title: Optical lattice quantum Hall effect

abstract:
  We explore the behavior of interacting bosonic atoms in an optical lattice
subject to a large artificial magnetic field. We extend earlier investigations
of this system where the number of magnetic flux quanta per unit cell alpha is
close to a simple rational number [Phys. Rev. Lett. 96, 180407 (2006)].
Interesting topological states such as the Laughlin and Read-Rezayi states can
occur even if the atoms experience a weak trapping potential in one direction.
An explicit numerical calculation near alpha = 1/2 shows that the system
exhibits a striped vortex lattice phase of one species, which is analogous to
the behavior of a two-species system for small alpha. We also investigate
methods to probe the encountered states. These include spatial correlation
functions and the measurement of noise correlations in time of flight expanded
atomic clouds. Characteristic differences arise which allow for an
identification of the respective quantum Hall states. We furthermore discuss
that a counterintuitive flow of the Hall current occurs for certain values of
alpha.


title: BCS superconductivity of Dirac electrons in graphene layers

abstract:
  Possible superconductivity of electrons with the Dirac spectrum is analyzed
using the BCS model. We calculate the critical temperature, the superconducting
energy gap, and supercurrent as functions of the doping level and of the
pairing interaction strength. Zero doping is characterized by existence of the
quantum critical point such that the critical temperature vanishes below some
finite value of the interaction strength. However, the critical temperature
remains finite for any nonzero electron or hole doping level when the Fermi
energy is shifted away from the Dirac point of the normal-state electron
spectrum. We analyze the behavior of the characteristic length scales, i.e.,
the London penetration depth and the coherence length, which determine the
critical magnetic fields.


title: Capacity of Gaussian MIMO Bidirectional Broadcast Channels

abstract:
  We consider the broadcast phase of a three-node network, where a relay node
establishes a bidirectional communication between two nodes using a spectrally
efficient two-phase decode-and-forward protocol. In the first phase the two
nodes transmit their messages to the relay node. Then the relay node decodes
the messages and broadcasts a re-encoded composition of them in the second
phase. We consider Gaussian MIMO channels and determine the capacity region for
the second phase which we call the Gaussian MIMO bidirectional broadcast
channel.


title: Nanosized superparamagnetic precipitates in cobalt-doped ZnO

abstract:
  The existence of semiconductors exhibiting long-range ferromagnetic ordering
at room temperature still is controversial. One particularly important issue is
the presence of secondary magnetic phases such as clusters, segregations,
etc... These are often tedious to detect, leading to contradictory
interpretations. We show that in our cobalt doped ZnO films grown
homoepitaxially on single crystalline ZnO substrates the magnetism
unambiguously stems from metallic cobalt nano-inclusions. The magnetic behavior
was investigated by SQUID magnetometry, x-ray magnetic circular dichroism, and
AC susceptibility measurements. The results were correlated to a detailed
microstructural analysis based on high resolution x-ray diffraction,
transmission electron microscopy, and electron-spectroscopic imaging. No
evidence for carrier mediated ferromagnetic exchange between diluted cobalt
moments was found. In contrast, the combined data provide clear evidence that
the observed room temperature ferromagnetic-like behavior originates from
nanometer sized superparamagnetic metallic cobalt precipitates.


title:
Constraints on Dark Energy from Galaxy Cluster Gas Mass Fraction versus
  Redshift data

abstract:
  We use the Allen et al. (2008) galaxy cluster gas mass fraction versus
redshift data to constrain parameters of three different dark energy models: a
cosmological constant dominated one ($\Lambda$CDM); the XCDM parameterization
of dark energy; and a slowly-rolling scalar field model with inverse-power-law
potential energy density. (Instead of using the Monte Carlo Markov Chain
method, when integrating over nuisance parameters we use an alternative method
of introducing an auxiliary random variable.) The resulting constraints are
consistent with, and typically more constraining than, those derived from other
cosmological data. A time-independent cosmological constant is a good fit to
the galaxy cluster data, but slowly evolving dark energy cannot yet be ruled
out.


title: Thermonuclear Reflect AB-Reactor

abstract:
  The author offers a new kind of thermonuclear reflect reactor. The remarkable
feature of this new reactor is a three net AB reflector, which confines the
high temperature plasma. The plasma loses part of its energy when it contacts
with the net but this loss can be compensated by an additional permanent plasma
heating. When the plasma is rarefied (has a small density), the heat flow to
the AB reflector is not large and the temperature in the triple reflector net
is lower than 2000 - 3000 K. This offered AB-reactor has significantly less
power then the currently contemplated power reactors with magnetic or inertial
confinement (hundreds-thousands of kW, not millions of kW). But it is enough
for many vehicles and ships and particularly valuable for tunnelers, subs and
space apparatus, where air to burn chemical fuel is at a premium or simply not
available.
  The author has made a number of innovations in this reactor, researched its
theory, developed methods of computation, made a sample computation of typical
project. The main point of preference for the offered reactor is its likely
cheapness as a power source.
  Key words: Micro-thermonuclear reactor, Multi-reflex AB-thermonuclear
reactor, Self-magnetic AB-thermonuclear reactor, aerospace thermonuclear
engine.


title:
Lower Bounds on the Minimum Pseudodistance for Linear Codes with $q$-ary
  PSK Modulation over AWGN

abstract:
  We present lower bounds on the minimum pseudocodeword effective Euclidean
distance (or minimum "pseudodistance") for coded modulation systems using
linear codes with $q$-ary phase-shift keying (PSK) modulation over the additive
white Gaussian noise (AWGN) channel. These bounds apply to both binary and
nonbinary coded modulation systems which use direct modulation mapping of coded
symbols. The minimum pseudodistance may serve as a first-order measure of
error-correcting performance for both linear-programming and message-passing
based receivers. In the case of a linear-programming based receiver, the
minimum pseudodistance may be used to form an exact bound on the codeword error
rate of the system.


title:
Triangle angles and sides in progression and the diophantine equation
  x^2+3y^2 =z^2

abstract:
  The main result of this paper, is the complete parametric description of the
family of triangles which have integer sidelengths and with one angle being
sixty degrees.


title:
The commensurate phase of multiferroic HoMn2O5 studied by X-ray magnetic
  scattering

abstract:
  The commensurate phase of multiferroic HoMn2O5 was studied by X-ray magnetic
scattering, both off resonance and in resonant conditions at the Ho-L3 edge.
Below 40 K, magnetic ordering at the Ho sites is induced by the main Mn
magnetic order parameter, and its temperature dependence is well accounted for
by a simple Curie-Weiss susceptibility model. A lattice distortion of
periodicity twice that of the magnetic order is also evidenced. Azimuthal scans
confirm the model of the magnetic structure recently refined from neutron
diffraction data for both Mn and Ho sites, indicating that the two sublattices
interact via magnetic superexchange.


title: Fold maps, framed immersions and smooth structures

abstract:
  For each integer q>0 there is a cohomology theory such that the zero
cohomology group of a manifold N of dimension n is a certain group of cobordism
classes of proper fold maps of manifolds of dimension n+q into N. We prove a
splitting theorem for the spectrum representing the cohomology theory of fold
maps. For even q, the splitting theorem implies that the cobordism group of
fold maps to a manifold N is a sum of q/2 cobordism groups of framed immersions
to N and a group related to diffeomorphism groups of manifolds of dimension
q+1. Similarly, in the case of odd q, the cobordism group of fold maps splits
off (q-1)/2 cobordism groups of framed immersions.
  The proof of the splitting theorem gives a partial splitting of the homotopy
cofiber sequence of Thom spectra in the Madsen-Weiss approach to diffeomorphism
groups of manifolds.


title: Fourier Spectra of Binomial APN Functions

abstract:
  In this paper we compute the Fourier spectra of some recently discovered
binomial APN functions. One consequence of this is the determination of the
nonlinearity of the functions, which measures their resistance to linear
cryptanalysis. Another consequence is that certain error-correcting codes
related to these functions have the same weight distribution as the
2-error-correcting BCH code. Furthermore, for fields of odd degree, our results
provide an alternative proof of the APN property of the functions.


title: Analytic Functions of a Quaternionic Variable

abstract:
  Here we follow the basic analysis that is common for real and complex
variables and find how it can be applied to a quaternionic variable.
Non-commutativity of the quaternion algebra poses obstacles for the usual
manipulations; but we show how many of those obstacles can be overcome. After a
tiny bit of linear algebra we look at the beginnings of differential calculus.
The surprising result is that the first order term in the expansion of
F(x+delta) is a compact formula involving both F'(x) and [F(x) - F(x*)]/(x-x*).


title:
Stability in $H^{1/2}$ of the sum of $K$ solitons for the Benjamin-Ono
  equation

abstract:
  This note proves the orbital stability in the energy space $H^{1/2}$ of the
sum of widely-spaced 1-solitons for the Benjamin-Ono equation, with speeds
arranged so as to avoid collisions.


title:
Observation of entanglement between two light beams spanning an octave
  in optical frequency

abstract:
  We have experimentally demonstrated how two beams of light separated by an
octave in frequency can become entangled after their interaction in a
second-order nonlinear medium. The entangler consisted of a nonlinear crystal
placed within an optical resonator that was strongly driven by coherent light
at the fundamental and second-harmonic wavelengths. An inter-conversion between
the fields created quantum correlations in the amplitude and phase quadratures,
which were measured by two independent homodyne detectors. Analysis of the
resulting correlation matrix revealed a wavefunction inseparability of 0.74(1)
< 1 thereby satisfying the criterion of entanglement.


title:
Trivial, Critical and Near-critical Scaling Limits of Two-dimensional
  Percolation

abstract:
  It is natural to expect that there are only three possible types of scaling
limits for the collection of all percolation interfaces in the plane: (1) a
trivial one, consisting of no curves at all, (2) a critical one, in which all
points of the plane are surrounded by arbitrarily large loops and every
deterministic point is almost surely surrounded by a countably infinite family
of nested loops with radii going to zero, and (3) an intermediate one, in which
every deterministic point of the plane is almost surely surrounded by a largest
loop and by a countably infinite family of nested loops with radii going to
zero. We show how one can prove this using elementary arguments, with the help
of known scaling relations for percolation.
  The trivial limit corresponds to subcritical and supercritical percolation,
as well as to the case when the density p approaches the critical probability,
p_c, sufficiently slowly as the lattice spacing is sent to zero. The second
type corresponds to critical percolation and to a faster approach of p to p_c.
The third, or near-critical, type of limit corresponds to an intermediate speed
of approach of p to p_c. The fact that in the near-critical case a
deterministic point is a.s. surrounded by a largest loop demonstrates the
persistence of a macroscopic correlation length in the scaling limit and the
absence of scale invariance.


