title: The strong profinite genus of a finitely presented group can be infinite

abstract:
  We construct the first example of a finitely-presented, residually-finite
group that contains an infinite sequence of non-isomorphic finitely-presented
subgroups such that each of the inclusion maps induces an isomorphism of
profinite completions.


title: Bending of Sparklers

abstract:
  A new equation is proposed to explain the curvature of spent sparklers. We
found the state of a segment of the sparkler to depend strongly on the state of
its spent segments. The equation is nearly able to produce the sparkler shape
for a range of lengths and for all elevation angles. The method proposed here
is likely to explain any phenomena in nature related to an evolving length
scale associated with some material that becomes progressively stiff or dry,
such as the growth of resin exuded from trees. The equation can produce a very
rich spectrum of shapes by varying material parameters (density,
temperature-dependent strength), heating temperature, elevation angle, and
gravitational acceleration. This might provide new insights into explaining
many shapes in nature or man-made structures.


title: Quatre applications du lemme de Zalcman \`a la dynamique complexe

abstract:
  We give four applications of Zalcman's lemma to the dynamics of rational maps
on the Riemann sphere: a parameter analogue of a proof of the density of
repelling cycles in the Julia sets;similarity between the Mandelbrot set and
the Julia sets; a construction of the Lyubich-Minsky lamination and its
variant; and a unified characterization of conical points by Lyubich-Minsky and
those by Martin-Mayer.


title: Using PT-symmetry for switching applications

abstract:
  This work introduces a new class of PT-symmetry grating assisted devices for
switching or modulation applications. Their operation is based on a four-wave
interaction, thus marking a step in the further development of PT-symmetry
devices which currently are essentially based on two-wave interactions. A
remarkable feature of the new device is that all their properties also hold for
the case of imperfect PT-symmetry operation, corresponding to the important
practical case of fixed losses.


title: Measuring the heat exchange of a quantum process

abstract:
  Very recently, interferometric methods have been proposed to measure the full
statistics of work performed on a driven quantum system [Dorner et al. Phys.
Rev. Lett. 110 230601 (2013)] and [Mazzola et al. Phys. Rev. Lett. 110 230602
(2013)]. The advantage of such schemes is that they replace the necessity to
make projective measurements by performing phase estimation on an appropriately
coupled ancilla qubit. These proposals are one possible route to the tangible
experimental exploration of quantum thermodynamics, a subject which is the
centre of much current attention due to the current control of mesoscopic
quantum systems. In this Letter we demonstrate that a modification of the phase
estimation protocols can be used in order to measure the heat distribution of a
quantum process. In addition we demonstrate how our scheme may be implemented
using ion trap technology. Our scheme should pave the way for the first
experimental explorations of the Landauer principle and hence the intricate
energy to information conversion in mesoscopic quantum systems.


title:
Long-lived nonequilibrium states in the Hubbard model with an electric
  field

abstract:
  We study the single-band Hubbard model in the presence of a large spatially
uniform electric field out of equilibrium. Using the Keldysh nonequilibrium
formalism, we solve the problem using perturbation theory in the Coulomb
interaction U. We present numerical results for the charge current, the total
energy of the system and the double occupancy on an infinite-dimensional
hypercubic lattice with nearest-neighbor hopping. The system is isolated from
an external bath and is in the paramagnetic state. We show that an electric
field pulse can drive the system to a steady nonequilibrium state, which does
not evolve into a thermal state. We compare results obtained within
second-order perturbation theory (SOPT), self-consistent second-order
perturbation theory (SCSOPT) and iterated perturbation theory (IPT). We also
discuss the importance of initial conditions for a system which is not coupled
to an external bath.


title:
Strong coupling constant of h$_{b}$ vector to the pseudoscalar and
  vector $B_{c}$ mesons in QCD sum rules

abstract:
  The strong coupling constant g$_{h_{b}B_{c}^{PS}B_{c}^{V}}$ is calculated
using the three-point QCD sum rules method. We use correlation functions to
obtain these strong coupling constants with contributions of both B$_{c}^{PS} $
and B$_{c}^{V}$mesons as off-shell states. The contributions of two gluon
condensates as a radiative correction are considered. The results show that
g$_{h_{b}B_{c}^{PS}B_{c}^{V}}=8.80\pm 2.84 GeV^{-1}$and g$_{h_{b}B_{c}^{V}
B_{c}^{PS}}=9.34\pm 3.12 GeV^{-1}$ in the $B_{c}^{PS}$ and $B_{c}^{V}$
off-shell state, respectively.


title: Short-Range Correlations in Magnetite above the Verwey Temperature

abstract:
  Magnetite, Fe$_3$O$_4$, is the first magnetic material discovered and
utilized by mankind in Ancient Greece, yet it still attracts attention due to
its puzzling properties. This is largely due to the quest for a full and
coherent understanding of the Verwey transition that occurs at $T_V=124$ K and
is associated with a drop of electric conductivity and a complex structural
phase transition. A recent detailed analysis of the structure, based on single
crystal diffraction, suggests that the electron localization pattern contains
linear three-Fe-site units, the so-called trimerons. Here we show that whatever
the electron localization pattern is, it partially survives up to room
temperature as short-range correlations in the high-temperature cubic phase,
easily discernible by diffuse scattering. Additionally, {\it ab initio}
electronic structure calculations reveal that characteristic features in these
diffuse scattering patterns can be correlated with the Fermi surface topology.


title:
Redrawing the Boundaries on Purchasing Data from Privacy-Sensitive
  Individuals

abstract:
  We prove new positive and negative results concerning the existence of
truthful and individually rational mechanisms for purchasing private data from
individuals with unbounded and sensitive privacy preferences. We strengthen the
impossibility results of Ghosh and Roth (EC 2011) by extending it to a much
wider class of privacy valuations. In particular, these include privacy
valuations that are based on ({\epsilon}, {\delta})-differentially private
mechanisms for non-zero {\delta}, ones where the privacy costs are measured in
a per-database manner (rather than taking the worst case), and ones that do not
depend on the payments made to players (which might not be observable to an
adversary). To bypass this impossibility result, we study a natural special
setting where individuals have mono- tonic privacy valuations, which captures
common contexts where certain values for private data are expected to lead to
higher valuations for privacy (e.g. having a particular disease). We give new
mech- anisms that are individually rational for all players with monotonic
privacy valuations, truthful for all players whose privacy valuations are not
too large, and accurate if there are not too many players with too-large
privacy valuations. We also prove matching lower bounds showing that in some
respects our mechanism cannot be improved significantly.


title:
Comment on `Critical scalar field collapse in AdS$_3$: an analytical
  approach'

abstract:
  We comment on the derivation of an analytical solution presented in
arXiv:1309.1629, show that it belongs to a family of separable solutions
previously constructed in arXiv:gr-qc/0109002, and question its relevance to
critical collapse.


title: Herschel-ATLAS/GAMA: SDSS cross-correlation induced by weak lensing

abstract:
  We report a highly significant ($>10\sigma$) spatial correlation between
galaxies with $S_{350\mu\rm m}\ge 30\,$mJy detected in the equatorial fields of
the \textsl{Herschel} Astrophysical Terahertz Large Area Survey (H-ATLAS) with
estimated redshifts $\gtrsim 1.5$, and SDSS or GAMA galaxies at $0.2\le z\le
0.6$. The significance of the cross-correlation is much higher than those
reported so far for samples with non-overlapping redshift distributions
selected in other wavebands. Extensive, realistic simulations of clustered
sub-mm galaxies amplified by foreground structures confirm that the
cross-correlation is explained by weak gravitational lensing ($\mu<2$). The
simulations also show that the measured amplitude and range of angular scales
of the signal are larger than can be accounted for by galaxy-galaxy weak
lensing. However, for scales $\lesssim 2\,$arcmin, the signal can be reproduced
if SDSS/GAMA galaxies act as signposts of galaxy groups/clusters with halo
masses in the range $10^{13.2}$--$10^{14.5} M_{\odot}$. The signal detected on
larger scales appears to reflect the clustering of such halos.


title: A direct proof that $\ell_\infty^{(3)}$ has generalized roundness zero

abstract:
  Metric spaces of generalized roundness zero have interesting non-embedding
properties. For instance, we note that no metric space of generalized roundness
zero is isometric to any metric subspace of any $L_{p}$-space for which $0 < p
\leq 2$. Lennard, Tonge and Weston gave an indirect proof that
$\ell_{\infty}^{(3)}$ has generalized roundness zero by appealing to highly
non-trivial isometric embedding theorems of Bretagnolle Dacunha-Castelle and
Krivine, and Misiewicz. In this paper we give a direct proof that
$\ell_{\infty}^{(3)}$ has generalized roundness zero. This provides insight
into the combinatorial geometry of $\ell_{\infty}^{(3)}$ that causes the
generalized roundness inequalities to fail. We complete the paper by noting a
characterization of real quasi-normed spaces of generalized roundness zero.


title: Rational homotopy theory of automorphisms of manifolds

abstract:
  We study the rational homotopy types of classifying spaces of automorphism
groups of smooth simply connected manifolds of dimension at least five. We give
dg Lie algebra models for the homotopy automorphisms and the block
diffeomorphisms of such manifolds.
  Moreover, we use these models to calculate the rational cohomology of the
classifying spaces of the homotopy automorphisms and block diffeomorphisms of
the manifold #^g S^d x S^d relative to an embedded disk as g tends to infinity.
The answer is expressed in terms of stable cohomology of arithmetic groups and
invariant Lie algebra cohomology. Through an extension of Kontsevich's work on
graph complexes, we relate our results to the (unstable) homology of
automorphisms of free groups with boundaries.


title: Fuzzballs and black hole thermodynamics

abstract:
  The fuzzball construction resolves the black hole information paradox by
making spacetime end just before the horizon is reached. But if there is no
traditional horizon, then do we lose the elegant relations of black hole
thermodynamics? Using an argument similar to modular invariance, we argue that
the answer is no; the completeness of fuzzball states implies that the generic
fuzzball indeed reproduces the thermal properties attributed to the traditional
hole.


