title: Stability Analysis of Convection in the Intracluster Medium

abstract:
  We use the machinery usually employed for studying the onset of
Rayleigh--B\'enard convection in hydro- and magnetohydro-dynamic settings to
address the onset of convection induced by the magnetothermal instability and
the heat-flux-buoyancy-driven-instability in the weakly-collisional magnetized
plasma permeating the intracluster medium. Since most of the related numerical
simulations consider the plasma being bounded between two `plates' on which
boundary conditions are specified, our strategy provides a framework that could
enable a more direct connection between analytical and numerical studies. We
derive the conditions for the onset of these instabilities considering the
effects of induced magnetic tension resulting from a finite plasma beta. We
provide expressions for the Rayleigh number in terms of the wave vector
associated with a given mode, which allow us to characterize the modes that are
first to become unstable. For both the heat-flux-buoyancy-driven-instability
and the magnetothermal instability, oscillatory marginal stable states are
possible.


title:
The Relative Growth of Black Holes and of the Stellar Components of
  Galaxies

abstract:
  Recent observations indicate that the mass of Supermassive Black Holes
(SMBHs) correlate differently with different galaxy stellar components.
Comparing such observations with the results of "ab initio" galaxy formation
models can provide insight on the mechanisms leading to the growth of SMBHs.
Here we use a state-of-the-art semi-analytic model of galaxy formation to
investigate the correlation of the different galaxy stellar components with the
mass of the central SMBH. The stellar mass in the disc, in the bulge, and in
the pseudo-bulge of galaxies is related to quiescent star formation, to galaxy
interactions, and to the loss of angular momentum following disc instabilities,
respectively. Consistently with recent findings, we find that while the
predicted bulge masses are tightly correlated with the SMBH masses, the
correlation between the latter and the galactic discs shows a much larger
scatter, in particular when bulgeless galaxies are considered. In addition, we
obtain that the predicted masses of pseudo-bulges shows little or
no-correlation with the masses of SMBHs. We track the histories of merging,
star formation, and SMBH accretion to investigate the physical processes at the
origin of such findings within the context of cosmological models of galaxy
formation. Finally, we discuss the effects of variations of our assumed
fiducial model on the results.


title:
Adaptive Learning Rate via Covariance Matrix Based Preconditioning for
  Deep Neural Networks

abstract:
  Adaptive learning rate algorithms such as RMSProp are widely used for
training deep neural networks. RMSProp offers efficient training since it uses
first order gradients to approximate Hessian-based preconditioning. However,
since the first order gradients include noise caused by stochastic
optimization, the approximation may be inaccurate. In this paper, we propose a
novel adaptive learning rate algorithm called SDProp. Its key idea is effective
handling of the noise by preconditioning based on covariance matrix. For
various neural networks, our approach is more efficient and effective than
RMSProp and its variant.


title: New Physics / Resonances in Vector Boson Scattering at the LHC

abstract:
  Vector boson scattering is (together with the production of multiple
electroweak gauge bosons) the key process in the current run 2 of LHC to probe
the microscopic nature of electroweak symmetry breaking. Deviations from the
Standard Model are generically parameterized by higher-dimensional operators,
however, there is a subtle issue of perturbative unitarity for such approaches
for the process above. We discuss a parameter-free unitarization prescription
to get physically meaningful predictions. In the second part, we construct
simplified models for generic new resonances that can appear in vector boson
scattering, with a special focus on the technicalities of tensor resonances.


title: The impact of sunlight on high-latitude equivalent currents

abstract:
  Ground magnetic field measurements can be mathematically related to an
overhead ionospheric equivalent current. In this study we look in detail at how
the global equivalent current, calculated using more than 30 years of SuperMAG
magnetometer data, changes with sunlight conditions. The calculations are done
using spherical harmonic analysis in quasi-dipole coordinates, a technique
which leads to improved accuracy compared to previous studies. Sorting the data
according to the location of the sunlight terminator and orientation of the
interplanetary magnetic field (IMF), we find that the equivalent current
resembles ionospheric convection patterns on the sunlit side of the terminator
but not on the dark side. On the dark side, with southward IMF, the current is
strongly dominated by a dawn cell and the current across the polar cap has a
strong dawnward component. The contrast between the sunlit and dark side
increases with increasing values of the $\mathit{F}_{10.7}$ index, showing that
increasing solar EUV flux changes not only the magnitude but also the
morphology of the equivalent current system. The results are consistent with a
recent study showing that Birkeland currents indirectly determine the
equivalent current in darkness and that Hall currents dominate in sunlight.
This has implication for the interpretation of ground magnetic field
measurements and suggests that the magnetic disturbances at conjugate points
will be asymmetrical when the solar illumination is different.


title: Minimal surfaces for Hitchin representations

abstract:
  Given a reductive representation $\rho: \pi_1(S)\rightarrow G$, there exists
a $\rho$-equivariant harmonic map $f$ from the universal cover of a fixed
Riemann surface $\Sigma$ to the symmetric space $G/K$ associated to $G$. If the
Hopf differential of $f$ vanishes, the harmonic map is then minimal. In this
paper, we investigate the properties of immersed minimal surfaces inside
symmetric space associated to a subloci of Hitchin component: $q_n$ and
$q_{n-1}$ case. First, we show that the pullback metric of the minimal surface
dominates a constant multiple of the hyperbolic metric in the same conformal
class and has a strong rigidity property. Secondly, we show that the immersed
minimal surface is never tangential to any flat inside the symmetric space. As
a direct corollary, the pullback metric of the minimal surface is always
strictly negatively curved. In the end, we find a fully decoupled system to
approximate the coupled Hitchin system.


title: Majorana Edge Modes with Gain and Loss

abstract:
  We consider a non-Hermitian generalization of the Kitaev model and study the
existence of stable Majorana zero energy modes. We show that they exist in the
limit of zero chemical potential even if balanced gain and loss are randomly
distributed along the lattice. We show that Majorana zero modes also appear if
the chemical potential is different from zero provided that not the full
Hamiltonian but the non-Hermitian part of the Hamiltonian is PT symmetric.


title: On Quantum Tensor Product Codes

abstract:
  We present a general framework for the construction of quantum tensor product
codes (QTPC). In a classical tensor product code (TPC), its parity check matrix
is con- structed via the tensor product of parity check matrices of the two
component codes. We show that by adding some constraints on the component
codes, several classes of dual-containing TPCs can be obtained. By selecting
different types of component codes, the proposed method enables the
construction of a large family of QTPCs and they can provide a wide variety of
quantum error control abilities. In particular, if one of the component codes
is selected as a burst-error-correction code, then QTPCs have quantum
multiple-burst-error-correction abilities, provided these bursts fall in
distinct subblocks. Compared with concatenated quantum codes (CQC), the
component code selections of QTPCs are much more exible than those of CQCs
since only one of the component codes of QTPCs needs to satisfy the
dual-containing restriction. We show that it is possible to construct QTPCs
with parameters better than other classes of quantum error-correction codes
(QECC), e.g., CQCs and quantum BCH codes. Many QTPCs are obtained with
parameters better than previously known quantum codes available in the
literature. Several classes of QTPCs that can correct multiple quantum bursts
of errors are constructed based on reversible cyclic codes and
maximum-distance-separable (MDS) codes.


title: $p$-subgroups of units in $\mathbb{Z}G$

abstract:
  We consider the question whether a Sylow like theorem is valid in the
normalized units of integral group rings of finite groups. After a short survey
on the known results we show that this is the case for integral group rings of
Frobenius groups. This completes work of M.A. Dokuchaev, S.O. Juriaans and V.
Bovdi and M. Hertweck. We analyze projective linear simple groups and show what
can be achieved for p-subgroups with known methods.


title:
Ergodic measures on spaces of infinite matrices over non-Archimedean
  locally compact fields

abstract:
  Let $F$ be a non-discrete non-Archimedean locally compact field and
$\mathcal{O}_F$ the ring of integers in $F$. The main results of this paper are
Theorem 1.2 that classifies ergodic probability measures on the space
$\mathrm{Mat}(\mathbb{N}, F)$ of infinite matrices with enties in $F$ with
respect to the natural action of the group $\mathrm{GL}(\infty,\mathcal{O}_F)
\times \mathrm{GL}(\infty,\mathcal{O}_F)$ and Theorem 1.6 that, for non-dyadic
$F$, classifies ergodic probability measures on the space
$\mathrm{Sym}(\mathbb{N}, F)$ of infinite symmetric matrices with respect to
the natural action of the group $\mathrm{GL}(\infty,\mathcal{O}_F)$.


title: Stable extrapolation of analytic functions

abstract:
  This paper examines the problem of extrapolation of an analytic function for
$x > 1$ given perturbed samples from an equally spaced grid on $[-1,1]$.
Mathematical folklore states that extrapolation is in general hopelessly
ill-conditioned, but we show that a more precise statement carries an
interesting nuance. For a function $f$ on $[-1,1]$ that is analytic in a
Bernstein ellipse with parameter $\rho > 1$, and for a uniform perturbation
level $\epsilon$ on the function samples, we construct an asymptotically best
extrapolant $e(x)$ as a least squares polynomial approximant of degree $M^*$
given explicitly. We show that the extrapolant $e(x)$ converges to $f(x)$
pointwise in the interval $I_\rho\in[1,(\rho+\rho^{-1})/2)$ as $\epsilon \to
0$, at a rate given by a $x$-dependent fractional power of $\epsilon$. More
precisely, for each $x \in I_{\rho}$ we have
  \[
  |f(x) - e(x)| = \mathcal{O}\left( \epsilon^{-\log r(x) / \log\rho} \right),
\qquad\qquad r(x) = \frac{x+\sqrt{x^2-1}}{\rho},
  \] up to log factors, provided that the oversampling conditioning is
satisfied. That is,
  \[
  M^* \leq \frac{1}{2} \sqrt{N},
  \] which is known to be needed from approximation theory. In short,
extrapolation enjoys a weak form of stability, up to a fraction of the
characteristic smoothness length. The number of function samples, $N+1$, does
not bear on the size of the extrapolation error provided that it obeys the
oversampling condition. We also show that one cannot construct an
asymptotically more accurate extrapolant from $N+1$ equally spaced samples than
$e(x)$, using any other linear or nonlinear procedure. The proofs involve
original statements on the stability of polynomial approximation in the
Chebyshev basis from equally spaced samples and these are expected to be of
independent interest.


