obtained for a Galactic
potential that includes spiral arms. The orbital characteristics are compared
and discussed for these three cases. Tidal radii and destruction rates are also
computed and discussed.


title: Notes on formal smoothness

abstract:
  The definition of an S-category is proposed by weakening the axioms of a
Q-category introduced by Kontsevich and Rosenberg. Examples of Q- and
S-categories and (co)smooth objects in such categories are given.


title: Massive Vector Scattering in Lee-Wick Gauge Theory

abstract:
  We demonstrate that amplitudes describing scattering of longitudinally
polarized massive vector bosons present in non-Abelian Lee-Wick gauge theory do
not grow with energy and, hence, satisfy the constraints imposed by
perturbative unitarity. This result contrasts with the widely-known violation
of perturbative unitarity in the standard model with a very heavy Higgs. Our
conclusions are valid to all orders of perturbation theory and depend on the
existence of a formulation of the theory in which all operators are of
dimension four or less. This can be thought of as a restriction on the kinds of
higher dimension operator which can be included in the higher derivative
formulation of the theory.


title:
A New Approach to the Study of Stellar Populations in Early-Type
  Galaxies: K-band Spectral Indices and an Application to the Fornax Cluster

abstract:
  New measurements of K-band spectral features are presented for eleven
early-type galaxies in the nearby Fornax galaxy cluster. Based on these
measurements, the following conclusions have been reached: (1) in galaxies with
no signatures of a young stellar component, the K-band Na I index is highly
correlated with both the optical metallicity indicator [MgFe]' and central
velocity dispersion; (2) in the same galaxies, the K-band Fe features saturate
in galaxies with sigma > 150 km/s while Na I (and [MgFe]') continues to
increase; (3) [Si/Fe] (and possibly [Na/Fe]) is larger in all observed Fornax
galaxies than in Galactic open clusters with near-solar metallicity; (4) in
various near-IR diagnostic diagrams, galaxies with signatures of a young
stellar component (strong Hbeta, weak [MgFe]') are clearly separated from
galaxies with purely old stellar populations; furthermore, this separation is
consistent with the presence of an increased number of M-giant stars (most
likely to be thermally pulsating AGB stars); (5) the near-IR diagrams discussed
here seem as efficient for detecting putatively young stellar components in
early-type galaxies as the more commonly used age/metallicity diagnostic plots
using optical indices (e.g Hbeta vs. [MgFe]').


title: D-branes on AdS flux compactifications

abstract:
  We study D-branes in N=1 flux compactifications to AdS_4. We derive their
supersymmetry conditions and express them in terms of background generalized
calibrations. Basically because AdS has a boundary, the analysis of stability
is more subtle and qualitatively different from the usual case of Minkowski
compactifications. For instance, stable D-branes filling AdS_4 may wrap trivial
internal cycles. Our analysis gives a geometric realization of the
four-dimensional field theory approach of Freedman and collaborators.
Furthermore, the one-to-one correspondence between the supersymmetry conditions
of the background and the existence of generalized calibrations for D-branes is
clarified and extended to any supersymmetric flux background that admits a
time-like Killing vector and for which all fields are time-independent with
respect to the associated time. As explicit examples, we discuss supersymmetric
D-branes on IIA nearly Kaehler AdS_4 flux compactifications.


title:
Recovery of p-modes in the combined 2004-2005 MOST observations of
  Procyon

abstract:
  Procyon A, a bright F5 IV-V Sun-like star, is justifiably regarded as a prime
asteroseismological target. This star was repeatedly observed by MOST, a
specialized microsatellite providing long-term, non-interrupted broadband
photometry of bright targets. So far, the widely anticipated p modes eluded
direct photometric detection, though numerous independent approaches hinted for
the presence of signals in the f~0.5-1.5 mHz range. Implementation of an
alternative approach in data processing, as well as combination of the MOST
data from 2004 and 2005 (264189 measurements in total) helps to reduce the
instrumental noise affecting previous reductions, bringing the 3-sigma
detection limit down to ~5.5 part-per-million in the f=0.8-1.2 mHz range. This
enables to cross-identifiy 16 p-mode frequencies (though not their degrees)
which were previously detected via high-precision radial velocity measurements,
and provides an estimate of the large spacing, delta_nu =0.0540 mHz at f~1 mHz.
The relatively low average amplitude of the detected modes, a=5.8+/-0.6 ppm,
closely matches the amplitudes inferred from the ground-based spectroscopy and
upper limits projected from WIRE photometry. This also explains why such
low-amplitude signals eluded the direct-detection approach which exclusively
relied on the MOST 2004 (or 2005) data processed by a standard pipeline.


