title: Energy calculations of charged point defects on surfaces

abstract:
  We present a virtual ionic crystal (VIC) method to calculate energies of
charged point defects on surfaces. No artificial charge but an actual
zero-dimensional (0D) species is introduced to charge a defect. Effect of
dielectric substrate on lattice energy is depressed through suitable
configuration of the unit cell. The lattice energy approximates to Madelung
energy with defect and 0D species considered as point charges in vacuum. Energy
required to charge the defect is derived from charge quantity on the defect in
VIC, energy of unit cell, and energy required to charge the 0D species.


title: Early Decay of Peccei-Quinn Fermion and the IceCube Neutrino Events

abstract:
  IceCube observed high-energy neutrino flux in the energy region from TeV to
PeV. The decay of a massive long-lived particle in the early universe can be
the origin of the IceCube neutrino events, which we call an "early decay
scenario." In this paper, we construct a particle physics model that contains
such a massive long-lived particle based on the Peccei-Quinn model. We
calculate the present neutrino flux, taking account of realistic initial energy
distributions of particles produced by the decay of the massive long-lived
particle. We show that the early decay scenario naturally fits into the
Peccei-Quinn model, and that the neutrino flux observed by IceCube can be
explained in such a framework. We also see that, based on that model, a
consistent cosmological history that explains the abundance of the massive
long-lived particle is realized.


title: Superconformal minimal models and admissible Jack polynomials

abstract:
  We give new proofs of the rationality of the N=1 superconformal minimal model
vertex operator superalgebras and of the classification of their modules in
both the Neveu-Schwarz and Ramond sectors. For this, we combine the standard
free field realisation with the theory of Jack symmetric functions. A key role
is played by Jack symmetric polynomials with a certain negative parameter that
are labelled by admissible partitions. These polynomials are shown to describe
free fermion correlators, suitably dressed by a symmetrising factor. The
classification proofs concentrate on explicitly identifying Zhu's algebra and
its twisted analogue. Interestingly, these identifications do not use an
explicit expression for the non-trivial vacuum singular vector. While the
latter is known to be expressible in terms of an Uglov symmetric polynomial or
a linear combination of Jack superpolynomials, it turns out that standard Jack
polynomials (and functions) suffice to prove the classification.


title: On interaction-free measurement

abstract:
  This manuscript is inspired by the paper [2]. In the paper, they investigate
a method to detect existence of an object with arbitrarily small interaction.
Below, we sketch their protocol to motivate the present manuscript. The object
of their protocol is to detect whether the given blackbox interact with input
states or not, with negligible distortion of the blackbox, and high detection
probability. In this paper, we do two things. First, we prove the above
mentioned protocol is optimal in a certain setting. The main tool here is
adversary method, a classical method in query complexity. Second, we present a
protocol to detect unitary operations with negligible error and no distortion
of the input at all.


title: Inverting face embeddings with convolutional neural networks

abstract:
  Deep neural networks have dramatically advanced the state of the art for many
areas of machine learning. Recently they have been shown to have a remarkable
ability to generate highly complex visual artifacts such as images and text
rather than simply recognize them.
  In this work we use neural networks to effectively invert low-dimensional
face embeddings while producing realistically looking consistent images. Our
contribution is twofold, first we show that a gradient ascent style approaches
can be used to reproduce consistent images, with a help of a guiding image.
Second, we demonstrate that we can train a separate neural network to
effectively solve the minimization problem in one pass, and generate images in
real-time. We then evaluate the loss imposed by using a neural network instead
of the gradient descent by comparing the final values of the minimized loss
function.


title:
Micro-interventions in urban transport from pattern discovery on the
  flow of passengers and on the bus network

abstract:
  In this paper, we describe a case study in a big metropolis, in which from
data collected by digital sensors, we tried to understand mobility patterns of
persons using buses and how this can generate knowledge to suggest
interventions that are applied incrementally into the transportation network in
use. We have first estimated an Origin-Destination matrix of buses users from
datasets about the ticket validation and GPS positioning of buses. Then we
represent the supply of buses with their routes through bus stops as a complex
network, which allowed us to understand the bottlenecks of the current scenario
and, in particular, applying community discovery techniques, to identify
clusters that the service supply infrastructure has. Finally, from the
superimposing of the flow of people represented in the OriginDestination matrix
in the supply network, we exemplify how micro-interventions can be prospected
by means of an example of the introduction of express routes.


title:
Path-Following Algorithms for Beamforming and Signal Splitting in RF
  Energy Harvesting Networks

abstract:
  We consider the joint design of transmit beamforming and receive
signal-splitting ratios in the downlink of a wireless network with simultaneous
radio-frequency (RF) information and energy transfer. Under constraints on the
signal-to-interference-plus-noise ratio (SINR) at each user and the total
transmit power at the base station, the design objective is to maximize either
the sum harvested energy or the minimum harvested energy. We develop a
computationally efficient path-following method to solve these challenging
nonconvex optimization problems. We mathematically show that the proposed
algorithms iteratively progress and converge to locally optimal solutions.
Simulation results further show that these locally optimal solutions are the
same as the globally optimal solutions for the considered practical network
settings.


title:
Chiral phase transitions in the linear sigma model in the Tsallis
  nonextensive statistics

abstract:
  We studied chiral phase transitions in the Tsallis nonextensive statistics
which has two parameters, the temperature $T$ and entropic parameter $q$. The
linear sigma model was used in this study. The critical temperature,
condensate, masses, and energy density were calculated under the massless free
particle approximation. The critical temperature decreases as $q$ increases.
The condensate at $q>1$ is smaller than that at $q=1$. The sigma mass at $q>1$
is heavier than the mass at $q=1$ at high temperature, while the sigma mass at
$q>1$ is lighter than the mass at $q=1$ at low temperature. The pion mass at
$q>1$ is heavier than the mass at $q=1$. The energy density increases
remarkably as $q$ increases. The $q$ dependence in the case of the
$q$-expectation value is weaker than that in the case of the conventional
expectation value with a Tsallis distribution. The parameter $q$ should be
smaller than $4/3$ from energetic point of view. The validity of the Tsallis
statistics can be determined by the difference in $q$ of the restriction for
$5/4 < q < 4/3$ when the interaction is weak, because the parameter $q$ is
smaller than $5/4$ in the case of the conventional expectation value with a
Tsallis distribution.


title: Small flow-time representation of fermion bilinear operators

abstract:
  Fermion bilinear operators of mass dimension~$3$, such as the axial-vector
and vector currents, the pseudo-scalar and scalar densities, whose
normalizations are fixed by Ward--Takahashi (WT) relations, are related to
small flow-time behavior of composite operators of fermion fields evolved by
L\"uscher's flow equation. The representations can be useful in lattice
numerical simulations, as recently demonstrated by the WHOT QCD collaboration
for the chiral condensation of the $N_f=2+1$ quantum chromodynamics (QCD) at
finite temperature.


title: Cut-elimination for SBL

abstract:
  In this paper we give a terminating cut-elimination procedure for a logic
calculus SBL. SBL corresponds to the second order arithmetic
Pi^{1}_{2}-Separation and Bar Induction.


title: Social- and Mobility-Aware Device-to-Device Content Delivery

abstract:
  Mobile online social network services have seen a rapid increase, in which
the huge amount of user-generated social media contents propagating between
users via social connections has significantly challenged the traditional
content delivery paradigm: First, replicating all of the contents generated by
users to edge servers that well "fit" the receivers becomes difficult due to
the limited bandwidth and storage capacities. Motivated by device-to-device
(D2D) communication that allows users with smart devices to transfer content
directly, we propose replicating bandwidth-intensive social contents in a
device-to-device manner. Based on large-scale measurement studies on social
content propagation and user mobility patterns in edge-network regions, we
observe that (1) Device-to-device replication can significantly help users
download social contents from nearby neighboring peers; (2) Both social
propagation and mobility patterns affect how contents should be replicated; (3)
The replication strategies depend on regional characteristics ({\em e.g.}, how
users move across regions).
  Using these measurement insights, we propose a joint \emph{propagation- and
mobility-aware} content replication strategy for edge-network regions, in which
social contents are assigned to users in edge-network regions according to a
joint consideration of social graph, content propagation and user mobility. We
formulate the replication scheduling as an optimization problem and design
distributed algorithm only using historical, local and partial information to
solve it. Trace-driven experiments further verify the superiority of our
proposal: compared with conventional pure movement-based and popularity-based
approach, our design can significantly ($2-4$ times) improve the amount of
social contents successfully delivered by device-to-device replication.


title: Oscillatory Motion of a Camphor Grain in a One-Dimensional Finite Region

abstract:
  The motion of a self-propelled particle is affected by its surroundings, such
as boundaries or external fields. In this paper, we investigated the
bifurcation of the motion of a camphor grain, as a simple actual self-propelled
system, confined in a one-dimensional finite region. A camphor grain exhibits
oscillatory motion or remains at rest around the center position in a
one-dimensional finite water channel, depending on the length of the water
channel and the resistance coefficient. A mathematical model including the
boundary effect is analytically reduced to an ordinary differential equation.
Linear stability analysis reveals that the Hopf bifurcation occurs, reflecting
the symmetry of the system.


title: Existence of charge-density waves in two-dimensional ionic Hubbard model

abstract:
  We rigorously investigated the charge-charge correlation function of the
ionic Hubbard model in two dimensions by reflection positivity. We prove the
existence of charge-density waves for large staggered potential $\Delta$ (i.e.,
$\frac{\Delta}{2}+2V>U$) at low temperatures, where $U$ and $V$ are the on-site
and nearest-neighbor Coulomb repulsions, respectively. The results are
consistent with previous numerical simulation results. We argue that the
absence of charge-density waves for $\Delta=0$ and $U$ are large enough (i.e.,
$U>\frac{\Delta}{2}$+2V).


