title:
Astrophysical Fluids of Novae: High Resolution Pre-decay X-ray spectrum
  of V4743 Sagittarii

abstract:
  Eight X-ray observations of V4743 Sgr (2002), observed with Chandra and
XMM-Newton are presented. The nova turned off some time between days 301.9 and
371, and the X-ray flux subsequently decreased from day 301.9 to 526 following
an exponential decline time scale of $(96 \pm 3)$ days. We use the absorption
lines present in the SSS spectrum for diagnostic purposes, and characterize the
physics and the dynamics of the expanding atmosphere during the explosion of
the nova. The information extracted from this first stage is then used as input
for computing full photoionization models of the ejecta in V4743 Sgr. The SSS
spectrum is modeled with a simple black-body and multiplicative Gaussian lines,
which provides us of a general kinematical picture of the system, before it
decays to its faint phase (Ness et al. 2003). In the grating spectra taken
between days 180.4 and 370, we can resolve the line profiles of absorption
lines arising from H-like and He-like C, N, and O, including transitions
involving higher principal quantum numbers. Except for a few interstellar
lines, all lines are significantly blue-shifted, yielding velocities between
1000 and 6000 km/s which implies an ongoing mass loss. It is shown that
significant expansion and mass loss occur during this phase of the explosion,
at a rate $\dot{M} \approx (3-5) \times 10^{-4} ~ (\frac{L}{L_{38}}) ~
M_{\odot}/yr$. Our measurements show that the efficiency of the amount of
energy used for the motion of the ejecta, defined as the ratio between the
kinetic luminosity $L_{\rm kin}$ and the radiated luminosity $L_{\rm rad}$, is
of the order of one.


title:
Microscopic Theory of Resistive Switching in Ordered Insulators:
  Electronic vs. Thermal Mechanism

abstract:
  We investigate the dramatic switch of resistance in ordered correlated
insulators, when driven out of equilibrium by a strong voltage bias.
Microscopic calculations on a driven-dissipative lattice of interacting
electrons explain the main experimental features of resistive switching (RS),
such as the hysteretic $I$-$V$ curves and the formation of hot conductive
filaments. The energy-resolved electron distribution at the RS reveals the
underlying nonequilibrium electronic mechanism, namely Landau-Zener tunneling,
and also justifies a thermal description where the hot-electron temperature,
estimated from the first moment of the distribution, matches the equilibrium
phase transition temperature. We discuss the tangled relationship between
filament growth and negative differential resistance, and the influence of
crystallographic structure and disorder in the RS.


title:
Nondeterminism and an abstract formulation of Ne\v{c}iporuk's lower
  bound method

abstract:
  A formulation of "Ne\v{c}iporuk's lower bound method" slightly more inclusive
than the usual complexity-measure-specific formulation is presented. Using this
general formulation, limitations to lower bounds achievable by the method are
obtained for several computation models, such as branching programs and Boolean
formulas having access to a sublinear number of nondeterministic bits. In
particular, it is shown that any lower bound achievable by the method of
Ne\v{c}iporuk for the size of nondeterministic and parity branching programs is
at most $O(n^{3/2}/\log n)$.


title: Geoplotlib: a Python Toolbox for Visualizing Geographical Data

abstract:
  We introduce geoplotlib, an open-source python toolbox for visualizing
geographical data. geoplotlib supports the development of hardware-accelerated
interactive visualizations in pure python, and provides implementations of dot
maps, kernel density estimation, spatial graphs, Voronoi tesselation,
shapefiles and many more common spatial visualizations. We describe geoplotlib
design, functionalities and use cases.


title: Prospecies of algebras I: Basic properties

abstract:
  In this paper, we generalise part of the theory of hereditary algebras to the
context of prospecies of algebras. Here, a prospecies is a generalisation of
Gabriel's concept of species gluing algebras via projective bimodules along a
quiver to obtain a new algebra. This provides a categorical perspective on a
recent paper by Gei\ss, Leclerc, and Schr\"oer. In particular, we construct a
corresponding preprojective algebra, and establish a theory of a separated
prospecies yielding a stable equivalence between certain functorially finite
subcategories.


title:
X-ray outflows of active galactic nuclei warm absorbers: A 900 ks
  Chandra simulated spectrum

abstract:
  We report on the performance of the statistical, X-ray absorption lines
identification procedure XLINE-ID. As illustration, it is used to estimate the
time averaged gas density $n_H(r)$ of a representative AGN's warm absorber
($T\approx 10^5$~K) X-ray simulated spectrum. The method relies on three key
ingredients: (1) a well established emission continuum level; (2) a robust grid
of photoionisation models spanning several orders of magnitude in gas density
($n_H$), plasma column density ($N_H$), and in ionization states; (3)
theoretical curves of growth for a large set of atomic lines. By comparing
theoretical and observed equivalent widths of a large set of lines, spanning
highly ionized charge states from O, Ne, Mg, Si, S, Ar, and the Fe L-shell and
K-shell, we are able to infer the location of the X-ray warm absorber.


title:
Explanation for Cancer in Rats, Mice and Humans due to Cell Phone
  Radiofrequency Radiation

abstract:
  Very recently, the National Toxicology Program reported a correlation between
exposure to whole body 900 MHz radiofrequency radiation and cancer in the
brains and hearts of Sprague Dawley male rats. This paper proposes the
following explanation for these results. The neurons around the rat's brain and
heart form closed electrical circuits and, following Faraday's Law, 900 MHz
radiofrequency radiation induces 900 MHz electrical currents in these neural
circuits. In turn, these 900 MHz currents in the neural circuits generate
sufficient localized heat in the neural cell axons to shift the equilibrium
concentration of carcinogenic radicals to higher levels and thus, to higher
incidences of cancer. This model is then applied to mice and humans.


title: Bumpy metrics on spheres and minimal index growth

abstract:
  The existence of two geometrically distinct closed geodesics on an
$n$-dimensional sphere $S^n$ with a non-reversible and bumpy Finsler metric was
shown independently by Duan--Long [7] and the author [27]. We simplify the
proof of this statement by the following observation: If for some $N \in
\mathbb{N}$ all closed geodesics of index $\le N$ of a non-reversible and bumpy
Finsler metric on $S^n$ are geometrically equivalent to the closed geodesic $c$
then there is a covering $c^r$ of minimal index growth, i.e. $${\rm
ind}(c^{rm})=m {\rm ind}(c^r)-(m-1)(n-1)$$ for all $m \ge 1$ with ${\rm
ind}\left(c^{rm}\right)\le N.$ But this leads to a contradiction for $N
=\infty$ as pointed out by Goresky--Hingston [13]. We also discuss
perturbations of Katok metrics on spheres of even dimension carrying only
finitely many closed geodesics. For arbitrarily large $L>0$ we obtain on $S^2$
a metric of positive flag curvature carrying only two closed geodesics of
length $<L$ which do not intersect.


title: Low-degree factors of random polynomials

abstract:
  Motivated by the question of whether a random polynomial with integer
coefficients is likely to be irreducible, we study the probability that a monic
polynomial with integer coefficients has a low-degree factor over the integers,
which is equivalent to having a low-degree algebraic root. It is known in
certain cases that random polynomials with integer coefficients are very likely
to be irreducible, and our project can be viewed as part of the general program
of testing whether this is a universal behavior exhibited by many random
polynomial models.
  Our main result shows that pointwise delocalization of the roots of a random
polynomial can be used to imply that the polynomial is unlikely to have a
low-degree factor over the integers. We apply our main result to a number of
models of random polynomials, including characteristic polynomials of random
matrices, where strong delocalization results are known. Studying a variety of
random matrix models---including iid matrices, symmetric matrices, elliptical
matrices, and adjacency matrices of random graphs and digraphs---we show that,
for a random square matrix with integer entries, the characteristic polynomial
is unlikely to have a low-degree factor over the integers, which is equivalent
to the matrix having an eigenvalue that is algebraic with low degree. Having a
low-degree algebraic eigenvalue generalizes the questions of whether the matrix
has a rational eigenvalue and whether the matrix is singular (i.e., has an
eigenvalue equal to zero).


title: Understanding Predictability and Exploration in Human Mobility

abstract:
  Predictive models for human mobility have important applications in many
fields such as traffic control, ubiquitous computing and contextual
advertisement. The predictive performance of models in literature varies quite
broadly, from as high as 93% to as low as under 40%. In this work we
investigate which factors influence the accuracy of next-place prediction,
using a high-precision location dataset of more than 400 users for periods
between 3 months and one year. We show that it is easier to achieve high
accuracy when predicting the time-bin location than when predicting the next
place. Moreover we demonstrate how the temporal and spatial resolution of the
data can have strong influence on the accuracy of prediction. Finally we
uncover that the exploration of new locations is an important factor in human
mobility, and we measure that on average 20-25% of transitions are to new
places, and approx. 70% of locations are visited only once. We discuss how
these mechanisms are important factors limiting our ability to predict human
mobility.


title: The basic physics of the binary black hole merger GW150914

abstract:
  The first direct gravitational-wave detection was made by the Advanced Laser
Interferometer Gravitational Wave Observatory on September 14, 2015. The
GW150914 signal was strong enough to be apparent, without using any waveform
model, in the filtered detector strain data. Here, features of the signal
visible in the data are analyzed using concepts from Newtonian physics and
general relativity, accessible to anyone with a general physics background. The
simple analysis presented here is consistent with the fully
general-relativistic analyses published elsewhere,in showing that the signal
was produced by the inspiral and subsequent merger of two black holes. The
black holes were each of approximately 35 Msun, still orbited each other as
close as ~350 km apart, and subsequently merged to form a single black hole.
Similar reasoning, directly from the data, is used to roughly estimate how far
these black holes were from the Earth, and the energy that they radiated in
gravitational waves.


title:
Optical determination of the Neel vector in a CuMnAs thin-film
  antiferromagnet

abstract:
  Recent breakthroughs in electrical detection and manipulation of
antiferromagnets have opened a new avenue in the research of non-volatile
spintronic devices. Antiparallel spin sublattices in antiferromagnets,
producing zero dipolar fields, lead to the insensitivity to magnetic field
perturbations, multi-level stability, ultra-fast spin dynamics and other
favorable characteristics which may find utility in fields ranging from
magnetic memories to optical signal processing. However, the absence of a net
magnetic moment and the ultra-short magnetization dynamics timescales make
antiferromagnets notoriously difficult to study by common magnetometers or
magnetic resonance techniques. In this paper we demonstrate the experimental
determination of the Neel vector in a thin film of antiferromagnetic CuMnAs
which is the prominent material used in the first realization of
antiferromagnetic memory chips. We employ a femtosecond pump-probe
magneto-optical experiment based on magnetic linear dichroism. This table-top
optical method is considerably more accessible than the traditionally employed
large scale facility techniques like neutron diffraction and X-ray magnetic
dichroism measurements. This optical technique allows an unambiguous direct
determination of the Neel vector orientation in thin antiferromagnetic films
utilized in devices directly from measured data without fitting to a
theoretical model.


