title: The universal semigroup of a $\Gamma$-semigroup

abstract:
  Given a $\Gamma$-semigroup $S$, we construct a semigroup $\Sigma$ in such a
way that one sided ideals and quasi-ideals of $S$ can be regarded as one sided
ideals and quasi-ideals respectively of $\Sigma$. This correspondence and other
properties of $\Sigma$, allow us to obtain several results for $S$ without
having the need to work directly with it, but solely employing well known
results of semigroup theory. For example, we obtain the Green's theorem for
$\Gamma$-semigroups found in \cite{PT}, as a corollary of the usual Green's
theorem in semigroups. Also we prove that, if $S$ is a $\Gamma$-semigroup and
$\gamma_{0} \in \Gamma$ such that $S_{\gamma_{0}}$ is a completely simple
semigroup, then for every $\gamma \in \Gamma$, $S_{\gamma}$ is completely
simple too.


title: Motifs in Triadic Random Graphs based on Steiner Triple Systems

abstract:
  Conventionally, pairwise relationships between nodes are considered to be the
fundamental building blocks of complex networks. However, over the last decade
the overabundance of certain sub-network patterns, so called motifs, has
attracted high attention. It has been hypothesized, these motifs, instead of
links, serve as the building blocks of network structures.
  Although the relation between a network's topology and the general properties
of the system, such as its function, its robustness against perturbations, or
its efficiency in spreading information is the central theme of network
science, there is still a lack of sound generative models needed for testing
the functional role of subgraph motifs. Our work aims to overcome this
limitation.
  We employ the framework of exponential random graphs (ERGMs) to define novel
models based on triadic substructures. The fact that only a small portion of
triads can actually be set independently poses a challenge for the formulation
of such models. To overcome this obstacle we use Steiner Triple Systems (STS).
These are partitions of sets of nodes into pair-disjoint triads, which thus can
be specified independently. Combining the concepts of ERGMs and STS, we suggest
novel generative models capable of generating ensembles of networks with
non-trivial triadic Z-score profiles. Further, we discover inevitable
correlations between the abundance of triad patterns, which occur solely for
statistical reasons and need to be taken into account when discussing the
functional implications of motif statistics. Moreover, we calculate the degree
distributions of our triadic random graphs analytically.

categories: physics.soc-ph cond-mat.stat-mech cs.SI physics.data-an


title: The detectability of habitable exomoons with Kepler

abstract:
  In this paper, the detectability of habitable exomoons orbiting around giant
planets in M-dwarf systems using Transit Timing Variations (TTVs) and Transit
Timing Durations (TDVs) with Kepler-class photometry is investigated. Light
curves of systems with various configurations were simulated around M-dwarf
hosts of mass 0.5 Msun and radius 0.55 Rsun. Jupiter-like giant planets which
offer the best potential for hosting habitable exomoons were considered with
rocky super-Earth-mass moons. The detectability is measured by using the
phase-correlation between TTV and TDV signals. Since the TDV signal is
typically weaker than the TTV signal, confirmation of an exomoon detection will
depend on being able to detect a TDV signal. We find that exomoons around
planets orbiting within the habitable zone of an M-dwarf host star can produce
both detectable TTV and TDV signatures with Kepler-class photometry. While
aliasing between the planet period and moon period may hinder exomoon
detection, we also find some strong correlation signatures in our simulation
(eg. correlation: >0.7) which would provide convincing exomoon signatures. With
the addition of red noise stellar variability, correlations generally weaken.
However simulated examples with planet masses less than around 25 Mearth, moons
of mass 8-10 Mearth and specific values of planet and moon periods still yield
detectable correlation in 25-50% of cases. Our simulation indicates that Kepler
provides one of the best available opportunities for exomoon detection.


title: Generalized (2+1) dimensional black hole by Noether symmetry

abstract:
  We use the Noether symmetry approach to find $f(R)$ theory of $(2+1)$
dimensional gravity and $(2+1)$ dimensional black hole solution consistent with
this $f(R)$ gravity and the associated symmetry. We obtain $f({R})=D_1
R({n}/{n+1})({R}/{K})^{1/n}+D_2 R+D_3$, where the constant term $D_3$ plays no
dynamical role. Then, we find general spherically symmetric solution for this
$f(R)$ gravity which is potentially capable of being as a black hole. Moreover,
in the special case $D_1=0, D_2={1}$, namely $f(R)=R+D_3$, we obtain a
generalized BTZ black hole which, other than common conserved charges $m$ and
$J$, contains a new conserved charge Q. It is shown that this conserved charge
corresponds to the freedom in the choice of the constant term $D_3$ and
represents symmetry of the action under the transformation $R \rightarrow
R'=R+D_3$ along the killing vector $\partial_{R}$. The ordinary BTZ black hole
is obtained as the special case where $D_3$ is {\it fixed} to be proportional
to the infinitesimal cosmological constant and consequently the symmetry is
broken via Q=0. We study the thermodynamics of the generalized BTZ black hole
and show that its entropy can be described by the Cardy-Verlinde formula.


title:
Field-angle dependence of the quasiparticle scattering inside a vortex
  core in unconventional superconductors

abstract:
  We theoretically investigate the quasiparticle scattering rate $\varGamma$
inside a vortex core in the existence of non-magnetic impurities distributed
randomly in a superconductor. We show that the dependence of $\varGamma$ on the
magnetic field direction is sensitive to the sign of the pair potential. The
behavior of $\varGamma$ is quite different between an s-wave and a d-wave pair
potential, where these are assumed to have the same amplitude anisotropy, but a
sign change only for the d-wave one. It is suggested that measurements of the
microwave surface impedance with changing applied-field directions would be
used for the phase-sensitive identification of pairing symmetry.


title: Whitney extension operators without loss of derivatives

abstract:
  For a compact set, we characterize the existence of a linear extension
operator E for the space of Whitney jets without loss of derivatives, that is,
E satisfies the best possible continuity estimates: The supremum of all partial
derivatives up to order n of E(f) is less or equal than a constant times the
n-th Whitney norm of f. The characterization is a surprisingly simple purely
geometric condition telling in a way that at all its points, the set is big
enough in all directions.


title:
Phase transitions, hysteresis, and hyperbolicity for self-organized
  alignment dynamics

abstract:
  We provide a complete and rigorous description of phase transitions for
kinetic models of self-propelled particles interacting through alignment. These
models exhibit a competition between alignment and noise. Both the alignment
frequency and noise intensity depend on a measure of the local alignment. We
show that, in the spatially homogeneous case, the phase transition features
(number and nature of equilibria, stability, convergence rate, phase diagram,
hysteresis) are totally encoded in how the ratio between the alignment and
noise intensities depend on the local alignment. In the spatially inhomogeneous
case, we derive the macroscopic models associated to the stable equilibria and
classify their hyperbolicity according to the same function.


title:
The elementary closure of the class Nr_nCA_m for m\geq n+1 is not
  finitely axiomatizable, futhermore for any finite k\geq 1, there is A\in
  Nr_{\omega}CA_{\omeg+k}that is not SNr_{\omega}CA_{\omega+k+1}

abstract:
  We show that for 1<n<m, the class Nr_nCA_m known to be non-elementary is
pseudo elementary. When n and m are finite we use a two sorted theory, when n
is finite and m infinite we use a three sorted one, and finally when both are
infinite we use a four sorted defining theory. Our non finite axiomatizability
result, follows from the fact that for 2<n<m, and any r\in \omega there exists
a finite (Monk like) algebra C(m,n,r), such that C(m,n,r)\in Nr_nCA_m
C(m,n,r)\notin SNr_nCA_{m+1}, and any non trivial ultraproduct on r of such
algebras in in ElNr_nCA_m. Finally we use such algebras, to show that for
infinite dimension there is an algebra A\in Nr_{\alpha}\CA_{\apha+k} that is
not in SNr_{\alpha}CA_{\alpha+k+1} (\alpha an infinite ordinal).


title: Logics to which the class of neat reducts is sensitive to

abstract:
  Let L be a quantifier predicate logic. Let K be a class of algebras. We say
that K is sensitive to L, if there is an algebra in K, that is L interpretable
into an another algebra, and this latter algebra is elementary equivalent to an
algebra not in K. (In particular, if L is L_{\omega,\omega}, this means that K
is not elementary). We show that the class of neat reducts of every dimension
is sensitive to quantifier free predicate logics with infinitary conjunctions;
for finite dimensions, we do not need infinite conjunctions.


title: Results on Polyadic Algebras

abstract:
  While every polyadic algebra ($\PA$) of dimension 2 is representable, we show
that not every atomic polyadic algebra of dimension two is completely
representable; though the class is elementary. Using higly involved
constructions of Hirsch and Hodkinson we show that it is not elementary for
higher dimensions a result that, to the best of our knowledge, though easily
destilled from the literature, was never published. We give a uniform flexible
way of constructing weak atom structures that are not strong, and we discuss
the possibility of extending such result to infinite dimensions. Finally we
show that for any finite $n>1$, there are two $n$ dimensional polyadic atom
structures $\At_1$ and $\At_2$ that are $L_{\infty,\omega}$ equivalent, and
there exist atomic $\A,\B\in \PA_n$, such that $\At\A=\At_1$ and $\At\B=
\At_2$, $\A\in \Nr_n\PA_{\omega}$ and $\B\notin \Nr_n\PA_{n+1}$. This can also
be done for infinite dimensions (but we omit the proof)


title:
Semi-metal-insulator transition on the surface of a topological
  insulator with in-plane magnetization

abstract:
  A thin film of ferromagnetically ordered material proximate to the surface of
a three-dimensional topological insulator explicitly breaks the time-reversal
symmetry of the surface states. For an out-of-plane ferromagnetic order
parameter on the surface, the parity is also broken, since the Dirac fermions
become massive. This leads in turn to the generation of a topological
Chern-Simons term by quantum fluctuations. On the other hand, for an in-plane
magnetization the surface states remain gapless for the non-interacting Dirac
fermions. In this work we study the possibility of spontaneous breaking of
parity due to a dynamical gap generation on the surface in the presence of a
local, Hubbard-like, interaction of strength $g$ between the Dirac fermions. A
gap and a Chern-Simons term are generated for $g$ larger than some critical
value, g_c, provided the number of Dirac fermions, $N$, is odd. For an even
number of Dirac fermions the masses are generated in pairs having opposite
signs, and no Chern-Simons term is generated. We discuss our results in the
context of recent experiments in EuS/Bi_2Se_3 heterostructures.


