title: Non-Truthful Position Auctions Are More Robust to Misspecification

abstract:
  In the standard single-dimensional model of position auctions, bidders agree
on the relative values of the positions and each of them submits a single bid
that is interpreted in terms of these values. Motivated by current practice in
sponsored search we consider a situation where the auctioneer uses estimates of
the relative values, which may be imprecise, and show that under both complete
and incomplete information a non-truthful mechanism is able to support an
efficient outcome in equilibrium for a wider range of these estimates than the
VCG mechanism. We thus exhibit a property of the VCG mechanism that may help
explain the surprising rarity with which it is used even in settings with unit
demand, a relative lack of robustness to misspecification of the bidding
language. The result for complete information concerns the generalized
second-price mechanism and lends additional theoretical support to the use of
this mechanism in practice. Particularly interesting from a technical
perspective is the result for incomplete information, which is driven by a
surprising connection between equilibrium bids in the VCG mechanism and the
generalized first-price mechanism.


title:
A Griffith-Euler-Bernoulli theory for thin brittle beams derived from
  nonlinear models in variational fracture mechanics

abstract:
  We study a planar thin brittle beam subject to elastic deformations and
cracks described in terms of a nonlinear Griffith energy functional acting on
$SBV$ deformations of the beam. In particular we consider the case in which
elastic bulk contributions due to finite bending of the beam are comparable to
the surface energy which is necessary to completely break the beam into several
large pieces. In the limit of vanishing aspect ratio we rigorously derive an
effective Griffith-Euler-Bernoulli functional which acts on piecewise $W^{2,2}$
regular curves representing the midline of the beam. The elastic part of this
functional is the classical Euler-Bernoulli functional for thin beams in the
bending dominated regime in terms of the curve's curvature. In addition there
also emerges a fracture term proportional to the number of discontinuities of
the curve and its first derivative.


title: Mean curvature flow of area decreasing maps between Riemann surfaces

abstract:
  In this article we give a complete description of the evolution of an area
decreasing map $f:M\to N$ induced by its mean curvature in the situation where
$M$ and $N$ are complete Riemann surfaces with bounded geometry, $M$ being
compact, for which their sectional curvatures $\sigma_M$, $\sigma_N$ satisfy
$\min\sigma_M\ge\sup\sigma_N$.


title: Optical switching and bistability in a four-level atomic systems

abstract:
  We explore the coherent control of nonlinear absorption of intense laser
fields in four-level atomic systems. For instance, in a four-level ladder
system, a coupling field creates electromagnetically induced transparency (EIT)
with Aulter-Townes doublet for the probe field while the control field is
absent. A large absorption peak appears at resonance as the control field is
switched on. We show how such a large absorption leads to optical switching.
Further, this large absorption gets diminished and a transparency window
appears due to the saturation effects as the strength of the probe field is
increased. We further demonstrate that the threshold of the optical bistability
can be modified by suitable choices of the coupling and the control fields. In
a four-level Y-type configuration, the effect of the control field on saturable
absorption (SA) and reverse saturable absorption (RSA) is highlighted in the
context of nonlinear absorption of the probe field. We achieve RSA and SA in a
simple atomic system just by applying a control field.


title: Conformal Invariance of Graphene Sheets

abstract:
  Suspended graphene sheets exhibit correlated random deformations that can be
studied under the framework of rough surfaces with a Hurst (roughness) exponent
$0.72 \pm 0.01$. Here, we show that, independent of the temperature, the
iso-height lines at the percolation threshold have a well-defined fractal
dimension and are conformally invariant, sharing the same statistical
properties as Schramm-Loewner evolution (SLE$_{\kappa}$) curves with
$\kappa=2.24\pm0.07$. Interestingly, iso-height lines of other rough surfaces
are not necessarily conformally invariant even if they have the same Hurst
exponent, e.g. random Gaussian surfaces. We have found that the distribution of
the modulus of the Fourier coefficients plays an important role on this
property. Our results not only introduce a new universality class and place the
study of suspended graphene membranes within the theory of critical phenomena,
but also provide hints on the long-standing question about the origin of
conformal invariance in iso-height lines of rough surfaces.


title:
Forward Modelling of Standing Kink Modes in Coronal Loops II.
  Applications

abstract:
  Magnetohydrodynamic waves are believed to play a significant role in coronal
heating, and could be used for remote diagnostics of solar plasma. Both the
heating and diagnostic applications rely on a correct inversion (or backward
modelling) of the observables into the thermal and magnetic structures of the
plasma. However, owing to the limited availability of observables, this is an
ill-posed issue. Forward Modelling is to establish a plausible mapping of
plasma structuring into observables. In this study, we set up forward models of
standing kink modes in coronal loops and simulate optically thin emissions in
the extreme ultraviolet bandpasses, and then adjust plasma parameters and
viewing angles to match three events of transverse loop oscillations observed
by the Solar Dynamics Observatory/Atmospheric Imaging Assembly. We demonstrate
that forward models could be effectively used to identify the oscillation
overtone and polarization, to reproduce the general profile of oscillation
amplitude and phase, and to predict multiple harmonic periodicities in the
associated emission intensity and loop width variation.


title: Backtesting Lambda Value at Risk

abstract:
  A new risk measure, the lambda value at risk (Lambda VaR), has been recently
proposed from a theoretical point of view as a generalization of the value at
risk (VaR). The Lambda VaR appears attractive for its potential ability to
solve several problems of the VaR. In this paper we propose three nonparametric
backtesting methodologies for the Lambda VaR which exploit different features.
Two of these tests directly assess the correctness of the level of coverage
predicted by the model. One of these tests is bilateral and provides an
asymptotic result. A third test assess the accuracy of the Lambda VaR that
depends on the choice of the P&L distribution. However, this test requires the
storage of more information. Finally, we perform a backtesting exercise and we
compare our results with the ones from Hitaj and Peri (2015)


title: The LHAASO experiment: from Gamma-Ray Astronomy to Cosmic Rays

abstract:
  LHAASO is expected to be the most sensitive project to face the open problems
in Galactic cosmic ray physics through a combined study of photon- and charged
particle-induced extensive air showers in the energy range 10$^{11}$ -
10$^{17}$ eV. This new generation multi-component experiment will be able of
continuously surveying the gamma-ray sky for steady and transient sources from
about 100 GeV to PeV energies, thus opening for the first time the
10$^2$--10$^3$ TeV range to the direct observations of the high energy cosmic
ray sources.
  In addition, the different observables (electronic, muonic and Cherenkov
components) that will be measured in LHAASO will allow the study of the origin,
acceleration and propagation of the radiation through a measurement of energy
spectrum, elemental composition and anisotropy with unprecedented resolution.
The installation of the experiment started at very high altitude in China
(Daocheng site, Sichuan province, 4410 m a.s.l.). The commissioning of one
fourth of the detector will be implemented in 2018. The completion of the
installation is expected by the end of 2021.


title: Hard X-ray view of microlensing events in RX J1131-1231

abstract:
  RX J1131-1231 is a gravitationally lensed system which includes four images
of a quasar lensed by an elliptical galaxy. The flux in the individual images
is known to be affected by microlensing effect in the visible and X-ray bands.
We study the multi-wavelength properties of RX J1131-1231 over a broad energy
range, from optical to hard X-ray, during the periods of the microlensing
caustic crossings. We aim to constrain the spatial extent of the X-ray emission
region at different energies. We combine the data of the source monitoring in
the visible band with the X-ray data of the Burst Alert Telescope (BAT) on
board of SWIFT satellite and Chandra X-ray observatory. Inspecting the broad
band spectrum and lightcurves of the source we identify several microlensing
caustic crossing events, and study the details of variability of the source
during these events. The caustic crossings of image A on MJD 55150 and 55500
produce strong variations of the overall X-ray flux from the source. In the
soft X-ray band, the caustic crossing events are characterised by the
exponential growth / decay of the flux ratio between the source images with the
exponentiating time scale T_d~60 d, which corresponds to the caustic transit
time of the source of the size ~10^{14} cm. Variability induced by the
microlensing dominates the overall variability of the sum of the fluxes of four
images of the source which should also be detectable in the hard X-ray
lightcurve, if the hard X-ray source is comparably compact. Non-detection of
the caustic crossing events in the SWIFT/BAT lightcurve of the source indicates
that geometry of the region of emission of X-rays with energies above 15 keV is
different from that of the lower energy X-rays, with the hard X-ray emission an
order of magnitude larger in size.


title: Security of Quantum Key Distribution

abstract:
  The security issues facing quantum key distribution (QKD) are explained,
herein focusing on those issues that are cryptographic and information
theoretic in nature and not those based on physics. The problem of security
criteria is addressed. It is demonstrated that an attacker's success
probabilities are the fundamental criteria of security that any theoretic
security criterion must relate to in order to have operational significance.
The errors committed in the prevalent interpretation of the trace distance
criterion are analyzed. The security proofs of QKD protocols are discussed and
assessed in regard to three main features: their validity, completeness, and
adequacy of the achieved numerical security level. Problems are identified in
all these features. It appears that the QKD security situation is quite
different from the common perception that a QKD-generated key is nearly
perfectly secure. Built into our discussion is a simple but complete
quantitative description of the information theoretic security of classical key
distribution that is also applicable to the quantum situation. In the
appendices, we provide a brief outline of the history of some major QKD
security proofs, a rather unfavorable comparison of current QKD proven security
with that of conventional symmetric key ciphers, and a list of objections and
answers concerning some major points of the paper.


title: Minimal dilatation in Penner's construction

abstract:
  For all orientable closed surfaces, we determine the minimal dilatation among
mapping classes arising from Penner's construction. We also discuss
generalisations to surfaces with punctures.


