title: Ricci flow and birational surgery

abstract:
  We study the formation of finite time singularities of the Kahler-Ricci flow
in relation to high codimensional birational surgery in algebraic geometry. We
show that the Kahler-Ricci flow on an n-dimensionl Kahler manifold contracts a
complex submanifold $\mathbb{P}^m$ with normal bundle
$\oplus_{j=1}^{n-m}\mathcal{O}_{\mathbb{P}^m}(-a_j)$ for $a_j\in\mathbb{Z}^+$
and $\sum_{j=1}^{n-m} a_j \leq m$ in Gromov-Hausdorff topology with suitable
initial Kahler class. We also show that the Kahler-Ricci flow resolves a family
of isolated singularities uniquely in Gromov-Hausdorff topology. In particular,
we construct global and local examples of metric flips by the Kahler-Ricci flow
as a continuous path in Gromov-Hausdorff topology.


title: Bowman-Bradley type theorem for finite multiple zeta values

abstract:
  The multiple zeta values are multivariate generalizations of the values of
the Riemann zeta function at positive integers. The Bowman-Bradley theorem
asserts that the multiple zeta values at the sequences obtained by inserting a
fixed number of twos between 3,1,...,3,1 add up to a rational multiple of a
power of \pi. We show that an analogous theorem holds in a very strong sense
for finite multiple zeta values, which have been investigated by Hoffman and
Zhao among others and recently recast by Zagier.


title:
Asymptotic formula for the solution of the Stokes problem with a small
  perturbation of the domain in two and three dimensions

abstract:
  In this paper we consider the resolvent Stokes problem in the case there is a
small perturbation of the domain caused by a perturbed boundary. Firstly, we
prove that the solution of Stokes problem is continuous due to this small
perturbation. Secondly, we derive the first-order term in the displacement
field perturbation that due to the deformation of the domain. It is worth
emphasizing that even though only the first-order term is given, our method
enables us to derive higher-order terms as well. The derivation is rigorous and
based on layer potential techniques.


title: Overview of Visualization Tools for Web Browser History Data

abstract:
  Nowadays, the Web has become one of the most widespread platforms for
information change and retrieval. As it becomes easier to publish documents, as
the number of users, and thus publishers, increases and as the number of
documents grows, searching for information is turning into a cumbersome and
time-consuming operation. Because of the loose interconnection between
documents, people have difficulty remembering where they have been and
returning to previously visited pages. Navigation through the web faces
problems of locating oneself with respect to space and time. The idea of
graphical assistance navigation is to help users to find their paths in
hyperspace by adapting the style of link presentation to the goals, knowledge
and other characteristics of an individual user. We first introduce the
concepts related to web navigation; we then present an overview of different
graphical navigation tools and techniques. We conclude by presenting a
comparative table of these tools based on some pertinent criteria.


title:
On K\"ahler metrisability of two-dimensional complex projective
  structures

abstract:
  We derive necessary conditions for a complex projective structure on a
complex surface to arise via the Levi-Civita connection of a (pseudo-)K\"ahler
metric. Furthermore we show that the (pseudo-)K\"ahler metrics defined on some
domain in the projective plane which are compatible with the standard complex
projective structure are in one-to-one correspondence with the hermitian forms
on $\mathbb{C}^3$ whose rank is at least two. This is achieved by prolonging
the relevant finite-type first order linear differential system to closed form.
Along the way we derive the complex projective Weyl and Liouville curvature
using the language of Cartan geometries.


title: A chaotic image encryption scheme owning temp-value feedback

abstract:
  This paper presents a novel efficient chaotic image encryption scheme, in
which the temp-value feedback mechanism is introduced to the permutation and
diffusion procedures. Firstly, a simple trick is played to map the plain-image
pixels to the initial condition of the Logistic map. Then, a pseudorandom
number sequence (PRNS) is obtained from iterating the map. The permutation
procedure is carried out by a permutation sequence which is generated by
comparing the PRNS and its sorted version. The diffusion procedure is composed
of two reversely executed rounds. During each round, the current plain-image
pixel and the last cipher-image pixel are used to produce the current
cipher-image pixel with the help of the Logistic map and a pseudorandom number
generated by the Chen system. To enhance the efficiency, only expanded XOR
operation and modulo 256 addition are employed during diffusion. Experimental
results show that the new scheme owns a large key space and can resist the
differential attack. It is also efficient.


title: Rerouting Excitation Transfer in the Fenna-Matthews-Olson Complex

abstract:
  We investigate, using the Hierarchy method, the entanglement and the
excitation transfer efficiency of the Fenna-Matthews-Olson complex under two
different local modifications: the suppression of transitions between
particular sites and localized changes to the protein environment. We find that
inhibiting the connection between the site-5 and site-6, or disconnecting
site-5 from the complex completely, leads to an dramatic enhancement of the
entanglement between site-6 and site-7. Similarly, the transfer efficiency
actually increases if site-5 is disconnected from the complex entirely. We
further show that if site-5 and site-7 are conjointly removed, the efficiency
falls. This suggests that while not contributing to the transport efficiency in
a normal complex, site-5 introduces a redundant transport route in case of
damage to site-7. Our results suggest an overall robustness of excitation
energy transfer in the FMO complex under mutations, local defects, and other
abnormal situations.


title: One-pion production in neutrino-nucleus collisions

abstract:
  We use our model for neutrino pion production on the nucleon to study pion
production on a nucleus. The model is conveniently modified to include
in-medium corrections and its validity is extended up to 2 GeV neutrino
energies by the inclusion of new resonant contributions in the production
process. Our results are compared with recent MiniBooNE data measured in
mineral oil. Our total cross sections are below data for neutrino energies
above 1 GeV. As with other theoretical calculations, the agreement with data
improves if we neglect pion final state interaction. This is also the case for
differential cross sections convoluted over the neutrino flux.


title: Direct view on the ultrafast carrier dynamics in graphene

abstract:
  The ultrafast dynamics of excited carriers in graphene is closely linked to
the Dirac spectrum and plays a central role for many electronic and
optoelectronic applications. Harvesting energy from excited electron-hole
pairs, for instance, is only possible if these pairs can be separated before
they lose energy to vibrations, merely heating the lattice. While the hot
carrier dynamics in graphene could so far only be accessed indirectly, we here
present a direct time-resolved view on the Dirac cone by angle-resolved
photoemission (ARPES). This allows us to show the quasi-instant thermalisation
of the electron gas to a temperature of more than 2000 K; to determine the
time-resolved carrier density; to disentangle the subsequent decay into
excitations of optical phonons and acoustic phonons (directly and via
supercollisions); and to show how the presence of the hot carrier distribution
affects the lifetime of the states far below the Fermi energy.


title:
Osteology of a Near-Complete Skeleton of Tenontosaurus tilletti
  (Dinosauria: Ornithopoda) from the Cloverly Formation, Montana, USA

abstract:
  The character diagnosis of Tenontosaurus tilletti has been revised and
redefined into a more robust and quantifiable state. Significant emphasis is
placed on constructing phylogenetic definition in such a method, as it prevents
occlusion of true character states by alleviating potential individual
interpretational bias. Previous placement within the Iguanodontia is refuted
based on the lack of character affinity with the defining synapomorphies of the
clade. The clade Hypsilophodontidae (=Hypsilophodontia), along with
Iguanodontia, however is deemed to be in critical need of refinement to account
for recent discoveries and re-classifications of certain euornithopods. Several
of the synapomorphies are out-dated and deemed redundant in favour of a more
quantifiable approach. Re- definition of these clades is critical if the
current state of basal euornithopodan relationships is to be resolved.
Phylogenetic studies must be approached from a multidisciplinary perspective;
integration of tectonostratigraphical, ontogenetic, palaeoecological, and
biomechanical data with sets of well-defined primary homologies are essential
in increasing phylogenetic resolution and generating stratigraphically feasible
ancestor-descendant relationships. Material attributed to Tenontosaurus
tilletti is in need of strict re-analysis; the significant quantity of
specimens attributed to this species is potentially the result of poor
stratigraphic constraints and the vast spatiotemporal span occupied. Future
revision of this material is expected to reveal temporal variations on the
species -level inherently linked to environmental evolution, as well as
possibly provide clues to sexual dimorphism in contemporaneous, yet
morphologically distinct tenontosaurs.


title: Resilience of Dynamic Overlays through Local Interactions

abstract:
  This paper presents a self-organizing protocol for dynamic (unstructured P2P)
overlay networks, which allows to react to the variability of node arrivals and
departures. Through local interactions, the protocol avoids that the departure
of nodes causes a partitioning of the overlay. We show that it is sufficient to
have knowledge about 1st and 2nd neighbours, plus a simple interaction P2P
protocol, to make unstructured networks resilient to node faults. A simulation
assessment over different kinds of overlay networks demonstrates the viability
of the proposal.


title: Lexicographic identifying codes

abstract:
  An identifying code in a graph is a set of vertices which intersects all the
symmetric differences between pairs of neighbourhoods of vertices. Not all
graphs have identifying codes; those that do are referred to as twin-free. In
this paper, we design an algorithm that finds an identifying code in a
twin-free graph on n vertices in O(n^3) binary operations, and returns a
failure if the graph is not twin-free. We also determine an alternative for
sparse graphs with a running time of O(n^2d log n) binary operations, where d
is the maximum degree. We also prove that these algorithms can return any
identifying code with minimum cardinality, provided the vertices are correctly
sorted.


title: An explicit formula for the cubic Szeg\"o equation

abstract:
  We derive an explicit formula for the general solution of the cubic Szeg\"o
equation and of the evolution equation of the corresponding hierarchy. As an
application, we prove that all the solutions corresponding to finite rank
Hankel operators are quasiperiodic.


title: Decomposable and Indecomposable Algebras of Degree 8 and Exponent 2

abstract:
  We study the decomposition of central simple algebras of exponent 2 into
tensor products of quaternion algebras. We consider in particular
decompositions in which one of the quaternion algebras contains a given
quadratic extension. Let $B$ be a biquaternion algebra over $F(\sqrt{a})$ with
trivial corestriction. A degree 3 cohomological invariant is defined and we
show that it determines whether $B$ has a descent to $F$. This invariant is
used to give examples of indecomposable algebras of degree 8 and exponent 2
over a field of 2-cohomological dimension 3 and over a field $\mathbb M(t)$
where the $u$-invariant of $\mathbb M$ is 8 and $t$ is an indeterminate. The
construction of these indecomposable algebras uses Chow group computations
provided by A. S. Merkurjev in Appendix.


