title: On the Expressiveness of TPTL and MTL over \omega-Data Words

abstract:
  Metric Temporal Logic (MTL) and Timed Propositional Temporal Logic (TPTL) are
prominent extensions of Linear Temporal Logic to specify properties about data
languages. In this paper, we consider the class of data languages of
non-monotonic data words over the natural numbers. We prove that, in this
setting, TPTL is strictly more expressive than MTL. To this end, we introduce
Ehrenfeucht-Fraisse (EF) games for MTL. Using EF games for MTL, we also prove
that the MTL definability decision problem ("Given a TPTL-formula, is the
language defined by this formula definable in MTL?") is undecidable. We also
define EF games for TPTL, and we show the effect of various syntactic
restrictions on the expressiveness of MTL and TPTL.


title: A Comprehensive Assessment Strategy for Physics Laboratory Courses

abstract:
  The objective of physics laboratory training is to develop, in students, a
variety of important cognitive and psycho-motor abilities related to
experimental physics. These include conceptual understanding, procedural
understanding, experimental skills and the experimental problem solving
ability. It has been noted that strategies adopted for the assessment of what
students learn and develop through a laboratory course are often inconsistent
with the objectives of the laboratory courses. The author has developed a
comprehensive assessment strategy which can be used at the school, college and
university level. The strategy is based on four tools of assessment, namely,
test on conceptual understanding, test on procedural understanding, an
experimental test, and the continuous assessment. The relative weightage for
each of the four tools depends on the level and emphasis of the laboratory
course. The four tools of assessment, with respect to the type of questions,
design, grading schemes, administration of each tool have been described with a
few sample questions for each tool of assessment. This assessment strategy is
being practiced and its effectiveness studied during a series of special
courses in experimental physics in India. Furthermore, a survey was carried out
with university teachers from across India to check the acceptability and
feasibility of using this strategy for larger number of students in
universities and most of the participating teachers supported the use of this
strategy.


title:
An alternative explanation of the dibaryon suggested by experiments at
  the WASA facility at the FZ Julich Cooler synchrotron

abstract:
  A series of publications of the WASA collaboration culminates in a recent
paper of Pricking, Bashkanov and Clement [1] claiming a dibaryon resonance at
2370 MeV. However, as explained here, there are logical flaws in this result. A
natural alternative arises from the reaction pd -> N N*(1440)p_s where p_s is a
spectator proton. There is supporting evidence from a recent experiment of
Mielke et al. on dp -> 3He-piplus-piminus


title: One-loop renormalization in a toy model of Horava-Lifshitz gravity

abstract:
  We present a one loop calculation in the context of Horava-Lifshitz gravity.
Due to the complexity of the calculation in the full theory we focus here on
the study of a toy model, namely the conformal reduction of the z=2 projectable
theory in 2+1 dimensions. For this value of the dimension there are no
gravitons, hence the conformal mode is the only physical degree of freedom, and
thus we expect our toy model to lead to qualitatively correct answers regarding
the perturbative renormalization of the full theory. We find that Newton's
constant (dimensionless in Horava-Lifshitz gravity) is asymptotically free.
However, the DeWitt supermetric approaches its Weyl invariant form with the
same speed and the effective interaction coupling remains constant along the
flow. In other words, the would-be asymptotic freedom associated to the running
Newton's constant is exactly balanced by the strong coupling of the scalar mode
as the Weyl invariant limit is approached. We conclude that in such model the
UV limit is singular at one loop order, and we argue that a similar phenomenon
can be expected in the full theory, even in higher dimensions.


title: Clifford-Klein forms and a-hyperbolic rank

abstract:
  The porpose of this article is to introduce and investigate properties of a
tool (the a-hyperbolic rank) which enables us to obtain new examples of
homogeneous spaces G/H which admit and do not admit almost compact
Clifford-Klein forms. We achieve this goal by exploring in greater detail the
technique of adjoint orbits developed by Okuda combined with the well-known
conditions of Benoist. We find easy-to-check conditions on G and H expressed
directly in terms of the Satake diagrams of the corresponding Lie algebras, in
cases when G is a real form of a complex Lie group of types A, D or E6. One of
the advantages of this approach is the fact that we don't need to know the
embedding of H into G. Using the a-hyperbolic rank we also show that the
homogeneous space G/H of reductive type of the real form of E6 (of the IV type)
admits compact Clifford-Klein forms if and only if H is compact. Inspired by
the work of Okuda on symmetric spaces G/H we classify all 3-symmetric spaces
admitting almost compact Clifford-Klein forms.


title:
A Novel Approach to Encourage Students Independent Thinking in the
  Physics Laboratory

abstract:
  The objectives of physics laboratory courses include fostering conceptual
understanding and development of several important cognitive, psycho-motor,
attitudinal and affective abilities. In most of the Indian colleges and
universities (and probably at many other places all over the world) the usual
practice of performing a set of experiments, in a cook-book mode, seldom helps
students achieve the objectives of the physics laboratory courses and develop
the abilities and skills required to become a successful experimental
physicist. This paper describes the details of an instructional approach
designed and being followed by the author for a past few years, to encourage
students independent thinking in the physics laboratory. This instructional
approach encourages students active participation, independent thinking and
offers an opportunity to learn how to think scientifically during traditional
physics laboratory courses without major curriculum and content changes. Here,
guided problem solving approach is adopted by combining problem-solving and
guided design modes of instruction. In this approach an experiment is presented
as an experimental problem with well thought procedural instructions. During a
typical laboratory session, first an introductory demonstration is presented to
each group of a few students separately for the first twenty minutes by the
mentors as a prelude to the problem and the remaining laboratory time is made
available for students to independently solve the experimental problem. The
paper also illustrates the approach by describing a familiar experimental
problem and the demonstration on Electromagnetic damping with some details of
the experimental arrangement, which is being used by the author for training of
students and teachers at the introductory university level.


title: Motion of a rough disc in Newtonian aerodynamics

abstract:
  Dynamics of rough discs in a rarified media is considered. We study possible
trajectories of centers of discs. The main result of the paper is the
following: any finite rectifiable curve can be approximated by trajectories of
centers of rough discs, provided the parameters of the system and the rough
structure are specially chosen.


title:
Filters and smoothers for self-exciting Markov modulated counting
  processes

abstract:
  We consider a self-exciting counting process, the parameters of which depend
on a hidden finite-state Markov chain. We derive the optimal filter and
smoother for the hidden chain based on observation of the jump process. This
filter is in closed form and is finite dimensional. We demonstrate the
performance of this filter both with simulated data, and by analysing the
`flash crash' of 6th May 2010 in this framework.


title:
Variants of an explicit kernel-split panel-based Nystr\"om
  discretization scheme for Helmholtz boundary value problems

abstract:
  The incorporation of analytical kernel information is exploited in the
construction of Nystr\"om discretization schemes for integral equations
modeling planar Helmholtz boundary value problems. Splittings of kernels and
matrices, coarse and fine grids, high-order polynomial interpolation, product
integration performed on the fly, and iterative solution are some of the
numerical techniques used to seek rapid and stable convergence of computed
fields in the entire computational domain.


title:
Toward bio-inspired information processing with networks of nano-scale
  switching elements

abstract:
  Unconventional computing explores multi-scale platforms connecting
molecular-scale devices into networks for the development of scalable
neuromorphic architectures, often based on new materials and components with
new functionalities. We review some work investigating the functionalities of
locally connected networks of different types of switching elements as
computational substrates. In particular, we discuss reservoir computing with
networks of nonlinear nanoscale components. In usual neuromorphic paradigms,
the network synaptic weights are adjusted as a result of a training/learning
process. In reservoir computing, the non-linear network acts as a dynamical
system mixing and spreading the input signals over a large state space, and
only a readout layer is trained. We illustrate the most important concepts with
a few examples, featuring memristor networks with time-dependent and history
dependent resistances.


title:
Notes on analytical study of holographic superconductors with Lifshitz
  scaling in external magnetic field

abstract:
  We employ the matching method to analytically investigate the holographic
superconductors with Lifshitz scaling in an external magnetic field. We discuss
systematically the restricted conditions for the matching method and find that
this analytic method is not always powerful to explore the effect of external
magnetic field on the holographic superconductors unless the matching point is
chosen in an appropriate range and the dynamical exponent $z$ satisfies the
relation $z=d-1$ or $z=d-2$. From the analytic treatment, we observe that
Lifshitz scaling can hinder the condensation to be formed, which can be used to
back up the numerical results. Moreover, we study the effect of Lifshitz
scaling on the upper critical magnetic field and reproduce the well-known
relation obtained from Ginzburg-Landau theory.


title: Parity-time-symmetric closed form optical quadrimer waveguides

abstract:
  A closed form PT symmetric quadrimer optical waveguide structure, reminiscent
of the four-state quantum system found in quantum optics, is studied. The beam
dynamics of the structure is studied numerically. The effect of inclusion of
nonlinearity and dispersion is also briefly investigated and discussed


title: Agent-based models for latent liquidity and concave price impact

abstract:
  We revisit the "epsilon-intelligence" model of Toth et al.(2011), that was
proposed as a minimal framework to understand the square-root dependence of the
impact of meta-orders on volume in financial markets. The basic idea is that
most of the daily liquidity is "latent" and furthermore vanishes linearly
around the current price, as a consequence of the diffusion of the price
itself. However, the numerical implementation of Toth et al. was criticised as
being unrealistic, in particular because all the "intelligence" was conferred
to market orders, while limit orders were passive and random. In this work, we
study various alternative specifications of the model, for example allowing
limit orders to react to the order flow, or changing the execution protocols.
By and large, our study lends strong support to the idea that the square-root
impact law is a very generic and robust property that requires very few
ingredients to be valid. We also show that the transition from super-diffusion
to sub-diffusion reported in Toth et al. is in fact a cross-over, but that the
original model can be slightly altered in order to give rise to a genuine phase
transition, which is of interest on its own. We finally propose a general
theoretical framework to understand how a non-linear impact may appear even in
the limit where the bias in the order flow is vanishingly small.


title: Basic loci in Shimura varieties of Coxeter type

abstract:
  This paper is a contribution to the general problem of giving an explicit
description of the basic locus in the reduction modulo $p$ of Shimura
varieties. Motivated by \cite{Vollaard-Wedhorn} and
\cite{Rapoport-Terstiege-Wilson}, we classify the cases where the basic locus
is (in a natural way) the union of classical Deligne-Lusztig sets associated to
Coxeter elements. We show that if this is satisfied, then the Newton strata and
Ekedahl-Oort strata have many nice properties.


