title: Quantized vortices in atomic Bose-Einstein condensates

abstract:
  In this review, we give an overview of the experimental and theoretical
advances in the physics of quantized vortices in dilute atomic-gas
Bose--Einstein condensates in a trapping potential, especially focusing on
experimental research activities and their theoretical interpretations. Making
good use of the atom optical technique, the experiments have revealed many
novel structural and dynamic properties of quantized vortices by directly
visualizing vortex cores from an image of the density profiles. These results
lead to a deep understanding of superfluid hydrodynamics of such systems.
Typically, vortices are stabilized by a rotating potential created by a laser
beam, magnetic field, and thermal gas. Finite size effects and inhomogeneity of
the system, originating from the confinement by the trapping potential, yield
unique vortex dynamics coupled with the collective excitations of the
condensate. Measuring the frequencies of the collective modes is an accurate
tool for clarifying the character of the vortex state. The topics included in
this review are the mechanism of vortex formation, equilibrium properties, and
dynamics of a single vortex and those of a vortex lattice in a rapidly rotating
condensate.


title: Signals of the QCD Phase Transition in the Heavens

abstract:
  The modern phase diagram of strongly interacting matter reveals a rich
structure at high-densities due to phase transitions related to the chiral
symmetry of quantum chromodynamics (QCD) and the phenomenon of color
superconductivity. These exotic phases have significant impacts on high-density
astrophysics as the properties of neutron stars and the evolution of
astrophysical systems as proto-neutron stars, core-collapse supernovae and
neutron star mergers. Most recent pulsar mass measurements and constraints on
neutron star radii are critically discussed. Astrophysical signals for exotic
matter and phase transitions in high-density matter proposed recently in the
literature are outlined. A strong first order phase transition leads to the
emergence of a third family of compact stars besides white dwarfs and neutron
stars. The different microphysics of quark matter results in an enhanced r-mode
stability window for rotating compact stars compared to normal neutron stars.
Future telescope and satellite data will allow to extract signals from phase
transitions in dense matter in the heavens and will reveal properties of the
phases of dense QCD. Spectral line profiles out of x-ray bursts will determine
the mass-radius ratio of compact stars. Gravitational wave patterns from
collapsing neutron stars or neutron star mergers will even be able to constrain
the stiffness of the quark matter equation of state. Future astrophysical data
can therefore provide a crucial cross-check to the exploration of the QCD phase
diagram with the heavy-ion program of the CBM detector at the FAIR facility.


title: Weak-field limit of conformal Weyl gravity

abstract:
  We study the weak-field limit of the conformal Weyl gravity suggested by
Mannheim as an alternative to Einstein's General Relativity modeling both dark
matter and dark energy. We solve the field equations of the theory in the
weak-field approximation for an arbitrary spherically symmetric static
distribution of matter in the physical gauge with constant scalar field.
Analysing the obtained solution, we conclude that the conformal theory of
gravitaty is inconsistent with the Solar-system observational data.


title: Rotational Modulation of M/L Dwarfs due to Magnetic Spots

abstract:
  We find periodic I-band variability in two ultracool dwarfs, TVLM 513-46546
and 2MASS J00361617+1821104, on either side of the M/L dwarf boundary. Both of
these targets are short-period radio transients, with the detected I-band
periods matching those found at radio wavelengths (P=1.96 hr for TVLM
513-46546, and P=3 hr for 2MASS J00361617+1821104). We attribute the detected
I-band periodicities to the periods of rotation of the dwarfs, supported by
radius estimates and measured $v$ sin $i$ values for the objects. Based on the
detected period of rotation of TVLM 513-46546 (M9) in the I-band, along with
confirmation of strong magnetic fields from recent radio observations, we argue
for magnetically induced spots as the cause of this periodic variability. The
I-band rotational modulation of L3.5 dwarf 2MASS J00361617+1821104 appeared to
vary in amplitude with time. We conclude that the most likely cause of the
I-band variability for this object is magnetic spots, possibly coupled with
time-evolving features such as dust clouds.


title:
Exploring the Physical Basis of Solar Cycle Predictions: Flux Transport
  Dynamics and Persistence of Memory in Advection versus Diffusion Dominated
  Solar Convection Zones

abstract:
  The predictability, or lack thereof, of the solar cycle is governed by
numerous separate physical processes that act in unison in the interior of the
Sun. Magnetic flux transport and the finite time delay it introduces,
specifically in the so-called Babcock-Leighton models of the solar cycle with
spatially segregated source regions for the alpha and omega effects, play a
crucial rule in this predictability. Through dynamo simulations with such a
model, we study the physical basis of solar cycle predictions by examining two
contrasting regimes, one dominated by diffusive magnetic flux transport in the
solar convection zone, the other dominated by advective flux transport by
meridional circulation. Our analysis shows that diffusion plays an important
role in flux transport, even when the solar cycle period is governed by the
meridional flow speed. We further examine the persistence of memory of past
cycles in the advection and diffusion dominated regimes through stochastically
forced dynamo simulations. We find that in the advection-dominated regime, this
memory persists for up to three cycles, whereas in the diffusion-dominated
regime, this memory persists for mainly one cycle. This indicates that solar
cycle predictions based on these two different regimes would have to rely on
fundamentally different inputs - which may be the cause of conflicting
predictions. Our simulations also show that the observed solar cycle
amplitude-period relationship arises more naturally in the diffusion dominated
regime, thereby supporting those dynamo models in which diffusive flux
transport plays a dominant role in the solar convection zone.


title: A Dirac type result on Hamilton cycles in oriented graphs

abstract:
  We show that for each \alpha>0 every sufficiently large oriented graph G with
\delta^+(G),\delta^-(G)\ge 3|G|/8+ \alpha |G| contains a Hamilton cycle. This
gives an approximate solution to a problem of Thomassen. In fact, we prove the
stronger result that G is still Hamiltonian if
\delta(G)+\delta^+(G)+\delta^-(G)\geq 3|G|/2 + \alpha |G|. Up to the term
\alpha |G| this confirms a conjecture of H\"aggkvist. We also prove an Ore-type
theorem for oriented graphs.


title:
Generalized squeezing operators, bipartite Wigner functions and
  entanglement via Wehrl's entropy functionals

abstract:
  We introduce a new class of unitary transformations based on the su(1,1) Lie
algebra that generalizes, for certain particular representations of its
generators, well-known squeezing transformations in quantum optics. To
illustrate our results, we focus on the two-mode bosonic representation and
show how the parametric amplifier model can be modified in order to generate
such a generalized squeezing operator. Furthermore, we obtain a general
expression for the bipartite Wigner function which allows us to identify two
distinct sources of entanglement, here labelled by dynamical and kinematical
entanglement. We also establish a quantitative estimate of entanglement for
bipartite systems through some basic definitions of entropy functionals in
continuous phase-space representations.


title:
Introduction to Tropical Geometry (notes from the IMPA lectures in
  Summer 2007)

abstract:
  These condensed notes treat some basic notions in Tropical Geometry
(varieties, cycles, modifications, equivalence). These topics are to be
extended, illustrated and included to the upcoming book project
http://www.math.toronto.edu/mikha/book.pdf .


title:
A template bank to search for gravitational waves from inspiralling
  compact binaries: II. Phenomenological model

abstract:
  Matched filtering is used to search for gravitational waves emitted by
inspiralling compact binaries in data from ground-based interferometers. One of
the key aspects of the detection process is the deployment of a set of
templates, also called a template bank, to cover the astrophysically
interesting region of the parameter space. In a companion paper, we described
the template-bank algorithm used in the analysis of LIGO data to search for
signals from non-spinning binaries made of neutron star and/or stellar-mass
black holes; this template bank is based upon physical template families. In
this paper, we describe the phenomenological template bank that was used to
search for gravitational waves from non-spinning black hole binaries (from
stellar mass formation) in the second, third and fourth LIGO science runs. We
briefly explain the design of the bank, whose templates are based on a
phenomenological detection template family. We show that this template bank
gives matches greater than 95% with the physical template families that are
expected to be captured by the phenomenological templates.


title:
Disproof of modularity of moduli space of CY 3-folds of double covers of
  P3 ramified along eight planes in general positions

abstract:
  We prove that the moduli space of Calabi-Yau 3-folds coming from eight planes
of $P^3$ in general positions is not modular. In fact we show the stronger
statement that the Zariski closure of the monodromy group is actually the whole
$Sp(20,R)$. We construct an interesting submoduli, which we call
\emph{hyperelliptic locus}, over which the weight 3 $Q$-Hodge structure is the
third wedge product of the weight 1 $Q$-Hodge structure on the corresponding
hyperelliptic curve. The non-extendibility of the hyperelliptic locus inside
the moduli space of a genuine Shimura subvariety is proved.


title:
Possibility of a modification of life time of radioactive elements by
  magnetic monopoles

abstract:
  A simple explanation of the fact that light magnetic monopoles have not been
observed at accelerator experiments is given. It is based on a possibility of
violation of C invariance in the electromagnetic interactions. Because of the
difficulty of monopole registration, two interconnected problems arise: to
formulate a theory describing monopole production (it should include a new
force beyond the Standard Model of electroweak interaction), and to point the
way to monopole observation. We consider a possibility, closely related to some
experiments, of a modification of life time of radioactive elements by magnetic
monopoles. The first part of the article is devoted to purely electromagnetic
impact of monopoles, caused by the vertex M --> M + gamma. The second part,
more speculative one, is based on experimental evidences in favour of the
existence of some axial vector currents, responsible for a new force, which can
stimulate, or suppress, decays of radioactive elements.


title:
Exact Solutions of the Equations of Relativistic Hydrodynamics
  Representing Potential Flows

abstract:
  We use a connection between relativistic hydrodynamics and scalar field
theory to generate exact analytic solutions describing non-stationary
inhomogeneous flows of the perfect fluid with one-parametric equation of state
(EOS) $p = p(\epsilon)$. For linear EOS $p = \kappa \epsilon$ we obtain
self-similar solutions in the case of plane, cylindrical and spherical
symmetries. In the case of extremely stiff EOS ($\kappa=1$) we obtain
''monopole + dipole'' and ''monopole + quadrupole'' axially symmetric
solutions. We also found some nonlinear EOSs that admit analytic solutions.


title: Computational details on the disproof of modularity

abstract:
  The purpose of these notes is to provide the details of the Jacobian ring
computations carried out in [1], based on the computer algebra system Magma
[2].