title: Central limit theorems in linear dynamics

abstract:
  Given a bounded operator $T$ on a Banach space $X$, we study the existence of
a probability measure $\mu$ on $X$ such that, for many functions $f:X\to\mathbb
K$, the sequence $(f+\dots+f\circ T^{n-1})/\sqrt n$ converges in distribution
to a Gaussian random variable.


title: Totally reducible holonomies of torsion-free affine connections

abstract:
  That announcement gives the structure of totally reducible linear Lie
algebras which are the Lie algebra of the holonomy group of (at least) one
torsion-free connection. The result uses the (already known) classi cation of
the irreducible ones and some previous (unpublished) works by the author giving
the classi cation for the pseudo-riemannian totally reducible case. One
describes those Lie subalgebras through a general structure theorem involving
two constructions and some lists. These constructions give new examples of non
irreducible totally reducible holonomy algebras and also recover some
irreducible ones which seem missing in the previous classi cation.


title: Mean field spin glasses treated with PDE techniques

abstract:
  Following an original idea of F. Guerra, in this notes we analyze the
Sherrington-Kirkpatrick model from different perspectives, all sharing the
underlying approach which consists in linking the resolution of the statistical
mechanics of the model (e.g. solving for the free energy) to well-known partial
differential equation (PDE) problems (in suitable spaces). The plan is then to
solve the related PDE using techniques involved in their native field and
lastly bringing back the solution in the proper statistical mechanics
framework. Within this strand, after a streamlined test-case on the Curie-Weiss
model to highlight the methods more than the physics behind, we solve the SK
both at the replica symmetric and at the 1-RSB level, obtaining the correct
expression for the free energy via an analogy to a Fourier equation and for the
self-consistencies with an analogy to a Burger equation, whose shock wave
develops exactly at critical noise level (triggering the phase transition). Our
approach, beyond acting as a new alternative method (with respect to the
standard routes) for tackling the complexity of spin glasses, links symmetries
in PDE theory with constraints in statistical mechanics and, as a novel result
from the theoretical physics perspective, we obtain a new class of polynomial
identities (namely of Aizenman-Contucci type but merged within the Guerra's
broken replica measures), whose interest lies in understanding, via the recent
Panchenko breakthroughs, how to force the overlap organization to the
ultrametric tree predicted by Parisi.

categories: cond-mat.dis-nn cond-mat.stat-mech math-ph math.MP


title: Macroscopically-observable probability currents in finite populations

abstract:
  In finite-size population models, one can derive Fokker-Planck equations to
describe the fluctuations of the species numbers about the deterministic
behaviour. In the steady state of populations comprising two or more species,
it is permissible for a probability current to flow. In such a case, the system
does not relax to equilibrium but instead reaches a non-equilibrium steady
state. In a two-species model, these currents form cycles (e.g., ellipses) in
probability space. We investigate the conditions under which such currents are
solely responsible for macroscopically-observable cycles in population
abundances. We find that this can be achieved when the deterministic limit
yields a circular neutrally-stable manifold. We further discuss the efficacy of
one-dimensional approximation to the diffusion on the manifold, and obtain
estimates for the macroscopically-observable current around this manifold by
appealing to Kramers' escape rate theory.


title: Anomalous Observers in the Subjectively Identical Reference Class

abstract:
  Anthropic reasoning is a critical tool to understand probabilities,
especially in a large universe or multiverse. According to anthropic reasoning,
we should consider ourselves typical among members of a reference class that
must include all subjectively indistinguishable observers. We discuss here
whether such a reference class, which we assume must include computer
simulations, must also include computers that replay previous simulations,
magnetic tapes that store but do not "run" the simulation, and even abstract
mathematical functions. We do not see any clear criterion for excluding these
anomalous observers, but their presence is deeply troubling to the idea of
anthropic reasoning.


title:
Anharmonic properties from a generalized third order ab~initio approach:
  theory and applications to graphite and graphene

abstract:
  We have implemented a generic method, based on the 2n+1 theorem within
density functional perturbation theory, to calculate the anharmonic scattering
coefficients among three phonons with arbitrary wavevectors. The method is used
to study the phonon broadening in graphite and graphene mono- and bi-layer. The
broadening of the high-energy optical branches is highly nonuniform and
presents a series of sudden steps and spikes. At finite temperature, the two
linearly dispersive acoustic branches TA and LA of graphene have nonzero
broadening for small wavevectors. The broadening in graphite and bi-layer
graphene is, overall, very similar to the graphene one, the most remarkable
feature being the broadening of the quasi acoustical ZO' branch. Finally, we
study the intrinsic anharmonic contribution to the thermal conductivity of the
three systems, within the single mode relaxation time approximation. We find
the conductance to be in good agreement with experimental data for the
out-of-plane direction but to underestimate it by a factor 2 in-plane.


title: On the extension to mean curvature flow in lower dimension

abstract:
  In this paper, we prove that if $M_t\subset \mathbb{R}^{n+1}$, $2\leq n\leq
6$, is the $n$-dimensional closed embedded $\mathcal{F}-$stable solution to
mean curvature flow with mean curvature of $M_t$ is uniformly bounded on
$[0,T)$ for $T<\infty$, then the flow can be smoothly extended over time $T$.


title: Quantum quench in an atomic one-dimensional Ising chain

abstract:
  We study non-equilibrium dynamics for an ensemble of tilted one-dimensional
atomic Bose-Hubbard chains after a sudden quench to the vicinity of the
transition point of the Ising paramagnetic to anti-ferromagnetic quantum phase
transition. The quench results in coherent oscillations for the orientation of
effective Ising spins, detected via oscillations in the number of
doubly-occupied lattice sites. We characterize the quench by varying the system
parameters. We report significant modification of the tunneling rate induced by
interactions and show clear evidence for collective effects in the oscillatory
response.


title:
On the components of spaces of curves on the 2-sphere with geodesic
  curvature in a prescribed interval

abstract:
  We obtain simple characterizations of the connected components of the space
of closed curves on the 2-sphere whose geodesic curvatures are constrained to
lie in an open interval $(\kappa_1,\kappa_2)$, in terms of $\kappa_1$ and
$\kappa_2$. Many results concerning the topology of these spaces are
established. In particular, we determine the homeomorphism class of some of
these components.


title:
Direct evidence for a gapless $Z_2$ spin liquid by frustrating N\'eel
  antiferromagnetism

abstract:
  By direct calculations of the spin gap in the frustrated Heisenberg model on
the square lattice, with nearest- ($J_1$) and next-nearest-neighbor ($J_2$)
super-exchange couplings, we provide a solid evidence that the spin-liquid
phase in the frustrated regime $0.45 \lesssim J_2/J_1 \lesssim 0.6$ is gapless.
Our numerical method is based on a variational wave function that is {\it
systematically} improved by the application of few Lanczos steps and allows us
to obtain reliable extrapolations in the thermodynamic limit. The peculiar
nature of the non-magnetic state is unveiled by the existence of S=1 gapless
excitations at $k=(\pi,0)$ and $(0,\pi)$. The magnetic transition can be
described and interpreted by a variational state that is built from Abrikosov
fermions having a $Z_2$ gauge structure and four Dirac points in the spinon
spectrum.


title: Greedy algorithms for high-dimensional eigenvalue problems

abstract:
  In this article, we present two new greedy algorithms for the computation of
the lowest eigenvalue (and an associated eigenvector) of a high-dimensional
eigenvalue problem, and prove some convergence results for these algorithms and
their orthogonalized versions. The performance of our algorithms is illustrated
on numerical test cases (including the computation of the buckling modes of a
microstructured plate), and compared with that of another greedy algorithm for
eigenvalue problems introduced by Ammar and Chinesta.


title:
Strong field effects on physics processes at the Interaction Point of
  future linear colliders

abstract:
  Future lepton colliders will be precision machines whose physics program
includes close study of the Higgs sector and searches for new physics via
polarised beams. The luminosity requirements of such machines entail very
intense lepton bunches at the interaction point with associated strong
electromagnetic fields. These strong fields not only lead to obvious phenomena
such as beamstrahlung, but also potentially affect every particle physics
process via virtual exchange with the bunch fields. For precision studies,
strong field effects have to be understood to the sub-percent level. Strong
external field effects can be taken into account exactly via the Furry Picture
or, in certain limits, via the Quasi-classical Operator method . Significant
theoretical development is in progress and here we outline the current state of
play.


title:
A reflection model for the cyclotron lines in the spectra of X-ray
  pulsars

abstract:
  Cyclotron resonance scattering features observed in the spectra of some X-ray
pulsars show significant changes of the line energy with the pulsar luminosity.
At high luminosities, these variations are often associated with the onset and
growth of the accretion column, which is believed to be the origin of the
observed emission and of the cyclotron lines. However, this scenario inevitably
implies large gradient of the magnetic field strength within the line-forming
region, which makes the formation of the observed line-like features
problematic. Moreover, the observed variation of the cyclotron line energy is
much smaller than could be anticipated for the corresponding luminosity
changes. We argue here that a more physically realistic situation is that the
cyclotron line forms when the radiation emitted by the accretion column is
reflected from the neutron star surface, where the gradient of the magnetic
field strength is significantly smaller. We develop here the reflection model
and apply it to explain the observed variations of the cyclotron line energy in
a bright X-ray pulsar V 0332+53 over a wide range of luminosities.


title:
Generalized Effective Potential Landau Theory for Bosonic Quadratic
  Superlattices

abstract:
  We study the properties of the Bose-Hubbard model for a quadratic optical
superlattice. To this end we generalize a recently established effective
potential Landau theory for a single component to the case of multi components
and find not only the characteristic incompressible solid phases with
fractional filling, but also obtain the underlying quantum phase diagram in the
whole parameter region at zero temperature. Comparing our analytic results with
corresponding ones from quantum Monte Carlo simulations demonstrates the high
accuracy of the generalized effective potential Landau theory (GEPLT). Finally,
we comment on the advantages and disadvantages of the GEPLT in view of a direct
comparison with a corresponding decoupled mean-field theory.