title:
The Compatibility of Flare Temperatures Observed with AIA, GOES, and
  RHESSI

abstract:
  We test the compatibility and biases of multi-thermal flare DEM (differential
emission measure) peak temperatures determined with AIA with those determined
by GOES and RHESSI using the isothermal assumption. In a set of 149 M- and
X-class flares observed during the first two years of the SDO mission, AIA
finds DEM peak temperatures at the time of the peak GOES 1-8 A flux to have an
average of Tp = 12.0+/-2.9 MK and Gaussian DEM widths of log10(sigma_T) =
0.50+/-0.13. From GOES observations of the same 149 events, a mean temperature
of Tp = 15.6+/-2.4 MK is inferred, which is systematically higher by a factor
of TGOES/TAIA = 1.4+/-0.4. We demonstrate that this discrepancy results from
the isothermal assumption in the inversion of the GOES filter ratio. From
isothermal fits to photon spectra at energies of E ~ 6-12 keV of 61 of these
events, RHESSI finds the temperature to be higher still by a factor of
TRHESSI/TAIA = 1.9+/-1.0. We find that this is partly a consequence of the
isothermal assumption. However, RHESSI is not sensitive to the low-temperature
range of the DEM peak, and thus RHESSI samples only the high-temperature tail
of the DEM function. This can also contribute to the discrepancy between AIA
and RHESSI temperatures. The higher flare temperatures found by GOES and RHESSI
imply correspondingly lower emission measures. We conclude that self-consistent
flare DEM temperatures and emission measures require simultaneous fitting of
EUV (AIA) and soft X-ray (GOES and RHESSI) fluxes.


title:
The VV'P form factors in resonance chiral theory and the pi-eta-eta'
  light-by-light contribution to the muon g-2

abstract:
  The description of the VV'P form factors (V,V' stands for vector particles
and P for a pseudoscalar meson) for different particles virtualities remains a
challenge for the theory of strong interactions. While their chiral limit is
well understood, recent measurements of the gamma^* omega pi^0 and gamma^*
gamma pi^0 form factors at high photon virtualities seem to depart from the
simplest scaling behavior suggested by QCD. Here we attempt to describe them in
their whole measured energy regimes within the Resonance Chiral Theory, a
framework which naturally incorporates the chiral limit constraints and extends
to higher energies by including the resonances as active fields.
  Specifically, we obtained an accurate description of the data up to 2 GeV on
the former form factor by including three multiplets of vector resonances. Good
agreement with measurements of the latter was possible even in the single
resonance approximation, although we propose to measure the e^+e^- to
mu^+mu^-pi^0 cross-section and di-muon invariant mass distribution to better
characterize this form factor. We have then evaluated the pion exchange
contribution to the muon g-2 obtaining (6.66\pm0.21)x10^{-10} with an accurate
determination of the errors. We have also recalled that approximating the whole
pion exchange by the pion pole contribution underestimates the corresponding
result for the anomaly (by (15,20)%). Based on these results, we have predicted
the eta^(\prime) transition form factors obtaining good agreement with data and
obtained their respective contributions to the muon anomaly. In this way, the
contribution of the three lightest pseudoscalars to it yields
(10.47\pm0.54)x10^{-10}, in agreement with previous evaluations but with
smaller error.


title:
Functionalized Germanene as a Prototype of Large-Gap Two-Dimensional
  Topological Insulators

abstract:
  We propose new two-dimensional (2D) topological insulators (TIs) in
functionalized germanenes (GeX, X=H, F, Cl, Br or I) using first-principles
calculations. We find GeI is a 2D TI with a bulk gap of about 0.3 eV, while
GeH, GeF, GeCl and GeBr can be transformed into TIs with sizeable gaps under
achievable tensile strains. A unique mechanism is revealed to be responsible
for large topologically-nontrivial gap obtained: owing to the
functionalization, the $\sigma$ orbitals with stronger spin-orbit coupling
(SOC) dominate the states around the Fermi level, instead of original $\pi$
orbitals with weaker SOC; thereinto, the coupling of the $p_{xy}$ orbitals of
Ge and heavy halogens in forming the $\sigma$ orbitals also plays a key role in
the further enlargement of the gaps in halogenated germanenes. Our results
suggest a realistic possibility for the utilization of topological effects at
room temperature.


title:
Generation of phase-matched circularly-polarized extreme ultraviolet
  high harmonics for magnetic circular dichroism spectroscopy

abstract:
  Circularly-polarized extreme UV and X-ray radiation provides valuable access
to the structural, electronic and magnetic properties of materials. To date,
this capability was available only at large-scale X-ray facilities such as
synchrotrons. Here we demonstrate the first bright, phase-matched, extreme UV
circularly-polarized high harmonics and use this new light source for magnetic
circular dichroism measurements at the M-shell absorption edges of Co. We show
that phase matching of circularly-polarized harmonics is unique and robust,
producing a photon flux comparable to the linearly polarized high harmonic
sources that have been used very successfully for ultrafast element-selective
magneto-optic experiments. This work thus represents a critical advance that
makes possible element-specific imaging and spectroscopy of multiple elements
simultaneously in magnetic and other chiral media with very high spatial and
temporal resolution, using tabletop-scale setups.


title: Faraday signature of magnetic helicity from reduced depolarization

abstract:
  Using one-dimensional models, we show that a helical magnetic field with an
appropriate sign of helicity can compensate the Faraday depolarization
resulting from the superposition of Faraday-rotated polarization planes from a
spatially extended source. For radio emission from a helical magnetic field,
the polarization as a function of the square of the wavelength becomes
asymmetric with respect to zero. Mathematically speaking, the resulting
emission occurs then either at observable or at unobservable (imaginary)
wavelengths. We demonstrate that rotation measure (RM) synthesis allows for the
reconstruction of the underlying Faraday dispersion function in the former
case, but not in the latter. The presence of positive magnetic helicity can
thus be detected by observing positive RM in highly polarized regions in the
sky and negative RM in weakly polarized regions. Conversely, negative magnetic
helicity can be detected by observing negative RM in highly polarized regions
and positive RM in weakly polarized regions. The simultaneous presence of two
magnetic constituents with opposite signs of helicity is shown to possess
signatures that can be quantified through polarization peaks at specific
wavelengths and the gradient of the phase of the Faraday dispersion function.
Similar polarization peaks can tentatively also be identified for the
bi-helical magnetic fields that are generated self-consistently by a dynamo
from helically forced turbulence, even though the magnetic energy spectrum is
then continuous. Finally, we discuss the possibility of detecting magnetic
fields with helical and non-helical properties in external galaxies using the
Square Kilometre Array.


title: Dynamics and Stability of Chiral Fluid

abstract:
  Starting from the linear sigma model with constituent quarks we derive the
chiral fluid dynamics where hydrodynamic equations for the quark fluid are
coupled to the equation of motion for the order-parameter field. In a static
system at thermal equilibrium this model leads to a chiral phase transition
which, depending on the choice of the quark-meson coupling constant, could be a
crossover or a first order one. We investigate the stability of the chiral
fluid in the static and expanding backgrounds by considering the evolution of
perturbations with respect to the mean-field solution. In the static background
the spectrum of plane-wave perturbations consists of two branches, one
corresponding to the sound waves and another to the sigma-meson excitations.
For large couplings these two branches "cross" and the excitation spectrum
acquires exponentially growing modes. The stability analysis is also done for
the Bjorken-like background solution by explicitly solving the time-dependent
differential equation for perturbations in the eta-space. In this case the
growth rate of unstable modes is significantly reduced.


title: An Epistemic model of Quantum State with Ontic Probability Amplitude

abstract:
  We first prove that ontological models of the quantum state which are capable
of reproducing the Born probability rule and fall in the class of
$\psi$-epistemic models are inconsistent with the Sch{\"o}dinger time
evolution. We then model the ontic state space as a complex projective Hilbert
space that embeds the projective Hilbert space of quantum mechanics and define
a minimalist epistemic state as an average over a set of "hidden states" in the
larger space. We show that such a model incorporates probability amplitudes and
admits an epistemic interpretation of quantum states. Finally, we prove a
second theorem to show that such a model is compatible with locality but ontic
models are not.


title:
Learning $\ell_1$-based analysis and synthesis sparsity priors using
  bi-level optimization

abstract:
  We consider the analysis operator and synthesis dictionary learning problems
based on the the $\ell_1$ regularized sparse representation model. We reveal
the internal relations between the $\ell_1$-based analysis model and synthesis
model. We then introduce an approach to learn both analysis operator and
synthesis dictionary simultaneously by using a unified framework of bi-level
optimization. Our aim is to learn a meaningful operator (dictionary) such that
the minimum energy solution of the analysis (synthesis)-prior based model is as
close as possible to the ground-truth. We solve the bi-level optimization
problem using the implicit differentiation technique. Moreover, we demonstrate
the effectiveness of our leaning approach by applying the learned analysis
operator (dictionary) to the image denoising task and comparing its performance
with state-of-the-art methods. Under this unified framework, we can compare the
performance of the two types of priors.


title:
Perfect alignment and preferential orientation of nitrogen-vacancy
  centers during CVD growth of diamond on (111) surfaces

abstract:
  Synthetic diamond production is key to the development of quantum metrology
and quantum information applications of diamond. The major quantum sensor and
qubit candidate in diamond is the nitrogen-vacancy (NV) color center. This
lattice defect comes in four different crystallographic orientations leading to
an intrinsic inhomogeneity among NV centers that is undesirable in some
applications. Here, we report a microwave plasma-assisted chemical vapor
decomposition (MPCVD) diamond growth technique on (111)-oriented substrates
that yields perfect alignment ($94\pm2%$) of as-grown NV centers along a single
crystallographic direction. In addition, clear evidence is found that the
majority ($74\pm4%$) of the aligned NV centers were formed by the nitrogen
being first included in the (111) growth surface and then followed by the
formation of a neighboring vacancy on top. The achieved homogeneity of the
grown NV centers will tremendously benefit quantum information and metrology
applications.


title:
Revisiting loss-specific training of filter-based MRFs for image
  restoration

abstract:
  It is now well known that Markov random fields (MRFs) are particularly
effective for modeling image priors in low-level vision. Recent years have seen
the emergence of two main approaches for learning the parameters in MRFs: (1)
probabilistic learning using sampling-based algorithms and (2) loss-specific
training based on MAP estimate. After investigating existing training
approaches, it turns out that the performance of the loss-specific training has
been significantly underestimated in existing work. In this paper, we revisit
this approach and use techniques from bi-level optimization to solve it. We
show that we can get a substantial gain in the final performance by solving the
lower-level problem in the bi-level framework with high accuracy using our
newly proposed algorithm. As a result, our trained model is on par with highly
specialized image denoising algorithms and clearly outperforms
probabilistically trained MRF models. Our findings suggest that for the
loss-specific training scheme, solving the lower-level problem with higher
accuracy is beneficial. Our trained model comes along with the additional
advantage, that inference is extremely efficient. Our GPU-based implementation
takes less than 1s to produce state-of-the-art performance.


