title:
Excitation of the Delta(1232) isobar in deuteron charge exchange on
  hydrogen at 1.6, 1.8, and 2.3 GeV

abstract:
  The charge-exchange break-up of polarised deuterons pol{d}p -> {pp}n, where
the final {pp} diproton system has a very low excitation energy and hence is
mainly in the 1S0 state, is a powerful tool to probe the spin-flip terms in the
proton-neutron charge-exchange scattering. Recent measurements with the ANKE
spectrometer at the COSY storage ring at 1.6, 1.8, and 2.27 GeV have extended
these studies into the pion-production regime in order to investigate the
mechanism for the excitation of the Delta(1232) isobar in the pol{d}p -> {pp}X
reaction. Values of the differential cross section and two deuteron tensor
analysing powers, A_{xx} and A_{yy}, have been extracted in terms of the
momentum transfer to the diproton or the invariant mass Mx of the unobserved
system X. The unpolarised cross section in the high Mx region is well described
in a model that includes only direct excitation of the Delta isobar through
undistorted one pion exchange. However, the cross section is grossly
underestimated for low Mx, even when Delta excitation in the projectile
deuteron is included in the calculation. Furthermore, direct Delta production
through one pion exchange only reproduces the angular dependence of the
difference between the two tensor analysing powers.


title:
Universal size effects for populations in group-outcome decision-making
  problems

abstract:
  Elections constitute a paradigm of decision-making problems that have puzzled
experts of different disciplines for decades. We study two decision-making
problems, where groups make decisions that impact only themselves as a group.
In both studied cases, participation in local elections and the number of
democratic representatives at different scales (from local to national), we
observe a universal scaling with the constituency size. These results may be
interpreted as constituencies having a hierarchical structure, where each group
of $N$ agents, at each level of the hierarchy, is divided in about $N^{\delta}$
subgroups with $\delta \approx 1/3$. Following this interpretation, we propose
a phenomenological model of vote participation where abstention is related to
the perceived link of an agent to the rest of the constituency and which
reproduces quantitatively the observed data.


title:
A high order cell-centered semi-Lagrangian scheme for multi-dimensional
  kinetic simulations of neutral gas flows

abstract:
  The term `Convected Scheme' (CS) refers to a family of algorithms, most
usually applied to the solution of Boltzmann's equation, which uses a method of
characteristics in an integral form to project an initial cell forward to a
group of final cells. As such the CS is a `forward-trajectory' semi-Lagrangian
scheme. For multi-dimensional simulations of neutral gas flows, the
cell-centered version of this semi-Lagrangian (CCSL) scheme has advantages over
other options due to its implementation simplicity, low memory requirements,
and easier treatment of boundary conditions. The main drawback of the CCSL-CS
to date has been its high numerical diffusion in physical space, because of the
2$^{\text{nd}}$ order remapping that takes place at the end of each time step.
By means of a Modified Equation Analysis, it is shown that a high order
estimate of the remapping error can be obtained a priori, and a small
correction to the final position of the cells can be applied upon remapping, in
order to achieve full compensation of this error. The resulting scheme is
4$^{\text{th}}$ order accurate in space while retaining the desirable
properties of the CS: it is conservative and positivity-preserving, and the
overall algorithm complexity is not appreciably increased. Two monotone (i.e.
non-oscillating) versions of the fourth order CCSL-CS are also presented: one
uses a common flux-limiter approach; the other uses a non-polynomial
reconstruction to evaluate the derivatives of the density function. The method
is illustrated in simple one- and two-dimensional examples, and a fully 3D
solution of the Boltzmann equation describing expansion of a gas into vacuum
through a cylindrical tube.


title: On $f$-bi-harmonic maps between Riemannian manifolds

abstract:
  Both bi-harmonic map and $f$-harmonic map have nice physical motivation and
applications. In this paper, by combination of these two harmonic maps, we
introduce and study $f$-bi-harmonic maps as the critical points of the
$f$-bi-energy functional $\frac{1}{2}\int_M f|\tau (\phi)|^2dv_{g}$. This class
of maps generalizes both concepts of harmonic maps and bi-harmonic maps. We
first derive the $f$-biharmonic map equation and then use it to study
$f$-bi-harmonicity of some special maps, including conformal maps between
manifolds of same dimensions, some product maps between direct product manifold
and singly warped product manifold, some projection maps from and some
inclusion maps into a warped product manifold.


title:
The structure of site percolation models on three-dimensional square
  lattices

abstract:
  In this paper we consider the structure of site percolation models on
three-dimensional square lattices with various shapes of (1,d)-neighborhood.
For these models, are proposed iso- and anisotropic modifications of the
invasion percolation algorithm with (1,0)- and (1,d)-neighborhoods. All the
above algorithms are special cases of the anisotropic invasion percolation
algorithm on the n-dimensional lattice with a (1,d)-neighborhood. This
algorithm is the basis for the package SPSL, released under GNU GPL-3 using the
free programming language R.


title:
Quantum interference-enhanced deep sub-Doppler cooling of 39 K atoms in
  gray molasses

abstract:
  We report enhanced sub-Doppler cooling of the bosonic atoms of $^{39}$K
facilitated by formation of dark states tuned for the Raman resonance in the
$\Lambda-$configuration near the D1 transition. Temperature of about 12 $\mu$K
is achieved in the two stage D2-D1 molasses and spans a very large parameter
region where quantum interference persists robustly. We also present results on
enhanced radiation heating with sub-natural linewidth (0.07$\Gamma$) and
signature Fano like profile of a coherently driven 3-level atomic system. The
Optical Bloch Equations relevant for the three-level atom in bichromatic light
field is solved with the method of continued fractions to show that cooling
occurs only for a small velocity class of atoms, emphasizing the need for
pre-cooling in D2 molasses stage.


title: Rosenbrock-Krylov Methods for Large Systems of Differential Equations

abstract:
  This paper develops a new class of Rosenbrock-type integrators based on a
Krylov space solution of the linear systems. The new family, called
Rosenbrock-Krylov (Rosenbrock-K), is well suited for solving large scale
systems of ODEs or semi-discrete PDEs. The time discretization and the Krylov
space approximation are treated as a single computational process, and the
Krylov space properties are an integral part of the new Rosenbrock-K order
condition theory developed herein. Consequently, Rosenbrock-K methods require a
small number of basis vectors determined solely by the temporal order of
accuracy. The subspace size is independent of the ODE under consideration, and
there is no need to monitor the errors in linear system solutions at each
stage. Numerical results show favorable properties of Rosenbrock-K methods when
compared to current Rosenbrock and Rosenbrock-W schemes.


title: Particle Physics in The United States, A Personal View

abstract:
  I present my views on the future of America's program in particle physics. I
discuss a variety of experimental initiatives that do have the potential to
make transformative impacts on our discipline and should be included in our
program, as well as others that do not and should not.


title:
NEMESYS: Enhanced Network Security for Seamless Service Provisioning in
  the Smart Mobile Ecosystem

abstract:
  As a consequence of the growing popularity of smart mobile devices, mobile
malware is clearly on the rise, with attackers targeting valuable user
information and exploiting vulnerabilities of the mobile ecosystems. With the
emergence of large-scale mobile botnets, smartphones can also be used to launch
attacks on mobile networks. The NEMESYS project will develop novel security
technologies for seamless service provisioning in the smart mobile ecosystem,
and improve mobile network security through better understanding of the threat
landscape. NEMESYS will gather and analyze information about the nature of
cyber-attacks targeting mobile users and the mobile network so that appropriate
counter-measures can be taken. We will develop a data collection infrastructure
that incorporates virtualized mobile honeypots and a honeyclient, to gather,
detect and provide early warning of mobile attacks and better understand the
modus operandi of cyber-criminals that target mobile devices. By correlating
the extracted information with the known patterns of attacks from wireline
networks, we will reveal and identify trends in the way that cyber-criminals
launch attacks against mobile devices.


title: The Cooling of Coronal Plasmas. iv: Catastrophic Cooling of Loops

abstract:
  We examine the radiative cooling of coronal loops and demonstrate that the
recently identified catastrophic cooling (Reale and Landi, 2012) is due to the
inability of a loop to sustain radiative / enthalpy cooling below a critical
temperature, which can be > 1 MK in flares, 0.5 - 1 MK in active regions and
0.1 MK in long tenuous loops. Catastrophic cooling is characterised by a rapid
fall in coronal temperature while the coronal density changes by a small
amount. Analytic expressions for the critical temperature are derived and show
good agreement with numerical results. This effect limits very considerably the
lifetime of coronal plasmas below the critical temperature.


title:
Infrared and Raman spectroscopy measurements of a transition in the
  crystal structure and a closing of the energy gap of BiTeI under pressure

abstract:
  BiTeI is a giant Rashba spin splitting system, in which a non-centro
symmetric topological phase has recently been suggested to appear under high
pressure. We investigated the optical properties of this compound, reflectivity
and transmission, under pressures up to $15$ GPa. The gap feature in the
optical conductivity vanishes above $p \sim 9$ GPa and does not reappear up to
at least $15$ GPa. The plasma edge, associated with intrinsically doped charge
carriers, is smeared out through a phase transition at $9$ GPa. Using high
pressure Raman spectroscopy, we follow the vibrational modes of BiTeI,
providing additional clear evidence that the transition at 9 GPa involves a
change of crystal structure. This change of crystal structure possibly inhibits
the high-pressure topological phase from occurring.


title: Fast Autocorrelated Context Models for Data Compression

abstract:
  A method is presented to automatically generate context models of data by
calculating the data's autocorrelation function. The largest values of the
autocorrelation function occur at the offsets or lags in the bitstream which
tend to be the most highly correlated to any particular location. These offsets
are ideal for use in predictive coding, such as predictive partial match (PPM)
or context-mixing algorithms for data compression, making such algorithms more
efficient and more general by reducing or eliminating the need for ad-hoc
models based on particular types of data. Instead of using the definition of
the autocorrelation function, which considers the pairwise correlations of data
requiring O(n^2) time, the Weiner-Khinchin theorem is applied, quickly
obtaining the autocorrelation as the inverse Fast Fourier transform of the
data's power spectrum in O(n log n) time, making the technique practical for
the compression of large data objects. The method is shown to produce the
highest levels of performance obtained to date on a lossless image compression
benchmark.


