title: The Capacity of Symmetric Private Information Retrieval

abstract:
  Private information retrieval (PIR) is the problem of retrieving as
efficiently as possible, one out of $K$ messages from $N$ non-communicating
replicated databases (each holds all $K$ messages) while keeping the identity
of the desired message index a secret from each individual database. Symmetric
PIR (SPIR) is a generalization of PIR to include the requirement that beyond
the desired message, the user learns nothing about the other $K-1$ messages.
The information theoretic capacity of SPIR (equivalently, the reciprocal of
minimum download cost) is the maximum number of bits of desired information
that can be privately retrieved per bit of downloaded information. We show that
the capacity of SPIR is $1-1/N$ regardless of the number of messages $K$, if
the databases have access to common randomness (not available to the user) that
is independent of the messages, in the amount that is at least $1/(N-1)$ bits
per desired message bit, and zero otherwise. Extensions to the capacity region
of SPIR and the capacity of finite length SPIR are provided.


title: Dynamics and Biases of Online Attention: The Case of Aircraft Crashes

abstract:
  The Internet not only has changed the dynamics of our collective attention,
but also through the transactional log of online activities, provides us with
the opportunity to study attention dynamics at scale. In this paper, we
particularly study attention to aircraft incidents and accidents using
Wikipedia transactional data in two different language editions, English and
Spanish. We study both the editorial activities on and the viewership of the
articles about airline crashes. We analyse how the level of attention is
influenced by different parameters such as number of deaths, airline region,
and event locale and date. We find evidence that the attention given by
Wikipedia editors to pre-Wikipedia aircraft incidents and accidents depends on
the region of the airline for both English and Spanish editions. North American
airline companies receive more prompt coverage in English Wikipedia. We also
observe that the attention given by Wikipedia visitors is influenced by the
airline region but only for events with high number of deaths. Finally we show
that the rate and time span of the decay of attention is independent of the
number of deaths and a fast decay within about a week seems to be universal. We
discuss the implications of these findings in the context of attention bias.

categories: physics.soc-ph cs.CY cs.SI physics.data-an


title: Single Spin Magnetic Resonance

abstract:
  Different approaches have improved the sensitivity of either electron or
nuclear magnetic resonance to the single spin level. For optical detection it
has essentially become routine to observe a single electron spin or nuclear
spin. Typically, the systems in use are carefully designed to allow for single
spin detection and manipulation, and of those systems, diamond spin defects
rank very high, being so robust that they can be addressed, read out and
coherently controlled even under ambient conditions and in a versatile set of
nanostructures. This renders them as a new type of sensor, which has been shown
to detect single electron and nuclear spins among other quantities like force,
pressure and temperature. Adapting pulse sequences from classic NMR and EPR,
and combined with high resolution optical microscopy, proximity to the target
sample and nanoscale size, the diamond sensors have the potential to constitute
a new class of magnetic resonance detectors with single spin sensitivity. As
diamond sensors can be operated under ambient conditions, they offer potential
application across a multitude of disciplines. Here we review the different
existing techniques for magnetic resonance, with a focus on diamond defect spin
sensors, showing their potential as versatile sensors for ultra-sensitive
magnetic resonance with nanoscale spatial resolution.


title: A short guide to pure point diffraction in cut-and-project sets

abstract:
  We briefly review the diffraction of quasicrystals and then give an
elementary alternative proof of the diffraction formula for regular
cut-and-project sets, which is based on Bochner's theorem from Fourier
analysis. This clarifies a common view that the diffraction of a quasicrystal
is determined by the diffraction of its underlying lattice. To illustrate our
approach, we will also treat a number of well-known explicitly solvable
examples.


title: Spin-multipole effects in binary black holes and the test-body limit

abstract:
  We discuss the effects of the black holes' spin-multipole structure in the
orbital dynamics of binary black holes according to general relativity,
focusing on the leading-post-Newtonian-order couplings at each order in an
expansion in the black holes' spins. We first review previous widely confirmed
results up through fourth order in spin, observe suggestive patterns therein,
and discuss how the results can be extrapolated to all orders in spin with
minimal information from the test-body limit. We then justify this
extrapolation by providing a complete derivation within the post-Newtonian
framework of a canonical Hamiltonian for a binary black hole, for generic
orbits and spin orientations, which encompasses the leading post-Newtonian
orders at all orders in spin. At the considered orders, the results reveal a
precise equivalence between arbitrary-mass-ratio two-spinning-black-hole
dynamics and the motion of a test black hole in a Kerr spacetime, as well as an
intriguing relationship to geodesic motion in a Kerr spacetime.


title: Computing area in presentations of the trivial group

abstract:
  We give polynomial-time dynamic-programming algorithms finding the areas of
words in the presentations $\langle a, b \mid a, b \rangle$ and $\langle a, b
\mid a^k, b^k; \ k \in \mathbb{N} \rangle$ of the trivial group.
  In the first of these two cases, area was studied under the name spelling
length by Majumdar, Robbins and Zyskin in the context of the design of liquid
crystals. We explain how the problem of calculating it can be reinterpreted in
terms of RNA-folding. In the second, area is what Jiang called width and
studied when counting fixed points for self-maps of a compact surface,
considered up to homotopy. In 1991 Grigorchuk and Kurchanov gave an algorithm
computing width and asked whether it could be improved to polynomial time. We
answer this affirmatively.


title: Inquiry-based learning in a first-year honors course

abstract:
  We describe a case study of a problem-solving section, using the "Harkness"
discussion method, of an honors multivariable calculus course. Students in the
problem-solving section had equivalent outcomes on exams, reported higher
ratings in self-assessments of skills, and took more math classes in the
following year, compared to students in the lecture-based sections.


title:
Emergent Structural Mechanisms for High-Density Collective Motion
  Inspired by Human Crowds

abstract:
  Collective motion of large human crowds often depends on their density. In
extreme cases like heavy metal concerts and Black Friday sales events, motion
is dominated by physical interactions instead of conventional social norms.
Here, we study an active matter model inspired by situations when large groups
of people gather at a point of common interest. Our analysis takes an approach
developed for jammed granular media and identifies Goldstone modes, soft spots,
and stochastic resonance as structurally-driven mechanisms for potentially
dangerous emergent collective motion.


title:
High spatial frequency laser induced periodic surface structure
  formation in germanium by mid-IR femtosecond pulses

abstract:
  Formation of high spatial frequency laser induced periodic surface structures
(HSFL) in germanium by femtosecond mid-IR pulses with wavelengths between
$\lambda=2.0$ and $3.6 \; \mathrm{\mu m}$ was studied with varying angle of
incidence and polarization. The period of these structures varied from
$\lambda/3$ to $\lambda/8$. A modified surface-scattering model including Drude
excitation and the optical Kerr effect explains spatial period scaling of HSFL
across the mid-IR wavelengths. Transmission electron microscopy (TEM) shows the
presence of a $30 \; \mathrm{n m}$ amorphous layer above the structure of
crystalline germanium. Various mechanisms including two photon absorption and
defect-induced amorphization are discussed as probable causes for the formation
of this layer.


title: Exact electronic bands for a periodic Poschl-Teller potential

abstract:
  We show that supersymmetry is a simple but powerful tool to exactly solve
quantum mechanics problems. Here, the supersymmetric approach is used to
analyse a quantum system with periodic P\"oschl-Teller potential, and to find
out the exact energy spectra and the corresponding band structure.


title: The Nuclear Symmetry Energy

abstract:
  The nuclear symmetry energy characterizes the variation of the binding energy
as the neutron to proton ratio of a nuclear system is varied. This is one of
the most important features of nuclear physics in general, since it is just
related to the two component nature of the nuclear systems. As such it is one
of the most relevant physical parameters that affect the physics of many
phenomena and nuclear processes. This review paper presents a survey of the
role and relevance of the nuclear symmetry energy in different fields of
research and of the accuracy of its determination from the phenomenology and
from the microscopic many-body theory. In recent years, a great interest was
devoted not only to the Nuclear Matter symmetry energy at saturation density
but also to its whole density dependence, which is an essential ingredient for
our understanding of many phenomena. We analyze the nuclear symmetry energy in
different realms of nuclear physics and astrophysics. In particular we consider
the nuclear symmetry energy in relation to nuclear structure, astrophysics of
Neutron Stars and supernovae, and heavy ion collision experiments, trying to
elucidate the connections of these different fields on the basis of the
symmetry energy peculiarities. The interplay between experimental and
observational data and theoretical developments is stressed. The expected
future developments and improvements are schematically addressed, together with
most demanded experimental and theoretical advances for the next few years.


title:
Tilt-Induced Phase Transitions in Even-Denominator Fractional Quantum
  Hall States at the ZnO Interface

abstract:
  Even denominator fractional quantum Hall states in a ZnO quantum well reveal
interesting phase transitions in a tilted magnetic field. We have analyzed the
planar electron gas in ZnO, confined in a parabolic potential in the third
dimension, perpendicular to the plane of the electron gas. Since the Landau
level gap is very small in this system we have included the screened Coulomb
potential in order to include the effects of all the Landau levels. We observe
an incompressible state - compressible state phase transition induced by the
tilted field. Additionally, the 5/2 state has been experimentally found to be
missing in this system. We however propose that a wider quantum well may help
to stabilize the incompressible phase at the 5/2 filling factor.


title: Parabolic Conjugation and Commuting Varieties

abstract:
  We consider the conjugation-action of an arbitrary upper-block parabolic
subgroup of the general linear group on the variety of nilpotent matrices in
its Lie algebra. Lie-theoretically, it is natural to wonder about the number of
orbits of this action. We translate the setup to a representation-theoretic one
and obtain a finiteness criterion which classifies all actions with only a
finite number of orbits over an arbitrary infinite field. These results are
applied to commuting varieties and nested punctual Hilbert schemes.