title:
The influence of the matter along the line of sight and in the lens
  environment on the strong gravitational lensing

abstract:
  We investigate the influence of the matter along the line of sight and in the
lens environment on the image configurations, relative time delays, and the
resulting models of strong gravitational lensing. The distribution of matter in
space and properties of gravitationally bound haloes are based on the
Millennium Simulation. In our numerical experiments we consider isolated lens
in a uniform universe model and the same lens surrounded by close neighbours
and/or objects close to the line of sight which gives four different
descriptions of the light propagation. We compare the results of the lens
modeling which neglects effects of the environment and line of sight, when
applied to image configurations resulting from approaches partially or fully
taking into account these effects. We show that for a source at the redshift
z=2 the effects are indeed important and may prevent successful fitting of lens
models in a substantial part of simulated image configurations, especially when
the relative time delays are taken into account. To have good constraints on
the models we limit ourselves to configurations of four images. We consider
eighty lenses and large number of source positions in each case. The influence
of the lens neighbourhood and the line of sight introduces the spread into the
fitted values of the deflection angles which translates into the spread in the
lens velocity dispersion of 4 per cent. Similarly for the lens axis ratio we
get the spread of 10 per cent and for the Hubble's constant of 6 per cent. When
averaged over all lenses and all image configurations considered, the median
fitted values of the parameters (including the Hubble's constant) do not differ
more than 1 per cent from their values used in simulations.


title:
On the role of Gittins index in singular stochastic control:
  semi-explicit solutions via the Wiener-Hopf factorisation

abstract:
  This paper examines a class of singular stochastic control problems with
convex objective functions. In Section 2, we use tools from convex analysis to
derive necessary and sufficient first order conditions for this class of
optimisation problems. The main result of this paper is Theorem 9 which uses
results from optimal stopping to establish the link between singular stochastic
control and Gittin's index without the need to appeal to the representation
result in [5]. In Sections 3-5 we assume the singular control problem is driven
by a L\'{e}vy process. Expressions for the Gittin's index are derived in terms
of the Wiener-Hopf factorisation. This allows us to broaden the class of
parameterised optimal stopping problems with explicit solutions examined in [6]
and derive explicit solutions to the singular control problems studied in
Section 2. In Section 4, we apply our results to the `monotone follower'
problem which originates in [7] and [28]. In Section 5, we apply our results to
an irreversible investment problem which has been studied in [9], [35] and
[40].


title:
Radiative rates for E1, E2, M1, and M2 transitions among the
  3s$^2$3p$^5$, 3s3p$^6$, and 3s$^2$3p$^4$3d configurations of Cl-like W LVIII

abstract:
  We report calculations of energy levels, radiative decay rates, and lifetimes
for transitions among the 3s$^2$3p$^5$, 3s3p$^6$, and 3s$^2$3p$^4$3d
configurations of Cl-like W LVIII. The general-purpose relativistic atomic
structure package (GRASP) has been adopted for our calculations. Comparisons
are made with the most recent results of Mohan et al. [Can. J. Phys. {\bf 92}
(2014) xxx] and discrepancies in lifetimes are noted, up to four orders of
magnitude in some instances. Our energy levels are estimated to be accurate to
better than 0.5\%, whereas results for radiative rates and lifetimes should be
accurate to better than 20\%.


title: Alignment of D-state Rydberg molecules

abstract:
  We report on the formation of ultralong-range Rydberg D-state molecules via
photoassociation in an ultracold cloud of rubidium atoms. By applying a
magnetic offset field on the order of 10 G and high resolution spectroscopy, we
are able to resolve individual rovibrational molecular states. A full theory,
using the Born-Oppenheimer approximation including s- and p-wave scattering,
reproduces the measured binding energies. The calculated molecular
wavefunctions show that in the experiment we can selectively excite stationary
molecular states with an extraordinary degree of alignment or anti-alignment
with respect to the magnetic field axis.


title: A bi-level view of inpainting - based image compression

abstract:
  Inpainting based image compression approaches, especially linear and
non-linear diffusion models, are an active research topic for lossy image
compression. The major challenge in these compression models is to find a small
set of descriptive supporting points, which allow for an accurate
reconstruction of the original image. It turns out in practice that this is a
challenging problem even for the simplest Laplacian interpolation model. In
this paper, we revisit the Laplacian interpolation compression model and
introduce two fast algorithms, namely successive preconditioning primal dual
algorithm and the recently proposed iPiano algorithm, to solve this problem
efficiently. Furthermore, we extend the Laplacian interpolation based
compression model to a more general form, which is based on principles from
bi-level optimization. We investigate two different variants of the Laplacian
model, namely biharmonic interpolation and smoothed Total Variation
regularization. Our numerical results show that significant improvements can be
obtained from the biharmonic interpolation model, and it can recover an image
with very high quality from only 5% pixels.


title:
Characterizing the quiescent X-ray variability of the black hole low
  mass x-ray binary V404 Cyg

abstract:
  We conducted the first long-term (75 days) X-ray monitoring of the black hole
low mass X-ray binary V404 Cyg, with the goal of understanding and
characterizing its variability during quiescence. The X-ray light curve of V404
shows several flares on timescales of hours with a count rate change of a
factor of about 5-8. The root mean square variability is Fvar = 57.0(3.2)
percent. The first order structure function is consistent with both a power
spectrum of index -1 (flicker noise), or with a power spectrum of index 0
(white noise), implying that the light curve is variable on timescales from
days to months. The X-ray spectrum is well fitted by a power law with spectral
index {\Gamma} = 2.10 - 2.35, and we found that the spectral shape remains
roughly constant as the flux changes. A constant spectral shape with respect to
a change in the X-ray flux may favour a scenario in which the X-ray emission is
dominated by synchrotron radiation produced in a jet.


title:
The effect of confinement and stiffness on the conformational change of
  a semiflexible homopolymer chain

abstract:
  We analyse the nature of the confinement of an infinitely long (and finite)
linear semiflexible homo-polymer chain confined in between two geometrical
constraints (A&B) under good solvent condition in two dimensions. The
constraints are stair shaped impenetrable lines. A lattice model of fully
directed self avoiding walk is used to list information of walks of the
confined chain and the exact enumeration technique is used for the canonical
ensemble of conformations of the confined chain to discuss equilibrium
statistics of the chain. We obtain the probability of polymerization of the
confined flexible chain segments with either one end (polymer trains) or both
the ends of the confined chain lying on the stair shaped constraints (polymer
bridge and arc). We have also calculated the force of confinement exerted by
the constraints on to the chain or the force exerted by the chain on the
geometrical constraints using grand canonical ensemble theory and discuss
nature of variation of the force.


title:
Vaidya Solutions in General Covariant Ho\v{r}ava-Lifshitz Gravity
  without Projectability: Infrared Limit

abstract:
  In this paper, we have studied nonstationary radiative spherically symmetric
spacetime, in general covariant theory ($U(1)$ extension) of
Ho\v{r}ava-Lifshitz gravity without the projectability condition and in the
infrared limit. The Newtonian prepotential $\varphi$ was assumed null. We have
shown that there is not the analogue of the Vaidya's solution in the
Ho\v{r}ava-Lifshitz Theory (HLT), as we know in the General Relativity Theory
(GRT). Therefore, we conclude that the gauge field $A$ should interact with the
null radiation field of the Vaidya's spacetime in the HLT.


title: The Snell law for quaternionic potentials

abstract:
  By using the analogy between optics and quantum mechanics, we obtain the
Snell law for the planar motion of quantum particles in the presence of
quaternionic potentials.


title: Black phosphorus field-effect transistors

abstract:
  Two-dimensional crystals have emerged as a new class of materials with novel
properties that may impact future technologies. Experimentally identifying and
characterizing new functional two-dimensional materials in the vast material
pool is a tremendous challenge, and at the same time potentially rewarding. In
this work, we succeed in fabricating field-effect transistors based on
few-layer black phosphorus crystals with thickness down to a few nanometers.
Drain current modulation on the order of 10E5 is achieved in samples thinner
than 7.5 nm at room temperature, with well-developed current saturation in the
IV characteristics, both are important for reliable transistor performance of
the device. Sample mobility is also found to be thickness dependent, with the
highest value up to ~ 1000 cm2/Vs obtained at thickness ~ 10 nm. Our results
demonstrate the potential of black phosphorus thin crystal as a new
two-dimensional material for future applications in nano-electronic devices.


title: Squeezed light

abstract:
  The squeezed state of the electromagnetic field can be generated in many
nonlinear optical processes and finds a wide range of applications in quantum
information processing and quantum metrology. This article reviews the basic
properties of single-and dual-mode squeezed light states, methods of their
preparation and detection, as well as their quantum technology applications.


title: The Morpho-kinematics of Planetary Nebulae with Binary Central Stars

abstract:
  It is now clear that a binary formation pathway is responsible for a
significant fraction of planetary nebulae, and this increased sample of known
binaries means that we are now in a position to begin to constrain their
influence on the formation and evolution of their host nebulae. Here, we will
review current understanding of how binarity influences the resulting nebulae,
based on observations and modelling of both the central binary systems and the
planetary nebulae themselves. We will also highlight the most important
test-cases which have proved the most interesting in studying the evolution of
binaries into and through the planetary nebula phase.


title: ALMA reveals the feeding of the Seyfert 1 nucleus in NGC 1566

abstract:
  We report ALMA observations of CO(3-2) emission in the Seyfert 1 galaxy NGC
1566, at a spatial resolution of 25 pc. Our aim is to investigate the
morphology and dynamics of the gas inside the central kpc, and to probe nuclear
fueling and feedback phenomena. NGC 1566 has a nuclear bar of 1.7 kpc radius
and a conspicuous grand design spiral starting from this radius. The ALMA field
of view, of diameter 0.9 kpc, lies well inside the nuclear bar and reveals a
molecular trailing spiral structure from 50 to 300~pc in size, which is
contributing to fuel the nucleus, according to its negative gravity torques.
  The spiral starts with a large pitch angle from the center and then winds up
in a pseudo-ring at the inner Lindblad resonance (ILR) of the nuclear bar.
  This is the first time that a trailing spiral structure is clearly seen
driving the gas inwards inside the ILR ring of the nuclear bar. This phenomenon
shows that the massive central black hole has a significant dynamical influence
on the gas, triggering its fueling.
  The gaseous spiral is well correlated with the dusty spiral seen through
extinction in HST images, and also with a spiral feature emitting 0.87mm
continuum. This continuum emission must come essentially from cold dust heated
by the interstellar radiation field. The HCN(4-3) and HCO+(4-3) lines were
simultaneously mapped and detected in the nuclear spiral. The HCO+(4-3) line is
3 times stronger than the HCN(4-3), as expected when star formation excitation
dominates over active galactic nucleus (AGN) heating. The CO(3-2)/HCO+(4-3)
integrated intensity ratio is \sim 100.
  The molecular gas is in remarkably regular rotation, with only slight
non-circular motions at the periphery of the nuclear spiral arms. These
perturbations are quite small, and no outflow nor AGN feedback is detected.


