title:
Testing the Kerr black hole hypothesis: comparison between the
  gravitational wave and the iron line approaches

abstract:
  The recent announcement of the detection of gravitational waves by the
LIGO/Virgo collaboration has opened a new window to test the nature of
astrophysical black holes. Konoplya & Zhidenko have shown how the LIGO data of
GW 150914 can constrain possible deviations from the Kerr metric. In this
letter, we compare their constraints with those that can be obtained from
accreting black holes by fitting their reflected X-ray spectrum, the so-called
iron line method. We simulate observations with eXTP, a next generation X-ray
mission, finding constraints much stronger than those obtained by Konoplya &
Zhidenko. Our results can at least show that, contrary to what is quite
commonly believed, it is not obvious that gravitational waves are the most
powerful approach to test strong gravity. In the presence of high quality data
and with the systematics under control, the iron line method may provide
competitive constraints.


title:
Stochastic resonance controlled upregulation of internal noise after
  hearing loss as a putative correlate of tinnitus-related neuronal
  hyperactivity

abstract:
  Subjective tinnitus (ST) is generally assumed to be a consequence of hearing
loss (HL). In animal studies acoustic trauma can lead to behavioral signs of
ST, in human studies ST patients without increased hearing thresholds were
found to suffer from so called hidden HL. Additionally, ST is correlated with
pathologically increased spontaneous firing rates and neuronal hyperactivity
(NH) along the auditory pathway. Homeostatic plasticity (HP) has been proposed
as a compensation mechanism leading to the development of NH, arguing that
after HL initially decreased mean firing rates of neurons are subsequently
restored by increased spontaneous rates. However all HP models fundamentally
lack explanatory power since the function of keeping mean firing rate constant
remains elusive as does the benefit this might have in terms of information
processing. Furthermore the neural circuitry being able to perform the
comparison of preferred with actual mean firing rate remains unclear. Here we
propose an entirely new interpretation of ST related development of NH in terms
of information theory. We suggest that stochastic resonance (SR) plays a key
role in short- and long-term plasticity within the auditory system and is the
ultimate cause of NH and ST. SR has been found ubiquitous in neuroscience and
refers to the phenomenon that sub-threshold, unperceivable signals can be
transmitted by adding noise to sensor input. We argue that after HL, SR serves
to lift signals above the increased hearing threshold, hence subsequently
decreasing thresholds again. The increased amount of internal noise is the
correlate of the NH, which finally leads to the development of ST, due to
neuronal plasticity along the auditory pathway. We demonstrate the plausibility
of our hypothesis by using a computational model and provide exemplarily
findings of human and animal studies that are consistent with our model.


title: Magnetic fields on a wide range of scales in star-forming galaxies

abstract:
  A key ingredient in the evolution of galaxies is the star formation cycle.
Recent progress in the study of magnetic fields is revealing the close
connection between star formation and its effect on the small-scale structure
in the magnetized interstellar medium (ISM). In this contribution we describe
how the modern generation of radio telescopes is being used to probe the
physics of the ISM through sensitive multiwavelength surveys of gas and
magnetic fields, from the inner star forming disk and outward into the galaxy
outskirts where large-scale magnetic fields may also play a key role. We
highlight unique pioneering efforts towards performing and scientifically
exploiting large-scale surveys of the type that the SKA will undertake
routinely. Looking to the future, we describe plans for using the Square
Kilometre Array (SKA) and its pathfinders to gain important new insights into
the cosmic history of galaxy evolution.


title: Closing in on minimal dark matter and radiative neutrino masses

abstract:
  We study one-loop radiative neutrino mass models in which one of the
beyond-the-standard model fields is either a hypercharge-zero fermion quintet
(minimal dark matter) or a hypercharge-zero scalar septet. By systematically
classifying all possible one-loop such models we identify various processes
that render the neutral component of these representations (dark matter)
cosmologically unstable. Thus, our findings show that these scenarios are in
general not reconcilable with dark matter stability unless tiny couplings or
additional ad hoc symmetries are assumed, in contrast to minimal dark matter
models where stability is entirely due to the standard model gauge symmetry.
For some variants based on higher-order loops we find that $\alpha_2$ reaches a
Landau pole at rather low scales, a couple orders of magnitude from the
characteristic scale of the model itself. Thus, we argue that some of these
variations although consistent with dark matter stability and phenomenological
constraints are hard to reconcile with perturbativity criteria.


title: On the decomposition threshold of a given graph

abstract:
  We study the $F$-decomposition threshold $\delta_F$ for a given graph $F$.
Here an $F$-decomposition of a graph $G$ is a collection of edge-disjoint
copies of $F$ in $G$ which together cover every edge of $G$. (Such an
$F$-decomposition can only exist if $G$ is $F$-divisible, i.e. if $e(F)\mid
e(G)$ and each vertex degree of $G$ can be expressed as a linear combination of
the vertex degrees of $F$.)
  The $F$-decomposition threshold $\delta_F$ is the smallest value ensuring
that an $F$-divisible graph $G$ on $n$ vertices with
$\delta(G)\ge(\delta_F+o(1))n$ has an $F$-decomposition. Our main results imply
the following for a given graph $F$, where $\delta_F^\ast$ is the fractional
version of $\delta_F$ and $\chi:=\chi(F)$:
  (i) $\delta_F\le \max\{\delta_F^\ast,1-1/(\chi+1)\}$;
  (ii) if $\chi\ge 5$, then
$\delta_F\in\{\delta_F^{\ast},1-1/\chi,1-1/(\chi+1)\}$;
  (iii) we determine $\delta_F$ if $F$ is bipartite.
  In particular, (i) implies that $\delta_{K_r}=\delta^\ast_{K_r}$. Our proof
involves further developments of the recent `iterative' absorbing approach.


title:
The radial Regge trajectories and leptonic widths of the isovector
  mesons

abstract:
  It is shown that two physical phenomena are important for high excitations:
(i) the screening of the universal gluon-exchange potential and (ii) the
flattening of the confining potential owing to creation of quark loops, and
both effects are determined quantitatively. Taking the first effect into
account, we predict the masses of the ground states with $l=0,1,2$ in agreement
with experiment. The flattening effect ensures the observed linear behaviour of
the radial Regge trajectories $M^2(n)=m_0^2 + n_r \mu^2$ GeV$^2$, where the
slope $\mu^2$ is very sensitive to the parameter $\gamma$, which determines the
weakening of the string tension $\sigma(r)$ at large distances. For the
$\rho$-trajectory the linear behaviour starts with $n_r=1$ and the values
$\mu^2=1.40(2)$~GeV$^2$ for $\gamma=0.40$ and $\mu^2=1.34(1)$~GeV$^2$ for
$\gamma=0.45$ are obtained. For the excited states the leptonic widths:
$\Gamma_{\rm ee}(\rho(775))=7.0(3)$~keV, $\Gamma_{\rm
ee}(\rho(1450))=1.7(1)$~keV, $\Gamma_{\rm ee}(\rho(1900))=1.0(1)$~keV,
$\Gamma_{\rm ee}(\rho(2150))=0.7(1)$~keV, and $\Gamma_{\rm
ee}(1\,{}^3D_1)=0.26(5)$~keV are calculated, if these states are considered as
purely $q\bar q$ states. The width $\Gamma_{\rm ee}(\rho(1700))$ increases if
$\rho(1700)$ is mixed with the $2\,{}^3S_1$ state, giving for a mixing angle
$\theta=21^\circ$ almost equal widths: $\Gamma_{\rm
ee}(\rho(1700))=0.75(6)$~keV and $\Gamma_{\rm ee}(1450)=1.0(1)$~keV.


title:
The SPURS Algorithm for Resampling an Irregularly Sampled Signal onto a
  Cartesian Grid

abstract:
  We present an algorithm for resampling a function from its values on a
non-Cartesian grid onto a Cartesian grid. This problem arises in many
applications such as MRI, CT, radio astronomy and geophysics. Our algorithm,
termed SParse Uniform ReSampling (SPURS), employs methods from modern sampling
theory to achieve a small approximation error while maintaining low
computational cost. The given non-Cartesian samples are projected onto a
selected intermediate subspace, spanned by integer translations of a compactly
supported kernel function. This produces a sparse system of equations
describing the relation between the nonuniformly spaced samples and a vector of
coefficients representing the projection of the signal onto the chosen
subspace. This sparse system of equations can be solved efficiently using
available sparse equation solvers. The result is then projected onto the
subspace in which the sampled signal is known to reside. The second projection
is implemented efficiently using a digital linear shift invariant (LSI) filter
and produces uniformly spaced values of the signal on a Cartesian grid. The
method can be iterated to improve the reconstruction results. We then apply
SPURS to reconstruction of MRI data from nonuniformly spaced k-space samples.
Simulations demonstrate that SPURS outperforms other reconstruction methods
while maintaining a similar computational complexity over a range of sampling
densities and trajectories as well as various input SNR levels.


title:
Gyrokinetic simulations of fusion plasmas using a spectral velocity
  space representation

abstract:
  Magnetic confinement fusion reactors suffer severely from heat and particle
losses through turbulent transport, which has inspired the construction of ever
larger and more expensive reactors. Numerical simulations are vital to their
design and operation, but particle collisions are too infrequent for fluid
descriptions to be valid. Instead, strongly magnetised fusion plasmas are
described by the gyrokinetic equations, a nonlinear integro-differential system
for evolving the particle distribution functions in a five-dimensional position
and velocity space, and the consequent electromagnetic field. Due to the high
dimensionality, simulations of small reactor sections require hundreds of
thousands of CPU hours on High Performance Computing platforms.
  We develop a Hankel-Hermite spectral representation for velocity space that
exploits structural features of the gyrokinetic system. The representation
exactly conserves discrete free energy in the absence of explicit dissipation,
while our Hermite hypercollision operator captures Landau damping with few
variables. Calculation of the electromagnetic fields becomes purely local,
eliminating inter-processor communication in, and vastly accelerating, searches
for linear instabilities. We implement these ideas in SpectroGK, an efficient
parallel code.
  Turbulent fusion plasmas may dissipate free energy through linear phase
mixing to fine scales in velocity space, as in Landau damping, or through a
nonlinear cascade to fine scales in physical space, as in hydrodynamic
turbulence. Using SpectroGK to study saturated electrostatic drift-kinetic
turbulence, we find that the nonlinear cascade suppresses linear phase mixing
at energetically-dominant scales, so the turbulence is fluid-like. We use this
observation to derive Fourier-Hermite spectra for the electrostatic potential
and distribution function, and confirm these spectra with simulations.