title:
Superresolved optical imaging through higher-order spatial frequency
  harmonic generation without beating the diffraction limit of light

abstract:
  We proposed a method to achieve superresolved optical imaging without beating
the diffraction limit of light. This is achieved by magnifying the ideal
optical image of the object through higher-order spatial frequency generation
while keeping the size of the effective point spread function of the optical
imaging system unchanged. A proof-of-principle experiment was demonstrated in a
modified $4f$-imaging system, where the spatial frequency of a two-line source
was doubled or tripled on the confocal Fourier plane of the $4f$-imaging system
through a light pulse storage and retrieval process based on the
electromagnetically induced transparency effect in a Pr$^{3+}$:$\rm Y_2SiO_5$
crystal, and an originally unresolvable image of the two line sources in the
conventional $4f$-imaging system became resolvable with the spatial frequency
doubling or tripling. Our results offer an original way towards improving
optical imaging resolution without beating the diffraction limit of light,
which is totally different from the existing superresolution methods to
overcome the diffraction limit.


title: Emergence of collective intonation in the musical performance of crowds

abstract:
  The average individual is typically a mediocre singer, with a rather
restricted capacity to sing a melody in tune. Yet when many singers are
assembled to perform collectively, the resulting melody of the crowd is
suddenly perceived by an external listener as perfectly tuned -as if it was
actually a choral performance- even if each individual singer is out of tune.
This collective phenomenon is an example of a wisdom of crowds effect that can
be routinely observed in music concerts or other social events, when a group of
people spontaneously sings at unison. In this paper we rely on the
psychoacoustic properties of pitch and provide a simple mechanistic explanation
for the onset of this emergent behavior.


title:
Weight-adjusted discontinuous Galerkin methods: wave propagation in
  heterogeneous media

abstract:
  Time-domain discontinuous Galerkin (DG) methods for wave propagation require
accounting for the inversion of dense elemental mass matrices, where each mass
matrix is computed with respect to a parameter-weighted L2 inner product. In
applications where the wavespeed varies spatially at a sub-element scale, these
matrices are distinct over each element, necessitating additional storage. In
this work, we propose a weight-adjusted DG (WADG) method which reduces storage
costs by replacing the weighted L2 inner product with a weight-adjusted inner
product. This equivalent inner product results in an energy stable method, but
does not increase storage costs for locally varying weights. A-priori error
estimates are derived, and numerical examples are given illustrating the
application of this method to the acoustic wave equation with heterogeneous
wavespeed.


title:
Constraining the Rate of Primordial Black-Hole Explosions and Extra
  Dimension Scale using a Low-Frequency Radio Antenna Array

abstract:
  An exploding primordial black-hole (PBH) may produce a single pulse of
electromagnetic radiation detectable at the low-frequency end of the radio
spectrum. Furthermore, a radio transient from an exploding PBH could be a
signature of an extra spatial dimension. We describe here an approach for
searching for PBH explosions using a low-frequency radio antenna array, and as
a practical example, the results of a such a search using the
Eight-meter-wavelength Transient Array (ETA). No compelling astrophysical
signal was detected in $\approx 4$ hours of data implying an observational
upper limit on the rate of exploding PBHs is $4.2 \times 10^{-7}
\,\rm{pc}^{-3}\,\rm{yr}^{-1}$ for an exploding PBH with a fireball Lorentz
factor of $10^{4.5}$ for the standard scenario of Page and Hawking. This rate
limit is the strongest constraint yet set for PBH explosions with this fireball
Lorentz factor. Observations ($\sim300$ hours) using the Arecibo Observatory
were used to set a stronger constraint on the rate of PBH explosions for a
fireball Lorentz factor of $10^{4.6}$ but the limit set by those observations
for the fireball Lorentz factor considered here are less stringent by more than
an order of magnitude. The limits considered here are applicable to exploding
PBHs in the halo of the Galaxy. These observations also imply an upper limit of
$2.0 \times 10^{-4} \,\rm{pc}^{-3}\,\rm{yr}^{-1}$ on the rate of PBH explosions
in the context of certain extra dimension models as described by Kavic et al.
This rate limit is for a fireball Lorentz factor of $10^{4.3}$ which
corresponds to an extra dimension compactification scale of $3.0 \times
10^{-18}$m.


title:
Iterative Learning of Answer Set Programs from Context Dependent
  Examples

abstract:
  In recent years, several frameworks and systems have been proposed that
extend Inductive Logic Programming (ILP) to the Answer Set Programming (ASP)
paradigm. In ILP, examples must all be explained by a hypothesis together with
a given background knowledge. In existing systems, the background knowledge is
the same for all examples; however, examples may be context-dependent. This
means that some examples should be explained in the context of some
information, whereas others should be explained in different contexts. In this
paper, we capture this notion and present a context-dependent extension of the
Learning from Ordered Answer Sets framework. In this extension, contexts can be
used to further structure the background knowledge. We then propose a new
iterative algorithm, ILASP2i, which exploits this feature to scale up the
existing ILASP2 system to learning tasks with large numbers of examples. We
demonstrate the gain in scalability by applying both algorithms to various
learning tasks. Our results show that, compared to ILASP2, the newly proposed
ILASP2i system can be two orders of magnitude faster and use two orders of
magnitude less memory, whilst preserving the same average accuracy. This paper
is under consideration for acceptance in TPLP.


title:
Daala: Building A Next-Generation Video Codec From Unconventional
  Technology

abstract:
  Daala is a new royalty-free video codec that attempts to compete with
state-of-the-art royalty-bearing codecs. To do so, it must achieve good
compression while avoiding all of their patented techniques. We use technology
that is as different as possible from traditional approaches to achieve this.
This paper describes the technology behind Daala and discusses where it fits in
the newly created AV1 codec from the Alliance for Open Media. We show that
Daala is approaching the performance level of more mature, state-of-the art
video codecs and can contribute to improving AV1.


title:
Simultaneous Observations of Giant Pulses from Pulsar PSR B0950+08 at 42
  MHz and 74 MHz

abstract:
  We report the detection of giant pulse emission from PSR~B0950+08 in 12 hours
of observations made simultaneously at 42~MHz and 74~MHz, using the first
station of the Long Wavelength Array, LWA1. We detected 275 giant pulses (in
0.16\% of the pulse periods) and 465 giant pulses (0.27\%) at 42 and 74~MHz,
respectively. The pulsar is weaker and produces less frequent giant pulses than
at 100~MHz. Here, giant pulses are taken as having $\geq$ 10 times the flux
density of an average pulse; their cumulative distribution of pulse strength
follows a power law, with a index of $-$4.1 at 42~MHz and $-$5.1 at 74~MHz,
which is much less steep than would be expected if we were observing the tail
of a Gaussian distribution of normal pulses. We detected no other transient
pulses in a wide dispersion measure range from 1 to 5000~pc~cm$^{-3}$. There
were 128 giant pulses detected within in the same periods from both 42 and
74~MHz, which means more than half of them are not generated in a wide band. We
use CLEAN-based algorithm to analyze the temporal broadening and conclude that
the scattering effect from the interstellar medium can not be observed. We
calculated the altitude $r$ of the emission region using the dipolar magnetic
field model. We found $r$(42~MHz) = 29.27~km ($0.242\%$ of $R_{LC}$) and
$r$(74~MHz) = 29.01~km ($0.240\%$ of $R_{LC}$) for the average pulse, while for
giant pulses, $r$(42~MHz) = 29.10~km ($0.241\%$ of $R_{LC}$) and $r$(74~MHz) =
28.95~km ($0.240\%$ of $R_{LC}$). Giant pulses, which have a double-peak
structure, have a smaller mean peak-to-peak separation compared to the average
pulse.


title:
Quantum Criticality in the Ferromagnetic Superconductor UCoGe under
  Pressure and Magnetic Field

abstract:
  The pressure-temperature phase diagram of the orthorhombic ferromagnetic
superconductor UCoGe was determined by resistivity measurements up to
$10.5~$GPa. The Curie temperature $T_C$ is suppressed with pressure and
vanishes at the critical pressure $p_c\approx1~$GPa. Superconductivity is
observed in both the ferromagnetic state at low pressure, and in the
paramagnetic state above $p_c$ up to about 4$~$GPa. Non-Fermi liquid behavior
appears in a large pressure range. The resistivity varies linearly with
temperature around $p_c$ and evolves continuously with pressure to a $T^2$
Fermi-liquid behavior for $p \gtrapprox 5$~GPa. The residual resistivity as a
function of pressure shows a maximum far above $p_c$ at $p^\star=7.2~$GPa and
the amplitude of the inelastic scattering term of the resistivity decreases by
more than one order in magnitude at $p^\star$, which appears to mark the
entrance into a weakly correlated regime. The pressure dependence of the upper
critical field for magnetic field applied along the $b$ and $c$ axis
illustrates the drastic difference in the field dependence of the ferromagnetic
superconducting pairing. While for $H\parallel b$ axis $H_{c2}(T)$ is driven by
the suppression of the ferromagnetic order, it is dominated by the strong
initial suppression of the ferromagnetic fluctuations for a field applied in
the easy magnetization axis $c$.


title:
Simultaneous Observations of Giant Pulses from Pulsar PSR B0031-07 at 38
  MHz and 74 MHz

abstract:
  The first station of the Long Wavelength Array (LWA1) was used to study
PSR~B0031-07 with simultaneous observations at 38 and 74~MHz. We found that 158
(0.35\%) of the observed pulses at 38~MHz and 221 (0.49\%) of the observed
pulses at 74~MHz qualified as giant pulses in a total of 12 hours of
observations. Giant pulses are defined as having flux densities of a factor of
$\geq$ 90 times that of an average pulse at 38~MHz and $\geq$ 80 times that of
an average pulse at 74~MHz. The cumulative distribution of pulse strength
follows a power law, with an index of $-$4.2 at 38~MHz and $-$4.9 at 74~MHz.
This distribution has a much more gradual slope than would be expected if
observing the tail of a Gaussian distribution of normal pulses. The dispersion
measure value which resulted in the largest signal-to-noise for dedispersed
pulses was DM $=10.9$~pc~cm$^{-3}$. No other transient pulses were detected in
the data in the wide dispersion measure range from 1 to 5000~pc~cm$^{-3}$.
There were 12 giant pulses detected within the same period from both 38 and
74~MHz, meaning that the majority of them are not generated in a wide band.


