title:
Probing the quantum coherence of a nanomechanical resonator using a
  superconducting qubit II: Implementation

abstract:
  We describe a possible implementation of the nanomechanical quantum
superposition generation and detection scheme described in the preceding,
companion paper [Armour A D and Blencowe M P 2008 New. J. Phys. Submitted]. The
implementation is based on the circuit quantum electrodynamics (QED) set-up,
with the addition of a mechanical degree of freedom formed out of a suspended,
doubly-clamped segment of the superconducting loop of a dc SQUID located
directly opposite the centre conductor of a coplanar waveguide (CPW). The
relative merits of two SQUID based qubit realizations are addressed, in
particular a capacitively coupled charge qubit and inductively coupled flux
qubit. It is found that both realizations are equally promising, with
comparable qubit-mechanical resonator mode as well as qubit-microwave resonator
mode coupling strengths.


title: Two-photon decay of pseudoscalar quarkonia

abstract:
  We report on our recent evaluation of the two-photon width of the
pseudoscalar quarkonia, eta_c(nS) and eta_b(nS) in an approach based on
Heavy-Quark Spin Symmetry (HQSS). To what concerns the 1S state eta_c, our
parameter-free computation agrees with experiments, as well as most of other
theoretical works. On the other hand, our computation for the 2S-state looks 2S
like a confirmation that there may exist an anomaly related to the decay of
eta_c(2S), especially in the light of the new preliminary result of the Belle
collaboration. We also point out that the essentially model-independent ratio
of eta_b two-photon width to the Upsilon leptonic width and the eta_b
two-photon width could be used to extract the strong coupling constant alpha_s.


title:
Products of Ordinary Differential Operators by Evaluation and
  Interpolation

abstract:
  It is known that multiplication of linear differential operators over ground
fields of characteristic zero can be reduced to a constant number of matrix
products. We give a new algorithm by evaluation and interpolation which is
faster than the previously-known one by a constant factor, and prove that in
characteristic zero, multiplication of differential operators and of matrices
are computationally equivalent problems. In positive characteristic, we show
that differential operators can be multiplied in nearly optimal time.
Theoretical results are validated by intensive experiments.


title: Relative entropy and the Bekenstein bound

abstract:
  Elaborating on a previous work by Marolf et al, we relate some exact results
in quantum field theory and statistical mechanics to the Bekenstein universal
bound on entropy. Specifically, we consider the relative entropy between the
vacuum and another state, both reduced to a local region. We propose that, with
the adequate interpretation, the positivity of the relative entropy in this
case constitutes a well defined statement of the bound in flat space. We show
that this version arises naturally from the original derivation of the bound
from the generalized second law when quantum effects are taken into account. In
this formulation the bound holds automatically, and in particular it does not
suffer from the proliferation of the species problem. The results suggest that
while the bound is relevant at the classical level, it does not introduce new
physical constraints semiclassically.


title: The Dichotomy of the Halo of the Milky Way

abstract:
  We summarize evidence that the halo of the Milky Way comprises two different,
and broadly overlapping, stellar components. The two structures exhibit
different chemical compositions, spatial distributions, and kinematics. These
results were obtained through an analysis of more than 20,000 calibration stars
from the Sloan Digital Sky Survey (SDSS). The duality of the stellar halo
directly impacts galaxy formation models, for the Milky Way and other large
spirals.


title:
Young stars and brown dwarfs surrounding Alnilam (eps Ori) and Mintaka
  (del Ori)

abstract:
  Aims: We look for new regions for the search of substellar objects. Methods:
Two circular areas, 45 arcmin-radius each, centred on the young massive star
systems Alnilam and Mintaka in the Orion Belt, have been explored. The regions
are very young (less than 10 Ma), have low extinction, and are neighbours to
sigma Orionis (~3 Ma), a young open cluster very rich in brown dwarfs and
planetary-mass objects. We have used Virtual Observatory tools, the
astro-photometric Tycho-2, DENIS and 2MASS catalogues, 10 control fields at
similar galactic latitudes, and X-ray, mid-infrared and spectroscopic data from
the literature. Results: We have compiled exhaustive lists of known young stars
and new candidate members in the Ori OB1b association, and of fore- and
background sources. A total of 136 stars display features of extreme youth,
like early spectral types, lithium in absorption, or mid-infrared flux excess.
Other two young brown dwarf and 289 star candidates have been identified from
an optical/near-infrared colour-magnitude diagram. We list additional 74 known
objects that might belong to the association. This catalogue can serve as an
input for characterisation of the stellar and high-mass substellar populations
in the Orion Belt. Finally, we have investigated the surface densities and
radial distributions of young objects surrounding Alnilam and Mintaka, and
compared them with those in the sigma Orionis cluster. We report a new open
cluster centred on Mintaka. Conclusions: Both regions can be analogs to the
sigma Orionis cluster, but more massive, more extended, slightly older, and
less radially concentrated.


title: Measuring the top quark mass with m_T2 at the LHC

abstract:
  We investigate the possibility to measure the top quark mass using the
collider variable $m_{T2}$ at the LHC experiment. Monte Carlo studies of
$m_{T2}$ are performed with the events corresponding to the dilepton decays of
$t\bar{t}$ produced at the LHC with 10 $fb^{-1}$ integrated luminosity. Our
analysis suggests that the top quark mass can be determined by the $m_{T2}$
variable alone with a good precision at the level of 1 GeV.


title: Matrix Theory of Type IIB Plane Wave from Membranes

abstract:
  We write down a maximally supersymmetric one parameter deformation of the
field theory action of Bagger and Lambert. We show that this theory on RxT^2 is
invariant under the superalgebra of the maximally supersymmetric Type IIB plane
wave. It is argued that this theory holographically describes the Type IIB
plane wave in the discrete light-cone quantization (DLCQ).


title: On Periodic solutions for a reduction of Benney chain

abstract:
  We study periodic solutions for a quasi-linear system, which is the so called
dispersionless Lax reduction of the Benney moments chain. This question
naturally arises in search of integrable Hamiltonian systems of the form $
H=p^2/2+u(q,t) $ Our main result classifies completely periodic solutions for 3
by 3 system. We prove that the only periodic solutions have the form of
traveling waves, so in particular, the potential $u$ is a function of a linear
combination of $t$ and $q$. This result implies that the there are no
nontrivial cases of existence of the fourth power integral of motion for $H$:
if it exists, then it is equal necessarily to the square of the quadratic one.
Our method uses two new general observations. The first is the genuine
non-linearity of the maximal and minimal eigenvalues for the system. The second
observation uses the compatibility conditions of Gibonns-Tsarev in order to
give certain exactness for the system in Riemann invariants. This exactness
opens a possibility to apply the Lax analysis of blow up of smooth solutions,
which usually does not work for systems of higher order.


title: Magnetic breakdown induced Peierls transition

abstract:
  We predict the new type of phase transition in quasi one-dimensional system
of interacting electrons at high magnetic fields, the stabilization of a
density wave which transforms a two dimensional open Fermi surface into a
periodic chain of large pockets with small distances between them. We show that
quantum tunneling of electrons between the neighboring closed orbits enveloping
these pockets transforms the electron spectrum into a set of extremely narrow
energy bands and gaps that decreases the total electron energy, thus leading to
a \emph{magnetic breakdown induced density wave} ground state analogous to the
well-known instability of Peierls type.


title:
Impact of Spatial Correlation on the Finite-SNR Diversity-Multiplexing
  Tradeoff

abstract:
  The impact of spatial correlation on the performance limits of multielement
antenna (MEA) channels is analyzed in terms of the diversity-multiplexing
tradeoff (DMT) at finite signal-to-noise ratio (SNR) values. A lower bound on
the outage probability is first derived. Using this bound accurate finite-SNR
estimate of the DMT is then derived. This estimate allows to gain insight on
the impact of spatial correlation on the DMT at finite SNR. As expected, the
DMT is severely degraded as the spatial correlation increases. Moreover, using
asymptotic analysis, we show that our framework encompasses well-known results
concerning the asymptotic behavior of the DMT.


title: Noncanonical number systems in the integers

abstract:
  The well known binary and decimal representations of the integers, and other
similar number systems, admit many generalisations. Here, we investigate
whether still every integer could have a finite expansion on a given integer
base b, when we choose a digit set that does not contain 0. We prove that such
digit sets exist and we provide infinitely many examples for every base b with
|b|\ge 4, and for b=-2. For the special case b=-2, we give a full
characterisation of all valid digit sets.


title:
Push & Pull: autonomous deployment of mobile sensors for a complete
  coverage

abstract:
  Mobile sensor networks are important for several strategic applications
devoted to monitoring critical areas. In such hostile scenarios, sensors cannot
be deployed manually and are either sent from a safe location or dropped from
an aircraft. Mobile devices permit a dynamic deployment reconfiguration that
improves the coverage in terms of completeness and uniformity.
  In this paper we propose a distributed algorithm for the autonomous
deployment of mobile sensors called Push&Pull. According to our proposal,
movement decisions are made by each sensor on the basis of locally available
information and do not require any prior knowledge of the operating conditions
or any manual tuning of key parameters.
  We formally prove that, when a sufficient number of sensors are available,
our approach guarantees a complete and uniform coverage. Furthermore, we
demonstrate that the algorithm execution always terminates preventing movement
oscillations.
  Numerous simulations show that our algorithm reaches a complete coverage
within reasonable time with moderate energy consumption, even when the target
area has irregular shapes. Performance comparisons between Push&Pull and one of
the most acknowledged algorithms show how the former one can efficiently reach
a more uniform and complete coverage under a wide range of working scenarios.


title: Spectroscopic Signatures of Massless Gap Opening in Graphene

abstract:
  Gap opening in graphene is usually discussed in terms of a
semiconducting-like spectrum, where the appearance of a finite gap at the Dirac
point is accompanied by a finite mass for the fermions. In this Letter we
propose a gap scenario from graphene which preserves the massless characters of
the carriers. This approach explains recent spectroscopic measurements carried
out in epitaxially-grown graphene, ranging from photoemission to optical
transmission.


title:
Mutually unbiased bases, orthogonal Latin squares, and hidden-variable
  models

abstract:
  Mutually unbiased bases encapsulate the concept of complementarity - the
impossibility of simultaneous knowledge of certain observables - in the
formalism of quantum theory. Although this concept is at the heart of quantum
mechanics, the number of these bases is unknown except for systems of dimension
being a power of a prime. We develop the relation between this physical problem
and the mathematical problem of finding the number of mutually orthogonal Latin
squares. We derive in a simple way all known results about the unbiased bases,
find their lower number, and disprove the existence of certain forms of the
bases in dimensions different than power of a prime. Using the Latin squares,
we construct hidden-variable models which efficiently simulate results of
complementary quantum measurements.