title: The type Iax supernova, SN 2015H: a white dwarf deflagration candidate

abstract:
  We present results based on observations of SN 2015H which belongs to the
small group of objects similar to SN 2002cx, otherwise known as type Iax
supernovae. The availability of deep pre-explosion imaging allowed us to place
tight constraints on the explosion epoch. Our observational campaign began
approximately one day post-explosion, and extended over a period of about 150
days post maximum light, making it one of the best observed objects of this
class to date. We find a peak magnitude of M$_r$ = -17.27 $\pm$ 0.07, and a
($\Delta m_{15})_r$ = 0.69 $\pm$ 0.04. Comparing our observations to synthetic
spectra generated from simulations of deflagrations of Chandrasekhar mass
carbon-oxygen white dwarfs, we find reasonable agreement with models of weak
deflagrations that result in the ejection of ~0.2 M$_{\odot}$ of material
containing ~0.07 M$_{\odot}$ of 56Ni. The model light curve however, evolves
more rapidly than observations, suggesting that a higher ejecta mass is to be
favoured. Nevertheless, empirical modelling of the pseudo-bolometric light
curve suggests that $\lesssim$0.6 M_sun of material was ejected, implying that
the white dwarf is not completely disrupted, and that a bound remnant is a
likely outcome.


title: Homogenization of a stationary flow of a generalized Newtonian fluid

abstract:
  We perform the homogenization process avoiding the necessity of testing the
weak formulation of the initial and homogenized systems by corresponding weak
solutions. We show that the stress tensor for homogenized problem depends on
the gradient involving the limit of a sequence selected from a family of
solutions of initial problems.


title:
Applying the expanding photosphere and standardized candle methods to
  Type II-Plateau supernovae at cosmologically significant redshifts: the
  distance to SN 2013eq

abstract:
  Based on optical imaging and spectroscopy of the Type II-Plateau SN 2013eq,
we present a comparative study of commonly used distance determination methods
based on Type II supernovae. The occurrence of SN 2013eq in the Hubble flow (z
= 0.041 +/- 0.001) prompted us to investigate the implications of the
difference between "angular" and "luminosity" distances within the framework of
the expanding photosphere method (EPM) that relies upon a relation between flux
and angular size to yield a distance. Following a re-derivation of the basic
equations of the EPM for SNe at non-negligible redshifts, we conclude that the
EPM results in an angular distance. The observed flux should be converted into
the SN rest frame and the angular size, theta, has to be corrected by a factor
of (1+z)^2. Alternatively, the EPM angular distance can be converted to a
luminosity distance by implementing a modification of the angular size. For SN
2013eq, we find EPM luminosity distances of D_L = 151 +/- 18 Mpc and D_L = 164
+/- 20 Mpc by making use of different sets of dilution factors taken from the
literature. Application of the standardized candle method for Type II-P SNe
results in an independent luminosity distance estimate (D_L = 168 +/- 16 Mpc)
that is consistent with the EPM estimate.


title:
Empirical Parameterization of Nucleon-Nucleon Elastic Scattering
  Amplitude at High Beam Momenta for Glauber Calculations and Monte Carlo
  Simulations

abstract:
  A parameterization of the nucleon-nucleon elastic scattering amplitude is
needed for future experiments with nucleon and nuclear beams in the beam
momentum range of 2 -- 50 GeV/c/nucleon. There are many parameterizations of
the amplitude at $P_{lab} >$ 25--50 GeV/c, and at $P_{lab} \leq$ 5 GeV/c. Our
paper is aimed to cover the range between 5 -- 50 GeV/c.
  The amplitude is used in Glauber calculations of various cross sections and
Monte Carlo simulations of nucleon-nucleon scatterings. Usually, the
differential nucleon-nucleon elastic scattering cross sections are described by
an exponential expression. Corresponding experimental data on $pp$ interactions
at $|t|>$ 0.005 (GeV/c)$^2$ and $|t|\leq$ 0.125 (GeV/c)$^2$ have been fit. We
propose formulae to approximate the beam momentum dependence of these
parameters in the momentum range considered. The same was done for $np$
interactions at $|t|\leq$ 0.5 (GeV/c)$^2$. Expressions for the momentum
dependence of the total and elastic cross sections, and the ratio of real to
imaginary parts of the amplitude at zero momentum transfer are also given for
$pp$ and $np$ collisions. These results are sufficient for a first
approximation of the Glauber calculations. For more exact calculations we fit
the data at $|t|>$ 0.005 (GeV/c)$^2$ without restrictions on the maximum value
of $|t|$ using an expression based on two coherent exponential. The parameters
of the fits are found for the beam momentum range 2 -- 50 GeV/c.


title: Principal Symbol of Euler-Lagrange Operators

abstract:
  We shall introduce the principal symbol for Euler-Lagrange operators and use
them to charac- terise well-posed initial value problems. We shall clarify how
constraints can arise in Lagrangian covariant theories by extending the
standard treatment in GR. Finally, we sketch a quantization procedure based on
what done in LQG.


title:
Structured and Efficient Variational Deep Learning with Matrix Gaussian
  Posteriors

abstract:
  We introduce a variational Bayesian neural network where the parameters are
governed via a probability distribution on random matrices. Specifically, we
employ a matrix variate Gaussian \cite{gupta1999matrix} parameter posterior
distribution where we explicitly model the covariance among the input and
output dimensions of each layer. Furthermore, with approximate covariance
matrices we can achieve a more efficient way to represent those correlations
that is also cheaper than fully factorized parameter posteriors. We further
show that with the "local reprarametrization trick"
\cite{kingma2015variational} on this posterior distribution we arrive at a
Gaussian Process \cite{rasmussen2006gaussian} interpretation of the hidden
units in each layer and we, similarly with \cite{gal2015dropout}, provide
connections with deep Gaussian processes. We continue in taking advantage of
this duality and incorporate "pseudo-data" \cite{snelson2005sparse} in our
model, which in turn allows for more efficient sampling while maintaining the
properties of the original model. The validity of the proposed approach is
verified through extensive experiments.


title:
Asymptotic Expansions for Stationary Distributions of Nonlinearly
  Perturbed Semi-Markov Processes. I

abstract:
  New algorithms for construction of asymptotic expansions for stationary
distributions of nonlinearly perturbed semi-Markov processes with finite phase
spaces are presented. These algorithms are based on a special technique of
sequential phase space reduction, which can be applied to processes with an
arbitrary asymptotic communicative structure of phase spaces. Asymptotic
expansions are given in two forms, without and with explicit bounds for
remainders.


title: Convergence rate for the hedging error of a path-dependent example

abstract:
  We consider a Brownian functional $F=g\bigl(\int_0^T \eta(s) dW_s\bigr)$ with
$g \in L_2(\gamma)$ and a singular deterministic $\eta$. We deduce the
$L_2$-convergence rate for the approximation $F^{(n)} = E F + \int_0^T
\phi^{(n)}(s) dW_s$ for a class of piecewise constant predictable integrands
$\phi^{(n)}$ from the fractional smoothness of $g$ quantified by Besov spaces
and the rate of singularity of $\eta$.


title: Dense cloud cores revealed by CO in the low metallicity dwarf galaxy WLM

abstract:
  Understanding stellar birth requires observations of the clouds in which they
form. These clouds are dense and self-gravitating, and in all existing
observations, they are molecular with H_2 the dominant species and CO the best
available tracer. When the abundances of carbon and oxygen are low compared to
hydrogen, and the opacity from dust is also low, as in primeval galaxies and
local dwarf irregular galaxies, CO forms slowly and is easily destroyed, so it
is difficult for it to accumulate inside dense clouds. Here we report
interferometric observations of CO clouds in the local group dwarf irregular
galaxy Wolf-Lundmark-Melotte (WLM), which has a metallicity that is 13% of the
solar value and 50% lower than the previous CO detection threshold. The clouds
are tiny compared to the surrounding atomic and H_2 envelopes, but they have
typical densities and column densities for CO clouds in the Milky Way. The
normal CO density explains why star clusters forming in dwarf irregulars have
similar densities to star clusters in giant spiral galaxies. The low cloud
masses suggest that these clusters will also be low mass, unless some
galaxy-scale compression occurs, such as an impact from a cosmic cloud or other
galaxy. If the massive metal-poor globular clusters in the halo of the Milky
Way formed in dwarf galaxies, as is commonly believed, then they were probably
triggered by such an impact.


title: Search for Higgs portal DM at the ILC

abstract:
  Higgs portal dark matter (DM) models are simple interesting and viable DM
models. There are three types of the models depending on the DM spin: scalar,
fermion and vector DM models. In this paper, we consider renormalizable,
unitary and gauge invariant Higgs portal DM models, and study how large
parameter regions can be surveyed at the International Linear Collider (ILC)
experiment at $\sqrt{s}=500$ GeV. For the Higgs portal singlet fermion and
vector DM cases, the force mediator involves two scalar propagators, the
SM-like Higgs boson and the dark Higgs boson. We show that their interference
generates interesting and important patterns in the mono-$Z$ plus missing $E_T$
signatures at the ILC, and the results are completely different from those
obtained from the Higgs portal DM models within the effective field theories.
In addition, we show that it would be possible to distinguish the spin of DM in
the Higgs portal scenarios, if the shape of the recoil-mass distribution is
observed. We emphasize that the interplay between these collider observations
and those in the direct detection experiments has to be performed in the model
with renomalizability and unitarity to combine the model analyses in different
scales.


title:
Extending the Learning by Teaching Canvas System: Maximising Academic
  Learning Time

abstract:
  Time plays an integral role in the realm of e-learning modules. plaimi
previously described a canvas for composing e-learning modules. By
transitivity, time needs to play an integral role in this canvas. This paper
investigates some of the ways it can play said role. Four angles are
considered: insights offered by viewing a module composition as a chronicle of
modules, the importance of length estimation in time allocation, heightening
retention via spaced repetition, and synchronisation attempts at facilitating
collaborative learning. The features discovered by this investigation are
discussed in a principled learning context, which particularly emphasises
academic learning time. Some concrete suggestions are made; to implement:
order-awareness, user estimation of module length, spaced-repetition-awareness,
and post-module self-assessment. Suggestions for further research are also
given.


title: On the Whittle Index for Restless Multi-armed Hidden Markov Bandits

abstract:
  We consider a restless multi-armed bandit in which each arm can be in one of
two states. When an arm is sampled, the state of the arm is not available to
the sampler. Instead, a binary signal with a known randomness that depends on
the state of the arm is available. No signal is available if the arm is not
sampled. An arm-dependent reward is accrued from each sampling. In each time
step, each arm changes state according to known transition probabilities which
in turn depend on whether the arm is sampled or not sampled. Since the state of
the arm is never visible and has to be inferred from the current belief and a
possible binary signal, we call this the hidden Markov bandit. Our interest is
in a policy to select the arm(s) in each time step that maximizes the infinite
horizon discounted reward. Specifically, we seek the use of Whittle's index in
selecting the arms. We first analyze the single-armed bandit and show that in
general, it admits an approximate threshold-type optimal policy when there is a
positive reward for the `no-sample' action. We also identify several special
cases for which the threshold policy is indeed the optimal policy. Next, we
show that such a single-armed bandit also satisfies an approximate-indexability
property. For the case when the single-armed bandit admits a threshold-type
optimal policy, we perform the calculation of the Whittle index for each arm.
Numerical examples illustrate the analytical results.


