title: Gauss map on the theta divisor and Green's functions

abstract:
  In an earlier paper we constructed a Cartier divisor on the theta divisor of
a principally polarised abelian variety whose support is precisely the
ramification locus of the Gauss map. In this note we discuss a Green's function
associated to this locus. For jacobians we relate this Green's function to the
canonical Green's function of the corresponding Riemann surface.


title: Fredholm determinants and the statistics of charge transport

abstract:
  Using operator algebraic methods we show that the moment generating function
of charge transport in a system with infinitely many non-interacting Fermions
is given by a determinant of a certain operator in the one-particle Hilbert
space. The formula is equivalent to a formula of Levitov and Lesovik in the
finite dimensional case and may be viewed as its regularized form in general.
Our result embodies two tenets often realized in mesoscopic physics, namely,
that the transport properties are essentially independent of the length of the
leads and of the depth of the Fermi sea.


title: On Hadwiger Conjecture

abstract:
  We propose an algorithm to reduce a k-chromatic graph to a complete graph of
largest possible order through a well defined sequence of contractions. We
introduce a new matrix called transparency matrix and state its properties. We
then define correct contraction procedure to be executed to get largest
possible complete graph from given connected graph. We finally give a
characterization for k-chromatic graphs and use it to settle Hadwigers
conjecture.


title:
\chi_{c0,2} decay into light meson pairs and its implication of the
  scalar meson structures

abstract:
  In light of the recent data from BES collaboration for $\chi_{c0}\to VV$,
$PP$ and $SS$, and from CLEO-c for $\eta\eta$, $\eta^\prime\eta^\prime$ and
$\eta\eta^\prime$, we present a detailed analysis of the decays of heavy
quarkonia into light meson pairs such as $\chi_{c0,2}\to VV$, $PP$ and $SS$ in
a recently proposed parametrization scheme. An overall agreement with the data
is achieved in $\chi_{c0,2}\to VV$ and $PP$, while in $\chi_{c0}\to SS$ we find
that a possible existence of glueball-$q\bar{q}$ mixings is correlated with the
OZI-rule violations, which can be further examined at CLEO-c and BESIII in
$\chi_{c0}\to SS$ measurement.


title: Compact Corigid Objects in Triangulated Categories and Co-t-structures

abstract:
  In the work of Hoshino, Kato and Miyachi, the authors look at t-structures
induced by a compact object, C, of a triangulated category, T, which is rigid
in the sense of Iyama and Yoshino. Hoshino, Kato and Miyachi show that such an
object yields a non-degenerate t-structure on T whose heart es equivalent to
Mod(End(C)^op). Rigid objects in a triangulated category can be thought of as
behaving like chain differential graded algebras (DGAs).
  Analogously, looking at objects which behave like cochain DGAs naturally
gives the dual notion of a corigid object. Here, we see that a compact corigid
object, S, of a triangulated category, T, induces a structure similar to a
t-structure which we shall call a co-t-structure. We also show that the coheart
of this non-degenerate co-t-structure is equivalent to Mod(End(S)^op), and
hence an abelian subcategory of T.


title: Roughness of undoped graphene and its short-range induced gauge field

abstract:
  We present both numerical and analytical study of graphene roughness with a
crystal structure including $500 \times 500$ atoms. The roughness can
effectively result in a random gauge field and has important consequences for
its electronic structure. Our results show that its height fluctuations in
small scales have scaling behavior with a temperature dependent roughness
exponent in the interval of $ 0.6 < \chi < 0.7 $. The correlation function of
height fluctuations depends upon temperature with characteristic length scale
of $ \approx 90 {\AA}$ (at room temperature). We show that the correlation
function of the induced gauge field has a short-range nature with correlation
length of about $\simeq 2-3 {\AA}$. We also treat the problem analytically by
using the Martin-Siggia-Rose method. The renormalization group flows did not
yield any delocalized-localized transition arising from the graphene roughness.
Our results are in good agreement with recent experimental observations.


title: Relaxation dynamics in fluids of platelike colloidal particles

abstract:
  The relaxation dynamics of a model fluid of platelike colloidal particles is
investigated by means of a phenomenological dynamic density functional theory.
The model fluid approximates the particles within the Zwanzig model of
restricted orientations. The driving force for time-dependence is expressed
completely by gradients of the local chemical potential which in turn is
derived from a density functional -- hydrodynamic interactions are not taken
into account. These approximations are expected to lead to qualitatively
reliable results for low densities as those within the isotropic-nematic
two-phase region. The formalism is applied to model an initially spatially
homogeneous stable or metastable isotropic fluid which is perturbed by
switching a two-dimensional array of Gaussian laser beams. Switching on the
laser beams leads to an accumulation of colloidal particles in the beam
centers. If the initial chemical potential and the laser power are large enough
a preferred orientation of particles occurs breaking the symmetry of the laser
potential. After switching off the laser beams again the system can follow
different relaxation paths: It either relaxes back to the homogeneous isotropic
state or it forms an approximately elliptical high-density core which is
elongated perpendicular to the dominating orientation in order to minimize the
surface free energy. For large supersaturations of the initial isotropic fluid
the high-density cores of neighboring laser beams of the two-dimensional array
merge into complex superstructures.


title:
Influence of growth parameters on structural properties and bandgap of
  InN epilayers deposited in a showerhead MOVPE system

abstract:
  From a detailed analysis of InN epilayers deposited in a close-coupled
showerhead metalorganic vapour phase epitaxy (MOVPE) system under various
conditions we investigate the effect of growth parameters on the lattice
constants of the InN layer. The layers are under significant internal
hydrostatic stress which influences the optical properties. Samples typically
fall into two broad categories of stress, with resultant luminescence emission
around 0.8eV and 1.1eV. We can correlate the internal stress in the layer and
the value of the optical absorption edge, and the PL emission wavelength.


title: How Do Quasicrystals Grow?

abstract:
  Using molecular simulations, we show that the aperiodic growth of
quasicrystals is controlled by the ability of the growing quasicrystal
`nucleus' to incorporate kinetically trapped atoms into the solid phase with
minimal rearrangement. In the system under investigation, which forms a
dodecagonal quasicrystal, we show that this process occurs through the
assimilation of stable icosahedral clusters by the growing quasicrystal. Our
results demonstrate how local atomic interactions give rise to the long-range
aperiodicity of quasicrystals.


title: Sterile neutrino oscillations after first MiniBooNE results

abstract:
  In view of the recent results from the MiniBooNE experiment we revisit the
global neutrino oscillation fit to short-baseline neutrino data by adding one
or two sterile neutrinos with eV-scale masses to the three Standard Model
neutrinos, and for the first time we consider also the global fit with three
sterile neutrinos. Four-neutrino oscillations of the (3+1) type have been only
marginally allowed before the recent MiniBooNE results, and become even more
disfavored with the new data (at the level of $4\sigma$). In the framework of
so-called (3+2) five-neutrino mass schemes we find severe tension between
appearance and disappearance experiments at the level of more than $3\sigma$,
and hence no satistfactory fit to the global data is possible in (3+2) schemes.
This tension remains also when a third sterile neutrino is added, and the
quality of the global fit does not improve significantly in a (3+3) scheme. It
should be noted, however, that in models with more than one sterile neutrino
the MiniBooNE results are in perfect agreement with the LSND appearance
evidence, thanks to the possibility of CP violation available in such
oscillation schemes. Furthermore, if disappearance data are not taken into
account (3+2) oscillations provide an excellent fit to the full MiniBooNE
spectrum including the event excess at low energies.


title: Reconstructing weak values without weak measurements

abstract:
  I propose a scheme for reconstructing the weak value of an observable without
the need for weak measurements. The post-selection in weak measurements is
replaced by an initial projector measurement. The observable can be measured
using any form of interaction, including projective measurements. The
reconstruction is effected by measuring the change in the expectation value of
the observable due to the projector measurement. The weak value may take
nonclassical values if the projector measurement disturbs the expectation value
of the observable.


title:
An all-optical ion-loading technique for scalable microtrap
  architectures

abstract:
  An experimental demonstration of a novel all-optical technique for loading
ion traps, that has particular application to microtrap architectures, is
presented. The technique is based on photo-ionisation of an atomic beam created
by pulsed laser ablation of a calcium target, and provides improved temporal
control compared to traditional trap loading methods. Ion loading rates as high
as 125 ions per second have so far been observed. Also described are
observations of trap loading where Rydberg state atoms are photo-ionised by the
ion Doppler cooling laser.


title:
Bistability of optically-induced nuclear spin orientation in quantum
  dots

abstract:
  We demonstrate that bistability of the nuclear spin polarization in optically
pumped semiconductor quantum dots is a general phenomenon possible in dots with
a wide range of parameters. In experiment, this bistability manifests itself
via the hysteresis behavior of the electron Zeeman splitting as a function of
either pump power or external magnetic field. In addition, our theory predicts
that the nuclear polarization can strongly influence the charge dynamics in the
dot leading to bistability in the average dot charge.


title:
Spectroscopic distinction between the normal state pseudogap and the
  superconducting gap of cuprate high T_{c} superconductors

abstract:
  We report on broad-band infrared ellipsometry measurements of the c-axis
conductivity of underdoped RBa_{2}Cu_{3}O_{7-d} (R=Y, Nd, and La) single
crystals. Our data provide a detailed account of the spectral weight (SW)
redistributions due to the normal state pseudogap (PG) and the superconducting
(SC) gap. They show that these phenomena involve different energy scales,
exhibit distinct doping dependencies and thus are likely of different origin.
In particular, the SW redistribution in the PG state closely resembles the one
of a conventional charge- or spin density wave (CDW or SDW) system.


title: Non-topological solitons in field theories with kinetic self-coupling

abstract:
  We investigate some fundamental features of a class of non-linear
relativistic lagrangian field theories with kinetic self-coupling. We focus our
attention upon theories admitting static, spherically symmetric solutions in
three space dimensions which are finite-energy and stable. We determine general
conditions for the existence and stability of these non-topological soliton
solutions. In particular, we perform a linear stability analysis that goes
beyond the usual Derrick-like criteria. On the basis of these considerations we
obtain a complete characterization of the soliton-supporting members of the
aforementioned class of non-linear field theories. We then classify the family
of soliton-supporting theories according to the central and asymptotic
behaviors of the soliton field, and provide illustrative explicit examples of
models belonging to each of the corresponding sub-families. In the present work
we restrict most of our considerations to one and many-components scalar
models. We show that in these cases the finite-energy static spherically
symmetric solutions are stable against charge-preserving perturbations,
provided that the vacuum energy of the model vanishes and the energy density is
positive definite. We also discuss briefly the extension of the present
approach to models involving other types of fields, but a detailed study of
this more general scenario will be addressed in a separate publication.