title: Supergravity from Gauge Theory

abstract:
  Gauge/gravity duality is the conjecture that string theories have dual
descriptions as gauge theories. Weakly-coupled gravity is dual to
strongly-coupled gauge theories, ideal for lattice calculations. I will show
precision lattice calculations that confirm large-N continuum D0-brane quantum
mechanics correctly reproduces the leading-order supergravity prediction for a
black hole's internal energy---the first leading-order test of the
duality---and constrains stringy corrections.


title:
On Uniform Large-Scale Volume Growth for the Carnot-Carath\'eodory
  Metric on Unbounded Model Hypersurfaces in $\mathbb{C}^2$

abstract:
  We consider the rate of volume growth of large Carnot-Carath\'eodory metric
balls on a class of unbounded model hypersurfaces in $\mathbb{C}^2$. When the
hypersurface has a uniform global structure, we show that a metric ball of
radius $\delta \gg 1$ either has volume on the order of $\delta^3$ or
$\delta^4$. We also give necessary and sufficient conditions on the
hypersurface to display either behavior.


title: Model-based STFT phase recovery for audio source separation

abstract:
  For audio source separation applications, it is common to estimate the
magnitude of the short-time Fourier transform (STFT) of each source. In order
to further synthesizing time-domain signals, it is necessary to recover the
phase of the corresponding complex-valued STFT. Most authors in this field
choose a Wiener-like filtering approach which boils down to using the phase of
the original mixture. In this paper, a different standpoint is adopted. Many
music events are partially composed of slowly varying sinusoids and the STFT
phase increment over time of those frequency components takes a specific form.
This allows phase recovery by an unwrapping technique once a short-term
frequency estimate has been obtained. Herein, a novel iterative source
separation procedure is proposed which builds upon these results. It consists
in minimizing the mixing error by means of the auxiliary function method. This
procedure is initialized by exploiting the unwrapping technique in order to
generate estimates that benefit from a temporal continuity property.
Experiments conducted on realistic music pieces show that, given accurate
magnitude estimates, this procedure outperforms the state-of-the-art consistent
Wiener filter.


title: Skew-signings of positive weighted digraphs

abstract:
  An arc-weighted digraph is a pair $(D,\omega)$ where $D$ is a digraph and
$\omega$ is an \emph{arc-weight function} that assigns\ to each arc $uv$ of $D$
a nonzero real number $\omega(uv)$. Given an arc-weighted digraph $(D,\omega)$
with vertices $v_{1},\ldots,v_{n}$, the weighted adjacency matrix of
$(D,\omega)$ is defined as the matrix $A(D,\omega)=[a_{ij}]$ where
$a_{ij}=\omega(v_{i}v_{j})$, if $v_{i}v_{j}\ $an arc of $D$ and $0$ otherwise.
Let $(D,\omega)$ be a positive arc-weighted digraphs and assume that $D$ is
loopless and symmetric. A skew-signing of $(D,\omega)$ is an arc-weight
function $\omega^{\prime}$ such that $\omega^{\prime}(uv)=\pm \omega(uv)$ and
$\omega^{\prime}(uv)\omega^{\prime}(vu)<0$ for every arc $uv$ of $D$. In this
paper, we give necessary and sufficient conditions under which the
characteristic polynomial of $A(D,\omega^{\prime})$ is the same for every
skew-signing $\omega^{\prime}$ of $(D,\omega)$. Our Main Theorem generalizes a
result of Cavers et al (2012) about skew-adjacency matrices of graphs.


title:
Ricci curvature and eigenvalue estimates for the magnetic Laplacian on
  manifolds

abstract:
  In this paper, we present a Lichnerowicz type estimate and (higher order)
Buser type estimates for the magnetic Laplacian on a closed Riemannian manifold
with a magnetic potential. These results relate eigenvalues, magnetic fields,
Ricci curvature, and Cheeger type constants.


title: Neutron-gamma competition for $\beta$-delayed neutron emission

abstract:
  We present a coupled Quasi-particle Random Phase Approximation and
Hauser-Feshbach (QRPA+HF) model for calculating delayed particle emission. This
approach uses microscopic nuclear structure information which starts with
Gamow-Teller strength distributions in the daughter nucleus, and then follows
the statistical decay until the initial available excitation energy is
exhausted. Explicitly included at each particle emission stage is $\gamma$-ray
competition. We explore this model in the context of neutron emission of
neutron-rich nuclei and find that neutron-gamma competition can lead to both
increases and decreases in neutron emission probabilities, depending on the
system considered. A second consequence of this formalism is a prediction of
more neutrons on average being emitted after $\beta$-decay for nuclei near the
neutron dripline compared to models that do not consider the statistical decay.


title:
Ternary Semiconductors NiZrSn and CoZrBi with half-Heusler structure: a
  first-principles study

abstract:
  The ternary semiconductors NiZrSn and CoZrBi with C1_b crystal structure are
introduced by calculating their basic structural, electronic and phononic
properties using density functional theory. Both the gradient-corrected PBE
functional and the hybrid functional HSE06 are employed. While NiZrSn is found
to be a small-band-gap semiconductor (E_g = 0.46 eV in PBE and 0.60 eV in
HSE06), CoZrBi has a band gap of 1.01 eV in PBE (1.34 eV in HSE06). Moreover,
effective masses and deformation potentials are reported. In both materials
ABC, the intrinsic point defects introduced by species A (Ni or Co) are
calculated. The Co-induced defects in CoZrBi are found to have a higher
formation energy compared to Ni-induced defects in NiZrSn. The interstitial Ni
atom (Ni_i ) as well as the V_Ni Ni_i complex introduce defect states in the
band gap, whereas the Ni vacancy (V_Ni) only reduces the size of the band gap.
Motivated by the reported use of NiZrSn for thermoelectric applications, the
Seebeck coefficient of both materials is calculated. We find that CoZrBi
displays a rather large thermopower of up to 500 micro-V/K when p-doped,
whereas NiZrSn possesses its maximum thermopower in the n-type regime. The
reported difficulties in achieving p-type doping in NiZrSn could be
rationalized by the unintended formation of Ni_i^2+ in conjunction with
extrinsic acceptors, resulting in their compensation. Moreover, it is found
that all types of defects considered, when present in concentrations as large
as 3%, tend to reduce the thermopower compared to ideal bulk crystals at
T=600K. For NiZrSn, the calculated thermodynamic data suggest that additional
Ni impurities could be removed by annealing, leading to precipitation of a
metallic Ni_2ZrSn phase.


title: Iterative importance sampling algorithms for parameter estimation

abstract:
  In parameter estimation problems one computes a posterior distribution over
uncertain parameters defined jointly by a prior distribution, a model, and
noisy data. Markov Chain Monte Carlo (MCMC) is often used for the numerical
solution of such problems. An alternative to MCMC is importance sampling, which
can exhibit near perfect scaling with the number of cores on high performance
computing systems because samples are drawn independently. However, finding a
suitable proposal distribution is a challenging task. Several sampling
algorithms have been proposed over the past years that take an iterative
approach to constructing a proposal distribution. We investigate the
applicability of such algorithms by applying them to two realistic and
challenging test problems, one in subsurface flow, and one in combustion
modeling. More specifically, we implement importance sampling algorithms that
iterate over the mean and covariance matrix of Gaussian or multivariate
t-proposal distributions. Our implementation leverages massively parallel
computers, and we present strategies to initialize the iterations using
"coarse" MCMC runs or Gaussian mixture models.


title: Local approximation using Hermite functions

abstract:
  We develop a wavelet like representation of functions in $L^p(\mathbb{R})$
based on their Fourier--Hermite coefficients; i.e., we describe an expansion of
such functions where the local behavior of the terms characterize completely
the local smoothness of the target function. In the case of continuous
functions, a similar expansion is given based on the values of the functions at
arbitrary points on the real line. In the process, we give new proofs for the
localization of certain kernels, as well as some very classical estimates such
as the Markov--Bernstein inequality.


title:
Observational Constraints on $f(T)$ gravity from varying fundamental
  constants

abstract:
  We use observations related to the variation of fundamental constants, in
order to impose constraints on the viable and most used $f(T)$ gravity models.
In particular, for the fine-structure constant we use direct measurements
obtained by different spectrographic methods, while for the effective Newton's
constant we use a model-dependent reconstruction, using direct observational
Hubble parameter data, in order to investigate its temporal evolution. We
consider two $f(T)$ models and we quantify their deviation from $\Lambda$CDM
cosmology through a sole parameter. Our analysis reveals that this parameter
can be slightly different from its $\Lambda$CDM value, however the best-fit
value is very close to the $\Lambda$CDM one. Hence, $f(T)$ gravity is
consistent with observations, nevertheless, as every modified gravity, it may
exhibit only small deviations from $\Lambda$CDM cosmology, a feature that must
be taken into account in any $f(T)$ model-building.


title: De-Conflated Semantic Representations

abstract:
  One major deficiency of most semantic representation techniques is that they
usually model a word type as a single point in the semantic space, hence
conflating all the meanings that the word can have. Addressing this issue by
learning distinct representations for individual meanings of words has been the
subject of several research studies in the past few years. However, the
generated sense representations are either not linked to any sense inventory or
are unreliable for infrequent word senses. We propose a technique that tackles
these problems by de-conflating the representations of words based on the deep
knowledge it derives from a semantic network. Our approach provides multiple
advantages in comparison to the past work, including its high coverage and the
ability to generate accurate representations even for infrequent word senses.
We carry out evaluations on six datasets across two semantic similarity tasks
and report state-of-the-art results on most of them.


title: The scalar-plus-compact property in spaces without reflexive subspaces

abstract:
  A hereditarily indecomposable Banach space $\mathfrak{X}_{\mathfrak{nr}}$ is
constructed that is the first known example of a $\mathscr{L}_\infty$-space not
containing $c_0$, $\ell_1$, or reflexive subspaces and answers a question posed
by J. Bourgain. Moreover, the space $\mathfrak{X}_{\mathfrak{nr}}$ satisfies
the "scalar-plus-compact" property and it is the first known space without
reflexive subspaces having this property. It is constructed using the
Bourgain-Delbaen method in combination with a recent version of saturation
under constraints in a mixed-Tsirelson setting. As a result, the space
$\mathfrak{X}_{\mathfrak{nr}}$ has a shrinking finite dimensional decomposition
and does not contain a boundedly complete sequence.


