title: Strong Ramsey Games: Drawing on an infinite board

abstract:
  We consider the strong Ramsey-type game $\mathcal{R}^{(k)}(\mathcal{H},
\aleph_0)$, played on the edge set of the infinite complete $k$-uniform
hypergraph $K^k_{\mathbb{N}}$. Two players, called FP (the first player) and SP
(the second player), take turns claiming edges of $K^k_{\mathbb{N}}$ with the
goal of building a copy of some finite predetermined $k$-uniform hypergraph
$\mathcal{H}$. The first player to build a copy of $\mathcal{H}$ wins. If no
player has a strategy to ensure his win in finitely many moves, then the game
is declared a draw.
  In this paper, we construct a $5$-uniform hypergraph $\mathcal{H}$ such that
$\mathcal{R}^{(5)}(\mathcal{H}, \aleph_0)$ is a draw. This is in stark contrast
to the corresponding finite game $\mathcal{R}^{(5)}(\mathcal{H}, n)$, played on
the edge set of $K^5_n$. Indeed, using a classical game-theoretic argument
known as \emph{strategy stealing} and a Ramsey-type argument, one can show that
for every $k$-uniform hypergraph $\mathcal{G}$, there exists an integer $n_0$
such that FP has a winning strategy for $\mathcal{R}^{(k)}(\mathcal{G}, n)$ for
every $n \geq n_0$.


title: A Higher Order Equilibrium Finite Element Method

abstract:
  In this paper a mixed spectral element formulation is presented for planar,
linear elasticity. The degrees of freedom for the stress are integrated
traction components, i.e. surface force components. As a result the tractions
between elements are continuous. The formulation is based on minimization of
the complementary energy subject to the constraints that the stress field
should satisfy equilibrium of forces and moments. The Lagrange multiplier which
enforces equilibrium of forces is the displacement field and the Lagrange
multiplier which enforces equilibrium of moments is the rotation. The
formulation satisfies equilibrium of forces pointwise if the body forces are
piecewise polynomial. Equilibrium of moments is weakly satisfied. Results of
the method are given on orthogonal and curvilinear domains and an example with
a point singularity is given.


title: CV-MDI Quantum Key Distribution via Satellite

abstract:
  In this work we analyze a measurement-device-independent (MDI) protocol to
establish continuous-variable (CV) quantum key distribution (QKD) between two
ground stations. We assume communication occurs between the ground stations via
satellite over two independent atmospheric-fading channels dominated by
turbulence-induced beam wander. In this MDI protocol the measurement device is
the satellite itself, and the security of the protocol is analyzed through an
equivalent entanglement-based swapping scheme. We quantify the positive impact
the fading channels can have on the final quantum key rates, demonstrating how
the protocol is able to generate a positive key rate even over high-loss
atmospheric channels. This is somewhat counter-intuitive given that the same
outcome is only possible in the low-loss regime for a measurement device
centrally positioned in a fiber-optic channel. Our results show that useful
space-based quantum key generation rates between two ground stations are
possible even when the relay satellite is held by an adversary. The cost in key
rate incurred by altering the status of the satellite from trustworthy to
untrustworthy is presented.


title:
Joint remote preparation of an arbitrary four-qubit |\c{hi}>-type
  entangled state

abstract:
  We present two schemes for joint remote preparation of an arbitrary
four-qubit j\c{hi}i -type entangled state via three three- and (N+1)-qubit GHZ
states as the quantum channel, respectively. In these schemes, two senders (or
N senders) share the original state which they wish to help the receiver to
remotely prepare. To complete the JRSP schemes, several novel sets of mutually
orthogonal basis vectors are introduced. It is shown that, only if two senders
(or N senders) collaborate with each other, and perform projective measurements
under suitable measuring basis on their own qubits respectively, the receiver
can reconstruct the original state by means of some appropriate unitary
operations and suitable C-NOT gates. Compared with the previous schemes for the
JRSP of four-qubit |\c{hi}>-type state, the advantages of the present schemes
are that the total successful probability of JRSP can reach 1 and the
entanglement resource can be reduced


title: Is the GW150914-GBM really associated with the GW150914?

abstract:
  Finding the electromagnetic (EM) counterpart is critically important for a
gravitational wave event. Although many efforts have been made to search for
the purported EM counterpart of GW150914, the first gravitational wave event
detected by LIGO, only Fermi/GBM reported an excess above background (i.e.
GW150914-GBM) at 0.4 s after the LIGO trigger time, that is possibly associated
with this GW event (Connaughton et al. 2016). However, since there is no
significant detection by the INTEGRAL/SPI-ACS around the time of GW150914-GBM,
a great debate has been raised about whether GW150914-GBM is of astrophysical
origin and associated with the GW150914 (Savchenko et al. 2016). In order to
answer this question, we re-analyzed the GBM data with a straightforward but
sophisticated method. We find that the excess of GW150914-GBM mostly comes from
those detectors with bad viewing angles to the GW event, whereas the good
viewing detectors see nothing significant beyond background fluctuation around
the trigger time of GW150914. This finding suggests that GW150914-GBM is very
unlikely associated with the GW150914. Given that GW150914-GBM is the only
event found by GBM that is possibly associated with this GW event in a
comprehensive search, we conclude that GBM did not detect any electromagnetic
radiation from the GW150914.


title: The Bees Algorithm for the Vehicle Routing Problem

abstract:
  In this thesis we present a new algorithm for the Vehicle Routing Problem
called the Enhanced Bees Algorithm. It is adapted from a fairly recent
algorithm, the Bees Algorithm, which was developed for continuous optimisation
problems. We show that the results obtained by the Enhanced Bees Algorithm are
competitive with the best meta-heuristics available for the Vehicle Routing
Problem (within 0.5% of the optimal solution for common benchmark problems). We
show that the algorithm has good runtime performance, producing results within
2% of the optimal solution within 60 seconds, making it suitable for use within
real world dispatch scenarios.


title:
Holonomic quantum computation in the ultrastrong-coupling regime of
  circuit QED

abstract:
  We present an experimentally feasible scheme to implement holonomic quantum
computation in the ultrastrong-coupling regime of light-matter interaction. The
large anharmonicity and the Z2 symmetry of the quantum Rabi model allow us to
build an effective three-level {\Lambda}-structured artificial atom for quantum
computation. The proposed physical implementation includes two gradiometric
flux qubits and two microwave resonators where single-qubit gates are realized
by a two-tone driving on one physical qubit, and a two-qubit gate is achieved
with a time-dependent coupling between the field quadratures of both
resonators. Our work paves the way for scalable holonomic quantum computation
in ultrastrongly coupled systems.


title:
Separating Electroweak and Strong interactions in Drell-Yan processes at
  LHC: leptons angular distributions and reference frames

abstract:
  Among the physics goals of LHC experiments, precision tests of the Standard
Model in the Strong and Electroweak sectors play an important role. Because of
nature of the proton-proton processes, observables based on the measurement of
the direction and energy of leptons provide the most precise signatures. In the
present paper, we concentrate on the angular distribution of Drell-Yan process
leptons, in the lepton-pair rest-frame. The vector nature of the intermediate
state imposes that distributions are to a good precision described by spherical
polynomials of at most second order.
  We show that with the proper choice of the coordinate frames, only one
coefficient in this polynomial decomposition remains sizable, even in the
presence of one or two high $p_T$ jets. The necessary stochastic choice of the
frames relies on probabilities independent from any coupling constants.
  This remains true when one or two partons accompany the lepton pairs. In this
way electroweak effects can be better separated from strong interaction ones
for the benefit of the interpretation of the measurements.
  Our study exploits properties of single gluon emission matrix elements which
are clearly visible if a conveniently chosen form of their representation is
used. We rely also on distributions obtained from matrix element based Monte
Carlo generated samples of events with two leptons and up to two additional
partons in test samples. Incoming colliding protons' partons are distributed
accordingly to PDFs and are strictly collinear to the corresponding beams.


title:
Semiclassical dynamics of Dirac and Weyl particles in rotating
  coordinates

abstract:
  The semiclassical kinetic theory of Dirac particles in the presence of
external electromagnetic fields and global rotation is established. To provide
the Hamiltonian formulation of Dirac particles a symplectic two-form which is a
matrix in spin indices is proposed. The particle number and current densities
for the Dirac particles are acquired in the helicity basis. Following a similar
procedure, semiclassical kinetic theory of the Weyl particles is accomplished.
It is shown that the phase-space dynamics of the Weyl and Dirac particles is
directly linked. The anomalous chiral effects due to the external
electromagnetic fields and angular velocity of the frame are calculated.

categories: hep-th cond-mat.mes-hall math-ph math.MP


title:
Approximation by complex Szasz-Durrmeyer-Chlodowsky operators in compact
  disks

abstract:
  In the present article, we deal with the overconvergence of the
Sz?asz-Durrmeyer-Chlodowsky operators. Here we study the approximation
properties e.g. upper estimates, Voronovskaja type result for these operators
attached to analytic functions in compact disks. Also, we discuss the exact
order in simultaneous approximation by these operators and its derivatives and
the asymptotic result with quantitative upper estimate. In such a way, we put
in evidence the overconvergence phenomenon for the Sz?asz-Durrmeyer-Chlodowsky
operators, namely the extensions of approximation properties with exact
quantitative estimates and orders of these convergencies to sets in the complex
plane that contain the interval [0,\infty).


title:
Line-depth-ratio temperatures for the close binary nu Octantis: new
  evidence supporting the conjectured retrograde planet

abstract:
  We explore the possibly that either star-spots or pulsations are the cause of
a periodic radial-velocity signal (P~400 days) from the K-giant binary nu
Octantis (P~1050 days, e~0.25), alternatively conjectured to have a retrograde
planet. Our study is based on temperatures derived from 22 line-depth ratios
(LDRs) for nu Oct and twenty calibration stars. Empirical evidence and
stability modelling provide unexpected support for the planet since other
standard explanations (star-spots, pulsations and additional stellar masses)
each have credibility problems. However, the proposed system presents
formidable challenges to planet-formation and stability theories: it has by far
the smallest stellar separation of any claimed planet-harbouring binary
(a_bin~2.6 au) and an equally unbelievable separation ratio (a_pl/a_bin~0.5),
hence the necessity that the circumstellar orbit be retrograde.
  The LDR analysis of 215 nu Oct spectra acquired between 2001--2007, from
which the RV perturbation was first revealed, have no significant periodicity
at any frequency. The LDRs recover the original 21 stellar temperatures with an
average accuracy of 45+/-25 K. The 215 nu Oct temperatures have a standard
deviation of only 4.2 K. Assuming the host primary is not pulsating, the
temperatures converted to magnitude differences strikingly mimic the very
stable photometric Hipparcos observations 15 years previously, implying the
long-term stability of the star and demonstrating a novel use of LDRs as a
photometric gauge. Our results provide substantial new evidence that
conventional star-spots and pulsations are unlikely causes of the RV
perturbation. The controversial system deserves continued attention, including
with higher resolving-power spectra for bisector and LDR analyses.