title: Caching Improvement Using Adaptive User Clustering

abstract:
  In this article we explore one of the most promising technologies for 5G
wireless networks using an underlay small cell network, namely proactive
caching. Using the increase in storage technologies and through studying the
users behavior, peak traffic can be reduced through proactive caching of the
content that is most probable to be requested. We propose a new method, in
which, instead of caching the most popular content, the users within the
network are clustered according to their content popularity and the caching is
done accordingly. We present also a method for estimating the number of
clusters within the network based on the Akaike information criterion. We
analytically derive a closed form expression of the hit probability and we
propose an optimization problem in which the small base stations association
with clusters is optimized.


title:
Energy exchange and localization in essentially nonlinear oscillatory
  systems: canonical formalism

abstract:
  Over recent years, a lot of progress has been achieved in understanding of
the relationship between localization and transport of energy in essentially
nonlinear oscillatory systems. In this paper we are going to demonstrate that
the structure of the resonance manifold can be conveniently described in terms
of canonical action-angle variables. Such formalism has important theoretical
advantages: all resonance manifolds may be described at the same level of
complexity, appearance of additional conservation laws on these manifolds is
easily proven both in autonomous and non-autonomous settings. The harmonic
balance - based complexification approach, used in many previous studies on the
subject, is shown to be a particular case of the canonical formalism. Moreover,
application of the canonic averaging allows treatment of much broader variety
of dynamical models. As an example, energy exchanges in systems of coupled
trigonometrical and vibro-impact oscillators are considered.


title:
Realization of uniform synthetic magnetic fields by periodically shaking
  an optical square lattice

abstract:
  Shaking a lattice system, by modulating the location of its sites
periodically in time, is a powerful method to create effective magnetic fields
in engineered quantum systems, such as cold gases trapped in optical lattices.
However, such schemes are typically associated with space-dependent effective
masses (tunneling amplitudes) and non-uniform flux patterns. In this work we
investigate this phenomenon theoretically, by computing the effective
Hamiltonians and quasienergy spectra associated with several kinds of
lattice-shaking protocols. A detailed comparison with a method based on moving
lattices, which are added on top of a main static optical lattice, is provided.
This study allows the identification of novel shaking schemes, which
simultaneously provide uniform effective mass and magnetic flux, with direct
implications for cold-atom experiments and photonics.


title: What controls the local time extent of flux transfer events?

abstract:
  Flux transfer events (FTEs) are the manifestation of bursty and/or patchy
magnetic reconnection at the magnetopause. We compare two sequences of the
ionospheric signatures of flux transfer events observed in global auroral
imagery and coherent ionospheric radar measurements. Both sequences were
observed during very similar seasonal and interplanetary magnetic field (IMF)
conditions, though with differing solar wind speed. A key observation is that
the signatures differed considerably in their local time extent. The two
periods are 26 August 1998, when the IMF had components
$\mathit{B}_{\mathit{z}}$ $\approx$ -10 nT and $\mathit{B}_{\mathit{y}}$
$\approx$ 9 nT and the solar wind speed was $\mathit{V}_{\mathit{x}}$ $\approx$
650 km $s^{-1}$, and 31 August 2005, IMF $\mathit{B}_{\mathit{z}}$ $\approx$ -7
nT, $\mathit{B}_{\mathit{y}}$ $\approx$ 17 nT, and $\mathit{V}_{\mathit{x}}$
$\approx$ 380 km $s^{-1}$. In the first case, the reconnection rate was
estimated to be near 160 kV, and the FTE signatures extended across at least 7
h of magnetic local time (MLT) of the dayside polar cap boundary. In the
second, a reconnection rate close to 80 kV was estimated, and the FTEs had a
MLT extent of roughly 2 h. We discuss the ramifications of these differences
for solar wind-magnetosphere coupling.


title:
On Advantages of the Kelvin Mapping in Finite Element Implementations of
  Deformation Processes

abstract:
  Classical continuum mechanical theories operate on three-dimensional
Eu-clidian space using scalar, vector, and tensor-valued quantities usually up
to the order of four. For their numerical treatment, it is common practice to
transform the relations into a matrix-vector format. This transformation is
usually performed using the so-called Voigt mapping. This mapping does not
preserve tensor character leaving significant room for error as stress and
strain quantities follow from different mappings and thus have to be treated
differently in certain mathematical operations. Despite its conceptual and
notational difficulties having been pointed out, the Voigt mapping remains the
foundation of most current finite element programmes. An alternative is the
so-called Kelvin mapping which has recently gained recognition in studies of
theoretical mechanics. This article is concerned with benefits of the Kelvin
mapping in numerical modelling tools such as finite element software. The
decisive difference to the Voigt mapping is that Kelvin's method preserves
tensor character, and thus the numerical matrix notation directly corresponds
to the original tensor notation. Further benefits in numerical implementations
are that tensor norms are calculated identically without distinguishing stress
or strain-type quantities and tensor equations can be directly transformed into
matrix equations without additional considerations. The only implementational
changes are related to a scalar factor in certain finite element matrices and
hence, harvesting the mentioned benefits comes at very little cost.


title: Long term behaviour of two interacting birth-and-death processes

abstract:
  In this paper we study the long term evolution of a continuous time Markov
chain formed by two interacting birth-and-death processes. The interaction
between the processes is modelled by transition rates which are functions with
suitable monotonicity properties. This is in line with the approach proposed by
Gauss G.F. and Kolmogorov A.N. for modelling interaction between species in
ecology. We obtain conditions for transience/recurrence of the Markov chain and
describe in detail its asymptotic behaviour in special transient cases. In
particular, we find that in some of these cases the Markov chain escapes to
infinity in an unusual way, and the corresponding trajectories can be rather
precisely described.


title: Estimation of cold plasma outflow during geomagnetic storms

abstract:
  Low-energy ions of ionospheric origin constitute a significant contributor to
the magnetospheric plasma population. Measuring cold ions is difficult though.
Observations have to be done at sufficiently high altitudes and typically in
regions of space where spacecraft attain a positive charge due to solar
illumination. Cold ions are therefore shielded from the satellite particle
detectors. Furthermore, spacecraft can only cover key regions of ion outflow
during segments of their orbit, so additional complications arise if continuous
longtime observations, such as during a geomagnetic storm, are needed. In this
paper we suggest a new approach, based on a combination of synoptic
observations and a novel technique to estimate the flux and total outflow
during the various phases of geomagnetic storms. Our results indicate large
variations in both outflow rates and transport throughout the storm. Prior to
the storm main phase, outflow rates are moderate, and the cold ions are mainly
emanating from moderately sized polar cap regions. Throughout the main phase of
the storm, outflow rates increase and the polar cap source regions expand.
Furthermore, faster transport, resulting from enhanced convection, leads to a
much larger supply of cold ions to the near-Earth region during geomagnetic
storms.


title: Type-II singularities of two-convex immersed mean curvature flow

abstract:
  We show that any strictly mean convex translator of dimension $n\geq 3$ which
admits a cylindrical estimate and a corresponding gradient estimate is
rotationally symmetric. As a consequence, we deduce that any translating
solution of the mean curvature flow which arises as a blow-up limit of a
two-convex mean curvature flow of compact immersed hypersurfaces of dimension
$n\geq 3$ is rotationally symmetric. The proof is rather robust, and applies to
a more general class of translator equations. As a particular application, we
prove an analogous result for a class of flows of embedded hypersurfaces which
includes the flow of two-convex hypersurfaces by the two-harmonic mean
curvature.


title:
Three-dimensional electromagnetic modeling of practical superconductors
  for power applications

abstract:
  HTS are feasible for hight power applications because of the smaller
consumption demand of the cooling system in comparison to the whole power
device. Real industral devices contain superconductors with 2D and 3D geometry
(coated conductors tapes represent an example of 2D geometry, since the
superconducting layer is very thin). In order to know the feasibility and the
optimum design of a certain device, there is a need of software tools. These
Numerical tools have hight requirements like fast computation, a physical model
for any E(J) relation of the superconductor and any complex geometry such as
coils, motors and generators, where E is the electric field and J is the
current density. In this work we present a 3D variational model based on a
functional that restricts the problem in the superconductor volume. We show the
magnetization process of a thin film and a 3D bulk sample. We compare our model
of the thin film geometry with the thin film formula, reaching a good
agreement. We also compare a striated tape, where the filaments are connected
by linear material, with a FEM model. We present several results for a thin
film with constant critical current density, Jc, magnetic-field dependent Jc,
and an anisotropic E(J) relation. For the latter, E is not parallel to J when
the magnetic flux density is not perpendicular to J (force free situation). The
last studied situation is the 3D cubic sample. We find the time dependence of
the current density and AC loss for each situation. In the cubic bulk sample,
we found a non-negligible component of the current density in the direction of
the applied field. The presented numerical method is very promising for 3D
modeling of superconducting samples and power applications.


title: Magnetic noise spectrum measurement by an atom laser in gravity

abstract:
  Bose-Einstein condensates of ultracold atoms can be used to sense
fluctuations of the magnetic field by means of transitions into untrapped
hyperfine states. It has been shown recently that counting the outcoupled atoms
can yield the power spectrum of the magnetic noise. We calculate the spectral
resolution function which characterizes the condensate as a noise measurement
device in this scheme. We use the description of the radio-frequency
outcoupling scheme of an atom laser which takes into account the gravitational
acceleration. Employing both an intuitive and the exact three-dimensional and
fully quantum mechanical approach we derive the position-dependent spectral
resolution function for condensates of different size and shape.


title:
The use of deep learning in image segmentation, classification and
  detection

abstract:
  Recent years have shown that deep learned neural networks are a valuable tool
in the field of computer vision. This paper addresses the use of two different
kinds of network architectures, namely LeNet and Network in Network (NiN). They
will be compared in terms of both performance and computational efficiency by
addressing the classification and detection problems. In this paper, multiple
databases will be used to test the networks. One of them contains images
depicting burn wounds from pediatric cases, another one contains an extensive
number of art images and other facial databases were used for facial keypoints
detection.


title: Spectral gap characterization of full type III factors

abstract:
  We give a spectral gap characterization of fullness for type $\mathrm{III}$
factors which is the analog of a theorem of Connes in the tracial case. Using
this criterion, we generalize a theorem of Jones by proving that if $M$ is a
full factor and $\sigma : G \rightarrow \mathrm{Aut}(M)$ is an outer action of
a discrete group $G$ whose image in $\mathrm{Out}(M)$ is discrete then the
crossed product von Neumann algebra $M \rtimes_\sigma G$ is also a full factor.
We apply this result to prove the following conjecture of Tomatsu-Ueda: the
continuous core of a type $\mathrm{III}_1$ factor $M$ is full if and only if
$M$ is full and its $\tau$ invariant is the usual topology on $\mathbb{R}$.


