title: A Time Series Forest for Classification and Feature Extraction

abstract:
  We propose a tree ensemble method, referred to as time series forest (TSF),
for time series classification. TSF employs a combination of the entropy gain
and a distance measure, referred to as the Entrance (entropy and distance)
gain, for evaluating the splits. Experimental studies show that the Entrance
gain criterion improves the accuracy of TSF. TSF randomly samples features at
each tree node and has a computational complexity linear in the length of a
time series and can be built using parallel computing techniques such as
multi-core computing used here. The temporal importance curve is also proposed
to capture the important temporal characteristics useful for classification.
Experimental studies show that TSF using simple features such as mean,
deviation and slope outperforms strong competitors such as one-nearest-neighbor
classifiers with dynamic time warping, is computationally efficient, and can
provide insights into the temporal characteristics.


title: Consequences of Spontaneous Lorentz Violation in Gravity

abstract:
  A brief summary of some of the main consequences of spontaneous Lorentz
violation in gravity is presented, including evasion of a no-go theorem,
concomitant spontaneous diffeomorphism breaking, the appearance of massless
Nambu-Goldstone modes and massive Higgs modes, and the possibility of a Higgs
mechanism in gravity.


title: Expressing Second-order Sentences in Intuitionistic Dependence Logic

abstract:
  Intuitionistic dependence logic was introduced by Abramsky and Vaananen
(2009) as a variant of dependence logic under a general construction of Hodges'
(trump) team semantics. It was proven that there is a translation from
intuitionistic dependence logic sentences into second order logic sentences. In
this paper, we prove that the other direction is also true, therefore
intuitionistic dependence logic is equivalent to second order logic on the
level of sentences.


title:
Collective dynamics in systems of active Brownian particles with
  dissipative interactions

abstract:
  We use computer simulations to study the onset of collective motion in
systems of interacting active particles. Our model is a swarm of active
Brownian particles with internal energy depot and interactions inspired by the
dissipative particle dynamics method, imposing pairwise friction force on the
nearest neighbours. We study orientational ordering in a 2D system as a
function of energy influx rate and particle density. The model demonstrates a
transition into the ordered state on increasing the particle density and
increasing the input power. Although both the alignment mechanism and the
character of individual motion in our model differ from those in the
well-studied Vicsek model, it demonstrates identical statistical properties and
phase behaviour.


title: Power-law Decay and the Ergodic-Nonergodic Transition in Simple Fluids

abstract:
  It is well known that mode coupling theory (MCT) leads to a two step
power-law time decay in dense simple fluids. We show that much of the
mathematical machinery used in the MCT analysis can be taken over to the
analysis of the systematic theory developed in the Fundamental Theory of
Statistical Particle Dynamics (arXiv:0905.4904). We show how the power-law
exponents can be computed in the second-order approximation where we treat
hard-sphere fluids with statics described by the Percus-Yevick solution.


title: On measure expansive diffeomorphisms

abstract:
  Let $f: M \to M$ be a diffeomorphism defined on a compact boundaryless
$d$-dimensional manifold $M$, $d\geq 2$. C. Morales has proposed the notion of
measure expansiveness. In this note we show that diffeomorphisms in a residual
subset far from homoclinic tangencies are measure expansive.
  We also show that surface diffeomorphisms presenting homoclinic tangencies
can be $C^1$-approximated by non-measure expansive diffeomorphisms.


title: Cupolets and a Chaotic Analog of Entanglement

abstract:
  This paper discusses applications of a particular control technique that can
be used to very efficiently stabilize a chaotic system onto a large subset of
the unstable periodic orbits that are typically embedded in the system. The
control method is adapted from one developed by Hayes, Grebogi, and Ott, and
the resulting (stabilized) orbits are known as cupolets (Chaotic, Unstable,
Periodic, Orbit-LETS). Cupolets exhibit the interesting property that a given
set of controls will uniquely identify a cupolet, independent of its initial
condition. Practical applications of cupolets already include data compression,
secure communication, and image processing. We demonstrate how cupolets from
two interacting chaotic systems may be induced into a state of mutual and
self-sustaining stabilization, in a manner that may be an analog of quantum
entanglement.


title: Single Dirac-Cone State and Quantum Hall Effects in Honeycomb Structure

abstract:
  A honeycomb lattice system has four types of Dirac electrons corresponding to
the spin and valley degrees of freedom. We consider a state that contains only
one type of massless electrons and three types of massive ones, which we call
the single Dirac-cone state. We analyze quantum Hall (QH) effects in this
state. We make a detailed investigation of the Chern and spin-Chern numbers. We
make clear the origin of unconventional QH effects discovered in graphene. We
also show that the single Dirac-cone state may have arbitrary large spin-Chern
numbers in magnetic field. Such a state will be generated in antiferromagnetic
transition-metal oxides under electric field or silicene with antiferromagnetic
order under electric field.


title: Quantum Gravity: Meaning and Measurement

abstract:
  A discussion of the meaning of a physical concept cannot be separated from
discussion of the conditions for its ideal measurement. We assert that
quantization is no more than the invocation of the quantum of action in the
explanation of some process or phenomenon, and does not imply an assertion of
the fundamental nature of such a process. This leads to an ecumenical approach
to the problem of quantization of the gravitational field. There can be many
valid approaches, each of which should be judged by the domain of its
applicability to various phenomena. If two approaches have overlapping domains,
the relation between them then itself becomes a subject of study. We advocate
an approach to general relativity based on the unimodular group, which
emphasizes the physical significance and measurability of the conformal and
projective structures. A discussion of the method of matched asymptotic
expansions, and of the weakness of terrestrial sources compared with
astrophysical and cosmological sources, leads us to suggest theoretical studies
of gravitational radiation based on retrodiction (observation) rather than
prediction (experimentation).


title:
An l^{p}-Version of von Neumann Dimension for Banach Space
  Representation of Sofic Groups II

abstract:
  In previous work, we defined extended versions of von Neumann dimension for
Banach space representations of sofic groups. The main application was a
definition of l^{p}-dimension and, using this, a proof that the actions of a
countable discrete group G on l^{p}(G)^{oplus n} are pairwise non-isomorphic.
We answer most of the Conjectures stated at the end of the previous paper "An
l^{p}-Version of von Neumann Dimension for Banach Space Representation of Sofic
Groups." Tackling the case of finte-dimensional representations involved
passing to equivalence relations. This is part of current research to be
explained in the paper "An l^{p}-Version of von Neumann Dimension for
Representations of Equivalence Relations."


title: Fluid transport by active elastic membranes

abstract:
  A flexible membrane deforming its shape in time can self-propel in a viscous
fluid. Alternatively, if the membrane is anchored, its deformation will lead to
fluid transport. Past work in this area focused on situations where the
deformation kinematics of the membrane were prescribed. Here we consider models
where the deformation of the membrane is not prescribed, but instead the
membrane is internally forced. Both the time-varying membrane shape, and the
resulting fluid motion, result then from a balance between prescribed internal
active stresses, internal passive resistance, and external viscous stresses. We
introduce two specific models for such active internal forcing: one where a
distribution of active bending moments is prescribed, and one where active
inclusions exert normal stresses on the membrane by pumping fluid through it.
In each case, we asymptotically calculate the membrane shape and the fluid
transport velocities for small forcing amplitudes, and recover our results
using scaling analysis.


title:
Orientational order in concentrated suspensions of spherical
  microswimmers

abstract:
  We use numerical simulations to probe the dynamics of concentrated
suspensions of spherical microswimmers interacting hydrodynamically. Previous
work in the dilute limit predicted orientational instabilities of aligned
suspensions for both pusher and puller swimmers, which we confirm
computationally. Unlike previous work, we show that isotropic suspensions of
spherical swimmers are also always unstable. Both types of initial conditions
develop long-time polar order, of a nature which depends on the hydrodynamic
signature of the swimmer but very weakly on the volume fraction up to very high
volume fractions.


title:
High-energy deformation of filaments with internal structure and
  localized torque-induced melting of DNA

abstract:
  We develop a continuum elastic approach to examining the bending mechanics of
semiflexible filaments with a local internal degree of freedom that couples to
the bending modulus. We apply this model to study the nonlinear mechanics of a
double stranded DNA oligomer (shorter than its thermal persistence length)
whose free ends are linked by a single standed DNA chain. This construct,
studied by Qu et al. [Europhys. Lett., $\bf{94}$, 18003, 2011], displays
nonlinear strain softening associated with the local melting of the double
stranded DNA under applied torque and serves as a model system with which to
study the nonlinear elasticity of DNA under large energy deformations. We show
that one can account quantitatively for the observed bending mechanics using an
augmented worm-like chain model, the helix coil worm-like chain. We also
predict that the highly bent and partially molten dsDNA should exhibit
particularly large end-to-end fluctuations associated with the fluctuation of
the length of the molten region, and propose appropriate experimental tests. We
suggest that the augmented worm-like chain model discussed here is a useful
analytic approach to the nonlinear mechanics of DNA or other biopolymer
systems.


title: On surface links whose link groups are abelian

abstract:
  We study surface links whose link groups are free abelian, and construct
various stimulating and highly non-trivial examples of such surface links.


title:
Constraints on the Holographic Dark Energy Model from Type Ia
  Supernovae, WMAP7, Baryon Acoustic Oscillation and Redshift-Space Distortion

abstract:
  In this paper, we use the joint measurement of geometry and growth rate from
matter density perturbations to constrain the holographic dark energy model.
The geometry measurement includes type Ia supernovae (SN Ia) Union2.1, full
information of cosmic microwave background (CMB) from WMAP-7yr and baryon
acoustic oscillation (BAO). For the growth rate of matter density
perturbations, the results $f(z)\sigma_8(z)$ measured from the redshift-space
distortion (RSD) in the galaxy power spectrum are employed. Via the Markov
Chain Monte Carlo method, we try to constrain the model parameters space. The
jointed constraint shows that $c=0.750_{- 0.0999- 0.173- 0.226}^{+ 0.0976+
0.215+ 0.319}$ and $\sigma_8=0.763_{- 0.0465- 0.0826- 0.108}^{+ 0.0477+ 0.0910+
0.120}$ with $1,2,3\sigma$ regions. After marginalizing the other irrelevant
model parameters, we show the evolution of the equation of state of HDE with
respect to the redshift $z$. Though the current cosmic data points favor a
phantom like HDE Universe for the mean values of the model parameters in the
future, it can behave like quintessence in $3\sigma$ regions.