title: Mass transport in a strongly sheared binary mixture of Maxwell molecules

abstract:
  Transport coefficients associated with the mass flux of a binary mixture of
Maxwell molecules under uniform shear flow are exactly determined from the
Boltzmann kinetic equation. A normal solution is obtained via a
Chapman--Enskog-like expansion around a local shear flow distribution that
retains all the hydrodynamics orders in the shear rate. In the first order of
the expansion the mass flux is proportional to the gradients of mole fraction,
pressure, and temperature but, due to the anisotropy induced in the system by
the shear flow, mutual diffusion, pressure diffusion and thermal diffusion
tensors are identified instead of the conventional scalar coefficients. These
tensors are obtained in terms of the shear rate and the parameters of the
mixture (particle masses, concentrations, and force constants). The description
is made both in the absence and in the presence of an external thermostat
introduced in computer simulations to compensate for the viscous heating. As
expected, the analysis shows that there is not a simple relationship between
the results with and without the thermostat. The dependence of the three
diffusion tensors on the shear rate is illustrated in the tracer limit case,
the results showing that the deviation of the generalized transport
coefficients from their equilibrium forms is in general quite important.
Finally, the generalized transport coefficients associated with the momentum
and heat transport are evaluated from a model kinetic equation of the Boltzmann
equation.


title: A Sudoku Game for People with Motor Impairments

abstract:
  Computer games are motivating and beneficial in learning different
educational skills. Most people use their fingers, hands, and arms when using a
computer game. However, for people with motor disabilities this task can be a
barrier. We present a new Sudoku game for people whose motion is impaired,
called Sudoku 4ALL. With this special interface a person can control the game
with the voice or with a single switch. Our research aims to cautiously search
for issues that might be appropriate for computational support and to build
enabling technologies that increase individuals' functional independence in a
game environment.


title: Spin-orbit coupling effects in one-dimensional ballistic quantum wires

abstract:
  We study the spin-dependent electronic transport through a one-dimensional
ballistic quantum wire in the presence of Rashba spin-orbit interaction. In
particular, we consider the effect of the spin-orbit interaction resulting from
the lateral confinement of the two-dimensional electron gas to the
one-dimensional wire geometry. We generalize a situation suggested earlier [P.
Streda and P. Seba, Phys. Rev. Lett. 90, 256601 (2003)] which allows for
spin-polarized electron transport. As a result of the lateral confinement, the
spin is rotated out of the plane of the two-dimensional system. We furthermore
investigate the spin-dependent transmission and the polarization of an electron
current at a potential barrier. Finally, we construct a lattice model which
shows similar low-energy physics. In the future, this lattice model will allow
us to study how the electron-electron interaction affects the transport
properties of the present setup.


title: Joint Bayesian component separation and CMB power spectrum estimation

abstract:
  We describe and implement an exact, flexible, and computationally efficient
algorithm for joint component separation and CMB power spectrum estimation,
building on a Gibbs sampling framework. Two essential new features are 1)
conditional sampling of foreground spectral parameters, and 2) joint sampling
of all amplitude-type degrees of freedom (e.g., CMB, foreground pixel
amplitudes, and global template amplitudes) given spectral parameters. Given a
parametric model of the foreground signals, we estimate efficiently and
accurately the exact joint foreground-CMB posterior distribution, and therefore
all marginal distributions such as the CMB power spectrum or foreground
spectral index posteriors. The main limitation of the current implementation is
the requirement of identical beam responses at all frequencies, which restricts
the analysis to the lowest resolution of a given experiment. We outline a
future generalization to multi-resolution observations. To verify the method,
we analyse simple models and compare the results to analytical predictions. We
then analyze a realistic simulation with properties similar to the 3-yr WMAP
data, downgraded to a common resolution of 3 degree FWHM. The results from the
actual 3-yr WMAP temperature analysis are presented in a companion Letter.


title:
A new semilocal convergence theorem for the Weierstrass method from data
  at one point

abstract:
  In this paper we present a new semilocal convergence theorem from data at one
point for the Weierstrass iterative method for the simultaneous computation of
polynomial zeros. The main result generalizes and improves all previous ones in
this area.


title:
Spitzer-MIPS survey of the young stellar content in the Vela Molecular
  Cloud-D

abstract:
  A new, unbiased Spitzer-MIPS imaging survey (~1.8 square degs) of the young
stellar content of the Vela Molecular Cloud-D is presented. The survey is
complete down to 5mJy and 250mJy at 24micron (mu) and 70mu, respectively. 849
sources are detected at 24mu and 52 of them also have a 70mu counterpart. The
VMR-D region is one that we have already partially mapped in dust and gas
millimeter emission, and we discuss the correlation between the Spitzer compact
sources and the mm contours. About half of the 24mu sources are located inside
the region delimited by the 12CO(1-0) contours (corresponding to only one third
of the full area mapped with MIPS) with a consequent density increase of about
100% of the 24mu sources [four times for 70mu ones] moving from outside to
inside the CO contours. About 400 sources have a 2MASS counterpart. So we have
constructed a Ks vs. Ks-[24] diagram and identified the protostellar
population. We find an excess of Class I sources in VMR-D in comparison with
other star forming regions. This result is reasonably biased by the sensitivity
limits, or, alternatively, may reflect a very short lifetime (<=10^6yr) of the
protostellar content in this cloud. The MIPS images have identified embedded
cool objects in most of the previously identified starless cores; in addition,
there are 6 very young, possibly Class 0 objects identified. Finally we report
finding of the driving sources for a set of five out of six very compact
protostellar jets previously discovered in near-infrared images.


title: Fermionic Quasi-free States and Maps in Information Theory

abstract:
  This paper and the results therein are geared towards building a basic
toolbox for calculations in quantum information theory of quasi-free fermionic
systems. Various entropy and relative entropy measures are discussed and the
calculation of these reduced to evaluating functions on the one-particle
component of quasi-free states.
  The set of quasi-free affine maps on the state space is determined and fully
characterized in terms of operations on one-particle subspaces. For a subclass
of trace preserving completely positive maps and for their duals, Choi matrices
and Jamiolkowski states are discussed.


title:
A complex semigroup approach to group algebras of infinite dimensional
  Lie groups

abstract:
  A host algebra of a topological group G is a C^*-algebra whose
representations are in one-to-one correspondence with certain continuous
unitary representations of G. In this paper we present an approach to host
algebras for infinite dimensional Lie groups which is based on complex
involutive semigroups. Any locally bounded absolute value \alpha on such a
semigroup S leads in a natural way to a C^*-algebra C^*(S,\alpha), and we
describe a setting which permits us to conclude that this C^*-algebra is a host
algebra for a Lie group G. We further explain how to attach to any such host
algebra an invariant weak-*-closed convex set in the dual of the Lie algebra of
G enjoying certain nice convex geometric properties. If G is the additive group
of a locally convex space, we describe all host algebras arising this way. The
general non-commutative case is left for the future.


title: Lie groups of bundle automorphisms and their extensions

abstract:
  We describe natural abelian extensions of the Lie algebra $\aut(P)$ of
infinitesimal automorphisms of a principal bundle over a compact manifold $M$
and discuss their integrability to corresponding Lie group extensions. Already
the case of a trivial bundle $P = M \times K$ is quite interesting. In this
case, we show that essentially all central extensions of the gauge algebra
$C^\infty(M,\fk)$ can be obtained from three fundamental types of cocycles with
values in one of the spaces $\fz := C^\infty(M,V)$, $\Omega^1(M,V)$ and
$\Omega^1(M,V)/\dd C^\infty(M,V)$. These cocycles extend to $\aut(P)$, and,
under the assumption that $TM$ is trivial, we also describe the space
$H^2({\cal V}(M),\fz)$ classifying the twists of these extensions. We then show
that all fundamental types have natural generalizations to non-trivial bundles
and explain under which conditions they extend to $\aut(P)$ and integrate to
global Lie group extensions.


title: On convexity of the frequency response of a stable polynomial

abstract:
  In the complex plane, the frequency response of a univariate polynomial is
the set of values taken by the polynomial when evaluated along the imaginary
axis. This is an algebraic curve partitioning the plane into several connected
components. In this note it is shown that the component including the origin is
exactly representable by a linear matrix inequality if and only if the
polynomial is stable, in the sense that all its roots have negative real parts.


title:
Broadband dielectric response of CaCu3Ti4O12: From dc to the electronic
  transition regime

abstract:
  We report on phonon properties and electronic transitions in CaCu3Ti4O12, a
material which reveals a colossal dielectric constant at room temperature
without any ferroelectric transition. The results of far- and mid-infrared
measurements are compared to those obtained by broadband dielectric and
millimeter-wave spectroscopy on the same single crystal. The unusual
temperature dependence of phonon eigenfrequencies, dampings and ionic plasma
frequencies of low lying phonon modes are analyzed and discussed in detail.
Electronic excitations below 4 eV are identified as transitions between full
and empty hybridized oxygen-copper bands and between oxygen-copper and
unoccupied Ti 3d bands. The unusually small band gap determined from the
dc-conductivity (~200 meV) compares well with the optical results.


title:
Direct measurements of the effects of salt and surfactant on interaction
  forces between colloidal particles at water-oil interfaces

abstract:
  The forces between colloidal particles at a decane-water interface, in the
presence of low concentrations of a monovalent salt (NaCl) and of the
surfactant sodium dodecylsulfate (SDS) in the aqueous subphase, have been
studied using laser tweezers. In the absence of electrolyte and surfactant,
particle interactions exhibit a long-range repulsion, yet the variation of the
interaction for different particle pairs is found to be considerable. Averaging
over several particle pairs was hence found to be necessary to obtain reliable
assessment of the effects of salt and surfactant. It has previously been
suggested that the repulsion is consistent with electrostatic interactions
between a small number of dissociated charges in the oil phase, leading to a
decay with distance to the power -4 and an absence of any effect of electrolyte
concentration. However, the present work demonstrates that increasing the
electrolyte concentration does yield, on average, a reduction of the magnitude
of the interaction force with electrolyte concentration. This implies that
charges on the water side also contribute significantly to the electrostatic
interactions. An increase in the concentration of SDS leads to a similar
decrease of the interaction force. Moreover the repulsion at fixed SDS
concentrations decreases over longer times. Finally, measurements of three-body
interactions provide insight into the anisotropic nature of the interactions.
The unique time-dependent and anisotropic interactions between particles at the
oil-water interface allow tailoring of the aggregation kinetics and structure
of the suspension structure.


title: Wrong Priors

abstract:
  All priors are not created equal. There are right and there are wrong priors.
That is the main conclusion of this contribution. I use, a cooked-up example
designed to create drama, and a typical textbook example to show the
pervasiveness of wrong priors in standard statistical practice.


