title:
In silico design of metal-dielectric nanocomposites for solar energy
  applications

abstract:
  Recently, a homogenization procedure has been proposed, based on the tight
lower bounds of the Bergman-Milton formulation, and successfully applied to
dilute ternary nanocomposites to predict optical data without using any fitting
parameters [Garcia et al. Phys. Rev. B, 75, 045439 (2007)]. The procedure has
been extended and applied to predict the absorption coefficient of a quaternary
nanocomposite consisting of Cu, Ag, and Au nanospheres embedded in a SiO2 host
matrix. Significant enhancement of the absorption coefficient is observed over
the spectral range 350-800 nm. The magnitude of this enhancement can be
controlled by varying the nanosphere diameter and the individual metal volume
fraction with respect to the host matrix. We have determined the optimal
composition resulting in enhanced broadband (350nm-800nm) absorption of the
solar spectrum using a simulated annealing algorithm. Fabricating such
composite materials with a desired optical absorption has potential
applications in solar energy harvesting.


title:
Blazar Gamma-Rays, Shock Acceleration, and the Extragalactic Background
  Light

abstract:
  The observed spectra of blazars, their intrinsic emission, and the underlying
populations of radiating particles are intimately related. The use of these
sources as probes of the extragalactic infrared background, a prospect
propelled by recent advances in TeV-band telescopes, soon to be augmented by
observations by NASA's upcoming Gamma-Ray Large Area Space Telescope (GLAST),
has been a topic of great recent interest. Here, it is demonstrated that if
particles in blazar jets are accelerated at relativistic shocks, then gamma-ray
spectra with indices less than 1.5 can be produced. This, in turn, loosens the
upper limits on the near infrared extragalactic background radiation previously
proposed. We also show evidence hinting that TeV blazars with flatter spectra
have higher intrinsic TeV gamma-ray luminosities and we indicate that there may
be a correlation of flatness and luminosity with redshift.


title:
Extreme recoils: impact on the detection of gravitational waves from
  massive black hole binaries

abstract:
  Recent numerical simulations of coalescences of highly spinning massive black
hole binaries (MBHBs) suggest that the remnant can suffer a recoil velocity of
the order of few thousands km/s. We study here, by means of dedicated
simulations of black holes build--up, how such extreme recoils could affect the
cosmological coalescence rate of MBHBs, placing a robust lower limit for the
predicted number of gravitational wave (GW) sources detectable by future
space--borne missions (such as LISA). We consider two main routes for black
hole formation: one where seeds are light remnants of Population III stars
(~10^2 \msun), and one where seeds are much heavier (>~10^4 \msun), formed via
the direct gas collapse in primordial nuclear disks. We find that extreme
recoil velocities do not compromise the efficient MBHB detection by LISA. If
seeds are already massive and/or relatively rare, the detection rate is reduced
by only ~15%. The number of detections drops substantially (by ~60%) if seeds
are instead light and abundant, but in this case the number of predicted
coalescences is so high that at least ~10 sources in a three year observation
are guaranteed.


title: Dynamical clustering of counterions on flexible polyelectrolytes

abstract:
  Molecular dynamics simulations are used to study the local dynamics of
counterion-charged polymer association at charge densities above and below the
counterion condensation threshold. Surprisingly, the counterions form
weakly-interacting clusters which exhibit short range orientational order, and
which decay slowly due to migration of ions across the diffuse double layer.
The cluster dynamics are insensitive to an applied electric field, and
qualitatively agree with the available experimental data. The results are
consistent with predictions of the classical theory only over much longer time
scales.


title:
On the Transfer of Adiabatic Fluctuations through a Nonsingular
  Cosmological Bounce

abstract:
  We study the transfer of cosmological perturbations through a nonsingular
cosmological bounce in a special model in which the parameters of the bounce
and the equation of state of matter are chosen such as to allow for an exact
calculation of the evolution of the fluctuations. We find that the growing mode
of the metric fluctuations in the contracting phase goes over into the growing
mode in the expanding phase, a result which is different from what is obtained
in analyses in which fluctuations are matched at a singular hypersurface.
Consequences for Ekpyrotic cosmology are discussed in a limit when the equation
of state of a fluid becomes large.


title: Local three-nucleon interaction from chiral effective field theory

abstract:
  The three-nucleon (NNN) interaction derived within the chiral effective field
theory at the next-to-next-to-leading order (N2LO) is regulated with a function
depending on the magnitude of the momentum transfer. The regulated NNN
interaction is then local in the coordinate space, which is advantages for some
many-body techniques. Matrix elements of the local chiral NNN interaction are
evaluated in a three-nucleon basis. Using the ab initio no-core shell model
(NCSM) the NNN matrix elements are employed in 3H and 4He bound-state
calculations.


title: A more direct representation for complex relativity

abstract:
  An alternative to the representation of complex relativity by self-dual
complex 2-forms on the spacetime manifold is presented by assuming that that
the bundle of real 2-forms is given an almost-complex structure. From this, one
can define a complex orthogonal structure on the bundle of 2-forms, which
results in a more direct representation of the complex orthogonal group in
three complex dimensions. The geometrical foundations of general relativity are
then presented in terms of the bundle of oriented complex orthogonal 3-frames
on the bundle of 2-forms in a manner that essentially parallels their
construction in terms of self-dual complex 2-forms. It is shown that one can
still discuss the Debever-Penrose classification of the Riemannian curvature
tensor in terms of the representation presented here.


title: The effects of Chern-Simons gravity on bodies orbiting the Earth

abstract:
  One of the possible low-energy consequences of string theory is the addition
of a Chern-Simons term to the standard Einstein-Hilbert action of general
relativity. It can be argued that the quintessence field should couple to this
Chern-Simons term, and if so, it drives in the linearized theory a
parity-violating interaction between the gravito-electric and gravitomagnetic
fields. In this paper, the linearized spacetime for Chern-Simons gravity around
a massive spinning body is found to include new modifications to the
gravitomagnetic field that have not appeared in previous work. The orbits of
test bodies and the precession of gyroscopes in this spacetime are calculated,
leading to new constraints on the Chern-Simons parameter space due to current
satellite experiments.


title:
1E 1547.0-5408: a radio-emitting magnetar with a rotation period of 2
  seconds

abstract:
  The variable X-ray source 1E 1547.0-5408 was identified by Gelfand & Gaensler
(2007) as a likely magnetar in G327.24-0.13, an apparent supernova remnant. No
X-ray pulsations have been detected from it. Using the Parkes radio telescope,
we discovered pulsations with period P = 2.069 s. Using the Australia Telescope
Compact Array, we localized these to 1E 1547.0-5408. We measure dP/dt =
(2.318+-0.005)e-11, which for a magnetic dipole rotating in vacuo gives a
surface field strength of 2.2e14 G, a characteristic age of 1.4 kyr, and a
spin-down luminosity of 1.0e35 ergs/s. Together with its X-ray characteristics,
these rotational parameters of 1E 1547.0-5408 prove that it is a magnetar, only
the second known to emit radio waves. The distance is ~9 kpc, derived from the
dispersion measure of 830 pc/cc. The pulse profile at a frequency of 1.4 GHz is
extremely broad and asymmetric due to multipath propagation in the ISM, as a
result of which only approximately 75% of the total flux at 1.4 GHz is pulsed.
At higher frequencies the profile is more symmetric and has FWHM = 0.12P.
Unlike in normal radio pulsars, but in common with the other known
radio-emitting magnetar, XTE J1810-197, the spectrum over 1.4-6.6 GHz is flat
or rising, and we observe large, sudden changes in the pulse shape. In a
contemporaneous Swift X-ray observation, 1E 1547.0-5408 was detected with
record high flux, f_X(1-8 keV) ~ 5e-12 ergs/cm^2/s, 16 times the historic
minimum. The pulsar was undetected in archival radio observations from 1998,
implying a flux < 0.2 times the present level. Together with the transient
behavior of XTE J1810-197, these results suggest that radio emission is
triggered by X-ray outbursts of usually quiescent magnetars.


title: One-dimensional quantum wires: A pedestrian approach to bosonization

abstract:
  In these lecture notes we will consider systems in which the motion of
electrons is confined to one dimension (1D). In these so-called quantum wires
electron-electron interaction effects play an important role because the
restricted dimensions enhance the scattering between the electrons and
completely destroy the quasi-particle picture. New density wave excitations
appear that are described by bosonic operators. Here, we will develop this
bosonic description, following a pedestrian approach which does not require any
previous knowledge in field theory methods. These notes therefore serve as a
detailed introduction into bosonization by carefully deriving the most
fundamental formulas.


title:
The DEEP2 Galaxy Redshift Survey: Color and Luminosity Dependence of
  Galaxy Clustering at z~1

abstract:
  We present measurements of the color and luminosity dependence of galaxy
clustering at z~1 in the DEEP2 Galaxy Redshift Survey. Using volume-limited
subsamples in bins of both color and luminosity, we find that: 1) The
clustering dependence is much stronger with color than with luminosity and is
as strong with color at z~1 as is found locally. We find no dependence of the
clustering amplitude on color for galaxies on the red sequence, but a
significant dependence on color for galaxies within the blue cloud. 2) For
galaxies in the range L/L*~0.7-2, a stronger large-scale luminosity dependence
is seen for all galaxies than for red and blue galaxies separately. The
small-scale clustering amplitude depends significantly on luminosity for blue
galaxies, with brighter samples having a stronger rise on scales r_p<0.5 Mpc/h.
3) Redder galaxies exhibit stronger small-scale redshift-space distortions
("fingers of god"), and both red and blue populations show large-scale
distortions in xi(r_p,pi) due to coherent infall. 4) While the clustering
length, r_0, increases smoothly with galaxy color (in narrow bins), its
power-law exponent, gamma, exhibits a sharp jump from the blue cloud to the red
sequence. The intermediate color `green' galaxy population likely includes
transitional galaxies moving from the blue cloud to the red sequence; on large
scales green galaxies are as clustered as red galaxies but show infall
kinematics and a small-scale correlation slope akin to the blue galaxy
population. 5) We compare our results to a semi-analytic galaxy formation model
applied to the Millenium Run simulation. Differences between the data and the
model suggest that in the model star formation is shut down too efficiently in
satellite galaxies.


title: Colored Unparticles

abstract:
  We examine a scenario where the new physics at the LHC includes an
approximate conformal field theory, where some of the degrees of freedom (aka
"unparticles") carry a color charge. We present a simple argument showing that
the production cross section for scalar unparticles mediated by a gauge
interaction is given by (2-d) times the standard particle expression, where d
is the scaling dimension of the unparticle field. We explicitly check that this
is indeed the case, which involves non trivial cancellations between different
Feynman diagrams, for the process q qbar to scalar unparticles.


