title:
Two-Component Fractional Quantum Hall Effect in the Half-Filled Lowest
  Landau Level in an Asymmetric Wide Quantum Well

abstract:
  We investigate theoretically the fractional quantum Hall effect at
half-filling in the lowest Landau level observed in asymmetric wide quantum
wells. The asymmetry can be achieved by a potential bias applied between the
two sides of the well. Within exact-diagonalization calculations in the
spherical geometry, we find that the incompressible state is described in terms
of a two-component wave function. Its overlap with the ground state can be
optimized with the help of a rotation in the space of the pseudospin, which
mimics the lowest two electronic subbands.


title:
Electron-vibrational interaction in the 5d states of Eu2+ ions in
  Sr6-xEuxBP5O20 (x=0.01; 0.03; 0.05; 0.07; 0.09; 0.11; 0.13; 0.15)

abstract:
  In the present paper we report on the combined experimental and theoretical
study of the Sr6-xEuxBP5O20 (x=0.01; 0.03; 0.05; 0.07; 0.09; 0.11; 0.13; 0.15)
phosphors. Details of the samples preparation and spectroscopic measurements
are followed by the analysis of the room-temperature absorption and emission
spectra, which yielded the main parameters of the electron-phonon coupling,
such as Huang-Rhys factor, Stokes shift, effective phonon energy, and
zero-phonon line position were determined for the first time for the studied
system. The obtained parameters were used to model the emission band shapes,
which perfectly reproduce the experimental results for all samples.


title:
Controllable emission of a dipolar source coupled with a
  magneto-dielectric resonant subwavelength scatterer

abstract:
  We demonstrate experimentally and theoretically that a local excitation of a
single scatterer of relative dielectric permittivity {\epsilon} = 6 permits to
excite broad dipolar and quadrupolar electric and magnetic resonances that
shape the emission pattern in an un- precedented way. By suitably positioning
the feed with respect to the sphere at a ?=3 distance, this compact antenna is
able to spectrally sort the electromagnetic emission ei- ther in the forward or
in the backward direction, together with a high gain in directivity. Materials
with {\epsilon} = 6 can be found in the whole spectrum of frequencies promising
Mie antennas to become an enabling technology in numbers of applications,
ranging from quantum single photon sources to telecommunications.


title: A stochastic model for speculative bubbles

abstract:
  This paper aims to provide a simple modelling of speculative bubbles and
derive some quantitative properties of its dynamical evolution. Starting from a
description of individual speculative behaviours, we build and study a second
order Markov process, which after simple transformations can be viewed as a
turning two-dimensional Gaussian process. Then, our main problem is to ob- tain
some bounds for the persistence rate relative to the return time to a given
price. In our main results, we prove with both spectral and probabilistic
methods that this rate is almost proportional to the turning frequency {\omega}
of the model and provide some explicit bounds. In the continuity of this
result, we build some estimators of {\omega} and of the pseudo-period of the
prices. At last, we end the paper by a proof of the quasi-stationary
distribution of the process, as well as the existence of its persistence rate.


title: Chiral symmetry and lattice fermions

abstract:
  Lattice gauge theory and chiral perturbation theory are among the primary
tools for understanding non-perturbative aspects of QCD. I review several
subtle and sometimes controversial issues that arise when combining these
techniques. Among these are one failure of partially quenched chiral
perturbation theory when the valence quarks become lighter than the average sea
quark mass and a potential ambiguity in comparisons of perturbative and lattice
properties of non-degenerate quarks.


title: Structuring multi-dimensional subshifts

abstract:
  We study two relations on multi-dimensional subshifts: A pre-order based on
the patterns configurations contain and the Cantor-Bendixson rank. We exhibit
several structural properties of two-dimensional subshifts: We characterize the
simplest aperiodic configurations in countable SFTs, we give a combinatorial
characterization of uncountable subshifts, we prove that there always exists
configurations without any periodicity but that have the simplest possible
combinatorics in countable SFTs. Finally, we prove that some Cantor-Bendixson
ranks are impossible for countable SFTs, leaving only a few unknown cases.


title:
Coefficient Matrices Computation of Structural Vector Autoregressive
  Model

abstract:
  In this paper we present the Large Inverse Cholesky (LIC) method, an
efficient method for computing the coefficient matrices of a Structural Vector
Autoregressive (SVAR) model.


title:
Balanced Viscosity (BV) solutions to infinite-dimensional
  rate-independent systems

abstract:
  Balanced Viscosity solutions to rate-independent systems arise as limits of
regularized rate-independent flows by adding a superlinear vanishing-viscosity
dissipation.
  We address the main issue of proving the existence of such limits for
infinite-dimensional systems and of characterizing them by a couple of
variational properties that combine a local stability condition and a balanced
energy-dissipation identity.
  A careful description of the jump behavior of the solutions, of their
differentiability properties, and of their equivalent representation by time
rescaling is also presented.
  Our techniques rely on a suitable chain-rule inequality for functions of
bounded variation in Banach spaces, on refined lower semicontinuity-compactness
arguments, and on new BV-estimates that are of independent interest.


title: A Fundamental System of Seminorms for $A(K)$

abstract:
  Let $K\subset\R^d$ be compact and $A(K)$ the space of germs of real analytic
functions on $K$ with its natural (LF)-topology. This topology can be given by
$A(K)=\limind_{k\to+\infty} A_k$ where $A_k=\{(f_\alpha)_{\alpha\in\N_0^d}\in
C(K)^{\N_0^d}\,:\, \|f\|_k:=\sup_{x\in K} \frac{|f^{(\alpha)}(x)|}{\alpha!}
k^{-|\alpha|}< +\infty\}.$ Based on this description we give in the present
note an explicit fundamental system of seminorms for $A(K)$.


title:
Characterization of potential smoothness and Riesz basis property of
  Hill-Scr\"odinger operators with singular periodic potentials in terms of
  periodic, antiperiodic and Neumann spectra

abstract:
  The Hill operators Ly=-y''+v(x)y, considered with singular complex valued
\pi-periodic potentials v of the form v=Q' with Q in L^2([0,\pi]), and subject
to periodic, antiperiodic or Neumann boundary conditions have discrete spectra.
For sufficiently large n, the disc {z: |z-n^2|<n} contains two periodic (if n
is even) or antiperiodic (if n is odd) eigenvalues \lambda_n^-, \lambda_n^+ and
one Neumann eigenvalue \nu_n. We show that rate of decay of the sequence
|\lambda_n^+-\lambda_n^-|+|\lambda_n^+ - \nu_n| determines the potential
smoothness, and there is a basis consisting of periodic (or antiperiodic) root
functions if and only if for even (respectively, odd) n, \sup_{\lambda_n^+\neq
\lambda_n^-}{|\lambda_n^+-\nu_n|/|\lambda_n^+-\lambda_n^-|} < \infty.


title: Lunar laser ranging: the millimeter challenge

abstract:
  Lunar laser ranging has provided many of the best tests of gravitation since
the first Apollo astronauts landed on the Moon. The march to higher precision
continues to this day, now entering the millimeter regime, and promising
continued improvement in scientific results. This review introduces key aspects
of the technique, details the motivations, observables, and results for a
variety of science objectives, summarizes the current state of the art,
highlights new developments in the field, describes the modeling challenges,
and looks to the future of the enterprise.


title:
Periodic and stationary solutions of nonlinear evolution equations -
  translation along trajectories method

abstract:
  This is a habilitation self-report describing results on forced periodic
solutions of partial differential equations. Here averaging principle in the
spirit of Bogoliubov and Mitropolsky for ODE's and Henry for parabolic
equations are used together with topological methods such as fixed point index
and topological degree.


title: On some random walks driven by spread-out measures

abstract:
  Let $G$ be a finitely generated group equipped with a symmetric generating $%
k $-tuple $S$. Let $|\cdot|$ and $V$ be the associated word length and volume
growth function. Let $\nu$ be a probability measure such that $% \nu(g)\simeq
[(1+|g|)^2V(|g|)]^{-1}$. We prove that if $G$ has polynomial volume growth then
$\nu^{(n)}(e) \simeq V(\sqrt{n\log n})^{-1}$. We also obtain assorted estimates
for other spread-out probability measures.


title: Generating Explanations for Biomedical Queries

abstract:
  We introduce novel mathematical models and algorithms to generate (shortest
or k different) explanations for biomedical queries, using answer set
programming. We implement these algorithms and integrate them in BIOQUERY-ASP.
We illustrate the usefulness of these methods with some complex biomedical
queries related to drug discovery, over the biomedical knowledge resources
PHARMGKB, DRUGBANK, BIOGRID, CTD, SIDER, DISEASE ONTOLOGY and ORPHADATA. To
appear in Theory and Practice of Logic Programming (TPLP).


title: Tropical Cramer Determinants Revisited

abstract:
  We prove general Cramer type theorems for linear systems over various
extensions of the tropical semiring, in which tropical numbers are enriched
with an information of multiplicity, sign, or argument. We obtain existence or
uniqueness results, which extend or refine earlier results of Gondran and
Minoux (1978), Plus (1990), Gaubert (1992), Richter-Gebert, Sturmfels and
Theobald (2005) and Izhakian and Rowen (2009). Computational issues are also
discussed; in particular, some of our proofs lead to Jacobi and Gauss-Seidel
type algorithms to solve linear systems in suitably extended tropical
semirings.


title: Crystal bases as tuples of integer sequences

abstract:
  We describe a set $\mathcal{R}^{\infty}$ consisting of tuples of integer
sequences and provide certain explicit maps on it. We show that this defines a
semiregular crystal for $\mathfrak{sl}_{n+1}$ and $\mathfrak{sp}_{2n}$
respectively. Furthermore we define for any dominant integral weight $\lambda$
a connected subcrystal $\mathcal{R}(\lambda)$ in $\mathcal{R}^{\infty}$, such
that this crystal is isomorphic to the crystal graph $B(\lambda)$. Finally we
provide an explicit description of these connected crystals
$\mathcal{R}(\lambda)$.


title: Cavity optomechanics in gallium phosphide microdisks

abstract:
  We demonstrate gallium phosphide (GaP) microdisk optical cavities with
intrinsic quality factors $ > 2.8\times10^{5}$ and mode volumes $< 10
(\lambda/n)^3$, and study their nonlinear and optomechanical properties. For
optical intensities up to $8.0\times10^4$ intracavity photons, we observe
optical loss in the microcavity to decrease with increasing intensity,
indicating that saturable absorption sites are present in the GaP material, and
that two-photon absorption is not significant. We observe optomechanical
coupling between optical modes of the microdisk around 1.5 $\mu$m and several
mechanical resonances, and measure an optical spring effect consistent with a
theoretically predicted optomechanical coupling rate $g_0/2\pi \sim 30$ kHz for
the fundamental mechanical radial breathing mode at 488 MHz.