title:
Cross-correlating Planck CMB lensing with SDSS: Lensing-lensing and
  galaxy-lensing cross-correlations

abstract:
  We present results from cross-correlating Planck CMB lensing maps with the
Sloan Digital Sky Survey (SDSS) galaxy lensing shape catalog and BOSS galaxy
catalogs. For galaxy position vs. CMB lensing cross-correlations, we measure
the convergence signal around the galaxies in configuration space, using the
BOSS LOWZ ($z\sim0.30$) and CMASS ($z\sim0.57$) samples. With fixed Planck 2015
cosmology, doing a joint fit with the galaxy clustering measurement, for the
LOWZ (CMASS) sample we find a galaxy bias $b_g=1.75\pm0.04$ ($1.95\pm 0.02$)
and galaxy-matter cross-correlation coefficient $r_{cc}=1.0\pm0.2$ ($0.8\pm
0.1$) using $20<r_p<70h^{-1}$Mpc, consistent with results from galaxy-galaxy
lensing. Using the same scales and including the galaxy-galaxy lensing
measurements, we constrain $\Omega_m=0.284\pm0.024$ and relative calibration
bias between the CMB lensing and galaxy lensing to be
$b_\gamma=0.82^{+0.15}_{-0.14}$. The combination of galaxy lensing and CMB
lensing also allows us to measure the cosmological distance ratios (with
$z_l\sim0.3$, $z_s\sim0.5$) $\mathcal R=\frac{D_s D_{l,*}}{D_*
D_{l,s}}=2.68\pm0.29$, consistent with predictions from the Planck 2015
cosmology ($\mathcal R=2.35$). We detect the galaxy position-CMB convergence
cross-correlation at small scales, $r_p<1h^{-1}$Mpc, and find consistency with
lensing by NFW halos of mass $M_h\sim10^{13}h^{-1}M_\odot$. Finally, we measure
the CMB lensing-galaxy shear cross-correlation, finding an amplitude of
$A=0.76\pm0.23$ ($z_\text{eff}=0.35$, $\theta<2^\circ$) with respect to Planck
2015 $\Lambda$CDM predictions ($1\sigma$-level consistency). We do not find
evidence for relative systematics between the CMB and SDSS galaxy lensing.


title:
Active Ranking from Pairwise Comparisons and when Parametric Assumptions
  Don't Help

abstract:
  We consider sequential or active ranking of a set of n items based on noisy
pairwise comparisons. Items are ranked according to the probability that a
given item beats a randomly chosen item, and ranking refers to partitioning the
items into sets of pre-specified sizes according to their scores. This notion
of ranking includes as special cases the identification of the top-k items and
the total ordering of the items. We first analyze a sequential ranking
algorithm that counts the number of comparisons won, and uses these counts to
decide whether to stop, or to compare another pair of items, chosen based on
confidence intervals specified by the data collected up to that point. We prove
that this algorithm succeeds in recovering the ranking using a number of
comparisons that is optimal up to logarithmic factors. This guarantee does not
require any structural properties of the underlying pairwise probability
matrix, unlike a significant body of past work on pairwise ranking based on
parametric models such as the Thurstone or Bradley-Terry-Luce models. It has
been a long-standing open question as to whether or not imposing these
parametric assumptions allows for improved ranking algorithms. For stochastic
comparison models, in which the pairwise probabilities are bounded away from
zero, our second contribution is to resolve this issue by proving a lower bound
for parametric models. This shows, perhaps surprisingly, that these popular
parametric modeling choices offer at most logarithmic gains for stochastic
comparisons.


title:
Neutrino masses from an approximate mixing matrix with $\theta_{13}\neq
  0$

abstract:
  An approximate neutrino mixing matrix is formutated by using the standard
neutrino mixing matrix as a basis and experimental data of neutrino
oscillations as inputs. By using the resulted approximate neutrino mixing
matrix to proceed the neutrino mass matrix and constraining the resulted
neutrino mass matrix with zero texture:
$M_{\nu}(1,1)=M_{\nu}(1,3)=M_{\nu}(3,1)=0$, we can have neutrino masses as
function of mixing angle $\theta_{13}$ with normal hierarchy:
$m_{1}<m_{2}<m_{3}$. By taking the central value of mixing angle
$\theta_{13}=9^{o}$ that gives $\epsilon=0.16$ and using the squared mass
difference: $\Delta m_{32}^{2}$ for normal hierarchy, we then obtained neutrino
masses: $m_{1}=0.00847$ eV, $m_{2}=0.01215$ eV, and $m_{3}=0.05062$ eV which
can predict the squared mass difference for solar neutrino precisely with the
experimental result: $\Delta m_{21}^{2}=7.59\times 10^{-5}~{\rm eV^{2}}$


title:
Computation and Stability of Traveling Waves in Second Order Evolution
  Equations

abstract:
  The topic of this paper are nonlinear traveling waves occuring in a system of
damped waves equations in one space variable. We extend the freezing method
from first to second order equations in time. When applied to a Cauchy problem,
this method generates a comoving frame in which the solution becomes
stationary. In addition it generates an algebraic variable which converges to
the speed of the wave, provided the original wave satisfies certain spectral
conditions and initial perturbations are sufficiently small. We develop a
rigorous theory for this effect by recourse to some recent nonlinear stability
results for waves in first order hyperbolic systems. Numerical computations
illustrate the theory for examples of Nagumo and FitzHugh-Nagumo type.


title:
Insights from Synthetic Star-forming Regions: III. Calibration of
  Measurement Techniques of Star-formation Rates

abstract:
  Through an extensive set of realistic synthetic observations (produced in
Paper I), we assess in this part of the paper series (Paper III) how the choice
of observational techniques affects the measurement of star-formation rates
(SFRs) in star-forming regions. We test the accuracy of commonly used
techniques and construct new methods to extract the SFR, so that these findings
can be applied to measure the SFR in real regions throughout the Milky Way. We
investigate diffuse infrared SFR tracers such as those using 24 {\mu}m, 70
{\mu}m and total infrared emission, which have been previously calibrated for
global galaxy scales. We set up a toy model of a galaxy and show that the
infrared emission is consistent with the intrinsic SFR using extra-galactic
calibrated laws (although the consistency does not prove their reliability).
For local scales, we show that these techniques produce completely unreliable
results for single star-forming regions, which are governed by different
characteristic timescales. We show how calibration of these techniques can be
improved for single star-forming regions by adjusting the characteristic
timescale and the scaling factor and give suggestions of new calibrations of
the diffuse star-formation tracers. We show that star-forming regions that are
dominated by high-mass stellar feedback experience a rapid drop in infrared
emission once high-mass stellar feedback is turned on, which implies different
characteristic timescales. Moreover, we explore the measured SFRs calculated
directly from the observed young stellar population. We find that the measured
point sources follow the evolutionary pace of star formation more directly than
diffuse star-formation tracers.


title:
A novel high-contrast imaging technique based on optical tunneling to
  search for faint companions around bright stars at the limit of diffraction

abstract:
  We present a novel application of optical tunneling in the context of
high-angular resolution, high-contrast techniques with the aim of improving
direct imaging capabilities of faint companions in the vicinity of bright
stars. In contrast to existing techniques like coronagraphy, we apply
well-established techniques from integrated optics to exclusively extinct a
very narrow angular direction coming from the sky. This extinction is achieved
in the pupil plane and does not suffer from diffraction pattern residuals. We
give a comprehensive presentation of the underlying theory as well as first
laboratory results.


title:
The Dragonfly Nearby Galaxies Survey. I. Substantial variation in the
  diffuse stellar halos around spiral galaxies

abstract:
  Galaxies are thought to grow through accretion; as less massive galaxies are
disrupted and merge over time, their debris results in diffuse, clumpy stellar
halos enveloping the central galaxy. Here we present a study of the variation
in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies
Survey (DNGS). The survey consists of wide field, deep ($\mu_{g} > 31$ mag
arcsec$^{-2}$) optical imaging of nearby galaxies using the Dragonfly Telephoto
Array. Our sample includes eight spiral galaxies with stellar masses similar to
that of the Milky Way, inclinations of $16-90$ degrees and distances between
$7-18$ Mpc. We construct stellar mass surface density profiles from the
observed $g$-band surface brightness in combination with the $g-r$ color as a
function of radius, and compute the halo fractions from the excess stellar mass
(relative to a disk$+$bulge fit) beyond $5$ half-mass radii. We find a mean
halo fraction of $0.009 \pm 0.005$ and a large RMS scatter of
$1.01^{+0.9}_{-0.26}$ dex. The peak-to-peak scatter is a factor of $>100$ --
while some galaxies feature strongly structured halos resembling that of M31,
three of the eight have halos that are completely undetected in our data. We
conclude that spiral galaxies as a class exhibit a rich variety in stellar halo
properties, implying that their assembly histories have been highly
non-uniform. We find no convincing evidence for an environmental or stellar
mass dependence of the halo fraction in the sample.


title: On the geometrical interpretation of scale-invariant models of inflation

abstract:
  We study the geometrical properties of scale-invariant two-field models of
inflation. In particular, we show that when the field-derivative space in the
Einstein frame is maximally symmetric during inflation, the inflationary
predictions can be universal and independent of the details of the theory.


title: Directional Detection of Dark Matter with Two-Dimensional Targets

abstract:
  We propose two-dimensional materials as targets for direct detection of dark
matter. Using graphene as an example, we focus on the case where dark matter
scattering deposits sufficient energy on a valence-band electron to eject it
from the target. We show that the sensitivity of graphene to dark matter of MeV
to GeV mass can be comparable, for similar exposure and background levels, to
that of semiconductor targets such as silicon and germanium. Moreover, a
two-dimensional target is an excellent directional detector, as the ejected
electron retains information about the angular dependence of the incident dark
matter particle. This proposal can be implemented by the PTOLEMY experiment,
presenting for the first time an opportunity for directional detection of
sub-GeV dark matter.


title:
Exploring Systematic Effects in the Relation Between Stellar Mass, Gas
  Phase Metallicity, and Star Formation Rate

abstract:
  There is evidence that the well-established mass-metallicity relation in
galaxies is correlated with a third parameter: star formation rate (SFR). The
strength of this correlation may be used to disentangle the relative importance
of different physical processes (e.g., infall of pristine gas, metal-enriched
outflows) in governing chemical evolution. However, all three parameters are
susceptible to biases that might affect the observed strength of the relation
between them. We analyze possible sources of systematic error, including sample
bias, application of signal-to-noise ratio cuts on emission lines, choice of
metallicity calibration, uncertainty in stellar mass determination, aperture
effects, and dust. We present the first analysis of the relation between
stellar mass, gas phase metallicity, and SFR using strong line abundance
diagnostics from Dopita et al. (2013) for ~130,000 star-forming galaxies in the
Sloan Digital Sky Survey and provide a detailed comparison of these diagnostics
in an appendix. Using these abundance diagnostics yields a 30-55% weaker
anti-correlation between metallicity and SFR at fixed stellar mass than that
reported by Mannucci et al. (2010). We find that, for all abundance
diagnostics, the anti-correlation with SFR is stronger for the relatively few
galaxies whose current SFRs are elevated above their past average SFRs. This is
also true for the new abundance diagnostic of Dopita et al. (2016), which gives
anti-correlation between metallicity and SFR only in the high specific star
formation rate (sSFR) regime, in contrast to the recent results of Kashino et
al. (2016). The poorly constrained strength of the relation between stellar
mass, metallicity, and SFR must be carefully accounted for in theoretical
studies of chemical evolution.