title:
Inspection and Test Process Integration Based on Explicit Test
  Prioritization Strategies

abstract:
  Today's software quality assurance techniques are often applied in isolation.
Consequently, synergies resulting from systematically integrating different
quality assurance activities are often not exploited. Such combinations promise
benefits, such as a reduction in quality assurance effort or higher defect
detection rates. The integration of inspection and testing, for instance, can
be used to guide testing activities. For example, testing activities can be
focused on defect-prone parts based upon inspection results. Existing
approaches for predicting defect-prone parts do not make systematic use of the
results from inspections. This article gives an overview of an integrated
inspection and testing approach, and presents a preliminary case study aiming
at verifying a study design for evaluating the approach. First results from
this preliminary case study indicate that synergies resulting from the
integration of inspection and testing might exist, and show a trend that
testing activities could be guided based on inspection results.


title: Magnetic catalysis in flavored ABJM

abstract:
  We study the magnetic catalysis of chiral symmetry breaking in the ABJM
Chern-Simons matter theory with unquenched flavors in the Veneziano limit. We
consider a magnetized D6-brane probe in the background of a flavored black hole
which includes the backreaction of massless smeared flavors in the ABJM
geometry. We find a holographic realization for the running of the quark mass
due to the dynamical flavors. We compute several thermodynamic quantities of
the brane probe and analyze the effects of the dynamical quarks on the
fundamental condensate and on the phase diagram of the model. The dynamical
flavors have an interesting effect on the magnetic catalysis. At zero
temperature and fixed magnetic field, the magnetic catalysis is suppressed for
small bare quark masses whereas it is enhanced for large values of the mass.
When the temperature is non-zero there is a critical magnetic field, above
which the magnetic catalysis takes place. This critical magnetic field
decreases with the number of flavors, which we interpret as an enhancement of
the catalysis.


title:
Determination of $e^{+} e^{-}$ Beam Polarization for Optimal Gauge Boson
  Discovery Limits

abstract:
  Extra neutral gauge bosons suggested by models beyond the standard model can
indirectly show up in $e^{+} e^{-}$ collisions through off-resonance deviations
of various physical observables from the corresponding standard model values.
We considered leptonic observables and studied the dependence of the deviations
on the polarizations of the positron and electron beams. We showed that, for a
given model, the magnitude of the deviation of a given observable can attain
its maximum value if the polarizations of the positron and electron beams are
properly chosen. We determined, for a given model, a single set of beam
polarization so that if this set is employed in measuring all considered
observables, it produces the highest extra gauge boson discovery limits.


title: On a nonsymmetric Ornstein-Uhlenbeck semigroup and its generator

abstract:
  If we add a simple rotation term to both the Ornstein-Uhlenbeck semigroup and
the definition of the H-derivative, then analogue to the classical Malliavin
calculus on the real Wiener space [I. Shigekawa, Stochastic analysis, 2004], we
get a normal but nonsymmetric Ornstein-Uhlenbeck operator $L$ on the complex
Wiener space. The eigenfunctions of the operator $L$ are given. In addition,
the hypercontractivity for the nonsymmetric Ornstein-Uhlenbeck semigroup is
shown.


title:
Flavored pions and kaons at next-to-leading order in mixed-action
  staggered chiral perturbation theory

abstract:
  Different versions of improved staggered fermions can be used as valence
quarks to reduce discretization effects in lattice QCD calculations while
increasing statistics on existing staggered gauge ensembles. Such mixed-action
simulations can be used to improve determinations of light quark masses,
Gasser-Leutwyler couplings, decay constants, and other parameters relevant to
particle phenomenology. We recall the generalization of ordinary, unmixed
staggered chiral perturbation theory required to describe data from lattice
calculations with a mixed action such as with HYP staggered valence quarks and
asqtad sea quarks. We calculate the next-to-leading order loop diagrams
contributing to the masses and decay constants of the flavored pseudo-Goldstone
bosons of all tastes and here report results for the decay constants and
valence-valence masses.


title:
A study of crossover from 3D ferrimagnetic Bulk $NiCr_{2}O_{4}$ compound
  into 2D spin-glass like nanophase

abstract:
  In this report, the magnetic behaviour of $NiCr_{2}O_{4}$ bulk and
nanoparticle samples under different applied magnetic field has been
investigated extensively. Nanoparticles of $NiCr_{2}O_{4}$ were obtained by
mechanical milling of polycrystalline powder prepared by polyol method. FC-ZFC
measurement of bulk at different applied magnetic field has revealed the
existence of a ferrimagnetic transition around 66K followed by an
antiferromagnetic transition close to 30K. However, its nano counterpart has
shown remarkable change in magnetic properties - a suppression of ferrimagnetic
transition accompanied by strengthening low temperature magnetic phase and
observation of a new transition at 90K ($T_P$), which is weakly magnetic in
nature. The frequency dependent ac susceptibility data of nanoparticle have
been fitted to the well known de Almedia-Thouless equation and a $H^{2/3}$
dependence of the low temperature peak is observed with a resulting zero field
freezing temperature ($T_f^0$) equal to 10.1K. Further, the dynamical behaviour
near freezing temperature has been analysed in terms of critical behaviour and
the obtained fitted parameters values being as $\tau_0$(relaxation time
constant) = $3.6 X 10^{-6}s$, $T_f^0=8.7$K and $z\nu = 11.1$. Moreover,
Vogel-Fulcher law has been used to understand the nature of freezing transition
and the parameter after fitting are obtained as $E_a/k_B = 58.9$K, $\tau_0 =
5.22 \times 10^{-8}$ and $T_0 = 8.03$K. Finally, the spin-glass phase is
concluded. Moreover, in contrast to bulk, the $H^{2/3}$ dependence of freezing
temperature of nanoparticle sample (75h) does support the 2D surface like spin
glass nature.


title: Mean-Field Dynamics of Fermions with Relativistic Dispersion

abstract:
  We extend the derivation of the time-dependent Hartree-Fock equation recently
obtained in [2] to fermions with a relativistic dispersion law. The main new
ingredient is the propagation of semiclassical commutator bounds along the
pseudo-relativistic Hartree-Fock evolution.


title: Electron dynamics in graphene with gate-defined quantum dots

abstract:
  We use numerically exact Chebyshev expansion and kernel polynomial methods to
study transport through circular graphene quantum dots in the framework of a
tight-binding honeycomb lattice model. Our focus lies on the regime where
individual modes of the electrostatically defined dot dominate the charge
carrier dynamics. In particular, we discuss the scattering of an injected Dirac
electron wave packet for a single quantum dot, electron confinement in the dot,
the optical excitation of dot-bound modes, and the propagation of an electronic
excitation along a linear array of dots.


title: Service based hight-speed railway base station arrangement

abstract:
  To provide stable and high data rate wireless access for passengers in the
train, it is necessary to properly deploy base stations along the railway. We
consider this issue from the perspective of service, which is defined as the
integral of the time-varying instantaneous channel capacity. With large-scale
fading assumption, it will be shown that the total service of each base station
is inversely proportional to the velocity of the train. Besides, we find that
if the ratio of the service provided by a base station in its service region to
its total service is given, the base station interval (i.e. the distance
between two adjacent base stations) is a constant regardless of the velocity of
the train. On the other hand, if a certain amount of service is required, the
interval will increase with the velocity of the train. The above results apply
not only to simple curve rails, like line rail and arc rail, but also to any
irregular curve rail, provided that the train is travelling at a constant
velocity. Furthermore, the new developed results are applied to analyze the
on-off transmission strategy of base stations.


title: Exponential inequalities for martingales with applications

abstract:
  The paper is devoted to establishing some general exponential inequalities
for supermartingales. The inequalities improve or generalize many exponential
inequalities of Bennett, Freedman, de la Pe\~{n}a, Pinelis and van de Geer.
Moreover, our concentration inequalities also improve some known inequalities
for sums of independent random variables. Applications associated with linear
regressions, autoregressive processes and branching processes are provided. In
particular, an interesting application of {de la Pe\~{n}a's} inequality to
self-normalized deviations is also provided.


title: Hidden-charm decays of $X(3915)$ and $Z(3930)$ as the P-wave charmonia

abstract:
  In this work, we investigate the $X(3915)$ and $Z(3930)$ decays into
$J/\psi\omega$ with the $\chi_{c0}^\prime(2P)$ and $\chi_{c2}^\prime (2P)$
assignments to $X(3915)$ and $Z(3930)$, respectively. The results show that the
decay width of $Z(3930)\to J/\psi\omega$ is at least one order smaller than
that of $X(3915)\to J/\psi\omega$. This observation explains why only one
structure $X(3915)$ has been observed in the $J/\psi\omega$ invariant mass
spectrum for the process $\gamma\gamma\to J/\psi\omega $.


title: Channel Service Based High Speed Railway Base Station Arrangement

abstract:
  With the rapid development of high-speed railways, demands on high mobility
wireless communication increase greatly. To provide stable and high data rate
wireless access for users in the train, it is necessary to properly deploy base
stations along the railway. In this paper, we consider this issue from the
perspective of channel service which is defined as the integral of the
time-varying instantaneous channel capacity. It will show that the total
service quantity of each base station is a constant. In order to keep high
service efficiency of the railway communication system with multiple base
stations along the railway, we need to use the time division to schedule the
multiple stations and allow one base station to work when the train is running
close to it. In this way, we find a fact that if the ratio of the service
quantity provided by each station to its total service quantity is given, the
base station interval(i.e. the distance between two adjacent base stations) is
a constant, regardless of the speed of the train. On the other hand, interval
between two neighboring base stations will increase with the speed of the
train. Furthermore, using the concept of channel service, we also analyze the
transmission strategy of base stations.


title: Thermoelectric effects in molecular quantum dots with contacts

abstract:
  We consider the steady-state thermoelectric transport through a vibrating
molecular quantum dot that is contacted to macroscopic leads. For moderate
electron-phonon interaction strength and comparable electronic and phononic
timescales, we investigate the impact of the formation of a local polaron on
the thermoelectric properties of the junction. We apply a variational
Lang-Firsov transformation and solve the equations of motion in the
Kadanoff-Baym formalism up to second order in the dot-lead coupling parameter.
We calculate the thermoelectric current and voltage for finite temperature
differences in the resonant and inelastic tunneling regimes. For a near
resonant dot level, the formation of a local polaron can boost the
thermoelectric effect because of the Franck-Condon blockade. The line shape of
the thermoelectric voltage signal becomes asymmetrical due to the varying
polaronic character of the dot state and in the nonlinear transport regime,
vibrational signatures arise.


