title:
Ordered phases in the Holstein-Hubbard model: Interplay of strong
  Coulomb interaction and electron-phonon coupling

abstract:
  We study the Holstein-Hubbard model at half filling to explore ordered phases
including su- perconductivity (SC), antiferromagnetism (AF), and charge order
(CO) in situations where the electron-electron and electron-phonon interactions
are strong (~ electronic bandwidth). The model is solved in the dynamical
mean-field approximation using a continuous-time quantum Monte Carlo impurity
solver. We determine the superconducting transition temperature (Tc) and the SC
order parameter and show that the phonon-induced retardation or the strong
Coulomb interaction leads to a significant reduction and shift of the Tc dome
if one interprets the system as having an effective static interaction Ueff
given by the Hubbard U reduced by the phonon-mediated attraction in the static
limit. This behavior is analyzed by comparison to an effective static model in
the polaron representation with a reduced bandwidth. We also determine the
finite-temperature phase diagram including AF and CO. In the moderate-coupling
regime, there is a hysteretic region of AF and CO around Ueff = 0, while the
two phases are separated by a paramagnetic metal in the weak-coupling regime
and a paramagnetic insulator in the strong coupling regime.


title:
Ambiguities and Subtleties in Fermion Mass Terms in Practical Quantum
  Field Theory

abstract:
  This is a review on structure of the fermion mass terms in quantum field
theory, under the perspective of its practical applications in the real physics
of Nature -- specifically, we discuss fermion mass structure in the Standard
Model of high energy physics, which successfully describes fundamental physics
up to the TeV scale. The review is meant to be pedagogical, with detailed
mathematics presented beyond the level one can find any easily in the
textbooks. The discussions, however, bring up important subtleties and
ambiguities about the subject that may be less than well appreciated. In fact,
the naive perspective of the nature and masses of fermions as one would easily
drawn from the presentations of fermion fields and their equations of motion
from a typical textbook on quantum field theory leads to some confusing or even
wrong statements which we clarify here. In particular, we illustrate clearly
that a Dirac fermion mass eigenstate is mathematically equivalent to two
degenerated Majorana fermion mass eigenstates at least so long as the mass
terms are concerned. There are further ambiguities and subtleties in the exact
description of the eigenstate(s). Especially, for the case of neutrinos, the
use of the Dirac or Majorana terminology may be mostly a matter of choice. The
common usage of such terminology is rather based on the broken $SU(2)$ charges
of the related Weyl spinors hence conventional and may not be unambiguously
extended to cover more complicate models.


title:
Weak Interactions in Top-Quark Pair Production at Hadron Colliders: An
  Update

abstract:
  Weak corrections for top-quark pair production at hadron colliders are
revisited. Predictions for collider energies of 8 TeV, adopted to the recent
LHC run, and for 13 as well as 14 TeV, presumably relevant for the next round
of LHC experiments, are presented. Kinematic regions with large momentum
transfer are identified, where the corrections become large and may lead to
strong distortions of differential distributions, thus mimicking anomalous top
quark couplings. As a complementary case we investigate the threshold region,
corresponding to configurations with small relative velocity between top and
antitop quark, which is particularly sensitive to the top-quark Yukawa
coupling. We demonstrate, that nontrivial upper limits on this coupling,
complementary to those recently derived by the CMS and the ATLAS collaorations,
are well within reach of ongoing experiments. In addition we suggest a
prescription that allows the implementation of these corrections in current
Monte Carlo generators. Furthermore, the weak corrections have been included in
the publicly available Hathor library. The numerical results presented in this
article use the same setup as the recently calculated NNLO QCD corrections. The
results can thus be combined to give the most precise theoretical predictions.


title: Exact ground states of correlated electrons on pentagon chains

abstract:
  We construct a class of exact ground states for correlated electrons on
pentagon chains in the high density region and discuss their physical
properties. In this procedure the Hamiltonian is first cast in a positive
semidefinite form using composite operators as a linear combination of creation
operators acting on the sites of finite blocks. In the same step, the
interaction is also transformed to obtain terms which require for their minimum
eigenvalue zero at least one electron on each site. The transformed Hamiltonian
matches the original Hamiltonian through a nonlinear system of equations whose
solutions place the deduced ground states in restricted regions of the
parameter space. In the second step, nonlocal product wave functions in
position space are constructed. They are proven to be unique ground states
which describe non-saturated ferromagnetic and correlated half metallic states.
These solutions emerge when the strength of the Hubbard interaction $U_i$ is
site dependent inside the unit cell. In the deduced phases, the interactions
tune the bare dispersive band structure such to develop an effective upper flat
band. We show that this band flattening effect emerges for a broader class of
chains and is not restricted to pentagon chains. For the characterization of
the deduced solutions, uniqueness proofs, exact ground state expectation values
for long-range hopping amplitudes and correlation functions are also
calculated. The study of physical reasons which lead to the appearance of
ferromagnetism has revealed a new mechanism for the emergence of an ordered
phase, described here in details (because of lack of space see the continuation
in the paper).


title:
Stokes Matrices for the Quantum Cohomologies of Orbifold Projective
  Lines

abstract:
  We prove the Dubrovin's conjecture for the Stokes matrices for the quantum
cohomology of orbifold projective lines. The conjecture states that the Stokes
matrix of the first structure connection of the Frobenius manifold constructed
from the Gromov-Witten theory coincides with the Euler matrix of a full
exceptional collection of the bounded derived category of the coherent sheaves.
Our proof is based on the homological mirror symmetry, primitive forms of
affine cusp polynomials and the Picard-Lefschetz theory.


title: Time-Energy Measure for Quantum Processes

abstract:
  Quantum mechanics sets limits on how fast quantum processes can run given
some system energy through time-energy uncertainty relations, and they imply
that time and energy are tradeoff against each other. Thus, we propose to
measure the time-energy as a single unit for quantum channels. We consider a
time-energy measure for quantum channels and compute lower and upper bounds of
it using the channel Kraus operators. For a special class of channels (which
includes the depolarizing channel), we can obtain the exact value of the
time-energy measure. One consequence of our result is that erasing quantum
information requires $\sqrt{(n+1)/n}$ times more time-energy resource than
erasing classical information, where $n$ is the system dimension.


title: Compressive Sensing of Sparse Tensors

abstract:
  Compressive sensing (CS) has triggered enormous research activity since its
first appearance. CS exploits the signal's sparsity or compressibility in a
particular domain and integrates data compression and acquisition, thus
allowing exact reconstruction through relatively few non-adaptive linear
measurements. While conventional CS theory relies on data representation in the
form of vectors, many data types in various applications such as color imaging,
video sequences, and multi-sensor networks, are intrinsically represented by
higher-order tensors. Application of CS to higher-order data representation is
typically performed by conversion of the data to very long vectors that must be
measured using very large sampling matrices, thus imposing a huge computational
and memory burden. In this paper, we propose Generalized Tensor Compressive
Sensing (GTCS)--a unified framework for compressive sensing of higher-order
tensors which preserves the intrinsic structure of tensor data with reduced
computational complexity at reconstruction. GTCS offers an efficient means for
representation of multidimensional data by providing simultaneous acquisition
and compression from all tensor modes. In addition, we propound two
reconstruction procedures, a serial method (GTCS-S) and a parallelizable method
(GTCS-P). We then compare the performance of the proposed method with Kronecker
compressive sensing (KCS) and multi way compressive sensing (MWCS). We
demonstrate experimentally that GTCS outperforms KCS and MWCS in terms of both
reconstruction accuracy (within a range of compression ratios) and processing
speed. The major disadvantage of our methods (and of MWCS as well), is that the
compression ratios may be worse than that offered by KCS.


title: 2-blocks with abelian defect groups

abstract:
  We give a classification, up to Morita equivalence, of 2-blocks of
quasi-simple groups with abelian defect groups. As a consequence, we show that
Donovan's conjecture holds for elementary abelian 2-groups, and that the
entries of the Cartan matrices are bounded in terms of the defect for arbitrary
abelian 2-groups. We also show that a block with defect groups of the form
$C_{2^m} \times C_{2^m}$ for $m \geq 2$ has one of two Morita equivalence types
and hence is Morita equivalent to the Brauer correspondent block of the
normaliser of a defect group. This completes the analysis of the Morita
equivalence types of 2-blocks with abelian defect groups of rank 2, from which
we conclude that Donovan's conjecture holds for such 2-groups. A further
application is the completion of the determination of the number of irreducible
characters in a block with abelian defect groups of order 16. The proof uses
the classification of finite simple groups.


title: From rough path estimates to multilevel Monte Carlo

abstract:
  New classes of stochastic differential equations can now be studied using
rough path theory (e.g. Lyons et al. [LCL07] or Friz--Hairer [FH14]). In this
paper we investigate, from a numerical analysis point of view, stochastic
differential equations driven by Gaussian noise in the aforementioned sense.
Our focus lies on numerical implementations, and more specifically on the
saving possible via multilevel methods. Our analysis relies on a subtle
combination of pathwise estimates, Gaussian concentration, and multilevel
ideas. Numerical examples are given which both illustrate and confirm our
findings.


title: On a superquadratic elliptic system with strongly indefinite structure

abstract:
  In this paper, we consider the elliptic system \begin{equation*}
  \left\{\begin{array}{ll}
  -\Delta u=g(x,v)\,\, \textnormal{in}\Omega, & \hbox{}
  -\Delta v=f(x,u)\,\,\textnormal{in}\Omega, & \hbox{}
u=v=0\textnormal{on}\partial\Omega, & \hbox{}
  \end{array}
  \right. \end{equation*} where $\Omega$ is a bounded smooth domain in
$\mathbb{R}^N$, and $f$ and $g$ satisfy a general superquadratic condition. By
using variational methods, we prove the existence of infinitely many solutions.
Our argument relies on the application of a generalized variant fountain
theorem for strongly indefinite functionals. Previous results in the topic are
improved.


title: The openness conjecture for plurisubharmonic functions

abstract: We give a proof of the openness conjecture of Demailly and Koll\'ar.


title: Adapting the Stochastic Block Model to Edge-Weighted Networks

abstract:
  We generalize the stochastic block model to the important case in which edges
are annotated with weights drawn from an exponential family distribution. This
generalization introduces several technical difficulties for model estimation,
which we solve using a Bayesian approach. We introduce a variational algorithm
that efficiently approximates the model's posterior distribution for dense
graphs. In specific numerical experiments on edge-weighted networks, this
weighted stochastic block model outperforms the common approach of first
applying a single threshold to all weights and then applying the classic
stochastic block model, which can obscure latent block structure in networks.
This model will enable the recovery of latent structure in a broader range of
network data than was previously possible.


