title: The efficiency of resonant relaxation around a massive black hole

abstract:
  Resonant relaxation (RR) is a rapid relaxation process that operates in the
nearly-Keplerian potential near a massive black hole (MBH). RR dominates the
dynamics of compact remnants that inspiral into a MBH and emit gravitational
waves (extreme mass ratio inspiral events, EMRIs). RR can either increase the
EMRI rate, or strongly suppress it, depending on its still poorly-determined
efficiency. We use small-scale Newtonian N-body simulations to measure the RR
efficiency and to explore its possible dependence on the stellar number density
profile around the MBH, and the mass-ratio between the MBH and a star (a
single-mass stellar population is assumed). We develop an efficient and robust
procedure for detecting and measuring RR in N-body simulations. We present a
suite of simulations with a range of stellar density profiles and mass-ratios,
and measure the mean RR efficiency in the near-Keplerian limit. We do not find
a statistically significant dependence on the density profile or the
mass-ratio. Our numerical determination of the RR efficiency in the Newtonian,
single-mass population approximations, suggests that RR will likely enhance the
EMRI rate by a factor of a few over the rates predicted assuming only slow
stochastic two-body relaxation.


title:
Analytical Approach to the Local Contact Potential Difference on (001)
  Ionic Surfaces: Implications for Kelvin Probe Force Microscopy

abstract:
  An analytical model of the electrostatic force between the tip of a
non-contact Atomic Force Microscope (nc-AFM) and the (001) surface of an ionic
crystal is reported. The model is able to account for the atomic contrast of
the local contact potential difference (CPD) observed while nc-AFM-based Kelvin
Probe Force Microscopy (KPFM) experiments. With the goal in mind to put in
evidence this short-range electrostatic force, the Madelung potential arising
at the surface of the ionic crystal is primarily derived. The expression of the
force which is deduced can be split into two major contributions: the first
stands for the coupling between the microscopic structure of the tip apex and
the capacitor formed between the tip, the ionic crystal and the
counter-electrode; the second term depicts the influence of the Madelung
surface potential on the mesoscopic part of the tip, independently from its
microscopic structure. These short-range electrostatic forces are in the range
of ten pico-Newtons. When explicitly considering the crystal polarization, an
analytical expression of the bias voltage to be applied on the tip to
compensate for the local CPD, i.e. to cancel the short-range electrostatic
force, is derived. The compensated CPD has the lateral periodicity of the
Madelung surface potential. However, the strong dependence on the tip geometry,
the applied modulation voltage as well as the tip-sample distance, which can
even lead to an overestimation of the real surface potential, makes
quantitative KPFM measurements of the local CPD extremely difficult.


title:
On the Colored Jones Polynomial, Sutured Floer homology, and Knot Floer
  homology

abstract:
  Let K in S^3 be a knot, and let \widetilde{K} denote the preimage of K inside
its double branched cover, \Sigma(K). We prove, for each integer n > 1, the
existence of a spectral sequence from Khovanov's categorification of the
reduced n-colored Jones polynomial of the mirror of K to the knot Floer
homology of (\Sigma(K),\widetilde{K}) (when n odd) and to (S^3, K # K) (when n
even). A corollary of our result is that Khovanov's categorification of the
reduced n-colored Jones polynomial detects the unknot whenever n>1.


title: Non-Abelian magnetic monopole in a Bose-Einstein condensate

abstract:
  Recently, an effective non-Abelian magnetic field with a topology of a
monopole was shown to emerge from the adiabatic motion of multilevel atoms in
spatially varying laser fields [J. Ruseckas et al., Phys. Rev. Lett. 95, 010404
(2005)]. We study this monopole in a Bose-Einstein condensate (BEC) of
degenerate dressed states and find that the topological charge of the
pseudospin cancels the monopole charge resulting in a vanishing gauge invariant
charge. As a function of the laser wavelength, different stationary states are
classified in terms of their effect to the monopole part of the magnetic field
and a cross-over to vortex ground state is observed.


title:
Angle-Resolved Photoelectron Spectroscopy Studies of the Many-Body
  Effects in the Electronic Structure of High-Tc Cuprates

abstract:
  After an extended introduction, the thesis considers the electronic
properties of BSCCO and the recent progress in understanding the electronic
structure of this material. The main result of this part of the work is a model
of the Green's function that is later used for calculating the two-particle
excitation spectrum. Then, the matrix element effects in the photoemission
spectra of cuprates are discussed with a focus on the recently discovered
anomalous behavior of the ARPES spectra that partially originates from the
momentum-dependent photoemission matrix element. The momentum- and excitation
energy dependence of the anomalous high-energy dispersion, termed "waterfalls",
is covered in full detail. Finally, the work describes the relation of ARPES
with other experimental methods, such as INS spectroscopy. For the optimally
doped bilayer Bi-based cuprate, the renormalized two-particle correlation
function in the superconducting state is calculated from ARPES data within an
itinerant model based on the random phase approximation (RPA). Additionally,
two other applications of the same approach are briefly sketched: the relation
of ARPES to FT-STS, and the nesting properties of Fermi surfaces in
two-dimensional charge density wave compounds.


title: Quantum kinetic theory for fermions in temporally varying backrounds

abstract:
  We derive quantum kinetic equations for fermions in a homogeneous
time-dependent background in presence of decohering collisions, by use of the
Schwinger-Keldysh CTP-formalism. The quantum coherence (between particles and
antiparticles) is found to arise from new spectral solutions for the dynamical
2-point correlation function in the mean field limit. The physical density
matrix $\rho$ and its dynamics is shown to be necessarily dependent on the
extrenous information on the system, and expressions that relate $\rho$ to
fundamental coherence functions and fermionic particle and antiparticle numbers
are derived. For an interacting system we demonstrate how smooth decoherence
effects are induced by collisions. As special applications we study the
production of unstable particles during the preheating stage of the inflation
and an evolution of an initially quantum $\rho$ towards a statistical limit
including decoherence and thermalisation.


title: Two Generalizations of Tensor Products, Beyond Vector Spaces

abstract:
  Two successive generalizations of the usual tensor products are given. One
can be constructed for arbitrary binary operations, and not only for
semigroups, groups or vector spaces. The second one, still more general, is
constructed for arbitrary generators on sets.


title: Slip and flow of hard-sphere colloidal glasses

abstract:
  We study the flow of concentrated hard-sphere colloidal suspensions along
smooth, non-stick walls using cone-plate rheometry and simultaneous confocal
microscopy. In the glass regime, the global flow shows a transition from
Herschel-Bulkley behavior at large shear rate to a characteristic Bingham slip
response at small rates, absent for ergodic colloidal fluids. Imaging reveals
both the `solid' microstructure during full slip and the local nature of the
`slip to shear' transition. Both the local and global flow are described by a
phenomenological model, and the associated Bingham slip parameters exhibit
characteristic scaling with size and concentration of the hard spheres.


title:
Measurement of the hyperfine splitting of the 6S$_{1/2}$ level in
  rubidium

abstract:
  We present a measurement of the hyperfine splitting of the 6S$_{1/2}$ excited
level of rubidium using two photon absorption spectroscopy in a glass cell. The
values we obtain for the magnetic dipole constant A are 239.18(03) MHz and
807.66(08) MHz for $^{85}$Rb and $^{87}$Rb, respectively. The combination of
the magnetic moments of the two isotopes and our measurements show a hyperfine
anomaly in this atomic excited state. The observed hyperfine anomaly difference
has a value of $_{87}\delta_{85}=-0.0036(2)$ due to the finite distribution of
nuclear magnetization, the Bohr-Weisskopf effect.


title:
Shape transition in ZnO nanostructures and its effect on blue-green
  photoluminescence

abstract:
  We report that ZnO nanostructures synthesized by chemical route undergo a
shape transition at ~ 20 nm from spherical to hexagonal morphology thereby
changing the spectral components of the blue-green emission. Spherically shaped
nanocrystals (size range 11 -18 nm) show emission in the range of 555-564 nm
and the emission shifts to the longer wavelength as the size increases. On the
other hand, rods and hexagonal platelets (size range 20-85 nm), which is the
equilibrium morphology after the shape transition, show emission near 465-500
nm and it shifts to shorter wavelength as the size increases. The shape
transition also leads to relaxation of microstrain in the system. Our analysis
shows that the visible emission originates from a defect layer on the
nanostructure surface which is affected by the shape transition. The change in
the spectral component of the blue green emission on change of shape has been
explained as arising from band bending due to depletion layer in smaller
spherical particles which is absent in the larger particles with flat faces.


title: Mean curvature flow via convex functions on Grassmannian manifolds

abstract:
  Using the convex functions in Grassmannian manifolds we can carry out
interior estimates for mean curvature flow of higher codimension. In this way
some of the results of Ecker-Huisken can be generalized to higher codimension


title:
Ultrafast switching time and third order nonlinear coefficients of
  microwave treated single walled carbon nanotube suspensions

abstract:
  Microwave treated water soluble and amide functionalized single walled carbon
nanotubes have been investigated using femtosecond degenerate pump-probe and
nonlinear transmission experiments. The time resolved differential transmission
using 75 femtosecond pulse with the central wavelength of 790 nm shows a
bi-exponential ultrafast photo-bleaching with time constants of of 160 fs (130
fs) and 920 fs (300 fs) for water soluble (amide functionalized) nanotubes.
Open and closed aperture z-scans show saturation absorption and positive
(negative) nonlinear refraction for water soluble (amide functionalized)
nanotubes. Two photon absorption coefficient,beata ~250 cm/GW (650 cm/GW) and
nonlinear index, gamma ~ 15 cm^2/pW (-30 cm^2/pW) are obtained from the
theoretical fit in the saturation limit to the data for two types of nanotubes.


title: Rayleigh-Ritz variation method and connected-moments polynomial approach

abstract:
  We show that the connected-moments polynomial approach proposed recently is
equivalent to the well known Rayleigh-Ritz variation method in the Krylov
space. We compare the latter with one of the original connected-moments methods
by means of a numerical test on an anharmonic oscillator


title:
Living in a Void: Testing the Copernican Principle with Distant
  Supernovae

abstract:
  A fundamental presupposition of modern cosmology is the Copernican Principle;
that we are not in a central, or otherwise special region of the Universe.
Studies of Type Ia supernovae, together with the Copernican Principle, have led
to the inference that the Universe is accelerating in its expansion. The usual
explanation for this is that there must exist a `Dark Energy', to drive the
acceleration. Alternatively, it could be the case that the Copernican Principle
is invalid, and that the data has been interpreted within an inappropriate
theoretical frame-work. If we were to live in a special place in the Universe,
near the centre of a void where the local matter density is low, then the
supernovae observations could be accounted for without the addition of dark
energy. We show that the local redshift dependence of the luminosity distance
can be used as a clear discriminant between these two paradigms. Future surveys
of Type Ia supernovae that focus on a redshift range of ~0.1-0.4 will be
ideally suited to test this hypothesis, and hence to observationally determine
the validity of the Copernican Principle on new scales, as well as probing the
degree to which dark energy must be considered a necessary ingredient in the
Universe.


