title: The Research of Thomas P. Branson

abstract:
  The Midwest Geometry Conference 2007 was devoted to the substantial
mathematical legacy of Thomas P. Branson who passed away unexpectedly the
previous year. This contribution to the Proceedings briefly introduces this
legacy. We also take the opportunity of recording his bibliography. Thomas
Branson was on the Editorial Board of SIGMA and we are pleased that SIGMA is
able to publish the Proceedings.


title: Weak Lensing Effects on the Galaxy Three-Point Correlation Function

abstract:
  We study the corrections to the galaxy three-point correlation function
(3PCF) induced by weak lensing magnification due to the matter distribution
along the line of sight. We consistently derive all the correction terms
arising up to second order in perturbation theory and provide analytic
expressions as well as order of magnitude estimates for their relative
importance. The magnification contributions depend on the geometry of the
projected triangle on the sky plane, and scale with different powers of the
number count slope and redshift of the galaxy sample considered. We evaluate
all terms numerically and show that, depending on the triangle configuration as
well as the galaxy sample considered, weak lensing can in general significantly
contribute to and alter the three-point correlation function observed through
galaxy and quasar catalogs.


title: Interface dynamics in shear-banding flow of giant micelles

abstract:
  We report on a non trivial dynamics of the interface between shear bands
following a start-up of flow in a semi-dilute wormlike micellar system
investigated using a combination of mechanical and optical measurements. During
the building of the banding structure, we observed the stages of formation,
migration of the interface between bands and finally the destabilization of
this interface along the vorticity axis. The mechanical signature of these
processes has been indentified in the time series of the shear stress. The
interface instability occurs all along the stress plateau, the asymptotic
wavelength of the patterns increasing with the control parameter typically from
a fraction of the gap width to about four times the gap width. Three main
regimes of dynamics are highlighted : a spatially stable oscillating mode
approximately at the middle of the coexistence region flanked by two ranges
where the dynamics appears more exotic with propagative and chaotic events
respectively at low and high shear rates. The distribution of small particles
seeded in the solution strongly suggests that the flow is three-dimensional.
Finally, we demonstrate that the shear-banding scenario described in this paper
is not specific to our system.


title: Magnetic barriers in graphene nanoribbons

abstract:
  A theoretical study of the transport properties of zigzag and armchair
graphene nanoribbons with a magnetic barrier on top is presented. The magnetic
barrier modifies the energy spectrum of the nanoribbons locally, which results
in an energy shift of the conductance steps towards higher energies. The
magnetic barrier also induces Fabry-Perot type oscillations, provided the edges
of the barrier are sufficiently sharp. The lowest propagating state present in
zigzag and metallic armchair nanoribbons prevent confinement of the charge
carriers by the magnetic barrier. Disordered edges in nanoribbons tend to
localize the lowest propagating state, which get delocalized in the magnetic
barrier region. Thus, in sharp contrast to the case of two-dimensional
graphene, the charge carriers in graphene nanoribbons cannot be confined by
magnetic barriers. We also present a novel method based on the Green's function
technique for the calculation of the magnetosubband structure, Bloch states and
magnetoconductance of the graphene nanoribbons in a perpendicular magnetic
field. Utilization of this method greatly facilitates the conductance
calculations, because, in contrast to excising methods, the present method does
not require self-consistent calculations for the surface Green's function.


title: First-principles study of the optical properties of MgxTi(1-x)H2

abstract:
  The optical and electronic properties of Mg-Ti hydrides are studied using
first-principles density functional theory. Dielectric functions are calculated
for MgxTi(1-x)H2 with compositions x = 0.5, 0.75, and 0.875. The structure is
that of fluorite TiH2 where both Mg and Ti atoms reside at the Ti positions of
the lattice. In order to assess the effect of randomness in the Mg and Ti
occupations we consider both highly ordered structures, modeled with simple
unit cells of minimal size, and models of random alloys. These are simulated by
super cells containing up to 64 formula units (Z = 64). All compositions and
structural models turn out metallic, hence the dielectric functions contain
interband and intraband free electron contributions. The former are calculated
in the independent particle random phase approximation. The latter are modeled
based upon the intraband plasma frequencies, which are also calculated from
first-principles. Only for the models of the random alloys we obtain a black
state, i.e. low reflection and transmission in the energy range from 1 to 6 eV.


title:
Uniqueness of fast travelling fronts in reaction-diffusion equations
  with delay

abstract:
  We consider positive travelling fronts of the time-delayed reaction-diffusion
equation with the monostable birth function. Our main result says that for
every fixed and sufficiently large velocity c, the positive travelling front is
unique (modulo translations). To prove the uniqueness, we introduce a small
parameter 1/c and realize the Lyapunov-Schmidt reduction in a scale of Banach
spaces.


title:
GaAs photonic crystal cavity with ultra-high Q: microwatt nonlinearity
  at 1.55 $\mu $m

abstract:
  We have realized and measured a GaAs nanocavity in a slab photonic crystal
based on the design by Kuramochi et al. [Appl. Phys.Lett., \textbf{88}, 041112,
(2006)]. We measure a quality factor Q=700,000, which proves that ultra-high Q
nanocavities are also feasible in GaAs. We show that, due to larger two-photon
absorption (TPA) in GaAs, nonlinearities appear at the microwatt-level and will
be more functional in gallium arsenide than in silicon nanocavities.


title:
Stochastic Dynamical Structure (SDS) of Nonequilibrium Processes in the
  Absence of Detailed Balance. III: potential function in local stochastic
  dynamics and in steady state of Boltzmann-Gibbs type distribution function

abstract:
  From a logic point of view this is the third in the series to solve the
problem of absence of detailed balance. This paper will be denoted as SDS III.
The existence of a dynamical potential with both local and global meanings in
general nonequilibrium processes has been controversial. Following an earlier
explicit construction by one of us (Ao, J. Phys. {\bf A37}, L25 '04,
arXiv:0803.4356, referred to as SDS II), in the present paper we show
rigorously its existence for a generic class of situations in physical and
biological sciences. The local dynamical meaning of this potential function is
demonstrated via a special stochastic differential equation and its global
steady-state meaning via a novel and explicit form of Fokker-Planck equation,
the zero mass limit. We also give a procedure to obtain the special stochastic
differential equation for any given Fokker-Planck equation. No detailed balance
condition is required in our demonstration. For the first time we obtain here a
formula to describe the noise induced shift in drift force comparing to the
steady state distribution, a phenomenon extensively observed in numerical
studies. The comparison to two well known stochastic integration methods, Ito
and Stratonovich, are made ready. Such comparison was made elsewhere (Ao, Phys.
Life Rev. {\bf 2} (2005) 117. q-bio/0605020).

categories: q-bio.QM cond-mat.dis-nn cond-mat.stat-mech nlin.AO physics.chem-ph q-bio.MN


title: Testing Consistency of Two Histograms

abstract:
  Several approaches to testing the hypothesis that two histograms are drawn
from the same distribution are investigated. We note that single-sample
continuous distribution tests may be adapted to this two-sample grouped data
situation. The difficulty of not having a fully-specified null hypothesis is an
important consideration in the general case, and care is required in estimating
probabilities with ``toy'' Monte Carlo simulations. The performance of several
common tests is compared; no single test performs best in all situations.


title: All orders asymptotic expansion of large partitions

abstract:
  The generating function which counts partitions with the Plancherel measure
(and its q-deformed version), can be rewritten as a matrix integral, which
allows to compute its asymptotic expansion to all orders. There are
applications in statistical physics of growing/melting crystals, T.A.S.E.P.,
and also in algebraic geometry. In particular we compute the Gromov-Witten
invariants of the X_p Calabi-Yau 3-fold, and we prove a conjecture of M.
Marino, that the generating functions F_g of Gromov--Witten invariants of X_p,
come from a matrix model, and are the symplectic invariants of the mirror
spectral curve.

categories: math-ph cond-mat.stat-mech hep-th math.MP


title:
Search for Correlations between HiRes Stereo Events and Active Galactic
  Nuclei

abstract:
  We have searched for correlations between the pointing directions of
ultrahigh energy cosmic rays observed by the High Resolution Fly's Eye
experiment and Active Galactic Nuclei (AGN) visible from its northern
hemisphere location. No correlations, other than random correlations, have been
found. We report our results using search parameters prescribed by the Pierre
Auger collaboration. Using these parameters, the Auger collaboration concludes
that a positive correlation exists for sources visible to their southern
hemisphere location. We also describe results using two methods for determining
the chance probability of correlations: one in which a hypothesis is formed
from scanning one half of the data and tested on the second half, and another
which involves a scan over the entire data set. The most significant
correlation found occurred with a chance probability of 24%.


title: A strong coupling expansion for N=4 SYM theory and other SCFT's

abstract:
  Recent progress towards understanding a strong coupling expansion for various
superconformal field theories in four dimensions is described. First, the case
of the maximally supersymmetric Yang Mills theory is analyzed, as well as many
calculations that can be done directly at strong coupling and matched to the
AdS dual geometry. Also, this understanding is extended to other AdS duals
where the sphere is replaced by a Sasaki-Einstein manifold. Particular emphasis
is made on matching exactly part of the supergravity dual spectrum of various
of these field theories by using wave function methods.


title:
Microscale fluid flow induced by thermoviscous expansion along a
  traveling wave

abstract:
  The thermal expansion of a fluid combined with a temperature-dependent
viscosity introduces nonlinearities in the Navier-Stokes equations unrelated to
the convective momentum current. The couplings generate the possibility for net
fluid flow at the microscale controlled by external heating. This novel
thermo-mechanical effect is investigated for a thin fluid chamber by a
numerical solution of the Navier-Stokes equations and analytically by a
perturbation expansion. A demonstration experiment confirms the basic mechanism
and quantitatively validates our theoretical analysis.


title: On the Sum-Capacity of Degraded Gaussian Multiaccess Relay Channels

abstract:
  The sum-capacity is studied for a K-user degraded Gaussian multiaccess relay
channel (MARC) where the multiaccess signal received at the destination from
the K sources and relay is a degraded version of the signal received at the
relay from all sources, given the transmit signal at the relay. An outer bound
on the capacity region is developed using cutset bounds. An achievable rate
region is obtained for the decode-and-forward (DF) strategy. It is shown that
for every choice of input distribution, the rate regions for the inner (DF) and
outer bounds are given by the intersection of two K-dimensional polymatroids,
one resulting from the multiaccess link at the relay and the other from that at
the destination. Although the inner and outer bound rate regions are not
identical in general, for both cases, a classical result on the intersection of
two polymatroids is used to show that the intersection belongs to either the
set of active cases or inactive cases, where the two bounds on the K-user
sum-rate are active or inactive, respectively. It is shown that DF achieves the
capacity region for a class of degraded Gaussian MARCs in which the relay has a
high SNR link to the destination relative to the multiaccess link from the
sources to the relay. Otherwise, DF is shown to achieve the sum-capacity for an
active class of degraded Gaussian MARCs for which the DF sum-rate is maximized
by a polymatroid intersection belonging to the set of active cases. This class
is shown to include the class of symmetric Gaussian MARCs where all users
transmit at the same power.