title:
SuperNova Acceleration Probe (SNAP): Investigating Photometric Redshift
  Optimization

abstract:
  The aim of this paper is to investigate ways to optimize the accuracy of
photometric redshifts for a SNAP like mission. We focus on how the accuracy of
the photometric redshifts depends on the magnitude limit and signal-to-noise
ratio, wave-length coverage, number of filters and their shapes and observed
galaxy type. We use simulated galaxy catalogs constructed to reproduce observed
galaxy luminosity functions from GOODS, and derive photometric redshifts using
a template fitting method. By using a catalog that resembles real data, we can
estimate the expected number density of galaxies for which photometric
redshifts can be derived. We find that the accuracy of photometric redshifts is
strongly dependent on the signal-to-noise (S/N) (i.e., S/N>10 is needed for
accurate photometric redshifts). The accuracy of the photometric redshifts is
also dependent on galaxy type, with smaller scatter for earlier type galaxies.
Comparing results using different filter sets, we find that including the
U-band is important for decreasing the fraction of outliers, i.e.,
``catastrophic failures''. Using broad overlapping filters with resolution
~4gives better photometric redshifts compared to narrower filters (resolution
>~5) with the same integration time. We find that filters with square response
curves result in a slightly higher scatter, mainly due to a higher fraction of
outliers at faint magnitudes. We also compare a 9-filter set to a 17-filter
set, where we assume that the available exposure time per filter in the latter
set is half that of the first set. We find that the 9-filter set gives more
accurate redshifts for a larger number of objects and reaches higher redshift,
while the 17-filter set is gives better results at bright magnitudes.


title: Peptide Folding Kinetics from Replica Exchange Molecular Dynamics

abstract:
  We show how accurate kinetic information, such as the rates of protein
folding and unfolding, can be extracted from replica-exchange molecular
dynamics (REMD) simulations. From the brief and continuous trajectory segments
between replica exchanges, we estimate short-time propagators in conformation
space and use them to construct a master equation. For a helical peptide in
explicit water, we determine the rates of transitions both locally between
microscopic conformational states and globally for folding and unfolding. We
show that accurate rates in the ~1/(100 ns) to ~1/(1 ns) range can be obtained
from REMD with exchange times of 5 ps, in excellent agreement with results from
long equilibrium molecular dynamics.

categories: cond-mat.soft cond-mat.stat-mech physics.chem-ph q-bio.BM q-bio.QM


title: Inelastic final-state interaction

abstract:
  The final-state interaction in multichannel decay processes is sytematically
studied with application to B decay in mind. Since the final-state inteaction
is intrinsically interwoven with the decay interaction in this case, no simple
phase theorem like "Watson's theorem" holds for experimentally observed final
states. We first examine in detail the two-channel problem as a toy-model to
clarify the issues and to remedy common mistakes made in earlier literature.
Realistic multichannel problems are too challenging for quantitative analysis.
To cope with mathematical complexity, we introduce a method of approximation
that is applicable to the case where one prominant inelastic channel dominates
over all others. We illustrate this approximation method in the amplitude of
the decay B to pi K fed by the intermediate states of a charmed meson pair.
Even with our approximation we need more accurate information of strong
interactions than we have now. Nonethless we are able to obtain some insight in
the issue and draw useful conclusions on general fearyres on the strong phases.


title:
Evidence for line-of-sight structure in a comparison of X-ray and
  optical observations of the high-redshift cluster RCS043938-2904.7

abstract:
  We present new Chandra observations of a high redshift (z~1) galaxy cluster
discovered in the Red-Sequence Cluster Survey (RCS): RCS043938-2904.7. X-ray
luminosity measurements and mass estimates are consistent with L_X-T_X and
M_delta-T_X relationships obtained from low-redshift data. Assuming a single
cluster, X-ray mass estimates are a factor of ~10-100 below the red-sequence
optical richness mass estimate. Optical spectroscopy reveals that this cluster
comprises two components which are close enough to perhaps be physically
associated. We present simple modeling of this two-component system which then
yields an X-ray mass and optical richness consistent with expectations from
statistical samples of lower redshift clusters. An unexpectedly high gas mass
fraction is measured assuming a single cluster, which independently supports
this interpretation. Additional observations will be necessary to confirm the
excess gas mass fraction and to constrain the mass distribution.


title: Strange quark contribution to nucleon form factors

abstract:
  We discuss methods for the calculation of disconnected diagrams and their
application to various form factors of the nucleon. In particular, we present
preliminary results for the strange contribution to the scalar and axial form
factors, calculated with N_f=2 dynamical flavors of Wilson fermions on an
anisotropic lattice.


title:
Anisotropic magnetoresistance involves metal-insulator transition in
  single crystal La0.77Ca0.23MnO3

abstract: The paper has been withdrawn for some reasons


title:
Size effects in the exchange coupling between two electrons in quantum
  wire quantum dots

abstract:
  We theoretically investigate the properties of a two-electron system confined
in the three-dimensional potential of coupled quantum dots formed in a quantum
wire. For this purpose, we implement a variational Heitler-London method that
minimize the system energies with respect to variational parameters in electron
trial wavefunctions. We find that tunneling and exchange couplings
exponentially decay with increasing inter-dot distance and inter-dot barrier
height. In the quasi-one-dimensional limit achieved by reducing the wire
diameter, we find that the overlap between the dots decreases, which results in
a drop of the exchange coupling. We also discuss the validity of our
variational Heitler-London method with respect to the model potential
parameters, and compare our results with available experimental data to find
good agreement between the two approaches.


title:
Modification of Abel-Plana formula for functions with non-integrable
  branch-points

abstract:
  The Abel-Plana formula is a widely used tool for calculations in Casimir type
problems. In this note we present a particular explicit modification of the
Generalized Abel-Plana formula for the functions with non-integrable
branch-point singularities.