title: Mod-phi convergence I: Normality zones and precise deviations

abstract:
  In this paper, we use the framework of mod-$\phi$ convergence to prove
precise large or moderate deviations for quite general sequences of real valued
random variables $(X_{n})_{n \in \mathbb{N}}$, which can be lattice or
non-lattice distributed. We establish precise estimates of the fluctuations
$P[X_{n} \in t_{n}B]$, instead of the usual estimates for the rate of
exponential decay $\log( P[X_{n}\in t_{n}B])$. Our approach provides us with a
systematic way to characterise the normality zone, that is the zone in which
the Gaussian approximation for the tails is still valid. Besides, the residue
function measures the extent to which this approximation fails to hold at the
edge of the normality zone.
  The first sections of the article are devoted to a proof of these abstract
results and comparisons with existing results. We then propose new examples
covered by this theory and coming from various areas of mathematics: classical
probability theory, number theory (statistics of additive arithmetic
functions), combinatorics (statistics of random permutations), random matrix
theory (characteristic polynomials of random matrices in compact Lie groups),
graph theory (number of subgraphs in a random Erd\H{o}s-R\'enyi graph), and
non-commutative probability theory (asymptotics of random character values of
symmetric groups). In particular, we complete our theory of precise deviations
by a concrete method of cumulants and dependency graphs, which applies to many
examples of sums of "weakly dependent" random variables. The large number as
well as the variety of examples hint at a universality class for second order
fluctuations.


title: How does group interaction and its severance affect life expectancy?

abstract:
  The phenomenon of apoptosis observed in cell cultures consists in the fact
that unless cells permanently receive a "Stay alive" signal from their
neighbors, they are bound to die. A natural question is whether manifestations
of this apoptosis paradigm can also be observed in other organizations of
living organisms. In this paper we report results from a two-year long campaign
of experiments on three species of ants and one species of (tephritid) fruit
flies. In these experiments individuals were separated from their colony and
kept in isolation either alone or in groups of 10 individuals. The overall
conclusion is that "singles" have a shorter life expectancy than individuals in
the groups of 10. This observation holds for ants as well as for fruit flies.
The paper also provides compelling evidence of a similar effect in married
versus unmarried (i.e. single, widowed or divorced) people. A natural question
concerns the dynamic of the transition between the two regimes. Observation
suggests an abrupt (rather than smooth) transition and this conclusion seems to
hold for ants, fruit flies and humans as well. We call it a shock transition.
In addition, for red fire ants Solenopsis invicta, it was observed that
individuals in groups of 10 that also comprise one queen, die much faster than
those in similar groups without queens. The paper also examines the
corresponding survivorship curves from the perspective of the standard
classification into 3 types. The survivorship curves of ants (whether single or
in groups of 10) are found to be of type II whereas those of the fruit fly
Bactrocera dorsalis are rather of type III. In this connection it is recalled
that the survivorship curve of the fruit fly Drosophila melanogaster is of type
I, i.e. of same type as for humans.


title: Inferring Fences in a Concurrent Program Using SC proof of Correctness

abstract:
  Most proof systems for concurrent programs assume the underlying memory model
to be sequentially consistent (SC), an assumption which does not hold for
modern multicore processors. These processors, for performance reasons,
implement relaxed memory models. As a result of this relaxation a program,
proved correct on the SC memory model, might execute incorrectly. To ensure its
correctness under relaxation, fence instructions are inserted in the code. In
this paper we show that the SC proof of correctness of an algorithm, carried
out in the proof system of [Sou84], identifies per-thread instruction orderings
sufficient for this SC proof. Further, to correctly execute this algorithm on
an underlying relaxed memory model it is sufficient to respect only these
orderings by inserting fence instructions.


title: A compactness theorem in Finsler geometry

abstract:
  Let (M.F) be a complete Finsler manifold and P be a minimal and compact
submanifold of M. Ric_k(x), x in M is a differential invariant that
interpolates between the flag curvature and the Ricci curvature. We prove that
if on any geodesic c(t) emanating orthogonally from P we have
\int_{0}^{\infty}\mathbf{Ric}_{k}(t)>0, then M is compact.


title:
S-duality of tree-level S-matrix elements in D$_3$-brane effective
  action

abstract:
  Recently it has been speculated that the S-matrix elements on the world
volume of D$_3$-branes should satisfy the ward identity corresponding to the
S-duality transformations. For a single brane and in the low energy limit, this
indicates that in the abelian Dirac-Born-Indeld-Chern-Simons theory the
combination of contact terms and tree-level massless poles in an $n$-point
function should satisfy the S-duality. In this paper we examine in details the
S-matrix element of three gauge bosons and one two-form and the S-matrix
element of six gauge bosons in favor of the above proposal.


title:
The two regimes of the cosmic sSFR evolution are due to spheroids and
  discs

abstract:
  This paper aims at explaining the two phases in the observed specific star
formation rate (sSFR), namely the high (>3/Gyr) values at z>2 and the smooth
decrease since z=2. In order to do this, we compare to observations the
specific star formation rate evolution predicted by well calibrated models of
chemical evolution for elliptical and spiral galaxies, using the additional
constraints on the mean stellar ages of these galaxies (at a given mass). We
can conclude that the two phases of the sSFR evolution across cosmic time are
due to different populations of galaxies. At z>2 the contribution comes from
spheroids: the progenitors of present-day massive ellipticals (which feature
the highest sSFR) as well as halos and bulges in spirals (which contribute with
average and lower-than-average sSFR). In each single galaxy the sSFR decreases
rapidly and the star formation stops in <1 Gyr. However the combination of
different generations of ellipticals in formation might result in an apparent
lack of strong evolution of the sSFR (averaged over a population) at high
redshift. The z<2 decrease is due to the slow evolution of the gas fraction in
discs, modulated by the gas accretion history and regulated by the Schmidt law.
The Milky Way makes no exception to this behaviour.


title:
General classification of charged test particle circular orbits in
  Reissner--Nordstr\"om spacetime

abstract:
  We investigate charged particles circular motion in the gravitational field
of a charged mass distribution described by the Reissner-Nordstr\"om spacetime.
We introduce a set of independent parameters completely characterizing the
different spatial regions in which circular motion is allowed. We provide most
complete classification of circular orbits for different sets of particle and
source charge-to-mass ratios. We study both black holes and naked singularities
and show that the behavior of charged particles depend drastically on the type
of source. Our analysis shows in an alternative manner that the behavior of
circular orbits can in principle be used to distinguish between black holes and
naked singularities. From this analysis, special limiting values for the
dimensionless charge of black hole and naked singularity emerge, namely,
Q/M=1/2, $Q/M=\sqrt{13}/5$ and $Q/M=\sqrt{2/3}$ for the black hole case and
Q/M=1, $Q/M=5/ (2 \sqrt{6})$, $Q/M=3 \sqrt{6}/7$, and finally $Q/M= \sqrt{9/8}$
for the naked singularity case. Similarly and surprisingly, analogue limits
emerge for the orbiting particles charge-to-mass ratio $\epsilon$, for positive
charges $\epsilon=1$, $\epsilon=2$ and $\epsilon=M/Q$. These limits play an
important role in the study of the coupled electromagnetic and gravitational
interactions, and the investigation of the role of the charge in the
gravitational collapse of compact objects.


title: Very-High-Precision Calculations in Physics

abstract:
  This is the introductory part of my Ph.D thesis, defended at the Faculty of
Science and Technology, NTNU on December 10, 2012.


title:
Optimal execution comparison across risks and dynamics, with solutions
  for displaced diffusions

abstract:
  We solve a version of the optimal trade execution problem when the mid asset
price follows a displaced diffusion. Optimal strategies in the adapted class
under various risk criteria, namely value-at-risk, expected shortfall and a new
criterion called "squared asset expectation" (SAE), related to a version of the
cost variance measure, are derived and compared. It is well known that
displaced diffusions (DD) exhibit dynamics which are in-between arithmetic
Brownian motions (ABM) and geometric Brownian motions (GBM) depending of the
choice of the shift parameter. Furthermore, DD allows for changes in the
support of the mid asset price distribution, allowing one to include a minimum
permitted value for the mid price, either positive or negative. We study the
dependence of the optimal solution on the choice of the risk aversion
criterion. Optimal solutions across criteria and asset dynamics are comparable
although differences are not negligible for high levels of risk aversion and
low market impact assets. This is illustrated with numerical examples.


title: The CASTOR calorimeter at the CMS experiment

abstract:
  The CASTOR Calorimeter at the CMS experiment is an electromagnetic/hadronic
calorimeter which covers the very forward region of the detector (-6.6 < eta <
-5.2). CASTOR is a Cherenkov sampling calorimeter, consisting of quartz and
tungsten plates, with an overall depth of 10 interaction lengths, able to
detect penetrating cascade particles. It is segmented in 16 transversal and 14
longitudinal sections. Surrounding the beam pipe, its design is determined by
space constraints and restricted to materials which tolerate a high radiation
level. In this presentation we report on the operational experience and
measurements with the CASTOR calorimeter during the 2010 data taking at the
LHC, with proton-proton and heavy ion collisions. An overview of the broad
physics program which can be accessed with CASTOR, as well as the status of
published and ongoing physics analyses and detector studies are presented.


title: Phase-Sensitive Flux-Flow resistivity in Unconventional Superconductors

abstract:
  We theoretically investigate the magnetic-field-angle dependence of the
flux-flow resistivity $\rho_{\rm f}$ in unconventional superconductors. Two
contributions to $\rho_{\rm f}$ are considered: one is the quasiparticle (QP)
relaxation time $\tau(\bm{k}_{\rm F})$ and the other is $\omega_0(\bm{k}_{\rm
F})$, which is a counterpart to the interlevel spacing of the QP bound states
in the quasiclassical approach. Here, $\bm{k}_{\rm F}$ denotes the position on
a Fermi surface. Numerical calculations are conducted for a line-node s-wave
and a d-wave pair potential with the same anisotropy of their amplitudes, but
with a sign change only for a d-wave one. We show that the field-angle
dependence of $\rho_{\rm f}$ differs prominently between s-wave and d-wave
pairs, reflecting the phase of the pair potentials. We also discuss the case
where $\tau$ is constant and compare it with the more general case where $\tau$
depends on $\bm{k}_{\rm F}$.