title:
Cloud Radio Access meets Heterogeneous Small Cell Networks: A Cognitive
  Hierarchy Perspective

abstract:
  In this paper, the problem of distributed power allocation is considered for
the downlink of a cloud radio access network (CRAN) that is coexisting with a
heterogeneous network. In this multi-tier system, the heterogeneous network
base stations (BSs) as well as the CRAN remote radio heads seek to choose their
optimal power to maximize their users' rates. The problem is formulated as a
noncooperative game in which the players are the CRAN's cloud and the BSs.
Given the difference of capabilities between the CRAN and the various BSs, the
game is cast within the framework of cognitive hierarchy theory. In this
framework, players are organized in a hierarchy in such a way that a player can
choose its strategy while considering players of only similar or lower
hierarchies. Using such a hierarchical design, one can reduce the interference
caused by the CRAN and high-powered base stations on low-powered BSs. For this
game, the properties of the Nash equilibrium and the cognitive hierarchy
equilibrium are analyzed. Simulation results show that the proposed cognitive
hierarchy model yields significant performance gains, in terms of the total
rate, reaching up to twice the rate achieved by a classical noncooperative
game's Nash equilibrium.


title:
Deep Recurrent Models with Fast-Forward Connections for Neural Machine
  Translation

abstract:
  Neural machine translation (NMT) aims at solving machine translation (MT)
problems using neural networks and has exhibited promising results in recent
years. However, most of the existing NMT models are shallow and there is still
a performance gap between a single NMT model and the best conventional MT
system. In this work, we introduce a new type of linear connections, named
fast-forward connections, based on deep Long Short-Term Memory (LSTM) networks,
and an interleaved bi-directional architecture for stacking the LSTM layers.
Fast-forward connections play an essential role in propagating the gradients
and building a deep topology of depth 16. On the WMT'14 English-to-French task,
we achieve BLEU=37.7 with a single attention model, which outperforms the
corresponding single shallow model by 6.2 BLEU points. This is the first time
that a single NMT model achieves state-of-the-art performance and outperforms
the best conventional model by 0.7 BLEU points. We can still achieve BLEU=36.3
even without using an attention mechanism. After special handling of unknown
words and model ensembling, we obtain the best score reported to date on this
task with BLEU=40.4. Our models are also validated on the more difficult WMT'14
English-to-German task.


title: The Chasm at Depth Four, and Tensor Rank : Old results, new insights

abstract:
  Agrawal and Vinay [AV08] showed how any polynomial size arithmetic circuit
can be thought of as a depth four arithmetic circuit of subexponential size.
The resulting circuit size in this simulation was more carefully analyzed by
Korian [Koiran] and subsequently by Tavenas [Tav13]. We provide a simple proof
of this chain of results. We then abstract the main ingredient to apply it to
formulas and constant depth circuits, and show more structured depth reductions
for them.
  In an apriori surprising result, Raz [Raz10] showed that for any $n$ and $d$,
such that $ \omega(1) \leq d \leq O\left(\frac{\log n}{\log\log n}\right)$,
constructing explicit tensors $T:[n]^d \rightarrow F$ of high enough rank would
imply superpolynomial lower bounds for arithmetic formulas over the field $F$.
Using the additional structure we obtain from our proof of the depth reduction
for arithmetic formulas, we give a new and arguably simpler proof of this
connection. We also extend this result for homogeneous formulas to show that,
in fact, the connection holds for any $d$ such that $\omega(1) \leq d \leq
n^{o(1)}$.


title:
Drastic changes of electronic structure and crystal chemistry upon
  oxidation of SnII2TiO4E2 into SnIV2TiO6: an ab initio study

abstract:
  From DFT based calculations establishing energy-volume equations of state and
electron localization mapping, the electronic structure and crystal chemistry
changes from Sn2TiO4 to Sn2TiO6 by oxidation are rationalized; the key effect
being the destabilization of divalent tin SnII towards tetravalent state SnIV
leading to rutile Sn2TiO6 as experimentally observed. The subsequent electronic
structure change is highlighted in the relative change of the electronic band
gap which increases from ~1eV up to 2.2 eV and the 1.5 times increase of the
bulk modulus assigned to the change from covalently SnII based compound to the
more ionic SnIV one. Such trends are also confronted with the relevant
properties of black SnIIO characterized by very small band gap.


title:
Improved Approximation of Storage-Rate Tradeoff for Caching with
  Multiple Demands

abstract:
  Caching at the network edge has emerged as a viable solution for alleviating
the severe capacity crunch in modern content centric wireless networks by
leveraging network load-balancing in the form of localized content storage and
delivery. In this work, we consider a cache-aided network where the cache
storage phase is assisted by a central server and users can demand multiple
files at each transmission interval. To service these demands, we consider two
delivery models - $(1)$ centralized content delivery where user demands at each
transmission interval are serviced by the central server via multicast
transmissions; and $(2)$ device-to-device (D2D) assisted distributed delivery
where users multicast to each other in order to service file demands. For such
cache-aided networks, we present new results on the fundamental cache storage
vs. transmission rate tradeoff. Specifically, we develop a new technique for
characterizing information theoretic lower bounds on the storage-rate tradeoff
and show that the new lower bounds are strictly tighter than cut-set bounds
from literature. Furthermore, using the new lower bounds, we establish the
optimal storage-rate tradeoff to within a constant multiplicative gap. We show
that, for multiple demands per user, achievable schemes based on repetition of
schemes for single demands are order-optimal under both delivery models.


title:
Order-2 Asymptotic Optimality of the Fully Distributed Sequential
  Hypothesis Test

abstract:
  This work analyzes the asymptotic performances of fully distributed
sequential hypothesis testing procedures as the type-I and type-II error rates
approach zero, in the context of a sensor network without a fusion center. In
particular, the sensor network is defined by an undirected graph, where each
sensor can observe samples over time, access the information from the adjacent
sensors, and perform the sequential test based on its own decision statistic.
Different from most literature, the sampling process and the information
exchange process in our framework take place simultaneously (or, at least in
comparable time-scales), thus cannot be decoupled from one another. Two
message-passing schemes are considered, based on which the distributed
sequential probability ratio test (DSPRT) is carried out respectively. The
first scheme features the dissemination of the raw samples. Although the sample
propagation based DSPRT is shown to yield the asymptotically optimal
performance at each sensor, it incurs excessive inter-sensor communication
overhead due to the exchange of raw samples with index information. The second
scheme adopts the consensus algorithm, where the local decision statistic is
exchanged between sensors instead of the raw samples, thus significantly
lowering the communication requirement compared to the first scheme. In
particular, the decision statistic for DSPRT at each sensor is updated by the
weighted average of the decision statistics in the neighbourhood at every
message-passing step. We show that, under certain regularity conditions, the
consensus algorithm based DSPRT also yields the order-2 asymptotically optimal
performance at all sensors.


title: Measuring a transmon qubit in circuit QED: dressed squeezed states

abstract:
  Using circuit QED, we consider the measurement of a superconducting transmon
qubit via a coupled microwave resonator. For ideally dispersive coupling,
ringing up the resonator produces coherent states with frequencies matched to
transmon energy states. Realistic coupling is not ideally dispersive, however,
so transmon-resonator energy levels hybridize into joint eigenstate ladders of
the Jaynes-Cummings type. Previous work has shown that ringing up the resonator
approximately respects this ladder structure to produce a coherent state in the
eigenbasis (a dressed coherent state). We numerically investigate the validity
of this coherent state approximation to find two primary deviations. First,
resonator ring-up leaks small stray populations into eigenstate ladders
corresponding to different transmon states. Second, within an eigenstate ladder
the transmon nonlinearity shears the coherent state as it evolves. We then show
that the next natural approximation for this sheared state in the eigenbasis is
a dressed squeezed state, and derive simple evolution equations for such states
using a hybrid phase-Fock-space description.


title:
Robust And Optimal Opportunistic Scheduling For Downlink 2-Flow Network
  Coding With Varying Channel Quality and Rate Adaptation (New Simulation
  Figures)

abstract:
  This paper considers the downlink traffic from a base station to two
different clients. When assuming infinite backlog, it is known that
inter-session network coding (INC) can significantly increase the throughput.
However, the corresponding scheduling solution (when assuming dynamic arrivals
instead and requiring bounded delay) is still nascent. For the 2-flow downlink
scenario, we propose the first opportunistic INC + scheduling solution that is
provably optimal for time-varying channels, i.e., the corresponding stability
region matches the optimal Shannon capacity. Specifically, we first introduce a
new binary INC operation, which is distinctly different from the traditional
wisdom of XORing two overheard packets. We then develop a queue-length-based
scheduling scheme and prove that it, with the help of the new INC operation,
achieves the optimal stability region with time-varying channel quality. The
proposed algorithm is later generalized to include the capability of rate
adaptation. Simulation results show that it again achieves the optimal
throughput with rate adaptation. A byproduct of our results is a scheduling
scheme for stochastic processing networks (SPNs) with random departure, which
relaxes the of deterministic departure in the existing results.


title:
Considerations about Chopper Configuration at a time-of-flight SANS
  Instrument at a Spallation Source

abstract:
  In any neutron scattering experiment the measurement of the position of the
scattered neutrons and their respective velocities is necessary. In order to do
so, a position sensitive detector as well as a way to determine the velocities
is needed. Measuring the velocities can either be done by using only a single
wavelength and therefore velocity or by creating pulses, where the start and
end time of each pulse is known and registering the time of arrival at the
detector, which is the case we want to consider here. This pulse shaping
process in neutron scattering instruments is usually done by using a
configuration of several choppers. This set of choppers is then used to define
both the beginning and the end of the pulse. Additionally there is of course
also a selection in phase space determining the final resolution that can be
achieved by the instrument. Taking into account the special requirements of a
specific instrument, here a small-angle neutron scattering instrument, creates
an additional set of restrictions that have to be taken into account. In this
manuscript a chopper configuration for two possible settings, namely a maximum
flux and a high-resolution mode will be presented.


title: Limits of Generalized Quaternion Groups

abstract:
  In the space of marked group, we determine the structure of groups which are
limit points of the set of all generalized quaternion groups.


title:
Spin-orbit coupling effects on the stability of two competing structures
  in Pb/Si(111) and Pb/Ge(111)

abstract:
  Using first-principles density-functional theory (DFT) calculations, we
investigate the 4/3-monolayer structure of Pb on the Si(111) or Ge(111) surface
within the two competing structural models termed the H$_3$ and T$_4$
structures. We find that the spin-orbit coupling (SOC) influences the relative
stability of the two structures in both the Pb/Si(111) and Pb/Ge(111) systems:
i.e., our DFT calculation without including the SOC predicts that the T$_4$
structure is energetically favored over the H$_3$ structure by ${\Delta}E$ = 25
meV for Pb/Si(111) and 22 meV for Pb/Ge(111), but the inclusion of SOC reverses
their relative stability as ${\Delta}E$ = $-$12 and $-$7 meV, respectively. Our
analysis shows that the SOC-induced switching of the ground state is attributed
to a more asymmetric surface charge distribution in the H$_3$ structure, which
gives rise to a relatively larger Rashba spin splitting of surface states as
well as a relatively larger pseudo-gap opening compared to the T$_4$ structure.
By the nudged elastic band calculation, we obtain a sizable energy barrier from
the H$_3$ to the T$_4$ structure as ${\sim}$0.59 and ${\sim}$0.27 eV for
Pb/Si(111) and Pb/Ge(111), respectively. It is thus likely that the two
energetically competing structures can coexist at low temperatures.


