title:
The AMIGA sample of isolated galaxies XII. Revision of the isolation
  degree for AMIGA galaxies using the SDSS

abstract:
  In the framework of the AMIGA project we present a revision of the
environment for galaxies in the Catalogue of Isolated Galaxies (CIG,
Karachentseva 1973) using the ninth data release of the Sloan Digital Sky
Survey (SDSS-DR9). The aims of this study are to refine the photometric-based
AMIGA sample of isolated galaxies and to provide an improvement of the
quantification of the isolation degree with respect to previous works, using
both photometry and spectroscopy. We developed an automatic method to search
for neighbours within a projected area of 1 Mpc radius centred on each primary
galaxy to revise the CIG isolation criteria. Of the 636 CIG galaxies considered
in the photometric study, 426 galaxies fulfil the CIG isolation criteria within
1 Mpc, taking into account projected neighbours. Of the 411 CIG galaxies
considered in the spectroscopic study, 347 galaxies fulfil the CIG isolation
criteria when a criterion about redshift difference is added. The available
redshifts allow us to reject background neighbours and thus improve the
photometric assessment. For the first time, the environment and the isolation
degree of AMIGA galaxies are quantified using digital data. The use of the SDSS
database permits one to identify fainter and smaller-size satellites than in
previous AMIGA works. About 50% of the neighbours considered as potential
companions in the photometric study are in fact background objects. We also
find that about 92% of the neighbour galaxies that show recession velocities
similar to the corresponding CIG galaxy are not considered by the CIG isolation
criteria as potential companions, which may have a considerable influence on
the evolution of the central CIG galaxy.


title: "It from bit" and the quantum probability rule

abstract:
  I argue that, on the subjective Bayesian interpretation of probability, "it
from bit" requires a generalization of probability theory. This does not get us
all the way to the quantum probability rule because an extra constraint, known
as noncontextuality, is required. I outline the prospects for a derivation of
noncontextuality within this approach and argue that it requires a realist
approach to physics, or "bit from it". I then explain why this does not
conflict with "it from bit". This version of the essay includes an addendum
responding to the open discussion that occurred on the FQXi website. It is
otherwise identical to the version submitted to the contest.


title: Weak Integer Additive Set-Indexers of Certain Graph Products

abstract:
  An integer additive set-indexer is defined as an injective function
$f:V(G)\rightarrow 2^{\mathbb{N}_0}$ such that the induced function $g_f:E(G)
\rightarrow 2^{\mathbb{N}_0}$ defined by $g_f (uv) = f(u)+ f(v)$ is also
injective, where $f(u)+f(v)$ is the sumset of $f(u)$ and $f(v)$. If $g_f(uv)=k
\forall uv\in E(G)$, then $f$ is said to be a $k$-uniform integer additive
set-indexers. An integer additive set-indexer $f$ is said to be a weak integer
additive set-indexer if $|g_f(uv)|=max(|f(u)|,|f(v)|) \forall uv\in E(G)$. We
have some characteristics of the graphs which admit weak integer additive
set-indexers. We already have some results on the admissibility of weak integer
additive set-indexer by certain graphs and finite graph operations. In this
paper, we study further characteristics of certain graph products like
cartesian product and corona of two weak IASI graphs and their admissibility of
weak integer additive set-indexers and provide some useful results on these
types of set-indexers.


title:
Electric charge and potential distribution in twisted multilayer
  graphene

abstract:
  The specifics of charge screening and electrostatic potential spatial
distribution in multilayered graphene films placed in between charged
substrates is theoretically analyzed. It is shown that by varying the areal
charge densities on the substrates and/or the thickness of the graphene stack
one may tune the doped carriers distribution over the system. When the charge
densities on the substrates are weak, the carriers distribution and
electrostatic potential profile agree with semimetallic properties of graphene.
However, when the amount of the donated charge is sufficiently large the
transition to a metallic-like behavior of the graphene layers occurs. The
possibilities for experimental observation of the predicted transition are
discussed.


title: Phase-Averaged Gamma-Ray Spectra from MSPs

abstract:
  {\it Fermi}-LAT has detected pulsed gamma-ray emissions with high confidences
from more than 40 millisecond pulsars (MSPs). Here we study the phase-averaged
gamma-ray properties of MSPs by using revised version of a self-consistent
outer gap model. In this model, a strong multipole magnetic field near the
stellar surface for a MSP is assumed and such a field will be close to the
surface magnetic fields ($\sim 10^{11}- 10^{12}$ G) of young ulsars; the outer
gap of a MSP is controlled by photon-photon pair production process, where the
effects of magnetic inclination angle ($\alpha$) and magnetic geometry have
been taken into account, therefore the fractional size of the outer gap is a
function of not only pulsar's period and magnetic field strength but also
magnetic inclination angle and radial distance to the neutron star, the inner
boundary of the outer gap can be estimated by the pair production process of
the gamma-ray photons which are produced by the back-flowing particles through
the null charge surface; inside the outer gap, a Gaussian distribution of the
parallel electric field along the trans-field thickness is assumed, and the
gamma-ray emission is represented by the emission from the average radial
distance along the central field lines of the outer gap. Using this model, the
phase-averaged gamma-ray spectra are calculated and compared with the observed
spectra of 37 MSPs given by the second {\it Fermi}-LAT catalog of gamma-ray
pulsars, our results show that the {\it Fermi}-LAT results can be well
explained by this model. The thermal X-ray emission properties from MSPs are
also investigated.


title:
A new GPU-accelerated hydrodynamical code for numerical simulation of
  interacting galaxies

abstract:
  In this paper a new scalable hydrodynamic code GPUPEGAS (GPU-accelerated
PErformance Gas Astrophysic Simulation) for simulation of interacting galaxies
is proposed. The code is based on combination of Godunov method as well as on
the original implementation of FlIC method, specially adapted for
GPU-implementation. Fast Fourier Transform is used for Poisson equation
solution in GPUPEGAS. Software implementation of the above methods was tested
on classical gas dynamics problems, new Aksenov's test and classical
gravitational gas dynamics problems. Collisionless hydrodynamic approach was
used for modelling of stars and dark matter. The scalability of GPUPEGAS
computational accelerators is shown.


title: Anderson localization for the completely resonant phases

abstract:
  For the almost Mathieu operator $ (H_{\lambda,\alpha,\theta}u)
(n)=u(n+1)+u(n-1)+ \lambda v(\theta+n\alpha)u(n)$, Avila and Jitomirskaya guess
that for every phase $ \theta \in \mathscr{R} \triangleq\{\theta\in
\mathbb{R}\;| \; 2\theta + \alpha \mathbb{Z} \in \mathbb{Z}\}$,
$H_{\lambda,\alpha,\theta}$ satisfies Anderson localization if $ |\lambda| >
e^{ 2 \beta}$. In the present paper, we show that for every phase $ \theta \in
\mathscr{R} $, $H_{\lambda,\alpha,\theta}$ satisfies Anderson localization if $
|\lambda| > e^{ 7 \beta}$.


title:
Absolutely Continuous Spectrum for the Quasi-periodic Schr\"{o}dinger
  Operator in Exponential Regime

abstract:
  Avila and Jitomirskaya prove that the quasi-periodic Schr\"{o}dinger operator
$H_{\lambda v,\alpha,\theta}$ has purely absolutely continuous spectrum for
$\alpha $ in sub-exponential regime (i.e., $\beta(\alpha)=0$) with small
$\lambda$, if $v$ is real analytic in a strip of real axis. In the present
paper, we show that for all $\alpha$ with $0<\beta(\alpha)<\infty$, $H_{\lambda
v,\alpha,\theta}$ has purely absolutely continuous spectrum with small
$\lambda$, if $v$ is real analytic in strip $ |\Im x|< C\beta $, where $C$ is a
large absolute constant.


title: Two automated techniques for analyzing and debugging Mpi-based programs

abstract:
  Message Passing Interface (MPI) is the most commonly used paradigm in writing
parallel programs since it can be employed not only within a single processing
node but also across several connected ones. Data flow analysis concepts,
techniques and tools are needed to understand and analyze MPI-based programs to
detect bugs arise in these programs. In this paper we propose two automated
techniques to analyze and debug MPI-based programs source codes.


title:
Anchors for the Cosmic Distance Scale: the Cepheids U Sgr, CF Cas and
  CEab Cas

abstract:
  New and existing X-ray, UBVJHKsW(1-4), and spectroscopic observations were
analyzed to constrain fundamental parameters for M25, NGC 7790, and dust along
their sight-lines. The star clusters are of particular importance given they
host the classical Cepheids U Sgr, CF Cas, and the visual binary Cepheids CEa
and CEb Cas. Precise results from the multiband analysis, in tandem with a
comprehensive determination of the Cepheids' period evolution (dP/dt) from ~140
years of observations, helped resolve concerns raised regarding the clusters
and their key Cepheid constituents. Specifically, distances derived for members
of M25 and NGC 7790 are 630+-25 pc and 3.40+-0.15 kpc, respectively.


title:
Cosmology with massive neutrinos I: towards a realistic modeling of the
  relation between matter, haloes and galaxies

abstract:
  By using a suite of large box-size N-body simulations that incorporate
massive neutrinos as an extra set of particles, we investigate the impact of
neutrino masses on the spatial distribution of dark matter haloes and galaxies.
We compute the bias between the spatial distribution of dark matter haloes and
the overall matter and cold dark matter distributions using statistical tools
such as the power spectrum and the two-point correlation function. Overall we
find a scale-dependent bias on large scales for the cosmologies with massive
neutrinos. However, our results indicate that the scale-dependence in the bias
is reduced if the latter is computed with respect to the cold dark matter
distribution only. We find that the value of the bias on large scales is
reasonably well reproduced by the Tinker fitting formula once the linear cold
dark matter power spectrum is used, instead of the total matter power spectrum.
We investigate whether scale-dependent bias really comes from purely neutrino's
effect or from nonlinear gravitational collapse of haloes. For this purpose, we
address the $\Omega_\nu$-$\sigma_8$ degeneracy and find that such degeneracy is
not perfect, implying that neutrinos imprint a slight scale dependence on the
large-scale bias. Finally, by using a simple halo occupation distribution (HOD)
model, we investigate the impact of massive neutrinos on the distribution of
galaxies within dark matter haloes. We use the main galaxy sample in the Sloan
Digital Sky Survey II Data Release 7 to investigate if the small-scale galaxy
clustering alone can be used to discriminate among different cosmological
models with different neutrino masses. Our results suggest that different
choices of the HOD parameters can reproduce the observational measurements
relatively well, and we quantify the difference between the values of the HOD
parameters between massless and massive neutrino cosmologies.