title:
Propagation of a binary signal along a chain of triangular graphane
  nanoclusters

abstract:
  In this paper, we study the dynamic properties of a linear array of graphane
triangular molecules that transmit a binary signal. The electronic properties
of nanoclusters are studied using calculations based on first principles, with
hybrid potentials. The dynamic of the system is studied by solving the
time-dependent Schrodinger equation. Our results show that a linear array of
these nanostructures under clock operations, allow to transmit binary
information, with a efficiency close to unity.


title:
Infinitely Improvable Upper Bound Estimates for Acoustical Polaron
  Ground State Energy

abstract:
  It was shown that an infinite convergent sequence of improving non-increasing
upper bounds to the ground state energy of a slow-moving acoustical polaron can
be obtained by means of generalized variational method. The proposed approach
is especially well-suited for massive analytical and numerical computations of
experimentally measurable properties of realistic polarons and can be
elaborated even further, without major alterations, to allow for treatment of
various polaron-type models.

categories: math-ph cond-mat.stat-mech math.MP quant-ph


title: Rigidity Results for Hermitian-Einstein manifolds

abstract:
  A differential operator introduced by A. Gray on the unit sphere bundle of a
K\"ahler-Einstein manifold is studied. A lower bound for the first eigenvalue
of the Laplacian for the Sasaki metric on the unit sphere bundle of a
K\"ahler-Einstein manifold is derived. Some rigidity theorems classifying
complex space forms amongst compact Hermitian surfaces and the product of two
projective lines amongst all K\"ahler-Einstein surfaces are then derived.


title: Thwarting Selfish Behavior in 802.11 WLANs

abstract:
  The 802.11e standard enables user configuration of several MAC parameters,
making WLANs vulnerable to users that selfishly configure these parameters to
gain throughput. In this paper we propose a novel distributed algorithm to
thwart such selfish behavior. The key idea of the algorithm is for honest
stations to react, upon detecting a selfish station, by using a more aggressive
configuration that penalizes this station. We show that the proposed algorithm
guarantees global stability while providing good response times. By conducting
a game theoretic analysis of the algorithm based on repeated games, we also
show its effectiveness against selfish stations. Simulation results confirm
that the proposed algorithm optimizes throughput performance while discouraging
selfish behavior. We also present an experimental prototype of the proposed
algorithm demonstrating that it can be implemented on commodity hardware.


title: Adjusting chaotic indicators to curved spacetimes

abstract:
  In this work, chaotic indicators, which have been established in the
framework of classical mechanics, are reformulated in the framework of general
relativity in such a way that they are invariant under coordinate
transformation. For achieving this, the prescription for reformulating mLCE
given by [Y. Sota, S. Suzuki, and K.-I. Maeda, Classical Quantum Gravity 13,
1241 (1996)] is adopted. Thus, the geodesic deviation vector approach is
applied, and the proper time is utilized as measure of time. Following the
aforementioned prescription, the chaotic indicators FLI, MEGNO, GALI, and APLE
are reformulated. In fact, FLI has been reformulated by adapting other
prescriptions in the past, but not by adapting the Sota et al. one. By using
one of these previous reformulations of FLI, an approximative expression giving
MEGNO as function of FLI has been applied on non-integrable curved spacetimes
in a recent work. In the present work the reformulation of MEGNO is provided by
adjusting the definition of the indicator to the Sota et al. prescription.
GALI, and APLE are reformulated in the framework of general relativity for the
first time. All the reformulated indicators by the Sota et al. prescription are
tested and compared for their efficiency to discern order from chaos.


title:
Superconvergence for Neumann boundary control problems governed by
  semilinear elliptic equations

abstract:
  This paper is concerned with the discretization error analysis of semilinear
Neumann boundary control problems in polygonal domains with pointwise
inequality constraints on the control. The approximations of the control are
piecewise constant functions. The state and adjoint state are discretized by
piecewise linear finite elements. In a postprocessing step approximations of
locally optimal controls of the continuous optimal control problem are
constructed by the projection of the respective discrete adjoint state.
Although the quality of the approximations is in general affected by corner
singularities a convergence order of $h^2|\ln h|^{3/2}$ is proven for domains
with interior angles smaller than $2\pi/3$ using quasi-uniform meshes. For
larger interior angles mesh grading techniques are used to get the same order
of convergence.


title: Target-skyrmions and skyrmion clusters in nanowires of chiral magnets

abstract:
  In bulk non-centrosymmetric magnets the chiral Dzyaloshinskii-Moriya exchange
stabilizes tubular skyrmions with a reversed magnetization in their centers.
While the double-twist is favorable in the center of a skyrmion, it gives rise
to an excess of the energy density at the outskirt. Therefore, magnetic
anisotropies are required to make skyrmions more favorable than the conical
spiral state in bulk materials. Using Monte Carlo simulations, we show that in
magnetic nanowires unusual skyrmions with a doubly twisted core and a number of
concentric helicoidal undulations (target-skyrmions) are thermodynamically
stable even in absence of single-ion anisotropies. Such skyrmions are free of
magnetic charges and, since the angle describing the direction of magnetization
at the surface depends on the radius of the nanowire and an applied magnetic
field, they carry a non-integer skyrmion charge s > 1. This state competes with
clusters of spatially separated s=1 skyrmions. For very small radii, the
target-skyrmion transforms into a skyrmion with s < 1, that resembles the
vortex-like state stabilized by surface-induced anisotropies.


title: Cosmological Constant in the Imaginary-Time Field Theory

abstract:
  The origins of the cosmological constant are discussed from the perspective
of the imaginary-time field theory. The concept of the thermal time, which is
related to the Tolman-Ehrehfest relation, and the conformal invariance of the
actions are applied to account for the relation between the scale factor of the
FRW metric and the temperature of the vacuum. Finite values of the cosmological
constant from the DeWitt-Schwinger representation and the Casimir effect with a
large separation between two plates are derived. The induced energy density is
found to be uniform over the space and independent of the evolution of the
universe, and the equation of state ratio is indeed $w=-1$. From the point of
view presented here, the largest discrepancy of the vacuum energy between the
theoretical and the experimental sides can be conciliated. And the value of the
cosmological constant corresponds to a characteristic temperature of vacuum
determined by the history of the universe.


title:
Compact operators and algebraic $K$-theory for groups which act properly
  and isometrically on Hilbert space

abstract:
  We prove the $K$-theoretic Farrell-Jones conjecture for groups as in the
title with coefficient rings and $C^*$-algebras which are stable with respect
to compact operators. We use this and Higson-Kasparov's result that the
Baum-Connes conjecture with coefficients holds for such groups, to show that if
$G$ is as in the title then the algebraic and the $C^*$-crossed products of $G$
with a stable $C^*$-algebra have the same $K$-theory.


title:
Heat Kernels on the AdS(2) cone and Logarithmic Corrections to Extremal
  Black Hole Entropy

abstract:
  We develop new techniques to efficiently evaluate heat kernel coefficients
for the Laplacian in the short-time expansion on spheres and hyperboloids with
conical singularities. We then apply these techniques to explicitly compute the
logarithmic contribution to black hole entropy from an N=4 vector multiplet
about a Z(N) orbifold of the near-horizon geometry of quarter--BPS black holes
in N=4 supergravity. We find that this vanishes, matching perfectly with the
prediction from the microstate counting. We also discuss possible
generalisations of our heat kernel results to higher-spin fields over Z(N)
orbifolds of higher-dimensional spheres and hyperboloids.


title: A histories perspective on characterising quantum non-locality

abstract:
  We introduce a framework for studying non-locality and contextuality inspired
by the path integral formulation of quantum theory. We prove that the existence
of a strongly positive joint quantum measure -- the quantum analogue of a joint
probability measure -- on a set of experimental probabilities implies the
Navascues-Pironio-Acin (NPA) condition $Q^1$ and is implied by the stronger NPA
condition $Q^{1+AB}$. A related condition is shown to be equivalent to
$Q^{1+AB}$.


title:
On the analyticity of periodic gravity water waves with integrable
  vorticity function

abstract:
  We prove that the streamlines and the profile of periodic gravity water waves
traveling over a flat bed with wavespeed which exceeds the horizontal velocity
of all fluid particles are real-analytic graphs if the vorticity function is
merely integrable.


title: Universal physics of three bosons with isospin

abstract:
  We show that there exist two types of universal phenomena for three-boson
systems with isospin degrees of freedom. In the isospin symmetric limit, there
is only one universal three-boson bound state with the total isospin one, whose
binding energy is proportional to that of the two-boson bound state. With large
isospin symmetry breaking, the standard Efimov states of three identical bosons
appear at low energies. Both phenomena can be realized by three pions with the
pion mass appropriately tuned in lattice QCD simulations, or by spin-one bosons
in cold atom experiments. Implication to the in-medium softening of multi-pion
states is also discussed.

categories: hep-ph cond-mat.quant-gas hep-lat nucl-th


title:
Normal Form and Nekhoroshev stability for nearly-integrable Hamiltonian
  systems with unconditionally slow aperiodic time dependence

abstract:
  The aim of this paper is to extend the results of Giorgilli and Zehnder for
aperiodic time dependent systems to a case of general nearly-integrable convex
analytic Hamiltonians. The existence of a normal form and then a stability
result are shown in the case of a slow aperiodic time dependence that, under
some smallness conditions, is independent on the size of the perturbation.


title: A generalization of weight polynomials to matroids

abstract:
  Generalizing polynomials previously studied in the context of linear codes,
we define weight polynomials and an enumerator for a matroid $M$. Our main
result is that these polynomials are determined by Betti numbers associated
with graded minimal free resolutions of the Stanley-Reisner ideals of $M$ and
so-called elongations of $M$. Generalizing Greene's theorem from coding theory,
we show that the enumerator of a matroid is equivalent to its Tutte polynomial.


title:
Combinatorics of simple marked mesh patterns in 132-avoiding
  permutations

abstract:
  We present some combinatorial interpretations for coefficients appearing in
series partitioning the permutations avoiding 132 along marked mesh patterns.
We identify for patterns in which only one parameter is non zero the
combinatorial family in bijection with 132-avoiding permutations and also
preserving the statistic counted by the marked mesh pattern.


