title: Chimera states in hierarchical networks of Van der Pol oscillators

abstract:
  Chimera states are complex spatio-temporal patterns that consist of
coexisting domains of coherent and incoherent dynamics. We analyse chimera
states in networks of Van der Pol oscillators with hierarchical coupling
topology. We investigate the stepwise transition from a nonlocal to a
hierarchical topology, and propose the network clustering coefficient as a
measure to establish a link between the existence of chimera states and the
compactness of the initial base pattern of a hierarchical topology; we show
that a large clustering coefficient promotes the occurrence of chimeras.
Depending on the level of hierarchy and base pattern, we obtain chimera states
with different numbers of incoherent domains. We investigate the chimera
regimes as a function of coupling strength and nonlinearity parameter of the
individual oscillators. The analysis of a network with larger base pattern
resulting in larger clustering coefficient reveals two different types of
chimera states and highlights the increasing role of amplitude dynamics.


title:
Exact Renormalisation Group Equations and Loop Equations for Tensor
  Models

abstract:
  In this paper, we review some general formulations of exact renormalisation
group equations and loop equations for tensor models and tensorial group field
theories. We illustrate the use of these equations in the derivation of the
leading order expectation values of observables in tensor models. Furthermore,
we use the exact renormalisation group equations to establish a suitable
scaling dimension for interactions in Abelian tensorial group field theories
with a closure constraint. We also present analogues of the loop equations for
tensor models.


title: Pattern recognition on the quantum Bloch sphere

abstract:
  We introduce a framework suitable for describing pattern recognition task
using the mathematical language of density matrices. In particular, we provide
a one-to-one correspondence between patterns and pure density operators. This
correspondence enables us to: i) represent the Nearest Mean Classifier (NMC) in
terms of quantum objects, ii) introduce a Quantum Classifier (QC). By comparing
the QC with the NMC on different 2D datasets, we show the first classifier can
provide additional information that are particularly beneficial on a classical
computer with respect to the second classifier.


title: Transits of extrasolar moons around luminous giant planets

abstract:
  Beyond Earth-like planets, moons can be habitable, too. No exomoons have been
securely detected, but they could be extremely abundant. Young Jovian planets
can be as hot as late M stars, with effective temperatures of up to 2000 K.
Transits of their moons might be detectable in their infrared photometric light
curves if the planets are sufficiently separated ($\gtrsim10$ AU) from the
stars to be directly imaged. The moons will be heated by radiation from their
young planets and potentially by tidal friction. Although stellar illumination
will be weak beyond 5 AU, these alternative energy sources could liquify
surface water on exomoons for hundreds of Myr. A Mars-mass H$_2$O-rich moon
around $\beta$ Pic b would have a transit depth of $1.5\times10^{-3}$, in reach
of near-future technology.


title:
Structure of the polynomials in preconditioned BiCG algorithms and the
  switching direction of preconditioned systems

abstract:
  We present a theorem that defines the direction of a preconditioned system
for the bi-conjugate gradient (BiCG) method, and we extend it to preconditioned
bi-Lanczos-type algorithms. We show that the direction of a preconditioned
system is switched by construction and by the settings of the initial shadow
residual vector. We analyze and compare the polynomial structures of four
preconditioned BiCG algorithms.


title:
Structure of the preconditioned system in various preconditioned
  conjugate gradient squared algorithms

abstract:
  An improved preconditioned conjugate gradient squared (PCGS) algorithm has
recently been proposed, and it performs much better than the conventional PCGS
algorithm. In this paper, the improved PCGS algorithm is verified as a
coordinative to the left-preconditioned system, and it has the advantages of
both the conventional and the left-PCGS; this is done by comparing, analyzing,
and executing numerical examinations of various PCGS algorithms, including
another improved one. We show that the direction of the preconditioned system
for the CGS method is determined by the operations of $\alpha_k$ and $\beta_k$
in the PCGS algorithm. By comparing the logical structures of these algorithms,
we show that the direction of the preconditioned system can be switched by the
construction and setting of the initial shadow residual vector.


title: Exact BPS domain walls at finite gauge coupling

abstract:
  Bogomol'nyi-Prasad-Sommerfield solitons in models with spontaneously broken
gauge symmetry have been intensively studied at infinite gauge coupling limit,
where the governing equation -- so-called master equation -- is exactly
solvable. Except for a handful of special solutions, the standing impression is
that analytic results at finite coupling are generally unavailable. The aim of
this paper is to demonstrate, using domain walls in Abelian-Higgs models as the
simplest example, that exact solitons at finite gauge coupling can be readily
obtained if the number of Higgs fields ($N_F$) is large enough. In particular,
we present a family of exact solutions, describing $N$ domain walls at
arbitrary positions in models with at least $N_F \geq 2N+1$. We have also found
that adding together any pair of solution can produce a new exact solution if
the combined tension is below a certain limit.


title:
A comparative study of protocols for secure quantum communication under
  noisy environment: single-qubit-based protocols versus entangled-state-based
  protocols

abstract:
  The effect of noise on various protocols of secure quantum communication has
been studied. Specifically, we have investigated the effect of amplitude
damping, phase damping, squeezed generalized amplitude damping, Pauli type as
well as various collective noise models on the protocols of quantum key
distribution, quantum key agreement,quantum secure direct quantum communication
and quantum dialogue. From each type of protocol of secure quantum
communication, we have chosen two protocols for our comparative study; one
based on single qubit states and the other one on entangled states. The
comparative study reported here has revealed that single-qubit-based schemes
are generally found to perform better in the presence of amplitude damping,
phase damping, squeezed generalized amplitude damping noises, while
entanglement-based protocols turn out to be preferable in the presence of
collective noises. It is also observed that the effect of noise entirely
depends upon the number of rounds of quantum communication involved in a scheme
of quantum communication. Further, it is observed that squeezing, a completely
quantum mechanical resource present in the squeezed generalized amplitude
channel, can be used in a beneficial way as it may yield higher fidelity
compared to the corresponding zero squeezing case.


title: Phase diagram of the two-fluid Lipkin model: a butterfly catastrophe

abstract:
  Background: In the last few decades quantum phase transitions have been of
great interest in Nuclear Physics. In this context, two-fluid algebraic models
are ideal systems to study how the concept of quantum phase transition evolves
when moving into more complex systems, but the number of publications along
this line has been scarce up to now.
  Purpose: We intend to determine the phase diagram of a two-fluid Lipkin
model, that resembles the nuclear proton-neutron interacting boson model
Hamiltonian, using both numerical results and analytic tools, i.e., catastrophe
theory, and to compare the mean-field results with exact diagonalizations for
large systems. Method: The mean-field energy surface of a consistent-Q-like
two-fluid Lipkin Hamiltonian is studied and compared with exact results coming
from a direct diagonalization. The mean-field results are analyzed using the
framework of catastrophe theory.
  Results: The phase diagram of the model is obtained and the order of the
different phase-transition lines and surfaces is determined using a catastrophe
theory analysis.
  Conclusions: There are two first order surfaces in the phase diagram, one
separating the spherical and the deformed shapes, while the other separates two
different deformed phases. A second order line, where the later surfaces merge,
is found. This line finishes in a transition point with a divergence in the
second order derivative of the energy that corresponds to a tricritical point
in the language of the Ginzburg-Landau theory for phase transitions.


title: A note on rough statistical convergence

abstract:
  In this paper, we introduce the notions of pointwise rough statistical
convergence and rough statistically Cauchy sequences of real valued functions
in the line of A. (T$\ddot{u}$rkmenoglu) G$\ddot{o}$khan and M.
G$\ddot{u}$ng$\ddot{o}$r \cite{Tu1}. Furthermore we study thier equivalence.


title:
Absence of Giant Spin Splitting in the Two-Dimensional Electron Liquid
  at the Surface of SrTiO$_3$ (001)

abstract:
  We reinvestigate the putative giant spin splitting at the surface of
SrTiO$_3$ reported by Santander-Syro $et~al.$ [Nature Mat. 13, 1085 (2014)].
Our spin- and angle-resolved photoemission experiments on (001) oriented
surfaces supporting a two-dimensional electron liquid with high carrier density
show no detectable spin polarization in the photocurrent. We demonstrate that
this result excludes a giant spin splitting while it is fully consistent with
the unconventional Rashba-like splitting seen in band structure calculations
that reproduce the experimentally observed ladder of quantum confined subbands.


title:
Protecting suppliers' private information: the case of stock levels and
  the impact of correlated items

abstract:
  A marketplace is defined where the private data of suppliers (e.g.,
prosumers) are protected, so that neither their identity nor their level of
stock is made known to end customers, while they can sell their products at a
reduced price. A broker acts as an intermediary, which takes care of providing
the items missing to meet the customers' demand and allows end customers to
take advantages of reduced prices through the subscription of option contracts.
Formulas are provided for the option price under three different probability
models for the availability of items. Option pricing allows the broker to
partially transfer its risk on end customers.


title: A note on rough statistical convergence of order $\alpha$

abstract:
  In this paper, in the line of Aytar\cite{Ay2} and \c{C}olak \cite{Co}, we
introduce the notion of rough statistical convergence of order $\alpha$ in
normed linear spaces and study some properties of the set of all rough
statistical limit points of order $\alpha$.


title: On the Monogamy of Holographic $n$-partite Information

abstract:
  We investigate the monogamy of holographic $n$-partite information for a
system consisting of $n$ disjoint parallel strips with the same width and
separation in AdS and AdS black brane geometries. More precisely, we study the
sign of this quantity, \emph{e.g.} for $n=4, 5$, in various dimensions and for
different parameters. Our results show that for quantum field theories with
holographic duals, the holographic 4-partite information is always positive and
the sign of holographic 5-partite information is found to be negative in the
dual strongly coupled $1+1$ dimensional CFT. This latter result indicates that
the holographic 4-partite information is monogamous. We also find the critical
points corresponding to the possible phase transitions of these quantities.


title: X-ray-binary spectra in the lamp post model

abstract:
  [Abridged] Context. The high-energy radiation from black-hole binaries may be
due to the reprocessing of a lamp located on the black hole axis, emitting
X-rays. The observed spectrum is made of 3 components: the direct spectrum; the
thermal bump; and the reflected spectrum made of the Compton hump and the
iron-line complex.
  Aims. We aim at computing accurately the complete reprocessed spectrum
(thermal bump + reflected) of black-hole binaries over the entire X-ray band.
We also determine the strength of the direct component. Our choice of
parameters is adapted to a source showing an important thermal component.
  Methods. We compute in full GR the illumination of a thin disk by a lamp
along the rotation axis. We use the ATM21 radiative transfer code to compute
the spectrum emitted along the disk. We ray trace this local spectrum to
determine the reprocessed spectrum as observed at infinity. We discuss the
dependence of the local and ray-traced spectra on the emission angle and spin.
  Results. We show the importance of the angle dependence of the total disk
specific intensity spectrum emitted by the illuminated atmosphere when the
thermal disk emission if fully taken into account. High spin implies high
temperature in the inner regions, so the emitted thermal disk spectrum covers
the iron-line complex. As a result we locally observe absorption lines produced
in the hot disk atmosphere. Absorption lines are narrow and disappear after ray
tracing the local spectrum.
  Conclusions. Our results mainly highlight the importance of considering the
angle dependence of the local spectrum when computing reprocessed spectra, as
was already found in a recent study. The main new result of our work is to show
the importance of computing the thermal bump of the spectrum, as this feature
can change considerably the observed iron-line complex.