title: Folding Gravitational-Wave Interferometers

abstract:
  The sensitivity of kilometer-scale terrestrial gravitational wave
interferometers is limited by mirror coating thermal noise. We explore the
effect of folding the arm cavities of such interferometers. While simple
folding alone does not reduce the mirror coating thermal noise, it makes the
folding mirror the critical mirror, opening up a variety of design and upgrade
options.


title:
High fidelity point-spread function retrieval in the presence of
  electrostatic, hysteretic pixel response

abstract:
  We employ electrostatic conversion drift calculations to match CCD pixel
signal covariances observed in flat field exposures acquired using candidate
sensor devices for the LSST Camera. We thus constrain pixel geometry
distortions present at the end of integration, based on signal images recorded.
We use available data from several operational voltage parameter settings to
validate our understanding. Our primary goal is to optimize flux point-spread
function (FPSF) estimation quantitatively, and thereby minimize sensor-induced
errors which may limit performance in precision astronomy applications. We
consider alternative compensation scenarios that will take maximum advantage of
our understanding of this underlying mechanism in data processing pipelines
currently under development.
  To quantitatively capture the pixel response in high-contrast/high dynamic
range operational extrema, we propose herein some straightforward laboratory
tests that involve altering the time order of source illumination on sensors,
within individual test exposures. Hence the word {\it hysteretic} in the title
of this paper.


title:
Text authorship identified using the dynamics of word co-occurrence
  networks

abstract:
  The identification of authorship in disputed documents still requires human
expertise, which is now unfeasible for many tasks owing to the large volumes of
text and authors in practical applications. In this study, we introduce a
methodology based on the dynamics of word co-occurrence networks representing
written texts to classify a corpus of 80 texts by 8 authors. The texts were
divided into sections with equal number of linguistic tokens, from which time
series were created for 12 topological metrics. The series were proven to be
stationary (p-value>0.05), which permits to use distribution moments as
learning attributes. With an optimized supervised learning procedure using a
Radial Basis Function Network, 68 out of 80 texts were correctly classified,
i.e. a remarkable 85% author matching success rate. Therefore, fluctuations in
purely dynamic network metrics were found to characterize authorship, thus
opening the way for the description of texts in terms of small evolving
networks. Moreover, the approach introduced allows for comparison of texts with
diverse characteristics in a simple, fast fashion.


title:
OpenCL-accelerated object classification in video streams using Spatial
  Pooler of Hierarchical Temporal Memory

abstract:
  We present a method to classify objects in video streams using a
brain-inspired Hierarchical Temporal Memory (HTM) algorithm. Object
classification is a challenging task where humans still significantly
outperform machine learning algorithms due to their unique capabilities. We
have implemented a system which achieves very promising performance in terms of
recognition accuracy. Unfortunately, conducting more advanced experiments is
very computationally demanding; some of the trials run on a standard CPU may
take as long as several days for 960x540 video streams frames. Therefore we
have decided to accelerate selected parts of the system using OpenCL. In
particular, we seek to determine to what extent porting selected and
computationally demanding parts of a core may speed up calculations.
  The classification accuracy of the system was examined through a series of
experiments and the performance was given in terms of F1 score as a function of
the number of columns, synapses, $min\_overlap$ and $winners\_set\_size$. The
system achieves the highest F1 score of 0.95 and 0.91 for $min\_overlap=4$ and
256 synapses, respectively. We have also conduced a series of experiments with
different hardware setups and measured CPU/GPU acceleration. The best kernel
speed-up of 632x and 207x was reached for 256 synapses and 1024 columns.
However, overall acceleration including transfer time was significantly lower
and amounted to 6.5x and 3.2x for the same setup.


title: A strong-lensing elliptical galaxy in the MaNGA survey

abstract:
  I report discovery of a new galaxy-scale gravitational lens system,
identified using public data from the MaNGA survey, as part of a systematic
search for lensed background line-emitters. The lens is SDSS
J170124.01+372258.0, a giant elliptical galaxy with velocity dispersion
$\sigma=256$ km/s, at a redshift of $z_l=0.122$. After modelling and
subtracting the target galaxy light, the integral-field data-cube reveals
[OII], [OIII] and H$\beta$ emission lines corresponding to a source at
$z_s=0.791$, forming an identifiable ring around the galaxy center. The
Einstein radius is $R_{Ein} \approx 2.3$ arcsec, projecting to ~5 kpc at the
distance of the lens. The total projected lensing mass is $(3.6\pm0.6) \times
10^{11} M_\odot$, and the total J-band mass-to-light ratio is $3.0\pm0.7$ solar
units. Plausible estimates of the likely dark matter content could reconcile
this with a Milky-Way-like initial mass function (for which M/L~1.5 is
expected), but heavier IMFs are by no means excluded with the present data. An
alternative interpretation of the system, with a more complex source plane, is
also discussed. The discovery of this system bodes well for future lens
searches based on MaNGA and other integral-field spectroscopic surveys.


title: Electronic Density of States for Incommensurate Layers

abstract:
  We prove that the electronic density of states (DOS) for 2D incommensurate
layered structures, where Bloch theory does not apply, is well-defined as the
thermodynamic limit of finite clusters. In addition, we obtain an explicit
representation formula for the DOS as an integral over local configurations.
Next, based on this representation formula, we propose a novel algorithm for
computing electronic structure properties in incommensurate heterostructures,
which overcomes limitations of the common approach to artificially strain a
large supercell and then apply Bloch theory.


title:
Diffraction intensities of a class of binary Pisot substitutions via
  exponential sums

abstract:
  This paper is concerned with the study of diffraction intensities of a
relevant class of binary Pisot substitutions via exponential sums. Arithmetic
properties of algebraic integers are used to give a new and constructive proof
of the fact that there are no diffraction intensities outside the Fourier
module of the underlying cut and project schemes. The results are then applied
in the context of random substitutions.


title: Real space CMB temperature and polarization formulas

abstract:
  I derive formulas for the real space CMB temperature and polarization by
solving the first order Boltzmann equation for the Stokes parameters I, Q and
U.


title: R-connectivity Augmentation in Trees

abstract:
  A \emph{vertex separator} of a connected graph $G$ is a set of vertices
removing which will result in two or more connected components and a
\emph{minimum vertex separator} is a set which contains the minimum number of
such vertices, i.e., the cardinality of this set is least among all possible
vertex separator sets. The cardinality of the minimum vertex separator refers
to the connectivity of the graph G. A connected graph is said to be
$k-connected$ if removing exactly $k$ vertices, $ k\geq 1$, from the graph,
will result in two or more connected components and on removing any $(k-1)$
vertices, the graph is still connected. A \emph{connectivity augmentation} set
is a set of edges which when augmented to a $k$-connected graph $G$ will
increase the connectivity of $G$ by $r$, $r \geq 1$, making the graph
$(k+r)$-$connected$ and a \emph{minimum connectivity augmentation} set is such
a set which contains a minimum number of edges required to increase the
connectivity by $r$. In this paper, we shall investigate a $r$-$connectivity$
augmentation in trees, $r \geq 2$. As part of lower bound study, we show that
any minimum $r$-connectivity augmentation set in trees requires at least $
\lceil\frac{1}{2} \sum\limits_{i=1}^{r-1} (r-i) \times l_{i} \rceil $ edges,
where $l_i$ is the number of vertices with degree $i$. Further, we shall
present an algorithm that will augment a minimum number of edges to make a tree
$(k+r)$-connected.


title:
Bridging the Gap: Incorporating a Semantic Similarity Measure for
  Effectively Mapping PubMed Queries to Documents

abstract:
  The main approach of traditional information retrieval (IR) is to examine how
many words from a query appear in a document. A drawback of this approach,
however, is that it may fail to detect relevant documents where no or only few
words from a query are found. The semantic analysis methods such as LSA (latent
semantic analysis) and LDA (latent Dirichlet allocation) have been proposed to
address the issue, but their performance is not superior compared to common IR
approaches. Here we present a query-document similarity measure motivated by
the Word Mover's Distance. Unlike other similarity measures, the proposed
method relies on neural word embeddings to compute the distance between words.
This process helps identify related words when no direct matches are found
between a query and a document. Our method is efficient and straightforward to
implement. The experimental results on TREC Genomics data show that our
approach outperforms the BM25 ranking function by an average of 12% in mean
average precision. Furthermore, for a real-world dataset collected from the
PubMed search logs, we combine the semantic measure with BM25 using a learning
to rank method, which leads to improved ranking scores by up to 25%. This
experiment demonstrates that the proposed approach and BM25 nicely complement
each other and together produce superior performance.


title: Six variations on a theme: almost planar graphs

abstract:
  A graph is apex if it can be made planar by deleting a vertex, that is,
$\exists v$ such that $G-v$ is planar. We define the related notions of edge
apex, $\exists e$ such that $G-e$ is planar, and contraction apex, $\exists e$
such that $G/e$ is planar, as well as the analogues with a universal
quantifier: $\forall v$, $G-v$ planar; $\forall e$, $G-e$ planar; and $\forall
e$, $G/e$ planar. The Graph Minor Theorem of Robertson and Seymour ensures that
each of these six gives rise to a finite set of obstruction graphs. For the
three definitions with universal quantifiers we determine this set. For the
remaining properties, apex, edge apex, and contraction apex, we show there are
at least 36, 55, and 82 obstruction graphs respectively. We give two similar
approaches to almost nonplanar ($\exists e$, $G+e$ is nonplanar and $\forall
e$, $G+e$ is nonplanar) and determine the corresponding minor minimal graphs.


title:
Interlace properties for the real and imaginary parts of the wave
  functions of complex-valued potentials with real spectrum

abstract:
  Some general properties of the wave functions of complex-valued potentials
with real spectrum are studied. The main results are presented in a series of
lemmas, corollaries and theorems that are satisfied by the zeros of the real
and imaginary parts of the wave functions on the real line. In particular, it
is shown that such zeros interlace so that the corresponding probability
densities $\rho(x)$ are never null. We find that the profile of the imaginary
part $V_I(x)$ of a given complex-valued potential determines the number and
distribution of the maxima and minima of the related probability densities. Our
conjecture is that $V_I(x)$ must be continuous in $\mathbb R$, and that its
integral over all the real line must be equal to zero in order to get control
on the distribution of the maxima and minima of $\rho(x)$. The applicability of
these results is shown by solving the eigenvalue equation of different complex
potentials, these last being either ${\cal PT}$-symmetric or not invariant
under the ${\cal PT}$-transformation.