title:
First-principles calculations and bias-dependent STM measurements at the
  alpha-Sn/Ge(111) surface: a clear indication for the 1U2D configuration

abstract:
  The nature of the alpha-Sn/Ge(111) surface is still a matter of debate. In
particular, two possible configurations have been proposed for the 3x3 ground
state of this surface: one with two Sn adatoms in a lower position with respect
to the third one (1U2D) and the other with opposite configuration (2U1D). By
means of first-principles quasiparticle calculations we could simulate STM
images as a function of bias voltage and compare them with STM experimental
results at 78K, obtaining an unambiguous indication that the stable
configuration for the alpha-Sn/Ge(111) surface is the 1U2D. The possible
inequivalence of the two down Sn adatoms is also discussed.


title: Projective spectrum in Banach algebras

abstract:
  For a tuple $A=(A_0, A_1, ..., A_n)$ of elements in a unital Banach algebra
${\mathcal B}$, its {\em projective spectrum} $p(A)$ is defined to be the
collection of $z=[z_0, z_1, ..., z_n]\in \pn$ such that $A(z)=z_0A_0+z_1A_1+...
+z_nA_n$ is not invertible in ${\mathcal B}$. The pre-image of $p(A)$ in
${\cc}^{n+1}$ is denoted by $P(A)$. When ${\mathcal B}$ is the $k\times k$
matrix algebra $M_k(\cc)$, the projective spectrum is a projective
hypersurface. In infinite dimensional cases, projective spectrums can be very
complicated, but also have some properties similar to that of hypersurfaces.
When $A$ is commutative, $P(A)$ is a union of hyperplanes. When ${\mathcal B}$
is reflexive or is a $C^*$-algebra, the {\em projective resolvent set}
$P^c(A):=\cc^{n+1}\setminus P(A)$ is shown to be a disjoint union of domains of
holomorphy. Later part of this paper studies Maurer-Cartan type ${\mathcal
B}$-valued 1-form $A^{-1}(z)dA(z)$ on $P^c(A)$. As a consequence, we show that
if ${\mathcal B}$ is a $C^*$-algebra with a trace $\phi$, then
$\phi(A^{-1}(z)dA(z))$ is a nontrivial element in the de Rham cohomology space
$H^1_d(P^c(A), \cc)$.


title: Fibred surfaces with general pencils of genus 5

abstract:
  Let $f:S \fr B$ be a surface fibration with fibres of genus 5. We find a
linear relation between the fundamental invariants of the surface. Namely
$K_f^2=\chi_f+N$ where $N$ is the number of trigonal fibres. Our proof is based
on the analysis of the relative canonical algebra $\cal{R}(f)$.


title:
A test of the CPL parameterization for rapid dark energy equation of
  state transitions

abstract:
  We test the robustness and flexibility of the Chevallier-Polarski-Linder
(CPL) parameterization of the Dark Energy equation of state $w(z)=w_0+w_a
\frac{z}{1+z}$ in recovering a four-parameter step-like fiducial model. We
constrain the parameter space region of the underlying fiducial model where the
CPL parameterization offers a reliable reconstruction. It turns out that non
negligible biases leak into the results for recent ($z<2.5$) rapid transitions,
but that CPL yields a good reconstruction in all other cases. The presented
analysis is performed with supernova Ia data as forecasted for a space mission
like SNAP/JDEM, combined with future expectations for the CMB shift parameter
$R$ and the BAO parameter $A$.


title: A practical procedure to find matching priors for frequentist inference

abstract:
  In the manuscript, we present a practical way to find the matching priors
proposed by Welch & Peers (1963) and Peers (1965). We investigate the use of
saddlepoint approximations combined with matching priors and obtain p-values of
the test of an interest parameter in the presence of nuisance parameter. The
advantage of our procedure is the flexibility of choosing different initial
conditions so that one can adjust the performance of the test. Two examples
have been studied, with coverage verified via Monte Carlo simulation. One
relates to the ratio of two exponential means, and the other relates the
logistic regression model. Particularly, we are interested in small sample
settings.


title:
Gravitational waves from deflagration bubbles in first-order phase
  transitions

abstract:
  The walls of bubbles in a first-order phase transition can propagate either
as detonations, with a velocity larger than the speed of sound, or
deflagrations, which are subsonic. We calculate the gravitational radiation
that is produced by turbulence during a phase transition which develops via
deflagration bubbles. We take into account the fact that a deflagration wall is
preceded by a shock front which distributes the latent heat throughout space
and influences other bubbles. We show that turbulence can induce peak values of
$\Omega_{GW}$ as high as $\sim 10^{-9}$. We discuss the possibility of
detecting at LISA gravitational waves produced in the electroweak phase
transition with wall velocities $v_w\lesssim 10^{-1}$, which favor electroweak
baryogenesis.


title: Arrest of Fluid Demixing by Nanoparticles: A Computer Simulation Study

abstract:
  We use lattice Boltzmann simulations to investigate the formation of arrested
structures upon demixing of a binary solvent containing neutrally wetting
colloidal particles. Previous simulations for symmetric fluid quenches pointed
to the formation of `bijels': bicontinuous interfacially jammed emulsion gels.
These should be created when a glassy monolayer of particles forms at the
fluid-fluid interface, arresting further demixing, and rigidifying the
structure. Experimental work has broadly confirmed this scenario, but shows
that bijels can also be formed in volumetrically asymmetric quenches. Here we
present new simulation results for such quenches, compare these to the
symmetric case, and find a crossover to an arrested droplet phase at strong
asymmetry. We then make extensive new analyses of the post-arrest dynamics in
our simulated bijel and droplet structures, on time scales comparable to the
Brownian time for colloid motion. Our results suggest that, on these
intermediate time scales, the effective activation barrier to ejection of
particles from the fluid-fluid interface is smaller by at least two orders of
magnitude than the corresponding barrier for an isolated particle on a flat
interface.


title:
Physical properties of the new Uranium ternary compounds U3Bi4M3 (M=Ni,
  Rh)

abstract:
  We report the properties of two new isostructural compounds, U3Bi4Ni3 and
U3Bi4Rh3. The first of these compounds is non-metallic, and the second is a
nearly ferromagnetic metal, both as anticipated from their electron count
relative to other U-based members of the larger 3-4-3 family. For U3Bi4Rh3, a
logarithmic increase of C/T below 3 K, a resistivity proportional to T^4/3, and
the recovery of Fermi-liquid behavior in both properties with applied fields
greater than 3T, suggest that U3Bi4Rh3 may be a new example of a material
displaying ferromagnetic quantum criticality.


title: Concentration-diffusion effects in viscous incompressible flows

abstract:
  Given a finite sequence of times $0<t_1<...<t_N$, we construct an example of
a smooth solution of the free nonstationnary Navier--Stokes equations in
$\R^d$, $d=2,3$, such that: (i) The velocity field $u(x,t)$ is spatially poorly
localized at the beginning of the evolution but tends to concentrate until, as
the time $t$ approaches $t_1$, it becomes well-localized. (ii) Then $u$ spreads
out again after $t_1$, and such concentration-diffusion phenomena are later
reproduced near the instants $t_2$, $t_3$, ...


title: Fast soliton scattering by attractive delta impurities

abstract:
  We study the Gross-Pitaevskii equation with an attractive delta function
potential and show that in the high velocity limit an incident soliton is split
into reflected and transmitted soliton components plus a small amount of
dispersion. We give explicit analytic formulas for the reflected and
transmitted portions, while the remainder takes the form of an error. Although
the existence of a bound state for this potential introduces difficulties not
present in the case of a repulsive potential, we show that the proportion of
the soliton which is trapped at the origin vanishes in the limit.


title: On the approximability of minmax (regret) network optimization problems

abstract:
  In this paper the minmax (regret) versions of some basic polynomially
solvable deterministic network problems are discussed. It is shown that if the
number of scenarios is unbounded, then the problems under consideration are not
approximable within $\log^{1-\epsilon} K$ for any $\epsilon>0$ unless NP
$\subseteq$ DTIME$(n^{\mathrm{poly} \log n})$, where $K$ is the number of
scenarios.


title: Blow-ups and resolutions of strong K\"ahler with torsion metrics

abstract:
  On a compact complex manifold we study the behaviour of strong K\"ahler with
torsion (strong KT) structures under small deformations of the complex
structure and the problem of extension of a strong KT metric. In this context
we obtain the analogous result of Miyaoka extension theorem. Studying the
blow-up of a strong KT manifold at a point or along a complex submanifold, we
prove that a complex orbifold endowed with a strong KT metric admits a strong
KT resolution. In this way we obtain new examples of compact simply-connected
strong KT manifolds.


title: Moving constraints as stabilizing controls in classical mechanics

abstract:
  The paper analyzes a Lagrangian system which is controlled by directly
assigning some of the coordinates as functions of time, by means of
frictionless constraints. In a natural system of coordinates, the equations of
motions contain terms which are linear or quadratic w.r.t.time derivatives of
the control functions. After reviewing the basic equations, we explain the
significance of the quadratic terms, related to geodesics orthogonal to a given
foliation. We then study the problem of stabilization of the system to a given
point, by means of oscillating controls. This problem is first reduced to the
weak stability for a related convex-valued differential inclusion, then studied
by Lyapunov functions methods. In the last sections, we illustrate the results
by means of various mechanical examples.


title: A Field Guide to Recent Work on the Foundations of Statistical Mechanics

abstract:
  This is an extensive review of recent work on the foundations of statistical
mechanics. Subject matters discussed include: interpretation of probability,
typicality, recurrence, reversibility, ergodicity, mixing, coarse graining,
past hypothesis, reductionism, phase average, thermodynamic limit,
interventionism, entropy.


title:
Spin-stiffness of anisotropic Heisenberg model on square lattice and
  possible mechanism for pinning of the electronic liquid crystal direction in
  YBCO

abstract:
  Using series expansions and spin-wave theory we calculate the spin-stiffness
anisotropy $\rho_{sx}/\rho_{sy}$ in Heisenberg models on the square lattice
with anisotropic couplings $J_x,J_y$. We find that for the weakly anisotropic
spin-half model ($J_x\approx J_y$), $\rho_{sx}/\rho_{sy}$ deviates
substantially from the naive estimate $\rho_{sx}/\rho_{sy} \approx J_x/J_y$. We
argue that this deviation can be responsible for pinning the electronic liquid
crystal direction, a novel effect recently discovered in YBCO. For
completeness, we also study the spin-stiffness for arbitrary anisotropy
$J_x/J_y$ for spin-half and spin-one models. In the limit of $J_y/J_x\to 0$,
when the model reduces to weakly coupled chains, the two show dramatically
different behavior. In the spin-one model, the stiffness along the chains goes
to zero, implying the onset of Haldane-gap phase, whereas for spin-half the
stiffness along the chains increases monotonically from a value of $0.18 J_x$
for $J_y/J_x=1$ towards $0.25 J_x$ for $J_y/J_x\to 0$. Spin-wave theory is
extremely accurate for spin-one but breaks down for spin-half presumably due to
the onset of topological terms.


