title: An active efficient coding model of the optokinetic nystagmus

abstract:
  Optokinetic nystagmus (OKN) is an involuntary eye movement responsible for
stabilizing retinal images in the presence of relative motion between an
observer and the environment. Fully understanding the development of
optokinetic nystagmus requires a neurally plausible computational model that
accounts for the neural development and the behavior. To date, work in this
area has been limited. We propose a neurally plausible framework for the joint
development of disparity and motion tuning in the visual cortex, the
optokinetic and vergence eye movements. This framework models the joint
emergence of both perception and behavior, and accounts for the importance of
the development of normal vergence control and binocular vision in achieving
normal monocular OKN (mOKN) behaviors. Because the model includes behavior, we
can simulate the same perturbations as performed in past experiments, such as
artificially induced strabismus. The proposed model agrees both qualitatively
and quantitatively with a number of findings from the literature on both
binocular vision as well as the optokinetic reflex. Finally, our model also
makes quantitative predictions about the OKN behavior using the same methods
used to characterize the OKN in the experimental literature.


title: On the 2-linearity of the free group

abstract:
  We construct an action of the free group $F_n$ on the homotopy category of
projective modules over a finite dimensional zigzag algebra. The main theorem
in the paper is that this action is faithful. We describe the relationship
between homotopy classes of paths in the punctured disc and complexes of
projective zigzag modules and explore the connection between gradings on the
zigzag algebra and monoids in $F_n$. We use this connection to give homological
constructions of the standard and Bessis dual word length metrics on the free
group.


title: Proposal for a spin MOSFET based on spin gapless semiconductors

abstract:
  We propose a spintronic metal oxide semiconductor field effect transistor
(spin MOSFET) where a spin gapless semiconductor (SGS) constitutes the channel
and the drain is a ferromagnetic metal. SGS exhibit a non-zero band gap in only
one of the spin sub-bands and feature complete spin polarization at finite
temperature. We present an analytical model of the device and comment the
properties relevant for devices applications. Our results boost SGS as a new
paradigm for the spin MOSFET concept.


title:
Compact Galactic Planetary Nebulae: A HST/WFC3 Morphological Catalog,
  and a Study of their Role in the Galaxy

abstract:
  We present the images of a \textit{Hubble Space Telescope}
(\textit{HST}/WFC3) snapshot program of angularly compact Galactic planetary
nebulae (PNe), acquired with the aim of studying their size, evolutionary
status, and morphology. PNe that are smaller than $\sim4\arcsec$ are
underrepresented in most morphological studies, and today they are less well
studied than their immediate evolutionary predecessors, the pre-planetary
nebulae. The images have been acquired in the light of
[\ion{O}{3}]$\lambda5007$, which is commonly used to classify the PN
morphology, in the UV continuum with the aim of detecting the central star
unambiguously, and in the $I-$band to detect a cool stellar companion, if
present. The sample of 51 confirmed PNe exhibits nearly the full range of
primary morphological classes, with the distribution more heavily weighted
toward bipolar PNe, but with total of aspherical PNe almost identical to that
of the general Galactic sample. A large range of microstructures is evident in
our sample as well, with many nebulae displaying attached shells, halos, ansae,
and internal structure in the form of arcs, rings, and spirals. Various
aspherical structures in a few PNe, including detached arcs, suggest an
interaction with the ISM. We studied the observed sample of compact Galactic
PNe in the context of the general Galactic PN population, and explore whether
their physical size, spatial distribution, reddening, radial metallicity
gradient, and possible progenitors, are peculiar within the population of
Galactic PNe. We found that these compact Galactic PNe, which have been
selected based on apparent dimensions, constitute a diverse Galactic PN
population that is relatively uniformly distributed across the Galactic disk,
including the outskirts of our Galaxy. This unique sample will be used in the
future to probe the old Galactic disk population.


title:
Outlier Edge Detection Using Random Graph Generation Models and
  Applications

abstract:
  Outliers are samples that are generated by different mechanisms from other
normal data samples. Graphs, in particular social network graphs, may contain
nodes and edges that are made by scammers, malicious programs or mistakenly by
normal users. Detecting outlier nodes and edges is important for data mining
and graph analytics. However, previous research in the field has merely focused
on detecting outlier nodes. In this article, we study the properties of edges
and propose outlier edge detection algorithms using two random graph generation
models. We found that the edge-ego-network, which can be defined as the induced
graph that contains two end nodes of an edge, their neighboring nodes and the
edges that link these nodes, contains critical information to detect outlier
edges. We evaluated the proposed algorithms by injecting outlier edges into
some real-world graph data. Experiment results show that the proposed
algorithms can effectively detect outlier edges. In particular, the algorithm
based on the Preferential Attachment Random Graph Generation model consistently
gives good performance regardless of the test graph data. Further more, the
proposed algorithms are not limited in the area of outlier edge detection. We
demonstrate three different applications that benefit from the proposed
algorithms: 1) a preprocessing tool that improves the performance of graph
clustering algorithms; 2) an outlier node detection algorithm; and 3) a novel
noisy data clustering algorithm. These applications show the great potential of
the proposed outlier edge detection techniques.


title:
Brown dwarf disks with ALMA: evidence for truncated dust disks in
  Ophiuchus

abstract:
  The study of the properties of disks around young brown dwarfs can provide
important clues on the formation of these very low-mass objects and on the
possibility of forming planetary systems around them. The presence of warm
dusty disks around brown dwarfs is well known, based on near- and mid-infrared
studies. High angular resolution observations of the cold outer disk are
limited; we used ALMA to attempt a first survey of young brown dwarfs in the
$\rho$-Oph star-forming region. All 17 young brown dwarfs in our sample were
observed at 890 $\mu $m in the continuum at $\sim0.\!^{\prime\prime}5$ angular
resolution. The sensitivity of our observations was chosen to detect $\sim0.5$
M$_\oplus$ of dust. We detect continuum emission in 11 disks ($\sim65$\%\ of
the total), and the estimated mass of dust in the detected disks ranges from
$\sim0.5$ to $\sim6$ M$_\oplus$. These disk masses imply that planet formation
around brown dwarfs may be relatively rare and that the supra-Jupiter mass
companions found around some brown dwarfs are probably the result of a binary
system formation. We find evidence that the two brightest disks in $\rho$-Oph
have sharp outer edges at R<~25 AU, in contrast to disks around Taurus brown
dwarfs. This difference may suggest that the different environment in
$\rho$-Oph may lead to significant differences in disk properties. A comparison
of the M$_{disk}$/M$_\ast$ ratio for brown dwarf and solar-mass systems also
shows a possible deficit of mass in brown dwarfs, which could support the
evidence for dynamical truncation of disks in the substellar regime. These
findings are still tentative and need to be put on firmer grounds by studying
the gaseous disks around brown dwarfs and by performing a more systematic and
unbiased survey of the disk population around the more massive stars.


title: A Torelli type theorem for exp-algebraic curves

abstract:
  An exp-algebraic curve consists of a compact Riemann surface $S$ together
with $n$ equivalence classes of germs of meromorphic functions modulo germs of
holomorphic functions, $\HH = \{ [h_1], \cdots, [h_n] \}$, with poles of orders
$d_1, \cdots, d_n \geq 1$ at points $p_1, \cdots, p_n$. This data determines a
space of functions $\OO_{\HH}$ (respectively, a space of $1$-forms
$\Omega^0_{\HH}$) holomorphic on the punctured surface $S' = S - \{p_1, \cdots,
p_n\}$ with exponential singularities at the points $p_1, \cdots, p_n$ of types
$[h_1], \cdots, [h_n]$, i.e., near $p_i$ any $f \in \OO_{\HH}$ is of the form
$f = ge^{h_i}$ for some germ of meromorphic function $g$ (respectively, any
$\omega \in \Omega^0_{\HH}$ is of the form $\omega = \alpha e^{h_i}$ for some
germ of meromorphic $1$-form).
  For any $\omega \in \Omega^0_{\HH}$ the completion of $S'$ with respect to
the flat metric $|\omega|$ gives a space $S^* = S' \cup \RR$ obtained by adding
a finite set $\RR$ of $\sum_i d_i$ points, and it is known that integration
along curves produces a nondegenerate pairing of the relative homology
$H_1(S^*, \RR ; \C)$ with the deRham cohomology group defined by $H^1_{dR}(S,
\HH) := \Omega^0_{\HH}/d\OO_{\HH}$.
  There is a degree zero line bundle $L_{\HH}$ associated to an exp-algebraic
curve, with a natural isomorphism between $\Omega^0_{\HH}$ and the space
$W_{\HH}$ of meromorphic $L_{\HH}$-valued $1$-forms which are holomorphic on
$S'$, so that $H_1(S^*, \RR ; \C)$ maps to a subspace $K_{\HH} \subset
W^*_{\HH}$. We show that the exp-algebraic curve $(S, \HH)$ is determined
uniquely by the pair $(L_{\HH},\, K_{\HH} \subset W^*_{\HH})$.


title: Limited Random Walk Algorithm for Big Graph Data Clustering

abstract:
  Graph clustering is an important technique to understand the relationships
between the vertices in a big graph. In this paper, we propose a novel
random-walk-based graph clustering method. The proposed method restricts the
reach of the walking agent using an inflation function and a normalization
function. We analyze the behavior of the limited random walk procedure and
propose a novel algorithm for both global and local graph clustering problems.
Previous random-walk-based algorithms depend on the chosen fitness function to
find the clusters around a seed vertex. The proposed algorithm tackles the
problem in an entirely different manner. We use the limited random walk
procedure to find attracting vertices in a graph and use them as features to
cluster the vertices. According to the experimental results on the simulated
graph data and the real-world big graph data, the proposed method is superior
to the state-of-the-art methods in solving graph clustering problems. Since the
proposed method uses the embarrassingly parallel paradigm, it can be
efficiently implemented and embedded in any parallel computing environment such
as a MapReduce framework. Given enough computing resources, we are capable of
clustering graphs with millions of vertices and hundreds millions of edges in a
reasonable time.


title: High Level Synthesis with a Dataflow Architectural Template

abstract:
  In this work, we present a new approach to high level synthesis (HLS), where
high level functions are first mapped to an architectural template, before
hardware synthesis is performed. As FPGA platforms are especially suitable for
implementing streaming processing pipelines, we perform transformations on
conventional high level programs where they are turned into multi-stage
dataflow engines [1]. This target template naturally overlaps slow memory data
accesses with computations and therefore has much better tolerance towards
memory subsystem latency. Using a state-of-the-art HLS tool for the actual
circuit generation, we observe up to 9x improvement in overall performance when
the dataflow architectural template is used as an intermediate compilation
target.