title: Solving OSCAR regularization problems by proximal splitting algorithms

abstract:
  The OSCAR (octagonal selection and clustering algorithm for regression)
regularizer consists of a L_1 norm plus a pair-wise L_inf norm (responsible for
its grouping behavior) and was proposed to encourage group sparsity in
scenarios where the groups are a priori unknown. The OSCAR regularizer has a
non-trivial proximity operator, which limits its applicability. We reformulate
this regularizer as a weighted sorted L_1 norm, and propose its grouping
proximity operator (GPO) and approximate proximity operator (APO), thus making
state-of-the-art proximal splitting algorithms (PSAs) available to solve
inverse problems with OSCAR regularization. The GPO is in fact the APO followed
by additional grouping and averaging operations, which are costly in time and
storage, explaining the reason why algorithms with APO are much faster than
that with GPO. The convergences of PSAs with GPO are guaranteed since GPO is an
exact proximity operator. Although convergence of PSAs with APO is may not be
guaranteed, we have experimentally found that APO behaves similarly to GPO when
the regularization parameter of the pair-wise L_inf norm is set to an
appropriately small value. Experiments on recovery of group-sparse signals
(with unknown groups) show that PSAs with APO are very fast and accurate.


title: Geography of irregular Gorenstein 3-folds

abstract:
  In this paper, we study the explicit geography problem of irregular
Gorenstein minimal 3-folds of general type. We generalize the classical
Noether-Castelnuovo inequalities for irregular surfaces to irregular 3-folds
according to the Albanese dimension.


title:
Global Existence of Solutions of the Semiclassical Einstein Equation for
  Cosmological Spacetimes

abstract:
  We study the solutions of the semiclassical Einstein equation in flat
cosmological spacetimes driven by a massive conformally coupled scalar field.
In particular, we show that it is possible to give initial conditions at finite
time to get a state for the quantum field which gives finite expectation values
for the stress-energy tensor. Furthermore, it is possible to control this
expectation value by means of a global estimate on regular cosmological
spacetimes. The obtained estimates permit to write a theorem about the
existence and uniqueness of the local solutions encompassing both the spacetime
metric and the matter field simultaneously. Finally, we show that one can
always extend local solutions up to a point where the scale factor becomes
singular or the Hubble function reaches a critical value $H_c = 180\pi/G$,
which both correspond to a divergence of the scalar curvature, namely a
spacetime singularity.


title: Quantum-Reduced Loop-Gravity: Relation with the Full Theory

abstract:
  The quantum-reduced loop-gravity technique has been introduced for dealing
with cosmological models. We show that it can be applied rather generically:
anytime the spatial metric can be gauge-fixed to a diagonal form. The technique
selects states based on reduced graphs with Livine-Speziale coherent
intertwiners and could simplify the analysis of the dynamics in the full
theory.


title: Directed Ratchet Transport in Granular Crystals

abstract:
  Directed-ratchet transport (DRT) in a one-dimensional lattice of spherical
beads, which serves as a prototype for granular crystals, is investigated. We
consider a system where the trajectory of the central bead is prescribed by a
biharmonic forcing function with broken time-reversal symmetry. By comparing
the mean integrated force of beads equidistant from the forcing bead, two
distinct types of directed transport can be observed ---spatial and temporal
DRT. Based on the value of the frequency of the forcing function relative to
the cutoff frequency, the system can be categorized by the presence and
magnitude of each type of DRT. Furthermore, we investigate and quantify how
varying additional parameters such as the biharmonic weight affects DRT
velocity and magnitude. Finally, friction is introduced into the system and is
found to significantly inhibit spatial DRT. In fact, for sufficiently low
forcing frequencies, the friction may even induce a switching of the DRT
direction.


title: Large C*-algebras of universally measurable operators

abstract:
  For a C*-algebra A, G. Pedersen defined the concept of universal
measurability for self-adjoint elements of A**, the universal enveloping
algebra of A. Although he was unable to show that U, the set of universally
measurable elements, is a Jordan algebra, he showed that U contains a large
Jordan algebra, U_0. We show by means of a 2 x 2 matrix trick that U_0 is in
fact the real part of a C*-algebra. If it is ever shown that U is always a
C*-algebra, then the same trick will show that U is the real part of a
C*-algebra.


title:
On the Non-Uniqueness of Solutions to the Average Cost HJB for
  Controlled Diffusions with Near-Monotone Costs

abstract:
  We present a theorem for verification of optimality of controlled diffusions
under the average cost criterion with near-monotone running cost, without
invoking any blanket stability assumptions. The implications of this result to
the policy iteration algorithm are also discussed.


title:
Exciton fission via ultrafast long-range resonant tunnelling in organic
  photovoltaic diodes

abstract:
  We present an exciton/lattice model of the electronic dynamics of primary
photoexcitations in a polymeric semiconductor heterojunction which includes
both polymer pi-stacking, energetic disorder, and phonon relaxation. Results
from our model are consistent with a wide range of recent experimental evidence
that excitons decay directly to well-defined polarons on a sub-100 fs
timescale, which is substantially faster than exciton relaxation processes.
Averaging over multiple samples, we find that as the interfacial offset is
increased, a substantial fraction of the density of electronic states in the
energy region about the initial exciton carries significant charge-transfer
character with two charges separated in the outer regions of the model lattice.
The results indicate a slight increase in the density of such current-producing
states if the region close to the interface is more disordered. However, since
their density of states overlaps the excitation line-shape of the primary
exciton, we show that it is possible that the exciton can decay directly into
current-producing states via tunneling on an ultrafast time-scale. We find this
process to be independent of the location of energetic disorder in the system,
and hence we expect exciton fission via resonant tunnelling to be a ubiquitous
feature of these systems.


title:
Quantum spin-liquid behavior in the spin-1/2 random Heisenberg
  antiferromagnet on the triangular lattice

abstract:
  Experimental quest for the hypothetical "quantum spin liquid" state has
recently met a few promising candidate materials including organic salts
\kappa-(ET)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2, S=1/2 triangular-lattice
Heisenberg antiferromagnets consisting of molecular dimers. These compounds
exhibit no magnetic ordering nor the spin freezing down to very low
temperature, while various physical quantities exhibit gapless behaviors.
Recent dielectric measurements revealed the glassy dielectric response
suggesting the random freezing of the electric polarization degrees of freedom.
Inspired by this observation, we propose as a minimal model of the observed
quantum spin-liquid behavior the S=1/2 antiferromagnetic Heisenberg on the
triangular lattice with a quenched randomness in the exchange interaction. We
study both zero- and finite-temperature properties of the model by an exact
diagonalization method, to find that when the randomness exceeds a critical
value the model exhibits a quantum spin-liquid ground state. This
randomness-induced quantum spin-liquid state exhibits gapless behaviors
including the temperature-linear specific heat. The results provide a
consistent explanation of the recent experimental observations on organic
salts.


title:
The magnetic and structural properties near the Lifshitz point in
  Fe1+xTe

abstract:
  We construct a phase diagram of the parent compound Fe1+xTe as a function of
interstitial iron x in terms of the electronic, structural, and magnetic
properties. For a concentration of x < 10%, Fe1+xTe undergoes a "semimetal" to
metal transition at approximately 70 K that is also first-order and coincident
with a structural transition from a tetragonal to a monoclinic unit cell. For x
~ 14%, Fe1+xTe undergoes a second-order phase transition at approximately 58 K
corresponding to a "semimetal" to "semimetal" transition along with a
structural orthorhombic distortion. At a critical concentration of x ~ 11%,
Fe1+xTe undergoes two transitions: the higher temperature one is a second-order
transition to an orthorhombic phase with incommensurate magnetic ordering and
temperature-dependent propagation vector, while the lower temperature one
corresponds to nucleation of a monoclinic phase with a nearly commensurate
magnetic wavevector. While both structural and magnetic transitions display
similar critical behavior for x < 10% and near the critical concentration of x
~ 11%, samples with large interstitial iron concentrations show a marked
deviation between the critical response indicating a decoupling of the order
parameters. Analysis of temperature dependent inelastic neutron data reveals
incommensurate magnetic fluctuations throughout the Fe1+xTe phase diagram are
directly connected to the "semiconductor"-like resistivity above T_N and
implicates scattering from spin fluctuations as the primary reason for the
semiconducting or poor metallic properties. The results suggest that doping
driven Fermi surface nesting maybe the origin of the gapless and incommensurate
spin response at large interstitial concentrations.


title:
Numerical Solutions of Fredholm Integral Equations Using Bernstein
  Polynomials

abstract:
  In this paper, Bernstein piecewise polynomials are used to solve the integral
equations numerically. A matrix formulation is given for a non-singular linear
Fredholm Integral Equation by the technique of Galerkin method. In the Galerkin
method, the Bernstein polynomials are used as the approximation of basis
functions. Examples are considered to verify the effectiveness of the proposed
derivations, and the numerical solutions guarantee the desired accuracy.


title:
Giant magnetization canting due to symmetry breaking in zigzag Co chains
  on Ir(001)

abstract:
  We demonstrate a canted magnetization of biatomic zigzag Co chains grown on
the 5 x 1 reconstructed Ir(001) surface using density functional theory
calculations and spin-polarized scanning tunneling microscopy (SP-STM)
experiments. Biatomic Co chains grow in three different structural
configurations and are all in a ferromagnetic state. Two chain types possess
high symmetry due to two equivalent atomic strands and an easy magnetization
direction which is along one of the principal crystallographic axes. The easy
magnetization axis of the zigzag Co chains is canted away from the surface
normal by an angle of 33 degrees. This giant effect is caused by the broken
chain symmetry on the substrate in combination with the strong spin-orbit
coupling of Ir. SP-STM measurements confirm stable ferromagnetic order of the
zigzag chains with a canted magnetization.


title: Magnetic fields in A stars besides Ap stars

abstract:
  I review ongoing efforts to understand the incidence of magnetism in
intermediate-mass stars that are different from the magnetic Ap stars. This
includes the search for magnetic fields in chemically peculiar stars of the Am
and HgMn types as well as in normal A and late-B stars. I discuss different
techniques for detection of weak stellar magnetic fields and present a critical
evaluation of the recent magnetic detections in non-Ap stars. Special attention
is given to the magnetic status of HgMn stars and to the discovery of weak
polarization signatures in Sirius and Vega.