title:
Computing the variance of a conditional expectation via non-nested Monte
  Carlo

abstract:
  Computing the variance of a conditional expectation has often been of
importance in uncertainty quantification. Sun et al. has introduced an unbiased
nested Monte Carlo estimator, which they call $1\frac{1}{2}$-level simulation
since the optimal inner-level sample size is bounded as the computational
budget increases. In this letter we construct unbiased non-nested Monte Carlo
estimators based on the so-called pick-freeze scheme due to Sobol'. An
extension of our approach to compute higher order moments of a conditional
expectation is also discussed.


title:
Comment on "Solution of the $\alpha$-Potential Mystery in the $\gamma$
  Process and Its Impact on the Nd/Sm Ratio in Meteorites"

abstract:
  A competition of the low-energy Coulomb excitation (CE) with the compound
nucleus (CN) formation in $\alpha$-induced reactions below the Coulomb barrier
has been assumed by Rauscher [Phys. Rev. Lett. 111, 061104 (2013)] in order to
use the same optical model (OM) potential for description of the latter and the
alpha-particle emission as well. In this Comment we show that the corresponding
partial waves and integration radii provide evidence for the distinct account
of the CE cross section and OM total-reaction cross section.


title:
Hydrogen molecular ions for improved determination of fundamental
  constants

abstract:
  The possible use of high-resolution rovibrational spectroscopy of the
hydrogen molecular ions H + 2 and HD + for an independent determination of
several fundamental constants is analyzed. While these molecules had been
proposed for metrology of nuclear-to-electron mass ratios, we show that they
are also sensitive to the radii of the proton and deuteron and to the Rydberg
constant at the level of the current discrepancies colloquially known as the
proton size puzzle. The required level of accuracy, in the 10 --12 range, can
be reached both by experiments, using Doppler-free two-photon spectroscopy
schemes, and by theoretical predictions. It is shown how the measurement of
several well-chosen rovibrational transitions may shed new light on the
proton-radius puzzle, provide an alternative accurate determination of the
Rydberg constant, and yield new values of the proton-to-electron and
deuteron-to-proton mass ratios with one order of magnitude higher precision.


title: A Kam Theorem for Space-Multidimensional Hamiltonian PDE

abstract:
  We present an abstract KAM theorem, adapted to space-multidimensional
hamiltonian PDEs with smoothing non-linearities. The main novelties of this
theorem are that: $\bullet$ the integrable part of the hamiltonian may contain
a hyperbolic part and as a consequence the constructed invariant tori may be
unstable. $\bullet$ It applies to singular perturbation problem. In this paper
we state the KAM-theorem and comment on it, give the main ingredients of the
proof, and present three applications of the theorem .


title: On Koszulity of Finite Posets

abstract:
  We prove in a unifying way several equivalent descriptions of Koszul rings,
some of which being well known in the literature. Most of them are stated in
terms of coring theoretical properties of $\Tor_n^A(R,R)$. As an application of
these characterizations we investigate the Koszulity of the incidence rings for
finite graded posets. Based on these results, we describe an algorithm to
produce new classes of Koszul posets (i.e. graded posets whose incidence rings
are Koszul). Specific examples of Koszul posets are included.


title:
Neutron depolarization imaging of the hydrostatic pressure dependence of
  inhomogeneous ferromagnets

abstract:
  The investigation of fragile and potentially inhomogeneous forms of
ferromagnetic order under extreme conditions, such as low temperatures and high
pressures, is of central interest for areas such as geophysics, correlated
electron systems, as well as the optimization of materials synthesis for
applications where particular material properties are required. We report
neutron depolarization imaging measurements on the weak ferromagnet Ni$_3$Al
under pressures up to 10kbar using a Cu:Be clamp cell. Using a polychromatic
neutron beam with wavelengths $\lambda\geq$ 4\AA in combination with $^3$He
neutron spin filter cells as polarizer and analyzer we were able to track
differences of the pressure response in inhomogeneous samples by virtue of high
resolution neutron depolarization imaging. This provides spatially resolved and
non-destructive access to the pressure dependence of the magnetic properties of
inhomogeneous ferromagnetic materials.


title: Non-equilibrium quantum mechanics: A 'hot quantum soup' of paramagnons

abstract:
  Motivated by recent measurements of the lifetime (decay width) of paramagnons
in quantum antiferromagnet TlCuCl3, we investigate paramagnon decay in a heat
bath and formulate an appropriate quantum theory. Our formulation can be split
into two regimes: (i) a non-perturbative, 'hot quantum soup' regime where
paramagnon width is comparable to its energy; (ii) usual perturbative regime
where paramagnon width is significantly lower than its energy. Close to the
Neel tempera- ture the paramagnon width becomes comparable to its energy and
falls into the hot quantum soup regime. To describe this regime we develop a
new finite frequency, finite temperature technique for a nonlinear quantum
field theory; the 'golden rule of quantum kinetics'. The formulation is generic
and applicable to any three dimensional quantum antiferromagnet in the vicinity
of a quantum critical point. Specifically we apply our results to TlCuCl3 and
find agreement with experimental data. Additionally, we show that logarithmic
running of the coupling constant in the upper critical dimension changes the
commonly accepted picture of the quantum disordered and quantum critical
regimes.


title:
Heat-Treatment-Induced Switching of Magnetic States in the Doped Polar
  Semiconductor Ge$_{1-x}$Mn$_x$Te

abstract:
  Cross-control of a material property - manipulation of a physical quantity
(e.g., magnetisation) by a nonconjugate field (e.g., electrical field) - is a
challenge in fundamental science and also important for technological device
applications. It has been demonstrated that magnetic properties can be
controlled by electrical and optical stimuli in various magnets. Here we find
that heat-treatment allows the control over two competing magnetic phases in
the Mn-doped polar semiconductor GeTe. The onset temperatures $T_{\rm c}$ of
ferromagnetism vary at low Mn concentrations by a factor of five to six with a
maximum $T_{\rm c} \approx 180$ K, depending on the selected phase. Analyses in
terms of synchrotron x-ray diffraction and energy dispersive x-ray spectroscopy
indicate a possible segregation of the Mn ions, which is responsible for the
high-$T_{\rm c}$ phase. More importantly, we demonstrate that the two states
can be switched back and forth repeatedly from either phase by changing the
heat-treatment of a sample, thereby confirming magnetic phase-change- memory
functionality.


title: Dual Local-Global Contextual Pathways for Recognition in Aerial Imagery

abstract:
  Visual context is important in object recognition and it is still an open
problem in computer vision. Along with the advent of deep convolutional neural
networks (CNN), using contextual information with such systems starts to
receive attention in the literature. At the same time, aerial imagery is
gaining momentum. While advances in deep learning make good progress in aerial
image analysis, this problem still poses many great challenges. Aerial images
are often taken under poor lighting conditions and contain low resolution
objects, many times occluded by trees or taller buildings. In this domain, in
particular, visual context could be of great help, but there are still very few
papers that consider context in aerial image understanding. Here we introduce
context as a complementary way of recognizing objects. We propose a dual-stream
deep neural network model that processes information along two independent
pathways, one for local and another for global visual reasoning. The two are
later combined in the final layers of processing. Our model learns to combine
local object appearance as well as information from the larger scene at the
same time and in a complementary way, such that together they form a powerful
classifier. We test our dual-stream network on the task of segmentation of
buildings and roads in aerial images and obtain state-of-the-art results on the
Massachusetts Buildings Dataset. We also introduce two new datasets, for
buildings and road segmentation, respectively, and study the relative
importance of local appearance vs. the larger scene, as well as their
performance in combination. While our local-global model could also be useful
in general recognition tasks, we clearly demonstrate the effectiveness of
visual context in conjunction with deep nets for aerial image understanding.


title: Groups in which Squares and Cubes Commute

abstract:
  If for all $a, b$ in a group $G$, we have that $a^2b^2 = b^2a^2$ and $a^3b^3
= b^3a^3$ then does the group necessarily have to be abelian? This paper shows
that the answer is affirmative for finite groups as well as certain classes of
infinite groups. In general we show that if $G$ is an infinite group in which
squares commute and cubes commute then the set of torsion elements of $G$
denoted by $T(G)$ has to be an abelian normal subgroup of $G$.


title:
Structural and magnetic properties of FeMn$_x$ ($x=$1...6) chains
  supported on Cu$_2$N / Cu (100)

abstract:
  Heterogeneous atomic magnetic chains are built by atom manipulation on a
Cu$_2$N/Cu (100) substrate. Their magnetic properties are studied and
rationalized by a combined scanning tunneling microscopy (STM) and density
functional theory (DFT) work completed by model Hamiltonian studies. The chains
are built using Fe and Mn atoms ontop of the Cu atoms along the N rows of the
Cu$_2$N surface. Here, we present results for FeMn$_x$ ($x$=1...6) chains
emphasizing the evolution of the geometrical, electronic, and magnetic
properties with chain size. By fitting our results to a Heisenberg Hamiltonian
we have studied the exchange-coupling matrix elements $J$ for different chains.
For the shorter chains, $x \leq 2$, we have included spin-orbit effects in the
DFT calculations, extracting the magnetic anisotropy energy. Our results are
also fitted to a simple anisotropic spin Hamiltonian and we have extracted
values for the longitudinal-anisotropy $D$ and transversal-anisotropy $E$
constants. These parameters together with the values for $J$ allow us to
compute the magnetic excitation energies of the system and to compare them with
the experimental data.


title: A new population of terrestrial gamma-ray flashes in the RHESSI data

abstract:
  Terrestrial gamma-ray flashes (TGFs) are the most energetic photon phenomenon
occurring naturally on Earth. An outstanding question is as follows: Are these
flashes just a rare exotic phenomenon or are they an intrinsic part of
lightning discharges and therefore occurring more frequently than previously
thought? All measurements of TGFs so far have been limited by the dynamic range
and sensitivity of spaceborne instruments. In this paper we show that there is
a new population of weak TGFs that has not been identified by search
algorithms. We use the World Wide Lightning Location Network (WWLLN) to
identify lightning that occurred in 2006 and 2012 within the 800 km field of
view of Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). By
superposing 740,210 100 ms RHESSI data intervals, centered at the time of the
WWLLN detected lightning, we identify at least 141 and probably as many as 191
weak TGFs that were not part of the second RHESSI data catalogue. This supports
the suggestion that the global TGF production rate is larger than previously
reported.


title:
Image segmentation with superpixel-based covariance descriptors in
  low-rank representation

abstract:
  This paper investigates the problem of image segmentation using superpixels.
We propose two approaches to enhance the discriminative ability of the
superpixel's covariance descriptors. In the first one, we employ the
Log-Euclidean distance as the metric on the covariance manifolds, and then use
the RBF kernel to measure the similarities between covariance descriptors. The
second method is focused on extracting the subspace structure of the set of
covariance descriptors by extending a low rank representation algorithm on to
the covariance manifolds. Experiments are carried out with the Berkly
Segmentation Dataset, and compared with the state-of-the-art segmentation
algorithms, both methods are competitive.