title:
On the Application of Viscoelastic & Viscoplastic Constitutive Relations
  in the CFD Bio-Fluid Simulations

abstract:
  Considerations on implementation of the stress-strain constitutive relations
applied in Computational Fluid dynamics (CFD) simulation of cardiovascular
flows have been addressed extensively in the literature. However, the matter is
yet controversial. The author suggests that the choice of non-Newtonian models
and the consideration of non-Newtonian assumption versus the Newtonian
assumption is very application oriented and cannot be solely dependent on the
vessel size. In the presented work, where a renal disease patient-specific
geometry is used, the non-Newtonian effects manifest insignificant, while the
vessel is considered to be medium to small which, according to the literature,
suggest a strict use of non-Newtonian formulation. The insignificance of the
non-Newtonian effects specially manifests in Wall Shear Stress (WSS) along the
walls of the numerical domain, where the differences between Newtonian
calculated WSS and non-Newtonian calculated WSS is barely visible.


title: Kernel Ridge Regression via Partitioning

abstract:
  In this paper, we investigate a divide and conquer approach to Kernel Ridge
Regression (KRR). Given n samples, the division step involves separating the
points based on some underlying disjoint partition of the input space (possibly
via clustering), and then computing a KRR estimate for each partition. The
conquering step is simple: for each partition, we only consider its own local
estimate for prediction. We establish conditions under which we can give
generalization bounds for this estimator, as well as achieve optimal minimax
rates. We also show that the approximation error component of the
generalization error is lesser than when a single KRR estimate is fit on the
data: thus providing both statistical and computational advantages over a
single KRR estimate over the entire data (or an averaging over random
partitions as in other recent work, [30]). Lastly, we provide experimental
validation for our proposed estimator and our assumptions.


title: Superadiabatic quantum heat engine with a multiferroic working medium

abstract:
  A quantum thermodynamic cycle with a chiral multiferroic working substance
such as $\textrm{LiCu}_{2}\textrm{O}_{2}$ is presented. Shortcuts to
adiabaticity are employed to achieve an efficient, finite time quantum
thermodynamic cycle which is found to depend on the spin ordering. The emergent
electric polarization associated with the chiral spin order, i.e. the
magnetoelectric coupling, renders possible steering of the spin order by an
external electric field and hence renders possible an electric-field control of
the cycle. Due to the intrinsic coupling between of the spin and the electric
polarization, the cycle performs an electro-magnetic work. We determine this
work's mean square fluctuations, the irreversible work, and the output power of
the cycle. We observe that the work mean square fluctuations are increased with
the duration of the adiabatic strokes while the irreversible work and the
output power of the cycle show a non-monotonic behavior. In particular the
irreversible work vanishes at the end of the quantum adiabatic strokes. This
fact confirms that the cycle is reversible. Our theoretical findings evidence
the existence of a system inherent maximal output power. By implementing a
Lindblad master equation we quantify the role of thermal relaxations on the
cycle efficiency. We also discuss the role of entanglement encoded in the
non-collinear spin order as a resource to affect the quantum thermodynamic
cycle.


title: Two-atom quantum gate in hybrid cavity optomechanics

abstract:
  Tracing the dynamics of a quantum system using a mesoscopic device is an
important topic of interest nowadays. Here we show how a mesoscopic mechanical
oscillator steers the dynamics of a coupled two-atom system and gives rise to a
two-qubit SWAP gate. We have theoretically studied a generic hybrid
atom-optomechanical system where two identical atoms in $\Lambda$ configuration
are trapped inside the cavity and the cavity mode mediates the interaction
between the atoms and the mechanical oscillator. Adiabatic elimination of the
lossy channels is adopted which in turn gives rise to an effective Hamiltonian
that is responsible for a two-atom SWAP gate controlled by the mechanical
motion of the oscillator. The validity of the proposal for successful
implementation is assessed using presently available experimental parameters.


title:
CP asymmetry in heavy Majorana neutrino decays at finite temperature:
  the hierarchical case

abstract:
  We consider the simplest realization of leptogenesis with one heavy Majorana
neutrino species much lighter than the other ones. In this scenario, when the
temperature of the early universe is smaller than the lightest Majorana
neutrino mass, we compute at first order in the Standard Model couplings and,
for each coupling, at leading order in the termperature the CP asymmetry in the
decays of the lightest neutrino into leptons and anti-leptons. We perform the
calculation using a hierarchy of two effective field theories organized as
expansions in the inverse of the heavy-neutrino masses. In the ultimate
effective field theory, leading thermal corrections proportional to the Higgs
self coupling and the gauge couplings are encoded in one single operator of
dimension five, whereas corrections proportional to the top Yukawa coupling are
encoded in four operators of dimension seven, which we compute.


title:
Off-Diagonal Deformations of Kerr Metrics and Black Ellipsoids in
  Heterotic Supergravity

abstract:
  Geometric methods for constructing exact solutions of motion equations with
first order $\alpha ^{\prime}$ corrections to the heterotic supergravity action
implying a non-trivial Yang-Mills sector and six dimensional, 6-d,
almost-K\"ahler internal spaces are studied. In 10-d spacetimes, general
parametrizations for generic off-diagonal metrics, nonlinear and linear
connections and matter sources, when the equations of motion decouple in very
general forms are considered. This allows us to construct a variety of exact
solutions when the coefficients of fundamental geometric/physical objects
depend on all higher dimensional spacetime coordinates via corresponding
classes of generating and integration functions, generalized effective sources
and integration constants. Such generalized solutions are determined by generic
off-diagonal metrics and nonlinear and/or linear connections. In particular, as
configurations which are warped/compactified to lower dimensions and for
Levi-Civita connections. The corresponding metrics can have (non) Killing
and/or Lie algebra symmetries and/or describe (1+2)-d and/or (1+3)-d domain
wall configurations, with possible warping nearly almost-K\"ahler manifolds,
with gravitational and gauge instantons for nonlinear vacuum configurations and
effective polarizations of cosmological and interaction constants encoding
string gravity effects. A series of examples of exact solutions describing
generic off-diagonal supergravity modifications to black hole/ ellipsoid and
solitonic configurations are provided and analyzed. We prove that it is
possible to reproduce the Kerr and other type black solutions in general
relativity (with certain types of string corrections) in 4-d and to generalize
the solutions to non-vacuum configurations in (super) gravity/ string theories.


title:
Domain Wall Spin Structures in Mesoscopic Fe Rings probed by High
  Resolution SEMPA

abstract:
  We present a combined theoretical and experimental study of the energetic
stability and accessibility of different domain wall spin configurations in
mesoscopic magnetic iron rings. The evolution is investigated as a function of
the width and thickness in a regime of relevance to devices, while Fe is chosen
as a material due to its simple growth in combination with attractive magnetic
properties including high saturation magnetization and low intrinsic
anisotropy. Micromagnetic simulations are performed to predict the lowest
energy states of the domain walls, which can be either the transverse or vortex
wall spin structure, in good agreement with analytical models, with simulations
revealing the expected low temperature configurations observable on relaxation
of the magnetic structure from saturation in an external field. In the latter
case, following the domain wall nucleation process, transverse domain walls are
found at larger widths and thicknesses than would be expected by comparing the
competing energy terms demonstrating the importance of metastability of the
states. The simulations are compared to high resolution experimental images of
the magnetization using scanning electron microscopy with polarization analysis
to provide a phase diagram of the various spin configurations. In addition to
the vortex and simple symmetric transverse domain wall, a significant range of
geometries are found to exhibit highly asymmetric transverse domain walls with
properties distinct from the symmetric transverse wall. Simulations of the
asymmetric walls reveal an evolution of the domain wall tilting angle with ring
thickness. Analysis of all the data reveals that in addition to the geometry,
the influence of materials properties, defects and thermal activation all need
to be taken into account in order to understand and reliably control the
experimentally accessible states, as needed for devices.


title: Speed of Gravitational Waves and the Fate of Scalar-Tensor Gravity

abstract:
  The direct detection of gravitational waves (GWs) is an invaluable new tool
to probe gravity and the nature of cosmic acceleration. A large class of
scalar-tensor theories predict that GWs propagate with velocity different than
the speed of light, a difference that can be $\mathcal{O}(1)$ for many models
of dark energy. We determine the conditions behind the anomalous GW speed,
namely that the scalar field spontaneously breaks Lorentz invariance and
couples to the metric perturbations via the Weyl tensor. If these conditions
are realized in nature, the delay between GW and electromagnetic (EM) signals
from distant events will run beyond human timescales, making it impossible to
measure the speed of GWs using neutron star mergers or other violent events. We
present a robust strategy to exclude or confirm an anomalous speed of GWs using
eclipsing binary systems, whose EM phase can be exquisitely determined. he
white dwarf binary J0651+2844 is a known example of such system that can be
used to probe deviations in the GW speed as small as $c_g/c-1\gtrsim 2\cdot
10^{-12}$ when LISA comes online. This test will either eliminate many
contender models for cosmic acceleration or wreck a fundamental pillar of
general relativity.


title: H2S in the L1157-B1 Bow shock

abstract:
  Sulfur-bearing molecules are highly reactive in the gas phase of the ISM.
However, the form in which most of the sulfur is locked onto interstellar dust
grains is unknown. By taking advantage of the short time-scales of shocks in
young molecular outflows, one could track back the main form of sulfur in the
ices. In this paper, six transitions of H$_2$S and its isotopologues in the
L1157-B1 bowshock have been detected using data from the Herschel-CHESS survey
and the IRAM-30m ASAI large program. These detections are used to calculate the
properties of H$_2$S gas in L1157-B1 through use of a rotation diagram and to
explore the possible carriers of sulfur on the grains. The isotopologue
detections allow the first calculation of the H$_2$S deuteration fraction in an
outflow from a low mass protostar. The fractional abundance of H$_2$S in the
region is found to be 6.0$\times$10$^{-7}$ and the deuteration fraction is
2$\times$10$^{-2}$. In order to investigate the form of sulfur on the grains, a
chemical model is run with four different networks, each with different
branching ratios for the freeze out of sulfur bearing species into molecules
such as OCS and H$_2$S. It is found that the model best fits the data when at
least half of each sulfur bearing species hydrogenates when freezing. We
therefore conclude that a significant fraction of sulfur in L1157-B1 is likely
to be locked in H$_2$S on the grains.