title:
X-ray Observations of Optically Selected Giant Elliptical-Dominated
  Galaxy Groups

abstract:
  We present a combined optical and X-ray analysis of three optically selected
X-ray bright groups with giant elliptical galaxies in the center. These massive
ellipticals were targeted for XMM-Newton X-ray observations based on their
large velocity dispersions and their proximity to a nearby ROSAT X-ray source.
Additionally, these targets are significantly brighter in the optical than
their nearest neighbors. We show that one of these systems meets the standard
criteria for a fossil group. While the other two systems have a prominent
magnitude gap in the E/S0 ridgeline, they do not appear to have reached the
fossil-like final stage of group evolution.


title: New Proof of the Equation $\sum_{k=1}^\infty \frac{\mu(k)}{k}=0.$

abstract: This is an English translation of Edmund Landau's Doctoral Dissertation.


title: Hilbert modular forms of weight 1/2 and theta functions

abstract:
  Serre and Stark found a basis for the space of modular forms of weight 1/2 in
terms of theta series. In this paper, we generalize their result - under
certain mild restrictions on the level and character - to the case of weight
1/2 Hilbert modular forms over a totally real field of narrow class number 1.
The methods broadly follow those of Serre-Stark; however we are forced to
overcome technical difficulties which arise when we move out of Q.


title: On metrics of positive Ricci curvature conformal to MxR^m

abstract:
  Let (M, g) be a closed Riemannian manifold and gE the Euclidean metric. We
show that for m > 1, (M x R^m, (g + gE)) is not conformal to a positive
Einstein manifold. Moreover, (M x R^m, (g + gE)) is not conformal to a
Riemannian manifold of positive Ricci curvature, through a smooth, radial,
positive, integrable function of R^m, for m > 1. These results are motivated by
some recent questions on Yamabe constants.


title:
Superconductivity at 41 K and its competition with spin-density-wave
  instability in layered CeO$_{1-x}$F$_x$FeAs

abstract:
  A series of layered CeO$_{1-x}$F$_x$FeAs compounds with x=0 to 0.20 are
synthesized by solid state reaction method. Similar to the LaOFeAs, the pure
CeOFeAs shows a strong resistivity anomaly near 145 K, which was ascribed to
the spin-density-wave instability. F-doping suppresses this instability and
leads to the superconducting ground state. Most surprisingly, the
superconducting transition temperature could reach as high as 41 K. The very
high superconducting transition temperature strongly challenges the classic BCS
theory based on the electron-phonon interaction. The very closeness of the
superconducting phase to the spin-density-wave instability suggests that the
magnetic fluctuations play a key role in the superconducting paring mechanism.
The study also reveals that the Ce 4f electrons form local moments and ordered
antiferromagnetically below 4 K, which could coexist with superconductivity.


title: Effects of rf Current on Spin Transfer Torque Induced Dynamics

abstract:
  The impact of radiofrequency (rf) currents on the direct current (dc) driven
switching dynamics in current-perpendicular-to-plane nanoscale spin valves is
demonstrated. The rf currents dramatically alter the dc driven free layer
magnetization reversal dynamics as well as the dc switching level. This occurs
when the frequency of the rf current is tuned to a frequency range around the
dc driven magnetization precession frequencies. For these frequencies,
interactions between the dc driven precession and the injected rf induce
frequency locking and frequency pulling effects that lead to a measurable
dependence of the critical switching current on the frequency of the injected
rf. Based on macrospin simulations, including dc as well as rf spin torque
currents, we explain the origin of the observed effects.


title: Evidence for universal scaling in the spin-glass phase

abstract:
  We perform Monte Carlo simulations of Ising spin-glass models in three and
four dimensions, as well as of Migdal-Kadanoff spin glasses on a hierarchical
lattice. Our results show strong evidence for universal scaling in the
spin-glass phase in all three models. Not only does this allow for a clean way
to compare results obtained from different coupling distributions, it also
suggests that a so far elusive renormalization group approach within the
spin-glass phase may actually be feasible.


title:
Supernova progenitors and iron density evolution from SN rate evolution
  measurements

abstract:
  Using an extensive compilation of literature supernova rate data we study to
which extent its evolution constrains the star formation history, the
distribution of the type Ia supernova (SNIa) progenitor's lifetime, the mass
range of core-collapse supernova (CCSN) progenitors, and the evolution of the
iron density in the field.
  We find that the diagnostic power of the cosmic SNIa rate on their progenitor
model is relatively weak. More promising is the use of the evolution of the
SNIa rate in galaxy clusters. We find that the CCSN rate is compatible with a
Salpeter IMF, with a minimum mass for their progenitors > 10 Msun. We estimate
the evolution in the field of the iron density released by SNe and find that in
the local universe the iron abundance should be ~ 0.1 solar. We discuss the
difference between this value and the iron abundance in clusters.


title: A Multiply Imaged Luminous Infrared Galaxy Behind the Bullet Cluster

abstract:
  We present evidence for a Spitzer-selected luminous infrared galaxy (LIRG)
behind the Bullet Cluster. The galaxy, originally identified in IRAC photometry
as a multiply imaged source, has a spectral energy distribution consistent with
a highly extincted (A_V~3.3), strongly star-forming galaxy at z=2.7. Using our
strong gravitational lensing model presented in Bradac et al. (2006), we find
that the magnifications are 10 to 50 for the three images of the galaxy. The
implied infrared luminosity is consistent with the galaxy being a LIRG, with a
stellar mass of M_*~2e11 M_Sun and a star formation rate of ~90 M_Sun/yr. With
lensed fluxes at 24 microns of 0.58 mJy and 0.39 mJy in the two brightest
images, this galaxy presents a unique opportunity for detailed study of an
obscured starburst with star fomation rate comparable to that of L* galaxies at
z>2.


title:
Collider Signals of Maximal Flavor Violation: Same-Sign Leptons from
  Same-Sign Tops at the Tevatron

abstract:
  In models of maximal flavor violation (MxFV) there is at least one new scalar
$\Phi_{FV}$ which couples to the quarks via $\Phi_{FV} q_i q_j \propto
\xi_{ij}$ where $\xi_{i3},\xi_{3i} \sim V_{tb}$ for $i = 1,2$ and $\xi_{33}
\sim V_{td}$ and $V$ is the CKM matrix. In this article, we explore the
potential phenomenological implications of MxFV for collider experiments. We
study MxFV signals of same-sign leptons from same-sign top-quark pair
production at the Tevatron and at the LHC. We show that the current Tevatron
dataset has strong sensitivity to this signature, for which there are no
current limits. For example, if $m_{\Phi_{FV}} \sim 200$ GeV and the MxFV
coupling $\xi$ has a natural value of $\sim 1$, we expect $\sim 12$ MxFV events
to survive a selection requiring a pair of same-sign leptons, a tagged $b$-jet
and missing transverse energy, over a background of approximately 4-5 events.


title:
Approximating a Behavioural Pseudometric without Discount for<br>
  Probabilistic Systems

abstract:
  Desharnais, Gupta, Jagadeesan and Panangaden introduced a family of
behavioural pseudometrics for probabilistic transition systems. These
pseudometrics are a quantitative analogue of probabilistic bisimilarity.
Distance zero captures probabilistic bisimilarity. Each pseudometric has a
discount factor, a real number in the interval (0, 1]. The smaller the discount
factor, the more the future is discounted. If the discount factor is one, then
the future is not discounted at all. Desharnais et al. showed that the
behavioural distances can be calculated up to any desired degree of accuracy if
the discount factor is smaller than one. In this paper, we show that the
distances can also be approximated if the future is not discounted. A key
ingredient of our algorithm is Tarski's decision procedure for the first order
theory over real closed fields. By exploiting the Kantorovich-Rubinstein
duality theorem we can restrict to the existential fragment for which more
efficient decision procedures exist.


title:
Condensate fraction in a 2D Bose gas measured across the Mott-insulator
  transition

abstract:
  We realize a single-band 2D Bose-Hubbard system with Rb atoms in an optical
lattice and measure the condensate fraction as a function of lattice depth,
crossing from the superfluid to the Mott-insulating phase. We quantitatively
identify the location of the superfluid to normal transition by observing when
the condensed fraction vanishes. Our measurement agrees with recent quantum
Monte Carlo calculations for a finite-sized 2D system to within experimental
uncertainty.


title:
Convergence of the Eilenberg-Moore spectral sequence for generalized
  cohomology theories

abstract:
  We prove that the Morava-$K$-theory-based Eilenberg-Moore spectral sequence
has good convergence properties whenever the base space is a $p$-local finite
Postnikov system with vanishing $(n+1)$st homotopy group.


title:
The electron transport through a quantum dot in the Coulomb blockade
  regime: Non-equilibrium Green's functions based model

abstract:
  We explore electron transport through a quantum dot coupled to the source and
drain charge reservoirs We trace the transition from the Coulomb blockade
regime to Kondo regime in the electron transport through the dot occuring when
we gradually strengthen the coupling of the dot to the charge reservoirs. The
current-voltage $(I-V)$ characteristics are calculated using the equations of
motion approach within the nonequilibrium Green's functions formalism (NEGF)
beyond the Hartree-Fock approximation. We show that within the Coulomb blockade
regime the $I-V$ characteristics for the quantum dot containing a single
spin-degenerated level with the energy $E_0 $ include two steps whose locations
are determined by the values of $ E_0 $ and the energy of Coulomb interaction
of electrons in the dot $U.$ The heights of the steps are related as $2:1$
which is consistent with the results obtained by means of the transition rate
equations.


title:
Time Structure of Ultra-High Energy Cosmic Ray Sources and Consequences
  for Multi-messenger Signatures

abstract:
  The latest results on the sky distribution of ultra-high energy cosmic ray
sources have consequences for their nature and time structure. If the sources
accelerate predominantly nuclei of atomic number A and charge Z and emit
continuously, their luminosity in cosmic rays above ~6x10^{19} eV can be no
more than a fraction of ~5x10^{-4} Z^{-2} of their total power output. Such
sources could produce a diffuse neutrino flux that gives rise to several events
per year in neutrino telescopes of km^3 size. Continuously emitting sources
should be easily visible in photons below ~100 GeV, but not in TeV gamma-rays
which are likely absorbed within the source. For episodic sources that are
beamed by a Lorentz factor Gamma, the bursts or flares have to last at least
~0.1 Gamma^{-4} A^{-4} yr. A considerable fraction of the flare luminosity
could go into highest energy cosmic rays, in which case the rate of flares per
source has to be less than ~5x10^{-3} Gamma^4 A^4 Z^2 yr^{-1}. Episodic sources
should have detectable variability both at GLAST and TeV energies, but neutrino
fluxes may be hard to detect.