title: Optimal Dividend Payout Model with Risk Sensitive Preferences

abstract:
  We consider a discrete-time dividend payout problem with risk sensitive
shareholders. It is assumed that they are equipped with a risk aversion
coefficient and construct their discounted payoff with the help of the
exponential premium principle. This leads to a non-expected recursive utility
of the dividends. Within such a framework not only the expected value of the
dividends is taken into account but also their variability. Our approach is
motivated by a remark in Gerber and Shiu (2004). We deal with the finite and
infinite time horizon problems and prove that, even in general setting, the
optimal dividend policy is a band policy. We also show that the policy
improvement algorithm can be used to obtain the optimal policy and the
corresponding value function. Next, an explicit example is provided, in which
the optimal policy of a barrier type is shown to exist. Finally, we present
some numerical studies and discuss the influence of the risk sensitive
parameter on the optimal dividend policy.


title:
PETALO, a new concept for a Positron Emission TOF Apparatus based on
  Liquid xenOn

abstract:
  This master thesis presents a new type of Positron Emission TOF Apparatus
using Liquid xenOn (PETALO). The detector is based in the Liquid Xenon
Scintillating Cell (LXSC). The cell is a box filled with liquid xenon (LXe)
whose transverse dimensions are chosen to optimize packing and with a thickness
optimized to contain a large fraction of the incoming photons. The entry and
exit faces of the box (relative to the incoming gammas direction) are
instrumented with large silicon photomultipliers (SiPMs), coated with a
wavelength shifter, tetraphenyl butadiene (TPB). The non-instrumented faces are
covered by reflecting Teflon coated with TPB. In this thesis we show that the
LXSC can display an energy resolution of 5% FWHM, much better than that of
conventional solid scintillators such as LSO/LYSO. The LXSC can measure the
interaction point of the incoming photon with a resolution in the three
coordinates of 1 mm. The very fast scintillation time of LXe (2 ns) and the
availability of suitable sensors and electronics permits a coincidence
resolution time (CRT) in the range of 100-200 ps, again much better than any
current PET-TOF system. The LXSC constitutes the core of a high-sensitivity,
nuclear magnetic resonance compatible, PET device, with enhanced Time Of Flight
(TOF) sensitivity.


title:
Around Uncertainty Principles of Ingham-type on $\R^n$, $\T^n$ and Two
  Step Nilpotent Lie Groups

abstract:
  Classical results due to Ingham and Paley-Wiener characterize the existence
of nonzero functions supported on certain subsets of the real line in terms of
the pointwise decay of the Fourier transforms. We view these results as
uncertainty principles for Fourier transforms. We prove certain analogues of
these uncertainty principles on the $n$-dimensional Euclidean space, the
$n$-dimensional torus and connected, simply connected two step nilpotent Lie
groups. We also use these results to show a unique continuation property of
solutions to the initial value problem for time-dependent Schr\"odinger
equations on the Euclidean space and a class of connected, simply connected two
step nilpotent Lie groups.


title: Recent progress in determining p-class field towers

abstract:
  For a fixed prime p, the p-class tower F(p,infinity,K) of a number field K is
considered to be known if a pro-p presentation of the Galois group H = Gal(
F(p,infinity,K)/K ) is given. In the last few years, it turned out that the
Artin pattern AP(K) = (tau(K),kappa(K)) consisting of targets tau(K) =
(Cl(p,L)) and kernels kappa(K) = (ker(J(L/K)) of class extensions J(L/K):
Cl(p,K) --> Cl(p,L) to unramified abelian subfields L/K of the Hilbert p-class
field F(p,1,K) only suffices for determining the two-stage approximation G =
H/H" of H. Additional techniques had to be developed for identifying the group
H itself: searching strategies in descendant trees of finite p-groups, iterated
and multilayered IPADs of second order, and the cohomological concept of
Shafarevich covers involving relation ranks. This enabled the discovery of
three-stage towers of p-class fields over quadratic base fields K = Q(
squareroot(d) ) for p = 2,3,5. These non-metabelian towers reveal the new
phenomenon of various tree topologies expressing the mutual location of the
groups H and G.


title: Extrinsic curvature in 2-dimensional Causal Dynamical Triangulation

abstract:
  Causal Dynamical Triangulations (CDT) is a non-perturbative quantisation of
general relativity. Ho\v{r}ava-Lifshitz gravity on the other hand modifies
general relativity to allow for perturbative quan- tisation. Past work has
given rise to the speculation that Ho\v{r}ava-Lifshitz gravity might correspond
to the continuum limit of CDT. In this paper we add another piece to this
puzzle by applying the CDT quantisation prescription directly to
Ho\v{r}ava-Lifshitz gravity in 2 dimensions. We derive the continuum
Hamiltonian and we show that it matches exactly the Hamiltonian one derives
from canonically quantising the Ho\v{r}ava-Lifshitz action. Unlike the standard
CDT case, here the intro- duction of a foliated lattice does not impose further
restriction on the configuration space and, as a result, lattice quantisation
does not leave any imprint on continuum physics as expected.


title: Horizontally Scalable Submodular Maximization

abstract:
  A variety of large-scale machine learning problems can be cast as instances
of constrained submodular maximization. Existing approaches for distributed
submodular maximization have a critical drawback: The capacity - number of
instances that can fit in memory - must grow with the data set size. In
practice, while one can provision many machines, the capacity of each machine
is limited by physical constraints. We propose a truly scalable approach for
distributed submodular maximization under fixed capacity. The proposed
framework applies to a broad class of algorithms and constraints and provides
theoretical guarantees on the approximation factor for any available capacity.
We empirically evaluate the proposed algorithm on a variety of data sets and
demonstrate that it achieves performance competitive with the centralized
greedy solution.


title:
One-electron singular spectral features of the 1D Hubbard model at
  finite magnetic field

abstract:
  The momentum, electronic density, spin density, and interaction dependences
of the exponents that control the $(k,\omega)$-plane singular features of the
$\sigma =\uparrow,\downarrow$ one-electron spectral functions of the 1D Hubbard
model at finite magnetic field are studied. The usual half-filling concepts of
one-electron lower Hubbard band and upper Hubbard band are defined for all
electronic density and spin density values and the whole finite repulsion range
in terms of the rotated electrons associated with the model Bethe-ansatz
solution. Such rotated electrons are the link of the non-perturbative relation
between the electrons and the pseudofermions. Our results further clarify the
microscopic processes through which the pseudofermion dynamical theory accounts
for the $\sigma $ one-electron matrix elements between the ground state and
excited energy eigenstates.


title: Betti splittings for powers of sums of ideals

abstract:
  Let $A$ and $B$ be standard graded polynomial rings over a field $k$ and $I$
and $J$ be non-zero, proper homogeneous ideals contained in $A$ and $B$,
respectively. Denote by $P$ the sum of $I$ and $J$ in $R=A\otimes_k B$. Under
reasonable conditions on $k, I$ and $J$, we provide exact formulas and describe
the asymptotic behavior of the depth and the regularity of the powers of $P$ in
terms of the data of $I$ and $J$. Thereby, we strengthen previous work of H.T.
H\`a, N.V. Trung and T.N. Trung. Our main technical result says that, under the
aforementioned conditions, for all $s\ge 0$ and all $n\ge 1$, the simple
decomposition $I^sP^n=I^{s+1}P^{n-1}+I^sJ^n$ yields a Betti splitting for
$I^sP^n$. A decomposition of an ideal $L$ as a sum of two subideals is called a
Betti splitting if the minimal free resolution of $L$ is completely determined
by those of the summands and their intersection.


title: Entanglement Entropy of A Simple Non-minimal Coupling Model

abstract:
  We evaluate the entanglement entropy of a non-minimal coupling
Einstein-scalar theory with two approaches in classical Euclidean gravity. By
analysing the equation of motion, we find that the entangled surface is
restricted to be a minimal surface. The entanglement entropy formula is derived
directly from the approach of regularized conical singularity. On the other
hand, by expressing Ricci scalar of the conical spacetime, we obtain the same
result. In addition, we generalize the reduced geometric approach to Riemann
tensor and its derivations.


title: Subshifts with sparse traces

abstract:
  We study two-dimensional subshifts whose horizontal trace (a.k.a. projective
subdynamics) contains only points of finite support. Our main result is a
classification result for such subshifts satisfying a minimality property. As
corollaries, we obtain new proofs for various known results on traces of SFTs,
nilpotency and decidability of cellular automata, topological full groups and
the subshift of prime numbers. We also construct various (sofic) examples
illustrating the concepts.


title: Breaking Through the Full-Duplex Wi-Fi Capacity Gain

abstract:
  In this work we identify a seminal design guideline that prevents current
Full-Duplex (FD) MAC protocols to scale the FD capacity gain (i.e. 2x the
half-duplex throughput) in single-cell Wi-Fi networks. Under such guideline
(referred to as 1:1), a MAC protocol attempts to initiate up to two
simultaneous transmissions in the FD bandwidth. Since in single-cell Wi-Fi
networks MAC performance is bounded by the PHY layer capacity, this implies
gains strictly less than 2x over half-duplex at the MAC layer. To face this
limitation, we argue for the 1:N design guideline. Under 1:N, FD MAC protocols
'see' the FD bandwidth through N>1 orthogonal narrow-channel PHY layers. Based
on theoretical results and software defined radio experiments, we show the 1:N
design can leverage the Wi-Fi capacity gain more than 2x at and below the MAC
layer. This translates the denser modulation scheme incurred by channel
narrowing and the increase in the spatial reuse offer enabled by channel
orthogonality. With these results, we believe our design guideline can inspire
a new generation of Wi-Fi MAC protocols that fully embody and scale the FD
capacity gain.


title: On stable constant mean curvature surfaces with free boundary

abstract:
  In [20], Ros and Vergasta proved that an immersed orientable compact stable
constant mean curvature surface $\Sigma$ with free boundary in a closed ball
$B\subset\mathbb{R}^3$ must be a planar equator, a spherical cap or a surface
of genus 1 with at most two boundary components. In this article, by using a
modified Hersch type balancing argument, we complete their work by proving that
$\Sigma$ cannot have genus 1.


title:
Software startuppers took the medias paycheck Medias fightback happens
  through startup culture and abstraction shifts

abstract:
  The collapse of old print media and journalism happened when the Internet,
its solutions, services and communities became mature and mobile devices
reached the market. The reader abandoned printed dailies for free and mobile
access to information. The business of core industries of the early Internet
and mobile communication, the mobile network manufacturers and operators are
also in stagnation and decline. Therefore these industries may have similar
interests to improve or even restructure their own businesses as well as to
establish totally new business models by going into media and journalism.
  This paper analyses, first, the production flows and business models of the
old and present media species. Second, it analyses the current market
positioning of the network manufacturers and operators. Third, the paper
suggests two avenues for media and journalism and the network manufacturers and
operators, the Trio, to join their forces to update journalism and make all
three stagnating industries great again. Last, we propose further research,
development and discussion on the topic and envision possible futures for
journalism, if the three would engage in cooperation. We see that the
discussion should consist of ethical, societal and philosophical subjects
because the development of the Internet solutions are based on 'technology
first' actions.
  We find and outline a tremendous opportunity to create a new industry with
new actors through combining the interests of the network manufacturers,
network operators and journalism in a systemic solution through a strategic
alliance and collaboration Fig. 1. Software startuppers with their applications
and communities will be the drivers for this abstraction shift in media and
journalism.