title: A Systematic Approach to Blocking Convolutional Neural Networks

abstract:
  Convolutional Neural Networks (CNNs) are the state of the art solution for
many computer vision problems, and many researchers have explored optimized
implementations. Most implementations heuristically block the computation to
deal with the large data sizes and high data reuse of CNNs. This paper explores
how to block CNN computations for memory locality by creating an analytical
model for CNN-like loop nests. Using this model we automatically derive
optimized blockings for common networks that improve the energy efficiency of
custom hardware implementations by up to an order of magnitude. Compared to
traditional CNN CPU implementations based on highly-tuned, hand-optimized BLAS
libraries,our x86 programs implementing the optimal blocking reduce the number
of memory accesses by up to 90%.


title:
The class of the affine line is a zero divisor in the Grothendieck ring:
  via $G_2$-Grassmannians

abstract:
  Motivated by [Bor] and [Mar], we show the equality $\left([X] - [Y]\right)
\cdot [\mathbb{A}^1] = 0$ in the Grothendieck ring of varieties, where $(X, Y)$
is a pair of Calabi-Yau 3-folds cut out from the pair of Grassmannians of type
$G_2$.


title:
Convergence of a Vector Penalty Projection Scheme for the Navier-Stokes
  Equations with moving body

abstract:
  In this paper, we analyse a Vector Penalty Projection Scheme (see [1]) to
treat the displacement of a moving body in incompressible viscous flows in the
case where the interaction of the fluid on the body can be neglected. The
presence of the obstacle inside the computational domain is treated with a
penalization method introducing a parameter $\eta$. We show the stability of
the scheme and that the pressure and velocity converge towards a limit when the
penalty parameter $\epsilon$, which induces a small divergence and the time
step $\delta$t tend to zero with a proportionality constraint $\epsilon$ =
$\lambda$$\delta$t. Finally, when $\eta$ goes to 0, we show that the problem
admits a weak limit which is a weak solution of the Navier-Stokes equations
with no-sleep condition on the solid boundary. R{\'e}sum{\'e} Dans ce travail
nous analysons un sch{\'e}ma de projection vectorielle (voir [1]) pour traiter
le d{\'e}placement d'un corps solide dans un fluide visqueux incompressible
dans le cas o` u l'interaction du fluide sur le solide est n{\'e}gligeable. La
pr{\'e}sence de l'obstacle dans le domaine solide est mod{\'e}lis{\'e}e par une
m{\'e}thode de p{\'e}nalisation. Nous montrons la stabilit{\'e} du sch{\'e}ma
et la convergence des variables vitesse-pression vers une limite quand le param
etre $\epsilon$ qui assure une faible divergence et le pas de temps $\delta$t
tendent vers 0 avec une contrainte de proportionalit{\'e} $\epsilon$ =
$\lambda$$\delta$t. Finalement nous montrons que leprob{\`i} eme converge au
sens faible vers une solution des equations de Navier-Stokes avec une condition
aux limites de non glissement sur lafront{\`i} ere immerg{\'e}e quand le param
etre de p{\'e}nalisation $\eta$ tend vers 0.


title: Active Discriminative Text Representation Learning

abstract:
  We propose a new active learning (AL) method for text classification with
convolutional neural networks (CNNs). In AL, one selects the instances to be
manually labeled with the aim of maximizing model performance with minimal
effort. Neural models capitalize on word embeddings as representations
(features), tuning these to the task at hand. We argue that AL strategies for
multi-layered neural models should focus on selecting instances that most
affect the embedding space (i.e., induce discriminative word representations).
This is in contrast to traditional AL approaches (e.g., entropy-based
uncertainty sampling), which specify higher level objectives. We propose a
simple approach for sentence classification that selects instances containing
words whose embeddings are likely to be updated with the greatest magnitude,
thereby rapidly learning discriminative, task-specific embeddings. We extend
this approach to document classification by jointly considering: (1) the
expected changes to the constituent word representations; and (2) the model's
current overall uncertainty regarding the instance. The relative emphasis
placed on these criteria is governed by a stochastic process that favors
selecting instances likely to improve representations at the outset of
learning, and then shifts toward general uncertainty sampling as AL progresses.
Empirical results show that our method outperforms baseline AL approaches on
both sentence and document classification tasks. We also show that, as
expected, the method quickly learns discriminative word embeddings. To the best
of our knowledge, this is the first work on AL addressing neural models for
text classification.


title: Gluon fragmentation functions in the Nambu-Jona-Lasinio model

abstract:
  We derive gluon fragmentation functions in the Nambu-Jona-Lasinio (NJL) model
by treating a gluon as a pair of color lines formed by fictitious quark and
anti-quark ($q\bar q$). Gluon elementary fragmentation functions are obtained
from the quark and anti-quark elementary fragmentation functions for emitting
specific mesons in the NJL model under the requirement that the $q\bar q$ pair
maintains in the flavor-singlet state after meson emissions. An integral
equation, which iterates the gluon elementary fragmentation functions to all
orders, is then solved to yield the gluon fragmentation functions at a model
scale. It is observed that these solutions are stable with respect to variation
of relevant model parameters, especially after QCD evolution to a higher scale
is implemented. We show that the inclusion of the gluon fragmentation functions
into the theoretical predictions from only the quark fragmentation functions
greatly improves the agreement with the SLD data for the pion and kaon
productions in $e^+e^-$ annihilation. Our proposal provides a plausible
construct for the gluon fragmentation functions, which are supposed to be null
in the NJL model.


title:
Quality factor enhancement of Nano electromechanical systems by
  capacitive driving beyond the resonance

abstract:
  Nano electromechanical systems are considered as ultra sensitive devices for
mass and force detection. Capacitive actuation is widely used in these devices
but is known to degrade the quality factor of the resonator due to DC
electrostatic damping. We report the enhancement of the quality factor of SiC
vibrating nanowires detected nano optomechanically and electrically by applying
an AC capacitive driving at a frequency above both the resonance frequency and
the electrical cutoff frequency. Self-oscillations are demonstrated for optimal
conditions. We developed an analytical model of the phenomenon and showed that
it can lead to an improvement of the force sensitivity. *
anthony.ayari@univ-lyon1.fr 1


title:
Stability of periodic waves of 1D cubic nonlinear Schr{\"o}dinger
  equations

abstract:
  We study the stability of the cnoidal, dnoidal and snoidal elliptic functions
as spatially-periodic standing wave solutions of the 1D cubic nonlinear
Schr{\"o}dinger equations. First, we give global variational characterizations
of each of these periodic waves, which in particular provide alternate proofs
of their orbital stability with respect to same-period perturbations,
restricted to certain subspaces. Second, we prove the spectral stability of the
cnoidal waves against same-period perturbations (in a certain parameter range),
and provide an alternate proof of this (known) fact for the snoidal waves,
which does not rely on complete integrability. Third, we give a rigorous
version of a formal asymptotic calculation of Rowlands to establish the
instability of a class of real-valued periodic waves in 1D, which includes the
cnoidal waves of the 1D cubic focusing nonlinear Schr{\"o}dinger equation,
against perturbations with period a large multiple of their fundamental period.
Finally, we develop a numerical method to compute the minimizers of the energy
with fixed mass and momentum constraints. Numerical experiments support and
complete our analytical results.


title: Spreadsheet Probabilistic Programming

abstract:
  Spreadsheet workbook contents are simple programs. Because of this,
probabilistic programming techniques can be used to perform Bayesian inversion
of spreadsheet computations. What is more, existing execution engines in
spreadsheet applications such as Microsoft Excel can be made to do this using
only built-in functionality. We demonstrate this by developing a native Excel
implementation of both a particle Markov Chain Monte Carlo variant and
black-box variational inference for spreadsheet probabilistic programming. The
resulting engine performs probabilistically coherent inference over spreadsheet
computations, notably including spreadsheets that include user-defined
black-box functions. Spreadsheet engines that choose to integrate the
functionality we describe in this paper will give their users the ability to
both easily develop probabilistic models and maintain them over time by
including actuals via a simple user-interface mechanism. For spreadsheet
end-users this would mean having access to efficient and probabilistically
coherent probabilistic modeling and inference for use in all kinds of decision
making under uncertainty.


title:
Word Representation Models for Morphologically Rich Languages in Neural
  Machine Translation

abstract:
  Dealing with the complex word forms in morphologically rich languages is an
open problem in language processing, and is particularly important in
translation. In contrast to most modern neural systems of translation, which
discard the identity for rare words, in this paper we propose several
architectures for learning word representations from character and morpheme
level word decompositions. We incorporate these representations in a novel
machine translation model which jointly learns word alignments and translations
via a hard attention mechanism. Evaluating on translating from several
morphologically rich languages into English, we show consistent improvements
over strong baseline methods, of between 1 and 1.5 BLEU points.


title: Conditional Generative Moment-Matching Networks

abstract:
  Maximum mean discrepancy (MMD) has been successfully applied to learn deep
generative models for characterizing a joint distribution of variables via
kernel mean embedding. In this paper, we present conditional generative moment-
matching networks (CGMMN), which learn a conditional distribution given some
input variables based on a conditional maximum mean discrepancy (CMMD)
criterion. The learning is performed by stochastic gradient descent with the
gradient calculated by back-propagation. We evaluate CGMMN on a wide range of
tasks, including predictive modeling, contextual generation, and Bayesian dark
knowledge, which distills knowledge from a Bayesian model by learning a
relatively small CGMMN student network. Our results demonstrate competitive
performance in all the tasks.