title:
Towards a systematic characterization of the potential of demand side
  management

abstract:
  With an increasing share of electric energy produced from non-dispatchable
renewable sources both energy storage and demand side management might gain
tremendously in importance. While there has been significant progress in
general properties and technologies of energy storage, the systematic
characterization of features particular to demand side management such as its
intermittent, time-dependent potential seems to be lagging behind. As a
consequence, the development of efficient and sustainable strategies for demand
side management and its integration into large-scale energy system models are
impeded. This work introduces a novel framework for a systematic time-resolved
characterization of the potential for demand side management. It is based on
the specification of individual devices both with respect to their scheduled
demand and their potential of load shifting. On larger scales sector-specific
profiles can straightforwardly be taken into account. The potential for demand
side management is then specified in terms of size and capacity of an
equivalent storage device. This intermediate layer of abstraction isolates the
gross effects and opportunities of demand side management from questions
concerning the operation of individual devices, which eases the integration of
the results in existing schemes for the commitment of production units and
system models. The novel framework is applicable for conceptual or predictive
approaches and for real-time optimization and operation of energy systems
involving demand side management.


title:
Searchlight-based multi-voxel pattern analysis of fMRI by
  cross-validated MANOVA

abstract:
  Multi-voxel pattern analysis (MVPA) is a fruitful and increasingly popular
complement to traditional univariate methods of analyzing neuroimaging data. We
propose to replace the standard 'decoding' approach to searchlight-based MVPA,
measuring the performance of a classifier by its accuracy, with a method based
on the multivariate form of the general linear model. Following the
well-established methodology of multivariate analysis of variance (MANOVA), we
define a measure that directly characterizes the structure of multi-voxel data,
the pattern distinctness $D$. Our measure is related to standard multivariate
statistics, but we apply cross-validation to obtain an unbiased estimate of its
population value, independent of the amount of data or its partitioning into
'training' and 'test' sets. The estimate $\hat D$ can therefore serve not only
as a test statistic, but as an interpretable measure of multivariate effect
size. The pattern distinctness generalizes the Mahalanobis distance to an
arbitrary number of classes, but also the case where there are no classes of
trials because the design is described by parametric regressors. It is defined
for arbitrary estimable contrasts, including main effects (pattern differences)
and interactions (pattern changes). In this way, our approach makes the full
analytical power of complex factorial designs known from univariate fMRI
analyses available to MVPA studies. Moreover, we show how the results of a
factorial analysis can be used to obtain a measure of pattern stability, the
equivalent of 'cross-decoding'.


title: The detectability of eccentric binary pulsars

abstract:
  Studies of binary pulsars provide insight into various theories of physics.
Detection of such systems is challenging due to the Doppler modulation of the
pulsed signal caused by the orbital motion of the pulsar. We investigated the
loss of sensitivity in eccentric binary systems for different types of
companions. This reduction of sensitivity should be considered in future
population synthesis models for binary pulsars. This loss can be recovered
partially by employing the `acceleration search' algorithm and even better by
using the `acceleration-jerk search' algorithm.


title:
Structure of longitudinal chromomagnetic fields in high energy
  collisions

abstract:
  We compute expectation values of spatial Wilson loops in the forward light
cone of high-energy collisions. We consider ensembles of gauge field
configurations generated from a classical Gaussian effective action as well as
solutions of high-energy renormalization group evolution with fixed and running
coupling. The initial fields correspond to a color field condensate exhibiting
domain-like structure over distance scales of order the saturation scale. At
later times universal scaling emerges at large distances for all ensembles,
with a nontrivial critical exponent. Finally, we compare the results for the
Wilson loop to the two-point correlator of magnetic fields.


title:
FullSWOF: A free software package for the simulation of shallow water
  flows

abstract:
  Numerical simulations of flows are required for numerous applications, and
are usually carried out using shallow water equations. We describe the FullSWOF
software which is based on up-to-date finite volume methods and well-balanced
schemes to solve this kind of equations. It consists of a set of open source
C++ codes, freely available to the community, easy to use, and open for further
development. Several features make FullSWOF particularly suitable for
applications in hydrology: small water heights and wet-dry transitions are
robustly handled, rainfall and infiltration are incorporated, and data from
grid-based digital topographies can be used directly. A detailed mathematical
description is given here, and the capabilities of FullSWOF are illustrated
based on analytic solutions and datasets of real cases. The codes, available in
1D and 2D versions, have been validated on a large set of benchmark cases,
which are available together with the download information and documentation at
http://www.univ-orleans.fr/mapmo/soft/FullSWOF/.


title:
Lower bounds on the communication complexity of two-party (quantum)
  processes

abstract:
  The process of state preparation, its transmission and subsequent measurement
can be classically simulated through the communication of some amount of
classical information. Recently, we proved that the minimal communication cost
is the minimum of a convex functional over a space of suitable probability
distributions. It is now proved that this optimization problem is the dual of a
geometric programming maximization problem, which displays some appealing
properties. First, the number of variables grows linearly with the input size.
Second, the objective function is linear in the input parameters and the
variables. Finally, the constraints do not depend on the input parameters.
These properties imply that, once a feasible point is found, the computation of
a lower bound on the communication cost in any two-party process is linearly
complex. The studied scenario goes beyond quantum processes and includes the
communication complexity scenario introduced by Yao. We illustrate the method
by analytically deriving some non-trivial lower bounds. Finally, we conjecture
the lower bound $n 2^n$ for a noiseless quantum channel with capacity $n$
qubits. This bound can have an interesting consequence in the context of the
recent quantum-foundational debate on the reality of the quantum state.


title: Cognitive Robotics: for never was a story of more woe than this

abstract:
  We are now on the verge of the next technical revolution - robots are going
to invade our lives. However, to interact with humans or to be incorporated
into a human "collective" robots have to be provided with some human-like
cognitive abilities. What does it mean? - nobody knows. But robotics research
communities are trying hard to find out a way to cope with this problem.
Meanwhile, despite abundant funding these efforts did not lead to any
meaningful result (only in Europe, only in the past ten years, Cognitive
Robotics research funding has reached a ceiling of 1.39 billion euros). In the
next ten years, a similar budget is going to be spent to tackle the Cognitive
Robotics problems in the frame of the Human Brain Project. There is no reason
to expect that this time the result will be different. I would like to try to
explain why I'm so unhappy about this.


title:
Towards the selection of patients requiring ICD implantation by
  automatic classification from Holter monitoring indices

abstract:
  The purpose of this study is to optimize the selection of prophylactic
cardioverter defibrillator implantation candidates. Currently, the main
criterion for implantation is a low Left Ventricular Ejection Fraction (LVEF)
whose specificity is relatively poor. We designed two classifiers aimed to
predict, from long term ECG recordings (Holter), whether a low-LVEF patient is
likely or not to undergo ventricular arrhythmia in the next six months. One
classifier is a single hidden layer neural network whose variables are the most
relevant features extracted from Holter recordings, and the other classifier
has a structure that capitalizes on the physiological decomposition of the
arrhythmogenic factors into three disjoint groups: the myocardial substrate,
the triggers and the autonomic nervous system (ANS). In this ad hoc network,
the features were assigned to each group; one neural network classifier per
group was designed and its complexity was optimized. The outputs of the
classifiers were fed to a single neuron that provided the required probability
estimate. The latter was thresholded for final discrimination A dataset
composed of 186 pre-implantation 30-mn Holter recordings of patients equipped
with an implantable cardioverter defibrillator (ICD) in primary prevention was
used in order to design and test this classifier. 44 out of 186 patients
underwent at least one treated ventricular arrhythmia during the six-month
follow-up period. Performances of the designed classifier were evaluated using
a cross-test strategy that consists in splitting the database into several
combinations of a training set and a test set. The average arrhythmia
prediction performances of the ad-hoc classifier are NPV = 77% $\pm$ 13% and
PPV = 31% $\pm$ 19% (Negative Predictive Value $\pm$ std, Positive Predictive
Value $\pm$ std). According to our study, improving prophylactic
ICD-implantation candidate selection by automatic classification from ECG
features may be possible, but the availability of a sizable dataset appears to
be essential to decrease the number of False Negatives.


title:
Separating electric field and thermal effects across the metal-insulator
  transition in vanadium oxide nanobeams

abstract:
  We present results from an experimental study of the equilibrium and
non-equilibrium transport properties of vanadium oxide nanobeams near the
metal-insulator transition (MIT). Application of a large electric field in the
insulating phase across the nanobeams produces an abrupt MIT and the individual
roles of thermal and non-thermal effects in driving the transition are studied.
Transport measurements at temperatures ($T$) far below the critical temperature
($T_c$) of MIT, in several nanoscale vanadium oxide devices, show that both $T$
and electric field play distinctly separate, but critical roles in inducing the
MIT. Specifically, at $T << T_c$ electric field dominates the MIT through an
avalanche-type process, whereas thermal effects become progressively critical
as $T$ approaches $T_c$.


title: Analysis of Probabilistic Basic Parallel Processes

abstract:
  Basic Parallel Processes (BPPs) are a well-known subclass of Petri Nets. They
are the simplest common model of concurrent programs that allows unbounded
spawning of processes. In the probabilistic version of BPPs, every process
generates other processes according to a probability distribution. We study the
decidability and complexity of fundamental qualitative problems over
probabilistic BPPs -- in particular reachability with probability 1 of
different classes of target sets (e.g. upward-closed sets). Our results concern
both the Markov-chain model, where processes are scheduled randomly, and the
MDP model, where processes are picked by a scheduler.