title:
Inequality on $t_\nu(K)$ defined by Livingston and Naik and its
  applications

abstract:
  Let $D_+(K,t)$ denote the positive $t$-twisted double of $K$. For a fixed
integer-valued additive concordance invariant $\nu$ that bounds the smooth four
genus of a knot and determines the smooth four genus of positive torus knots,
Livingston and Naik defined $t_\nu(K)$ to be the greatest integer $t$ such that
$\nu(D_+(K,t)) = 1$. Let $K_1$ and $K_2$ be any knots then we prove the
following inequality : $t_\nu(K_1) + t_\nu(K_2) \leq t_\nu(K_1 \# K_2) \leq
min(t_\nu(K_1) - t_\nu(-K_2), t_\nu(K_2) - t_\nu(-K_1)).$ As an application we
show that $t_\tau(K) \neq t_s(K)$ for infinitely many knots and that their
difference can be arbitrarily large, where $t_\tau(K)$ (respectively $t_s(K)$)
is $t_\nu(K)$ when $\nu$ is Ozv\'{a}th-Szab\'{o} invariant $\tau$ (respectively
when $\nu$ is normalized Rasmussen $s$ invariant).


title:
Closed-orbit theory for photodetachment in a time-dependent electric
  field

abstract:
  The standard closed-orbit theory is extended for the photodetachment of
negative ions in a time-dependent electric field. The time-dependent
photodetachment rate is specifically studied in the presence of a single-cycle
terahertz pulse, based on exact quantum simulations and semiclassical analysis.
We find that the photodetachment rate is unaffected by a weak terahertz field,
but oscillates complicatedly when the terahertz pulse gets strong enough. Three
types of closed classical orbits are identified for the photoelectron motion in
a strong single-cycle terahertz pulse, and their connections with the
oscillatory photodetachment rate are established quantitatively by generalizing
the standard closed-orbit theory to a time-dependent form. By comparing the
negative hydrogen and fluorine ions, both the in-phase and antiphase
oscillations can be observed, depending on a simple geometry of the contributed
closed classical orbits. On account of its generality, the presented theory
provides an intuitive understanding from a time-dependent viewpoint for the
photodetachment dynamics driven by an external electric field oscillating at
low frequency.


title:
Recent Developments in Helioseismic Analysis Methods and Solar Data
  Assimilation

abstract:
  We review recent advances and results in enhancing and developing
helioseismic analysis methods and in solar data assimilation. In the first part
of this paper we will focus on selected developments in time-distance and
global helioseismology. In the second part, we review the application of data
assimilation methods on solar data. Relating solar surface observations as well
as helioseismic proxies with solar dynamo models by means of the techniques
from data assimilation is a promising new approach to explore and to predict
the magnetic activity cycle of the Sun.


title:
Asymptotic Expansions for Stationary Distributions of Nonlinearly
  Perturbed Semi-Markov Processes. II

abstract:
  Asymptotic expansions with explicit upper bounds for remainders are given for
stationary distributions of nonlinearly perturbed semi-Markov processes with
finite phase spaces. The corresponding algorithms are based on a special
technique of sequential phase space reduction, which can be applied to
processes with an arbitrary asymptotic communicative structure of phase spaces.


title: Topological Semimetals Predicted from First-principles Calculations

abstract:
  We have given a summary on our theoretical predictions of three kinds of
topological semimetals (TSMs), namely, Dirac semimetal (DSM), Weyl semimetal
(WSM) and Node-Line Semimetal (NLSM). TSMs are new states of quantum matters,
which are different with topological insulators. They are characterized by the
topological stability of Fermi surface, whether it encloses band crossing
point, i.e., Dirac cone like energy node, or not. They are distinguished from
each other by the degeneracy and momentum space distribution of the nodal
points. To realize these intriguing topological quantum states is quite
challenging and crucial to both fundamental science and future application. In
2012 and 2013, Na$_3$Bi and Cd$_3$As$_2$ were theoretically predicted to be
DSM, respectively. Their experimental verifications in 2014 have ignited the
hot and intensive studies on TSMs. The following theoretical prediction of
nonmagnetic WSM in TaAs family stimulated a second wave and many experimental
works have come out in this year. In 2014, a kind of three dimensional crystal
of carbon has been proposed to be NLSM due to negligible spin-orbit coupling
and coexistence of time-reversal and inversion symmetry. Though the final
experimental confirmation of NLSM is still missing, there have been several
theoretical proposals, including Cu$_3$PdN from us. In the final part, we have
summarized the whole family of TSMs and their relationship.


title:
A new class of high order semi-Lagrangian schemes for rarefied gas
  dynamics

abstract:
  In this paper we genealize the fast semi-Lagrangian scheme developed in [J.
Comput. Phys., Vol. 255, 2013, pp 680-698] to the case of high order
reconstructions of the distribution function. The original first order accurate
semi-Lagrangian scheme is supplemented with polynomial reconstructions of the
distribution function and of the collisional operator leading to an effective
high order accurate numerical scheme for all regimes, from extremely rarefied
gas to highly collisional siuation. The main idea relies on updating at each
time step the extreme points of the distribution function for each velocity of
the lattice instead of updating the solution in the cell centers, these
extremes points being located at different positions for any fixed velocity of
the lattice. The result is a class of scheme which permits to preserve the
structure of the solution over very long times compared to existing schemes
from the literature. We propose a proof of concept of this new approach along
with numerical tests and comparisons with classical numerical methods.


title:
Fourier ptychographic reconstruction using Poisson maximum likelihood
  and truncated Wirtinger gradient

abstract:
  Fourier ptychographic microscopy (FPM) is a novel computational coherent
imaging technique for high space-bandwidth product imaging. Mathematically,
Fourier ptychographic (FP) reconstruction can be implemented as a phase
retrieval optimization process, in which we only obtain low resolution
intensity images corresponding to the sub-bands of the sample's high resolution
(HR) spatial spectrum, and aim to retrieve the complex HR spectrum. In real
setups, the measurements always suffer from various degenerations such as
Gaussian noise, Poisson noise, speckle noise and pupil location error, which
would largely degrade the reconstruction. To efficiently address these
degenerations, we propose a novel FP reconstruction method under a gradient
descent optimization framework in this paper. The technique utilizes Poisson
maximum likelihood for better signal modeling, and truncated Wirtinger gradient
for error removal. Results on both simulated data and real data captured using
our laser FPM setup show that the proposed method outperforms other
state-of-the-art algorithms. Also, we have released our source code for
non-commercial use.


title: Topic Modeling Using Distributed Word Embeddings

abstract:
  We propose a new algorithm for topic modeling, Vec2Topic, that identifies the
main topics in a corpus using semantic information captured via
high-dimensional distributed word embeddings. Our technique is unsupervised and
generates a list of topics ranked with respect to importance. We find that it
works better than existing topic modeling techniques such as Latent Dirichlet
Allocation for identifying key topics in user-generated content, such as
emails, chats, etc., where topics are diffused across the corpus. We also find
that Vec2Topic works equally well for non-user generated content, such as
papers, reports, etc., and for small corpora such as a single-document.


title:
SN 2015bn: a detailed multi-wavelength view of a nearby superluminous
  supernova

abstract:
  We present observations of SN 2015bn (= PS15ae = CSS141223-113342+004332 =
MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift
$z=0.1136$. As well as being one of the closest SLSNe I yet discovered, it is
intrinsically brighter ($M_U\approx-23.1$) and in a fainter galaxy
($M_B\approx-16.0$) than other SLSNe at $z\sim0.1$. We used this opportunity to
collect the most extensive dataset for any SLSN I to date, including
densely-sampled spectroscopy and photometry, from the UV to the NIR, spanning
$-$50 to +250 days from optical maximum. SN 2015bn fades slowly, but exhibits
surprising undulations in the light curve on a timescale of 30-50 days,
especially in the UV. The spectrum shows extraordinarily slow evolution except
for a rapid transformation between +7 and +20-30 days. No narrow emission lines
from slow-moving material are observed at any phase. We derive physical
properties including the bolometric luminosity, and find slow velocity
evolution and non-monotonic temperature and radial evolution. A deep radio
limit rules out a healthy off-axis gamma-ray burst, and places constraints on
the pre-explosion mass loss. The data can be consistently explained by a
$\gtrsim10\,{\rm M}_\odot$ stripped progenitor exploding with $\sim
10^{51}\,$erg kinetic energy, forming a magnetar with a spin-down timescale of
$\sim20$ days (thus avoiding a gamma-ray burst) that reheats the ejecta and
drives ionization fronts. The most likely alternative scenario -- interaction
with $\sim20\,{\rm M}_\odot$ of dense, inhomogeneous circumstellar material --
can be tested with continuing radio follow-up.


title: New Luminous ON Spectra from the Galactic O-Star Spectroscopic Survey

abstract:
  Two new ON supergiant spectra (bringing the total known to seven) and one new
ONn giant (total of this class now eight) are presented; they have been
discovered by the Galactic O-Star Spectroscopic Survey. These rare objects
represent extremes in the mixing of CNO-cycled material to the surfaces of
evolved, late-O stars, by uncertain mechanisms in the first category but likely
by rotation in the second. The two supergiants are at the hot edge of the
class, which is a selection effect from the behavior of defining N III and C
III absorption blends, related to the tendency toward emission (Of effect) in
the former. An additional N/C criterion first proposed by Bisiacchi et al. is
discussed as a means to alleviate that effect, and it is relevant to the two
new objects. The entire ON supergiant class is discussed; they display a
fascinating diversity of detail undoubtedly related to the complexities of
their extended atmospheres and winds that are sensitive to small differences in
physical parameters, as well as to binary effects in some cases.
Serendipitously, we have found significant variability in the spectrum of a
little-known hypergiant with normal N, C spectra selected as a comparison for
the anomalous objects. In contrast to the supergiants, the ONn spectra are
virtual (nitrogen)-carbon copies of one another except for the degrees of line
broadening, which emphasizes their probable unique origin and hence amenability
to definitive astrophysical interpretation.


title:
Analytical solution of the second Stokes problem with variable amplitude
  on behaviour of gas over oscillation surface. Part I: eigenvalues and
  eigensolutions

abstract:
  In the present work the second Stokes problem about behaviour of the rarefied
gas filling half-space is formulated. A plane limiting half-space makes
harmonious fluctuations with variable amplitude in the plane. The amplitude
changes on the exponential law. The kinetic equation with model integral of
collisions in the form $\tau$-model is used. The case of diffusion reflexions
of gas molecules from a wall is considered. Eigen solutions (continuous modes)
of the initial kinetic equation corresponding to the continuous spectrum are
searched. Properties of dispersion function are studied. It is investigated the
discrete spectrum of the problem consisting of zero of the dispersion functions
in the complex plane. It is shown, that number of zero of dispersion function
to equally doubled index of problem coefficient. The problem coefficient is
understood as the relation of boundary values of dispersion function from above
and from below on the real axis. Further are eigen solutions (discrete modes)
of the initial kinetic equation corresponding to the discrete spectrum are
searched. In the end of work the general solution of the kinetic equation in
the form expansion under eigen solutions with unknown coefficients
corresponding to discrete and continuous spectra is constructed.