title:
Semilocal convergence of two iterative methods for simultaneous
  computation of polynomial zeros

abstract:
  In this paper we study some iterative methods for simultaneous approximation
of polynomial zeros. We give new semilocal convergence theorems with error
bounds for Ehrlich's and Nourein's iterations. Our theorems generalize and
improve recent results of Zheng and Huang [J. Comput. Math. 18 (2000),
113--122], Petkovi\'c and Herceg [J. Comput. Appl. Math. 136 (2001), 283--307]
and Nedi\'c [Novi Sad J. Math. 31 (2001), 103--111]. We also present a new
sufficient condition for simple zeros of a polynomial.


title:
A Compromise between Neutrino Masses and Collider Signatures in the
  Type-II Seesaw Model

abstract:
  A natural extension of the standard $SU(2)_{\rm L} \times U(1)_{\rm Y}$ gauge
model to accommodate massive neutrinos is to introduce one Higgs triplet and
three right-handed Majorana neutrinos, leading to a $6\times 6$ neutrino mass
matrix which contains three $3\times 3$ sub-matrices $M_{\rm L}$, $M_{\rm D}$
and $M_{\rm R}$. We show that three light Majorana neutrinos (i.e., the mass
eigenstates of $\nu_e$, $\nu_\mu$ and $\nu_\tau$) are exactly massless in this
model, if and only if $M_{\rm L} = M_{\rm D} M_{\rm R}^{-1} M_{\rm D}^T$
exactly holds. This no-go theorem implies that small but non-vanishing neutrino
masses may result from a significant but incomplete cancellation between
$M_{\rm L}$ and $M_{\rm D} M_{\rm R}^{-1} M_{\rm D}^T$ terms in the Type-II
seesaw formula, provided three right-handed Majorana neutrinos are of ${\cal
O}(1)$ TeV and experimentally detectable at the LHC. We propose three simple
Type-II seesaw scenarios with the $A_4 \times U(1)_{\rm X}$ flavor symmetry to
interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such
a TeV-scale neutrino model can be tested in two complementary ways: (1)
searching for possible collider signatures of lepton number violation induced
by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and
(2) searching for possible consequences of unitarity violation of the $3\times
3$ neutrino mixing matrix in the future long-baseline neutrino oscillation
experiments.


title: A Synthetical Weights' Dynamic Mechanism for Weighted Networks

abstract:
  We propose a synthetical weights' dynamic mechanism for weighted networks
which takes into account the influences of strengths of nodes, weights of links
and incoming new vertices. Strength/Weight preferential strategies are used in
these weights' dynamic mechanisms, which depict the evolving strategies of many
real-world networks. We give insight analysis to the synthetical weights'
dynamic mechanism and study how individual weights' dynamic strategies interact
and cooperate with each other in the networks' evolving process. Power-law
distributions of strength, degree and weight, nontrivial strength-degree
correlation, clustering coefficients and assortativeness are found in the model
with tunable parameters representing each model. Several homogenous
functionalities of these independent weights' dynamic strategy are generalized
and their synergy are studied.


title: Maximum Entropy Principle for the Microcanonical Ensemble

abstract:
  We derive the microcanonical ensemble from the Maximum Entropy Principle
(MEP) using the phase space volume entropy of P. Hertz. Maximizing this entropy
with respect to the probability distribution with the constraints of
normalization and average energy, we obtain the condition of constant energy.
This approach is complementary to the traditional derivation of the
microcanonical ensemble from the MEP using Shannon entropy and assuming a
priori that the energy is constant which results in equal probabilities.


title: Total angular momentum from Dirac eigenspinors

abstract:
  The eigenvalue problem for Dirac operators, constructed from two connections
on the spinor bundle over closed spacelike 2-surfaces, is investigated. A class
of divergence free vector fields, built from the eigenspinors, are found,
which, for the lowest eigenvalue, reproduce the rotation Killing vectors of
metric spheres, and provide rotation BMS vector fields at future null infinity.
This makes it possible to introduce a well defined, gauge invariant spatial
angular momentum at null infinity, which reduces to the standard expression in
stationary spacetimes. The general formula for the angular momentum flux
carried away be the gravitational radiation is also derived.


title:
On the Metallicity-Color Relations and Bimodal Color Distributions in
  Extragalactic Globular Cluster Systems

abstract:
  We perform a series of numerical experiments to study how the nonlinear
metallicity--color relations predicted by different stellar population models
affect the color distributions observed in extragalactic globular cluster
systems. % We present simulations in the $UBVRIJHK$ bandpasses based on five
different sets of simple stellar population (SSP) models. The presence of
photometric scatter in the colors is included as well. % We find that unimodal
metallicity distributions frequently ``project'' into bimodal color
distributions. The likelihood of this effect depends on both the mean and
dispersion of the metallicity distribution, as well as of course on the SSP
model used for the transformation. % Adopting the Teramo-SPoT SSP models for
reference, we find that optical--to--near-IR colors should be favored with
respect to other colors to avoid the bias effect in globular cluster color
distributions discussed by \citet{yoon06}. In particular, colors such as \vh\
or \vk are more robust against nonlinearity of the metallicity--color relation,
and an observed bimodal distribution in such colors is more likely to indicate
a true underlying bimodal metallicity distribution. Similar conclusions come
from the simulations based on different SSP models, although we also identify
exceptions to this result.


title: Johnson Type Bounds on Constant Dimension Codes

abstract:
  Very recently, an operator channel was defined by Koetter and Kschischang
when they studied random network coding. They also introduced constant
dimension codes and demonstrated that these codes can be employed to correct
errors and/or erasures over the operator channel. Constant dimension codes are
equivalent to the so-called linear authentication codes introduced by Wang,
Xing and Safavi-Naini when constructing distributed authentication systems in
2003. In this paper, we study constant dimension codes. It is shown that
Steiner structures are optimal constant dimension codes achieving the
Wang-Xing-Safavi-Naini bound. Furthermore, we show that constant dimension
codes achieve the Wang-Xing-Safavi-Naini bound if and only if they are certain
Steiner structures. Then, we derive two Johnson type upper bounds, say I and
II, on constant dimension codes. The Johnson type bound II slightly improves on
the Wang-Xing-Safavi-Naini bound. Finally, we point out that a family of known
Steiner structures is actually a family of optimal constant dimension codes
achieving both the Johnson type bounds I and II.


title:
Techniques for the calculation of electroweak radiative corrections at
  the one-loop level and results for W-physics at LEP200

abstract:
  We review the techniques necessary for the calculation of virtual electroweak
and soft photonic corrections at the one-loop level. In particular we describe
renormalization, calculation of one-loop integrals and evaluation of one-loop
Feynman amplitudes. We summarize many explicit results of general relevance. We
give the Feynman rules and the explicit form of the counter terms of the
electroweak standard model, we list analytical expressions for scalar one-loop
integrals and reduction of tensor integrals, we present the decomposition of
the invariant matrix element for processes with two external fermions and we
give the analytic form of soft photonic corrections. These techniques are
applied to physical processes with external W-bosons. We present the full set
of analytical formulae and the corresponding numerical results for the decay
width of the W-boson and the top quark. We discuss the cross section for the
production of W-bosons in e^{+}e^{-}-annihilaton including all O(alpha)
radiative corrections and finite width effects. Improved Born approximations
for these processes are given.


title:
Brane backreactions and the Fischler-Susskind mechanism in conformal
  field theory

abstract:
  The backreaction of D-branes on closed string moduli is studied in perturbed
conformal field theory. To this end we analyse the divergences in the modular
integral of the annulus diagram. By the Fischler-Susskind mechanism, these
divergences lead to additional terms in the bulk renormalisation group
equations. We derive explicit expressions for these backreaction terms, and
follow the resulting renormalisation group flow in several examples, finding
agreement with geometric expectations.


title: Growth of Subharmonic Functions

abstract:
  In this course of lectures we give an account of the growth theory of
subharmonic functions, which is directed towards its applications to entire
functions of one and several complex variables.


title: Angular momentum of isolated systems

abstract:
  Penrose's twistorial approach to the definition of angular momentum at null
infinity is developed so that angular momenta at different cuts can be
meaningfully compared. This is done by showing that the twistor spaces
associated with different cuts of scri can be identified as manifolds (but not
as vector spaces). The result is a well-defined, Bondi-Metzner-Sachs-invariant
notion of angular momentum in a radiating space-time; the difficulties and
ambiguities previously encountered are attached to attempts to express this in
special-relativistic terms, and in particular to attempts to identify a single
Minkowski space of origins. Unlike the special-relativistic case, the angular
momentum cannot be represented by a purely j=1 quantity M_{ab}, but has
higher-j contributions as well. Applying standard kinematic prescriptions,
these higher-j contributions are shown to correspond precisely to the shear.
Thus it appears that shear and angular momentum should be regarded as different
aspects of a single unified concept.


title: Two-scale homogenization of piezoelectric perforated structures

abstract:
  We are interested in the homogenization of elastic-electric coupling
equation, with rapidly oscillating coefficients, in periodically perforated
piezoelectric body. We justify the two first terms in the usual asymptotic
development of the problem solution. For the main convergence results of this
paper, we use the notion of {\it two-scale convergence}. A two-scale
homogenized system is obtained as the limit of the periodic problem. While in
the static limit the method provides homogenized electroelastic coefficients
whicht coincide with those deduced from other homogenization techniques
(asymptotic homogenization, $\Gamma$-convergence).


title: On the Protocol Composition Logic PCL

abstract:
  A recent development in formal security protocol analysis is the Protocol
Composition Logic (PCL). We identify a number of problems with this logic as
well as with extensions of the logic, as defined in
[DDMP05,HSD+05,He05,Dat05,Der06,DDMR07]. The identified problems imply strong
restrictions on the scope of PCL, and imply that some currently claimed PCL
proofs cannot be proven within the logic, or make use of unsound axioms. Where
possible, we propose solutions for these problems.


