title:
Negative-Tension Branes and Tensionless 1/2 Brane in Boundary Conformal
  Field Theory

abstract:
  In the framework of boundary conformal field theory we consider a flat
unstable D$p$-brane in the presence of a large constant electromagnetic field.
Specifically, we study the case that the electromagnetic field satisfy the
following three conditions: (i) a constant electric field is turned on along
the $x^1$ direction ($E_{1}\ne 0$); (ii) the determinant of the matrix $(\eta +
F)$ is negative so that it lies in the physical region ($-\det (\eta + F)>0$);
(iii) the 11-component of its cofactor is positive to the large electromagnetic
field. In this case, we identify exactly marginal deformations depending on the
spatial coordinate $x^1$. They correspond to tachyon profiles of hyperbolic
sine, exponential, and hyperbolic cosine types. Boundary states are constructed
for these deformations by utilizing T-duality approach and also by directly
solving the overlap conditions in BCFT. The exponential type deformation gives
a tensionless half brane connecting the perturbative string vacuum and one of
the true tachyon vacua, while the others have negative tensions. This is in
agreement with the results obtained in other approaches.


title: Higgs boson decays to four fermions through an abelian hidden sector

abstract:
  We consider a generic abelian hidden sector that couples to the Standard
Model only through gauge-invariant renormalizable operators. This allows the
exotic Higgs boson to mix with the Standard Model Higgs boson, and the exotic
abelian gauge boson to mix with the Standard Model hypercharge gauge boson. One
immediate consequence of spontaneous breaking of the hidden sector gauge group
is the possible decay of the lightest Higgs boson into four fermions through
intermediate exotic gauge bosons. We study the implications of this decay for
Higgs boson phenomenology at the Fermilab Tevatron Collider and the CERN Large
Hadron Collider. Our emphasis is on the four lepton final state.


title:
Two-photon detuning and decoherence in cavity electromagnetically
  induced transparency for quantized fields

abstract:
  The interaction of a quantized field with three-level atoms in $\Lambda$
configuration inside a two-mode cavity is analyzed in the small noise
approximation. The atoms are in a two-photon detuning with respect to the
carriers of the field. We calculate the stationary quadrature noise spectrum of
the field outside the cavity in the case where the input probe field is a
squeezed state and the input pump field is a coherent state. The mean value of
the field is unaltered in all the analysis: the atoms shows electromagnetically
induced transparency (EIT). The effect of the atoms' base level decoherence in
the cavity output field is also studied. It is found that the output field is
very sensitive to two-photon detuning.


title: What Millisecond Pulsars Can Tell Us About Matter In The Galaxy

abstract:
  I demonstrate that precision timing of millisecond pulsars possess the
capabilities of detecting the gravitational effects of intervening galactic
substructure. This analysis is applicable to all types of collapsed baryons
including stars, planets, and MACHOs, as well as many types of dark matter,
including primordial black holes, scalar miniclusters, and sufficiently dense
clumps of cold dark matter. The physical signal is quantified and decomposed
into observable and unobservable components; templates for the observable
signals are also presented. Additionally, I calculate the expected changes in
the observed period and period derivatives that will result from intervening
matter. I find that pulsar timing is potentially a very useful tool for probing
the nature of dark matter and to learn more about the substructure present
within our galaxy.


title:
Conditional Mass Functions and Merger Rates of Dark Matter Halos in the
  Ellipsoidal Collapse Model

abstract:
  Analytic models based on spherical and ellipsoidal gravitational collapse
have been used to derive the mass functions of dark matter halos and their
progenitors (the conditional mass function). The ellipsoidal model generally
provides a better match to simulation results, but there has been no simple
analytic expression in this model for the conditional mass function that is
accurate for small time steps, a limit that is important for generating halo
merger trees and computing halo merger rates. We remedy the situation by
deriving accurate analytic formulae for the first-crossing distribution, the
conditional mass function, and the halo merger rate in the ellipsoidal collapse
model in the limit of small look-back times. We show that our formulae provide
a closer match to the Millennium simulation results than those in the spherical
collapse model and the ellipsoidal model of Sheth & Tormen (2002).


title: Kinematics of massive stars in the Small Magellanic Cloud

abstract:
  We present radial velocities for 2045 stars in the Small Magellanic Cloud
(SMC), obtained from the 2dF survey by Evans et al. (2004). The great majority
of these stars are of OBA type, tracing the dynamics of the young stellar
population. Dividing the sample into ad hoc `bar' and `wing' samples (north and
south, respectively, of the line: $\delta$ = -77$^{\circ}$50' + [4$\alpha$]',
where $\alpha$ is in minutes of time) we find that the velocities in the SMC
bar show a gradient of 26.3 +/- 1.6 km/s/deg. at a position angle of 126 +/- 4
deg. The derived gradient in the bar is robust to the adopted line of
demarcation between the two samples. The largest redshifts are found in the SMC
wing, in which the velocity distribution appears distinct from that in the bar,
most likely a consequence of the interaction between the Magellanic Clouds that
is predicted to have occurred 0.2 Gyr ago. The mean velocity for all stars in
the sample is +172.0 +/- 0.2 km/s (redshifted by ~20 km/s when compared to
published results for older populations), with a velocity dispersion of 30
km/s.


title:
Weighing the Quiescent Central Black Hole in an Elliptical Galaxy with
  X-ray Emitting Gas

abstract:
  We present a Chandra study of the hot ISM in the giant elliptical galaxy
NGC4649. In common with other group-centred ellipticals, its temperature
profile rises with radius in the outer parts of the galaxy, from ~0.7keV at
2kpc to ~0.9keV by 20kpc. However, within the central ~2kpc the trend reverses
and the temperature peaks at ~1.1keV within the innermost 200pc. Under the
assumption of hydrostatic equilibrium, we demonstrate that the central
temperature spike arises due to the gravitational influence of a quiescent
central super-massive black hole. We constrain the black hole mass (MBH) to
$(3.35^{+0.67}_{-0.95})\times 10^9$Msun (90% confidence), in good agreement
with stellar kinematics measurements. This is the first direct measurement of
MBH based on studies of hydrostatic X-ray emitting gas, which are sensitive to
the most massive black holes, and is a crucial validation of both
mass-determination techniques. This agreement clearly demonstrates the gas must
be close to hydrostatic, even in the very centre of the galaxy, which is
consistent with the lack of morphological disturbances in the X-ray image.
NGC4649 is now one of only a handful of galaxies for which MBH has been
measured by more than one method. At larger radii, we were able to decompose
the gravitating mass profile into stellar and dark matter (DM) components.
Unless one accounts for the DM, a standard Virial analysis of the stars
dramatically over-estimates the stellar mass of the galaxy. We find the
measured J-band stellar mass-to-light ratio, 1.37+/-0.10 Msun/Lsun, is in good
agreement with simple stellar population model calculations for this object.


title: Braneworld Isotropization and Magnetic Fields

abstract:
  We consider a magnetic Bianchi I braneworld, embedded in between two
Schwarzschild-AdS spacetimes, boosted equal amounts in opposite directions and
compare them to the analagous solution in four-dimensional General Relativity.
The efficient dissipation of anisotropy on the brane is explicitly
demonstrated, a process we dub braneworld isotropization. From the bulk point
of view, we attribute this to anisotropic energy being carried into the bulk by
hot gravitons leaving the brane. From the brane point of view this can be
interpreted in terms of the production of particles in the dual CFT. We explain
how this result enables us to gain a better understanding of the behaviour of
anisotropic branes already studied in the literature. We also show how there is
evidence of particles being over-produced, and comment on how this may
ultimately provide a possible observational signature of braneworlds.


title:
The trispectrum of 21-cm background anisotropies as a probe of
  primordial non-Gaussianity

abstract:
  The 21-cm anisotropies from the neutral hydrogen distribution prior to the
era of reionization is a sensitive probe of primordial non-Gaussianity. Unlike
the case with cosmic microwave background, 21-cm anisotropies provide
multi-redshift information with frequency selection and is not damped at
arcminute angular scales. We discuss the angular trispectrum of the 21-cm
background anisotropies and discuss how the trispectrum signal generated by the
primordial non-Gaussianity can be measured with the three-to-one correlator and
the corresponding angular power spectrum. We also discuss the separation of
primordial non-Gaussian information in the trispectrum with that generated by
the subsequent non-linear gravitational evolution of the density field. While
with the angular bispectrum of 21-cm anisotropies one can limit the second
order corrections to the primordial fluctuations below f_NL< 1, using the
trispectrum information we suggest that the third order coupling term, f_2 or
g_NL, can be constrained to be arounde 10 with future 21-cm observations over
the redshift interval of 50 to 100.


title: NNNLO results on top-quark pair production near threshold

abstract:
  We present new results on the NNNLO top-antitop production cross section near
threshold from potential and ultrasoft gluon corrections. The new
non-logarithmic third-order terms are in the 10% range and lead to a
significant reduction in the theoretical error.


title: Mixtures of strongly interacting bosons in optical lattices

abstract:
  We investigate the properties of strongly interacting heteronuclear
boson-boson mixtures loaded in realistic optical lattices, with particular
emphasis on the physics of interfaces. In particular, we numerically reproduce
the recent experimental observation that the addition of a small fraction of K
induces a significant loss of coherence in Rb, providing a simple explanation.
We then investigate the robustness against the inhomogeneity typical of
realistic experimental realizations of the glassy quantum emulsions recently
predicted to occur in strongly interacting boson-boson mixtures on ideal
homogeneous lattices.


title:
Centrality dependence of charged hadron and strange hadron elliptic flow
  from sqrt(s_NN) = 200 GeV Au+Au collisions

abstract:
  We present STAR results on the elliptic flow v_2 of charged hadrons, strange
and multi-strange particles from sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC.
The detailed study of the centrality dependence of v_2 over a broad transverse
momentum range is presented. Comparison of different analysis methods are made
in order to estimate systematic uncertainties. In order to discuss the non-flow
effect, we have performed the first analysis of v_2 with the Lee-Yang Zero
method for K_s^0 and Lambda.
  In the relatively low p_T region, p_T <= 2 GeV/c, a scaling with m_T - m is
observed for identified hadrons in each centrality bin studied. However, we do
not observe v_2(p_T) scaled by the participant eccentricity to be independent
of centrality. At higher p_T, 2 GeV/c <= p_T <= 6 GeV/c, v_2 scales with quark
number for all hadrons studied. For the multi-strange hadron Omega, which does
not suffer appreciable hadronic interactions, the values of v_2 are consistent
with both m_T -m scaling at low p_T and number-of-quark scaling at intermediate
p_T. As a function of collision centrality, an increase of p_T-integrated v_2
scaled by the participant eccentricity has been observed, indicating a stronger
collective flow in more central Au+Au collisions.