title: Density dependence of the nuclear energy-density functional

abstract:
  The explicit density (rho) dependence in the coupling coefficients of the
non-relativistic nuclear energy-density functional (EDF) encodes effects of
three-nucleon forces and dynamical correlations. The necessity for a coupling
coefficient in the form of a small fractional power of rho is empirical and the
power often chosen arbitrarily. Consequently, precision-oriented
parameterisations risk overfitting and loss of predictive power.
  Observing that the Fermi momentum kF~rho^1/3 is a key variable in Fermi
systems, we examine if a power hierarchy in kF can be inferred from the
properties of homogeneous matter in a domain of densities which is relevant for
nuclear structure and neutron stars. For later applications we want to
determine an EDF that is of good quality but not overtrained. We fit polynomial
and other functions of rho^1/3 to existing microscopic calculations of the
energy of symmetric and pure neutron matter and analyze the fits. We select a
form and parameter set which we found robust and examine the parameters'
naturalness and the resulting extrapolations. A statistical analysis confirms
that low-order terms like rho^1/3 and rho^2/3 are the most relevant ones. It
also hints at a different power hierarchy for symmetric vs. pure neutron
matter, supporting the need for more than one rho^a terms in non-relativistic
EDFs. The EDF we propose accommodates adopted properties of nuclear matter near
saturation. Importantly, its extrapolation to dilute or asymmetric matter
reproduces a range of existing microscopic results, to which it has not been
fitted. It also predicts neutron-star properties consistent with observations.
The coefficients display naturalness.
  Once determined for homogeneous matter, EDFs of the present form can be
mapped onto Skyrme-type ones for use in nuclei. The statistical analysis can be
extended to higher orders and for different ab initio calculations.


title:
On the Design of MAC Protocol and Transmission Scheduling for Internet
  of Things

abstract:
  With the ubiquitous sensing enabled by wireless sensor network technologies,
Internet of Things (IoT) is developed to many areas of modern day living. The
inexpensive IoT devices and platforms capable of wireless communications enable
the ability to measure, infer and understand environmental indicators, from
delicate ecologies and natural resources to urban environments. In this paper,
we firstly investigate a scalable multimode-based MAC protocol, IoT-MAC, which
consists of a channel contention period and a data transmission period, to
reduce contention of channel access due to coexist of many IoT devices.
Secondly, we study a data transmission scheduling algorithm to maximise data
collection under the constraints of radio link quality and remaining energy of
the IoT node, while ensuring a fair access to the radio channel. To study the
performance of data reception rate, packet loss rate and latency, we evaluate
the IoT-MAC and scheduling algorithm with varying data rate and different
network scale.


title:
Individual Cr atom in a semiconductor quantum dot: optical
  addressability and spin-strain coupling

abstract:
  We demonstrate the optical addressability of the spin of an individual
Chromium atom (Cr) embedded in a semiconductor quantum dot. The emission of
Cr-doped quantum dots and their evolution in magnetic field reveal a large
magnetic anisotropy of the Cr spin induced by local strain. This results in the
zero field splitting of the 0, +-1 and +-2 Cr spin states and in a
thermalization on the magnetic ground states 0 and +-1. The observed strong
spin to strain coupling of Cr is of particular interest for the development of
hybrid spin-mechanical devices where coherent mechanical driving of an
individual spin in an oscillator is needed. The magneto-optical properties of
Cr-doped quantum dots are modelled by a spin Hamiltonian including the
sensitivity of the Cr spin to the strain and the influence of the quantum dot
symmetry on the carrier-Cr spin coupling.


title:
Observation of collective coupling between an engineered ensemble of
  macroscopic artificial atoms and a superconducting resonator

abstract:
  The hybridization of distinct quantum systems is now seen as an effective way
to engineer the properties of an entire system leading to applications in
quantum metamaterials, quantum simulation, and quantum metrology. One well
known example is superconducting circuits coupled to ensembles of microscopic
natural atoms. In such cases, the properties of the individual atom are
intrinsic, and so are unchangeable. However, current technology allows us to
fabricate large ensembles of macroscopic artificial atoms such as
superconducting flux qubits, where we can really tailor and control the
properties of individual qubits. Here, we demonstrate coherent coupling between
a microwave resonator and several thousand superconducting flux qubits, where
we observe a large dispersive frequency shift in the spectrum of 250 MHz
induced by collective behavior. These results represent the largest number of
coupled superconducting qubits realized so far. Our approach shows that it is
now possible to engineer the properties of the ensemble, opening up the way for
the controlled exploration of the quantum many-body system.


title: Learning Term Weights for Ad-hoc Retrieval

abstract:
  Most Information Retrieval models compute the relevance score of a document
for a given query by summing term weights specific to a document or a query.
Heuristic approaches, like TF-IDF, or probabilistic models, like BM25, are used
to specify how a term weight is computed. In this paper, we propose to leverage
learning-to-rank principles to learn how to compute a term weight for a given
document based on the term occurrence pattern.


title: Mixed curvature measures of translative integral geometry

abstract:
  The curvature measures of a set $X$ with singularities are measures
concentrated on the normal bundle of $X$, which describe the local geometry of
the set $X$. For given finitely many convex bodies or, more generally, sets
with positive reach, the translative integral formula for curvature measures
relates the integral mean of the curvature measures of the intersections of the
given sets, one fixed and the others translated, to the mixed curvature
measures of the given sets. In the case of two sets of positive reach, a
representation of these mixed measures in terms of generalized curvatures,
defined on the normal bundles of the sets, is known. For more than two sets, a
description of mixed curvature measures in terms of rectifiable currents has
been derived previously. Here we provide a representation of mixed curvatures
measures of sets with positive reach based on generalized curvatures.
  The special case of convex polyhedra is treated in detail.


title: A revised model of fluid transport optimization in Physarum polycephalum

abstract:
  Optimization of fluid transport in the slime mold Physarum polycephalum has
been the subject of several modeling efforts in recent literature. Existing
models assume that the tube adaptation mechanism in P. polycephalum's tubular
network is controlled by the sheer amount of fluid flow through the tubes. We
put forward the hypothesis that the controlling variable may instead be the
flow's pressure gradient along the tube. We carry out the stability analysis of
such a revised mathematical model for a parallel-edge network, proving that the
revised model supports the global flow-optimizing behavior of the slime mold
for a substantially wider class of response functions compared to previous
models. Simulations also suggest that the same conclusion may be valid for
arbitrary network topologies.


title: Black hole kicks as new gravitational wave observables

abstract:
  Generic black hole binaries radiate gravitational waves anisotropically,
imparting a recoil, or kick, velocity to the merger remnant. If a component of
the kick along the line of sight is present, gravitational waves emitted during
the final orbits and merger will be gradually Doppler shifted as the kick
builds up. We develop a simple prescription to capture this effect in existing
waveform models, showing that future gravitational wave experiments will be
able to perform direct measurements, not only of the black hole kick velocity,
but also of its accumulation profile. In particular, the eLISA space mission
will measure supermassive black hole kick velocities as low as ~500 km/s, which
are expected to be a common outcome of black hole binary coalescence following
galaxy mergers. Black hole kicks thus constitute a promising new observable in
the growing field of gravitational wave astronomy.

categories: gr-qc astro-ph.CO astro-ph.GA astro-ph.HE


title: Design Study of a Superconducting Gantry for Carbon Beam Therapy

abstract:
  This paper describes the design study of a gantry for a carbon beam. The
designed gantry is compact such that its size is comparable to the size of the
proton gantry. This is possible by introducing superconducting double helical
coils for dipole magnets. The gantry optics is designed in such a way that it
provides rotation-invariant optics and variable beam size as well as
point-to-parallel scanning of a beam. For large-aperture magnet,
three-dimensional magnetic field distribution is obtained by invoking a
computer code, and a number of particles are tracked by integrating equations
of motion numerically together with three-dimensional interpolation. The
beam-shape distortion due to the fringe field is reduced to an acceptable level
by optimizing the coil windings with the help of genetic algorithm.
Higher-order transfer coefficients are calculated and shown to be reduced
greatly with appropriate optimization of the coil windings.


title:
Asymptotic of the distribution and harmonic moments for a supercritical
  branching process in a random environment

abstract:
  Let $(Z_n)$ be a supercritical branching process in an independent and
identically distributed random environment $\xi$. We show the exact decay rate
of the probability $\mathbb{P}(Z_n=j | Z_0 = k)$ as $n \to \infty$, for each $j
\geq k,$ assuming that $\mathbb{P} (Z_1 = 0) =0$. We also determine the
critical value for the existence of harmonic moments of the random variable
$W=\lim_{n\to\infty}\frac{Z_n}{\mathbb E (Z_n|\xi)}$ under a simple moment
condition.


title:
Response of a mechanical oscillator in an optomechanical cavity driven
  by a finite bandwidth squeezed vacuum excitation

abstract:
  In this paper, we theoretically investigate the displacement and momentum
fluctuations spectra of the movable mirror in a standard optomechanical system
driven by a finite bandwidth squeezed vacuum light accompanying a coherent
laser field. Two cases in which the squeezed vacuum is generated by degenerated
and non-degenerate parametric oscillators (DPO and NDPO) are considered. We
find that for the case of finite bandwidth squeezed vacuum injection, the two
spectra exhibit unique features, which strongly differ from those of broadband
squeezing excitation. In particular, the spectra exhibit a three-peaked and a
four-peaked structure, respectively, for the squeezing injection from DPO and
NDPO. Besides, some anomalous characteristics of the spectra such as
squeezing-induced pimple, hole burning, and dispersive profile are found to be
highly sensitive to the squeezing parameters and the temperature of the mirror.
We also evaluate the mean-square fluctuations in position and momentum
quadratures of the movable mirror and analyze the influence of the squeezing
parameters of the input field on the mechanical squeezing. It will be shown
that the parameters of driven squeezed vacuum affects the squeezing. We find
the optimal mechanical squeezing is achievable via finite bandwidth squeezed
vacuum injection which is affected by the intensity of squeezed vacuum. We also
show that the phase of incident squeezed vacuum determines whether position or
momentum squeezing occurs. Our proposed scheme not only provides a feasible
experimental method to detect and characterize squeezed light by optomechanical
systems, but also suggests a way for controllable transfer of squeezing from an
optical field to a mechanical oscillator.


