title:
Probing Oort Cloud and Local Interstellar Medium Properties via Dust
  Produced in Cometary Collisions

abstract:
  The Oort Cloud remains one of the most poorly explored regions of the Solar
System. We propose that its properties can be constrained by studying a
population of dust grains produced in collisions of comets in the outer Solar
System. We explore the dynamics of micron-size grains outside the heliosphere
(beyond ~250 AU), which are affected predominantly by the magnetic field of the
interstellar medium (ISM) flow past the Sun. We derive analytic models for the
production and motion of small particles as a function of their birth location
in the Cloud and calculate the particle flux and velocity distribution in the
inner Solar System. These models are verified by direct numerical simulations.
We show that grains originating in the Oort Cloud have a unique distribution of
arrival directions, which should easily distinguish them from both
interplanetary and interstellar dust populations. We also demonstrate that the
distribution of particle arrival velocities is uniquely determined the mass
distribution and dust production rate in the Cloud. Cometary collisions within
the Cloud produce a flux of micron-size grains in the inner Solar System of up
to several per square meter per year. The next-generation dust detectors may be
sensitive enough to detect and constrain this dust population, which will
illuminate us about the Oort Cloud's properties. We also show that the
recently-detected mysterious population of large (micron-size) unbound
particles, which seems to arrive with the ISM flow is unlikely to be generated
by collisions of comets in the Oort Cloud.


title: The $(k,\ell)$-rainbow index of random graphs

abstract:
  A tree in an edge colored graph is said to be a rainbow tree if no two edges
on the tree share the same color. Given two positive integers $k$, $\ell$ with
$k\geq 3$, the \emph{$(k,\ell)$-rainbow index} $rx_{k,\ell}(G)$ of $G$ is the
minimum number of colors needed in an edge-coloring of $G$ such that for any
set $S$ of $k$ vertices of $G$, there exist $\ell$ internally disjoint rainbow
trees connecting $S$. This concept was introduced by Chartrand et. al., and
there have been very few related results about it. In this paper, We establish
a sharp threshold function for $rx_{k,\ell}(G_{n,p})\leq k$ and
$rx_{k,\ell}(G_{n,M})\leq k,$ respectively, where $G_{n,p}$ and $G_{n,M}$ are
the usually defined random graphs.


title: Limit Synchronization in Markov Decision Processes

abstract:
  Markov decision processes (MDP) are finite-state systems with both strategic
and probabilistic choices. After fixing a strategy, an MDP produces a sequence
of probability distributions over states. The sequence is eventually
synchronizing if the probability mass accumulates in a single state, possibly
in the limit. Precisely, for 0 <= p <= 1 the sequence is p-synchronizing if a
probability distribution in the sequence assigns probability at least p to some
state, and we distinguish three synchronization modes: (i) sure winning if
there exists a strategy that produces a 1-synchronizing sequence; (ii)
almost-sure winning if there exists a strategy that produces a sequence that
is, for all epsilon > 0, a (1-epsilon)-synchronizing sequence; (iii) limit-sure
winning if for all epsilon > 0, there exists a strategy that produces a
(1-epsilon)-synchronizing sequence.
  We consider the problem of deciding whether an MDP is sure, almost-sure,
limit-sure winning, and we establish the decidability and optimal complexity
for all modes, as well as the memory requirements for winning strategies. Our
main contributions are as follows: (a) for each winning modes we present
characterizations that give a PSPACE complexity for the decision problems, and
we establish matching PSPACE lower bounds; (b) we show that for sure winning
strategies, exponential memory is sufficient and may be necessary, and that in
general infinite memory is necessary for almost-sure winning, and unbounded
memory is necessary for limit-sure winning; (c) along with our results, we
establish new complexity results for alternating finite automata over a
one-letter alphabet.


title:
Thickness Effects in the Resonance of Metasurfaces made of SRRs ans
  C-SRRs

abstract:
  Different periodical Frequency Selective Surfaces(FSS) whose unit cell are
the Split Ring Resonators (SRR) or related geometries and their corresponding
complementary screens were studied. This kind of FSS, sometimes called
metasurfaces, have the advantage of avoiding secondary grating lobes because of
the small electrical size of the unit cell. The main aim of this paper is to
investigate the effects of the metal thickness for these FSSs. It was found
that the quality factor decrease for unconnected elements (strips) and increase
for connected elements (slots). Besides, as the thickness increases, the
resonance frequency decrease for the case of unconnected elements while
increases for connected elements.


title: Exploring the total Galactic extinction with SDSS BHB stars

abstract:
  Aims: We used 12,530 photometrically-selected blue horizontal branch (BHB)
stars from the Sloan Digital Sky Survey (SDSS) to estimate the total extinction
of the Milky Way at the high Galactic latitudes, $R_V$ and $A_V$ in each line
of sight. Methods: A Bayesian method was developed to estimate the reddening
values in the given lines of sight. Based on the most likely values of
reddening in multiple colors, we were able to derive the values of $R_V$ and
$A_V$.
  Results: We selected 94 zero-reddened BHB stars from seven globular clusters
as the template. The reddening in the four SDSS colors for the northern
Galactic cap were estimated by comparing the field BHB stars with the template
stars. The accuracy of this estimation is around 0.01\,mag for most lines of
sight. We also obtained $<R_V>$ to be around 2.40$\pm1.05$ and $A_V$ map within
an uncertainty of 0.1\,mag. The results, including reddening values in the four
SDSS colors, $A_V$, and $R_V$ in each line of sight, are released on line. In
this work, we employ an up-to-date parallel technique on GPU card to overcome
time-consuming computations. We plan to release online the C++ CUDA code used
for this analysis.
  Conclusions: The extinction map derived from BHB stars is highly consistent
with that from Schlegel, Finkbeiner & Davis(1998). The derived $R_V$ is around
2.40$\pm1.05$. The contamination probably makes the $R_V$ be larger.


title:
Ancient Light from Young Cosmic Cities: Physical and Observational
  Signatures of Galaxy Proto-Clusters

abstract:
  For a complete picture of galaxy cluster formation, it is important that we
start probing the early epoch of z~2-7 during which clusters and their galaxies
first began to form. Because the study of these so-called "proto-clusters" is
currently limited by small number statistics, widely varying selection
techniques and assumptions, we have performed a systematic study of cluster
formation utilizing cosmological simulations. We use the Millennium Simulations
to track the evolution of dark matter and galaxies in ~3,000 clusters from the
earliest times to z=0. We define an effective radius R_e for proto-clusters and
characterize their growth in size and mass. We show that the progenitor regions
of galaxy clusters (M>10^14 M_sun/h) can already be identified at least up to
z~5, provided that the galaxy overdensities, delta_gal, are measured on a
sufficiently large scale (R_e~5-10 cMpc). We present the overdensities in
matter, DM halos, and galaxies as functions of present-day cluster mass,
redshift, bias, and window size that can be used to interpret the structures
found in real surveys. We derive the probability that a structure having a
delta_gal, defined by a set of observational selection criteria, is indeed a
proto-cluster, and show how their z=0 masses can already be estimated long
before virialization. Galaxy overdensity profiles as a function of radius are
presented. We further show how their projected surface overdensities decrease
as the uncertainties in redshift measurements increase. We provide a table of
proto-cluster candidates selected from the literature, and discuss their
properties in the light of our simulations predictions. This work provides the
general framework that will allow us to extend the study of cluster formation
out to much higher redshifts using the large number of proto-clusters that are
expected to be discovered in, e.g., the upcoming HETDEX and HSC surveys.


title:
A Line Source in Minkowski for the de Sitter Spacetime Scalar Green's
  Function: Massive Case

abstract:
  For certain classes of space(time)s embeddable in a higher dimensional flat
space(time), it appears possible to compute the minimally coupled massless
scalar Green's function in the former by convolving its cousin in the latter
with an appropriate scalar charge density. The physical interpretation is that
beings residing in the higher dimensional flat space(time) may set up sources
to fool the observer confined on the lower dimensional curved submanifold that
she is detecting the field generated by a space(time) point source in her own
world. In this paper we extend the general formula to include a non-zero mass.
We then employ it to derive the Green's function of the massive wave operator
in (d >= 2)-dimensional de Sitter spacetime and that of the Helmholtz
differential operator -- the Laplacian plus a "mass term" -- on the (d >=
2)-sphere. For both cases, the trajectories of the scalar sources are the same
as that of the massless case, while the required scalar charge densities are
determined by solving an eigenvalue equation. To source these massive Green's
functions, we show that the (d+1)-dimensional Minkowski/Euclidean
experimentalists may choose to use either massive or massless scalar line
charges. In de Sitter spacetime, the embedding method employed here leads
directly to a manifest separation between the null cone versus tail terms of
the Green's functions.


title: Instability of Evaporation Fronts in the Interstellar Medium

abstract:
  The neutral component of the interstellar medium is segregated into the cold
neutral medium (CNM) and warm neutral medium (WNM) as a result of thermal
instability. It was found that a plane-parallel CNM-WNM evaporation interface,
across which the CNM undergoes thermal expansion, is linearly unstable to
corrugational disturbances, in complete analogy with the Darrieus-Landau
instability (DLI) of terrestrial flames. We perform a full linear stability
analysis as well as nonlinear hydrodynamic simulations of the DLI of such
evaporation fronts in the presence of thermal conduction. We find that the DLI
is suppressed at short length scales by conduction. The length and time scales
of the fastest growing mode are inversely proportional to the evaporation flow
speed of the CNM and its square, respectively. In the nonlinear stage, the DLI
saturates to a steady state where the front deforms to a finger-like shape
protruding toward the WNM, without generating turbulence. The evaporation rate
at nonlinear saturation is larger than the initial plane-parallel value by a
factor of 2.4 when the equilibrium thermal pressure is 1800 k_B cm^-3 K. The
degrees of front deformation and evaporation-rate enhancement at nonlinear
saturation are determined primarily by the density ratio between the CNM and
WNM. We demonstrate that the Field length in the thermally unstable medium
should be resolved by at least four grid points to obtain reliable numerical
outcomes involving thermal instability.