title: Examining exotic structure of proton-rich nucleus $^{23}$Al

abstract:
  The longitudinal momentum distribution (P_{//}) of fragments after one-proton
removal from ^{23} Al and reaction cross sections (\sigma_R) for
  ^{23,24} Al on carbon target at 74A MeV have been measured. The ^{23,24} Al
ions were produced through projectile fragmentation of 135 A MeV ^{28} Si
primary beam using RIPS fragment separator at RIKEN. P_{//} is measured by a
direct time-of-flight (TOF) technique, while \sigma_R is determined using a
transmission method. An enhancement in \sigma_R is observed for ^{23} Al
compared with ^{24} Al. The P_{//} for ^{22} Mg fragments from ^{23} Al breakup
has been obtained for the first time. FWHM of the distributions has been
determined to be 232 \pm 28 MeV/c. The experimental data are discussed by using
Few-Body Glauber model. Analysis of P_{//} demonstrates a dominant d-wave
configuration for the valence proton in ground state of ^{23} Al, indicating
that ^{23} Al is not a proton halo nucleus.


title: Microcanonical phase transitions in small systems

abstract:
  When studying the thermodynamic properties of mesoscopic systems the most
appropriate microcanonical entropy is the volume entropy, i.e. the logarithm of
the volume of phase space enclosed by the hypersurface of constant energy. For
systems with broken ergodicity, the volume entropy has discontinuous jumps at
values of energy that correspond to separatrix trajectories. Simultaneously
there is a convex intruder in the entropy function and a region of negative
specific heat below such critical energies. We illustrate this with a simple
model composed of a chain of 3 particles which interact via a Lennard-Jones
potential.


title:
Phase diagram of two-flavor quark matter: Gluonic phase at nonzero
  temperature

abstract:
  The phase structure of neutral two-flavor quark matter at nonzero temperature
is studied. Our analysis is performed within the framework of a gauged
Nambu--Jona-Lasinio model and the mean-field approximation. We compute the free
energy of the gluonic phase (gluonic cylindrical phase II) in a self-consistent
manner and investigate the phase transition from the gluonic phase to the
2SC/g2SC/NQ phases. We briefly consider the phase diagram in the plane of
coupling strength versus temperature and discuss the mixed phase consisting of
the normal quark and 2SC phases.


title: On some asymptotically flat manifolds with non maximal volume growth

abstract:
  Asymptotically flat manifolds with Euclidean volume growth are known to be
ALE. In this paper, we consider a class of asymptotically flat manifolds with
slower volume growth and prove that their asymptotic geometry is that of a
fibration over an ALE manifold. In particular, we show that gravitational
instantons with cubic volume growth are ALF.


title:
Linear response subordination to intermittent energy release in
  off-equilibrium aging dynamics

abstract:
  The interpretation of experimental and numerical data describing
off-equilibrium aging dynamics crucially depends on the connection between
spontaneous and induced fluctuations. The hypothesis that linear response
fluctuations are statistically subordinated to irreversible outbursts of
energy, so-called quakes, leads to predictions for averages and fluctuations
spectra of physical observables in reasonable agreement with experimental
results [see e.g. Sibani et al., Phys. Rev. B74:224407, 2006]. Using
simulational data from a simple but representative Ising model with plaquette
interactions, direct statistical evidence supporting the hypothesis is
presented and discussed in this work.
  A strict temporal correlation between quakes and intermittent magnetization
fluctuations is demonstrated. The external magnetic field is shown to bias the
pre-existent intermittent tails of the magnetic fluctuation distribution, with
little or no effect on the Gaussian part of the latter. Its impact on energy
fluctuations is shown to be negligible.
  Linear response is thus controlled by the quakes and inherits their temporal
statistics. These findings provide a theoretical basis for analyzing
intermittent linear response data from aging system in the same way as thermal
energy fluctuations, which are far more difficult to measure.


title: Flux saturation number of superconducting rings

abstract:
  The distributions of electrical current and magnetic field in a thin-film
superconductor ring is calculated by solving the London equation. The maximum
amount of flux trapped by the hole, the fluxoid saturation number, is obtained
by limiting the current density by the depairing current. The results are
compare it with similar results derived for the bulk case of a long hollow
cylinder [Nordborg & Vinokur, Phys. Rev. B 62, 12408 (2000)]. In the limit of
small holes our result reduces to the Pearl solution for an isolated vortex in
a thin film. For large hole radius, the ratio between saturation numbers in
bulk and film superconductors is proportional to the square root of the hole
size.


title: Spin asymmetries in jet-hyperon production at LHC

abstract:
  We consider polarized Lambda hyperon production in proton-proton scattering,
p p -> (\Lambda^\uparrow jet) jet X, in the kinematical region of the LHC
experiments, in particular the ALICE experiment. We present a new Lambda
polarization observable that arises from the Sivers effect in the fragmentation
process. It can be large even at midrapidity and therefore, is of interest for
high energy hadron collider experiments. Apart from its potential to shed light
on the mechanisms behind the phenomenon of Lambda polarization arising in
unpolarized hadronic collisions, the new observable in principle also allows to
test the possible color flow dependence of single spin asymmetries and the
(non)universality of transverse momentum dependent fragmentation functions.


title: The Horn conjecture for compact selfadjoint operators

abstract:
  We determine the possible eigenvalues of compact selfadjoint operators
A,B,C... with the property that A=B+C+... When all these operators are
positive, the eigenvalues were known to be subject to certain inequalities
which extend Horn's inequalities from the finite-dimensional case when A=B+C.
We find the proper extension of the Horn inequalities and show that they, along
with their reverse analogues, provide a complete characterization. Our results
also allow us to discuss the more general situation where only some of the
eigenvalues of the operators are specified. A special case is the requirement
that B+C+... be positive of rank at most r.


title: Universality of the diffusion wake in the gauge-string duality

abstract:
  As a particle moves through a fluid, it may generate a laminar wake behind
it. In the gauge-string duality, we show that such a diffusion wake is created
by a heavy quark moving through a thermal plasma and that it has a universal
strength when compared to the total drag force exerted on the quark by the
plasma. The universality extends over all asymptotically anti-de Sitter
supergravity constructions with arbitrary scalar matter. We discuss how these
results relate to the linearized hydrodynamic approximation and how they bear
on our understanding of di-hadron correlators in heavy ion collisions.


title: Thermodynamic scaling of diffusion in supercooled Lennard-Jones liquids

abstract:
  The manner in which the intermolecular potential u(r) governs structural
relaxation in liquids is a long standing problem in condensed matter physics.
Herein we show that diffusion coefficients for simulated Lennard-Jones m-6
liquids (8<m<36) in normal and moderately supercooled states are a unique
function of the variable rho^g/T, where rho is density and T is temperature.
The scaling exponent g is a material specific constant whose magnitude is
related to the steepness of the repulsive part of u(r), evaluated around the
distance of closest approach between particles probed in the supercooled
regime. Approximations of u(r) in terms of inverse power laws are also
discussed.


title: Geometry of invariant domains in complex semi-simple Lie groups

abstract:
  We investigate the joint action of two real forms of a semi-simple complex
Lie group S by left and right multiplication. After analyzing the orbit
structure, we study the CR structure of closed orbits. The main results are an
explicit formula of the Levi form of closed orbits and the determination of the
Levi cone of generic orbits. Finally, we apply these results to prove
q-completeness of certain invariant domains in S.


title: Persistence in a Random Bond Ising Model of Socio-Econo Dynamics

abstract:
  We study the persistence phenomenon in a socio-econo dynamics model using
computer simulations at a finite temperature on hypercubic lattices in
dimensions up to 5. The model includes a ` social\rq local field which contains
the magnetization at time $t$. The nearest neighbour quenched interactions are
drawn from a binary distribution which is a function of the bond concentration,
$p$. The decay of the persistence probability in the model depends on both the
spatial dimension and $p$. We find no evidence of ` blocking\rq in this model.
We also discuss the implications of our results for possible applications in
the social and economic fields. It is suggested that the absence, or otherwise,
of blocking could be used as a criterion to decide on the validity of a given
model in different scenarios.

categories: q-fin.GN cond-mat.dis-nn physics.comp-ph physics.soc-ph q-fin.ST


title:
Holographic description of glueballs in a deformed AdS-dilaton
  background

abstract:
  We investigate the mass spectra of scalar and vector glueballs in the
so-called bottom-up approach of the AdS/QCD correspondence. The holographic
model of QCD includes a static dilaton background field. We study the
constraints on the masses coming from perturbing the dilaton field and the
geometry of the bulk.


title:
Response Uniformity of the ATLAS Liquid Argon Electromagnetic
  Calorimeter

abstract:
  The construction of the ATLAS electromagnetic liquid argon calorimeter
modules is completed and all the modules are assembled and inserted in the
cryostats. During the production period four barrel and three endcap modules
were exposed to test beams in order to assess their performance, ascertain the
production quality and reproducibility, and to scrutinize the complete energy
reconstruction chain from the readout and calibration electronics to the signal
and energy reconstruction. It was also possible to check the full Monte Carlo
simulation of the calorimeter. The analysis of the uniformity, resolution and
extraction of constant term is presented. Typical non-uniformities of 0.5% and
typical global constant terms of 0.6% are measured for the barrel and end-cap
modules.


title:
HST/NICMOS Observations of Fast Infrared Flickering in the Microquasar
  GRS 1915+105

abstract:
  We report infrared observations of the microquasar GRS 1915+105 using the
NICMOS instrument of the Hubble Space Telescope during 9 visits in April-June
2003. During epochs of high X-ray/radio activity near the beginning and end of
this period, we find that the $1.87 $\um infrared flux is generally low ($\sim
2$ mJy) and relatively steady. However, during the X-ray/radio ``plateau''
state between these epochs, we find that the infrared flux is significantly
higher ($\sim 4-6$ mJy), and strongly variable. In particular, we find events
with amplitudes $\sim 20-30$% occurring on timescales of $\sim 10-20$s
(e-folding timescales of $\sim 30$s). These flickering timescales are several
times faster than any previously-observed infrared variability in GRS 1915+105
and the IR variations exceed corresponding X-ray variations at the same ($\sim
8s$) timescale. These results suggest an entirely new type of infrared
variability from this object. Based on the properties of this flickering, we
conclude that it arises in the plateau-state jet outflow itself, at a distance
$<2.5$ AU from the accretion disk. We discuss the implications of this work and
the potential of further flickering observations for understanding jet
formation around black holes.


title: Remarks on Our Understanding of Quantum Mechanics

abstract:
  Interpretations of key concepts, such as uncertainty relations, kinetic
energy, value of an observable, probability distributions, the projection or
collapse of a wave function postulate, and discrete versus continuous values,
that appear in several excellent textbooks on quantum mechanics are reviewed
and found not to be consistent with our current understanding of quantum
theory. Possible alternatives are suggested.


title: Characterizations of Sobolev inequalities on metric spaces

abstract:
  We present isocapacitary characterizations of Sobolev inequalities in very
general metric measure spaces.