title: Canonical modules of complexes

abstract:
  We define the notion of the canonical module of a complex. We then consider
Serre's conditions for a complex and study their relationship to the local
cohomology of the canonical module and its ring of endomorphisms.


title: Normalizers of Primitive Permutation Groups

abstract:
  Let $G$ be a transitive normal subgroup of a permutation group $A$ of finite
degree $n$. The factor group $A/G$ can be considered as a certain Galois group
and one would like to bound its size. One of the results of the paper is that
$|A/G| < n$ if $G$ is primitive unless $n = 3^{4}$, $5^4$, $3^8$, $5^8$, or
$3^{16}$. This bound is sharp when $n$ is prime. In fact, when $G$ is
primitive, $|\mathrm{Out}(G)| < n$ unless $G$ is a member of a given infinite
sequence of primitive groups and $n$ is different from the previously listed
integers. Many other results of this flavor are established not only for
permutation groups but also for linear groups and Galois groups.


title:
The Nonlinear Analytical Envelope Equation in quadratic nonlinear
  crystals

abstract:
  We here derive the so-called Nonlinear Analytical Envelope Equation (NAEE)
inspired by the work of Conforti et al. [M. Conforti, A. Marini, T. X. Tran, D.
Faccio, and F. Biancalana, "Interaction between optical fields and their
conjugates in nonlinear media," Opt. Express 21, 31239-31252 (2013)], whose
notation we follow. We present a complete model that includes $\chi^{(2)}$
terms [M. Conforti, F. Baronio, and C. De Angelis, "Nonlinear envelope equation
for broadband optical pulses in quadratic media," Phys. Rev. A 81, 053841
(2010)], $\chi^{(3)}$ terms, and then extend the model to delayed Raman effects
in the $\chi^{(3)}$ term. We therefore get a complete model for ultrafast pulse
propagation in quadratic nonlinear crystals similar to the Nonlinear Wave
Equation in Frequency domain [H. Guo, X. Zeng, B. Zhou, and M. Bache,
"Nonlinear wave equation in frequency domain: accurate modeling of ultrafast
interaction in anisotropic nonlinear media," J. Opt. Soc. Am. B 30, 494-504
(2013)], but where the envelope is modelled rather than the electrical field
while still keeping a sub-carrier level resolution. The advantage of the
envelope formation is that the physical origin of the additional terms that are
included to model the physics at the carrier level becomes more clear, in
contrast to the electric field equations that are more "black box" expansions
of the electrical field. We also point out that by comparing our results to a
very similar model and widely used model [G. Genty, P. Kinsler, B. Kibler, and
J. M. Dudley, "Nonlinear envelope equation modeling of sub-cycle dynamics and
harmonic generation in nonlinear waveguides," Opt. Express 15, 5382-5387
(2007)], the Raman terms presented there will most likely lead to an
artificially lower Raman effect.


title: On a certain family of U(b)-modules

abstract:
  We report on results of Kra\'skiewicz and the author, and Watanabe on KP
modules materializing Schubert polynomials, and filtrations having KP modules
as their subquotients. We discuss applications of KP filtrations and ample KP
bundles to positivity, due respectively to Watanabe and Fulton. The article
corresponds to the talk given by the author at the conference "IMPANGA 15" in
April 2015.


title: Ferromagnetic resonance and magnetic damping in C-doped Mn5Ge3

abstract:
  Ferromagnetic resonance (FMR) was used to investigate the static and dynamic
magnetic properties of carbon-doped Mn5Ge3 (C$_{0.1}$ and C$_{0.2}$) thin films
grown on Ge(111). The temperature dependence of magnetic anisotropy shows an
increased perpendicular magneto-crystalline contribution at 80K with an
in-plane easy axis due to the large shape contribution. We find that our
samples show a small FMR linewidth (corresponding to an intrinsic magnetic
damping parameter $\alpha$=0.005), which is a measure of the spin relaxation
and directly related with the magnetic and structural quality of the material.
In the perpendicular-to-plane geometry, the FMR linewidth shows a minimum at
around 200K for all the samples, which seems to be not correlated to the
C-doping. The magnetic relaxation parameters have been determined and indicate
the two-magnon scattering as the main extrinsic contribution. We observe a
change in the main contribution from scattering centres in Mn5Ge3C0.2 at low
temperatures, which could be related to the minimum in linewidth.


title:
Room-temperature transport of indirect excitons in (Al,Ga)N/GaN quantum
  wells

abstract:
  We report on the exciton propagation in polar (Al,Ga)N/GaN quantum wells over
several micrometers and up to room temperature. The key ingredient to achieve
this result is the crystalline quality of GaN quantum wells (QWs) grown on GaN
template substrate. By comparing microphotoluminescence images of two identical
QWs grown on sapphire and on GaN, we reveal the twofold role played by GaN
substrate in the transport of excitons. First, the lower threading dislocation
densities in such structures yield higher exciton radiative efficiency, thus
limiting nonradiative losses of propagating excitons. Second, the absence of
the dielectric mismatch between the substrate and the epilayer strongly limits
the photon guiding effect in the plane of the structure,making exciton
transport easier to distinguish from photon propagation. Our results pave the
way towards room-temperature gate-controlled exciton transport in wide-bandgap
polar heterostructures.


title:
Quantum gravity corrections to the standard model Higgs in Einstein and
  $R^2$ gravity

abstract:
  We evaluate quantum gravity corrections to the standard model Higgs potential
$V(\phi)$ a la Coleman-Weinberg and examine the stability question of $V(\phi)$
at scales of Planck mass $M_{\rm Pl}$. We compute the gravity one-loop
corrections by using the momentum cut-off in Einstein gravity. The gravity
corrections affect the potential in a significant manner for the value of
$\Lambda= (1 - 3)M_{\rm Pl}.$ In view of reducing the UV cut-off dependence we
also make a similar study in the $R^2$ gravity.


title: Plethystic identities and mixed Hodge structures of character varieties

abstract:
  I demonstrate how certain identities for Macdonald's polynomials established
by Garsia, Haiman and Tesler, together with the conjecture of Hausel, Letellier
and Villegas imply explicit relations between mixed Hodge polynomials of
different character varieties.


title: The Hydrodynamics of Active Systems

abstract:
  This is a series of four lectures presented at the 2015 Enrico Fermi summer
school in Varenna. The aim of the lectures is to give an introduction to the
hydrodynamics of active matter concentrating on low Reynolds number examples
such as cells and molecular motors. Lecture 1 introduces the hydrodynamics of
single active particles, covering the Stokes equation and the Scallop Theorem,
and stressing the link between autonomous activity and the dipolar symmetry of
the far flow field. In lecture 2 I discuss applications of this mathematics to
the behaviour of microswimmers at surfaces and in external flows, and describe
our current understanding of how swimmers stir the surrounding fluid. Lecture 3
concentrates on the collective behaviour of active particles, modelled as an
active nematic. I write down the equations of motion and motivate the form of
the active stress. The resulting hydrodynamic instability leads to a state
termed active turbulence characterised by strong jets and vortices in the flow
field and the continual creation and annihilation of pairs of topological
defects. Lecture 4 compares simulations of active turbulence to experiments on
suspensions of microtubules and molecular motors. I introduce lyotropic active
nematics and discuss active anchoring at interfaces.


title: A nonstiff solution for the stochastic neutron point kinetics equations

abstract:
  We propose an approach to solve the stochastic neutron point kinetics
equations using an adaptation of the diagonalization-decomposition method
(DDM). This new approach (Double-DDM) yields a nonstiff solution for the
stochastic formulation, allowing the calculation of the neutron and precursor
densities at any time of interest without the need of using progressive time
steps. We use Double-DDM to compute results for stochastic problems with
constant, linear, and sinusoidal reactivities. We show that these results
strongly agree with those obtained by other approaches established in the
literature. We also compute and analyze the first four statistical moments of
the solutions.


title:
Multivariate Krawtchouk polynomials and composition birth and death
  processes

abstract:
  This paper defines the multivariate Krawtchouk polynomials, orthogonal on the
multinomial distribution, and summarizes their properties as a review. The
multivariate Krawtchouk polynomials are symmetric functions of orthogonal sets
of functions defined on each of N multinomial trials. The dual multivariate
Krawtchouk polynomials, which also have a polynomial structure, are seen to
occur naturally as spectral orthogonal polynomials in a Karlin and McGregor
spectral representation of transition functions in a composition birth and
death process. In this Markov composition process in continuous time there are
N independent and identically distributed birth and death processes each with
support 0,1, .... The state space in the composition process is the number of
processes in the different states 0,1,... Dealing with the spectral
representation requires new extensions of the multivariate Krawtchouk
polynomials to orthogonal polynomials on a multinomial distribution with a
countable infinity of states.


title: A Proof of the Bar\'at-Thomassen Conjecture

abstract:
  The Bar\'at-Thomassen conjecture asserts that for every tree $T$ on $m$
edges, there exists a constant $k_T$ such that every $k_T$-edge-connected graph
with size divisible by $m$ can be edge-decomposed into copies of $T$. So far
this conjecture has only been verified when $T$ is a path or when $T$ has
diameter at most 4. Here we prove the full statement of the conjecture.


title:
Decomposing highly edge-connected graphs into homomorphic copies of a
  fixed tree

abstract:
  The Tree Decomposition Conjecture by Bar\'at and Thomassen states that for
every tree $T$ there exists a natural number $k(T)$ such that the following
holds: If $G$ is a $k(T)$-edge-connected simple graph with size divisible by
the size of $T$, then $G$ can be edge-decomposed into subgraphs isomorphic to
$T$. So far this conjecture has only been verified for paths, stars, and a
family of bistars. We prove a weaker version of the Tree Decomposition
Conjecture, where we require the subgraphs in the decomposition to be
isomorphic to graphs that can be obtained from $T$ by vertex-identifications.
We call such a subgraph a homomorphic copy of $T$. This implies the Tree
Decomposition Conjecture under the additional constraint that the girth of $G$
is greater than the diameter of $T$. As an application, we verify the Tree
Decomposition Conjecture for all trees of diameter at most 4.


