title: An X-ray Survey in SA 57 with XMM-Newton

abstract:
  The maximum number density of Active Galactic Nuclei (AGNs), as deduced from
X-ray studies, occurs at z<~1, with lower luminosity objects peaking at smaller
redshifts. Optical studies lead to a different evolutionary behaviour, with a
number density peaking at z~2 independently of the intrinsic luminosity, but
this result is limited to active nuclei brighter than the host galaxy. A
selection based on optical variability can detect low luminosity AGNs (LLAGNs),
where the host galaxy light prevents the identification by non-stellar colours.
We want to collect X-ray data in a field where it exists an optically-selected
sample of "variable galaxies'', i.e. variable objects with diffuse appearance,
to investigate the X-ray and optical properties of the population of AGNs,
particularly of low luminosity ones, where the host galaxy is visible. We
observed a field of 0.2 deg^2 in the Selected Area 57, for 67ks with
XMM-Newton. We detected X-ray sources, and we correlated the list with a
photographic survey of SA 57, complete to B_J~23 and with available
spectroscopic data. We obtained a catalogue of 140 X-ray sources to limiting
fluxes 5x10^-16, 2x10^-15 erg/cm^2/s in the 0.5-2 keV and 2-10 keV
respectively, 98 of which are identified in the optical bands. The X-ray
detection of part of the variability-selected candidates confirms their AGN
nature. Diffuse variable objects populate the low luminosity side of the
sample. Only 25/44 optically-selected QSOs are detected in X-rays. 15% of all
QSOs in the field have X/O<0.1.


title:
The centrality dependence of elliptic flow, the hydrodynamic limit, and
  the viscosity of hot QCD

abstract:
  We show that the centrality and system-size dependence of elliptic flow
measured at RHIC are fully described by a simple model based on eccentricity
scaling and incomplete thermalization. We argue that the elliptic flow is at
least 25% below the (ideal) ``hydrodynamic limit'', even for the most central
Au-Au collisions. This lack of perfect equilibration allows for estimates of
the effective parton cross section in the Quark-Gluon Plasma and of its
viscosity to entropy density ratio. We also show how the initial conditions
affect the transport coefficients and thermodynamic quantities extracted from
the data, in particular the viscosity and the speed of sound.


title: Advection-dominated accretion flows with causal viscosity

abstract:
  We present the basic equations and sample solutions for the steady-state
global transonic solutions of the advection-dominated accretion flows (ADAFs)
with a causal viscosity prescription. The procedures for the stable numerical
calculations and all explicit formula for obtaining the solutions of ADAFs are
also presented. We solve the transonic solutions of ADAFs by using the explicit
numerical integrations, as in the Runge-Kutta method. In this calculation
method, we first solve the physical values at the sonic radius where
L'Hopital's rule is used. Then, we numerically solve the coupled differential
equations of the radial velocity, the angular momentum, and the sound speed
from the sonic radius in the inward and outward directions. By the calculation
procedures presented in this paper, we can cover all parameter spaces of the
transonic solutions of ADAFs. Sample transonic solutions for ADAF-thick disk
and ADAF-thin disk are presented. The explicit formula for the analytical
expansion around the singular points, the sonic and the viscous points, are
presented. If we set the diffusion timescale to null, the formalism in this
study becomes the formalism of the acausal viscosity that is usually used in
past studies for calculating of the ADAF structure.


title: Atomic physics experiments with trapped and cooled highly charged ions

abstract:
  Trapping and cooling techniques have become very important for many
fundamental experiments in atomic physics. When applied to highly charged ions
confined in Penning traps, these procedures are very effective for testing
quantum electrodynamics in extreme electromagnetic fields produced by heavy
highly charged ions such as uranium U$^{91+}$. In addition, fundamental
constants or nuclear ground state properties can be determined with high
accuracy in these simple systems. Finally, by studying a single trapped
radioactive ion, its nuclear decay can be studied in detail by observing the
disappearance of the signal of the mother and the appearance of that of the
daughter isotope. Such experiments on highly charged ions at extremely low
energy will become possible by the HITRAP facility which is currently being
built up at GSI. Also the future Facility for Antiproton and Ion Research
(FAIR) will be briefly described which is expected to be operational by 2014.


title:
Low frequency dispersive estimates for the wave equation in higher
  dimensions

abstract:
  We prove dispersive estimates at low frequency in dimensions n greater or
equal to 4 for the wave equation for a very large class of real-valued
potentials, provided the zero is neither an eigenvalue nor a resonance.


title:
Searching for coronal radio emission from protostars using
  Very-Long-Baseline Interferometry

abstract:
  In order to directly study the role of magnetic fields in the immediate
vicinity of protostars, we use Very-Long-Baseline Interferometry (VLBI), aiming
at the detection of non-thermal centimetric radio emission. This is technically
the only possibility to study coronal emission at sub-AU resolution. We
performed VLBI observations of the four nearby protostars HL Tau, LDN 1551
IRS5, EC 95, and YLW 15 in order to look for compact non-thermal centimetric
radio emission. For maximum sensitivity, we used the High Sensitivity Array
(HSA) where possible, involving the Very Long Baseline Array (VLBA), the phased
Very Large Array (VLA), as well as the Arecibo, Green Bank, and Effelsberg
radio telescopes. While all four protostars were detected in VLA-only data,
only one source (YLW 15 VLA 2) was detected in the VLBI data. The possibility
of non-detections due to free-free absorption, possibly depending on source
geometry, is considered. For YLW 15 VLA 2, the prospects for an accurate orbit
determination appear to be good.


title:
Weakly Compact "Matrices", Fubini-Like Property and Extension of Densely
  Defined Semigroups of Operators

abstract:
  Taking matrix as a synonym for a numerical function on the Cartesian product
of two (in general, infinite) sets, a simple purely algebraic "reciprocity
property" says that the set of rows spans a finite-dim space iff the set of
columns does so. Similar topological reciprocity properties serve to define
strongly compact and weakly compact matrices, featured in the well-known basic
facts about almost periodic functions and about compact operators. Some
properties, especially for the weak compact case, are investigated, such as the
connection with the matrix having a Fubini-like property for general means.
These are applied to prove possibility of extension to the entire semigroup of
bounded densely defined semigroups of operators in a Banach space with weak
continuity properties.


title: Pseudo-supersymmetry and a Tale of Alternate Realities

abstract:
  We discuss how all variant 10d and 11d maximal supergravities, including star
supergravities and supergravities in different signatures, can be obtained as
different real slices of three complex actions. As an application we study the
recently introduced domain-wall/cosmology correspondence in this approach. We
give an example in 9d and 10d where the domain-wall and corresponding cosmology
can be viewed as different real slices of the same complex solution. We argue
how in this case the pseudo-supersymmetry of the cosmological solutions can be
understood as the invariance under supersymmetry of a variant supergravity.


title:
Tuning Spontaneous Emission versus Forster Energy Transfer in Biological
  Systems by Manipulating the Density of Photonic States

abstract:
  We theoretically discuss how to tune the competition between Forster transfer
and spontaneous emission in a continuous and nondestructive fashion. The
proposed approach is especially suitable for delicate biological systems like
light harvesting complexes and fluorescent protein oligomers. We demonstrate
that the manipulation of the density of photonic states at the emission
frequency of the energy donor results in a change of the quantum efficiencies
of the competing energy transfer and spontaneous emission processes. This
change will be manifested in a modification of the donor and acceptor emission
intensities. Thus, by controlling the local density of photonic states Forster
coupled systems can be manipulated and analyzed without the need to physically
separate donor and acceptor chromophores for individual analysis, which is of
interest, for example, for oligomeric reef coral fluorescent proteins.


title:
Covers of Multiplicative Groups of Algebraically Closed Fields of
  Arbitrary Characteristic

abstract:
  We show that algebraic analogues of universal group covers, surjective group
homomorphisms from a $\mathbb{Q}$-vector space to $F^{\times}$ with "standard
kernel", are determined up to isomorphism of the algebraic structure by the
characteristic and transcendence degree of $F$ and, in positive characteristic,
the restriction of the cover to finite fields. This extends the main result of
"Covers of the Multiplicative Group of an Algebraically Closed Field of
Characteristic Zero" (B. Zilber, JLMS 2007), and our proof fills a hole in the
proof given there.


title: Measurement of D mesons Production in Deep Inelastic Scattering at HERA

abstract:
  Charm production in deep inelastic scattering has been measured with the ZEUS
detector at HERA using an integrated luminosity of 82 pb^{-1}. Charm has been
tagged by reconstructing D^{*+}, D^0, D^{+} and D_s^+ (+ c.c.) charm mesons.
The charm hadrons were measured in the kinematic range p_T(D^{*+},D^0,D^{+}) >
3 GeV, p_T(D_s^+)>2 GeV and |\eta(D)| < 1.6 for 1.5 < Q^2 < 1000 GeV^2 and 0.02
< y < 0.7. The production cross sections were used to extract charm
fragmentation ratios and the fraction of c quarks hadronising into a particular
charm meson in the kinematic range considered. The cross sections were compared
to the predictions of next-to-leading-order QCD, and extrapolated to the full
kinematic region in p_T(D) and \eta(D) in order to determine the open-charm
contribution, F_2^{c\bar{c}}(x,Q^2), to the proton structure function F_2.


title: Path integral quantization of scalar fluctuations above a kink

abstract:
  We quantize scalar fluctuations in 1+1 dimensions above a classical
background kink. The properties of the effective action for the corresponding
classical field are studied with an exact functional method, alternative to
exact Wilsonian renormalization, where the running parameter is a bare mass,
and the regulator of the quantum theory is fixed. We extend this approach, in
an appendix, to a Yukawa interaction in higher dimension.


title: The critical temperature for the BCS equation at weak coupling

abstract:
  For the BCS equation with local two-body interaction $\lambda V(x)$, we give
a rigorous analysis of the asymptotic behavior of the critical temperature as
$\lambda \to 0$. We derive necessary and sufficient conditions on $V(x)$ for
the existence of a non-trivial solution for all values of $\lambda>0$.

categories: cond-mat.supr-con cond-mat.other math-ph math.MP


title:
Enumerating permutations avoiding more than three Babson - Steingr\'\i
  msson patterns

abstract:
  Not long ago, Claesson and Mansour proposed some conjectures about the
enumeration of the permutations avoiding more than three Babson - Steingr\'\i
msson patterns (generalized patterns of type $(1,2)$ or $(2,1)$). The avoidance
of one, two or three patterns has already been considered. Here, the cases of
four and five forbidden patterns are solved and the exact enumeration of the
permutations avoiding them is given, confirming the conjectures of Claesson and
Mansour. The approach we use can be easily extended to the cases of more than
five forbidden patterns.


