title: Multiple-Description Coding by Dithered Delta-Sigma Quantization

abstract:
  We address the connection between the multiple-description (MD) problem and
Delta-Sigma quantization. The inherent redundancy due to oversampling in
Delta-Sigma quantization, and the simple linear-additive noise model resulting
from dithered lattice quantization, allow us to construct a symmetric and
time-invariant MD coding scheme. We show that the use of a noise shaping filter
makes it possible to trade off central distortion for side distortion.
Asymptotically as the dimension of the lattice vector quantizer and order of
the noise shaping filter approach infinity, the entropy rate of the dithered
Delta-Sigma quantization scheme approaches the symmetric two-channel MD
rate-distortion function for a memoryless Gaussian source and MSE fidelity
criterion, at any side-to-central distortion ratio and any resolution. In the
optimal scheme, the infinite-order noise shaping filter must be minimum phase
and have a piece-wise flat power spectrum with a single jump discontinuity. An
important advantage of the proposed design is that it is symmetric in rate and
distortion by construction, so the coding rates of the descriptions are
identical and there is therefore no need for source splitting.


title: Stable curved solitonic surfaces in nonholonomic frame

abstract:
  Assuming the stability of soliton surfaces of vanishing Ricci sectional
curvature of soliton metric in the nonholonomic frame, we find a solution for
the metric in the approximation of weak constant torsion curves with constant
Frenet curvature. The computation of the Riemann tensor of the soliton metric
shows that it does not vanish and therefore the solution is nontrivial.
Heisenberg solitonic equation is also used to constrain the the soliton Riemann
metric. The new feature here is that the coordinate curves on the soliton-like
surface are composed of hydrodynamical filaments.


title: Origins of the Combinatorial Basis of Entropy

abstract:
  The combinatorial basis of entropy, given by Boltzmann, can be written $H =
N^{-1} \ln \mathbb{W}$, where $H$ is the dimensionless entropy, $N$ is the
number of entities and $\mathbb{W}$ is number of ways in which a given
realization of a system can occur (its statistical weight). This can be
broadened to give generalized combinatorial (or probabilistic) definitions of
entropy and cross-entropy: $H=\kappa (\phi(\mathbb{W}) +C)$ and $D=-\kappa
(\phi(\mathbb{P}) +C)$, where $\mathbb{P}$ is the probability of a given
realization, $\phi$ is a convenient transformation function, $\kappa$ is a
scaling parameter and $C$ an arbitrary constant. If $\mathbb{W}$ or
$\mathbb{P}$ satisfy the multinomial weight or distribution, then using
$\phi(\cdot)=\ln(\cdot)$ and $\kappa=N^{-1}$, $H$ and $D$ asymptotically
converge to the Shannon and Kullback-Leibler functions. In general, however,
$\mathbb{W}$ or $\mathbb{P}$ need not be multinomial, nor may they approach an
asymptotic limit. In such cases, the entropy or cross-entropy function can be
{\it defined} so that its extremization ("MaxEnt'' or "MinXEnt"), subject to
the constraints, gives the ``most probable'' (``MaxProb'') realization of the
system. This gives a probabilistic basis for MaxEnt and MinXEnt, independent of
any information-theoretic justification.
  This work examines the origins of the governing distribution $\mathbb{P}$....
(truncated)


title: Spectral methods and cluster structure in correlation-based networks

abstract:
  We investigate how in complex systems the eigenpairs of the matrices derived
from the correlations of multichannel observations reflect the cluster
structure of the underlying networks. For this we use daily return data from
the NYSE and focus specifically on the spectral properties of weight W_{ij} =
|C|_{ij} - \delta_{ij} and diffusion matrices D_{ij} = W_{ij}/s_j- \delta_{ij},
where C_{ij} is the correlation matrix and s_i = \sum_j W_{ij} the strength of
node j. The eigenvalues (and corresponding eigenvectors) of the weight matrix
are ranked in descending order. In accord with the earlier observations the
first eigenvector stands for a measure of the market correlations. Its
components are to first approximation equal to the strengths of the nodes and
there is a second order, roughly linear, correction. The high ranking
eigenvectors, excluding the highest ranking one, are usually assigned to market
sectors and industrial branches. Our study shows that both for weight and
diffusion matrices the eigenpair analysis is not capable of easily deducing the
cluster structure of the network without a priori knowledge. In addition we
have studied the clustering of stocks using the asset graph approach with and
without spectrum based noise filtering. It turns out that asset graphs are
quite insensitive to noise and there is no sharp percolation transition as a
function of the ratio of bonds included, thus no natural threshold value for
that ratio seems to exist. We suggest that these observations can be of use for
other correlation based networks as well.


title: The Blazhko behavior of RV UMa

abstract:
  RV UMa is one of the most extensively studied RR Lyrae stars showing Blazhko
modulation. Its photometric observations cover more than 90 years. The
published photoelectric observations of RV UMa obtained at the Konkoly
Observatory (Kanyo, 1976) were re-considered and completed with previously
unpublished data. During the time interval of the observations the periods of
both the pulsation and the modulation varied within the ranges of 0.000007 and
0.9 days, respectively. We have found a definite but not strict inverse
relation between the pulsation and modulation periods of RV UMa.


title: Results of the photometry of the spotted dM1-2e star EY Draconis

abstract:
  We have observed EY Draconis with the 24`` telescope of Konkoly Observatory
in Budapest for 64 nights. In the first obse rving season the star produced a
stable light curve for more than 60 rotation periods, however, the light curves
observe d in the next season and the spot modelling show clear evidence of the
evolution of the spotted stellar surface. The chan ges of the maximum
brightness level suggests the existence of a longer period of about 300 days,
which seems to be confir med by the ROTSE archival data.


title:
Metabolite essentiality elucidates robustness of Escherichia coli
  metabolism

abstract:
  Complex biological systems are very robust to genetic and environmental
changes at all levels of organization. Many biological functions of Escherichia
coli metabolism can be sustained against single-gene or even multiple-gene
mutations by using redundant or alternative pathways. Thus, only a limited
number of genes have been identified to be lethal to the cell. In this regard,
the reaction-centric gene deletion study has a limitation in understanding the
metabolic robustness. Here, we report the use of flux-sum, which is the
summation of all incoming or outgoing fluxes around a particular metabolite
under pseudo-steady state conditions, as a good conserved property for
elucidating such robustness of E. coli from the metabolite point of view. The
functional behavior, as well as the structural and evolutionary properties of
metabolites essential to the cell survival, was investigated by means of a
constraints-based flux analysis under perturbed conditions. The essential
metabolites are capable of maintaining a steady flux-sum even against severe
perturbation by actively redistributing the relevant fluxes. Disrupting the
flux-sum maintenance was found to suppress cell growth. This approach of
analyzing metabolite essentiality provides insight into cellular robustness and
concomitant fragility, which can be used for several applications, including
the development of new drugs for treating pathogens.


title:
On the equivalence of the microcanonical and the canonical ensembles: a
  geometrical approach

abstract:
  In this paper, we consider the volume enclosed by the microcanonical ensemble
in phase space as a statistical ensemble. This can be interpreted as an
intermediate image between the microcanonical and the canonical pictures. By
maintaining the ergodic hypothesis over this ensemble, that is, the
equiprobability of all its accessible states, the equivalence of this ensemble
in the thermodynamic limit with the microcanonical and the canonical ensembles
is suggested by means of geometrical arguments. The Maxwellian and the
Boltzmann-Gibbs distributions are obtained from this formalism. In the
appendix, the derivation of the Boltzmann factor from a new microcanonical
image of the canonical ensemble is also given.


title: Remarks on symplectic twistor spaces

abstract:
  We consider some classical fibre bundles furnished with almost complex
structures of twistor type, deduce their integrability in some cases and study
\textit{self-holomorphic} sections of a \textit{symplectic} twistor space. With
these we define a moduli space of $\omega$-compatible complex structures. We
recall the theory of flag manifolds in order to study the Siegel domain and
other domains alike, which is the fibre of the referred twistor space. Finally
the structure equations for the twistor of a Riemann surface with the canonical
symplectic-metric connection are deduced, based on a given conformal coordinate
on the surface. We then relate with the moduli space defined previously.


title: The alternative model of the spherical oscillator

abstract:
  The quasiradial wave functions and energy spectra of the alternative model of
spherical oscillator on the $D$-dimensional sphere and two-sheeted hyperboloid
are found.


title: Broadcasting of continuous variable entanglement

abstract:
  We present a scheme for broadcasting of continuous variable entanglement. We
show how an initial two-mode squeezed state of the electromagnetic field shared
by two distant parties can be broadcasted into two nonlocal bipartite entangled
states. Our protocol uses a local linear amplifier and a beam splitter at each
end. We compute the fidelity of the output entangled states and show that the
broadcasting can be implemented for a variety of input squeezed states and
amplifier phases.


title:
Multifractal spectrum of phase space related to generalized
  thermostatistics

abstract:
  We consider a self-similar phase space with specific fractal dimension $d$
being distributed with spectrum function $f(d)$. Related thermostatistics is
shown to be governed by the Tsallis formalism of the non-extensive statistics,
where the non-additivity parameter is equal to ${\bar\tau}(q)\equiv
1/\tau(q)>1$, and the multifractal function $\tau(q)= qd_q-f(d_q)$ is the
specific heat determined with multifractal parameter $q\in [1,\infty)$. In this
way, the equipartition law is shown to take place. Optimization of the
multifractal spectrum function $f(d)$ derives the relation between the
statistical weight and the system complexity. It is shown the statistical
weight exponent $\tau(q)$ can be modeled by hyperbolic tangent deformed in
accordance with both Tsallis and Kaniadakis exponentials to describe arbitrary
multifractal phase space explicitly. The spectrum function $f(d)$ is proved to
increase monotonically from minimum value $f=-1$ at $d=0$ to maximum one $f=1$
at $d=1$. At the same time, the number of monofractals increases with growth of
the phase space volume at small dimensions $d$ and falls down in the limit
$d\to 1$.


title: Gravitational Lorentz Violation and Superluminality via AdS/CFT Duality

abstract:
  A weak quantum mechanical coupling is constructed permitting superluminal
communication within a preferred region of a gravitating AdS_5 spacetime. This
is achieved by adding a spatially non-local perturbation of a special kind to
the Hamiltonian of a four-dimensional conformal field theory with a
weakly-coupled AdS dual, such as maximally supersymmetric Yang-Mills theory. In
particular, two issues are given careful treatment: (1) the UV-completeness of
our deformed CFT, guaranteeing the existence of a ``deformed string theory''
AdS dual, and (2) the demonstration that superluminal effects can take place in
AdS, both on its boundary as well as in the bulk. Exotic Lorentz-violating
properties such as these may have implications for tests of General Relativity,
addressing the cosmological constant problem, or probing "behind'' horizons.
Our construction may give insight into the interpretation of wormhole solutions
in Euclidean AdS gravity.