title:
I-V analysis of high-energy lithium-ion-irradiated Si and GaAs solar
  cells

abstract:
  Space-grade Si and GaAs solar cells were irradiated with 15 and 40 MeV
lithium ions. Dark-IV analysis (with and without illumination) reveals
differences in the effects of such irradiation on the different cell types


title:
Multi-Sensor Fusion Method using Dynamic Bayesian Network for Precise
  Vehicle Localization and Road Matching

abstract:
  This paper presents a multi-sensor fusion strategy for a novel road-matching
method designed to support real-time navigational features within advanced
driving-assistance systems. Managing multihypotheses is a useful strategy for
the road-matching problem. The multi-sensor fusion and multi-modal estimation
are realized using Dynamical Bayesian Network. Experimental results, using data
from Antilock Braking System (ABS) sensors, a differential Global Positioning
System (GPS) receiver and an accurate digital roadmap, illustrate the
performances of this approach, especially in ambiguous situations.


title:
Lagrangian Investigation of Auto-ignition in a Hydrogen Jet Flame in a
  Vitiated Co-flow: Animations of Particle Trajectories in Composition Space
  from PDF Model Calculations

abstract:
  PDF model calculations have been performed of the Cabra lifted hydrogen flame
in a vitiated co-flow. Particle trajectories are extracted from the Lagrangian
particle method used to solve the modeled PDF equation. The particle
trajectories in the mixture fraction-temperature plane reveal (at successive
downstream locations): essentially inert mixing between the cold fuel jet and
the hot co-flow; the auto-ignition of very lean particles; and, subsequent
mixing and reaction, leading to near-equilibrium compositions. The purpose of
this paper is to present animations of the particle trajectories obtained using
different turbulent mixing models.


title: Surprises in the suddenly-expanded infinite well

abstract:
  I study the time-evolution of a particle prepared in the ground state of an
infinite well after the latter is suddenly expanded. It turns out that the
probability density $|\Psi(x, t)|^{2}$ shows up quite a surprising behaviour:
for definite times, {\it plateaux} appear for which $|\Psi(x, t)|^{2}$ is
constant on finite intervals for $x$. Elements of theoretical explanation are
given by analyzing the singular component of the second derivative
$\partial_{xx}\Psi(x, t)$. Analytical closed expressions are obtained for some
specific times, which easily allow to show that, at these times, the density
organizes itself into regular patterns provided the size of the box in large
enough; more, above some critical time-dependent size, the density patterns are
independent of the expansion parameter. It is seen how the density at these
times simply results from a construction game with definite rules acting on the
pieces of the initial density.


title: Light fermion masses and chiral freedom

abstract:
  Within the scenario of chiral freedom we compute the quark and lepton masses
of the first two generations in terms of their chiral couplings. This allows us
to make a rough estimate of the size of the chiral couplings, narrowing down
the uncertainty in the chiron contribution to low energy observables, like the
anomalous magnetic moment of the muon. We also extract information about the
chiron mass which determines the size of possible chiron effects at the LHC.


title:
CR-Invariants and the Scattering Operator for Complex Manifolds with
  Boundary

abstract:
  The purpose of this paper is to describe certain CR-covariant differential
operators on a strictly pseudoconvex CR manifold $M$ as residues of the
scattering operator for the Laplacian on an ambient complex K\"{a}hler manifold
$X$ having $M$ as a `CR-infinity.' We also characterize the CR $Q$-curvature in
terms of the scattering operator. Our results parallel earlier results of
Graham and Zworski \cite{GZ:2003}, who showed that if $X$ is an asymptotically
hyperbolic manifold carrying a Poincar\'{e}-Einstein metric, the $Q$-curvature
and certain conformally covariant differential operators on the `conformal
infinity' $M$ of $X$ can be recovered from the scattering operator on $X$. The
results in this paper were announced in \cite{HPT:2006}.


title: Monolithic or hierarchical star formation? A new statistical analysis

abstract:
  We consider an analytic model of cosmic star formation which incorporates
supernova feedback, gas accretion and enriched outflows, reproducing the
history of cosmic star formation, metallicity, supernovae type II rates and the
fraction of baryons allocated to structures. We present a new statistical
treatment of the available observational data on the star formation rate and
metallicity that accounts for the presence of possible systematics. We then
employ a Bayesian Markov Chain Monte Carlo method to compare the predictions of
our model with observations and derive constraints on the 7 free parameters of
the model. We find that the dust correction scheme one chooses to adopt for the
star formation data is critical in determining which scenario is favoured
between a hierarchical star formation model, where star formation is prolonged
by accretion, infall and merging, and a monolithic scenario, where star
formation is rapid and efficient. We distinguish between these modes by
defining a characteristic minimum mass, M > 10^{11} M_solar, in our fiducial
model, for early type galaxies where star formation occurs efficiently. Our
results indicate that the hierarchical star formation model can achieve better
agreement with the data, but that this requires a high efficiency of
supernova-driven outflows. In a monolithic model, our analysis points to the
need for a mechanism that drives metal-poor winds, perhaps in the form of
supermassive black hole-induced outflows. Furthermore, the relative absence of
star formation beyond z ~ 5 in the monolithic scenario requires an alternative
mechanism to dwarf galaxies for reionizing the universe at z ~ 11, as required
by observations of the microwave background. While the monolithic scenario is
less favoured in terms of its quality-of-fit, it cannot yet be excluded.


title: Classification of nonproduct states with maximum stabilizer dimension

abstract:
  Nonproduct n-qubit pure states with maximum dimensional stabilizer subgroups
of the group of local unitary transformations are precisely the generalized
n-qubit Greenberger-Horne-Zeilinger states and their local unitary equivalents,
for n greater than or equal to 3 but not equal to 4. We characterize the Lie
algebra of the stabilizer subgroup for these states. For n=4, there is an
additional maximal stabilizer subalgebra, not local unitary equivalent to the
former. We give a canonical form for states with this stabilizer as well.


title:
Quantifying the Cosmic Web I: The large-scale halo
  ellipticity-ellipticity and ellipticity-direction correlations

abstract:
  The formation of dark matter halos tends to occur anisotropically along the
filaments of the Cosmic Web, which induces both ellipticity-ellipticity (EE)
correlations between the shapes of halos, as well as ellipticity-direction (ED)
cross-correlations between halo shapes and the directions to neighboring halos.
We analyze the halo catalogue and the semi-analytic galaxy catalogue of the
recent Millennium Run Simulation to measure the EE and ED correlations
numerically at four different redshifts (z=0, 0.5, 1 and 2). For the EE
correlations, we find that (i) the major-axis correlation is strongest while
the intermediate-axis correlation is weakest; (ii) the signal is significant at
distances out to 10 Mpc/h; (iii) the signal decreases as z decreases; (iv) and
its behavior depends strongly on the halo mass scale, with larger masses
showing stronger correlations at large distances. For the ED correlations, we
find that (i) the correlations are much stronger than the EE correlations, and
are significant even out to distances of 50 Mpc/h; (ii) the signal also
decreases as z decreases; (iii) and it increases with halo mass at all
distances. We also provide empirical fitting functions for the EE and ED
correlations. The EE correlations are found to scale linearly with the linear
density correlation function, xi(r). While the ED cross-correlation is found to
scale as xi^{1/2}(r) at large distances beyond 10 Mpc/h. The best-fit values of
the fitting parameters for the EE and the ED correlations are all determined
through chi^{2}-statistics. Our results may be useful for quantifying the
filamentary distribution of dark matter halos over a wide range of scales.


title: High-energy black hole production

abstract:
  Black hole production in high-energy collisions is briefly surveyed. Included
is a summary of recent developments and open problems relevant to collider
(LHC) production, as well as of some theoretical issues pointing towards
fundamental principles of quantum gravity.


title: Spike synchronization of a chaotic array as a phase transition

abstract:
  We study how a coupled array of spiking chaotic systems synchronizes to an
external driving in a short time. Synchronization means spike separation at
adjacent sites much shorter than the average inter-spike interval; a local lack
of synchronization is called a defect. The system displays sudden spontaneous
defect disappearance at a critical coupling strength. Below critical coupling,
the system reaches order at a definite amplitude of an external input; this
order persists for a fixed time slot. Thus, the array behaves as an excitable
system, even though the single element lacks such a property. The above
features provide a dynamical explanation of feature binding in perceptual
tasks.


title: Density Perturbations in the Universe from Massive Vector Fields

abstract:
  I discuss the possibility of using a massive vector field to generate the
density perturbation in the Universe. I find that a scale-invariant
superhorizon spectrum of vector field perturbations is possible to generate
during inflation. The associated curvature perturbation is imprinted onto the
Universe following the curvaton scenario. The mechanism does not generate a
long-range anisotropy because an oscillating massive vector field behaves as a
pressureless isotropic fluid.


title: Deformation quantization for actions of the affine group

abstract:
  We define a universal deformation formula (UDF) for the actions of the affine
group on Frechet algebras. More precisely, starting with any associative
Frechet algebra which the affine group acts on in a strongly continuous and
isometrical manner, the UDF produces a family of topological associative
algebra structures on the space of smooth vectors of the action deforming the
initial product. The deformation field obtained is based over an infinite
dimensional parameter space naturally associated with the space of
pseudo-differential operators on the real line. This note also presents some
geometrical aspects of the UDF and in particular its relation with hyperbolic
geometry.


title: On the oscillations in Mercury's obliquity

abstract:
  One major objective of MESSENGER and BepiColombo spatial missions is to
accurately measure Mercury's rotation and its obliquity in order to obtain
constraints on internal structure of the planet. Which is the obliquity's
dynamical behavior deriving from a complete spin-orbit motion of Mercury
simultaneously integrated with planetary interactions? We have used our SONYR
model integrating the spin-orbit N-body problem applied to the solar System
(Sun and planets). For lack of current accurate observations or ephemerides of
Mercury's rotation, and therefore for lack of valid initial conditions for a
numerical integration, we have built an original method for finding the
libration center of the spin-orbit system and, as a consequence, for avoiding
arbitrary amplitudes in librations of the spin-orbit motion as well as in
Mercury's obliquity. The method has been carried out in two cases: (1) the
spin-orbit motion of Mercury in the 2-body problem case (Sun-Mercury) where an
uniform precession of the Keplerian orbital plane is kinematically added at a
fixed inclination (S2K case), (2) the spin-orbit motion of Mercury in the
N-body problem case (Sun and planets) (Sn case). We find that the remaining
amplitude of the oscillations in the Sn case is one order of magnitude larger
than in the S2K case, namely 4 versus 0.4 arcseconds (peak-to-peak). The mean
obliquity is also larger, namely 1.98 versus 1.80 arcminutes, for a difference
of 10.8 arcseconds. These theoretical results are in a good agreement with
recent radar observations but it is not excluded that it should be possible to
push farther the convergence process by drawing nearer still more precisely to
the libration center.