title: Quantum Go

abstract:
  We introduce a new board game based on the ancient Chinese game of Go (Weiqi,
Igo, Baduk). The key difference from the original game is that players no
longer alternatively play single stones on the board but instead they take
turns placing pairs of entangled go stones. A phenomenon of quantum-like
collapse occurs when one of the stones in an entangled pair is directly in
contact with at least one other stone. The player to whom the entangled pair
belongs must then remove one of the stones in the pair from the board. The aim
of the game is still to surround more territory than the opponent and as the
number of stones increases, all the entangled pairs of stones eventually reduce
to single stones. Quantum Go provides an interesting and tangible illustration
of quantum concepts such as superposition, entanglement and collapse.


title: Effect of number scaling on entangled states in quantum mechanics

abstract:
  A summary of number structure scaling is followed by a description of the
effects of number scaling in nonrelativistic quantum mechanics. The description
extends earlier work to include the effects on the states of two or more
interacting particles. Emphasis is placed on the effects on entangled states.
The resulting scaling field is generalized to describe the effects on these
states. It is also seen that one can use fiber bundles with fibers associated
with single locations of the underlying space to describe the effects of
scaling on arbitrary numbers of particles.


title: Reaction-diffusion with stochastic decay rates

abstract:
  Understanding anomalous transport and reaction kinetics due to microscopic
physical and chemical disorder is a long-standing goal in many fields including
geophysics, biology, and engineering. We consider reaction-diffusion
characterized by fluctuations in both transitions times and decay rates. We
introduce and analyze a model framework that explicitly connects microscopic
fluctuations with the mescoscopic description. For broad distributions of
transport and reaction time scales we compute the particle density and derive
the equations governing its evolution, finding power-law decay of the survival
probability, and spatially heterogeneous decay that leads to subdiffusion and
an asymptotically stationary surviving-particle density. These anomalies are
clearly attributable to non-Markovian effects that couple transport and
chemical properties in both reaction and diffusion terms.


title: Universal groups for right-angled buildings

abstract:
  In 2000, M. Burger and S. Mozes introduced universal groups acting on trees
with a prescribed local action. We generalize this concept to groups acting on
right-angled buildings. When the right-angled building is thick and irreducible
of rank at least 2 and each of the local permutation groups is transitive and
generated by its point stabilizers, we show that the corresponding universal
group is a simple group.
  When the building is locally finite, these universal groups are compactly
generated totally disconnected locally compact groups, and we describe the
structure of the maximal compact open subgroups of the universal groups as a
limit of generalized wreath products.


title: On the observability of bow shocks of Galactic runaway OB stars

abstract:
  Massive stars that have been ejected from their parent cluster and
supersonically sailing away through the interstellar medium (ISM) are
classified as exiled. They generate circumstellar bow shock nebulae that can be
observed. We present two-dimensional, axisymmetric hydrodynamical simulations
of a representative sample of stellar wind bow shocks from Galactic OB stars in
an ambient medium of densities ranging from n_ISM=0.01 up to 10.0/cm3.
Independently of their location in the Galaxy, we confirm that the infrared is
the most appropriated waveband to search for bow shocks from massive stars.
Their spectral energy distribution is the convenient tool to analyze them since
their emission does not depend on the temporary effects which could affect
unstable, thin-shelled bow shocks. Our numerical models of Galactic bow shocks
generated by high-mass (~40 Mo) runaway stars yield H$\alpha$ fluxes which
could be observed by facilities such as the SuperCOSMOS H-Alpha Survey. The
brightest bow shock nebulae are produced in the denser regions of the ISM. We
predict that bow shocks in the field observed at Ha by means of
Rayleigh-sensitive facilities are formed around stars of initial mass larger
than about 20 Mo. Our models of bow shocks from OB stars have the emission
maximum in the wavelength range 3 <= lambda <= 50 micrometer which can be up to
several orders of magnitude brighter than the runaway stars themselves,
particularly for stars of initial mass larger than 20 Mo.


title:
Commentary (invited update) to article "Spatiotemporal optical
  solitons", by B. A. Malomed, D. Mihalache, F. Wise, and L. Torner, J. Opt. B:
  Quantum Semiclass. Opt. 7, R53-R72 (2005)

abstract:
  This is an invited short update of the topic covered by the review article,
which aims to briefly survey progress made in theoretical and experimental
studies of multidimensional solitons since the publication of the review. The
Commentary was invited as an addition to the original review article that will
be reprinted in an e-book celebrating the 50th anniversary of Journal of
Physics B (incorporating Journal of Optics B: Quantum and Semiclassical
Optics).


title: Universal scalings for laser acceleration of electrons in ion channels

abstract:
  Direct laser acceleration of electrons in ion channels is investigated in a
general case when the laser phase velocity is greater than (or equal to) the
speed of light. Using the similarity of the equations of motion for
ultra-relativistic electrons, we develop a universal scaling theory that gives
the maximum possible energy that can be attained by an electron for given laser
and plasma parameters. The theory predicts appearance of forbidden zones in the
phase space of the particle, which manifests itself as an energy gain
threshold. We apply the developed theory to find the conditions needed for an
energy enhancement via a resonant interaction between the third harmonic of
betatron oscillations and the laser wave. The theory is also used to analyze
electron dynamics in a circularly polarized laser.


title:
Study of Growth Properties of InAs Islands on Nucleation Sites Defined
  by Focused Ion Beam

abstract:
  This work describes morphological and crystalline properties of the InAs
islands grown on templates created by focused ion beam (FIB) on indium
phosphide (InP) substrates. Regular arrangements of shallow holes are created
on the InP (001) surfaces, acting as preferential nucleation sites for InAs
islands grown by Metal-Organic Vapor Phase Epitaxy. Ion doses ranging from
$10^{15}$ to $10^{16}$ $Ga^{+}$/$cm^{2}$ were used and islands were grown for
two sub-monolayer coverages. We observe the formation of clusters in the inner
surfaces of the FIB produced cavities and show that for low doses templates the
nanostructures are mainly coherent while templates created with large ion doses
lead to the growth of incoherent islands with larger island density. The
modified island growth is described by a simple model based on the surface
potential and the net adatom flow to the cavities. We observe that obtained
morphologies result from a competition between coarsening and coalescence
mechanisms.


title:
Some properties of optimal functions for sphere packing in dimensions 8
  and 24

abstract:
  We study some sequences of functions of one real variable and conjecture that
they converge uniformly to functions with certain positivity and growth
properties. Our conjectures imply a conjecture of Cohn and Elkies, which in
turn implies the complete solution to the sphere packing problem in dimensions
8 and 24. We give numerical evidence for these conjectures as well as some
arithmetic properties of the hypothetical limiting functions. The conjectures
are of greatest interest in dimension 24, in light of Viazovska's recent
solution to the Cohn-Elkies conjecture (and consequently the sphere packing
problem) in dimension 8.


title: Studying the molecular gas towards the R Coronae Australis dark cloud

abstract:
  The R Coronae Australis dark cloud is one of the closest star-forming regions
to the Sun. The cloud is known to be very active in star formation, harboring
many Herbig-Haro objects (HHs) and Molecular Hydrogen emission-line Objects
(MHOs). In this work we present results from molecular observations (a
$5.5^{'}\times5.5^{'}$ map of $^{12}$CO J$=3-2$ and HCO$^{+}$ J$=4-3$, and a
single spectrum of N$_{2}$H$^{+}$ J$=4-3$) obtained with the Atacama
Submillimeter Telescope Experiment (ASTE) towards the R CrA dark cloud with an
angular and spectral resolution of 22$^{"}$ and 0.11 km s$^{-1}$, respectively.
From the $^{12}$CO J$=3-2$ line we found kinematical spectral features strongly
suggesting the presence of outflows towards a region populated by several HHs
and MHOs. Moreover, most of these objects lie within an HCO$^{+}$ maximum,
suggesting that its emission arises from an increasement of its abundance due
to the chemistry triggered by the outflow activity. Additionally, we are
presenting the first reported detection of N$_{2}$H$^{+}$ in the J$=4-3$ line
towards the R CrA dark cloud.


title: Tetraquark States with Open Flavors

abstract:
  In this work, we estimate the masses of tetraquark states with four different
flavors by virtue of QCD sum rules, in both $b$ and $c$ sectors. We construct
four $[8_c]_{\bar{b} s} \otimes [8_c]_{\bar{d} u}$ tetraquark currents with
$J^P = 0^+$, and then perform analytic calculation up to dimension eight in the
Operator Product Expansion (OPE). We keep terms which are linear in the strange
quark mass $m_s$, and in the end find two possible tetraquark states with
masses $(5.57 \pm 0.15)$ and $(5.58 \pm 0.15)$ GeV. We find that their
charmed-partner masses lie in $(2.54 \pm 0.13)$ and $(2.55 \pm 0.13)$ GeV,
respectively and are hence accessible in experiments like BESIII and Belle.


title:
Analysis of the radiative decays $\Sigma_Q \to \Lambda_Q \gamma$ and
  $\Xi^\prime_Q \to \Xi_Q \gamma$ in light cone sum rules

abstract:
  The light cone sum rules method is used in studying the radiative decays
$\Sigma_Q \to \Lambda_Q \gamma$ and $\Xi^\prime_Q \to \Xi_Q \gamma$. Firstly,
the sum rules for the form factor $F_2(Q^2=0)$ responsible for these
transitions is constructed. Using this result the decay widths of the
above--mentioned decays are calculated and analyzed. A comparison of our
predictions on the decay widths of considered transitions with the predictions
of the other approaches is presented.


title:
On the Harnack inequality for degenerate and singular elliptic equations
  with unbounded lower order terms via sliding paraboloids

abstract:
  We use the method of sliding paraboloids to establish a Harnack inequality
for linear, degenerate and singular elliptic equation with unbounded lower
order terms. The equations we consider include uniformly elliptic equations and
linearized Monge-Amp\`ere equations. Our argument allows us to prove the
doubling estimate for functions which, at points of large gradient, are
solutions of (degenerate and singular) elliptic equations with unbounded drift.