title: Cold Milky Way Hi gas in filaments

abstract:
  We investigate data from the Galactic Effelsberg--Bonn HI Survey (EBHIS),
supplemented with data from the third release of the Galactic All Sky Survey
(GASS III) observed at Parkes. We explore the all sky distribution of the local
Galactic HI gas with $|v_{\rm LSR}| < 25 $ kms$^{-1}$ on angular scales of 11'
to 16'. Unsharp masking (USM) is applied to extract small scale features. We
find cold filaments that are aligned with polarized dust emission and conclude
that the cold neutral medium (CNM) is mostly organized in sheets that are,
because of projection effects, observed as filaments. These filaments are
associated with dust ridges, aligned with the magnetic field measured on the
structures by Planck at 353 GHz. The CNM above latitudes $|b|>20^\circ$ is
described by a log-normal distribution, with a median Doppler temperature
$T_{\rm D} = 223$ K, derived from observed line widths that include turbulent
contributions. The median neutral hydrogen (HI) column density is $N_{\rm HI}
\simeq 10^{19.1}\,{\rm cm^{-2}}$. These CNM structures are embedded within a
warm neutral medium (WNM) with $N_{\rm HI} \simeq 10^{20} {\rm cm^{-2}}$.
Assuming an average distance of 100 pc, we derive for the CNM sheets a
thickness of $< 0.3$ pc. Adopting a magnetic field strength of $B_{\rm tot} =
(6.0 \pm 1.8)\mu$G, proposed by Heiles & Troland 2005, and assuming that the
CNM filaments are confined by magnetic pressure, we estimate a thickness of
0.09 pc. Correspondingly the median volume density is in the range $ 14 < n <
47 {\rm cm^{-3}}$.


title:
On occupation times of the first and third quadrants for planar Brownian
  motion

abstract:
  An open problem of interest, first infused into the applied probability
community in the work of Bingham and Doney in 1988, (see \cite{Bingham}) is
stated as follows: find the distribution of the quadrant occupation time of
planar Brownian motion. In this short communication, we study an alternate
formulation of this longstanding open problem: let $X(t), Y(t), t \geq 0$ be
standard Brownian motions starting at $x,y$ respectively. Find the distribution
of the total time $T=Leb\{t \in [0,1]: X(t) \times Y(t) >0\}$, when $x=y=0$,
i.e., the occupation time of the union of the first and third quadrants. If two
adjacent quadrants are used, the problem becomes much easier and the
distribution of $T$ follows the arcsine law.


title: Local motifs in GeS$_2$-Ga$_2$S$_3$ glasses

abstract:
  The structure of (GeS$_2$)$_{0.75}$(Ga$_2$S$_3$)$_{0.25}$ and
(GeS$_2$)$_{0.83}$(Ga$_2$S$_3$)$_{0.17}$ glasses was investigated by Raman
scattering, high energy X-ray diffraction and extended X-ray absorption fine
structure (EXAFS) measurements at the Ga and Ge K-edges. The reverse Monte
Carlo simulation technique (RMC) was used to obtain structural models
compatible with diffraction and EXAFS datasets. It was found that the
coordination number of Ga is close to four. While Ge atoms have only S
neighbors, Ga binds to S as well as to Ga atoms showing a violation of chemical
ordering in GeS$_2$-Ga$_2$S$_3$ glasses. Analysis of the corner- and
edge-sharing between [GeS$_{4/2}$] units revealed that about 30% of germanium
atoms participate in the edge-shared tetrahedra.


title: Multicolour Ramsey Numbers of Odd Cycles

abstract:
  We show that for any positive integer $r$ there exists an integer $k$ and a
$k$-colouring of the edges of $K_{2^{k}+1}$ with no monochromatic odd cycle of
length less than $r$. This makes progress on a problem of Erd\H{o}s and Graham
and answers a question of Chung. We use these colourings to give new lower
bounds on the $k$-colour Ramsey number of the odd cycle and prove that, for all
odd $r$ and all $k$ sufficiently large, there exists a constant $\epsilon =
\epsilon(r) > 0$ such that $R_{k}(C_{r}) > (r-1)(2+\epsilon)^{k-1}$.


title:
Classical logic and intuitionistic logic: equivalent formulations in
  natural deduction, G\"odel-Kolmogorov-Glivenko translation

abstract:
  This report first shows the equivalence bewteen several formulations of
classical logic in intuitionistic logic (tertium non datur, reductio ad
absurdum, Pierce's law). Then it establishes the correctness of the
G\"odel-Kolmogorov translation, whose restriction to the propositional case is
due to Glivenko. This translation maps a formula $F$ of first order logic to a
formula $F^{\lnot\lnot}$ in such a way that $F$ is provable in classical logic
if and only if $F^{\lnot\lnot}$ is provable in intuitionistic logic. All formal
proofs are presented in natural deduction.
  These questions are well-known proof theoretical facts, but in textbooks,
they are often ignored or left to the reader. Because of the combinatorial
difficulty of some of the needed formal proofs, we hope that this report may be
useful, in particular to students and colleagues from other areas.


title: QED Radiative Corrections to Low-Energy Moller and Bhabha Scattering

abstract:
  We present a treatment of the next-to-leading-order radiative corrections to
unpolarized Moller and Bhabha scattering without resorting to
ultra-relativistic approximations. We extend existing soft-photon radiative
corrections with new hard-photon bremsstrahlung calculations so that the effect
of photon emission is taken into account for any photon energy. This
formulation is intended for application in the OLYMPUS experiment and the
upcoming DarkLight experiment, but is applicable to a broad range of
experiments at energies where QED is a sufficient description.


title: Close packing of rods on spherical surfaces

abstract:
  We study the optimal packing of short, hard spherocylinders confined to lie
tangential to a spherical surface, using simulated annealing and molecular
dynamics simulations. For clusters of up to twelve particles, we map out the
changes in the geometry of the closest-packed configuration as a function of
the aspect ratio $L/D$, where $L$ is the cylinder length and $D$ the diameter
of the rods. We find a rich variety of cluster structures. For larger clusters,
we find that the best-packed configurations up to around 100 particles are
highly dependent on the exact number of particles and aspect ratio. For even
larger clusters, we find largely disordered clusters for very short rods ($L/D
= 0.25$), while slightly longer rods ($L/D = 0.5$ or $1$) prefer a global
baseball-like geometry of smectic-like domains, similar to the behavior of
large-scale nematic shells. Our results provide predictions for experimentally
realizable systems of colloidal rods trapped at the interface of emulsion
droplets.


title:
Improving performance in quantum mechanics with explicit incentives to
  correct mistakes

abstract:
  An earlier investigation found that the performance of advanced students in a
quantum mechanics course did not automatically improve from midterm to final
exam on identical problems even when they were provided the correct solutions
and their own graded exams. Here, we describe a study, which extended over four
years, in which upper-level undergraduate students in a quantum physics course
were given four identical problems in both the midterm exam and final exam.
Approximately half of the students were given explicit incentives to correct
their mistakes in the midterm exam. In particular, they could get back up to
50\% of the points lost on each midterm exam problem. The solutions to the
midterm exam problems were provided to all students in both groups but those
who corrected their mistakes were provided the solution after they submitted
their corrections to the instructor. The performance on the same problems on
the final exam suggests that students who were given incentives to correct
their mistakes significantly outperformed those who were not given an
incentive. The incentive to correct the mistakes had greater impact on the
final exam performance of students who had not performed well on the midterm
exam.


title: A quantum random walk of a Bose-Einstein condensate in momentum space

abstract:
  Each step in a quantum random walk is typically understood to have two basic
components; a `coin-toss' which produces a random superposition of two states,
and a displacement which moves each component of the superposition by different
amounts. Here we suggest the realization of a walk in momentum space with a
spinor Bose-Einstein condensate subject to a quantum ratchet realized with a
pulsed, off-resonant optical lattice. By an appropriate choice of the lattice
detuning, we show how the atomic momentum can be entangled with the internal
spin states of the atoms. For the coin-toss, we propose to use a microwave
pulse to mix these internal states. We present experimental results showing an
optimized quantum ratchet, and through a series of simulations, demonstrate how
our proposal gives extraordinary control of the quantum walk. This should allow
for the investigation of possible biases, and classical-to-quantum dynamics in
the presence of natural and engineered noise.


title: Learning Shapes by Convex Composition

abstract:
  We present a mathematical and algorithmic scheme for learning the principal
geometric elements in an image or 3D object. We build on recent work that
convexifies the basic problem of finding a combination of a small number shapes
that overlap and occlude one another in such a way that they "match" a given
scene as closely as possible. This paper derives general sufficient conditions
under which this convex shape composition identifies a target composition. From
a computational standpoint, we present two different methods for solving the
associated optimization programs. The first method simply recasts the problem
as a linear program, while the second uses the alternating direction method of
multipliers with a series of easily computed proximal operators.


title:
A Model of Selective Advantage for the Efficient Inference of Cancer
  Clonal Evolution

abstract:
  Recently, there has been a resurgence of interest in rigorous algorithms for
the inference of cancer progression from genomic data. The motivations are
manifold: (i) growing NGS and single cell data from cancer patients, (ii) need
for novel Data Science and Machine Learning algorithms to infer models of
cancer progression, and (iii) a desire to understand the temporal and
heterogeneous structure of tumor to tame its progression by efficacious
therapeutic intervention. This thesis presents a multi-disciplinary effort to
model tumor progression involving successive accumulation of genetic
alterations, each resulting populations manifesting themselves in a cancer
phenotype. The framework presented in this work along with algorithms derived
from it, represents a novel approach for inferring cancer progression, whose
accuracy and convergence rates surpass the existing techniques. The approach
derives its power from several fields including algorithms in machine learning,
theory of causality and cancer biology. Furthermore, a modular pipeline to
extract ensemble-level progression models from sequenced cancer genomes is
proposed. The pipeline combines state-of-the-art techniques for sample
stratification, driver selection, identification of fitness-equivalent
exclusive alterations and progression model inference. Furthermore, the results
are validated by synthetic data with realistic generative models, and
empirically interpreted in the context of real cancer datasets; in the later
case, biologically significant conclusions are also highlighted. Specifically,
it demonstrates the pipeline's ability to reproduce much of the knowledge on
colorectal cancer, as well as to suggest novel hypotheses. Lastly, it also
proves that the proposed framework can be applied to reconstruct the
evolutionary history of cancer clones in single patients, as illustrated by an
example from clear cell renal carcinomas.


title:
Content Providers Volunteering to Pay Network Providers: Better than
  Neutrality?

abstract:
  This paper studies the effects on user welfare of imposing network
neutrality, using a game-theoretic model of provider interactions based on a
two-sided market framework: we assume that the platform--the last-mile access
providers (ISPs)--are monopolists, and consider content providers (CPs) entry
decisions. All decisions affect the choices made by users, who are sensitive
both to CP and ISP investments (in content creation and quality-of-service,
respectively). In a non-neutral regime, CPs and ISPs can charge each other,
while such charges are prohibited in the neutral regime. We assume those
charges (if any) are chosen by CPs, a direction rarely considered in the
literature, where they are assumed fixed by ISPs.
  Our analysis suggests that, unexpectedly, more CPs enter the market in a
non-neutral regime where they pay ISPs, than without such payments.
Additionally, in this case ISPs tend to invest more than in the neutral regime.
From our results, the best regime in terms of user welfare is parameter
dependent, calling for caution in designing neutrality regulations.