title: Galaxy Zoo: Observing Secular Evolution Through Bars

abstract:
  In this paper, we use the Galaxy Zoo 2 dataset to study the behavior of bars
in disk galaxies as a function of specific star formation rate (SSFR), and
bulge prominence. Our sample consists of 13,295 disk galaxies, with an overall
(strong) bar fraction of $23.6\pm 0.4\%$, of which 1,154 barred galaxies also
have bar length measurements. These samples are the largest ever used to study
the role of bars in galaxy evolution. We find that the likelihood of a galaxy
hosting a bar is anti-correlated with SSFR, regardless of stellar mass or bulge
prominence. We find that the trends of bar likelihood and bar length with bulge
prominence are bimodal with SSFR. We interpret these observations using
state-of-the-art simulations of bar evolution which include live halos and the
effects of gas and star formation. We suggest our observed trends of bar
likelihood with SSFR are driven by the gas fraction of the disks; a factor
demonstrated to significantly retard both bar formation and evolution in
models. We interpret the bimodal relationship between bulge prominence and bar
properties as due to the complicated effects of classical bulges and central
mass concentrations on bar evolution, and also to the growth of disky
pseudobulges by bar evolution. These results represent empirical evidence for
secular evolution driven by bars in disk galaxies. This work suggests that bars
are not stagnant structures within disk galaxies, but are a critical
evolutionary driver of their host galaxies in the local universe ($z<1$).


title: Dynamical Origin for the 125 GeV Higgs; a Hybrid setup

abstract:
  We describe a hybrid framework for electroweak symmetry breaking (EWSB), in
which the Higgs mechanism is combined with a Nambu-Jona-Lasinio mechanism. The
model introduces an unconstrained scalar (i.e., acts as "fundamental" but not
the SM field) and a strongly coupled doublet of heavy quarks with a mass around
500 GeV, which forms a condensate at a compositeness scale \Lambda ~ O(1) TeV.
This setup is matched at that scale to a tightly constrained hybrid two Higgs
doublet model, where both the composite and unconstrained scalars participate
in EWSB. This allows us to get a good candidate for the recently observed 125
GeV scalar which has properties very similar to the Standard Model Higgs. The
heavier (mostly composite) CP-even scalar has a mass around 500 GeV, while the
pseudoscalar and the charged Higgs particles have masses in the range 200 -300
GeV.


title:
Simulations of Ion Acceleration at Non-relativistic Shocks. I.
  Acceleration Efficiency

abstract:
  We use 2D and 3D hybrid (kinetic ions - fluid electrons) simulations to
investigate particle acceleration and magnetic field amplification at
non-relativistic astrophysical shocks. We show that diffusive shock
acceleration operates for quasi-parallel configurations (i.e., when the
background magnetic field is almost aligned with the shock normal) and, for
large sonic and Alfv\'enic Mach numbers, produces universal power-law spectra
proportional to p^(-4), where p is the particle momentum. The maximum energy of
accelerated ions increases with time, and it is only limited by finite box size
and run time. Acceleration is mainly efficient for parallel and quasi-parallel
strong shocks, where 10-20% of the bulk kinetic energy can be converted to
energetic particles, and becomes ineffective for quasi-perpendicular shocks.
Also, the generation of magnetic turbulence correlates with efficient ion
acceleration, and vanishes for quasi-perpendicular configurations. At very
oblique shocks, ions can be accelerated via shock drift acceleration, but they
only gain a factor of a few in momentum, and their maximum energy does not
increase with time. These findings are consistent with the degree of
polarization and the morphology of the radio and X-ray synchrotron emission
observed, for instance, in the remnant of SN 1006. We also discuss the
transition from thermal to non-thermal particles in the ion spectrum
(supra-thermal region), and we identify two dynamical signatures peculiar of
efficient particle acceleration, namely the formation of an upstream precursor
and the alteration of standard shock jump conditions.


title: Recent QCD Results From ATLAS

abstract:
  A survey of recent QCD results using the ATLAS detector at the LHC is
presented.


title: The ATLAS Tile Calorimeter Calibration and Performance

abstract:
  A brief summary of the hadronic calorimeter calibration systems and
performance results, in the ATLAS detector at the LHC is given.


title: Results on QCD jet production at ATLAS and CMS

abstract:
  The production of jets at the Large Hadron Collider (LHC) at TeV
centre-of-mass energy is summarized, including results from both the ATLAS and
CMS detectors. Current jet performance is described, followed by inclusive jet
and multi-jet measurements in various final state configurations. Finally some
results on heavy flavour and jet substructure are presented.


title:
Herschel SPIRE and PACS observations of the red supergiant VY CMa:
  analysis of the molecular line spectra

abstract:
  We present an analysis of the far-infrared and submillimetre molecular
emission line spectrum of the luminous M-supergiant VY CMa, observed with the
SPIRE and PACS spectrometers aboard the Herschel Space Observatory. Over 260
emission lines were detected in the 190-650-micron SPIRE FTS spectra, with
one-third of the observed lines being attributable to H2O. Other detected
species include CO, 13CO, H2^18O, SiO, HCN, SO, SO2, CS, H2S, and NH3. Our
model fits to the observed 12CO and 13CO line intensities yield a 12C/13C ratio
of 5.6+-1.8, consistent with measurements of this ratio for other M
supergiants, but significantly lower than previously estimated for VY CMa from
observations of lower-J lines. The spectral line energy distribution for twenty
SiO rotational lines shows two temperature components: a hot component at 1000
K, which we attribute to the stellar atmosphere and inner wind, plus a cooler
~200 K component, which we attribute to an origin in the outer circumstellar
envelope. We fit the line fluxes of 12CO, 13CO, H2O and SiO, using the SMMOL
non-LTE line transfer code, with a mass-loss rate of 1.85x10^-4 Msun yr^-1
between 9 R* and 350 R*. To fit the observed line fluxes of 12CO, 13CO, H2O and
SiO with SMMOL non-LTE line radiative transfer code, along with a mass-loss
rate of 1.85x10^-4 Msun yr^-1.
  To fit the high rotational lines of CO and H2O, the model required a rather
flat temperature distribution inside the dust condensation radius, attributed
to the high H2O opacity. Beyond the dust condensation radius the gas
temperature is fitted best by an r^-0.5 radial dependence, consistent with the
coolant lines becoming optically thin. Our H2O emission line fits are
consistent with an ortho:para ratio of 3 in the outflow.


title: Vacuum Bubbles in the Presence of a Relativistic Fluid

abstract:
  First order phase transitions are characterized by the nucleation and
evolution of bubbles. The dynamics of cosmological vacuum bubbles, where the
order parameter is independent of other degrees of freedom, are well known;
more realistic phase transitions in which the order parameter interacts with
the other constituents of the Universe is in its infancy. Here we present
high-resolution lattice simulations that explore the dynamics of bubble
evolution in which the order parameter is coupled to a relativistic fluid. We
use a generic, toy potential, that can mimic physics from the GUT scale to the
electroweak scale.


title:
Exoplanet Transit Spectroscopy Using WFC3: WASP-12 b, WASP-17 b, and
  WASP-19 b

abstract:
  We report analysis of transit spectroscopy of the extrasolar planets WASP-12
b, WASP-17 b, and WASP-19 b using the Wide Field Camera 3 on the HST. We
analyze the data for a single transit for each planet using a strategy similar
in certain aspects to the techniques used by Berta et al. (2012), but we extend
their methodology to allow us to correct for channel- or wavelength-dependent
instrumental effects by utilizing the band-integrated time series and
measurements of the drift of the spectrum on the detector over time. We achieve
almost photon-limited results for individual spectral bins, but the
uncertainties in the transit depth for the the band-integrated data are
exacerbated by the uneven sampling of the light curve imposed by the orbital
phasing of HST's observations. Our final transit spectra for all three objects
are consistent with the presence of a broad absorption feature at 1.4 microns
potentially due to water. However, the amplitude of the absorption is less than
that expected based on previous observations with Spitzer, possibly due to
hazes absorbing in the NIR or non-solar compositions. The degeneracy of models
with different compositions and temperature structures combined with the low
amplitude of any features in the data preclude our ability to place unambiguous
constraints on the atmospheric composition without additional observations with
WFC3 to improve the S/N and/or a comprehensive multi-wavelength analysis.


title:
X-ray Decay Lines from Heavy Nuclei in Supernova Remnants as a Probe of
  the r-Process Origin and the Birth Periods of Magnetars

abstract:
  The origin of rapid neutron capture (r-process) nuclei remains one of the
longest standing mysteries in nuclear astrophysics. Core collapse supernovae
(SNe) and neutron star binary mergers are likely r-process sites, but little
evidence yet exists for their in situ formation in such environments. Motivated
by the advent of sensitive new or planned X-ray telescopes such as the Nuclear
Spectroscopic Telescope Array (NuSTAR) and the Large Observatory for X-ray
Timing (LOFT), we revisit the prospects for the detection of X-ray decay lines
from r-process nuclei in young or nearby supernova remnants. For all remnants
planned to be observed by NuSTAR (and several others), we conclude that
r-process nuclei are detectable only if the remnant possesses a large
overabundance O > 1e3 relative to the average yield per SN. Prospects are
better for the next Galactic SN (assumed age of 3 years and distance of 10
kpc), for which an average r-process yield is detectable via the 10.7(9.2) keV
line complexes of Os194 by LOFT at 6 sigma (5 sigma) confidence; the 27.3 keV
line complex of Sb125 is detectable by NuSTAR at 2 sigma for O > 2. We also
consider X-rays lines from the remnants of Galactic magnetars, motivated by the
much higher r-process yields of the magneto-rotationally driven SNe predicted
to birth magnetars. The ~ 3.6-3.9 keV lines of Sn126 are potentially detectable
in the remnants of the magnetars 1E1547.0-5408 and 1E2259+586 by LOFT for an
assumed r-process yield predicted by recent simulations. The (non-)detection of
these lines can thus probe whether magnetars are indeed born with millisecond
periods. Finally, we consider a blind survey of the Galactic plane with LOFT
for r-process lines from the most recent binary neutron star merger remnant,
concluding that a detection is unlikely without additional information on the
merger location.