title:
In situ observation of strongly interacting ferromagnetic domains in a
  shaken optical lattice

abstract:
  Solid state systems derive their richness from the interplay between
interparticle interactions and novel band structures that deviate from those of
free particles. Strongly interacting systems, where both of these phenomena are
of equal importance, exhibit a variety of theoretically interesting and
practically useful phases. Systems of ultracold atoms are rapidly emerging as
precise and controllable simulators, and it is precisely in this strongly
interacting regime where simulation is the most useful. Here we demonstrate how
to hybridize Bloch bands in optical lattices to introduce long-range
ferromagnetic order in an itinerant atomic system. We find spontaneously broken
symmetry for bosons with a double-well dispersion condensing into one of two
distinct minima, which we identify with spin-up and spin-down. The density
dynamics following a rapid quench to the ferromagnetic state confirm quantum
interference between the two states as the mechanism for symmetry breaking.
Unlike spinor condensates, where interaction is driven by small spin-dependent
differences in scattering length, our interactions scale with the scattering
length itself, leading to domains which equilibrate rapidly and develop sharp
boundaries characteristic of a strongly interacting ferromagnet.


title: Black holes and equivariant charge vectors in N=2,d=4 supergravity

abstract:
  We extend previous investigations on the construction of extremal
supersymmetric and non-supersymmetric solutions in the H-FGK formalism to
"unconventional" solutions with anharmonic terms. We show how the use of "fake"
charge vectors equivariant under duality transformations simplifies and
clarifies the task of identification of the attractors of the theory.


title: Exotic coactions

abstract:
  If a locally compact group G acts on a C*-algebra B, we have both full and
reduced crossed products, and each has a coaction of G. We investigate "exotic"
coactions in between, that are determined by certain ideals E of the
Fourier-Stieltjes algebra B(G) -- an approach that is inspired by recent work
of Brown and Guentner on new C*-group algebra completions. We actually carry
out the bulk of our investigation in the general context of coactions on a
C*-algebra A. Buss and Echterhoff have shown that not every coaction comes from
one of these ideals, but nevertheless the ideals do generate a wide array of
exotic coactions. Coactions determined by these ideals E satisfy a certain
"E-crossed product duality", intermediate between full and reduced duality. We
give partial results concerning exotic coactions, with the ultimate goal being
a classification of which coactions are determined by ideals of B(G).


title:
Weighted gamma-K-functional and gamma-Modulus of Smoothness on the
  Semiaxis

abstract:
  In this paper we investigate the gamma-relative differentiation by the
motivation of amending the order of the weighted polynomial approximation on
the semiaxis for certain functions. With the help of this we give some
definitions of generalized Sobolev spaces, K-functionals and moduli of
smoothness. We prove theorems for estimating these things with each other, in
the case of first order we prove equivalence. We remark some possible
applications and other generalizations too.


title:
Coherent dynamics of Rydberg atoms in cosmic microwave background
  radiation

abstract:
  Rydberg atoms excited by cold blackbody radiation are shown to display
long-lived quantum coherences on timescales of tens of picoseconds. By solving
non-Markovian equations of motion with no free parameters we obtain the time
evolution of the density matrix, and demonstrate that the blackbody-induced
temporal coherences manifest as slowly decaying (100 ps) quantum beats in
time-resolved fluorescence. An analytic model shows the dependence of the
coherent dynamics on the energy splitting between atomic eigenstates,
transition dipole moments, and coherence time of the radiation. Experimental
detection of the fluorescence signal from a trapped ensemble of $10^8$ Rydberg
atom is discussed, but shown to be technically challenging at present,
requiring CMB amplification somewhat beyond current practice.


title:
Type III sigma-spectral triples and quantum statistical mechanical
  systems

abstract:
  Spectral triples and quantum statistical mechanical systems are two important
constructions in noncommutative geometry. In particular, both lead to
interesting reconstruction theorems for a broad range of geometric objects,
including number fields, spin manifolds, graphs. There are similarities between
the two structures, and we show that the notion of type III sigma-spectral
triple, introduced recently by Connes and Moscovici, provides a natural bridge
between them. We investigate explicit examples, related to the Bost-Connes
quantum statistical mechanical system and to Riemann surfaces and graphs.


title: Information Criteria for Deciding between Normal Regression Models

abstract:
  Regression models fitted to data can be assessed on their goodness of fit,
though models with many parameters should be disfavored to prevent
over-fitting. Statisticians' tools for this are little known to physical
scientists. These include the Akaike Information Criterion (AIC), a penalized
goodness-of-fit statistic, and the AICc, a variant including a small-sample
correction. They entered the physical sciences through being used by
astrophysicists to compare cosmological models; e.g., predictions of the
distance-redshift relation. The AICc is shown to have been misapplied, being
applicable only if error variances are unknown. If error bars accompany the
data, the AIC should be used instead. Erroneous applications of the AICc are
listed in an appendix. It is also shown how the variability of the AIC
difference between models with a known error variance can be estimated. This
yields a significance test that can potentially replace the use of `Akaike
weights' for deciding between such models. Additionally, the effects of model
misspecification are examined. For regression models fitted to data sets
without (rather than with) error bars, they are major: the AICc may be shifted
by an unknown amount. The extent of this in the fitting of physical models
remains to be studied.


title: Coulomb corrections to density and temperature in heavy ion collisions

abstract:
  A recently proposed method, based on quadrupole and multiplicity fluctuations
in heavy ion collisions, is modified in order to take into account distortions
due to the Coulomb field. The classical and quantum limits for fermions are
discussed. In the classical case we find that the temperature determined from
${}^3He$ and ${}^3H$, after the Coulomb correction, are very similar to those
obtained from neutrons within the Constrained Molecular Dynamics (CoMD)
approach. In the quantum case, the proton temperature becomes very similar to
neutron's, while densities are not sensitive to the Coulomb corrections.


title: On the Importance of Conceptual Thinking Outside the Simulation Box

abstract:
  Any ambitious construction project requires architects for its design and
engineers who apply the design to the real world. As scientific research shifts
towards large groups which focus on the engineering aspects of linking data to
existing models, architectural skills are becoming rare among young theorists.
Senior researchers should mentor qualified students and postdocs to think
creatively about the big picture without unwarranted loyalty to ancient
blueprints from past generations of architects.


title: Sudden expansion of Mott insulators in one dimension

abstract:
  We investigate the expansion of bosons and fermions in a homogeneous lattice
after a sudden removal of the trapping potential using exact numerical methods.
As a main result, we show that in one dimension, both bosonic and fermionic
Mott insulators expand with the same velocity, irrespective of the interaction
strength, provided the expansion starts from the ground state of the trapped
gas. Furthermore, their density profiles become identical during the expansion:
The asymptotic density dynamics is identical to that of initially localized,
non-interacting particles, and the asymptotic velocity distribution is flat.
The expansion velocity for initial correlated Mott insulating states is
therefore independent of the interaction strength and particle statistics.
Interestingly, this non-equilibrium dynamics is sensitive to the interaction
driven quantum phase transition in the Bose-Hubbard model: While being constant
in the Mott phase, the expansion velocity decreases in the superfluid phase and
vanishes for large systems in the non-interacting limit. These results are
compared to the set-up of a recent experiment [PRL 110, 205301 (2013)], where
the trap opening was combined with an interaction quench from infinitely strong
interactions to finite values. We carry out an analogous analysis for a
two-component Fermi gas, with similar observations. In addition, we study the
effect of breaking the integrability of hard-core bosons in different ways:
While the fast ballistic expansion from the ground state of Mott insulators in
one dimension remains unchanged for finite interactions, we observe strong
deviations from this behavior on a two-leg ladder even in the hard-core case.
This change in dynamics bares similarities with the dynamics in the dimensional
crossover from one to two dimensions observed in the aformentioned experimental
study.


title: Conductivity low-energy asymptotics for monolayer graphene

abstract:
  Electron scattering problem in the monolayer graphene with short-range
impurities is considered. The main novel element in the suggested model is the
band asymmetry of the defect potential in the 2+1-dimensional Dirac equation.
This asymmetry appears naturally if the defect violates the symmetry between
sublattices. Our goal in the present paper is to take into account a local band
asymmetry violation arising due to the defect presence. We analyze the effect
of the electron scattering on the electronic transport parameters in the
monolayer graphene. The explicit exact formula obtained for S-matrix for the
suggested delta-shell potential model allowed us to study the asymptotic
behavior of such characteristics as scattering phases, transport cross section,
the transport relaxation time and the conductivity for small values of the
Fermi energy. The obtained results are in a good agreement with the
experimental data which shows that the considered model is reasonable.


title: Remarks on the error term in Chebotarev Density Theorem

abstract:
  We discuss various effective forms of Chebotarev's density theorem, answering
a question of Serre and a question of Murty, Murty and Seradha.


title: Subword complexes and edge subdivisions

abstract:
  For a finite Coxeter group, a subword complex is a simplicial complex
associated with a pair (Q, \pi), where Q is a word in the alphabet of simple
reflections, $\pi$ is a group element. We discuss the transformations of such a
complex induced by braid moves of the word Q. We show that under certain
conditions, this transformation is a composition of edge subdivisions and
inverse edge subdivisions. In such a case, we describe how the H- and the
\gamma-polynomials change under this operation. This case includes all braid
moves for groups with simply-laced Coxeter diagrams.


title: A Characterization of Approximation Resistance

abstract:
  A predicate f:{-1,1}^k -> {0,1} with \rho(f) = \frac{|f^{-1}(1)|}{2^k} is
called {\it approximation resistant} if given a near-satisfiable instance of
CSP(f), it is computationally hard to find an assignment that satisfies at
least \rho(f)+\Omega(1) fraction of the constraints.
  We present a complete characterization of approximation resistant predicates
under the Unique Games Conjecture. We also present characterizations in the
{\it mixed} linear and semi-definite programming hierarchy and the
Sherali-Adams linear programming hierarchy. In the former case, the
characterization coincides with the one based on UGC. Each of the two
characterizations is in terms of existence of a probability measure with
certain symmetry properties on a natural convex polytope associated with the
predicate.


title: Nearest neighbor Markov dynamics on Macdonald processes

abstract:
  Macdonald processes are certain probability measures on two-dimensional
arrays of interlacing particles introduced by Borodin and Corwin
(arXiv:1111.4408 [math.PR]). They are defined in terms of nonnegative
specializations of the Macdonald symmetric functions and depend on two
parameters (q,t), where 0<= q, t < 1. Our main result is a classification of
continuous time, nearest neighbor Markov dynamics on the space of interlacing
arrays that act nicely on Macdonald processes.
  The classification unites known examples of such dynamics and also yields
many new ones. When t = 0, one dynamics leads to a new integrable interacting
particle system on the one-dimensional lattice, which is a q-deformation of the
PushTASEP (= long-range TASEP). When q = t, the Macdonald processes become the
Schur processes of Okounkov and Reshetikhin (arXiv:math/0107056 [math.CO]). In
this degeneration, we discover new Robinson--Schensted-type correspondences
between words and pairs of Young tableaux that govern some of our dynamics.


