title: Tail Risk Premia for Long-Term Equity Investors

abstract:
  We use the P&L on a particular class of swaps, representing variance and
higher moments for log returns, as estimators in our empirical study on the
S&P500 that investigates the factors determining variance and higher-moment
risk premia. This class is the discretisation invariant sub-class of swaps with
Neuberger's aggregating characteristics. Besides the market excess return,
momentum is the dominant driver for both skewness and kurtosis risk premia,
which exhibit a highly significant negative correlation. By contrast, the
variance risk premium responds positively to size and negatively to growth, and
the correlation between variance and tail risk premia is relatively low
compared with previous research, particularly at high sampling frequencies.
These findings extend prior research on determinants of these risk premia.
Furthermore, our meticulous data-construction methodology avoids unwanted
artefacts which distort results.


title:
One-dimensional two-orbital SU(N) ultracold fermionic quantum gases at
  incommensurate filling: a low-energy approach

abstract:
  We investigate the zero-temperature phase diagram of two-orbital SU(N)
fermionic models at incommensurate filling which are directly relevant to
strontium and ytterbium ultracold atoms loading into a one-dimensional optical
lattice. Using a low-energy approach that takes into account explicitly the
SU(N) symmetry, we find that a spectral gap for the nuclear-spin degrees of
freedom is formed for generic interactions. Several phases with one or two
gapless modes are then stabilized which describe the competition between
different density instabilities. In stark contrast to the N=2 case, no dominant
pairing instabilities emerge and the leading superfluid one is rather formed
from bound states of 2N fermions.


title: VIP 2: Experimental tests of the Pauli Exclusion Principle for electrons

abstract:
  The Pauli Exclusion Principle (PEP) was famously discovered in 1925 by the
austrian physicist Wolfgang Pauli. Since then, it underwent several
experimental tests. Starting in 2006, the VIP (Violation of the Pauli
Principle) experiment looked for 2p to 1s X-ray transitions in copper, where 2
electrons are present in the 1s state before the transition happens. These
transitions violate the PEP, and the lack of detection of the corresponding
X-ray photons lead to a preliminary upper limit for the violation of the PEP of
4.7 * 10^(-29). The follow-up experiment VIP 2 is currently in the testing
phase and will be transported to its final destination, the underground
laboratory of Gran Sasso in Italy, in autumn 2015. Several improvements
compared to its predecessor like the use of new X-ray detectors and active
shielding from background gives rise to a goal for the improvement of the upper
limit of the probability for the violation of the Pauli Exclusion Principle of
2 orders of magnitude.


title:
The perimeter generating functions of three-choice, imperfect, and
  1-punctured staircase polygons

abstract:
  We consider the isotropic perimeter generating functions of three-choice,
imperfect, and 1-punctured staircase polygons, whose 8th order linear Fuchsian
ODEs are previously known. We derive simple relationships between the three
generating functions, and show that all three generating functions are joint
solutions of a common 12th order Fuchsian linear ODE. We find that the 8th
order differential operators can each be rewritten as a direct sum of a direct
product, with operators no larger than 3rd order. We give closed-form
expressions for all the solutions of these operators in terms of $_2F_1$
hypergeometric functions with rational and algebraic arguments. The solutions
of these linear differential operators can in fact be expressed in terms of two
modular forms, since these $_2F_1$ hypergeometric functions can be expressed
with two, rational or algebraic, pullbacks.


title:
Non-Gaussian semi-stable laws arising in sampling of finite point
  processes

abstract:
  A finite point process is characterized by the distribution of the number of
points (the size) of the process. In some applications, for example, in the
context of packet flows in modern communication networks, it is of interest to
infer this size distribution from the observed sizes of sampled point
processes, that is, processes obtained by sampling independently the points of
i.i.d. realizations of the original point process. A standard nonparametric
estimator of the size distribution has already been suggested in the
literature, and has been shown to be asymptotically normal under suitable but
restrictive assumptions. When these assumptions are not satisfied, it is shown
here that the estimator can be attracted to a semi-stable law. The assumptions
are discussed in the case of several concrete examples. A major theoretical
contribution of this work are new and quite general sufficient conditions for a
sequence of i.i.d. random variables to be attracted to a semi-stable law.


title:
A compact, integrated silicon device for the generation of
  spectrally-filtered, pair-correlated photons

abstract:
  The third-order non-linearity of silicon gives rise to a spontaneous
four-wave mixing process in which correlated photon pairs are generated.
Sources based on this effect can be used for quantum computation and
cryptography, and can in principle be integrated with standard CMOS fabrication
technology and components. However, one of the major challenges is the on-chip
demultiplexing of the photons, and in particular the filtering of the pump
power, which is many orders of magnitude larger than that of the signal and
idler photons. Here, we propose a photonic crystal coupled-cavity system
designed so that the coupling of the pump mode to the output channel is
strictly zero due to symmetry. We further analyze this effect in presence of
fabrication disorder and find that, even then, a pump suppression of close to
40 dB can be achieved in state-of-the art systems. Due to the small mode
volumes and high quality factors, our system is also expected to have a
generation efficiency much higher than in standard micro-ring systems. Those
two considerations make a strong case for the integration of our proposed
design in future on-chip quantum technologies.


title:
Multiple particle-hole pair creation in the Fermi-Hubbard model by a
  pump laser

abstract:
  We study the Fermi-Hubbard model in the strongly correlated Mott phase under
the influence of a harmonically oscillating electric field, e.g., a pump laser.
In the Peierls representation, this pump field can be represented as an
oscillating phase of the hopping rate $J(t)$, such that the effective
time-averaged rate $\bar J$ is reduced, i.e., switching the pump laser suddenly
is analogous to a quantum quench. Apart from this time-averaged rate $\bar J$,
it is well known that the oscillating component of $J(t)$ can resonantly create
particle-hole pairs if the pump frequency $\omega_{\rm pump}$ equals (or a
little exceeds) the Mott gap. In addition, we find that it is possible to
create multiple pairs if $\omega_{\rm pump}$ is near an integer multiple of the
gap. These findings should be relevant for pump-probe experiments.


title:
On Dirichlet problem for fractional $p$-Laplacian with singular
  nonlinearity

abstract:
  In this article, we study the following fractional $p$-Laplacian equation
with critical growth singular nonlinearity \begin{equation*}
  \quad (-\De_{p})^s u = \la u^{-q} + u^{\alpha}, u>0 \; \text{in}\; \Om,\quad
u = 0 \; \mbox{in}\; \mb R^n \setminus\Om. \end{equation*} where $\Om$ is a
bounded domain in $\mb{R}^n$ with smooth boundary $\partial \Om$, $n > sp, s
\in (0,1), \la >0, 0 < q \leq 1 $ and $\alpha\le p^*_s-1$. We use variational
methods to show the existence and multiplicity of positive solutions of above
problem with respect to parameter $\la$.


title:
Effect of dimensionality on sliding charge density waves. The case of
  the quasi-two dimensional TbTe$_3$ system probed by coherent x-ray
  diffraction

abstract:
  We report on sliding Charge Density Wave (CDW) in the quasi two-dimensional
TbTe$_3$ system probed by coherent x-ray diffraction combined with {\it
in-situ} transport measurements. We show that the non-Ohmic conductivity in
TbTe$_3$ is made possible thanks to a strong distortion of the CDW. Our
diffraction experiment versus current shows first that the CDW remains
undeformed below the threshold current I$_S$ and then suddenly rotates and
reorders by motion above threshold. Contrary to quasi-one dimensional systems,
the CDW in TbTe$_3$ does not display any phase shifts below I$_S$ and tolerates
only slow spatial variations of the phase above. This is a first observation of
CDW behavior in the bulk in a quasi-two dimensional system allowing collective
transport of charges at room temperature.


title: Robustness of the far-field response of nonlocal plasmonic ensembles

abstract:
  Contrary to classical predictions, the optical response of few-nm plasmonic
particles depends on particle size due to effects such as nonlocality and
electron spill-out. Ensembles of such nanoparticles (NPs) are therefore
expected to exhibit a nonclassical inhomogeneous spectral broadening due to
size distribution. For a normal distribution of free-electron NPs, and within
the simple nonlocal Hydrodynamic Drude Model (HDM), both the nonlocal blueshift
and the plasmon linewidth are shown to be considerably affected by ensemble
averaging. Size-variance effects tend however to conceal nonlocality to a
lesser extent when the homogeneous size-dependent broadening of individual NPs
is taken into account, either through a local size-dependent damping (SDD)
model or through the Generalized Nonlocal Optical Response (GNOR) theory. The
role of ensemble averaging is further explored in realistic distributions of
noble-metal NPs, as encountered in experiments, while an analytical expression
to evaluate the importance of inhomogeneous broadening through measurable
quantities is developed. Our findings are independent of the specific
nonclassical theory used, thus providing important insight into a large range
of experiments on nanoscale and quantum plasmonics.


title:
Converse Bounds for Noisy Group Testing with Arbitrary Measurement
  Matrices

abstract:
  We consider the group testing problem, in which one seeks to identify a
subset of defective items within a larger set of items based on a number of
noisy tests. While matching achievability and converse bounds are known in
several cases of interest for i.i.d.~measurement matrices, less is known
regarding converse bounds for arbitrary measurement matrices. We address this
by presenting two converse bounds for arbitrary matrices and general noise
models. First, we provide a strong converse bound ($\mathbb{P}[\mathrm{error}]
\to 1$) that matches existing achievability bounds in several cases of
interest. Second, we provide a weak converse bound ($\mathbb{P}[\mathrm{error}]
\not\to 0$) that matches existing achievability bounds in greater generality.


title: Jamming vs. Caging in Three Dimensional Jamming Percolation

abstract:
  We investigate a three-dimensional kinetically-constrained model that
exhibits two types of phase transitions at different densities. At the jamming
density $ \rho_J $ there is a mixed-order phase transition in which a finite
fraction of the particles become frozen, but the other particles may still
diffuse throughout the system. At the caging density $ \rho_C > \rho_J $, the
mobile particles are trapped in finite cages and no longer diffuse. The caging
transition occurs due to a percolation transition of the unfrozen sites, and we
numerically find that it is a continuous transition with the same critical
exponents as random percolation.


title: Partial Recovery Bounds for the Sparse Stochastic Block Model

abstract:
  In this paper, we study the information-theoretic limits of community
detection in the symmetric two-community stochastic block model, with
intra-community and inter-community edge probabilities $\frac{a}{n}$ and
$\frac{b}{n}$ respectively. We consider the sparse setting, in which $a$ and
$b$ do not scale with $n$, and provide upper and lower bounds on the proportion
of community labels recovered on average. We provide a numerical example for
which the bounds are near-matching for moderate values of $a - b$, and matching
in the limit as $a-b$ grows large.