title: Clusters of microRNAs emerge by new hairpins in existing transcripts

abstract:
  Genetic linkage may result in the expression of multiple products from a
polycistronic transcript, under the control of a single promoter. In animals,
protein-coding polycistronic transcripts are rare. However, microRNAs are
frequently clustered in the genomes of animals, and these clusters are often
transcribed as a single unit. The evolution of microRNA clusters has been the
subject of much speculation, and a selective advantage of clusters of
functionally related microRNAs is often proposed. However, the origin of
microRNA clusters has not been so far explored. Here we study the evolution of
microRNA clusters in Drosophila melanogaster. We observed that the majority of
microRNA clusters arose by the de novo formation of new microRNA-like hairpins
in existing microRNA transcripts. Some clusters also emerged by tandem
duplication of a single microRNA. Comparative genomics show that these clusters
are unlikely to split or undergo rearrangements. We did not find any instances
of clusters appearing by rearrangement of pre-existing microRNA genes. We
propose a model for microRNA cluster evolution in which selection over one of
the microRNAs in the cluster interferes with the evolution of the other linked
microRNAs. Our analysis suggests that the study of microRNAs and small RNAs
must consider linkage associations.


title: Enveloping Algebras and Cohomology of Leibniz Pairs

abstract:
  We introduce the enveloping algebra for a Leibniz pair, and show that the
category of modules over a Leibniz pair is isomorphic to the category of left
modules over its enveloping algebra. Consequently, we show that the cohomology
theory for a Leibniz pair introduced by Flato, Gerstenhaber and Voronov can be
interpreted by Ext-groups of modules over the enveloping algebra.


title: Containment of Nested Regular Expressions

abstract:
  Nested regular expressions (NREs) have been proposed as a powerful formalism
for querying RDFS graphs, but research in a more general graph database context
has been scarce, and static analysis results are currently lacking. In this
paper we investigate the problem of containment of NREs, and show that it can
be solved in PSPACE, i.e., the same complexity as the problem of containment of
regular expressions or regular path queries (RPQs).


title:
The Hyades Cluster: Identification of a Planetary System and Escaping
  White Dwarfs

abstract:
  Recently, some hot DA-type white dwarfs have been proposed to plausibly be
escaping members of the Hyades. We used hydrogen Balmer lines to measure the
radial velocities of seven such stars and confirm that three, and perhaps two
others, are/were indeed cluster members and one is not. The other candidate
Hyad is strongly magnetic and its membership status remains uncertain. The
photospheres of at least one quarter of field white dwarf stars are "polluted"
by elements heavier than helium that have been accreted. These stars are
orbited by extended planetary systems that contain both debris belts and major
planets. We surveyed the seven classical single Hyades white dwarfs and the
newly identified (escaping) Hyades white dwarfs and found calcium in the
photosphere of LP 475-242 of type DBA (now DBAZ), thus implying the presence of
an orbiting planetary system. The spectrum of white dwarf GD 31, which may be,
but probably is not, an escaping member of the Hyades, displays calcium
absorption lines; these originate either from the interstellar medium or, less
likely, from a gaseous circumstellar disk. If GD 31 was once a Hyades member,
then it would be the first identified white dwarf Hyad with a cooling age >340
Myr.


title: The Reachability Problem for Affine Functions on the Integers

abstract:
  We consider the problem of determining, given x, y in Z^k and a finite set F
of affine functions on Z^k, whether y is reachable from x by applying the
functions F. We also consider the analogous problem over N^k. These problems
are known to be undecidable for k >= 2. We give 2-EXPTIME algorithms for both
problems in the remaining case k = 1. The exact complexities remain open,
although we show a simple NP lower bound.


title: Charge Relaxation in a Single Electron Si/SiGe Double Quantum Dot

abstract:
  We measure the interdot charge relaxation time T_1 of a single electron
trapped in an accumulation mode Si/SiGe double quantum dot. The energy level
structure of the charge qubit is determined using photon assisted tunneling,
which reveals the presence of a low lying excited state. We systematically
measure T_1 as a function of detuning and interdot tunnel coupling and show
that it is tunable over four orders of magnitude, with a maximum of 45
microseconds for our device configuration. Measured relaxation times are
consistent with a phonon mediated energy relaxation process and indicate that
low lying excited states may have important implications in the development of
silicon spin qubits.


title: A memetic algorithm for the minimum sum coloring problem

abstract:
  Given an undirected graph $G$, the Minimum Sum Coloring problem (MSCP) is to
find a legal assignment of colors (represented by natural numbers) to each
vertex of $G$ such that the total sum of the colors assigned to the vertices is
minimized. This paper presents a memetic algorithm for MSCP based on a tabu
search procedure with two neighborhoods and a multi-parent crossover operator.
Experiments on a set of 77 well-known DIMACS and COLOR 2002-2004 benchmark
instances show that the proposed algorithm achieves highly competitive results
in comparison with five state-of-the-art algorithms. In particular, the
proposed algorithm can improve the best known results for 17 instances. We also
provide upper bounds for 18 additional instances for the first time.


abstract:
  We show that two Weyl group actions on the Springer sheaf with arbitrary
coefficients, one defined by Fourier transform and one by restriction, agree up
to a twist by the sign character. This generalizes a familiar result from the
setting of l-adic cohomology, making it applicable to modular representation
theory. We use the Weyl group actions to define a Springer correspondence in
this generality, and identify the zero weight spaces of small representations
in terms of this Springer correspondence.


title:
X-ray source variability study of the M 31 central field using Chandra
  HRC-I

abstract:
  [Abridged] The central field of the Andromeda galaxy (M 31) has been
monitored, using the Chandra HRC-I detector (about 0.1-10 keV energy range)
from 2006 to 2012 with the main aim to detect X-rays from optical novae. We
present a systematic analysis of all X-ray sources found in the 41 nova
monitoring observations, along with 23 M 31 central field HRC-I observations
available from the Chandra data archive starting in December 1999. Based on
these observations, we studied the X-ray long-term variability of the source
population and especially of X-ray binaries in M 31. We created a catalogue of
sources, detected in the 64 available observations, which add up to a total
exposure of about 1 Ms. We present a point-source catalogue, containing 318
X-ray sources with detailed long-term variability information, 28 of which are
published for the first time. The spatial and temporal resolution of the
catalogue allows us to classify 115 X-ray binary candidates showing high X-ray
variability or even outbursts in addition to 14 globular cluster X-ray binary
candidates showing no significant variability. The analysis may suggest, that
outburst sources are less frequent in globular clusters than in the field of M
31. We detected 7 supernova remnants, one of which is a new candidate and in
addition resolved the first X-rays from a known radio supernova remnant.
Besides 33 known optical nova/X-ray source correlations, we also discovered one
previously unknown super-soft X-ray outburst and several new nova candidates.
The catalogue contains a large sample of detailed long-term X-ray light curves
in the M 31 central field, which helps to understand the X-ray population of
our neighbouring spiral galaxy M 31.


title: Ergodic properties of {\beta}-adic Halton sequences

abstract:
  We investigate a parametric extension of the classical s-dimensional Halton
sequence, where the bases are special Pisot numbers. In a one- dimensional
setting the properties of such sequences have already been in- vestigated by
several authors [5, 8, 23, 28]. We use methods from ergodic theory to in order
to investigate the distribution behavior of multidimen- sional versions of such
sequences. As a consequence it is shown that the Kakutani-Fibonacci
transformation is uniquely ergodic.


title: Dirac Neutrinos with $S_4$ Flavor Symmetry in Warped Extra Dimensions

abstract:
  We present a warped extra dimension model with the custodial symmetry
$SU(2)_L\times SU(2)_R\times U(1)_X\times P_{LR}$ based on the flavor symmetry
$S_4\times Z_2\times Z'_2$, and the neutrinos are taken to be Dirac particles.
At leading order, the democratic lepton mixing is derived exactly, and the high
dimensional operators introduce corrections of order $\lambda_c$ to all the
three lepton mixing angles such that agreement with the experimental data can
be achieved. The neutrino mass spectrum is predicted to be of the inverted
hierarchy and the second octant of $\theta_{23}$ is preferred. We suggest the
modified democratic mixing, which is obtained by permuting the second and the
third rows of the democratic mixing matrix, should be a good first order
approximation to understanding sizable $\theta_{13}$ and the first octant of
$\theta_{23}$. The constraints on the model from the electroweak precision
measurements are discussed. Furthermore, we investigate the lepton mixing
patterns for all the possible residual symmetries $G_{\nu}$ and $G_{l}$ in the
neutrino and charged lepton sectors, respectively.


title:
Supporting Material for: Capillary-like Fluctuations of a Solid-Liquid
  Interface in a Non-Cohesive Granular System

abstract:
  In this supplementary paper we present some details on the solid-liquid
interface detection, the deduction of the non-equilibrium free energy, the
analysis of the granular temperature and energy per mode, a validation of the
small slope approximation, a description of the Langevin dynamics, and the
error analysis.


title:
Isotopic Yield Distributions of Transfer- and Fusion-Induced Fission
  from 238U+12C Reactions in Inverse Kinematics

abstract:
  A novel method to access the complete identification in atomic number Z and
mass A of fragments produced in low-energy fission of actinides is presented.
This method, based on the use of multi- nucleon transfer and fusion reactions
in inverse kinematics, is applied in this work to reactions between a 238U beam
and a 12C target to produce and induce fission of moderately excited actinides.
The fission fragments are detected and fully identified with the VAMOS
spectrometer of GANIL, allowing the measurement of fragment yields of several
hundreds of isotopes in a range between A ~ 80 and ~ 160, and from Z ~ 30 to ~
64. For the first time, complete isotopic yield distributions of fragments from
well-defined fissioning systems are available. Together with the precise
measurement of the fragment emission angles and velocities, this technique
gives further insight into the nuclear-fission process.


title:
Design of a High Intensity Neutron Source for Neutron-Induced Fission
  Yield Studies

abstract:
  The upgraded IGISOL facility with JYFLTRAP, at the accelerator laboratory of
the University of Jyv\"askyl\"a, has been supplied with a new cyclotron which
will provide protons of the order of 100 {\mu}A with up to 30 MeV energy, or
deuterons with half the energy and intensity. This makes it an ideal place for
measurements of neutron-induced fission products from various actinides, in
view of proposed future nuclear fuel cycles. The groups at Uppsala University
and University of Jyv\"askyl\"a are working on the design of a neutron
converter that will be used as neutron source in fission yield studies. The
design is based on simulations with Monte Carlo codes and a benchmark
measurement that was recently performed at The Svedberg Laboratory in Uppsala.
In order to obtain a competitive count rate the fission targets will be placed
very close to the neutron converter. The goal is to have a flexible design that
will enable the use of neutron fields with different energy distributions. In
the present paper, some considerations for the design of the neutron converter
will be discussed, together with different scenarios for which fission targets
and neutron energies to focus on.