title:
Inferring tree causal models of cancer progression with probability
  raising

abstract:
  Existing techniques to reconstruct tree models of progression for
accumulative processes, such as cancer, seek to estimate causation by combining
correlation and a frequentist notion of temporal priority. In this paper, we
define a novel theoretical framework called CAPRESE (CAncer PRogression
Extraction with Single Edges) to reconstruct such models based on the notion of
probabilistic causation defined by Suppes. We consider a general reconstruction
setting complicated by the presence of noise in the data due to biological
variation, as well as experimental or measurement errors. To improve tolerance
to noise we define and use a shrinkage-like estimator. We prove the correctness
of our algorithm by showing asymptotic convergence to the correct tree under
mild constraints on the level of noise. Moreover, on synthetic data, we show
that our approach outperforms the state-of-the-art, that it is efficient even
with a relatively small number of samples and that its performance quickly
converges to its asymptote as the number of samples increases. For real cancer
datasets obtained with different technologies, we highlight biologically
significant differences in the progressions inferred with respect to other
competing techniques and we also show how to validate conjectured biological
relations with progression models.


title: Braneworld solutions for F(R) models with non-constant curvature

abstract:
  This work deal with braneworld scenarios with generalized gravity. We
investigate models where the potential of the scalar field is polynomial or
nonpolynomial. We obtain exact and approximated solutions for the scalar field,
warp factor and energy density, in the complex scenario with no restriction on
the scalar curvature. In particular, we describe the case where the brane may
split, engendering internal structure, with the splitting caused by the same
parameter that controls deviation from standard gravity.


title:
The coupled-cluster approach to quantum many-body problem in a
  three-Hilbert-space reinterpretation

abstract:
  The quantum many-body bound-state problem in its computationally successful
coupled cluster method (CCM) representation is reconsidered. In conventional
practice one factorizes the ground-state wave functions $|\Psi\rangle= e^S
|\Phi\rangle$ which live in the "physical" Hilbert space ${\cal H}^{(P)}$ using
an elementary ansatz for $|\Phi\rangle$ plus a formal expansion of $S$ in an
operator basis of multi-configurational creation operators. In our paper a
reinterpretation of the method is proposed. Using parallels between the CCM and
the so called quasi-Hermitian, alias three-Hilbert-space (THS), quantum
mechanics, the CCM transition from the known microscopic Hamiltonian (denoted
by usual symbol $H$), which is self-adjoint in ${\cal H}^{(P)}$, to its
effective lower-case isospectral avatar $\hat{h}=e^{-S} H e^S$, is assigned a
THS interpretation. In the opposite direction, a THS-prescribed, non-CCM,
innovative reinstallation of Hermiticity is shown to be possible for the CCM
effective Hamiltonian $\hat{h}$, which only appears manifestly non-Hermitian in
its own ("friendly") Hilbert space ${\cal H}^{(F)}$. This goal is achieved via
an ad hoc amendment of the inner product in ${\cal H}^{(F)}$, thereby yielding
the third ("standard") Hilbert space ${\cal H}^{(S)}$. Due to the resulting
exact unitary equivalence between the first and third spaces, ${\cal
H}^{(P)}\sim {\cal H}^{(S)}$, the indistinguishability of predictions
calculated in these alternative physical frameworks is guaranteed.

categories: quant-ph cond-mat.str-el math-ph math.MP nucl-th


title: Color ordering in QCD

abstract:
  We derive color decompositions of arbitrary tree and one-loop QCD amplitudes
into color ordered objects called primitive amplitudes. Furthermore, we derive
general fermion flip and reversion identities spanning the null space among the
primitive amplitudes and use them to prove that all color ordered tree
amplitudes of massless QCD can be written as linear combinations of color
ordered tree amplitudes of $\mathcal{N}=4$ super Yang-Mills theory.


title:
Photoassociation of ultracold LiRb* molecules: observation of high
  efficiency and unitarity-limited rate saturation

abstract:
  We report the production of ultracold heteronuclear 7Li85Rb molecules in
excited electronic states by photoassociation (PA) of ultracold 7Li and 85Rb
atoms. PA is performed in a dual-species 7Li-85Rb magneto-optical trap (MOT)
and the PA resonances are detected using trap loss spectroscopy. We identify
several strong PA resonances below the Li (2s 2S1/2) + Rb (5p 2P3/2) asymptote
and experimentally determine the long range C6 dispersion coefficients. We find
a molecule formation rate (P_LiRb) of 3.5x10^7 s^-1 and a PA rate coefficient
(K_PA) of 1.3x10^-10 cm^3/s, the highest among heteronuclear bi-alkali
molecules. At large PA laser intensity, we observe the saturation of the PA
rate coefficient (K_PA) close to the theoretical value at the unitarity limit.


title: Survival of classical and quantum particles in the presence of traps

abstract:
  We present a detailed comparison of the motion of a classical and of a
quantum particle in the presence of trapping sites, within the framework of
continuous-time classical and quantum random walk. The main emphasis is on the
qualitative differences in the temporal behavior of the survival probabilities
of both kinds of particles. As a general rule, static traps are far less
efficient to absorb quantum particles than classical ones. Several lattice
geometries are successively considered: an infinite chain with a single trap, a
finite ring with a single trap, a finite ring with several traps, and an
infinite chain and a higher-dimensional lattice with a random distribution of
traps with a given density. For the latter disordered systems, the classical
and the quantum survival probabilities obey a stretched exponential asymptotic
decay, albeit with different exponents. These results confirm earlier
predictions, and the corresponding amplitudes are evaluated. In the
one-dimensional geometry of the infinite chain, we obtain a full analytical
prediction for the amplitude of the quantum problem, including its dependence
on the trap density and strength.


title: Response to noise of a spin transfer vortex based nano-oscillator

abstract:
  We investigate experimentally and analytically the impact of thermal noise on
the sustained gyrotropic mode of vortex magnetization in spin transfer
nano-oscillators and its consequence on the linewidth broadening due to the
different nonlinear contributions. Performing some time domain measurements, we
are able to extract separately the phase noise and the amplitude noise at room
temperature for several values of dc current and perpendicular field. For a
theoretical description of the experiments, we extend the general model of
nonlinear auto-oscillators to the case of vortex core dynamics and provide some
analytical expressions of the response-to-noise of the system as the coupling
coefficient between the phase and the amplitude of the vortex core dynamics due
to the nonlinearities. From the analysis of our experimental results, we
demonstrate the major role of the amplitude-to-phase noise conversion on the
linewidth broadening, and propose some solutions to improve the spectral
coherence of vortex based spin transfer nano-oscillators.


title:
A McKean optimal transportation perspective on Feynman-Kac formulae with
  application to data assimilation

abstract:
  Data assimilation is the task of combining mathematical models with
observational data. From a mathematical perspective data assimilation leads to
Bayesian inference problems which can be formulated in terms of Feynman-Kac
formulae. In this paper we focus on the sequential nature of many data
assimilation problems and their numerical implementation in form of Monte Carlo
methods. We demonstrate how sequential data assimilation can be interpreted as
time-dependent Markov processes, which is often referred to as the McKean
approach to Feynman-Kac formulae. It is shown that the McKean approach has very
natural links to coupling of random variables and optimal transportation. This
link allows one to propose novel sequential Monte Carlo methods/particle
filters. In combination with localization these novel algorithms have the
potential of beating the curse of dimensionality, which has prevented particle
filters from being applied to spatially extended systems.


title: Long-Distance Quantum Transport Dynamics in Macromolecules

abstract:
  Using renormalization group methods, we develop a rigorous coarse-grained
representation of the dissipative dynamics of quantum excitations propagating
inside open macromolecular systems. We show that, at very low spatial
resolution, this quantum transport theory reduces to a modified Brownian
process, in which quantum delocalization effects are accounted for by means of
an effective term in the Onsager-Machlup functional. Using this formulation, we
derive a simple analytic solution for the time-dependent probability of
observing the quantum excitation at a given point in the macromolecule. This
formula can be used to predict the migration of natural or charged quantum
excitations in a variety of molecular systems including biological and organic
polymers, organic crystalline transistors or photosynthetic complexes. For
illustration purpose, we apply this method to investigate intelastic electornic
hole transport in a long homo-DNA chain.


title: Probing zero-modes of defect in Kitaev quantum wire

abstract:
  The Kitaev quantum wire (KQW) model with open boundary possesses two Majorana
edge modes. When the local chemical potential on a defect site is much higher
than that on other sites and than the hopping energy, the electron hopping is
blocked at this site. We show that the existence of such a defect on a closed
KQW also gives rise to two low-energy modes, which can simulate the edge modes.
The energies of the defect modes vanish to zero as the local chemical potential
of the defect increase to infinity. We develop a quantum Langevin equation to
study the transport of KQW for both open and closed cases. We find that when
the lead is contacted with the site beside the defect, we can observe two
splitted peaks around the zero-bias voltage in the differential conductance
spectrum. While if the lead is contacted with the bulk of the quantum wire far
from the the defect or the open edges, we cannot observe any zero-bias peak.


title:
Scanning Gate Imaging of quantum point contacts and the origin of the
  0.7 Anomaly

abstract:
  The origin of the anomalous transport feature appearing at conductance G
\approx 0.7 x (2e2/h) in quasi-1D ballistic devices - the so-called 0.7 anomaly
- represents a long standing puzzle. Several mechanisms were proposed to
explain it, but a general consensus has not been achieved. Proposed
explanations are based on quantum interference, Kondo effect, Wigner
crystallization, and more. A key open issue is whether point defects that can
occur in these low-dimensional devices are the physical cause behind this
conductance anomaly. Here we adopt a scanning gate microscopy technique to map
individual impurity positions in several quasi-1D constrictions and correlate
these with conductance characteristics. Our data demonstrate that the 0.7
anomaly can be observed irrespective of the presence of localized defects, and
we conclude that the 0.7 anomaly is a fundamental property of low-dimensional
systems.