title: Lyman-alpha Emitters During the Early Stages of Reionization

abstract:
  We investigate the potential of exploiting Lya Emitters (LAEs) to constrain
the volume-weighted mean neutral hydrogen fraction of the IGM, x_H, at high
redshifts (specifically z~9). We use "semi-numerical'' simulations to
efficiently generate density, velocity, and halo fields at z=9 in a 250 Mpc
box, resolving halos with masses M>2.2e8 solar masses. We construct ionization
fields corresponding to various values of x_H. With these, we generate LAE
luminosity functions and "counts-in-cell'' statistics. As in previous studies,
we find that LAEs begin to disappear rapidly when x_H > 0.5. Constraining
x_H(z=9) with luminosity functions is difficult due to the many uncertainties
inherent in the host halo mass <--> Lya luminosity mapping. However, using a
very conservative mapping, we show that the number densities derived using the
six z~9 LAEs recently discovered by Stark et al. (2007) imply x_H < 0.7. On a
more fundamental level, these LAE number densities, if genuine, require
substantial star formation in halos with M < 10^9 solar masses, making them
unique among the current sample of observed high-z objects. Furthermore,
reionization increases the apparent clustering of the observed LAEs. We show
that a ``counts-in-cell'' statistic is a powerful probe of this effect,
especially in the early stages of reionization. Specifically, we show that a
field of view (typical of upcoming IR instruments) containing LAEs has >10%
higher probability of containing more than one LAE in a x_H>0.5 universe than a
x_H=0 universe with the same overall number density. With this statistic, a
fully ionized universe can be robustly distinguished from one with x_H > 0.5
using a survey containing only ~ 20--100 galaxies.


title:
The Sightline to Q2343-BX415: Clues to Galaxy Formation in a Quasar
  Environment

abstract:
  (Abridged) We have discovered a strong DLA coincident in redshift with the
faint QSO Q2343-BX415 (R = 20.2, z_em = 2.57393). Follow-up observations at
intermediate spectral resolution reveal that the metal lines associated with
this 'proximate' DLA consist of two sets of absorption components. One set is
moving towards the quasar with velocities of ~ 150-600 km/s; this gas is highly
ionized and does not fully cover the continuum source, suggesting that it is
physically close to the active nucleus. The other, which accounts for most of
the neutral gas, is blueshifted relative to the QSO, with the strongest
component at ~ -160 km/s. We consider the possibility that the PDLA arises in
the outflowing interstellar medium of the host galaxy of Q2343-BX415, an
interpretation supported by strong C IV and N V absorption at nearby
velocities, and by the intense radiation field longward of the Lyman limit
implied by the high C II*/H I ratio. If Q2343-BX415 is the main source of these
UV photons, then the PDLA is located at either ~ 8 or ~ 37 kpc from the active
nucleus. Alternatively, the absorber may be a foreground star-forming galaxy
unrelated to the quasar and coincidentally at the same redshift, but our deep
imaging and follow-up spectroscopy of the field of Q2343-BX415 has not yet
produced a likely candidate. We measure the abundances of 14 elements in the
PDLA, finding an overall metallicity of ~ 1/5 solar and a normal pattern of
relative element abundances for this metallicity. Thus, in this PDLA there is
no evidence for the super-solar metallicities that have been claimed for some
proximate, high ionization, systems.


title: Ovrview: The Shape of Hadrons

abstract:
  In this article we address the physical basis of the deviation of hadron
shapes from spherical symmetry (non-spherical amplitudes) with focus on the
nucleon and $\Delta$. An overview of both the experimental methods and results
and the current theoretical understanding of the issue is presented. At the
present time the most quantitative method is the $\gamma^{*} p \to \Delta$
reaction for which significant non-spherical electric (E2) and Coulomb
quadrupole (C2) amplitudes have been observed with good precision as a function
of Q^{2} from the photon point through 6 GeV^{2}. Quark model calculations for
these quadrupole amplitudes are at least an order of magnitude too small and
even have the wrong sign. Lattice QCD, chiral effective field theory, and
dynamic model calculations which include the effects of the pion-cloud are in
approximate agreement with experiment. This is expected due to the spontaneous
breaking of chiral symmetry in QCD and the resulting, long range (low Q^{2})
effects of the pion-cloud. Other observables such as nucleon form factors and
virtual Compton scattering experiments indicate that the pion-cloud is playing
a significant role in nucleon structure. Semi-inclusive deep inelastic
scattering experiments with transverse polarized beam and target also show the
effect of non-zero quark angular momentum.


title:
Functional relations from the Yang-Baxter algebra: Eigenvalues of the
  XXZ model with non-diagonal twisted and open boundary conditions

abstract:
  In this work we consider a functional method in the theory of exactly
solvable models based on the Yang-Baxter algebra. Using this method we derive
the eigenvalues of the XXZ model with non-diagonal twisted and open boundary
conditions for general values of the anisotropy and boundary parameters.


title: Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies

abstract:
  We present stellar velocity dispersion profiles for seven Milky Way dwarf
spheroidal (dSph) satellite galaxies. We have measured 8394 line-of-sight
velocities (+/- 2.5 km/s) for 6804 stars from high-resolution spectra obtained
at the Magellan and MMT telescopes. We combine these new data with previously
published velocities to obtain the largest available kinematic samples, which
include more than 5500 dSph members. All the measured dSphs have stellar
velocity dispersion of order 10 km/s that remains approximately constant with
distance from the dSph center, out to and in some cases beyond the radius at
which the mean surface brightness falls to the background level. Assuming dSphs
reside within dark matter halos characterized by the NFW density profile, we
obtain reasonable fits to the empirical velocity dispersion profiles. These
fits imply that, among the seven dSphs, M_vir ~ 10^[8-9] M_sun. The mass
enclosed at a radius of 600 pc, the region common to all data sets, ranges from
(2-7) x 10^7 M_sun .


title: An Extremely Massive Dry Galaxy Merger in a Moderate Redshift Cluster

abstract:
  We have identified perhaps the largest major galaxy merger ever seen. While
analysing Spitzer IRAC images of CL0958+4702, an X-ray selected cluster at
z=0.39, we discovered an unusual plume of stars extending $\gtrsim$110 kpc
outward from the bright central galaxy (BCG). Three galaxies 1-1.5 mag fainter
than the BCG lie within 17 kpc (projected) of the BCG and are probably
participating in the merger. The plume is detected in all four IRAC channels
and at optical wavelengths in images from the WIYN telescope; the surface
brightness is remarkably high ($\mu_r\approx$24.8 mag arcsec$^{-2}$ at 50 kpc).
The optical and infrared colors are consistent with those of other BCGs,
suggesting that the plume is composed of old stars and negligible recent star
formation (hence a "dry merger"). The luminosity in the plume is at least
equivalent to a 4L^* galaxy. A diffuse halo extending 110 kpc from the BCG in
one IRAC image suggests the total amount of diffuse light is L_r\sim
1.3x10^{11}h^{-2} L_sun. A Chandra observation shows an X-ray image and
spectrum typical of moderate-mass clusters. We use MMT/Hectospec to measure 905
redshifts in a 1 deg^2 region around the cluster. The velocities of two of the
BCG companions indicate a merger timescale for the companion galaxies of
$\sim$110 Myr and $\sim$0.5-1 Gyr for the plume. We conclude that the BCG and
intracluster light of CL0958 is formed by major mergers at moderate redshifts.
After the major merger is complete, CL0958 will likely become a fossil cluster.


title:
The quantum vs classical aspects of one dimensional electron-phonon
  systems revisited by the renormalization group method

abstract:
  An extension of the renormalization group method that includes the effect of
retardation for the interactions of a fermion gas is used to re-examine the
quantum and classical properties of Peierls- like states in one dimension. For
models of spinless and spin-1/2 fermions interacting with either intra or
intermolecular phonons the quantum corrections to the Peierls gap at
half-filling are determined at arbitrary phonon frequency. The nature of
quantum-classical transitions is clarified in weak coupling.


title: Beltrami States for Compressible Barotropic Flows

abstract:
  Beltrami states for compressible barotropic flows are deduced by minimizing
the total kinetic energy while keeping the total helicity constant. A
Hamiltonian basis for these Beltrami states is also sketched.


title: Cover slip external cavity diode laser

abstract:
  The design of a 671 nm diode laser with a mode-hop-free tuning range of 40
GHz is described. This long tuning range is achieved by simultaneously ramping
the external cavity length with the laser injection current. The external
cavity consists of a microscope cover slip mounted on piezoelectric actuators.
In such a configuration the laser output pointing remains fixed, independent of
its frequency. Using a diode with an output power of 5-7 mW, the laser
linewidth was found to be smaller than 30 MHz. This cover slip cavity and
feedforward laser current control system is simple, economical, robust, and
easy to use for spectroscopy, as we demonstrate with lithium vapor and lithium
atom beam experiments.


title:
Is there a link between the neutron-star spin and the frequency of the
  kilohertz quasi-periodic oscillations?

abstract:
  There is a general consensus that the frequencies of the kilohertz
Quasi-Periodic Oscillations (kHz QPOs) in neutron-star low-mass X-ray binaries
are directly linked to the spin of the neutron star. The root of this idea is
the apparent clustering of the ratio of the frequency difference of the kHz
QPOs and the neutron-star spin frequency, $\Delta\nu/\nu_s$, at around 0.5 and
1 in ten systems for which these two quantities have been measured. Here we
reexamine all available data of sources for which there exist measurements of
two simultaneous kHz QPOs and spin frequencies, and we advance the possibility
that $\Delta\nu$ and $\nu_s$ are not related to each other. We discuss ways in
which this possibility could be tested with current and future observations.


title: Nearing the Horizon of a Heterotic String

abstract:
  It is argued that recent developments point to the existence of an AdS_3 x
S^2 x T^5 holographic dual for the 2D CFT living on the worldsheet of N
coincident heterotic strings in a T^5 compactification, which can in turn be
described by an exact worldsheet CFT. A supergravity analysis is shown to imply
that the global supergroup is Osp(4^*|4), with 16 supercharges and an affine
extension given, surprisingly, by a nonlinear N=8 2D superconformal algebra.
Possible supergroups with 16 supercharges are also found to match the expected
symmetries for T^n compactification with 0<=n<=7.


title: Greybody Factors for d-Dimensional Black Holes

abstract:
  Gravitational greybody factors are analytically computed for static,
spherically symmetric black holes in d-dimensions, including black holes with
charge and in the presence of a cosmological constant (where a proper
definition of greybody factors for both asymptotically dS and AdS spacetimes is
provided). This calculation includes both the low-energy case --where the
frequency of the scattered wave is small and real-- and the asymptotic case
--where the frequency of the scattered wave is very large along the imaginary
axis-- addressing gravitational perturbations as described by the
Ishibashi-Kodama master equations, and yielding full transmission and
reflection scattering coefficients for all considered spacetime geometries. At
low frequencies a general method is developed, which can be employed for all
three types of spacetime asymptotics, and which is independent of the details
of the black hole. For asymptotically dS black holes the greybody factor is
different for even or odd spacetime dimension, and proportional to the ratio of
the areas of the event and cosmological horizons. For asymptotically AdS black
holes the greybody factor has a rich structure in which there are several
critical frequencies where it equals either one (pure transmission) or zero
(pure reflection, with these frequencies corresponding to the normal modes of
pure AdS spacetime). At asymptotic frequencies the computation of the greybody
factor uses a technique inspired by monodromy matching, and some universality
is hidden in the transmission and reflection coefficients. For either charged
or asymptotically dS black holes the greybody factors are given by non-trivial
functions, while for asymptotically AdS black holes the greybody factor
precisely equals one (corresponding to pure blackbody emission).