title:
An instability due to the nonlinear coupling of p-modes to g-modes:
  Implications for coalescing neutron star binaries

abstract:
  A weakly nonlinear fluid wave propagating within a star can be unstable to
three-wave interactions. The resonant parametric instability is a well-known
form of three-wave interaction in which a primary wave of frequency $\omega_a$
excites a pair of secondary waves of frequency $\omega_b+\omega_c \simeq
\omega_a$. Here we consider a nonresonant form of three-wave interaction in
which a low-frequency primary wave excites a high-frequency p-mode and a
low-frequency g-mode such that $\omega_b+\omega_c >>\omega_a$. We show that a
p-mode can couple so strongly to a g-mode of similar radial wavelength that
this type of interaction is unstable even if the primary wave amplitude is
small. As an application, we analyze the stability of the tide in coalescing
neutron star binaries to p-g mode coupling. We find that the equilibrium tide
and dynamical tide are both p-g unstable at gravitational wave frequencies
f_{gw} > 20 Hz and drive p-g pairs to significant energies on very short
timescales (much less than the orbital decay time). Resonant parametric
coupling to the tide is, by contrast, either stable or drives modes at a much
smaller rate. We do not solve for the saturation of the instability and
therefore cannot say precisely how it influences neutron star binaries.
However, we show that if even a single daughter mode saturates near its wave
breaking amplitude, the p-g instability of the equilibrium tide: (i) induces
significant orbital phase errors ($\Delta \phi$ > 1 radian) that accumulate
primarily at low frequencies (f_{gw} < 50 Hz) and (ii) heats the neutron star
core to T~10^{10} K. Since there are >100 unstable daughters, $\Delta \phi$ and
T are potentially much larger than these values. Tides might therefore
significantly influence the gravitational wave signal and electromagnetic
emission from neutron star binaries at much larger orbital separations than
previously thought.


title:
An l^{p}-Version of von Neumann Dimension for Representations of
  Equivalence Relations

abstract:
  In our previous paper, "l^{p}-Version of von Neumann Dimension for Banach
Space Representations of Sofic Groups," we define an extended version of von
Neumann dimension for actions of a sofic group on a Banach space. This
dimension was studied especially for the translation action of G on l^{p}(G),
as well as the multiplication on the non-commutative L^{p} space associated
with the group von Neumann algebra. We discuss how one can similarly define an
extended dimension for representations of an equivalence relation. We also
define an analogue of l^{2}-Betti numbers for equivalence relations in the
l^{p}-case, this may shed some light on the conjectured relation between cost
and first l^{2}-Betti number.


title: On the Relationship between D'Angelo q-type and Catlin q-type

abstract:
  We establish inequalities relating two measurements of the order of contact
of q-dimensional complex varieties with a real hypersurface.


title: Near Infrared Circular Polarization Images of NGC 6334-V

abstract:
  We present results from deep imaging linear and circular polarimetry of the
massive star-forming region NGC 6334- V. These observations show high degrees
of circular polarization (CP), as much as 22 % in the Ks band, in the infrared
nebula associated with the outflow. The CP has an asymmetric positive/negative
pattern and is very extended (~80" or 0.65 pc). Both the high CP and its
extended size are larger than those seen in the Orion CP region.
Three-dimensional Monte Carlo light-scattering models are used to show that the
high CP may be produced by scattering from the infrared nebula followed by
dichroic extinction by an optically thick foreground cloud containing aligned
dust grains. Our results show not only the magnetic field orientation of around
young stellar objects but also the structure of circumstellar matter such as
outflow regions and their parent molecular cloud along the line of sight. The
detection of the large and extended CP in this source and the Orion nebula may
imply the CP origin of the biological homochirality on Earth.


title: The distribution of $k$-tuples of reduced residues

abstract:
  In 1940 Paul Erd\H{o}s made a conjecture about the distribution of reduced
residues. Here we study the distribution of $k$-tuple of reduced residues.


title:
Two meromorphic mappings sharing 2n + 2 hyperplanes regardless of
  multiplicity

abstract:
  Nevanlinna showed that two non-constant meromorphic functions on $\mathbb C$
must be linked by a M\"{o}bius transformation if they have the same inverse
images counted with multiplicities for four distinct values. After that this
results is generalized by Gundersen to the case where two meromorphic functions
share two values ignoring multiplicity and share other two values with
multiplicities trucated by 2. Previously, the first author proved that for
$n\ge 2,$ there are at most two linearly nondegenerate meromorphic mappings of
$\mathbb C^m$ into $\mathbb P^n(\mathbb C)$ sharing $2n+2$ hyperplanes
ingeneral position ignoring multiplicity. In this article, we will show that if
two meromorphic mappings $f$ and $g$ of $\mathbb C^m$ into $\mathbb P^n(\mathbb
C)$ share $2n+1$ hyperplanes ignoring multiplicity and another hyperplane with
multiplicities trucated by $n+1$ then the map $f\times g$ is algebraically
degenerate.


title:
Efficient Tree Tensor Network States (TTNS) for Quantum Chemistry:
  Generalizations of the Density Matrix Renormalization Group Algorithm

abstract:
  We investigate tree tensor network states for quantum chemistry. Tree tensor
network states represent one of the simplest generalizations of matrix product
states and the density matrix renormalization group. While matrix product
states encode a one-dimensional entanglement structure, tree tensor network
states encode a tree entanglement structure, allowing for a more flexible
description of general molecules. We describe an optimal tree tensor network
state algorithm for quantum chemistry. We introduce the concept of
half-renormalization which greatly improves the efficiency of the calculations.
Using our efficient formulation we demonstrate the strengths and weaknesses of
tree tensor network states versus matrix product states. We carry out benchmark
calculations both on tree systems (hydrogen trees and \pi-conjugated
dendrimers) as well as non-tree molecules (hydrogen chains, nitrogen dimer, and
chromium dimer). In general, tree tensor network states require much fewer
renormalized states to achieve the same accuracy as matrix product states. In
non-tree molecules, whether this translates into a computational savings is
system dependent, due to the higher prefactor and computational scaling
associated with tree algorithms. In tree like molecules, tree network states
are easily superior to matrix product states. As an ilustration, our largest
dendrimer calculation with tree tensor network states correlates 110 electrons
in 110 active orbitals.


title: On Improving Roth's Theorem in the Primes

abstract:
  Let $A\subset\left\{ 1,\dots,N\right\} $ be a set of prime numbers containing
no non-trivial arithmetic progressions. Suppose that $A$ has relative density
$\alpha=|A|/\pi(N)$, where $\pi(N)$ denotes the number of primes in the set
$\left\{ 1,\dots,N\right\} $. By modifying Helfgott and De Roton's work, we
improve their bound and show that $$\alpha\ll\frac{\left(\log\log\log
N\right)^{6}}{\log\log N}.$$


title:
Nodal gap in iron-based superconductor CsFe$_2$As$_2$ probed by
  quasiparticle heat transport

abstract:
  The thermal conductivity of iron-based superconductor CsFe$_2$As$_2$ single
crystal ($T_c =$ 1.81 K) was measured down to 50 mK. A significant residual
linear term $\kappa_0/T$ = 1.27 mW K$^{-2}$ cm$^{-1}$ is observed in zero
magnetic field, which is about 1/10 of the normal-state value in upper critical
field $H_{c2}$. In low magnetic field, $\kappa_0/T$ increases rapidly with
field. The overall field dependence of $\kappa_0/T$ for our CsFe$_2$As$_2$
(with residual resistivity $\rho_0$ = 1.80 $\mu\Omega$ cm) lies between the
dirty KFe$_2$As$_2$ (with $\rho_0$ = 3.32 $\mu\Omega$ cm) and the clean
KFe$_2$As$_2$ (with $\rho_0$ = 0.21 $\mu\Omega$ cm). These results strongly
suggest nodal superconducting gap in CsFe$_2$As$_2$, similar to its sister
compound KFe$_2$As$_2$.


title: Signature of strange dibaryons in kaon- and photon-induced reactions

abstract:
  We examine how the signature of the strange dibaryon resonances shows up in
scattering amplitudes and observables of the three-body $\bar{K}NN$-$\pi Y N
(Y=\Sigma, \Lambda)$ system on the physical real energy axis. The so-called
point method is applied to handle logarithmic singularities that appear in
solving the Alt-Grassberger-Sandhas equations for the real scattering energies.
By taking two different kinds of models for the two-body $\bar{K}N$-$\pi
\Sigma$ subsystem, both of which reproduce the available data equally well but
give quite a different resonance-pole structure for $\Lambda(1405)$, we also
investigate whether the strange-dibaryon production reactions can be used for
disentangling the nature of $\Lambda(1405)$.


title: Copper red glazes: a coating with two families of particles

abstract:
  In order to explain the origin of the deep red color of copper glazes on
ceramics, a ceramist has elaborated, by firing under reducing atmosphere, a
significant number of tiles. The analysis of the structure and composition of a
representative sample by TEM and EELS, followed by an optical characterization
and an optical modeling using the radiative transfer approach (four-flux model)
have enabled a comprehensive explanation of the origin of the color in these
glazes. The presence of two families of copper nanoparticles in the vitreous
matrix. The first, purely absorbing, of diameter 10-50 nm, essentially creates
color by a substractive process. The second, due to its larger diameter, 100 nm
or more, mainly acts on color by scattering of the visible light. Both act
competitively in the layer. A color chart of all the hues which can be reached
by this technique has eventually been theoretically calculated.


title: False Variable Selection Rates in Regression

abstract:
  There has been recent interest in extending the ideas of False Discovery
Rates (FDR) to variable selection in regression settings. Traditionally the FDR
in these settings has been defined in terms of the coefficients of the full
regression model. Recent papers have struggled with controlling this quantity
when the predictors are correlated. This paper shows that this full model
definition of FDR suffers from unintuitive and potentially undesirable behavior
in the presence of correlated predictors. We propose a new false selection
error criterion, the False Variable Rate (FVR), that avoids these problems and
behaves in a more intuitive manner. We discuss the behavior of this criterion
and how it compares with the traditional FDR, as well as presenting guidelines
for determining which is appropriate in a particular setting. Finally, we
present a simple estimation procedure for FVR in stepwise variable selection.
We analyze the performance of this estimator and draw connections to recent
estimators in the literature.