title: The Mathematics

abstract:
  This is an essay that considering the knowledge structure and language of a
different nature, attempts to build on an explanation of the object of study
and characteristics of the mathematical science. We end up with a learning
cycle of mathematics and a paradigm for education, namely Learn to structure.


title:
Surveys of the Galactic Center and the Nature of the Galactic Center
  Lobe

abstract:
  The Galactic center (GC) is a dense and chaotic region filled with unusual
sources, such as intense star forming regions, dense star clusters, nonthermal
radio filaments, and a massive black hole. The proximity of the GC region makes
it an ideal place to study the unusual processes that tend to manifest
themselves in Galactic nuclei. This thesis uses single-dish and interferometric
radio continuum, radio recombination line, polarized radio continuum, and
mid-IR observations to study the wide variety of physical processes seen in the
GC region on physical scales from 0.1 to 100 parsecs. These observations
provide one of the most sensitive studies of the radio continuum emission in
the central 500 parsecs. I also study the properties of nonthermal radio
filaments, which can constrain their origin and the structure of the magnetic
field in the GC region.
  The presence of massive star clusters and a massive black hole suggest that
starburst and AGN phenomena can manifest themselves in our Galaxy. This thesis
explores this possibility by studying a 150-pc-tall, shell-like structure
called the Galactic center lobe (GCL). Our observations examine the spectral
index, dust emission, polarized continuum emission, and ionized gas throughout
the GCL. I find strong evidence supporting the idea that the GCL is a true
three-dimensional shell located in the GC region with nested layers of ionized,
magnetized, and mid-IR--emitting components. I compare the physical conditions
of the GCL to proposed models for its origin and find best agreement with
starburst outflows seen in other galaxies, yet consistent with the currently
observed pressure and star formation rate in the central tens of parsecs of our
Galaxy. (abridged)


title:
Dynamical Computation on Coefficients of Electroweak Chiral Lagrangian
  from One-doublet and Topcolor-assisted Technicolor Models

abstract:
  Based on previous studies deriving the chiral Lagrangian for pseudo scalar
mesons from the first principle of QCD, we derive the electroweak chiral
Lagrangian and build up a formulation for computing its coefficients from
one-doublet technicolor model and a schematic topcolor-assisted technicolor
model. We find that the coefficients of the electroweak chiral Lagrangian for
the topcolor-assisted technicolor model are divided into three parts: direct
TC2 interaction part, TC1 and TC2 induced effective Z' particle contribution
part, and ordinary quarks contribution part. The first two parts are computed
in this paper and we show that the direct TC2 interaction part is the same as
that in the one-doublet technicolor model, while effective Z' contributions are
at least proportional to the p^2 order parameter \beta_1 in the electroweak
chiral Lagrangian and typical features of topcolor-assisted technicolor model
are that it only allows positive T and U parameters and the T parameter varies
in the range 0\sim 1/(25\alpha), the upper bound of T parameter will decrease
as long as Z' mass become large. The S parameter can be either positive or
negative depending on whether the Z' mass is large or small. The Z' mass is
also bounded above and the upper bound depend on value of T parameter. We
obtain the values for all the coefficients of the electroweak chiral Lagrangian
up to order of p^4.


title:
Large underground, liquid based detectors for astro-particle physics in
  Europe: scientific case and prospects

abstract:
  This document reports on a series of experimental and theoretical studies
conducted to assess the astro-particle physics potential of three future
large-scale particle detectors proposed in Europe as next generation
underground observatories. The proposed apparatus employ three different and,
to some extent, complementary detection techniques: GLACIER (liquid Argon TPC),
LENA (liquid scintillator) and MEMPHYS (\WC), based on the use of large mass of
liquids as active detection media. The results of these studies are presented
along with a critical discussion of the performance attainable by the three
proposed approaches coupled to existing or planned underground laboratories, in
relation to open and outstanding physics issues such as the search for matter
instability, the detection of astrophysical- and geo-neutrinos and to the
possible use of these detectors in future high-intensity neutrino beams.


title: Particle Motion in the Rotating Black Ring Metric

abstract:
  In this paper, the equations of motion for geodesics in the neutral rotating
Black Ring metric are derived and the separability of these equations is
considered. The bulk of the paper is concerned with sets of solutions where the
geodesic equations can be examined analytically - specifically geodesics
confined to the axis of rotation, geodesics restricted to the equatorial plane,
and geodesics that circle through the centre of the ring. The geodesics on the
rotational axis behave like a particle in a potential well, while the geodesics
confined to the equatorial plane mimic those of the Schwarzschild metric. It is
shown that it is impossible to have circular orbits that pass through the ring,
but some numerical results are presented which suggest that it is possible to
have bound orbits that circle through the ring.


title: Homological Epimorphisms of Differential Graded Algebras

abstract:
  Let R and S be differential graded algebras. In this paper we give a
characterisation of when a differential graded R-S-bimodule M induces a full
embedding of derived categories M\otimes - :D(S)--> D(R). In particular, this
characterisation generalises the theory of Geigle and Lenzing's homological
epimorphisms of rings. Furthermore, there is an application of the main result
to Dwyer and Greenlees's Morita theory.


title:
A search for X-ray counterparts of the millisecond pulsars in the
  globular cluster M28 (NGC 6626)

abstract:
  A recent radio survey of globular clusters has increased the number of
millisecond pulsars drastically. M28 is now the globular cluster with the third
largest population of known pulsars, after Terzan 5 and 47 Tuc. This prompted
us to revisit the archival Chandra data on M28 to evaluate whether the newly
discovered millisecond pulsars find a counterpart among the various X-ray
sources detected in M28 previously. The radio position of PSR J1824-2452H is
found to be in agreement with the position of CXC 182431-245217 while some
faint unresolved X-ray emission near to the center of M28 is found to be
coincident with the millisecond pulsars PSR J1824-2452G, J1824-2452J,
J1824-2452I and J1824-2452E.


title:
Effective inverse spectral problem for rational Lax matrices and
  applications

abstract:
  We reconstruct a rational Lax matrix of size R+1 from its spectral curve (the
desingularization of the characteristic polynomial) and some additional data.
Using a twisted Cauchy--like kernel (a bi-differential of bi-weight (1-nu,nu))
we provide a residue-formula for the entries of the Lax matrix in terms of
bases of dual differentials of weights nu and 1-nu respectively. All objects
are described in the most explicit terms using Theta functions. Via a sequence
of ``elementary twists'', we construct sequences of Lax matrices sharing the
same spectral curve and polar structure and related by conjugations by rational
matrices. Particular choices of elementary twists lead to construction of
sequences of Lax matrices related to finite--band recurrence relations (i.e.
difference operators) sharing the same shape. Recurrences of this kind are
satisfied by several types of orthogonal and biorthogonal polynomials. The
relevance of formulae obtained to the study of the large degree asymptotics for
these polynomials is indicated.


title:
Magnetotransport properties of strained (Ga0.95, Mn0.05)As epilayers
  close to the metal-insulator transition: Description using Aronov-Altshuler
  three-dimensional scaling theory

abstract:
  The magnitude of the anisotropic magnetoresistance (AMR) and the longitudinal
resistance in compressively strained (Ga0.95, Mn0.05)As epilayers were measured
for the first time down to temperatures as low as 30 mK. Below temperatures of
3K the conductivity decreases ~ T^1/3 over two orders of magnitude in
temperature. The conductivity can be well described within the framework of a
3D scaling theory of Anderson's transition in the presence of spin scattering
in semiconductors. It is shown that the samples are on the metallic side but
very close to the metal-insulator transition (MIT). At lowest temperatures a
decrease in the AMR effect is observed, which is assigned to changes in the
coupling between the remaining itinerant carriers and the local Mn 5/2-spin
moments.


title:
Sensitivity of the spherical gravitational wave detector MiniGRAIL
  operating at 5 K

abstract:
  We present the performances and the strain sensitivity of the first spherical
gravitational wave detector equipped with a capacitive transducer and read out
by a low noise two-stage SQUID amplifier and operated at a temperature of 5 K.
We characterized the detector performance in terms of thermal and electrical
noise in the system output sygnal. We measured a peak strain sensitivity of
$1.5\cdot 10^{-20} Hz^{-1/2}$ at 2942.9 Hz. A strain sensitivity of better than
$5\cdot 10{-20}Hz{-1/2}$ has been obtained over a bandwidth of 30 Hz. We expect
an improvement of more than one order of magnitude when the detector will
operate at 50 mK. Our results represent the first step towards the development
of an ultracryogenic omnidirectional detector sensitive to gravitational
radiation in the 3kHz range.


title: An Energy Efficiency Perspective on Training for Fading Channels

abstract:
  In this paper, the bit energy requirements of training-based transmission
over block Rayleigh fading channels are studied. Pilot signals are employed to
obtain the minimum mean-square-error (MMSE) estimate of the channel fading
coefficients. Energy efficiency is analyzed in the worst case scenario where
the channel estimate is assumed to be perfect and the error in the estimate is
considered as another source of additive Gaussian noise. It is shown that bit
energy requirement grows without bound as the snr goes to zero, and the minimum
bit energy is achieved at a nonzero snr value below which one should not
operate. The effect of the block length on both the minimum bit energy and the
snr value at which the minimum is achieved is investigated. Flash training
schemes are analyzed and shown to improve the energy efficiency in the low-snr
regime. Energy efficiency analysis is also carried out when peak power
constraints are imposed on pilot signals.


title:
On the Low-SNR Capacity of Phase-Shift Keying with Hard-Decision
  Detection

abstract:
  The low-snr capacity of M-ary PSK transmission over both the additive white
Gaussian noise (AWGN) and fading channels is analyzed when hard-decision
detection is employed at the receiver. Closed-form expressions for the first
and second derivatives of the capacity at zero snr are obtained. The
spectral-efficiency/bit-energy tradeoff in the low-snr regime is analyzed by
finding the wideband slope and the bit energy required at zero spectral
efficiency. Practical design guidelines are drawn from the
information-theoretic analysis. The fading channel analysis is conducted for
both coherent and noncoherent cases, and the performance penalty in the
low-power regime for not knowing the channel is identified.