title: q-Terms, singularities and the extended Bloch group

abstract:
  Our paper originated from a generalization of the Volume Conjecture to
multisums of $q$-hypergeometric terms. This generalization was sketched by
Kontsevich in a problem list in Aarhus University in 2006; \cite{Ko}. We
introduce the notion of a $q$-hypergeometric term (in short, $q$-term). The
latter is a product of ratios of $q$-factorials in linear forms in several
variables. In the first part of the paper, we show how to construct elements of
the Bloch group (and its extended version) given a \qterm. Their image under
the Bloch-Wigner map or the Rogers dilogarithm is a finite set of periods of
weight 2, in the sense of Kontsevich-Zagier. In the second part of the paper we
introduce the notion of a special $q$-term, its corresponding sequence of
polynomials, and its generating series. Examples of special $q$-terms come
naturally from Quantum Topology, and in particular from planar projections of
knots. The two parts are tied together by a conjecture that relates the
singularities of the generating series of a special $q$-term with the periods
of the corresponding elements of the extended Bloch group. In some cases (such
as the $4_1$ knot), the conjecture is known.


title: Semigroups of valuations on local rings

abstract:
  In this paper the question of which semigroups are realizable as the
semigroup of values attained on a Noetherian local ring which is dominated by a
valuation is considered. We give some striking examples, indicating that there
may be no constraints on the semigroup beyond those known classically.


title: Spin solitons in magnetized pair plasmas

abstract:
  A set of fluid equations, taking into account the spin properties of the
electrons and positrons in a magnetoplasma, are derived. The
magnetohydrodynamic limit of the pair plasma is investigated. It is shown that
the microscopic spin properties of the electrons and positrons can lead to
interesting macroscopic and collective effects in strongly magnetized plasmas.
In particular, it is found that new Alfvenic solitary structures, governed by a
modified Korteweg-de Vries equation, are allowed in such plasmas. These
solitary structures vanish if the quantum spin effects are neglected. Our
results should be of relevance for astrophysical plasmas, e.g. in pulsar
magnetospheres.


title: Protein-DNA interactions: reaching and recognizing the targets

abstract:
  This paper has been withdrawn because of the requirement from the journal
where the modified version of the paper is to be published.


title: Embedding the Pentagon

abstract:
  The Pentagon Model is an explicit supersymmetric extension of the Standard
Model, which involves a new strongly-interacting SU(5) gauge theory at
TeV-scale energies. We show that the Pentagon can be embedded into an SU(5) x
SU(5) x SU(5) gauge group at the GUT scale. The doublet-triplet splitting
problem, and proton decay compatible with experimental bounds, can be
successfully addressed in this context. The simplest approach fails to provide
masses for the lighter two generations of quarks and leptons; however, this
problem can be solved by the addition of a pair of antisymmetric tensor fields
and an axion.


title:
Renormalized spin wave excitations in the antiferromagnetic
  Heisenberg-Kondo model for heavy fermions

abstract:
  Recent inelastic neutron scattering experiments in CeIn3 and CePd2Si2 single
crystals, measured spin wave excitations at low temperatures. These two heavy
fermion compounds exhibit antiferromagnetic long-range order, but a strong
competition between the Ruderman-Kittel-Kasuya-Yosida(RKKY) interaction and
Kondo effect is evidenced by their nearly equal Neel and Kondo temperatures.
Our aim is to show how magnons such as measured in the antiferromagnetic phase
of these Ce compounds, can be described with a microscopic Heisenberg-Kondo
model as introduced by J.R.Iglesias, C.Lacroix and B.Coqblin, used before for
studies of the non-magnetic phase. The model includes the correlated Ce-4f
electrons hybridized with the conduction band, and we consider competing RKKY
(Heisenberg-like J_{H}) and Kondo (J_{K}) antiferromagnetic couplings. Carrying
on a series of unitary transformations, we perturbatively derive a second-order
effective Hamiltonian which, projected onto the antiferromagnetic electron
ground state, describes the spin wave excitations, renormalized by their
interaction with correlated itinerant electrons. We numerically study how the
different parameters of the model influence the renormalization of the magnons,
yielding useful information for the analysis of inelastic neutron scattering
experiments in antiferromagnetic heavy fermion compounds. We also compare our
results with available experimental data, finding good agreement with the spin
wave measurements in cubic CeIn3.


title: The Mirage of w=-1

abstract:
  We demonstrate that cosmic microwave background observations consistent with
a cosmological constant universe predict in a well-defined sense that lower
redshift measures will nearly automatically deliver w=-1 for the dark energy
equation of state value unless they are sensitive to w(z). Thus low redshift
data pointing to w=-1 does not truly argue for a cosmological constant. Even
the simplest question of whether the equation of state of dark energy is equal
to the cosmological constant therefore requires experiments able to sensitively
constrain time variation w(z) and not merely a constant w. We also note a
number of issues regarding parametrization of w(z), demonstrating that the
standard form w(z)=w_0+w_a z/(1+z) is robust but use of high order polynomials
and cutting off the high redshift behavior can be pathological.


title:
Goal-oriented Atomistic-Continuum Adaptivity for the Quasicontinuum
  Approximation

abstract:
  We give a goal-oriented a posteriori error estimator for the
atomistic-continuum modeling error in the quasicontinuum method, and we use
this estimator to design an adaptive algorithm to compute a quantity of
interest to a given tolerance by using a nearly minimal number of atomistic
degrees of freedom. We present computational results that demonstrate the
effectiveness of our algorithm for a periodic array of dislocations described
by a Frenkel-Kontorova type model.


title: CP Asymmetry in Charged Higgs Decays to Chargino-Neutralino

abstract:
  We analyze the charge-parity (CP) asymmetry in the charged Higgs boson decays
to chargino-neutralino pairs, H^- -> chargino_i + neutralino_j. We show first
that these modes have a large branching ratio for m_H^- > 600 GeV. We use
Cutkosky rules to obtain the analytical formulas needed for the evaluation of
the asymmetry under consideration. We then calculate the CP asymmetry in
chargino-neutralino decays by including supersymmetric mass bounds, as well as
constraints from b -> s gamma, (g-2)_mu, Delta\rho and electric dipole moments.
Finally, we discuss observability of the asymmetry at the LHC by calculating
the number of required charged Higgs events to observe the asymmetry for each
decay channel. We show that the inclusion of constraints considerably reduces
the projected CP asymmetry, and that the optimal channel for observing the
asymmetry is H^- -> chargino_1 + neutralino_2.


title:
The ACS Survey of Galactic Globular Clusters: M54 and Young Populations
  in the Sagittarius Dwarf Spheroidal Galaxy

abstract:
  We present new Hubble Space Telescope photometry of the massive globular
cluster M54 (NGC 6715) and the superposed core of the tidally disrupted
Sagittarius (Sgr) dSph galaxy as part of the ACS Survey of Galactic Globular
Clusters. Our deep (F606W~26.5), high-precision photometry yields an
unprecedentedly detailed color-magnitude diagram showing the extended blue
horizontal branch and multiple main sequences of the M54+Sgr system. The
distance and reddening to M54 are revised usingboth isochrone and main-sequence
fitting to (m-M)_0=17.27 and E(B-V)=0.15. Preliminary assessment finds the
M54+Sgr field to be dominated by the old metal-poor populations of Sgr and the
globular cluster. Multiple turnoffs indicate the presence of at least two
intermediate-aged star formation epochs with 4 and 6 Gyr ages and [Fe/H]=-0.4
to -0.6. We also clearly show, for the first time, a prominent, 2.3 Gyr old Sgr
population of near-solar abundance. A trace population of even younger (0.1-0.8
Gyr old), more metal-rich ([Fe/H]\sim0.6) stars is also indicated. The Sgr
age-metallicity relation is consistent with a closed-box model and multiple
(4-5) star formation bursts over the entire life of the satellite, including
the time since Sgr began disrupting.


title:
High-pressure x-ray diffraction study of SrMoO4 and pressure-induced
  structural changes

abstract:
  SrMoO4 was studied under compression up to 25 GPa by angle-dispersive x-ray
diffraction. A phase transition was observed from the scheelite-structured
ambient phase to a monoclinic fergusonite phase at 12.2(9) GPa with cell
parameters a = 5.265(9) A, b = 11.191(9) A, c = 5.195 (5) A, and beta = 90.9, Z
= 4 at 13.1 GPa. There is no significant volume collapse at the phase
transition. No additional phase transitions were observed and on release of
pressure the initial phase is recovered, implying that the observed structural
modifications are reversible. The reported transition appeared to be a
ferroelastic second-order transformation producing a structure that is a
monoclinic distortion of the low-pressure phase and was previously observed in
compounds isostructural to SrMoO4. A possible mechanism for the transition is
proposed and its character is discussed in terms of the present data and the
Landau theory. Finally, the EOS is reported and the anisotropic compressibility
of the studied crystal is discussed in terms of the compression of the Sr-O and
Mo-O bonds.


title: Collective modes of CP(3) Skyrmion crystals in quantum Hall ferromagnets

abstract:
  The two-dimensional electron gas in a bilayer quantum Hall system can sustain
an interlayer coherence at filling factor nu=1 even in the absence of tunneling
between the layers. This system has low-energy charged excitations which may
carry textures in real spin or pseudospin. Away from filling factor nu =1 a
finite density of these is present in the ground state of the 2DEG and forms a
crystal. Depending on the relative size of the various energy scales, such as
tunneling (Delta_SAS), Zeeman coupling (Delta_Z) or electrical bias (Delta_b),
these textured crystal states can involve spin, pseudospin, or both
intertwined. In this article, we present a comprehensive numerical study of the
collective excitations of these textured crystals using the GRPA. For the pure
spin case, at finite Zeeman coupling the state is a Skyrmion crystal with a
gapless phonon mode, and a separate Goldstone mode that arises from a broken
U(1) symmetry. At zero Zeeman coupling, we demonstrate that the constituent
Skyrmions break up, and the resulting state is a meron crystal with 4 gapless
modes. In contrast, a pure pseudospin Skyrme crystal at finite tunneling has
only the phonon mode. For Delta_SAS=0, the state evolves into a meron crystal
and supports an extra gapless U(1) mode in addition to the phonon. For a CP(3)
Skyrmion crystal, we find a U(1) gapless mode in the presence of the
symmetry-breaking fields. In addition, a second mode with a very small gap is
present in the spectrum.