title:
Reliability-Aware Overlay Architectures for FPGAs: Features and Design
  Challenges

abstract:
  The FPGA overlay architectures have been mainly proposed to improve design
productivity, circuit portability and system debugging. In this paper, we
address the use of overlay architectures for building fault tolerant SRAM-based
FPGA systems and discuss the main features and design challenges of a
reliability-aware overlay architecture.


title: Nash estimates and upper bounds for non-homogeneous Kolmogorov equations

abstract:
  We prove a Gaussian upper bound for the fundamental solutions of a class of
ultra-parabolic equations in divergence form. The bound is independent on the
smoothness of the coefficients and generalizes some classical results by Nash,
Aronson and Davies. The class considered has relevant applications in the
theory of stochastic processes, in physics and in mathematical finance.


title: Soft GPGPUs for Embedded FPGAs: An Architectural Evaluation

abstract:
  We present a customizable soft architecture which allows for the execution of
GPGPU code on an FPGA without the need to recompile the design. Issues related
to scaling the overlay architecture to multiple GPGPU multiprocessors are
considered along with application-class architectural optimizations. The
overlay architecture is optimized for FPGA implementation to support efficient
use of embedded block memories and DSP blocks. This architecture supports
direct CUDA compilation of integer computations to a binary which is executable
on the FPGA-based GPGPU. The benefits of our architecture are evaluated for a
collection of five standard CUDA benchmarks which are compiled using standard
GPGPU compilation tools. Speedups of 44x, on average, versus a MicroBlaze
microprocessor are achieved. We show dynamic energy savings versus a soft-core
processor of 80% on average. Application-customized versions of the soft GPGPU
can be used to further reduce dynamic energy consumption by an average of 14%.


title: Generalisations of Fisher Matrices

abstract:
  Fisher matrices play an important role in experimental design and in data
analysis. Their primary role is to make predictions for the inference of model
parameters - both their errors and covariances. In this short review, I outline
a number of extensions to the simple Fisher matrix formalism, covering a number
of recent developments in the field. These are: (a) situations where the data
(in the form of (x,y) pairs) have errors in both x and y; (b) modifications to
parameter inference in the presence of systematic errors, or through fixing the
values of some model parameters; (c) Derivative Approximation for LIkelihoods
(DALI) - higher-order expansions of the likelihood surface, going beyond the
Gaussian shape approximation; (d) extensions of the Fisher-like formalism, to
treat model selection problems with Bayesian evidence.


title:
Extension of the constant exchange probability method to
  multi-dimensional replica exchange Monte Carlo applied to the tri-critical
  spin-1 Blume-Capel model

abstract:
  In replica exchange Monte Carlo (REM), tuning of the temperature set and the
exchange scheduling are crucial in improving the accuracy and reducing
calculation time. In multi-dimensional simulated tempering, the first order
phase transition is accessible. Therefore it is important to study the tuning
of parameter set and the scheduling of exchanges in the parallel counterpart,
the multi-dimensional REM. We extend Hukushima's constant exchange probability
method to multi-dimensional REM for the parameter set. We further propose a
combined method to use this set and the Bittner-Nussbaumer-Janke's PT tau
algorithm for scheduling. We test the proposed method in two-dimensional spin-1
Blume-Capel model and find that it works efficiently, including the vicinity of
the first order phase transition.


title:
Enabling Effective FPGA Debug using Overlays: Opportunities and
  Challenges

abstract:
  FPGAs are going mainstream. Major companies that were not traditionally
FPGA-focused are now seeking ways to exploit the benefits of reconfigurable
technology and provide it to their customers. In order to do so, a debug
ecosystem that provides for effective visibility into a working design and
quick debug turn-around times is essential. Overlays have the opportunity to
play a key role in this ecosystem. In this overview paper, we discuss how an
overlay fabric that allows the user to rapidly add debug instrumentation to a
design can be created and exploited. We discuss the requirements of such an
overlay and some of the research challenges and opportunities that need to be
addressed. To make our exposition concrete, we use two previously-published
examples of overlays that have been developed to implement debug
instrumentation.


title: Hydrodynamic interaction between particles near elastic interfaces

abstract:
  We present an analytical calculation of the hydrodynamic interaction between
two spherical particles near an elastic interface such as a cell membrane. The
theory predicts the frequency dependent self- and pair-mobilities accounting
for the finite particle size up to the 5th order in the ratio between particle
diameter and wall distance as well as between diameter and interparticle
distance. We find that particle motion towards a membrane with pure bending
resistance always leads to mutual repulsion similar as in the well-known case
of a hard-wall. In the vicinity of a membrane with shearing resistance,
however, we observe an attractive interaction in a certain parameter range
which is in contrast to the behavior near a hard wall. This attraction might
facilitate surface chemical reactions. Furthermore, we show that there exists a
frequency range in which the pair-mobility for perpendicular motion exceeds its
bulk value, leading to short-lived superdiffusive behavior. Using the
analytical particle mobilities we compute collective and relative diffusion
coefficients. The appropriateness of the approximations in our analytical
results is demonstrated by corresponding boundary integral simulations which
are in excellent agreement with the theoretical predictions.


title:
Non-parametric threshold estimation for classical risk process perturbed
  by diffusion

abstract:
  In this paper,we consider a macro approximation of the flow of a risk
reserve, The process is observed at discrete time points. Because we cannot
directly observe each jump time and size then we will make use of a technique
for identifying the times when jumps larger than a suitably defined threshold
occurred. We estimate the jump size and survival probability of our risk
process from discrete observations.


title:
An Area-Efficient FPGA Overlay using DSP Block based Time-multiplexed
  Functional Units

abstract:
  Coarse grained overlay architectures improve FPGA design productivity by
providing fast compilation and software-like programmability. Throughput
oriented spatially configurable overlays typically suffer from area overheads
due to the requirement of one functional unit for each compute kernel
operation. Hence, these overlays have often been of limited size, supporting
only relatively small compute kernels while consuming considerable FPGA
resources. This paper examines the possibility of sharing the functional units
among kernel operations for reducing area overheads. We propose a linear
interconnected array of time-multiplexed FUs as an overlay architecture with
reduced instruction storage and interconnect resource requirements, which uses
a fully-pipelined, architecture-aware FU design supporting a fast context
switching time. The results presented show a reduction of up to 85% in FPGA
resource requirements compared to existing throughput oriented overlay
architectures, with an operating frequency which approaches the theoretical
limit for the FPGA device.


title: Neighborhood Mixture Model for Knowledge Base Completion

abstract:
  Knowledge bases are useful resources for many natural language processing
tasks, however, they are far from complete. In this paper, we define a novel
entity representation as a mixture of its neighborhood in the knowledge base
and apply this technique on TransE-a well-known embedding model for knowledge
base completion. Experimental results show that the neighborhood information
significantly helps to improve the results of the TransE model, leading to
better performance than obtained by other state-of-the-art embedding models on
three benchmark datasets for triple classification, entity prediction and
relation prediction tasks.


title: On the quantum spin glass transition on the Bethe lattice

abstract:
  We investigate the ground-state properties of a disorderd Ising model with
uniform transverse field on the Bethe lattice, focusing on the quantum phase
transition from a paramagnetic to a glassy phase that is induced by reducing
the intensity of the transverse field. We use a combination of quantum Monte
Carlo algorithms and exact diagonalization to compute R\'enyi entropies,
quantum Fisher information, correlation functions and order parameter. We
locate the transition by means of the peak of the R\'enyi entropy and we find
agreement with the transition point estimated from the emergence of finite
values of the Edwards-Anderson order parameter and from the peak of the
correlation length. We interpret the results by means of a mean-field theory in
which quantum fluctuations are treated as massive particles hopping on the
interaction graph. We see that the particles are delocalized at the transition,
a fact that points towards the existence of possibly another transition deep in
the glassy phase where these particles localize, therefore leading to a
many-body localized phase.


title:
Physical realization of a quantum spin liquid based on a novel
  frustration mechanism

abstract:
  Unlike conventional magnets where the magnetic moments are partially or
completely static in the ground state, in a quantum spin liquid they remain in
collective motion down to the lowest temperatures. The importance of this state
is that it is coherent and highly entangled without breaking local symmetries.
Such phenomena is usually sought in simple lattices where antiferromagnetic
interactions and/or anisotropies that favor specific alignments of the magnetic
moments are "frustrated" by lattice geometries incompatible with such order
e.g. triangular structures. Despite an extensive search among such compounds,
experimental realizations remain very few. Here we describe the investigation
of a novel, unexplored magnetic system consisting of strong ferromagnetic and
weaker antiferromagnetic isotropic interactions as realized by the compound
Ca$_{10}$Cr$_7$O$_{28}$. Despite its exotic structure we show both
experimentally and theoretically that it displays all the features expected of
a quantum spin liquid including coherent spin dynamics in the ground state and
the complete absence of static magnetism.


title: A degenerate chemotaxis system with flux limitation: Finite-time blow-up

abstract:
  This paper is concerned with radially symmetric solutions of the
parabolic-elliptic version of the Keller-Segel system with flux limitation, as
given by
  \begin{equation}
  \left\{ \begin{array}{l} \displaystyle u_t=\nabla \cdot \Big(\frac{u\nabla
u}{\sqrt{u^2+|\nabla u|^2}}\Big) - \chi \, \nabla \cdot \Big(\frac{u\nabla
v}{\sqrt{1+|\nabla v|^2}}\Big), \\[1mm]
  0=\Delta v - \mu + u,
  \end{array} \right.
  \qquad \qquad (\star)
  \end{equation} under the initial condition $u|_{t=0}=u_0>0$ and no-flux
boundary conditions in a ball $\Omega\subset R^n$, where $\chi>0$ and
$\mu:=\frac{1}{|\Omega|} \int_\Omega u_0$.
  A previous result [3] has asserted global existence of bounded classical
solutions for arbitrary positive radial initial data $u_0\in C^3(\bar\Omega)$
when either $n\ge 2$ and $\chi<1$, or $n=1$ and $ \int_\Omega
u_0<\frac{1}{\sqrt{(\chi^2-1)_+}}$.
  This present paper shows that these conditions are essentially optimal:
Indeed, it is shown that if the taxis coefficient is large enough in the sense
that $\chi>1$, then for any choice of
  \begin{equation}
  \left\{ \begin{array}{ll} m>\frac{1}{\sqrt{\chi^2-1}} \quad & \mbox{if } n=1,
\\[2mm] m>0 \mbox{ is arbitrary } \quad & \mbox{if } n\ge 2,
  \end{array} \right.
  \end{equation} there exist positive initial data $u_0\in C^3(\bar\Omega)$
satisfying $ \int_\Omega u_0=m$ which are such that for some $T>0$, ($\star$)
possesses a uniquely determined classical solution $(u,v)$ in $\Omega\times
(0,T)$ blowing up at time $T$ in the sense that $\limsup_{t\nearrow T}
\|u(\cdot,t)\|_{L^\infty(\Omega)}=\infty$.\abs
  This result is derived by means of a comparison argument applied to the
doubly degenerate scalar parabolic equation satisfied by the mass accumulation
function associated with ($\star$).