title: From N M2's to N D2's

abstract:
  In this short note, we reduce the N=6, U(N)xU(N) Chern-Simons gauge theories
to N=8, U(N) Yang-Mills gauge theories. This process corresponds to recovering
the world-volume theory of N D2-branes from that of N M2-branes in an
intermediate energy range. The supersymmetries are enhanced because in this
limit the branes localize far away from the orbifold singularity. Our main
scheme is exactly in accordance with Mukhi and Papageorgakis's earlier work,
although the Higgs mechanism becomes trickier in the present case. We also
speculate on applying the scheme to a large class of new Bagger-Lambert models
more generally.


title: Suppressing Spin Qubit Dephasing by Nuclear State Preparation

abstract:
  Coherent spin states in semiconductor quantum dots offer promise as
electrically controllable quantum bits (qubits) with scalable fabrication. For
few-electron quantum dots made from gallium arsenide (GaAs), fluctuating
nuclear spins in the host lattice are the dominant source of spin decoherence.
We report a method of preparing the nuclear spin environment that suppresses
the relevant component of nuclear spin fluctuations below its equilibrium value
by a factor of ~ 70, extending the inhomogeneous dephasing time for the
two-electron spin state beyond 1 microsecond. The nuclear state can be readily
prepared by electrical gate manipulation and persists for > 10 seconds.


title: Electronic noise-free measurements of squeezed light

abstract:
  We study the implementation of a correlation measurement technique for the
characterization of squeezed light. We show that the sign of the covariance
coefficient revealed from the time resolved correlation data allow us to
distinguish between squeezed, coherent and thermal states. In contrast to the
traditional method of characterizing squeezed light, involving measurement of
the variation of the difference photocurrent, the correlation measurement
method allows to eliminate the contribution of the electronic noise, which
becomes a crucial issue in experiments with dim sources of squeezed light.


title:
An interferometric study of the low-mass protostar IRAS 16293-2422:
  small scale organic chemistry

abstract:
  Aims: To investigate the chemical relations between complex organics based on
their spatial distributions and excitation conditions in the low-mass young
stellar objects IRAS 16293-2422 A and B. Methods: Interferometric observations
with the Submillimeter Array have been performed at 5''x3'' resolution
revealing emission lines of HNCO, CH3CN, CH2CO, CH3CHO and C2H5OH. Rotational
temperatures are determined from rotational diagrams when a sufficient number
of lines are detected. Results: Compact emission is detected for all species
studied here. For HNCO and CH3CN it mostly arises from source A, CH2CO and
C2H5OH have comparable strength for both sources and CH3CHO arises exclusively
from source B. HNCO, CH3CN and CH3CHO have rotational temperatures >200 K. The
(u,v)-visibility data reveal that HNCO also has extended cold emission.
Conclusions: The abundances of the molecules studied here are very similar
within factors of a few to those found in high-mass YSOs. Thus the chemistry
between high- and low-mass objects appears to be independent of luminosity and
cloud mass. Bigger abundance differences are seen between the A and B source.
The HNCO abundance relative to CH3OH is ~4 times higher toward A, which may be
due to a higher initial OCN- ice abundances in source A compared to B.
Furthermore, not all oxygen-bearing species are co-existent. The different
spatial behavior of CH2CO and C2H5OH compared with CH3CHO suggests that
hydrogenation reactions on grain-surfaces are not sufficient to explain the
observed gas phase abundances. Selective destruction of CH3CHO may result in
the anti-coincidence of these species in source A. These results illustrate the
power of interferometric compared with single dish data in terms of testing
chemical models.


title: Bell test for the free motion of material particles

abstract:
  We present a scheme to establish non-classical correlations in the motion of
two macroscopically separated massive particles without resorting to
entanglement in their internal degrees of freedom. It is based on the
dissociation of a diatomic molecule with two temporally separated Feshbach
pulses generating a motional state of two counter-propagating atoms that is
capable of violating a Bell inequality by means of correlated single particle
interferometry. We evaluate the influence of dispersion on the Bell
correlation, showing it to be important but manageable in a proposed
experimental setup. The latter employs a molecular BEC of fermionic Lithium
atoms, uses laser-guided atom interferometry, and seems to be within the reach
of present-day technology.


title: Leading neutrons from polarized pp collisions

abstract:
  We calculate the cross section and single-spin azimuthal asymmetry, A_n(t)
for inclusive neutron production in pp collisions at forward rapidities
relative to the polarized proton. Absorptive corrections to the pion pole
generate a relative phase between the spin-flip and non-flip amplitudes, which
leads to an appreciable spin asymmetry. However, the asymmetry observed
recently in the PHENIX experiment at RHIC at very small |t|~0.01GeV^2 cannot be
explained by this mechanism.


title: Fermionic superfluid properties in a one-dimensional optical lattice

abstract:
  We discuss various superfluid properties of a two-component Fermi system in
the presence of a tight one-dimensional periodic potential in a
three-dimensional system. We use a zero temperature mean field theory and
derive analytical expressions for the Josephson current, the sound velocity and
the center of mass oscillations in the BCS-Bose Einstein condensation crossover
region.


title: A Multidimensional Central Sets Theorem

abstract:
  The Theorems of Hindman and van der Waerden belong to the classical theorems
of partition Ramsey Theory. The Central Sets Theorem is a strong simultaneous
extension of both theorems that applies to general commutative semigroups. We
give a common extension of the Central Sets Theorem and Ramsey's Theorem.


title:
Toward detection of terrestrial planets in the habitable zone of our
  closest neighbor: Proxima Centauri

abstract:
  The precision of radial velocity (RV) measurements to detect indirectly
planetary companions of nearby stars has improved to enable the discovery of
extrasolar planets in the Neptune and Super-Earth mass range. Discoveries of
Earth-like planets by means of ground-based RV programs will help to determine
the parameter Eta_Earth, the frequency of potentially habitable planets around
other stars. In search of low-mass planetary companions we monitored Proxima
Centauri (M5V) as part of our M dwarf program. In the absence of a significant
detection, we use these data to demonstrate the general capability of the RV
method in finding terrestrial planets. For late M dwarfs the classic liquid
surface water habitable zone (HZ) is located close to the star, in which
circumstances the RV method is most effective. We want to demonstrate that late
M dwarfs are ideal targets for the search of terrestrial planets with the RV
technique. We obtained differential RV measurements of Proxima Cen over a time
span of 7 years with the UVES spectrograph at the ESO VLT. We determine upper
limits to the masses of companions in circular orbits by means of numerical
simulations. The RV data of Proxima Cen have a total rms scatter of 3.1 m/s and
a period search does not reveal any significant signals. As a result of our
companion limit calculations, we find that we successfully recover all test
signals with RV amplitudes corresponding to planets with m sin i > 2 - 3
M_Earth residing inside the HZ of Proxima Cen with a statistical significance
of >99%. Over the same period range, we can recover 50% of the test planets
with masses of m sin i > 1.5 - 2.5 M_Earth. Based on our simulations, we
exclude the presence of any planet in a circular orbit with m sin i > 1
M_Neptune at separations of a < 1 AU.


title: NLO QCD corrections to pp -> ttbb+X via quark anti-quark annihilation

abstract:
  The process pp -> top anti-top bottom anti-bottom + X represents a very
important background reaction to searches at the LHC, in particular to top
anti-top H production where the Higgs boson decays into a bottom anti-bottom
pair. A successful analysis of top anti-top H at the LHC requires the knowledge
of direct top anti-top bottom anti-bottom production at NLO in QCD. We take the
first step in this direction upon calculating the NLO QCD corrections to the
subprocess initiated by quark anti-quark annihilation.


title:
Towards first-principles understanding of the metal-insulator transition
  in fluid alkali metals

abstract:
  By treating the electron-ion interaction as perturbation in the
first-principles Hamiltonian, we have calculated the density response functions
of a fluid alkali metal to find an interesting charge instability due to
anomalous electronic density fluctuations occurring at some finite wave vector
${\bi Q}$ in a dilute fluid phase above the liquid-gas critical point. Since
$|{\bi Q}|$ is smaller than the diameter of the Fermi surface, this instability
necessarily impedes the electric conduction, implying its close relevance to
the metal-insulator transition in fluid alkali metals.


title: Strong characterizing sequences of countable groups

abstract:
  Andr\'as Bir\'o and Vera S\'os prove that for any subgroup $G$ of $\T$
generated freely by finitely many generators there is a sequence $A\subset \N$
such that for all $\beta \in \T$ we have ($\|.\|$ denotes the distance to the
nearest integer) $$\beta\in G \Rightarrow \sum_{n\in A} \| n \beta\| <
\infty,\quad \quad \quad \beta\notin G \Rightarrow \limsup_{n\in A, n \to
\infty} \|n \beta\| > 0. $$ We extend this result to arbitrary countable
subgroups of $\T$. We also show that not only the sum of norms but the sum of
arbitrary small powers of these norms can be kept small. Our proof combines
ideas from the above article with new methods, involving a filter
characterization of subgroups of $\T$.


title:
A Three-Decade Outburst of the LMC Luminous Blue Variable R127 Draws to
  a Close

abstract:
  The paradigmatic Luminous Blue Variable R127 in the Large Magellanic Cloud
has been found in the intermediate, peculiar early-B state, and substantially
fainter in visual light, signaling the final decline from its major outburst
that began between 1978 and 1980. This transformation was detected in 2008
January, but archival data show that it began between early 2005 and early
2007. In fact, significant changes from the maximum, peculiar A-type spectrum,
which was maintained from 1986 through 1998, had already begun the following
year, coinciding with a steep drop in visual light. We show detailed
correspondences between the spectrum and light, in which the decline mimics the
rise. Moreover, these trends are not monotonic but are characterized by
multiple spikes and dips, which may provide constraints on the unknown outburst
mechanism. Intensive photometric and spectroscopic monitoring of R127 should
now resume, to follow the decline presumably back to the quiescent Ofpe/WN9
state, in order to fully document the remainder of this unique observational
opportunity.