title: Fluctuation-driven heterogeneous chemical processes

abstract:
  We explore a new framework for describing the kinetics of a heterogeneous
chemical reaction where two particles of the same chemical species form a
reaction product of another chemical species on the surface of a seed particle.
Traditional treatments neglect the effect of statistical fluctuations in
populations. We employ techniques in a manner analogous to the treatment of
quantum systems to develop a stochastic description of processes beyond the
mean field approximation.


title: Short and Long Range Screening of Optical Singularities

abstract:
  Screening of topological charges (singularities) is discussed for paraxial
optical fields with short and with long range correlations. For short range
screening the charge variance in a circular region with radius $R$ grows
linearly with $R$, instead of with $R^{2}$ as expected in the absence of
screening; for long range screening it grows faster than $R$: for a field whose
autocorrelation function is the zero order Bessel function J_{0}, the charge
variance grows as R ln R$. A J_{0} correlation function is not attainable in
practice, but we show how to generate an optical field whose correlation
function closely approximates this form. The charge variance can be measured by
counting positive and negative singularities inside the region A, or more
easily by counting signed zero crossings on the perimeter of A. \For the first
method the charge variance is calculated by integration over the charge
correlation function C(r), for the second by integration over the zero crossing
correlation function Gamma(r). Using the explicit forms of C(r) and of Gamma(r)
we show that both methods of calculation yield the same result. We show that
for short range screening the zero crossings can be counted along a straight
line whose length equals P, but that for long range screening this
simplification no longer holds. We also show that for realizable optical
fields, for sufficiently small R, the charge variance goes as R^2, whereas for
sufficiently large R, it grows as R. These universal laws are applicable to
both short and pseudo-long range correlation functions.


title:
Three-body equations of motion in successive post-Newtonian
  approximations

abstract:
  There are periodic solutions to the equal-mass three-body (and N-body)
problem in Newtonian gravity. The figure-eight solution is one of them. In this
paper, we discuss its solution in the first and second post-Newtonian
approximations to General Relativity. To do so we derive the canonical
equations of motion in the ADM gauge from the three-body Hamiltonian. We then
integrate those equations numerically, showing that quantities such as the
energy, linear and angular momenta are conserved down to numerical error. We
also study the scaling of the initial parameters with the physical size of the
triple system. In this way we can assess when general relativistic results are
important and we determine that this occur for distances of the order of 100M,
with M the total mass of the system. For distances much closer than those,
presumably the system would completely collapse due to gravitational radiation.
This sets up a natural cut-off to Newtonian N-body simulations. The method can
also be used to dynamically provide initial parameters for subsequent full
nonlinear numerical simulations.


title: Integrable dynamics of Toda-type on the square and triangular lattices

abstract:
  In a recent paper we constructed an integrable generalization of the Toda law
on the square lattice. In this paper we construct other examples of integrable
dynamics of Toda-type on the square lattice, as well as on the triangular
lattice, as nonlinear symmetries of the discrete Laplace equations on the
square and triangular lattices. We also construct the $\tau$ - function
formulations and the Darboux-B\"acklund transformations of these novel
dynamics.


title:
Direct Observation of Cosmic Strings via their Strong Gravitational
  Lensing Effect: I. Predictions for High Resolution Imaging Surveys

abstract:
  We use current theoretical estimates for the density of long cosmic strings
to predict the number of strong gravitational lensing events in astronomical
imaging surveys as a function of angular resolution and survey area. We show
that angular resolution is the most important factor, and that interesting
limits on the dimensionless string tension Gmu/c^2 can be obtained by existing
and planned surveys. At the resolution of the Hubble Space Telescope (0.14"),
it is sufficient to survey of order a few square degrees -- well within reach
of the current HST archive -- to probe the regime Gmu/c^2 ~ 10^{-7}. If lensing
by cosmic strings is not detected, such a survey would improve the limit on the
string tension by a factor of two over that available from the cosmic microwave
background. Future high resolution imaging surveys, covering a few hundred
square degrees or more, either from space in the optical or from large-format
radio telescopes on the ground, would be able to further lower this limit to
Gmu/c^2 < 10^{-8}.


title: Extending a theorem of Herstein

abstract:
  Just infinite algebras have been considered from various perspectives; a
common thread in these treatments is that the notion of just infinite is an
extension of the notion of simple. We reinforce this generalization by
considering some well-known results of Herstein regarding simple rings and
their Lie and Jordan structures and extend these results to their just infinite
analogues. In particular, we prove that if A is a just infinite associative
algebra, of characteristic not 2,3, or 5, then the Lie algebra
$[A,A]/(Z\cap[A,A])$ is also just infinite (where Z denotes the center of A).


title: Giant proximity effect in a phase-fluctuating superconductor

abstract:
  When a tunneling barrier between two superconductors is formed by a normal
material that would be a superconductor in the absence of phase fluctuations,
the resulting Josephson effect can undergo an enormous enhancement. We
establish this novel proximity effect by a general argument as well as a
numerical simulation and argue that it may underlie recent experimental
observations of the giant proximity effect between two cuprate superconductors
separated by a barrier made of the same material rendered normal by severe
underdoping.