title: States of Negative Energy and $AdS_5 \times S_5/Z_k$

abstract:
  We develop a careful definition of energy for nonsupersymmetric warped
product asymptotically $AdS_d \times M_q$ solutions which include a nonzero
p-form. In the case of an electric p-form extending along all the AdS
directions, and in particular in the case of self-dual fields like those used
in the Freund-Rubin construction, the Hamiltonian is well defined only if a
particular asymptotic gauge for the p-form is used. Rather surprisingly,
asymptotically this gauge is time dependent, despite the fact the field and
metric are not. We then consider a freely orbifolded $AdS_5 \times S_5$ and
demonstrate that the standard boundary conditions allow states of arbitrarily
negative energy. The states consist of time symmetric initial data describing
bubbles that are regular up to singularities due to smeared D3-branes. We
discuss the evolution of this data and point out that if the usual boundary
conditions are enforced such bubbles may never reach infinity.


title:
Optical Identification of a DNA-Wrapped Carbon Nanotube: Signs of
  Helically Broken Symmetry

abstract:
  High intrinsic mobility and small, biologically-compatible size make
single-walled carbon nanotubes (SWNTs) in demand for the next generation of
electronic devices. Further, the wide range of available bandgaps due to
changes in diameter and symmetry give SWNTs greater versatility than
traditional semiconductors. Single-stranded DNA has been employed to make these
desirable properties accessible for large scale fabrication of devices. Because
single-stranded DNA can helically wrap a SWNT, forming a stable hybrid
structure, DNA/polymer wrapping has been used to disperse bundles of
intrinsically hydrophobic SWNTs into individual tubes in aqueous solution. The
ability to isolate individual tubes, make them soluble, and separate them
according to symmetry would enable fabrication of SWNT optoelectronic devices
that benefit from the unique electronic properties of specific nanotube
structures. Envisioning optoelectronic applications of nanotubes, we
investigate whether the optical properties of DNA-wrapped SWNT materials are
different than those of pristine SWNTs. Our previous work found that
bandstructures of DNA-SWNTs were indeed affected by the charged wrap. That is,
the direct optical bandgap, $E_{11}$, decreases, but changes are fairly small.
This is consistent with the available experimental data in standard
experimental geometry in which incident light is polarized along the SWNT axis.
Here we consider optical absorption of light with perpendicular (or circular)
polarization with respect to the tube axis, which has been measured
experimentally for SWNTs dispersed using a surfactant. In this geometry we find
qualitative changes in the absorption spectra of SWNTs upon hybridization with
DNA, including strong optical circular dichroism in non-chiral SWNTs.


title: Comments on the Bagger-Lambert theory and multiple M2-branes

abstract:
  We study the SO(8) superconformal theory proposed recently by Bagger and
Lambert as a possible worldvolume theory for multiple M2-branes. For their
explicit example with gauge group SO(4), we rewrite the theory (originally
formulated in terms of a three-algebra) as an ordinary SU(2) \times SU(2) gauge
theory with bifundamental matter. In this description, the parity invariance of
the theory, required for a proper description of M2-branes, is clarified. We
describe the subspace of scalar field configurations on which the potential
vanishes, and note that this does not coincide with the moduli space for a
stack of M2-branes. Finally, we point out a difficulty in constructing the
required set of superconformal primary operators which should be present in the
correct theory describing multiple M2-branes.


title:
Gravitational waves from pulsations of neutron stars described by
  realistic Equations of State

abstract:
  In this work we discuss the time-evolution of nonspherical perturbations of a
nonrotating neutron star described by a realistic Equation of State (EOS). We
analyze 10 different EOS for a large sample of neutron star models. Various
kind of generic initial data are evolved and the corresponding gravitational
wave signals are computed. We focus on the dynamical excitation of fluid and
spacetime modes and extract the corresponding frequencies. We employ a
constrained numerical algorithm based on standard finite differencing schemes
which permits stable and long term evolutions. Our code provides accurate
waveforms and allows to capture, via Fourier analysis of the energy spectra,
the frequencies of the fluid modes with an accuracy comparable to that of
frequency domain calculations. The results we present here are useful for
provindig comparisons with simulations of nonlinear oscillations of (rotating)
neutron star models as well as testbeds for 3D nonlinear codes.


title: Largeness of LERF and 1-relator groups

abstract:
  We consider largeness of groups given by a presentation of deficiency 1,
where the group is respectively free-by-cyclic, LERF or 1-relator. We give the
first examples of (finitely generated free)-by-(infinite cyclic) word
hyperbolic groups which are large, show that a LERF deficiency 1 group with
first Betti number at least 2 is large or the integers times the integers, and
show that 2-generator 1-relator groups where the relator has height 1 obey the
dichotomy that either the group is large or all its finite images are
metacyclic.


title: Central K-band kinematics and line strength maps of NGC 1399

abstract:
  In this paper we present for the first time high spatial resolution K-band
maps of the central kinematical and near-infrared spectral properties of the
giant cD galaxy in the Fornax cluster, NGC 1399. We confirm the presence of a
central velocity dispersion dip within radius < 0.2" seen in previous long-slit
studies. Our velocity dispersion maps give evidence for a non-symmetric
structure in this central area by showing three sigma peaks to the north-east,
south-east and west of the galaxy centre. Additionally we measure near-IR line
strength indices at unprecedented spatial resolution in NGC 1399. The most
important features we observe in our 2-dimensional line strength maps are drops
in Na I and CO(2-0) line strength in the nuclear region of the galaxy,
coinciding spatially with the drop in sigma. The observed line strength and
velocity dispersion changes suggest a scenario where the centre of NGC 1399
harbours a dynamically cold subsystem with a distinct stellar population.


title:
Simulations of Ultrarelativistic Magnetodynamic Jets from Gamma-ray
  Burst Engines

abstract:
  Long-duration gamma-ray bursts (GRBs) require an engine capable of driving a
jet of plasma to ultrarelativistic bulk Lorentz factors of up to several
hundred and into narrow opening angles of a few degrees. We use global
axisymmetric stationary solutions of magnetically-dominated (force-free)
ultrarelativistic jets to test whether the popular magnetic-driving paradigm
can generate the required Lorentz factors and opening angles. Our global
solutions are obtained via time-dependent relativistic ideal magnetodynamical
numerical simulations which follow the jet from the central engine to beyond
six orders of magnitude in radius. Our model is primarily motivated by the
collapsar model, in which a jet is produced by a spinning black hole or neutron
star and then propagates through a massive stellar envelope. We find that the
size of the presupernova progenitor star and the radial profile of pressure
inside the star determine the terminal Lorentz factor and opening angle of the
jet. At the radius where the jet breaks out of the star, our well-motivated
fiducial model generates a Lorentz factor $\gamma\sim 400$ and a half-opening
angle $\theta_j\sim 2^\circ$, consistent with observations of many
long-duration GRBs. Other models with slightly different parameters give
$\gamma$ in the range 100 to 5000 and $\theta_j$ from $0.1^\circ$ to
$10^\circ$, thus reproducing the range of properties inferred for GRB jets. A
potentially observable feature of some of our solutions is that the maximum
Poynting flux in the jet is found at $\theta \sim \theta_j$ with the jet power
concentrated in a hollow cone, while the maximum in the Lorentz factor occurs
at an angle $\theta$ substantially smaller than $\theta_j$ also in a hollow
cone. [abridged]


title: A Candidate Brightest Proto-Cluster Galaxy at z = 3.03

abstract:
  We report the discovery of a very bright (m_R = 22.2) Lyman break galaxy at z
= 3.03 that appears to be a massive system in a late stage of merging. Deep
imaging reveals multiple peaks in the brightness profile with angular
separations of ~0.''8 (~25 h^-1 kpc comoving). In addition, high
signal-to-noise ratio rest-frame UV spectroscopy shows evidence for ~5
components based on stellar photospheric and ISM absorption lines with a
velocity dispersion of sigma ~460 km s^-1 for the three strongest components.
Both the dynamics and high luminosity, as well as our analysis of a LCDM
numerical simulation, suggest a very massive system with halo mass M ~ 10^13
M_solar. The simulation finds that all halos at z = 3 of this mass contain
sub-halos in agreement with the properties of these observed components and
that such systems typically evolve into M ~ 10^14 M_solar halos in groups and
clusters by z = 0. This discovery provides a rare opportunity to study the
properties and individual components of z ~ 3 systems that are likely to be the
progenitors to brightest cluster galaxies.


title: Higgsflation at the GUT scale in a Higgsless Universe

abstract:
  We revisit inflation in induced gravity. Our focus is on models where the low
scale Planck mass is completely determined by the breaking of the scaling
symmetry in the field theory sector. The Higgs-like field which breaks the
symmetry with a GUT-scale vacuum expectation value has non-minimal couplings to
the curvature, induced by the gravitational couplings of the other light fields
in the theory, so that its expectation value controls the gravitational
strength. This field can drive inflation, and give a low energy universe in
very good agreement with the cosmological observations. The low energy dynamics
of the Standard Model cannot be unitarized by the Higgsflaton, which decouples
from the low energy theory, both because it picks up a large mass and because
its direct couplings to the low energy modes are weakened. Instead, the short
distance behavior of the Standard Model may be regulated by the dynamics of
other light degrees of freedom, such as in Higgsless models.


title: Single top quark production at LHC with anomalous Wtb couplings

abstract:
  We investigate single top production in the presence of anomalous Wtb
couplings. We explicitly show that, if these couplings arise from gauge
invariant effective operators, the only relevant couplings for single top
production and decay are the usual gamma^mu and sigma^mu nu q_nu terms, where q
is the W boson momentum. This happens even in the single top production
processes where the Wtb interaction involves off-shell top and/or bottom
quarks. With this parameterisation for the Wtb vertex, we obtain expressions
for the dependence on anomalous couplings of the single top cross sections, for
(i) the t-channel process, performing a matching between tj and t bbar j
production, where j is a light jet; (ii) s-channel t bbar production; (iii)
associated tW- production, including the correction from tW- bbar. We use these
expressions to estimate, with a fast detector simulation, the simultaneous
limits which the measurement of single top cross sections at LHC will set on
V_tb and possible anomalous couplings. Finally, a combination with top decay
asymmetries and angular distributions is performed, showing how the limits can
be improved when the latter are included in a global fit to Wtb couplings.