title:
Effect of different Dzyaloshinskii-Moriya interactions on entanglement
  in the Heisenberg XYZ chain

abstract:
  In this paper, we study the thermal entanglement in a two-qubit Heisenberg
XYZ system with different Dzyaloshinskii-Moriya (DM) couplings. We show that
different DM coupling parameters have different influences on the entanglement
and the critical temperature. In addition, we find that when $J_{i}$
($i$-component spin coupling interaction) is the largest spin coupling
coefficient, $D_{i}$ ($i$-component DM interaction) is the most efficient DM
control parameter, which can be obtained by adjusting the direction of DM
interaction.


title: Theory of Rumour Spreading in Complex Social Networks

abstract:
  We introduce a general stochastic model for the spread of rumours, and derive
mean-field equations that describe the dynamics of the model on complex social
networks (in particular those mediated by the Internet). We use analytical and
numerical solutions of these equations to examine the threshold behavior and
dynamics of the model on several models of such networks: random graphs,
uncorrelated scale-free networks and scale-free networks with assortative
degree correlations. We show that in both homogeneous networks and random
graphs the model exhibits a critical threshold in the rumour spreading rate
below which a rumour cannot propagate in the system. In the case of scale-free
networks, on the other hand, this threshold becomes vanishingly small in the
limit of infinite system size. We find that the initial rate at which a rumour
spreads is much higher in scale-free networks than in random graphs, and that
the rate at which the spreading proceeds on scale-free networks is further
increased when assortative degree correlations are introduced. The impact of
degree correlations on the final fraction of nodes that ever hears a rumour,
however, depends on the interplay between network topology and the rumour
spreading rate. Our results show that scale-free social networks are prone to
the spreading of rumours, just as they are to the spreading of infections. They
are relevant to the spreading dynamics of chain emails, viral advertising and
large-scale information dissemination algorithms on the Internet.

categories: physics.soc-ph cond-mat.stat-mech cs.CR physics.bio-ph


title:
Effect of Oxygen Content on the Properties of the HoBaCo2O5+x Layered
  Cobaltite

abstract:
  In this work we present the result of the first experimental investigation of
the role of oxygen content on the properties of the HoBaCo2O5+delta layered
cobaltite. We have measured the variation of oxygen content as a function of
temperature and oxygen partial pressure by means of thermogravimetry coupled to
chemical titration analysis. On selected samples of accurately known oxygen
content we have undertaken a systematic investigation of their structural,
thermal and magnetic properties by means of x-ray diffraction, differential
scanning calorimetry and magnetometry. The overall results gained by this study
confirm the central role of oxygen content on the properties of these materials
suggesting that, for the Ho composition, even very slight variation of the
order of delta=0.01 has a dramatic influence on the magnetic and transport
properties of the samples. In addition, we have presented results showing the
strategy to check the quality of samples prepared at selected oxygen contents
by annealing procedures.


title:
Evolution towards J\"uttner equilibrium: Manifestly covariant
  correlation dynamics

abstract:
  Replaced by the new article arXiv:0901.1425 because the J\"uttner
distribution has been revised and the second author been removed.


title: A variant of the Hales-Jewett Theorem

abstract:
  It was shown by V. Bergelson that any set B with positive upper
multiplicative density contains nicely intertwined arithmetic and geometric
progressions: For each positive integer k there exist integers a,b,d such that
$ {b(a+id)^j:i,j \in\nhat k}\subset B. $ In particular one cell of each finite
partition of the positive integers contains such configurations. We prove a
Hales-Jewett type extension of this partition theorem.


title:
Nonclassical equivalence transformations associated with a parameter
  identification problem

abstract:
  A special class of symmetry reductions called nonclassical equivalence
transformations is discussed in connection to a class of parameter
identification problems represented by partial differential equations. These
symmetry reductions relate the forward and inverse problems, reduce the
dimension of the equation, yield special types of solutions, and may be
incorporated into the boundary conditions as well. As an example, we discuss
the nonlinear stationary heat conduction equation and show that this approach
permits the study of the model on new types of domains. Our MAPLE routine
GENDEFNC which uses the package DESOLV (authors Carminati and Vu) has been
updated for this propose and its output is the nonlinear partial differential
equation system of the determining equations of the nonclassical equivalence
transformations.


title: The chemical evolution of Manganese in different stellar systems

abstract:
  Aims. To model the chemical evolution of manganese relative to iron in three
different stellar systems: the solar neighbourhood, the Galactic bulge and the
Sagittarius dwarf spheroidal galaxy, and compare our results with the recent
and homogeneous observational data. Methods. We adopt three chemical evolution
models well able to reproduce the main properties of the solar vicinity, the
galactic Bulge and the Sagittarius dwarf spheroidal. Then, we compare different
stellar yields in order to identify the best set to match the observational
data in these systems. Results. We compute the evolution of manganese in the
three systems and we find that in order to reproduce simultaneously the [Mn/Fe]
versus [Fe/H] in the Galactic bulge, the solar neighbourhood and Sagittarius,
the type Ia SN Mn yield must be metallicity-dependent. Conclusions. We conclude
that the different histories of star formation in the three systems are not
enough to reproduce the different behaviour of the [Mn/Fe] ratio, unlike the
situation for [alpha/Fe]; rather, it is necessary to invoke
metallicity-dependent type Ia SN Mn yields, as originally suggested by
McWilliam, Rich & Smecker-Hane in 2003.


title:
Extended Optical Model Analyses of Elastic Scattering and Fusion Cross
  Section Data for the 9Be+28Si, 144Sm, and 208Pb Systems at
  Near-Coulomb-Barrier Energies using Double Folding Potential

abstract:
  Based on the extended optical model with the double folding potential, in
which the polarization potential is decomposed into direct reaction (DR) and
fusion parts, simultaneous $\chi^{2}$ analyses are performed of elastic
scattering and fusion cross section data for the $^{9}$Be+$^{28}$Si,
$^{144}$Sm, and $^{208}$Pb systems at near-Coulomb-barrier energies. We find
that the real part of the resultant DR part of the polarization potential is
systematically repulsive for all the targets considered, which is consistent
with the results deduced from the Continuum Discretized Coupled Channel (CDCC)
calculations taking into account the polarization effects due to breakup.
Further, it is found that both DR and fusion parts of the extracted
polarization potentials satisfy the dispersion relation.


title: Dust in Interstellar Clouds, Evolved Stars and Supernovae

abstract:
  Outflows of pre-main-sequence stars drive shocks into molecular material
within 0.01 - 1 pc of the young stars. The shock-heated gas emits infrared,
millimeter and submillimeter lines of many species including. Dust grains are
important charge carriers and play a large role in coupling the magnetic field
and flow of neutral gas. Some effects of the dust on the dynamics of oblique
shocks began to emerge in the 1990s. However, detailed models of these shocks
are required for the calculation of the grain sputtering contribution to gas
phase abundances of species producing observed emissions. We are developing
such models. Some of the molecular species introduced into the gas phase by
sputtering in shocks or by thermally driven desorption in hot cores form on
grain surfaces. Recently laboratory studies have begun to contribute to the
understanding of surface reactions and thermally driven desorption important
for the chemistry of star forming clouds. Dusty plasmas are prevalent in many
evolved stars just as well as in star forming regions. Radiation pressure on
dust plays a significant role in mass loss from some post-main-sequence stars.
The mechanisms leading to the formation of carbonaceous dust in the stellar
outflows are similar to those important for soot formation in flames. However,
nucleation in oxygen-rich outflows is less well understood and remains a
challenging research area. Dust is observed in supernova ejecta that have not
passed through the reverse shocks that develop in the interaction of ejecta
with ambient media. Dust is detected in high redshift galaxies that are
sufficiently young that the only stars that could have produced the dust were
so massive that they became supernovae. Consequently, the issue of the survival
of dust in strong supernova shocks is of considerable interest.


title: Magnetic field-induced gapless state in multiband superconductors

abstract:
  We investigate theoretically the properties of s-wave multiband
superconductors in the weak coupling (BCS) limit in the presence of
pair-breaking effects of magnetic field. It is shown that a qualitatively new
gapless superconducting state must appear in quasi-2D superconductors in
magnetic fields parallel to the plane, corresponding to a Sarma state induced
on one of the Fermi surfaces. The emergence of the new state in s-wave
multiband superconductors in the absence of anisotropy or spin-orbit
interaction is usually accompanied by a zero-temperature first-order
metamagnetic phase transition. For anisotropic or non s-wave multiband
superconductors the order of the zero-temperature metamagnetic transition
depends on model parameters, and it may take the form of a smooth crossover.
The details of the temperature-magnetic field phase diagram for multiband
superconductors are investigated analytically at zero temperature and
numerically at a finite temperature. It is shown the zero-temperatures
first-order phase transition gives rise to a critical region on the B-T phase
diagram. We suggest possible experiments to detect the new gapless state.


title:
Extended emission-line regions in low-redshift quasars: Dependence on
  nuclear spectral properties

abstract:
  We searched for the presence of extended emission-line regions (EELRs) around
low-redshift QSOs. We observed a sample of 20 mainly radio-quiet low-redshift
quasars (z<0.3) by means of integral field spectroscopy. After decomposing the
extended and nuclear emission components, we constructed [OIII] 5007
narrow-band images of the EELR to measure the total flux. From the same data we
obtained high S/N (>50) nuclear spectra to measure properties such as
[OIII]/Hbeta flux ratios, FeII equivalent widths and Hbeta line widths. A
significant fraction of the quasars (8/20) show a luminous EELR, with detected
linear sizes of several kpc. Whether or not a QSO has a luminous EELR is
strongly related with nuclear properties, in the sense that an EELR was
detected in objects with low FeII equivalent width and large Hbeta FWHM. The
EELRs were detected preferentially in QSOs with larger black hole masses. There
is no discernible relation, however, between EELR detection and QSO luminosity
and Eddington ratio.


title: Duality for Borel measurable cost functions

abstract:
  We consider the Monge-Kantorovich transport problem in an abstract measure
theoretic setting. Our main result states that duality holds if $c:X\times Y\to
[0,\infty)$ is an arbitrary Borel measurable cost function on the product of
Polish spaces $X,Y$. In the course of the proof we show how to relate a non -
optimal transport plan to the optimal transport costs via a ``subsidy''
function and how to identify the dual optimizer. We also provide some examples
showing the limitations of the duality relations.