title: {\sigma}-Galois theory of linear difference equations

abstract:
  We develop a Galois theory for systems of linear difference equations with an
action of an endomorphism {\sigma}. This provides a technique to test whether
solutions of such systems satisfy {\sigma}-polynomial equations and, if yes,
then characterize those. We also show how to apply our work to study
isomonodromic difference equations and difference algebraic properties of
meromorphic functions.


title: Weakening idempotency in K-theory

abstract:
  We show that the K-theory of C*-algebras can be defined by pairs of matrices
satisfying less strict relations than idempotency.


title: Regularity of K\"ahler-Ricci flow

abstract:
  In this short note we announce a regularity theorem for K\"ahler-Ricci flow
on a compact Fano manifold (K\"ahler manifold with positive first Chern class)
and its application to the limiting behavior of K\"ahler-Ricci flow on Fano
3-manifolds. Moreover, we also present a partial $C^0$ estimate to the
K\"ahler-Ricci flow under the regularity assumption, which extends previous
works on K\"ahler-Einstein metrics and shrinking K\"ahler-Ricci solitons (cf.
\cite{Ti90}, \cite{DoSu12}, \cite{Ti12}, \cite{PSS12}). The detailed proof will
appear in \cite{TiZh13}.


title: Continuous hull of a combinatorial pentagonal tiling as an inverse limit

abstract:
  In the article "Construction of the continuous hull for the combinatorics of
a regular pentagonal tiling of the plane" we constructed a compact topological
space for the combinatorics of "A regular pentagonal tiling of the plane",
which we call the continuous hull. We also constructed a substitution map on
the space which turns out to be a homeomorphism, and so the pair given by the
continuous hull and the substitution map yields a dynamical system. In this
paper we show how we can write this dynamical system as another dynamical
system given by an inverse limit and a right shift map.


title: Ship wakes: Kelvin or Mach angle?

abstract:
  From the analysis of a set of airborne images of ship wakes, we show that the
wake angles decrease as $U^{-1}$ at large velocities, in a way similar to the
Mach cone for supersonic airplanes. This previously unnoticed Mach-like regime
is in contradiction with the celebrated Kelvin prediction of a constant angle
of $19.47\degree$ independent of the ship's speed. We propose here a model,
confirmed by numerical simulations, in which the finite size of the disturbance
explains this transition between the Kelvin and Mach regimes at a Froude number
$Fr = U/\sqrt{gL} \simeq 0.5$, where $L$ is the hull ship length.


title: Determining the Higgs spin and parity in the diphoton decay channel

abstract:
  We calculate the diphoton distribution in the decay of arbitrary spin-0 and
spin-2 bosons produced from gluon fusion, taking into account the fact that
gluons inside an unpolarized proton are generally linearly polarized. The gluon
polarization brings about a difference in the transverse momentum distribution
of positive and negative parity states. At the same time, it causes the
azimuthal distribution of the photon pair to be non-isotropic for several
spin-2 coupling hypotheses, allowing one to distinguish these from the
isotropic scalar and pseudoscalar distributions.


title: Dynamical entanglement in coupled optical cavities

abstract:
  We study the evolution of a photonic state in a coupled pair of anharmonic
cavities and compare it with the corresponding system of two coupled harmonic
cavities. The photons in the anharmonic cavities interact with a two-level atom
and are described within the Jaynes-Cummings model. Starting from an eigenstate
of the Jaynes-Cummings model with N photons, the evolution of this state in the
presence of photon tunneling between the cavities is studied. We evaluate the
spectral density, the dynamics of the return as well as the transition
amplitudes and the probability for the dynamical creation of a N00N state.


title: Z2 peak of noise correlations in a quantum spin Hall insulator

abstract:
  We investigate the current noise correlations at a quantum point contact in a
quantum spin Hall structure, focusing on the effect of a weak magnetic field in
the presence of disorder. For the case of two equally biased terminals we
discover a robust peak: the noise correlations vanish at $B = 0 $ and are
negative for $B\not = 0 $. We find that the character of this peak is
intimately related to the interplay between time reversal symmetry and the
helical nature of the edge states and call it the Z2 peak.


title: Anisotropies in the Gravitational Wave Background from Preheating

abstract:
  We investigate the anisotropies in the gravitational wave (GW) background
produced at preheating after inflation. Using lattice field theory simulations
of a massless preheating model, we show that the GW amplitude depends
sensitively on the value of the decay product field chi coupled to the inflaton
phi, with the only requisite that chi is light during inflation. We find a
strong anisotropy in the amplitude of the GW background on large angular
scales, the details of which strongly depend on the reheating dynamics. We
expect similar conclusions for a wide class of inflationary models with light
scalar fields. If future direct detection GW experiments are capable of
detecting the GW produced by preheating, they should also be able to detect
this effect. This could eventually provide a powerful way to distinguish
between different inflationary and preheating scenarios.


title:
Ricci curvature type lower bounds for sub-Riemannian structures on
  Sasakian manifolds

abstract:
  Measure contraction properties are generalizations of the notion of Ricci
curvature lower bounds in Riemannian geometry to more general metric measure
spaces. In this paper, we give sufficient conditions for a Sasakian manifold
equipped with a natural sub-Riemannian distance to satisfy these properties.
Moreover, the sufficient conditions are defined by the Tanaka-Webster
curvature. This generalizes the earlier work in \cite{AgLe1} for the three
dimensional case and in \cite{Ju} for the Heisenberg group. To obtain our
results we use the intrinsic Jacobi equations along sub-Riemannian extremals,
coming from the theory of canonical moving frames for curves in Lagrangian
Grassmannians \cite{LiZe1, LiZe2}. The crucial new tool here is a certain
decoupling of the corresponding matrix Riccati equation. It is also worth
pointing out that our method leads to exact formulas for the measure
contraction in the case of the corresponding homogeneous models in the
considered class of sub-Riemannian structures.


title:
Bethe Ansatz solution of the small polaron with nondiagonal boundary
  terms

abstract:
  The small polaron with generic, nondiagonal boundary terms is investigated
within the framework of quantum integrability. The fusion hierarchy of the
transfer matrices and its truncation for particular values of the anisotropy
parameter are both employed, so that the spectral problem is formulated in
terms of a TQ equation. The solution of this equation for generic boundary
conditions is based on a deformation of the diagonal case. The eigenvalues of
the model are extracted and the corresponding Bethe Ansatz equations are
presented. Finally, we comment on the eigenvectors of the model and explicitly
compute the eigenstate of the model which evolves into the Fock vacuum when the
off-diagonal boundary terms are switched off.


title:
Orientational ordering of colloidal dispersions by application of time
  dependent external forces

abstract:
  We present a method of organizing incoherent motion of a colloidal suspension
to produce synchronized, coherent motion. This method exploits general features
of rotational response to time-dependent forcing, and it does not require
interaction between the particles. We report two methods of achieving
orientational alignment of an ensemble of identical colloids by means of a
time-dependent, but spatially uniform forcing: a) a piecewise constant force
alternating between two directions and b) a force uniformly rotating about an
axis. The physical origin of the forcing may be e.g., sedimentation or
electrophoresis. We will demonstrate that these forcing methods achieve
alignment both by analyzing the equations of motion and by simulation. We find
the conditions guaranteeing alignment, discuss the limitations of these
methods, and suggest possible applications. Examples of such forcing include
electrophoresis and sedimentation.


title: Whistler instability in a semi-relativistic bi-Maxwellian plasma

abstract:
  Employing linearized Vlasov-Maxwell system, the Weibel instability embedded
in an ambient magnetic field is discussed for a semi-relativistic bi-Maxwellian
distribution hoping such a scenario occurs in some relativistic environments
e.g., gamma-ray burst sources and relativistic jet sources, supernovae, and
galactic cosmic rays where the perpendicular temperature is much dominated over
the parallel . The dispersion relations are analyzed analytically along with
the graphical representation and the estimates of the growth rate are presented
along with the instability threshold condition in the limiting cases i.e.,
xi<=1 (resonant case) and xi>>1 (non-resonant case). It is observed that the
relativistic effect suppresses the instability and also lowers the threshold
for the instability to set in. The ambient magnetic field contribution to
instability appears only in non-resonant case resulting in reduction of growth
rate. However, the effect of the ambient magnetic field is diminished as we go
from the weak relativistic regime to the highly relativistic one. We also note
that the ambient magnetic field generates real oscillations and the
reletivistic effect reduces these oscillations. Further for field free case
i.e., B0=0, the growth rates for Weibel instabilities are also presented in a
semi-relativistic bi- Maxwellian plasma for both the limiting cases.


title:
Hierarchical Fractal Weyl Laws for Chaotic Resonance States in Open
  Mixed Systems

abstract:
  In open chaotic systems the number of long-lived resonance states obeys a
fractal Weyl law, which depends on the fractal dimension of the chaotic saddle.
We study the generic case of a mixed phase space with regular and chaotic
dynamics. We find a hierarchy of fractal Weyl laws, one for each region of the
hierarchical decomposition of the chaotic phase-space component. This is based
on our observation of hierarchical resonance states localizing on these
regions. Numerically this is verified for the standard map and a hierarchical
model system.


title:
Spin instabilities of infinite nuclear matter and effective tensor
  interactions

abstract:
  We study the effects of the tensor force, present in modern effective
nucleon-nucleon interactions, in the spin instability of nuclear and neutron
matter. Stability conditions of the system against certain very low energy
excitation modes are expressed in terms of Landau parameters. It is shown that
in the spin case, the stability conditions are equivalent to the condition
derived from the spin susceptibility, which is obtained as the zero-frequency
and long-wavelength limit of the spin response function calculated in the
Random Phase Approximation. Zero-range forces of the Skyrme type and
finite-range forces of M3Y and Gogny type are analyzed. It is shown that for
the Skyrme forces considered, the tensor effects are sizeable, and tend to
increase the spin instability which appears at smaller densities than in the
case that the tensor is not taken into account. On the contrary, the tensor
contribution of finite range forces to the spin susceptibility is small or
negligible for both isospin channels of symmetric nuclear matter as well as for
neutron matter. A comparison with the spin susceptibility provided by realistic
interactions is also presented.