title:
Biquadratic antisymmetric exchange and the magnetic phase diagram of
  magnetoelectric CuFeO$_2$

abstract:
  Biquadratic {\it antisymmetric} exchange terms of the form $ - [C_{ij}
e^{\alpha}_{ij}({\bf s}_i\times{\bf s}_j)_z]^2$, where ${\bf e}_{ij}$ is the
unit vector connecting sites $i$ and $j$ and $\alpha = x,y$, due partially to
magnetoelectric coupling effects, are shown to be responsible for the spin-flop
helical phase in CuFeO$_2$ at low magnetic field and temperature. Usual
biquadratic {\it symmetric} exchange, likely due to magnetoelastic coupling, is
found to support the stability of axial magnetic states at higher fields in
this nearly-Heisenberg like stacked triangular antiferromagnet. A model
Hamiltonian which also includes substantial interplane and higher-neighbor
intraplane exchange interactions, reproduces the unique series of observed
commensurate and incommensurate periodicity phases with increasing applied
magnetic field in this highly frustrated system. The magnetic field-temperature
phase diagram is discussed in terms of a Landau-type free energy.


title:
Cosmic-Ray Events as Background in Imaging Atmospheric Cherenkov
  Telescopes

abstract:
  The dominant background for observations of gamma-rays in the energy region
above 50 GeV with Imaging Atmospheric Cherenkov telescopes are cosmic-ray
events. The images of most of the cosmic ray showers look significantly
different from those of gamma-rays and are therefore easily discriminated.
However, a small fraction of events seems to be indistinguishable from
gamma-rays. This constitutes an irreducible background to the observation of
high-energy gamma-ray sources, and limits the sensitivity achievable with a
given instrument. Here, a Monte Carlo study of gamma-like cosmic-ray events is
presented. The nature of gamma-like cosmic-ray events, the shower particles
that are responsible for the gamma-like appearance, and the dependence of these
results on the choice of the hadronic interaction model are investigated. Most
of the gamma-like cosmic ray events are characterised by the production of
high-energy pi0's early in the shower development which dump most of the shower
energy into electromagnetic sub-showers. Also Cherenkov light from single muons
can mimic gamma-rays in close-by pairs of telescopes. Differences of up to 25%
in the collection area for gamma-like proton showers between QGSJet/FLUKA and
Sibyll/FLUKA simulations have been found.


title: Fermion Masses and Mixings in GUTs with Non-Canonical U(1)_Y

abstract:
  We discuss fermion masses and mixings in models derived from orbifold GUTs
such that gauge coupling unification is achieved without low energy
supersymmetry by utilizing a non-canonical U(1)_Y. A gauged U(1)_X flavor
symmetry plays an essential role, and the Green-Schwarz mechanism is invoked in
anomaly cancellations. Models containing vector-like particles with masses
close to M_{GUT} are also discussed.


title:
Generalized rotational hamiltonians from nonlinear angular momentum
  algebras

abstract:
  Higgs algebras are used to construct rotational Hamiltonians. The
correspondence between the spectrum of a triaxial rotor and the spectrum of a
cubic Higgs algebra is demonstrated. It is shown that a suitable choice of the
parameters of the polynomial algebra allows for a precise identification of
rotational properties. The harmonic limit is obtained by a contraction of the
algebra, leading to a linear symmetry.


title: Anomalous dimensions at twist-3 in the sl(2) sector of N=4 SYM

abstract:
  We consider twist-3 operators in the sl(2) sector of N=4 SYM built out of
three scalar fields with derivatives. We extract from the Bethe Ansatz
equations of this sector the exact lowest anomalous dimension gamma(s) of
scaling fields for several values of the operator spin s. We propose compact
closed expressions for the spin dependence of gamma(s) up to the four loop
level and show that they obey a simple new twist-3 transcendentality principle.
As a check, we reproduce the four loop universal cusp anomalous dimension
governing the logarithmic large spin limit of gamma(s).


title: A Gravity Dual and LHC Study of Single-Sector Supersymmetry Breaking

abstract:
  We propose a gravitational dual of ``single-sector'' models of supersymmetry
breaking which contain no messenger sector and naturally explain the scale of
supersymmetry breaking and the fermion mass hierarchy. In five dimensions these
models can be given a simple interpretation. Inspired by flux-background
solutions of type IIB supergravity, a metric background that deviates from
AdS_5 in the IR breaks supersymmetry, while the fermion mass hierarchy results
from the wavefunction overlap of bulk fermions with a UV-confined Higgs field.
The first and second generation squarks and sleptons, which are localized near
the IR brane, directly feel the supersymmetry breaking and obtain masses of
order 10 TeV. These are interpreted as composite states of the dual 4D theory.
The gauginos and third generation squarks and sleptons are elementary states
that obtain soft masses of order 1 TeV at the loop level via direct gauge
mediation. This particle spectrum leads to distinctive signatures at the LHC,
similar to the usual gauge mediation with a neutralino NLSP that decays
promptly to a gravitino LSP, but with lower event rates. Nevertheless we show
that with 1-10 fb^{-1} of LHC data "single-sector" models can easily be
detected above background and distinguished from conventional gravity and gauge
mediation.


title:
The subpulse modulation properties of pulsars at 92 cm and the frequency
  dependence of subpulse modulation

abstract:
  A large sample of pulsars has been observed to study their subpulse
modulation at an observing wavelength (when achievable) of both 21 and 92 cm
using the Westerbork Synthesis Radio Telescope. In this paper we present the
92-cm data and a comparison is made with the already published 21-cm results.
We analysed 191 pulsars at 92 cm using fluctuation spectra. The sample of
pulsars is as unbiased as possible towards any particular pulsar
characteristics. For 15 pulsars drifting subpulses are discovered for the first
time and 26 of the new drifters found in the 21-cm data are confirmed. We
discovered nulling for 8 sources and 8 pulsars are found to intermittently emit
single pulses that have pulse energies similar to giant pulses. It is estimated
that at least half of the total population of pulsars have drifting subpulses
when observations with a high enough signal-to-noise ratio would be available.
It could well be that the drifting subpulse mechanism is an intrinsic property
of the emission mechanism itself, although for some pulsars it is difficult or
impossible to detect. Drifting subpulses are in general found at both
frequencies, although the chance of detecting drifting subpulses is possibly
slightly higher at 92 cm. It appears that the youngest pulsars have the most
disordered subpulses and the subpulses become more and more organized into
drifting subpulses as the pulsar ages. The correlations with the modulation
indices are argued to be consistent with the picture in which the radio
emission can be divided in a drifting subpulse signal plus a quasi-steady
signal which becomes, on average, stronger at high observing frequencies. The
measured values of P3 at the two frequencies are highly correlated, but there
is no evidence for a correlation with other pulsar parameters.


title: Simulating spin systems on IANUS, an FPGA-based computer

abstract:
  We describe the hardwired implementation of algorithms for Monte Carlo
simulations of a large class of spin models. We have implemented these
algorithms as VHDL codes and we have mapped them onto a dedicated processor
based on a large FPGA device. The measured performance on one such processor is
comparable to O(100) carefully programmed high-end PCs: it turns out to be even
better for some selected spin models. We describe here codes that we are
currently executing on the IANUS massively parallel FPGA-based system.


title:
Space of Quantum Theory Representations of Natural Numbers, Integers,
  and Rational Numbers

abstract:
  This paper extends earlier work on quantum theory representations of natural
numbers N, integers I, and rational numbers Ra to describe a space of these
representations and transformations on the space. The space is parameterized by
4-tuple points in a parameter set. Each point, (k,m,h,g), labels a specific
representation of X = N, I, Ra as a Fock space F^{X}_{k,m,h} of states of
finite length strings of qukits q and a string state basis B^{X}_{k,m,h,g}. The
pair (m,h) locates the q string in a square integer lattice I \times I, k is
the q base, and the function g fixes the gauge or basis states for each q. Maps
on the parameter set induce transformations on on the representation space.
There are two shifts, a base change operator W_{k',k}, and a basis or gauge
transformation function U_{k}. The invariance of the axioms and theorems for N,
I, and Ra under any transformation is discussed along with the dependence of
the properties of W_{k',k} on the prime factors of k' and k. This suggests that
one consider prime number q's, q_{2}, q_{3}, q_{5}, etc. as elementary and the
base k q's as composites of the prime number q's.


title: Averages of b-hadron properties at the end of 2006

abstract:
  This article reports the world averages for measurements on b-hadron
properties obtained by the Heavy Flavor Averaging Group (HFAG) using the
available results at the end of 2006. In the averaging, the input parameters
used in the various analyses are adjusted (rescaled) to common values, and all
known correlations are taken into account. The averages include lifetimes,
neutral meson mixing parameters, parameters of semileptonic decays, branching
fractions of B decays to final states with open charm, charmonium and no charm,
and measurements related to CP asymmetries.


title: A class of generalized complex Hermite polynomials

abstract:
  A class of generalized complex polynomials of Hermite type, suggested by a
special magnetic Schrodinger operator, is introduced and some related basic
properties are discussed.


title:
A family of (2+1)-dimensional hydrodynamic type systems possessing
  pseudopotential

abstract:
  We construct a family of integrable hydrodynamic type systems with three
independent and n>1 dependent variables in terms of solutions of linear system
of PDEs with rational coefficients. We choose the existence of a
pseudopotential as a criterion of integrability. In the case n=2 this family is
a general solution of the classification problem for such systems. We give also
an elliptic analog of this family in the case n>2.


title:
Dual nature of improper ferroelectricity in a magnetoelectric
  multiferroic

abstract:
  Using first principles calculations, we study the microscopic origin of
ferroelectricity (FE) induced by magnetic order in the orthorhombic HoMnO3. We
obtain the largest ferroelectric polarization observed in the whole class of
improper magnetic ferroelectrics to date. We find that the two proposed
mechanisms for FE in multiferroics, lattice- and electronic-based, are
simultaneously active in this compound: a large portion of the ferroelectric
polarization arises due to quantum-mechanical effects of electron orbital
polarization, in addition to the conventional polar atomic displacements. An
interesting mechanism for switching the magnetoelectric domains by an electric
field via a 180-degree coherent rotation of Mn spins is also proposed.


title: The Rise of Big Bang Models, from Myth to Theory and Observations

abstract:
  We provide an epistemological analysis of the developments of relativistic
cosmology from 1917 to 2006, based on the seminal articles by Einstein, de
Sitter, Friedmann, Lemaitre, Hubble, Gamow and other main historical figures of
the field. It appears that most of the ingredients of the present-day standard
cosmological model, such as the accelation of the expansion due to a repulsive
dark energy, the interpretation of the cosmological constant as vacuum energy
or the possible non-trivial topology of space, had been anticipated by
Lemaitre, although his papers remain desperately unquoted.