title:
Interplay of symmetries and other integrability quantifiers in finite
  dimensional integrable nonlinear dynamical systems

abstract:
  In this work, we establish a connection between the extended Prelle-Singer
procedure with other widely used analytical methods to identify integrable
systems in the case of $n^{th}$-order nonlinear ordinary differential equations
(ODEs). By synthesizing these methods we bring out the interlink between Lie
point symmetries, contact symmetries, $\lambda$-symmetries, adjoint-symmetries,
null forms, Darboux polynomials, integrating factors, Jacobi last multiplier
and generalized $\lambda$-symmetries corresponding to the $n^{th}$-order ODEs.
We also prove these interlinks with suitable examples. By exploiting these
interconnections, the characteristic quantities associated with different
methods can be deduced without solving the associated determining equations.


title:
Spatio-temporal correlations in models of collective motion ruled by
  different dynamical laws

abstract:
  Information transfer is an essential factor in determining the robustness of
collective behaviour in biological systems with distributed control. The most
direct way to study the information transfer mechanisms is to experimentally
detect the propagation across the system of a signal triggered by some
perturbation. However, for field experiments this method is inefficient, as the
possibilities of the observer to perturb the group are limited and empirical
observations must rely on rare natural perturbations. An alternative way is to
use spatio-temporal correlations to assess the information transfer mechanism
directly from the spontaneous fluctuations of the system, without the need to
have an actual propagating signal on record. We test the approach on ground
truth data provided by numerical simulations in three dimensions of two models
of collective behaviour characterized by very different dynamical equations and
information transfer mechanisms: the classic Vicsek model, describing an
overdamped noninertial dynamics and the inertial spin model, characterized by
an un- derdamped inertial dynamics. By using dynamical finite size scaling, we
show that spatio-temporal correlations are able to distinguish unambiguously
the diffusive information transfer mechanism of the Vicsek model from the
linear mechanism of the inertial spin model.


title: On gauged maximal d=8 supergravities

abstract:
  We study the gauging of maximal $d=8$ supergravity using the embedding tensor
formalism. We focus on SO$(3)$ gaugings, study all the possible choices of
gauge fields and construct explicitly the bosonic actions (including the
complicated Chern-Simons terms) for all these choices, which are parametrized
by a parameter associated to the 8-dimensional SL$(2,\mathbb{R})$ duality group
that relates all the possible choices which are, ultimately, equivalent from
the purely 8-dimensional point of view. Our result proves that the theory
constructed by Salam and Sezgin by Scherk-Schwarz compactification of $d=11$
supergravity and the theory constructed in Ref.~\cite{AlonsoAlberca:2000gh} by
dimensional reduction of the so called ``massive 11-dimensional supergravity''
proposed by Meessen and Ort\'{\i}n in Ref.~\cite{Meessen:1998qm} are indeed
related by an SL$(2,\mathbb{R})$ duality even though they have two completely
different 11-dimensional origins.


title:
A compact light readout system for longitudinally segmented shashlik
  calorimeters

abstract:
  The longitudinal segmentation of shashlik calorimeters is challenged by dead
zones and non-uniformities introduced by the light collection and readout
system. This limitation can be overcome by direct fiber-photosensor coupling,
avoiding routing and bundling of the wavelength shifter fibers and embedding
ultra-compact photosensors (SiPMs) in the bulk of the calorimeter. We present
the first experimental test of this readout scheme performed at the CERN PS-T9
beamline in 2015 with negative particles in the 1-5~GeV energy range. In this
paper, we demonstrate that the scheme does not compromise the energy resolution
and linearity compared with standard light collection and readout systems. In
addition, we study the performance of the calorimeter for partially contained
charged hadrons to assess the $e/\pi$ separation capability and the response of
the photosensors to direct ionization.


title: On the global dynamics of periodic triangular maps

abstract:
  This paper is an extension of an earlier paper that dealt with global
dynamics in autonomous triangular maps. In the current paper, we extend the
results on global dynamics of autonomous triangular maps to periodic
non-autonomous triangular maps. We show that, under certain conditions, the
orbit of every point in a periodic non-autonomous triangular map converges to a
fixed point (respectively, periodic orbit of period $p$) if and only if there
is no periodic orbit of prime period two (respectively, periodic orbits of
prime period greater than $p$).


title: Lattice Landau gauge quark propagator and the quark-gluon vertex

abstract:
  We report preliminary results of our ongoing lattice computation of the
Landau gauge quark propagator and the soft gluon limit of the quark-gluon
vertex with 2 flavors of dynamical O(a) improved Wilson fermions.


title: On the symmetries of a nonlinear non-polynomial oscillator

abstract:
  In this paper, we unearth symmetries of different types of a nonlinear
non-polynomial oscillator. The symmetries which we report here are
adjoint-symmetries, contact symmetries and telescopic vector fields. We also
obtain Jacobi last multipliers and Darboux polynomials as a by-product of our
procedure. All the aforementioned quantities are derived from a Theorem proved
by Muriel and Romero. The procedure which we present here is applicable to a
class of nonlinear oscillator equations.


title: Upper bounds for the dominant dimension of Nakayama and related algebras

abstract:
  Optimal upper bounds are provided for the dominant dimensions of Nakayama
algebras and more generally algebras $A$ with an idempotent $e$ such that there
is a minimal faithful injective-projective module $eA$ and such that $eAe$ is a
Nakayama algebra. This answers a question of Abrar and proves a conjecture of
Yamagata for monomial algebras.


title: Shuffling matrices, Kronecker product and Discrete Fourier Transform

abstract:
  We define and investigate a family of permutations matrices, called shuffling
matrices, acting on a set of $N=n_1\cdots n_m$ elements, where $m\geq 2$ and
$n_i\geq 2$ for any $i=1,\ldots, m$. These elements are identified with the
vertices of the $m$-th level of a rooted tree with branch indices $(n_1,\ldots,
n_m)$. Each of such matrices is induced by a permutation of $Sym(m)$ and it
turns out that, in the case in which one considers the cyclic permutation $(1\
\ldots\ m)$, the corresponding permutation is the classical perfect shuffle. We
give a combinatorial interpretation of these permutations in terms of
lexicographic order of the vertices of the tree. This allows us to describe
their fixed points. We show that our permutation matrices can be used to let
the Kronecker product of matrices commute or, more generally, rearrange in an
arbitrary order. Moreover, we show that the group generated by such
permutations does depend only on the branch indices of the tree, but it is
independent from their order. In the case in which such indices coincide, we
prove that the corresponding group is a copy of $Sym(m)$ inside $Sym(n^m)$.
Finally, we give an application of shuffling matrices in the context of the
Discrete Fourier Transform.


title:
Anisotropic electronic structure and transport properties of the
  $\mathcal{H}$-$0$ hyperhoneycomb lattice

abstract:
  Carbon, being one of the most versatile elements of the periodic table, forms
solids and molecules with often unusual properties. Recently, a novel family of
three-dimensional graphitic carbon structures, the so-called hyperhoneycomb
lattices, has been proposed, with the possibility of being topological
insulators [K. Mullen, B. Uchoa and D. T. Glatzhofer, Phys. Rev. Lett. 115,
026403 (2015)]. In this work, we present electronic structure calculations for
one member ($\mathcal{H}$-0) of this family, using Density Functional Theory
and non-equilibrium Green's functions transport calculations to show that the
$\mathcal{H}$-0 structure should have strongly anisotropic electronic
properties, being an insulator or a conductor depending on the crystalline
orientation chosen for transport. Calculations in the framework of Extended
H\"uckel Theory indicate that these properties can only be understood if one
considers at least $2^{nd}$ nearest-neighbor interactions between carbon atoms,
invalidating some of the conclusions of Ref. [K. Mullen, B. Uchoa and D. T.
Glatzhofer, Phys. Rev. Lett. 115, 026403 (2015)], at least for this particular
material.


title:
Search for $B^{+}\rightarrow K^{+} \tau^{+}\tau^{-}$ at the BaBar
  experiment

abstract:
  We search for the rare flavor-changing neutral current process
$B^{+}\rightarrow K^{+}\tau^{+}\tau^{-}$ using data from the BABAR experiment.
The data sample, collected at the center-of-mass energy of the $\Upsilon{(4S)}$
resonance, corresponds to a total integrated luminosity of 424 fb$^{-1}$ and to
471 million $B\overline{B}$ pairs. We reconstruct one $B$ meson, produced in
the $\Upsilon{(4S)}\rightarrow B^{+} B^{-}$ decay, in one of many hadronic
decay modes and search for activity compatible with a $B^{+}\rightarrow K^{+}
\tau^{+}\tau^{-}$ decay in the rest of the event. Each $\tau$ lepton is
required to decay leptonically into an electron or muon and neutrinos.
Comparing the expected number of background events with the data sample after
applying the selection criteria, we do not find evidence for a signal. The
measured branching fraction is ($1.31^{+0.66}_{-0.61}$(
stat.)$^{+0.35}_{-0.25}$( sys.)$) \times 10^{-3}$ with an upper limit, at the
90\% confidence level, of $\mathcal{B}(B^{+}\rightarrow
K^{+}\tau^{+}\tau^{-})$$< 2.25\times 10^{-3}$.


title:
Two-particle system in noncommutative space with preserved rotational
  symmetry

abstract:
  We consider a system of two particles in noncommutative space which is
rotationally invariant. It is shown that the coordinates of the center-of-mass
position and the coordinates of relative motion satisfy noncommutative algebra
with corresponding effective tensors of noncommutativity. The hydrogen atom is
studied as a two-particle system. We find the corrections to the energy levels
of the hydrogen atom up to the second order over the parameter of
noncommutativity.


title:
Discrete breathers in an array of self-excited oscillators: exact
  solutions and stability

abstract:
  Dynamics of array of coupled self-excited oscillators is considered. Model of
Franklin bell is adopted as a mechanism for the self-excitation. The model
allows derivation of exact analytic solutions for discrete breathers (DBs), and
extensive exploration of their stability in the space of parameters. The DB
solutions exist for all frequencies in the attenuation zone, but lose stability
via Neimark-Sacker bifurcation near the boundary of propagation zone. Besides
the well-known DBs with exponential localization, the considered system
possesses additional and novel type of solutions - discrete breathers with main
frequency in the propagation zone of the chain. The amplitude of oscillations
in this solution is maximal at the localization site and then exponentially
approaches constant value at infinity. We also derive these solutions in closed
analytic form. They are stable in a narrow region of system parameters bounded
by Neimark-Sacker and pitchfork bifurcations.