title:
Probing new physics with flavor physics (and probing flavor physics with
  new physics)

abstract:
  This is a written version of a series of lectures aimed at graduate students
and postdoctoral fellows in particle theory/string theory/particle experiment
familiar with the basics of the Standard Model. We begin with an overview of
flavor physics and its implications for new physics. We emphasize the "new
physics flavor puzzle". Then, we give four specific examples of flavor
measurements and the lessons that have been (or can be) drawn from them: (i)
Charm physics: lessons for supersymmetry from the upper bound on $\Delta m_D$.
(ii) Bottom physics: model independent lessons on the KM mechanism and on new
physics in neutral B mixing from $S_{\psi K_S}$. (iii) Top physics and beyond:
testing minimal flavor violation at the LHC. (iv) Neutrino physics:
interpreting the data on neutrino masses and mixing within flavor models.


title:
Systematics of String Loop Corrections in Type IIB Calabi-Yau Flux
  Compactifications

abstract:
  We study the behaviour of the string loop corrections to the N=1 4D
supergravity Kaehler potential that occur in flux compactifications of IIB
string theory on general Calabi-Yau three-folds. We give a low energy
interpretation for the conjecture of Berg, Haack and Pajer for the form of the
loop corrections to the Kaehler potential. We check the consistency of this
interpretation in several examples. We show that for arbitrary Calabi-Yaus, the
leading contribution of these corrections to the scalar potential is always
vanishing, giving an "extended no-scale structure". This result holds as long
as the corrections are homogeneous functions of degree -2 in the 2-cycle
volumes. We use the Coleman-Weinberg potential to motivate this cancellation
from the viewpoint of low-energy field theory. Finally we give a simple formula
for the 1-loop correction to the scalar potential in terms of the tree-level
Kaehler metric and the correction to the Kaehler potential. We illustrate our
ideas with several examples. A companion paper will use these results in the
study of Kaehler moduli stabilisation.


title: Point estimation with exponentially tilted empirical likelihood

abstract:
  Parameters defined via general estimating equations (GEE) can be estimated by
maximizing the empirical likelihood (EL). Newey and Smith [Econometrica 72
(2004) 219--255] have recently shown that this EL estimator exhibits desirable
higher-order asymptotic properties, namely, that its $O(n^{-1})$ bias is small
and that bias-corrected EL is higher-order efficient. Although EL possesses
these properties when the model is correctly specified, this paper shows that,
in the presence of model misspecification, EL may cease to be root n convergent
when the functions defining the moment conditions are unbounded (even when
their expectations are bounded). In contrast, the related exponential tilting
(ET) estimator avoids this problem. This paper shows that the ET and EL
estimators can be naturally combined to yield an estimator called exponentially
tilted empirical likelihood (ETEL) exhibiting the same $O(n^{-1})$ bias and the
same $O(n^{-2})$ variance as EL, while maintaining root n convergence under
model misspecification.


title: Blowups of Heterotic Orbifolds using Toric Geometry

abstract:
  Heterotic orbifold models are promising candidates for models with MSSM like
spectra. But orbifolds only correspond to a special place in moduli space, the
bigger picture is described by the moduli space of Calabi-Yau spaces. In this
talk we will make explicit connections between both points of view. To this end
we study blowups of orbifold singularities using both explicit constructions
and toric geometry techniques. We show that matching of all orbifold models in
blowups are possible.


title:
Conductance quantization and snake states in graphene magnetic
  waveguides

abstract:
  We consider electron waveguides (quantum wires) in graphene created by
suitable inhomogeneous magnetic fields. The properties of uni-directional snake
states are discussed. For a certain magnetic field profile, two spatially
separated counter-propagating snake states are formed, leading to conductance
quantization insensitive to backscattering by impurities or irregularities of
the magnetic field.


title: A nearly tight memory-redundancy trade-off for one-pass compression

abstract:
  Let $s$ be a string of length $n$ over an alphabet of constant size $\sigma$
and let $c$ and $\epsilon$ be constants with (1 \geq c \geq 0) and (\epsilon >
0). Using (O (n)) time, (O (n^c)) bits of memory and one pass we can always
encode $s$ in (n H_k (s) + O (\sigma^k n^{1 - c + \epsilon})) bits for all
integers (k \geq 0) simultaneously. On the other hand, even with unlimited
time, using (O (n^c)) bits of memory and one pass we cannot always encode $s$
in (O (n H_k (s) + \sigma^k n^{1 - c - \epsilon})) bits for, e.g., (k = \lceil
(c + \epsilon / 2) \log_\sigma n \rceil).


title: Room temperature triggered single-photon source in the near infrared

abstract:
  We report the realization of a solid-state triggered single-photon source
with narrow emission in the near infrared at room temperature. It is based on
the photoluminescence of a single nickel-nitrogen NE8 colour centre in a
chemical vapour deposited diamond nanocrystal. Stable single-photon emission
has been observed in the photoluminescence under both continuous-wave and
pulsed excitations. The realization of this source represents a step forward in
the application of diamond-based single-photon sources to Quantum Key
Distribution (QKD) under practical operating conditions.


title: Quantum random access memory

abstract:
  A random access memory (RAM) uses n bits to randomly address N=2^n distinct
memory cells. A quantum random access memory (qRAM) uses n qubits to address
any quantum superposition of N memory cells. We present an architecture that
exponentially reduces the requirements for a memory call: O(log N) switches
need be thrown instead of the N used in conventional (classical or quantum) RAM
designs. This yields a more robust qRAM algorithm, as it in general requires
entanglement among exponentially less gates, and leads to an exponential
decrease in the power needed for addressing. A quantum optical implementation
is presented.


title: Cram\'{e}r-type large deviations for samples from a finite population

abstract:
  Cram\'{e}r-type large deviations for means of samples from a finite
population are established under weak conditions. The results are comparable to
results for the so-called self-normalized large deviation for independent
random variables. Cram\'{e}r-type large deviations for the finite population
Student $t$-statistic are also investigated.


title: The actual Rees--Sciama effect from the Local Universe

abstract:
  Observations of the Cosmic Microwave Background (CMB) have revealed an
unexpected quadrupole-octopole alignment along a preferred axis pointing toward
the Virgo cluster. We here investigate whether this feature can be explained in
the framework of the concordance model by secondary anisotropies produced by
the non-linear evolution of the gravitational potential, the so-called
Rees-Sciama (RS) effect. We focus on the effect caused by the local
superclusters, which we calculate using a constrained high-resolution
hydrodynamical simulation, based on the IRAS 1.2-Jy all-sky galaxy redshift
survey, which reproduces the main structures of our Universe out to a distance
of 110 Mpc from our Galaxy. The resulting RS effect peaks at low multipoles and
has a minimum/maximum amplitude of -6.6\mu K 1.9\mu K. Even though its
quadrupole is well aligned with the one measured for the CMB, its amplitude is
not sufficient to explain the observed magnitude of the quadrupole/octopole
alignment. In addition, we analyze the WMAP-3 data with a linear matched filter
in an attempt to determine an upper limit for the RS signal amplitude on large
scales. We found that it is possible to infer a weak upper limit of 30\mu K for
its maximum amplitude.


title: The role of symmetries in adiabatic quantum algorithms

abstract:
  Exploiting the similarity between adiabatic quantum algorithms and quantum
phase transitions, we argue that second-order transitions -- typically
associated with broken or restored symmetries -- should be advantageous in
comparison to first-order transitions. Guided by simple examples we construct
an alternative adiabatic algorithm for the NP-complete problem {\em Exact Cover
3}. We show numerically that its average performance (for the considered cases
up to ${\cal O}\{20\}$ qubits) is better than that of the conventional scheme.
The run-time of adiabatic algorithms is not just determined by the minimum
value of the fundamental energy gap (between the ground state and the exited
states), but also by its curvature at the critical point. The proposed
symmetry-restoring adiabatic quantum algorithm only contains contributions
linear and quadratic in the Pauli matrices and can be generalized to other
problem Hamiltonians which are decomposed of terms involving one and two
qubits. We show how the factoring problem can be cast into such a quadratic
form. These findings suggest that adiabatic quantum algorithms can solve a
large class of NP problems much faster than the Grover search routine (which
corresponds to a first-order transition and yields a quadratic enhancement
only).


title:
Limits on spin-dependent WIMP-nucleon cross-sections from the first
  ZEPLIN-II data

abstract:
  The first underground data run of the ZEPLIN-II experiment has set a limit on
the nuclear recoil rate in the two-phase xenon detector for direct dark matter
searches. In this paper the results from this run are converted into the limits
on spin-dependent WIMP-proton and WIMP-neutron cross-sections. The minimum of
the curve for WIMP-neutron cross-section corresponds to 0.07 pb at a WIMP mass
of around 65 GeV.


title: Superconductivity without attraction in a quasi-one-dimensional metal

abstract:
  An array of one-dimensional conductors coupled by transverse hopping and
interaction is studied with the help of a variational wave function. This wave
function is devised as to account for one-dimensional correlation effects. We
show that under broad conditions our system possesses the superconducting
ground state even if no attraction is present. The superconducting mechanism is
of many-body nature and deviates substantially from BCS. The phase diagram of
the model is mapped. It consists of two ordered phases competing against each
other: density wave, spin or charge, and unconventional superconductivity.
These phases are separated by the first order transition. The symmetry of the
superconducting order parameter is a non-universal property. It depends on
particulars of the Hamiltonian. Within the framework of our model possible
choices are the triplet $f$-wave and the singlet $d_{xy}$-wave. Organic
quasi-one-dimensional superconductors have similar phase diagram.


title: Posterior convergence rates of Dirichlet mixtures at smooth densities

abstract:
  We study the rates of convergence of the posterior distribution for Bayesian
density estimation with Dirichlet mixtures of normal distributions as the
prior. The true density is assumed to be twice continuously differentiable. The
bandwidth is given a sequence of priors which is obtained by scaling a single
prior by an appropriate order. In order to handle this problem, we derive a new
general rate theorem by considering a countable covering of the parameter space
whose prior probabilities satisfy a summability condition together with certain
individual bounds on the Hellinger metric entropy. We apply this new general
theorem on posterior convergence rates by computing bounds for Hellinger
(bracketing) entropy numbers for the involved class of densities, the error in
the approximation of a smooth density by normal mixtures and the concentration
rate of the prior. The best obtainable rate of convergence of the posterior
turns out to be equivalent to the well-known frequentist rate for integrated
mean squared error $n^{-2/5}$ up to a logarithmic factor.