title:
The State of the Warm and Cold Gas in the Extreme Starburst at the Core
  of the Phoenix Galaxy Cluster (SPT-CLJ2344-4243)

abstract:
  [Abridged] We present new optical integral field spectroscopy (Gemini South)
and submillimeter spectroscopy (Submillimeter Array) of the central galaxy in
the Phoenix cluster (SPT-CLJ2344-4243). This cluster was previously reported to
have a massive starburst (~800 Msun/yr) in the central, brightest cluster
galaxy, most likely fueled by the rapidly-cooling intracluster medium. These
new data reveal a complex emission-line nebula, extending for >30 kpc from the
central galaxy. The total Halpha luminosity, assuming Halpha/Hbeta = 2.85, is
L_Ha = 7.6 +/- 0.4 x10^43 erg/s, making this the most luminous emission line
nebula detected in the center of a cool core cluster. Overall, the relative
fluxes of the low-ionization lines (e.g., [O II], Hbeta) to the UV continuum
are consistent with photoionization by young stars. In both the center of the
galaxy and in a newly-discovered highly-ionized plume to the north of the
galaxy, the ionization ratios are consistent with both shocks and AGN
photoionization. We speculate that this extended plume may be a galactic wind,
driven and partially photoionized by both the starburst and central AGN. We
find evidence for shocks throughout the ISM of the central galaxy, most likely
driven by a combination of stellar winds from massive young stars,
core-collapse supernovae, and the central AGN. In addition to the warm, ionized
gas, we detect a substantial amount of cold, molecular gas via the CO(3-2)
transition, coincident in position with the galaxy center. We infer a molecular
gas mass of M_H2 = 2.2 +/- 0.6 x10^10 Msun, which implies that the starburst
will consume its fuel in ~30 Myr if it is not replenished. The combination of
the high level of turbulence in the warm phase and the high L_IR/M_H2 ratio
suggests that this violent starburst may be in the process of quenching itself.


title:
The Megasecond Chandra XVP Observation of NGC 3115: Witnessing the Flow
  of Hot Gas within the Bondi Radius

abstract:
  Observational confirmation of hot accretion model predictions has been
hindered by the challenge to resolve spatially the Bondi radii of black holes
with X-ray telescopes. Here, we use the Megasecond Chandra X-ray Visionary
Project (XVP) observation of the NGC~3115 supermassive black hole to place the
first direct observational constraints on the spatially and spectroscopically
resolved structures of the X-ray emitting gas inside the Bondi radius of a
black hole. We measured temperature and density profiles of the hot gas from a
fraction out to tens of the Bondi radius (R_B = 2.4-4.8 arcsec = 112-224 pc).
The projected temperature jumps significantly from ~0.3 keV beyond 5 arcsec to
~0.7 keV within ~4-5 arcsec, but then abruptly drops back to ~0.3 keV within ~3
arcsec. This is contrary to the expectation that the temperature should rise
toward the center for a radiatively inefficient accretion flow. A hotter
thermal component of ~1 keV inside 3 arcsec (~150 pc) is revealed using a two
component thermal model, with the cooler ~0.3 keV thermal component dominating
the spectra. We argue that the softer emission comes from diffuse gas
physically located within $\sim 150$~pc from the black hole. The density
profile is broadly consistent with rho ~ r^{-1} within the Bondi radius for
either the single temperature or the two-temperature model. The X-ray data
alone with physical reasoning argue against the absence of a black hole,
supporting that we are witnessing the onset of the gravitational influence of
the supermassive black hole.


title: Why does the effective field theory of inflation work?

abstract:
  The effective field theory (EFT) of inflation has become the preferred method
for computing cosmological correlation functions of the curvature fluctuation,
$\zeta$. It makes explicit use of the soft breaking of time diffeomorphisms by
the inflationary background to organize the operators expansion in the action
of the Goldstone mode $\pi$ associated with this breaking. Despite its
ascendancy, there is another method for calculating $\zeta$ correlators,
involving the direct calculation of the so-called Horndeski action order by
order in powers of $\zeta$ and its derivatives. The question we address in this
work is whether or not the $\zeta$ correlators calculated in these seemingly
different ways are in fact the same. The answer is that the actions to cubic
order in either set of variables do indeed give rise to the same $\zeta$
bispectra, but that to make this equivalence manifest requires a careful
understanding of the non-linear transformations relating $\pi$ to $\zeta$ and
how boundary terms in the actions are affected by imposing this relation. As a
by product of our study we find that the calculations in the $\pi$ language can
be simplified considerably in a way that allows us to use only the linear part
of the $\pi-\zeta$ relation simply by changing the coefficients of some of the
operators in the EFT. We also note that a proper accounting of the boundary
terms will be of the greatest importance when computing the bispectrum for more
general initial states than the Bunch-Davies one.


title:
Muon g-2 and LHC phenomenology in the $L_\mu-L_\tau$ gauge symmetric
  model

abstract:
  In this paper, we consider phenomenology of a model with an $L_\mu-L_\tau$
gauge symmetry. Since the muon couples to the $L_\mu-L_\tau$ gauge boson
(called $Z''$ boson), its contribution to the muon anomalous magnetic moment
(muon g-2) can account for the discrepancy between the standard model
prediction and the experimental measurements. On the other hand, the $Z''$
boson does not interact with the electron and quarks, and hence there are no
strong constraints from collider experiments even if the $Z''$ boson mass is of
the order of the electroweak scale. We show an allowed region of a parameter
space in the $L_\mu-L_\tau$ symmetric model, taking into account consistency
with the electroweak precision measurements as well as the muon g-2. We study
the Large Hadron Collider (LHC) phenomenology, and show that the current and
future data would probe the interesting parameter space for this model.


title:
Extinction and Dust Geometry in M83 HII Regions: A Hubble Space
  Telescope/WFC3 Study

abstract:
  We present HST/WFC3 narrow-band imaging of the starburst galaxy M83 targeting
the hydrogen recombination lines (H$\beta$, H$\alpha$ and Pa$\beta$), which we
use to investigate the dust extinction in the HII regions. We derive extinction
maps with 6 parsec spatial resolution from two combinations of hydrogen lines
(H$\alpha$/H$\beta$ and H$\alpha$/Pa$\beta$), and show that the longer
wavelengths probe larger optical depths, with $A_V$ values larger by $\gtrsim$1
mag than those derived from the shorter wavelengths. This difference leads to a
factor $\gtrsim$2 discrepancy in the extinction-corrected H$\alpha$ luminosity,
a significant effect when studying extragalactic HII regions. By comparing
these observations to a series of simple models, we conclude that a large
diversity of absorber/emitter geometric configurations can account for the
data, implying a more complex physical structure than the classical foreground
"dust screen" assumption. However, most data points are bracketed by the
foreground screen and a model where dust and emitters are uniformly mixed. When
averaged over large ($\gtrsim$100--200 pc) scales, the extinction becomes
consistent with a "dust screen", suggesting that other geometries tend to be
restricted to more local scales. Moreover, the extinction in any region can be
described by a combination of the foreground screen and the uniform mixture
model with weights of 1/3 and 2/3 in the center ($\lesssim$2 kpc),
respectively, and 2/3 and 1/3 for the rest of the disk. This simple
prescription significantly improves the accuracy of the dust extinction
corrections and can be especially useful for pixel-based analyses of galaxies
similar to M83.


title: Multipole Love Relations

abstract:
  Gravitational-wave observations in the near future may allow us to measure
tidal deformabilities of neutron stars, which leads us to the understanding of
physics at nuclear density. In principle, the gravitational waveform depends on
various tidal parameters, which correlate strongly. Therefore, it would be
useful if one can express such tidal parameters with a single parameter. Here,
we report on universal relations among various $\ell$-th (dimensionless)
electric, magnetic and shape tidal deformabilities in neutron stars and quark
stars that do not depend sensitively on the equation of state. Such relations
allow us to break the degeneracy among the tidal parameters. In this paper, we
focus on gravitational waves from non-spinning neutron-star binary inspirals.
We first derive the leading contribution of the $\ell$-th electric and $\ell=2$
magnetic tidal deformabilities to the gravitational-wave phase, which enters at
$2\ell +1$ and $6$ post-Newtonian orders relative to the leading Newtonian one
respectively. We then calculate the useful number of gravitational-wave cycles
and show that not only the $\ell=2$ but also $\ell=3$ electric tidal
deformabilities are important for parameter estimation with third-generation
gravitational-wave detectors such as LIGO III and Einstein Telescope. Although
the correlation between the $\ell=2$ and $\ell=3$ electric tidal
deformabilities deteriorate the measurement accuracy of the former
deformability parameter, one can increase its measurement accuracy
significantly by using the universal relation. We provide a fitting formula for
the LIGO III noise curve in the Appendix.


title:
The Next Generation Virgo Cluster Survey - Infrared (NGVS-IR): I. A new
  Near-UV/Optical/Near-IR Globular Cluster selection tool

abstract:
  The NGVS-IR project (Next Generation Virgo Survey - Infrared) is a contiguous
near-infrared imaging survey of the Virgo cluster of galaxies. It complements
the optical wide-field survey of Virgo (NGVS). The current state of NGVS-IR
consists of Ks-band imaging of 4 deg^2 centered on M87, and J and Ks-band
imaging of 16 deg^2 covering the region between M49 and M87. In this paper, we
present the observations of the central 4 deg^2 centered on Virgo's core
region. The data were acquired with WIRCam on the Canada-France-Hawaii
Telescope and the total integration time was 41 hours distributed in 34
contiguous tiles. A survey-specific strategy was designed to account for
extended galaxies while still measuring accurate sky brightness within the
survey area. The average 5\sigma limiting magnitude is Ks=24.4 AB mag and the
50% completeness limit is Ks=23.75 AB mag for point source detections, when
using only images with better than 0.7" seeing (median seeing 0.54"). Star
clusters are marginally resolved in these image stacks, and Virgo galaxies with
\mu_Ks=24.4 AB mag arcsec^-2 are detected. Combining the Ks data with optical
and ultraviolet data, we build the uiK color-color diagram which allows a very
clean color-based selection of globular clusters in Virgo. This diagnostic plot
will provide reliable globular cluster candidates for spectroscopic follow-up
campaigns needed to continue the exploration of Virgo's photometric and
kinematic sub-structures, and will help the design of future searches for
globular clusters in extragalactic systems. Equipped with this powerful new
tool, future NGVS-IR investigations based on the uiK diagram will address the
mapping and analysis of extended structures and compact stellar systems in and
around Virgo galaxies.


