title:
Protected Rabi oscillation induced by natural interactions among
  physical qubits

abstract:
  For a system composed of nine qubits, we show that natural interactions among
the qubits induce the time evolution that can be regarded, at discrete times,
as the Rabi oscillation of a logical qubit. Neither fine tuning of the
parameters nor switching of the interactions is necessary. Although
straightforward application of quantum error correction fails, we propose a
protocol by which the logical Rabi oscillation is protected against all
single-qubit errors. The present method thus opens a simple and realistic way
of protecting the unitary time evolution against noise.


title:
The role of pressure anisotropy on the maximum mass of cold compact
  stars

abstract:
  We study the physical features of a class of exact solutions for cold compact
anisotropic stars. The effect of pressure anisotropy on the maximum mass and
surface redshift is analysed in the Vaidya-Tikekar model. It is shown that
maximum compactness, redshift and mass increase in the presence of anisotropic
pressures; numerical values are generated which are in agreement with
observation.


title: Carlitz q-Bernoulli numbers and q-Stirling numbers

abstract:
  In this paper we consider carlitz q-Bernoulli numbers and q-stirling numbers
of the first and the second kind. From these numbers we derive many interesting
formulae associated with q-Bernoulli numbers.


title: A p-adic analogue of a formula of Ramanujan

abstract:
  During his lifetime, Ramanujan provided many formulae relating binomial sums
to special values of the Gamma function. Based on numerical computations, Van
Hamme recently conjectured $p$-adic analogues to such formulae. Using a
combination of ordinary and Gaussian hypergeometric series, we prove one of
these conjectures.


title: Structure of Ann-categories and Mac Lane - Shukla cohomology

abstract:
  In this paper we study the structure of a class of categories having two
operations which satisfy axioms analoguos to that of rings. Such categories are
called "Ann - categories". We obtain the classification theorems for regular
Ann - categories and Ann - functors by using Mac Lane - Shukla cohomology of
rings. These results give new interpretations of the cohomology groups and of
the rings


title:
A combinatorial realization of the Heisenberg action on the space of
  conformal blocks

abstract:
  This paper has been withdrawn by the author. Improved versions
(arXiv:1109.5548 and arXiv:0708.4190) are accepted.


title: Stability properties for the higher dimensional catenoid in $\rr^{n+1}$

abstract:
  This paper concerns some stability properties of higher dimensional catenoids
in $\rr^{n+1}$ with $n\ge 3$. We prove that higher dimensional catenoids have
index one. We use $\delta$-stablity for minimal hypersurfaces and show that the
catenoid is $\frac 2n$-stable and a complete $\frac 2n$-stable minimal
hypersurface is a catenoid or a hyperplane provided the second fundamental form
satisfies some decay conditions.


title: HST/STIS spectroscopy of the environment in the starburst core of M82

abstract:
  [Abridged] We present high-resolution optical HST/STIS observations made with
two slits crossing four of the brightest starburst clumps in the vicinity of
the nucleus of M82. These provide H_alpha kinematics, extinction, electron
density and emission measures. From the radial velocity curves we confirm the
presence of a stellar bar, and find that the super star cluster M82-A1 has a
position and radial velocity consistent with it being at the end of one of the
unique x2 bar orbits formed by an inner Lindblad resonance. We derive a new
model for the orientation of the bar and disc with respect to the main
starburst clumps, and propose that clump A has formed within the bar region as
a result of gas interactions between the bar orbits, whereas region C lies at
the edge of the bar and regions D and E are located further out from the
nucleus but heavily obscured. We derive extremely high interstellar densities,
corresponding to ISM pressures of P/k ~ 0.5-1.0 x 10^7 cm^-3 K, and discuss the
implications of the measured gas properties surrounding the nuclear star
clusters on the production and evolution of the galactic wind. Despite varying
pressures, the ionization parameter is uniform down to parsec-scales, and we
discuss why this might be so. Where the S/N of our spectra are high enough, we
identify multiple emission-line components. Through detailed Gaussian
line-fitting, we identify a ubiquitous broad (200-300 km/s) underlying
component to the bright H_alpha line, and discuss the physical mechanism(s)
that could be responsible for such widths. We conclude that the evaporation
and/or ablation of material from interstellar gas clouds caused by the impact
of the high-energy photons and fast-flowing cluster winds produces a highly
turbulent layer on the surface of the clouds from which the emission arises.


title:
Ab-initio calculation of the vibrational modes of SiH4, H2SiO, Si10H16,
  and Si10H14O

abstract:
  We have studied the normal modes of hydrogenated and oxidized silicon
nanocrystals, namely SiH4 (silan), H2SiO (silanon), Si10H16 and Si10H14O. The
small clusters (SiH4 and H2SiO) have been used for convergence tests and their
bondlengths and frequencies have been compared with experimental and
theoretical reference data. For the large clusters (Si10H16 and Si10H14O) we
have investigated the vibrational density of states where we have identified
the oxygen-related spectral features. The vibrational modes have been also
analyzed with respect to the displacement patterns. The calculations have been
carried out within the density-functional and density-functional perturbation
theory using the local-density approximation.


title:
Observation of $\psi(4415)\to D \bar D{}^{*}_2(2460)$ decay using
  initial-state radiation

abstract:
  We report the first observation of the $\psi(4415)$ resonance in the reaction
$\e^+e^-\to D^0 D^-\pi^+$ and a measurement of its cross section in the
center-of-mass energy range $4.0\mathrm{GeV}$ to $5.0\mathrm{GeV}$ with initial
state radiation. From a study of resonant structure in $\psi(4415)$ decay we
conclude that the $\psi(4415)\to D^0 D^-\pi^+$ decay is dominated by
$\psi(4415)\to D \bar D{}^{*}_2(2460)$. We obtain $\mathcal{B}(\psi(4415)\to
D^0 D^-\pi^+_{\mathrm {non-resonant}})/\mathcal{B}(\psi(4415)\to D \bar
D{}^{*}_2(2460)\to D^0 D^-\pi^+)<0.22$ at 90% C.L. The analysis is based on a
data sample collected with the Belle detector with an integrated luminosity of
673 $\mathrm{fb}^{-1}$.


title: Autocatalytic reaction on low-dimensional substrates

abstract:
  We discuss a model for the autocatalytic reaction $A+B\to 2A$ on substrates
where the reactants perform a compact exploration of the space, i.e., on
lattices whose spectral dimension $\tilde{d}$ is $< 2$. For finite systems, the
total time $\tau$ for the reaction to end scales according to two different
regimes, for high and low concentrations of reactants. The functional
dependence of $\tau$ on the volume of the substrate and the concentration of
reactants is discussed within a mean-field approximation. Possible applications
are discussed.


title: Destruction of Anderson localization by a weak nonlinearity

abstract:
  We study numerically a spreading of an initially localized wave packet in a
one-dimensional discrete nonlinear Schr\"odinger lattice with disorder. We
demonstrate that above a certain critical strength of nonlinearity the Anderson
localization is destroyed and an unlimited subdiffusive spreading of the field
along the lattice occurs. The second moment grows with time $ \propto
t^\alpha$, with the exponent $\alpha$ being in the range $0.3 - 0.4$. For small
nonlinearities the distribution remains localized in a way similar to the
linear case.


title: Anisotropic magnetoresistance in nanocontacts

abstract:
  We present ab initio calculations of the evolution of anisotropic
magnetoresistance (AMR) in Ni nanocontacts from the ballistic to the tunnel
regime. We find an extraordinary enhancement of AMR, compared to bulk, in two
scenarios. In systems without localized states, like chemically pure break
junctions, large AMR only occurs if the orbital polarization of the current is
large, regardless of the anisotropy of the density of states. In systems that
display localized states close to the Fermi energy, like a single electron
transistor with ferromagnetic electrodes, large AMR is related to the variation
of the Fermi energy as a function of the magnetization direction.


title: On surface tension for compact stars

abstract:
  In an earlier treatment it was demonstrated that general relativity gives
higher values of surface tension in strange stars with quark matter than
neutron stars.We generate the modified Tolman-Oppenheimer-Volkoff equation to
incorporate anisotropic matter and use this to show that pressure anisotropy
provides for a wide range of behaviour in the surface tension than is the case
with isotropic pressures. In particular it is possible that anisotropy
drastically decreases the value of the surface tension.


title: Phase Transitions in Pressurised Semiflexible Polymer Rings

abstract:
  We propose and study a model for the equilibrium statistical mechanics of a
pressurised semiflexible polymer ring. The Hamiltonian has a term which couples
to the algebraic area of the ring and a term which accounts for bending
(semiflexibility). The model allows for self-intersections. Using a combination
of Monte Carlo simulations, Flory-type scaling theory, mean-field
approximations and lattice enumeration techniques, we obtain a phase diagram in
which collapsed and inflated phases are separated by a continuous transition.
The scaling properties of the averaged area as a function of the number of
units of the ring are derived. For large pressures, the asymptotic behaviour of
the area is calculated for both discrete and lattice versions of the model. For
small pressures, the area is obtained through a mapping onto the quantum
mechanical problem of an electron moving in a magnetic field. The simulation
data agree well with the analytic and mean-field results.


title: A construction of Horikawa surface via Q-Gorenstein smoothings

abstract:
  In this article we prove that Fintushel-Stern's construction of Horikawa
surface, which is obtained from an elliptic surface via a rational blow-down
surgery in smooth category, can be performed in complex category. The main
technique involved is Q-Gorenstein smoothings.


title:
Optical polarizabilities of large molecules measured in near-field
  interferometry

abstract:
  We discuss a novel application of matter wave interferometry to characterize
the scalar optical polarizability of molecules at 532 nm. The interferometer
presented here consists of two material absorptive gratings and one central
optical phase grating. The interaction of the molecules with the standing light
wave is determined by the optical dipole force and is therefore directly
dependent on the molecular polarizability at the wavelength of the diffracting
laser light. By comparing the observed matter-wave interference contrast with a
theoretical model for several intensities of the standing light wave and
molecular velocities we can infer the polarizability in this first
proof-of-principle experiment for the fullerenes C60 and C70 and we find a good
agreement with literature values.


title: CP Violation in Two Zero Texture Neutrino Mass Matrices

abstract:
  It has been shown that the neutrino mass matrices with two texture zeros in
the charged lepton basis predict non-zero 1-3 mixing and are necessarily CP
violating with one possible exception in class C for maximal mixing.


title: Do we know eventually p(e)?