title: Incoherent Quantum Control

abstract:
  Conventional approaches for controlling open quantum systems use coherent
control which affects the system's evolution through the Hamiltonian part of
the dynamics. Such control, although being extremely efficient for a large
variety of problems, has limited capabilities, e.g., if the initial and desired
target states have density matrices with different spectra or if a control
field needs to be designed to optimally transfer different initial states to
the same target state. Recent research works suggest extending coherent control
by including active manipulation of the non-unitary (i.e., incoherent) part of
the evolution. This paper summarizes recent results specifically for incoherent
control by the environment (e.g., incoherent radiation or a gaseous medium)
with a kinematic description of controllability and landscape analysis.


title: Stability of bounded global solutions for Navier-Stokes equations

abstract:
  In this paper some kind of asymptotic behavior of the solutions for the
Navier-Stokes system on abstract Banach spaces is studied under the existence
of global in time solutions. The asymptotic stability of the zero solution is
also shown.


title:
When is star formation episodic? A delay differential equation negative
  feedback model

abstract:
  We introduce a differential equation for star formation in galaxies that
incorporates negative feedback with a delay. When the feedback is
instantaneous, solutions approach a self-limiting equilibrium state. When there
is a delay, even though the feedback is negative, the solutions can exhibit
cyclic and episodic solutions. We find that periodic or episodic star formation
only occurs when two conditions are satisfied. Firstly the delay timescale must
exceed a cloud consumption timescale. Secondly the feedback must be strong.
This statement is quantitatively equivalent to requiring that the timescale to
approach equilibrium be greater than approximately twice the cloud consumption
timescale. The period of oscillations predicted is approximately 4 times the
delay timescale. The amplitude of the oscillations increases with both feedback
strength and delay time.
  We discuss applications of the delay differential equation (DDE) model to
star formation in galaxies using the cloud density as a variable. The DDE model
is most applicable to systems that recycle gas and only slowly remove gas from
the system. We propose likely delay mechanisms based on the requirement that
the delay time is related to the observationally estimated time between
episodic events. The proposed delay timescale accounting for episodic star
formation in galaxy centers on periods similar to P 10 Myrs, irregular galaxies
with P 100 Myrs, and the Milky Way disk with P~ 2Gyr, could be that for
exciting turbulence following creation of massive stars, that for gas pushed
into the halo to return and interact with the disk and that for spiral density
wave evolution, respectively.


title:
Small-scale structure formation properties of chilled sterile neutrinos
  as dark matter

abstract:
  We calculate the free-streaming length and the phase space density of
dark-matter sterile neutrinos produced from decays, at the electroweak scale,
of a gauge singlet in the Higgs sector. These quantities, which depend on the
dark-matter production mechanism, are relevant to the study of small-scale
structure formation and may be used to constrain or rule out dark-matter
candidates.


title: Black Holes in Higher Dimensions

abstract:
  We review black hole solutions of higher-dimensional vacuum gravity, and of
higher-dimensional supergravity theories. The discussion of vacuum gravity is
pedagogical, with detailed reviews of Myers-Perry solutions, black rings, and
solution-generating techniques. We discuss black hole solutions of maximal
supergravity theories, including black holes in anti-de Sitter space. General
results and open problems are discussed throughout.


title: Group actions and rational ideals

abstract:
  We develop the theory of rational ideals for arbitrary associative algebras R
without assuming the standard finiteness conditions, noetherianness or the
Goldie property. The Amitsur-Martindale ring of quotients replaces the
classical ring of quotients which underlies the previous definition of rational
ideals but is not available in a general setting.
  Our main result concerns rational actions of an affine algebraic group G on
R. Working over an algebraically closed base field, we prove an existence and
uniqueness result for generic rational ideals: for every G-rational ideal I of
R, the closed subset of the rational spectrum Rat R that is defined by I is the
closure of a unique G-orbit in Rat R. Under additional Goldie hypotheses, this
was established earlier by Moeglin and Rentschler (in characteristic zero) and
by Vonessen (in arbitrary characteristic), answering a question of Dixmier.


title: A Modified K\"ahler-Ricci Flow

abstract:
  In this note, a modified K\"ahler-Ricci flow is introduced and studied. The
main point is to show the flexibility of K\"ahler-Ricci flow and summarize some
useful techniques.


title: Self-diffusion in binary blends of cyclic and linear polymers

abstract:
  A lattice model is used to estimate the self-diffusivity of entangled cyclic
and linear polymers in blends of varying compositions. To interpret simulation
results, we suggest a minimal model based on the physical idea that constraints
imposed on a cyclic polymer by infiltrating linear chains have to be released,
before it can diffuse beyond a radius of gyration. Both, the simulation, and
recently reported experimental data on entangled DNA solutions support the
simple model over a wide range of blend compositions, concentrations, and
molecular weights.


title: Climbing a Legendrian mountain range without Stabilization

abstract:
  We introduce a new braid-theoretic framework with which to understand the
Legendrian and transversal classification of knots, namely a Legendrian Markov
Theorem without Stabilization which induces an associated transversal Markov
Theorem without Stabilization. We establish the existence of a nontrivial
knot-type specific Legendrian and transversal MTWS by enhancing the Legendrian
mountain range for the (2,3)-cable of a (2,3)-torus knot provided by Etnyre and
Honda, and showing that elementary negative flypes allow us to move toward
maximal tb value without having to use Legendrian stabilization. In doing so we
obtain new ways to visualize convex tori and Legendrian divides and rulings,
using tilings and braided rectangular diagrams.


title: Photoconductivity of an intrinsic graphen

abstract:
  We examine the photoconductivity of an intrinsic graphene associated with
far- and mid-infrared irradiation at low temperatures. The model under
consideration accounts for the excitation of the electron-hole pairs by
incident radiation, the interband generation-recombination transitions due to
thermal radiation, and the intraband energy relaxation due to acoustic phonon
scattering. The momentum relaxation is assumed to be caused by elastic
scattering. The pertinent collision integrals are adapted for the case of the
massless energy spectrum of carriers that interact with the longitudinal
acoustic mode and the thermal radiation. It is found that the photoconductivity
is determined by an interplay between weak energy relaxation and
generation-recombination processes. Due to this the threshold of nonlinear
response is fairly low.


title: Mastering the Master Space

abstract:
  Supersymmetric gauge theories have an important but perhaps under-appreciated
notion of a master space, which controls the full moduli space. For
world-volume theories of D-branes probing a Calabi-Yau singularity X the
situation is particularly illustrative. In the case of one physical brane, the
master space F is the space of F-terms and a particular quotient thereof is X
itself. We study various properties of F which encode such physical quantities
as Higgsing, BPS spectra, hidden global symmetries, etc. Using the plethystic
program we also discuss what happens at higher number N of branes. This letter
is a summary and some extensions of the key points of a longer companion paper
arXiv:0801.1585.


title: Probing the Binary Black Hole Merger Regime with Scalar Perturbations

abstract:
  We present results obtained by scattering a scalar field off the curved
background of a coalescing binary black hole system. A massless scalar field is
evolved on a set of fixed backgrounds, each provided by a spatial hypersurface
generated numerically during a binary black hole merger. We show that the
scalar field scattered from the merger region exhibits quasinormal ringing once
a common apparent horizon surrounds the two black holes. This occurs earlier
than the onset of the perturbative regime as measured by the start of the
quasinormal ringing in the gravitational waveforms. We also use the scalar
quasinormal frequencies to associate a mass and a spin with each hypersurface,
and observe the compatibility of this measure with the horizon mass and spin
computed from the dynamical horizon framework.


title: Hypervelocity Stars: From the Galactic Center to the Halo

abstract:
  Hypervelocity stars (HVS) traverse the Galaxy from the central black hole to
the outer halo. We show that the Galactic potential within 200 pc acts as a
high pass filter preventing low velocity HVS from reaching the halo. To trace
the orbits of HVS throughout the Galaxy, we construct two forms of the
potential which reasonably represent the observations in the range 5--100,000
pc, a simple spherically symmetric model and a bulge-disk-halo model. We use
the Hills mechanism (disruption of binaries by the tidal field of the central
black hole) to inject HVS into the Galaxy and compute the observable spatial
and velocity distributions of HVS with masses in the range 0.6--4 Msun. These
distributions reflect the mass function in the Galactic Center, properties of
binaries in the Galactic Center, and aspects of stellar evolution and the
injection mechanism. For 0.6--4 Msun main sequence stars, the fraction of
unbound HVS and the asymmetry of the velocity distribution for their bound
counterparts increases with stellar mass. The density profiles for unbound HVS
decline with distance from the Galactic Center approximately as r^{-2} (but are
steeper for the most massive stars which evolve off the main sequence during
their travel time from the Galactic Center); the density profiles for the bound
ejecta decline with distance approximately as r^{-3}. In a survey with a
limiting visual magnitude V of 23, the detectability of HVS (unbound or bound)
increases with stellar mass.


title:
L-infinity algebra connections and applications to String- and
  Chern-Simons n-transport

abstract:
  We give a generalization of the notion of a Cartan-Ehresmann connection from
Lie algebras to L-infinity algebras and use it to study the obstruction theory
of lifts through higher String-like extensions of Lie algebras. We find
(generalized) Chern-Simons and BF-theory functionals this way and describe
aspects of their parallel transport and quantization.
  It is known that over a D-brane the Kalb-Ramond background field of the
string restricts to a 2-bundle with connection (a gerbe) which can be seen as
the obstruction to lifting the PU(H)-bundle on the D-brane to a U(H)-bundle. We
discuss how this phenomenon generalizes from the ordinary central extension
U(1) -> U(H) -> PU(H) to higher categorical central extensions, like the
String-extension BU(1) -> String(G) -> G. Here the obstruction to the lift is a
3-bundle with connection (a 2-gerbe): the Chern-Simons 3-bundle classified by
the first Pontrjagin class. For G = Spin(n) this obstructs the existence of a
String-structure. We discuss how to describe this obstruction problem in terms
of Lie n-algebras and their corresponding categorified Cartan-Ehresmann
connections. Generalizations even beyond String-extensions are then
straightforward. For G = Spin(n) the next step is "Fivebrane structures" whose
existence is obstructed by certain generalized Chern-Simons 7-bundles
classified by the second Pontrjagin class.