title:
A Galaxy Photometric Redshift Catalog for the Sloan Digital Sky Survey
  Data Release 6

abstract:
  We present and describe a catalog of galaxy photometric redshifts (photo-z's)
for the Sloan Digital Sky Survey (SDSS) Data Release 6 (DR6). We use the
Artificial Neural Network (ANN) technique to calculate photo-z's and the
Nearest Neighbor Error (NNE) method to estimate photo-z errors for ~ 77 million
objects classified as galaxies in DR6 with r < 22. The photo-z and photo-z
error estimators are trained and validated on a sample of ~ 640,000 galaxies
that have SDSS photometry and spectroscopic redshifts measured by SDSS, 2SLAQ,
CFRS, CNOC2, TKRS, DEEP, and DEEP2. For the two best ANN methods we have tried,
we find that 68% of the galaxies in the validation set have a photo-z error
smaller than sigma_{68} =0.021 or $0.024. After presenting our results and
quality tests, we provide a short guide for users accessing the public data.


title:
Lensing Corrections to Features in the Angular Two-Point Correlation
  Function and Power Spectrum

abstract:
  It is well known that magnification bias, the modulation of galaxy or quasar
source counts by gravitational lensing, can change the observed angular
correlation function. We investigate magnification-induced changes to the shape
of the observed correlation function w(\theta) and the angular power spectrum
C_{\ell}, paying special attention to the matter-radiation equality peak and
the baryon wiggles. Lensing mixes the correlation function of the source
galaxies with the matter correlation at the lower redshifts of the lenses.
Since the lenses probe structure nearer to the observer, the angular scale
dependence of the lensing terms is different from that of the sources, thus the
observed correlation function is distorted. We quantify how the lensing
corrections depend on the width of the selection function, the galaxy bias b,
and the number count slope s. The correction increases with redshift and larger
corrections are present for sources with steep number count slopes and/or broad
redshift distributions. The most drastic changes to C_{\ell} occur for
measurements at z >~1.5 and \ell <~ 100. For the source distributions we
consider, magnification bias can shift the matter-radiation equality scale by
1-6% at z ~ 1.5 and by z ~ 3.5 the shift can be as large as 30%. The baryon
bump in \theta^2w(\theta) is shifted by <~ 1% and the width is typically
increased by ~10%. Shifts of >~ 0.5% and broadening of >~ 20% occur only for
very broad selection functions and/or galaxies with (5s-2)/b>~2. However, near
the baryon bump the magnification correction is not constant but a gently
varying function which depends on the source population. Depending on how the
w(\theta) data is fitted, this correction may need to be accounted for when
using the baryon acoustic scale for precision cosmology.


title: Towards conformal invariance of 2D lattice models

abstract:
  Many 2D lattice models of physical phenomena are conjectured to have
conformally invariant scaling limits: percolation, Ising model, self-avoiding
polymers, ... This has led to numerous exact (but non-rigorous) predictions of
their scaling exponents and dimensions. We will discuss how to prove the
conformal invariance conjectures, especially in relation to Schramm-Loewner
Evolution.


title:
Survey Requirements for Accurate and Precise Photometric Redshifts for
  Type Ia Supernovae

abstract:
  In this paper we advance the simple analytic photometric redshift estimator
for Type Ia supernovae (SNe Ia) proposed by Wang (2007), and use it to study
simulated SN Ia data. We find that better than 0.5% accuracy in z_phot (with
RMS[(z_phot-z_spec)/(1+z_spec)]<0.005) is possible for SNe Ia with well sampled
lightcurves in three observed passbands (riz) with a signal-to-noise ratio of
25 at peak brightness, if the extinction by dust is negligible. The
corresponding bias in z_phot (the mean of (z_phot-z_spec)) is 5.4\times
10^{-4}. If dust extinction is taken into consideration in the riz
observer-frame lightcurves, the accuracy in z_phot deteriorates to 4.4%, with a
bias in z_phot of 8.0\times 10^{-3}. Adding the g band lightcurve improves the
accuracy in z_phot to 2.5%, and reduces the bias in z_phot to -1.5\times
10^{-3}. Our results have significant implications for the design of future
photometric surveys of SNe Ia from both ground and space telescopes. Accurate
and precise photometric redshifts boost the cosmological utility of such
surveys.


title:
Analytic Formulation, Exact Solutions, and Generalizations of the
  Elephant and the Alzheimer Random Walks

abstract:
  An analytic formulation of memory-possessing random walks introduced recently
[Cressoni et al., Phys. Rev. Lett. 98, 070603 (2007) and Sch\"utz and Trimper,
Phys. Rev. E 70, 045101 (2004)] for Alzheimer behavior and related phenomena is
provided along with exact solutions on the basis of Fokker-Planck equations.
The solution of a delay-differential equation derived for the purpose is shown
to produce log-periodic oscillations and to coincide rather accurately with
previously published computer simulation results. Generalizations along several
directions are also constructed on the basis of the formalism.


title: Polarization probes of vorticity in heavy ion collisions

abstract:
  We discuss the information that can be deduced from a measurement of particle
(hyperon or vector meson) polarization in ultrarelativistic nuclear collisions.
We describe the sensitivity of polarization to initial conditions, hydrodynamic
evolution and mean free path, and find that the polarization observable is
sensitive to all details and stages of the system's evolution. We suggest that
an experimental investigation covering production plane and reaction plane
polarizations, as well as the polarization of jet-associated particles in the
plane defined by the jet and particle direction, can help in disentangling the
factors contributing to this observable. Scans of polarization in energy and
rapidity might also point to a change in the system's properties.


title: Unparticle Physics with Jets

abstract:
  Using methods of effective field theory, we show that after resummation of
Sudakov logarithms the spectral densities of interacting quark and gluon fields
in ordinary quantum field theories such as QCD are virtually indistinguishable
from those of "unparticles" of a hypothetical conformal sector coupled to the
Standard Model, recently studied by Georgi. Unparticles are therefore less
exotic that originally thought. Models in which a hidden sector weakly coupled
to the Standard Model contains a QCD-like theory, which confines at some scale
much below the characteristic energy of a given process, can give rise to
signatures closely resembling those from unparticles.


title:
From the Einstein-Cartan to the Ashtekar-Barbero canonical constraints,
  passing through the Nieh-Yan functional

abstract:
  The Ashtekar-Barbero constraints for General Relativity with fermions are
derived from the Einstein-Cartan canonical theory rescaling the state
functional of the gravity-spinor coupled system by the exponential of the
Nieh-Yan functional. A one parameter quantization ambiguity naturally appears
and can be associated with the Immirzi parameter.


title: Tracking the Orbital and Super-orbital Periods of SMC X-1

abstract:
  The High Mass X-ray Binary (HMXB) SMC X-1 demonstrates an orbital variation
of 3.89 days and a super-orbital variation with an average length of 55 days.
As we show here, however, the length of the super-orbital cycle varies by
almost a factor of two, even across adjacent cycles. To study both the orbital
and super-orbital variation we utilize lightcurves from the Rossi X-ray Timing
Explorer All Sky Monitor (RXTE-ASM). We employ the orbital ephemeris from
Wojdowski et al. (1998) to obtain the average orbital profile, and we show that
this profile exhibits complex modulation during non-eclipse phases.
Additionally, a very interesting ``bounceback'' in X-ray count rate is seen
during mid-orbital eclipse phases, with a softening of the emission during
these periods. This bounceback has not been previously identified in pointed
observations. We then define a super-orbital ephemeris (the phase of the
super-orbital cycle as a function of date) based on the ASM lightcurve and
analyze the trend and distribution of super-orbital cycle lengths. SMC X-1
exhibits a bimodal distribution of these lengths, similar to what has been
observed in other systems (e.g., Her X-1), but with more dramatic changes in
cycle length. There is some hint, but not conclusive evidence, for a dependence
of the super-orbital cycle length upon the underlying orbital period, as has
been observed previously for Her X-1 and Cyg X-2. Using our super-orbital
ephemeris we are also able to create an average super-orbital profile over the
71 observed cycles, for which we witness overall hardening of the spectrum
during low count rate times. We combine the orbital and super-orbital
ephemerides to study the correlation between the orbital and super-orbital
variations in the system.


title:
Conformal invariance in random cluster models. I. Holomorphic fermions
  in the Ising model

abstract:
  We construct discrete holomorphic observables in the Ising model at
criticality and show that they have conformally covariant scaling limits (as
mesh of the lattice tends to zero). In the sequel those observables are used to
construct conformally invariant scaling limits of interfaces. Though Ising
model is often cited as a classical example of conformal invariance, it seems
that ours is the first paper where it is actually established.


title: An exact chiral spin liquid with non-Abelian anyons

abstract:
  We establish the existence of a chiral spin liquid (CSL) as the exact ground
state of the Kitaev model on a decorated honeycomb lattice, which is obtained
by replacing each site in the familiar honeycomb lattice with a triangle. The
CSL state spontaneously breaks time reversal symmetry but preserves other
symmetries. There are two topologically distinct CSLs separated by a quantum
critical point. Interestingly, vortex excitations in the topologically
nontrivial (Chern number $\pm 1$) CSL obey non-Abelian statistics.


title: Microscopic Wrinkles on Supported Surfactant Monolayers

abstract:
  We discuss mechanical buckling instabilities of a rigid film under
compression interacting repulsively with a substrate through a thin fluid
layer. The buckling occurs at a characteristic wavelength that increases as the
1/4th power of the bending stiffness, like a gravitational instability studied
previously by Milner et al. However, the potential can affect the
characteristic buckling wavelength strongly, as predicted by Huang and Suo. If
the potential changes sufficiently sharply with thickness, this instability is
continuous, with an amplitude varying as the square root of overpressure. We
discuss three forms of interaction important for the case of Langmuir
monolayers transferred to a substrate: Casimir-van der Waals interaction,
screened charged double-layer interaction and the Sharma potential. We verify
these predictions numerically in the Van der Waals case.


title: A solid angle theory for real polytopes

abstract:
  We extend many theorems from the context of solid angle sums over rational
polytopes to the context of solid angle sums over real polytopes. Moreover, we
consider any real dilation parameter, as opposed to the traditional integer
dilation parameters. One of the main results is an extension of Macdonald's
solid angle quasipolynomial for rational polytopes to a real analytic function
of the dilation parameter, for any real convex polytope.