title: On the Probability of Relative Primality in the Gaussian Integers

abstract:
  This paper studies the interplay between probability, number theory, and
geometry in the context of relatively prime integers in the ring of integers of
a number field. In particular, probabilistic ideas are coupled together with
integer lattices and the theory of zeta functions over number fields in order
to show that $$P(\gcd(z_{1},z_{2})=1) = \frac{1}{\zeta_{\Q(i)}(2)}$$ where
$z_{1},z_{2} \in \mathbb{Z}[i]$ are randomly chosen and $\zeta_{\Q(i)}(s)$ is
the Dedekind zeta function over the Gaussian integers. Our proof outlines a
lattice-theoretic approach to proving the generalization of this theorem to
arbitrary number fields that are principal ideal domains.


title: Two different physical interpretations of Schroedinger equation

abstract:
  The assumptions added by Bohr and concerning the Hilbert space (formed by all
solutions of Schroedinger equation) changed fundamentally the original physical
interpretation of these solutions proposed earlier by Schroedinger. This new
alternative was refused by Einstein on the basis of the EPR Gedankenexperiment,
but accepted fully for microscopic reality by scientific community. Both the
quantum alternatives were discussed, however, again later. Bell tried to find a
possibility how to decide between them; he generalized Einstein's
Gedankenexperiment assuming that also spins of two detected particles would be
measured. He derived then some inequality for a special combination of four
coincidence probabilities, and it was commonly assumed that his inequality held
for the original Schroedinger interpretation but not in Bohr's Copenhagen
quantum mechanics; without any actual proof having been given. Corresponding
experiments were proposed and finished in 1982. The violation of Bell's
inequality was then interpreted as decisive victory of Bohr's theory. However,
it will be shown that Bell's inequality has been interpreted mistakenly. It has
been based always on some assumption that does not hold in any probabilistic
theory (i.e., in the given spin experiment) but only in deterministic classical
theory. There is not any argument for preferring the Copenhagen quantum
mechanics and against Einstein's critical standpoint. Some other consequences
will be mentioned, too.


title: Inverse indirect magnetic exchange

abstract:
  Magnetic moments strongly coupled to the spins of conduction electrons in a
nanostructure can confine the conduction-electron motion due to scattering at
almost localized Kondo singlets. We study the resulting local-moment formation
in the conduction-electron system and the magnetic exchange coupling mediated
by the Kondo singlets. Its distance dependence is oscillatory and induces
robust ferro- or antiferromagnetic order in multi-impurity systems.


title:
Multiple charge density wave transitions in Lu_{2} Ir_{3} Si_{5} single
  crystal

abstract:
  The physical properties of the single-crystalline samples of Lu_{2} Ir_{3}
Si_{5} have been investigated by magnetic susceptibility, resistivity and heat
capacity studies. We observed multiple charge density wave (CDW) transitions in
all the measurements. A strong thermal hysteresis at these transitions suggests
a possible first order CDW ordering. In addition, the first order nature is
ascertained by a very narrow and a huge cusp (62 J/mol K) in the zero field
specific heat data which also suggests a strong interchain coupling. By
applying a field of 9T in the specific heat measurement, one of the CDW
transitions is suppressed.


title: Introduction to Judea Pearl's Do-Calculus

abstract:
  This is a purely pedagogical paper with no new results. The goal of the paper
is to give a fairly self-contained introduction to Judea Pearl's do-calculus,
including proofs of his 3 rules.


title: Kapitza-Dirac effect in the relativistic regime

abstract:
  A relativistic description of the Kapitza-Dirac effect in the so-called Bragg
regime with two and three interacting photons is presented by investigating
both numerical and perturbative solutions of the Dirac equation in momentum
space. We demonstrate that spin-flips can be observed in the two-photon and the
three-photon Kapitza-Dirac effect for certain parameters. During the
interaction with the laser field the electron's spin is rotated, and we give
explicit expressions for the rotation axis and the rotation angle. The
off-resonant Kapitza-Dirac effect, that is, when the Bragg condition is not
exactly fulfilled, is described by a generalized Rabi theory. We also analyze
the in-field quantum dynamics as obtained from the numerical solution of the
Dirac equation.


title:
Comments on: Antarctic Automatic Weather Station Program: 30 Years of
  Polar Observations

abstract:
  Recently Lazzara et al. (2012) presented a review of the technical and
scientific progress in deployment, data collection and analysis of the
Automated Weather Stations (AWS) in the Antarctic. In the subsection entitled
Science Applications using AWS Observations, the authors briefly account for
several scientific occurrences of meteorological data collected by AWS.


title: Holographic Photon Production with Magnetic Field in Anisotropic Plasmas

abstract:
  We investigate the thermal photon production from constant magnetic field in
a strongly coupled and anisotropic plasma via the gauge/gravity duality. The
dual geometry with pressure anisotropy is generated from the axion-dilaton
gravity action introduced by Mateos and Trancancelli and the magnetic field is
coupled to fundamental matters(quarks) through the D3/D7 embeddings. We find
that the photon spectra with different quark mass are enhanced at large
frequency when the photons are emitted parallel to the anisotropic direction
with larger pressure or perpendicular to the magnetic field. However, in the
opposite conditions for the emitted directions, the spectra approximately
saturate isotropic results in the absence of magnetic field. On the other hand,
a resonance emerges at moderate frequency for the photon spectrum with heavy
quarks when the photons move perpendicular to the magnetic field. The resonance
is more robust when the photons are polarized along the magnetic field. On the
contrary, in the presence of pressure anisotropy, the resonance will be
suppressed. There exist competing effects of magnetic field and pressure
anisotropy on meson melting in the strongly coupled super Yang-Mills plasma,
while we argue that the suppression led by anisotropy may not be applied to the
quark gluon plasma.


title: Construction of hyperbolic Riemann surfaces with large systoles

abstract:
  Let $S$ be a compact hyperbolic Riemann surface of genus $g \geq 2$. We call
a systole a shortest simple closed geodesic in $S$ and denote by
$\mathop{sys}(S)$ its length. Let $\mathop{msys(g)}$ be the maximal value that
$\mathop{sys}(\cdot)$ can attain among the compact Riemann surfaces of genus
$g$. We call a (globally) maximal surface $S_{max}$ a compact Riemann surface
of genus $g$ whose systole has length $\mathop{msys}(g)$. In Section 2 we use
cutting and pasting techniques to construct compact hyperbolic Riemann surfaces
with large systoles from maximal surfaces. This enables us to prove several
inequalities relating $\mathop{msys}(\cdot)$ of different genera. In Section 3
we derive similar intersystolic inequalities for non-compact hyperbolic Riemann
surfaces with cusps.


title:
On the homology of the moduli space of plane sheaves with Hilbert
  polynomial 5m+3

abstract:
  We compute the Hodge numbers of the moduli space of semi-stable sheaves on
the complex projective plane supported on quintic curves and having Euler
characteristic 3. For this purpose we study the fixed-point set for a certain
torus action on the moduli space.


title:
Modified equations in the theory of induced gravity. Solution to the
  cosmological constant problem

abstract:
  This research is an extension of the author's article \cite{zar}, in which
conformally invariant generalization of string theory was suggested to
higher-dimensional objects. Special cases of the proposed theory are Einstein's
theory of gravity and string theory. This work is devoted to the formation of
self-consistent equations of the theory of induced gravity \cite{zar},
\cite{zari} in the presence of matter in the form of a perfect fluid that
interacts with scalar fields. The study is done to solve these equations for
the case of the cosmological model. In this model time-evolving gravitational
and cosmological "constants" take place which are determined by the square of
scalar fields. The values of which can be matched with the observational data.
The equations that describe the theory have solutions that can both match with
the solutions of the standard theory of gravity as well as it can differ from
it. This is due to the fact that the fundamental "constants" of the theory,
such as gravitational and cosmological, can evolve over time and also depend of
the coordinates. Thus, in a rather general case the theory describes the two
systems (stages): Einstein and "evolving" or "restructuring" (the name
suggested by the author). This process is similar to the phenomenon of phase
transition, where the different phases (Einstein gravity system, but with
different constants) transit into each other.


title:
Rapid growth of superradiant instabilities for charged black holes in a
  cavity

abstract:
  Confined scalar fields, either by a mass term or by a mirror-like boundary
condition, have unstable modes in the background of a Kerr black hole. Assuming
a time dependence as $e^{-i\omega t}$, the growth time-scale of these unstable
modes is set by the inverse of the (positive) imaginary part of the frequency,
Im$(\omega)$, which reaches a maximum value of the order of Im$(\omega)M\sim
10^{-5}$, attained for a mirror-like boundary condition, where $M$ is the black
hole mass. In this paper we study the minimally coupled Klein-Gordon equation
for a charged scalar field in the background of a Reissner-Nordstr\"om black
hole and show that the unstable modes, due to a mirror-like boundary condition,
can grow several orders of magnitude faster than in the rotating case: we have
obtained modes with up to Im$(\omega)M\sim 0.07$. We provide an understanding,
based on an analytic approximation, to why the instability in the charged case
has a smaller timescale than in the rotating case. This faster growth, together
with the spherical symmetry, makes the charged case a promising model for
studies of the fully non-linear development of superradiant instabilities.


title: Computing K-Trivial Sets by Incomplete Random Sets

abstract:
  Every K-trivial set is computable from an incomplete Martin-L\"of random set,
i.e., a Martin-L\"of random set that does not compute 0'.


title:
Comparison of charge modulations in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and
  YBa$_2$Cu$_3$O$_{6.6}$

abstract:
  A charge modulation has recently been reported in (Y,Nd)Ba$_2$Cu$_3$O$_{6+x}$
[Ghiringhelli {\em et al.} Science 337, 821 (2013)]. Here we report Cu $L_3$
edge soft x-ray scattering studies comparing the lattice modulation associated
with the charge modulation in YBa$_2$Cu$_3$O$_{6.6}$ with that associated with
the well known charge and spin stripe order in La$_{1.875}$Ba$_{0.125}$CuO$_4$.
We find that the correlation length in the CuO$_2$ plane is isotropic in both
cases, and is $259 \pm 9$ \AA for La$_{1.875}$Ba$_{0.125}$CuO$_4$ and $55 \pm
15$ \AA for YBa$_2$Cu$_3$O$_{6.6}$. Assuming weak inter-planar correlations of
the charge ordering in both compounds, we conclude that the order parameters of
the lattice modulations in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and
YBa$_2$Cu$_3$O$_{6.6}$ are of the same order of magnitude.