title: Surjective Kuiper isometries

abstract:
  Characterizations of surjective isometries with respect to the Kuiper
distance on three classes of Borel probability measures of $\mathbb{R}$ (or
equivalently, probability distribution functions) are presented here. These
classes are the set of continuous, absolute continuous and general measures.


title:
Three-particle correlation from a Many-Body Perspective: Trions in a
  Carbon Nanotube

abstract:
  Trion states of three correlated particles (e.g., two electrons and one hole)
are essential to understand the optical spectra of doped or gated
nanostructures, like carbon nanotubes or transition-metal dichalcogenides. We
develop a theoretical many-body description for such correlated states using an
ab-initio approach. It can be regarded as an extension of the widely used $GW$
method and Bethe-Salpeter equation, thus allowing for a direct comparison with
excitons. We apply this method to a semiconducting (8,0) carbon nanotube, and
find that the lowest optically active trions are red-shifted by $\sim 130$ meV
compared to the excitons, confirming experimental findings for similar tubes.
Moreover, our method provides detailed insights in the physical nature of trion
states. In the prototypical carbon nanotube we find a variety of different
excitations, discuss the spectra, energy compositions, and correlated wave
functions.


title:
Measurement-only verifiable blind quantum computing with quantum input
  verification

abstract:
  Verifiable blind quantum computing is a secure delegated quantum computing
where a client with a limited quantum technology delegates her quantum
computing to a server who has a universal quantum computer. The client's
privacy is protected (blindness) and the correctness of the computation is
verifiable by the client in spite of her limited quantum technology
(verifiability). There are mainly two types of protocols for verifiable blind
quantum computing: the protocol where the client has only to generate
single-qubit states, and the protocol where the client needs only the ability
of single-qubit measurements. The latter is called the measurement-only
verifiable blind quantum computing. If the input of the client's quantum
computing is a quantum state whose classical efficient description is not known
to the client, there was no way for the measurement-only client to verify the
correctness of the input. Here we introduce a new protocol of measurement-only
verifiable blind quantum computing where the correctness of the quantum input
is also verifiable.


title:
Magnetism of the antiferromagnetic spin-$\frac{1}{2}$ tetramer compound
  CuInVO$_5$

abstract:
  We measured the temperature dependence of the magnetic susceptibility and
specific heat and the magnetic-field dependence of the magnetization of
CuInVO$_5$. An antiferromagnetically ordered state appears below $T_{\rm N} =
2.7$ K. We observed a $\frac{1}{2}$ quantum magnetization plateau above 30 T at
1.3 K. We show that the spin system consists of antiferromagnetic
spin-$\frac{1}{2}$ tetramers with $J_1 = 240 \pm 20$ and $J_2 = -142 \pm 10$ K
for the intratetramer interactions.


title: A fixed point theorem for monotone asyptotic nonexpansive mappings

abstract:
  Let C be a nonempty, bounded, closed, and convex subset of a Banach space X
and $T : C \rightarrow C$ be a monotone asymptotic nonexpansive mapping. In
this paper, we investigate the existence of fixed points of T. In particular,
we establish an analogue to the original Goebel and Kirk's fixed point theorem
for asymptotic nonexpansive mappings.


title:
Explicit solutions for a nonlinear model on the honeycomb and triangular
  lattices

abstract:
  We study a simple nonlinear model defined on the honeycomb and triangular
lattices. We propose a bilinearization scheme for the field equations and
demonstrate that the resulting system is closely related to the well-studied
integrable models, such as the Hirota bilinear difference equation and the
Ablowitz-Ladik system. This result is used to derive the two sets of explicit
solutions: the N-soliton solutions and ones constructed of the Toeplitz
determinants.


title: Bubble drag reduction requires large bubbles

abstract:
  In the maritime industry, the injection of air bubbles into the turbulent
boundary layer under the ship hull is seen as one of the most promising
techniques to reduce the overall fuel consumption. However, the exact mechanism
behind bubble drag reduction is unknown. Here we show that bubble drag
reduction in turbulent flow dramatically depends on the bubble size. By adding
minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise
completely unchanged strongly turbulent Taylor-Couette flow containing bubbles,
we dramatically reduce the drag reduction from more than 40% to about 4%,
corresponding to the trivial effect of the bubbles on the density and viscosity
of the liquid. The reason for this striking behavior is that the addition of
surfactants prevents bubble coalescence, leading to much smaller bubbles. Our
result demonstrates that bubble deformability is crucial for bubble drag
reduction in turbulent flow and opens the door for an optimization of the
process.


title:
DeepWriter: A Multi-Stream Deep CNN for Text-independent Writer
  Identification

abstract:
  Text-independent writer identification is challenging due to the huge
variation of written contents and the ambiguous written styles of different
writers. This paper proposes DeepWriter, a deep multi-stream CNN to learn deep
powerful representation for recognizing writers. DeepWriter takes local
handwritten patches as input and is trained with softmax classification loss.
The main contributions are: 1) we design and optimize multi-stream structure
for writer identification task; 2) we introduce data augmentation learning to
enhance the performance of DeepWriter; 3) we introduce a patch scanning
strategy to handle text image with different lengths. In addition, we find that
different languages such as English and Chinese may share common features for
writer identification, and joint training can yield better performance.
Experimental results on IAM and HWDB datasets show that our models achieve high
identification accuracy: 99.01% on 301 writers and 97.03% on 657 writers with
one English sentence input, 93.85% on 300 writers with one Chinese character
input, which outperform previous methods with a large margin. Moreover, our
models obtain accuracy of 98.01% on 301 writers with only 4 English alphabets
as input.


title: Highly dense mobile networks with random fadings

abstract:
  Master thesis at TU Berlin with Wolfgang K\"{o}nig, April 2016.
  We investigate a wireless network where the users are located according to a
Poisson point process in a bounded subset of R^d, in the high-density limit.
Assuming that the users have i.i.d. random fadings, interpreted as their
loudnesses, we describe the large deviation properties of rare frustration
events. This provides a variational formula, which we analyze in more detail,
in order to describe the most likely settings with unusually many users who
experience bad connection. We also compare effects coming from the random
spatial positions of the users with effects coming from the random fadings.
  Keywords: wireless communication, relaying, random fadings, high-density
limit, large deviations, discretization, frustration probabilities, minimizers
of relative entropy, average loudness.


title:
Born-Jordan and Weyl Quantizations of the 2D Anisotropic Harmonic
  Oscillator

abstract:
  We apply the Born-Jordan and Weyl quantization formulas for polynomials in
canonical coordinates to the constants of motion of some examples of the
superintegrable 2D anisotropic harmonic oscillator. Our aim is to study the
behaviour of the algebra of the constants of motion after the different
quantization procedures. In the examples considered, we have that the Weyl
formula always preserves the original superintegrable structure of the system,
while the Born-Jordan formula, when producing different operators than the
Weyl's one, does not.


title: Carrier frequencies, holomorphy and unwinding

abstract:
  We prove that functions of intrinsic-mode type (a classical models for
signals) behave essentially like holomorphic functions: adding a pure carrier
frequency $e^{int}$ ensures that the anti-holomorphic part is much smaller than
the holomorphic part $ \| P_{-}(f)\|_{L^2} \ll \|P_{+}(f)\|_{L^2}.$ This
enables us to use techniques from complex analysis, in particular the
\textit{unwinding series}. We study its stability and convergence properties
and show that the unwinding series can stabilize and show that the unwinding
series can provide a high resolution time-frequency representation, which is
robust to noise.


title:
A Cloud-Based and RESTful Internet of Things Platform to Foster Smart
  Grid Technologies Integration and Re-Usability

abstract:
  Currently, one of the hottest topics in the Internet of Things (IoT) research
domain regards the issue to overcome the heterogeneity of proprietary
technologies and systems so as to enable the integration of applications and
devices developed for different environments in a single interoperable
framework. Towards this objective, virtualization is widely used to foster
integration and creation of new services and applications. Similar benefits are
expected by its application in the smart grid arena. The use of a
virtualization middleware is expected to enrich the capabilities and
opportunities related to the use of smart grid devices. In this paper, we
propose key features for an interoperable, re-usable, elastic and secure smart
grid architecture which is cloud-based and relies on REST APIs. To highlight
the benefits, a practical case study is presented, where outlined
functionalities are implemented in a cloud-based IoT platform. The advantages
brought by the proposed middleware in terms of interoperability, re-usability,
privacy and elasticity of the underlying infrastructure are discussed.


title:
Stochastic approximation of quasi-stationary distributions on compact
  spaces and applications

abstract:
  In the continuity of a recent paper ([6]), dealing with finite Markov chains,
this paper proposes and analyzes a recursive algorithm for the approximation of
the quasi-stationary distribution of a general Markov chain living on a compact
metric space killed in finite time. The idea is to run the process until
extinction and then to bring it back to life at a position randomly chosen
according to the (possibly weighted) empirical occupation measure of its past
positions. General conditions are given ensuring the convergence of this
measure to the quasi-stationary distribution of the chain. We then apply this
method to the numerical approximation of the quasi-stationary distribution of a
diffusion process killed on the boundary of a compact set and to the estimation
of the spectral gap of irreducible Markov processes. Finally, the sharpness of
the assumptions is illustrated through the study of the algorithm in a
non-irreducible setting.


title: Hilbert-Kunz theory for binoids

abstract:
  We develop Hilbert-Kunz theory in a combinatorial setting namely for binoids.
We show that the Hilbert-Kunz multiplicity for commutative, finitely generated,
semipositive, cancellative and reduced binoids exists and is a rational number.
This implies that the corresponding Hilbert-Kunz multiplicity for the binoid
algebras does not depend on the characteristic.