title: Rotating surface solitons

abstract:
  We introduce a novel type of surface waves that form at the edge of guiding
structures consisting of several concentric rings. Such surface waves rotate
steadily upon propagation and, in contrast to nonrotating waves, for high
rotation frequencies they do not exhibit power thresholds for their existence.
There exists an upper limit for the surface wave ro-tation frequency, which
depends on the radius of the outer guiding ring and on its depth.


title: Redshift Distortions as a Probe of Gravity

abstract:
  Redshift distortion measurements from galaxy surveys include sensitivity to
the gravitational growth index distinguishing other theories from Einstein
gravity. This gravitational sensitivity is substantially free from uncertainty
in the effective equation of state of the cosmic expansion history. We also
illustrate the bias in the traditional application to matter density
determination using f=Omega_m(a)^{0.6}, and how to avoid it.


title:
H3+ in Diffuse Interstellar Clouds: a Tracer for the Cosmic-Ray
  Ionization Rate

abstract:
  Using high resolution infrared spectroscopy we have surveyed twenty
sightlines for H3+ absorption. H3+ is detected in eight diffuse cloud
sightlines with column densities varying from 0.6x10^14 cm^-2 to 3.9x10^14
cm^-2. This brings to fourteen the total number of diffuse cloud sightlines
where H3+ has been detected. These detections are mostly along sightlines
concentrated in the Galactic plane, but well dispersed in Galactic longitude.
The results imply that abundant H3+ is common in the diffuse interstellar
medium. Because of the simple chemistry associated with H3+ production and
destruction, these column density measurements can be used in concert with
various other data to infer the primary cosmic-ray ionization rate, zeta_p.
Values range from 0.5x10^-16 s^-1 to 3x10^-16 s^-1 with an average of 2x10^-16
s^-1. Where H3+ is not detected the upper limits on the ionization rate are
consistent with this range. The average value of zeta_p is about an order of
magnitude larger than both the canonical rate and rates previously reported by
other groups using measurements of OH and HD. The discrepancy is most likely
due to inaccurate measurements of rate constants and the omission of effects
which were unknown when those studies were performed. We believe that the
observed column density of H3+ is the most direct tracer for the cosmic-ray
ionization rate due to its simple chemistry. Recent models of diffuse cloud
chemistry require cosmic-ray ionization rates on the order of 10^-16 s^-1 to
reproduce observed abundances of various atomic and molecular species, in rough
accord with our observational findings.


title:
Possible co-existence of local itinerancy and global localization in a
  quasi-one-dimensional conductor

abstract:
  In the chain compound PrBa$_2$Cu$_4$O$_8$ localization appears simultaneously
with a dimensional crossover in the electronic ground state when the scattering
rate in the chains exceeds the hopping rate between the chains. Here we report
the discovery of a large, transverse magnetoresistance in PrBa$_2$Cu$_4$O$_8$
in the localized regime. This result suggests a novel form of localization
whereby electrons retain their metallic (quasi-one-dimensional) character over
a microscopic length scale despite the fact that macroscopically, they exhibit
localized (one-dimensional) behavior.


title: Bifurcation of the ACT map

abstract:
  In this paper, we study the Arneodo-Coullet-Tresser map $
F(x,y,z)=(ax-b(y-z), bx+a(y-z), cx-dx^k+e z)$ where $a,b,c,d,e$ are real with
$bd\neq 0$ and $k>1$ is an integer. We obtain stability regions for fixed
points of $F$ and symmetric period-2 points while $c$ and $e$ vary as
parameters. Varying $a$ and $e$ as parameters, we show that there is a
hyperbolic invariant set on which $F$ is conjugate to the full shift on two or
three symbols. We also show that chaotic behaviors of $F$ while $c$ and $d$
vary as parameters and $F$ is near an anti-integrable limit. Some numerical
results indicates $F$ has Hopf bifurcation, strange attractors, and nested
structure of invariant tori.


title: Theory of Electromotive Force Induced by Domain Wall Motion

abstract:
  We formulate a theory on the dynamics of conduction electrons in the presence
of moving magnetic textures in ferromagnetic materials. We show that the
variation of local magnetization in both space and time gives rise to
topological fields, which induce electromotive forces on the electrons.
Universal results are obtained for the emf induced by both transverse and
vortex domain walls traveling in a magnetic film strip, and their measurement
may provide clear characterization on the motion of such walls.


title: On the uniqueness of certain families of holomorphic disks

abstract:
  A Zoll metric is a Riemannian metric whose geodesics are all circles of equal
length. Via the twistor correspondence of LeBrun and Mason, a Zoll metric on
the 2 dimensional sphere corresponds to a family of holomorphic disks in CP_2
with boundary in a totally real submanifold P. In this paper, we show that for
a fixed totally real submanifold P, such a family is unique if it exists,
implying that the twistor correspondence of LeBrun and Mason is injective. One
of the key ingredients in the proof is the blow-up and blow-down constructions
in the sense of Melrose.


title: Can rigidly rotating polytropes be sources of the Kerr metric?

abstract:
  We use a recent result by Cabezas et al. to build up an approximate solution
to the gravitational field created by a rigidly rotating polytrope. We solve
the linearized Einstein equations inside and outside the surface of zero
pressure including second-order corrections due to rotational motion to get an
asymptotically flat metric in a global harmonic coordinate system. We prove
that if the metric and their first derivatives are continuous on the matching
surface up to this order of approximation, the multipole moments of this metric
cannot be fitted to those of the Kerr metric.


title: Quasi-one-dimensional polarized Fermi superfluids

abstract:
  We calculate the zero temperature phase diagram of a polarized two-component
Fermi gas in an array of weakly-coupled parallel one-dimensional (1D) 'tubes'
produced by a two-dimensional optical lattice. Increasing the lattice strength
drives a crossover from three-dimensional (3D) to 1D behavior, stabilizing the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulated superfluid phase. We argue
that the most promising regime for observing the FFLO phase is in the quasi-1D
regime, where the atomic motion is largely 1D but there is weak tunneling in
the other directions that stabilizes long range order. In the FFLO phase, we
describe a phase transition where the quasiparticle spectrum changes from
gapless near the 3D regime to gapped in quasi-1D.


title: Integral cohomology of certain Picard modular surfaces

abstract:
  Let Gamma be a congruence subgroup of the Picard modular group of an
imaginary number field k, and let D be the associated symmetric space. We
describe a method to compute the integral cohomology of the locally symmetric
space Gamma\D. The method is implemented for the case k=Q(i) and k=Q(sqrt(-3)),
and the cohomology is computed for various Gamma.


title: Takai Duality for Crossed Products by Hilbert C*-bimodules

abstract:
  We discuss the crossed product by the dual action of the circle on the
crossed product of a C*-algebra A by a Hilbert C*-bimodule X. When X is an A-A
Morita equivalence bimodule, the double crossed product is shown to be Morita
equivalent to the C*-algebra A.


title:
Monte-Carlo simulation for fragment mass and kinetic energy
  distributions from neutron induced fission of 235U

abstract:
  The mass and kinetic energy distribution of nuclear fragments from thermal
neutron induced fission of 235U have been studied using a Monte-Carlo
simulation. Besides reproducing the pronounced broadening on the standard
deviation of the final fragment kinetic energy distribution $\sigma_{e}(m)$
around the mass number m = 109, our simulation also produces a second
broadening around m = 125, that is in agreement with the experimental data
obtained by Belhafaf et al. These results are consequence of the
characteristics of the neutron emission, the variation in the primary fragment
mean kinetic energy and the yield as a function of the mass.


title: The Adiabatic Instability on Cosmology's Dark Side

abstract:
  We consider theories with a nontrivial coupling between the matter and dark
energy sectors. We describe a small scale instability that can occur in such
models when the coupling is strong compared to gravity, generalizing and
correcting earlier treatments. The instability is characterized by a negative
sound speed squared of an effective coupled dark matter/dark energy fluid. Our
results are general, and applicable to a wide class of coupled models and
provide a powerful, redshift-dependent tool, complementary to other
constraints, with which to rule many of them out. A detailed analysis and
applications to a range of models are presented in a longer companion paper.


title: Pyroxenes: A new class of multiferroics

abstract:
  Pyroxenes with the general formula $AM$Si$_2$O$_6$ ($A$ = mono- or divalent
metal, $M$ = di- or trivalent metal) are shown to be a new class of
multiferroic materials. In particular, we have found so far that
NaFeSi$_2$O$_6$ becomes ferroelectric in a magnetically ordered state below
$\simeq 6$ K. Similarly, magnetically driven ferroelectricity is also detected
in the Li homologues, LiFeSi$_2$O$_6$ ($T_C \simeq 18$ K) and LiCrSi$_2$O$_6$
($T_C \simeq 11$ K). In all these monoclinic systems the electric polarization
can be strongly modified by magnetic fields. Measurements of magnetic
susceptibility, pyroelectric current and dielectric constants (and their
dependence on magnetic field) are performed using a natural crystal of aegirine
(NaFeSi$_2$O$_6$) and synthetic crystals of LiFeSi$_2$O$_6$ and LiCrSi$_2$O$_6$
grown from melt solution. For NaFeSi$_2$O$_6$ a temperature versus magnetic
field phase diagram for NaFeSi$_2$O$_6$ is proposed. Exchange constants are
computed on the basis of {\it ab initio} band structure calculations. The
possibility of a spiral magnetic structure caused by frustration as origin of
the multiferroic behaviour is discussed. We propose that other pyroxenes may
also be multiferroic, and that the versatility of this family offers an
exceptional opportunity to study general conditions for and mechanisms of
magnetically driven ferroelectricity.


title: Some Monotonicity Properties of Gamma and $q$-gamma Functions

abstract:
  We prove some properties of completely monotonic functions and apply them to
obtain results on gamma and $q$-gamma functions.