title: QCD Corrections to K-Kbar Mixing in R-symmetric Supersymmetric Models

abstract:
  The leading-log QCD corrections to K-Kbar mixing in R-symmetric
supersymmetric models are computed using effective field theory techniques. The
spectrum topology where the gluino is significantly heavier than the squarks is
motivated and focused on. It is found that, like in the MSSM, QCD corrections
can tighten the kaon mass difference bound by roughly a factor of three. CP
violation is also briefly considered, where QCD corrections can constrain
phases to be as much as a factor of ten smaller than the uncorrected value.


title: Preferred extensions as stable models

abstract:
  Given an argumentation framework AF, we introduce a mapping function that
constructs a disjunctive logic program P, such that the preferred extensions of
AF correspond to the stable models of P, after intersecting each stable model
with the relevant atoms. The given mapping function is of polynomial size
w.r.t. AF. In particular, we identify that there is a direct relationship
between the minimal models of a propositional formula and the preferred
extensions of an argumentation framework by working on representing the
defeated arguments. Then we show how to infer the preferred extensions of an
argumentation framework by using UNSAT algorithms and disjunctive stable model
solvers. The relevance of this result is that we define a direct relationship
between one of the most satisfactory argumentation semantics and one of the
most successful approach of non-monotonic reasoning i.e., logic programming
with the stable model semantics.


title: Coronal Temperature as an Age Indicator

abstract:
  The X-ray spectra of late type stars can generally be well fitted by a two
temperature component model of the corona. We fnd that the temperature of both
components are strong functions of stellar age, although the temperature of the
hotter plasma in the corona shows a larger scatter and is probably affected by
the activity of stars, such as flares. We confirm the power-law decay of the
temperature of the hot plasma, but the temperature of the cool component decays
linearly with log (age).


title: Damping of Type I X-ray Burst Oscillations by Convection

abstract:
  I construct a simple model of the convective burning layer during a type I
X-ray burst to investigate the effects convection has on the stability of the
layer to nonradial oscillations. A linear perturbation analysis demonstrates
that the region is stable to nonradial oscillations when energy transport is
convection-dominated, but it is unstable when energy transport is
radiation-dominated. Thus, efficient convection always dampens oscillations.
These results may explain the nondetection of oscillations during the peak of
some X-ray bursts.


title: The elliptic GL(n) dynamical quantum group as an h-Hopf algebroid

abstract:
  Using the language of h-Hopf algebroids which was introduced by Etingof and
Varchenko, we construct a dynamical quantum group, F_ell(GL(n)), from the
elliptic solution of the quantum dynamical Yang-Baxter equation with spectral
parameter associated to the Lie algebra sl_n. We apply the generalized FRST
construction and obtain an h-bialgebroid F_ell(M(n)). Natural analogs of the
exterior algebra and their matrix elements, elliptic minors, are defined and
studied. We show how to use the cobraiding to prove that the elliptic
determinant is central. Localizing at this determinant and constructing an
antipode we obtain the h-Hopf algebroid F_ell(GL(n)).


title:
Approaching the Capacity of Wireless Networks through Distributed
  Interference Alignment

abstract:
  Recent results establish the optimality of interference alignment to approach
the Shannon capacity of interference networks at high SNR. However, the extent
to which interference can be aligned over a finite number of signalling
dimensions remains unknown. Another important concern for interference
alignment schemes is the requirement of global channel knowledge. In this work
we provide examples of iterative algorithms that utilize the reciprocity of
wireless networks to achieve interference alignment with only local channel
knowledge at each node. These algorithms also provide numerical insights into
the feasibility of interference alignment that are not yet available in theory.


title:
Performance comparison between p-i-n tunneling transistors and
  conventional MOSFETs

abstract:
  Field-effect transistors based on band-to-band tunneling (BTBT) have gained a
lot of recent interest due to their potential for reducing power dissipation in
integrated circuits. In this paper we present a detailed performance comparison
between conventional n-i-n MOSFET transistors, and BTBT transistors based on
the p-i-n geometry (p-i-n TFET), using semiconducting carbon nanotubes as the
model channel material. Quantum transport simulations are performed using the
nonequilibrium Green's function formalism including realistic phonon
scattering. We find that the TFET can indeed produce subthreshold swings below
the conventional MOSFET limit of 60mV/decade at room temperature leading to
smaller off-currents and standby power dissipation. Phonon assisted tunneling,
however, limits the off-state performance benefits that could have been
achieved otherwise. Under on-state conditions the drive current and the
intrinsic device delay of the TFET are mainly governed by the tunneling barrier
properties. On the other hand, the switching energy for the TFET is observed to
be fundamentally smaller than that for the MOSFET, reducing the dynamic power
dissipation. Aforementioned reasons make the p-i-n geometry well suited for low
power applications.


title: Solar-type Magnetic Reconnection Model for Magnetar Giant Flare

abstract:
  We present a theoretical model describing magnetar giant flares on the basis
of solar flare/coronal mass ejection theory. In our model, a preflare activity
plays a crucial role in driving evaporating flows and supplying baryonic
matters into the magnetosphere. The loaded baryonic matter, that is called
"prominence", is then gradually uplifted via crustal cracking with maintaining
a quasi-force-free equilibrium of the magnetosphere. Finally the prominence is
erupted by the magnetic pressure force due to the loss of equilibrium triggered
by the explosive magnetic reconnection. The giant flare should be induced as a
final outcome of the prominence eruption accompanied by large-scale field
reconfigurations. An essential difference between solar and magnetar flares is
the control process of their evolutionary dynamics. The flaring activity on
magnetars is mainly controlled by the radiative process unlike the solar flare
governed by the electron conduction. It is highly suggestive that our model is
accountable for the physical properties of the extraordinary giant flare
observed on 2004 December 27 from SGR1806-20, including the source of baryonic
matters loaded in the expanding ejecta observed after the giant burst.


title:
Spanning sets for Moebius vertex algebras satisfying arbitrary
  difference conditions

abstract:
  Spanning sets for vertex operator algebras satisfying difference-zero and
difference-one conditions have been extensively studied in the recent years. In
this paper, we extend these results. More specifically, we show that for a
suitably chosen generating set, any N-graded Moebius vertex algebra is spanned
by monomials satisfying a difference-N ordering condition.


title: Top Quark Pair plus Large Missing Energy at the LHC

abstract:
  We study methods of extracting new physics signals in final states with a
top-quark pair plus large missing energy at the LHC. We consider two typical
examples of such new physics: pair production of a fermionic top partner (a
$T'$ in Little Higgs models for example) and of a scalar top partner (a
$\tilde{t}$ in SUSY). With a commonly-adopted discrete symmetry under which non
Standard Model particles are odd, the top partner is assumed to decay
predominantly to a top quark plus a massive neutral stable particle $A^0$. We
focus on the case in which one of the top quarks decays leptonically and the
other decays hadronically, $pp \to {\tt} A^0A^0 X \to bj_1j_2 \bar b\ell^-
\bar\nu A^0A^0 X + c.c.$, where the $A^0$s escape detection. We identify a key
parameter for the signal observation: the mass splitting between the top
partner and the missing particle. We reconstruct a transverse mass for the
lepton-missing transverse energy system to separate the real $W$ background
from the signal and propose a definition for the reconstructed top quark mass
that allows it to take unphysical values as an indication of new physics. We
perform a scan over the two masses to map out the discovery reach at the LHC in
this channel. We also comment on the possibility of distinguishing between
scalar and fermionic top partners using collider signatures.


title:
A conjectured lower bound for the cohomological dimension of elliptic
  spaces. Some results in some simple cases

abstract:
  Here we prove some special cases of the following conjecture: that the sum of
the Betti numbers of a 1-connected elliptic space is greater than the total
rank of its homotopy groups. Our main tool is Sullivan's minimal model.


title:
Quantum Phase Transitions beyond the Landau's Paradigm in Sp(4) Spin
  System

abstract:
  We propose quantum phase transitions beyond the Landau's paradigm of Sp(4)
spin Heisenberg models on the triangular and square lattices, motivated by the
exact Sp(4)$\simeq$ SO(5) symmetry of spin-3/2 fermionic cold atomic system
with only $s-$wave scattering. On the triangular lattice, we study a phase
transition between the $\sqrt{3}\times\sqrt{3}$ spin ordered phase and a $Z_2$
spin liquid phase, this phase transition is described by an O(8) sigma model in
terms of fractionalized spinon fields, with significant anomalous scaling
dimensions of spin order parameters. On the square lattice, we propose a
deconfined critical point between the Neel order and the VBS order, which is
described by the CP(3) model, and the monopole effect of the compact U(1) gauge
field is expected to be suppressed at the critical point.


title:
Spatially resolved dusty torus toward the red supergiant WOH G64 in the
  Large Magellanic Cloud

abstract:
  We present N-band spectro-interferometric observations of the red supergiant
WOH G64 in the Large Magellanic Cloud (LMC) using MIDI at the Very Large
Telescope Interferometer (VLTI). The location of WOH G64 on the H-R diagram
based on the previously estimated luminosities is in serious disagreement with
the current stellar evolution theory. The dust envelope around WOH G64 has been
spatially resolved with a baseline of ~60 m--the first MIDI observations to
resolve an individual stellar source in an extragalactic system. The observed
N-band visibilities show a slight decrease from 8 to 10 micron and a gradual
increase longward of 10 micron, reflecting the 10 micron silicate feature in
self-absorption. The visibilities measured at four position angles differing by
~60 degrees but at approximately the same baseline length (~60 m) do not show a
noticeable difference, suggesting that the object appears nearly
centrosymmetric. The observed N-band visibilities and spectral energy
distribution can be reproduced by an optically and geometrically thick silicate
torus model viewed close to pole-on. The luminosity of the central star is
derived to be 2.8 x 10^5 Lsun, which is by a factor of 2 lower than the
previous estimates based on spherical models. The lower luminosity newly
derived from our MIDI observations and two-dimensional modeling brings the
location of WOH G64 on the H-R diagram in much better agreement with
theoretical evolutionary tracks for a 25 Msun star. We also identify the H2O
absorption features at 2.7 and 6 micron in the spectra obtained with the
Infrared Space Observatory and the Spitzer Space Telescope. The 2.7 micron
feature originates in the photosphere and/or the extended molecular layers,
while the 6 micron feature is likely to be of circumstellar origin.


title: Convergence rates for adaptive finite elements

abstract:
  In this article we prove that it is possible to construct, using
newest-vertex bisection, meshes that equidistribute the error in $H^1$-norm,
whenever the function to approximate can be decomposed as a sum of a regular
part plus a singular part with singularities around a finite number of points.
This decomposition is usual in regularity results of Partial Differential
Equations (PDE). As a consequence, the meshes turn out to be quasi-optimal, and
convergence rates for adaptive finite element methods (AFEM) using Lagrange
finite elements of any polynomial degree are obtained.