title:
Dipolar polaritons in microcavity-embedded coupled quantum wells in
  electric and magnetic fields

abstract:
  We present a precise calculation of spatially-indirect exciton states in
semiconductor coupled quantum wells and polaritons formed from their coupling
to the optical mode of a microcavity. We include the presence of electric and
magnetic fields applied perpendicular to the quantum well plane. Our model
predicts the existence of polaritons which are in the strong coupling regime
and at the same time possess a large static dipole moment. We demonstrate, in
particular, that a magnetic field can compensate for the reduction in
light-matter coupling that occurs when an electric field impresses a dipole
moment on the polariton.


title:
Emission of neutron-proton and proton-proton pairs in electron
  scattering induced by meson-exchange currents

abstract:
  We use a relativistic model of meson-exchange currents to compute the
proton-neutron and proton-proton yields in $(e,e')$ scattering from $^{12}$C in
the 2p-2h channel. We compute the response functions and cross section with the
relativistic Fermi gas model for a range of kinematics from intermediate to
high momentum transfers. We find a large contribution of neutron-proton
configurations in the initial state, as compared to proton-proton pairs. The
different emission probabilities of distinct species of nucleon pairs are
produced in our model only by meson-exchange currents, mainly by the $\Delta$
isobar current. We also analyze the effect of the exchange contribution and
show that the direct/exchange interference strongly affects the determination
of the np/pp ratio.


title:
Study of the process $e^+e^-\to\omega\eta\pi^0$ in the energy range
  $\sqrt{s} <2$ GeV with the SND detector

abstract:
  The process $e^+e^-\to\omega\eta\pi^0$ is studied in the energy range
$1.45-2.00$ GeV using data with an integrated luminosity of 33 pb$^{-1}$
accumulated by the SND detector at the $e^+e^-$ collider VEPP-2000. The
$e^+e^-\to\omega\eta\pi^0$ cross section is measured for the first time. The
cross section has a threshold near 1.75 GeV. Its value is about 2 nb in the
energy range $1.8-2.0$ GeV. The dominant intermediate state for the process
$e^+e^- \to \omega\eta\pi^0$ is found to be $\omega a_0(980)$.


title:
Expansion complexity and linear complexity of sequences over finite
  fields

abstract:
  The linear complexity is a measure for the unpredictability of a sequence
over a finite field and thus for its suitability in cryptography. In 2012, Diem
introduced a new figure of merit for cryptographic sequences called expansion
complexity. We study the relationship between linear complexity and expansion
complexity. In particular, we show that for purely periodic sequences both
figures of merit provide essentially the same quality test for a sufficiently
long part of the sequence. However, if we study shorter parts of the period or
nonperiodic sequences, then we can show, roughly speaking, that the expansion
complexity provides a stronger test. We demonstrate this by analyzing a
sequence of binomial coefficients modulo $p$. Finally, we establish a
probabilistic result on the behavior of the expansion complexity of random
sequences over a finite field.


title: A Soft Processor Overlay with Tightly-coupled FPGA Accelerator

abstract:
  FPGA overlays are commonly implemented as coarse-grained reconfigurable
architectures with a goal to improve designers' productivity through balancing
flexibility and ease of configuration of the underlying fabric. To truly
facilitate full application acceleration, it is often necessary to also include
a highly efficient processor that integrates and collaborates with the
accelerators while maintaining the benefits of being implemented within the
same overlay framework. This paper presents an open-source soft processor that
is designed to tightly-couple with FPGA accelerators as part of an overlay
framework. RISC-V is chosen as the instruction set for its openness and
portability, and the soft processor is designed as a 4-stage pipeline to
balance resource consumption and performance when implemented on FPGAs. The
processor is generically implemented so as to promote design portability and
compatibility across different FPGA platforms. Experimental results show that
integrated software-hardware applications using the proposed tightly-coupled
architecture achieve comparable performance as hardware-only accelerators while
the proposed architecture provides additional run-time flexibility. The
processor has been synthesized to both low-end and high-performance FPGA
families from different vendors, achieving the highest frequency of 268.67MHz
and resource consumption comparable to existing RISC-V designs.


title:
Bending back stress chains and unique behaviour of granular matter in
  cylindrical geometries

abstract:
  We analyse the general solutions for the stress field in planar annuli of
isostatic media, a model often used for marginally rigid granular materials in
Couette cells. We demonstrate that these solutions are much richer than in
rectangular symmetries. Even for uniform media, stress chains are found to
curve, broaden away from the stress source, attenuate and leak stress into a
cone of influence. Most spectacularly, stress chains may bend back and transmit
forces oppositely to the original direction. None of these phenomena arises in
solutions for uniform media in Cartesian coordinates. We further analyse
non-uniform media, which exhibit chain branching and stress leakage from the
chains. These results are directly relevant to the many experiments on granular
materials, carried out in Couette cells. They also shed light on, and are
supported by, hitherto unexplained experimental observations of curved and
back-bending chains, which we point out. In particular, we use our results to
provide a new interpretation for the pattern of slip lines observed
experimentally.


title:
Analytical model for release calculations in solid thin-foils ISOL
  targets

abstract:
  A detailed analytical model has been developed to simulate isotope-release
curves from thin-foils ISOL targets. It involves the separate modelling of
diffusion and effusion inside the target. The former has been modelled using
both first and second Fick's law. The latter, effusion from the surface of the
target material to the end of the ionizer, was simulated with the Monte Carlo
code MolFlow+. The calculated delay-time distribution for this process was then
fitted using a double-exponential function. The release curve obtained from the
convolution of diffusion and effusion shows good agreement with experimental
data from two different target geometries used at ISOLDE. Moreover, the
experimental yields are well reproduced when combining the release fraction
with calculated in-target production.


title:
Pseudo-Riemannian almost hypercomplex homogeneous spaces with
  irreducible isotropy

abstract:
  We classify homogeneous pseudo-Riemannian manifolds of index 4 which admit an
invariant almost hyper-Hermitian structure and an H-irreducible isotropy group.
The main result is that all these spaces are flat except in dimension 12.


title: Shear-stress fluctuations in self-assembled transient elastic networks

abstract:
  Focusing on shear-stress fluctuations we investigate numerically a simple
generic model for self-assembled transient networks formed by repulsive beads
reversibly bridged by ideal springs. With $\Delta dt$ being the sampling time
and $t_*(f) \sim 1/f$ the Maxwell relaxation time (set by the spring
recombination frequency $f$) the dimensionless parameter $\Delta x = dt/t_*(f)$
is systematically scanned from the liquid limit ($\Delta dx \gg 1)$ to the
solid limit ($\Delta x \ll 1$) where the network topology is quenched and an
ensemble average over $m$ independent configurations is required. Generalizing
previous work on permanent networks it is shown that the shear-stress
relaxation modulus $G(t)$ may be efficiently determined for all $\Delta x$
using the simple-average expression $G(t) = \mu_A - h(t)$ with $\mu_A = G(0)$
characterizing the canonical-affine shear transformation of the system at $t=0$
and $h(t)$ the (rescaled) mean-square displacement of the instantaneous shear
stress as a function of time $t$. This relation is compared to the standard
expression $G(t) = C(t)$ using the (rescaled) shear-stress autocorrelation
function $C(t)$. Lower bounds for the $m$ configurations required by both
relations are given.


title: Discretized Approaches to Schematization

abstract:
  To produce cartographic maps, simplification is typically used to reduce
complexity of the map to a legible level. With schematic maps, however, this
simplification is pushed far beyond the legibility threshold and is instead
constrained by functional need and resemblance. Moreover, stylistic geometry is
often used to convey the schematic nature of the map. In this paper we explore
discretized approaches to computing a schematic shape $S$ for a simple polygon
$P$. We do so by overlaying a plane graph $G$ on $P$ as the solution space for
the schematic shape. Topological constraints imply that $S$ should describe a
simple polygon. We investigate two approaches, simple map matching and
connected face selection, based on commonly used similarity metrics.
  With the former, $S$ is a simple cycle $C$ in $G$ and we quantify resemblance
via the Fr\'echet distance. We prove that it is NP-hard to compute a cycle that
approximates the minimal Fr\'echet distance over all simple cycles in a plane
graph $G$. This result holds even if $G$ is a partial grid graph, if area
preservation is required and if we assume a given sequence of turns is
specified.
  With the latter, $S$ is a connected face set in $G$, quantifying resemblance
via the symmetric difference. Though the symmetric difference seems a less
strict measure, we prove that it is NP-hard to compute the optimal face set.
This result holds even if $G$ is full grid graph or a triangular or hexagonal
tiling, and if area preservation is required. Moreover, it is independent of
whether we allow the set of faces to have holes or not.


title:
Quantitative estimates on localized finite differences for the
  fractional Poisson problem, and applications to regularity and spectral
  stability

abstract:
  We establish new quantitative estimates for localized finite differences of
solutions to the Poisson problem for the fractional Laplace operator with
homogeneous Dirichlet conditions of solid type settled in bounded domains
satisfying the Lipschitz cone regularity condition. We then apply these
estimates to obtain (i)~regularity results for solutions of fractional Poisson
problems in Besov spaces; (ii)~quantitative stability estimates for solutions
of fractional Poisson problems with respect to domain perturbations;
(iii)~quantitative stability estimates for eigenvalues and eigenfunctions of
fractional Laplace operators with respect to domain perturbations.


title:
Optimal Scheduling of Reliability-Constrained Relaying System under
  Outdated CSI in the Finite Blocklength Regime

abstract:
  Under the assumption of outdated channel state information (CSI) at the
source, we consider the finite blocklength (FBL) throughput of a two-hop
relaying system. Previous work has considered this setting so far only for the
infinite blocklength case, where decoding can be arbitrarily reliable as long
as operating below the Shannon limit. In contrast, in the FBL regime residual
decoding errors can not be avoided even when transmitting below the Shannon
limit. This makes the scheduling problem at the source more vulnerable to
transmission errors, where we investigate the trade-off between the choice of
so called scheduling weights to avoid transmission errors and the resulting
coding rate. We show that the corresponding maximization of the throughput
under a reliability constraint can be solved efficiently by iterative
algorithms. Nevertheless, the optimal solution requires a recomputation of the
scheduling weights prior to each transmission. Thus, we also study heuristics
relying on choosing the scheduling weights only once. Through numerical
analysis, we first provide insights on the structure of the throughout under
different scheduling weights and channel correlation coefficients. We then turn
to the comparison of the optimal scheduling with the heuristic and show that
the performance gap between them is only significant for relay systems with
high average signal-to-noise ratios (SNR) on the backhaul and relaying link. In
particular, the optimal scheduling scheme provides most value in case that the
data transmission is subject to strict reliability constraints, justifying the
significant additional computational burden.