title:
Molecular Beam Epitaxy grown (Ga,Mn)(As,P) with perpendicular to plane
  magnetic easy axis

abstract:
  We present an experimental investigation of the magnetic, electrical and
structural properties of Ga0.94Mn0.06As1-yPy layers grown by molecular beam
epitaxy on GaAs substrates for y less than or equal to 0.3. X-ray diffraction
measurements reveal that the layers are under tensile strain which gives rise
to a magnetic easy axis perpendicular to the plane of the layers. The strength
of the magnetic anisotropy and the coercive field increase as the phosphorous
concentration is increased. The resistivity of all samples shows metallic
behaviour with the resistivity increasing as y increases. These materials will
be useful for studies of micromagnetic phenomena requiring metallic
ferromagnetic material with perpendicular magnetic anisotropy.


title:
New c-cbar structure around 3764 MeV at BES and predictions from
  unquenching the confinement spectrum

abstract:
  This paper has been withdrawn by the authors as a consequence of their
misinterpretation of the BES experiment in 0807.0494


title: Fixed point theory and trace for bicategories

abstract:
  The Lefschetz fixed point theorem follows easily from the identification of
the Lefschetz number with the fixed point index. This identification is a
consequence of the functoriality of the trace in symmetric monoidal categories.
There are refinements of the Lefschetz number and the fixed point index that
give a converse to the Lefschetz fixed point theorem. An important part of this
theorem is the identification of these different invariants. We define a
generalization of the trace in symmetric monoidal categories to a trace in
bicategories with shadows. We show the invariants used in the converse of the
Lefschetz fixed point theorem are examples of this trace and that the
functoriality of the trace provides some of the necessary identifications. The
methods used here do not use simplicial techniques and so generalize readily to
other contexts.


title:
The ALICE detector and trigger strategy for diffractive and
  electromagnetic processe

abstract:
  The ALICE detector at the Large Hadron Collider (LHC) consists of a central
barrel, a muon spectrometer, zero degree calorimeters and additional detectors
which are used for trigger purposes and for event classification. The main
detector systems of relevance for measuring diffractive and electromagnetic
processes are described. The trigger strategy for such measurements is
outlined. The physics potential of studying diffractive and electromagnetic
processes at the LHC is presented by discussing possible signatures of the
Odderon.


title:
The symbiotic star CH Cygni. II. The broad Ly alpha emission line
  explained by shocks

abstract:
  Context. In 1985, at the end of the active phase 1977-1986, a broad (4000
km/s) Ly alpha line appeared in the symbiotic system CH Cygni that had never
been observed previously. Aims. In this work we investigate the origin of this
anomalous broad Ly alpha line. Methods. We suggest a new interpretation of the
broad Ly alpha based on the theory of charge transfer reactions between ambient
hydrogen atoms and post-shock protons at a strong shock front. Results. We have
found that the broad Ly alpha line originated from the blast wave created by
the outburst, while the contemporary optical and UV lines arose from the nebula
downstream of the expanding shock in the colliding wind scenario.


title:
Coupled Hamiltonian systems with extended affine Weyl group symmetry of
  type $D_3^{(2)}$

abstract:
  We find a two-parameter family of ordinary differential systems in dimension
five with the affine Weyl group symmetry of type $D_3^{(2)}$. We show its
symmetry and holomorphy conditions. This is the second example which gave
higher order Painlev\'e type systems of type $D_{3}^{(2)}$. By obtaining its
first integrals of polynomial type, we can obtain a two-parameter family of
coupled Hamiltonian systems in dimension four with the polynomial Hamiltonian.


title:
Simulations of Large-scale WiFi-based Wireless Networks:
  Interdisciplinary Challenges and Applications

abstract:
  Wireless Fidelity (WiFi) is the fastest growing wireless technology to date.
In addition to providing wire-free connectivity to the Internet WiFi technology
also enables mobile devices to connect directly to each other and form highly
dynamic wireless adhoc networks. Such distributed networks can be used to
perform cooperative communication tasks such ad data routing and information
dissemination in the absence of a fixed infrastructure. Furthermore, adhoc
grids composed of wirelessly networked portable devices are emerging as a new
paradigm in grid computing. In this paper we review computational and
algorithmic challenges of high-fidelity simulations of such WiFi-based wireless
communication and computing networks, including scalable topology maintenance,
mobility modelling, parallelisation and synchronisation. We explore
similarities and differences between the simulations of these networks and
simulations of interacting many-particle systems, such as molecular dynamics
(MD) simulations. We show how the cell linked-list algorithm which we have
adapted from our MD simulations can be used to greatly improve the
computational performance of wireless network simulators in the presence of
mobility, and illustrate with an example from our simulation studies of worm
attacks on mobile wireless adhoc networks.


title: Blocks and families for cyclotomic Hecke algebras

abstract:
  The families of characters, defined by Lusztig for Weyl groups, play an
important role in the representation theory of finite reductive groups. The
definition of Rouquier for the families of characters in terms of blocks of the
Hecke algebra has made possible the generalization of this notion to the case
of complex reflection groups. In this article, we study the Rouquier blocks of
the cyclotomic Hecke algebras and we show that they depend on numerical data
determined by the generic Hecke algebra. Moreover, we provide the algorithm and
the results of their determination for all exceptional complex reflection
groups.


title:
Stellar disks of Collisional Ring Galaxies I. New multiband images,
  Radial intensity and color profiles, and confrontation with N-body
  simulations

abstract:
  We present new multi-band imaging data in the optical (BVRI and Halpha) and
near infrared bands (JHK) of 15 candidate ring galaxies from the sample of
Appleton & Marston (1997). We use these data to obtain color composite images,
global magnitudes and colors of both the ring galaxy and its companion(s), and
radial profiles of intensity and colors. We find that only nine of the observed
galaxies have multi-band morphologies expected for the classical collisional
scenario of ring formation, indicating the high degree of contamination of the
ring galaxy sample by galaxies without a clear ring morphology. The radial
intensity profiles, obtained by masking the off-centered nucleus, peak at the
position of the ring, with the profiles in the continuum bands broader than
that in the Halpha line. The images as well as the radial intensity and color
profiles clearly demonstrate the existence of the pre-collisional stellar disk
outside the star-forming ring, which is in general bluer than the disk internal
to the ring. The stellar disk seems to have retained its size, with the disk
outside the ring having a shorter exponential scale length as compared to the
values expected in normal spiral galaxies of comparable masses. The rings in
our sample of galaxies are found to be located preferentially at around
half-way through the stellar disk. The most likely reason for this preference
is bias against detecting rings when they are close to the center (they would
be confused with the resonant rings), and at the edge of the disk the gas
surface density may be below the critical density required for star formation.
Most of the observed characteristics point to relatively recent collisions (<80
Myr ago) according to the N-body simulations of Gerber et al. (1996).


title:
On thermodynamics of N=6 superconformal Chern-Simons theories at strong
  coupling

abstract:
  Recently it has been conjectured that N=6, U(N)_{k} \times U(N)_{-k}
Chern-Simons theory is dual to M-theory on AdS_4\times S^7/Z_{k}. By studying
one-loop correction to the M-theory effective action, we calculate the
correction to the entropy of thermal field theory at strong coupling. For large
k level, we have also found the alpha' correction to the entropy from the
string correction of the type IIA effective action. The structure of these two
corrections at strong t'Hooft coupling are different.


title:
Effects of Strain on Orbital Ordering and Magnetism at the Perovskite
  Oxide Interfaces: LaMnO$_3$/SrMnO$_3$

abstract:
  We study how strain affects orbital ordering and magnetism at the interface
between SrMnO$_3$ and LaMnO$_3$ from density-functional calculations and
interpret the basic results in terms of a three-site Mn-O-Mn model. Magnetic
interaction between the Mn atoms is governed by a competition between the
antiferromagnetic superexchange of the Mn t$_{2g}$ core spins and the
ferromagnetic double exchange of the itinerant e$_g$ electrons. While the core
electrons are relatively unaffected by the strain, the orbital character of the
itinerant electron is strongly affected, which in turn causes a large change in
the strength of the ferromagnetic double exchange. The epitaxial strain
produces the tetragonal distortion of the MnO$_6$ octahedron, splitting the
Mn-e$_g$ states into x$^2$-y$^2$ and 3z$^2$-1 states, with the former being
lower in energy, if the strain is tensile in the plane, and opposite if the
strain is compressive. For the case of the tensile strain, the resulting higher
occupancy of the x$^2$-y$^2$ orbital enhances the in-plane ferromagnetic double
exchange owing to the larger electron hopping in the plane, causing at the same
time a reduction of the out-of-plane double exchange. This reduction is large
enough to be overcome by antiferromagnetic superexchange, which wins to produce
a net antiferromagnetic interaction between the out-of-plane Mn atoms. For the
case of the in-plane compressive strain, the reverse happens, viz., that the
higher occupancy of the 3z$^2$-1 orbital results in the out-of-plane
ferromagnetic interaction, while the in-plane magnetic interaction remains
antiferromagnetic. Concrete density-functional results are presented for the
(LaMnO$_3$)$_1$/(SrMnO$_3$)$_1$ and (LaMnO$_3$)$_1$/(SrMnO$_3$)$_3$
superlattices for various strain conditions.


title:
The symbiotic star CH Cygni. I. An analysis of the shocked nebulae at
  different epochs

abstract:
  Context. We analyse the line and continuum spectra of the symbiotic system CH
Cygni. Aims. To show that the colliding-wind model is valid to explain this
symbiotic star at different phases. Methods. Peculiar observed features such as
flickering, radio variation, X-ray emission, as well as the distribution of the
nebulae and shells throughout the system are investigated by modelling the
spectra at different epochs. The models account consistently for shock and
photoionization and are constrained by absolute fluxes. Results. We find that
the reverse shock between the stars leads to the broad lines observed during
the active phases, as well as to radio and hard X-ray emission, while the
expanding shock is invoked to explain the data during the transition phases.


title: Is gravitational entropy quantized ?

abstract:
  In Einstein's gravity, the entropy of horizons is proportional to their area.
Several arguments given in the literature suggest that, in this context, both
area and entropy should be quantized with an equally spaced spectrum for large
quantum numbers. But in more general theories (like, for e.g, in the black hole
solutions of Gauss-Bonnet or Lanczos-Lovelock gravity) the horizon entropy is
\emph{not} proportional to area and the question arises as to which of the two
(if at all) will have this property. We give a general argument that in all
Lanczos-Lovelock theories of gravity, it is the \emph{entropy} that has equally
spaced spectrum. In the case of Gauss-Bonnet gravity, we use the asymptotic
form of quasi normal mode frequencies to explicitly demonstrate this result.
Hence, the concept of a quantum of area in Einstein Hilbert (EH) gravity needs
to be replaced by a concept of \emph{quantum of entropy} in a more general
context.


