title: Deep optical observations of the gamma-ray pulsar J0357+3205

abstract:
  A middle-aged radio-quiet pulsar J0357+3205 was discovered in gamma-rays with
$Fermi$ and later in X-rays with $Chandra$ and $XMM$-$Newton$ observatories. It
produces an unusual thermally-emitting pulsar wind nebula observed in X-rays.
Deep optical observations were obtained to search for the pulsar optical
counterpart and its nebula using the Gran Telescopio Canarias (GTC). The direct
imaging mode in the Sloan $g'$ band was used. Archival X-ray data were
reanalysed and compared with the optical data. No pulsar optical counterpart
was detected down to $g'\geq~28_{\cdotp}^{\text{m}}1$. No pulsar nebula was
either identified in the optical. We confirm early results that the X-ray
spectrum of the pulsar consists of a nonthermal power-law component of the
pulsar magnetospheric origin dominating at high energies and a soft thermal
component from the neutron star surface. Using magnetised partially ionised
hydrogen atmosphere models in X-ray spectral fits we found that the thermal
component can come from entire surface of the cooling neutron star with a
temperature of 36$^{+9}_{-6}$ eV, making it one of the coldest among cooling
neutron stars known. The surface temperature agrees with the standard neutron
star cooling scenario. The optical upper limit does not put any additional
constraints on the thermal component, however it implies a strong spectral
break for the nonthermal component between the optical and X-rays as is
observed in other middle-aged pulsars. The thermal emission from the entire
surface of the neutron star likely dominates over the nonthermal emission in
the UV range. Observations of the PSR J0357+3205 in this range are promising to
put more stringent constraints on its thermal properties.


title:
Determination of Intrinsic Magnetic Response from Local Measurements of
  Fringing Fields

abstract:
  Micron-sized Hall bars and micro-SQUIDs are now used routinely to measure the
local static and dynamic magnetic response with micron-scale spatial
resolution. While this provides a powerful new tool, determining the intrinsic
magnetization presents new challenges, as it requires correcting for
demagnetization fields that vary widely with position on a sample. In this
paper we develop a method to correct for the demagnetization effect at local
points of a rectangular prism shaped sample using a finite element analysis of
Maxwell's equation applied to local Hall sensor measurements calibrated by bulk
measurements of the magnetization. This method can be generalized to other
geometric shapes to analyze data obtained with local magnetic probes.


title: A novel radioguided surgery technique exploiting $\beta^{-}$ decays

abstract:
  The background induced by the high penetration power of the gamma radiation
is the main limiting factor of the current Radio-guided surgery (RGS). To
partially mitigate it, a RGS with beta+ emitting radio-tracers has been
suggested in literature.
  Here we propose the use of beta- emitting radio-tracers and beta- probes and
discuss the advantage of this method with respect to the previously explored
ones: the electron low penetration power allows for simple and versatile probes
and could extend RGS to tumours for which background originating from nearby
healthy tissue makes gamma probes less effective. We developed a beta- probe
prototype and studied its performances on phantoms. By means of a detailed
simulation we have also extrapolated the results to estimate the performances
in a realistic case of meningioma, pathology which is going to be our first
in-vivo test case. A good sensitivity to residuals down to 0.1ml can be reached
within 1s with an administered activity smaller than those for PET-scans thus
making the radiation exposure to medical personnel negligible.


title: Legendrian cycles and curvatures

abstract:
  Properties of general Legendrian cycles $T$ acting in ${\mathbb R}^d\times
S^{d-1}$ are studied. In particular, we give short proofs for certain
uniqueness theorems with respect to the projections on the first and second
component of such currents: In general, $T$ is determined by its restriction to
the Gauss curvature form - this result goes back to J. Fu - and in the
full-dimensional case also by the restriction to the surface area form. As a
tool a version of the Constancy theorem for Lipschitz submanifolds is shown.


title: Counterfactual quantum certificate authorization

abstract:
  We present a multi-partite protocol in a counterfactual paradigm. In
counterfactual quantum cryptography, secure information is transmitted between
two spatially separated parties even when there is no physical travel of
particles transferring the information between them. We propose here a
tripartite counterfactual quantum protocol for the task of certificate
authorization. Here a trusted third party, Alice, authenticates an entity Bob
(e.g., a bank) that a client Charlie wishes to securely transact with. The
protocol is counterfactual with respect to either Bob or Charlie. We prove its
security against a general incoherent attack, where Eve attacks single
particles.


title:
Status of the Zee-Babu model for neutrino mass and possible tests at a
  like-sign linear collider

abstract:
  We provide an updated scan of the allowed parameter space of the two-loop
Zee-Babu model for neutrino mass. Taking into account most recent experimental
data on $\mu\to e\gamma$ as well as the mixing angle $\theta_{13}$ we obtain
lower bounds on the masses of the singly and doubly charged scalars of between
1 to 2 TeV, with some dependence on perturbativity and fine-tuning
requirements. This makes the scalars difficult to observe at LHC with 14 TeV
even with optimistic assumptions on the luminosity, and would require a
multi-TeV linear collider to see the scalar resonances. We point out, however,
that a sub-TeV linear collider in the like-sign mode may be able to observe
lepton flavour violating processes such as $e^- e^- \to \mu^- \mu^-$ due to
contact interactions induced by the doubly charged scalar with masses up to
around 10 TeV. We investigate the possibility to distinguish the Zee-Babu model
from the Higgs triplet model using such processes.


title: A principle of quantumness

abstract:
  Quantum correlations and other phenomena characteristic to a quantum world
can be understood as simply consequences of a principle derived from the
postulates of Quantum Mechanics. This explanatory principle states that these
phenomena specific to the quantum world are caused by the tension between the
constraints, or initial conditions, imposed by incompatible observations. This
tension is found to be at the root of Bohr's complementarity, Heisenberg's
uncertainty, results concerning nonlocality, contextuality, quantum
correlations in time and space. This tension requires the presence of
noncommuting observables, but noncommutativity doesn't always lead to the
tension, and the two concepts are not exactly the same, as it will be explained
and exemplified.


title: On the Localisation Theorem for rational Cherednik algebra modules

abstract:
  Let $W$ be a complex reflection group of the form $G(l,1,n)$. Following
[BK12, BPW12, Gor06, GS05, GS06, KR08, MN11], the theory of deform quantising
conical symplectic resolutions allows one to study the category of modules for
the spherical Cherednik algebra, $U_\textbf{c}(W)$, via a functor, $\mathbb
T_{\textbf{c},\theta}$, which takes invariant global sections of certain
twisted sheaves on some Nakajima quiver variety $Y_\theta$.
  A parameter for the Cherednik algebra, $\textbf{c}$, is considered `good' if
there exists a choice of GIT parameter $\theta$, such that $\mathbb
T_{\textbf{c},\theta}$ is exact and `bad' otherwise. By calculating the
Kirwan--Ness strata for $\theta=\pm(1,\ldots,1)$ and using criteria of [MN13],
it is shown that the set of all bad parameters is bounded. The criteria are
then used to show that, for the cases $W=\mathfrak S_n, \mu_3, B_2$, all
parameters are good.


title: Traffic experiment reveals the nature of car-following

abstract:
  As a typical self-driven many-particle system far from equilibrium, traffic
flow exhibits diverse fascinating non-equilibrium phenomena, most of which are
closely related to traffic flow stability and specifically the
growth/dissipation pattern of disturbances. However, the traffic theories have
been controversial due to a lack of precise traffic data. We have studied
traffic flow from a new perspective by carrying out large-scale car-following
experiment on an open road section, which overcomes the intrinsic deficiency of
empirical observations. The experiment has shown clearly the nature of
car-following, which runs against the traditional traffic flow theory.
Simulations show that by removing the fundamental notion in the traditional
car-following models and allowing the traffic state to span a two-dimensional
region in velocity-spacing plane, the growth pattern of disturbances has
changed qualitatively and becomes qualitatively or even quantitatively in
consistent with that observed in the experiment.


title:
Robust Phase Retrieval and Super-Resolution from One Bit Coded
  Diffraction Patterns

abstract:
  In this paper we study a realistic setup for phase retrieval, where the
signal of interest is modulated or masked and then for each modulation or mask
a diffraction pattern is collected, producing a coded diffraction pattern (CDP)
[CLM13]. We are interested in the setup where the resolution of the collected
CDP is limited by the Fraunhofer diffraction limit of the imaging system.
  We investigate a novel approach based on a geometric quantization scheme of
phase-less linear measurements into (one-bit) coded diffraction patterns, and a
corresponding recovery scheme. The key novelty in this approach consists in
comparing pairs of coded diffractions patterns across frequencies: the one bit
measurements obtained rely on the order statistics of the un-quantized
measurements rather than their values . This results in a robust phase
recovery, and unlike currently available methods, allows to efficiently perform
phase recovery from measurements affected by severe (possibly unknown) non
linear, rank preserving perturbations, such as distortions. Another important
feature of this approach consists in the fact that it enables also
super-resolution and blind-deconvolution, beyond the diffraction limit of a
given imaging system.


title: A novel teleparallel dark energy model

abstract:
  Although equivalent to general relativity, teleparallel gravity is
conceptually speaking a completely different theory. In this theory, the
gravitational field is described by torsion, not by curvature. By working in
this context, a new model is proposed in which the four-derivative of a
canonical scalar field representing dark energy is nonminimally coupled to the
"vector torsion". This type of coupling is motivated by the fact that a scalar
field couples to torsion through its four-derivative, which is consistent with
local spacetime kinematics regulated by the de Sitter group $SO(1,4)$. It is
found that the current state of accelerated expansion of the Universe
corresponds to a late-time attractor that can be (i) a dark-energy-dominated de
Sitter solution ($\omega_{\phi}=-1$), (ii) a quintessence-type solution with
$\omega_{\phi}\geq-1$, or (iii) a phantom-type $\omega_{\phi}<-1$ dark energy.


title: Testing Inflation and Curvaton Scenarios with CMB Distortions

abstract:
  Prior to recombination, Silk damping causes the dissipation of energy from
acoustic waves into the monopole of the Cosmic Microwave Background (CMB),
resulting in spectral distortions. These can be used to probe the primordial
scalar power spectrum on smaller scales than it is possible with CMB
anisotropies. An enhancement of power on these scales is nevertheless required
for the resulting distortions to be detectable by future experiments like
PIXIE. In this paper, we examine all 49 single-field inflation models listed by
Martin et al. in the Encyclopaedia Inflationaris [1] and find that only one of
these may lead to a detectable level of distortions in a tuned region of its
parameter space, namely the original hybrid model. Three effective multi-field
scenarios are also studied: with softly and suddenly turning trajectories, and
with a mild waterfall trajectory. Softly turning trajectories do not induce
distortions at any detectable level, whereas a sudden turn in the field space
or a mild waterfall trajectory predicts a peak (plus damped oscillations in the
sudden turn case) in the scalar power spectrum, which can lead to an observable
amount of CMB distortions. Finally, another scenario leading to potentially
detectable distortions involves a curvaton whose blue spectrum is subdominant
on CMB angular scales and overtakes the inflaton spectrum on smaller scales. In
this case however, we show that the bounds from ultra compact minihaloes are
not satisfied. Expectations for an ultimate PRISM-class experiment
characterized by an improvement in sensitivity by a factor of ten are discussed
for some models.