title: Combinatorial dichotomies and cardinal invariants

abstract:
  Assuming the P-ideal dichotomy, we attempt to isolate those cardinal
characteristics of the continuum that are correlated with two well-known
consequences of the proper forcing axiom. We find a cardinal invariant
$\mathfrak{x}$ such that the statement that $\mathfrak{x} > {\omega}_{1}$ is
equivalent to the statement that 1, $\omega$, ${\omega}_{1}$, $\omega \times
{\omega}_{1}$, and ${\left[{\omega}_{1}\right]}^{< \omega}$ are the only
cofinal types of directed sets of size at most ${\aleph}_{1}$. We investigate
the corresponding problem for the partition relation ${\omega}_{1} \rightarrow
({\omega}_{1}, \alpha)^2$ for all $\alpha < {\omega}_{1}$. To this effect, we
investigate partition relations for pairs of comparable elements of a coherent
Suslin tree $\mathbb{S}$. We show that a positive partition relation for such
pairs follows from the maximal amount of the proper forcing axiom compatible
with the existence of $\mathbb{S}$. As a consequence we conclude that after
forcing with the coherent Suslin tree $\mathbb{S}$ over a ground model
satisfying this relativization of the proper forcing axiom, ${\omega}_{1}
~\rightarrow {({\omega}_{1}, \alpha)}^{2}$ for all $\alpha < {\omega}_{1}$. We
prove that this positive partition relation for $\mathbb{S}$ cannot be improved
by showing in $\mathrm{ZFC}$ that $\mathbb{S} \not\rightarrow ({\aleph}_{1},
\omega+2)^2$.


title: A network model for cellular aging

abstract:
  What is aging? Mechanistic answers to this question remain elusive despite
decades of research. Here, we propose a mathematical model of cellular aging
based on a model gene interaction network. Our network model is made of only
non-aging components - the biological functions of gene interactions decrease
with a constant mortality rate. Death of a cell occurs in the model when an
essential gene loses all of its interactions to other genes, equivalent to the
deletion of an essential gene. Gene interactions are stochastic based on a
binomial distribution. We show that the defining characteristic of biological
aging, the exponential increase of mortality rate over time, can arise from
this gene network model during the early stage of aging. Hence, we demonstrate
that cellular aging is an emergent property of this model network. Our model
predicts that the rate of aging, defined by the Gompertz coefficient, is
approximately proportional to the average number of active interactions per
gene and that the stochastic heterogeneity of gene interactions is an important
factor in the dynamics of the aging process. This theoretic framework offers a
mechanistic foundation for the pleiotropic nature of aging and can provide
insights on cellular aging.


title: An Inventory of Preposition Relations

abstract:
  We describe an inventory of semantic relations that are expressed by
prepositions. We define these relations by building on the word sense
disambiguation task for prepositions and propose a mapping from preposition
senses to the relation labels by collapsing semantically related senses across
prepositions.


title: Graphic lambda calculus

abstract:
  We introduce and study graphic lambda calculus, a visual language which can
be used for representing untyped lambda calculus, but it can also be used for
computations in emergent algebras or for representing Reidemeister moves of
locally planar tangle diagrams.


title: Dirac equation in (1+3) and (2+2) dimensions

abstract:
  We develop a systematic method to derive the Majorana representation of the
Dirac equation in (1+3)-dimensions. We compare with similar approach in
(2+2)-dimensions . We argue that our formalism can be useful to have a better
understanding of possible Majorana fermions.


title: Laminations from the Main Cubioid

abstract:
  According to a recent paper \cite{bopt13}, polynomials from the closure
$\bar{\rm PHD}_3$ of the {\em Principal Hyperbolic Domain} ${\rm PHD}_3$ of the
cubic connectedness locus have a few specific properties. The family
$\mathrm{CU}$ of all polynomials with these properties is called the \emph{Main
Cubioid}. In this paper we describe the set $\mathrm{CU}^c$ of laminations
which can be associated to polynomials from $\mathrm{CU}$.


title: Comparison of progenitor mass estimates for the type IIP SN 2012A

abstract:
  We present the one-year long observing campaign of SN 2012A which exploded in
the nearby (9.8 Mpc) irregular galaxy NGC 3239. The photometric evolution is
that of a normal type IIP supernova. The absolute maximum magnitude, with MB =
-16.23 +- 0.16 mag. SN2012A reached a peak luminosity of about 2X10**42 erg/s,
which is brighter than those of other SNe with a similar 56Ni mass. The latter
was estimated from the luminosity in the exponential tail of the light curve
and found to be M(56Ni) = 0.011 +-0.004 Msun. The spectral evolution of SN
2012A is also typical of SN IIP, from the early spectra dominated by a blue
continuum and very broad (~10**4 km/s) Balmer lines, to the late-photospheric
spectra characterized by prominent P-Cygni features of metal lines (Fe II, Sc
II, Ba II, Ti II, Ca II, Na ID). The photospheric velocity is moderately low,
~3X10**3 km/s at 50 days, for the low optical depth metal lines. The nebular
spectrum obtained 394 days after the shock breakout shows the typical features
of SNe IIP and the strength of the [O I] doublet suggests a progenitor of
intermediate mass, similar to SN 2004et (~15 Msun). A candidate progenitor for
SN 2012A has been identified in deep, pre-explosion K'-band Gemini North (NIRI)
images, and found to be consistent with a star with a bolometric magnitude
-7.08+-0.36 (log L/Lsun = 4.73 +- 0.14$ dex). The magnitude of the recovered
progenitor in archival images points toward a moderate-mass 10.5 (-2/+4.5) Msun
star as the precursor of SN 2012A. The explosion parameters and progenitor mass
were also estimated by means of a hydrodynamical model, fitting the bolometric
light curve, the velocity and the temperature evolution. We found a best fit
for a kinetic energy of 0.48 foe, an initial radius of 1.8X10**13 cm and ejecta
mass of 12.5 Msun.


title:
Nucleon-Nucleon scattering from the dispersive N/D method:
  next-to-leading order study

abstract:
  We consider nucleon-nucleon ($NN$) interactions from Chiral Effective Field
Theory applying the $N/D$ method. The dynamical input is given by the
discontinuity of the $NN$ partial-wave amplitudes across the left-hand cut
(LHC) calculated in Chiral Perturbation Theory (ChPT) by including one-pion
exchange (OPE), once-iterated OPE and leading irreducible two-pion exchange
(TPE). We discuss both uncoupled and coupled partial-waves. We show
algebraically that the resulting integral equation has a unique solution when
the input is taken only from OPE because it is of the Fredholm type with a
squared integrable kernel and an inhomogeneous term. Phase shifts and mixing
angles are typically rather well reproduced, and a clear improvement of the
results obtained previously with only OPE is manifest. We also show that the
contributions to the discontinuity across the LHC are amenable to a chiral
expansion. Our method also establishes correlations between the $S$-wave
effective ranges and scattering lengths based on unitarity, analyticity and
chiral symmetry.


title:
Intrinsic galaxy shapes and alignments II: Modelling the intrinsic
  alignment contamination of weak lensing surveys

abstract:
  Intrinsic galaxy alignments constitute the major astrophysical systematic of
forthcoming weak gravitational lensing surveys but also yield unique insights
into galaxy formation and evolution. We build analytic models for the
distribution of galaxy shapes based on halo properties extracted from the
Millennium Simulation, differentiating between early- and late-type galaxies as
well as central galaxies and satellites. The resulting ellipticity correlations
are investigated for their physical properties and compared to a suite of
current observations. The best-faring model is then used to predict the
intrinsic alignment contamination of planned weak lensing surveys. We find that
late-type galaxy models generally have weak intrinsic ellipticity correlations,
marginally increasing towards smaller galaxy separation and higher redshift.
The signal for early-type models at fixed halo mass strongly increases by three
orders of magnitude over two decades in galaxy separation, and by one order of
magnitude from z=0 to z=2. The intrinsic alignment strength also depends
strongly on halo mass, but not on galaxy luminosity at fixed mass, or galaxy
number density in the environment. We identify models that are in good
agreement with all observational data, except that all models over-predict
alignments of faint early-type galaxies. The best model yields an intrinsic
alignment contamination of a Euclid-like survey between 0.5-10% at z>0.6 and on
angular scales larger than a few arcminutes. Cutting 20% of red foreground
galaxies using observer-frame colours can suppress this contamination by up to
a factor of two.


title: Entanglement due to noncommutativity in the phase-space

abstract:
  The entanglement criterion for continuous variable systems and the conditions
under which the uncertainty relations are fulfilled are generalized to the case
of a noncommutative (NC) phase-space. The quantum nature and the separability
of NC two-mode Gaussian states are examined. It is shown that the entanglement
of Gaussian states may be exclusively induced by switching on the
noncommutative deformation.


title:
Continuum and Kinetic Simulations of the Neutral Gas Flow in an
  Industrial Physical Vapor Deposition Reactor

abstract:
  Magnetron sputtering used for physical vapor deposition processes often
requires gas pressures well below 1 Pa. Under these conditions the gas flow in
the reactor is usually determined by a Knudsen number of about one, i.e., a
transition regime between the hydrodynamic and the rarefied gas regime. In the
first, the gas flow is well described by the Navier-Stokes equations, while in
the second a kinetic approach via the Boltzmann equation is necessary. In this
paper the neutral gas flow of argon and molecular nitrogen gas inside an
industrial scale plasma reactor was simulated using both a fluid model and a
fully kinetic Direct Simulation Monte Carlo model. By comparing both model
results the validity of the fluid model was checked. Although in both models a
Maxwell-Boltzmann energy distribution of the neutral particles is the natural
outcome, the results of the gas flow differ significantly. The fluid model
description breaks down, due to the inappropriate assumption of a fluid
continuum. This is due to exclusion of non-local effects in the multi
dimensional velocity space, as well as invalid gas/wall interactions. Only the
kinetic model is able to provide an accurate physical description of the gas
flow in the transition regime. Our analysis is completed with a brief
investigation of different definitions of the local Knudsen number. We conclude
that the most decisive parameter - the spatial length scale L - has to be very
careful chosen in order to obtain a reasonable estimate of the gas flow regime.