title:
Experimental Verification of the Quantized Conductance of Photonic
  Crystal Waveguides

abstract:
  We report experiments that demonstrate the quantization of the conductance of
photonic crystal waveguides. To obtain a diffusive wave, we have added all the
transmitted channels for all the incident angles. The conductance steps have
equal height and a width of one half the wavelength used. Detailed numerical
results agree very well with the novel experimental results.


title:
Correction to ``Knotted Hamiltonian cycles in spatial embeddings of
  complete graphs"

abstract:
  We state and prove a correct version of a theorem presented in an earlier
paper.


title: Brill-Noether theory of binary curves

abstract: Final version, to appear in Mathematical Research Letters.


title: Superuniversality in phase-ordering disordered ferromagnets

abstract:
  The phase-ordering kinetics of the ferromagnetic two-dimensional Ising model
with uniform bond disorder is investigated by intensive Monte Carlo
simulations. Simple ageing behaviour is observed in the single-time correlator
and the two-time responses and correlators. The dynamical exponent z and the
autocorrelation exponent lambda_C only depend on the ratio eps/T, where eps
describes the width of the distribution of the disorder, whereas a more
complicated behaviour is found for the non-equilibrium exponent a of the
two-time response as well as for the autoresponse exponent lambda_R. The
scaling functions are observed to depend only on the dimensionless ratio eps/T.
If the length scales are measured in terms of the time-dependent domain size
L(t), the form of the scaling functions is in general independent of both eps
and T. Conditions limiting the validity of this `superuniversality' are
discussed.


title: Long-term Photometric Analysis of the Active W UMa-type System TU Bootis

abstract:
  We present multi-color light curves for the W UMa-type eclipsing binary TU
Boo for two epochs separated by 22 years. An analysis of the O-C diagram
indicates the earlier observations took place right in the middle of a major
period change, thus allowing for a unique study on mass transfer and period
changes in this W UMa-type system. We compute model fits to our light curves,
along with the only other published set, using the Wilson-Devinney program, and
find temporally correlated changes in the size of the secondary component with
anomalies in the O-C diagram. We investigate the cause of these changes and
find support for the existence of rapid, large-scale mass transfer between the
components. We postulate that this interaction allows them to maintain nearly
equal surface temperatures despite having achieved only marginal contact. We
also find support for the evolutionary scenario in which TU Boo has undergone a
mass ratio reversal in the past due to large-scale mass transfer so that what
is presently the secondary component of TU Boo is in an advanced evolutionary
state, oversized due to a helium-enriched core, with a total system age of
$\geq$ 10 Gyr.


title:
Approximation of the Semigroup generated by the Robin Laplacian in terms
  of the Gaussian Semigroup

abstract:
  For smooth bounded open sets in euclidean space, we construct corresponding
contractive linear extension operators for the space of continuous functions
which preserve regularity of functions in the domain of the Robin Laplacian. We
also prove a Trotter-like approximation for the semigroup generated by the
Laplacian subject to Robin boundary conditions in terms of these extension
operators. The limiting case of Dirichlet boundary conditions is treated
separately.


title: On Weyl resolutions associated to Frobenius twists

abstract:
  We construct Weyl resolutions associated to certain Frobenius twists of
divided powers. Using these and other related complexes we obtain the Weyl
filtration dimension of the Schur algebras S(2,r), a result due to A. Parker.


title: Some Insight into Many Constituent Dynamics

abstract:
  A description of many constituent (particle) systems with fuzzy initial
conditions is proposed with the help of the field language. In this language
correlation functions are defined and equations for them are derived in the
free Fock space. Additional conditions for their solutions are postulated. The
closure problem for polynomial, rational, local and nonlocal interactions is
considered with exploitation of left or right invertibility of used operators.
Some general remarks concerning symmetry and multi-scale descriptions are
given.


title: The mass loss rates of sdB stars

abstract:
  The effects of gravitational settling and radiative levitation in the stellar
atmospheres and envelopes of subdwarf B (sdB) stars strongly depend on the
presence of weak winds. In the paper the existence of weak radiatively driven
winds is investigated from a theoretical point of view for sdB stars of half a
solar mass, effective temperatures between 25000 K and 35000 K, and surface
gravities log g between about 5.0 and 6.0 (cgs units). According to the
results, weak winds with mass-loss rates of the order E-11 solar masses per
year may exist only for the most luminous sdB stars. For the more compact ones,
the decoupling of the metals from the bulk matter (hydrogen and helium) is
expected in the wind region, because the momentum exchange via Coulomb
collisions is not effective enough. Thus multicomponent effects are of great
importance. We suggest that only the metals may be expelled from the star,
whereas hydrogen and helium are in hydrostatic equilibrium.


title: On the Kauffman bracket skein module of surgery on a (2,2b) torus link

abstract:
  We show that the Kauffman bracket skein modules of certain manifolds obtained
from integral surgery on a (2,2b) torus link are finitely generated, and list
the generators for select examples.


title: Noncommutative field theory with the Wick-Voros product

abstract:
  We study the noncommutative scalar field theory in the presence of the
Wick-Voros product (or normally ordered product), a variant of the more studied
Moyal product. We discuss both the classical and the quantum field theory in
the quartic potential case, and calculate the Green's functions up to one loop,
for the two and four points cases.


title:
Constrain on possible pairing symmetry in a two-orbital model of
  FeAs-based superconductors

abstract:
  In this work, we establish a few exact identities through commutation of
intra-orbital and inter-orbital on-site pairings with a two-orbital model
describing newly discovered FeAs-based superconductors. Applying the conclusion
drawn from rigorous relation and physical interpretation, we give constraints
on the possible symmetries of the superconducting pairing of the model. Hence
the favorable pairings in newly discovered high-temperature oxypnictide
superconductors are proposed.


title: Algorithm Selection as a Bandit Problem with Unbounded Losses

abstract:
  Algorithm selection is typically based on models of algorithm performance,
learned during a separate offline training sequence, which can be prohibitively
expensive. In recent work, we adopted an online approach, in which a
performance model is iteratively updated and used to guide selection on a
sequence of problem instances. The resulting exploration-exploitation trade-off
was represented as a bandit problem with expert advice, using an existing
solver for this game, but this required the setting of an arbitrary bound on
algorithm runtimes, thus invalidating the optimal regret of the solver. In this
paper, we propose a simpler framework for representing algorithm selection as a
bandit problem, with partial information, and an unknown bound on losses. We
adapt an existing solver to this game, proving a bound on its expected regret,
which holds also for the resulting algorithm selection technique. We present
preliminary experiments with a set of SAT solvers on a mixed SAT-UNSAT
benchmark.


title: An exactly solvable supersymmetric spin chain of BC_N type

abstract:
  We construct a new exactly solvable supersymmetric spin chain related to the
BC_N extended root system, which includes as a particular case the BC_N version
of the Polychronakos-Frahm spin chain. We also introduce a supersymmetric spin
dynamical model of Calogero type which yields the new chain in the large
coupling limit. This connection is exploited to derive two different
closed-form expressions for the chain's partition function by means of
Polychronakos's freezing trick. We establish a boson-fermion duality relation
for the new chain's spectrum, which is in fact valid for a large class of (not
necessarily integrable) spin chains of BC_N type. The exact expressions for the
partition function are also used to study the chain's spectrum as a whole,
showing that the level density is normally distributed even for a moderately
large number of particles. We also determine a simple analytic approximation to
the distribution of normalized spacings between consecutive levels which fits
the numerical data with remarkable accuracy. Our results provide further
evidence that spin chains of Haldane-Shastry type are exceptional integrable
models, in the sense that their spacings distribution is not Poissonian, as
posited by the Berry-Tabor conjecture for "generic'' quantum integrable
systems.


title: Expanders via Random Spanning Trees

abstract:
  Motivated by the problem of routing reliably and scalably in a graph, we
introduce the notion of a splicer, the union of spanning trees of a graph. We
prove that for any bounded-degree n-vertex graph, the union of two random
spanning trees approximates the expansion of every cut of the graph to within a
factor of O(log n). For the random graph G_{n,p}, for p> c log{n}/n, two
spanning trees give an expander. This is suggested by the case of the complete
graph, where we prove that two random spanning trees give an expander. The
construction of the splicer is elementary -- each spanning tree can be produced
independently using an algorithm by Aldous and Broder: a random walk in the
graph with edges leading to previously unvisited vertices included in the tree.
  A second important application of splicers is to graph sparsification where
the goal is to approximate every cut (and more generally the quadratic form of
the Laplacian) using only a small subgraph of the original graph.
Benczur-Karger as well as Spielman-Srivastava have shown sparsifiers with O(n
log n/eps^2)$ edges that achieve approximation within factors 1+eps and 1-eps.
Their methods, based on independent sampling of edges, need Omega(n log n)
edges to get any approximation (else the subgraph could be disconnected) and
leave open the question of linear-size sparsifiers. Splicers address this
question for random graphs by providing sparsifiers of size O(n) that
approximate every cut to within a factor of O(log n).


title:
Regular polynomial interpolation and approximation of global solutions
  of linear partial differential equations

abstract:
  We consider regular polynomial interpolation algorithms on recursively
defined sets of interpolation points which approximate global solutions of
arbitrary well-posed systems of linear partial differential equations.
  Convergence of the 'limit' of the recursively constructed family of
polynomials to the solution and error estimates are obtained from a priori
estimates for some standard classes of linear partial differential equations,
i.e. elliptic and hyperbolic equations. Another variation of the algorithm
allows to construct polynomial interpolations which preserve systems of linear
partial differential equations at the interpolation points. We show how this
can be applied in order to compute higher order terms of WKB-approximations of
fundamental solutions of a large class of linear parabolic equations. The error
estimates are sensitive to the regularity of the solution. Our method is
compatible with recent developments for solution of higher dimensional partial
differential equations, i.e. (adaptive) sparse grids, and weighted Monte-Carlo,
and has obvious applications to mathematical finance and physics.


title: Twisted Noncommutative Field Theory: Wick-Voros vs Moyal

abstract:
  We present a comparison of the noncommutative field theories built using two
different star products: Moyal and Wick-Voros (or normally ordered). We compare
the two theories in the context of the noncommutative geometry determined by a
Drinfeld twist, and the comparison is made at the level of Green's functions
and S-matrix. We find that while the Green's functions are different for the
two theories, the S-matrix is the same in both cases, and is different from the
commutative case.