title:
Inhomogeneous Magnetic-Field Response of YBa2Cu3Oy and La2-xSrxCuO4
  Persisting above the Bulk Superconducting Transition Temperature

abstract:
  We report that in YBa2Cu3Oy and La2-xSrxCuO4 there is a spatially
inhomogeneous response to magnetic field for temperatures T extending well
above the bulk superconducting transition temperature Tc. An inhomogeneous
magnetic response is observed above Tc even in ortho-II YBa2Cu3O6.50, which has
highly ordered doping. The degree of the field inhomogeneity above Tc tracks
the hole doping dependences of both Tc and the density of the superconducting
carriers below Tc, and therefore is apparently coupled to superconductivity.


title:
Detecting quasars at very high redshift with next generation X-ray
  telescopes

abstract:
  The next generation of X-ray telescopes have the potential to detect faint
quasars at very high redshift and probe the early growth of massive black holes
(BHs). We present modelling of the evolution of the optical and X-ray AGN
luminosity function at 2 < z < 6 based on a CDM merger-driven model for the
triggering of nuclear activity combined with a variety of fading laws. We
extrapolate the merger-driven models to z > 6 for a range of BH growth
scenarios. We predict significant numbers of sources at z ~ 6 with fluxes just
an order of magnitude below the current detection limits and thus detectable
with XEUS and Constellation-X, relatively independently of the fading law
chosen. The predicted number of sources at even higher redshift depends
sensitively on the early growth history of BHs. For passive evolution models in
which BHs grow constantly at their Eddington limit, detectable BHs may be rare
beyond z ~ 10 even with Generation-X. However, in the more probable scenario
that BH growth at z > 6 can be described by passive evolution with a small duty
cycle, or by our merger driven accretion model, then we predict that XEUS and
Generation-X will detect significant numbers of black holes out to z ~ 10 and
perhaps beyond.


title:
Mott transition and superconductivity in the strongly correlated organic
  superconductor $\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}]$Br

abstract:
  The magnetic field effect on the phase diagram of the organic Mott system
$\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br in which the bandwidth was tuned by
the substitution of deuterated molecules was studied by means of the
resistivity measurements performed in magnetic fields. The lower critical point
of the first-order Mott transition, which ended on the upper critical field
$H_{\rm c2}$-temperature plane of the superconductivity, was determined
experimentally in addition to the previously observed upper critical end point.
The lower critical end point moved to a lower temperature with the suppression
of $T_{\rm c}$ in magnetic fields and the Mott transition recognized so far as
the $S$-shaped curve reached $T =$ 0 when $H > H_{\rm c2}$ in the end.


title: Toroidal Crystals

abstract:
  Crystalline assemblages of identical sub-units packed together and
elastically bent in the form of a torus have been found in the past ten years
in a variety of systems of surprisingly different nature, such as viral
capsids, self-assembled monolayers and carbon nanomaterials. In this Letter we
analyze the structural properties of toroidal crystals and we provide a unified
description based on the elastic theory of defects in curved geometries. We
find ground states characterized by the presence of 5-fold disclinations on the
exterior of the torus and 7-fold disclinations in the interior. The number of
excess disclinations is controlled primarily by the aspect ratio of the torus,
suggesting a novel mechanism for creating toroidal templates with precisely
controlled valency via functionalization of the defect sites.


title:
The Correlation Function of Optically Selected Galaxy Clusters in the
  Sloan Digital Sky Survey

abstract:
  We measure the two-point spatial correlation function for clusters selected
from the photometric MaxBCG galaxy cluster catalog for the Sloan Digital Sky
Survey (SDSS). We evaluate the correlation function for several cluster samples
using different cuts in cluster richness. Fitting the results to power-laws,
$\xi_{cc}(r) = (r/R_0)^{-\gamma}$, the estimated correlation length $R_0$ as a
function of richness is broadly consistent with previous cluster observations
and with expectations from N-body simulations. We study how the linear bias
parameter scales with richness and compare our results to theoretical
predictions. Since these measurements extend to very large scales, we also
compare them to models that include the baryon acoustic oscillation feature and
that account for the smoothing effects induced by errors in the cluster
photometric redshift estimates. For the largest cluster sample, corresponding
to a richness threshold of $\Ng\ge 10$, we find only weak evidence, of about
$1.4-1.7\sigma$ significance, for the baryonic acoustic oscillation signature
in the cluster correlation function.


title: A Clean Slepton Mixing Signal at the LHC

abstract:
  In supersymmetric scenarios where the scalar tau lepton is stable or
long-lived, a search for a decay mode chi0 --> stau + mu at the LHC has a good
sensitivity to the flavor mixing in the scalar lepton sector. We demonstrate
that the sensitivities to the mixing angle at the level of sin(theta)=0.15 are
possible with an integrated luminosity of 100fb^{-1} if the total production
cross section of supersymmetric particles is of the order of 1pb. The
sensitivity to the mixing parameter can be better than the experimental bound
from the tau --> mu + gamma decay depending on model parameters.


title: Rayleigh's Stretched String

abstract:
  We obtain rigorous a priori upper and lower bounds to the exact period of the
celebrated Rayleigh stretched string differential equation.


title: First Images of R Aquarii and its Asymmetric H$_{2}$O Shell

abstract:
  We report imaging observations of the symbotic long-period Mira variable R
Aquarii (R Aqr) at near-infrared and radio wavelengths. The near-infrared
observations were made with the IOTA imaging interferometer in three
narrow-band filters centered at 1.51, 1.64, and 1.78 $\mu$m, which sample
mainly water, continuum, and water features, respectively. Our near-infrared
fringe visibility and closure phase data are analyzed using three models. (a) A
uniform disk model with wavelength-dependent sizes fails to fit the visibility
data, and is inconsistent with the closure phase data. (b) A three- component
model, comprising a Mira star, water shell, and an off-axis point source,
provide a good fit to all data. (c) A model generated by a constrained image
reconstruction analysis provides more insight, suggesting that the water shell
is highly non-uniform, i.e., clumpy. The VLBA observations of SiO masers in the
outer molecular envelope show evidence of turbulence, with jet-like features
containing velocity gradients.


title:
Particle separation by Stokes number for small neutrally buoyant spheres
  in a fluid

abstract:
  It is a commonly observed phenomenon that spherical particles with inertia in
an incompressible fluid do not behave as ideal tracers. Due to the inertia of
the particle, the dynamics are described in a four dimensional phase space and
thus can differ considerably from the ideal tracer dynamics. Using finite time
Lyapunov exponents we compute the sensitivity of the final position of a
particle with respect to its initial velocity, relative to the fluid and thus
partition the relative velocity subspace at each point in configuration space.
The computations are done at every point in the relative velocity subspace,
thus giving a sensitivity field. The Stokes number being a measure of the
independence of the particle from the underlying fluid flow, acts as a
parameter in determining the variation in these partitions. We demonstrate how
this partition framework can be used to segregate particles by Stokes number in
a fluid. The fluid model used for demonstration is a two dimensional cellular
flow.


title:
Beyond Thresholding: Analysis and Improvements for Deterministic
  Parameter Estimation

abstract:
  Hard-threshold estimators are popular in signal processing applications. We
provide a detailed study of using hard-threshold estimators for estimating an
unknown deterministic signal when additive white Gaussian noise corrupts
observations. The analysis, depending heavily on Cram{\'e}r-Rao bounds,
motivates piecewise-linear estimation as a simple improvement to hard
thresholding. We compare the performance of two piecewise-linear estimators to
a hard-threshold estimator. When either piecewise-linear estimator is optimized
for the decay rate of the basis coefficients, its performance is better than
the best possible with hard thresholding.


title: How to Evade a No-Go Theorem in Flavor Symmetries

abstract:
  A no-go theorem in flavor symmetries is reviewed. The theorem asserts that we
cannot bring any flavor symmetry into mass matrix model in which number of
Higgs scalars is, at most, one for each sector (e.g. H_u and H_d for up- and
down-quark sectors, respectively). Such the strong constraint comes from the
SU(2)_L symmetry. Possible three options to evade the theorem are discussed.


title: On the appearance of Eisenstein series through degeneration

abstract:
  Let $\Gamma$ be a Fuchsian group of the first kind acting on the hyperbolic
upper half plane $\mathbb H$, and let $M = \Gamma \backslash \mathbb H$ be the
associated finite volume hyperbolic Riemann surface. If $\gamma$ is parabolic,
there is an associated (parabolic) Eisenstein series, which, by now, is a
classical part of mathematical literature. If $\gamma$ is hyperbolic, then,
following ideas due to Kudla-Millson, there is a corresponding hyperbolic
Eisenstein series. In this article, we study the limiting behavior of parabolic
and hyperbolic Eisenstein series on a degenerating family of finite volume
hyperbolic Riemann surfaces. In particular, we prove the following result. If
$\gamma \in \Gamma$ corresponds to a degenerating hyperbolic element, then a
multiple of the associated hyperbolic Eisenstein series converges to parabolic
Eisenstein series on the limit surface.


title:
Linear-Optical Implementation of Perfect Discrimination between
  Single-bit Unitary Operations

abstract:
  Discrimination of unitary operations is a fundamental quantum information
processing task. Assisted with linear optical elements, we experimentally
demonstrate perfect discrimination between single-bit unitary operations using
two methods--sequential scheme and parallel scheme. The complexity and resource
consumed in these two schemes are analyzed and compared.


title:
Direct evidence for inversion formula in multifractal financial
  volatility measure

abstract:
  The inversion formula for conservative multifractal measures was unveiled
mathematically a decade ago, which is however not well tested in real complex
systems. In this Letter, we propose to verify the inversion formula using
high-frequency turbulent financial data. We construct conservative volatility
measure based on minutely S&P 500 index from 1982 to 1999 and its inverse
measure of exit time. Both the direct and inverse measures exhibit nice
multifractal nature, whose scaling ranges are not irrelevant. Empirical
investigation shows that the inversion formula holds in financial markets.


title:
s-wave Superconductivity due to Suhl-Kondo Mechanism in
  Na$_x$CoO$_2\cdot y$H$_2$O: Effect of Coulomb Interaction and Trigonal
  Distortion

abstract:
  To study the electron-phonon mechanism of superconductivity in NaxCoO2, we
perform semiquantitative analysis of the electron-phonon interaction (EPI)
between relevant optical phonons (breathing and shear phonons) and t_{2g}
electrons (a_{1g} and e_g' electrons) in the presence of trigonal distortion.
We consider two kinds of contributions to the EPI; the EPI originating from the
Coulomb potential of O ions and that originating from the d-p transfer integral
between Co and O in CoO_6 octahedron. We find that the EPI for shear phonons,
which induces the interorbital hopping of electrons, is large in NaxCoO_2
because of the trigonal distortion of CoO_2 layer. For this reason, Tc for
s-wave pairing is prominently enlarged owing to interorbital hopping of Cooper
pairs induced by shear phonons, even if the top of e_g' electron band is close
to but below the Fermi level as suggested experimentally. This mechanism of
superconductivity is referred to as the valence-band Suhl-Kondo (SK) mechanism.
Since the SK mechanism is seldom damaged by the Coulomb repulsion, s-wave
superconductivity is realized irrespective of large Coulomb interaction U~5 eV
at Co sites. We also study the oxygen isotope effect on Tc, and find that it
becomes very small due to strong Coulomb interaction. Finally, we discuss the
possible mechanism of anisotropic s-wave superconducting state in NaxCoO2,
resulting from the coexistence of strong EPI and the antiferromagnetic
fluctuations.