title: The Complexity of Orbits of Computably Enumerable Sets

abstract:
  The goal of this paper is to announce there is a single orbit of the c.e.
sets with inclusion, $\E$, such that the question of membership in this orbit
is $\Sigma^1_1$-complete. This result and proof have a number of nice
corollaries: the Scott rank of $\E$ is $\wock +1$; not all orbits are
elementarily definable; there is no arithmetic description of all orbits of
$\E$; for all finite $\alpha \geq 9$, there is a properly $\Delta^0_\alpha$
orbit (from the proof).
  A few small corrections made in this version


title:
HD147506b: A Super-Massive Planet in an Eccentric Orbit Transiting a
  Bright Star

abstract:
  We report the discovery of a massive (Mp = 9.04+/-0.50 MJup) planet
transiting the bright (V = 8.7) F8 star HD 147506, with an orbital period of
5.63341+/-0.00013 days and an eccentricity of e = 0.520+/-0.010. From the
transit light curve we determine that the radius of the planet is Rp =
0.982^{+0.038}_{0.105}RJup. HD 147506b (also coined HAT-P-2b) has a mass about
9 times the average mass of previously-known transiting exoplanets, and a
density of rho = 11.9 g cm-3, greater than that of rocky planets like the
Earth. Its mass and radius are marginally consistent with theories of structure
of massive giant planets composed of pure H and He, and may require a large
(~100 Earth mass) core to account for. The high eccentricity causes a 9-fold
variation of insolation of the planet between peri- and apastron. Using
follow-up photometry, we find that the center of transit is Tmid =
2,454,212.8559 +/- 0.0007 (HJD), and the transit duration is 0.177 +/-0.002 d.


title:
Radiative transfer and the energy equation in SPH simulations of star
  formation

abstract:
  We introduce and test a new and highly efficient method for treating the
thermal and radiative effects influencing the energy equation in SPH
simulations of star formation. The method uses the density, temperature and
gravitational potential of each particle to estimate a mean optical depth,
which then regulates the particle's heating and cooling. The method captures --
at minimal computational cost -- the effects of (i) the rotational and
vibrational degrees of freedom of H2, H2 dissociation, H0 ionisation, (ii)
opacity changes due to ice mantle melting, sublimation of dust, molecular
lines, H-, bound-free and free-free processes and electron scattering; (iv)
external irradiation; and (v) thermal inertia. The new algorithm reproduces the
results of previous authors and/or known analytic solutions. The computational
cost is comparable to a standard SPH simulation with a simple barotropic
equation of state. The method is easy to implement, can be applied to both
particle- and grid-based codes, and handles optical depths 0<tau<10^{11}.


title: Training Optimization for Gauss-Markov Rayleigh Fading Channels

abstract:
  In this paper, pilot-assisted transmission over Gauss-Markov Rayleigh fading
channels is considered. A simple scenario, where a single pilot signal is
transmitted every T symbols and T-1 data symbols are transmitted in between the
pilots, is studied. First, it is assumed that binary phase-shift keying (BPSK)
modulation is employed at the transmitter. With this assumption, the training
period, and data and training power allocation are jointly optimized by
maximizing an achievable rate expression. Achievable rates and energy-per-bit
requirements are computed using the optimal training parameters. Secondly, a
capacity lower bound is obtained by considering the error in the estimate as
another source of additive Gaussian noise, and the training parameters are
optimized by maximizing this lower bound.


title:
Influence of the single-particle Zeeman energy on the quantum Hall
  ferromagnet at high filling factors

abstract:
  In a recent paper [B. A. Piot et al., Phys. Rev. B 72, 245325 (2005)], we
have shown that the lifting of the electron spin degeneracy in the integer
quantum Hall effect at high filling factors should be interpreted as a
magnetic-field-induced Stoner transition. In this work, we extend the analysis
to investigate the influence of the single-particle Zeeman energy on the
quantum Hall ferromagnet at high filling factors. The single-particle Zeeman
energy is tuned through the application of an additional in-plane magnetic
field. Both the evolution of the spin polarization of the system and the
critical magnetic field for spin splitting are well described as a function of
the tilt angle of the sample in the magnetic field.


title: Performance Analysis for Multichannel Reception of OOFSK Signaling

abstract:
  In this paper, the error performance of on-off frequency shift keying (OOFSK)
modulation over fading channels is analyzed when the receiver is equipped with
multiple antennas. The analysis is conducted in two cases: the coherent
scenario where the fading is perfectly known at the receiver, and the
noncoherent scenario where neither the receiver nor the transmitter knows the
fading coefficients. For both cases, the maximum a posteriori probability (MAP)
detection rule is derived and analytical probability of error expressions are
obtained. The effect of fading correlation among the receiver antennas is also
studied. Simulation results indicate that for sufficiently low duty cycle
values, lower probability of error values with respect to FSK signaling are
achieved. Equivalently, when compared to FSK modulation, OOFSK with low duty
cycle requires less energy to achieve the same probability of error, which
renders this modulation a more energy efficient transmission technique.


title:
Interaction of modulated pulses in the nonlinear Schroedinger equation
  with periodic potential

abstract:
  We consider a cubic nonlinear Schroedinger equation with periodic potential.
In a semiclassical scaling the nonlinear interaction of modulated pulses
concentrated in one or several Bloch bands is studied. The notion of closed
mode systems is introduced which allows for the rigorous derivation of a finite
system of amplitude equations describing the macroscopic dynamics of these
pulses.


title: Error Probability Analysis of Peaky Signaling over Fading Channels

abstract:
  In this paper, the performance of signaling strategies with high
peak-to-average power ratio is analyzed in both coherent and noncoherent fading
channels. Two recently proposed modulation schemes, namely on-off binary
phase-shift keying and on-off quaternary phase-shift keying, are considered.
For these modulation formats, the optimal decision rules used at the detector
are identified and analytical expressions for the error probabilities are
obtained. Numerical techniques are employed to compute the error probabilities.
It is concluded that increasing the peakedness of the signals results in
reduced error rates for a given power level and hence improve the energy
efficiency.


title:
Effective Lagrangian at Cubic Order in Electromagnetic Fields and Vacuum
  Birefringence

abstract:
  The effective Lagrangian of electromagnetic fields at the cubic order in
field strength has been considered. This generalized Lagrangian is motivated by
electrodynamics on non-commutative spaces. We find the canonical and
symmetrical energy-momentum tensors and show that they possess non-zero traces.
The propagation of a linearly polarized laser beam in the external transverse
magnetic field is investigated. We evaluate the induced ellipticity which
allows us to obtain a constraint on parameters introduced from the PVLAS
experimental data.


title: Semiclassical wave propagation for large times

abstract:
  We study solutions of the time dependent Schr\"odinger equation on Riemannian
manifolds with oscillatory initial conditions given by Lagrangian states.
Semiclassical approximations describe these solutions for small h (where h is
the semiclassical parameter), but their accuracy for large times is in general
only understood up to the Ehrenfest time T ~ ln(1/h), and the most difficult
case is the one where the underlying classical system is chaotic.
  We show that on surfaces of constant negative curvature semiclassical
approximations remain accurate for times at least up to T ~ h^(-1/2) in the
case that the Lagrangian state is associated with an unstable manifold of the
geodesic flow.


title: Packing-Dimension Profiles and Fractional Brownian Motion

abstract:
  In order to compute the packing dimension of orthogonal projections
  Falconer and Howroyd (1997) introduced a family of packing dimension profiles
${\rm Dim}_s$ that are parametrized by real numbers $s>0$. Subsequently,
Howroyd (2001) introduced alternate $s$-dimensional packing dimension profiles
$\hbox{${\rm P}$-$\dim$}_s$ and proved, among many other things, that
$\hbox{${\rm P}$-$\dim$}_s E={\rm Dim}_s E$ for all integers $s>0$ and all
analytic sets $E\subseteq\R^N$. The goal of this article is to prove that
$\hbox{${\rm P}$-$\dim$}_s E={\rm Dim}_s E$ for all real numbers $s>0$ and
analytic sets $E\subseteq\R^N$. This answers a question of Howroyd (2001, p.
159). Our proof hinges on a new property of fractional Brownian motion.


title:
Angular distribution studies on the two-photon ionization of
  hydrogen-like ions: Relativistic description

abstract:
  The angular distribution of the emitted electrons, following the two-photon
ionization of the hydrogen-like ions, is studied within the framework of second
order perturbation theory and the Dirac equation. Using a density matrix
approach, we have investigated the effects which arise from the polarization of
the incoming light as well as from the higher multipoles in the expansion of
the electron--photon interaction. For medium- and high-Z ions, in particular,
the non-dipole contributions give rise to a significant change in the angular
distribution of the emitted electrons, if compared with the electric-dipole
approximation. This includes a strong forward emission while, in dipole
approxmation, the electron emission always occurs symmetric with respect to the
plane which is perpendicular to the photon beam. Detailed computations for the
dependence of the photoelectron angular distributions on the polarization of
the incident light are carried out for the ionization of H, Xe$^{53+}$, and
U$^{91+}$ (hydrogen-like) ions.


title:
Effect of a small disruption of the Ca site on the geometrically
  frustrated magnetic behavior of Ca3CoRhO6

abstract:
  The compound, Ca3CoRhO6, containing magnetic Co-Rh chains intervened by Ca
ions, has been known to be one of the few exhibiting partially disordered
antiferromagnetic structure (PDA) due to geometrical frustration. Here, we
report the influence of partial replacement of Ca by Y on the magnetic
anomalies by investigating the solid solution, Ca(3-x)Y(x)CoRhO6 by bulk
measurements. There are profound changes in the magnetic behavior, the most
notable one being that the features attributable to spin-chain magnetism and
PDA structure get suppressed dramatically by a small replacement of Ca by Y (x=
0.15), despite the fact that the magnetic chain is not disrupted. This finding
suggests that this compound is on the verge of PDA-structural-instability.


title: Symmetry Relations for Trajectories of a Brownian Motor

abstract:
  A Brownian Motor is a nanoscale or molecular device that combines the effects
of thermal noise, spatial or temporal asymmetry, and directionless input energy
to drive directed motion. Because of the input energy, Brownian motors function
away from thermodynamic equilibrium and concepts such as linear response
theory, fluctuation dissipation relations, and detailed balance do not apply.
The {\em generalized} fluctuation-dissipation relation, however, states that
even under strongly thermodynamically non-equilibrium conditions the ratio of
the probability of a transition to the probability of the time-reverse of that
transition is the exponent of the change in the internal energy of the system
due to the transition. Here, we derive an extension of the generalized
fluctuation dissipation theorem for a Brownian motor for the ratio between the
probability for the motor to take a forward step and the probability to take a
backward step.