title: Substructure in bulk velocities of Milky Way disk stars

abstract:
  We find that Galactic disk stars near the anticenter exhibit velocity
asymmetries in both the Galactocentric radial and vertical components across
the mid-plane as well as azimuthally. These findings are based on LAMOST
spectroscopic velocities for a sample of ~400,000 F-type stars, combined with
proper motions from the PPMXL catalog for which we have derived corrections to
the zero points based in part on spectroscopically discovered galaxies and QSOs
from LAMOST. In the region within 2 kpc outside the Sun's radius and +/-2 kpc
from the Galactic midplane, we show that stars above the plane exhibit net
outward radial motions with downward vertical velocities, while stars below the
plane have roughly the opposite behavior. We discuss this in the context of
other recent findings, and conclude that we are likely seeing the signature of
vertical disturbances to the disk due to an external perturbation.


title:
Wiedemann-Franz law and non-vanishing temperature scale across the
  field-tuned quantum critical point of YbRh2Si2

abstract:
  The in-plane thermal conductivity kappa(T) and electrical resistivity rho(T)
of the heavy-fermion metal YbRh2Si2 were measured down to 50 mK for magnetic
fields H parallel and perpendicular to the tetragonal c axis, through the
field-tuned quantum critical point, Hc, at which antiferromagnetic order ends.
The thermal and electrical resistivities, w(T) and rho(T), show a linear
temperature dependence below 1 K, typical of the non-Fermi liquid behavior
found near antiferromagnetic quantum critical points, but this dependence does
not persist down to T = 0. Below a characteristic temperature T* ~ 0.35 K,
which depends weakly on H, w(T) and rho(T) both deviate downward and converge
in the T = 0 limit. We propose that T* marks the onset of short-range magnetic
correlations, persisting beyond Hc. By comparing samples of different purity,
we conclude that the Wiedemann-Franz law holds in YbRh2Si2, even at Hc,
implying that no fundamental breakdown of quasiparticle behavior occurs in this
material. The overall phenomenology of heat and charge transport in YbRh2Si2 is
similar to that observed in the heavy-fermion metal CeCoIn5, near its own
field-tuned quantum critical point.


title:
A spectroscopic sample of massive, evolved z~2 galaxies: Implications
  for the evolution of the mass-size relation

abstract:
  We present deep, near-infrared HST/WFC3 grism spectroscopy and imaging for a
sample of 14 galaxies at z~2 selected from a mass-complete photometric catalog
in the COSMOS field. By combining the grism observations with photometry in 30
bands, we derive accurate constraints on their redshifts, stellar masses, ages,
dust extinction and formation redshifts. We show that the slope and scatter of
the z~2 mass-size relation of quiescent galaxies is consistent with the local
relation, and confirm previous findings that the sizes for a given mass are
smaller by a factor of two to three. Finally, we show that the observed
evolution of the mass-size relation of quiescent galaxies between z=2 and 0 can
be explained by quenching of increasingly larger star-forming galaxies, at a
rate dictated by the increase in the number density of quiescent galaxies with
decreasing redshift. However, we find that the scatter in the mass-size
relation should increase in the quenching-driven scenario in contrast to what
is seen in the data. This suggests that merging is not needed to explain the
evolution of the median mass-size relation of massive galaxies, but may still
be required to tighten its scatter, and explain the size growth of individual
z=2 galaxies quiescent galaxies.


title:
The COS-Halos Survey: Rationale, Design, and A Census of Circumgalactic
  Neutral Hydrogen

abstract:
  We present the design and methods of the COS-Halos survey, a systematic
investigation of the gaseous halos of 44 z = 0.15-0.35 galaxies using
background QSOs observed with the Cosmic Origins Spectrograph aboard the Hubble
Space Telescope. This survey has yielded 39 spectra of z_em ~ 0.5 QSOs with S/N
~ 10-15 per resolution element. The QSO sightlines pass within 150 physical kpc
of the galaxies, which span early and late types over stellar mass log M* /
Msun= 9.5 - 11.5. We find that the CGM exhibits strong HI, averaging 1 Ang in
Lya equivalent width out to 150 kpc, with 100% covering fraction for
star-forming galaxies and 75% covering for passive galaxies. We find good
agreement in column densities between this survey and previous studies over
similar range of impact parameter. There is weak evidence for a difference
between early- and late-type galaxies in the strength and distribution of HI.
Kinematics indicate that the detected material is bound to the host galaxy,
such that >~90% of the detected column density is confined within +/-200 km
s^-1 of the galaxies. This material generally exists well below the halo virial
temperatures at T<~ 10^5 K. We evaluate a number of possible origin scenarios
for the detected material, and in the end favor a simple model in which the
bulk of the detected HI arises in a bound, cool, low-density photoionized
diffuse medium that is generic to all L* galaxies and may harbor a total
gaseous mass comparable to galactic stellar masses.


title:
Di-Higgs final states augMT2ed -- selecting $hh$ events at the high
  luminosity LHC

abstract:
  Higgs boson self-interactions can be investigated via di-Higgs ($pp\to hh+X$)
production at the LHC. With a small ${\cal{O}}(30)$ fb Standard Model
production cross section, and a large $t\bar t$ background, this measurement
has been considered challenging, even at a luminosity-upgraded LHC. We
demonstrate that by using simple kinematic bounding variables, of the sort
already employed in existing LHC searches, the dominant $t\bar t$ background
can be largely eliminated. Simulations of the signal and the dominant
background demonstrate the prospect for measurement of the di-Higgs production
cross section at the 30% level using 3/ab of integrated luminosity at a
high-luminosity LHC. This corresponds to a Higgs self-coupling determination
with 60% accuracy in the $b\bar b \tau^+\tau^-$ mode, with potential for
further improvements from e.g. subjet technologies and from additional di-Higgs
decay channels.


title: An Exceptional Radio Flare in Markarian 421

abstract:
  In September 2012, the high-synchrotron-peaked (HSP) blazar Markarian 421
underwent a rapid wideband radio flare, reaching nearly twice the brightest
level observed in the centimeter band in over three decades of monitoring. In
response to this event we carried out a five epoch centimeter- to
millimeter-band multifrequency Very Long Baseline Array (VLBA) campaign to
investigate the aftermath of this emission event. Rapid radio variations are
unprecedented in this object and are surprising in an HSP BL Lac object. In
this flare, the 15 GHz flux density increased with an exponential doubling time
of about 9 days, then faded to its prior level at a similar rate. This is
comparable with the fastest large-amplitude centimeter-band radio variability
observed in any blazar. Similar flux density increases were detected up to
millimeter bands. This radio flare followed about two months after a similarly
unprecedented GeV gamma-ray flare (reaching a daily E>100 MeV flux of (1.2 +/-
0.7)x10^(-6) ph cm^(-2) s^(-1)) reported by the Fermi Large Area Telescope
(LAT) collaboration, with a simultaneous tentative TeV detection by ARGO-YBJ. A
cross-correlation analysis of long-term 15 GHz and LAT gamma-ray light curves
finds a statistically significant correlation with the radio lagging ~40 days
behind, suggesting that the gamma-ray emission originates upstream of the radio
emission. Preliminary results from our VLBA observations show brightening in
the unresolved core region and no evidence for apparent superluminal motions or
substantial flux variations downstream.


title:
Identification of red supergiants in nearby galaxies with mid-IR
  photometry

abstract:
  The role of episodic mass loss in massive star evolution is one of the most
important open questions of current stellar evolution theory. Episodic mass
loss produces dust and therefore causes evolved massive stars to be very
luminous in the mid-infrared and dim at optical wavelengths. We aim to increase
the number of investigated luminous mid-IR sources to shed light on the late
stages of these objects. To achieve this we employed mid-IR selection criteria
to identity dusty evolved massive stars in two nearby galaxies. The method is
based on mid-IR colors, using 3.6 {\mu}m and 4.5 {\mu}m photometry from
archival Spitzer Space Telescope images of nearby galaxies and J-band
photometry from 2MASS. We applied our criteria to two nearby star-forming dwarf
irregular galaxies, Sextans A and IC 1613, selecting eight targets, which we
followed up with spectroscopy. Our spectral classification and analysis yielded
the discovery of two M-type supergiants in IC 1613, three K-type supergiants
and one candidate F-type giant in Sextans A, and two foreground M giants. We
show that the proposed criteria provide an independent way for identifying
dusty evolved massive stars, that can be extended to all nearby galaxies with
available Spitzer/IRAC images at 3.6 {\mu}m and 4.5 {\mu}m.


title: Do We Expect Most AGN to Live in Disks?

abstract:
  Recent observations have indicated that a large fraction of the low to
intermediate luminosity AGN population lives in disk-dominated hosts, while the
more luminous quasars live in bulge-dominated hosts, in conflict with some
previous model predictions. We therefore build and compare a semi-empirical
model for AGN fueling which accounts for both merger and non-merger
'triggering.' In particular, we show that the 'stochastic accretion' model - in
which fueling in disk galaxies is essentially a random process arising whenever
dense gas clouds reach the nucleus - provides a good match to the present
observations at low/intermediate luminosities. However it falls short of the
high-luminosity population. We combine this with models for major
merger-induced AGN fueling, which lead to rarer but more luminous events, and
predict the resulting abundance of disk-dominated and bulge-dominated AGN host
galaxies as a function of luminosity and redshift. We compile and compare
observational constraints from z~0-2. The models and observations generically
show a transition from disk to bulge dominance in hosts near the Seyfert-quasar
transition, at all redshifts. 'Stochastic' fueling dominates AGN by number
(dominant at low luminosity), and dominates BH growth below the knee in the
present-day BH mass function (<10^7 M_sun). However it accounts for just ~10%
of BH mass growth at masses >10^8 M_sun. In total, fueling in disky hosts
accounts for ~30% of the total AGN luminosity density/BH mass density. The
combined model also accurately predicts the AGN luminosity function and
clustering/bias as a function of luminosity and redshift; however, we argue
that these are not sensitive probes of BH fueling mechanisms.


title:
A Precision Multi-Band Two-Epoch Photometric Catalog of 44 Million
  Sources in the Northern Sky from Combination of the USNO-B and Sloan Digital
  Sky Survey Catalogs

abstract:
  A key science driver for the next generation of wide-field optical and radio
surveys is the exploration of the time variable sky. These surveys will have
unprecedented sensitivity and areal coverage, but will be limited in their
ability to detect variability on time scales longer than the lifetime of the
surveys. We present a new precision, multi-epoch photometric catalog that spans
60 years by combining the USNO-B and SDSS Data Release 9 catalogs. We
recalibrate the photometry of the original USNO-B catalog and create a catalog
with two epochs of photometry in up to five different bands for 43,647,887
optical point sources that lie in the DR9 footprint of the northern sky. The
recalibrated objects span a magnitude range 14 < m < 20 and are accurate to
$\approx$ 0.1 mag. We minimize the presence of spurious objects and those with
inaccurate magnitudes by identifying and removing several sources of systematic
errors in the two originating catalogs, with a focus on spurious objects that
exhibit large apparent magnitude variations. After accounting for these
effects, we find $\approx$ 250,000 stars and quasars that show significant (>
4$\sigma$) changes in brightness between the USNO-B and SDSS DR9 epochs. We
discuss the historical value of the catalog and its application to the study of
long time-scale, large amplitude variable stars and quasars.