title:
Effect of core--mantle and tidal torques on Mercury's spin axis
  orientation

abstract:
  The rotational evolution of Mercury's mantle and its core under conservative
and dissipative torques is important for understanding the planet's spin state.
Dissipation results from tides and viscous, magnetic and topographic
core--mantle interactions. The dissipative core--mantle torques take the system
to an equilibrium state wherein both spins are fixed in the frame precessing
with the orbit, and in which the mantle and core are differentially rotating.
This equilibrium exhibits a mantle spin axis that is offset from the Cassini
state by larger amounts for weaker core--mantle coupling for all three
dissipative core--mantle coupling mechanisms, and the spin axis of the core is
separated farther from that of the mantle, leading to larger differential
rotation. The relatively strong core--mantle coupling necessary to bring the
mantle spin axis to its observed position close to the Cassini state is not
obtained by any of the three dissipative core--mantle coupling mechanisms. For
a hydrostatic ellipsoidal core--mantle boundary, pressure coupling dominates
the dissipative effects on the mantle and core positions, and dissipation
together with pressure coupling brings the mantle spin solidly to the Cassini
state. The core spin goes to a position displaced from that of the mantle by
about 3.55 arcmin nearly in the plane containing the Cassini state. With the
maximum viscosity considered of $\nu\sim 15.0\,{\rm cm^2/s}$ if the coupling is
by the circulation through an Ekman boundary layer or $\nu\sim 8.75\times
10^5\,{\rm cm^2/s}$ for purely viscous coupling, the core spin lags the
precessing Cassini plane by 23 arcsec, whereas the mantle spin lags by only
0.055 arcsec. Larger, non hydrostatic values of the CMB ellipticity also result
in the mantle spin at the Cassini state, but the core spin is moved closer to
the mantle spin.


title:
Low-temperature large-distance asymptotics of the transversal two-point
  functions of the XXZ chain

abstract:
  We derive the low-temperature large-distance asymptotics of the transversal
two-point functions of the XXZ chain by summing up the asymptotically dominant
terms of their expansion into form factors of the quantum transfer matrix. Our
asymptotic formulae are numerically efficient and match well with known results
for vanishing magnetic field and for short distances and magnetic fields below
the saturation field.

categories: cond-mat.stat-mech hep-th math-ph math.MP


title: Phosphorene: A New 2D Material with High Carrier Mobility

abstract:
  Preceding the current interest in layered materials for electronic
applications, research in the 1960's found that black phosphorus combines high
carrier mobility with a fundamental band gap. We introduce its counterpart,
dubbed few-layer phosphorene, as a new 2D p-type material. Same as graphene and
MoS2, phosphorene is flexible and can be mechanically exfoliated. We find
phosphorene to be stable and, unlike graphene, to have an inherent, direct and
appreciable band-gap that depends on the number of layers. Our transport
studies indicate a carrier mobility that reflects its structural anisotropy and
is superior to MoS2. At room temperature, our phosphorene field-effect
transistors with 1.0 um channel length display a high on-current of 194 mA/mm,
a high hole field-effect mobility of 286 cm2/Vs, and an on/off ratio up to 1E4.
We demonstrate the possibility of phosphorene integration by constructing the
first 2D CMOS inverter of phosphorene PMOS and MoS2 NMOS transistors.


title:
A conditional compression distance that unveils insights of the genomic
  evolution

abstract:
  We describe a compression-based distance for genomic sequences. Instead of
using the usual conjoint information content, as in the classical Normalized
Compression Distance (NCD), it uses the conditional information content. To
compute this Normalized Conditional Compression Distance (NCCD), we need a
normal conditional compressor, that we built using a mixture of static and
dynamic finite-context models. Using this approach, we measured chromosomal
distances between Hominidae primates and also between Muroidea (rat and mouse),
observing several insights of evolution that so far have not been reported in
the literature.


title:
Quasimodular instanton partition function and the elliptic solution of
  Korteweg-de Vries equations

abstract:
  The Gauge/Bethe correspondence relates Omega-deformed N=2 supersymmetric
gauge theories to some quantum integrable models, in simple cases the
integrable models can be treated as solvable quantum mechanics models. For
SU(2) gauge theory with an adjoint matter, or with 4 fundamental matters, the
potential of corresponding quantum model is the elliptic function. If the mass
of matter takes special value then the potential is an elliptic solution of KdV
hierarchy. We show that the deformed prepotential of gauge theory can be
obtained from the average densities of conserved charges of the classical KdV
solution, the UV gauge coupling dependence is assembled into the Eisenstein
series. The gauge theory with adjoint mass is taken as the example.


title: A New Proof of Fitzgerald's Characterization of Primitive Polynomials

abstract:
  We give a new proof of Fitzgerald's criterion for primitive polynomials over
a finite field. Existing proofs essentially use the theory of linear
recurrences over finite fields. Here, we give a much shorter and self-contained
proof which does not use the theory of linear recurrences.


title: Schwinger effect in de Sitter space

abstract:
  We consider Schwinger pair production in 1+1 dimensional de Sitter space,
filled with a constant electric field $E$. This can be thought of as a model
for describing false vacuum decay beyond the semiclassical approximation, where
pairs of a quantum field $\phi$ of mass $m$ and charge $e$ play the role of
vacuum bubbles. We find that the adiabatic "in" vacuum associated with the flat
chart develops a space-like expectation value for the current $J$, which
manifestly breaks the de Sitter invariance of the background fields. We derive
a simple expression for $J(E)$, showing that both "upward" and "downward"
tunneling contribute to the build-up of the current. For heavy fields, with
$m^2\gg eE,H^2$, the current is exponentially suppressed, in agreement with the
results of semiclassical instanton methods. Here $H$ is the inverse de Sitter
radius. On the other hand, light fields with $ m \ll H$ lead to a phenomenon of
infrared hyperconductivity, where a very small electric field $mH \lesssim eE
\ll H^2$ leads to a very large current $J \sim H^3 /E$. We also show that all
Hadamard states for $\phi$ necessarily break de Sitter invariance. Finally, we
comment on the role of initial conditions, and "persistence of memory" effects.


title:
A Tale of Two Distributions: From Few To Many Vortices In
  Quasi-Two-Dimensional Bose-Einstein Condensates

abstract:
  Motivated by the recent successes of particle models in capturing the
precession and interactions of vortex structures in quasi-two-dimensional
Bose-Einstein condensates, we revisit the relevant systems of ordinary
differential equations. We consider the number of vortices $N$ as a parameter
and explore the prototypical configurations ("ground states") that arise in the
case of few or many vortices. In the case of few vortices, we modify the
classical result of Havelock [Phil. Mag. ${\bf 11}$, 617 (1931)] illustrating
that vortex polygons in the form of a ring are unstable for $N \geq7$.
Additionally, we reconcile this modification with the recent identification of
symmetry breaking bifurcations for the cases of $N=2,\dots,5$. We also briefly
discuss the case of a ring of vortices surrounding a central vortex (so-called
$N+1$ configuration). We finally examine the opposite limit of large $N$ and
illustrate how a coarse-graining, continuum approach enables the accurate
identification of the radial distribution of vortices in that limit.


title: Thickness Estimation of the Si Thin Films: a Simulation Study

abstract:
  We propose a theoretical study for Si thin film thickness measurement that is
based on incident low energy electron beam on the film and counting the
transmitted/incident electron fraction. It estimates the thin film thickness
distribution from a exponential relation which obtained from counting the
fraction of transmitted/incident electron at different thicknesses. By using
this obtained equation, it is possible to estimate unknown thickness of the Si
thin film. In order to calculate the Si thin film thickness estimation, the
energy of the incident electron beams is varied from 6-12 keV, while the
thickness of the Si film is varied between 100-400 nm. The most significant
feature of this method is that no expensive instruments are required. As
anticipated, the proposed method shows that there is a relationship between
film thickness and incident beam energy, which by using this relationship, we
can find unknown film thickness in 1-D and 2-D conditions. Other advantages
include wide measurement range, no calibration need and simple method.
Additionally, an investigation by different beam energies helps to avoid
artefact from this method. All calculations were done by CASINO numerical
simulation package.


title: Statistics of co-occurring keywords on Twitter

abstract:
  Online social media such as the micro-blogging site Twitter has become a rich
source of real-time data on online human behaviors. Here we analyze the
occurrence and co-occurrence frequency of keywords in user posts on Twitter.
From the occurrence rate of major international brand names, we provide
examples on predictions of brand-user behaviors. From the co-occurrence rates,
we further analyze the user-perceived relationships between international brand
names and construct the corresponding relationship networks. In general the
user activity on Twitter is highly intermittent and we show that the occurrence
rate of brand names forms a highly correlated time signal.


title:
Local CP-violation and electric charge separation by magnetic fields
  from lattice QCD

abstract:
  We study local CP-violation on the lattice by measuring the local correlation
between the topological charge density and the electric dipole moment of
quarks, induced by a constant external magnetic field. This correlator is found
to increase linearly with the external field, with the coefficient of
proportionality depending only weakly on temperature. Results are obtained on
lattices with various spacings, and are extrapolated to the continuum limit
after the renormalization of the observables is carried out. This
renormalization utilizes the gradient flow for the quark and gluon fields. Our
findings suggest that the strength of local CP-violation in QCD with physical
quark masses is about an order of magnitude smaller than a model prediction
based on nearly massless quarks in domains of constant gluon backgrounds with
topological charge. We also show numerical evidence that the observed local
CP-violation correlates with spatially extended electric dipole structures in
the QCD vacuum.


title:
Rigorous bounds on the effective moduli of composites and inhomogeneous
  bodies with negative-stiffness phases

abstract:
  We review the theoretical bounds on the effective properties of linear
elastic inhomogeneous solids (including composite materials) in the presence of
constituents having non-positive-definite elastic moduli (so-called
negative-stiffness phases). We show that for statically stable bodies the
classical displacement-based variational principles for Dirichlet and Neumann
boundary problems hold but that the dual variational principle for traction
boundary problems does not apply. We illustrate our findings by the example of
a coated spherical inclusion whose stability conditions are obtained from the
variational principles. We further show that the classical Voigt upper bound on
the linear elastic moduli in multi-phase inhomogeneous bodies and composites
applies and that it imposes a stability condition: overall stability requires
that the effective moduli do not surpass the Voigt upper bound. This
particularly implies that, while the geometric constraints among constituents
in a composite can stabilize negative-stiffness phases, the stabilization is
insufficient to allow for extreme overall static elastic moduli (exceeding
those of the constituents). Stronger bounds on the effective elastic moduli of
isotropic composites can be obtained from the Hashin-Shtrikman variational
inequalities, which are also shown to hold in the presence of negative
stiffness.