title: A proposed new route to d0 magnetism in semiconductors

abstract:
  Here we propose to induce magnetism in semiconductor utilizing the unique
properties of the interstitial defect to act as the magnetic impurity within
the alpha-PbO crystal structure. The Pbi interstitial generates the p-localized
state with two on-site electrons to obey the Hund's rule for their ordering. It
is demonstrated that instead of Pb interstitial other non-magnetic impurities
of s^2p^{x} outer shell configuration can be applied to induce d0 magnetism
with possibility to tune the local magnetic moments mu_B by varying a number of
electrons 1< x< 3. The magnetic coupling between such defects is found to be
driven by the long-range order interactions that in combination with high
defect solubility promises the magnetic percolation to remain above the room
temperature.


title:
Constructing $2m$-variable Boolean functions with optimal algebraic
  immunity based on polar decomposition of $\mathbb{F}_{2^{2m}}^*$

abstract:
  Constructing $2m$-variable Boolean functions with optimal algebraic immunity
based on decomposition of additive group of the finite field
$\mathbb{F}_{2^{2m}}$ seems to be a promising approach since Tu and Deng's
work. In this paper, we consider the same problem in a new way. Based on polar
decomposition of the multiplicative group of $\mathbb{F}_{2^{2m}}$, we propose
a new construction of Boolean functions with optimal algebraic immunity. By a
slight modification of it, we obtain a class of balanced Boolean functions
achieving optimal algebraic immunity, which also have optimal algebraic degree
and high nonlinearity. Computer investigations imply that this class of
functions also behave well against fast algebraic attacks.


title: The Stability of Delaunay Triangulations

abstract:
  We introduce a parametrized notion of genericity for Delaunay triangulations
which, in particular, implies that the Delaunay simplices of $\delta$-generic
point sets are thick. Equipped with this notion, we study the stability of
Delaunay triangulations under perturbations of the metric and of the vertex
positions. We quantify the magnitude of the perturbations under which the
Delaunay triangulation remains unchanged.


title:
Un mod\`ele bool\'een pour l'\'enum\'eration des siphons et des pi\`eges
  minimaux dans les r\'eseaux de Petri

abstract:
  Petri-nets are a simple formalism for modeling concurrent computation.
Recently, they have emerged as a powerful tool for the modeling and analysis of
biochemical reaction networks, bridging the gap between purely qualitative and
quantitative models. These networks can be large and complex, which makes their
study difficult and computationally challenging. In this paper, we focus on two
structural properties of Petri-nets, siphons and traps, that bring us
information about the persistence of some molecular species. We present two
methods for enumerating all minimal siphons and traps of a Petri-net by
iterating the resolution of a boolean model interpreted as either a SAT or a
CLP(B) program. We compare the performance of these methods with a
state-of-the-art dedicated algorithm of the Petri-net community. We show that
the SAT and CLP(B) programs are both faster. We analyze why these programs
perform so well on the models of the repository of biological models
biomodels.net, and propose some hard instances for the problem of minimal
siphons enumeration.


title:
Water in star-forming regions with Herschel (WISH). IV. A survey of
  low-J H2O line profiles toward high-mass protostars

abstract:
  To understand the origin of water line emission and absorption during
high-mass star formation, we decompose high-resolution Herschel-HIFI line
spectra toward 19 high-mass star-forming regions into three distinct physical
components. Protostellar envelopes are usually seen as narrow absorptions or
emissions in the H2O 1113 and 1669 GHz ground-state lines, the H2O 987 GHz
excited-state line, and the H2O-18 1102 GHz ground-state line. Broader features
due to outflows are usually seen in absorption in the H2O 1113 and 1669 GHz
lines, in 987 GHz emission, and not seen in H2O-18, indicating a low column
density and a high excitation temperature. The H2O 1113 and 1669 GHz spectra
show narrow absorptions by foreground clouds along the line of sight, which
have a low column density and a low excitation temperature, although their H2O
ortho/para ratios are close to 3.
  The intensities of the H2O 1113 and 1669 GHz lines do not show significant
trends with luminosity, mass, or age. In contrast, the 987 GHz line flux
increases with luminosity and the H2O-18 line flux decreases with mass.
Furthermore, appearance of the envelope in absorption in the 987 GHz and H2O-18
lines seems to be a sign of an early evolutionary stage.
  We conclude that the ground state transitions of H2O trace the outer parts of
the envelopes, so that the effects of star formation are mostly noticeable in
the outflow wings. These lines are heavily affected by absorption, so that line
ratios of H2O involving the ground states must be treated with caution. The
average H2O abundance in high-mass protostellar envelopes does not change much
with time. The 987 GHz line appears to be a good tracer of the mean weighted
dust temperature of the source, which may explain why it is readily seen in
distant galaxies.


title:
K\"othe-Bochner spaces and some geometric properties related to
  rotundity and smoothness

abstract:
  In 2000 Kadets et al. introduced the notions of acs, luacs and uacs spaces,
which form common generalisations of well-known rotundity and smoothness
properties of Banach spaces. In a recent preprint the author introduced some
further related notions and investigated the behaviour of these geometric
properties under the formation of absolute sums. This paper is in a sense a
continuation of the previous work. Here we will study the behaviour of said
properties under the formation of K\"othe-Bochner spaces, thereby generalising
some results of Sirotkin on the acs, luacs and uacs properties of $L^p$-Bochner
spaces.


title: On-Chip Random Spectrometer

abstract:
  Light scattering in disordered media has been studied extensively due to its
prevalence in natural and artificial systems [1]. In the field of photonics
most of the research has focused on understanding and mitigating the effects of
scattering, which are often detrimental. For certain applications, however,
intentionally introducing disorder can actually improve the device performance,
e.g., in photovoltaics optical scattering improves the efficiency of light
harvesting [2-5]. Here, we utilize multiple scattering in a random photonic
structure to build a compact on-chip spectrometer. The probe signal diffuses
through a scattering medium generating wavelength-dependent speckle patterns
which can be used to recover the input spectrum after calibration. Multiple
scattering increases the optical pathlength by folding the paths in a confined
geometry, enhancing the spectral decorrelation of speckle patterns and thus
increasing the spectral resolution. By designing and fabricating the
spectrometer on a silicon wafer, we are able to efficiently channel the
scattered light to the detectors, minimizing the reflection loss. We
demonstrate spectral resolution of 0.75 nm at a wavelength of 1500 nm in a 25
{\mu}m by 50 {\mu}m random structure. Furthermore, the phenomenal control
afforded by semiconductor nanofabrication technology enabled us to engineer the
disorder to reduce the out-of-plane scattering loss. Such a compact,
high-resolution spectrometer that is integrated on a silicon chip and robust
against fabrication imperfections is well suited for lab-on-a-chip spectroscopy
applications.


title:
Effect of uniaxially anisotropic Fermi surface on the quasiparticle
  scattering inside a vortex core in unconventional superconductors

abstract:
  We theoretically study the dependence of the quasiparticle (QP) scattering
rate $\varGamma$ on the uniaxial anisotropy of a Fermi surface with changing
the magnetic field angle $\alpha_{\rm M}$. We consider the QP scattering due to
the non-magnetic impurities inside a single vortex core. The field-angle
dependence of the quasiparticle scattering rate $\varGamma(\alpha_{\rm M})$ is
sensitive to the sign-change of the pair potential. We show that with
increasing the two dimensionality of the system, $\varGamma(\alpha_{\rm M})$
reflects more clearly whether there is the sign-change in the pair potential.


title:
The velocity dispersion profile of NGC 6388 from resolved-star
  spectroscopy: no evidence of a central cusp and new constraints on the black
  hole mass

abstract:
  By combining high spatial resolution and wide-field spectroscopy performed,
respectively, with SINFONI and FLAMES at the ESO/VLT we measured the radial
velocities of more than 600 stars in the direction of NGC 6388, a Galactic
globular cluster which is suspected to host an intermediate-mass black hole.
Approximately 55% of the observed targets turned out to be cluster members. The
cluster velocity dispersion has been derived from the radial velocity of
individual stars: 52 measurements in the innermost 2", and 276 stars located
between 18" and 600". The velocity dispersion profile shows a central value of
~13 km/s, a flat behavior out to ~60" and a decreasing trend outwards. The
comparison with spherical and isotropic models shows that the observed density
and velocity dispersion profiles are inconsistent with the presence of a
central black hole more massive than ~2000 Msol. These findings are at odds
with recent results obtained from integrated light spectra, showing a velocity
dispersion profile with a steep central cusp of 23-25 km/s at r<2" and
suggesting the presence of a black hole with a mass of 17,000 Msol (Lutzgendorf
et al. 2011). We also found some evidence of systemic rotation with amplitude
Arot ~8 km/s in the innermost 2" (0.13 pc), decreasing to Arot= 3.2 km/s at
18"<r<160".


title: Tomography scheme for two spin-1/2 qubits in a double quantum dot

abstract:
  We present a scheme for full quantum state tomography tailored for two spin
qubits in a double quantum dot. A set of 15 quantum states allows to determine
the density matrix in this two-qubit space by projective measurement. In this
paper we choose a set gained from mutually unbiased bases. We determine how
those 15 projections can be represented by charge measurements after a
spin-to-charge conversion and the application of quantum gates. The quantum
gates include exchange-based gates as well as rotations by electron spin
resonance (ESR). We assume the experimental realization of ESR operations to be
more difficult than the exchange gate operation. Therefore, it is an important
result that the ESR gates are limited by a pi/2 rotation for one of the
electron spins per measurement.


title: Change in Recessive Lethal Alleles Frequency in Inbred Populations

abstract:
  In a population practicing consanguineous marriage, rare recessive lethal
alleles (RRLA) have higher chances of affecting phenotypes. As inbreeding
causes more homozygosity and subsequently more deaths, the loss of individuals
with RRLA decreases the frequency of these alleles. Although this phenomenon is
well studied in general, here some hitherto unstudied cases are presented. An
analytical formula for the RRLA frequency is presented for infinite monoecious
population practicing several different types of inbreeding. In finite diecious
populations, it is found that more severe inbreeding leads to quicker RRLA
losses, making the upcoming generations healthier. A population of size 10,000
practicing 30% half-sib marriages loses more than 95% of its RRLA in 100
generations; a population practicing 30% cousin marriages loses about 75% of
its RRLA. Our findings also suggest that given enough resources to grow, a
small inbred population will be able to rebound while losing the RRLA.