title: f(R) Quantum Cosmology

abstract:
  We have quantized a flat cosmological model in the context of the metric f(R)
models, using the causal Bohmian quantum theory. The equations are solved and
then we have obtained how the quantum corrections influence the classical
equations.


title: A Commentary on Ruppeiner Metrics for Black Holes

abstract:
  There has been some recent controversy regarding the Ruppeiner metrics that
are induced by Reissner-Nordstrom (and Reissner-Nordstrom-like) black holes.
Most infamously, why does this family of metrics turn out to be flat, how is
this outcome to be physically understood, and can/should the formalism be
suitably modified to induce curvature? In the current paper, we provide a novel
interpretation of this debate. For the sake of maximal analytic clarity and
tractability, some supporting calculations are carried out for the relatively
simple model of a rotating BTZ black hole.


title: Tachyon Condensation on Separated Brane-Antibrane System

abstract:
  We study the effect of tachyon condensation on a brane antibrane pair in
superstring theory separated in the transverse direction. The static properties
of the tachyon potential analyzed using level truncated string field theory
reproduces the desired property that the dependence of the minimum value of the
potential on the initial distance of separation between the branes decreases as
we include higher level terms. The rolling tachyon solution constructed using
the conformal field theory methods shows that if the initial separation between
the branes is less than a critical distance then the solution is described by
an exactly marginal deformation of the original conformal field theory where
the correlation functions of the deformed theory are determined completely in
terms of the correlation functions of the undeformed theory without any need to
regularize the theory. Using this we give an expression for the pressure on the
brane-antibrane system as a power series expansion in \exp(C x^0) for an
appropriate constant C.


title: Sheaves on local Calabi-Yau varieties

abstract:
  We investigate sheaves supported on the zero section of the total space of a
locally-free sheaf E on a smooth, projective variety X when the top exterior
power of E is isomorphic to the canonical bundle of X. We rephrase this
construction using the language of A-infinity algebra and provide a simple
characterisation of the case E is simply the canonical bundle itself.


title:
Construction and solution of a Wannier-functions based Hamiltonian in
  the pseudopotential plane-wave framework for strongly correlated materials

abstract:
  Ab initio determination of model Hamiltonian parameters for strongly
correlated materials is a key issue in applying many-particle theoretical tools
to real narrow-band materials. We propose a self-contained calculation scheme
to construct, with an ab initio approach, and solve such a Hamiltonian. The
scheme uses a Wannier-function-basis set, with the Coulomb interaction
parameter U obtained specifically for these Wannier functions via constrained
Density functional theory (DFT) calculations. The Hamiltonian is solved by
Dynamical Mean-Field Theory (DMFT) with the effective impurity problem treated
by the Quantum Monte Carlo (QMC) method. Our scheme is based on the
pseudopotential plane-wave method, which makes it suitable for developments
addressing the challenging problem of crystal structural relaxations and
transformations due to correlation effects. We have applied our scheme to the
"charge transfer insulator" material nickel oxide and demonstrate a good
agreement with the experimental photoemission spectra.


title: Observations of time delayed all-optical routing in a slow light regime

abstract:
  We report an observation of a delayed all-optical routing/switching
phenomenon based on ultraslow group velocity of light via nondegenerate
four-wave mixing processes in a defected solid medium. Unlike previous
demonstrations of enhanced four-wave mixing processes using the slow light
effects, the present observation demonstrates a direct retrieval of the
resonant Raman-pulse excited spin coherence into photon coherence through
coherence conversion processes.


title: Strong Localization of Positive Charge in DNA

abstract:
  Microscopic mechanisms of positive charge transfer in DNA remain unclear. A
quantum state of electron hole in DNA is determined by the competition of a
pi-stacking interaction $b$ smearing a charge between different base pairs and
interaction $\lambda$ with the local environment which attempts to trap charge.
To determine which interaction dominates we investigated charge quantum states
in various $(GC)_{n}$ sequences choosing DNA parameters satisfying experimental
data for the balance of charge transfer rates $G^{+} \leftrightarrow
G_{n}^{+}$, $n=2,3$ \cite{FredMain}. We show that experimental data can be
consistent with theory only under an assumption $b\ll \lambda$ meaning that
charge is typically localized within a single $G$ site. Consequently any DNA
sequence including the one consisting of identical base pairs behaves more like
an insulating material than a molecular conductor.


title: On Number of Nflation Fields

abstract:
  We study the Nflation model, in which a collection of massive scalar fields
drive the inflation simultaneously. We find, when the number of fields is
larger than the square of ratio of the Planck scale $M_p$ to the average value
$\bar m$ of fields masses, the slow roll inflation region will disappear. This
suggests that in order to make Nflation responsible for our observable
universe, the number of fields driving the Nflation must be bounded by the
above ratio. This result is also consistent with recent arguments from black
hole physics.


title: Perelman's W-functional and stability of K\"ahler-Ricci flow

abstract:
  In this expository note, we study the second variation of Perelman's entropy
on the space of Kahler metrics at a K\"ahler-Ricci soliton. We prove that the
entropy is stable in the sense of variations. In particular, Perelman's entropy
is stable along the K\"ahler-Ricci flow. The Chinese version of this note has
appeared in a volume in honor of professor K.C.Chang (Scientia Sinica Math., 46
(2016), 685-696).


title:
Harmonic Analysis of Stochastic Equations and Backward Stochastic
  Differential Equations

abstract:
  The BMO martingale theory is extensively used to study nonlinear
multi-dimensional stochastic equations (SEs) in $\cR^p$ ($p\in [1, \infty)$)
and backward stochastic differential equations (BSDEs) in $\cR^p\times \cH^p$
($p\in (1, \infty)$) and in $\cR^\infty\times \bar{\cH^\infty}^{BMO}$, with the
coefficients being allowed to be unbounded. In particular, the probabilistic
version of Fefferman's inequality plays a crucial role in the development of
our theory, which seems to be new. Several new results are consequently
obtained. The particular multi-dimensional linear case for SDEs and BSDEs are
separately investigated, and the existence and uniqueness of a solution is
connected to the property that the elementary solutions-matrix for the
associated homogeneous SDE satisfies the reverse H\"older inequality for some
suitable exponent $p\ge 1$. Finally, we establish some relations between
Kazamaki's quadratic critical exponent $b(M)$ of a BMO martingale $M$ and the
spectral radius of the solution operator for the $M$-driven SDE, which lead to
a characterization of Kazamaki's quadratic critical exponent of BMO martingales
being infinite.


title: Some results for the Perelman LYH-type inequality

abstract:
  Let $(M,g(t))$, $0\le t\le T$, $\partial M\ne\phi$, be a compact
$n$-dimensional manifold, $n\ge 2$, with metric $g(t)$ evolving by the Ricci
flow such that the second fundamental form of $\partial M$ with respect to the
unit outward normal of $\partial M$ is uniformly bounded below on $\partial
M\times [0,T]$. We will prove a global Li-Yau gradient estimate for the
solution of the generalized conjugate heat equation on $M\times [0,T]$. We will
give another proof of Perelman's Li-Yau-Hamilton type inequality for the
fundamental solution of the conjugate heat equation on closed manifolds without
using the properties of the reduced distance. We will also prove various
gradient estimates for the Dirichlet fundamental solution of the conjugate heat
equation.


title: Dynamical solution of supergravity

abstract:
  We present a class of dynamical solutions for an intersecting D4-D8 brane
system in ten-dimensional type IIA supergravity. The dynamical solutions
reduces to a static warped AdS_6 x S^4 geometry in a certain spacetime region.
We also consider lower-dimensional effective theories for the warped
compactification of general p-brane system. It is found that an effective
(p+1)-dimensional description is not possible in general due to the
entanglement of the transverse coordinates and the (p+1)-dimensional
coordinates in the metric components. Then we discuss cosmological solutions.
We find a solution that behaves like a Kasner-type cosmological solution at
$\tau\to\infty$, while it reduces to a warped static solution at $\tau\to0$,
where $\tau$ is the cosmic time.


title: The Gravisphere Method Algorithm Programming

abstract:
  The action sphere method program is written. The initial conditions set at
pericenter of planetocentric orbits. When action sphere radius is reached, the
heliocentric orbit is calculated and data redirected to numeric integration
program. The method is useful for capture and collision problem investigation.
The very preliminary numeric results were obtained and discussed. A manifold in
orbital elements space, leads to temporary capture about 50 year (4 Jupiter
revolutions), was found.


title:
Growth of a One Dimensional Quasiperiodic Covering with Locally
  Determined Decorations

abstract:
  A growth mechanism for a perfect one-dimensional (1D) quasiperiodic structure
is presented with a local covering rule. We use rectangular tiles with two
different types of string decorations. The string position in a tile is allowed
to move when the tile is attached to an existing patch. By adjusting the
position properly with local information, we show that a growth of perfect
quasiperiodic structure is possible. This observation may provide new insight
into how quasicrystals grow with perfect quasiperiodic order.


title:
Polarization and frequency disentanglement of photons via stochastic
  polarization mode dispersion

abstract:
  We investigate the quantum decoherence of frequency and polarization
variables of photons via polarization mode dispersion in optical fibers. By
observing the analogy between the propagation equation of the field and the
Schr\"odinger equation, we develop a master equation under Markovian
approximation and analytically solve for the field density matrix. We identify
distinct decay behaviors for the polarization and frequency variables for
single-photon and two-photon states. For the single photon case, purity
functions indicate that complete decoherence for each variable is possible only
for infinite fiber length. For entangled two-photon states passing through
separate fibers, entanglement associated with each variable can be completely
destroyed after characteristic finite propagation distances. In particular, we
show that frequency disentanglement is independent of the initial polarization
status. For propagation of two photons in a common fiber, the evolution of a
polarization singlet state is addressed. We show that while complete
polarization disentanglement occurs at a finite propagation distance, frequency
entanglement could survive at any finite distance for gaussian states.