title:
A First Look at the Impact of NNNLO Theory Uncertainties on Top Mass
  Measurements at the ILC

abstract:
  A scan of the top production threshold at a future electron-positron collider
provides the possibility for a precise measurement of the top quark mass in
theoretically well-defined mass schemes. With statistical uncertainties of 20
MeV or below, systematics will likely dominate the total uncertainty of the
measurement. This contribution presents a first look at the impact of the
renormalization scale uncertainties in recent NNNLO calculations of the top
pair production cross section in the threshold region on the measurement of the
top quark mass at the International Linear Collider.


title: Macroscopic self-reorientation of interacting two-dimensional crystals

abstract:
  Microelectromechanical systems, which can be moved or rotated with nanometre
precision, already find applications in such fields like radio-frequency
electronics, micro-attenuators, sensors and many others. Especially interesting
are those which allow fine control over the motion on atomic scale due to
self-alignment mechanisms and forces acting on the atomic level. Such machines
can produce well-controlled movements as a reaction to small changes of the
external parameters. Here we demonstrate that, for the system of graphene on
hexagonal boron nitride, the interplay between the van der Waals and elastic
energies results in graphene mechanically self-rotating towards the hexagonal
boron nitride crystallographic directions. Such rotation is macroscopic (for
graphene flakes of tens of micrometres the tangential movement can be on
hundreds of nanometres) and can be used for reproducible manufacturing of
aligned van der Waals heterostructures.


title:
Population balances in case of crossing characteristic curves:
  Application to T-cells immune response

abstract:
  The progression of a cell population where each individual is characterized
by the value of an internal variable varying with time (e.g. size, weight, and
protein concentration) is typically modeled by a Population Balance Equation, a
first order linear hyperbolic partial differential equation. The
characteristics described by internal variables usually vary monotonically with
the passage of time. A particular difficulty appears when the characteristic
curves exhibit different slopes from each other and therefore cross each other
at certain times. In particular such crossing phenomenon occurs during T-cells
immune response when the concentrations of protein expressions depend upon each
other and also when some global protein (e.g. Interleukin signals) is also
involved which is shared by all T-cells. At these crossing points, the linear
advection equation is not possible by using the classical way of hyperbolic
conservation laws. Therefore, a new Transport Method is introduced in this
article which allowed us to find the population density function for such
processes. The newly developed Transport method (TM) is shown to work in the
case of crossing and to provide a smooth solution at the crossing points in
contrast to the classical PDF techniques.


title: Evaluating the word-expert approach for Named-Entity Disambiguation

abstract:
  Named Entity Disambiguation (NED) is the task of linking a named-entity
mention to an instance in a knowledge-base, typically Wikipedia. This task is
closely related to word-sense disambiguation (WSD), where the supervised
word-expert approach has prevailed. In this work we present the results of the
word-expert approach to NED, where one classifier is built for each target
entity mention string. The resources necessary to build the system, a
dictionary and a set of training instances, have been automatically derived
from Wikipedia. We provide empirical evidence of the value of this approach, as
well as a study of the differences between WSD and NED, including ambiguity and
synonymy statistics.


title:
Iron-rich solar particle events measured by SOHO/ERNE during two solar
  cycles

abstract:
  We study the differences in the heavy ion composition of solar energetic
particle (SEP) events between solar cycles 23 and 24. We have surveyed the
SOHO/ERNE heavy ion data from the beginning of solar cycle 23 until the end of
June 2015, that is, well into the declining phase of cycle 24. We used this
long observation period to study the properties of heavy ions (from C to Fe)
and to compare the two solar cycles in this respect. We surveyed the data for
SEP events with enhancements in the Fe/C and Fe/O intensity ratios in the
energy range 5-15 MeV per nucleon, and associated the events with solar flare
and coronal mass ejections (CME) when possible. We studied the properties of
heavy ions in these events and compared the average relative abundances of
heavy ions between the two solar cycles. We found that fewer days had C and O
intensities higher than ~10$^{-3}$
cm$^{-2}$sr$^{-1}$s$^{-1}$(MeVn$^{-1}$)$^{-1}$ during solar cycle 24 than
during cycle 23. For Fe this difference was clear even at lower intensities. We
also found that fewer days had Fe/(C+O) > 0.183 during cycle 24. We identified
86 SEP events with at least one Fe-rich day, 65 of which occurred during cycle
23 and only 21 during cycle 24. We found that impulsive events have been almost
completely absent during cycle 24. Mean abundances of heavy ions in the events
were found to be significantly lower during cycle 24 than in cycle 23. Our
results reflect the reduced solar activity in cycle 24 and indicate lower
efficiency of particle acceleration processes for both gradual and impulsive
SEP events in cycle 24.


title: Latent heat and the Fourier law

abstract:
  We present computer simulations run with a stochastic cellular automaton
which describes $d=1$ particle systems connected to reservoirs which keep two
different densities at the endpoints. We fix the parameters so that there is a
phase transition (of the van der Waals type) and observe that if the densities
at the boundaries are metastable then, after a transient, the system reaches an
apparently stationary regime where the current flows from the reservoir with
smaller density to the one with larger density.


title:
Mixed-Hybrid and Vertex-Discontinuous-Galerkin Finite Element Modeling
  of Multiphase Compositional Flow on 3D Unstructured Grids

abstract:
  Problems of interest in hydrogeology and hydrocarbon resources involve
complex heterogeneous geological formations. Such domains are most accurately
represented in reservoir simulations by unstructured computational grids.
Finite element methods accurately describe flow on unstructured meshes with
complex geometries, and their flexible formulation allows implementation on
different grid types. In this work, we consider for the first time the
challenging problem of fully compositional three-phase flow in 3D unstructured
grids, discretized by any combination of tetrahedra, prisms, and hexahedra. We
employ a mass conserving mixed hybrid finite element (MHFE) method to solve for
the pressure and flux fields. The transport equations are approximated with a
higher-order vertex-based discontinuous Galerkin (DG) discretization. We show
that this approach outperforms a face-based implementation of the same
polynomial order. These methods are well suited for heterogeneous and fractured
reservoirs, because they provide globally continuous pressure and flux fields,
while allowing for sharp discontinuities in compositions and saturations. The
higher-order accuracy improves the modeling of strongly non-linear flow, such
as gravitational and viscous fingering. We review the literature on
unstructured reservoir simulation models, and present many examples that
consider gravity depletion, water flooding, and gas injection in oil saturated
reservoirs. We study convergence rates, mesh sensitivity, and demonstrate the
wide applicability of our chosen finite element methods for challenging
multiphase flow problems in geometrically complex subsurface media.


title: A Neural Approach to Blind Motion Deblurring

abstract:
  We present a new method for blind motion deblurring that uses a neural
network trained to compute estimates of sharp image patches from observations
that are blurred by an unknown motion kernel. Instead of regressing directly to
patch intensities, this network learns to predict the complex Fourier
coefficients of a deconvolution filter to be applied to the input patch for
restoration. For inference, we apply the network independently to all
overlapping patches in the observed image, and average its outputs to form an
initial estimate of the sharp image. We then explicitly estimate a single
global blur kernel by relating this estimate to the observed image, and finally
perform non-blind deconvolution with this kernel. Our method exhibits accuracy
and robustness close to state-of-the-art iterative methods, while being much
faster when parallelized on GPU hardware.


title: Background independence in a background dependent renormalization group

abstract:
  Within the derivative expansion of conformally reduced gravity, the modified
split Ward identities are shown to be compatible with the flow equations if and
only if either the anomalous dimension vanishes or the cutoff profile is chosen
to be power law. No solutions exist if the Ward identities are incompatible. In
the compatible case, a clear reason is found for why Ward identities can still
forbid the existence of fixed points; however, for any cutoff profile, a
background independent (and parametrisation independent) flow equation is
uncovered. Finally, expanding in vertices, the combined equations are shown
generically to become either over-constrained or highly redundant beyond the
six-point level.


title:
Malaria elimination campaigns in the Lake Kariba region of Zambia: a
  spatial dynamical model

abstract:
  Background As more regions approach malaria elimination, understanding how
different interventions interact to reduce transmission becomes critical. The
Lake Kariba area of Southern Province, Zambia, is part of a multi-country
elimination effort and presents a particular challenge as it is an
interconnected region of variable transmission intensities.
  Methods In 2012-13, six rounds of mass-screen-and-treat drug campaigns were
carried out in the Lake Kariba region. A spatial dynamical model of malaria
transmission in the Lake Kariba area, with transmission and climate modeled at
the village scale, was calibrated to the 2012-13 prevalence survey data, with
case management rates, insecticide-treated net usage, and drug campaign
coverage informed by surveillance. The model was used to simulate the effect of
various interventions implemented in 2014-22 on reducing regional transmission,
achieving elimination by 2022, and maintaining elimination through 2028.
  Findings The model captured the spatio-temporal trends of decline and rebound
in malaria prevalence in 2012-13 at the village scale. Simulations predicted
that elimination required repeated mass drug administrations coupled with
simultaneous increase in net usage. Drug campaigns targeted only at high-burden
areas were as successful as campaigns covering the entire region.
  Interpretation Elimination in the Lake Kariba region is possible through
coordinating mass drug campaigns with high-coverage vector control. Targeting
regional hotspots is a viable alternative to global campaigns when human
migration within an interconnected area is responsible for maintaining
transmission in low-burden areas.


title: The Helstrom Bound

abstract:
  Quantum state discrimination between two wave functions on a ring is
considered. The optimal minimum-error probability is known to be given by the
Helstrom bound. A new strategy is introduced by inserting instantaneously two
impenetrable barriers dividing the ring into two chambers. In the process, the
candidate wave functions, as the insertion points become nodes, get entangled
with the barriers and can, if judiciously chosen, be distinguished with smaller
error probability. As a consequence, the Helstrom bound under idealised
conditions can be violated.


title:
Measurement of transverse energy at midrapidity in Pb-Pb collisions at
  $\sqrt{s_{\rm NN}} = 2.76$ TeV

abstract:
  We report the transverse energy ($E_{\mathrm T}$) measured with ALICE at
midrapidity in Pb-Pb collisions at ${\sqrt{s_{\mathrm {NN}}}}$ = 2.76 TeV as a
function of centrality. The transverse energy was measured using identified
single particle tracks. The measurement was cross checked using the
electromagnetic calorimeters and the transverse momentum distributions of
identified particles previously reported by ALICE. The results are compared to
theoretical models as well as to results from other experiments. The mean
$E_{\mathrm T}$ per unit pseudorapidity ($\eta$), $\langle $d$E_{\mathrm
T}/$d$\eta \rangle$, in 0-5% central collisions is 1737 $\pm$ 6(stat.) $\pm$
97(sys.) GeV. We find a similar centrality dependence of the shape of $\langle
$d$E_{\mathrm T}/$d$\eta \rangle$ as a function of the number of participating
nucleons to that seen at lower energies. The growth in $\langle $d$E_{\mathrm
T}/$d$\eta \rangle$ at the LHC ${\sqrt{s_{\mathrm {NN}}}}$ exceeds
extrapolations of low energy data. We observe a nearly linear scaling of
$\langle $d$E_{\mathrm T}/$d$\eta \rangle$ with the number of quark
participants. With the canonical assumption of a 1 fm/$c$ formation time, we
estimate that the energy density in 0-5% central Pb-Pb collisions at
${\sqrt{s_{\mathrm {NN}}}}$ = 2.76 TeV is 12.3 $\pm$ 1.0 GeV/fm$^3$\xspace and
that the energy density at the most central 80 fm$^2$ of the collision is at
least 21.5 $\pm$ 1.7 GeV/fm$^3$. This is roughly 2.3 times that observed in
0-5% central Au-Au collisions at ${\sqrt{s_{\mathrm {NN}}}}$ = 200 GeV.