title:
Nuclear modification of psi^prime, chi_c and J/psi production in d+Au
  collisions at sqrt(s_NN) = 200 GeV

abstract:
  We present results for three charmonia states (psi^prime, chi_c and J/psi) in
d+Au collisions at |y|<0.35 and sqrt(s_NN)=200 GeV. We find that the
modification of the psi^prime yield relative to that of the J/psi scales
approximately with charged-particle multiplicity at midrapidity across p+A,
d+Au, and A+A results from the Super Proton Synchrotron and the Relativistic
Heavy Ion Collider. In large impact-parameter collisions we observe a similar
suppression for the psi^prime and J/psi, while in small impact-parameter
collisions the more weakly bound psi^prime is more strongly suppressed. Owing
to the short time spent traversing the Au nucleus, the larger psi^prime
suppression in central events is not explained by an increase of the nuclear
absorption due to meson formation time effects.


title:
Robust energy transfer mechanism and critically balanced turbulence via
  non-resonant triads in nonlinear wave systems

abstract:
  A robust energy transfer mechanism is found in nonlinear wave systems, which
favours transfers towards modes interacting via non-resonant triads, applicable
in meteorology, nonlinear optics and plasma wave turbulence. Transfer
efficiency is maximal when the frequency mismatch of the non-resonant triad
balances the system's nonlinear frequency: at intermediate levels of
oscillation amplitudes an instability is triggered that explores unstable
manifolds of periodic orbits, so turbulent cascades are most efficient at
intermediate nonlinearity. Numerical simulations confirm analytical
predictions.


title: Three remarks on Matula numbers

abstract:
  In SIAM Review 10, page 273, D. W. Matula described a bijection between N and
the set of topological rooted trees; the number is called the Matula number of
the rooted tree. The Gutman-Ivic-Matula (GIM) function g(n) computes the number
of edges of the unique tree with Matula number n. Since there is a prefix-free
code for the set of prime numbers such that the codelength of each prime p is
2g(p), we show how some properties of the GIM function can be obtained
trivially from coding theorems.


title: Gas rotation in galaxy clusters: signatures and detectability in X-rays

abstract:
  We study simple models of massive galaxy clusters in which the intracluster
medium (ICM) rotates differentially in equilibrium in the cluster gravitational
potential. We obtain the X-ray surface brightness maps, evaluating the isophote
flattening due to the gas rotation. Using a set of different rotation laws, we
put constraint on the amplitude of the rotation velocity, finding that rotation
curves with peak velocity up to \sim 600 km s^-1 are consistent with the
ellipticity profiles of observed clusters. We convolve each of our models with
the instrument response of the X-ray Calorimeter Spectrometer on board the
ASTRO-H to calculate the simulated X-ray spectra at different distance from the
X-ray centre. We demonstrate that such an instrument will allow us to measure
rotation of the ICM in massive clusters, even with rotation velocities as low
as \sim 100 km s^-1


title: Distributed Minimum Cut Approximation

abstract:
  We study the problem of computing approximate minimum edge cuts by
distributed algorithms. We use a standard synchronous message passing model
where in each round, $O(\log n)$ bits can be transmitted over each edge (a.k.a.
the CONGEST model). We present a distributed algorithm that, for any weighted
graph and any $\epsilon \in (0, 1)$, with high probability finds a cut of size
at most $O(\epsilon^{-1}\lambda)$ in $O(D) + \tilde{O}(n^{1/2 + \epsilon})$
rounds, where $\lambda$ is the size of the minimum cut. This algorithm is based
on a simple approach for analyzing random edge sampling, which we call the
random layering technique. In addition, we also present another distributed
algorithm, which is based on a centralized algorithm due to Matula [SODA '93],
that with high probability computes a cut of size at most $(2+\epsilon)\lambda$
in $\tilde{O}((D+\sqrt{n})/\epsilon^5)$ rounds for any $\epsilon>0$.
  The time complexities of both of these algorithms almost match the
$\tilde{\Omega}(D + \sqrt{n})$ lower bound of Das Sarma et al. [STOC '11], thus
leading to an answer to an open question raised by Elkin [SIGACT-News '04] and
Das Sarma et al. [STOC '11].
  Furthermore, we also strengthen the lower bound of Das Sarma et al. by
extending it to unweighted graphs. We show that the same lower bound also holds
for unweighted multigraphs (or equivalently for weighted graphs in which
$O(w\log n)$ bits can be transmitted in each round over an edge of weight $w$),
even if the diameter is $D=O(\log n)$. For unweighted simple graphs, we show
that even for networks of diameter $\tilde{O}(\frac{1}{\lambda}\cdot
\sqrt{\frac{n}{\alpha\lambda}})$, finding an $\alpha$-approximate minimum cut
in networks of edge connectivity $\lambda$ or computing an
$\alpha$-approximation of the edge connectivity requires $\tilde{\Omega}(D +
\sqrt{\frac{n}{\alpha\lambda}})$ rounds.


title: Absolute cross-section normalization of magnetic neutron scattering data

abstract:
  We discuss various methods to obtain the resolution volume for neutron
scattering experiments, in order to perform absolute normalization on inelastic
magnetic neutron scattering data. Examples from previous experiments are given.
We also try to provide clear definitions of a number of physical quantities
which are commonly used to describe neutron magnetic scattering results,
including the dynamic spin correlation function and the imaginary part of the
dynamic susceptibility. Formulas that can be used for general purposes are
provided and the advantages of the different normalization processes are
discussed.


title:
An Intelligent System to Detect, Avoid and Maintain Potholes: A Graph
  Theoretic Approach

abstract:
  In this paper, we propose a conceptual framework where a centralized system,
classifies the road based upon the level of damage. The centralized system also
identifies the traffic intensity thereby prioritizing the roads that need quick
action to be taken upon. Moreover, the system helps the driver to detect the
level of damage to the road stretch and route the vehicle from an alternative
path to its destination. The system sends a feedback to the concerned
authorities for a quick response to the condition of the roads. The system we
use comprises a laser sensor and pressure sensors in shock absorbers to detect
and quantify the intensity of the pothole, a centralized server which maintains
a database of locations of all the potholes which can be accessed by another
unit inside the vehicle. A point to point connection device is also installed
in vehicles so that, when a vehicle detects a pothole which is not in the
database, all the vehicles within a range of 20 meters are warned about the
pothole. The system computes a route with least number of potholes which is
nearest to the desired destination . If the destination is unknown, then the
system will check for potholes in the current road and displays the level of
damage. The system is flexible enough that the destination can be added,
removed or changed any time during the travel. The best possible route is
suggested by the system upon the alteration. We prove that the algorithm
returns an efficient path with least number of potholes.


title: Quasinormal Quantization in deSitter Spacetime

abstract:
  A scalar field in four-dimensional deSitter spacetime (dS_4) has quasinormal
modes which are singular on the past horizon of the south pole and decay
exponentially towards the future. These are found to lie in two complex
highest-weight representations of the dS_4 isometry group SO(4,1). The
Klein-Gordon norm cannot be used for quantization of these modes because it
diverges. However a modified `R-norm', which involves reflection across the
equator of a spatial S^3 slice, is nonsingular. The quasinormal modes are shown
to provide a complete orthogonal basis with respect to the R-norm. Adopting the
associated R-adjoint effectively transforms SO(4,1) to the symmetry group
SO(3,2) of a 2+1-dimensional CFT. It is further shown that the conventional
Euclidean vacuum may be defined as the state annihilated by half of the
quasinormal modes, and the Euclidean Green function obtained from a simple mode
sum. Quasinormal quantization contrasts with some conventional approaches in
that it maintains manifest dS-invariance throughout. The results are expected
to generalize to other dimensions and spins.


title: Denoising the 3-Base Periodicity Walks of DNA Sequences in Gene Finding

abstract:
  A nonlinear Tracking-Differentiator is one-input-two-output system that can
generate smooth approximation of measured signals and get the derivatives of
the signals. The nonlinear tracking-Differentiator is explored to denoise and
generate the derivatives of the walks of the 3-periodicity of DNA sequences. An
improved algorithm for gene finding is presented using the nonlinear
Tracking-Differentiator. The gene finding algorithm employs the 3-base
periodicity of coding region. The 3-base periodicity DNA walks are denoised and
tracked using the nonlinear Tracking-Differentiator. Case studies demonstrate
that the nonlinear Tracking-Differentiator is an effective method to improve
the accuracy of the gene finding algorithm.


title: Time in Quantum Mechanics

abstract:
  The failure of conventional quantum theory to recognize time as an observable
and to admit time operators is addressed. Instead of focusing on the existence
of a time operator for a given Hamiltonian, we emphasize the role of the
Hamiltonian as the generator of translations in time to construct time states.
Taken together, these states constitute what we call a timeline, or quantum
history, that is adequate for the representation of any physical state of the
system. Such timelines appear to exist even for the semi-bounded and discrete
Hamiltonian systems ruled out by Pauli's theorem. However, the step from a
timeline to a valid time operator requires additional assumptions that are not
always met. Still, this approach illuminates the crucial issue surrounding the
construction of time operators, and establishes quantum histories as legitimate
alternatives to the familiar coordinate and momentum bases of standard quantum
theory.


title: The scaling limits of near-critical and dynamical percolation

abstract:
  We prove that near-critical percolation and dynamical percolation on the
triangular lattice $\eta \mathbb{T}$ have a scaling limit as the mesh $\eta \to
0$, in the "quad-crossing" space $\mathcal{H}$ of percolation configurations
introduced by Schramm and Smirnov. The proof essentially proceeds by
"perturbing" the scaling limit of the critical model, using the pivotal
measures studied in our earlier paper. Markovianity and conformal covariance of
these new limiting objects are also established.


title:
Using CMB polarization to constrain the anomalous nature of the Cold
  Spot with an incomplete sky-coverage

abstract:
  Recent results of the ESA Planck satellite have confirmed the existence of
some anomalies in the statistical distribution of the cosmic microwave
background (CMB) anisotropies. One of the most intriguing anomalies is the Cold
Spot, firstly detected in the WMAP data by Vielva et al. (2004). In a later
paper, Vielva et al. (2011) developed a method to probe the anomalous nature of
the Cold Spot by using the cross-correlation of temperature and polarization of
the CMB fluctuations. Whereas this work was built under the assumption of
analysing full-sky data, in the present paper we extend such approach to deal
with realistic data sets with a partial sky-coverage. In particular, we exploit
the radial and tangential polarization patterns around temperature spots. We
explore the capacity of the method to distinguish between a standard Gaussian
CMB scenario and an alternative one, in which the Cold Spot arises from a
physical process that does not present correlated polarization features (e.g.,
topological defects), as a function of the instrumental-noise level. Moreover,
we consider more in detail the case of an ideal noise-free experiment and those
ones with the expected instrumental-noise levels in QUIJOTE and Planck
experiments. We also present an application to the 9-year WMAP data, without
being able to obtain firm conclusions, with a significance level of 32%. In the
ideal case, the alternative scenario could be rejected at a significance level
of around 1%, whereas for expected noise levels of QUIJOTE and Planck
experiments the corresponding significance levels are 1.5% and 7.4%,
respectively.