title:
The Matryoshka Run: Eulerian Refinement Strategy to Study Statistics of
  Turbulence in Virialized Cosmic Structures

abstract:
  We study the statistical properties of turbulence driven by structure
formation in a massive merging galaxy cluster at z=0. The development of
turbulence is ensured as the largest eddy turnover time is much shorter than
the Hubble time independent of mass and redshift. We achieve a large dynamic
range of spatial scales through a novel Eulerian refinement strategy where the
cluster volume is refined with progressively finer uniform nested grids during
gravitational collapse. This provides an unprecedented resolution of 7.3 h^{-1}
kpc across the virial volume. The probability density functions of various
velocity derived quantities exhibit the features characteristic of fully
developed compressible turbulence observed in dedicated periodic-box
simulations. Shocks generate only 60% of the total vorticity within \rvir/3
region and 40% beyond that. We compute second and third order, longitudinal and
transverse, structure functions for both solenoidal and compressional
components, in the cluster core, virial region and beyond. The structure
functions exhibit a well defined inertial range. The injection scale is
comparable to the virial radius but increases towards the outskirts. Within
\rvir/3, the spectral slope of the solenoidal component is close to
Kolmogorov's, but for the compressional component is substantially steeper and
close to Burgers'; the flow is mostly solenoidal and statistically rigorously
consistent with fully developed, homogeneous and isotropic turbulence. Small
scale anisotropy appears due to numerical artifact. Towards the virial region,
the flow becomes compressional, the structure functions flatter and modest
genuine anisotropy appear. In comparison, mesh adaptivity based on Lagrangian
refinement and the same finest resolution, leads to lack of turbulent power on
small scale and excess thereof on large scales, and unreliable density weighted
structure functions.


title:
Orbits of radial migrators and non-migrators around a spiral arm in
  N-body simulations

abstract:
  Recent numerical N-body simulations of spiral galaxies have shown that spiral
arms in N-body simulations seem to rotate at a similar speed to the local
rotation speed of the stellar disc material. This in turn yields winding,
transient and recurrent spiral structure, whose co-rotating nature gives rise
to changes in the angular momentum (radial migration) of star particles close
to the spiral arm at many radii. From high resolution N-body simulations, we
highlight the evolution of strongly migrating star particles (migrators) and
star particles that do not migrate (non-migrators) around a spiral arm. We
investigate the individual orbit histories of migrators and non-migrators and
find that there are several types of migrator and non-migrator, each with
unique radial evolution. We contrast each type of orbit to establish the
reasons for the differences between them. We find that the positive (negative)
migrators sustain a position behind (in front of) the spiral arm, and feel
continuous tangential force as long as the spiral arm persists. On the other
hand, non-migrators stay close to the spiral arm, and pass or are passed by the
spiral arm one or two times. Although they gain or lose the angular momentum
when they are behind or in front of the spiral arm, their net angular momentum
change becomes close to zero. We discuss also the long term effects of radial
migration on the radial metallicity distribution and radial angular momentum
and mass profiles. [Abridged]


title: Fermi-LAT and the Gamma-Ray Line Search

abstract:
  A distinct signature for dark matter in the form of weakly interacting
massive particles (WIMPs) would be the detection of a monochromatic spectral
line in the gamma-ray sky. The Fermi-LAT collaboration has searched for such a
line in the energy range from 5 to 300 GeV in five sky regions around the
Galactic centre. No globally significant line is detected, and 95% CL upper
limits on monochromatic-line strengths are presented. The smallest search
region reveals a line-like structure at 133 GeV with a local significance of
2.9 sigma after 4.4 years of data, which translates to less than 1 sigma global
significance from a trial factor of around 200.


title:
Improved Spectrum Mobility using Virtual Reservation in Collaborative
  Cognitive Radio Networks

abstract:
  Cognitive radio technology would enable a set of secondary users (SU) to
opportunistically use the spectrum licensed to a primary user (PU). On the
appearance of this PU on a specific frequency band, any SU occupying this band
should free it for PUs. Typically, SUs may collaborate to reduce the impact of
cognitive users on the primary network and to improve the performance of the
SUs. In this paper, we propose and analyze the performance of virtual
reservation in collaborative cognitive networks. Virtual reservation is a novel
link maintenance strategy that aims to maximize the throughput of the cognitive
network through full spectrum utilization. Our performance evaluation shows
significant improvements not only in the SUs blocking and forced termination
probabilities but also in the throughput of cognitive users.


title: Spontaneous Analogy by Piggybacking on a Perceptual System

abstract:
  Most computational models of analogy assume they are given a delineated
source domain and often a specified target domain. These systems do not address
how analogs can be isolated from large domains and spontaneously retrieved from
long-term memory, a process we call spontaneous analogy. We present a system
that represents relational structures as feature bags. Using this
representation, our system leverages perceptual algorithms to automatically
create an ontology of relational structures and to efficiently retrieve analogs
for new relational structures from long-term memory. We provide a demonstration
of our approach that takes a set of unsegmented stories, constructs an ontology
of analogical schemas (corresponding to plot devices), and uses this ontology
to efficiently find analogs within new stories, yielding significant
time-savings over linear analog retrieval at a small accuracy cost.


title: How can star formation be sustained?

abstract:
  There is overwhelming evidence that the Milky Way has formed its stars at a
rel- atively constant rate throughout the Hubble time. This implies that its
stock of cold gas was not in place since the beginning but it has been acquired
slowly through gas accretion. The gas accretion must have been at low
metallicity in order to reconcile the metallicities observed in the disc with
the predictions of chemical evolution models. But how does this gas accretion
take place? I review the current evidence of gas accretion into the Milky Way
and similar galaxies through the infall of cold gas clouds and satellites. The
conclusion from these studies is that the infalling gas at high column
densities observed in HI emission is a least one order of magnitude below the
value required to sustain star formation, thus accretion must come from a
different channel. The likely reservoir for gas accretion is the cosmological
corona of virial-temperature gas in which every galaxy must be embedded. At the
interface between the disc and the corona the cold high-metallicity disc gas
and the hot coronal medium must mix efficiently and this mix- ing causes the
cooling and accretion of the lower corona. I show how this mechanism reproduces
the kinematics of the neutral extraplanar gas in the Milky Way and other nearby
galaxies and the ionised high-velocity clouds observed in HST spectra. I
conclude with the speculation that the loss in efficiency of the disc-corona
interaction is the ultimate cause for the evolution of disc galaxies towards
the red sequence.


title: The Barrett-Crane model: asymptotic measure factor

abstract:
  The original spin foam model construction for 4D gravity by Barrett and Crane
suffers from a few troubling issues. In the simple examples of the vertex
amplitude they can be summarized as the existence of contributions to the
asymptotics from non geometric configurations. Even restricted to geometric
contributions the amplitude is not completely worked out. While the phase is
known to be the Regge action, the so called measure factor has remained
mysterious for a decade. In the toy model case of the 6j symbol this measure
factor has a nice geometric interpretation of $V^{-1/2}$ leading to
speculations that a similar interpretation should be possible also in the 4D
case. In this paper we provide the first geometric interpretation of the
geometric part of the asymptotic for the spin foam consisting of two glued
4-simplices (decomposition of the 4-sphere) in the Barrett-Crane model in the
large internal spin regime.


title: Polytope Bounds on Multivariate Value Sets

abstract:
  We improve upon the upper bounds for the cardinality of the value set of a
multivariable polynomial map over a finite field using the polytope of the
polynomial. This generalizes earlier bounds only dependent on the degree of a
polynomial.


title:
Scaling Graph-based Semi Supervised Learning to Large Number of Labels
  Using Count-Min Sketch

abstract:
  Graph-based Semi-supervised learning (SSL) algorithms have been successfully
used in a large number of applications. These methods classify initially
unlabeled nodes by propagating label information over the structure of graph
starting from seed nodes. Graph-based SSL algorithms usually scale linearly
with the number of distinct labels (m), and require O(m) space on each node.
Unfortunately, there exist many applications of practical significance with
very large m over large graphs, demanding better space and time complexity. In
this paper, we propose MAD-SKETCH, a novel graph-based SSL algorithm which
compactly stores label distribution on each node using Count-min Sketch, a
randomized data structure. We present theoretical analysis showing that under
mild conditions, MAD-SKETCH can reduce space complexity at each node from O(m)
to O(log m), and achieve similar savings in time complexity as well. We support
our analysis through experiments on multiple real world datasets. We observe
that MAD-SKETCH achieves similar performance as existing state-of-the-art
graph- based SSL algorithms, while requiring smaller memory footprint and at
the same time achieving up to 10x speedup. We find that MAD-SKETCH is able to
scale to datasets with one million labels, which is beyond the scope of
existing graph- based SSL algorithms.


title:
Joint DOA and Array Manifold Estimation for a MIMO Array Using Two
  Calibrated Antennas

abstract:
  A simple scheme for joint direction of arrival (DOA) and array manifold
estimation for a MIMO array system is proposed, where only two transmit
antennas are calibrated initially. It first obtains a set of initial DOA
results by employing a rotational invariance property between two sets of
received data, and then more accurate DOA and array manifold estimation is
obtained through a local searching algorithm with several iterations. No strict
half wavelength spacing is required for the uncalibrated antennas to avoid the
spatial aliasing problem.


title: Towards Gigayear Storage Using a Silicon-Nitride/Tungsten Based Medium

abstract:
  Current digital data storage systems are able to store huge amounts of data.
Even though the data density of digital information storage has increased
tremendously over the last few decades, the data longevity is limited to only a
few decades. If we want to preserve anything about the human race which can
outlast the human race itself, we require a data storage medium designed to
last for 1 million to 1 billion years. In this paper a medium is investigated
consisting of tungsten encapsulated by siliconnitride which, according to
elevated temperature tests, will last for well over the suggested time.


title: Quantum entanglement in plasmonic waveguides with near-zero mode indices

abstract:
  We investigate the quantum entanglement between two quantum dots in a
plasmonic waveguide with near-zero mode index, considering the dependence of
concurrence on interdot distance, quantum dot-waveguide frequency detuning and
coupling strength ratio. High concurrence is achieved for a wide range of
interdot distance due to the near-zero mode index, which largely relaxes the
strict requirement of interdot distance in conventional dielectric waveguides
or metal nanowires. The proposed quantum dot-waveguide system with near-zero
phase variation along the waveguide near the mode cutoff frequency shows very
promising potential in quantum optics and quantum information processing.


title: Quantifying the benefits of vehicle pooling with shareability networks

abstract:
  Taxi services are a vital part of urban transportation, and a considerable
contributor to traffic congestion and air pollution causing substantial adverse
effects on human health. Sharing taxi trips is a possible way of reducing the
negative impact of taxi services on cities, but this comes at the expense of
passenger discomfort quantifiable in terms of a longer travel time. Due to
computational challenges, taxi sharing has traditionally been approached on
small scales, such as within airport perimeters, or with dynamical ad-hoc
heuristics. However, a mathematical framework for the systematic understanding
of the tradeoff between collective benefits of sharing and individual passenger
discomfort is lacking. Here we introduce the notion of shareability network
which allows us to model the collective benefits of sharing as a function of
passenger inconvenience, and to efficiently compute optimal sharing strategies
on massive datasets. We apply this framework to a dataset of millions of taxi
trips taken in New York City, showing that with increasing but still relatively
low passenger discomfort, cumulative trip length can be cut by 40% or more.
This benefit comes with reductions in service cost, emissions, and with split
fares, hinting towards a wide passenger acceptance of such a shared service.
Simulation of a realistic online system demonstrates the feasibility of a
shareable taxi service in New York City. Shareability as a function of trip
density saturates fast, suggesting effectiveness of the taxi sharing system
also in cities with much sparser taxi fleets or when willingness to share is
low.