title:
Formation of silicon monoxide by radiative association: the impact of
  resonances

abstract:
  Detailed quantum chemistry calculations within the multireference
configuration interaction approximation with the Davidson correction (MRCI+Q)
are presented using an aug-cc-pV6Z basis set, for the potential energy curves
and transition dipole moments between low lying molecular states of singlet
spin symmetry for the SiO molecule. The high quality molecular data are used to
obtain radiative association cross sections and rate coefficients for
collisions between ground state Si and O atoms. Quantal calculations are
compared with semiclassical results. Using a quantum kinetic theory of
radiative association in which quasibound levels are assumed to be in local
thermodynamic equilibrium, we find that resonances play an important role in
enhancing the rate coefficients at low temperatures by several orders of
magnitude from that predicted by standard quantum scattering formulations.
These new molecular formation rates may have important implications for
applications in astrophysics.


title: Cyber-Physical Systems Security: a Systematic Mapping Study

abstract:
  Cyber-physical systems are integrations of computation, networking, and
physical processes. Due to the tight cyber-physical coupling and to the
potentially disrupting consequences of failures, security here is one of the
primary concerns. Our systematic mapping study sheds some light on how security
is actually addressed when dealing with cyber-physical systems. The provided
systematic map of 118 selected studies is based on, for instance, application
fields, various system components, related algorithms and models, attacks
characteristics and defense strategies. It presents a powerful comparison
framework for existing and future research on this hot topic, important for
both industry and academia.


title: RT Cru: a look into the X-ray emission of a peculiar symbiotic star

abstract:
  Symbiotic stars are a heterogeneous class of interacting binaries. Among
them, RT Cru has been classified as prototype of a subclass that is
characterised by hard X-ray spectra extending past ~20 keV. We analyse ~8.6 Ms
of archival INTEGRAL data collected in the period 2003-2014, ~140 ks of
Swift/XRT data, and a Suzaku observation of 39 ks, to study the spectral X-ray
emission and investigate the nature of the compact object. Based on the 2MASS
photometry, we estimate the distance to the source of 1.2-2.4 kpc. The X-ray
spectrum obtained with Swift/XRT, JEM-X, IBIS/ISGRI, and Suzaku data is well
fitted by a cooling flow model modified by an absorber that fully covers the
source and two partial covering absorbers. Assuming that the hard X-ray
emission of RT Cru originates from an optically thin boundary layer around a
non-magnetic white dwarf, we estimated a mass of the WD of about 1.2 M_Sun. The
mass accretion rate obtained for this source might be too high for the
optically thin boundary layer scenario. Therefore we investigate other
plausible scenarios to model its hard X-ray emission. We show that,
alternatively, the observed X-ray spectrum can be explained with the X-ray
emission from the post-shock region above the polar caps of a magnetised white
dwarf with mass ~0.9-1.1 M_Sun.


title: Area-width scaling in generalised Motzkin paths

abstract:
  We consider a generalised version of Motzkin paths, where horizontal steps
have length $\ell$, with $\ell$ being a fixed positive integer. We first give
the general functional equation for the area-length generating function of this
model. Using a heuristic ansatz, we derive the area-length scaling behaviour in
terms of a scaling function in one variable for the special cases of Dyck,
(standard) Motzkin and Schr\"oder paths, before generalising our approach to
arbitrary $\ell$. We then derive an expression for the generating function of
Schr\"oder paths and analyse the scaling behaviour of this function rigorously
in the vicinity of the tri-critical point of the model by applying the method
of steepest descents for the case of two coalescing saddle points. Our results
show that for Dyck and Schr\"oder paths, the heuristic scaling ansatz
reproduces the rigorous results.


title:
A Study of the 2012 January 19 Complex Type II Radio Burst Using Wind,
  SOHO, and STEREO Observations

abstract:
  We report on a case study of the complex type II radio burst of 2012 January
19 and its association with a white light coronal mass ejection (CME). The
complexity can be described as the appearance of an additional type II burst
component and strong intensity variation. The dynamic spectrum shows a pair of
type II bursts with fundamental harmonic structures, one confined to
decameter-hectometric (DH) wavelengths and the other extending to kilometric
(km) wavelengths. By comparing the speeds obtained from white-light images with
that speed of the shock inferred from the drift rate, we show that the source
of the short-lived DH component is near the nose.


title: Light-Sound Interaction in Nanoscale Silicon Waveguides

abstract:
  This thesis studies the interaction between near-infrared light and gigahertz
sound in nanoscale silicon waveguides. Chapter 2 introduces photon-phonon
coupling and its theoretical description, describing basic mechanisms and
developing a quantum field theory of the process. Chapter 3 explores the
dynamical effects in both waveguides and cavities. It also proves a connection
between the Brillouin gain coefficient and the vacuum coupling rate. Chapter 4
deals with the observation of Brillouin scattering in nanoscale silicon
waveguides. The waveguides tightly confine $193 \, \text{THz}$ light and $10 \,
\text{GHz}$ acoustic vibrations. The acoustic quality factor remains limited to
about $300$ because of leakage into silica substrate. These waveguides are
optically transparent in a narrow band of frequencies at a pump power of $25 \,
\text{mW}$. Besides this amplification, we translate a $10 \, \text{GHz}$
microwave signal across $1 \, \text{THz}$. Chapter 5 extends the experimental
work of chapter 4 by fabricating a cascade of fully suspended nanowires held by
silica anchors. This enhances the mechanical quality factor from $300$ to
$1000$, enabling the observation of Brillouin amplification exceeding the
propagation losses in silicon. The amount of amplification is mostly limited by
a rapid drop in acoustic quality as the number of suspensions increases. We
propose a mechanism to cancel this inhomogeneous broadening. Chapter 6 looks at
the potential of narrow silicon slot waveguides to enhance the optomechanical
coupling. For certain dimensions, these waveguides support opto-acoustic modes
with an interaction efficiency simulated an order of magnitude above those of
single-nanobeam systems.


title: Average-case Hardness of RIP Certification

abstract:
  The restricted isometry property (RIP) for design matrices gives guarantees
for optimal recovery in sparse linear models. It is of high interest in
compressed sensing and statistical learning. This property is particularly
important for computationally efficient recovery methods. As a consequence,
even though it is in general NP-hard to check that RIP holds, there have been
substantial efforts to find tractable proxies for it. These would allow the
construction of RIP matrices and the polynomial-time verification of RIP given
an arbitrary matrix. We consider the framework of average-case certifiers, that
never wrongly declare that a matrix is RIP, while being often correct for
random instances. While there are such functions which are tractable in a
suboptimal parameter regime, we show that this is a computationally hard task
in any better regime. Our results are based on a new, weaker assumption on the
problem of detecting dense subgraphs.


title: On the Structure of Anomalous Composite Higgs Models

abstract:
  We describe the anomaly structure of an composite Higgs model in which the
$SO(5)/SO(4)$ coset structure of the minimal model is extended by an
additional, non-linearly-realized $U(1)_{\eta}$. In addition, we show that the
effective lagrangian admits a term that, like the Wess-Zumino-Witten term in
the chiral lagrangian for QCD, is not invariant under the non-linearly realized
symmetries, but rather changes by a total derivative. This term is unlike the
Wess-Zumino-Witten term in that it does not arise from anomalies. If present,
it may give rise to the rare decay $\eta \rightarrow h W^+ W^- Z$. The
phenomenology of the singlet in this model differs from that in a model based
on $SO(6)/SO(5)$, in that couplings to both gluons and photons, arising via
anomalies, are present. We show that while some tuning is needed to accommodate
flavour and electroweak precision constraints, the model is no worse than the
minimal model in this regard.


title:
Response Regimes in Equivalent Mechanical Model of Strongly Nonlinear
  Liquid Sloshing

abstract:
  We consider equivalent mechanical model of liquid sloshing in
partially-filled cylindrical vessel; the model treats both the regime of linear
sloshing, and strongly nonlinear sloshing regime. The latter is related to
hydraulic impacts applied to the vessel walls. These hydraulic impacts are
commonly simulated with the help of high-power potential and dissipation
functions. For the sake of analytic exploration, we substitute this traditional
approach by treatment of an idealized vibro-impact system with
velocity-dependent restitution coefficient. The obtained reduced model is
similar to recently explored system of linear primary oscillator with attached
vibro-impact energy sink. The ratio of modal mass of the first sloshing mode to
the total mass of the liquid and the tank serves as a natural small parameter
for multiple-scale analysis. In the case of external ground forcing,
steady-state responses and chaotic strongly modulated responses are revealed.
All analytical predictions of the reduced vibro-impact model are validated
against direct numerical simulations of initial equivalent model with
high-power smooth potential and dissipation functions, and good agreement is
observed.


title: Heavy-quark spin symmetry partners of the $X(3872)$ revisited

abstract:
  We revisit the consequences of the heavy-quark spin symmetry for the possible
spin partners of the $X(3872)$. We confirm that, if the $X(3872)$ were a
$D\bar{D}^*$ molecular state with the quantum numbers $J^{PC}=1^{++}$, then in
the strict heavy-quark limit there should exist three more hadronic molecules
degenerate with the $X(3872)$, with the quantum numbers $0^{++}$, $1^{+-}$, and
$2^{++}$ in line with previous results reported in the literature. We
demonstrate that this result is robust with respect to the inclusion of the
one-pion exchange interaction between the $D$ mesons. However, this is true
only if all relevant partial waves as well as particle channels which are
coupled via the pion-exchange potential are taken into account. Otherwise, the
heavy-quark symmetry is destroyed even in the heavy-quark limit. Finally, we
solve the coupled-channel problem in the $2^{++}$ channel with nonperturbative
pions beyond the heavy-quark limit and, contrary to the findings of previous
calculations with perturbative pions, find for the spin-2 partner of the
$X(3872)$ a significant shift of the mass as well as a width of the order of 50
MeV.