title:
Quantitative Determination of Enhanced and Suppressed Transmission
  through Subwavelength Slit Arrays in Silver Films

abstract:
  Measurement of the transmitted intensity from a coherent monomode light
source through a series of subwavelength slit arrays in Ag films, with varying
array pitch and number of slits, demonstrate enhancement (suppression) by as
much as a factor of 6 (9) when normalized to that of an isolated slit.
Pronounced minima in the transmitted intensity were observed at array pitches
corresponding to lambda_SPP, 2lambda_SPP, and 3lambda_SPP where lambda_SPP is
the wavelength of the surface plasmon polariton (SPP). Increasing the number of
slits to more than four does not increase appreciably the per-slit transmission
intensity. These results are consistent with a model for interference between
SPPs and the incident wave that fits well the measured transmitted intensity
profile.


title:
Study and characterization by magnetophonon resonance of the energy
  structuring in GaAs/AlAs quantum-wire superlattices

abstract:
  We present the characterization of the band structure of GaAs/AlAs
quantum-wire 1D superlattices performed by magnetophonon resonance with pulsed
magnetic fields up to 35 T. The samples, generated by the "atomic saw method"
from original quantum-well 2D superlattices, underwent substantial
modifications of their energy bands built up on the X-states of the bulk. We
have calculated the band structure by a finite element method and we have
studied the various miniband structures built up of the masses m_t and m_l of
GaAs and AlAs at the point X. From an experimental point of view, the main
result is that in the 2D case we observe only resonances when the magnetic
field B is applied along the growth axis whereas in the 1D case we obtain
resonances in all magnetic field configurations. The analysis of the maxima (or
minima for B // E) in the resistivity rho_xy as a function of B allows us to
account, qualitatively and semi-quantitatively, for the band structure
theoretically expected.


title:
Statistical mechanics and thermodynamic limit of self-gravitating
  fermions in D dimensions

abstract:
  We discuss the statistical mechanics of a system of self-gravitating fermions
in a space of dimension $D$. We plot the caloric curves of the self-gravitating
Fermi gas giving the temperature as a function of energy and investigate the
nature of phase transitions as a function of the dimension of space. We
consider stable states (global entropy maxima) as well as metastable states
(local entropy maxima). We show that for $D\ge 4$, there exists a critical
temperature (for sufficiently large systems) and a critical energy below which
the system cannot be found in statistical equilibrium. Therefore, for $D\ge 4$,
quantum mechanics cannot stabilize matter against gravitational collapse. This
is similar to a result found by Ehrenfest (1917) at the atomic level for
Coulombian forces. This makes the dimension D=3 of our universe very particular
with possible implications regarding the anthropic principle. Our study enters
in a long tradition of scientific and philosophical papers who studied how the
dimension of space affects the laws of physics.


title:
Zero temperature solutions of the Edwards-Anderson model in random
  Husimi Lattices

abstract:
  We solve the Edwards-Anderson model (EA) in different Husimi lattices. We
show that, at T=0, the structure of the solution space depends on the parity of
the loop sizes. Husimi lattices with odd loop sizes have always a trivial
paramagnetic solution stable under 1RSB perturbations while, in Husimi lattices
with even loop sizes, this solution is absent. The range of stability under
1RSB perturbations of this and other RS solutions is computed analytically
(when possible) or numerically. We compute the free-energy, the complexity and
the ground state energy of different Husimi lattices at the level of the 1RSB
approximation. We also show, when the fraction of ferromagnetic couplings
increases, the existence, first, of a discontinuous transition from a
paramagnetic to a spin glass phase and latter of a continuous transition from a
spin glass to a ferromagnetic phase.


title:
On the design-consistency property of hierarchical Bayes estimators in
  finite population sampling

abstract:
  We obtain a limit of a hierarchical Bayes estimator of a finite population
mean when the sample size is large. The limit is in the sense of ordinary
calculus, where the sample observations are treated as fixed quantities. Our
result suggests a simple way to correct the hierarchical Bayes estimator to
achieve design-consistency, a well-known property in the traditional
randomization approach to finite population sampling. We also suggest three
different measures of uncertainty of our proposed estimator.


title: Mapping the dark trajectory of the Bullet Cluster

abstract:
  We model the electrons/positrons produced by dark matter annihilations in the
colliding galaxy cluster system 1E0657-56 (the bullet cluster). These charged
particles, confined by the Magnetic field, clearly trace the path of the
bullet, which passes through the main cluster with a speed of 3000-5000 km/s.
Adding the effect of dark matter substructure (subhalos) in each cluster we
find the annihilation rate is enhancedgreatly and the density of positrons in
the trail is similar to that within the bullet cluster. This opens the door to
unambiguous detection of the annihilation signal through the SZ effect, at
significant separation from the thermal electrons.


title:
On rates of convergence for posterior distributions in
  infinite-dimensional models

abstract:
  This paper introduces a new approach to the study of rates of convergence for
posterior distributions. It is a natural extension of a recent approach to the
study of Bayesian consistency. In particular, we improve on current rates of
convergence for models including the mixture of Dirichlet process model and the
random Bernstein polynomial model.


title: Sticky obstacles to intramolecular energy flow

abstract:
  Vibrational energy flows unevenly in molecules, repeatedly going back and
forth between trapping and roaming. We identify bottlenecks between diffusive
and chaotic behavior, and describe generic mechanisms of these transitions,
taking the carbonyl sulphide molecule OCS as a case study. The bottlenecks are
found to be lower-dimensional tori; their bifurcations and unstable manifolds
govern the transition mechanisms.


title: Cosmological Constraints on New Agegraphic Dark Energy

abstract:
  In this work, we consider the cosmological constraints on the new agegraphic
dark energy (NADE) proposed in arXiv:0708.0884, by using the observational data
of type Ia supernovae (SNIa), the shift parameter from cosmic microwave
background (CMB) and the baryon acoustic oscillation (BAO) peak from large
scale structures (LSS). Thanks to its special analytic features in the
radiation-dominated and matter-dominated epochs, NADE is a single-parameter
model in practice because once the single model parameter $n$ is given, all
other physical quantities of NADE can be determined correspondingly. The joint
analysis gives the best-fit value (with $1\sigma$ uncertainty)
$n=2.716^{+0.111}_{-0.109}$, and the derived $\Omega_{m0}$, $\Omega_{q0}$ and
$w_{q0}$ (with $1\sigma$ uncertainties) are $0.295^{+0.020}_{-0.020}$,
$0.705^{+0.020}_{-0.020}$ and $-0.794^{+0.006}_{-0.005}$, respectively. In
addition, we find that the coincidence problem could be solved naturally in the
NADE model provided that $n$ is of order unity.


title:
Random telegraph noise from magnetic nanoclusters in the ferromagnetic
  semiconductor (Ga,Mn)As

abstract:
  Measurements of the low frequency electrical noise in the ferromagnetic
semiconductor (Ga,Mn)As reveal an enhanced integrated noise at low temperature.
For moderate localization, we find a 1/f normalized power spectrum density over
the entire range of temperatures studied (4.2K < T < 70K). However, for
stronger localization and a high density of Mn interstitials, we observe
Lorentzian noise spectra accompanied by random telegraph noise. Magnetic field
dependence and annealing studies suggest that interstitial Mn defects couple
with substitutional Mn atoms to form nanoscale magnetic clusters characterized
by a net moment of about 20 Bohr magnetons whose fluctuations modulate hole
transport.


title: Resolvable designs with large blocks

abstract:
  Resolvable designs with two blocks per replicate are studied from an
optimality perspective. Because in practice the number of replicates is
typically less than the number of treatments, arguments can be based on the
dual of the information matrix and consequently given in terms of block
concurrences. Equalizing block concurrences for given block sizes is often, but
not always, the best strategy. Sufficient conditions are established for
various strong optimalities and a detailed study of E-optimality is offered,
including a characterization of the E-optimal class. Optimal designs are found
to correspond to balanced arrays and an affine-like generalization.


title: Morita classes of algebras in modular tensor categories

abstract:
  We consider algebras in a modular tensor category C. If the trace pairing of
an algebra A in C is non-degenerate we associate to A a commutative algebra
Z(A), called the full centre, in a doubled version of the category C. We prove
that two simple algebras with non-degenerate trace pairing are
Morita-equivalent if and only if their full centres are isomorphic as algebras.
This result has an interesting interpretation in two-dimensional rational
conformal field theory; it implies that there cannot be several incompatible
sets of boundary conditions for a given bulk theory.


title:
On the dynamics of point vortices in a quantum gas confined in an
  annular region

abstract:
  The dynamics of one and two pointlike vortices in a planar quantum gas of
spin-0 particles confined in an annular region is considered. New analytical
and numerical solutions are found. The concept of stationarity radius, related
to the doubly connected nature of the annulus, is defined. It is seen that the
existence of these radii has great impact on the behaviour of the vortices. It
is shown that, because of the existence of the stationarity radii, vortices
exhibit similar behaviour regardless of the sign of their winding number. The
energetically stable vortex solutions are studied qualitatively.


title: A First Exposure to Statistical Mechanics for Life Scientists

abstract:
  Statistical mechanics is one of the most powerful and elegant tools in the
quantitative sciences. One key virtue of statistical mechanics is that it is
designed to examine large systems with many interacting degrees of freedom,
providing a clue that it might have some bearing on the analysis of the
molecules of living matter. As a result of data on biological systems becoming
increasingly quantitative, there is a concomitant demand that the models set
forth to describe biological systems be themselves quantitative. We describe
how statistical mechanics is part of the quantitative toolkit that is needed to
respond to such data. The power of statistical mechanics is not limited to
traditional physical and chemical problems and there are a host of interesting
ways in which these ideas can be applied in biology. This article reports on
our efforts to teach statistical mechanics to life science students and
provides a framework for others interested in bringing these tools to a
nontraditional audience in the life sciences.


title: Gegenbauer tau methods with and without spurious eigenvalues

abstract:
  It is proven that a class of Gegenbauer tau approximations to a 4th order
differential eigenvalue problem of hydrodynamic type provide real, negative and
distinct eigenvalues, as is the case for the exact solutions. This class of
Gegenbauer tau methods includes Chebyshev and Legendre Galerkin and `inviscid'
Galerkin but does not include Chebyshev and Legendre tau. Rigorous and
numerical results show that the results are sharp: positive or complex
eigenvalues arise outside of this class. The widely used modified tau approach
is proved to be equivalent to the Galerkin method.