title: Control of a Bicycle Using Virtual Holonomic Constraints

abstract:
  The paper studies the problem of making Getz's bicycle model traverse a
strictly convex Jordan curve with bounded roll angle and bounded speed. The
approach to solving this problem is based on the virtual holonomic constraint
(VHC) method. Specifically, a VHC is enforced making the roll angle of the
bicycle become a function of the bicycle's position along the curve. It is
shown that the VHC can be automatically generated as a periodic solution of a
scalar periodic differential equation, which we call virtual constraint
generator. Finally, it is shown that if the curve is sufficiently long as
compared to the height of the bicycle's centre of mass and its wheel base, then
the enforcement of a suitable VHC makes the bicycle traverse the curve with a
steady-state speed profile which is periodic and independent of initial
conditions. An outcome of this work is a proof that the constrained dynamics of
a Lagrangian control system subject to a VHC are generally not Lagrangian.


title:
On the Gorensteinness of broken circuit complexes and Orlik--Terao
  ideals

abstract:
  It is proved that the broken circuit complex of an ordered matroid is
Gorenstein if and only if it is a complete intersection. Several
characterizations for a matroid that admits such an order are then given, with
particular interest in the $h$-vector of broken circuit complexes of the
matroid. As an application, we prove that the Orlik--Terao algebra of a
hyperplane arrangement is Gorenstein if and only if it is a complete
intersection. Interestingly, our result shows that the complete intersection
property (and hence the Gorensteinness as well) of the Orlik--Terao algebra can
be determined from the last two nonzero entries of its $h$-vector.


title:
Efficient methods for computing observation impact in 4D-Var data
  assimilation

abstract:
  This paper presents a practical computational approach to quantify the effect
of individual observations in estimating the state of a system. Such an
analysis can be used for pruning redundant measurements, and for designing
future sensor networks. The mathematical approach is based on computing the
sensitivity of the reanalysis (unconstrained optimization solution) with
respect to the data. The computational cost is dominated by the solution of a
linear system, whose matrix is the Hessian of the cost function, and is only
available in operator form. The right hand side is the gradient of a scalar
cost function that quantifies the forecast error of the numerical model. The
use of adjoint models to obtain the necessary first and second order
derivatives is discussed. We study various strategies to accelerate the
computation, including matrix-free iterative solvers, preconditioners, and an
in-house multigrid solver. Experiments are conducted on both a small-size
shallow-water equations model, and on a large-scale numerical weather
prediction model, in order to illustrate the capabilities of the new
methodology.


title:
Convergence in distribution for filtering processes associated to Hidden
  Markov Models with densities

abstract:
  Consider a filtering process associated to a hidden Markov model with
densities for which both the state space and the observation space are
complete, separable, metric spaces. If the underlying, hidden Markov chain is
strongly ergodic and the filtering process fulfills a certain coupling
condition we prove that, in the limit, the distribution of the filtering
process is independent of the initial distribution of the hidden Markov chain.
If furthermore the hidden Markov chain is uniformly ergodic, then we prove that
the filtering process converges in distribution.


title: The Main Cubioid

abstract:
  We discuss different analogs of the main cardioid in the parameter space of
cubic polynomials, and establish relationships between them.


title: Quadratic-like dynamics of cubic polynomials

abstract:
  A small perturbation of a quadratic polynomial with a non-repelling fixed
point gives a polynomial with an attracting fixed point and a Jordan curve
Julia set, on which the perturbed polynomial acts like angle doubling. However,
there are cubic polynomials with a non-repelling fixed point, for which no
perturbation results into a polynomial with Jordan curve Julia set. Motivated
by the study of the closure of the Cubic Principal Hyperbolic Domain, we
describe such polynomials in terms of their quadratic-like restrictions.


title:
Lightweight Contention Management for Efficient Compare-and-Swap
  Operations

abstract:
  Many concurrent data-structure implementations use the well-known
compare-and-swap (CAS) operation, supported in hardware by most modern
multiprocessor architectures for inter-thread synchronization. A key weakness
of the CAS operation is the degradation in its performance in the presence of
memory contention.
  In this work we study the following question: can software-based contention
management improve the efficiency of hardware-provided CAS operations? Our
performance evaluation establishes that lightweight contention management
support can greatly improve performance under medium and high contention levels
while typically incurring only small overhead when contention is low.


title:
Non-polar (11-20) InGaN quantum dots with short exciton lifetimes grown
  by metal-organic vapor phase epitaxy

abstract:
  We report on the optical characterization of non-polar a-plane InGaN quantum
dots (QDs) grown by metal-organic vapor phase epitaxy using a short nitrogen
anneal treatment at the growth temperature. Spatial and spectral mapping of
sub-surface QDs have been achieved by cathodoluminescence at 8 K.
Microphotoluminescence studies of the QDs reveal resolution limited sharp peaks
with typical linewidth of 1 meV at 4.2 K. Time-resolved photoluminescence
studies suggest the excitons in these QDs have a typical lifetime of 538 ps,
much shorter than that of the c-plane QDs, which is strong evidence of the
significant suppression of the internal electric fields.


title:
On the existence of steady periodic capillary-gravity stratified water
  waves

abstract:
  We prove the existence of small steady periodic capillary-gravity water waves
for general stratified flows, where we allow for stagnation points in the flow.
We establish the existence of both laminar and non-laminar flow solutions for
the governing equations. This is achieved by using bifurcation theory and
estimates based on the ellipticity of the system, where we regard, in turn, the
mass-flux and surface tension as bifurcation parameters.


title:
Design of Digital Response in Enzyme-Based Bioanalytical Systems for
  Information Processing Applications

abstract:
  We investigate performance and optimization of the "digital" bioanalytical
response. Specifically, we consider the recently introduced approach of a
partial input conversion into inactive compounds, resulting in the "branch
point effect" similar to that encountered in biological systems. This
corresponds to an "intensity filter," which can yield a binary-type
sigmoid-response output signal of interest in information and signal processing
and in biosensing applications. We define measures for optimizing the response
for information processing applications based on the kinetic modeling of the
enzymatic reactions involved, and apply the developed approach to the recently
published data for glucose detection.


title:
Ro-vibrational relaxation of HCN in collisions with He: Rigid bender
  treatment of the bending-rotation interaction

abstract:
  We present a new theoretical method to treat atom-rigid bender inelastic
collisions at the Close Coupling level (RBCC) in the space fixed frame. The
coupling between rotation and bending is treated exactly within the rigid
bender approximation and we obtain the cross section for the rotational
transition between levels belonging to different bending levels. The results of
this approach are compared with those obtained when using the rigid bender
averaged approximation (RBAA) introduced in our previous work dedicated to this
system. We discuss the validity of this approximation and of the previous
studies based on rigid linear HCN.


title:
On Universal Equivalence of Partially Commutative Metabelian Lie
  Algebras

abstract:
  In this paper, we consider partially commutative metabelian Lie algebras
whose defining graphs are cycles. We show that such algebras are universally
equivalent iff the corresponding cycles have the same length. Moreover, we give
an example showing that the class of partially commutative metabelian Lie
algebras such that their defining graphs are trees is not separable by
universal theory in the class of all partially commutative metabelian Lie
algebras.


title:
Time and space dependence of electromagnetic field in relativistic
  heavy-ion collisions

abstract:
  Exact analytical solution for the space-time evolution of electromagnetic
field in electrically conducting nuclear matter produced in heavy-ion
collisions is discussed. It is argued that the parameter that controls the
strength of the matter effect on the field evolution is $\sigma\gamma b$, where
$\sigma$ is electrical conductivity, $\gamma$ is the Lorentz boost-factor and
$b$ is the characteristic transverse size of the matter. When this parameter is
of the order one or larger, which is the case at RHIC and LHC, space-time
dependence of electromagnetic field is completely different form that in
vacuum.


title:
Preliminary DIMM and MASS Nighttime Seeing Measurements at PEARL, in the
  Canadian High Arctic

abstract:
  Results of deploying a Differential Image Motion Monitor (DIMM) and a DIMM
combined with a Multi-Aperture Scintillation Sensor (MASS/DIMM) are reported
for campaigns in 2011 and 2012 on the roof of the Polar Environment Atmospheric
Research Laboratory (PEARL). This facility is on a 610-m-high ridge at latitude
80 degrees N, near the Eureka weatherstation on Ellesmere Island, Canada. The
median seeing at 8-m elevation is 0.85 arcsec or better based on DIMM data
alone, but is dependent on wind direction, and likely includes a component due
to the PEARL building itself. Results with MASS/DIMM yield a median seeing less
than 0.76 arcsec. A semi-empirical model of seeing versus ground wind speed is
introduced which allows agreement between these datasets, and with previous
boundary-layer profiling by lunar scintillometry from the same location. This
further suggests that best 20 percentile seeing reaches 0.53 arcsec, of which
typically 0.30 arcsec is due to the free atmosphere. Some discussion for
guiding future seeing instrumentation and characterization at this site is
provided.


title: Compact submanifolds supporting singular interactions

abstract:
  A quantum particle moving under the influence of singular interactions on
embedded surfaces furnish an interesting example from the spectral point of
view. In these problems, the possible occurrence of a bound state is perhaps
the most important aspect. Such systems can be introduced as quadratic forms
and generically they do not require renormalization. Yet an alternative path
through the resolvent is also beneficial to study various properties. In the
present work, we address these issues for compact surfaces embedded in a class
of ambient manifolds. We discover that there is an exact bound state solution
written in terms of the heat kernel of the ambient manifold for a range of
coupling strengths. Moreover, we develop techniques to estimate bounds on the
ground state energy when several surfaces, each of which admits a bound state
solution, coexist.


title: A Calculus for Higher Spin Interactions

abstract:
  Higher spin theories can be efficiently described in terms of auxiliary
St\"uckelberg or projective space field multiplets. By considering how higher
spin models couple to scale, these approaches can be unified in a conformal
geometry/tractor calculus framework. We review these methods and apply them to
higher spin vertices to obtain a generating function for massless, massive and
partially massless three-point interactions.


title:
A bundle method using two polyhedral approximations of the
  epsilon-enlargement of a maximal monotone operator

abstract:
  In this work, we develop a variant of a bundle method in order to find a zero
of a maximal monotone operator. This algorithm relies on two polyhedral
approximations of the epsilon-enlargement of the considered operator, via a
systematic use of the transportation formula. Moreover, the use of a double
polyhedral approximation in our algorithm could inspire other bundle methods
for the case where the given operator can be split as the sum of two other
maximal monotone operators.