title:
Capturing Trojans and Irregular Satellites - the key required to unlock
  planetary migration

abstract:
  It is now accepted that the Solar system's youth was a dynamic and chaotic
time. The giant planets migrated significant distances to reach their current
locations, and evidence of that migration's influence on the Solar system
abounds. That migration's pace, and the distance over which it occurred, is
still heavily debated. Some models feature systems in which the giant planets
were initially in an extremely compact configuration, in which Uranus and
Neptune are chaotically scattered into the outer Solar system. Others feature
architectures that were initially more relaxed, and smoother, more sedate
migration. To determine which of these scenarios best represents the formation
of our Solar system, we must turn to the structure of the system's small body
populations, in which the scars of that migration are still clearly visible.
  We present the first results of a program investigating the effect of giant
planet migration on the reservoirs of small bodies that existed at that time.
As the planets migrate, they stir these reservoirs, scattering vast numbers of
small bodies onto dynamically unstable orbits in the outer Solar system. The
great majority of those bodies are rapidly removed from the system, through
collisions and ejections, but a small number become captured as planetary
Trojans or irregular satellites. Others are driven by the migration, leading to
a significant sculpting of the asteroid belt and trans-Neptunian region.
  The capture and retention efficiencies to these stable reservoirs depend on
the particular migration scenario used. Advocates of chaotic migration from an
initially compact scenario argue that smoother, more sedate migration cannot
explain the observed populations of Trojans and irregular satellites. Our
results draw a strikingly different picture, revealing that such smooth
migration is perfectly capable of reproducing the observed populations.


title: Quantum signal transmission through a single-qubit chain

abstract:
  A system of a two-level atom of an impurity (qubit) inserted into a periodic
chain coupled to the continuum is studied with the use of the effective
non-Hermitian Hamiltonian. Exact solutions are derived for the quasistationary
eigenstates, their complex energies, and transport properties. Due to the
presence of the qubit, two long-lived states corresponding to the ground and
excited states of the qubit emerge outside the Bloch energy band. These states
remain essentially localized at the qubit even in the limit of sufficiently
strong coupling between the chain and the environment when the super-radiant
states are formed. The transmission through the chain is studied as a function
of the continuum coupling strength and the chain-qubit coupling; the perfect
resonance transmission takes place through isolated resonances at weak and
strong continuum coupling, while the transmission is lowered in the
intermediate regime.


title:
Anomalous globular clusters: insights from neutron capture elements
  abundances

abstract:
  Thanks to the large amount of spectroscopic and photometric data assembled in
the last couple of decades, the assumption that all globular clusters (GCs)
contain a simple mono-metallic stellar population has been modified. Besides
the common variations in the elements created/destroyed in the H-burning
processes, spreads and/or multi-modalities in heavier elements have been
detected in a few objects. Among the most remarkable chemical inhomogeneity in
these anomalous objects is the internal variation in the neutron-capture
(n-capture) elements, that can provide some information about the material from
which stars were born. I report a summary of the chemical pattern observed in
GCs where variations in n-capture have been detected, and the connection
between these chemical features and the distribution of stars along the
color-magnitude diagrams in the context of the lively debate on multiple
stellar populations.


title: A Class of Extended Hypergeometric Functions and Its Applications

abstract:
  Recently, there emerges different versions of beta function and
hypergeometric functions containing extra parameters. Gaining enlightenment
from these ideas, we will first introduce a new extension of generalized
hypergeometric function and then put forward some fundamental results in the
paper. Next, we will derive some properties of certain functions like extended
Gauss hypergeometric functions, extended Appell's hypergeometric functions
$\mathbf{F}_{1}^{(\kappa_{l})}$, $\mathbf{F}_{2}^{(\kappa_{l})}$, and extended
Lauricella's hypergeometric function
$\mathbf{F}_{D,(\kappa_{l})}^{(r)}$,$\mathbf{F}_{A,(\kappa_{l})}^{(r)}$,
including transformation formulas, finite sum representations, Mellin-Barnes
type integral representations and recurrence relations. Moreover, by using some
new integral representation which will be presented in this paper, a
Hardy-Hilbert type inequality involving extended Gauss hypergeometric functions
will be established.


title: Analysis of Evidence Using Formal Event Reconstruction

abstract:
  This paper expands upon the finite state machine approach for the formal
analysis of digital evidence. The proposed method may be used to support the
feasibility of a given statement by testing it against a relevant system model.
To achieve this, a novel method for modeling the system and evidential
statements is given. The method is then examined in a case study example.


title: Infinite transitivity on universal torsors

abstract:
  Let X be an algebraic variety covered by open charts isomorphic to the affine
space and q: X' \to X be the universal torsor over X. We prove that the
automorphism group of the quasiaffine variety X' acts on X' infinitely
transitively. Also we find wide classes of varieties X admitting such a
covering.


title: Two Propositions Involving the Standard Representation of $S_n$

abstract:
  We present here two standalone results from a forthcoming work on the
analysis of Markov chains using the representation theory of $S_n$. First, we
give explicit formulas for the decompositions of tensor powers of the defining
and standard representations of $S_n$. Secondly, we prove that any Markov chain
on $S_n$ starting with one fixed point and whose increment distributions are
class measures will always average exactly one fixed point.


title:
Testing general scalar-tensor gravity and massive gravity with cluster
  lensing

abstract:
  We explore the possibility of testing modified gravity exhibiting the
Vainshtein mechanism against observations of cluster lensing. We work in the
most general scalar-tensor theory with second-order field equations
(Horndeski's theory), and derive static and spherically symmetric solutions,
for which the scalar field is screened below a certain radius. It is found that
the essential structure of the problem in the most general case can be captured
by the program of classifying Vainshtein solutions out of different solutions
to a quintic equation, as has been performed in the context of massive gravity.
The key effect on gravitational lensing is that the second derivative of the
scalar field can substantially be large at the transition from screened to
unscreened regions, leaving a dip in the convergence. This allows us to put
observational constraints on parameters characterizing the general
scalar-tensor modification of gravity. We demonstrate how this occurs in
massive gravity as an example, and discuss its observational signatures in
cluster lensing.


title:
Convergence of European Lookback Options with Floating Strike in the
  Binomial Model

abstract:
  In this article we study the convergence of a European lookback option with
floating strike evaluated with the binomial model of Cox-Ross-Rubinstein to its
evaluation with the Black-Scholes model. We do the same for its delta. We
confirm that these convergences are of order 1/Sqrt(n). For this, we use the
binomial model of Cheuk-Vorst which allows us to write the price of the option
using a double sum. Based on an improvement of a lemma of Lin-Palmer, we are
able to give the precise value of the term in 1/Sqrt(n) in the expansion of the
error; we also obtain the value of the term in 1/n if the risk free interest
rate is non zero. This modelisation will also allow us to determine the first
term in the expansion of the delta.


title:
Escaping particle fluxes in the atmospheres of close-in exoplanets. ii.
  reduced mass loss rates and anisotropic winds

abstract:
  We constructed a multi-fluid two-dimensional hydrodynamic model with detailed
radiative transfer to depict the escape of particles. We found that the tidal
forces supply significant accelerations and result in anisotropic winds. An
important effect of the tidal forces is that it severely depresses the outflow
of particles near the polar regions. As a consequence, most particles escape
the surface of the planet from the regions of low-latitude. Comparing the tidal
and non-tidal locking cases, we found that their optical depths are very
different so that the flows also emerge with a different pattern. In the case
of the non-tidal locking, the radial velocities at the base of the wind are
higher than the meridional velocities. However, in the case of tidal locking,
the meridional velocities dominate the flow at the base of the wind, and they
can transfer effectively mass and energy from the day sides to the night sides.
Further, we also found that the differences of the winds show middle extent at
large radii. It expresses that the structure of the wind at the base can be
changed by the two-dimensional radiative transfer due to large optical depths,
but the extent is reduced with an increase in radius. Because the escape is
depressed in the polar regions, the mass loss rate predicted by the non-tidal
locking model, in the order of magnitude of $10^{10}$ g s$^{-1}$, is a factor
of 2 lower than that predicted by one-dimensional hydrodynamic model. The
results of tidal locking show that the mass loss rate is decreased a order of
magnitude, only 4.3$\times$ $10^{9}$ g s$^{-1}$, due to large optical depths on
the night side. We also found that the distributions of hydrogen atoms show
clear variations from the day side to night side, thus the origin of the excess
absorption in Ly $\alpha$ should be reexamined by using multi-dimensional
hydrodynamic models.


title: Modeling DNA Dynamics by Path Integrals

abstract:
  Complementary strands in DNA double helix show temporary fluctuational
openings which are essential to biological functions such as transcription and
replication of the genetic information. Such large amplitude fluctuations,
known as the breathing of DNA, are generally localized and, microscopically,
are due to the breaking of the hydrogen bonds linking the base pairs
(\emph{bps}). I apply imaginary time path integral techniques to a mesoscopic
Hamiltonian which accounts for the helicoidal geometry of a short circular DNA
molecule. The \emph{bps} displacements with respect to the ground state are
interpreted as time dependent paths whose amplitudes are consistent with the
model potential for the hydrogen bonds. The portion of the paths configuration
space contributing to the partition function is determined by selecting the
ensemble of paths which fulfill the second law of thermodynamics. Computations
of the thermodynamics in the denaturation range show the energetic advantage
for the equilibrium helicoidal geometry peculiar of B-DNA. I discuss the
interplay between twisting of the double helix and anharmonic stacking along
the molecule backbone suggesting an interesting relation between intrinsic
nonlinear character of the microscopic interactions and molecular topology.


title:
A sampling theorem on shift-invariant spaces associated with the
  fractional Fourier transform domain

abstract:
  As a generalization of the Fourier transform, the fractional Fourier
transform was introduced and has been further investigated both in theory and
in applications of signal processing. We obtain a sampling theorem on
shift-invariant spaces associated with the fractional Fourier transform domain.
The resulting sampling theorem extends not only the classical
Whittaker-Shannon-Kotelnikov sampling theorem associated with the fractional
Fourier transform domain, but also extends the prior sampling theorems on
shift-invariant spaces.


title: Classification of involutions on Enriques surfaces

abstract:
  We present the classification of involutions on Enriques surfaces. We
classify those into 18 types with the help of the lattice theory due to
Nikulin. We also give all examples of the classification.


title: A Primer on Surface Plasmon-Polaritons in Graphene

abstract:
  We discuss the properties of surface plasmons-polaritons in graphene and
describe three possible ways of coupling electromagnetic radiation in the
terahertz (THz) spectral range to this type of surface waves. (i) the
attenuated total reflection (ATR) method using a prism in the Otto
configuration, (ii) graphene micro-ribbon arrays or monolayers with modulated
conductivity, (iii) a metal stripe on top of the graphene layer, and (iv)
graphene-based gratings. The text provides a number of original results along
with their detailed derivation and discussion.