title:
An involution on the K-theory of bimonoidal categories with
  anti-involution

abstract:
  We construct a combinatorially defined involution on the algebraic $K$-theory
of the ring spectrum associated to a bimonoidal category with anti-involution.
Particular examples of such are braided bimonoidal categories. We investigate
examples such as algebraic K-theory of connective complex and real topological
K-theory and Waldhausen's K-theory of spaces of the form BBG, for abelian
groups G. We show that the involution agrees with the classical one for a
bimonoidal category associated to a ring and prove that it is not trivial in
the above mentioned examples.


title: Athena: A New Code for Astrophysical MHD

abstract:
  A new code for astrophysical magnetohydrodynamics (MHD) is described. The
code has been designed to be easily extensible for use with static and adaptive
mesh refinement. It combines higher-order Godunov methods with the constrained
transport (CT) technique to enforce the divergence-free constraint on the
magnetic field. Discretization is based on cell-centered volume-averages for
mass, momentum, and energy, and face-centered area-averages for the magnetic
field. Novel features of the algorithm include (1) a consistent framework for
computing the time- and edge-averaged electric fields used by CT to evolve the
magnetic field from the time- and area-averaged Godunov fluxes, (2) the
extension to MHD of spatial reconstruction schemes that involve a
dimensionally-split time advance, and (3) the extension to MHD of two different
dimensionally-unsplit integration methods. Implementation of the algorithm in
both C and Fortran95 is detailed, including strategies for parallelization
using domain decomposition. Results from a test suite which includes problems
in one-, two-, and three-dimensions for both hydrodynamics and MHD are given,
not only to demonstrate the fidelity of the algorithms, but also to enable
comparisons to other methods. The source code is freely available for download
on the web.


title: Geodesic manifolds with a transitive subset of smooth biLipschitz maps

abstract:
  This paper is connected with the problem of describing path metric spaces
that are homeomorphic to manifolds and biLipschitz homogeneous, i.e., whose
biLipschitz homeomorphism group acts transitively.
  Our main result is the following. Let $X = G/H$ be a homogeneous manifold of
a Lie group $G$ and let $d$ be a geodesic distance on $X$ inducing the same
topology. Suppose there exists a subgroup $G_S$ of $G$ that acts transitively
on $X$, such that each element $g \in G_S$ induces a locally biLipschitz
homeomorphism of the metric space $(X,d)$. Then the metric is locally
biLipschitz equivalent to a sub-Riemannian metric. Any such metric is defined
by a bracket generating $G_S$-invariant sub-bundle of the tangent bundle.
  The result is a consequence of a more general fact that requires a transitive
family of uniformly biLipschitz diffeomorphisms with a control on their
differentials. It will be relevant that the group acting transitively on the
space is a Lie group and so it is locally compact, since, in general, the whole
group of biLipschitz maps, unlikely the isometry group, is not locally compact.
  Our method also gives an elementary proof of the following fact. Given a
Lipschitz sub-bundle of the tangent bundle of a Finsler manifold, then both the
class of piecewise differentiable curves tangent to the sub-bundle and the
class of Lipschitz curves almost everywhere tangent to the sub-bundle give rise
to the same Finsler-Carnot-Carath\'eodory metric, under the condition that the
topologies induced by these distances coincide with the manifold topology.


title: Effect of Metal Element in Catalytic Growth of Carbon Nanotubes

abstract:
  Using first principles calculations, we model the chemical vapor deposition
(CVD) growth of carbon nanotubes (CNT) on nanoparticles of late transition (Ni,
Pd, Pt) and coinage (Cu, Ag, Au) metals. The process is analyzed in terms of
the binding of mono- and diatomic carbon species, their diffusion pathways, and
the stability of the growing CNT. We find that the diffusion pathways can be
controlled by the choice of the catalyst and the carbon precursor. Binding of
the CNT through armchair edges is more favorable than through zigzag ones, but
the relative stability varies significantly among the metals. Coinage metals,
in particular Cu, are found to favor CVD growth of CNTs at low temperatures and
with narrow chirality distributions.


title:
Boundedness and convergence for singular integrals of measures separated
  by Lipschitz graphs

abstract:
  We shall consider the truncated singular integral operators T_{\mu,
K}^{\epsilon}f(x)=\int_{\mathbb{R}^{n}\setminus B(x,\epsilon)}K(x-y)f(y)d\mu y
and related maximal operators $T_{\mu,K}^{\ast}f(x)=\underset{\epsilon
>0}{\sup}| T_{\mu,K}^{\epsilon}f(x)|$. We shall prove for a large class of
kernels $K$ and measures $\mu$ and $\nu$ that if $\mu$ and $\nu$ are separated
by a Lipschitz graph, then $T_{\nu,K}^{\ast}:L^p(\nu)\to L^p(\mu)$ is bounded
for $1<p<\infty$. We shall also show that the truncated operators $T_{\mu,
K}^{\epsilon}$ converge weakly in some dense subspaces of $L^2(\mu)$ under mild
assumptions for the measures and the kernels.


title: Composition of Ices in Low-Mass Extrasolar Planets

abstract:
  We study the formation conditions of icy planetesimals in protoplanetary
disks in order to determine the composition of ices in small and cold
extrasolar planets. Assuming that ices are formed from hydrates, clathrates,
and pure condensates, we calculate their mass fractions with respect to the
total quantity of ices included in planetesimals, for a grid of disk models. We
find that the composition of ices weakly depends on the adopted disk
thermodynamic conditions, and is rather influenced by the initial composition
of the gas phase. The use of a plausible range of molecular abundance ratios
and the variation of the relative elemental carbon over oxygen ratio in the gas
phase of protoplanetary disks, allow us to apply our model to a wide range of
planetary systems. Our results can thus be used to constrain the icy/volatile
phase composition of cold planets evidenced by microlensing surveys,
hypothetical ocean-planets and carbon planets, which could be detected by Corot
or Kepler.


title:
Asymptotic Properties of the Maximum Likelihood Estimator for Stochastic
  Parabolic Equations with Additive Fractional Brownian Motion

abstract:
  A parameter estimation problem is considered for a diagonaliazable stochastic
evolution equation using a finite number of the Fourier coefficients of the
solution. The equation is driven by additive noise that is white in space and
fractional in time with the Hurst parameter $H\geq 1/2$.
  The objective is to study asymptotic properties of the maximum likelihood
estimator as the number of the Fourier coefficients increases. A necessary and
sufficient condition for consistency and asymptotic normality is presented in
terms of the eigenvalues of the operators in the equation.


title: Dynamics of symmetric dynamical systems with delayed switching

abstract:
  We study dynamical systems that switch between two different vector fields
depending on a discrete variable and with a delay. When the delay reaches a
problem-dependent critical value so-called event collisions occur. This paper
classifies and analyzes event collisions, a special type of discontinuity
induced bifurcations, for periodic orbits. Our focus is on event collisions of
symmetric periodic orbits in systems with full reflection symmetry, a symmetry
that is prevalent in applications. We derive an implicit expression for the
Poincare map near the colliding periodic orbit. The Poincare map is piecewise
smooth, finite-dimensional, and changes the dimension of its image at the
collision. In the second part of the paper we apply this general result to the
class of unstable linear single-degree-of-freedom oscillators where we detect
and continue numerically collisions of invariant tori. Moreover, we observe
that attracting closed invariant polygons emerge at the torus collision.


title: Cryptanalysis of Two McEliece Cryptosystems Based on Quasi-Cyclic Codes

abstract:
  We cryptanalyse here two variants of the McEliece cryptosystem based on
quasi-cyclic codes. Both aim at reducing the key size by restricting the public
and secret generator matrices to be in quasi-cyclic form. The first variant
considers subcodes of a primitive BCH code. We prove that this variant is not
secure by finding and solving a linear system satisfied by the entries of the
secret permutation matrix.
  The other variant uses quasi-cyclic low density parity-check codes. This
scheme was devised to be immune against general attacks working for McEliece
type cryptosystems based on low density parity-check codes by choosing in the
McEliece scheme more general one-to-one mappings than permutation matrices. We
suggest here a structural attack exploiting the quasi-cyclic structure of the
code and a certain weakness in the choice of the linear transformations that
hide the generator matrix of the code. Our analysis shows that with high
probability a parity-check matrix of a punctured version of the secret code can
be recovered in cubic time complexity in its length. The complete
reconstruction of the secret parity-check matrix of the quasi-cyclic low
density parity-check codes requires the search of codewords of low weight which
can be done with about $2^{37}$ operations for the specific parameters
proposed.


title: The Galactic gamma-ray club

abstract:
  The exclusive Galactic gamma-ray club has opened up to new members. Supernova
remnants, pulsar wind nebulae, and massive binary systems hosting a compact
object have recently joined the young pulsars as firmly established sources of
gamma rays in the Milky Way. Massive young stellar clusters are on the waiting
list to join the club. Only the fine imaging recently obtained at TeV energies
could resolve specific sources. The samples are sparse, but raise exciting
questions. The jet or pulsar-wind origin of the emission in binaries has been
hotly debated, but it seems that both types of systems have been recently
detected. The nature of the radiation in shock accelerators is still
questioned: do nuclei contribute a lot, a little, or not to the gamma rays and
what energy do they carry away from the shock budget? The acceleration process
and the structural evolution of the pulsar winds are still uncertain. The
magnetic field distribution in all these systems is a key, but poorly
constrained, ingredient to model the multi-wavelength data, particle transport
and electron ageing. It must, however, be determined in order to efficiently
probe particle distributions and the acceleration mechanisms. The source
samples soon to be expected from GLAST and the Cherenkov telescopes should
bring new valuable test cases and they will, for the first time, shed
statistical light on the collective behaviour of these different types of
accelerators.


title: Study of B Meson Decays with Excited eta and eta' Mesons

abstract:
  Using 383 million BBbar pairs from the BaBar data sample, we report results
for branching fractions of six charged B-meson decay modes, where a charged
kaon recoils against a charmless resonance decaying to KKbar* or etapipi final
states with mass in the range (1.2-1.8)gev/c^2. We observe a significant
enhancement at the low KK*bar invariant mass which is interpreted as B+ -->
eta(1475)K+, find evidence for the decay B+ --> eta(1295)K+, and place upper
limits on the decays B+ --> eta(1405)K+, B+ --> f_1(1285)K+, B+ -->
f_1(1420)K+, and B+ --> phi(1680)K+.