title:
Variable Doppler shifts of the thermal wind absorption lines in low-mass
  X-ray binaries

abstract:
  In this paper we address the general applicability of the method pioneered by
\citet{Zhang2012} in which the motion of the compact object can be tracked
using wind X-ray absorption lines. We present the velocity measurements of the
thermal wind lines observed in the X-ray spectrum of a few low-mass X-ray
binaries: GX 13+1, H 1743$-$322, GRO J1655$-$40 and GRS 1915+105. We find that
the variability in the velocity of the wind lines in about all of the sources
is larger than conceivable radial velocity variations of the compact object. GX
13+1 provides a potential exception, although it would require the red giant
star to be massive with a mass of $\approx 5-6\ M_{\odot}$. We conclude that
the variability of the source luminosity occurring on a time scale of
days/months can affect the outflow properties making it difficult to track the
orbital motion of the compact object using current observations. Given the
intrinsic variability of the outflows we suggest that low-mass X-ray binaries
showing stable coronae instead of an outflow (e.g. 4U 1254$-$69, MXB 1659$-$29,
4U 1624$-$49) could be more suitable targets for tracking the orbital motion of
the compact object.


title: The Diffuse Galactic Far-Ultraviolet Sky

abstract:
  We present an all sky map of the diffuse Galactic far ultraviolet (1344-1786
Angstroms) background using GALEX data, covering 65% of the sky with 11.79
arcmin square pixels. We investigate the dependence of the background on
Galactic coordinates, finding that a standard cosecant model of intensity is
not a valid fit. Furthermore, we compare our map to Galactic all sky maps of
100 micron emission, N_HI column, and H-alpha intensity. We measure a
consistent low level FUV intensity at zero-points for other Galactic
quantities, indicating a 300 CU non-scattered isotropic component to the
diffuse FUV. There is also a linear relationship between FUV and 100 micron
emission below 100 micron values of 8 MJy/sr. We find a similar linear
relationship between FUV and NHI below 10^21 square cm. The relationship
between FUV and H-alpha intensity has no such constant cutoff. For all Galactic
quantities, the slope of the linear portion of the relationship decreases with
Galactic latitude. A modified cosecant model, taking into account dust
scattering asymmetry and albedo, is able to accurately fit the diffuse FUV at
latitudes above 20 degrees. The best fit model indicates an albedo, a, of 0.62
+- 0.04 and a scattering asymmetry function, g, of 0.78 +- 0.05. Deviations
from the model fit may indicate regions of excess FUV emission from
fluorescence or shock fronts, while low latitude regions with depressed FUV
emission are likely the result of self-shielding dusty clouds.


title:
Two-dimensional superfluidity of exciton-polaritons requires strong
  anisotropy

abstract:
  Fluids of exciton-polaritons, excitations of two dimensional quantum wells in
optical cavities, show collective phenomena akin to Bose condensation. However,
a fundamental difference from standard condensates stems from the finite
life-time of these excitations, which necessitate continuous driving to
maintain a steady state. A basic question is whether a two dimensional
condensate with long range algebraic correlations can exist under these
non-equilibrium conditions. Here we show that such driven two-dimensional Bose
systems cannot exhibit algebraic superfluid order except in low-symmetry,
anisotropic systems. Our result implies, in particular, that recent apparent
evidence for Bose condensation of exciton-polaritons must be an intermediate
scale crossover phenomenon, while the true long distance correlations fall off
exponentially. We obtain these results through a mapping of the long-wavelength
condensate dynamics onto the anisotropic Kardar-Parisi-Zhang equation.


title:
GUT predictions for quark-lepton Yukawa coupling ratios with messenger
  masses from non-singlets

abstract:
  We propose new predictions from Grand Unified Theories (GUTs) (applicable to
both supersymmetric (SUSY) and non-SUSY models) for the ratios of quark and
lepton Yukawa couplings. These new predictions arise from splitting the masses
of the messenger fields for the GUT scale Yukawa operators by Clebsch-Gordan
factors from GUT symmetry breaking. This has the effect that these factors
enter inversely in the predicted quark-lepton Yukawa coupling ratios, leading
to new possible GUT predictions. We systematically construct the new
predictions that can be realised in this way in SU(5) GUTs and Pati-Salam
unified theories and discuss model building applications.


title: A condensed matter realization of the axial magnetic effect

abstract:
  The axial magnetic effect, i.e., the generation of an energy current parallel
to an axial magnetic field coupling with opposite signs to left- and
right-handed fermions is a non-dissipative transport phenomenon intimately
related to the gravitational contribution to the axial anomaly. An axial
magnetic field emerges naturally in condensed matter in the so called Weyl
semi-metals. We present a measurable implementation of the axial magnetic
effect. We show that the edge states of a Weyl semimetal at finite temperature
possess a temperature dependent angular momentum in the direction of the vector
potential intrinsic to the system. Such a realization provides a plausible
context for the experimental confirmation of the elusive gravitational anomaly.


title:
Gauge Color Codes: Optimal Transversal Gates and Gauge Fixing in
  Topological Stabilizer Codes

abstract:
  Color codes are topological stabilizer codes with unusual transversality
properties. Here I show that their group of transversal gates is optimal and
only depends on the spatial dimension, not the local geometry. I also introduce
a generalized, subsystem version of color codes. In 3D they allow the
transversal implementation of a universal set of gates by gauge fixing, while
error-detecting measurements involve only 4 or 6 qubits.


title: A Family of WISPy Dark Matter Candidates

abstract:
  Dark matter made from non-thermally produced bosons can have very low,
possibly sub-eV masses. Axions and hidden photons are prominent examples of
such "dark" very weakly interacting light (slim) particles (WISPs). A suitable
mechanism for their non-thermal production is the misalignment mechanism. Their
dominant interaction with Standard Model (SM) particles is via photons. In this
note we want to go beyond these standard examples and discuss a wide range of
scalar and pseudo-scalar bosons interacting with SM matter fermions via
derivative interactions. Suitably light candidates arise naturally as
pseudo-Nambu-Goldstone bosons. In particular we are interested in examples,
inspired by familons, whose interactions have a non-trivial flavor structure.


title: Asymptotically Safe Starobinsky Inflation

abstract:
  We revisit Starobinsky inflation in a quantum gravitational context, by means
of the exact Renormalisation Group (RG). We calculate the non-perturbative beta
functions for Newton's `constant' G and the dimensionless R^2 coupling, and
show that there exists an attractive UV fixed point where the latter one
vanishes but not the former one, and we provide the corresponding beta
functions. The smallness of the R^2 coupling, required for agreement with
inflationary observables, is naturally ensured by its vanishing at the UV fixed
point, ensuring the smallness of the primordial fluctuations, as well as
providing a theoretical motivation for the initial conditions needed for
successful inflation in this context. We discuss the corresponding RG dynamics,
showing both how inflationary and classical observations define the
renormalisation conditions for the couplings, and also how the UV regime is
connected with lower energies along the RG flow. Finally, we discuss the
consistency of our results when higher order curvature corrections are
included, and show that they are robust to the inclusion of R^3 corrections.


title:
Critical integer quantum Hall topology and the integrable Maryland model
  as a topological quantum critical point

abstract:
  One dimensional tight binding models such as Aubry-Andre-Harper (AAH) model
(with onsite cosine potential) and the integrable Maryland model (with onsite
tangent potential) have been the subject of extensive theoretical research in
localization studies. AAH can be directly mapped onto the two dimensional
Hofstadter model which manifests the integer quantum Hall topology on a
lattice. However, no such connection has been made for the Maryland model (MM).
In this work, we describe a generalized model that contains AAH and MM as the
limiting cases with the MM lying precisely at a topological quantum phase
transition (TQPT) point. A remarkable feature of this critical point is that
the 1D MM retains well defined energy gaps whereas the equivalent 2D model
becomes gapless, signifying the 2D nature of the TQPT.


title:
Targeting supermassive black hole binaries and gravitational wave
  sources for the pulsar timing array

abstract:
  This paper presents a technique to search for supermassive black hole
binaries (MBHBs) in the Sloan Digital Sky Survey (SDSS). The search is based on
the peculiar properties of merging galaxies that are found in a mock galaxy
catalog from the Millennium Simulation. MBHBs are expected to be the main
gravitational wave (GW) sources for pulsar timing arrays (PTAs); however, it is
still unclear if the observed GW signal will be produced by a few single MBHBs,
or if it will have the properties of a stochastic background. The goal of this
work is to produce a map of the sky in which each galaxy is assigned a
probability of having suffered a recent merger, and of hosting a MBHB that
could be detected by PTAs. This constitutes a step forward in the understanding
of the expected PTA signal: the skymap can be used to investigate the
clustering properties of PTA sources and the spatial distribution of the
observable GW signal power; moreover, galaxies with the highest probabilities
could be used as inputs in targeted searches for individual GW sources. We also
investigate the distribution of neighboring galaxies around galaxies hosting
MBHBs, finding that the most likely detectable PTA sources are located in dense
galaxy environments. Different techniques are used in the search, including
Bayesian and Machine Learning algorithms, with consistent outputs. Our method
generates a list of galaxies classified as MBHB hosts, that can be combined
with other searches to effectively reduce the number of misclassifications. The
spectral coverage of the SDSS reaches less than a fifth of the sky, and the
catalog becomes severely incomplete at large redshifts; however, this technique
can be applied in the future to larger catalogs to obtain complete,
observationally-based information of the expected GW signal detectable by PTAs.


title: Non-thermal Dark Matter: A Selective Apercu

abstract: I provide a review of some recent work on non-thermal dark matter.


title: Homological Product Codes

abstract:
  Quantum codes with low-weight stabilizers known as LDPC codes have been
actively studied recently due to their simple syndrome readout circuits and
potential applications in fault-tolerant quantum computing. However, all
families of quantum LDPC codes known to this date suffer from a poor distance
scaling limited by the square-root of the code length. This is in a sharp
contrast with the classical case where good families of LDPC codes are known
that combine constant encoding rate and linear distance. Here we propose the
first family of good quantum codes with low-weight stabilizers. The new codes
have a constant encoding rate, linear distance, and stabilizers acting on at
most $\sqrt{n}$ qubits, where $n$ is the code length. For comparison, all
previously known families of good quantum codes have stabilizers of linear
weight. Our proof combines two techniques: randomized constructions of good
quantum codes and the homological product operation from algebraic topology. We
conjecture that similar methods can produce good stabilizer codes with
stabilizer weight $n^a$ for any $a>0$. Finally, we apply the homological
product to construct new small codes with low-weight stabilizers.