title:
Deterministic Design of Low-Density Parity-Check Codes for Binary
  Erasure Channels

abstract:
  We propose a deterministic method to design irregular Low-Density
Parity-Check (LDPC) codes for binary erasure channels (BEC). Compared to the
existing methods, which are based on the application of asymptomatic analysis
tools such as density evolution or Extrinsic Information Transfer (EXIT) charts
in an optimization process, the proposed method is much simpler and faster.
Through a number of examples, we demonstrate that the codes designed by the
proposed method perform very closely to the best codes designed by
optimization. An important property of the proposed designs is the flexibility
to select the number of constituent variable node degrees P. The proposed
designs include existing deterministic designs as a special case with P = N-1,
where N is the maximum variable node degree. Compared to the existing
deterministic designs, for a given rate and a given d > 0, the designed
ensembles can have a threshold in d-neighborhood of the capacity upper bound
with smaller values of P and N. They can also achieve the capacity of the BEC
as N, and correspondingly P and the maximum check node degree tend to infinity.


title: Admissible local systems for a class of line arrangements

abstract:
  A rank one local system $\LL$ on a smooth complex algebraic variety $M$ is
admissible roughly speaking if the dimension of the cohomology groups
$H^m(M,\LL)$ can be computed directly from the cohomology algebra $H^*(M,\C)$.
  We say that a line arrangement $\A$ is of type $\CC_k$ if $k \ge 0 $ is the
minimal number of lines in $\A$ containing all the points of multiplicity at
least 3. We show that if $\A$ is a line arrangement in the classes $\CC_k$ for
$k\leq 2$, then any rank one local system $\LL$ on the line arrangement
complement $M$ is admissible. Partial results are obtained for the class
$\CC_3$.


title:
On some difficulties with a posterior probability approximation
  technique

abstract:
  In Scott (2002) and Congdon (2006), a new method is advanced to compute
posterior probabilities of models under consideration. It is based solely on
MCMC outputs restricted to single models, i.e., it is bypassing reversible jump
and other model exploration techniques. While it is indeed possible to
approximate posterior probabilities based solely on MCMC outputs from single
models, as demonstrated by Gelfand and Dey (1994) and Bartolucci et al. (2006),
we show that the proposals of Scott (2002) and Congdon (2006) are biased and
advance several arguments towards this thesis, the primary one being the
confusion between model-based posteriors and joint pseudo-posteriors. From a
practical point of view, the bias in Scott's (2002) approximation appears to be
much more severe than the one in Congdon's (2006), the later being often of the
same magnitude as the posterior probability it approximates, although we also
exhibit an example where the divergence from the true posterior probability is
extreme.


title:
Light Deflection, Lensing, and Time Delays from Gravitational Potentials
  and Fermat's Principle in the Presence of a Cosmological Constant

abstract:
  The contribution of the cosmological constant to the deflection angle and the
time delays are derived from the integration of the gravitational potential as
well as from Fermat's Principle. The findings are in agreement with recent
results using exact solutions to Einstein's equations and reproduce precisely
the new $\Lambda$-term in the bending angle and the lens equation. The
consequences on time delay expressions are explored. While it is known that
$\Lambda$ contributes to the gravitational time delay, it is shown here that a
new $\Lambda$-term appears in the geometrical time delay as well. Although
these newly derived terms are perhaps small for current observations, they do
not cancel out as previously claimed. Moreover, as shown before, at galaxy
cluster scale, the $\Lambda$ contribution can be larger than the second-order
term in the Einstein deflection angle for several cluster lens systems.


title: Photon-assistant Fano resonance in coupled multiple quantum dots

abstract:
  Based on calculations of the electronic structure of coupled multiple quantum
dots, we study systemically the transport properties of the system driven by an
ac electric field. We find qualitative difference between transport properties
of double coupled quantum dots (DQDs) and triple quantum dots. For both
symmetrical and asymmetrical configurations of coupled DQDs, the field can
induce the photon-assisted Fano resonances in current-AC frequency curve in
parallel DQDs, and a symmetric resonance in serial DQDs. For serially coupled
triple quantum dots(STQDs), it is found that the $\Lambda$-type energy level
has remarkable impact on the transport properties. For an asymmetric (between
left and right dots) configuration, there is a symmetric peak due to resonant
photon induced mixing between left/right dot and middle dot. In the symmetric
configuration, a Fano asymmetric line shape appears with the help of ``trapping
dark state". Here the interesting coherent trapping phenomena, which usual
appear in quantum optics, play an essential role in quantum electronic
transport. We provide a clear physics picture for the Fano resonance and
convenient ways to tune the Fano effects.


title:
Gamma-rays from binary system with energetic pulsar and Be star with
  aspherical wind: PSR B1259-63/SS2883

abstract:
  At least one massive binary system containing an energetic pulsar, PSR
B1259-63/SS2883, has been recently detected in the TeV gamma-rays by the HESS
telescopes. These gamma-rays are likely produced by particles accelerated in
the vicinity of the pulsar and/or at the pulsar wind shock, in comptonization
of soft radiation from the massive star. However, the process of gamma-ray
production in such systems can be quite complicated due to the anisotropy of
the radiation field, complex structure of the pulsar wind termination shock and
possible absorption of produced gamma-rays which might initiate leptonic
cascades. In this paper we consider in detail all these effects. We calculate
the gamma-ray light curves and spectra for different geometries of the binary
system PSR B1259-63/SS2883 and compare them with the TeV gamma-ray
observations. We conclude that the leptonic IC model, which takes into account
the complex structure of the pulsar wind shock due to the aspherical wind of
the massive star, can explain the details of the observed gamma-ray light
curve.


title: Theory of Domain Wall Dynamics under Current

abstract:
  Microscopic theory of domain wall dynamics under electric current is
reviewed. Domain wall is treated as rigid and planar. The spin-transfer torque
and forces on the wall are derived based on the $s$-$d$ exchange interaction
between localized spins and conduction electrons, treating non-adiabaticity
expressed by the gauge field perturbatively. Effect of spin relaxation is also
studied.


title:
Approximate l-state solutions of the D-dimensional Schrodinger equation
  for Manning-Rosen potential

abstract:
  The Schr\"{o}dinger equation in $D$-dimensions for the Manning-Rosen
potential with the centrifugal term is solved approximately to obtain bound
states eigensolutions (eigenvalues and eigenfunctions). The
Nikiforov-Uvarov(NU) method is used in the calculations. We present numerical
calculations of energy eigenvalues to two- and four-dimensional systems for
arbitrary quantum numbers $n$ and $l$ with three different values of the
potential parameter $\alpha .$ It is shown that because of the interdimensional
degeneracy of eigenvalues, we can also reproduce eigenvalues of a upper/lower
dimensional sytem from the well-known eigenvalues of a lower/upper dimensional
system by means of the transformation $(n,l,D)\to (n,l\pm 1,D\mp 2)$. This
solution reduces to the Hulth\'{e}n potential case.


title:
Non-commutative geometry inspired higher-dimensional charged, black
  holes

abstract:
  We obtain a new, exact, solution of the Einstein's equation in higher
dimensions. The source is given by a static spherically symmetric, Gaussian
distribution of mass and charge. De-localization of mass and charge is due to
the presence of a "minimal length" in the spacetime fabric, coming from quantum
gravitational effects, e.g. string induced non-commutative geometry. The
resulting metric describes a regular, i.e. curvature singularity free, charged
black hole in higher dimensions. The metric smoothly interpolates between
Reissner-Nordstrom geometry at large distance, and deSitter spacetime at short
distance. Thermodynamical properties of the black hole are investigated and the
form of the Area Law is determined. We show that back reaction effects are
negligible even near the temperature maximum for any reasonable number of extra
dimensions. We study pair creation and show that the upper bound on the
discharge time increases with the number of extra dimensions.


title: The norm game in a mean-field society

abstract:
  Mean field Master equations for the norm game are investigated. The
strategies are: to obey the norm or not and to punish those who break it or
not. The punishment, the temptation, the punishment cost and the relaxation of
vengeance are modeled by four parameters; for the fixed points, only two ratios
of these parameters are relevant. The analysis reveals two phases; in one of
them, nobody obeys the norm and nobody punishes. This phase is stable if the
punishment is small enough. In the other phase, the proportion of defectors
depends on the parameters and in some cases it can be arbitrarily small. A
transcritical bifurcation appears between the two phases. Numerical
calculations show that the relaxation time shows a sharp maximum at the
bifurcation point. The model is adapted also for the case of two mutually
punishing groups. A difference between the solutions for two groups appears if
the punishment of one group by the other is weaker, than the opposite.


title: Capacity of Sparse Wideband Channels with Partial Channel Feedback

abstract:
  This paper studies the ergodic capacity of wideband multipath channels with
limited feedback. Our work builds on recent results that have established the
possibility of significant capacity gains in the wideband/low-SNR regime when
there is perfect channel state information (CSI) at the transmitter.
Furthermore, the perfect CSI benchmark gain can be obtained with the feedback
of just one bit per channel coefficient. However, the input signals used in
these methods are peaky, that is, they have a large peak-to-average power
ratios. Signal peakiness is related to channel coherence and many recent
measurement campaigns show that, in contrast to previous assumptions, wideband
channels exhibit a sparse multipath structure that naturally leads to coherence
in time and frequency. In this work, we first show that even an instantaneous
power constraint is sufficient to achieve the benchmark gain when perfect CSI
is available at the receiver. In the more realistic non-coherent setting, we
study the performance of a training-based signaling scheme. We show that
multipath sparsity can be leveraged to achieve the benchmark gain under both
average as well as instantaneous power constraints as long as the channel
coherence scales at a sufficiently fast rate with signal space dimensions. We
also present rules of thumb on choosing signaling parameters as a function of
the channel parameters so that the full benefits of sparsity can be realized.


title: On the Decay of Soliton Excitations

abstract:
  In field theory the scattering about spatially extended objects, such as
solitons, is commonly described by small amplitude fluctuations. Since soliton
configurations often break internal symmetries, excitations exist that arise
from quantizing the modes that are introduced to restore these symmetries.
These modes represent collective distortions and cannot be treated as small
amplitude fluctuations. Here we present a method to embrace their contribution
to the scattering matrix. In essence this allows us to compute the decay widths
of such collective excitations. As an example we consider the Skyrme model for
baryons and explain that the method helps to solve the long--standing Yukawa
problem in chiral soliton models.