abstract:
  A quasi-particle model is employed to derive from available lattice QCD
calculations an equation of state useable in hydrodynamical simulations of the
expansion stage of strongly interacting matter created in ultra-relativistic
heavy-ion collisions. Various lattice results give an astonishing agreement of
the pressure as a function of energy density at large energy densities supposed
the pseudo-critical temperature is in the range $170 \pm 15$ MeV, while in the
transition region the equation of state is not yet well constrained. Therefore,
one can construct a family of equations of state by bridging the uncertain
region from the uniquely given high-energy density region part to a hadronic
equation of state by suitable interpolation together with the extrapolation to
non-zero baryon density by means of the quasi-particle model. We present a
series of tests of the model, discuss the chiral extrapolation and the role of
Landau damping. We also briefly sketch the path of cosmic matter in the early
universe in the phase diagram.


title:
Enhancement of the Gilbert damping constant due to spin pumping in
  noncollinear ferromagnet/nonmagnet/ferromagnet trilayer systems

abstract:
  We analyzed the enhancement of the Gilbert damping constant due to spin
pumping in non-collinear ferromagnet / non-magnet / ferromagnet trilayer
systems. We show that the Gilbert damping constant depends both on the
precession angle of the magnetization of the free layer and on the direction of
the magntization of the fixed layer. We find the condition to be satisfied to
realize strong enhancement of the Gilbert damping constant.


title:
Single-crystal growth and magnetic properties of the metallic molybdate
  pyrochlore Sm2Mo2O7

abstract:
  We have successfully grown cm3-size single crystals of the
metallic-ferromagnet Sm2Mo2O7 by the floating-zone method using an infrared-red
image furnace. The growth difficulties and the remedies found using a 2-mirror
image furnace are discussed. Magnetization studies along the three crystalline
axes of the compound are presented and discussed based on our recent proposal
of an ordered spin-ice ground state for this compound


title: Generalised compact spheres in electric fields

abstract:
  We present exact solutions to the Einstein-Maxwell system of equations in
spherically symmetric gravitational fields with a specified form of the
electric field intensity. The condition of pressure isotropy yields a
difference equation with variable, rational coefficients. In an earlier
treatment this condition was integrated by first transforming it to a
hypergeometric equation. We demonstrate that it is possible to obtain a more
general class of solutions to the Einstein-Maxwell system both in the form of
special functions and elementary functions. Our results contain particular
solutions found previously including models of charged relativistic spheres and
uncharged neutron star models.


title: On the moduli stack of commutative, 1-parameter formal Lie groups

abstract:
  We attempt to develop a general algebro-geometric study of the moduli stack
of commutative, 1-parameter formal Lie groups. We emphasize the pro-algebraic
structure of this stack: it is the inverse limit, over varying n, of moduli
stacks of n-buds, and these latter stacks are algebraic. Our main results
pertain to aspects of the height stratification relative to fixed prime p on
the stacks of buds and formal Lie groups. We conclude with a largely expository
account of some foundational material on limits in bicategories.


title: Effects of Unparticles on Running of Gauge Couplings

abstract:
  Unparticles charged under a gauge group can contribute to the running of the
gauge coupling. We show that a scalar unparticle of scaling dimension d
contributes to the \beta function a term that is (2-d) times that from a scalar
particle in the same representation. This result has important implications on
asymptotic freedom. An unparticle with d>2, in contrast to its matter
counterpart, can speed up the approach to asymptotic freedom for a non-Abelian
gauge theory and has the tendency to make an Abelian theory also asymptotically
free. For not spoiling the excellent agreement of the standard model (SM) with
precision tests, the infrared cut-off, m, of such an unparticle would be high
but might still be reachable at colliders such as LHC and ILC. Furthermore, if
the unparticle scale \Lambda_\calU is high enough, unparticles could
significantly modify the unification pattern of the SM gauge couplings. For
instance, with 3 scalar unparticles of d\sim 2.5 in the adjoint representation
of the strong gauge group but neutral under the electroweak one, the three
gauge couplings would unify at a scale of \sim 8\times 10^{12} {\rm GeV}, which
is several orders of magnitude below the supersymmetric unification scale.


title: Electron-electron Relaxation in Disordered Interacting Systems

abstract:
  We study the relaxation of a non-equilibrium carrier distribution under the
influence of the electron-electron interaction in the presence of disorder.
Based on the Anderson model, our Hamiltonian is composed from a single particle
part including the disorder and a two-particle part accounting for the Coulomb
interaction. We apply the equation-of-motion approach for the density matrix,
which provides a fully microscopic description of the relaxation. Our results
show that the nonequlibrium distribution in this closed and internally
interacting system relaxes exponentially fast during the initial dynamics. This
fast relaxation can be described by a phenomenological damping rate. The total
single particle energy decreases in the redistribution process, keeping the
total energy of the system fixed. It turns out that the relaxation rate
decreases with increasing disorder.


title: Finite dimensional modules and perpendicular subcategories

abstract:
  We explain how, under some hypotheses, one can construct a sequence of finite
dimensional $kG$-modules that lie in certain prescribed additive subcategories,
but whose direct limits do not. We use these to show that many of the
triangulated quotients of $\Mod$ are not generated, as triangulated categories,
by the corresponding quotient of $\mod$ considered as a full subcategory.


title: Swift/XRT monitoring of five orbital cycles of LSI +61 303

abstract:
  LSI +61 303 is one of the most interesting high-mass X-ray binaries owing to
its spatially resolved radio emission and its TeV emission, generally
attributed to non-thermal particles in an accretion-powered relativistic jet or
in the termination shock of the relativistic wind of a young pulsar. Also, the
nature of the compact object is still debated. Only LS 5039 and PSR B1259-63
(which hosts a non-accreting millisecond pulsar) have similar characteristics.
We study the X-ray emission from LSI +61 303 covering both short-term and
orbital variability. We also investigate the source spectral properties in the
soft X-ray (0.3-10 keV) energy range. 25 snapshot observations of LSI +61 303
have been collected in 2006 with the XRT instrument on-board the Swift
satellite over a period of four months, corresponding to about five orbital
cycles. Since individual data sets have too few counts for a meaningful
spectral analysis, we extracted a cumulative spectrum. The count rate folded at
the orbital phase shows a clear modulation pattern at the 26.5 days period and
suggests that the X-ray peak occurs around phase 0.65. Moreover, the X-ray
emission appears to be variable on a timescale of ~1 ks. The cumulative
spectrum is well described by an absorbed power-law model, with hydrogen column
density Nh=(5.7+/-0.3)E+21 cm^-2 and photon index 1.78+/-0.05. No accretion
disk signatures, such as an iron line, are found in the spectrum.


title:
A radio air shower surface detector as an extension for IceCube and
  IceTop

abstract:
  The IceCube neutrino detector is built into the Antarctic ice sheet at the
South Pole to measure high energy neutrinos. For this, 4800 photomultiplier
tubes (PMTs) are being deployed at depths between 1450 and 2450 meters into the
ice to measure neutrino induced charged particles like muons. IceTop is a
surface air shower detector consisting of 160 Cherenkov ice tanks located on
top of IceCube. To extend IceTop, a radio air shower detector could be built to
significantly increase the sensitivity at higher shower energies and for
inclined showers. As air showers induced by cosmic rays are a major part of the
muonic background in IceCube, IceTop is not only an air shower detector, but
also a veto to reduce the background in IceCube. Air showers are detectable by
radio signals with a radio surface detector. The major emission process is the
coherent synchrotron radiation emitted by e+ e- shower particles in the Earths
magnetic field (geosynchrotron effect). Simulations of the expected radio
signals of air showers are shown. The sensitivity and the energy threshold of
different antenna field configurations are estimated.


title: Predictions from type II see-saw mechanism in SU(5)

abstract:
  We propose a simple, testable, SU(5) model within the context of the type II
neutrino see-saw mechanism. It is based on requiring renormalizability, the
absence of any other matter fields besides those already present in the
Standard Model and consistency with all experimental data. These "minimal"
requirements, together with group-theoretical considerations, uniquely
determine the model and lead to interesting implications. The model predicts
correlation between a light SU(2) triplet boson responsible for the type II
see-saw mechanism and observable proton decay signatures. It also allows for an
enhanced production of doubly charged Higgs particles through the WW fusion
process due to a built-in custodial symmetry. This could also have profound
impact on the explicit realization of electroweak symmetry breaking. The model
also predicts the existence of a light scalar that transforms as a colour octet
and electroweak doublet, with interesting phenomenological consequences.


title: Existence and properties of geometric quotients

abstract:
  In this paper, we study quotients of groupoids and coarse moduli spaces of
stacks in a general setting. Geometric quotients are not always categorical,
but we present a natural topological condition under which a geometric quotient
is categorical. We also show the existence of geometric quotients of finite
flat groupoids and give explicit local descriptions. Exploiting similar
methods, we give an easy proof of the existence of quotients of flat groupoids
with finite stabilizers. As the proofs do not use noetherian methods and are
valid for general algebraic spaces and algebraic stacks, we obtain a slightly
improved version of Keel and Mori's theorem.


title:
Communication regimes in opinion dynamics: Changing the number of
  communicating agents

abstract:
  This article contributes in four ways to the research on time-discrete
continuous opinion dynamics with compromising agents. First, communication
regimes are introduced as an elementary concept of opinion dynamic models.
Second, we develop a model that covers two major models of continuous opinion
dynamics, i.e. the basic model of Deffuant and Weisbuch as well as the model of
Krause and Hegselmann. To combine these models, which handle different numbers
of communicating agents, we convert the convergence parameter of Deffuant and
Weisbuch into a parameter called self-support. Third, we present simulation
results that shed light on how the number of communicating agents but also how
the self-support affect opinion dynamics. The fourth contribution is a
theoretically driven criterion when to stop a simulation and how to extrapolate
to infinite many steps.


title:
On the interrelation between monopoles, vortices, topological charge and
  chiral symmetry breaking: an analysis using overlap fermions for SU(2)

abstract:
  We study the properties of configurations from which P-vortices on one hand
or Abelian monopoles on the other hand have been removed. We find that the zero
modes and the band of non-zero modes close to zero disappear from the spectrum
of the overlap Dirac operator, confirming the absence of topological charge and
quark condensate. The different behavior of the modified ensembles under
smearing compared to the unmodified Monte Carlo ensemble corroborates these
findings. The gluonic topological susceptibility rapidly approaches zero in
accordance with Q_{index}=0. The remaining (ultraviolet) monopoles without
vortices and -- to a less extent -- the remaining vortices without monopoles
are unstable under smearing whereas smearing of the unmodified Monte Carlo
ensemble effects the monopoles and vortices only by smoothing, reducing the
density only slightly.