title:
Probing the quantum coherence of a nanomechanical resonator using a
  superconducting qubit: I. Echo scheme

abstract:
  We propose a scheme in which the quantum coherence of a nanomechanical
resonator can be probed using a superconducting qubit. We consider a mechanical
resonator coupled capacitively to a Cooper-pair box and assume that the
superconducting qubit is tuned to the degeneracy point so that its coherence
time is maximised and the electro-mechanical coupling can be approximated by a
dispersive Hamiltonian. When the qubit is prepared in a superposition of states
this drives the mechanical resonator progressively into a superposition which
in turn leads to apparent decoherence of the qubit. Applying a suitable control
pulse to the qubit allows its population to be inverted resulting in a reversal
of the resonator dynamics. However, the resonator's interactions with its
environment mean that the dynamics is not completely reversible. We show that
this irreversibility is largely due to the decoherence of the mechanical
resonator and can be inferred from appropriate measurements on the qubit alone.
Using estimates for the parameters involved based on a specific realization of
the system we show that it should be possible to carry out this scheme with
existing device technology.


title:
Near-Maximal Mixing of Scalar Gluonium and Quark Mesons: A Gaussian
  Sum-Rule Analysis

abstract:
  Gaussian QCD sum-rules are ideally suited to the study of mixed states of
gluonium (glueballs) and quark ($q\bar q$) mesons because of their capability
to resolve widely-separated states of comparable strength. The analysis of the
Gaussian QCD sum-rules (GSRs) for all possible two-point correlation functions
of gluonic and non-strange ($I=0$) quark scalar ($J^{PC}=0^{++}$) currents is
discussed. For the non-diagonal sum-rule of gluonic and $q\bar q$ currents we
show that perturbative and gluon condensate contributions are chirally
suppressed compared to non-perturbative effects of the quark condensate, mixed
condensate, and instantons, implying that the mixing of quark mesons and
gluonium is of non-perturbative origin. The independent predictions of the
masses and relative coupling strengths from the non-diagonal and the two
diagonal GSRs are remarkably consistent with a scenario of two states with
masses of approximately 1 GeV and 1.4 GeV that couple to significant mixtures
of quark and gluonic currents. The mixing is nearly maximal with the heavier
mixed state having a slightly larger coupling to gluonic currents than the
lighter state.


title: Effective metrics in the non-minimal Einstein-Yang-Mills-Higgs theory

abstract:
  We formulate a self-consistent non-minimal five-parameter
Einstein-Yang-Mills-Higgs (EYMH) model and analyse it in terms of effective
(associated, color and color-acoustic) metrics. We use a formalism of
constitutive tensors in order to reformulate master equations for the gauge,
scalar and gravitational fields and reconstruct in the algebraic manner the
so-called associated metrics for the Yang-Mills field. Using WKB-approximation
we find color metrics for the Yang-Mills field and color-acoustic metric for
the Higgs field in the framework of five-parameter EYMH model. Based on
explicit representation of these effective metrics for the EYMH system with
uniaxial symmetry, we consider cosmological applications for Bianchi-I, FLRW
and de Sitter models. We focus on the analysis of the obtained expressions for
velocities of propagation of longitudinal and transversal color and
color-acoustic waves in a (quasi)vacuum interacting with curvature; we show
that curvature coupling results in time variations of these velocities. We
show, that the effective metrics can be regular or can possess singularities
depending on the choice of the parameters of non-minimal coupling in the
cosmological models under discussion. We consider a physical interpretation of
such singularities in terms of phase velocities of color and color-acoustic
waves, using the terms ``wave stopping'' and ``trapped surface''.


title: Parapuzzle of the Multibrot set and typical dynamics of unimodal maps

abstract:
  We study the parameter space of unicritical polynomials $f_c:z\mapsto z^d+c$.
For complex parameters, we prove that for Lebesgue almost every $c$, the map
$f_c$ is either hyperbolic or infinitely renormalizable. For real parameters,
we prove that for Lebesgue almost every $c$, the map $f_c$ is either
hyperbolic, or Collet-Eckmann, or infinitely renormalizable. These results are
based on controlling the spacing between consecutive elements in the
``principal nest'' of parapuzzle pieces.


title: Microphysical analogues of flyby anomalies

abstract:
  We discuss Doppler shift and interferometric measurements in analogy to the
recently reported macroscopic flyby anomalies.


title: Alpha-Alpha scattering, chiral symmetry and 8Be lifetime

abstract:
  Alpha-alpha scattering is discussed in terms of a chiral two pion exchange
potential which turns out to be attractive and singular at the origin, hence
demanding renormalization. When 8Be is treated as a resonance state a model
independent correlation between the Q-factor and lifetime 1/Gamma for the decay
into two alpha particles arises. For a wide range of parameters compatible with
potential model analyses of low energy pi-alpha scattering it is found Gamma =
4.4(4)eV} in fairly good agreement with the experimental value Gamma = 5.57
(25) eV. The remaining discrepancy as well as the phase shift up to ELAB=15MeV
could be accommodated by the leading nuclear peripheral contributions due to
the 3H+p and 3He+n continuum.


title:
Dissipation characteristics of quantized spin waves in nano-scaled
  magnetic ring structures

abstract:
  The spatial profiles and the dissipation characteristics of spin-wave
quasi-eigenmodes are investigated in small magnetic Ni$_{81}$Fe$_{19}$ ring
structures using Brillouin light scattering microscopy. It is found, that the
decay constant of a mode decreases with increasing mode frequency. Indications
for a contribution of three-magnon processes to the dissipation of higher-order
spin-wave quasi-eigenmodes are found.


title: Multiple M2-branes and the Embedding Tensor

abstract:
  We show that the Bagger-Lambert theory of multiple M2-branes fits into the
general construction of maximally supersymmetric gauge theories using the
embedding tensor technique. We apply the embedding tensor technique in order to
systematically obtain the consistent gaugings of N=8 superconformal theories in
2+1 dimensions. This leads to the Bagger-Lambert theory, with the embedding
tensor playing the role of the four-index antisymmetric tensor defining a
``3-algebra''. We present an alternative formulation of the theory in which the
embedding tensor is replaced by a set of unrestricted scalar fields. By taking
these scalar fields to be parity-odd, the Chern-Simons term can be made
parity-invariant.


title: To how many politicians should government be left?

abstract:
  The quality of governance of institutions, corporations and countries depends
on the ability of efficient decision making within the respective boards or
cabinets. Opinion formation processes within groups are size dependent. It is
often argued - as now e.g. in the discussion of the future size of the European
Commission - that decision making bodies of a size beyond 20 become strongly
inefficient. We report empirical evidence that the performance of national
governments declines with increasing membership and undergoes a qualitative
change in behavior at a particular group size. We use recent UNDP, World Bank
and CIA data on overall government efficacy, i.e. stability, the quality of
policy formulation as well as human development indices of individual countries
and relate it to the country's cabinet size. We are able to understand our
findings through a simple physical model of opinion dynamics in groups.


title: Refinement Equations and Spline Functions

abstract:
  In this paper, we exploit the relation between the regularity of refinable
functions with non-integer dilations and the distribution of powers of a fixed
number modulo 1, and show the nonexistence of a non-trivial {\bf C}^{\infty}
solution of the refinement equation with non-integer dilations. Using this, we
extend the results on the refinable splines with non-integer dilations and
construct a counterexample to some conjecture concerning the refinable splines
with non-integer dilations. Finally, we study the box splines satisfying the
refinement equation with non-integer dilation and translations. Our study
involves techniques from number theory and harmonic analysis.


title: Scalar mesons in weak semileptonic decays of $B_{(s)}$

abstract:
  The transition form factors of $B_{(s)} \to S$, with $S$ denoting a scalar
meson, are investigated in the light-cone sum rules approach. The numerical
values are approximately twice as large as that estimated in the light-front
quark model and QCD sum rules approach. Using these form factors, we present
the analysis of the decay rates for $B \to a_0(1450) l \bar{\nu}_l $, $B \to
K^{\ast}_0(1430) l \bar{l}$, $B_s \to K^{\ast}_0(1430) l \bar{\nu}_l$ and $B_s
\to f_0(1500) l \bar{l}$ with $l=e, \mu, \tau$. The results indicate that
magnitudes of $BR(\bar{B}_0 \to a_0(1450) l \bar{\nu}_l)$ and $BR(B_s \to
K^{\ast}_0(1430) l \bar{\nu}_l)$ can arrive at the order of $10^{-4}$, which
can be measured in the future experiments to clarify the inner structure of
scalar mesons. It is also observed that $BR(B \to K^{\ast}_0(1430) \tau^+
\tau^-)$ and $BR(B_s \to f_0(1500) \tau^+ \tau^-)$ are an order of magnitude
smaller than the corresponding channels of $e^+ e^-$ and $\mu^+ \mu^-$ final
states due to the heavily suppressed phase space . Moreover, the longitudinal
lepton polarization asymmetry for $B \to K^{\ast}_0(1430) l \bar{l}$ and $B_s
\to f_0(1500) l \bar{l}$ are also investigated, whose values are close to -1
for the $e^+ e^-$ and $\mu^+ \mu^-$ pair except the region close to the end
points.


title: Can Born Infeld Gravity Explain Galaxy Rotation Curves?

abstract:
  A Born-Infeld theory has been proposed in order to explain both dark matter
and dark energy. We show that the approximation used to deduce the flat
rotation curves in this model breaks down at large distances in a spherically
symmetric configuration.


title:
Multipoint Pad\'e Approximants to Complex Cauchy Transforms with Polar
  Singularities

abstract:
  We study diagonal multipoint Pad\'e approximants to sums of a Cauchy
transform of a complex measure and a rational function. The measure is assumed
to have compact regular support included into the real line and an argument of
bounded variation on the support. For interpolation sets whose normalized
counting measures converge sufficiently fast in the weak-star sense to some
conjugate-symmetric distribution, we show that the counting measures of poles
of the approximants converge to the balayage of that distribution onto the
support of the measure, in the weak-star sense, that the approximants
themselves converge in capacity to the approximated function outside the
support of the measure, and that the poles of the additional rational function
attract at least as many poles of the approximants as their multiplicity and
not much more.