title: Code Similarity on High Level Programs

abstract:
  This paper presents a new approach for code similarity on High Level
programs. Our technique is based on Fast Dynamic Time Warping, that builds a
warp path or points relation with local restrictions. The source code is
represented into Time Series using the operators inside programming languages
that makes possible the comparison. This makes possible subsequence detection
that represent similar code instructions. In contrast with other code
similarity algorithms, we do not make features extraction. The experiments show
that two source codes are similar when their respective Time Series are
similar.


title:
Nuclear Bar Catalyzed Star Formation: 13^CO, C18^O and Molecular Gas
  Properties in the Nucleus of Maffei 2

abstract:
  (Abridged) We present resolution maps of CO, its isotopologues, and HCN from
in the center of Maffei 2. The J=1-0 rotational lines of 12^CO, 13^CO, C18^O
and HCN, and the J=2-1 lines of 13^CO and C18^O were observed with the OVRO and
BIMA arrays. The 2-1/1-0 line ratios of the isotopologues constrain the bulk of
the molecular gas to originate in low excitation, subthermal gas. From LVG
modeling, we infer that the central GMCs have n(H_2) ~10^2.75 cm^-3 and T_k ~
30 K. Continuum emission at 3.4 mm, 2.7 mm and 1.4 mm was mapped to determine
the distribution and amount of HII regions and dust. Column densities derived
from C18^O and 1.4 mm dust continuum fluxes indicate the CO conversion factor
in the center of Maffei 2 is lower than Galactic by factors of ~2-4. Gas
morphology and the clear ``parallelogram'' in the Position-Velocity diagram
shows that molecular gas orbits within the potential of a nuclear (~220 pc)
bar. The nuclear bar is distinct from the bar that governs the large scale
morphology of Maffei 2. Giant molecular clouds in the nucleus are nonspherical
and have large linewidths. Dense gas and star formation are concentrated at the
sites of the x_1-x_2 orbit intersections of the nuclear bar, suggesting that
the starburst is dynamically triggered.


title: Negativity and contextuality are equivalent notions of nonclassicality

abstract:
  Two notions of nonclassicality that have been investigated intensively are:
(i) negativity, that is, the need to posit negative values when representing
quantum states by quasiprobability distributions such as the Wigner
representation, and (ii) contextuality, that is, the impossibility of a
noncontextual hidden variable model of quantum theory (also known as the
Bell-Kochen-Specker theorem). Although both of these notions were meant to
characterize the conditions under which a classical explanation cannot be
provided, we demonstrate that they prove inadequate to the task and we argue
for a particular way of generalizing and revising them. With the refined
version of each in hand, it becomes apparent that they are in fact one and the
same. We also demonstrate the impossibility of noncontextuality or
nonnegativity in quantum theory with a novel proof that is symmetric in its
treatment of measurements and preparations.


title: Vortex lattice transitions in cyclic spinor condensates

abstract:
  We study the energetics of vortices and vortex lattices produced by rotation
in the cyclic phase of F=2 spinor Bose condensates. In addition to the familiar
triangular lattice predicted by Tkachenko for $^4$He, many more complex
lattices appear in this system as a result of the spin degree of freedom. In
particular, we predict a magnetic-field-driven transition from a triangular
lattice to a honeycomb lattice. Other transitions and lattice geometries are
driven at constant field by changes in the temperature-dependent ratio of
charge and spin stiffnesses, including a transition through an aperiodic vortex
structure.


title:
Linear response and stability of ordered phases of diblock copolymer
  melts

abstract:
  An efficient pseudo-spectral numerical method is introduced for calculating a
self-consistent field (SCF) approximation for the linear susceptibility of
ordered phases in block copolymer melts (sometimes referred to as the random
phase approximation). Our method is significantly more efficient than that used
in the first calculations of this quantity by Shi, Laradji and coworkers,
allowing for the study of more strongly segregated structures. We have
re-examined the stability of several phases of diblock copolymer melts, and
find that some conclusions of Laradji et al. regarding the stability of the
Gyroid phase were the result of insufficient spatial resolution. We find that
an epitaxial (k=0) instability of the Gyroid phase with respect to the
hexagonal phase that was considered previously by Matsen competes extremely
closely with an instability that occurs at a nonzero crystal wavevector k.


title: An extension theorem for conformal gauge singularities

abstract:
  We analyse conformal gauge, or isotropic, singularities in cosmological
models in general relativity. Using the calculus of tractors, we find
conditions in terms of tractor curvature for a local extension of the conformal
structure through a cosmological singularity and prove a local extension
theorem.


title:
Probing the photonic local density of states with electron energy loss
  spectroscopy

abstract:
  Electron energy-loss spectroscopy (EELS) performed in transmission electron
microscopes is shown to directly render the photonic local density of states
(LDOS) with unprecedented spatial resolution, currently below the nanometer.
Two special cases are discussed in detail: (i) 2D photonic structures with the
electrons moving along the translational axis of symmetry and (ii) quasi-planar
plasmonic structures under normal incidence. Nanophotonics in general and
plasmonics in particular should benefit from these results connecting the
unmatched spatial resolution of EELS with its ability to probe basic optical
properties like the photonic LDOS.