title: Noisy population recovery in polynomial time

abstract:
  In the noisy population recovery problem of Dvir et al., the goal is to learn
an unknown distribution $f$ on binary strings of length $n$ from noisy samples.
For some parameter $\mu \in [0,1]$, a noisy sample is generated by flipping
each coordinate of a sample from $f$ independently with probability
$(1-\mu)/2$. We assume an upper bound $k$ on the size of the support of the
distribution, and the goal is to estimate the probability of any string to
within some given error $\varepsilon$. It is known that the algorithmic
complexity and sample complexity of this problem are polynomially related to
each other.
  We show that for $\mu > 0$, the sample complexity (and hence the algorithmic
complexity) is bounded by a polynomial in $k$, $n$ and $1/\varepsilon$
improving upon the previous best result of $\mathsf{poly}(k^{\log\log
k},n,1/\varepsilon)$ due to Lovett and Zhang.
  Our proof combines ideas from Lovett and Zhang with a \emph{noise attenuated}
version of M\"{o}bius inversion. In turn, the latter crucially uses the
construction of \emph{robust local inverse} due to Moitra and Saks.


title: Permutation groups and derangements of odd prime order

abstract:
  Let $G$ be a transitive permutation group of degree $n$. We say that $G$ is
$2'$-elusive if $n$ is divisible by an odd prime, but $G$ does not contain a
derangement of odd prime order. In this paper we study the structure of
quasiprimitive and biquasiprimitive $2'$-elusive permutation groups, extending
earlier work of Giudici and Xu on elusive groups. As an application, we use our
results to investigate automorphisms of finite arc-transitive graphs of prime
valency.


title:
From quantum foundations via natural language meaning to a theory of
  everything

abstract:
  In this paper we argue for a paradigmatic shift from `reductionism' to
`togetherness'. In particular, we show how interaction between systems in
quantum theory naturally carries over to modelling how word meanings interact
in natural language. Since meaning in natural language, depending on the
subject domain, encompasses discussions within any scientific discipline, we
obtain a template for theories such as social interaction, animal behaviour,
and many others.


title: Detection of CH3SH in protostar IRAS 16293-2422

abstract:
  The nature of the main sulphur reservoir in star forming regions is a long
standing mystery. The observed abundance of sulphur-bearing species in dense
clouds is only about 0.1 per cent of the same quantity in diffuse clouds.
Therefore, the main sulphur species in star forming regions of the interstellar
medium are still unknown. IRAS 16293-2422 is one of the regions where
production of S-bearing species is favourable due to its conditions which
allows the evaporation of ice mantles. We carried out observations in the 3 mm
band towards the solar type protostar IRAS 16293-2422 with the IRAM 30m
telescope. We observed a single frequency setup with the EMIR heterodyne 3 mm
receiver with an Lower Inner (LI) tuning frequency of 89.98 GHz. Several lines
of the complex sulphur species CH3SH were detected. Observed abundances are
compared with simulations using the NAUTILUS gas-grain chemical model.
Modelling results suggest that CH3SH has the constant abundance of 4e-9
(compared to H2) for radii lower than 200 AU and is mostly formed on the
surfaces. Detection of CH3SH indicates that there may be several new families
of S-bearing molecules (which could form starting from CH3SH) which have not
been detected or looked for yet.


title:
A Low Complexity VLSI Architecture for Multi-Focus Image Fusion in DCT
  Domain

abstract:
  Due to the confined focal length of optical sensors, focusing all objects in
a scene with a single sensor is a difficult task. To handle such a situation,
image fusion methods are used in multi-focus environment. Discrete Cosine
Transform (DCT) is a widely used image compression transform, image fusion in
DCT domain is an efficient method. This paper presents a low complexity
approach for multi-focus image fusion and its VLSI implementation using DCT.
The proposed method is evaluated using reference/non-reference fusion measure
criteria and the obtained results asserts it's effectiveness. The maximum
synthesized frequency on FPGA is found to be 221 MHz and consumes 42% of FPGA
resources. The proposed method consumes very less power and can process 4K
resolution images at the rate of 60 frames per second which makes the hardware
suitable for handheld portable devices such as camera module and wireless image
sensors.


title: Investigation of $B\bar B$ four-quark systems using lattice QCD

abstract:
  We investigate $B \bar B$ systems by computing potentials of two static
quarks in the presence of two quarks of finite mass using lattice QCD. By
solving the Schr\"odinger equation we check whether these potentials are
sufficiently attractive to host bound states. Particular focus is put on the
experimentally most promising bottomonium-like tetraquark candidate $Z_b^\pm$
with quantum numbers $I(J^P)=1(1^+)$.


title: The Group Inverse of extended Symmetric and Periodic Jacobi Matrices

abstract:
  In this work, we explicitly compute the group inverse of symmetric and
periodic Jacobi matrices.


title: Spatial multi-LRU Caching for Wireless Networks with Coverage Overlaps

abstract:
  This article introduces a novel family of decentralised caching policies,
applicable to wireless networks with finite storage at the edge-nodes
(stations). These policies are based on the Least-Recently-Used replacement
principle, and are, here, referred to as spatial multi-LRU. Based on these,
cache inventories are updated in a way that provides content diversity to users
who are covered by, and thus have access to, more than one station. Two
variations are proposed, namely the multi-LRU-One and -All, which differ in the
number of replicas inserted in the involved caches. By introducing spatial
approximations, we propose a Che-like method to predict the hit probability,
which gives very accurate results under the Independent Reference Model (IRM).
It is shown that the performance of multi-LRU increases the more the
multi-coverage areas increase, and it approaches the performance of other
proposed centralised policies, when multi-coverage is sufficient. For IRM
traffic multi-LRU-One outperforms multi-LRU-All, whereas when the traffic
exhibits temporal locality the -All variation can perform better.


title:
Matter Power Spectrum in Hidden Neutrino Interacting Dark Matter Models:
  A Closer Look at the Collision Term

abstract:
  Dark Matter (DM) models providing possible alternative solutions to the
small- scale crisis of standard cosmology are nowadays of growing interest. We
consider DM interacting with light hidden fermions via well motivated
fundamental operators showing the resultant matter power spectrum is suppressed
on subgalactic scales within a plausible parameter region. Our basic
description of the evolution of cosmological perturbations relies on a fully
consistent first principles derivation of a perturbed Fokker-Planck type
equation, generalizing existing literature. The cosmological perturbation of
the Fokker-Planck equation is presented for the first time in two different
gauges, where the results transform into each other according to the rules of
gauge transformation. Furthermore, our focus lies on a derivation of a broadly
applicable and easily computable collision term showing important
phenomenological differences to other existing approximations. As one of the
main results and concerning the small-scale crisis, we show the equal
importance of vector and scalar boson mediated interactions between DM and
light fermions.


title:
Functional complexity emerging from anatomical constraints in the brain:
  the significance of network modularity and rich-clubs

abstract:
  The large-scale structural ingredients of the brain and neural connectomes
have been identified in recent years. These are, similar to the features found
in many other real networks: the arrangement of brain regions into modules and
the presence of highly connected regions (hubs) forming rich-clubs. Here, we
examine how modules and hubs shape the collective dynamics on networks and we
find that both ingredients lead to the emergence of complex dynamics. Comparing
the connectomes of C. elegans, cats, macaques and humans to surrogate networks
in which either modules or hubs are destroyed, we find that functional
complexity always decreases in the perturbed networks. A comparison between
simulated and empirically obtained resting-state functional connectivity
indicates that the human brain, at rest, lies in a dynamical state that
reflects the largest complexity its anatomical connectome can host. Last, we
generalise the topology of neural connectomes into a new hierarchical network
model that successfully combines modular organisation with rich-club forming
hubs. This is achieved by centralising the cross-modular connections through a
preferential attachment rule. Our network model hosts more complex dynamics
than other hierarchical models widely used as benchmarks.


title: Enhanced estimation of loss in the presence of Kerr nonlinearity

abstract:
  We address the characterization of dissipative bosonic channels and show that
estimation of the loss rate by Gaussian probes (coherent or squeezed) is
improved in the presence of Kerr nonlinearity. In particular, enhancement of
precision may be substantial for short interaction time, i.e. for media of
moderate size, e.g. biological samples. We analyze in detail the behaviour of
the quantum Fisher information (QFI), and determine the values of nonlinearity
maximizing the QFI as a function of the interaction time and of the parameters
of the input signal. We also discuss the precision achievable by photon
counting and quadrature measurement and present additional results for
truncated, few-photon, probe signals. Finally, we discuss the origin of the
precision enhancement, showing that it cannot be linked quantitatively to the
non-Gaussianity of the interacting probe signal.


title:
Perfect photon absorption in nonlinear regime of cavity quantum
  electrodynamics

abstract:
  It has been shown that perfect photon absorption can occur in the linear
excitation regime of cavity quantum electrodynamics (CQED), in which photons
from two identical light fields coupled into two ends of the cavity are
completely absorbed and result in excitation of the polariton state of the CQED
system. The output light from the cavity is totally suppressed by the
destructive interference and the polariton state can only decay incoherently
back to the ground state. Here we analyze the perfect photon absorption and
onset of optical bistability in the nonlinear regime of the CQED and show that
the perfect photon absorption persists in the nonlinear regime of the CQED
below the threshold of the optical bistability. Therefore the perfect photon
absorption is a phenomenon that can be observed in both linear and nonlinear
regimes of CQED. Furthermore, our study reveals for the first time that the
optical bistability is influenced by the input-light interference and can be
manipulated by varying the relative phase of the two input fields.


title:
The Invisible Hand of Laplace: the Role of Market Structure in Price
  Convergence and Oscillation

abstract:
  A fundamental question about a market is under what conditions, and then how
rapidly, does price signaling cause price equilibration. Qualitatively, this
ought to depend on how well-connected the market is. We address this question
quantitatively for a certain class of Arrow-Debreu markets with continuous-time
proportional t\^{a}tonnement dynamics. We show that the algebraic connectivity
of the market determines the effectiveness of price signaling equilibration.
This also lets us study the rate of external noise that a market can tolerate
and still maintain near-equilibrium prices.