title:
Localized nonlinear functional equations and two sampling problems in
  signal processing

abstract:
  Let $1\le p\le \infty$. In this paper, we consider solving a nonlinear
functional equation $$f(x)=y,$$ where $x, y$ belong to $\ell^p$ and $f$ has
continuous bounded gradient in an inverse-closed subalgebra of ${\mathcal
B}(\ell^2)$, the Banach algebra of all bounded linear operators on the Hilbert
space $\ell^2$. We introduce strict monotonicity property for functions $f$ on
Banach spaces $\ell^p$ so that the above nonlinear functional equation is
solvable and the solution $x$ depends continuously on the given data $y$ in
$\ell^p$. We show that the Van-Cittert iteration converges in $\ell^p$ with
exponential rate and hence it could be used to locate the true solution of the
above nonlinear functional equation. We apply the above theory to handle two
problems in signal processing: nonlinear sampling termed with instantaneous
companding and subsequently average sampling; and local identification of
innovation positions and qualification of amplitudes of signals with finite
rate of innovation.


title: Resolution Algorithms and Deformations

abstract:
  An algorithm for resolution of singularities in characteristic zero is
described. It is expressed in terms of multi-ideals, that essentially are
defined as a finite sequence of pairs, each one consiting of a sheaf of ideals
and a positive integer. This approach is particularly simple and, as indicated
by some results shown here, it seems suitable for applications to a good theory
of simultaneous algorithmic resolution of singularities, specially for families
parametrized by the spectrum of an artinian ring.


title: The 1/N Expansion of Tensor Models Beyond Perturbation Theory

abstract:
  We analyze in full mathematical rigor the most general quartically perturbed
invariant probability measure for a random tensor. Using a version of the Loop
Vertex Expansion (which we call the mixed expansion) we show that the cumulants
write as explicit series in 1/N plus bounded rest terms. The mixed expansion
recasts the problem of determining the subleading corrections in 1/N into a
simple combinatorial problem of counting trees decorated by a finite number of
loop edges.
  As an aside, we use the mixed expansion to show that the (divergent)
perturbative expansion of the tensor models is Borel summable and to prove that
the cumulants respect an uniform scaling bound. In particular the quartically
perturbed measures fall, in the N to infinity limit, in the universality class
of Gaussian tensor models.


title: Measurement-based classical computation

abstract:
  Measurement-based quantum computation (MBQC) is a model of quantum
computation, in which computation proceeds via adaptive single qubit
measurements on a multi-qubit quantum state. It is computationally equivalent
to the circuit model. Unlike the circuit model, however, its classical analog
is little studied. Here we present a classical analog of MBQC whose
computational complexity presents a rich structure. To do so, we identify
uniform families of quantum computations (refining the circuits introduced by
Bremner, Jozsa and Shepherd in Proc. R. Soc. A 467, 459 (2011)) whose output is
likely hard to exactly simulate (sample) classically. We demonstrate that these
circuit families can be efficiently implemented in the MBQC model without
adaptive measurement, and thus can be achieved in a classical analog of MBQC
whose resource state is a probability distribution which has been created
quantum mechanically. Such states (by definition) violate no Bell inequality,
but nevertheless exhibit non-classicality when used as a computational resource
- an imprint of their quantum origin.


title: Andrews-Curtis and Nielsen equivalence relations on some infinite groups

abstract:
  The Andrews-Curtis conjecture asserts that, for a free group $F_n$ of rank
$n$ and a free basis $(x_1,...,x_n)$, any normally generating tuple
$(y_1,...,y_n)$ is Andrews-Curtis equivalent to $(x_1,...,x_n)$. This
equivalence corresponds to the actions of $\operatorname{Aut}F_n$ and of $F_n$
on normally generating $n$-tuples. The equivalence corresponding to the action
of $\operatorname{Aut}F_n$ on generating $n$-tuples is called Nielsen
equivalence. The conjecture for arbitrary finitely generated group has its own
importance to analyse potential counter-examples to the original conjecture. We
study the Andrews-Curtis and Nielsen equivalence in the class of finitely
generated groups for which every maximal subgroup is normal, including
nilpotent groups and Grigorchuk groups.


title:
On Normal Forms for Levi-flat hypersurfaces with an Isolated Line
  Singularity

abstract:
  We prove the existence of normal forms for some local real-analytic Levi-flat
hypersurfaces with an isolated line singularity. We also give sufficient
conditions for that a Levi-flat hypersurface with a complex line as singularity
to be a pullback of a real-analytic curve in C via a holomorphic function.


title: Diffeomorphism groups of balls and spheres

abstract:
  In this paper we discuss the relationship between groups of diffeomorphisms
of spheres and balls. We survey results of a topological nature and then
address the relationship as abstract (discrete) groups. We prove that the
identity component Diff_0(S^{2n-1}) of the group of smooth diffeomorphisms of
S^{2n+1} admits no nontrivial homomorphisms to the group of C^1 diffeomorphisms
of the ball B^m for any n and m. This result generalizes theorems of Ghys and
Herman.
  We also examine finitely generated subgroups of Diff_0(S^n) and produce an
example of a finitely generated torsion free group Gamma with an action on the
circle by smooth diffeomorphisms that does not extend to a C^1 action of Gamma
on the disc.


title: Genetic Soundtracks: Creative Matching of Audio to Video

abstract:
  The matching of the soundtrack in a movie or a video can have an enormous
influence in the message being conveyed and its impact, in the sense of
involvement and engagement, and ultimately in their aesthetic and entertainment
qualities. Art is often associated with creativity, implying the presence of
inspiration, originality and appropriateness. Evolutionary systems provides us
with the novelty, showing us new and subtly different solutions in every
generation, possibly stimulating the creativity of the human using the system.
In this paper, we present Genetic Soundtracks, an evolutionary approach to the
creative matching of audio to a video. It analyzes both media to extract
features based on their content, and adopts genetic algorithms, with the
purpose of truncating, combining and adjusting audio clips, to align and match
them with the video scenes.


title:
Identification of a high-velocity compact nebular filament 2.2 arcsec
  south of the Galactic Centre

abstract:
  The central parsec of the Milky Way is a very special region of our Galaxy;
it contains the supermassive black hole associated with Sgr A* as well as a
significant number of early-type stars and a complex structure of streamers of
neutral and ionized gas, within two parsecs from the centre, representing a
unique laboratory. We report the identification of a high velocity compact
nebular filament 2.2 arcsec south of Sgr A*. The structure extends over ~1
arcsec and presents a strong velocity gradient of ~200 km s^{-1} arcsec^{-1}.
The peak of maximum emission, seen in [Fe III] and He I lines, is located at
d{\alpha} = +0.20 +/- 0.06 arcsec and d{\delta} = -2.20 +/- 0.06 arcsec with
respect to Sgr A*. This position is near the star IRS 33N. The velocity at the
emission peak is Vr = -267 km s^{-1}. The filament has a position angle of PA =
115{\degr} +/- 10{\degr}, similar to that of the Bar and of the Eastern Arm at
that position. The peak position is located 0.7 arcsec north of the binary
X-ray and radio transient CXOGX J174540.0-290031, a low-mass X-ray binary with
an orbital period of 7.9 hr. The [Fe III] line emission is strong in the
filament and its vicinity. These lines are probably produced by shock heating
but we cannot exclude some X-ray photoionization from the low-mass X-ray
binary. Although we cannot rule out the idea of a compact nebular jet, we
interpret this filament as a possible shock between the Northern and the
Eastern Arm or between the Northern Arm and the mini-spiral "Bar".


title: A near-infrared catalogue of the Galactic novae in the VVV survey area

abstract:
  Near-IR data of Classical Novae contain useful information about the ejected
gas mass and the thermal emission by dust formed during eruption, and provide
independent methods to classify the objects according to the colour of their
progenitors, and the fading rate and features seen after eruption. The VISTA
Variables in the Via Lactea survey (VVV) is a near-IR ESO Public Survey mapping
the MW bulge and southern plane. Data taken during 2010-2011 covered the entire
area in the JHKs bands plus some epochs in Ks-band of the ongoing VVV
variability campaign. We used the novae list provided by VSX/AAVSO catalogue to
search for all objects within the VVV area. We used the VVV data to create a
near-IR catalogue of the known Galactic novae in the 562 sq.deg. area covered
by VVV. The VVV near-IR catalogue of novae contains JHKs photometry of 93
objects completed as of December 2012. We also checked in the ongoing VVV
variability campaign for the light-curves of novae that erupted in the last
years. VVV images can also be used to discover and study novae by searching for
the expanding shell. Since objects are seen at different distances and
reddening levels, the colour-magnitude and colour-colour diagrams show the
novae spread in magnitude as well as in colour. Dereddened colours and
reddening-free indices were used with caution and cannot be a good approach in
all cases since the distance and spectral features prevent more conclusive
results for some extreme objects. Light-curves for some recent novae are
presented. Thanks to its high spatial resolution in the near-IR, and large
Ks-range, the VVV survey can be a major contributor for the search and study of
novae in the most crowded and high-extinction regions of the Milky Way. The VVV
survey area contains ~35 of all known novae in the Galaxy.


title:
All electrically controlled quantum gates for single heavy hole spin
  qubits

abstract:
  In this paper, several nanodevices which realize basic single heavy hole
qubit operations are proposed and supported by time dependent self consistent
Poisson-Schr\"{o}dinger calculations using a four band heavy hole-light hole
model. In particular we propose a set of nanodevices which can act as Pauli X,
Y, Z quantum gates and as a gate that acts similar as a Hadamard gate (i.e. it
creates a balanced superposition of basis states but with an additional phase
factor) on the heavy hole spin qubit. We also present the design and simulation
of a gated semiconductor nanodevice which can realize an arbitrary sequence of
all these proposed single quantum logic gates. The proposed devices exploit the
self-focusing effect of the hole wave function which allows for guiding the
hole along a given path in the form of a stable soliton-like wave packet.
Thanks to the presence of the Dresselhaus spin orbit coupling, the motion of
the hole along a certain direction is equivalent to the application of an
effective magnetic field which induces in turn a coherent rotation of the heavy
hole spin. The hole motion and consequently the quantum logic operation is
initialized only by weak static voltages applied to the electrodes which cover
the nanodevice. The proposed gates allow for an all electric and ultrafast
(tens of picoseconds) heavy hole spin manipulation and give the possibility to
implement a scalable architecture of heavy hole spin qubits for quantum
computation applications.


title: Minimal Flavour Violation and Anomalous Top Decays

abstract:
  Top quark physics at the LHC may open a window to physics beyond the standard
model and even lead us to an understanding of the phenomenon "flavour".
However, current flavour data is a strong hint that no "new physics" with a
generic flavour structure can be expected in the TeV scale. In turn, if there
is "new physics" at the TeV scale, it must be "minimally flavour violating".
This has become a widely accepted assumption for "new physics" models. In this
paper we propose a model-independent scheme to test minimal flavour violation
for the anomalous charged $Wtq$, $q\in{d,s,b}$, and flavour-changing $Vtq$,
$q\in{u,c}$ and $V\in{Z,\gamma,g}$ couplings within an effective field theory
framework, i.e., in a model-independent way. We perform a spurion analysis of
our effective field theory approach and calculate the decay rates for the
anomalous top-quark decays in terms of the effective couplings for different
helicities by using a two-Higgs doublet model of type II, under the assumption
that the top-quark is produced at a high-energy collision and decays as a
quasi-free particle.