title:
Frustration of decoherence in $Y$-shaped superconducting Josephson
  networks

abstract:
  We examine the possibility that pertinent impurities in a condensed matter
system may help in designing quantum devices with enhanced coherent behaviors.
For this purpose, we analyze a field theory model describing Y- shaped
superconducting Josephson networks. We show that a new finite coupling stable
infrared fixed point emerges in its phase diagram; we then explicitly evidence
that, when engineered to operate near by this new fixed point, Y-shaped
networks support two-level quantum systems, for which the entanglement with the
environment is frustrated. We briefly address the potential relevance of this
result for engineering finite-size superconducting devices with enhanced
quantum coherence. Our approach uses boundary conformal field theory since it
naturally allows for a field-theoretical treatment of the phase slips
(instantons), describing the quantum tunneling between degenerate levels.


title:
Nature of the superconductor-insulator transition in disordered
  superconductors

abstract:
  As a superconducting thin film becomes disordered and subject to an
increasing magnetic field, a point is reached when it undergoes a transition
from a superconducting to an insulating state. We use the Bogoliubov-De-Gennes
equations and a novel Monte-Carlo approach to study this transition
numerically, starting from a microscopic hamiltonian. The key effect of
disorder is to create 'islands' of strong superconductivity, coupled by regions
that are only weakly superconducting. In the case of weak disorder, an
increasing magnetic field eventually destroys the superconducting state
throughout the material, leading to an insulator. On the other hand, when
disorder is strong, superconductivity persists in the islands, and the effect
of a magnetic field is to suppress the coupling between them, resulting in
strong superconducting phase fluctuations, again leading to an insulating
state. These findings may be relevant to the high-temperature superconductors,
where intrinsic disorder may play a role.


title:
An 8-dimensional realization of the Clifford algebra in the
  5-dimensional Galilean space-time

abstract:
  We give an 8-dimensional realization of the Clifford algebra in the
5-dimensional Galilean space-time by using a dimensional reduction from the
$(5+1)$ Minkowski space-time to the $(4+1)$ Minkowski space-time which
encompasses the Galilean space-time. A set of solutions of the Dirac-type
equation in the 5-dimensional Galilean space-time is obtained, based on the
Pauli representation of $8\times 8$ gamma matrices. In order to find an
explicit solution, we diagonalize the Klein-Gordon divisor by using the
Galilean boost.


title: CPT theorem in a (5+1) Galilean space-time

abstract:
  We extend the 5-dimensional Galilean space-time to a (5+1) Galilean
space-time in order to define a parity transformation in a covariant manner.
This allows us to discuss the discrete symmetries in the Galilean space-time,
which is embedded in the (5+1) Minkowski space-time. We discuss the Dirac-type
field, for which we give the 8\times 8 gamma matrices explicitly. We
demonstrate that the CPT theorem holds in the (5+1) Galilean space-time.


title: Guided Modes of Elliptical Metamaterial Waveguides

abstract:
  The propagation of guided electromagnetic waves in open elliptical
metamaterial waveguide structures is investigated. The waveguide contains a
negative-index media core, where the permittivity, $\epsilon$ and permeability
$\mu$ are negative over a given bandwidth. The allowed mode spectrum for these
structures is numerically calculated by solving a dispersion relation that is
expressed in terms of Mathieu functions. By probing certain regions of
parameter space, we find the possibility exists to have extremely localized
waves that transmit along the surface of the waveguide.


title: S@M, a Mathematica Implementation of the Spinor-Helicity Formalism

abstract:
  In this paper we present the package S@M (Spinors@Mathematica) which
implements the spinor-helicity formalism in Mathematica. The package allows the
use of complex-spinor algebra along with the multi-purpose features of
Mathematica. The package defines the spinor objects with their basic properties
along with functions to manipulate them. It also offers the possibility of
evaluating the spinorial objects numerically at every computational step. The
package is therefore well suited to be used in the context of on-shell
technology, in particular for the evaluation of scattering amplitudes at tree-
and loop-level.


title:
Principal Component Analysis of the Time- and Position-Dependent Point
  Spread Function of the Advanced Camera for Surveys

abstract:
  We describe the time- and position-dependent point spread function (PSF)
variation of the Wide Field Channel (WFC) of the Advanced Camera for Surveys
(ACS) with the principal component analysis (PCA) technique. The time-dependent
change is caused by the temporal variation of the $HST$ focus whereas the
position-dependent PSF variation in ACS/WFC at a given focus is mainly the
result of changes in aberrations and charge diffusion across the detector,
which appear as position-dependent changes in elongation of the astigmatic core
and blurring of the PSF, respectively. Using >400 archival images of star
cluster fields, we construct a ACS PSF library covering diverse environments of
the $HST$ observations (e.g., focus values). We find that interpolation of a
small number ($\sim20$) of principal components or ``eigen-PSFs'' per exposure
can robustly reproduce the observed variation of the ellipticity and size of
the PSF. Our primary interest in this investigation is the application of this
PSF library to precision weak-lensing analyses, where accurate knowledge of the
instrument's PSF is crucial. However, the high-fidelity of the model judged
from the nice agreement with observed PSFs suggests that the model is
potentially also useful in other applications such as crowded field stellar
photometry, galaxy profile fitting, AGN studies, etc., which similarly demand a
fair knowledge of the PSFs at objects' locations. Our PSF models, applicable to
any WFC image rectified with the Lanczos3 kernel, are publicly available.