title: A sharp exceptional set estimate for visibility

abstract:
  A Borel set $B \subset \mathbb{R}^{n}$ is visible from $x \in
\mathbb{R}^{n}$, if the radial projection of $B$ with base point $x$ has
positive $\mathcal{H}^{n - 1}$ measure. I prove that if $\dim B > n - 1$, then
$B$ is visible from every point $x \in \mathbb{R}^{n} \setminus E$, where $E$
is an exceptional set with dimension $\dim E \leq 2(n - 1) - \dim B$. This is
the sharp bound for all $n \geq 2$.
  Many parts of the proof were already contained in a recent previous paper by
P. Mattila and the author, where a weaker bound for $\dim E$ was derived as a
corollary from a certain slicing theorem. Here, no improvement to the slicing
result is obtained; in brief, the main observation of the present paper is that
the proof method gives the optimal result, when applied directly to the
visibility problem.


title: Online Dual Coordinate Ascent Learning

abstract:
  The stochastic dual coordinate-ascent (S-DCA) technique is a useful
alternative to the traditional stochastic gradient-descent algorithm for
solving large-scale optimization problems due to its scalability to large data
sets and strong theoretical guarantees. However, the available S-DCA
formulation is limited to finite sample sizes and relies on performing multiple
passes over the same data. This formulation is not well-suited for online
implementations where data keep streaming in. In this work, we develop an {\em
online} dual coordinate-ascent (O-DCA) algorithm that is able to respond to
streaming data and does not need to revisit the past data. This feature embeds
the resulting construction with continuous adaptation, learning, and tracking
abilities, which are particularly attractive for online learning scenarios.


title: On exact solutions of nonlinear acoustic equations

abstract:
  Solutions of nonlinear acoustic equations describing propagation of strong
sound pulses with account of curvature of wave fronts in multi-dimensional
geometry are obtained from simple physical considerations. The form of these
solutions suggests ansatz suitable for finding solutions of much more general
equations of Khokhlov-Zabolotskaya type. General method is illustrated by an
example of nonlinear sound pulse focused in one transverse direction and
defocused in the other direction.


title: Characterizations of abstract stable homotopy theories

abstract:
  In this paper we establish new characterizations of stable derivators,
thereby obtaining additional interpretations of the passage from (pointed)
topological spaces to spectra and, more generally, of the stabilization. We
show that a derivator is stable if and only if homotopy finite limits and
homotopy finite colimits commute, and there are variants for sufficiently
finite Kan extensions. As an additional reformulation, a derivator is stable if
and only if it admits a zero object and if partial cone and partial fiber
morphisms commute on squares.


title:
Advancing Trace Recovery Evaluation - Applied Information Retrieval in a
  Software Engineering Context

abstract:
  Successful development of software systems involves efficient navigation
among software artifacts. One state-of-practice approach to structure
information is to establish trace links between artifacts, a practice that is
also enforced by several development standards. Unfortunately, manually
maintaining trace links in an evolving system is a tedious task. To tackle this
issue, several researchers have proposed treating the capture and recovery of
trace links as an Information Retrieval (IR) problem. The work contains a
Systematic Literature Review (SLR) of previous evaluations of IR-based trace
recovery. We show that a majority of previous evaluations have been
technology-oriented, conducted in "the cave of IR evaluation", using small
datasets as experimental input. Also, software artifacts originating from
student projects have frequently been used in evaluations. We conducted a
survey among traceability researchers, and found that a majority consider
student artifacts to be only partly representative to industrial counterparts.
Our findings call for additional case studies to evaluate IR-based trace
recovery within the full complexity of an industrial setting. Also, this thesis
contributes to the body of empirical evidence of IR-based trace recovery in two
experiments with industrial software artifacts. The technology-oriented
experiment highlights the clear dependence between datasets and the accuracy of
IR-based trace recovery, in line with findings from the SLR. The human-oriented
experiment investigates how different quality levels of tool output affect the
tracing accuracy of engineers. Finally, we present how tools and methods are
evaluated in the general field of IR research, and propose a taxonomy of
evaluation contexts tailored for IR-based trace recovery.


title:
Closed flux tubes in D=2+1 SU(N) gauge theories: dynamics and effective
  string description

abstract:
  We extend our earlier calculations of the spectrum of closed flux tubes in
SU(N) gauge theories in 2+1 dimensions, with a focus on questions raised by
recent theoretical progress on the effective string action of long flux tubes
and the world-sheet action for flux tubes of moderate lengths. Our new
calculations in SU(4) and SU(8) provide evidence that the leading O(1/l^gamma)
non-universal correction to the flux tube ground state energy does indeed have
a power gamma greater than or equal to 7. We perform a study in SU(2), where we
can traverse the length at which the Nambu-Goto ground state becomes tachyonic,
to obtain an all-N view of the spectrum. Our comparison of the k=2 flux tube
excitation energies in SU(4) and SU(6) suggests that the massive world sheet
excitation associated with the k=2 binding has a scale that knows about the
group and hence the theory in the bulk, and we comment on the potential
implications of world sheet massive modes for the bulk spectrum. We provide a
quantitative analysis of the surprising (near-)orthogonality of flux tubes
carrying flux in different SU(N) representations, which implies that their
screening by gluons is highly suppressed even at small N.


title:
An HST Survey for 100-1000 AU Companions around Young Stellar Objects in
  the Orion Molecular Clouds: Evidence for Environmentally Dependent
  Multiplicity

abstract:
  We present a near-IR survey for the visual multiples in the Orion molecular
clouds region at separations between 100 and 1000 AU. These data were acquired
at 1.6~$\mu$m with the NICMOS and WFC3 cameras on the Hubble Space Telescope.
Additional photometry was obtained for some of the sources at 2.05~$\mu$m with
NICMOS and in the $L'$-band with NSFCAM2 on the IRTF. Towards 129 protostars
and 197 pre-main sequence stars with disks observed with WFC3, we detect 21 and
28 candidate companions between the projected separations of 100---1000 AU, of
which less than 5 and 8, respectively, are chance line of sight coincidences.
The resulting companion fraction ($CF$) after the correction for the line of
sight contamination is 14.4$^{+1.1}_{-1.3}$% for protostars and
12.5$^{+1.2}_{-0.8}$% for the pre-main sequence stars. These values are similar
to those found for main sequence stars, suggesting that there is little
variation in the $CF$ with evolution, although several observational biases may
mask a decrease in the $CF$ from protostars to the main sequence stars. After
segregating the sample into two populations based on the surrounding surface
density of YSOs, we find that the $CF$ in the high stellar density regions
($\Sigma_{YSO} > 45$~pc$^{-2}$) is approximately 50% higher than that found in
the low stellar density regions ($\Sigma_{YSO} < 45$~pc$^{-2}$). We interpret
this as evidence for the elevated formation of companions at 100 to 1000 AU in
the denser environments of Orion. We discuss possible reasons for this elevated
formation.


title: Enhancing Contention Resolution ALOHA using Combining Techniques

abstract:
  Recently, random access protocols have acquired a new wave of interest, not
only from the satellite communication community, but also from researchers
active in fields like Internet of Things and machine-to-machine. Asynchronous
(slot- and frame-wise) ALOHA-like random access protocols, are very attractive
for such applications, enabling low complexity transmitters and avoiding time
synchronization requirements. Evolutions of ALOHA employ time diversity through
proactive replication of packets, but the time diversity is not fully exploited
at the receiver. Combining techniques, as selection combining and maximal-ratio
combining, are beneficial and are adopted in the enhanced contention resolution
ALOHA (ECRA) scheme, presented here. A tight approximation of the packet loss
rate for asynchronous random access, including ECRA, well suited for the low
channel load region is derived. Finally, ECRA is evaluated in terms of spectral
efficiency, throughput and packet loss rate in comparison with recent
protocols, showing that it is able to largely outperform both slotted
synchronous and asynchronous schemes.


title: A Survey on Domain-Specific Languages for Machine Learning in Big Data

abstract:
  The amount of data generated in the modern society is increasing rapidly. New
problems and novel approaches of data capture, storage, analysis and
visualization are responsible for the emergence of the Big Data research field.
Machine Learning algorithms can be used in Big Data to make better and more
accurate inferences. However, because of the challenges Big Data imposes, these
algorithms need to be adapted and optimized to specific applications. One
important decision made by software engineers is the choice of the language
that is used in the implementation of these algorithms. Therefore, this
literature survey identifies and describes domain-specific languages and
frameworks used for Machine Learning in Big Data. By doing this, software
engineers can then make more informed choices and beginners have an overview of
the main languages used in this domain.


title: Virtual cycles of gauged Witten equation

abstract:
  We construct virtual cycles on moduli spaces of perturbed gauged Witten
equation over a fixed smooth r -spin curve, under the framework of [TX15].
Together with the wall-crossing formula proved in the companion paper [TX19],
it completes the construction of the correlation function for the gauged linear
sigma model announced in [TX16] as well as the proof of its invariance.


title: Evidence for a direct collapse black hole in the Lyman-alpha source CR7

abstract:
  Throughout the epoch of reionization the most luminous Ly{\alpha} emitters
are capable of ionizing their own local bubbles. The CR7 galaxy at $z \approx
6.6$ stands out for its combination of exceptionally bright Ly{\alpha} and HeII
1640 Angstrom line emission but absence of metal lines. As a result CR7 may be
the first viable candidate host of a young primordial starburst or direct
collapse black hole. High-resolution spectroscopy reveals a +160 km s$^{-1}$
velocity offset between the Ly{\alpha} and HeII line peaks while the spatial
extent of the Ly{\alpha} emitting region is $\sim 16$ kpc. The observables are
indicative of an outflow signature produced by a strong central source. We
present one-dimensional radiation-hydrodynamics simulations incorporating
accurate Ly{\alpha} feedback and ionizing radiation to investigate the nature
of the CR7 source. We find that a Population III star cluster with $10^5$ K
blackbody emission ionizes its environment too efficiently to generate a
significant velocity offset. However, a massive black hole with a nonthermal
Compton-thick spectrum is able to reproduce the Ly{\alpha} signatures as a
result of higher photon trapping and longer potential lifetime. For both
sources, Ly{\alpha} radiation pressure turns out to be dynamically important.