title:
On Properties of the Support of Capacity-Achieving Distributions for
  Additive Noise Channel Models with Input Cost Constraints

abstract:
  We study the classical problem of characterizing the channel capacity and its
achieving distribution in a generic fashion. We derive a simple relation
between three parameters: the input-output function, the input cost function
and the noise probability density function, one which dictates the type of the
optimal input. In Layman terms we prove that the support of the optimal input
is bounded whenever the cost grows faster than a cut-off rate equal to the
logarithm of the noise PDF evaluated at the input-output function. Furthermore,
we prove a converse statement that says whenever the cost grows slower than the
cut-off rate, the optimal input has necessarily an unbounded support. In
addition, we show how the discreteness of the optimal input is guaranteed
whenever the triplet satisfy some analyticity properties. We argue that a
suitable cost function to be imposed on the channel input is one that grows
similarly to the cut-off rate. Our results are valid for any cost function that
is super-logarithmic. They summarize a large number of previous channel
capacity results and give new ones for a wide range of communication channel
models, such as Gaussian mixtures, generalized-Gaussians and heavy-tailed noise
models, that we state along with numerical computations.


title: Independent component analysis for tensor-valued data

abstract:
  In preprocessing tensor-valued data, e.g. images and videos, a common
procedure is to vectorize the observations and subject the resulting vectors to
one of the many methods used for independent component analysis (ICA). However,
the tensor structure of the original data is lost in the vectorization and, as
a more suitable alternative, we propose the matrix- and tensor fourth order
blind identification (MFOBI and TFOBI). In these tensorial extensions of the
classic fourth order blind identification (FOBI) we assume a Kronecker
structure for the mixing and perform FOBI simultaneously on each direction of
the observed tensors. We discuss the theory and assumptions behind MFOBI and
TFOBI and provide two different algorithms and related estimates of the
unmixing matrices along with their asymptotic properties. Finally, simulations
are used to compare the method's performance with that of classical FOBI for
vectorized data and we end with a real data clustering example.


title:
Fast synthesis of Fe1.1Se1-xTex superconductors in a self-heating and
  furnace-free way

abstract:
  A fast and furnace-free method of combustion synthesis is employed for the
first time to synthesize iron-based superconductors. Using this method,
Fe1.1Se1-xTex (0<=x<=1) samples can be prepared from self-sustained reactions
of element powders in only tens of seconds. The obtained Fe1.1Se1-xTex samples
show clear zero resistivity and corresponding magnetic susceptibility drop at
around 10-14 K. The Fe1.1Se0.33Te0.67 sample shows the highest onset Tc of
about 14 K, and its upper critical field is estimated to be approximately 54 T.
Compared with conventional solid state reaction for preparing polycrystalline
FeSe samples, combustion synthesis exhibits much-reduced time and energy
consumption, but offers comparable superconducting properties. It is expected
that the combustion synthesis method is available for preparing plenty of
iron-based superconductors, and in this direction further related work is in
progress.


title: Lepton Flavor Violation in Exclusive $b\to s$ Decays

abstract:
  Starting from the general effective hamiltonian relevant to the $b\to s$
transitions, we derive the expressions for the full angular distributions of
the $B \to K^{(\ast )} \ell_1 \ell_2$ decay modes, as well as for ${\cal B}(B_s
\to \ell_1\ell_2 )$ ($\ell_1\neq \ell_2$). We point out the differences in the
treatment of the lepton flavor violating modes with respect to the lepton
flavor conserving ones. Concerning the relevant Wilson coefficients we evaluate
them in two different scenarios: (i) The (pseudo-)scalar coefficients are
obtained using the (pseudo-)scalar coupling extracted from the experimental
non-zero value of ${\cal B}(h\to \mu\tau)$, (ii) Revisiting a $Z^\prime$-model
in which the flavor changing neutral couplings are allowed. We provide the
numerical estimates of the branching fractions of the above-mentioned modes in
both scenarios.


title: Distribution of tunnelling times for quantum electron transport

abstract:
  In electron transport, the tunnelling time is the time taken for an electron
to tunnel out of a system after it has tunnelled in. We define the tunnelling
time distribution for quantum processes in a dissipative environment and
develop a practical approach for calculating it, where the environment is
described by the general Markovian master equation. We illustrate the theory by
using the rate equation to compute the tunnelling time distribution for
electron transport through a molecular junction. The tunnelling time
distribution is exponential, which indicates that Markovian quantum tunnelling
is a Poissonian statistical process. The tunnelling time distribution is used
not only to study the quantum statistics of tunnelling along the average
electric current but also to analyse extreme quantum events where an electron
jumps against the applied voltage bias. The average tunnelling time shows
distinctly different temperature dependance for p- and n-type molecular
junction and therefore provides a sensitive tool to probe the alignment of
molecular orbitals relative to the electrode Fermi energy.


title:
Distributed Scheduling in Multiple Access with Bursty Arrivals and Delay
  Constraints

abstract:
  A multiple access system with bursty data arrivals to the terminals is
considered. The users are frame-synchronized, with variable sized packets
independently arriving in each slot at every transmitter. Each packet needs to
be delivered to a common receiver within a certain number of slots specified by
a maximum delay constraint. The key assumption is that the terminals know only
their own packet arrival process, i.e. the arrivals at the rest of the
terminals are unknown to each transmitter, except for their statistics. For
this interesting distributed multiple access model, we design novel online
communication schemes which transport the arriving data without any outage,
while ensuring the delay constraint. In particular, the transmit powers in each
slot are chosen in a distributed manner, ensuring at the same time that the
joint power vector is sufficient to support the distributed choice of
data-rates employed in that slot. The proposed schemes not only are optimal for
minimizing the average transmit sum-power, but they also considerably
outperform conventional orthogonal multiple access techniques like TDMA.


title: The Physics of Protein Self-Assembly

abstract:
  Understanding protein self-assembly is important for many biological and
industrial processes. Proteins can self-assemble into crystals, filaments,
gels, and other amorphous aggregates. The final forms include virus capsids and
condensed phases associated with diseases, such as amyloid fibrils. Although
seemingly different, these assemblies all originate from fundamental protein
interactions and are driven by similar thermodynamic and kinetic factors. Here
we review recent advances in understanding protein self-assembly through a soft
condensed matter perspective with an emphasis on three specific systems:
globular proteins, viruses and amyloid fibers. We conclude with a discussion of
unanswered questions in the field.


title:
Asymptotic regimes for hadron diffractive scatterings and coulomb
  interaction. Arguments for the black disk mode

abstract:
  Comparative analysis of the interplay of hadron and Coulomb interactions in
$pp^\pm$ scattering amplitudes is performed in a broad energy interval,
$\sqrt{s}=1-10^6$ TeV, for two extreme cases: for the asymptotic interactions
of hadrons in black disk and resonant disk modes. The interactions are
discussed in terms of the $K$-matrix function technique. In the asymptotic
regime the real part of the hadronic amplitude is concentrated in both cases on
the boundary of the disks in the impact parameter space but the LHC energy
region is not asymptotic for the resonant disk mode that lead to a specific
interplay of hadronic and coulombic amplitudes. For the $pp$ scattering at
$\sqrt{s}\sim 10$ TeV an interplay of the hadron and Coulomb interactions in
the resonant disk modes is realized in a shoulder in $d\sigma_{el}/d{\bf q}^2$
at ${\bf q}^2\sim 0.0025-0.0075$ GeV$^2$. The absence of such a shoulder in the
data at 8 TeV can be considered as an argument against the resonant disk mode.


title:
Analysis of the Forward Search using some new results for martingales
  and empirical processes

abstract:
  The Forward Search is an iterative algorithm for avoiding outliers in a
regression analysis suggested by Hadi and Simonoff (J. Amer. Statist. Assoc. 88
(1993) 1264-1272), see also Atkinson and Riani (Robust Diagnostic Regression
Analysis (2000) Springer). The algorithm constructs subsets of "good"
observations so that the size of the subsets increases as the algorithm
progresses. It results in a sequence of regression estimators and forward
residuals. Outliers are detected by monitoring the sequence of forward
residuals. We show that the sequences of regression estimators and forward
residuals converge to Gaussian processes. The proof involves a new iterated
martingale inequality, a theory for a new class of weighted and marked
empirical processes, the corresponding quantile process theory, and a fixed
point argument to describe the iterative aspect of the procedure.


title: Carbon stars in the X-shooter Spectral Library

abstract:
  We provide a new collection of spectra of 35 carbon stars obtained with the
ESO/VLT X-shooter instrument as part of the X-shooter Spectral Library project.
The spectra extend from 0.3$\mu$m to 2.4$\mu$m with a resolving power above
$\sim$ 8000. The sample contains stars with a broad range of (J-K) color and
pulsation properties located in the Milky Way and the Magellanic Clouds. We
show that the distribution of spectral properties of carbon stars at a given
(J-K) color becomes bimodal (in our sample) when (J-K) is larger than about
1.5. We describe the two families of spectra that emerge, characterized by the
presence or absence of the absorption feature at 1.53$\mu$m, generally
associated with HCN and C$_2$H$_2$. This feature appears essentially only in
large-amplitude variables, though not in all observations. Associated spectral
signatures that we interpret as the result of veiling by circumstellar matter,
indicate that the 1.53$\mu$m feature might point to episodes of dust production
in carbon-rich Miras.


title:
Comment on "Broken translational and rotational symmetry via charge
  stripe order in underdoped YBa2Cu3O6+y"

abstract:
  Comin et al. [Science 347, 1335 (2015)] have interpreted their resonant X-ray
scattering experiment as indicating that charge inhomogeneities in the family
of high-temperature superconductors YBa2Cu3O6+y (YBCO) have the character of
one-dimensional stripes rather than two-dimensional checkerboards. The present
comment shows that one cannot distinguish between stripes and checkerboards on
the basis of the above experiment.


title: The local effect of Dark Energy in galaxy clusters

abstract:
  Recently, observational data and high precision mapping of the local velocity
field of Local Group and Virgo cluster have revealed a linear velocity-distance
relation of the outermost galaxies, properly referred to as Local Hubble Flow.
By means of direct N-body method, we performed several simulations in which a
galaxy cluster undergoes the action of the Dark Energy force and of the
gravitational one induced by the gas. We reproduced the so-called Hubble
diagrams, to highlight the outflow of the galaxies lying in the external region
of the cluster. Our preliminary results suggest that the observed outflow of
galaxies is likely due to the local effect of Dark Energy. Furthermore, the
accuracy of the N-body method used, allows us to follow the merging process
among some galaxies with the aim to reproduce the formation of a single compact
object in the centre of the cluster.