title: Floating Point Representations in Quantum Circuit Synthesis

abstract:
  We provide a non-deterministic quantum protocol that approximates the single
qubit rotations R_x(2a^2 b^2)$ using R_x(2a) and R_x(2b) and a constant number
of Clifford and T operations. We then use this method to construct a "floating
point" implementation of a small rotation wherein we use the aforementioned
method to construct the exponent part of the rotation and also to combine it
with a mantissa. This causes the cost of the synthesis to depend more strongly
on the relative (rather than absolute) precision required. We analyze the mean
and variance of the \Tcount required to use our techniques and provide new
lower bounds for the T-count for ancilla free synthesis of small single-qubit
axial rotations. We further show that our techniques can use ancillas to beat
these lower bounds with high probability. We also discuss the T-depth of our
method and see that the vast majority of the cost of the resultant circuits can
be shifted to parallel computation paths.


title:
Comment on "Two Fundamental Experimental Tests of Nonclassicality with
  Qutrits"

abstract:
  In a recent paper [arXiv:1301.2887] Ahrens et al. claim that our "(...)
experiment on qutrits does not test Klyachko et al.'s inequality, but an
inequality with extra correlations" and that the "(...) experiment cannot be
considered a proper test of a noncontextuality inequality, since the same
observable is measured with different setups in different contexts". We
disagree with these claims. In this note we briefly re-state how our test of
the non-contextuality inequality was constructed. We explain how we keep the
context of measurements when switching between different terms of the tested
inequality, and we argue that we did in fact test the Klyachko, Can, Binicioglu
and Shumovsky inequality. In doing so, we also clarify why our experiment is
indeed a proper test of noncontextual realism.


title:
Optimal Scheduling for Energy Harvesting Transmitters with Hybrid Energy
  Storage

abstract:
  We consider data transmission with an energy harvesting transmitter which has
a hybrid energy storage unit composed of a perfectly efficient super-capacitor
(SC) and an inefficient battery. The SC has finite space for energy storage
while the battery has unlimited space. The transmitter can choose to store the
harvested energy in the SC or in the battery. The energy is drained from the SC
and the battery simultaneously. In this setting, we consider the offline
throughput maximization problem by a deadline over a point-to-point channel. In
contrast to previous works, the hybrid energy storage model with finite and
unlimited storage capacities imposes a generalized set of constraints on the
transmission policy. As such, we show that the solution generalizes that for a
single battery and is obtained by applying directional water-filling algorithm
multiple times.


title: Remarks on Semimodules

abstract:
  This is a study of universal problems for semimodules, in particular
coequalizers, coproducts, and tensor products. Furthermore the structure theory
of semiideals of the semiring of natural numbers is extended.


title: Ligand Discrimination in Myoglobin from Linear-Scaling DFT+U

abstract:
  Myoglobin modulates the binding of diatomic molecules to its heme group via
hydrogen-bonding and steric interactions with neighboring residues, and is an
important benchmark for computational studies of biomolecules. We have
performed calculations on the heme binding site and a significant proportion of
the protein environment (more than 1000 atoms) using linear-scaling density
functional theory and the DFT+U method to correct for self-interaction errors
associated with localized 3d states. We confirm both the hydrogen-bonding
nature of the discrimination effect (3.6 kcal/mol) and assumptions that the
relative strain energy stored in the protein is low (less than 1 kcal/mol). Our
calculations significantly widen the scope for tackling problems in drug design
and enzymology, especially in cases where electron localization, allostery or
long-ranged polarization influence ligand binding and reaction.

categories: physics.chem-ph cond-mat.str-el physics.bio-ph q-bio.BM


title: Half-Saturation Constants in Functional Responses

abstract:
  Our aim is to provide an overview of half-saturation constants reported in
literature and to explore their consistency with body size. In many ecological
models, intake of nutrients by plants and consumption of food by animals is
considered to be a hyperbolic function of the nutrient concentration and the
food density, respectively. However, data on the concentration (or density) at
which half of the maximum intake rate is reached are scarce, limiting the
applicability of the computational models. The meta-analysis was conducted on
literature published worldwide. Most studies focused on algae and
invertebrates, whereas some included fish, birds and mammals. The
half-saturation constants obtained were linked to body size using ordinary
regression analysis. The observed trends were compared to those noted in
reviews on other density parameters. Half-saturation constants for different
clades range within one or two orders of magnitude. Although these constants
are inherently variable, exploring allometric relationships across different
taxa helps to improve consistent parameterization of ecological models.


title: Augmented Reality in Astrophysics

abstract:
  Augmented Reality consists of merging live images with virtual layers of
information. The rapid growth in the popularity of smartphones and tablets over
recent years has provided a large base of potential users of Augmented Reality
technology, and virtual layers of information can now be attached to a wide
variety of physical objects. In this article, we explore the potential of
Augmented Reality for astrophysical research with two distinct experiments: (1)
Augmented Posters and (2) Augmented Articles. We demonstrate that the emerging
technology of Augmented Reality can already be used and implemented without
expert knowledge using currently available apps. Our experiments highlight the
potential of Augmented Reality to improve the communication of scientific
results in the field of astrophysics. We also present feedback gathered from
the Australian astrophysics community that reveals evidence of some interest in
this technology by astronomers who experimented with Augmented Posters. In
addition, we discuss possible future trends for Augmented Reality applications
in astrophysics, and explore the current limitations associated with the
technology. This Augmented Article, the first of its kind, is designed to allow
the reader to directly experiment with this technology.


title:
Ursa Major II - Reproducing the observed properties through tidal
  disruption

abstract:
  Recent deep photometry of the dwarf spheroidal Ursa Major II's morphology,
and spectroscopy of individual stars, have provided a number of new constraints
on its properties. With a velocity dispersion $\sim$6 km s$^{-1}$, and under
the assumption that the galaxy is virialised, the mass-to-light ratio is found
to be approaching $\sim$2000 - apparently heavily dark matter dominated. Using
N-Body simulations, we demonstrate that the observed luminosity, ellipticity,
irregular morphology, velocity gradient, and the velocity dispersion can be
well reproduced through processes associated with tidal mass loss, and in the
absence of dark matter. These results highlight the considerable uncertainty
that exists in measurements of the dark matter content of Ursa Major II. The
dynamics of the inner tidal tails, and tidal stream, causes the observed
velocity dispersion of stars to be boosted to values of $>$5 km s$^{-1}$ ($>$20
km s$^{-1}$ at times). This effect is responsible for raising the velocity
dispersion of our model to the observed values in UMaII. We test an iterative
rejection technique for removing unbound stars from samples of UMaII stars
whose positions on the sky, and line-of-sight velocities, are provided. We find
this technique is very effective at providing an accurate bound mass from this
information, and only fails when the galaxy has a bound mass less than 10$%$ of
its initial mass. However when $<2%$ mass remains bound, mass overestimation by
$>$3 orders of magnitude are seen. Additionally we find that mass measurements
are sensitive to measurement uncertainty in line-of-sight velocities.
Measurement uncertainties of 1-4 km s$^{-1}$ result in mass overestimates by a
factor of $\sim$1.3-5.7.


title:
A discontinuous Galerkin method for solving the fluid and MHD equations
  in astrophysical simulations

abstract:
  A discontinuous Galerkin (DG) method suitable for large-scale astrophysical
simulations on Cartesian meshes as well as arbitrary static and moving Voronoi
meshes is presented. Most major astrophysical fluid dynamics codes use a finite
volume (FV) approach. We demonstrate that the DG technique offers distinct
advantages over FV formulations on both static and moving meshes. The DG method
is also easily generalized to higher than second-order accuracy without
requiring the use of extended stencils to estimate derivatives (thereby making
the scheme highly parallelizable). We implement the technique in the AREPO code
for solving the fluid and the magnetohydrodynamic (MHD) equations. By examining
various test problems, we show that our new formulation provides improved
accuracy over FV approaches of the same order, and reduces post-shock
oscillations and artificial diffusion of angular momentum. In addition, the DG
method makes it possible to represent magnetic fields in a locally
divergence-free way, improving the stability of MHD simulations and moderating
global divergence errors, and is a viable alternative for solving the MHD
equations on meshes where Constrained-Transport (CT) cannot be applied. We find
that the DG procedure on a moving mesh is more sensitive to the choice of slope
limiter than is its FV method counterpart. Therefore, future work to improve
the performance of the DG scheme even further will likely involve the design of
optimal slope limiters. As presently constructed, our technique offers the
potential of improved accuracy in astrophysical simulations using the moving
mesh AREPO code as well as those employing adaptive mesh refinement (AMR).


title:
Up Sector of Minimal Flavor Violation: Top Quark Properties and Direct D
  meson CP violation

abstract:
  Minimal Flavor Violation in the up-type quark sector leads to particularly
interesting phenomenology due to the interplay of flavor physics in the charm
sector and collider physics from flavor changing processes in the top sector.
We study the most general operators that can affect top quark properties and
$D$ meson decays in this scenario, concentrating on two CP violating operators
for detailed studies. The consequences of these effective operators on charm
and top flavor changing processes are generically small, but can be enhanced if
there exists a light flavor mediator that is a Standard Model gauge singlet
scalar and transforms under the flavor symmetry group. This flavor mediator can
satisfy the current experimental bounds with a mass as low as tens of GeV and
explain observed $D$-meson direct CP violation. Additionally, the model
predicts a non-trivial branching fraction for a top quark decay that would
mimic a dijet resonance.