title: Focusing of gamma-rays with Laue lenses: first results

abstract:
  We report on the first results obtained from our development project of
focusing gamma-rays ($>$60 keV) by using Laue lenses. The first lens prototype
model has been assembled and tested. We describe the technique adopted and the
lens focusing capabilities at about 100 keV.


title:
Supergravity dual of Chern-Simons Yang-Mills theory with N=6,8
  superconformal IR fixed point

abstract:
  We construct a solution of eleven dimensional supergravity corresponding to a
stack of M2 branes localized at the center of a particular eight dimensional
hyper-Kaehler manifold constructed by Gauntlett, Gibbons, Papadopoulos, and
Townsend, generalizing the earlier construction of Cherkis and Hashimoto. In
the decoupling limit, this solution is dual to a Chern-Simons/Yang-Mills/Matter
theory in 2+1 dimensions with N=3 supersymmetry, which flows in the infra red
to a superconformal Chern-Simons/Matter system preserving N=6,8 supersymmetry,
constructed recently by Aharony, Bergman, Jafferis, and Maldacena.


title:
Extraction of characteristic constants in QCD with perturbative and
  nonperturbative methods

abstract:
  Part I is devoted to the extraction of the QCD coupling from a bound state
approach at low energy scales, where unphysical singularities make the
RG-improved pQCD useless. Theoretical results on the meson spectrum based on a
Bethe-Salpeter formalism adjusted for QCD have been exploited for the
determination of experimental values of \alpha_s below 1GeV by comparison with
the data. Results quantitatively confirm the recently developed Analytic
Perturbation Theory approach to IR phenomena down to 200 MeV. Below this scale
the extracted values give a hint about the vanishing of the QCD coupling as Q^2
goes to zero.
  In part II the possibility of inferring the spin-dependent gluon distribution
from scaling violations is addressed by performing a NLO analysis of inclusive
DIS data in pQCD. In addition, this work presents a phenomenological study of
open-charm photoproduction in the polarized case, which is tailored to the
COMPASS experiment in view of upcoming data. It is shown that current inclusive
data allow a reliable determination of the gluon first moment, whereas the
x-shape is significantly affected by the assumed functional form. On the other
hand, studies of charm pseudo-data reveal that the open-charm approach should
be capable to reduce the bias induced by the choice of input densities, and to
pin down the x-shape of the gluon polarization.


title:
The metallicity distribution of the halo and the satellites of the Milky
  way in the hierarchical merging paradigm

abstract:
  To account for the observed differential metallicity distribution (DMD) of
the Milky Way halo, a semi-analytical model is presented in the framework of
the hierarchical merging paradigm for structure formation. It is assumed that
the Milky Way halo is composed of a number of sub-haloes with properties either
as observed in the dwarf satellite galaxies of the Local group (shape of
metallicity distribution, effective yield) or derived from calculations of
structure formation (sub-halo distribution function). With reasonable
assumptions for the parameters involved, we find that the overall shape and
effective yield of the Galactic halo DMD can be reproduced in the framework of
such a simple model. The low metallicity tail of the DMD presents a defficiency
of stars with respect to the simple model predictions (akin to the G-dwarf
problem in the solar neighborhood); it is suggested that an early infall phase
can account for that problem, as well as for the observed DMDs of dwarf
satellite galaxies.Accretion of galaxies similar (but not identical) to the
progenitors of present day dwarf satellites of the Milky Way may well have
formed the Galactic halo.


title: Theory for superfluidity in a Bose system

abstract:
  We present a microscopic theory for superfluidity in an interacting
many-particle Bose system (such as liquid $^4$He). We show that, similar to
superconductivity in superconductors, superfluidity in a Bose system arises
from pairing of particles of opposite momenta. We show the existence of an
energy gap in single-particle excitation spectrum in the superfluid state and
the existence of a specific heat jump at the superfluid transition. We derive
an expression for superfluid particle density $n_s$ as a function of
temperature $T$ and superfluid velocity ${\bf v}_s$. We show that
superfluid-state free energy density $F$ is an increasing function of $v_s$
(i.e., $\partial F/\partial v_s > 0$), which indicates that a superfluid has a
tendency to remain motionless (this result qualitatively explains the
Hess-Fairbank effect, which is analogous to the Meissner effect in
superconductors). We further speculate the existence of the equation ${\bf
j}=-\Lambda\nabla\times \text{\boldmath $\omega$}$, where ${\bf j} = n_s{\bf
v}_s$ is the superfluid current density, $\text{\boldmath
$\omega$}=\nabla\times {\bf v}_s$ the superfluid vorticity, and $\Lambda$ a
positive constant (with the help of this equation, the Hess-Fairbank effect can
be quantitatively described).


title:
Cross-sections and analyzing powers for $(p,n)$ reactions on ${}^{3}{\rm
  He}$ and ${}^{4}{\rm He}$ at 346 MeV

abstract:
  The cross-sections and analyzing powers for $(p,n)$ reactions on ${}^{3}{\rm
He}$ and ${}^{4}{\rm He}$ have been measured at a bombarding energy of $T_p$ =
346 MeV and reaction angles of $\theta_{\rm lab}$ =
$9.4^{\circ}$--$27^{\circ}$.
  The energy transfer spectra for ${}^{3}{\rm He}(p,n)$ at large $\theta_{\rm
lab}$ ($\ge$ $16^{\circ}$) are dominated by quasielastic contributions, and can
be reasonably reproduced by plane-wave impulse approximation (PWIA)
calculations for quasielastic scattering.
  By contrast, the known $L$ = 1 resonances in ${}^{4}{\rm Li}$ are clearly
observed near the threshold in the ${}^{4}{\rm He}(p,n)$ spectra.
  Because these contributions are remarkable at small angles, the energy
spectra are significantly different from those expected for quasielastic
scattering.
  The data are compared with the PWIA calculations, and it is found that the
quasielastic contributions are dominant at large $\theta_{\rm lab}$ ($\ge$
$22^{\circ}$).
  The nuclear correlation effects on the quasielastic peak for ${}^{4}{\rm
He}(p,n)$ are also discussed.


title:
The SAURON project - XII. Kinematic substructures in early-type
  galaxies: evidence for disks in fast rotators

abstract:
  [Abridged] We analysed two-dimensional maps of 48 early-type galaxies
obtained with the SAURON and OASIS integral-field spectrographs using
kinemetry, a generalisation of surface photometry to the higher order moments
of the line-of-sight velocity distribution (LOSVD). In the SAURON sample, we
find that 31% of early-type galaxies are single component systems. 91% of the
multi-components systems have two kinematic subcomponents, the rest having
three. In addition, 29% of galaxies have kinematically decoupled components,
nuclear components with significant kinematic twists. We find that the velocity
maps of fast rotators closely resemble those of inclined disks, except in the
transition regions between kinematic subcomponents. In terms of E/S0
classification, this means that 74% of Es and 92% of S0s have components with
disk-like kinematics. For the majority of fast rotators, the kinematic axial
ratios are equal to or less than their photometric axial ratios, contrary to
what is predicted with isotropic Jeans models viewed at different inclinations.
The position angles of fast rotators are constant, while they vary abruptly in
slow rotators. Velocity dispersion maps of face-on galaxies have shapes similar
to the distribution of light. We constructed local (bin-by-bin) h3 - V/sigma
and h4 - V/sigma diagrams from SAURON observations. We confirm the classical
anti-correlation of h3 and V\sigma, but we also find that h3 is almost zero in
some objects or even weakly correlated with V/sigma. The distribution of h4 for
fast and slow rotators is mildly positive on average. The difference between
slow and fast rotators is traceable throughout all moments of the LOSVD, with
evidence for different intrinsic shapes and orbital contents and, hence, likely
different evolutionary paths.


title: Isotope effect in quasi-two-dimensional metal-organic antiferromagnets

abstract:
  Although the isotope effect in superconducting materials is well-documented,
changes in the magnetic properties of antiferromagnets due to isotopic
substitution are seldom discussed and remain poorly understood. This is perhaps
surprising given the possible link between the quasi-two-dimensional (Q2D)
antiferromagnetic and superconducting phases of the layered cuprates. Here we
report the experimental observation of shifts in the N\'{e}el temperature and
critical magnetic fields ($\Delta T_{\rm N}/T_{\rm N}\approx 4%$; $\Delta
B_{\rm c}/B_{\rm c}\approx 4%$) in a Q2D organic molecular antiferromagnets on
substitution of hydrogen for deuterium. These compounds are characterized by
strong hydrogen bonds through which the dominant superexchange is mediated. We
evaluate how the in-plane and inter-plane exchange energies evolve as the
hydrogens on different ligands are substituted, and suggest a possible
mechanism for this effect in terms of the relative exchange efficiency of
hydrogen and deuterium bonds.


title: A Search for the Near-Infrared Counterpart to GCRT J1745-3009

abstract:
  We present an optical/near-infrared search for a counterpart to the
perplexing radio transient GCRT J1745-3009, a source located ~1 degree from the
Galactic Center. Motivated by some similarities to radio bursts from nearby
ultracool dwarfs, and by a distance upper limit of 70 pc for the emission to
not violate the 1e12 K brightness temperature limit for incoherent radiation,
we searched for a nearby star at the position of GCRT J1745-3009. We found only
a single marginal candidate, limiting the presence of any late-type star to >1
kpc (spectral types earlier than M9), >200 pc (spectral types L and T0-T4), and
>100 pc (spectral types T4-T7), thus severely restricting the possible local
counterparts to GCRT J1745-3009. We also exclude any white dwarf within 1 kpc
or a supergiant star out to the distance of the Galactic Center as possible
counterparts. This implies that GCRT J1745-3009 likely requires a coherent
emission process, although whether or not it reflects a new class of sources is
unclear.


title: Neutralino Dark Matter from Indirect Detection Revisited

abstract:
  We revisit indirect detection possibilities for neutralino dark matter,
emphasizing the complementary roles of different approaches. While thermally
produced dark matter often requires large astrophysical "boost factors" to
observe antimatter signals, the physically motivated alternative of non-thermal
dark matter can naturally provide interesting signals, for example from light
wino or Higgsino dark matter. After a brief review of cosmic ray propagation,
we discuss signals for positrons, antiprotons, synchrotron radiation and gamma
rays from wino annihilation in the galactic halo, and examine their
phenomenology. For pure wino dark matter relevant to the LHC, PAMELA and GLAST
should report signals.