title: Binding energies of semirelativistic N-boson systems

abstract:
  General analytic energy bounds are derived for N-boson systems governed by
semirelativistic Hamiltonians of the form
  H=\sum_{i=1}^N \sqrt(p_i^2+m^2) + \sum_{1=i<j}^N V(r_{ij}), where V(r) is a
static attractive pair potential. A translation-invariant model Hamiltonian H_c
is constructed. We conjecture that <H> \ge <H_c> generally, and we prove this
for N=3, and for N=4 when m=0. The conjecture is also valid generally for the
harmonic oscillator and in the nonrelativistic large-m limit. This formulation
allows reductions to scaled 3- or 4-body problems, whose spectral bottoms
provide energy lower bounds. The example of the ultrarelativistic linear
potential is studied in detail and explicit upper- and lower-bound formulas are
derived and compared with earlier bounds.


title:
Fueling the central engine of radio galaxies. I. The molecular/dusty
  disk of 4C 31.04

abstract:
  We report the detection of a massive (M(gas) > 5x10^9 Msun) molecular/dusty
disk of 1.4kpc-size fueling the central engine of the Compact Symmetric Object
(CSO) 4C31.04 based on high-resolution (0.5''--1.2'') observations done with
the IRAM Plateau de Bure interferometer (PdBI). These observations allow for
the first time to detect and map the continuum emission from dust at 218GHz in
the disk of a CSO. The case for a massive disk is confirmed by the detection of
strong HCO+(1--0) line emission and absorption. The molecular gas mass of
4C31.04 is in the range 0.5x10^10--5x10^10Msun. While the distribution and
kinematics of the gas correspond roughly to those of a rotating disk, we find
evidence of distortions and non-circular motions suggesting that the disk is
not in a dynamically relaxed state. We discuss the implications of these
results for the general understanding of the evolution of radio galaxies.


title: Two-loop QED corrections to Bhabha scattering

abstract:
  We obtain a simple relation between massless and massive scattering
amplitudes in gauge theories in the limit where all kinematic invariants are
large compared to particle masses. We use this relation to derive the two-loop
QED corrections to large-angle Bhabha scattering.


title:
Sub-arcsecond CO(1-0) and CO(2-1) observations of the ultraluminous
  infrared galaxy IRAS 10190+1322

abstract:
  We present the results of high resolution mapping of the CO(1-0) and CO(2-1)
emission of the ultraluminous infrared galaxy (ULIRG) IRAS 10190+1322, with the
IRAM interferometer, down to an angular resolution of ~0.3 arcsec. This object
is composed of two interacting galaxies with a projected nuclear separation of
6 kpc, and was selected to analyze the physical and dynamical properties of the
molecular gas in each galaxy in order to study the conditions that lead a
galaxy pair to become ultraluminous in the infrared. With the exception of Arp
220, the closest ULIRG, this is the first time that the CO emission is
morphologically and kinematically resolved in the two interacting galaxies of a
ULIRG system. In one of the galaxies the molecular gas is highly concentrated,
distributed in a circumnuclear disk of 1.7 kpc in size. The molecular gas in
the presumably less infrared luminous galaxy is distributed in a more extended
disk of 7.4 kpc. The molecular gas mass accounts for ~10% of the dynamical mass
in each galaxy. Both objects are rich enough in molecular gas, Mgas ~ 4 10^9
Msun, as to experience an infrared ultraluminous phase.


title:
A Search for Planets Transiting the M Dwarf Debris Disk Host, AU
  Microscopii

abstract:
  We present high cadence, high precision multi-band photometry of the young,
M1Ve, debris disk star, AU Microscopii. The data were obtained in three
continuum filters spanning a wavelength range from 4500\AA to 6600\AA, plus
H$\alpha$, over 28 nights in 2005. The lightcurves show intrinsic stellar
variability due to starspots with an amplitude in the blue band of 0.051
magnitudes and a period of 4.847 days. In addition, three large flares were
detected in the data which all occur near the minimum brightness of the star.
We remove the intrinsic stellar variability and combine the lightcurves of all
the filters in order to search for transits by possible planetary companions
orbiting in the plane of the nearly edge-on debris disk. The combined final
lightcurve has a sampling of 0.35 minutes and a standard deviation of 6.8
millimags (mmag). We performed Monte Carlo simulations by adding fake transits
to the observed lightcurve and find with 95% significance that there are no
Jupiter mass planets orbiting in the plane of the debris disk on circular
orbits with periods, P $\le 5$ days. In addition, there are no young
Neptune-like planets (with radii 2.5$\times$ smaller than the young Jupiter) on
circular orbits with periods, P $\le 3$ days.


title: Phases of QCD, Polyakov Loop and Quasiparticles

abstract:
  QCD thermodynamics is studied using a model which combines Polyakov loop
dynamics with spontaneous chiral symmetry breaking and its restoration (the
PNJL model). The input is fixed entirely by pure-gauge lattice QCD results and
by pion properties in vacuum. Successful comparisons with results from thermal
lattice QCD are achieved, including extrapolations to finite quark chemical
potential. The phase diagram and selected susceptibilities for two quark
flavors are investigated with inclusion of diquark degrees of freedom.


title: Dressing and Wrapping

abstract:
  We prove that the validity of the recently proposed dressed, asymptotic Bethe
ansatz for the planar AdS/CFT system is indeed limited at weak coupling by
operator wrapping effects. This is done by comparing the Bethe ansatz
predictions for the four-loop anomalous dimension of finite-spin twist-two
operators to BFKL constraints from high-energy scattering amplitudes in N=4
gauge theory. We find disagreement, which means that the ansatz breaks down for
length-two operators at four-loop order. Our method supplies precision tools
for multiple all-loop tests of the veracity of any yet-to-be constructed set of
exact spectral equations. Finally we present a conjecture for the exact
four-loop anomalous dimension of the family of twist-two operators, which
includes the Konishi field.


title:
Statistics of Core Lifetimes in Numerical Simulations of Turbulent,
  Magnetically Supercritical Molecular Clouds

abstract:
  We present measurements of the mean dense core lifetimes in numerical
simulations of magnetically supercritical, turbulent, isothermal molecular
clouds, in order to compare with observational determinations. "Prestellar"
lifetimes (given as a function of the mean density within the cores, which in
turn is determined by the density threshold n_thr used to define them) are
consistent with observationally reported values, ranging from a few to several
free-fall times. We also present estimates of the fraction of cores in the
"prestellar", "stellar'', and "failed" (those cores that redisperse back into
the environment) stages as a function of n_thr. The number ratios are measured
indirectly in the simulations due to their resolution limitations. Our approach
contains one free parameter, the lifetime of a protostellar object t_yso (Class
0 + Class I stages), which is outside the realm of the simulations. Assuming a
value t_yso = 0.46 Myr, we obtain number ratios of starless to stellar cores
ranging from 4-5 at n_thr = 1.5 x 10^4 cm^-3 to 1 at n_thr = 1.2 x 10^5 cm^-3,
again in good agreement with observational determinations. We also find that
the mass in the failed cores is comparable to that in stellar cores at n_thr =
1.5 x 10^4 cm^-3, but becomes negligible at n_thr = 1.2 x 10^5 cm^-3, in
agreement with recent observational suggestions that at the latter densities
the cores are in general gravitationally dominated. We conclude by noting that
the timescale for core contraction and collapse is virtually the same in the
subcritical, ambipolar diffusion-mediated model of star formation, in the model
of star formation in turbulent supercritical clouds, and in a model
intermediate between the previous two, for currently accepted values of the
clouds' magnetic criticality.


title:
On Energy Efficient Hierarchical Cross-Layer Design: Joint Power Control
  and Routing for Ad Hoc Networks

abstract:
  In this paper, a hierarchical cross-layer design approach is proposed to
increase energy efficiency in ad hoc networks through joint adaptation of
nodes' transmitting powers and route selection. The design maintains the
advantages of the classic OSI model, while accounting for the cross-coupling
between layers, through information sharing. The proposed joint power control
and routing algorithm is shown to increase significantly the overall energy
efficiency of the network, at the expense of a moderate increase in complexity.
Performance enhancement of the joint design using multiuser detection is also
investigated, and it is shown that the use of multiuser detection can increase
the capacity of the ad hoc network significantly for a given level of energy
consumption.


title: What do we really know about mass loss on the AGB?

abstract:
  Mass loss rate formulae are derived from observations or from suites of
models. For theoretical models, the following have all been identified as
factors greatly influencing the atmospheric structure and mass loss rates:
Pulsation with piston amplitude scaling appropriately with stellar L; dust
nucleation and growth, with radiation pressure and grain-gas interactions and
appropriate dependence on temperature and density; non-grey opacity with at
least 51 frequency samples; non-LTE and departures from radiative equilibrium
in the compressed and expanding flows; and non-equilibrium processes affecting
the composition (grain formation; molecular chemistry). No one set of models
yet includes all the factors known to be important. In fact, it is very
difficult to construct a model that can simultaneously include these factors
and be useful for computing spectra. Therefore, although theoretical model
grids are needed to separate the effects of M,L,R and/or $T_{\mathrm{eff}}$ or
Z on the mass loss rates, these models must be carefully checked against
observations. Getting the right order of magnitude for the mass loss rate is
only the first step in such a comparison, and is not sufficient to determine
whether the mass loss formula is correct. However, there are observables that
do test the validity of mass loss formulae as they depend directly on $d\log
\dot M/d\log L$, $d\log \dot M/d\log R$, or $d\log \dot M/d\log P$.


title:
Spectral fluctuations of tridiagonal random matrices from the
  beta-Hermite ensemble

abstract:
  A time series delta(n), the fluctuation of the nth unfolded eigenvalue was
recently characterized for the classical Gaussian ensembles of NxN random
matrices (GOE, GUE, GSE). It is investigated here for the beta-Hermite ensemble
as a function of beta (zero or positive) by Monte Carlo simulations. The
fluctuation of delta(n) and the autocorrelation function vary logarithmically
with n for any beta>0 (1<<n<<N). The simple logarithmic behavior reported for
the higher-order moments of delta(n) for the GOE (beta=1) and the GUE (beta=2)
is valid for any positive beta and is accounted for by Gaussian distributions
whose variances depend linearly on ln(n). The 1/f noise previously demonstrated
for delta(n) series of the three Gaussian ensembles, is characterized by
wavelet analysis both as a function of beta and of N. When beta decreases from
1 to 0, for a given and large enough N, the evolution from a 1/f noise at
beta=1 to a 1/f^2 noise at beta=0 is heterogeneous with a ~1/f^2 noise at the
finest scales and a ~1/f noise at the coarsest ones. The range of scales in
which a ~1/f^2 noise predominates grows progressively when beta decreases.
Asymptotically, a 1/f^2 noise is found for beta=0 while a 1/f noise is the rule
for beta positive.