title: The Top-Antitop Threshold at the ILC: NNLL QCD Uncertainties

abstract:
  We discuss the top-antitop production cross section near threshold at a
future linear collider accounting for the NNLL QCD corrections to the anomalous
dimension of the leading S-wave production current computed recently within
renormalization-group-improved NRQCD perturbation theory. We argue that the
still unknown soft NNLL mixing corrections are negligible so that the NNLL QCD
corrections to the total cross section can be considered complete for practical
purposes. Based on combined variations of the renormalization and matching
scales and the overall size of the perturbative corrections we estimate that
the NNLL QCD total cross section has a normalization uncertainty of 5% at
threshold. We present results for the total cross section and also for the
experimentally more relevant case, when moderate cuts are imposed on the
reconstructed top and antitop invariant masses.


title: A high-dispersion molecular gas component in nearby galaxies

abstract:
  We present a comprehensive study of the velocity dispersion of the atomic
(HI) and molecular (H2) gas components in the disks (R < R25) of a sample of 12
nearby spiral galaxies with moderate inclinations. Our analysis is based on
sensitive high resolution data from the THINGS (atomic gas) and HERACLES
(molecular gas) surveys. To obtain reliable measurements of the velocity
dispersion, we stack regions several kilo-parsecs in size, after accounting for
intrinsic velocity shifts due to galactic rotation and large-scale motions. We
stack using various parameters: the galacto-centric distance, star formation
rate surface density, HI surface density, H2 surface density, and total gas
surface density. We fit single Gaussian components to the stacked spectra and
measure median velocity dispersions for HI of 11.9 +/- 3.1 km/s and for H2 of
12.0 +/- 3.9 km/s. The CO velocity dispersions are thus, surprisingly, very
similar to the corresponding ones of HI, with an average ratio of
sigma(HI)/sigma(CO) = 1.0 +/- 0.2 irrespective of the stacking parameter. The
measured CO velocity dispersions are significantly higher (factor 2) than the
traditional picture of a cold molecular gas disk associated with star
formation. The high dispersion implies an additional thick molecular gas disk
(possibly as thick as the HI disk). Our finding is in agreement with recent
sensitive measurements in individual edge-on and face-on galaxies and points
towards the general existence of a thick disk of molecular gas, in addition to
the well-known thin disk in nearby spiral galaxies.


title: Forced Fluid Dynamics from Gravity in Arbitrary Dimensions

abstract:
  We consider long wavelength solutions to the Einstein-dilaton system with
negative cosmological constant which are dual, under the AdS/CFT
correspondence, to solutions of the conformal relativistic Navier-Stokes
equations with a dilaton-dependent forcing term. Certain forced fluid flows are
known to exhibit turbulence; holographic duals of forced fluid dynamics are
therefore of particular interest as they may aid efforts towards an explicit
model of holographic steady state turbulence. In recent work, Bhattacharyya et
al have constructed long wavelength asymptotically locally AdS_5 bulk
spacetimes with a slowly varying boundary dilaton field which are dual to
forced fluid flows on the 4-dimensional boundary. In this paper, we generalise
their work to arbitrary spacetime dimensions; we explicitly compute the dual
bulk metric, the fluid dynamical stress tensor and Lagrangian to second order
in a boundary derivative expansion.


title: Constraints on Majorana Dark Matter from a Fourth Lepton Family

abstract:
  We study the possibility of dark matter in the form of heavy neutrinos from a
fourth lepton family with helicity suppressed couplings such that dark matter
is produced thermally via annihilations in the early Universe. We present all
possible constraints for this scenario coming from LHC and collider physics,
underground direct detectors, neutrino telescopes, and indirect astrophysical
searches. Although we embed the WIMP candidate within a model of composite
dynamics, the majority of our results are model independent and applicable to
all models where heavy neutrinos with suppressed couplings account for the dark
matter abundance.


title: Prediction of a Weyl Semimetal in Hg$_{1-x-y}$Cd$_x$Mn$_y$Te

abstract:
  We study strained Hg$_{1-x-y}$Cd$_x$Mn$_y$Te in a magnetic field using a
$\bm{k}\cdot\bm{p}$ model and predict that the system is a Weyl semimetal with
two nodes in an experimentally reasonable region of the phase diagram. We also
predict two signatures of the Weyl semimetal phase which arise from tunability
of the Weyl node splitting. First, we find that the Hall conductivity is
proportional to the average Mn ion spin and thus is strongly temperature
dependent. Second, we find an unusual magnetic field angle dependence of the
Hall conductivity; in particular, we predict a peak in $\sigma_{xy}$ as a
function of field angle in the $xz$-plane and a finite $\sigma_{yz}$ as the
$x$-component of the field goes to 0.


title: Discovery of a 6.4 h black hole binary in NGC 4490

abstract:
  We report on the discovery with Chandra of a strong modulation (~90% pulsed
fraction) at ~6.4 h from the source CXOU J123030.3+413853 in the star-forming,
low-metallicity spiral galaxy NGC 4490, which is interacting with the irregular
companion NGC 4485. This modulation, confirmed also by XMM-Newton observations,
is interpreted as the orbital period of a binary system. The spectra from the
Chandra and XMM-Newton observations can be described by a power-law model with
photon index ~1.5. During these observations, which span from 2000 November to
2008 May, the source showed a long-term luminosity variability by a factor of
~5, between ~2E+38 and 1.1E+39 erg/s (for a distance of 8 Mpc). The maximum
X-ray luminosity, exceeding by far the Eddington limit of a neutron star,
indicates that the accretor is a black hole. Given the high X-ray luminosity,
the short orbital period and the morphology of the orbital light curve, we
favour an interpretation of CXOU J123030.3+413853 as a rare high-mass X-ray
binary system with a Wolf-Rayet star as a donor, similar to Cyg X-3. This would
be the fourth system of this kind known in the local Universe. CXOU
J123030.3+413853 can also be considered as a transitional object between high
mass X-ray binaries and ultraluminous X-ray sources (ULXs), the study of which
may reveal how the properties of persistent black-hole binaries evolve entering
the ULX regime.


title:
Phase diagram and pair Tomonaga-Luttinger liquid in a Bose-Hubbard model
  with flat bands

abstract:
  To explore superfluidity in flat-band systems, we consider a Bose-Hubbard
model on a cross-linked ladder with $\pi$ flux, which has a flat band with a
gap between the other band for noninteracting particles, where we study the
effect of the on-site repulsion nonperturbatively. For low densities, we find
exact degenerate ground states, each of which is a Wigner solid with
nonoverlapping Wannier states on the flat band. At higher densities, the
many-body system, when projected onto the lower flat band, can be mapped to a
spin-chain model. This mapping enables us to reveal the existence of a
Tomonaga-Luttinger liquid comprising it pairs of bosons. Interestingly, the
high- and low- density regions have an overlap, where the two phases coexist.


title: Contributions to the model theory of partial differential fields

abstract:
  In this thesis three topics on the model theory of partial differential
fields are considered: the generalized Galois theory for partial differential
fields, geometric axioms for the theory of partial differentially closed
fields, and the existence and properties of the model companion of the theory
of partial differential fields with an automorphism. The approach taken here to
these subjects is to relativize the algebro geometric notions of prolongation
and D-variety to differential notions with respect to a fixed differential
structure.


title:
Noninvasive Measurement of the Pressure Distribution in a Deformable
  Micro-Channel

abstract:
  Direct and noninvasive measurement of the pressure distribution in test
sections of a micro-channel is a challenging, if not an impossible, task. Here,
we present an analytical method for extracting the pressure distribution in a
deformable micro-channel under flow. Our method is based on a measurement of
the channel deflection profile as a function of applied \emph{hydrostatic}
pressure; this initial measurement generates "constitutive curves" for the
deformable channel. The deflection profile under flow is then matched to the
constitutive curves, providing the \emph{hydrodynamic} pressure distribution.
The method is validated by measurements on planar micro-fluidic channels
against analytic and numerical models. The accuracy here is independent of the
nature of the wall deformations and is not degraded even in the limit of large
deflections, $\zeta_{\rm{max}}/2h_{0}= {\cal{O}}(1)$, with $\zeta_{\rm{max}}$
and $2h_0$ being the maximum deflection and the unperturbed height of the
channel, respectively. We discuss possible applications of the method in
characterizing micro-flows, including those in biological systems.


title: High energy rho meson leptoproduction

abstract:
  We investigate the longitudinal and transverse polarized cross-sections of
the leptoproduction of the rho meson in the high energy limit. Our model is
based on the computation of the impact factor gamma*(lambda_gamma) ->
rho(lambda_rho) using the twist expansion in the forward limit and expressed in
the impact parameter space. This treatment involves in the final stage the
twist 2 and twist 3 distribution amplitudes (DAs) of the rho meson and the
dipole scattering amplitude. Taking models that exist for the DAs and for the
dipole cross-section, we get a phenomenological model for the helicity
amplitudes, we compare our predictions with HERA data and get a fairly good
description for large enough virtualities of the photon.


title:
Light-Front Quantum Chromodynamics: A framework for the analysis of
  hadron physics

abstract:
  An outstanding goal of physics is to find solutions that describe hadrons in
the theory of strong interactions, Quantum Chromodynamics (QCD). For this goal,
the light-front Hamiltonian formulation of QCD (LFQCD) is a complementary
approach to the well-established lattice gauge method. LFQCD offers access to
the hadrons' nonperturbative quark and gluon amplitudes, which are directly
testable in experiments at existing and future facilities. We present an
overview of the promises and challenges of LFQCD in the context of unsolved
issues in QCD that require broadened and accelerated investigation. We identify
specific goals of this approach and address its quantifiable uncertainties.