title: The contribution of red dwarfs and white dwarfs to the halo dark matter

abstract:
  The nature of the several microlensing events observed by the MACHO team
towards the LMC still remains controversial. Low-mass substellar objects and
stars with masses larger than ~1 M_{sun} have been ruled out as major
components of a MACHO galactic halo, while stars of half solar masses are the
most probable candidates. In this paper we assess jointly the relative
contributions of both red dwarfs and white dwarfs to the mass budget of the
galactic halo. In doing so we use a Monte Carlo simulator which incorporates
up-to-date evolutionary sequences of both red dwarfs and white dwarfs as well
as detailed descriptions of our Galaxy and of the LMC. We explore the complete
mass range between 0.08 and 1 M_{sun} as possible microlensing candidates and
we compare the synthetic populations obtained with our simulator with the
results obtained by the MACHO and EROS experiments. Our results indicate that,
despite that the contribution of the red dwarf population increases by a factor
of 2 the value of the optical depth obtained when taking into account the white
dwarf population alone, it is still insufficient to explain the number of
events claimed by the MACHO team. Finally, we find that the contribution to the
halo dark matter of the whole population under study is smaller than 10% at the
95% conficence level.


title: Surface tension in the dilute Ising model. The Wulff construction

abstract:
  We study the surface tension and the phenomenon of phase coexistence for the
Ising model on $\mathbbm{Z}^d$ ($d \geqslant 2$) with ferromagnetic but random
couplings. We prove the convergence in probability (with respect to random
couplings) of surface tension and analyze its large deviations : upper
deviations occur at volume order while lower deviations occur at surface order.
We study the asymptotics of surface tension at low temperatures and relate the
quenched value $\tau^q$ of surface tension to maximal flows (first passage
times if $d = 2$). For a broad class of distributions of the couplings we show
that the inequality $\tau^a \leqslant \tau^q$ -- where $\tau^a$ is the surface
tension under the averaged Gibbs measure -- is strict at low temperatures. We
also describe the phenomenon of phase coexistence in the dilute Ising model and
discuss some of the consequences of the media randomness. All of our results
hold as well for the dilute Potts and random cluster models.

categories: math.PR cond-mat.stat-mech math-ph math.MP


title: Fine Gradings of Low-Rank Complex Lie Algebras and of Their Real Forms

abstract:
  In this review paper, we treat the topic of fine gradings of Lie algebras.
This concept is important not only for investigating the structural properties
of the algebras, but, on top of that, the fine gradings are often used as the
starting point for studying graded contractions or deformations of the
algebras. One basic question tackled in the work is the relation between the
terms 'grading' and 'group grading'. Although these terms have originally been
claimed to coincide for simple Lie algebras, it was revealed later that the
proof of this assertion was incorrect. Therefore, the crucial statements about
one-to-one correspondence between fine gradings and MAD-groups had to be
revised and re-formulated for fine group gradings instead. However, there is
still a hypothesis that the terms 'grading' and 'group grading' coincide for
simple complex Lie algebras. We use the MAD-groups as the main tool for finding
fine group gradings of the complex Lie algebras $A_3 \cong D_3$, $B_2 \cong
C_2$, and $D_2$. Besides, we develop also other methods for finding the fine
(group) gradings. They are useful especially for the real forms of the complex
algebras, on which they deliver richer results than the MAD-groups. Systematic
use is made of the faithful representations of the three Lie algebras by
$4\times 4$ matrices: $A_3 = sl(4,\mathbb C)$, $C_2 = sp(4,\mathbb C)$, $D_2 =
o(4,\mathbb C)$. The inclusions $sl(4,\mathbb C)\supset sp(4,\mathbb C)$ and
$sl(4,\mathbb C) \supset o(4,\mathbb C)$ are important in our presentation,
since they allow to employ one of the methods which considerably simplifies the
calculations when finding the fine group gradings of the subalgebras
$sp(4,\mathbb C)$ and $o(4,\mathbb C)$.


title:
Non-exponential tunneling and control of microwave absorption lineshapes
  via Fano resonance for electrons on Helium

abstract:
  We consider the application of a small in-plane magnetic field to electrons
on a helium surface in a perpendicular magnetic field. Certain states that were
bound to the helium surface then dissolve into the continuum turning into
long-lived resonances. As a result microwave absorption lines acquire an
asymmetric Fano lineshape that is tunable by varying the microwave polarisation
or the in-plane magnetic field. Electrons trapped in a formerly bound state
will tunnel off the surface of helium; we show that under suitable
circumstances this ``radioactive decay'' can show damped oscillations rather
than a simple exponential decay. The mechanism for oscillatory exponential
decay is not specific to electrons on Helium and this effect may also be
relevant elsewhere in physics.


title: Spin-orbit coupling in ferromagnetic Nickel

abstract:
  We use the Gutzwiller variational theory to investigate the electronic and
the magnetic properties of fcc-Nickel. Our particular focus is on the effects
of the spin-orbit coupling. Unlike standard relativistic band-structure
theories, we reproduce the experimental magnetic moment direction and we
explain the change of the Fermi-surface topology that occurs when the magnetic
moment direction is rotated by an external magnetic field. The Fermi surface in
our calculation deviates from early de-Haas--van-Alphen (dHvA) results. We
attribute these discrepancies to an incorrect interpretation of the raw dHvA
data.


title:
Understanding correlation effects for ion conduction in polymer
  electrolytes

abstract:
  Polymer electrolytes typically exhibit diminished ionic conductivity due to
the presence of correlation effects between the cations and anions.
Microscopically, transient ionic aggregates, e.g. {\it ion-pairs}, {\it
ion-triplets} or higher order ionic clusters, engender ionic correlations.
Employing {\it all-atom} simulation of a model polymer electrolyte comprising
of poly(ethylene oxide) and lithium iodide, the ionic correlations are explored
through construction of elementary functions between pairs of the ionic species
that qualitatively explains the spatio-temporal nature of these correlations.
Furthermore, commencing from the exact Einstein-like equation describing the
collective diffusivity of the ions in terms of the average diffusivity of the
ions (i.e. the self terms) and the correlations from distinct pairs of ions,
several phenomenological parameters are introduced to keep track of the
simplification procedure that finally boils down to the recently proposed
phenomenological model by Stolwijk-Obeidi (SO) [N. A. Stolwijk and S. Obeidi,
Phys. Rev. Lett. 93, 125901, 2004]. The approximation parameters, which can be
retrieved from simulations, point to the necessity of additional information in
order to fully describe the correlation effects apart from merely the fraction
of ion-pairs which apparently accounts for the correlations originating from
only the nearest neighbor structural correlations. These parameters are close
to but not exactly unity as assumed in the SO model. Finally, as an application
of the extended SO model one is able to estimate the dynamics of the free and
non-free ions as well as their fractions from the knowledge of the single
particle diffusivities and the collective diffusivity of the ions.


title:
Phase instability induced by polar nanoregions in a relaxor
  ferroelectric system

abstract:
  Local inhomogeneities known as polar nanoregions (PNR) play a key role in
governing the dielectric properties of relaxor ferroelectrics - a special class
of material that exhibits an enormous electromechanical response and is easily
polarized with an external field. Using neutron inelastic scattering methods,
we show that the PNR can also significantly affect the structural properties of
the relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (PZN-4.5%PT). A strong
interaction is found between the PNR and the propagation of sound waves, i.e.
acoustic phonons, the visibility of which can be enhanced with an external
electric field. A comparison between acoustic phonons propagating along
different directions reveals a large asymmetry in the lattice dynamics that is
induced by the PNR. We suggest that a phase instability induced by this
PNR-phonon interaction may contribute to the ultrahigh piezoelectric response
of this and related relaxor ferroelectric materials. Our results also naturally
explain the emergence of the various observed monoclinic phases in these
systems.


title: Stone-Weierstrass type theorems for large deviations

abstract:
  We give a general version of Bryc's theorem valid on any topological space
and with any algebra $\mathcal{A}$ of real-valued continuous functions
separating the points, or any well-separating class. In absence of exponential
tightness, and when the underlying space is locally compact regular and
$\mathcal{A}$ constituted by functions vanishing at infinity, we give a
sufficient condition on the functional $\Lambda(\cdot)_{\mid \mathcal{A}}$ to
get large deviations with not necessarily tight rate function. We obtain the
general variational form of any rate function on a completely regular space;
when either exponential tightness holds or the space is locally compact
Hausdorff, we get it in terms of any algebra as above. Prohorov-type theorems
are generalized to any space, and when it is locally compact regular the
exponential tightness can be replaced by a (strictly weaker) condition on
$\Lambda(\cdot)_{\mid \mathcal{A}}$.


title:
Effect of gauge-field interaction on fermion transport in 2D: Hartree
  conductivity correction and dephasing

abstract:
  We consider the quantum corrections to the conductivity of fermions
interacting via a Chern-Simons gauge field, and concentrate on the Hartree-type
contributions. The first-order Hartree approximation is only valid in the limit
of weak coupling \lambda to the gauge field, and results in an antilocalizing
conductivity correction, \sim \lambda^2 g \ln^2 T (g is the conductance). In
the case of strong coupling, an infinite summation of higher-order terms is
necessary, including both the virtual (renormalization) and real (dephasing)
processes. At intermediate temperatures 1/g^2\tau<<T<<1/g\tau (\tau is the
transport time), the T-dependence of the conductivity is determined by the
Hartree correction. At low temperatures T<<1/g^2\tau, the Hartree correction
assumes a logarithmic form with a coefficient of order unity. As a result, the
negative exchange contribution becomes dominant, yielding localization in the
limit of zero T. We further discuss dephasing at strong coupling and show that
the dephasing rates are of the order of T, owing to the interplay of inelastic
scattering and renormalization. On the other hand, the dephasing length is
anomalously short, L_\phi<<L_T. For the case of composite fermions with
long-range Coulomb interaction, the Hartree correction has the usual
T-dependence, and for realistic g is overcompensated by the negative exchange
contribution due to the gauge-boson and scalar parts of the interaction. In
this case, the dephasing length L_\phi is of the order of L_T for not too low T
and exceeds L_T for T<1/g\tau.


title: Nondecoupling of a terascale isosinglet quark and rare K and B decays

abstract:
  We examine recent extensions of the standard model with an up-type vectorlike
isosinglet T quark that mixes dominantly with the top quark. We take under
scrutiny the nondecoupling effects which may reveal such a new heavy fermion
through loop diagrams relevant for rare decays such as K-->pi nu nu-bar,
B-->pi(K) nu nu-bar, and B_{s,d}-->mu^+ mu^-. After demonstrating in detail the
cancellation between the leading nondecoupling terms, we show that two residual
forms ~ s^2 ln{m_T^2} and ~ s^4 m_T^2 act in complementary way, so that the
maximal allowed values of the decay rates are practically independent of m_T.
While they correspond to ~ 20% or ~ 30% corrections to the SM rates for K-->pi
nu nu-bar and B-->pi(K) nu nu-bar, an increase by ~ 50% for B_{s,d}-->mu^+ mu^-
decays offers a possibility to reveal an additional isosinglet state by
measurements of these decays at the Large Hadron Collider.