title: Nonlinear Schr\"odinger equation on real hyperbolic spaces

abstract:
  We consider the Schr\"odinger equation with no radial assumption on real
hyperbolic spaces. We obtain sharp dispersive and Strichartz estimates for a
large family of admissible pairs. As a first consequence, we get strong
well-posedness results for NLS. Specifically, for small intial data, we prove
$L^2$ and $H^1$ global well-posedness for any subcritical nonlinearity (in
contrast with the Euclidean case) and with no gauge invariance assumption on
the nonlinearity $F$. On the other hand, if $F$ is gauge invariant, $L^2$
charge is conserved and hence, as in the Euclidean case, it is possible to
extend local $L^2$ solutions to global ones. The corresponding argument in
$H^1$ requires the conservation of energy, which holds under the stronger
condition that $F$ is defocusing. Recall that global well-posedness in the
gauge invariant case was already proved by Banica, Carles & Staffilani, for
small radial $L^2$ data and for large radial $H^1$ data. The second important
application of our global Strichartz estimates is "scattering" for NLS both in
$L^2$ and in $H^1$, with no radial or gauge invariance assumption. Notice that,
in the Euclidean case, this is only possible for the critical power
$\gamma=1+\frac4n$ and can be false for subcritical powers while, on hyperbolic
spaces, global existence and scattering of small $L^2$ solutions holds for all
powers $1<\gamma\le1+\frac4n$. If we restrict to defocusing nonlinearities $F$,
we can extend the $H^1$ scattering results of Banica, Carles & Staffilani to
the nonradial case. Also there is no distinction anymore between short range
and long range nonlinearity : the geometry of hyperbolic spaces makes every
power-like nonlinearity short range.


title:
Tuning Coherent Radiative Thermal Conductance in Multilayer Photonic
  Crystals

abstract:
  We consider coherent radiative thermal conductance of a multilayer photonic
crystal. The crystal consists of alternating layers of lossless dielectric
slabs and vacuum, where heat is conducted only through photons. We show that
such a structure can have thermal conductance below vacuum over the entire high
temperature range, due to the presence of partial band gap in most of the
frequency range, as well as the suppression of evanescent tunneling between
slabs at higher frequencies. The thermal conductance of this structure is
highly tunable by varying the thickness of the vacuum layers.


title:
UV excess measures of accretion onto young very low-mass stars and brown
  dwarfs

abstract:
  Low-resolution spectra from 3000-9000 AA of young low-mass stars and brown
dwarfs were obtained with LRIS on Keck I. The excess UV and optical emission
arising in the Balmer and Paschen continua yields mass accretion rates ranging
from 2e-12 to 1e-8 Mo/yr. These results are compared with {\it HST}/STIS
spectra of roughly solar-mass accretors with accretion rates that range from
2e-10 to 5e-8 Mo/yr. The weak photospheric emission from M-dwarfs at <4000 A
leads to a higher contrast between the accretion and photospheric emission
relative to higher-mass counterparts. The mass accretion rates measured here
are systematically 4-7 times larger than those from H-alpha emission line
profiles, with a difference that is consistent with but unlikely to be
explained by the uncertainty in both methods. The accretion luminosity
correlates well with many line luminosities, including high Balmer and many He
I lines. Correlations of the accretion rate with H-alpha 10% width and line
fluxes show a large amount of scatter. Our results and previous accretion rate
measurements suggest that accretion rate is proportional to M^(1.87+/-0.26) for
accretors in the Taurus Molecular Cloud.


title:
Quantized Multimode Precoding in Spatially Correlated Multi-Antenna
  Channels

abstract:
  Multimode precoding, where the number of independent data-streams is adapted
optimally, can be used to maximize the achievable throughput in multi-antenna
communication systems. Motivated by standardization efforts embraced by the
industry, the focus of this work is on systematic precoder design with
realistic assumptions on the spatial correlation, channel state information
(CSI) at the transmitter and the receiver, and implementation complexity. For
spatial correlation of the channel matrix, we assume a general channel model,
based on physical principles, that has been verified by many recent measurement
campaigns. We also assume a coherent receiver and knowledge of the spatial
statistics at the transmitter along with the presence of an ideal, low-rate
feedback link from the receiver to the transmitter. The reverse link is used
for codebook-index feedback and the goal of this work is to construct precoder
codebooks, adaptable in response to the statistical information, such that the
achievable throughput is significantly enhanced over that of a fixed,
non-adaptive, i.i.d. codebook design. We illustrate how a codebook of
semiunitary precoder matrices localized around some fixed center on the
Grassmann manifold can be skewed in response to the spatial correlation via
low-complexity maps that can rotate and scale submanifolds on the Grassmann
manifold. The skewed codebook in combination with a lowcomplexity statistical
power allocation scheme is then shown to bridge the gap in performance between
a perfect CSI benchmark and an i.i.d. codebook design.


title: Corrections to Gravity due to a Sol Manifold Extra Dimensional Space

abstract:
  The corrections to the gravitational potential due to a Sol extra dimensional
compact manifold, denoted as $M_A^3$, are studied. The total spacetime is of
the form $M^4\times M_A^3$. The range of the Sol corrections is investigated
and compared to the range of the $T^3$ corrections.


title: Anomalies and O-plane charges in orientifolded brane tilings

abstract:
  We investigate orientifold of brane tilings. We clarify how the cancellations
of gauge anomaly and Witten's anomaly are guaranteed by the conservation of the
D5-brane charge. We also discuss the relation between brane tilings and the
dual Calabi-Yau cones realized as the moduli spaces of gauge theories. Two
types of flavor D5-branes in brane tilings and corresponding superpotentials of
fundamental quark fields are proposed, and it is shown that the massless loci
of these quarks in the moduli space correctly reproduce the worldvolume of
flavor D7-branes in the Calabi-Yau cone dual to the fivebrane system.


title: Passive States for Essential Observers

abstract:
  The aim of this note is to present a unified approach to the results given in
\cite{bb99} and \cite{bs04} which also covers examples of models not presented
in these two papers (e.g. $d$-dimensional Minkowski space-time for $d\geq 3$).
Assuming that a state is passive for an observer travelling along certain
(essential) worldlines, we show that this state is invariant under the isometry
group, is a KMS-state for the observer at a temperature uniquely determined by
the structure constants of the Lie algebra involved and fulfills (a variant of)
the Reeh-Schlieder property. Also the modular objects associated to such a
state and the observable algebra of an observer are computed and a version of
weak locality is examined.


title: Why are AGN found in High Mass Galaxies?

abstract:
  We use semi-analytic models implemented in the Millennium Simulation to
analyze the merging histories of dark matter haloes and of the galaxies that
reside in them. We assume that supermassive black holes only exist in galaxies
that have experienced at least one major merger. Only a few percent of galaxies
with stellar masses less than $M_* < 10^{10} M_{\odot}$ are predicted to have
experienced a major merger and to contain a black hole. The fraction of
galaxies with black holes increases very steeply at larger stellar masses. This
agrees well with the observed strong mass dependence of the fraction of nearby
galaxies that contain either low-luminosity (LINER-type) or higher-luminosity
(Seyfert or composite-type) AGN. We then investigate when the major mergers
that first create the black holes are predicted to occur. High mass galaxies
are predicted to have formed their black holes at very early epochs. The
majority of low mass galaxies never experience a major merger and hence do not
contain a black hole, but a significant fraction of the supermassive black
holes that do exist in low mass galaxies are predicted to have formed recently.


title:
Experimental sub-Rayleigh resolution by an unseeded high-gain optical
  parametric amplifier for quantum lithography

abstract:
  Quantum lithography proposes to adopt entangled quantum states in order to
increase resolution in interferometry. In the present paper we experimentally
demonstrate that the output of a high-gain optical parametric amplifier can be
intense yet exhibits quantum features, namely, sub-Rayleigh fringes, as
proposed by Agarwal et al. (Phys. Rev. Lett. 86, 1389 (2001)). We investigate
multiphoton states generated by a high-gain optical parametric amplifier
operating with a quantum vacuum input for a gain values up to 2.5. The
visibility has then been increased by means of three-photon absorption. The
present article opens interesting perspectives for the implementation of such
an advanced interferometrical setup.


title:
How to detect weak emergent broken-symmetries of the Kagome
  antiferromagnet from Raman spectroscopy

abstract:
  We show that the magnetic Raman response of a spin-liquid is independent of
the polarizations of the light for triangular symmetries. In contrast, a
ground-state that has a broken symmetry shows characteristic oscillations when
the polarizations are rotated. This would allow to detect weak broken
symmetries and emergent order-parameters. We focus on the Kagome
antiferromagnet where no conventional long-range order has been found so far,
and present the Raman cross-section of a spin-liquid and a valence bond crystal
(VBC) using a random phase approximation.


title: NNLO QCD analysis of the virtual photon structure functions

abstract:
  The next-to-next-to-leading order (NNLO) QCD analysis is performed for the
virtual photon structure functions which can be measured in the double-tag
events in two-photon processes in $e^+e^-$ collisions. We investigate the
perturbative QCD evaluation of $F_2^\gamma(x,Q^2,P^2)$ to NNLO and
$F_L^\gamma(x,Q^2,P^2)$ to NLO with and without taking into account the target
mass effects, which are relevant for the large $x$ region. We also carry out
the phenomenological analysis for the experimentally accessible effective
structure function $F_{\rm eff}^\gamma=F_2^\gamma+(3/2)F_L^\gamma$.


title: On some smooth projective two-orbits varieties with Picard number 1

abstract:
  We classify all smooth projective horospherical varieties with Picard number
1. We prove that the automorphism group of any such variety X acts with at most
two orbits and that this group still acts with only two orbits on X blown up at
the closed orbit. We characterize all smooth projective two-orbits varieties
with Picard number 1 that satisfy this latter property.


title: Form factors in RQM approaches: constraints from space-time translations

abstract:
  Different relativistic quantum mechanics approaches have recently been used
to calculate properties of various systems, form factors in particular. It is
known that predictions, which most often rely on a single-particle current
approximation, can lead to predictions with a very large range. It was shown
that accounting for constraints related to space-time translations could
considerably reduce this range. It is shown here that predictions can be made
identical for a large range of cases. These ones include the following
approaches: instant form, front form, and "point-form" in arbitrary momentum
configurations and a dispersion-relation approach which can be considered as
the approach which the other ones should converge to. This important result
supposes both an implementation of the above constraints and an appropriate
single-particle-like current. The change of variables that allows one to
establish the equivalence of the approaches is given. Some points are
illustrated with numerical results for the ground state of a system consisting
of scalar particles.


title:
Electroluminescence emission from polariton states in GaAs-based
  semiconductor microcavities

abstract:
  The authors report the observation of electroluminescence from GaAs-based
semiconductor microcavities in the strong coupling regime. At low current
densities the emission consists of two peaks, which exhibit anti-crossing
behaviour as a function of detection angle and thus originate from polariton
states. With increasing carrier injection we observe a progressive transition
from strong to weak coupling due to screening of the exciton resonance by free
carriers. The demonstration that polariton emission can be excited by
electrical injection is encouraging for future development of polariton lasers.