title:
Phase Dependent Forcing and Synchronization in the three-sphere model of
  Chlamydomonas

abstract:
  The green alga {\it Chlamydomonas} swims with synchronized beating of its two
flagella, and is experimentally observed to exhibit run-and-tumble behaviour
similar to bacteria. Recently we studied a simple hydrodynamic three-sphere
model of {\it Chlamydomonas} with a phase dependent driving force which can
produce run-and-tumble behaviour when intrinsic noise is added, due to the
non-linear mechanics of the system. Here, we consider the noiseless case and
explore numerically the parameter space in the driving force profiles, which
determine whether or not the synchronized state evolves from a given initial
condition, as well as the stability of the synchronized state. We find that
phase dependent forcing, or a beat pattern, is necessary for stable
synchronization in the geometry we work with.

categories: cond-mat.soft physics.bio-ph physics.flu-dyn q-bio.CB


title:
Mrk 421 as a case study for TeV and X-ray variability in leptohadronic
  models

abstract:
  We investigate the origin of high-energy emission in blazars within the
context of the leptohadronic one-zone model. We find that $\gamma$-ray emission
can be attributed to synchrotron radiation either from protons or from
secondary leptons produced via photohadronic processes. These possibilities
imply differences not only in the spectral energy distribution (SED) but also
in the variability signatures, especially in the X- and $\gamma$-ray regime.
Thus, the temporal behavior of each leptohadronic scenario can be used to probe
the particle population responsible for the high-energy emission as it can give
extra information not available by spectral fits. In the present work we apply
these ideas to the non-thermal emission of Mrk 421. We focus on the
observations of March 2001, since during that period Mrk 421 showed multiple
flares that have been observed in detail both in X-rays and $\gamma$-rays.
First, we obtain pre-flaring fits to the SED using the different types of
leptohadronic scenarios. Then, we introduce random-walk type, small-amplitude
variations on the injection compactness or on the maximum energy of radiating
particles and follow the subsequent response of the radiated photon spectrum.
For each leptohadronic scenario, we calculate the X-ray and $\gamma$-ray fluxes
and investigate their possible correlation. Whenever the `input' variations
lead, apart from flux variability, also to spectral variability, we present the
resulting relations between the spectral index and the flux, both in X-rays and
$\gamma$-rays. We find that proton synchrotron models are favoured
energetically but require fine tuning between electron and proton parameters to
reproduce the observed quadratic behaviour between X-rays and TeV
$\gamma-$rays. On the other hand, models based on pion-decay can reproduce this
behaviour in a much more natural way.


title: Current Sheets and Collisionless Damping in Kinetic Plasma Turbulence

abstract:
  We present the first study of the formation and dissipation of current sheets
at electron scales in a wave-driven, weakly collisional, 3D kinetic turbulence
simulation. We investigate the relative importance of dissipation associated
with collisionless damping via resonant wave-particle interactions versus
dissipation in small-scale current sheets in weakly collisional plasma
turbulence. Current sheets form self-consistently from the wave-driven
turbulence, and their filling fraction is well correlated to the electron
heating rate. However, the weakly collisional nature of the simulation
necessarily implies that the current sheets are not significantly dissipated
via Ohmic dissipation. Rather, collisionless damping via the Landau resonance
with the electrons is sufficient to account for the measured heating as a
function of scale in the simulation, without the need for significant Ohmic
dissipation. This finding suggests the possibility that the dissipation of the
current sheets is governed by resonant wave-particle interactions and that the
locations of current sheets correspond spatially to regions of enhanced
heating.


title: Shortest Repetition-Free Words Accepted by Automata

abstract:
  We consider the following problem: given that a finite automaton $M$ of $N$
states accepts at least one $k$-power-free (resp., overlap-free) word, what is
the length of the shortest such word accepted? We give upper and lower bounds
which, unfortunately, are widely separated.


title: Standardized network reconstruction of E. coli metabolism

abstract:
  We have created a genome-scale network reconstruction of Escherichia coli
metabolism. Existing reconstructions were improved in terms of annotation
standards, to facilitate their subsequent use in dynamic modelling. The
resultant network is available from EcoliNet (http://ecoli.sf.net/).


title: On the subgroups of finite Abelian groups of rank three

abstract:
  We describe the subgroups of the group $\Z_m \times \Z_n \times \Z_r$ and
derive a simple formula for the total number $s(m,n,r)$ of the subgroups, where
$m,n,r$ are arbitrary positive integers. An asymptotic formula for the function
$n\mapsto s(n,n,n)$ is also deduced.


title: Simple fermionic dark matter models and Higgs boson couplings

abstract:
  We consider a simple extension of the Standard Model (SM) that incorporates a
Majorana fermion dark matter and a charged scalar particle with a coupling to
the SM leptons through renormalizable terms. Another renormalizable term
involving the charged scalar and the Higgs boson gives rise to interactions
between the dark matter and SM quarks at the one-loop level, which induce the
elastic scatterings between dark matter and nucleus. The same term also affects
the effective coupling of the Higgs boson to diphoton through a one-loop
diagram with the charged scalar. Therefore, our model predicts a correlation
between the spin-independent cross section for dark matter-nucleus elastic
scatterings and a new contribution to the effective Higgs boson coupling to
diphoton. When the spin-dependent cross section is large enough to be tested in
future direct dark matter detection experiments, the Higgs-diphoton decay rate
shows a sizable deviation from the SM prediction. We also consider the case
where the fermion dark matter is a Dirac particle. Most of discussions is
similar to the Majorana case, but we find that the magnetic dipole moment of
the Dirac fermion dark matter is loop-induced and this interaction dominates
the spin-independent cross section for dark matter-nucleus elastic scatterings.
We find that the resultant cross section is about an order of magnitude below
the current experimental bound and hence can be tested in the near future.


title:
Observational evidence that massive cluster galaxies were forming stars
  at z~2.5 and did not grow in mass at later times

abstract:
  Using Spitzer 3.6 micron data we derived the luminosity function and the mass
function of galaxies in five z>1.4 clusters selected to have a firm
intracluster medium detection. The five clusters differ in richness
(ISCSJ1438.1+3414 and XMMXCSJ2215.9-1738 are twice as rich as ISCSJ1432.4+3250,
IDCSJ1426.5+3508, and JKCS041) and morphological appareance. At the median
redshift z=1.5, from the 150 member galaxies of the five clusters, we derived a
characteristic magnitude of 16.92+/-0.13 in the [3.6] band and a characteristic
mass of lgM*=11.30+/-0.05 Msol. We find that the characteristic luminosity and
mass does not evolve between z=1 and 1.4<z<1.8, directly ruling out ongoing
mass assembly between these epochs because massive galaxies are already present
up to z=1.8. Lower-redshift build-up epochs have already been ruled out by
previous works, leaving only z>1.8 as a possible epoch for the mass build up.
However, the observed values of m^* at very high redshift are too bright for
galaxies without any star formation immediately preceding the observed redshift
and therefore imply a star formation episode not earlier than z_f=2.5. For the
first time, mass/luminosity functions are able to robustly distinguish tiny
differences between formation redshifts and to set {\it upper} limits to the
epoch of the last star-formation episode.


title: The electromagnetic spike solutions

abstract:
  The aim of this paper is to use the existing relation between polarized
electromagnetic Gowdy spacetimes and vacuum Gowdy spacetimes to find explicit
solutions for electromagnetic spikes by a procedure which has been developed by
one of the authors for gravitational spikes. We present new inhomogeneous
solutions which we call the EME and MEM electromagnetic spike solutions.


title: A class of Finsler surfaces whose geodesics are circles

abstract:
  We determine all Finsler metrics of Randers type for which the Riemannian
part is a scalar multiple of the Euclidean metric, on an open subset of the
Euclidean plane, whose geodesics are circles. We show that the Riemannian part
must be of constant Gaussian curvature, and that for every such Riemannian
metric there is a class of Randers metrics satisfying the condition, determined
up to the addition of a total derivative, depending on a single parameter. As
one of several applications we exhibit a Finsler metric whose geodesics are the
oriented horocycles in the Poincare disk, in each of the two possible
orientations.


title:
Centers of near-infrared luminescence in bismuth-doped TlCl and CsI
  crystals

abstract:
  A comparative first-principles study of possible bismuth-related centers in
TlCl and CsI crystals is performed and the results of computer modeling are
compared with the experimental data. The calculated spectral properties of the
bismuth centers suggest that the IR luminescence observed in TlCl:Bi is most
likely caused by Bi--Vac(Cl) centers (Bi^+ ion in thallium site and a
negatively charged chlorine vacancy in the nearest anion site). On the
contrary, Bi^+ substitutional ions and Bi_2^+ dimers are most likely
responsible for the IR luminescence observed in CsI:Bi.


title:
Log-majorization of the moduli of the eigenvalues of a matrix polynomial
  by tropical roots

abstract:
  We show that the sequence of moduli of the eigenvalues of a matrix polynomial
is log-majorized, up to universal constants, by a sequence of "tropical roots"
depending only on the norms of the matrix coefficients. These tropical roots
are the non-differentiability points of an auxiliary tropical polynomial, or
equivalently, the opposites of the slopes of its Newton polygon. This extends
to the case of matrix polynomials some bounds obtained by Hadamard, Ostrowski
and P\'olya for the roots of scalar polynomials. We also obtain new bounds in
the scalar case, which are accurate for "fewnomials" or when the tropical roots
are well separated.


title: Origami-based spintronics in graphene

abstract:
  We show that periodically folded graphene sheets with enhanced spin-orbit
interaction due to curvature effects can carry spin polarized currents and have
gaps in the electronic spectrum in the presence of weak magnetic fields. Our
results indicate that such origami-like structures can be used efficiently in
spintronic applications.


title: Selected Experimental Results from Heavy Ion Collisions at LHC

abstract:
  We review a subset of experimental results from the heavy-ion collisions at
the Large Hadron Collider (LHC) facility at CERN. Excellent consistency is
observed across all the experiments at the LHC (at center of mass energy of
2.76 TeV) for the measurements such as charged particle multiplicity density,
azimuthal anisotropy coefficients and nuclear modification factor of charged
hadrons. Comparison to similar measurements from the Relativistic Heavy Ion
Collider (RHIC) at lower energy (center of mass energy of 200 GeV) suggests
that system formed at LHC has a higher energy density, larger system size, and
lives for a longer time. These measurements are compared to model calculations
to obtain physical insights on the properties of matter created at the RHIC and
LHC.