title: On the observation of the spin resonance in superconducting CeCoIn_5

abstract:
  Recent observation of a resonance spin excitation at (1/2,1/2,1/2) in the
superconducting state of CeCoIn_5 [C. Stock et al., Phys. Rev. Lett. {\bf 100}
087001 (2008)] was interpreted as an evidence for d_{x^2-y^2} gap symmetry, by
analogy with the cuprates. This is true if the resonance is a spin exciton. We
argue that such description is undermined by the three-dimensionality of
CeCoIn_5. We show that in 3D systems the excitonic resonance only emerges at
strong coupling, and is weak. We argue in favor of the alternative, magnon
scenario, which does not require a d_{x^2-y^2} gap.


title:
Transport coefficients of off-lattice mesoscale-hydrodynamics simulation
  techniques

abstract:
  The viscosity and self-diffusion constant of particle-based mesoscale
hydrodynamic methods, multi-particle collision dynamics (MPC) and dissipative
particle dynamics (DPD), are investigated, both with and without
angular-momentum conservation. Analytical results are derived for fluids with
an ideal-gas equation of state and a finite-time-step dynamics, and compared
with simulation data. In particular, the viscosity is derived in a general form
for all variants of the MPC method. In general, very good agreement between
theory and simulations is obtained.


title:
Linearity conditions on the Jacobian ideal and logarithmic--meromorphic
  comparison for free divisors

abstract:
  In this paper we survey the role of D-module theory in the comparison between
logarithmic and meromorphic de Rham complexes of integrable logarithmic
connections with respect to free divisors, and we present some new linearity
conditions on the Jacobian ideal which arise in this setting.


title: Next-to-leading order QCD corrections to t-tbar-Z production at the LHC

abstract:
  We present a calculation of the full next-to-leading order QCD corrections to
the scattering process pp \to t tbar Z. This channel will be used to measure
the t tbar Z electroweak couplings at the Large Hadron Collider. These
couplings cannot be directly measured in current experiments. To obtain these
results, we utilize a novel, completely numerical approach to performing higher
order QCD calculations. We find that for reasonable values of the
renormalization and factorization scales the QCD corrections increase the
leading order result by 35 percent, while reducing the theoretical error
arising from uncalculated higher order corrections to approximately 10 percent.


title:
Understanding Segmental Dynamics in Polymer Electrolytes: A Computer
  Study

abstract:
  We study the segmental dynamics of poly(ethylene oxide) (PEO) from
microscopic simulations in the neat polymer and a polymer electrolyte
(PEO/LiBF$_4$) by analyzing the normal modes. We verify the applicability of
the Rouse theory, specifically for the polymer electrolyte where dynamic
heterogeneities, arising from cation-polymer interactions, alter the mobility
non-uniformly along the chains. We find that the Rouse modes for both the
systems are orthogonal despite the presence of non-exponential relaxation of
the modes and violation of the Gaussian self-similarity of the chains. The
slowdown of the segmental dynamics in the polymer electrolyte is rationalised
by an order of magnitude increase in the friction coefficient for those
monomers which are bound by cations. In general, for the electrolyte the Rouse
predictions for the dynamics of segments (both free and/or bound) agree well
except for very short times.


title: A note on Todorov surfaces

abstract:
  Let $S$ be a {\em Todorov surface}, {\it i.e.}, a minimal smooth surface of
general type with $q=0$ and $p_g=1$ having an involution $i$ such that $S/i$ is
birational to a $K3$ surface and such that the bicanonical map of $S$ is
composed with $i.$
  The main result of this paper is that, if $P$ is the minimal smooth model of
$S/i,$ then $P$ is the minimal desingularization of a double cover of $\mathbb
P^2$ ramified over two cubics. Furthermore it is also shown that, given a
Todorov surface $S$, it is possible to construct Todorov surfaces $S_j$ with
$K^2=1,...,K_S^2-1$ and such that $P$ is also the smooth minimal model of
$S_j/i_j,$ where $i_j$ is the involution of $S_j.$ Some examples are also
given, namely an example different from the examples presented by Todorov in
\cite{To2}.


title:
Mott-Insulator Transition for Ultracold Fermions in Two-Dimensional
  Optical Lattices

abstract:
  In this work we study ultracold Fermions confined in a two-dimensional
optical lattice and we explore the Mott-insulator transition with the
Fermi-Hubbard model. On the basis of a mean-field approach, we study the phase
diagrams in the presence of a harmonic trapping potential. Local Mott-insulator
phases are shown to be generally situated in the center of the trap and
correspond to a vanishing variance of the local density. We then study the
effects induced by rotation on the Mott-insulator phase transition. In
particular, we show that the phase boundary reproduces the edge of the
Hofstadter butterfly.


title: Fracture size effects from disordered lattice models

abstract:
  We study size effects in the fracture strength of notched disordered samples
using numerical simulations of lattice models for fracture. In particular, we
consider the random fuse model, the random spring model and the random beam
model, which all give similar results. These allow us to establish and
understand the crossover between a regime controlled by disorder-induced
statistical effects and a stress-concentration controlled regime ruled by
fracture mechanics. The crossover is described by a scaling law that accounts
for the presence of fracture process zone which we quantify by averaging over
several disordered configurations of the model. The models allow to study the
development of the fracture process zone as the load is increased and to
express this in terms of crack resistance (R-curve).


title: Coherent Graphene Devices: Movable Mirrors, Buffers and Memories

abstract:
  We theoretically report that, at a sharp electrostatic step potential in
graphene, massless Dirac fermions can obtain Goos-H\"{a}nchen-like shifts under
total internal reflection. Based on these results, we study the coherent
propagation of the quasiparticles along a sharp graphene \emph{p-n-p} waveguide
and derive novel dispersion relations for the guided modes. Consequently,
coherent graphene devices (e.g. movable mirrors, buffers and memories) induced
only by the electric field effect can be proposed.


title:
Three-dimensional metamaterials with an ultra-high effective refractive
  index over broad bandwidth

abstract:
  The authors introduce a general mechanism, based on electrostatic and
magnetostatic considerations, for designing three-dimensional isotopic
metamaterials that possess an enhanced refractive index over an extremely large
frequency range. The mechanism allows nearly independent control of effective
electric permittivity and magnetic permeability without the use of resonant
elements.


title: On equations of double planes with $p_g=q=1$

abstract:
  This paper describes how to compute equations of plane models of minimal Du
Val double planes of general type with $p_g=q=1$ and $K^2=2,...,8.$ A double
plane with $K^2=8$ having bicanonical map not composed with the associated
involution is also constructed. The computations are done using the algebra
system Magma.


title: Semicircle Law of Vandermonde Ensemble

abstract:
  In the present paper, we give a simple proof of the level density of fixed
trace square ensemble.We derive the integral equation of the level density of
fixed trace square ensemble.Then we analyze the asymptotic behavior of the
level density.


title:
Counting the Number of Site Swap Juggling Patterns with Respect to
  Particular Ceilings

abstract:
  Site swap is a mathematical notation used by jugglers to communicate, create
and study complex juggling patterns. Determining the number of possible site
swap juggling patterns with respect to certain limiting parameters such as
number of balls etc., is a problem that has been much studied and solved by
many mathematicians. However, when the patterns have a throw height restriction
(ceiling) the problem becomes difficult and is in general still open. In this
article we derive some formulae for computing the number of possible juggling
patterns with respect to certain ceiling types.


title: Two-dimensional Markovian holonomy fields

abstract:
  We define a notion of Markov process indexed by curves drawn on a compact
surface and taking its values in a compact Lie group. We call such a process a
two-dimensional Markovian holonomy field. The prototype of this class of
processes, and the only one to have been constructed before the present work,
is the canonical process under the Yang-Mills measure, first defined by Ambar
Sengupta and later by the author . The Yang-Mills measure sits in the class of
Markovian holonomy fields very much like the Brownian motion in the class of
Levy processes. We prove that every regular Markovian holonomy field determines
a Levy process of a certain class on the Lie group in which it takes its
values, and construct, for each Levy process in this class, a Markovian
holonomy field to which it is associated. When the Lie group is in fact a
finite group, we give an alternative construction of this Markovian holonomy
field as the monodromy of a random ramified principal bundle.


title:
Random changes of flow topology in two dimensional and geophysical
  turbulence

abstract:
  We study the two dimensional (2D) stochastic Navier Stokes (SNS) equations in
the inertial limit of weak forcing and dissipation. The stationary measure is
concentrated close to steady solutions of the 2D Euler equation. For such
inertial flows, we prove that bifurcations in the flow topology occur either by
changing the domain shape, the nonlinearity of the vorticity-stream function
relation, or the energy. Associated to this, we observe in SNS bistable
behavior with random changes from dipoles to unidirectional flows. The
theoretical explanation being very general, we infer the existence of similar
phenomena in experiments and in models of geophysical flows.


title:
Inducement of Spin-pairing and Correlated Semi-metallic State in
  Mott-Hubbard Quantum Dot Array

abstract:
  We model a quantum dot-array (with one electron per dot) comprising of two
(or more than two) coupled dots by an extended Hubbard Hamiltonian to
investigate the role played by the inter-dot tunneling amplitude td, together
with intra-dot (U) and inter-dot(U1) coulomb repulsions, in the singlet /
triplet bound state formation and evolution of the system from the
Mott-insulator-like state to a correlated semi-metallic state via
charge-bond-order route. In the presence of magnetic field, td is complex due
to the appearance of Peierls phase factor. We introduce a short-ranged
inter-dot capacitive coupling U0, assumed to be non-zero for nearest-neighbor
dots only, for the bound state analysis. The study indicates that, while for
the tunable parameter d = (2td/U0) greater than unity only the possibility of
the triplet bound state formation exists, for d less than one both triplet and
singlet states are possible. The bound states are formed due to tunneling and
capacitive dot-bondings with coulomb interactions (U,U1) playing marginal role.
The interaction U, however, is found to play, together with complex td, an
important role in the evolution of the double quantum dot system from the
insulator-like state to that of a correlated semi-metallic state through
charge-bond-ordering route.


title: Mean values with cubic characters

abstract:
  We investigate various mean value problems involving order three primitive
Dirichlet characters. In particular, we obtain an asymptotic formula for the
first moment of central values of the Dirichlet L-functions associated to this
family, with a power saving in the error term. We also obtain a large-sieve
type result for order three (and six) Dirichlet characters.


title: Lectures on Lie groups over local fields

abstract:
  These are the lecture notes of a 2-hour mini-course on Lie groups over local
fields presented at the "Workshop on Totally Disconnected Groups, Graphs and
Geometry" at the Heinrich-Fabri-Institut Blaubeuren in May 2007.
  The goal of the notes is to provide an introduction to p-adic Lie groups and
Lie groups over fields of formal Laurent series, with an emphasis on relations
to the structure theory of totally disconnected, locally compact groups. In
particular, they contain a discussion of the scale, tidy subgroups and
contraction groups for automorphisms of Lie groups over local fields.
  Special attention is paid to the case of Lie groups over local fields of
positive characteristic.