title:
Optimistic versus Pessimistic--Optimal Judgemental Bias with Reference
  Point

abstract:
  This paper develops a model of reference-dependent assessment of subjective
beliefs in which loss-averse people optimally choose the expectation as the
reference point to balance the current felicity from the optimistic
anticipation and the future disappointment from the realisation. The choice of
over-optimism or over-pessimism depends on the real chance of success and
optimistic decision makers prefer receiving early information. In the portfolio
choice problem, pessimistic investors tend to trade conservatively, however,
they might trade aggressively if they are sophisticated enough to recognise the
biases since low expectation can reduce their fear of loss.


title:
Study of internal structures of 9,10Be and 10B in scattering of 4He from
  9Be

abstract:
  A study of inelastic scattering and single-particle transfer reactions was
performed by an alpha beam at 63 MeV on a 9$Be target. Angular distributions of
the differential cross sections for the 9Be(4He,4He')9Be*, 9Be(4He,3He)10Be and
9Be(4He,t)10B reactions were measured. Experimental angular distributions of
the differential cross sections for the ground state and a few low-lying states
were analyzed in the framework of the optical model, coupled channels and
distorted-wave Born approximation. An analysis of the obtained spectroscopic
factors was performed.


title: The Vertical Structure of the F Ring of Saturn from Ring-Plane Crossings

abstract:
  We present a photometric model of the rings of Saturn which includes the main
rings and an F ring, inclined to the main rings, with a Gaussian vertical
profile of optical depth. This model reproduces the asymmetry in brightness
between the east and west ansae of the rings of Saturn that was observed by the
Hubble Space Telescope (HST) within a few hours after the Earth ring-plane
crossing (RPX) of 10 August 1995. The model shows that during this observation
the inclined F ring unevenly blocked the east and west ansae of the main rings.
The brightness asymmetry produced by the model is highly sensitive to the
vertical thickness and radial optical depth of the F ring. The F ring model
that best matches the observations has a vertical full width at half maximum of
13 +/- 7 km and an equivalent depth of 10 +/- 4 km. The model also reproduces
the shape of the HST profiles of ring brightness vs. distance from Saturn, both
before and after the time of ring-plane crossing. Smaller asymmetries observed
before the RPX, when the Earth was on the dark side of the rings, cannot be
explained by blocking of the main rings by the F ring or vice versa and are
probably instead due to the intrinsic longitudinal variation exhibited by the F
ring.


title: Shape oscillation of a levitated drop in an acoustic field

abstract:
  A `star drop' refers to the patterns created when a drop, flattened by some
force, is excited into shape mode oscillations. These patterns are perhaps best
understood as the two dimensional analog to the more common three dimensional
shape mode oscillations. In this fluid dynamics video an ultrasonic standing
wave was used to levitate a liquid drop. The drop was then flattened into a
disk by increasing the field strength. This flattened drop was then excited to
create star drop patterns by exciting the drop at its resonance frequency.
Different oscillatory modes were induced by varying the drop radius, fluid
properties, and frequency at which the field strength was modulated.


title:
The Fossilized Birth-Death Process: A Coherent Model of Fossil
  Calibration for Divergence Time Estimation

abstract:
  Time-calibrated species phylogenies are critical for addressing a wide range
of questions in evolutionary biology, such as those that elucidate historical
biogeography or uncover patterns of coevolution and diversification. Because
molecular sequence data are not informative on absolute time, external data,
most commonly fossil age estimates, are required to calibrate estimates of
species divergence dates. For Bayesian divergence-time methods, the common
practice for calibration using fossil information involves placing arbitrarily
chosen parametric distributions on internal nodes, often disregarding most of
the information in the fossil record. We introduce the 'fossilized birth-death'
(FBD) process, a model for calibrating divergence-time estimates in a Bayesian
framework, explicitly acknowledging that extant species and fossils are part of
the same macroevolutionary process. Under this model, absolute node age
estimates are calibrated by a single diversification model and arbitrary
calibration densities are not necessary. Moreover, the FBD model allows for
inclusion of all available fossils. We performed analyses of simulated data and
show that node-age estimation under the FBD model results in robust and
accurate estimates of species divergence times with realistic measures of
statistical uncertainty, overcoming major limitations of standard divergence
time estimation methods. We then used this model to estimate the speciation
times for a dataset composed of all living bears, indicating that the genus
Ursus diversified in the late Miocene to mid Pliocene.


title: Holomorphic polygons and smooth 4-manifold invariants

abstract:
  Any smooth, closed oriented 4-manifold has a surface diagram of arbitrarily
high genus g>2 that specifies it up to diffeomorphism. The goal of this paper
is to prove the following statement: For any smooth, closed oriented 4-manifold
M, there is a sequence of weak A-infinity algebras indexed by g, and the
homotopy equivalence class of each entry of this sequence is a diffeomorphism
invariant of M.


title: Stable motivic pi_1 of low-dimensional fields

abstract:
  Let k be a field with cohomological dimension less than 3; we call such
fields low-dimensional. Examples include algebraically closed fields, finite
fields and function fields thereof, local fields, and number fields with no
real embeddings. We determine the 1-column of the motivic Adams-Novikov
spectral sequence over k. Combined with rational information we use this to
compute the first stable motivic homotopy group of the sphere spectrum over k.
Our main result affirms Morel's pi_1-conjecture in the case of low-dimensional
fields. We also determine stable motivic pi_1 in integer weights other than -2,
-3, and -4.


title: Excited Sessile Drops Dance Harmonically

abstract:
  In our fluid dynamics video, we demonstrate our method of visualizing and
identifying various mode shapes of mechanically oscillated sessile drops. By
placing metal mesh under an oscillating drop and projecting light from below,
the drop's shape is visualized by the visually deformed mesh pattern seen in
the top view. The observed modes are subsequently identified by their number of
layers and sectors. An alternative identification associates them with
spherical harmonics, as demonstrated in the tutorial. Clips of various observed
modes are presented, followed by a 10-second quiz of mode identification.


title: Hypergraph Colouring and Degeneracy

abstract:
  A hypergraph is "$d$-degenerate" if every subhypergraph has a vertex of
degree at most $d$. A greedy algorithm colours every such hypergraph with at
most $d+1$ colours. We show that this bound is tight, by constructing an
$r$-uniform $d$-degenerate hypergraph with chromatic number $d+1$ for all
$r\geq2$ and $d\geq1$. Moreover, the hypergraph is triangle-free, where a
"triangle" in an $r$-uniform hypergraph consists of three edges whose union is
a set of $r+1$ vertices.


title: Taylor approximation of incomplete Radner equilibrium models

abstract:
  In the setting of exponential investors and uncertainty governed by Brownian
motions we first prove the existence of an incomplete equilibrium for a general
class of models. We then introduce a tractable class of exponential-quadratic
models and prove that the corresponding incomplete equilibrium is characterized
by a coupled set of Riccati equations. Finally, we prove that these
exponential-quadratic models can be used to approximate the incomplete models
we studied in the first part.


title: Dimension of monopoles on asymptotically conic 3-manifolds

abstract:
  The virtual dimensions of both framed and unframed SU(2) magnetic monopoles
on asymptotically conic 3-manifolds are obtained by computing the index of a
Fredholm extension of the associated deformation complex. The unframed
dimension coincides with the one obtained by Braam for conformally compact
3-manifolds. The computation follows from the application of a Callias-type
index theorem.


title: Dynamics of Coalescence-Induced Jumping Water Droplets

abstract:
  This fluid dynamics video shows the different interaction mechanisms of
coalescence-induced droplet jumping during condensation on a nanostructured
superhydrophobic surface. High speed imaging was used to show jumping behavior
on superhydrophobic copper oxide and carbon nanotube surfaces. Videos
demonstrating multi-jumping droplets, jumping droplet return to the surface,
and droplet-droplet electrostatic repulsions were analyzed. Experiments using
external electric fields in conjunction with high speed imaging in a custom
built experimental chamber were used to show that all coalescence-induced
jumping droplets on superhydrophobic surfaces become positively charged upon
leaving the surface, which is detailed in the video.


title:
Contact process on generalized Fibonacci chains: infinite-modulation
  criticality and double-log periodic oscillations

abstract:
  We study the nonequilibrium phase transition of the contact process with
aperiodic transition rates using a real-space renormalization group as well as
Monte-Carlo simulations. The transition rates are modulated according to the
generalized Fibonacci sequences defined by the inflation rules A $\to$ AB$^k$
and B $\to$ A. For $k=1$ and 2, the aperiodic fluctuations are irrelevant, and
the nonequilibrium transition is in the clean directed percolation universality
class. For $k\ge 3$, the aperiodic fluctuations are relevant. We develop a
complete theory of the resulting unconventional "infinite-modulation" critical
point which is characterized by activated dynamical scaling. Moreover,
observables such as the survival probability and the size of the active cloud
display pronounced double-log periodic oscillations in time which reflect the
discrete scale invariance of the aperiodic chains. We illustrate our theory by
extensive numerical results, and we discuss relations to phase transitions in
other quasiperiodic systems.


title: Statistical earthquake focal mechanism forecasts

abstract:
  Forecasts of the focal mechanisms of future earthquakes are important for
seismic hazard estimates and Coulomb stress and other models of earthquake
occurrence. Here we report on a high-resolution global forecast of earthquake
rate density as a function of location, magnitude, and focal mechanism. In
previous publications we reported forecasts of 0.5 degree spatial resolution,
covering the latitude range magnitude, and focal mechanism. In previous
publications we reported forecasts of 0.5 degree spatial resolution, covering
the latitude range from -75 to +75 degrees, based on the Global Central Moment
Tensor earthquake catalog. In the new forecasts we've improved the spatial
resolution to 0.1 degree and the latitude range from pole to pole. Our focal
mechanism estimates require distance-weighted combinations of observed focal
mechanisms within 1000 km of each grid point. Simultaneously we calculate an
average rotation angle between the forecasted mechanism and all the surrounding
mechanisms, using the method of Kagan & Jackson proposed in 1994. This average
angle reveals the level of tectonic complexity of a region and indicates the
accuracy of the prediction. The procedure becomes problematical where longitude
lines are not approximately parallel, and where earthquakes are so sparse that
an adequate sample spans very large distances. North or south of 75 degrees,
the azimuths of points 1000 km away may vary by about 35 degrees. We solved
this problem by calculating focal mechanisms on a plane tangent to the earth's
surface at each forecast point, correcting for the rotation of the longitude
lines at the locations of earthquakes included in the averaging. The
corrections are negligible between -30 and +30 degrees latitude, but outside
that band uncorrected rotations can be significantly off.