title: Solitons and AdS String Solutions

abstract:
  In this contribution we describe some soliton based techniques for generating
classical AdS string solutions. The methods introduced are useful for further
understanding of rotating AdS configurations with spikes which correspond to
higher twist operators in SYM theory. The main identification (accomplished in
arXiv:0712.1193) between solitons and string spikes is reviewed and extended.
We describe how inverse scattering technique can be applied for reconstructing
AdS string configurations from soliton solutions of sinh-Gordon theory (in the
example of ${\rm AdS}_3$).


title:
A measure of the impact of future dark energy experiments based on
  discriminating power among quintessence models

abstract:
  We evaluate the ability of future data sets to discriminate among different
quintessence dark energy models. This approach gives an alternative measure for
assessing the impact of future experiments, as compared with the large body of
literature that compares experiments in abstract parameter spaces and more
recent work that evaluates the constraining power of experiments on individual
parameter spaces of specific quintessence models. We use the Dark Energy Task
Force (DETF) models of future data sets, and compare the discriminative power
of experiments designated by the DETF as Stages 2, 3, and 4. Our work reveals a
minimal increase in discriminating power when comparing Stage 3 to Stage 2, but
a very striking increase in discriminating power when going to Stage 4. We also
see evidence that even modest improvements over DETF Stage 4 could result in
even more dramatic discriminating power among quintessence dark energy models.
We develop and demonstrate the technique of using the independently measured
modes of the equation of state as a common parameter space in which to compare
the different quintessence models, and we argue that this technique is a
powerful one. We use the PNGB, Exponential, Albrecht-Skordis, and Inverse
Tracker (or Inverse Power Law) quintessence models for this work. One of our
main results is that the goal of discriminating among these models sets a
concrete measure on the capabilities of future dark energy experiments.
Experiments have to be somewhat better than DETF Stage 4 simulated experiments
to fully meet this goal.


title: Twisted cscK metrics and K\"ahler slope stability

abstract:
  We introduce a cohomological obstruction to solving the constant scalar
curvature K\"ahler (cscK) equation twisted by a semipositive form, appearing in
works of Fine and Song-Tian. Geometrically this gives an obstruction for a
manifold to be the base of a holomorphic submersion carrying a cscK metric in
certain ``adiabatic'' classes. In turn this produces many new examples of
general type threefolds with classes which do not admit a cscK representative.
When the twist vanishes our obstruction extends the slope stability of
Ross-Thomas to effective divisors on a K\"ahler manifold. Thus we find examples
of non-projective slope unstable manifolds.


title: The Yale liquid argon time projection chamber

abstract:
  In this paper we give a thorough description of a liquid argon time
projection chamber designed, built and operated at Yale. We present results
from a calibration run where cosmic rays have been observed in the detector, a
first in the US.


title: Fermion zero mode and superfluid weight

abstract:
  We propose one possible mechanism for deconfinement based on an SU(2)
slave-boson theory. Resorting to an effective field theory approach, we show
that introduction of an isospin interaction potential gives rise to a fermion
zero mode in an instanton-hedgehog configuration. As a result, meron-type
vortices are allowed. We demonstrate how emergence of such vortices results in
the doping-independent decreasing ratio of superfluid weight.


title: Prominence and control: The weighted rich-club effect

abstract:
  Complex systems are often characterized by large-scale hierarchical
organizations. Whether the prominent elements, at the top of the hierarchy,
share and control resources or avoid one another lies at the heart of a
system's global organization and functioning. Inspired by network perspectives,
we propose a new general framework for studying the tendency of prominent
elements to form clubs with exclusive control over the majority of a system's
resources. We explore associations between prominence and control in the fields
of transportation, scientific collaboration, and online communication.


title: Optical Spectra of the High Voltage Erosive Water Discharge

abstract:
  In the present paper kinetics of emission spectra of the high voltage erosive
water discharge at near ultraviolet and visible spectral ranges has been
investigated. Obtained results show a similarity of physical properties of this
discharge (and of corresponding plasmoids) to that of some other types of
erosional discharges which also result in the formation of dust-gas fireballs.


title: Tension-induced multistability in inextensible helical ribbons

abstract:
  We study the non-monotonic force-extension behaviour of helical ribbons using
a new model for inextensible elastic strips. Unlike previous rod models our
model predicts hysteresis behaviour for low-pitch ribbons of arbitrary material
properties. Associated with it is a first-order transition between two
different helical states as observed in experiments with cholesterol ribbons.
Numerical solutions show non-uniform uncoiling with hysteresis also occurring
under controlled tension. They furthermore reveal a new uncoiling scenario in
which a ribbon of very low pitch shears under tension and successively releases
a sequence of almost planar loops. Our results may be relevant for nanoscale
devices such as force probes.


title: Reconstructing Single Field Inflationary Actions From CMBR Data

abstract:
  This paper describes a general program for deriving the action of single
field inflation models with nonstandard kinetic energy terms using CMBR power
spectrum data. This method assumes that an action depends on a set of
undetermined functions, each of which is a function of either the inflaton wave
function or its time derivative. The scalar, tensor and non-gaussianity of the
curvature perturbation spectrum are used to derive a set of reconstruction
equations whose solution set can specify up to three of the undetermined
functions. The method is then used to find the undetermined functions in
various types of actions assuming power law type scalar and tensor spectra. In
actions that contain only two unknown functions, the third reconstruction
equation implies a consistency relation between the non-gaussianty, sound speed
and slow roll parameters. In particular we focus on reconstructing a
generalized DBI action with an unknown potential and warp factor. We find that
for realistic scalar and tensor spectra, the reconstructed warp factor and
potential are very similar to the theoretically derived result. Furthermore,
physical consistency of the reconstructed warp factor and potential imposes
strict constraints on the scalar and tensor spectral indices.


title:
Backward retrieval in optical quantum memory controlled by an external
  field

abstract:
  A scheme for backward retrieval in optical quantum memories in which
information is stored in collective states of an extended resonant atomic
ensemble is developed such that phase conjugation can be implemented by
application of an external nonuniform electric (magnetic) field without use of
coherent exciting pulses. The possibilities of realizing such a scheme using
resonant solid-state materials are discussed.


title: Global Analysis of Helicity Parton Densities and Their Uncertainties

abstract:
  We present a new analysis of the helicity parton distributions of the
nucleon. The analysis takes into account the available data from inclusive and
semi-inclusive polarized deep inelastic scattering, as well as from polarized
pp scattering at RHIC. For the first time, all theoretical calculations are
performed fully at next-to-leading order (NLO) of perturbative QCD, using a
method that allows to incorporate the NLO corrections in a very fast and
efficient way in the analysis. We find evidence for a rather small gluon
polarization in the nucleon, over a limited region of momentum fraction, and
for interesting flavor patterns in the polarized sea.


title: Gaugino-pair production in polarized and unpolarized hadron collisions

abstract:
  We present an exploratory study of gaugino-pair production in polarized and
unpolarized hadron collisions, focusing on the correlation of beam polarization
and gaugino/Higgsino mixing in the general Minimal Supersymmetric Standard
Model. Helicity-dependent cross sections induced by neutral and charged
electroweak currents and squark exchanges are computed analytically in terms of
generalized charges, defined similarly for chargino-pair, neutralino-chargino
associated, and neutralino-pair production. Our results confirm and extend
those obtained previously for negligible Yukawa couplings and nonmixing
squarks. Assuming that the lightest chargino mass is known, we show numerically
that measurements of the longitudinal single-spin asymmetry at the existing
polarized pp collider RHIC and at possible polarization upgrades of the
Tevatron or the LHC would allow for a determination of the gaugino/Higgsino
fractions of charginos and neutralinos. The theoretical uncertainty coming from
factorization scale and squark mass variations and the expected experimental
error on the lightest chargino mass is generally smaller than the one induced
by the polarized parton densities, so that more information on the latter would
considerably improve on the analysis.


title: The AdS/CFT/Unparticle Correspondence

abstract:
  We examine the correspondence between the anti-de Sitter (AdS) description of
conformal field theories (CFTs) and the unparticle description of CFTs. We show
how unparticle actions are equivalent to holographic boundary actions for
fields in AdS, and how massive unparticles provide a new type of infrared
cutoff that can be simply implemented in AdS by a soft breaking of conformal
symmetry. We also show that processes involving scalar unparticles with
dimensions d_s<2 or fermion unparticles with dimensions d_f<5/2 are insensitive
to ultraviolet cutoff effects. Finally we show that gauge interactions for
unparticles can be described by bulk gauge interactions in AdS and that they
correspond to minimal gauging of the non-local effective action, and we compute
the fermion unparticle production cross-section.


title: Non-Gaussianity from Symmetry

abstract:
  We point out that a light scalar field fluctuating around a symmetry-enhaced
point can generate large non-Gaussianity in density fluctuations. We name such
a particle as an "ungaussiton", a scalar field dominantly produced by the
quantum fluctuations,generating sizable non-Gaussianity in the density
fluctuations. We derive a consistency relation between the bispectrum and the
trispectrum, tau_NL = 10^3 f_NL^(4/3), which can be extended to arbitrary high
order correlation functions. If such a relation is confirmed by future
observations, it will strongly support this mechanism.


title: The Assembly of Galaxy Clusters

abstract:
  We study the formation of fifty-three galaxy cluster-size dark matter halos
formed within a pair of cosmological LCDM N-body simulations, and track the
accretion histories of cluster subhalos with masses large enough to host 0.1L*
galaxies. By associating subhalos with cluster galaxies, we find the majority
of galaxies in clusters experience no pre-processing in the group environment
prior to their accretion into the cluster. On average, ~70% of cluster galaxies
fall into the cluster potential directly from the field, with no luminous
companions in their host halos at the time of accretion; and less than ~12% are
accreted as members of groups with five or more galaxies. Moreover, we find
that cluster galaxies are significantly less likely to have experienced a
merger in the recent past (~6 Gyr) than a field halo of the same mass. These
results suggest that local, cluster processes like ram-pressure stripping,
galaxy harassment, or strangulation play the dominant role in explaining the
difference between cluster and field populations at a fixed stellar mass; and
that pre-evolution or past merging in the group environment is of secondary
importance for setting cluster galaxy properties for most clusters. The
accretion times for z = 0 cluster members are quite extended, with ~20%
incorporated into the cluster halo more than 7 Gyr ago and ~20% within the last
2 Gyr. By comparing the observed morphological fractions in cluster and field
populations, we estimate an approximate timescale for late-type to early-type
transformation within the cluster environment to be ~6 Gyr.