title:
A combined study of source, detector and matter non-standard neutrino
  interactions at DUNE

abstract:
  We simultaneously investigate source, detector and matter non-standard
neutrino interactions at the proposed DUNE experiment. Our analysis is
performed using a Markov Chain Monte Carlo exploring the full parameter space.
We find that the sensitivity of DUNE to the standard oscillation parameters is
worsened due to the presence of non-standard neutrino interactions. In
particular, there are degenerate solutions in the leptonic mixing angle
$\theta_{23}$ and the Dirac CP-violating phase $\delta$. We also compute the
expected sensitivities at DUNE to the non-standard interaction parameters. We
find that the sensitivities to the matter non-standard interaction parameters
are substantially stronger than the current bounds (up to a factor of about
15). Furthermore, we discuss correlations between the source/detector and
matter non-standard interaction parameters and find a degenerate solution in
$\theta_{23}$. Finally, we explore the effect of statistics on our results.


title:
CARMA Large Area Star Formation Survey: Dense Gas in the Young L1451
  Region of Perseus

abstract:
  We present a 3 mm spectral line and continuum survey of L1451 in the Perseus
Molecular Cloud. These observations are from the CARMA Large Area Star
Formation Survey (CLASSy), which also imaged Barnard 1, NGC 1333, Serpens Main
and Serpens South. L1451 is the survey region with the lowest level of star
formation activity---it contains no confirmed protostars. HCO+, HCN, and N2H+
(J=1-0) are all detected throughout the region, with HCO+ the most spatially
widespread, and molecular emission seen toward 90% of the area above N(H_2)
column densities of 1.9x10^21 cm^-2. HCO+ has the broadest velocity dispersion,
near 0.3 km/s on average, compared to ~0.15 km/s for the other molecules, thus
representing a range from supersonic to subsonic gas motions. Our non-binary
dendrogram analysis reveals that the dense gas traced by each molecule has
similar hierarchical structure, and that gas surrounding the candidate first
hydrostatic core (FHSC), L1451-mm, and other previously detected single-dish
continuum clumps have similar hierarchical structure; this suggests that
different sub-regions of L1451 are fragmenting on the pathway to forming young
stars. We determined the three-dimensional morphology of the largest detectable
dense gas structures to be relatively ellipsoidal compared to other CLASSy
regions, which appeared more flattened at largest scales. A virial analysis
shows the most centrally condensed dust structures are likely unstable against
collapse. Additionally, we identify a new spherical, centrally condensed N2H+
feature that could be a new FHSC candidate. The overall results suggest L1451
is a young region starting to form its generation of stars within turbulent,
hierarchical structures.


title: The LPM effect in sequential bremsstrahlung: dimensional regularization

abstract:
  The splitting processes of bremsstrahlung and pair production in a medium are
coherent over large distances in the very high energy limit, which leads to a
suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. Of recent
interest is the case when the coherence lengths of two consecutive splitting
processes overlap (which is important for understanding corrections to standard
treatments of the LPM effect in QCD). In previous papers, we have developed
methods for computing such corrections without making soft-gluon
approximations. However, our methods require consistent treatment of canceling
ultraviolet (UV) divergences associated with coincident emission times, even
for processes with tree-level amplitudes. In this paper, we show how to use
dimensional regularization to properly handle the UV contributions. We also
present a simple diagnostic test that any consistent UV regularization method
for this problem needs to pass.


title:
The JCMT Gould Belt Survey: A First Look at Southern Orion A with
  SCUBA-2

abstract:
  We present the JCMT Gould Belt Survey's first look results of the southern
extent of the Orion A Molecular Cloud ($\delta \leq
-5\mathrm{:}31\mathrm{:}27.5$). Employing a two-step structure identification
process, we construct individual catalogues for large-scale regions of
significant emission labelled as islands and smaller-scale subregions called
fragments using the 850 $\mu$m continuum maps obtained using SCUBA-2. We
calculate object masses, sizes, column densities, and concentrations. We
discuss fragmentation in terms of a Jeans instability analysis and highlight
interesting structures as candidates for follow-up studies. Furthermore, we
associate the detected emission with young stellar objects (YSOs) identified by
Spitzer and Herschel. We find that although the population of active
star-forming regions contains a wide variety of sizes and morphologies, there
is a strong positive correlation between the concentration of an emission
region and its calculated Jeans instability. There are, however, a number of
highly unstable subregions in dense areas of the map that show no evidence of
star formation. We find that only $\sim$72\% of the YSOs defined as Class 0+I
and flat-spectrum protostars coincide with dense 850 $\mu$m emission structures
(column densities $>3.7\times10^{21}\mathrm{\:cm}^{-2}$). The remaining 28\% of
these objects, which are expected to be embedded in dust and gas, may be
misclassified. Finally, we suggest that there is an evolution in the velocity
dispersion of young stellar objects such that sources which are more evolved
are associated with higher velocities.


title:
Hiding Planets Behind a Big Friend: Mutual Inclinations of Multi-Planet
  Systems with External Companions

abstract:
  The {\it Kepler} mission has detected thousands of planetary systems with 1-7
transiting planets packed within 0.7~au from their host stars. There is an
apparent excess of single-transit planet systems that cannot be explained by
transit geometries alone, when a single planetary mutual inclination dispersion
is assumed. This suggests that the observed compact planetary systems have at
least two different architectures. We present a scenario where the "Kepler
dichotomy" may be explained by the action of an external giant planet or
stellar companion misaligned with the inner multi-planet system. The external
companion excites mutual inclinations of the inner planets, causing such
systems to appear as "Kepler singles" in transit surveys. We derive approximate
analytic expressions (in various limiting regimes), calibrated with numerical
calculations, for the mutual inclination excitations for various planetary
systems and perturber properties (mass $m_p$, semi-major axis $a_p$ and
inclination $\theta_p$). In general, the excited mutual inclination increases
with $m_p/a_p^3$ and $\theta_p$, although secular resonances may lead to large
mutual inclinations even for small $\theta_p$. We discuss the implications of
our results for understanding the dynamical history of transiting planet
systems with known external perturbers.


title: Anisotropic expansion of a thermal dipolar Bose gas

abstract:
  We report on the anisotropic expansion of ultracold bosonic dysprosium gases
at temperatures above quantum degeneracy and develop a quantitative theory to
describe this behavior. The theory expresses the post-expansion aspect ratio in
terms of temperature and microscopic collisional properties by incorporating
Hartree-Fock mean-field interactions, hydrodynamic effects, and
Bose-enhancement factors. Our results extend the utility of expansion imaging
by providing accurate thermometry for dipolar thermal Bose gases, reducing
error in expansion thermometry from tens of percent to only a few percent.
Furthermore, we present a simple method to determine scattering lengths in
dipolar gases, including near a Feshbach resonance, through observation of
thermal gas expansion.


title:
Generalized Electromagnetism of Subdimensional Particles: A Spin Liquid
  Story

abstract:
  It has recently been shown that there exists a class of stable gapless spin
liquids in 3+1 dimensions described by higher rank tensor U(1) gauge fields,
giving rise to an emergent tensor electromagnetism. The tensor gauge field of
these theories couples naturally to subdimensional particles (such as
fractons), which are restricted by gauge invariance to move only along
lower-dimensional subspaces of the system. We here work out some of the basic
generalized electromagnetic properties of subdimensional particles coupled to
tensor electromagnetism, such as generalized electrostatic fields, potential
formulations, Lorentz forces, Maxwell equations, and Biot-Savart laws. Some
concepts from conventional electromagnetism will carry over directly, while
others require significant modification.


title:
Striations in the Taurus molecular cloud: Kelvin-Helmholtz instability
  or MHD waves?

abstract:
  The origin of striations aligned along the local magnetic field direction in
the translucent envelope of the Taurus molecular cloud is examined with new
observations of 12CO and 13CO J=2-1 emission obtained with the 10~m
submillimeter telescope of the Arizona Radio Observatory. These data identify a
periodic pattern of excess blue and redshifted emission that is responsible for
the striations. For both 12CO and 13CO, spatial variations of the J=2-1 to
J=1-0 line ratio are small and are not spatially correlated with the striation
locations. A medium comprised of unresolved CO emitting substructures (cells)
with a beam area filling factor less than unity at any velocity is required to
explain the average line ratios and brightness temperatures. We propose that
the striations result from the modulation of velocities and the beam filling
factor of the cells as a result of either the Kelvin-Helmholtz instability or
magnetosonic waves propagating through the envelope of the Taurus molecular
cloud. Both processes are likely common features in molecular clouds that are
sub-Alfvenic and may explain low column density, cirrus-like features similarly
aligned with the magnetic field observed throughout the interstellar medium in
far-infrared surveys of dust emission.


title:
Consistent parameter fixing in the quark-meson model with vacuum
  fluctuations

abstract:
  We revisit the renormalization prescription for the quark-meson model in an
extended mean-field approximation, where vacuum quark fluctuations are
included. At a given cutoff scale the model parameters are fixed by fitting
vacuum quantities, typically including the sigma-meson mass $m_\sigma$ and the
pion decay constant $f_\pi$. In most publications the latter is identified with
the expectation value of the sigma field, while for $m_\sigma$ the curvature
mass is taken. When quark loops are included, this prescription is however
inconsistent, and the correct identification involves the renormalized pion
decay constant and the sigma pole mass. In the present article we investigate
the influence of the parameter-fixing scheme on the phase structure of the
model at finite temperature and chemical potential. Despite large differences
between the model parameters in the two schemes, we find that in homogeneous
matter the effect on the phase diagram is relatively small. For inhomogeneous
phases, on the other hand, the choice of the proper renormalization
prescription is crucial. In particular, we show that if renormalization effects
on the pion decay constant are not considered, the model does not even present
a well-defined renormalized limit when the cutoff is sent to infinity.