title:
Unifying the flavor origin of dark matter with leptonic nonzero
  $\theta_{13}$

abstract:
  We propose a flavor symmetric approach to unify the origin of dark matter
(DM) with the non-zero $\theta_{13}$ in the lepton sector. In this framework,
breaking of a $U(1)$ flavor symmetry to a remnant $Z_2$ ensures the stability
of the DM and gives rise to a modification to the existing $A_4$-based
tri-bimaximal neutrino mixing to attain the required non-zero $\sin
\theta_{13}$. This results in a range of Higgs portal coupling of the DM which
can be potentially accessible at various ongoing and future direct and collider
search experiments.


title:
An Ensemble-Proper Orthogonal Decomposition Method for the Nonstationary
  Navier-Stokes Equations

abstract:
  The definition of partial differential equation (PDE) models usually involves
a set of parameters whose values may vary over a wide range. The solution of
even a single set of parameter values may be quite expensive. In many cases,
e.g., optimization, control, uncertainty quantification, and other settings,
solutions are needed for many sets of parameter values. We consider the case of
the time-dependent Navier-Stokes equations for which a recently developed
ensemble-based method allows for the efficient determination of the multiple
solutions corresponding to many parameter sets. The method uses the average of
the multiple solutions at any time step to define a linear set of equations
that determines the solutions at the next time step. To significantly further
reduce the costs of determining multiple solutions of the Navier-Stokes
equations, we incorporate a proper orthogonal decomposition (POD) reduced-order
model into the ensemble-based method. The stability and convergence results for
the ensemble-based method are extended to the ensemble-POD approach. Numerical
experiments are provided that illustrate the accuracy and efficiency of
computations determined using the new approach.


title: Phenomenology of the Utilitarian Supersymmetric Standard Model

abstract:
  We study the 2010 specific version of the 2002 proposed $U(1)_X$ extension of
the supersymmetric standard model, which has no $\mu$ term and conserves baryon
number and lepton number separately and automatically. We consider in detail
the scalar sector as well as the extra $Z_X$ gauge boson, and their
interactions with the necessary extra color-triplet particles of this model,
which behave as leptoquarks. We show how the diphoton excess at 750 GeV,
recently observed at the LHC, may be explained within this context. We identify
a new fermion dark-matter candidate and discuss its properties. An important
byproduct of this study is the discovery of relaxed supersymmetric constraints
on the Higgs boson's mass of 125 GeV.


title: Revisiting Batch Normalization For Practical Domain Adaptation

abstract:
  Deep neural networks (DNN) have shown unprecedented success in various
computer vision applications such as image classification and object detection.
However, it is still a common annoyance during the training phase, that one has
to prepare at least thousands of labeled images to fine-tune a network to a
specific domain. Recent study (Tommasi et al. 2015) shows that a DNN has strong
dependency towards the training dataset, and the learned features cannot be
easily transferred to a different but relevant task without fine-tuning. In
this paper, we propose a simple yet powerful remedy, called Adaptive Batch
Normalization (AdaBN) to increase the generalization ability of a DNN. By
modulating the statistics in all Batch Normalization layers across the network,
our approach achieves deep adaptation effect for domain adaptation tasks. In
contrary to other deep learning domain adaptation methods, our method does not
require additional components, and is parameter-free. It archives
state-of-the-art performance despite its surprising simplicity. Furthermore, we
demonstrate that our method is complementary with other existing methods.
Combining AdaBN with existing domain adaptation treatments may further improve
model performance.


title:
Abstractions of Varying Decentralization Degree for Coupled Multi-Agent
  Systems

abstract:
  In this report, we aim at the development of a decentralized abstraction
framework for multi-agent systems under coupled constraints, with the
possibility for a varying degree of decentralization. The methodology is based
on the analysis employed in our recent work, where decentralized abstractions
based exclusively on the information of each agent's neighbors were derived. In
the first part of this report, we define the notion each agent's m-neighbor
set, which constitutes a measure for the employed degree of decentralization.
Then, sufficient conditions are provided on the space and time discretization
that provides the abstract system's model, which guarantee the extraction of a
transition system with quantifiable transition possibilities.


title:
The Subspace Voyager: Exploring High-Dimensional Data along a Continuum
  of Salient 3D Subspaces

abstract:
  Analyzing high-dimensional data and finding hidden patterns is a difficult
problem and has attracted numerous research efforts. Automated methods can be
useful to some extent but bringing the data analyst into the loop via
interactive visual tools can help the discovery process tremendously. An
inherent problem in this effort is that humans lack the mental capacity to
truly understand spaces exceeding three spatial dimensions. To keep within this
limitation, we describe a framework that decomposes a high-dimensional data
space into a continuum of generalized 3D subspaces. Analysts can then explore
these 3D subspaces individually via the familiar trackball interface, but using
additional facilities to smoothly transition to adjacent subspaces for expanded
space comprehension. Since the number of such subspaces suffers from
combinatorial explosion, we provide a set of data-driven subspace selection and
navigation tools which can guide users to interesting subspaces and views. A
subspace trail map allows users to manage the explored subspaces, and also
helps them navigate within and across any higher-dimensional subspaces
identified by clustering. Both trackball and trail map are each embedded into a
word cloud of attribute labels, sized according to the relevance of the
associated data dimensions in the currently selected subspace. Finally, a view
gallery helps users keep their bearings and return to interesting subspaces and
views. We demonstrate our system via several use cases in a diverse set of
application areas, such as cluster analysis and refinement, information
discovery, and supervised training of classifiers.


title:
On the Kantorovich's theorem for Newton's method for solving generalized
  equations under the majorant condition

abstract:
  In this paper we consider a version of the Kantorovich's theorem for solving
the generalized equation $F(x)+T(x)\ni 0$, where $F$ is a Fr\'echet derivative
function and $T$ is a set-valued and maximal monotone acting between Hilbert
spaces. We show that this method is quadratically convergent to a solution of
$F(x)+T(x)\ni 0$. We have used the idea of majorant function, which relaxes the
Lipschitz continuity of the derivative $F'$. It allows us to obtain the optimal
convergence radius, uniqueness of solution and also to solving generalized
equations under Smale's condition.


title: Broken Detailed Balance of Filament Dynamics in Active Networks

abstract:
  Myosin motor proteins drive vigorous steady-state fluctuations in the actin
cytoskeleton of cells. Endogenous embedded semiflexible filaments such as
microtubules, or added filaments such as single-walled carbon nanotubes are
used as novel tools to non-invasively track equilibrium and non-equilibrium
fluctuations in such biopolymer networks. Here we analytically calculate shape
fluctuations of semiflexible probe filaments in a viscoelastic environment,
driven out of equilibrium by motor activity. Transverse bending fluctuations of
the probe filaments can be decomposed into dynamic normal modes. We find that
these modes no longer evolve independently under non-equilibrium driving. This
effective mode coupling results in non-zero circulatory currents in a
conformational phase space, reflecting a violation of detailed balance. We
present predictions for the characteristic frequencies associated with these
currents and investigate how the temporal signatures of motor activity
determine mode correlations, which we find to be consistent with recent
experiments on microtubules embedded in cytoskeletal networks.


title:
Radio Weak Lensing Shear Measurement in the Visibility Domain - I.
  Methodology

abstract:
  The high sensitivity of the new generation of radio telescopes such as the
Square Kilometre Array (SKA) will allow cosmological weak lensing measurements
at radio wavelengths that are competitive with optical surveys. We present an
adaptation to radio data of lensfit, a method for galaxy shape measurement
originally developed and used for optical weak lensing surveys. This likelihood
method uses an analytical galaxy model and makes a Bayesian marginalisation of
the likelihood over uninteresting parameters. It has the feature of working
directly in the visibility domain, which is the natural approach to adopt with
radio interferometer data, avoiding systematics introduced by the imaging
process. As a proof of concept, we provide results for visibility simulations
of individual galaxies with flux density S >= 10 muJy at the phase centre of
the proposed SKA1-MID baseline configuration, adopting 12 frequency channels in
the band 950 - 1190 MHz. Weak lensing shear measurements from a population of
galaxies with realistic flux and scalelength distributions are obtained after
natural gridding of the raw visibilities. Shear measurements are expected to be
affected by "noise bias": we estimate the bias in the method as a function of
signal-to-noise ratio (SNR). We obtain additive and multiplicative bias values
that are comparable to SKA1 requirements for SNR > 18 and SNR > 30,
respectively. The multiplicative bias for SNR > 10 is comparable to that found
in ground-based optical surveys such as CFHTLenS, and we anticipate that
similar shear measurement calibration strategies to those used for optical
surveys may be used to good effect in the analysis of SKA radio interferometer
data.


title: Traffic regulation via controlled speed limit

abstract:
  We study an optimal control problem for traffic regulation via variable speed
limit. The traffic flow dynamics is described with the
Lighthill-Whitham-Richards (LWR) model with Newell-Daganzo flux function. We
aim at minimizing the $L^2$ quadratic error to a desired outflow, given an
inflow on a single road. We first provide existence of a minimizer and compute
analytically the cost functional variations due to needle-like variation in the
control policy. Then, we compare three strategies: instantaneous policy; random
exploration of control space; steepest descent using numerical expression of
gradient. We show that the gradient technique is able to achieve a cost within
10% of random exploration minimum with better computational performances.


title:
Parabolic free boundary price formation models under market size
  fluctuations

abstract:
  In this paper we propose an extension of the Lasry-Lions price formation
model which includes fluctuations of the numbers of buyers and vendors. We
analyze the model in the case of deterministic and stochastic market size
fluctuations and present results on the long time asymptotic behavior and
numerical evidence and conjectures on periodic, almost periodic and stochastic
fluctuations. The numerical simulations extend the theoretical statements and
give further insights into price formation dynamics.


title: States and channels in quantum mechanics without complex numbers

abstract:
  In the presented note we aim at exploring the possibility of abandoning
complex numbers in the representation of quantum states and operations. We
demonstrate a simplified version of quantum mechanics in which the states are
represented using real numbers only. The main advantage of this approach is
that the simulation of the $n$-dimensional quantum system requires $n^2$ real
numbers, in contrast to the standard case where $n^4$ real numbers are
required. The main disadvantage is the lack of hermicity in the representation
of quantum states. Using Mathematica computer algebra system we develop a set
of functions for manipulating real-only quantum states. With the help of this
tool we study the properties of the introduced representation and the induced
representation of quantum channels.