title:
Topologically slice knots that are not smoothly slice in any definite
  4-manifold

abstract:
  We prove that there exist infinitely many topologically slice knots which
cannot bound a smooth null-homologous disk in any definite 4-manifold.
Furthermore, we show that we can take such knots so that they are linearly
independent in the the knot concordance group.


title: First detection of gas-phase methanol in a protoplanetary disk

abstract:
  The first detection of gas-phase methanol in a protoplanetary disk (TW Hya)
is presented. In addition to being one of the largest molecules detected in
disks to date, methanol is also the first disk organic molecule with an
unambiguous ice chemistry origin. The stacked methanol emission, as observed
with ALMA, is spectrally resolved and detected across six velocity channels
($>3 \sigma$), reaching a peak signal-to-noise of $5.5\sigma$, with the
kinematic pattern expected for TW~Hya. Using an appropriate disk model, a
fractional abundance of $3\times 10^{-12} - 4 \times 10^{-11}$ (with respect to
H$_2$) reproduces the stacked line profile and channel maps, with the favoured
abundance dependent upon the assumed vertical location (midplane versus
molecular layer). The peak emission is offset from the source position
suggesting that the methanol emission has a ring-like morphology: the analysis
here suggests it peaks at $\approx 30$~AU reaching a column density $\approx
3-6\times10^{12}$~cm$^{-2}$. In the case of TW Hya, the larger (up to mm-sized)
grains, residing in the inner 50~AU, may thus host the bulk of the disk ice
reservoir. The successful detection of cold gas-phase methanol in a
protoplanetary disk implies that the products of ice chemistry can be explored
in disks, opening a window to studying complex organic chemistry during
planetary system formation.


title: Tukey Order, Calibres and the Rationals

abstract:
  One partially ordered set, $Q$, is a Tukey quotient of another, $P$, denoted
$P \geq_T Q$, if there is a map $\phi : P \to Q$ carrying cofinal sets of $P$
to cofinal sets of $Q$. Let $X$ be a space and denote by $\mathcal{K}(X)$ the
set of compact subsets of $X$, ordered by inclusion. For certain separable
metrizable spaces $M$, Tukey upper and lower bounds of $\mathcal{K}(M)$ are
calculated. Results on invariants of $\mathcal{K}(M)$'s are deduced. The
structure of all $\mathcal{K}(M)$'s under $\le_T$ is investigated. Particular
emphasis is placed on the position of $\mathcal{K}(M)$ when $M$ is: completely
metrizable, the rationals $\mathbb{Q}$, co-analytic or analytic.


title: New telescope designs suitable for massively-multiplexed spectroscopy

abstract:
  We present two novel designs for a telescope suitable for
massively-multiplexed spectroscopy. The first is a very wide field Cassegrain
telescope optimised for fibre feeding. It provides a Field Of View (FOV) of 2.5
degrees diameter with a 10m primary mirror. It is telecentric and works at F/3,
optimal for fibre injection. As an option, a gravity invariant focus for the
central 10 arc-minutes can be added, to host, for instance, a giant integral
field unit (IFU). It has acceptable performance in the 360-1300 nm wavelength
range. The second concept is an innovative five mirror telescope design based
on a Three Mirror Anastigmatic (TMA) concept. The design provides a large FOV
in a convenient, gravity- invariant focal plane, and is scalable to a range of
telescope diameters. As specific example, we present a 10m telescope with a 1.5
degree diameter FOV and a relay system that allows simultaneous spectroscopy
with 10,000 mini-IFUs over a square degree, or, alternatively a 17.5 square
arcminutes giant IFU, by using 240 MUSE-type spectrographs. We stress the
importance of developing the telescope and instrument designs for both cases.


title: Phoretic flow induced by asymmetric confinement

abstract:
  Internal phoretic flows due to the interactions of solid boundaries with
local chemical gradients may be created using chemical patterning.
Alternatively, we demonstrate here that internal flows might also be induced by
geometric asymmetries of chemically-homogeneous surfaces. We characterise the
circulatory flow created in a cavity enclosed between two eccentric cylindrical
walls of uniform chemical activity. Local gradients of the diffusing solute
induce a slip flow along the surface of the cylinders, leading to a circulatory
bulk flow pattern which can be solved analytically in the diffusive limit. The
flow strength can be controlled by adjusting the relative positions of the
cylinders and an optimal configuration is identified. These results provide a
model system for tunable phoretic pumps.


title:
Analytic solutions of the geodesic equation for U(1)^2 dyonic rotating
  black holes

abstract:
  In this article we derive the geodesic equations in the $\text{U(1)}^2$
dyonic rotating black hole spacetime. We present their solutions in terms of
the Kleinian $\sigma$-function and in special cases in terms of the
Weierstra{\ss} $\wp$-, $\sigma$- and $\zeta$-functions. To give a list of all
possible orbits, we analyse the geodesic motion of test particles and light
using parametric diagrams and effective potentials.


title:
Statistics of the two-point cross-covariance function of solar
  oscillations

abstract:
  Context: The cross-covariance of solar oscillations observed at pairs of
points on the solar surface is a fundamental ingredient in time-distance
helioseismology. Wave travel times are extracted from the cross-covariance
function and are used to infer the physical conditions in the solar interior.
Aims: Understanding the statistics of the two-point cross-covariance function
is a necessary step towards optimizing the measurement of travel times.
Methods: By modeling stochastic solar oscillations, we evaluate the variance of
the cross-covariance function as function of time-lag and distance between the
two points. Results: We show that the variance of the cross-covariance is
independent of both time-lag and distance in the far field, i.e., when they are
large compared to the coherence scales of the solar oscillations. Conclusions:
The constant noise level for the cross-covariance means that the
signal-to-noise ratio for the cross-covariance is proportional to the amplitude
of the expectation value of the cross-covariance. This observation is important
for planning data analysis efforts.


title:
Laplace-transformed atomic orbital-based M{\o}ller-Plesset perturbation
  theory for relativistic two-component Hamiltonians

abstract:
  We present a formulation of Laplace-transformed atomic orbital-based
second-order M{\o}ller-Plesset perturbation theory (MP2) energies for
two-component Hamiltonians in the Kramers-restricted formalism. This low-order
scaling technique can be used to enable correlated relativistic calculations
for large molecular systems. We show that the working equations to compute the
relativistic MP2 energy differ by merely a change of algebra (quaternion
instead of real) from their non-relativistic counterparts. With a
proof-of-principle implementation we study the effect of the nuclear charge on
the magnitude of half-transformed integrals and show that for light elements
spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we
investigate the effect of separation of charge distributions on the Coulomb and
exchange energy con- tributions, which show the same long-range decay with the
inter-electronic / atomic distance as for non-relativistic MP2. A linearly
scaling implementation is possible if the proper distance behavior is
introduced to the quaternion Schwarz-type estimates as for non-relativistic
MP2.


title: Mass dependence and isospin dependence of short-range correlated pairs

abstract:
  The target-mass number dependence of nucleon-nucleon pairs with short-range
correlations is explored in a physically transparent geometrical model within a
zero-range approximation. The observed $A$ dependence of 2-nucleon ejection
cross sections in $(e,e')$ reactions is found to reflect the mass dependence of
nuclear density distributions. A parametrization of this $A$ dependence is
given. The $A$ dependence of proton-proton vs.\ proton-neutron pairs relative
to $^{12}$C is also analyzed in this model. It can be understood using simple
combinatorics without any additional isospin dependence.


title:
On unified theory for scalar conservation laws with fluxes and sources
  discontinuous with respect to the unknown

abstract:
  We deal with the Cauchy problem for multi-dimensional scalar conservation
laws, where the fluxes and the source terms can be discontinuous functions of
the unknown. The main novelty of the paper is the introduction of a~kinetic
formulation for the considered problem. To handle the discontinuities we work
in the framework of re-parametrization of the flux and the source functions,
which was previously used for Kru\v{z}kov entropy solutions. Within this
approach we obtain a fairly complete picture: existence of entropy measure
valued solutions, entropy weak solutions and their equivalence to the kinetic
solution. The results of existence and uniqueness follow under the assumption
of H\"{o}lder continuity at zero of the flux. The source term, what is another
novelty for the studies on problems with discontinuous flux, is only assumed to
be one-side Lipschitz, not necessarily monotone function.


title:
Maximum entropy states of collisionless systems with long-range
  interaction and different degrees of mixing

abstract:
  Dynamics of many-particle systems with long-range interaction is
collisionless and governed by the Vlasov equation. This dynamics is a flow of a
six-dimensional incompressible liquid with uncountable integrals of motion. If
the flow possesses the statistical property of mixing, each liquid element
spreads over the entire accessible space. I derive the equilibrium
microcanonical maximum entropy states of this liquid for different degrees of
mixing $M$. This $M$ is the number of liquid elements which are statistically
independent. To count microstates of a liquid, I develop analog of the discrete
combinatorics for continuous systems by introducing the ensemble of phase
subspaces and making contact with the Shannon-McMillan-Breiman theorem from the
ergodic theory. If $M$ is much larger than the total number of particles $N$,
then the equilibrium distribution function (DF) is found to be exactly of the
Fermi-Dirac form. If the system is ergodic but without mixing, $M=0$, the DF is
a formal expression which coincides with the famous DF obtained by Lynden-Bell.
If the mixing is incomplete and $M\sim N$, the exponentials, which are present
in Lynden-Bell's DF, appear with certain weight given by the entropy of mixing.
For certainty, the \ long-range interaction is taken in the form of the Newton
and Coulomb potential in three dimensional space, but the applicability of the
method developed in the paper is not restricted to this case. The analogy of
the obtained statistics to the Fermi-Dirac statistics allows for expressing the
entropy of the system via its total energy and chemical potentials of liquid's
elements. The effect of the long-range interaction to the basic thermodynamic
relations is demonstrated.