title: A Variational Algorithm for Bayesian Variable Selection

abstract:
  There has been an intense development on the estimation of a sparse
regression coefficient vector in statistics, machine learning and related
fields. In this paper, we focus on the Bayesian approach to this problem, where
sparsity is incorporated by the so-called spike-and-slab prior on the
coefficients. Instead of replying on MCMC for posterior inference, we propose a
fast and scalable algorithm based on variational approximation to the posterior
distribution. The updating scheme employed by our algorithm is different from
the one proposed by Carbonetto and Stephens (2012). Those changes seem crucial
for us to show that our algorithm can achieve asymptotic consistency even when
the feature dimension diverges exponentially fast with the sample size.
Empirical results have demonstrated the effectiveness and efficiency of the
proposed algorithm.


title:
NIMBUS: A Hybrid Cloud-Crowd Realtime Architecture for Visual Learning
  in Interactive Domains

abstract:
  Robotic architectures that incorporate cloud-based resources are just now
gaining popularity. However, researchers have very few investigations into
their capabilities to support claims of their feasibility. We propose a novel
method to exchange quality for speed of response. Further, we back this
assertion with empirical findings from experiments performed with Amazon
Mechanical Turk and find that our method improves quality in exchange for
response time in our cognitive architecture.


title:
Primate specific retrotransposons, SVAs, in the evolution of networks
  that alter brain function

abstract:
  The hominid-specific non-LTR retrotransposon termed SINE VNTR Alu (SVA) is
the youngest of the transposable elements in the human genome. The propagation
of the most ancient SVA type A took place about thirteen millions years ago
ago, and the youngest SVA types appeared in the human genome after the
chimpanzee divergence. Functional enrichment analysis of genes associated with
SVA insertions demonstrated their strong link to multiple ontological
categories attributed to brain function and the disorders. SVA types that
expanded their presence in the human genome at different stages of hominoid
life history were also associated with progressively evolving behavioural
features that indicated a potential impact of SVA propagation on a cognitive
ability of a modern human. The SVA-associated genes were highly cross-linked in
functional networks suggesting an accumulative impact of functional alterations
potentially caused by SVA insertions. Our analysis uncovered a potential role
of SVAs in evolution of human CNS and especially emergence of functional trends
relevant to social and parental behaviour. It also supports models which
explain in part how brain function can be modulated by both the immune and
reproductive systems based on the gene expression patterns and gene pathways
potentially altered by SVA insertions.


title:
Limits on Einstein's Equivalence Principle from the first localized Fast
  Radio Burst FRB 150418

abstract:
  Fast Radio Bursts have recently been used to place limits on Einstein's
Equivalence Principle via observations of time delays between photons of
different radio frequencies by \citet{wei15}. These limits on differential
post-Newtonian parameters ($\Delta \gamma<2.52\times10^{-8}$) are the best yet
achieved but still rely on uncertain assumptions, namely the relative
contributions of dispersion and gravitational delays to the observed time
delays and the distances to FRBs. Also very recently, the first FRB host galaxy
has likely been identified, providing the first redshift-based distance
estimate to FRB 150418 \citep{kea16}. Moreover, consistency between the
\omegaigm\ estimate from FRB 150418 and \omegaigm~expected from $\Lambda$CDM
models and WMAP observations leads one to conclude that the observed time delay
for FRB 150418 is highly dominated by dispersion, with any gravitational delays
small contributors. This points to even tighter limits on $\Delta \gamma$. In
this paper, the technique of \citet{wei15} is applied to FRB 150418 to produce
a limit of $\Delta \gamma < 1 - 2\times10^{-9}$, approximately an order of
magnitude better than previous limits and in line with expectations by
\citet{wei15} for what could be achieved if the dispersive delay is separated
from other effects. Future substantial improvements in such limits will depend
on accurately determining the contribution of individual ionized components to
the total observed time delays for FRBs.


title:
Test of the diffusing-diffusivity mechanism using near-wall colloidal
  dynamics

abstract:
  The diffusing-diffusivity mechanism proposed by Chubynsky and Slater [PRL
113, 098302, 2014] predicts that, in environments where the diffusivity changes
gradually, the displacement distribution becomes non-Gaussian, even though the
mean-squared displacement (MSD) grows linearly with time. Here, we report
single-particle tracking measurements of the diffusion of colloidal spheres
near a planar wall. Because the local effective diffusivity is known, we have
been able to carry out the first direct test of this mechanism for diffusion in
inhomogeneous media.


title: Bounds for spherical codes

abstract:
  A set $C$ of unit vectors in $\mathbb{R}^d$ is called an $L$-spherical code
if $x \cdot y \in L$ for any distinct $x,y$ in $C$. Spherical codes have been
extensively studied since their introduction in the 1970's by Delsarte,
Goethals and Seidel. In this note we prove a conjecture of Bukh on the maximum
size of spherical codes. In particular, we show that for any set of $k$ fixed
angles, one can choose at most $O(d^k)$ lines in $\mathbb{R}^d$ such that any
pair of them forms one of these angles.


title: Life, The Mind, and Everything

abstract:
  Incompleteness theorems of Godel, Turing, Chaitin, and Algorithmic
Information Theory have profound epistemological implications. Incompleteness
limits our ability to ever understand every observable phenomenon in the
universe. Incompleteness limits the ability of evolutionary processes from
finding optimal solutions. Incompleteness limits the detectability of machine
consciousness. This is an effort to convey these thoughts and results in a
somewhat entertaining manner.


title: Generalizing Koopman Theory to allow for inputs and control

abstract:
  We develop a new generalization of Koopman operator theory that incorporates
the effects of inputs and control. Koopman spectral analysis is a theoretical
tool for the analysis of nonlinear dynamical systems. Moreover, Koopman is
intimately connected to Dynamic Mode Decomposition (DMD), a method that
discovers spatial-temporal coherent modes from data, connects local-linear
analysis to nonlinear operator theory, and importantly creates an equation-free
architecture allowing investigation of complex systems. In actuated systems,
standard Koopman analysis and DMD are incapable of producing input-output
models; moreover, the dynamics and the modes will be corrupted by external
forcing. Our new theoretical developments extend Koopman operator theory to
allow for systems with nonlinear input-output characteristics. We show how this
generalization is rigorously connected and generalizes a recent development
called Dynamic Mode Decomposition with control (DMDc). We demonstrate this new
theory on nonlinear dynamical systems, including a standard
Susceptible-Infectious-Recovered model with relevance to the analysis of
infectious disease data with mass vaccination (actuation).


title:
Stereotype threat? Effects of inquiring about test takers' gender on
  conceptual test performance in physics

abstract:
  It has been found that activation of a stereotype, for example by indicating
one's gender before a test, typically alters performance in a way consistent
with the stereotype, an effect called "stereotype threat". On a standardized
conceptual physics assessment, we found that asking test takers to indicate
their gender right before taking the test did not deteriorate performance
compared to an equivalent group who did not provide gender information.
Although a statistically significant gender gap was present on the standardized
test whether or not students indicated their gender, no gender gap was observed
on the multiple-choice final exam students took, which included both
quantitative and conceptual questions on similar topics.


title:
Thermal properties of Rhea's Poles: Evidence for a Meter-Deep
  Unconsolidated Subsurface Layer

abstract:
  Cassini's Composite Infrared Spectrometer (CIRS) observed both of Rhea's
polar regions during two flybys on 2013/03/09 and 2015/02/10. The results show
Rhea's southern winter pole is one of the coldest places directly observed in
our solar system: temperatures of 25.4+/-7.4 K and 24.7+/-6.8 K are inferred.
The surface temperature of the northern summer pole is warmer: 66.6+/-0.6 K.
Assuming the surface thermophysical properties of both polar regions are
comparable then these temperatures can be considered a summer and winter
seasonal temperature constraint for the polar region. These observations
provide solar longitude coverage at 133 deg and 313 deg for the summer and
winter poles respectively, with additional winter temperature constraint at 337
deg. Seasonal models with bolometric albedos of 0.70-0.74 and thermal inertias
of 1-46 MKS can provide adequate fits to these temperature constraints. Both
these albedo and thermal inertia values agree (within error) with those
previously observed on both Rhea's leading and trailing hemispheres.
Investigating the seasonal temperature change of Rhea's surface is particularly
important, as the seasonal wave is sensitive to deeper surface temperatures
(~10cm to m) than the more commonly reported diurnal wave (<1cm). The low
thermal inertia derived here implies that Rhea's polar surfaces are highly
porous even at great depths. Analysis of a CIRS 10 to 600 cm-1 stare
observation, taken between 16:22:33 and 16:23:26 UT on 2013/03/09 centered on
71.7 W, 58.7 S provides the first analysis of a thermal emissivity spectrum on
Rhea. The results show a flat emissivity spectrum with negligible emissivity
features. A few possible explanations exist for this flat emissivity spectrum,
but the most likely for Rhea is that the surface is both highly porous and
composed of small particles (less than approximately 50 um).


title: Equivariant Corks

abstract:
  For suitable finite groups G, we construct contractible 4-manifolds C with an
effective G-action on $\partial C$ whose associated pairs (C,g) for all $g \in
G$ are distinct smoothings of the pair $(C,\partial C)$. Indeed C embeds in a
4-manifold so that cutting out C and regluing using distinct elements of G
yield distinct smooth 4-manifolds.


title: Perturbation growth in accreting filaments

abstract:
  We use smoothed particle hydrodynamic simulations to investigate the growth
of perturbations in infinitely long, initially sub-critical but accreting
filaments. The growth of these perturbations leads to filament fragmentation
and the formation of cores. Most previous work on this subject has been
confined to the growth and fragmentation of equilibrium filaments and has found
that there exists a preferential fragmentation length scale which is roughly 4
times the filament's diameter. Our results show a more complicated dispersion
relation with a series of peaks linking perturbation wavelength and growth
rate. These are due to gravo-acoustic oscillations along the longitudinal axis
during the sub-critical phase of growth. The positions of the peaks in growth
rate have a strong dependence on both the mass accretion rate onto the filament
and the temperature of the gas. When seeded with a multi-wavelength density
power spectrum there exists a clear preferred core separation equal to the
largest peak in the dispersion relation. Our results allow one to estimate a
minimum age for a filament which is breaking up into regularly spaced
fragments, as well as a maximum accretion rate. We apply the model to
observations of filaments in Taurus by Tafalla & Hacar (2015) and find
accretion rates consistent with those estimated by Palmeirim et al. (2013).