title: Double Froggatt--Nielsen Mechanism

abstract:
  We present a doubly parametric extension of the standard Froggatt--Nielsen
(FN) mechanism. As is well known, mass matrices of the up- and down-type quark
sectors and the charged lepton sector in the standard model can be parametrized
well by a parameter $\lambda$ which is usually taken to be the sine of the
Cabibbo angle ($\lambda = \sin\theta_\text{C} \simeq 0.225$). However, in the
neutrino sector, there is still room to realize the two neutrino mass squared
differences $\Delta m_\text{sol}^2$ and $\Delta m_\text{atm}^2$, two large
mixing angles $\theta _{12}$ and $\theta _{23}$, and non-zero $\theta _{13}$.
Then we consider an extension with an additional parameter $\rho$ in addition
to $\lambda$. Taking the relevant FN charges for a power of $\lambda~(=0.225)$
and additional FN charges for a power of $\rho$, which we assume to be less
than one, we can reproduce the ratio of the two neutrino mass squared
differences and three mixing angles. In the normal neutrino mass hierarchy, we
show several patterns for taking relevant FN charges and the magnitude of
$\rho$. We find that if $\sin \theta_{23}$ is measured more precisely, we can
distinguish each pattern. This is testable in the near future, for example in
neutrino oscillation experiments. In addition, we predict the Dirac
CP-violating phase for each pattern.


title: Edwards polaron formation : From one to three dimension

abstract:
  Employing a self-consistent (optimized) variational diagonalization scheme,
we investigate the formation of polaronic quasiparticles in a spinless
fermion-boson transport model that couples the movement of charge carriers to
fluctuations and correlations of a background medium. The background is
parameterized by bosonic degrees of freedom. The variational fermion-boson
Hilbert space is constructed to achieve high accuracy in one to three spatial
dimensions with modest computational requirements. To characterize the
ground-state properties of the Edwards model in the single-particle sector, we
present exact numerical results for the polaron band dispersion, quasiparticle
weight, Drude weight, mass enhancement, and the particle-boson correlations in
a wide parameter regime. In the Edwards model, transport will be quasifree,
diffusive or boson-assisted in the weakly fermion-boson coupled,
fluctuation-dominated or strongly correlated regimes, respectively. Thereby
correlated transport is not only assisted but also limited by the bosonic
excitations. As a result, the Drude weight remains finite even in the limit of
very small boson frequencies. For a strongly correlated background, closed
loops are important, in any dimension, to generate a finite effective particle
mass even when the free fermion has an infinite mass.


title:
The Spitzer-IRAC/MIPS Extragalactic survey (SIMES) in the South Ecliptic
  Pole field

abstract:
  We present the Spitzer-IRAC/MIPS Extragalactic survey (SIMES) in the South
Ecliptic Pole (SEP) field. The large area covered (7.7 deg$^2$), together with
one of the lowest Galactic cirrus emissions in the entire sky and a very
extensive coverage by Spitzer, Herschel, Akari, and GALEX, make the SIMES field
ideal for extragalactic studies. The elongated geometry of the SIMES area
($\approx$4:1), allowing for a significant cosmic variance reduction, further
improves the quality of statistical studies in this field. Here we present the
reduction and photometric measurements of the Spitzer/IRAC data. The survey
reaches a depth of 1.93 and 1.75 $\mu$Jy (1$\sigma$) at 3.6 and 4.5 $\mu$m,
respectively. We discuss the multiwavelength IRAC--based catalog, completed
with optical, mid-- and far--IR observations. We detect 341,000 sources with
F$_{3.6\mu m} \geq 3\sigma$. Of these, 10% have an associated 24 $\mu$m
counterpart, while 2.7% have an associated SPIRE source. We release the catalog
through the NASA/IPAC Infrared Science Archive (IRSA). Two scientific
applications of these IRAC data are presented in this paper: first we compute
integral number counts at 3.6 $\mu$m. Second, we use the [3.6]--[4.5] color
index to identify galaxy clusters at z$>$1.3. We select 27 clusters in the full
area, a result consistent with previous studies at similar depth.


title:
Determination of scattering time and of valley occupation in
  transition-metal dichalcogenides doped by field effect

abstract:
  The transition-metal dichalcogenides have attracted a lot of attention as a
possible stepping-stone toward atomically thin and flexible field-effect
transistors. One key parameter to describe the charge transport is the time
between two successive scattering events - the transport scattering time. In a
recent report, we have shown that it is possible to use density functional
theory to obtain the band structure of two-dimensional semiconductors in
presence of field effect doping. Here, we report a simple method to extract the
scattering time from the experimental conductivity and from the knowledge of
the band structure. We apply our approach to monolayers and multilayers of
MoS$_2$, MoSe$_2$, MoTe$_2$, WS$_2$, and WSe$_2$ in presence of a gate. In
WS$_2$, for which accurate measurements of mobility have been published, we
find that the scattering time is inversely proportional to the density of
states at the Fermi level. Finally, we show that it is possible to identify the
critical doping at which different valleys start to be occupied from the
doping-dependence of the conductivity.


title:
Time-resolved spin-torque switching in MgO-based perpendicularly
  magnetized tunnel junctions

abstract:
  We study ns scale spin-torque-induced switching in perpendicularly magnetized
tunnel junctions (pMTJ). Although the switching voltages match with the
macrospin instability threshold, the electrical signatures of the reversal
indicate the presence of domain walls in junctions of various sizes. In the
antiparallel (AP) to parallel (P) switching, a nucleation phase is followed by
an irreversible flow of a wall through the sample at an average velocity of 40
m/s with back and forth oscillation movements indicating a Walker propagation
regime. A model with a single-wall locally responding to the spin-torque
reproduces the essential dynamical signatures of the reversal. The P to AP
transition has a complex dynamics with dynamical back-hopping whose probability
increases with voltage. We attribute this back-hopping to the instability of
the nominally fixed layers.


title:
BANZKP: a Secure Authentication Scheme Using Zero Knowledge Proof for
  WBANs

abstract:
  -Wireless body area network(WBAN) has shown great potential in improving
healthcare quality not only for patients but also for medical staff. However,
security and privacy are still an important issue in WBANs especially in
multi-hop architectures. In this paper, we propose and present the design and
the evaluation of a secure lightweight and energy efficient authentication
scheme BANZKP based on an efficient cryptographic protocol, Zero Knowledge
Proof (ZKP) and a commitment scheme. ZKP is used to confirm the identify of the
sensor nodes, with small computational requirement, which is favorable for body
sensors given their limited resources, while the commitment scheme is used to
deal with replay attacks and hence the injection attacks by committing a
message and revealing the key later. Our scheme reduces the memory requirement
by 56.13 % compared to TinyZKP [13], the comparable alternative so far for Body
Area Networks, and uses 10 % less energy.


title: Wetting hysteresis induced by nanodefects

abstract:
  Wetting of actual surfaces involves diverse hysteretic phenomena stemming
from ever-present imperfections. Here we clarify the origin of wetting
hysteresis for a liquid front advancing or receding across an isolated defect
of nanometric size. Various kinds of chemical and topographical nanodefects are
investigated which represent salient features of actual heterogeneous surfaces.
The most probable wetting path across surface heterogeneities is identified by
combining, within an innovative approach, microscopic classical density
functional theory and the string method devised for the study of rare events.
The computed rugged free energy landscape demonstrates that hysteresis emerges
as a consequence of metastable pinning of the liquid front at the defects; the
barriers for thermally activated defect crossing, the pinning force, and
hysteresis are quantified and related to the geometry and chemistry of the
defects allowing for the occurrence of nanoscopic effects. The main result of
our calculations is that even weak nanoscale defects, which are difficult to
characterize in generic microfluidic experiments, can be the source of a
plethora of hysteretical phenomena, including the pinning of nanobubbles.


title: Reflected brownian motion: selection, approximation and linearization

abstract:
  We construct a family of SDEs whose solutions select a reflected Brownian
flow as well as a stochastic damped transport process (W\_t). The latter gives
a representation for the solutions to the heat equation for differential
1-forms with the absolute boundary conditions; it evolves pathwise by the Ricci
curvature in the interior, by the shape operator on the boundary and driven by
the boundary local time, and has its normal part erased on the boundary. On the
half line this construction selects the Skorohod solution (and its derivative
with respect to initial points), not the Tanaka solution. On the half space
this agrees with the construction of N. Ikeda and S. Watanabe
\cite{Ikeda-Watanabe} by Poisson point processes. This leads also to an
approximation for the boundary local time in the topology of uniform
convergence; not in the semi-martingale topology, indicating the difficulty for
the convergence of solutions of a family of random ODE's, with nice
coefficients, to the solution of an equation with jumps and driven by the local
time. In addition, We note that (W\_t) is the weak derivative of a family of
reflected Brownian motions with respect to the starting point.


title:
Application of photon detectors in the VIP2 experiment to test the Pauli
  Exclusion Principle

abstract:
  The Pauli Exclusion Principle (PEP) was introduced by the austrian physicist
Wolfgang Pauli in 1925. Since then, several experiments have checked its
validity. From 2006 until 2010, the VIP (VIolation of the Pauli Principle)
experiment took data at the LNGS underground laboratory to test the PEP. This
experiment looked for electronic 2p to 1s transitions in copper, where 2
electrons are in the 1s state before the transition happens. These transitions
violate the PEP. The lack of detection of X-ray photons coming from these
transitions resulted in a preliminary upper limit for the violation of the PEP
of $4.7 \times 10^{-29}$. Currently, the successor experiment VIP2 is under
preparation. The main improvements are, on one side, the use of Silicon Drift
Detectors (SDDs) as X-ray photon detectors. On the other side an active
shielding is implemented, which consists of plastic scintillator bars read by
Silicon Photomultipliers (SiPMs). The employment of these detectors will
improve the upper limit for the violation of the PEP by around 2 orders of
magnitude.


title:
Smooth solutions to discounted reward control problems with unbounded
  discount rate and financial applications

abstract:
  We consider a discounted reward control problem in continuous time stochastic
environment where the discount rate might be an unbounded function of the
control process. We provide a set of general assumptions to ensure that there
exists a smooth classical solution to the corresponding HJB equation. Moreover,
some verification reasoning are provided and the possible extension to dynamic
games is discussed. At the end of the paper consumption - investment problems
arising in financial economics are considered.