title: Casimir Forces in a Piston Geometry at Zero and Finite Temperatures

abstract:
  We study Casimir forces on the partition in a closed box (piston) with
perfect metallic boundary conditions. Related closed geometries have generated
interest as candidates for a repulsive force. By using an optical path
expansion we solve exactly the case of a piston with a rectangular cross
section, and find that the force always attracts the partition to the nearest
base. For arbitrary cross sections, we can use an expansion for the density of
states to compute the force in the limit of small height to width ratios. The
corrections to the force between parallel plates are found to have interesting
dependence on the shape of the cross section. Finally, for temperatures in the
range of experimental interest we compute finite temperature corrections to the
force (again assuming perfect boundaries).


title: Dynamical percolation on general trees

abstract:
  H\"aggstr\"om, Peres, and Steif (1997) have introduced a dynamical version of
percolation on a graph $G$. When $G$ is a tree they derived a necessary and
sufficient condition for percolation to exist at some time $t$. In the case
that $G$ is a spherically symmetric tree, H\"aggstr\"om, Peres, and Steif
(1997) derived a necessary and sufficient condition for percolation to exist at
some time $t$ in a given target set $D$. The main result of the present paper
is a necessary and sufficient condition for the existence of percolation, at
some time $t\in D$, in the case that the underlying tree is not necessary
spherically symmetric. This answers a question of Yuval Peres (personal
communication). We present also a formula for the Hausdorff dimension of the
set of exceptional times of percolation.


title: Are Superhumps Good Measures of the Mass Ratio for AM CVn Systems?

abstract:
  We extend recent work that included the effect of pressure forces to derive
the precession rate of eccentric accretion discs in cataclysmic variables to
the case of double degenerate systems. We find that the logical scaling of the
pressure force in such systems results in predictions of unrealistically high
primary masses. Using the prototype AM CVn as a calibrator for the magnitude of
the effect, we find that there is no scaling that applies consistently to all
the systems in the class. We discuss the reasons for the lack of a superhump
period to mass ratio relationship analogous to that known for SU UMa systems
and suggest that this is because these secondaries do not have a single valued
mass-radius relationship. We highlight the unreliability of mass-ratios derived
by applying the SU UMa expression to the AM CVn binaries.


title: A Modest Proposal for the Astronomical Community

abstract:
  Inspired by a recent astro-ph posting, I propose a creation of an Alternative
History astro-ph archive (althistastro-ph). Such an archive would serve as a
final resting place for the various telescope (and possibly other) proposals
that were not successful. As we all know, from both submitting proposals and
also from serving on various time allocation committees, many excellent
proposals ``do not make it''. Creating such an AltHist archive would serve many
goals, including venting the frustration of the authors and also providing
possible amusement for the readers. These are worthy goals, but they alone
would not warrant creating such an archive. The truly useful role of
AltHistAstro-ph archive would be to match astronomers with unappreciated ideas
with other astronomers with underutilized resources, hopefully leading in some
cases to resurrection of old proposals and resulting publications in the
regular astro-ph archive. Given the possible danger of a low signal-to-noise
and possible confusion, a creation of a separate archive seems like a good
idea, although it should be noted that low signal-to-noise is achieved on
astro-ph quite often already. Finally, I include my own excellent, but rejected
(twice), HST proposal, as an example of a potential AltHistAstro-ph posting.


title:
DSR and Canonical Transformations: A Comment on a ``A Lagrangian for DSR
  particle and the role of noncommutativity''

abstract:
  The aim of this comment is to call to the attention of DSR readers a basic
fact. The introduction of noncommutative structures in problems like the one
addressed in [1] is not necessary for the understanding of DSR physics. It can
be described just as the relativistic free particle problem in a different
parametrization.


title: Formality of function spaces

abstract:
  Let $X$ be a nilpotent space such that there exists $p\geq 1$ with
$H^p(X,\mathbb Q) \ne 0$ and $H^n(X,\mathbb Q)=0$ if $n>p$. Let $Y$ be a
m-connected space with $m\geq p+1$ and $H^*(Y,\mathbb Q)$ is finitely generated
as algebra. We assume that $X$ is formal and there exists $p$ odd such that
$H^p(X,\mathbb Q) \ne 0$. We prove that if the space $\mathcal F(X,Y)$ of
continuous maps from $X$ to $Y$ is formal, then $Y$ has the rational homotopy
type of a product of Eilenberg Mac Lane spaces. At the opposite, we exhibit an
example of a formal space $\mathcal F(S^2,Y)$ where $Y$ is not rationally
equivalent to a product of Eilenberg Mac Lane spaces.


title:
Photolytically generated aerosols in the mesosphere and thermosphere of
  Titan

abstract:
  Analysis of the Cassini Ultraviolet Imaging Spectrometer (UVIS) stellar and
solar occultations at Titan to date include 12 species: N$_{2}$ (nitrogen),
CH$_{4}$ (methane), C$_{2}$H$_{2}$ (acetylene), C$_{2}$H$_{4}$ (ethylene),
C$_{2}$H$_{6}$ (ethane), C$_{4}$H$_{2}$ (diacetylene), C$_{6}$H$_{6}$
(benzene), C$_{6}$N$_{2}$ (dicyanodiacetylene), C$_{2}$N$_{2}$ (cyanogen), HCN
(hydrogen cyanide), HC$_{3}$N (cyanoacetylene), and aerosols distinguished by a
structureless continuum extinction (absorption plus scattering) of photons in
the EUV. The introduction of aerosol particles, retaining the same refractive
index properties as tholin with radius $\sim$125 \AA and using Mie theory,
provides a satisfactory fit to the spectra. The derived vertical profile of
aerosol density shows distinct structure, implying a reactive generation
process reaching altitudes more than 1000 km above the surface. A photochemical
model presented here provides a reference basis for examining the chemical and
physical processes leading to the distinctive atmospheric opacity at Titan. We
find that dicyanodiacetylene is condensable at $\sim$650 km, where the
atmospheric temperature minimum is located. This species is the simplest
molecule identified to be condensable. Observations are needed to confirm the
existence and production rates of dicyanodiacetylene.


title:
Mid-infrared laser light nulling experiment using single-mode conductive
  waveguides

abstract:
  Aims: In the context of space interferometry missions devoted to the search
of exo-Earths, this paper investigates the capabilities of new single mode
conductive waveguides at providing modal filtering in an infrared and
monochromatic nulling experiment; Methods: A Michelson laser interferometer
with a co-axial beam combination scheme at 10.6 microns is used. After
introducing a Pi phase shift using a translating mirror, dynamic and static
measurements of the nulling ratio are performed in the two cases where modal
filtering is implemented and suppressed. No additional active control of the
wavefront errors is involved. Results: We achieve on average a statistical
nulling ratio of 2.5e-4 with a 1-sigma upper limit of 6e-4, while a best null
of 5.6e-5 is obtained in static mode. At the moment, the impact of external
vibrations limits our ability to maintain the null to 10 to 20 seconds.;
Conclusions: A positive effect of SM conductive waveguide on modal filtering
has been observed in this study. Further improvement of the null should be
possible with proper mechanical isolation of the setup.


title: G\"odel Incompleteness and the Black Hole Information Paradox

abstract:
  Semiclassical reasoning suggests that the process by which an object
collapses into a black hole and then evaporates by emitting Hawking radiation
may destroy information, a problem often referred to as the black hole
information paradox. Further, there seems to be no unique prediction of where
the information about the collapsing body is localized. We propose that the
latter aspect of the paradox may be a manifestation of an inconsistent
self-reference in the semiclassical theory of black hole evolution. This
suggests the inadequacy of the semiclassical approach or, at worst, that
standard quantum mechanics and general relavity are fundamentally incompatible.
One option for the resolution for the paradox in the localization is to
identify the G\"odel-like incompleteness that corresponds to an imposition of
consistency, and introduce possibly new physics that supplies this
incompleteness. Another option is to modify the theory in such a way as to
prohibit self-reference. We discuss various possible scenarios to implement
these options, including eternally collapsing objects, black hole remnants,
black hole final states, and simple variants of semiclassical quantum gravity.


title: Superstatistics, thermodynamics, and fluctuations

abstract:
  A thermodynamic-like formalism is developed for superstatistical systems
based on conditional entropies. This theory takes into account large-scale
variations of intensive variables of systems in nonequilibrium stationary
states. Ordinary thermodynamics is recovered as a special case of the present
theory, and corrections to it can be systematically evaluated. A generalization
of Einstein's relation for fluctuations is presented using a maximum entropy
condition.


title:
Two components of depolarization currents in PVDF caused by relaxation
  of homo- and heterocharge

abstract:
  The procedure has been developed for extracting homocharge and heterocharge
currents from experimentally measured thermally stimulated depolarization
currents of corona poled PVDF. Application of different depolarization modes
supplemented with the isothermal currents allowed to obtain such parameters of
relaxation processes, as activation energies, characteristic frequencies and
time constants.


title: Comparison of Discrete and Continuous Wavelet Transforms

abstract:
  In this paper we outline several points of view on the interplay between
discrete and continuous wavelet transforms; stressing both pure and applied
aspects of both. We outline some new links between the two transform
technologies based on the theory of representations of generators and
relations. By this we mean a finite system of generators which are represented
by operators in Hilbert space. We further outline how these representations
yield sub-band filter banks for signal and image processing algorithms.


title: Strong CP, Up-Quark Mass, and the Randall-Sundrum Microscope

abstract:
  In the Randall-Sundrum model, setting the ratio of up and down quark masses
$m_u/m_d << 1$, relevant to the strong CP problem, does not require chiral
symmetry or fine-tuning, due to exponential bulk fermion profiles. We point out
that such geometric suppression of the mass of a fermion magnifies the masses
of its corresponding Kaluza-Klein (KK) states. In this sense, these KK states
act as "microscopes" for probing light quark and lepton masses. In simple
realizations, this hypothesis can be testable at future colliders, like the
LHC, by measuring the spectrum of level-1 KK fermions. The microscope can then
provide an experimental test for the vanishing of $m_u$ in the ultraviolet,
independently of non-perturbative determinations, by lattice simulations or
other means, at hadronic scales. We also briefly comment on application of our
microscope idea to other fermions, such as the electron and neutrinos.