title: Fibered orbifolds and crystallographic groups

abstract:
  In this paper, we prove that a normal subgroup N of an n-dimensional
crystallographic group G determines a geometric fibered orbifold structure on
the flat orbifold E^n/G, and conversely every geometric fibered orbifold
structure on E^n/G is determined by a normal subgroup N of G, which is maximal
in its commensurability class of normal subgroups of G. In particular, we prove
that E^n/G is a fiber bundle, with totally geodesic fibers, over a
b-dimensional torus, where b is the first Betti number of G.
  Let N be a normal subgroup of G which is maximal in its commensurability
class. We study the relationship between the exact sequence 1 -> N -> G -> G/N
-> 1 splitting and the corresponding fibration projection having an affine
section. If N is torsion-free, we prove that the exact sequence splits if and
only if the fibration projection has an affine section. If the generic fiber F
= Span(N)/N has an ordinary point that is fixed by every isometry of F, we
prove that the exact sequence always splits. Finally, we describe all the
geometric fibrations of the orbit spaces of all 2- and 3-dimensional
crystallographic groups building on the work of Conway and Thurston.


title: SN 1994W: An Interacting Supernova or Two Interacting Shells?

abstract:
  We present a multi-epoch quantitative spectroscopic analysis of the Type IIn
SN 1994W, an event interpreted by Chugai et al. as stemming from the
interaction between the ejecta of a SN and a 0.4Msun circumstellar shell
ejected 1.5yr before core collapse. During the brightening phase, our models
suggest that the source of optical radiation is not unique, perhaps associated
with an inner optically-thick Cold Dense Shell (CDS) and outer optically-thin
shocked material. During the fading phase, our models support a single source
of radiation, an hydrogen-rich optically-thick layer with a near-constant
temperature of ~7000K that recedes from a radius of 4.3x10^15 at peak to
2.3x10^15cm 40 days later. We reproduce the hybrid narrow-core broad-wing line
profile shapes of SN 1994W at all times, invoking an optically-thick
photosphere exclusively (i.e., without any external optically-thick shell). In
SN 1994W, slow expansion makes scattering with thermal electrons a key escape
mechanism for photons trapped in optically-thick line cores, and allows the
resulting broad incoherent electron-scattering wings to be seen around narrow
line cores. In SNe with larger expansion velocities, the thermal broadening due
to incoherent scattering is masked by the broad profile and the dominant
frequency redshift occasioned by bulk motions. Given the absence of broad lines
at all times and the very low 56Ni yields, we speculate whether SN 1994W could
have resulted from an interaction between two ejected shells without core
collapse. The high conversion efficiency of kinetic to thermal energy may not
require a SN-like energy budget for SN1994W.


title: The centralizer of an element in an endomorphism ring

abstract: We have results about the centralizer.


title: Dynamic scattering channels of a double barrier structure

abstract:
  We calculate analytically the Floquet scattering matrix for a periodically
driven double-barrier structure. Our approach takes into account dynamical
effects which become necessarily important when electrons propagate through a
system subject to a fast drive. It is convenient to represent the Floquet
scattering amplitude as a sum of amplitudes corresponding to different times
spent by an electron inside the structure. These amplitudes define dynamical
scattering channels. Then we represent the dc current generated by the
structure as a sum of two generic contributions. The first one is due to
photon-assisted interference processes within the same channel and the second
one is due to inter-channel interference processes. At zero temperature both
contributions are present while at high temperatures and/or high driving
frequencies only the former survives.


title: Classical solutions for the Carroll-Field-Jackiw-Proca electrodynamics

abstract:
  In the present work, we investigate classical solutions of the
Maxwell-Carroll-Field-Jackiw-Proca (MCFJP) electrodynamics for the cases a
purely timelike and spacelike Lorentz-violating (LV) background. Starting from
the MCFJP Lagrangian and the associated wave equations written for the
potential four-vector, the tensor form of the Green function is achieved. In
the timelike case, the components of the stationary Green function are
explicitly written. The classical solutions for the electric and magnetic field
strengths are then evaluated, being observed that the electric sector is not
modified by the LV background, keeping the Maxwell-Proca behavior. The magnetic
field associated with a charge in uniform motion presents an oscillating
behavior that also provides an oscillating MCFJ solution (in the limit of a
vanishing Proca mass), but does not recover the Maxwell-Proca solution in the
limit of vanishing background. In the spacelike case, the stationary Green
function is written and also explicitly carried out in the regime of a small
background. The electric and magnetic fields reveal to possess an exponentially
decaying behavior, that recover the Maxwell-Proca solutions.


title: Sunyaev-Zel'dovich effect in the Virgo cluster from WMAP and ROSAT data

abstract:
  WMAP observations at mm wavelengths are sensitive to the Sunyaev-Zel'dovich
effect in galaxy clusters. Among all the objects in the sky, the Virgo cluster
is expected to provide the largest integrated signal. Based on models
compatible with the X-ray emission observed in the ROSAT All Sky Survey, we
predict a two-sigma detection of the SZ effect from Virgo in the WMAP 3-year
data. Our analysis reveals a 3-sigma signal on scales of 5 degrees, although
the frequency dependence deviates from the theoretical expectation for the SZ
effect. The main sources of uncertainty are instrumental noise, and most
importantly, possible contamination from point sources and diffuse
back/foregrounds. In particular, a population of unresolved extragalactic
sources in Virgo would explain the observed intensity and frequency dependence.
In order to resolve this question one needs to wait for experiments like Planck
to achieve the required accuracy.


title: Parabolically induced representations of graded Hecke algebras

abstract:
  We study the representation theory of graded Hecke algebras, starting from
scratch and focusing on representations that are obtained with induction from a
discrete series representation of a parabolic subalgebra. We determine all
intertwining operators between such parabolically induced representations, and
use them to parametrize the irreducible representations.


title: Mimicking the QCD equation of state with a dual black hole

abstract:
  We present numerical and analytical studies of the equation of state of
translationally invariant black hole solutions to five-dimensional gravity
coupled to a single scalar. As an application, we construct a family of black
holes that closely mimics the equation of state of quantum chromodynamics at
zero chemical potential.


title: Modeling the Non-Thermal X-ray Tail Emission of Anomalous X-ray Pulsars

abstract:
  The paradigm for Anomalous X-ray Pulsars (AXPs) has evolved recently with the
discovery by INTEGRAL and RXTE of flat, hard X-ray components in three AXPs.
These non-thermal spectral components differ dramatically from the steeper
quasi-power-law tails seen in the classic X-ray band in these sources, and can
naturally be attributed to activity in the magnetosphere. Resonant, magnetic
Compton upscattering is a candidate mechanism for generating this new
component, since it is very efficient in the strong fields present near AXP
surfaces. In this paper, results from an inner magnetospheric model for
upscattering of surface thermal X-rays in AXPs are presented, using a kinetic
equation formalism and employing a QED magnetic scattering cross section.
Characteristically flat and strongly-polarized emission spectra are produced by
non-thermal electrons injected in the emission region. Spectral results depend
strongly on the observer's orientation and the magnetospheric locale of the
scattering, which couple directly to the angular distributions of photons
sampled. Constraints imposed by the Comptel upper bounds for these AXPs are
mentioned.


title: Four-dimensional Osserman metrics of neutral signature

abstract:
  In the algebraic context, we show that null Osserman, spacelike Osserman, and
timelike Osserman are equivalent conditions for a model of signature (2,2). We
also classify the null Jordan Osserman models of signature (2,2). In the
geometric context, we show that a pseudo-Riemannian manifold of signature (2,2)
is null Jordan Osserman if and only if either it has constant sectional
curvature or it is locally a complex space form.


title: The Structure of the DoAr 25 Circumstellar Disk

abstract:
  We present high spatial resolution (< 0.3" = 40$ AU) Submillimeter Array
observations of the 865 micron continuum emission from the circumstellar disk
around the young star DoAr 25. Despite its bright millimeter emission, this
source exhibits only a comparatively small infrared excess and low accretion
rate, suggesting that the material and structural properties of the inner disk
may be in an advanced state of evolution. A simple model of the physical
conditions in the disk is derived from the submillimeter visibilities and the
complete spectral energy distribution using a Monte Carlo radiative transfer
code. For the standard assumption of a homogeneous grain size distribution at
all disk radii, the results indicate a shallow surface density profile, $\Sigma
\propto r^{-p}$ with p = 0.34, significantly less steep than a steady-state
accretion disk (p = 1) or the often adopted minimum mass solar nebula (p =
1.5). Even though the total mass of material is large (M_d = 0.10 M_sun), the
densities inferred in the inner disk for such a model may be too low to
facilitate any mode of planet formation. However, alternative models with
steeper density gradients (p = 1) can explain the observations equally well if
substantial grain growth in the planet formation region (r < 40 AU) has
occurred. We discuss these data in the context of such models with dust
properties that vary with radius and highlight their implications for
understanding disk evolution and the early stages of planet formation.


title:
`Tail-end' Bondi-Hoyle accretion in young star clusters: Implications
  for disks, planets, and stars

abstract:
  Young stars orbiting in the gravitational potential well of forming star
clusters pass through the cluster's dense molecular gas and can experience
Bondi-Hoyle accretion from reservoirs outside their individual protostellar
cloud cores. Accretion can occur for several million years after the stars
form, but before the cluster disperses. This accretion is predominantly onto
the disk and not the star. N-body simulations of stars orbiting in three young
model clusters containing 30, 300, and 3000 stars are presented. The
simulations include the gravitational potential of the molecular gas which
smoothly disperses over time. The clusters have a star formation efficiency of
33% and a radius of 0.22 pc. We find that the disks surrounding solar-mass
stars in the N=30 cluster accretes ~0.01 M_sol (~1 minimum-mass solar nebula,
MMSN) per Myr. The accretion rate scales as M^2.1 for stars of mass M. The
accretion rate is ~5 times lower for N=3000 cluster, due to its higher stellar
velocities and higher temperature. The Bondi-Hoyle accretion rates onto the
disks are several times lower than accretion rates observed directly onto young
stars (e.g., Muzerolle et al 2005): these two accretion rates follow the same
M^2 behavior and may be related. The accreted disk mass is large enough that it
may have a substantial and unappreciated effect on disk structure and the
formation of planetary systems. We discuss a variety of implications of this
process, including its effect on metallicity differences between cluster stars,
compositional differences between a star and its disk, the formation of
terrestrial and gas-giant planets, and isotopic anomalies observed in our Solar
System.