title: Spectral numbers in Floer theories

abstract:
  The chain complexes underlying Floer homology theories typically carry a
real-valued filtration, allowing one to associate to each Floer homology class
a spectral number defined as the infimum of the filtration levels of chains
representing that class. These spectral numbers have been studied extensively
in the case of Hamiltonian Floer homology by Oh, Schwarz, and others. We prove
that the spectral number associated to any nonzero Floer homology class is
always finite, and that the infimum in the definition of the spectral number is
always attained. In the Hamiltonian case, this implies that what is known as
the ``nondegenerate spectrality'' axiom holds on all closed symplectic
manifolds. Our proofs are entirely algebraic and apply to any Floer-type theory
(including Novikov homology) satisfying certain standard formal properties. The
key ingredient is a theorem about the existence of best approximations of
arbitrary elements of finitely generated free modules over Novikov rings by
elements of prescribed submodules with respect to a certain family of
non-Archimedean metrics.


title: Adiabatic instability in coupled dark energy-dark matter models

abstract:
  We consider theories in which there exists a nontrivial coupling between the
dark matter sector and the sector responsible for the acceleration of the
universe. Such theories can possess an adiabatic regime in which the
quintessence field always sits at the minimum of its effective potential, which
is set by the local dark matter density. We show that if the coupling strength
is much larger than gravitational, then the adiabatic regime is always subject
to an instability. The instability, which can also be thought of as a type of
Jeans instability, is characterized by a negative sound speed squared of an
effective coupled dark matter/dark energy fluid, and results in the exponential
growth of small scale modes. We discuss the role of the instability in specific
coupled CDM and Mass Varying Neutrino (MaVaN) models of dark energy, and
clarify for these theories the regimes in which the instability can be evaded
due to non-adiabaticity or weak coupling.


title: Analysis on disconnected sets

abstract:
  Some aspects of analysis on disconnected sets are briefly discussed, more
along the lines of regions with infinitely many components than Cantor sets.


title: Properties of charge density waves in La$_{2-x}$Ba$_{x}$CuO$_4$

abstract:
  We report a comprehensive x-ray scattering study of charge density wave
(stripe) ordering in $\rm La_{2-x}Ba_xCuO_4 (x \approx 1/8)$, for which the
superconducting $T_c$ is greatly suppressed. Strong superlattice reflections
corresponding to static ordering of charge stripes were observed in this
sample. The structural modulation at the lowest temperature was deduced based
on the intensity of over 70 unique superlattice positions surveyed. We found
that the charge order in this sample is described with one-dimensional charge
density waves, which have incommensurate wave-vectors (0.23, 0, 0.5) and (0,
0.23, 0.5) respectively on neighboring $\rm CuO_2$ planes. The structural
modulation due to the charge density wave order is simply sinusoidal, and no
higher harmonics were observed. Just below the structural transition
temperature, short-range charge density wave correlation appears, which
develops into a large scale charge ordering around 40 K, close to the spin
density wave ordering temperature. However, this charge ordering fails to grow
into a true long range order, and its correlation length saturates at $\sim
230\AA$, and slightly decreases below about 15 K, which may be due to the onset
of two-dimensional superconductivity.


title: New UltraCool and Halo White Dwarf Candidates in SDSS Stripe 82

abstract:
  A 2.5 x 100 degree region along the celestial equator (Stripe 82) has been
imaged repeatedly from 1998 to 2005 by the Sloan Digital Sky Survey. A new
catalogue of ~4 million light-motion curves, together with over 200 derived
statistical quantities, for objects in Stripe 82 brighter than r~21.5 has been
constructed by combining these data by Bramich et al. (2007). This catalogue is
at present the deepest catalogue of its kind. Extracting the ~130000 objects
with highest signal-to-noise ratio proper motions, we build a reduced proper
motion diagram to illustrate the scientific promise of the catalogue. In this
diagram disk and halo subdwarfs are well-separated from the cool white dwarf
sequence. Our sample of 1049 cool white dwarf candidates includes at least 8
and possibly 21 new ultracool H-rich white dwarfs (T_eff < 4000K) and one new
ultracool He-rich white dwarf candidate identified from their SDSS optical and
UKIDSS infrared photometry. At least 10 new halo white dwarfs are also
identified from their kinematics.


title:
Study of time lags in HETE-2 Gamma-Ray Bursts with redshift: search for
  astrophysical effects and Quantum Gravity signature

abstract:
  The study of time lags between spikes in Gamma-Ray Bursts light curves in
different energy bands as a function of redshift may lead to the detection of
effects due to Quantum Gravity. We present an analysis of 15 Gamma-Ray Bursts
with measured redshift, detected by the HETE-2 mission between 2001 and 2006 in
order to measure time lags related to astrophysical effects and search for
Quantum Gravity signature in the framework of an extra-dimension string model.
The use of photon-tagged data allows us to consider various energy ranges.
Systematic effects due to selection and cuts are evaluated. No significant
Quantum Gravity effect is detected from the study of the maxima of the light
curves and a lower limit at 95% Confidence Level on the Quantum Gravity scale
parameter of 3.2x10**15 GeV is set.


title: The Role of Solvent Fluctuations in Hydrophobic Assembly

abstract:
  We use a coarse grained solvent model to study the self assembly of two
nano-scale hydrophobic particles in water. We show how solvent degrees of
freedom are involved in the process. By using tools of transition path
sampling, we elucidate the reaction coordinates describing the assembly. In
accord with earlier expectations, we find that fluctuations of the
liquid-vapor-like interface surrounding the solutes are significant, in this
case leading to the formation of a vapor tunnel between the two solute
particles. This tunnel accelerates assembly. While considering this specific
model system, the approach we use illustrates a methodology that is broadly
applicable.


title: Almost solutions of equations in permutations

abstract:
  We will say that the permutations f_1,...,f_n is an e-solution of an equation
if the normalized Hamming distance between its l.h.p. and r.h.p. is less than
e. We give a sufficient conditions when near to an e-solution exists an exact
solution and some examples when there does not exist such a solution.


title:
Parameter estimation in diagonalizable bilinear stochastic parabolic
  equations

abstract:
  A parameter estimation problem is considered for a stochastic parabolic
equation with multiplicative noise under the assumption that the equation can
be reduced to an infinite system of uncoupled diffusion processes. From the
point of view of classical statistics, this problem turns out to be singular
not only for the original infinite-dimensional system but also for most
finite-dimensional projections. This singularity can be exploited to improve
the rate of convergence of traditional estimators as well as to construct
completely new closed-form exact estimator.


title: Long Term Radio Monitoring of SN 1993J

abstract:
  We present our observations of the radio emission from supernova (SN) 1993J,
in M 81 (NGC 3031), made with the VLA, from 90 to 0.7 cm, as well as numerous
measurements from other telescopes. The combined data set constitutes probably
the most detailed set of measurements ever established for any SN outside of
the Local Group in any wavelength range. Only SN 1987A in the LMC has been the
subject of such an intensive observational program. The radio emission evolves
regularly in both time and frequency, and the usual interpretation in terms of
shock interaction with a circumstellar medium (CSM) formed by a pre-SN stellar
wind describes the observations rather well considering the complexity of the
phenomenon. However: 1) The 85 - 110 GHz measurements at early times are not
well fitted by the parameterization, unlike the cm wavelength measurements. 2)
At mid-cm wavelengths there is some deviation from the fitted radio light
curves. 3) At a time ~3100 days after shock breakout, the decline rate of the
radio emission steepens without change in the spectral index. This decline is
best described as an exponential decay starting at day 3100 with an e-folding
time of ~1100 days. 4) The best overall fit to all of the data is a model
including both non-thermal synchrotron self-absorption (SSA) and a thermal
free-free absorbing (FFA) components at early times, evolving to a constant
spectral index, optically thin decline rate, until the break in that decline
rate. Moreover, neither a purely SSA nor a purely FFA absorbing models can
provide a fit that simultaneously reproduces the light curves, the spectral
index evolution, and the brightness temperature evolution. 5) The radio and
X-ray light curves exhibit similar behavior and suggest a sudden drop in the SN
progenitor mass-loss rate at ~8000 years prior to shock breakout.


title:
Looking for Super-Earths in the HD 189733 System: A Search for Transits
  in Most Space-Based Photometry

abstract:
  We have made a comprehensive transit search for exoplanets down to ~1.5 - 2
Earth radii in the HD 189733 system, based on 21-days of nearly uninterrupted
broadband optical photometry obtained with the MOST (Microvariability &
Oscillations of STars) satellite in 2006. We have searched these data for
realistic limb-darkened transits from exoplanets other than the known hot
Jupiter, HD 189733b, with periods ranging from about 0.4 days to one week.
Monte Carlo statistical tests of the data with synthetic transits inserted into
the data-set allow us to rule out additional close-in exoplanets with sizes
ranging from about 0.15 - 0.31 RJ (Jupiter radii), or 1.7 - 3.5 RE (Earth
radii) on orbits whose planes are near that of HD 189733b. These null results
constrain theories that invoke lower-mass hot Super-Earth and hot Neptune
planets in orbits similar to HD 189733b due to the inward migration of this hot
Jupiter. This work also illustrates the feasibility of discovering smaller
transiting planets around chromospherically active stars.


title: Characterizing Heavy-Tailed Distributions Induced by Retransmissions

abstract:
  Consider a generic data unit of random size L that needs to be transmitted
over a channel of unit capacity. The channel availability dynamics is modeled
as an i.i.d. sequence {A, A_i},i>0 that is independent of L. During each period
of time that the channel becomes available, say A_i, we attempt to transmit the
data unit. If L<A_i, the transmission was considered successful; otherwise, we
wait for the next available period and attempt to retransmit the data from the
beginning. We investigate the asymptotic properties of the number of
retransmissions N and the total transmission time T until the data is
successfully transmitted. In the context of studying the completion times in
systems with failures where jobs restart from the beginning, it was shown that
this model results in power law and, in general, heavy-tailed delays. The main
objective of this paper is to uncover the detailed structure of this class of
heavy-tailed distributions induced by retransmissions. More precisely, we study
how the functional dependence between P[L>x] and P[A>x] impacts the
distributions of N and T. In particular, we discover several functional
criticality points that separate classes of different functional behavior of
the distribution of N. We also discuss the engineering implications of our
results on communication networks since retransmission strategy is a
fundamental component of the existing network protocols on all communication
layers, from the physical to the application one.