title: The homology of the stable non-orientable mapping class group

abstract:
  Combining results of Wahl, Galatius--Madsen--Tillmann--Weiss and Korkmaz one
can identify the homotopy-type of the classifying space of the stable
non-orientable mapping class group $N_\infty$ (after plus-construction). At odd
primes p, the F_p-homology coincides with that of $Q_0(HP^\infty_+)$, but at
the prime 2 the result is less clear. We identify the F_2-homology as a Hopf
algebra in terms of the homology of well-known spaces. As an application we
tabulate the integral stable homology of $N_\infty$ in degrees up to six.
  As in the oriented case, not all of these cohomology classes have a geometric
interpretation. We determine a polynomial subalgebra of $H^*(N_\infty ; F_2)$
consisting of geometrically-defined characteristic classes.


title:
A different derivation of the acceleration of a particle in a
  non-inertial reference frame

abstract:
  A new derivation of the acceleration of a particle in a non-inertial
reference frame, including the Coriolis effect, is developed using the geometry
of complex numbers in the complex plane.


title:
The Charge Form Factor of the Neutron at Low Momentum Transfer from the
  $^{2}\vec{\rm H}(\vec{\rm e},{\rm e}'{\rm n}){\rm p}$ Reaction

abstract:
  We report new measurements of the neutron charge form factor at low momentum
transfer using quasielastic electrodisintegration of the deuteron.
Longitudinally polarized electrons at an energy of 850 MeV were scattered from
an isotopically pure, highly polarized deuterium gas target. The scattered
electrons and coincident neutrons were measured by the Bates Large Acceptance
Spectrometer Toroid (BLAST) detector. The neutron form factor ratio
$G^{n}_{E}/G^{n}_{M}$ was extracted from the beam-target vector asymmetry
$A_{ed}^{V}$ at four-momentum transfers $Q^{2}=0.14$, 0.20, 0.29 and 0.42
(GeV/c)$^{2}$.


title: On The Warped Heterotic Axion

abstract:
  We study the axion in a warped heterotic background. It is shown that the
axion decay constant, f_a, is sensitive to the warped mass scale of the throat.
As an explicit model, we construct a novel AdS-like geometry in heterotic
string theory. We demonstrate that in this background f_a is given by the mass
scale of the longest throat in the compactification. The question of obtaining
f_a within the required bound 10^9--10^12 GeV is reduced to the construction of
a throat inside the heterotic string theory compactification with warped mass
scale in the above range. This provides a natural mechanism for realising the
axion in heterotic string theory.


title: Void Nucleation, Growth, and Coalescence in Irradiated Metals

abstract:
  A novel computational treatment of dense, stiff, coupled reaction rate
equations is introduced to study the nucleation, growth, and possible
coalescence of cavities during neutron irradiation of metals. Radiation damage
is modeled by the creation of Frenkel pair defects and helium impurity atoms. A
multi-dimensional cluster size distribution function allows independent
evolution of the vacancy and helium content of cavities, distinguishing voids
and bubbles. A model with sessile cavities and no cluster-cluster coalescence
can result in a bimodal final cavity size distribution with coexistence of
small, high-pressure bubbles and large, low-pressure voids. A model that
includes unhindered cavity diffusion and coalescence ultimately removes the
small helium bubbles from the system, leaving only large voids. The terminal
void density is also reduced and the incubation period and terminal swelling
rate can be greatly altered by cavity coalescence. Temperature-dependent
trapping of voids/bubbles by precipitates and alterations in void surface
diffusion from adsorbed impurities and internal gas pressure may give rise to
intermediate swelling behavior through their effects on cavity mobility and
coalescence.


title: Ordered magnetic phases of the frustrated spin-dimer compound Ba3Mn2O8

abstract:
  Ba3Mn2O8 is a spin-dimer compound based on pairs of S=1, 3d^2, Mn^{5+} ions
arranged on a triangular lattice. Antiferromagnetic intradimer exchange leads
to a singlet ground state in zero-field. Here we present the first results of
thermodynamic measurements for single crystals probing the high-field ordered
states of this material associated with closing the spin gap to the excited
triplet states. Specific heat, magnetocaloric effect, and torque magnetometry
measurements were performed in magnetic fields up to 32 T and temperatures down
to 20 mK. For fields above H_{c1} ~ 8.7 T, these measurements reveal a single
magnetic phase for H parallel to c, but two distinct phases (approximately
symmetric about the center of the phase diagram) for H perpendicular to c.
Analysis of the simplest possible spin Hamiltonian describing this system
yields candidates for these ordered states corresponding to a simple spiral
structure for H parallel to c, and to two distinct modulated phases for H
perpendicular to c. Both single-ion anisotropy and geometric frustration play
crucial roles in defining the phase diagram.


title:
Observations and modelling of a clumpy galaxy at z=1.6: Spectroscopic
  clues to the origin and evolution of chain galaxies

abstract:
  We investigate the properties of a clump-cluster galaxy at redshift 1.57. The
morphology of this galaxy is dominated by eight star-forming clumps in optical
observations, and has photometric properties typical of most clump-cluster and
chain galaxies. Its complex asymmetrical morphology has led to the suggestion
that this system is a group merger of several initially separate
proto-galaxies. We performed H_alpha integral field spectroscopy of this system
using SINFONI on VLT UT4. These observations reveal a large-scale velocity
gradient throughout the system, but with large local kinematic disturbances.
Using a numerical model of gas-rich disk fragmentation, we find that clump
interactions and migration can account for the observed disturbed rotation. On
the other hand, the global rotation would not be expected for a multiply
merging system. We further find that this system follows the stellar mass vs.
metallicity, star formation rate and size relations expected for a disk at this
redshift, and exhibits a disk-like radial metallicity gradient, so that the
scenario of internal disk fragmentation is the most likely one. A red and
metallic central concentration appears to be a bulge in this proto-spiral
clumpy galaxy. A chain galaxy at redshift 2.07 in the same field also shows
disk-like rotation. Such systems are likely progenitors of the present-day
bright spiral galaxies, forming their exponential disks through clump migration
and disruption and fueling their bulges. Our present results show that
disturbed morphologies and kinematics are not necessarily signs of galaxy
mergers and interactions, and can instead result from the internal evolution of
primordial disks.


title: (A)dS exchanges and partially-massless higher spins

abstract:
  We determine the current exchange amplitudes for free totally symmetric
tensor fields $\vf_{\mu_1 ... \mu_s}$ of mass $M$ in a $d$-dimensional $dS$
space, extending the results previously obtained for $s=2$ by other authors.
Our construction is based on an unconstrained formulation where both the
higher-spin gauge fields and the corresponding gauge parameters $\Lambda_{\mu_1
>... \mu_{s-1}}$ are not subject to Fronsdal's trace constraints, but
compensator fields $\alpha_{\mu_1 ... \mu_{s-3}}$ are introduced for $s > 2$.
The free massive $dS$ equations can be fully determined by a radial dimensional
reduction from a $(d+1)$-dimensional Minkowski space time, and lead for all
spins to relatively handy closed-form expressions for the exchange amplitudes,
where the external currents are conserved, both in $d$ and in $(d+1)$
dimensions, but are otherwise arbitrary. As for $s=2$, these amplitudes are
rational functions of $(ML)^2$, where $L$ is the $dS$ radius. In general they
are related to the hypergeometric functions $_3F_2(a,b,c;d,e;z)$, and their
poles identify a subset of the "partially-massless" discrete states, selected
by the condition that the gauge transformations of the corresponding fields
contain some non-derivative terms. Corresponding results for $AdS$ spaces can
be obtained from these by a formal analytic continuation, while the massless
limit is smooth, with no van Dam-Veltman-Zakharov discontinuity.


title:
A large N phase transition in the continuum two dimensional SU(N) X
  SU(N) principal chiral model

abstract:
  It is established by numerical means that the continuum large N principal
chiral model in two dimensions has a phase transition in a smoothed two point
function at a critical distance of the order of the correlation length.


title: The meaning of 1 in l(l+1)

abstract:
  The magnitude of the angular momentum ($J^2$) in quantum mechanics is larger
than expected from a classical model. We explain this deviation in terms of
quantum fluctuations. A standard quantum mechanical calculation gives the
correct interpretation of the components of the angular momentum in the vector
model in terms of projections and fluctuations. We show that the addition of
angular momentum in quantum mechanics gives results consistent with the
classical intuition in this vector model.


title:
Galactic Outflows and the pollution of the Galactic Environment by
  Supernovae

abstract:
  We here explore the effects of the SN explosions into the environment of
star-forming galaxies like the Milky Way. Successive randomly distributed and
clustered SNe explosions cause the formation of hot superbubbles that drive
either fountains or galactic winds above the galactic disk, depending on the
amount and concentration of energy that is injected by the SNe. In a galactic
fountain, the ejected gas is re-captured by the gravitational potential and
falls back onto the disk. From 3D nonequilibrium radiative cooling
hydrodynamical simulations of these fountains, we find that they may reach
altitudes up to about 5 kpc in the halo and thus allow for the formation of the
so called intermediate-velocity-clouds (IVCs) which are often observed in the
halos of disk galaxies. The high-velocity-clouds that are also observed but at
higher altitudes (of up to 12 kpc) require another mechanism to explain their
production. We argue that they could be formed either by the capture of gas
from the intergalactic medium and/or by the action of magnetic fields that are
carried to the halo with the gas in the fountains. Due to angular momentum
losses to the halo, we find that the fountain material falls back to smaller
radii and is not largely spread over the galactic disk. Instead, the SNe ejecta
fall nearby the region where the fountain was produced, a result which is
consistent with recent chemical models of the galaxy. The fall back material
leads to the formation of new generations of molecular clouds and to supersonic
turbulence feedback in the disk.


title:
Temperature Differences in the Cepheid Instability Strip Require
  Differences in the Period-Luminosity Relation in Slope and Zero Point

abstract:
  A graphical and an algebraic demonstration is made to show why the slope and
zero point of the Cepheid period-luminosity (P-L) relation is rigidly coupled
with the slope and zero point of the Cepheid instability strip in the HR
diagram. The graphical demonstration uses an arbitrary (toy) ridge line in the
instability strip, while the algebraic demonstration uses the pulsation
equation into which the observed P-L relations for the Galaxy and the LMC are
put to predict the temperature zero points and slopes of the instability
strips. Agreement between the predicted and measured instability strip slopes
argue that the observed P-L differences between the Galaxy and LMC are real. In
another proof, the direct evidence for different P-L slopes in different
galaxies is shown by comparing the Cepheid data in the Galaxy, the combined
data in NGC 3351 and NGC 4321, in M31, LMC, SMC, IC 1613, NGC 3109, and in
Sextans A+B. The P-L slopes for the Galaxy, NGC 3351, NGC 4321, and M31 are
nearly identical and are the steepest in the sample. The P-L slopes decrease
monotonically with metallicity in the order listed, showing that the P-L
relation is not the same in different galaxies, complicating their use in
calibrating the extragalactic distance scale.