title:
The Shaping of the Multipolar Pre-Planetary Nebula CRL 618 by
  Multi-directional Bullets

abstract:
  In order to understand the formation of the multipolar structures of the
pre-planetary nebula (PPN) CRL 618, we perform 3D simulations using a
multi-directional bullet model. The optical lobes of CRL 618 and fast molecular
outflows at the tips of the lobes have been found to have similar expansion
ages of ~ 100 yr. Additional fast molecular outflows were found near the source
along the outflow axes with ages of ~ 45 yr, suggesting a second episode of
bullet ejections. Thus, in our simulations, two episodes of bullet ejections
are assumed. The shaping process is simulated using the ZEUS-3D hydrodynamics
code that includes molecular and atomic cooling. In addition, molecular
chemistry is also included to calculate the CO intensity maps. Our results show
the following: (1) Multi-epoch bullets interacting with the toroidal dense core
can produce the collimated multiple lobes as seen in CRL 618. The total mass of
the bullets is ~ 0.034 solar mass, consistent with the observed high-velocity
CO emission in fast molecular outflows. (2) The simulated CO J=3-2 intensity
maps show that the low-velocity cavity wall and the high-velocity outflows
along the lobes are reasonably consistent with the observations. The
position-velocity diagram of the outflows along the outflow axes shows a linear
increase of velocity with distance, similar to the observations. The ejections
of these bullets could be due to magneto-rotational explosions or nova-like
explosions around a binary companion.


title: Beware of the Small-World neuroscientist!

abstract:
  The SW has undeniably been one of the most popular network descriptors in the
neuroscience literature. Two main reasons for its lasting popularity are its
apparent ease of computation and the intuitions it is thought to provide on how
networked systems operate. Over the last few years, some pitfalls of the SW
construct and, more generally, of network summary measures, have widely been
acknowledged.


title:
On stabilizing the variance of dynamic functional brain connectivity
  time series

abstract:
  Assessment of dynamic functional brain connectivity (dFC) based on fMRI data
is an increasingly popular strategy to investigate temporal dynamics of the
brain's large-scale network architecture. Current practice when deriving
connectivity estimates over time is to use the Fisher transform which aims to
stabilize the variance of correlation values that fluctuate around varying true
correlation values. It is however unclear how well the stabilization of signal
variance performed by the Fisher transform works for each connectivity time
series, when the true correlation is assumed to be fluctuating. This is of
importance because many subsequent analyses either assume or perform better
when the time series have stable variance or adheres to an approximate Gaussian
distribution. In this paper, using simulations and analysis of resting-state
fMRI data, we analyze the effect of applying different variance stabilization
strategies on connectivity time-series. We here focus our investigation on the
Fisher transform, the Box Cox transform and an approach that combines both
transforms. Our results show that, if the intention of stabilizing the variance
is to use metrics on the time series where stable variance or a Gaussian
distribution is desired (e.g. clustering), the Fisher transform is not optimal
and may even skew connectivity time series away from being Gaussian. Further,
we show that the suboptimal performance of the Fisher transform can be
substantially improved by including an additional Box-Cox transformation after
the dFC time series has been Fisher transformed.


title:
Peculiar Lapse of Periodic Eclipsing Event at Low Mass X-ray Binary GRS
  1747$-$312 during Suzaku Observation in 2009

abstract:
  GRS 1747$-$312 is a neutron star Low-Mass X-ray Binary in the globular
cluster Terzan 6, located at a distance of 9.5 kpc from the Earth. During its
outbursts, periodic eclipses were known to occur. Observations for the
outbursts were performed with Chandra in 2004 and Swift in 2013. XMM-Newton
observed its quiescent state in 2004. In addition, when Suzaku observed it in
2009 as a part of Galactic center mapping observations, GRS 1747$-$312 was
found to be in a low luminosity state with $L_{\rm x} \sim 1.2 \times 10^{35}$
erg s$^{-1}$. All of the observations except for XMM-Newton included the time
of the eclipses predicted. We analyzed archival data of these observations.
During the Chandra and Swift observations, we found clear flux decreases at the
expected time of the eclipses. During the Suzaku observation, however, there
were no clear signs for the predicted eclipses. The lapse of the predicted
eclipses during the Suzaku observation can be explained by a contaminant source
quite close to GRS 1747$-$312. When GRS 1747$-$312 is in the quiescent state,
we observe X-rays from the contaminant source rather than from GRS 1747$-$312.
However, we have no clear evidence for the contaminant source in our data. The
lapse might also be explained by thick material ($N_{\rm H} > 10^{24}$
cm$^{-2}$ ) between the neutron star and the companion star, though the origin
of the thick material is not clear.


title:
Heterogeneous Multi-Tier Networks: Improper Signaling For Joint
  Rate-Energy Optimization

abstract:
  Wireless nodes in future communication systems need to overcome three
barriers when compared to their transitional counterparts, namely to support
significantly higher data rates, have long-lasting energy supplies and remain
fully operational in interference-limited heterogeneous networks. This could be
partially achieved by providing three promising features, which are radio
frequency (RF) energy harvesting, improper Gaussian signaling and operating in
full-duplex communication mode, i.e., transmit and receive at the same time
within the same frequency band. In this paper, we consider these aspects
jointly in a multi-antenna heterogeneous two-tier network. In this network, the
users in the femto- cell are sharing the scarce resources with the cellular
users in the macro-cell and have to cope with the interference from the
macro-cell base station as well as the transmitter noise and residual self-
interference (RSI) due to imperfect full-duplex operation. Interestingly
enough, while these impairments are detrimental from the achievable rate
perspective, they are beneficial from the energy harvesting aspect as they
carry RF energy. In this paper, we consider this natural trade-off jointly and
propose appropriate optimization problems for beamforming and optimal resource
allocation. Moreover, various receiver structures are employed for both
information detection (ID) and energy harvesting (EH) capabilities. The paper
aims at characterizing the trade-off between the achievable rates and harvested
energies. Rate and energy maximization problems are thoroughly investigated.
Finally, the numerical illustrations demonstrate the impact of energy
harvesting on the achievable rate performance.


title: Existence of Self-Cheeger sets on Riemannian manifolds

abstract:
  Let $(\mathcal{M},g)$ be a compact Riemannian manifold of dimension $N\geq
2$. We prove the existence of a family $(\Omega_\varepsilon)_{\varepsilon\in
(0,\varepsilon_0)}$ of self-Cheeger sets in $(\mathcal{M},g)$ . The domains
$\Omega_\varepsilon\subset\mathcal{M}$ are perturbations of geodesic balls of
radius $\varepsilon$ centered at $p \in \mathcal{M}$, and in particular, if
$p_0$ is a non-degenerate critical point of the scalar curvature of $g$, then
the family $(\partial \Omega_\varepsilon)_{\varepsilon \in (0,\varepsilon_0)}$
constitutes a smooth foliation of a neighborhood of $p_0$.


title: A star forming ring around Kappa Ori 250 pc from the Sun

abstract:
  X-rays are a powerful probe of activity in early stages of star formation.
They allow us to identify young stars even after they have lost the IR
signatures of circumstellar disks and provide constraints on their distance.
Here we report on XMM-Newton observations which detect 121 young stellar
objects (YSOs) in two fields between L1641S and $\kappa$ Ori. These
observations extend the Survey of Orion A with XMM and Spitzer (SOXS). The YSOs
are contained in a ring of gas and dust apparent at millimeter wavelengths, and
in far-IR and near-IR surveys. The X-ray luminosity function of the young
stellar objects detected in the two fields indicates a distance of 250-280 pc,
much closer than the Orion A cloud and similar to distance estimates of
$\kappa$ Ori. We propose that the ring is a 5-8 pc diameter shell that has been
swept up by $\kappa$ Ori. This ring contains several groups of stars detected
by Spitzer and WISE including one surrounding the Herbig Ae/Be stars V1818 Ori.
In this interpretation, the $\kappa$ Ori ring is one of several shells swept up
by massive stars within the Orion Eridanus Superbubble, and is unrelated to the
southern portion of Orion A / L1641 S.


title: A new approach to the Tarry-Escott problem

abstract:
  In this paper we describe a new method of obtaining ideal solutions of the
well-known Tarry-Escott problem, that is, the problem of finding two distinct
sets of integers $x_i,\;i=1,\,2,\,\dots,\,k+1$ and
$y_i,\;i=1,\,2,\,\dots,\,k+1$ such that $ \sum_{i=1}^{k+1} x_i^r =
\sum_{i=1}^{k+1} y_i^r,\;\;\;r = 1,\,2,\,\dots,\,k$, where $k$ is a given
positive integer. When $k > 3$, only a limited number of parametric/ numerical
ideal solutions of the Tarry-Escott problem are known. In this paper, by
applying the new method mentioned above, we find several new parametric ideal
solutions of the problem when $k \leq 7$. The ideal solutions obtained by this
new approach are more general and very frequently, simpler than the ideal
solutions obtained by the earlier methods. We also obtain new parametric
solutions of certain diophantine systems that are closely related to the
Tarry-Escott problem. These solutions are also more general and simpler than
the solutions of these diophantine systems published earlier.


title:
Sets of bounded remainder for the continuous irrational rotation on
  $[0,1)^2$

abstract:
  We study sets of bounded remainder for the two-dimensional continuous
irrational rotation $(\{x_1+t\}, \{x_2+t\alpha \})_{t \geq 0}$ in the unit
square. In particular, we show that for almost all $\alpha$ and every starting
point $(x_1, x_2)$, every polygon $S$ with no edge of slope $\alpha$ is a set
of bounded remainder. Moreover, every convex set $S$ whose boundary is twice
continuously differentiable with positive curvature at every point is a bounded
remainder set for almost all $\alpha$ and every starting point $(x_1, x_2)$.
Finally we show that these assertions are, in some sense, best possible.


title:
Approximation of a free Poisson process by systems of freely independent
  particles

abstract:
  Let $\sigma$ be a non-atomic, infinite Radon measure on $\mathbb R^d$, for
example, $d\sigma(x)=z\,dx$ where $z>0$. We consider a system of freely
independent particles $x_1,\dots,x_N$ in a bounded set $\Lambda\subset\mathbb
R^d$, where each particle $x_i$ has distribution
$\frac1{\sigma(\Lambda)}\,\sigma$ on $\Lambda$ and the number of particles,
$N$, is random and has Poisson distribution with parameter $\sigma(\Lambda)$.
If the particles were classically independent rather than freely independent,
this particle system would be the restriction to $\Lambda$ of the Poisson point
process on $\mathbb R^d$ with intensity measure $\sigma$. In the case of free
independence, this particle system is not the restriction of the free Poisson
process on $\mathbb R^d$ with intensity measure $\sigma$. Nevertheless, we
prove that this is true in an approximative sense: if bounded sets
$\Lambda^{(n)}$ ($n\in\mathbb N$) are such that
$\Lambda^{(1)}\subset\Lambda^{(2)}\subset\Lambda^{(3)}\subset\dotsm$ and
$\bigcup_{n=1}^\infty \Lambda^{(n)}=\mathbb R^d$, then the corresponding
particle system in $\Lambda^{(n)}$ converges (as $n\to\infty$) to the free
Poisson process on $\mathbb R^d$ with intensity measure $\sigma$. We also prove
the following $N/V$-limit: Let $N^{(n)}$ be a determinstic sequence of natural
numbers such that $\lim_{n\to\infty}N^{(n)}/\sigma(\Lambda^{(n)})=1$. Then the
system of $N^{(n)}$ freely independent particles in $\Lambda^{(n)}$ converges
(as $n\to\infty$) to the free Poisson process. We finally extend these results
to the case of a free L\'evy white noise (in particular, a free L\'evy process)
without free Gaussian part.