title: Tripartite Blind Quantum Computation

abstract:
  This paper proposes a model of tripartite blind quantum computation (TBQC),
in which three independent participants hold different resources and accomplish
a computational task through cooperation. The three participants are called
C,S,T separately, where C needs to compute on his private data, and T has the
required quantum algorithm, and S provides sufficient quantum computational
resources. Then two concrete TBQC protocols are constructed. The first protocol
is designed based on Broadbent-Fitzsimons-Kashefi protocol, and it cannot
prevent from collusive attack of two participants. Then based on universal
quantum circuit, we present the second protocol which can prevent from
collusive attack. In the latter protocol, for each appearance of $R$-gate in
the circuit, one call to a classical AND-BOX is required for privacy.


title:
Spin-wave excitation and propagation in microstructured waveguides of
  yttrium iron garnet (YIG)/Pt bilayers

abstract:
  We present an experimental study of spin-wave excitation and propagation in
microstructured waveguides patterned from a 100 nm thick yttrium iron garnet
(YIG)/platinum (Pt) bilayer. The life time of the spin waves is found to be
more than an order of magnitude higher than in comparably sized metallic
structures despite the fact that the Pt capping enhances the Gilbert damping.
Utilizing microfocus Brillouin light scattering spectroscopy, we reveal the
spin-wave mode structure for different excitation frequencies. An exponential
spin-wave amplitude decay length of 31 {\mu}m is observed which is a
significant step towards low damping, insulator based micro-magnonics.


title: Well-rounded sublattices of planar lattices

abstract:
  A lattice in Euclidean $d$-space is called well-rounded if it contains $d$
linearly independent vectors of minimal length. This class of lattices is
important for various questions, including sphere packing or homology
computations. The task of enumerating well-rounded sublattices of a given
lattice is of interest already in dimension 2, and has recently been treated by
several authors. In this paper, we analyse the question more closely in the
spirit of earlier work on similar sublattices and coincidence site sublattices.
Combining explicit geometric considerations with known techniques from the
theory of Dirichlet series, we arrive, after a considerable amount of
computation, at asymptotic results on the number of well-rounded sublattices up
to a given index in any planar lattice. For the two most symmetric lattices,
the square and the hexagonal lattice, we present detailed results.


title: Toward a geometric analogue of Dirichlet's unit theorem

abstract:
  In this note, we propose a geometric analogue of Dirichlet's unit theorem on
arithmetic varieties, that is, if X is a normal projective variety over a
finite field and D is a pseudo-effective Q-Cartier divisor on X, does it follow
that D is Q-effective? We also give affirmative answers on an abelian variety
and a projective bundle over a curve.


title: On relative birational geometry and Nagata's compactification

abstract:
  In 2011, the first author introduced (relative) Riemann-Zariski spaces
corresponding to a morphism of schemes and established their basic properties.
In this paper we clarify that theory and extend it to morphisms between
algebraic spaces. As an application, a new proof of Nagata's compactification
theorem for algebraic spaces is obtained.


title:
A parallel repetition theorem for entangled two-player one-round games
  under product distributions

abstract:
  We show a parallel repetition theorem for the entangled value $\omega^*(G)$
of any two-player one-round game $G$ where the questions $(x,y) \in
\mathcal{X}\times\mathcal{Y}$ to Alice and Bob are drawn from a product
distribution on $\mathcal{X}\times\mathcal{Y}$. We show that for the $k$-fold
product $G^k$ of the game $G$ (which represents the game $G$ played in parallel
$k$ times independently),
  $ \omega^*(G^k)
=\left(1-(1-\omega^*(G))^3\right)^{\Omega\left(\frac{k}{\log(|\mathcal{A}|
\cdot |\mathcal{B}|)}\right)} $, where $\mathcal{A}$ and $\mathcal{B}$
represent the sets from which the answers of Alice and Bob are drawn.


title:
Strong plasmon reflection at nanometer-size gaps in monolayer graphene
  on SiC

abstract:
  We employ tip-enhanced infrared near-field microscopy to study the plasmonic
properties of epitaxial quasi-free-standing monolayer graphene on silicon
carbide. The near-field images reveal propagating graphene plasmons, as well as
a strong plasmon reflection at gaps in the graphene layer, which appear at the
steps between the SiC terraces. When the step height is around 1.5 nm, which is
two orders of magnitude smaller than the plasmon wavelength, the reflection
signal reaches 20% of its value at graphene edges, and it approaches 50% for
step heights as small as 5 nm. This intriguing observation is corroborated by
numerical simulations, and explained by the accumulation of a line charge at
the graphene termination. The associated electromagnetic fields at the graphene
termination decay within a few nanometers, thus preventing efficient plasmon
transmission across nanoscale gaps. Our work suggests that plasmon propagation
in graphene-based circuits can be tailored using extremely compact
nanostructures, such as ultra-narrow gaps. It also demonstrates that
tip-enhanced near-field microscopy is a powerful contactless tool to examine
nanoscale defects in graphene.


title: Bias in parametric estimation: reduction and useful side-effects

abstract:
  The bias of an estimator is defined as the difference of its expected value
from the parameter to be estimated, where the expectation is with respect to
the model. Loosely speaking, small bias reflects the desire that if an
experiment is repeated indefinitely then the average of all the resultant
estimates will be close to the parameter value that is estimated. The current
paper is a review of the still-expanding repository of methods that have been
developed to reduce bias in the estimation of parametric models. The review
provides a unifying framework where all those methods are seen as attempts to
approximate the solution of a simple estimating equation. Of particular focus
is the maximum likelihood estimator, which despite being asymptotically
unbiased under the usual regularity conditions, has finite-sample bias that can
result in significant loss of performance of standard inferential procedures.
An informal comparison of the methods is made revealing some useful practical
side-effects in the estimation of popular models in practice including: i)
shrinkage of the estimators in binomial and multinomial regression models that
guarantees finiteness even in cases of data separation where the maximum
likelihood estimator is infinite, and ii) inferential benefits for models that
require the estimation of dispersion or precision parameters.


title:
Clover fermions in the adjoint representation and simulations of
  supersymmetric Yang-Mills theory

abstract:
  Clover improvement is the standard choice for lattice simulations of QCD,
when the lattice artefacts coming from Wilson fermions have to be reduced.
However, the clover improvement is not limited to QCD, but can be applied to a
wider range of theories with fermions in higher representations of the gauge
group SU(N), like the adjoint fermions required by supersymmetry or by
technicolor theories. We present the calculation of the clover coefficient up
to one loop order with standard perturbation theory for these models.
Applications of clover fermions to supersymmetric Yang-Mills theory are also
discussed.


title:
On the effective potential, Horava-Lifshitz-like theories and finite
  temperature

abstract:
  We calculate the one-loop effective potential at finite temperature for the
Horava-Lifshitz-like QED and Yukawa-like theories for arbitrary values of the
critical exponent and the space-time dimension. Additional remarks on the zero
temperature situation are also presented.


title: Theory of rare charm decays

abstract:
  Recent disagreement between experimental measurments of CP violating
asymmetry in D -> K+ K- and D ->pi+ pi- and theoretical Standard model
expectation motivated many studies within the Standard model and beyond. Rare
charm decays offer new probe of possible signals beyond Standard model. CP
conserving and CP violating contributions within the Standard model and beyond
are reviewed for inclusive c -> u gamma and c ->u l+ l- and exclusive D ->V
gamma, D ->P+ P-, D+ -> pi+ l+ l-, D -> l+ l- decays.


title:
Quantifying the loss of information in source attribution problems using
  the adjoint method in global models of atmospheric chemical transport

abstract:
  It is of crucial importance to be able to identify the location of
atmospheric pollution sources in our planet. Global models of atmospheric
transport in combination with diverse Earth observing systems are a natural
choice to achieve this goal. It is shown that the ability to successfully
reconstruct the location and magnitude of an instantaneous source in global
chemical transport models (CTMs) decreases rapidly as a function of the time
interval between the pollution release and the observation time. A simple way
to quantitatively characterize this phenomenon is proposed based on the
effective -undesired- numerical diffusion present in current Eulerian CTMs and
verified using idealized numerical experiments. The approach presented consists
of using the adjoint-based optimization method in a state-of-the-art CTM,
GEOS-Chem, to reconstruct the location and magnitude of a realistic pollution
plume for multiple time scales. The findings obtained from these numerical
experiments suggest a time scale of 2 days after which the accuracy of the
adjoint-based optimization methodology is compromised considerably in current
global CTMs. In conjunction with the mean atmospheric velocity, the
aforementioned time scale leads to an estimate of a length scale of about
1700km, downwind from the source, beyond which measurements, in conjunction
with current global CTMs, may not be successfully utilized to reconstruct
continuous-in-time sources. The approach presented here can be utilized to
characterize the capabilities and limitations of adjoint-based optimization
inversions in other regional and global Eulerian CTMs.


title:
N-point Statistics of Large-Scale Structure in the Zel'dovich
  Approximation

abstract:
  Motivated by the results presented in a companion paper, here we give a
simple analytical expression for the matter n-point functions in the Zel'dovich
approximation (ZA) both in real and in redshift space (including the angular
case). We present numerical results for the 2-dimensional redshift-space
correlation function, as well as for the equilateral configuration for the
real-space 3-point function. We compare those to the tree-level results. Our
analysis is easily extendable to include Lagrangian bias, as well as
higher-order perturbative corrections to the ZA. The results should be
especially useful for modelling probes of large-scale structure in the linear
regime, such as the Baryon Acoustic Oscillations. We make the numerical code
used in this paper freely available.


title: Local-to-global extensions of D-modules in positive characteristic

abstract:
  In "On the calculation of some differential Galois groups" (Invent. Math. 87
(1987), no. 1), Katz defines the notion of a special flat connection on the
complex affine line minus the origin, and he shows that the functor which
restricts a flat connection to the punctured disc around the point at infinity
gives rise to an equivalence between the category of special flat connections
and the category of differential modules on the field of Laurent series over
the complex numbers.
  In this article, we prove the corresponding statement over an algebraically
closed field k of positive characteristic. The role of flat connections is
played by vector bundles carrying an action of the (full) ring of differential
operators. We call such objects stratified bundles. The formal local variant on
the field of Laurent series k((t)) is called iterated differential module. We
define the notion of a special stratified bundle on the affine line over k
minus the origin, and show that restriction to the punctured disc around the
point at infinity induces an equivalence between the category of special
stratified bundles and iterated differential modules. This extends one of the
main results of "Local-to-global extensions of representations of fundamental
groups" (N. Katz, Ann. Inst. Fourier (Grenoble) 36 (1986), no. 4), and has
several interesting consequences which extend well-known statements about
\'etale fundamental groups to higher dimensional fundamental groups.