title:
Quantifying structural damage from self-irradiation in a plutonium
  superconductor

abstract:
  The 18.5 K superconductor PuCoGa5 has many unusual properties, including
those due to damage induced by self-irradiation. The superconducting transition
temperature decreases sharply with time, suggesting a radiation-induced Frenkel
defect concentration much larger than predicted by current radiation damage
theories. Extended x-ray absorption fine-structure measurements demonstrate
that while the local crystal structure in fresh material is well ordered, aged
material is disordered much more strongly than expected from simple defects,
consistent with strong disorder throughout the damage cascade region. These
data highlight the potential impact of local lattice distortions relative to
defects on the properties of irradiated materials and underscore the need for
more atomic-resolution structural comparisons between radiation damage
experiments and theory.


title:
Exploring the Local Milky Way: M Dwarfs as Tracers of Galactic
  Populations

abstract:
  We have assembled a spectroscopic sample of low-mass dwarfs observed as part
of the Sloan Digital Sky Survey along one Galactic sightline, designed to
investigate the observable properties of the thin and thick disks. This sample
of ~7400 K and M stars also has measured ugriz photometry, proper motions, and
radial velocities. We have computed UVW space motion distributions, and
investigate their structure with respect to vertical distance from the Galactic
Plane. We place constraints on the velocity dispersions of the thin and thick
disks, using two-component Gaussian fits. We also compare these kinematic
distributions to a leading Galactic model. Finally, we investigate other
possible observable differences between the thin and thick disks, such as
color, active fraction and metallicity.


title: Persistence of Induced Wormholes in Brane Worlds

abstract:
  Higher-dimensional black holes have long been considered within the context
of brane worlds. Recently, it was shown that the brane-world ethos also permits
the consideration of higher-dimensional wormholes. When such a wormhole,
preexisting in the bulk, impinges upon our universe, taken to be a
positive-tension 3-brane, it induces the creation in our universe of a wormhole
of ordinary dimensionality. The throat of this wormhole might fully constrict,
pinch off, and thus birth a baby universe. Alternatively, the induced wormhole
might persist. I show that persistence is more likely and note that the
persistent wormhole manifests as a particle-like object whose interaction with
cosmic matter is purely gravitational. As such it may be considered a viable
candidate for the sort of weakly interacting massive particle long believed to
be the prime constituent of cold dark matter.


title: Sparse and stable Markowitz portfolios

abstract:
  We consider the problem of portfolio selection within the classical Markowitz
mean-variance framework, reformulated as a constrained least-squares regression
problem. We propose to add to the objective function a penalty proportional to
the sum of the absolute values of the portfolio weights. This penalty
regularizes (stabilizes) the optimization problem, encourages sparse portfolios
(i.e. portfolios with only few active positions), and allows to account for
transaction costs. Our approach recovers as special cases the
no-short-positions portfolios, but does allow for short positions in limited
number. We implement this methodology on two benchmark data sets constructed by
Fama and French. Using only a modest amount of training data, we construct
portfolios whose out-of-sample performance, as measured by Sharpe ratio, is
consistently and significantly better than that of the naive evenly-weighted
portfolio which constitutes, as shown in recent literature, a very tough
benchmark.


title: High energy scattering in Quantum Chromodynamics

abstract:
  In this series of three lectures, we discuss several aspects of high energy
scattering among hadrons in Quantum Chromodynamics. The first lecture is
devoted to a description of the parton model, Bjorken scaling and the scaling
violations due to the evolution of parton distributions with the transverse
resolution scale. The second lecture describes parton evolution at small
momentum fraction x, the phenomenon of gluon saturation and the Color Glass
Condensate (CGC). In the third lecture, we present the application of the CGC
to the study of high energy hadronic collisions, with emphasis on
nucleus-nucleus collisions. In particular, we provide the outline of a proof of
high energy factorization for inclusive gluon production.


title: A renormalization approach to irrational rotations

abstract:
  We introduce a renormalization procedure which allows us to study in a
unified and concise way different properties of the irrational rotations on the
unit circle $\beta \mapsto \set{\alpha+\beta}$, $\alpha \in \R\setminus \Q$. In
particular we obtain sharp results for the diffusion of the walk on $\Z$
generated by the location of points of the sequence $\{n\alpha +\beta\}$ on a
binary partition of the unit interval. Finally we give some applications of our
method.


title: Near-Field Focusing Plates and Their Design

abstract:
  This paper describes the design of near-field focusing plates, which are
grating-like structures that can focus electromagnetic radiation to spots or
lines of arbitrarily small subwavelength dimension. A general procedure is
outlined for designing a near-field plate given a desired image, and its
implementation at microwave frequencies is discussed. Full-wave (method of
moments) simulations clearly demonstrate the near-field plate's ability to
overcome the diffraction limit. Finally, it is shown that the performance of
near-field plates is weakly affected by losses.


title:
Evidence for charged B meson decays to a1(1260)+/- pi0 and a1(1260)0
  pi+/-

abstract:
  We present measurements of the branching fractions for the decays B+/- -->
a1(1260)+/- pi0 and B+/- --> a1(1260)0 pi+/- from a data sample of 232 * 10^6
BB pairs produced in e+e- annihilation through the Y(4S) resonance. We measure
the branching fraction B(B+/- --> a1(1260)+/- pi0) * B(a1(1260)+/- --> pi- pi+
pi+/-) = (13.2 +/- 2.7 +/- 2.1) * 10^-6 with a significance of 4.2 sigma, and
the branching fraction B(B+/- --> a1(1260)0 pi+/-) * B(a1(1260)0 --> pi- pi+
pi0) = (20.4 +/- 4.7 +/- 3.4) * 10^-6 with a significance of 3.8 sigma, where
the first error quoted is statistical and the second is systematic.


title:
Evidence for a dynamic phase transition in [Co/Pt]_3 magnetic
  multilayers

abstract:
  A dynamic phase transition (DPT) with respect to the period P of an applied
alternating magnetic field has been observed previously in numerical
simulations of magnetic systems. However, experimental evidence for this DPT
has thus far been limited to qualitative observations of hysteresis loop
collapse in studies of hysteresis loop area scaling. Here, we present
significantly stronger evidence for the experimental observation of this DPT,
in a [Co(4 A)/Pt(7 A)]_3-multilayer system with strong perpendicular
anisotropy. We applied an out-of-plane, time-varying (sawtooth) field to the
[Co/Pt]_3 multilayer, in the presence of a small additional constant field,
H_b. We then measured the resulting out-of-plane magnetization time series to
produce nonequilibrium phase diagrams (NEPDs) of the cycle-averaged
magnetization, Q, and its variance, Var(Q), as functions of P and H_b. The
experimental NEPDs are found to strongly resemble those calculated from
simulations of a kinetic Ising model under analagous conditions. The similarity
of the experimental and simulated NEPDs, in particular the presence of a
localized peak in the variance Var(Q) in the experimental results, constitutes
strong evidence for the presence of this DPT in our magnetic multilayer
samples. Technical challenges related to the hysteretic nature and response
time of the electromagnet used to generate the time-varying applied field
precluded us from extracting meaningful critical scaling exponents from the
current data. However, based on our results, we propose refinements to the
experimental procedure which could potentially enable the determination of
critical exponents in the future.


title:
An Introduction to Relativistic Quantum Mechanics. I. From Relativity to
  Dirac Equation

abstract:
  By using the general concepts of special relativity and the requirements of
quantum mechanics, Dirac equation is derived and studied. Only elementary
knowledge of spin and rotations in quantum mechanics and standard handlings of
linear algebra are employed for the development of the present work.


title: Periodic complementary sets of binary sequences

abstract:
  Let PCS_p^N denote a set of p binary sequences of length N such that the sum
of their periodic auto-correlation functions is a delta-function. In the 1990,
Boemer and Antweiler addressed the problem of constructing such sequences. They
presented a table covering the range p <= 12, N <= 50 and showing in which
cases it was known at that time whether such sequences exist, do not exist, or
the question of existence is undecided. The number of undecided cases was
rather large.
  Subsequently the number of undecided cases was reduced to 26 by the author.
In the present note, several cyclic difference families are constructed and
used to obtain new sets of periodic binary sequences. Thereby the original
problem of Boemer and Antweiler is completely solved.


title: Designing Conducting Polymers Using Bioinspired Ant Algorithms

abstract:
  Ant algorithms are inspired in real ants and the main idea is to create
virtual ants that travel into the space of possible solution depositing virtual
pheromone proportional to how good a specific solution is. This creates a
autocatalytic (positive feedback) process that can be used to generate
automatic solutions to very difficult problems. In the present work we show
that these algorithms can be used coupled to tight-binding hamiltonians to
design conducting polymers with pre-specified properties. The methodology is
completely general and can be used for a large number of optimization problems
in materials science.


abstract:
  We characterize Banach spaces with polynomial numerical index 1 when they
have the Radon-Nikod\'ym property. The holomorphic numerical index is
introduced and the characterization of the Banach space with holomorphic
numerical index 1 is obtained when it has the Radon-Nikod\'ym property.


title:
Structural and transport properties of
  GaAs/delta<Mn>/GaAs/InxGa1-xAs/GaAs quantum wells

abstract:
  We report results of investigations of structural and transport properties of
GaAs/Ga(1-x)In(x)As/GaAs quantum wells (QWs) having a 0.5-1.8 ML thick Mn
layer, separated from the QW by a 3 nm thick spacer. The structure has hole
mobility of about 2000 cm2/(V*s) being by several orders of magnitude higher
than in known ferromagnetic two-dimensional structures. The analysis of the
electro-physical properties of these systems is based on detailed study of
their structure by means of high-resolution X-ray diffractometry and
glancing-incidence reflection, which allow us to restore the depth profiles of
structural characteristics of the QWs and thin Mn containing layers. These
investigations show absence of Mn atoms inside the QWs. The quality of the
structures was also characterized by photoluminescence spectra from the QWs.
Transport properties reveal features inherent to ferromagnetic systems: a
specific maximum in the temperature dependence of the resistance and the
anomalous Hall effect (AHE) observed in samples with both "metallic" and
activated types of conductivity up to ~100 K. AHE is most pronounced in the
temperature range where the resistance maximum is observed, and decreases with
decreasing temperature. The results are discussed in terms of interaction of
2D-holes and magnetic Mn ions in presence of large-scale potential fluctuations
related to random distribution of Mn atoms. The AHE values are compared with
calculations taking into account its "intrinsic" mechanism in ferromagnetic
systems.


title: Effects of Compton scattering on the Gamma Ray Spectra of Solar flares

abstract:
  Using fully relativistic GEANT4 simulation tool kit, the transport of
energetic electrons generated in solar flares was Monte-Carlo simulated, and
resultant bremsstrahlung gamma-ray spectra were calculated. The solar
atmosphere was approximated by 10 vertically-stacked zones. The simulation took
into account two important physical processes,that the bremsstrahlung photons
emitted by precipitating relativistic electrons are strongly forward beamed
toward the photosphere, and that the majority of these gamma-rays must be
Compton back-scattered by the solar atmosphere in order to reach the observer.
Then, the Compton degradation was found to make the observable gamma-ray
spectra much softer than is predicted by simple analytic calculations. The
gamma-ray signals were found to be enhanced by several conditions, including a
broad pitch-angle distribution of the electrons, a near-limb flare longitude,
and a significant tilt in the magnetic field lines if the flare longitude is
rather small. These results successfully explain several important flare
properties observed in the hard X-ray to gamma-ray range, including in
particular those obtained with Yohkoh. A comparison of the Yohkoh spectrum from
a GOES X3.7 class limb flare on 1998 November 22, with a simulation assuming a
broad electron pitch-angle distribution, suggests that gamma-rays from this
particular solar flare were a mixture of direct bremsstrahlung photons and
their Comptonization.