title:
Far-field fluorescence microscopy beyond the diffraction limit:
  Fluorescence imaging with ultrahigh resolution

abstract:
  Fluorescence microscopy is an important and extensively utilised tool for
imaging biological systems. However, the image resolution that can be obtained
has a limit as defined through the laws of diffraction. Demand for improved
resolution has stimulated research into developing methods to image beyond the
diffraction limit based on far-field fluorescence microscopy techniques. Rapid
progress is being made in this area of science with methods emerging that
enable fluorescence imaging in the far-field to possess a resolution well
beyond the diffraction limit. This review outlines developments in far-field
fluorescence methods which enable ultrahigh resolution imaging and application
of these techniques to biology. Future possible trends and directions in
far-field fluorescence imaging with ultrahigh resolution are also outlined.


title: Sterile neutrino signals from supernovae

abstract:
  We investigate the effects of a mixing of active and sterile neutrinos on the
ratios of supernova electron neutrino flux ($F_e$) and antineutrino flux
($F_{\bar e}$) to the total flux of the other neutrino and antineutrino
flavours ($F_a$). We assume that the heaviest (in the normal hierarchy)
Standard Model neutrino $\nu_3$ mixes with a sterile neutrino resulting in a
pair of mass eigenstates with a small mass gap. Using the density matrix
formalism we solve numerically the the evolution of neutrino states in the
envelope of a supernova and determine the flux ratios $F_e/F_a$ and
$F_{\bar{e}}/F_a$ as a function of the active-sterile mixing angle and for the
experimentally allowed range of the standard active-active mixing angle
$\theta_{13}$.


title: Ergodic properties of a class of non-Markovian processes

abstract:
  We study a fairly general class of time-homogeneous stochastic evolutions
driven by noises that are not white in time. As a consequence, the resulting
processes do not have the Markov property. In this setting, we obtain
constructive criteria for the uniqueness of stationary solutions that are very
close in spirit to the existing criteria for Markov processes.
  In the case of discrete time, where the driving noise consists of a
stationary sequence of Gaussian random variables, we give optimal conditions on
the spectral measure for our criteria to be applicable. In particular, we show
that under a certain assumption on the spectral density, our assumptions can be
checked in virtually the same way as one would check that the Markov process
obtained by replacing the driving sequence by a sequence of independent
identically distributed Gaussian random variables is strong Feller and
topologically irreducible. The results of the present article are based on
those obtained previously in the continuous time context of diffusions driven
by fractional Brownian motion.


title: Crowd turbulence: the physics of crowd disasters

abstract:
  The panic stampede is a serious concern during mass events like soccer
championship games. Despite huge numbers of security forces and crowd control
measures, hundreds of lives are lost in crowd disasters each year. An analysis
of video recordings of the annual pilgrimage in Makkah reveals how high-density
crowds develop to turbulent dynamics and earthquake-like eruptions, which is
impossible to control.


title:
Stability of Metastable Vacua in Gauge Mediated SUSY Breaking Models
  with Ultra Light Gravitino

abstract:
  Recently Murayama and Nomura proposed a simple scheme to construct the gauge
mediation models, using metastable supersymmetry breaking vacua. It has a
possibility to predict the ultra light gravitino mass m_{3/2} \lesssim 16 eV,
while such a light gravitino may destabilize the metastable vacua. We
investigate stability of the metastable vacuum of their model. The transition
rate from the false vacuum to true ones is evaluated by numerical calculation,
including the Coleman-Weinberg potential destabilizing the metastable vacuum.
It is found that when the messenger sector is minimal, stability of the
metastable vacuum imposes an upperbound on squark mass M_{\tilde q} for the
ultra light gravitino as M_{\tilde q} \lesssim 1800 GeV at most. Squarks with
this mass may be found in the LHC experiments.


title:
Browsing through 3D representations of unstructured picture collections:
  an empirical study

abstract:
  The paper presents a 3D interactive representation of fairly large picture
collections which facilitates browsing through unstructured sets of icons or
pictures. Implementation of this representation implies choosing between two
visualization strategies: users may either manipulate the view (OV) or be
immersed in it (IV). The paper first presents this representation, then
describes an empirical study (17 participants) aimed at assessing the utility
and usability of each view. Subjective judgements in questionnaires and
debriefings were varied: 7 participants preferred the IV view, 4 the OV one,
and 6 could not choose between the two. Visual acuity and visual exploration
strategies seem to have exerted a greater influence on participants'
preferences than task performance or feeling of immersion.


title: NMSSM neutralino dark matter

abstract:
  We study the viability of the lightest neutralino as a dark matter candidate
in the Next-to-Minimal Supersymmetric Standard Model. Taking into account
accelerator constraints as well as bounds on low-energy observables, and
imposing consistency with present bounds on the neutralino relic density, we
address the prospects for the direct detection of neutralino dark matter. We
find regions of the allowed parameter space where the neutralino detection
cross section is within the reach of dark matter detectors, essentially owing
to the presence of very light singlet-like Higgses, and to either singlino
dominated or very light neutralinos.


title: Thermal gravitational waves

abstract:
  There is a lot of current interest in sources of gravitational waves and
active ongoing projects to detect such radiation, such as the LIGO project.
These are long wavelength, low frequency gravitational waves. LISA would be
sensitive to much longer wavelengths and lower fluxes. However compact stellar
objects can generate high frequency thermal gravitational radiation, which in
the case of hot neutron stars can be high. Also white dwarfs and main-sequence
stars can generate such radiation from plasma-Coulomb collisions. Again gamma
ray bursts and relativistic jets could also be sources of such radiation.
Terminal stages of evaporating black holes could also generate high frequency
gravitational radiation. A comparative study is made of the thermal
gravitational wave emission from all of the above sources, and the background
flux is estimated. The earliest phases of the universe close to the Planck
scale would also leave remnant thermal gravitational waves. The integrated
thermal gravitational flux as the universe expands is also estimated and
compared with that from all the discrete sources discussed above. Possible
schemes to detect such sources of high frequency thermal gravitational
radiation are discussed and the physical principles involved are elaborated.


title: Higgs-mass predictions

abstract: A compilation of Higgs-mass predictions is proposed


title:
Transitions involving conical magnetic phases in a model with bilinear
  and biquadratic interactions

abstract:
  In a previous work a model was proposed for the phase transitions of crystals
with localized magnetic moments which at low temperature have a "conical"
arrangement that at higher T transforms into a more symmetrical structure
(depending on the compound) before becoming totally disordered. The model
assumes bilinear and biquadratic interactions between magnetic moments up to
the fifth neighbours, and for any given T the structure with the least free
energy is obtained by a mean-field approximation (MFA). The interaction
constants are derived from ab initio energy calculations. In this work we
improve upon that model modifying the MFA in such a way that a continuous
(instead of discontinuous) spectrum of excited states is available to the
system. In the previous work, which dealt with LaMn_2Ge_2 and LaMn_2Si_2, we
found that transitions to different structures can be obtained for increasing
T, in good qualitative agreement with experiment. The critical temperatures,
however, were exaggerately high. With the new MFA we obtain essentially the
same behaviour concerning the phase transitions, and critical temperatures much
closer to the experimental ones.


title: Fluctuations in the Site Disordered Traveling Salesman Problem

abstract:
  We extend a previous statistical mechanical treatment of the traveling
salesman problem by defining a discrete "site disordered'' problem in which
fluctuations about saddle points can be computed. The results clarify the basis
of our original treatment, and illuminate but do not resolve the difficulties
of taking the zero temperature limit to obtain minimal path lengths.


title: Lens spaces obtainable by surgery on doubly primitive knots

abstract:
  In this paper, we consider which lens spaces are obtainable by Dehn surgery
described by Berge on doubly primitive knots. It is given an algorithm to
decide whether a given lens space is obtainable by such surgery. Also included
is a complete characterization of such surgery yielding lens spaces with Klein
bottles.


title: Lorentz violation and the proper-time method

abstract:
  In this paper, we apply the proper-time method to generate the
Lorentz-violating Chern-Simons terms in the four-dimensional Yang-Mills and
non-linearized gravity theories. It is shown that the coefficient of the
induced Chern-Simons term is finite but regularization dependent.


title:
Sharp phase transition and critical behaviour in 2D divide and colour
  models

abstract:
  Consider subcritical Bernoulli bond percolation with fixed parameter p<p_c.
We define a dependent site percolation model by the following procedure: for
each bond cluster, we colour all vertices in the cluster black with probability
r and white with probability 1-r, independently of each other. On the square
lattice, defining the critical probabilities for the site model and its dual,
r_c(p) and r_c^*(p) respectively, as usual, we prove that r_c(p)+r_c^*(p)=1 for
all subcritical p. On the triangular lattice, where our method also works, this
leads to r_c(p)=1/2, for all subcritical p. On both lattices, we obtain
exponential decay of cluster sizes below r_c(p), divergence of the mean cluster
size at r_c(p), and continuity of the percolation function in r on [0,1]. We
also discuss possible extensions of our results, and formulate some natural
conjectures. Our methods rely on duality considerations and on recent
extensions of the classical RSW theorem.


title: Measurement of particle and bubble accelerations in turbulence

abstract:
  We use an extended laser Doppler technique to track optically the velocity of
individual particles in a high Reynolds number turbulent flow. The particle
sizes are of the order of the Kolmogorov scale and the time resolution, 30
microseconds, resolves the fastest scales of the fluid motion. Particles are
tracked for mean durations of the order of 10 Kolmogorov time scales. The
fastest scales of the particle motion are resolved and the particle
acceleration is measured. For neutrally buoyant particles, our measurement
matches the performance of the silicon strip detector technique introduced at
Cornell University \cite{Voth,MordantCornell}. This reference dynamics is then
compared to that of slightly heavier solid particles (density 1.4) and to air
bubbles. We observe that the acceleration variance strongly depends on the
particle density: bubbles experience higher accelerations than fluid particles,
while heavier particles have lower accelerations. We find that the probability
distribution functions of accelerations normalized to the variance are very
close although the air bubbles have a much faster dynamics.


title:
Quasi-quark spectrum in the chiral symmetric phase from the
  Schwinger-Dyson equation

abstract:
  We non-perturbatively study the fermion spectrum in the chiral symmetric
phase from the Schwinger-Dyson equation with the Feynman gauge, in which we
perform an analytic continuation of the solution on the imaginary time axis to
the real time axis with a method employing an integral equation. It is shown
that the fermion spectrum has two peaks, which correspond to the normal
quasi-fermion and the plasmino, although these peaks in the strong coupling
region are very broad, owing to multiple scatterings with gauge bosons. We find
that the thermal mass of the quasi-fermion saturates at some value of the gauge
coupling, beyond which the thermal (pole) mass satisfies $M \sim T$,
independently of the value of the gauge coupling. We also comment on the
appearance of a three-peak structure in the fermion spectrum as a
non-perturbative effect.