title: Perturbative Unitarity of Inflationary Models with Features

abstract:
  We consider the pertubative consistency of inflationary models with features
with effective field theory methods. By estimating the size of one-loop
contributions to the three-point function, we find the energy scale where their
contribution is of the same order of the tree-level amplitude. It is well-known
that beyond that scale, perturbative unitarity is lost and the theory is no
more under theoretical control. Requiring that all the relevant energy scales
of the problem are below this cutoff, we derive a strong upper bound on the
sharpness of the feature, or equivalently on its characteristic time scale,
which is independent on the amplitude of the feature itself. We point out that
the sharp features which seem to provide better fits to the CMB power spectrum
are already outside this bound, questioning the consistency of the models that
predict them.


title: On a generalization of compensated compactness in the $L^p-L^q$ setting

abstract:
  We investigate conditions under which, for two sequences $(u_r)$ and $(v_r)$
weakly converging to $u$ and $v$ in $L^p(R^d;R^N)$ and $L^{q}(R^d;R^N)$,
respectively, $1/p+1/q \leq 1$, a quadratic form
$q(x;u_r,v_r)=\sum\limits_{j,m=1}^N q_{j m}(x)u_{j r} v_{m r}$ converges toward
$q(x;u,v)$ in the sense of distributions. The conditions involve fractional
derivatives and variable coefficients, and they represent a generalization of
the known compensated compactness theory. The proofs are accomplished using a
recently introduced $H$-distribution concept. We apply the developed techniques
to a nonlinear (degenerate) parabolic equation.


title: Permutation classes and polyomino classes with excluded submatrices

abstract:
  This article introduces an analogue of permutation classes in the context of
polyominoes. For both permutation classes and polyomino classes, we present an
original way of characterizing them by avoidance constraints (namely, with
excluded submatrices) and we discuss how canonical such a description by
submatrix-avoidance can be. We provide numerous examples of permutation and
polyomino classes which may be defined and studied from the submatrix-avoidance
point of view, and conclude with various directions for future research on this
topic.


title: A combinatorial definition of the Theta-invariant from Heegaard diagrams

abstract:
  The invariant $\Theta$ is an invariant of rational homology 3-spheres $M$
equipped with a combing $X$ over the complement of a point. It is related to
the Casson-Walker invariant $\lambda$ by the formula
$\Theta(M,X)=6\lambda(M)+p_1(X)/4$, where $p_1$ is an invariant of combings
that is simply related to a Gompf invariant. In [arXiv:1209.3219], we proved a
combinatorial formula for the $\Theta$-invariant in terms of Heegaard diagrams,
equipped with decorations that define combings, from the definition of $\Theta$
as an algebraic intersection in a configuration space. In this article, we
prove that this formula defines an invariant of pairs $(M,X)$ without referring
to configuration spaces, and we prove that this invariant is the sum of $6
\lambda(M)$ and $p_1(X)/4$ for integral homology spheres, by proving surgery
formulae both for the combinatorial invariant and for $p_1$.


title: Fluctuations at the edges of the spectrum of the full rank deformed GUE

abstract:
  We consider a full rank deformation of the GUE $W_N+A_N$ where $A_N$ is a
full rank Hermitian matrix of size $N$ and $W_N$ is a GUE. The empirical
eigenvalue distribution $\mu_{A_N}$ of $A_N$ converges to a probability
distribution $\nu$. We identify all the possible limiting eigenvalue statistics
at the edges of the spectrum, including outliers, edges and merging points of
connected components of the limiting spectrum. The results are stated in terms
of a deterministic equivalent of the empirical eigenvalue distribution of
$W_N+A_N$, namely the free convolution of the semi-circle distribution and the
empirical eigenvalues distribution of $A_N$.


title:
Amenability notions of hypergroups and some applications to locally
  compact groups

abstract:
  Different notions of amenability on hypergroups and their relations are
studied. Developing Leptin's theorem for discrete hypergroups, we characterize
the existence of a bounded approximate identity for hypergroup Fourier
algebras. We study the Leptin condition for discrete hypergroups derived from
the representation theory of some classes of compact groups. Studying
amenability of the hypergroup algebras for discrete commutative hypergroups, we
obtain some results on amenability properties of some central Banach algebras
on compact and discrete groups.


title: Modular statistics for subgraph counts in sparse random graphs

abstract:
  Answering a question of Kolaitis and Kopparty, we show that, for given
integer $q>1$ and pairwise nonisomorphic connected graphs $G_1...G_k$, if
$p=p(n) $ is such that $\Pr(G_{n,p}\supseteq G_i)\to 1$ $\forall i$, then, with
$\xi_i$ the number of copies of $G_i$ in $G_{n,p}$, $(\xi_1...\xi_k)$ is
asymptotically uniformly distributed on ${\bf Z}_q^k$.


title:
Quantitative bounds on the discrete spectrum of non self-adjoint quantum
  magnetic Hamiltonians

abstract:
  We establish Lieb-Thirring type inequalities for non self-adjoint relatively
compact perturbations of certain operators of mathematical physics. We apply
our results to quantum Hamiltonians of Schr{\"o}dinger and Pauli with constant
magnetic field of strength $b\textgreater{}0$. In particular, we use these
bounds to obtain some information on the distribution of the eigenvalues of the
perturbed operators in the neighborhood of their essential spectrum.


title: Improvements on the accelerated integer GCD algorithm

abstract:
  The present paper analyses and presents several improvements to the algorithm
for finding the $(a,b)$-pairs of integers used in the $k$-ary reduction of the
right-shift $k$-ary integer GCD algorithm. While the worst-case complexity of
Weber's "Accelerated integer GCD algorithm" is $\cO\l(\log_\phi(k)^2\r)$, we
show that the worst-case number of iterations of the while loop is exactly
$\tfrac 12 \l\lfloor \log_{\phi}(k)\r\rfloor$, where $\phi := \tfrac 12
\l(1+\sqrt{5}\r)$.\par We suggest improvements on the average complexity of the
latter algorithm and also present two new faster residual algorithms: the
sequential and the parallel one. A lower bound on the probability of avoiding
the while loop in our parallel residual algorithm is also given.


title: Persistence of some additive functionals of Sinai's walk

abstract:
  We are interested in Sinai's walk $(S\_n)\_{n\in\mathbb{N}}$. We prove that
the annealed probability that $\sum\_{k=0}^n f(S\_k)$ is strictly positive for
all $n\in[1,N]$ is equal to $1/(\log N)^{\frac{3-\sqrt{5}}{2}+o(1)}$, for a
large class of functions $f$, and in particular for $f(x)=x$. The persistence
exponent $\frac{3-\sqrt{5}}{2}$ first appears in a non-rigorous paper of Le
Doussal, Monthus and Fischer, with motivations coming from physics. The proof
relies on techniques of localization for Sinai's walk and uses results of
Cheliotis about the sign changes of the bottom of valleys of a two-sided
Brownian motion.


title:
Classes of hypercomplex polynomials of discrete variable based on the
  quasi-monomiality principle

abstract:
  With the aim of derive a quasi-monomiality formulation in the context of
discrete hypercomplex variables, one will amalgamate through a
Clifford-algebraic structure of signature $(0,n)$ the umbral calculus framework
with Lie-algebraic symmetries. The exponential generating function ({\bf EGF})
carrying the {\it continuum} Dirac operator $D=\sum_{j=1}^n\e_j\partial_{x_j}$
together with the Lie-algebraic representation of raising and lowering
operators acting on the lattice $h\BZ^n$ is used to derive the corresponding
hypercomplex polynomials of discrete variable as Appell sets with membership on
the space Clifford-vector-valued polynomials. Some particular examples
concerning this construction such as the hypercomplex versions of falling
factorials and the Poisson-Charlier polynomials are introduced. Certain
applications from the view of interpolation theory and integral transforms are
also discussed.


title: Dining Cryptographers are Practical

abstract:
  The dining cryptographers protocol provides information-theoretically secure
sender and recipient untraceability. However, the protocol is considered to be
impractical because a malicious participant may disrupt the communication. We
propose an implementation which provides information-theoretical security for
senders and recipients, and in which a disruptor with limited computational
capabilities can easily be detected.


title: Theory of integer quantum Hall polaritons in graphene

abstract:
  We present a theory of the cavity quantum electrodynamics of the graphene
cyclotron resonance. By employing a canonical transformation, we derive an
effective Hamiltonian for the system comprised of two neighboring Landau levels
dressed by the cavity electromagnetic field (integer quantum Hall polaritons).
This generalized Dicke Hamiltonian, which contains terms that are quadratic in
the electromagnetic field and respects gauge invariance, is then used to
calculate thermodynamic properties of the quantum Hall polariton system.
Finally, we demonstrate that the generalized Dicke description fails when the
graphene sheet is heavily doped, i.e. when the Landau level spectrum of 2D
massless Dirac fermions is approximately harmonic. In this case we `integrate
out' the Landau levels in valence band and obtain an effective Hamiltonian for
the entire stack of Landau levels in conduction band, as dressed by strong
light-matter interactions.


title:
An Optimized Semantic Web Service Composition Method Based on Clustering
  and Ant Colony Algorithm

abstract:
  In today's Web, Web Services are created and updated on the fly. For
answering complex needs of users, the construction of new web services based on
existing ones is required. It has received a great attention from different
communities. This problem is known as web services composition. However, it is
one of big challenge problems of recent years in a distributed and dynamic
environment. Web services can be composed manually but it is a time consuming
task. The automatic web service composition is one of the key features for
future the semantic web. The various approaches in field of web service
compositions proposed by the researchers. In this paper, we propose a novel
architecture for semantic web service composition using clustering and Ant
colony algorithm.


title: The Tongue as an Excitable Medium

abstract:
  Geographic tongue (GT) is a benign condition affecting approximately 2% of
the population, whereby the papillae covering the upper part of the tongue are
lost due to a slowly expanding inflammation. The resultant dynamical appearance
of the tongue has striking similarities with well known phenomena observed in
excitable media, such as forest fires, cardiac dynamics and chemically-driven
reaction-diffusion systems. Here we explore the dynamics associated with GT
from a dynamical systems perspective, utilizing cellular automata simulations.
We emphasize similarities with other excitable systems as well as unique
features observed in GT. Our results shed light on the evolution of the
inflammation and contribute to the classification of the severity of the
condition, based on the characteristic patterns observed in GT patients.