title: Uniforming n-place functions on ds(alpha)

abstract:
  In this paper the Erdos-Rado theorem is generalized to the class of well
founded trees.


title: Bose-Einstein condensation on a superconducting atom chip

abstract:
  We have produced a Bose-Einstein condensate (BEC) on an atom chip using only
superconducting wires in a cryogenic environment. We observe the onset of
condensation for 10^4 atoms at a temperature of 100 nK. This result opens the
way for studies of atom losses and decoherence in a BEC interacting with a
superconducting surface. Studies of dipole-blockade with long-lived Rydberg
atoms in a small and dense atomic sample are underway.


title:
On the Effects of Idiotypic Interactions for Recommendation Communities
  in Artificial Immune Systems

abstract:
  It has previously been shown that a recommender based on immune system
idiotypic principles can out perform one based on correlation alone. This paper
reports the results of work in progress, where we undertake some investigations
into the nature of this beneficial effect. The initial findings are that the
immune system recommender tends to produce different neighbourhoods, and that
the superior performance of this recommender is due partly to the different
neighbourhoods, and partly to the way that the idiotypic effect is used to
weight each neighbours recommendations.


title: Is X(3872) {\sl Really} a Molecular State?

abstract:
  After taking into account both the pion and sigma meson exchange potential,
we have performed a dynamical calculation of the $D^0\bar{D}^{\ast0}$ system.
The $\sigma$ meson exchange potential is repulsive from heavy quark symmetry
and numerically important for a loosely bound system. Our analysis disfavors
the interpretation of X(3872) as a loosely bound molecular state if we use the
experimental $D^\ast D\pi$ coupling constant $g=0.59$ and a reasonable cutoff
around 1 GeV, which is the typical hadronic scale. Bound state solutions with
negative eigenvalues for the $D\bar{D}^\ast$ system exist only with either a
very large coupling constant (two times of the experimental value) or a large
cutoff ($\Lambda \sim 6$ GeV or $\beta \sim 6$ GeV$^2$). In contrast, there
probably exists a loosely bound S-wave $B\bar{B}^\ast$ molecular state. Once
produced, such a molecular state would be rather stable since its dominant
decay mode is the radiative decay through $B^\ast\to B \gamma$. Experimental
search of these states will be very interesting.


title: Quaternate generalization of Pfaffian state at $\nu=5/2$

abstract:
  We consider a quaternately generalized Pfaffian
QGPf$(\frac{1}{J(z_i,z_j,z_k,z_l)})[J(z_1,...,z_N)]^2$ in which the square of
Vandermonde determinant, $[J(z_1,...,z_N)]^2$, implies the upmost Landau level
is half filled. This wave function is the unique highest density zero energy
state of a special short range interacting Hamiltonian. One can think this
quaternate composite fermion liquid as a competing ground state of Moore-Read
(MR) Pfaffian state at $\nu=5/2$. The degeneracy of the quasihole excitations
above the QGPf is higher than that of Moore-Read even Read-Rezayi quasiholes.
The QGPf is related to a unitary conformal field theory with $Z_2\times Z_2$
parafermions in coset space $SU(3)_2/U(1)^2$ . Because of the level-rank
duality between $SU(3)_2$ and $SU(2)_3$ in conformal field theory, these
quasiholes above this QGPf state obeying non-abelian anyonic statistics are
expected to support the universal quantum computation at $\nu=5/2$ as
Read-Rezayi quasiholes at $\nu=13/5$. The edge states of QGPf are very
different from those of the Pfaffian's.


title:
Cosmic rays and the magnetic field of the nearby starburst galaxy NGC
  253

abstract:
  Using radio polarimetry we study the connection between the transport of
cosmic rays (CR's), the three-dimensional magnetic field structure, and
features of other ISM phases in the halo of NGC 253. We present a new sensitive
radio continuum map of NGC 253 obtained from combined VLA and Effelsberg
observations at lambda 6.2 cm. We find a prominent radio halo with a
scaleheight of the thick radio disk of 1.7 kpc. The linear dependence between
the local scaleheight of the vertical continuum emission and the cosmic ray
electron (CRE) lifetime requires a vertical CR bulk speed of 270 km s^-1. The
magnetic field structure of NGC 253 resembles an ``X''-shaped configuration
where the orientation of the large-scale magnetic field is plane-parallel only
in the inner regions of the disk and at small distances from the galactic
midplane. At larger galactocentric radii and further away from the midplane the
vertical component becomes important. This is most clearly visible at the
location of the ``radio spur'' southeast of the nucleus, where the magnetic
field orientation is almost vertical. We made a simple model for the dominant
toroidal (r,phi) magnetic field component using a spiral magnetic field with
prescribed inclination and pitch angle. The residual poloidal (r,phi,z)
magnetic field component which was revealed by subtracting the model from the
observations shows a distinct ``X''-shaped magnetic field orientation centered
on the nucleus. The orientation angle of the poloidal magnetic field is
consistent with a magnetic field transport described by the superposition of
the vertical CR bulk speed and the rotation velocity. Hence, we propose a disk
wind which transports cosmic rays, magnetic field, and (partially) ionized gas
from the disk into the halo.


title:
Results of the ROTOR-program. II. The long-term photometric variability
  of weak-line T Tauri stars

abstract:
  T Tauri stars exhibit variability on all timescales, whose origin is still
debated. On WTTS the variability is fairly simple and attributed to long-lived,
ubiquitous cool spots. We investigate the long term variability of WTTS,
extending up to 20 years in some cases, characterize it statistically and
discuss its implications for our understanding of these stars. We have obtained
a unique, homogeneous database of photometric measurements for WTTS extending
up to 20 years. It contains more than 9 000 UBV R observations of 48 WTTS. All
the data were collected at Mount Maidanak Observatory (Uzbekistan) and they
constitute the longest homogeneous record of accurate WTTS photometry ever
assembled. Definitive rotation periods for 35 of the 48 stars are obtained.
Phased light curves over 5 to 20 seasons are now available for analysis. Light
curve shapes, amplitudes and colour variations are obtained for this sample and
various behaviors exhibited, discussed and interpreted. Our main conclusion is
that most WTTS have very stable long term variability with relatively small
changes of amplitude or mean light level. The long term variability seen
reflects modulation in the cold spot distributions. Photometric periods are
stable over many years, and the phase of minimum light can be stable as well
for several years. On the long term, spot properties do change in subtle ways,
leading to secular variations in the shape and amplitudes of the light curves.


title:
The Influence of Dust Formation Modelling on Na I and K I Line Profiles
  in Substellar Atmospheres

abstract:
  We aim to understand the correlation between cloud formation and alkali line
formation in substellar atmospheres.We perform line profile calculations for Na
I and K I based on the coupling of our kinetic model for the formation and
composition of dust grains with 1D radiative transfer calculations in
atmosphere models for brown dwarfs and giant gas planets. The Na I and K I line
profiles sensibly depend on the way clouds are treated in substellar atmosphere
simulations. The kinetic dust formation model results in the highest
pseudo-continuum compared to the limiting cases.


title: Geometric structures on loop and path spaces

abstract:
  Is is known that the loop space associated to a Riemannian manifold admits a
quasi-symplectic structure. This article shows that this structure is not
likely to recover the underlying Riemannian metric by proving a result that is
a strong indication of the "almost" independence of the quasi-symplectic
structure with respect to the metric. Finally conditions to have contact
structures on these spaces are studied.


title: Message Transfer in a Communication Network

abstract:
  We study message transfer in a $2-d$ communication network of regular nodes
and randomly distributed hubs. We study both single message transfer and
multiple message transfer on the lattice. The average travel time for single
messages travelling between source and target pairs of fixed separations shows
$q-$exponential behaviour as a function of hub density with a characteristic
power-law tail, indicating a rapid drop in the average travel time as a
function of hub density. This power-law tail arises as a consequence of the
log-normal distribution of travel times seen at high hub densities. When many
messages travel on the lattice, a congestion-decongestion transition can be
seen. The waiting times of messages in the congested phase show a Gaussian
distribution, whereas the decongested phase shows a log-normal distribution.
Thus, the congested or decongested behaviour is encrypted in the behaviour of
the waiting time distributions.

categories: physics.soc-ph cond-mat.stat-mech nlin.AO physics.data-an


title: A Recommender System based on the Immune Network

abstract:
  The immune system is a complex biological system with a highly distributed,
adaptive and self-organising nature. This paper presents an artificial immune
system (AIS) that exploits some of these characteristics and is applied to the
task of film recommendation by collaborative filtering (CF). Natural evolution
and in particular the immune system have not been designed for classical
optimisation. However, for this problem, we are not interested in finding a
single optimum. Rather we intend to identify a sub-set of good matches on which
recommendations can be based. It is our hypothesis that an AIS built on two
central aspects of the biological immune system will be an ideal candidate to
achieve this: Antigen - antibody interaction for matching and antibody -
antibody interaction for diversity. Computational results are presented in
support of this conjecture and compared to those found by other CF techniques.


title:
Energy and angular momentum of general 4-dimensional stationary
  axi-symmetric spacetime in teleparallel geometry

abstract:
  We derive an exact general axi-symmetric solution of the coupled
gravitational and electromagnetic fields in the tetrad theory of gravitation.
The solution is characterized by four parameters $M$ (mass), $Q$ (charge), $a$
(rotation) and $L$ (NUT). We then, calculate the total exterior energy using
the energy-momentum complex given by M{\o}ller in the framework of
Weitzenb$\ddot{o}$ck geometry. We show that the energy contained in a sphere is
shared by its interior as well as exterior. We also calculate the components of
the spatial momentum to evaluate the angular momentum distribution. We show
that the only non-vanishing components of the angular momentum is in the Z
direction.


title: The Danger Theory and Its Application to Artificial Immune Systems

abstract:
  Over the last decade, a new idea challenging the classical self-non-self
viewpoint has become popular amongst immunologists. It is called the Danger
Theory. In this conceptual paper, we look at this theory from the perspective
of Artificial Immune System practitioners. An overview of the Danger Theory is
presented with particular emphasis on analogies in the Artificial Immune
Systems world. A number of potential application areas are then used to provide
a framing for a critical assessment of the concept, and its relevance for
Artificial Immune Systems.


title:
Partnering Strategies for Fitness Evaluation in a Pyramidal Evolutionary
  Algorithm

abstract:
  This paper combines the idea of a hierarchical distributed genetic algorithm
with different inter-agent partnering strategies. Cascading clusters of
sub-populations are built from bottom up, with higher-level sub-populations
optimising larger parts of the problem. Hence higher-level sub-populations
search a larger search space with a lower resolution whilst lower-level
sub-populations search a smaller search space with a higher resolution. The
effects of different partner selection schemes for (sub-)fitness evaluation
purposes are examined for two multiple-choice optimisation problems. It is
shown that random partnering strategies perform best by providing better
sampling and more diversity.