title:
Uncovering the hidden quantum critical point in disordered massless
  Dirac and Weyl semi-metals

abstract:
  We study the properties of the avoided or hidden quantum critical point
(AQCP) in three dimensional Dirac and Weyl semi-metals in the presence of short
range potential disorder. By computing the averaged density of states (along
with its second and fourth derivative at zero energy) with the kernel
polynomial method (KPM) we systematically tune the effective length scale that
eventually rounds out the transition and leads to an AQCP. We show how to
determine the strength of the avoidance, establishing that it is not controlled
by the long wavelength component of the disorder. Instead, the amount of
avoidance can be adjusted via the tails of the probability distribution of the
local random potentials. A binary distribution with no tails produces much less
avoidance than a Gaussian distribution. We introduce a double Gaussian
distribution to interpolate between these two limits. As a result we are able
to make the length scale of the avoidance sufficiently large so that we can
accurately study the properties of the underlying transition (that is
eventually rounded out), unambiguously identify its location, and provide
accurate estimates of the critical exponents $\nu=1.01\pm0.06$ and
$z=1.50\pm0.04$. We also show that the KPM expansion order introduces an
effective length scale that can also round out the transition in the scaling
regime near the AQCP.


title: Nonparametric Maximum Entropy Probability Density Estimation

abstract:
  Given a sample of independent and identically distributed random variables, a
novel nonparametric maximum entropy method is presented to estimate the
underlying continuous univariate probability density function (pdf). Estimates
are found by maximizing a log-likelihood function based on single order
statistics after transforming through a sequence of trial cumulative
distribution functions that iteratively improve using a Monte Carlo random
search method. Improvement is quantified by assessing the random variables
against the statistical properties of sampled uniform random data. Quality is
determined using an empirically derived scoring function that is scaled to be
sample size invariant. The scoring function identifies atypical fluctuations,
for which threshold values are set to define objective criteria that prevent
under-fitting as trial iterations continue to improve the model pdf, and,
stopping the iteration cycle before over-fitting occurs. No prior knowledge
about the data is required. An ensemble of pdf models is used to reflect
uncertainties due to statistical fluctuations in random samples, and the
quality of the estimates is visualized using scaled residual quantile plots
that show deviations from size-invariant statistics. These considerations
result in a tractable method that holistically employs key principles of random
variables and their statistical properties combined with employing orthogonal
basis functions and data-driven adaptive algorithms. Benchmark tests show that
the pdf estimates readily converge to the true pdf as sample size increases.
Robust results are demonstrated on several test probability densities that
include cases with discontinuities, multi-resolution scales, heavy tails and
singularities in the pdf, suggesting a generally applicable approach for
statistical inference.


title:
Constraining stochastic gravitational wave background from weak lensing
  of CMB B-modes

abstract:
  A stochastic gravitational wave background (SGWB) will affect the CMB
anisotropies via weak lensing. Unlike weak lensing due to large scale structure
which only deflects photon trajectories, a SGWB has an additional effect of
rotating the polarization vector along the trajectory. We study the relative
importance of these two effects, deflection \& rotation, specifically in the
context of E-mode to B-mode power transfer caused by weak lensing due to SGWB.
Using weak lensing distortion of the CMB as a probe, we derive constraints on
the spectral energy density ($\Omega_{GW}$) of the SGWB, sourced at different
redshifts, without assuming any particular model for its origin. We present
these bounds on $\Omega_{GW}$ for different power-law models characterizing the
SGWB, indicating the threshold above which observable imprints of SGWB must be
present in CMB.


title: Multicritical behavior in dissipative Ising models

abstract:
  We analyze theoretically the many-body dynamics of a dissipative Ising model
in a transverse field using a variational approach. We find that the steady
state phase diagram is substantially modified compared to its equilibrium
counterpart, including the appearance of a multicritical point belonging to a
different universality class. Building on our variational analysis, we
establish a field-theoretical treatment corresponding to a dissipative variant
of a Ginzburg-Landau theory, which allows us to compute the upper critical
dimension of the system. Finally, we present a possible experimental
realization of the dissipative Ising model using ultracold Rydberg gases.


title: Filtering interlopers from galaxy surveys

abstract:
  We present Intercut, a Python-based program that applies secondary line
identification and photometric cuts to mock galaxy surveys, in order to
simulate interloper identification. This program can be used to optimize the
removal of interloper contamination in upcoming surveys. Intercut reads a mock
galaxy survey and an emission line sensitivity and simulates interloper removal
through secondary line identification and broad-band photometry. This program
is designed to use the COSMOS mock catalog, although the program can be
modified for an alternative mock catalog. The output of the program returns an
interloper fraction for each emission line, as well as the total fraction over
all lines, as a function of redshift. We test Intercut by predicting interloper
rates for the WFIRST emission line sensitivity, finding agreement with previous
work. This program is publically available on Github


title:
The eras of radiation, matter, and dark energy: new information from the
  Planck Collaboration

abstract:
  Data released by the Planck Collaboration in 2015 imply new dates for the era
of radiation, the era of matter, and the era of dark energy. The era of
radiation ended, and the era of matter began, when the density of radiation
dropped below that of matter. This happened 50,953 \pm 2236 years after the
time of infinite redshift when the ratio a(t)/a_0 of scale factors was (2.9332
\pm 0.0711) x 10^{-4}. The era of matter ended, and the era of dark energy
began, when the density of matter dropped below that of dark energy (assumed
constant). This happened 10.1928 \pm 0.0375 Gyr after the time of infinite
redshift when the scale-factor ratio was 0.7646 \pm 0.0168. The era of dark
energy started 3.606 billion years ago.
  In this pedagogical paper, five figures trace the evolution of the densities
of radiation and matter, the scale factor, and the redshift through the eras of
radiation, matter, and dark energy.


title:
Technical Report: Towards a Universal Code Formatter through Machine
  Learning

abstract:
  There are many declarative frameworks that allow us to implement code
formatters relatively easily for any specific language, but constructing them
is cumbersome. The first problem is that "everybody" wants to format their code
differently, leading to either many formatter variants or a ridiculous number
of configuration options. Second, the size of each implementation scales with a
language's grammar size, leading to hundreds of rules.
  In this paper, we solve the formatter construction problem using a novel
approach, one that automatically derives formatters for any given language
without intervention from a language expert. We introduce a code formatter
called CodeBuff that uses machine learning to abstract formatting rules from a
representative corpus, using a carefully designed feature set. Our experiments
on Java, SQL, and ANTLR grammars show that CodeBuff is efficient, has excellent
accuracy, and is grammar invariant for a given language. It also generalizes to
a 4th language tested during manuscript preparation.


title:
An Asymptotic Preserving Maxwell Solver Resulting in the Darwin Limit of
  Electrodynamics

abstract:
  In plasma simulations, where the speed of light divided by a characteristic
length is at a much higher frequency than other relevant parameters in the
underlying system, such as the plasma frequency, implicit methods begin to play
an important role in generating efficient solutions in these multi-scale
problems. Under conditions of scale separation, one can rescale Maxwell's
equations in such a way as to give a magneto static limit known as the Darwin
approximation of electromagnetics. In this work, we present a new approach to
solve Maxwell's equations based on a Method of Lines Transpose (MOL$^T$)
formulation, combined with a fast summation method with computational
complexity $O(N\log{N})$, where $N$ is the number of grid points (particles).
Under appropriate scaling, we show that the proposed schemes result in
asymptotic preserving methods that can recover the Darwin limit of
electrodynamics.


title: Highly efficient light-emitting diodes based on intramolecular rotation

abstract:
  The efficiency of an organic light-emitting diode (OLED) is fundamentally
governed by the spin of recombining electron-hole pairs (singlet and triplet
excitons), since triplets cannot usually emit light. The singlet-triplet energy
gap, a key factor for efficient utilization of triplets, is normally positive.
Here we show that in a family of materials with amide donor and carbene
acceptor moieties linked by a metal, this energy gap for singlet and triplet
excitons with charge-transfer character can be tuned from positive to negative
values via the rotation of donor and acceptor about the metal-amide bond. When
the gap is close to zero, facile intersystem crossing is possible, enabling
efficient emission from singlet excitons. We demonstrate solution-processed
LEDs with exceptionally high quantum efficiencies (near-100% internal and >27%
external quantum efficiencies), and current and power efficiencies (87 cd/A and
75 lm/W) comparable to, or exceeding, those of state-of-the-art
vacuum-processed OLEDs and quantum dot LEDs.


title:
Correlations in quantum thermodynamics: Heat, work, and entropy
  production

abstract:
  We provide a characterization of energy in the form of exchanged heat and
work between two interacting constituents of a closed, bipartite, correlated
quantum system. By defining a binding energy we derive a consistent quantum
formulation of the first law of thermodynamics, in which the role of
correlations becomes evident, and this formulation reduces to the standard
classical picture in relevant systems. We next discuss the emergence of the
second law of thermodynamics under certain---but fairly general---conditions
such as the Markovian assumption. We illustrate the role of correlations and
interactions in thermodynamics through two examples.


title: Infrared vertically-illuminated photodiode for chip alignment feedback

abstract:
  We report on vertically-illuminated photodiodes fabricated in the
GlobalFoundries 45nm 12SOI node and on a packaging concept for
optically-interconnected chips. The photodiodes are responsive at 1180 nm, a
wavelength currently used in chip-to-chip communications. They have further a
wide field-of-view which enables chip-to-board positional feedback in
chip-board assemblies. Monolithic integration enables on-chip processing of the
positional data.


title:
The origin of most massive black holes at high-z: BLUETIDES and the next
  quasar frontier

abstract:
  The growth of the most massive black holes in the early universe, consistent
with the detection of highly luminous quasars at $z> 6$ implies sustained,
critical accretion of material to grow and power them. Given a black hole seed
scenario, it is still uncertain which conditions in the early Universe allow
the fastest black hole growth. Large scale hydrodynamical cosmological
simulations of structure formation allow us to explore the conditions conducive
to the growth of the earliest supermassive black holes. We use the cosmological
hydrodynamic simulation BlueTides, which incorporates a variety of baryon
physics in a (400 Mpc/h)^3 volume with 0.7 trillion particles to follow the
earliest phases of black hole critical growth. At z=8 the most massive black
holes (a handful) approach masses of 10^8 Msun with the most massive (with M_BH
= 4 x 10^8 Msun ) being found in an extremely compact spheroid-dominated host
galaxy. Examining the large-scale environment of hosts, we find that the
initial tidal field is more important than overdensity in setting the
conditions for early BH growth. In regions of low tidal fields gas accretes
'cold' onto the black hole and falls along thin, radial filaments straight into
the center forming the most compact galaxies and most massive black holes at
earliest times. Regions of high tidal fields instead induce larger coherent
angular momenta and influence the formation of the first population of massive
compact disks. The extreme early growth depends on the early interplay of high
gas densities and the tidal field that shapes the mode of accretion. Mergers
play a minor role in the formation of the first generation, rare massive BHs.