title: Formation and decay of hadronic resonances in the QGP

abstract:
  Hadronic resonances can play a pivotal role in providing experimental
evidence for partial chiral symmetry restoration in the deconfined quark-gluon
phase produced at RHIC. Their lifetimes, which are comparable to the lifetime
of the partonic plasma phase, make them an invaluable tool to study medium
modifications to the resonant state due to the chiral transition. In this paper
we show that the heavier, but still abundant, light and strange quark
resonances K*, phi, Delta and Lambda* have large probability to be produced
well within the plasma phase due to their short formation times. We demonstrate
that, under particular kinematic conditions, these resonances can be formed and
will decay inside the partonic state, but still carry sufficient momentum to
not interact strongly with the hadronic medium after the QCD phase transition.
Thus, K*, phi, Delta and Lambda* should exhibit the characteristic property
modifications which can be attributed to chiral symmetry restoration, such as
mass shifts, width broadening or branching ratio modifications.


title:
The regularity and exponential decay of solution for a linear wave
  equation associated with two-point boundary conditions

abstract:
  This paper is concerned with the existence and the regularity of global
solutions to the linear wave equation associated with two-point type boundary
conditions. We also investigate the decay properties of the global solutions to
this problem by the construction of a suitable Lyapunov functional.


title:
Geometric discrete analogues of tangent bundles and constrained
  Lagrangian systems

abstract:
  Discretizing variational principles, as opposed to discretizing differential
equations, leads to discrete-time analogues of mechanics, and, systematically,
to geometric numerical integrators. The phase space of such variational
discretizations is often the set of configuration pairs, analogously
corresponding to initial and terminal points of a tangent vectors. We develop
alternative discrete analogues of tangent bundles, by extending tangent vectors
to finite curve segments, one curve segment for each tangent vector. Towards
flexible, high order numerical integrators, we use these discrete tangent
bundles as phase spaces for discretizations of the variational principles of
Lagrangian systems, up to the generality of nonholonomic mechanical systems
with nonlinear constraints. We obtain a self-contained and transparent
development, where regularity, equations of motion, symmetry and momentum, and
structure preservation, all have natural expressions.


title: Quasi-Instantons and Supersymmetry Breaking

abstract:
  We show that supersymmetric gauge theories with a product gauge group admit
quasi-instantons, which, like instantons, sit at the absolute minimum of the
action in the corresponding topological sector. However, unlike ordinary
instantons which preserve part of the supersymmetry, these break all
supersymmetries of the action. We also provide a generalization where
quasi-instantons take value in the associated Lie algebra of the recently
proposed 3-algebras. When the structure constants and the metric of the algebra
are covariantly constant, the gauge bundle admits new topological sectors with
quasi-instantons at the minimum of the action.


title:
A First-Order Non-Homogeneous Markov Model for the Response of Spiking
  Neurons Stimulated by Small Phase-Continuous Signals

abstract:
  We present a first-order non-homogeneous Markov model for the
interspike-interval density of a continuously stimulated spiking neuron. The
model allows the conditional interspike-interval density and the stationary
interspike-interval density to be expressed as products of two separate
functions, one of which describes only the neuron characteristics, and the
other of which describes only the signal characteristics. This allows the use
of this model to predict the response when the underlying neuron model is not
known or well determined. The approximation shows particularly clearly that
signal autocorrelations and cross-correlations arise as natural features of the
interspike-interval density, and are particularly clear for small signals and
moderate noise. We show that this model simplifies the design of spiking neuron
cross-correlation systems, and describe a four-neuron mutual inhibition network
that generates a cross-correlation output for two input signals.


title: Generation of finite wave trains in excitable media

abstract:
  Spatiotemporal control of excitable media is of paramount importance in the
development of new applications, ranging from biology to physics. To this end
we identify and describe a qualitative property of excitable media that enables
us to generate a sequence of traveling pulses of any desired length, using a
one-time initial stimulus. The wave trains are produced by a transient
pacemaker generated by a one-time suitably tailored spatially localized finite
amplitude stimulus, and belong to a family of fast pulse trains. A second
family, of slow pulse trains, is also present. The latter are created through a
clumping instability of a traveling wave state (in an excitable regime) and are
inaccessible to single localized stimuli of the type we use. The results
indicate that the presence of a large multiplicity of stable, accessible,
multi-pulse states is a general property of simple models of excitable media.


title:
A Parameter Study of Classical Be Star Disk Models Constrained by
  Optical Interferometry

abstract:
  We have computed theoretical models of circumstellar disks for the classical
Be stars $\kappa$ Dra, $\beta$ Psc, and $\upsilon$ Cyg. Models were constructed
using a non-LTE radiative transfer code developed by \citet{sig07} which
incorporates a number of improvements over previous treatments of the disk
thermal structure, including a realistic chemical composition. Our models are
constrained by direct comparison with long baseline optical interferometric
observations of the H$\alpha$ emitting regions and by contemporaneous H$\alpha$
line profiles. Detailed comparisons of our predictions with H$\alpha$
interferometry and spectroscopy place very tight constraints on the density
distributions for these circumstellar disks.


title:
Error analysis of variational integrators of unconstrained Lagrangian
  systems

abstract:
  A complete error analysis of variational integrators is obtained, by blowing
up the discrete variational principles, all of which have a singularity at zero
time-step. Divisions by the time step lead to an order that is one less than
observed in simulations, a deficit that is repaired with the help of a new
past-future symmetry.


title:
Gauge Theories with Time Dependent Couplings and their Cosmological
  Duals

abstract:
  We consider the N=4 SYM theory in flat 3+1 dimensional spacetime with a time
dependent coupling constant which vanishes at $t=0$, like $g_{YM}^2=t^p$. In an
analogous quantum mechanics toy model we find that the response is singular.
The energy diverges at $t=0$, for a generic state. In addition, if $p>1$ the
phase of the wave function has a wildly oscillating behavior, which does not
allow it to be continued past $t=0$. A similar effect would make the gauge
theory singular as well, though nontrivial effects of renormalization could
tame this singularity and allow a smooth continuation beyond $t=0$. The gravity
dual in some cases is known to be a time dependent cosmology which exhibits a
space-like singularity at $t=0$. Our results, if applicable in the gauge theory
for the case of the vanishing coupling, imply that the singularity is a genuine
sickness and does not admit a meaningful continuation. When the coupling
remains non-zero and becomes small at $t=0$, the curvature in the bulk becomes
of order the string scale. The gauge theory now admits a time evolution beyond
this point. In this case, a finite amount of energy is produced which possibly
thermalizes and leads to a black hole in the bulk.


title:
System-size independence of directed flow at the Relativistic Heavy-Ion
  Collider

abstract:
  We measure directed flow ($v_1$) for charged particles in Au+Au and Cu+Cu
collisions at $\sqrt{s_{NN}} =$ 200 GeV and 62.4 GeV, as a function of
pseudorapidity ($\eta$), transverse momentum ($p_t$) and collision centrality,
based on data from the STAR experiment. We find that the directed flow depends
on the incident energy but, contrary to all existing models, not on the size of
the colliding system at a given centrality. We extend the validity of the
limiting fragmentation concept to different collision systems, and investigate
possible explanations for the observed sign change in $v_1(p_t)$.


title: Model based IVHM system for the solid rocket booster

abstract:
  We report progress in the development of a model-based hybrid probabilistic
approach to an on-board IVHM for solid rocket boosters (SRBs) that can
accommodate the abrupt changes of the model parameters in various nonlinear
dynamical off-nominal regimes. The work is related to the ORION mission
program. Specifically, a case breach fault for SRBs is considered that takes
into account burning a hole through the rocket case, as well as ablation of the
nozzle throat under the action of hot gas flow. A high-fidelity model (HFM) of
the fault is developed in FLUENT in cylindrical symmetry. The results of the
FLUENT simulations are shown to be in good agreement with quasi-stationary
approximation and analytical solution of a system of one-dimensional partial
differential equations (PDEs) for the gas flow in the combustion chamber and in
the hole through the rocket case.


title:
Coping with the Pais-Uhlenbeck oscillator's ghosts in a canonical
  approach

abstract:
  A {\em complex} canonical transformation is found that takes the fourth order
derivative Pais-Uhlenbeck oscillator into two independent harmonic oscillators
thus showing that this model has energy bounded from below, unitary
time-evolution and no negative norm states, or ghosts. Such transformation
yields a positive definite inner product consistent with reality conditions in
the Hilbert space. The method is illustrated by eliminating the negative norm
states in a complex oscillator. Extensions to other higher order mechanical
models and field theory are discussed.


title: Ergodic BSDEs and related PDEs with Neumann boundary conditions

abstract:
  We study a new class of ergodic backward stochastic differential equations
(EBSDEs for short) which is linked with semi-linear Neumann type boundary value
problems related to ergodic phenomenas. The particularity of these problems is
that the ergodic constant appears in Neumann boundary conditions. We study the
existence and uniqueness of solutions to EBSDEs and the link with partial
differential equations. Then we apply these results to optimal ergodic control
problems.


title:
Low-energy constraints on kappa-Minkowski extension of the Standard
  Model

abstract:
  We investigate the phenomenological consequences of kappa-Minkowski extension
of the Standard Model, working in the linear order in inverse $\kappa$. At this
order the *-deformed Lagrangian can be expanded in the series of dimension five
operators that have non-trivial transformation properties under the ordinary
Lorentz invariance. Such operators cause the Lorentz-violating signatures at
low energies, and in particular lead to the anomalous spin precession linked to
the external direction. The experimental bounds on this phenomenon then
restrict parameter $\kappa$ to be above 10^{23} GeV, making it difficult to
impose a direct connection between this theory and quantum gravity.


title:
Mean asymptotic behaviour of radix-rational sequences and dilation
  equations (Extended version)

abstract:
  The generating series of a radix-rational sequence is a rational formal power
series from formal language theory viewed through a fixed radix numeration
system. For each radix-rational sequence with complex values we provide an
asymptotic expansion for the sequence of its Ces\`aro means. The precision of
the asymptotic expansion depends on the joint spectral radius of the linear
representation of the sequence; the coefficients are obtained through some
dilation equations. The proofs are based on elementary linear algebra.