title: Measuring Supermassive Black Hole Spins in Active Galactic Nuclei

abstract:
  Measuring the spins of supermassive black holes (SMBHs) in active galactic
nuclei (AGN) can inform us about the relative role of gas accretion vs. mergers
in recent epochs of the life of the host galaxy and its AGN. Recent advances in
theory and observation have enabled spin measurements for a handful of SMBHs
thus far, but this science is still very much in its infancy. Herein, I discuss
how and why we seek to measure black hole spin in AGN, using recent results
from long X-ray observing campaigns on three radio-quiet AGN (MCG-6-30-15, NGC
3783 and Fairall 9) to illustrate this process and its caveats. I then present
our current knowledge of the distribution of SMBH spins in the local universe.
I also address prospects for improving the accuracy, precision and quantity of
these spin constraints in the next decade and beyond with instruments such as
NuSTAR, Astro-H and a future generation large-area X-ray telescope.


title:
Generation of high-frequency combs locked to atomic resonances by
  quantum phase modulation

abstract:
  A general mechanism for the generation of frequency combs referenced to
atomic resonances is put forward. The mechanism is based on the periodic phase
control of a quantum system's dipole response. We develop an analytic
description of the comb spectral structure, depending on both the atomic and
the phase-control properties. We further suggest an experimental implementation
of our scheme: Generating a frequency comb in the soft-x-ray spectral region,
which can be realized with currently available techniques and radiation
sources. The universality of this mechanism allows the generalization of
frequency-comb technology to arbitrary frequencies, including the hard-x-ray
regime by using reference transitions in highly charged ions.


title:
Propagation of Phonon in a Curved Space Induced by Strain Fields
  Instantons

abstract:
  We show that for a \textbf{multiple-connected} space the low energy strain
fields excitations are given by instantons. Dirac fermions with a chiral mass
and a pairing field propagates effectively in a multiple conected space. When
the elastic strain field response is probed one finds that it is given by the
\textbf{Pointriagin} characteristic. As a result the space time metric is
modified. Applying an external stress field we observe that the phonon path
bends in the transverse direction to the initial direction.


title:
Binding Energetics of Substitutional and Interstitial Helium and
  Di-Helium Defects with Grain Boundary Structure in alpha-Fe

abstract:
  The formation/binding energetics and length scales associated with the
interaction between He atoms and grain boundaries in BCC alpha-Fe was explored.
Ten different low Sigma grain boundaries from the <100> and <110> symmetric
tilt grain boundary systems were used. In this work, we then calculated
formation/binding energies for 1-2 He atoms in the substitutional and
interstitial sites (HeV, He2V, HeInt, He2Int) at all potential grain boundary
sites within 15 Angstroms of the boundary (52826 simulations total). The
present results provide detailed information about the interaction energies and
length scales of 1-2 He atoms with grain boundaries for the structures
examined. A number of interesting new findings emerge from the present study.
For instance, we find that the Sigma3(112) twin boundary in BCC Fe possesses a
much smaller binding energy than other boundaries, which corresponds in long
time dynamics simulations to the ability of an interstitial He defect to break
away from the boundary in simulations on the order of nanoseconds, in contrast
to other boundaries. Additionally, we find that the calculated
formation/binding energies for substitutional He (i.e., He in a monovacancy)
correlates well (R>0.9) with interstitial He, substitutional He2, and
interstitial He2 energies for the same atomic site. This correlation asserts
that the local environment surrounding each site strongly influences the He
defect energies and that highly accurate quantum mechanics calculations of
lower order defects may be an adequate predictor of higher order defects. The
present work shows that the binding and formation energies for He defects are
important for understanding the physics of He diffusion and trapping by grain
boundaries, which can be important for modeling He interactions in
polycrystalline steels.


title: Cold dust but warm gas in the unusual elliptical galaxy NGC 4125

abstract:
  Data from the Herschel Space Observatory have revealed an unusual elliptical
galaxy, NGC 4125, which has strong and extended submillimeter emission from
cold dust but only very strict upper limits to its CO and HI emission.
Depending on the dust emissivity, the total dust mass is 2-5x10^6 Msun. While
the neutral gas-to-dust mass ratio is extremely low (< 12-30), including the
ionized gas traced by [CII] emission raises this limit to < 39-100. The dust
emission follows a similar r^{1/4} profile to the stellar light and the dust to
stellar mass ratio is towards the high end of what is found in nearby
elliptical galaxies. We suggest that NGC 4125 is currently in an unusual phase
where evolved stars produced in a merger-triggered burst of star formation are
pumping large amounts of gas and dust into the interstellar medium. In this
scenario, the low neutral gas-to-dust mass ratio is explained by the gas being
heated to temperatures >= 10^4 K faster than the dust is evaporated. If
galaxies like NGC 4125, where the far-infrared emission does not trace neutral
gas in the usual manner, are common at higher redshift, this could have
significant implications for our understanding of high redshift galaxies and
galaxy evolution.


Supporting Information: Short and long time drop dynamics on lubricated
  substrates


title: Compensation functions for factors of shifts of finite type

abstract:
  We consider an infinite-to-one factor map from an irreducible shift of finite
type X to a sofic shift Y. A compensation function relates equilibrium states
on X to equilibrium states on Y. The p-Dini condition is given as a way of
measuring the smoothness of a continuous function, with 1-Dini corresponding to
functions with summable variation. Two types of compensation functions are
defined in terms of this condition. We show that the relative equilibrium
states of a 1-Dini function f over a fully supported invariant measure on Y are
themselves fully supported, and have positive relative entropy. We then show
that there exists a compensation function which is p-Dini for all p > 1 which
has relative equilibrium states supported on a finite-to-one subfactor.


title:
To Stack or Not to Stack: Spectral Energy Distribution Properties of
  Lya-Emitting Galaxies at z=2.1

abstract:
  We use the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey
(CANDELS) GOODS-S multi-wavelength catalog to identify counterparts for 20 Lya
Emitting (LAE) galaxies at z=2.1. We build several types of stacked Spectral
Energy Distributions (SEDs) of these objects. We combine photometry to form
average and median flux-stacked SEDs, and postage stamp images to form average
and median image-stacked SEDs. We also introduce scaled flux stacks that
eliminate the influence of variation in overall brightness. We use the SED
fitting code SpeedyMC to constrain the physical properties of individual
objects and stacks. Our LAEs at z = 2.1 have stellar masses ranging from 2x10^7
Msun - 8x10^9 Msun (median = 3x10^8 Msun), ages ranging from 4 Myr to 500 Myr
(median =100 Myr), and E(B-V) between 0.02 and 0.24 (median = 0.12). We do not
observe strong correlations between Lya equivalent width (EW) and stellar mass,
age, or E(B-V). The Lya radiative transfer (q) factors of our sample are
predominantly close to one and do not correlate strongly with EW or E(B-V),
implying that Lya radiative transfer prevents Lya photons from resonantly
scattering in dusty regions. The SED parameters of the flux stacks match the
average and median values of the individual objects, with the flux-scaled
median SED performing best with reduced uncertainties. Median image-stacked
SEDs provide a poor representation of the median individual object, and none of
the stacking methods captures the large dispersion of LAE properties.


title:
Kinematic active region formation in a three-dimensional solar dynamo
  model

abstract:
  We propose a phenomenological technique for modelling the emergence of active
regions within a three-dimensional, kinematic dynamo framework. By imposing
localised velocity perturbations, we create emergent flux-tubes out of toroidal
magnetic field at the base of the convection zone, leading to the eruption of
active regions at the solar surface. The velocity perturbations are calibrated
to reproduce observed active region properties (including the size and flux of
active regions, and the distribution of tilt angle with latitude), resulting in
a more consistent treatment of flux-tube emergence in kinematic dynamo models
than artificial flux deposition. We demonstrate how this technique can be used
to assimilate observations and drive a kinematic 3D model, and use it to study
the characteristics of active region emergence and decay as a source of
poloidal field. We find that the poloidal components are strongest not at the
solar surface, but in the middle convection zone, in contrast with the common
assumption that the poloidal source is located near the solar surface. We also
find that, while most of the energy is contained in the lower convection zone,
there is a good correlation between the evolution of the surface and interior
magnetic fields.


title:
Excited electronic states from a variational approach based on
  symmetry-projected Hartree--Fock configurations

abstract:
  Recent work from our research group has demonstrated that symmetry-projected
Hartree--Fock (HF) methods provide a compact representation of molecular ground
state wavefunctions based on a superposition of non-orthogonal Slater
determinants. The symmetry-projected ansatz can account for static correlations
in a computationally efficient way. Here we present a variational extension of
this methodology applicable to excited states of the same symmetry as the
ground state. Benchmark calculations on the C$_2$ dimer with a modest basis
set, which allows comparison with full configuration interaction results,
indicate that this extension provides a high quality description of the
low-lying spectrum for the entire dissociation profile. We apply the same
methodology to obtain the full low-lying vertical excitation spectrum of
formaldehyde, in good agreement with available theoretical and experimental
data, as well as to a challenging model $C_{2v}$ insertion pathway for BeH$_2$.
The variational excited state methodology developed in this work has two
remarkable traits: it is fully black-box and will be applicable to fairly large
systems thanks to its mean-field computational cost.


title: Motion of spin polariton bullets in semiconductor microcavities

abstract:
  The dynamics of optical switching in semiconductor microcavities in the
strong coupling regime is studied using time- and spatially-resolved
spectroscopy. The switching is triggered by polarised short pulses which create
spin bullets of high polariton density. The spin packets travel with speeds of
the order of 106 m/s due to the ballistic propagation and drift of
exciton-polaritons from high to low density areas. The speed is controlled by
the angle of incidence of the excitation beams, which changes the polariton
group velocity.


title:
A Low-Fluorine Solution with the F/Ba Mole Ratio of 2 for the
  Fabrication of YBCO Films

abstract:
  In the reported low-fluorine MOD-YBCO studies, the lowest F/Ba mole ratio of
the precursor solution was 4.5. However, further lowering the F/Ba ratio is
important according to the researches of YBCO thick film. On the other hand,
the F/Ba ratio is necessary to be at least 2 for the full conversion of the Ba
precursor to BaF_2 to avoid the formation of BaCO_3, which is detrimental to
the superconducting performance. In this study, a novel solution with the F/Ba
mole ratio of 2 was developed, in which the fluorine content was only about
10.3% of that used in the conventional TFA-MOD method. Attenuated total
reflectance-Fourier transformed-infrared spectra(ATR-FT-IR) revealed that
BaCO_3 was remarkably suppressed in the as-pyrolyzed film and eliminated at 700
Celsius degree. Thus YBCO films with a critical current density (J_c) over 5 MA
cm^{-2} (77 K, 0 T, 200 nm thickness) could be obtained on LAO single crystal
substrates. In-situ FT-IR spectra showed that no obvious fluorinated gaseous
by-products were detected in the pyrolysis step, which indicated that all of
the F atoms might remain in the film as fluorides. X-ray diffraction (XRD)
\theta/2\theta-scan showed that BaF_2, but neither YF_3 nor CuF_2, was detected
in the films quenched at 400 - 800 Celsius degree. The formation priority of
BaF_2 over YF_3 and CuF_2 was interpreted by the chemical equilibrium of the
potential reactions. Our study could enlarge the synthesis window of the
precursor solution for MOD-YBCO fabrication and open a gate to study the
fluorine content in the precursor solution continuously and systematically.