title: A counterexample to 'Algebraic function fields with small class number'

abstract:
  I give a counter example of function field over GF(2) of genus 4 with class
number one. This result contradicts a previous result in [2], Section 2 so that
proof is wrong.


title: Effective field theory from modified gravity with massive modes

abstract:
  Massive gravitational modes in effective field theories can be recovered by
extending General Relativity and taking into account generic functions of the
curvature invariants, not necessarily linear in the Ricci scalar R. In
particular, adopting the minimal extension of f(R) gravity, an effective field
theory with massive modes is straightforwardly recovered. This approach allows
to evade shortcomings like ghosts and discontinuities if a suitable choice of
expansion parameters is performed.


title: Exceptional points in open and PT symmetric systems

abstract:
  Exceptional points (EPs) determine the dynamics of open quantum systems and
cause also PT symmetry breaking in PT symmetric systems. From a mathematical
point of view, this is caused by the fact that the phases of the wavefunctions
(eigenfunctions of a non-Hermitian Hamiltonian) relative to one another are not
rigid when an EP is approached. The system is therefore able to align with the
environment to which it is coupled and, consequently, rigorous changes of the
system properties may occur. We compare analytically as well as numerically the
eigenvalues and eigenfunctions of a $2\times 2$ matrix that is characteristic
of either open quantum systems at high level density or of PT symmetric optical
lattices. In both cases, the results show clearly the influence of the
environment onto the system in the neighborhood of EPs. Although the systems
are very different from one another, the eigenvalues and eigenfunctions
indicate the same characteristic features.


title:
Generation and stabilization of a three-qubit entangled W state in
  circuit QED via quantum feedback control

abstract:
  Circuit cavity quantum electrodynamics (QED) is proving to be a powerful
platform to implement quantum feedback control schemes due to the ability to
control superconducting qubits and microwaves in a circuit. Here, we present a
simple and promising quantum feedback control scheme for deterministic
generation and stabilization of a three-qubit $W$ state in the superconducting
circuit QED system. The control scheme is based on continuous joint Zeno
measurements of multiple qubits in a dispersive regime, which enables us not
only to infer the state of the qubits for further information processing but
also to create and stabilize the target $W$ state through adaptive quantum
feedback control. We simulate the dynamics of the proposed quantum feedback
control scheme using the quantum trajectory approach with an effective
stochastic maser equation obtained by a polaron-type transformation method and
demonstrate that in the presence of moderate environmental decoherence, the
average state fidelity higher than $0.9$ can be achieved and maintained for a
considerable long time (much longer than the single-qubit decoherence time).
This control scheme is also shown to be robust against measurement inefficiency
and individual qubit decay rate differences. Finally, the comparison of the
polaron-type transformation method to the commonly used adiabatic elimination
method to eliminate the cavity mode is presented.


title:
A non-grey analytical model for irradiated atmospheres. II: Analytical
  vs. numerical solutions

abstract:
  The recent discovery and characterization of the diversity of the atmospheres
of exoplanets and brown dwarfs calls for the development of fast and accurate
analytical models. We quantify the accuracy of the analytical solution derived
in paper I for an irradiated, non-grey atmosphere by comparing it to a
state-of-the-art radiative transfer model. Then, using a grid of numerical
models, we calibrate the different coefficients of our analytical model for
irradiated solar-composition atmospheres of giant exoplanets and brown dwarfs.
  We show that the so-called Eddington approximation used to solve the angular
dependency of the radiation field leads to relative errors of up to 5% on the
temperature profile. We show that for realistic non-grey planetary atmospheres,
the presence of a convective zone that extends to optical depths smaller than
unity can lead to changes in the radiative temperature profile on the order of
20% or more. When the convective zone is located at deeper levels (such as for
strongly irradiated hot Jupiters), its effect on the radiative atmosphere is
smaller. We show that the temperature inversion induced by a strong absorber in
the optical, such as TiO or VO is mainly due to non-grey thermal effects
reducing the ability of the upper atmosphere to cool down rather than an
enhanced absorption of the stellar light as previously thought.
  Finally, we provide a functional form for the coefficients of our analytical
model for solar-composition giant exoplanets and brown dwarfs. This leads to
fully analytical pressure-temperature profiles for irradiated atmospheres with
a relative accuracy better than 10% for gravities between 2.5m/s^2 and 250
m/s^2 and effective temperatures between 100 K and 3000 K. This is a great
improvement over the commonly used Eddington boundary condition.


title:
Analysis of regularized inversion of data corrupted by white Gaussian
  noise

abstract:
  Tikhonov regularization is studied in the case of linear pseudodifferential
operator as the forward map and additive white Gaussian noise as the
measurement error. The measurement model for an unknown function $u(x)$ is
\begin{eqnarray*} m(x) = Au(x) + \delta\hspace{.2mm}\varepsilon(x),
\end{eqnarray*} where $\delta>0$ is the noise magnitude. If $\varepsilon$ was
an $L^2$-function, Tikhonov regularization gives an estimate \begin{eqnarray*}
T_\alpha(m) = \text{argmin}_{u\in H^r}\big\{\|A u-m\|_{L^2}^2+
\alpha\|u\|_{H^r}^2 \big\}\end{eqnarray*} for $u$ where $\alpha=\alpha(\delta)$
is the regularization parameter. Here penalization of the Sobolev norm $
\|u\|_{H^r}$ covers the cases of standard Tikhonov regularization ($r=0$) and
first derivative penalty ($r=1$).
  Realizations of white Gaussian noise are almost never in $L^2$, but do belong
to $H^s$ with probability one if $s<0$ is small enough. A modification of
Tikhonov regularization theory is presented, covering the case of white
Gaussian measurement noise. Furthermore, the convergence of regularized
reconstructions to the correct solution as $\delta\rightarrow 0$ is proven in
appropriate function spaces using microlocal analysis. The convergence of the
related finite-dimensional problems to the infinite-dimensional problem is also
analysed.


title: Non-standard Models and the Sociology of Cosmology

abstract:
  I review some theoretical ideas in cosmology different from the standard "Big
Bang": the quasi-steady state model, the plasma cosmology model,
non-cosmological redshifts, alternatives to non-baryonic dark matter and/or
dark energy, and others. Cosmologists do not usually work within the framework
of alternative cosmologies because they feel that these are not at present as
competitive as the standard model. Certainly, they are not so developed, and
they are not so developed because cosmologists do not work on them. It is a
vicious circle. The fact that most cosmologists do not pay them any attention
and only dedicate their research time to the standard model is to a great
extent due to a sociological phenomenon (the "snowball effect" or
"groupthink"). We might well wonder whether cosmology, our knowledge of the
Universe as a whole, is a science like other fields of physics or a predominant
ideology.


title: Si$_3$N$_4$ optomechanical crystals in the resolved-sideband regime

abstract:
  We demonstrate sideband-resolved Si$_3$N$_4$ optomechanical crystals
supporting $10^5$ quality factor optical modes at 980 nm, coupled to $\approx4$
GHz frequency mechanical modes with quality factors of $\approx3000$.
Optomechanical electromagnetically induced transparency and absorption are
observed at room temperature and in atmosphere with intracavity photon numbers
of the order of $10^4$.


title:
The effect of linkage on establishment and survival of locally
  beneficial mutations

abstract:
  When organisms adapt to spatially heterogeneous environments, selection may
drive divergence at multiple genes. If populations under divergent selection
also exchange migrants, we expect genetic differentiation to be high at
selected loci, relative to the baseline caused by migration and genetic drift.
Indeed, empirical studies have found peaks of putatively adaptive
differentiation. These are highly variable in length, some of them extending
over several hundreds of thousands of base pairs. How can such 'islands of
divergence' be explained? Physical linkage produces elevated levels of
differentiation at loci close to genes under selection. However, whether this
is enough to account for the observed patterns of divergence is not well
understood. Here, we investigate the fate of a locally beneficial mutation that
arises in linkage to an existing migration-selection polymorphism and derive
two important quantities: the probability that the mutation becomes
established, and the expected time to its extinction. We find that intermediate
levels of recombinations are sometimes favourable, and that physical linkage
can lead to strongly elevated invasion probabilities and extinction times. We
provide a rule of thumb for when this is the case. Moreover, we quantify the
long-term effect of polygenic local adaptation on linked neutral variation.


title: A J-function for inhomogeneous spatio-temporal point processes

abstract:
  We propose a new summary statistic for inhomogeneous intensity-reweighted
moment stationary spatio-temporal point processes. The statistic is defined
through the n-point correlation functions of the point process and it
generalises the J-function when stationarity is assumed. We show that our
statistic can be represented in terms of the generating functional and that it
is related to the inhomogeneous K-function. We further discuss its explicit
form under some specific model assumptions and derive a ratio-unbiased
estimator. We finally illustrate the use of our statistic on simulated data.


title: Does Life Come from Water or Fluids?

abstract:
  In the present work the Stochastic generalization of the quantum hydrodynamic
analogy (SQHA) is used to obtain the far from equilibrium kinetics for a real
gas and its fluid phase. In gasses and their liquids, interacting by
Lennard-Jones potentials whose mean distance is bigger than the quantum
correlation distance and than the molecular interaction distance r0, it is
possible to define a Fokker-Plank type equation of motion as a function of the
mean phase space molecular volume that far from equilibrium shows maximizing
the dissipation of a part of the generalized SQHA-free energy. In the case of a
real gas with no chemical reactions and at quasi-isothermal conditions, the
principle disembogues into the maximum free energy dissipation confirming the
experimental outputs of electro-convective instability. In this case, the model
shows that the transition to stationary states with higher free energy can
happen and that, in incompressible fluids, the increase of free energy is
almost given by a decrease of entropy leading to the appearance of self-ordered
structures. The output of the theory showing that the generation of order, via
energy dissipation, is more efficient in fluids than in gasses, because of
their incompressibility, leads to the re-conciliation between physics and
biology furnishing the eplanation why the life was born in water. The
theoretical output also suggests that the search for life out of the earth must
consider the possibility to find it in presence of liquid phases different from
water.