title: On the number of support points of maximin and Bayesian optimal designs

abstract:
  We consider maximin and Bayesian $D$-optimal designs for nonlinear regression
models. The maximin criterion requires the specification of a region for the
nonlinear parameters in the model, while the Bayesian optimality criterion
assumes that a prior for these parameters is available. On interval parameter
spaces, it was observed empirically by many authors that an increase of
uncertainty in the prior information (i.e., a larger range for the parameter
space in the maximin criterion or a larger variance of the prior in the
Bayesian criterion) yields a larger number of support points of the
corresponding optimal designs. In this paper, we present analytic tools which
are used to prove this phenomenon in concrete situations. The proposed
methodology can be used to explain many empirically observed results in the
literature. Moreover, it explains why maximin $D$-optimal designs are usually
supported at more points than Bayesian $D$-optimal designs.


title: Some Open Problems in Quantum Information Theory

abstract:
  Some open questions in quantum information theory (QIT) are described. Most
of them were presented in Banff during the BIRS workshop on Operator Structures
in QIT 11-16 February 2007. New material has been added in view of the recent
counter-examples to p-norm multiplicativity.


title: On Edge-Disjoint Pairs Of Matchings

abstract:
  For a graph G, consider the pairs of edge-disjoint matchings whose union
consists of as many edges as possible. Let H be the largest matching among such
pairs. Let M be a maximum matching of G. We show that 5/4 is a tight upper
bound for |M|/|H|.


title: Triplet spin resonance of the Haldane compound with interchain coupling

abstract:
  Spin resonance absorption of the triplet excitations is studied
experimentally in the Haldane magnet PbNi2V2O8. The spectrum has features of
spin S=1 resonance in a crystal field, with all three components, corresponding
to transitions between spin sublevels, being observable. The resonance field is
temperature dependent, indicating the renormalization of excitation spectrum in
interaction between the triplets. Magnetic resonance frequencies and critical
fields of the magnetization curve are consistent with a boson version of the
macroscopic field theory [Affleck 1992, Farutin & Marchenko 2007], implying the
field induced ordering at the critical field, while contradict the previously
used approach of noninteracting spin chains.


title: A random walk approximation to fractional Brownian motion

abstract:
  We present a random walk approximation to fractional Brownian motion where
the increments of the fractional random walk are defined as a weighted sum of
the past increments of a Bernoulli random walk.


title:
Solving QCD evolution equations in rapidity space with Markovian Monte
  Carlo

abstract:
  This work covers methodology of solving QCD evolution equation of the parton
distribution using Markovian Monte Carlo (MMC) algorithms in a class of models
ranging from DGLAP to CCFM. One of the purposes of the above MMCs is to test
the other more sophisticated Monte Carlo programs, the so-called Constrained
Monte Carlo (CMC) programs, which will be used as a building block in the
parton shower MC. This is why the mapping of the evolution variables (eikonal
variable and evolution time) into four-momenta is also defined and tested. The
evolution time is identified with the rapidity variable of the emitted parton.
The presented MMCs are tested independently, with ~0.1% precision, against the
non-MC program APCheb especially devised for this purpose.


title:
Uncovering the Active Galactic Nuclei in Low-Ionization Nuclear
  Emission-Line Regions with Spitzer

abstract:
  The impact of active galactic nuclei on low-ionization nuclear emission-line
regions (LINERs) remains a vigorous field of study. We present preliminary
results from a study of the mid-infrared atomic emission lines of LINERs with
the Spitzer Space Telescope. We assess the ubiquity and properties of AGN in
LINERs using this data. We discuss what powers the mid-infrared emission lines
and conclude that the answer depends unsurprisingly on the emission line
ionization state and, more interestingly, on the infrared luminosity.


title:
Complete enumeration of two-Level orthogonal arrays of strength $d$ with
  $d+2$ constraints

abstract:
  Enumerating nonisomorphic orthogonal arrays is an important, yet very
difficult, problem. Although orthogonal arrays with a specified set of
parameters have been enumerated in a number of cases, general results are
extremely rare. In this paper, we provide a complete solution to enumerating
nonisomorphic two-level orthogonal arrays of strength $d$ with $d+2$
constraints for any $d$ and any run size $n=\lambda2^d$. Our results not only
give the number of nonisomorphic orthogonal arrays for given $d$ and $n$, but
also provide a systematic way of explicitly constructing these arrays. Our
approach to the problem is to make use of the recently developed theory of
$J$-characteristics for fractional factorial designs. Besides the general
theoretical results, the paper presents some results from applications of the
theory to orthogonal arrays of strength two, three and four.


title:
Lower Bounds for the Complexity of the Voronoi Diagram of Polygonal
  Curves under the Discrete Frechet Distance

abstract:
  We give lower bounds for the combinatorial complexity of the Voronoi diagram
of polygonal curves under the discrete Frechet distance. We show that the
Voronoi diagram of n curves in R^d with k vertices each, has complexity
Omega(n^{dk}) for dimension d=1,2 and Omega(n^{d(k-1)+2}) for d>2.


title:
Correlated behavior of conductance and phase rigidity in the transition
  from the weak-coupling to the strong-coupling regime

abstract:
  We study the transmission through different small systems as a function of
the coupling strength $v$ to the two attached leads. The leads are identical
with only one propagating mode $\xi^E_C$ in each of them. Besides the
conductance $G$, we calculate the phase rigidity $\rho$ of the scattering wave
function $\Psi^E_C$ in the interior of the system. Most interesting results are
obtained in the regime of strongly overlapping resonance states where the
crossover from staying to traveling modes takes place. The crossover is
characterized by collective effects. Here, the conductance is plateau-like
enhanced in some energy regions of finite length while corridors with zero
transmission (total reflection) appear in other energy regions. This
transmission picture depends only weakly on the spectrum of the closed system.
It is caused by the alignment of some resonance states of the system with the
propagating modes $\xi^E_C$ in the leads. The alignment of resonance states
takes place stepwise by resonance trapping, i.e. it is accompanied by the
decoupling of other resonance states from the continuum of propagating modes.
This process is quantitatively described by the phase rigidity $\rho$ of the
scattering wave function. Averaged over energy in the considered energy window,
$<G>$ is correlated with $1-<\rho>$. In the regime of strong coupling, only two
short-lived resonance states survive each aligned with one of the channel wave
functions $\xi^E_C$. They may be identified with traveling modes through the
system. The remaining $M-2$ trapped narrow resonance states are well separated
from one another.


title: Moduli Vacuum Bubbles Produced by Evaporating Black Holes

abstract:
  We consider a model with a toroidally compactified extra dimension giving
rise to a temperature-dependent 4d effective potential with one-loop
contributions due to the Casimir effect, along with a 5d cosmological constant.
The forms of the effective potential at low and high temperatures indicates a
possibility for the formation of a domain wall bubble, formed by the modulus
scalar field, surrounding an evaporating black hole. This is viewed as an
example of a recently proposed black hole vacuum bubble arising from
matter-sourced moduli fields in the vicinity of an evaporating black hole [D.
Green, E. Silverstein, and D. Starr, Phys. Rev. D74, 024004 (2006),
arXiv:hep-th/0605047]. The black hole bubble can be highly opaque to lower
energy particles and photons, and thereby entrap them within. For high
temperature black holes, there may also be a symmetry-breaking black hole
bubble of false vacuum of the type previously conjectured by Moss [I.G. Moss,
Phys. Rev. D32,1333 (1985)], tending to reflect low energy particles from its
wall. A double bubble composed of these two different types of bubble may form
around the black hole, altering the hole's emission spectrum that reaches
outside observers. Smaller mass black holes that have already evaporated away
could have left vacuum bubbles behind that contribute to the dark matter.


title:
Distinguishing the Littlest Higgs model with T-parity from supersymmetry
  at the LHC using trileptons

abstract:
  We analyse hadronically quiet trilepton signatures in the T-parity conserving
Littlest Higgs model and in R-parity conserving supersymmetry at the Large
Hadron Collider. We identify the regions of the parameter space where such
signals can reveal the presence of these new physics models above the Standard
Model background and distinguish them from each other, even in a situation when
the mass spectrum of the Littlest Higgs model resembles the supersymmetric
pattern.


title:
Uniformly root-$N$ consistent density estimators for weakly dependent
  invertible linear processes

abstract:
  Convergence rates of kernel density estimators for stationary time series are
well studied. For invertible linear processes, we construct a new density
estimator that converges, in the supremum norm, at the better, parametric, rate
$n^{-1/2}$. Our estimator is a convolution of two different residual-based
kernel estimators. We obtain in particular convergence rates for such
residual-based kernel estimators; these results are of independent interest.


title: Global versus Local Aspects of Critical Collapse

abstract:
  This thesis deals with critical collapse of a massless scalar field coupled
to Einstein's equations in spherical symmetry. The system is numerically
investigated from both global and local points of view using a characteristic
slicing and radial compactification. We find that the critical exponent that
characterizes the discretely self-similar solution can be extracted both
locally, in the self-similar region and globally, e.g. from the news function.
In this sense, self-similarity is observable from future null infinity. For
subcritical evolutions we have numerically analyzed the exponents of power-law
tails and have found agreement with analytical calculations for radiation along
null infinity and along timelike lines. We argue that for astrophysical
observers the relevant falloff rate is that of future null infinity. We have
also investigated the behavior of quasinormal modes (QNM) in near-critical
evolutions. Although the perturbation theory underlying QNMs requires a fixed
black hole background, we have found a surprising correlation between the
radiation signal with the period of the first QNM determined by the
time-dependent Bondi mass. In this context, we have also been able to verify a
stationarity criterion based on QNMs for the Vaidya metric, which models the
time-dependent Schwarzschild background.


title:
Consistently Solving the Simplicity Constraints for Spinfoam Quantum
  Gravity

abstract:
  We give an independent derivation of the Engle-Pereira-Rovelli spinfoam model
for quantum gravity which recently appeared in [arXiv:0705.2388]. Using the
coherent state techniques introduced earlier in [arXiv:0705.0674], we show that
the EPR model realizes a consistent imposition of the simplicity constraints
implementing general relativity from a topological BF theory.


title: Non-Minimal Inflation on the Warped DGP Brane

abstract:
  We construct an inflation model with inflaton non-minimally coupled to
gravity on a warped DGP brane. Using an exponential potential, we calculate
scalar power spectrum, spectral index and the running of the spectral index. We
show that for a suitable range of non-minimal coupling it is possible to exit
the inflationary phase spontaneously and without any mechanism, even in the
case that minimal inflation can not exit spontaneously. By a detailed analysis
of parameter space, we study the constraints imposed on the non-minimal
coupling from recent observational data.


