title:
A pressure-induced topological phase with large Berry curvature in
  Pb$_{1-x}$Sn$_x$Te

abstract:
  The picture of how a gap closes in a semiconductor has been radically
transformed by topological concepts. Instead of the gap closing and immediately
re-opening, topological arguments predict that, in the absence of inversion
symmetry, a metallic phase protected by Weyl nodes persists over a finite
interval of the tuning parameter (e.g. pressure $P$) . The gap re-appears when
the Weyl nodes mutually annihilate. We report evidence that Pb$_{1-x}$Sn$_x$Te
exhibits this topological metallic phase. Using pressure to tune the gap, we
have tracked the nucleation of a Fermi surface droplet that rapidly grows in
volume with $P$. In the metallic state we observe a large Berry curvature which
dominates the Hall effect. Moreover, a giant negative magnetoresistance is
observed in the insulating side of phase boundaries, in accord with \emph{ab
initio} calculations. The results confirm the existence of a topological
metallic phase over a finite pressure interval.


title: Imaging snake orbits at graphene n-p junctions

abstract:
  We consider conductance mapping of the snake-orbits confined along the n-p
junction defined in graphene by the electrostatic doping in the quantum Hall
regime. We explain the periodicity of conductance oscillations at the magnetic
field and the Fermi energy scales by the properties of the n-p junction as a
conducting channel. We evaluate the conductance maps for a floating gate
scanning the surface of the device. In the quantum Hall conditions the currents
flow near the edges of the sample and along the n-p junction. The conductance
mapping resolves only the n-p junction and not the edges. The conductance
oscillations along the junction are found in the maps with periodicity related
to the cyclotron orbits of the scattering current. Stronger probe potentials
provide support to localized resonances at one of the sides of the junction
with current loops that interfere with the n-p junction currents. The
interference results in a series of narrow lines parallel to the junction with
positions that strongly depend on the magnetic field through the Aharonov-Bohm
effect. The consequences of a limited transparency of finite width n-p
junctions are also discussed.


title:
Asymptotic behavior of supercuspidal representations and Sato-Tate
  equidistribution for families

abstract:
  We establish properties of families of automorphic representations as we vary
prescribed supercuspidal representations at a given finite set of primes. For
the tame supercuspidals constructed by J.-K. Yu we prove the limit multiplicity
property with error terms. Thereby we obtain a Sato-Tate equidistribution for
the Hecke eigenvalues of these families. The main new ingredient is to show
that the orbital integrals of matrix coefficients of tame supercuspidal
representations with increasing formal degree on a connected reductive $p$-adic
group tend to zero uniformly for every noncentral semisimple element.


title: Functional renormalization group studies of nuclear and neutron matter

abstract:
  Functional renormalization group (FRG) methods applied to calculations of
isospin-symmetric and asymmetric nuclear matter as well as neutron matter are
reviewed. The approach is based on a chiral Lagrangian expressed in terms of
nucleon and meson degrees of freedom as appropriate for the hadronic phase of
QCD with spontaneously broken chiral symmetry. Fluctuations beyond mean-field
approximation are treated solving Wetterich's FRG flow equations. Nuclear
thermodynamics and the nuclear liquid-gas phase transition are investigated in
detail, both in symmetric matter and as a function of the proton fraction in
asymmetric matter. The equations of state at zero temperature of symmetric
nuclear matter and pure neutron matter are found to be in good agreement with
advanced ab-initio many-body computations. Contacts with perturbative many-body
approaches (in-medium chiral perturbation theory) are discussed. As an
interesting test case, the density dependence of the pion mass in the medium is
investigated. The question of chiral symmetry restoration in nuclear and
neutron matter is addressed. A stabilization of the phase with spontaneously
broken chiral symmetry is found to persist up to high baryon densities once
fluctuations beyond mean-field are included. Neutron star matter including beta
equilibrium is discussed under the aspect of the constraints imposed by the
existence of two-solar-mass neutron stars.


title: Geometry of Polysemy

abstract:
  Vector representations of words have heralded a transformational approach to
classical problems in NLP; the most popular example is word2vec. However, a
single vector does not suffice to model the polysemous nature of many
(frequent) words, i.e., words with multiple meanings. In this paper, we propose
a three-fold approach for unsupervised polysemy modeling: (a) context
representations, (b) sense induction and disambiguation and (c) lexeme (as a
word and sense pair) representations. A key feature of our work is the finding
that a sentence containing a target word is well represented by a low rank
subspace, instead of a point in a vector space. We then show that the subspaces
associated with a particular sense of the target word tend to intersect over a
line (one-dimensional subspace), which we use to disambiguate senses using a
clustering algorithm that harnesses the Grassmannian geometry of the
representations. The disambiguation algorithm, which we call $K$-Grassmeans,
leads to a procedure to label the different senses of the target word in the
corpus -- yielding lexeme vector representations, all in an unsupervised manner
starting from a large (Wikipedia) corpus in English. Apart from several
prototypical target (word,sense) examples and a host of empirical studies to
intuit and justify the various geometric representations, we validate our
algorithms on standard sense induction and disambiguation datasets and present
new state-of-the-art results.


title:
A data augmentation methodology for training machine/deep learning gait
  recognition algorithms

abstract:
  There are several confounding factors that can reduce the accuracy of gait
recognition systems. These factors can reduce the distinctiveness, or alter the
features used to characterise gait, they include variations in clothing,
lighting, pose and environment, such as the walking surface. Full invariance to
all confounding factors is challenging in the absence of high-quality labelled
training data. We introduce a simulation-based methodology and a
subject-specific dataset which can be used for generating synthetic video
frames and sequences for data augmentation. With this methodology, we generated
a multi-modal dataset. In addition, we supply simulation files that provide the
ability to simultaneously sample from several confounding variables. The basis
of the data is real motion capture data of subjects walking and running on a
treadmill at different speeds. Results from gait recognition experiments
suggest that information about the identity of subjects is retained within
synthetically generated examples. The dataset and methodology allow studies
into fully-invariant identity recognition spanning a far greater number of
observation conditions than would otherwise be possible.


title:
Vibrations of Periodically Poled Lithium Niobate Bar with 0.3-mm Long
  Domains

abstract:
  The three dimensional vibrations in a periodically poled ZX-cut Lithium
Niobate thin bar with 0.3-mm long domains are considered. The acoustical
vibrations may be excited by the 1) longitudinal acousto-electric current when
a radio frequency voltage is parallel to the x-axis, and 2) transverse electric
field when a radio frequency voltage is parallel to the z-axis. The
computations by the Final Element Method reveal all the three displacements
along the x, y, and z crystallographic axes. The amplitudes may be different
for two types of vibration excitations. The positions of peaks in admittance
versus frequency correlate with the frequencies of maximum acoustic amplitudes.
The superlattice with 0.3-mm long domains along the x-axis is fabricated in the
z-cut 0.5-mm-thick wafer. The experimental data on the radio frequency
admittance versus frequency is in agreement with the corresponding theoretical
computations.


title: Multi-Boson Interactions at the LHC

abstract:
  This review covers results on the production of all possible electroweak
boson pairs and 2-to-1 vector boson fusion at the CERN Large Hadron Collider
(LHC) in proton-proton collisions at a center of mass energy of 7 and 8 TeV.
The data were taken between 2010 and 2012. Limits on anomalous triple gauge
couplings (aTGCs) then follow. In addition, data on electroweak triple gauge
boson production and 2-to-2 vector boson scattering yield limits on anomalous
quartic gauge boson couplings (aQGCs). The LHC hosts two general purpose
experiments, ATLAS and CMS, which have both reported limits on aTGCs and aQGCs
which are herein summarized. The interpretation of these limits in terms of an
effective field theory is reviewed, and recommendations are made for testing
other types of new physics using multi-gauge boson production.


title: Prototypical topological orbital ferromagnet $\gamma$-FeMn

abstract:
  We predict from first principles an entirely topological orbital
magnetization in the noncoplanar bulk antiferromagnet $\gamma$-FeMn originating
in the nontrivial topology of the underlying spin structure, without any
reference to spin-orbit interaction. Studying the influence of strain,
composition ratio, and spin texture on the topological orbital magnetization
and the accompanying topological Hall effect, we promote the scalar spin
chirality as key mechanism lifting the orbital degeneracy. The system is thus a
prototypical topological orbital ferromagnet, the macroscopic orbital
magnetization of which is prominent even without spin-orbit coupling. One of
the remarkable features of $\gamma$-FeMn is the possibility for pronounced
orbital magnetostriction mediated by the complex spin topology in real space.


title:
Detection prospects for conformally constrained vector-portal dark
  matter

abstract:
  We work with a UV conformal U(1)' extension of the Standard Model, motivated
by the hierarchy problem and recent collider anomalies. This model admits
fermionic vector portal WIMP dark matter charged under the U(1)' gauge group.
The asymptotically safe boundary conditions can be used to fix the coupling
parameters, which allows the observed thermal relic abundance to constrain the
mass of the dark matter particle. This highly restricts the parameter space,
allowing strong predictions to be made. The parameter space of several UV
conformal U(1)' scenarios will be explored, and both bounds and possible
signals from direct and indirect detection observation methods will be
discussed.


title:
Cohomological rigidity of manifolds defined by right-angled
  3-dimensional polytopes

abstract:
  A family of closed manifolds is called cohomologically rigid if a cohomology
ring isomorphism implies a diffeomorphism for any two manifolds in the family.
We establish cohomological rigidity for large families of 3-dimensional and
6-dimensional manifolds defined by 3-dimensional polytopes.
  We consider the class P of 3-dimensional combinatorial simple polytopes,
different from a tetrahedron, whose facets do not form 3- and 4-belts. This
class includes mathematical fullerenes, i.e. simple 3-polytopes with only
5-gonal and 6-gonal facets. By a theorem of Pogorelov, any polytope from P
admits a right-angled realisation in Lobachevsky 3-space, which is unique up to
isometry.
  Our families of smooth manifolds are associated with polytopes from the class
P. The first family consists of 3-dimensional small covers of polytopes from P,
or hyperbolic 3-manifolds of Loebell type. The second family consists of
6-dimensional quasitoric manifolds over polytopes from P. Our main result is
that both families are cohomologically rigid, i.e. two manifolds M and M' from
either of the families are diffeomorphic if and only if their cohomology rings
are isomorphic. We also prove that if M and M' are diffeomorphic, then their
corresponding polytopes are combinatorially equivalent. These results are
intertwined with the classical subjects of geometry and topology, such as
combinatorics of 3-polytopes, the Four Colour Theorem, aspherical manifolds,
diffeomorphism classification of 6-manifolds and invariance of Pontryagin
classes. The proofs use techniques of toric topology.