title:
Criticality in inhomogeneous magnetic systems: Application to quantum
  ferromagnets

abstract:
  We consider a $\phi^4$-theory with a position-dependent distance from the
critical point. One realization of this model is a classical ferromagnet
subject to non-uniform mechanical stress. We find a sharp phase transition
where the envelope of the local magnetization vanishes uniformly. The
first-order transition in a quantum ferromagnet also remains sharp. The
universal mechanism leading to a tricritical point in an itinerant quantum
ferromagnet is suppressed, and in principle one can recover a quantum critical
point with mean-field exponents. Observable consequences of these results are
discussed.


title: A Generic Test of Modified Gravity Models which Emulate Dark Matter

abstract:
  We propose a generic test for models in which gravity is modified to do away
with dark matter. These models tend to have gravitons couple to a different
metric than ordinary matter. A strong test of such models comes from comparing
the arrival time of the gravitational wave pulse from a cosmological event such
as a supernova with the arrival times of the associated pulses of neutrinos and
photons. For SN 1987a we show that the gravity wave would have arrived 5.3 days
after the neutrino pulse.


title:
An Analysis of the Shapes of Interstellar Extinction Curves. V. The
  IR-Through-UV Curve Morphology

abstract:
  We study the IR-through-UV interstellar extinction curves towards 328
Galactic B and late-O stars. We use a new technique which employs stellar
atmosphere models in lieu of unreddened "standard" stars. This technique is
capable of virtually eliminating spectral mismatch errors in the curves. It
also allows a quantitative assessment of the errors and enables a rigorous
testing of the significance of relationships between various curve parameters,
regardless of whether their uncertainties are correlated. Analysis of the
curves gives the following results: (1) In accord with our previous findings,
the central position of the 2175 A extinction bump is mildly variable, its
width is highly variable, and the two variations are unrelated. (2) Strong
correlations are found among some extinction properties within the UV region,
and within the IR region. (3) With the exception of a few curves with extreme
(i.e., large) values of R(V), the UV and IR portions of Galactic extinction
curves are not correlated with each other. (4) The large sightline-to-sightline
variation seen in our sample implies that any average Galactic extinction curve
will always reflect the biases of its parent sample. (5) The use of an average
curve to deredden a spectral energy distribution (SED) will result in
significant errors, and a realistic error budget for the dereddened SED must
include the observed variance of Galactic curves. While the observed large
sightline-to-sightline variations, and the lack of correlation among the
various features of the curves, make it difficult to meaningfully characterize
average extinction properties, they demonstrate that extinction curves respond
sensitively to local conditions. Thus, each curve contains potentially unique
information about the grains along its sightline.


title: Accreting Neutron Stars in Low-Mass X-Ray Binary Systems

abstract:
  Using the Rossi X-ray Timing Explorer (RossiXTE), astronomers have discovered
that disk-accreting neutron stars with weak magnetic fields produce three
distinct types of high-frequency X-ray oscillations. These oscillations are
powered by release of the binding energy of matter falling into the strong
gravitational field of the star or by the sudden nuclear burning of matter that
has accumulated in the outermost layers of the star. The frequencies of the
oscillations reflect the orbital frequencies of gas deep in the gravitational
field of the star and/or the spin frequency of the star. These oscillations can
therefore be used to explore fundamental physics, such as strong-field gravity
and the properties of matter under extreme conditions, and important
astrophysical questions, such as the formation and evolution of millisecond
pulsars. Observations using RossiXTE have shown that some two dozen neutron
stars in low-mass X-ray binary systems have the spin rates and magnetic fields
required to become millisecond radio-emitting pulsars when accretion ceases,
but that few have spin rates above about 600 Hz. The properties of these stars
show that the paucity of spin rates greater than 600 Hz is due in part to the
magnetic braking component of the accretion torque and to the limited amount of
angular momentum that can be accreted in such systems. Further study will show
whether braking by gravitational radiation is also a factor. Analysis of the
kilohertz oscillations has provided the first evidence for the existence of the
innermost stable circular orbit around dense relativistic stars that is
predicted by strong-field general relativity. It has also greatly narrowed the
possible descriptions of ultradense matter.


title: Emission and absorption noise in the fractional quantum Hall effect

abstract:
  We compute the high-frequency emission and absorption noise in a fractional
quantum Hall effect (FQHE) sample at arbitrary temperature. We model the edges
of the FQHE as chiral Luttinger liquids (LL) and we use the non-equilibrium
perturbative Keldysh formalism. We find that the non-symmetrized high frequency
noise contains important signatures of the electron-electron interactions that
can be used to test the Luttinger liquid physics, not only in FQHE edge states,
but possibly also in other one-dimensional systems such as carbon nanotubes. In
particular we find that the emission and absorption components of the excess
noise (defined as the difference between the noise at finite voltage and at
zero voltage) are different in an interacting system, as opposed to the
non-interacting case when they are identical. We study the resonance features
which appear in the noise at the Josephson frequency (proportional to the
applied voltage), and we also analyze the effect of the distance between the
measurement point and the backscattering site. Most of our analysis is
performed in the weak backscattering limit, but we also compute and discuss
briefly the high-frequency noise in the tunneling regime.


title: Magnetosonic solitons in a dusty plasma slab

abstract:
  The existence of magnetosonic solitons in dusty plasmas is investigated. The
nonlinear magnetohydrodynamic equations for a warm dusty magnetoplasma are thus
derived. A solution of the nonlinear equations is presented. It is shown that,
due to the presence of dust, static structures are allowed. This is in sharp
contrast to the formation of the so called shocklets in usual magnetoplasmas. A
comparatively small number of dust particles can thus drastically alter the
behavior of the nonlinear structures in magnetized plasmas.


title:
Thermal noise informatics: Totally secure communication via a wire;
  Zero-power communication; and Thermal noise driven computing

abstract:
  Very recently, it has been shown that thermal noise and its artificial
versions (Johnson-like noises) can be utilized as an information carrier with
peculiar properties therefore it may be proper to call this topic Thermal Noise
Informatics. Zero Power (Stealth) Communication, Thermal Noise Driven
Computing, and Totally Secure Classical Communication are relevant examples. In
this paper, while we will briefly describe the first and the second subjects,
we shall focus on the third subject, the secure classical communication via
wire. This way of secure telecommunication utilizes the properties of
Johnson(-like) noise and those of a simple Kirchhoff's loop. The communicator
is unconditionally secure at the conceptual (circuit theoretical) level and
this property is (so far) unique in communication systems based on classical
physics. The communicator is superior to quantum alternatives in all known
aspects, except the need of using a wire. In the idealized system, the
eavesdropper can extract zero bit of information without getting uncovered. The
scheme is naturally protected against the man-in-the-middle attack. The
communication can take place also via currently used power lines or phone
(wire) lines and it is not only a point-to-point communication like quantum
channels but network-ready. Tests have been carried out on a model-line with
ranges beyond the ranges of any known direct quantum communication channel and
they indicate unrivalled signal fidelity and security performance. This simple
device has single-wire secure key generation/sharing rates of 0.1, 1, 10, and
100 bit/second for copper wires with diameters/ranges of 21 mm / 2000 km, 7 mm
/ 200 km, 2.3 mm / 20 km, and 0.7 mm / 2 km, respectively and it performs with
0.02% raw-bit error rate (99.98 % fidelity).


title: Numerical metric extraction in AdS/CFT

abstract:
  An iterative method for recovering the bulk information in asymptotically AdS
spacetimes is presented. We consider zero energy spacelike geodesics and their
relation to the entanglement entropy in three dimensions to determine the
metric in certain symmetric cases. A number of comparisons are made with an
alternative extraction method presented in arXiv:hep-th/0609202, and the two
methods are then combined to allow metric recovery in the most general type of
static, spherically symmetric setups. We conclude by extracting the mass and
density profiles for a toy model example of a gas of radiation in
(2+1)-dimensional AdS.


title: Fluctuation-enhanced sensing

abstract:
  We present a short survey on fluctuation-enhanced gas sensing. We compare
some of its main characteristics with those of classical sensing. We address
the problem of linear response, information channel capacity, missed alarms and
false alarms.


title: Quantitative relations between corruption and economic factors

abstract:
  We report quantitative relations between corruption level and economic
factors, such as country wealth and foreign investment per capita, which are
characterized by a power law spanning multiple scales of wealth and investments
per capita. These relations hold for diverse countries, and also remain stable
over different time periods. We also observe a negative correlation between
level of corruption and long-term economic growth. We find similar results for
two independent indices of corruption, suggesting that the relation between
corruption and wealth does not depend on the specific measure of corruption.
The functional relations we report have implications when assessing the
relative level of corruption for two countries with comparable wealth, and for
quantifying the impact of corruption on economic growth and foreign
investments.


title: QED Electrical Conductivity using the 2PI Effective Action

abstract:
  In this article we calculate the electrical conductivity in QED using the 2PI
effective action. We use a modified version of the usual 2PI effective action
which is defined with respect to self-consistent solutions of the 2-point
functions. We show that the green functions obtained from this modified
effective action satisfy ward identities and that the conductivity obtained
from the kubo relation is gauge invariant. We work to 3-loop order in the
modified 2PI effective action and show explicitly that the resulting expression
for the conductivity contains the square of the amplitude that corresponds to
all binary collision and production processes.


title:
Probing dark energy with cluster counts and cosmic shear power spectra:
  including the full covariance

abstract:
  (Abridged) Combining cosmic shear power spectra and cluster counts is
powerful to improve cosmological parameter constraints and/or test inherent
systematics. However they probe the same cosmic mass density field, if the two
are drawn from the same survey region, and therefore the combination may be
less powerful than first thought. We investigate the cross-covariance between
the cosmic shear power spectra and the cluster counts based on the halo model
approach, where the cross-covariance arises from the three-point correlations
of the underlying mass density field. Fully taking into account the
cross-covariance as well as non-Gaussian errors on the lensing power spectrum
covariance, we find a significant cross-correlation between the lensing power
spectrum signals at multipoles l~10^3 and the cluster counts containing halos
with masses M>10^{14}Msun. Including the cross-covariance for the combined
measurement degrades and in some cases improves the total signal-to-noise
ratios up to plus or minus 20% relative to when the two are independent. For
cosmological parameter determination, the cross-covariance has a smaller effect
as a result of working in a multi-dimensional parameter space, implying that
the two observables can be considered independent to a good approximation. We
also discuss that cluster count experiments using lensing-selected mass peaks
could be more complementary to cosmic shear tomography than mass-selected
cluster counts of the corresponding mass threshold. Using lensing selected
clusters with a realistic usable detection threshold (S/N~6 for a ground-based
survey), the uncertainty on each dark energy parameter may be roughly halved by
the combined experiments, relative to using the power spectra alone.