title: The Early Years of String Theory: A Personal Perspective

abstract:
  This article surveys some of the highlights in the development of string
theory through the first superstring revolution in 1984. The emphasis is on
topics in which the author was involved, especially the observation that
critical string theories provide consistent quantum theories of gravity and the
proposal to use string theory to construct a unified theory of all fundamental
particles and forces.


title: Quantum state tomography using a single apparatus

abstract:
  The density matrix of a two-level system (spin, atom) is usually determined
by measuring the three non-commuting components of the Pauli vector. This
density matrix can also be obtained via the measurement data of two commuting
variables, using a single apparatus. This is done by coupling the two-level
system to a mode of radiation field, where the atom-field interaction is
described with the Jaynes--Cummings model. The mode starts its evolution from a
known coherent state. The unknown initial state of the atom is found by
measuring two commuting observables: the population difference of the atom and
the photon number of the field. We discuss the advantages of this setup and its
possible applications.


title: Metrics for sparse graphs

abstract:
  Recently, Bollob\'as, Janson and Riordan introduced a very general family of
random graph models, producing inhomogeneous random graphs with $\Theta(n)$
edges. Roughly speaking, there is one model for each {\em kernel}, i.e., each
symmetric measurable function from $[0,1]^2$ to the non-negative reals,
although the details are much more complicated. A different connection between
kernels and random graphs arises in the recent work of Borgs, Chayes, Lov\'asz,
S\'os, Szegedy and Vesztergombi. They introduced several natural metrics on
dense graphs (graphs with $n$ vertices and $\Theta(n^2)$ edges), showed that
these metrics are equivalent, and gave a description of the completion of the
space of all graphs with respect to any of these metrics in terms of {\em
graphons}, which are essentially bounded kernels. One of the most appealing
aspects of this work is the message that sequences of inhomogeneous
quasi-random graphs are in a sense completely general: any sequence of dense
graphs contains such a subsequence.
  Our aim here is to briefly survey these results, and then to investigate to
what extent they can be generalized to graphs with $o(n^2)$ edges. Although
many of the definitions extend in a simple way, the connections between the
various metrics, and between the metrics and random graph models, turn out to
be much more complicated than in the dense case. We shall prove many partial
results, and state even more conjectures and open problems, whose resolution
would greatly enhance the currently rather unsatisfactory theory of metrics on
sparse graphs. This paper deals mainly with graphs with $o(n^2)$ but
$\omega(n)$ edges: a companion paper [arXiv:0812.2656] will discuss the (more
problematic still) case of {\em extremely sparse} graphs, with O(n) edges.


title:
Ultralong-range radiative excitation transfer between quantum dots in a
  planar microcavity

abstract:
  We study the system of two quantum dots lying on the central plane of a
planar semiconductor microcavity. By solving the full Maxwell problem, we
demonstrate that the rate of resonant excitation transfer between the two dots
decays as $d^{-1/2}$ as a function of the distance $d$ at long distance. This
very long-range mechanism is due to the leaky and guided modes of the
microcavity, which act as effective radiative transfer channels. At short
distance, the $d^{-3}$ dependence of the F\"orster mechanism, induced by the
electrostatic dipole-dipole interaction, is recovered.


title: Cartesian Bicategories II

abstract:
  The notion of cartesian bicategory, introduced by Carboni and Walters for
locally ordered bicategories, is extended to general bicategories. It is shown
that a cartesian bicategory is a symmetric monoidal bicategory.


title: Cross Curvature Flow on Locally Homogenous Three-manifolds (I)

abstract:
  Chow and Hamilton introduced the cross curvature flow on closed 3-manifolds
with negative or positive sectional curvature. In this paper, we study the
negative cross curvature flow in the case of locally homogenous metrics on
3-manifolds. In each case, we describe the long time behavior of the solutions
of the corresponding ODE system.


title: Some graph properties determined by edge zeta functions

abstract:
  Stark and Terras introduced the edge zeta function of a finite graph in 1996.
The edge zeta function is the reciprocal of a polynomial in twice as many
variables as edges in the graph and can be computed in polynomial time. We look
at graph properties which we can determine using the edge zeta function. In
particular, the edge zeta function is enough to deduce the clique number, the
number of Hamiltonian cycles, and whether a graph is perfect or chordal.
Actually computing these properties takes exponential time. Finally, we present
a new example illustrating that the Ihara zeta function cannot necessarily do
the same.


title:
The Absolute, Relative and Multi-Wavelength Calibration of the Pierre
  Auger Observatory Fluorescence Detectors

abstract:
  Absolute calibration of the Pierre Auger Observatory fluorescence detectors
uses a 375 nm light source at the telescope aperture. This end-to-end technique
accounts for the combined effects of all detector components in a single
measurement. The relative response has been measured at wavelengths of 320,
337, 355, 380 and 405 nm, defining a spectral response curve which has been
normalized to the absolute calibration. Before and after each night of data
taking a relative calibration of the phototubes is performed. This relative
calibration is used to track both short and long term changes in the detector's
response. A cross check of the calibration in some phototubes is performed
using an independent laser technique. Overall uncertainties, current results
and future plans are discussed.


title: Frobenius Objects in Cartesian Bicategories

abstract:
  Maps (left adjoint arrows) between Frobenius objects in a cartesian
bicategory B are precisely comonoid homomorphisms and, for A Frobenius and any
T in B, map(B)(T,A) is a groupoid.


title: Probing non-Riemannian spacetime geometry

abstract:
  The equations of motion for matter in non-Riemannian spacetimes are derived
via a multipole method. It is found that only test bodies with microstructure
couple to the non-Riemannian spacetime geometry. Consequently it is impossible
to detect spacetime torsion with the satellite experiment Gravity Probe B,
contrary to some recent claims in the literature.


title: Stochastic bounds for two-layer loss systems

abstract:
  This paper studies multiclass loss systems with two layers of servers, where
each server at the first layer is dedicated to a certain customer class, while
the servers at the second layer can handle all customer classes. The routing of
customers follows an overflow scheme, where arriving customers are
preferentially directed to the first layer. Stochastic comparison and coupling
techniques are developed for studying how the system is affected by packing of
customers, altered service rates, and altered server configurations. This
analysis leads to easily computable upper and lower bounds for the performance
of the system.


title: Microtubule dynamics depart from wormlike chain model

abstract:
  Thermal shape fluctuations of grafted microtubules were studied using high
resolution particle tracking of attached fluorescent beads. First mode
relaxation times were extracted from the mean square displacement in the
transverse coordinate. For microtubules shorter than 10 um, the relaxation
times were found to follow an L^2 dependence instead of L^4 as expected from
the standard wormlike chain model. This length dependence is shown to result
from a complex length dependence of the bending stiffness which can be
understood as a result of the molecular architecture of microtubules. For
microtubules shorter than 5 um, high drag coefficients indicate contributions
from internal friction to the fluctuation dynamics.


title: Rank-based estimation for all-pass time series models

abstract:
  An autoregressive-moving average model in which all roots of the
autoregressive polynomial are reciprocals of roots of the moving average
polynomial and vice versa is called an all-pass time series model. All-pass
models are useful for identifying and modeling noncausal and noninvertible
autoregressive-moving average processes. We establish asymptotic normality and
consistency for rank-based estimators of all-pass model parameters. The
estimators are obtained by minimizing the rank-based residual dispersion
function given by Jaeckel [Ann. Math. Statist. 43 (1972) 1449--1458]. These
estimators can have the same asymptotic efficiency as maximum likelihood
estimators and are robust. The behavior of the estimators for finite samples is
studied via simulation and rank estimation is used in the deconvolution of a
simulated water gun seismogram.


title:
A Two-Parameter Family of Infinite-Dimensional Diffusions in the Kingman
  Simplex

abstract:
  The aim of the paper is to introduce a two-parameter family of
infinite-dimensional diffusion processes X(alpha,theta) related to Pitman's
two-parameter Poisson-Dirichlet distributions PD(alpha,theta). The diffusions
X(alpha,theta) are obtained in a scaling limit transition from certain finite
Markov chains on partitions of natural numbers. The state space of
X(alpha,theta) is an infinite-dimensional simplex called the Kingman simplex.
  In the special case when parameter alpha vanishes, our finite Markov chains
are similar to Moran-type model in population genetics, and our diffusion
processes reduce to the infinitely-many-neutral-alleles diffusion model studied
by Ethier and Kurtz (1981).
  Our main results extend those of Ethier and Kurtz to the two-parameter case
and are as follows: The Poisson-Dirichlet distribution PD(alpha,theta) is a
unique stationary distribution for the corresponding process X(alpha,theta);
the process is ergodic and reversible; the spectrum of its generator is
explicitly described. The general two-parameter case seems to fall outside the
setting of models of population genetics, and our approach differs in some
aspects from that of Ethier and Kurtz.
  We also consider the case of degenerate series of parameters alpha and theta
and conclude that the diffusions in finite-dimensional simplexes studied by
Ethier and Kurtz (1981) arise as a special case of our two-parameter family of
diffusions.


title:
Searching for targets on a model DNA: Effects of inter-segment hopping,
  detachment and re-attachment

abstract:
  For most of the important processes in DNA metabolism, a protein has to reach
a specific binding site on the DNA. The specific binding site may consist of
just a few base pairs while the DNA is usually several millions of base pairs
long. How does the protein search for the target site? What is the most
efficient mechanism for a successful search? Motivated by these fundamental
questions on intracellular biological processes, we have developed a model for
searching a specific site on a model DNA by a single protein. We have made a
comparative quantitative study of the efficiencies of sliding, inter-segmental
hoppings and detachment/re-attachments of the particle during its search for
the specific site on the DNA. We also introduce some new quantitative measures
of {\it efficiency} of a search process by defining a relevant quantity, which
can be measured in {\it in-vitro} experiments.


title:
Derivation of the quantum probability law from minimal non-demolition
  measurement

abstract:
  One more derivation of the quantum probability rule is presented in order to
shed more light on the versatile aspects of this fundamental law. It is shown
that the change of state in minimal quantum non-demolition measurement, also
known as ideal measurement, implies the probability law in a simple way.
Namely, the very requirement of minimal change of state, put in proper
mathematical form, gives the well known Lueders formula, which contains the
probability rule.


title: On the well posedness of Robinson Trautman Maxwell solutions

abstract:
  We show that the so called Robinson-Trautman-Maxwell equations do not
constitute a well posed initial value problem. That is, the dependence of the
solution on the initial data is not continuous in any norm built out from the
initial data and a finite number of its derivatives. Thus, they can not be used
to solve for solutions outside the analytic domain.