title: Complex Hadamard Matrices, Instantaneous Uniform Mixing and Cubes

abstract:
  We study the continuous-time quantum walks on graphs in the adjacency algebra
of the $n$-cube and its related distance regular graphs.
  For $k\geq 2$, we find graphs in the adjacency algebra of $(2^{k+2}-8)$-cube
that admit instantaneous uniform mixing at time $\pi/2^k$ and graphs that have
perfect state transfer at time $\pi/2^k$.
  We characterize the folded $n$-cubes, the halved $n$-cubes and the folded
halved $n$-cubes whose adjacency algebra contains a complex Hadamard matrix. We
obtain the same conditions for the characterization of these graphs admitting
instantaneous uniform mixing.


title:
A proportional hazard model for the estimation of ionosphere storm
  occurrence risk

abstract:
  Severe Ionosphere magnetic storms are feared events for integrity and
continuity of navigation systems such as EGNOS, the European SBAS
(Satellite-Based Augmentation System) complementing GPS and an accurate
modelling of this event probability is necessary. Our aim for the work
presented in this paper is to give an estimation of the frequency of such
extreme magnetic storms per time unit (year) throughout a solar cycle. Thus, we
develop an innovative approach based on a proportional hazard model, inspired
by the Cox model, with time dependent covariates. The number of storms during a
cycle is supposed to be a non-homogeneous Poisson process. The intensity of
this process could be expressed as the product of a baseline risk and a risk
factor. Contrary to what is done in the Cox model, the baseline risk is one
parameter of interest (and not a nuisance one), it is the intensity to
estimate. As in Extreme Value Theory, all the high level events will be used to
make estimation and the results will be extrapolated to the extreme level ones.
After a precise description of the model, we present the estimation results and
a model extension. A prediction for the current solar cycle (24th) is also
proposed.


title: A Bellman approach for regional optimal control problems in $\R^N$

abstract:
  This article is a continuation of a previous work where we studied infinite
horizon control problems for which the dynamic, running cost and control space
may be different in two half-spaces of some euclidian space $\R^N$. In this
article we extend our results in several directions: $(i)$ to more general
domains; $(ii)$ by considering finite horizon control problems; $(iii)$ by
weaken the controlability assumptions. We use a Bellman approach and our main
results are to identify the right Hamilton-Jacobi-Bellman Equation (and in
particular the right conditions to be put on the interfaces separating the
regions where the dynamic and running cost are different) and to provide the
maximal and minimal solutions, as well as conditions for uniqueness. We also
provide stability results for such equations.


title: Comparison of density functionals for nitrogen impurities in ZnO

abstract:
  Hybrid functionals and empirical correction schemes are compared to
conventional semi-local density functional theory (DFT) calculations in order
to assess the predictive power of these methods concerning the formation energy
and the charge transfer level of impurities in the wide-gap semiconductor ZnO.
While the generalized gradient approximation fails to describe the electronic
structure of the N impurity in ZnO correctly, methods that widen the band gap
of ZnO by introducing additional non-local potentials yield the formation
energy and charge transfer level of the impurity in reasonable agreement with
hybrid functional calculations. Summarizing the results obtained with different
methods, we corroborate earlier findings that the formation of substitutional N
impurities at the oxygen site in ZnO from N atoms is most likely slightly
endothermic under oxygen-rich preparation conditions, and introduces a deep
level more than 1eV above the valence band edge of ZnO. Moreover, the
comparison of methods elucidates subtle differences in the predicted electronic
structure, e.g. concerning the orientation of unoccupied orbitals in the
crystal field and the stability of the charged triplet state of the N impurity.
Further experimental or theoretical analysis of these features could provide
useful tests for validating the performance of DFT methods in their application
to defects in wide-gap materials.


title:
The interface of GaP(100) and H2O studied by photoemission and
  reflection anisotropy spectroscopy

abstract:
  We study the initial interaction of adsorbed H2O with P-rich and Ga-rich
GaP(100) surfaces. Atomically well defined surfaces are prepared by
metal-organic vapour phase epitaxy and transferred contamination-free to
ultra-high vacuum, where water is adsorbed at room temperature. Finally, the
surfaces are annealed in vapour phase ambient. During all steps, the impact on
the surface properties is monitored with in-situ reflection anisotropy
spectroscopy (RAS). Photoelectron spectroscopy and low-energy electron
diffraction are applied for further in-system studies. After exposure up to
saturation of the RA spectra, the Ga-rich (2 x 4) surface reconstruction
exhibits a sub-monolayer coverage in form of a mixture of molecularly and
dissociatively adsorbed water. For the p(2 x 2)/c(4 x 2) P-rich surface
reconstruction, a new c(2 x 2) superstructure forms upon adsorption and the
uptake of adsorbate is significantly reduced when compared to the Ga-rich
surface. Our findings show that microscopic surface reconstructions of GaP(100)
greatly impact the mechanism of initial interface formation with water, which
could benefit the design of e.g. photoelectrochemical water splitting devices.


title:
Dispersive and soliton perturbations of finite-genus solutions of the
  KdV equation: computational results

abstract:
  All solutions of the Korteweg -- de Vries equation that are bounded on the
real line are physically relevant, depending on the application area of
interest. Usually, both analytical and numerical approaches consider solution
profiles that are either spatially localized or (quasi)periodic. In this paper,
we discuss a class of solutions that is a nonlinear superposition of these two
cases: their asymptotic state for large $|x|$ is (quasi)periodic, but they may
contain solitons, with or without dispersive tails. Such scenarios might occur
in the case of localized perturbations of previously present sea swell, for
instance. Such solutions have been discussed from an analytical point of view
only recently. We numerically demonstrate different features of these
solutions.


title: Lorentz Invariant CPT Violation for a Class of Nonlocal Thirring Model

abstract:
  It is possible to construct Lorentz invariant CPT violating models for
Nonlocal Quantum Field Theory. In this article, we present a class of Nonlocal
Thirring Models, in which the CPT invariance is violated while the Lorentz
invariance is present. As a result, in certain cases the mass-splitting between
particle and antiparticle are identified.


title:
Quantum and classical correlations and Werner states in finite spin
  linear arrays

abstract:
  Pairwise quantum correlations in the ground state of a N-spins
antiferromagnetic chain described by the Heisenberg model with nearest neighbor
exchange coupling are investigated. By varying a single coupling between two
neighboring sites it is possible to drive spins from entangled to disentangled
states, reversibly. For even N the two-spin density matrix is written in the
form of a Werner state, allowing identification of the weight parameter with
the usual spin-spin correlation function $\langle S_i^z \, S_j^z \rangle =
\Gamma_{ij}$. The correlation functions show universal behavior in the
$\Gamma$-dependence. This study presents a concrete possibility for the
practical demonstration of entanglement control, opening alternatives for
probing non-classical correlations and the realization of Werner states in
familiar condensed matter systems. All required fabrication and measurement
ingredients are currently available.


title: On Stable Hypersurfaces with Vanishing Scalar Curvature

abstract:
  We will prove that \emph{there are no stable complete hypersurfaces of
$\mathbb{R}^4$ with zero scalar curvature, polynomial volume growth and such
that $\dfrac{(-K)}{H^3}\geq c>0$ everywhere, for some constant $c>0$}, where
$K$ denotes the Gauss-Kronecker curvature and $H$ denotes the mean curvature of
the immersion. Our second result is the Bernstein type one \emph{there is no
entire graphs of $\mathbb{R}^4$ with zero scalar curvature such that
$\dfrac{(-K)}{H^3}\geq c>0$ everywhere}. At last, it will be proved that, if
there exists a stable hypersurface with zero scalar curvature and
$\dfrac{(-K)}{H^3}\geq c>0$ everywhere, that is, with volume growth greater
than polynomial, then its tubular neighborhood is not embedded for suitable
radius.


title: Model Theoretic Characterisations of Description Logics

abstract:
  This thesis studies the model theoretic properties of the Description Logics
(DLs) ALC, ALCI, ALCQ, as well as ALCO, ALCQO, ALCQIO and EL.
  TBoxes of ALC, ALCI and ALCQ are characterised as fragments of FO which are
invariant under global bisimulation and disjoint unions. The logics ALCO, ALCQO
and ALCQIO, which incorporate individuals, are characterised w.r.t. to the
class K of all interpretations which interpret individuals as singleton sets.
The characterisations for TBoxes of ALCO and ALCQO both require additionally
that an FO-sentence is, under certain circumstances, preserved under forward
generated subinterpretations. FO-sentences equivalent to ALCQIO-TBoxes, are -
due to ALCQIO's inverse roles - characterised similarly but are required to be
preserved under generated subinterpretations.
  EL as sub-boolean DL is characterised on concept level as the FO-fragment
which is preserved under simulation and preserved under direct products.
Equally valid is the characterisation by being preserved under simulation and
having minimal models. For EL-TBoxes, a global version of simulation was not
sufficient but FO-sentences of EL-TBoxes are invariant under global
equi-simulation, disjoint unions and direct products.
  For each of these description logics, the characteristic concepts are
explicated and the characterisation is accompanied by an investigation under
which notion of saturation the logic in hand enjoys the
Hennessy-and-Milner-Property.
  As application of the results we determine the minimal globally bisimilar
companion w.r.t. ALCQO-bisimulation and introduce the L1-to-L2-rewritability
problem for TBoxes, where L1 and L2 are (description) logics. The latter is the
problem to decide whether or not an L1-TBox can be equivalently expressed as
L2-TBox. We give algorithms which decide ALCI-to-ALC-rewritability and
ALC-to-EL-rewritability. (See also abstract in the thesis.)


title:
Interatomic potential for the calculation of barrier distributions in
  amorphous oxides

abstract:
  Amorphous oxides are important for implants, optics, and gate insulators.
Understanding the effects of oxide doping is crucial to optimize performance.
Here we report energy barrier distributions for amorphous tantala and doped
oxides using a new set of computationally efficient, two-body potentials that
reproduce the structural properties of the samples. The distributions can be
directly compared to experiment and used to calculate physical quantities such
as internal friction.