title:
Characterization of Maximally Random Jammed Sphere Packings: II.
  Correlation Functions and Density Fluctuations

abstract:
  In the first paper of this series, we introduced Voronoi correlation
functions to characterize the structure of maximally random jammed (MRJ) sphere
packings across length scales. In the present paper, we determine a variety of
correlation functions that can be rigorously related to effective physical
properties of MRJ sphere packings and compare them to the corresponding
statistical descriptors for overlapping spheres and equilibrium hard-sphere
systems. Such structural descriptors arise in rigorous bounds and formulas for
effective transport properties, diffusion and reactions constants, elastic
moduli, and electromagnetic characteristics. First, we calculate the two-point,
surface-void, and surface-surface correlation functions, for which we derive
explicit analytical formulas for finite hard-sphere packings. We show
analytically how the contacts between spheres in the MRJ packings translate
into distinct functional behaviors of these two-point correlation functions
that do not arise in the other two models examined here. Then, we show how the
spectral density distinguishes the MRJ packings from the other disordered
systems in that the spectral density vanishes in the limit of infinite
wavelengths. These packings are hyperuniform, which means that density
fluctuations on large length scales are anomalously suppressed. Moreover, we
study and compute exclusion probabilities and pore size distributions as well
as local density fluctuations. We conjecture that for general disordered
hard-sphere packings, a central limit theorem holds for the number of points
within an spherical observation window. Our analysis links problems of interest
in material science, chemistry, physics, and mathematics. In the third paper,
we will evaluate bounds and estimates of a host of different physical
properties of the MRJ sphere packings based on the structural characteristics
analyzed in this paper.


title: Split NMSSM with electroweak baryogenesis

abstract:
  In light of the Higgs boson discovery we reconsider generation of the baryon
asymmetry in the non-minimal split Supersymmetry model with an additional
singlet superfield in the Higgs sector. We find that successful baryogenesis
during the first order electroweak phase transition is possible within
phenomenologically viable part of the model parameter space. We discuss several
phenomenological consequences of this scenario, namely, predictions for the
electric dipole moments of electron and neutron and collider signatures of
light charginos and neutralinos.


title:
Measurement uncertainty relations for discrete observables: Relative
  entropy formulation

abstract:
  We introduce a new information-theoretic formulation of quantum measurement
uncertainty relations, based on the notion of relative entropy between
measurement probabilities. In the case of a finite-dimensional system and for
any approximate joint measurement of two target discrete observables, we define
the entropic divergence as the maximal total loss of information occurring in
the approximation at hand. For fixed target observables, we study the joint
measurements minimizing the entropic divergence, and we prove the general
properties of its minimum value. Such a minimum is our uncertainty lower bound:
the total information lost by replacing the target observables with their
optimal approximations, evaluated at the worst possible state. The bound turns
out to be also an entropic incompatibility degree, that is, a good
information-theoretic measure of incompatibility: indeed, it vanishes if and
only if the target observables are compatible, it is state-independent, and it
enjoys all the invariance properties which are desirable for such a measure. In
this context, we point out the difference between general approximate joint
measurements and sequential approximate joint measurements; to do this, we
introduce a separate index for the tradeoff between the error of the first
measurement and the disturbance of the second one. By exploiting the symmetry
properties of the target observables, exact values, lower bounds and optimal
approximations are evaluated in two different concrete examples: (1) a couple
of spin-1/2 components (not necessarily orthogonal); (2) two Fourier conjugate
mutually unbiased bases in prime power dimension. Finally, the entropic
incompatibility degree straightforwardly generalizes to the case of many
observables, still maintaining all its relevant properties; we explicitly
compute it for three orthogonal spin-1/2 components.


title: Human collective intelligence as distributed Bayesian inference

abstract:
  Collective intelligence is believed to underly the remarkable success of
human society. The formation of accurate shared beliefs is one of the key
components of human collective intelligence. How are accurate shared beliefs
formed in groups of fallible individuals? Answering this question requires a
multiscale analysis. We must understand both the individual decision mechanisms
people use, and the properties and dynamics of those mechanisms in the
aggregate. As of yet, mathematical tools for such an approach have been
lacking. To address this gap, we introduce a new analytical framework: We
propose that groups arrive at accurate shared beliefs via distributed Bayesian
inference. Distributed inference occurs through information processing at the
individual level, and yields rational belief formation at the group level. We
instantiate this framework in a new model of human social decision-making,
which we validate using a dataset we collected of over 50,000 users of an
online social trading platform where investors mimic each others' trades using
real money in foreign exchange and other asset markets. We find that in this
setting people use a decision mechanism in which popularity is treated as a
prior distribution for which decisions are best to make. This mechanism is
boundedly rational at the individual level, but we prove that in the aggregate
implements a type of approximate "Thompson sampling"---a well-known and highly
effective single-agent Bayesian machine learning algorithm for sequential
decision-making. The perspective of distributed Bayesian inference therefore
reveals how collective rationality emerges from the boundedly rational decision
mechanisms people use.


title:
Upper Chromospheric Magnetic Field of a Sunspot Penumbra: Observations
  of Fine Structure

abstract:
  The fine-structure of magnetic field of a sunspot penumbra in the upper
chromosphere is to be explored and compared to that in the photosphere. High
spatial resolution spectropolarimetric observations were recorded with the
1.5-meter GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The
observed spectral domain includes the upper chromospheric He I triplet at
1083.0 nm and the photospheric Si I 1082.7 nm and Ca I 1083.3 nm spectral
lines. The upper chromospheric magnetic field is obtained by inverting the He I
triplet assuming a Milne-Eddington type model atmosphere. A height dependent
inversion was applied to the Si I 1082.7 nm and Ca I 1083.3 nm lines to obtain
the photospheric magnetic field. We find that the inclination of the magnetic
field shows variations in the azimuthal direction both in the photosphere, but
also in the upper chromosphere. The chromospheric variations remarkably well
coincide with the variations in the inclination of the photospheric field and
resemble the well-known spine and inter-spine structure in the photospheric
layers of penumbrae. The typical peak-to-peak variations in the inclination of
the magnetic field in the upper chromosphere is found to be 10-15 degree, i.e.,
roughly half the variation in the photosphere. In contrast, the magnetic field
strength of the observed penumbra does not show variations on small spatial
scales in the upper chromosphere. Thanks to the high spatial resolution
observations possible with the GREGOR telescope at 1.08 microns, we find that
the prominent small-scale fluctuations in the magnetic field inclination, which
are a salient part of the property of sunspot penumbral photospheres, also
persist in the chromosphere, although at somewhat reduced amplitudes. Such a
complex magnetic configuration may facilitate penumbral chromospheric dynamic
phenomena, such as penumbral micro-jets or transient bright dots.


title: The Peaks of Eternal Light: a Near-term Property Issue on the Moon

abstract:
  The Outer Space Treaty makes it clear that the Moon is the province of all
mankind, with the latter ordinarily understood to exclude state or private
appropriation of any portion of its surface. However, there are indeterminacies
in the Treaty and in space law generally over the issue of appropriation. These
indeterminacies might permit a close approximation to a property claim or some
manner of quasi-property. The recently revealed highly inhomogeneous
distribution of lunar resources changes the context of these issues. We
illustrate this altered situation by considering the Peaks of Eternal Light.
They occupy about one square kilometer of the lunar surface. We consider a
thought experiment in which a Solar telescope is placed on one of the Peaks of
Eternal Light at the lunar South pole for scientific research. Its operation
would require nondisturbance, and hence that the Peak remain unvisited by
others, effectively establishing a claim of protective exclusion and de facto
appropriation. Such a telescope would be relatively easy to emplace with todays
technology and so poses a near-term property issue on the Moon. While effective
appropriation of a Peak might proceed without raising some of the familiar
problems associated with commercial development (especially lunar mining), the
possibility of such appropriation nonetheless raises some significant issues
concerning justice and the safeguarding of scientific practice on the lunar
surface. We consider this issue from scientific, technical, ethical and policy
viewpoints.


title: Effect of interfaces on the nearby Brownian motion

abstract:
  Near-boundary Brownian motion is a classic hydrodynamic problem of great
importance in a variety of fields, from biophysics to micro-/nanofluidics.
However, due to challenges in experimental measurements of near-boundary
dynamics, the effect of interfaces on Brownian motion has remained elusive.
Here, we report a computational study of this effect using microsecond-long
large-scale molecular dynamics simulations and our newly developed Green-Kubo
relation for friction at the liquid-solid interface. Our computer experiment
unambiguously reveals that the t^(-3/2) long-time decay of the velocity
autocorrelation function of a Brownian particle in bulk liquid is replaced by a
t^(-5/2) decay near a boundary. We discover a general breakdown of traditional
no-slip boundary condition at short time scales and we show that this breakdown
has a profound impact on the near-boundary Brownian motion. Our results
demonstrate the potential of Brownian-particle based micro-/nano-sonar to probe
the local wettability of liquid-solid interfaces.


title:
Contribution of \sigma-meson exchange to elastic lepton-proton
  scattering

abstract:
  Lepton mass effects play a decisive role in description of elastic
lepton-proton scattering when the beam's energy is comparable to the mass of
the lepton. The future MUSE experiment, which is devised to solve the "Proton
Radius Puzzle", is going to cover the corresponding kinematic region for a
scattering of muons by a proton target. We anticipate that helicity-flip meson
exchanges will make a difference in comparison of elastic electron-proton
versus muon-proton scattering in MUSE. In this article, we estimate the
$\sigma$ meson exchange contribution in the $t$-channel. This contribution,
mediated by two-photon coupling of $\sigma$, is calculated to be at most $\sim
0.1 \%$ for muons in the kinematics of MUSE and it is about 3 orders in
magnitude larger than for electrons because of the lepton-mass difference.


title: 2-Variable Frobenius Problem in Z[\sqrt M]

abstract:
  Suppose that m is a positive integer, not a perfect square. We present a
formula solution to the 2-variable Frobenius problem in Z[\sqrt m] of the
"first kind" ([3]).