title:
Multi-band superconductivity and nanoscale inhomogeneity at oxide
  interfaces

abstract:
  The two-dimensional electron gas at the LaTiO3/SrTiO3 or LaAlO3/SrTiO3 oxide
interfaces becomes superconducting when the carrier density is tuned by gating.
The measured resistance and superfluid density reveal an inhomogeneous
superconductivity resulting from percolation of filamentary structures of
superconducting "puddles" with randomly distributed critical temperatures,
embedded in a non-superconducting matrix. Following the evidence that
superconductivity is related to the appearance of high-mobility carriers, we
model intra-puddle superconductivity by a multi-band system within a weak
coupling BCS scheme. The microscopic parameters, extracted by fitting the
transport data with a percolative model, yield a consistent description of the
dependence of the average intra-puddle critical temperature and superfluid
density on the carrier density.


title:
Gevrey Regularity for Solutions of the Non-Cutoff Boltzmann Equation:
  Spatially Inhomogeneous Case

abstract:
  In this paper we consider the non-cutoff Boltzmann equation in spatially
inhomogeneous case. We prove the propagation of Gevrey regularity for the
so-called smooth Maxwellian decay solutions to the Cauchy problem of spatially
inhomogeneous Boltzmann equation, and obtain Gevrey regularity of order
$1/(2s)$ in the velocity variable $v$ and order 1 in the space variable $x$.
The strategy relies on our recent results for spatially homogeneous case (J.
Diff. Equ. 253(4) (2012), 1172-1190. DOI: 10.1016/j.jde.2012.04.023). Rather,
we need much more intricate analysis additionally in order to handle with the
coupling of the double variables. Combining with the previous result mentioned
above, it gives a whole characterization of the Gevrey regularity of the
particular kind of solutions to the non-cutoff Boltzmann.


title: On the Reynolds number expansion for the Navier-Stokes equations

abstract:
  In a previous paper of ours [Nonlinear Anal. 2012] we have considered the
incompressible Navier-Stokes (NS) equations on a d-dimensional torus T^d, in
the functional setting of the Sobolev spaces H^n(T^d) of divergence free, zero
mean vector fields (n > d/2+1). In the cited work we have presented a general
setting for the a posteriori analysis of approximate solutions of the NS Cauchy
problem; given any approximate solution u_a, this allows to infer a lower bound
T_c on the time of existence of the exact solution u and to construct a
function R_n such that || u(t) - u_a(t) ||_n <= R_n(t) for t in [0,T_c). In
certain cases it is T_c = + infinity, so global existence is granted for u. In
the present paper the framework of [Nonlinear Anal., 2012] is applied using as
an approximate solution an expansion u^N(t) = Sum_{j=0}^N R^j u_j(t), where R
is the Reynolds number. This allows, amongst else, to derive the global
existence of u when R is below some critical value R_{*} (increasing with N in
the examples that we analyze). After a general discussion about the Reynolds
expansion and its a posteriori analysis, we consider the expansions of orders
N=1,2,5 in dimension d=3, with the initial datum of Behr, Necas and Wu [M2AN,
2001]. Computations of order N=5 yield a quantitative improvement of the
results previously obtained for this initial datum in [Nonlinear Anal. 2012],
where a Galerkin approximate solution was employed in place of the Reynolds
expansion.


title:
Sharp Weighted Inequalities for Multilinear Fractional Maximal Operator
  and Fractional Integrals

abstract:
  In this paper, we study the weighted inequality for multilinear fractional
maximal operators and fractional integrals. We give sharp weighted estimates
for both operators.


title: Are Friends Overrated? A Study for the Social News Aggregator Digg.com

abstract:
  The key feature of online social networks (OSN) is the ability of users to
become active, make friends and interact via comments, videos or messages with
those around them. This social interaction is typically perceived as critical
to the proper functioning of these platforms; therefore, a significant share of
OSN research in the recent past has investigated the characteristics and
importance of these social links, studying the networks' friendship relations
through their topological properties, the structure of the resulting
communities and identifying the role and importance of individual members
within these networks.
  In this paper, we present results from a multi-year study of the online
social network Digg.com, indicating that the importance of friends and the
friend network in the propagation of information is less than originally
perceived. While we do note that users form and maintain a social structure
along which information is exchanged, the importance of these links and their
contribution is very low: Users with even a nearly identical overlap in
interests react on average only with a probability of 2% to information
propagated and received from friends. Furthermore, in only about 50% of stories
that became popular from the entire body of 10 million news we find evidence
that the social ties among users were a critical ingredient to the successful
spread. Our findings indicate the presence of previously unconsidered factors,
the temporal alignment between user activities and the existence of additional
logical relationships beyond the topology of the social graph, that are able to
drive and steer the dynamics of such OSNs.


title: Fidelity of the surface code in the presence of a bosonic bath

abstract:
  We study the resilience of the surface code to decoherence caused by the
presence of a bosonic bath. This approach allows us to go beyond the standard
stochastic error model commonly used to quantify decoherence and error
threshold probabilities in this system. The full quantum mechanical system-bath
dynamics is computed exactly over one quantum error correction cycle. Since all
physical qubits interact with the bath, space-time correlations between errors
are taken into account. We compute the fidelity of the surface code as a
function of the quantum error correction time. The calculation allows us to map
the problem onto an Ising-like statistical spin model with two-body
interactions and a fictitious temperature which is related to the inverse bath
coupling constant. The model departs from the usual Ising model in the sense
that interactions can be long ranged and can involve complex exchange
couplings; in addition, the number of allowed configurations is restricted by
the syndrome extraction. Using analytical estimates and numerical calculations,
we argue that, in the limit of an infinite number of physical qubits, the spin
model sustain a phase transition which can be associated to the existence of an
error threshold in the surface code. An estimate of the transition point is
given for the case of nearest-neighbor interactions.


title:
Model comparison of the dark matter profiles of Fornax, Sculptor, Carina
  and Sextans

abstract:
  We use orbit based dynamical models to fit the 2nd and 4th moments of the
line of sight velocity distributions of the Fornax, Sculptor, Carina and
Sextans dwarf spheroidal galaxies. Our goal is to compare dark matter profile
models of these four systems using Bayesian evidence. We consider NFW, Einasto
and several cored profiles for their dark halos and present the probability
distribution functions of the model parameters. When considering each system
separately, we find there is no preference for one of these specific parametric
density profiles. However, the combined evidence shows that it is unlikely that
all galaxies are embedded in the same type of cored profiles of the form
\rho_{DM} \propto 1/(1 + r^2)^{\beta/2}, where \beta = 3, 4. For each galaxy,
we also obtain an almost model independent, and therefore accurate, measurement
of the logarithmic slope of the dark matter density distribution at a radius ~
r_{-3}, i.e. where the logarithmic slope of the stellar density profile is -3.
This slope ranges from ~ -1.4 for Fornax to ~ -1.1 for Sextans, both at ~ 1
kpc. All our best fit models essentially have the same mass distribution over a
large range in radius (from just below r_{-3} to the last measured data point).
This remarkable finding likely implies much stronger constraints on the
characteristics that subhalos extracted from cosmological simulations should
have in order to host the dSph galaxies around the Milky Way.


title: First Neutron Spectrometry Measurement at the HL-2A Tokamak

abstract:
  A compact neutron spectrometer based on the liquid scintillator is presented
for neutron energy spectrum measurements at the HL-2A tokamak. The spectrometer
was well characterized and a fast digital pulse shape discrimination software
was developed using the charge comparison method. A digitizer data acquisition
system with a maximum frequency of 1 MHz can work under an environment with a
high count rate at HL-2A tokamak. Specific radiation and magnetic shielding for
the spectrometer were designed for the neutron spectrum measurement at the
HL-2A tokamak. For pulse height spectrum analysis, dedicated numerical
simulation utilizing NUBEAM combined with GENESIS was performed to obtain the
neutron energy spectrum. Subsequently, the transportation process from the
plasma to the detector was evaluated with Monte Carlo calculations. The
distorted neutron energy spectrum was folded with the response matrix of the
liquid scintillation spectrometer, and good consistency was found between the
simulated and measured pulse height spectra. This neutron spectrometer based on
a digital acquisition system could be well adopted for the investigation of the
auxiliary heating behavior and the fast-ion related phenomenon on different
tokamak devices.


title: The Construction of Dual-trace Factor in Yang-Mills Theory

abstract:
  Recently, a BCJ dual of the color-ordered formula for Yang-Mills amplitude
was proposed, where the dual-trace factor satisfies cyclic symmetry and
KK-relation. In this paper, we present a systematic construction of the
dual-trace factor based on its proposed relations to kinematic numerators in
dual-DDM form. We show that the construction presented respects relabeling
symmetry. In addition, we show that using relabeling symmetry as conditions,
the same construction can be solved independently.


title:
Extrapolation of the Solar Coronal Magnetic Field from SDO/HMI
  Magnetogram by a CESE--MHD--NLFFF Code

abstract:
  Due to the absence of direct measurement, the magnetic field in the solar
corona is usually extrapolated from the photosphere in numerical way. At the
moment, the nonlinear force-free field (NLFFF) model dominates the physical
models for field extrapolation in the low corona. Recently we have developed a
new NLFFF model with MHD relaxation to reconstruct the coronal magnetic field.
This method is based on CESE--MHD model with the
conservation-element/solution-element (CESE) spacetime scheme. In this paper,
we report the application of the CESE--MHD--NLFFF code to \SDO/HMI data with
magnetograms sampled for two active regions (ARs), NOAA AR 11158 and 11283,
both of which were very non-potential, producing X-class flares and eruptions.
The raw magnetograms are preprocessed to remove the force and then inputted
into the extrapolation code. Qualitative comparison of the results with the
\SDO/AIA images shows that our code can reconstruct magnetic field lines
resembling the EUV-observed coronal loops. Most important structures of the
active regions are reproduced excellently, like the highly-sheared field lines
that suspend filaments in AR 11158 and twisted flux rope which corresponds to a
sigmoid in AR 11283. Quantitative assess of the results shows that the
force-free constraint is fulfilled very well in the strong-field regions but
apparently not that well in the weak-field regions because of data noise and
numerical errors in the small currents.


title:
The effective potential of the confinement order parameter in the
  Hamiltonian approach

abstract:
  The effective potential of the order parameter for confinement is calculated
for SU(N) Yang--Mills theory in the Hamiltonian approach. Compactifying one
spatial dimension and using a background gauge fixing, this potential is
obtained within a variational approach by minimizing the energy density for
given background field. In this formulation the inverse length of the
compactified dimension represents the temperature. Using Gaussian trial wave
functionals we establish an analytic relation between the propagators in the
background gauge at finite temperature and the corresponding zero-temperature
propagators in Coulomb gauge. In the simplest truncation, neglecting the ghost
and using the ultraviolet form of the gluon energy, we recover the Weiss
potential. We explicitly show that the omission of the ghost drastically
increases the transition temperature. From the full non-perturbative potential
(with the ghost included) we extract a critical temperature of the
deconfinement phase transition of 269 MeV for the gauge group SU(2) and 283 MeV
for SU(3).