title: Bounds on 2m/r for static perfect fluids

abstract:
  For spherically symmetric relativistic perfect fluid models, the well-known
Buchdahl inequality provides the bound $2 M/R \leq 8/9$, where $R$ denotes the
surface radius and $M$ the total mass of a solution. By assuming that the ratio
$p/\rho$ be bounded, where $p$ is the pressure, $\rho$ the density of
solutions, we prove a sharper inequality of the same type, which depends on the
actual bound imposed on $p/\rho$. As a special case, when we assume the
dominant energy condition $p/\rho \leq 1$, we obtain $2 M/R \leq 6/7$.


title: Decoherence due to the Horizon after Inflation

abstract:
  The fluctuations in the inflaton field at the end of inflation which seed the
density perturbations are prepared in a pure quantum state. It is generally
assumed that some physics causes this pure state to decohere so that it should
be treated probabilistically. We show that the entanglement entropy between the
universe inside our observable horizon and that outside our horizon is
sufficient to do this. For the modes which are super-Hubble at the end of
inflation, this entanglement entropy grows with volume inside the horizon,
rather than with the horizon's area, and is proportional to the number of
e-folds since Hubble crossing.


title: Some Non-Unimodal Level Algebras

abstract:
  In 2005, building on his own recent work and that of F. Zanello, A. Iarrobino
discovered some constructions that, he conjectured, would yield level algebras
with non-unimodal Hilbert functions. This thesis provides proofs of
non-unimodality for Iarrobino's level algebras, as well as for other level
algebras that the author has constructed along similar lines. The key technical
contribution is to extend some results published by Iarrobino in 1984.
Iarrobino's results provide insight into some naturally arising vector
subspaces of the vector space R_d of forms of fixed degree in a polynomial ring
in several variables. In this thesis, the problem is approached by
combinatorial methods and results similar to Iarrobino's are proved for a
different class of vector subspaces of R_d.
  The combinatorial methods involve the definition of a new class of matrices
called L-Matrices, which have useful properties that are inherited by their
submatrices. A particular class of square L-Matrices, associated with some
specialized partially ordered sets having interesting combinatorial properties,
is identified. For this class of L-Matrices, necessary and sufficient
conditions are given that they be nonsingular. Several larger questions are
discussed whose answers are incrementally improved by the knowledge that the
new non-unimodal level algebras exist.


title: An approximate version of the Loebl-Komlos-Sos conjecture

abstract:
  Loebl, Komlos, and Sos conjectured that if at least half of the vertices of a
graph G have degree at least some natural number k, then every tree with at
most k edges is a subgraph of G. Our main result is an approximate version of
this conjecture for large enough n=|V(G)|, assumed that n=O(k). Our result
implies an asymptotic bound for the Ramsey number of trees. We prove that
r(T_k,T_m)\leq k+m+o(k+m),as k+m tends to infinity.


title: On the approximation by weighted ridge functions

abstract:
  We characterize the best $L_{2}$ approximation to a multivariate function by
linear combinations of ridge functions multiplied by some fixed weight
functions. In the special case when the weight functions are constants, we
propose explicit formulas for both the best approximation and approximation
error.


title:
On spectral analysis of a magnetic Schrodinger operator on planar mixed
  automorphic forms

abstract:
  We characterize the space of the so-called planar mixed automorphic forms of
type $(\nu,\mu)$ with respect to an equivariant pair $(\rho,\tau)$ as the image
of the usual automorphic forms by an appropriate transform and we investigate
some concrete basic spectral properties of a magnetic Schrodinger operator
acting on them. The associated polynomials constitute classes of generalized
complex polynomials of Hermite type.


title: On minimal norms on $M_n$

abstract:
  In this note, we show that for each minimal norm $N(\cdot)$ on the algebra
$M_n$ of all $n \times n$ complex matrices, there exist norms $\|\cdot\|_1$ and
$\|\cdot\|_2$ on ${\mathbb C}^n$ such that $$N(A)=\max\{\|Ax\|_2: \|x\|_1=1,
x\in {\mathbb C}^n\}$$ for all $A \in M_n$. This may be regarded as an
extension of a known result on characterization of minimal algebra norms.


title: Inner disk regions revealed by infrared interferometry

abstract:
  I review the results obtained by long-baseline interferometry at infrared
wavelengths on the innermost regions around young stars. These observations
directly probe the location of the dust and gas in the disks. The
characteristic sizes of these regions found are larger than previously thought.
These results have motivated in part a new class of models of the inner disk
structure. However the precise understanding of the origin of these low
visibilities is still in debate. Mid-infrared observations have probed disk
emission over a larger range of scales revealing mineralogy gradients in the
disk. Recent spectrally resolved observations allow the dust and gas to be
studied separately. The few results shows that the Brackett gamma emission can
find its origin either in a wind or in a magnetosphere but there are no
definitive answers yet. In a certain number of cases, the very high spatial
resolution seems to reveal very close companions. In any case, these results
provide crucial information on the structure and physical properties of disks
surrounding young stars especially as initial conditions for planet formation.


title:
Coherent hard x-rays from attosecond pulse train-assisted harmonic
  generation

abstract:
  High-order harmonic generation from atomic systems is considered in the
crossed fields of a relativistically strong infrared laser and a weak
attosecond-pulse train of soft x-rays. Due to one-photon ionization by the
x-ray pulse, the ionized electron obtains a starting momentum that compensates
the relativistic drift which is induced by the laser magnetic field, and allows
the electron to efficiently emit harmonic radiation upon recombination with the
atomic core in the relativistic regime. In this way, short pulses of coherent
hard x-rays of up to 40 keV energy and 10 as duration can be brought about.


title: Disordered Correlated Kondo-lattice model

abstract:
  We propose a self-consistent approximate solution of the disordered
Kondo-lattice model (KLM) to get the interconnected electronic and magnetic
properties of 'local-moment' systems like diluted ferromagnetic semiconductors.
Aiming at $(A_{1-x}M_x)$ compounds, where magnetic (M) and non-magnetic (A)
atoms distributed randomly over a crystal lattice, we present a theory which
treats the subsystems of itinerant charge carriers and localized magnetic
moments in a homologous manner. The coupling between the localized moments due
to the itinerant electrons (holes) is treated by a modified RKKY-theory which
maps the KLM onto an effective Heisenberg model. The exchange integrals turn
out to be functionals of the electronic selfenergy guaranteeing selfconsistency
of our theory. The disordered electronic and magnetic moment systems are both
treated by CPA-type methods.
  We discuss in detail the dependencies of the key-terms such as the long range
and oscillating effectice exchange integrals, 'the local-moment' magnetization,
the electron spin polarization, the Curie temperature as well as the electronic
and magnonic quasiparticle densities of states on the concentration $x$ of
magnetic ions, the carrier concentration $n$, the exchange coupling $J$, and
the temperature. The shape and the effective range of the exchange integrals
turn out to be strongly $x$-dependent. The disorder causes anomalies in the
spin spectrum especially in the low-dilution regime, which are not observed in
the mean field approximation.


title: An Initial Assessment of a Clear Air Turbulence Forecasting Product

abstract:
  Clear air turbulence, also known as CAT, can cause damage to an aircrafts
structure and, in severe cases, harm passengers. Though CAT has been thoroughly
studied since the mid 1960s, scientists have not been able to create an
accurate forecasting device. The product tested is known as the
Deformation-Vertical Shear Index (DVSI), created by Knox, Ellrod, and Williams.
The DVSI is currently used by several commercial carriers and military
aircraft. The general feedback has been positive; however, results indicate
that the product tends to overestimate CAT intensity.


title:
Quasi-normal modes of a black hole localized on a codimension-two brane
  of finite tension

abstract:
  We calculate the quasi-normal modes of black holes localized on a 3-brane of
finite tension embedded in six-dimensional flat spacetime. Using the WKB
approximation, we obtain the frequencies of various types of perturbation both
analytically and numerically for arbitrary brane tension. We thus extend
earlier analytical results which were derived for a brane of small tension.


title: Decoupling and Destabilizing in Spontaneously Broken Supersymmetry

abstract:
  The supersymmetric analog of the Goldberger-Treiman relation plays a critical
role in the low energy effective theory of models in which supersymmetry is
spontaneously broken in a hidden sector. The interactions that connect the
hidden and visible sectors break a global symmetry, which implies that the low
energy theory must be constructed consistently in inverse powers of the
messenger scale. The Goldberger-Treiman relation determines the couplings of
the Goldstino to the visible sector fields. These couplings are fixed by the
soft supersymmetry breaking terms within a power counting scheme that is stable
under radiative corrections. We describe the power counting of the low energy
effective theory, first for a toy model of extended technicolor and then for
the supersymmetric standard model. One implication of this work for
supersymmetry phenomenology is the observation that Goldstino loops can
destabilize the weak scale if the low energy theory is not constructed
consistently. Another is that Goldstino loops induce all visible sector
operators not forbidden by symmetries. The magnitudes of these operators are
determined by the consistent power counting of the low energy effective theory.


title: Chandra X-Ray Observation of the Globular Cluster GLIMPSE-C01

abstract:
  We have observed the recently discovered rich star cluster GLIMPSE-C01 for 46
ks with the Chandra X-ray Observatory. Seventeen X-ray sources with
luminosities greater than 0.6e31 ergs/s were discovered, one of which is likely
a quiescent low-mass X-ray binary. The spatial distribution of these X-ray
sources with respect to the NIR and IR images of the cluster, combined with the
luminosity and spectral hardness distributions of the sources, provide strong
evidence that GLIMPSE-C01 is a rich Galactic globular cluster.


title: Star Formation Thresholds

abstract:
  To make predictions for the existence of ``dark galaxies'', it is necessary
to understand what determines whether a gas cloud will form stars. Star
formation thresholds are generally explained in terms of the Toomre criterion
for gravitational instability. I contrast this theory with the
thermo-gravitational instability hypothesis of Schaye (2004), in which star
formation is triggered by the formation of a cold gas phase and which predicts
a nearly constant surface density threshold. I argue that although the Toomre
analysis is useful for the global stability of disc galaxies, it relies on
assumptions that break down in the outer regions, where star formation
thresholds are observed. The thermo-gravitational instability hypothesis can
account for a number of observed phenomena, some of which were thought to be
unrelated to star formation thresholds.