title: Combinatorial coding in neural populations

abstract:
  To evaluate the nature of the neural code in the cerebral cortex, we have
used a combination of theory and experiment to assess how information is
represented in a realistic cortical population response. We have shown how a
sensory stimulus could be estimated on a biologically-realistic time scale,
given brief individual responses from a population of neurons with similar
response properties. For neurons in extrastriate motion area MT, a
combinatorial code, one that keeps track of the cell identity of action
potentials and silences in individual neurons across the population, carries
twice as much information about visual motion as does spike count averaged over
the same group of cells. The combinatorial code is more informative because of
the diverse firing rate dynamics of MT neurons in response to constant motion
stimuli, and is robust to neuron-neuron correlations. We provide a theoretical
motivation for these observations that challenges commonly held ideas about the
nature of cortical coding at the level of single neurons and neural
populations.


title: Recorded Step Directional Mutation for Faster Convergence

abstract:
  Two meta-evolutionary optimization strategies described in this paper
accelerate the convergence of evolutionary programming algorithms while still
retaining much of their ability to deal with multi-modal problems. The
strategies, called directional mutation and recorded step in this paper, can
operate independently but together they greatly enhance the ability of
evolutionary programming algorithms to deal with fitness landscapes
characterized by long narrow valleys. The directional mutation aspect of this
combined method uses correlated meta-mutation but does not introduce a full
covariance matrix. These new methods are thus much more economical in terms of
storage for problems with high dimensionality. Additionally, directional
mutation is rotationally invariant which is a substantial advantage over
self-adaptive methods which use a single variance per coordinate for problems
where the natural orientation of the problem is not oriented along the axes.


title: Scattering of acoustic waves by a magnetic cylinder

abstract:
  With the aim of studying magnetic effects in time-distance helioseismology,
we use the first-order Born approximation to compute the scattering of acoustic
plane waves by a magnetic cylinder embedded in a uniform medium. We show, by
comparison with the exact solution, that the travel-time shifts computed in the
Born approximation are everywhere valid to first order in the ratio of the
magnetic to the gas pressures. We also show that, for arbitrary magnetic field
strength, the Born approximation is not valid in the limit where the radius of
the magnetic cylinder tends to zero.


title: Set families with a forbidden subposet

abstract:
  We asymptotically determine the size of the largest family F of subsets of
{1,...,n} not containing a given poset P if the Hasse diagram of P is a tree.
This is a qualitative generalization of several known results including
Sperner's theorem.


title:
The congruence subgroup property for the hyperelliptic modular group:
  the open surface case

abstract:
  Let ${\cal M}_{g,n}$ and ${\cal H}_{g,n}$, for $2g-2+n>0$, be, respectively,
the moduli stack of $n$-pointed, genus $g$ smooth curves and its closed
substack consisting of hyperelliptic curves. Their topological fundamental
groups can be identified, respectively, with $\Gamma_{g,n}$ and $H_{g,n}$, the
so called Teichm{\"u}ller modular group and hyperelliptic modular group. A
choice of base point on ${\cal H}_{g,n}$ defines a monomorphism
$H_{g,n}\hookrightarrow\Gamma_{g,n}$.
  Let $S_{g,n}$ be a compact Riemann surface of genus $g$ with $n$ points
removed. The Teichm\"uller group $\Gamma_{g,n}$ is the group of isotopy classes
of diffeomorphisms of the surface $S_{g,n}$ which preserve the orientation and
a given order of the punctures. As a subgroup of $\Gamma_{g,n}$, the
hyperelliptic modular group then admits a natural faithful representation
$H_{g,n}\hookrightarrow\operatorname{Out}(\pi_1(S_{g,n}))$.
  The congruence subgroup problem for $H_{g,n}$ asks whether, for any given
finite index subgroup $H^\lambda$ of $H_{g,n}$, there exists a finite index
characteristic subgroup $K$ of $\pi_1(S_{g,n})$ such that the kernel of the
induced representation $H_{g,n}\to\operatorname{Out}(\pi_1(S_{g,n})/K)$ is
contained in $H^\lambda$. The main result of the paper is an affirmative answer
to this question for $n\geq 1$.


title: The Complex Structure of the Cl 1604 Supercluster at z~0.9

abstract:
  The Cl1604 supercluster at z=0.9 is one of a small handful of such structures
discovered in the high redshift universe, and is the first target observed as
part of the Observations of Redshift Evolution in Large Scale Environments
(ORELSE) Survey. To date, Cl1604 is the largest structure mapped at z~1, with
the most constituent clusters and the largest number of spectroscopically
confirmed member galaxies. In this paper we present the results of a
spectroscopic campaign to create a three-dimensional map of Cl1604 and to
understand the contamination by fore- and background large scale structures.
Combining new Deep Imaging Multi-object Spectrograph observations with previous
data yields redshifts for 1,383 extragalactic objects in a ~ 0.08 sq. deg
region, 449 of which are supercluster members. We examine the complex three
dimensional structure of Cl1604, providing velocity dispersions for eight of
the member clusters and groups. Our extensive spectroscopic dataset is used to
examine potential biases in cluster velocity dispersion measurements in the
presence of overlapping structures and filaments. We also discuss other
structures found along the line-of-sight, including a filament at z=0.6 and two
serendipitously discovered clusters/groups at z~1.2.


title:
A Novel Method to Construct Stationary Solutions of the Vlasov Maxwell
  system

abstract:
  A novel method to derive stationary solutions of the Vlasov-Maxwell system is
established. This method is based on the assumption that the deviation of the
velocity distribution from the Maxwell-Boltzmann distribution can be expanded
by the Hermite polynomials. By applying our method, a new two-dimensional
equilibrium is derived, which may provide an initial setup for investigations
of three-dimensional collisionless reconnection of magnetic fields.


title: Tomography of the Solar Interior

abstract:
  Solar oscillations consist of a rich spectrum of internal acoustic waves and
surface gravity waves, stochastically excited by turbulent convection. They
have been monitored almost continuously over the last ten years with
high-precision Doppler images of the solar surface. The purpose of
helioseismology is to retrieve information about the structure and the dynamics
of the solar interior from the frequencies, phases, and amplitudes of solar
waves. Methods of analysis are being developed to make three-dimensional images
of subsurface motions and temperature inhomogeneities in order to study
convective structures and regions of magnetic activity, like sunspots.


title: Quark-Hadron Duality in Neutron (3He) Spin Structure

abstract:
  We present experimental results of the first high-precision test of
quark-hadron duality in the spin-structure function g_1 of the neutron and
$^3$He using a polarized 3He target in the four-momentum-transfer-squared range
from 0.7 to 4.0 (GeV/c)^2. Global duality is observed for the spin-structure
function g_1 down to at least Q^2 = 1.8 (GeV/c)^2 in both targets. We have also
formed the photon-nucleon asymmetry A_1 in the resonance region for 3He and
found no strong Q^2-dependence above 2.2 (GeV/c)^2.


title: Combinatorics of binomial primary decomposition

abstract:
  An explicit lattice point realization is provided for the primary components
of an arbitrary binomial ideal in characteristic zero. This decomposition is
derived from a characteristic-free combinatorial description of certain primary
components of binomial ideals in affine semigroup rings, namely those that are
associated to faces of the semigroup. These results are intimately connected to
hypergeometric differential equations in several variables.


title:
Curvature induced optical phonon frequency shift in metallic carbon
  nanotubes

abstract:
  The quantum corrections to the frequencies of the $\Gamma$ point longitudinal
optical (LO) and transverse optical (TO) phonon modes in carbon nanotubes are
investigated theoretically. The frequency shift and broadening of the TO phonon
mode strongly depend on the curvature effect due to a special electron-phonon
coupling in carbon nanotubes, which is shown by the Fermi energy dependence of
the frequency shift for different nanotube chiralities. It is also shown that
the TO mode near the $\Gamma$ point decouples from electrons due to local gauge
symmetry and that a phonon mixing between LO and TO modes is absent due to
time-reversal symmetry. Some comparison between theory and experiment is
presented.


title:
Categorified quantum sl(2) and equivariant cohomology of iterated flag
  varieties

abstract:
  A 2-category was introduced in arXiv:0803.3652 [math.QA] that categorifies
Lusztig's integral version of quantum sl(2). Here we construct for each
positive integer N arepresentation of this 2-category using the equivariant
cohomology of iterated flag varieties. This representation categorifies the
irreducible (N+1)-dimensional representation of quantum sl(2).


title: Anomaly and Hawking radiation from regular black holes

abstract:
  We consider the Hawking radiation from two regular black holes, the minimal
model and the noncommutative black hole. The flux of Hawking radiation is
derived by applying the anomaly cancellation method proposed by Robinson and
Wilczek. Two regular black holes have the same radiation pattern except for the
detailed expression for the Hawking temperature. The resulting flux of the
energy-momentum tensor is shown to be precisely the same with the thermal flux
from each regular black hole at the Hawking temperature.


title:
State Estimation Over Wireless Channels Using Multiple Sensors:
  Asymptotic Behaviour and Optimal Power Allocation

abstract:
  This paper considers state estimation of linear systems using analog amplify
and forwarding with multiple sensors, for both multiple access and orthogonal
access schemes. Optimal state estimation can be achieved at the fusion center
using a time varying Kalman filter. We show that in many situations, the
estimation error covariance decays at a rate of $1/M$ when the number of
sensors $M$ is large. We consider optimal allocation of transmission powers
that 1) minimizes the sum power usage subject to an error covariance constraint
and 2) minimizes the error covariance subject to a sum power constraint. In the
case of fading channels with channel state information the optimization
problems are solved using a greedy approach, while for fading channels without
channel state information but with channel statistics available a sub-optimal
linear estimator is derived.


title:
On the double natured solutions to the two-temperature external soft
  photon comptonized accretion disks

abstract:
  We have analyzed pair production in the innermost region of a two-temperature
external soft photon comptonized accretion disk. We have shown that, if the
viscosity parameter is greater than a temperature and r dependent critical
value, the solution to the disk equation is double valued: one, advection
dominated and the other, radiation dominated. When the viscosity parameter is
below this critical value, the accretion rate has to be confined within a
region limited by a minimum and a maximum accretion rates in order to have two
steady state solutions. These critical accretion rates are shown to be
dependent on r, on the temperature and on the viscosity parameter . Depending
on the combination of the parameters, the advection dominated solution may not
be physically consistent.