title: On Search Engine Evaluation Metrics

abstract:
  The search engine evaluation research has quite a lot metrics available to
it. Only recently, the question of the significance of individual metrics
started being raised, as these metrics' correlations to real-world user
experiences or performance have generally not been well-studied. The first part
of this thesis provides an overview of previous literature on the evaluation of
search engine evaluation metrics themselves, as well as critiques of and
comments on individual studies and approaches. The second part introduces a
meta-evaluation metric, the Preference Identification Ratio (PIR), that
quantifies the capacity of an evaluation metric to capture users' preferences.
Also, a framework for simultaneously evaluating many metrics while varying
their parameters and evaluation standards is introduced. Both PIR and the
meta-evaluation framework are tested in a study which shows some interesting
preliminary results; in particular, the unquestioning adherence to metrics or
their ad hoc parameters seems to be disadvantageous. Instead, evaluation
methods should themselves be rigorously evaluated with regard to goals set for
a particular study.


title:
Skyrmions with varying size and helicity in composition-spread
  helimagnetic alloys

abstract:
  The chirality, i.e. left or right handedness, is an important notion in a
broad range of science. In condensed matter, this occurs not only in molecular
or crystal forms but also in magnetic structures. A magnetic skyrmion, a
topologically-stable spin vortex structure, as observed in chiral-lattice
helimagnets is one such example; the spin swirling direction (skyrmion
helicity) should be closely related to the underlying lattice chirality via the
relativistic spin-orbit coupling (SOC). Here, we report on the correlation
between skyrmion helicity and crystal chirality as observed by Lorentz
transmission electron microscopy (TEM) and convergent-beam electron diffraction
(CBED) on the composition-spread alloys of helimagnets Mn1-xFexGe over a broad
range (x = 0.3 - 1.0) of the composition. The skyrmion lattice constant or the
skyrmion size shows non-monotonous variation with the composition x,
accompanying a divergent behavior around x = 0.8, where the correlation between
magnetic helicity and crystal chirality is reversed. The underlying mechanism
is a continuous x-variation of the SOC strength accompanying sign reversal in
the metallic alloys. This may offer a promising way to tune the skyrmion size
and helicity.


title:
Parallelizing Wang-Landau algorithm in the field: the micromagnetic
  ensemble

abstract:
  It is shown in this work how the Wang-Landau algorithm can be parallelized
through the concept of the micromagnetic ensemble, when the Hamiltonian
contains both spin interaction and the external field terms, and thus
energy-magnetization plane is used for characterizing the density of states.
Within this framework random walk is performed on mutually independent
micromagnetic lines, and can thus be paralellized on a computer grid, without
need for shared memory among individual processes. This approach pushes forward
significantly the size of the systems that may be addressed on current computer
hardware (from currently reported $42\times 42$ to at least $256\times 256$ in
the case of two dimensional systems), and should turn out important for diverse
studies where field dependent behavior is essential.


title: Differential Frequency-dependent Delay from the Pulsar Magnetosphere

abstract:
  Some radio pulsars show clear drifting subpulses, in which subpulses are seen
to drift in pulse longitude in a systematic pattern. Here we examine how the
drifting subpulses of PSR B0809+74 evolve with time and observing frequency. We
show that the subpulse period (P3) is constant on timescales of days, months
and years, and between 14-5100 MHz. Despite this, the shapes of the driftbands
change radically with frequency. Previous studies have concluded that, while
the subpulses appear to move through the pulse window approximately linearly at
low frequencies (< 500 MHz), a discrete step of 180 degrees in subpulse phase
is observed at higher frequencies (> 820 MHz) near to the peak of the average
pulse profile. We use LOFAR, GMRT, GBT, WSRT and Effelsberg 100-m data to
explore the frequency-dependence of this phase step. We show that the size of
the subpulse phase step increases gradually, and is observable even at low
frequencies. We attribute the subpulse phase step to the presence of two
separate driftbands, whose relative arrival times vary with frequency - one
driftband arriving 30 pulses earlier at 20 MHz than it does at 1380 MHz, whilst
the other arrives simultaneously at all frequencies. The drifting pattern which
is observed here cannot be explained by either the rotating carousel model or
the surface oscillation model, and could provide new insight into the physical
processes happening within the pulsar magnetosphere.


title: Metrics for measuring distances in configuration spaces

abstract:
  In order to characterize molecular structures we introduce configurational
fingerprint vectors which are counterparts of quantities used experimentally to
identify structures. The Euclidean distance between the configurational
fingerprint vectors satisfies the properties of a metric and can therefore
safely be used to measure dissimilarities between configurations in the high
dimensional configuration space. We show that these metrics correlate well with
the RMSD between two configurations if this RMSD is obtained from a global
minimization over all translations, rotations and permutations of atomic
indices. We introduce a Monte Carlo approach to obtain this global minimum of
the RMSD between configurations.


title: Time and the Algebraic Theory of Moments

abstract:
  We introduce the notion of an extended moment in time, the duron. This is a
region of temporal ambiguity which arises naturally in the nature of process
which we take to be basic. We introduce an algebra of process and show how it
is related to, but different from, the monoidal category introduced by Abramsky
and Coecke. By considering the limit as the duration of the moment approaches
the infinitesimal, we obtain a pair of dynamical equations, one expressed in
terms of a commutator and the other which is expressed in terms of an
anti-commutator. These two coupled real equations are equivalent to the
Schr\"odinger equation and its dual.
  We then construct a bi-algebra, which allows us to make contact with the
thermal quantum field theory introduced by Umezawa. This allows us to link
quantum mechanics with thermodynamics. This approach leads to two types of
time, one is Schr\"odinger time, the other is an irreversible time that can be
associated with a movement between inequivalent vacuum states. Finally we
discuss the relation between our process algebra and the thermodynamic origin
of time.


title: Hensel's Lemma, Backward Dynamics and p-adic Approximations

abstract:
  The problem of backward dynamics over the ring of p-adic integers is studied.
It is shown that Inverse Limit Theory provides the right framework. Backward
iterations of a polynomial with p-adic integer coefficients are constructed by
solving congruences modulo powers of p, which inturn are solved by Hensel's
lifting lemma.


title:
Conditional Gradient Algorithms for Norm-Regularized Smooth Convex
  Optimization

abstract:
  Motivated by some applications in signal processing and machine learning, we
consider two convex optimization problems where, given a cone $K$, a norm
$\|\cdot\|$ and a smooth convex function $f$, we want either 1) to minimize the
norm over the intersection of the cone and a level set of $f$, or 2) to
minimize over the cone the sum of $f$ and a multiple of the norm. We focus on
the case where (a) the dimension of the problem is too large to allow for
interior point algorithms, (b) $\|\cdot\|$ is "too complicated" to allow for
computationally cheap Bregman projections required in the first-order proximal
gradient algorithms. On the other hand, we assume that {it is relatively easy
to minimize linear forms over the intersection of $K$ and the unit
$\|\cdot\|$-ball}. Motivating examples are given by the nuclear norm with $K$
being the entire space of matrices, or the positive semidefinite cone in the
space of symmetric matrices, and the Total Variation norm on the space of 2D
images. We discuss versions of the Conditional Gradient algorithm capable to
handle our problems of interest, provide the related theoretical efficiency
estimates and outline some applications.


title: X-ray binaries powered by massive stellar black holes

abstract:
  The mass of stellar black holes (BHs) is currently thought to be in the 3-20
Msun range, but is highly uncertain: recent observations indicate the existence
of at least one BH with mass >20 Msun. The metallicity of the progenitor star
strongly influences the mass of the remnant, as only metal-poor stars can have
a final mass higher than ~40 Msun, and are expected to directly collapse into
BHs with mass >25 Msun. By means of N-body simulations, we investigate the
formation and evolution of massive stellar BHs (MSBHs, with mass >25 Msun) in
young dense star clusters. We study the effects of MSBHs on the population of
X-ray sources.


title:
Lyman break and UV-selected galaxies at $z \sim 1$ I. Stellar
  populations from ALHAMBRA survey

abstract:
  We take advantage of the exceptional photometric coverage provided by the
combination of GALEX data in the UV and the ALHAMBRA survey in the optical and
near-IR to analyze the physical properties of a sample of 1225 GALEX-selected
Lyman break galaxies (LBGs) at $0.8 \lesssim z \lesssim 1.2$ located in the
COSMOS field. This is the largest sample of LBGs studied at that redshift range
so far. According to a spectral energy distribution (SED) fitting with
synthetic stellar population templates, we find that LBGs at $z \sim 1$ are
mostly young galaxies with a median age of 341 Myr and have intermediate dust
attenuation, $\ < E_s (B-V) \ > \sim 0.20$. Due to their selection criterion,
LBGs at $z \sim 1$ are UV-bright galaxies and have high dust-corrected total
SFR, with a median value of 16.9 $M_\odot {\rm yr}^{-1}$. Their median stellar
mass is $\log{\left(M_*/M_\odot \right)} = 9.74$. We obtain that the
dust-corrected total SFR of LBGs increases with stellar mass and the specific
SFR is lower for more massive galaxies. Only 2% of the galaxies selected
through the Lyman break criterion have an AGN nature. LBGs at $z \sim 1$ are
mostly located over the blue cloud of the color-magnitude diagram of galaxies
at their redshift, with only the oldest and/or the dustiest deviating towards
the green valley and red sequence. Morphologically, 69% of LBGs are disk-like
galaxies, with the fraction of interacting, compact, or irregular systems being
much lower, below 12%. LBGs have a median effective radius of 2.5 kpc and
bigger galaxies have higher total SFR and stellar mass. Comparing to their
high-redshift analogues, we find evidence that LBGs at lower redshifts are
bigger, redder in the UV continuum, and have a major presence of older stellar
populations in their SEDs. However, we do not find significant difference in
the distributions of stellar mass or dust attenuation.


title: Young star cluster evolution and metallicity

abstract:
  Young star clusters (SCs) are the cradle of stars and the site of important
dynamical processes. We present N-body simulations of young SCs including
recipes for metal-dependent stellar evolution and mass loss by stellar winds.
We show that metallicity affects significantly the collapse and post-core
collapse phase, provided that the core collapse timescale is of the same order
of magnitude as the lifetime of massive stars. In particular, the reversal of
core collapse is faster for metal-rich SCs, where stellar winds are stronger.
As a consequence, the half-mass radius of metal-poor SCs expands more than that
of metal-rich SCs.


title: A criterion for compatibility of conformal and projective structures

abstract:
  In a space-time, a conformal structure is defined by the distribution of
light-cones. Geodesics are traced by freely falling particles, and the
collection of all unparameterized geodesics determines the projective structure
of the space-time. The article contains a formulation of the necessary and
sufficient conditions for these structures to be compatible, i.e. to come from
a metric tensor which is then unique up to a constant factor. The theorem
applies to all dimensions and signatures.