title:
Multiscale Monte Carlo equilibration: Two-color QCD with two fermion
  flavors

abstract:
  We demonstrate the applicability of a recently proposed multiscale
thermalization algorithm to two-color quantum chromodynamics (QCD) with two
mass-degenerate fermion flavors. The algorithm involves refining an ensemble of
gauge configurations that had been generated using a renormalization group (RG)
matched coarse action, thereby producing a fine ensemble that is close to the
thermalized distribution of a target fine action; the refined ensemble is
subsequently rethermalized using conventional algorithms. Although the
generalization of this algorithm from pure Yang-Mills theory to QCD with
dynamical fermions is straightforward, we find that in the latter case, the
method is susceptible to numerical instabilities during the initial stages of
rethermalization when using the hybrid Monte Carlo algorithm. We find that
these instabilities arise from large fermion forces in the evolution, which are
attributed to an accumulation of spurious near-zero modes of the Dirac
operator. We propose a simple strategy for curing this problem, and demonstrate
that rapid thermalization--as probed by a variety of gluonic and fermionic
operators--is possible with the use of this solution. In addition, we study the
sensitivity of rethermalization rates to the RG matching of the coarse and fine
actions, and identify effective matching conditions based on a variety of
measured scales.


title:
Quadrupole association and dissociation of hydrogen in the early
  Universe

abstract:
  Radiative association and photodissociation rates are calculated for
quadrupole transitions of H2. A complete set of bound and unbound states are
included in a self-consistent master equation to obtain steady-state
concentrations for a dilute system of hydrogen atoms and molecules.
Phenomenological rate constants computed from the steady-state concentrations
satisfy detailed balance for any combination of matter and radiation
temperature. Simple formulas are derived for expressing the steady-state
distributions in terms of equilibrium distributions. The rate constant for
radiative association is found to be generally small for all temperature
combinations. The photodissociation rate constant for quadrupole transitions is
found to dominate the rate constants for other H2 photodestruction mechanisms
for radiation temperatures less than or equal to 3000 K. Implications for the
formation and destruction of H2 in the early universe are discussed.


title:
Some estimators of the PMF and CDF of the Logarithmic Series
  Distribution

abstract:
  This article addresses the different methods of estimation of the probability
mass function (PMF) and the cumulative distribution function (CDF) for the
Logarithmic Series distribution. Following estimation methods are considered:
uniformly minimum variance unbiased estimator (UMVUE), maximum likelihood
estimator (MLE), percentile estimator (PCE), least square estimator (LSE),
weighted least square estimator (WLSE). Monte Carlo simulations are performed
to compare the performances of the proposed methods of estimation.


title:
A Systematic Evaluation and Benchmark for Person Re-Identification:
  Features, Metrics, and Datasets

abstract:
  Person re-identification (re-id) is a critical problem in video analytics
applications such as security and surveillance. The public release of several
datasets and code for vision algorithms has facilitated rapid progress in this
area over the last few years. However, directly comparing re-id algorithms
reported in the literature has become difficult since a wide variety of
features, experimental protocols, and evaluation metrics are employed. In order
to address this need, we present an extensive review and performance evaluation
of single- and multi-shot re-id algorithms. The experimental protocol
incorporates the most recent advances in both feature extraction and metric
learning. To ensure a fair comparison, all of the approaches were implemented
using a unified code library that includes 11 feature extraction algorithms and
22 metric learning and ranking techniques. All approaches were evaluated using
a new large-scale dataset that closely mimics a real-world problem setting, in
addition to 16 other publicly available datasets: VIPeR, GRID, CAVIAR,
DukeMTMC4ReID, 3DPeS, PRID, V47, WARD, SAIVT-SoftBio, CUHK01, CHUK02, CUHK03,
RAiD, iLIDSVID, HDA+ and Market1501. The evaluation codebase and results will
be made publicly available for community use.


title: Discovery of a two-dimensional topological insulator in SiTe

abstract:
  Two-dimensional (2D) topological insulators (TIs), a new state of quantum
matter, are promising for achieving the low-power-consuming electronic devices
owning to the remarkable robustness of their conducting edge states against
backscattering. Currently, the major challenge to further studies and possible
applications is the lack of suitable materials, which should be with high
feasibility of fabrication and sizeable nontrivial gaps. Here, we demonstrate
through first-principles calculations that SiTe 2D crystal is a promising 2D TI
with a sizeable nontrivial gap of 0.220 eV. This material is dynamically and
thermally stable. Most importantly, it could be easily exfoliated from its
three-dimensional superlattice due to the weakly bonded layered structure.
Moreover, strain engineering can effectively control its nontrivial gap and
even induce a topological phase transition. Our results provide a realistic
candidate for experimental explorations and potential applications of 2D TIs.


title: Continuity results for TV-minimizers

abstract:
  This paper deals with continuity preservation when minimizing generalized
total variation with a $L^2$ fidelity term or a Dirichlet boundary condition.
We extend several recent results in the two cases, mainly by showing comparison
principles for the prescribed mean curvature problem satisfied by the
level-sets of such minimizers.


title: Fedosov dg manifolds associated with Lie pairs

abstract:
  Given any pair $(L,A)$ of Lie algebroids, we construct a differential graded
manifold $(L[1]\oplus L/A,Q)$, which we call Fedosov dg manifold. We prove that
the cohomological vector field $Q$ constructed on $L[1]\oplus L/A$ by the
Fedosov iteration method arises as a byproduct of the
Poincar\'e--Birkhoff--Witt map established in arXiv:1408.2903. Finally, using
the homological perturbation lemma, we establish a quasi-isomorphism of
Dolgushev--Fedosov type: the differential graded algebras of functions on the
dg manifolds $(A[1],d_A)$ and $(L[1]\oplus L/A,Q)$ are homotopy equivalent.


title: Irreducible Theta Divisors of PPAV's are Strongly F-regular

abstract:
  We study the birational geometry of irregular varieties and the singularities
of Theta divisors of PPAV's in positive characteristic by applying recent
generic vanishing results of Hacon and Patakfalvi. In particular, we prove that
irreducible Theta divisors of principally polarized abelian varieties are
strongly F-regular, which extends an old result of Ein and Lazarsfeld to fields
of positive characteristic. In order to prove this, we formulate a positive
characteristic analogue of another result of Ein and Lazarsfeld, to the effect
that the Albanese image of a smooth projective variety of maximal Albanese
dimension with vanishing holomorphic Euler characteristic is fibered by abelian
subvarieties.


title:
Continuation of Nesterov's Smoothing for Regression with Structured
  Sparsity in High-Dimensional Neuroimaging

abstract:
  Predictive models can be used on high-dimensional brain images for diagnosis
of a clinical condition. Spatial regularization through structured sparsity
offers new perspectives in this context and reduces the risk of overfitting the
model while providing interpretable neuroimaging signatures by forcing the
solution to adhere to domain-specific constraints. Total Variation (TV)
enforces spatial smoothness of the solution while segmenting predictive regions
from the background. We consider the problem of minimizing the sum of a smooth
convex loss, a non-smooth convex penalty (whose proximal operator is known) and
a wide range of possible complex, non-smooth convex structured penalties such
as TV or overlapping group Lasso. Existing solvers are either limited in the
functions they can minimize or in their practical capacity to scale to
high-dimensional imaging data. Nesterov's smoothing technique can be used to
minimize a large number of non-smooth convex structured penalties but
reasonable precision requires a small smoothing parameter, which slows down the
convergence speed. To benefit from the versatility of Nesterov's smoothing
technique, we propose a first order continuation algorithm, CONESTA, which
automatically generates a sequence of decreasing smoothing parameters. The
generated sequence maintains the optimal convergence speed towards any globally
desired precision. Our main contributions are: To propose an expression of the
duality gap to probe the current distance to the global optimum in order to
adapt the smoothing parameter and the convergence speed. We provide a
convergence rate, which is an improvement over classical proximal gradient
smoothing methods. We demonstrate on both simulated and high-dimensional
structural neuroimaging data that CONESTA significantly outperforms many
state-of-the-art solvers in regard to convergence speed and precision.


title:
Fields of rationality of automorphic representations: the case of
  unitary groups

abstract:
  This paper examines fields of rationality in families of cuspidal automorphic
representations of unitary groups. Specifically, for a fixed $A$ and a
sufficiently large family $\mathcal{F}$, a small proportion of representations
$\pi\in \mathcal{F}$ will satisfy $[\mathbb{Q}(\pi):\mathbb{Q}] \leq A$. Like
earlier work of Shin and Templier, the result depends on a Plancherel
equidistribution result for the local components of representations in
families. An innovation of our work is an upper bound on the number of discrete
series $GL_n(L)$ representations with small field of rationality, counted with
appropriate multiplicity, which in turn depends upon an asymptotic character
expansion of Murnaghan and formal degree computations of Aubert and Plymen.


title:
FRIDA: diffraction-limited imaging and integral-field spectroscopy for
  the GTC

abstract:
  FRIDA is a diffraction-limited imager and integral-field spectrometer that is
being built for the adaptive-optics focus of the Gran Telescopio Canarias. In
imaging mode FRIDA will provide scales of 0.010, 0.020 and 0.040 arcsec/pixel
and in IFS mode spectral resolutions of 1500, 4000 and 30,000. FRIDA is
starting systems integration and is scheduled to complete fully integrated
system tests at the laboratory by the end of 2017 and to be delivered to GTC
shortly thereafter. In this contribution we present a summary of its design,
fabrication, current status and potential scientific applications.


title:
Approximation and Schauder bases in M\"untz spaces $M_{\Lambda ,C}$ of
  continuous functions

abstract:
  In this article M\"untz spaces $M_{\Lambda ,C}$ of continuous functions
supplied with the absolute maximum norm are considered. An approximation of
functions in M\"untz spaces $M_{\Lambda ,C}$ of continuous functions by Fourier
series is studied. An existence of Schauder bases in M\"untz spaces $M_{\Lambda
,C}$ is investigated.


title: On divisors computing MLD's and LCT's

abstract:
  We show that if a divisor centered over a point on a smooth surface computes
a minimal log discrepancy, then the divisor also computes a log canonical
threshold. To prove the result, we study the asymptotic log canonical threshold
of the graded sequence of ideals associated to a divisor over a variety. We
systematically study this invariant and also prove a result describing which
divisors compute asymptotic log canonical thresholds.


title:
Convergence to Equilibrium in the Free Fokker-Planck Equation With a
  Double-Well Potential

abstract:
  We consider the one-dimensional free Fokker-Planck equation $\frac{\partial
\mu\_t}{\partial t} = \frac{\partial}{\partial x} \left[ \mu\_t \left( \frac12
V' - H\mu\_t \right) \right]$, where $H$ denotes the Hilbert transform and $V$
is a particular double-well quartic potential, namely $V(x) = \frac14 x^4 +
\frac{c}{2} x^2$, with $-2 \le c < 0$. We prove that the solution $(\mu\_t)\_{t
\ge 0}$ of this PDE converges to the equilibrium measure $\mu\_V$ as $t$ goes
to infinity, which provides a first result of convergence in a non-convex
setting. The proof involves free probability and complex analysis techniques.