title:
Enhanced Directional Smoothing Algorithm for Edge-Preserving Smoothing
  of Synthetic-Aperture Radar Images

abstract:
  Synthetic aperture radar (SAR) images are subject to prominent speckle noise,
which is generally considered a purely multiplicative noise process. In theory,
this multiplicative noise is that the ratio of the standard deviation to the
signal value, the "coefficient of variation," is theoretically constant at
every point in a SAR image. Most of the filters for speckle reduction are based
on this property. Such property is irrelevant for the new filter structure,
which is based on directional smoothing (DS) theory, the enhanced directional
smoothing (EDS) that removes speckle noise from SAR images without blurring
edges. We demonstrate the effectiveness of this new filtering method by
comparing it to established speckle noise removal techniques on SAR images.


title: Absorption of light dark matter in semiconductors

abstract:
  Semiconductors are by now well-established targets for direct detection of
MeV to GeV dark matter via scattering off electrons. We show that semiconductor
targets can also detect significantly lighter dark matter via an absorption
process. When the dark matter mass is above the band gap of the semiconductor
(around an eV), absorption proceeds by excitation of an electron into the
conduction band. Below the band gap, multi-phonon excitations enable absorption
of dark matter in the 0.01 eV to eV mass range. Energetic dark matter particles
emitted from the sun can also be probed for masses below an eV. We derive the
reach for absorption of a relic kinetically mixed dark photon or pseudoscalar
in germanium and silicon, and show that existing direct detection results
already probe new parameter space. With only a moderate exposure, low-threshold
semiconductor target experiments can exceed current astrophysical and
terrestrial constraints on sub-keV bosonic dark matter.


title: The Global Higgs as a Signal for Compositeness at the LHC

abstract:
  The radial excitation of the global symmetry-breaking vacuum in composite
Higgs models, called the "global Higgs", has been recently a focus of
investigation. In this paper we study the prospects for detecting this
composite scalar at the 13 TeV LHC. We compute the global Higgs production
rates and estimate the discovery potential of a global Higgs decaying into top
quark pairs and into Higgs and electroweak gauge bosons with subsequent
hadronic decays. The global Higgs may also decay into fermion resonances such
as top partners, providing a new window into compositeness. We show that top
partner jets can be effectively unresolved in some regions of the parameter
space. Such "boosted top partner" signatures would deserve the development of
dedicated substructure analyses.


title:
Two dimensional spin liquids with $\mathbb{Z}_2$ topological order in an
  array of quantum wires

abstract:
  Insulating $\mathbb{Z}_2$ spin liquids are a phase of matter with bulk
anyonic quasiparticle excitations and ground state degeneracies on manifolds
with non-trivial topology. In this paper, we construct a time-reversal
symmetric $\mathbb{Z}_2$ spin liquid in two spatial dimensions using an array
of quantum wires. We identify the anyons as kinks in the appropriate
Luttinger-liquid description, compute their mutual statistics and construct
local operators that transport these quasiparticles. We also present a
construction of a fractionalized Fermi-liquid (FL*) by coupling the spin sector
of the $\mathbb{Z}_2$ spin-liquid to a Fermi-liquid via a Kondo-like coupling.


title: A Diagnostic for Localizing Red Giant Differential Rotation

abstract:
  We present a simple diagnostic that can be used to constrain the location of
the differential rotation in red giants with measured mixed mode rotational
splittings. Specifically, in red giants with radii $\sim 4R_\odot$, the
splittings of p-dominated modes (sound wave dominated) relative to those of
g-dominated modes (internal gravity wave dominated) are sensitive to how much
of the differential rotation resides in the outer convection zone versus the
radiative interior of the red giant. An independently measured surface rotation
rate significantly aids breaking degeneracies in interpreting the measured
splittings. We apply our results to existing observations of red giants,
particularly those of Kepler-56, and find that most of the differential
rotation resides in the radiative region rather than in the convection zone.
This conclusion is consistent with results in the literature from rotational
inversions, but our results are insensitive to some of the uncertainties in the
inversion process and can be readily applied to large samples of red giants
with even a modest number of measured rotational splittings. We argue that
differential rotation in the radiative interior strongly suggests that angular
momentum transport in red giants is dominated by local fluid instabilities
rather than large-scale magnetic stresses.


title:
Type Ibn Supernovae Show Photometric Homogeneity and Spectral Diversity
  at Maximum Light

abstract:
  Type Ibn supernovae (SNe) are a small yet intriguing class of explosions
whose spectra are characterized by low-velocity helium emission lines with
little to no evidence for hydrogen. The prevailing theory has been that these
are the core-collapse explosions of very massive stars embedded in helium-rich
circumstellar material (CSM). We report optical observations of six new SNe
Ibn: PTF11rfh, PTF12ldy, iPTF14aki, iPTF15ul, SN 2015G, and iPTF15akq. This
brings the sample size of such objects in the literature to 22. We also report
new data, including a near-infrared spectrum, on the Type Ibn SN 2015U. In
order to characterize the class as a whole, we analyze the photometric and
spectroscopic properties of the full Type Ibn sample. We find that, despite the
expectation that CSM interaction would generate a heterogeneous set of light
curves, as seen in SNe IIn, most Type Ibn light curves are quite similar in
shape, declining at rates around 0.1 mag/day during the first month after
maximum light, with a few significant exceptions. Early spectra of SNe Ibn come
in at least two varieties, one that shows narrow P Cygni lines and another
dominated by broader emission lines, both around maximum light, which may be an
indication of differences in the state of the progenitor system at the time of
explosion. Alternatively, the spectral diversity could arise from viewing-angle
effects or merely from a lack of early spectroscopic coverage. Together, the
relative light curve homogeneity and narrow spectral features suggest that the
CSM consists of a spatially confined shell of helium surrounded by a less dense
extended wind.


title: Two-Loop Beam and Soft Functions for Rapidity-Dependent Jet Vetoes

abstract:
  Jet vetoes play an important role in many analyses at the LHC. Traditionally,
jet vetoes have been imposed using a restriction on the transverse momentum
$p_{Tj}$ of jets. Alternatively, one can also consider jet observables for
which $p_{Tj}$ is weighted by a smooth function of the jet rapidity $y_j$ that
vanishes as $|y_j| \to \infty$. Such observables are useful as they provide a
natural way to impose a tight veto on central jets but a looser one at forward
rapidities. We consider two such rapidity-dependent jet veto observables,
$\mathcal{T}_{Bj}$ and $\mathcal{T}_{Cj}$, and compute the required beam and
dijet soft functions for the jet-vetoed color-singlet production cross section
at two loops. At this order, clustering effects from the jet algorithm become
important. The dominant contributions are computed fully analytically while
corrections that are subleading in the limit of small jet radii are expressed
in terms of finite numerical integrals. Our results enable the full NNLL'
resummation and are an important step towards N3LL resummation for cross
sections with a $\mathcal{T}_{Bj}$ or $\mathcal{T}_{Cj}$ jet veto.


title:
Joint constraints on the Galactic dark matter halo and Galactic Centre
  from hypervelocity stars

abstract:
  The mass assembly history of the Milky Way can inform both theory of galaxy
formation and the underlying cosmological model. Thus, observational
constraints on the properties of both its baryonic and dark matter contents are
sought. Here we show that hypervelocity stars (HVSs) can in principle provide
such constraints. We model the observed velocity distribution of HVSs, produced
by tidal break-up of stellar binaries caused by Sgr A*. Considering a Galactic
Centre (GC) binary population consistent with that inferred in more
observationally accessible regions, a fit to current HVS data with significance
level > 5\% can only be obtained if the escape velocity from the GC to 50 kpc
is $V_G < 850$ km/s, regardless of the enclosed mass distribution. When a NFW
matter density profile for the dark matter halo is assumed, haloes with $V_G <
850$ km/s are in agreement with predictions in the $\Lambda$CDM model and that
a subset of models around $M_{200} \sim 0.5-1.5 \times 10^{12}$ solar masses
and $r_s < 35$ kpc can also reproduce Galactic circular velocity data. HVS data
alone cannot currently exclude potentials with $V_G > 850$ km/s. Finally,
specific constraints on the halo mass from HVS data are highly dependent on the
assumed baryonic mass potentials. This first attempt to simultaneously
constrain GC and dark halo properties is primarily hampered by the paucity and
quality of data. It nevertheless demonstrates the potential of our method, that
may be fully realised with the ESA Gaia mission.


title:
Orbital alignment and starspot properties in the WASP-52 planetary
  system

abstract:
  We report 13 high-precision light curves of eight transits of the exoplanet
WASP-52b, obtained by using four medium-class telescopes, through different
filters, and adopting the defocussing technique. One transit was recorded
simultaneously from two different observatories and another one from the same
site but with two different instruments, including a multi-band camera.
Anomalies were clearly detected in five light curves and modelled as starspots
occulted by the planet during the transit events. We fitted the clean light
curves with the jktebop code, and those with the anomalies with the prism+gemc
codes in order to simultaneously model the photometric parameters of the
transits and the position, size and contrast of each starspot. We used these
new light curves and some from the literature to revise the physical properties
of the WASP-52 system. Starspots with similar characteristics were detected in
four transits over a period of 43 days. In the hypothesis that we are dealing
with the same starspot, periodically occulted by the transiting planet, we
estimated the projected orbital obliquity of WASP-52b to be lambda = 3.8 \pm
8.4 degree. We also determined the true orbital obliquity, psi = 20 \pm 50
degree, which is, although very uncertain, the first measurement of psi purely
from starspot crossings. We finally assembled an optical transmission spectrum
of the planet and searched for variations of its radius as a function of
wavelength. Our analysis suggests a flat transmission spectrum within the
experimental uncertainties.


title: Gyrokinetic treatment of a grazing angle magnetic field

abstract:
  We develop a gyrokinetic treatment for ions in the magnetic presheath, close
to the plasma-wall boundary. We focus on magnetic presheaths with a small
magnetic field to wall angle, $\alpha \ll 1$ (in radians). Characteristic
lengths perpendicular to the wall in such a magnetic presheath scale with the
typical ion Larmor orbit size, $\rho_{\text{i}}$. The smallest scale length
associated with variations parallel to the wall is taken to be across the
magnetic field, and ordered $l = \rho_{\text{i}} / \delta$, where $ \delta \ll
1$ is assumed. The scale lengths along the magnetic field line are assumed so
long that variations associated with this direction are neglected. These
orderings are consistent with what we expect close to the divertor target of a
tokamak. We allow for a strong component of the electric field $\vec{E}$ in the
direction normal to the electron repelling wall, with strong variation in the
same direction. The large change of the electric field over an ion Larmor
radius distorts the orbit so that it is not circular. We solve for the lowest
order orbits by identifying coordinates, which consist of constants of
integration, an adiabatic invariant and a gyrophase, associated with periodic
ion motion in the system with $\alpha = \delta = 0$. By using these new
coordinates as variables in the limit $\alpha \sim \delta \ll 1$, we obtain a
generalized ion gyrokinetic equation. We find another quantity that is
conserved to first order and use this to simplify the gyrokinetic equation,
solving it in the case of a collisionless magnetic presheath. Assuming a
Boltzmann response for the electrons, a form of the quasineutrality equation
that exploits the change of variables is derived. The gyrokinetic and
quasineutrality equations give the ion distribution function and electrostatic
potential in the magnetic presheath if the entrance boundary condition is
specified.