title:
Fast alternating bi-directional preconditioner for the 2D high-frequency
  Lippmann-Schwinger equation

abstract:
  This paper presents a fast iterative solver for Lippmann-Schwinger equation
for high-frequency waves scattered by a smooth medium with a compactly
supported inhomogeneity. The solver is based on the sparsifying preconditioner
and a domain decomposition approach similar to the method of polarized traces.
The iterative solver has two levels, the outer level in which a sparsifying
preconditioner for the Lippmann-Schwinger equation is constructed, and the
inner level, in which the resulting sparsified system is solved fast using an
iterative solver preconditioned with a bi-directional matrix-free variant of
the method of polarized traces. The complexity of the construction and
application of the preconditioner is $\mathcal{O}(N)$ and
$\mathcal{O}(N\log{N})$ respectively, where $N$ is the number of degrees of
freedom. Numerical experiments in 2D indicate that the number of iterations in
both levels depends weakly on the frequency resulting in method with an overall
$\mathcal{O}(N\log{N})$ complexity.


title: Quantum walk on a spin network

abstract:
  We apply a discrete quantum walk from a quantum particle on a discrete
quantum spacetime from loop quantum gravity and show that the related
Entanglement Entropy can drive a entropic force. We apply this concepts to
propose a model of a walker position topologically encoded on a spin network.


title:
Thermal radiative and thermodynamic properties of solid and liquid
  uranium and plutonium carbides in the visible-near infrared range

abstract:
  The knowledge of thermal radiative and thermodynamic properties of uranium
and plutonium carbides under extreme conditions is essential for designing a
new metallic fuel materials for next generation of a nuclear reactor. The
present work is devoted to the study of the thermal radiative and thermodynamic
properties of liquid and solid uranium and plutonium carbides at their
melting/freezing temperatures. The Stefan-Boltzmann law, total energy density,
number density of photons, Helmholtz free energy density, internal energy
density, enthalpy density, entropy density, heat capacity at constant volume,
pressure, and normal total emissivity are calculated using experimental data
for the frequency dependence of the normal spectral emissivity of liquid and
solid uranium and plutonium carbides in the visible-near infrared range. It is
shown that the thermal radiative and thermodynamic functions of uranium carbide
have a slight difference during liquid-to-solid transition. Unlike UC, such a
difference between these functions have not been established for plutonium
carbide. The calculated values for the normal total emissivity of uranium and
plutonium carbides at their melting temperatures is in good agreement with
experimental data. The obtained results allow to calculate the thermal
radiative and thermodynamic properties of liquid and solid uranium and
plutonium carbides for any size of samples. Based on the model of Hagen-Rubens
and the Wiedemann-Franz law, a new method to determine the thermal conductivity
of metals and carbides at the melting points is proposed.


title:
Performance Analysis of uniaxially strained Monolayer Black Phosphorus
  and Blue Phosphorus n-MOSFET and p-MOSFET

abstract:
  In this work, we present a computational study on the possibility of strain
engineering in monolayer Black Phosphorus (black P) and Blue Phosphorus (blue
P) based MOSFETs. The material properties like band structure, carrier
effective masses, carrier densities at band extrema are evaluated using
Generalized Gradient Approximation (GGA) in Density Functional Theory
(DFT).Thereafter self-consistent Non-Equilibrium Greens Function (NEGF)
simulations are carried out to study the device performance metrics (such as
output characteristics, ON currents, transconductance etc.) of such strained
black P and blue P based MOSFETs. Our simulations show that carrier effective
masses in blue P are more sensitive to strain applied in both zigzag and
armchair directions. Blue P is more responsive in strain engineering for n-MOS
and p-MOS. Except for black P based FETs with strain in armchair direction,
overall the blue P (black P) n-MOSFET (p-MOSFET) show moderate to significant
improvement in performance with tensile (compressive) strain in the transport
directions.


title:
Peculiarities of Ehrenfest equation for solids strained by uniaxial or
  hydrostatic pressure

abstract:
  The Ehrenfest equation is derived rigorously for the case when an 'effective'
volume V* = AV of the strained solids is a continuous function of the
temperature. The Ehrenfest equation for strained solids is generalized to an
arbitrary temperature. Far from 0 K (in contrast to the situation near 0 K) the
phase transition temperature derivative with respect to uniaxial pressure
depends on the temperature expansion coefficient of an ' effective' volume. For
Rochelle salt strained by a uniaxial pressure at room temperature the
predominant contribution into this dependence is made by the coefficient A. At
the second order phase transition under uniaxial pressure the 'effective' (but
not true) volume is the continuous function of the temperature. The Ehrenfest
equation for solids strained by hydrostatic pressure can be presented as a sum
of three linear parts proportional to the crystal linear thermal expansion
coefficients along the axes a, b, c. These parts are equal to the second order
transition temperature derivative with respect to hydrostatic (but not
uniaxial) pressure,


title:
Substrate effect and nanoindentation fracture toughness based on pile up
  and failure

abstract:
  The effect of substrate was studied using nanoindentation on thin films. Soft
films on hard substrate showed more pile up than usual which was attributed to
the dislocation pile up at the film substrate interface. The effect of tip
blunting on the load depth and hardness plots of nanoindentation was shown. The
experimental date of variation of Vickers hardness with film thickness and
loads were fitted and new parameters were analyzed. The delaminated area was
analyzed using geometrical shapes using optical view of the failure region
along with the load displacement Indentation fracture using Nanoindentation
using Berkovich indenter has been studied. Indentation fracture toughness (KR)
was analyzed based on computational programs. The contact mechanics during
nanoindentation was studied with parameters related to indenter shape and tip
sharpness. Elastic, plastic and total energies were computationally determined.
The energy difference was related to shear stress being generated with elastic
to plastic transition. Change in the nature of residual stress was related to
film thickness.


title:
Vibration analysis of a pre-stressed graphene sheet embedded in a
  deformable matrix

abstract:
  The effect of the initial uniaxial stress and a surrounding elastic matrix on
the transverse vibration response of a single-layered graphene sheet (SLGS) is
investigated through a theoretical formulation that is based on the nonlocal
Kirchhoff plate theory. The surrounding elastic matrix of the SLGS is modeled
as a foundation of the Pasternak-type. The elliptic partial differential
equation governing the dynamics of the pre-stressed SLGS is solved with the
Rayleigh method. Numerical results from the analyses reveal different level of
sensitivity of the vibration response of the SLGS to changes in the control
parameters of the model. Pareto charts of the effect of the control parameters
in the mathematical model show the shear modulus of the foundation to have the
most dominant influence on the fundamental natural frequency of the SLGS. The
small-scale effect is found to have more pronounced effect on the vibration
response of the SLGS when it is fully clamped at the four edges.


title:
Experimental investigation of the detection mechanism in WSi nanowire
  superconducting single photon detectors

abstract:
  We use quantum detector tomography to investigate the detection mechanism in
WSi nanowire superconducting single photon detectors (SSPDs). To this purpose,
we fabricated a 250nm wide and 250nm long WSi nanowire and measured its
response to impinging photons with wavelengths ranging from $\lambda$ = 900 nm
to $\lambda$ = 1650 nm. Tomographic measurements show that the detector
response depends on the total excitation energy only. Moreover, for energies Et
> 0.8eV the current energy relation is linear, similar to what was observed in
NbN nanowires, whereas the current-energy relation deviates from linear
behaviour for total energies below 0.8eV.


title:
Variational aspects of homogeneous geodesics on generalized flag
  manifolds and applications

abstract:
  We study conjugate points along homogeneous geodesics in generalized flag
manifolds. This is done by analyzing the second variation of the energy of such
geodesics. We also give an example of how the homogeneous Ricci flow can evolve
in such way to produce conjugate points in the complex projective space
$\mathbb{C} P^{2n+1} = Sp(n+1)/({U}(1)\times{Sp}(n))$.


title: Impact of peer interaction on conceptual test performance

abstract:
  We analyze the effectiveness of working in pairs on the Conceptual Survey of
Electricity and Magnetism test in a calculus-based introductory physics course.
Students who collaborated with a peer showed significantly larger normalized
gain on individual testing than those who did not collaborate. We did not find
statistically significant differences between the performance of students who
were given an opportunity to formulate their own response before the peer
discussions, compared to those who were not. Peer collaboration also shows
evidence for co-construction of knowledge. Discussions with individual students
show that students themselves value peer interaction. We discuss the effect of
pairing students with different individual achievements.


title:
Features of formation of a distributive infrastructure of e-commerce in
  Russia

abstract:
  Article about objective laws of formation of a distributive infrastructure of
e-commerce. The distributive infrastructure of e-commerce, according to the
author, plays an important role in formation of network economy. The author
opens strategic value of institutional regulation of distributive logistics for
the decision problems of modernization of Russian economy.


title:
The role of volume in order book dynamics: a multivariate Hawkes process
  analysis

abstract:
  We show that multivariate Hawkes processes coupled with the nonparametric
estimation procedure first proposed in Bacry and Muzy (2015) can be
successfully used to study complex interactions between the time of arrival of
orders and their size, observed in a limit order book market. We apply this
methodology to high-frequency order book data of futures traded at EUREX.
Specifically, we demonstrate how this approach is amenable not only to analyze
interplay between different order types (market orders, limit orders,
cancellations) but also to include other relevant quantities, such as the order
size, into the analysis, showing also that simple models assuming the
independence between volume and time are not suitable to describe the data.


title: Measuring A Truncated Disk in Aquila X-1

abstract:
  We present NuSTAR and Swift observations of the neutron star Aquila X-1
during the peak of its July 2014 outburst. The spectrum is soft with strong
evidence for a broad Fe K\alpha line. Modeled with a relativistically broadened
reflection model, we find that the inner disk is truncated with an inner radius
of 15+/-3 R_G. The disk is likely truncated by either the boundary layer and/or
a magnetic field. Associating the truncated inner disk with pressure from a
magnetic field gives an upper limit of B<5+/-2x10^8G. Although the radius is
truncated far from the stellar surface, material is still reaching the neutron
star surface as evidenced by the X-ray burst present in the t NuSTAR
observation.