title: Scaling for speed on the water

abstract:
  Dimensional analysis combined with limited experimental data for the
performance of fully submerged propellers have been available since the 1950s.
I present two new scale-free hydrodynamic predictions for the relative
performance of both submerged and surface-piercing propellers. Larger p/D
(pitch to diameter ratio) are more favorable for peak peopeller efficiency and
higher speeds; lower p/D are more favorable for carrying loads at low speeds.
This conflicts with the common advice to swing as large a diameter as slowly as
possible but diameter D has dimensions while p/D is dimensionless, and useful
hydrodynamic recommendations must be given in terms of dimensionless variables.
For the surface piercing case I compare my scaling predictions with empirical
data using a single case in each class as a baseline. One scaling law allows
propeller diameter to be predicted from an established baseline where shaft hp
and shaft RPM are the variables. The second prediction is inferred from Froude
nr. scaling and allows boat speed to be predicted based on shaft horsepower
(shp) and weight, given a known baseline in the same class of drag coefficient.
I also discuss the existing available data on surface piercing propellers and
compare the data with both typical competition data and speed records. In the
context of the p/D ratio I discuss the limits on both too high and too low gear
ratios. I state for the first time a basic requirement for setting the leading
edge camber of surface piercing propellers for optimal acceleration and top
speed. I end by using the basic hydrodynamic ideas of circulation conservation
and vortex stretching to provide a qualitative picture via the tip vortices of
the physics of blade ventilation in surface piercing.


title:
A valuative criterion for uniform K-stability of $\mathbb{Q}$-Fano
  varieties

abstract:
  We give a simple necessary and sufficient condition for uniform K-stability
of $\mathbb{Q}$-Fano varieties.


title:
Asteroseismic determination of fundamental parameters of sun-like stars
  using multi-layered neural networks

abstract:
  The advent of space-based observatories such as CoRoT and Kepler has enabled
the testing of our understanding of stellar evolution on thousands of stars.
Evolutionary models typically require five input parameters, the mass, initial
Helium abundance, initial metallicity, mixing- length (assumed to be constant
over time), and the age to which the star must be evolved. Some of these
parameters are also very useful in characterizing the associated planets and in
studying galactic archaeology. How to obtain these parameters from observations
rapidly and accurately, specifically in the context of surveys of thousands of
stars, is an outstanding ques- tion, one that has eluded straightforward
resolution. For a given star, we typically measure the effective temperature
and surface metallicity spectroscopically and low-degree oscillation
frequencies through space observatories. Here we demonstrate that statistical
learning, using artificial neural networks, is successful in determining the
evolutionary parameters based on spectroscopic and seismic measurements. Our
trained networks show robustness over a broad range of parameter space, and
critically, are entirely computationally inexpensive and fully automated. We
analyze the observations of a few stars using this method and the results com-
pare well to inferences obtained using other techniques. This method is both
computationally cheap and inferentially accurate, paving the way for analyzing
the vast quantities of stellar observations from past, current, and future
missions.


title: Superconducting Phase Domains for Memory Applications

abstract:
  In this work we study theoretically the properties of S-F/N-sIS type
Josephson junctions in the frame of the quasiclassical Usadel formalism. The
structure consists of two superconducting electrodes (S), a tunnel barrier (I),
a combined normal metal/ferromagnet (N/F) interlayer and a thin superconducting
film (s). We demonstrate the breakdown of a spatial uniformity of the
superconducting order in the s-film and its decomposition into domains with a
phase shift $\pi $ . The effect is sensitive to the thickness of the s layer
and the widths of the F and N films in the direction along the sIS interface.
We predict the existence of a regime where the structure has two energy minima
and can be switched between them by an electric current injected laterally into
the structure. The state of the system can be non-destructively read by an
electric current flowing across the junction.


title:
Comparative evaluation of state-of-the-art algorithms for SSVEP-based
  BCIs

abstract:
  Brain-computer interfaces (BCIs) have been gaining momentum in making
human-computer interaction more natural, especially for people with
neuro-muscular disabilities. Among the existing solutions the systems relying
on electroencephalograms (EEG) occupy the most prominent place due to their
non-invasiveness. However, the process of translating EEG signals into computer
commands is far from trivial, since it requires the optimization of many
different parameters that need to be tuned jointly. In this report, we focus on
the category of EEG-based BCIs that rely on Steady-State-Visual-Evoked
Potentials (SSVEPs) and perform a comparative evaluation of the most promising
algorithms existing in the literature. More specifically, we define a set of
algorithms for each of the various different parameters composing a BCI system
(i.e. filtering, artifact removal, feature extraction, feature selection and
classification) and study each parameter independently by keeping all other
parameters fixed. The results obtained from this evaluation process are
provided together with a dataset consisting of the 256-channel, EEG signals of
11 subjects, as well as a processing toolbox for reproducing the results and
supporting further experimentation. In this way, we manage to make available
for the community a state-of-the-art baseline for SSVEP-based BCIs that can be
used as a basis for introducing novel methods and approaches.


title: Fe3O4(110)-(1x3) Revisited: Periodic (111) Nano-Facets

abstract:
  The structure of the Fe3O4(110)-(1x3) surface was studied with scanning
tunneling microscopy (STM), low-energy electron diffraction (LEED), and
reflection high energy electron diffraction (RHEED). The so-called
one-dimensional reconstruction is characterised by bright rows that extend
hundreds of nanometers in the [1-10] direction and have a periodicity of 2.52
nm in [001] in STM. It is concluded that this reconstruction is the result of a
periodic faceting to expose {111}-type planes with a lower surface energy.


title:
Learning by replicator and best-response: the importance of being
  indifferent

abstract:
  This paper compares two learning processes, namely those generated by
replicator and best-response dynamics, from the point of view of the
asymptotics of play. We base our study on the intersection of the basins of
attraction of locally stable pure Nash equilibria for replicator and
best-response dynamics. Local stability implies that the basin of attraction
has positive measure but there are examples where the intersection of the basin
of attraction for replicator and best-response dynamics is arbitrarily small.
We provide conditions, involving the existence of an unstable interior Nash
equilibrium, for the basins of attraction of any locally stable pure Nash
equilibrium under replicator and best-response dynamics to intersect in a set
of positive measure. Hence, for any choice of initial conditions in sets of
positive measure, if a pure Nash equilibrium is locally stable, the outcome of
learning under either procedure coincides. We provide examples illustrating the
above, including some for which the basins of attraction exactly coincide for
both learning dynamics. We explore the role that indifference sets play in the
coincidence of the basins of attraction of the stable Nash equilibria.


title: The radius of the rho meson determined from its decay constant

abstract:
  We present a unified model describing electroweak properties of the pi and
rho mesons. Using a general method of relativistic parametrization of matrix
elements of local operators, adjusted for the nondiagonal in total angular
momentum case, we calculate the rho-meson lepton-decay constant f_rho using the
same parameters of free constituent quarks that have ensured exclusively good
results for the pi meson previously. The only free parameter, characterizing
quark interactions, which include additional spin-spin contribution and hence
differ from the $\pi$-meson case, is fixed by matching the decay constant to
its experimental value. The mean square charge radius is calculated,
<r^2_rho>=(0.56+-0.04) fm^2. This result verifies, for the rho-meson case, the
conjecture of equality between electromagnetic and strong radii of hadrons
tested previously for proton, pi and K mesons.


title: Composite BPS skyrmions from an exact isospin symmetry breaking

abstract:
  We study the BPS Skyrme model with potentials breaking the isospin symmetry
and analyse how properties of exact solitonic solutions depend on a form of the
isospin breaking potential. In the case of the strong symmetry breaking a new
topologic structure is observed which enables us to decompose a BPS skyrmion
into a lower dimensional defect localised on a brane (kink). We investigate
some thermodynamical properties of such solitons as well as the role of the
symmetry breaking potential in the resulting mean-field equation of state.


title:
Rydberg systems in parallel electric and magnetic fields: an improved
  method for finding exceptional points

abstract:
  Exceptional points are special parameter points in spectra of open quantum
systems, at which resonance energies degenerate and the associated eigenvectors
coalesce. Typical examples are Rydberg systems in parallel electric and
magnetic fields, for which we solve the Schr\"odinger equation in a complete
basis to calculate the resonances and eigenvectors. Starting from an avoided
crossing within the parameter-dependent spectra and using a two-dimensional
matrix model, we develop an iterative algorithm to calculate the field
strengths and resonance energies of exceptional points and to verify their
basic properties. Additionally, we are able to visualise the wave functions of
the degenerate states. We report the existence of various exceptional points.
For the hydrogen atom these points are in an experimentally inaccessible regime
of field strengths. However, excitons in cuprous oxide in parallel electric and
magnetic fields, i. e., the corresponding hydrogen analogue in a solid state
body, provide a suitable system, where the high-field regime can be reached at
much smaller external fields and for which we propose an experiment to detect
exceptional points.

categories: quant-ph cond-mat.mes-hall nlin.CD physics.atom-ph


title:
5G Waveforms for Overlay D2D Communications: Effects of Time-Frequency
  Misalignment

abstract:
  This paper analyses a scenario where a Device-To-Device (D2D) pair coexists
with an Orthogonal Frequency Division Multiplexing (OFDM) based incumbent
network. D2D transmitter communicates in parts of spectrum left free by
cellular users, while respecting a given spectral mask. The D2D pair is
misaligned in time and frequency with the cellular users. Furthermore, the D2D
pair utilizes alternative waveforms to OFDM proposed for 5G. In this study, we
show that it is not worth synchronising the D2D pair in time with respect to
the cellular users. Indeed, the interference injected into the incumbent
network has small variations with respect to time misalignment. We provide
interference tables that encompass both time and frequency misalignment. We use
them to analyse the maximum rate achievable by the D2D pair when it uses
different waveforms. Then, we present numerical results showing what waveform
should be utilized by the D2D pair according to the time-frequency resources
that are not used by the incumbent network. Our results show that the delay
induced by linearly convolved waveforms make them hardly applicable to short
time windows, but that they dominate OFDM for long transmissions, mainly in the
case where cellular users are very sensitive to interference.