title:
Node Isolation of Secure Wireless Sensor Networks under a Heterogeneous
  Channel Model

abstract:
  We investigate the secure connectivity of wireless sensor networks under a
heterogeneous random key predistribution scheme and a heterogeneous channel
model. In particular, we study a random graph formed by the intersection of an
inhomogeneous random key graph with an inhomogeneous Erd\H{o}s-R\'enyi graph.
The former graph is naturally induced by the heterogeneous random key
predistribution scheme while the latter graph constitutes a heterogeneous
on/off channel model; wherein, the wireless channel between a class-$i$ node
and a class-$j$ node is on with probability $\alpha_{ij}$ independently. We
present conditions (in the form of zero-one laws) on how to scale the
parameters of the intersection model so that it has no isolated node with high
probability as the number of nodes gets large. We also present numerical
results to support these zero-one laws in the finite-node regime.


title: A new content format for immersive experiences

abstract:
  The arrival of head-mounted displays (HMDs) to the consumer market requires a
novel content format that is, first, adapted to the specificities of immersive
displays and, second, that takes into account the current reality of
multi-display media consumption. We review the requirements for such content
format and report on existing initiatives, some of our own, towards
implementing such content format.


title:
On capacity of optical communications over a lossy bosonic channel with
  a receiver employing the most general coherent electro-optic feedback control

abstract:
  We study the problem of designing optical receivers to discriminate between
multiple coherent states using coherent processing receivers---i.e., one that
uses arbitrary coherent feedback control and quantum-noise-limited direct
detection---which was shown by Dolinar to achieve the minimum error probability
in discriminating any two coherent states. We first derive and re-interpret
Dolinar's binary-hypothesis minimum-probability-of-error receiver as the one
that optimizes the information efficiency at each time instant, based on
recursive Bayesian updates within the receiver. Using this viewpoint, we
propose a natural generalization of Dolinar's receiver design to discriminate
$M$ coherent states each of which could now be a codeword, i.e., a sequence of
$N$ coherent states each drawn from a modulation alphabet. We analyze the
channel capacity of the pure-loss optical channel with a general
coherent-processing receiver in the low-photon number regime and compare it
with the capacity achievable with direct detection and the Holevo limit
(achieving the latter would require a quantum joint-detection receiver). We
show compelling evidence that despite the optimal performance of Dolinar's
receiver for the binary coherent-state hypothesis test (either in error
probability or mutual information), the asymptotic communication rate
achievable by such a coherent-processing receiver is only as good as direct
detection. This suggests that in the infinitely-long codeword limit, all
potential benefits of coherent processing at the receiver can be obtained by
designing a good code and direct detection, with no feedback within the
receiver.


title:
Theory of noiseless phase-mixing amplification in a cavity
  optomechanical system

abstract:
  The investigation of the ultimate limits imposed by quantum mechanics on
amplification represents an important topic both on a fundamental level and
from the perspective of potential applications. We propose here a novel setup
for an optomechanical amplifier, constituted by a mechanical resonator
dispersively coupled to an optomechanical cavity asymmetrically driven around
both mechanical sidebands. We show that, on general grounds, the present
amplifier operates in a novel regime-- which we here call phase-mixing
amplification. At the same time, for a suitable choice of parameters, the
amplifier proposed here operates as a phase-sensitive amplifier. Furthermore,
we show that both configurations allow amplification below the standard quantum
limit in a parameter range compatible with current experiments in microwave
circuit optomechanics.


title:
Baryon-Strangeness Correlations in Au+Au Collisions at
  $\sqrt{s_\mathrm{NN}}$=7.7-200 GeV from the UrQMD model

abstract:
  Fluctuations and correlations of conserved charges are sensitive observables
for studying the QCD phase transition and critical point in high-energy
heavy-ion collisions. We have studied the centrality and energy dependence of
mixed-cumulants (up to fourth order) between net-baryon and net-strangeness in
Au+Au collisions at $\sqrt{s_{NN}}$= 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV
from UrQMD model. To compare with other theoretical calculations, we normalize
these mixed-cumulants by various order cumulants of net-strangeness
distributions. We found that the results obtained from UrQMD calculations are
comparable with the results from Lattice QCD at low temperature and hadron
resonance gas model. The ratios of mixed-cumulants
($R_{11}^{BS},R_{13}^{BS},R_{22}^{BS}$,~$R_{31}^{BS}$) from UrQMD calculations
show weak centrality dependence. However, the mixed-cumulant ratios
$R_{11}^{BS}$ and $R_{31}^{BS}$ show strong increase at low energy, while the
$R_{13}^{BS}$ snd $R_{22}^{BS}$ are similar at different energies. Furthermore,
we have also studied the correlations between different hadron species and
their contributions to the net-baryon and net-strangeness correlations. These
models studies can provide baselines for searching for the signals of QCD phase
transition and critical point in heavy-ion collisions.


title:
Thermoelectric power as a probe of density of states in correlated
  actinide materials: the case of PuCoGa$_{5}$ superconductor

abstract:
  We present measurements of the thermoelectric power of the plutonium-based
unconventional superconductor PuCoGa$_{5}$. The data is interpreted within a
phenomenological model for the quasiparticle density of states of intermediate
valence systems and the results are compared with results obtained from
photoemission spectroscopy. The results are consistent with intermediate
valence nature of 5$f$-electrons, furthermore, we propose that measurements of
the Seebeck coefficient can be used as a probe of density of states in this
material, thereby providing a link between transport measurements and
photoemission in strongly correlated materials. We discuss these results and
their implications for the electronic structure determination of other strongly
correlated systems, especially actinide materials.


title: Hilbert's 16th problem on a period annulus and Nash space of arcs

abstract:
  This article introduces an algebro-geometric setting for the space of
bifurcation functions involved in the local Hilbert's 16th problem on a period
annulus. Each possible bifurcation function is in one-to-one correspondence
with a point in the exceptional divisor $E$ of the canonical blow-up
$B_I{\mathbb C}^n$ of the Bautin ideal $I$. In this setting, the notion of
essential perturbation, first proposed by Iliev, is defined via irreducible
components of the Nash space of arcs $ Arc(B_I\mathbb C^n,E)$. The example of
planar quadratic vector fields in the Kapteyn normal form is further discussed.


title:
Adjusting for Unmeasured Spatial Confounding with Distance Adjusted
  Propensity Score Matching

abstract:
  Propensity score matching is a common tool for adjusting for observed
confounding in observational studies, but is known to have limitations in the
presence of unmeasured confounding. In many settings, researchers are
confronted with spatially-indexed data where the relative locations of the
observational units may serve as a useful proxy for unmeasured confounding that
varies according to a spatial pattern. We develop a new method, termed Distance
Adjusted Propensity Score Matching (DAPSm) that incorporates information on
units' spatial proximity into a propensity score matching procedure. We show
that DAPSm can adjust for both observed and some forms of unobserved
confounding and evaluate its performance relative to several other reasonable
alternatives for incorporating spatial information into propensity score
adjustment. The method is motivated by and applied to a comparative
effectiveness investigation of power plant emission reduction technologies
designed to reduce population exposure to ambient ozone pollution. Ultimately,
DAPSm provides a framework for augmenting a "standard" propensity score
analysis with information on spatial proximity and provides a transparent and
principled way to assess the relative trade offs of prioritizing observed
confounding adjustment versus spatial proximity adjustment.


title:
Learning a Probabilistic Latent Space of Object Shapes via 3D
  Generative-Adversarial Modeling

abstract:
  We study the problem of 3D object generation. We propose a novel framework,
namely 3D Generative Adversarial Network (3D-GAN), which generates 3D objects
from a probabilistic space by leveraging recent advances in volumetric
convolutional networks and generative adversarial nets. The benefits of our
model are three-fold: first, the use of an adversarial criterion, instead of
traditional heuristic criteria, enables the generator to capture object
structure implicitly and to synthesize high-quality 3D objects; second, the
generator establishes a mapping from a low-dimensional probabilistic space to
the space of 3D objects, so that we can sample objects without a reference
image or CAD models, and explore the 3D object manifold; third, the adversarial
discriminator provides a powerful 3D shape descriptor which, learned without
supervision, has wide applications in 3D object recognition. Experiments
demonstrate that our method generates high-quality 3D objects, and our
unsupervisedly learned features achieve impressive performance on 3D object
recognition, comparable with those of supervised learning methods.


title:
Measurement of the $ZZ$ production cross section in $pp$ collisions at
  $\sqrt{s}$ = 8 TeV using the $ZZ\to\ell^{-}\ell^{+}\ell^{\prime
  -}\ell^{\prime +}$ and $ZZ\to\ell^{-}\ell^{+}\nu\bar{\nu}$ channels with the
  ATLAS detector

abstract:
  A measurement of the $ZZ$ production in the $\ell^{-}\ell^{+}\ell^{\prime
-}\ell^{\prime +}$ and $\ell^{-}\ell^{+}\nu\bar{\nu}$ channels $(\ell = e,
\mu)$ in proton--proton collisions at $\sqrt{s} = 8$ TeV at the Large Hadron
Collider at CERN, using data corresponding to an integrated luminosity of 20.3
fb$^{-1}$ collected by the ATLAS experiment in 2012 is presented. The fiducial
cross sections for $ZZ\to\ell^{-}\ell^{+}\ell^{\prime -}\ell^{\prime +}$ and
$ZZ\to \ell^{-}\ell^{+}\nu\bar{\nu}$ are measured in selected phase-space
regions. The total cross section for $ZZ$ events produced with both $Z$ bosons
in the mass range 66 to 116 GeV is measured from the combination of the two
channels to be
$7.3\pm0.4\textrm{(stat)}\pm0.3\textrm{(syst)}\pm0.2\textrm{(lumi)}$ pb, which
is consistent with the Standard Model prediction of $6.6^{+0.7}_{-0.6}$ pb. The
differential cross sections in bins of various kinematic variables are
presented. The differential event yield as a function of the transverse
momentum of the leading $Z$ boson is used to set limits on anomalous neutral
triple gauge boson couplings in $ZZ$ production.


title:
Mapping current fluctuations of stochastic pumps to nonequilibrium
  steady states

abstract:
  We show that current fluctuations in a stochastic pump can be robustly mapped
to fluctuations in a corresponding time-independent nonequilibrium steady
state. We thus refine a recently proposed mapping so that it ensures
equivalence of not only the averages, but also optimal representation of
fluctuations in currents and density. Our mapping leads to a natural
decomposition of the entropy production in stochastic pumps similar to the
"housekeeping" heat. As a consequence of the decomposition of entropy
production, the current fluctuations in weakly perturbed stochastic pumps are
shown to satisfy a universal bound determined by the steady state entropy
production.