title:
Fourier Coefficients for Degenerate Eisenstein Series and the Descending
  Decomposition

abstract:
  We determine the unipotent orbits attached to degenerate Eisenstein series on
general linear groups. This confirms a conjecture of David Ginzburg. This also
shows that any unipotent orbit of general linear groups does occur as the
unipotent orbit attached to a specific automorphic representation. The key
ingredient is a root-theoretic result. To prove it, we introduce the notion of
the descending decomposition, which expresses every Weyl group element as a
product of simple reflections in a certain way. It is suitable for induction
and allows us to translate the question into a combinatorial statement.


title: A Reverse Shock in GRB 160509A

abstract:
  We present the second multi-frequency radio detection of a reverse shock in a
$\gamma$-ray burst. By combining our extensive radio observations of the
Fermi-LAT GRB 160509A at $z = 1.17$ up to $20$ days after the burst with Swift
X-ray observations and ground-based optical and near-infrared data, we show
that the afterglow emission comprises distinct reverse shock and forward shock
contributions: the reverse shock emission dominates in the radio band at
$\lesssim10~$days, while the forward shock emission dominates in the X-ray,
optical, and near-infrared bands. Through multi-wavelength modeling, we
determine a circumburst density of $n_0\approx10^{-3}~$cm$^{-3}$, supporting
our previous suggestion that a low-density circumburst environment is conducive
to the production of long-lasting reverse shock radiation in the radio band. We
infer the presence of a large excess X-ray absorption column, $N_{\rm H}
\approx 1.5\times10^{22}~$cm$^{-2}$, and a high rest-frame optical extinction,
$A_{\rm V}\approx3.4~$mag. We identify a jet break in the X-ray light curve at
$t_{\rm jet}\approx6~$d, and thus derive a jet opening angle of $\theta_{\rm
jet}\approx4~$deg, yielding a beaming-corrected kinetic energy and radiated
$\gamma$-ray energy of $E_{\rm K}\approx4\times10^{50}~$erg and
$E_{\gamma}\approx1.3\times10^{51}~$erg ($1$-$10^4~$keV, rest frame),
respectively. Consistency arguments connecting the forward and reverse shocks
suggest a deceleration time of $t_{\rm dec} \approx 460~$s$~\approx T_{90}$, a
Lorentz factor of $\Gamma(t_{\rm dec})\approx330$, and a reverse shock to
forward shock fractional magnetic energy density ratio of $R_{\rm
B}\equiv\epsilon_{\rm B,RS}/\epsilon_{\rm B,FS}\approx8$.


title: Structure-based prediction of protein-folding transition paths

abstract:
  We propose a general theory to describe the distribution of protein-folding
transition paths. We show that transition paths follow a predictable sequence
of high-free-energy transient states that are separated by free-energy
barriers. Each transient state corresponds to the assembly of one or more
discrete, cooperative units, which are determined directly from the native
structure. We show that the transition state on a folding pathway is reached
when a small number of critical contacts are formed between a specific set of
substructures, after which folding proceeds downhill in free energy. This
approach suggests a natural resolution for distinguishing parallel folding
pathways and provides a simple means to predict the rate-limiting step in a
folding reaction. Our theory identifies a common folding mechanism for proteins
with diverse native structures and establishes general principles for the
self-assembly of polymers with specific interactions.


title:
Parabolic Anderson Model with space-time homogeneous Gaussian noise and
  rough initial condition

abstract:
  In this article, we study the Parabolic Anderson Model driven by a space-time
homogeneous Gaussian noise on $\mathbb{R}_{+} \times \mathbb{R}^d$, whose
covariance kernels in space and time are locally integrable non-negative
functions, which are non-negative definite (in the sense of distributions). We
assume that the initial condition is given by a signed Borel measure on
$\mathbb{R}^d$, and the spectral measure of the noise satisfies Dalang's (1999)
condition. Under these conditions, we prove that this equation has a unique
solution, and we investigate the magnitude of the $p$-th moments of the
solution, for any $p \geq 2$. In addition, we show that this solution has a
H\"older continuous modification with the same regularity and under the same
condition as in the case of the white noise in time, regardless of the temporal
covariance function of the noise.


title:
Randomized coverings of a convex body with its homothetic copies, and
  illumination

abstract:
  We present a probabilistic model of illuminating a convex body by
independently distributed light sources. In addition to recovering C.A. Rogers'
upper bounds for the illumination number, we improve previous estimates of J.
Januszewski and M. Nasz\'odi for a generalized version of the illumination
parameter.


title:
Production of highly-polarized positrons using polarized electrons at
  MeV energies

abstract:
  The Polarized Electrons for Polarized Positrons experiment at the injector of
the Continuous Electron Beam Accelerator Facility has demonstrated for the
first time the efficient transfer of polarization from electrons to positrons
produced by the polarized bremsstrahlung radiation induced by a polarized
electron beam in a high-$Z$ target. Positron polarization up to 82\% have been
measured for an initial electron beam momentum of 8.19~MeV/$c$, limited only by
the electron beam polarization. This technique extends polarized positron
capabilities from GeV to MeV electron beams, and opens access to polarized
positron beam physics to a wide community.


title:
Probing the Stau-Neutralino Coannihilation Region at the LHC with a soft
  tau lepton and an ISR jet

abstract:
  We present a feasibility study, to search for dark matter at the LHC, in
events with one soft hadronically decaying tau lepton and missing transverse
energy recoiling against a hard $p_{T}$ jet from initial state radiation. This
methodology allows the search for Supersymmetry in compressed mass spectra
regions, where the mass difference between the lightest neutralino,
$\tilde\chi_1^0$, and the stau (the tau superpartner), $\tilde{\tau}$, is
small. Several theoretical models predict a direct connection between thermal
Bino dark matter and staus within this scenario. We show that compressed
regions, not excluded by ATLAS nor CMS experiments, are opened up with the
increase in experimental sensitivity reached with the proposed methodology. The
requirement of a hard jet from initial state radiation combined with a soft tau
lepton is effective in reducing Standard Model backgrounds, providing expected
significances greater than 3$\sigma$ for $\tilde{\chi}_{1}^{\pm}$ masses up to
300 GeV and $\tilde{\tau}$-$\tilde{\chi}_{1}^{0}$ mass gaps below 25 GeV with
only 30 fb$^{-1}$ of 13 TeV data from the LHC.


title: BlackHoleCam: fundamental physics of the Galactic center

abstract:
  Einstein's General Theory of Relativity (GR) successfully describes gravity.
The most fundamental predictions of GR are black holes (BHs), but in spite of
many convincing BH candidates in the Universe, there is no conclusive
experimental proof of their existence using astronomical observations in the
electromagnetic spectrum. Are BHs real astrophysical objects? Does GR hold in
its most extreme limit or are alternatives needed? The prime target to address
these fundamental questions is in the center of our own Galaxy, which hosts the
closest and best-constrained supermassive BH candidate in the Universe,
Sagittarius A* (Sgr A*). Three different types of experiments hold the promise
to test GR in a strong-field regime using observations of Sgr A* with
new-generation instruments. The first experiment aims to image the relativistic
plasma emission which surrounds the event horizon and forms a "shadow" cast
against the background, whose predicted size (~50 microarcseconds) can now be
resolved by upcoming VLBI experiments at mm-waves such as the Event Horizon
Telescope (EHT). The second experiment aims to monitor stars orbiting Sgr A*
with the upcoming near-infrared interferometer GRAVITY at the Very Large
Telescope (VLT). The third experiment aims to time a radio pulsar in tight
orbit about Sgr A* using radio telescopes (including the Atacama Large
Millimeter Array or ALMA). The BlackHoleCam project exploits the synergy
between these three different techniques and aims to measure the main BH
parameters with sufficient precision to provide fundamental tests of GR and
probe the spacetime around a BH in any metric theory of gravity. Here, we
review our current knowledge of the physical properties of Sgr A* as well as
the current status of such experimental efforts towards imaging the event
horizon, measuring stellar orbits, and timing pulsars around Sgr A*.


title: Classically stable non-singular cosmological bounces

abstract:
  One of the fundamental questions of theoretical cosmology is whether the
universe can undergo a non-singular bounce, i.e., smoothly transit from a
period of contraction to a period of expansion through violation of the null
energy condition (NEC) at energies well below the Planck scale and at finite
values of the scale factor such that the entire evolution remains classical. A
common claim has been that a non-singular bounce either leads to ghost or
gradient instabilities or a cosmological singularity. In this letter, we
examine cubic Galileon theories and present a procedure for explicitly
constructing examples of a non-singular cosmological bounce without
encountering any pathologies and maintaining a sub-luminal sound speed for
co-moving curvature modes throughout the NEC violating phase. We also discuss
the relation between our procedure and earlier work.


title:
Potential benefits of a block-space GPU approach for discrete
  tetrahedral domains

abstract:
  The study of data-parallel domain re-organization and thread-mapping
techniques are relevant topics as they can increase the efficiency of GPU
computations when working on spatial discrete domains with non-box-shaped
geometry. In this work we study the potential benefits of applying a succint
data re-organization of a tetrahedral data-parallel domain of size
$\mathcal{O}(n^3)$ combined with an efficient block-space GPU map of the form
$g:\mathbb{N} \rightarrow \mathbb{N}^3$. Results from the analysis suggest that
in theory the combination of these two optimizations produce significant
performance improvement as block-based data re-organization allows a coalesced
one-to-one correspondence at local thread-space while $g(\lambda)$ produces an
efficient block-space spatial correspondence between groups of data and groups
of threads, reducing the number of unnecessary threads from $O(n^3)$ to
$O(n^2\rho^3)$ where $\rho$ is the linear block-size and typically $\rho^3 \ll
n$. From the analysis, we obtained that a block based succint data
re-organization can provide up to $2\times$ improved performance over a linear
data organization while the map can be up to $6\times$ more efficient than a
bounding box approach. The results from this work can serve as a useful guide
for a more efficient GPU computation on tetrahedral domains found in spin
lattice, finite element and special n-body problems, among others.