title: Cosmic String Detection via Microlensing of Stars

abstract:
  Cosmic superstrings are produced towards the end of the brane inflation. If
the string tension is low enough, loops tend to be relatively long-lived. The
resultant string network is expected to contain many loops which are smaller
than typical Galactic scales. Cosmic expansion damps the center of mass motion
of the loops which then cluster like cold dark matter. Loops will lens stars
within the galaxy and local group. We explore microlensing of stars as a tool
to detect and to characterize some of the fundamental string and string network
properties, including the dimensionless string tension $G \mu/c^2$ and the
density of string loops within the Galaxy. As $G \mu \to 0$ the intrinsic
microlensing rate diverges as $1/\sqrt{G \mu}$ but experimental detection will
be limited by shortness of the lensing timescale and/or smallness of the
bending angle which each vary $\propto G \mu$. We find that detection is
feasible for a range of tensions. As an illustration, the planned optical
astrometric survey mission, Gaia, should be able to detect numerous
microlensing events for string networks with tensions $10^{-10} \simless G \mu
\simless 10^{-6}$. A null result for optical microlensing implies $G \mu
\simless 10^{-10}$. If lensing of a given source is observed it will repeat
because the internal motions of the loop are relativistic but the center of
mass motion may be much smaller, of order the halo velocity. This distinctive
hallmark $\sim 1000$ repetitions, suggests a useful method for confirmation of
a potential lensing detection.


title:
Interaction Correction of Conductivity Near a Ferromagnetic Quantum
  Critical Point

abstract:
  We calculate the temperature dependence of conductivity due to interaction
correction for a disordered itinerant electron system close to a ferromagnetic
quantum critical point which occurs due to a spin density wave instability. In
the quantum critical regime, the crossover between diffusive and ballistic
transport occurs at a temperature $T^{\ast}=1/[\tau \gamma (E_{F}\tau)^{2}]$,
where $\gamma$ is the parameter associated with the Landau damping of the spin
fluctuations, $\tau$ is the impurity scattering time, and $E_{F}$ is the Fermi
energy. For a generic choice of parameters, $T^{\ast}$ is few orders of
magnitude smaller than the usual crossover scale $1/\tau$. In the ballistic
quantum critical regime, the conductivity has a $T^{(d-1)/3}$ temperature
dependence, where $d$ is the dimensionality of the system. In the diffusive
quantum critical regime we get $T^{1/4}$ dependence in three dimensions, and
$\ln^2 T$ dependence in two dimensions. Away from the quantum critical regime
we recover the standard results for a good metal.


title: Explicit Rational Solution of the KZ Equation (example)

abstract:
  We investigate the Knizhnik-Zamolodchikov linear differential system. The
coefficients of this system are rational functions. We have proved that the
solution of the KZ system is rational when k is equal to two and n is equal to
three (see [5]) . In this paper, we construct the corresponding solution in the
explicit form.


title: Quantum expanders from any classical Cayley graph expander

abstract:
  We give a simple recipe for translating walks on Cayley graphs of a group G
into a quantum operation on any irrep of G. Most properties of the classical
walk carry over to the quantum operation: degree becomes the number of Kraus
operators, the spectral gap becomes the gap of the quantum operation (viewed as
a linear map on density matrices), and the quantum operation is efficient
whenever the classical walk and the quantum Fourier transform on G are
efficient. This means that using classical constant-degree constant-gap
families of Cayley expander graphs on e.g. the symmetric group, we can
construct efficient families of quantum expanders.


title:
Dynamics of femtosecond magnetization reversal induced by circularly
  polarized light in the presence of fluctuations and dissipation

abstract:
  Magnetization reversal by a femtosecond circularly polarized laser pulse has
been recently demonstrated in rare-earth doped transition metals (RE-TM). The
switching mechanism has been attributed to an inverse Faraday effect and
thermal effects. Based on the parameters provided in the experimental work, we
show that this claim is unlikely to give rise to femtosecond reversal. Using a
hybrid itinerant-localized picture of the RE-TM system, we propose
  a new mechanism that requires the presence of the rare earth element to
reduce the symmetry of the system as well as
  a strong enhancement of spin-orbit coupling between the d electrons and the f
moments in the presence of the laser. Our model does not require
  the heating close to the Curie temperature of the sample.


title:
Cosmic Microwave Background Statistics for a Direction-Dependent
  Primordial Power Spectrum

abstract:
  Statistical isotropy of primordial perturbations is a common assumption in
cosmology, but it is an assumption that should be tested. To this end, we
develop cosmic microwave background statistics for a primordial power spectrum
that depends on the direction, as well as the magnitude, of the Fourier
wavevector. We first consider a simple estimator that searches in a
model-independent way for anisotropy in the square of the temperature (and/or
polarization) fluctuation. We then construct the minimum-variance estimators
for the coefficients of a spherical-harmonic expansion of the
direction-dependence of the primordial power spectrum. To illustrate, we apply
these statistics to an inflation model with a quadrupole dependence of the
primordial power spectrum on direction and find that a power quadrupole as
small as 2.0% can be detected with the Planck satellite.


title:
Precise radial velocities of giant stars. III. Spectroscopic stellar
  parameters

abstract:
  Context: A radial velocity survey of about 380 G and K giant stars is ongoing
at Lick observatory. For each star we have a high signal to noise ratio
template spectrum, which we use to determine spectroscopic stellar parameters.
Aim: The aim of this paper is to present spectroscopic stellar parameters, i.e.
effective temperature, surface gravity, metallicity and rotational velocity for
our sample of G and K giant stars. Methods: Effective temperatures, surface
gravities and metallicities are determined from the equivalent width of iron
lines. Rotational velocities are determined from the full width at half maximum
(FWHM) of moderate spectral lines. A calibration between the FWHM and total
broadening (rotational velocity and macro turbulence) is obtained from stars in
common between our sample and the sample from Gray (1989). Results: The
metallicity we derive is essentially equal to the literature values, while the
effective temperature and surface gravity are slightly higher by 56 K and 0.15
dex, respectively. Our rotational velocities are comparable with the ones
obtained by Gray (1989), but somewhat higher than the ones obtained by de
Medeiros & Mayor (1999), consistent with the different diagnostics used.
Conclusions: We are able to determine spectroscopic stellar parameters for
about 380 G and K giant stars in a uniform way (112 stars are being analysed
spectroscopically for the first time). For stars available in the literature,
we find reasonable agreement between literature values and values determined in
the present work. In addition, we show that the metallicity enhancement of
companion hosting stars might also be valid for giant stars, with the
planet-hosting giants being 0.13 +/- 0.03 dex (i.e. 35 +/- 10%) more metal-rich
than our total sample of stars.


title: The influence of polaron size on the conductivity of poly-DNA

abstract:
  The velocity of polaron migration in the long poly-DNA chain (~40 base pairs)
in an applied electric field has been studied within a polaron model. We found
that the polaron velocity strongly depends on the polaron size. A small polaron
shows a slow propagation and strong tolerance to the electric field, while a
large polaron is much faster and less stable with increasing electric field.
Moreover, the conductance of the DNA molecule within the polaron model is found
to be sensitive to structural disorders in the DNA geometry, but that
dependence diminishes with increasing temperature.


title:
Physical interpretation of the near-infrared colours of low redshift
  galaxies

abstract:
  We use empirical techniques to interpret the near-infrared colours of a
sample of 5800 galaxies drawn from Sloan Digital Sky Survey (SDSS) main
spectroscopic sample with YJHK photometry from the UK Infrared Deep Sky Survey
(UKIDSS) data release one. We study correlations between near-IR colours
measured within SDSS fibre and physical parameters derived from the spectra.
These parameters include specific star formation rate, stellar age, metallicity
and dust attenuation. All correlations are analyzed for samples of galaxies
that are closely matched in redshift, in stellar mass and in concentration
index. Whereas more strongly star-forming galaxies have bluer optical colours,
the opposite is true at near-IR wavelengths -- galaxies with higher specific
star formation rate have redder near-IR colours. This result agrees
qualitatively with the predictions of models in which Thermally Pulsing
Asymptotic Giant Branch (TP-AGB) stars dominate the H and K-band light of a
galaxy following a burst of star formation. We also find a surprisingly strong
correlation between the near-IR colours of star-forming galaxies and their dust
attenuation as measured from the Balmer decrement. Unlike optical colours,
however, near-IR colours exhibit very little dependence on galaxy inclination.
This suggests that the correlation of near-IR colours with dust attenuation
arises because TP-AGB stars are the main source of dust in the galaxy. Finally,
we compare the near-IR colours of the galaxies in our sample to the predictions
of three different stellar population models: the Bruzual & Charlot 2003 model,
a preliminary version of a new model under development by Charlot & Bruzual,
which includes a new prescription for AGB star evolution, and the Maraston 2005
model.


title: Surface tank-treading: propulsion of Purcell's toroidal swimmer

abstract:
  In this work we address the "smoking ring" propulsion technique, originally
proposed by E. M. Purcell. We first consider self-locomotion of a
doughnut-shaped swimmer powered by surface tank-treading. Different modes of
surface motion are assumed and propulsion velocity and swimming efficiency are
determined. The swimmer is propelled against the direction of its outer surface
motion, the inner surface having very little affect. The simplest swimming mode
corresponding to constant angular velocity, can achieve propulsion speeds of up
to 66% of the surface tank-treading velocity and swimming efficiency of up to
13%. Higher efficiency is possible for more complicated modes powered by
twirling of extensible surface. A potential practical design of a swimmer
motivated by Purcell's idea is proposed and demonstrated numerically. Lastly,
the explicit solution is found for a two-dimensional swimmer composed of two
counter-rotating disks, using complex variable techniques.


title: Representing probabilistic data via ontological models

abstract:
  Ontological models are attempts to quantitatively describe the results of a
probabilistic theory, such as Quantum Mechanics, in a framework exhibiting an
explicit realism-based underpinning. Unlike either the well known
quasi-probability representations, or the "r-p" vector formalism, these models
are contextual and by definition only involve positive probability
distributions (and indicator functions). In this article we study how the
ontological model formalism can be used to describe arbitrary statistics of a
system subjected to a finite set of preparations and measurements. We present
three models which can describe any such empirical data and then discuss how to
turn an indeterministic model into a deterministic one. This raises the issue
of how such models manifest contextuality, and we provide an explicit example
to demonstrate this. In the second half of the paper we consider the issue of
finding ontological models with as few ontic states as possible.


title: Beyond Two Dark Energy Parameters

abstract:
  Our ignorance of the dark energy is generally described by a two-parameter
equation of state. In these approaches a particular {\it ad hoc} functional
form is assumed, and only two independent parameters are incorporated. We
propose a model-independent, multi-parameter approach to fitting the dark
energy, and show that next-generation surveys will constrain the equation of
state in three or more independent redshift bins to better than 10%. Future
knowledge of the dark energy will surpass two numbers (e.g., [$w_0$,$w_1$] or
[$w_0$,$w_a$]), and we propose a more flexible approach to the analysis of
present and future data.