title:
Interaction of a Point Charge and a Magnet: Comments on "Hidden
  Mechanical Momentum Due to Hidden Nonelectromagnetic Forces"

abstract:
  The interaction of a point charge and a magnetic moment (and by extension a
point charge and a solenoid) is explored within well-defined point-charge
magnetic-moment models where full calculations are possible. It is shown
explicitly how the "hidden mechanical momentum" is introduced by the "hidden"
external forces of constraint, requiring a prescribed response (through order
1/c^2) of the system to electromagnetic forces. These external forces often go
unmentioned in the textbook and research literature. The dependence of "hidden
mechanical momentum" upon detailed external (nonelectromagnetic) forces may
undermine the idea's usefulness in describing nature. Some statements of
dubious validity in the textbook literature are noted.


title: On the critical dipole moment in one-dimension

abstract:
  We calculate the minimum magnitude an electric dipole must have for a 1D
system, interacting through the dipole, to support bound states.


title: Minimal Homogenous Liaison and Licci Ideals

abstract:
  We study the linkage classes of homogeneous ideals in polynomial rings. An
ideal is said to be homogeneously licci if it can be linked to a complete
intersection using only homogeneous regular sequences at each step. We ask a
natural question:
  if $I$ is homogeneously licci, then can it be linked to a complete
intersection by linking using regular sequences of forms of smallest possible
degree at each step (we call such ideals minimally homogeneously licci)? In
this paper we answer this question in the negative. In particular, for every
$n\geq 28$ we construct a set of $n$ points in $\mathbb P^3$ which are
homogeneously licci, but not minimally homogeneously licci. Moreover, we prove
that one cannot distinguish between the classes of homogeneously licci and
non-licci ideals based only on their Hilbert functions, nor distinguish between
homogeneously licci and minimally homogeneously licci ideals based solely on
the graded Betti numbers. Finally, by taking hypersurface sections, we show
that the natural question has a negative answer whenever the height of the
ideal is at least three.


title:
New insight into cataract formation -- enhanced stability through mutual
  attraction

abstract:
  Small-angle neutron scattering experiments and molecular dynamics simulations
combined with an application of concepts from soft matter physics to complex
protein mixtures provide new insight into the stability of eye lens protein
mixtures. Exploring this colloid-protein analogy we demonstrate that weak
attractions between unlike proteins help to maintain lens transparency in an
extremely sensitive and non-monotonic manner. These results not only represent
an important step towards a better understanding of protein condensation
diseases such as cataract formation, but provide general guidelines for tuning
the stability of colloid mixtures, a topic relevant for soft matter physics and
industrial applications.


title: Z_3 Dark Matter and Two-Loop Neutrino Mass

abstract:
  Dark matter is usually distinguished from ordinary matter by an odd-even
parity, i.e. the discrete symmetry Z_2. The new idea of Z_3 dark matter is
proposed with a special application to generating radiative Majorana neutrino
masses in two-loop order.


title:
Delayed neutrino-driven supernova explosions aided by the standing
  accretion-shock instability

abstract:
  We present results of 2D hydrodynamic simulations of stellar core collapse,
which confirm that the neutrino-heating mechanism remains viable for the
explosion of a wider mass range of supernova progenitors with iron cores. We
used an energy-dependent treatment of the neutrino transport based on the
"ray-by-ray plus" approximation, in which the number, energy, and momentum
equations are closed with a variable Eddington factor obtained by iteratively
solving a model Boltzmann equation. We focus on the evolution of a 15 Msun
progenitor and show that shock revival and the explosion are initiated at about
600 ms post bounce, powered by neutrino energy deposition. Similar to previous
findings for an 11.2 Msun star, but significantly later, the onset of the
explosion is fostered by the standing accretion shock instability (SASI). This
instability exhibits highest growth rates for the dipole and quadrupole modes,
which lead to large-amplitude bipolar shock oscillations and push the shock to
larger radii, thus increasing the time accreted matter is exposed to neutrino
heating in the gain layer. Therefore also convective overturn behind the shock
is strengthened. A "soft" nuclear equation of state that causes a rapid
contraction and a smaller radius of the forming neutron star and thus a fast
release of gravitational binding energy, seems to be more favorable for an
explosion. Rotation has the opposite effect because it leads to a more extended
and cooler neutron star and thus lower neutrino luminosities and mean energies
and overall less neutrino heating. Neutron star g-mode oscillations and the
acoustic mechanism play no important role in our simulations. (abridged)


title:
Energy-level pinning and the 0.7 spin state in one dimension: GaAs
  quantum wires studied using finite-bias spectroscopy

abstract:
  We study the effects of electron-electron interactions on the energy levels
of GaAs quantum wires (QWs) using finite-bias spectroscopy. We probe the energy
spectrum at zero magnetic field, and at crossings of opposite-spin-levels in
high in-plane magnetic field B. Our results constitute direct evidence that
spin-up (higher energy) levels pin to the chemical potential as they populate.
We also show that spin-up and spin-down levels abruptly rearrange at the
crossing in a manner resembling the magnetic phase transitions predicted to
occur at crossings of Landau levels. This rearranging and pinning of subbands
provides a phenomenological explanation for the 0.7 structure, a
one-dimensional (1D) nanomagnetic state, and its high-B variants.


title: Desorption From Interstellar Ices

abstract:
  The desorption of molecular species from ice mantles back into the gas phase
in molecular clouds results from a variety of very poorly understood processes.
We have investigated three mechanisms; desorption resulting from H_2 formation
on grains, direct cosmic ray heating and cosmic ray induced photodesorption.
Whilst qualitative differences exist between these processes (essentially
deriving from the assumptions concerning the species-selectivity of the
desorption and the assumed threshold adsorption energies, E_t) all three
processes are found to be potentially very significant in dark cloud
conditions. It is therefore important that all three mechanisms should be
considered in studies of molecular clouds in which freeze-out and desorption
are believed to be important.
  Employing a chemical model of a typical static molecular core and using
likely estimates for the quantum yields of the three processes we find that
desorption by H_2 formation probably dominates over the other two mechanisms.
However, the physics of the desorption processes and the nature of the dust
grains and ice mantles are very poorly constrained. We therefore conclude that
the best approach is to set empirical constraints on the desorption, based on
observed molecular depletions - rather than try to establish the desorption
efficiencies from purely theoretical considerations. Applying this method to
one such object (L1689B) yields upper limits to the desorption efficiencies
that are consistent with our understanding of these mechanisms.


title:
Estimating the expectation values of spin 1/2 observables with finite
  resources

abstract:
  We examine the problem of estimating the expectation values of two
observables when we have a finite number of copies of an unknown qubit state.
Specifically we examine whether it is better to measure each of the observables
separately on different copies or to perform a joint measurement of the
observables on each copy. We find that joint measurements can sometimes provide
an advantage over separate measurements, but only if we make estimates of an
observable based solely on the results of measurements of that observable. If
we instead use both sets of results to estimate each observable then we find
that individual measurements will be better. Finally we consider estimating the
expectation values of three complementary observables for an unknown qubit.


title:
Ground state capture in $^{14}$N(p,$\gamma$)$^{15}$O studied above the
  259 keV resonance at LUNA

abstract:
  We report on a new measurement of $^{14}$N(p,$\gamma$)$^{15}$O for the ground
state capture transition at $E_p$ = 360, 380 and 400 keV, using the 400 kV LUNA
accelerator. The true coincidence summing effect --the major source of error in
the ground state capture determination-- has been significantly reduced by
using a Clover--type gamma detector.


title: The Distances of SNR W41 and overlapping HII regions

abstract:
  New HI images from the VLA Galactic Plane Survey show prominent absorption
features associated with the supernovae remnant G23.3-0.3 (SNR W41). We
highlight the HI absorption spectra and the $^{13}$CO emission spectra of eight
small regions on the face of W41, including four HII regions, three non-thermal
emission regions and one unclassified region. The maximum velocity of
absorption for W41 is 78$\pm$2 km/s and the CO cloud at radial velocity
95$\pm$5 km/s is behind W41. Because an extended TeV source, a diffuse X-ray
enhancement and a large molecular cloud at radial velocity 77$\pm$5 km/s are
also projected at the center of W41, these yield the kinematic distance of 3.9
to 4.5 kpc for W41. For HII regions, our analyses reveal that both G23.42-0.21
and G23.07+0.25 are at the far kinematic distances ($\sim$9.9 kpc and $\sim$
10.6 kpc respectively) of their recombination-line velocities (103$\pm$0.5 km/s
and 89.6$\pm$2.1 km/s respectively), G23.07-0.37 is at the near kinematic
distance (4.4$\pm$0.3 kpc) of its recombination-line velocity (82.7$\pm$2.0
km/s), and G23.27-0.27 is probably at the near kinematic distance (4.1$\pm$0.3
kpc) of its recombination-line velocity (76.1$\pm$0.6 km/s).


title:
Lagrange Instability of Geodesics in Curved Double Twisted Liquid
  Crystals

abstract:
  It is shown that curved and flat helical double twisted liquid crystal (DTLC)
in blue phase, can be unstable (stable) depending of the sign, negative
(positive) of sectional curvature, depending on the pitch of the helix of the
nematic crystal. In both cases Cartan torsion is presented. It is also shown
that the instability or stability depends on the value of the pitch of the
helix in nematic crystals. Frank energy stability A similar result using the
method of Frank energy stability in the twist of cholesteric liquid crystal was
given by Kiselev and Sluckin [PRE 71(2005)], where the free twist number
determines the equilibrium value of the cholesteric liquid crystals (CLC) pitch
of the helix. As a final example we solve the geodesic equations in twisted
nematics with variable pitch helix and non-constant torsion. This
non-Riemannian geometrical approach, also seems to unify two recent analysis of
cylindrical columns given by Santangelo et al [PRL 99,(2007)] and the curved
crystal endowed with torsion, given by Vitelli et al [Proc Nat Acad Sci
(2006)]. Stability of toroidal curved surfaces were also previously considered
by Bowick et al [PRE 69,(2004)], as an example of curvature-induced defect.
Investigation of the Lagrangean instability may be useful in the investigation
of HIV viruses and proteins.


title:
Magnetic-field dependence of the critical currents in a periodic
  coplanar array of narrow superconducting strip

abstract:
  We calculate the magnetic-field dependence of the critical current due to
both geometrical edge barriers and bulk pinning in a periodic coplanar array of
narrow superconducting strips. We find that in zero or low applied magnetic
fields the critical current can be considerably enhanced by the edge barriers,
but in modest applied magnetic fields the critical current reduces to that due
to bulk pinning alone.