title:
Large intersection properties in Diophantine approximation and dynamical
  systems

abstract:
  We investigate the large intersection properties of the set of points that
are approximated at a certain rate by a family of affine subspaces. We then
apply our results to various sets arising in the metric theory of Diophantine
approximation, in the study of the homeomorphisms of the circle and in the
perturbation theory for Hamiltonian systems.


title:
High Spatial Resolution Spectroscopy of W51 IRS2E and IRS2W: Two Very
  Massive Young Stars in Early Formation Stages

abstract:
  We present $K$-band spectra of the near infrared counterparts to IRS2E and
IRS2W which is associated with the ultracompact HII region W51d, both of them
embedded sources in the Galactic compact HII region W51 IRS2. The high spatial
resolution observations were obtained with the laser guide star facility and
Near infrared Integral Field Spectrograph (NIFS) mounted at the Gemini North
observatory. The spectrum of the ionizing source of W51d shows the photospheric
features NIII (21155 \AA) in emission and HeII (21897 \AA) in absorption which
lead us to classify it as an young O3 type star. We detected CO overtone in
emission at 23000 \AA in the spectrum of IRS2E, suggesting that it is a massive
young object still surrounded by an accretion disc, probably transitioning from
the hot core phase to an ultracompact HII region.


title:
The Subpulse Modulation Properties of Pulsars and its Frequency
  Dependence

abstract:
  A large sample of about two hundred pulsars have been observed to study their
subpulse modulation at an observing wavelength of (when achievable) both 21 and
92 cm using the Westerbork Synthesis Radio Telescope. For 57 pulsars drifting
subpulses are discovered for the first time and are confirmed for many others.
This leads to the conclusion that it could well be that the drifting subpulse
mechanism is an intrinsic property of the emission mechanism itself, although
for some pulsars it is difficult or impossible to detect. It appears that the
youngest pulsars have the most disordered subpulses and the subpulses become
more and more organized into drifting subpulses as the pulsar ages. Drifting
subpulses are in general found at both frequencies and the measured values of
P3 at the two frequencies are highly correlated, showing the broadband nature
of this phenomenon. Also the modulation indices measured at the two frequencies
are clearly correlated, although at 92 cm they are on average possibly higher.
The correlations with the modulation indices are argued to be consistent with
the picture in which the radio emission is composed out of a drifting subpulse
signal plus a quasi-steady signal which becomes, on average, stronger at high
observing frequencies. There is no obvious correlation found between P3 and the
pulsar age (or any other pulsar parameter) contrary to reports in the past.


title: Conformal SO(2,4) Transformations for the Helical AdS String Solution

abstract:
  By applying the conformal SO(2,4) transformations to the folded rotating
string configuration with two spins given by a certain limit from the helical
string solution in AdS_3 x S^1, we construct new string solutions whose
energy-spin relations are characterized by the boost parameter. When two
SO(2,4) transformations are performed with two boost parameters suitably
chosen, the straight folded rotating string solution with one spin in AdS_3 is
transformed in the long string limit into the long spiky string solution whose
expression is given from the helical string solution in AdS_3 by making a limit
that the modulus parameter becomes unity.


title:
Spectroscopy of 24Al and extraction of Gamow-Teller strengths with the
  24Mg(3He,t) reaction at 420 MeV

abstract:
  The 24Mg(3He,t)24Al reaction has been studied at E(3He)=420 MeV. An energy
resolution of 35 keV was achieved. Gamow-Teller strengths to discrete levels in
24Al are extracted by using a recently developed empirical relationship for the
proportionality between Gamow-Teller strengths and differential cross sections
at zero momentum transfer. Except for small discrepancies for a few weak
excitations, good agreement with previous 24Mg(p,n) data and nuclear-structure
calculations using the USDA/B interactions in the sd shell-model space is
found. The excitation energy of several levels in 24Al of significance for
determination of the 23Mg(p,gamma)24Al thermonuclear reaction rate were
measured. Results are consistent with two of the three previous (3He,t)
measurements, performed at much lower beam energies. However, a new state at
Ex(24Al)=2.605(10) MeV was found and is the third state above the proton
separation energy.


title: Wall Crossing Formula for N=4 Dyons: A Macroscopic Derivation

abstract:
  We derive the wall crossing formula for the decay of a quarter BPS dyon into
a pair of half-BPS dyons by analyzing the quantum dynamics of multi-centered
black holes in N=4 supersymmetric string theories. Our analysis encompasses the
cases where the final decay products are non-primitive dyons. The results are
in agreement with the microscopic formula for the dyon spectrum in the special
case of heterotic string theory on T^6.


title: Bandpass Dependence of X-ray Temperatures in Galaxy Clusters

abstract:
  We explore the band dependence of the inferred X-ray temperature of the
intracluster medium (ICM) for 192 well-observed galaxy clusters selected from
the Chandra Data Archive. If the hot ICM is nearly isothermal in the projected
region of interest, the X-ray temperature inferred from a broad-band (0.7-7.0
keV) spectrum should be identical to the X-ray temperature inferred from a
hard-band (2.0-7.0 keV) spectrum. However, if unresolved cool lumps of gas are
contributing soft X-ray emission, the temperature of a best-fit
single-component thermal model will be cooler for the broad-band spectrum than
for the hard-band spectrum. Using this difference as a diagnostic, the ratio of
best-fitting hard-band and broad-band temperatures may indicate the presence of
cooler gas even when the X-ray spectrum itself may not have sufficient
signal-to-noise to resolve multiple temperature components. To test this
possible diagnostic, we extract X-ray spectra from core-excised annular regions
for each cluster in our archival sample. We compare the X-ray temperatures
inferred from single-temperature fits when the energy range of the fit is
0.7-7.0 keV (broad) and when the energy range is 2.0/(1+z)-7.0 keV (hard). We
find that the hard-band temperature is significantly higher, on average, than
the broad-band temperature. Upon further exploration, we find this temperature
ratio is enhanced preferentially for clusters which are known merging systems.
In addition, cool-core clusters tend to have best-fit hard-band temperatures
that are in closer agreement with their best-fit broad-band temperatures. We
show, using simulated spectra, that this diagnostic is sensitive to secondary
cool components (TX = 0.5-3.0 keV) with emission measures >10-30% of the
primary hot component.


title:
Quantum Control of Ultra-cold Atoms: Uncovering a Novel Connection
  between Two Paradigms of Quantum Nonlinear Dynamics

abstract:
  Controlling the translational motion of cold atoms using optical lattice
potentials is of both theoretical and experimental interest. By designing two
on-resonance time sequences of kicking optical lattice potentials, a novel
connection between two paradigms of nonlinear mapping systems, i.e., the kicked
rotor model and the kicked Harper model, is established. In particular, it is
shown that Hofstadter's butterfly quasi-energy spectrum in periodically driven
quantum systems may soon be realized experimentally, with the effective Planck
constant tunable by varying the time delay between two sequences of control
fields. Extensions of this study are also discussed. The results are intended
to open up a new generation of cold-atom experiments of quantum nonlinear
dynamics


title:
Asymptotic normalization coefficients (nuclear vertex constants) for
  $p+^7Be\to ^8B$ and the direct $^7Be(p,\gamma)^8B$ astrophysical S-factors at
  solar energies

abstract:
  A new analysis of the precise experimental astrophysical S-factors for the
direct capture $^7Be(p,\gamma)$ $^8B$ reaction [A.J.Junghans et al.Phys.Rev. C
68 (2003) 065803 and L.T. Baby et al. Phys.Rev. C 67 (2003) 065805] is carried
out based on the modified two - body potential approach in which the direct
astrophysical S-factor, $ {\rm S_{17}(E)}$, is expressed in terms of the
asymptotic normalization constants for $p+^7Be\to ^8B$ and two additional
conditions are involved to verify the peripheral character of the reaction
under consideration. The Woods-Saxon potential form is used for the bound
($p+^7Be$)- state wave function and for the $p^7Be$- scattering wave function.
New estimates are obtained for the $^{\glqq}$indirectly measured\grqq values of
the asymptotic normalization constants (the nuclear vertex constants) for the
$p+^7Be\to ^8B$ and $S_{17}(E)$ at E$\le$ 115 keV, including $E$=0. These
values of $S_{17}(E)$ and asymptotic normalization constants have been used for
getting information about the $^{\glqq}$indirectly measured\grqq values of the
$s$ wave average scattering length and the $p$ wave effective range parameters
for $p^7Be$- scattering.


title:
Well-Tempered Metadynamics: A Smoothly Converging and Tunable
  Free-Energy Method

abstract:
  We present a method for determining the free energy dependence on a selected
number of collective variables using an adaptive bias. The formalism provides a
unified description which has metadynamics and canonical sampling as limiting
cases. Convergence and errors can be rigorously and easily controlled. The
parameters of the simulation can be tuned so as to focus the computational
effort only on the physically relevant regions of the order parameter space.
The algorithm is tested on the reconstruction of alanine dipeptide free energy
landscape.


title:
Doping variation of anisotropic charge and orbital dynamics in
  Y1-xCaxVO3 : Comparison with La1-xSrxVO3

abstract:
  The doping variation of charge and orbital dynamics in perovskite-type
Y1-xCaxVO3 (0<x<0.1) is investigated by measurements of the optical
conductivity and Raman scattering spectra in comparison with the
larger-bandwidth system La1-xSrxVO3. We also take into consideration the
magnitude of the GdFeO3-type orthorhombic lattice distortion, which is large
and small in Y1-xCaxVO3 and La1-xSrxVO3, respectively, and discuss its effect
on the evolution of charge dynamics. The optical conductivity spectra show that
the doped hole is well localized and forms the small polaron like state. The
hole dynamics in Y1-xCaxVO3 is nearly isotropic up to the doping level of the
orbital order-disorder transition, while that in La1-xSrxVO3 is anisotropic in
the lightly doped region due to the one-dimensional orbital exchange
interaction. The possible origin of the difference in the hole dynamics is
discussed in terms of the local lattice distortion, which is induced by the
formation of the small polaron like state and becomes more significant for the
reduced one-electron bandwidth. In addition, the optical Mott-gap excitation in
the nominally C-type spin and $G$-type orbital ordered phase is distinct from
that for La1-xSrxVO3 in its intensity and spectral shape. This suggests that
the orthorhombic lattice distortion enhances the modification of the spin and
orbital ordering from the pure C-type and G-type, respectively. The systematic
study of Raman scattering spectra has shown that the dynamic G-type spin and
C-type orbital correlation subsists at low temperatures in the doping induced
phase of the nominally C-type SO and G-type OO.