title: Crack Roughness in the 2D Random Threshold Beam Model

abstract:
  We study the scaling of two-dimensional crack roughness using large scale
beam lattice systems. Our results indicate that the crack roughness obtained
using beam lattice systems does not exhibit anomalous scaling in sharp contrast
to the simulation results obtained using scalar fuse lattices. The local and
global roughness exponents ($\zeta_{loc}$ and $\zeta$, respectively) are equal
to each other, and the two-dimensional crack roughness exponent is estimated to
be $\zeta_{loc} = \zeta = 0.64 \pm 0.02$. Removal of overhangs (jumps) in the
crack profiles eliminates even the minute differences between the local and
global roughness exponents. Furthermore, removing these jumps in the crack
profile completely eliminates the multiscaling observed in other studies. We
find that the probability density distribution $p(\Delta h(\ell))$ of the
height differences $\Delta h(\ell) = [h(x+\ell) - h(x)]$ of the crack profile
obtained after removing the jumps in the profiles follows a Gaussian
distribution even for small window sizes ($\ell$).


title: Anomalous Roughness of Fracture Surfaces in 2D Fuse Models

abstract:
  We study anomalous scaling and multiscaling of two-dimensional crack profiles
in the random fuse model using both periodic and open boundary conditions. Our
large scale and extensively sampled numerical results reveal the importance of
crack branching and coalescence of microcracks, which induce jumps in the
solid-on-solid crack profiles. Removal of overhangs (jumps) in the crack
profiles eliminates the multiscaling observed in earlier studies and reduces
anomalous scaling. We find that the probability density distribution $p(\Delta
h(\ell))$ of the height differences $\Delta h(\ell) = [h(x+\ell) - h(x)]$ of
the crack profile obtained after removing the jumps in the profiles has the
scaling form $p(\Delta h(\ell)) = <\Delta h^2(\ell)>^{-1/2} ~f(\frac{\Delta
h(\ell)}{<\Delta h^2(\ell)>^{1/2}})$, and follows a Gaussian distribution even
for small bin sizes $\ell$. The anomalous scaling can be summarized with the
scaling relation $[\frac{<\Delta h^2(\ell)>^{1/2}}{<\Delta
h^2(L/2)>^{1/2}}]^{1/\zeta_{loc}} + \frac{(\ell-L/2)^2}{(L/2)^2} = 1$, where
$<\Delta h^2(L/2)>^{1/2} \sim L^{\zeta}$.


title: On sections of genus two Lefschetz fibrations

abstract:
  In this note we find new relations in the mapping class group of a genus two
surface with n boundary components for n=1,..., 8 which induce a genus two
Lefschetz fibration $CP^2#13CP^2bar \to S^2$ with n disjoint sections. As a
consequence, we observe any holomorphic genus 2 Lefschetz fibration without
separating singular fibers admits a section.


title: CMB polarization induced by stochastic magnetic fields

abstract:
  The complete calculation of the CMB polarization observables (i.e. E- and
B-modes) is reported within the conventional $\Lambda$CDM paradigm supplemented
by a stochastic magnetic field. Intriguing perspectives for present and
forthcoming CMB polarization experiments are outlined.


title: Inverse Vector Operators

abstract:
  In different branches of physics, we frequently deal with vector del operator
($\vec{\nabla}$). This del operator is generally used to find curl or
divergence of a vector function or gradient of a scalar function. In many
important cases, we need to know the parent vector whose curl or divergence is
known or require to find the parent scalar function whose gradient is known.
But the task is not very easy, especially in case of finding vector potential
whose curl is known. Here,'inverse curl', 'inverse divergence' and 'inverse
gradient' operators are defined to solve those problems easily. All operators
are defined in the orthogonal curvilinear co-ordinate system.


title: Cosmology of the very early universe

abstract:
  We study cosmological solutions for the very early universe beginning at the
Planck scale for a universe containing radiation, curvature and, as a
simplification of a possible scalar field potential, a cosmological constant
term. The solutions are the natural counterpart of the well known results for a
post-inflationary universe of non-relativistic matter, curvature and a
cosmological constant. Contrary to the common belief that inflation arises
independently of the initial curvature we show that in the positive curvature
case the universe collapses again into a Big Crunch without allowing the
cosmological term to dominate and to produce inflation. There is a critical
value for the cosmological constant which divide the regions where inflation is
allowed from those where inflation cannot occur. One can also have loitering
solutions where the scale factor remains almost constant growing to produce
inflation (or decreasing to a Big Crunch) after a time which depends on the
amount of energy above (or below) the critical energy. At the critical energy
the solution approaches asymptotically a particular value for the scale factor
(Einstein's static pre-inflationary universe). The cases where the cosmological
term vanishes or becomes negative are also studied providing a complete
discussion of Friedmann models.


title:
Scaling Laws and Temperature Profiles for Solar and Stellar Coronal
  Loops with Non-uniform Heating

abstract:
  The bulk of solar coronal radiative loss consists of soft X-ray emission from
quasi-static loops at the cores of Active Regions. In order to develop
diagnostics for determining the heating mechanism of these loops from
observations by coronal imaging instruments, I have developed analytical
solutions for the temperature structure and scaling laws of loop strands for a
wide range of heating functions, including footpoint heating, uniform heating,
and heating concentrated at the loop apex. Key results are that the temperature
profile depends only weakly on the heating distribution -- not sufficiently to
be of significant diagnostic value -- and that the scaling laws survive for
this wide range of heating distributions, but with the constant of
proportionality in the RTV scaling law ($P_{0}L \thicksim T_{max}^3$) depending
on the specific heating function. Furthermore, quasi-static analytical
solutions do not exist for an excessive concentration of heating near the loop
footpoints, a result in agreement with recent numerical simulations. It is
demonstrated that a generalization of the solutions to the case of a strand
with a variable diameter leads to only relatively small correction factors in
the scaling laws and temperature profiles for constant diameter loop strands. A
quintet of leading theoretical coronal heating mechanisms is shown to be
captured by the formalism of this paper, and the differences in thermal
structure between them may be verified through observations. Preliminary
results from full numerical simulations demonstrate that, despite the
simplifying assumptions, the analytical solutions from this paper are stable
and accurate.


title: Good moduli spaces for Artin stacks

abstract:
  We develop the theory of associating moduli spaces with nice geometric
properties to arbitrary Artin stacks generalizing Mumford's geometric invariant
theory and tame stacks.


title:
Mapping the dynamic interactions between vortex species in highly
  anisotropic superconductors

abstract:
  Here we use highly sensitive magnetisation measurements performed using a
Hall probe sensor on single crystals of highly anisotropic high temperature
superconductors $Bi_{2}Sr_{2}CaCu_{2}O_{8}$ to study the dynamic interactions
between the two species of vortices that exist in such superconductors. We
observe a remarkable and clearly delineated high temperature regime that
mirrors the underlying vortex phase diagram. Our results map out the parameter
space over which these dynamic interaction processes can be used to create
vortex ratchets, pumps and other fluxonic devices.


title: Holographic Hadro-Quarkonium

abstract:
  We consider the recently suggested model for some resonances near the open
charm threshold as bound states of charmonium inside excited light mesons. It
is argued in the soft-wall holographic model of QCD that such states of heavy
quarkonium necessarily exist at sufficiently large spin of the light meson. The
bound state is provided by the dilaton exchange through the 5D bulk. We also
argue that the decay of such bound systems into mesons with open heavy flavors
due to splitting of the heavy quarkonium can be treated as semiclassical
tunneling and is suppressed. This behavior is in agreement with the known
relative suppression of the decay of the discussed charmonium-like resonances
into channels with D mesons.


title: Transitivity of Surface Dynamics Lifted to Abelian Covers

abstract:
  A homeomorphism f of a manifold M is called H_1-transitive if there is a
transitive lift of an iterate of f to the universal Abelian cover \tM. Roughly
speaking, this means that f has orbits which repeatedly and densely explore all
elements of H_1(M). For a rel pseudo-Anosov map \phi of a compact surface M we
show that the following are equivalent: (a) \phi is H_1-transitive, (b) the
action of \phi on H_1(M) has spectral radius one, and (c) the lifts of the
invariant foliations of \phi to \tM have dense leaves. The proof relies on a
characterization of transitivity for twisted \Z^d-extensions of a transitive
subshift of finite type.


title: Novel Schemes for Directly Measuring Entanglement of General States

abstract:
  An intrinsic relation between maximally entangled states and entanglement
measures is revealed, which plays a role in establishing connections for
different entanglement quantifiers. We exploit the basic idea and propose a
framework to construct schemes for directly measuring entanglement of general
states. In particular, we demonstrate that rank-1 local factorizable projective
measurements, which are achievable with only one copy of entangled state
involved at a time in a sequential way, are sufficient to directly determine
the concurrence of arbitrary two-qubit entangled state.


title: On central tendency and dispersion measures for intervals and hypercubes

abstract:
  The uncertainty or the variability of the data may be treated by considering,
rather than a single value for each data, the interval of values in which it
may fall. This paper studies the derivation of basic description statistics for
interval-valued datasets. We propose a geometrical approach in the
determination of summary statistics (central tendency and dispersion measures)
for interval-valued variables.


title: Self-accelerated brane Universe with warped extra dimension

abstract:
  We propose a cosmological model which exhibits the phenomenon of
self-acceleration: the Universe is attracted to the phase of accelerated
expansion at late times even in the absence of the cosmological constant. The
self-acceleration is inevitable in the sense that it cannot be neutralized by
any negative explicit cosmological constant. The model is formulated in the
framework of brane-world theories with a warped extra dimension. The key
ingredient of the model is the brane-bulk energy transfer which is carried by
bulk vector fields with a sigma-model-like boundary condition on the brane. We
explicitly find the 5-dimensional metric corresponding to the late-time de
Sitter expansion on the brane; this metric describes an AdS_5 black hole with
growing mass. The present value of the Hubble parameter implies the scale of
new physics of order 1 TeV, where the proposed model has to be replaced by
putative UV-completion. The mechanism leading to the self-acceleration has
AdS/CFT interpretation as occurring due to specific dynamics of conformal
matter interacting with external "electric" fields. The Universe expansion
history predicted by the model is distinguishable from the standard LambdaCDM
cosmology.