title: Positron scattering and annihilation in hydrogen-like ions

abstract:
  Diagrammatic many-body theory is used to calculate the scattering phase
shifts, normalized annihilation rates $Z_{\rm eff}$ and annihilation gamma
spectra for positron collisions with the hydrogen-like ions He$^+$, Li$^{2+}$,
B$^{4+}$ and F$^{8+}$. Short-range electron-positron correlations and
longer-range positron-ion correlations are accounted for by evaluating nonlocal
corrections to the annihilation vertex and the exact positron self-energy. The
numerical calculation of the many-body theory diagrams is performed using
B-spline basis sets. To elucidate the r\^ole of the positron-ion repulsion, the
annihilation rate is also estimated analytically in the Coulomb-Born
approximation. It is found that the energy dependence and magnitude of $Z_{\rm
eff}$ is governed by the Gamow factor that characterizes the suppression of the
positron wave function near the ion. For all of the H-like ions, the
correlation enhancement of the annihilation rate is found to be predominantly
due to corrections to the annihilation vertex, while the corrections to the
positron wave function play only a minor r\^ole. Results of the calculations
for $s$, $p$ and d-wave incident positrons of energies up to the positronium
formation threshold are presented. Where comparison is possible, our values are
in excellent agreement with the results obtained using other, e.g.,
variational, methods. The annihilation vertex enhancement factors obtained in
the present calculations are found to scale approximately as
$1+(1.6+0.46\ell)/Z_i$, where $Z_i$ is the net charge of the ion and $\ell$ is
the positron orbital angular momentum. Our results for positron annihilation in
H-like ions provide insights into the problem of positron annihilation with
core electrons in atoms and condensed matter systems, which have similar
binding energies.


title: Maximum st-flow in directed planar graphs via shortest paths

abstract:
  Minimum cuts have been closely related to shortest paths in planar graphs via
planar duality - so long as the graphs are undirected. Even maximum flows are
closely related to shortest paths for the same reason - so long as the source
and the sink are on a common face. In this paper, we give a correspondence
between maximum flows and shortest paths via duality in directed planar graphs
with no constraints on the source and sink. We believe this a promising avenue
for developing algorithms that are more practical than the current
asymptotically best algorithms for maximum st-flow.


title: Towards a semantic and statistical selection of association rules

abstract:
  The increasing growth of databases raises an urgent need for more accurate
methods to better understand the stored data. In this scope, association rules
were extensively used for the analysis and the comprehension of huge amounts of
data. However, the number of generated rules is too large to be efficiently
analyzed and explored in any further process. Association rules selection is a
classical topic to address this issue, yet, new innovated approaches are
required in order to provide help to decision makers. Hence, many interesting-
ness measures have been defined to statistically evaluate and filter the
association rules. However, these measures present two major problems. On the
one hand, they do not allow eliminating irrelevant rules, on the other hand,
their abun- dance leads to the heterogeneity of the evaluation results which
leads to confusion in decision making. In this paper, we propose a two-winged
approach to select statistically in- teresting and semantically incomparable
rules. Our statis- tical selection helps discovering interesting association
rules without favoring or excluding any measure. The semantic comparability
helps to decide if the considered association rules are semantically related
i.e comparable. The outcomes of our experiments on real datasets show promising
results in terms of reduction in the number of rules.


title: Considerations on Gravity as an Entropic Force and Entangled States

abstract:
  Verlinde's ideas considered gravity as an emergent force originated from
entropic concepts. This hypothesis generated a huge number of papers through
the last recent years concerning classical and quantum approaches about the
issue. In a recent paper Kobakhidze, using ultra-cold neutrons experiment,
claimed that Verlinde's entropic gravity is not correct. In this letter, by
considering the nonadditivity property of the holographic screen, where we
assumed that the bits are entangled states, we showed that it is possible to
confirm Verlinde's formalism.


title:
Parallel Gaussian Process Regression with Low-Rank Covariance Matrix
  Approximations

abstract:
  Gaussian processes (GP) are Bayesian non-parametric models that are widely
used for probabilistic regression. Unfortunately, it cannot scale well with
large data nor perform real-time predictions due to its cubic time cost in the
data size. This paper presents two parallel GP regression methods that exploit
low-rank covariance matrix approximations for distributing the computational
load among parallel machines to achieve time efficiency and scalability. We
theoretically guarantee the predictive performances of our proposed parallel
GPs to be equivalent to that of some centralized approximate GP regression
methods: The computation of their centralized counterparts can be distributed
among parallel machines, hence achieving greater time efficiency and
scalability. We analytically compare the properties of our parallel GPs such as
time, space, and communication complexity. Empirical evaluation on two
real-world datasets in a cluster of 20 computing nodes shows that our parallel
GPs are significantly more time-efficient and scalable than their centralized
counterparts and exact/full GP while achieving predictive performances
comparable to full GP.


title: Semantic Web Search based on Ontology Modeling using Protege Reasoner

abstract:
  The Semantic Web works on the existing Web which presents the meaning of
information as well-defined vocabularies understood by the people. Semantic
Search, at the same time, works on improving the accuracy if a search by
understanding the intent of the search and providing contextually relevant
results. This paper describes a semantic approach toward web search through a
PHP application. The goal was to parse through a user's browsing history and
return semantically relevant web pages for the search query provided.


title:
An Algorithm for Splitting Parallel Sums of Linearly Composed Monotone
  Operators, with Applications to Signal Recovery

abstract:
  We present a new primal-dual splitting algorithm for structured monotone
inclusions in Hilbert spaces and analyze its asymptotic behavior. A novelty of
our framework, which is motivated by image recovery applications, is to
consider inclusions that combine a variety of monotonicity-preserving
operations such as sums, linear compositions, parallel sums, and a new notion
of parallel composition. The special case of minimization problems is studied
in detail, and applications to signal recovery are discussed. Numerical
simulations are provided to illustrate the implementation of the algorithm.


title:
A Symmetric Rank-one Quasi Newton Method for Non-negative Matrix
  Factorization

abstract:
  As we all known, the nonnegative matrix factorization (NMF) is a dimension
reduction method that has been widely used in image processing, text
compressing and signal processing etc. In this paper, an algorithm for
nonnegative matrix approximation is proposed. This method mainly bases on the
active set and the quasi-Newton type algorithm, by using the symmetric rank-one
and negative curvature direction technologies to approximate the Hessian
matrix. Our method improves the recent results of those methods in [Pattern
Recognition, 45(2012)3557-3565; SIAM J. Sci. Comput., 33(6)(2011)3261-3281;
Neural Computation, 19(10)(2007)2756-2779, etc.]. Moreover, the object function
decreases faster than many other NMF methods. In addition, some numerical
experiments are presented in the synthetic data, imaging processing and text
clustering. By comparing with the other six nonnegative matrix approximation
methods, our experiments confirm to our analysis.


title:
Bias deconstructed: Unravelling the scale dependence of halo bias using
  real space measurements

abstract:
  We explore the scale dependence of halo bias using real space
cross-correlation measurements in N-body simulations and in Pinocchio, an
algorithm based on Lagrangian Perturbation Theory. Recent work has shown how to
interpret such real space measurements in terms of k-dependent bias in Fourier
space, and how to remove the k-dependence to reconstruct the k-independent
peak-background split halo bias parameters. We compare our reconstruction of
the linear bias, which requires no free parameters, with previous estimates
from N-body simulations which were obtained directly in Fourier space at large
scales, and find very good agreement. Our reconstruction of the quadratic bias
is similarly parameter-free, although in this case there are no previous
Fourier space measurements to compare with. Our analysis of N-body simulations
explicitly tests the predictions of the excursion set peaks (ESP) formalism of
Paranjape et al. (2013) for the scale dependence of bias; we find that the ESP
predictions accurately describe our measurements. In addition, our measurements
in Pinocchio serve as a useful, successful consistency check between Pinocchio
and N-body simulations that is not accessible to traditional measurements.


title:
Considerations for a cosmological extension of modified Newtonian
  dynamics connections to conformal gravity and Rindler force theories

abstract:
  Modified Newtonian dynamics (MOND) can be obtained by modifying the entropic
formulation of gravity, this is achieved by considering the quantum statistical
nature of the degrees of freedom on the holographic screen. Through this frame
work, we find some constraints on a cosmological extension for MOND, with no
additional auxiliary fields. The connections between MOND to conformal gravity
and Rindler force gravity are examined. These two alternative gravity theories
are subsequently considered as possible cosmological extensions of MOND.


title:
Efficient Single Photon Absorption by Optimized Superconducting Nanowire
  Geometries

abstract:
  We report on simulation results that shows optimum photon absorption by
superconducting nanowires can happen at a fill-factor that is much less than
100%. We also present experimental results on high performance of our
superconducting nanowire single photon detectors realized using NbTiN on
oxidized silicon.


title:
Heat transport through quantum Hall edge states: Tunneling versus
  capacitive coupling to reservoirs

abstract:
  We study the heat transport along an edge state of a two-dimensional electron
gas in the quantum Hall regime, in contact to two reservoirs at different
temperatures. We consider two exactly solvable models for the edge state
coupled to the reservoirs. The first one corresponds to filling $\nu=1$ and
tunneling coupling to the reservoirs. The second one corresponds to integer or
fractional filling of the sequence $\nu=1/m$ (with $m$ odd), and capacitive
coupling to the reservoirs. In both cases we solve the problem by means of
non-equilibrium Green function formalism. We show that heat propagates chirally
along the edge in the two setups. We identify two temperature regimes, defined
by $\Delta$, the mean level spacing of the edge. At low temperatures, $T<
\Delta$, finite size effects play an important role in heat transport, for both
types of contacts. The nature of the contacts manifest themselves in different
power laws for the thermal conductance as a function of the temperature. For
capacitive couplings a highly non-universal behavior takes place, through a
prefactor that depends on the length of the edge as well as on the coupling
strengths and the filling fraction. For larger temperatures, $T>\Delta$,
finite-size effects become irrelevant, but the heat transport strongly depends
on the strength of the edge-reservoir interactions, in both cases. The thermal
conductance for tunneling coupling grows linearly with $T$, whereas for the
capacitive case it saturates to a value that depends on the coupling strengths
and the filling factors of the edge and the contacts.


title: Entanglement Spectrum of Composite Fermion States in Real Space

abstract:
  We study the entanglement spectra of many particle systems in states which
are closely related to products of Slater determinants or products of
permanents, or combinations of the two. Such states notably include the
Laughlin and Jain composite fermion states which describe most of the observed
conductance plateaus of the fractional quantum Hall effect. We identify a set
of 'Entanglement Wave Functions' (EWF), for subsets of the particles, which
completely describe the entanglement spectra of such product wave functions,
both in real space and in particle space. A subset of the EWF for the Laughlin
and Jain states can be recognized as Composite Fermion states. These states
provide an exact description of the low angular momentum sectors of the real
space entanglement spectrum (RSES) of these trial wave functions and a physical
explanation of the branches of excitations observed in the RSES of the Jain
states.