title:
Dwarf Galaxy Formation with H2-Regulated Star Formation: II. Gas-Rich
  Dark Galaxies at Redshift 2.5

abstract:
  We present a cosmological hydrodynamic simulation of the formation of dwarf
galaxies at redshifts z>~2.5 using a physically-motivated model for
H2-regulated star formation. Our simulation, performed using the Enzo code and
reaching a peak resolution of 109 proper parsecs at z=2.5, extends the results
of Kuhlen et al. (2012) to significantly lower redshifts. We show that a star
formation prescription regulated by the local H2 abundance leads to the
suppression of star formation in dwarf galaxy halos with M_h <~ 10^10 Msun and
to a large population of gas-rich "dark galaxies" at z=2.5 with low star
formation efficiencies and gas depletion timescales >20 Gyr. The fraction of
dark galaxies is 60% at M_h ~ 10^10 Msun and increases rapidly with decreasing
halo mass. Dark galaxies form late and their gaseous disks never reach the
surface densities, > ~5700 Msun / pc^2 (Z/10^-3 Zsun)^(-0.88), that are
required to build a substantial molecular fraction. Despite this large
population of dark galaxies, we show that our H2-regulated simulation is
consistent with both the observed luminosity function of galaxies and the
cosmological mass density of neutral gas at z>~2.5. Moreover, our results
provide a theoretical explanation for the recent detection in fluorescent
Ly-alpha emission of gaseous systems at high redshift with little or no
associated star formation. We further propose that H2-regulation may offer a
fresh solution to a number of outstanding "dwarf galaxy problems" in LambdaCDM.
In particular, H2-regulation leads galaxy formation to become effectively
stochastic on mass scales of M_h ~ 10^10 Msun, and thus these massive dwarfs
are not "too big to fail".


title: Neutrino mass hierarchy determination with IceCube-PINGU

abstract:
  We discuss the neutrino mass hierarchy determination with atmospheric
neutrinos in PINGU (Precision IceCube Next Generation Upgrade), based on a
simulation with the GLoBES software including the full three flavor framework
and parameter degeneracy, and we compare it to long-baseline experiment
options. We demonstrate that the atmospheric mass hierarchy sensitivity depends
on the achievable experiment properties and we identify the main targets for
optimization, whereas the impact of a large number of tested systematical
errors turns out to be small. Depending on the values of theta_23, delta, and
the true hierarchy, a 90% CL to 3sigma discovery after three years of operation
seems conceivable. We also emphasize the synergy with existing beam and reactor
experiments, driven by NOvA, such as the complementary coverage of the
parameter space. Finally, we point out that a low intensity neutrino beam with
a relatively short decay pipe could be used to determine the mass hierarchy
with a sensitivity comparable to the LBNE experiment irrespective of the
directional resolution of the detector.


title:
A simple scaling for the minimum instability time-scale of two widely
  spaced planets

abstract:
  Long-term instability in multi-planet exosystems is a crucial consideration
when confirming putative candidates, analyzing exoplanet populations,
constraining the age of exosystems, and identifying the sources of white dwarf
pollution. Two planets which are Hill stable are separated by a wide-enough
distance to ensure that they will never collide. However, Hill stable planetary
systems may eventually manifest Lagrange instability when the outer planet
escapes or the inner planet collides with the star. We show empirically that
for two nearly coplanar Hill stable planets with eccentricities less than about
0.3, instability can manifest itself only after a time corresponding to X
initial orbits of the inner planet, where log_{10}(X) is of the order of 5.2
mu^{-0.18} and mu is the planet-star mass ratio measured in (Jupiter mass/Solar
mass). This relation applies to any type of equal-mass secondaries, and
suggests that two low-eccentricity Hill stable terrestrial-mass or smaller-mass
planets should be Lagrange stable throughout the main sequence lifetime of any
white dwarf progenitor. However, Hill stable giant planets are not guaranteed
to be Lagrange stable, particularly within a few tens of percent beyond the
critical Hill separation. Our scaling represents a useful "rule of thumb" for
planetary population syntheses or individual systems for which performing
detailed long-term integrations is unfeasible.


title:
Measuring the X-ray Background in the Reionization Era with First
  Generation 21 cm Experiments

abstract:
  The X-ray background during the epoch of reionization is currently poorly
constrained. We demonstrate that it is possible to use first generation 21 cm
experiments to calibrate it. Using the semi-numerical simulation, 21cmFAST, we
calculate the dependence of the 21 cm power spectrum on the X-ray background
flux. Comparing the signal to the sensitivity of the Murchison Widefield Array
(MWA) we find that in the redshift interval z=8-14 the 21 cm signal is
detectable based on the upper limit set by the present-day unresolved soft
X-ray background. We show that there is no degeneracy between the X-ray
production efficiency and the Lyman-Alpha production efficiency and that the
degeneracy with the ionization fraction of the intergalactic medium can be
broken.


title: Bottom-heavy initial mass function in a nearby compact L*-galaxy

abstract:
  We present orbit-based dynamical models and stellar population analysis of
galaxy SDSS J151741.75-004217.6, a low-redshift (z=0.116) early-type galaxy
(ETG) which, for its moderate luminosity, has an exceptionally high velocity
dispersion. We aim to determine the central black hole mass (M_bh), the i-band
stellar mass-to-light ratio, and the low-mass slope of the initial mass
function (IMF). Combining constraints from HST imaging and longslit kinematic
data with those from fitting the SDSS spectrum with stellar populations models
of varying IMF, we show that this galaxy has a large fraction of low-mass
stars, significantly higher than implied even by a Salpeter IMF. We exclude a
Chabrier/Kroupa as well as a unimodal (i.e. single-segment) IMF, while a
bimodal (low-mass tapered) shape is consistent with the dynamical constraints.
Thereby, our study demonstrates that a very bottom-heavy IMF can exist even in
an L* ETG. We place an upper limit of ~10^{10.5}M_sun on M_bh, which still
leaves open the possibility of an extremely massive BH.


title: From Gamma-Ray Bursts/Hypernovae To Black-Hole Binaries

abstract:
  In this work I summarize a model of binary stellar evolution involving Case C
mass transfer followed by a common envelope that strips away the hydrogen from
the core of the primary star at the cost of shrinking the orbital separation
and then, through tidal interaction, spins it up. This model is then used to
produce the possible progenitors of long gamma-ray burst / hypernova (GRB/HN)
explosions. As the core collapses with the newly supplied angular momentum it
produces a Kerr black hole surrounded by an accretion disk. Energy is extracted
from the rotation of the black hole (BH) through the Blandford-Znajek (BZ)
mechanism to power both, the long gamma-ray burst and the accompanying
hypernova (supernova type Ic broad line). If the binary survives the asymmetric
mass loss its remnant is a black-hole binary that may eventually be observed as
a soft X-ray transient (SXT) when the companion evolves and starts to transfer
mass back to the black hole. A comparison with a sample of black-hole binaries
where the masses and orbital periods are well constrained is performed.


title: Search for Rayleigh scattering in the atmosphere of GJ1214b

abstract:
  We investigate the atmosphere of GJ1214b, a transiting super-Earth planet
with a low mean density, by measuring its transit depth as a function of
wavelength in the blue optical portion of the spectrum. It is thought that this
planet is either a mini-Neptune, consisting of a rocky core with a thick,
hydrogen-rich atmosphere, or a planet with a composition dominated by water.
Most observations favor a water-dominated atmosphere with a small scale-height,
however, some observations indicate that GJ1214b could have an extended
atmosphere with a cloud layer muting the molecular features. In an atmosphere
with a large scale-height, Rayleigh scattering at blue wavelengths is likely to
cause a measurable increase in the apparent size of the planet towards the
blue. We observed the transit of GJ1214b in the B-band with the FOcal Reducing
Spectrograph (FORS) at the Very Large Telescope (VLT) and in the g-band with
both ACAM on the William Hershel Telescope (WHT) and the Wide Field Camera
(WFC) at the Isaac Newton Telescope (INT). We find a planet-to-star radius
ratio in the B-band of 0.1162+/-0.0017, and in the g-band 0.1180+/-0.0009 and
0.1174+/-0.0017 for the WHT & INT observations respectively. These optical data
do not show significant deviations from previous measurements at longer
wavelengths. In fact, a flat transmission spectrum across all wavelengths best
describes the combined observations. When atmospheric models are considered a
small scale-height water-dominated model fits the data best.


title: Sabidussi Versus Hedetniemi for Three Variations of the Chromatic Number

abstract:
  We investigate vector chromatic number, Lovasz theta of the complement, and
quantum chromatic number from the perspective of graph homomorphisms. We prove
an analog of Sabidussi's theorem for each of these parameters, i.e. that for
each of the parameters, the value on the Cartesian product of graphs is equal
to the maximum of the values on the factors. We also prove an analog of
Hedetniemi's conjecture for Lovasz theta of the complement, i.e. that its value
on the categorical product of graphs is equal to the minimum of its values on
the factors. We conjecture that the analogous results hold for vector and
quantum chromatic number, and we prove that this is the case for some special
classes of graphs.


title:
Phases in two dimensional $p_x+ip_y$ superconducting systems with
  next-nearest-neighbor interactions

abstract:
  A chiral $p_x+ip_y$ superconductor on a square lattice with nearest and
next-nearest hopping and pairing terms is considered. Gap closures, as various
parameters of the system are varied, are found analytically and used to
identify the topological phases. The phases are characterized by Chern numbers
(ranging from -3 to 3), and (numerically) by response to introduction of weak
disorder, edges, and magnetic fields in an extreme type-II limit, focusing on
the low-energy modes (which presumably become zero-energy Majorana modes for
large lattices and separations). Several phases are found, including a phase
with Chern number 3 that cannot be thought of in terms of a single range of
interaction, and phase with Chern number 2 that may host an additional,
disorder resistant, Majorana mode. The energies of the vortex quasiparticle
modes were found to oscillate as vortex position varied. The spatial length
scale of these oscillations was found for various points in the Chern number 3
phase which increased as criticality was approached.


title: Realizing chiral fermions in the type IIB matrix model at finite N

abstract:
  We discuss how chiral fermions can appear in the type IIB matrix model, which
is considered to be a nonperturbative formulation of superstring theory. In
particular, we are concerned with a constructive definition of the theory, in
which we start with a finite-N configuration and take the large-N limit later
on. We point out that there exists a certain necessary condition which the
structure of the extra dimensions should satisfy. As an example, we consider a
previous proposal using intersecting branes and show that chiral fermions can
indeed be realized in four dimensions by introducing a matrix counterpart of
warped space-time. This is remarkable in view of the well-known difficulty in
realizing chiral fermions in lattice gauge theory.


title: Modeling the Phase-Space Distribution around Massive Halos

abstract:
  The comparison between dynamical mass and lensing mass provides a targeted
test for a wide range of modified gravity models. In our previous paper we
showed, through numerical simulations, that the measurement of the
line-of-sight velocity dispersion around stacked massive clusters whose lensing
masses are known allows for stringent constraints on modified gravity on scales
of 2 - 15 Mpc/h. In this work we develop a semi-analytical approach based on
the halo model to describe the phase-space distribution and the line-of-sight
velocity dispersion for different tracers. The model distinguishes
contributions from the halo pairwise velocity and the virial velocity within
halos. We also discuss observational complications, in particular the
contribution from Hubble flow, and show how our model can incorporate these
complications. We then incorporate the effects of modified gravity
(specifically, f(R) and braneworld models), and show that the model predictions
are in excellent agreement with modified gravity simulations. More broadly, the
phase-space distribution provides a sensitive test of our understanding of
hierarchical structure formation when confronted with observations via this
model.