title: Group C*-algebras without the completely bounded approximation property

abstract:
  It is proved that:
  (1) The Fourier algebra A(G) of a simple Lie group G of real rank at least 2
with finite center does not have a multiplier bounded approximate unit.
  (2) The reduced C*-algebra of any lattice in a non-compact simple Lie group
of real rank at least 2 with finite center does not have the completely bounded
approximation property.
  Hence, the results obtained by J. de Canniere and the author for SO(n,1), n
at least 2, and by M. Cowling for SU(n,1) do not generalize to simple Lie
groups of real rank at least 2.


title: Phase-only signal reconstruction by MagnitudeCut

abstract:
  In this paper, we present a new algorithm, called MagnitudeCut, for
recovering a signal from the phase of its Fourier transform. We casted our
recovering problem into a new convex optimization problem, and then solved it
by the block coordinate descent algorithm and the interior point algorithm, in
which the iteration process consists of matrix vector product and inner
product. We used the new method for reconstruction of a set of signal/image.
The simulation results reveal that the proposed MagnitudeCut method can
reconstruct the original signal with fewer sampling number of the phase
information than that of the Greedy algorithm and iterative method under the
same reconstruction error. Moreover, our algorithm can also reconstruct the
symmetric image from its Fourier phase.


title:
On the Estimation Performance and Convergence Rate of the Generalized
  Power Method for Phase Synchronization

abstract:
  An estimation problem of fundamental interest is that of phase
synchronization, in which the goal is to recover a collection of phases using
noisy measurements of relative phases. It is known that in the Gaussian noise
setting, the maximum likelihood estimator (MLE) has an expected squared
$\ell_2$-estimation error that is on the same order as the Cram\'er-Rao lower
bound. Moreover, even though the MLE is an optimal solution to a non-convex
quadratic optimization problem, it can be found with high probability using
semidefinite programming (SDP), provided that the noise power is not too large.
In this paper, we study the estimation and convergence performance of a
recently-proposed low-complexity alternative to the SDP-based approach, namely,
the generalized power method (GPM). Our contribution is twofold. First, we
bound the rate at which the estimation error decreases in each iteration of the
GPM and use this bound to show that all iterates---not just the MLE---achieve
an estimation error that is on the same order as the Cram\'er-Rao bound. Our
result holds under the least restrictive assumption on the noise power and
gives the best provable bound on the estimation error known to date. It also
implies that one can terminate the GPM at any iteration and still obtain an
estimator that has a theoretical guarantee on its estimation error. Second, we
show that under the same assumption on the noise power as that for the
SDP-based method, the GPM will converge to the MLE at a linear rate with high
probability. This answers a question raised in [3] and shows that the GPM is
competitive in terms of both theoretical guarantees and numerical efficiency
with the SDP-based method. At the heart of our convergence rate analysis is a
new error bound for the non-convex quadratic optimization formulation of the
phase synchronization problem, which could be of independent interest.


title: Graphene with vacancies: supernumerary zero modes

abstract:
  The density of states, $\varrho(E)$, of graphene is investigated within the
tight binding (H\"uckel) approximation in the presence of vacancies. They
induce a non-vanishing density of zero modes, $n_\text{zm}$, that act as midgap
states: $\varrho(E)=n_\text{zm}\delta(E) + \text{smooth}$. As is well known,
the actual number of zero modes per sample can in principle exceed the
sublattice imbalance: $N_\text{zm}\geq |N_\text{A}-N_\text{B}|$, where
$N_\text{A}$, $N_\text{B}$ denote the number of carbon atoms in each
sublattice. In this work, we establish a stronger relation that is valid in the
thermodynamic limit and that involves the concentration of zero-modes:
$n_\text{zm}>|c_\text{A}-c_\text{B}|$, where $c_\text{A}$ and $c_\text{B}$
denote the concentration of vacancies per sublattice; in particular,
$n_\text{zm}$ is non-vanishing even in the case of balanced disorder,
$N_\text{A}/N_\text{B}=1$. Adopting terminology from benzoid graph theory, the
excess modes associated with the current carrying backbone (percolation
cluster) are called supernumerary. In the simplest cases such modes can be
associated with structural elements of internal boundaries like dangling bonds.
Our result suggest that the continuum limit of bipartite hopping models
supports nontrivial "supernumerary" terms that escape the present continuum
descriptions.


title:
An Optimal Algorithm for l1-Heavy Hitters in Insertion Streams and
  Related Problems

abstract:
  We give the first optimal bounds for returning the $\ell_1$-heavy hitters in
a data stream of insertions, together with their approximate frequencies,
closing a long line of work on this problem. For a stream of $m$ items in $\{1,
2, \dots, n\}$ and parameters $0 < \epsilon < \phi \leq 1$, let $f_i$ denote
the frequency of item $i$, i.e., the number of times item $i$ occurs in the
stream. With arbitrarily large constant probability, our algorithm returns all
items $i$ for which $f_i \geq \phi m$, returns no items $j$ for which $f_j \leq
(\phi -\epsilon)m$, and returns approximations $\tilde{f}_i$ with $|\tilde{f}_i
- f_i| \leq \epsilon m$ for each item $i$ that it returns. Our algorithm uses
$O(\epsilon^{-1} \log\phi^{-1} + \phi^{-1} \log n + \log \log m)$ bits of
space, processes each stream update in $O(1)$ worst-case time, and can report
its output in time linear in the output size. We also prove a lower bound,
which implies that our algorithm is optimal up to a constant factor in its
space complexity. A modification of our algorithm can be used to estimate the
maximum frequency up to an additive $\epsilon m$ error in the above amount of
space, resolving Question 3 in the IITK 2006 Workshop on Algorithms for Data
Streams for the case of $\ell_1$-heavy hitters. We also introduce several
variants of the heavy hitters and maximum frequency problems, inspired by rank
aggregation and voting schemes, and show how our techniques can be applied in
such settings. Unlike the traditional heavy hitters problem, some of these
variants look at comparisons between items rather than numerical values to
determine the frequency of an item.


title:
Permuting Incomplete Paired Data: A Novel Exact and Asymptotic Correct
  Randomization Test

abstract:
  Various statistical tests have been developed for testing the equality of
means in matched pairs with missing values. However, most existing methods are
commonly based on certain distributional assumptions such as normality,
0-symmetry or homoscedasticity of the data. The aim of this paper is to develop
a statistical test that is robust against deviations from such assumptions and
also leads to valid inference in case of heteroscedasticity or skewed
distributions. This is achieved by applying a novel randomization approach. The
resulting test procedure is not only shown to be asymptotically correct but is
also finitely exact if the distribution of the data is invariant with respect
to the considered randomization group. Its small sample performance is further
studied in an extensive simulation study and compared to existing methods.
Finally, an illustrative data example is analyzed.


title:
Vacuum Rabi Splitting in Nanomechanical QED System with Nonlinear
  Resonator

abstract:
  Considering the intrinsic nonlinearity in a nanomechanical resonator coupled
to a charge qubit, vacuum Rabi splitting effect is studied in a nanomechanical
QED (qubit-resonator) system. A driven nonlinear Jaynes-Cummings model
describes the dynamics of this qubit-resonator system. Using quantum regression
theorem and master equation approach, we have calculated the two-time
correlation spectrum analytically. In the weak driving limit, these analytical
results clarify the influence of the driving strength and nonlinearity
parameter on the correlation spectrum. Also, numerical calculations confirm
these analytical results.


title:
Structural, electronic and optical properties of well-known primary
  explosive: Mercury fulminate

abstract:
  Mercury Fulminate (MF) is one of the well-known primary explosives since 17th
century and it has rendered invaluable service over many years. However, the
correct molecular and crystal structures are determined recently after 300
years of its discovery. In the present study, we report pressure dependent
structural, elastic, electronic and optical properties of MF. Non-local
correction methods have been employed to capture the weak van der Waals
interactions in layered and molecular energetic MF. Among the non-local
correction methods tested, optB88-vdW method works well for the investigated
compound. The obtained equilibrium bulk modulus reveals that MF is softer than
the well known primary explosives Silver Fulminate (SF), silver azide and lead
azide. MF exhibits anisotropic compressibility (b>a>c) under pressure,
consequently the corresponding elastic moduli decrease in the following order:
C22>C11>C33. The structural and mechanical properties suggest that MF is more
sensitive to detonate along c-axis (similar to RDX) due to high compressibility
of Hg...O non-bonded interactions along that axis. Electronic structure and
optical properties were calculated including spin-orbit (SO) interactions using
full potential linearized augmented plane wave method within recently developed
Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The calculated TB-mBJ
electronic structures of SF and MF show that these compounds are indirect
bandgap insulators. Also, SO coupling is found to be more pronounced for 4d and
5d-states of Ag and Hg atoms of SF and MF, respectively. Partial density of
states and electron charge density maps were used to describe the nature of
chemical bonding. Ag-C bond is more directional than Hg-C bond which makes SF
to be more unstable than MF. The effect of SO coupling on optical properties
has also been studied and found to be significant for both of the compounds.


title:
A class of globally solvable Markovian quadratic BSDE systems and
  applications

abstract:
  We establish existence and uniqueness for a wide class of Markovian systems
of backward stochastic differential equations (BSDE) with quadratic
nonlinearities. This class is characterized by an abstract structural
assumption on the generator, an a-priori local-boundedness property, and a
locally-H\"older-continuous terminal condition. We present easily verifiable
sufficient conditions for these assumptions and treat several applications,
including stochastic equilibria in incomplete financial markets, stochastic
differential games, and martingales on Riemannian manifolds.


title: Alternative multiplications and non-associativity in physics

abstract:
  Some physical systems like the quantum mechanics with magnetic charges or
field theoretical models appearing in the context of string theory are
formulated in terms of non-associative algebras. Hence, demand non-associative
star products for its description. However, unlike its associative counterpart
the situation with non-associative star products is quite unclear. At the
moment it is not evident which condition should be used instead of the
associativity in the definition of the non-associative star multiplication. In
mathematics, the natural generalization of the associativity is the requirement
that the multiplication should be alternative, the associator of three elements
should vanish if each two of them are equal. We show that for the alternative
closed star product the integrated associator vanishes. In particular, it means
that on-shell there will be no violation of associativity in string scattering
amplitudes. We discuss the examples of the alternative and closed star
products. In particular, it is constructed the star product corresponding to
the algebra of octonions.