title:
Riemannian cubics on the group of diffeomorphisms and the Fisher-Rao
  metric

abstract:
  We study a second-order variational problem on the group of diffeomorphisms
of the interval [0, 1] endowed with a right-invariant Sobolev metric of order
2, which consists in the minimization of the acceleration. We compute the
relaxation of the problem which involves the so-called Fisher-Rao functional a
convex functional on the space of measures. This relaxation enables the
derivation of several optimality conditions and, in particular, a sufficient
condition which guarantees that a given path of the initial problem is also a
minimizer of the relaxed one. This sufficient condition is related to the
existence of a solution to a Riccati equation involving the path acceleration.


title: On the conjecture of the norm Schwarz inequality

abstract:
  For any positive invertible matrix $A$ and any normal matrix $B$ in
$M_{n}({\Bbb C})$, we investigate whether the inequality $ ||A\sharp
(B^{*}A^{-1}B)||\geq ||B|| $ is true or not, where $\sharp$ denotes the
geometric mean and $||\cdot||$ denotes the operator norm. We will solve this
problem negatively. The related topics are also discussed.


title: DCNNs on a Diet: Sampling Strategies for Reducing the Training Set Size

abstract:
  Large-scale supervised classification algorithms, especially those based on
deep convolutional neural networks (DCNNs), require vast amounts of training
data to achieve state-of-the-art performance. Decreasing this data requirement
would significantly speed up the training process and possibly improve
generalization. Motivated by this objective, we consider the task of adaptively
finding concise training subsets which will be iteratively presented to the
learner. We use convex optimization methods, based on an objective criterion
and feedback from the current performance of the classifier, to efficiently
identify informative samples to train on. We propose an algorithm to decompose
the optimization problem into smaller per-class problems, which can be solved
in parallel. We test our approach on standard classification tasks and
demonstrate its effectiveness in decreasing the training set size without
compromising performance. We also show that our approach can make the
classifier more robust in the presence of label noise and class imbalance.


title: Singular decompositions of a cap product

abstract:
  In the case of a compact orientable pseudomanifold, a well-known theorem of
M. Goresky and R. MacPherson says that the cap product with a fundamental class
factorizes through the intersection homology groups. In this work, we show that
this classical cap product is compatible with a cap product in intersection
(co)-homology, that we have previously introduced. If the pseudomanifold is
also normal, for any commutative ring of coefficients, the existence of a
classical Poincar\'e duality isomorphism is equivalent to the existence of an
isomorphism between the intersection homology groups corresponding to the zero
and the top perversities.


title:
Production of deuterium, tritium, and $^3$He in central Pb+Pb collisions
  at 20A, 30A, 40A, 80A, and 158A GeV at the CERN SPS

abstract:
  Production of $d$, $t$, and $^3$He nuclei in central Pb+Pb interactions was
studied at five collision energies ($\sqrt{s_{NN}}=$ 6.3, 7.6, 8.8, 12.3, and
17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum spectra,
rapidity distributions, and particle ratios were measured. Yields are compared
to predictions of statistical models. Phase-space distributions of light nuclei
are discussed and compared to those of protons in the context of a coalescence
approach. The coalescence parameters $B_2$ and $B_3$, as well as coalescence
radii for $d$ and $^3$He were determined as a function of transverse mass at
all energies.


title: Reconstruction of infinite matroids from their 3-connected minors

abstract:
  We show that any infinite matroid can be reconstructed from the torsos of a
tree-decomposition over its 2-separations, together with local information at
the ends of the tree. We show that if the matroid is tame then this local
information is simply a choice of whether circuits are permitted to use that
end. The same is true if each torso is planar, with all gluing elements on a
common face.


title:
Context-Aware Proactive Content Caching with Service Differentiation in
  Wireless Networks

abstract:
  Content caching in small base stations or wireless infostations is considered
to be a suitable approach to improve the efficiency in wireless content
delivery. Placing the optimal content into local caches is crucial due to
storage limitations, but it requires knowledge about the content popularity
distribution, which is often not available in advance. Moreover, local content
popularity is subject to fluctuations since mobile users with different
interests connect to the caching entity over time. Which content a user prefers
may depend on the user's context. In this paper, we propose a novel algorithm
for context-aware proactive caching. The algorithm learns context-specific
content popularity online by regularly observing context information of
connected users, updating the cache content and observing cache hits
subsequently. We derive a sublinear regret bound, which characterizes the
learning speed and proves that our algorithm converges to the optimal cache
content placement strategy in terms of maximizing the number of cache hits.
Furthermore, our algorithm supports service differentiation by allowing
operators of caching entities to prioritize customer groups. Our numerical
results confirm that our algorithm outperforms state-of-the-art algorithms in a
real world data set, with an increase in the number of cache hits of at least
14%.


title: Study on the microwave ion source of 100-MeV proton linac

abstract:
  A microwave ion source is used as an ion source of 100-MeV proton accelerator
at Korea Multipurpose Accelerator Complex (KOMAC). The specifications of the
ion source are 50 keV in energy and 20 mA in peak current. The plasma is
operated in CW mode using magnetron and the pulse beam is extracted using
semiconductor switch located in the extraction power supply. The beam
characteristics were measured based on the pulse voltage and current. A test
stand was also installed to study the beam characteristics of the ion source in
off-line. In this paper, the pulse beam characteristics of the ion source are
presented and the installation of the test stand is reported.


title: Defect-induced magnetic structure of CuMnSb

abstract:
  Ab initio total energy calculations show that the antiferromagnetic (111)
order is not the ground state for the ideal CuMnSb Heusler alloy in contrast to
the results of neutron diffraction experiments. It is known, that Heusler
alloys usually contain various defects depending on the sample preparation. We
have therefore investigated magnetic phases of CuMnSb assuming the most common
defects which exist in real experimental conditions. The full-potential
supercell approach and a Heisenberg model approach using the coherent potential
approximation are adopted. The results of the total energy supercell
calculations indicate that defects that bring Mn atoms close together promote
the antiferromagnetic (111) structure already for a low critical defect
concentrations ($\approx$ 3%). A detailed study of exchange interactions
between Mn-moments further supports the above stabilization mechanism. Finally,
the stability of the antiferromagnetic (111) order is enhanced by inclusion of
electron correlations in narrow Mn-bands. The present refinement structure
analysis of neutron scattering experiment supports theoretical conclusions.


title: A non-Markovian Dissipative Maryland Model

abstract:
  The so-called Maryland model is a linear version of the quantum kicked rotor;
it exhibits Anderson localization in momentum space. By turning the kicks into
a Markovian stochastic process, the dynamics becomes a dissipative quantum
process described by a discrete family of completely positive maps that allows
to explicitly study the relation between divisibility of the maps and the
degree of memory of the process.


title: For-loops in Logic Programming

abstract:
  Logic programming has traditiLogic programming has traditionally lacked
devices for expressing iterative tasks. To overcome this problem, this paper
proposes iterative goal formulas of the form $\seqandq{x}{L} G$ where $G$ is a
goal, $x$ is a variable, and $L$ is a list. $\seqandq{x}{L}$ is called a
parallel bounded quantifier. These goals allow us to specify the following
task: iterate $G$ with $x$ ranging over all the elements of $L$. onally lacked
devices for expressing iterative tasks. To overcome this problem, this paper
proposes iterative goal formulas of the form $\seqandq{x}{L} G$ where $G$ is a
goal, $x$ is a variable, and $L$ is a list. $\seqandq{x}{L}$ is called a
parallel bounded quantifier. These goals allow us to specify the following
task: iterate $G$ with $x$ ranging over all the elements of $L$.


title:
An Empirically grounded Agent Based simulator for the Air Traffic
  Management in the SESAR scenario

abstract:
  In this paper we present a simulator allowing to perform policy experiments
relative to the air traffic management. Different SESAR solutions can be
implemented in the model to see the reaction of the different stakeholders as
well as other relevant metrics (delays, safety, etc). The model describes both
the strategic phase associated to the planning of the flight trajectories and
the tactical modifications occurring in the en-route phase. An implementation
of the model is available as open-source and freely accessible by any user.
  More specifically, different procedures related to business trajectories and
free-routing are tested and we illustrate the capabilities of the model on
airspace implementing these concepts. After performing numerical simulations
with the model, we show that in a free-routing scenario the controllers perform
less operations although they are dispersed over a larger portion of the
airspace. This can potentially increase the complexity of conflict detection
and resolution for controllers.
  In order to investigate this specific aspect, we consider some metrics used
to measure traffic complexity. We first show that in non-free-routing
situations our simulator deals with complexity in a way similar to what humans
would do. This allows us to be confident that the results of our numerical
simulations relative to the free-routing can reasonably forecast how human
controllers would behave in this new situation. Specifically, our numerical
simulations show that most of the complexity metrics decrease with
free-routing, while the few metrics which increase are all linked to the flight
level changes. This is a non-trivial result since intuitively the complexity
should increase with free-routing because of problematic geometries and more
dispersed conflicts over the airspace.


title:
Torques and angular momentum: Counter-rotation in galaxies and ring
  galaxies

abstract:
  We present an alternate origin scenario to explain the observed phenomena of
(1) counter-rotation between different galaxy components and (2) the formation
of ring galaxies. We suggest that these are direct consequences of the galaxy
being acted upon by a torque which causes a change in its primordial spin
angular momentum first observed as changes in the gas kinematics or
distribution. We suggest that this torque is exerted by the gravitational force
between nearby galaxies. This origin requires the presence of at least one
companion galaxy in the vicinity - we find a companion galaxy within 750 kpc
for 51/57 counter-rotating galaxies and literature indicates that all ring
galaxies have a companion galaxy thus giving observable credence to this
origin. Moreover in these 51 galaxies, we find a kinematic offset between
stellar and gas heliocentric velocities $>50$ kms$^{-1}$ for several galaxies
if the separation between the galaxies $<$ 100 kpc. This, we suggest, indicates
a change in the orbital angular momentum of the torqued galaxies. A major
difference between the torque origin suggested here and the existing model of
gas accretion/galaxy collision, generally used to explain the above two
phenomena, is that the torque acts on the matter of the same galaxy whereas in
the latter case gas, with different properties, is brought in from outside. An
important implication of our study is that mutual gravity torques acting on the
galaxy can explain the formation of warps, polar ring galaxies and lenticular
galaxies. We conclude that mutual gravity torques play an important role in the
dynamical evolution of galaxies and that they naturally explain several galaxy
observables.