title:
Gamma Rays From Dark Matter Subhalos Revisited: Refining the Predictions
  and Constraints

abstract:
  Utilizing data from the ELVIS and Via Lactea-II simulations, we characterize
the local dark matter subhalo population, and use this information to refine
the predictions for the gamma-ray fluxes arising from annihilating dark matter
in this class of objects. We find that the shapes of nearby subhalos are
significantly altered by tidal effects, and are generally not well described by
NFW density profiles, instead prefering power-law profiles with an exponential
cutoff. From the subhalo candidates detected by the Fermi Gamma-Ray Space
Telescope, we place limits on the dark matter annihilation cross section that
are only modestly weaker than those based on observations of dwarf galaxies. We
also calculate the fraction of observable subhalos that are predicted to be
spatially extended at a level potentially discernible to Fermi.

categories: astro-ph.HE astro-ph.CO astro-ph.GA hep-ph


title: Recoil-sensitive lithium interferometer without a subrecoil sample

abstract:
  We report simultaneous conjugate Ramsey-Bord\'e interferometers with a sample
of low-mass (lithium-7) atoms at 50 times the recoil temperature. We optically
pump the atoms to a magnetically insensitive state using the $2S_{1/2} -
2P_{1/2}$ line. Fast stimulated Raman beam splitters address a broad velocity
class and unavoidably drive two conjugate interferometers that overlap
spatially. We show that detecting the summed interference signals of both
interferometers, using state labeling, allows recoil measurements and
suppression of phase noise from vibrations. The use of "warm" atoms allows for
simple, efficient, and high-flux atom sources and broadens the applicability of
recoil-sensitive interferometry to particles that remain difficult to trap and
cool.


title: Classifying exact categories via Wakamatsu tilting

abstract:
  Using the Morita-type embedding, we show that any exact category with enough
projectives has a realization as a (pre)resolving subcategory of a module
category. When the exact category has enough injectives, the image of the
embedding can be described in terms of Wakamatsu tilting (=semi-dualizing)
subcategories. If moreover the exact category has higher kernels, then its
image coincides with the category naturally associated with a cotilting
subcategory up to summands. We apply these results to the representation theory
of artin algebras. In particular, we show that the ideal quotient of a module
category by a functorially finite subcategory closed under submodules is a
torsionfree class of some module category.


title:
On the Network Reliability Problem of the Heterogeneous Key
  Predistribution Scheme

abstract:
  We consider the network reliability problem in wireless sensor networks
secured by the heterogeneous random key predistribution scheme. This scheme
generalizes Eschenauer-Gligor scheme by considering the cases when the network
comprises sensor nodes with varying level of resources; e.g., regular nodes vs.
cluster heads. The scheme induces the inhomogeneous random key graph, denoted
$\mathbb{G}(n;\pmb{\mu},\pmb{K},P)$. We analyze the reliability of
$\mathbb{G}(n;\pmb{\mu},\pmb{K},P)$ against random link failures. Namely, we
consider $\mathbb{G}(n;\pmb{\mu},\pmb{K}, P,\alpha)$ formed by deleting each
edge of $\mathbb{G}(n;\pmb{\mu},\pmb{K},P)$ independently with probability
$1-\alpha$, and study the probability that the resulting graph i) has no
isolated node; and ii) is connected. We present scaling conditions on
$\pmb{K}$, $P$, and $\alpha$ such that both events take place with probability
zero or one, respectively, as the number of nodes gets large. We present
numerical results to support these in the finite-node regime.


title: Low-power photothermal self-oscillation of bimetallic nanowires

abstract:
  We investigate the nonlinear mechanics of a bimetallic, optically absorbing
SiN-Nb nanowire in the presence of incident laser light and a reflecting Si
mirror. Situated in a standing wave of optical intensity and subject to
photothermal forces, the nanowire undergoes self-induced oscillations at low
incident light thresholds of $<1\, \rm{\mu W}$ due to engineered strong
temperature-position ($T$-$z$) coupling. Along with inducing self-oscillation,
laser light causes large changes to the mechanical resonant frequency
$\omega_0$ and equilibrium position $z_0$ that cannot be neglected. We present
experimental results and a theoretical model for the motion under laser
illumination. In the model, we solve the governing nonlinear differential
equations by perturbative means to show that self-oscillation amplitude is set
by the competing effects of direct $T$-$z$ coupling and $2\omega_0$ parametric
excitation due to $T$-$\omega_0$ coupling. We then study the linearized
equations of motion to show that the optimal thermal time constant $\tau$ for
photothermal feedback is $\tau \to \infty$ rather than the widely reported
$\omega_0 \tau = 1$. Lastly, we demonstrate photothermal quality factor ($Q$)
enhancement of driven motion as a means to counteract air damping.
Understanding photothermal effects on micromechanical devices, as well as
nonlinear aspects of optics-based motion detection, can enable new device
applications as oscillators or other electronic elements with smaller device
footprints and less stringent ambient vacuum requirements.


title: The segregation of baryons and dark matter during halo assembly

abstract:
  The standard galaxy formation theory assumes that baryons and dark matter are
initially well-mixed before becoming segregated due to radiative cooling. We
use non-radiative hydrodynamical simulations to explicitly examine this
assumption and find that baryons and dark matter can also be segregated because
of different physics obeyed by gas and dark matter during the build-up of the
halo. As a result, baryons in many haloes do not originate from the same
Lagrangian region as the dark matter. When using the fraction of corresponding
dark matter and gas particles in the initial conditions (the "paired fraction")
as a proxy of the dark matter and gas segregation strength of a halo, on
average about $25$ percent of the baryonic and dark matter of the final halo
are segregated in the initial conditions. This is at odds with the assumption
of the standard galaxy formation model. A consequence of this effect is that
the baryons and dark matter of the same halo initially experience different
tidal torques and thus their angular momentum vectors are often misaligned. The
degree of the misalignment is largely preserved during later halo assembly and
can be understood with the tidal torque theory. The result challenges the
precision of some semi-analytical approaches which utilize dark matter halo
merger trees to infer properties of gas associated to dark matter haloes.


title: Redefining the Axion Window

abstract:
  A major goal of axion searches is to reach inside the parameter space region
of realistic axion models. Currently, the boundaries of this region depend on
somewhat arbitrary criteria, and it would be desirable to specify them in terms
of precise phenomenological requirements. We consider hadronic axion models and
classify the representations $R_Q$ of the new heavy quarks $Q$. By requiring
that $i)$ the $Q$ are sufficiently short lived to avoid issues with long lived
strongly interacting relics, $ii)$ no Landau poles are induced below the Planck
scale, fifteen cases are selected, which define a phenomenologically preferred
axion window bounded by a maximum (minimum) value of the axion-photon coupling
about twice (four times) larger than commonly assumed. Allowing for more than
one $R_Q$, larger couplings, as well as complete axion-photon decoupling,
become possible.


title: Properties of distance spaces with power triangle inequalities

abstract:
  Metric spaces provide a framework for analysis and have several very useful
properties. Many of these properties follow in part from the triangle
inequality. However, there are several applications in which the triangle
inequality does not hold but in which we may still like to perform analysis.
This paper investigates what happens if the triangle inequality is removed all
together, leaving what is called a distance space, and also what happens if the
triangle inequality is replaced with a much more general two parameter
relation, which is herein called the "power triangle inequality". The power
triangle inequality represents an uncountably large class of inequalities, and
includes the triangle inequality, relaxed triangle inequality, and inframetric
inequality as special cases. The power triangle inequality is defined in terms
of a function that is herein called the "power triangle function". The power
triangle function is itself a power mean, and as such is continuous and
monotone with respect to its exponential parameter, and also includes the
operations of maximum, minimum, mean square, arithmetic mean, geometric mean,
and harmonic mean as special cases.


title: $(H,\rho)$-induced dynamics and the quantum game of life

abstract:
  We propose an extended version of quantum dynamics for a certain system S,
whose evolution is ruled by a Hamiltonian $H$, its initial conditions, and a
suitable set $\rho$ of {\em rules}, acting repeatedly on S. The resulting
dynamics is not necessarily periodic or quasi-periodic, as one could imagine
for conservative systems with a finite number of degrees of freedom. In fact,
it may have quite different behaviors depending on the explicit forms of $H$,
$\rho$ as well as on the initial conditions. After a general discussion on this
$(H,\rho)$-{\em induced dynamics}, we apply our general ideas to extend the
classical game of life, and we analyze several aspects of this extension.


title: Dependence of X-ray Burst Models on Nuclear Masses

abstract:
  X-ray burst model predictions of light curves and final composition of the
nuclear ashes are affected by uncertain nuclear masses. However, not all of
these masses are determined experimentally with sufficient accuracy. Here we
identify remaining nuclear mass uncertainties in X-ray burst models using a one
zone model that takes into account the changes in temperature and density
evolution caused by changes in the nuclear physics. Two types of bursts are
investigated - a typical mixed H/He burst with a limited rp-process and an
extreme mixed H/He burst with an extended rp-process. When allowing for a
3$\sigma$ variation only three remaining nuclear mass uncertainties affect the
light curve predictions of a typical H/He burst ($^{27}$P, $^{61}$Ga, and
$^{65}$As), and only three additional masses affect the composition strongly
($^{80}$Zr, $^{81}$Zr, and $^{82}$Nb). A larger number of mass uncertainties
remains to be addressed for the extreme H/He burst with the most important
being $^{58}$Zn, $^{61}$Ga, $^{62}$Ge, $^{65}$As, $^{66}$Se, $^{78}$Y,
$^{79}$Y, $^{79}$Zr, $^{80}$Zr, $^{81}$Zr, $^{82}$Zr, $^{82}$Nb, $^{83}$Nb,
$^{86}$Tc, $^{91}$Rh, $^{95}$Ag, $^{98}$Cd, $^{99}$In, $^{100}$In, and
$^{101}$In. The smallest mass uncertainty that still impacts composition
significantly when varied by 3$\sigma$ is $^{85}$Mo with 16 keV uncertainty.
For one of the identified masses, $^{27}$P, we use the isobaric mass multiplet
equation (IMME) to improve the mass uncertainty, obtaining an atomic mass
excess of -716(7) keV. The results provide a roadmap for future experiments at
advanced rare isotope beam facilities, where all the identified nuclides are
expected to be within reach for precision mass measurements.