title:
Convex hull: Incremental variations on the Akl-Toussaint heuristics
  Simple, optimal and space-saving convex hull algorithms

abstract:
  Convex hulls are a fundamental geometric tool used in a number of algorithms.
A famous paper by Akl and Toussaint in 1978 described a way to reduce the
number of points involved in the computation, which is since known as the
Akl-Toussaint heuristics. This paper first studies what this heurstics really
represents in terms of reduction of points and demonstrates that the optimum
selection is reached using an octogon as the remaining number of points is in
O(sqrt(N)) rather than the usual O(N). Then it focuses on optimising the
overall computational efficiency in a convex hull computation. Although the
heuristics is usually used as a first step in computations one can obtain the
convex hull directly from the heuristics's basis. First a simple incremental
implementation is described, and if the number of characteristic points of the
Akl-Toussaint heuristics p is taken as a parametre the convex hull is then
computed in a O(N(p+h/p)) average complexity or O(Nh) asymptotic complexity.
Given the relative constant factor of 1/p however experimental results show
that this algorithm should be considered linear in average. Worst-case
complexity is in O(N^2) and space complexity is O(h) but could be O(1) if the
required output is the array of convex vertices's indexes. Then a remark on why
the basic incremental method should be preferred for average cases is made.
Finally an optimal linear algorithm both in average and worst-case and using a
minimal space complexity in O(sqrt(N)) in average (or O(1) if in-place
computation is allowed) is presented.


title: On finite rank Hankel operators

abstract:
  For self-adjoint Hankel operators of finite rank, we find an explicit formula
for the total multiplicity of their negative and positive spectra. We also show
that very strong perturbations, for example, a perturbation by the Carleman
operator, do not change the total number of negative eigenvalues of finite rank
Hankel operators.


title: About the congruence $\sum_{k=1}^n k^{f(n)} \equiv 0 \textrm{(mod n)} $

abstract:
  In this paper we characterize, in terms of the prime divisors of $n$, the
pairs $(k,n)$ for which $n$ divides $\sum_{j=1}^n j^{k}$. As an application, we
study the sets $\mathcal{M}_f :=\{n: n \textrm{divides} \sum_{j=1}^n j^{f(n)}
\}$ for some choices of $f$.


title:
New Variables for Classical and Quantum Gravity in all Dimensions V.
  Isolated Horizon Boundary Degrees of Freedom

abstract:
  In this paper, we generalise the treatment of isolated horizons in loop
quantum gravity, resulting in a Chern-Simons theory on the boundary in the
four-dimensional case, to non-distorted isolated horizons in 2(n+1)-dimensional
spacetimes. The key idea is to generalise the four-dimensional isolated horizon
boundary condition by using the Euler topological density of a spatial slice of
the black hole horizon as a measure of distortion. The resulting symplectic
structure on the horizon coincides with the one of higher-dimensional
SO(2(n+1))-Chern-Simons theory in terms of a Peldan-type hybrid connection and
resembles closely the usual treatment in 3+1 dimensions. We comment briefly on
a possible quantisation of the horizon theory. Here, some subtleties arise
since higher-dimensional non-Abelian Chern-Simons theory has local degrees of
freedom. However, when replacing the natural generalisation to higher
dimensions of the usual boundary condition by an equally natural stronger one,
it is conceivable that the problems originating from the local degrees of
freedom are avoided, thus possibly resulting in a finite entropy.


title:
New Interpretation of the Recent Result of AMS-02 and Multi-component
  Decaying Dark Matters with non-Abelian Discrete Flavor Symmetry

abstract:
  Recently the AMS-02 experiment has released the data of positron fraction
with much small statistical error. Because of the small error, it is no longer
easy to fit the data with a single dark matter for a fixed diffusion model and
dark matter profile. In this paper, we propose a new interpretation of the data
that it originates from decay of two dark matter. This interpretation gives a
rough threshold of the lighter DM component. When DM decays into leptons, the
positron fraction in the cosmic ray depends on the flavor of the final states,
and this is fixed by imposing non-Abelian discrete symmetry in our model. By
assuming two gauge-singlet fermionic decaying DM particles, we show that a
model with non-Abelian discrete flavor symmetry, e.g. $T_{13}$, can give a much
better fitting to the AMS-02 data compared with single dark matter scenario.
Few dimension six operators of universal leptonic decay of DM particles are
allowed in our model since its decay operators are constrained by the $T_{13}$
symmetry. We also show that the lepton masses and mixings are consistent with
current experimental data, due to the flavor symmetry.


title: Maps of Computer Science

abstract:
  We describe a practical approach for visual exploration of research papers.
Specifically, we use the titles of papers from the DBLP database to create what
we call maps of computer science (MoCS). Words and phrases from the paper
titles are the cities in the map, and countries are created based on word and
phrase similarity, calculated using co-occurrence. With the help of heatmaps,
we can visualize the profile of a particular conference or journal over the
base map. Similarly, heatmap profiles can be made of individual researchers or
groups such as a department. The visualization system also makes it possible to
change the data used to generate the base map. For example, a specific journal
or conference can be used to generate the base map and then the heatmap
overlays can be used to show the evolution of research topics in the field over
the years. As before, individual researchers or research groups profiles can be
visualized using heatmap overlays but this time over the journal or conference
base map. Finally, research papers or abstracts easily generate visual
abstracts giving a visual representation of the distribution of topics in the
paper. We outline a modular and extensible system for term extraction using
natural language processing techniques, and show the applicability of methods
of information retrieval to calculation of term similarity and creation of a
topic map. The system is available at mocs.cs.arizona.edu.


title: Modeling Nucleon Generalized Parton Distributions

abstract:
  We discuss building models for nucleon generalized parton distributions
(GPDs) H and E that are based on the formalism of double distributions (DDs).
We found that the usual "DD+D-term" construction should be amended by an extra
term, \xi E^1_+(x,\xi) built from the \alpha/\beta moment of the
  DD e(\beta,\alpha) that generates GPD E(x,\xi). Unlike the D-term, this
function has support in the whole -1 \leq x \leq 1 region, and in general does
not vanish at the border points |x|=\xi.


title:
Image Classification by Feature Dimension Reduction and Graph based
  Ranking

abstract:
  Dimensionality reduction (DR) of image features plays an important role in
image retrieval and classification tasks. Recently, two types of methods have
been proposed to improve the both the accuracy and efficiency for the
dimensionality reduction problem. One uses Non-negative matrix factorization
(NMF) to describe the image distribution on the space of base matrix. Another
one for dimension reduction trains a subspace projection matrix to project
original data space into some low-dimensional subspaces which have deep
architecture, so that the low-dimensional codes would be learned. At the same
time, the graph based similarity learning algorithm which tries to exploit
contextual information for improving the effectiveness of image rankings is
also proposed for image class and retrieval problem. In this paper, after above
two methods mentioned are utilized to reduce the high-dimensional features of
images respectively, we learn the graph based similarity for the image
classification problem. This paper compares the proposed approach with other
approaches on an image database.


title: Operators That Attain their Minima

abstract:
  In this paper we study the theory of operators on complex Hilbert spaces,
which attain their minimum in the unit sphere. We prove some important results
concerning the characterization of the N*, and also AN* operators, see
respectively Definition 1.1 and Definition 1.3. The injective property plays an
important role in these operators, and shall be established by these classes.


title:
Quantum limit of laser cooling in dispersively- and
  dissipatively-coupled optomechanical systems

abstract:
  Mechanical oscillators can be cooled by coupling them to an optical or
microwave cavity. Going beyond the standard quantum noise approach we find an
analytic expression for the steady-state phonon number in systems where the
position of the mechanical oscillator modulates the cavity frequency as well as
the cavity line width. We trace the origin for the quantum limit of cooling to
fluctuations in the optical force both at and away from the mechanical
frequency. Finally, we calculate the minimal phonon number for the different
types of coupling. Our study elucidates how to beneficially combine dispersive
and dissipative optomechanical coupling.


title:
Interpretation of the time delay in the ionization of Coulomb and
  two-center systems

abstract:
  We consider the time delay of electron detachment from a Coulomb center and
two-center systems in the process of ionization. It is shown that the
attosecond streaking, most usual method of time delay measure, can be formally
described by placing a virtual detector of the arrival time delay at a certain
distance from the center of the system. This approach allows derivation of a
simple formula for Coulomb-laser coupling that perfectly agrees with the
results of numerical solution of the time-dependent Schrodinger equation. The
dependence of the time delay upon the energy, the angular momentum projection,
and the azimuthal quantum number is studied for the ionization of molecular
hydrogen ion. Finally, we propose a physical interpretation of singularities,
arising when the formal expression for the time delay is applied to the
ionization of molecular hydrogen.


title:
Reconcile the AMS-02 positron fraction and Fermi-LAT/HESS total
  $e^{\pm}$ spectra by the primary electron spectrum hardening

abstract:
  The recently reported positron fraction up to $\sim 350$ GeV by AMS-02 seems
to have tension with the total electron/positron spectra detected by Fermi and
HESS, for either pulsar or dark matter annihilation/decay scenario as the
primary positron sources. In this work we will show that the tension will be
removed by an adjustment of the primary electron spectrum. If the primary
electron spectrum becomes harder above $\sim50$ GeV, similar as the cosmic ray
nuclei spectrum, the AMS-02 positron fraction and Fermi/HESS data can be well
fitted by both the pulsar and dark matter models. This result indicates that
there should be a common origin of the cosmic ray nuclei and the primary
electrons. Furthermore, this study also implies that the properties of the
extra sources derived from the fitting to the AMS-02 data should depend on the
form of background.