title: Solitary magnons in the $S={5\over2}$ antiferromagnet CaFe$_{2}$O$_{4}$

abstract:
  CaFe$_{2}$O$_{4}$ is a $S={5\over 2}$ anisotropic antiferromagnet based upon
zig-zag chains having two competing magnetic structures, denoted as the A
($\uparrow \uparrow \downarrow \downarrow$) and B ($\uparrow \downarrow
\uparrow \downarrow$) phases, which differ by the $c$-axis stacking of
ferromagnetic stripes. We apply neutron scattering to demonstrate that the
competing A and B phase order parameters results in magnetic antiphase
boundaries along $c$ which freeze on the timescale of $\sim$ 1 ns at the onset
of magnetic order at 200 K. Using high resolution neutron spectroscopy, we find
quantized spin wave levels and measure 9 such excitations localized in regions
$\sim$ 1-2 $c$-axis lattice constants in size. We discuss these in the context
of solitary magnons predicted to exist in anisotropic systems. The magnetic
anisotropy affords both competing A+B orders as well as localization of spin
excitations in a classical magnet.


title: Optimal control and zero-sum games for Markov chains of mean-field type

abstract:
  We establish existence of Markov chains of mean-field type with unbounded
jump intensities by means of a fixed point argument using the Total Variation
distance. We further show existence of nearly-optimal controls and, using a
Markov chain backward SDE approach, we suggest conditions for existence of an
optimal control and a saddle-point for respectively a control problem and a
zero-sum differential game associated with payoff functionals of mean-field
type, under dynamics driven by such Markov chains of mean-field type.


title: Artificial Atoms Based on Correlated Materials

abstract:
  Low-dimensional electron systems fabricated from quantum matter have in
recent years become available and are being explored with great intensity. This
article gives an overview of the fundamental properties of such systems and
summarizes the state of the field. We furthermore present and consider the
concept of artificial atoms fabricated from quantum materials, anticipating
remarkable scientific advances and possibly important applications of this new
field of research. The surprising properties of these artificial atoms and of
molecules or even of solids assembled from them are presented and discussed.

categories: cond-mat.str-el cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.supr-con


title: Astrophysical imaging of Kerr black holes with scalar hair

abstract:
  We address the astrophysical imaging of a family of deformed Kerr black holes
(BHs). These are stationary, asymptotically flat black hole (BH) spacetimes,
that are solutions of General Relativity minimally coupled to a massive,
complex scalar field: Kerr BHs with scalar hair (KBHsSH). Such BHs bifurcate
from the vacuum Kerr solution and can be regarded as a horizon within a
rotating boson star. In a recent letter, it was shown that KBHsSH can exhibit
very distinct shadows from the ones of their vacuum counterparts. The setup
therein, however, considered the light source to be a celestial sphere
sufficiently far away from the BH. Here, we analyse KBHsSH surrounded by an
emitting torus of matter, simulating a more realistic astrophysical
environment, and study the corresponding lensing of light as seen by a very far
away observer, to appropriately model ground-based observations of Sgr A*. We
find that the differences in imaging between KBHsSH and comparable vacuum Kerr
BHs remain, albeit less dramatic than those observed for the corresponding
shadows in the previous setup. In particular, we highlight two observables that
might allow differentiating KBHsSH and Kerr BHs. The first is the angular size
of the photon ring (in a Kerr spacetime) or lensing ring (in a KBHSH
spacetime), the latter being significantly smaller for sufficiently
non-Kerr-like spacetimes. The second is the existence of an edge in the
intensity distribution (the photon ring in Kerr spacetime). This edge can
disappear for very non-Kerr-like KBHsSH. It is plausible, therefore, that
sufficiently precise Very Long Baseline Interferometric observations of BH
candidates can constrain this model.


title:
Characterization of protein complexes using chemical cross-linking
  coupled electrospray mass spectrometry

abstract:
  Identification and characterization of large protein complexes is a mainstay
of biochemical toolboxes. Utilization of cross-linking chemicals can facilitate
the capture and identification of transient or weak interactions of a transient
nature. Here we describe a detailed methodology for cell culture based
proteomic approach. We describe the generation of cells stably expressing green
fluorescent protein (GFP)- tagged proteins under the tetracycline-inducible
promoter and subsequent proteomic analysis of GFP-interacting proteins. We
include a list of proteins that were identified as interactors of GFP.


title: Conformal invariance in driven diffusive systems at high currents

abstract:
  We consider space-time correlations in driven diffusive systems which undergo
a fluctuation into a regime with an atypically large current or dynamical
activity. For a single conserved mass we show that the spatio-temporal density
correlations in one space dimension are given by conformally invariant field
theories with central charge $c=1$, corresponding to a ballistic universality
class with dynamical exponent $z=1$. We derive a phase diagram for atypical
behaviour that besides the conformally invariant regime exhibits a regime of
phase separation for atypically low current or activity. On the phase
transition line, corresponding to typical behaviour, the dynamics belongs to
the Kardar-Parisi-Zhang universality class with dynamical exponent $z=3/2$,
except for a diffusive point with $z=2$. We demonstrate the validity of the
theory for the one-dimensional asymmetric simple exclusion process with both
periodic and open boundaries by exact results for the dynamical structure in
the limit of maximal current.


title: Polymer translocation through nano-pores in vibrating thin membranes

abstract:
  Polymer translocation is a promising strategy for the next-generation DNA
sequencing technologies. The use of biological and synthetic nano-pores,
however, still suffers from serious drawbacks. In particular, the width of the
membrane layer can accommodate several bases at the same time, making difficult
accurate sequencing applications. More recently, the use of graphene membranes
has paved the way to new sequencing capabilities, with the possibility to
measure transverse currents, among other advances. The reduced thickness of
these new membranes poses new questions on the effect of deformability and
vibrations of the membrane on the translocation process, two features which are
not taken into account in the well-established theoretical frameworks. Here, we
make a first step forward in this direction. We report numerical simulation
work on a model system simple enough to allow gathering significant insight on
the effect of these features on the average translocation time, with
appropriate statistical significance. We have found that the interplay between
thermal fluctuations and the deformability properties of the nano-pore play a
crucial role in determining the process. We conclude by discussing new
directions for further work.


title:
Experimental and causal view on information integration in autonomous
  agents

abstract:
  The amount of digitally available but heterogeneous information about the
world is remarkable, and new technologies such as self-driving cars, smart
homes, or the internet of things may further increase it. In this paper we
present preliminary ideas about certain aspects of the problem of how such
heterogeneous information can be harnessed by autonomous agents. After
discussing potentials and limitations of some existing approaches, we
investigate how \emph{experiments} can help to obtain a better understanding of
the problem. Specifically, we present a simple agent that integrates video data
from a different agent, and implement and evaluate a version of it on the novel
experimentation platform \emph{Malmo}. The focus of a second investigation is
on how information about the hardware of different agents, the agents' sensory
data, and \emph{causal} information can be utilized for knowledge transfer
between agents and subsequently more data-efficient decision making. Finally,
we discuss potential future steps w.r.t.\ theory and experimentation, and
formulate open questions.


title:
Evidence for strong lattice effects as revealed from huge unconventional
  oxygen isotope effects on the pseudogap temperature in
  La$_{2-x}$Sr$_{x}$CuO$_{4}$

abstract:
  The oxygen isotope ($^{16}$O/$^{18}$O) effect (OIE) on the pseudogap
(charge-stripe ordering) temperature $T^{\ast}$ is investigated for the cuprate
superconductor La$_{2-x}$Sr$_{x}$CuO$_{4}$ as a function of doping $x$ by means
of x-ray absorption near edge structure (XANES) studies. A strong $x$ dependent
and sign reversed OIE on $T^{\ast}$ is observed. The OIE exponent
$\alpha_{T^{\ast}}$ systematically decreases from $\alpha_{T^{\ast}} = -
0.6(1.3)$ for $x = 0.15$ to $\alpha_{T^{\ast}} = - 4.4(1.1)$ for $x = 0.06$,
corresponding to increasing $T^{\ast}$ and decreasing superconducting
transition temperature $T_{c}$. Both $T^{\ast}(^{16}{\rm O})$ and
$T^{\ast}(^{18}{\rm O})$ exhibit a linear doping dependence with different
slopes and critical end points (where $T^{\ast}(^{16}{\rm O})$ and
$T^{\ast}(^{18}{\rm O})$ fall to zero) at $x_{c}(^{16}{\rm O}) = 0.201(4)$ and
$x_{c}(^{18}{\rm O}) = 0.182(3)$, indicating a large positive OIE of $x_{c}$
with an exponent of $\alpha_{x_{c}} = 0.84(22)$. The remarkably large and
strongly doping dependent OIE on $T^{\ast}$ signals a substantial involvement
of the lattice in the formation of the pseudogap, consistent with a polaronic
approach to cuprate superconductivity and the vibronic character of its ground
state.


title:
Hardy Inequalities for the Heisenberg Laplacian on convex bounded
  polytopes

abstract:
  We prove a Hardy-type inequality for the gradient of the Heisenberg Laplacian
on open bounded convex polytopes on the first Heisenberg Group. The integral
weight of the Hardy inequality is given by the distance function to the
boundary measured with respect to the Carnot-Carath\'{e}odory metric. The
constant depends on the number of hyperplanes, given by the boundary of the
convex polytope, which are not orthogonal to the hyperplane $x_3=0$.


title: On degeneration of tensors and algebras

abstract:
  An important building block in all current asymptotically fast algorithms for
matrix multiplication are tensors with low border rank, that is, tensors whose
border rank is equal or very close to their size. To find new asymptotically
fast algorithms for matrix multiplication, it seems to be important to
understand those tensors whose border rank is as small as possible, so called
tensors of minimal border rank.
  We investigate the connection between degenerations of associative algebras
and degenerations of their structure tensors in the sense of Strassen. It
allows us to describe an open subset of $n \times n \times n$ tensors of
minimal border rank in terms of smoothability of commutative algebras. We
describe the smoothable algebra associated to the Coppersmith-Winograd tensor
and prove a lower bound for the border rank of the tensor used in the "easy
construction" of Coppersmith and Winograd.