title: Recognition of finite exceptional groups of Lie type

abstract:
  Let $q$ be a prime power and let $G$ be an absolutely irreducible subgroup of
$GL_d(F)$, where $F$ is a finite field of the same characteristic as $\F_q$,
the field of $q$ elements. Assume that $G \cong G(q)$, a quasisimple group of
exceptional Lie type over $\F_q$ which is neither a Suzuki nor a Ree group. We
present a Las Vegas algorithm that constructs an isomorphism from $G$ to the
standard copy of $G(q)$. If $G \not\cong {}^3 D_4(q)$ with $q$ even, then the
algorithm runs in polynomial time, subject to the existence of a discrete log
oracle.


title: Pattern Avoidance in Extensions of Comb-Like Posets

abstract:
  This paper investigates pattern avoidance in linear extensions of a certain
class of partially ordered set. Since the question of enumerating pattern
avoiding linear extensions of posets in general is a very hard one, we focus
instead on certain partially ordered sets called combs. Combs consist of a
fully ordered spine, and several fully ordered teeth, where each tooth
coincides with a corresponding element of the spine. We consider two natural
assignments of integers to elements of the combs; we refer to the resulting
integer posets as type-alpha combs and type-beta combs. In this paper, we
enumerate the linear extensions of type-alpha and type-beta combs which avoid
some of the length-three pattern. Most notably, the number of linear extensions
of type-beta combs which avoid 312 is shown to be the same as the number 1/(st
+ 1)*(s(t+1) choose s) of (t+1)-ary trees on s nodes, where t is the length of
each tooth, and s is the length of the comb spine, or equivalently, the number
of its teeth. We also investigate the enumeration of linear extensions of
type-alpha and type-beta combs avoiding multiple length-three patterns.


title: The Population of Tiny Near-Earth Objects Observed by NEOWISE

abstract:
  Only a very small fraction of the asteroid population at size scales
comparable to the object that exploded over Chelyabinsk, Russia has been
discovered to date, and physical properties are poorly characterized. We
present previously unreported detections of 106 close approaching near-Earth
objects (NEOs) by the Wide-field Infrared Survey Explorer mission's NEOWISE
project. These infrared observations constrain physical properties such as
diameter and albedo for these objects, many of which are found to be smaller
than 100 m. Because these objects are intrinsically faint, they were detected
by WISE during very close approaches to the Earth, often at large apparent
on-sky velocities. We observe a trend of increasing albedo with decreasing
size, but as this sample of NEOs was discovered by visible light surveys, it is
likely that selection biases against finding small, dark NEOs influence this
finding.


title: New structure for orthogonal quantum group invariants

abstract:
  Based on the orthogonal Labastida-Mari{\~n}o-Ooguri-Vafa conjecture made by
L. Chen & Q. Chen [5], we derive an infinite product formula for Chern-Simons
partition functions, which generalizes the Liu-Peng's [19] recent results to
the orthogonal case. Symmetry property of this new infinite product structure
is also discussed.


title: Active learning in pre-service science teacher education

abstract:
  We report a course on teaching in physics lab for teachers enrolled in
Formative Active Training, which actually allows to obtain the teacher
qualification in Italy. The course was designed with the purpose of showing in
practice what means active learning in physics and how effective activities can
be realized in practice. Two different type of teachers attended to the course,
a small group, with physics or mathematics degree, for teacher qualification in
secondary school of second grade (age 14-19) and a more numerous group for
qualification in secondary school of first grade (age 11-14), usually with a
different science degree such as biology, environmental sciences and so on. We
compare this training in physics lab between the two groups and with other
experiences we performed in previous years in pre-service education and
updating courses for teachers in-service.


title: Revisiting the physics of Fano resonances for nanoparticle oligomers

abstract:
  We present a new and robust approach for interpreting the physics of Fano
resonances in planar oligomer structures of both metallic and dielectric
nanoparticles. We reveal a key mechanism for Fano resonances by demonstrating
that such resonances can be generated purely from the interference of
nonorthogonal collective eigenmodes, which are clearly identified based on the
coupled-dipole approximation. We prove analytically a general theorem to
identify the number of collective eigenmodes that can be excited in ring-type
nanoparticle oligomers and further demonstrate that no dark mode excitation is
necessary for existence of Fano resonances in symmetric oligomers. As a
consequence, we unify the understanding of Fano resonances for both plasmonic
and all-dielectric oligomers.


title: Fault-Tolerant Quantum Computation with Constant Overhead

abstract:
  What is the minimum number of extra qubits needed to perform a large
fault-tolerant quantum circuit? Working in a common model of fault-tolerance, I
show that in the asymptotic limit of large circuits, the ratio of physical
qubits to logical qubits can be a constant. The construction makes use of
quantum low-density parity check codes, and the asymptotic overhead of the
protocol is equal to that of the family of quantum error-correcting codes
underlying the fault-tolerant protocol.


title: Cosmology of Multi-Singlet-Scalar Extensions of the Standard Model

abstract:
  An extension of the Standard Model by extra scalar singlets was considered.
Theoretical (unitarity, vacuum stability, triviality) and cosmological (dark
matter relic abundance, direct detection experiments, constraints on dark
matter self-interaction) constraints were discussed.


title:
Lower bounds on the mix norm of passive scalars advected by
  incompressible enstrophy-constrained flows

abstract:
  Consider a diffusion-free passive scalar $\theta$ being mixed by an
incompressible flow $u$ on the torus $\mathbb{T}^d$. Our aim is to study how
well this scalar can be mixed under an enstrophy constraint on the advecting
velocity field.Our main result shows that the mix-norm
($||\theta(t)||_{H^{-1}}$) is bounded below by an exponential function of time.
The exponential decay rate we obtain is not universal and depends on the size
of the support of the initial data. We also perform numerical simulations and
confirm that the numerically observed decay rate scales similarly to the
rigorous lower bound, at least for a significant initial period of time. The
main idea behind our proof is to use recent work of Crippa and DeLellis ('08)
making progress towards the resolution of Bressan's rearrangement cost
conjecture.


title: Stochastic thermodynamics of hidden pumps

abstract:
  We show that a reversible pumping mechanism operating between two states of a
kinetic network can give rise to Poisson transitions between these two states.
An external observer, for whom the pumping mechanism is not accessible, will
observe a Markov chain satisfying local detailed balance with an emerging
effective force induced by the hidden pump. Due to the reversibility of the
pump, the actual entropy production turns out to be lower than the coarse
grained entropy production estimated from the flows and affinities of the
resulting Markov chain. Moreover, in presence of a large time scale separation
between the fast pumping dynamics and the slow network dynamics, a finite
current with zero dissipation may be produced. We make use of these general
results to build a synthetase-like kinetic scheme able to reversibly produce
high free energy molecules at a finite rate and a rotatory motor achieving
100\% efficiency at finite speed.


title: From the function-sheaf dictionary to quasicharacters of $p$-adic tori

abstract:
  We consider the rigid monoidal category of character sheaves on a smooth
commutative group scheme $G$ over a finite field $k$ and expand the scope of
the function-sheaf dictionary from connected commutative algebraic groups to
this setting. We find the group of isomorphism classes of character sheaves on
$G$ and show that it is an extension of the group of characters of $G(k)$ by a
cohomology group determined by the component group scheme of $G$. We also
classify all morphisms in the category character sheaves on $G$. As an
application, we study character sheaves on Greenberg transforms of locally
finite type N\'eron models of algebraic tori over local fields. This provides a
geometrization of quasicharacters of $p$-adic tori.


title: Constraining gamma-ray propagation on cosmic distances

abstract:
  Studying the propagation of gamma rays on cosmological distances encompasses
a variety of scientific fields, focusing on diffuse radiation fields such as
the extragalactic background light, on the probe of the magnetism of the
Universe on large scales, and on physics beyond the standard models of
cosmology and particle physics. The measurements, constraints and hints from
observations of gamma-ray blazars by airborne and ground-based instruments are
briefly reviewed. These observations point to gamma-ray cosmology as one of the
major science cases of the Cherenkov Telescope Array, CTA.


title: Weak arithmetic equivalence

abstract:
  Inspired by the invariant of a number field given by its zeta function, we
define the notion of {\it weak arithmetic equivalence}, and show that under
certain ramification hypothesis, this equivalence determines the local root
numbers of the number field. This is analogous to a result of Rohrlich on the
local root numbers of a rational elliptic curve. Additionally, we prove that
for tame non-totally real number fields, the integral trace form is invariant
under weak arithmetic equivalence.


title:
World-leading science with SPIRou - the nIR spectropolarimeter /
  high-precision velocimeter for CFHT

abstract:
  SPIRou is a near-infrared (nIR) spectropolarimeter / velocimeter proposed as
a new-generation instrument for CFHT. SPIRou aims in particular at becoming
world-leader on two forefront science topics, (i) the quest for habitable
Earth-like planets around very- low-mass stars, and (ii) the study of low-mass
star and planet formation in the presence of magnetic fields. In addition to
these two main goals, SPIRou will be able to tackle many key programs, from
weather patterns on brown dwarf to solar-system planet atmospheres, to dynamo
processes in fully-convective bodies and planet habitability. The science
programs that SPIRou proposes to tackle are forefront (identified as first
priorities by most research agencies worldwide), ambitious (competitive and
complementary with science programs carried out on much larger facilities, such
as ALMA and JWST) and timely (ideally phased with complementary space missions
like TESS and CHEOPS).
  SPIRou is designed to carry out its science mission with maximum efficiency
and optimum precision. More specifically, SPIRou will be able to cover a very
wide single-shot nIR spectral domain (0.98-2.35 \mu m) at a resolving power of
73.5K, providing unpolarized and polarized spectra of low-mass stars with a
~15% average throughput and a radial velocity (RV) precision of 1 m/s.