title: Direct Measurement of Periodic Electric Forces in Liquids

abstract:
  The electric forces acting on an atomic force microscope tip in solution have
been measured using a microelectrochemical cell formed by two periodically
biased electrodes. The forces were measured as a function of lift height and
bias amplitude and frequency, providing insight into electrostatic interactions
in liquids. Real-space mapping of the vertical and lateral components of
electrostatic forces acting on the tip from the deflection and torsion of the
cantilever is demonstrated. This method enables direct probing of electrostatic
and convective forces involved in electrophoretic and dielectroforetic
self-assembly and electrical tweezer operation in liquid environments.


title: On the need to enhance physical insight via mathematical skills

abstract:
  It is becoming common to hear teaching advice about spending more time on the
"physics of the problem" so that students will get more physical insight and
develop a stronger intuition that can be very helpful when thinking about
physics problems. Based on this type of justification, mathematical skills such
as the ability to compute moments of inertia, center of mass, or gravitational
fields from mass distributions, and electrical fields from charge distributions
are considered "distracting mathematics" and therefore receive less attention.
We argue a) that this approach can have a negative influence on student
reasoning when dealing with questions of rotational dynamics, a highly
non-intuitive subject where even instructors may fail to provide correct
answers, and b) that exposure of students to mathematical reasoning and to a
wide range of computational techniques to obtain the moment of inertia of
different mass distributions will make students more comfortable with the
subject of rotational dynamics, thus improving their physical insight on the
topic.


title: The Nature of the Compact X-ray Source in Supernova Remnant RCW 103

abstract:
  The discovery of the 6.67 hr periodicity in the X-ray source 1E 161348-5055
associated with the supernova remnant RCW 103 has raised interesting
suggestions about the nature of the X-ray source. Here we argue that in either
accreting neutron star or magnetar model, a supernova fallback disk may be a
critical ingredient in theoretical interpretations of 1E 161348-5055. We
further emphasize the effect of fallback disks on the evolution of young
compact objects in various ways, and suggest that even SS 433 could also be
powered by fallback disk accretion process.


title: Cross Validation for Comparing Multiple Density Estimation Procedures

abstract:
  We demonstrate the consistency of cross validation for comparing multiple
density estimators using simple inequalities on the likelihood ratio. In
nonparametric problems, the splitting of data does not require the domination
of test data over the training/estimation data, contrary to Shao (1993). The
result is complementary to that of Yang (2005) and Yang (2006).


title: On Information Theory, Spectral Geometry and Quantum Gravity

abstract:
  We show that there exists a deep link between the two disciplines of
information theory and spectral geometry. This allows us to obtain new results
on a well known quantum gravity motivated natural ultraviolet cutoff which
describes an upper bound on the spatial density of information. Concretely, we
show that, together with an infrared cutoff, this natural ultraviolet cutoff
beautifully reduces the path integral of quantum field theory on curved space
to a finite number of ordinary integrations. We then show, in particular, that
the subsequent removal of the infrared cutoff is safe.


title: Information flow between composite stock index and individual stocks

abstract:
  We investigate the strength and the direction of information transfer in the
U.S. stock market between the composite stock price index of stock market and
prices of individual stocks using the transfer entropy. Through the
directionality of the information transfer, we find that individual stocks are
influenced by the index of the market.


title: The Effect of Variability on the Estimation of Quasar Black Hole Masses

abstract:
  We investigate the time-dependent variations of ultraviolet (UV) black hole
mass estimates of quasars in the Sloan Digital Sky Survey (SDSS). From SDSS
spectra of 615 high-redshift (1.69 < z < 4.75) quasars with spectra from two
epochs, we estimate black hole masses, using a single-epoch technique which
employs an additional, automated night-sky-line removal, and relies on UV
continuum luminosity and CIV (1549A) emission line dispersion. Mass estimates
show variations between epochs at about the 30% level for the sample as a
whole. We determine that, for our full sample, measurement error in the line
dispersion likely plays a larger role than the inherent variability, in terms
of contributing to variations in mass estimates between epochs. However, we use
the variations in quasars with r-band spectral signal-to-noise ratio greater
than 15 to estimate that the contribution to these variations from inherent
variability is roughly 20%. We conclude that these differences in black hole
mass estimates between epochs indicate variability is not a large contributer
to the current factor of two scatter between mass estimates derived from low-
and high-ionization emission lines.


title: Localization of Matters on Pure Geometrical Thick Branes

abstract:
  In the literatures, several types of thick smooth brane configurations in a
pure geometric Weyl integrable 5-dimensional space time have been presented.
The Weyl geometry is a non-Riemannian modification of 5-dimensional
Kaluza--Klein (KK) theory. All these thick brane solutions preserve
4-dimensional Poincar\'e invariance, and some of them break $Z_2$--symmetry
along the extra dimension. In this paper, we study localization of various
matter fields on these pure geometrical thick branes, which also localize the
graviton. We present the shape of the potential of the corresponding
Schr$\mathrm{\ddot{o}}$dinger problem and obtain the lowest KK mode. It is
showed that, for both spin 0 scalars and spin 1 vectors, there exists a
continuum gapless spectrum of KK states with $m^2>0$. But only the massless
mode of scalars is found to be normalizable on the brane. However, for the
massless left or right chiral fermion localization, there must be some kind of
Yukawa coupling. For a special coupling, there exist a series of discrete
massive KK modes with $m^2 >0$. It is also showed that for a given coupling
constant only one of the massless chiral modes is localized on the branes.


title: Symmetries of spatial graphs and Simon invariants

abstract:
  An ordered and oriented 2-component link L in the 3-sphere is said to be
achiral if it is ambient isotopic to its mirror image ignoring the orientation
and ordering of the components. Kirk-Livingston showed that if L is achiral
then the linking number of L is not congruent to 2 modulo 4. In this paper we
study orientation-preserving or reversing symmetries of 2-component links,
spatial complete graphs on 5 vertices and spatial complete bipartite graphs on
3+3 vertices in detail, and determine the necessary conditions on linking
numbers and Simon invariants for such links and spatial graphs to be symmetric.


title: Pirogov-Sinai Theory With New Contours for Symmetric Models

abstract:
  The contour argument was introduced by Peierls for two dimensional Ising
model. Peierls benefited from the particular symmetries of the Ising model. For
non-symmetric models the argument was developed by Pirogov and Sinai. It is
very general and rather difficult. Intuitively clear that the Peierls argument
does work for any symmetric model. But contours defined in Pirogov-Sinai theory
do not work if one wants to use Peierls argument for more general symmetric
models. We give a new definition of contour which allows relatively easier
prove the main result of the Pirogov-Sinai theory for symmetric models. Namely,
our contours allow us to apply the classical Peierls argument (with contour
removal operation).


title:
Faithful qubit transmission against collective noise without ancillary
  qubits

abstract:
  We present a faithful qubit transmission scheme with linear optics against
collective noise, not resorting to ancillary qubits. Its set-up is composed of
three unbalanced polarization interferometers, based on a polarizing beam
splitter, a beam splitter and a half-wave plate, which makes this scheme more
feasible than others with present technology. The fidelity of successful
transmission is 1, independent of the parameters of the collective noise, and
the success probability for obtaining an uncorrupted state can be improved to
100% with some time delayers. Moreover, this scheme has some good applications
in one-way quantum communication for rejecting the errors caused by the
collective noise in quantum channel.


title: Twisted Gauge and Gravity Theories on the Groenewold-Moyal Plane

abstract:
  Recent work [hep-th/0504183,hep-th/0508002] indicates an approach to the
formulation of diffeomorphism invariant quantum field theories (qft's) on the
Groenewold-Moyal (GM) plane. In this approach to the qft's, statistics gets
twisted and the S-matrix in the non-gauge qft's becomes independent of the
noncommutativity parameter theta^{\mu\nu}. Here we show that the noncommutative
algebra has a commutative spacetime algebra as a substructure: the Poincare,
diffeomorphism and gauge groups are based on this algebra in the twisted
approach as is known already from the earlier work of [hep-th/0510059]. It is
natural to base covariant derivatives for gauge and gravity fields as well on
this algebra. Such an approach will in particular introduce no additional gauge
fields as compared to the commutative case and also enable us to treat any
gauge group (and not just U(N)). Then classical gravity and gauge sectors are
the same as those for \theta^{\mu \nu}=0, but their interactions with matter
fields are sensitive to theta^{\mu \nu}. We construct quantum noncommutative
gauge theories (for arbitrary gauge groups) by requiring consistency of twisted
statistics and gauge invariance. In a subsequent paper (whose results are
summarized here), the locality and Lorentz invariance properties of the
S-matrices of these theories will be analyzed, and new non-trivial effects
coming from noncommutativity will be elaborated.
  This paper contains further developments of [hep-th/0608138] and a new
formulation based on its approach.

categories: hep-th gr-qc hep-ph math-ph math.MP math.QA


title: Bohmian Mechanics at Space-Time Singularities. I. Timelike Singularities

abstract:
  We develop an extension of Bohmian mechanics to a curved background
space-time containing a singularity. The present paper focuses on timelike
singularities. We use the naked timelike singularity of the super-critical
Reissner-Nordstrom geometry as an example. While one could impose boundary
conditions at the singularity that would prevent the particles from falling
into the singularity, we are interested here in the case in which particles
have positive probability to hit the singularity and get annihilated. The wish
for reversibility, equivariance, and the Markov property then dictates that
particles must also be created by the singularity, and indeed dictates the rate
at which this must occur. That is, a stochastic law prescribes what comes out
of the singularity. We specify explicit equations of a non-rigorous model
involving an interior-boundary condition on the wave function at the
singularity, which can be used also in other versions of quantum theory besides
Bohmian mechanics. As the resulting theory involves particle creation and
annihilation, it can be regarded as a quantum field theory, and the stochastic
process for the Bohmian particles is analogous to Bell-type quantum field
theories.