title: Non-Standard Models, Solar Neutrinos, and Large \theta_{13}

abstract:
  Solar neutrino experiments have yet to see directly the transition region
between matter-enhanced and vacuum oscillations. The transition region is
particularly sensitive to models of non-standard neutrino interactions and
propagation. We examine several such non-standard models, which predict a
lower-energy transition region and a flatter survival probability for the ^{8}B
solar neutrinos than the standard large-mixing angle (LMA) model. We find that
while some of the non-standard models provide a better fit to the solar
neutrino data set, the large measured value of \theta_{13} and the size of the
experimental uncertainties lead to a low statistical significance for these
fits. We have also examined whether simple changes to the solar density profile
can lead to a flatter ^{8}B survival probability than the LMA prediction, but
find that this is not the case for reasonable changes. We conclude that the
data in this critical region is still too poor to determine whether any of
these models, or LMA, is the best description of the data.


title:
Numerical Gradient Schemes for Heat Equations Based on the Collocation
  Polynomial and Hermite Interpolation

abstract:
  As is well-known, the advantage of the high-order compact difference scheme
(H-OCD) is unconditionally stable and convergent with the order $O(\tau^2+h^4)$
under the maximum norm. In this article, a new numerical gradient scheme based
on the collocation polynomial and Hermite interpolation is presented. Moreover,
the convergence order of this kind of method is also $O(\tau^2+h^4)$ under the
discrete maximum norm when the space step size is just twice the one of H-OCD
method, which accelerates the computational process and makes the result much
smoother to some extent. In addition, some corresponding analyses are made and
the Richardson extrapolation technique is also considered in time direction.
The results of numerical experiments are also consistent with these theoretical
analysis.


title: Comment on: "Classical signature of quantum annealing"

abstract:
  In a recent preprint (arXiv:1305.4904) entitled "Classical signature of
quantum annealing" Smolin and Smith point out that a bimodal distribution
presented in (arXiv:1304.4595) for the success probability in the D-Wave device
does not in itself provide sufficient evidence for quantum annealing, by
presenting a classical model that also exhibits bimodality. Here we analyze
their model and in addition present a similar model derived from the
semi-classical limit of quantum spin dynamics, which also exhibits a bimodal
distribution. We find that in both cases the correlations between the success
probabilities of these classical models and the D-Wave device are weak compared
to the correlations between a simulated quantum annealer and the D-Wave device.
Indeed, the evidence for quantum annealing presented in arXiv:1304.4595 is not
limited to the bimodality, but relies in addition on the success probability
correlations between the D-Wave device and the simulated quantum annealer. The
Smolin-Smith model and our semi-classical spin model both fail this correlation
test.


title:
A waveguide overloaded cavity kicker for the HLS II longitudinal
  feedback system

abstract:
  In the upgrade project of Hefei Light Source (HLS II), a new digital
longitudinal bunch-by-bunch feedback system will be developed to suppress the
coupled bunch instabilities in the storage ring effectively. We design a new
waveguide overloaded cavity longitudinal feedback kicker as the feedback
actuator. The beam pipe of the kicker is racetrack shape so as to avoid a
transition part to the octagonal vacuum chamber. The central frequency and the
bandwidth of the kicker have been simulated and optimized to achieve design
goals by the HFSS code. The higher shunt impedance can be obtained by using a
nose cone to reduce the feedback power requirement. Before the kicker cavity
was installed in the storage ring, a variety of measurements were carried out
to check its performance. All these results of simulation and measurement are
presented.


title: On the uniform tiling with electrical resistors

abstract:
  We calculate the effective resistance between two arbitrary lattice points on
infinite strip of the triangular lattice (ladder network) in one dimension, and
on infinite modified square and Union Jack lattices in two dimensions, and on
infinite decorated simple cubic and base-centered cubic lattices in three
dimensions by using the general lattice Green's function method


title:
Unleashing Positive Feedback: Linking the Rates of Star Formation,
  Supermassive Black Hole Accretion and Outflows in Distant Galaxies

abstract:
  Pressure-regulated star formation is a simple variant on the usual
supernova-regulated star formation efficiency that controls the global star
formation rate as a function of cold gas content in star-forming galaxies, and
accounts for the Schmidt-Kennicutt law in both nearby and distant galaxies.
Inclusion of AGN-induced pressure, by jets and/or winds that flow back onto a
gas-rich disk, can lead under some circumstances to significantly enhanced star
formation rates, especially at high redshift and most likely followed by the
more widely accepted phase of star formation quenching. Simple expressions are
derived that relate supermassive black hole growth, star formation and outflow
rates. The ratios of black hole to spheroid mass and of both black hole
accretion and outflow rates to star formation rate are predicted as a function
of time. I suggest various tests of the AGN-triggered star formation
hypothesis.


title: The quantum angular Calogero-Moser model

abstract:
  The rational Calogero-Moser model of n one-dimensional quantum particles with
inverse-square pairwise interactions (in a confining harmonic potential) is
reduced along the radial coordinate of R^n to the `angular Calogero-Moser
model' on the sphere S^{n-1}. We discuss the energy spectrum of this quantum
system, its degeneracies and the eigenstates. The spectral flow with the
coupling parameter yields isospectrality for integer increments. Decoupling the
center of mass before effecting the spherical reduction produces a `relative
angular Calogero-Moser model', which is analyzed in parallel. We generalize our
considerations to the Calogero-Moser models associated with Coxeter groups.
Finally, we attach spin degrees of freedom to our particles and extend the
results to the spin-Calogero system.


title:
The detection of FIR emission from high redshift star-forming galaxies
  in the ECDF-S

abstract:
  ABRIDGED: We have used the LABOCA Survey of the ECDF-S (LESS) to investigate
rest-frame FIR emission from typical SF systems (LBGs) at redshift 3, 4, and 5.
We initially concentrate on LBGs at z~3 and select three subsamples on stellar
mass, extinction corrected SF and rest-frame UV-magnitude. We produce composite
870micron images of the typical source in our subsamples, obtaining ~4sigma
detections and suggesting a correlation between FIR luminosity and stellar
mass. We apply a similar procedure to our full samples at z~3, 4, 4.5 and 5 and
do not obtain detections - consistent with a simple scaling between FIR
luminosity and stellar mass. In order to constrain the FIR SED of these systems
we explore their emission at multiple wavelengths spanning the peak of dust
emission at z~3 using the Herschel SPIRE observations of the field. We obtain
detections at multiple wavelengths for both our stellar mass and UV-magnitude
selected samples, and find a best-fit SED with T_dust in the ~33-41K range. We
calculate L_FIR, obscured SFRs and M_dust, and find that a significant fraction
of SF in these systems is obscured. Interestingly, our extinction corrected SFR
sample does not display the large FIR fluxes predicted from its red UV-spectral
slope. This suggests that the method of assuming an intrinsic UV-slope and
correcting for dust attenuation may be invalid for this sample - and that these
are not in fact the most actively SF systems. All of our z~3 samples fall on
the `main sequence' of SF galaxies at z~3 and our detected subsamples are
likely to represent the high obscuration end of LBGs at their epoch. We compare
the FIR properties of our subsamples with various other populations, finding
that our stellar mass selected sample shows similar FIR characteristics to SMGs
at the same epoch and therefore potentially represents the low L_FIR end of the
high redshift FIR luminosity function.


title: Bending forces plastically deform growing bacterial cell walls

abstract:
  Cell walls define a cell shape in bacteria. They are rigid to resist large
internal pressures, but remarkably plastic to adapt to a wide range of external
forces and geometric constraints. Currently, it is unknown how bacteria
maintain their shape. In this work, we develop experimental and theoretical
approaches and show that mechanical stresses regulate bacterial cell-wall
growth. By applying a precisely controllable hydrodynamic force to growing
rod-shaped Escherichia coli and Bacillus subtilis cells, we demonstrate that
the cells can exhibit two fundamentally different modes of deformation. The
cells behave like elastic rods when subjected to transient forces, but deform
plastically when significant cell wall synthesis occurs while the force is
applied. The deformed cells always recover their shape. The experimental
results are in quantitative agreement with the predictions of the theory of
dislocation-mediated growth. In particular, we find that a single dimensionless
parameter, which depends on a combination of independently measured physical
properties of the cell, can describe the cell's responses under various
experimental conditions. These findings provide insight into how living cells
robustly maintain their shape under varying physical environments.


title:
Measuring the total and baryonic mass profiles of the very massive
  CASSOWARY 31 strong lens. A fossil system at z ~ 0.7?

abstract:
  We investigate the total and baryonic mass distributions in deflector number
31 of the Cambridge And Sloan Survey Of Wide ARcs in the skY (CASSOWARY). We
confirm spectroscopically a four-image lensing system at redshift 1.4870 with
VLT/X-shooter observations. The lensed images are distributed around a bright
early-type galaxy at redshift 0.683, surrounded by several smaller galaxies at
similar photometric redshifts. We use available optical and X-ray data to
constrain the deflector total, stellar, and hot gas mass through, respectively,
strong lensing, stellar population analysis, and plasma modelling. We derive a
total mass projected within the Einstein radius R_Ein = 70 kpc of (40 +/- 1) x
10^12 M_Sun, and a central logarithmic slope of -1.7 +/- 0.2 for the total mass
density. Despite a very high stellar mass and velocity dispersion of the
central galaxy of (3 +/- 1) x 10^12 M_Sun and (450 +/- 80) km/s, respectively,
the cumulative stellar-to-total mass profile of the deflector implies a
remarkably low stellar mass fraction of 20% (3%-6%) in projection within the
central galaxy effective radius R_e = 25 kpc (R = 100 kpc). We also find that
the CSWA 31 deflector has properties suggesting it to be among the most distant
and massive fossil systems studied so far. The unusually strong central dark
matter dominance and the possible fossil nature of this system renders it an
interesting target for detailed tests of cosmological models and structure
formation scenarios.


title: Translated Chemical Reaction Networks

abstract:
  Many biochemical and industrial applications involve complicated networks of
simultaneously occurring chemical reactions. Under the assumption of mass
action kinetics, the dynamics of these chemical reaction networks are governed
by systems of polynomial ordinary differential equations. The steady states of
these mass action systems have been analysed via a variety of techniques,
including elementary flux mode analysis, algebraic techniques (e.g. Groebner
bases), and deficiency theory. In this paper, we present a novel method for
characterizing the steady states of mass action systems. Our method explicitly
links a network's capacity to permit a particular class of steady states,
called toric steady states, to topological properties of a related network
called a translated chemical reaction network. These networks share their
reaction stoichiometries with their source network but are permitted to have
different complex stoichiometries and different network topologies. We apply
the results to examples drawn from the biochemical literature.