title:
The nature of pulses delayed by 5 mcs in scintillation detectors from
  showers with the energy above 1E17 eV

abstract:
  Here we consider EAS events with energy above 1E17 eV with recorded pulses
delayed by t>=5 mcs in scintillation detectors with different thresholds: 10, 5
and 1.8 MeV. In order to identify pulses from electrons, muons and neutrons,
experimental data were compared to computational results performed within the
framework of QGSJET01d model. Preliminary, one may speculate of registration of
low-energy electrons arisen from moderation of neutrons in a detector or a
medium surrounding a detector or in the snow cover and frozen crust (albedo
particles). The fact that such pulses were registered mostly in low-threshold
detectors confirms this hypothesis.


title: The Role of the Core Energy in the Vortex Nernst Effect

abstract:
  We present an analytical study of diamagnetism and transport in a film with
superconducting phase fluctuations, formulated in terms of vortex dynamics
within the Debye-H\"uckle approximation. We find that the diamagnetic and
Nernst signals decay strongly with temperature in a manner which is dictated by
the vortex core energy. Using the theory to interpret Nernst measurements of
underdoped La$_{2-x}$Sr$_x$CuO$_4$ above the critical temperature regime we
obtain a considerably better fit to the data than a fit based on Gaussian
order-parameter fluctuations. Our results indicate that the core energy in this
system scales roughly with the critical temperature and is significantly
smaller than expected from BCS theory. Furthermore, it is necessary to assume
that the vortex mobility is much larger than the Bardeen-Stephen value in order
to reconcile conductivity measurements with the same vortex picture. Therefore,
either the Nernst signal is not due to superconducting phase fluctuations, or
that vortices in underdoped La$_{2-x}$Sr$_x$CuO$_4$ have highly unconventional
properties.


title: Depth-dependent Parallel Visualization with 3D Stylized Dense Tubes

abstract:
  We present a parallel visualization algorithm for the illustrative rendering
of depth-dependent stylized dense tube data at interactive frame rates. While
this computation could be efficiently performed on a GPU device, we target a
parallel framework to enable it to be efficiently running on an ordinary
multi-core CPU platform which is much more available than GPUs for common
users. Our approach is to map the depth information in each tube onto each of
the visual dimensions of shape, color, texture, value, and size on the basis of
Bertin's semiology theory. The purpose is to enable more legible displays in
the dense tube environments. A major contribution of our work is an efficient
and effective parallel depthordering algorithm that makes use of the message
passing interface (MPI) with VTK. We evaluated our framework with
visualizations of depth-stylized tubes derived from 3D diffusion tensor MRI
data by comparing its efficiency with several other alternative parallelization
platforms running the same computations. As our results show, the
parallelization framework we proposed can efficiently render highly dense 3D
data sets like the tube data and thus is useful as a complement to parallel
visualization environments that rely on GPUs.


title:
Exclusive photoproduction of J/psi and psi(2S) states in pp and AA
  collisions at the LHC

abstract:
  In this contribution we report on the investigations of the exclusive
production of J/psi and psi(2S) states in proton-proton and nucleus-nucleus
reactions at the LHC using the theoretical framework of light-cone dipole
formalism.


title:
Generic vanishing in characteristic $p>0$ and the characterization of
  ordinary abelian varieties

abstract:
  We prove a generic vanishing type statement in positive characteristic and
apply it to prove positive characteristic versions of Kawamata's theorems: a
characterization of smooth varieties birational to ordinary abelian varieties
and the surjectivity of the Albanese map when the Frobenius stable Kodaira
dimension is zero.


title: Bandits with Switching Costs: T^{2/3} Regret

abstract:
  We study the adversarial multi-armed bandit problem in a setting where the
player incurs a unit cost each time he switches actions. We prove that the
player's $T$-round minimax regret in this setting is
$\widetilde{\Theta}(T^{2/3})$, thereby closing a fundamental gap in our
understanding of learning with bandit feedback. In the corresponding
full-information version of the problem, the minimax regret is known to grow at
a much slower rate of $\Theta(\sqrt{T})$. The difference between these two
rates provides the \emph{first} indication that learning with bandit feedback
can be significantly harder than learning with full-information feedback
(previous results only showed a different dependence on the number of actions,
but not on $T$.)
  In addition to characterizing the inherent difficulty of the multi-armed
bandit problem with switching costs, our results also resolve several other
open problems in online learning. One direct implication is that learning with
bandit feedback against bounded-memory adaptive adversaries has a minimax
regret of $\widetilde{\Theta}(T^{2/3})$. Another implication is that the
minimax regret of online learning in adversarial Markov decision processes
(MDPs) is $\widetilde{\Theta}(T^{2/3})$. The key to all of our results is a new
randomized construction of a multi-scale random walk, which is of independent
interest and likely to prove useful in additional settings.


title:
Hydrodynamic causes and effects of air bubbles rising in very viscous
  media

abstract:
  Detailed understanding of two-phase gas liquid flows is imperative for
developing efficient multi-phase reactors through precise control of mixing and
reaction kinetics. The bubble column is a good apparatus for elementary studies
of such flows. In the current study experiments are conducted to assess the
effect of liquid viscosity on flow dynamics inside a bubble column. Corn oil
and water are used as the continuous media, and air was the dispersed media.
The objective of this effort is to use the results for a qualitative validation
of the numerical simulations.


title:
Pre-neutron-emission mass distributions for reaction $^{238}$U(n, f) up
  to 60 MeV

abstract:
  The pre-neutron-emission mass distributions for reaction $^{238}$U(n, f) up
to 60 MeV are systematically studied with an empirical fission potential model.
The energy dependence of the peaks and valleys of the pre-neutron-emission mass
distributions is described by an exponential form based on the newly measured
data. The energy dependence of evaporation neutrons before scission is also
considered, which plays a crucial role for the reasonable description of the
mass distributions. The measured data for the pre-neutron-emission mass
distributions for reaction $^{238}$U(n, f) are reasonably well reproduced up to
60 MeV. The mass distributions at unmeasured energies are also predicted with
this approach.


title: Fractionalization of Interstitials in Curved Colloidal Crystals

abstract:
  Understanding the out-of equilibrium behaviour of point defects in crystals,
yields insights into the nature and fragility of the ordered state, as well as
being of great practical importance. In some rare cases defects are
spontaneously healed - a one-dimensional crystal formed by a line of identical
charged particles, for example, can accommodate an interstitial (extra
particle) by a re-adjusting all particle positions to even out the spacing. In
sharp contrast, particles organized into a perfect hexagonal crystal in the
plane cannot accommodate an interstitial by a simple re-adjustment of the
particle spacing - the interstitial remains instead trapped between lattice
sites and diffuses by hopping, leaving the crystal permanently defected. Here
we report on the behavior of interstitials in colloidal crystals on curved
surfaces. Using optical tweezers operated independently of three dimensional
imaging, we insert a colloidal interstitial in a lattice of similar particles
on flat and curved (positively and negatively) oil-glycerol interfaces and
image the ensuing dynamics. We find that, unlike in flat space, the curved
crystals self-heal through a collective rearrangement that re-distributes the
increased density associated with the interstitial. The self-healing process
can be interpreted in terms of an out of equilibrium interaction of topological
defects with each other and with the underlying curvature. Our observations
suggest the existence of "particle fractionalization" on curved surface
crystals.


title: A Quantum Information Retrieval Approach to Memory

abstract:
  As computers approach the physical limits of information storable in memory,
new methods will be needed to further improve information storage and
retrieval. We propose a quantum inspired vector based approach, which offers a
contextually dependent mapping from the subsymbolic to the symbolic
representations of information. If implemented computationally, this approach
would provide exceptionally high density of information storage, without the
traditionally required physical increase in storage capacity. The approach is
inspired by the structure of human memory and incorporates elements of
Gardenfors' Conceptual Space approach and Humphreys et al.'s matrix model of
memory.


title:
The Penrose inequality for asymptotically locally hyperbolic spaces with
  nonpositive mass

abstract:
  In the asymptotically locally hyperbolic setting it is possible to have
metrics with scalar curvature at least -6 and negative mass when the genus of
the conformal boundary at infinity is positive. Using inverse mean curvature
flow, we prove a Penrose inequality for these negative mass metrics. The
motivation comes from a previous result of P. Chru\'sciel and W. Simon, which
states that the Penrose inequality we prove implies a static uniqueness theorem
for negative mass Kottler metrics.


abstract:
  A novel linear classification method that possesses the merits of both the
Support Vector Machine (SVM) and the Distance-weighted Discrimination (DWD) is
proposed in this article. The proposed Distance-weighted Support Vector Machine
method can be viewed as a hybrid of SVM and DWD that finds the classification
direction by minimizing mainly the DWD loss, and determines the intercept term
in the SVM manner. We show that our method inheres the merit of DWD, and hence,
overcomes the data-piling and overfitting issue of SVM. On the other hand, the
new method is not subject to imbalanced data issue which was a main advantage
of SVM over DWD. It uses an unusual loss which combines the Hinge loss (of SVM)
and the DWD loss through a trick of axillary hyperplane. Several theoretical
properties, including Fisher consistency and asymptotic normality of the DWSVM
solution are developed. We use some simulated examples to show that the new
method can compete DWD and SVM on both classification performance and
interpretability. A real data application further establishes the usefulness of
our approach.


title:
Flexible High-dimensional Classification Machines and Their Asymptotic
  Properties

abstract:
  Classification is an important topic in statistics and machine learning with
great potential in many real applications. In this paper, we investigate two
popular large margin classification methods, Support Vector Machine (SVM) and
Distance Weighted Discrimination (DWD), under two contexts: the
high-dimensional, low-sample size data and the imbalanced data. A unified
family of classification machines, the FLexible Assortment MachinE (FLAME) is
proposed, within which DWD and SVM are special cases. The FLAME family helps to
identify the similarities and differences between SVM and DWD. It is well known
that many classifiers overfit the data in the high-dimensional setting; and
others are sensitive to the imbalanced data, that is, the class with a larger
sample size overly influences the classifier and pushes the decision boundary
towards the minority class. SVM is resistant to the imbalanced data issue, but
it overfits high-dimensional data sets by showing the undesired data-piling
phenomena. The DWD method was proposed to improve SVM in the high-dimensional
setting, but its decision boundary is sensitive to the imbalanced ratio of
sample sizes. Our FLAME family helps to understand an intrinsic connection
between SVM and DWD, and improves both methods by providing a better trade-off
between sensitivity to the imbalanced data and overfitting the high-dimensional
data. Several asymptotic properties of the FLAME classifiers are studied.
Simulations and real data applications are investigated to illustrate the
usefulness of the FLAME classifiers.