title: Efficient Wireless Security Through Jamming, Coding and Routing

abstract:
  There is a rich recent literature on how to assist secure communication
between a single transmitter and receiver at the physical layer of wireless
networks through techniques such as cooperative jamming. In this paper, we
consider how these single-hop physical layer security techniques can be
extended to multi-hop wireless networks and show how to augment physical layer
security techniques with higher layer network mechanisms such as coding and
routing. Specifically, we consider the secure minimum energy routing problem,
in which the objective is to compute a minimum energy path between two network
nodes subject to constraints on the end-to-end communication secrecy and
goodput over the path. This problem is formulated as a constrained optimization
of transmission power and link selection, which is proved to be NP-hard.
Nevertheless, we show that efficient algorithms exist to compute both exact and
approximate solutions for the problem. In particular, we develop an exact
solution of pseudo-polynomial complexity, as well as an epsilon-optimal
approximation of polynomial complexity. Simulation results are also provided to
show the utility of our algorithms and quantify their energy savings compared
to a combination of (standard) security-agnostic minimum energy routing and
physical layer security. In the simulated scenarios, we observe that, by
jointly optimizing link selection at the network layer and cooperative jamming
at the physical layer, our algorithms reduce the network energy consumption by
half.


title: Upper critical field of high quality single crystals of KFe$_2$As$_2$

abstract:
  Measurements of temperature-dependent in-plane resistivity, $\rho(T)$, were
used to determine the upper critical field and its anisotropy in high quality
single crystals of stoichiometric iron arsenide superconductor KFe$_2$As$_2$.
The crystals were characterized by residual resistivity ratio,
$\rho(300K)/\rho(0)$ up to 3000 and resistive transition midpoint temperature,
$T_c$=3.8 K, significantly higher than in previous studies on the same
material. We find increased $H_{c2}(T)$ for both directions of the magnetic
field, which scale with the increased $T_c$. This unusual linear $H_{c2}(T_c)$
scaling is not expected for orbital limiting mechanism of the upper critical
field in clean materials.


title:
Ground-state phase diagram and critical temperature of two-component
  Bose gases with Rashba spin-orbit coupling

abstract:
  Ground-state phase diagram of two-component Bose gases with Rashba spin-orbit
coupling is determined via a variational approach. A phase in which the fully
polarized condensate occupies zero momentum is identified. This zero-momentum
phase competes with the spin density wave phase when interspecies interaction
is stronger than intraspecies interaction, and the former one is always the
ground state for weak spin-orbit coupling. When the energies of these two
phases are close, there is a phase separation between them. At finite
temperature, such a zero-momentum condensation can be induced by a
ferromagnetic phase transition in normal state. The spontaneous spin
polarization removes the degeneracy of quasiparticles' energy minima, and
consequently the modified density of state accommodates a Bose condensation to
appear below a critical temperature.


title: The Bogomolov multiplier of rigid finite groups

abstract:
  The Bogomolov multiplier of a finite group $G$ is defined as the subgroup of
the Schur multiplier consisting of the cohomology classes vanishing after
restriction to all abelian subgroups of $G$. This invariant of $G$ plays an
important role in birational geometry of quotient spaces $V/G$. We show that in
many cases the vanishing of the Bogomolov multiplier is guaranteed by the
rigidity of $G$ in the sense that it has no outer class-preserving
automorphisms.


title: Recollements of Module Categories

abstract:
  We establish a correspondence between recollements of abelian categories up
to equivalence and certain TTF-triples. For a module category we show,
moreover, a correspondence with idempotent ideals, recovering a theorem of
Jans. Furthermore, we show that a recollement whose terms are module categories
is equivalent to one induced by an idempotent element, thus answering a
question by Kuhn.


title:
Reductive linear differential algebraic groups and the Galois groups of
  parameterized linear differential equations

abstract:
  We develop the representation theory for reductive linear differential
algebraic groups (LDAGs). In particular, we exhibit an explicit sharp upper
bound for orders of derivatives in differential representations of reductive
LDAGs, extending existing results, which were obtained for SL(2) in the case of
just one derivation. As an application of the above bound, we develop an
algorithm that tests whether the parameterized differential Galois group of a
system of linear differential equations is reductive and, if it is, calculates
it.


title: Symmetry-Aware Marginal Density Estimation

abstract:
  The Rao-Blackwell theorem is utilized to analyze and improve the scalability
of inference in large probabilistic models that exhibit symmetries. A novel
marginal density estimator is introduced and shown both analytically and
empirically to outperform standard estimators by several orders of magnitude.
The developed theory and algorithms apply to a broad class of probabilistic
models including statistical relational models considered not susceptible to
lifted probabilistic inference.


title: Locally exact modifications of numerical schemes

abstract:
  We present a new class of exponential integrators for ordinary differential
equations: locally exact modifications of known numerical schemes. Local
exactness means that they preserve the linearization of the original system at
every point. In particular, locally exact integrators preserve all fixed points
and are A-stable. We apply this approach to popular schemes including Euler
schemes, implicit midpoint rule and trapezoidal rule. We found locally exact
modifications of discrete gradient schemes (for symmetric discrete gradients
and coordinate increment discrete gradients) preserving their main geometric
property: exact conservation of the energy integral (for arbitrary
multidimensional Hamiltonian systems in canonical coordinates). Numerical
experiments for a 2-dimensional anharmonic oscillator show that locally exact
schemes have very good accuracy in the neighbourhood of stable equilibrium,
much higher than suggested by the order of new schemes (locally exact
modification sometimes increases the order but in many cases leaves it
unchanged).


title:
Gaussian Mixture Regression model with logistic weights, a penalized
  maximum likelihood approach

abstract:
  We wish to estimate conditional density using Gaussian Mixture Regression
model with logistic weights and means depending on the covariate. We aim at
selecting the number of components of this model as well as the other
parameters by a penalized maximum likelihood approach. We provide a lower bound
on penalty, proportional up to a logarithmic term to the dimension of each
model, that ensures an oracle inequality for our estimator. Our theoretical
analysis is supported by some numerical experiments.


title:
Linear stability of Perelman's $\nu$-entropy on symmetric spaces of
  compact type

abstract:
  Following Cao-Hamilton-Ilmanen, in this paper we study the linear stability
of Perelman's $\nu$-entropy on Einstein manifolds with positive Ricci
curvature. We observe the equivalence between the linear stability restricted
to the transversal traceless symmetric 2-tensors and the stability of Einstein
manifolds with respect to the Hilbert action. As a main application, we give a
full classification of linear stability of the $\nu$-entropy on symmetric
spaces of compact type. In particular, we exhibit many more linearly stable and
linearly unstable examples than previously known and also the first linearly
stable examples, other than the standard spheres, whose second variations are
negative definite.


title:
A Two-Dimensional Approach to Evaluate the Scientific Production of
  Countries (Case Study: The Basic Sciences)

abstract:
  The quantity and quality of scientific output of the topmost 50 countries in
the four basic sciences (agricultural and biological sciences, chemistry,
mathematics, and physics and astronomy) are studied in the period of the recent
12 years (1996-2007). In order to rank the countries, a novel two-dimensional
method is proposed, which is inspired by the H-index and other methods based on
quality and quantity measures. The countries data are represented in a
"quantity-quality diagram", and partitioned by a conventional statistical
algorithm (k-means), into three clusters, members of which are rather the same
in all of the basic sciences. The results offer a new perspective on the global
positions of countries with regards to their scientific output.


title: Some remarks on regular integers modulo $n$

abstract:
  An integer $k$ is called regular (mod $n$) if there exists an integer $x$
such that $k^2x\equiv k$ (mod $n$). This holds true if and only if $k$
possesses a weak order (mod $n$), i.e., there is an integer $m\ge 1$ such that
$k^{m+1} \equiv k$ (mod $n$). Let $\varrho(n)$ denote the number of regular
integers (mod $n$) in the set $\{1,2,\ldots,n\}$. This is an analogue of
Euler's $\phi$ function. We introduce the multidimensional generalization of
$\varrho$, which is the analogue of Jordan's function. We establish identities
for the power sums of regular integers (mod $n$) and for some other finite sums
and products over regular integers (mod $n$), involving the Bernoulli
polynomials, the Gamma function and the cyclotomic polynomials, among others.
We also deduce an analogue of Menon's identity and investigate the maximal
orders of certain related functions.


title:
Phyllosilicate Emission from Protoplanetary Disks: Is the Indirect
  Detection of Extrasolar Water Possible?

abstract:
  Phyllosilicates are hydrous minerals formed by interaction between rock and
liquid water and are commonly found in meteorites originating in the asteroid
belt. Collisions between asteroids contribute to zodiacal dust, which therefore
reasonably could include phyllosilicates. Collisions between planetesimals in
protoplanetary disks may also produce dust containing phyllosilicates. These
minerals possess characteristic emission features in the mid-infrared and could
be detectable in extrasolar protoplanetary disks. Here we determine whether
phyllosilicates in protoplanetary disks are detectable in the infrared using
instruments such as those on board the Spitzer Space Telescope and SOFIA
(Stratospheric Observatory for Infrared Astronomy). We calculate opacities for
the phyllosilicates most common in meteorites and compute the emission of
radiation from a protoplanetary disk using a 2-layer radiative transfer model.
We find that phyllosilicates present at the 3% level lead to observationally
significant differences in disk spectra, and should therefore be detectable
using infrared observations and spectral modeling. Detection of phyllosilicates
in a protoplanetary disk would be diagnostic of liquid water in planetesimals
in that disk and would demonstrate similarity to our own Solar System. We also
discuss use of phyllosilicate emission to test the "waterworlds" hypothesis,
which proposes that liquid water in planetesimals should correlate with the
inventory of short-lived radionuclides in planetary systems, especially 26Al.


title: Physics of Electrolytic Gas Evolution

abstract:
  A brief analysis of the physics and effects of electrolytic gas evolution is
presented. Aspects considered include bubble nucleation, growth, and
detachment, enhancement of mass and heat transfer, and decrease of apparent
electrical conductivity of bubble containing electrolytes. This analysis is
mainly oriented to hydrogen/oxygen evolving electrodes.


title: Photon emission in neutral current interactions with nucleons and nuclei

abstract:
  We report on our study of photon emission induced by Enu ~ 1 GeV
(anti)neutrino neutral current interactions with nucleons and nuclei. This
process is an important background for nu_e appearance oscillation experiments.
At the relevant energies, the reaction is dominated by the excitation of the
Delta (1232) resonance but there are also non-resonant contributions that,
close to threshold, are fully determined by the effective chiral Lagrangian of
strong interactions. We have obtained differential and integrated cross section
for the (anti)neutrino-nucleon scattering and compare them with previous
results. Furthermore, we have extended the model to nuclear targets taking into
account Fermi motion, Pauli blocking and the in-medium modifications of the
Delta properties. This study is important in order to reduce systematic effects
in neutrino oscillation experiments.