title: Effects of chiral helimagnets on vortex states in a superconductor

abstract:
  We have investigated vortex states in chiral helimagnet/superconductor
bilayer systems under an applied external magnetic field Happl, using the
Ginzburg-Landau equations. Effect of the chiral helimagnet on the
superconductor is taken as a magnetic field HCHM, which is perpendicular to the
superconductor and oscillates spatially. For Happl = 0 and weak HCHM, there
appear pairs of up-and down-vortices. Increasing Happl, down-vortices gradually
disappear, and number of up-vortices increases in the large magnetic field
region. Then, up-vortices form parallel, triangular, or square structures.


title:
A pointwise finite-dimensional reduction method for a fully coupled
  system of Einstein-Lichnerowicz type

abstract:
  We construct non-compactness examples for the fully coupled
Einstein-Lichnerowicz constraint system in the focusing case. The construction
is obtained by combining pointwise a priori asymptotic analysis techniques,
finite-dimensional reductions and a fixed-point argument.
  More precisely, we perform a fixed-point procedure on the remainders of the
expected blow-up decomposition. The argument consists of an involved
finite-dimensional reduction coupled with a ping-pong method. To overcome the
non-variational structure of the system, we work with remainders which belong
to strong function spaces and not merely to energy spaces. Performing both the
ping-pong argument and the finite-dimensional reduction therefore heavily
relies on a priori pointwise asymptotic techniques.


title: The closest to $0$ spectral number of the partial theta function

abstract:
  The {\em spectrum} of the partial theta function $\theta :=\sum
_{j=0}^{\infty}q^{j(j+1)/2}x^j$ is the set of values of $q\in \mathbb{C}$,
$0<|q|<1$, for which $\theta (q,.)$ has a multiple zero. We show that the only
element of the spectrum belonging to the disk $\mathbb{D}_{0.31}$ is
$0.3092493386\ldots$.


title: On the paper 'Role of potentials in the Aharonov-Bohm effect'

abstract:
  When the magnetic vector potential is expressed in terms of the magnetic
field it, is found to be explicitly non-local in space. This gives support to
the conclusions of Aharonov et al. in a recent comment, that the Aharonov-Bohm
effect may be interpreted as being either due to a local gauge potential or
else due to non-local gauge-invariant fields but not due to local
gauge-invariant fields.


title:
Charge Transport through Conjugated Azomethine-based Single Molecules
  for Optoelectronic Applications

abstract:
  The single-molecule conductance of a 3-ring, conjugated azomethine was
studied using the mechanically controlled breakjunction technique. Charge
transport properties are found to be comparable to vinyl-based analogues;
findings are supported with density functional calculations. The simple
preparation and good transport properties make azomethine-based molecules an
attractive class for use in polymer and single-molecule organic electronics.


title: Expectation on Observation of Supernova Remnants with the LHAASO Project

abstract:
  Supernova remnants (SNRs) are believed to be the most important acceleration
sites for cosmic rays (CRs) below $\sim10^{15}$ eV in the Galaxy. High energy
photons, either directly from the shocks of the SNRs or indirectly from the
interaction between SNRs and the nearby clouds, are crucial probes for the CR
acceleration. Big progresses on observations of SNRs have been achieved by
space- and ground-based $\gamma$-ray facilities. However, whether $\gamma$-rays
come from accelerated hadrons or not, as well as their connection with the CRs
observed at Earth, remains in debate. Large High Altitude Air Shower
Observatory (LHAASO), the next generation experiment, is designed to survey the
northern part of the very high energy $\gamma$-ray sky from $\sim 0.3$ TeV to
PeV with the sensitivity of $\lesssim1\%$ of the Crab nebula flux. In this
paper, we indicate that LHAASO will be dedicated to enlarging the $\gamma$-ray
SNR samples and improving the spectral and morphological measurements. These
measurements, especially at energies above 30 TeV, will be important for us to
finally understand the CR acceleration in SNRs.


title: Damped Arrow-Hurwicz algorithm for sphere packing

abstract:
  We consider algorithms that, from an arbitrarily sampling of $N$ spheres
(possibly overlapping), find a close packed configuration without overlapping.
These problems can be formulated as minimization problems with non-convex
constraints. For such packing problems, we observe that the classical iterative
Arrow-Hurwicz algorithm does not converge. We derive a novel algorithm from a
multi-step variant of the Arrow-Hurwicz scheme with damping. We compare this
algorithm with classical algorithms belonging to the class of linearly
constrained Lagrangian methods and show that it performs better. We provide an
analysis of the convergence of these algorithms in the simple case of two
spheres in one spatial dimension. Finally, we investigate the behaviour of our
algorithm when the number of spheres is large.


title:
On the Optimal Linear Convergence Rate of a Generalized Proximal Point
  Algorithm

abstract:
  The proximal point algorithm (PPA) has been well studied in the literature.
In particular, its linear convergence rate has been studied by Rockafellar in
1976 under certain condition. We consider a generalized PPA in the generic
setting of finding a zero point of a maximal monotone operator, and show that
the condition proposed by Rockafellar can also sufficiently ensure the linear
convergence rate for this generalized PPA. Indeed we show that these linear
convergence rates are optimal. Both the exact and inexact versions of this
generalized PPA are discussed. The motivation to consider this generalized PPA
is that it includes as special cases the relaxed versions of some splitting
methods that are originated from PPA. Thus, linear convergence results of this
generalized PPA can be used to better understand the convergence of some widely
used algorithms in the literature. We focus on the particular convex
minimization context and specify Rockafellar's condition to see how to ensure
the linear convergence rate for some efficient numerical schemes, including the
classical augmented Lagrangian method proposed by Hensen and Powell in 1969 and
its relaxed version, the original alternating direction method of multipliers
(ADMM) by Glowinski and Marrocco in 1975 and its relaxed version (i.e., the
generalized ADMM by Eckstein and Bertsekas in 1992). Some refined conditions
weaker than existing ones are proposed in these particular contexts.


title:
Charge inversion and topological phase transition at a twist angle
  induced van Hove singularity of bilayer graphene

abstract:
  Van Hove singularities (VHS's) in the density of states play an outstanding
and diverse role for the electronic and thermodynamic properties of crystalline
solids. At the critical point the Fermi surface connectivity changes and
topological properties undergo a transition. Opportunities to systematically
pass a VHS at the turn of a voltage knob and study its diverse impact are
however rare. With the advent of van der Waals heterostructures, control over
the atomic registry of neigbouring graphene layers offers an unprecedented tool
to generate a low energy VHS easily accessible with conventional gating. Here
we have addressed magnetotransport when the chemical potential crosses the
twist angle induced VHS in twisted bilayer graphene. A topological phase
transition is experimentally disclosed in the abrupt conversion of electrons to
holes or vice versa, a loss of a non-zero Berry phase and distinct sequences of
integer quantum Hall states above and below the singularity.


title: Localizing the Ensemble Kalman Particle Filter

abstract:
  Ensemble methods such as the Ensemble Kalman Filter (EnKF) are widely used
for data assimilation in large-scale geophysical applications, as for example
in numerical weather prediction (NWP). There is a growing interest for physical
models with higher and higher resolution, which brings new challenges for data
assimilation techniques because of the presence of non-linear and non-Gaussian
features that are not adequately treated by the EnKF. We propose two new
localized algorithms based on the Ensemble Kalman Particle Filter (EnKPF), a
hybrid method combining the EnKF and the Particle Filter (PF) in a way that
maintains scalability and sample diversity. Localization is a key element of
the success of EnKFs in practice, but it is much more challenging to apply to
PFs. The algorithms that we introduce in the present paper provide a compromise
between the EnKF and the PF while avoiding some of the problems of localization
for pure PFs. Numerical experiments with a simplified model of cumulus
convection based on a modified shallow water equation show that the proposed
algorithms perform better than the local EnKF. In particular, the PF nature of
the method allows to capture non-Gaussian characteristics of the estimated
fields such as the location of wet and dry areas.


title:
A TEM study of morphological and structural degradation phenomena in
  LiFePO4-CB cathodes

abstract:
  LiFePO4-based cathodes suffer from various degradation mechanisms which
influences the battery performance. In this paper morphological and structural
degradation phenomena in laboratory cathodes made of LiFePO4 (LFP) mixed with
carbon black (CB) in an 1 mol L-1 LiPF6 in EC:DMC (1:1 by weight) electrolyte
are investigated by transmission electron microscopy (TEM) at various
preparation, assembling, storage and cycling stages. High-resolution TEM
(HRTEM) imaging shows that continuous SEI layers are formed on the LFP
particles and that both storage and cycling affects the formation. Additionally
loss of CB crystallinity, CB aggregation and agglomeration is observed.
Charge-discharge curves and impedance spectra measured during cycling confirm
that these degradation mechanisms reduce the cathode conductivity and capacity.


title: Pancharatnam phase in non-separable states of light

abstract:
  We generate the non-separable state of polarization and orbital angular
momentum (OAM) using a laser beam. The generated state undergoes a cyclic
polarization evolution which introduces a Pancharatnam geometric phase to the
polarization state and in turn a relative phase in the non-separable state. We
experimentally study the violation of Bell - CHSH inequality for different
Pancharatnam phases introduced by various cyclic polarization evolutions with
linear and circular states as measurement bases. While measuring in linear
bases, the Bell-CHSH parameter oscillates with Pancharatnam phase. One can
overcome this dependence by introducing a relative phase in one of the
projecting state. However for measurement in circular bases, the Pancharatnam
phase does not affect the Bell-CHSH violation.


title: More properties of the Ramanujan sequence

abstract:
  The Ramanujan sequence $ \{\theta_{n}\}_{n \geq 0}$, defined as $$
\theta_{0}= \frac{1}{2} \ , \ \ \
  \theta_{n} = \left(\ \ \frac{e^{n}}{2} - \sum_{k=0}^{n-1} \frac{n^{k}}{k !} \
\
  \right) \cdot \frac{n !}{n^{n}} \ , \ \ n \geq 1 \ ,$$ has been studied on
many occasions and in many different contexts. J.Adell and P.Jodra (2008) and
S. Koumandos (2013) showed, respectively, that the sequences $\{\theta_{n}\}_{n
\geq 0}$ and $\{4/135 - n \cdot (\theta_{n}- 1/3 )\}_{n \geq 0}$ are completely
monotone. In the present paper we establish that the sequence
$\{(n+1)(\theta_{n}- 1/3 )\}_{n \geq 0}$ is also completely monotone.
Furthermore, we prove that the analytic function $(\theta_{1}- 1/3 )^{-1}
\sum_{n=1}^{\infty} (\theta_{n}- 1/3 ) \cdot z^{n} / n^{\alpha} $ is
universally starlike for every $ \alpha \geq 1 $ in the slit domain $
\mathbb{C} \setminus [1,\infty)$. This seems to be the first result putting the
Ramanujan sequence into the context of analytic univalent functions and is a
step towards a previous stronger conjecture, proposed by S.Ruscheweyh,
L.Salinas and T.Sugawa in 2009, namely that the function $(\theta_{1}- 1/3
)^{-1} \sum_{n=1}^{\infty} (\theta_{n}- 1/3 ) \cdot z^{n} $ is universally
convex.