title: The Battle of the Bulge: Decay of the Thin, False Cosmic String

abstract:
  We consider the decay of cosmic strings that are trapped in the false vacuum
in a theory of scalar electrodynamics in 3+1 dimensions. We restrict our
analysis to the case of thin-walled cosmic strings which occur when large
magnetic flux trapped inside the string. Thus the string looks like a tube of
fixed radius, at which it is classically stable. The core of the string
contains magnetic flux in the true vacuum, while outside the string, separated
by a thin wall, is the false vacuum. The string decays by tunnelling to a
configuration which is represented by a bulge, where the region of true vacuum
within, is ostensibly enlarged. The bulge can be described as the meeting, of a
kink soliton anti-soliton pair, along the length of the string. It can be
described as a bulge appearing in the initial string, starting from the string
of small, classically stable radius, expanding to a fat string of large,
classically unstable (to expansion) radius and then returning back to the
string of small radius along its length. This configuration is the bounce point
of a corresponding O(2) symmetric instanton, which we can determine
numerically. Once the bulge appears it explodes in real time. The kink soliton
anti-soliton pair recede from each other along the length of the string with a
velocity that quickly approaches the speed of light, leaving behind a fat tube.
At the same time the radius of the fat tube that is being formed, expands
(transversely) as it is no longer classically stable, converting false vacuum
to the true vacuum with ever diluting magnetic field within. The rate of this
expansion is determined by the energy difference between the true vacuum and
the false vacuum. Our analysis could be applied to a network, of cosmic strings
formed in the very early universe or vortex lines in a superheated
superconductor.


title: Extremal Metrics On Ruled Manifolds

abstract:
  In this paper, we consider a compact Kahler manifold with extremal Kahler
metric and a Mumford stable holomorphic bundle over it. We proved that, if the
holomorphic vector field defining the extremal Kahler metric is liftable to the
bundle and if the bundle is relatively stable with respect to the action of
automorphisms of the manifold, then there exist extremal Kahler metrics on the
projectivization of the dual vector bundle.


title:
Identifying the most crucial parameters of the initial curvature profile
  for primordial black hole formation

abstract:
  Primordial black holes (PBHs) are an important tool in cosmology to probe the
primordial spectrum of small-scale curvature perturbations that reenter the
cosmological horizon during radiation domination epoch. We numerically solve
the evolution of spherically symmetric highly perturbed configurations to
clarify the criteria of PBHs formation using an extremely wide class of
curvature profiles characterized by five parameters, (in contrast to only two
parameters used in all previous papers) which specify the curvature profiles
not only at the central region but also at the outer boundary of
configurations. It is shown that formation or non-formation of PBHs is
determined entirely by only two master parameters one of which can be presented
as an integral of curvature over initial configurations and the other is
presented in terms of the position of the boundary and the edge of the core.


title:
Is the late near-infrared bump in short-hard GRB 130603B due to the
  Li-Paczynski kilonova?

abstract:
  Short-hard gamma-ray bursts (GRBs) are widely believed to be produced by the
merger of two binary compact objects, specifically by two neutron stars or by a
neutron star orbiting a black hole. According to the Li-Paczynski kilonova
model, the merger would launch sub-relativistic ejecta and a
near-infrared/optical transient would then occur, lasting up to days, which is
powered by the radioactive decay of heavy elements synthesized in the ejecta.
The detection of a late bump using the {\em Hubble Space Telescope} ({\em HST})
in the near-infrared afterglow light curve of the short-hard GRB 130603B is
indeed consistent with such a model. However, as shown in this Letter, the
limited {\em HST} near-infrared lightcurve behavior can also be interpreted as
the synchrotron radiation of the external shock driven by a wide mildly
relativistic outflow. In such a scenario, the radio emission is expected to
peak with a flux of $\sim 100 \mu$Jy, which is detectable for current radio
arrays. Hence, the radio afterglow data can provide complementary evidence on
the nature of the bump in GRB 130603B. It is worth noting that good
spectroscopy during the bump phase in short-hard bursts can test validity of
either model above, analogous to spectroscopy of broad-lined Type Ic supernova
in long-soft GRBs.


title: Fast magnetosonic modes of cylindrical magnetotail

abstract:
  FMS modes are studied in the model of the magnetotail as a cylinder with
plasma sheet. The presence of the plasma sheet leads to a significant
modification of the modes existing in the magnetotail in the form of a cylinder
with no plasma sheet. Azimuthal scales of the FMS modes differ significantly
between the lobes and the plasma sheet. The azimuthal scale in the plasma sheet
is much smaller than that in the magnetotail lobes. FMS waves with certain
parameters are strongly reflected from the boundary between the lobes and the
plasma sheet and are very weak in the plasma sheet.


title: Creative ideas for actualizing student potential

abstract:
  Human creativity is a multifaceted phenomenon with cognitive, attitudinal,
intrapersonal interpersonal, practical, socio-cultural, economic, and
environmental aspects. It can be challenging to incorporate creativity in
classrooms. Teachers tend to inhibit creativity by focusing on reproduction of
knowledge, obedience and passivity in class, and correct responses, which are
easier to evaluate than creative ones. Teaching in such a way as to discourage
creative answers and approaches may lead to higher scores on standardized tests
(with all the sociological, marketplace, and political consequences that
entails). Teachers claim to value creativity, but to hold negative attitudes
toward, and show little tolerance of, attributes associated with creativity,
such as risk taking, impulsivity, and independence. When teachers do encourage
creativity, it is often the case that neither teacher nor students knows what
the expectations are. Moreover, students fear that they will be critically
judged if they produce something in which they have invested at a personal
level. Despite the potentially threatening aspects of encouraging creative
classrooms, no other investment in education could be more important and
rewarding. The phrase 'creative potential' is generally used to refer to how
likely a given individual is to manifest creative works in the future, as
assessed by scores on creativity tests. The concept of potentiality and its
relationship to actuality and context has been studied in depth by physicists.
This chapter explores how the physical conception of potentiality can shed
light on the notion of potential as it applies in the classroom, and in
particular, on how we conceive of and actualize students' creative potential.
We then discuss methods that will help optimize the creative potential of
students in less threatening ways.


title:
Dark Side of Creativity - Dangling from a Tassel on the Fabric of
  Socially Constructed Reality: Reflections on the Creative Writing Process

abstract:
  This chapter begins with an investigation into experiences of depression,
alienation, and self-abuse amongst the highly creative. After this journey to
the dark side, it may be uplifting to see that Mother Nature may have a few
tricks up her sleeve to minimize the extent to which we succumb to the negative
aspects of creativity while still benefiting from its riches. Finally, we
discuss another sobering aspect of creativity--the fact that many of our
inventions are dangerous to ourselves, our planet, and the other living things
we share it with--and discuss how a creation intimately reflects the structure
of the worldview(s) of its creators. Although the discussion focuses primarily
on creative writers, we believe that it relevant to creativity in other
domains, particularly the arts, and to a lesser extent science, engineering,
and business.


title:
The influence of magnetic field on the pion superfluidity and phase
  structure in the NJL model

abstract:
  The influence of the magnetic field on the pion superfluidity and the phase
structure is analyzed in the framework of the two-flavor
Nambu--Jona-Lasinio(NJL) model. To do this, we first derive the thermodynamic
potential from the Lagrangian density of the NJL model in the mean field
approximation. Using this thermodynamic potential, we get the gap equation of
the chiral condensate and the pion condensate. The effect of external magnetic
field on the pion condensate is not simple promotion or suppression, which we
will discuss in detail in the paper. It is shown that the tricritical point on
the pion superfluidity phase transition line moves to the space with smaller
isospin chemical potential and higher temperature when the external magnetic
field becomes stronger. The influence of external magnetic field on the chiral
condensate is also studied.


title: Witt vectors, semirings, and total positivity

abstract:
  We extend the big and $p$-typical Witt vector functors from commutative rings
to commutative semirings. In the case of the big Witt vectors, this is a
repackaging of some standard facts about monomial and Schur positivity in the
combinatorics of symmetric functions. In the $p$-typical case, it uses
positivity with respect to an apparently new basis of the $p$-typical symmetric
functions. We also give explicit descriptions of the big Witt vectors of the
natural numbers and of the nonnegative reals, the second of which is a
restatement of Edrei's theorem on totally positive power series. Finally we
give some negative results on the relationship between truncated Witt vectors
and $k$-Schur positivity, and we give ten open questions.


title:
Symmetric Reduction and Hamilton-Jacobi Equations of the Controlled
  Underwater Vehicle-Rotor System

abstract:
  In this paper, we first give the regular point reduction and the two types of
Hamilton-Jacobi equation for a regular controlled Hamiltonian (RCH) system with
symmetry and momentum map on the generalization of a semidirect product Lie
group. Next, as an application of the theoretical results, we consider the
underwater vehicle with two internal rotors as a regular point reducible RCH
system, in the cases of coincident and non-coincident centers of buoyancy and
gravity, we derive precisely the geometric constraint conditions of the reduced
symplectic form for the dynamical vector field of the regular point reducible
controlled underwater vehicle-rotor system, that is, the two types of
Hamilton-Jacobi equation for the reduced controlled underwater vehicle-rotor
system by calculation in detail, respectively. These researches reveal the
deeply internal relationships of the geometrical structures of phase spaces,
the dynamical vector fields and controls of the system.


title: Filter-And-Forward Relay Design for MIMO-OFDM Systems

abstract:
  In this paper, the filter-and-forward (FF) relay design for multiple-input
multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM)
systems is considered. Due to the considered MIMO structure, the problem of
joint design of the linear MIMO transceiver at the source and the destination
and the FF relay at the relay is considered. As the design criterion, the
minimization of weighted sum mean-square-error (MSE) is considered first, and
the joint design in this case is approached based on alternating optimization
that iterates between optimal design of the FF relay for a given set of MIMO
precoder and decoder and optimal design of the MIMO precoder and decoder for a
given FF relay filter. Next, the joint design problem for rate maximization is
considered based on the obtained result regarding weighted sum MSE and the
existing result regarding the relationship between weighted MSE minimization
and rate maximization. Numerical results show the effectiveness of the proposed
FF relay design and significant performance improvement by FF relays over
widely-considered simple AF relays for MIMO-ODFM systems.


title: Increasing sensing resolution with error correction

abstract:
  The signal to noise ratio of quantum sensing protocols scales with the square
root of the coherence time. Thus, increasing this time is a key goal in the
field. Dynamical decoupling has proven to be efficient in prolonging the
coherence times for the benefit of quantum sensing. However, dynamical
decoupling can only push the sensitivity up to a certain limit. In this work we
present a new approach to increasing the coherence time further through error
correction which can improve the efficiency of quantum sensing beyond the
fundamental limits of current state of the art methods.