title: The Secrecy Graph and Some of its Properties

abstract:
  A new random geometric graph model, the so-called secrecy graph, is
introduced and studied. The graph represents a wireless network and includes
only edges over which secure communication in the presence of eavesdroppers is
possible. The underlying point process models considered are lattices and
Poisson point processes. In the lattice case, analogies to standard bond and
site percolation can be exploited to determine percolation thresholds. In the
Poisson case, the node degrees are determined and percolation is studied using
analytical bounds and simulations. It turns out that a small density of
eavesdroppers already has a drastic impact on the connectivity of the secrecy
graph.


title:
Correlation Strength, Gaps and Particle-Hole Asymmetry in High-Tc
  Cuprates: a Dynamical Mean Field Study of the Three-Band Copper-Oxide Model

abstract:
  The three-band model relevant to high temperature copper-oxide
superconductors is solved using single-site dynamical mean field theory and a
tight-binding parametrization of the copper and oxygen bands. For a band
filling of one hole per unit cell the metal/charge-transfer-insulator phase
diagram is determined. The electron spectral function, optical conductivity and
quasiparticle mass enhancement are computed as functions of electron and hole
doping for parameters such that the corresponding to the paramagnetic metal and
charge-transfer insulator sides of the one hole per cell phase diagram. The
optical conductivity is computed using the Peierls phase approximation for the
optical matrix elements. The calculation includes the physics of "Zhang-Rice
singlets". The effects of antiferromagnetism on the magnitude of the gap and
the relation between correlation strength and doping-induced changes in state
density are determined. Three band and one band models are compared. The two
models are found to yield quantitatively consistent results for all energies
less than about 4eV, including energies in the vicinity of the charge-transfer
gap. Parameters on the insulating side of the metal/charge-transfer insulator
phase boundary lead to gaps which are too large and near-gap conductivities
which are too small relative to data. The results place the cuprates clearly in
the intermediate correlation regime, on the paramagnetic metal side of the
metal/charge-transfer insulator phase boundary.


title:
Probing individual topological tunnelling events of a quantum field via
  their macroscopic consequences

abstract:
  Phase slips are topological fluctuation events that carry the superconducting
order-parameter field between distinct current carrying states. Owing to these
phase slips low-dimensional superconductors acquire electrical resistance. In
quasi-one-dimensional nanowires it is well known that at higher temperatures
phase slips occur via the process of thermal barrier-crossing by the
order-parameter field. At low temperatures, the general expectation is that
phase slips should proceed via quantum tunnelling events, which are known as
quantum phase slips (QPS). Here we report strong evidence for individual
quantum tunnelling events undergone by the superconducting order-parameter
field in homogeneous nanowires.We accomplish this via measurements of the
distribution of switching currents-the high-bias currents at which
superconductivity gives way to resistive behaviour-whose width exhibits a
rather counter-intuitive, monotonic increase with decreasing temperature. We
outline a stochastic model of phase slip kinetics which relates the basic phase
slip rates to switching rates. Comparison with this model indicates that the
phase predominantly slips via thermal activation at high temperatures but at
sufficiently low temperatures switching is caused by individual topological
tunnelling events of the order-parameter field, i.e., QPS. Importantly,
measurements on several wires show that quantum fluctuations tend to dominate
over thermal fluctuations at larger temperatures in wires having larger
critical currents. This fact provides strong supports the view that the
anomalously high switching rates observed at low temperatures are indeed due to
QPS, and not consequences of extraneous noise or hidden inhomogeneity of the
wire.


title:
Origin of the ~150 K Anomaly in LaOFeAs; Competing Antiferromagnetic
  Superexchange Interactions, Frustration, and Structural Phase Transition

abstract:
  From first principles calculations we find that the nearest and next nearest
neighbor superexchange interactions between Fe ions in LaOFeAs are large,
antiferromagnetic (AF), and give rise to a frustrated magnetic ground state
which consists of two interpenerating AF square sublattices with
M(Fe)=0.48$\mu_B$. The system lowers its energy further by removing the
frustration via a structural distortion. These results successfully explain the
magnetic and structural phase transitions in LaOFeAs recently observed by
neutron scattering. The presence of competing strong antiferromagnetic exchange
interactions and the frustrated ground state suggest that magnetism and
superconductivity in doped LaOFeAs may be strongly coupled, much like in the
high-T$_c$ cuprates.


title:
Density inhomogeneity driven percolation metal-insulator transition and
  dimensional crossover in graphene nanoribbons

abstract:
  Transport in graphene nanoribbons with an energy gap in the spectrum is
considered in the presence of random charged impurity centers. At low carrier
density, we predict and establish that the system exhibits a density
inhomogeneity driven two dimensional metal-insulator transition that is in the
percolation universality class. For very narrow graphene nanoribbons (with
widths smaller than the disorder induced length-scale), we predict that there
should be a dimensional crossover to the 1D percolation universality class with
observable signatures in the transport gap. In addition, there should be a
crossover to the Boltzmann transport regime at high carrier densities. The
measured conductivity exponent and the critical density are consistent with
this percolation transition scenario.


title:
Relaxation of a one-dimensional Mott insulator after an interaction
  quench

abstract:
  We obtain the exact time evolution for the one-dimensional integrable
fermionic 1/r Hubbard model after a sudden change of its interaction parameter,
starting from either a metallic or a Mott-insulating eigenstate. In all cases
the system relaxes to a new steady state, showing that the presence of the Mott
gap does not inhibit relaxation. The properties of the final state are
described by a generalized Gibbs ensemble. We discuss under which conditions
such ensembles provide the correct statistical description of isolated
integrable systems in general. We find that generalized Gibbs ensembles do
predict the properties of the steady state correctly, provided that the
observables or initial states are sufficiently uncorrelated in terms of the
constants of motion.


title:
Screening, Kohn anomaly, Friedel oscillation, and RKKY interaction in
  bilayer graphene

abstract:
  We calculate the screening function in bilayer graphene (BLG) both in the
intrinsic (undoped) and the extrinsic (doped) regime within random phase
approximation, comparing our results with the corresponding single layer
graphene (SLG) and the regular two dimensional electron gas (2DEG). We find
that the Kohn anomaly is strongly enhanced in BLG. We also discuss the Friedel
oscillation and the RKKY interaction, which are associated with the
non-analytic behavior of the screening function at $q=2k_F$. We find that the
Kohn anomaly, the Friedel oscillation, and the RKKY interaction are all
qualitatively different in the BLG compared with the SLG and the 2DEG.


title:
The Gamma Ray Burst section of the White Paper on the Status and Future
  of Very High Energy Gamma Ray Astronomy: A Brief Preliminary Report

abstract:
  This is a short report on the preliminary findings of the gamma ray burst
(GRB) working group for the white paper on the status and future of very high
energy (VHE; >50 GeV) gamma-ray astronomy. The white paper discusses the status
of past and current attempts to observe GRBs at GeV-TeV energies, including a
handful of low-significance, possible detections. The white paper concentrates
on the potential of future ground-based gamma-ray experiments to observe the
highest energy emission ever recorded for GRBs, particularly for those that are
nearby and have high Lorentz factors in the GRB jet. It is clear that the
detection of VHE emission would have strong implications for GRB models, as
well as cosmic ray origin. In particular, the extended emission phase
(including both afterglow emission and possible flaring) of nearby long GRBs
could provide the best possibility for detection. The difficult-to-obtain
observations during the prompt phase of nearby long GRBs and short GRBs could
also provide particularly strong constraints on the opacity and bulk Lorentz
factors surrounding the acceleration site. The synergy with upcoming and
existing observatories will, of course, be critical for both identification of
GRBs and for multiwavelength/multimessenger studies.


title: PC1643+4631A,B: The Lyman-Alpha Forest at the Edge of Coherence

abstract:
  This is the first measurement and detection of coherence in the intergalactic
medium (IGM) at substantially high redshift (z~3.8) and on large physical
scales (~2.5 h^-1 Mpc). We perform the measurement by presenting new
observations from Keck LRIS of the high redshift quasar pair PC 1643+4631A, B
and their Ly-alpha absorber coincidences. This experiment extends multiple
sightline quasar absorber studies to higher redshift, higher opacity, larger
transverse separation, and into a regime where coherence across the IGM becomes
weak and difficult to detect. We fit 222 discrete Ly-alpha absorbers to
sightline A and 211 to sightline B. Relative to a Monte Carlo pairing test
(using symmetric, nearest neighbor matching) the data exhibit a 4sigma excess
of pairs at low velocity splitting (<150 km/s), thus detecting coherence on
transverse scales of ~2.5 h^-1 Mpc. We use spectra extracted from an SPH
simulation to analyze symmetric pair matching, transmission distributions as a
function of redshift and compute zero-lag cross-correlations to compare with
the quasar pair data. The simulations agree with the data with the same
strength (~4sigma) at similarly low velocity splitting above random chance
pairings. In cross-correlation tests, the simulations agree when the mean flux
(as a function of redshift) is assumed to follow the prescription given by
Kirkman et al. (2005). While the detection of flux correlation (measured
through coincident absorbers and cross-correlation amplitude) is only
marginally significant, the agreement between data and simulations is
encouraging for future work in which even better quality data will provide the
best insight into the overarching structure of the IGM and its understanding as
shown by SPH simulations.


title:
Let there be Light: the Emergence of Structure out of the Dark Ages in
  the Early Universe

abstract:
  The initial conditions of our Universe can be summarized on a single sheet of
paper. Yet the Universe is full of complex structures today, such as stars,
galaxies and groups of galaxies. In this review I describe the standard
theoretical model for how complexity emerged from the simple initial state of
the Universe at early cosmic times through the action of gravity. In order to
test and inform the related theoretical calculations, large-aperture telescopes
and arrays of radio antennae are currently being designed and constructed. The
actual transition from simplicity to complexity has not been observed as of
yet. The simple initial conditions were already traced in maps of the microwave
background radiation, but the challenge of detecting the first generation of
galaxies defines one of the exciting frontiers in the future of cosmology. Once
at hand, the missing images of the infant Universe might potentially surprise
us and revise our current ideas.


title: The Prograde Orbit of Exoplanet TrES-2b

abstract:
  We monitored the Doppler shift of the G0V star TrES-2 throughout a transit of
its giant planet. The anomalous Doppler shift due to stellar rotation (the
Rossiter-McLaughlin effect) is discernible in the data, with a signal-to-noise
ratio of 2.9, even though the star is a slow rotator. By modeling this effect
we find that the planet's trajectory across the face of the star is tilted by
-9 +/- 12 degrees relative to the projected stellar equator. With 98%
confidence, the orbit is prograde.