title: Capacity of a Class of Modulo-Sum Relay Channels

abstract:
  This paper characterizes the capacity of a class of modulo additive noise
relay channels, in which the relay observes a corrupted version of the noise
and has a separate channel to the destination. The capacity is shown to be
strictly below the cut-set bound in general and achievable using a
quantize-and-forward strategy at the relay. This result confirms a conjecture
by Ahlswede and Han about the capacity of channels with rate limited state
information at the destination for this particular class of channels.


title:
The evolution of interstellar clouds in a streaming hot plasma including
  heat conduction

abstract:
  To examine the evolution of giant molecular clouds in the stream of a hot
plasma we performed two-dimensional hydrodynamical simulations that take full
account of self-gravity, heating and cooling effects and heat conduction by
electrons. We use the thermal conductivity of a fully ionized hydrogen plasma
proposed by Spitzer and a saturated heat flux according to Cowie & McKee in
regions where the mean free path of the electrons is large compared to the
temperature scaleheight. Significant structural and evolutionary differences
occur between simulations with and without heat conduction. Dense clouds in
pure dynamical models experience dynamical destruction by Kelvin-Helmholtz (KH)
instability. In static models heat conduction leads to evaporation of such
clouds. Heat conduction acting on clouds in a gas stream smooths out steep
temperature and density gradients at the edge of the cloud because the
conduction timescale is shorter than the cooling timescale. This diminishes the
velocity gradient between the streaming plasma and the cloud, so that the
timescale for the onset of KH instabilities increases, and the surface of the
cloud becomes less susceptible to KH instabilities. The stabilisation effect of
heat conduction against KH instability is more pronounced for smaller and less
massive clouds. As in the static case more realistic cloud conditions allow
heat conduction to transfer hot material onto the cloud's surface and to mix
the accreted gas deeper into the cloud.


title: Amplitude Analysis of the decay D^0 --> K^- K^+ pi^0

abstract:
  Using 385 fb^-1 of e^+e^- collisions at the CM energies of around 10.6 GeV
recorded by the BaBar experiment, we study the amplitudes of the singly
Cabibbo-suppressed decay D^0 --> K^- K^+ pi^0. We measure the strong phase
difference between the D0bar and D0 decays to the K^*(892)^+ K^- state to be
-35.5 +/- 1.9 (stat) +/- 2.2 (syst) degrees, and their amplitude ratio to be
0.599 +/- 0.013 (stat) +/- 0.011 (syst). We observe significant contributions
from the Kpi and K^-K^+ scalar and vector amplitudes, and analyze the moments
of the cosine of the helicity angle in these systems. We find no evidence for
charged, scalar kappa(800) state, nor for higher spin states. We also perform a
model-independent partial wave analysis of the K^-K^+ system in a limited mass
range around 1 GeV/c^2. We study several models for Kpi S-wave amplitude, and
describe which one is favored by our data.


title:
Search for Baryonic Resonances Decaying to Xi pi in Deep-Inelastic
  Scattering at HERA

abstract:
  A search for narrow baryonic resonances decaying into Xi- pi- or Xi- pi+ and
their antiparticles is carried out with the H1 detector using deep inelastic
scattering events at HERA in the range of negative photon four-momentum
transfer squared 2 < Q^2 < 100 GeV^2. No signal is observed for a new baryonic
state in the mass range 1600 - 2300 MeV in either the doubly charged or the
neutral decay channels. The known baryon Xi0 is observed through its decay mode
into Xi- pi+. Upper limits are given on the ratio of the production rates of
new baryonic states, such as the hypothetical pentaquark states Xi^{--}_{5q} or
Xi^{0}_{5q}, relative to the Xi0 baryon state.


title:
4-Dimensional General Relativity from the instrinsic spatial geometry of
  SO(3) Yang--Mills theory

abstract:
  In this paper we derive 4-dimensional General Relativity from three
dimensions, using the intrinsic spatial geometry inherent in Yang--Mills theory
which has been exposed by previous authors as well as as some properties of the
Ashtekar variables. We provide various interesting relations, including the
fact that General Relativity can be written as a Yang--Mills theory where the
antiself-dual Weyl curvature replaces the Yang--Mills coupling constant. We
have generalized the results of some previous authors, covering Einsteins
spaces, to include more general spacetime geometries.


Comment on "Time Step Sensitivity of Nonlinear Atmospheric Models:
  Numerical Convergence, Truncation Error Growth, and Ensemble Design" Teixeira
  et al. (2007)


title:
The Sextet Arcs: a Strongly Lensed Lyman Break Galaxy in the ACS
  Spectroscopic Galaxy Survey towards Abell 1689

abstract:
  We present results of the HST Advanced Camera for Surveys spectroscopic
ground-based redshift survey in the field of A1689. We measure 98 redshifts,
increasing the number of spectroscopically confirmed objects by sixfold. We
present two spectra from this catalog of the Sextet Arcs, images which arise
from a strongly-lensed Lyman Break Galaxy (LBG) at a redshift of z=3.038.
Gravitational lensing by the cluster magnifies its flux by a factor of ~16 and
produces six separate images with a total r-band magnitude of r_625=21.7. The
two spectra, each of which represents emission from different regions of the
LBG, show H I and interstellar metal absorption lines at the systemic redshift.
Significant variations are seen in Ly-alpha profile across a single galaxy,
ranging from strong absorption to a combination of emission plus absorption. A
spectrum of a third image close to the brightest arc shows Ly-alpha emission at
the same redshift as the LBG, arising from either another spatially distinct
region of the galaxy, or from a companion galaxy close to the LBG. Taken as a
group, the Ly-alpha equivalent width in these three spectra decreases with
increasing equivalent width of the strongest interstellar absorption lines. We
discuss how these variations can be used to understand the physical conditions
in the LBG. Intrinsically, this LBG is faint, ~0.1L*, and forming stars at a
modest rate, ~4 solar masses per year. We also detect absorption line systems
toward the Sextet Arcs at z=2.873 and z=2.534. The latter system is seen across
two of our spectra.


title:
Transient Charging and Discharging of Spin-polarized Electrons in a
  Quantum Dot

abstract:
  We study spin-polarized transient transport in a quantum dot coupled to two
ferromagnetic leads subjected to a rectangular bias voltage pulse.
Time-dependent spin-resolved currents, occupations, spin accumulation, and
tunneling magnetoresistance (TMR) are calculated using both nonequilibrium
Green function and master equation techniques. Both parallel and antiparallel
leads' magnetization alignments are analyzed. Our main findings are: a
dynamical spin accumulation that changes sign in time, a short-lived pulse of
spin polarized current in the emitter lead (but not in the collector lead), and
a dynamical TMR that develops negative values in the transient regime. We also
observe that the intra-dot Coulomb interaction can enhance even further the
negative values of the TMR.


title:
Inclusive cross section and double helicity asymmetry for \pi^0
  production in p+p collisions at sqrt(s)=200 GeV: Implications for the
  polarized gluon distribution in the proton

abstract:
  The PHENIX experiment presents results from the RHIC 2005 run with polarized
proton collisions at sqrt(s)=200 GeV, for inclusive \pi^0 production at
mid-rapidity. Unpolarized cross section results are given for transverse
momenta p_T=0.5 to 20 GeV/c, extending the range of published data to both
lower and higher p_T. The cross section is described well for p_T < 1 GeV/c by
an exponential in p_T, and, for p_T > 2 GeV/c, by perturbative QCD. Double
helicity asymmetries A_LL are presented based on a factor of five improvement
in uncertainties as compared to previously published results, due to both an
improved beam polarization of 50%, and to higher integrated luminosity. These
measurements are sensitive to the gluon polarization in the proton, and exclude
maximal values for the gluon polarization.


title: Valence Quarks Polarization from COMPASS

abstract:
  A first evaluation of the polarized valence quark distribution $\Delta
u_v(x)+\Delta d_v(x)$ from the COMPASS experiment (CERN/SPS) is presented. The
data were collected by COMPASS in the years 2002--2004 using a 160 GeV
polarized muon beam scattered off a large polarized $^6$LiD target and cover
the range $1< Q^2 < 100$ GeV$^2$ and $0.006<x<0.7$. The analysis is based on
the difference asymmetry, $A^{h^+ - h^-}$, for hadrons of opposite charges,
which gives a direct access to the polarization of valence quarks.


title:
Investigations of the Non-Linear LMC Cepheid Period-Luminosity Relation
  with Testimator and Schwarz Information Criterion Methods

abstract:
  In this paper, we investigate the linearity versus non-linearity of the Large
Magellanic Cloud (LMC) Cepheid period-luminosity (P-L) relation using two
statistical approaches not previously applied to this problem: the testimator
method and the Schwarz Information Criterion (SIC). The testimator method is
extended to multiple stages for the first time, shown to be unbiased and the
variance of the estimated slope can be proved to be smaller than the standard
slope estimated from linear regression theory. The Schwarz Information
Criterion (also known as the Bayesian Information Criterion) is more
conservative than the Akaike Information Criterion and tends to choose lower
order models. By using simulated data sets, we verify that these statistical
techniques can be used to detect intrinsically linear and/or non-linear P-L
relations. These methods are then applied to independent LMC Cepheid data sets
from the OGLE project and the MACHO project, respectively. Our results imply
that there is a change of slope in longer period ranges for all of the data
sets. This strongly supports previous results, obtained from independent
statistical tests, that the observed LMC P-L relation is non-linear with a
break period at/around 10 days.


title: Intermediate inflation or late time acceleration?

abstract:
  The expansion rate of `Intermediate inflation' lies between the exponential
and power law expansion but corresponding accelerated expansion does not start
at the onset of cosmological evolution. Present study of `Intermediate
inflation' reveals that it admits scaling solution and has got a natural exit
form it at a later epoch of cosmic evolution, leading to late time
acceleration. The corresponding scalar field responsible for such feature is
also found to be a tracker field for both gravity with canonical and some
non-canonical form of kinetic term. Thus the so called Intermediate inflation
should be considered as yet another dark energy model with asymptotic de-Sitter
expansion.