title: Constraining relativistic models through heavy ion collisions

abstract:
  Relativistic models can be successfully applied to the description of compact
star properties in nuclear astrophysics as well as to nuclear matter and finite
nuclei properties, these studies taking place at low and moderate temperatures.
Nevertheless, all results are model dependent and so far it is unclear whether
some of them should be discarded. Moreover, in the regime of hot hadronic
matter very few calculations exist using these relativistic models, in
particular when applied to particle yields in heavy ion collisions.
  In the present work we comment on the known constraints that can help the
selection of adequate models in this regime and investigate the main
differences that arise when the particle production during a Au+Au collision at
RHIC is calculated with different models.


title:
Architecture Optimization of a 3-DOF Translational Parallel Mechanism
  for Machining Applications, the Orthoglide

abstract:
  This paper addresses the architecture optimization of a 3-DOF translational
parallel mechanism designed for machining applications. The design optimization
is conducted on the basis of a prescribed Cartesian workspace with prescribed
kinetostatic performances. The resulting machine, the Orthoglide, features
three fixed parallel linear joints which are mounted orthogonally and a mobile
platform which moves in the Cartesian x-y-z space with fixed orientation. The
interesting features of the Orthoglide are a regular Cartesian workspace shape,
uniform performances in all directions and good compactness. A small-scale
prototype of the Orthoglide under development is presented at the end of this
paper.


title:
The Structure and the Distance of Collinder 121 from Hipparcos and
  Photometry: Resolving the Discrepancy

abstract:
  We present further arguments that the Hipparcos parallaxes for some of the
clusters and associations represented in the Hipparcos catalog should be used
with caution in the study of the Galactic structure. It has been already shown
that the discrepancy between the Hipparcos and ground based parallaxes for
several clusters including the Pleiades, Coma Ber and NGC 6231 can be resolved
by recomputing the Hipparcos astrometric solutions with an improved algorithm
diminishing correlated errors in the attitude parameters. Here we present new
parallaxes obtained with this algorithm for another group of stars with
discrepant data - the galactic cluster Cr 121. The original Hipparcos
parallaxes led de Zeeuw et al. to conclude that Cr 121 and the surrounding
association of OB stars form a relatively compact and coherent moving group at
a distance of 550 -- 600 pc. Our corrected parallaxes reveal a different
spatial distribution of young stellar populace in this area. Both the cluster
Cr 121 and the extended OB association are considerably more distant (750 --
1000 pc), and the latter has a large depth probably extending beyond 1 kpc.
Therefore, not only are the recalculated parallaxes in complete agreement with
the photometric uvbybeta parallaxes, but the structure of the field they reveal
is no longer in discrepancy with that found by the photometric method.


title:
Zonal Shear Flows with a Free Surface: Hamiltonian Formulation and
  Linear and Nonlinear Stability

abstract:
  General theoretical results via a Hamiltonian formulation are developed for
zonal shear flows with the inclusion of the vortex stretching effect of the
deformed free surface. These results include a generalization of the
Flierl-Stern-Whitehead zero angular momentum theorem} for localized nonlinear
structures on or off the beta-plane, and sufficient conditions for linear and
nonlinear stability in the Liapunov sense - the latter are derived via bounds
on the equilibrium potential vorticity gradient.


title: Orthogonal measurement-assisted quantum control

abstract:
  Existing algorithms for the optimal control of quantum observables are based
on locally optimal steps in the space of control fields, or as in the case of
genetic algorithms, operate on the basis of heuristics that do not explicitly
take into account details pertaining to the geometry of the search space. We
present globally efficient algorithms for quantum observable control that
follow direct or close-to-direct paths in the domain of unitary dynamical
propagators, based on partial reconstruction of these propagators at successive
points along the search trajectory through orthogonal observable measurements.
These algorithms can be implemented experimentally and offer an alternative to
the adaptive learning control approach to optimal control experiments (OCE).
Their performance is compared to that of local gradient-based control
optimization.


title:
An algebraic formulation of Thurston's characterization of rational
  functions

abstract:
  Following Douady-Hubbard and Bartholdi-Nekrashevych, we give an algebraic
formulation of Thurston's characterization of rational functions. The
techniques developed are applied to the analysis of the dynamics on the set of
free homotopy classes of simple closed curves induced by a rational function.
The resulting finiteness results yield new information on the global dynamics
of the pullback map on Teichm\"uller space used in the proof of the
characterization theorem.


title: Three-dimensional AdS gravity and extremal CFTs at c=8m

abstract:
  We note that Witten's proposed duality between extremal c=24k CFTs and
three-dimensional anti-de Sitter gravity may possibly be extended to central
charges that are multiples of 8, for which extremal self-dual CFTs are known to
exist up to c=40. All CFTs of this type with central charge 24 or higher,
provided that they exist, have the required mass gap and may serve as candidate
duals to three-dimensional gravity at the corresponding values of the
cosmological constant. Here, we compute the genus one partition function of
these theories up to c=88, we give exact and approximate formulas for the
degeneracies of states, and we determine the genus two partition functions of
the theories up to c=40.


title:
The Impact of Noise Correlation and Channel Phase Information on the
  Data-Rate of the Single-Symbol ML Decodable Distributed STBCs

abstract:
  Very recently, we proposed the row-monomial distributed orthogonal space-time
block codes (DOSTBCs) and showed that the row-monomial DOSTBCs achieved
approximately twice higher bandwidth efficiency than the repetitionbased
cooperative strategy [1]. However, we imposed two limitations on the
row-monomial DOSTBCs. The first one was that the associated matrices of the
codes must be row-monomial. The other was the assumption that the relays did
not have any channel state information (CSI) of the channels from the source to
the relays, although this CSI could be readily obtained at the relays without
any additional pilot signals or any feedback overhead. In this paper, we first
remove the row-monomial limitation; but keep the CSI limitation. In this case,
we derive an upper bound of the data-rate of the DOSTBC and it is larger than
that of the row-monomial DOSTBCs in [1]. Secondly, we abandon the CSI
limitation; but keep the row-monomial limitation. Specifically, we propose the
row-monomial DOSTBCs with channel phase information (DOSTBCs-CPI) and derive an
upper bound of the data-rate of those codes. The rowmonomial DOSTBCs-CPI have
higher data-rate than the DOSTBCs and the row-monomial DOSTBCs. Furthermore, we
find the actual row-monomial DOSTBCs-CPI which achieve the upper bound of the
data-rate.


title: The Early Evolution of Massive Stars: Radio Recombination Line Spectra

abstract:
  Velocity shifts and differential broadening of radio recombination lines are
used to estimate the densities and velocities of the ionized gas in several
hypercompact and ultracompact HII regions. These small HII regions are thought
to be at their earliest evolutionary phase and associated with the youngest
massive stars. The observations suggest that these HII regions are
characterized by high densities, supersonic flows and steep density gradients,
consistent with accretion and outflows that would be associated with the
formation of massive stars.


title: On the almost sure spiraling of geodesics in negatively curved manifolds

abstract:
  Given a negatively curved geodesic metric space $M$, we study the statistical
asymptotic penetration behavior of (locally) geodesic lines of $M$ in small
neighborhoods of points, of closed geodesics, and of other compact (locally)
convex subsets of $M$. We prove Khintchine-type and logarithme law-type results
for the spiraling of geodesic lines around these objets. As a consequence in
the tree setting, we obtain Diophantine approximation results of elements of
non-archimedian local fields by quadratic irrational ones.


title: On the symmetric subscheme of Hilbert scheme of points

abstract:
  We consider the Hilbert scheme Hilb^{d+1}(C^d) of (d+1) points in affine
d-space C^d (d > 2), which includes the square of any maximal ideal. We
describe equations for the most symmetric affine open subscheme of
Hilb^{d+1}(C^d), in terms of Schur modules. In addition we prove that
Hilb^{d+1}(C^d) is reducible for n>d>11.


title: Scaling and universality of multipartite entanglement at criticality

abstract:
  Using the geometric entanglement measure, we study the scaling of
multipartite entanglement in several 1D models at criticality, specifically the
linear harmonic chain and the XY spin chain encompassing both the Ising and XX
critical models. Our results provide convincing evidence that 1D models at
criticality exhibit a universal logarithmic scaling behavior ~(c/12)log l in
the multipartite entanglement per region for a partition of the system into
regions of size l, where c is the central charge of the corresponding
universality class in conformal field theory.


title: Fluctuations in 21cm Emission After Reionization

abstract:
  The fluctuations in the emission of redshifted 21cm photons from neutral
inter-galactic hydrogen will provide an unprecedented probe of the reionization
era. Conventional wisdom assumes that this 21cm signal disappears as soon as
reionization is complete, when little atomic hydrogen is left through most of
the volume of the inter-galactic medium (IGM). However observations of damped
Ly-alpha absorbers indicate that the fraction of hydrogen in its neutral form
is significant by mass at all redshifts. Here we use a physically-motivated
model to show that residual neutral gas, confined to dense regions in the IGM
with a high recombination rate, will generate a significant post-reionization
21cm signal. We show that the power-spectrum of fluctuations in this signal
will be detectable by the first generation of low-frequency observatories at a
signal-to-noise that is comparable to that achievable in observations of the
reionization era. The statistics of 21cm fluctuations will therefore probe not
only the pre-reionization IGM, but rather the entire process of HII region
overlap, as well as the appearance of the diffuse ionized IGM.


title: A prediction for bubbling geometries

abstract:
  We study the supersymmetric circular Wilson loops in N=4 Yang-Mills theory.
Their vacuum expectation values are computed in the parameter region that
admits smooth bubbling geometry duals. The results are a prediction for the
supergravity action evaluated on the bubbling geometries for Wilson loops.


title: General marginal deformations in open superstring field theory

abstract:
  We construct analytic solutions of open superstring field theory for any
exactly marginal deformation in any boundary superconformal field theory when
properly renormalized operator products of the marginal operator are given. Our
construction is an extension of the general framework for marginal deformations
developed in arXiv:0707.4472 for open bosonic string field theory, and the
solutions are based on integrated vertex operators which are closely related to
finite deformations in boundary superconformal field theory.