title:
Visualizing Angular Momentum Eigenstates using the Spin Coherent State
  Representation

abstract:
  Orbital angular momentum eigenfunctions are readily understood in terms of
spherical harmonic wavefunctions. However, the quantum mechanical phenomenon of
spin is often said to be mysterious and hard to visualize, with no classical
analogue. Many textbooks give a heuristic and somewhat unsatisfying picture of
a precessing spin vector. Here we advocate for the "spin wavefunction" in the
spin coherent state representation as a striking, elegant, and mathematically
meaningful visual tool. We also demonstrate that cartographic projections such
as the Hammer projection are useful for visualizing wavefunctions defined on
spherical surfaces.


title: Tracking Sentiment in Mail: How Genders Differ on Emotional Axes

abstract:
  With the widespread use of email, we now have access to unprecedented amounts
of text that we ourselves have written. In this paper, we show how sentiment
analysis can be used in tandem with effective visualizations to quantify and
track emotions in many types of mail. We create a large word--emotion
association lexicon by crowdsourcing, and use it to compare emotions in love
letters, hate mail, and suicide notes. We show that there are marked
differences across genders in how they use emotion words in work-place email.
For example, women use many words from the joy--sadness axis, whereas men
prefer terms from the fear--trust axis. Finally, we show visualizations that
can help people track emotions in their emails.


title:
Decentralized identification and control of networks of coupled mobile
  platforms through adaptive synchronization of chaos

abstract:
  In this paper we propose an application of adaptive synchronization of chaos
to detect changes in the topology of a mobile robotic network. We assume that
the network may evolve in time due to the relative motion of the mobile robots
and due to unknown environmental conditions, such as the presence of obstacles
in the environment. We consider that each robotic agent is equipped with a
chaotic oscillator whose state is propagated to the other robots through
wireless communication, with the goal of synchronizing the oscillators. We
introduce an adaptive strategy that each agent independently implements to: (i)
estimate the net coupling of all the oscillators in its neighborhood and (ii)
synchronize the state of the oscillators onto the same time evolution. We show
that by using this strategy, synchronization can be attained and changes in the
network topology can be detected. We go one step forward and consider the
possibility of using this information to control the mobile network. We show
the potential applicability of our technique to the problem of maintaining a
formation between a set of mobile platforms, which operate in an inhomogeneous
and uncertain environment. We discuss the importance of using chaotic
oscillators and validate our methodology by numerical simulations.


title:
Hierarchical cross-linking in physical alginate gels: a rheological and
  dynamic light scattering investigation

abstract:
  We investigate the dynamics of alginate gels, an important class of
biopolymer-based viscoelastic materials, by combining mechanical tests and
non-conventional, time-resolved light scattering methods. Two relaxation modes
are observed upon applying a compressive or shear stress. Dynamic light
scattering and diffusive wave spectroscopy measurements reveal that these modes
are associated with discontinuous rearrangement events that restructure the gel
network via anomalous, non-diffusive microscopic dynamics. We show that these
dynamics are due to both thermal activation and internal stress stored during
gelation and propose a scenario where a hierarchy of cross-links with different
life times is responsible for the observed complex behavior. Measurements at
various temperatures and sample ages are presented to support this scenario.


title: Sidon Sets and graphs without 4-cycles

abstract:
  The problem of determining the maximum number of edges in an $n$-vertex graph
that does not contain a 4-cycle has a rich history in extremal graph theory.
Using Sidon sets constructed by Bose and Chowla, for each odd prime power $q$
we construct a graph with $q^2 - q - 2$ vertices that does not contain a
4-cycle and has at least $\frac{1}{2}q^3 - q^2 - O(q^{3/4})$ edges. This
disproves a conjecture of Abreu, Balbuena, and Labbate concerning the Tur\'{a}n
number $\mathrm{ex}(q^2 - q - 2, C_4)$.


title: Free resolution of powers of monomial ideals and Golod rings

abstract:
  Let $S = \mathbb{K}[x_1, \dots, x_n]$ be the polynomial ring over a field
$\mathbb{K}$. In this paper we present a criterion for componentwise linearity
of powers of monomial ideals. In particular, we prove that if a square-free
monomial ideal $I$ contains no variable and some power of $I$ is componentwise
linear, then $I$ satisfies gcd condition. For a square-free monomial ideal $I$
which contains no variable, we show that $S/I$ is a Golod ring provided that
for some integer $s\geq 1$, the ideal $I^s$ has linear quotient with respect to
a monomial order. We also provide a lower bound for some Betti numbers of
powers of a square-free monomial ideal which is generated in a single degree.


title: Using Nuances of Emotion to Identify Personality

abstract:
  Past work on personality detection has shown that frequency of lexical
categories such as first person pronouns, past tense verbs, and sentiment words
have significant correlations with personality traits. In this paper, for the
first time, we show that fine affect (emotion) categories such as that of
excitement, guilt, yearning, and admiration are significant indicators of
personality. Additionally, we perform experiments to show that the gains
provided by the fine affect categories are not obtained by using coarse affect
categories alone or with specificity features alone. We employ these features
in five SVM classifiers for detecting five personality traits through essays.
We find that the use of fine emotion features leads to statistically
significant improvement over a competitive baseline, whereas the use of coarse
affect and specificity features does not.


title:
Linear temperature dependence of electron spin resonance linewidths in
  La0.7Ca0.3MnO3 and YBaMn2O6

abstract:
  We analyze recent electron spin resonance (ESR) experiments in La0.7Ca0.3MnO3
and YBaMn2O6 focusing on the behavior of the linewidth at high temperatures
where it is a linear function of the temperature. Noting that the g-factors of
the resonances are characteristic of the Mn4+ ion in a cubic environment, we
make the assumption that the linewidth involves the static susceptibility of
the Mn4+ spins which we analyze in the molecular field approximation. We
conclude that the linear dependence on temperature is associated with the
susceptibility having a Curie or Curie-Weiss form while the
temperature-dependent relaxation mechanism has a microscopic rate proportional
to the temperature. In La0.7Ca0.3MnO3, the Mn4+ susceptibility has the
ferromagnetic Curie-Weiss form, and the static contribution to the linewidth
arising from distortions of the oxygen octahedra is absent due to motional
narrowing brought on by the rapid hopping of the eg polarons. In YBaMn2O6
either of two scenarios is possible. The Mn4+ susceptibility above 520 K is
Curie-like and the static term is present, or the susceptibility has the
antiferromagnetic Curie-Weiss form and the static term is absent due to
motional narrowing. It is concluded that the Curie model, with offsetting
double exchange and and superexchange Curie-Weiss parameters, is the more
likely scenario. It is suggested that the linear-T variation of the linewidth
in both materials arises from either a Korringa-like mechanism involving
interactions with mobile carriers or from a spin-phonon process coming from
interactions between the Mn4+ ions and the lattice vibrations.


title: Emergent Newtonian dynamics and the geometric origin of mass

abstract:
  We consider a set of macroscopic (classical) degrees of freedom coupled to an
arbitrary many-particle Hamiltonian system, quantum or classical. These degrees
of freedom can represent positions of objects in space, their angles, shape
distortions, magnetization, currents and so on. Expanding their dynamics near
the adiabatic limit we find the emergent Newton's second law (force is equal to
the mass times acceleration) with an extra dissipative term. In systems with
broken time reversal symmetry there is an additional Coriolis type force
proportional to the Berry curvature. We give the microscopic definition of the
mass tensor relating it to the non-equal time correlation functions in
equilibrium or alternatively expressing it through dressing by virtual
excitations in the system. In the classical (high-temperature) limit the mass
tensor is given by the product of the inverse temperature and the Fubini-Study
metric tensor determining the natural distance between the eigenstates of the
Hamiltonian. For free particles this result reduces to the conventional
definition of mass. This finding shows that any mass, at least in the classical
limit, emerges from the distortions of the Hilbert space highlighting deep
connections between any motion (not necessarily in space) and geometry. We
illustrate our findings with four simple examples.


title: Sudden Decoherence Transitions for Quantum Discord

abstract:
  We investigate the disappearance of discord in 2- and multi-qubit systems
subject to decohering influences. We formulate the computation of quantum
discord in terms of the generalized Bloch vector, which gives useful insights
on the time evolution of quantum coherence for the open system, particularly
the comparison of entanglement and discord. And we show that the analytical
calculation of the global geometric discord is NP-hard in the number of qubits.
We present an efficient numerical method to calculating the quantum discord for
a certain important class of multipartite states. In agreement with previous
work for 2-qubit cases, (Mazzola et al., Phys. Rev. Lett. 104, 200401 (2010)),
we find situations in which there is a sudden transition from classical to
quantum decoherence characterized by the discord remaining relatively robust
(classical decoherence) until a certain point from where it begins to decay
quickly whereas the classical correlation decays more slowly (quantum
decoherence). However, we find that as the number of qubits increases, the
chance of this kind of transition occurring becomes small.


title:
Planets spinning up their host stars: a twist on the age-activity
  relationship

abstract:
  It is a long-standing question in exoplanet research if Hot Jupiters can
influence the magnetic activity of their host stars. While cool stars usually
spin down with age and become inactive, an input of angular momentum through
tidal interaction, as seen for example in close binaries, can preserve high
activity levels over time. This may also be the case for cool stars hosting a
Hot Jupiter. However, selection effects from planet detection methods often
dominate the activity levels seen in samples of exoplanet host stars, and
planet-induced, systematically enhanced stellar activity has not been detected
unambiguously so far. We have developed an approach to identify planet-induced
stellar spin-up avoiding the selection biases from planet detection, by using
visual proper motion binaries in which only one of the stars possesses a Hot
Jupiter. This approach immediately rids one of the ambiguities of detection
biases: with two co-eval stars, the second star acts as a negative control. We
present results from our ongoing observational campaign at X-ray wavelengths
and in the optical, and present several outstanding systems which display
significant age/activity discrepancies presumably caused by their Hot Jupiters.