title:
Finite dimensionality of global attractor for the solutions to 3D
  viscous primitive equations of large-scale moist atmosphere

abstract:
  Under general boundary conditions we consider the finiteness of the Hausdorff
and fractal dimensions of the global attractor for the strong solution of the
3D moist primitive equations with viscosity. Firstly, we obtain time-uniform
estimates of the first-order time derivative of the strong solutions in
$L^2(\mho)$. Then, to prove the finiteness of the Hausdorff and fractal
dimensions of the global attractor, the common method is to obtain the uniform
boundedness of the strong solution in $H^2(\mho)$ to establish the squeezing
property of the solution operator. But it is difficult to achieve due to the
boundary conditions and complicated structure of the 3D moist primitive
equations. To overcome the difficulties, we try to use the uniform boundedness
of the derivative of the strong solutions with respect to time $t$ in
$L^2(\mho)$ to prove the uniform continuity of the global attractor. Finally,
using the uniform continuity of the global attractor we establish the squeezing
property of the solution operator which implies the finiteness of the Hausdorff
and fractal dimensions of the global attractor.


title:
Power generation on a solar photovoltaic modules integrated
  Lighter-than-Air Platform at a low altitude

abstract:
  Use of lighter than air platforms (aerostats and airships) for reconnaissance
and surveillance over long periods can be facilitated by generation of power
on-board through solar photovoltaic arrays. Attempts to integrate solar
photovoltaic modules on such contoured surfaces leads to multiple challenges
ranging from the choice of solar modules, determination of best method of their
integration with the lighter than air platform, and design of the array layout
in order to optimize the loss of power due to non-uniform illumination. This
paper describes the method of designing such a system and suggests strategies
for overcoming these challenges. The issue of non-uniform illumination has been
tackled by maximum power point tracking using the scanning window technique for
maximizing power generation and an algorithm of distributed maximum power point
tracking has been suggested for further improvement. The procedure described in
this paper can be used for obtaining the optimum power generation capability of
a solar photovoltaic array mounted on a lighter than air platform of a given
volume and payload carrying capability.


title:
A synoptic approach to the seismic sensing of heterogeneous fractures:
  from geometric reconstruction to interfacial characterization

abstract:
  A non-iterative waveform sensing approach is proposed toward (i) geometric
reconstruction of penetrable fractures, and (ii) quantitative identification of
their heterogeneous contact condition by seismic i.e. elastic waves. To this
end, the fracture support $\Gamma$ (which may be non-planar and unconnected) is
first recovered without prior knowledge of the interfacial condition by way of
the recently established approaches to non-iterative waveform tomography of
heterogeneous fractures, e.g. the methods of generalized linear sampling and
topological sensitivity. Given suitable approximation $\breve\Gamma$ of the
fracture geometry, the jump in the displacement field across $\breve\Gamma$
i.e. the fracture opening displacement (FOD) profile is computed from remote
sensory data via a regularized inversion of the boundary integral
representation mapping the FOD to remote observations of the scattered field.
Thus obtained FOD is then used as input for solving the traction boundary
integral equation on $\breve\Gamma$ for the unknown (linearized) contact
parameters. In this study, linear and possibly dissipative interactions between
the two faces of a fracture are parameterized in terms of a symmetric,
complex-valued matrix $\boldsymbol{K}(\boldsymbol{\xi})$ collecting the normal,
shear, and mixed-mode coefficients of specific stiffness. To facilitate the
high-fidelity inversion for $\boldsymbol{K}(\boldsymbol{\xi})$, a 3-step
regularization algorithm is devised to minimize the errors stemming from the
inexact geometric reconstruction and FOD recovery. The performance of the
inverse solution is illustrated by a set of numerical experiments where a
cylindrical fracture, endowed with two example patterns of specific stiffness
coefficients, is illuminated by plane waves and reconstructed in terms of its
geometry and heterogeneous (dissipative) contact condition.


title:
Towards Rock-paper-scissors patterns in the Optional Public Goods Game
  under random mobility

abstract:
  Social dilemmas concern a natural conflict between cooperation and self
interests among individuals in large populations. The emergence of cooperation
and its maintenance is the key for the understanding of fundamental concepts
about the evolution of species. In order to understand the mechanisms involved
in this framework, here we study the Optional Public Good Games with focus on
the effects of diffusive aspects in the emergent patterns of cyclic dominance
between the strategies. Differently from other works, we showed that
rock-paper-scissors (RPS) patterns occur by introducing a simple kind of random
mobility in a lattice sparsely occupied. Such pattern has been revealed to be
very important in the conservation of the species in ecological and social
environments. The goal of this paper is to show that we do not need more
elaborated schemes for construction of the neighbourhood in the game to observe
RPS patterns as suggested in the literature. As an interesting additional
result, in this contribution we also propose an alternative method to quantify
the RPS density in a quantitative context of the game theory which becomes
possible to perform a finite size scaling study. Such approach can be very
interesting to be applied in other games generically.


title: Strong Evidence Against A Non-Degenerate Companion in SN 2012cg

abstract:
  Even though SN 2012cg is one of the best-studied Type Ia Supernovae to date,
the nature of its progenitor system has been debated in numerous studies.
Specifically, it is difficult to reconcile recent claims of the detection of a
$\sim 6 \rm{M}_\odot$ main-sequence companion with recent deep, late-time
H$\alpha{}$ flux limits. In this study we add three new constraints: 1) We
analyze new high-signal-to-noise, nebular-phase, LBT/MODS spectrum of SN 2012cg
and place an upper limit on the amount of low-velocity, solar-abundance
material removed from a possible companion of $ < 7.8 \times 10^{-3}
\rm{M}_\odot$. 2) We use Swift X-ray observations to constrain the preexplosion
mass-loss rate to be $\dot M<10^{-6}\,$ $\rm{M}_\odot$ yr$^{-1}$ for
$v_\textrm{w}=100\,\rm{km\,s^{-1}}$. 3) We carefully reanalyze a prediscovery
MASTER image and, with published light curves of SN 2012cg, we estimate the
time of first light and conservatively constrain the radius of a Roche-lobe
overflowing companion to be $< 0.24 \rm{R}_\odot$. These observations disagree
with a large nearby companion, and, when considered with other studies of SN
2012cg's progenitor system, essentially rule out a non-degenerate companion.


title:
The Joker: A custom Monte Carlo sampler for binary-star and exoplanet
  radial velocity data

abstract:
  Given sparse or low-quality radial-velocity measurements of a star, there are
often many qualitatively different stellar or exoplanet companion orbit models
that are consistent with the data. The consequent multimodality of the
likelihood function leads to extremely challenging search, optimization, and
MCMC posterior sampling over the orbital parameters. Here we create a custom
Monte Carlo sampler for sparse or noisy radial-velocity measurements of
two-body systems that can produce posterior samples for orbital parameters even
when the likelihood function is poorly behaved. The six standard orbital
parameters for a binary system can be split into four non-linear parameters
(period, eccentricity, argument of pericenter, phase) and two linear parameters
(velocity amplitude, barycenter velocity). We capitalize on this by building a
sampling method in which we densely sample the prior pdf in the non-linear
parameters and perform rejection sampling using a likelihood function
marginalized over the linear parameters. With sparse or uninformative data, the
sampling obtained by this rejection sampling is generally multimodal and dense.
With informative data, the sampling becomes effectively unimodal but too
sparse: in these cases we follow the rejection sampling with standard MCMC. The
method produces correct samplings in orbital parameters for data that include
as few as three epochs. The Joker can therefore be used to produce proper
samplings of multimodal pdfs, which are still informative and can be used in
hierarchical (population) modeling. We give some examples that show how the
posterior pdf depends sensitively on the number and time coverage of the
observations and their uncertainties.


title:
Fermion-induced quantum critical points in two-dimensional Dirac
  semimetals

abstract:
  In this paper we investigate the nature of quantum phase transitions between
two-dimensional Dirac semimetals and $Z_3$-ordered phases (e.g. Kekule
valence-bond solid), where cubic terms of the order parameter are allowed in
the quantum Landau-Ginzberg theory and the transitions are putatively
first-order. From large-$N$ renormalization group (RG) analysis, we find that
fermion-induced quantum critical points (FIQCPs) [Z.-X. Li et al., Nature
Communications 8, 314 (2017)] occur when $N$ (the number of flavors of
four-component Dirac fermions) is larger than a critical value $N_c$.
Remarkably, from the knowledge of spacetime supersymmetry, we obtain an exact
lower bound for $N_c$, i.e., $N_c>1/2$. (Here the "1/2" flavor of
four-component Dirac fermions is equivalent to one flavor of four-component
Majorana fermions). Moreover, we show that the emergence of two length scales
is a typical phenomenon of FIQCPs and obtain two different critical exponents,
i.e., $\nu$$\neq$$\nu'$, by large-$N$ RG calculations. We further give a brief
discussion on possible experimental realizations of FIQCPs.


title: Cosmic Microwave Background Science at Commercial Airline Altitudes

abstract:
  Obtaining high-sensitivity measurements of degree-scale cosmic microwave
background (CMB) polarization is the most direct path to detecting primordial
gravitational waves. Robustly recovering any primordial signal from the
dominant foreground emission will require high-fidelity observations at
multiple frequencies, with excellent control of systematics. We explore the
potential for a new platform for CMB observations, the Airlander 10 hybrid air
vehicle, to perform this task. We show that the Airlander 10 platform,
operating at commercial airline altitudes, is well-suited to mapping
frequencies above 220 GHz, which are critical for cleaning CMB maps of dust
emission. Optimizing the distribution of detectors across frequencies, we
forecast the ability of Airlander 10 to clean foregrounds of varying complexity
as a function of altitude, demonstrating its complementarity with both existing
(Planck) and ongoing (C-BASS) foreground observations. This novel platform
could play a key role in defining our ultimate view of the polarized microwave
sky.


title: The inner structure of early-type galaxies in the Illustris simulation

abstract:
  Early-type galaxies provide unique tests for the predictions of the cold dark
matter cosmology and the baryonic physics assumptions entering models for
galaxy formation. In this work, we use the Illustris simulation to study
correlations of three main properties of early-type galaxies, namely, the
stellar orbital anisotropies, the central dark matter fractions and the central
radial density slopes, as well as their redshift evolution since $z=1.0$. We
find that lower-mass galaxies or galaxies at higher redshift tend to be bluer
in rest-frame colour, have higher central gas fractions, and feature more
tangentially anisotropic orbits and steeper central density slopes than their
higher-mass or lower-redshift counterparts, respectively. The projected central
dark matter fraction within the effective radius shows a very mild mass
dependence but positively correlates with galaxy effective radii due to the
aperture effect. The central density slopes obtained by combining strong
lensing measurements with single aperture kinematics are found to differ from
the true density slopes. We identify systematic biases in this measurement to
be due to two common modelling assumptions, isotropic stellar orbital
distributions and power-law density profiles. We also compare the properties of
early-type galaxies in Illustris to those from existing galaxy and strong
lensing surveys, we find in general broad agreement but also some tension,
which poses a potential challenge to the stellar formation and feedback models
adopted by the simulation.