title:
Experimental observation of 1/f noise in quasi-bidimensionnal turbulent
  flows

abstract:
  We report the experimental observation of $1/f^{\alpha}$ noise in
quasi-bidimensionnal turbulence of an electromagnetically forced flow. The
large scale velocity $U_L$ exhibits this power-law spectrum with $\alpha \simeq
0.7$ over a range of frequencies smaller than both the characteristic turn-over
frequency and the damping rate of the flow. By studying the statistical
properties of sojourn time in each polarity of $U_L$, we demonstrate that the
$1/f^{\alpha}$ noise is generated by a renewal process, defined by a two-state
model given by the polarities of the large scale circulation. The statistical
properties of this renewal process are shown to control the value of the
exponent $\alpha$.


title:
Approximation in M\"untz spaces $M_{\Lambda ,p}$ of $L_p$ functions for
  $1<p<\infty $ and bases

abstract:
  M\"untz spaces satisfying the M\"untz and gap conditions are considered. A
Fourier approximation of functions in the M\"untz spaces $M_{\Lambda ,p}$ of
$L_p$ functions is studied, where $1<p<\infty $. It is proved that up to an
isomorphism and a change of variables these spaces are contained in Weil-Nagy's
class. Moreover, existence of Schauder bases in the M\"untz spaces $M_{\Lambda
,p}$ is investigated.


title: 1/f noise in turbulent flows

abstract:
  We report the experimental observation of $1/f$ fluctuations in three
different turbulent flow configurations: the large scale velocity driven by a
two-dimensional turbulent flow, the magnetic field generated by a turbulent
swirling flow of liquid sodium and the pressure fluctuations due to vorticity
filaments in a swirling flow. For these three systems, $1/f$ noise is shown to
result from the dynamics of coherent structures that display transitions
between a small number of states. The interevent duration is distributed as a
power-law. The exponent of this power-law and the nature of the dynamics
(transition between symmetric states or asymmetric ones) select the exponent of
the $1/f$ fluctuations.


title: Impact of Service Sector Loads on Renewable Resource Integration

abstract:
  Urban areas consist of a mix of households and services, such as offices,
shops, schools, etc. Yet most urban energy models only consider household load
profiles, omitting the service sector. Realistic assessment of the potential
for renewable resource integration in cities requires models that include
detailed demand and generation profiles. Detailed generation profiles are
available for many resources. Detailed demand profiles, however, are currently
only available for households and not for the service sector. This paper
addresses this gap. The paper (1) proposes a novel approach to devise synthetic
service sector demand profiles based on a combination of a large number of
different data sources, and (2) uses these profiles to study the impact of the
service sector on the potential for renewable resource integration in urban
energy systems, using the Netherlands as a case study. The importance of the
service sector is addressed in a broad range of solar and wind generation
scenarios, and in specific time and weather conditions (in a single scenario).
Results show that including the service sector leads to statistically
significantly better estimations of the potential of renewable resource
integration in urban areas. In specific time and weather conditions, including
the service sector results in estimations that are up to 33% higher than if
only households are considered. The results can be used by researchers to
improve urban energy systems models, and by decision-makers and practitioners
for grid planning, operation and management}.


title:
Examples of interacting particle systems on $\mathbb{Z}$ as Pfaffian
  point processes II - coalescing branching random walks and annihilating
  random walks with immigration

abstract:
  Two classes of interacting particle systems on $\mathbb{Z}$ are shown to be
Pfaffian point processes at fixed times, and for all deterministic initial
conditions. The first comprises coalescing and branching random walks, the
second annihilating random walks with pairwise immigration. Various limiting
Pfaffian point processes on $\mathbb{R}$ are found by diffusive rescaling,
including the point set process for the Brownian net.


title:
Interactive Fuzzy Goal Programming Based on Taylor Series to Solve
  Multiobjective Nonlinear Programming Problems with Interval Type 2 Fuzzy
  Numbers

abstract:
  This paper presents an interactive fuzzy goal programming (FGP) approach for
solving multiobjective nonlinear programming problems (MONLPP) with interval
type 2 fuzzy numbers (IT2 FNs). The cost and time of the objective functions,
the resources, and the requirements of each kind of resources are taken to be
trapezoidal IT2 FNs. Here, the considered problem is first transformed into an
equivalent crisp MONLPP, and then the transformed MONLPP is converted into an
equivalent Multiobjective Linear Programming Problem (MOLPP). By using a
procedure based on Taylor series, this problem is reduced into a single
objective linear programming problem (LPP) which can be easily solved by Maple
18.02 optimization toolbox. Finally, the proposed solution procedure is
illustrated by two numerical examples.


title:
A Direct Prediction of the Shape Parameter -- a purely scattered data
  approach

abstract:
  Unlike the previous papers of the author, which are in an evenly spaced data
setting, we present an approach which predicts the optimal value of the shape
parameter contained in the muiltiquadrics and inverse multiquadrics in a purely
scattered data setting. For the purpose of practical application, this approach
is expected to be more useful.


title:
Propagation of high-energy neutrinos in a background of ultralight
  scalar dark matter

abstract:
  If high-energy neutrinos propagate in a background of ultralight scalar field
particles of dark matter ($m_\varphi \sim 10^{-23}$eV), neutrino-dark matter
interactions can play a role and affect the neutrino flux. In this work we
analyse this effect using transport equations that account for the neutrino
regeneration as well as absorption, and we consider the neutrino flux
propagation in the extragalactic medium and also through the galactic halo of
dark matter. We show the results for the final flux to arrive on Earth for
different cases of point and diffuse neutrino fluxes. {We conclude that this
type of neutrino interactions with ultralight scalar particles as dark matter
can yield very different results in the neutrino flux and in the flavor ratios
that can be measured in neutrino detectors such as IceCube.


title:
Szeg\H{o}-type asymptotics for ray sequences of Frobenius-Pad\'e
  approximants

abstract:
  Let $\widehat\sigma$ be a Cauchy transform of a possibly complex-valued Borel
measure $\sigma$ and $\{p_n\}$ be a system of orthonormal polynomials with
respect to a measure $\mu$,
$\mathrm{supp}(\mu)\cap\mathrm{supp}(\sigma)=\varnothing$. An $(m,n)$-th
Frobenius-Pad\'e approximant to $\widehat\sigma$ is a rational function $P/Q$,
$\mathrm{deg}(P)\leq m$, $\mathrm{deg}(Q)\leq n$, such that the first $m+n+1$
Fourier coefficients of the linear form $Q\widehat\sigma-P$ vanish when the
form is developed into a series with respect to the polynomials $p_n$. We
investigate the convergence of the Frobenius-Pad\'e approximants to
$\widehat\sigma$ along ray sequences $\frac n{n+m+1}\to c>0$, $n-1\leq m$, when
$\mu$ and $\sigma$ are supported on intervals on the real line and their
Radon-Nikodym derivatives with respect to the arcsine distribution of the
respective interval are holomorphic functions.


title: Dynamic Filter Networks

abstract:
  In a traditional convolutional layer, the learned filters stay fixed after
training. In contrast, we introduce a new framework, the Dynamic Filter
Network, where filters are generated dynamically conditioned on an input. We
show that this architecture is a powerful one, with increased flexibility
thanks to its adaptive nature, yet without an excessive increase in the number
of model parameters. A wide variety of filtering operations can be learned this
way, including local spatial transformations, but also others like selective
(de)blurring or adaptive feature extraction. Moreover, multiple such layers can
be combined, e.g. in a recurrent architecture. We demonstrate the effectiveness
of the dynamic filter network on the tasks of video and stereo prediction, and
reach state-of-the-art performance on the moving MNIST dataset with a much
smaller model. By visualizing the learned filters, we illustrate that the
network has picked up flow information by only looking at unlabelled training
data. This suggests that the network can be used to pretrain networks for
various supervised tasks in an unsupervised way, like optical flow and depth
estimation.


title: VIME: Variational Information Maximizing Exploration

abstract:
  Scalable and effective exploration remains a key challenge in reinforcement
learning (RL). While there are methods with optimality guarantees in the
setting of discrete state and action spaces, these methods cannot be applied in
high-dimensional deep RL scenarios. As such, most contemporary RL relies on
simple heuristics such as epsilon-greedy exploration or adding Gaussian noise
to the controls. This paper introduces Variational Information Maximizing
Exploration (VIME), an exploration strategy based on maximization of
information gain about the agent's belief of environment dynamics. We propose a
practical implementation, using variational inference in Bayesian neural
networks which efficiently handles continuous state and action spaces. VIME
modifies the MDP reward function, and can be applied with several different
underlying RL algorithms. We demonstrate that VIME achieves significantly
better performance compared to heuristic exploration methods across a variety
of continuous control tasks and algorithms, including tasks with very sparse
rewards.


title:
Task Assignment on Spatial Crowdsourcing [Experiments and Analyses]
  (Technical Report)

abstract:
  Recently, with the rapid development of mobile devices and the crowdsourcing
platforms, the spatial crowdsourcing has attracted much attention from the
database community. Specifically, spatial crowdsourcing refers to sending a
location-based request to workers according to their positions, and workers
need to physically move to specified locations to conduct tasks. Many works
have studied task assignment problems in spatial crowdsourcing, however, their
problem settings are different from each other. Thus, it is hard to compare the
performances of existing algorithms on task assignment in spatial
crowdsourcing. In this paper, we present a comprehensive experimental
comparison of most existing algorithms on task assignment in spatial
crowdsourcing. Specifically, we first give general definitions about spatial
workers and spatial tasks based on definitions in the existing works such that
the existing algorithms can be applied on the same synthetic and real data
sets. Then, we provide an uniform implementation for all the tested algorithms
of task assignment problems in spatial crowdsourcing (open sourced). Finally,
based on the results on both synthetic and real data sets, we discuss the
strengths and weaknesses of tested algorithms, which can guide future research
on the same area and practical implementations of spatial crowdsourcing
systems.


title:
Nonlinear Geometric Optics method based multi-scale numerical schemes
  for highly-oscillatory transport equations

abstract:
  We introduce a new numerical strategy to solve a class of oscillatory
transport PDE models which is able to captureaccurately the solutions without
numerically resolving the high frequency oscillations {\em in both space and
time}.Such PDE models arise in semiclassical modeling of quantum dynamics with
band-crossings, and otherhighly oscillatory waves. Our first main idea is to
use the nonlinear geometric optics ansatz, which builds theoscillatory phase
into an independent variable. We then choose suitable initial data, based on
the Chapman-Enskog expansion, for the new model. For a scalar model, we prove
that so constructed model will have certain smoothness, and consequently, for a
first order approximation scheme we prove uniform error estimates independent
of the (possibly small) wave length. The method is extended to systems arising
from a semiclassical model for surface hopping, a non-adiabatic quantum dynamic
phenomenon. Numerous numerical examples demonstrate that the method has the
desired properties.