title: Computation of the Ramsey Numbers $R(C_4,K_9)$ and $R(C_4,K_{10})$

abstract:
  The Ramsey number $R(C_4,K_m)$ is the smallest $n$ such that any graph on $n$
vertices contains a cycle of length four or an independent set of order $m$.
With the help of computer algorithms we obtain the exact values of the Ramsey
numbers $R(C_4,K_9)=30$ and $R(C_4,K_{10})=36$. New bounds for the next two
open cases are also presented.


title: Properties of Bose gas in a lattice model (strong interaction)

abstract:
  The doubts concerning validity of gas approximation for strong interaction
(for example, hard spheres) are expressed. A contradictory example - a Bose
system in a lattice model - is considered. Namely, the X-Y model for spin 1/2
is taken. A state with spins directed downwards is considered to be vacuum with
respect to the particles. An inverse spin (+1/2) corresponds to a particle.
There is an usual band spectrum (one band) for a single particle. A trial
function is written for a multiple particle system. This function was shown to
be a good one within a macroscopic limit, when the particle and lattice site
numbers tend to infinity (the ratio of energy standard deviation to average
energy tends to zero). A result within the gas limit (particle number is small
compared with the lattice site number) is compared with that obtained via
generally accepted approach.


title:
Testing excitation models of rapidly oscillating Ap stars with
  interferometry

abstract:
  Rapidly oscillating Ap stars are unique objects in the potential they offer
to study the interplay between a number of important physical phenomena, in
particular, pulsations, magnetic fields, diffusion, and convection.
Nevertheless, the simple understanding of how the observed pulsations are
excited in these stars is still in progress. In this work we perform a test to
what is possibly the most widely accepted excitation theory for this class of
stellar pulsators. The test is based on the study of a subset of members of
this class for which stringent data on the fundamental parameters are available
thanks to interferometry. For three out of the four stars considered in this
study, we find that linear, non-adiabatic models with envelope convection
suppressed around the magnetic poles can reproduce well the frequency region
where oscillations are observed. For the fourth star in our sample no agreement
is found, indicating that a new excitation mechanism must be considered. For
the three stars whose observed frequencies can be explained by the excitation
models under discussion, we derive the minimum angular extent of the region
where convection must be suppressed. Finally, we find that the frequency
regions where modes are expected to be excited in these models is very
sensitive to the stellar radius. This opens the interesting possibility of
determining this quantity and related ones, such as the effective temperature
or luminosity, from comparison between model predictions and observations, in
other targets for which these parameters are not well determined.


title: Exceptional collections on 2-adically uniformised fake projective planes

abstract:
  We show that there exist exceptional collections of length 3 consisting of
line bundles on the three fake projective planes that have a 2-adic
uniformisation with torsion free covering group. We also compute the Hochschild
cohomology of the right orthogonal of the subcategory of the bounded derived
category of coherent sheaves generated by these exceptional collections.


title:
Comment on "Extended Born-Infeld theory and the bouncing magnetic
  universe"

abstract:
  In a recent paper [Phys. Rev. D{\bf 85}, 023528 (2012)] the authors proposed
a generalized Born-Infeld electrodynamics coupled to general relativity which
produces a nonsingular bouncing universe. For a magnetic universe the resulting
cosmic evolution inevitably interpolates between asymptotic de Sitter states.
Here we shall show that (i) the above theory does not have the standard weak
field Maxwell limit, (ii) a sudden curvature singularity -- not better than the
big bang -- arises, (iii) the speed of sound squared is a negative quantity
signaling instability against small perturbations of the background energy
density, and that (iv) the conclusion about the inevitability of the asymptotic
vacuum regime in a magnetic universe is wrong.


title:
Impurity bound states and disorder-induced orbital and magnetic order in
  the s+- state of Fe-based superconductors

abstract:
  We study the presence of impurity bound states within a five-band Hubbard
model relevant to iron-based superconductors. In agreement with earlier
studies, we find that in the absence of Coulomb correlations there exists a
range of repulsive impurity potentials where in-gap states are generated. In
the presence of weak correlations, these states are generally pushed to the
edges of the gap, whereas for larger correlations the onsite impurity potential
induces a local magnetic region which reintroduces the low-energy bound states
into the gap.


title:
A finite presentation for the twist subgroup of the mapping class group
  of a nonorientable surface

abstract:
  Let $N_{g,s}$ denote the nonorientable surface of genus g with s boundary
components. Recently Paris and Szepietowski obtained an explicit finite
presentation for the mapping class group $M(N_{g,s})$ of the surface $N_{g,s}$,
where $s\in{0,1}$ and $g+s>3$. Following this work we obtain a finite
presentation for the subgroup $T(N_{g,s})$ of $M(N_{g,s})$ generated by Dehn
twists.


title: Gregory-Laflamme instability of BTZ black hole in new massive gravity

abstract:
  We find the Gregory-Laflamme $s$-mode instability of the non-rotating BTZ
black hole in new massive gravity. This instability shows that the BTZ black
hole could not exist as a stable static solution to the new massive gravity.
For non-rotating BTZ black string in four dimensions, however, it is
demonstrated that the BTZ black string can be stable against the metric
perturbation.


title:
Curvature dependence of the interfacial heat and mass transfer
  coefficients

abstract:
  Nucleation is often accompanied by heat transfer between the surroundings and
a nucleus of a new phase. The interface between two phases gives an additional
resistance to this transfer. For small nuclei the interfacial curvature is
high, which affects not only equilibrium quantities such as surface tension,
but also the transport properties. In particular, high curvature affects the
interfacial resistance to heat and mass transfer. We develop a framework for
determining the curvature dependence of the interfacial heat and mass transfer
resistances. We determine the interfacial resistances as a function of a
curvature. The analysis is performed for a bubble of a one-component fluid and
may be extended to various nuclei of multicomponent systems. The curvature
dependence of the interfacial resistances is important in modeling transport
processes in multiphase systems.


title: Non-thermal WIMPs as Dark Radiation

abstract:
  It has been thought that only light species could behave as radiation and
account for the dark radiation observed recently by Planck, WMAP9, South Pole
and ATACAMA telescopes. In this work we will show that GeV scale WIMPs can
plausibly account for the dark radiation as well. Heavy WIMPs might mimic the
effect of a half neutrino species if some of their fraction were produced
non-thermally after the thermal freeze-out. In addition, we will show how BBN,
CMB and Structure Formation bounds might be circumvented.


title:
Ultrafast supercontinuum fiber-laser based pump-probe scanning MOKE
  microscope for the investigation of electron spin dynamics in semiconductors
  at cryogenic temperatures with picosecond time and micrometer spatial
  resolution

abstract:
  We describe a two-color pump-probe scanning magneto-optical Kerr effect
(MOKE) microscope which we have developed to investigate electron spin
phenomena in semiconductors at cryogenic temperatures with picosecond time and
micrometer spatial resolution. The key innovation of our microscope is the
usage of an ultrafast `white light' supercontinuum fiber-laser source which
provides access to the whole visible and near-infrared spectral range. Our Kerr
microscope allows for the independent selection of the excitation and detection
energy while avoiding the necessity to synchronize the pulse trains of two
separate picosecond laser systems. The ability to independently tune the pump
and probe wavelength enables the investigation of the influence of excitation
energy on the optically induced electron spin dynamics in semiconductors. We
demonstrate picosecond real-space imaging of the diffusive expansion of
optically excited electron spin packets in a (110) GaAs quantum well sample to
illustrate the capabilities of the instrument.


title: Orbifold instantons, moment maps and Yang-Mills theory with sources

abstract:
  We revisit the problem of constructing instantons on ADE orbifolds R^4/\Gamma
and point out some subtle relations with the complex structure on the orbifold.
We consider generalized instanton equations on R^4/\Gamma which are BPS
equations for the Yang-Mills equations with an external current. The relation
between level sets of the moment maps in the hyper-Kaehler quotient
construction of the instanton moduli space and sources in the Yang-Mills
equations is discussed. We describe two types of spherically-symmetric
\Gamma-equivariant connections on complex V-bundles over R^4/\Gamma which are
tailored to the way in which the orbifold group acts on the fibres. Some
explicit abelian and nonabelian SU(2)-invariant solutions to the nstanton
equations on the orbifold are worked out.


title:
Decays of Zb -> Upsilon + pi via triangle diagrams in heavy meson
  molecules

abstract:
  Bottomonium-like resonances Zb(10610) and Zb'(10650) are good candidates of
hadronic molecules composed of BBbar* (or B*Bbar) and B*Bbar*, respectively.
Considering Zb (Zb') as heavy meson molecules, we investigate the decays of
Zb(')^+ -> Upsilon (nS) pi^+$ in terms of the heavy meson effective theory. We
find that the intermediate B (B*) and Bbar (Bbar*) meson loops and the form
factors play a significant role to reproduce the experimental values of the
decay widths. We also predict the decay widths of Zc^+ -> J/\psi pi^+ and
psi(2S) pi^+ for a charmonium-like resonance Zc which has been reported
recently in experiments.


title: Cocycle invariants of codimension 2-embeddings of manifolds

abstract:
  We consider the classical problem of a position of n-dimensional manifold M
in R^{n+2}. We show that we can define the fundamental (n+1)-cycle and the
shadow fundamental (n+2)-cycle for a fundamental quandle of a knotting M to
R^{n+2}. In particular, we show that for any fixed quandle, quandle coloring,
and shadow quandle coloring, of a diagram of M embedded in R^{n+2} we have
(n+1)- and (n+2)-(co)cycle invariants (i.e. invariant under Roseman moves). We
speculate on a similar construction for general Yang-Baxter operators.


title: An algebraic analysis of the graph modularity

abstract:
  One of the most relevant tasks in network analysis is the detection of
community structures, or clustering. Most popular techniques for community
detection are based on the maximization of a quality function called
modularity, which in turn is based upon particular quadratic forms associated
to a real symmetric modularity matrix $M$, defined in terms of the adjacency
matrix and a rank one null model matrix. That matrix could be posed inside the
set of relevant matrices involved in graph theory, alongside adjacency,
incidence and Laplacian matrices. This is the reason we propose a graph
analysis based on the algebraic and spectral properties of such matrix. In
particular, we propose a nodal domain theorem for the eigenvectors of $M$; we
point out several relations occurring between graph's communities and
nonnegative eigenvalues of $M$; and we derive a Cheeger-type inequality for the
graph optimal modularity.