title:
On magnetic inhibition of photospheric macro-turbulence generated in the
  iron-bump opacity zone of O-stars

abstract:
  Massive, hot OB-stars show clear evidence of strong macroscopic broadening
(in addition to rotation) in their photospheric spectral lines. This paper
examines the occurrence of such "macro-turbulence" in slowly rotating O-stars
with strong, organised surface magnetic fields. Focusing on the CIV 5811A line,
we find evidence for significant macro-turbulent broadening in all stars except
NGC1624-2, which also has (by far) the strongest magnetic field. Instead, the
very sharp CIV lines in NGC1624-2 are dominated by magnetic Zeeman broadening,
from which we estimate a dipolar field of approximately 20 kG. By contrast,
magnetic broadening is negligible in the other stars (due to their weaker field
strengths, on order 1 kG), and their CIV profiles are typically very broad and
similar to corresponding lines observed in non-magnetic O-stars. Quantifying
this by an isotropic, Gaussian macro-turbulence, we derive vmac = 2.2 (+-
0.9/2.2) km/s for NGC1624-2, and vmac = 20-65 km/s for the rest of the magnetic
sample. We use these observational results to test the hypothesis that the
field can stabilise the atmosphere and suppress the generation of
macro-turbulence down to stellar layers where the magnetic pressure PB and the
gas pressure Pg are comparable. Using a simple grey atmosphere to estimate the
temperature T0 at which PB = Pg, we find that T0 > Teff for all investigated
magnetic stars, but that T0 reaches the ~160000 K layers associated with the
iron opacity-bump in hot stars only for NGC1624-2. This is consistent with the
view that the responsible physical mechanism for photospheric O-star
macro-turbulence may be stellar gravity-mode oscillations excited by
sub-surface convection zones, and suggests that a sufficiently strong magnetic
field can suppress such iron-bump generated convection and associated
pulsational excitation.


title: Absorbing boundary condition for Bloch-Floquet eigenmodes

abstract:
  We present an absorbing boundary condition for electromagnetic frequency
domain simulations of photonic crystals and metamaterials. This boundary
condition can simultaneously absorb multiple Bloch-Floquet eigenmodes of a
periodic crystal, including both propagating and evanescent modes. The photonic
crystal or metamaterial in question can include lossy, active, anisotropic and
even bi-anisotropic inclusions. The absorbing boundary condition is dependent
on an orthogonality condition for Bloch-Floquet eigenmodes, a generalized
version of which is presented here. We test this absorbing boundary condition
numerically and present the results.


title: Algorithms of an optimal integer tree labeling

abstract:
  Suppose we label the vertices of a tree by positive integers. The weight of
an edge is defined by a monotonically increasing function of the absolute value
of the difference of the labels of its endpoints. We define the total cost of
the labeling to be the sum of weight of all the edges.The problem we consider
is that of determining for a given tree G and given a labeling of the leaves of
G the minimum total cost labellings of G. In this paper we present an algorithm
that works for any cost function satisfies the condition of monotony mentioned
above. In a case of the function defined as the absolute value of the
difference of the labels the fast algorithm is presented.


title:
Magnetoconductance signatures of subband structure in semiconductor
  nanowires

abstract:
  The radial confining potential in a semiconductor nanowire plays a key role
in determining its quantum transport properties. Previous reports have shown
that an axial magnetic field induces flux-periodic conductance oscillations
when the electronic states are confined to a shell. This effect is due to the
coupling of orbital angular momentum to the magnetic flux. Here, we perform
calculations of the energy level structure, and consequently the conductance,
for more general cases ranging from a flat potential to strong surface band
bending. The transverse states are not confined to a shell, but are distributed
across the nanowire. It is found that, in general, the subband energy spectrum
is aperiodic as a function of both gate voltage and magnetic field. In
principle, this allows for precise identification of the occupied subbands from
the magnetoconductance patterns of quasi-ballistic devices. The aperiodicity
becomes more apparent as the potential flattens. A quantitative method is
introduced for matching features in the conductance data to the subband
structure resulting from a particular radial potential, where a functional form
for the potential is used that depends on two free parameters. Finally, a
short-channel InAs nanowire FET device is measured at low temperature in search
of conductance features that reveal the subband structure. Features are
identified and shown to be consistent with three specific subbands. The
experiment is analyzed in the context of the weak localization regime, however,
we find that the subband effects predicted for ballistic transport should
remain visible when back scattering dominates over interband scattering, as is
expected for this device.


title:
Quantum Phase Transition between Z2 spin liquid and columnar Valence
  Bond Crystals on a Triangular lattice

abstract:
  We study the quantum phase transition between the $Z_2$ spin liquid and
valence bond solid (VBS) orders on a triangular lattice. With a fully isotropic
triangular lattice, the transition from a columnar or resonating-plaquette VBS
order can be either first order or there could be two transitions with an
intermediate phase. If the transition splits into two, then the $Z_2$ spin
liquid will first experience a first order $q=3$ Potts transition to a new
nematic $Z_2$ spin liquid that breaks the $2\pi/3$ lattice rotation symmetry
(but retain translation symmetry unlike the VBS states). The second transition
will then take this new nematic $Z_2$ spin liquid to a columnar or
resonating-plaquette VBS state through a second order $3d$ XY$^*$ transition.
On a distorted triangular lattice, the degeneracy between some of the different
columnar VBS orders is lifted, and the phase transition can reduce to a single
$3d$ XY$^*$ transition.


title:
Local conservation laws and the structure of the many-body localized
  states

abstract:
  We construct a complete set of local integrals of motion that characterize
the many-body localized (MBL) phase. Our approach relies on the assumption that
local perturbations act locally on the eigenstates in the MBL phase, which is
supported by numerical simulations of the random-field XXZ spin chain. We
describe the structure of the eigenstates in the MBL phase and discuss the
implications of local conservation laws for its non-equilibrium quantum
dynamics. We argue that the many-body localization can be used to protect
coherence in the system by suppressing relaxation between eigenstates with
different local integrals of motion.


title:
Ramp dynamics of phonons in an ion trap: entanglement generation and
  cooling

abstract:
  We show that the ramp dynamics of phonons in an one-dimensional ion trap can
be used for both generating multi-particle entangled states and motional state
cooling of a string of trapped ions. We study such ramp dynamics using an
effective Bose-Hubbard model which describes these phonons at low energies and
show that specific protocols, involving site-specific dynamical tuning of the
on-site potential of the model, can be used to generate entangled states and to
achieve motional state cooling without involving electronic states of the ions.
We compare and contrast our schemes for these to the earlier suggested ones and
discuss specific experiments to realize the suggested protocols.


title: Efficient Direct Evaporative Cooling in an Atom Chip Magnetic Trap

abstract:
  We demonstrate direct evaporative cooling of $^{87}$Rb atoms confined in a
dimple trap produced by an atom chip. By changing the two chip currents and two
external bias fields, we show theoretically that the trap depth can be lowered
in a controlled way with no change in the trap frequencies or the value of the
field at the trap center. Experimentally, we maximized the decrease in trap
depth by allowing some loosening of the trap. In total, we reduced the trap
depth by a factor of 20. The geometric mean of the trap frequencies was reduced
by less than a factor of 6. The measured phase space density in the final two
stages increased by more than two orders of magnitude, and we estimate an
increase of four orders of magnitude over the entire sequence. A subsequent rf
evaporative sweep of only a few megahertz produced Bose-Einstein condensates.
We also produce condensates in which raising the trap bottom pushes hotter
atoms into an rf "knife" operating at a fixed frequency of 5\,MHz.


title: Cold versus Warm Dark Matter simulations of a galaxy group

abstract:
  The differences between cold (CDM) and warm (WDM) dark matter in the
formation of a group of galaxies is examined by running two identical
simulations where in the WDM case the initial power spectrum has been altered
to mimic a 1keV dark matter particle. The CDM initial conditions were
constrained to reproduce at z = 0 the correct local environment within which a
"Local Group" (LG) of galaxies may form. Two significant differences between
the two simulations are found. While in the CDM case a group of galaxies that
resembles the real LG forms, the WDM run fails to reproduce a viable LG,
instead forming a diffuse group which is still expanding at z = 0. This is
surprising since, due to the suppression of small scale power in its power
spectrum, WDM is naively expected to only affect the collapse of small haloes
and not necessarily the dynamics on a scale of a group of galaxies. Furthermore
the concentration of baryons in halo center's is greater in CDM than in WDM and
the properties of the disks differ.


title: Main-Belt Comet P/2012 T1 (PANSTARRS)

abstract:
  We present initial results from observations and numerical analyses aimed at
characterizing main-belt comet P/2012 T1 (PANSTARRS). Optical monitoring
observations were made between October 2012 and February 2013 using the
University of Hawaii 2.2 m telescope, the Keck I telescope, the Baade and Clay
Magellan telescopes, Faulkes Telescope South, the Perkins Telescope at Lowell
Observatory, and the Southern Astrophysical Research (SOAR) telescope. The
object's intrinsic brightness approximately doubles from the time of its
discovery in early October until mid-November and then decreases by ~60%
between late December and early February, similar to photometric behavior
exhibited by several other main-belt comets and unlike that exhibited by
disrupted asteroid (596) Scheila. We also used Keck to conduct spectroscopic
searches for CN emission as well as absorption at 0.7 microns that could
indicate the presence of hydrated minerals, finding an upper limit CN
production rate of QCN<1.5x10^23 mol/s, from which we infer a water production
rate of QH2O<5x10^25 mol/s, and no evidence of the presence of hydrated
minerals. Numerical simulations indicate that P/2012 T1 is largely dynamically
stable for >100 Myr and is unlikely to be a recently implanted interloper from
the outer solar system, while a search for potential asteroid family
associations reveal that it is dynamically linked to the ~155 Myr-old Lixiaohua
asteroid family.


title: TOF-PET detector concept based on organic scintillators

abstract:
  In this contribution we present a new concept of the large acceptance
detector systems based on organic scintillators which may allow for
simultaneous diagnostic of large fraction of the human body. Novelty of the
concept lies in employing large blocks of polymer scintillators instead of
crystals as detectors of annihilation quanta, and in using predominantly the
timing of signals instead of their amplitudes.

categories: physics.ins-det hep-ex nucl-ex physics.med-ph


title: Quarkonium Results in PbPb Collisions at CMS

abstract:
  We summarize the results from the study of charmonium and bottomonium via the
dimuon decay channel in PbPb collisions with the CMS experiment. We discuss the
observation of sequential suppression of the Upsilon states. We present
preliminary results of prompt J/psi and psi' production, as well as of
non-prompt J/psis coming from the weak decay of b-quarks. This latter
measurement is sensitive to b-quark energy loss. We discuss the results and
compare to model predictions.