title: Cloud Computing: a Prologue

abstract:
  An emerging internet based super computing model is represented by cloud
computing. Cloud computing is the convergence and evolution of several concepts
from virtualization, distributed storage, grid, and automation management to
enable a more flexible approach for deploying and scaling applications.
However, cloud computing moves the application software and databases to the
large data centers, where the management of the data and services may not be
fully trustworthy. The concept of cloud computing on the basis of the various
definitions available in the industry and the characteristics of cloud
computing are being analyzed in this paper. The paper also describes the main
cloud service providers and their products followed by primary cloud computing
operating systems.


title:
Non-mean-field Critical Exponent in a Mean-field Model : Dynamics versus
  Statistical Mechanics

abstract:
  The mean-field theory tells that the classical critical exponent of
susceptibility is the twice of that of magnetization. However, the linear
response theory based on the Vlasov equation, which is naturally introduced by
the mean-field nature, makes the former exponent half of the latter for
families of quasistationary states having second order phase transitions in the
Hamiltonian mean-field model and its variances. We clarify that this strange
exponent is due to existence of Casimir invariants which trap the system in a
quasistationary state for a time scale diverging with the system size. The
theoretical prediction is numerically confirmed by $N$-body simulations for the
equilibrium states and a family of quasistationary states.


title: Centrality of Trees for Capacitated k-Center

abstract:
  There is a large discrepancy in our understanding of uncapacitated and
capacitated versions of network location problems. This is perhaps best
illustrated by the classical k-center problem: there is a simple tight
2-approximation algorithm for the uncapacitated version whereas the first
constant factor approximation algorithm for the general version with capacities
was only recently obtained by using an intricate rounding algorithm that
achieves an approximation guarantee in the hundreds.
  Our paper aims to bridge this discrepancy. For the capacitated k-center
problem, we give a simple algorithm with a clean analysis that allows us to
prove an approximation guarantee of 9. It uses the standard LP relaxation and
comes close to settling the integrality gap (after necessary preprocessing),
which is narrowed down to either 7, 8 or 9. The algorithm proceeds by first
reducing to special tree instances, and then solves such instances optimally.
Our concept of tree instances is quite versatile, and applies to natural
variants of the capacitated k-center problem for which we also obtain improved
algorithms. Finally, we give evidence to show that more powerful preprocessing
could lead to better algorithms, by giving an approximation algorithm that
beats the integrality gap for instances where all non-zero capacities are
uniform.


title:
Global boundedness of the fundamental solution of parabolic equations
  with unbounded coefficients

abstract:
  The purpose of this paper is to obtain an upper bound for the fundamental
solution for parabolic Cauchy problem u'=Au, where A is a second order elliptic
partial differential operator with unbounded coefficients such that its
potential and the potential of the formal adjoint of the operator A are bounded
from below.


title:
A penalized algorithm for event-specific rate models for recurrent
  events

abstract:
  We introduce a covariate-specific total variation penalty in two
semiparametric models for the rate function of recurrent event process. The two
models are a stratified Cox model, introduced in Prentice et al. (1981), and a
stratified Aalen's additive model. We show the consistency and asymptotic
normality of our penalized estimators. We demonstrate, through a simulation
study, that our estimators outperform classical estimators for small to
moderate sample sizes. Finally an application to the bladder tumour data of
Byar (1980) is presented.


title: Adaptive piecewise polynomial estimation via trend filtering

abstract:
  We study trend filtering, a recently proposed tool of Kim et al. [SIAM Rev.
51 (2009) 339-360] for nonparametric regression. The trend filtering estimate
is defined as the minimizer of a penalized least squares criterion, in which
the penalty term sums the absolute $k$th order discrete derivatives over the
input points. Perhaps not surprisingly, trend filtering estimates appear to
have the structure of $k$th degree spline functions, with adaptively chosen
knot points (we say ``appear'' here as trend filtering estimates are not really
functions over continuous domains, and are only defined over the discrete set
of inputs). This brings to mind comparisons to other nonparametric regression
tools that also produce adaptive splines; in particular, we compare trend
filtering to smoothing splines, which penalize the sum of squared derivatives
across input points, and to locally adaptive regression splines [Ann. Statist.
25 (1997) 387-413], which penalize the total variation of the $k$th derivative.
Empirically, we discover that trend filtering estimates adapt to the local
level of smoothness much better than smoothing splines, and further, they
exhibit a remarkable similarity to locally adaptive regression splines. We also
provide theoretical support for these empirical findings; most notably, we
prove that (with the right choice of tuning parameter) the trend filtering
estimate converges to the true underlying function at the minimax rate for
functions whose $k$th derivative is of bounded variation. This is done via an
asymptotic pairing of trend filtering and locally adaptive regression splines,
which have already been shown to converge at the minimax rate [Ann. Statist. 25
(1997) 387-413]. At the core of this argument is a new result tying together
the fitted values of two lasso problems that share the same outcome vector, but
have different predictor matrices.


title: Top Polarization in Sbottom Decays at the LHC

abstract:
  We perform a comprehensive analysis of the polarization of the top quarks
originating from sbottom-pair production at the LHC, followed by sbottom decays
to top+chargino. We study moreover the expected net polarization of top quarks
produced in sbottom-to-chargino and stop-to-neutralino decays in scenarios with
small chargino - neutralino mass difference, where these decays may be hard to
distinguish. We show that, in contrast to top quarks produced via the Standard
Model processes, the average polarization of top quarks originating from these
SUSY decays can obtain any value between +1 and -1. We further study the effect
of this polarization on the top quark decay kinematics. On the one hand this
may be used to construct measures of this polarization, on the other hand it
may be used to enhance the search reach in certain scenarios. Exploiting top
polarization may also prove useful for searches for "natural" SUSY with light
higgsinos, which is typically very difficult to detect at the LHC.


title:
Evaluation of the Coulomb and exchange integrals for higher excited
  states of helium atom, taking into account the interaction between magnetic
  moments of the electrons

abstract:
  We have calculated the total energy of the helium atom in higher excited
state. The Coulomb and exchange integrals are evaluated via spherical
harmonics. The interaction of the magnetic moments of the electrons between
them and also with the magnetic moments of the nucleus was taken into account
through a cosine term in the Coulomb potential. The obtained results are in
agreement with experimental data.


title:
New results on the anomalous precursor diamagnetism in the underdoped
  La1.9Sr0.1CuO4 superconductor

abstract:
  The new results summarized here, including a brief comparison with the
paraconductivity, further suggest that the anomalous precursor (above Tc)
diamagnetism recently observed in the underdoped La1.9Sr0.1CuO4 superconductor
could be attributed to the presence, in addition to the conventional
superconducting pair fluctuations, of Tc-inhomogeneities with long
characteristic lengths associated with chemical disorder.


title: Atomistic Full-Band Simulations of Monolayer MoS2 Transistors

abstract:
  We study the transport properties of deeply scaled monolayer MoS2 n-channel
metal-oxide-semiconductor field effect transistors (MOSFETs) using full-band
ballistic quantum transport simulations with an atomistic tight-binding
Hamiltonian obtained from density functional theory. Our simulations suggest
that monolayer MoS2 MOSFETs can provide near-ideal subthreshold slope, and
suppression of drain-induced barrier lowering (DIBL) and gate-induced drain
leakage (GIDL). However, these full-band simulations also exhibit limited
transconductance. These ballistic simulations also exhibit negative
differential resistance (NDR) in the output characteristics associated with the
narrow width in energy of the lowest conduction band, but this NDR may be
substantially reduced or eliminated by scattering in MoS2.


title:
Replenish and relax: explaining logarithmic annealing in disordered
  materials

abstract:
  Fatigue and aging of materials are, in large part, determined by the
evolution of the atomic-scale structure in response to strains and
perturbations. This coupling between microscopic structure and long time scales
remains one of the main challenges in materials study. Focusing on a model
system, ion-damaged crystalline silicon, we combine nanocalorimetric
experiments with an off-lattice kinetic Monte Carlo simulation to identify the
atomistic mechanisms responsible for the structural relaxation over long time
scales. We relate the logarithmic relaxation, observed in a number of systems,
with heat-release measurements. The microscopic mechanism associated with
logarithmic relaxation can be described as a two-step replenish and relax
process. As the system relaxes, it reaches deeper energy states with
logarithmically growing barriers that need to be unlocked to replenish the
heat-releasing events leading to lower energy configurations.


title:
Fermionization of two-component few-fermion systems in a one-dimensional
  harmonic trap

abstract:
  The nature of strongly interacting Fermi gases and magnetism is one of the
most important and studied topics in condensed-matter physics. Still, there are
many open questions. A central issue is under what circumstances strong
short-range repulsive interactions are enough to drive magnetic correlations.
Recent progress in the field of cold atomic gases allows to address this
question in very clean systems where both particle numbers, interactions and
dimensionality can be tuned. Here we study fermionic few-body systems in a one
dimensional harmonic trap using a new rapidly converging effective-interaction
technique, plus a novel analytical approach. This allows us to calculate the
properties of a single spin-down atom interacting with a number of spin-up
particles, a case of much recent experimental interest. Our findings indicate
that, in the strongly interacting limit, spin-up and spin-down particles want
to separate in the trap, which we interpret as a microscopic precursor of
one-dimensional ferromagnetism in imbalanced systems. Our predictions are
directly addressable in current experiments on ultracold atomic few-body
systems.


title:
Three-dimensional anisotropic fluctuation diamagnetism around the
  superconducting transition of Ba(1-x)KxFe2As2 single crystals in the
  finite-field (or Prange) regime

abstract:
  The magnetization around the superconducting transition was recently measured
in a high-quality Ba(1-x)KxFe2As2 single crystal with magnetic fields applied
along and transverse to the crystal Fe-layers [J. Mosqueira et al., Phys. Rev.
B 83, 094519 (2011)]. Here we extend this study to the finite field (or Prange)
regime, in which the magnetic susceptibility is expected to be strongly
dependent on the applied magnetic field. These measurements are analyzed in the
framework of the three-dimensional anisotropic Ginzburg Landau (3D-aGL)
approach generalized to the short wavelength regime through the introduction of
a total-energy cutoff in the fluctuation spectrum. The results further confirm
the adequacy of GL approaches to describe the fluctuation effects close to the
superconducting transition of these materials.