title:
Power Allocation and Time-Domain Artificial Noise Design for Wiretap
  OFDM with Discrete Inputs

abstract:
  Optimal power allocation for orthogonal frequency division multiplexing
(OFDM) wiretap channels with Gaussian channel inputs has already been studied
in some previous works from an information theoretical viewpoint. However,
these results are not sufficient for practical system design. One reason is
that discrete channel inputs, such as quadrature amplitude modulation (QAM)
signals, instead of Gaussian channel inputs, are deployed in current practical
wireless systems to maintain moderate peak transmission power and receiver
complexity. In this paper, we investigate the power allocation and artificial
noise design for OFDM wiretap channels with discrete channel inputs. We first
prove that the secrecy rate function for discrete channel inputs is nonconcave
with respect to the transmission power. To resolve the corresponding nonconvex
secrecy rate maximization problem, we develop a low-complexity power allocation
algorithm, which yields a duality gap diminishing in the order of
O(1/\sqrt{N}), where N is the number of subcarriers of OFDM. We then show that
independent frequency-domain artificial noise cannot improve the secrecy rate
of single-antenna wiretap channels. Towards this end, we propose a novel
time-domain artificial noise design which exploits temporal degrees of freedom
provided by the cyclic prefix of OFDM systems {to jam the eavesdropper and
boost the secrecy rate even with a single antenna at the transmitter}.
Numerical results are provided to illustrate the performance of the proposed
design schemes.


title:
The Phase Transition of Matrix Recovery from Gaussian Measurements
  Matches the Minimax MSE of Matrix Denoising

abstract:
  Let $X_0$ be an unknown $M$ by $N$ matrix. In matrix recovery, one takes $n <
MN$ linear measurements $y_1,..., y_n$ of $X_0$, where $y_i = \Tr(a_i^T X_0)$
and each $a_i$ is a $M$ by $N$ matrix. For measurement matrices with Gaussian
i.i.d entries, it known that if $X_0$ is of low rank, it is recoverable from
just a few measurements. A popular approach for matrix recovery is Nuclear Norm
Minimization (NNM). Empirical work reveals a \emph{phase transition} curve,
stated in terms of the undersampling fraction $\delta(n,M,N) = n/(MN)$, rank
fraction $\rho=r/N$ and aspect ratio $\beta=M/N$. Specifically, a curve
$\delta^* = \delta^*(\rho;\beta)$ exists such that, if $\delta >
\delta^*(\rho;\beta)$, NNM typically succeeds, while if $\delta <
\delta^*(\rho;\beta)$, it typically fails. An apparently quite different
problem is matrix denoising in Gaussian noise, where an unknown $M$ by $N$
matrix $X_0$ is to be estimated based on direct noisy measurements $Y = X_0 +
Z$, where the matrix $Z$ has iid Gaussian entries. It has been empirically
observed that, if $X_0$ has low rank, it may be recovered quite accurately from
the noisy measurement $Y$. A popular matrix denoising scheme solves the
unconstrained optimization problem $\text{min} \| Y - X \|_F^2/2 + \lambda
\|X\|_* $. When optimally tuned, this scheme achieves the asymptotic minimax
MSE $\cM(\rho) = \lim_{N \goto \infty} \inf_\lambda \sup_{\rank(X) \leq \rho
\cdot N} MSE(X,\hat{X}_\lambda)$. We report extensive experiments showing that
the phase transition $\delta^*(\rho)$ in the first problem coincides with the
minimax risk curve $\cM(\rho)$ in the second problem, for {\em any} rank
fraction $0 < \rho < 1$.


title:
Volume Fluctuation and Autocorrelation Effects in the Moment Analysis of
  Net-proton Multiplicity Distributions in Heavy-Ion Collisions

abstract:
  Moments (Variance ($\sigma^2$), Skewness($S$), Kurtosis($\kappa$)) of
multiplicity distributions of conserved quantities, such as
net-baryon,net-charge and net-strangeness, are predicted to be sensitive to the
correlation length of the system and connected to the thermodynamic
susceptibilities computed in Lattice QCD and Hadron Resonance Gas (HRG) model.
In this paper, we present several measurement artifacts that could lead to
volume fluctuation and auto-correlation effects in the moment analysis of
net-proton multiplicity distributions in heavy-ion collisions using the UrQMD
model. We discuss methods to overcome these artifacts so that the extracted
moments could be used to obtain physical conclusions. In addition we present
methods to properly estimate the statistical errors in moment analysis.


title: Measurements of the Secondary Electron Emission of Some Insulators

abstract:
  Charging up the surface of an insulator after beam impact can lead either to
reverse sign of field between the surface and collector of electrons for case
of thick sample or appearance of very high internal field for thin films. Both
situations discard correct measurements of secondary electron emission (SEE)
and can be avoided via reducing the beam dose. The single pulse method with
pulse duration of order of tens microseconds has been used. The beam pulsing
was carried out by means of an analog switch introduced in deflection plate
circuit which toggles its output between "beam on" and "beam off" voltages
depending on level of a digital pulse. The error in measuring the beam current
for insulators with high value of SEE was significantly reduced due to the use
for this purpose a titanium sample having low value of the SEE with DC method
applied. Results obtained for some not coated insulators show considerable
increase of the SEE after baking out at 3500C what could be explained by the
change of work function. Titanium coatings on alumina exhibit results close to
the ones for pure titanium and could be considered as an effective
antimultipactor coating.


title: Measurements of the Secondary Electron Emission from Rare Gases at 4.2K

abstract:
  Dependence of the secondary electron yield (SEY) from the primary beam
incident energy and the coverage has been measured for neon, argon, krypton and
xenon condensed on a target at 4.2K. The beam energy ranged between 100 eV and
3 keV, the maximal applied coverage have made up 12000, 4700, 2500 and 1400
monolayers correspondingly for neon, argon, krypton and xenon. The SEY results
for these coverages can be considered as belonging only to investigated gases
without influence of the target material. The SEY dependencies versus the
primary beam energy for all gases comprise only an ascending part and
therefore, the maximal measured SEY values have been obtained for the beam
energy of 3keV and have made up 62, 73, 60.5 and 52 for neon, argon, krypton
and xenon correspondingly. Values of the first cross-over have made up 21 eV
for neon, 14 eV for argon, 12.5 eV for krypton and 10.5 eV for xenon. An
internal field appearing across a film due to the beam impact can considerably
affect the SEY measurements that demanded the beam current to be reduced till
9.0E-10A. Duration of the beam impact varied between 500 \mu sec and 250 \mu
sec. It was found that reliable SEY measurements can also be taken on a charged
surface if the charge was acquired due to beam impact with electrons of higher
energy. All SEY measurements for once applied coverage have been carried out
for whole range of incident energies from 3 keV down to 100 eV without renewing
the film. Developing of pores inside of a deposited film can significantly
increase the SEY as it was observed during warming up the target.


title: On product type actions of G_q

abstract:
  We will study a faithful product type action of G_q that is the q-deformation
of a connected semisimple compact Lie group G, and prove that such an action is
induced from a minimal action of the maximal torus T of G_q. This enables us to
classify product type actions of SU_q(2) up to conjugacy. We also compute the
intrinsic group of G_{q,\Omega}, the 2-cocycle deformation of G_q that is
naturally associated with the quantum flag manifold T\backslash G_q.


title:
Constraints on NonCommutative Spectral Action from Gravity Probe B and
  Torsion Balance Experiments

abstract:
  Noncommutative spectral geometry offers a purely geometric explanation for
the standard model of strong and electroweak interactions, including a
geometric explanation for the origin of the Higgs field. Within this framework,
the gravitational, the electroweak and the strong forces are all described as
purely gravitational forces on a unified noncommutative space-time. In this
study, we infer a constraint on one of the three free parameters of the model,
namely the one characterising the coupling constants at unification, by
linearising the field equations in the limit of weak gravitational fields
generated by a rotating gravitational source, and by making use of recent
experimental data. In particular, using data obtained by Gravity Probe B, we
set a lower bound on the Weyl term appearing in the noncommutative spectral
action, namely $\beta \gtrsim 10^{-6}$m$^{-1}$. This constraint becomes
stronger once we use results from torsion balance experiments, leading to
$\beta \gtrsim 10^{4}$m$^{-1}$. The latter is much stronger than any constraint
imposed so far to curvature squared terms.


title: The Heston Riemannian distance function

abstract:
  The Heston model is a popular stock price model with stochastic volatility
that has found numerous applications in practice. In the present paper, we
study the Riemannian distance function associated with the Heston model and
obtain explicit formulas for this function using geometrical and analytical
methods. Geometrical approach is based on the study of the Heston geodesics,
while the analytical approach exploits the links between the Heston distance
function and the sub-Riemannian distance function in the Grushin plane. For the
Grushin plane, we establish an explicit formula for the Legendre-Fenchel
transform of the limiting cumulant generating function and prove a partial
large deviation principle that is true only inside a special set.


title: On-line list coloring of matroids

abstract:
  A coloring of a matroid is proper if elements of the same color form an
independent set. A theorem of Seymour asserts that a k-colorable matroid is
also colorable from any lists of size k. In this note we generalize this
theorem to the on-line setting. We prove that a coloring of a matroid from
lists of size k is possible even if appearances of colors in the lists are
recovered color by color by an adversary, while our job is to assign a color
immediately after it is recovered. We also prove a more general weighted
version of our result with lists of varying sizes. In consequence we get a
simple necessary and sufficient condition for matroid list colorability in
general case. The main tool we use is the multiple basis exchange property,
which we give a simple proof.


title:
Robust Low-Rank LCMV Beamforming Algorithms Based on Joint Iterative
  Optimization Strategies

abstract:
  This chapter presents reduced-rank linearly constrained minimum variance
(LCMV) algorithms based on the concept of joint iterative optimization of
parameters. The proposed reduced-rank scheme is based on a constrained robust
joint iterative optimization (RJIO) of parameters according to the minimum
variance criterion. The robust optimization procedure adjusts the parameters of
a rank-reduction matrix, a reduced-rank beamformer and the diagonal loading in
an alternating manner. LCMV expressions are developed for the design of the
rank-reduction matrix and the reduced-rank beamformer. Stochastic gradient and
recursive least-squares adaptive algorithms are then devised for an efficient
implementation of the RJIO robust beamforming technique. Simulations for a
application in the presence of uncertainties show that the RJIO scheme and
algorithms outperform in convergence and tracking performances existing
algorithms while requiring a comparable complexity.