title:
Carrier-impurity spin transfer dynamics in paramagnetic II-VI diluted
  magnetic semiconductors in the presence of a wave-vector-dependent magnetic
  field

abstract:
  Quantum kinetic equations of motion for carrier and impurity spins in
paramagnetic II-VI diluted magnetic semiconductors in a $\mathbf{k}$-dependent
effective magnetic field are derived, where the carrier-impurity correlations
are taken into account. In the Markov limit, rates for the electron-impurity
spin transfer can be derived for electron spins parallel and perpendicular to
the impurity spins corresponding to measurable decay rates in Kerr experiments
in Faraday and Voigt geometry. Our rigorous microscopic quantum kinetic
treatment automatically accounts for the fact that, in an individual spin
flip-flop scattering process, a spin flip of an electron is necessarily
accompanied by a flop of an impurity spin in the opposite direction and the
corresponding change of the impurity Zeeman energy influences the final energy
of the electron after the scattering event. This shift in the electron energies
after a spin flip-flop scattering processes, which usually has been overlooked
in the literature, turns out to be especially important in the case of
extremely diluted magnetic semiconductors in an external magnetic field. As a
specific example for a $\mathbf{k}$-dependent effective magnetic field the
effects of a Rashba field on the dynamics of the carrier-impurity correlations
in a Hg$_{1-x-y}$Cd$_y$Mn$_x$Te quantum well are described. It is found that,
although accounting for the Rashba interaction in the dynamics of the
correlations leads to a modified $\mathbf{k}$-space dynamics, the time
evolution of the total carrier spin is not significantly influenced.
Furthermore, a connection between the present theory and the description of
collective carrier-impurity precession modes is presented.


title: From $\mu$-Calculus to Alternating Tree Automata using Parity Games

abstract:
  $\mu$-Calculus and automata on infinite trees are complementary ways of
describing infinite tree languages. The correspondence between $\mu$-Calculus
and alternating tree automaton is used to solve the satisfiability and model
checking problems by compiling the modal $\mu$-Calculus formula into an
alternating tree automata. Thus advocating an automaton model specially
tailored for working with modal $\mu$-Calculus. The advantage of the automaton
model is its ability to deal with arbitrary branching in a much simpler way as
compare to the one proposed by Janin and Walukiewicz. Both problems (i.e.,
model checking and satisfiability) are solved by reduction to the corresponding
problems of alternating tree automata, namely to the acceptance and the
non-emptiness problems, respectively. These problems, in turn, are solved using
parity games where semantics of alternating tree automata is translated to a
winning strategy in an appropriate parity game.


title: The geometry of second-order ordinary differential equations

abstract:
  These are lecture notes of the Summer school on the geometry of differential
equations held in Nordfjordeid, Norway in 1996. They cover geometric structures
related to scalar second order ODEs, the construction of the associated Cartan
connection, techniques for computing invariants of differential equations
starting from the Cartan connection, recognition of symmetric 2nd order ODEs by
their differential invariants and the constructive aspects of the local
equivalence problem.


title: Binary linear codes with at most 4 weights

abstract:
  For the past decades, linear codes with few weights have been widely studied,
since they have applications in space communications, data storage and
cryptography. In this paper, a class of binary linear codes is constructed and
their weight distribution is determined. Results show that they are at most
4-weight linear codes. Additionally, these codes can be used in secret sharing
schemes.


title: A gamma-ray spectroscopy survey of Omani meteorites

abstract:
  The gamma-ray activities of 33 meteorite samples (30 ordinary chondrites, 1
Mars meteorite, 1 iron, 1 howardite) collected during Omani-Swiss meteorite
search campaigns 2001-2008 were nondestructively measured using an ultra-low
background gamma-ray detector. The results provide several types of
information: Potassium and thorium concentrations were found to range within
typical values for the meteorite types. Similar mean 26Al activities in groups
of ordinary chondrites with a) weathering degrees W0-1 and low 14C terrestrial
age and b) weathering degree W3-4 and high 14C terrestrial age are mostly
consistent with activities observed in recent falls. The older group shows no
significant depletion in 26Al. Among the least weathered samples one meteorite
(SaU 424) was found to contain detectable 22Na identifying it as recent fall
close to the year 2000. Based on an estimate of the surface area searched, the
corresponding fall rate is ~120 events/106 km2*a, consistent with other
estimations. Twelve samples from the large JaH 091 strewn field (total mass
~4.5 t) show significant variations of 26Al activities, including the highest
values measured, consistent with a meteoroid radius of ~115 cm. Activities of
238U daughter elements demonstrate terrestrial contamination with 226Ra and
possible loss of 222Rn. Recent contamination with small amounts of 137Cs is
ubiquitous. We conclude that gamma-ray spectroscopy of a selection of
meteorites with low degrees of weathering is particularly useful to detect
recent falls among meteorites collected in hot deserts.


title:
Stress tensor for a scalar field in a spatially varying background
  potential: Divergences, "renormalization," anomalies, and Casimir forces

abstract:
  Motivated by a desire to understand quantum fluctuation energy densities and
stress within a spatially varying dielectric medium, we examine the vacuum
expectation value for the stress tensor of a scalar field with arbitrary
conformal parameter, in the background of a given potential that depends on
only one spatial coordinate. We regulate the expressions by incorporating a
temporal-spatial cutoff in the (imaginary) time and transverse-spatial
directions. The divergences are captured by the zeroth- and second-order WKB
approximations. Then the stress tensor is "renormalized" by omitting the terms
that depend on the cutoff. The ambiguities that inevitably arise in this
procedure are both duly noted and restricted by imposing certain physical
conditions; one result is that the renormalized stress tensor exhibits the
expected trace anomaly. The renormalized stress tensor exhibits no pressure
anomaly, in that the principle of virtual work is satisfied for motions in a
transverse direction. We then consider a potential that defines a wall, a
one-dimensional potential that vanishes for $z<0$ and rises like $z^\alpha$,
$\alpha>0$, for $z>0$. The full finite stress tensor is computed numerically
for the two cases where explicit solutions to the differential equation are
available, $\alpha=1$ and 2. The energy density exhibits an inverse linear
divergence as the boundary is approached from the inside for a linear
potential, and a logarithmic divergence for a quadratic potential. Finally, the
interaction between two such walls is computed, and it is shown that the
attractive Casimir pressure between the two walls also satisfies the principle
of virtual work (i.e., the pressure equals the negative derivative of the
energy with respect to the distance between the walls).


title:
HYPERgeometric functions DIfferential REduction: Mathematica-based
  packages for the differential reduction of generalizedhypergeometric
  functions: Fc hypergeometric function of three variables

abstract:
  We present a further extension of the HYPERDIRE project, which is devoted to
the creation of a set of Mathematica-based program packages for manipulations
with Horn-type hypergeometric functions on the basis of differential equations.
Specifically, we present the implementation of the differential reduction for
the Lauricella function $F_C$ of three variables.


title:
Magnetization Dynamics of Topological Defects and the Spin Solid in
  Kagome Artificial Spin Ice

abstract:
  We report broadband spin-wave spectroscopy on kagome artificial spin ice
(ASI) made of large arrays of interconnected Ni$_{80}$Fe$_{20}$ nanobars.
Spectra taken in saturated and disordered states exhibit a series of resonances
with characteristic magnetic field dependencies. Making use of micromagnetic
simulations, we identify resonances that reflect the spin-solid-state and
monopole-antimonopole pairs on Dirac strings. The latter resonances allow for
the generation of highly-charged vertices in ASIs via microwave assisted
switching. Our findings open further perspectives for fundamental studies on
ASIs and their usage in reprogrammable magnonics.


title: Computing local zeta functions of groups, algebras, and modules

abstract:
  We develop a practical method for computing local zeta functions of groups,
algebras, and modules in fortunate cases. Using our method, we obtain a
complete classification of generic local representation zeta functions
associated with unipotent algebraic groups of dimension at most six. We also
determine the generic local subalgebra zeta functions associated with
$\mathfrak{gl}_2(\mathbf{Q})$. Finally, we introduce and compute examples of
graded subobject zeta functions.


title:
Approximate and Approximate Null-Controllability of a Class of Piecewise
  Linear Markov Switch Systems

abstract:
  We propose an explicit, easily-computable algebraic criterion for approximate
null-controllability of a class of general piecewise linear switch systems with
multiplicative noise. This gives an answer to the general problem left open in
[13]. The proof relies on recent results in [4] allowing to reduce the dual
stochastic backward system to a family of ordinary differential equations.
Second, we prove by examples that the notion of approximate controllability is
strictly stronger than approximate null-controllability. A sufficient criterion
for this stronger notion is also provided. The results are illustrated on a
model derived from repressed bacterium operon (given in [19] and reduced in
[5]).


title: Double q-Analytic q-Hermite Binomial Formula and q-Traveling Waves

abstract:
  Motivated by derivation of the Dirac type delta-function for quantum states
in Fock-Bargmann representation, we find q-binomial expansion in terms of
q-Hermite polynomials, analytic in two complex arguments. Based on this
representation, we introduce a new class of complex functions of two complex
arguments, which we call the double q-analytic functions. The real version of
these functions describe the q-analogue of traveling waves, which is not
preserving the shape during evolution as the usual traveling wave. For
corresponding q-wave equation we solve IVP in the q-D'Alembert form.


title: Rainbow vertex-connection and forbidden subgraphs

abstract:
  A path in a vertex-colored graph is called \emph{vertex-rainbow} if its
internal vertices have pairwise distinct colors. A graph $G$ is \emph{rainbow
vertex-connected} if for any two distinct vertices of $G$, there is a
vertex-rainbow path connecting them. For a connected graph $G$, the
\emph{rainbow vertex-connection number} of $G$, denoted by $rvc(G)$, is defined
as the minimum number of colors that are required to make $G$ rainbow
vertex-connected. In this paper, we find all the families $\mathcal{F}$ of
connected graphs with $|\mathcal{F}|\in\{1,2\}$, for which there is a constant
$k_\mathcal{F}$ such that, for every connected $\mathcal{F}$-free graph $G$,
$rvc(G)\leq diam(G)+k_\mathcal{F}$, where $diam(G)$ is the diameter of $G$.


title: A Brief Comment on Multi-Gluon Amplitudes and Double Parton Interactions

abstract:
  A typical contribution to a color ordered multi-gluon amplitude, which can
split into two weakly correlated two-body gluon scattering amplitudes and may
thus contribute to a Double Parton Interaction, is briefly discussed. We find
that the color ordered amplitude is not enhanced in the typical configuration
generated by a DPI, where the transverse momenta of final state gluons are
compensated pairwise, while a dominant contribution to the multi-gluon
amplitude is due to terms proportional to the fusion amplitude of two initial
state gluons. Which corresponds to an amplitude effectively describing a two
rather than a three-body partonic interaction.