title:
Currency Derivatives Pricing for Markov-modulated Merton Jump-diffusion
  Spot Forex Rate

abstract:
  We derived similar to Bo et al. (2010) results but in the case when the
dynamics of the FX rate is driven by a general Merton jump-diffusion process.
The main results of our paper are as follows: 1) formulas for the Esscher
transform parameters which ensure that the martingale condition for the
discounted foreign exchange rate is a martingale for a general Merton
jump--diffusion process are derived; using the values of these parameters we
proceeded to a risk-neural measure and provide new formulas for the
distribution of jumps, the mean jump size, and the Poisson process intensity
with respect to the measure; pricing formulas for European call foreign
exchange options have been given as well; 2) obtained formulas are applied to
the case of the exponential processes; 3) numerical simulations of European
call foreign exchange option prices for different parameters are also provided;
4) codes for Matlab functions used in numerical simulations of option prices
are given.


title:
Anyonic statistics and large horizon diffeomorphisms for Loop Quantum
  Gravity Black Holes

abstract:
  We investigate the role played by large diffeomorphisms of quantum Isolated
Horizons for the statistics of LQG Black Holes by means of their relation to
the braid group. To this aim the symmetries of Chern-Simons theory are
recapitulated with particular regard to the aforementioned type of
diffeomorphisms. For the punctured spherical horizon, these are elements of the
mapping class group of $S^2$, which is almost isomorphic to a corresponding
braid group on this particular manifold. The mutual exchange of quantum
entities in two dimensions is achieved by the braid group, rendering the
statistics anyonic. With this we argue that the quantum Isolated Horizon model
of LQG based on $SU(2)_k$-Chern-Simons theory explicitly exhibits non-abelian
anyonic statistics. In this way a connection to the theory behind the
fractional quantum Hall effect and that of topological quantum computation is
established, where non-abelian anyons play a significant role.


title: New self dualities and duality cascades

abstract:
  New self-dualities involving two index tensors are derived. These new
self-dualities are used to build various duality cascades. Both vector like and
chiral cascades are presented. Aside from ending in confinement, these duality
cascades can also end in interacting conformal field theories, free field
theories, and meta-stable supersymmetry breaking. Higgsing effects are built
into the self-duality so that when the gauge groups are small enough,
supersymmetry is broken through the rank condition. Dynamical supersymmetry
restoration occurs far from the SUSY breaking vacuum resulting in a long lived
meta-stable vacuum. It is found that Coulomb branches are critical in the
stabilization of runaways and dynamical supersymmetry restoration.


title: Measurement of the Kerr nonlinear refractive index of Cs vapor

abstract:
  Atomic vapors are systems well suited for nonlinear optics studies but very
few direct measurements of their nonlinear refractive index have been reported.
Here we use the z-scan technique to measure the Kerr coefficient, $n_2$, for a
Cs vapor. Our results are analyzed through a four-level model, and we show that
coherence between excited levels as well as cross-population effects contribute
to the Kerr-nonlinearity.


title:
Investigating evidence for different black hole accretion modes since
  redshift z~1

abstract:
  Chandra data in the COSMOS, AEGIS-XD and 4Ms CDFS are combined with
optical/near-IR photometry to determine the rest-frame U-V vs V-J colours of
X-ray AGN hosts at mean redshifts 0.40 and 0.85. This combination of colours
(UVJ) provides an efficient means of separating quiescent from star-forming,
including dust reddened, galaxies. Morphological information emphasises
differences between AGN split by their UVJ colours. AGN in quiescent galaxies
are dominated by spheroids, while star-forming hosts are split between bulges
and disks. The UVJ diagram of AGN hosts is then used to set limits on the
accretion density associated with evolved and star-forming systems. Most of the
black hole growth since z~1 is associated with star-forming hosts.
Nevertheless, ~15-20% of the X-ray luminosity density since z~1, is taking
place in the quiescent region of the UVJ diagram. For the z~0.40 subsample,
there is tentative evidence (2sigma significance), that AGN split by their UVJ
colours differ in Eddington ratio. AGN in star-forming hosts dominate at high
Eddington ratios, while AGN in quiescent hosts become increasingly important as
a fraction of the total population toward low Eddington ratios. At higher
redshift, z~0.8, such differences are significant at the 2sigma level only at
Eddington ratios >1e-3. These findings are consistent with scenarios in which
diverse accretion modes are responsible for the build-up of SMBHs at the
centres of galaxies. We compare our results with the GALFORM semi-analytic
model, which postulates two black hole fuelling modes, the first linked to
star-formation and the second occuring in passive galaxies. GALFORM predicts a
larger fraction of black hole growth in quiescent galaxies at z<1, compared to
the data. Relaxing the strong assumption of the model that passive AGN hosts
have zero star-formation rate could reconcile this disagreement.


title:
The gravity dual of supersymmetric gauge theories on a squashed $S^1
  \times S^3$

abstract:
  We present a new one-parameter family of supersymmetric solutions deforming
AdS_5. This is constructed as an asymptotically locally anti de Sitter (AlAdS)
solution of five-dimensional minimal gauged supergravity, with topology R x R^4
and a non-trivial graviphoton field, and can be uplifted to ten or eleven
dimensional supergravities. An analytic continuation of this solution yields
the gravity dual to a class of four-dimensional N=1 supersymmetric gauge
theories on a curved manifold with topology S^1 x S^3, comprising an SU(2) x
U(1)-symmetric squashed three-sphere, with a non-trivial background gauge field
coupling to the R-symmetry current. We compute the holographically renormalised
on-shell action and interpret it in terms of the Casimir energy of the dual
field theory. We also determine the holographic conserved charges of the
solution and discuss relations between them.


title:
The origin of the Far-infrared continuum of z ~ 6 quasars: a radiative
  transfer model for SDSS J1148+5251

abstract:
  We investigate the origin of the FIR continuum of SDSS J1148+5251, using it
as a prototype for the more general class of high-luminosity high-redshift
QSOs. We run the radiative transfer code TRADING to follow the transfer of
radiation from the central source and from stellar sources through the dusty
environment of the host galaxy. The model is based on the output of the
semi-analytical merger tree code, GAMETE/QSOdust, which enables to predict the
evolution of the host galaxy and of its nuclear black hole, following the star
formation history and chemical evolution -- including dust -- in all the
progenitor galaxies of SDSS J1148+5251. We find that the radiation emitted by
the central source can also provide an important source of heating for the dust
distributed in the host galaxy, powering at least 30% and up to 70% of the
observed far infrared emission at rest-frame wavelengths [20 - 1000]micron. The
remaining fraction is contributed by stellar sources and can only be achieved
if the host galaxy is able to sustain a star formation rate of ~ 900 Msun/yr at
z=6.4. This points to a co-evolution scenario where, during their hierarchical
assembly, the first SMBHs and their host galaxies first grow at the same pace
until the black hole reaches a mass of ~ 2 10^8 Msun and starts growing faster
than its host, reaching the bright quasar phase when the black hole and stellar
mass fall within the scatter of the scaling relation observed in local
galaxies. This same evolutionary scenario has been recently shown to explain
the properties of a larger sample of 5 < z <6.4 QSOs, and imply that current
dynamical mass measurements may have missed an important fraction of the host
galaxy stellar mass. We conclude that the FIR luminosity of high-z quasars is a
sensitive tracer of the rapidly changing physical conditions in the host
galaxy.


title:
Galaxy luminosity function and Tully-Fisher relation: reconciled through
  rotation-curve studies

abstract:
  The relation between galaxy luminosity L and halo virial velocity v_vir
required to fit the galaxy luminosity function differs from the observed
Tully-Fisher relation between L and disc speed v_rot. Hence the problem of
reproducing the galaxy luminosity function and the Tully-Fisher relation
simultaneously has plagued semianalytic models since their inception. Here we
study the relation between v_rot and v_vir by fitting observational average
rotation curves of disc galaxies binned in luminosity. We show that the v_rot -
v_vir relation that we obtain in this way can fully account for this seeming
inconsistency. Therefore, the reconciliation of the luminosity function with
the Tully-Fisher relation rests on the complex dependence of v_rot on v_vir,
which arises because the ratio of stellar mass to dark matter mass is a strong
function of halo mass.


title:
Nature's Starships. I. Observed Abundances and Relative Frequencies of
  Amino Acids in Meteorites

abstract:
  The class of meteorites called carbonaceous chondrites are examples of
material from the solar system which have been relatively unchanged from the
time of their initial formation. These meteorites have been classified
according to the temperatures and physical conditions of their parent
planetesimals. We collate available data on amino acid abundance in these
meteorites and plot the concentrations of different amino acids for each
meteorite within various meteorite subclasses. We plot average concentrations
for various amino acids across meteorites separated by subclass and petrologic
type. We see a predominance in the abundance and variety of amino acids in CM2
and CR2 meteorites. The range in temperature corresponding to these subclasses
indicates high degrees of aqueous alteration, suggesting aqueous synthesis of
amino acids. Within the CM2 and CR2 subclasses, we identify trends in relative
frequencies of amino acids to investigate how common amino acids are as a
function of their chemical complexity. These two trends (total abundance and
relative frequencies) can be used to constrain formation parameters of amino
acids within planetesimals. Our organization of the data supports an onion
shell model for the temperature structure of planetesimals. The least altered
meteorites (type 3) and their amino acids originated near cooler surface
regions. The most active amino acid synthesis likely took place at intermediate
depths (type 2). The most altered materials (type 1) originated furthest toward
parent body cores. This region is likely too hot to either favor amino acid
synthesis or for amino acids to be retained after synthesis.


title: The Wolf-Rayet stars in M31: I. Analysis of the late-type WN stars

abstract:
  Context: Comprehensive studies of Wolf-Rayet stars were performed in the past
for the Galactic and the LMC population. The results revealed significant
differences, but also unexpected similarities between the WR populations of
these different galaxies. Analyzing the WR stars in M31 will extend our
understanding of these objects in different galactic environments. Aims: The
present study aims at the late-type WN stars in M31. The stellar and wind
parameters will tell about the formation of WR stars in other galaxies with
different metallicity and star formation histories. The obtained parameters
will provide constraints to the evolution of massive stars in the environment
of M31. Methods: We used the latest version of the Potsdam Wolf-Rayet model
atmosphere code to analyze the stars via fitting optical spectra and
photometric data. To account for the relatively low temperatures of the late
WN10 and WN11 subtypes, our WN models have been extended into this temperature
regime. Results: Stellar and atmospheric parameters are derived for all known
late-type WN stars in M31 with available spectra. All of these stars still have
hydrogen in their outer envelopes, some of them up to 50% by mass. The stars
are located on the cool side of the zero age main sequence in the
Hertzsprung-Russell diagram, while their luminosities range from $10^5$ to
$10^6$ Lsun. It is remarkable that no star exceeds $10^6$ Lsun. Conclusions: If
formed via single-star evolution, the late-type WN stars in M31 stem from an
initial mass range between 20 and 60 Msun. From the very late-type WN9-11
stars, only one star is located in the S Doradus instability strip. We do not
find any late-type WN stars with the high luminosities known in the Milky Way.