title: Multi-component Dark Matter through a Radiative Higgs Portal

abstract:
  We study a multi-component dark matter model where interactions with the
Standard Model are primarily via the Higgs boson. The model contains
vector-like fermions charged under $SU(2)_W \times U(1)_Y$ and under the dark
gauge group, $U(1)^\prime$. This results in two dark matter candidates. A
spin-1 and a spin-1/2 candidate, which have loop and tree-level couplings to
the Higgs, respectively. We explore the resulting effect on the dark matter
relic abundance, while also evaluating constraints on the Higgs invisible width
and from direct detection experiments. Generally, we find that this model is
highly constrained when the fermionic candidate is the predominant fraction of
the dark matter relic abundance.


title: A Refined Count of BPS States in the D1/D5 System

abstract:
  We examine the low-lying quarter BPS spectrum of a 2d conformal field theory
with target Sym$^N(K3)$ at various points in the moduli space, and look at a
more refined count than the ordinary elliptic genus. We compute growth of the
spectrum at both the symmetric orbifold point, as well as at the supergravity
point in the moduli space. Finally we do a decomposition of the spectra into
$\mathcal{N}=4$ characters and discuss possible relations to interesting
symmetry groups. A similar analysis is done with $T^4$.


title:
X-ray Reflection and An Exceptionally Long Thermonuclear Helium Burst
  from IGR J17062-6143

abstract:
  Thermonuclear X-ray bursts from accreting neutron stars power brief but
strong irradiation of their surroundings, providing a unique way to study
accretion physics. We analyze MAXI/GSC and Swift/XRT spectra of a day-long
flash observed from IGR J17062-6143 in 2015. It is a rare case of recurring
bursts at a low accretion luminosity of 0.15% Eddington. Spectra from MAXI,
Chandra, and NuSTAR observations taken between the 2015 burst and the previous
one in 2012 are used to determine the accretion column. We find it to be
consistent with the burst ignition column of 5x10^10 g cm^-2, which indicates
that it is likely powered by burning in a deep helium layer. The burst flux is
observed for over a day, and decays as a straight power law: F~t^-1.15. The
burst and persistent spectra are well described by thermal emission from the
neutron star, Comptonization of this emission in a hot optically thin medium
surrounding the star, and reflection off the photoionized accretion disk. At
the burst peak, the Comptonized component disappears, when the burst may
dissipate the Comptonizing gas, and it returns in the burst tail. The
reflection signal suggests that the inner disk is truncated at ~100
gravitational radii before the burst, but may move closer to the star during
the burst. At the end of the burst, the flux drops below the burst cooling
trend for 2 days, before returning to the pre-burst level.


title:
The deep OB star population in Carina from the VST Photometric H$\alpha$
  Survey (VPHAS+)

abstract:
  Massive OB stars are critical to the ecology of galaxies, and yet our
knowledge of OB stars in the Milky Way, fainter than $V \sim 12$, remains
patchy. Data from the VST Photometric H$\alpha$ Survey (VPHAS+) permit the
construction of the first deep catalogues of blue excess-selected OB stars,
without neglecting the stellar field. A total of 14900 candidates with 2MASS
cross-matches are blue-selected from a 42 square-degree region in the Galactic
Plane, capturing the Carina Arm over the Galactic longitude range $282^{\circ}
\lesssim \ell \lesssim 293^{\circ}$. Spectral energy distribution fitting is
performed on these candidates' combined VPHAS+ $u,g,r,i$ and 2MASS $J,H,K$
magnitudes. This delivers: effective temperature constraints, statistically
separating O from early-B stars; high-quality extinction parameters, $A_0$ and
$R_V$ (random errors typically $< 0.1$). The high-confidence O-B2 candidates
number 5915 and a further 5170 fit to later B spectral type. Spectroscopy of
276 of the former confirms 97% of them. The fraction of emission line stars
among all candidate B stars is 7--8% . Greyer ($R_V > 3.5$) extinction laws are
ubiquitous in the region, over the distance range 2.5--3 kpc to $\sim$10~kpc.
Near prominent massive clusters, $R_V$ tends to rise, with particularly large
and chaotic excursions to $R_V \sim 5$ seen in the Carina Nebula. The data
reveal a hitherto unnoticed association of 108 O-B2 stars around the O5If$+$
star LSS 2063 ($\ell = 289.77^{\circ}$, $b = -1.22^{\circ}$). Treating the OB
star scale-height as a constant within the thin disk, we find an orderly mean
relation between extinction ($A_0$) and distance in the Galactic longitude
range, $287.6^{\circ} < \ell < 293.5^{\circ}$, and infer the subtle onset of
thin-disk warping. A halo around NGC 3603, roughly a degree in diameter, of
$\sim$500 O-B2 stars with $4 < A_0 (\rm{mag}) < 7$ is noted.


title: Galactic rotation in Gaia DR1

abstract:
  The spatial variations of the velocity field of local stars provide direct
evidence of Galactic differential rotation. The local divergence, shear, and
vorticity of the velocity field---the traditional Oort constants---can be
measured based purely on astrometric measurements and in particular depend
linearly on proper motion and parallax. I use data for 304,267 main-sequence
stars from the Gaia DR1 Tycho-Gaia Astrometric Solution to perform a local,
precise measurement of the Oort constants at a typical heliocentric distance of
230 pc. The pattern of proper motions for these stars clearly displays the
expected effects from differential rotation. I measure the Oort constants to
be: A = 15.3+/-0.4 km/s/kpc, B = -11.9+/-0.4 km/s/kpc, C = -3.2+/-0.4 km/s/kpc
and K = -3.3+/-0.6 km/s/kpc, with no color trend over a wide range of stellar
populations. These first confident measurements of C and K clearly demonstrate
the importance of non-axisymmetry for the velocity field of local stars and
they provide strong constraints on non-axisymmetric models of the Milky Way.


title: Floquet symmetry-protected topological phases in cold atomic systems

abstract:
  We propose and analyze two distinct routes toward realizing interacting
symmetry-protected topological (SPT) phases via periodic driving. First, we
demonstrate that a driven transverse-field Ising model can be used to engineer
complex interactions which enable the emulation of an equilibrium SPT phase.
This phase remains stable only within a parametric time scale controlled by the
driving frequency, beyond which its topological features break down. To
overcome this issue, we consider an alternate route based upon realizing an
intrinsically Floquet SPT phase that does not have any equilibrium analog. In
both cases, we show that disorder, leading to many-body localization, prevents
runaway heating and enables the observation of coherent quantum dynamics at
high energy densities. Furthermore, we clarify the distinction between the
equilibrium and Floquet SPT phases by identifying a unique micromotion-based
entanglement spectrum signature of the latter. Finally, we propose a unifying
implementation in a one-dimensional chain of Rydberg-dressed atoms and show
that protected edge modes are observable on realistic experimental time scales.

categories: cond-mat.quant-gas cond-mat.dis-nn cond-mat.str-el quant-ph


title: Large-N correlation functions in ${\cal N} = 2$ superconformal QCD

abstract:
  We study extremal correlation functions of chiral primary operators in the
large-N SU(N) ${\cal N} = 2$ superconformal QCD theory and present new results
based on supersymmetric localization. We discuss extensively the
basis-independent data that can be extracted from these correlators using the
leading order large-N matrix model free energy given by the four-sphere
partition function. Special emphasis is given to single-trace 2- and 3-point
functions as well as a new class of observables that are scalars on the
conformal manifold. These new observables are particular quadratic combinations
of the structure constants of the chiral ring. At weak 't Hooft coupling we
present perturbative results that, in principle, can be extended to arbitrarily
high order. We obtain closed-form expressions up to the first subleading order.
At strong coupling we provide analogous results based on an approximate
Wiener-Hopf method.


title: Observation of a Nematic Quantum Hall Liquid on the Surface of Bismuth

abstract:
  Nematic quantum fluids with wavefunctions that break the underlying
crystalline symmetry can form in interacting electronic systems. We examine the
quantum Hall states that arise in high magnetic fields from anisotropic hole
pockets on the Bi(111) surface. Spectroscopy performed with a scanning
tunneling microscope shows that a combination of local strain and many-body
Coulomb interactions lift the six-fold Landau level (LL) degeneracy to form
three valley-polarized quantum Hall states. We image the resulting anisotropic
LL wavefunctions and show that they have a different orientation for each
broken-symmetry state. The wavefunctions correspond precisely to those expected
from pairs of hole valleys and provide a direct spatial signature of a nematic
electronic phase.


title:
The Tarantula Massive Binary Monitoring project: II. A first SB2 orbital
  and spectroscopic analysis for the Wolf-Rayet binary R145

abstract:
  We present the first SB2 orbital solution and disentanglement of the massive
Wolf-Rayet binary R145 (P = 159d) located in the Large Magellanic Cloud. The
primary was claimed to have a stellar mass greater than 300Msun, making it a
candidate for the most massive star known. While the primary is a known late
type, H-rich Wolf-Rayet star (WN6h), the secondary could not be so far
unambiguously detected. Using moderate resolution spectra, we are able to
derive accurate radial velocities for both components. By performing
simultaneous orbital and polarimetric analyses, we derive the complete set of
orbital parameters, including the inclination. The spectra are disentangled and
spectroscopically analyzed, and an analysis of the wind-wind collision zone is
conducted.
  The disentangled spectra and our models are consistent with a WN6h type for
the primary, and suggest that the secondary is an O3.5 If*/WN7 type star. We
derive a high eccentricity of e = 0.78 and minimum masses of M1 sin^3 i ~ M2
sin^3 i ~ 13 +- 2 Msun, with q = M2 / M1 = 1.01 +- 0.07. An analysis of
emission excess stemming from a wind-wind collision yields a similar
inclination to that obtained from polarimetry (i = 39 +- 6deg). Our analysis
thus implies M1 = 53^{+40}_{-20} and M2 = 54^{+40}_{-20} Msun, excluding M1 >
300Msun. A detailed comparison with evolution tracks calculated for single and
binary stars, as well as the high eccentricity, suggest that the components of
the system underwent quasi-homogeneous evolution and avoided mass-transfer.
This scenario would suggest current masses of ~ 80 Msun and initial masses of
Mi,1 ~ 105 and Mi,2 ~ 90Msun, consistent with the upper limits of our derived
orbital masses, and would imply an age of ~2.2 Myr.


title:
Field-free, spin-current control of magnetization in non-collinear
  chiral antiferromagnets

abstract:
  Non-collinear chiral antiferromagnets like Mn3Sn and Mn3Ge are known to show
gigantic anomalous Hall response depending on the orientation of their inverse
chiral magnetic order of Mn atoms in Kagome layers. Here we study the stability
of such magnetic order in the absence of external magnetic fields on the basis
of stochastic Landau-Lifshitz-Gilbert equation for a simplified two-dimensional
model of these materials. We find that even without external magnetic fields,
the ordered state is, once formed, highly stable against thermal fluctuations.
Moreover, we show that if Mn spins are well confined inside each Kagome layers,
by injecting spin-current using spin-filtering effect of ferromagnetic metals,
we can control the in-plane magnetic structure in a field free way.