title: Observations of X-ray Flares from Gamma Ray Bursts

abstract:
  Swift-XRT observations of the X-ray emission from gamma ray bursts (GRBs) and
during the GRB afterglow have led to many new results during the past two
years. One of these exciting results is that approximately 1/3-1/2 of GRBs
contain detectable X-ray flares. The mean fluence of the X-ray flares is ~10
times less than that of the initial prompt emission, but in some cases the
flare is as energetic as the prompt emission itself. The flares display fast
rises and decays, and they sometimes occur at very late times relative to the
prompt emission (sometimes as late as 10^5 s after T_0) with very high peak
fluxes relative to the underlying afterglow decay that has clearly begun prior
to some flares. The temporal and spectral properties of the flares are found to
favor models in which flares arise due to the same GRB internal engine
processes that spawned the prompt GRB emission. Therefore, both long and short
GRB internal engine models must be capable of producing high fluences in the
X-ray band at very late times.


title: Neutrino factory optimization for non-standard interactions

abstract:
  We study the optimization of a neutrino factory with respect to non-standard
neutral current neutrino interactions, and compare the results to those
obtained without non-standard interactions. We discuss the muon energy,
baselines, and oscillation channels as degrees of freedom. Our conclusions are
based on both analytical calculations and on a full numerical simulation of the
neutrino factory setup proposed by the international design study (IDS-NF). We
consider all possible non-standard parameters, and include their complex
phases. We identify the impact of the different parameters on the golden,
silver, and disappearance channels. We come to the conclusion that, even in the
presence of non-standard interactions, the performance of the neutrino factory
hardly profits from a silver channel detector, unless the muon energy is
significantly increased compared to the IDS-NF setup. Apart from the
dispensable silver channel detector, we demonstrate that the IDS-NF setup is
close to optimal even if non-standard interactions are considered. We find that
one very long baseline is a key component in the search for non-standard
interactions, in particular for |\epsilon^m_{\mu\tau}| and
|\epsilon^m_{\tau\tau}|.


title: Cosmology of the closed string tachyon

abstract:
  The spacetime physics of bulk closed string tachyon condensation is studied
at the level of a two-derivative effective action. We derive the unique
perturbative tachyon potential consistent with a full class of linearized
tachyonic deformations of supercritical string theory. The solutions of
interest deform a general linear dilaton background by the insertion of purely
exponential tachyon vertex operators. In spacetime, the evolution of the
tachyon drives an accelerated contraction of the universe and, absent
higher-order corrections, the theory collapses to a cosmological singularity in
finite time, at arbitrarily weak string coupling. When the tachyon exhibits a
null symmetry, the worldsheet dynamics are known to be exact and well-defined
at tree level. We prove that if the two-derivative effective action is free of
non-gravitational singularities, higher-order corrections always resolve the
spacetime curvature singularity of the null tachyon. The resulting theory
provides an explicit mechanism by which tachyon condensation can generate or
terminate the flow of cosmological time in string theory. Additional particular
solutions can resolve an initial singularity with a tachyonic phase at weak
coupling, or yield solitonic configurations that localize the universe along
spatial directions.


title: Disorder on the landscape

abstract:
  Disorder on the string theory landscape may significantly affect dynamics of
eternal inflation leading to the possibility for some vacua on the landscape to
become dynamically preferable over others. We systematically study effects of a
generic disorder on the landscape starting by identifying a sector with
built-in disorder -- a set of de Sitter vacua corresponding to
compactifications of the Type IIB string theory on Calabi-Yau manifolds with a
number of warped Klebanov-Strassler throats attached randomly to the bulk part
of the Calabi-Yau. Further, we derive continuum limit of the vacuum dynamics
equations on the landscape. Using methods of dynamical renormalization group we
determine the late time behavior of the probability distribution for an
observer to measure a given value of the cosmological constant. We find the
diffusion of the probability distribution to significantly slow down in sectors
of the landscape where the number of nearest neighboring vacua for any given
vacuum is small. We discuss relation of this slow-down with phenomenon of
Anderson localization in disordered media.


title: An Overview of Quantum Computing for Technology Managers

abstract:
  Faster algorithms, novel cryptographic mechanisms, and alternative methods of
communication become possible when the model underlying information and
computation changes from a classical mechanical model to a quantum mechanical
one. Quantum algorithms perform a select set of tasks vastly more efficiently
than any classical algorithm, but for many tasks it has been proved that
quantum algorithms provide no advantage. The breadth of quantum computing
applications is still being explored. Major application areas include security
and the many fields that would benefit from efficient quantum simulation. The
quantum information processing viewpoint provides insight into classical
algorithmic issues as well as a deeper understanding of entanglement and other
non-classical aspects of quantum physics. This overview is aimed at technology
managers who wish to gain a high level understanding of quantum information
processing, particularly quantum computing.


title: Smooth surfaces with non-simply-connected complements

abstract:
  We give two constructions of surfaces in simply-connected 4-manifolds with
non simply-connected complements. One is an iteration of the twisted rim
surgery introduced by the first author. We also construct, for any group G
satisfying some simple conditions, a simply-connected symplectic manifold
containing a symplectic surface whose complement has fundamental group G. In
each case, we produce infinitely many smoothly inequivalent surfaces that are
equivalent up to smooth s-cobordism and hence are topologically equivalent for
good groups.


title: Influence of the relict cosmological constant on accretion discs

abstract:
  Surprisingly, the relict cosmological constant has a crucial influence on
properties of accretion discs orbiting black holes in quasars and active
galactic nuclei. We show it by considering basic properties of both the
geometrically thin and thick accretion discs in the Kerr-de Sitter black-hole
(naked-singularity) spacetimes. Both thin and thick discs must have an outer
edge allowing outflow of matter into the outer space, located nearby the so
called static radius, where the gravitational attraction of a black hole is
balanced by the cosmological repulsion. Jets produced by thick discs can be
significantly collimated after crossing the static radius. Extension of discs
in quasars is comparable with extension of the associated galaxies, indicating
a possibility that the relict cosmological constant puts an upper limit on
extension of galaxies.


title:
Dynamics and density evolution in piecewise deterministic growth
  processes

abstract:
  A new sufficient condition is proved for the existence of stochastic
semigroups generated by the sum of two unbounded operators. It is applied to
one-dimensional piecewise deterministic Markov processes, where we also discuss
the existence of a unique stationary density and give sufficient conditions for
asymptotic stability.


title: Experimental quantum coding against photon loss error

abstract:
  A significant obstacle for practical quantum computation is the loss of
physical qubits in quantum computers, a decoherence mechanism most notably in
optical systems. Here we experimentally demonstrate, both in the quantum
circuit model and in the one-way quantum computer model, the smallest
non-trivial quantum codes to tackle this problem. In the experiment, we encode
single-qubit input states into highly-entangled multiparticle codewords, and we
test their ability to protect encoded quantum information from detected
one-qubit loss error. Our results prove the in-principle feasibility of
overcoming the qubit loss error by quantum codes.


title:
Calculations of the Energy Accommodation Coefficient for Gas-Surface
  Interactions

abstract:
  Calculations are carried out for the energy accommodation coefficient at a
gas-surface interface using a recently developed classical mechanical theory of
atom-surface collisions that includes both direct scattering and
trapping-desorption processes in the physisorption well of the interaction
potential. Full three-dimensional calculations are compared with the available
data for the accommodation of rare gases at a tungsten surface and good
agreement is found for the heavier gases for which classical physics is
expected to be valid at all measured temperatures.


title:
Effective Viscosity of Dilute Bacterial Suspensions: A Two-Dimensional
  Model

abstract:
  Suspensions of self-propelled particles are studied in the framework of
two-dimensional (2D) Stokesean hydrodynamics. A formula is obtained for the
effective viscosity of such suspensions in the limit of small concentrations.
This formula includes the two terms that are found in the 2D version of
Einstein's classical result for passive suspensions. To this, the main result
of the paper is added, an additional term due to self-propulsion which depends
on the physical and geometric properties of the active suspension. This term
explains the experimental observation of a decrease in effective viscosity in
active suspensions.


title: Comment on "The shape and composition of interstellar silicate grains"

abstract:
  This Comment is in response to an Erratum to the paper entitled "The shape
and composition of interstellar silicate grains" (Min et al., A&A, 462, 667-676
(2007). The Erratum corrects erroneously cited data but upholds the paper's
original conclusions that GEMS are not remnant interstellar grains and that
most GEMS formed in the early solar system. In our Comment, we show that the
correct data in fact strengthen the relationship between GEMS and interstellar
silicates, contrary to the conclusions of Min et al. in their Erratum. We also
explore the validity of the isotopic and bulk chemical bases for comparison and
present additional indicators of past ISM radiation processing of silicates.


title:
Quantum hydrodynamics and nonlinear differential equations for
  degenerate Fermi gas

abstract:
  We present new nonlinear differential equations for spacetime correlation
functions of Fermi gas in one spatial dimension. The correlation functions we
consider describe non-stationary processes out of equilibrium. The equations we
obtain are integrable equations. They generalize known nonlinear differential
equations for correlation functions at equilibrium and provide vital tools to
study non-equilibrium dynamics of electronic systems. The method we developed
is based only on Wick's theorem and the hydrodynamic description of the Fermi
gas. Differential equations appear directly in bilinear form.

categories: cond-mat.mes-hall cond-mat.str-el math-ph math.MP nlin.SI


title: Object Re-Use & Exchange: A Resource-Centric Approach

abstract:
  The OAI Object Reuse and Exchange (OAI-ORE) framework recasts the
repository-centric notion of digital object to a bounded aggregation of Web
resources. In this manner, digital library content is more integrated with the
Web architecture, and thereby more accessible to Web applications and clients.
This generalized notion of an aggregation that is independent of repository
containment conforms more closely with notions in eScience and eScholarship,
where content is distributed across multiple services and databases. We provide
a motivation for the OAI-ORE project, review previous interoperability efforts,
describe draft ORE specifications and report on promising results from early
experimentation that illustrate improved interoperability and reuse of digital
objects.


title: Anomalous Effects in Air While Cooling Water

abstract:
  Water is a unique compound with many anomalies and properties not fully
understood. Designing an experiment in the laboratory to study such anomalies,
we set up a series of experiments where a tube was placed inside a sealed
container with thermocouples attached to the outer surface of the tube and in
the air adjacent to the tube. Alternately, deionized water and other compounds
were added to the tube and cooled to freezing. Several of the thermocouples
suspended in the air and adjacent to the tube showed thermal oscillations as
the overall temperature of the container was decreasing. The temperature of the
thermocouples increased and decreased in a sinusoidal way during part of the
cool down to freezing. Thermal oscillations as large as 3 degrees Celsius were
recorded with typical frequencies of about 5 oscillations per minute.