title: Tracking Switched Dynamic Network Topologies from Information Cascades

abstract:
  Contagions such as the spread of popular news stories, or infectious
diseases, propagate in cascades over dynamic networks with unobservable
topologies. However, "social signals" such as product purchase time, or blog
entry timestamps are measurable, and implicitly depend on the underlying
topology, making it possible to track it over time. Interestingly, network
topologies often "jump" between discrete states that may account for sudden
changes in the observed signals. The present paper advocates a switched dynamic
structural equation model to capture the topology-dependent cascade evolution,
as well as the discrete states driving the underlying topologies. Conditions
under which the proposed switched model is identifiable are established.
Leveraging the edge sparsity inherent to social networks, a recursive
$\ell_1$-norm regularized least-squares estimator is put forth to jointly track
the states and network topologies. An efficient first-order proximal-gradient
algorithm is developed to solve the resulting optimization problem. Numerical
experiments on both synthetic data and real cascades measured over the span of
one year are conducted, and test results corroborate the efficacy of the
advocated approach.


title: Defending Non-Bayesian Learning against Adversarial Attacks

abstract:
  This paper addresses the problem of non-Bayesian learning over multi-agent
networks, where agents repeatedly collect partially informative observations
about an unknown state of the world, and try to collaboratively learn the true
state. We focus on the impact of the adversarial agents on the performance of
consensus-based non-Bayesian learning, where non-faulty agents combine local
learning updates with consensus primitives. In particular, we consider the
scenario where an unknown subset of agents suffer Byzantine faults -- agents
suffering Byzantine faults behave arbitrarily. Two different learning rules are
proposed.


title: Efficient Routing for Cost Effective Scale-out Data Architectures

abstract:
  Efficient retrieval of information is of key importance when using Big Data
systems. In large scale-out data architectures, data are distributed and
replicated across several machines. Queries/tasks to such data architectures,
are sent to a router which determines the machines containing the requested
data. Ideally, to reduce the overall cost of analytics, the smallest set of
machines required to satisfy the query should be returned by the router.
Mathematically, this can be modeled as the set cover problem, which is NP-hard,
thus making the routing process a balance between optimality and performance.
Even though an efficient greedy approximation algorithm for routing a single
query exists, there is currently no better method for processing multiple
queries than running the greedy set cover algorithm repeatedly for each query.
This method is impractical for Big Data systems and the state-of-the-art
techniques route a query to all machines and choose as a cover the machines
that respond fastest. In this paper, we propose an efficient technique to
speedup the routing of a large number of real-time queries while minimizing the
number of machines that each query touches (query span). We demonstrate that by
analyzing the correlation between known queries and performing query
clustering, we can reduce the set cover computation time, thereby significantly
speeding up routing of unknown queries. Experiments show that our incremental
set cover-based routing is 2.5 times faster and can return on average 50% fewer
machines per query when compared to repeated greedy set cover and baseline
routing techniques.


title:
A Microscopic Description of the Granular Fluidity Field in Nonlocal
  Flow Modeling

abstract:
  A recent granular rheology based on an implicit `granular fluidity' field has
been shown to quantitatively predict many nonlocal phenomena. However, the
physical nature of the field has not been identified. Here, the granular
fluidity is found to be a kinematic variable given by the velocity fluctuation
and packing fraction. This is verified with many discrete element simulations,
which show the operational fluidity definition, solutions of the fluidity
model, and the proposed microscopic formula all agree. Kinetic theoretical and
Eyring-like explanations shed insight into the obtained form.


title: New examples of higher-dimensional minimal hypersurfaces

abstract:
  The main results of the paper are Proposition 3 and 4 which provide an
effective way to construct minimal hypersurfaces in a Euclidean space. We
demonstrate our technique by several new examples. This note is English
translation of an earlier draft version written (in Russian) in September 1999.
The final version of the paper will be published somewhere else.


title:
Dynamics of the complex rational delay recursive sequence
  $\displaystyle{z_{n+1}=\frac{\alpha+\beta z_{n-k}}{\gamma - z_{n}}}$

abstract:
  Dynamics of the delay rational difference equation
$\displaystyle{z_{n+1}=\frac{\alpha+\beta z_{n-k}}{\gamma - z_{n}}}$ with
complex parameters $\alpha$, $\beta$, $\gamma$ and arbitrary complex initial
conditions is investigated. Existence of prime period two solutions and higher
order periods are ensured in the complex parameters unlike in the case of real
parameters of the same rational difference equation. In addition, a new
dynamical behavior, chaotic solutions of the difference equation are ensured
computationally.


title: Random Polygon to Ellipse: A Generalization

abstract:
  This paper generalizes the result of Elmachtoub et al to any weighted
barycenter, where a transformation is considered which takes an arbitrary point
of division $\xi \in (0,1)$ of the segments of a polygon with $n$ vertices. We
then consider connecting these new points to form another polygon, and iterate
this process. After considering properties of our generalized transformation
matrix, a surprisingly elegant interplay of elementary complex analysis and
linear algebra is used to find a closed form for our iterative process. We then
specify the new limiting ellipse, $\mathcal{E}$, which has oscillating
semi-axes. Along the way we find that the case for $\xi = 1/2$ enjoys some
special optimality conditions, and periodicity of the ellipse $\mathcal{E}$ is
analyzed as well. To conclude, an even more generalized case is considered:
taking a different point of division for every segment of our polygon
$\mathcal{P} (\vec{x}^{(0)}, \vec{y}^{(0)})$.


title:
A tractable method for describing complex couplings between neurons and
  population rate

abstract:
  Neurons within a population are strongly correlated, but how to simply
capture these correlations is still a matter of debate. Recent studies have
shown that the activity of each cell is influenced by the population rate,
defined as the summed activity of all neurons in the population. However, an
explicit, tractable model for these interactions is still lacking. Here we
build a probabilistic model of population activity that reproduces the firing
rate of each cell, the distribution of the population rate, and the linear
coupling between them. This model is tractable, meaning that its parameters can
be learned in a few seconds on a standard computer even for large population
recordings. We inferred our model for a population of 160 neurons in the
salamander retina. In this population, single-cell firing rates depended in
unexpected ways on the population rate. In particular, some cells had a
preferred population rate at which they were most likely to fire. These complex
dependencies could not be explained by a linear coupling between the cell and
the population rate. We designed a more general, still tractable model that
could fully account for these non-linear dependencies. We thus provide a simple
and computationally tractable way to learn models that reproduce the dependence
of each neuron on the population rate.


title:
First evidence of coherent $K^{+}$ meson production in neutrino-nucleus
  scattering

abstract:
  Neutrino-induced charged-current coherent kaon production,
$\nu_{\mu}A\rightarrow\mu^{-}K^{+}A$, is a rare, inelastic electroweak process
that brings a $K^+$ on shell and leaves the target nucleus intact in its ground
state. This process is significantly lower in rate than neutrino-induced
charged-current coherent pion production, because of Cabibbo suppression and a
kinematic suppression due to the larger kaon mass. We search for such events in
the scintillator tracker of MINERvA by observing the final state $K^+$, $\mu^-$
and no other detector activity, and by using the kinematics of the final state
particles to reconstruct the small momentum transfer to the nucleus, which is a
model-independent characteristic of coherent scattering. We find the first
experimental evidence for the process at $3\sigma$ significance.


title: Baryogenesis from Decaying Magnetic Helicity

abstract:
  As a result of the Standard Model chiral anomalies, baryon number is violated
in the early universe in the presence of a hypermagnetic field with varying
helicity. We investigate whether the matter / anti-matter asymmetry of the
universe can be created from the decaying helicity of a primordial
(hyper)magnetic field before and after the electroweak phase transition. In
this model, baryogenesis occurs without $(B-L)$-violation, since the $(B+L)$
asymmetry generated by the hypermagnetic field counteracts the washout by
electroweak sphalerons. At the electroweak crossover, the hypermagnetic field
becomes an electromagnetic field, which does not source $(B+L)$. Although the
sphalerons remain in equilibrium for a time, washout is avoided since the
decaying magnetic helicity sources chirality. The relic baryon asymmetry is
fixed when the electroweak sphaleron freezes out. Under reasonable assumptions,
a baryon asymmetry of $n_B / s \simeq 4 \times 10^{-12}$ can be generated from
a maximally helical, right-handed (hyper)magnetic field that has a field
strength of $B_0 \simeq 10^{-14} \, {\rm Gauss}$ and coherence length of
$\lambda_{0} \simeq 1 \, {\rm pc}$ today. Relaxing an assumption that relates
$\lambda_0$ to $B_0$, the model predicts $n_B / s \gtrsim 10^{-10}$, which
could potentially explain the observed baryon asymmetry of the universe.


title:
BFKL effects and central rapidity dependence in Mueller-Navelet jet
  production at 13 TeV LHC

abstract:
  A study of the production of Mueller-Navelet jets at 13 TeV LHC is presented,
including BFKL resummation effects and investigating three different variants
of the BLM scale optimization method. It is shown how the cross section and the
azimuthal observables are affected by the exclusion of the events where, for a
given rapidity interval between the two jets, one of these is produced in the
central region.


title:
Efficiently Inferring Pairwise Subtree Prune-and-Regraft Adjacencies
  between Phylogenetic Trees

abstract:
  We develop a time-optimal $O(mn^2)$-time algorithm to construct the subtree
prune-regraft (SPR) graph on a collection of m phylogenetic trees with n
leaves. This improves on the previous bound of $O(mn^3)$. Such graphs are used
to better understand the behaviour of phylogenetic methods and recommend
parameter choices and diagnostic criteria. The limiting factor in these
analyses has been the difficulty in constructing such graphs for large numbers
of trees. We also develop the first efficient algorithms for constructing the
nearest-neighbor interchange (NNI) and tree bisection-and-reconnection (TBR)
graphs


title: Existence of valuations with smallest normalized volume

abstract:
  Li introduced the normalized volume of a valuation due to its relation to
K-semistability. He conjectured that over a klt singularity there exists a
valuation with smallest normalized volume. We prove this conjecture and provide
an example to show that such a valuation need not be divisorial.


title: The Tune of Love and the Nature(ness) of Spacetime

abstract:
  The black hole information paradox is among the most outstanding puzzles in
physics. I argue here there is yet another black hole quandary which, in light
of the recent direct detection of gravitational waves by Advanced LIGO, reveals
a new window to probe the nature of spacetime in the forthcoming era of
'precision gravity.'