title: On the Conditions for Neutron-Rich Gamma-Ray Burst Outflows

abstract:
  We calculate the structure and neutron content of neutrino-heated MHD winds
driven from the surface of newly-formed magnetars (``proto-magnetars'') and
from the midplane of hyper-accreting disks, two of the possible central engines
for gamma-ray bursts (GRBs) and hyper-energetic supernovae (SNe). Both the
surface of proto-magnetars and the midplane of neutrino-cooled accretion flows
(NDAFs) are electron degenerate and neutron-rich (neutron-to-proton ratio n/p
>> 1). If this substantial free neutron excess is preserved to large radii in
ultra-relativistic outflows, several important observational consequences may
result. Weak interaction processes, however, can drive n/p to ~1 in the
nondegenerate regions that obtain just above the surfaces of NDAFs and
proto-magnetars. Our calculations show that mildly relativistic neutron-rich
outflows from NDAFs are possible in the presence of a strong poloidal magnetic
field. However, we find that neutron-rich winds possess a minimum mass-loss
rate that likely precludes simultaneously neutron-rich and ultra-relativistic
(Lorentz factor > 100) NDAF winds accompanying a substantial accretion power.
In contrast, proto-magnetars are capable of producing neutron-rich
long-duration GRB outflows ~10-30 seconds following core bounce for
sub-millisecond rotation periods; such outflows would, however, accompany only
extremely energetic events, in which the GRB + SN energy budget exceeds ~ 4e52
ergs. Neutron-rich highly relativistic outflows may also be produced during
some short-duration GRBs by geometrically thick accretion disks formed from
compact object mergers. The implications for r-process nucleosynthesis, optical
transients due to non-relativistic neutron-rich winds, and Nickel production in
proto-magnetar and NDAF winds are also briefly discussed.


title: Optimal quantum adversary lower bounds for ordered search

abstract:
  The goal of the ordered search problem is to find a particular item in an
ordered list of n items. Using the adversary method, Hoyer, Neerbek, and Shi
proved a quantum lower bound for this problem of (1/pi) ln n + Theta(1). Here,
we find the exact value of the best possible quantum adversary lower bound for
a symmetrized version of ordered search (whose query complexity differs from
that of the original problem by at most 1). Thus we show that the best lower
bound for ordered search that can be proved by the adversary method is (1/pi)
ln n + O(1). Furthermore, we show that this remains true for the generalized
adversary method allowing negative weights.


title: Cosmology, Thermodynamics and Matter Creation

abstract:
  Several approaches to the matter creation problem in the context of
cosmological models are summarily reviewed. A covariant formulation of the
general relativistic imperfect simple fluid endowed with a process of matter
creation is presented. By considering the standard big bang model, it is shown
how the recent results of Prigogine et alii \cite{1} can be recovered and, at
the same time their limits of validity are explicited.


title:
Homological algebra of semimodules and semicontramodules: Semi-infinite
  homological algebra of associative algebraic structures

abstract:
  We develop the basic constructions of homological algebra in the
(appropriately defined) unbounded derived categories of modules over algebras
over coalgebras over noncommutative rings (which we call semialgebras over
corings). We define double-sided derived functors SemiTor and SemiExt of the
functors of semitensor product and semihomomorphisms, and construct an
equivalence between the exotic derived categories of semimodules and
semicontramodules.
  Certain (co)flatness and/or (co)projectivity conditions have to be imposed on
the coring and semialgebra to make the module categories abelian (and the
cotensor product associative). Besides, for a number of technical reasons we
mostly have to assume that the basic ring has a finite homological dimension
(no such assumptions about the coring and semialgebra are made).
  In the final sections we construct model category structures on the
categories of complexes of semi(contra)modules, and develop relative
nonhomogeneous Koszul duality theory for filtered semialgebras and
quasi-differential corings.
  Our motivating examples come from the semi-infinite cohomology theory.
Comparison with the semi-infinite (co)homology of Tate Lie algebras and graded
associative algebras is established in appendices, and the semi-infinite
homology of a locally compact topological group relative to an open profinite
subgroup is defined. An application to the correspondence between complexes of
representations of an infinite-dimensional Lie algebra on the complementary
central charge levels ($c$ and $26-c$ for the Virasoro) is worked out.


title: The depth of a knot tunnel

abstract:
  The theory of tunnel number 1 knots detailed in our previous paper, The tree
of knot tunnels, provides a non-negative integer invariant called the depth of
the tunnel. We give various results related to the depth invariant. Noting that
it equals the minimum number of Goda-Scharlemann-Thompson tunnel moves needed
to construct the tunnel, we calculate the number of distinct minimal sequences
of tunnel moves that can produce a given tunnel. Next, we give a recursion that
tells the minimum bridge number of a knot having a tunnel of depth D. The rate
of growth of this value improves the known estimates of the growth of bridge
number as a function of the Hempel distance of the associated Heegaard
splitting. We also give various upper bounds for bridge number in terms of the
cabling constructions needed to produce a tunnel of a knot, showing in
particular that the maximum bridge number of a knot produced by N cabling
constructions is the (N+2)nd Fibonacci number. Finally, we explicitly compute
the slope parameters for the "short" tunnels of torus knots. In particular, we
find a sequence of such tunnels for which the bridge numbers of the associated
knots, as a function of the depth, achieve the minimum growth rate. The actual
minimum bridge number at a given depth cannot be achieved by a torus knot.


title:
Limit distribution theory for maximum likelihood estimation of a
  log-concave density

abstract:
  We find limiting distributions of the nonparametric maximum likelihood
estimator (MLE) of a log-concave density, that is, a density of the form
$f_0=\exp\varphi_0$ where $\varphi_0$ is a concave function on $\mathbb{R}$.
The pointwise limiting distributions depend on the second and third derivatives
at 0 of $H_k$, the "lower invelope" of an integrated Brownian motion process
minus a drift term depending on the number of vanishing derivatives of
$\varphi_0=\log f_0$ at the point of interest. We also establish the limiting
distribution of the resulting estimator of the mode $M(f_0)$ and establish a
new local asymptotic minimax lower bound which shows the optimality of our mode
estimator in terms of both rate of convergence and dependence of constants on
population values.


title: Coefficient of tangential restitution for the linear dashpot model

abstract:
  The linear dashpot model for the inelastic normal force between colliding
spheres leads to a constant coefficient of normal restitution,
$\epsilon_n=$const., which makes this model very popular for the investigation
of dilute and moderately dense granular systems. For two frequently used models
for the tangential interaction force we determine the coefficient of tangential
restitution $\epsilon_t$, both analytically and by numerical integration of
Newton's equation. Although $\epsilon_n=$const. for the linear-dashpot model,
we obtain pronounced and characteristic dependencies of the tangential
coefficient on the impact velocity $\epsilon_t=\epsilon_t(\vec{g})$. The
results may be used for event-driven simulations of granular systems of
frictional particles.


title: Low energy scattering with a nontrivial pion

abstract:
  An earlier calculation in a generalized linear sigma model showed that the
well-known current algebra formula for low energy pion pion scattering held
even though the massless Nambu Goldstone pion contained a small admixture of a
two-quark two-antiquark field. Here we turn on the pion mass and note that the
current algebra formula no longer holds exactly. We discuss this small
deviation and also study the effects of an SU(3) symmetric quark mass type term
on the masses and mixings of the eight SU(3) multiplets in the model. We
calculate the s wave scattering lengths, including the beyond current algebra
theorem corrections due to the scalar mesons, and observe that the model can
fit the data well. In the process, we uncover the way in which linear sigma
models give controlled corrections (due to the presence of scalar mesons) to
the current algebra scattering formula. Such a feature is commonly thought to
exist only in the non-linear sigma model approach.


title: Quantum Sensor Miniaturization

abstract:
  The classical bound on image resolution defined by the Rayleigh limit can be
beaten by exploiting the properties of quantum mechanical entanglement. If
entangled photons are used as signal states, the best possible resolution is
instead given by the Heisenberg limit, an improvement proportional to the
number of entangled photons in the signal. In this paper we present a novel
application of entanglement by showing that the resolution obtained by an
imaging system utilizing separable photons can be achieved by an imaging system
making use of entangled photons, but with the advantage of a smaller aperture,
thus resulting in a smaller and lighter system. This can be especially valuable
in satellite imaging where weight and size play a vital role.


title: Efficient computation of p-adic heights

abstract:
  We analyse and drastically improve the running time of the algorithm of
Mazur, Stein and Tate for computing the canonical cyclotomic p-adic height of a
point on an elliptic curve E/Q, where E has good ordinary reduction at p >= 5.


title: Magnetic Fields in Irregular Galaxies

abstract:
  Magnetic fields are an important component of the interstellar medium,
especially in low-mass galaxies like irregulars where the magnetic pressure may
be significant. However, few irregular galaxies have observed magnetic field
structures. Using the VLA, the GBT, and the ATCA, we have observed several
irregular galaxies in the radio continuum to determine their magnetic field
structures. Here we report on our results for the galaxies NGC 4214 and NGC
1569.


title: Search for IR Emission from Intracluster Dust in A2029

abstract:
  We have searched for IR emission from the intracluster dust (ICD) in the
galaxy cluster A2029. Weak signals of enhanced extended emission in the cluster
are detected at both 24 and 70 micron. However, the signals are
indistinguishable from the foreground fluctuations. The 24 versus 70 micron
color map does not discriminate the dust emission in the cluster from the
cirrus emission. After excluding the contamination from the point sources, we
obtain upper limits for the extended ICD emission in A2029, 5 x 10^3 Jy/sr at
24 micron and 5 x 10^4 Jy/sr at 70 micron. The upper limits are generally
consistent with the expectation from theoretical calculations and support a
dust deficiency in the cluster compared to the ISM in our galaxy. Our results
suggest that even with the much improved sensitivity of current IR telescopes,
a clear detection of the IR emission from ICD may be difficult due to cirrus
noise.


title: Normal Hopf subalgebras in cocycle deformations of finite groups

abstract:
  Let $G$ be a finite group and let $\pi: G \to G'$ be a surjective group
homomorphism. Consider the cocycle deformation $L = H^{\sigma}$ of the Hopf
algebra $H = k^G$ of $k$-valued linear functions on $G$, with respect to some
convolution invertible 2-cocycle $\sigma$. The (normal) Hopf subalgebra $k^{G'}
\subseteq k^G$ corresponds to a Hopf subalgebra $L' \subseteq L$. Our main
result is an explicit necessary and sufficient condition for the normality of
$L'$ in $L$.