title: Rapid Mixing of Gibbs Sampling on Graphs that are Sparse on Average

abstract:
  In this work we show that for every $d < \infty$ and the Ising model defined
on $G(n,d/n)$, there exists a $\beta_d > 0$, such that for all $\beta <
\beta_d$ with probability going to 1 as $n \to \infty$, the mixing time of the
dynamics on $G(n,d/n)$ is polynomial in $n$. Our results are the first
polynomial time mixing results proven for a natural model on $G(n,d/n)$ for $d
> 1$ where the parameters of the model do not depend on $n$. They also provide
a rare example where one can prove a polynomial time mixing of Gibbs sampler in
a situation where the actual mixing time is slower than $n \polylog(n)$. Our
proof exploits in novel ways the local treelike structure of Erd\H{o}s-R\'enyi
random graphs, comparison and block dynamics arguments and a recent result of
Weitz.
  Our results extend to much more general families of graphs which are sparse
in some average sense and to much more general interactions. In particular,
they apply to any graph for which every vertex $v$ of the graph has a
neighborhood $N(v)$ of radius $O(\log n)$ in which the induced sub-graph is a
tree union at most $O(\log n)$ edges and where for each simple path in $N(v)$
the sum of the vertex degrees along the path is $O(\log n)$. Moreover, our
result apply also in the case of arbitrary external fields and provide the
first FPRAS for sampling the Ising distribution in this case. We finally
present a non Markov Chain algorithm for sampling the distribution which is
effective for a wider range of parameters. In particular, for $G(n,d/n)$ it
applies for all external fields and $\beta < \beta_d$, where $d \tanh(\beta_d)
= 1$ is the critical point for decay of correlation for the Ising model on
$G(n,d/n)$.


title:
ACS imaging of star clusters in M51. I. Identification and radius
  distribution

abstract:
  We use HST/ACS observations of the spiral galaxy M51 in F435W, F555W and
F814W to select a large sample of star clusters with accurate effective radius
measurements in an area covering the complete disc of M51. We present the
dataset and study the radius distribution and relations between radius, colour,
arm/interarm region, galactocentric distance, mass and age. We select a sample
of 7698 (F435W), 6846 (F555W) and 5024 (F814W) slightly resolved clusters and
derive their effective radii by fitting the spatial profiles with analytical
models convolved with the point spread function. The radii of 1284 clusters are
studied in detail. We find cluster radii between 0.5 and ~10 pc, and one
exceptionally large cluster candidate with a radius of 21.6 pc. The median
radius is 2.1 pc. We find 70 clusters in our sample which have colours
consistent with being old GC candidates and we find 6 new "faint fuzzy"
clusters in, or projected onto, the disc of M51. The radius distribution can
not be fitted with a power law, but a log-normal distribution provides a
reasonable fit to the data. This indicates that shortly after the formation of
the clusters from a fractal gas, their radii have changed in a non-uniform way.
We find an increase in radius with colour as well as a higher fraction of
redder clusters in the interarm regions, suggesting that clusters in spiral
arms are more compact. We find a correlation between radius and galactocentric
distance which is considerably weaker than the observed correlation for old
Milky Way GCs. We find weak relations between cluster luminosity and radius,
but we do not observe a correlation between cluster mass and radius.


title: Pseudoduality and Conserved Currents in Sigma Models

abstract:
  We discuss the current conservation laws in sigma models based on a compact
Lie groups of the same dimensionality and connected to each other via
pseudoduality transformations in two dimensions. We show that pseudoduality
transformations induce an infinite number of nonlocal conserved currents on the
pseudodual manifold.


title: Type I singularities and the Phantom Menace

abstract:
  We consider the future dynamics of a transient phantom dominated phase of the
universe in LQC and in the RS braneworld, which both have a non-standard
Friedmann equation. We find that for a certain class of potentials, the Hubble
parameter oscillates with simple harmonic motion in the LQC case and therefore
avoids any future singularity. For more general potentials we find that damping
effects eventually lead to the Hubble parameter becoming constant. On the other
hand in the braneworld case we find that although the type I singularity can be
avoided, the scale factor still diverges at late times.


title:
Low density expansion and isospin dependence of nuclear energy
  functional: comparison between relativistic and Skyrme models

abstract:
  In the present work we take the non relativistic limit of relativistic models
and compare the obtained functionals with the usual Skyrme parametrization.
Relativistic models with both constant couplings and with density dependent
couplings are considered. While some models present very good results already
at the lowest order in the density, models with non-linear terms only reproduce
the energy functional if higher order terms are taken into account in the
expansion.


title: Quantized Transport in Graphene p-n Junctions in Magnetic Field

abstract:
  Recent experimental work on locally gated graphene layers resulting in p-n
junctions have revealed quantum Hall effect in their transport behavior. We
explain the observed conductance quantization which is fractional in the
bipolar regime and integer in the unipolar regime in terms of quantum Hall edge
modes propagating along and across the p-n interface. In the bipolar regime the
electron and hole modes can mix at the p-n boundary, leading to current
partition and quantized shot noise plateaus similar to those of conductance,
while in the unipolar regime transport is noiseless. These quantum Hall
phenomena reflect the massless Dirac character of charge carriers in graphene,
with particle-hole interplay manifest in mode mixing and noise in the bipolar
regime.


title: The Local Galaxy 8 micron Luminosity Function

abstract:
  A SST survey in the NOAO Deep-Wide Field in Bo\"otes provides a complete,
8-micron-selected sample of galaxies to a limiting (Vega) magnitude of 13.5. In
the 6.88 deg$^2$ field sampled, 79% of the 4867 galaxies have spectroscopic
redshifts, allowing an accurate determination of the local (z<0.3) galaxy
luminosity function. Stellar and dust emission can be separated on the basis of
observed galaxy colors. Dust emission (mostly PAH) accounts for 80% of the 8
micron luminosity, stellar photospheres account for 19%, and AGN emission
accounts for roughly 1 %. A sub-sample of the 8 micron-selected galaxies have
blue, early-type colors, but even most of these have significant PAH emission.
The luminosity functions for the total 8 micron luminosity and for the dust
emission alone are both well fit by Schechter functions. For the 8 micron
luminosity function, the characteristic luminosity is \nu L_{\nu}^*(8.0
\micron) = 1.8 \times 10^{10}$ \Lsun while for the dust emission alone it is
1.6 x 10^{10}$ \Lsun\null. The average 8 \micron luminosity density at z<0.3 is
3.1 x 10^7 \Lsun Mpc^{-3}, and the average luminosity density from dust alone
is 2.5 x 10^7 \Lsun Mpc^{-3}. This luminos ity arises predominantly from
galaxies with 8 \micron luminosities ($\nu L_{\nu}$) between $2\times 10^9$ and
$2 x 10^{10}$ \Lsun, i.e., normal galaxies, not LIRGs or ULIRGs.


title: d-Wave Pairing State in Terms of the Zhang-Rice Singlets

abstract:
  In cuprate superconductors doping is believed to create holes on the O-sites,
which couple antiferromagnetically with holes on the Cu-sites to form the
so-called Zhang-Rice singlets. Here we study a d-wave pairing state based on
the Zhang-Rice singlet states. Upper and lower bounds of an off-diagonal
long-range order parameter with d-wave symmetry for this state are estimated.
We also introduce a concrete model with on-site Coulomb repulsion and kinds of
antiferromagnetic interactions whose ground state is this d-wave pairing state.


title: UV Star Formation Rates in the Local Universe

abstract:
  We measure star formation rates of ~50,000 optically-selected galaxies in the
local universe (z~0.1), spanning a range from gas-rich dwarfs to massive
ellipticals. We obtain dust-corrected SFRs by fitting the GALEX (UV) and SDSS
(optical) photometry to a library of population synthesis models that include
dust attenuation. For star-forming galaxies, our UV-based SFRs compare
remarkably well with those derived from SDSS H alpha. Deviations from perfect
agreement between these two methods are due to differences in the dust
attenuation estimates. In contrast to H alpha, UV provides reliable SFRs for
galaxies with weak or no H alpha emission, and where H alpha is contaminated
with an emission from an AGN. We use full-SED SFRs to calibrate a simple
prescription that uses GALEX UV magnitudes to produce good SFRs for normal
star-forming galaxies. The specific SFR is considered as a function of stellar
mass for (1) star-forming galaxies with no AGN, (2) those hosting an AGN, and
for (3) galaxies without H alpha emission. We find that the three have distinct
star formation histories, with AGN lying intermediate between the star-forming
and the quiescent galaxies. Normal star forming galaxies (without an AGN) lie
on a relatively narrow linear sequence. Remarkably, galaxies hosting a strong
AGN appear to represent the massive continuation of this sequence. Weak AGN,
while also massive, have lower SFR, sometimes extending to the realm of
quiescent galaxies. We propose an evolutionary sequence for massive galaxies
that smoothly connects normal star-forming galaxies to quiescent (red sequence)
galaxies via strong and weak AGN. We confirm that some galaxies with no H alpha
emission show signs of SF in the UV. We derive a UV-based cosmic SFR density at
z=0.1 with smaller total error than previous measurements (abridged).


title:
Real analytic solutions for marginal deformations in open superstring
  field theory

abstract:
  We construct analytic solutions for marginal deformations satisfying the
reality condition in open superstring field theory formulated by Berkovits when
operator products made of the marginal operator and the associated
superconformal primary field are regular. Our strategy is based on the recent
observation by Erler that the problem of finding solutions for marginal
deformations in open superstring field theory can be reduced to a problem in
the bosonic theory of finding a finite gauge parameter for a certain pure-gauge
configuration labeled by the parameter of the marginal deformation. We find a
gauge transformation generated by a real gauge parameter which infinitesimally
changes the deformation parameter and construct a finite gauge parameter by its
path-ordered exponential. The resulting solution satisfies the reality
condition by construction.


title: Metastable Vacua in Perturbed Seiberg-Witten Theories

abstract:
  We show that, for a generic choice of a point on the Coulomb branch of any
N=2 supersymmetric gauge theory, it is possible to find a superpotential
perturbation which generates a metastable vacuum at the point. For theories
with SU(N) gauge group, such a superpotential can be expressed as a sum of
single-trace terms for N=2 and 3. If the metastable point is chosen at the
origin of the moduli space, we can show that the superpotential can be a
single-trace operator for any N. In both cases, the superpotential is a
polynomial of degree 3N of the vector multiplet scalar field.


title:
The Mean and Scatter of the Velocity Dispersion-Optical Richness
  Relation for maxBCG Galaxy Clusters

abstract:
  The distribution of galaxies in position and velocity around the centers of
galaxy clusters encodes important information about cluster mass and structure.
Using the maxBCG galaxy cluster catalog identified from imaging data obtained
in the Sloan Digital Sky Survey, we study the BCG-galaxy velocity correlation
function. By modeling its non-Gaussianity, we measure the mean and scatter in
velocity dispersion at fixed richness. The mean velocity dispersion increases
from 202+/-10 km/s for small groups to more than 854+/-102 km/s for large
clusters. We show the scatter to be at most 40.5+/-3.5%, declining to
14.9+/-9.4% in the richest bins. We test our methods in the C4 cluster catalog,
a spectroscopic cluster catalog produced from the Sloan Digital Sky Survey DR2
spectroscopic sample, and in mock galaxy catalogs constructed from N-body
simulations. Our methods are robust, measuring the scatter to well within
one-sigma of the true value, and the mean to within 10%, in the mock catalogs.
By convolving the scatter in velocity dispersion at fixed richness with the
observed richness space density function, we measure the velocity dispersion
function of the maxBCG galaxy clusters. Although velocity dispersion and
richness do not form a true mass-observable relation, the relationship between
velocity dispersion and mass is theoretically well characterized and has low
scatter. Thus our results provide a key link between theory and observations up
to the velocity bias between dark matter and galaxies.