title:
On the Semantic Relationship between Probabilistic Soft Logic and Markov
  Logic

abstract:
  Markov Logic Networks (MLN) and Probabilistic Soft Logic (PSL) are widely
applied formalisms in Statistical Relational Learning, an emerging area in
Artificial Intelligence that is concerned with combining logical and
statistical AI. Despite their resemblance, the relationship has not been
formally stated. In this paper, we describe the precise semantic relationship
between them from a logical perspective. This is facilitated by first extending
fuzzy logic to allow weights, which can be also viewed as a generalization of
PSL, and then relate that generalization to MLN. We observe that the
relationship between PSL and MLN is analogous to the known relationship between
fuzzy logic and Boolean logic, and furthermore the weight scheme of PSL is
essentially a generalization of the weight scheme of MLN for the many-valued
setting.


title:
Generalized Connes-Chern characters in KK-theory with an application to
  weak invariants of topological insulators

abstract:
  We use constructive bounded Kasparov K-theory to investigate the numerical
invariants stemming from the internal Kasparov products $K_i(\mathcal A) \times
KK^i(\mathcal A, \mathcal B) \rightarrow K_0(\mathcal B) \rightarrow \mathbb
R$, $i=0,1$, where the last morphism is provided by a tracial state. For the
class of properly defined finitely-summable Kasparov $(\mathcal A,\mathcal
B)$-cycles, the invariants are given by the pairing of K-theory of $\mathcal B$
with an element of the periodic cyclic cohomology of $\mathcal B$, which we
call the generalized Connes-Chern character. When $\mathcal A$ is a twisted
crossed product of $\mathcal B$ by $\mathbb Z^k$, $\mathcal A = \mathcal B
\rtimes_\xi^\theta \mathbb Z^k$, we derive a local formula for the character
corresponding to the fundamental class of a properly defined Dirac cycle.
Furthermore, when $\mathcal B = C(\Omega) \rtimes_{\xi'}^{\phi} \mathbb Z^j$,
with $C(\Omega)$ the algebra of continuous functions over a disorder
configuration space, we show that the numerical invariants are connected to the
weak topological invariants of the complex classes of topological insulators,
defined in the physics literature. The end products are generalized index
theorems for these weak invariants, which enable us to predict the range of the
invariants and to identify regimes of strong disorder in which the invariants
remain stable. The latter will be reported in a subsequent publication.

categories: math.OA cond-mat.dis-nn math-ph math.KT math.MP


title:
The case for duality violations in the analysis of hadronic $\tau$
  decays

abstract:
  We discuss why, in the determination of $\alpha_s(m_{\tau}^2)$ from hadronic
$\tau$ decays, two important assumptions made in most of previous analyses,
namely the neglect of higher-dimension condensates and of Duality Violations
(DVs), have introduced uncontrolled systematic errors into this determination.
Although the use of pinched weights is usually offered as a justification of
these assumptions, we explain why it is not possible to simultaneously suppress
these two contributions; particularly since the Operator Product Expansion is
expected to be an asymptotic, rather than a convergent expansion. There is not
only experimental and theoretical evidence for DVs, but they also affect the
extraction of $\alpha_s(m_{\tau}^2)$.


title: $\alpha_s$ analyses from hadronic tau decays with OPAL and ALEPH data

abstract:
  Recently, we extracted the strong coupling, $\alpha_s(m_\tau^2)$, from the
revised ALEPH data for non-strange hadronic tau decays. Our analysis is based
on a method previously used for the determination of the strong coupling from
OPAL data. In our strategy, we employ different moments of the spectral
functions both with and without pinching, including Duality Violations, in
order to obtain fully self-consistent analyses that do not rely on untested
assumptions (such as the smallness of higher dimension contributions in the
OPE). Here we discuss the $\alpha_s$ values obtained from the ALEPH and the
OPAL data, the robustness of the analysis, as well as non-perturbative
contributions from DVs and the OPE. We show that, although the $\alpha_s$
determination is sound, non-perturbative effects limit the accuracy with which
one can extract the strong coupling from tau decay data. Finally, we discuss
the compatibility of the data sets and the possibility of a combined analysis.


title: Canonical idempotents of multiplicity-free families of algebras

abstract:
  Any multiplicity-free family of finite dimensional algebras has a canonical
complete set of of pairwise orthogonal primitive idempotents in each level. We
give various methods to compute these idempotents. In the case of symmetric
group algebras over a field of characteristic zero, the set of canonical
idempotents is precisely the set of seminormal idempotents constructed by
Young. As an example, we calculate the canonical idempotents for semisimple
Brauer algebras.


title: Les Vari\'et\'es de Hecke-Hilbert aux points classiques de poids $1$

abstract:
  We show that the Eigenvariety attached to Hilbert modular forms over a
totally real field $F$ is smooth at the points corresponding to certain
classical weight one theta series and we give a precise criterion for etaleness
over the weight space at those points. In the case where the theta series has
real multiplication, we construct a non-classical overconvergent generalised
eigenform and compute its Fourier coefficients in terms of $p$-adic logarithms
of algebraic numbers. Our approach uses deformations and pseudo-deformations of
Galois representations.


title: Curvature-driven molecular flows on membrane surfaces

abstract:
  Morphological change of bilayer membrane in vivo is not a spontaneous
procedure but modulated by various types of proteins in general. Most of these
modulations are associated with the localization of related proteins in the
crowded lipid environment in bilayer membrane. This work presents an
mathematical model for the localization of multiple species of diffusion
molecules on membrane surfaces. We start with the energetic description of the
distributions of molecules on curved membrane surface, by assembling the
bending energy of bilayer membrane and the entropic energy of diffusive
molecules. We introduce the spontaneous curvature of molecules in membrane, and
define the spontaneous curvature of bilayer membrane as a function of the
molecule concentrations on membrane surfaces. This connection gives rise to a
drift-diffusion equation to govern the gradient flows of the surface molecule
concentrations. We recast the energetic formulation and the related governing
equations in the Eulerian framework by using a phase field function that
defines the membrane morphology. Computational simulations with the proposed
mathematical model and related numerical techniques predict the molecular
localization on membrane surfaces at locations with preferred mean curvature.


title:
Hidden Markov Models on Variable Blocks with a Modal Clustering
  Algorithm and Applications

abstract:
  Motivated by high-throughput single-cell cytometry data with applications to
vaccine development and immunological research, we consider statistical
clustering in large-scale data that contain multiple rare clusters. We propose
a new hierarchical mixture model, namely Hidden Markov Model on Variable Blocks
(HMM-VB), and a new mode search algorithm called Modal Baum-Welch (MBW) for
efficient clustering. Exploiting the widely accepted chain-like dependence
among groups of variables in the cytometry data, we propose to treat the
hierarchy of variable groups as a figurative time line and employ a HMM-type
model, namely HMM-VB. We also propose to use mode-based clustering, aka modal
clustering, and overcome the exponential computational complexity by MBW. In a
series of experiments on simulated data HMM-VB and MBW have better performance
than existing methods. We also apply our method to identify rare cell subsets
in cytometry data and examine its strengths and limitations.


title:
On the Convergence Rate of Average Consensus and Distributed
  Optimization over Unreliable Networks

abstract:
  We consider the problems of reaching average consensus and solving
consensus-based optimization over unreliable communication networks wherein
packets may be dropped accidentally during transmission. Existing work either
assumes that the link failures affect the communication on both directions or
that the message senders {\em know exactly}, in each iteration, how many of
their outgoing links are functioning properly. In this paper, we consider
directed links, and we {\em do not} require each node know its current outgoing
degree.
  First, we propose and characterize the convergence rate of reaching average
consensus. Then we apply our robust consensus update to the classical
distributed dual averaging method wherein the consensus update is used as the
information aggregation primitive. We show that the local iterates converge to
a common optimum of the global objective at rate $O(\frac{1}{\sqrt{t}})$, where
$t$ is the number of iterations, matching the failure-free performance of the
distributed dual averaging method.


title:
knor: A NUMA-Optimized In-Memory, Distributed and Semi-External-Memory
  k-means Library

abstract:
  k-means is one of the most influential and utilized machine learning
algorithms. Its computation limits the performance and scalability of many
statistical analysis and machine learning tasks. We rethink and optimize
k-means in terms of modern NUMA architectures to develop a novel
parallelization scheme that delays and minimizes synchronization barriers. The
\textit{k-means NUMA Optimized Routine} (\textsf{knor}) library has (i)
in-memory (\textsf{knori}), (ii) distributed memory (\textsf{knord}), and (iii)
semi-external memory (\textsf{knors}) modules that radically improve the
performance of k-means for varying memory and hardware budgets. \textsf{knori}
boosts performance for single machine datasets by an order of magnitude or
more. \textsf{knors} improves the scalability of k-means on a memory budget
using SSDs. \textsf{knors} scales to billions of points on a single machine,
using a fraction of the resources that distributed in-memory systems require.
\textsf{knord} retains \textsf{knori}'s performance characteristics, while
scaling in-memory through distributed computation in the cloud. \textsf{knor}
modifies Elkan's triangle inequality pruning algorithm such that we utilize it
on billion-point datasets without the significant memory overhead of the
original algorithm. We demonstrate \textsf{knor} outperforms distributed
commercial products like H$_2$O, Turi (formerly Dato, GraphLab) and Spark's
MLlib by more than an order of magnitude for datasets of $10^7$ to $10^9$
points.


title:
Exploring high-level Perspectives on Self-Configuration Capabilities of
  Systems

abstract:
  Optimization of product performance repetitively introduces the need to make
products adaptive in a more general sense. This more general idea is often
captured under the term 'self-configuration'. Despite the importance of such
capability, research work on this feature appears isolated by technical
domains. It is not easy to tell quickly whether the approaches chosen in
different technological domains introduce new ideas or whether the differences
just reflect domain idiosyncrasies. For the sake of easy identification of key
differences between systems with self-configuring capabilities, I will explore
higher level concepts for understanding self-configuration, such as the
{\Omega}-units, in order to provide theoretical instruments for connecting
different areas of technology and research.


title:
Non-singlet coefficient functions for charged-current deep-inelastic
  scattering to the third order in QCD

abstract:
  We have calculated the coefficient functions for the structure functions F_2,
F_L and F_3 in nu-nubar charged-current deep-inelastic scattering (DIS) at the
third order in the strong coupling alpha_s, thus completing the description of
unpolarized inclusive W^(+-) exchange DIS to this order of massless
perturbative QCD. In this brief note, our new results are presented in terms of
compact approximate expressions that are sufficiently accurate for
phenomenological analyses. For the benefit of such analyses we also collect, in
a unified notation, the corresponding lower-order contributions and the flavour
non-singlet coefficient functions for nu+nubar charged-current DIS. The
behaviour of all six third-order coefficient functions at small Bjorken-x is
briefly discussed.