title:
How hard is deciding trivial versus nontrivial in the dihedral coset
  problem?

abstract:
  We study the hardness of the dihedral hidden subgroup problem. It is known
that lattice problems reduce to it, and that it reduces to random subset sum
with density $> 1$ and also to quantum sampling subset sum solutions. We
examine a decision version of the problem where the question asks whether the
hidden subgroup is trivial or order two. The decision problem essentially asks
if a given vector is in the span of all coset states. We approach this by first
computing an explicit basis for the coset space and the perpendicular space. We
then look at the consequences of having efficient unitaries that use this
basis. We show that if a unitary maps the basis to the standard basis in any
way, then that unitary can be used to solve random subset sum with constant
density $>1$. We also show that if a unitary can exactly decide membership in
the coset subspace, then the collision problem for subset sum can be solved for
density $>1$ but approaching $1$ as the problem size increases. This
strengthens the previous hardness result that implementing the optimal POVM in
a specific way is as hard as quantum sampling subset sum solutions.


title: Quantum cellular automata and free quantum field theory

abstract:
  In a series of recent papers it has been shown how free quantum field theory
can be derived without using mechanical primitives (including space-time,
special relativity, quantization rules, etc.), but only considering the easiest
quantum algorithm encompassing a countable set of quantum systems whose network
of interactions satisfies the simple principles of unitarity, homogeneity,
locality, and isotropy. This has opened the route to extending the axiomatic
information-theoretic derivation of the quantum theory of abstract systems to
include quantum field theory. The inherent discrete nature of the informational
axiomatization leads to an extension of quantum field theory to a quantum
cellular automata theory, where the usual field theory is recovered in a regime
where the discrete structure of the automata cannot be probed. A simple
heuristic argument sets the scale of discreteness to the Planck scale, and the
customary physical regime where discreteness is not visible is the relativistic
one of small wavevectors. In this paper we provide a thorough derivation from
principles that in the most general case the graph of the quantum cellular
automaton is the Cayley graph of a finitely presented group, and showing how
for the case corresponding to Euclidean emergent space (where the group resorts
to an Abelian one) the automata leads to Weyl, Dirac and Maxwell field dynamics
in the relativistic limit. We conclude with some perspectives towards the more
general scenario of non-linear automata for interacting quantum field theory.


title:
Quantum algorithms for abelian difference sets and applications to
  dihedral hidden subgroups

abstract:
  Difference sets are basic combinatorial structures that have applications in
signal processing, coding theory, and cryptography. We consider the problem of
identifying a shifted version of the characteristic function of a (known)
difference set. We present a generic quantum algorithm that can be used to
tackle any hidden shift problem for any difference set in any abelian group. We
discuss special cases of this framework where the resulting quantum algorithm
is efficient. This includes: a) Paley difference sets based on quadratic
residues in finite fields, which allows to recover the shifted Legendre
function quantum algorithm, b) Hadamard difference sets, which allows to
recover the shifted bent function quantum algorithm, and c) Singer difference
sets based on finite geometries. The latter class allows us to define instances
of the dihedral hidden subgroup problem that can be efficiently solved on a
quantum computer.


title:
Multi-reference perturbation theory with Cholesky decomposition for the
  density matrix renormalization group

abstract:
  We present a second-order N-electron valence state perturbation theory
(NEVPT2) based on a density matrix renormalization group (DMRG) reference wave
function that exploits a Cholesky decomposition of the two-electron repulsion
integrals (CD-DMRG-NEVPT2). With a parameter-free multireference perturbation
theory approach at hand, the latter allows us to efficiently describe static
and dynamic correlation in large molecular systems. We demonstrate the
applicability of CD-DMRG-NEVPT2 for spin-state energetics of spin-crossover
complexes involving calculations with more than 1000 atomic basis functions. We
first assess in a study of a heme model the accuracy of the strongly- and
partially-contracted variant of CD-DMRG-NEVPT2 before embarking on resolving a
controversy about the spin ground state of a cobalt tropocoronand complex.

categories: physics.chem-ph cond-mat.str-el physics.comp-ph quant-ph


title: LBVs and Statistical Inference

abstract:
  Smith and Tombleson (2015) asserted that statistical tests disprove the
standard view of LBVs, and proposed a far more complex scenario to replace it.
But Humphreys et al. (2016) showed that Smith and Tombleson's Magellanic "LBV"
sample was a mixture of physically different classes of stars, and genuine LBVs
are in fact statistically consistent with the standard view. Smith (2016)
recently objected at great length to this result. Here we note that he
misrepresented some of the arguments, altered the test criteria, ignored some
long-recognized observational facts, and employed inadequate statistical
procedures. This case illustrates the dangers of uncareful statistical
sampling, as well as the need to be wary of unstated assumptions.


title: Software Quality Metrics for Geant4: An Initial Assessment

abstract:
  In the context of critical applications, such as shielding and radiation
protection, ensuring the quality of simulation software they depend on is of
utmost importance. The assessment of simulation software quality is important
not only to determine its adoption in experimental applications, but also to
guarantee reproducibility of outcome over time.
  In this study, we present initial results from an ongoing analysis of Geant4
code based on established software metrics. The analysis evaluates the current
status of the code to quantify its characteristics with respect to documented
quality standards; further assessments concern evolutions over a series of
release distributions. We describe the selected metrics that quantify software
attributes ranging from code complexity to maintainability, and highlight what
metrics are most effective at evaluating radiation transport software quality.
The quantitative assessment of the software is initially focused on a set of
Geant4 packages, which play a key role in a wide range of experimental
applications and are representative of different software development
processes. We provide an interpretation of the data resulting from measurements
on the selected Geant4 packages, and discuss methods to improve them.
  This work can be used as a baseline for evaluating correlations between
software quality embedded in the Geant4 development process and simulation
observables produced by Geant4-based applications. The result provide
constructive guidance both to improve key software tools, such as Geant4, and
to estimate their contribution in risk analyses concerning sensitive
applications.


title: A quasiconformal composition problem for the Q-spaces

abstract:
  Given a quasiconformal mapping $f:\mathbb R^n\to\mathbb R^n$ with $n\ge2$, we
show that (un-)boundedness of the composition operator ${\bf C}_f$ on the
spaces $Q_{\alpha}(\mathbb R^n)$ depends on the index $\alpha$ and the
degeneracy set of the Jacobian $J_f$. We establish sharp results in terms of
the index $\alpha$ and the local/global self-similar Minkowski dimension of the
degeneracy set of $J_f$. This gives a solution to [Problem 8.4, 3] and also
reveals a completely new phenomenon, which is totally different from the known
results for Sobolev, BMO, Triebel-Lizorkin and Besov spaces. Consequently,
Tukia-V\"ais\"al\"a's quasiconformal extension $f:\mathbb R^n\to\mathbb R^n$ of
an arbitrary quasisymmetric mapping $g:\mathbb R^{n-p}\to \mathbb R^{n-p}$ is
shown to preserve $Q_{\alpha} (\mathbb R^n)$ for any $(\alpha,p)\in
(0,1)\times[2,n)\cup(0,1/2)\times\{1\}$. Moreover, $Q_{\alpha}(\mathbb R^n)$ is
shown to be invariant under inversions for all $0<\alpha<1$.


title: Communication-Efficient Parallel Block Minimization for Kernel Machines

abstract:
  Kernel machines often yield superior predictive performance on various tasks;
however, they suffer from severe computational challenges. In this paper, we
show how to overcome the important challenge of speeding up kernel machines. In
particular, we develop a parallel block minimization framework for solving
kernel machines, including kernel SVM and kernel logistic regression. Our
framework proceeds by dividing the problem into smaller subproblems by forming
a block-diagonal approximation of the Hessian matrix. The subproblems are then
solved approximately in parallel. After that, a communication efficient line
search procedure is developed to ensure sufficient reduction of the objective
function value at each iteration. We prove global linear convergence rate of
the proposed method with a wide class of subproblem solvers, and our analysis
covers strongly convex and some non-strongly convex functions. We apply our
algorithm to solve large-scale kernel SVM problems on distributed systems, and
show a significant improvement over existing parallel solvers. As an example,
on the covtype dataset with half-a-million samples, our algorithm can obtain an
approximate solution with 96% accuracy in 20 seconds using 32 machines, while
all the other parallel kernel SVM solvers require more than 2000 seconds to
achieve a solution with 95% accuracy. Moreover, our algorithm can scale to very
large data sets, such as the kdd algebra dataset with 8 million samples and 20
million features.


title: Twisting, mutation and knot Floer homology

abstract:
  Let $\mathcal{L}$ be a knot with a fixed positive crossing and
$\mathcal{L}_n$ the link obtained by replacing this crossing with $n$ positive
twists. We prove that the knot Floer homology
$\widehat{\text{HFK}}(\mathcal{L}_n)$ `stabilizes' as $n$ goes to infinity.
This categorifies a similar stabilization phenomenon of the Alexander
polynomial. As an application, we construct an infinite family of prime,
positive mutant knots with isomorphic bigraded knot Floer homology groups.
Moreover, given any pair of positive mutants, we describe how to derive a
corresponding infinite family positive mutants with isomorphic bigraded
$\widehat{\text{HFK}}$ groups, Seifert genera, and concordance invariant
$\tau$.


title: AngularJS in the Wild: A Survey with 460 Developers

abstract:
  To implement modern web applications, a new family of JavaScript frameworks
has emerged, using the MVC pattern. Among these frameworks, the most popular
one is AngularJS, which is supported by Google. In spite of its popularity,
there is not a clear knowledge on how AngularJS design and features affect the
development experience of Web applications. Therefore, this paper reports the
results of a survey about AngularJS, including answers from 460 developers. Our
contributions include the identification of the most appreciated features of
AngularJS (e.g., custom interface components, dependency injection, and two-way
data binding) and the most problematic aspects of the framework (e.g.,
performance and implementation of directives).