title:
A fully solvable equilibrium self-assembly process: fine tuning the
  clusters size and the connectivity in patchy particle systems

abstract:
  Self-assembly is the mechanism that controls the formation of well defined
structures from disordered pre-existing parts. Despite the importance of
self-assembly as a manufacturing method and the increasingly large number of
experimental realizations of complex self-assembled nano aggregates,
theoretical predictions are lagging behind. Here we show that for a non-trivial
self-assembly phenomenon, originating branched loop-less clusters, it is
possible to derive a fully predictive parameter-free theory of equilibrium
self-assembly by combining the Wertheim theory for associating liquids with the
Flory-Stockmayer approach for chemical gelation.


title: Testing modified gravity with globular cluster velocity dispersions

abstract:
  Globular clusters (GCs) in the Milky Way have characteristic velocity
dispersions that are consistent with the predictions of Newtonian gravity, and
may be at odds with Modified Newtonian Dynamics (MOND). We discuss a modified
gravity (MOG) theory that successfully predicts galaxy rotation curves, galaxy
cluster masses and velocity dispersions, lensing, and cosmological
observations, yet produces predictions consistent with Newtonian theory for
smaller systems, such as GCs. MOG produces velocity dispersion predictions for
GCs that are independent of the distance from the galactic center, which may
not be the case for MOND. New observations of distant GCs may produce strong
criteria that can be used to distinguish between competing gravitational
theories.


title: Gas phase sorting of nanoparticles

abstract:
  We discuss Stark deflectometry of micro-modulated molecular beams for the
enrichment of biomolecular isomers as well as single-wall carbon nanotubes and
we demonstrate the working principle of this idea with fullerenes. The sorting
is based on the species-dependent polarizability-to-mass ratio $\alpha/m$. The
device is compatible with a high molecular throughput, and the spatial
micro-modulation of the beam permits to obtain a fine spatial resolution and a
high sorting sensitivity.

categories: quant-ph cond-mat.mtrl-sci physics.atm-clus physics.bio-ph physics.chem-ph


title: The asymptotic geometry of right-angled Artin groups, I

abstract:
  We study atomic right-angled Artin groups -- those whose defining graph has
no cycles of length less than five, and no separating vertices, separating
edges, or separating vertex stars. We show that these groups are not
quasi-isometrically rigid, but that an intermediate form of rigidity does hold.
We deduce from this that two atomic groups are quasi-isometric iff they are
isomorphic.


title: Magnetic flows on Sol-manifolds: dynamical and symplectic aspects

abstract:
  We consider magnetic flows on compact quotients of the 3-dimensional solvable
geometry Sol determined by the usual left-invariant metric and the
distinguished monopole. We show that these flows have positive Liouville
entropy and therefore are never completely integrable. This should be compared
with the known fact that the underlying geodesic flow is completely integrable
in spite of having positive topological entropy. We also show that for a large
class of twisted cotangent bundles of solvable manifolds every compact set is
displaceable.


title:
Effect of Charged Scalar Loops on Photonic Decays of a Fermiophobic
  Higgs

abstract:
  Higgs bosons with very suppressed couplings to fermions ("Fermiophobic Higgs
bosons", h_f) can decay to two photons (\gamma\gamma) with a branching ratio
significantly larger than that expected for the Standard Model Higgs boson for
m_{h_f}<150 GeV. Such a particle would give a clear signal at the LHC and can
arise in the Two Higgs Doublet Model (type I) in which h_f -> \gamma\gamma is
mediated by W^+ and charged Higgs boson (H^+) loops. We show that the H^+ loops
can cause both constructive and destructive contributions with a magnitude
considerably larger than the anticipated precision in the measurement of the
photonic decay channel at future hadron and lepton colliders.


title: H\"older forms and integrability of invariant distributions

abstract:
  We prove an inequality for H\"older continuous differential forms on compact
manifolds in which the integral of the form over the boundary of a sufficiently
small, smoothly immersed disk is bounded by a certain multiplicative convex
combination of the volume of the disk and the area of its boundary. This
inequality has natural applications in dynamical systems, where H\"older
continuity is ubiquitous. We give two such applications. In the first one, we
prove a criterion for the existence of global cross sections to Anosov flows in
terms of their expansion-contraction rates. The second application provides an
analogous criterion for non-accessibility of partially hyperbolic
diffeomorphisms.


title:
Predicting Solar Flares by Data Assimilation in Avalanche Models. I.
  Model Design and Validation

abstract:
  Data assimilation techniques, developed in the last two decades mainly for
weather prediction, produce better forecasts by taking advantage of both
theoretical/numerical models and real-time observations. In this paper, we
explore the possibility of applying the data-assimilation techniques known as
4D-VAR to the prediction of solar flares. We do so in the context of a
continuous version of the classical cellular-automaton-based self-organized
critical avalanche models of solar flares introduced by Lu and Hamilton
(Astrophys. J., 380, L89, 1991). Such models, although a priori far removed
from the physics of magnetic reconnection and magneto-hydrodynamical evolution
of coronal structures, nonetheless reproduce quite well the observed
statistical distribution of flare characteristics. We report here on a large
set of data assimilation runs on synthetic energy release time series. Our
results indicate that, despite the unpredictable (and unobservable) stochastic
nature of the driving/triggering mechanism within the avalanche model, 4D-VAR
succeeds in producing optimal initial conditions that reproduce adequately the
time series of energy released by avalanches/flares. This is an essential first
step towards forecasting real flares.


title: Circumstellar Magnetic Field Diagnostics from Line Polarization

abstract:
  Given that dynamically significant magnetic fields in at least some massive
stars have now been measured, our contribution addresses the question, to what
extent can fields be directly detected in circumstellar gas? The question
speaks directly to the very interesting topic of line-driving physics coupled
with magnetized plasmas, and how this coupling produces structure in the wind
flow. We focus our attention on weak-field diagnostics. These come in two main
types: the Hanle effect, which pertains to coherence effects for linear
polarization from line scattering, and the weak longitudinal Zeeman effect,
which pertains to circular polarization in lines.


title: On the Hopf-Schur group of a field

abstract:
  Let k be any field. We consider the Hopf-Schur group of k, defined as the
subgroup of the Brauer group of k consisting of classes that may be represented
by homomorphic images of Hopf algebras over k. We show here that twisted group
algebras and abelian extensions of k are quotients of cocommutative and
commutative Hopf algebras over k, respectively. As a consequence we prove that
any tensor product of cyclic algebras over k is a quotient of a Hopf algebra
over k, revealing so that the Hopf-Schur group can be much larger than the
Schur group of k.


title:
Statics and dynamics of a cylindrical droplet under an external body
  force

abstract:
  We study the rolling and sliding motion of droplets on a corrugated substrate
by Molecular Dynamics simulations. Droplets are driven by an external body
force (gravity) and we investigate the velocity profile and dissipation
mechanisms in the steady state. The cylindrical geometry allows us to consider
a large range of droplet sizes. The velocity of small droplets with a large
contact angle is dominated by the friction at the substrate and the velocity of
the center of mass scales like the square root of the droplet size. For large
droplets or small contact angles, however, viscous dissipation of the flow
inside the volume of the droplet dictates the center of mass velocity that
scales linearly with the size. We derive a simple analytical description
predicting the dependence of the center of mass velocity on droplet size and
the slip length at the substrate. In the limit of vanishing droplet velocity we
quantitatively compare our simulation results to the predictions and good
agreement without adjustable parameters is found.


title: Fossil Groups in the Sloan Digital Sky Survey

abstract:
  A search for fossil groups in the Sloan Digital Sky Survey was performed
using virtual observatory tools. A cross-match of the positions of all SDSS
Luminous Red Galaxies (with r < 19 and measured spectroscopic redshifts) with
sources in the ROSAT All-Sky Survey catalog resulted in a list of elliptical
galaxies with extended X-ray emission (with a galaxy/ROSAT-source distance of
less than 0.5 arcmin in all cases). A search for neighbors of the selected
elliptical galaxies within a radius of $0.5 h_{70}^{-1}$ Mpc was conducted
taking into account the r-band magnitudes and spectroscopic or photometric
redshifts of all objects within this area, leading to a sample of 34 candidate
fossil groups. Considering this sample, the estimated space density of fossil
systems is $n =(1.0 \pm 0.6) \times 10^{-6}$ $h_{50}^3$ Mpc$^{-3}$.


title:
Vector and Axial Nucleon Form Factors:A Duality Constrained
  Parameterization

abstract:
  We present new parameterizations of vector and axial nucleon form factors. We
maintain an excellent descriptions of the form factors at low momentum
transfers, where the spatial structure of the nucleon is important, and use the
Nachtman scaling variable xi to relate elastic and inelastic form factors and
impose quark-hadron duality constraints at high momentum transfers where the
quark structure dominates. We use the new vector form factors to re-extract
updated values of the axial form factor from neutrino experiments on deuterium.
  We obtain an updated world average value from neutrino-d and pion
electroproduction experiments of M_A = 1.014 +- 0.014 GeV/c2. Our
parameterizations are useful in modeling neutrino interactions at low energies
(e.g. for neutrino oscillations experiments). The predictions for high momentum
transfers can be tested in the next generation electron and neutrino scattering
experiments.


title:
Vitaly Ginzburg and High Temperature Superconductivity: Personal
  Reminiscences

abstract:
  I offer some personal reminiscences from the period of 1976-1983, when I was
a M. Sc. and then a Ph.D. student in Vitaly L. Ginzburg's High Temperature
Superconductivity group at the P.N. Lebedev Institute in Moscow


title: Chaoticity Parameter Lambda in Hanbury-Brown Twiss Interferometry

abstract:
  In Hanbury-Brown-Twiss interferometry measurements using identical bosons,
the chaoticity parameter lambda has been introduced phenomenologically to
represent the momentum correlation function at zero relative momentum. It is
useful to study an exactly solvable problem in which the lambda parameter and
its dependence on the coherence properties of the boson system can be worked
out in great detail. We are therefore motivated to study the state of a gas of
noninteracting identical bosons at various temperatures held together in a
harmonic oscillator potential that arises either externally or from bosons' own
mean fields. We determine the degree of Bose-Einstein condensation and its
momentum correlation function as a function of the attributes of the boson
environment. The parameter lambda can then be evaluated from the momentum
correlation function. We find that the lambda(p,T) parameter is a sensitive
function of both the average pair momentum p and the temperature T, and the
occurrence of lambda=1 is not a consistent measure of the absence of a coherent
condensate fraction. In particular, for large values of p, the lambda parameter
attains the value of unity even for significantly coherent systems with large
condensate fractions. We find that if a pion system maintains a static
equilibrium within its mean field, and if it contains a root-mean-squared
radius, a pion number, and a temperature typical of those in high-energy
heavy-ion collisions, then it will contain a large fraction of the
Bose-Einstein pion condensate.