title:
1d Quantum Harmonic Oscillator Perturbed by a Potential with Logarithmic
  Decay

abstract:
  In this paper we prove an infinite dimensional KAM theorem, in which the
assumptions on the derivatives of perturbation in \cite{GT} are weakened from
polynomial decay to logarithmic decay. As a consequence, we apply it to 1d
quantum harmonic oscillators and prove the reducibility of a linear harmonic
oscillator, $T=- \frac{d^2}{dx^2}+x^2$, on $L^2(\R)$ perturbed by a
quasi-periodic in time potential $V(x,\omega t; \omega)$ with logarithmic
decay. This entails the pure-point nature of the spectrum of the Floquet
operator $K$, where K:=-{\rm i}\sum_{k=1}^n\omega_k\frac{\partial}{\partial
\theta_k}- \frac{d^2}{dx^2}+x^2+\varepsilon V(x,\theta;\omega), is defined on
$L^2(\R) \otimes L^2(\T^n)$ and the potential $V(x,\theta;\omega)$ has
logarithmic decay as well as its gradient in $\omega$.


title: Convergence proof for the multigrid method of the nonlocal model

abstract:
  Recently, nonlocal models attract the wide interests of scientist. They
mainly come from two applied scientific fields: peridyanmics and anomalous
diffusion. Even though the matrices of the algebraic equation corresponding the
nonlocal models are usually Toeplitz (denote a0 as the principal diagonal
element, a1 as the trailing diagonal element, etc). There are still some
differences for the models in these two fields. For the model of anomalous
diffusion, a0/a1 is uniformly bounded; most of the time, a0/a1 of the model for
peridyanmics is unbounded as the stepsize h tends to zero. Based on the uniform
boundedness of a0/a1, the convergence of the two-grid method is well
established [Chan, Chang, and Sun, SIAM J. Sci. Comput., 19 (1998), pp.
516--529; Pang and Sun, J. Comput. Phys., 231 (2012), pp. 693--703; Chen, Wang,
Cheng, and Deng, BIT, 54 (2014), pp. 623--647]. This paper provides the
detailed proof of the convergence of the two-grid method for the nonlocal model
of peridynamics. Some special cases of the full multigrid and the V-cycle
multigrid are also discussed. The numerical experiments are performed to verify
the convergence.


title:
Non-negativity constraints in the one-dimensional discrete-time phase
  retrieval problem

abstract:
  Phase retrieval problems occur in a width range of applications in physics
and engineering such as crystallography, astronomy, and laser optics. Common to
all of them is the recovery of an unknown signal from the intensity of its
Fourier transform. Because of the well-known ambiguousness of these problems,
the determination of the original signal is generally challenging. Although
there are many approaches in the literature to incorporate the assumption of
non-negativity of the solution into numerical algorithms, theoretical
considerations about the solvability with this constraint occur rarely. In this
paper, we consider the one-dimensional discrete-time setting and investigate
whether the usually applied a priori non-negativity can overcame the
ambiguousness of the phase retrieval problem or not. We show that the assumed
non-negativity of the solution is usually not a sufficient a priori condition
to ensure uniqueness in one-dimensional phase retrieval. More precisely, using
an appropriate characterization of the occurring ambiguities, we show that
neither the uniqueness nor the ambiguousness are rare exceptions.


title: Dynamics of Carroll Strings

abstract:
  We construct the canonical action of a Carroll string doing the Carroll limit
of a canonical relativistic string. We also study the Killing symmetries of the
Carroll string, which close under an infinite dimensional algebra. The
tensionless limit and the Carroll $p$-brane action are also discussed.


title: AdS-Carroll Branes

abstract:
  Coset methods are used to determine the action of a co-dimension one brane
(domain wall) embedded in (d+1)-dimensional AdS space in the Carroll limit in
which the speed of light goes to zero. The action is invariant under the
non-linearly realized symmetries of the AdS-Carroll spacetime. The
Nambu-Goldstone field exhibits a static spatial distribution for the brane with
a time varying momentum density related to the brane's spatial shape as well as
the AdS-C geometry. The AdS-C vector field dual theory is obtained.


title:
Strong Correlations, Strong Coupling and s-wave Superconductivity in
  Hole-doped BaFe2As2 Single Crystals

abstract:
  We present a comprehensive study of the low-temperature heat capacity and
thermal expansion of single crystals of the hole-doped Ba1-xKxFe2As2 series
(0<x<1) and the end-members RbFe2As2 and CsFe2As2. A large increase of the
Sommerfeld coefficient is observed with both decreasing band filling and
isovalent substitution (K, Rb, Cs) revealing a strong enhancement of electron
correlations and the possible proximity of these materials to a Mott insulator.
This trend is well reproduced theoretically by our Density-Functional Theory +
Slave-Spin (DFT+SS) calculations, confirming that 122-iron pnictides are
effectively Hund metals, in which sizable Hund's coupling and orbital
selectivity are the key ingredients for tuning correlations. We also find
direct evidence for the existence of a coherence-incoherence crossover between
a low-temperature heavy Fermi liquid and a highly incoherent high-temperature
regime similar to heavy fermion systems. In the superconducting state, clear
signatures of multiband superconductivity are observed with no evidence for
nodes in the energy gaps, ruling out the existence of a doping-induced change
of symmetry (from s to d-wave). We argue that the disappearance of the electron
band in the range 0.4<x<1.0 is accompanied by a strong-to-weak coupling
crossover and that this shallow band remains involved in the superconducting
pairing, although its contribution to the normal state fades away. Differences
between hole- and electron-doped BaFe2As2 series are emphasized and discussed
in terms of strong pair breaking by potential scatterers beyond the Born limit.


title:
Backstepping Design for Incremental Stability of Stochastic Hamiltonian
  Systems with Jumps

abstract:
  Incremental stability is a property of dynamical systems ensuring the uniform
asymptotic stability of each trajectory rather than a fixed equilibrium point
or trajectory. Here, we introduce a notion of incremental stability for
stochastic control systems and provide its description in terms of existence of
a notion of so-called incremental Lyapunov functions. Moreover, we provide a
backstepping controller design scheme providing controllers along with
corresponding incremental Lyapunov functions rendering a class of stochastic
control systems, namely, stochastic Hamiltonian systems with jumps,
incrementally stable. To illustrate the effectiveness of the proposed approach,
we design a controller making a spring pendulum system in a noisy environment
incrementally stable.


title: Chebyshev Inequalities for Products of Random Variables

abstract:
  We derive sharp probability bounds on the tails of a product of symmetric
non-negative random variables using only information about their first two
moments. If the covariance matrix of the random variables is known exactly,
these bounds can be computed numerically using semidefinite programming. If
only an upper bound on the covariance matrix is available, the probability
bounds on the right tails can be evaluated analytically. The bounds under
precise and imprecise covariance information coincide for all left tails as
well as for all right tails corresponding to quantiles that are either
sufficiently small or sufficiently large. We also prove that all left
probability bounds reduce to the trivial bound 1 if the number of random
variables in the product exceeds an explicit threshold. Thus, in the worst
case, the weak-sense geometric random walk defined through the running product
of the random variables is absorbed at 0 with certainty as soon as time exceeds
the given threshold. The techniques devised for constructing Chebyshev bounds
for products can also be used to derive Chebyshev bounds for sums, maxima and
minima of non-negative random variables.


title:
Dynamic Computation Offloading for Mobile-Edge Computing with Energy
  Harvesting Devices

abstract:
  Mobile-edge computing (MEC) is an emerging paradigm to meet the
ever-increasing computation demands from mobile applications. By offloading the
computationally intensive workloads to the MEC server, the quality of
computation experience, e.g., the execution latency, could be greatly improved.
Nevertheless, as the on-device battery capacities are limited, computation
would be interrupted when the battery energy runs out. To provide satisfactory
computation performance as well as achieving green computing, it is of
significant importance to seek renewable energy sources to power mobile devices
via energy harvesting (EH) technologies. In this paper, we will investigate a
green MEC system with EH devices and develop an effective computation
offloading strategy. The execution cost, which addresses both the execution
latency and task failure, is adopted as the performance metric. A
low-complexity online algorithm, namely, the Lyapunov optimization-based
dynamic computation offloading (LODCO) algorithm is proposed, which jointly
decides the offloading decision, the CPU-cycle frequencies for mobile
execution, and the transmit power for computation offloading. A unique
advantage of this algorithm is that the decisions depend only on the
instantaneous side information without requiring distribution information of
the computation task request, the wireless channel, and EH processes. The
implementation of the algorithm only requires to solve a deterministic problem
in each time slot, for which the optimal solution can be obtained either in
closed form or by bisection search. Moreover, the proposed algorithm is shown
to be asymptotically optimal via rigorous analysis. Sample simulation results
shall be presented to verify the theoretical analysis as well as validate the
effectiveness of the proposed algorithm.


abstract:
  We investigate questions involving Aronszajn trees, square principles, and
stationary reflection. We first consider two strengthenings of
$\square(\kappa)$ introduced by Brodsky and Rinot for the purpose of
constructing $\kappa$-Souslin trees. Answering a question of Rinot, we prove
that the weaker of these strengthenings is compatible with stationary
reflection at $\kappa$ but the stronger is not. We then prove that, if $\mu$ is
a singular cardinal, $\square_\mu$ implies the existence of a special
$\mu^+$-tree with a $\mathrm{cf}(\mu)$-ascent path, thus answering a question
of L\"ucke.


title: On pattern avoiding indecomposable permutations

abstract:
  Comtet introduced the notion of indecomposable permutations in 1972. A
permutation is indecomposable if and only if it has no proper prefix which is
itself a permutation. Indecomposable permutations were studied in the
literature in various contexts. In particular, this notion has been proven to
be useful in obtaining non-trivial enumeration and equidistribution results on
permutations.
  In this paper, we give a complete classification of indecomposable
permutations avoiding a classical pattern of length 3 or 4, and of
indecomposable permutations avoiding a non-consecutive vincular pattern of
length 3. Further, we provide a recursive formula for enumerating $12\cdots
k$-avoiding indecomposable permutations for $k\geq 3$. Several of our results
involve the descent statistic. We also provide a bijective proof of a fact
relevant to our studies.