title: Inflationary Cosmology

abstract:
  I give a general review of the history of inflationary cosmology and of its
present status.


title:
Is Modified Gravity Required by Observations? An Empirical Consistency
  Test of Dark Energy Models

abstract:
  We apply the technique of parameter-splitting to existing cosmological data
sets, to check for a generic failure of dark energy models. Given a dark energy
parameter, such as the energy density Omega_Lambda or equation of state w, we
split it into two meta-parameters with one controlling geometrical distances,
and the other controlling the growth of structure. Observational data spanning
Type Ia Supernovae, the cosmic microwave background (CMB), galaxy clustering,
and weak gravitational lensing statistics are fit without requiring the two
meta-parameters to be equal. This technique checks for inconsistency between
different data sets, as well as for internal inconsistency within any one data
set (e.g., CMB or lensing statistics) that is sensitive to both geometry and
growth. We find that the cosmological constant model is consistent with current
data. Theories of modified gravity generally predict a relation between growth
and geometry that is different from that of general relativity.
Parameter-splitting can be viewed as a crude way to parametrize the space of
such theories. Our analysis of current data already appears to put sharp limits
on these theories: assuming a flat universe, current data constrain the
difference Omega_Lambda(geom) - Omega_Lambda(grow) to be -0.0044 +/- 0.0058
(68% C.L.); allowing the equation of state w to vary, the difference w(geom) -
w(grow) is constrained to be 0.37 +/- 0.37 (68% C.L.). Interestingly, the
region w(grow) > w(geom), which should be generically favored by theories that
slow structure formation relative to general relativity, is quite restricted by
data already. We find w(grow) < -0.80 at 2 sigma. As an example, the best-fit
flat Dvali-Gabadadze-Porrati (DGP) model approximated by our parametrization
lies beyond the 3 sigma contour for constraints from all the data sets.


title:
Dark energy constraints from cosmic shear power spectra: impact of
  intrinsic alignments on photometric redshift requirements

abstract:
  Cosmic shear constrains cosmology by exploiting the apparent alignments of
pairs of galaxies due to gravitational lensing by intervening mass clumps.
However galaxies may become (intrinsically) aligned with each other, and with
nearby mass clumps, during their formation. This effect needs to be
disentangled from the cosmic shear signal to place constraints on cosmology. We
use the linear intrinsic alignment model as a base and compare it to an
alternative model and data. If intrinsic alignments are ignored then the dark
energy equation of state is biased by ~50 per cent. We examine how the number
of tomographic redshift bins affects uncertainties on cosmological parameters
and find that when intrinsic alignments are included two or more times as many
bins are required to obtain 80 per cent of the available information. We
investigate how the degradation in the dark energy figure of merit depends on
the photometric redshift scatter. Previous studies have shown that lensing does
not place stringent requirements on the photometric redshift uncertainty, so
long as the uncertainty is well known. However, if intrinsic alignments are
included the requirements become a factor of three tighter. These results are
quite insensitive to the fraction of catastrophic outliers, assuming that this
fraction is well known. We show the effect of uncertainties in photometric
redshift bias and scatter. Finally we quantify how priors on the intrinsic
alignment model would improve dark energy constraints.


title:
A duality between pairs of split decompositions for a $Q$-polynomial
  distance-regular graph

abstract:
  Let $\Gamma$ denote a $Q$-polynomial distance-regular graph with diameter $D
\geq 3$ and standard module $V$. Recently Ito and Terwilliger introduced four
direct sum decompositions of $V$; we call these the $(\mu,\nu)$--{\it split
decompositions} of $V$, where $\mu, \nu \in \lbrace \downarrow, \uparrow
\rbrace$. In this paper we show that the ($\downarrow,\downarrow$)--split
decomposition and the ($\uparrow,\uparrow$)--split decomposition are dual with
respect to the standard Hermitian form on $V$. We also show that the
($\downarrow,\uparrow$)--split decomposition and the
($\uparrow,\downarrow$)--split decomposition are dual with respect to the
standard Hermitian form on $V$.


title: Brownian subordinators and fractional Cauchy problems

abstract:
  A Brownian time process is a Markov process subordinated to the absolute
value of an independent one-dimensional Brownian motion. Its transition
densities solve an initial value problem involving the square of the generator
of the original Markov process. An apparently unrelated class of processes,
emerging as the scaling limits of continuous time random walks, involve
subordination to the inverse or hitting time process of a classical stable
subordinator. The resulting densities solve fractional Cauchy problems, an
extension that involves fractional derivatives in time. In this paper, we will
show a close and unexpected connection between these two classes of processes,
and consequently, an equivalence between these two families of partial
differential equations.


title: Beyond Caustic Crossings: Properties of Binary Microlensing Light Curves

abstract:
  Binary microlensing light curves have a variety of morphologies. Many are
indistinguishable from point lens light curves. Of those that deviate from the
point lens form, caustic crossing light curves have tended to dominate
identified binary lens events. Other distinctive signatures of binary lenses
include significant asymmetry, multiple peaks, and repeating events. We have
quantified, using high resolution simulations, the theoretically expected
relative numbers of each type of binary lens event, based on its measurable
characteristics. We find that a microlensing survey with current levels of
photometric uncertainty and sampling should find at least as many non-caustic
crossing binary lens events as caustic crossing events; in future surveys with
more sensitive photometry, the contribution of distinctive non-caustic crossing
events will be even greater. To try to explain why caustic crossing light
curves appear to be so dominant among the published binary lensing events, we
investigate the influence of several physical effects, including blending,
sampling rate, and various binary populations.


title: The spine which was no spine

abstract:
  Let T_n be the Teichmueller space of flat metrics on the n-dimensional torus
and identify SL(n,Z) with the corresponding mapping class group. We prove that
the subset Y consisting of those points at which the systoles generate the
fundamental group of the torus is, for n > 4, not contractible. In particular,
Y is not an SL(n,Z)-equivariant deformation retract of T_n.


title: Radiation hardness of diamond and silicon sensors compared

abstract:
  The radiation hardness of silicon charged particle sensors is compared with
single crystal and polycrystalline diamond sensors, both experimentally and
theoretically. It is shown that for Si- and C-sensors, the NIEL hypothesis,
which states that the signal loss is proportional to the Non-Ionizing Energy
Loss, is a good approximation to the present data. At incident proton and
neutron energies well above 0.1 GeV the radiation damage is dominated by the
inelastic cross section, while at non-relativistic energies the elastic cross
section prevails. The smaller inelastic nucleon-Carbon cross section and the
light nuclear fragments imply that at high energies diamond is an order of
magnitude more radiation hard than silicon, while at energies below 0.1 GeV the
difference becomes significantly smaller.


title: Topological insulators beyond the Brillouin zone via Chern parity

abstract:
  The topological insulator is an electronic phase stabilized by spin-orbit
coupling that supports propagating edge states and is not adiabatically
connected to the ordinary insulator. In several ways it is a spin-orbit-induced
analogue in time-reversal-invariant systems of the integer quantum Hall effect
(IQHE). This paper studies the topological insulator phase in disordered
two-dimensional systems, using a model graphene Hamiltonian introduced by Kane
and Mele as an example. The nonperturbative definition of a topological
insulator given here is distinct from previous efforts in that it involves
boundary phase twists that couple only to charge, does not refer to edge
states, and can be measured by pumping cycles of ordinary charge. In this
definition, the phase of a Slater determinant of electronic states is
determined by a Chern parity analogous to Chern number in the IQHE case.
Numerically we find, in agreement with recent network model studies, that the
direct transition between ordinary and topological insulators that occurs in
band structures is a consequence of the perfect crystalline lattice.
Generically these two phases are separated by a metallic phase, which is
allowed in two dimensions when spin-orbit coupling is present. The same
approach can be used to study three-dimensional topological insulators.


title:
Interference between two independent electrons: observation of
  two-particle Aharonov-Bohm interference

abstract:
  Very much like the ubiquitous quantum interference of a single particle with
itself, quantum interference of two independent, but indistinguishable,
particles is also possible. This interference is a direct result of quantum
exchange statistics, however, it is observed only in the joint probability to
find the particles in two separated detectors. Here we report the first
observation of such interference fringes between two independent and
non-interacting electrons in an interferometer proposed by Yurke et al. and
Samuelsson et al. Our experiment resembles the "Hanbury Brown and Twiss" (HBT)
experiment, which was performed with classical waves. In the experiment, two
independent and mutually incoherent electron beams were each partitioned into
two trajectories. The combined four trajectories enclosed an Aharonov-Bohm (AB)
flux (but not the two trajectories of a single electron). While individual
currents were found to be independent of the AB flux, as expected, the
cross-correlation between current fluctuations in two opposite points across
the device exhibited strong AB oscillations. This is a direct signature of
orbital entanglement between two electrons even though they never interact with
each other.


title:
Experimental realization of one-way quantum computing with two-photon
  four-qubit cluster states

abstract:
  We report an experimental realization of one-way quantum computing on a
two-photon four-qubit cluster state. This is accomplished by developing a
two-photon cluster state source entangled both in polarization and spatial
modes. With this special source, we implemented a highly efficient Grover's
search algorithm and high-fidelity two qubits quantum gates. Our experiment
demonstrates that such cluster states could serve as an ideal source and a
building block for rapid and precise optical quantum computation.


title:
The integrals in Gradshteyn and Ryzhik. Part 3: Combinations of
  Logarithms and Exponentials

abstract:
  We present the evaluation of a family of exponential-logarithmic integrals.
These have integrands of the form P(exp(x),ln(x)) where P is a polynomial. The
examples presented here appear in sections 4.33, 4.34 and 4.35 in the classical
table of integrals by I. Gradshteyn and I. Ryzhik.


title:
Line tension and structure of smectic liquid crystal multilayers at the
  air-water interface

abstract:
  At the air/water interface, 4,-8-alkyl[1,1,-biphenyl]-4-carbonitrile (8CB)
domains with different thicknesses coexist in the same Langmuir film, as
multiple bilayers on a monolayer. The edge dislocation at the domain boundary
leads to line tension, which determines the domain shape and dynamics. By
observing the domain relaxation process starting from small distortions, we
find that the line tension is linearly dependent on the thickness difference
between the coexisting phases in the film. Comparisons with theoretical
treatments in the literature suggest that the edge dislocation at the boundary
locates near the center of the film, which means that the 8CB multilayers are
almost symmetric with respect to the air/water interface.