title:
Convex Optimization for Binary Classifier Aggregation in Multiclass
  Problems

abstract:
  Multiclass problems are often decomposed into multiple binary problems that
are solved by individual binary classifiers whose results are integrated into a
final answer. Various methods, including all-pairs (APs), one-versus-all (OVA),
and error correcting output code (ECOC), have been studied, to decompose
multiclass problems into binary problems. However, little study has been made
to optimally aggregate binary problems to determine a final answer to the
multiclass problem. In this paper we present a convex optimization method for
an optimal aggregation of binary classifiers to estimate class membership
probabilities in multiclass problems. We model the class membership probability
as a softmax function which takes a conic combination of discrepancies induced
by individual binary classifiers, as an input. With this model, we formulate
the regularized maximum likelihood estimation as a convex optimization problem,
which is solved by the primal-dual interior point method. Connections of our
method to large margin classifiers are presented, showing that the large margin
formulation can be considered as a limiting case of our convex formulation.
Numerical experiments on synthetic and real-world data sets demonstrate that
our method outperforms existing aggregation methods as well as direct methods,
in terms of the classification accuracy and the quality of class membership
probability estimates.


title: Arguments using ontological and causal knowledge

abstract:
  We investigate an approach to reasoning about causes through argumentation.
We consider a causal model for a physical system, and look for arguments about
facts. Some arguments are meant to provide explanations of facts whereas some
challenge these explanations and so on. At the root of argumentation here, are
causal links ({A_1, ... ,A_n} causes B) and ontological links (o_1 is_a o_2).
We present a system that provides a candidate explanation ({A_1, ... ,A_n}
explains {B_1, ... ,B_m}) by resorting to an underlying causal link
substantiated with appropriate ontological links. Argumentation is then at work
from these various explaining links. A case study is developed: a severe storm
Xynthia that devastated part of France in 2010, with an unaccountably high
number of casualties.


title: Optimal Efficiency of a Noisy Quantum Heat Engine

abstract:
  In this article we use optimal control to maximize the efficiency of a
quantum heat engine executing the Otto cycle in the presence of external noise.
We optimize the engine performance for both amplitude and phase noise. In the
case of phase damping we additionally show that the ideal performance of a
noiseless engine can be retrieved in the adiabatic (long time) limit. The
results obtained here are useful in the quest for absolute zero, the design of
quantum refrigerators that can cool a physical system to the lowest possible
temperature. They can also be applied to the optimal control of a collection of
classical harmonic oscillators sharing the same time-dependent frequency and
subjected to similar noise mechanisms. Finally, our methodology can be used for
the optimization of other interesting thermodynamic processes.


title:
Independence of the metric in the fine $C^0$-topology of a function
  space

abstract:
  We prove that, for any topological space $X$ and any metric space $(Y,d)$,
the fine topology on the space of continuous functions from $X$ into $Y$ is
independent of the metric $d$.


title:
Simple Semi-Distributed Lifetime Maximizing Strategy via Power
  Allocation in Collaborative Beamforming for Wireless Sensor Networks

abstract:
  Energy-efficient communication is an important issue in wireless sensor
networks (WSNs) consisting of large number of energy-constrained sensor nodes.
Indeed, sensor nodes have different energy budgets assigned to data
transmission at individual nodes. Therefore, without energy-aware transmission
schemes, energy can deplete from sensor nodes with smaller energy budget faster
than from the rest of the sensor nodes in WSNs. This reduces the coverage area
as well as the lifetime of WSNs. Collaborative beamforming (CB) has been
proposed originally to achieve directional gain, however, it also inherently
distributes the corresponding energy consumption over the collaborative sensor
nodes. In fact, CB can be seen as a physical layer solution (versus the media
access control/network layer solution) to balance the lifetimes of individual
sensor nodes and extend the lifetime of the whole WSN. However, the
introduction of energy-aware CB schemes is critical for extending the WSNs
lifetime.
  In this paper, CB with power allocation (CB-PA) is developed to extend the
lifetime of a cluster of collaborative sensor nodes by balancing the individual
sensor node lifetimes. A novel strategy is proposed to utilize the residual
energy information available at each sensor node. It adjusts the energy
consumption rate at each sensor node while achieving the required average
signal-to-noise ratio (SNR) at the destination. It is a semi-distributed
strategy and it maintains average SNR. Different factors affecting the energy
consumption are studied as well. Simulation results show that CB-PA outperforms
CB with Equal Power Allocation (CB-EPA) in terms of extending the lifetime of a
cluster of collaborative nodes.


title:
Ergodic Theory and Diophantine approximation for translation surfaces
  and linear forms

abstract:
  We derive results on the distribution of directions of saddle connections on
translation surfaces using only the Birkhoff ergodic theorem applied to the
geodesic flow on the moduli space of translation surfaces. Our techniques,
together with an approximation argument, also give an alternative proof of a
weak version of a classical theorem in multi-dimensional Diophantine
approximation due to W. Schmidt \cite{SchmidtMetrical, SchmidtMetrical2}. The
approximation argument allows us to deduce the Birkhoff genericity of almost
all lattices in a certain submanifold of the space of unimodular lattices from
the Birkhoff genericity of almost all lattices in the whole space and similarly
for the space of affine unimodular lattices.


title:
Existence and Spectral Theory for Weak Solutions of Neumann and
  Dirichlet Problems for Linear Degenerate Elliptic Operators with Rough
  Coefficients

abstract:
  In this paper we study existence and spectral properties for weak solutions
of Neumann and Dirichlet problems associated to second order linear degenerate
elliptic partial differential operators $X$, with rough coefficients of the
form $$X=-\text{div}(P\nabla )+{\bf HR}+{\bf S^\prime G} +F$$ in a geometric
homogeneous space setting where the $n\times n$ matrix function $P=P(x)$ is
allowed to degenerate. We give a maximum principle for weak solutions of
$Xu\leq 0$ and follow this with a result describing a relationship between
compact projection of the degenerate Sobolev space $QH^{1,p}$ into $L^q$ and a
Poincar\'e inequality with gain adapted to $Q$.


title:
Excitonic instabilities and spontaneous time-reversal symmetry breaking
  on the honeycomb lattice

abstract:
  We elucidate the close relationship between spontaneous time-reversal
symmetry breaking and the physics of excitonic instabilities in strongly
correlated multiband systems. The underlying mechanism responsible for the
spontaneous breaking of time-reversal symmetry in a many-body system is closely
related to the Cooper-like pairing instability of interband particle-hole pairs
involving higher order symmetries. Studies of such pairing instabilites have,
however, mainly focused on the mean-field aspects of the virtual exciton
condensate, which ignores the presence of the underlying collective Fermi
liquid excitations. We show that this relationship can be exploited to
systematically derive the coupling of the condensate order-parameter to the
intraband Fermi liquid particle-hole excitations. Surprisingly, we find that
the static susceptibility is negative in the ordered phase when the coupling to
the Fermi liquid collective excitations are included, suggesting that a uniform
condensate of virtual excitons, with or without time reversal breaking, is an
unstable phase at T=0.


title: A Peered Bulletin Board for Robust Use in Verifiable Voting Systems

abstract:
  The Web Bulletin Board (WBB) is a key component of verifiable election
systems. It is used in the context of election verification to publish evidence
of voting and tallying that voters and officials can check, and where
challenges can be launched in the event of malfeasance. In practice, the
election authority has responsibility for implementing the web bulletin board
correctly and reliably, and will wish to ensure that it behaves correctly even
in the presence of failures and attacks. To ensure robustness, an
implementation will typically use a number of peers to be able to provide a
correct service even when some peers go down or behave dishonestly. In this
paper we propose a new protocol to implement such a Web Bulletin Board,
motivated by the needs of the vVote verifiable voting system. Using a
distributed algorithm increases the complexity of the protocol and requires
careful reasoning in order to establish correctness. Here we use the Event-B
modelling and refinement approach to establish correctness of the peered design
against an idealised specification of the bulletin board behaviour. In
particular we show that for n peers, a threshold of t > 2n/3 peers behaving
correctly is sufficient to ensure correct behaviour of the bulletin board
distributed design. The algorithm also behaves correctly even if honest or
dishonest peers temporarily drop out of the protocol and then return. The
verification approach also establishes that the protocols used within the
bulletin board do not interfere with each other. This is the first time a
peered web bulletin board suite of protocols has been formally verified.


title:
Magnetic field tomography, helical magnetic fields and Faraday
  depolarization

abstract:
  Wide-band radio polarization observations offer the possibility to recover
information about the magnetic fields in synchrotron sources, such as details
of their three-dimensional configuration, that has previously been
inaccessible. The key physical process involved is the Faraday rotation of the
polarized emission in the source (and elsewhere along the wave's propagation
path to the observer). In order to proceed, reliable methods are required for
inverting the signals observed in wavelength space into useful data in Faraday
space, with robust estimates of their uncertainty. In this paper, we examine
how variations of the intrinsic angle of polarized emission $\psi_{0}$ with the
Faraday depth $\phi$ within a source affect the observable quantities. Using
simple models for the Faraday dispersion $F(\phi)$ and $\psi_{0}(\phi)$, along
with the current and planned properties of the main radio interferometers, we
demonstrate how degeneracies among the parameters describing the magneto-ionic
medium can be minimised by combining observations in different wavebands. We
also discuss how depolarization by Faraday dispersion due to a random component
of the magnetic field attenuates the variations in the spectral energy
distribution of the polarization and shifts its peak towards shorter
wavelengths. This additional effect reduces the prospect of recovering the
characteristics of the magnetic field helicity in magneto-ionic media dominated
by the turbulent component of the magnetic field.


title:
Boosting the voltage gain of graphene FETs through a differential
  amplifier scheme with positive feedback

abstract:
  We study a possible circuit solution to overcome the problem of low voltage
gain of short-channel graphene FETs. The circuit consists of a fully
differential amplifier with a load made of a cross-coupled transistor pair.
Starting from the device characteristics obtained from self-consistent
ballistic quantum transport simulations, we explore the circuit parameter space
and evaluate the amplifier performance in terms of dc voltage gain and voltage
gain bandwidth. We show that the dc gain can be effectively improved by the
negative differential resistance provided by the cross-coupled pair. Contact
resistance is the main obstacle to achieving gain bandwidth products in the
terahertz range. Limitations of the proposed amplifier are identified with its
poor linearity and relatively large Miller capacitance.


title:
Curvature Decay Estimates of Graphical Mean Curvature Flow in Higher
  Codimensions

abstract:
  We derive pointwise curvature estimates for graphical mean curvature flows in
higher codimensions. To the best of our knowledge, this is the first such
estimates without assuming smallness of first derivatives of the defining map.
An immediate application is a convergence theorem of the mean curvature flow of
the graph of an area decreasing map between flat Riemann surfaces.