title: Subleading soft photons and large gauge transformations

abstract:
  Lysov, Pasterski and Strominger have shown how Low's subleading soft photon
theorem can be understood as Ward identities of new symmetries of massless QED.
In this paper we offer a different perspective and show that there exists a
class of large $U(1)$ gauge transformations such that (i) the associated
(electric and magnetic) charges can be computed from first principles (ii)
their Ward identities are equivalent to Low's theorem. Our framework paves the
way to analyze the sub-subleading theorem in gravity in terms of Ward
identities associated to large diffeomorphisms.


title:
Level Up Your Strategy: Towards a Descriptive Framework for Meaningful
  Enterprise Gamification

abstract:
  Gamification initiatives are currently top-of-mind for many organizations
seeking to engage their employees in creative ways, improve their productivity,
and drive positive behavioural outcomes in their workforce - ultimately leading
to positive business outcomes on the whole. Despite its touted benefits, little
empirical research has been done to date to investigate technological and
individual personal factors that determine the success or failure of enterprise
gamification initiatives. In this article, we provide a summary of our
preliminary research findings from three case studies of gamification
initiatives across different business contexts and present an empirically
validated descriptive framework that details the key success factors for
enterprise gamification. Our adaptation of the mechanics, dynamics, and
aesthetics (MDA) framework for enterprise gamification aims to explicate the
connections between end-user motivations, interactive gameplay elements, and
technology features and functions that constitute effective gamification
interventions in the enterprise. Following a discussion of the core elements in
the framework and their interrelationships, the implications of our research
are presented in the form of guidelines for the management and design of
gamification initiatives and applications. The research findings presented in
this article can potentially aid in the development of game mechanics that
translate into positive user experiences and foster higher levels of employee
engagement. Additionally, our research findings provide insights on key success
factors for the effective adoption and institutionalization of enterprise
gamification initiatives in organizations, and subsequently help them enhance
the performance of their employees and drive positive business outcomes.


title:
Some results on exponential synchronization of nonlinear systems (long
  version)

abstract:
  Based on recent works on transverse exponential stability, we establish some
necessary and sufficient conditions for the existence of a (locally)
exponential synchronizing control law. We show that the existence of a
structured synchronizer is equivalent to the existence of a stabilizer for the
individual linearized systems (on the synchronization manifold) by a linear
state feedback. This, in turn, is also equivalent to the existence of a
symmetric covariant tensor field, which satisfies a Control Matrix Function
inequality. Based on this result, we provide the construction of such
synchronizer via backstepping approaches. In some particular cases, we show how
global exponential synchronization may be obtained.


title: Phenomenology of the Sterile Neutrinos

abstract:
  In this thesis we investigate several topics in neutrino physics, with an em-
phasis on the phenomenology of the sterile neutrinos. We study the existence of
a light sterile neutrino within the so called 3+1 scenario using the data of
the medium baseline reactor experiments. We will also probe the parameters of
the Large Extra Dimension model with the high energy atmospheric data of the
IceCube experiment, and will find an equivalence between the Kaluza Klein modes
and the sterile neutrinos. We will study the secret interaction of the ster-
ile neutrinos which is proposed to solve the tension between cosmology and the
sterile neutrino hypothesis. In addition to these, we will show that a minimal
2-Higgs-Doublet-Model extended with a U(1) or Z_2 symmetry cannot explain the
smallness of the neutrino masses.


title: Inf-sup stability of geometrically unfitted Stokes finite elements

abstract:
  The paper shows an inf-sup stability property for several well-known 2D and
3D Stokes elements on triangulations which are not fitted to a given smooth or
polygonal domain. The property implies stability and optimal error estimates
for a class of unfitted finite element methods for the Stokes and Stokes
interface problems, such as Nitsche-XFEM or cutFEM. The error analysis is
presented for the Stokes problem. All assumptions made in the paper are
satisfied once the background mesh is shape-regular and fine enough.


title:
A signal of competitive dominance in mid-latitude herbaceous plant
  communities

abstract:
  Understanding the main determinants of species coexistence across space and
time is a central question in ecology. However, ecologists still know little
about the scales and conditions at which biotic interactions matter and how
these interact with the environment to structure species assemblages. Here we
use recent theory developments to analyze plant distribution and trait data
across Europe and find that plant height clustering is related to both
evapotranspiration and gross primary productivity. This clustering is a signal
of interspecies competition between plants, which is most evident in
mid-latitude ecoregions, where conditions for growth (reflected in actual
evapotranspiration rates and gross primary productivities) are optimal. Away
from this optimum, climate severity likely overrides the effect of competition,
or other interactions become increasingly important. Our approach bridges the
gap between species-rich competition theories and large-scale species
distribution data analysis.


title:
Doubly-resonant saddle-nodes in $(\mathbb{C}^{3},0)$ and the fixed
  singularity at infinity in the Painlev\'e equations (part III): local
  analytic classification

abstract:
  In this work, following [Bit15] and [Bit16a], we consider analytic singular
vector fields in $(\mathbb{C}^{3},0)$ with an isolated and doubly-resonant
singularity of saddle-node type at the origin. Such vector fields come from
irregular two-dimensional differential systems with two opposite non-zero
eigenvalues, and appear for instance when studying the irregular singularity at
infinity in Painlev{\'e} equations (P\_j), j=I...V , for generic values of the
parameters. Under suitable assumptions, we provide an analytic classification
under the action of fibered diffeomorphisms, based on the study of the Stokes
diffeomorphisms obtained by comparing consecutive sectorial normalizing maps
{\`a} la Martinet-Ramis / Stolovitch. These normalizing maps over sectorial
domains are obtained in the main theorem of [Bit16a], which is analogous to the
classical one due to Hukuhara-Kimura-Matuda for saddle-nodes in
$\mathbb{C}^{3}$. We also prove that these maps are in fact the Gevrey-1 sums
of the formal normalizing map, the existence of which has been proved in
[Bit15].


title: The Gaia-ESO survey: Metal-rich bananas in the bulge

abstract:
  We analyse the kinematics of $\sim 2000$ giant stars in the direction of the
Galactic bulge, extracted from the Gaia-ESO survey in the region $-10^\circ
\lesssim \ell \lesssim 10^\circ$ and $-11^\circ \lesssim b \lesssim -3^\circ$.
We find distinct kinematic trends in the metal rich ($\mathrm{[M/H]}>0$) and
metal poor ($\mathrm{[M/H]}<0$) stars in the data. The velocity dispersion of
the metal-rich stars drops steeply with latitude, compared to a flat profile in
the metal-poor stars, as has been seen previously. We argue that the metal-rich
stars in this region are mostly on orbits that support the boxy-peanut shape of
the bulge, which naturally explains the drop in their velocity dispersion
profile with latitude. The metal rich stars also exhibit peaky features in
their line-of-sight velocity histograms, particularly along the minor axis of
the bulge. We propose that these features are due to stars on resonant orbits
supporting the boxy-peanut bulge. This conjecture is strengthened through the
comparison of the minor axis data with the velocity histograms of resonant
orbits generated in simulations of buckled bars. The 'banana' or 2:1:2 orbits
provide strongly bimodal histograms with narrow velocity peaks that resemble
the Gaia-ESO metal-rich data.


title: Opto acoustical gravitational bar detector with cryogenic mirrors

abstract:
  Enhancing of sensitivity of the opto-acoustical gravitational wave (GW)
antenna OGRAN installed in the underground facilities of Baksan Neutrino
Observatory is analyzed. Calculations are presented showing a sensitivity
improving on two orders of value after a cooling the solid body acoustical part
of the antenna to the nitrogen temperature. A possibility of keeping of the
same optical scheme of the antenna at low temperature is discussed. Design of
modernized construction for cryogenic version of the antenna OGRAN is
described. Test experiments with cooled pilot model carrying cryogenic mirrors
illuminated by the optical pump up to 0.5 W are presented.


title: Thermodynamics of Van der Waals Fluids with quantum statistics

abstract:
  We consider thermodynamics of the van der Waals fluid of quantum systems. We
derive general relations of thermodynamic functions and parameters of any ideal
gas and the corresponding van der Waals fluid. This provides unambiguous
generalization of the classical van der Waals theory to quantum statistical
systems. As an example, we apply the van der Waals fluid with fermi statistics
to characterize the liquid-gas critical point in nuclear matter. We also
introduce the Bose-Einstein condensation in the relativistic van der Waals
boson gas, and argue, that it exhibits two-phase structure separated in space.


title: Magnetic Helicity Reversals in a Cyclic Convective Dynamo

abstract:
  We investigate the role of magnetic helicity in promoting cyclic magnetic
activity in a global, 3D, magnetohydrodynamic (MHD) simulation of a convective
dynamo. This simulation is characterized by coherent bands of toroidal field
that exist within the convection zone, with opposite polarities in the northern
and southern hemispheres. Throughout most of the cycle, the magnetic helicity
in these bands is negative in the northern hemisphere and positive in the
southern hemisphere. However, during the declining phase of each cycle, this
hemispheric rule reverses. We attribute this to a global restructuring of the
magnetic topology that is induced by the interaction of the bands across the
equator. This band interaction appears to be ultimately responsible for, or at
least associated with, the decay and subsequent reversal of both the toroidal
bands and the polar fields. We briefly discuss the implications of these
results within the context of solar observations, which also show some
potential evidence for toroidal band interactions and helicity reversals.


title: The reachable set of single-mode unstable quadratic Hamiltonians

abstract:
  The question of open-loop control in the Gaussian regime may be cast by
asking which Gaussian unitary transformations are reachable by turning on and
off a given set of quadratic Hamiltonians. For compact groups, including finite
dimensional unitary groups, the well known Lie algebra rank criterion provides
a sufficient and necessary condition for the reachable set to cover the whole
group. Because of the non-compact nature of the symplectic group, which
corresponds to Gaussian unitary transformations, this criterion turns out to be
still necessary but not sufficient for Gaussian systems. If the control
Hamiltonians are unstable, in a sense made rigorous in the main text, the
peculiar situation may arise where the rank criterion is satisfied and yet not
all symplectic transformations are reachable. Here, we address this situation
for one degree of freedom and study the properties of the reachable set under
unstable control Hamiltonians. First, we provide a partial analytical
characterisation of the reachable set and prove that no orthogonal
(`energy-preserving' or `passive' in the literature) symplectic operations may
be reached with such controls. Then, we apply numerical optimal control
algorithms to demonstrate a complete characterisation of the set in specific
cases.