title:
The data processing pipeline for the Herschel SPIRE Fourier Transform
  Spectrometer

abstract:
  We present the data processing pipeline to generate calibrated data products
from the Spectral and Photometric Imaging Receiver (SPIRE) imaging Fourier
Transform Spectrometer on the Herschel Space Observatory. The pipeline
processes telemetry from SPIRE observations and produces calibrated spectra for
all resolution modes. The spectrometer pipeline shares some elements with the
SPIRE photometer pipeline, including the conversion of telemetry packets into
data timelines and calculation of bolometer voltages. We present the following
fundamental processing steps unique to the spectrometer: temporal and spatial
interpolation of the scan mechanism and detector data to create interferograms;
Fourier transformation; apodization; and creation of a data cube. We also
describe the corrections for various instrumental effects including first- and
second-level glitch identification and removal, correction of the effects due
to emission from the Herschel telescope and from within the spectrometer
instrument, interferogram baseline correction, temporal and spatial phase
correction, non-linear response of the bolometers, and variation of instrument
performance across the focal plane arrays. Astronomical calibration is based on
combinations of observations of standard astronomical sources and regions of
space known to contain minimal emission.


title: Evolution of electron Fermi surface with doping in cobaltates

abstract:
  The notion of the electron Fermi surface is one of the characteristic
concepts in the field of condensed matter physics, and it plays a crucial role
in the understanding of the physical properties of doped Mott insulators. Based
on the t-J model, we study the nature of the electron Fermi surface in the
cobaltates, and qualitatively reproduce the essential feature of the evolution
of the electron Fermi surface with doping. It is shown that the underlying
hexagonal electron Fermi surface obeys Luttinger's theorem. The theory also
predicts a Fermi-arc phenomenon at the low-doped regime, where the region of
the hexagonal electron Fermi surface along the \Gamma-K direction is suppressed
by the electron self-energy, and then six disconnected Fermi arcs located at
the region of the hexagonal electron Fermi surface along the \Gamma-M direction
emerge. However, this Fermi-arc phenomenon at the low-doped regime weakens with
the increase of doping.


title:
Bumblebees minimize control challenges by combining active and passive
  modes in unsteady winds

abstract:
  The natural wind environment that volant insects encounter is unsteady and
highly complex, posing significant flight control and stability challenges.
Unsteady airflows can range from structured chains of discrete vortices shed in
the wake of an object to fully developed chaotic turbulence. It is critical to
understand the flight control strategies insects employ to safely navigate in
natural environments. We combined experiments on free flying bumblebees with
high fidelity numerical simulations and lower order modeling to identify the
salient mechanics that mediate insect flight in unsteady winds. We trained
bumblebees to fly upwind towards an artificial flower in a wind tunnel under
steady wind and in a von Karman street (23Hz) formed in the wake of a cylinder.
The bees displayed significantly higher movement in the unsteady vortex street
compared to steady winds. Correlation analysis revealed that at lower
frequencies, less than 10 Hz, in both steady and unsteady winds the bees
mediated lateral movement with body roll, typical casting motion. At higher
frequencies in unsteady winds there was a negative correlation between body
roll and lateral accelerations. Numerical simulations of a bumblebee in similar
conditions permitted the separation of the passive and active components of the
flight trajectories. Comparison between the free-flying and numerical bees
revealed a novel mechanism that enables bees to passively ride out high
frequency perturbations while performing active maneuvers and corrections at
lower frequencies. The capacity of maintaining stability by combining passive
and active modes at different timescales provides a viable means for volant
animals and machines to tackle the control challenges posed by complex
airflows.


title:
Isotropic geometry of graph surfaces associated with product production
  functions in economics

abstract:
  A production function is a mathematical formalization in economics which
denotes the relations between the output generated by a firm, an industry or an
economy and the inputs that have been used in obtaining it. In this paper, we
study the product production functions of 2 variables in terms of the geometry
of their associated graph surfaces in the isotropic 3-space I^{3}. In
particular, we derive several classification results for the graph surfaces of
product production functions in I^{3} with constant curvature.


title: Segmental Recurrent Neural Networks for End-to-end Speech Recognition

abstract:
  We study the segmental recurrent neural network for end-to-end acoustic
modelling. This model connects the segmental conditional random field (CRF)
with a recurrent neural network (RNN) used for feature extraction. Compared to
most previous CRF-based acoustic models, it does not rely on an external system
to provide features or segmentation boundaries. Instead, this model
marginalises out all the possible segmentations, and features are extracted
from the RNN trained together with the segmental CRF. In essence, this model is
self-contained and can be trained end-to-end. In this paper, we discuss
practical training and decoding issues as well as the method to speed up the
training in the context of speech recognition. We performed experiments on the
TIMIT dataset. We achieved 17.3 phone error rate (PER) from the first-pass
decoding --- the best reported result using CRFs, despite the fact that we only
used a zeroth-order CRF and without using any language model.


title:
Numerically Fitting The Electron Fermi Energy and The Electron Fraction
  in A Neutron Star

abstract:
  Based on the basic definition of Fermi energy of degenerate and relativistic
electrons, we obtain a special solution to electron Fermi energy, $E_{\rm
F}(e)$, and express $E_{\rm F}(e)$ as a function of electron fraction, $Y_{e}$,
and matter density, $\rho$. Several useful analytical formulae for $Y_{e}$ and
$\rho$ within classical models and the work of Dutra et al. 2014 (Type-2) in
relativistic mean field theory are obtained using numerically fitting. When
describing the mean-field Lagrangian, density, we adopt the TMA parameter set,
which is remarkably consistent with with the updated astrophysical observations
of neutron stars. Due to the importance of the density dependence of the
symmetry energy, $S$, in nuclear astrophysics, a brief discussion on the
symmetry parameters $S_v$ and $L$ (the slope of $S$) is presented. Combining
these fit formulae with boundary conditions for different density regions, we
can evaluate the value of $E_{\rm F}(e)$ in any given matter density, and
obtain a schematic diagram of $E_{\rm F}(e)$ as a continuous function of
$\rho$. Compared with previous study on the electron Fermi energy in other
models, our methods of calculating $E_{\rm F}(e)$ are more simple and
convenient, and can be universally suitable for the relativistic electron
regions in the circumstances of common neutron stars. We have deduced a general
expression of $E_{\rm F}(e)$ and $n_{e}$, which could be used to indirectly
test whether one EoS of a NS is correct in our future studies on neutron star
matter properties. Since URCA reactions are expected in the center of a massive
star due to high-value electron Fermi energy and electron fraction, this study
could be useful in the future studies on the NS thermal evolution.


title:
Non equilibrium optical properties in semiconductors from
  first--principles: a combined theoretical and experimental study of bulk
  silicon

abstract:
  The calculation of the equilibrium optical properties of bulk silicon by
using the Bethe--Salpeter equation solved in the Kohn--Sham basis represents a
cornerstone in the development of an ab--initio approach to the optical and
electronic properties of materials. Nevertheless calculations of the {\em
transient} optical spectrum using the same efficient and successful scheme are
scarce. We report, here, a joint theoretical and experimental study of the
transient reflectivity spectrum of bulk silicon. Femtosecond transient
reflectivity is compared to a parameter--free calculation based on the
non--equilibrium Bethe--Salpeter equation. By providing an accurate description
of the experimental results we disclose the different phenomena that determine
the transient optical response of a semiconductor. We give a parameter--free
interpretation of concepts like bleaching, photo--induced absorption and
stimulated emission, beyond the Fermi golden rule. We also introduce the
concept of optical gap renormalization, as a generalization of the known
mechanism of band gap renormalization. The present scheme successfully
describes the case of bulk silicon, showing its universality and accuracy.


title:
Finding the Nucleoli of Large Cooperative Games: A Disproof with
  Counter-Example

abstract:
  Nguyen and Thomas (2016) claimed that they have found a method to compute the
nucleoli of games with more than $50$ players using nested linear programs
(LP). Unfortunately, this claim is false. They incorrectly applied the indirect
proof by "$A \land \neg B$ implies $A \land \neg A$" to conclude that "if $A$
then $B$" is valid. In fact, they prove that a truth implies a falsehood. As
established by Meinhardt (2015a), this is a wrong statement. Therefore, instead
of giving a proof of their main Theorem 4b, they give a disproof. It comes as
no surprise to us that the flow game example presented by these authors to
support their arguments is obviously a counter-example of their algorithm. We
show that the computed solution by this algorithm is neither the nucleolus nor
a core element of the flow game. Moreover, the stopping criterion of all
proposed methods is wrong, since it does not satisfy one of Kohlberg's
properties (cf. Kohlberg (1971)). As a consequence, none of these algorithms is
robust.


title: On the vortex filament conjecture for Euler flows

abstract:
  In this paper, we study the evolution of a vortex filament in an
incompressible ideal fluid. Under the assumption that the vorticity is
concentrated along a smooth curve in $\mathbb{R}^3$, we prove that the curve
evolves to leading order by binormal curvature flow. Our approach combines new
estimates on the distance of the corresponding Hamiltonian-Possion structures
with stability estimates recently developed in Ref. 15.


title: Possible $B^{(\ast)} \bar{K}$ hadronic molecule state

abstract:
  In the present work, we estimate the decays of the $X(5568)$ and $X(5616)$ in
a $B \bar{K}$ and a $B^\ast \bar{K}$ $S$-wave hadronic molecule scenarios,
respectively, which may corresponding to the structure observed by D0
Collaboration. Our estimation indicates both $B\bar{K}$ and $B^\ast \bar{K}$
hadronic molecule decay widths could explain the experimental data in a proper
model parameter range.


title: Fetishizing Food in Digital Age: #foodporn Around the World

abstract:
  What food is so good as to be considered pornographic? Worldwide, the popular
#foodporn hashtag has been used to share appetizing pictures of peoples'
favorite culinary experiences. But social scientists ask whether #foodporn
promotes an unhealthy relationship with food, as pornography would contribute
to an unrealistic view of sexuality. In this study, we examine nearly 10
million Instagram posts by 1.7 million users worldwide. An overwhelming (and
uniform across the nations) obsession with chocolate and cake shows the
domination of sugary dessert over local cuisines. Yet, we find encouraging
traits in the association of emotion and health-related topics with #foodporn,
suggesting food can serve as motivation for a healthy lifestyle. Social
approval also favors the healthy posts, with users posting with healthy
hashtags having an average of 1,000 more followers than those with unhealthy
ones. Finally, we perform a demographic analysis which shows nation-wide trends
of behavior, such as a strong relationship (r=0.51) between the GDP per capita
and the attention to healthiness of their favorite food. Our results expose a
new facet of food "pornography", revealing potential avenues for utilizing this
precarious notion for promoting healthy lifestyles.