title: Optical fiber read-out for liquid argon scintillation light

abstract:
  In this paper we describe the performance of a light detector for Ar
scintillation light made of wavelength-shifting (WLS) fibers connected to
Silicon-Photomultipliers (SiPM). The setup was conceived to be used as
anti-Compton veto for high purity germanium (HPGe) detectors operated directly
in liquid Argon (LAr). Background suppression efficiencies for different
radioactive sources were measured in a test cryostat with about 800 kg LAr.
This work was part of the R\&D effort for the GERDA experiment.


title:
La corrispondenza tra Celeste Clericetti e Luigi Cremona dal 1871 al
  1887 nelle lettere conservate presso l'Istituto Mazziniano di Genova

abstract:
  The content of this paper is the noted transcription of the 48 letters that
Celeste Clericetti wrote to Luigi Cremona and the 10 letters that Cremona wrote
to Clericetti between 1871 and 1887. The correspondence is stored at the
Istituto Mazziniano, Museo del Risorgimento in Genova and is now available at
www.luigi-cremona.it
  -----
  La corrispondenza qui riprodotta, composta da 48 lettere scritte da Celeste
Clericetti a Luigi Cremona e 10 lettere scritte da Cremona a Clericetti tra il
1871 e il 1887, si trova a Genova (Istituto Mazziniano, Museo del Risorgimento)
e ora anche sul sito www.luigi-cremona.it La trascrizione ha un ampio apparato
di note e comprende i cenni biografici di tutti i nomi citati nelle lettere.


title: Nickel-cobalt-titanate thin films - new sustainable magnetic oxides

abstract:
  Single phase nickel-cobalt-titanate thin films with a formula A1+2xTi1-xO3,
where A is Ni2+,Co2+ and -0.25<x<1, were grown by pulsed laser deposition on
sapphire substrates. There is a large window in which both Ni/Co ratio and x
can be chosen independently. In the prototype ilmenite and corundum structures
one third of the octahedra are vacant. The reported structure is obtained by
filling vacant (x>0) or emptying filled (x<0) octahedra. When x = 1 all
octahedra are filled. Two factors controlling the magnetism and crystal
distortion are identified. First is a direct overlap between the adjacent
cation d-orbitals resulting in a bond formation and magnetic interactions
between the cations. This is most clearly revealed as a crystal distortion in
the x approximately 0 compositions with approximately equal amounts of Ni and
Co: the distortion of the x approximately 0 compound is a function of Ni/Co
ratio. The second factor is x, which controls the cation shift towards a vacant
octahedron. The displacement decreases and the symmetry increases with
decreasing Ti content as was revealed by x-ray diffraction and Raman
spectroscopy. When all octahedra are filled the cations prefer octahedron
center positions. Also the number density of cations has increased by a factor
of 50 percent when compared to the ilmenite structure. The number density
ratios of Ni/Co cations between x=1 and x=0 compounds is 3. The Raman and x-ray
diffraction data collected on samples with x = 1 or close to 1 are interpreted
in terms of P63/mmc space group.


title:
A crystallographic model of the {557} habit planes in low-carbon
  martensitic steels

abstract:
  Low-alloy steels are constituted of twenty-four variants of lath martensite
that exhibit gradients of orientations from Kurdjumov-Sachs (KS) to
Nishiyama-Wassermann (NW). They are structured into four packets on each of the
common close-packed plane {111}fcc// {110}bcc; and each packet is composed of
three blocks constituted by pairs of low-misoriented variants. The habit planes
reported in literature for this type of martensite are {557}fcc, but it is not
clear whether they correspond to the laths or to the blocks. In this paper, we
present crystallographic calculations proving that the average of the two KS
distortions associated with the variants in a block is exactly a NW distortion.
A new method of averaging distortion matrices was introduced for this purpose.
It is also shown that the {575}fcc planes are let untilted by this NW
distortion, and are thus good theoretical candidates for the observed habit
planes. The predicted {575}fcc planes, however, do not contain any of the
common close-packed directions of the two variants in the block, which is in
apparent contradiction with the current view. In order to clarify this point,
some Electron BackScatter Diffraction (EBSD) maps were acquired on different
low-carbon steels; the prior austenitic grains were automatically reconstructed
and the traces of the habit planes predicted by the different models were
analyzed and compared to the morphologies. This experimental work shows that
{575}fcc planes are the habit plane of the blocks, and that the habit plane of
one block often dominates the others, which impedes to discriminate the
different models. The advantages of our model are its simplicity, the absence
of fitting parameters, and the symmetric role played by the variants the
blocks.


title: Inhomogeneous Josephson junction chains for superinductance optimization

abstract:
  We report a theoretical study of the low-frequency impedance of a Josephson
junction chain whose parameters vary in space. Our goal is to find the optimal
spatial profile which maximizes the total inductance of the chain without
shrinking the low-frequency window where the chain behaves as an inductor. If
the spatial modulation is introduced by varying the junction areas, we find
that the best result is obtained for a spatially homogeneous chain, reported
earlier in the literature. An improvement over the homogeneous result can be
obtained by representing the junctions by SQUIDs with different loop areas, so
the inductances can be varied by applying a magnetic field. Still, we find that
this improvement becomes less important for longer chains.


title: Extreme Regimes in Quantum Gravity

abstract:
  The thesis is divided into two parts. In the first part the low-energy limit
of quantum gravity is analysed, whereas in the second we deal with the
high-energy domain. In the first part, by applying the effective field theory
point of view to the quantization of general relativity, detectable, though
tiny, quantum effects in the position of Newtonian Lagrangian points of the
Earth-Moon system are found. In order to make more realistic the quantum
corrected model proposed, the full three-body problem where the Earth and the
Moon interact with a generic massive body and the restricted four-body problem
involving the perturbative effects produced by the gravitational presence of
the Sun in the Earth-Moon system are also studied. After that, a new quantum
theory having general relativity as its classical counterpart is analysed. By
exploiting this framework, an innovative interesting prediction involving the
position of Lagrangian points within the context of general relativity is
described. Furthermore, the new pattern provides quantum corrections to the
relativistic coordinates of Earth-Moon libration points of the order of few
millimetres. The second part of the thesis deals with the Riemannian curvature
characterizing the boosted form assumed by the Schwarzschild-de Sitter metric.
The analysis of the Kretschmann invariant and the geodesic equation shows that
the spacetime possesses a "scalar curvature singularity" within a 3-sphere and
that it is possible to define what we here call "boosted horizon", a sort of
elastic wall where all particles are surprisingly pushed away, suggesting that
such "boosted geometries" are ruled by a sort of "antigravity effect".
Eventually, the equivalence with the coordinate shift method is invoked in
order to demonstrate that all $\delta^2$ terms appearing in the Riemann
curvature tensor give vanishing contribution in distributional sense.


title:
Integrable cosmological models in the Einstein and in the Jordan frames
  and Bianchi-I cosmology

abstract:
  We study integrable models in the Bianchi I metric case with scalar fields
minimally and non-minimally coupled with gravity and the correspondence between
their general solutions. Using the model with a minimally coupled scalar field
and a constant potential as an example, we demonstrate how to obtain the
general solutions of the corresponding models in the Jordan frame.


title: Spin orbit torque in disordered antiferromagnets

abstract:
  We investigate the current-induced spin-orbit torque in antiferromangnetic
materials in the presence of Rashba spin orbit coupling using both the linear
response theory and the non-equilibrium Green's function technique implemented
on a tight-binding model. We show that a staggered spin density arises from
interband contributions. The effect of the disorder is restricted to the
diminution of the torque magnitude and does not bring any anomalous behavior to
the dependences of the torque on the spin orbit strength and the exchange
interaction between the antiferromagnetic local moments and the itinerant
electrons spins. We prove that the spin orbit torque is robust against the
application of the disorder compared to the case of the antiferromagnetic
spin-valve spin transfer torque.


title:
On the relation between non-exponential Scrape Off Layer profiles and
  the dynamics of filaments

abstract:
  A theoretical framework is developed to clarify the relation between the
profiles of density and temperature in the Scrape Off Layer (SOL) with the
fluctuations (filaments) that generate them. The framework is based on the
dynamics of independent filaments and on their statistical behaviour and can be
used to rigorously understand the mechanisms that lead to the non-exponential
nature of the radial SOL profiles as well as the increase of the relative
fluctuation amplitude in the far SOL. Several models for the dynamics of the
filaments, which can be applied to the framework, are derived and discussed for
the purpose of identifying how different assumptions lead to the emergence of
features in the profiles. It is found that multiple alternative models can
explain the observations, thus motivating more stringent and focused
experimental analysis. In particular, radially accelerating filaments, less
efficient parallel exhaust and also a statistical distribution of the velocity
of the filaments can all contribute to induce flatter profiles in the far SOL.
A quite general result is the resiliency of the non-exponential nature of the
profiles. At the same time, several of the models discussed can also capture
the increase of the relative fluctuation amplitude observed in the far SOL. It
is also shown that several scenarios are compatible with the broadening of the
SOL, which could be caused by charge exchange interactions with neutral
particles or by a significant radial acceleration of the filaments.


title:
Origin of the large positive magnetoresistance in Ge1-xMnx granular thin
  films

abstract:
  GeMn granular thin films are a unique and promising material for spintronics
applications due to large positive magnetoresistance (MR). Previous studies on
GeMn have suggested that the large MR is related to nanospinodal decomposition
of GeMn into Mn-rich ferromagnetic nanoparticles and Mn-poor paramagnetic
matrix. However, its microscopic origin of the MR has not been clarified yet.
Here, using X-ray magnetic circular dichroism (XMCD), which is extremely
sensitive to the local magnetic state of each atom, we investigate the magnetic
properties of the nanoparticles and the matrix in GeMn separately. We find that
the MR ratio is proportional to the product of the magnetizations originating
from the nanoparticles and the matrix. This result indicates that
spin-polarized holes in the nanoparticles penetrate into the matrix and that
these holes undergo spin-disorder magnetic scattering by the paramagnetic Mn
atoms in the matrix, which induces the large MR.


title: Dirac-semimetal phase diagram of two-dimensional black phosphorus

abstract:
  Black phosphorus (BP), a layered van der Waals material, reportedly has a
band gap sensitive to external perturbations and manifests a Dirac-semimetal
phase when its band gap is closed. Previous studies were focused on effects of
each perturbation, lacking a unified picture for the band-gap closing and the
Dirac-semimetal phase. Here, using pseudospins from the glide-reflection
symmetry, we study the electronic structures of mono- and bilayer BP and
construct the phase diagram of the Dirac-semimetal phase in the parameter space
related to pressure, strain, and electric field. We find that the
Dirac-semimetal phase in BP layers is singly connected in the phase diagram,
indicating the phase is topologically identical regardless of the gap-closing
mechanism. Our findings can be generalized to the Dirac semimetal phase in
anisotropic layered materials and can play a guiding role in search for a new
class of topological materials and devices.