title: Interpreting $W$ mass measurements in the SMEFT

abstract:
  Measurements of the $W^\pm$ mass ($m_W$) provide an important consistency
check of the Standard Model (SM) and constrain the possibility of physics
beyond the SM. Precision measurements of $m_W$ at hadron colliders are inferred
from kinematic distributions of transverse variables. We examine how this
inference is modified when considering the presence of physics beyond the SM
expressed in terms of local contact operators. We show that Tevatron
measurements of $m_W$ using transverse variables are transparent and applicable
as consistent constraints in the Standard Model Effective Field Theory (SMEFT)
with small measurement bias. This means that the leading challenge to
interpreting these measurements in the SMEFT is the pure theoretical
uncertainty in how these measurements are mapped to Lagrangian parameters. We
stress the need to avoid using naive combinations of Tevatron and LEPII
measurements of $m_W$ without the introduction of any SMEFT theoretical error
to avoid implicit UV assumptions. In a companion paper, we implement our
procedure to consistently incorporate $m_W$ measurements into a global fit.


title:
Valence Fluctuations in the Extended Anderson Lattice Model with
  Quasiperiodicity

abstract:
  We study valence fluctuations in the extended Anderson model on
two-dimensional Penrose lattice, using the real-space dynamical mean-field
theory combined with the continuous-time Monte Carlo method. Calculating
$f$-electron number, $c$-$f$ spin correlations, and magnetic susceptibility at
each site, we find site-dependent formations of the singlet state and valence
distribution at low temperatures, which are reflected by the quasiperiodic
lattice structure. The bulk magnetic susceptibility is also addressed.


title:
Transmit Beamforming for Interference Exploitation in the Underlay
  Cognitive Radio Z-channel

abstract:
  This paper introduces novel transmit beamforming approaches for the cognitive
radio (CR) Z-channel. The proposed transmission schemes exploit non-causal
information about the interference at the SBS to re-design the CR beamforming
optimization problem. This is done with the objective to improve the quality of
service (QoS) of secondary users by taking advantage of constructive
interference in the secondary link. The beamformers are designed to minimize
the worst secondary user's symbol error probability (SEP) under constraints on
the instantaneous total transmit power, and the power of the instantaneous
interference in the primary link. The problem is formulated as a bivariate
probabilistic constrained programming (BPCP) problem. We show that the BPCP
problem can be transformed for practical SEPs into a convex optimization
problem that can be solved, e.g., by the barrier method. A computationally
efficient tight approximate approach is also developed to compute the
near-optimal solutions. Simulation results and analysis show that the average
computational complexity per downlink frame of the proposed approximate problem
is comparable to that of the conventional CR downlink beamforming problem. In
addition, both the proposed methods offer significant performance improvements
as compared to the conventional CR downlink beamforming, while guaranteeing the
QoS of primary users on an instantaneous basis, in contrast to the average QoS
guarantees of conventional beamformers.


title:
Work, work fluctuations, and the work distribution in a thermal
  non-equilibrium steady state

abstract:
  Long-ranged correlations generically exist in non-equilibrium fluid systems.
In the case of a non-equilibrium steady state caused by a temperature gradient
the correlations are especially long-ranged and strong. The anomalous light
scattering predicted to exist in these systems is well-confirmed by numerous
experiments. Recently the Casimir force or pressure due to these fluctuations
or correlations have been discussed in great detail. In this paper the notion
of a Casimir work is introduced and a novel way to measure the non-equilibrium
Casimir force is suggested. In particular, the non-equilibrium Casimir force is
related to a non-equilibrium heat and not, as in equilibrium, to a volume
derivative of an average energy. The non-equilibrium work fluctuations are
determined and shown to be very anomalous compared to equilibrium work
fluctuations. The non-equilibrium work distribution is also computed, and
contrasted to work distributions in systems with short-range correlations.
Again, there is a striking difference in the two cases. Formal theories of work
and work distributions in non-equilibrium steady states are not explicit enough
to illustrate any of these interesting features.


title:
On the combined use of GW approximation and cumulant expansion in the
  calculations of quasiparticle spectra: The paradigm of Si valence bands

abstract:
  Since the earliest implementations of the various GW approximations and
cumulant expansion in the calculations of quasiparticle propagators and
spectra, several attempts have been made to combine the advantageous properties
and results of these two theoretical approaches. While the GW plus cumulant
approach has proven successful in interpreting photoemission spectroscopy data
in solids, the formal connection between the two methods has not been
investigated in detail. By introducing a general bijective integral
representation of the cumulants, we can rigorously identify at which point
these two approximations can be connected for the paradigmatic model of
quasiparticle interaction with the dielectric response of the system that has
been extensively exploited in recent interpretations of the satellite
structures in photoelectron spectra. We establish a protocol for consistent
practical implementation of the thus established GW+cumulant scheme, and
illustrate it by comprehensive state-of-the-art first-principles calculations
of intrinsic angle-resolved photoemission spectra from Si valence bands.


title: Coherent vs. measurement-based feedback for controlling a single qubit

abstract:
  We compare the performance of continuous coherent feedback, implemented using
an ideal single-qubit controller, to that of continuous measurement-based
feedback for the task of controlling the state of a single qubit. Here the
basic dynamical resource is the ability to couple the system to a
traveling-wave field (for example, a transmission line) via a system
observable, and the fundamental limitation is the maximum rate that is
available for this coupling. We focus on the question of the best achievable
control given ideal controllers. To obtain a fair comparison we acknowledge
that the amplification involved in measurement-based control allows the
controller to use macroscopic fields to apply feedback forces to the system, so
it is natural to allow these feedback forces to be much larger than the
mesoscopic coupling to the transmission line that mediates both the measurement
for measurement-based control and the coupling to the mesoscopic controller for
coherent control. Interestingly our numerical results indicate that under the
above platform for comparison, coherent feedback is able to exactly match the
performance of measurement-based feedback given ideal controllers. We also
discuss various properties of, and control mechanisms for, coherent feedback
networks.


title: Fast and accurate normalization of vectors and quaternions

abstract:
  We present fast and accurate ways to normalize two and three dimensional
vectors and quaternions and compute their length. Our approach is an adaptation
of ideas used in the linear algebra library LAPACK, and we believe that the
computational geometry and computer aided design communities are not aware of
the possibility of speeding up these fundamental operations in the robust way
proposed here.


title: User fluctuation in communities: a forum case

abstract:
  Understanding fluctuation of users help stakeholders to provide a better
support to communities. Below we present an experiment where we detect
communities, their evolution and based on the data characterize users that
stay, leave or join a community. Using a resulted feature set and logistic
regression we operate with models of users that are joining and users that are
staying in a community. In the related work we emphasize a number of features
we will include in our future experiments to enhance train accuracy. This work
represents a first from a series of experiments devoted to user fluctuation in
communities.


title:
Opportunities for Price Manipulation by Aggregators in Electricity
  Markets

abstract:
  Aggregators are playing an increasingly crucial role in the integration of
renewable generation in power systems. However, the intermittent nature of
renewable generation makes market interactions of aggregators difficult to
monitor and regulate, raising concerns about potential market manipulation by
aggregators. In this paper, we study this issue by quantifying the profit an
aggregator can obtain through strategic curtailment of generation in an
electricity market. We show that, while the problem of maximizing the benefit
from curtailment is hard in general, efficient algorithms exist when the
topology of the network is radial (acyclic). Further, we highlight that
significant increases in profit are possible via strategic curtailment in
practical settings.


title: Literature survey on low rank approximation of matrices

abstract:
  Low rank approximation of matrices has been well studied in literature.
Singular value decomposition, QR decomposition with column pivoting, rank
revealing QR factorization (RRQR), Interpolative decomposition etc are
classical deterministic algorithms for low rank approximation. But these
techniques are very expensive $(O(n^{3})$ operations are required for $n\times
n$ matrices). There are several randomized algorithms available in the
literature which are not so expensive as the classical techniques (but the
complexity is not linear in n). So, it is very expensive to construct the low
rank approximation of a matrix if the dimension of the matrix is very large.
There are alternative techniques like Cross/Skeleton approximation which gives
the low-rank approximation with linear complexity in n . In this article we
review low rank approximation techniques briefly and give extensive references
of many techniques.


title: Graphical Models for Optimal Power Flow

abstract:
  Optimal power flow (OPF) is the central optimization problem in electric
power grids. Although solved routinely in the course of power grid operations,
it is known to be strongly NP-hard in general, and weakly NP-hard over tree
networks. In this paper, we formulate the optimal power flow problem over tree
networks as an inference problem over a tree-structured graphical model where
the nodal variables are low-dimensional vectors. We adapt the standard dynamic
programming algorithm for inference over a tree-structured graphical model to
the OPF problem. Combining this with an interval discretization of the nodal
variables, we develop an approximation algorithm for the OPF problem. Further,
we use techniques from constraint programming (CP) to perform interval
computations and adaptive bound propagation to obtain practically efficient
algorithms. Compared to previous algorithms that solve OPF with optimality
guarantees using convex relaxations, our approach is able to work for arbitrary
distribution networks and handle mixed-integer optimization problems. Further,
it can be implemented in a distributed message-passing fashion that is scalable
and is suitable for "smart grid" applications like control of distributed
energy resources. We evaluate our technique numerically on several benchmark
networks and show that practical OPF problems can be solved effectively using
this approach.

categories: cs.SY cs.AI cs.CE math.OC physics.soc-ph


title: Proceedings of the 7th International Workshop on Physics and Computation

abstract:
  This volume constitutes the proceedings of the 7th International Workshop on
Physics and Computation (PC 2016). The workshop was held on the 14th of July
2016 in Manchester, UK, as a satellite workshop to UCNC 2016, the 15th
International Conference on Unconventional Computation and Natural Computation.
  The goal of the workshop series is to bring together researches working on
the interaction between physics and the theory of computation. This
intrinsically interdisciplinary domain of research strives to go beyond the
traditional use of mathematics as a tool to model and understand the behaviour
of physical systems. Instead, it looks to the the theory of computation and
information to provide new insights into physical systems and processes, and,
in turn, how these insights can lead to new methods, models and notation of
computation and new approaches to computational and mathematical problems.
Topics falling into this category at the interface of physics and computation
that are within the scope of the conference include, amongst many others, the
axiomatisation of physics, hypercomputation, the role of information in
physical systems, quantum information, randomness in physics, theories of
measurement, and the philosophy of physics and computation.


title: Response of a spin valve to a spin battery

abstract:
  It is shown that spin valves under suitable symmetry conditions exhibit an
ON-OFF response to a spin battery, and are therefore perfect spin transistors.
While a spin valve driven by a charge battery displays the usual GMR (Giant
Magneto-Resistance), this means that a pure spin current or pure spin
accumulation can generate an infinite magnetoresistance (IMR). Magnetic tunnel
junctions as well as CPP (current perpendicular to plane) or CIP (current in
plane) metallic trilayers are discussed.