title: Neutrino masses and ordering via multimessenger astronomy

abstract:
  We define the theoretical framework and deduce the conditions under which
multi-messenger astronomy can provide useful information about neutrino masses
and their ordering. The framework uses time differences between the arrival of
neutrinos and the other light messenger, i.e. the graviton, emitted in
astrophysical catastrophes. We also provide a preliminary feasibility study
elucidating the experimental reach and challenges for planned neutrino
detectors such as Hyper-Kamiokande as well as future several megaton detectors.
This study shows that future experiments can be useful in testing independently
the cosmological bounds on absolute neutrino masses. Concretely the success of
such measurements depends crucially on the available rate of astrophysical
events and further requires development of high resolution timing besides the
advocated need of megaton size detectors.


title: Classifying Unidentified Gamma-ray Sources

abstract:
  During its first 2 years of mission the Fermi-LAT instrument discovered more
than 1,800 gamma-ray sources in the 100 MeV to 100 GeV range. Despite the
application of advanced techniques to identify and associate the Fermi-LAT
sources with counterparts at other wavelengths, about 40% of the LAT sources
have no a clear identification remaining "unassociated". The purpose of my
Ph.D. work has been to pursue a statistical approach to identify the nature of
each Fermi-LAT unassociated source. To this aim, we implemented advanced
machine learning techniques, such as logistic regression and artificial neural
networks, to classify these sources on the basis of all the available gamma-ray
information about location, energy spectrum and time variability. These
analyses have been used for selecting targets for AGN and pulsar searches and
planning multi-wavelength follow-up observations. In particular, we have
focused our attention on the search of possible radio-quiet millisecond pulsar
(MSP) candidates in the sample of the Fermi-LAT unidentified sources. These
objects have not yet been detected but their discovery would have a formidable
impact for our understanding of the MSP gamma-ray emission mechanism.


title:
Cost Optimisation of an Instrument Suite at an Accelerator-Driven
  Spallation Source

abstract:
  This artcile presents an optimisation of performance and cost of neutron
scattering instrumentation at the European Spallation Source. This is done by
trading detailed cost functions against beam transmission functions in a
multi-dimensional, yet simple, parameter space. On the one hand, the neutron
guide cost increases as a power of the desired beam divergence, and inversely
with the minimum wavelength, due to the supermirror coating needed. On the
other hand, the more neutrons are transported to the instrument the greater are
the shielding costs to deal with the gamma rays that result from the eventual
absorption of the neutrons. There are additional factors in that many of the
parameters defining the neutron guide geometry are continuous variables, and
the straightness of the guide increases the transmission of high energy
spallation products, which affect the specifications of particularly heavy
hardware, such as heavy shutters and additional shielding, beam stops etc. Over
the suite of 16 instruments, a maximum potential cost saving is identified in
the vicinity of 20 M\euro \,, with negligible penalties on instrument
performance and bandwidth, by trading minimum neutron wavelength $\lambda$
against total optical costs and shielding costs. Finally, these cost
calculations are shown to be consistent with those at real world, existing
spallation source facilities.


title: Damped vacuum states of light

abstract:
  We consider one-dimensional propagation of quantum light in the presence of a
block of material, with a full account of dispersion and absorption. The
electromagnetic zero-point energy for some frequencies is damped (suppressed)
by the block below the free-space value, while for other frequencies it is
increased. We also calculate the regularized (Casimir) zero-point energy at
each frequency and find that it too is damped below the free-space value (zero)
for some frequencies. The total Casimir energy is positive.


title: M-curves and symmetric products

abstract:
  Let $(X , \sigma)$ be a geometrically irreducible smooth projective M-curve
of genus $g$ defined over the field of real numbers. We prove that the $n$-th
symmetric product of $(X , \sigma)$ is an M-variety for $n=2 ,3$ and $n\geq 2g
-1$.


title:
Oracle Estimation of a Change Point in High Dimensional Quantile
  Regression

abstract:
  In this paper, we consider a high-dimensional quantile regression model where
the sparsity structure may differ between two sub-populations. We develop
$\ell_1$-penalized estimators of both regression coefficients and the threshold
parameter. Our penalized estimators not only select covariates but also
discriminate between a model with homogeneous sparsity and a model with a
change point. As a result, it is not necessary to know or pretest whether the
change point is present, or where it occurs. Our estimator of the change point
achieves an oracle property in the sense that its asymptotic distribution is
the same as if the unknown active sets of regression coefficients were known.
Importantly, we establish this oracle property without a perfect covariate
selection, thereby avoiding the need for the minimum level condition on the
signals of active covariates. Dealing with high-dimensional quantile regression
with an unknown change point calls for a new proof technique since the quantile
loss function is non-smooth and furthermore the corresponding objective
function is non-convex with respect to the change point. The technique
developed in this paper is applicable to a general M-estimation framework with
a change point, which may be of independent interest. The proposed methods are
then illustrated via Monte Carlo experiments and an application to tipping in
the dynamics of racial segregation.


title:
Interference effect between $\phi$ and $\Lambda(1520)$ production
  channels in the $\gamma p \rightarrow K^+K^-p$ reaction near threshold

abstract:
  The $\phi$-$\Lambda(1520)$ interference effect in the $\gamma p\to K^+K^-p$
reaction has been measured for the first time in the energy range from 1.673 to
2.173 GeV. The relative phases between $\phi$ and $\Lambda(1520)$ production
amplitudes were obtained in the kinematic region where the two resonances
overlap. The measurement results support strong constructive interference when
$K^+K^-$ pairs are observed at forward angles, but destructive interference for
proton emission at forward angles. Furthermore, the observed interference
effect does not account for the $\sqrt{s}=2.1$ GeV bump structure in forward
differential cross sections for $\phi$ photoproduction. This fact suggests
possible exotic structures such as a hidden-strangeness pentaquark state, a new
Pomeron exchange and rescattering processes via other hyperon states.


title: Center of the quantum affine vertex algebra in type A

abstract:
  We consider the quantum vertex algebra associated with the double Yangian in
type A as defined by Etingof and Kazhdan. We show that its center is a
commutative associative algebra and construct algebraically independent
families of topological generators of the center at the critical level.


title: Linearly degenerate hierarchies of quasiclassical SDYM type

abstract:
  We demonstrate that SDYM equations for the Lie algebra of one-dimensional
vector fields represent a natural reduction in the framework of general
linearly degenerate dispersionless hierarchy. We define the reduction in terms
of wave functions, introduce generating relation, Lax-Sato equations and the
dressing scheme for the reduced hierarchy. Multidimensional case is also
discussed.


title: A Solution Theory for a General Class of SPDEs

abstract:
  In this article we present a way of treating stochastic partial differential
equations with multiplicative noise by rewriting them as stochastically
perturbed evolutionary equations in the sense of \cite{picardbook}, where a
general solution theory for deterministic evolutionary equations has been
developed. This allows us to present a unified solution theory for a general
class of SPDEs which we believe has great potential for further
generalizations. We will show that many standard stochastic PDEs fit into this
class as well as many other SPDEs such as the stochastic Maxwell equation and
time-fractional stochastic PDEs with multiplicative noise on sub-domains of
$\Rd$. The approach is in spirit similar to the approach in
\cite{dapratozabczyk}, but complementing it in the sense that it does not
involve semi-group theory and allows for an effective treatment of coupled
systems of SPDEs. In particular, the existence of a (regular) fundamental
solution or Green's function is not required.


title:
High pressure structural, electronic, and optical properties of
  polymorphic InVO4 phases

abstract:
  In the present work, we report a detailed density functional theory
calculation on polymorphic InVO$_4$ phases by means of projector augmented wave
method. The computed first-order structural phase transformation from
orthorhombic \emph{(Cmcm)} to monoclinic \emph{(P2/c)} structure is found to
occur around 5.6 GPa along with a large volume collapse of 16.6$\%$, which is
consistent with previously reported experimental data. This transformation also
leads to an increase in the coordination number of vanadium atom from 4 to 6.
The computed equilibrium and high pressure structural properties of both
InVO$_4$ phases, including unit cell parameters, equation of state, and bulk
moduli, are in good agreement with the available experimental data. In
addition, compressibility is found to be highly anisotropic and the
\emph{b}-axis being more compressible than the other for both the structures.
Electronic band structures for both the phases were calculated, and the band
gap for orthorhombic and monoclinic InVO$_4$ are found to be 4.02 and 1.67 eV,
respectively, within the Tran-Blaha Modified Becke-Johnson potential as
implemented in linearized augmented planewave method. We further examined the
optical properties such as dielectric function, refractive index, and
absorption spectra for both the structures. From the implications of these
results, it can be proposed that the high pressure InVO$_4$ phase can be more
useful than orthorhombic phase for photo catalytic applications.


title:
An Extension Theorem for convex functions of class $C^{1,1}$ on Hilbert
  spaces

abstract:
  Let $\mathbb{H}$ be a Hilbert space, $E \subset \mathbb{H}$ be an arbitrary
subset and $f: E \rightarrow \mathbb{R}, \: G: E \rightarrow \mathbb{H}$ be two
functions. We give a necessary and sufficient condition on the pair $(f,G)$ for
the existence of a \textit{convex} function $F\in C^{1,1}(\mathbb{H})$ such
that $F=f$ and $\nabla F =G$ on $E$. We also show that, if this condition is
met, $F$ can be taken so that $\textrm{Lip}(\nabla F) = \textrm{Lip}(G)$. We
give a geometrical application of this result, concerning interpolation of sets
by boundaries of $C^{1,1}$ convex bodies in $\mathbb{H}$. Finally, we give a
counterexample to a related question concerning smooth convex extensions of
smooth convex functions with derivatives which are not uniformly continuous.


title: 3-nets realizing a diassociative loop in a projective plane

abstract:
  A \textit{$3$-net} of order $n$ is a finite incidence structure consisting of
points and three pairwise disjoint classes of lines, each of size $n$, such
that every point incident with two lines from distinct classes is incident with
exactly one line from each of the three classes. The current interest around
$3$-nets (embedded) in a projective plane $PG(2,K)$, defined over a field $K$
of characteristic $p$, arose from algebraic geometry. It is not difficult to
find $3$-nets in $PG(2,K)$ as far as $0<p\le n$. However, only a few infinite
families of $3$-nets in $PG(2,K)$ are known to exist whenever $p=0$, or $p>n$.
Under this condition, the known families are characterized as the only $3$-nets
in $PG(2,K)$ which can be coordinatized by a group. In this paper we deal with
$3$-nets in $PG(2,K)$ which can be coordinatized by a diassociative loop $G$
but not by a group. We prove two structural theorems on $G$. As a corollary, if
$G$ is commutative then every non-trivial element of $G$ has the same order,
and $G$ has exponent $2$ or $3$. We also discuss the existence problem for such
$3$-nets.