title: Hot and dense matter beyond relativistic mean field theory

abstract:
  Properties of hot and dense matter are calculated in the framework of quantum
hadro-dynamics by including contributions from two-loop (TL) diagrams arising
from the exchange of iso-scalar and iso-vector mesons between nucleons. Our
extension of mean-field theory (MFT) employs the same five density-independent
coupling strengths which are calibrated using the empirical properties at the
equilibrium density of iso-spin symmetric matter. Results of calculations from
the MFT and TL approximations are compared for conditions of density,
temperature, and proton fraction encountered in astrophysics applications
involving compact objects. The TL results for the equation of state (EOS) of
cold pure neutron matter at sub- and near-nuclear densities agree well with
those of modern quantum Monte Carlo and effective field-theoretical approaches.
Although the high-density EOS in the TL approximation for neutron-star matter
is substantially softer than its MFT counterpart, it is able to support a
$2M_\odot$ neutron star required by recent precise determinations. In addition,
radii of $1.4M_\odot$ stars are smaller by $\sim 1$ km than obtained in MFT. In
contrast to MFT, the TL results also give a better account of the
single-particle or optical potentials extracted from analyses of medium-energy
proton-nucleus and heavy-ion experiments. In degenerate conditions, the thermal
variables are well reproduced by results of Landau's Fermi-Liquid theory in
which density-dependent effective masses feature prominently. The ratio of the
thermal components of pressure and energy density expressed as
$\Gamma_{th}=1+(P_{th}/\epsilon_{th})$, often used in astrophysical
simulations, exhibits a stronger dependence on density than on proton fraction
and temperature in both MFT and TL calculations. The prominent peak of
$\Gamma_{th}$ at supra-nuclear density found in MFT is, however, suppressed in
TL calculations.


title: Swap-invariant and exchangeable random measures

abstract:
  In this work we analyze the concept of swap-invariance, which is a weaker
variant of exchangeability. A random vector $\xi$ in $\mathbb{R}^n$ is called
swap-invariant if $\,{\mathbf E}\,\big| \!\sum_j u_j \xi_j \big|\,$ is
invariant under all permutations of $(\xi_1, \ldots, \xi_n)$ for each $u \in
\mathbb{R}^n$. We extend this notion to random measures. For a swap-invariant
random measure $\xi$ on a measure space $(S,\mathcal{S},\mu)$ the vector
$(\xi(A_1), \ldots, \xi(A_n))$ is swap-invariant for all disjoint $A_j \in
\mathcal{S}$ with equal $\mu$-measure. Various characterizations of
swap-invariant random measures and connections to exchangeable ones are
established. We prove the ergodic theorem for swap-invariant random measures
and derive a representation in terms of the ergodic limit and an exchangeable
random measure. Moreover we show that diffuse swap-invariant random measures on
a Borel space are trivial. As for random sequences two new representations are
obtained using different ergodic limits.


title: Game-Theoretic Semantics for Alternating-Time Temporal Logic

abstract:
  We introduce versions of game-theoretic semantics (GTS) for Alternating-Time
Temporal Logic (ATL). In GTS, truth is defined in terms of existence of a
winning strategy in a semantic evaluation game, and thus the game-theoretic
perspective appears in the framework of ATL on two semantic levels: on the
object level in the standard semantics of the strategic operators, and on the
meta-level where game-theoretic logical semantics is applied to ATL. We unify
these two perspectives into semantic evaluation games specially designed for
ATL. The game-theoretic perspective enables us to identify new variants of the
semantics of ATL based on limiting the time resources available to the verifier
and falsifier in the semantic evaluation game. We introduce and analyse an
unbounded and (ordinal) bounded GTS and prove these to be equivalent to the
standard (Tarski-style) compositional semantics. We show that in these both
versions of GTS, truth of ATL formulae can always be determined in finite time,
i.e., without constructing infinite paths. We also introduce a non-equivalent
finitely bounded semantics and argue that it is natural from both logical and
game-theoretic perspectives.


title: Analysis of the mean squared derivative cost function

abstract:
  In this paper, we investigate the mean squared derivative cost functions that
arise in various applications such as in motor control, biometrics and optimal
transport theory. We provide qualitative properties, explicit analytical
formulas and computational algorithms for the cost functions. We also perform
numerical simulations to illustrate the analytical results. In addition, as a
by-product of our analysis, we obtain an explicit formula for the inverse of a
Wronskian matrix that is of independent interest in linear algebra and
differential equations theory.


title: The mesoscopic magnetron as an open quantum system

abstract:
  Motivated by the emergence of materials with mean free paths on the order of
microns, we propose a novel class of solid state radiation sources based on
reimplementing classical vacuum tube designs in semiconductors. Using materials
with small effective masses, these devices should be able to access the
terahertz range. We analyze the DC and AC operation of the simplest such
device, the cylindrical diode magnetron, using effective quantum models. By
treating the magnetron as an open quantum system, we show that it continues to
operate as a radiation source even if its diameter is only a few tens of
magnetic lengths.


title:
Challenges to Self-Acceleration in Modified Gravity from Gravitational
  Waves and Large-Scale Structure

abstract:
  With the advent of gravitational-wave astronomy marked by the aLIGO GW150914
and GW151226 observations, a measurement of the cosmological speed of gravity
will likely soon be realized. We show that a confirmation of equality to the
speed of light as indicated by indirect Galactic observations will have
important consequences for a very large class of alternative explanations of
the late-time accelerated expansion of our Universe. It will break the dark
degeneracy of self-accelerated Horndeski scalar-tensor theories in the
large-scale structure that currently limits a rigorous discrimination between
acceleration from modified gravity and from a cosmological constant or dark
energy. Signatures of a self-acceleration must then manifest in the linear,
unscreened cosmological structure. We describe the minimal modification
required for self-acceleration with standard gravitational-wave speed and show
that its maximum likelihood yields a 3-sigma poorer fit to cosmological
observations compared to a cosmological constant. Hence, equality between the
speeds challenges the concept of cosmic acceleration from a genuine
scalar-tensor modification of gravity.


title:
New physics in the kinematic distributions of $\bar B\to
  D^{(*)}\tau^-(\to\ell^-\bar\nu_\ell\nu_\tau)\bar\nu_\tau$

abstract:
  We investigate the experimentally-accessible kinematic distributions of the
$\bar B\to D^{(*)}\tau^-(\to\ell^-\bar\nu_\ell\nu_\tau)\bar\nu_\tau$ decays.
Specifically, we study the decay rates as functions of the $B\to D^{(*)}$
transferred squared momentum, the energy of the final charged lepton and the
angle of its 3-momentum relative to the 3-momentum of the recoiling $D^{(*)}$.
The angular distribution allows to introduce new observables, like a
forward-backward asymmetry, which are complementary to the total rates. We
present analytic formulas for the observable 3-fold 5-body differential decay
rates, study the predictions in the Standard Model and investigate the effects
in different new-physics scenarios that we characterize using an effective
field theory framework.


title:
A computational study of high-speed microdroplet impact onto a smooth
  solid surface

abstract:
  Numerical solutions of high-speed microdroplet impact onto a smooth solid
surface are computed, using the interFoam VoF solver of the OpenFOAM CFD
package. Toward the solid surface, the liquid microdroplet is moving with an
impinging gas flow, simulating the situation of ink droplets being deposited
onto substrate with a collimated mist jet in the Optomec Aerosol Jet printing
process. The computed values of maximum spread factor, for the range of
parameters of practical interest to Aerosol Jet printing, were found in very
good agreement with some of the correlation formulas proposed by previous
authors in the literature. Combining formulas selected from different authors
with appropriate modifications yields a maximum spread factor formula that can
be used for first-order evaluations of deposited in droplet size during the
Aerosol Jet technology development. The computational results also illustrate
droplet impact dynamics with lamella shape evolution throughout the spreading,
receding-relaxation, and wetting equilibrium phases, consistent with that
observed and described by many previous authors. This suggests a
scale-invariant nature of the basic droplet impact behavior such that
experiments with larger droplets at the same nondimensional parameter values
may be considered for studying microdroplet impact dynamics. Significant free
surface oscillations can be observed when the droplet viscosity is relatively
low. The border line between periodic free surface oscillations and aperiodic
creeping to capillary equilibrium free surface shape appears at the value of
Ohnesorge number around 0.25. Droplet bouncing after receding is prompted with
large contact angles at solid surface (as consistent with findings reported in
the literature), but can be suppressed by increasing the droplet viscosity.


title: Why Firewalls Need Not Exist

abstract:
  The firewall paradox for black holes is often viewed as indicating a conflict
between unitarity and the equivalence principle. We elucidate how the paradox
manifests as a limitation of semiclassical theory, rather than presents a
conflict between fundamental principles. Two principal features of the
fundamental and semiclassical theories address two versions of the paradox: the
entanglement and typicality arguments. First, the physical Hilbert space
describing excitations on a fixed black hole background in the semiclassical
theory is exponentially smaller than the number of physical states in the
fundamental theory of quantum gravity. Second, in addition to the Hilbert space
for physical excitations, the semiclassical theory possesses an unphysically
large Fock space built by creation and annihilation operators on the fixed
black hole background. Understanding these features not only eliminates the
necessity of firewalls but also leads to a new picture of Hawking emission
contrasting pair creation at the horizon.


title: Quantum Supremacy through the Quantum Approximate Optimization Algorithm

abstract:
  The Quantum Approximate Optimization Algorithm (QAOA) is designed to run on a
gate model quantum computer and has shallow depth. It takes as input a
combinatorial optimization problem and outputs a string that satisfies a high
fraction of the maximum number of clauses that can be satisfied. For certain
problems the lowest depth version of the QAOA has provable performance
guarantees although there exist classical algorithms that have better
guarantees. Here we argue that beyond its possible computational value the QAOA
can exhibit a form of Quantum Supremacy in that, based on reasonable complexity
theoretic assumptions, the output distribution of even the lowest depth version
cannot be efficiently simulated on any classical device. We contrast this with
the case of sampling from the output of a quantum computer running the Quantum
Adiabatic Algorithm (QADI) with the restriction that the Hamiltonian that
governs the evolution is gapped and stoquastic. Here we show that there is an
oracle that would allow sampling from the QADI but even with this oracle, if
one could efficiently classically sample from the output of the QAOA, the
Polynomial Hierarchy would collapse. This suggests that the QAOA is an
excellent candidate to run on near term quantum computers not only because it
may be of use for optimization but also because of its potential as a route to
establishing quantum supremacy.


title: On the additive chromatic number of several families of graphs

abstract:
  The Additive Coloring Problem is a variation of the Coloring Problem where
labels of $\{1,\ldots,k\}$ are assigned to the vertices of a graph $G$ so that
the sum of labels over the neighborhood of each vertex is a proper coloring of
$G$. The least value $k$ for which $G$ admits such labeling is called
\emph{additive chromatic number} of $G$. This problem was first presented by
Czerwi\'nski, Grytczuk and \.Zelazny who also proposed a conjecture that for
every graph $G$, the additive chromatic number never exceeds the classic
chromatic number. Up to date, the conjecture has been proved for complete
graphs, trees, non-3-colorable planar graphs with girth at least 13 and
non-bipartite planar graphs with girth at least 26. In this work, we show that
the conjecture holds for split graphs. We also present exact formulas for
computing the additive chromatic number for some subfamilies of split graphs
(complete split, headless spiders and complete sun), regular bipartite,
complete multipartite, fan, windmill, circuit, wheel, cycle sun and wheel sun.