title: Quantum criticality in a metallic spin liquid

abstract:
  When magnetic order is suppressed by frustrated interactions, spins form a
highly correlated fluctuating "spin liquid" state down to low temperatures.
Magnetic order of local moments can also be suppressed when they are fully
screened by conduction electrons through the Kondo effect. Thus, the
combination of strong geometrical frustration and Kondo screening may lead to
novel types of quantum phase transitions. We report low-temperature
thermodynamic measurements on the frustrated Kondo lattice Pr$_2$Ir$_2$O$_7$,
which displays a chiral spin liquid state below 1.5 K due to the frustrated
interaction between Ising 4f local moments and their interplay with Ir
conduction electrons. Our results provide a first clear example of zero-field
quantum critical scaling that emerges in a spin liquid state of a highly
frustrated metal.


title: Magneto-Optical Trapping of Holmium Atoms

abstract:
  We demonstrate sub-Doppler laser cooling and magneto-optical trapping of the
rare earth element Holmium. Atoms are loaded from an atomic beam source and
captured in six-beam $\sigma_+ - \sigma_-$ molasses using a strong $J=15/2
\leftrightarrow J=17/2$ cycling transition at $\lambda=410.5 \rm nm$. Due to
the small difference in hyperfine splittings and Land\'e $g$-factors in the
lower and upper levels of the cooling transition the MOT is self-repumped
without additional repump light, and deep sub-Doppler cooling is achieved with
the magnetic trap turned on. We measure the leakage out of the cycling
transition to metastable states and find a branching ratio $\sim 10^{-5}$ which
is adequate for state resolved measurements on hyperfine encoded qubits.


title:
Hierarchical fragmentation and differential star formation in the
  Galactic "Snake": infrared dark cloud G11.11-0.12

abstract:
  We present Submillimeter Array (SMA) $\lambda =$ 0.88 and 1.3 mm broad band
observations, and the Jansky Very Large Array (VLA) observations in $\rm{NH_3}$
$(J,K) = (1,1)$ up to $(5,5)$, $\rm{H_2O}$ and $\rm{CH_3OH}$ maser lines toward
the two most massive molecular clumps in infrared dark cloud (IRDC)
G11.11-0.12. Sensitive high-resolution images reveal hierarchical fragmentation
in dense molecular gas from the $\sim 1$ pc clump scale down to $\sim 0.01$ pc
condensation scale. At each scale, the mass of the fragments is orders of
magnitude larger than the Jeans mass. This is common to all four IRDC clumps we
studied, suggesting that turbulence plays an important role in the early stages
of clustered star formation. Masers, shock heated $\rm{NH_3}$ gas, and outflows
indicate intense ongoing star formation in some cores while no such signatures
are found in others. Furthermore, chemical differentiation may reflect the
difference in evolutionary stages among these star formation seeds. We find
$\rm{NH_3}$ ortho/para ratios of $1.1\pm0.4$, $2.0\pm0.4$, and $3.0\pm0.7$
associated with three outflows, and the ratio tends to increase along the
outflows downstream. Our combined SMA and VLA observations of several IRDC
clumps present the most in depth view so far of the early stages prior to the
hot core phase, revealing snapshots of physical and chemical properties at
various stages along an apparent evolutionary sequence.


title:
Embodied social interaction constitutes social cognition in pairs of
  humans: A minimalist virtual reality experiment

abstract:
  Scientists have traditionally limited the mechanisms of social cognition to
one brain, but recent approaches claim that interaction also realizes cognitive
work. Experiments under constrained virtual settings revealed that interaction
dynamics implicitly guide social cognition. Here we show that embodied social
interaction can be constitutive of agency detection and of experiencing
another`s presence. Pairs of participants moved their "avatars" along an
invisible virtual line and could make haptic contact with three identical
objects, two of which embodied the other`s motions, but only one, the other`s
avatar, also embodied the other`s contact sensor and thereby enabled responsive
interaction. Co-regulated interactions were significantly correlated with
identifications of the other`s avatar and reports of the clearest awareness of
the other`s presence. These results challenge folk psychological notions about
the boundaries of mind, but make sense from evolutionary and developmental
perspectives: an extendible mind can offload cognitive work into its
environment.


title: Proof of the $1$-factorization and Hamilton Decomposition Conjectures

abstract:
  In this paper we prove the following results (via a unified approach) for all
sufficiently large $n$:
  (i) [$1$-factorization conjecture] Suppose that $n$ is even and $D\geq
2\lceil n/4\rceil -1$. Then every $D$-regular graph $G$ on $n$ vertices has a
decomposition into perfect matchings. Equivalently, $\chi'(G)=D$.
  (ii) [Hamilton decomposition conjecture] Suppose that $D \ge \lfloor n/2
\rfloor $. Then every $D$-regular graph $G$ on $n$ vertices has a decomposition
into Hamilton cycles and at most one perfect matching.
  (iii) [Optimal packings of Hamilton cycles] Suppose that $G$ is a graph on
$n$ vertices with minimum degree $\delta\ge n/2$. Then $G$ contains at least
${\rm reg}_{\rm even}(n,\delta)/2 \ge (n-2)/8$ edge-disjoint Hamilton cycles.
Here $\text{reg}_{\text{even}}(n,\delta)$ denotes the degree of the largest
even-regular spanning subgraph one can guarantee in a graph on $n$ vertices
with minimum degree $\delta$.
  (i) was first explicitly stated by Chetwynd and Hilton. (ii) and the special
case $\delta= \lceil n/2 \rceil$ of (iii) answer questions of Nash-Williams
from 1970. All of the above bounds are best possible.


title: Transmission of correlated Gaussian packets through a delta-potential

abstract:
  We study the evolution of the most general initial Gaussian packet with
nonzero correlation coefficient between the coordinate and momentum operators
in the presence of a repulsive delta potential barrier, using the known exact
propagator of the time-dependent Schr\"odinger equation. For the initial packet
localized far enough from the barrier, we define the transmission coefficient
as the probability of discovering the particle in the whole semi-axis on the
other side of the barrier. It appears that the asymptotical transmission
coefficient (calculated in the large time limit) depends on two dimensionless
parameters: the normalized ratio of the potential strength to the initial mean
value of momentum and the ratio of the initial momentum dispersion to the
initial mean value of momentum. For small values of the second parameter the
result is reduced to the well known formula for the transparency of the delta
barrier, obtained in the plane wave approximation by solving the stationary
Schr\"odinger equation. For big values of the second parameter, the
transmission coefficient can be much bigger than that calculated in the plane
wave approximation. For a fixed initial spread of the packet in the coordinate
space, the initial correlation coefficient influences the transparency of the
barrier only indirectly, through the increase of the initial momentum
dispersion.


title:
Strong converse for the classical capacity of optical quantum
  communication channels

abstract:
  We establish the classical capacity of optical quantum channels as a sharp
transition between two regimes---one which is an error-free regime for
communication rates below the capacity, and the other in which the probability
of correctly decoding a classical message converges exponentially fast to zero
if the communication rate exceeds the classical capacity. This result is
obtained by proving a strong converse theorem for the classical capacity of all
phase-insensitive bosonic Gaussian channels, a well-established model of
optical quantum communication channels, such as lossy optical fibers, amplifier
and free-space communication. The theorem holds under a particular
photon-number occupation constraint, which we describe in detail in the paper.
Our result bolsters the understanding of the classical capacity of these
channels and opens the path to applications, such as proving the security of
noisy quantum storage models of cryptography with optical links.


title: Spin and Valley Noise in Two-Dimensional Dirac Materials

abstract:
  We develop a theory for optical Faraday rotation noise in two-dimensional
Dirac materials. In contrast to spin noise in conventional semiconductors, we
find that the Faraday rotation fluctuations are influenced not only by spins
but also the valley degrees of freedom attributed to intervalley scattering
processes. We illustrate our theory with two-dimensional transition metal
dichalcogenides and discuss signatures of spin and valley noise in the Faraday
noise power spectrum. We propose optical Faraday noise spectroscopy as a
technique for probing both spin and valley relaxation dynamics in
two-dimensional Dirac materials.


title:
Least Squares Shadowing for Sensitivity Analysis of Turbulent Fluid
  Flows

abstract:
  Computational methods for sensitivity analysis are invaluable tools for
aerodynamics research and engineering design. However, traditional sensitivity
analysis methods break down when applied to long-time averaged quantities in
turbulent fluid flow fields, specifically those obtained using high-fidelity
turbulence simulations. This is because of a number of dynamical properties of
turbulent and chaotic fluid flows, most importantly high sensitivity of the
initial value problem, popularly known as the "butterfly effect".
  The recently developed least squares shadowing (LSS) method avoids the issues
encountered by traditional sensitivity analysis methods by approximating the
"shadow trajectory" in phase space, avoiding the high sensitivity of the
initial value problem. The following paper discusses how the least squares
problem associated with LSS is solved. Two methods are presented and are
demonstrated on a simulation of homogeneous isotropic turbulence and the
Kuramoto-Sivashinsky (KS) equation, a 4th order chaotic partial differential
equation. We find that while LSS computes fairly accurate gradients, faster,
more efficient linear solvers are needed to apply both LSS methods presented in
this paper to larger simulations.

categories: physics.comp-ph math.DS nlin.CD physics.flu-dyn


title:
Proof of the 1-factorization and Hamilton decomposition conjectures II:
  the bipartite case

abstract:
  In a sequence of four papers, we prove the following results (via a unified
approach) for all sufficiently large $n$:
  (i) [1-factorization conjecture] Suppose that $n$ is even and $D \geq 2\lceil
n/4\rceil -1$. Then every $D$-regular graph $G$ on $n$ vertices has a
decomposition into perfect matchings. Equivalently, $\chi'(G)=D$.
  (ii) [Hamilton decomposition conjecture] Suppose that $D \ge \lfloor n/2
\rfloor $. Then every $D$-regular graph $G$ on $n$ vertices has a decomposition
into Hamilton cycles and at most one perfect matching.
  (iii) [Optimal packings of Hamilton cycles] Suppose that $G$ is a graph on
$n$ vertices with minimum degree $\delta\ge n/2$. Then $G$ contains at least
${\rm reg}_{\rm even}(n,\delta)/2 \ge (n-2)/8$ edge-disjoint Hamilton cycles.
Here ${\rm reg}_{\rm even}(n,\delta)$ denotes the degree of the largest
even-regular spanning subgraph one can guarantee in a graph on $n$ vertices
with minimum degree $\delta$.
  According to Dirac, (i) was first raised in the 1950s. (ii) and the special
case $\delta= \lceil n/2 \rceil$ of (iii) answer questions of Nash-Williams
from 1970. All of the above bounds are best possible. In the current paper, we
prove the above results for the case when $G$ is close to a complete balanced
bipartite graph.