title: Propeller outflows from an MRI disc

abstract:
  We present the results of axisymmetric simulations of MRI-driven accretion
onto a rapidly rotating, magnetized star accreting in the propeller regime. The
stellar magnetosphere corotates with the star, forming a centrifugal barrier at
the disc-magnetosphere boundary which inhibits matter accretion onto the star.
Instead, the disc matter accumulates at the disc-magnetosphere interface and
slowly diffuses into the inner magnetosphere where it picks up angular momentum
and is quickly ejected from the system as an outflow. Due to the interaction of
the matter with the magnetosphere, this wind is discontinuous and is launched
as discrete plasmoids. If the ejection rate is lower than the disc accretion
rate, the matter accumulates at the disc-magnetosphere boundary faster than it
can be ejected. In this case, accretion onto the star proceeds through the
episodic accretion instability in which episodes of matter accumulation are
followed by simultaneous accretion and ejection. During the accretion phase of
this instability in which matter flows onto the star in funnel streams, we
observe a corresponding rise in the outflow rate. Both the accretion and
ejection processes observed in our simulations are highly non-stationary. The
stars undergo strong spin-down due to the coupling of the stellar field with
the disc and corona and we measure the spin-down timescales of around 1 Myr for
a typical CTTS in the propeller regime.


title:
Vacuum Varieties, Holomorphic Bundles and Complex Structure
  Stabilization in Heterotic Theories

abstract:
  We discuss the use of gauge fields to stabilize complex structure moduli in
Calabi-Yau three-fold compactifications of heterotic string and M-theory. The
requirement that the gauge fields in such models preserve supersymmetry leads
to a complicated landscape of vacua in complex structure moduli space. We
develop methods to systematically map out this multi-branched vacuum space, in
a computable and explicit manner. In analyzing the resulting vacua, it is found
that the associated Calabi-Yau three-folds are sometimes stabilized at a value
of complex structure resulting in a singular compactification manifold. We
describe how it is possible to resolve these singularities, in some cases,
while maintaining computational control over the moduli stabilization
mechanism. The discussion is illustrated throughout the paper with explicit
worked examples.


title: From state integrals to q-series

abstract:
  It is well-known to the experts that multi-dimensional state integrals of
products of Faddeev's quantum dilogarithm which arise in Quantum Topology can
be written as finite sums of products of basic hypergeometric series in
q=e^{2\pi i\tau} and \tilde{q}=e^{-2\pi i/\tau}. We illustrate this fact by
giving a detailed proof for a family of one-dimensional integrals which
includes state-integral invariants of 4_1 and 5_2 knots.


title: Partial regularity for singular solutions to the Monge-Ampere equation

abstract:
  We prove that solutions to the Monge-Ampere inequality $$\det D^2u \geq 1$$
in $\mathbb{R}^n$ are strictly convex away from a singular set of Hausdorff
$n-1$ dimensional measure zero. Furthermore, we show this is optimal by
constructing solutions to $\det D^2u = 1$ with singular set of Hausdorff
dimension as close as we like to $n-1$. As a consequence we obtain $W^{2,1}$
regularity for the Monge-Ampere equation with bounded right hand side and
unique continuation for the Monge-Ampere equation with sufficiently regular
right hand side.


title: Tracking the Tracker from its Passive Sonar ML-PDA Estimates

abstract:
  Target motion analysis with wideband passive sonar has received much
attention. Maximum likelihood probabilistic data-association (ML-PDA)
represents an asymptotically efficient estimator for deterministic target
motion, and is especially well-suited for low-observable targets; the results
presented here apply to situations with higher signal to noise ratio as well,
including of course the situation of a deterministic target observed via clean
measurements without false alarms or missed detections. Here we study the
inverse problem, namely, how to identify the observing platform (following a
two-leg motion model) from the results of the target estimation process, i.e.
the estimated target state and the Fisher information matrix, quantities we
assume an eavesdropper might intercept. We tackle the problem and we present
observability properties, with supporting simulation results.


title:
Demonstration of Low Emittance in the Cornell Energy Recovery Linac
  Injector Prototype

abstract:
  We present a detailed study of the six-dimensional phase space of the
electron beam produced by the Cornell Energy Recovery Linac Photoinjector, a
high-brightness, high repetition rate (1.3 GHz) DC photoemission source
designed to drive a hard x-ray energy recovery linac (ERL). A complete
simulation model of the injector has been constructed, verified by measurement,
and optimized. Both the horizontal and vertical 2D transverse phase spaces, as
well as the time-resolved (sliced) horizontal phase space, were simulated and
directly measured at the end of the injector for 19 pC and 77 pC bunches at
roughly 8 MeV. These bunch charges were chosen because they correspond to 25 mA
and 100 mA average current if operating at the full 1.3 GHz repetition rate.
The resulting 90% normalized transverse emittances for 19 (77) pC/bunch were
0.23 +/- 0.02 (0.51 +/- 0.04) microns in the horizontal plane, and 0.14 +/-
0.01 (0.29 +/- 0.02) microns in the vertical plane, respectively. These
emittances were measured with a corresponding bunch length of 2.1 +/- 0.1 (3.0
+/- 0.2) ps, respectively. In each case the rms momentum spread was determined
to be on the order of 1e-3. Excellent overall agreement between measurement and
simulation has been demonstrated. Using the emittances and bunch length
measured at 19 pC/bunch, we estimate the electron beam quality in a 1.3 GHz, 5
GeV hard x-ray ERL to be at least a factor of 20 times better than that of
existing storage rings when the rms energy spread of each device is considered.
These results represent a milestone for the field of high-brightness,
high-current photoinjectors.


title: Spectral dimension and diffusion in multi-scale spacetimes

abstract:
  Starting from a classical-mechanics stochastic model encoded in a Langevin
equation, we derive the natural diffusion equation associated with three
classes of multiscale spacetimes (with weighted, ordinary, and "q-Poincar\'e"
symmetries). As a consistency check, the same result is obtained by inspecting
the propagation of a quantum-mechanical particle in a disordered environment.
The solution of the diffusion equation displays a time-dependent diffusion
coefficient and represents a probabilistic process, classified according to the
statistics of the noise in the Langevin equation. We thus illustrate, also with
pictorial aids, how spacetime geometries can be more completely catalogued not
only through their Hausdorff and spectral dimension, but also by a stochastic
process. The spectral dimension of multifractional spacetimes is then computed
and compared with what was found in previous studies, where a diffusion
equation with some open issues was assumed rather than derived. These issues
are here discussed and solved, and they point towards the model with
q-Poincar\'e symmetries.

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


title: Attractive Inverse Square Potential, U(1) Gauge, and Winding Transitions

abstract:
  The inverse square potential arises in a variety of different quantum
phenomena, yet notoriously it must be handled with care: it suffers from
pathologies rooted in the mathematical foundations of quantum mechanics. We
show that its recently studied conformality-breaking corresponds to an
infinitely smooth winding-unwinding topological transition for the {\it
classical} statistical mechanics of a one-dimensional system: this describes
the the tangling/untangling of floppy polymers under a biasing torque. When the
ratio between torque and temperature exceeds a critical value the polymer
undergoes tangled oscillations, with an extensive winding number. At lower
torque or higher temperature the winding number per unit length is zero.
Approaching criticality, the correlation length of the order parameter---the
extensive winding number---follows a Kosterlitz-Thouless type law. The model is
described by the Wilson line of a (0+1) $U(1)$ gauge theory, and applies to the
tangling/untangling of floppy polymers and to the winding/diffusing kinetics in
diffusion-convection-reactions.


title: Is Shafer General Bayes?

abstract:
  This paper examines the relationship between Shafer's belief functions and
convex sets of probability distributions. Kyburg's (1986) result showed that
belief function models form a subset of the class of closed convex probability
distributions. This paper emphasizes the importance of Kyburg's result by
looking at simple examples involving Bernoulli trials. Furthermore, it is shown
that many convex sets of probability distributions generate the same belief
function in the sense that they support the same lower and upper values. This
has implications for a decision theoretic extension. Dempster's rule of
combination is also compared with Bayes' rule of conditioning.


title: Modifiable Combining Functions

abstract:
  Modifiable combining functions are a synthesis of two common approaches to
combining evidence. They offer many of the advantages of these approaches and
avoid some disadvantages. Because they facilitate the acquisition,
representation, explanation, and modification of knowledge about combinations
of evidence, they are proposed as a tool for knowledge engineers who build
systems that reason under uncertainty, not as a normative theory of evidence.


title: Dempster-Shafer vs. Probabilistic Logic

abstract:
  The combination of evidence in Dempster-Shafer theory is compared with the
combination of evidence in probabilistic logic. Sufficient conditions are
stated for these two methods to agree. It is then shown that these conditions
are minimal in the sense that disagreement can occur when any one of them is
removed. An example is given in which the traditional assumption of conditional
independence of evidence on hypotheses holds and a uniform prior is assumed,
but probabilistic logic and Dempster's rule give radically different results
for the combination of two evidence events.


title: Higher Order Probabilities

abstract:
  A number of writers have supposed that for the full specification of belief,
higher order probabilities are required. Some have even supposed that there may
be an unending sequence of higher order probabilities of probabilities of
probabilities.... In the present paper we show that higher order probabilities
can always be replaced by the marginal distributions of joint probability
distributions. We consider both the case in which higher order probabilities
are of the same sort as lower order probabilities and that in which higher
order probabilities are distinct in character, as when lower order
probabilities are construed as frequencies and higher order probabilities are
construed as subjective degrees of belief. In neither case do higher order
probabilities appear to offer any advantages, either conceptually or
computationally.


title:
Belief in Belief Functions: An Examination of Shafer's Canonical
  Examples

abstract:
  In the canonical examples underlying Shafer-Dempster theory, beliefs over the
hypotheses of interest are derived from a probability model for a set of
auxiliary hypotheses. Beliefs are derived via a compatibility relation
connecting the auxiliary hypotheses to subsets of the primary hypotheses. A
belief function differs from a Bayesian probability model in that one does not
condition on those parts of the evidence for which no probabilities are
specified. The significance of this difference in conditioning assumptions is
illustrated with two examples giving rise to identical belief functions but
different Bayesian probability distributions.


title: Do We Need Higher-Order Probabilities and, If So, What Do They Mean?

abstract:
  The apparent failure of individual probabilistic expressions to distinguish
uncertainty about truths from uncertainty about probabilistic assessments have
prompted researchers to seek formalisms where the two types of uncertainties
are given notational distinction. This paper demonstrates that the desired
distinction is already a built-in feature of classical probabilistic models,
thus, specialized notations are unnecessary.