title: Electric Field Conjugation with the Project 1640 coronagraph

abstract:
  The Project 1640 instrument on the 200-inch Hale telescope at Palomar
Observatory is a coronagraphic instrument with an integral field spectrograph
at the back end, designed to find young, self-luminous planets around nearby
stars. To reach the necessary contrast for this, the PALM-3000 adaptive optics
system corrects for fast atmospheric speckles, while CAL, a phase-shifting
interferometer in a Mach-Zehnder configuration, measures the quasistatic
components of the complex electric field in the pupil plane following the
coronagraphic stop. Two additional sensors measure and control low-order modes.
These field measurements may then be combined with a system model and data
taken separately using a white-light source internal to the AO system to
correct for both phase and amplitude aberrations. Here, we discuss and
demonstrate the procedure to maintain a half-plane dark hole in the image plane
while the spectrograph is taking data, including initial on-sky performance.


title: The mechanism why colliders could create quasi-stable black holes

abstract:
  It has been postulated that black holes could be created in particle
collisions within the range of the available energies for nowadays colliders
(LHC). In this paper we analyze the evaporation of a type of black holes that
are candidates for this specific behaviour, namely, small black holes on a
brane in a world with large extra-dimensions. We examine their evolution under
the assumption that energy conservation is satisfied during the process and
compare it with the standard evaporation approach. We claim that, rather than
undergoing a quick total evaporation, black holes become quasi-stable. We
comment on the (absence of) implications for safety of this result. We also
discuss how the presence of black holes together with the correctness of the
energy conservation approach might be experimentally verified.


title: A Singlet Extension of the MSSM with a Dark Matter Portal

abstract:
  The minimal extension of the MSSM (NMSSM) has been widely studied in the
search for a natural solution to the $\mu$ problem. In this work, we consider a
variation of the NMSSM where an extra singlet is added and a Peccei-Quinn
symmetry is imposed. We study its neutralino sector and compute the
annihilation cross section of the lightest neutralino. We use existent
cosmological and collider data to constrain the parameter space and consider
the lightest neutralino, which is very light, as a dark matter candidate.


title: The range of a random walk on a comb

abstract:
  The graph obtained from the integer grid Z x Z by the removal of all
horizontal edges that do not belong to the x-axis is called a comb. In a random
walk on a graph, whenever a walker is at a vertex v, in the next step it will
visit one of the neighbors of v, each with probability 1/d(v), where d(v)
denotes the degree of v. We answer a question of Cs\'aki, Cs\"org\"o, F\"oldes,
R\'ev\'esz, and Tusn\'ady by showing that the expected number of vertices
visited by a random walk on the comb after n steps is
(1/(2\sqrt{2\pi})+o(1))\sqrt n\log n. This contradicts a claim of Weiss and
Havlin.


title: Causal Inference in Observational Studies with Non-Binary Treatments

abstract:
  Propensity score methods have become a part of the standard toolkit for
applied researchers who wish to ascertain causal effects from observational
data. While they were originally developed for binary treatments, several
researchers have proposed generalizations of the propensity score methodology
for non-binary treatment regimes. Such extensions have widened the
applicability of propensity score methods and are indeed becoming increasingly
popular themselves. In this article, we closely examine the two main
generalizations of propensity score methods, namely, the propensity function
(P-FUNCTION) of Imai and van Dyk (2004) and the generalized propensity score
(GPS) of Hirano and Imbens (2004), along with recent extensions of the GPS that
aim to improve its robustness. We compare the assumptions, theoretical
properties, and empirical performance of these alternative methodologies. On a
theoretical level, the GPS and its extensions are advantageous in that they can
be used to estimate the full dose response function rather than the simple
average treatment effect that is typically estimated with the P-FUNCTION.
Unfortunately, our analysis shows that in practice response models often used
with the original GPS are less flexible than those typically used with
propensity score methods and are prone to misspecification. We compare new and
existing methods that improve the robustness of the GPS and propose methods
that use the P-FUNCTION to estimate the dose response function. We illustrate
our findings and proposals through simulation studies, including one based on
an empirical application.


title:
Reverse Coarse-graining for Equation-free Modeling: Application to
  Multiscale Molecular Dynamics

abstract:
  Constructing atom-resolved states from low-resolution data is of practical
importance in many areas of science and engineering. This problem is addressed
in this paper in the context of multiscale factorization methods for molecular
dynamics. These methods capture the crosstalk between atomic and coarse-grained
scales arising in macromolecular systems. This crosstalk is accounted for by
Trotter factorization, which is used to separate the all-atom from the
coarse-grained phases of the computation. In this approach, short molecular
dynamics runs are used to advance in time the coarse-grained variables, which
in turn guide the all-atom state. To achieve this coevolution, an all-atom
microstate consistent with the updated coarse-grained variables must be
recovered. This recovery is cast here as a non-linear optimization problem that
is solved with a quasi-Newton method. The approach yields a Boltzmann-relevant
microstate whose coarse-grained representation and some of its fine-scale
features are preserved. Embedding this algorithm in multiscale factorization is
shown to be accurate and scalable for simulating proteins and their assemblies.


title: Comparison of fine structural mice via coarse iteration

abstract:
  Let M be a fine structural mouse. Let D be a fully backgrounded
L[E]-construction computed inside an iterable coarse premouse S. We describe a
process comparing M with D, through forming iteration trees on M and on S. We
then prove that this process succeeds.


title:
Observation of longitudinal and transverse self-injections in
  laser-plasma accelerators

abstract:
  Laser-plasma accelerators can produce high quality electron beams, up to
giga-electronvolts in energy, from a centimeter scale device. The properties of
the electron beams and the accelerator stability are largely determined by the
injection stage of electrons into the accelerator. The simplest mechanism of
injection is self-injection, in which the wakefield is strong enough to trap
cold plasma electrons into the laser wake. The main drawback of this method is
its lack of shot-to-shot stability. Here we present experimental and numerical
results that demonstrate the existence of two different self-injection
mechanisms. Transverse self-injection is shown to lead to low stability and
poor quality electron beams, because of a strong dependence on the intensity
profile of the laser pulse. In contrast, longitudinal injection, which is
unambiguously observed for the first time, is shown to lead to much more stable
acceleration and higher quality electron beams.


title:
Uniform Infall toward the Cometary H II Region in the G34.26+0.15
  Complex?

abstract:
  Gas accretion is a key process in star formation. However, the gas infall
detections in high-mass star forming regions with high-spatial resolution
observations are rare. Here we report the detection of gas infall towards a
cometary ultracompact H{\sc ii} region "C" in G34.26+0.15 complex. The hot core
associated with "C" has a mass of $\sim$76 M$_{\sun}$ and a volume density of
1.1$\times10^{8}$ cm$^{-3}$. The HCN (3--2), HCO$^{+}$ (1--0) lines observed by
single-dishes and the CN (2--1) lines observed by the SMA show redshifted
absorption features, indicating gas infall. We found a linear relationship
between the line width and optical depth of the CN (2--1) lines. Those
transitions with larger optical depth and line width have larger absorption
area. However, the infall velocities measured from different lines seem to be
constant, indicating the gas infall is uniform. We also investigated the
evolution of gas infall in high-mass star forming regions. At stages prior to
hot core phase, the typical infall velocity and mass infall rate are $\sim$ 1
km s$^{-1}$ and $\sim10^{-4}$ M$_{\sun}\cdot$yr$^{-1}$, respectively. While in
more evolved regions, the infall velocity and mass infall rates can reach as
high as serval km s$^{-1}$ and $\sim10^{-3}-10^{-2}$ M$_{\sun}\cdot$yr$^{-1}$,
respectively. Accelerated infall has been detected towards some hypercompact
H{\sc ii} and ultracompact H{\sc ii} regions. However, the acceleration
phenomenon becomes inapparent in more evolved ultracompact H{\sc ii} regions
(e.g. G34.26+0.15).


title: pcigale: porting Code Investigating Galaxy Emission to Python

abstract:
  We present pcigale, the port to Python of CIGALE (Code Investigating Galaxy
Emission) a Fortran spectral energy distribution (SED) fitting code developed
at the Laboratoire d'Astrophysique de Marseille. After recalling the specifics
of the SED fitting method, we show the gains in modularity and versatility
offered by Python, as well as the drawbacks compared to the compiled code.


title: The Geometry of Orbifolds via Lie Groupoids

abstract:
  The purpose of this thesis is to use the language of orbifold groupoids to
describe the geometry and topology of orbifolds, highlighting advantages and
disadvantages of this language as they arise.


title: On some colored Eulerian quasisymmetric functions

abstract:
  Recently, Hyatt introduced some colored Eulerian quasisymmetric function to
study the joint distribution of excedance number and major index on colored
permutation groups. We show how Hyatt's generating function formula for the
fixed point colored Eulerian quasisymmetric functions can be deduced from the
Decrease value theorem of Foata and Han. Using this generating function
formula, we prove two symmetric function generalizations of the
Chung-Graham-Knuth symmetrical Eulerian identity for some flag Eulerian
quasisymmetric functions, which are specialized to the flag excedance numbers.
Combinatorial proofs of those symmetrical identities are also constructed.
  We also study some other properties of the flag Eulerian quasisymmetric
functions. In particular, we confirm a recent conjecture of Mongelli [Journal
of Combinatorial Theory, Series A, 120 (2013) 1216--1234] about the unimodality
of the generating function of the flag excedances over the type B derangements.
Moreover, colored versions of the hook factorization and admissible inversions
of permutations are found, as well as a new recurrence formula for the
$(\maj-\exc,\fexc)$-$q$-Eulerian polynomials.
  We introduce a colored analog of Rawlings major index on colored permutations
and obtain an interpretation of the colored Eulerian quasisymmetric functions
as sums of some fundamental quasisymmetric functions related with them, by
applying Stanley's $P$-partition theory and a decomposition of the Chromatic
quasisymmetric functions due to Shareshian and Wachs.


title: Predicting Adoption Probabilities in Social Networks

abstract:
  In a social network, adoption probability refers to the probability that a
social entity will adopt a product, service, or opinion in the foreseeable
future. Such probabilities are central to fundamental issues in social network
analysis, including the influence maximization problem. In practice, adoption
probabilities have significant implications for applications ranging from
social network-based target marketing to political campaigns; yet, predicting
adoption probabilities has not received sufficient research attention. Building
on relevant social network theories, we identify and operationalize key factors
that affect adoption decisions: social influence, structural equivalence,
entity similarity, and confounding factors. We then develop the
locally-weighted expectation-maximization method for Na\"ive Bayesian learning
to predict adoption probabilities on the basis of these factors. The principal
challenge addressed in this study is how to predict adoption probabilities in
the presence of confounding factors that are generally unobserved. Using data
from two large-scale social networks, we demonstrate the effectiveness of the
proposed method. The empirical results also suggest that cascade methods
primarily using social influence to predict adoption probabilities offer
limited predictive power, and that confounding factors are critical to adoption
probability predictions.