title:
3D stellar kinematics at the Galactic center: measuring the nuclear star
  cluster spatial density profile, black hole mass, and distance

abstract:
  We present 3D kinematic observations of stars within the central 0.5 pc of
the Milky Way nuclear star cluster using adaptive optics imaging and
spectroscopy from the Keck telescopes. Recent observations have shown that the
cluster has a shallower surface density profile than expected for a dynamically
relaxed cusp, leading to important implications for its formation and
evolution. However, the true three dimensional profile of the cluster is
unknown due to the difficulty in de-projecting the stellar number counts. Here,
we use spherical Jeans modeling of individual proper motions and radial
velocities to constrain for the first time, the de-projected spatial density
profile, cluster velocity anisotropy, black hole mass ($M_\mathrm{BH}$), and
distance to the Galactic center ($R_0$) simultaneously. We find that the inner
stellar density profile of the late-type stars, $\rho(r)\propto r^{-\gamma}$ to
have a power law slope $\gamma=0.05_{-0.60}^{+0.29}$, much more shallow than
the frequently assumed Bahcall $\&$ Wolf slope of $\gamma=7/4$. The measured
slope will significantly affect dynamical predictions involving the cluster,
such as the dynamical friction time scale. The cluster core must be larger than
0.5 pc, which disfavors some scenarios for its origin. Our measurement of
$M_\mathrm{BH}=5.76_{-1.26}^{+1.76}\times10^6$ $M_\odot$ and
$R_0=8.92_{-0.55}^{+0.58}$ kpc is consistent with that derived from stellar
orbits within 1$^{\prime\prime}$ of Sgr A*. When combined with the orbit of
S0-2, the uncertainty on $R_0$ is reduced by 30% ($8.46_{-0.38}^{+0.42}$ kpc).
We suggest that the MW NSC can be used in the future in combination with
stellar orbits to significantly improve constraints on $R_0$.


title: A note on generalized Dirac eigenvalues for split holonomy and torsion

abstract:
  We study the Dirac spectrum on compact Riemannian spin manifolds $M$ equipped
with a metric connection $\nabla$ with skew torsion $T\in\Lambda^3 M$ in the
situation where the tangent bundle splits under the holonomy of $\nabla$ and
the torsion of $\nabla$ is of `split' type. We prove an optimal lower bound for
the first eigenvalue of the Dirac operator with torsion that generalizes
Friedrich's classical Riemannian estimate.


title: New constraints on the cooling of the Central Compact Object in Cas A

abstract:
  To examine the previously claimed fast cooling of the Central Compact Object
(CCO) in the Cas A supernova remnant (SNR), we analyzed two Chandra
observations of this CCO, taken in a setup minimizing instrumental spectral
distortions. We fit the two CCO X-ray spectra from 2006 and 2012 with hydrogen
and carbon neutron star atmosphere models. The temperature and flux changes in
the 5.5 years between the two epochs depend on the adopted constraints on the
fitting parameters and the uncertainties of the effective area calibrations. If
we allow a change of the equivalent emitting region size, R_Em, the effective
temperature remains essentially the same. If R_Em is held constant, the
best-fit temperature change is negative, but its statistical significance
ranges from 0.8sigma to 2.5sigma, depending on the model. If we assume that the
optical depth of the ACIS filter contaminant in 2012 was +/-10% different from
its default calibration value, the significance of the temperature drop becomes
0.8sigma to 3.1sigma, for the carbon atmospheres with constant R_Em. Thus, we
do not see a statistically significant temperature drop in our data, but the
involved uncertainties are too large to firmly exclude the previously reported
fast cooling. Our analysis indicate a decrease of 4%-6% (1.9-2.9sigma
significance) for the absorbed flux in the energy range 0.6-6keV between 2006
and 2012, most prominent in the 1.4-1.8 keV energy range. It could be caused by
unaccounted changes of the detector response or contributions from unresolved
SNR material along the line of sight to the CCO.


title: Three dimensional Seiberg-like duality and tropical cluster algebra

abstract:
  Seiberg-like duality of three dimensional N=2 Chern-Simons-Matter quiver
gauge theory is shown to have a chiral double tropical cluster algebra
structure. We use cluster algebra results to study combinatorial aspects of
these theories such as classification, supersymmetry breaking, etc.


title: LHC searches examined via the RPV MSSM

abstract:
  We confront the ATLAS and CMS new physics searches with simplified models
from R-parity violating (RPV) supersymmetry that contain naturally light stops
and higgsinos. We emphasize the important role played by searches for exotic
heavy quarks and leptoquarks and discuss how these searches could be modified
to better address RPV scenarios. We also argue that it would be useful to
design searches for new physics based on the ttbar cross section measurements,
to enhance searches for taus + jets + MET with regions with b tagging and
reduced MET requirements, and to expand the search program for all-jet final
states, especially in the presence of multiple b-jets.


title:
Phenomenology of supersymmetric models with anomalous symmetries
  $U(1)_{H}$

abstract:
  We adopt in this thesis a new approach by assuming a set of $H$-charges that
give rise to a self-consistent model of $R$-parity breaking and baryon-number
violation. As a consequence of our $H$-charge assignments, it is not possible
to generate a Majorana mass term for left-handed neutrinos. However, a neutrino
Dirac matrix can be built after the introduction of right-handed neutrinos with
proper $H$-charges. We also show that by adding a second flavon field with
fractional charge, it is possible to build a Majorana neutrino mass matrix. In
both cases an anarchical matrix. The consequences for collider physics are
mentioned. We will generalize the mechanism of obtain $R$--parity from an
horizontal symmetry to the context of $SU(5)$ SUSY $+ \widehat{N}$, and
computable group theoretical coefficients that, at leading order, determine the
structure of the neutrino mass matrix in a parameter independent way.


title:
Equidistribution of polynomial sequences in function fields, with
  applications

abstract:
  We prove a function field analog of Weyl's classical theorem on
equidistribution of polynomial sequences. Our result covers the case when the
degree of the polynomial is greater than or equal to the characteristic of the
field, which is a natural barrier when applying the Weyl differencing process
to function fields. We also discuss applications to van der Corput and
intersective sets in function fields.


title: Regime shifts in models of dryland vegetation

abstract:
  Drylands are pattern-forming systems showing self-organized vegetation
patchiness, multiplicity of stable states and fronts separating domains of
alternative stable states. Pattern dynamics, induced by droughts or
disturbances, can result in desertification shifts from patterned vegetation to
bare soil. Pattern-formation theory suggests various scenarios for such
dynamics; an abrupt global shift involving a fast collapse to bare soil, a
gradual global shift involving the expansion and coalescence of bare-soil
domains, and an incipient shift to a hybrid state consisting of stationary
bare-soil domains in an otherwise periodic pattern. Using models of dryland
vegetation we address the question which of these scenarios can be realized. We
found that the models can be split into two groups: models that exhibit
multiplicity of periodic-pattern and bare-soil states, and models that exhibit,
in addition, multiplicity of hybrid states. Furthermore, in all models we could
not identify parameter regimes in which bare-soil domains expand into vegetated
domains. The significance of these findings is that while models belonging to
the first group can only exhibit abrupt shifts, model belonging to the second
group can also exhibit gradual and incipient shifts. A discussion of open
problems concludes the paper.


title:
A precise measurement of the $W$-boson mass with the Collider Detector
  at Fermilab

abstract:
  We present a measurement of the $W$-boson mass, $M_W$, using data
corresponding to 2.2/fb of integrated luminosity collected in ppbar collisions
at $\sqrt{s}$ = 1.96 TeV with the CDF II detector at the Fermilab Tevatron. The
selected sample of 470126 $W\to e\nu$ candidates and 624708 $W\to\mu\nu$
candidates yields the measurement $M_W = 80387\pm 12$ (stat) $\pm 15$ (syst)$ =
80387 \pm 19$ MeV$/c^2$ . This is the most precise single measurement of the
$W$-boson mass to date.


title:
Spin-Resolved Self-Doping Tunes the Intrinsic Half-Metallicity of AlN
  Nanoribbons

abstract:
  We present a first-principles theoretical study of electric field-and
strain-controlled intrinsic half-metallic properties of zigzagged aluminium
nitride (AlN) nanoribbons. We show that the half-metallic property of AlN
ribbons can undergo a transition into fully-metallic or semiconducting behavior
with application of an electric field or uniaxial strain. An external
transverse electric field induces a full charge screening that renders the
material semiconducting. In contrast, as uniaxial strain varies from
compressive to tensile, a spin-resolved selective self-doping increases the
half-metallic character of the ribbons. The relevant strain-induced changes in
electronic properties arise from band structure modifications at the Fermi
level as a consequence of a spin-polarized charge transfer between pi-orbitals
of the N and Al edge atoms in a spin-resolved self-doping process. This band
structure tunability indicates the possibility ofdesigning magnetic nanoribbons
with tunable electronic structure by deriving edge states from elements with
sufficiently different localization properties. Finite temperature molecular
dynamics reveal a thermally stable half-metallic nanoribbon up to room
temperature.


title: Strongly badly approximable matrices in fields of power series

abstract:
  We study the notion of strongly badly approximable matrices in the field of
power series over a field $K$. We prove a transference principle in this
setting, and show that such matrices exist when $K$ is infinite.


title: Spectrum-Adapted Tight Graph Wavelet and Vertex-Frequency Frames

abstract:
  We consider the problem of designing spectral graph filters for the
construction of dictionaries of atoms that can be used to efficiently represent
signals residing on weighted graphs. While the filters used in previous
spectral graph wavelet constructions are only adapted to the length of the
spectrum, the filters proposed in this paper are adapted to the distribution of
graph Laplacian eigenvalues, and therefore lead to atoms with better
discriminatory power. Our approach is to first characterize a family of systems
of uniformly translated kernels in the graph spectral domain that give rise to
tight frames of atoms generated via generalized translation on the graph. We
then warp the uniform translates with a function that approximates the
cumulative spectral density function of the graph Laplacian eigenvalues. We use
this approach to construct computationally efficient, spectrum-adapted, tight
vertex-frequency and graph wavelet frames. We give numerous examples of the
resulting spectrum-adapted graph filters, and also present an illustrative
example of vertex-frequency analysis using the proposed construction.


title:
Second Harmonic Generation in Subdiffractive Two-Dimensional Photonic
  Crystals

abstract:
  The PhD thesis is devoted to the study of second harmonic generation of
narrow beams in photonic crystals. The basic idea is that if both frequencies,
the fundamental and second harmonics are in the region of self-collimation,
then the second harmonics of narrow beams can be very efficient. The beams do
not spread diffractively during propagation and interaction. The phase matching
is ensured for all components of the interacting beams. This allows to enhance
the nonlinear interaction efficiency several times. The thesis rewises the
theory of self-collimation of narrow beams in photonic crystals, and presents
the theory of second harmonics in photonic crystals. Calculations in photonic
crystals of different configurations are presented, and the recommendations to
experimental realisations are given.


title: The Theory of Quasiconformal Mappings in Higher Dimensions, I

abstract:
  We present a survey of the many and various elements of the modern
higher-dimensional theory of quasiconformal mappings and their wide and varied
application. It is unified (and limited) by the theme of the author's
interests. Thus we will discuss the basic theory as it developed in the 1960s
in the early work of F.W. Gehring and Yu G. Reshetnyak and subsequently explore
the connections with geometric function theory, nonlinear partial differential
equations, differential and geometric topology and dynamics as they ensued over
the following decades. We give few proofs as we try to outline the major
results of the area and current research themes. We do not strive to present
these results in maximal generality, as to achieve this considerable technical
knowledge would be necessary of the reader. We have tried to give a feel of
where the area is, what are the central ideas and problems and where are the
major current interactions with researchers in other areas. We have also added
a bit of history here and there. We have not been able to cover the many recent
advances generalising the theory to mappings of finite distortion and to
degenerate elliptic Beltrami systems which connects the theory closely with the
calculus of variations and nonlinear elasticity, nonlinear Hodge theory and
related areas, although the reader may see shadows of this aspect in parts.