title: Progress in finite temperature lattice QCD

abstract:
  I review recent progress in finite temperature lattice calculations,
including the determination of the transition temperature, equation of state,
screening of static quarks and meson spectral functions.


title:
On measure-preserving ${\mathcal C}^1$ transformations of compact-open
  subsets of non-archimedean local fields

abstract:
  We introduce the notion of a \emph{locally scaling} transformation defined on
a compact-open subset of a non-archimedean local field. We show that this class
encompasses the Haar measure-preserving transformations defined by ${\mathcal
C}^1$ (in particular, polynomial) maps, and prove a structure theorem for
locally scaling transformations. We use the theory of polynomial approximation
on compact-open subsets of non-archimedean local fields to demonstrate the
existence of ergodic Markov, and mixing Markov transformations defined by such
polynomial maps. We also give simple sufficient conditions on the Mahler
expansion of a continuous map $\mathbb Z_p \to \mathbb Z_p$ for it to define a
Bernoulli transformation.


title: The Omega Effect as a Discriminant for Space-Time Foam

abstract:
  If there is CPT violation, the nature of entanglement for neutral meson pairs
produced in meson factories may, on general grounds, be affected. The new form
of entanglement is the omega effect. Gravitational decoherence, due to
space-time foam, may be one route for deviations from CPT invariance. Two
models of space-time foam are considered. One, based on non-critical string
theory, is able to produce the new correlations in a natural way. The other,
based on the paradigm of thermal-like baths, is shown to be surprisingly
resistant to producing the effect even on exercising a total freedom of choice
for the state of the bath


title:
High-Level Correlated Approach to the Jellium Surface Energy, Without
  Uniform-Electron-Gas Input

abstract:
  We resolve the long-standing controversy over the surface energy of simple
metals: Density functional methods that require uniform-electron-gas input
agree with each other at many levels of sophistication, but not with high-level
correlated calculations like Fermi Hypernetted Chain and Diffusion Monte Carlo
(DMC) that predict the uniform-gas correlation energy. Here we apply a very
high-level correlated approach, the inhomogeneous Singwi-Tosi-Land-Sj\"olander
(ISTLS) method, and find that the density functionals are indeed reliable
(because the surface energy is "bulk-like"). ISTLS values are close to
recently-revised DMC values. Our work also vindicates the previously-disputed
use of uniform-gas-based nonlocal kernels in time-dependent density functional
theory.


title: A Note on $\aleph_{0}$-injective Rings

abstract:
  A ring $R$ is called right $\aleph_{0}$-injective if every homomorphism from
a countably generated right ideal of $R$ to $R_{R}$ can be extended to a
homomorphism from $R_{R}$ to $R_{R}$. In this note, some characterizations of
$\aleph_{0}$-injective rings are given. It is proved that if $R$ is semilocal,
then $R$ is right $\aleph_{0}$-injective if and only if every homomorphism from
a countably generated small right ideal of $R$ to $R_{R}$ can be extended to
one from $R_{R}$ to $R_{R}$. It is also shown that if $R$ is right noetherian
and left $\aleph_{0}$-injective, then $R$ is \emph{QF}. This result can be
considered as an approach to the Faith-Menal conjecture.


title:
An infinite dimensional Schur-Horn theorem and majorization theory with
  applications to operator ideals

abstract:
  The main result of this paper is the extension of the Schur-Horn Theorem to
infinite sequences: For two nonincreasing nonsummable sequences x and y that
converge to 0, there exists a compact operator A with eigenvalue list y and
diagonal sequence x if and only if y majorizes x (\sum_{j=1}^n x_j \le
\sum_{j=1}^n y_j for all n) if and only if x = Qy for some orthostochastic
matrix Q. The similar result requiring equality of the infinite series in the
case that the sequences x and y are summable is an extension of a recent
theorem by Arveson and Kadison. Our proof depends on the construction and
analysis of an infinite product of T-transform matrices. Further results on
majorization for infinite sequences providing "intermediate" sequences
generalize known results from the finite case. Majorization properties and
invariance under various classes of stochastic matrices are then used to
characterize arithmetic mean closed operator ideals.


title:
A chain rule for Goodwillie derivatives of functors from spectra to
  spectra

abstract:
  We prove a chain rule for the Goodwillie calculus of functors from spectra to
spectra. We show that the (higher) derivatives of a composite functor $FG$ at a
base object $X$ are given by taking the composition product (in the sense of
symmetric sequences) of the derivatives of $F$ at $G(X)$ with the derivatives
of $G$ at $X$. We also consider the question of finding $P_n(FG)$, and give an
explicit formula for this when $F$ is homogeneous.