title: On the extension complexity of combinatorial polytopes

abstract:
  In this paper we extend recent results of Fiorini et al. on the extension
complexity of the cut polytope and related polyhedra. We first describe a
lifting argument to show exponential extension complexity for a number of
NP-complete problems including subset-sum and three dimensional matching. We
then obtain a relationship between the extension complexity of the cut polytope
of a graph and that of its graph minors. Using this we are able to show
exponential extension complexity for the cut polytope of a large number of
graphs, including those used in quantum information and suspensions of cubic
planar graphs.


title: Reconstructing curves from lengths of projections onto lines

abstract:
  In this paper, we address the problem of reconstructing a curve from the
lengths of its projections onto lines. We first note that the curve itself is
not uniquely determined from these measurements. However, we find that a curve
determines a measure on projective space which, as a function on Borel subsets
of projective space, returns the length of curve parallel to elements of the
set. We show that the projected length data can be expressed as the cosine
transform of this measure on projective space. The cosine transform is a well
studied integral transform on the sphere which is known to be injective. We
conclude that the measured length data uniquely determines the associated
measure on projective space. We then characterize the class of curves that
produce a common measure by starting with the case of piecewise linear curves
and then passing to limits to obtain results for more general curves.


title: The rational homology of real toric manifolds

abstract:
  This is an extended abstract for a talk given at the mini-workshop
"Cohomology rings and fundamental groups of hyperplane arrangements, wonderful
compactifications, and real toric varieties", held in Oberwolfach, September
30-October 6, 2012. We describe a formula (obtained in joint work with Alvise
Trevisan) for computing the Betti numbers of real toric manifolds, based on a
study of cohomology with coefficients in rank one local systems for various
polyhedral products. Applying this formula, we recover Henderson's computation
of the Betti numbers of real Hessenberg varieties. We conclude with a
discussion of the formality question in this context.


title: Adaptive Space-Time Beamforming in Radar Systems

abstract:
  The goal of this chapter is to review the recent work and advances in the
area of space-time beamforming algorithms and their application to radar
systems. These systems include phased-array \cite{melvin} and multi-input
multi-output (MIMO) radar systems \cite{haimo_08}, mono-static and bi-static
radar systems and other configurations \cite{melvin}. Furthermore, this chapter
also describes in detail some of the most successful space-time beamforming
algorithms that exploit low-rank and sparsity properties as well as the use of
prior-knowledge to improve the performance of STAP algorithms in radar systems.


title:
Quark Transverse Momentum Distributions inside a nucleon : a Light-Front
  Hamiltonian Dynamics study

abstract:
  Through an impulse approximation analysis of single spin Sivers and Collins
asymmetries in the Bjorken limit, the possibility to extract the quark
transverse-momentum distributions in the neutron from semi-inclusive deep
inelastic electron scattering off polarized 3He is illustrated. The analysis is
generalized to finite momentum transfers in a light-front Poincare' covariant
framework, defining the light-front spin-dependent spectral function of a J=1/2
system. The definition of the light-front spin-dependent spectral function for
constituent quarks in the nucleon allows us to show that, within the
light-front dynamics, only three of the six leading twist T-even
transverse-momentum distributions are independent.


title: Non parametric finite translation mixtures with dependent regime

abstract:
  In this paper we consider non parametric finite translation mixtures. We
prove that all the parameters of the model are identifiable as soon as the
matrix that defines the joint distribution of two consecutive latent variables
is non singular and the translation parameters are distinct. Under this
assumption, we provide a consistent estimator of the number of populations, of
the translation parameters and of the distribution of two consecutive latent
variables, which we prove to be asymptotically normally distributed under mild
dependency assumptions. We propose a non parametric estimator of the unknown
translated density. In case the latent variables form a Markov chain (Hidden
Markov models), we prove an oracle inequality leading to the fact that this
estimator is minimax adaptive over regularity classes of densities.


title:
Remark on the off-diagonal expansion of the Bergman kernel on compact
  K\"ahler manifolds

abstract:
  In this short note, we compare our previous works on the off-diagonal
expansion of the Bergman kernel and the recent preprint of Lu-Shiffman
(arxiv.1301.2166). In particular, we note that the vanishing of the coefficient
of p^{-1/2} is implicitly contained in Dai-Liu-Ma's work (J. Differential Geom.
72 (2006), no. 1, 1-41) and was explicitly stated in our book (Holomorphic
Morse inequalities and Bergman kernels, Progress in Math., vol. 254,
Birkh\"auser, 2007).


title: Provable Advantage for Quantum Strategies in Random Symmetric XOR Games

abstract:
  Non-local games are widely studied as a model to investigate the properties
of quantum mechanics as opposed to classical mechanics. In this paper, we
consider a subset of non-local games: symmetric XOR games of $n$ players with
0-1 valued questions. For this class of games, each player receives an input
bit and responds with an output bit without communicating to the other players.
The winning condition only depends on XOR of output bits and is constant w.r.t.
permutation of players.
  We prove that for almost any $n$-player symmetric XOR game the entangled
value of the game is $\Theta (\frac{\sqrt{\ln{n}}}{n^{1/4}})$ adapting an old
result by Salem and Zygmund on the asymptotics of random trigonometric
polynomials. Consequently, we show that the classical-quantum gap is $\Theta
(\sqrt{\ln{n}})$ for almost any symmetric XOR game.


title:
The relationship between the neutral hydrogen and dark mass in the
  galaxies

abstract:
  Starting from Bosma' (1981) paper, it was demonstrated by different authors
that the observed shape of rotation curves of many spiral galaxies can be
explained if to assume that the radial density distribution of the dark matter
is correlated with the distribution of $HI$: the column densities of the dark
matter and $HI$ are proportional. We show that this correlation is obviously to
be an artifact and can be explained by assuming that the gas surface density is
approximately equal or in general proportional to the critical density for the
local gravitational stability of gaseous layer.


title: Dual subgradient algorithms for large-scale nonsmooth learning problems

abstract:
  "Classical" First Order (FO) algorithms of convex optimization, such as
Mirror Descent algorithm or Nesterov's optimal algorithm of smooth convex
optimization, are well known to have optimal (theoretical) complexity estimates
which do not depend on the problem dimension. However, to attain the
optimality, the domain of the problem should admit a "good proximal setup". The
latter essentially means that 1) the problem domain should satisfy certain
geometric conditions of "favorable geometry", and 2) the practical use of these
methods is conditioned by our ability to compute at a moderate cost {\em
proximal transformation} at each iteration. More often than not these two
conditions are satisfied in optimization problems arising in computational
learning, what explains why proximal type FO methods recently became methods of
choice when solving various learning problems. Yet, they meet their limits in
several important problems such as multi-task learning with large number of
tasks, where the problem domain does not exhibit favorable geometry, and
learning and matrix completion problems with nuclear norm constraint, when the
numerical cost of computing proximal transformation becomes prohibitive in
large-scale problems. We propose a novel approach to solving nonsmooth
optimization problems arising in learning applications where Fenchel-type
representation of the objective function is available. The approach is based on
applying FO algorithms to the dual problem and using the {\em accuracy
certificates} supplied by the method to recover the primal solution. While
suboptimal in terms of accuracy guaranties, the proposed approach does not rely
upon "good proximal setup" for the primal problem but requires the problem
domain to admit a Linear Optimization oracle -- the ability to efficiently
maximize a linear form on the domain of the primal problem.


title:
A characterization of varieties whose universal cover is a bounded
  symmetric domain without ball factors

abstract:
  We give two characterizations of varieties whose universal cover is a bounded
symmetric domain without ball factors in terms of the existence of a
holomorphic endomorphism \s of the tensor product T\otimes T' of the tangent
bundle T with the cotangent bundle T'. To such a curvature type tensor \s one
associates the first Mok characteristic cone S, obtained by projecting on T the
intersection of ker (\s) with the space of rank 1 tensors. The simpler
characterization requires that the projective scheme associated to S be a
finite union of projective varieties of given dimensions and codimensions in
their linear spans which must be skew and generate.


title: Resistive MHD model for cylindrical plasma expansion in a magnetic field

abstract:
  The study of hot plasma expansion in a magnetic field is of interest for many
laboratory and astrophysical applications. In this paper, an exactly solvable
analytical model is proposed for an expanding resistive plasma in an external
magnetic field in the regime in which the magnetic field does not perturb the
plasma motion. The model is based on a class of exact solutions for the purely
radial expansion of the plasma in the absence of a magnetic field. This
approximation permits the reduction of the electromagnetic problem to
consideration of a diffusion equation for the magnetic field. Explicit
solutions are derived for a resistive cylindrical plasma expanding into a
uniform ambient magnetic field. Some numerical examples related to the
laser-produced plasma experiments are presented.


title: A new population of ultra-long duration gamma-ray bursts

abstract:
  We present comprehensive multiwavelength observations of three gamma-ray
bursts (GRBs) with durations of several thousand seconds. We demonstrate that
these events are extragalactic transients; in particular we resolve the
long-standing conundrum of the distance of GRB 101225A (the "Christmas-day
burst"), finding it to have a redshift z=0.847, and showing that two apparently
similar events (GRB 111209A and GRB 121027A) lie at z=0.677 and z=1.773
respectively. The systems show extremely unusual X-ray and optical lightcurves,
very different from classical GRBs, with long lasting highly variable X-ray
emission and optical light curves that exhibit little correlation with the
behaviour seen in the X-ray. Their host galaxies are faint, compact, and highly
star forming dwarf galaxies, typical of "blue compact galaxies". We propose
that these bursts are the prototypes of a hitherto largely unrecognized
population of ultra-long GRBs, that while observationally difficult to detect
may be astrophysically relatively common. The long durations may naturally be
explained by the engine driven explosions of stars of much larger radii than
normally considered for GRB progenitors which are thought to have compact
Wolf-Rayet progenitor stars. However, we cannot unambiguously identify
supernova signatures within their light curves or spectra. We also consider the
alternative possibility that they arise from the tidal disruption of stars by
supermassive black holes.


title:
Synthesis and properties of charge-ordered thallium halide perovskites,
  CsTl1+0.5Tl3+0.5X3 (X = F, Cl)- theoretical precursors for superconductivity?

abstract:
  Recently CsTlCl3 and CsTlF3 perovskites were theoretically predicted to be
potential superconductors if they are optimally doped. The synthesis of these
two compounds, together with a complete characterization of the samples are
reported. CsTlCl3 is obtained as orange crystals in two different polymorphs: a
tetragonal (I4/m) and a cubic (Fm-3m) phase. CsTlF3 is formed as a light brown
powder, also as a double cubic perovskite (Fm-3m). In all three CsTlX3 phases
Tl1+ and Tl3+ were located in two different crystallographic positions that
accommodate their different bond lengths. In CsTlCl3 some Tl vacancies are
found in the Tl1+ position. The charge ordering between Tl1+ and Tl3+ was
confirmed by x-ray absorption and Raman spectroscopy. The Raman spectroscopy of
CsTlCl3 under high pressure (58 GPa) did not indicate any phase transition to a
possible single Tl2+ state. However, the highly insulating material becomes
less resistive with increasing high pressure, while undergoing a change in the
optical properties, from transparent to deeply opaque red, indicative of a
decrease of the band gap. The theoretical design and experimental validation of
the existence of CsTlF3 and CsTlCl3 cubic perovskites is the necessary first
step in confirming the theoretical prediction of superconductivity in these
materials.