title:
Experimental Validation of a Microscopic Ellipsoidal Particle Model
  Immersed in Fluid Flow

abstract:
  A simulation of ellipsoidal particles inside a fluid flow is presented and
validated from our own lab size experiments where data has been recorded using
a camera set-up and post-processing of the pictures. The model is based on
Jeffery's equation, where the orientation and position of the particles are
influenced by the surrounding fluid. Additionally, particle-particle
interaction and particle-wall interaction are taken into account.


title: Asymptotic upper bounds on progression-free sets in $\mathbb{Z}_p^n$

abstract:
  We show that any subset of $\mathbb{Z}_p^n$ ($p$ an odd prime) without
$3$-term arithmetic progression has size $O(p^{cn})$, where
$c:=1-\frac{1}{18\log p}<1$. In particular, we find an upper bound of
$O(2.84^n)$ on the maximum size of an affine cap in $GF(3)^n$.


title: Top-Quark Properties at the LHC

abstract:
  A review of recent measurements of top-quark properties is presented.
Inclusive and differential top-quark pair charge asymmetry measurements using
the full Run I dataset are found to be in agreement with the standard model
(SM) predictions. Results of spin correlation in top-quark pairs are presented
and interpreted in terms of the SM predicted values and new physics models.
Limits are set on flavour-changing neutral currents (FCNC), in particular with
a Higgs boson in the final state.


title: Finite subgroups of Ham and Symp

abstract:
  Let $(X,\omega)$ be a compact symplectic manifold of dimension $2n$ and let
$Ham(X,\omega)$ be its group of Hamiltonian diffeomorphisms. We prove the
existence of a constant $C$, depending on $X$ but not on $\omega$, such that
any finite subgroup $G\subset Ham(X,\omega)$ has an abelian subgroup
$A\subseteq G$ satisfying $[G:A]\leq C$, and $A$ can be generated by $n$
elements or fewer. If $b_1(X)=0$ we prove an analogous statement for the entire
group of symplectomorphisms of $(X,\omega)$. If $b_1(X)\neq 0$ we prove the
existence of a constant $C'$ depending only on $X$ such that any finite
subgroup $G\subset Symp(X,\omega)$ has a subgroup $N\subseteq G$ which is
either abelian or $2$-step nilpotent and which satisfies $[G:N]\leq C'$.
  These results are deduced from the classification of the finite simple
groups, the topological rigidity of hamiltonian loops, and the following
theorem, which we prove in this paper. Let $E$ be a complex vector bundle over
a compact, connected, smooth and oriented manifold $M$; suppose that the real
rank of $E$ is equal to the dimension of $M$, and that $\langle
e(E),[M]\rangle\neq 0$, where $e(E)$ is the Euler class of $E$; then there
exists a constant $C"$ such that, for any prime $p$ and any finite $p$-group
$G$ acting on $E$ by vector bundle automorphisms preserving an almost complex
structure on $M$, there is a subgroup $G_0\subseteq G$ satisfying
$M^{G_0}\neq\emptyset$ and $[G:G_0]\leq C"$.


title:
Quantifying Uncertainties in the 2004 Sumatra-Andaman Earthquake Source
  Parameters by Stochastic Inversion

abstract:
  Usual inversion for earthquake source parameters from tsunami wave data
incorporates subjective elements. Noisy and possibly insufficient data also
results in instability and non-uniqueness in most deterministic inversions.
Here we employ the satellite altimetry data for the 2004 Sumatra-Andaman
tsunami event to invert the source parameters. Using a finite fault model that
represents the extent of rupture and the geometry of the trench, we perform a
non-linear joint inversion of the slips, rupture velocities and rise times with
minimal a priori constraints. Despite persistently good waveform fits, large
variance and skewness in the joint parameter distribution constitute a
remarkable feature of the inversion. These uncertainties suggest the need for
objective inversion strategies that should incorporate more sophisticated
physical models in order to significantly improve the performance of early
warning systems.


title:
The Design of a Drag-Free CubeSat and the Housing for its Gravitational
  Reference Sensor

abstract:
  A Drag-Free CubeSat mission has been proposed to demonstrate the feasibility
of a Gravitational Reference Sensor (GRS) with an optical readout for a 3 units
(3U) spacecraft. A purely drag-free object is defined by the absence of all
external forces other than gravity, which are shielded by the spacecraft. In a
real case, the TM will still be affected by disturbances. Several of them are
passively reduced by the design of the TM housing. This system is a
thick-walled aluminium box that holds the shadow sensors and shields the TM.
The housing has an effect on the mechanical, thermal and magnetic environment
around the TM. All of them have been analysed. The mechanical vibrations have
to fit the launch environment and the modes have to be outside of the
measurement range (0.0001 - 1 Hz). The magnetic field has to be reduced by a
0.01 factor. The temperature difference between internal opposing surfaces,
determining pressure on the TM, has to be below 10^-3(1 mHz/f)1/3 K Hz^-1/2.
The housing, together with the TM, the sensors and the UV LEDs for charging
control, constitutes the GRS, which would then fit into a 1U. The other 2Us are
occupied by the caging mechanism that constraints the TM during launch, the
thrusters, the Attitude Determination And Control System (ADACS) and the
electronics. The Drag-Free CubeSat will be the result of the combined efforts
of Stanford, University of Florida, KACST and NASA and will be the first
drag-free mission with an optical readout and the first GRS designed within the
limits of a 3U small satellite. In the first section, this paper briefly
updates on the main characteristics and systems of the project. Particular
emphasis is then given to the recently designed housing, its expected
performance and the open issues.


title: Light sterile neutrino sensitivity of 163Ho experiments

abstract:
  We explore the sensitivity of $^{163}$Ho electron capture experiments to
neutrino masses in the standard framework of three-neutrino mixing and in the
framework of 3+1 neutrino mixing with a sterile neutrino which mixes with the
three standard active neutrinos, as indicated by the anomalies found in
short-baseline neutrino oscillations experiments. We calculate the sensitivity
to neutrino masses and mixing for different values of the energy resolution of
the detectors, of the unresolved pileup fraction and of the total statistics of
events, considering the expected values of these parameters in the two planned
stages of the ECHo project (ECHo-1k and ECHo-1M). We show that an extension of
the ECHo-1M experiment with the possibility to collect $10^{16}$ events will be
competitive with the KATRIN experiment. This statistics will allow to explore
part of the 3+1 mixing parameter space indicated by the global analysis of
short-baseline neutrino oscillation experiments. In order to cover all the
allowed region, a statistics of about $10^{17}$ events will be needed.


title:
Jump stochastic differential equations with non-Lipschitz and
  superlinearly growing coefficients

abstract:
  In the paper, we consider the no-explosion condition and pathwise uniqueness
for SDEs driven by a Poisson random measure with coefficients that are
super-linear and non-Lipschitz. We give a comparison theorem in the
one-dimensional case under some additional condition. Moreover, we study the
non-contact property and the continuity with respect to the space variable of
the stochastic flow. As an application, we will show that there exists a unique
strong solution for SDEs with coefficients like $x\log|x|$.


title: Singularities in Negami's splitting formula for the Tutte polynomial

abstract:
  The n-sum graph Negami's splitting formula for the Tutte polynomial is not
valid in the region $(x-1)(y-1)=q$ for $q=1,2,\ldots n-1$ with the additional
region $y=1$ if $n>3$. This region corresponds to (up to prefactors and change
of variables) the Ising model, the $q$-state Potts model, the number of
spanning forest generator and particularizations of these. We show splitting
formulas for these specializations.


title:
Large phonon-drag enhancement induced by narrow quantum confinement at
  the LaAlO3/SrTiO3 interface

abstract:
  The thermoelectric power of the two-dimensional electron system (2DES) at the
LaAlO3/SrTiO3 interface is explored below room temperature, in comparison with
that of Nb-doped SrTiO3 single crystals. For the interface we find a region
below T =50 K where thermopower is dominated by phonon-drag, whose amplitude is
hugely amplified with respect to the corresponding bulk value, reaching values
~mV/K and above. The phonon-drag enhancement at the interface is traced back to
the tight carrier confinement of the 2DES, and represents a sharp signature of
strong electron-acoustic phonon coupling at the interface.


title: Clustering-based redshift estimation: application to VIPERS/CFHTLS

abstract:
  We explore the accuracy of the clustering-based redshift estimation proposed
by M\'enard et al. (2013) when applied to VIPERS and CFHTLS real data. This
method enables us to reconstruct redshift distributions from measurement of the
angular clus- tering of objects using a set of secure spectroscopic redshifts.
We use state of the art spectroscopic measurements with iAB < 22.5 from the
VIMOS Public Extragalactic Redshift Survey (VIPERS) as reference population to
infer the redshift distribution of galaxies from the Canada-France-Hawaii
Telescope Legacy Survey (CFHTLS) T0007 release. VIPERS provides a nearly
representative sample to the flux limit iAB < 22.5 at redshift > 0.5 which
allows us to test the accuracy of the clustering-based red- shift
distributions. We show that this method enables us to reproduce the true mean
color-redshift relation when both populations have the same magnitude limit. We
also show that this technique allows the inference of redshift distributions
for a population fainter than the one of reference and we give an estimate of
the color-redshift mapping in this case. This last point is of great interest
for future large redshift surveys which suffer from the need of a complete
faint spectroscopic sample.


title:
The VIMOS Public Extragalactic Redshift Survey (VIPERS). The coevolution
  of galaxy morphology and colour to z~1

abstract:
  We explore the evolution of the statistical distribution of galaxy
morphological properties and colours over the redshift range $0.5<z<1$,
combining high-quality imaging data from the CFHT Legacy Survey with the large
number of redshifts and extended photometry from the VIPERS survey. Galaxy
structural parameters are measured by fitting S\'ersic profiles to $i$-band
images and then combined with absolute magnitudes, colours and redshifts, to
trace the evolution in a multi-parameter space. We analyse, using a new method,
the combination of colours and structural parameters of early- and late-type
galaxies in luminosity--redshift space. We found that both the rest-frame
colour distributions in the (U-B) vs. (B-V) plane and the S\'ersic index
distributions are well fitted by a sum of two Gaussians, with a remarkable
consistency of red-spheroidal and blue-disky galaxy populations, over the
explored redshift ($0.5<z<1$) and luminosity ($-1.5<B-B_*<1.0$) ranges. The
combination of the UBV rest-frame colour and S\'ersic index $n$ as a function
of redshift and luminosity allows us to present the structure of early- and
late-type galaxies and their evolution. We found that early type galaxies
display only a slow change of their concentrations since $z\sim1$; it is
already established by $z\sim1$ and depends much more strongly on their
luminosities. In contrast, late-type galaxies get clearly more concentrated
with cosmic time since $z\sim1$, with only little evolution in colour, which
remains dependent mainly on their luminosity. This flipped luminosity (mass)
and redshift dependence likely reflects different evolutionary tracks of early-
and late-type galaxies before and after $z\sim1$. The combination of rest-frame
colours and S\'ersic index $n$ as a function of redshift and luminosity leads
to a precise statistical description of the structure of galaxies and their
evolution.