title:
Detection of the magnetar SGR J1745-2900 up to 291 GHz with evidence of
  polarized millimetre emission

abstract:
  In Torne et al. (2015), we showed detections of SGR J1745-2900 up to 225 GHz
(1.33 mm); at that time the highest radio frequency detection of pulsar
emission. In this work, we present the results of new observations of the same
magnetar with detections up to 291 GHz (1.03 mm), together with evidence of
linear polarization in its millimetre emission. SGR J1745-2900 continues to
show variability and is, on average, a factor $\sim$4 brighter in the
millimetre band than in our observations of July 2014. The new measured
spectrum is slightly inverted, with $\left<\alpha\right> = +0.4\pm0.2$ (for
$S_{\nu} \propto \nu^{\alpha})$. However, the spectrum does not seem to be well
described by a single power law, which might be due to the intrinsic
variability of the source, or perhaps a turn-up somewhere between 8.35 and 87
GHz. These results may help us to improve our still incomplete model of pulsar
emission and, in addition, they further support the search for and study of
pulsars located at the Galactic Centre using millimetre wavelengths.


title: Capture and Decay of Electroweak WIMPonium

abstract:
  The spectrum of Weakly-Interacting-Massive-Particle (WIMP) dark matter
generically possesses bound states when the WIMP mass becomes sufficiently
large relative to the mass of the electroweak gauge bosons. The presence of
these bound states enhances the annihilation rate via resonances in the
Sommerfeld enhancement, but they can also be produced directly with the
emission of a low-energy photon. In this work we compute the rate for SU(2)
triplet dark matter (the wino) to bind into WIMPonium -- which is possible via
single-photon emission for wino masses above 5 TeV for relative velocity v <
O(10^{-2}) -- and study the subsequent decays of these bound states. We present
results with applications beyond the wino case, e.g. for dark matter inhabiting
a nonabelian dark sector; these include analytic capture and transition rates
for general dark sectors in the limit of vanishing force carrier mass,
efficient numerical routines for calculating positive and negative-energy
eigenstates of a Hamiltonian containing interactions with both massive and
massless force carriers, and a study of the scaling of bound state formation in
the short-range Hulthen potential. In the specific case of the wino, we find
that the rate for bound state formation is suppressed relative to direct
annihilation, and so provides only a small correction to the overall
annihilation rate. The soft photons radiated by the capture process and by
bound state transitions could permit measurement of the dark matter's quantum
numbers; for wino-like dark matter, such photons are rare, but might be
observable by a future ground-based gamma-ray telescope combining large
effective area and a low energy threshold.


title: Replica trick and string winding

abstract:
  We apply the replica trick to compute the entropy of a cylinder amplitude in
string theory. We focus on the contribution from non-perturbative winding modes
and impose tadpole cancellation to understand the correct prescription for
integrating over moduli. Choosing the entangling surface to cut longitudinally
over the whole length of the cylinder, we obtain an answer that is interpreted
as the entropy of a density matrix. We recast this result in target space
language, both in the open and closed string picture.


title: Does turbulence determine the initial mass function?

abstract:
  We test the hypothesis that the initial mass function (IMF) is determined by
the density probability distribution function (PDF) produced by supersonic
turbulence. We compare 14 simulations of star cluster formation in 50 solar
mass molecular cloud cores where the initial turbulence contains either purely
solenoidal or purely compressive modes, in each case resolving fragmentation to
the opacity limit to determine the resultant IMF. We find statistically
indistinguishable IMFs between the two sets of calculations, despite a factor
of two difference in the star formation rate and in the standard deviation of
$\log(\rho)$. This suggests that the density PDF, while determining the star
formation rate, is not the primary driver of the IMF.


title:
The SELGIFS data challenge: generating synthetic observations of CALIFA
  galaxies from hydrodynamical simulations

abstract:
  In this work we present a set of synthetic observations that mimic the
properties of the Integral Field Spectroscopy (IFS) survey CALIFA, generated
using radiative transfer techniques applied to hydrodynamical simulations of
galaxies in a cosmological context. The simulated spatially-resolved spectra
include stellar and nebular emission, kinematic broadening of the lines, and
dust extinction and scattering. The results of the radiative transfer
simulations have been post-processed to reproduce the main properties of the
CALIFA V500 and V1200 observational setups. The data has been further formatted
to mimic the CALIFA survey in terms of field of view size, spectral range and
sampling. We have included the effect of the spatial and spectral Point Spread
Functions affecting CALIFA observations, and added detector noise after
characterizing it on a sample of 20 galaxies. The simulated datacubes are
suited to be analyzed by the same algorithms used on real IFS data. In order to
provide a benchmark to compare the results obtained applying IFS observational
techniques to our synthetic datacubes, and test the calibration and accuracy of
the analysis tools, we have computed the spatially-resolved properties of the
simulations. Hence, we provide maps derived directly from the hydrodynamical
snapshots or the noiseless spectra, in a way that is consistent with the values
recovered by the observational analysis algorithms. Both the synthetic
observations and the product datacubes are public and can be found in the
collaboration website http://astro.ft.uam.es/selgifs/data_challenge/.


title: Violation of f-sum Rule with Generalized Kinetic Energy

abstract:
  Motivated by the normal state of the cuprates in which the f-sum rule
increases faster than a linear function of the particle density, we derive a
conductivity sum rule for a system in which the kinetic energy operator in the
Hamiltonian is a general function of the momentum squared. Such a kinetic
energy arises in scale invariant theories and can be derived within the context
of holography. Our derivation of the f-sum rule is based on the gauge couplings
of a non-local Lagrangian in which the kinetic operator is a fractional
Laplacian of order $\alpha$. We find that the f-sum rule in this case deviates
from the standard linear dependence on the particle density. We find two
regimes. At high temperatures and low densities, the sum rule is proportional
to $nT^{\frac{\alpha-1}{\alpha}}$ where $T$ is the temperature. At low
temperatures and high densities, the sum rule is proportional to
$n^{1+\frac{2(\alpha-1)}{d}}$ with $d$ being the number of spatial dimensions.
The result in the low temperature and high density limit, when $\alpha < 1$,
can be used to qualitatively explain the behavior of the effective number of
charge carriers in the cuprates at various doping concentrations.


title: Convectively driven sinks and magnetic fields in the quiet Sun

abstract:
  We study the relation between mesogranular flows, convectively driven sinks
and magnetic fields using high spatial resolution spectropolarimetric data
acquired with the Imaging Magnetograph eXperiment on board Sunrise. We obtain
the horizontal velocity flow fields of two quiet-Sun regions (31.2 $\times$
31.2 Mm$^{2}$) via local correlation tracking. Mesogranular lanes and the
central position of sinks are identified using Lagrange tracers. We find
$6.7\times10^{-2}$ sinks per Mm$^{2}$ in the two observed regions. The sinks
are located at the mesogranular vertices and turn out to be associated with (1)
horizontal velocity flows converging to a central point and (2) long-lived
downdrafts. The spatial distribution of magnetic fields in the quiet Sun is
also examined. The strongest magnetic fields are preferentially located at
sinks. We find that 40 \% of the pixels with longitudinal component of the
magnetic field stronger than 500 G are located in the close neighborhood of
sinks. In contrast, the small-scale magnetic loops detected by Mart\'{i}nez
Gonz\'{a}lez et al. in the same two observed areas do not show any preferential
distribution at mesogranular scales. The study of individual examples reveals
that sinks can play an important role in the evolution of quiet-Sun magnetic
features.


title: Interpretation of Lepton Flavor Violation

abstract:
  The observation of a charged-lepton flavor violating process would be a
definite sign for physics beyond the Standard Model, but would actually only
prove that one particular linear combination of lepton numbers is violated. We
categorize lepton-flavor-violating processes by their quantum numbers and show
how their discovery can be interpreted model independently, studying in
particular which processes are required to establish that the entire flavor
group is broken. We also comment on total lepton number, seeing as lepton
number violation practically implies lepton flavor violation as well.


title: Simulating cosmologies beyond $\Lambda$CDM with PINOCCHIO

abstract:
  We present a method that extends the capabilities of the PINpointing
Orbit-Crossing Collapsed HIerarchical Objects (PINOCCHIO) code, allowing it to
generate accurate dark matter halo mock catalogues in cosmological models where
the linear growth factor and the growth rate depend on scale. Such cosmologies
comprise, among others, models with massive neutrinos and some classes of
modified gravity theories. We validate the code by comparing the halo
properties from PINOCCHIO against N-body simulations, focusing on cosmologies
with massive neutrinos: $\nu\Lambda$CDM. We analyse the halo mass function,
halo two-point correlation function, halo power spectrum and the moments of the
halo density field, showing that PINOCCHIO reproduces the results from
simulations with the same level of precision as the original code
($\sim5-10\%$). We demonstrate that the abundance of halos in cosmologies with
massless and massive neutrinos from PINOCCHIO matches very well the outcome of
simulations, and point out that PINOCCHIO can reproduce the
$\Omega_\nu-\sigma_8$ degeneracy that affects the halo mass function. We show
that the clustering properties of the halos from PINOCCHIO matches accurately
those from simulations both in real and redshift-space, in the latter case up
to $k=0.3~h~{\rm Mpc}^{-1}$. We finally point out that the first moments of the
halo density field from simulations are precisely reproduced by PINOCCHIO. We
emphasize that the computational time required by PINOCCHIO to generate mock
halo catalogues is orders of magnitude lower than the one needed for N-body
simulations. This makes this tool ideal for applications like covariance matrix
studies within the standard $\Lambda$CDM model but also in cosmologies with
massive neutrinos or some modified gravity theories.


title:
Consistent Chiral Kinetic Theory in Weyl Materials: Chiral Magnetic
  Plasmons

abstract:
  We argue that the correct definition of the electric current in the chiral
kinetic theory for Weyl materials should include the Chern-Simons contribution
that makes the theory consistent with the local conservation of the electric
charge in electromagnetic and strain-induced pseudoelectromagnetic fields. By
making use of such a kinetic theory, we study the plasma frequencies of
collective modes in Weyl materials in constant magnetic and pseudomagnetic
fields, taking into account the effects of dynamical electromagnetism. We show
that the collective modes are chiral plasmons. While the plasma frequency of
the longitudinal collective mode coincides with the Langmuir one, this mode is
unusual because it is characterized not only by oscillations of the electric
current density, but also by oscillations of the chiral current density. The
latter are triggered by a dynamical version of the chiral electric separation
effect. We also find that the plasma frequencies of the transverse modes split
up in a magnetic field. This finding suggests an efficient means of extracting
the chiral shift parameter from the measurement of the plasma frequencies in
Weyl materials.