title: Flexible Invariants Through Semantic Collaboration

abstract:
  Modular reasoning about class invariants is challenging in the presence of
dependencies among collaborating objects that need to maintain global
consistency. This paper presents semantic collaboration: a novel methodology to
specify and reason about class invariants of sequential object-oriented
programs, which models dependencies between collaborating objects by semantic
means. Combined with a simple ownership mechanism and useful default schemes,
semantic collaboration achieves the flexibility necessary to reason about
complicated inter-object dependencies but requires limited annotation burden
when applied to standard specification patterns. The methodology is implemented
in AutoProof, our program verifier for the Eiffel programming language (but it
is applicable to any language supporting some form of representation
invariants). An evaluation on several challenge problems proposed in the
literature demonstrates that it can handle a variety of idiomatic collaboration
patterns, and is more widely applicable than the existing invariant
methodologies.


title:
Implementing a strand of a scalable fault-tolerant quantum computing
  fabric

abstract:
  Quantum error correction (QEC) is an essential step towards realising
scalable quantum computers. Theoretically, it is possible to achieve
arbitrarily long protection of quantum information from corruption due to
decoherence or imperfect controls, so long as the error rate is below a
threshold value. The two-dimensional surface code (SC) is a fault-tolerant
error correction protocol} that has garnered considerable attention for actual
physical implementations, due to relatively high error thresholds ~1%, and
restriction to planar lattices with nearest-neighbour interactions. Here we
show a necessary element for SC error correction: high-fidelity parity
detection of two code qubits via measurement of a third syndrome qubit. The
experiment is performed on a sub-section of the SC lattice with three
superconducting transmon qubits, in which two independent outer code qubits are
joined to a central syndrome qubit via two linking bus resonators. With
all-microwave high-fidelity single- and two-qubit nearest-neighbour entangling
gates, we demonstrate entanglement distributed across the entire sub-section by
generating a three-qubit Greenberger-Horne-Zeilinger (GHZ) state with fidelity
~94%. Then, via high-fidelity measurement of the syndrome qubit, we
deterministically entangle the otherwise un-coupled outer code qubits, in
either an even or odd parity Bell state, conditioned on the syndrome state.
Finally, to fully characterize this parity readout, we develop a new
measurement tomography protocol to obtain a fidelity metric (90% and 91%). Our
results reveal a straightforward path for expanding superconducting circuits
towards larger networks for the SC and eventually a primitive logical qubit
implementation.


title: Compact families of Jordan curves and convex hulls in three dimensions

abstract:
  We prove that for certain families of semi-algebraic convex bodies in 3
dimensions, the convex hull of $n$ disjoint bodies has $O(n\lambda_s(n))$
features, where $s$ is a constant depending on the family: $\lambda_s(n)$ is
the maximum length of order-$s$ Davenport-Schinzel sequences with $n$ letters.
The argument is based on an apparently new idea of `compact families' of convex
bodies or discs, and of `crossing content' of disc intersections.


title:
Localization and number of visited valleys for a transient diffusion in
  random environment

abstract:
  We consider a transient diffusion in a $(-\kappa/2)$-drifted Brownian
potential $W\_{\kappa}$ with $0\textless{}\kappa\textless{}1$. We prove its
localization at time $t$ in the neighborhood of some random points depending
only on the environment, which are the positive $h\_t$-minima of the
environment, for $h\_t$ a bit smaller than $\log t$. We also prove an Aging
phenomenon for the diffusion, a renewal theorem for the hitting time of the
farthest visited valley, and provide a central limit theorem for the number of
valleys visited up to time $t$. The proof relies on a decomposition of the
trajectory of $W\_{\kappa}$ in the neighborhood of $h\_t$-minima, with the help
of results of A. Faggionato, and on a precise analysis of exponential
functionals of $W\_{\kappa}$ and of $W\_{\kappa}$ Doob-conditioned to stay
positive.


title: Visco-potential flows in electrohydrodynamics

abstract:
  In this study we consider the problem of the interface motion under the
capillary-gravity and an external electric forces. The infinitely deep fluid
layer is assumed to be viscous, perfectly conducting and the flow to be
incompressible. The weak viscous effects are introduced using the
Helmholtz-Leray decomposition and the visco-potential flow approach. The
electric charge distributions above and on the free surface are considered.
Finally, we derive some linearized analytical solutions for the free surface
elevation shape under the localised pressure distribution and the combined
action of the forces mentioned hereinabove.


title: Learning Reputation in an Authorship Network

abstract:
  The problem of searching for experts in a given academic field is hugely
important in both industry and academia. We study exactly this issue with
respect to a database of authors and their publications. The idea is to use
Latent Semantic Indexing (LSI) and Latent Dirichlet Allocation (LDA) to perform
topic modelling in order to find authors who have worked in a query field. We
then construct a coauthorship graph and motivate the use of influence
maximisation and a variety of graph centrality measures to obtain a ranked list
of experts. The ranked lists are further improved using a Markov Chain-based
rank aggregation approach. The complete method is readily scalable to large
datasets. To demonstrate the efficacy of the approach we report on an extensive
set of computational simulations using the Arnetminer dataset. An improvement
in mean average precision is demonstrated over the baseline case of simply
using the order of authors found by the topic models.


title: SOFA: An Extensible Logical Optimizer for UDF-heavy Dataflows

abstract:
  Recent years have seen an increased interest in large-scale analytical
dataflows on non-relational data. These dataflows are compiled into execution
graphs scheduled on large compute clusters. In many novel application areas the
predominant building blocks of such dataflows are user-defined predicates or
functions (UDFs). However, the heavy use of UDFs is not well taken into account
for dataflow optimization in current systems.
  SOFA is a novel and extensible optimizer for UDF-heavy dataflows. It builds
on a concise set of properties for describing the semantics of Map/Reduce-style
UDFs and a small set of rewrite rules, which use these properties to find a
much larger number of semantically equivalent plan rewrites than possible with
traditional techniques. A salient feature of our approach is extensibility: We
arrange user-defined operators and their properties into a subsumption
hierarchy, which considerably eases integration and optimization of new
operators. We evaluate SOFA on a selection of UDF-heavy dataflows from
different domains and compare its performance to three other algorithms for
dataflow optimization. Our experiments reveal that SOFA finds efficient plans,
outperforming the best plans found by its competitors by a factor of up to 6.


title:
Accurate parameters of the oldest known rocky-exoplanet hosting system:
  Kepler-10 revisited

abstract:
  Since the discovery of Kepler-10, the system has received considerable
interest because it contains a small, rocky planet which orbits the star in
less than a day. The system's parameters, announced by the Kepler team and
subsequently used in further research, were based on only 5 months of data. We
have reanalyzed this system using the full span of 29 months of Kepler
photometric data, and obtained improved information about its star and the
planets. A detailed asteroseismic analysis of the extended time series provides
a significant improvement on the stellar parameters: Not only can we state that
Kepler-10 is the oldest known rocky-planet-harboring system at 10.41 +/- 1.36
Gyr, but these parameters combined with improved planetary parameters from new
transit fits gives us the radius of Kepler-10b to within just 125 km. A new
analysis of the full planetary phase curve leads to new estimates on the
planetary temperature and albedo, which remain degenerate in the Kepler band.
Our modeling suggests that the flux level during the occultation is slightly
lower than at the transit wings, which would imply that the nightside of this
planet has a non-negligible temperature.


title:
Search for the process $e^+e^-\to J/\psi + X(1835)$ at
  $\sqrt{s}\approx10.6$GeV

abstract:
  We report the results of a search for the $X(1835)$ state in the process
$e^+e^-\to J/\psi+X(1835)$ using a data sample of 672 fb$^{-1}$ collected with
the Belle detector at and near the $\Upsilon(4S)$ resonance at the KEKB
asymmetric-energy $e^+e^-$ collider. No significant evidence is found for this
process, and an upper limit is set on its cross section times the branching
fraction: $\sigma_{\rm Born}(e^+e^- \to J/\psi X(1835)) \cdot$ {${\cal
B}(X(1835)\to \ge 3$ charged tracks)} $< 1.3 \ {\rm fb}$ at 90% confidence
level.


title: New Bounds for the Traveling Salesman Constant

abstract:
  Let $X_1, X_2, \dots, X_n$ be independent and uniformly distributed random
variables in the unit square $[0,1]^2$ and let $L(X_1, \dots, X_n)$ be the
length of the shortest traveling salesman path through these points. In 1959,
Beardwood, Halton $\&$ Hammersley proved the existence of a universal constant
$\beta$ such that $$ \lim_{n \rightarrow \infty}{n^{-1/2}L(X_1, \dots, X_n)} =
\beta \qquad \mbox{almost surely.}$$ The best bounds for $\beta$ are still the
ones originally established by Beardwood, Halton $\&$ Hammersley $0.625 \leq
\beta \leq 0.922$. We slightly improve both upper and lower bounds.


title: Series expansions for $1/\pi^m$ and $\pi^m$

abstract:
  By means of the telescoping method, we establish two sum- mation formulas on
sine function. As the special cases of them, several interesting series
expansions for $1/\pi^m$ and $\pi^m$.


title:
Semiclassical spectral asymptotics for a magnetic Schr\"odinger operator
  with non-vanishing magnetic field

abstract:
  We consider a magnetic Schr\"odinger operator $H^h$, depending on a
semiclassical parameter $h>0$, on a compact Riemannian manifold. We assume that
there is no electric field. We suppose that the minimal value $b_0$ of the
intensity of the magnetic field $b$ is strictly positive. We give a survey of
the results on asymptotic behavior of the eigenvalues of the operator $H^h$ in
the semiclassical limit.


title: Heat equation and Poisson equation in matrix geometry

abstract:
  In this paper, we study the Poisson equation and heat equation in a model
matrix geometry $M_n$. Our main results are about the Poisson equation and
global behavior of the heat equation on $M_n$. We can show that if $c_0$ is the
initial positive definite matrix in $M_n$, then $c(t)$ exists for all time and
is positive definite too. We can also show the entropy stability of the
solutions to the heat equation.


title: On the genus of the commuting graphs of finite non-abelian groups

abstract:
  The commuting graph of a non-abelian group is a simple graph in which the
vertices are the non-central elements of the group, and two distinct vertices
are adjacent if and only if they commute. In this paper, we classify (up to
isomorphism) all finite non-abelian groups whose commuting graphs are acyclic,
planar or toroidal. We also derive explicit formulas for the genus of the
commuting graphs of some well-known class of finite non-abelian groups, and
show that, every collection of finite non-abelian groups whose commuting graphs
have the same genus is finite.