title:
Linear Time Algorithms Based on Multilevel Prefix Tree for Finding
  Shortest Path with Positive Weights and Minimum Spanning Tree in a Networks

abstract:
  In this paper I present general outlook on questions relevant to the basic
graph algorithms; Finding the Shortest Path with Positive Weights and Minimum
Spanning Tree. I will show so far known solution set of basic graph problems
and present my own. My solutions to graph problems are characterized by their
linear worst-case time complexity. It should be noticed that the algorithms
which compute the Shortest Path and Minimum Spanning Tree problems not only
analyze the weight of arcs (which is the main and often the only criterion of
solution hitherto known algorithms) but also in case of identical path weights
they select this path which walks through as few vertices as possible. I have
presented algorithms which use priority queue based on multilevel prefix tree
-- PTrie. PTrie is a clever combination of the idea of prefix tree -- Trie, the
structure of logarithmic time complexity for insert and remove operations,
doubly linked list and queues. In C++ I will implement linear worst-case time
algorithm computing the Single-Destination Shortest-Paths problem and I will
explain its usage.


title: Stability of the Front under a Vlasov-Fokker-Planck Dynamics

abstract:
  We consider a kinetic model for a system of two species of particles
interacting through a longrange repulsive potential and a reservoir at given
temperature. The model is described by a set of two coupled Vlasov-Fokker-Plank
equations. The important front solution, which represents the phase boundary,
is a one-dimensional stationary solution on the real line with given asymptotic
values at infinity. We prove the asymptotic stability of the front for small
symmetric perturbations.


title:
Rough solutions of the Einstein constraint equations with nonconstant
  mean curvature

abstract:
  We consider the conformal decomposition of Einstein's constraint equations
introduced by Lichnerowicz and York, on a compact manifold with boundary. We
use order relations on appropriate Banach spaces to derive weak solution
generalizations of known sub- and super-solutions (barriers) for the
Hamiltonian constraint. The barriers are combined with variational methods to
establish existence of solutions to the Hamiltonian constraint in the
intersection of the space of essentially bounded functions and the Sobolev
space H1. The result is established for scalar curvature R of the background
metric having any sign; non-negative R requires additional positivity
assumptions either on the matter energy density or on the trace-free
divergence-free part of the extrinsic curvature. Although the formulation is
different, the result can be viewed as lowering the regularity of the recent
result of Maxwell on rough CMC solutions. We also establish existence of
non-CMC solutions of the Hamiltonian and momentum constraint equations. The
result is obtained using fixed-point iteration and compactness arguments
directly, rather than by building a contraction map. The non-CMC result can be
viewed as a type of extension of the regularity of the 1996 non-CMC result of
Isenberg and Moncrief to lower regularity and to scalar curvature R having any
sign.


title:
On causally asymmetric versions of Occam's Razor and their relation to
  thermodynamics

abstract:
  In real-life statistical data, it seems that conditional probabilities for
the effect given their causes tend to be less complex and smoother than
conditionals for causes, given their effects. We have recently proposed and
tested methods for causal inference in machine learning using a formalization
of this principle.
  Here we try to provide some theoretical justification for causal inference
methods based upon such a ``causally asymmetric'' interpretation of Occam's
Razor. To this end, we discuss toy models of cause-effect relations from
classical and quantum physics as well as computer science in the context of
various aspects of complexity.
  We argue that this asymmetry of the statistical dependences between cause and
effect has a thermodynamic origin. The essential link is the tendency of the
environment to provide independent background noise realized by physical
systems that are initially uncorrelated with the system under consideration
rather than being finally uncorrelated. This link extends ideas from the
literature relating Reichenbach's principle of the common cause to the second
law.


title: Observability and nonlinear filtering

abstract:
  This paper develops a connection between the asymptotic stability of
nonlinear filters and a notion of observability. We consider a general class of
hidden Markov models in continuous time with compact signal state space, and
call such a model observable if no two initial measures of the signal process
give rise to the same law of the observation process. We demonstrate that
observability implies stability of the filter, i.e., the filtered estimates
become insensitive to the initial measure at large times. For the special case
where the signal is a finite-state Markov process and the observations are of
the white noise type, a complete (necessary and sufficient) characterization of
filter stability is obtained in terms of a slightly weaker detectability
condition. In addition to observability, the role of controllability in filter
stability is explored. Finally, the results are partially extended to
non-compact signal state spaces.


title: Orbit semigroups and the representation type of quivers

abstract:
  We show that a finite, connected quiver Q without oriented cycles is a Dynkin
or Euclidean quiver if and only if all orbit semigroups of representations of Q
are saturated.


title:
Age of the Universe, Average Deceleration Parameter and Possible
  Implications for the End of Cosmology

abstract:
  A new expression to the total age of the Universe is derived in terms of the
average deceleration parameter. This kinematic result holds regardless of the
curvature of the universe as well as of the underlying gravity theory. It
remains valid even in the context of brane-world motivated cosmologies. Since
the present age parameter of the Universe is accurately adjusted to $H_0t_0 =
1$, it is shown that the time averaged value of the deceleration parameter is
zero. This also means that the cosmic age today is exactly the one predicted by
a relativistic flat cosmological model filled by K-matter, a fluid satisfying
the equation of state $p = -{{1/3}}\rho$. By assuming the validity of this
relation (in an average long time meaning), it is argued that the decelerating
stages of the expansion must exactly be compensated by the accelerated phases,
as if the observed Universe coasts forever. If this is true, the present
accelerating stage must be followed by a subsequent decelerating phase as
predicted by some recent scalar field and brane-world motivated cosmologies.


title: Immersed Turnovers In Hyperbolic 3-Orbifolds

abstract:
  We show that any immersion, which is not a covering of an embedded
2-orbifold, of a totally geodesic hyperbolic turnover in a complete orientable
hyperbolic 3-orbifold is contained in a hyperbolic 3-suborbifold with totally
geodesic boundary, called the "turnover core,'' whose volume is bounded from
above by a function depending only on the area of the given turnover.
Furthermore, we show that, for a given type of turnover, there are only
finitely many possibilities for the turnover core. As a corollary, if the
volume of a complete orientable hyperbolic 3-orbifold is at least 2\pi and if
the fundamental group of the orbifold contains the fundamental group of a
hyperbolic turnover (i.e., a triangle group), then the orbifold contains an
embedded hyperbolic turnover.


title:
Does Simple Two-Dimensional Hubbard Model Account for High-Tc
  Superconductivity in Copper Oxides?

abstract:
  We reexamine whether the essence of high-Tc superconductivity is contained in
doped Hubbard models on the square lattice by using recently developed
pre-projected Gaussian-basis Monte Carlo method. The superconducting
correlations of the dx2-y2 wave symmetry in the ground state at distance r
decays essentially as inverse cubic of r. The upper bound of the correlation at
long distances estimated by this unbiased method is 0.001, indicating that
recent extensions of dynamical mean-field theories and variational methods
yielded at least an order of magnitude overestimates of it. The correlations
are too weak for the realistic account of the cuprate high-Tc
superconductivity.


title:
Generation of the second-harmonic Bessel beams via nonlinear Bragg
  diffraction

abstract:
  We generate conical second-harmonic radiation by transverse excitation of a
two-dimensional annular periodically-poled nonlinear photonic structure with a
fundamental Gaussian beam. We show that these conical waves are the far-field
images of the Bessel beams generated in a crystal by parametric frequency
conversion assisted by nonlinear Bragg diffraction.


title: Quiver coefficients of Dynkin type

abstract:
  We study the Grothendieck classes of quiver cycles, i.e. invariant closed
subvarieties of the representation space of a quiver. For quivers without
oriented loops we show that the class of a quiver cycle is determined by quiver
coefficients, which generalize the earlier studied quiver coefficients for
equioriented quivers of type A. We conjecture that quiver coefficients satisfy
positivity and finiteness properties. Our main result is a formula for the
quiver coefficients for orbit closures of Dynkin type with rational
singularities, which confirms the finiteness conjecture. This formula is based
on Reineke's desingularization of such orbit closures. For quivers of type A3,
we give positive combinatorial formulas for the quiver coefficients, which
confirm the full conjecture. We also interpret quiver coefficients as formulas
for degeneracy loci defined by quivers of vector bundle maps.


title:
Brownian-time Brownian motion SIEs on $\Rp\times\Rd$: Ultra Regular
  direct and lattice-limits solutions and fourth order SPDEs links

abstract:
  We delve deeper into the compelling regularizing effect of the Brownian-time
Brownian motion density, $\KBtxy$, on the space-time-white-noise-driven
stochastic integral equation we call BTBM SIE, which we recently introduced. In
sharp contrast to second order heat-based SPDEs--whose real-valued mild
solutions are confined to $d=1$--we prove the existence of solutions to the
BTBM SIE in $d=1,2,3$ with dimension-dependent and striking Holder regularity,
under both less than Lipschitz and Lipschitz conditions. In space, we show an
unprecedented nearly local Lipschitz regularity for $d=1,2$--roughly, the SIE
is spatially twice as regular as the Brownian sheet in these dimensions--and
nearly local H\"older 1/2 regularity in d=3. In time, our solutions are locally
H\"older continuous with exponent $\gamma\in(0,(4-d)/(8))$ for $1\le d\le3$. To
investigate our SIE, we (a) introduce the Brownian-time random walk and we use
it to formulate the spatial lattice version of the BTBM SIE; and (b) develop a
delicate variant of Stroock-Varadhan martingale approach, the K-martingale
approach, tailor-made for a wide variety of kernel SIEs including BTBM SIEs and
the mild forms of many SPDEs of different orders on the lattice. Here,
solutions types to our SIE are both direct and limits of their lattice version.
The BTBM SIE is intimately connected to intriguing fourth order SPDEs in two
ways. First, we show that it is connected to the diagonals of a new
unconventional fourth order SPDE we call parametrized BTBM SPDE. Second,
replacing $\KBtxy$ by the intimately connected kernel of our recently
introduced imaginary-Brownian time-Brownian-angle process (IBTBAP), our SIE
becomes the mild form of a Kuramoto-Sivashinsky SPDE with linear PDE part.
Ideas developed here are adapted in separate papers to give a new approach, via
our explicit IBTBAP representation, to many KS-type SPDEs in multi spatial
dimensions.


title:
Effect of linear density of states on the quasi-particle dynamics and
  small electron-phonon coupling in graphite

abstract:
  We obtained the spectral function of very high quality natural graphite
single crystals using angle resolved photoelectron spectroscopy (ARPES). A
clear separation of non-bonding and bonding bands and asymmetric lineshape are
observed. The asymmetric lineshapes are well accounted for by the finite
photoelectron escape depth and the band structure. The extracted width of the
spectral function (inverse of the photohole life time) near the K point is,
beyond the maximum phonon energy, approximately proportional to the energy as
expected from the linear density of states near the Fermi energy. The upper
bound for the electron-phonon coupling constant is about 0.2, a much smaller
value than the previously reported one.