title:
A Lorentz Violating Theory: Its Nonminimal Extension in the Photon
  Sector

abstract:
  The relentless efforts of the physics community has not yet availed us the
solution of how to unify the Quantum Mechanics with General Relativity, a
puzzle that has engaged the minds of the physicists for almost a century. The
insufficiency of today's and foreseeable future's technology for a direct reach
into the Planck energies at which the fundamental theory, the Quantum Theory of
Gravity, lies has lead to the search of the low energy effects of that
fundamental Planck level theory irregardless of the details of it. In this
thesis, one of the leading candidates of such an exotic effect, that is the
violation of Lorentz and CPT symmetries is analyzed. The action level effective
field theoretical framework for such an analysis called Standard Model
Extension has already been in the literature for the last two decades; here,
the nonminimal photon sector of such a framework is examined from a quantum
field theoretical point of view. All possible polarization vectors for
different kinds of CPT violations, the generic forms of the dispersion
relations that these polarization vectors satisfy, and the corresponding
propagators of the photon field are explicitly calculated. Special models of
Lorentz violations are introduced, and a particular one called vacuum
orthogonal model is analyzed extensively. It is found that this particular form
of Lorentz violation cannot induce any effects that is detectable in the vacuum
propagation of the photon. Isotropic and leading order cases of the Lorentz
violation is studied and this found result is explicitly shown.


title:
Categorization of problems to assess and improve proficiency as teachers
  and learners

abstract:
  We describe how graduate students categorize introductory mechanics problems
based on the similarity of their solutions. Graduate students were asked at the
end of a teaching assistant training class to categorize problems from their
own perspective and from the perspective of typical introductory physics
students whom they were teaching. We compare their categorizations with the
categorizations by introductory physics students and physics faculty who
categorized the same problems. The utility of categorization as a tool for
teaching assistant training and faculty development workshops is discussed.


title:
Assessing Student Expertise in Introductory Physics with Isomorphic
  Problems, Part II: Effect of Some Potential Factors on Problem Solving and
  Transfer

abstract:
  In this companion paper, we explore the use of isomorphic problem pairs
(IPPs) to assess introductory physics students' ability to solve and
successfully transfer problem-solving knowledge from one context to another in
mechanics. We call the paired problems "isomorphic" because they require the
same physics principle to solve them. We analyze written responses and
individual discussions to a range of isomorphic problems. We examine potential
factors that may help or hinder transfer of problem-solving skills from one
problem in a pair to the other. For some paired isomorphic problems, one
context often turned out to be easier for students in that it was more often
correctly solved than the other. When quantitative and conceptual questions
were paired and given back to back, students who answered both questions in the
IPP often performed better on the conceptual questions than those who answered
the corresponding conceptual questions only. Although students often took
advantage of the quantitative counterpart to answer a conceptual question of an
IPP correctly, when only given the conceptual question, students seldom tried
to convert it into a quantitative question, solve it and then reason about the
solution conceptually. Misconceptions associated with friction in some problems
were so robust that pairing them with isomorphic problems not involving
friction did not help students discern their underlying similarities.
Alternatively, from the knowledge in pieces perspective, the activation of the
knowledge resource related to friction was so strongly and automatically
triggered by the context, which is outside the conscious control of the
student, that students did not look for analogies with paired problems or other
aids that may be present.


title:
A statistical shape space model of the palate surface trained on 3D MRI
  scans of the vocal tract

abstract:
  We describe a minimally-supervised method for computing a statistical shape
space model of the palate surface. The model is created from a corpus of
volumetric magnetic resonance imaging (MRI) scans collected from 12 speakers.
We extract a 3D mesh of the palate from each speaker, then train the model
using principal component analysis (PCA). The palate model is then tested using
3D MRI from another corpus and evaluated using a high-resolution optical scan.
We find that the error is low even when only a handful of measured coordinates
are available. In both cases, our approach yields promising results. It can be
applied to extract the palate shape from MRI data, and could be useful to other
analysis modalities, such as electromagnetic articulography (EMA) and
ultrasound tongue imaging (UTI).


title:
Using Categorization of Problems as an Instructional Tool to Help
  Introductory Students Learn Physics

abstract:
  The ability to categorize problems based upon underlying principles, rather
than contexts, is considered a hallmark of expertise in physics problem
solving. With inspiration from a classic study by Chi, Feltovich, and Glaser,
we compared the categorization of 25 introductory mechanics problems based upon
similarity of solution by students in large calculus-based introductory courses
with physics faculty and Ph.D. students. Here, we summarize the study and
suggest that a categorization task, especially when conducted with students
working with peers in small groups, can be an effective pedagogical tool to
help students in introductory physics courses learn to discern the underlying
similarity between problems with diverse contexts but the same underlying
physics principles.


title: Tetrahedral Units: For Dodecahedral Super-Structures

abstract:
  Different novel organic-chemical possibilities for tetrahedral building units
are considered, with attention to their utility in constructing different
super-structures. As a representative construction we consider the use of sets
of 20 such identical tetrahedral units to form a super-dodecahedron.


title:
On a fractional class of analytic function defined by using a new
  operator

abstract:
  In this article, we impose a new class of fractional analytic functions in
the open unit disk. By considering this class, we define a fractional operator,
which is generalized Salagean and Ruscheweyh differential operators. Moreover,
by means of this operator, we introduce an interesting subclass of functions
which are analytic and univalent. Furthermore, this effort covers coefficient
bounds, distortions theorem, radii of starlikeness, convexity, bounded turning,
extreme points and integral means inequalities of functions belongs to this
class. Finally, applications involving certain fractional operators are
illustrated.


title:
Effects of low anisotropy on interacting holographic and new agegraphic
  scalar fields models of dark energy

abstract:
  A spatially homogeneous and anisotropic Bianchi type I universe is studied
with the interacting holographic and new agegraphic scalar fields models of
dark energy.
  Given, the framework of the anisotropic model, both the dynamics and
potential of these scalar field models according to the evolutionary behavior
of both dark energy models are reconstructed. We also investigate the
cosmological evolution of interacting dark energy models, and compare it with
observational data and schematic diagram.
  In order to do so, we focus on observational determinations of the expansion
history $H(z)$. Next, we evaluate effects of anisotropy on various topics, such
as evolution of the growth of perturbations in the linear regime, statefinder
diagnostic, Sandage-Loeb (SL) test and distance modulus from holographic and
new agegraphic dark energy models and compare the results with standard FRW and
$\Lambda$CDM and $w$CDM models.
  Our numerical result show the effects of the interaction and anisotropy on
the evolutionary behavior the new agegraphic scalar field models


title:
Thermal condensate structure and cosmological energy density of the
  Universe

abstract:
  The aim of this paper is the study of thermal vacuum condensate for scalar
and fermion fields. We analyze the thermal states at the temperature of the
cosmic microwave background (CMB) and we show that the vacuum expectation value
of the energy momentum tensor density of photon fields reproduces the energy
density and pressure of the CMB. We perform the computations in the formal
framework of the thermo field dynamics. We also consider the case of neutrinos
and thermal states at the temperature of the neutrino cosmic background.
Consistency with the estimated lower bound of the sum of the active neutrino
masses is verified. In the boson sector, non trivial contribution to the energy
of the universe is given by particles of masses of the order of $10^{-4}eV$
compatible with the ones of the axion-like particles. The fractal self-similar
structure of the thermal radiation is also discussed and related to the
coherent structure of the thermal vacuum.


title: The third exactly solvable hypergeometric quantum-mechanical potential

abstract:
  We introduce the third independent exactly solvable hypergeometric potential,
after the Eckart and the P\"oschl-Teller potentials, which is proportional to
an energy-independent parameter and has a shape that is independent of this
parameter. The general solution of the Schr\"odinger equation for this
potential is written through fundamental solutions each of which presents an
irreducible combination of two Gauss hypergeometric functions. The potential is
an asymmetric step-barrier with variable height and steepness. Discussing the
transmission above such a barrier, we derive a compact formula for the
reflection coefficient.


title: Effect of Misconception on Transfer in Problem Solving

abstract:
  We examine the effect of misconceptions about friction on students' ability
to solve problems and transfer from one context to another. We analyze written
responses to paired isomorphic problems given to introductory physics students
and discussions with a subset of students. Misconceptions associated with
friction in problems were sometimes so robust that pairing them with isomorphic
problems not involving friction did not help students fully discern their
underlying similarities.


title:
Kinematics of symmetric Galactic longitudes to probe the spiral arms of
  the Milky Way with Gaia

abstract:
  We model the effects of the spiral arms of the Milky Way on the disk stellar
kinematics in the Gaia observable space. We also estimate the Gaia capabilities
of detecting the predicted signatures. We use both controlled orbital
integrations in analytic potentials and self-consistent simulations. We
introduce a new strategy, which consists of comparing the stellar kinematics of
symmetric Galactic longitudes (+l and -l), in particular the median transverse
velocity (from parallaxes and proper motions). This approach does not require
the assumption of an axisymmetric model. The typical differences between the
transverse velocity in symmetric longitudes in the models are of ~2 km/s, but
can be larger than 10 km/s for certain longitudes and distances. The kinematic
differences for +l and -l show trends that depend on the properties of spiral
arms. Thus, this method can be used to quantify the importance of the effects
of spiral arms on the orbits of stars in the different disk regions, and to
constrain the location of the arms, main resonances and, thus, pattern speed.
Moreover, the method allows us to test the dynamical nature of the spiral
structure (e.g. grand design versus transient multiple arms). We estimate the
number of stars of each spectral type that Gaia will observe in representative
Galactic longitudes, their errors in distance and transverse velocity, and the
error in computing the median velocity as a function of distance. We will be
able to measure the median transverse velocity with Gaia data, with precision
smaller than ~1 km/s up to distances of ~4-6 kpc for certain giant stars, and
up to ~2-4 kpc and better kinematic precision (<= 0.5 km\s) for certain
sub-giants and dwarfs. These are enough to measure the typical signatures seen
in the models. We also show that a similar strategy can be used with
line-of-sight velocities from other upcoming spectroscopic surveys.(Abridged)