title:
Superspace Gauge Fixing in Yang-Mills Matter Coupled Conformal
  Supergravity

abstract:
  In $D=4$, $\cal{N}=1$ conformal superspace, the Yang-Mills matter coupled
supergravity system is constructed where the Yang-Mills gauge interaction is
introduced by extending the superconformal group to include the K\"ahler
isometry group of chiral matter fields. There are two gauge-fixing procedures
to get to the component Poincar\'e supergravity: one via the superconformal
component formalism and the other via the Poincar\'e superspace formalism.
These two types of superconformal gauge-fixing conditions are analyzed in
detail and their correspondence is clarified.


title:
Experimental evidence of effective <111> atomic exchanges in a B2
  intermetallic alloy

abstract:
  We report on an atomic-scale X-ray Photon Correlation Spectroscopy study on
Fe-rich FeAl in the B2-ordered regime revealing effective <111>-exchanges of
atoms on the Al-sublattice. The diffusion mechanism responsible for these
exchanges is the dominating process for chemical diffusion and therefore
controls long-range material transport in the system. Comparison with previous
atomistic results shows that the dominance of further exchanges can be
characteristic at moderate temperatures where the system is highly ordered.


title: On some differences between number fields and function fields

abstract:
  The analogy between the arithmetic of varieties over number fields and the
arithmetic of varieties over function fields is a leading theme in arithmetic
geometry. This analogy is very powerful but there are some gaps. In this note
we will show how the presence of isotrivial varieties over function fields (the
analogous of which do not seems to exist over number fields) breaks this
analogy. Some counterexamples to a statement similar to Northcott Theorem are
proposed. In positive characteristic, some explicit counterexamples to
statements similar to Lang and Vojta conjectures are given.


title: A remark on the convergence of Betti numbers in the thermodynamic regime

abstract:
  The convergence of the expectations of Betti numbers of \v{C}ech complexes
built on binomial point processes in the thermodynamic regime is established.


title: Kernel Spectral Clustering

abstract:
  We investigate the question of studying spectral clustering in a Hilbert
space where the set of points to cluster are drawn i.i.d. according to an
unknown probability distribution whose support is a union of compact connected
components. We modify the algorithm proposed by Ng, Jordan and Weiss in order
to propose a new algorithm that automatically estimates the number of clusters
and we characterize the convergence of this new algorithm in terms of
convergence of Gram operators. We also give a hint of how this approach may
lead to learn transformation-invariant representations in the context of image
classification.


title:
Emergent lattices with geometrical frustration in doped extended Hubbard
  models

abstract:
  Spontaneous charge ordering occurring in correlated systems may be considered
as a possible route to generate effective lattice structures with
unconventional couplings. For this purpose we investigate the phase diagram of
doped extended Hubbard models on two lattices: (i) the honeycomb lattice with
on-site $U$ and nearest-neighbor $V$ Coulomb interactions at $3/4$ filling
($n=3/2$) and (ii) the triangular lattice with on-site $U$, nearest-neighbor
$V$, and next-nearest-neighbor $V'$ Coulomb interactions at $3/8$ filling
($n=3/4$). We consider various approaches including mean-field approximations,
perturbation theory, and variational Monte Carlo. For the honeycomb case (i),
charge order induces an effective triangular lattice at large values of $U/t$
and $V/t$, where $t$ is the nearest-neighbor hopping integral. The
nearest-neighbor spin exchange interactions on this effective triangular
lattice are antiferromagnetic in most of the phase diagram, while they become
ferromagnetic when $U$ is much larger than $V$. At $U/t\sim (V/t)^3$,
ferromagnetic and antiferromagnetic exchange interactions nearly cancel out,
leading to a system with four-spin ring-exchange interactions. On the other
hand, for the triangular case (ii) at large $U$ and finite $V'$, we find no
charge order for small $V$, an effective kagome lattice for intermediate $V$,
and one-dimensional charge order for large $V$. These results indicate that
Coulomb interactions induce [case (i)] or enhance [case(ii)] emergent
geometrical frustration of the spin degrees of freedom in the system, by
forming charge order.


title: CUB models: a preliminary fuzzy approach to heterogeneity

abstract:
  In line with the increasing attention paid to deal with uncertainty in
ordinal data models, we propose to combine Fuzzy models with \cub models within
questionnaire analysis. In particular, the focus will be on \cub models'
uncertainty parameter and its interpretation as a preliminary measure of
heterogeneity, by introducing membership, non-membership and uncertainty
functions in the more general framework of Intuitionistic Fuzzy Sets. Our
proposal is discussed on the basis of the Evaluation of Orientation Services
survey collected at University of Naples Federico II.


title:
Likelihood analysis for a class of spatial geostatistical compositional
  models

abstract:
  We propose a model-based geostatistical approach to deal with regionalized
compositions. We combine the additive-log-ratio transformation with
multivariate geostatistical models whose covariance matrix is adapted to take
into account the correlation induced by the compositional structure. Such
specification allows the usage of standard likelihood methods for parameters
estimation. For spatial prediction we combined a back-transformation with the
Gauss-Hermite method to approximate the conditional expectation of the
compositions. We analyze particle size fractions of the top layer of a soil for
agronomic purposes which are typically expressed as proportions of sand, clay
and silt. Additionally a simulation study assess the small sample properties of
the maximum likelihood estimator.


title:
Copper-Doped Colloidal Semiconductor Quantum Wells for Luminescent Solar
  Concentrators

abstract:
  Doping of bulk semiconductors has revealed widespread success in
optoelectronic applications. In the past few decades, substantial effort has
been engaged for doping at the nanoscale. Recently, doped zero-dimensional
quantum dots made of semiconductor nanocrystals have been demonstrated to be
promising materials for luminescent solar concentrators (LSCs) as they can be
engineered for providing Stokes-shifted tunable emission in the solar spectrum.
However, existing doped colloidal quantum dots suffer from moderately low
quantum efficiency and intrinsically small absorption cross-section, which
together fundamentally limit their effective usage. Here, we show the first
account of copper doping into two-dimensional atomically flat CdSe colloidal
quantum wells. Copper doping via post-synthesis partial cation exchange into
3-5 monolayers of CdSe and CdSe/CdS core-shell colloidal quantum wells (CQWs)
enables Stokes-shifted, tunable dopant induced highly efficient
photoluminescence emission having high quantum efficiencies (>43%), accompanied
by an order of magnitude higher absorption cross-section than that of the doped
quantum dots. Based on these exceptional properties, we demonstrated a flexible
prototype luminescent solar concentrators using these newly synthesized doped
colloidal quantum wells. These findings may open up new directions for
deployment of CQWs in LSCs for advanced solar light harvesting technologies.


title:
Level sequence and splitting identification of closely-spaced energy
  levels by angle-resolved analysis of the fluorescence light

abstract:
  The angular distribution and linear polarization of the fluorescence light
following the resonant photoexcitation is investigated within the framework of
the density matrix and second-order perturbation theory. Emphasis has been
placed on "signatures" for determining the level sequence and splitting of
intermediate (partially) overlapping resonances, if analyzed as a function of
the photon energy of the incident light. Detailed computations within the
multiconfiguration Dirac-Fock method have been performed especially for the
$1s^{2}2s^{2}2p^{6}3s\;\, J_{i}=1/2 \,+\, \gamma_{1} \:\rightarrow\:
(1s^{2}2s2p^{6}3s)_{1}3p_{3/2}\;\, J=1/2, \, 3/2
  \:\rightarrow\: 1s^{2}2s^{2}2p^{6}3s\;\, J_{f}=1/2 \,+\, \gamma_{2}$
photoexcitation and subsequent fluorescence emission of atomic sodium. A
remarkably strong dependence of the angular distribution and linear
polarization of the $\gamma_{2}$ fluorescence emission is found upon the level
sequence and splitting of the intermediate $(1s^{2}2s2p^{6}3s)_{1}3p_{3/2}\;\,
J=1/2, \, 3/2$ overlapping resonances owing to their finite lifetime
(linewidth). We therefore suggest that accurate measurements of the angular
distribution and linear polarization might help identify the sequence and small
splittings of closely-spaced energy levels, even if they can not be
spectroscopically resolved.


title: A tensorial description of particle perception in black-hole physics

abstract:
  In quantum field theory in curved backgrounds, one typically distinguishes
between objective, tensorial, quantities such as the Renormalized Stress-Energy
Tensor (RSET) and subjective, non-tensorial, quantities such as Bogoliubov
coefficients which encode perception effects associated with the specific
trajectory of a detector. In this work we propose a way to treat both objective
and subjective notions on an equal tensorial footing. For that purpose, we
define a new tensor which we will call the Perception Renormalized
Stress-Energy Tensor (PeRSET). The PeRSET is defined as the subtraction of the
RSET corresponding to two different vacuum states. Based on this tensor we can
define perceived energy densities and fluxes. The PeRSET helps to have a more
organized and systematic understanding of various results in the literature
regarding quantum field theory in black hole spacetimes. We illustrate the
physics encoded in this tensor by working out various examples of special
relevance.


title: Implications of the Gravitational Wave Event GW150914

abstract:
  The era of gravitational-wave astronomy began on 14 September 2015, when the
LIGO Scientific Collaboration detected the merger of two $\sim 30 M_\odot$
black holes at a distance of $\sim 400$ Mpc. This event has facilitated
qualitatively new tests of gravitational theories, and has also produced
exciting information about the astrophysical origin of black hole binaries. In
this review we discuss the implications of this event for gravitational physics
and astrophysics, as well as the expectations for future detections. In brief:
(1) because the spins of the black holes could not be measured accurately and
because mergers are not well calculated for modified theories of gravity, the
current analysis of GW150914 does not place strong constraints on gravity
variants that change only the generation of gravitational waves, but (2) it
does strongly constrain alterations of the propagation of gravitational waves
and alternatives to black holes. Finally, (3) many astrophysical models for the
origin of heavy black hole binaries such as the GW150914 system are in play,
but a reasonably robust conclusion that was reached even prior to the detection
is that the environment of such systems needs to have a relatively low
abundance of elements heavier than helium.