title:
Modeling Electrochemical Decomposition of Fluoroethylene Carbonate on
  Silicon Anode Surfaces in Lithium Ion Batteries

abstract:
  Fluoroethylene carbonate (FEC) shows promise as an electrolyte additive for
improving passivating solid-electrolyte interphase (SEI) films on silicon
anodes used in lithium ion batteries (LIB). We apply density functional theory
(DFT), ab initio molecular dynamics (AIMD), and quantum chemistry techniques to
examine excess-electron-induced FEC molecular decomposition mechanisms that
lead to FEC-modified SEI. We consider one- and two-electron reactions using
cluster models and explicit interfaces between liquid electrolyte and model
Li(x)Si(y) surfaces, respectively. FEC is found to exhibit more varied reaction
pathways than unsubstituted ethylene carbonate. The initial bond-breaking
events and products of one- and two-electron reactions are qualitatively
similar, with a fluoride ion detached in both cases. However, most one-electron
products are charge-neutral, not anionic, and may not coalesce to form
effective Li+-conducting SEI unless they are further reduced or take part in
other reactions. The implications of these reactions to silicon-anode based LIB
are discussed.


title:
Far-field subwavelength imaging from a single broadband antenna in
  combined with strongly disordered medium

abstract:
  The far-field subwavlength imaging is a challenging issue. In this letter we
demonstrate numerically that the far-field subwavelength imaging of weakly
scattering objects can be obtained by processing the data acquired by a single
antenna, which benefits from the use of the strongly disordered medium. A
mathematical model has been proposed for solving such problem based on the idea
of sparse reconstruction. Moreover, this study leads to an important conclusion
that the strongly disordered medium can serves as an efficient apparatus for
the single-antenna compressive measurement, which shifts the complexity of
devising compressive sensing (CS) hardware from the design, fabrication and
electronic control. The proposed method and associated results can find
applications in several imaging disciplines, such as optics, THz, RF or
ultrasound imaging.


title:
Explicit evolution relations with orbital elements for eccentric,
  inclined, elliptic and hyperbolic restricted few-body problems

abstract:
  Planetary, stellar and galactic physics often rely on the general restricted
gravitational N-body problem to model the motion of a small-mass object under
the influence of much more massive objects. Here, I formulate the general
restricted problem entirely and specifically in terms of the commonly-used
orbital elements of semimajor axis, eccentricity, inclination, longitude of
ascending node, argument of pericentre, and true anomaly, without any
assumptions about their magnitudes. I derive the equations of motion in the
general, unaveraged case, as well as specific cases, with respect to both a
bodycentric and barycentric origin. I then reduce the equations to three-body
systems, and present compact singly- and doubly-averaged expressions which can
be readily applied to systems of interest. This method recovers classic
Lidov-Kozai and Laplace-Lagrange theory in the test particle limit to any
order, but with fewer assumptions, and reveals a complete analytic solution for
the averaged planetary pericentre precession in coplanar circular circumbinary
systems to at least the first three nonzero orders in semimajor axis ratio.
Finally, I show how the unaveraged equations may be used to express resonant
angle evolution in an explicit manner that is not subject to expansions of
eccentricity and inclination about small nor any other values.


title: Exceptional N=1 Duality

abstract:
  Four dimensional N=1 supersymmetric gauge theory with gauge group SU(N_c) and
matter in the adjoint and fundamental representations gives rise to a series of
fixed points with an ADE classification. The A and D series exhibit
generalizations of Seiberg duality. We propose a similar duality for the E7
theory.


title:
Implementation of robust image artifact removal in SWarp through clipped
  mean stacking

abstract:
  We implement an algorithm for detecting and removing artifacts from
astronomical images by means of outlier rejection during stacking. Our method
is capable of addressing both small, highly significant artifacts such as
cosmic rays and, by applying a filtering technique to generate single frame
masks, larger area but lower surface brightness features such as secondary
(ghost) images of bright stars. In contrast to the common method of building a
median stack, the clipped or outlier-filtered mean stacked point-spread
function (PSF) is a linear combination of the single frame PSFs as long as the
latter are moderately homogeneous, a property of great importance for weak
lensing shape measurement or model fitting photometry. In addition, it has
superior noise properties, allowing a significant reduction in exposure time
compared to median stacking. We make publicly available a modified version of
SWarp that implements clipped mean stacking and software to generate single
frame masks from the list of outlier pixels.


title: Detection of Ultraviolet Halos around Highly Inclined Galaxies

abstract:
  We report the discovery of diffuse ultraviolet light around late-type
galaxies out to 5-20 kpc from the midplane using Swift and GALEX images. The
emission is consistent with the stellar outskirts in the early-type galaxies
but not in the late-type galaxies, where the emission is quite blue and
consistent with a reflection nebula powered by light escaping from the galaxy
and scattering off dust in the halo. Our results agree with expectations from
halo dust discovered in extinction by Menard et al. (2010) to within a few kpc
of the disk and imply a comparable amount of hot and cold gas in galaxy halos
(a few x 10^8 Msun within 20 kpc) if the dust resides primarily in Mg II
absorbers. The results also highlight the potential of UV photometry to study
individual galaxy halos.


title:
The clustering of galaxies in the SDSS-III Baryon Oscillation
  Spectroscopic Survey: mock galaxy catalogues for the low-redshift sample

abstract:
  We present one thousand mock galaxy catalogues for the analysis of the Low
Redshift Sample (LOWZ, effective redshift z ~ 10.32) of the Baryon Oscillation
Spectroscopic Survey Data Releases 10 and 11. These mocks have been created
following the PTHalos method of Manera13 et al. (2013) revised to include new
developments. The main improvement is the introduction of a redshift dependence
in the Halo Occupation Distribution in order to account for the change of the
galaxy number density with redshift. These mock catalogues are used in the
analyses of the LOWZ galaxy clustering by the BOSS collaboration.


title:
Constraining the epoch of reionization with the variance statistic:
  simulations of the LOFAR case

abstract:
  Several experiments are underway to detect the cosmic redshifted 21-cm signal
from neutral hydrogen from the Epoch of Reionization (EoR). Due to their very
low signal-to-noise ratio, these observations aim for a statistical detection
of the signal by measuring its power spectrum. We investigate the extraction of
the variance of the signal as a first step towards detecting and constraining
the global history of the EoR. Signal variance is the integral of the signal's
power spectrum, and it is expected to be measured with a high significance. We
demonstrate this through results from a simulation and parameter estimation
pipeline developed for the Low Frequency Array (LOFAR)-EoR experiment. We show
that LOFAR should be able to detect the EoR in 600 hours of integration using
the variance statistic. Additionally, the redshift ($z_r$) and duration
($\Delta z$) of reionization can be constrained assuming a parametrization. We
use an EoR simulation of $z_r = 7.68$ and $\Delta z = 0.43$ to test the
pipeline. We are able to detect the simulated signal with a significance of 4
standard deviations and extract the EoR parameters as $z_r =
7.72^{+0.37}_{-0.18}$ and $\Delta z = 0.53^{+0.12}_{-0.23}$ in 600 hours,
assuming that systematic errors can be adequately controlled. We further show
that the significance of detection and constraints on EoR parameters can be
improved by measuring the cross-variance of the signal by cross-correlating
consecutive redshift bins.


title: Massive Gravity

abstract:
  We review recent progress in massive gravity. We start by showing how
different theories of massive gravity emerge from a higher-dimensional theory
of general relativity, leading to the Dvali-Gabadadze-Porrati model, cascading
gravity and ghost-free massive gravity. We then explore their theoretical and
phenomenological consistency, proving the absence of Boulware-Deser ghosts and
reviewing the Vainshtein mechanism and the cosmological solutions in these
models. Finally we present alternative and related models of massive gravity
such as new massive gravity, Lorentz-violating massive gravity and non-local
massive gravity.


title: Contextuality supplies the magic for quantum computation

abstract:
  Quantum computers promise dramatic advantages over their classical
counterparts, but the answer to the most basic question "What is the source of
the power in quantum computing?" has remained elusive. Here we prove a
remarkable equivalence between the onset of contextuality and the possibility
of universal quantum computation via magic state distillation. This is a
conceptually satisfying link because contextuality provides one of the
fundamental characterizations of uniquely quantum phenomena and, moreover,
magic state distillation is the leading model for experimentally realizing
fault-tolerant quantum computation. Furthermore, this connection suggests a
unifying paradigm for the resources of quantum information: the nonlocality of
quantum theory is a particular kind of contextuality and nonlocality is already
known to be a critical resource for achieving advantages with quantum
communication. In addition to clarifying these fundamental issues, this work
advances the resource framework for quantum computation, which has a number of
practical applications, such as characterizing the efficiency and trade-offs
between distinct theoretical and experimental schemes for achieving robust
quantum computation and bounding the overhead cost for the classical simulation
of quantum algorithms.


title: The Formation and Early Evolution of Young Massive Clusters

abstract:
  We review the formation and early evolution of the most massive and dense
young stellar clusters, focusing on the role they can play in our understanding
of star and planet formation as a whole. Young massive cluster (YMC) progenitor
clouds in the Galactic Center can accumulate to a high enough density without
forming stars that the initial protostellar densities are close to the final
stellar density. For this to hold in the disk, the time scale to accumulate the
gas to such high densities must be much shorter than the star formation
timescale. Otherwise the gas begins forming stars while it is being accumulated
to high density. The distinction between the formation regimes in the two
environments is consistent with the predictions of environmentally-dependent
density thresholds for star formation. This implies that stars in YMCs of
similar total mass and radius can have formed at widely different initial
protostellar densities. The fact that no systematic variations in fundamental
properties are observed between YMCs in the disk and Galactic Center suggests
stellar mass assembly is not strongly affected by the initial protostellar
density. We review recent theoretical advances and summarize the debate on
three key open questions: the initial (proto)stellar distribution, infant
(im)mortality and age spreads within YMCs. We conclude: the initial
protostellar distribution is likely hierarchical; YMCs likely experienced a
formation history that was dominated by gas exhaustion rather than gas
expulsion; YMCs are dynamically stable from a young age; and YMCs have age
spreads much smaller than their mean age. Finally, we show that it is plausible
that metal-rich globular clusters may have formed in a similar way to YMCs in
nearby galaxies. In summary, the study of YMC formation bridges star/planet
formation in the solar neighborhood to the oldest structures in the local
Universe. [abridged]