title:
Assessing the reliability of Friends-of-Friends groups on the future
  Javalambre Physics of the Accelerating Universe Astrophysical Survey

abstract:
  We have performed a detailed analysis of the ability of the
friends-of-friends algorithm in identifying real galaxy systems in deep surveys
such as the future Javalambre Physics of the Accelerating Universe
Astrophysical Survey. Our approach is two-fold, i.e., assessing the reliability
of the algorithm in both real and redshift space. In the latter, our intention
is also to determine the degree of accuracy that could be achieved when using
spectroscopic or photometric redshift determinations as a distance indicator.
We have built a light-cone mock catalogue using synthetic galaxies constructed
from the Millennium Run Simulation I plus a semi-analytical model of galaxy
formation. We have explored different ways to define the proper linking length
parameters of the algorithm in order to perform an identification of galaxy
groups as suitable as possible in each case. We find that, when identifying
systems in redshift space using spectroscopic information, the linking lengths
should take into account the variation of the luminosity function with redshift
as well as the linear redshift dependence of the radial fiducial velocity in
the line of sight direction. When testing purity and completeness of the group
samples, we find that the best resulting group sample reaches values of 40% and
70% of systems with high levels of purity and completeness, respectively, when
using spectroscopic information. When identifying systems using photometric
redshifts, we adopted a probabilistic approach to link galaxies in the line of
sight direction. Our result suggests that it is possible to identify a sample
of groups with less than 40% false identification at the same time as we
recover around 60% of the true groups. This modified version of the algorithm
can be applied to deep surveys provided that the linking lengths are selected
appropriately for the science to be done with the data.


title:
Conditional global existence and scattering for a semi-linear Skyrme
  equation with large data

abstract:
  We study a generalization of energy super-critical wave maps due to Adkins
and Nappi that can also be viewed as a simplified version of the Skyrme model.
These are maps from 1+3 dimensional Minkowski space that take values in the
3-sphere, and it follows that every finite energy Adkins-Nappi wave map has a
fixed topological degree which is an integer. Here we initiate the study of the
large data dynamics for Adkins-Nappi wave maps by proving that there is no type
II blow-up in the class of maps with topological degree zero. In particular,
any degree zero map whose critical norm stays bounded must be global-in-time
and scatter to zero as time tends to infinity.


title:
FiWi Access Networks Based on Next-Generation PON and Gigabit-Class WLAN
  Technologies: A Capacity and Delay Analysis (Extended Version)

abstract:
  Current Gigabit-class passive optical networks (PONs) evolve into
next-generation PONs, whereby high-speed 10+ Gb/s time division multiplexing
(TDM) and long-reach wavelength-broadcasting/routing wavelength division
multiplexing (WDM) PONs are promising near-term candidates. On the other hand,
next-generation wireless local area networks (WLANs) based on frame aggregation
techniques will leverage physical layer enhancements, giving rise to
Gigabit-class very high throughput (VHT) WLANs. In this paper, we develop an
analytical framework for evaluating the capacity and delay performance of a
wide range of routing algorithms in converged fiber-wireless (FiWi) broadband
access networks based on different next-generation PONs and a Gigabit-class
multi-radio multi-channel WLAN-mesh front-end. Our framework is very flexible
and incorporates arbitrary frame size distributions, traffic matrices,
optical/wireless propagation delays, data rates, and fiber faults. We verify
the accuracy of our probabilistic analysis by means of simulation for the
wireless and wireless-optical-wireless operation modes of various FiWi network
architectures under peer-to-peer, upstream, uniform, and nonuniform traffic
scenarios. The results indicate that our proposed optimized FiWi routing
algorithm (OFRA) outperforms minimum (wireless) hop and delay routing in terms
of throughput for balanced and unbalanced traffic loads, at the expense of a
slightly increased mean delay at small to medium traffic loads.


title:
B_{s,d} -> l+ l- in the Standard Model with Reduced Theoretical
  Uncertainty

abstract:
  We combine our new results for the O(alpha_em) and O(alpha_s^2) corrections
to B_{s,d} -> l^+ l^-, and present updated branching ratio predictions for
these decays in the standard model. Inclusion of the new corrections removes
major theoretical uncertainties of perturbative origin that have just begun to
dominate over the parametric ones. For the recently observed muonic decay of
the B_s meson, our calculation gives BR(B_s -> mu^+ mu^-) = (3.65 +_ 0.23) *
10^(-9).


title:
Modelling of thin isotropic elastic plates with small piezoelectric
  inclusions and distributed electric circuits. Models for inclusions larger or
  comparable to the thickness of the plate

abstract:
  This paper is the second part of a work devoted to the modelling of thin
elastic plates with small, periodically distributed piezoelectric inclusions.
We consider the equations of linear elasticity coupled with the electrostatic
equation, with various kinds of electric boundary conditions. We derive the
corresponding effective models when the thickness $a$ of the plate and the
characteristic dimension $\varepsilon $ of the inclusions tend\ together to
zero, in the two following situations: first when $a \simeq \varepsilon$,
second when $a/\varepsilon$ tends to zero.


title: Cosmology from cross correlation of CMB lensing and galaxy surveys

abstract:
  In recent years cross correlation of lensing of the Cosmic Microwave
Background (CMB) with other large scale structure (LSS) tracers has been used
as a method to detect CMB lensing. Current experiments are also becoming
sensitive enough to measure CMB lensing without the help of auxiliary tracers.
As data quality improves rapidly, it has been suggested that the CMB
lensing-LSS cross correlation may provide new insights into parameters
describing cosmological structure growth. In this work we perform forecasts
that combine the lensing potential auto power spectrum from various future CMB
experiments, the galaxy power spectrum from galaxy surveys, as well as the
cross power spectrum between the two, marginalizing over a number galactic and
non-galactic cosmological parameters. We find that the CMB lensing-LSS cross
correlation contains significant information on parameters such as the redshift
distribution and bias of LSS tracers. We also find that the cross correlation
information will lead to independent probes of cosmological parameters such as
neutrino mass and the reionization optical depth.


title: Major Substructure in the M31 Outer Halo: the South-West Cloud

abstract:
  We undertake the first detailed analysis of the stellar population and
spatial properties of a diffuse substructure in the outer halo of M31. The
South-West Cloud lies at a projected distance of ~100 kpc from the centre of
M31, and extends for at least ~50 kpc in projection. We use Pan-Andromeda
Archaeological Survey photometry of red giant branch stars to determine a
distance to the South-West Cloud of 793 +/- 45 kpc. The metallicity of the
cloud is found to be [Fe/H] = -1.3 +/- 0.1. This is consistent with the
coincident globular clusters PAndAS-7 and PAndAS-8, which have metallicities
determined using an independent technique of [Fe/H] = -1.35 +/- 0.15. We
measure a brightness for the Cloud of M_V = -12.1 mag; this is ~75 per cent of
the luminosity implied by the luminosity-metallicity relation. Under the
assumption that the South-West Cloud is the visible remnant of an accreted
dwarf satellite, this suggests that the progenitor object was amongst M31's
brightest dwarf galaxies prior to disruption.


title: Bayesian nonparametric inference on the Stiefel manifold

abstract:
  The Stiefel manifold $V_{p,d}$ is the space of all $d \times p$ orthonormal
matrices, with the $d-1$ hypersphere and the space of all orthogonal matrices
constituting special cases. In modeling data lying on the Stiefel manifold,
parametric distributions such as the matrix Langevin distribution are often
used; however, model misspecification is a concern and it is desirable to have
nonparametric alternatives. Current nonparametric methods are Fr\'echet mean
based. We take a fully generative nonparametric approach, which relies on
mixing parametric kernels such as the matrix Langevin. The proposed kernel
mixtures can approximate a large class of distributions on the Stiefel
manifold, and we develop theory showing posterior consistency. While there
exists work developing general posterior consistency results, extending these
results to this particular manifold requires substantial new theory. Posterior
inference is illustrated on a real-world dataset of near-Earth objects.


title: Anisotropic g factor in InAs self-assembled quantum dots

abstract:
  We investigate the wave functions, spectrum, and g-factor anisotropy of
low-energy electrons confined to self-assembled, pyramidal InAs quantum dots
(QDs) subject to external magnetic and electric fields. We present the
construction of trial wave functions for a pyramidal geometry with hard-wall
confinement. We explicitly find the ground and first excited states and show
the associated probability distributions and energies. Subsequently, we use
these wave functions and 8-band $k\cdot p$ theory to derive a Hamiltonian
describing the QD states close to the valence band edge. Using a perturbative
approach, we find an effective conduction band Hamiltonian describing
low-energy electronic states in the QD. From this, we further extract the
magnetic field dependent eigenenergies and associated g factors. We examine the
g factors regarding anisotropy and behavior under small electric fields. In
particular, we find strong anisotropies, with the specific shape depending
strongly on the considered QD level. Our results are in good agreement with
recent measurements [Takahashi et al., Phys. Rev. B 87, 161302 (2013)] and
support the possibility to control a spin qubit by means of g-tensor
modulation.


title:
Capacity and Delay Analysis of Next-Generation Passive Optical Networks
  (NG-PONs) - Extended Version

abstract:
  Building on the Ethernet Passive Optical Network (EPON) and Gigabit PON
(GPON) standards, Next-Generation (NG) PONs (i) provide increased data rates,
split ratios, wavelengths counts, and fiber lengths, as well as (ii) allow for
all-optical integration of access and metro networks. In this paper we provide
a comprehensive probabilistic analysis of the capacity (maximum mean packet
throughput) and packet delay of subnetworks that can be used to form NG-PONs.
Our analysis can cover a wide range of NG-PONs through taking the minimum
capacity of the subnetworks making up the NG-PON and weighing the packet delays
of the subnetworks. Our numerical and simulation results indicate that our
analysis quite accurately characterizes the throughput-delay performance of
EPON/GPON tree networks, including networks upgraded with higher data rates and
wavelength counts. Our analysis also characterizes the trade-offs and
bottlenecks when integrating EPON/GPON tree networks across a metro area with a
ring, a Passive Star Coupler (PSC), or an Arrayed Waveguide Grating (AWG) for
uniform and non-uniform traffic. To the best of our knowledge, the presented
analysis is the first to consider multiple PONs interconnected via a metro
network.