title: Graded identities of matrix algebras and the universal graded algebra

abstract:
  We consider fine G-gradings on M_n(C) (i.e. gradings of the matrix algebra
over the complex numbers where each component is 1 dimensional). Groups which
provide such a grading are known to be solvable. We consider the T-ideal of
G-graded identities and show that it is generated by a special type of binomial
identities which we call elementary. In particular we show that the ideal of
graded identities is finitely generated as a T-ideal. Next, given such grading
we construct a universal algebra U_{G,c} in two different ways: one by means of
polynomial identities and the other one by means of a generic two-cocycle (this
parallels the classical constructions in the non-graded case). We show that a
suitable central localization of U_{G,c} is Azumaya over its center and
moreover, its homomorphic images are precisely the G-graded forms of M_n(C).
Finally, we consider the ring of central quotients Q(U_{G,c}) (this is an
F-central simple algebra where F=Frac(Z) and Z is the center of of U_{G,c}).
Using an earlier results of the authors (see E. Aljadeff, D. Haile and M.
Natapov, Projective bases of division algebras and groups of central type,
Israel J. Math.146 (2005) 317-335 and M. Natapov arXiv:0710.5468v1 [math.RA])
we show that this is a division algebra for a very explicit (and short) family
of nilpotent groups. As a consequence, for groups G such that Q(U_{G,c}) is not
a division algebra, one can find a non identity polynomial p(x_{i,g}) such that
p(x_{i,g})^r is a graded identity for some integer r. We illustrate this
phenomenon with a fine G-grading of M_6(C) where G is a semidirect product of
S_3 and C_6.


title:
The Quantum-Classical and Mind-Brain Linkages: The Quantum Zeno Effect
  in Binocular Rivalry

abstract:
  A quantum mechanical theory of the relationship between perceptions and brain
dynamics based on von Neumann's theory of measurments is applied to a recent
quantum theoretical treatment of binocular rivaly that makes essential use of
the quantum Zeno effect to give good fits to the complex available empirical
data. The often-made claim that decoherence effects in the warm, wet, noisy
brain must eliminate quantum effects at the macroscopic scale pertaining to
perceptions is examined, and it is argued, on the basis of fundamental
principles. that the usual decoherence effects will not upset the quantum Zeno
effect that is being exploited in the cited work.


title: The quadrupole collective model from a Cartan-Weyl perspective

abstract:
  The matrix elements of the quadrupole variables and canonic conjugate
momenta, emerging from collective nuclear models are calculated within a
$SU(1,1)\times O(5)$ basis. Using a harmonic oscillator implementation of the
SU(1,1) degree of freedom, it can be shown that the matrix elements of the
quadrupole phonon creation and annihilation operators can be calculated in a
pure algebraic way, making use of an intermediate state method.


title: Ramsey-type problem for an almost monochromatic K_4

abstract:
  In this short note we prove that there is a constant $c$ such that every
k-edge-coloring of the complete graph K_n with n > 2^{ck} contains a K_4 whose
edges receive at most two colors. This improves on a result of Kostochka and
Mubayi, and is the first exponential bound for this problem.


title: One loop photon-graviton mixing in an electromagnetic field: Part 2

abstract:
  In part 1 of this series compact integral representations had been obtained
for the one-loop photon-graviton amplitude involving a charged spin 0 or spin
1/2 particle in the loop and an arbitrary constant electromagnetic field. In
this sequel, we study the structure and magnitude of the various polarization
components of this amplitude on-shell. Explicit expressions are obtained for a
number of limiting cases.


title: AgInSe2 Nanorods: A semiconducting material for saturable absorber

abstract:
  AgInSe2 nanorods (NRs) with diameter of 15 nm have been investigated for
their nonlinear optical responses by using Z-scan and transient absorption
techniques with femtosecond laser pulses of photon energy greater than the
bandgap. At excitation irradiance of 20 GW/cm2, AgInSe2 NRs reveal saturation
in the nonlinear absorption and optical Kerr nonlinearity with a recovery time
determined to be a few ten picoseconds. Such large saturable absorption and
Kerr nonlinearity exhibit a third-order susceptibility of 1.2 x 10-8 esu and a
figure of merit of 0.04 esu.cm.s-1, making AgInSe2 NRs a promising candidate
for saturable absorption devices.

categories: nlin.SI cond-mat.mtrl-sci cond-mat.soft physics.chem-ph physics.optics


title: Effects of Quasar Feedback in Galaxy Groups

abstract:
  We study the effect of quasar feedback on distributions of baryons and
properties of intracluster medium in galaxy groups using high-resolution
numerical simulations. We use the entropy-conserving Gadget code that includes
gas cooling and star formation, modified to include a physically-based model of
quasar feedback. For a sample of ten galaxy group-sized dark matter halos with
masses in the range of 1 to $5\times 10^{13} M_{\odot}/h$, star formation is
suppressed by more than 50% in the inner regions due to the additional pressure
support by quasar feedback, while gas is driven from the inner region towards
the outer region of the halos. As a result, the average gas density is 50%
lower in the inner region and 10% higher in the outer region in the simulation,
compared to a similar simulation with no quasar feedback. Gas pressure is
lowered by about 40% in the inner region and higher in the outer region, while
temperature and entropy are enhanced in the inner region by about 20-40%. The
total group gas fraction in the two simulations generally differs by less than
10%. We also find a small change of the total thermal Sunyaev-Zeldovich
distortion, leading to 10% changes in the microwave angular power spectrum at
angular scales below two arcminutes.