title:
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Star formation
  history of passive galaxies

abstract:
  We trace the evolution and the star formation history of passive galaxies,
using a subset of the VIMOS Public Extragalactic Redshift Survey (VIPERS). We
extracted from the VIPERS survey a sample of passive galaxies in the redshift
range 0.4<z<1.0 and stellar mass range 10<$log(M_{star}/M_{\odot})$<12. The
sample was selected using an evolving cut in the rest-frame U-V color
distribution and additional quality-ensuring cuts. We use the stacked spectra
to measure the 4000$\AA$ break (D4000) and the $H\delta$ Lick index
($H\delta_{A}$) with high precision. We compare the results with a grid of
synthetic spectra to constrain the star formation epochs of these galaxies. We
characterize the formation redshift-stellar mass relation for
intermediate-redshift passive galaxies. We find that at $z\sim1$ stellar
populations in low-mass passive galaxies are younger than in high-mass passive
galaxies, similarly to what is observed at the present epoch. Over the full
analyzed redshift and stellar mass range, the $D4000$ index increases with
redshift, while $H\delta_{A}$ gets lower. This implies that the stellar
populations are getting older with increasing stellar mass. Comparison to the
spectra of passive galaxies in the SDSS survey shows that the shape of the
relations of $D4000$, and $H\delta_{A}$ with stellar mass has not changed
significantly with redshift. Assuming a single burst formation, this implies
that high-mass passive galaxies formed their stars at $z_{form}\sim2$, while
low-mass galaxies formed their main stellar population more recently, at
$z_{form}\sim1$. The consistency of these results, obtained using two
independent estimator of the formation redshift ($D4000$ and $H\delta_{A}$),
further strengthens a scenario in which star formation proceeds from higher- to
lower-mass systems as time passes, i.e. what has become known as the
'downsizing' picture.


title:
Study of the inner dust envelope and stellar photosphere of the AGB star
  R Doradus using SPHERE/ZIMPOL

abstract:
  We use high-angular-resolution images obtained with SPHERE/ZIMPOL to study
the photosphere, the warm molecular layer, and the inner wind of the close-by
oxygen-rich AGB star R Doradus. We present observations in filters V,
cntH$\alpha$, and cnt820 and investigate the surface brightness distribution of
the star and of the polarised light produced in the inner envelope. Thanks to
second-epoch observations in cntH$\alpha$, we are able to see variability on
the stellar photosphere. We find that in the first epoch the surface brightness
of R Dor is asymmetric in V and cntH$\alpha$, the filters where molecular
opacity is stronger, while in cnt820 the surface brightness is closer to being
axisymmetric. The second-epoch observations in cntH$\alpha$ show that the
morphology of R Dor changes completely in a timespan of 48 days to a more
axisymmetric and compact configuration. The polarised intensity is asymmetric
in all epochs and varies by between a factor of 2.3 and 3.7 with azimuth for
the different images. We fit the radial profile of the polarised intensity
using a spherically symmetric model and a parametric description of the dust
density profile, $\rho(r)=\rho_\circ r^{-n}$. On average, we find exponents of
$- 4.5 \pm 0.5$ that correspond to a much steeper density profile than that of
a wind expanding at constant velocity. The dust densities we derive imply an
upper limit for the dust-to-gas ratio of $\sim 2\times10^{-4}$ at 5.0
$R_\star$. Given the uncertainties in observations and models, this value is
consistent with the minimum values required by wind-driving models for the
onset of a wind, of $\sim 3.3\times10^{-4}$. However, if the steep density
profile we find extends to larger distances from the star, the dust-to-gas
ratio will quickly become too small for the wind of R Dor to be driven by the
grains that produce the scattered light.


title: Special Bohr - Sommerfeld geometry on Riemann surfaces: toy problems

abstract:
  Special Bohr - Sommerfeld geometry, first formulated for simply connected
symplectic manifolds (or for simple connected algebraic varieties), gives rise
to some natural problems for the simplest example in non simply connected case.
Namely for any algebraic curve one can define a correspondence between
holomorphic differentials and certain finite graphs. Here we ask some natural
questions appear with this correspondence. It is a partial answer to the
question of A. Varchenko about possibility of applications of Special Bohr
-Sommerfeld geometry in non simply connected case. The russian version has been
translated.


title:
Convergence to traveling waves in the Fisher-Kolmogorov equation with a
  non-Lipschitzian reaction term

abstract:
  We consider the semi linear Fisher-Kolmogorov-Petrovski-Piscounov equation
for the advance of an advantageous gene in biology. Its non-smooth reaction
function $f(u)$ allows for the introduction of travelling waves with a new
profile. We study existence, uniqueness, and long-time asymptotic behavior of
the solutions $u(x,t)$, $(x,t)\in \mathbb{R}\times \mathbb{R}_+$. We prove also
the existence and uniqueness (up to a spatial shift) of a travelling wave $U$.
Our main result is the uniform convergence (for $x\in \mathbb{R}$) of every
solution $u(x,t)$ of the Cauchy problem to a single traveling wave $U(x-ct +
\zeta)$ as $t\to \infty$. The speed $c$ and the travelling wave $U$ are
determined uniquely by $f$, whereas the shift $\zeta$ is determined by the
initial data.


title: Luminosity distributions of Type Ia Supernovae

abstract:
  We have assembled a dataset of 165 low redshift, $z<$0.06, publicly available
type Ia supernovae (SNe Ia). We produce maximum light magnitude ($M_{B}$ and
$M_{V}$) distributions of SNe Ia to explore the diversity of parameter space
that they can fill. Before correction for host galaxy extinction we find that
the mean $M_{B}$ and $M_{V}$ of SNe Ia are $-18.58\pm0.07$mag and
$-18.72\pm0.05$mag respectively. Host galaxy extinction is corrected using a
new method based on the SN spectrum. After correction, the mean values of
$M_{B}$ and $M_{V}$ of SNe Ia are $-19.10\pm0.06$ and $-19.10\pm0.05$mag
respectively. After correction for host galaxy extinction, `normal' SNeIa
($\Delta m_{15}(B)<1.6$mag) fill a larger parameter space in the
Width-Luminosity Relation (WLR) than previously suggested, and there is
evidence for luminous SNe Ia with large $\Delta m_{15}(B)$. We find a bimodal
distribution in $\Delta m_{15}(B)$, with a pronounced lack of transitional
events at $\Delta m_{15}(B)$=1.6 mag. We confirm that faster, low-luminosity
SNe tend to come from passive galaxies. Dividing the sample by host galaxy
type, SNe Ia from star-forming (S-F) galaxies have a mean $M_{B}=-19.20 \pm
0.05$ mag, while SNe Ia from passive galaxies have a mean $M_{B}=-18.57 \pm
0.24$ mag. Even excluding fast declining SNe, `normal' ($M_{B}<-18$ mag) SNe Ia
from S-F and passive galaxies are distinct. In the $V$-band, there is a
difference of 0.4$ \pm $0.13 mag between the median ($M_{V}$) values of the
`normal' SN Ia population from passive and S-F galaxies. This is consistent
with ($\sim 15 \pm $10)% of `normal' SNe Ia from S-F galaxies coming from an
old stellar population.


title: Kalman Filter Tracking on Parallel Architectures

abstract:
  Power density constraints are limiting the performance improvements of modern
CPUs. To address this we have seen the introduction of lower-power, multi-core
processors such as GPGPU, ARM and Intel MIC. To stay within the power density
limits but still obtain Moore's Law performance/price gains, it will be
necessary to parallelize algorithms to exploit larger numbers of lightweight
cores and specialized functions like large vector units. Track finding and
fitting is one of the most computationally challenging problems for event
reconstruction in particle physics. At the High-Luminosity Large Hadron
Collider (HL-LHC), for example, this will be by far the dominant problem. The
need for greater parallelism has driven investigations of very different track
finding techniques such as Cellular Automata or Hough Transforms. The most
common track finding techniques in use today, however, are those based on the
Kalman Filter. Significant experience has been accumulated with these
techniques on real tracking detector systems, both in the trigger and offline.
They are known to provide high physics performance, are robust, and are in use
today at the LHC. We report on porting these algorithms to new parallel
architectures. Our previous investigations showed that, using optimized data
structures, track fitting with a Kalman Filter can achieve large speedups both
with Intel Xeon and Xeon Phi. Additionally, we have previously shown first
attempts at track building with some speedup. We report here our progress
towards an end-to-end track reconstruction algorithm fully exploiting
vectorization and parallelization techniques in a simplified experimental
environment.


title: Learning activation functions from data using cubic spline interpolation

abstract:
  Neural networks require a careful design in order to perform properly on a
given task. In particular, selecting a good activation function (possibly in a
data-dependent fashion) is a crucial step, which remains an open problem in the
research community. Despite a large amount of investigations, most current
implementations simply select one fixed function from a small set of
candidates, which is not adapted during training, and is shared among all
neurons throughout the different layers. However, neither two of these
assumptions can be supposed optimal in practice. In this paper, we present a
principled way to have data-dependent adaptation of the activation functions,
which is performed independently for each neuron. This is achieved by
leveraging over past and present advances on cubic spline interpolation,
allowing for local adaptation of the functions around their regions of use. The
resulting algorithm is relatively cheap to implement, and overfitting is
counterbalanced by the inclusion of a novel damping criterion, which penalizes
unwanted oscillations from a predefined shape. Experimental results validate
the proposal over two well-known benchmarks.


title: Extreme Points of the Local Differential Privacy Polytope

abstract:
  We study the convex polytope of n x n stochastic matrices that define locally
differentially private mechanisms. We first present invariance properties of
the polytope and results reducing the number of constraints needed to define
it. Our main results concern the extreme points of the polytope. In particular,
we completely characterise these for matrices with 1, 2 or n non-zero columns.


title: Lower bounds for the dyadic Hilbert transform

abstract:
  In this paper, we seek lower bounds of the dyadic Hilbert transform (Haar
shift) of the form $\left\Vert S f\right\Vert_{L^2(K)}\geq C(I,K)\left\Vert
f\right\Vert_{L^2(I)}$ where $I$ and $K$ are two dyadic intervals and $f$
supported in $I$. If $I\subset K$ such bound exist while in the other cases
$K\subsetneq I$ and $K\cap I=\emptyset$ such bounds are only available under
additional constraints on the derivative of $f$. In the later case, we
establish a bound of the form $\left\Vert S f\right\Vert_{L^2(K)}\geq
C(I,K)|\left\langle f\right\rangle_I|$ where $\left\langle f\right\rangle_I$ is
the mean of $f$ over $I$. This sheds new light on the similar problem for the
usual Hilbert transform that we exploit.