title:
Many-to-many Correspondences between Partitions: Introducing a Cut-based
  Approach

abstract:
  Let $\mathcal{P}$ and $\mathcal{P}'$ be finite partitions of the set $V$.
Finding good correspondences between the parts of $\mathcal{P}$ and those of
$\mathcal{P}'$ is helpful in classification, pattern recognition, and network
analysis. Unlike common similarity measures for partitions that yield only a
single value, we provide specifics on how $\mathcal{P}$ and $\mathcal{P'}$
correspond to each other.
  To this end, we first define natural collections of best correspondences
under three constraints \cone, \ctwo, and \cthree. In case of \cone, the best
correspondences form a minimum cut basis of a certain bipartite graph, whereas
the other two lead to minimum cut bases of $\mathcal{P}$ \wrt $\mathcal{P}'$.
We also introduce a constraint, \cfour, which tightens \cthree; both are useful
for finding consensus partitions. We then develop branch-and-bound algorithms
for finding minimum $P_s$-$P_t$ cuts of $\mathcal{P}$ and thus $\vert
\mathcal{P} \vert -1$ best correspondences under \ctwo, \cthree, and \cfour,
respectively.
  In a case study, we use the correspondences to gain insight into a community
detection algorithm. The results suggest, among others, that only very minor
losses in the quality of the correspondences occur if the branch-and-bound
algorithm is restricted to its greedy core. Thus, even for graphs with more
than half a million nodes and hundreds of communities, we can find hundreds of
best or almost best correspondences in less than a minute.


title: Emergence of metapopulations and echo chambers in mobile agents

abstract:
  Multi-agent models often describe populations segregated either in the
physical space, i.e. subdivided in metapopulations, or in the ecology of
opinions, i.e. partitioned in echo chambers. Here we show how the interplay
between homophily and social influence controls the emergence of both kinds of
segregation in a simple model of mobile agents, endowed with a continuous
opinion variable. In the model, physical proximity determines a progressive
convergence of opinions but differing opinions result in agents moving away
from each others. This feedback between mobility and social dynamics determines
to the onset of a stable dynamical metapopulation scenario where physically
separated groups of like-minded individuals interact with each other through
the exchange of agents. The further introduction of confirmation bias in social
interactions, defined as the tendency of an individual to favor opinions that
match his own, leads to the emergence of echo chambers where different opinions
can coexist also within the same group. We believe that the model may be of
interest to researchers investigating the origin of segregation in the offline
and online world.


title:
One-loop superstring six-point amplitudes and anomalies in pure spinor
  superspace

abstract:
  We present the massless six-point one-loop amplitudes in the open and closed
superstring using BRST cohomology arguments from the pure spinor formalism. The
hexagon gauge anomaly is traced back to a class of kinematic factors in pure
spinor superspace which were recently introduced as BRST pseudo-invariants.
This complements previous work where BRST invariance arguments were used to
derive the non-anomalous part of the amplitude. The associated worldsheet
functions are non-singular and demonstrated to yield total derivatives on
moduli space upon gauge variation. These cohomology considerations yield an
efficient organizing principle for closed-string amplitudes that match
expectations from S-duality in the low-energy limit.


title: Millimeter-long Fiber Fabry-Perot cavities

abstract:
  We demonstrate fiber Fabry-Perot (FFP) cavities with concave mirrors that can
be operated at cavity lengths as large as 1.5mm without significant
deterioration of the finesse. This is achieved by using a laser dot machining
technique to shape spherical mirrors with ultralow roughness and employing
single-mode fibers with large mode area for good mode matching to the cavity.
Additionally, in contrast to previous FFPs, these cavities can be used over an
octave-spanning frequency range with adequate coatings. We also show directly
that shape deviations caused by the fiber's index profile lead to a finesse
decrease as observed in earlier attempts to build long FFP cavities, and show a
way to overcome this problem.


title:
Testing Interestingness Measures in Practice: A Large-Scale Analysis of
  Buying Patterns

abstract:
  Understanding customer buying patterns is of great interest to the retail
industry and has shown to benefit a wide variety of goals ranging from managing
stocks to implementing loyalty programs. Association rule mining is a common
technique for extracting correlations such as "people in the South of France
buy ros\'e wine" or "customers who buy pat\'e also buy salted butter and sour
bread." Unfortunately, sifting through a high number of buying patterns is not
useful in practice, because of the predominance of popular products in the top
rules. As a result, a number of "interestingness" measures (over 30) have been
proposed to rank rules. However, there is no agreement on which measures are
more appropriate for retail data. Moreover, since pattern mining algorithms
output thousands of association rules for each product, the ability for an
analyst to rely on ranking measures to identify the most interesting ones is
crucial. In this paper, we develop CAPA (Comparative Analysis of PAtterns), a
framework that provides analysts with the ability to compare the outcome of
interestingness measures applied to buying patterns in the retail industry. We
report on how we used CAPA to compare 34 measures applied to over 1,800 stores
of Intermarch\'e, one of the largest food retailers in France.


title: f(R)-Einstein-Palatini Formalism and smooth branes

abstract:
  In this work, we present the f(R)-Einstein-Palatini formalism in arbitrary
dimensions and the study of consistency applied to brane models, the so-called
braneworld sum rules. We show that it is possible a scenario of thick branes in
five dimensions with compact extra dimension in the framework of the
f(R)-Einstein-Palatini theory by the accomplishment of an assertive criteria.


title: Classification of point-group-symmetric orientational ordering tensors

abstract:
  The concept of symmetry breaking has been a propelling force in understanding
phases of matter. While rotational symmetry breaking is one of the most
prevalent examples, the rich landscape of orientational orders breaking the
rotational symmetries of isotropic space, i.e. $O(3)$, to a three-dimensional
point group remain largely unexplored, apart from simple examples such as
ferromagnetic or uniaxial nematic ordering. Here we provide an explicit
construction, utilizing a recently introduced gauge theoretical framework, to
address the three-dimensional point-group-symmetric orientational orders on a
general footing. This unified approach allows us to enlist order parameter
tensors for all three dimensional point groups. By construction, these tensor
order parameters are the minimal set of simplest tensors allowed by the
symmetries that uniquely characterize the orientational order. We explicitly
give these for the point groups $\{C_n, D_n, T, O, I\} \subset SO(3)$ and
$\{C_{nv}, S_n, C_{nh}, D_{nh}, D_{nd}, T_h, T_d, O_h, I_h\}\subset O(3)$ for
$n=\{1,2,3,4,6, \infty\}$. This central result may be perceived as a roadmap
for identifying exotic orientational orders that may become more and more in
reach in view of rapid experimental progress in e.g. nano-colloidal systems and
novel magnets.


title: A Yang-Mills field on the extremal Reissner-Nordstr\"om black hole

abstract:
  We consider a spherically symmetric (magnetic) $SU(2)$ Yang-Mills field
propagating on the exterior of the extremal Reissner-Nordstr\"om black hole.
Taking advantage of the conformal symmetry, we reduce the problem to the study
of the Yang-Mills equation in a geodesically complete spacetime with two
asymptotically flat ends. We prove the existence of infinitely many static
solutions (two of which are found in closed form) and determine the spectrum of
their linear perturbations and quasinormal modes. Finally, using the
hyperboloidal approach to the initial value problem, we describe the process of
relaxation to the static endstates of evolution for various initial data.


title: Diffraction theory and almost periodic distributions

abstract:
  We introduce and study the notions of translation bounded tempered
distributions, and autocorrelation for a tempered distrubution. We further
introduce the spaces of weakly, strongly and null weakly almost periodic
tempered distributions and show that for weakly almost periodic tempered
distributions the Eberlein decomposition holds. For translation bounded
measures all these notions coincide with the classical ones. We show that
tempered distributions with measure Fourier transform are weakly almost
periodic and that for this class, the Eberlein decomposition is exactly the
Fourier dual of the Lesbegue decomposition, with the Fourier-Bohr coefficients
specifying the pure point part of the Fourier transform. We complete the
project by looking at few interesting examples.


title: Friedmann-Robertson-Walker Braneworlds

abstract:
  We study the cosmological evolution with nonsingular branes generated by a
bulk scalar field coupled to gravity. The specific setup investigated leads to
branes with a time-dependent warp factor. We calculate the effective Hubble
parameter and the effective scale factor for the FRW branes obtained solutions.
The spatially dependent branes solutions also were found.


title:
ND-Tree-based update: a Fast Algorithm for the Dynamic Non-Dominance
  Problem

abstract:
  In this paper we propose a new method called ND-Tree-based update (or shortly
ND-Tree) for the dynamic non-dominance problem, i.e. the problem of online
update of a Pareto archive composed of mutually non-dominated points. It uses a
new ND-Tree data structure in which each node represents a subset of points
contained in a hyperrectangle defined by its local approximate ideal and nadir
points. By building subsets containing points located close in the objective
space and using basic properties of the local ideal and nadir points we can
efficiently avoid searching many branches in the tree. ND-Tree may be used in
multiobjective evolutionary algorithms and other multiobjective metaheuristics
to update an archive of potentially non-dominated points. We prove that the
proposed algorithm has sub-linear time complexity under mild assumptions. We
experimentally compare ND-Tree to the simple list, Quad-tree, and M-Front
methods using artificial and realistic benchmarks with up to 10 objectives and
show that with this new method substantial reduction of the number of point
comparisons and computational time can be obtained. Furthermore, we apply the
method to the non-dominated sorting problem showing that it is highly
competitive to some recently proposed algorithms dedicated to this problem.


title:
Constructing Landau framework for topological order: Quantum chains and
  ladders

abstract:
  We studied quantum phase transitions in the antiferromagnetic dimerized
spin-1/2 XY chain andvtwo-leg ladders. From analysis of several spin models we
present our main result: the framework to deal with topological orders and
hidden symmetries within the Landau paradigm. After mapping of the spin
Hamiltonians onto the tight-binding models with Dirac or Majorana fermions and,
when necessary, the mean-field approximation, the analysis can be done
analytically. By utilizing duality transformations the calculation of nonlocal
string order parameters is mapped onto the local order problem in some dual
representation and done without further approximations. Calculated phase
diagrams, phase boundaries, order parameters and their symmetries for each of
the phases provide a comprehensive quantitative Landau description of the
quantum critical properties of the models considered. Complementarily, the
phases with hidden orders can also be distinguished by the Pontryagin (winding)
numbers which we have calculated as well. This unified framework can be
straightforwardly applied for various spin chains and ladders, topological
insulators and superconductors. Applications to other systems are under way.