title: Dynamical properties of bidirectional charge-density-waves in ErTe$_3$

abstract:
  We report a strong difference in the sliding properties of the bidirectional
charge density wave (CDW) in the two-dimensional rare earth tritelluride
ErTe$_3$ which occurs below $T_{CDW1}=265$ K with a wave vector along $c$-axis
and below $T_{CDW2}=165$ K with a wave vector along $a$-axis; the excess
current carried by the motion of the CDW is 10 times less for the lower CDW
compared with the value of the upper one. We tentatively explain this result by
a stronger pinning of the lower temperature CDW intricated with the upper one,
which inhibits its motion and may generate a phase slippage lattice.


title:
Single-diffractive production of charmed mesons at the LHC within the
  $k_t$-factorization approach

abstract:
  We discuss the single diffractive production of $c \bar c$ pairs and charmed
mesons at the LHC. For a first time we propose a $k_t$-factorization approach
to the diffractive processes. The transverse momentum dependent diffractive
parton distributions are obtained from standard (collinear) diffractive parton
distributions used in the literature. In this calculation the transverse
momentum of the pomeron is neglected with respect to transverse momentum of
partons entering the hard process. We also perform the first evaluation of the
cross sections at the LHC using the diffractive transverse momentum dependent
parton distributions. The results of the new approach are compared with those
of the standard collinear one. Significantly larger cross sections are obtained
in the $k_t$-factorization approach where some part of higher-order effects is
effectively included. The differences between corresponding differential
distributions are discussed. Finally, we present a feasibility study of the
process at the LHC using proton tagging technique. The analysis suggests that
the measurement of single diffractive charm production is possible using ATLAS
and CMS/TOTEM detectors.


title:
Uniqueness of the scatterer for electromagnetic field with one incident
  plane wave

abstract:
  In this paper, we solve a longstanding open problem for determining the shape
of an obstacle from the knowledge of the electric (or magnetic) far field
pattern for the scattering of time-harmonic electromagnetic field. We show that
the electric (or magnetic) far field patten
${\mathbf{E}}^\infty(\boldsymbol{\beta}, {\boldsymbol{\alpha}}_0, k_0)$ (or
${\mathbf{H}}^\infty (\boldsymbol{\beta}, {\boldsymbol{\alpha}}_0, k_0)$),
known for all $\boldsymbol{\beta}\in {\mathbb S}^2$, where ${\mathbb {S}}^2$ is
the unit sphere in ${\mathbb{R}}^3$, ${\boldsymbol{\alpha}}_0\in
{\mathbb{S}}^2$ is fixed, $k_0>0$ is fixed, determines the obstacle $D$ and the
boundary condition on $\partial D$ uniquely. The boundary condition on
$\partial D$ is either the perfect conductor or the impedance one.


title: New kids on the block: an analysis of modern blockchains

abstract:
  Half a decade after Bitcoin became the first widely used cryptocurrency,
blockchains are receiving considerable interest from industry and the research
community. Modern blockchains feature services such as name registration and
smart contracts. Some employ new forms of consensus, such as proof-of-stake
instead of proof-of-work. However, these blockchains are so far relatively
poorly investigated, despite the fact that they move considerable assets. In
this paper, we explore three representative, modern blockchains---Ethereum,
Namecoin, and Peercoin. Our focus is on the features that set them apart from
the pure currency use case of Bitcoin. We investigate the blockchains' activity
in terms of transactions and usage patterns, identifying some curiosities in
the process. For Ethereum, we are mostly interested in the smart contract
functionality it offers. We also carry out a brief analysis of issues that are
introduced by negligent design of smart contracts. In the case of Namecoin, our
focus is how the name registration is used and has developed over time. For
Peercoin, we are interested in the use of proof-of-stake, as this consensus
algorithm is poorly understood yet used to move considerable value. Finally, we
relate the above to the fundamental characteristics of the underlying
peer-to-peer networks. We present a crawler for Ethereum and give statistics on
the network size. For Peercoin and Namecoin, we identify the relatively small
size of the networks and the weak bootstrapping process.


title:
Thermodynamics and holographic entanglement entropy for spherical black
  holes in 5D Gauss-Bonnet gravity

abstract:
  The holographic entanglement entropy is studied numerically in
(4+1)-dimensional spherically symmetric Gauss-Bonnet AdS black hole spacetime
with compact boundary. On the bulk side the black hole spacetime undergoes a
van der Waals-like phase transition in the extended phase space, which is
reviewed with emphasis on the behavior on the temperature-entropy plane. On the
boundary, we calculated the regularized HEE of a disk region of different
sizes. We find strong numerical evidence for the failure of equal area law for
isobaric curves on the temperature-HEE plane and for the correctness of first
law of entanglement entropy, and briefly give an explanation for why the latter
may serve as a reason for the former, i.e. the failure of equal area law on the
temperature-HEE plane.


title:
Eulerian triangulations: two-point function and hull perimeter
  statistics

abstract:
  We present a new derivation of the distance-dependent two-point function for
planar Eulerian triangulations and give expressions for more refined generating
functions where we also control hull perimeters. These results are obtained in
the framework of a new recursion relation for slice generating functions and
extend similar results obtained recently for triangulations and
quadrangulations. A number of explicit formulas are given for the statistics of
hull perimeters in infinitely large random planar Eulerian triangulations.


title:
Stochastic homogenization of nonconvex discrete energies with degenerate
  growth

abstract:
  We study the continuum limit of discrete, nonconvex energy functionals
defined on crystal lattices in dimensions $d\geq 2$. Since we are interested in
energy functionals with random (stationary and ergodic) pair interactions, our
problem corresponds to a stochastic homogenization problem. In the
non-degenerate case, when the interactions satisfy a uniform $p$-growth
condition, the homogenization problem is well-understood. In this paper, we are
interested in a degenerate situation, when the interactions neither satisfy a
uniform growth condition from above nor from below. We consider interaction
potentials that obey a $p$-growth condition with a random growth weight
$\lambda$. We show that if $\lambda$ satisfies the moment condition $\mathbb
E[\lambda^\alpha+\lambda^{-\beta}]<\infty$ for suitable values of $\alpha$ and
$\beta$, then the discrete energy $\Gamma$-converges to an integral functional
with a non-degenerate energy density. In the scalar case it suffices to assume
that $\alpha\geq 1$ and $\beta\geq\frac{1}{p-1}$ (which is just the condition
that ensures the non-degeneracy of the homogenized energy density). In the
general, vectorial case, we additionally require that $\alpha>1$ and
$\frac{1}{\alpha}+\frac{1}{\beta}\leq \frac{p}{d}$. Recently, there has been
considerable effort to understand periodic and stochastic homogenization of
elliptic equations and integral functionals with degenerate growth, as well as
related questions on the effective behavior of conductance models in
degenerate, random environments. The results in the present paper are to our
knowledge the first stochastic homogenization results for nonconvex energy
functionals with degenerate growth under moment conditions.


title: Equivalent Higher-order Guiding-center Hamiltonian Theories

abstract:
  Equivalent guiding-center Hamiltonian theories are constructed based on
higher-order Lie-transform perturbation methods. Higher-order guiding-center
theories are distinguished on the basis of whether correction terms associated
with magnetic-field nonuniformity appear either in the guiding-center
symplectic (Poisson-bracket) structure, in the guiding-center Hamiltonian, or
both. These theories are called equivalent because they describe the same
guiding-center magnetic-moment invariant. The present work presents the
detailed derivations of results that were summarized in a recent paper by
Tronko and Brizard [Phys. Plasmas 22, 112507 (2015)].


title:
On lifting and modularity of reducible residual Galois representations
  over imaginary quadratic fields

abstract:
  In this paper we study deformations of mod $p$ Galois representations $\tau$
(over an imaginary quadratic field $F$) of dimension $2$ whose
semi-simplification is the direct sum of two characters $\tau_1$ and $\tau_2$.
As opposed to our previous work we do not impose any restrictions on the
dimension of the crystalline Selmer group $H^1_{\Sigma}(F, {\rm Hom}(\tau_2,
\tau_1)) \subset {\rm Ext}^1(\tau_2, \tau_1)$. We establish that there exists a
basis $\mathcal{B}$ of $H^1_{\Sigma}(F, {\rm Hom}(\tau_2, \tau_1))$ arising
from automorphic representations over $F$ (Theorem 8.1). Assuming among other
things that the elements of $\mathcal{B}$ admit only finitely many crystalline
characteristic 0 deformations we prove a modularity lifting theorem asserting
that if $\tau$ itself is modular then so is its every crystalline
characteristic zero deformation (Theorems 8.2 and 8.5).


title: Asymptotics of heights in random trees constructed by aggregation

abstract:
  To each sequence $(a_n)$ of positive real numbers we associate a growing
sequence $(T_n)$ of continuous trees built recursively by gluing at step $n$ a
segment of length $a_n$ on a uniform point of the pre-existing tree, starting
from a segment $T_1$ of length $a_1$. Previous works on that model focus on the
influence of $(a_n)$ on the compactness and Hausdorff dimension of the limiting
tree. Here we consider the cases where the sequence $(a_n)$ is regularly
varying with a non-negative index, so that the sequence $(T_n)$ exploses. We
determine the asymptotics of the height of $T_n$ and of the subtrees of $T_n$
spanned by the root and $\ell$ points picked uniformly at random and
independently in $T_n$, for all $\ell \in \mathbb N$.


title: Emergent two-Higgs doublet models

abstract:
  We investigate origin of three features that are often assumed in analysis of
two-Higgs doublet models: (i) softly broken Z2 symmetry, (ii) CP invariant
Higgs potential, and (iii) degenerated mass spectra. We extend electroweak
gauge symmetry, introducing extra gauge symmetry and extra scalars, and we show
that our models effectively derive two-Higgs dou- blet models at low energy
which naturally hold the three features. We also find that the models can solve
the strong CP problem.


title:
Correlations of conserved number mixed susceptibilities in a hadron
  resonance gas model

abstract:
  The ratios of off-diagonal and diagonal susceptibilities of conserved charges
are studied using a hadron resonance gas (HRG) model with an emphasis towards
providing a proper baseline for comparison to the corresponding future
experimental measurements. We have studied the effect of kinematic acceptances,
transverse momentum ($p_T$) and pseudorapidity ($\eta$), and different charged
states on the ratios of the calculated susceptibilities. We find that the
effect of $p_T$ and $\eta$ acceptance on the ratio of the susceptibilities are
small relative to their dependence on the beam energy or the charged states of
the used particles. We also present a HRG based calculation for various
combinations of cumulant ratios of protons and pions, recently proposed as
robust observables (with no theoretical uncertainties) for critical point
search in the experiments. These results which increase as a function of
collision energy will provide a better baseline for non-critical point physics
compared to Poisson expectation.