title:
A Generalized Online Mirror Descent with Applications to Classification
  and Regression

abstract:
  Online learning algorithms are fast, memory-efficient, easy to implement, and
applicable to many prediction problems, including classification, regression,
and ranking. Several online algorithms were proposed in the past few decades,
some based on additive updates, like the Perceptron, and some on multiplicative
updates, like Winnow. A unifying perspective on the design and the analysis of
online algorithms is provided by online mirror descent, a general prediction
strategy from which most first-order algorithms can be obtained as special
cases. We generalize online mirror descent to time-varying regularizers with
generic updates. Unlike standard mirror descent, our more general formulation
also captures second order algorithms, algorithms for composite losses and
algorithms for adaptive filtering. Moreover, we recover, and sometimes improve,
known regret bounds as special cases of our analysis using specific
regularizers. Finally, we show the power of our approach by deriving a new
second order algorithm with a regret bound invariant with respect to arbitrary
rescalings of individual features.


title:
Linear Multifractional Stable Motion: wavelet estimation of $H(\cdot)$
  and $\al$ parameters

abstract:
  Linear Fractional Stable Motion (LFSM) of Hurst parameter $H$ and of
stability parameter $\al$, is one of the most classical extensions of the
well-known Gaussian Fractional Brownian Motion (FBM), to the setting of
heavy-tailed stable distributions \cite{SamTaq,EmMa}. In order to overcome some
limitations of its areas of application, coming from stationarity of its
increments as well as constancy over time of its self-similarity exponent,
Stoev and Taqqu introduced in \cite{stoev2004stochastic} an extension of LFSM,
called Linear Multifractional Stable Motion (LMSM), in which the Hurst
parameter becomes a function $H(\cdot)$ depending on the time variable $t$.
Similarly to LFSM, the tail heaviness of the marginal distributions of LMSM is
determined by $\al$; also, under some conditions, its self-similarity is
governed by $H(\cdot)$ and its path roughness is closely related to
$H(\cdot)-1/\al$. Namely, it was shown in \cite{stoev2004stochastic} that
$H(t_0)$ is the self-similarity exponent of LMSM at a time $t_0\neq 0$;
moreover, very recently, it was established in \cite{hamonier2012lmsm}, that
the quantities $\min_{t\in I} H(t)-1/\al$, and $H(t_0)-1/\al$, are respectively
the uniform H\"older exponent of LMSM on a compact interval $I$, and its local
H\"older exponent at $t_0$.
  The main goal of our article, is to construct, using wavelet coefficients of
LMSM, strongly consistent (i.e. almost surely convergent) statistical
estimators of $\min_{t\in I} H(t)$, $H(t_0)$, and $\al$; our estimation
results, are obtained when $\al\in (1,2)$, and, $H(\cdot)$ is a H\"older
function smooth enough, with values in a compact subinterval
$[\underline{H},\bar{H}]$ of $(1/\al,1)$.


title:
Angular dependence of the fluctuation magnetization vector above the
  superconducting transition of a highly anisotropic high-Tc cuprate

abstract:
  In highly anisotropic cuprate superconductors it is generally accepted that
the reversible magnetization vector, M, is essentially perpendicular to the
superconducting CuO2 layers in a wide range of crystal orientations with
respect to the applied magnetic field, H. In a recent work [J. Mosqueira et
al., Phys. Rev. B 84, 134504 (2011)] it is shown, however, that the dependence
of M on the H orientation in the reversible mixed state of a high-quality
Tl-based cuprate presents a notable deviation from this behavior. Here we
extend these measurements to the fluctuation region above Tc, in order to check
whether the above mentioned effect is also present.


title:
Phenomenology of electroweak bubbles and gravitational waves in the
  Littlest Higgs Model with T parity

abstract:
  We study the dynamics of electroweak bubbles in the scenario of a strong
first order inverse electroweak phase transition at the TeV scale involving the
global structure of the nonlinear sigma field in the littlest Higgs model with
T parity. Employing the one-loop order finite temperature effective potential,
we find that the pressure in the symmetric phase i.e., inside the bubble is
always greater than that in the asymmetric phase i.e., outside the bubble, so
that the bubbles are expanding. By calculating the fluid velocities in the two
phases we arrive at the condition of a supersonic deflagrated motion of the
bubble walls. We then discuss the generation of gravitational waves from the
collisions of such bubbles as well as from the turbulence of the plasma.


title: Detecting Directionality in Random Fields Using the Monogenic Signal

abstract:
  Detecting and analyzing directional structures in images is important in many
applications since one-dimensional patterns often correspond to important
features such as object contours or trajectories. Classifying a structure as
directional or non-directional requires a measure to quantify the degree of
directionality and a threshold, which needs to be chosen based on the
statistics of the image. In order to do this, we model the image as a random
field. So far, little research has been performed on analyzing directionality
in random fields. In this paper, we propose a measure to quantify the degree of
directionality based on the random monogenic signal, which enables a unique
decomposition of a 2D signal into local amplitude, local orientation, and local
phase. We investigate the second-order statistical properties of the monogenic
signal for isotropic, anisotropic, and unidirectional random fields. We analyze
our measure of directionality for finite-size sample images, and determine a
threshold to distinguish between unidirectional and non-unidirectional random
fields, which allows the automatic classification of images.


title:
A New Approach To Two-View Motion Segmentation Using Global Dimension
  Minimization

abstract:
  We present a new approach to rigid-body motion segmentation from two views.
We use a previously developed nonlinear embedding of two-view point
correspondences into a 9-dimensional space and identify the different motions
by segmenting lower-dimensional subspaces. In order to overcome nonuniform
distributions along the subspaces, whose dimensions are unknown, we suggest the
novel concept of global dimension and its minimization for clustering subspaces
with some theoretical motivation. We propose a fast projected gradient
algorithm for minimizing global dimension and thus segmenting motions from
2-views. We develop an outlier detection framework around the proposed method,
and we present state-of-the-art results on outlier-free and outlier-corrupted
two-view data for segmenting motion.


title: Non-Vertex-Balanced Factors in Random Graphs

abstract:
  We prove part of a conjecture by Johansson, Kahn and Vu \cite{JKV} regarding
threshold functions for the existence of an $H$-factor in a random graph \gnp.
We prove that the conjectured threshold function is correct for any graph $H$
which is not covered by its densest subgraphs. We also demonstrate that the
main result of \cite{JKV} generalises to multigraphs, digraphs, and a
multipartite model.


title: Fluids in motion: Contemporary artScience- inspiration and realization

abstract:
  I examine contemporary work in fluids in motion to demonstrate strong
connections between art, science and technology. In one burgeoning domain,
falling liquid drops impacting solid substrates or pools it is valuable to
compare how artists and scientists describe their goals and their use of high
speed digital photography to capture and measure events. I also examine the use
of devices beyond paint brushes to create pictures and views, including
installations and projections from computer simulations. In particular, Ned
Kahn whose installations in the public domain show various fluids in motion -
water, sand, fog, fire as turbulent boundary layers, vortex rings, whirlpools,
waterfalls, etc. Finally, I examine aspects of the role of digital technology
and its utilization by artists, museums and galleries for innovative displays.


title:
Determination of the calcium channel distribution in the olfactory
  system

abstract:
  In this paper we study a linear inverse problem with a biological
interpretation, which is modeled by a Fredholm integral equation of the first
kind. When the kernel in the Fredholm equation is represented by step func-
tions, we obtain identifiability, stability and reconstruction results.
Further- more, we provide a numerical reconstruction algorithm for the kernel,
whose main feature is that a non-regular mesh has to be used to ensure the
invert- ibility of the matrix representing the numerical discretization of the
system. Finally, a second identifiability result for a polynomial approximation
of degree less than nine of the kernel is also established.


title:
Conductance scaling in Kondo correlated quantum dots: role of level
  asymmetry and charging energy

abstract:
  The low temperature electrical conductance through correlated quantum dots
provides a sensitive probe of the physics (e.g., of Fermi-liquid vs
non-Fermi-liquid behavior) of such systems. Here, we investigate the role of
level asymmetry (gate voltage) and local Coulomb repulsion (charging energy) on
the low temperature and low field scaling properties of the linear conductance
of a quantum dot described by the single level Anderson impurity model. We use
the numerical renormalization group to quantify the regime of gate voltages and
charging energies where universal Kondo scaling may be observed and also
quantify the deviations from this universal behavior with increasing gate
voltage away from the Kondo regime and with decreasing charging energy. We also
compare our results with those from a recently developed method for linear and
non-linear transport, which is based on renormalized perturbation theory using
dual fermions, finding excellent agreement at particle-hole symmetry and for
all charging energies and reasonable agreement at small finite level asymmetry.
Our results could be a useful guide for detailed experiments on conductance
scaling in semiconductor and molecular quantum dots exhibiting the Kondo
effect.


title: Two-fold Mellin-Barnes transforms of Usyukina-Davydychev functions

abstract:
  In our previous paper [Nucl.Phys. B 870 (2013) 243], we showed that
multi-fold Mellin-Barnes (MB) transforms of Usyukina-Davydychev (UD) functions
may be reduced to two-fold MB transforms. The MB transforms were written there
as polynomials of logarithms of ratios of squares of the external momenta with
certain coefficients. We also showed that these coefficients have a
combinatoric origin. In this paper, we present an explicit formula for these
coefficients. The procedure of recovering the coefficients is based on taking
the double-uniform limit in certain series of smooth functions of two variables
which is constructed according to a pre-determined iterative way. The result is
obtained by using basic methods of mathematical analysis. We observe that the
finiteness of the limit of this iterative chain of smooth functions should
reflect itself in other mathematical constructions, too, since it is not
related in any way to the explicit form of the MB transforms. This finite
double-uniform limit is represented in terms of a differential operator with
respect to an auxiliary parameter which acts on the integrand of a certain
two-fold MB integral. To demonstrate that our result is compatible with
original representations of UD functions, we reproduce the integrands of these
original integral representations by applying this differential operator to the
integrand of the simple integral representation of the scalar triangle
four-dimensional integral J(1,1,1-e).