title:
On The Origin of Super-Hot Electrons from Intense Laser Interactions
  with Solid Targets having Moderate Scale Length Preformed Plasmas

abstract:
  We use PIC modeling to identify the acceleration mechanism responsible for
the observed generation of super-hot electrons in ultra-intense laser-plasma
interactions with solid targets with pre-formed plasma. We identify several
features of direct laser acceleration (DLA) that drive the generation of
super-hot electrons. We find that, in this regime, electrons that become
super-hot are primarily injected by a looping mechanism that we call
loop-injected direct acceleration (LIDA).


title:
Upper semicontinuity of KLV polynomials for certain blocks of
  Harish-Chandra modules

abstract:
  We show that the coefficients of Kazhdan-Lusztig-Vogan polynomials attached
to certain blocks of Harish-Chandra modules satisfy a monotonicity property
relative to the closure order on K-orbits in the flag variety.


title: Partial actions and KMS states on relative graph $C^*$-algebras

abstract:
  The relative graph $C^*$-algebras introduced by Muhly and Tomforde are
generalizations of both graph algebras and their Toeplitz extensions. For an
arbitrary graph $E$ and a subset $R$ of the set of regular vertices of $E$ we
show that the relative graph $C^*$-algebra $C^*(E, R)$ is isomorphic to a
partial crossed product for an action of the free group generated by the edge
set on the relative boundary path space. Given a time evolution on $C^*(E, R)$
induced by a function on the edge set, we characterize the KMS$_\beta$ states
and ground states using an abstract result of Exel and Laca. Guided by their
work on KMS states for Toeplitz-Cuntz-Krieger type algebras associated to
infinite matrices, we obtain complete descriptions of the convex sets of KMS
states of finite type and of KMS states of infinite type whose associated
measures are supported on recurrent infinite paths. This allows us to give a
complete concrete description of the convex set of all KMS states for a big
class of graphs which includes all finite graphs.


title: Bidding Games and Efficient Allocations

abstract:
  Richman games are zero-sum games, where in each turn players bid in order to
determine who will play next [Lazarus et al.'99]. We extend the theory to
impartial general-sum two player games called \emph{bidding games}, showing the
existence of pure subgame-perfect equilibria (PSPE). In particular, we show
that PSPEs form a semilattice, with a unique and natural \emph{Bottom
Equilibrium}.
  Our main result shows that if only two actions available to the players in
each node, then the Bottom Equilibrium has additional properties: (a) utilities
are monotone in budget; (b) every outcome is Pareto-efficient; and (c) any
Pareto-efficient outcome is attained for some budget.
  In the context of combinatorial bargaining, we show that a player with a
fraction of X% of the total budget prefers her allocation to X% of the possible
allocations. In addition, we provide a polynomial-time algorithm to compute the
Bottom Equilibrium of a binary bidding game.


title: A Divide-and-Conquer Solver for Kernel Support Vector Machines

abstract:
  The kernel support vector machine (SVM) is one of the most widely used
classification methods; however, the amount of computation required becomes the
bottleneck when facing millions of samples. In this paper, we propose and
analyze a novel divide-and-conquer solver for kernel SVMs (DC-SVM). In the
division step, we partition the kernel SVM problem into smaller subproblems by
clustering the data, so that each subproblem can be solved independently and
efficiently. We show theoretically that the support vectors identified by the
subproblem solution are likely to be support vectors of the entire kernel SVM
problem, provided that the problem is partitioned appropriately by kernel
clustering. In the conquer step, the local solutions from the subproblems are
used to initialize a global coordinate descent solver, which converges quickly
as suggested by our analysis. By extending this idea, we develop a multilevel
Divide-and-Conquer SVM algorithm with adaptive clustering and early prediction
strategy, which outperforms state-of-the-art methods in terms of training
speed, testing accuracy, and memory usage. As an example, on the covtype
dataset with half-a-million samples, DC-SVM is 7 times faster than LIBSVM in
obtaining the exact SVM solution (to within $10^{-6}$ relative error) which
achieves 96.15% prediction accuracy. Moreover, with our proposed early
prediction strategy, DC-SVM achieves about 96% accuracy in only 12 minutes,
which is more than 100 times faster than LIBSVM.


title: One remark on the b-semiampleness of the moduli part

abstract:
  In this short note we reduce the b-semiampleness conjecture for lc-trivial
fibrations to the b-semiampleness conjecture for klt-trivial fibrations.


title: Optically active mechanical modes of tapered optical fibers

abstract:
  Tapered optical fibers with a nanofiber waist are widely used tools for
efficient coupling of light to photonic devices or quantum emitters via the
nanofiber's evanescent field. In order to ensure well-controlled coupling, the
phase and polarization of the nanofiber guided light field have to be stable.
Here, we show that in typical tapered optical fibers these quantities exhibit
high-frequency thermal fluctuations. They originate from high-Q torsional
oscillations that opto-mechanically couple to the nanofiber-guided light. We
present a simple ab-initio theoretical model that quantitatively explains the
torsional mode spectrum and that can be used to design tapered optical fibers
with tailored mechanical properties.


title: Coarse-grained description of general oscillator networks

abstract:
  We propose a novel and systematic method for coarse-graining oscillator
networks described by phase equations. Our coarse-graining method enables us to
obtain the closed coarse-grained equations for a few effective eigenmodes,
which is based on the eigenvalue problem of the linearized system around the
phase-locked solution and a nonlinear transformation. We demonstrate our method
by applying it to oscillator dynamics on a random graph, which exhibits a
saddle-node bifurcation at the bifurcation point.


title: A holomorphic anomaly in the elliptic genus

abstract:
  We consider a class of gauged linear sigma models (GLSMs) in two dimensions
that flow to non-compact (2,2) superconformal field theories in the infra-red,
a prototype of which is the SL(2,\IR)/U(1) (cigar) coset. We compute the
elliptic genus of the GLSMs as a path-integral on the torus using
supersymmetric localization. We find that the result is a Jacobi-like form that
is non-holomorphic in the modular parameter $\tau$ of the torus, with mock
modular behavior. This agrees with a previously-computed expression in the
cigar coset. We show that the lack of holomorphicity of the elliptic genus
arises from the contributions of a compact boson with momentum and winding
around the torus. This boson has an axionic shift symmetry and plays the role
of a compensator field that is needed to cancel the chiral anomaly in the rest
of the theory.


title: VERITAS Observations of the Microquasar Cygnus X-3

abstract:
  We report results from TeV gamma-ray observations of the microquasar Cygnus
X-3. The observations were made with the Very Energetic Radiation Imaging
Telescope Array System (VERITAS) over a time period from 2007 June 11 to 2011
November 28. VERITAS is most sensitive to gamma rays at energies between 85 GeV
to 30 TeV. The effective exposure time amounts to a total of about 44 hours,
with the observations covering six distinct radio/X-ray states of the object.
No significant TeV gamma-ray emission was detected in any of the states, nor
with all observations combined. The lack of a positive signal, especially in
the states where GeV gamma rays were detected, places constraints on TeV
gamma-ray production in Cygnus X-3. We discuss the implications of the results.


title: T symmetry invariance tests in neutral meson decays

abstract:
  We outline how the time-reversal symmetry T can be systematically used to
test the Kobayashi-Maskawa mechanism embedded in the CKM matrix using pairs of
B mesons created at the Upsilon(4S) and pairs of D mesons from psi(3770).


title:
Observable Gravity Waves From U(1)_${B-L}$ Higgs and Coleman-Weinberg
  Inflation

abstract:
  We present a realistic non-supersymmetric inflation model based on a gauged
U(1)$_{B-L}$ symmetry and a tree-level Higgs potential. The inflaton is
identified with the scalar field which spontaneously breaks U(1)$_{B-L}$, and
we include radiative corrections \`a la Coleman-Weinberg in the inflaton
potential. If the scalar spectral index $n_s$ lies close to 0.96, as indicated
by the recent Planck and WMAP 9-yr measurements, the tensor-to-scalar ratio
$r$, a canonical measure for gravity waves, exceeds 0.01. Thus, according to
this model, gravity waves should be found in the near future. In this case, the
quantity $|dn_s/d \ln k|$ lies in the range $0.004-0.005$. Successful
baryogenesis can be realized in this class of models either via thermal or
non-thermal leptogenesis.


title: Nonlinear Parametric Inversion using Interpolatory Model Reduction

abstract:
  Nonlinear parametric inverse problems appear in several prominent
applications; one such application is Diffuse Optical Tomography (DOT) in
medical image reconstruction. Such inverse problems present huge computational
challenges, mostly due to the need for solving a sequence of large-scale
discretized, parametrized, partial differential equations (PDEs) in the forward
model. In this paper, we show how interpolatory parametric model reduction can
significantly reduce the cost of the inversion process in DOT by drastically
reducing the computational cost of solving the forward problems. The key
observation is that function evaluations for the underlying optimization
problem may be viewed as transfer function evaluations along the imaginary
axis; a similar observation holds for Jacobian evaluations as well. This
motivates the use of system-theoretic model order reduction methods. We discuss
the construction and use of interpolatory parametric reduced models as
surrogates for the full forward model. Within the DOT setting, these surrogate
models can approximate both the cost functional and the associated Jacobian
with very little loss of accuracy while significantly reducing the cost of the
overall inversion process. Four numerical examples illustrate the efficiency of
the proposed approach. Although we focus on DOT in this paper, we believe that
our approach is applicable much more generally.


title:
Fine properties of branch point singularities: Two-valued harmonic
  functions

abstract:
  In the 1980's, Almgren developed a theory of multi-valued Dirichlet energy
minimizing functions on $n$ dimensional domains and used it, in an essential
way, to bound the Hausdorff dimension of the singular sets of area minimizing
rectifiable currents of dimension $n$ and codimension $\geq 2$. Recent work of
the second author shows that two-valued $C^{1, \mu}$ harmonic functions on $n$
dimensional domains, which are typically-non-minimizing stationary points of
Dirichlet energy, play an essential role in the study of multiplicity 2 branch
points of stable codimension 1 rectifiable currents of dimension $n$. In all of
these cases (of multi-valued harmonic functions and minimal currents), it is
known that the branch sets have Hausdorff dimension $\leq n-2.$ In this paper
we initiate a study of the local structure of branch sets. We show that the
branch set of a two-valued Dirichlet energy minimizing function or a two-valued
$C^{1, \mu}$ harmonic function, in each closed ball of its domain, is either
empty or has positive $(n-2)$-dimensional Hausdorff measure and is equal to the
union of a finite number of locally compact, locally $(n-2)$-rectifiable sets.
Our method is inspired by the work of L. Simon on the structure of
singularities of minimal submanifolds in compact, multiplicity 1 classes.