title: Quantum Darwinism in quantum Brownian motion: the vacuum as a witness

abstract:
  We study quantum Darwinism -- the redundant recording of information about a
decohering system by its environment -- in zero-temperature quantum Brownian
motion. An initially nonlocal quantum state leaves a record whose redundancy
increases rapidly with its spatial extent. Significant delocalization (e.g., a
Schroedinger's Cat state) causes high redundancy: many observers can measure
the system's position without perturbing it. This explains the objective (i.e.
classical) existence of einselected, decoherence-resistant pointer states of
macroscopic objects.


title:
Entanglement and topological entropy of the toric code at finite
  temperature

abstract:
  We calculate exactly the von Neumann and topological entropies of the toric
code as a function of system size and temperature. We do so for systems with
infinite energy scale separation between magnetic and electric excitations, so
that the magnetic closed loop structure is fully preserved while the electric
loop structure is tampered with by thermally excited electric charges. We find
that the entanglement entropy is a singular function of temperature and system
size, and that the limit of zero temperature and the limit of infinite system
size do not commute. From the entanglement entropy we obtain the topological
entropy, which is shown to drop to half its zero-temperature value for any
infinitesimal temperature in the thermodynamic limit, and remains constant as
the temperature is further increased. Such discontinuous behavior is replaced
by a smooth decreasing function in finite-size systems. If the separation of
energy scales in the system is large but finite, we argue that our results hold
at small enough temperature and finite system size, and a second drop in the
topological entropy should occur as the temperature is raised so as to disrupt
the magnetic loop structure by allowing the appearance of free magnetic
charges. We interpret our results as an indication that the underlying magnetic
and electric closed loop structures contribute equally to the topological
entropy (and therefore to the topological order) in the system. Since each loop
structure \emph{per se} is a classical object, we interpret the quantum
topological order in our system as arising from the ability of the two
structures to be superimposed and appear simultaneously.


title:
An Atlas of the circumnuclear regions of 75 Seyfert galaxies in the
  near-UV with HST Advanced Camera for Surveys

abstract:
  We present an atlas of the central regions of 75 Seyfert galaxies imaged in
the near-UV with the Advanced Camera for Surveys of the Hubble Space Telescope
at an average resolution of ~10pc. These data complement archival high
resolution data from the Space Telescope at optical and near-IR wavelengths,
creating an extremely valuable dataset for astronomers with a broad range of
scientific interests. Our goal is to investigate the nature of the near-UV
light in these objects, its relation to the circumnuclear starburst phenomenon,
and the connection of this to the evolution and growth of the galaxy bulge and
central black hole. In this paper, we describe the near-UV morphology of the
objects and characterize the near-UV emission. We estimate the size and the
luminosity of the emitting regions and extract the luminosity profile. We also
determine the presence of unresolved compact nuclei. In addition, the
circumnuclear stellar cluster population is identified, and the contribution of
the stellar clusters to the total light, at this wavelength, is estimated. The
size of the sample allows us to draw robust statistical conclusions. We find
that {Seyfert 1} galaxies are completely dominated by its bright and compact
nucleus, that remains point-like at this resolution, while we find almost no
unresolved nucleus in Seyfert 2. The Seyfert types 1 and 2 are quite segregated
in an asymmetry vs compactness plot. Stellar clusters are found somewhat more
frequently in Sy2 (in ~70% of the galaxies) than in Sy1 (~57%), and contribute
more to the total light in Sy2, but this two differences seem to be mostly due
to the large contribution of the compact nucleus in Sy1, as the luminosity
distribution of the clusters is similar in both Sy types.


title: Astrophysical Accretion as an Analogue Gravity Phenomena

abstract:
  In recent years, strong analogies have been established between the physics
of acoustic perturbations in an inhomogeneous dynamical fluid system, and some
kinematic features of space-time in general relativity. An effective metric,
referred to as the `acoustic metric', which describes the geometry of the
manifold in which acoustic perturbations propagate, can be constructed. This
effective geometry can capture the properties of curved space-time in general
relativity. Physical models constructed utilizing such analogies are called
`analogue gravity models'. Classical analogue gravity effect may be observed
when acoustic perturbations propagate through a inhomogeneous transonic
classical fluid. The acoustic horizon, which resembles a black hole event
horizon in many ways, is generated at the transonic point in the fluid flow.
The acoustic horizon is essentially a null hyper surface, generators of which
are the acoustic null geodesics, i.e. the phonons. The acoustic horizon emits
acoustic radiation with quasi thermal phonon spectra, which is analogous to the
actual Hawking radiation. The temperature of the radiation emitted from the
acoustic horizon is referred to as the analogue Hawking temperature.
  It has been demonstrated that, in general, the transonic accretion in
astrophysics can be considered as an example of the classical analogue gravity
model naturally found in the Universe.


title:
Predicting the connectivity of primate cortical networks from
  topological and spatial node properties

abstract:
  The organization of the connectivity between mammalian cortical areas has
become a major subject of study, because of its important role in scaffolding
the macroscopic aspects of animal behavior and intelligence. In this study we
present a computational reconstruction approach to the problem of network
organization, by considering the topological and spatial features of each area
in the primate cerebral cortex as subsidy for the reconstruction of the global
cortical network connectivity. Starting with all areas being disconnected,
pairs of areas with similar sets of features are linked together, in an attempt
to recover the original network structure. Inferring primate cortical
connectivity from the properties of the nodes, remarkably good reconstructions
of the global network organization could be obtained, with the topological
features allowing slightly superior accuracy to the spatial ones. Analogous
reconstruction attempts for the C. elegans neuronal network resulted in
substantially poorer recovery, indicating that cortical area interconnections
are relatively stronger related to the considered topological and spatial
properties than neuronal projections in the nematode. The close relationship
between area-based features and global connectivity may hint on developmental
rules and constraints for cortical networks. Particularly, differences between
the predictions from topological and spatial properties, together with the
poorer recovery resulting from spatial properties, indicate that the
organization of cortical networks is not entirely determined by spatial
constraints.


title:
The Intrinsic Origin of Spin Echoes in Dipolar Solids Generated by
  Strong Pi Pulses

abstract:
  In spectroscopy, it is conventional to treat pulses much stronger than the
linewidth as delta-functions. In NMR, this assumption leads to the prediction
that pi pulses do not refocus the dipolar coupling. However, NMR spin echo
measurements in dipolar solids defy these conventional expectations when more
than one pi pulse is used. Observed effects include a long tail in the CPMG
echo train for short delays between pi pulses, an even-odd asymmetry in the
echo amplitudes for long delays, an unusual fingerprint pattern for
intermediate delays, and a strong sensitivity to pi-pulse phase. Experiments
that set limits on possible extrinsic causes for the phenomena are reported. We
find that the action of the system's internal Hamiltonian during any real pulse
is sufficient to cause the effects. Exact numerical calculations, combined with
average Hamiltonian theory, identify novel terms that are sensitive to
parameters such as pulse phase, dipolar coupling, and system size.
Visualization of the entire density matrix shows a unique flow of quantum
coherence from non-observable to observable channels when applying repeated pi
pulses.


title:
Exploring the Partonic Structure of Hadrons through the Drell-Yan
  Process

abstract:
  The Drell-Yan process is a standard tool for probing the partonic structure
of hadrons. Since the process proceeds through a quark-antiquark annihilation,
Drell-Yan scattering possesses a unique ability to selectively probe sea
distributions. This review examines the application of Drell-Yan scattering to
elucidating the flavor asymmetry of the nucleon's sea and nuclear modifications
to the sea quark distributions in unpolarized scattering. Polarized beams and
targets add an exciting new dimension to Drell-Yan scattering. In particular,
the two initial-state hadrons give Drell-Yan sensitivity to chirally-odd
transversity distributions.


title: Disordering Transitions and Peak Effect in Polydisperse Particle Systems

abstract:
  We show numerically that in a binary system of Yukawa particles, a dispersity
driven disordering transition occurs. In the presence of quenched disorder this
disordering transition coincides with a marked increase in the depinning
threshold, known as a peak effect. We find that the addition of poorly pinned
particles can increase the overall pinning in the sample by increasing the
amount of topological disorder present. If the quenched disorder is strong
enough to create a significant amount of topological disorder in the
monodisperse system, addition of a poorly pinned species generates further
disorder but does not produce a peak in the depinning force. Our results
indicate that for binary mixtures, optimal pinning occurs for topological
defect fraction densities of 0.2 to 0.25. For defect densities below this
range, the system retains orientational order. We determine the effect of the
pinning density, strength, and radius on the depinning peak and find that the
peak effect is more pronounced in weakly pinning systems.


title: Casimir effect in a 6D warped flux compactification model

abstract:
  We discuss Casimir effect of a massless, minimally coupled scalar field in a
6D warped flux compactification model and its implications for the hierarchy
and cosmological constant problems, which are longstanding puzzles in
phenomenology and cosmology. Due to the scale invariance of the background
theory, the 4D effective theory contains a volume modulus. To stabilize the
modulus, we consider one-loop corrections to the effective potential by the
Casimir effect. The one-loop effective potential for the volume modulus has a
form which is very similar to Coleman-Weinberg potential. We evaluate
coefficients appearing in the effective potential by employing zeta function
regularization and heat kernel analysis. The volume modulus is stabilized for
smaller degrees of warping, below a critical value, which depends on deficit
angle of the reference brane. After stabilizing the modulus, it is possible to
obtain observed values of the mass ratio between the fundamental energy scales
and a tiny effective cosmological constant (though its sign is negative). The
degree of warping should be tuned to be close to the critical value, not as
severely as the original fine-tuning.


title: Anisotropic ac dissipation at the surface of mesoscopic superconductors

abstract:
  In this work we study the ac dissipation of mesoscopic superconductors at
microwave frequencies using the time dependent Ginzburg-Landau equations. Our
numerical simulations show that the ac dissipation is strongly dependent on the
orientation of the ac magnetic field ($h_{ac}$) relative to the dc magnetic
field ($H_{dc}$). When $h_{ac}$ is parallel to $H_{dc}$ we observe that each
vortex penetration event produces a significant supression of the ac losses
because the imaginary part of the ac susceptibility as a function of $H_{dc}$
increases before the penetration of vortices, and then it decreases abruptly
after vortices have entered into the sample. In the second case, when $h_{ac}$
is perpendicular to $H_{dc}$, we observe that the jumps in dissipation occur at
the same values of $H_{dc}$ but are much smaller than in the parallel
configuration. The behavior of the dissipation in the perpendicular
configuration is similar to previous results obtained in recent microwave
experiments using mesoscopic litographed squares of Pb [J. Low Temp. Phys. 135,
119 (2004)].