title:
(Quantum) Fractional Brownian Motion and Multifractal Processes under
  the Loop of a Tensor Networks

abstract:
  We derive fractional Brownian motion and stochastic processes with
multifractal properties using a framework of network of Gaussian conditional
probabilities. This leads to the derivation of new representations of
fractional Brownian motion. These constructions are inspired from
renormalization. The main result of this paper consists of constructing each
increment of the process from two-dimensional gaussian noise inside the
light-cone of each seperate increment. Not only does this allows us to derive
fractional Brownian motion, we can introduce extensions with multifractal
flavour. In another part of this paper, we discuss the use of the multi-scale
entanglement renormalization ansatz (MERA), introduced in the study critical
systems in quantum spin lattices, as a method for sampling integrals with
respect to such multifractal processes. After proper calibration, a MERA
promises the generation of a sample of size $N$ of a multifractal process in
the order of $O(N\log(N))$, an improvement over the known methods, such as the
Cholesky decomposition and the circulant methods, which scale between $O(N^2)$
and $O(N^3)$.


title:
Distribution of postcritically finite polynomials iii: Combinatorial
  continuity

abstract:
  In the first part of the present paper, we continue our study of distribution
of postcritically finite parameters in the moduli space of polynomials: we show
the equidistribution of Misiurewicz parameters with prescribed combinatorics
toward the bifurcation measure. Our results essentially rely on a combinatorial
description of the escape locus and of the bifurcation measure developped by
Kiwi and Dujardin-Favre. In the second part of the paper, we construct a
bifurcation measure for the connectedness locus of the quadratic
anti-holomorphic family which is supported by a strict subset of the boundary
of the Tricorn. We also establish an approximation property by Misiurewicz
parameters in the spirit of the previous one. Finally, we answer a question of
Kiwi, exhibiting in the moduli space of degree 4 polynomials, non-trivial
Impression of specific combinatorics.


title: Non-Markovian Dynamics in Chiral Quantum Networks with Spins and Photons

abstract:
  We study the dynamics of chiral quantum networks consisting of nodes coupled
by unidirectional or asymmetric bidirectional quantum channels. In contrast to
familiar photonic networks where driven two-level atoms exchange photons via 1D
photonic nanostructures, we propose and study a setup where interactions
between the atoms are mediated by spin excitations (magnons) in 1D $XX$ spin
chains representing spin waveguides. While Markovian quantum network theory
eliminates quantum channels as structureless reservoirs in a Born-Markov
approximation to obtain a master equation for the nodes, we are interested in
non-Markovian dynamics. This arises from the nonlinear character of the
dispersion with band-edge effects, and from finite spin propagation velocities
leading to time delays in interactions. To account for the non-Markovian
dynamics we treat the quantum degrees of freedom of the nodes and connecting
channels as a composite spin system with the surrounding of the quantum network
as a Markovian bath, allowing for an efficient solution with time-dependent
density matrix renormalization group techniques. We illustrate our approach
showing non-Markovian effects in the driven-dissipative formation of quantum
dimers, and we present examples for quantum information protocols involving
quantum state transfer with engineered elements as basic building blocks of
quantum spintronic circuits.


title: Noncommutative multi-parameter Wiener-Wintner type ergodic theorem

abstract:
  In this paper, we establish a multi-parameter version of Bellow and Losert's
Wiener-Wintner type ergodic theorem for dynamical systems not necessarily being
commutative. More precisely, we introduce a weight class $\mathcal{D}$, which
is shown to strictly include the multi-parameter bounded Besicovitch weight
class, thus including the set
$$\Lambda_d=\left\{\{\lambda^{k_1}_1\dotsm\lambda^{k_d}_d\}_{(k_1,\dots,k_d)\in
\mathbb{N}^d}:\quad (\lambda_1,\dots,\lambda_d) \in \mathbb{T}^d\right\};$$
then prove a multi-parameter Bellow and Losert's Wiener-Wintner type ergodic
theorem for the class $\mathcal{D}$ and for noncommutative trace preserving
dynamical system $(\mathcal{M},\tau,\mathbf{T})$. Restricted to consider the
set $\Lambda_d$, we also prove a noncommutative multi-parameter analogue of
Bourgain's uniform Wiener-Wintner ergodic theorem.
  The noncommutativity and the multi-parameter induce some difficulties in the
proof. For instance, our arguments in proving the uniform convergence for a
dense subset turn out to be quite different since the "pointwise" argument does
not work in the noncommutative setting; to obtain the uniform convergence in
the largest spaces, we show maximal inequality between the Orlicz spaces, which
can not be deduced easily using classical extrapolation argument. Junge and
Xu's noncommutative maximal inequalities with optimal order, together with the
atomic decomposition of Orlicz spaces, play an essential role in overcoming the
second difficulty.


title:
Spatial Continuum Extensions of Asymmetric Gaussian Channels (Multiple
  Access and Broadcast)

abstract:
  This paper proposes a new model called \emph{spatial continuum asymmetric
channels} to study the channel capacity region of asymmetric scenarios in which
either one source transmits to a spatial density of receivers or a density of
transmitters transmit to a unique receiver.This approach is built upon the
classical broadcast channel (BC) and multiple access channel (MAC). For the
sake of consistency, the study is limited to Gaussian channels with power
constraints and is restricted to the asymptotic regime (zero-error
capacity).The reference scenario comprises one base station (BS) in Tx or Rx
mode, a spatial random distribution of nodes (resp. in Rx or Tx mode)
characterized by a probability spatial density $u(x)$ and a request for a
quantity of information with no delay constraint. This system is modeled as an
$\infty-$user asymmetric channel (BC or MAC). To derive the properties of this
model, a spatial discretization is performed and the equivalence with either a
BC or MAC is established. A discretization sequence is then defined to refine
infinitely the approximation. Achievability and capacity results are obtained
in the limit of this sequence. The uniform capacity is then defined as the
maximal symmetric achievable rate at which the distributed users can
transmit/receive with no delay constraint.The capacity region is also
established as the set of information distributions that are achievable. The
tightness of these limits and their practical interest are briefly illustrated
and discussed.


title: Twisted waveguide with a Neumann window

abstract:
  This paper is concerned with the study of theexistence/non-existence of the
discrete spectrum of the Laplaceoperator on a domain of $\mathbb R ^3$ which
consists in atwisted tube. This operator is defined by means of mixed
boundaryconditions. Here we impose Neumann Boundary conditions on abounded open
subset of the boundary of the domain (the Neumannwindow) and Dirichlet boundary
conditions elsewhere.


title:
Hadamard states for the Klein-Gordon equation on Lorentzian manifolds of
  bounded geometry

abstract:
  We consider the Klein-Gordon equation on a class of Lorentzian manifolds with
Cauchy surface of bounded geometry, which is shown to include examples such as
exterior Kerr, Kerr-de Sitter and Kerr-Kruskal spacetimes. In this setup, we
give an approximate diagonalization and a microlocal decomposition of the
Cauchy evolution using a time-dependent version of the pseu-dodifferential
calculus on Riemannian manifolds of bounded geometry. We apply this result to
construct all pure regular Hadamard states (and associated Feynman inverses),
where regular refers to the state's two-point function having Cauchy data given
by pseudodifferential operators. This allows us to conclude that there is a
one-parameter family of elliptic pseudodifferential operators that encodes both
the choice of (pure, regular) Hadamard state and the underlying spacetime
metric.


title: Should employers pay their employees better? An asset pricing approach

abstract:
  We uncover a new anomaly in asset pricing that is linked to the remuneration:
the more a company spends on salaries and benefits per employee, the better its
stock performs, on average. Moreover, the companies adopting similar
remuneration policies share a common risk, which is comparable to that of the
value premium. For this purpose,we set up an original methodology that uses
firm financial characteristics to build factors that are less correlated than
in the standard asset pricing methodology. We quantify the importance of these
factors from an asset pricing perspective by introducing the factor correlation
level as a directly accessible proxy of eigenvalues of the correlation matrix.
A rational explanation of the remuneration anomaly involves the positive
correlation between pay and employee performance.


title: Addendum to Pentapods with Mobility 2

abstract:
  In a foregoing publication the authors studied pentapods with mobility 2,
where neither all platform anchor points nor all base anchor points are located
on a line. It turned out that the given classification is incomplete. This
addendum is devoted to the discussion of the missing cases resulting in
additional solutions already known to Duporcq.


title:
Disentangling Brain Graphs: A Note on the Conflation of Network and
  Connectivity Analyses

abstract:
  Understanding the human brain remains the Holy Grail in biomedical science,
and arguably in all of the sciences. Our brains represent the most complex
systems in the world (and some contend the universe) comprising nearly one
hundred billion neurons with septillions of possible connections between them.
The structure of these connections engenders an efficient hierarchical system
capable of consciousness, as well as complex thoughts, feelings, and behaviors.
Brain connectivity and network analyses have exploded over the last decade due
to their potential in helping us understand both normal and abnormal brain
function. Functional connectivity (FC) analysis examines functional
associations between time series pairs in specified brain voxels or regions.
Brain network analysis serves as a distinct subfield of connectivity analysis
in which associations are quantified for all time series pairs to create an
interconnected representation of the brain (a brain network), which allows
studying its systemic properties. While connectivity analyses underlie network
analyses, the subtle distinction between the two research areas has generally
been overlooked in the literature, with them often being referred to
synonymously. However, developing more useful analytic methods and allowing for
more precise biological interpretations requires distinguishing these two
complementary domains.


title: Hyperelliptic Continued Fractions and Generalized Jacobians

abstract:
  For a complex polynomial $D(t)$ of even degree, one may define the continued
fraction of $\sqrt{D(t)}$. This was found relevant already by Abel in 1826, and
later by Chebyshev, concerning integration of (hyperelliptic) differentials;
they realized that, contrary to the classical case of square roots of positive
integers treated by Lagrange and Galois, we do not always have pre-periodicity
of the partial quotients. In this paper we shall prove that, however, a correct
analogue of Lagrange's theorem still exists in full generality: pre-periodicity
of the {\it degrees} of the partial quotients always holds. Apparently, this
fact was never noted before. This also yields a corresponding formula for the
degrees of the convergents, for which we shall prove new bounds which are
generally best possible (halving the known ones). We shall further study other
aspects of the continued fraction, like the growth of the heights of partial
quotients. Throughout, some striking phenomena appear, related to the geometry
of (generalized) Hyperelliptic Jacobians. Another conclusion central in this
paper concerns the poles of the convergents: there can be only finitely many
rational ones which occur infinitely many times. (This is crucial for
applications to a function field version of a question of McMullen.) Our
methods rely, among other things, on linking Pad\'e approximants and
convergents with divisor relations in generalized Jacobians; this shall allow
an application of a version for algebraic groups, proved in this paper, of the
Skolem-Mahler-Lech theorem.