title: On the Efficiency of the Walrasian Mechanism

abstract:
  Central results in economics guarantee the existence of efficient equilibria
for various classes of markets. An underlying assumption in early work is that
agents are price-takers, i.e., agents honestly report their true demand in
response to prices. A line of research in economics, initiated by Hurwicz
(1972), is devoted to understanding how such markets perform when agents are
strategic about their demands. This is captured by the \emph{Walrasian
Mechanism} that proceeds by collecting reported demands, finding clearing
prices in the \emph{reported} market via an ascending price t\^{a}tonnement
procedure, and returns the resulting allocation. Similar mechanisms are used,
for example, in the daily opening of the New York Stock Exchange and the call
market for copper and gold in London.
  In practice, it is commonly observed that agents in such markets reduce their
demand leading to behaviors resembling bargaining and to inefficient outcomes.
We ask how inefficient the equilibria can be. Our main result is that the
welfare of every pure Nash equilibrium of the Walrasian mechanism is at least
one quarter of the optimal welfare, when players have gross substitute
valuations and do not overbid. Previous analysis of the Walrasian mechanism
have resorted to large market assumptions to show convergence to efficiency in
the limit. Our result shows that approximate efficiency is guaranteed
regardless of the size of the market.


title:
Holographic polymer-dispersed liquid crystal Bragg grating integrated
  inside a solid core photonic crystal fiber

abstract:
  A polymer/liquid crystal-based fiber Bragg grating (PLC-FBG) is fabricated
with visible two-beam holography by photo-induced modulation of a
pre-polymer/LC solution infiltrated into the hollow channels of a solid core
photonic crystal fiber (PCF). The fabrication process and effects related to
the photonic bandgap guidance into the infiltrated PCF, and characterization of
the PLC-FBG are discussed. Experimental data here presented, demonstrate that
the liquid crystal inclusions of the PLC-FBG lead to high thermal and bending
sensitivities. The microscopic behavior of the polymer/liquid crystal phase
separation inside the PCF capillaries is examined using scanning electron
microscopy, while further discussed.


title:
Higgs Boson Decay Constraints on a Model with a Universal Extra
  Dimension

abstract:
  We investigate the impact of the latest data on Higgs boson branching ratios
on the minimal model with a Universal Extra Dimension (mUED). Combining
constraints from vacuum stability requirements with these branching ratio
measurements we are able to make realistic predictions for the signal strengths
in this model. We use these to find a lower bound of 1.3 TeV on the size
parameter $R^{-1}$ of the model at 95% confidence level, which is far more
stringent than any other reliable bound obtained till now.


title:
The Fried average entropy and slow entropy for actions of higher rank
  abelian groups

abstract:
  We consider two numerical entropy--type invariants for actions of $\Zk$,
invariant under a choice of generators and well-adapted for smooth actions
whose individual elements have positive entropy. We concentrate on the maximal
rank case, i.e. $\Zk,\,k\ge 2$ actions on $k+1$-dimensional manifolds. In this
case we show that for a fixed dimension (or, equivalently, rank) each of the
invariants determines the other and their values are closely related to
regulators in algebraic number fields. In particular, in contrast with the
classical case of $\mathbb Z$ actions the entropies of ergodic maximal rank
actions take only countably many values. Our main result is the dichotomy that
is best expressed under the assumption of weak mixing or, equivalently, no
periodic factors: either both invariants vanish, or their values are bounded
away from zero by universal constants. Furthermore, the lower bounds grow with
dimension: for the first invariant (the Fried average entropy) exponentially,
and for the second (the slow entropy) linearly.


title: The Complexity of Order Type Isomorphism

abstract:
  The order type of a point set in $R^d$ maps each $(d{+}1)$-tuple of points to
its orientation (e.g., clockwise or counterclockwise in $R^2$). Two point sets
$X$ and $Y$ have the same order type if there exists a mapping $f$ from $X$ to
$Y$ for which every $(d{+}1)$-tuple $(a_1,a_2,\ldots,a_{d+1})$ of $X$ and the
corresponding tuple $(f(a_1),f(a_2),\ldots,f(a_{d+1}))$ in $Y$ have the same
orientation. In this paper we investigate the complexity of determining whether
two point sets have the same order type. We provide an $O(n^d)$ algorithm for
this task, thereby improving upon the $O(n^{\lfloor{3d/2}\rfloor})$ algorithm
of Goodman and Pollack (1983). The algorithm uses only order type queries and
also works for abstract order types (or acyclic oriented matroids). Our
algorithm is optimal, both in the abstract setting and for realizable points
sets if the algorithm only uses order type queries.


title:
Switching of perpendicular magnetization by spin-orbit torques in the
  absence of external magnetic fields

abstract:
  Magnetization switching by current-induced spin-orbit torques (SOTs) is of
great interest due to its potential applications for ultralow-power memory and
logic devices. In order to be of technological interest, SOT effects need to
switch ferromagnets with a perpendicular (out-of-plane) magnetization.
Currently, however, this typically requires the presence of an in-plane
external magnetic field, which is a major obstacle for practical applications.
Here we report for the first time on SOT-induced switching of out-of-plane
magnetized Ta/Co20Fe60B20/TaOx structures without the need for any external
magnetic fields, driven by in-plane currents. This is achieved by introducing a
lateral structural asymmetry into our devices during fabrication. The results
show that a new field-like SOT is induced by in-plane currents in such
asymmetric structures. The direction of the current-induced effective field
corresponding to this new field-like SOT is out-of-plane, which facilitates
switching of perpendicular magnets. This work thus provides a pathway towards
bias-field-free SOT devices.


title: Limits on Lorentz and CPT violation from double beta decay

abstract:
  Deviations from Lorentz and CPT invariance in the neutrino sector and their
observable effects in double beta decay are studied. For two-neutrino double
beta decay, a spectral distortion and its properties are characterized for
different isotopes. Majorana couplings for Lorentz violation are studied and
shown to trigger neutrinoless double beta decay even for negligible Majorana
mass. Existing data are used to obtain first limits of $5 \times 10^{-9}$ for
18 individual coefficients and attainable sensitivities in current and future
experiments are presented.


title: Nonequilibrium Kinetic Study of Sintering of Dispersed Nanoparticles

abstract:
  Kinetic Monte Carlo approach is developed to study aspects of sintering of
dispersed nanoparticles of bimodal size distributions. We explore mechanisms of
neck development when sintering is initiated at elevated temperatures for
nanosize crystalline surfaces of particles of different sizes. Specifically,
the role of smaller particles fitting between larger particles, on the
sintering of the latter is considered. Formation of stable necks bridging
particles at the nanoscale was found to be governed by layering or clustering
mechanisms at the facing surfaces, with clustering leading to a much faster
formation of the bridging structure. Temperature, particle sizes and local
arrangement, as well as other geometrical factors were found to have a profound
effect on sintering mediated by a smaller particle placed in a void between
larger particles.


title:
On the Virtual Element Method for Three-Dimensional Elasticity Problems
  on Arbitrary Polyhedral Meshes

abstract:
  We explore the recently-proposed Virtual Element Method (VEM) for numerical
solution of boundary value problems on arbitrary polyhedral meshes. More
specifically, we focus on the elasticity equations in three-dimensions and
elaborate upon the key concepts underlying the first-order VEM. While the point
of departure is a conforming Galerkin framework, the distinguishing feature of
VEM is that it does not require an explicit computation of the trial and test
spaces, thereby circumventing a barrier to standard finite element
discretizations on arbitrary grids. At the heart of the method is a particular
kinematic decomposition of element deformation states which, in turn, leads to
a corresponding decomposition of strain energy. By capturing the energy of
linear deformations exactly, one can guarantee satisfaction of the engineering
patch test and optimal convergence of numerical solutions. The decomposition
itself is enabled by local projection maps that appropriately extract the rigid
body motion and constant strain components of the deformation. As we show,
computing these projection maps and subsequently the local stiffness matrices,
in practice, reduces to the computation of purely geometric quantities. In
addition to discussing aspects of implementation of the method, we present
several numerical studies in order to verify convergence of the VEM and
evaluate its performance for various types of meshes.


title:
Effect of disorder on the resistivity anisotropy near the electronic
  nematic phase transition in pure and electron-doped BaFe$_2$As$_2$

abstract:
  We show that the strain-induced resistivity anisotropy in the tetragonal
state of the representative underdoped Fe-arsenides BaFe$_2$As$_2$,
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ and Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ is
independent of disorder over a wide range of defect and impurity
concentrations. This result demonstrates that the anisotropy in the in-plane
resistivity in the paramagnetic orthorhombic state of this material is not due
to elastic scattering from anisotropic defects, and is most easily understood
in terms of an intrinsic anisotropy in the electronic structure.


title:
The two-dimensional Euler equations in Yudovich type space and
  $\mathrm{\textbf{bmo}}$-type space

abstract:
  We construct global-in-time, unique solutions of the two-dimensional Euler
equations in a Yudovich type space and a $\rm bmo$-type space. First, we show
the regularity of solutions for the two-dimensional Euler equations in the
Spanne space involving an unbounded and non-decaying vorticity. Next, we
establish an estimate with a logarithmic loss of regularity for the transport
equation in a bmo-type space by developing classical analysis tool such as the
John-Nirenberg inequality. We also optimize estimates of solutions to the
vorticity-stream formulation of the two-dimensional Euler equations with a
bi-Lipschitz vector field in bmo-type space by combining an observation
introduced by Yodovich with the so-called "quasi-conformal property" of the
incompressible.


title: Completeness of boundary traces of eigenfunctions

abstract:
  In this paper, we study the boundary traces of eigenfunctions on the boundary
of a smooth and bounded domain. An identity derived by B\"acker, F\"urstburger,
Schubert, and Steiner, expressing (in some sense) the asymptotic completeness
of the set of boundary traces in a frequency window of size O(1), is proved
both for Dirichlet and Neumann boundary conditions. We then prove a
semiclassical generalization of this identity.


title:
Time-Dependent Models for Blazar Emissions with the Second-Order Fermi
  Acceleration

abstract:
  The second-order Fermi acceleration (Fermi-II) driven by turbulence may be
responsible for the electron acceleration in blazar jets. We test this model
with time-dependent simulations. The hard electron spectrum predicted by the
Fermi-II process agrees with the hard photon spectrum of 1ES 1101-232. For
other blazars that show softer spectra, the Fermi-II model requires radial
evolution of the electron injection rate and/or diffusion coefficient in the
outflow. Such evolutions can yield a curved electron spectrum, which can
reproduce the synchrotron spectrum of Mrk 421 from the radio to the X-ray
regime.The photon spectrum in the GeV energy range of Mrk 421 is hard to fit
with a synchrotron self-Compton model. However, if we introduce an external
radio photon field with a luminosity of $4.9 \times
10^{38}~\mbox{erg}~\mbox{s}^{-1}$, GeV photons are successfully produced via
inverse Compton scattering. The temporal variability of the diffusion
coefficient or injection rate causes flare emission. The observed synchronicity
of X-ray and TeV flares implies a decrease of the magnetic field in the flaring
source region.