title: A Short Proof of Klee's Theorem

abstract:
  In 1959, Klee proved that a convex body $K$ is a polyhedron if and only if
all of its projections are polygons. In this paper, a new proof of this theorem
is given for convex bodies in $\mathbb{R}^3$.


title: Generalized hybrid metric-Palatini gravity

abstract:
  We introduce a new approach to modified gravity which generalizes the
recently proposed hybrid metric-Palatini gravity. The gravitational action is
taken to depend on a general function of both the metric and Palatini curvature
scalars. The dynamical equivalence with a non-minimally coupled bi-scalar field
gravitational theory is proved. The evolution of cosmological solutions is
studied using dynamical systems techniques.


title: Charged tori in spherical gravitational and dipolar magnetic fields

abstract:
  A Newtonian model of non-conductive, charged, perfect fluid tori orbiting in
combined spherical gravitational and dipolar magnetic fields is presented and
stationary, axisymmetric toroidal structures are analyzed. Matter in such tori
exhibits a purely circulatory motion and the resulting convection carries
charges into permanent rotation around the symmetry axis. As a main result, we
demonstrate the possible existence of off-equatorial charged tori and
equatorial tori with cusps enabling outflows of matter from the torus also in
the Newtonian regime. These phenomena represent qualitatively a new consequence
of the interplay between gravity and electromagnetism. From an astrophysical
point of view, our investigation can provide insight into processes that
determine the vertical structure of dusty tori surrounding accretion disks.


title: Asymptotic normality and greatest common divisors

abstract:
  We report on some statistical regularity properties of greatest common
divisors: for large random samples of integers, the number of coprime pairs and
the average of the gcd's of those pairs are approximately normal, while the
maximum of those gcd's (appropriately normalized) follows approximately a
Fr\'echet distribution approximately. We also consider $r$-tuples instead of
pairs, and moments other than the average.


title: A Real Nullstellensatz for Free Modules

abstract:
  Let $A$ be the algebra of all $n \times n$ matrices with entries from
$\RR[x_1,\ldots,x_d]$ and let $G_1,\ldots,G_m,F \in A$. We will show that
$F(a)v=0$ for every $a \in \RR^d$ and $v \in \RR^n$ such that $G_i(a)v=0$ for
all $i$ if and only if $F$ belongs to the smallest real left ideal of $A$ which
contains $G_1,\ldots,G_m$. Here a left ideal $J$ of $A$ is real if for every
$H_1,\ldots,H_k \in A$ such that $H_1^T H_1+\ldots+H_k^T H_k \in J+J^T$ we have
that $H_1,\ldots,H_k \in J$. We call this result the one-sided Real
Nullstellensatz for matrix polynomials. We first prove by induction on $n$ that
it holds when $G_1,\ldots,G_m,F$ have zeros everywhere except in the first row.
This auxiliary result can be formulated as a Real Nullstellensatz for the free
module $\RR[x_1,\ldots,x_d]^n$.


title:
Binary Quadratic forms and the Fourier coefficients of certain weight 1
  eta-quotients

abstract:
  We state and prove an identity which represents the most general eta-products
of weight 1 by binary quadratic forms. We discuss the utility of binary
quadratic forms in finding a multiplicative completion for certain
eta-quotients. We then derive explicit formulas for the Fourier coefficients of
certain eta-quotients of weight 1 and level 47, 71, 135,648 1024, and 1872.


title:
Nambu sum rule in the NJL models: from superfluidity to top quark
  condensation

abstract:
  It may appear that the recently found resonance at 125 GeV is not the only
Higgs boson. We point out the possibility that the Higgs bosons appear in
models of top-quark condensation, where the masses of the bosonic excitations
are related to the top quark mass by the sum rule similar to the Nambu sum rule
of the NJL models \cite{Nambu}. This rule was originally considered by Nambu
for superfluid $^3$He-B and for the BCS model of superconductivity. It relates
the two masses of bosonic excitations existing in each channel of Cooper
pairing to the fermion mass. An example of the Nambu partners is provided by
the amplitude and the phase modes in the BCS model describing Cooper pairing in
the s-wave channel. This sum rule suggests the existence of the Nambu partners
for the 125 GeV Higgs boson. Their masses can be predicted by the Nambu sum
rule under certain circumstances. For example, if there are only two states in
the given channel, the mass of the Nambu partner is $\sim$ 325 GeV. They
together satisfy the Nambu sum rule $M_1^2 + M_2^2 = 4 M_t^2$, where $M_t \sim
$174 GeV is the mass of the top quark. If there are two doubly degenerated
states, then the second mass is $\sim$ 210 GeV. In this case the Nambu sum rule
is $2 M_1^2 + 2 M_2^2 = 4 M_t^2$. In addition, the properties of the Higgs
modes in superfluid $^3$He-A, where the symmetry breaking is similar to that of
the Standard Model of particle physics, suggest the existence of two
electrically charged Higgs particles with masses around 245 GeV, which together
also obey the Nambu sum rule $M_+^2 + M_-^2 = 4 M_t^2$.


title: Supersymmetric probability distributions

abstract:
  We use anticommuting variables to study probability distributions of random
variables, that are solutions of Langevin's equation. We show that the
probability density always enjoys "worldpoint supersymmetry". The partition
function, however, may not. We find that the domain of integration can acquire
a boundary, that implies that the auxiliary field has a non-zero expectation
value, signalling spontaneous supersymmetry breaking. This is due to the
presence of "fermionic" zeromodes, whose contribution cannot be cancelled by a
surface term. This we prove by an explicit calculation of the regularized
partition function, as well as by computing the moments of the auxiliary field
and checking whether they satisfy the identities implied by Wick's theorem.
Nevertheless, supersymmetry manifests itself in the identities that are
satisfied by the moments of the scalar, whose expressions we can calculate,for
all values of the coupling constant. We also provide some quantitative
estimates concerning the visibility of supersymmetry breaking effects in the
identities for the moments and remark that the shape of the distribution of the
auxiliary field can influence quite strongly how easy it would be to mask them,
since the expectation value of the auxiliary field doesn't coincide with its
typical value.


title: A stochastic model for the evolution of the influenza virus

abstract:
  Consider a birth and death chain to model the number of types of a given
virus. Each type gives birth to a new type at rate $\lambda$ and dies at rate
1. Each type is also assigned a fitness. When a death occurs either the least
fit type dies (with probability $1-r$) or we kill a type at random (with
probability $r$). We show that this random killing has a large effect (for any
$r>0$) on the behavior of the model when $\lambda<1$. The behavior of the model
with $r>0$ and $\lambda<1$ is consistent with features of the phylogenetic tree
of influenza.


title:
A multilayer multiconfigurational time-dependent Hartree study of
  vibrationally coupled electron transport using the scattering state
  representation

abstract:
  The multilayer multiconfiguration time-dependent Hartree method is employed
to study vibrationally coupled charge transport in models of single molecule
junctions. To increase the efficiency of the simulation method, a
representation of the Hamiltonian in terms of the scattering states of the
underlying electronic Hamiltonian is used. It is found that with an appropriate
choice of the scattering states the artificial electron correlation present in
the original representation of the model is greatly reduced. This allows
efficient simulation of the steady-state currents in a wide physical parameter
space, which is demonstrated by several numerical examples.


title:
The galaxy cluster concentration-mass relation in dark energy
  cosmologies

abstract:
  We use numerical simulations of different dark energy cosmologies to
investigate the concentration-mass (c-M) relation in galaxy clusters. In
particular, we consider a reference Lambda cold dark matter (LambdaCDM) model,
two models with dynamical dark energy, viewed as a quintessence scalar field
[using a Ratra and Peebles (RP) and a supergravity (SUGRA) potential form], and
two extended quintessence models, one with positive and one with negative
coupling (EQp and EQn respectively), where the quintessence scalar field
interacts non-minimally with gravity (scalar-tensor theories). All the models
are normalized in order to match CMB data from Wilkinson Microwave Anisotropy
Probe 3 (WMAP3). [Abridged] We consider both the complete catalog of clusters
and groups and a subsample of relaxed objects. The c-M relation of our
reference LambdaCDM model is in good agreement with the results in literature,
and relaxed objects have a higher normalization and a shallower slope with
respect to the complete sample. For the different dark energy models, we find
that for LambdaCDM, RP and SUGRA the normalization of the c-M relation is
linked to the growth factor D+ and the power spectrum normalization sigma8,
with models having a higher value of sigma8 D+ having also a higher
normalization. This simple scheme is no longer valid for EQp and EQn because in
these models it is present a time dependent effective gravitational
interaction, whose redshift evolution depends on the sign of the coupling. This
leads to a decrease (increase) of the expected normalization in the EQp (EQn)
model. This result shows a direct manifestation of the coupling between gravity
and the quintessence scalar field characterizing EQ models that cannot be seen
at the background level but can be investigated in the non-linear regime.


title: Effects of electron-electron interactions in suspended graphene

abstract:
  We investigate the problem of dynamical gap generation in suspended graphene
by long-range Coulomb interactions at strong coupling with Dyson-Schwinger
equations. Including renormalization effects on the Fermi velocity we obtain a
critical coupling constant $\alpha_c=2.85$ which is larger than the bare
coupling $\alpha_0=2.19$ of suspended graphene. This suggests that at low
energies the running of the Fermi velocity prevents the emergence of a gapped
phase. Our calculation is thus in agreement with the experimental observation
that suspended graphene remains in the semimetal phase.


title:
Measurement of orbital asymmetry and strain in Co90Fe10/Ni multilayers
  and alloys: Origins of perpendicular anisotropy

abstract:
  We use broadband ferromagnetic resonance spectroscopy and x-ray diffraction
to investigate the fundamental origin of perpendicular anisotropy in
Co90Fe10/Ni multilayers. By careful evaluation of the spectroscopic g-factor,
we determine the orbital moment along the out-of-plane and in-plane directions.
For the multilayers, we find a direct relationship between the orbital moment
asymmetry and the perpendicular anisotropy, consistent with the theory of Bruno
[P.Bruno, Phys. Rev. B, 39, 865 (1989)]. A systematic x-ray diffraction study
revealed the presence of a trigonal strain as high as 0.7 % in some samples.
However, we found no direct correlation between the strain and the anisotropy,
indicating that the anisotropy is not dominated by magnetoelastic effects. In
order to further study the interface structure on the anisotropy, we prepared a
set of equivalent alloy samples. The strain in the alloy samples was comparable
to that of the multilayer samples; however the orbital moment asymmetry in the
alloy samples showed a very different trend allowing us to isolate the effect
of the interfaces in the multilayers.