title: Lengths of words in transformation semigroups generated by digraphs

abstract:
  Given a simple digraph $D$ on $n$ vertices (with $n\ge2$), there is a natural
construction of a semigroup $\langle D\rangle$ associated with $D$. For any
edge $(a,b)$ of $D$, let $a\to b$ be the idempotent of defect $1$ mapping $a$
to $b$ and fixing all vertices other than $a$; then define $\langle D\rangle$
to be the semigroup $\langle a\to b:(a,b)\in E(D)\rangle$. For $\alpha \in
\langle D \rangle$, let $\ell(D,\alpha)$ be the minimal length of a word in
$E(D)$ expressing $\alpha$. When $D=K_n$ is the complete undirected graph,
Howie and Iwahori, independently, obtained a formula to calculate
$\ell(K_n,\alpha)$, for any $\alpha \in \langle K_n \rangle = \text{Sing}_n$;
however, no analogous nontrivial results are known when $D \neq K_n$. In this
paper, we characterise all simple digraphs $D$ such that either
$\ell(D,\alpha)$ is equal to Howie-Iwahori's formula for all $\alpha \in
\langle D \rangle$, or $\ell(D,\alpha) = n - \text{fix}(\alpha)$ for all
$\alpha \in \langle D \rangle$, or $\ell(D,\alpha) = n - \text{rk}(\alpha)$ for
all $\alpha \in \langle D \rangle$. When $D$ is an acyclic digraph and $\alpha
\in \langle D \rangle$, we find a tight upper bound for $\ell(D,\alpha)$.
Finally, we study the case when $D$ is a strong tournament (which corresponds
to a smallest generating set of idempotents of defect $1$ of $\text{Sing}_n$),
and we propose some conjectures.


title: Trees

abstract:
  An algebraic formalism, developped with V. Glaser and R. Stora for the study
of the generalized retarded functions of quantum field theory, is used to prove
a factorization theorem which provides a complete description of the
generalized retarded functions associated with any tree graph. Integrating over
the variables associated to internal vertices to obtain the perturbative
generalized retarded functions for interacting fields arising from such graphs
is shown to be possible for a large category of space-times.


title:
The coherent cross section of vector mesons in ultraperipheral PbPb
  collisions at the LHC

abstract:
  The coherent cross section of $J/\psi$, $\rho$, $\phi$ are computed in dipole
model in the ultraperipheral PbPb collisions, the IP-Sat and IIM model are
applied in the calculation of the differential cross section of the dipole
scattering off the nucleon, three kinds of forward vector meson wave functions
are used in the overlap. The prediction of $J/\psi$ and $\rho$ is compared with
the experimental data of the ALICE Collaboration, and the prediction of $\phi$
is also given in this paper.


title:
Spin liquid versus long range magnetic order in the frustrated
  body-centered tetragonal lattice

abstract:
  An $SU({\rm n})$-symmetric generalization of the Heisenberg model for quantum
spin $S$ operators is used to investigate the geometrically frustrated
body-centered tetragonal (BCT) lattice with antiferromagnetic interlayer
coupling $J_1$ and intralayer first and second neighbor coupling $J_2$ and
$J_3$. Using complementary representations of the spin operators, we study the
phase diagram characterizing the ground state of the system. For small n, we
find that the most stable solutions correspond to four different families of
possible long range magnetic orders that are governed by $J_1$, $J_2$, and
$J_3$. First, some possible instabilities of these phases are identified for
$n=2$ in large $S$ expansions up to the linear spin-wave corrections. Then,
using a fermionic representation of the $SU({\rm n})$ spin operators for
$S=1/2$, we find that purely magnetic orders occur for ${\rm n}\le 3$ while
spin-liquid (SL) solutions are stabilized for ${\rm n}\ge 10$. The SL solution
governed by $J_1$ breaks the lattice translation symmetry. This Modulated SL is
associated to a commensurate ordering wave vector $(1,1,1)$. For $4\le {\rm
n}\le 9$, we show how competition between $J_1$, $J_2$, and $J_3$ can tune the
ground state from beeing magnetically ordered to a SL state. We discuss the
relevance of this scenario for correlated systems with BCT crystal structure.


title:
Magnetic structures and magnetic phase transitions in the Mn-doped
  orthoferrite TbFeO$_3$ studied by neutron powder diffraction

abstract:
  The magnetic structures and the magnetic phase transitions in the Mn-doped
orthoferrite TbFeO$_3$ studied using neutron powder diffraction are reported.
Magnetic phase transitions are identified at $T^\mathrm{Fe/Mn}_N \approx$ 295~K
where a paramagnetic-to-antiferromagnetic transition occurs in the Fe/Mn
sublattice, $T^\mathrm{Fe/Mn}_{SR} \approx$ 26~K where a spin-reorientation
transition occurs in the Fe/Mn sublattice and $T^\mathrm{R}_N \approx$ 2~K
where Tb-ordering starts to manifest. At 295~K, the magnetic structure of the
Fe/Mn sublattice in TbFe$_{0.5}$Mn$_{0.5}$O$_3$ belongs to the irreducible
representation $\Gamma_4$ ($G_xA_yF_z$ or $Pb'n'm$). A mixed-domain structure
of ($\Gamma_1 + \Gamma_4$) is found at 250~K which remains stable down to the
spin re-orientation transition at $T^\mathrm{Fe/Mn}_{SR}\approx$ 26~K. Below
26~K and above 250~K, the majority phase ($> 80\%$) is that of $\Gamma_4$.
Below 10~K the high-temperature phase $\Gamma_4$ remains stable till 2~K. At
2~K, Tb develops a magnetic moment value of 0.6(2)~$\mu_\mathrm{B}/$f.u. and
orders long-range in $F_z$ compatible with the $\Gamma_4$ representation. Our
study confirms the magnetic phase transitions reported already in a single
crystal of TbFe$_{0.5}$Mn$_{0.5}$O$_3$ and, in addition, reveals the presence
of mixed magnetic domains. The ratio of these magnetic domains as a function of
temperature is estimated from Rietveld refinement of neutron diffraction data.
Indications of short-range magnetic correlations are present in the low-$Q$
region of the neutron diffraction patterns at $T < T^\mathrm{Fe/Mn}_{SR}$.
These results should motivate further experimental work devoted to measure
electric polarization and magnetocapacitance of TbFe$_{0.5}$Mn$_{0.5}$O$_3$.


title:
Interplay of quark and meson degrees of freedom in near-threshold
  states: A practical parametrisation for line shapes

abstract:
  We propose a practical parametrisation for the line shapes of near-threshold
states compatible with all requirements of unitarity and analyticity. The
coupled-channel system underlying the proposed parametrisation includes bare
poles and an arbitrary number of elastic and inelastic channels treated fully
nonperturbatively. The resulting formulae are general enough to be used for a
simultaneous analysis of the data in all available production and decay
channels of the (system of) state(s) under consideration for a quite wide class
of reactions. As an example, we fit the experimental data currently available
for several decay channels for the charged $Z_b^{(\prime)}$ states in the
spectrum of bottomonia and find a good overall description of the data. We find
the present data to be consistent with the $Z_b(10610)$ as a virtual state and
with the $Z_b(10650)$ as a resonance, both residing very close to the
$B\bar{B}^*$ and $B^*\bar{B}^*$ threshold, respectively.


title:
A new approach to the experiment intended to test the weak equivalence
  principle for the neutron

abstract:
  A new approach to the free fall experiment with UCN is proposed. The idea is
that the experiment is performed with neutrons from different equidistant lines
of a discrete energy spectrum with a precisely known distance between the
lines. Such a spectrum may be formed by neutron diffraction from a moving phase
grating. Time-of-flight values of neutrons from different lines of the spectrum
must be measured. Neither the initial neutron energy, nor the geometry
parameters of the installation are required to be known in this method.


title:
Criteria for the Finiteness of the Strong $p$-Variation for L\'evy-type
  Processes

abstract:
  Using generalized Blumenthal--Getoor indices, we obtain criteria for the
finiteness of the $p$-variation of L\'evy-type processes. This class of
stochastic processes includes solutions of Skorokhod-type stochastic
differential equations (SDEs), certain Feller processes and solutions of L\'evy
driven SDEs. The class of processes is wider than in earlier contributions and
using fine continuity we are able to handle general measurable subsets of $R^d$
as state spaces. Furthermore, in contrast to previous contributions on the
subject, we introduce a local index in order to complement the upper index.
This local index yields a sufficient condition for the infiniteness of the
$p$-variation. We discuss various examples in order to demonstrate the
applicability of the method.


title: A coordinate description of partonic processes

abstract:
  We review a perturbative description of amplitudes in coordinate space,
aiming at an intuitive perspective on the roles of "long" and "short"
distances. We begin with coordinate-space leading regions for fixed-angle
scattering amplitudes, and develop approximations and factorizations in analogy
to similar procedures in momentum space. There are also applications to
products of Wilson lines, including the familiar cusp amplitude. We briefly
discuss cross sections from the coordinate viewpoint, and the mechanism by
which infrared singularities cancel in inclusive cross sections.


title:
Development of a fast plastic scintillation detector with time
  resolution of less than 10 ps

abstract:
  Timing-pick up detectors with excellent timing resolutions are essential in
many modern nuclear physics experiments. Aiming to develop a Time-Of-Flight
system with precision down to about 10 ps, we have made a systematic study of
the timing characteristic of TOF detectors, which consist of several
combinations of plastic scintillators and photomultiplier tubes. With the
conventional electronics, the best timing resolution of about 5.1 ps ({\sigma})
has been achieved for detectors with an area size of 3x1 cm2. It is found that
for data digitalization a combination of TAC and ADC can achieve a better time
resolution than currently available TDC. Simultaneously measurements of both
time and pulse height are very valuable for correction of time-walk effect.


title:
Mean velocity equation for fluctuating flow: Numerical evaluation for
  small Reynolds numbers

abstract:
  The mean veloctiy equation for fluctuating flow derived in an earlier paper
of the author has been applied to circular jet flow for low Reynolds numbers.
Numerical solutions have been obtained from an iteration starting with the
corresponding solution of the Navier-Stokes equation. Deviations become
distinct for Re > 30.