title: Precision Measurement of the Radiative $\Beta$ Decay of the Free Neutron

abstract:
  The standard model predicts that, in addition to a proton, an electron, and
an antineutrino, a continuous spectrum of photons is emitted in the $\beta$
decay of the free neutron. We report on the RDK II experiment which measured
the photon spectrum using two different detector arrays. An annular array of
bismuth germanium oxide scintillators detected photons from 14 to 782~keV. The
spectral shape was consistent with theory, and we determined a branching ratio
of 0.00335 $\pm$ 0.00005 [stat] $\pm$ 0.00015 [syst]. A second detector array
of large area avalanche photodiodes directly detected photons from 0.4 to
14~keV. For this array, the spectral shape was consistent with theory, and the
branching ratio was determined to be 0.00582 $\pm$ 0.00023 [stat] $\pm$ 0.00062
[syst]. We report the first precision test of the shape of the photon energy
spectrum from neutron radiative decay and a substantially improved
determination of the branching ratio over a broad range of photon energies.


title:
Caching Incentive Design in Wireless D2D Networks: A Stackelberg Game
  Approach

abstract:
  Caching in wireless device-to-device (D2D) networks can be utilized to
offload data traffic during peak times. However, the design of incentive
mechanisms is challenging due to the heterogeneous preference and selfish
nature of user terminals (UTs). In this paper, we propose an incentive
mechanism in which the base station (BS) rewards those UTs that share contents
with others using D2D communication. We study the cost minimization problem for
the BS and the utility maximization problem for each UT. In particular, the BS
determines the rewarding policy to minimize his total cost, while each UT aims
to maximize his utility by choosing his caching policy. We formulate the
conflict among UTs and the tension between the BS and the UTs as a Stackelberg
game. We show the existence of the equilibrium and propose an iterative
gradient algorithm (IGA) to obtain the Stackelberg Equilibrium. Extensive
simulations are carried out to evaluate the performance of the proposed caching
scheme and comparisons are drawn with several baseline caching schemes with no
incentives. Numerical results show that the caching scheme under our incentive
mechanism outperforms other schemes in terms of the BS serving cost and the
utilities of the UTs.


title: Landau-Zener-St\"uckelberg-Majorana lasing in circuit QED

abstract:
  We demonstrate amplification (and attenuation) of a probe signal by a driven
two-level quantum system in the Landau-Zener-St\"{u}ckelberg-Majorana regime by
means of an experiment, in which a superconducting qubit was strongly coupled
to a microwave cavity, in a conventional arrangement of circuit quantum
electrodynamics. Two different types of flux qubit, specifically a conventional
Josephson junctions qubit and a phase-slip qubit, show similar results, namely,
lasing at the working points where amplification takes place. The experimental
data are explained by the interaction of the probe signal with Rabi-like
oscillations. The latter are created by constructive interference of
Landau-Zener-St\"{u}ckelberg-Majorana (LZSM) transitions during the driving
period of the qubit. A detailed description of the occurrence of these
oscillations and a comparison of obtained data with both analytic and numerical
calculations are given.


title: Polynomial ideals from a nonlinear viewpoint

abstract:
  Classes of homogeneous polynomials between Banach spaces have been studied in
the last three decades from the perspective of the so-called ideal property: if
a polynomial P belongs to a class Q, then the composition u o P o v of P with
linear operators u and v belongs to Q as well. In an attempt to explore the
nonlinearity of the subject in a more consistent way, and taking into account
recent results in the field, in this paper we propose the study of classes of
homogeneous polynomials that are stable under the composition with homogeneous
polynomials. Some importante classes justify the study of the intermediate
concept of classes of polynomials Q such that if P belongs to Q, u is a linear
operator and Q is a homogeneous polynomial, then u o P o Q belongs to Q.


title:
Electrons diffraction scattering on a traveling wave - "Inelastic
  Kapitza-Dirac effect"

abstract:
  In this paper conceptual points regarding electrons elastic (Kapitza-Dirac
effect) and inelastic diffraction effect on the different type slowed
electromagnetic wave structures/light gratings are considered. From the unified
point of view it is analyzed the main works on this subject for last four
decades in chronological order, pointing out the essential peculiarity inherent
in induced Cherenkov, Compton, and undulator/wiggler processes too. This review
article has also a goal to resolve confusion in scientific literature connected
with the recently appeared paper [6] relating the electrons diffraction on a
traveling wave in a dielectric medium.


title: Class of exact memory-kernel master equations

abstract:
  A well-known situation in which a non-Markovian dynamics of an open quantum
system $S$ arises is when this is coherently coupled to an auxiliary system $M$
in contact with a Markovian bath. In such cases, while the joint dynamics of
$S$-$M$ is Markovian and obeys a standard (bipartite) Lindblad-type master
equation (ME), this is in general not true for the reduced dynamics of $S$.
Furthermore, there are several instances (\eg the dissipative Jaynes-Cummings
model) in which a {\it closed} ME for the $S$'s state {\it cannot} even be
worked out. Here, we find a class of bipartite Lindblad-type MEs such that the
reduced ME of $S$ can be derived exactly and in a closed form for any initial
product state of $S$-$M$. We provide a detailed microscopic derivation of our
result in terms of a mapping between two collision models


title: Polarization angle swings in blazars: The case of 3C 279

abstract:
  Over the past few years, several occasions of large, continuous rotations of
the electric vector position angle (EVPA) of linearly polarized optical
emission from blazars have been reported. These events are often coincident
with high energy gamma-ray flares and they have attracted considerable
attention, as they could allow one to probe the magnetic field structure in the
gamma-ray emitting region of the jet. The flat-spectrum radio quasar 3C279 is
one of the most prominent examples showing this behaviour. Our goal is to study
the observed EVPA rotations and to distinguish between a stochastic and a
deterministic origin of the polarization variability. We have combined multiple
data sets of R-band photometry and optical polarimetry measurements of 3C279,
yielding exceptionally well-sampled flux density and polarization curves that
cover a period of 2008-2012. Several large EVPA rotations are identified in the
data. We introduce a quantitative measure for the EVPA curve smoothness, which
is then used to test a set of simple random walk polarization variability
models against the data. 3C279 shows different polarization variation
characteristics during an optical low-flux state and a flaring state. The
polarization variation during the flaring state, especially the smooth approx.
360 degrees rotation of the EVPA in mid-2011, is not consistent with the tested
stochastic processes. We conclude that during the two different optical flux
states, two different processes govern the polarization variation, possibly a
stochastic process during the low-brightness state and a deterministic process
during the flaring activity.


title: Dopant-controlled single-electron pumping through a metallic island

abstract:
  We investigate a hybrid metallic island / single dopant electron pump based
on fully-depleted silicon on insulator technology. Electron transfer between
the central metallic island and the leads is controlled by resonant tunneling
through single phosphorus dopants in the barriers. Top gates above the barriers
are used control the resonance conditions. Applying radio frequency signals to
the gates, non-adiabatic quantized electron pumping is achieved. A simple
deterministic model is presented and confirmed by comparing measurements with
simulations.


title:
An Introduction to L\'evy and Feller Processes. Advanced Courses in
  Mathematics - CRM Barcelona 2014

abstract:
  These lecture notes are an extended version of my lectures on L\'evy and
L\'evy-type (Feller) processes given at the "Second Barcelona Summer School on
Stochastic Analysis" 2014 organized by the Centre de Recerca Matemaatica (CRM).
The lectures are aimed at advanced graduate and PhD students. In order to read
these notes, one should have sound knowledge of measure theoretic probability
theory and some background in stochastic processes, as it is covered in my
books "Measures, Integals and Martingales" (Cambridge University Press) and
"Brownian Motion" (de Gruyter).
  My purpose in these lectures is to give an introduction to Levy processes,
and to show how one can extend this approach to space inhomogeneous processes
which behave locally like L\'evy processes: L\'evy-type or Feller processes.
  These course notes will be published, together Davar Khoshnevisan's notes on
"Invariance and Comparison Principles for Parabolic SPDEs" as "From L\'evy-Type
Processes to Parabolic SPDEs" by the CRM, Barcelona and Birk\"auser, Cham 2017
(ISBN: 978-3-319-34119-4). The arXiv-version and the published version may
differ in layout, pagination and wording, but not in content


title:
Exact density profiles and symmetry classification for strongly
  interacting multi-component Fermi gases in tight waveguides

abstract:
  We consider a mixture of one-dimensional strongly interacting Fermi gases up
to six components, subjected to a longitudinal harmonic confinement. In the
limit of infinitely strong repulsions we provide an exact solution which
generalizes the one for the two-component mixture. We show that an imbalanced
mixture under harmonic confinement displays partial spatial separation among
the components, with a structure which depends on the relative population of
the various components. Furthermore, we provide a symmetry characterization of
the ground and excited states of the mixture introducing and evaluating a
suitable operator, namely the conjugacy class sum. We show that, even under
external confinement, the gas has a definite symmetry which corresponds to the
most symmetric one compatible with the imbalance among the components. This
generalizes the predictions of the Lieb-Mattis theorem for a fermionic mixture
with more than two components.


title: Magnetic properties of Fe$_5$SiB$_2$ and its alloys with P, S, and Co

abstract:
  Fe$_5$SiB$_2$ has been synthesized and magnetic measurements have been
carried out, revealing that M$_{\text{sat}}$ = 0.92 MA/m at T = 300 K. The M vs
T curve shows a broad peak around T = 160 K. The anisotropy constant, K$_1$,
estimated at T = 300 K, is 0.25 MJ/m$^3$. Theoretical analysis of Fe$_5$SiB$_2$
system has been carried out and extended to the full range of
Fe$_5$Si$_{1-x}$P$_x$B$_2$, Fe$_5$P$_{1-x}$S$_x$B$_2$, and
(Fe$_{1-x}$Co$_x$)$_5$SiB$_2$ compositions. The electronic band structures have
been calculated using the Full-Potential Local-Orbital Minimum-Basis Scheme
(FPLO-14). The calculated total magnetic moments are 9.20, 9.15, 9.59 and
2.42$\mu_B$ per formula units of Fe$_5$SiB$_2$, Fe$_5$PB$_2$, Fe$_5$SB$_2$, and
Co$_5$SiB$_2$, respectively. In agreement with experiment, magnetocrystalline
anisotropy energies (MAE's) calculated for T = 0 K changes from a negative
(easy-plane) anisotropy -0.28 MJ/m$^3$ for Fe$_5$SiB$_2$ to the positive
(easy-axis) anisotropy 0.35 MJ/m$^3$ for Fe$_5$PB$_2$. Further increase of the
number of p-electrons in Fe$_5$P$_{1-x}$S$_x$B$_2$ leads to an increase of MAE
up to 0.77 MJ/m$^3$ for the hypothetical Fe$_5$P$_{0.4}$S$_{0.6}$B$_2$
composition. Volume variation and fixed spin moment calculations (FSM)
performed for Fe$_5$SiB$_2$ show an inverse relation between MAE and magnetic
moment in the region down to about 15\% reduction of the spin moment. The
alloying of Fe$_5$SiB$_2$ with Co is proposed as a practical realization of
magnetic moment reduction, which ought to increase MAE. MAE calculated in
virtual crystal approximation (VCA) for a full range of
(Fe$_{1-x}$Co$_x$)$_5$SiB$_2$ compositions reaches the maximum value of 1.16
MJ/m$^3$ at Co concentration x = 0.3, with the magnetic moment 7.75$\mu_B$ per
formula unit. Thus, (Fe$_{0.7}$Co$_{0.3}$)$_5$SiB$_2$ is suggested as a
candidate for a rare-earth free permanent magnet.