title: Broadband optical isolator in fibre optics

abstract:
  We propose a broadband optical diode, which is composed of one achromatic
reciprocal quarter-wave plate and one non-reciprocal quarter-wave plate, both
placed between two crossed polarizers. The presented design of achromatic wave
plates relies on an adiabatic evolution of the Stokes vector, thus, the scheme
is robust and efficient. The possible simple implementation using fiber optics
is suggested.


title:
LISA-2020: An Intermediate Scale Space Gravitational Wave Observatory
  for This Decade

abstract:
  Over the last three decades, an exceptionally good science case has been made
for pursuing gravitational wave (GW) astronomy. This has engendered a worldwide
effort to detect the extremely weak signals generated by expected sources. With
the next round of upgrades the ground based instruments are likely to make the
first detections of the sources, and a new era of astronomy will begin,
possibly as early as 2017. Inconveniently, due to seismic noise and baseline
length issues, the low frequency (<10Hz) part of the spectrum, where the most
interesting events are expected, will not be accessible. The space-based
detector, LISA1, was conceived to fill this gap extending the observational
capability to about 10-4 Hz. Due to mission cost growth and severe budget
constraints, a flight prior to 2030 now seems very unlikely. This paper
examines the case for a scaled down mission that is comparable in cost and
duration to medium scale astrophysics missions such as the 1978 ($630M)
Einstein (HEAO 2) x-ray Observatory2, the 1989 ($680M) COBE Cosmic Background
Explorer3, and the 1999 ($420M) FUSE Far Ultraviolet Spectroscopic Explorer4.
We find that a mission of this class is possible if the measurement
requirements are somewhat relaxed and a baseline smaller than LISA is used. It
appears that such a mission could be launched by 2020 using a conventional
program development plan, possibly including international collaboration. It
would enable the timely development of this game-changing field of
astrophysics, complementing the expected ground results with observations of
massive black hole collisions. It would also serve as a stepping stone to LISA,
greatly reducing the risk profile of that mission.


title: Low-Density Structures in the Local Universe. II. Nearby Cosmic Voids

abstract:
  We present the results of the search for spherical volumes containing no
galaxies with luminosities brighter than the Magellanic Clouds in the Local
Supercluster and its vicinity. Within a distance of 40 Mpc from us, 89 cosmic
voids were discovered with the diameters of 24 to 12 Mpc, containing no
galaxies with absolute magnitudes brighter than M_K < -18.4. A list of these
voids and the sky distribution maps are given. It was found that 93% of
spherical voids overlap, forming three more extended percolated voids
(hypervoids). The largest of them, HV1, has 56 initial spherical cells and
extends in a horseshoe shape, enveloping the Local Volume and the Virgo
cluster. The Local Void (Tully, 1988) in the Hercules-Aquila region is the
closest part of the HV1. Another hypervoid, HV2, contains 22 spherical voids in
the Eridanus constellation, and the third compact hypervoid (HV3) comprises 6
spherical cells in the Bootes. The total volume of these voids incorporates
about 30% of the Local Universe. Among 2906 dwarf galaxies excluded from the
original sample (n = 10502) in the search for spherical volumes, only 68 are
located in the voids we have discovered. They are characterized by late
morphological types (85% are Ir, Im, BCD, Sm), absolute magnitudes M_B ranging
from -13.0 to -16.7, moderate star formation rates (log SSFR ~ -10
M_sun/(yr*L_sun) and gas reserves per luminosity unit twice to three times
larger than in the other dwarf galaxies located in normal environments. The
dwarf population of the voids shows a certain tendency to sit shallow near the
surfaces of cosmic voids.


title: Extendability of continuous maps is undecidable

abstract:
  We consider two basic problems of algebraic topology, the extension problem
and the computation of higher homotopy groups, from the point of view of
computability and computational complexity. The extension problem is the
following: Given topological spaces X and Y, a subspace A\subseteq X, and a
(continuous) map f:A->Y, decide whether f can be extended to a continuous map
\bar{f}:X->Y. All spaces are given as finite simplicial complexes and the map f
is simplicial. Recent positive algorithmic results, proved in a series of
companion papers, show that for (k-1)-connected Y, k>=2, the extension problem
is algorithmically solvable if the dimension of X is at most 2k-1, and even in
polynomial time when k is fixed. Here we show that the condition \dim X<=2k-1
cannot be relaxed: for \dim X=2k, the extension problem with (k-1)-connected Y
becomes undecidable. Moreover, either the target space Y or the pair (X,A) can
be fixed in such a way that the problem remains undecidable. Our second result,
a strengthening of a result of Anick, says that the computation of \pi_k(Y) of
a 1-connected simplicial complex Y is #P-hard when k is considered as a part of
the input.


title:
The 4-Dimensional Composite Higgs Model (4DCHM) and the 125 GeV
  Higgs-like signals at the LHC

abstract:
  We show that the 4-Dimensional Composite Higgs Model (4DCHM) could provide an
even better explanation than the Standard Model (SM) of the current Large
Hadron Collider (LHC) data pointing to the discovery of a neutral Higgs boson.
The full particle spectrum of this scenario is derived without any
approximation and implemented in automated computational tools to enable fast
phenomenological investigation. Several benchmark sets compliant with the
aforementioned data are presented and discussed.


title: Seesaw mechanism with four texture zeros in the neutrino Yukawa matrix

abstract:
  With the recent observation of nonzero \theta_{13}, five neutrino oscillation
parameters are now known. By imposing four zeros in the Yukawa coupling matrix
of the type I seesaw model, the number of parameters in the neutrino mass
matrix is reduced to seven, and we are able to make predictions for the
lightest neutrino mass, Dirac CP phase, and neutrinoless double beta decay.
Four texture zeros in the Yukawa coupling matrix is equivalent to either a
single texture zero or a single cofactor zero for an off-diagonal element of
the light neutrino mass matrix. We find strong similarities between single
texture zero models with one mass ordering and single cofactor zero models with
the opposite mass ordering. In the context of a specific class of single-flavor
leptogenesis models, we find additional constraints on the parameter space.


title:
Parsimonious Skew Mixture Models for Model-Based Clustering and
  Classification

abstract:
  In recent work, robust mixture modelling approaches using skewed
distributions have been explored to accommodate asymmetric data. We introduce
parsimony by developing skew-t and skew-normal analogues of the popular GPCM
family that employ an eigenvalue decomposition of a positive-semidefinite
matrix. The methods developed in this paper are compared to existing models in
both an unsupervised and semi-supervised classification framework. Parameter
estimation is carried out using the expectation-maximization algorithm and
models are selected using the Bayesian information criterion. The efficacy of
these extensions is illustrated on simulated and benchmark clustering data
sets.


title:
Extended evolution equations for neutrino propagation in astrophysical
  and cosmological environments

abstract:
  We derive the evolution equations for a system of neutrinos interacting among
themselves and with a matter background, based upon the
Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. This theoretical
framework gives an (unclosed) set of first-order coupled integro-differential
equations governing the evolution of the reduced density matrices. By employing
the hierarchy, we first rederive the mean-field evolution equations for the
neutrino one-body density matrix associated with a system of neutrinos and
antineutrinos interacting with matter and with an anisotropic neutrino
background. Then, we derive extended evolution equations to determine neutrino
flavor conversion beyond the commonly used mean-field approximation. To this
aim we include neutrino-antineutrino pairing correlations to the two-body
density matrix. The inclusion of these new contributions leads to an extended
evolution equation for the normal neutrino density and to an equation for the
abnormal one involving the pairing mean-field. We discuss the possible impact
of neutrino-antineutrino correlations on neutrino flavor conversion in the
astrophysical and cosmological environments, and possibly upon the supernova
dynamics. Our results can be easily generalized to an arbitrary number of
neutrino families.


title:
Radiative generation of the CPT-even gauge term of the SME from a
  dimension-five nonminimal coupling term

abstract:
  In this letter we show for the first time that the usual CPT-even gauge term
of the standard model extension (SME) can be radiatively generated, in a gauge
invariant level, in the context of a modified QED endowed with a dimension-five
nonminimal coupling term recently proposed in the literature. As a consequence,
the existing upper bounds on the coefficients of the tensor $(K_{F}) $ can be
used improve the bounds on the magnitude of the nonminimal coupling,
$\lambda(K_{F}),$ by the factors $10^{5}$ or $10^{25}.$ The nonminimal coupling
also generates higher-order derivative contributions to the gauge field
effective action quadratic terms.


title: Modeling Morphology of Social Network Cascades

abstract:
  Cascades represent an important phenomenon across various disciplines such as
sociology, economy, psychology, political science, marketing, and epidemiology.
An important property of cascades is their morphology, which encompasses the
structure, shape, and size. However, cascade morphology has not been rigorously
characterized and modeled in prior literature. In this paper, we propose a
Multi-order Markov Model for the Morphology of Cascades ($M^4C$) that can
represent and quantitatively characterize the morphology of cascades with
arbitrary structures, shapes, and sizes. $M^4C$ can be used in a variety of
applications to classify different types of cascades. To demonstrate this, we
apply it to an unexplored but important problem in online social networks --
cascade size prediction. Our evaluations using real-world Twitter data show
that $M^4C$ based cascade size prediction scheme outperforms the baseline
scheme based on cascade graph features such as edge growth rate, degree
distribution, clustering, and diameter. $M^4C$ based cascade size prediction
scheme consistently achieves more than 90% classification accuracy under
different experimental scenarios.


title: Lois de r\'eciprocit\'e sup\'erieures et points rationnels

abstract:
  Let C be the complex field and K=C((x,y)) or K=C((x))(y). Let G be a
connected linear algebraic group over K. Under the assumption that the
K-variety G is K-rational, i.e. that the function field is purely transcendant,
it was proved that a principal homogeneous space of G has a rational point over
K as soon as it has one over each completion of K with respect to a discrete
valuation. In this paper we show that one cannot in general do without the
K-rationality assumption. To produce our examples, we introduce a new type of
obstruction. It is based on higher reciprocity laws on a 2-dimensional scheme.
We also produce a family of principal homogeneous spaces for which the refined
obstruction controls exactly the existence of rational points.