title: Coulomb effects on the formation of proton halo nuclei

abstract:
  The exotic structures in the 2s_{1/2} states of five pairs of mirror nuclei
^{17}O-^{17}F, ^{26}Na-^{26}P, ^{27}Mg-^{27}P, ^{28}Al-^{28}P and
^{29}Si-^{29}P are investigated with the relativistic mean-field (RMF) theory
and the single-particle model (SPM) to explore the role of the Coulomb effects
on the proton halo formation. The present RMF calculations show that the exotic
structure of the valence proton is more obvious than that of the valence
neutron of its mirror nucleus, the difference of exotic size between each
mirror nuclei becomes smaller with the increase of mass number A of the mirror
nuclei and the ratios of the valence proton and valence neutron
root-mean-square (RMS) radius to the matter radius in each pair of mirror
nuclei all decrease linearly with the increase of A. In order to interpret
these results, we analyze two opposite effects of Coulomb interaction on the
exotic structure formation with SPM and find that the contribution of the
energy level shift is more important than that of the Coulomb barrier for light
nuclei. However, the hindrance of the Coulomb barrier becomes more obvious with
the increase of A. When A is larger than 34, Coulomb effects on the exotic
structure formation will almost become zero because its two effects counteract
with each other.


title: Vortex states in superconductors with strong Pauli-paramagnetic effect

abstract:
  Using the quasiclassical theory, we analyze the vortex structure of
strong-paramagnetic superconductors.There, induced paramagnetic moments are
accumulated exclusively around the vortex core. We quantitatively evaluate the
significant paramagnetic effect in the H-dependence of various quantities, such
as low temperature specific heat, Knight shift, magnetization and the flux line
lattice (FLL) form factor. The anomalous H-dependence of the FLL form factor
observed by the small angle neutron scattering in CeCoIn_5 is attributable to
the large paramagnetic contribution.


title: Suzaku wide-band observations of SN 1006

abstract:
  We report on the wide band spectra of SN 1006 as observed by Suzaku. Thermal
and nonthermal emission are successfully resolved thanks to the excellent
spectral response of Suzaku's X-ray CCD XIS. The nonthermal emission cannot be
reproduced by a simple power-law model but needs a roll-off at 5.7$\times
10^{16}$ Hz = 0.23 keV. The roll-off frequency is significantly higher in the
northeastern rim than in the southwestern rim. We also have placed the most
stringent upper limit of the flux above 10 keV using the Hard X-ray Detector.


title: Rational solutions of the Noumi and Yamada system of type $A_4^{(1)}$

abstract:
  In this paper, we completely classify the raional solutions of the Noumi and
Yamada system of type A_4^{(1)}, which is a generalization of the forth
Painlev\'e equation. The rational solutions are classified to three types by
the B\"acklund transformation group.


title:
A multi-objective optimization procedure to develop
  modified-embedded-atom-method potentials: an application to magnesium

abstract:
  We have developed a multi-objective optimization (MOO) procedure to construct
modified-embedded-atom-method (MEAM) potentials with minimal manual fitting.
This procedure has been applied successfully to develop a new MEAM potential
for magnesium. The MOO procedure is designed to optimally reproduce multiple
target values that consist of important materials properties obtained from
experiments and first-principles calculations based on density-functional
theory (DFT). The optimized target quantities include elastic constants,
cohesive energies, surface energies, vacancy formation energies, and the forces
on atoms in a variety of structures. The accuracy of the new potential is
assessed by computing several material properties of Mg and comparing them with
those obtained from other potentials previously published. We found that the
present MEAM potential yields a significantly better overall agreement with DFT
calculations and experiments.


title:
Optical and radio survey of Southern Compact Groups of galaxies. I.
  Pilot study of six groups

abstract:
  Multi-wavelength observations of Hickson's Compact Groups (HCGs) have shown
that many of these groups are physical bound structures and are in different
stage of evolution, from spiral-dominated systems to almost merged objects.
Very few studies have analysed the Southern Compact Groups (SCGs) sample, which
is though to be younger that HCGs, due to an on average higher number of spiral
galaxies. We present here the first results from optical and radio observations
on a pilot sample of SCGs.


title: Multi-Photon Interference and Temporal Distinguishability of Photons

abstract:
  A number of recent interference experiments involving multiple photons are
reviewed. These experiments include generalized photon bunching effects,
generalized Hong-Ou-Mandel interference effects and multi-photon interferometry
for demonstrations of multi-photon de Broglie wavelength. The multi-photon
states used in these experiments are from two pairs of photons in parametric
down-conversion. We find that the size of the interference effect in these
experiments, characterized by the visibility of interference pattern, is
governed by the degree of distinguishability among different pairs of photons.
Based on this discovery, we generalize the concept of multi-photon temporal
distinguishability and relate it to a number of multi-photon interference
effects. Finally, we make an attempt to interpret the coherence theory by the
multi-photon interference via the concept of temporal distinguishability of
photons.


title:
Soft gamma-ray galactic ridge emission as unveiled by SPI aboard
  INTEGRAL

abstract:
  The origin of the soft gamma-ray (200 keV - 1 MeV) galactic ridge emission is
one of the long-standing mysteries in the field of high-energy astrophysics.
Population studies at lower energies have shown that emission from accreting
compact objects gradually recedes in this domain, leaving place to another
source of gamma-ray emission that is characterised by a hard power-law spectrum
extending from 100 keV up to 100 MeV The nature of this hard component has
remained so far elusive, partly due to the lack of sufficiently sensitive
imaging telescopes that would be able to unveil the spatial distribution of the
emission. The SPI telescope aboard INTEGRAL allows now for the first time the
simultaneous imaging of diffuse and point-like emission in the soft gamma-ray
regime. We present here all-sky images of the soft gamma-ray continuum emission
that clearly reveal the morphology of the different emission components. We
discuss the implications of our results on the nature of underlying emission
processes and we put our results in perspective of GLAST studies of diffuse
galactic continuum emission.


title:
Semiparametrically efficient rank-based inference for shape II. Optimal
  R-estimation of shape

abstract:
  A class of R-estimators based on the concepts of multivariate signed ranks
and the optimal rank-based tests developed in Hallin and Paindaveine [Ann.
Statist. 34 (2006)] is proposed for the estimation of the shape matrix of an
elliptical distribution. These R-estimators are root-n consistent under any
radial density g, without any moment assumptions, and semiparametrically
efficient at some prespecified density f. When based on normal scores, they are
uniformly more efficient than the traditional normal-theory estimator based on
empirical covariance matrices (the asymptotic normality of which, moreover,
requires finite moments of order four), irrespective of the actual underlying
elliptical density. They rely on an original rank-based version of Le Cam's
one-step methodology which avoids the unpleasant nonparametric estimation of
cross-information quantities that is generally required in the context of
R-estimation. Although they are not strictly affine-equivariant, they are shown
to be equivariant in a weak asymptotic sense. Simulations confirm their
feasibility and excellent finite-sample performances.


title:
Farey Statistics in Time n^{2/3} and Counting Primitive Lattice Points
  in Polygons

abstract:
  We present algorithms for computing ranks and order statistics in the Farey
sequence, taking time O (n^{2/3}). This improves on the recent algorithms of
Pawlewicz [European Symp. Alg. 2007], running in time O (n^{3/4}). We also
initiate the study of a more general algorithmic problem: counting primitive
lattice points in planar shapes.


title:
d-alpha Correlation functions and collective motion in Xe+Au collisions
  at E/A=50 MeV

abstract:
  The interplay of the effects of geometry and collective motion on d-$\alpha$
correlation functions is investigated for central Xe+Au collisions at E/A=50
MeV. The data cannot be explained without collective motion, which could be
partly along the beam axis. A semi-quantitative description of the data can be
obtained using a Monte-Carlo model, where thermal emission is superimposed on
collective motion. Both the emission volume and the competition between the
thermal and collective motion influence significantly the shape of the
correlation function, motivating new strategies for extending intensity
interferometry studies to massive particles.


title:
Measurement of the near-threshold $e^+e^- \to D \bar D$ cross section
  using initial-state radiation

abstract:
  We report measurements of the exclusive cross section for $e^+e^- \to D \bar
D $, where $D=D^0$ or $D^+$, in the center-of-mass energy range from the $D
\bar D $ threshold to $5\mathrm{GeV}/c^2$ with initial-state radiation. The
analysis is based on a data sample collected with the Belle detector with an
integrated luminosity of 673 $\mathrm{fb}^{-1}$.


title:
2004 IMS Medallion Lecture: Local Rademacher complexities and oracle
  inequalities in risk minimization

abstract:
  Let $\mathcal{F}$ be a class of measurable functions $f:S\mapsto [0,1]$
defined on a probability space $(S,\mathcal{A},P)$. Given a sample
(X_1,...,X_n) of i.i.d. random variables taking values in S with common
distribution P, let P_n denote the empirical measure based on (X_1,...,X_n). We
study an empirical risk minimization problem $P_nf\to \min$, $f\in
\mathcal{F}$. Given a solution $\hat{f}_n$ of this problem, the goal is to
obtain very general upper bounds on its excess risk
\[\mathcal{E}_P(\hat{f}_n):=P\hat{f}_n-\inf_{f\in \mathcal{F}}Pf,\] expressed
in terms of relevant geometric parameters of the class $\mathcal{F}$. Using
concentration inequalities and other empirical processes tools, we obtain both
distribution-dependent and data-dependent upper bounds on the excess risk that
are of asymptotically correct order in many examples. The bounds involve
localized sup-norms of empirical and Rademacher processes indexed by functions
from the class. We use these bounds to develop model selection techniques in
abstract risk minimization problems that can be applied to more specialized
frameworks of regression and classification.


title:
Equivariant Birch-Swinnerton-Dyer conjecture for the base change of
  elliptic curves: An example

abstract:
  Let E be an elliptic curved defined over $\Q$ and let $K/\Q$ be a finite
Galois extension with Galois group G. The equivariant Birch-Swinnerton-Dyer
conjecture for $h^1(E\times_{\Q} K)(1)$ viewed as a motive over $\Q$ with
coefficients in $\Q[G]$ relates the twisted L-values associated with E with the
arithmetic invariants of the same. In this paper we prescribe an approach to
verify this conjecture for a given data. Using this approach, we verify the
conjecture for an elliptic curve of conductor 11 and an S_3-extension of $\Q$.


title: X-Rays From Massive OB Stars: Thermal Emission From Radiative Shocks

abstract:
  Chandra gratings spectra of a sample of 15 massive OB stars were analyzed
under the basic assumption that the X-ray emission is produced in an ensemble
of shocks formed in the winds driven by these objects. Shocks develop either as
a result of radiation-driven instabilities or due to confinement of the wind by
relatively strong magnetic field, and since they are radiative, a simple model
of their X-ray emission was developed that allows a direct comparison with
observations. According to our model, the shock structures (clumps, complete or
fractional shells) eventually become `cold' clouds in the X-ray sky of the
star. As a result, it is expected that for large covering factors of the hot
clumps, there is a high probability for X-ray absorption by the `cold' clouds,
resulting in blue-shifted spectral lines. Our analysis has revealed that such a
correlation indeed exists for the considered sample of OB stars. As to the
temperature characteristics of the X-ray emission plasma, the studied OB stars
fall in two groups: (i) one with plasma temperature limited to 0.1-0.4 keV;
(ii) the other wtih X-rays produced in plasmas at considerably higher
temperatures. We argue that the two groups correspond to different mechanisms
for the origin of X-rays: in radiative-driven instability shocks and in
magnetically-confined wind shocks, respectively.