title:
A new methodology for the extraction of anharmonic force constants from
  first principles density functional calculations

abstract:
  A new method for extracting force constants (FC) from first principles is
introduced. It requires small supercells but very accurate forces. In
principle, provided that forces are accurate enough, it can extract harmonic as
well as anharmonic FCs up to any neighbor shell. Symmetries of the FCs as well
as those of the lattice are used to reduce the number of parameters to be
calculated. Results are illustrated for the case of Lennard-Jones potential
where forces are exact and FCs can be calculated analytically, and Si in the
diamond structure. The latter are compared to previously calculated harmonic
FCs.


title:
Aspherical supernova explosions and formation of compact black hole
  low-mass X-ray binaries

abstract:
  It has been suggested that black-hole low-mass X-ray binaries (BHLMXBs) with
short orbital periods may have evolved from BH binaries with an
intermediate-mass secondary, but the donor star seems to always have higher
effective temperatures than measured in BHLMXBs (Justham, Rappaport &
Podsiadlowski 2006). Here we suggest that the secondary star is originally an
intermediate-mass ($\sim 2-5 M_{\sun}$) star, which loses a large fraction of
its mass due to the ejecta impact during the aspherical SN explosion that
produced the BH. The resulted secondary star could be of low-mass ($\la 1
M_{\sun}$). Magnetic braking would shrink the binary orbit, drive mass transfer
between the donor and the BH, producing a compact BHLMXB.


title:
Large deviations associated with Poisson--Dirichlet distribution and
  Ewens sampling formula

abstract:
  Several results of large deviations are obtained for distributions that are
associated with the Poisson--Dirichlet distribution and the Ewens sampling
formula when the parameter $\theta$ approaches infinity. The motivation for
these results comes from a desire of understanding the exact meaning of
$\theta$ going to infinity. In terms of the law of large numbers and the
central limit theorem, the limiting procedure of $\theta$ going to infinity in
a Poisson--Dirichlet distribution corresponds to a finite allele model where
the mutation rate per individual is fixed and the number of alleles going to
infinity. We call this the finite allele approximation. The first main result
of this article is concerned with the relation between this finite allele
approximation and the Poisson--Dirichlet distribution in terms of large
deviations. Large $\theta$ can also be viewed as a limiting procedure of the
effective population size going to infinity. In the second result a comparison
is done between the sample size and the effective population size based on the
Ewens sampling formula.


title:
On variability and spectral distortion of the fluorescent iron lines
  from black-hole accretion discs

abstract:
  We investigate properties of iron fluorescent line arising as a result of
illumination of a black hole accretion disc by an X-ray source located above
the disc surface. We study in details the light-bending model of variability of
the line, extending previous work on the subject.
  We indicate bending of photon trajectories to the equatorial plane, which is
a distinct property of the Kerr metric, as the most feasible effect underlying
reduced variability of the line observed in several objects. A model involving
an X-ray source with a varying radial distance, located within a few central
gravitational radii around a rapidly rotating black hole, close to the disc
surface, may explain both the elongated red wing of the line profile and the
complex variability pattern observed in MCG--6-30-15 by XMM-Newton.
  We point out also that illumination by radiation which returns to the disc
(following the previous reflection) contributes significantly to formation of
the line profile in some cases. As a result of this effect, the line profile
always has a pronounced blue peak (which is not observed in the deep minimum
state in MCG--6-30-15), unless the reflecting material is absent within the
innermost 2--3 gravitational radii.


title: Noncompact Shrinking 4-Solitons with Nonnegative Curvature

abstract:
  We prove the following: Let (M,g,X) be a noncompact four dimensional
shrinking soliton with bounded nonnegative curvature operator, then (M,g) is
isometric to R^4 or a finite quotient of S^2xR^2 or S^3xR. In the process we
also show that a complete shrinking soliton (M,g,X) with bounded curvature is
gradient and k-noncollapsed and the dilation of a Type I singularity is a
shrinking soliton. Further in dimension three we show shrinking solitons with
bounded curvature can be classified under only the assumption of Rc>= 0.


title: Ram pressure histories of cluster galaxies

abstract:
  Ram pressure stripping can remove significant amounts of gas from galaxies
that orbit in clusters and massive groups, and thus has a large impact on the
evolution of cluster galaxies. In this paper, we reconstruct the present-day
distribution of ram-pressure, and the ram pressure histories of cluster
galaxies. To this aim, we combine the Millennium Simulation and an associated
semi-analytic model of galaxy evolution with analytic models for the gas
distribution in clusters. We find that about one quarter of galaxies in massive
clusters are subject to strong ram-pressures that are likely to cause an
expedient loss of all gas. Strong ram-pressures occur predominantly in the
inner core of the cluster, where both the gas density and the galaxy velocity
are higher. Since their accretion onto a massive system, more than 64 per cent
of galaxies that reside in a cluster today have experienced strong
ram-pressures of $>10^{-11}$ dyn cm$^{-2}$ which most likely led to a
substantial loss of the gas.