title:
Continuity of the flow of KdV with regard to the Wasserstein metrics and
  application to an invariant measure

abstract:
  In this paper, we prove the continuity of the flow of KdV on spaces of
probability measures with respect to a combination of Wasserstein distances on
$H^s$, $s>0$ and $L^2$. We are motivated by the existence of an invariant
measure belonging to the spaces onto which these distances are defined.


title: Homological stability for spaces of embedded surfaces

abstract:
  We study the space of oriented genus g subsurfaces of a fixed manifold M, and
in particular its homological properties. We construct a "scanning map" which
compares this space to the space of sections of a certain fibre bundle over M
associated to its tangent bundle, and show that this map induces an isomorphism
on homology in a range of degrees.
  Our results are analogous to McDuff's theorem on configuration spaces,
extended from 0-manifolds to 2-manifolds.


title: An analysis of the $t_2-V$ model

abstract:
  We study a model (i.e., the $t_2-V$ model involving {\em
next-nearest-neighbor hopping} and nearest-neighbor repulsion) in one-dimension
that generically depicts the dominant transport mechanism in cooperative strong
electron-phonon interaction systems. Using analytic and numerical approaches,
hard-core-bosons are shown to typically undergo a striking discontinuous
transition from a superfluid to a supersolid. Topological inequivalence of
rings with even and odd number of sites is manifested through observable
differences (in structure factor peaks) at the transition. Connections are also
identified between the $t_2-V$ model and other topologically interesting
models.


title: Perturbative solution to the SIS epidemic on networks

abstract:
  Herein we provide a closed form perturbative solution to a general $M$-node
network SIS model using the transport rates between nodes as a perturbation
parameter. We separate the dynamics into a short-time regime and a
medium/long-time regime. We solve the short-time dynamics of the system and
provide a limit before which our explicit, analytical result of the first-order
perturbation for the medium/long-time regime is to be employed. These stitched
calculations provide an approximation to the full temporal dynamics for rather
general initial conditions.
  To further corroborate our results, we solve the mean-field equations
numerically for an infectious SIS outbreak in New Zealand (NZ, \emph{Aotearoa})
recomposed into 23 subpopulations where the virus is spread to different
subpopulations via (documented) air traffic data, and the country is
internationally quarantined. We demonstrate that our analytical predictions
compare well to the numerical solution.


title:
Iterated hyper-extensions and an idempotent ultrafilter proof of Rado's
  theorem

abstract:
  By using nonstandard analysis, and in particular iterated hyper-extensions,
we give foundations to a peculiar way of manipulating ultrafilters on the
natural numbers and their pseudo-sums. The resulting formalism is suitable for
applications in Ramsey theory of numbers. To illustrate the use of our
technique, we give a (rather) short proof of Milliken-Taylor's Theorem, and a
ultrafilter version of Rado's theorem about partition regularity of diophantine
equations.


title:
Characterizing the Life Cycle of Online News Stories Using Social Media
  Reactions

abstract:
  This paper presents a study of the life cycle of news articles posted online.
We describe the interplay between website visitation patterns and social media
reactions to news content. We show that we can use this hybrid observation
method to characterize distinct classes of articles. We also find that social
media reactions can help predict future visitation patterns early and
accurately.
  We validate our methods using qualitative analysis as well as quantitative
analysis on data from a large international news network, for a set of articles
generating more than 3,000,000 visits and 200,000 social media reactions. We
show that it is possible to model accurately the overall traffic articles will
ultimately receive by observing the first ten to twenty minutes of social media
reactions. Achieving the same prediction accuracy with visits alone would
require to wait for three hours of data. We also describe significant
improvements on the accuracy of the early prediction of shelf-life for news
stories.


title: Splittings of von Neumann rho-invariants of knots

abstract:
  We give a sufficient condition under which vanishing property of
Cochran-Orr-Teichner knot concordance obstructions splits under connected sum.
The condition is described in terms of self-annihilating submodules with
respect to higher-order Blanchfield linking forms. This extends results of
Levine and the authors on distinguishing knots with coprime Alexander
polynomials up to concordance. As an application, we show that the knots
constructed by Cochran, Orr and Teichner as the first examples of nonslice
knots with vanishing Casson-Gordon invariants are not concordant to any knot of
genus one.


title: Cluster Luttinger Liquids of Rydberg-dressed Atoms in Optical Lattices

abstract:
  We investigate the zero-temperature phases of bosonic and fermionic gases
confined to one dimension and interacting via a class of finite-range
soft-shoulder potentials (i.e. soft-core potentials with an additional
hard-core onsite interaction). Using a combination of analytical and numerical
methods, we demonstrate the stabilization of critical quantum liquids with
qualitatively new features with respect to the Tomonaga-Luttinger liquid
paradigm. These features result from frustration and cluster formation in the
corresponding classical ground-state. Characteristic signatures of these
liquids are accessible in state-of-the-art experimental setups with
Rydberg-dressed ground-state atoms trapped in optical lattices.


title:
The influence of repressive legislation on the structure of a social
  media network

abstract:
  Social media have been widely used to organize citizen movements. In 2012,
75% university and college students in Quebec, Canada, participated in mass
protests against an increase in tuition fees, mainly organized using social
media. To reduce public disruption, the government introduced special
legislation designed to impede protest organization. Here, we show that the
legislation changed the behaviour of social media users but not the overall
structure of their social network on Twitter. Thus, users were still able to
spread information to efficiently organize demonstrations using their social
network. This natural experiment shows the power of social media in political
mobilization, as well as behavioural flexibility in information flow over a
large number of individuals.


title:
Scattering amplitude and pomeron loops in perturbative QCD at large
  $N_c$

abstract:
  The amplitude for the collision of two hadrons with the lowest order pomeron
loop is calculated. Numerical calculations show that the loop contribution to
the amplitude begins to dominate the single pomeron exchange at rapidities
8-10. Full dependence of the triple-pomeron vertex on intermediate conformal
weights is taken into account.


title: Looking for extended nuclear emission in a sample of nearby QSOs

abstract:
  We present MIR sub-arcsec observations of Mrk 1383, a nearby QSO, part of a
sample of nearby QSOs currently being observed with the 10.4 m Gran Telescopio
de Canarias (GTC). The radial profile of the QSO is analyzed and we find that
most of the MIR emission is unresolved (\theta ~ 0.4", 600 pc) and consistent
with previous measurements from Spitzer (\theta ~ 4"). We derive the spectral
energy distribution (SED) of the nuclear emission, relatively uncontaminated by
starlight, combining measurements from the literature as a first step towards
characterizing the torus parameters in this QSO.


title:
Autonomous Algorithms for Centralized and Distributed Interference
  Coordination: A Virtual Layer Based Approach

abstract:
  Interference mitigation techniques are essential for improving the
performance of interference limited wireless networks. In this paper, we
introduce novel interference mitigation schemes for wireless cellular networks
with space division multiple access (SDMA). The schemes are based on a virtual
layer that captures and simplifies the complicated interference situation in
the network and that is used for power control. We show how optimization in
this virtual layer generates gradually adapting power control settings that
lead to autonomous interference minimization. Thereby, the granularity of
control ranges from controlling frequency sub-band power via controlling the
power on a per-beam basis, to a granularity of only enforcing average power
constraints per beam. In conjunction with suitable short-term scheduling, our
algorithms gradually steer the network towards a higher utility. We use
extensive system-level simulations to compare three distributed algorithms and
evaluate their applicability for different user mobility assumptions. In
particular, it turns out that larger gains can be achieved by imposing average
power constraints and allowing opportunistic scheduling instantaneously, rather
than controlling the power in a strict way. Furthermore, we introduce a
centralized algorithm, which directly solves the underlying optimization and
shows fast convergence, as a performance benchmark for the distributed
solutions. Moreover, we investigate the deviation from global optimality by
comparing to a branch-and-bound-based solution.


title:
Gradients of Stellar Population Properties and Evolution Clues in a
  Nearby Galaxy M 101

abstract:
  Multi-band photometric images from ultraviolet and optical to infrared are
collected to derive spatially resolved properties of a nearby Scd type galaxy M
101. With evolutionary stellar population synthesis models, two-dimensional
distributions and radial profiles of age, metallicity, dust attenuation, and
star formation timescale in the form of the Sandage star formation history are
obtained. When fitting with the models, we use the IRX-$A_\mathrm{FUV}$
relation, found to depend on a second parameter of birth rate b (ratio of
present and past-averaged star formation rate), to constrain the dust
attenuation. There are obvious parameter gradients in the disk of M101, which
supports the theory of an "inside-out disk" growth scenario. Two distinct disc
regions with different gradients of age and color are discovered, similar to
another late-type galaxy NGC 628. The metallicity gradient of the stellar
content is flatter than that of H {\sc ii} regions. The stellar disk is
optically thicker inside than outside and the global dust attenuation of this
galaxy is lower, compared with galaxies of similar and earlier morphological
type. We highlight that a variational star formation timescale describes the
real star formation history of a galaxy. The timescale increases steadily from
the center to the outskirt. We also confirm that the bulge in this galaxy is a
disk-like pseudobulge, whose evolution is likely to be induced by some secular
processes of the small bar with relatively young age, rich metal, and much
dust.


title:
Influence of exciton spin relaxation on the photoluminescence spectra of
  semimagnetic quantum dots

abstract:
  We present a comprehensive experimental and theoretical studies of
photoluminescence of single CdMnTe quantum dots with Mn content x ranging from
0.01 to 0.2. We distinguish three stages of the equilibration of the exciton-Mn
ion spin system and show that the intermediate stage, in which the exciton spin
is relaxed, while the total equilibrium is not attained, gives rise to a
specific asymmetric shape of the photoluminescence spectrum. From an excellent
agreement between the measured and calculated spectra we are able to evaluate
the exciton localization volume, number of paramagnetic Mn ions, and their
temperature for each particular dot. We discuss the values of these parameters
and compare them with results of other experiments. Furthermore, we analyze the
dependence of average Zeeman shifts and transition linewidths on the Mn content
and point out specific processes, which control these values at particular Mn
concentrations.


title: Canonization of analytic equivalences on the Carlson-Simpson forcing

abstract:
  We prove a canonization result for the Carlson-Simpson forcing in the spirit
of \cite{KSZ}. We generalize the weak form of the Carlson-Simpson theorem
(\cite{CaSi}) dealing with partitions without free blocks: instead of dealing
with finite Borel (resp. Baire-property) colorings we deal with (uncountable)
colorings such that the corresponding equivalence relation (two partitions are
equivalent if they are colored by the same color) is analytic.