title:
Application of Corona Discharge for Poling Ferroelectric and Nonlinear
  Optical Polymers

abstract:
  Four modifications of the corona triode are described for charging polar
polymers with ferroelectric or non-linear optical properties. Advantages of the
constant current modification of corona poling are illustrated and discussed.


title: Oblivious Transfer based on Key Exchange

abstract:
  Key-exchange protocols have been overlooked as a possible means for
implementing oblivious transfer (OT). In this paper we present a protocol for
mutual exchange of secrets, 1-out-of-2 OT and coin flipping similar to
Diffie-Hellman protocol using the idea of obliviously exchanging encryption
keys. Since, Diffie-Hellman scheme is widely used, our protocol may provide a
useful alternative to the conventional methods for implementation of oblivious
transfer and a useful primitive in building larger cryptographic schemes.


title: The integrals in Gradshteyn and Ryzhik. Part 4: The Gamma function

abstract:
  We present a systematic derivation of some definite integrals in the
classical table of Gradshteyn and Ryzhik that can be reduced to the gamma
function.


title: Non-abelian plasma instabilities for strong anisotropy

abstract:
  We numerically investigate gauge field instabilities in anisotropic SU(2)
plasmas using weak field initial conditions. The growth of unstable modes is
stopped by non-abelian effects for moderate anisotropy. If we increase the
anisotropy the growth continues beyond the non-abelian saturation bound. We
find strong indications that the continued growth is not due to over-saturation
of infrared field modes, but instead due to very rapid growth of high momentum
modes which are not unstable in the weak field limit. The saturation amplitude
strongly depends on the initial conditions. For strong initial fields we do not
observe the sustained growth.


title: Is there contextuality for a single qubit?

abstract:
  It was presented by Cabello and Nakamura [A. Cabello, Phys. Rev. Lett. 90,
190401 (2003)], that the Kochen-Specker theorem applies to two dimensions if
one uses Positive Operator-Valued Measures. We show that contextuality in their
models is not of the Kochen-Specker type. It is rather the result of not
keeping track of the whole system on which the measurement is performed. This
is connected to the fact that there is no one-to-one correspondence between
POVM elements and projectors on the extended Hilbert space and the same POVM
element has to originate from two different projectors when used in Cabello's
and Nakamura's models. Moreover, we propose a hidden-variable formulation of
the above models.


title:
Star formation at very low metallicity. I: Chemistry and cooling at low
  densities

abstract:
  We present a simplified chemical and thermal model designed to allow
computationally efficient study of the thermal evolution of metal-poor gas
within large numerical simulations. Our main simplification is the neglect of
the molecular chemistry of the heavy elements. The only molecular chemistry
retained within the model is the formation and destruction of molecular
hydrogen. Despite this major simplification, the model allows for accurate
treatment of the thermal evolution of the gas within a large volume of
parameter space. It is valid for temperatures 50 < T < 10000 K and
metallicities 0 < Z < 0.1 Z_solar. In gas with a metallicity Z = 0.1 Z_solar,
and in the absence of an incident ultraviolet radiation field, it is valid for
hydrogen number densities n_H < 500 / t_char cm^-3, where t_char is the size in
Myr of the characteristic physical timescale of interest in the problem. If Z
<< 0.1 Z_solar, or if a strong ultraviolet radiation field is present, then the
model remains accurate up to significantly higher densities. We also discuss
some possible applications of this model.


title: Normalizers of Irreducible Subfactors

abstract:
  We consider normalizers of an irreducible inclusion $N\subseteq M$ of
$\mathrm{II}_1$ factors. In the infinite index setting an inclusion
$uNu^*\subseteq N$ can be strict, forcing us to also investigate the semigroup
of one-sided normalizers. We relate these normalizers of $N$ in $M$ to
projections in the basic construction and show that every trace one projection
in the relative commutant $N'\cap < M,e_N>$ is of the form $u^*e_Nu$ for some
unitary $u\in M$ with $uNu^*\subseteq N$. This enables us to identify the
normalizers and the algebras they generate in several situations. In particular
each normalizer of a tensor product of irreducible subfactors is a tensor
product of normalizers modulo a unitary. We also examine normalizers of
irreducible subfactors arising from subgroup--group inclusions $H\subseteq G$.
Here the normalizers are the normalizing group elements modulo a unitary from
$L(H)$. We are also able to identify the finite trace $L(H)$-bimodules in
$\ell^2(G)$ as double cosets which are also finite unions of left cosets.


title: Quantum phase transition and entanglement in Li atom system

abstract:
  In this paper we study the quantum phase transition and entanglement in
s1=1/2 and s2=1 spin pair system by the exact diagonalization method. We show
that, for this exactly solvable quantum bi-spin system, entanglement appears
before quantum phase transition and disappears after it. Moreover, we show that
the von Neumann entropy, as a measure of entanglement, can reveal quantum phase
transition in this system.


title: The stability of poloidal magnetic fields in rotating stars

abstract:
  The stability of large-scale magnetic fields in rotating stars is explored,
using 3D numerical hydrodynamics to follow the evolution of an initial poloidal
field. It is found that the field is subject to an instability, located
initially on the magnetic equator, whereby the gas is displaced in a direction
parallel to the magnetic axis. If the magnetic axis is parallel to the rotation
axis, the rotation does not affect the initial linear growth of the
instability, but does restrict the growth of the instability outside of the
equatorial zone. The magnetic energy decays on a timescale which is a function
of the Alfv\'en crossing time and the rotation speed, but short compared to any
evolutionary timescale. No evidence is found for a possible stable end state to
evolve from an initial axisymmetric poloidal field. The field of an oblique
rotator is similarly unstable, in both cases regardless of the rotation speed.


title:
No-passing Rule in the Ground State Evolution of the Random-Field Ising
  Model

abstract:
  We exactly prove the no-passing rule in the ground state evolution of the
random-field Ising model (RFIM) with monotonically varying external field. In
particular, we show that the application of the no-passing rule can speed up
the calculation of the zero-temperature equilibrium $M(H)$ curve dramatically.


title: RKKY in half-filled bipartite lattices: graphene as an example

abstract:
  We first present a simple proof that for any bipartite lattice at half
filling the RKKY interaction is antiferromagnetic between impurities on
opposite (i.e., A and B) sublattices and is ferromagnetic between impurities on
the same sublattices. This result is valid on all length scales. We then focus
on the honeycomb lattice and examine the theorem in the long distance limit by
performing the low energy calculation using Dirac electrons. To find the
universal (cutoff free) result we perform the calculation in smooth cutoff
schemes, as we show that the calculation based on a sharp cutoff leads to wrong
results. We also find the long distance behavior of the RKKY interaction
between "plaquette" impurities in both coherent and incoherent regimes.


title: Geodesics on an ellipsoid in Minkowski space

abstract:
  We describe the geometry of geodesics on a Lorentz ellipsoid: give explicit
formulas for the first integrals (pseudo-confocal coordinates), curvature,
geodesically equivalent Riemannian metric, the invariant area-forms on the
time- and space-like geodesics and invariant 1-form on the space of null
geodesics. We prove a Poncelet-type theorem for null geodesics on the
ellipsoid: if such a geodesic close up after several oscillations in the
"pseudo-Riemannian belt", so do all other null geodesics on this ellipsoid.


title:
Note on XMM-Newton observations of the first unidentified TeV gamma-ray
  source TeV J2032+4130 by Horns et al. astro-ph/0705.0009

abstract:
  I comment on the -- apparent -- diffuse X-ray emission reported by Horns et
al. in their XMM observations of TeV J2032+4130


title: Cohomology of line bundles on compactified Jacobians

abstract:
  Let C be an integral projective curve with surficial singularities. We prove
that topologically trivial line bundles on the compactified Jacobian of C are
in one-to-one correspondence with line bundles on C (the autoduality
conjecture), and compute the cohomology of the line bundles. We also show that
the natural Fourier-Mukai functor between the derived categories of
quasi-coherent sheaves on the Jacobian and on the compactified Jacobian is
fully faithful.


title: On Solving General Linear Equations in the Set of Natural Numbers

abstract:
  In this paper one shows if the number of natural solutions of a general
linear equation is limited or not. Also, it is presented a method of solving
the Diophantine equation $ax-by=c$ in the set of natural numbers, and an
example of solving in $N$ a Diophantine equation with three variables.


title: Asymptotics for eigenvalues of a non-linear integral system

abstract:
  We show the asymptotic behavior of the eigenvalues of the non-linear integral
system related to the (p,q)-Laplacian.


title: 1-Factorizations of Cayley graphs

abstract:
  In this note we prove that all connected Cayley graphs of every finite group
$Q \times H$ are 1-factorizable, where $Q$ is any non-trivial group of 2-power
order and $H$ is any group of odd order.


title: On the automorphism group of a possible symmetric $(81,16,3)$ design

abstract:
  In this paper we study the automorphism group of a possible symmetric
$(81,16,3)$ design.


title:
Effect of temperature-dependent shape anisotropy on coercivity with
  aligned Stoner-Wohlfarth soft ferromagnets

abstract:
  The temperature variation effect of shape anisotropy on the coercivity,
HC(T), for the aligned Stoner-Wohlfarth (SW) soft ferromagnets, such as fcc Ni,
fcc Co and bcc Fe, are investigated within the framework of Neel-Brown (N-B)
analysis. An extended N-B equation is thus proposed,by introducing a single
dimensionless correction function, the reduced magnetization, m(\tao) =
MS(T)/MS(0), in which \tao = T/TC is the reduced temperature, MS(T) is the
saturation magnetization, and TC is the Curie temperature. The factor, m(\tao),
accounts for the temperature-dependent effect of the shape anisotropy. The
constants, H0 and E0, are for the switching field at zero temperature and the
potential barrier at zero field, respectively. According to this newly derived
equation, the blocking temperature above which the properties of
superparamagnetism show up is described by the expression, TB =
E0m^2(\tao)/[kBln(t/t0)], with the extra correction factor m^2(\tao). The
possible effect on HC(T) and the blocking temperature, TB, attributed to the
downshift of TC resulting from the finite size effect has been discussed also.