title:
Matters of Gravity, The Newsletter of the Topical Group on Gravitation
  of the American Physical Society, Volume 42, Fall 2013

abstract:
  GGR News: we hear that..., by David Garfinkle
  What's new in LIGO, by David Shoemaker
  News from NSF, by Pedro Marronetti
  Citation counts and indicies: Beware of bad data, by Clifford Will
  Research Briefs: Results from Planck, by William Jones
  Conference Reports: Gravity- Strings and Higher Dimensions, by Simon Ross
  Capra 16, by Leor Barack
  Reduced Order Modeling in General Relativity, by Michele Vallisneri


title: On-Chip Optical Squeezing

abstract:
  We present the first demonstration of all-optical squeezing in an on-chip
monolithically integrated CMOS-compatible platform. Our device consists of a
low loss silicon nitride microring optical parametric oscillator (OPO) with a
gigahertz cavity linewidth. We measure 1.7 dB (5 dB corrected for losses) of
sub-shot noise quantum correlations between bright twin beams generated in the
microring four-wave-mixing OPO pumped above threshold. This experiment
demonstrates a compact, robust, and scalable platform for quantum optics and
quantum information experiments on-chip.


title: Robust signals from a quantum-based magnetic compass sensor

abstract:
  A quantum-based magnetic compass sensor, mediated through radical pair
reactions, has been suggested to underlie the sensory ability of migrating
birds to receive directional information from the geomagnetic field. Here we
extend the currently available models by considering the effects of slow
fluctuations in the nuclear spin environment on the directional signal. We
quantitatively evaluate the robustness of signals under fluctuations on a
timescale longer than the lifetime of a radical pair, utilizing two models of
radical pairs. Our results suggest design principles for building a
radical-pair based compass sensor that is both robust and highly directional
sensitive.


title:
Vortex stability and permanent flow in nonequilibrium polariton
  condensates

abstract:
  We study the effects of imprinting a single-quantized vortex on the steady
state of a microcavity exciton-polariton condensate generated via parametric
scattering. Interestingly we observe two distinct regimes: In the first case,
at low polariton densities, the effect of the pulsed probe, containing the
vortex state, is to generate a gain response in the condensate lasting for tens
of picoseconds during which no dissipation of the circulating currents is
detected. In the second regime, at higher densities, the gain lasts much less
and the circulation is imprinted directly into the steady state, which acquires
permanent rotation for as long as the vortex remains within the condensate. We
use two different ways of measuring the circulation of the condensate and
demonstrate that in both cases, polariton condensation in the parametric
scattering regime can sustain permanent supercurrents.


title:
A lower bound on the fidelity between two states in terms of their Bures
  distance

abstract:
  Fidelity is a fundamental and ubiquitous concept in quantum information
theory. Fuchs-van de Graaf's inequalities deal with bounding fidelity from
above and below. In this paper, we give a lower bound on the quantum fidelity
between two states in terms of their Bures distance.


title:
Establishing a universal relation between gravitational waves and black
  hole lensing

abstract:
  Black hole lensing and gravitational waves are, respectively, closely
dependent of the property of the lens and radiation source. In this letter, a
universal relation between them is established for a rotating black hole acting
simultaneously as a lens and a gravitational wave source, in an asymptotically
flat spacetime. The relation only relies on the lens geometry and observable,
while is independent of the specific nature of the black hole. Therefore, the
possible gravitational wave sources could be located with modern astronomical
instrument from the side of the lensing without knowing the specific nature of
the black hole lens. Moreover, the low bound of the frequency of the
gravitational waves can also be well determined.


title:
Optimal Decentralized Control with Asymmetric One-Step Delayed
  Information Sharing

abstract:
  We consider optimal control of decentralized LQG problems for plants
controlled by two players having asymmetric information sharing patterns
between them. In one scenario, players are assumed to have a bidirectional
error-free, unlimited rate communication channel with no delay in one direction
and a unit delay in the other. In another scenario, the communication channel
is assumed to be unidirectional with a unit delay. Delayed information sharing
patterns in general do not admit linear optimal control laws and are thus
difficult to control optimally. However, in these scenarios, we show that the
problem has a partially nested information structure, and thus linear optimal
control laws exist. Summary statistics to characterize these laws are developed
and deterministic convex optimization problems are formulated whose solutions
yield the optimal control laws. The state feedback case is solved for both
scenarios and extended to output and partial output feedback in case of
bidirectional and unidirectional channels respectively.


title: Phase Transitions in Models of Bird Flocking

abstract:
  The aim of the present paper is to elucidate the transition from collective
to random behavior exhibited by various mathematical models of bird flocking.
In particular, we compare Vicsek's model [Viscek et al., Phys. Rev. Lett. 75,
1226 -- 1229 (1995)] with one based on topological considerations. The latter
model is found to exhibit a first order phase transition from flocking to
decoherence, as the 'noise parameter' of the problem is increased, whereas
Viscek's model gives a second order transition. Refining the topological model
in such a way that birds are influenced mostly by the birds in front of them,
less by the ones at their sides and not at all by those behind them (because
they do not see them), we find a behavior that lies in between the two models.
Finally, we propose a novel mechanism for preserving the flock's cohesion,
without imposing artificial boundary conditions or attracting forces.


title: An Introduction to Inversion in an Ellipse

abstract:
  In this paper we study the inversion in an ellipse and some properties, which
generalizes the classical inversion with respect to a circle. We also study the
inversion in an ellipse of lines, ellipses and other curves. Finally, we
generalize the Pappus Chain with respect to ellipses and the Pappus Chain
Theorem.


title:
Diffeomorphic Metric Mapping and Probabilistic Atlas Generation of
  Hybrid Diffusion Imaging based on BFOR Signal Basis

abstract:
  We propose a large deformation diffeomorphic metric mapping algorithm to
align multiple b-value diffusion weighted imaging (mDWI) data, specifically
acquired via hybrid diffusion imaging (HYDI), denoted as LDDMM-HYDI. We then
propose a Bayesian model for estimating the white matter atlas from HYDIs. We
adopt the work given in Hosseinbor et al. (2012) and represent the q-space
diffusion signal with the Bessel Fourier orientation reconstruction (BFOR)
signal basis. The BFOR framework provides the representation of mDWI in the
q-space and thus reduces memory requirement. In addition, since the BFOR signal
basis is orthonormal, the L2 norm that quantifies the differences in the
q-space signals of any two mDWI datasets can be easily computed as the sum of
the squared differences in the BFOR expansion coefficients. In this work, we
show that the reorientation of the $q$-space signal due to spatial
transformation can be easily defined on the BFOR signal basis. We incorporate
the BFOR signal basis into the LDDMM framework and derive the gradient descent
algorithm for LDDMM-HYDI with explicit orientation optimization. Additionally,
we extend the previous Bayesian atlas estimation framework for scalar-valued
images to HYDIs and derive the expectation-maximization algorithm for solving
the HYDI atlas estimation problem. Using real HYDI datasets, we show the
Bayesian model generates the white matter atlas with anatomical details.
Moreover, we show that it is important to consider the variation of mDWI
reorientation due to a small change in diffeomorphic transformation in the
LDDMM-HYDI optimization and to incorporate the full information of HYDI for
aligning mDWI.


title: The hard X-ray behavior of Aql X-1 during type-I bursts

abstract:
  We report the discovery of an anti-correlation between the soft and the hard
X-ray lightcurves of the X-ray binary Aql X-1 when bursting. This behavior may
indicate that the corona is cooled by the soft X-ray shower fed by the type-I
X-ray bursts, and that this process happens within a few seconds. Stacking the
Aql X-1 lightcurves of type-I bursts, we find a shortage in the 40--50 keV
band, delayed by 4.5$\pm$1.4 s with respect to the soft X-rays. The
photospheric radius expansion (PRE) bursts are different in that neither a
shortage nor an excess shows up in the hard X-ray lightcurve.


title: Vibrating wire alignment technique

abstract:
  Vibrating wire alignment technique is a kind of method which through
measuring the spatial distribution of magnetic field to do the alignment and it
can achieve very high alignment accuracy. Vibrating wire alignment technique
can be applied for magnet fiducialization and accelerator straight section
components alignment, it is a necessary supplement for conventional alignment
method. This article will systematically expound the international research
achievements of vibrating wire alignment technique, including vibrating wire
model analysis, system frequency calculation, wire sag calculation and the
relation between wire amplitude and magnetic induction intensity. On the basis
of model analysis this article will introduce the alignment method which based
on magnetic field measurement and the alignment method which based on amplitude
and phase measurement. Finally, some basic questions will be discussed and the
solutions will be given.


title: Interpretation of strange hadron production at LHC

abstract:
  We extend the SHM analysis of hadron production results showing here
consistency with the increased experimental data set, stability of the fit with
regard to inclusion of finite resonance widths and 2-star hyperon resonances.
We present new results on strangeness yield as a function of centrality and
present their interpretation in terms of QGP inspired model of strangeness
abundance in the hadronizing fireball.


title: Classical Simulation of Quantum Noise

abstract:
  Dephasing decoherence induced by interaction of one qubit with a quantum bath
can be simulated classically by random unitary evolution without the need for a
bath and this random unitary evolution is equivalent to the quantum case. For a
general dephasing model and a single qubit system, we explicitly construct the
noise functional and completely specify the random unitary evolution. To
demonstrate the technique, we applied our results to three paradigmatic models:
spin-boson, central spin, and quantum impurity. For multiple qubits, we
identify a class of generalized quantum dephasing models that can be simulated
classically. Finally we show that depolarizing quantum models can be simulated
classically for all dimensionalities of the principal system.


title: Fermions Tunneling from Plebanski-Demianski Black Holes

abstract:
  Hawking radiation spectrum via fermions tunneling is investigated through
horizon radii of Pleba$\acute{\textmd{n}}$ski-Demia$\acute{\textmd{n}}$ski
family of black holes. To this end, we determine the tunneling probabilities
for outgoing and incoming charged fermion particles and obtain their
corresponding Hawking temperatures. The graphical behavior of Hawking
temperatures and horizon radii (cosmological and event horizons) is also
studied. We find consistent results with those already available in literature.


title: Some constructions of compact quantum groups

abstract:
  The purpose of this paper is to consider some basic constructions in the
category of compact quantum groups --for example de case of extensions, of
Drinfeld twists, of matched pairs, of extensions, of linked pairs and of
cocycle Singer pairs -- with special emphasis in the finite dimensional
situation. We give conditions, in some cases necessary and sufficient, to
extend to the new objects the original compact structure. We illustrate the
results in the case of matched pairs of groups.