title: On the hardness of switching to a small number of edges

abstract:
  Seidel's switching is a graph operation which makes a given vertex adjacent
to precisely those vertices to which it was non-adjacent before, while keeping
the rest of the graph unchanged. Two graphs are called switching-equivalent if
one can be made isomorphic to the other one by a sequence of switches.
  Jel\'inkov\'a et al. [DMTCS 13, no. 2, 2011] presented a proof that it is
NP-complete to decide if the input graph can be switched to contain at most a
given number of edges. There turns out to be a flaw in their proof. We present
a correct proof.
  Furthermore, we prove that the problem remains NP-complete even when
restricted to graphs whose density is bounded from above by an arbitrary fixed
constant. This partially answers a question of Matou\v{s}ek and Wagner
[Discrete Comput. Geom. 52, no. 1, 2014].


title: Revisiting the R$\nu$MDM Models

abstract:
  Combining neutrino mass generation and a dark matter candidate in a unified
model has always been intriguing. We revisit the class of R$\nu$MDM models,
which incorporate minimal dark matter in radiative neutrino mass models based
on the one-loop ultraviolet completions of the Weinberg operator. The
possibility of an exact accidental $Z_2$ is completely ruled out in this
scenario. We study the phenomenology of one of the models with an approximate
$Z_2$ symmetry. In addition to the Standard Model particles, it contains two
real scalar quintuplets, one vector- like quadruplet fermion and a fermionic
quintuplet. The neutral component of the fermionic quintuplet serves as a good
dark matter candidate which can be tested by the future direct and indirect
detection experiments. The constraints from flavor physics and
electroweak-scale naturalness are also discussed.


title:
Ordering phenomena in a heterostructure of frustrated and unfrustrated
  triangular-lattice Ising layers

abstract:
  We study critical and magnetic properties of a bilayer Ising system
consisting of two triangular planes A and B, with the antiferromagnetic (AF)
coupling $J_{\rm A}$ and the ferromagnetic (FM) one $J_{\rm B}$ for the
respective layers, which are coupled by the interlayer interaction $J_{\rm AB}$
by using Monte Carlo simulations. When $J_{\rm A}$ and $J_{\rm B}$ are of the
same order, the unfrustrated FM plane orders first at a high temperature
$T_{c1} \sim J_{\rm B}$. The spontaneous FM order then exerts influence on the
other frustrated AF plane as an effective magnetic field, which subsequently
induces a ferrimagnetic order in this plane at low temperatures below $T_{c2}$.
When short-range order is developed in the AF plane while the influence of the
FM plane is still small, there appears a preemptive
Berezinskii-Kosterlitz-Thouless-like pseudocritical crossover regime just above
the ferrimagnetic phase transition point, where the short-distance behavior up
to a rather large length scale exponentially diverging in $\propto \JA / T$ is
controlled by a line of Gaussian fixed points at $T = 0$. In the crossover
region, a continuous variation in the effective critical exponent $4/9 \lesssim
\eta^{\rm eff} \lesssim 1/2$ is observed. The phase diagram by changing the
ratio $J_{\rm A}/J_{\rm B}$ is also investigated.


title:
On the effect of wear on asperity heigth distributions, and the
  corresponding effect in the mechanical response

abstract:
  Since the time of the original Greenwood & Williamson paper, it was noticed
that abrasion and wear lead to possibly bimodal distribution of asperity height
distribution, with the upper tail of asperities following from the
characteristics of the process. Using a limit case solution due to Borucki for
the wear of an originally Gaussian distribution, it is shown here that the tail
is indeed always Gaussian, but with different equivalent parameters. Therefore,
if the wear process is light, one obtains a bimodal distribution and both may
affect the resulting contact mechanics behaviour. In this short note, we
illustrate just the main features of the problem. We conclude that it is an
oversimplification to consider surfaces Gaussian.


title:
Giant spin Nernst effect induced by resonant scattering at surfaces of
  metallic films

abstract:
  A new concept realizing giant spin Nernst effect in nonmagnetic metallic
films is introduced. It is based on the idea of engineering an asymmetric
energy dependence of the longitudinal and transverse electrical conductivities,
as well as a pronounced energy dependence of the spin Hall angle in the
vicinity of the Fermi level by the resonant impurity states at the Fermi level.
We employ an analytical model and demonstrate the emergence of a giant spin
Nernst effect in Ag(111) films using {\it ab-initio} calculations combined with
the Boltzmann approach for transport properties arising from skew scattering
off impurities.


title:
$L^p\ (p>1)$ solutions of BSDEs with generators satisfying some
  non-uniform conditions in $t$ and $\omega$

abstract:
  This paper is devoted to the $L^p$ ($p>1$) solutions of one-dimensional
backward stochastic differential equations (BSDEs for short) with general time
intervals and generators satisfying some non-uniform conditions in $t$ and
$\omega$. An existence and uniqueness result, a comparison theorem and an
existence result for the minimal solutions are respectively obtained, which
considerably improve some known works. Some classical techniques used to deal
with the existence and uniqueness of $L^p$ ($p>1$) solutions of BSDEs with
Lipschitz or linear-growth generators are also developed in this paper.


title:
Event Search and Analytics: Detecting Events in Semantically Annotated
  Corpora for Search and Analytics

abstract:
  In this article, I present the questions that I seek to answer in my PhD
research. I posit to analyze natural language text with the help of semantic
annotations and mine important events for navigating large text corpora.
Semantic annotations such as named entities, geographic locations, and temporal
expressions can help us mine events from the given corpora. These events thus
provide us with useful means to discover the locked knowledge in them. I pose
three problems that can help unlock this knowledge vault in semantically
annotated text corpora: i. identifying important events; ii. semantic search;
and iii. event analytics.


title:
\textit{Ab initio} study of reactive collisions between Rb($^{2}S$) or
  Rb($^{2}P$) and OH$^{-}$($^{1}\Sigma^{+}$)

abstract:
  A theoretical rate constant for the associative detachment reaction
Rb($^{2}S$)$+$OH$^{-}$($^{1}\Sigma^{+}$)$\rightarrow \,$
RbOH($^{1}\Sigma^{+}$)$+\,e^{-}$ of 4$\,\times$10$^{-10}$cm$^{3}$s$^{-1}$ at
300 K has been calculated. This result agrees with the experimental rate
constant of 2$^{+2}_{-1}\,\times10^{-10}$cm$^{3}$s$^{-1}$ obtained by Deiglmayr
\textit{et al.} (Phys. Rev. A 86, 2012) for a temperature between 200 K and 600
K. A Langevin-based dynamics which depends on the crossing point between the
anion (RbOH$^{-}$) and neutral (RbOH) potential energy surfaces has been used.
The calculation were performed using the ECP28MDF effective core potential to
describe the rubidium atom at the CCSD(T) level of theory and extended basis
sets. The effect of ECPs and basis set on the height of the crossing point, and
hence the rate constant, has been investigated. The temperature dependence of
the latter is also discussed. Preliminary work on the potential energy surface
for the excited reaction channel Rb($^{2}P$)+OH$^{-}$($^{1}\Sigma^{+}$)
calculated at the CASSF-icMRCI level of theory is shown. We qualitatively
discuss the charge transfer and associative detachment reactions arising from
this excited entrance channel.


title:
Selecting M-giants with infra-red photometry: Distances, metallicities
  and the Sagittarius stream

abstract:
  Using a spectroscopically confirmed sample of M-giants, M-dwarfs and quasars
from the LAMOST survey, we assess how well WISE $\&$ 2MASS color-cuts can be
used to select M-giant stars. The WISE bands are very efficient at separating
M-giants from M-dwarfs and we present a simple classification that can produce
a clean and relatively complete sample of M-giants. We derive a new photometric
relation to estimate the metallicity for M-giants, calibrated using data from
the APOGEE survey. We find a strong correlation between the $(W1-W2)$ color and
$\rm [M/H]$, where almost all of the scatter is due to photometric
uncertainties. We show that previous photometric distance relations, which are
mostly based on stellar models, may be biased and devise a new empirical
distance relation, investigating trends with metallicity and star formation
history. Given these relations, we investigate the properties of M-giants in
the Sagittarius stream. The offset in the orbital plane between the leading and
trailing tails is reproduced and, by identifying distant M-giants in the
direction of the Galactic anti-center, we confirm that the previously detected
debris in the outer halo is the apocenter of the trailing tail. We also find
tentative evidence supporting an existing overdensity near the leading tail in
the Northern Galactic hemisphere, possibly an extension to the trailing tail
(so-called Branch C). We have measured the metallicity distribution along the
stream, finding a clear metallicity offset between the leading and trailing
tails, in agreement with models for the stream formation. We include an online
table of M-giants to facilitate further studies.


title:
Calibration of Radio Interferometers Using a Sparse DoA Estimation
  Framework

abstract:
  The calibration of modern radio interferometers is a significant challenge,
specifically at low frequencies. In this perspective, we propose a novel
iterative calibration algorithm, which employs the popular sparse
representation framework, in the regime where the propagation conditions shift
dissimilarly the directions of the sources. More precisely, our algorithm is
designed to estimate the apparent directions of the calibration sources, their
powers, the directional and undirectional complex gains of the array elements
and their noise powers, with a reasonable computational complexity. Numerical
simulations reveal that the proposed scheme is statistically efficient at low
SNR and even with additional non-calibration sources at unknown directions.


title:
Improved 2D Intelligent Driver Model simulating synchronized flow and
  evolution concavity in traffic flow

abstract:
  This paper firstly show that 2 Dimensional Intelligent Driver Model (Jiang et
al., PloS one, 9(4), e94351, 2014) is not able to replicate the synchronized
traffic flow. Then we propose an improved model by considering the difference
between the driving behaviors at high speeds and that at low speeds.
Simulations show that the improved model can reproduce the phase transition
from synchronized flow to wide moving jams, the spatiotemporal patterns of
traffic flow induced by traffic bottleneck, and the evolution concavity of
traffic oscillations (i.e. the standard deviation of the velocities of vehicles
increases in a concave/linear way along the platoon). Validating results show
that the empirical time series of traffic speed obtained from Floating Car Data
can be well simulated as well.