title:
An analytic solution for the minimal bathtub toy model: challenges in
  the star-formation history of high-z galaxies

abstract:
  We study the minimal ``bathtub" toy model as an analytic tool for capturing
key processes of galaxy evolution and identifying robust successes and
challenges in reproducing observations at high redshift. The source and sink
terms of the continuity equations for gas and stars are expressed in simple
terms from first principles. The assumed dependence of star-formation rate
(SFR) on gas mass self-regulates the system into a unique asymptotic behavior,
which is approximated by an analytic quasi-steady-state solution (QSS). We
address the validity of the QSS at different epochs independent of earlier
conditions. At high z, where the accretion is assumed to consist of gas only,
the specific SFR is robustly predicted to be sSFR = [(1+z)/3]^{5/2} Gyr^{-1},
slightly higher than the cosmological specific accretion rate, in agreement
with observations at z=3-8. The gas fraction is expected to decline slowly, and
the observations constrain the SFR efficiency per dynamical time to
epsilon=0.02. The stellar-to-virial mass ratio f_sv is predicted to be constant
in time, and the observed value requires an outflow mass-lading factor of
eta=1-3, depending on the penetration efficiency of gas into the galaxy.
However, at z=2, where stars are also accreted through mergers, the simplest
model has an apparent difficulty in matching observations. The model that
maximizes the sSFR, with the outflows fully recycled, falls short by a factor 3
in sSFR, and overestimates f_sv. With strong outflows, the model can reproduce
the observed f_sv but at the expense of underestimating the sSFR by an order of
magnitude. We discuss potential remedies including a bias due to the exclusion
of quenched galaxies.


title: Cross Section Measurements with Monoenergetic Muon Neutrinos

abstract:
  The monoenergetic 236 MeV muon neutrino from charged kaon decay-at-rest ($K^+
\rightarrow \mu^+ \nu_\mu$) can be used to produce a novel set of cross section
measurements. Applicable for short- and long-baseline accelerator-based
neutrino oscillation experiments, among others, such measurements would provide
a "standard candle" for the energy reconstruction and interaction kinematics
relevant for charged current neutrino events near this energy. This neutrino
can also be exercised as a unique known-energy, purely weak interacting probe
of the nucleus. A number of experiments are set to come online in the next few
years that will be able to collect and characterize thousands of these events.


title: Monojet versus rest of the world I: t-channel Models

abstract:
  Monojet searches using Effective Field Theory (EFT) operators are usually
interpreted as a robust and model independent constraint on direct detection
(DD) scattering cross-sections. At the same time, a mediator particle must be
present to produce the dark matter (DM) at the LHC. This mediator particle may
be produced on shell, so that direct searches for the mediating particle can
constrain the effective operator being applied to monojet constraints. In this
first paper, we do a case study on t-channel models in monojet searches, where
the (Standard Model singlet) DM is pair produced via a t-channel mediating
particle, whose supersymmetric analogue is the squark. We compare monojet
constraints to direct constraints on single or pair production of the mediator
from multi-jets plus missing energy searches and we identify the regions where
the latter dominate over the former. We show that computing bounds using
supersymmetric simplified models and in the narrow width approximation, as done
in previous work in the literature, misses important quantitative effects. We
perform a full event simulation and statistical analysis, and we compute the
effects of both on- and off-shell production of the mediating particle, showing
that for both the monojet and multi-jets plus missing energy searches,
previously derived bounds provided more conservative bounds than what can be
extracted by including all relevant processes in the simulation. Monojets and
searches for supersymmetry (SUSY) provide comparable bounds on a wide range of
the parameter space, with SUSY searches usually providing stronger bounds,
except in the regions where the DM particle and the mediator are very mass
degenerate. The EFT approximation rarely is able to reproduce the actual
limits. In a second paper to follow, we consider the case of s-channel
mediators.


title:
The Magneto-Sono-Luminescence and its signatures in photon and dilepton
  production in heavy ion collisions

abstract:
  The matter produced in the early stages of heavy ion collisions consists
mostly of gluons, and is penetrated by coherent magnetic field produced by
spectator nucleons. The fluctuations of gluonic matter in an external magnetic
field couple to real and virtual photons through virtual quark loops. We study
the resulting contributions to photon and dilepton production that stem from
the fluctuations of the stress tensor $T_{\mu\nu}$ in the background of a
coherent magnetic field $\vec{B}$. Our study extends significantly the earlier
work by two of us and Skokov, in which only the fluctuations of the trace of
the stress tensor $T_{\mu\mu}$ were considered (the coupling of $T_{\mu\mu}$ to
electromagnetic fields is governed by the scale anomaly). In the present paper
we derive more general relations using the Operator Product Expansion (OPE). We
also extend the previous study to the case of dileptons which offers the
possibility to discriminate between various production mechanisms. Among the
phenomena that we study are Magneto-Sono-Luminescence (MSL, the interaction of
magnetic field $\vec{B}(x,t)$ with the sound perturbations of the stress tensor
$\delta T_{\mu\nu}(x,t)$) and Magneto-Thermo-Luminescence (MTL, the interaction
of $\vec{B}(x,t)$ with smooth average $<T_{\mu\nu}>$). We calculate the rates
of these process and find that they can dominate the photon and dilepton
production at early stage of heavy ion collisions. We also point out the
characteristic signatures of MSL and MTL that can be used to establish their
presence and to diagnose the produced matter.


title: Naturalness and the Weak Gravity Conjecture

abstract:
  The weak gravity conjecture (WGC) is an ultraviolet consistency condition
asserting that an Abelian force requires a state of charge $q$ and mass $m$
with $q>m/m_{\rm Pl}$. We generalize the WGC to product gauge groups and study
its tension with the naturalness principle for a charged scalar coupled to
gravity. Reconciling naturalness with the WGC either requires a Higgs phase or
a low cutoff at $\Lambda \sim q m_{\rm Pl}$. If neither applies, one can
construct simple models that forbid a natural electroweak scale and whose
observation would rule out the naturalness principle.


title: The structure of invariants in conformal mechanics

abstract:
  We investigate the integrals of motion of general conformal mechanical
systems with and without confining harmonic potential as well as of the related
angular subsystems, by employing the SL(2,R) algebra and its representations.
In particular, via the tensor product of two representations we construct new
integrals of motion from old ones. Furthermore, the temporally periodic
observables (including the integrals) of the angular subsystem are explicitly
related to those of the full system in a confining harmonic potential. The
techniques are illustrated for the rational Calogero models and their angular
subsystems, where they generalize known methods for obtaining conserved charges
beyond the Liouville ones.


title:
The impact of galaxy geometry and mass evolution on the survival of star
  clusters

abstract:
  Direct N-body simulations of globular clusters in a realistic Milky Way-like
potential are carried out using the code NBODY6 to determine the impact of the
host galaxy disk mass and geometry on the survival of star clusters. A
relationship between disk mass and star cluster dissolution timescale is
derived. These N-body models show that doubling the mass of the disk from
5x10^10 solar masses to 10x10^10 solar masses halves the dissolution time of a
satellite star cluster orbiting the host galaxy at 6 kpc from the galactic
center. Different geometries in a disk of identical mass can determine either
the survival or dissolution of a star cluster orbiting within the inner 6 kpc
of the galactic center. Furthermore, disk geometry has measurable effects on
the mass loss of star clusters up to 15 kpc from the galactic center. N-body
simulations performed with a fine output time step show that at each disk
crossing the outer layers of star clusters experience an increase in velocity
dispersion of ~5% of the average velocity dispersion in the outer section of
star clusters. This leads to an enhancement of mass-loss -- a clearly
discernable effect of disk shocking. By running models with different
inclinations we determine that star clusters with an orbit perpendicular to the
Galactic plane have larger mass loss rates than both clusters evolving in the
Galactic plane or in an inclined orbit.


title:
Radio Galaxy populations and the multi-tracer technique: pushing the
  limits on primordial non-Gaussianity

abstract:
  We explore the use of different radio galaxy populations as tracers of
different mass halos and therefore, with different bias properties, to
constrain primordial non-Gaussianity of the local type. We perform a Fisher
matrix analysis based on the predicted auto and cross angular power spectra of
these populations, using simulated redshift distributions as a function of
detection flux and the evolution of the bias for the different galaxy types
(Star forming galaxies, Starburst galaxies, Radio-Quiet Quasars, FRI and FRII
AGN galaxies). We show that such a multi-tracer analysis greatly improves the
information on non-Gaussianity by drastically reducing the cosmic variance
contribution to the overall error budget. By using this method applied to
future surveys, we predict a constraint of sigma_fnl=3.6 on the local
non-Gaussian parameter for a galaxy detection flux limit of 10 \muJy and
sigma_fnl=2.2 for 1 \muJy. We show that this significantly improves on the
constraints obtained when using the whole undifferentiated populations
(sigma_fnl=48 for 10 \muJy and sigma_fnl=12 for 1 \muJy). We conclude that
continuum radio surveys alone have the potential to constrain primordial
non-Gaussianity to an accuracy at least a factor of two better than the present
constraints obtained with Planck data on the CMB bispectrum, opening a window
to obtain sigma_fnl~1 with the Square Kilometer Array.


title: Gaseous Spiral Structure and Mass Drift in Spiral Galaxies

abstract:
  We use hydrodynamic simulations to investigate nonlinear gas responses to an
imposed stellar spiral potential in disk galaxies. The gaseous medium is
assumed to be infinitesimally thin, isothermal, and unmagnetized. We consider
various spiral-arm models with differing strength and pattern speed. We find
that the extent and shapes of gaseous arms as well as the related mass drift
rate depend rather sensitively on the arm pattern speed. In models where the
arm pattern is rotating slow, the gaseous arms extend across the corotation
resonance (CR) all the way to the outer boundary, with a pitch angle slightly
smaller than that of the stellar counterpart. In models with a fast rotating
pattern, on the other hand, spiral shocks are much more tightly wound than the
stellar arms, and cease to exist in the regions near and outside the CR where
$\mathcal{M}_\perp/{\rm sin} p_* \ge 25-40$, with $\mathcal{M}_\perp$ denoting
the perpendicular Mach number of a rotating gas relative to the arms with pitch
angle $p_*$. Inside the CR, the arms drive mass inflows at a rate of $\sim
0.05-3.0 {\rm M}_\odot {\rm yr}^{-1}$ to the central region, with larger values
corresponding to stronger and slower arms. The contribution of the shock
dissipation, external torque, and self-gravitational torque to the mass inflow
is roughly 50%, 40%, and 10%, respectively. We demonstrate that the
distributions of line-of-sight velocities and spiral-arm densities can be a
useful diagnostic tool to distinguish if the spiral pattern is rotating fast or
slow.