title:
Electromagnetic Potential in Pre-Metric Electrodynamics: Causal
  Structure, Propagators and Quantization

abstract:
  An axiomatic approach to electrodynamics reveals that Maxwell electrodynamics
is just one instance of a variety of theories for which the name
electrodynamics is justified. They all have in common that their fundamental
input are Maxwell's equations $\textrm{d} F = 0$ (or $F = \textrm{d} A$) and
$\textrm{d} H = J$ and a constitutive law $H = # F$ which relates the field
strength two-form $F$ and the excitation two-form $H$. A local and linear
constitutive law defines what is called local and linear pre-metric
electrodynamics whose best known application are the effective description of
electrodynamics inside media including, e.g., birefringence. We analyze the
classical theory of the electromagnetic potential $A$ before we use methods
familiar from mathematical quantum field theory in curved spacetimes to
quantize it in a locally covariant way. Our analysis of the classical theory
contains the derivation of retarded and advanced propagators, the analysis of
the causal structure on the basis of the constitutive law (instead of a metric)
and a discussion of the classical phase space. This classical analysis sets the
stage for the construction of the quantum field algebra and quantum states.
Here one sees, among other things, that a microlocal spectrum condition can be
formulated in this more general setting.

categories: math-ph cond-mat.other gr-qc hep-th math.MP


title:
Closed form estimates for missing counts in multidimensional incomplete
  tables

abstract:
  A useful technique for analyzing incomplete tables is to model the missing
data mechanisms of the variables using log-linear models. In this paper, we use
log-linear parametrization and propose estimation methods for arbitrary
three-way and $n$-dimensional incomplete tables. All possible cases in which
data on one or more of the variables may be missing are considered. We provide
simple closed form estimates of expected cell counts and parameters for the
various missing data models. We also obtain explicit boundary estimates under
nonignorable nonresponse models. Finally, a real-life dataset is analyzed to
illustrate our results for modelling and estimation in multidimensional
incomplete tables.


title: Iterating free-field AdS/CFT: higher spin partition function relations

abstract:
  We find a simple relation between a free higher spin field partition function
on thermal quotient of AdS(d+1) and the partition function of the associated
d-dimensional conformal higher spin field on thermal quotient of AdS(d).
Starting with a conformal higher spin field defined on AdS(d) one may also
associate to it another conformal field in d-1 dimensions, thus "iterating"
AdS/CFT. We observe that in the case of d=4 this iteration leads to a "trivial"
3d higher spin conformal theory with parity-even non-local action: it describes
zero total number of dynamical degrees of freedom and the corresponding
partition function on thermal AdS(3) is equal to 1.


title: Diphotons from Diaxions

abstract:
  We study models in which the 750 GeV diphoton excess is due to a scalar
decaying to two pseudo-Nambu-Goldstone bosons that subsequently decay into two
pairs of highly boosted photons, misidentified as individual photons.
Performing a model independent analysis we find that, with axion mass around
$200$ MeV, this class of theories can naturally explain the observed signal
with a large width, without violating monojet constraints. At the same time the
requirement of a prompt axion decay can be satisfied only with a relatively
large axion-photon coupling, leading to many new charged particles at the TeV
scale. However, the required multiplicities of such fields is still moderately
reduced relative to models with direct diphoton production.


title: Dynamics and gravitational-wave emission of neutron-star merger remnants

abstract:
  The coalescence of a neutron-star binary is likely to result in the formation
of a neutron-star merger remnant for a large range of binary mass
configurations. The massive merger remnant shows strong oscillations, which are
excited by the merging process, and emits gravitational waves. Here we discuss
possibilities and prospects of inferring unknown stellar properties of neutron
stars by the detection of postmerger gravitational-wave emission, which thus
leads to constraints of the equation of state of high-density matter. In
particular, the dominant oscillation frequency of the postmerger remnant
provides tight limits to neutron-star radii. We mention first steps towards a
practical implementation of future gravitational-wave searches for the
postmerger emission. Moreover, we outline possibilities to estimate the unknown
maximum mass of nonrotating neutron stars from such types of measurements.
Finally, we review the origin and scientific implications of secondary peaks in
the gravitational-wave spectrum of neutron-star mergers and differences in the
dynamical behavior of the postmerger remnant depending on the binary
configuration. These considerations lead to a unified picture of the
post-merger gravitational-wave emission and the post-merger dynamics.


title:
Simulating topological phases and topological phase transitions with
  classical strings

abstract:
  The discovery of the topological insulators has fueled a surge of interests
in the topological phases in periodic systems. Topological insulators have bulk
energy gap and topologically protected gapless edge states. The edge states in
electronic systems have been detected by observing the transport properties the
Hgte quantum wells. The electromagnetic analogues of such electronic edge
states have been predicted and observed in photonic crystals, coupled
resonators and linear circuits. However, the edge state spectrums of the two
dimensional insulators and their electromagnetic analogues haven't been
directly measured and thus the gaplessness of the edge states hasn't been
experimentally confirmed. Here I show the classical strings are more convenient
choice to study the topological phases than the electromagnetic waves. I found
that classical strings with periodic densities can simulate a variety of
topological phases in condensed matter physics including two dimensional
topological insulators, three dimensional topological semimetals and weak
topological insulators. Because the eigenfrequencies and eigenfunctions of the
strings can be easily measured, not only the gapless edge state spectrum but
also the bulk topological invariant can now be directly observed. Further more
I show the topological phase transitions can be simulated by the strings. My
results show the richness of topological phases of mechanical waves. I
anticipate my work to be a starting point to study the topological properties
of mechanical waves. Even richer topological phases other than those have been
found in electronics systems can be explored when we use more general
mechanical waves e.g. waves in membranes with periodic densities. These phases
may provide guides to hunt novel topological properties in other branches of
science.


title: Controlling dynamical entanglement in a Josephson tunneling junction

abstract:
  We analyze the evolution of an entangled many-body state in a Josephson
tunneling junction. A N00N state, which is a superposition of two complementary
Fock states, appears in the evolution with sufficient probability only for a
moderate many-body interaction on an intermediate time scale. This time scale
is inversely proportional to the tunneling rate. Interaction between particles
supports entanglement: The probability for creating an entangled state decays
exponentially with the number of non-interacting particles, whereas it decays
only like the inverse square root of the number of interacting particles.


title:
Multiscale Gentlest Ascent Dynamics for Saddle Point in Effective
  Dynamics of Slow-Fast System

abstract:
  Here we present a multiscale method to calculate the saddle point associated
with the effective dynamics arising from a stochastic system which couples slow
deterministic drift and fast stochastic dynamics. This problem is motivated by
the transition states on free energy surfaces in chemical physics. Our method
is based on the gentlest ascent dynamics which couples the position variable
and the direction variable and has the local convergence to saddle points. The
dynamics of the direction vector is derived in terms of the covariance function
with respective to the equilibrium distribution of the fast stochastic process.
We apply the multiscale numerical methods to efficiently solve the obtained
multiscale gentlest ascent dynamics, {and discuss the acceleration techniques
based on the adaptive idea.} The examples of stochastic ordinary and partial
differential equations are presented.


title:
Evaluation of missing data mechanisms in two and three dimensional
  incomplete tables

abstract:
  The analysis of incomplete contingency tables is a practical and an
interesting problem. In this paper, we provide characterizations for the
various missing mechanisms of a variable in terms of response and non-response
odds for two and three dimensional incomplete tables. Log-linear
parametrization and some distinctive properties of the missing data models for
the above tables are discussed. All possible cases in which data on one, two or
all variables may be missing are considered. We study the missingness of each
variable in a model, which is more insightful for analyzing cross-classified
data than the missingness of the outcome vector. For sensitivity analysis of
the incomplete tables, we propose easily verifiable procedures to evaluate the
missing at random (MAR), missing completely at random (MCAR) and not missing at
random (NMAR) assumptions of the missing data models. These methods depend only
on joint and marginal odds computed from fully and partially observed counts in
the tables, respectively. Finally, some real-life datasets are analyzed to
illustrate our results, which are confirmed based on simulation studies.


title:
Unsupervised High-level Feature Learning by Ensemble Projection for
  Semi-supervised Image Classification and Image Clustering

abstract:
  This paper investigates the problem of image classification with limited or
no annotations, but abundant unlabeled data. The setting exists in many tasks
such as semi-supervised image classification, image clustering, and image
retrieval. Unlike previous methods, which develop or learn sophisticated
regularizers for classifiers, our method learns a new image representation by
exploiting the distribution patterns of all available data for the task at
hand. Particularly, a rich set of visual prototypes are sampled from all
available data, and are taken as surrogate classes to train discriminative
classifiers; images are projected via the classifiers; the projected values,
similarities to the prototypes, are stacked to build the new feature vector.
The training set is noisy. Hence, in the spirit of ensemble learning we create
a set of such training sets which are all diverse, leading to diverse
classifiers. The method is dubbed Ensemble Projection (EP). EP captures not
only the characteristics of individual images, but also the relationships among
images. It is conceptually simple and computationally efficient, yet effective
and flexible. Experiments on eight standard datasets show that: (1) EP
outperforms previous methods for semi-supervised image classification; (2) EP
produces promising results for self-taught image classification, where
unlabeled samples are a random collection of images rather than being from the
same distribution as the labeled ones; and (3) EP improves over the original
features for image clustering. The code of the method is available on the
project page.


title:
Conductance saturation in a series of highly transmitting molecular
  junctions

abstract:
  Understanding the properties of electronic transport across metal-molecule
interfaces is of central importance for controlling a large variety of
molecular-based devices such as organic light emitting diodes, nanoscale
organic spin-valves and single-molecule switches. One of the primary
experimental methods to reveal the mechanisms behind electronic transport
through metal-molecule interfaces is the study of conductance as a function of
molecule length in molecular junctions. Previous studies focused on transport
governed either by tunneling or hopping, both at low conductance. However, the
upper limit of conductance across molecular junctions has not been explored,
despite the great potential for efficient information transfer, charge
injection and recombination processes. Here, we study the conductance
properties of highly transmitting metal-molecule-metal interfaces, using a
series of single-molecule junctions based on oligoacenes with increasing
length. We find that the conductance saturates at an upper limit where it is
independent of molecule length. Furthermore, we show that this upper limit can
be controlled by the character of the orbital hybridization at the
metal-molecule interface. Using two prototype systems, in which the molecules
are contacted by either Ag or Pt electrodes, we reveal two different origins
for the saturation of conductance. In the case of Ag-based molecular junctions,
the conductance saturation is ascribed to a competition between energy level
alignment and level broadening, while in the case of Pt-based junctions, the
saturation is attributed to a band-like transport. The results are explained by
an intuitive model, backed by ab-initio transport calculations. Our findings
shed light on the mechanisms that constrain the conductance at the high
transmission limit, providing guiding principles for the design of highly
conductive metal-molecule interfaces.