title:
[Ne II] Observations of Gas Motions in Compact and Ultracompact H II
  Regions

abstract:
  We present high spatial and spectral resolution observations of sixteen
Galactic compact and ultracompact H II regions in the [Ne II] 12.8 microns fine
structure line. The small thermal width of the neon line and the high dynamic
range of the maps provide an unprecedented view of the kinematics of compact
and ultracompact H II regions. These observations solidify an emerging picture
of the structure of ultracompact H II regions suggested in our earlier studies
of G29.96-0.02 and Mon R2 IRS1; systematic surface flows, rather than
turbulence or bulk expansion, dominate the gas motions in the H II regions. The
observations show that almost all of the sources have significant (5-20 km/s)
velocity gradients and that most of the sources are limb-brightened. In many
cases, the velocity pattern implies tangential flow along a dense shell of
ionized gas. None of the observed sources clearly fits into the categories of
filled expanding spheres, expanding shells, filled blister flows, or cometary H
II regions formed by rapidly moving stars. Instead, the kinematics and
morphologies of most of the sources lead to a picture of H II regions confined
to the edges of cavities created by stellar wind ram pressure and flowing along
the cavity surfaces. In sources where the radio continuum and [Ne II]
morphologies agree, the majority of the ionic emission is blue-shifted relative
to nearby molecular gas. This is consistent with sources lying on the near side
of their natal clouds being less affected by extinction and with gas motions
being predominantly outward, as is expected for pressure-driven flows.


title:
A Multilinear Operator for Almost Product Evaluation of Hankel
  Determinants

abstract:
  In a recent paper we have presented a method to evaluate certain Hankel
determinants as almost products; i.e. as a sum of a small number of products.
The technique to find the explicit form of the almost product relies on
differential-convolution equations and trace calculations. In the trace
calculations a number of intermediate nonlinear terms involving determinants
occur, but only to cancel out in the end. In this paper, we introduce a class
of multilinear operators \gamma acting on tuples of matrices as an alternative
to the trace method. These operators do not produce extraneous nonlinear terms,
and can be combined easily with differentiation. The paper is self contained.
An example of an almost product evaluation using \gamma-operators is worked out
in detail and tables of the \gamma-operator values on various forms of matrices
are provided. We also present an explicit evaluation of a new class of Hankel
determinants and conjectures.


title: Joint Beamforming for Multiaccess MIMO Systems with Finite Rate Feedback

abstract:
  This paper considers multiaccess multiple-input multiple-output (MIMO)
systems with finite rate feedback. The goal is to understand how to efficiently
employ the given finite feedback resource to maximize the sum rate by
characterizing the performance analytically. Towards this, we propose a joint
quantization and feedback strategy: the base station selects the strongest
users, jointly quantizes their strongest eigen-channel vectors and broadcasts a
common feedback to all the users. This joint strategy is different from an
individual strategy, in which quantization and feedback are performed across
users independently, and it improves upon the individual strategy in the same
way that vector quantization improves upon scalar quantization. In our proposed
strategy, the effect of user selection is analyzed by extreme order statistics,
while the effect of joint quantization is quantified by what we term ``the
composite Grassmann manifold''. The achievable sum rate is then estimated by
random matrix theory. Due to its simple implementation and solid performance
analysis, the proposed scheme provides a benchmark for multiaccess MIMO systems
with finite rate feedback.


title:
Single flux quantum circuits with damping based on dissipative
  transmission lines

abstract:
  We propose and demonstrate the functioning of a special Rapid Single Flux
Quantum (RSFQ) circuit with frequency-dependent damping. This damping is
achieved by shunting individual Josephson junctions by pieces of open-ended RC
transmission lines. Our circuit includes a toggle flip-flop cell, Josephson
transmission lines transferring single flux quantum pulses to and from this
cell, as well as DC/SFQ and SFQ/DC converters. Due to the desired
frequency-dispersion in the RC line shunts which ensures sufficiently low noise
at low frequencies, such circuits are well-suited for integrating with the
flux/phase Josephson qubit and enable its efficient control.


title:
Anomalously large measured thermoelectric power factor in
  Sr$_{1-x}$La$_x$TiO$_3$ thin films due to SrTiO$_3$ substrate reduction

abstract:
  We report the observation that thermoelectric thin-films of La-doped SrTiO3
grown on SrTiO3 substrates yield anomalously high values of thermopower to give
extraordinary values of power factor at 300K. Thin-films of Sr0.98La0.02TiO3,
grown via pulsed laser deposition at low temperature and low pressure (450C,
10-7Torr), do not yield similarly high values when grown on other substrates.
The thin-film growth induces oxygen reduction in the SrTiO3 crystals, doping
the substrate n-type. It is found that the backside resistance of the SrTiO3
substrates is as low (~12ohm/square) as it is on the film-side after film
growth.


title: Weakly irreducible subgroups of $Sp(1,n+1)$

abstract:
  Connected weakly irreducible not irreducible subgroups of $Sp(1,n+1)\subset
SO(4,4n+4)$ that satisfy a certain additional condition are classified. This
will be used to classify connected holonomy groups of pseudo-hyper-K\"ahlerian
manifolds of index 4.


title:
Very Large Array Observations of Galactic Center OH 1720 MHz Masers in
  Sagittarius A East and in the Circumnuclear Disk

abstract:
  We present Very Large Array (VLA) radio interferometry observations of the
1720 MHz OH masers in the Galactic Center (GC). Most 1720 MHz OH masers arise
in regions where the supernova remnant Sgr A East is interacting with the
interstellar medium. The majority of the newly found 1720 MHz OH masers are
located to the northeast, independently indicating and confirming an area of
shock interaction with the +50 km/s molecular cloud (M-0.02-0.07) on the far
side of Sgr A East. The previously known bright masers in the southeast are
suggested to be the result of the interaction between two supernova remnants,
instead of between Sgr A East and the surrounding molecular clouds as generally
found elsewhere in the Galaxy. Together with masers north of the circumnuclear
disk (CND) they outline an interaction on the near side of Sgr A East. In
contrast to the interaction between the +50 km/s cloud and Sgr A East, OH
absorption data do not support a direct interaction between the CND material
and Sgr A East. We also present three new high-negative velocity masers,
supporting a previous single detection. The location and velocities of the
high-negative and high-positive velocity masers are consistent with being near
the tangent points of, and physically located in the CND. We argue that the
high velocity masers in the CND are pumped by dissipation between density
clumps in the CND instead of a shock generated by the supernova remnant. That
is, the CND masers are not coupled to the supernova remnant and are sustained
independently.


title: Asymptotic behavior of permutation records

abstract:
  We study the asymptotic behavior of two statistics defined on the symmetric
group S_n when n tends to infinity: the number of elements of S_n having k
records, and the number of elements of S_n for which the sum of the positions
of their records is k. We use a probabilistic argument to show that the scaled
asymptotic behavior of these statistics can be described by remarkably simple
functions.


title:
Electroexcitation of the Roper resonance for 1.7 < Q2 < 4.5 GeV2 in ep
  -> enpi+

abstract:
  The helicity amplitudes of the electroexcitation of the Roper resonance are
extracted for 1.7 < Q2 < 4.5 GeV2 from recent high precision JLab-CLAS cross
section and longitudinally polarized beam asymmetry data for pi+
electroproduction on protons at W=1.15-1.69 GeV. The analysis is made using two
approaches, dispersion relations and a unitary isobar model, which give
consistent results. It is found that the transverse helicity amplitude A_{1/2}
for the gamma* p -> N(1440)P11 transition, which is large and negative at Q2=0,
becomes large and positive at Q2 ~ 2 GeV2, and then drops slowly with Q2. The
longitudinal helicity amplitude S_{1/2}, which was previously found from CLAS
ep -> eppi0,enpi+ data to be large and positive at Q2=0.4,0.65 GeV2, drops with
Q2. Available model predictions for gamma* p -> N(1440)P11 allow us to conclude
that these results provide strong evidence in favor of N(1440)P11 as a first
radial excitation of the 3q ground state. The results of the present paper also
confirm the conclusion of our previous analysis for Q2 < 1 GeV2 that the
presentation of N(1440)P11 as a 3qG hybrid state is ruled out.


title:
Efficient stochastic sampling of first-passage times with applications
  to self-assembly simulations

abstract:
  Models of reaction chemistry based on the stochastic simulation algorithm
(SSA) have become a crucial tool for simulating complicated biological reaction
networks due to their ability to handle extremely complicated reaction networks
and to represent noise in small-scale chemistry. These methods can, however,
become highly inefficient for stiff reaction systems, those in which different
reaction channels operate on widely varying time scales. In this paper, we
develop two methods for accelerating sampling in SSA models: an exact method
and a scheme allowing for sampling accuracy up to any arbitrary error bound.
Both methods depend on analysis of the eigenvalues of continuous time Markov
model graphs that define the behavior of the SSA. We demonstrate these methods
for the specific application of sampling breakage times for multiply-connected
bond networks, a class of stiff system important to models of self-assembly
processes. We show theoretically and empirically that our eigenvalue methods
provide substantially reduced sampling times for a wide range of network
breakage models. These techniques are also likely to have broad use in
accelerating SSA models so as to apply them to systems and parameter ranges
that are currently computationally intractable.


title:
Linear, diatomic crystal: single-electron states and large-radius
  excitons

abstract:
  The large-radius exciton spectrum in a linear crystal with two atoms in the
unit cell was obtained using the single-electron eigenfunctions and the band
structure, which were found by the zero-range potential (ZRP) method. The
ground-state exciton binding energies for the crystal in vacuum appeared to be
larger than the corresponding energy gaps for any set of the crystal
parameters.


title: Hyperdeterminantal point processes

abstract:
  As well as arising naturally in the study of non-intersecting random paths,
random spanning trees, and eigenvalues of random matrices, determinantal point
processes (sometimes also called fermionic point processes) are relatively easy
to simulate and provide a quite broad class of models that exhibit repulsion
between points. The fundamental ingredient used to construct a determinantal
point process is a kernel giving the pairwise interactions between points: the
joint distribution of any number of points then has a simple expression in
terms of determinants of certain matrices defined from this kernel. In this
paper we initiate the study of an analogous class of point processes that are
defined in terms of a kernel giving the interaction between $2M$ points for
some integer $M$. The role of matrices is now played by $2M$-dimensional
"hypercubic" arrays, and the determinant is replaced by a suitable
generalization of it to such arrays -- Cayley's first hyperdeterminant. We show
that some of the desirable features of determinantal point processes continue
to be exhibited by this generalization.


title:
Femtosecond Demagnetization and Hot Hole Relaxation in Ferromagnetic
  GaMnAs

abstract:
  We have studied ultrafast photoinduced demagnetization in GaMnAs via
two-color time-resolved magneto-optical Kerr spectroscopy. Below-bandgap
midinfrared pump pulses strongly excite the valence band, while near-infrared
probe pulses reveal sub-picosecond demagnetization that is followed by an
ultrafast ($\sim$1 ps) partial recovery of the Kerr signal. Through comparison
with InMnAs, we attribute the signal recovery to an ultrafast energy relaxation
of holes. We propose that the dynamical polarization of holes through $p$-$d$
scattering is the source of the observed probe signal. These results support
the physical picture of femtosecond demagnetization proposed earlier for
InMnAs, identifying the critical roles of both energy and spin relaxation of
hot holes.