title: NuSTAR J163433-4738.7: A Fast X-ray Transient in the Galactic Plane

abstract:
  During hard X-ray observations of the Norma spiral arm region by the Nuclear
Spectroscopic Telescope Array (NuSTAR) in 2013 February, a new transient
source, NuSTAR J163433-4738.7, was detected at a significance level of 8-sigma
in the 3-10 keV bandpass. The source is consistent with having a constant
NuSTAR count rate over a period of 40 ks and is also detected simultaneously by
Swift at lower significance. The source is not significantly detected by
NuSTAR, Swift, or Chandra in the days before or weeks after the discovery of
the transient, indicating that the strong X-ray activity lasted for between
~0.5 and 1.5 days. Near-IR imaging observations were carried out before and
after the X-ray activity, but we are not able to identify the counterpart. The
combined NuSTAR and Swift energy spectrum is consistent with a power-law with a
photon index of Gamma = 4.1(+1.5)(-1.0) (90% confidence errors), a blackbody
with kT = 1.2+/-0.3 keV, or a bremsstrahlung model with kT = 3.0(+2.1)(-1.2)
keV. The reduced-chi2 values for the three models are not significantly
different, ranging from 1.23 to 1.44 for 8 degrees of freedom. The spectrum is
strongly absorbed with NH = 2.8(+2.3)(-1.4)e23 cm-2, 9(+15)(-7)e22 cm-2, and
1.7(+1.7)(-0.9)e23 cm-2, for the power-law, blackbody, and bremsstrahlung
models, respectively. Although the high column density could be due to material
local to the source, it is consistent with absorption from interstellar
material along the line of sight at a distance of 11 kpc, which would indicate
an X-ray luminosity >1e34 erg/s. Although we do not reach a definitive
determination of the nature of NuSTAR J163433-4738.7, we suggest that it may be
an unusually bright active binary or a magnetar.


title:
The power spectrum of solar convection flows from high-resolution
  observations and 3D simulations

abstract:
  We compare Fourier spectra of photospheric velocity fields from very high
resolution IMaX observations to those from recent 3D numerical
magnetoconvection models. We carry out a proper comparison by synthesizing
spectral lines from the numerical models and then applying to them the adequate
residual instrumental degradation that affects the observational data. Also,
the validity of the usual observational proxies is tested by obtaining
synthetic observations from the numerical boxes and comparing the velocity
proxies to the actual velocity values from the numerical grid.
  For the observations, data from the SUNRISE/IMaX instrument with about 120 km
spatial resolution are used, thus allowing the calculation of observational
Fourier spectra well into the subgranular range. For the simulations, we use
four series of runs obtained with the STAGGER code and synthesize the IMaX
spectral line (FeI 5250.2 A) from them. Proxies for the velocity field are
obtained via Dopplergrams (vertical component) and local correlation tracking
(horizontal component).
  A very good match between observational and simulated Fourier power spectra
is obtained for the vertical velocity data for scales between 200 km and 6 Mm.
Instead, a clear vertical shift is obtained when the synthetic observations are
not degraded. The match for the horizontal velocity data is much less
impressive because of the inaccuracies of the LCT procedure. Concerning the
internal comparison of the direct velocity values of the numerical boxes with
those from the synthetic observations, a high correlation (0.96) is obtained
for the vertical component when using the velocity values on the
log($tau_{500}$) = -1 surface in the box. The corresponding Fourier spectra are
near each other. A lower maximum correlation (0.5) is reached (at $tau_{500}$ =
1) for the horizontal velocities as a result of the coarseness of the LCT
procedure.


title: Tachyonic Anti-M2 Branes

abstract:
  We study the dynamics of anti-M2 branes in a warped Stenzel solution with M2
charges dissolved in fluxes by taking into account their full backreaction on
the geometry. The resulting supergravity solution has a singular magnetic
four-form flux in the near-brane region. We examine the possible resolution of
this singularity via the polarization of anti-M2 branes into M5 branes, and
compute the corresponding polarization potential for branes smeared on the
finite-size four-sphere at the tip of the Stenzel space. We find that the
potential has no minimum. We then use the potential for smeared branes to
compute the one corresponding to a stack of localized anti-M2 branes, and use
this potential to compute the force between two anti-M2 branes at tip of the
Stenzel space. We find that this force, which is zero in the probe
approximation, is in fact repulsive. This surprising result points to a
tachyonic instability of anti-M2 branes in backgrounds with M2 brane charge
dissolved in flux.


title: Monte Carlo simulation of stoquastic Hamiltonians

abstract:
  Stoquastic Hamiltonians are characterized by the property that their
off-diagonal matrix elements in the standard product basis are real and
non-positive. Many interesting quantum models fall into this class including
the Transverse field Ising Model (TIM), the Heisenberg model on bipartite
graphs, and the bosonic Hubbard model. Here we consider the problem of
estimating the ground state energy of a local stoquastic Hamiltonian $H$ with a
promise that the ground state of $H$ has a non-negligible correlation with some
`guiding' state that admits a concise classical description. A formalized
version of this problem called Guided Stoquastic Hamiltonian is shown to be
complete for the complexity class MA (a probabilistic analogue of NP). To prove
this result we employ the Projection Monte Carlo algorithm with a variable
number of walkers. Secondly, we show that the ground state and thermal
equilibrium properties of the ferromagnetic TIM can be simulated in polynomial
time on a classical probabilistic computer. This result is based on the
approximation algorithm for the classical ferromagnetic Ising model due to
Jerrrum and Sinclair (1993).


title: Spin and parity measurement of the Lambda(1405) baryon

abstract:
  A determination of the spin and parity of the $\Lambda(1405)$ is presented
using photoproduction data from the CLAS detector at Jefferson Lab. The
reaction $\gamma + p \to K^+ + \Lambda(1405)$ is analyzed in the decay channel
$\Lambda(1405) \to \Sigma^+ + \pi^-$, where the decay distribution to $\Sigma^+
\pi^-$ and the variation of the $\Sigma^+$ polarization with respect to the
$\Lambda(1405)$ polarization direction determines the parity. The
$\Lambda(1405)$ is produced, in the energy range $2.55 < W < 2.85$ GeV and for
$0.6 < \cos \theta_{K^+} < 0.9$, with polarization $P = 0.45 \pm 0.02
(\text{stat}) \pm 0.07 (\text{syst})$. The analysis shows that the decays are
in $S$ wave, with the $\Sigma^+$ polarized such that the $\Lambda(1405)$ has
spin-parity $J^P = 1/2^-$, as expected by most theories.


title: Connecting Dream Networks Across Cultures

abstract:
  Many species dream, yet there remain many open research questions in the
study of dreams. The symbolism of dreams and their interpretation is present in
cultures throughout history. Analysis of online data sources for dream
interpretation using network science leads to understanding symbolism in dreams
and their associated meaning. In this study, we introduce dream interpretation
networks for English, Chinese and Arabic that represent different cultures from
various parts of the world. We analyze communities in these networks, finding
that symbols within a community are semantically related. The central nodes in
communities give insight about cultures and symbols in dreams. The community
structure of different networks highlights cultural similarities and
differences. Interconnections between different networks are also identified by
translating symbols from different languages into English. Structural
correlations across networks point out relationships between cultures.
Similarities between network communities are also investigated by analysis of
sentiment in symbol interpretations. We find that interpretations within a
community tend to have similar sentiment. Furthermore, we cluster communities
based on their sentiment, yielding three main categories of positive, negative,
and neutral dream symbols.


title: Inhomogeneous recombinations during cosmic reionization

abstract:
  By depleting the ionizing photon budget available to expand cosmic HII
regions, recombining systems (or Lyman limit systems) can have a large impact
during (and following) cosmic reionization. Unfortunately, directly resolving
such structures in large-scale reionization simulations is computationally
impractical. Instead, here we implement a sub-grid prescription for tracking
inhomogeneous recombinations in the intergalactic medium. Building on previous
work parameterizing photo-heating feedback on star-formation, we present
large-scale, semi-numeric reionization simulations which self-consistently
track the local (sub-grid) evolution of both sources and sinks of ionizing
photons. Our simple, single-parameter model naturally results in both an
extended reionization and a modest, slowly-evolving emissivity, consistent with
observations. Recombinations are instrumental in slowing the growth of large
HII regions, and damping the rapid rise of the ionizing background in the late
stages of (and following) reionization. As a result, typical HII regions are
smaller by factors of $\sim 2-3$ throughout reionization. The large-scale
($k\lesssim 0.2\text{ Mpc$^{-1}$}$) ionization power spectrum is suppressed by
factors of $\gtrsim 2-3$ in the second half of reionization. Therefore properly
modeling recombinations is important in interpreting virtually all reionization
observables, including upcoming interferometry with the redshifted 21 cm line.
Consistent with previous works, we find the clumping factor of ionized gas to
be $C_{\rm HII}\sim 4$ at the end of reionization.


title: Entanglement spreading after a geometric quench in quantum spin chains

abstract:
  We investigate the entanglement spreading in the anisotropic spin-1/2
Heisenberg (XXZ) chain after a geometric quench. This corresponds to a sudden
change of the geometry of the chain or, in the equivalent language of
interacting fermions confined in a box trap, to a sudden increase of the trap
size. The entanglement dynamics after the quench is associated with the
ballistic propagation of a magnetization wavefront. At the free fermion point
(XX chain), the von-Neumann entropy S_A exhibits several intriguing dynamical
regimes. Specifically, at short times a logarithmic increase is observed,
similar to local quenches. This is accurately described by an analytic formula
that we derive from heuristic arguments. At intermediate times partial revivals
of the short-time dynamics are superposed with a power-law increase S_A
t^\alpha, with \alpha<1. Finally, at very long times a steady state develops
with constant entanglement entropy. As expected, since the model is integrable,
we find that the steady state is non thermal, although it exhibits extensive
entanglement entropy. We also investigate the entanglement dynamics after the
quench from a finite to the infinite chain (sudden expansion). While at long
times the entanglement vanishes, we demonstrate that its relaxation dynamics
exhibits a number of scaling properties. Finally, we discuss the short-time
entanglement dynamics in the XXZ chain in the gapless phase. The same formula
that describes the time dependence for the XX chain remains valid in the whole
gapless phase.