title:
An accurate geometric distance to the compact binary SS Cygni vindicates
  accretion disc theory

abstract:
  Dwarf novae are white dwarfs accreting matter from a nearby red dwarf
companion. Their regular outbursts are explained by a thermal-viscous
instability in the accretion disc, described by the disc instability model that
has since been successfully extended to other accreting systems. However, the
prototypical dwarf nova, SS Cygni, presents a major challenge to our
understanding of accretion disc theory. At the distance of 159 +/- 12 pc
measured by the Hubble Space Telescope, it is too luminous to be undergoing the
observed regular outbursts. Using very long baseline interferometric radio
observations, we report an accurate, model-independent distance to SS Cygni
that places the source significantly closer at 114 +/- 2 pc. This reconciles
the source behavior with our understanding of accretion disc theory in
accreting compact objects.


title:
Stellar Orbital Studies in Normal Spiral Galaxies I: Restrictions to the
  Pitch Angle

abstract:
  We built a family of non-axisymmetric potential models for normal non-barred
or weakly-barred spiral galaxies as defined in the simplest classification of
galaxies: the Hubble sequence. For this purpose a three-dimensional
self-gravitating model for spiral arms PERLAS is superimposed to the galactic
axisymmetric potentials. We analyze the stellar dynamics varying only the pitch
angle of the spiral arms, from 4$\deg$ to 40$\deg$, for an Sa galaxy, from
8$\deg$ to 45$\deg$, for an Sb galaxy, and from 10$\deg$ to 60$\deg$, for an Sc
galaxy. Self-consistency is indirectly tested through periodic orbital
analysis, and through density response studies for each morphological type.
Based on ordered behavior, periodic orbits studies show that for pitch angles
up to approximately $15\deg$, $18\deg$, and $20\deg$ for Sa, Sb and Sc
galaxies, respectively, the density response supports the spiral arms
potential, a requisite for the existence of a long-lasting large-scale spiral
structure. Beyond those limits, the density response tends to "avoid" the
potential imposed by mantaining lower pitch angles in the density response; in
that case the spiral arms may be explained as transient features rather than
long-lasting large-scale structures. In a second limit, from a phase space
orbital study based on chaotic behavior, we found that for pitch angles larger
than $\sim30\deg$, $\sim40\deg$ and $\sim50\deg$ for Sa, Sb, and Sc galaxies,
respectively, chaotic orbits dominate all phase space prograde region that
surrounds the periodic orbits sculpting the spiral arms and even destroying
them. This result seems to be in good agreement with observations of pitch
angles in typical isolated normal spiral galaxies.


title: Controllability transition and nonlocality in network control

abstract:
  A common goal in the control of a large network is to minimize the number of
driver nodes or control inputs. Yet, the physical determination of control
signals and the properties of the resulting control trajectories remain widely
under-explored. Here we show that: (i) numerical control fails in practice even
for linear systems if the controllability Gramian is ill-conditioned, which
occurs frequently even when existing controllability criteria are satisfied
unambiguously; (ii) the control trajectories are generally nonlocal in the
phase space, and their lengths are strongly anti-correlated with the numerical
success rate and number of control inputs; (iii) numerical success rate
increases abruptly from zero to nearly one as the number of control inputs is
increased, a transformation we term numerical controllability transition. This
reveals a trade-off between nonlocality of the control trajectory in the phase
space and nonlocality of the control inputs in the network itself. The failure
of numerical control cannot be overcome in general by merely increasing
numerical precision---successful control requires instead increasing the number
of control inputs beyond the numerical controllability transition.


title:
Star-forming Galactic Contrails at z=3.2 as a Source of Metal Enrichment
  and Ionizing Radiation

abstract:
  A spectroscopically detected Lyman alpha emitting halo at redshift 3.216 in
the GOODS-N field is found to reside at the convergence of several Lyman alpha
filaments. HST images show that some of the filaments are inhabited by
galaxies. Several of the galaxies in the field have pronounced head-tail
structures, which are partly aligned with each other. The blue colors of most
tails suggest the presence of young stars, with the emission from at least one
of the galaxies apparently dominated by high equivalent width Lyman alpha.
Faint, more diffuse, and similarly elongated, apparently stellar features, can
be seen over an area with a linear extent of at least 90 kpc. The region within
several arcseconds of the brightest galaxy exhibits spatially extended emission
by HeII, NV and various lower ionization metal lines. The gas-dynamical
features present are strongly reminiscent of ram-pressure stripped galaxies,
including evidence for recent star formation in the stripped contrails. Spatial
gradients in the appearance of several galaxies may represent a stream of
galaxies passing from a colder to a hotter intergalactic medium. The stripping
of gas from the in-falling galaxies, in conjunction with the occurrence of star
formation and stellar feedback in the galactic contrails suggests a mechanism
for the metal enrichment of the high redshift intergalactic medium that does
not depend on long-range galactic winds, at the same time opening a path for
the escape of ionizing radiation from galaxies.


title: Open String Self-energy on the Lightcone Worldsheet Lattice

abstract:
  We continue our study of open string perturbation theory on the lightcone
worldsheet lattice, which is an $M\times N$ rectangular grid. Here $M$ is the
number of $P^+$ units and $N$ is the number of $ix^+$ units. We extend our
previous analysis to the bosonic open string one planar loop self-energy. We
find that, when all open string coordinates satisfy Neumann conditions, the
ultraviolet worldsheet divergences associated with the closed string tachyon
and boundary effects can be cancelled by renormalization of bulk ($AM^1$) and
boundary ($BM^0$) worldsheet "cosmological constants". The bulk divergence for
the open string matches that for the closed string. The open string tachyon
mass shift displays the dilaton logarithmic divergence with the correct
coefficient for its consistent absorption by renormalization of the string
tension. The ultraviolet contribution to the open string gluon mass shift
vanishes, in accord with its interpretation as a gauge particle. We also find
that when the bosonic string ends on a D-brane additional negative powers of
$\ln M$ multiply the bulk and boundary divergences. These can no longer be
cancelled by the "cosmological constants", perhaps pointing to the need, in the
presence of D-branes, for the cancellations of divergences provided by
supersymmetry.


title:
Non-Abelian Topological Order on the Surface of a 3D Topological
  Superconductor from an Exactly Solved Model

abstract:
  Three dimensional topological superconductors (TScs) protected by time
reversal (T) symmetry are characterized by gapless Majorana cones on their
surface. Free fermion phases with this symmetry (class DIII) are indexed by an
integer n, of which n=1 is realized by the B-phase of superfluid Helium-3.
Previously it was believed that the surface must be gapless unless time
reversal symmetry is broken. Here we argue that a fully symmetric and gapped
surface is possible in the presence of strong interactions, if a special type
of topological order appears on the surface. The topological order realizes T
symmetry in an anomalous way, one that is impossible to achieve in purely two
dimensions. For odd n TScs, the surface topological order must be non-Abelian.
We propose the simplest non-Abelian topological order that contains electron
like excitations, SO(3)_6, with four quasiparticles, as a candidate surface
state. Remarkably, this theory has a hidden T invariance which however is
broken in any 2D realization. By explicitly constructing an exactly soluble
Walker-Wang model we show that it can be realized at the surface of a short
ranged entangled 3D fermionic phase protected by T symmetry, with bulk
electrons trasforming as Kramers pairs, i.e. T^2=-1 under time reversal. We
also propose an Abelian theory, the semion-fermion topological order, to
realize an even n TSc surface, for which an explicit model is derived using a
coupled layer construction. We argue that this is related to the n=2 TSc, and
use this to build candidate surface topological orders for n=4 and n=8 TScs.
The latter is equivalent to the three fermion state which is the surface
topological order of a Z2 bosonic topological phase protected by T invariance.
One particular consequence of this is that an n=16 TSc admits a trivially
gapped T-symmetric surface.


title: On the growth of Hermitian groups

abstract:
  A locally compact group G is said to be Hermitian if every selfadjoint
element of L^1(G) has real spectrum. Using Halmos' notion of capacity in Banach
algebras and a result of Jenkins, Fountain, Ramsay and Williamson we will put a
bound on the growth of Hermitian groups. In other words, we will show that if G
has a subset that grows faster than a certain constant, then G cannot be
Hermitian. Our result allows us to give new examples of non-Hermitian groups
which could not tackled by the existing theory. The examples include certain
infinite free Burnside groups, automorphism groups of trees, and p-adic general
and special linear groups.


title: Quantum Energy Teleportation between Spin Particles in a Gibbs State

abstract:
  Energy in a multipartite quantum system appears from an operational
perspective to be distributed to some extent non-locally because of
correlations extant among the system's components. This non-locality allows
users to transfer, in effect, locally accessible energy between sites of
different system components by LOCC (local operations and classical
communication). Quantum energy teleportation is a three-step LOCC protocol,
accomplished without an external energy carrier, for effectively transferring
energy between two physically separated, but correlated, sites. We apply this
LOCC teleportation protocol to a model Heisenberg spin particle pair initially
in a quantum thermal Gibbs state, making temperature an explicit parameter. We
find in this setting that energy teleportation is possible at any temperature,
even at temperatures above the threshold where the particles' entanglement
vanishes. This shows for Gibbs spin states that entanglement is not
fundamentally necessary for energy teleportation; correlation other than
entanglement can suffice. Dissonance---quantum correlation in separable
states---is in this regard shown to be a quantum resource for energy
teleportation, more dissonance being consistently associated with greater
energy yield. We compare energy teleportation from particle A to B in Gibbs
states with direct local energy extraction by a general quantum operation on B
and find a temperature threshold below which energy extraction by a local
operation is impossible. This threshold delineates essentially two regimes: a
high temperature regime where entanglement vanishes and the teleportation
generated by other quantum correlations yields only vanishingly little energy
relative to local extraction and a second low-temperature teleportation regime
where energy is available at B only by teleportation.


title: Hopf-cyclic cohomology of bicrossed product Hopf algebras

abstract:
  In this dissertation we study the coefficients spaces (SAYD modules) of
Hopf-cyclic cohomology theory over a certain family of bicrossed product Hopf
algebras, and we compute the Hopf-cyclic cohomology of such Hopf algebras with
coefficients. We associate a Hopf algebra, what we call a Lie-Hopf algebra, to
any matched pair of Lie groups, Lie algebras and affine algebraic groups via
the semi-dualization procedure of Majid. We then identify the SAYD modules over
Lie-Hopf algebras with the representations and corepresentations of the total
Lie group, Lie algebra or the affine algebraic group of the matched pair. First
we classify the SAYD modules that correspond only to the representations of a
total Lie group (algebra). We call them induced SAYD modules. We then
generalize this identification, focusing on the matched pair of Lie algebras.
We establish a one-to-one correspondence between the SAYD modules over the
Lie-Hopf algebra associated to a matched pair of Lie algebras and certain SAYD
modules over the total Lie algebra. Once the SAYD modules are associated to the
representations and the corepresentations of Lie algebras, nontrivial examples
can be constructed. This way, we illustrate a highly nontrivial 4-dimensional
SAYD module over the Schwarzian Hopf algebra H_{1S}. In addition, we discuss
the periodic cyclic cohomology of Lie-Hopf algebras with nontrivial SAYD
coefficients. We obtain a general van Est isomorphism identifying the periodic
cyclic cohomology of a Lie-Hopf algebra with the (relative) Lie algebra
cohomology of the corresponding total Lie algebra.