title: Which traces are spectral?

abstract:
  Among ideals of compact operators on a Hilbert space we identify a subclass
of those closed with respect to the logarithmic submajorization. Within this
subclass, we answer the questions asked by Pietsch \cite{Pietsch_nachrichten}
and by Dykema, Figiel, Weiss and Wodzicki \cite{DFWW}. In the first case, we
show that Lidskii-type formulae hold for every trace on such ideal. In the
second case, we provide the description of the commutator subspace associated
with a given ideal. Finally, we prove that a positive trace on an arbitrary
ideal is spectral if and only if it is monotone with respect to the logarithmic
submajorization.


title: Nuclear polarization effects in muonic atoms

abstract:
  We illustrate how nuclear polarization corrections in muonic atoms can be
formally connected to inelastic response functions of a nucleus. We first
discuss the point-nucleon approximation and then include finite-nucleon-size
corrections. As an example, we compare our ab-initio calculation of the third
Zemach moment in the muonic Helium-4 ion to previous phenomenological results.


title: An application of liaison theory to the Eisenbud-Green-Harris conjecture

abstract:
  In this paper, we apply liaison theory to the Eisenbud-Green-Harris
conjecture and prove that the conjecture holds for a certain subclass of
homogeneous ideals in the linkage class of a complete intersection ideal. In
the case of three variables, we prove that the conjecture holds for Gorenstein
ideals.


title: Crystalline Hodge cycles and Shimura curves in positive characteristics

abstract:
  In this paper, we seek an appropriate definition for a Shimura curve of Hodge
type in positive characteristics, i.e. a characterization of curves in positive
characteristics which are reduction of Shimura curve over the complex field.
Specifically, we study the liftablity of a curve in moduli space of principally
polarized abelian fourfolds over k, char k=p. We show that some conditions on
the crystalline Hodge cycles over such a curve imply that this curve can be
lifted to a Shimura curve.


title: Stationary Stability for Evolutionary Dynamics in Finite Populations

abstract:
  We demonstrate a vast expansion of the theory of evolutionary stability to
finite populations with mutation, connecting the theory of the stationary
distribution of the Moran process with the Lyapunov theory of evolutionary
stability. We define the notion of stationary stability for the Moran process
with mutation and generalizations, as well as a generalized notion of
evolutionary stability that includes mutation called an incentive stable state
(ISS) candidate. For sufficiently large populations, extrema of the stationary
distribution are ISS candidates and we give a family of Lyapunov quantities
that are locally minimized at the stationary extrema and at ISS candidates. In
various examples, including for the Moran and Wright-Fisher processes, we show
that the local maxima of the stationary distribution capture the
traditionally-defined evolutionarily stable states. The classical stability
theory of the replicator dynamic is recovered in the large population limit.
Finally we include descriptions of possible extensions to populations of
variable size and populations evolving on graphs.


title:
Resource Allocation for Cost Minimization in Limited Feedback MU-MIMO
  Systems with Delay Guarantee

abstract:
  In this paper, we design a resource allocation framework for the
delay-sensitive Multi-User MIMO (MU-MIMO) broadcast system with limited
feedback. Considering the scarcity and interrelation of the transmit power and
feedback bandwidth, it is imperative to optimize the two resources in a joint
and efficient manner while meeting the delay-QoS requirement. Based on the
effective bandwidth theory, we first obtain a closed-form expression of average
violation probability with respect to a given delay requirement as a function
of transmit power and codebook size of feedback channel. By minimizing the
total resource cost, we derive an optimal joint resource allocation scheme,
which can flexibly adjust the transmit power and feedback bandwidth according
to the characteristics of the system. Moreover, through asymptotic analysis,
some simple resource allocation schemes are presented. Finally, the theoretical
claims are validated by numerical results.


title: Generation of picosecond pulsed coherent state superpositions

abstract:
  We present the generation of approximated coherent state superpositions -
referred to as Schr\"odinger cat states - by the process of subtracting single
photons from picosecond pulsed squeezed states of light at 830 nm. The squeezed
vacuum states are produced by spontaneous parametric down-conversion (SPDC) in
a periodically poled KTiOPO4 crystal while the single photons are
probabilistically subtracted using a beamsplitter and a single photon detector.
The resulting states are fully characterized with time-resolved homodyne
quantum state tomography. Varying the pump power of the SPDC, we generated
different states which exhibit non-Gaussian behavior.


title: Connectivity for matroids based on rough sets

abstract:
  In mathematics and computer science, connectivity is one of the basic
concepts of matroid theory: it asks for the minimum number of elements which
need to be removed to disconnect the remaining nodes from each other. It is
closely related to the theory of network flow problems. The connectivity of a
matroid is an important measure of its robustness as a network. Therefore, it
is very necessary to investigate the conditions under which a matroid is
connected. In this paper, the connectivity for matroids is studied through
relation-based rough sets. First, a symmetric and transitive relation is
introduced from a general matroid and its properties are explored from the
viewpoint of matroids. Moreover, through the relation introduced by a general
matroid, an undirected graph is generalized. Specifically, the connection of
the graph can be investigated by the relation-based rough sets. Second, we
study the connectivity for matroids by means of relation-based rough sets and
some conditions under which a general matroid is connected are presented.
Finally, it is easy to prove that the connectivity for a general matroid with
some special properties and its induced undirected graph is equivalent. These
results show an important application of relation-based rough sets to matroids.


title: Matrix product is many-sorted algebra

abstract:
  It is known that a category of many-sorted algebras on pure sets of
similarity type is "concretely equivalent" to a category of single-sorted
algebras. In this paper, we characterize a single-sorted variety that
corresponds to a many-sorted variety. Such variety is also characterized by the
condition that is decomposable with respect to matrix product.


title:
Position-sensitive spectral splitting with a plasmonic nanowire on
  silicon chip

abstract:
  On-chip nanophotonics serves as the foundation for the new generation of
information technology, but it is challenged by the diffraction limit of light.
With the capabilities of confining light into (deep) subwavelength volumes,
plasmonics makes it possible to dramatically miniaturize optical devices so as
to integrate them into silicon chips. Here we demonstrate that by cascading
nano-corrugation gratings with different periodicities on silver nanowires atop
silicon, different colors can be spatially separated and chronologically
released at different grating junctions. The released light frequency depends
on the grating arrangement and corrugation periodicities. Hence the nanowire
acts as a spectral splitter for sorting/demultiplexing photons at different
nano-scale positions with a ten-femtosecond-level interval. Such nanowires can
be constructed further into compact 2D networks or circuits. We believe that
this study provides a new and promising approach for realizing
spatiotemporal-sensitive spectral splitting and optical signal processing on
nanoscales, and for general integration of nanophotonics with microelectronics.


title: A Unified Mechanism for Hydrogen Trapping at Metal Vacancies

abstract:
  Interaction between hydrogen (H) and metals is central to many materials
problems of scientific and technological importance. Chief among them is the
development of H storage and H-resistant materials. H segregation or trapping
at lattice defects, including vacancies, dislocations, grain boundaries, etc,
plays a crucial role in determining the properties of these materials. Here,
through first-principles simulations, we propose a unified mechanism involving
charge transfer induced strain destabilization to understand H segregation
behavior at vacancies. We discover that H prefers to occupy interstitials with
high pre-existing charge densities and the availability of such interstitials
sets the limit on H trapping capacity at a vacancy. Once the maximum H capacity
is reached, the dominant charge donors switch from the nearest-neighbor (NN) to
the next-nearest-neighbor (NNN) metal atoms. Accompanying with this long-range
charge transfer, a significant reorganization energy would occur, leading to
instability of the H-vacancy complex. The physical picture unveiled here
appears universal across the BCC series and is believed to be relevant to other
metals/defects as well. The insight gained from this study is expected to have
important implications for the design of H storage and H-resistant materials.


title:
Statistical and dynamical parts of the cumulants of conserved charges in
  relativistic heavy ion collisions

abstract:
  The Poisson-liked statistical fluctuations, which are caused by the finite
number of produced particles, are firstly estimated for the cumulants of
conserved charges, i.e., the cumulants of net-baryon, net-electric charge, and
net-strangeness. They turn out to be the same as those baselines derived from
Hadron Resonance Gas (HRG) model. The energy and centrality dependence of
net-proton cumulants at the Relativistic Heavy-Ion Collider (RHIC) are
demonstrated to be mainly caused by statistical fluctuations. Subtracting the
statistical fluctuations, the dynamical kurtosis of net- and total-proton from
two versions of the AMPT model and the UrQMD model at current RHIC beam
energies are presented. It is found that the observed sign change in the
kurtosis of net-proton can not be reproduced by these three transport models.
There is no significant difference between net- and total-proton kurtosis in
model calculations, in contrary to the data at RHIC.


title: Time optimal quantum control of two-qubit systems

abstract:
  We study the optimal quantum control of heteronuclear two-qubit systems
described by a Hamiltonian containing both nonlocal internal drift and local
control terms. We derive an explicit formula to compute the minimum time
required to steer the system from an initial state to a specified final state.
As applications the minimal time to implement Controlled-NOT gate, SWAP gate
and Controlled-U gate is calculated in detail. The experimental realizations of
these quantum gates are explicitly presented.


title: Off-The-Grid Spectral Compressed Sensing With Prior Information

abstract:
  Recent research in off-the-grid compressed sensing (CS) has demonstrated
that, under certain conditions, one can successfully recover a spectrally
sparse signal from a few time-domain samples even though the dictionary is
continuous. In this paper, we extend off-the-grid CS to applications where some
prior information about spectrally sparse signal is known. We specifically
consider cases where a few contributing frequencies or poles, but not their
amplitudes or phases, are known a priori. Our results show that equipping
off-the-grid CS with the known-poles algorithm can increase the probability of
recovering all the frequency components.


title: On the Benefit of Information Centric Networks for Traffic Engineering

abstract:
  Current Internet performs traffic engineering (TE) by estimating traffic
matrices on a regular schedule, and allocating flows based upon weights
computed from these matrices. This means the allocation is based upon a guess
of the traffic in the network based on its history. Information-Centric
Networks on the other hand provide a finer-grained description of the traffic:
a content between a client and a server is uniquely identified by its name, and
the network can therefore learn the size of different content items, and
perform traffic engineering and resource allocation accordingly. We claim that
Information-Centric Networks can therefore provide a better handle to perform
traffic engineering, resulting in significant performance gain.
  We present a mechanism to perform such resource allocation. We see that our
traffic engineering method only requires knowledge of the flow size (which, in
ICN, can be learned from previous data transfers) and outperforms a min-MLU
allocation in terms of response time. We also see that our method identifies
the traffic allocation patterns similar to that of min-MLU without having
access to the traffic matrix ahead of time. We show a very significant gain in
response time where min MLU is almost 50% slower than our ICN-based TE method.