title:
Initial fields and instability in the classical model of the heavy-ion
  collision

abstract:
  Color Glass Condensate (CGC) provides a classical description of dense gluon
matter at high energies. Using the McLerran-Venugopalan (MV) model we calculate
the initial energy density \epsilon(\tau) in the early stage of the
relativistic nucleus-nucleus collision. Our analytical formula reproduces the
quantitative results from lattice discretized simulations and leads to an
estimate \epsilon(\tau=0.1fm)=40-50GeV/fm^3 in the Au-Au collision at RHIC
energy. We then formulate instability with respect to soft fluctuations that
violate boost invariance inherent to hard CGC backgrounds. We find unstable
modes arising as a result of ensemble average over the initial CGC fields.


title: The Casimir Force in Randall Sundrum Models

abstract:
  We discuss and compare the effects of one extra dimension in the Randall
Sundrum models on the evaluation of the Casimir force between two parallel
plates. We impose the condition that the result reproduce the experimental
measurements within the known uncertainties in the force and the plate
separation, and get an upper bound kR < 20 if the curvature parameter k of
AdS_5 is equal to the Planck scale. Although the upper bound decreases as k
decreases, kR ~ 12, which is the required value for solving the hierarchy
problem, is consistent with the Casimir force measurements. For the case where
the 5th dimension is infinite, the correction to the Casimir force is very
small and negligible.


title: The Special McKay correspondence as an equivalence of derived categories

abstract:
  We give a new moduli construction of the minimal resolution of the
singularity of type 1/r(1,a) by introducing the Special McKay quiver. To
demonstrate that our construction trumps that of the G-Hilbert scheme, we show
that the induced tautological line bundles freely generate the bounded derived
category of coherent sheaves on X by establishing a suitable derived
equivalence. This gives a moduli construction of the Special McKay
correspondence for abelian subgroups of GL(2).


title:
A nearly optimal discrete query quantum algorithm for evaluating NAND
  formulas

abstract:
  We present an O(\sqrt{N}) discrete query quantum algorithm for evaluating
balanced binary NAND formulas and an O(N^{{1/2}+O(\frac{1}{\sqrt{\log N}})})
discrete query quantum algorithm for evaluating arbitrary binary NAND formulas.


title: Resolving the Formation of Protogalaxies. I. Virialization

abstract:
  (Abridged) Galaxies form in hierarchically assembling dark matter halos. With
cosmological three dimensional adaptive mesh refinement simulations, we explore
in detail the virialization of baryons in the concordance cosmology, including
optically thin primordial gas cooling. We focus on early protogalaxies with
virial temperatures of 10^4 K and their progenitors. Without cooling, virial
heating occurs in shocks close to the virial radius for material falling in
from voids. Material in dense filaments penetrates deeper to about half that
radius. With cooling the virial shock position shrinks and also the filaments
reach scales as small as a third the virial radius. The temperatures in
protogalaxies found in adiabatic simulations decrease by a factor of two from
the center and show flat entropy cores. In cooling halos the gas reaches virial
equilibrium with the dark matter potential through its turbulent velocities. We
observe turbulent Mach numbers ranging from one to three in the cooling cases.
This turbulence is driven by the large scale merging and interestingly remains
supersonic in the centers of these early galaxies even in the absence of any
feedback processes. The virial theorem is shown to approximately hold over 3
orders of magnitude in length scale with the turbulent pressure prevailing over
the thermal energy. The turbulent velocity distributions are Maxwellian and by
far dominate the small rotation velocities associated with the total angular
momentum of the galaxies. Decomposing the velocity field using the
Cauchy-Stokes theorem, we show that ample amounts of vorticity are present
around shocks even at the very centers of these objects.


title:
Adiabatic Rotation, Quantum Search and Preparation of Superposition
  States

abstract:
  We introduce the idea of using adiabatic rotation to generate superpositions
of a large class of quantum states. For quantum computing this is an
interesting alternative to the well-studied "straight line" adiabatic
evolution. In ways that complement recent results, we show how to efficiently
prepare three types of states: Kitaev's toric code state, the cluster state of
the measurement-based computation model and the history state used in the
adiabatic simulation of quantum circuit. We also show that the method, when
adapted for quantum search, provides quadratic speedup as other optimal methods
do with the advantages that the problem Hamiltonian is time-independent and
that the energy gap above the ground state is strictly nondecreasing with time.
Likewise the method can be used for optimization as an alternative to the usual
adiabatic algorithm.


title: Cohomology of Fiber Products of Local Rings

abstract:
  Let $S$ and $T$ be local rings with common residue field $k$, let $R$ be the
fiber product $S \times_k T$, and let $M$ be an $S$-module. The Poincar\'e
series $P^R_M$ of $M$ has been expressed in terms of $P^S_M$, $P^S_k$ and
$P^T_k$ by Kostrikin and Shafarevich, and by Dress and Kr\"amer. Here, an
explicit minimal resolution, as well as theorems on the structure of
$\Ext_R(k,k)$ and $\Ext_R(M,k)$ are given that illuminate these equalities.
Structure theorems for the cohomology modules of fiber products of modules are
also given. As an application of these results, we compute the depth of
cohomology modules over a fiber product.


title:
Colossal magnon-phonon coupling in multiferroic
  Eu$_{0.75}$Y$_{0.25}$MnO$_3$

abstract:
  We report the spectra of magnetically induced electric dipole absorption in
Eu$_{0.75}$Y$_{0.25}$MnO$_3$ from temperature dependent far infrared
spectroscopy (10-250 cm$^{-1}$). These spectra, which occur only in the $e||a$
polarization, consist of two relatively narrow electromagnon features that
onset at $T_{FE}=30$ K and a broad absorption band that persists to
temperatures well above $T_N=47$ K. The observed excitations account for the
step up of the static dielectric constant in the ferroelectric phase. The
electromagnon at 80 cm$^{-1}$ is observed to be strongly coupled to the nearby
lowest optical phonon which transfers more than 1/2 of its spectral weight to
the magnon. We attribute the origin of the broad background absorption to the
two magnon emission decay process of the phonon.


title: Triangulations of projective modules

abstract:
  We show that the category of projective modules over a graded commutative
ring admits a triangulation with respect to module suspension if and only if
the ring is a finite product of graded fields and exterior algebras on one
generator over a graded field (with a unit in the appropriate degree). We also
classify the ungraded commutative rings for which the category of projective
modules admits a triangulation with respect to the identity suspension.
Applications to two analogues of the generating hypothesis in algebraic
topology are given, and we translate our results into the setting of modules
over a symmetric ring spectrum or S-algebra.


title:
Gravitational collapse of spherically symmetric plasmas in
  Einstein-Maxwell spacetimes

abstract:
  We utilize a recent formulation of a spherically symmetric spacetime endowed
with a general decomposition of the energy momentum tensor [Phys. Rev. D, 75,
024031 (2007)] to derive equations governing spherically symmetric
distributions of electromagnetic matter. We show the system reduces to the
Reissner-Nordstrom spacetime in general, spherically symmetric coordinates in
the vacuum limit. Furthermore, we show reduction to the charged Vaidya
spacetime in non-null coordinates when certain equations of states are chosen.
A model of gravitational collapse is discussed whereby a charged fluid resides
within a boundary of finite radial extent on the initial hypersurface, and is
allowed to radiate charged particles. Our formalism allows for the discussion
of all regions in this model without the need for complicated matching schemes
at the interfaces between successive regions. As further examples we consider
the collapse of a thin shell of charged matter onto a Reissner-Nordstrom black
hole. Finally, we reduce the entire system of equations to the static case such
that we have the equations for hydrostatic equilibrium of a charged fluid.


title: Rough Sets Computations to Impute Missing Data

abstract:
  Many techniques for handling missing data have been proposed in the
literature. Most of these techniques are overly complex. This paper explores an
imputation technique based on rough set computations. In this paper,
characteristic relations are introduced to describe incompletely specified
decision tables.It is shown that the basic rough set idea of lower and upper
approximations for incompletely specified decision tables may be defined in a
variety of different ways. Empirical results obtained using real data are given
and they provide a valuable and promising insight to the problem of missing
data. Missing data were predicted with an accuracy of up to 99%.


title:
Asymptotics of Tracy-Widom distributions and the total integral of a
  Painlev\'e II function

abstract:
  The Tracy-Widom distribution functions involve integrals of a Painlev\'e II
function starting from positive infinity. In this paper, we express the
Tracy-Widom distribution functions in terms of integrals starting from minus
infinity. There are two consequences of these new representations. The first is
the evaluation of the total integral of the Hastings-McLeod solution of the
Painlev\'e II equation. The second is the evaluation of the constant term of
the asymptotic expansions of the Tracy-Widom distribution functions as the
distribution parameter approaches minus infinity. For the GUE Tracy-Widom
distribution function, this gives an alternative proof of the recent work of
Deift, Its, and Krasovsky. The constant terms for the GOE and GSE Tracy-Widom
distribution functions are new.


title: The discrepancy in G-band contrast: Where is the quiet Sun?

abstract:
  We compare the rms contrast in observed speckle reconstructed G-band images
with synthetic filtergrams computed from two magneto-hydrodynamic simulation
snapshots. The observations consist of 103 bursts of 80 frames each taken at
the Dunn Solar Telescope (DST), sampled at twice the diffraction limit of the
telescope. The speckle reconstructions account for the performance of the
Adaptive Optics (AO) system at the DST to supply reliable photometry. We find a
considerable discrepancy in the observed rms contrast of 14.1% for the best
reconstructed images, and the synthetic rms contrast of 21.5% in a simulation
snapshot thought to be representative of the quiet Sun. The areas of features
in the synthetic filtergrams that have positive or negative contrast beyond the
minimum and maximum values in the reconstructed images have spatial scales that
should be resolved. This leads us to conclude that there are fundamental
differences in the rms G-band contrast between observed and computed
filtergrams. On the basis of the substantially reduced granular contrast of
16.3% in the synthetic plage filtergram we speculate that the quiet-Sun may
contain more weak magnetic field than previously thought.