title:
First Test of High Frequency Gravity Waves from Inflation using ADVANCED
  LIGO

abstract:
  Inflation models ending in a first order phase transition produce
gravitational waves (GW) via bubble collisions of the true vacuum phase. We
demonstrate that these bubble collisions can leave an observable signature in
Advanced LIGO, an upcoming ground-based GW experiment. These GW are dependent
on two parameters of the inflationary model: $\varepsilon$ represents the
energy difference between the false vacuum and the true vacuum of the inflaton
potential, and $\chi$ measures how fast the phase transition ends ($\chi \sim$
the number of e-folds during the actual phase transition). Advanced LIGO will
be able to test the validity of single-phase transition models within the
parameter space $10^7 \rm{GeV}\lesssim \varepsilon^{1/4} \lesssim 10^{10}
\rm{GeV}$ and $0.19 \lesssim \chi \lesssim 1$. If inflation occurred through a
first order phase transition, then Advanced LIGO could be the first to discover
high frequency GW from inflation.


title: H-Infinity Optimal Decentralized Matching Model Is Not Always Rational

abstract:
  We construct structured H-Infinity optimal model matching problems with
rational coefficients, in which the optimal solution is not rational, in the
sense that the cost does not achieve its maximal lower bound on the set of
rational matching models, but the same maximal lower bound can be reached by
using a continuous non-rational matching model.


title: Metamaterial Van Hove Singularity

abstract:
  We introduce the photonic analogue of electronic Van Hove singularities (VHS)
in artificial media (metamaterials) with hyperbolic dispersion. Unlike photonic
and electronic crystals, the VHS in metamaterials is unrelated to the
underlying periodicity and occurs due to slow light modes in the structure. We
show that the VHS characteristics are manifested in the near-field local
density of optical states in spite of the losses, dispersion and finite unit
cell size of the hyperbolic metamaterial. Finally we show that this work should
lead to quantum, thermal, nano-lasing and biosensing applications of Van Hove
singularities in hyperbolic metamaterials achievable by current fabrication
technology.


title: On The Strength of Two Recurrence Theorems

abstract:
  This paper uses the framework of reverse mathematics to investigate the
strength of two recurrence theorems of topological dynamics. It establishes
that one of these theorems, the existence of an almost periodic point, lies
strictly between WKL and ACA (working over RCA_0). This is the first example of
a theorem with this property. It also shows the existence of an almost periodic
point is conservative over RCA_0 for Pi^1_1 sentences. These results establish
the existence of a new upwards-closed subclass of the PA degrees


title: Convexity of Decentralized Controller Synthesis

abstract:
  In decentralized control problems, a standard approach is to specify the set
of allowable decentralized controllers as a closed subspace of linear
operators. This then induces a corresponding set of Youla parameters. Previous
work has shown that quadratic invariance of the controller set implies that the
set of Youla parameters is convex. In this paper, we prove the converse. We
thereby show that the only decentralized control problems for which the set of
Youla parameters is convex are those which are quadratically invariant. We
further show that under additional assumptions, quadratic invariance is
necessary and sufficient for the set of achievable closed-loop maps to be
convex. We give two versions of our results. The first applies to bounded
linear operators on a Banach space and the second applies to (possibly
unstable) causal LTI systems in discrete or continuous time.


title:
Climbing, falling and jamming during ant locomotion in confined
  environments

abstract:
  Locomotion emerges from effective interactions of an individual with its
environment. Principles of biological terrestrial locomotion have been
discovered on unconfined vertical and horizontal substrates. However a
diversity of organisms construct, inhabit, and move within confined spaces.
Such animals are faced with locomotor challenges including limited limb range
of motion, crowding, and visual sensory deprivation. Little is known about how
these organisms accomplish their locomotor tasks, and such environments
challenge human-made devices. To gain greater insight into how animals move
within confined spaces we study the confined locomotion of the fire ant {\em
Solenopsis invicta}, which constructs subterranean tunnel networks (nests).
Laboratory experiments reveal that ants construct tunnels with diameter, D,
comparable to bodylength, L=3.5 $\pm$ 0.5 mm. Ants can move rapidly (> 9
bodylengths/sec) within these environments; their tunnels allow for effective
limb, body, and antennae interaction with walls which facilitate rapid
slip-recovery during ascending and descending climbs. To examine the limits of
slip-recovery in artificial tunnels we perform perturbations consisting of
rapid downward accelerations of the tunnels, which induce falls. Below a
critical tunnel diameter, $D_s = 1.31 \pm 0.02$ L, falls are always arrested
through rapid interaction of appendages and antennae with tunnel walls to jam
the falls. $D_s$ is comparable to the size of incipient nest tunnels (D = 1.06
$\pm$ 0.23 L) supporting our hypothesis that fire ants construct environments
which simplify their control task when moving through the nest, likely without
need for rapid nervous system intervention.


title:
Strain engineering of magnetic states of vacancy-decorated hexagonal
  boron nitride

abstract:
  Novel materials with tunable magnetic states play a significant role in the
development of next-generation spintronic devices. In this paper, we examine
the role of biaxial strain on the electronic properties of vacancy-decorated
hexagonal boron nitride (h-BN) monolayers using density functional theory
calculations. We found that the strain can lead to switching of the magnetic
state for h-BN monolayers with boron vacancy or divacancy. Our findings promise
a new route for the operation of low-dimensional spintronic devices.


title:
Simulations of Nanocrystals Under Pressure: Combining Electronic
  Enthalpy and Linear-Scaling Density-Functional Theory

abstract:
  We present an implementation in a linear-scaling density-functional theory
code of an electronic enthalpy method, which has been found to be natural and
efficient for the ab initio calculation of finite systems under hydrostatic
pressure. Based on a definition of the system volume as that enclosed within an
electronic density isosurface [Phys. Rev. Lett., 94, 145501 (2005)], it
supports both geometry optimizations and molecular dynamics simulations. We
introduce an approach for calibrating the parameters defining the volume in the
context of geometry optimizations and discuss their significance. Results in
good agreement with simulations using explicit solvents are obtained,
validating our approach. Size-dependent pressure-induced structural
transformations and variations in the energy gap of hydrogenated silicon
nanocrystals are investigated, including one comparable in size to recent
experiments. A detailed analysis of the polyamorphic transformations reveals
three types of amorphous structures and their persistence on depressurization
is assessed.


title: Non-topological condensates for the self-dual Chern-Simons-Higgs model

abstract:
  For the abelian self-dual Chern-Simons-Higgs model we address existence
issues of periodic vortex configurations -- the so-called condensates-- of
non-topological type as $k \to 0$, where $k>0$ is the Chern-Simons parameter.
We provide a positive answer to the long-standing problem on the existence of
non-topological condensates with magnetic field concentrated at some of the
vortex points (as a sum of Dirac measures) as $k \to 0$, a question which is of
definite physical interest.


title:
Diurnal astronomy: using sticks and threads to find our latitude on
  Earth

abstract:
  It is well known that the length and orientation of a shadow cast by a
vertical gnomon depends on the time of the day and on the season of the year.
But it also depends on the latitude of the site of observation. During the
equinoxes, the temporal sequence of the shadows cast by each of the points that
form any object follows a straight line from west to east. A simple
construction using sticks and threads can be used to materialize the plane of
celestial equator's local projection, giving us a way to calculate our
astronomical latitude during daytime with high precision.


title: Dynamical Modeling of Galaxy Mergers using Identikit

abstract:
  We present dynamical models of four interacting systems: NGC 5257/8, The
Mice, the Antennae, and NGC 2623. The parameter space of the encounters are
constrained using the Identikit model-matching and visualization tool.
Identikit utilizes hybrid N-body and test particle simulations to enable rapid
exploration of the parameter space of galaxy mergers. The Identikit-derived
matches of these systems are reproduced with self-consistent collisionless
simulations which show very similar results. The models generally reproduce the
observed morphology and \HI\ kinematics of the tidal tails in these systems
with reasonable properties inferred for the progenitor galaxies. The models
presented here are the first to appear in the literature for NGC 5257/8 and NGC
2623, and The Mice and the Antennae are compared with previously published
models. Based on the assumed mass model and our derived initial conditions, the
models indicate the four systems are currently being viewed 175-260 Myr after
first passage and cover a wide range of merger stages. In some instances there
are mismatches between the models and the data (e.g., in the length of a tail);
these are likely due to our adoption of a single mass model for all galaxies.
Despite the use of a single mass model, these results demonstrate the utility
of Identikit in constraining the parameter space for galaxy mergers when
applied to real data.


title: Harmonic Generation in Multi-Resonant Plasma Films

abstract:
  We investigate second and third harmonic generation in a slab of material
that displays plasma resonances at the pump and its harmonic frequencies.
Near-zero refractive indices and local field enhancement can deplete the pump
for kW/cm2 incident powers, without resorting to other resonant photonic
mechanisms. We show that low-threshold, highly-efficient nonlinear processes
are possible in the presence of losses and phase-mismatch in structures that
are 104 times shorter than typical KDP or LiNbO3 crystals, for relatively low
irradiance values.


title: Tailoring absorption in metal gratings with resonant ultra-thin bridges

abstract:
  We present a theoretical analysis of the effects of short range surface
plasmon polariton excitation on sub-wavelength bridges in metal gratings. We
show that localized resonances in thin metal bridges placed within the slit of
a free-standing silver grating dramatically modify transmission spectra and
boost absorption regardless of the periodicity of the grating. Additionally,
the interference of multiple localized resonances makes it possible to tailor
the absorption properties of ultrathin gratings, regardless of the apertures'
geometrical size. This tunable, narrow-band, enhanced-absorption mechanism
triggered by resonant, short range surface plasmon polaritons may also enhance
nonlinear optical processes like harmonic generation, in view of the large
third-order susceptibility of metals.