title:
Cold Dark Matter Substructure and Galactic Disks I: Morphological
  Signatures of Hierarchical Satellite Accretion

abstract:
  (Abridged) We conduct a series of high-resolution, dissipationless N-body
simulations to investigate the cumulative effect of substructure mergers onto
thin disk galaxies in the context of the LCDM paradigm of structure formation.
Our simulation campaign is based on a hybrid approach. Substructure properties
are culled directly from cosmological simulations of galaxy-sized cold dark
matter (CDM) halos. In contrast to what can be inferred from statistics of the
present-day substructure populations, accretions of massive subhalos onto the
central regions of host halos, where the galactic disk resides, since z~1
should be common occurrences. One host halo merger history is subsequently used
to seed controlled numerical experiments of repeated satellite impacts on an
initially-thin Milky Way-type disk galaxy. We show that these accretion events
produce several distinctive observational signatures in the stellar disk
including: a ring-like feature in the outskirts; a significant flare; a central
bar; and faint filamentary structures that (spuriously) resemble tidal streams.
The final distribution of disk stars exhibits a complex vertical structure that
is well-described by a standard ``thin-thick'' disk decomposition. We conclude
that satellite-disk encounters of the kind expected in LCDM models can induce
morphological features in galactic disks that are similar to those being
discovered in the Milky Way, M31, and in other disk galaxies. These results
highlight the significant role of CDM substructure in setting the structure of
disk galaxies and driving galaxy evolution. Upcoming galactic structure surveys
and astrometric satellites may be able to distinguish between competing
cosmological models by testing whether the detailed structure of galactic disks
is as excited as predicted by the CDM paradigm.


title: Kondo effect in an Antiferromagnetic metal

abstract:
  We study the fate of a spin-1/2 impurity in the itinerant antiferromagnetic
metallic phase via a renormalization group analysis and a variational
calculation. The local moment - conduction electron interaction hamiltonian in
an antiferromagnetic metal is spin non-conserving. We show that for a general
location of the impurity, the Kondo singularities still occur, but the ground
state has a partially unscreened moment. We calculate the magnitude of this
residual moment and the variation of the spin polarization with energy for a
substitutional impurity as a function of the staggered magnetization. The usual
Kondo effect only occurs if the impurity is placed at points where the
magnetization is zero.


title: On bilinear biquandles

abstract:
  We define a type of biquandle which is a generalization of symplectic
quandles. We use the extra structure of these bilinear biquandles to define new
knot and link invariants and give some examples.


title: Spontaneous Breaking of Space-Time Symmetries

abstract:
  Kinematical and dynamical mechanisms leading to the spontaneous breaking of
space-time symmetries are described. The symmetries affected are space and time
translations, space rotations, scale and conformal transformations.
Applications are made to solidification, string theory compactifications, the
analysis of stable theories with no ground states, supersymmetry breaking and
the determination of the value of the vacuum energy.


title: Linear Quantum Error Correction

abstract:
  We develop a generalized theory of quantum error correction (QEC) that
applies to any linear map, in particular maps that are not completely positive
(CP). This theory describes entanglement-assisted QEC for invertible noise
maps, which we use to provides an example of the physical implementation of
non-CP recovery maps. We argue that a consistent map-based theory of
fault-tolerant QEC (whether Markovian or not) requires linear, non-CP maps, and
that this impacts the value of the fault-tolerance threshold.


title: Why Do Only Some Galaxy Clusters Have Cool Cores?

abstract:
  Flux-limited X-ray samples indicate that about half of rich galaxy clusters
have cool cores. Why do only some clusters have cool cores while others do not?
In this paper, cosmological N-body + Eulerian hydrodynamic simulations,
including radiative cooling and heating, are used to address this question as
we examine the formation and evolution of cool core (CC) and non-cool core
(NCC) clusters. These adaptive mesh refinement simulations produce both CC and
NCC clusters in the same volume. They have a peak resolution of 15.6 h^{-1} kpc
within a (256 h^{-1} Mpc)^3 box. Our simulations suggest that there are
important evolutionary differences between CC clusters and their NCC
counterparts. Many of the numerical CC clusters accreted mass more slowly over
time and grew enhanced cool cores via hierarchical mergers; when late major
mergers occurred, the CC's survived the collisions. By contrast, NCC clusters
experienced major mergers early in their evolution that destroyed embryonic
cool cores and produced conditions that prevented CC re-formation. As a result,
our simulations predict observationally testable distinctions in the properties
of CC and NCC beyond the core regions in clusters. In particular, we find
differences between CC versus NCC clusters in the shapes of X-ray surface
brightness profiles, between the temperatures and hardness ratios beyond the
cores, between the distribution of masses, and between their supercluster
environs. It also appears that CC clusters are no closer to hydrostatic
equilibrium than NCC clusters, an issue important for precision cosmology
measurements.


title:
Cofinement, entropy, and single-particle dynamics of equilibrium
  hard-sphere mixtures

abstract:
  We use discontinuous molecular dynamics and grand-canonical transition-matrix
Monte Carlo simulations to explore how confinement between parallel hard walls
modifies the relationships between packing fraction, self-diffusivity, partial
molar excess entropy, and total excess entropy for binary hard-sphere mixtures.
To accomplish this, we introduce an efficient algorithm to calculate partial
molar excess entropies from the transition-matrix Monte Carlo simulation data.
We find that the species-dependent self-diffusivities of confined fluids are
very similar to those of the bulk mixture if compared at the same,
appropriately defined, packing fraction up to intermediate values, but then
deviate negatively from the bulk behavior at higher packing fractions. On the
other hand, the relationships between self-diffusivity and partial molar excess
entropy (or total excess entropy) observed in the bulk fluid are preserved
under confinement even at relatively high packing fractions and for different
mixture compositions. This suggests that the partial molar excess entropy,
calculable from classical density functional theories of inhomogeneous fluids,
can be used to predict some of the nontrivial dynamical behaviors of fluid
mixtures in confined environments.


title:
Transforming squeezed light into a large amplitude coherent state
  superposition

abstract:
  A quantum superposition of two coherent states of light with small amplitude
can be obtained by subtracting a photon from a squeezed vacuum state. In
experiments this preparation can be made conditioned on the detection of a
photon in the field from a squeezed light source. We propose and analyze an
extended measurement strategy which allows generation of high fidelity coherent
state superpositions with larger amplitude.


title: Spin torque contribution to the a.c. spin Hall conductivity

abstract:
  Using the recently proposed definition of a conserved spin-current operator
[J. Shi et al., Phys. Rev. Lett. 96, 076604 (2006)] we explore the frequency
dependent spin Hall conductivity for a two-dimensional electron gas with Rashba
and Dresselhaus spin-orbit interaction in response to an oscillating electric
field. We show that the optical spectrum of the spin Hall conductivity exhibit
remarkable changes when the new definition of spin current is applied. Such
behavior is mainly due to a significant contribution of the spin torque term
which is absent in the conventional form of the spin current. In addition, it
is observed that the magnitude and direction of the dynamic spin Hall current
strongly depends on the electric field frequency as with the interplay of the
spin-orbit coupling strengths.


title: Charge, geometry, and effective mass

abstract:
  Charge, like mass in Newtonian mechanics, is an irreducible element of
electromagnetic theory that must be introduced ab initio. Its origin is not
properly a part of the theory. Fields are then defined in terms of forces on
either masses--in the case of Newtonian mechanics, or charges in the case of
electromagnetism. General Relativity changed our way of thinking about the
gravitational field by replacing the concept of a force field with the
curvature of space-time. Mass, however, remained an irreducible element. It is
shown here that the Reissner-Nordstrom solution to the Einstein field equations
tells us that charge, like mass, has a unique space-time signature.


title: The zero-energy state in graphene in a high magnetic field

abstract:
  The fate of the charge-neutral Dirac point in graphene in a high magnetic
field $H$ has been investigated at low temperatures ($T\sim$ 0.3 K). In samples
with small $V_0$ (the gate voltage needed to access the Dirac point), the
resistance $R_0$ at the Dirac point diverges steeply with $H$, signalling a
crossover to an insulating state in intense field. The approach to the
insulating state is highly unusual. Despite the steep divergence in $R_0$, the
profile of $R_0$ vs. $T$ in fixed $H$ saturates to a $T$-independent value
below 2 K, consistent with charge carrying gapless excitations.


title: Ultra-high energy neutrino scattering

abstract:
  Estimates are made of the ultra-high energy neutrino cross sections based on
an extrapolation to very small Bjorken x of the logarithmic Froissart
dependence in x shown previously to provide an excellent fit to the measured
proton structure function F_2^p(x,Q^2) over a broad range of the virtuality
Q^2. Expressions are obtained for both the neutral current and the charged
current cross sections. Comparison with an extrapolation based on perturbative
QCD shows good agreement for energies where both fit data, but our rates are as
much as a factor of 10 smaller for neutrino energies above 10^9 GeV, with
important implications for experiments searching for extra-galactic neutrinos.


title:
The jamming transition and new percolation universality classes in
  particulate systems with attraction

abstract:
  We numerically study the jamming transition in particulate systems with
attraction by investigating their mechanical response at zero temperature. We
find three regimes of mechanical behavior separated by two critical
transitions--connectivity and rigidity percolation. The transitions belong to
different universality classes than their lattice counterparts, due to force
balance constraints. We also find that these transitions are unchanged at low
temperatures and resemble gelation transitions in experiments on colloidal and
silica gels.


title: Exact Cover with light

abstract:
  We suggest a new optical solution for solving the YES/NO version of the Exact
Cover problem by using the massive parallelism of light. The idea is to build
an optical device which can generate all possible solutions of the problem and
then to pick the correct one. In our case the device has a graph-like
representation and the light is traversing it by following the routes given by
the connections between nodes. The nodes are connected by arcs in a special way
which lets us to generate all possible covers (exact or not) of the given set.
For selecting the correct solution we assign to each item, from the set to be
covered, a special integer number. These numbers will actually represent delays
induced to light when it passes through arcs. The solution is represented as a
subray arriving at a certain moment in the destination node. This will tell us
if an exact cover does exist or not.