title: Two-loop world-sheet corrections in AdS_5 x S^5 superstring

abstract:
  We initiate the computation of the 2-loop quantum AdS_5 x S^5 string
corrections on the example of a certain string configuration in S^5 related by
an analytic continuation to a folded rotating string in AdS_5 in the ``long
string'' limit. The 2-loop term in the energy of the latter should represent
the subleading strong-coupling correction to the cusp anomalous dimension and
thus provide a further check of recent conjectures about the exact structure of
the Bethe ansatz underlying the AdS/CFT duality. We use the conformal gauge and
several choices of the \kappa-symmetry gauge. While we are unable to verify the
cancellation of 2d UV divergences we compute the bosonic contribution to the
effective action and also determine the non-trivial finite part of the
fermionic contribution. Both the bosonic and the fermionic contributions to the
string energy happen to be proportional to the Catalan's constant. The
resulting value for 2-loop superstring prediction for the subleading
coefficient a_2 in the scaling function matches the numerical value found in
hep-th/0611135 from the BES equation.


title: Fundamental Limits to Position Determination by Concentration Gradients

abstract:
  Position determination in biological systems is often achieved through
protein concentration gradients. Measuring the local concentration of such a
protein with a spatially-varying distribution allows the measurement of
position within the system. In order for these systems to work effectively,
position determination must be robust to noise. Here, we calculate fundamental
limits to the precision of position determination by concentration gradients
due to unavoidable biochemical noise perturbing the gradients. We focus on
gradient proteins with first order reaction kinetics. Systems of this type have
been experimentally characterised in both developmental and cell biology
settings. For a single gradient we show that, through time-averaging, great
precision can potentially be achieved even with very low protein copy numbers.
As a second example, we investigate the ability of a system with oppositely
directed gradients to find its centre. With this mechanism, positional
precision close to the centre improves more slowly with increasing averaging
time, and so longer averaging times or higher copy numbers are required for
high precision. For both single and double gradients, we demonstrate the
existence of optimal length scales for the gradients, where precision is
maximized, as well as analyzing how precision depends on the size of the
concentration measuring apparatus. Our results provide fundamental constraints
on the positional precision supplied by concentration gradients in various
contexts, including both in developmental biology and also within a single
cell.


title:
Linked by Loops: Network Structure and Switch Integration in Complex
  Dynamical Systems

abstract:
  Simple nonlinear dynamical systems with multiple stable stationary states are
often taken as models for switchlike biological systems. This paper considers
the interaction of multiple such simple multistable systems when they are
embedded together into a larger dynamical "supersystem." Attention is focused
on the network structure of the resulting set of coupled differential
equations, and the consequences of this structure on the propensity of the
embedded switches to act independently versus cooperatively. Specifically, it
is argued that both larger average and larger variance of the node degree
distribution lead to increased switch independence. Given the frequency of
empirical observations of high variance degree distributions (e.g., power-law)
in biological networks, it is suggested that the results presented here may aid
in identifying switch-integrating subnetworks as comparatively homogenous,
low-degree, substructures. Potential applications to ecological problems such
as the relationship of stability and complexity are also briefly discussed.

categories: q-bio.QM cond-mat.dis-nn math.DS nlin.CD


title:
Kondo Physics in Nanotubes: Magnetic-field dependence and
  singlet-triplet Kondo

abstract:
  In a single-walled carbon nanotube, we observe the spin-1/2 Kondo effect. The
energy of spin-resolved Kondo peaks is proportional to magnetic field at high
fields, contrary to recent reports. At lower fields, the energy falls below
this linear dependence, in qualitative agreement with theoretical expectations.
For even electron occupancy, we observe a spin-1 Kondo effect due to the
degeneracy of the triplet ground states. Tuning gate voltage within the same
Coulomb diamond drives a transition to a singlet ground state. We also
independently tune the energy difference between singlet and triplet states
with a magnetic field. The Zeeman splitting thus measured confirms the value of
the g-factor measured from the spin-1/2 Kondo feature.


title: A characterization of round spheres in terms of blocking light

abstract:
  A closed Riemannian manifold is said to have cross blocking if whenever
distinct points p and q are at distance less than the diameter, all light rays
from p can be shaded away from q with at most two point shades. Similarly, a
closed Riemannian manifold is said to have sphere blocking if for each point p,
all the light rays from p are shaded away from p by a single point shade. We
prove that Riemannian manifolds with cross and sphere blocking are isometric to
round spheres.


title: Sabbath Day Home Automation: "It's Like Mixing Technology and Religion"

abstract:
  We present a qualitative study of 20 American Orthodox Jewish families' use
of home automation for religious purposes. These lead users offer insight into
real-life, long-term experience with home automation technologies. We discuss
how automation was seen by participants to contribute to spiritual experience
and how participants oriented to the use of automation as a religious custom.
We also discuss the relationship of home automation to family life. We draw
design implications for the broader population, including surrender of control
as a design resource, home technologies that support long-term goals and
lifestyle choices, and respite from technology.


title: Capacity Gain from Two-Transmitter and Two-Receiver Cooperation

abstract:
  Capacity improvement from transmitter and receiver cooperation is
investigated in a two-transmitter, two-receiver network with phase fading and
full channel state information available at all terminals. The transmitters
cooperate by first exchanging messages over an orthogonal transmitter
cooperation channel, then encoding jointly with dirty paper coding. The
receivers cooperate by using Wyner-Ziv compress-and-forward over an analogous
orthogonal receiver cooperation channel. To account for the cost of
cooperation, the allocation of network power and bandwidth among the data and
cooperation channels is studied. It is shown that transmitter cooperation
outperforms receiver cooperation and improves capacity over non-cooperative
transmission under most operating conditions when the cooperation channel is
strong. However, a weak cooperation channel limits the transmitter cooperation
rate; in this case receiver cooperation is more advantageous.
Transmitter-and-receiver cooperation offers sizable additional capacity gain
over transmitter-only cooperation at low SNR, whereas at high SNR transmitter
cooperation alone captures most of the cooperative capacity improvement.


title: Cancellation for inclusions of C*-algebras of finite depth

abstract:
  Let B be a unital C*-algebra, let A be a unital subalgebra, and let E be a
conditional expectation from B to A with index-finite type and a quasi-basis of
n elements. Then the topological stable rank satisfies \tsr (B) \leq \tsr (A) +
n - 1. As an application, we show that if a unital inclusion A \subset B of
C*-algebras has index-finite type and finite depth, and A is simple with stable
rank one and Property (SP), then B has cancellation. In particular, if A is a
simple unital C*-algebra with stable rank one and Property (SP), and a finite
group G acts on A, then the crossed product has cancellation. Separately, if
the group is the integers, we obtain cancellation under the additional
hypotheses that the group action is outer and is trivial on K_0 (A).


title: Lower Bounds on Implementing Robust and Resilient Mediators

abstract:
  We consider games that have (k,t)-robust equilibria when played with a
mediator, where an equilibrium is (k,t)-robust if it tolerates deviations by
coalitions of size up to k and deviations by up to $t$ players with unknown
utilities. We prove lower bounds that match upper bounds on the ability to
implement such mediators using cheap talk (that is, just allowing communication
among the players). The bounds depend on (a) the relationship between k, t, and
n, the total number of players in the system; (b) whether players know the
exact utilities of other players; (c) whether there are broadcast channels or
just point-to-point channels; (d) whether cryptography is available; and (e)
whether the game has a $k+t)-punishment strategy; that is, a strategy that, if
used by all but at most $k+t$ players, guarantees that every player gets a
worse outcome than they do with the equilibrium strategy.


title: Evaluating Personal Archiving Strategies for Internet-based Information

abstract:
  Internet-based personal digital belongings present different vulnerabilities
than locally stored materials. We use responses to a survey of people who have
recovered lost websites, in combination with supplementary interviews, to paint
a fuller picture of current curatorial strategies and practices. We examine the
types of personal, topical, and commercial websites that respondents have lost
and the reasons they have lost this potentially valuable material. We further
explore what they have tried to recover and how the loss influences their
subsequent practices. We found that curation of personal digital materials in
online stores bears some striking similarities to the curation of similar
materials stored locally in that study participants continue to archive
personal assets by relying on a combination of benign neglect, sporadic
backups, and unsystematic file replication. However, we have also identified
issues specific to Internet-based material: how risk is spread by distributing
the files among multiple servers and services; the circular reasoning
participants use when they discuss the safety of their digital assets; and the
types of online material that are particularly vulnerable to loss. The study
reveals ways in which expectations of permanence and notification are violated
and situations in which benign neglect has far greater consequences for the
long-term fate of important digital assets.


title:
Perturbed Self-Similar Massless Scalar Field in Spherically Symmetric
  Spaceimes

abstract:
  In this paper, we investigate the linear perturbations of the spherically
symmetric spacetimes with kinematic self-similarity of the second kind. The
massless scalar field equations are solved which yield the background and an
exact solutions for the perturbed equations. We discuss the boundary conditions
of the resulting perturbed solutions. The possible perturbation modes turn out
to be stable as well as unstable. The analysis leads to the conclusion that
there does not exist any critical solution.


title: Quantile and Probability Curves Without Crossing

abstract:
  This paper proposes a method to address the longstanding problem of lack of
monotonicity in estimation of conditional and structural quantile functions,
also known as the quantile crossing problem. The method consists in sorting or
monotone rearranging the original estimated non-monotone curve into a monotone
rearranged curve. We show that the rearranged curve is closer to the true
quantile curve in finite samples than the original curve, establish a
functional delta method for rearrangement-related operators, and derive
functional limit theory for the entire rearranged curve and its functionals. We
also establish validity of the bootstrap for estimating the limit law of the
the entire rearranged curve and its functionals. Our limit results are generic
in that they apply to every estimator of a monotone econometric function,
provided that the estimator satisfies a functional central limit theorem and
the function satisfies some smoothness conditions. Consequently, our results
apply to estimation of other econometric functions with monotonicity
restrictions, such as demand, production, distribution, and structural
distribution functions. We illustrate the results with an application to
estimation of structural quantile functions using data on Vietnam veteran
status and earnings.


title: Bernstein-Szego Polynomials Associated with Root Systems

abstract:
  We introduce multivariate generalizations of the Bernstein-Szego polynomials,
which are associated to the root systems of the complex simple Lie algebras.
The multivariate polynomials in question generalize Macdonald's Hall-Littlewood
polynomials associated with root systems. For the root system of type A1
(corresponding to the Lie algebra SL (2;C)) the classic Bernstein-Szego
polynomials are recovered.


title: Crossed products by finite group actions with the Rokhlin property

abstract:
  We prove that a number of classes of separable unital C*-algebras are closed
under crossed products by finite group actions with the Rokhlin property,
including:
  (1) AI algebras, AT algebras, and related classes characterized by direct
limit decompositions using semiprojective building blocks.
  (2) Simple unital AH algebras with slow dimension growth and real rank zero.
  (3) C*-algebras with real rank zero or stable rank one.
  (4) C*-algebras whose quotients all satisfy the Universal Coefficient
Theorem.
  Along the way, we give a systematic treatment of the derivation of direct
limit decompositions from local approximation conditions by homomorphic images
which are not necessarily injective.