title: Feature and Variable Selection in Classification

abstract:
  The amount of information in the form of features and variables avail- able
to machine learning algorithms is ever increasing. This can lead to classifiers
that are prone to overfitting in high dimensions, high di- mensional models do
not lend themselves to interpretable results, and the CPU and memory resources
necessary to run on high-dimensional datasets severly limit the applications of
the approaches. Variable and feature selection aim to remedy this by finding a
subset of features that in some way captures the information provided best. In
this paper we present the general methodology and highlight some specific
approaches.


title:
Detection of An Unidentified Emission Line in the Stacked X-ray spectrum
  of Galaxy Clusters

abstract:
  We detect a weak unidentified emission line at E=(3.55-3.57)+/-0.03 keV in a
stacked XMM spectrum of 73 galaxy clusters spanning a redshift range 0.01-0.35.
MOS and PN observations independently show the presence of the line at
consistent energies. When the full sample is divided into three subsamples
(Perseus, Centaurus+Ophiuchus+Coma, and all others), the line is significantly
detected in all three independent MOS spectra and the PN "all others" spectrum.
It is also detected in the Chandra spectra of Perseus with the flux consistent
with XMM (though it is not seen in Virgo). However, it is very weak and located
within 50-110eV of several known faint lines, and so is subject to significant
modeling uncertainties. On the origin of this line, we argue that there should
be no atomic transitions in thermal plasma at this energy. An intriguing
possibility is the decay of sterile neutrino, a long-sought dark matter
particle candidate. Assuming that all dark matter is in sterile neutrinos with
m_s=2E=7.1 keV, our detection in the full sample corresponds to a neutrino
decay mixing angle sin^2(2theta)=7e-11, below the previous upper limits.
However, based on the cluster masses and distances, the line in Perseus is much
brighter than expected in this model. This appears to be because of an
anomalously bright line at E=3.62 keV in Perseus, possibly an Ar XVII
dielectronic recombination line, although its flux would be 30 times the
expected value and physically difficult to understand. In principle, such an
anomaly might explain our line detection in other subsamples as well, though it
would stretch the line energy uncertainties. Another alternative is the above
anomaly in the Ar line combined with the nearby 3.51 keV K line also exceeding
expectation by factor 10-20. Confirmation with Chandra and Suzaku, and
eventually Astro-H, are required to determine the nature of this new
line.(ABRIDGED)


title:
Molecule-optimized Basis Sets and Hamiltonians for Accelerated
  Electronic Structure Calculations of Atoms and Molecules

abstract:
  Molecule-optimized basis sets, based on approximate natural orbitals, are
developed for accelerating the convergence of quantum calculations with
strongly correlated (multi-referenced) electrons. We use a low-cost approximate
solution of the anti-Hermitian contracted Schr{\"o}dinger equation (ACSE) for
the one- and two-electron reduced density matrices (RDMs) to generate an
approximate set of natural orbitals for strongly correlated quantum systems.
The natural-orbital basis set is truncated to generate a molecule-optimized
basis set whose rank matches that of a standard correlation-consistent basis
set optimized for the atoms. We show that basis-set truncation by approximate
natural orbitals can be viewed as a one-electron unitary transformation of the
Hamiltonian operator and suggest an extension of approximate natural-orbital
truncations through two-electron unitary transformations of the Hamiltonian
operator, such as those employed in the solution of the ACSE. The
molecule-optimized basis set from the ACSE improves the accuracy of the
equivalent standard atom-optimized basis set at little additional computational
cost. We illustrate the method with the potential energy curves of hydrogen
fluoride and diatomic nitrogen. Relative to the hydrogen fluoride potential
energy curve from the ACSE in a polarized triple-zeta basis set, the ACSE curve
in a molecule-optimized basis set, equivalent in size to a polarized
double-zeta basis, has a nonparallelity error of 0.0154 a.u. which is
significantly better than the nonparallelity error of 0.0252 a.u. from the
polarized double-zeta basis set.


title:
Banach spaces of polynomials as "large" subspaces of
  $\mathbf{\ell^\infty}$-spaces

abstract:
  In this note we study Banach spaces of traces of real polynomials on $\mathbb
R^n$ to compact subsets equipped with supremum norms from the point of view of
Geometric Functional Analysis.


title:
Rigidity and flexibility in protein-protein interaction networks: a case
  study on neuromuscular disorders

abstract:
  Mutations in proteins can have deleterious effects on a protein's stability
and function, which ultimately causes particular diseases. Genetically
inherited muscular dystrophies (MDs) include several genetic diseases, which
cause increasing weakness in muscles and disability to perform muscular
functions progressively. Different types of mutations in the gene coding
translates into defunct proteins cause different neuro-muscular diseases.
Defunct protein interactions in human proteome may cause a stress to its
neighboring proteins and its modules. We therefore aimed to understand the
effects of mutated proteins on interacting partners in different muscular
dystrophies utilizing network biology to understand system properties of these
MDs subnetworks .We investigated rigidity and flexibility of protein-protein
interaction subnetworks associated with causative mutated genes showing high
mean interference values in muscular dystrophy. Rigid component related to
EEF1A1 subnetwork and members of 14.3.3 protein family formed the core of
network showed involvement in molecular function related to protein domain
specific binding. CACNA1S and CALM1 showing functionality related to
Voltage-dependent calcium channel demonstrated highest flexibility. The
interconnected subnets of proteins corresponding to known causative genes
having large genetic variants are shared in different muscular dystrophies
inferred towards comorbidity in diseases. The studies demonstrates core network
of MDs as highly rigid, constituting of large intermodular edges and
interconnected hub nodes suggesting high information transfer flow. The core
skeleton of the network is organized in protein specific domain binding. This
suggests neuro-muscular disorders may initiate due to interruption in molecular
function related with the core and its aggression may depend on the tolerance
level of the networks.


title: On Nonperiodic Euler Flows with H\"{o}lder Regularity

abstract:
  In [Isett,13], the first author proposed a strengthening of Onsager's
conjecture on the failure of energy conservation for incompressible Euler flows
with H\"{o}lder regularity not exceeding $1/3$. This stronger form of the
conjecture implies that anomalous dissipation will fail for a generic Euler
flow with regularity below the Onsager critical space $L_t^\infty
B_{3,\infty}^{1/3}$ due to low regularity of the energy profile. In this paper,
we establish two theorems that may be viewed as first steps towards
establishing the conjectured failure of energy regularity for generic solutions
with H\"{o}lder exponent less than $1/5$.
  Our first result shows that any non-negative function with compact support
and H\"older regularity $1/2$ can be prescribed as the energy profile of an
Euler flow in the class $C^{1/5-\epsilon}_{t,x}$. The exponent $1/2$ is sharp
in view of a regularity result of [Isett,13]. The proof employs an improved
greedy algorithm scheme that builds upon that in [Buckmaster-De
Lellis-Sz\'ekelyhidi, 13]. Our second result shows that any given smooth Euler
flow can be perturbed in $C^{1/5-\epsilon}_{t,x}$ on any pre-compact subset of
${\mathbb R}\times {\mathbb R}^3$ to violate energy conservation. In
particular, there exist nonzero $C^{1/5-\epsilon}_{t,x}$ solutions to Euler
with compact space-time support, generalizing previous work of the first author
[Isett,12] to the nonperiodic setting.


title: Percolation Approach to Initial Stage Effects in High Energy Collisions

abstract:
  Possible phase transition of strongly interacting matter from hadron to a
quark-gluon plasma state have in the past received considerable interest. The
clustering of color sources provides a framework of the the partonic
interactions in the initial stage of the collisions. The onset of
de-confinement transition is identified by the spanning percolation cluster in
2D percolation. In this talk results are presented both for the multiplicity
and the elliptic flow at RHIC and LHC energies. The thermodynamic quantities
temperature, equation of state and transport coefficient are obtained in the
framework of clustering of color sources. It is shown that the results are in
excellent agreement with the recent lattice QCD calculations(LQCD).


title: Profiles for the radial focusing 4d energy-critical wave equation

abstract:
  Consider a finite energy radial solution to the focusing energy critical
semilinear wave equation in 1+4 dimensions. Assume that this solution exhibits
type-II behavior, by which we mean that the critical Sobolev norm of the
evolution stays bounded on the maximal interval of existence. We prove that
along a sequence of times tending to the maximal forward time of existence, the
solution decomposes into a sum of dynamically rescaled solitons, a free
radiation term, and an error tending to zero in the energy space. If, in
addition, we assume that the critical norm of the evolution localized to the
light cone (the forward light cone in the case of global solutions and the
backwards cone in the case of finite time blow-up) is less than 2 times the
critical norm of the ground state solution W, then the decomposition holds
without a restriction to a subsequence.


title: Predicting Crowd Behavior with Big Public Data

abstract:
  With public information becoming widely accessible and shared on today's web,
greater insights are possible into crowd actions by citizens and non-state
actors such as large protests and cyber activism. We present efforts to predict
the occurrence, specific timeframe, and location of such actions before they
occur based on public data collected from over 300,000 open content web sources
in 7 languages, from all over the world, ranging from mainstream news to
government publications to blogs and social media. Using natural language
processing, event information is extracted from content such as type of event,
what entities are involved and in what role, sentiment and tone, and the
occurrence time range of the event discussed. Statements made on Twitter about
a future date from the time of posting prove particularly indicative. We
consider in particular the case of the 2013 Egyptian coup d'etat. The study
validates and quantifies the common intuition that data on social media (beyond
mainstream news sources) are able to predict major events.


title: Sparsity-Constrained Transportation Problem

abstract:
  We study the solution of a large-scale transportation problem with an
additional constraint on the sparsity of inbound flows. Such problems arise in
the management of inventory for online retailers that operate with many order
fulfillment centers; each stock-keeping unit is typically kept in a limited
number of these order fulfillment centers so as to reduce the operational
overhead in the supply chain network.
  We propose a computationally efficient algorithm that solves this
sparsity-constrained optimization problem while bypassing complexities of the
conventional integer programming approach. The effectiveness of the algorithm
is demonstrated through a series of numerical experiments on synthetic data.


title: A superconducting NbN detector for neutral nanoparticles

abstract:
  We present a proof-of-principle study of superconducting single photon
detectors (SSPD) for the detection of individual neutral
molecules/nanoparticles at low energies. The new detector is applied to
characterize a laser desorption source for biomolecules and it allows to
retrieve the arrival time distribution of a pulsed molecular beam containing
the amino acid tryptophan, the polypeptide gramicidin as well as insulin,
myoglobin and hemoglobin. We discuss the experimental evidence that the
detector is actually sensitive to isolated neutral particles.