title:
Determinant approach to the 2-Iterated q-Appell and mixed type q-Appell
  polynomials

abstract:
  In this article, the 2-iterated q-Appell family is introduced. Certain
2-iterated q-Appell and mixed type q-special polynomials are considered as
members of this family. The numbers related to these polynomials are obtained.
The determinant definitions for the 2-iterated q-Appell family and for the
2-iterated and mixed type q-Appell polynomials are established. The graphs of
some 2-iterated q-Appell and mixed type q-Appell polynomials are drawn for
different values of indices and the roots of these polynomials are also
investigated for certain values of index n by using Matlab. Finally, the
approximate solutions of the real zeros of these polynomials are given.


title: On Science, pseudoscience and String theory

abstract:
  The article discusses the demarcation problem; how to distinguish between
science and pseudoscience. It then examines the string theory under various
demarcation criteria to conclude that string theory cannot be considered as
science.


title: Nonequilibrium scenarios in cluster-forming quantum lattice models

abstract:
  We investigate the out-of-equilibrium physics of monodisperse bosonic
ensembles on a square lattice. The effective Hamiltonian description of these
systems is given in terms of an extended Hubbard model with cluster-forming
interactions relevant to experimental realizations with cold Rydberg-dressed
atoms. The ground state of the model, recently investigated in Phys. Rev. Lett.
123, 045301 (2019), features, aside from a superfluid and a stripe crystalline
phase occurring at small and large interaction strength $V$, respectively, a
rare first-order transition between an isotropic and an anisotropic stripe
supersolid at intermediate $V$. By means of quantum Monte Carlo calculations we
show that the equilibrium crystal may be turned into a glass by simulated
temperature quenches and that out-of-equilibrium isotropic (super)solid states
may emerge also when their equilibrium counterparts are anisotropic. These
out-of-equilibrium states are of experimental interest, their excess energy
with respect to the ground state being within the energy window typically
accessed in cold atom experiments. We find, after quenching, no evidence of
coexistence between superfluid and glassy behavior. Such an absence of
superglassiness is qualitatively explained.


title:
Local Canonical Correlation Analysis for Nonlinear Common Variables
  Discovery

abstract:
  In this paper, we address the problem of hidden common variables discovery
from multimodal data sets of nonlinear high-dimensional observations. We
present a metric based on local applications of canonical correlation analysis
(CCA) and incorporate it in a kernel-based manifold learning technique.We show
that this metric discovers the hidden common variables underlying the
multimodal observations by estimating the Euclidean distance between them. Our
approach can be viewed both as an extension of CCA to a nonlinear setting as
well as an extension of manifold learning to multiple data sets. Experimental
results show that our method indeed discovers the common variables underlying
high-dimensional nonlinear observations without assuming prior rigid model
assumptions.


title: Context Trees: Augmenting Geospatial Trajectories with Context

abstract:
  Exposing latent knowledge in geospatial trajectories has the potential to
provide a better understanding of the movements of individuals and groups.
Motivated by such a desire, this work presents the context tree, a new
hierarchical data structure that summarises the context behind user actions in
a single model. We propose a method for context tree construction that augments
geospatial trajectories with land usage data to identify such contexts. Through
evaluation of the construction method and analysis of the properties of
generated context trees, we demonstrate the foundation for understanding and
modelling behaviour afforded. Summarising user contexts into a single data
structure gives easy access to information that would otherwise remain latent,
providing the basis for better understanding and predicting the actions and
behaviours of individuals and groups. Finally, we also present a method for
pruning context trees, for use in applications where it is desirable to reduce
the size of the tree while retaining useful information.


title: Pulse-wise GRB correlation: implication as a cosmological tool

abstract:
  Gamma-ray bursts (GRBs) are cosmological explosions which carry valuable
information from the distant past of the expanding universe. One of the
greatest discoveries in modern cosmology is the finding of the accelerated
expansion of the universe using Type Ia supernovae (SN Ia) as standard candles.
However, due to the interstellar extinction SN Ia can be seen only up to a
redshift $z\sim 1.5$. GRBs are considered as the potential alternative to push
this limit to as high as $z\sim 10$, a redshift regime corresponding to an
epoch when the universe just started to form the first structures. There exist
several correlations between the energy and an observable of a GRB which can be
used to derive luminosity distance. In recent works, we have studied spectral
evolution within the individual pulses and obtained such correlations within
the pulses. Here we summarize our results of the pulse-wise GRB correlation
study. It is worth mentioning that all GRB correlations are still empirical,
and we cannot use them in cosmology unless we understand the basic physics of
GRBs. To this end, we need to investigate the prompt emission spectrum which is
so far generally described by the empirical Band function. We shall discuss our
current understanding of the radiation process particularly the finding of two
blackbodies and a powerlaw (the 2BBPL model) as the generic spectral model and
its implication. This is a work in progress and we expect to obtain the most
fundamental GRB correlation based on our improved spectral model.


title:
Optimization Schemes for Efficient Multiple Exciton Generation and
  Extraction in Colloidal Quantum Dots

abstract:
  Multiple exciton generation is a process in which more than one electron hole
pair is generated per absorbed photon. It allows us to increase the efficiency
of solar energy harvesting. Experimental studies have shown the multiple
exciton generation yield of 1.2 in isolated colloidal quantum dots. However
real photoelectric devices require the extraction of electron hole pairs to
electric contacts. We provide a systematic study of the corresponding quantum
coherent processes including extraction and injection and show that a proper
design of extraction and injection rates enhances the yield significantly up to
values around 1.6.


title: LQG Online Learning

abstract:
  Optimal control theory and machine learning techniques are combined to
formulate and solve in closed form an optimal control formulation of online
learning from supervised examples with regularization of the updates. The
connections with the classical Linear Quadratic Gaussian (LQG) optimal control
problem, of which the proposed learning paradigm is a non-trivial variation as
it involves random matrices, are investigated. The obtained optimal solutions
are compared with the Kalman-filter estimate of the parameter vector to be
learned. It is shown that the proposed algorithm is less sensitive to outliers
with respect to the Kalman estimate (thanks to the presence of the
regularization term), thus providing smoother estimates with respect to time.
The basic formulation of the proposed online-learning framework refers to a
discrete-time setting with a finite learning horizon and a linear model.
Various extensions are investigated, including the infinite learning horizon
and, via the so-called "kernel trick", the case of nonlinear models.


title:
Metamodel-based sensitivity analysis: Polynomial chaos expansions and
  Gaussian processes

abstract:
  Global sensitivity analysis is now established as a powerful approach for
determining the key random input parameters that drive the uncertainty of model
output predictions. Yet the classical computation of the so-called Sobol'
indices is based on Monte Carlo simulation, which is not affordable when
computationally expensive models are used, as it is the case in most
applications in engineering and applied sciences. In this respect metamodels
such as polynomial chaos expansions (PCE) and Gaussian processes (GP) have
received tremendous attention in the last few years, as they allow one to
replace the original, taxing model by a surrogate which is built from an
experimental design of limited size. Then the surrogate can be used to compute
the sensitivity indices in negligible time. In this chapter an introduction to
each technique is given, with an emphasis on their strengths and limitations in
the context of global sensitivity analysis. In particular, Sobol' (resp. total
Sobol') indices can be computed analytically from the PCE coefficients. In
contrast, confidence intervals on sensitivity indices can be derived
straightforwardly from the properties of GPs. The performance of the two
techniques is finally compared on three well-known analytical benchmarks
(Ishigami, G-Sobol and Morris functions) as well as on a realistic engineering
application (deflection of a truss structure).


title: GHZ states and PR boxes in the classical limit

abstract:
  A recent paper [1] argues that bipartite "PR-box" correlations, though
designed to respect relativistic causality, in fact violate relativistic
causality in the classical limit. As a test of Ref. [1], we consider GHZ
correlations as a tripartite version of PR-box correlations, and ask whether
the arguments of Ref. [1] extend to GHZ correlations. If they do - i.e. if they
show that GHZ correlations violate relativistic causality in the classical
limit - then Ref. [1] must be incorrect, since GHZ correlations are quantum
correlations and respect relativistic causality. But the arguments fail. We
also show that both PR-box correlations and GHZ correlations can be
retrocausal, but the retrocausality of PR-box correlations leads to
self-contradictory causal loops, while the retrocausality of GHZ correlations
does not.


title:
Efficient Pairwise Learning Using Kernel Ridge Regression: an Exact
  Two-Step Method

abstract:
  Pairwise learning or dyadic prediction concerns the prediction of properties
for pairs of objects. It can be seen as an umbrella covering various machine
learning problems such as matrix completion, collaborative filtering,
multi-task learning, transfer learning, network prediction and zero-shot
learning. In this work we analyze kernel-based methods for pairwise learning,
with a particular focus on a recently-suggested two-step method. We show that
this method offers an appealing alternative for commonly-applied
Kronecker-based methods that model dyads by means of pairwise feature
representations and pairwise kernels. In a series of theoretical results, we
establish correspondences between the two types of methods in terms of linear
algebra and spectral filtering, and we analyze their statistical consistency.
In addition, the two-step method allows us to establish novel algorithmic
shortcuts for efficient training and validation on very large datasets. Putting
those properties together, we believe that this simple, yet powerful method can
become a standard tool for many problems. Extensive experimental results for a
range of practical settings are reported.


title:
An averaged projected Robbins-Monro algorithm for estimating the
  parameters of a truncated spherical distribution

abstract:
  The objective of this work is to propose a new algorithm to fit a sphere on a
noisy 3D point cloud distributed around a complete or a truncated sphere. More
precisely, we introduce a projected Robbins-Monro algorithm and its averaged
version for estimating the center and the radius of the sphere. We give
asymptotic results such as the almost sure convergence of these algorithms as
well as the asymptotic normality of the averaged algorithm. Furthermore, some
non-asymptotic results will be given, such as the rates of convergence in
quadratic mean. Some numerical experiments show the efficiency of the proposed
algorithm on simulated data for small to moderate sample sizes.