title:
Simultaneous inference: When should hypothesis testing problems be
  combined?

abstract:
  Modern statisticians are often presented with hundreds or thousands of
hypothesis testing problems to evaluate at the same time, generated from new
scientific technologies such as microarrays, medical and satellite imaging
devices, or flow cytometry counters. The relevant statistical literature tends
to begin with the tacit assumption that a single combined analysis, for
instance, a False Discovery Rate assessment, should be applied to the entire
set of problems at hand. This can be a dangerous assumption, as the examples in
the paper show, leading to overly conservative or overly liberal conclusions
within any particular subclass of the cases. A simple Bayesian theory yields a
succinct description of the effects of separation or combination on false
discovery rate analyses. The theory allows efficient testing within small
subclasses, and has applications to ``enrichment,'' the detection of multi-case
effects.


title: On atomic analogue of Landau quantization

abstract:
  We have studied the physics of atoms with permanent electric dipole moment
and non vanishing magnetic moment interacting with an electric field and
inhomogeneous magnetic field. This system can be demonstrated as the atomic
analogue of Landau quantization of charged particles in a uniform magnetic
field. This Landau-like atomic problem is also studied with space-space
noncommutative coordinates.


title: Irreducible Representations of C*-crossed products by Finite Groups

abstract:
  We describe the structure of the irreducible representations of crossed
products of unital C*-algebras by actions of finite groups in terms of
irreducible representations of the C*-algebras on which the groups act. We then
apply this description to derive a characterization of irreducible
representations of crossed-products by finite cyclic groups in terms of
representations of the C*-algebra and its fixed point subalgebra. These results
are applied to crossed-products by the permutation group on three elements and
illustrated by various examples.


title: Geometric Realizations of Bi-Hamiltonian Completely Integrable Systems

abstract:
  In this paper we present an overview of the connection between completely
integrable systems and the background geometry of the flow. This relation is
better seen when using a group-based concept of moving frame introduced by Fels
and Olver in [Acta Appl. Math. 51 (1998), 161-213; 55 (1999), 127-208]. The
paper discusses the close connection between different types of geometries and
the type of equations they realize. In particular, we describe the direct
relation between symmetric spaces and equations of KdV-type, and the possible
geometric origins of this connection.


title: Characterization of the Sequential Product on Quantum Effects

abstract:
  We present a characterization of the standard sequential product of quantum
effects. The characterization is in term of algebraic, continuity and duality
conditions that can be physically motivated.


title: Existence criterion for Hall subgroups of finite groups

abstract:
  In the paper we obtain an existence criterion for Hall subgroups of finite
groups in terms of a composition series.


title: Optical Sum Rule in Strongly Correlated Systems

abstract:
  We discuss the problem of a possible "violation" of the optical sum rule in
the normal (non superconducting) state of strongly correlated electronic
systems, using our recently proposed DMFT+Sigma approach, applied to two
typical models: the "hot - spot" model of the pseudogap state and disordered
Anderson - Hubbard model. We explicitly demonstrate that the general Kubo
single band sum rule is satisfied for both models. However, the optical
integral itself is in general dependent on temperature and characteristic
parameters, such as pseudogap width, correlation strength and disorder
scattering, leading to effective "violation" of the optical sum rule, which may
be observed in the experiments.


title:
On the onset of interference effects during the formation of the
  Bose-Einstein condensate

abstract:
  In this paper we derive the equations characterizing the boundary layer which
describes the transition of the distribution function of a gas of weakly
interacting bosons to the distribution function of the gas in the presence of a
Bose-Einstein condensate. To this end, we first rederive the classical
Uehling-Uhlenbeck equation taking as a starting point the dynamics of a system
of many weakly interacting quantum particles. The solutions of the
Uehling-Uhlenbeck equation yield blow-up in finite time. Near the blow-up time
the approximations used to derive the Uehling-Uhlenbeck equation break down. We
derive the set of equations that describe the building of correlations and the
onset of quantum interference effects for the many-particle hamiltonian system
under the assumption that the blow-up for the Uehling-Uhlenbeck equation takes
place in a self-similar form.


title: Bateman On Light: Synchrotron Rays

abstract:
  For over a century physicists have sought a mathematical theory that unites
the dual, wave and corpuscle, behaviors that light exhibits. In the early
twentieth century H. Bateman was studying a solution that uses wave functions
with singularities to mark light quanta location in space and time as potential
singularities do for material particles. He published an incomplete,
mathematically obtuse paper applying his scheme to presciently predict
synchrotron rays well before they were experimentally observed. Here, I clarify
the presentation in Bateman's paper and supply a missing demonstration that it
does predict results observed nearly four decades later.


title:
Sparse estimation of large covariance matrices via a nested Lasso
  penalty

abstract:
  The paper proposes a new covariance estimator for large covariance matrices
when the variables have a natural ordering. Using the Cholesky decomposition of
the inverse, we impose a banded structure on the Cholesky factor, and select
the bandwidth adaptively for each row of the Cholesky factor, using a novel
penalty we call nested Lasso. This structure has more flexibility than regular
banding, but, unlike regular Lasso applied to the entries of the Cholesky
factor, results in a sparse estimator for the inverse of the covariance matrix.
An iterative algorithm for solving the optimization problem is developed. The
estimator is compared to a number of other covariance estimators and is shown
to do best, both in simulations and on a real data example. Simulations show
that the margin by which the estimator outperforms its competitors tends to
increase with dimension.


title:
Squashed Kerr-Godel Black Holes - Kaluza-Klein Black Holes with
  Rotations of Black Hole and Universe -

abstract:
  Applying squashing transformation to Kerr-Godel black hole solutions, we
present a new type of a rotating Kaluza-Klein black hole solution to the
five-dimensional Einstein-Maxwell theory with a Chern-Simon term. The new
solutions generated via the squashing transformation have no closed timelike
curve everywhere outside the black hole horizons. At the infinity, the metric
asymptotically approaches a twisted S^1 bundle over a four-dimensional
Minkowski space-time. One of the remarkable features is that the solution has
two independent rotation parameters along an extra dimension associated with
the black hole's rotation and the Godel's rotation. The space-time also admits
the existence of two disconnected ergoregions, an inner ergoregion and an outer
ergoregion. These two ergoregions can rotate in the opposite direction as well
as in the same direction.


title:
Hyperfine Fields in an Ag/Fe Multilayer Film Investigated with 8Li
  beta-Detected Nuclear Magnetic Resonance

abstract:
  Low energy $\beta$-detected nuclear magnetic resonance ($\beta$-NMR) was used
to investigate the spatial dependence of the hyperfine magnetic fields induced
by Fe in the nonmagnetic Ag of an Au(40 \AA)/Ag(200 \AA)/Fe(140 \AA) (001)
magnetic multilayer (MML) grown on GaAs. The resonance lineshape in the Ag
layer shows dramatic broadening compared to intrinsic Ag. This broadening is
attributed to large induced magnetic fields in this layer by the magnetic Fe
layer. We find that the induced hyperfine field in the Ag follows a power law
decay away from the Ag/Fe interface with power $-1.93(8)$, and a field
extrapolated to $0.23(5)$ T at the interface.


title: Skip sequencing: A decision problem in questionnaire design

abstract:
  This paper studies questionnaire design as a formal decision problem,
focusing on one element of the design process: skip sequencing. We propose that
a survey planner use an explicit loss function to quantify the trade-off
between cost and informativeness of the survey and aim to make a design choice
that minimizes loss. We pose a choice between three options: ask all
respondents about an item of interest, use skip sequencing, thereby asking the
item only of respondents who give a certain answer to an opening question, or
do not ask the item at all. The first option is most informative but also most
costly. The use of skip sequencing reduces respondent burden and the cost of
interviewing, but may spread data quality problems across survey items, thereby
reducing informativeness. The last option has no cost but is completely
uninformative about the item of interest. We show how the planner may choose
among these three options in the presence of two inferential problems, item
nonresponse and response error.


title: Coordinate descent algorithms for lasso penalized regression

abstract:
  Imposition of a lasso penalty shrinks parameter estimates toward zero and
performs continuous model selection. Lasso penalized regression is capable of
handling linear regression problems where the number of predictors far exceeds
the number of cases. This paper tests two exceptionally fast algorithms for
estimating regression coefficients with a lasso penalty. The previously known
$\ell_2$ algorithm is based on cyclic coordinate descent. Our new $\ell_1$
algorithm is based on greedy coordinate descent and Edgeworth's algorithm for
ordinary $\ell_1$ regression. Each algorithm relies on a tuning constant that
can be chosen by cross-validation. In some regression problems it is natural to
group parameters and penalize parameters group by group rather than separately.
If the group penalty is proportional to the Euclidean norm of the parameters of
the group, then it is possible to majorize the norm and reduce parameter
estimation to $\ell_2$ regression with a lasso penalty. Thus, the existing
algorithm can be extended to novel settings. Each of the algorithms discussed
is tested via either simulated or real data or both. The Appendix proves that a
greedy form of the $\ell_2$ algorithm converges to the minimum value of the
objective function.


title:
GALEX observations of Low Surface Brightness Galaxies: UV color and star
  formation efficiency

abstract:
  We present GALEX UV observations of a sample of Low Surface Brightness (LSB)
galaxies for which HI data are available, allowing us to estimate their star
formation efficiency. We find that the UV light extends to larger radii than
the optical light (some galaxies, but not all, look similar to the recently
discovered XUV-disk galaxies). Using a standard calibration to convert the UV
light into star formation rates, we obtain lower star formation efficiencies in
LSB galaxies than in high surface brightness galaxies by about one order of
magnitude.
  We show however that standard calibrations may not apply to these galaxies,
as the FUV-NUV color obtained from the two GALEX bands (FUV and NUV;
lambda_eff= 1516 and 2267 A, respectively) is redder than expected for star
forming galaxies. This color can be interpreted as a result of internal
extinction, modified Initial Mass Function or by star formation histories
characterized by bursts followed by quiescent phases. Our analysis favors this
latter hypothesis.


title:
Energy dependence of the charged multiplicity in deep inelastic
  scattering at HERA

abstract:
  The charged multiplicity distributions and the mean charged multiplicity have
been investigated in inclusive neutral current deep inelastic $ep$ scattering
with the ZEUS detector at HERA, using an integrated luminosity of 38.6
pb$^{-1}$. The measurements were performed in the current region of the Breit
frame, as well as in the current fragmentation region of the hadronic
centre-of-mass frame. The KNO-scaling properties of the data were investigated
and the energy dependence was studied using different energy scales. The data
are compared to results obtained in $\epem$ collisions and to previous DIS
measurements as well as to leading-logarithm parton-shower Monte Carlo
predictions.