title:
Cranked Hartree-Fock-Bogoliubov Calculation for Rotating Bose-Einstein
  Condensates

abstract:
  A rotating bosonic many-body system in a harmonic trap is studied with the
3D-Cranked Hartree-Fock-Bogoliubov method at zero temperature, which has been
applied to nuclear many-body systems at high spin. This method is a variational
method extended from the Hartree-Fock theory, which can treat the pairing
correlations in a self-consistent manner. An advantage of this method is that a
finite-range interaction between constituent particles can be used in the
calculation, unlike the original Gross-Pitaevskii approach. To demonstrate the
validity of our method, we present a calculation for a toy model, that is, a
rotating system of ten bosonic particles interacting through the repulsive
quadrupole-quadrupole interaction in a harmonic trap. It is found that the
yrast states, the lowest-energy states for the given total angular momentum,
does not correspond to the Bose-Einstein condensate, except a few special
cases. One of such cases is a vortex state, which appears when the total
angular momentum $L$ is twice the particle number $N$ (i.e., $L=2N$).


title:
Fault Classification in Cylinders Using Multilayer Perceptrons, Support
  Vector Machines and Guassian Mixture Models

abstract:
  Gaussian mixture models (GMM) and support vector machines (SVM) are
introduced to classify faults in a population of cylindrical shells. The
proposed procedures are tested on a population of 20 cylindrical shells and
their performance is compared to the procedure, which uses multi-layer
perceptrons (MLP). The modal properties extracted from vibration data are used
to train the GMM, SVM and MLP. It is observed that the GMM produces 98%, SVM
produces 94% classification accuracy while the MLP produces 88% classification
rates.


title: Two Scenarios of Breaking Chaotic Phase Synchronization

abstract:
  Two types of phase synchronization (accordingly, two scenarios of breaking
phase synchronization) between coupled stochastic oscillators are shown to
exist depending on the discrepancy between the control parameters of
interacting oscillators, as in the case of classical synchronization of
periodic oscillators. If interacting stochastic oscillators are weakly detuned,
the phase coherency of the attractors persists when phase synchronization
breaks. Conversely, if the control parameters differ considerably, the chaotic
attractor becomes phase-incoherent under the conditions of phase
synchronization break.


title: The Parameter-Less Self-Organizing Map algorithm

abstract:
  The Parameter-Less Self-Organizing Map (PLSOM) is a new neural network
algorithm based on the Self-Organizing Map (SOM). It eliminates the need for a
learning rate and annealing schemes for learning rate and neighbourhood size.
We discuss the relative performance of the PLSOM and the SOM and demonstrate
some tasks in which the SOM fails but the PLSOM performs satisfactory. Finally
we discuss some example applications of the PLSOM and present a proof of
ordering under certain limited conditions.


title:
On the Motion of Vortex Sheets with Surface Tension in the 3D Euler
  Equations with Vorticity

abstract:
  We prove well-posedness of vortex sheets with surface tension in the 3D
incompressible Euler equations with vorticity.


title: Neutral genetic drift can aid functional protein evolution

abstract:
  BACKGROUND: Many of the mutations accumulated by naturally evolving proteins
are neutral in the sense that they do not significantly alter a protein's
ability to perform its primary biological function. However, new protein
functions evolve when selection begins to favor other, "promiscuous" functions
that are incidental to a protein's biological role. If mutations that are
neutral with respect to a protein's primary biological function cause
substantial changes in promiscuous functions, these mutations could enable
future functional evolution.
  RESULTS: Here we investigate this possibility experimentally by examining how
cytochrome P450 enzymes that have evolved neutrally with respect to activity on
a single substrate have changed in their abilities to catalyze reactions on
five other substrates. We find that the enzymes have sometimes changed as much
as four-fold in the promiscuous activities. The changes in promiscuous
activities tend to increase with the number of mutations, and can be largely
rationalized in terms of the chemical structures of the substrates. The
activities on chemically similar substrates tend to change in a coordinated
fashion, potentially providing a route for systematically predicting the change
in one function based on the measurement of several others.
  CONCLUSIONS: Our work suggests that initially neutral genetic drift can lead
to substantial changes in protein functions that are not currently under
selection, in effect poising the proteins to more readily undergo functional
evolution should selection "ask new questions" in the future.


title: Air Shower Measurements in Karlsruhe

abstract:
  The Karlsruhe multi-detector set-ups KASCADE, KASCADE-Grande, and LOPES aim
on measurements of cosmic rays in the energy range of the so called knee
between 10^14 eV and 10^18 eV. The multidimensional analysis of the air shower
data measured by KASCADE indicates a distinct knee in the energy spectra of
light primary cosmic rays and an increasing dominance of heavy ones towards
higher energies. This provides, together with the results of large scale
anisotropy studies, implications for discriminating astrophysical models of the
origin of the knee. To improve the reconstruction quality and statistics at
higher energies, where the knee of the heavy primaries is expected at around
100 PeV, KASCADE has been extended by a factor 10 in area to the new experiment
KASCADE-Grande. LOPES is located on site of the KASCADE-Grande experiment. It
measures radio pulses from extensive air showers with the goal to establish
this renewed detection technique for future large scale experiments.


title: Topological Classification of Clusters in Condensed Phases

abstract:
  A methodology is developed to identify clusters in a bulk phase which are
topologically equivalent to certain reference clusters. The selected reference
clusters are the Morse clusters with 13 or less atoms and the 13 atom clusters
found in an FCC and an HCP crystal phase, consisting of an atom and its 12
nearest neighbours. The first step in using the method requires the bond
network of the bulk phase to be identified. The bonds may be identified in
terms of the distance between the atom pairs or by using a modified Voronoi
decomposition, introduced here. We then search for all the 3, 4 and 5 membered
shortest path rings and use these to identify some basic clusters. These basic
clusters are then combined to identify the above mentioned Morse and crystal
clusters. The larger Morse clusters (N>13) may be identified in terms of the
basic clusters and the smaller Morse clusters. This work has important
applications in studying the energy landscape of a bulk phase. As an example,
results from a limited preliminary study on the hard sphere fluid phase are
presented.


title: Using Images to create a Hierarchical Grid Spatial Index

abstract:
  This paper presents a hybrid approach to spatial indexing of two dimensional
data. It sheds new light on the age old problem by thinking of the traditional
algorithms as working with images. Inspiration is drawn from an analogous
situation that is found in machine and human vision. Image processing
techniques are used to assist in the spatial indexing of the data. A fixed grid
approach is used and bins with too many records are sub-divided hierarchically.
Search queries are pre-computed for bins that do not contain any data records.
This has the effect of dividing the search space up into non rectangular
regions which are based on the spatial properties of the data. The bucketing
quad tree can be considered as an image with a resolution of two by two for
each layer. The results show that this method performs better than the quad
tree if there are more divisions per layer. This confirms our suspicions that
the algorithm works better if it gets to look at the data with higher
resolution images. An elegant class structure is developed where the
implementation of concrete spatial indexes for a particular data type merely
relies on rendering the data onto an image.


title: Note on Breakup Densities in Fragmentation

abstract:
  This note elaborates the procedures involved in the derivation of breakup
densities in nuclear fragmentation. It is stressed that the formalism employed
in the analysis served only as a spectral fitting function and does not imply
any specific reaction mechanism.


title:
Displacement Detection with a Vibrating RF SQUID: Beating the Standard
  Linear Limit

abstract:
  We study a novel configuration for displacement detection consisting of a
nanomechanical resonator coupled to both, a radio frequency superconducting
interference device (RF SQUID) and to a superconducting stripline resonator. We
employ an adiabatic approximation and rotating wave approximation and calculate
the displacement sensitivity. We study the performance of such a displacement
detector when the stripline resonator is driven into a region of nonlinear
oscillations. In this region the system exhibits noise squeezing in the output
signal when homodyne detection is employed for readout. We show that
displacement sensitivity of the device in this region may exceed the upper
bound imposed upon the sensitivity when operating in the linear region. On the
other hand, we find that the high displacement sensitivity is accompanied by a
slowing down of the response of the system, resulting in a limited bandwidth.


title: Chiral Equivariant Cohomology III

abstract:
  This is the third of a series of papers on a new equivariant cohomology that
takes values in a vertex algebra, and contains and generalizes the classical
equivariant cohomology of a manifold with a Lie group action a la H. Cartan. In
this paper, we compute this cohomology for spheres and show that for any simple
connected group G, there is a sphere with infinitely many actions of G which
have distinct chiral equivariant cohomology, but identical classical
equivariant cohomology. Unlike the classical case, the description of the
chiral equivariant cohomology of spheres requires a substantial amount of new
structural theory, which we fully develop in this paper. This includes a
quasi-conformal structure, equivariant homotopy invariance, and the values of
this cohomology on homogeneous spaces. These results rely on crucial features
of the underlying vertex algebra valued complex that have no classical
analogues.


title:
Periodicity and criticality in the Olami-Feder-Christensen model of
  earthquakes

abstract:
  Characteristic versus critical features of earthquakes are studied on the
basis of the Olami-Feder-Christensen model. It is found that the local
recurrence-time distribution exhibits a sharp $\delta$-function-like peak
corresponding to rhythmic recurrence of events with a fixed ``period'' uniquely
determined by the transmission parameter of the model, together with a
power-law-like tail corresponding to scale-free recurrence of events. The model
exhibits phenomena closely resembling the asperity known in seismology.


title: Support vector machine for functional data classification

abstract:
  In many applications, input data are sampled functions taking their values in
infinite dimensional spaces rather than standard vectors. This fact has complex
consequences on data analysis algorithms that motivate modifications of them.
In fact most of the traditional data analysis tools for regression,
classification and clustering have been adapted to functional inputs under the
general name of functional Data Analysis (FDA). In this paper, we investigate
the use of Support Vector Machines (SVMs) for functional data analysis and we
focus on the problem of curves discrimination. SVMs are large margin classifier
tools based on implicit non linear mappings of the considered data into high
dimensional spaces thanks to kernels. We show how to define simple kernels that
take into account the unctional nature of the data and lead to consistent
classification. Experiments conducted on real world data emphasize the benefit
of taking into account some functional aspects of the problems.


title:
Un r\'esultat de consistance pour des SVM fonctionnels par interpolation
  spline

abstract:
  This Note proposes a new methodology for function classification with Support
Vector Machine (SVM). Rather than relying on projection on a truncated Hilbert
basis as in our previous work, we use an implicit spline interpolation that
allows us to compute SVM on the derivatives of the studied functions. To that
end, we propose a kernel defined directly on the discretizations of the
observed functions. We show that this method is universally consistent.