title:
Quantifying the effect of interannual ocean variability on the
  attribution of extreme climate events to human influence

abstract:
  In recent years, the climate change research community has become highly
interested in describing the anthropogenic influence on extreme weather events,
commonly termed "event attribution." Limitations in the observational record
and in computational resources motivate the use of uncoupled,
atmosphere/land-only climate models with prescribed ocean conditions run over a
short period, leading up to and including an event of interest. In this
approach, large ensembles of high-resolution simulations can be generated under
factual observed conditions and counterfactual conditions that might have been
observed in the absence of human interference; these can be used to estimate
the change in probability of the given event due to anthropogenic influence.
However, using a prescribed ocean state ignores the possibility that estimates
of attributable risk might be a function of the ocean state. Thus, the
uncertainty in attributable risk is likely underestimated, implying an
over-confidence in anthropogenic influence.
  In this work, we estimate the year-to-year variability in calculations of the
anthropogenic contribution to extreme weather based on large ensembles of
atmospheric model simulations. Our results both quantify the magnitude of
year-to-year variability and categorize the degree to which conclusions of
attributable risk are qualitatively affected. The methodology is illustrated by
exploring extreme temperature and precipitation events for the northwest coast
of South America and northern-central Siberia; we also provides results for
regions around the globe. While it remains preferable to perform a full
multi-year analysis, the results presented here can serve as an indication of
where and when attribution researchers should be concerned about the use of
atmosphere-only simulations.


title:
Self-dual codes and the non-existence of a quasi-symmetric 2-(37,9,8)
  design with intersection numbers 1 and 3

abstract:
  We prove that a certain binary linear code associated with the incidence
matrix of a quasi-symmetric 2-(37,9,8) design with intersection numbers 1 and 3
must be contained in an extremal doubly even self-dual code of length 40. Using
the classification of extremal doubly even self-dual codes of length 40, we
show that a quasi-symmetric 2-(37,9,8) design with intersection numbers 1 and 3
does not exist.


title: Fast and exact evaluation of box splines via the PP-form

abstract:
  For the class of non-degenerate box splines, we prove that these box splines
are piecewise polynomial. This is not a new result, it is in fact a well known
and useful property of box splines. However, our proof is constructive, and the
main result of this work is a corollary that follows from this proof, namely
one that gives an explicit construction scheme for the polynomial pieces in the
interior regions of any non-degenerate box spline.


title: Quench dynamics in integrable systems

abstract:
  These notes cover in some detail lectures I gave at the Les Houches Summer
School 2012. I describe here work done with Deepak Iyer with important
contributions from Hujie Guan. I discuss some aspects of the physics revealed
by quantum quenches and present a formalism for studying the quench dynamics of
integrable systems. The formalism presented generalizes an approach by Yudson
and is applied to Lieb-Liniger model which describes a gas of $N$ interacting
bosons moving on the continuous infinite line while interacting via a short
range potential. We carry out the quench from several initial states and for
any number of particles and compute the evolution of the density and the noise
correlations. In the long time limit the system dilutes and we find that for
any value of repulsive coupling independently of the initial state the system
asymptotes towards astrongly repulsive gas, while for any value of attractive
coupling, the system forms a maximal bound state that dominates at longer
times. In either case the system equilibrates but does not thermalize, an
effect that is consistent with prethermalization. These results can be
confronted with experiments. For much more detail see: Phys. Rev. A 87, 053628
(2013) on which these notes are based. Further applications of the approach to
the Heisenberg model and to the Anderson model will be presented elsewhere.


title: Studying the P_c(4450) resonance in J/psi photoproduction off protons

abstract:
  A resonance-like structure, the P_c(4450), has recently been observed in the
J/psi p spectrum by the LHCb collaboration. We discuss the feasibility of
detecting this structure in J/psi photoproduction in the CLAS12 experiment at
JLab. We present a first estimate of the upper limit for the branching ratio of
the P_c(4450) to J/psi p. Our estimates, which take into account the
experimental resolution effects, predict that it will be possible to observe a
sizable cross section close to the J/psi production threshold and shed light on
the P_c(4450) resonance in the future photoproduction measurements.


title:
Scalar clouds and the superradiant instability regime of Kerr-Newman
  black hole

abstract:
  In this paper, we study a physical system that is composed of massive charged
scalar field linearly coupled to a charged rotating Kerr-Newman black hole.
Given the parameters of black hole and a specific set of "quantum" numbers, the
parameter space of the scalar field, which is a plane spanned by its mass and
charge, is divided into five partitions by three simple constraint lines and
the existence line of scalar clouds. The physical properties of the system in
these partitions are presented. It is found that superradiant instability may
be possibly caused only in two of the partitions. In particular, it is shown
that both the mass and charge of the scalar clouds are bounded in a limited
region. Our results may be used to rapidly judge the possible occurrence of
superradiant instability and the existence of scalar clouds around a given
black hole.


title:
The location of the dust causing internal reddening of active galactic
  nuclei

abstract:
  We use the Balmer decrements of the broad-line regions (BLRs) and narrow-line
regions (NLRs) of active galactic nuclei (AGNs) as reddening indicators to
investigate the location of the dust for four samples of AGNs with reliable
estimates of the NLR contribution to the Balmer lines. Intercomparison of the
NLR and BLR Balmer decrements indicates that the reddening of the NLR sets a
lower limit to the reddening of the BLR. Almost no objects have high NLR
reddening but low BLR reddening. The reddening of the BLR is often
substantially greater than the reddening of the NLR. The BLR reddening is
correlated with the equivalent widths of [O III] lines and the intensity of the
[O III] lines relative to broad H\beta. We find these relationships to be
consistent with the predictions of a simple model where the additional dust
reddening the BLR is interior to the NLR. We thus conclude that the dust
causing the additional reddening of the accretion disc and BLR is mostly
located at a smaller radius than the NLR.


title: Consequences of the Inherent Density Dependence in Dirac Materials

abstract:
  Dirac materials are systems in which the dispersion is linear in the vicinity
of the Dirac points. As a consequence of this linear dispersion, these systems
exhibit unusual behavior and possess unique physical properties that are of
great interest. In this work we utilize the single walled carbon nanotube
(SWNT) as a model Dirac material and examine the system within the framework of
Tomanaga-Luttinger Liquid theory (TLL) revealing several unconventional
properties unique to these systems. Specifically, the exponents of the Green's
function are electron density independent leading to electron density
independent thermodynamic quantities and speed of sound; both of which are
vastly different from traditional TLL behavior. Additionally, we discuss the
implications the Virial Theorem has for this system; in particular, the total
average ground state energy is given by $E=\mathcal{B}/r_s$ where $\mathcal{B}$
is a constant independent of $r_s$. Finally, experimental techniques are
discussed in which these predictions of density independent exponents and their
behavior can be verified.


title:
On salesmen and tourists: two-step optimization in deterministic
  foragers

abstract:
  We explore a two-step optimization problem in random environments, the
so-called restaurant-coffee shop problem, where a walker aims at visiting the
nearest and better restaurant in an area and then move to the nearest and
better coffee-shop. This is an extension of the Tourist Problem, a one-step
optimization dynamics that can be viewed as a deterministic walk in a random
medium. A certain amount of heterogeneity in the values of the resources to be
visited causes the emergence of power-laws distributions for the steps
performed by the walker, similarly to a L\'{e}vy flight. The fluctuations of
the step lengths tend to decrease as a consequence of multiple-step planning,
thus reducing the foraging uncertainty. We find that the first and second steps
of each planned movement play very different roles in heterogeneous
environments. The two-step process improves only slightly the foraging
efficiency compared to the one-step optimization, at a much higher
computational cost. We discuss the implications of these findings for animal
and human mobility, in particular in relation to the computational effort that
informed agents should deploy to solve search problems.


title:
Resonant inelastic x-ray scattering study of entangled spin-orbital
  excitations in superconducting PrFeAsO0.7

abstract:
  Low-energy electron excitation spectra were measured on a single crystal of a
typical iron-based superconductor PrFeAsO$_{0.7}$ using resonant inelastic
X-ray scattering (RIXS) at the Fe-$L_3$ edge. Characteristic RIXS features are
clearly observed around 0.5, 1-1.5 and 2-3 eV energy losses. These excitations
are analyzed microscopically with theoretical calculations using a 22-orbital
model derived from first-principles electronic structure calculation. Based on
the agreement with the experiment, the RIXS features are assigned to Fe-$d$
orbital excitations which, at low energies, are accompanied by spin flipping
and dominated by Fe $d_{yz}$ and $d_{xz}$ orbital characters. Furthermore, our
calculations suggest dispersive momentum dependence of the RIXS excitations
below 0.5 eV, and predict remarkable splitting and merging of the lower-energy
excitations in momentum space. Those excitations, which were not observed in
the present experiment, highlight the potential of RIXS with an improved energy
resolution to unravel new details of the electronic structure of the iron-based
superconductors.


title:
Enhanced superconductivity, Kondo behavior and negative-curvature
  resistivity of oxygen-irradiated thin films of aluminium

abstract:
  We followed the evolution of the normal and superconducting properties of Al
thin films after each session of various successive oxygen irradiations at
ambient temperature. Such irradiated films, similar to the granular ones,
exhibit enhanced superconductivity, Kondo behavior and negative-curvature
resistivity. Two distinct roles of oxygen are identified: as a damage-causing
projectile and as an implanted oxidizing agent. The former gives rise to the
processes involved in the conventional recovery stages. The latter, considered
within the context of the Cabrera-Mott model, gives rise to a multistep process
which involves charges transfer and creation of stabilized vacancies and
charged defects. Based on the outcome of this multistep process, we consider
(i) the negative curvature resistivity as a manifestation of a
thermally-assisted liberation of trapped electric charges, (ii) the Kondo
contribution as a spin-flip scattering from paramagnetic, color-center-type
defects, and (iii) the enhancement of T_{c} as being due to a lattice softening
facilitated by the stabilized defects and vacancies. The similarity in the
phase diagrams of granular and irradiated films as well as the aging effects
are discussed along the same line of reasoning.


title: Dynamical analysis of generalised $f(R,\mathcal{L})$ theories

abstract:
  In this work, we use a dynamical system approach to analyse the viability of
$f(R,\mathcal{L})$ candidates for dark energy. We compare these with nonminimal
coupled $f(R)$ theories and study the solutions for exponential and power-law
forms in order to constraint the allowed range of model parameters.