title:
Origin of the Non-Linear Pressure Effects in Perovskite Manganites:
  Buckling of Mn-O-Mn Bonds and Jahn-Teller Distortion of the MnO6 Octahedra
  Induced by Pressure

abstract:
  High-pressure resistivity and x-ray diffraction have been measured on
La0.85MnO3-d. At low pressures the metal-insulator transition temperature (TMI)
increases linearly with pressure up to a critical pressure, P* ~ 3.4 GPa, which
is followed by reduction of TMI with increasing pressure. Analysis of the bond
distances and bond angles reveal that a bandwidth increase drives the in-crease
of TMI for pressure below P*. The reduction of TMI at higher pressures is found
to result from Jahn-Teller distortions of the MnO6 octahedra. The role of
anharmonic interatomic potential is discussed.


title: Solving the subset-sum problem with a light-based device

abstract:
  We propose a special computational device which uses light rays for solving
the subset-sum problem. The device has a graph-like representation and the
light is traversing it by following the routes given by the connections between
nodes. The nodes are connected by arcs in a special way which lets us to
generate all possible subsets of the given set. To each arc we assign either a
number from the given set or a predefined constant. When the light is passing
through an arc it is delayed by the amount of time indicated by the number
placed in that arc. At the destination node we will check if there is a ray
whose total delay is equal to the target value of the subset sum problem (plus
some constants).


title: Tail Asymptotics and Estimation for Elliptical Distributions

abstract:
  Let (X,Y) be a bivariate elliptical random vector with associated random
radius in the Gumbel max-domain of attraction. In this paper we obtain a second
order asymptotic expansion of the joint survival probability P(X > x, Y> y) for
x,y large. Further, based on the asymptotic bounds we discuss some aspects of
the statistical modelling of joint survival probabilities and the survival
conditional excess probability.


title:
Incompatibility of modulated checkerboard patterns with the neutron
  scattering resonance peak in cuprate superconductors

abstract:
  Checkerboard patterns have been proposed in order to explain STM experiments
on the cuprates BSCCO and Na-CCOC. However the presence of these patterns has
not been confirmed by a bulk probe such as neutron scattering. In particular,
simple checkerboard patterns are inconsistent with neutron scattering data, in
that they have low energy incommsensurate (IC) spin peaks rotated 45 degrees
from the direction of the charge IC peaks. However, it is unclear whether other
checkerboard patterns can solve the problem. In this paper, we have studied
more complicated checkerboard patterns ("modulated checkerboards") by using
spin wave theory and analyzed noncollinear checkerboards as well. We find that
the high energy response of the modulated checkerboards is inconsistent with
neutron scattering results, since they fail to exhibit a resonance peak at
(pi,pi), which has recently been shown to be a universal feature of cuprate
superconductors. We further argue that the newly proposed noncollinear
checkerboard also lacks a resonance peak. We thus conclude that to date no
checkerboard pattern has been proposed which satisfies both the low energy
constraints and the high energy constraints imposed by the current body of
experimental data in cuprate superconductors.


title: Solar System Constraints on Gauss-Bonnet Dark Energy

abstract:
  Quadratic curvature Gauss-Bonnet gravity may be the solution to the dark
energy problem, but a large coupling strength is required. This can lead to
conflict with laboratory and planetary tests of Newton's law, as well as light
bending. The corresponding constraints are derived. If applied directly to
cosmological scales, the resulting bound on the density fraction is |Omega_GB|
< 3.6 x 10^-32.


title: Some quasinilpotent generators of the hyperfinite $\mathrm{II}_1$ factor

abstract:
  For each sequence $\{c_n\}_n$ in $l_{1}(\N)$ we define an operator $A$ in the
hyperfinite $\mathrm{II}_1$-factor $\mathcal{R}$. We prove that these operators
are quasinilpotent and they generate the whole hyperfinite
$\mathrm{II}_1$-factor. We show that they have non-trivial, closed, invariant
subspaces affiliated to the von Neumann algebra and we provide enough evidence
to suggest that these operators are interesting for the hyperinvariant subspace
problem. We also present some of their properties. In particular, we show that
the real and imaginary part of $A$ are equally distributed, and we find a
combinatorial formula as well as an analytical way to compute their moments. We
present a combinatorial way of computing the moments of $A^{*}A$.


title: Linear Algebraic Groups without the Normalizer Theorem

abstract:
  One can develop the basic structure theory of linear algebraic groups (the
root system, Bruhat decomposition, etc.) in a way that bypasses several major
steps in the standard development, including the self-normalizing property of
Borel subgroups.


title: Pair creation supernovae at low and high redshift

abstract:
  Pair creation supernovae (PCSN) are thought to be produced from very massive
low metallicity stars. The spectacularly bright SN 2006gy does show signatures
expected from PCSNe. Here, we investigate the metallicity threshold below which
PCSN can form and estimate their occurrence rate. We perform stellar evolution
calculations for stars of 150$\mso$ and 250$\mso$ of low metallicity
(Z$_{\odot}$/5 and Z$_{\odot}$/20), and analyze their mass loss rates. We find
that the bifurcation between quasi-chemically homogeneous evolution for fast
rotation and conventional evolution for slower rotation, which has been found
earlier for massive low metallicity stars, persists in the mass range
considered here. Consequently, there are two separate PCSN progenitor types:
(I) Fast rotators produce PCSNe from very massive Wolf-Rayet stars, and (II)
Slower rotators that generate PCSNe in hydrogen-rich massive yellow
hypergiants. We find that hydrogen-rich PCSNe could occur at metallicities as
high as Z$_{\odot}$/3, which -- assuming standard IMFs are still valid to
estimate their birth rates -- results in a rate of about one PCSN per 1000
supernovae in the local universe, and one PCSN per 100 supernovae at a redshift
of $z=5$. PCSNe from WC-type Wolf-Rayet stars are restricted to much lower
metallicity.


title:
Nimesulide limits kainate-induced oxidative damage in the rat
  hippocampus

abstract:
  Kainate induces a marked expression of cyclooxygenase-2 after its systemic
administration. Because cyclooxygenase-2 activity is associated to the
production of reactive oxygen species, we investigated the effects of
nimesulide, a selective cyclooxygenase-2 inhibitor, on kainate-induced in vivo
oxidative damage in the rat hippocampus. A clinically relevant dose of
nimesulide (6 mg/kg, i.p.) was administered three times following kainate
application (9 mg/kg, i.p.). After 24 h of kainate administration, the drastic
decrease in hippocampal glutathione content and the significant increase in
lipid peroxidation were attenuated in nimesulide-treated rats, suggesting that
the induction of cyclooxygenase-2 is involved in kainate-mediated free radicals
formation.


title: The Qweak Experiment -- A search for new physics at the TeV Scale

abstract:
  A new precision measurement of the parity violating analyzing power in
longitudinally polarized electron scattering from the proton at very low Q^2 at
an incident energy of 1.16 GeV is in the final stages of preparation for
execution at Jefferson Laboratory (JLab). A 2200 hour measurement of the parity
violating asymmetry in elastic electron-proton scattering at Q^2 = 0.03
(GeV/c)^2 employing 180 microamp of 85% polarized beam on a 0.35 m long liquid
hydrogen target will determine the weak charge of the proton, Q_w = 1 -
4sin^2(theta_W), with 4% combined statistical and systematic errors. The
Standard Model makes a firm prediction of Q_w, based on the `running' of the
weak mixing angle sin^2(theta_W) from the Z-pole down to lower energies. Any
significant deviation of sin^2(theta_W) from its Standard Model prediction at
low Q^2 would constitute a signal of new physics. In the absence of new
physics, the envisaged experiment will provide a 0.3% determination of
sin^2(theta_W), making this a very competitive measurement of the weak mixing
angle. Complementary to the present experiment is a measurement of the weak
charge of the electron in parity violating Moller scattering at 11 GeV,
currently under consideration, with the upgraded CEBAF at JLab. The objective
of that experiment would be a measurement of sin2(theta_W) with a precision
comparable to or better than any individual measurement at the Z-pole.


title: Strong violations of Bell-type inequalities for Werner-like states

abstract:
  We investigate the violation of Bell-type inequalities for two-qubit
Werner-like states parametrized by the positive parameter 0<p<1. We use an
unbalanced homodyne detection scheme to obtain the quantum mechanical
probabilities. A violation of the Bell-Wigner and Janssens inequalities is
obtained for a large range of the parameter p. The range given by these
inequalities is greater than the one given by the Clauser-Horne inequality. The
range in which a violation is attained actually coincides with the range where
the Werner-like states are known to be nonseparabel, i.e., for p>1/3. However,
the improvement over the Clauser-Horne inequality is achieved at the price of
restricting the class of possible local hidden variable theories.


title: Isotopic composition of cosmic-ray sources

abstract:
  We use the GALPROP code and the Advanced Composition Explorer (ACE) data to
derive the cosmic ray (CR) isotopic composition at the sources. The composition
is derived for two propagation models, diffusive reacceleration and plain
diffusion. We show that the compositions derived assuming these two propagation
models are different. We also compare the isotopic composition at the sources
with the latest solar composition.


title:
Spin relaxation in $n$-type GaAs quantum wells with transient spin
  grating

abstract:
  By solving the kinetic spin Bloch equations, we study the time evolution of
the transient spin grating, whose spin polarization varies periodically in real
space, confined in (001) GaAs quantum wells. With this study we can investigate
the properties of both the spin transport and the spin relaxation at the same
time. The Fourier component of the spin signal decays double exponentially with
two decay rates $1/\tau_+$ and $1/\tau_-$. In high temperature regime, the
average of these two rates varies with the grating wave-vector $q$
quadratically, i.e., $(1/\tau_++1/\tau_-)/2=D_sq^2+1/\tilde{\tau}_s$, with
$D_s$ and $\tilde{\tau}_s$ representing the spin diffusion coefficient and the
average of the out-of-plane and the in-plane spin relaxation times
respectively. $\tau_{\pm}$ calculated from our theory are in good agreement
with the experimental data by Weber {\em et al.} [Phys. Rev. Lett. {\bf 98},
076604 (2007)]. By comparing $D_s$ with and without the electron-electron
Coulomb scattering, we calculate the contribution of Coulomb drag to the spin
diffusion coefficient. With the transient spin grating result, we further
reveal the relations among different characteristic parameters such as spin
diffusion coefficient $D_s$, spin relaxation time $\tau_s$, and spin injection
length $L_s$. We show that in the presence of the Dresselhaus and/or Rashba
spin-orbit coupling, the widely used relation $L_s=\sqrt{D_s\tau_s}$ is
generally inaccurate and can even be very wrong in some special cases. We
present an accurate way to extract the steady-state transport characteristic
parameters from the transient spin grating signals.