title:
Light-Front Dynamics and AdS/QCD Correspondence: Gravitational Form
  Factors of Composite Hadrons

abstract:
  Light-front holography is a remarkable feature of the AdS/CFT correspondence
between gravity in AdS space and conformal field theories in physical
space-time; it allows string modes $\Phi(z)$ in the anti-de Sitter (AdS) fifth
dimension to be precisely mapped to the light-front wavefunctions of hadrons in
physical space-time in terms of a specific light-front impact variable $\zeta$
which measures the separation of the quark and gluonic constituents within the
hadron. This mapping was originally obtained by matching the exact expression
for electromagnetic current matrix elements in AdS space with the corresponding
exact expression for the current matrix element using light-front theory in
physical space-time. In this paper we show that one obtains the identical
holographic mapping using matrix elements of the energy-momentum tensor. To
prove this, we show that there exists a correspondence between the matrix
elements of the energy-momentum tensor of the fundamental hadronic constituents
in QCD with the transition amplitudes describing the interaction of string
modes in AdS space with an external graviton field which propagates in the AdS
interior. The agreement of the results for electromagnetic and gravitational
hadronic transition amplitudes provides an important consistency test and
verification of holographic mapping from AdS to physical observables defined on
the light-front.


title: On the role of Convexity in Functional and Isoperimetric Inequalities

abstract:
  This is a continuation of our previous work 0712.4092. It is well known that
various isoperimetric inequalities imply their functional ``counterparts'', but
in general this is not an equivalence. We show that under certain convexity
assumptions (e.g. for log-concave probability measures in Euclidean space), the
latter implication can in fact be reversed for very general inequalities,
generalizing a reverse form of Cheeger's inequality due to Buser and Ledoux. We
develop a coherent single framework for passing between isoperimetric
inequalities, Orlicz-Sobolev functional inequalities and capacity inequalities,
the latter being notions introduced by Maz'ya and extended by
Barthe--Cattiaux--Roberto. As an application, we extend the known results due
to the latter authors about the stability of the isoperimetric profile under
tensorization, when there is no Central-Limit obstruction. As another
application, we show that under our convexity assumptions, $q$-log-Sobolev
inequalities ($q \in [1,2]$) are equivalent to an appropriate family of
isoperimetric inequalities, extending results of Bakry--Ledoux and
Bobkov--Zegarlinski. Our results extend to the more general setting of
Riemannian manifolds with density which satisfy the $CD(0,\infty)$
curvature-dimension condition of Bakry--\'Emery.


title: Sterile Neutrinos in a 6x6 Matrix Approach

abstract:
  Quark-lepton symmetry invites consideration of the existence of sterile
neutrinos. Long ago, we showed that this approach predicts large neutrino
mixing amplitudes. Using a Weyl spinor approach, we show, in an analytic
example, how this, and pseudo-Dirac pairing, can develop within a reduced rank
version of the conventional see-saw mechanism, from small intrinsic mixing
strengths. We show by numerical examples that mixing of active and sterile
neutrinos can affect the structure of oscillations relevant to extraction of
neutrino mixing parameters from neutrino oscillation data.


title: Deep-Elastic pp Scattering at LHC from Low-x Gluons

abstract:
  Deep-elastic pp scattering at c.m. energy 14 TeV at LHC in the momentum
transfer range 4 GeV*2 < |t| < 10 GeV*2 is planned to be measured by the TOTEM
group. We study this process in a model where the deep-elastic scattering is
due to a single hard collision of a valence quark from one proton with a
valence quark from the other proton. The hard collision originates from the
low-x gluon cloud around one valence quark interacting with that of the other.
The low-x gluon cloud can be identified as color glass condensate and has size
~0.3 F. Our prediction is that pp differential cross section in the large |t|
region decreases smoothly as momentum transfer increases. This is in contrast
to the prediction of pp differential cross section with visible oscillations
and smaller cross sections by a large number of other models.


title: Exclusive electroproduction of strange mesons with JLab 12 GeV

abstract:
  We summarize the physics topics which can be addressed by measurements of
high-Q^2 exclusive electroproduction of strange mesons, gamma* N -> phi N, K*
Lambda, K Lambda, K Sigma, at Jefferson Lab with 11 GeV beam energy. The
proposed investigations are aimed both at exploring the reaction mechanism
(dominance of point-like configurations) and extracting information about
baryon structure from the data (generalized parton distributions, or GPDs).
They include (a) probing the t-dependence of the nucleon's gluon GPD
(transverse spatial distribution of gluons) in phi meson production; (b)
separating the nucleon helicity-flip and nonflip quark GPDs in K* Lambda
production with measurement of the Lambda recoil polarization; (c) probing
strangeness polarization in the nucleon in K Lambda and K Sigma production.
These studies rely only on the analysis of cross section ratios, which are less
affected by the theoretical uncertainties of present GPD-based calculations
than absolute cross sections.


title: Genus four superstring measures

abstract:
  A main issue in superstring theory are the superstring measures. D'Hoker and
Phong showed that for genus two these reduce to measures on the moduli space of
curves which are determined by modular forms of weight eight and the bosonic
measure. They also suggested a generalisation to higher genus. We showed that
their approach works, with a minor modification, in genus three and we
announced a positive result also in genus four. Here we give the modular form
in genus four explicitly. Recently S. Grushevsky published this result as part
of a more general approach.


title: Current-induced domain wall motion in Rashba spin-orbit system

abstract:
  Current-induced magnetic domain wall motion, induced by transfer of spin
transfer effect due to exchange interaction, is expected to be useful for next
generation high-density storages. We here show that efficient domain wall
manipulation can be achieved by introduction of Rashba spin-orbit interaction,
which induces spin precession of conduction electron and acts as an effective
magnetic field. Its effect on domain wall motion depends on the wall
configuration. We found that the effect is significant for Bloch wall with the
hard axis along the current, since the effective field works as $\beta$ or
field-like term and removes the threshold current if in extrinsic pinning is
absent. For N\'eel wall and Bloch wall with easy axis perpendicular to Rashba
plane, the effective field induces a step motion of wall corresponding to a
rotation of wall plane by the angle of approximately $\pi$ at current lower
than intrinsic threshold. Rashba interaction would therefore be useful to
assist efficient motion of domain walls at low current.


title: Some remarks on point split commutators

abstract:
  Point splitting has been suggested as a way to deal with anomalous
commutators in quantum field theory. It has been pointed out by D.G.
Boulware[4] that in order to obtain a mathematically consistent theory the
Hamiltonian operator must be point split also. We will examine the effect of
point splitting the Hamiltonian for a free fermion field in 1-1D space-time. It
will be shown that when the Hamiltonian operator is point split then quantum
states will exist with less energy than the normal vacuum state. This requires
the vacuum state to be redefined.


title:
Algebro-Geometric Invariants of Finitely Generated Groups (The Profile
  of a Representation Variety)

abstract:
  If G is a finitely generated group, and A an algebraic group, then Hom(G,A)
is a possibly reducible algebraic variety denoted by R_A(G). Here we define the
profile function, P_d(R_A(G)), of the representation variety of G over A to be
P_d(R_A(G))=(N_d(R_A(G)),...,N_0(R_A(G))), where N_i(R_A(G)) stands for the
number of irreducible components of R_A(G) of dimension i, where 0\leq i\leq d,
and d=Dim(R_A(G)). We then use this invariant in the study of fg groups and
prove various results. In particular, we show that if G an orientable surface
group of genus g\geq 1, then P_d(R_{SL(2,C)}(G))\neq P_d(R_{PSL(2,C)}(G)). We
also show that the same holds for G a torus knot group with presentation
<x,y;x^p=y^t> where both p,t are greater than 2, and that the same also holds
when G is a the fundamental group of a compact non-orientable surface of genus
g\geq 3. Further, we show that if a group G can be n+1 generated, and presented
by <x_1,...,x_n,y ; W=y^p>, where W is a non-trivial word in F_n=<x_1,...,x_n>,
and A=PSL(2, C), that then Dim(R_{A}(G)) is equal to Max{3n, Dim(R_{A}(G'))+2
\} \leq 3n+1, where G'=<x_1,...,x_n; W=1>. We also give a condition
guaranteeing that the resulting algebraic variety is reducible.


title: Acoustic dispersion in a two-dimensional dipole system

abstract:
  We calculate the full density response function, and from it the
long-wavelength acoustic dispersion for a two-dimensional system of strongly
coupled point dipoles interacting through a 1/r^3 potential at arbitrary
degeneracy. Such a system has no RPA limit and the calculation has to include
correlations from the outset. We follow the Quasi-Localized Charge (QLC)
approach, accompanied by Molecular Dynamics (MD) simulations. Similarly to what
has been recently reported for the closely spaced classical electron-hole
bilayer [G. J. Kalman et al. Phys. Rev. Lett. 98, 236801 (2007)] and in marked
contrast to the RPA, we report a long-wavelength acoustic phase velocity that
is wholly maintained by particle correlations and varies linearly with the
dipole moment p. The oscillation frequency, calculated both in an extended QLC
approximation and in the Singwi-Tosi-Land-Sjolander approximation, is invariant
in form over the entire classical to quantum domains all the way down to zero
temperature. Based on our classical MD-generated pair distribution function
data and on ground-state energy data generated by recent quantum Monte Carlo
simulations on a bosonic dipole system [Astrakharchik et al, Phys. Rev. Lett.
98, 060405 (2007)], there is a good agreement between the QLCA kinetic sound
speeds and the standard thermodynamic sound speeds in both the classical and
quantum domains.


title:
The (Re-)Discovery of G350.1-0.3: A Young, Luminous Supernova Remnant
  and Its Neutron Star

abstract:
  We present an XMM-Newton observation of the long-overlooked radio source
G350.1-0.3. The X-ray spectrum of G350.1-0.3 can be fit by a shocked plasma
with two components: a high-temperature (1.5 keV) region with a low ionization
time scale and enhanced abundances, plus a cooler (0.36 keV) component in
ionization equilibrium and with solar abundances. The X-ray spectrum and the
presence of non-thermal, polarized, radio emission together demonstrate that
G350.1-0.3 is a young, luminous supernova remnant (SNR), for which archival HI
and 12-CO data indicate a distance of 4.5 kpc. The diameter of the source then
implies an age of only ~900 years. The SNR's distorted appearance, small size
and the presence of 12-CO emission along the SNR's eastern edge all indicate
that the source is interacting with a complicated distribution of dense ambient
material. An unresolved X-ray source, XMMU J172054.5-372652, is detected a few
arcminutes west of the brightest SNR emission. The thermal X-ray spectrum and
lack of any multi-wavelength counterpart suggest that this source is a neutron
star associated with G350.1-0.3, most likely a "central compact object", as
seen coincident with other young SNRs such as Cassiopeia A.