title: A Dressed Spin Qubit in Silicon

abstract:
  Coherent dressing of a quantum two-level system provides access to a new
quantum system with improved properties - a different and easily tuneable level
splitting, faster control, and longer coherence times. In our work we
investigate the properties of the dressed, donor-bound electron spin in
silicon, and probe its potential for the use as quantum bit in scalable
architectures. The two dressed spin-polariton levels constitute a quantum bit
that can be coherently driven with an oscillating magnetic field, an
oscillating electric field, by frequency modulating the driving field, or by a
simple detuning pulse. We measure coherence times of $T_{2\rho}^*=2.4$ ms and
$T_{2\rho}^{\rm Hahn}=9$ ms, one order of magnitude longer than those of the
undressed qubit. Furthermore, the use of the dressed states enables coherent
coupling of the solid-state spins to electric fields and mechanical
oscillations.


title:
Non-renormalization of the $V\bar cc$-vertices in ${\cal N}=1$
  supersymmetric theories

abstract:
  Using the Slavnov--Taylor identities we prove that the three-point ghost
vertices with a single line of the quantum gauge superfield are not
renormalized in all loops in ${\cal N}=1$ supersymmetric gauge theories. This
statement is verified by the explicit one-loop calculation made by the help of
the BRST invariant version of the higher covariant derivative regularization.
Using the restrictions to the renormalization constants which are imposed by
the non-renormalization of the considered vertices we express the exact NSVZ
$\beta$-function in terms of the anomalous dimensions of the Faddeev--Popov
ghosts and of the quantum gauge superfield. In the expression for the NSVZ
$\beta$-function obtained in this way the contributions of the Faddeev--Popov
ghosts and of the matter superfields have the same structure.


title:
The two gap transitions in Ge$_{1-x}$Sn$_x$: effect of
  non-substitutional complex defects

abstract:
  The existence of non-substitutional $\beta$-Sn defects in Ge$_{1-x}$Sn$_{x}$
was confirmed by emission channeling experiments [Decoster et al., Phys. Rev. B
81, 155204 (2010)], which established that although most Sn enters
substitutionally ($\alpha$-Sn) in the Ge lattice, a second significant fraction
corresponds to the Sn-vacancy defect complex in the split-vacancy configuration
( $\beta$-Sn ), in agreement with our previous theoretical study [Ventura et
al., Phys. Rev. B 79, 155202 (2009)]. Here, we present our electronic structure
calculation for Ge$_{1-x}$Sn$_{x}$, including substitutional $\alpha$-Sn as
well as non-substitutional $\beta$-Sn defects. To include the presence of
non-substitutional complex defects in the electronic structure calculation for
this multi-orbital alloy problem, we extended the approach for the purely
substitutional alloy by Jenkins and Dow [Jenkins and Dow, Phys. Rev. B 36, 7994
(1987)]. We employed an effective substitutional two-site cluster equivalent to
the real non-substitutional $\beta$-Sn defect, which was determined by a
Green's functions calculation. We then calculated the electronic structure of
the effective alloy purely in terms of substitutional defects, embedding the
effective substitutional clusters in the lattice. Our results describe the two
transitions of the fundamental gap of Ge$_{1-x}$Sn$_{x}$ as a function of the
total Sn-concentration: namely from an indirect to a direct gap, first, and the
metallization transition at higher $x$. They also highlight the role of
$\beta$-Sn in the reduction of the concentration range which corresponds to the
direct-gap phase of this alloy, of interest for optoelectronics applications.


title:
Reduced Wiener Chaos representation of random fields via basis
  adaptation and projection

abstract:
  A new characterization of random fields appearing in physical models is
presented that is based on their well-known Homogeneous Chaos expansions. We
take advantage of the adaptation capabilities of these expansions where the
core idea is to rotate the basis of the underlying Gaussian Hilbert space, in
order to achieve reduced functional representations that concentrate the
induced probability measure in a lower dimensional subspace. For a smooth
family of rotations along the domain of interest, the uncorrelated Gaussian
inputs are transformed into a Gaussian process, thus introducing a mesoscale
that captures intermediate characteristics of the quantity of interest.


title:
Search for violations of Lorentz invariance and $ CPT$ symmetry in $
  B^0_{(s)}$ mixing

abstract:
  Violations of $ CPT$ symmetry and Lorentz invariance are searched for by
studying interference effects in $ B^0$ mixing and in $ B^0_s$ mixing. Samples
of $ B^0\to J/\psi K^0_{\mathrm{S}}$ and $ B^0_s\to J/\psi K^+ K^-$ decays are
recorded by the LHCb detector in proton--proton collisions at centre-of-mass
energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3
fb$^{-1}$. No periodic variations of the particle-antiparticle mass differences
are found, consistent with Lorentz invariance and $ CPT$ symmetry. Results are
expressed in terms of the Standard Model Extension parameter $\Delta a_{\mu}$
with precisions of $ \mathcal{O}(10^{-15})$ and $ \mathcal{O}(10^{-14})$ GeV
for the $ B^0$ and $ B^0_s$ systems, respectively. With no assumption on
Lorentz (non-)invariance, the $ CPT$-violating parameter $z$ in the $ B^0_s$
system is measured for the first time and found to be $ \mathcal{R}e(z) =
-0.022 \pm 0.033 \pm 0.005$ and $ \mathcal{I}m(z) = 0.004 \pm 0.011\pm 0.002$,
where the first uncertainties are statistical and the second systematic.


title: The $E_8$ geometry from a Clifford perspective

abstract:
  This paper considers the geometry of $E_8$ from a Clifford point of view in
three complementary ways. Firstly, in earlier work, I had shown how to
construct the four-dimensional exceptional root systems from the 3D root
systems using Clifford techniques, by constructing them in the 4D even
subalgebra of the 3D Clifford algebra; for instance the icosahedral root system
$H_3$ gives rise to the largest (and therefore exceptional)
non-crystallographic root system $H_4$. Arnold's trinities and the McKay
correspondence then hint that there might be an indirect connection between the
icosahedron and $E_8$. Secondly, in a related construction, I have now made
this connection explicit for the first time: in the 8D Clifford algebra of 3D
space the $120$ elements of the icosahedral group $H_3$ are doubly covered by
$240$ 8-component objects, which endowed with a `reduced inner product' are
exactly the $E_8$ root system. It was previously known that $E_8$ splits into
$H_4$-invariant subspaces, and we discuss the folding construction relating the
two pictures. This folding is a partial version of the one used for the
construction of the Coxeter plane, so thirdly we discuss the geometry of the
Coxeter plane in a Clifford algebra framework. We advocate the complete
factorisation of the Coxeter versor in the Clifford algebra into exponentials
of bivectors describing rotations in orthogonal planes with the rotation angle
giving the correct exponents, which gives much more geometric insight than the
usual approach of complexification and search for complex eigenvalues. In
particular, we explicitly find these factorisations for the 2D, 3D and 4D root
systems, $D_6$ as well as $E_8$, whose Coxeter versor factorises as
$W=\exp(\frac{\pi}{30}B_C)\exp(\frac{11\pi}{30}B_2)\exp(\frac{7\pi}{30}B_3)\exp(\frac{13\pi}{30}B_4)$.

categories: math.RT hep-th math-ph math.GR math.MP math.QA


title: Berry Phase Transition in Twisted Bilayer Graphene

abstract:
  The electronic dispersion of a graphene bilayer is highly dependent on
rotational mismatch between layers and can be further manipulated by electrical
gating. This allows for an unprecedented control over electronic properties and
opens up the possibility of flexible band structure engineering. Here we
present novel magnetotransport data in a twisted bilayer, crossing the
energetic border between decoupled monolayers and coupled bilayer. In addition
a transition in Berry phase between pi and 2pi is observed at intermediate
magnetic fields. Analysis of Fermi velocities and gate induced charge carrier
densities suggests an important role of strong layer asymmetry for the observed
phenomena.


title:
Persistent currents, deformation and collectivity in the many-boson
  yrast problem on the circle

abstract:
  Properties of the yrast states of a system of $N$ bosons confined to a
one-dimensional ring and interacting via contact forces is examined both
variationally and by numerical diagonalizations. The latter allow for obtaining
numerical correlated many-body wave functions explicitly. The study of
correlation functions involving different yrast states indicates that a quantum
phase transition previously detected in the properties of the ground state in
the case of attractive two-body interactions is an yrast phenomenon involving
the onset of `deformation', in the sense given to this term by Bohr and
Mottelson in connection with the description of nuclear spectra, including
enhanced transition operators and emergence of a shared intrinsic correlation
structure. In this case the moment of inertia of the deformed state is
essentially the rigid moment of inertia, `intrinsic' states being essentially
degenerate.


title: Effective cones of cycles on blow-ups of projective space

abstract:
  In this paper, we study the cones of higher codimension (pseudo)effective
cycles on point blow-ups of projective space. We determine bounds on the number
of points for which these cones are generated by the classes of linear cycles,
and for which these cones are finitely generated. Surprisingly, we discover
that for (very) general points, the higher codimension cones behave better than
the cones of divisors. For example, for the blow-up $X_r^n$ of $\mathbb P^n$,
$n>4$, at $r$ very general points, the cone of divisors is not finitely
generated as soon as $r> n+3$, whereas the cone of curves is generated by the
classes of lines if $r \leq 2^n$. In fact, if $X_r^n$ is a Mori Dream Space
then all the effective cones of cycles on $X_r^n$ are finitely generated.


title:
Optimal sampling recovery of mixed order Sobolev embeddings via discrete
  Littlewood-Paley type characterizations

abstract:
  In this paper we consider the $L_q$-approximation of multivariate periodic
functions $f$ with $L_p$-bounded mixed derivative (difference). The (possibly
non-linear) reconstruction algorithm is supposed to recover the function from
function values, sampled on a discrete set of $n$ sampling nodes. The general
performance is measured in terms of (non-)linear sampling widths $\varrho_n$.
We conduct a systematic analysis of Smolyak type interpolation algorithms in
the framework of Besov-Lizorkin-Triebel spaces of dominating mixed smoothness
based on specifically tailored discrete Littlewood-Paley type
characterizations. As a consequence, we provide sharp upper bounds for the
asymptotic order of the (non-)linear sampling widths in various situations and
close some gaps in the existing literature. For example, in case $2\leq
p<q<\infty$ and $r>1/p$ the linear sampling widths
$\varrho_n^{\text{lin}}(S^r_pW(\mathbb{T}^d),L_q(\mathbb{T}^d))$ and
$\varrho^{\text{lin}}_n(S^r_{p,\infty}B(\mathbb{T}^d),L_q(\mathbb{T}^d))$ show
the asymptotic behavior of the corresponding Gelfand $n$-widths, whereas in
case $1 < p < q \leq 2$ and $r>1/p$ the linear sampling widths match the
corresponding linear widths. In the mentioned cases linear Smolyak
interpolation based on univariate classical trigonometric interpolation turns
out to be optimal.