title:
Tamagawa Numbers of elliptic curves with $C_{13}$ torsion over quadratic
  fields

abstract:
  Let $E$ be an elliptic curve over a number field $K$, $c_v$ the Tamagawa
number of $E$ at $v$, and let $c_E=\prod_{v}c_v$. Lorenzini proved that
$v_{13}(c_E)$ is postive for all elliptic curves over quadratic fields with a
point of order $13$. Krumm conjectured, based on extensive computation, that
the $13$-adic valuation of $c_E$ is even for all such elliptic curves. In this
note we prove this conjecture and furhtermore prove that there is an unique
such curve satisfying $v_{13}(c_E)=2$.


title:
Depict noise-driven nonlinear dynamic networks from output data by using
  high-order correlations

abstract:
  Many practical systems can be described by dynamic networks, for which modern
technique can measure their output signals, and accumulate extremely rich data.
Nevertheless, the network structures producing these data are often deeply
hidden in these data. Depicting network structures by analysing the available
data, i.e., the inverse problems turns to be of great significant. On one hand,
dynamics are often driven by various unknown facts, called noises. On the other
hand, network structures of practical systems are commonly nonlinear, and
different nonlinearities can provide rich dynamic features and meaningful
functions of realistic networks. So far, no method, both theoretically or
numerically, has been found to systematically treat the both difficulties
together. Here we propose to use high-order correlation computations (HOCC) to
treat nonlinear dynamics; use two-time correlations to treat noise effects; and
use suitable basis and correlator vectors to unifiedly depict all dynamic
nonlinearities and topological interaction links and noise statistical
structures. All the above theoretical frameworks are constructed in a closed
form and numerical simulations fully verify the validity of theoretical
predictions.


title:
Shear Melting and High Temperature Embrittlement: Theory and Application
  to Machining Titanium

abstract:
  We show that alloying with rare earth metals (REMs) can dramatically improve
the machineability of a range of titanium alloys, even though the REM is not
incorporated in the alloy matrix. The mechanism for this is that under cutting,
shear bands are formed within which the nano-precipitates of REM are shear
mixed. This lowers the melting point such that the mechanism of deformation
changes from dislocation mechanism to localised amorphisation and shear
softening. The material then fractures along the thin, amorphous shear-band.
Outside the shear band, the REM remains as precipitates. The new alloys have
similar mechanical properties and biocompatibility to conventional materials.


title:
Spin filtering and switching action in a diamond network with
  magnetic-nonmagnetic atomic distribution

abstract:
  We propose a simple model quantum network consisting of diamond-shaped
plaquettes with deterministic distribution of magnetic and non-magnetic atoms
in presence of a uniform external magnetic flux in each plaquette and predict
that such a simple model can be a prospective candidate for spin filter as well
as flux driven spintronic switch. The orientations and the amplitudes of the
substrate magnetic moments play a crucial role in the energy band engineering
of the two spin channels which essentially gives us a control over the spin
transmission leading to a spin filtering effect. The externally tunable
magnetic flux plays an important role in inducing a switch on-switch off effect
for both the spin states indicating the behavior like a spintronic switch. Even
a correlated disorder configuration in the on-site potentials and in the
magnetic moments may lead to disorder-induced spin filtering phenomenon where
one of the spin channel gets entirely blocked leaving the other one
transmitting over the entire allowed energy regime. All these features are
established by evaluating the density of states and the two terminal
transmission probabilities using the transfer-matrix formalism within a
tight-binding framework. Experimental realization of our theoretical study may
be helpful in designing new spintronic devices.

categories: cond-mat.mes-hall cond-mat.dis-nn cond-mat.mtrl-sci cond-mat.other


title: Spectral analysis of morse-smale gradient flows

abstract:
  On a smooth, compact and oriented manifold without boundary, we give a
complete description of the correlation function of a Morse-Smale gradient flow
satisfying a certain nonresonance assumption. This is done by analyzing
precisely the spectrum of the generator of such a flow acting on certain
anisotropic spaces of currents. In particular, we prove that this dynamical
spectrum is given by linear combinations with integer coefficients of the
Lyapunov exponents at the critical points of the Morse function. Via this
spectral analysis and in analogy with Hodge-de Rham theory, we give an
interpretation of the Morse complex as the image of the de Rham complex under
the spectral projector on the kernel of the generator of the flow. This allows
us to recover classical results from differential topology such as the Morse
inequalities and Poincar{\'e} duality.


title:
Parameter inference method for stochastic single-cell dynamics from
  tree-structured data

abstract:
  With the advance of experimental techniques such as time-lapse fluorescence
microscopy, the availability of single-cell trajectory data has vastly
increased, and so has the demand for computational methods suitable for
parameter inference with this type of data. However, most of the currently
available methods treat single-cell trajectories independently, ignoring the
mother-daughter relationships and the information provided by population
structure. This information is however essential if a process of interest
happens at cell division, or if it evolves slowly compared to the duration of
the cell cycle. In this work, we highlight the importance of tracking cell
lineage trees and propose a Bayesian framework for parameter inference on
tree-structured data. Our method relies on a combination of Sequential Monte
Carlo for likelihood approximation and Markov Chain Monte Carlo for parameter
sampling. We demonstrate the capabilities of our inference framework on two
simple examples in which the lineage tree information is necessary: one in
which the cell phenotype can only switch at cell division and another where the
cell type fluctuates randomly over timescales that extend well beyond the
lifetime of a single cell.


title: Breaking of Large Amplitude Electron Plasma Wave in a Maxwellian Plasma

abstract:
  The determination of maximum possible amplitude of a coherent longitudinal
plasma oscillation/wave is a topic of fundamental importance in non-linear
plasma physics. The amplitudes of these large amplitude plasma waves is limited
by a phenomena called wave breaking which may be induced by several non-linear
processes. It was shown by Coffey [T. P. Coffey, Phys. Fluids 14, 1402 (1971)]
using a "water-bag" distribution for electrons that, in a warm plasma the
maximum electric field amplitude and density amplitude implicitly depend on the
electron temperature, known as Coffey's limit. In this paper, the breaking of
large amplitude freely running electron plasma wave in a homogeneous warm
plasma where electron's velocity distribution is Maxwellian has been studied
numerically using 1D Particle in Cell (PIC) simulation method. It is found that
Coffey's propagating wave solutions, which was derived using a "water-bag"
distribution for electrons, also represent propagating waves in a Maxwellian
plasma. Coffey's wave breaking limit is also verified by loading Maxwellian
velocity distributions of different initial temperatures. A clear
correspondence between wave breaking and particle trapping is presented. Our
simulation results are also compared with the experimental results of B. S.
Bauer, A. Y. Wong, V. K. Decyk and G. Resenthal [Phys. Rev. Lett. 68, 3706
(1992)].


title:
Magnetization of the Mn$_{1-x}$Fe$_x$Si in high magnetic field up to 50
  T: possible evidence of a field-induced Griffiths phase

abstract:
  Magnetic properties of single crystals of Mn$_{1-x}$Fe$_x$Si solid solutions
with $x < 0.2$ are investigated by pulsed field technique in magnetic fields up
to 50 T. It is shown that magnetization of Mn$_{1-x}$Fe$_x$Si in the
paramagnetic phase follows power law $M(B) \sim B^\alpha$ with the exponents
$\alpha \sim 0.33-0.5$, which starts above characteristic fields $B_c \sim
1.5-7$ T depending on the sample composition and lasts up to highest used
magnetic field. Analysis of magnetization data including SQUID measurements in
magnetic fields below 5 T suggests that this anomalous behavior may be likely
attributed to the formation of a field-induced Griffiths phase in the presence
of spin-polaron effects.


title:
Exploring the reality of density substructures in the Palomar 5 stellar
  stream

abstract:
  We present an analysis of the presence of substructures in the stellar stream
of the Palomar 5 globular cluster, as derived from Sloan Digital Sky Survey
data. Using a matched filter technique, we recover the positions and sizes of
overdensities reported in previous studies. To explore the reality of these
structures, we also create an artificial model of the stream, in which we
construct a realistic background on top of which we add a perfectly smooth
stream structure, taking into account the effects of photometric completeness
and interstellar extinction. We find that the smooth artificial stream then
shows similarly-pronounced substructures as the real structure. Interestingly,
our best-fit N-body simulation does display real projected density variations
linked to stellar epicyclic motions, but these become less significant when
taking into account the SDSS star-count constraints. The substructures found
when applying our matched filter technique to the N-body particles converted
into observable stars are thus mostly unrelated to these epicyclic motions.
This analysis suggests that the majority of the previously-detected
substructures along the tidal tail of Palomar 5 are artefacts of observational
inhomogeneities.


title: Homoclinic points of 2-D and 4-D maps via the Parametrization Method

abstract:
  An interesting problem in solid state physics is to compute discrete breather
solutions in $\mathcal{N}$ coupled 1--dimensional Hamiltonian particle chains
and investigate the richness of their interactions. One way to do this is to
compute the homoclinic intersections of invariant manifolds of a saddle point
located at the origin of a class of $2\mathcal{N}$--dimensional invertible
maps. In this paper we apply the parametrization method to express these
manifolds analytically as series expansions and compute their intersections
numerically to high precision. We first carry out this procedure for a
2--dimensional (2--D) family of generalized Henon maps ($\mathcal{N}$=1), prove
the existence of a hyperbolic set in the non-dissipative case and show that it
is directly connected to the existence of a homoclinic orbit at the origin.
Introducing dissipation we demonstrate that a homoclinic tangency occurs beyond
which the homoclinic intersection disappears. Proceeding to $\mathcal{N}=2$, we
use the same approach to determine the homoclinic intersections of the
invariant manifolds of a saddle point at the origin of a 4--D map consisting of
two coupled 2--D cubic H\'enon maps. In dependence of the coupling the
homoclinic intersection is determined, which ceases to exist once a certain
amount of dissipation is present. We discuss an application of our results to
the study of discrete breathers in two linearly coupled 1--dimensional particle
chains with nearest--neighbor interactions and a Klein--Gordon on site
potential.


title:
Beamwidth Optimization in Millimeter Wave Small Cell Networks with Relay
  Nodes: A Swarm Intelligence Approach

abstract:
  Millimeter wave (mmWave) communications have been postulated as one of the
most disruptive technologies for future 5G systems. Among mmWave bands the
60-GHz radio technology is specially suited for ultradense small cells and
mobile data offloading scenarios. Many challenges remain to be addressed in
mmWave communications but among them deafness, or misalignment between
transmitter and receivers beams, and interference management lie among the most
prominent ones. In the recent years, scenarios considering negligible
interference on mmWave resource allocation have been rather common in
literature. To this end, interestingly, many open issues still need to be
addressed such as the applicability of noise-limited regime for mmWave.
Furthermore, in mmWave the beam-steering mechanism imposes a forced silence
period, in the course of which no data can be conveyed, that should not be
neglected in throughput/delay calculations. This paper introduces mmWave
enabled Small Cell Networks (SCNs) with relaying capabilities where as a result
of a coordinated meta-heuristically optimized beamwidth/alignment-delay
approach overall system throughput is optimized. Simulations have been conveyed
for three transmitter densities under TDMA and naive 'all-on' scheduling
producing average per node throughput increments of up to 248%. The paper
further elaborates on the off-balancing impact of alignment delay and
time-multiplexing strategies by illustrating how the foreseen transition that
increasing the number of transmitters produces in the regime of a fixed-node
size SCN in downlink operation fades out by a poor choice in the scheduling
strategy.