title: Quantum theory of optical temporal phase and instantaneous frequency

abstract:
  We propose a general quantum theory of optical phase and instantaneous
frequency in the time domain for slowly varying optical signals. Guided by
classical estimation theory, we design homodyne phase-locked loops that enable
quantum-limited measurements of temporal phase and instantaneous frequency.
Standard and Heisenberg quantum limits to such measurements are then derived.
For optical sensing applications, we propose multipass and Fabry-P\'erot
position and velocity sensors that take advantage of the signal-to-noise-ratio
enhancement effect of wideband angle modulation without requiring nonclassical
light. We also generalize our theory to three spatial dimensions for
nonrelativistic bosons and define an Hermitian fluid velocity operator, which
provides a theoretical underpinning to the current-algebra approach of quantum
hydrodynamics.


title:
Large amplitude coherent state superposition generated by a
  time-separated two-photon subtraction from a continuous wave squeezed vacuum

abstract:
  Theoretical analysis is given for a two-photon subtraction from a continuous
wave (CW) squeezed vacuum with finite time separation between two detection
events. In the CW photon subtraction process, the generated states are
inevitably described by temporal mutimode states. Our approach is based on
Schr\"{o}dinger picture which provides mathematically simple forms and an
intuitive understanding of its multimode structure. We show that, in our
process, the photon subtracted squeezed vacuum is generated in two temporal
modes and one of these modes acts as an ancillary mode to make the other one a
large amplitude coherent state superposition.


title: A Note on Approximately Divisible C$^*$-algebras

abstract:
  Let $\mathcal A$ be a separable, unital, approximately divisible
C$^*$-algebra. We show that $\mathcal A$ is generated by two self-adjoint
elements and the topological free entropy dimension of any finite generating
set of $\mathcal A$ is less than or equal to 1. In addition, we show that the
similarity degree of $\mathcal A$ is at most 5. Thus an approximately divisible
C$^*$-algebra has an affirmative answer to Kadison's similarity problem.


title:
Correlation between the energy shell structure and geometry in metallic
  nanoclusters: quasi-resonance states, isotope effect

abstract:
  Metallic nanoclusters displaying electronic shell structure exhibit the
special feature of a correlation between their geometry and the number of
delocalized electrons . Their shape evolution can be described as a quantum
oscillation between quasi-resonant states (prolate and oblate configurations)
whose amplitudes depend upon the degree of shell filling. The picture explains
the evolution of absorption spectra and predicts a peculiar isotope effect .


title:
A semi-empirical model for two-level system noise in superconducting
  microresonators

abstract:
  We present measurements of the low--temperature excess frequency noise of
four niobium superconducting coplanar waveguide microresonators, with center
strip widths $s_r$ ranging from 3 $\mu$m to 20 $\mu$m. For a fixed internal
power, we find that the frequency noise decreases rapidly with increasing
center strip width, scaling as $1/s_r^{1.6}$. We show that this geometrical
scaling is readily explained by a simple semi-empirical model which assumes a
surface distribution of independent two-level system fluctuators. These results
allow the resonator geometry to be optimized for minimum noise.


title: Redshifted 21cm Observations of High Redshift Quasar Proximity Zones

abstract:
  The introduction of low-frequency radio arrays is expected to revolutionize
the study of the reionization epoch. Observation of the contrast in redshifted
21cm emission between a large HII region and the surrounding neutral
inter-galactic medium (IGM) will be the simplest and most easily interpreted
signature. However the highest redshift quasars known are thought to reside in
an ionized IGM. Using a semi-analytic model we describe the redshifted 21cm
signal from the IGM surrounding quasars discovered using the i-drop out
technique (i.e. quasars at z~6). We argue that while quasars at z<6.5 seem to
reside in the post overlap IGM, they will still provide valuable probes of the
late stages of the overlap era because the light-travel time across a quasar
proximity zone should be comparable to the duration of overlap. For redshifted
21cm observations within a 32MHz bandpass, we find that the subtraction of a
spectrally smooth foreground will not remove spectral features due to the
proximity zone. These features could be used to measure the neutral hydrogen
content of the IGM during the late stages of reionization. The density of
quasars at z~6 is now well constrained. We use the measured quasar luminosity
function to estimate the prospects for discovery of high redshift quasars in
fields that will be observed by the Murchison Widefield Array.


title:
Non-universal dependence of spatiotemporal regularity on randomness in
  coupling connections

abstract:
  We investigate the spatiotemporal dynamics of a network of coupled nonlinear
oscillators, modeled by sine circle maps, with varying degrees of randomness in
coupling connections. We show that the change in the basin of attraction of the
spatiotemporal fixed point due to varying fraction of random links $p$, is
crucially related to the nature of the local dynamics. Even the qualitative
dependence of spatiotemporal regularity on $p$ changes drastically as the
angular frequency of the oscillators change, ranging from monotonic increase or
monotonic decrease, to non-monotonic variation. Thus it is evident here that
the influence of random coupling connections on spatiotemporal order is highly
non-universal, and depends very strongly on the nodal dynamics.


title: Ramification estimates for the hyperbolic Gauss map

abstract:
  We give the best possible upper bound on the number of exceptional values and
the totally ramified value number of the hyperbolic Gauss map for
pseudo-algebraic constant mean curvature one surfaces in the hyperbolic
three-space and some partial results on the Osserman problem for algebraic
case. Moreover, we study the value distribution of the hyperbolic Gauss map for
complete constant mean curvature one faces in de Sitter three-space.


title:
Atomic noise spectra in nonlinear magneto-optical rotation in a rubidium
  vapor

abstract:
  We have studied the noise spectra in a nonlinear magneto-optical rotation
experiment in a rubidium vapor. We observed the reduction of noise in the
intensity difference of two orthogonally polarized components of the laser
beam. The dependence of the noise level on both the frequency and the
longitudinal magnetic field has been studied. We found that the optimal
condition for the noise reduction is to work around zero longitudinal magnetic
field, where the intensity correlation between the two orthogonally polarized
components is maximum. Our results can be used to reduce or eliminate the
atomic excess noise, therefore improving the sensitivity of nonlinear
magneto-optical rotation magnetometers and other atom-optical based
applications.


title:
On solvability of a partial integral equation in the space
  ${L_2(\Omega\times\Omega)}$

abstract:
  In this paper we investigate solvability of a partial integral equation in
the space $L_2(\Omega\times\Omega),$ where $\Omega=[a,b]^\nu.$ We define a
determinant for the partial integral equation as a continuous function on
$\Omega$ and for a continuous kernels of the partial integral equation we give
explicit description of the solution.


title:
Physical Results from 2+1 Flavor Domain Wall QCD and SU(2) Chiral
  Perturbation Theory

abstract:
  We have simulated QCD using 2+1 flavors of domain wall quarks on a $(2.74
{\rm fm})^3$ volume with an inverse lattice scale of $a^{-1} = 1.729(28)$ GeV.
The up and down (light) quarks are degenerate in our calculations and we have
used four values for the ratio of light quark masses to the strange (heavy)
quark mass in our simulations: 0.217, 0.350, 0.617 and 0.884. We have measured
pseudoscalar meson masses and decay constants, the kaon bag parameter $B_K$ and
vector meson couplings. We have used SU(2) chiral perturbation theory, which
assumes only the up and down quark masses are small, and SU(3) chiral
perturbation theory to extrapolate to the physical values for the light quark
masses. While next-to-leading order formulae from both approaches fit our data
for light quarks, we find the higher order corrections for SU(3) very large,
making such fits unreliable. We also find that SU(3) does not fit our data when
the quark masses are near the physical strange quark mass. Thus, we rely on
SU(2) chiral perturbation theory for accurate results. We use the masses of the
$\Omega$ baryon, and the $\pi$ and $K$ mesons to set the lattice scale and
determine the quark masses. We then find $f_\pi = 124.1(3.6)_{\rm
stat}(6.9)_{\rm syst} {\rm MeV}$, $f_K = 149.6(3.6)_{\rm stat}(6.3)_{\rm syst}
{\rm MeV}$ and $f_K/f_\pi = 1.205(0.018)_{\rm stat}(0.062)_{\rm syst}$. Using
non-perturbative renormalization to relate lattice regularized quark masses to
RI-MOM masses, and perturbation theory to relate these to $\bar{\rm MS}$ we
find $ m_{ud}^{\bar{\rm MS}}(2 {\rm GeV}) = 3.72(0.16)_{\rm stat}(0.33)_{\rm
ren}(0.18)_{\rm syst} {\rm MeV}$ and $m_{s}^{\bar{\rm MS}}(2 {\rm GeV}) =
107.3(4.4)_{\rm stat}(9.7)_{\rm ren}(4.9)_{\rm syst} {\rm MeV}$.


title:
An efficient algorithm for granular dynamics simulation with
  complex-shaped objects

abstract:
  The most difficult aspect of the realistic modeling of granular materials is
how to capture the real shape of the particles. Here we present a method to
simulate granular materials with complex-shaped particles. The particle shape
is represented by the classical concept of a Minkowski sum, which permits the
representation of complex shapes without the need to define the object as a
composite of spherical or convex particles. A well defined interaction force
between these bodies is derived. The algorithm for identification of neighbor
particles reduces force calculations to O(N), where $N$ is the number of
particles. The algorithm is much more efficient, accurate and easier to
implement than other models. We investigate the existence of a statistical
equilibrium in granular systems with circular non-spherical particles in the
collisional. regime. We also investigate the limit state of dissipative
granular materials using biaxial test simulations. The results are consistent
with the classical assumption of the statistical mechanics for non-dissipative
systems, and the critical state theory of soils mechanics for dissipative
granular materials.


title: Cohen-Macaulay Monomial Ideals of Codimension 2

abstract:
  We give a structure theorem for Cohen Macaulay monomial ideals of codimension
2, and describe all possible relation matrices of such ideals. In case that the
ideal has a linear resolution, the relation matrices can be identified with the
spanning trees of a connected chordal graph with the property that each
distinct pair of maximal cliques of the graph has at most one vertex in common.


title: Quantum Interference Effects Among Helicities at LEP-II and Tevatron

abstract:
  A completely model-independent method of obtaining information on the spin
using the quantum interference effect among various helicity states was
proposed in a recent paper. Here we point out that this effect should be
demonstrable in the existing data on e^-e^+ \to W^+ W^- at LEP-II and p \bar{p}
\to Z^0 + j at Tevatron.