title: Inductive and Coinductive Components of Corecursive Functions in Coq

abstract:
  In Constructive Type Theory, recursive and corecursive definitions are
subject to syntactic restrictions which guarantee termination for recursive
functions and productivity for corecursive functions. However, many terminating
and productive functions do not pass the syntactic tests. Bove proposed in her
thesis an elegant reformulation of the method of accessibility predicates that
widens the range of terminative recursive functions formalisable in
Constructive Type Theory. In this paper, we pursue the same goal for productive
corecursive functions. Notably, our method of formalisation of coinductive
definitions of productive functions in Coq requires not only the use of ad-hoc
predicates, but also a systematic algorithm that separates the inductive and
coinductive parts of functions.


title:
Lattice and magnetic instabilities in CaFe2As2: A single crystal neutron
  diffraction study

abstract:
  Neutron diffraction measurements of a high quality single crystal of CaFe2As2
are reported. A sharp transition was observed between the high temperature
tetragonal and low temperature orthorhombic structures at TS = 172.5K (on
cooling) and 173.5K (on warming). Coincident with the structural transition we
observe a rapid, but continuous, ordering of the Fe moments, in a commensurate
antiferromagnetic structure is observed, with a saturated moment of
0.80(5)muB/Fe directed along the orthorhombic a-axis. The hysteresis of the
structural transition is 1K between cooling and warming and is consistent with
previous thermodynamic, transport and single crystal x-ray studies. The
temperature onset of magnetic ordering shifts rigidly with the structural
transition providing the clearest evidence to date of the coupling between the
structural and magnetic transitions in this material and the broader class of
iron arsenides.


title: Proposal for a nanoscale variable resistor/electromechanical transistor

abstract:
  A nanoscale variable resistor consisting of a metal nanowire (active
element), a dielectric, and a gate, is proposed. By means of the gate voltage,
stochastic transitions between different conducting states of the nanowire can
be induced, with a switching time as fast as picoseconds. With an appropriate
choice of dielectric, the transconductance of the device, which may also be
considered an ``electromechanical transistor,'' is shown to significantly
exceed the conductance quantum G_0=2e^2/h, a remarkable figure of merit for a
nanoscale device.


title:
Finite-size corrections in the SU(2) x SU(2) sector of type IIA string
  theory on AdS_4 x CP^3

abstract:
  We consider finite-size corrections in the SU(2) x SU(2) sector of type IIA
string theory on AdS_4 x CP^3, which is the string dual of the recently
constructed N=6 superconformal Chern-Simons theory of Aharony, Bergman,
Jafferis and Maldacena (ABJM theory). The string states we consider are in the
R x S^2 x S^2 subspace of AdS_4 x CP^3 with an angular momentum J on CP^3 being
large. We compute the finite-size corrections using two different methods, one
is to consider curvature corrections to the Penrose limit giving an expansion
in 1/J, the other by considering a low energy expansion in lambda'=lambda/J^2
of the string theory sigma-model, lambda being the 't Hooft coupling of the
dual ABJM theory. For both methods there are interesting issues to deal with.
In the near-pp-wave method there is a 1/\sqrt{J} interaction term for which we
use zeta-function regularization in order to compute the 1/J correction to the
energy. For the low energy sigma-model expansion we have to take into account a
non-trivial coupling to a non-dynamical transverse direction. We find agreement
between the two methods. At order lambda' and lambda'^2, for small lambda', our
results are analogous to the ones for the SU(2) sector in type IIB string
theory on AdS_5 x S^5. Instead at order lambda'^3 there are interactions
between the two two-spheres. We compare our results with the recently proposed
all-loop Bethe ansatz of Gromov and Vieira and find agreement.


title: Depth-zero base change for ramified U(2,1)

abstract:
  We give an explicit description of L-packets and quadratic base change for
depth-zero representations of ramified unitary groups in two and three
variables. We show that this base change lifting is compatible with a certain
lifting of families of representations of finite groups. We conjecture that
such a compatibility is valid in much greater generality.


title:
Rapid optical and X-ray timing observations of GX 339-4: flux
  correlations at the onset of a low/hard state

abstract:
  We present the discovery of optical/X-ray flux correlations on rapid
timescales in the low/hard state of the Galactic black hole GX 339-4. The
source had recently emerged from outburst and was associated with a
relatively-faint counterpart with mag V~17. The optical (VLT/ULTRACAM) and
X-ray (RXTE/PCA) data show a clear positive cross-correlation function (CCF)
signal, with the optical peak lagging X-rays by ~ 150 ms, preceded by a shallow
rise and followed by a steep decline along with broad anti-correlation dips.
Examination of the light curves shows that the main CCF features are reproduced
in superpositions of flares and dips. The CCF peak is narrow and the X-ray
auto-correlation function (ACF) is broader than the optical ACF, arguing
against reprocessing as the origin for the rapid optical emission. X-ray
flaring is associated with spectral hardening, but no corresponding changes are
detected around optical peaks and dips. The variability may be explained in the
context of synchrotron emission with interaction between a jet and a corona.
The complex CCF structure in GX 339-4 has similarities to that of another
remarkable X-ray binary XTE J1118+480, in spite of showing a weaker maximum
strength. Such simultaneous multi-wavelength, rapid timing studies provide key
constraints for modeling the inner regions of accreting stellar sources.


title:
Determination of stellar, orbital and planetary parameters using
  complete Monte-Carlo analysis -- the case of HAT-P-7b

abstract:
  The recently discovered transiting very hot Jupiter, HAT-P-7b, a planet
detected by the telescopes of HATNet, turned out to be among the ones subjected
to the highest irradiation from the parent star. As known, the combination of
photometric and spectroscopic data for such an object yields the stellar,
orbital and planetary parameters. In order to best characterize this particular
planet, we carried out a complex analysis based on a complete and simultaneous
Monte-Carlo solution using all available data. We included the discovery light
curves, partial follow-up light curves, the radial velocity data, and we used
the stellar evolution models to infer the stellar properties. This
self-consistent way of modeling provides the most precise estimate of the a
posteriori distributions of all of the system parameters of interest, and
avoids making assumptions on the values and uncertainties of any of the
internally derived variables describing the system. This analysis demonstrates
that even partial light curve information can be valuable. This may become very
important for future discoveries of planets with longer periods -- and
therefore longer transit durations -- where the chance of observing a full
event is small.


title: Is the Gini coefficient a stable measure of galaxy structure?

abstract:
  The Gini coefficient, a non-parametric measure of galaxy morphology, has
recently taken up an important role in the automated identification of galaxy
mergers. I present a critical assessment of its stability, based on a
comparison of HST/ACS imaging data from the GOODS and UDF surveys. Below a
certain signal-to-noise level, the Gini coefficient depends strongly on the
signal-to-noise ratio, and thus becomes useless for distinguishing different
galaxy morphologies. Moreover, at all signal-to-noise levels the Gini
coefficient shows a strong dependence on the choice of aperture within which it
is measured. Consequently, quantitative selection criteria involving the Gini
coefficient, such as a selection of merger candidates, cannot always be
straightforwardly applied to different datasets. I discuss whether these
effects could have affected previous studies that were based on the Gini
coefficient, and establish signal-to-noise limits above which measured Gini
values can be considered reliable.


title:
A Radio and Optical Polarization Study of the Magnetic Field in the
  Small Magellanic Cloud

abstract:
  We present a study of the magnetic field of the Small Magellanic Cloud (SMC),
carried out using radio Faraday rotation and optical starlight polarization
data. Consistent negative rotation measures (RMs) across the SMC indicate that
the line-of-sight magnetic field is directed uniformly away from us with a
strength 0.19 +/- 0.06 microGauss. Applying the Chandrasekhar-Fermi method to
starlight polarization data yields an ordered magnetic field in the plane of
the sky of strength 1.6 +/- 0.4 microGauss oriented at a position angle 4 +/-
12 degs, measured counter-clockwise from the great circle on the sky joining
the SMC to the Large Magellanic Cloud (LMC). We construct a three-dimensional
magnetic field model of the SMC, under the assumption that the RMs and
starlight polarization probe the same underlying large-scale field. The vector
defining the overall orientation of the SMC magnetic field shows a potential
alignment with the vector joining the center of the SMC to the center of the
LMC, suggesting the possibility of a "pan-Magellanic'' magnetic field. A
cosmic-ray driven dynamo is the most viable explanation of the observed field
geometry, but has difficulties accounting for the observed uni-directional
field lines. A study of Faraday rotation through the Magellanic Bridge is
needed to further test the pan-Magellanic field hypothesis.


title: EAZY: A Fast, Public Photometric Redshift Code

abstract:
  We describe a new program for determining photometric redshifts, dubbed EAZY.
The program is optimized for cases where spectroscopic redshifts are not
available, or only available for a biased subset of the galaxies. The code
combines features from various existing codes: it can fit linear combinations
of templates, it includes optional flux- and redshift-based priors, and its
user interface is modeled on the popular HYPERZ code. A novel feature is that
the default template set, as well as the default functional forms of the
priors, are not based on (usually highly biased) spectroscopic samples, but on
semi-analytical models. Furthermore, template mismatch is addressed by a novel
rest-frame template error function. This function gives different wavelength
regions different weights, and ensures that the formal redshift uncertainties
are realistic. We introduce a redshift quality parameter, Q_z, that provides a
robust estimate of the reliability of the photometric redshift estimate.
Despite the fact that EAZY is not "trained" on spectroscopic samples, the code
(with default parameters) performs very well on existing public datasets. For
K-selected samples in CDF-South and other deep fields we find a 1-sigma scatter
in dz/(1+z) of 0.034, and we provide updated photometric redshift catalogs for
the FIRES, MUSYC, and FIREWORKS surveys.


title:
Computational model for the formation of uniform silver spheres by
  aggregation of nanosize precursors

abstract:
  We present results of computational modeling of the formation of uniform
spherical silver particles prepared by rapid mixing of ascorbic acid and
silver-amine complex solutions in the absence of a dispersing agent. Using an
accelerated integration scheme to speed up the calculation of particle size
distributions in the latter stages, we find that the recently reported
experimental results -- some of which are summarized here -- can be modeled
effectively by the two-stage formation mechanism used previously to model the
preparation of uniform gold spheres. We treat both the equilibrium
concentration of silver atoms and the surface tension of silver precursor
nanocrystals as free parameters, and find that the experimental reaction time
scale is fit by a narrow region of this two-parameter space. The kinetic
parameter required to quantitatively match the final particle size is found to
be very close to that used previously in modeling the formation of gold
particles, suggesting that similar kinetics governs the aggregation process and
providing evidence that the two-stage model of burst nucleation of
nanocrystalline precursors followed by their aggregation to form the final
colloids can be applied to systems both with and without dispersing agents. The
model also reproduced semiquantitatively the effects of solvent viscosity and
temperature on the particle preparation.