title:
Photoionization of Co$^{+}$ and electron-impact excitation of Co$^{2+}$
  using the Dirac R-matrix method

abstract:
  Modelling of massive stars and supernovae (SNe) plays a crucial role in
understanding galaxies. From this modelling we can derive fundamental
constraints on stellar evolution, mass-loss processes, mixing, and the products
of nucleosynthesis. Proper account must be taken of all important processes
that populate and depopulate the levels (collisional excitation, de-excitation,
ionization, recombination, photoionization, bound-bound processes). For the
analysis of Type Ia SNe and core collapse SNe (Types Ib, Ic and II) Fe group
elements are particularly important. Unfortunately little data is currently
available and most noticeably absent are the photoionization cross-sections for
the Fe-peaks which have high abundances in SNe. Important interactions for both
photoionization and electron-impact excitation are calculated using the
relativistic Dirac Atomic $R$-matrix Codes (DARC) for low ionization stages of
cobalt. All results are calculated up to photon energies of 45 eV and electron
energies up to 20 eV. The wavefunction representation of Co III has been
generated using GRASP0 by including the dominant 3d$^7$, 3d$^6$[4s, 4p],
3p$^4$3d$^9$ and 3p$^6$3d$^9$ configurations, resulting in 292 fine structure
levels. Electron-impact collision strengths and Maxwellian averaged effective
collision strengths across a wide range of astrophysically relevant
temperatures are computed for Co III. In addition, statistically weighted
level-resolved ground and metastable photoionization cross-sections are
presented for Co II and compared directly with existing work.


title:
Sequential design of experiments for estimating percentiles of black-box
  functions

abstract:
  Estimating percentiles of black-box deterministic functions with random
inputs is a challenging task when the number of function evaluations is
severely restricted, which is typical for computer experiments. This article
proposes two new sequential Bayesian methods for percentile estimation based on
the Gaussian Process metamodel. Both rely on the Stepwise Uncertainty Reduction
paradigm, hence aim at providing a sequence of function evaluations that
reduces an uncertainty measure associated with the percentile estimator. The
proposed strategies are tested on several numerical examples, showing that
accurate estimators can be obtained using only a small number of functions
evaluations.


title:
The host galaxies of active galactic nuclei with powerful relativistic
  jets

abstract:
  We present deep Near-infrared (NIR) images of a sample of 19
intermediate-redshift ($0.3<z<1.0$) radio-loud active galactic nuclei (AGN)
with powerful relativistic jets ($L_{1.4GHz} >10^{27}$ WHz$^{-1}$), previously
classified as flat-spectrum radio quasars. We also compile host galaxy and
nuclear magnitudes for blazars from literature. The combined sample (this work
and compilation) contains 100 radio-loud AGN with host galaxy detections and a
broad range of radio luminosities $L_{1.4GHz} \sim 10^{23.7} -
10^{28.3}$~WHz$^{-1}$, allowing us to divide our sample into high-luminosity
blazars (HLBs) and low-luminosity blazars (LLBs). The host galaxies of our
sample are bright and seem to follow the $\mu_{e}$-$R_{eff}$ relation for
ellipticals and bulges. The two populations of blazars show different
behaviours in the \mnuc - \mbulge plane, where a statistically significant
correlation is observed for HLBs. Although it may be affected by selection
effects, this correlation suggests a close coupling between the accretion mode
of the central supermassive black hole and its host galaxy, that could be
interpreted in terms of AGN feedback. Our findings are consistent with
semi--analytical models where low--luminosity AGN emit the bulk of their energy
in the form of radio jets, producing a strong feedback mechanism, and
high--luminosity AGN are affected by galaxy mergers and interactions, which
provide a common supply of cold gas to feed both nuclear activity and star
formation episodes.


title:
DMRG-CASPT2 study of the longitudinal static second hyperpolarizability
  of all-trans polyenes

abstract:
  We have implemented internally contracted complete active space second order
perturbation theory (CASPT2) with the density matrix renormalization group
(DMRG) as active space solver [Y. Kurashige and T. Yanai, J. Chem. Phys. 135,
094104 (2011)]. Internally contracted CASPT2 requires to contract the
generalized Fock matrix with the 4-particle reduced density matrix (4-RDM) of
the reference wavefunction. The required 4-RDM elements can be obtained from
3-particle reduced density matrices (3-RDM) of different wavefunctions, formed
by symmetry-conserving single-particle excitations op top of the reference
wavefunction. In our spin-adapted DMRG code chemps2
[https://github.com/sebwouters/chemps2], we decompose these excited
wavefunctions as spin-adapted matrix product states, and calculate their 3-RDM
in order to obtain the required contraction of the generalized Fock matrix with
the 4-RDM of the reference wavefunction. In this work, we study the
longitudinal static second hyperpolarizability of all-trans polyenes
C$_{2n}$H$_{2n+2}$ [n = 4 - 12] in the cc-pVDZ basis set. DMRG-SCF and
DMRG-CASPT2 yield substantially lower values and scaling with system size
compared to RHF and MP2, respectively.


title: Advection of nematic liquid crystals by chaotic flow

abstract:
  Consideration is given to the effects of inhomogeneous shear flow (both
regular and chaotic) on nematic liquid crystals in a planar geometry. The
Landau--de Gennes equation coupled to an externally-prescribed flow field is
the basis for the study: this is solved numerically in a periodic spatial
domain. The focus is on a limiting case where the advection is passive, such
that variations in the liquid-crystal properties do not feed back into the
equation for the fluid velocity. The main tool for analyzing the results (both
with and without flow) is the identification of the fixed points of the
dynamical equations without flow, which are relevant (to varying degrees) when
flow is introduced. The fixed points are classified as stable/unstable and
further as either uniaxial or biaxial. Accordingly, various models of passive
shear flow are investigated, with the main focus being on the case where
tumbling is absent from the model. In this scenario, not only must advection of
the $Q$-tensor be considered, but also its co-rotation relative to the local
vorticity field. Thus, only the biaxial fixed point survives as a solution of
the $Q$-tensor dynamics under the imposition of a general flow field. For
certain flows for which co-rotation effects can effectively be ignored along
trajectories, both families of fixed points survive. In this scenario, the
system exhibits coarsening arrest, whereby the liquid-crystal domains are
`frozen in' to the flow structures and the growth in their size is thus
limited. The outcome (biaxial final state or a mixture of both families of
fixed points) can be understood in terms of the flow time- and length-scales
that manifest themselves through the co-rotational derivative. Some
consideration is also given to the specific case where tumbling is present;
here, the flow has a strong effect on the liquid-crystal morphology.


title: Applying Seamful Design in Location-based Mobile Museum Applications

abstract:
  The application of mobile computing is currently altering patterns of our
behavior to a greater degree than perhaps any other invention. In combination
with the introduction of power efficient wireless communication technologies,
such as Bluetooth Low Energy (BLE), designers are today increasingly empowered
to shape the way we interact with our physical surroundings and thus build
entirely new experiences. However, our evaluations of BLE and its abilities to
facilitate mobile location-based experiences in public environments revealed a
number of potential problems. Most notably, the position and orientation of the
user in combination with various environmental factors, such as crowds of
people traversing the space, were found to cause major fluctuations of the
received BLE signal strength. These issues are rendering a seamless functioning
of any location-based application practically impossible. Instead of achieving
seamlessness by eliminating these technical issues, we thus choose to advocate
the use of a seamful approach, i.e. to reveal and exploit these problems and
turn them into a part of the actual experience. In order to demonstrate the
viability of this approach, we designed, implemented and evaluated the Ghost
Detector - an educational location-based museum game for children. By
presenting a qualitative evaluation of this game and by motivating our design
decisions, this paper provides insight into some of the challenges and possible
solutions connected to the process of developing location-based BLE-enabled
experiences for public cultural spaces.


title:
Observation of intrinsically bright terrestrial gamma ray flashes from
  the Mediterranean basin

abstract:
  We present three terrestrial gamma ray flashes (TGFs) observed over the
Mediterranean basin by the Reuven Ramaty High Energy Solar Spectroscope Imager
(RHESSI) satellite. Since the occurrence of these events in the Mediterranean
region is quite rare, the characterisation of the events was optimised by
combining different approaches in order to better define the cloud of origin.
The TGFs on 7 November 2004 and 16 October 2006 came from clouds with cloud top
higher than 10-12 km where often a strong penetration into the stratosphere is
found. This kind of cloud is usually associated with heavy precipitation and
intense lightning activity. Nevertheless, the analysis of the cloud type based
on satellite retrievals shows that the TGF on 27 May 2004 was produced by an
unusual shallow convection. This result appears to be supported by the model
simulation of the particle distribution and phase in the upper troposphere. The
TGF on 7 November 2004 is among the brightest ever measured by RHESSI. The
analysis of the energy spectrum of this event is consistent with a production
altitude $\leq$12 km, which is in the upper part of the cloud, as found by the
meteorological analysis of the TGF-producing thunderstorm. This event must be
unusually bright at the source in order to produce such a strong signal in
RHESSI. We estimate that this TGF must contain $\sim$3x10$\rm ^{18}$ initial
photons with energy $>$1 MeV. This is 1 order of magnitude brighter than
earlier estimations of an average RHESSI TGF.


title: BTZ extensions of globally hyperbolic singular flat spacetimes

abstract:
  Minkowski space is the local model of 3 dimensionnal flat spacetimes. Recent
progress in the description of globally hyperbolic flat spacetimes showed
strong link between Lorentzian geometry and Teichm{\"u}ller space. We notice
that Lorentzian generalisations of conical singularities are useful for the
endeavours of descripting flat spacetimes, creating stronger links with
hyperbolic geometry and compactifying spacetimes. In particular massive
particles and extreme BTZ singular lines arise naturally. This paper is
three-fold. First, prove background local properties which will be useful for
future work. Second, generalise fundamental theorems of the theory of globally
hyperbolic flat spacetimes. Third, defining BTZ-extension and proving it
preserves Cauchy-maximality and Cauchy-completeness.


title:
Torus Actions, Fixed-Point Formulas, Elliptic Genera and positive
  curvature

abstract:
  We study fixed points of smooth torus actions on closed manifolds using fixed
point formulas and equivariant elliptic genera. We also give applications to
positively curved Riemannian manifolds with symmetry.