title: Motivic and quantum invariance under stratified Mukai flops

abstract:
  For stratified Mukai flops of type $A_{n,k}, D_{2k+1}$ and $E_{6,I}$, it is
shown the fiber product induces isomorphisms on Chow motives. In contrast to
(standard) Mukai flops, the cup product is generally not preserved. For $A_{n,
2}$, $D_5$ and $E_{6, I}$ flops, quantum corrections are found through
degeneration/deformation to ordinary flops.


title: A statistical analysis of probabilistic counting algorithms

abstract:
  This paper considers the problem of cardinality estimation in data stream
applications. We present a statistical analysis of probabilistic counting
algorithms, focusing on two techniques that use pseudo-random variates to form
low-dimensional data sketches. We apply conventional statistical methods to
compare probabilistic algorithms based on storing either selected order
statistics, or random projections. We derive estimators of the cardinality in
both cases, and show that the maximal-term estimator is recursively computable
and has exponentially decreasing error bounds. Furthermore, we show that the
estimators have comparable asymptotic efficiency, and explain this result by
demonstrating an unexpected connection between the two approaches.


title:
Novel oscillation for the indirect coupling between magnetic
  nanoparticles

abstract:
  We study the prospect of using magnetic nanoparticles for the diluted
magnetic seminconductors. The Ruderman-Kittel-Kasuya-Yosida formula is modified
by explicitly taking into account the role of charge carriers inside the
nanoparticles in addition to those in the medium. Calculations are done
analytically. The final form of the coupling between nanoparticles is similar
to the original formula except for additional phase terms which render a novel
oscillatory feature with respect to the particle size - an interesting analogy
to the same behavior when we vary their distance. This is to be contrasted to
the previous approach which did not include the inner carriers and only favored
a ferromagnetic coupling. The effect of inevitable deviations from a perfect
sphere is estimated by the Born approximation. Our derivations can be readily
generalized to finite temperatures.


title: The A4 flavor symmetry and neutrino phenomenology

abstract:
  It has been shown that tribimaximal mixing can be obtained by some particular
breaking pattern of the $A_4$ symmetry, wherein the extra $A_4$ triplet Higgs
scalars pick up certain fixed vacuum expectation value (VEV) alignments. We
have performed a detailed analysis of the different possible neutrino mass
matrices within the framework of the $A_4$ model. We take into account all
possible singlet and triplet Higgs scalars which leave the Lagrangian invariant
under $A_4$. We break $A_4$ spontaneously, allowing the Higgs to take any VEV
in general. We show that the neutrino mixing matrix deviates from tribimaximal,
both due to the presence of the extra Higgs singlets, as well as from the
deviation of the triplet Higgs VEV from its desired alignment, taken
previously. We solve the eigenvalue problem for a variety of these illustrative
cases and identify the ones where one obtains exact tribimaximal mixing. All
such cases require fine-tuning. We show which neutrino mass matrices would be
strongly disfavored by the current neutrino data. Finally, we study in detail
the phenomenology of the remaining viable mass matrices and establish the
deviation of the neutrino mixing from tribimaximal, both analytically as well
as numerically.


title:
Discovery of very high energy gamma-ray emission coincident with
  molecular clouds in the W28 (G6.4-0.1) field

abstract:
  We observed the W28 field (for ~40 h) at Very High Energy (VHE) gamma-ray
energies (E>0.1 TeV) with the H.E.S.S. Cherenkov telescopes. A reanalysis of
EGRET E>100 MeV data was also undertaken. Results from the NANTEN 4m telescope
Galactic plane survey and other CO observations have been used to study
molecular clouds. We have discovered VHE gamma-ray emission (HESSJ1801-233)
coincident with the northeastern boundary of W28, and a complex of sources
(HESSJ1800-240A, B and C) ~0.5 deg south of W28, in the Galactic disc. The VHE
differential photon spectra are well fit by pure power laws with indices
Gamma~2.3 to 2.7. The NANTEN ^{12}CO(J=1-0) data reveal molecular clouds
positionally associating with the VHE emission, spanning a ~15 km s^{-1} range
in local standard of rest velocity. The VHE/molecular cloud association could
indicate a hadronic origin for HESSJ1801-233 and HESSJ1800-240, and several
cloud components in projection may contribute to the VHE emission. The clouds
have components covering a broad velocity range encompassing the distance
estimates for W28 (~2 kpc), and extending up to ~4 kpc. Assuming a hadronic
origin, and distances of 2 and 4 kpc for cloud components, the required cosmic
ray density enhancement factors (with respect to the solar value) are in the
range ~10 to ~30. If situated at 2 kpc distance, such cosmic ray densities may
be supplied by a SNR like W28. Additionally and/or alternatively, particle
acceleration may come from several catalogued SNRs and SNR candidates, the
energetic ultra compact HII region W28A2, and the HII regions M8 and M20 along
with their associated open clusters. Further sub-mm observations would be
recommended to probe in detail the dynamics of the molecular clouds at
velocites >10 km s^{-1}, and their possible connection to W28.


title:
Majorizing measures and proportional subsets of bounded orthonormal
  systems

abstract:
  In this article we prove that for any orthonormal system $(\vphi_j)_{j=1}^n
\subset L_2$ that is bounded in $L_{\infty}$, and any $1 < k <n$, there exists
a subset $I$ of cardinality greater than $n-k$ such that on $\spa\{\vphi_i\}_{i
\in I}$, the $L_1$ norm and the $L_2$ norm are equivalent up to a factor $\mu
(\log \mu)^{5/2}$, where $\mu = \sqrt{n/k} \sqrt{\log k}$. The proof is based
on a new estimate of the supremum of an empirical process on the unit ball of a
Banach space with a good modulus of convexity, via the use of majorizing
measures.


title: Large Scale Structures at High Redshift in the GOODS Field

abstract:
  We present a catalogue of overdensities in the GOODS-South field. We find
various high density peaks that are embedded in structures diffused on the
entire field, up to z ~ 2.5. The slope of their colour-magnitude relation does
not show significative evolution with z. We find evidence that galaxies forming
these structures are more massive than galaxies located in low density regions.
We also analyse the variation of galaxy properties with the associated
environmental density and we find that the segregation of red galaxies with
density is stronger at low redshift and at high luminosities while it gets much
weaker for increasing z.


title: A rational approximation to <VV-AA> and its O(p^6) low-energy constant

abstract:
  Using a sequence of rational approximants and the large-Nc limit of QCD, we
estimate the value of the low-energy constant C_87 which appears in the
Lagrangian of Chiral Perturbation Theory at O(p^6).


title:
Efficient l_{alpha} Distance Approximation for High Dimensional Data
  Using alpha-Stable Projection

abstract:
  In recent years, large high-dimensional data sets have become commonplace in
a wide range of applications in science and commerce. Techniques for dimension
reduction are of primary concern in statistical analysis. Projection methods
play an important role. We investigate the use of projection algorithms that
exploit properties of the alpha-stable distributions. We show that l_{alpha}
distances and quasi-distances can be recovered from random projections with
full statistical efficiency by L-estimation. The computational requirements of
our algorithm are modest; after a once-and-for-all calculation to determine an
array of length k, the algorithm runs in O(k) time for each distance, where k
is the reduced dimension of the projection.


title: Trading Model with Pair Pattern Strategies

abstract:
  A simple trading model based on pair pattern strategy space with holding
periods is proposed. Power-law behaviors are observed for the return variance
$\sigma^2$, the price impact $H$ and the predictability $K$ for both models
with linear and square root impact functions. The sum of the traders' wealth
displays a positive value for the model with square root price impact function,
and a qualitative explanation is given based on the observation of the
conditional excess demand $<A|u>$. An evolutionary trading model is further
proposed, and the elimination mechanism effectively changes the behavior of the
traders highly performed in the model without evolution. The trading model with
other types of traders, e.g., traders with the MG's strategies and producers,
are also carefully studied.


title:
Stability of hypersurfaces with constant $r$-th anisotropic mean
  curvature

abstract:
  Given a positive function $F$ on $S^n$ which satisfies a convexity condition,
we define the $r$-th anisotropic mean curvature function $H^F_r$ for
hypersurfaces in $\mathbb{R}^{n+1}$ which is a generalization of the usual
$r$-th mean curvature function. Let $X:M\to \mathbb{R}^{n+1}$ be an
$n$-dimensional closed hypersurface with $H^F_{r+1}=$constant, for some $r$
with $0\leq r\leq n-1$, which is a critical point for a variational problem. We
show that $X(M)$ is stable if and only if $X(M)$ is the Wulff shape.


title:
Simulations of spiral galaxies with an active potential: molecular cloud
  formation and gas dynamics

abstract:
  We describe simulations of the response of a gaseous disc to an active spiral
potential. The potential is derived from an N-body calculation and leads to a
multi-armed time-evolving pattern. The gas forms long spiral arms typical of
grand design galaxies, although the spiral pattern is asymmetric. The primary
difference from a grand-design spiral galaxy, which has a consistent 2/4-armed
pattern, is that instead of passing through the spiral arms, gas generally
falls into a developing potential minimum and is released only when the local
minimum dissolves. In this case, the densest gas is coincident with the spiral
potential, rather than offset as in the grand-design spirals. We would there
fore expect no offset between the spiral shock and star formation, and no
obvious co-rotation radius. Spurs which occur in grand-design spirals when
large clumps are sheared off leaving the spiral arms, are rare in the active,
time-evolving spiral reported here. Instead, large branches are formed from
spiral arms when the underlying spiral potential is dissolving due to the
N-body dynamics. We find that the molecular cloud mass spectrum for the active
potential is similar to that for clouds in grand design calculations, depending
primarily on the ambient pressure rather than the nature of the potential. The
largest molecular clouds occur when spiral arms collide, rather than by
agglomeration within a spiral arm.


title:
Exact results and new insights for models defined over small world
  networks. First and second order phase transitions. II: Applications

abstract:
  We apply a novel method (presented in part I) to solve several small-world
models for which the method can be applied analytically: the Viana-Bray model
(which can be seen as a 0 or infinite dimensional small-world model), the
one-dimensional chain small-world model, and the small-world spherical model in
generic dimension. In particular, we analyze in detail the one-dimensional
chain small-world model with negative short-range coupling showing that in this
case, besides a second-order spin glass phase transition, there are two
critical temperatures corresponding to first- or second-order phase
transitions.