title: Assessing the quantumness of a damped two-level system

abstract:
  We perform a detailed analysis of the nonclassical properties of a damped
two-level system. We compute and compare three different criteria of
quantumness, the $l_1$-norm of coherence, the Leggett- Garg inequality and a
quantum witness based on the no-signaling in time condition. We show that all
three quantum indicators decay exponentially in time as a result of the
coupling to the thermal reservoir. We further demonstrate that the
corresponding characteristic times are identical and given by the coherence
half-life. These results quantify how violations of Leggett-Garg inequalities
and nonzero values of the quantum witness are connected to the coherence of the
two-level system.


title: Supersymmetry in the Fractional Quantum Hall Regime

abstract:
  Supersymmetry (SUSY) is a symmetry transforming bosons to fermions and vice
versa. Indications of its existence have been extensively sought after in
high-energy experiments. However, signatures of SUSY have yet to be detected.
In this manuscript we propose a condensed matter realization of SUSY on the
edge of a Read-Rezayi quantum Hall state, given by filling factors of the form
$\nu =\frac{k}{k+2}$, where $k$ is an integer. As we show, this strongly
interacting state exhibits an $\mathcal{N}=2$ SUSY. This allows us to use a
topological invariant - the Witten index - defined specifically for
supersymmetric theories, to count the difference between the number of bosonic
and fermionic zero-modes in a circular edge. In our system, we argue that the
edge hosts $k+1$ protected zero-modes. We further discuss the stability of SUSY
with respect to generic perturbations, and find that much of the above results
remain unchanged. In particular, these results directly apply to the
well-established $\nu=1/3$ Laughlin state, in which case SUSY is a highly
robust property of the edge theory. These results unveil a hidden topological
structure on the long-studied Read-Rezayi states.


title: Higher Categories and Topological Quantum Field Theories

abstract:
  We construct a state-sum type invariant of smooth closed oriented
$4$-manifolds out of a $G$-crossed braided spherical fusion category ($G$-BSFC)
for $G$ a finite group. The construction can be extended to obtain a
$(3+1)$-dimensional topological quantum field theory (TQFT). The invariant of
$4$-manifolds generalizes several known invariants in literature such as the
Crane-Yetter invariant from a ribbon fusion category and Yetter's invariant
from homotopy $2$-types. If the $G$-BSFC is concentrated only at the sector
indexed by the trivial group element, a cohomology class in $H^4(G,U(1))$ can
be introduced to produce a different invariant, which reduces to the twisted
Dijkgraaf-Witten theory in a special case. Although not proven, it is believed
that our invariants are strictly different from other known invariants. It
remains to be seen if the invariants are sensitive to smooth structures. It is
expected that the most general input to the state-sum type construction of
$(3+1)$-TQFTs is a spherical fusion $2$-category. We show that a $G$-BSFC
corresponds to a monoidal $2$-category with certain extra structure, but that
structure does not satisfy all the axioms of a spherical fusion $2$-category
given by M. Mackaay. Thus the question of what axioms properly define a
spherical fusion $2$-category is open.

categories: math.QA math-ph math.CT math.GT math.MP quant-ph


title: A Learned Representation For Artistic Style

abstract:
  The diversity of painting styles represents a rich visual vocabulary for the
construction of an image. The degree to which one may learn and parsimoniously
capture this visual vocabulary measures our understanding of the higher level
features of paintings, if not images in general. In this work we investigate
the construction of a single, scalable deep network that can parsimoniously
capture the artistic style of a diversity of paintings. We demonstrate that
such a network generalizes across a diversity of artistic styles by reducing a
painting to a point in an embedding space. Importantly, this model permits a
user to explore new painting styles by arbitrarily combining the styles learned
from individual paintings. We hope that this work provides a useful step
towards building rich models of paintings and offers a window on to the
structure of the learned representation of artistic style.


title:
First report of long term measurements of the {MGGL} laboratory in the
  {M}\'atra mountain range

abstract:
  Matra Gravitational and Geophysical Laboratory (MGGL) has been established
near Gy\"ongy\"osoroszi, Hungary in 2015, in the cavern system of an unused ore
mine. The Laboratory is located at 88~m below the surface, with the aim to
measure and analyse the advantages of the underground installation of third
generation gravitational wave detectors. Specialized instruments have been
installed to measure seismic, infrasound, electromagnetic noise, and the
variation of the cosmic muon flux. In the preliminary (RUN-0) test period,
March-August 2016, data collection has been accomplished. In this paper we
describe the research potential of the MGGL, list the installed equipments and
summarize the experimental results of RUN-0. Here we report RUN-0 data, that
prepares systematic and synchronized data collection of the next run period.


title: Dynamic Phases of Active Matter Systems with Quenched Disorder

abstract:
  Depinning and nonequilibrium transitions within sliding states in systems
driven over quenched disorder arise across a wide spectrum of size scales
ranging from atomic friction at the nanoscale, flux motion in type-II
superconductors at the mesoscale, colloidal motion in disordered media at the
microscale, and plate tectonics at geological length scales. Here we show that
active matter or self-propelled particles interacting with quenched disorder
under an external drive represents a new class of system that can also exhibit
pinning-depinning phenomena, plastic flow phases, and nonequilibrium sliding
transitions that are correlated with distinct morphologies and velocity-force
curve signatures. When interactions with the substrate are strong, a
homogeneous pinned liquid phase forms that depins plastically into a uniform
disordered phase and then dynamically transitions first into a moving stripe
coexisting with a pinned liquid and then into a moving phase separated state at
higher drives. We numerically map the resulting dynamical phase diagrams as a
function of external drive, substrate interaction strength, and self-propulsion
correlation length. These phases can be observed for active matter moving
through random disorder. Our results indicate that intrinsically nonequilibrium
systems can exhibit additional nonequilibrium transitions when subjected to an
external drive.


title:
Forward and Inverse Modeling of the Emission and Transmission Spectrum
  of GJ 436b: Investigating Metal Enrichment, Tidal Heating, and Clouds

abstract:
  The Neptune-mass GJ 436b is one of the most-studied transiting exoplanets
with repeated measurements of both its thermal emission and transmission
spectra. We build on previous studies to answer outstanding questions about
this planet, including its potentially high metallicity and tidal heating of
its interior. We present new observations of GJ 436b's thermal emission at 3.6
and 4.5 micron, which reduce uncertainties in estimates of GJ 436b's flux at
those wavelengths and demonstrate consistency between Spitzer observations
spanning more than 7 years. We analyze the Spitzer thermal emission photometry
and Hubble WFC3 transmission spectrum in tandem. We use a powerful dual-pronged
modeling approach, comparing these data to both self-consistent and retrieval
models. We vary the metallicity, intrinsic luminosity from tidal heating,
disequilibrium chemistry, and heat redistribution. We also study the effect of
clouds and photochemical hazes on the spectra, but do not find strong evidence
for either. The self-consistent and retrieval modeling combine to suggest that
GJ 436b has a high atmospheric metallicity, with best fits at or above several
hundred times solar metallicity, tidal heating warming its interior with
best-fit intrinsic effective effective temperatures around 300--350 K, and
disequilibrium chemistry. High metal-enrichments (>600x solar) can only occur
from the accretion of rocky, rather than icy, material. Assuming Tint~300--350
K, we find that Q'~2x10^5--10^6, larger than Neptune's Q', and implying a long
tidal circularization timescale for the planet's orbit. We suggest that
Neptune-mass planets may be a more diverse class than previously imagined, with
metal-enhancements potentially spanning several orders of magnitude, to perhaps
over 1000x solar metallicity. High fidelity observations with instruments like
JWST will be critical for characterizing this diversity.


title:
Comment on: `Single-shot simulations of dynamic quantum many-body
  systems' [arXiv:1501.03224]

abstract:
  In their recent paper [Nature Physics 15, 451 (2006)], Sakmann and Kasevich
study the formation of fringe patterns in ultra-cold Bose gases and claim:
`Here, we show how single shots can be simulated from numerical solutions of
the time-dependent many-body Schr\"odinger equation.' It would be remarkable if
they had solved this exponentially complex equation. Instead they solve
nonlinear equations with the aim to approximate the solution of the
Schr\"odinger equation. The authors proceed to criticize phase-space approaches
to simulating quantum dynamics and claim the impossibility of interpreting
single trajectories of the truncated Wigner (tW) method as single-shot
experimental outcomes. Here we aim to provide relevant context and elaborate
why we disagree with the authors' claims.


title: Kinematics of Magnetic Bright Features in the Solar Photosphere

abstract:
  Convective flows are known as the prime means of transporting magnetic fields
on the solar surface. Thus, small magnetic structures are good tracers of the
turbulent flows. We study the migration and dispersal of magnetic bright
features (MBFs) in intergranular areas observed at high spatial resolution with
Sunrise/IMaX. We describe the flux dispersal of individual MBFs as a diffusion
process whose parameters are computed for various areas in the quiet Sun and
the vicinity of active regions from seeing-free data. We find that magnetic
concentrations are best described as random walkers close to network areas
(diffusion index, gamma=1.0), travelers with constant speeds over a
supergranule (gamma=1.9-2.0), and decelerating movers in the vicinity of flux
emergence and/or within active regions (gamma=1.4-1.5). The three types of
regions host MBFs with mean diffusion coefficients of 130 km^2/s, 80-90 km^2/s,
and 25-70 km^2/s, respectively. The MBFs in these three types of regions are
found to display a distinct kinematic behavior at a confidence level in excess
of 95%.


title:
Master stability functions reveal diffusion-driven pattern formation in
  networks

abstract:
  We study diffusion-driven pattern-formation in networks of networks, a class
of multilayer systems, where different layers have the same topology, but
different internal dynamics. Agents are assumed to disperse within a layer by
undergoing random walks, while they can be created or destroyed by reactions
between or within a layer. We show that the stability of homogeneous steady
states can be analyzed with a master stability function approach that reveals a
deep analogy between pattern formation in networks and pattern formation in
continuous space.For illustration we consider a generalized model of ecological
meta-foodwebs. This fairly complex model describes the dispersal of many
different species across a region consisting of a network of individual
habitats while subject to realistic, nonlinear predator-prey interactions. In
this example the method reveals the intricate dependence of the dynamics on the
spatial structure. The ability of the proposed approach to deal with this
fairly complex system highlights it as a promising tool for ecology and other
applications.