title: Interacting vacuum energy in the dark sector

abstract:
  We analyse three cosmological scenarios with interaction in the dark sector,
which are particular cases of a general expression for the energy flux from
vacuum to matter. In the first case the interaction leads to a transition from
an unstable de Sitter phase to a radiation dominated universe, avoiding in this
way the initial singularity. In the second case the interaction gives rise to a
slow-roll power-law inflation. Finally, the third scenario is a concordance
model for the late-time universe, with the vacuum term decaying into cold dark
matter. We identify the physics behind these forms of interaction and show that
they can be described as particular types of the modified Chaplygin gas.


title: Vanishing superconformal indices and the chiral symmetry breaking

abstract:
  Superconformal indices of 4d \N=1 SYM theories with SU(N) and SP(2N) gauge
groups are investigated for N_f=N and N_f=N+1 flavors, respectively. These
indices vanish for generic values of the flavor fugacities. However, for a
singular submanifold of fugacities they behave like the Dirac delta functions
and describe the chiral symmetry breaking phenomenon. Similar picture holds for
partition functions of 3d supersymmetric field theories with the chiral
symmetry breaking.


title: UV and VUV ionization of organic molecules, clusters and complexes

abstract:
  The generation of organic particle beams is studied in combination with
photoionization using uv radiation at 266 nm and vuv light at 157 nm.
Single-photon ionization with pulsed vuv light turns out to be sensitive enough
to detect various large neutral biomolecular complexes ranging from metal-amino
acid complexes to nucleotide clusters and aggregates of polypeptides. Different
biomolecular clusters are shown to exhibit rather specific binding
characteristics with regard to the various metals that are co-desorbed in the
source. We also find that the ion signal of gramicidin can be increased by a
factor of fifteen when the photon energy is increased from 4.66 eV to 7.9 eV.


title:
Existence of Global Symmetry-Breaking Solutions in an Elastic
  Phase-Field Model for Lipid Bilayer Vesicles

abstract:
  We consider a well known model for lipid-bilayer membrane vesicles exhibiting
phase separation, incorporating a phase field with finite curvature elasticity.
We prove the existence of a plethora of equilibria, corresponding to
symmetry-breaking solutions of the Euler-Lagrange equations, via global
bifurcation from the spherical state. To the best of our knowledge, this
constitutes the first rigorous existence results for this class of problems. We
overcome several difficulties in carrying this out. Due to inherent in-plane
fluidity combined with finite curvature elasticity, neither the Eulerian
(spatial) nor the Lagrangian (material) description of the model lends itself
well to analysis. Instead we adopt a singularity-free radial-map description
that effectively eliminates the grossly underdetermined in-plane fluid
deformation. The resulting governing equations comprise a quasi-linear elliptic
system with lower-order nonlinear constraints. We then show the equivalence of
our problem to that of finding the zeros of compact vector field. The latter is
not routine; we obtain certain spectral estimates and then shift the principle
part of the operator. With this in hand, we combine well known group-theoretic
ideas for symmetry-breaking with global bifurcation theory to obtain our
results.


title: Etale cohomology, cofinite generation, and p-adic L-functions

abstract:
  For a prime number p and a number field k, we first study certain etale
cohomology groups with coefficients associated to a p-adic Artin representation
of its Galois group, where we twist the coefficients using a modified Tate
twist with a p-adic index. We show that those groups are cofinitely generated
and explicitly compute an additive Euler characteristic. When k is totally real
and the representation is even, we relate the order of vanishing of the p-adic
L-function at a point of its domain and the corank of such a cohomology group
with a suitable p-adic twist. If the groups are finite, then the value of the
p-adic L-function is non-zero and its p-adic absolute value is related to a
multiplicative Euler characteristic. For a negative integer n (and for 0 in
certain cases), this gives a proof of a conjecture by Coates and Lichtenbaum,
and a short proof of the equivariant Tamagawa number conjecture for classical
L-functions that do not vanish at n. For p=2 our results involving p-adic
L-functions depend on a conjecture in Iwasawa theory.


title: On dark degeneracy and interacting models

abstract:
  Cosmological background observations cannot fix the dark energy equation of
state, which is related to a degeneracy in the definition of the dark sector
components. Here we show that this degeneracy can be broken at perturbation
level by imposing two observational properties on dark matter. First, dark
matter is defined as the clustering component we observe in large scale
structures. This definition is meaningful only if dark energy is unperturbed,
which is achieved if we additionally assume, as a second condition, that dark
matter is cold, i.e. non-relativistic. As a consequence, dark energy models
with equation-of-state parameter $-1 \le\omega< 0$ are reduced to two
observationally distinguishable classes with $\omega = -1$, equally competitive
when tested against observations. The first comprises the $\Lambda$CDM model
with constant dark energy density. The second consists of interacting models
with an energy flux from dark energy to dark matter.


title: Dynamics of covering maps of the annulus I: semiconjugacies

abstract:
  It is often the case that a covering map of the open annulus is semiconjugate
to a map of the circle of the same degree. We investigate this possibility and
its consequences on the dynamics. In particular, we address the problem of the
classification up to conjugacy. However, there are examples which are not
semiconjugate to a map of the circle, and this opens new questions.


title: Electrokinetics of Polar Liquids in Contact with Non-Polar Surfaces

abstract:
  Zeta potentials of several polar protic (water, ethylene glycol, formamide)
as well as polar aprotic (dimethyl sulfoxide) liquids were measured in contact
with three non-polar surfaces using closed-cell electro-osmosis. The test
surfaces were chemisorbed monolayers of alkyl siloxanes, fluoroalkyl siloxanes
and polydimethylsiloxanes (PDMS) grafted on glass slides. All these liquids
exhibited substantial electrokinetics in contact with the non-polar surfaces
with these observations: the electrokinetic effect on the fluorocarbon-coated
surface is the strongest; and on a PDMS grafted surface, the effect is the
weakest. Even though these hygroscopic liquids contain small amounts of water,
the current models of charging based on the adsorption of hydroxide ions at the
interface or the dissociation of preexisting functionalities (e.g., silanol
groups) appear to be insufficient to account for the various facets of the
experimental observations. The results illustrate how ubiquitous the phenomenon
of electro-kinetics is with polar liquids contacting such apparently passive
non-polar surfaces. We hope that these results will inspire further
experimental and theoretical studies in this important area of research that
has potential practical implications.


title:
Devil's Staircase -- Rotation Number of Outer Billiard with Polygonal
  Invariant Curves

abstract:
  In this paper, we discuss rotation number on the invariant curve of a one
parameter family of outer billiard tables. Given a convex polygon $\eta$, we
can construct an outer billiard table $T$ by cutting out a fixed area from the
interior of $\eta$. $T$ is piece-wise hyperbolic and the polygon $\eta$ is an
invariant curve of $T$ under the billiard map $\phi$. We will show that, if
$\beta $ is a periodic point under the outer billiard map with rational
rotation number $\tau = p / q$, then the $n$th iteration of the billiard map is
not the local identity at $\beta$. This proves that the rotation number $\tau$
as a function of the area parameter is a devil's staircase function.


title:
High flux coherent supercontinuum soft X-ray source driven by a
  single-stage 10 mJ, kHz, Ti:sapphire laser amplifier

abstract:
  We demonstrate the highest flux tabletop source of coherent soft X-rays to
date, driven by a single-stage 10 mJ Ti:sapphire regenerative amplifier at 1
kHz. We first down-convert the laser to 1.3 um using a parametric amplifier,
before up-converting it to soft X-rays using high harmonic generation in a
high-pressure, phase matched, hollow waveguide geometry. The resulting
optimally phase matched broadband spectrum extends to 200 eV, with a soft X-ray
photon flux of > 10^6 photons/pulse/1% bandwidth at 1 kHz, corresponding to >
10^9 photons/s/1% bandwidth, or approximately a three order-of-magnitude
increase compared with past work. Finally, using this broad bandwidth X-ray
source, we demonstrate X-ray absorption spectroscopy of multiple elements and
transitions in molecules in a single spectrum, with a spectral resolution of
0.25 eV, and with the ability to resolve the near edge fine structure.


title: Prime ideals of skew PBW extensions

abstract:
  In this paper we describe the prime ideals of some important classes of skew
PBW extensions, using the classical technique of extending and contracting
ideals. Skew PBW extensions include as particular examples Weyl algebras,
enveloping algebras of finite-dimensional Lie algebras (and its quantization),
Artamonov quantum polynomials, diffusion algebras, Manin algebra of quantum
matrices, among many others.


title: Left and right centers in quasi-Poisson geometry of moduli spaces

abstract:
  We introduce left central and right central functions and left and right
leaves in quasi-Poisson geometry, generalizing central (or Casimir) functions
and symplectic leaves from Poisson geometry. They lead to a new type of
(quasi-)Poisson reduction, which is both simpler and more general than known
quasi-Hamiltonian reductions. We study these notions in detail for moduli
spaces of flat connections on surfaces, where the quasi-Poisson structure is
given by an intersection pairing on homology.


title:
Deformed phase space for 3d loop gravity and hyperbolic discrete
  geometries

abstract:
  We revisit the loop gravity space phase for 3D Riemannian gravity by
algebraically constructing the phase space
$T^*\mathrm{SU}(2)\sim\mathrm{ISO}(3)$ as the Heisenberg double of the Lie
group $\mathrm{SO}(3)$ provided with the trivial cocyle. Tackling the issue of
accounting for a non-vanishing cosmological constraint $\Lambda \ne 0$ in the
canonical framework of 3D loop quantum gravity, $\mathrm{SL}(2,\mathbb{C})$
viewed as the Heisenberg double of $\mathrm{SU}(2)$ provided with a non-trivial
cocyle is introduced as a phase space. It is a deformation of the flat phase
space $\mathrm{ISO}(3)$ and reproduces the latter in a suitable limit. The
$\mathrm{SL}(2,\mathbb{C})$ phase space is then used to build a new, deformed
LQG phase space associated to graphs. It can be equipped with a set of Gauss
constraints and flatness constraints, which form a first class system and
Poisson-generate local 3D rotations and deformed translations. We provide a
geometrical interpretation for this lattice phase space with constraints in
terms of consistently glued hyperbolic triangles, i.e. hyperbolic discrete
geometries, thus validating our construction as accounting for a constant
curvature $\Lambda<0$. Finally, using ribbon diagrams, we show that our new
model is topological.