title:
Neutron star cooling after deep crustal heating in the X-ray transient
  KS 1731-260

abstract:
  We simulate the cooling of the neutron star in the X-ray transient KS
1731-260 after the source returned to quiescence in 2001 from a long (>~ 12.5
yr) outburst state. We show that the cooling can be explained assuming that the
crust underwent deep heating during the outburst stage. In our best theoretical
scenario the neutron star has no enhanced neutrino emission in the core, and
its crust is thin, superfluid, and has the normal thermal conductivity. The
thermal afterburst crust-core relaxation in the star may be not over.


title: Quantum toboggans with two branch points

abstract:
  Wave functions describing quantum toboggans with two branch points (QT2) are
defined along complex contours of coordinates which spiral around these branch
points. The classification of QT2 is found in terms of certain ``winding
descriptors" $\varrho$. A mapping $x^{(\varrho)}(s) \to y^{(0)}(s)$ is then
presented which rectifies the contours for a subset of the simplest
$\varrho=\varrho_0$.


title:
Magneto-gyrotropic photogalvanic effects due to inter-subband absorption
  in quantum wells

abstract:
  We report on the observation of the magneto-photogalvanic effect (MPGE) due
to inter-subband transitions in (001)-oriented GaAs quantum wells. This effect
is related to the gyrotropic properties of the structures. It is shown that
inter-subband absorption of linearly polarized radiation may lead to
spin-related as well as spin independent photocurrents if an external magnetic
field is applied in the plane of the quantum well. The experimental results are
analyzed in terms of the phenomenological theory and microscopic models of MPGE
based on either asymmetric optical excitation or asymmetric relaxation of
carriers in k-space. We observed resonant photocurrents not only at oblique
incidence of radiation but also at normal incidence demonstrating that
conventionally applied selection rules for the inter-subband optical
transitions are not rigorous.


abstract:
  Discussion of "2004 IMS Medallion Lecture: Local Rademacher complexities and
oracle inequalities in risk minimization" by V. Koltchinskii [arXiv:0708.0083]


title: Soret Motion of a Charged Spherical Colloid

abstract:
  The thermophoretic motion of a charged spherical colloidal particle and its
accompanying cloud of counterions and co-ions in a temperature gradient is
studied theoretically. Using the Debye-Huckel approximation, the Soret drift
velocity of a weakly charged colloid is calculated analytically. For highly
charged colloids, the nonlinear system of electrokinetic equations is solved
numerically, and the effects of high surface potential, dielectrophoresis, and
convection are examined. Our results are in good agreement with some of the
recent experiments on highly charged colloids without using adjustable
parameters.


title: A useful correspondence between fluid convection and ecosystem operation

abstract:
  Both ecological systems and convective fluid systems are examples of open
systems which operate far-from-equilibrium. This article demonstrates that
there is a correspondence between a resource-consumer chemostat ecosystem and
the Rayleigh-Benard (RB) convective fluid system. The Lorenz dynamics of the RB
system can be translated into an ecosystem dynamics. Not only is there a
correspondence between the dynamical equations, also the physical
interpretations show interesting analogies. By using this fluid-ecosystem
analogy, we are able to derive the correct value of the size of convection
rolls by competitive fitness arguments borrowed from ecology. We finally
conjecture that the Lorenz dynamics can be extended to describe more complex
convection patterns that resemble ecological predation.


title: Fluctuations of a weakly interacting Bose-Einstein condensate

abstract:
  Fluctuations of the number of condensed atoms in a finite-size, weakly
interacting Bose gas confined in a box potential are investigated for
temperatures up to the critical region. The canonical partition functions are
evaluated using a recursive scheme for smaller systems, and a saddle-point
approximation for larger samples, that allows to treat realistic size systems
containing up to $N \sim 10^5$ particles. We point out the importance of
particle-number constrain and interactions between out of condensate atoms for
the statistics near the critical region. For sufficiently large systems the
crossover from the anomalous to normal scaling of the fluctuations is observed.
The excitations are described in a self-consistent way within the
Bogoliubov-Popov approximation, and the interactions between thermal atoms are
described by means of the Hartree-Fock method.


title:
Note sur la d\'etermination alg\'ebrique du groupe fondamental
  pro-r\'esoluble d'une courbe affine

abstract:
  Let X be a smooth projective algebraic curve of genus g minus $r\geq 1$
points defined over an algebraically closed field k of characteristic $p\geq
0$. The structure of the largest prime to p quotient of the \'etale fundamental
group is well known by transcendental methods : it is isomorphic to the largest
prime to p quotient of a free pro-finite group on 2g+r-1 generators. We show
that, with purely algebraic means, we can prove the corresponding result for
the largest pro-solvable quotient of these groups.


abstract:
  Discussion of ``2004 IMS Medallion Lecture: Local Rademacher complexities and
oracle inequalities in risk minimization'' by V. Koltchinskii [arXiv:0708.0083]


title:
Solving the cosmic lithium problems with primordial late-decaying
  particles

abstract:
  We investigate the modifications to predictions for the abundances of light
elements from standard Big-Bang nucleosynthesis when exotic late-decaying
particles with lifetimes exceeding ~1 sec are prominent in the early Universe.
Utilising a model-independent analysis of the properties of these long-lived
particles, we identify the parameter space associated with models that are
consistent with all observational data and hence resolve the much discussed
discrepancies between observations and theoretical predictions for the
abundances of Li^7 and Li^6.


title: Abundances on the Main Sequence of Omega Centauri

abstract:
  Abundance ratios of carbon, nitrogen and strontium relative to iron,
calculated using spectrum synthesis techniques, are given for a sample of main
sequence and turnoff stars that belong to the globular cluster omega Centauri.
The variations of carbon, nitrogen and/or strontium show several different
abundance patterns as a function of [Fe/H]. The source of the
enhancements/depletions in carbon, nitrogen and/or strontium may be enrichment
from asymptotic giant branch stars of low (1--3 solar masses) and intermediate
(3--8 solar masses) mass. Massive rotating stars which produce excess nitrogen
without carbon and oxygen overabundances may also play a role. These abundances
enable different contributors to be considered and incorporated into the
evolutionary picture of omega Cen.


title:
SDSS J150722.30+523039.8: a CV formed directly from a detached white
  dwarf/brown dwarf binary?

abstract:
  We present high-speed, three-colour photometry of the eclipsing cataclysmic
variable SDSS J150722.30+523039.8 (hereafter SDSS J1507). This system has an
orbital period of 66.61 minutes, placing it below the observed ``period
minimum'' for cataclysmic variables. We determine the system parameters via a
parameterised model of the eclipse fitted to the observed lightcurve by chi^2
minimisation. We obtain a mass ratio of q = 0.0623 +/- 0.0007 and an orbital
inclination i = 83.63 +/- 0.05 degrees. The primary mass is M_w = 0.90 +/- 0.01
M_sun. The secondary mass and radius are found to be M_r =0.056 +/- 0.001 M_sun
and R_r = 0.096 +/- 0.001 R_sun respectively. We find a distance to the system
of 160 +/- 10 pc. The secondary star in SDSS J1507 has a mass substantially
below the hydrogen burning limit, making it the second confirmed sub-stellar
donor in a cataclysmic variable.
  The very short orbital period of SDSS J1507 is readily explained if the
secondary star is nuclearly evolved, or if SDSS J1507 formed directly from a
detached white dwarf/brown dwarf binary. Given the lack of any visible
contribution from the secondary star, the very low secondary mass and the low
HeI(6678AA)/Halpha emission line ratio, we argue that SDSS J1507 probably
formed directly from a detached white dwarf/brown dwarf binary. If confirmed,
SDSS J1507 will be the first such system identified. The implications for
binary star evolution, the brown-dwarf desert and the common envelope phase are
discussed.


title:
Discussion of ``2004 IMS Medallion Lecture: Local Rademacher
  complexities and oracle inequalities in risk minimization'' by V.
  Koltchinskii


title:
On the well-posedness for the Ideal MHD equations in the
  Triebel-Lizorkin spaces

abstract:
  In this paper, we prove the local well-posedness for the Ideal MHD equations
in the Triebel-Lizorkin spaces and obtain blow-up criterion of smooth
solutions. Specially, we fill a gap in a step of the proof of the local
well-posedness part for the incompressible Euler equation in \cite{Chae1}.


title: Gamma-ray and neutrino diffuse emissions of the Galaxy above the TeV

abstract:
  In this contribution we will discuss recent results concerning the intensity
and the angular distribution of the gamma-ray and neutrino emissions as should
be originated from the hadronic scattering of cosmic rays (CR) with the
interstellar medium (ISM). We assumed that CR sources are supernova remnants
(SNR) and estimated the spatial distribution of primary nuclei by solving
numerically the diffusion equation. For the ISM, we considered recent models
for the 3D spatial distributions of molecular hydrogen. Respect to previous
results, we find the secondary gamma-ray and neutrino emissions to be more
peaked along the galactic equator and in the galactic centre which improves
significantly the perspectives of a positive detection. We compare our
predictions with the experimental limits/observations by MILAGRO and TIBET (for
the gamma-rays) and by AMANDA-II (for the neutrinos) and discuss the detection
perspectives for a km3 neutrino telescope to be built in the North hemisphere.


title:
Radiative and interelectronic-interaction corrections to the hyperfine
  splitting in highly charged B-like ions

abstract:
  The ground-state hyperfine splitting values of high-Z boronlike ions are
calculated. Calculation of the interelectronic-interaction contribution is
based on a combination of the 1/Z perturbation theory and the large-scale
configuration-interaction Dirac-Fock-Sturm method. The screened QED corrections
are evaluated utilizing an effective screening potential approach. Total
hyperfine splitting energies are presented for several B-like ions of
particular interest: {}^{45}Sc{}^{16+}, {}^{57}Fe{}^{21+}, {}^{207}Pb{}^{77+},
and {}^{209}Bi{}^{78+}. For lead and bismuth the experimental values of the 1s
hyperfine splitting are employed to improve significantly the theoretical
results by reducing the uncertainty due to the nuclear effects.


title: Constraint Algorithm for Extremals in Optimal Control Problems

abstract:
  A geometric method is described to characterize the different kinds of
extremals in optimal control theory. This comes from the use of a presymplectic
constraint algorithm starting from the necessary conditions given by
Pontryagin's Maximum Principle. Apart from the design of this general algorithm
useful for any optimal control problem, it is showed how it works to split the
set of extremals and, in particular, to characterize the strict abnormality. An
example of strict abnormal extremal for a particular control-affine system is
also given.