title: A Mathematical Model for Fingerprinting-based Localization Algorithms

abstract:
  A general theoretical framework for Fingerprinting Localization Algorithms
(FPS), given their popularity, can be utilized for their performance studies.
In this work, after setting up an abstract model for FPS, it is shown that
fingerprinting-based localization problem can be cast as a hypothesis testing
(HT) problem and therefore various results in HT literature can be used to
provide insights, guidelines and performance bounds for general FPS. This
framework results in characterization of scaling limits of localization
reliability in terms of number of measurements and other environmental
parameters. It is suggested that Kullback-Leibler (KL) divergence between
probability distributions of selected feature for fingerprinting at different
locations encapsulates information about both accuracy and latency and can be
used as a central performance metric for studying FPS. Although developed for
an arbitrary fingerprint, the framework is particularly used for studying
simple Received Signal Strength (RSS)- based algorithm. The effect of various
parameters on the performance of fingerprinting algorithms is discussed, which
includes path loss and fading characteristics, number of measurements at each
point, number of anchors and their position, and placement of training points.
Representative simulations and experimentation are used to verify validity of
the theoretical frameworks in realistic setups.


title: Observables, Disassembled

abstract:
  This paper argues that non-self-adjoint operators can be observables. There
are only four ways for this to occur: non-self-adjoint observables can either
be normal operators, or be symmetric, or have a real spectrum, or have none of
these three properties. I explore each of these four classes of observables,
arguing that the class of normal operators provides an equivalent formulation
of quantum theory, whereas the other classes considerably extend it.

categories: physics.hist-ph math-ph math.MP quant-ph


title: Can supernova remnants accelerate protons up to PeV energies?

abstract:
  Supernova remnants are believed to be the sources of galactic cosmic rays.
Within this framework, diffusive shock acceleration must operate in these
objects and accelerate protons all the way up to PeV energies. To do so,
significant amplification of the magnetic field at the shock is required. The
goal of this paper is to investigate the capability of supernova remnants to
accelerate PeV protons. We present analytic estimates of the maximum energy of
accelerated protons under various assumptions about the field amplification at
supernova remnant shocks. We show that acceleration up to PeV energies is
problematic in all the scenarios considered. This implies that either a
different (more efficient) mechanism of field amplification operates at
supernova remnant shocks, or that the sources of galactic cosmic rays in the
PeV energy range should be searched somewhere else.


title: Online and Random-order Load Balancing Simultaneously

abstract:
  We consider the problem of online load balancing under lp-norms: sequential
jobs need to be assigned to one of the machines and the goal is to minimize the
lp-norm of the machine loads. This generalizes the classical problem of
scheduling for makespan minimization (case l_infty) and has been thoroughly
studied. However, despite the recent push for beyond worst-case analyses, no
such results are known for this problem. In this paper we provide algorithms
with simultaneous guarantees for the worst-case model as well as for the
random-order (i.e. secretary) model, where an arbitrary set of jobs comes in
random order. First, we show that the greedy algorithm (with restart), known to
have optimal O(p) worst-case guarantee, also has a (typically) improved
random-order guarantee. However, the behavior of this algorithm in the
random-order model degrades with p. We then propose algorithm SIMULTANEOUSLB
that has simultaneously optimal guarantees (within constants) in both
worst-case and random-order models. In particular, the random-order guarantee
of SIMULTANEOUSLB improves as p increases.
  One of the main components is a new algorithm with improved regret for Online
Linear Optimization (OLO) over the non-negative vectors in the lq ball.
Interestingly, this OLO algorithm is also used to prove a purely probabilistic
inequality that controls the correlations arising in the random-order model, a
common source of difficulty for the analysis. Another important component used
in both SIMULTANEOUSLB and our OLO algorithm is a smoothing of the lp-norm that
may be of independent interest. This smoothness property allows us to see
algorithm SIMULTANEOUSLB as essentially a greedy one in the worst-case model
and as a primal-dual one in the random-order model, which is instrumental for
its simultaneous guarantees.


title:
Regge meets collinear in strongly-coupled $\mathcal{N} = 4$ super
  Yang-Mills

abstract:
  We revisit the calculation of the six-gluon remainder function in planar
$\mathcal{N} = 4$ super Yang-Mills theory from the strong coupling TBA in the
multi-Regge limit and identify an infinite set of kinematically subleading
terms. These new terms can be compared to the strong coupling limit of the
finite-coupling expressions for the impact factor and the BFKL eigenvalue
proposed by Basso et al. in arXiv:1407.3766, which were obtained from an
analytic continuation of the Wilson loop OPE. After comparing the results order
by order in those subleading terms, we show that it is possible to precisely
map both formalisms onto each other. A similar calculation can be carried out
for the seven-gluon amplitude, the result of which shows that the central
emission vertex does not become trivial at strong coupling.


title:
Enhanced van der Waals epitaxy via electron transfer-enabled interfacial
  dative bond formation

abstract:
  Enhanced van der Waals (vdW) epitaxy of semiconductors on layered vdW
substrate is identified as the formation of dative bonds. For example, despite
that NbSe2 is a vdW layered material, first-principles calculations reveal that
the bond strength at CdTe-NbSe2 interface is five times as large as that of vdW
interaction at CdTe-graphene interface. The unconventional chemistry here is
enabled by an effective net electron transfer from Cd dangling-bond states at
CdTe surface to metallic non-bonding NbSe2 states, which is a necessary
condition to activate the Cd for enhanced binding with Se.


title: About the effects of diffusion in electric tomography

abstract:
  The Maxwell equations for an homogeneous medium in which electric currents
are composed of Ohmic, diffusive and impressed currents are written in the
static approximation in which displacements currents are neglected. Closed
exact expressions are given for the solutions of the charge density, electric
field potential and the magnetic field intensity as functions of the impressed
currents and densities. Also, approximate formulae for these magnitudes are
derived. The solutions correctly reproduce the conclusions of a previous work
in which the relevance of Yukawa like potentials determined by diffusion
effects were identified. Within the approximate solutions, the effective
potential generated by the impressed sources is given by the superposition of
Yukawa potentials created by the impressed charges concentrated in a given
volume element. This representation makes evident that at small spatial
regions, the experimental detectors are able to measure spherically symmetrical
signals, indicating the presence of electric monopoles. The discussion also
allows to argue that the magnetic field tomographic signal becomes completely
independent of the presence of diffusion in the medium. The analysis also
permits to determine the range of space and temporal frequencies in which the
diffusion effects might become important in justifying the detection of
monopole signals.


title: Quasiparticle anisotropic hydrodynamics

abstract:
  We study an azimuthally-symmetric boost-invariant quark-gluon plasma using
quasiparticle anisotropic hydrodynamics including the effects of both shear and
bulk viscosities. We compare results obtained using the quasiparticle method
with the standard anisotropic hydrodynamics and viscous hydrodynamics. We
consider the predictions of the three methods for the differential particle
spectra and mean transverse momentum. We find that the three methods agree for
small shear viscosity to entropy density ratio, $\eta/s$, but show differences
at large $\eta/s$. Additionally, we find that the standard anisotropic
hydrodynamics method shows suppressed production at low transverse-momentum
compared to the other two methods, and the bulk-viscous correction can drive
the primordial particle spectra negative at large $p_T$ in viscous
hydrodynamics.


title: Discrimination power of a quantum detector

abstract:
  We investigate the ability of a quantum measurement device to discriminate
two states or, generically, two hypothesis. In full generality, the measurement
can be performed a number $n$ of times, and arbitrary pre-processing of the
states and post-processing of the obtained data is allowed. Even if the two
hypothesis correspond to orthogonal states, perfect discrimination is not
always possible. There is thus an intrinsic error associated to the measurement
device, which we aim to quantify, that limits its discrimination power. We
minimize various error probabilities (averaged or constrained) over all pairs
of $n$-partite input states. These probabilities, or their exponential rates of
decrease in the case of large $n$, give measures of the discrimination power of
the device. For the asymptotic rate of the averaged error probability, we
obtain a Chernoff-type bound, dual to the standard Chernoff bound for which the
state pair is fixed and the optimization is over all measurements. The key
point in the derivation is that i.i.d. states become optimal in asymptotic
settings. Minimum asymptotic rates are also obtained for constrained error
probabilities, dual to Stein's Lemma and Hoeffding's bound. We further show
that adaptive protocols where the state preparer gets feedback from the
measurer do not improve the asymptotic rates. These rates thus quantify the
ultimate discrimination power of a measurement device.


title: Irreducible local systems on nilpotent orbits

abstract:
  Let G be a simple, simply-connected algebraic group over the complex numbers
with Lie algebra $\mathfrak g$. The main result of this article is a proof that
each irreducible representation of the fundamental group of the orbit O through
a nilpotent element $e \in \mathfrak g$ lifts to a representation of a
Jacobson-Morozov parabolic subgroup of G associated to e. This result was shown
in some cases by Barbasch and Vogan in their study of unipotent representations
for complex groups and, in general, in an unpublished part of the author's
doctoral thesis. In the last section of the article, we state two applications
of this result, whose details will appear elsewhere: to answering a question of
Lusztig regarding special pieces in the exceptional groups (joint work with Fu,
Juteau, and Levy); and to computing the G-module structure of the sections of
an irreducible local system on O. A key aspect of the latter application is
some new cohomological statements that generalize those in earlier work of the
author.


title:
Self-aligned local electrolyte gating of 2D materials with nanoscale
  resolution

abstract:
  In the effort to make 2D materials-based devices smaller, faster, and more
efficient, it is important to control charge carrier at lengths approaching the
nanometer scale. Traditional gating techniques based on capacitive coupling
through a gate dielectric cannot generate strong and uniform electric fields at
this scale due to divergence of the fields in dielectrics. This field
divergence limits the gating strength, boundary sharpness, and pitch size of
periodic structures, and restricts possible geometries of local gates (due to
wire packaging), precluding certain device concepts, such as plasmonics and
transformation optics based on metamaterials. Here we present a new gating
concept based on a dielectric-free self-aligned electrolyte technique that
allows spatially modulating charges with nanometer resolution. We employ a
combination of a solid-polymer electrolyte gate and an ion-impenetrable
e-beam-defined resist mask to locally create excess charges on top of the gated
surface. Electrostatic simulations indicate high carrier density variations of
$\Delta n =10^{14}\text{cm}^{-2}$ across a length of 10 nm at the mask
boundaries on the surface of a 2D conductor, resulting in a sharp depletion
region and a strong in-plane electric field of $6\times10^8 \text{Vm}^{-1}$
across the so-created junction. We apply this technique to the 2D material
graphene to demonstrate the creation of tunable p-n junctions for
optoelectronic applications. We also demonstrate the spatial versatility and
self-aligned properties of this technique by introducing a novel graphene
thermopile photodetector.