title: Universal Matrix Completion

abstract:
  The problem of low-rank matrix completion has recently generated a lot of
interest leading to several results that offer exact solutions to the problem.
However, in order to do so, these methods make assumptions that can be quite
restrictive in practice. More specifically, the methods assume that: a) the
observed indices are sampled uniformly at random, and b) for every new matrix,
the observed indices are sampled afresh. In this work, we address these issues
by providing a universal recovery guarantee for matrix completion that works
for a variety of sampling schemes. In particular, we show that if the set of
sampled indices come from the edges of a bipartite graph with large spectral
gap (i.e. gap between the first and the second singular value), then the
nuclear norm minimization based method exactly recovers all low-rank matrices
that satisfy certain incoherence properties. Moreover, we also show that under
certain stricter incoherence conditions, $O(nr^2)$ uniformly sampled entries
are enough to recover any rank-$r$ $n\times n$ matrix, in contrast to the
$O(nr\log n)$ sample complexity required by other matrix completion algorithms
as well as existing analyses of the nuclear norm method.


title:
Modeling Increased Metal Production in Galaxy Clusters with
  Pair-Instability Supernovae

abstract:
  Galaxy clusters contain much more metal per star, typically 3 times as much,
than is produced in normal galaxies. We set out to determine what changes are
needed to the stellar mass function and supernovae rates to account for this
excess metal. In particular, we vary the Type Ia supernovae rate, IMF slope,
upper and lower mass cutoffs, and the merger rate of massive stars. We then use
existing simulation results for metal production from AGB stars, Type Ia SNe
and core-collapse SNe to calculate the total amount of each element produced
per solar mass of star formation. For models with very massive stars, we also
include metal production from pair-instability supernovae (PISNe).We find that
including PISNe makes it much easier to increase the amount of metal produced
per stellar mass. Therefore a separate population of high-mass stars is not
needed to produce the high amounts of metal found in galaxy clusters. We also
find that including at least some PISNe increases the abundance of
intermediate-mass elements relative to both oxygen and iron, consistent with
observations of ICM abundances.


title: Damping of a nanocantilever by paramagnetic spins

abstract:
  We compute damping of mechanical oscillations of a cantilever that contains
flipping paramagnetic spins. This kind of damping is mandated by the dynamics
of the total angular momentum, spin + mechanical. Rigorous expression for the
damping rate is derived in terms of measurable parameters. The effect of spins
on the quality factor of the cantilever can be significant in cantilevers of
small length that have large concentration of paramagnetic spins of atomic
and/or nuclear origin.


title:
On the role of symmetry in solving maximum lifetime problem in
  two-dimensional sensor networks

abstract:
  We analyze a continuous and discrete symmetries of the maximum lifetime
problem in two dimensional sensor networks. We show, how a symmetry of the
network and invariance of the problem under a given transformation group $G$
can be utilized to simplify its solution. We prove, that for a $G$-invariant
maximum lifetime problem there exists a $G$-invariant solution. Constrains
which follow from the $G$-invariance allow to reduce the problem and its
solution to a subset, an optimal fundamental region of the sensor network. We
analyze in detail solutions of the maximum lifetime problem invariant under a
group of isometry transformations of a two dimensional Euclidean plane.


title:
A new paradigm for petascale Monte Carlo simulation: Replica exchange
  Wang-Landau sampling

abstract:
  We introduce a generic, parallel Wang-Landau method that is naturally suited
to implementation on massively parallel, petaflop supercomputers. The approach
introduces a replica-exchange framework in which densities of states for
overlapping sub-windows in energy space are determined iteratively by
traditional Wang-Landau sampling. The advantages and general applicability of
the method are demonstrated for several distinct systems that possess discrete
or continuous degrees of freedom, including those with complex free energy
landscapes and topological constraints.


title: Molecular ions in the protostellar shock L1157-B1

abstract:
  We perform a complete census of molecular ions with an abundance larger than
1e-10 in the protostellar shock L1157-B1 by means of an unbiased
high-sensitivity survey obtained with the IRAM-30m and Herschel/HIFI. By means
of an LVG radiative transfer code the gas physical conditions and fractional
abundances of molecular ions are derived. The latter are compared with
estimates of steady-state abundances in the cloud and their evolution in the
shock calculated with the chemical model Astrochem. We detect emission from
HCO+, H13CO+, N2H+, HCS+, and, for the first time in a shock, from HOCO+, and
SO+. The bulk of the emission peaks at blueshifted velocity, ~ 0.5-3 km/s with
respect to systemic, has a width of ~ 4-8 km/s, and is associated with the
outflow cavities (T_kin ~ 20-70 K, n(H2) ~ 1e5 cm-3). Observed HCO+ and N2H+
abundances are in agreement with steady-state abundances in the cloud and with
their evolution in the compressed and heated gas in the shock for cosmic rays
ionization rate Z = 3e-16 s-1. HOCO+, SO+, and HCS+ observed abundances,
instead, are 1-2 orders of magnitude larger than predicted in the cloud; on the
other hand they are strongly enhanced on timescales shorter than the shock age
(~2000 years) if CO2, S or H2S, and OCS are sputtered off the dust grains in
the shock. The performed analysis indicates that HCO+ and N2H+ are a fossil
record of pre-shock gas in the outflow cavity, while HOCO+, SO+, and HCS+ are
effective shock tracers and can be used to infer the amount of CO2 and
sulphur-bearing species released from dust mantles in the shock. The observed
HCS+ (and CS) abundance indicates that OCS should be one of the main sulphur
carrier on grain mantles. However, the OCS abundance required to fit the
observations is 1-2 orders of magnitude larger than observed. Further studies
are required to fully understand the chemistry of sulphur-bearing species.


title: Picard groups on moduli of K3 surfaces with Mukai models

abstract:
  We discuss the Picard group of moduli space $\mathcal{K}_g$ of
quasi-polarized K3 surfaces of genus $g\leq 12$ and $g\neq 11$. In this range,
$\mathcal{K}_g$ is unirational and a general element in $\mathcal{K}_g$ is a
complete intersection with respect to a vector bundle on a homogenous space, by
the work of Mukai. In this paper, we find generators of the Picard group
$Pic_\mathbb{Q}(\mathcal{K}_g)$ using Noether-Lefschetz theory. This verifies
the Noether-Lefschetz conjecture on moduli of K3 surfaces in these cases.


title: Computational Limits for Matrix Completion

abstract:
  Matrix Completion is the problem of recovering an unknown real-valued
low-rank matrix from a subsample of its entries. Important recent results show
that the problem can be solved efficiently under the assumption that the
unknown matrix is incoherent and the subsample is drawn uniformly at random.
Are these assumptions necessary?
  It is well known that Matrix Completion in its full generality is NP-hard.
However, little is known if make additional assumptions such as incoherence and
permit the algorithm to output a matrix of slightly higher rank. In this paper
we prove that Matrix Completion remains computationally intractable even if the
unknown matrix has rank $4$ but we are allowed to output any constant rank
matrix, and even if additionally we assume that the unknown matrix is
incoherent and are shown $90%$ of the entries. This result relies on the
conjectured hardness of the $4$-Coloring problem. We also consider the positive
semidefinite Matrix Completion problem. Here we show a similar hardness result
under the standard assumption that $\mathrm{P}\ne \mathrm{NP}.$
  Our results greatly narrow the gap between existing feasibility results and
computational lower bounds. In particular, we believe that our results give the
first complexity-theoretic justification for why distributional assumptions are
needed beyond the incoherence assumption in order to obtain positive results.
On the technical side, we contribute several new ideas on how to encode hard
combinatorial problems in low-rank optimization problems. We hope that these
techniques will be helpful in further understanding the computational limits of
Matrix Completion and related problems.


title: Flux upper limits for 47 AGN observed with H.E.S.S. in 2004-2011

abstract:
  About 40% of the observation time of the High Energy Stereoscopic System
(H.E.S.S.) is dedicated to studying active galactic nuclei (AGN), with the aim
of increasing the sample of known extragalactic very-high-energy (VHE, E>100
GeV) sources and constraining the physical processes at play in potential
emitters. H.E.S.S. observations of AGN, spanning a period from April 2004 to
December 2011, are investigated to constrain their gamma-ray fluxes. Only the
47 sources without significant excess detected at the position of the targets
are presented. Upper limits on VHE fluxes of the targets were computed and a
search for variability was performed on the nightly time scale. For 41 objects,
the flux upper limits we derived are the most constraining reported to date.
These constraints at VHE are compared with the flux level expected from
extrapolations of Fermi-LAT measurements in the two-year catalog of AGN. The
H.E.S.S. upper limits are at least a factor of two lower than the extrapolated
Fermi-LAT fluxes for 11 objects. Taking into account the attenuation by the
extragalactic background light reduces the tension for all but two of them,
suggesting intrinsic curvature in the high-energy spectra of these two AGN.
Compilation efforts led by current VHE instruments are of critical importance
for target-selection strategies before the advent of the Cherenkov Telescope
Array, CTA.


title:
Modeling sequential data using higher-order relational features and
  predictive training

abstract:
  Bi-linear feature learning models, like the gated autoencoder, were proposed
as a way to model relationships between frames in a video. By minimizing
reconstruction error of one frame, given the previous frame, these models learn
"mapping units" that encode the transformations inherent in a sequence, and
thereby learn to encode motion. In this work we extend bi-linear models by
introducing "higher-order mapping units" that allow us to encode
transformations between frames and transformations between transformations.
  We show that this makes it possible to encode temporal structure that is more
complex and longer-range than the structure captured within standard bi-linear
models. We also show that a natural way to train the model is by replacing the
commonly used reconstruction objective with a prediction objective which forces
the model to correctly predict the evolution of the input multiple steps into
the future. Learning can be achieved by back-propagating the multi-step
prediction through time. We test the model on various temporal prediction
tasks, and show that higher-order mappings and predictive training both yield a
significant improvement over bi-linear models in terms of prediction accuracy.


title:
Thermal Model and Optimization of a Large Crystal Detector using a
  Metallic Magnetic Calorimeter

abstract:
  We established a simple thermal model of the heat flow in a large crystal
detector designed for a neutrinoless double beta decay experiment. The detector
is composed of a CaMoO$_{4}$ crystal and a metallic magnetic calorimeter (MMC).
The thermal connection between the absorber and the sensor consists of a gold
film evaporated on the crystal surface and gold bonding wires attached to this
film and the MMC sensor. The model describes athermal and thermal processes of
heat flow to the gold film. A successive experiment based on optimization
calculations of the area and thickness of the gold film showed a significant
improvement in the size and rise-time of the measured signals.


title: Sparsity averaging for radio-interferometric imaging

abstract:
  We propose a novel regularization method for compressive imaging in the
context of the compressed sensing (CS) theory with coherent and redundant
dictionaries. Natural images are often complicated and several types of
structures can be present at once. It is well known that piecewise smooth
images exhibit gradient sparsity, and that images with extended structures are
better encapsulated in wavelet frames. Therefore, we here conjecture that
promoting average sparsity or compressibility over multiple frames rather than
single frames is an extremely powerful regularization prior.