title: Geometric Structures of Collapsing Riemannian Manifolds I

abstract:
  Let (M^n_i,g_i,p_i) be a sequence of smooth pointed complete n-dimensional
Riemannian Manifolds with uniform bounds on the sectional curvatures and let
(X,d,p) be a metric space such that (M^n_i,g_i,p_i) -> (X,d,p) in the
Gromov-Hausdorff sense. Let O \subseteq X be the set of points x \in X such
that there exists a neighborhood of x which is isometric to an open set in a
Riemannian orbifold and let B = O^c be the complement set. Then we have the
sharp estimates dim_Haus(B) \leq min{n-5, dim_Haus(X)-3}, and further for
arbitrary x \in X we have that x \in O iff a neighborhood of x has bounded
Alexandroff curvature. In particular, if n \leq 4 then B is empty and (X,d) is
a Riemannian orbifold. Our main application is to prove that a collapsed limit
of Einstein four manifolds has a smooth Riemannian orbifold structure away from
a finite number of points, and that near these points the curvatures has a
-dist^{-2} lower bound.


title: One-dimensional space-discrete transport subject to Levy perturbations

abstract:
  In this paper we study a one-dimensional space-discrete transport equation
subject to additive Levy forcing. The explicit form of the solutions allows
their analytic study. In particular we discuss the invariance of the covariance
structure of the stationary distribution for Levy perturbations with finite
second moment. The situation of more general Levy perturbations lacking the
second moment is considered as well. We moreover show that some of the
properties of the solutions are pertinent to a discrete system and are not
reproduced by its continuous analogue.


title: Number Gossip

abstract:
  This article covers my talk at the Gathering for Gardner 2008, with some
additions.


title: Magnetic Effects in Global Star Formation

abstract:
  I review the effects of magnetic fields on star formation in galaxies. This
includes the effects of the magnetorotational instability (MRI) at galactic
scales, magneto-Jeans and swing instabilities, Parker instabilities, and the
effects of magnetic fields on the evolution of supernova-driven turbulence. I
argue that currently turbulent support by the MRI appears likely to be the most
important of these processes to regulating star formation.


title:
Large-N estimates of universal amplitudes of the CP^{N-1} theory and
  comparison with the JQ model

abstract:
  We present computations of certain finite-size scaling functions and
universal amplitude ratios in the large-N limit of the CP^{N-1} field theory.
We pay particular attention to the uniform susceptibility, the spin stiffness
and the specific heat. Field theoretic arguments have shown that the
long-wavelength description of the phase transition between the Neel and
valence bond solid states in square lattice S=1/2 anti-ferromagnets is expected
to be the non-compact CP^1 field theory. We provide a detailed comparison
between our field theoretic calculations and quantum Monte Carlo data close to
the Neel -VBS transition on a S=1/2 square-lattice model with competing
four-spin interactions (the JQ model).


title:
A Mean Field Analysis of Pairing in Asymmetric Fermi Systems at Finite
  Temperature

abstract:
  We study the phase diagram of a two component Fermi system with a weak
attractive interaction. Our analysis includes the leading order Hartree energy
shifts and pairing correlations at finite temperature and chemical potential
difference between the two fermion species. We show that in an asymmetric
system, the Hartree shift to the single particle energies are important for the
phase competition between normal and superfluid phase and can change the phase
transition curve qualitatively. At large asymmetry we find that a novel but
somewhat fragile superfluid state can be favored due to finite temperature
effects. We also investigate the transition between the normal phase and an
inhomogeneous superfluid phase to study how gradient instabilities evolve with
temperature and asymmetry. Finally, we adopt our analysis to study the density
profiles of similar asymmetric Fermi systems that are being observed in cold
atom experiments.


title: Isomorphism invariants of restricted enveloping algebras

abstract:
  Let $L$ and $H$ be finite-dimensional restricted Lie algebras over a perfect
field $\F$ such that $u(L)\cong u(H)$, where $u(L)$ is the restricted
enveloping algebra of $L$. We prove that if $L$ is $p$-nilpotent and abelian,
then $L\cong H$. We deduce that if $L$ is abelian and $\F$ is algebraically
closed, then $L\cong H$. We use these results to prove the main result of this
paper stating that if $L$ is $p$-nilpotent, then $L/L'^p+\gamma_3(L)\cong
H/H'^p+\gamma_3(H)$.


title:
Semiclassical analysis of low and zero energy scattering for one
  dimensional Schr\"odinger operators with inverse square potentials

abstract:
  This paper studies the scattering matrix $\Sigma(E;\hbar)$ of the problem \[
  -\hbar^2 \psi''(x) + V(x) \psi(x) = E\psi(x) \] for positive potentials $V\in
C^\infty(\R)$ with inverse square behavior as $x\to\pm\infty$. It is shown that
each entry takes the form
$\Sigma_{ij}(E;\hbar)=\Sigma_{ij}^{(0)}(E;\hbar)(1+\hbar \sigma_{ij}(E;\hbar))$
where $\Sigma_{ij}^{(0)}(E;\hbar)$ is the WKB approximation relative to the
{\em modified potential} $V(x)+\frac{\hbar^2}{4} \la x\ra^{-2}$ and the
correction terms $\sigma_{ij}$ satisfy $|\partial_E^k \sigma_{ij}(E;\hbar)| \le
C_k E^{-k}$ for all $k\ge0$ and uniformly in $(E,\hbar)\in (0,E_0)\times
(0,\hbar_0)$ where $E_0,\hbar_0$ are small constants. This asymptotic behavior
is not universal: if $-\hbar^2\partial_x^2 + V$ has a {\em zero energy
resonance}, then $\Sigma(E;\hbar)$ exhibits different asymptotic behavior as
$E\to0$. The resonant case is excluded here due to $V>0$.


title: Handedness of direct photons

abstract:
  The azimuthal asymmetry of direct photons originating from primary hard
scatterings between partons is calculated. This can be accounted for by the
inclusion of the color dipole orientation, which is sensitive to the rapid
variation of the nuclear profile. To this end we introduce the dipole
orientation within the saturation model of Golec-Biernat and W\"usthoff, while
preserving all its features at the cross-section level. We show that the direct
photon elliptic anisotropy v2 coming from this mechanism changes sign and
becomes negative for peripheral collisions, albeit it is quite small for
nuclear collisions at the RHIC energy.


title: Unitary gauge considered harmful

abstract:
  I informally review the Higgs mechanism, focusing on fundamental aspects
which should be common knowledge but apparently are not, explain why your
understanding of gauge symmetry breaking is a decreasing function of your
reliance on the unitary gauge, and discuss some implications for cosmology
(domains, dark energy, CMB cold spot).


title: Raman phonons in ReOFeAs (Re= Sm, La)

abstract:
  We report the polarized Raman spectra of undoped ReOFeAs (Re = Sm, La)
collected at room temperature from $ab$ surfaces of impurity free
microcrystals. The spectra exhibit sharp phonon lines on very weak electronic
scattering background. The frequency and symmetry of the four Raman phonons
involving out-of-plane atomic vibrations are found at 170 cm-1 (A1g, Sm), 201
cm-1 (A1g, As), 208 cm-1 (B1g, Fe), 345 cm-1(B1g, O) for SmOFeAs, and 162 cm-1
(A1g, La), 208 cm-1 (A1g, As), 201 cm-1 (B1g, Fe), 316 cm-1 (B1g, O) for
LaOFeAs.


title:
Evidence for a pseudogap in underdoped $Bi_2Sr_2CaCu_2O_{8+\delta}$ and
  $YBa_2Cu_3O_{6.50}$ from in-plane optical conductivity measurements

abstract:
  The real part of the in-plane optical self-energy data in underdoped
Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (Bi-2212) and ortho II
YBa$_{2}$Cu$_{3}$O$_{6.5}$ contains new and important information on the
pseudogap. Using a theoretical model approach we find that the density of state
lost below the pseudogap $\Delta_{pg}$ is accompanied with a pileup just above
this energy. The pileup along with a sharp mode in the bosonic spectral
function leads to an unusually rapid increase in the optical scattering rate
and a characteristically sloped peak in the real part of the optical
self-energy. These features are not found in optimally doped and overdoped
samples and represent a clearest signature so far of the opening of a pseudogap
in the in-plane optical conductivity.


title: An ubiquitous mechanism for waterlike anomalies

abstract:
  Using collision driven molecular dynamics a system of spherical particles
interacting through an effective two length scales potential is studied. The
potential can be tuned by means of a single parameter, $\lambda$, from a ramp
$(\lambda=0.5)$ to a square-shoulder potential $(\lambda=1.0)$ representing a
family of two length scales potential in which the shortest interaction
distance has higher potential energy than the largest interaction distance. For
all the potentials, ranging between the ramp and the square-shoulder, density
and structural anomalies were found, while the diffusion anomaly is found in
all but in the square-shoulder potential. The presence anomalies in
square-shoulder potential, not observed in previous simulations, confirm the
assumption that the two length scales potential is an ubiquitous ingredient for
a system to exhibit water-like anomalies


title: Parimutuel Betting on Permutations

abstract:
  We focus on a permutation betting market under parimutuel call auction model
where traders bet on the final ranking of n candidates. We present a
Proportional Betting mechanism for this market. Our mechanism allows the
traders to bet on any subset of the n x n 'candidate-rank' pairs, and rewards
them proportionally to the number of pairs that appear in the final outcome. We
show that market organizer's decision problem for this mechanism can be
formulated as a convex program of polynomial size. More importantly, the
formulation yields a set of n x n unique marginal prices that are sufficient to
price the bets in this mechanism, and are computable in polynomial-time. The
marginal prices reflect the traders' beliefs about the marginal distributions
over outcomes. We also propose techniques to compute the joint distribution
over n! permutations from these marginal distributions. We show that using a
maximum entropy criterion, we can obtain a concise parametric form (with only n
x n parameters) for the joint distribution which is defined over an
exponentially large state space. We then present an approximation algorithm for
computing the parameters of this distribution. In fact, the algorithm addresses
the generic problem of finding the maximum entropy distribution over
permutations that has a given mean, and may be of independent interest.


title: Temporal contribution to gravitational WKB-like calculations

abstract:
  Recently, it has been shown that the radiation arising from quantum fields
placed in a gravitational background (e.g. Hawking radiation) can be derived
using a quasi-classical calculation. Here we show that this method has a
previously overlooked temporal contribution to the quasi--classical amplitude.
The source of this temporal contribution lies in different character of time in
general relativity versus quantum mechanics. Only when one takes into account
this temporal contribution does one obtain the canonical temperature for the
radiation. Although in this letter the specific example of radiation in de
Sitter space--time is used, the temporal contribution is a general contribution
to the radiation given off by any gravitational background where the time
coordinate changes its signature upon crossing a horizon. Thus, the
quasi--classical method for gravitational backgrounds contains subtleties not
found in the usual quantum mechanical tunneling problem.