title:
The propagator of a relativistic particle via the path-dependent vector
  potential

abstract:
  The proper time formalism for a particle propagator in an external
electromagnetic field is combined with the path-dependent formulation of the
gauge theory to simplify the quasiclassical propagator. The latter is achieved
due to a specific choice of the gauge corresponding to the use of the classical
path in the path-dependent formulation of the gauge theory, which leads to the
cancellation of the interaction part of the action in the Feynman path
integral. A simple expression for the quasiclassical propagator is obtained in
all cases of the external field when the classical equation of motion in this
field is integrable. As an example, new simple expressions for the propagators
are derived for a spinless charged particle interacting with the following
fields: an arbitrary constant and uniform electromagnetic field, an arbitrary
plane wave and, finally, an arbitrary plane wave combined with an arbitrary
constant and uniform electromagnetic field. In all these cases the
quasiclassical propagator coincides with the exact result.


title:
The Host Galaxies of Type Ia Supernovae Discovered by the Palomar
  Transient Factory

abstract:
  We present spectroscopic observations of the host galaxies of 82 low-redshift
type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory (PTF).
We determine star-formation rates, gas-phase/stellar metallicities, and stellar
masses and ages of these objects. As expected, strong correlations between the
SN Ia light-curve width (stretch) and the host age/mass/metallicity are found:
fainter, faster-declining events tend to be hosted by older/massive/metal-rich
galaxies. There is some evidence that redder SNe Ia explode in higher
metallicity galaxies, but we found no relation between the SN colour and host
galaxy extinction based on the Balmer decrement, suggesting that the colour
variation of these SNe does not primarily arise from this source. SNe Ia in
higher-mass/metallicity galaxies also appear brighter after stretch/colour
corrections than their counterparts in lower mass hosts, and the stronger
correlation is with gas-phase metallicity suggesting this may be the more
important variable. We also compared the host stellar mass distribution to that
in galaxy targeted SN surveys and the high-redshift untargeted Supernova Legacy
Survey (SNLS). SNLS has many more low mass galaxies, while the targeted
searches have fewer. This can be explained by an evolution in the galaxy
stellar mass function, coupled with a SN delay-time distribution proportional
to $t^{-1}$. Finally, we found no significant difference in the
mass--metallicity relation of our SN Ia hosts compared to field galaxies,
suggesting any metallicity effect on the SN Ia rate is small.


title: A non-parametric efficient evaluation of Partial Directed Coherence

abstract:
  Studying the flow of information between different areas of the brain can be
performed by using the so-called Partial Directed Coherence. This measure is
usually evaluated by first identifying a multivariate autoregressive model, and
then by using Fourier transforms of the impulse responses identified and
applying appropriate normalizations. Here, we present another route to evaluate
the partial directed coherences in multivariate time series. The method
proposed is non parametric, and utilises the strong spectral factorization of
the inverse of the spectral density matrix of the multivariate process. To
perform the factorization, we have recourse to an algorithm developed by Davis
and his collaborators. We present simulations as well as an application on a
real data set (Local Field Potentials in the sleeping mouse) to illustrate the
methodology. A comparison to the usual approach in term of complexity is
detailed. For long AR models, the proposed approach is of interest.


title:
Determining heating time scales in solar active region cores from
  AIA/SDO Fe XVIII images

abstract:
  We present a study of the frequency of transient brightenings in the core of
solar active regions as observed in the Fe XVIII line component of AIA/SDO 94 A
filter images. The Fe XVIII emission is isolated using an empirical correction
to remove the contribution of "warm" emission to this channel. Comparing with
simultaneous observations from EIS/Hinode, we find that the variability
observed in Fe XVIII is strongly correlated with the emission from lines formed
at similar temperatures. We examine the evolution of loops in the cores of
active regions at various stages of evolution. Using a newly developed event
detection algorithm we characterize the distribution of event frequency,
duration, and magnitude in these active regions. These distributions are
similar for regions of similar age and show a consistent pattern as the regions
age. This suggests that these characteristics are important constraints for
models of solar active regions. We find that the typical frequency of the
intensity fluctuations is about 1400s for any given line-of-sight, i.e. about
2-3 events per hour. Using the EBTEL 0D hydrodynamic model, however, we show
that this only sets a lower limit on the heating frequency along that
line-of-sight.


title: Anomalous Viscosity of the Quark-Gluon Plasma

abstract:
  The shear viscosity of the quark-gluon plasma is predicted to be lower than
the collisional viscosity for weak coupling. The estimated ratio of the shear
viscosity to entropy density is rather close to the ratio calculated by N = 4
super Yang-Mills theory for strong coupling, which indicates that the
quark-gluon plasma might be strongly coupled. However, in presence of momentum
anisotropy, the Weibel instability can arise and drive the turbulent transport.
Shear viscosity can be lowered by enhanced collisionality due to turbulence,
but the decorrelation time and its relation to underlying dynamics and
color-magnetic fields have not been calculated self-consistently. In this
paper, we use resonance broadening theory for strong turbulence to calculate
the anomalous viscosity of the quark-gluon plasma for nonequilibrium. For
saturated Weibel instability, we estimate the scalings of the decorrelation
rate and viscosity and compare these with collisional transport. This
calculation yields an explicit connection between the underlying momentum space
anisotropy and the viscosity anomaly.


title:
Covariant and gauge-invariant linear scalar perturbations in multiple
  scalar field cosmologies

abstract:
  We derive a set of equations monitoring the evolution of covariant and
gauge-invariant linear scalar perturbations of
Friedman-Lema\^itre-Robertson-Walker models with multiple interacting
non-linear scalar fields. We use a dynamical systems' approach in order to
perform a stability analysis for some classes of scalar field potentials. In
particular, using a recent approximation for the inflationary dynamics of the
background solution, we derive conditions under which homogenization occurs for
chaotic (quadratic and quartic potentials) and new inflation. We also prove a
cosmic no-hair result for power-law inflation and its generalisation for two
scalar fields with independent exponential potentials (assisted power-law
inflation).


title:
On stratification, barotropic tides, and secular changes in surface
  tidal elevations: Two-layer analytical model

abstract:
  In this study the influence of stratification on surface tidal elevations in
a two-layer analytical model is examined. The model assumes linearized,
non-rotating, shallow-water dynamics in one dimension with astronomical forcing
and allows for arbitrary topography. Using a natural modal separation, both
large scale (barotropic) and small scale (baroclinic) components of the surface
tidal elevation are shown to be comparably affected by stratification. It is
also shown that the topography and basin boundaries affect the sensitivity of
the barotropic surface tide to stratification significantly. This paper,
therefore, provides a framework to understand how the presence of
stratification impacts barotropic as well as baroclinic tides, and how climatic
perturbations to oceanic stratification contribute to secular variations in
tides. Results from a realistic-domain global numerical two-layer tide model
are briefly examined and found to be qualitatively consistent with the
analytical model results.


title: The highest energy neutrinos: first evidence for cosmic origin

abstract:
  Developments in neutrino astronomy have been to a great extent motivated by
the search for the sources of the cosmic rays, leading at a very early stage to
the concept of a cubic kilometer neutrino detector. Almost four decades later
such an instrument, IceCube, is taking data and has produced the first evidence
for a flux of high-energy neutrinos of cosmic origin. After a brief review of
the history of the field, we will introduce IceCube and describe the first
analysis of data taken with the completed instrument. The atmospheric neutrino
flux cannot accommodate an excess of 28 neutrinos observed with energies above
60 TeV. We will briefly speculate on the origin of these events. Readers
interested specifically in IceCube results may refer directly to section 3.


title: Self-adjointness and boundedness in quadratic quantization

abstract:
  We construct a counter example showing, for the quadratic quantization, the
identity $(\Gamma(T))^*= \Gamma(T^*)$ is not necessarily true. We characterize
all operators on the one-particle algebra whose quadratic quantization are
self-adjoint operators on the quadratic Fock space. Finally, we discuss the
boundedness of the quadratic quantization.


title: Counter-examples to the minimal model theory in characteristic two

abstract:
  In this paper, we show that the minimal model theory does not hold in
characteristic two. More precisely, we construct counter-examples to the
relative abundance conjecture.


title:
Comment on: "On the swimming motion of spheroidal magnetotactic
  bacteria" [arXiv:1302.5787]

abstract:
  It is pointed out that a recent article [arXiv:1302.5787] on swimming of
magnetotactic bacteria is conceptually wrong.


title: Higher charge periodic monopoles

abstract:
  We consider singly periodic solutions to the SU(2) Bogomolny equations and
use the Nahm transform to generate a class of monopoles of charge k>2, thereby
extending known results for lower charge chains. Some simple scattering
processes are presented and a comparison made with geodesic motion of monopoles
in $\mathbb{R}^3$.


title:
Exploration in Interactive Personalized Music Recommendation: A
  Reinforcement Learning Approach

abstract:
  Current music recommender systems typically act in a greedy fashion by
recommending songs with the highest user ratings. Greedy recommendation,
however, is suboptimal over the long term: it does not actively gather
information on user preferences and fails to recommend novel songs that are
potentially interesting. A successful recommender system must balance the needs
to explore user preferences and to exploit this information for recommendation.
This paper presents a new approach to music recommendation by formulating this
exploration-exploitation trade-off as a reinforcement learning task called the
multi-armed bandit. To learn user preferences, it uses a Bayesian model, which
accounts for both audio content and the novelty of recommendations. A
piecewise-linear approximation to the model and a variational inference
algorithm are employed to speed up Bayesian inference. One additional benefit
of our approach is a single unified model for both music recommendation and
playlist generation. Both simulation results and a user study indicate strong
potential for the new approach.


title: Half-turn linked pairs of isometries of hyperbolic 4-space

abstract:
  In this paper we develop a complete theory of factorization for isometries of
hyperbolic 4-space. Of special interest is the case where a pair of isometries
is linked, that is, when a pair of isometries can be expressed each as
compositions of two involutions, one of which is common to both isometries.
  Here we develop a new theory of hyperbolic pencils and twisting planes
involving a new geometric construction, their half-turn banks. This enables us
to give complete results about each of the pair-types of isometries and their
simultaneous factorization by half-turns. That is, we provide geometric
conditions for each such pair to be linked by half-turns. The main result gives
a necessary and sufficient condition for any given pair of isometries to be
linked. We also provide a procedure for constructing a half-turn linked pair of
isometries of $\mathbb{H}^4$ that do not restrict to lower dimensions, yielding
an example that gives a negative answer to a question raised by Ara Basmajian
and Karan Puri.