title: The Promise Polynomial Hierarchy

abstract:
  The polynomial hierarchy is a grading of problems by difficulty, including P,
NP and coNP as the best known classes. The promise polynomial hierarchy is
similar, but extended to include promise problems. It turns out that the
promise polynomial hierarchy is considerably simpler to work with, and many
open questions about the polynomial hierarchy can be resolved in the promise
polynomial hierarchy.
  Our main theorem is that, in the world of promise problems, if phi has a weak
(Turing, Cook) reduction to SAT then phi has a strong (Karp, many-one)
reduction to UVAL2, where UVAL2(f) is the promise problem of finding the unique
x such that f(x,y)=1 for all y. We also give a complete promise problem for the
promise problem equivalent of UP intersect coUP.


title: STRIP-PET: a novel detector concept for the TOF-PET scanner

abstract:
  We briefly present a design of a new PET scanner based on strips of polymer
scintillators arranged in a barrel constituting a large acceptance detector.
The solution proposed is based on the superior timing properties of the polymer
scintillators. The position and time of the reaction of the gamma quanta in the
detector material will be determined based on the time of arrival of light
signals to the edges of the scintillator strips.


title: A gauss-kuzmin theorem and related questions for $\theta$-expansions

abstract:
  Using the natural extension for $\theta$-expansions, we give an
infinite-order-chain representation of the sequence of the incomplete quotients
of these expansions. Together with the ergodic behavior of a certain
homogeneous random system with complete connections, this allows us to solve a
variant of Gauss-Kuzmin problem for the above fraction expansion.


title: The J/{\psi} {\omega} Decay Channel of the X(3872) Charm Meson Molecule

abstract:
  Analyses of the J/{\psi} {\pi}+ {\pi}- decay channel of the X(3872) resonance
by the CDF, Belle, and LHCb collaborations have established its J^{PC} quantum
numbers as 1^{++}. An analysis of the \pi+ \pi- \pi 0 invariant mass
distribution in the J/{\psi} \pi+ \pi- \pi 0 decay channel by the Babar
collaboration indicated a preference for 2^{-+} over 1^{++}. We point out that
a proper evaluation of the chi^2 in that analysis increases the probability for
1^{++} from 7.1% to about 18.7%. In the case of quantum numbers 1^{++}, where
the X has an S-wave coupling to J/{\psi} {\omega}, the proximity of the
J/{\psi} {\omega} threshold to D^* Dbar thresholds and the narrow width of the
{\omega} suggest that the effects of scattering between J/{\psi} {\omega} and
charm meson pairs could be significant. We derive invariant mass distributions
for J/{\psi} \pi+ \pi- and \pi+ \pi- \pi 0 that take into account S-wave
scattering between the D^{*0} Dbar^0, D^{*+} D^-, and J/{\psi} {\omega}
channels. We also analyze the effects of scattering through the chi_{c1}(2P)
charmonium resonance. We find that scattering effects are unable to produce
significant changes in the shape of the \pi+ \pi- {\pi} 0 invariant mass
distribution.


title: Linear forms from the Gowers uniformity norm

abstract:
  This is a companion note to our paper 'A relative Szemer\'edi theorem',
elaborating on a concluding remark. In that paper, we showed how to prove a
relative Szemer\'edi theorem for $(r+1)$-term arithmetic progressions assuming
a linear forms condition. Here we show how to replace this condition with an
assumption about the Gowers uniformity norm $U^r$.


title:
The most controversial topics in Wikipedia: A multilingual and
  geographical analysis

abstract:
  We present, visualize and analyse the similarities and differences between
the controversial topics related to "edit wars" identified in 10 different
language versions of Wikipedia. After a brief review of the related work we
describe the methods developed to locate, measure, and categorize the
controversial topics in the different languages. Visualizations of the degree
of overlap between the top 100 lists of most controversial articles in
different languages and the content related to geographical locations will be
presented. We discuss what the presented analysis and visualizations can tell
us about the multicultural aspects of Wikipedia and practices of
peer-production. Our results indicate that Wikipedia is more than just an
encyclopaedia; it is also a window into convergent and divergent social-spatial
priorities, interests and preferences.

categories: physics.soc-ph cs.CL cs.DL cs.SI physics.data-an


title: Extensions of trivial inertial blocks

abstract:
  A false application of Proposition 4.10 causes a mistake in the proof of
Corollary 4.11


title:
The maximum of a symmetric next neighbor walk on the non-negative
  integers

abstract:
  We consider a one-dimensional discrete symmetric random walk with a
reflecting boundary at the origin. Generating functions are found for the 2-
dimensional probability distribution P{Sn = x,max1?j?n Sn = a} of being at
position x after n steps, while the maximal location that the walker has
achieved during these n steps is a. We also obtain the familiar (marginal)
1-dimensional distribution for Sn = x, but more importantly that for max1?j?n
Sj = a asymptotically at fixed a2/n. We are able to compute and compare the
expectations and variances of the two one-dimensional distributions, finding
that they have qualitatively similar forms, but differ quantitatively in the
anticipated fashion.


title: On the topology of the permutation pattern poset

abstract:
  The set of all permutations, ordered by pattern containment, forms a poset.
This paper presents the first explicit major results on the topology of
intervals in this poset. We show that almost all (open) intervals in this poset
have a disconnected subinterval and are thus not shellable. Nevertheless, there
seem to be large classes of intervals that are shellable and thus have the
homotopy type of a wedge of spheres. We prove this to be the case for all
intervals of layered permutations that have no disconnected subintervals of
rank 3 or more. We also characterize in a simple way those intervals of layered
permutations that are disconnected. These results carry over to the poset of
generalized subword order when the ordering on the underlying alphabet is a
rooted forest. We conjecture that the same applies to intervals of separable
permutations, that is, that such an interval is shellable if and only if it has
no disconnected subinterval of rank 3 or more. We also present a simplified
version of the recursive formula for the M\"obius function of decomposable
permutations given by Burstein et al.


title: Evolution of Accretion Disks in Tidal Disruption Events

abstract:
  During a stellar tidal disruption event (TDE), an accretion disk forms as
stellar debris returns to the disruption site and circularizes. Rather than
being confined within the circularizing radius, the disk can spread to larger
radii to conserve angular momentum. A spreading disk is a source of matter for
re-accretion at rates which can exceed the later stellar fallback rate,
although a disk wind can suppress its contribution to the central black hole
accretion rate. A spreading disk is detectible through a break in the central
accretion rate history, or, at longer wavelengths, by its own emission. We
model the evolution of TDE disk size and accretion rate, by accounting for the
time-dependent fallback rate, for the influence of wind losses in the early,
advective stage, and for the possibility of thermal instability for accretion
rates intermediate between the advection-dominated and gas-pressure dominated
states. The model provides a dynamic basis for modeling TDE light curves. All
or part of a young TDE disk will precess as a solid body due to Lense-Thirring
effect, and precession may manifest itself as quasi-periodic modulation of
light curve. The precession period increases with time. Applying our results to
the jetted TDE candidate Swift J1644+57, whose X-ray light curve shows numerous
quasi-periodic dips, we argue that the data best fit a scenario in which a
main-sequence star was fully disrupted by an intermediate mass black hole on an
orbit significantly inclined from the black hole equator, with the apparent jet
shutoff at t= 500 d corresponding to a disk transition from the advective state
to the gas-pressure dominated state.


title: Void Statistics and Hierarchical Scaling in the Halo Model

abstract:
  We study scaling behaviour of statistics of voids in the context of the halo
model of nonlinear large-scale structure. The halo model allows us to
understand why the observed galaxy void probability obeys hierarchical scaling,
even though the premise from which the scaling is derived is not satisfied. We
argue that the commonly observed negative binomial scaling is not fundamental,
but merely the result of the specific values of bias and number density for
typical galaxies. The model implies quantitative relations between void
statistics measured for two populations of galaxies, such as SDSS red and blue
galaxies, and their number density and bias.


title: Why QCD Explorer stage of the LHeC should have high(est) priority

abstract:
  The QCD Explorer will give opportunity to enlighten the origin of the 98.5%
portion of the visible universe's mass, clarify the nature of the strong
interactions from parton to nuclear level and provide precission pdf's for the
LHC. Especially the {\gamma}-nucleus option seems to be very promising for QCD
studies.


title:
A two end family of solutions for the Inhomogeneous Allen-Cahn equation
  in R^2

abstract:
  In this work we construct a family of entire bounded solution for the
singulary perturbed Inhomogeneous Allen-Cahn Equation
$\ep^2\div\left(a(x)\nabla u\right)-a(x)F'(u)=0$ in $\R^2$, where $\ep\to 0$.
The nodal set of these solutions is close to a "nondegenerate" curve which is
asymptotically two non paralell straight lines. Here $F'$ is a double-well
potential and $a$ is a smooth positive function. We also provide example of
curves and functions $a$ where our result applies. This work is in connection
with the results found by Z.Du and B.Lai, Z.Du and C.Gui, and F. Pacard and M.
Ritore, in "Transition layers for an inhomogeneus Allen-Cahn equation in
Riemannian Manifolds", "Interior layers for an inhomogeneous Allen-Cahn
equation", "From the constant mean curvature hypersurfaces to the gradient
theory of phase transitions" respectively, where they handle the compact case.


title: Shear dilatancy in marginal solids

abstract:
  Shearing stresses can change the volume of a material via a nonlinear effect
known as shear dilatancy. We calculate the elastic dilatancy coefficient of
soft sphere packings and random spring networks, two canonical models of
marginal solids close to their rigidity transition. We predict a dramatic
enhancement of dilatancy near rigidity loss in both materials, with a
surprising distinction: while packings expand under shear, networks contract.
We show that contraction in networks is due to the destabilizing influence of
increasing hydrostatic or uniaxial loads, which is counteracted in packings by
the formation of new contacts.


title:
Bilateral Credit Valuation Adjustment for Large Credit Derivatives
  Portfolios

abstract:
  We obtain an explicit formula for the bilateral counterparty valuation
adjustment of a credit default swaps portfolio referencing an asymptotically
large number of entities. We perform the analysis under a doubly stochastic
intensity framework, allowing for default correlation through a common jump
process. The key insight behind our approach is an explicit characterization of
the portfolio exposure as the weak limit of measure-valued processes associated
to survival indicators of portfolio names. We validate our theoretical
predictions by means of a numerical analysis, showing that counterparty
adjustments are highly sensitive to portfolio credit risk volatility as well as
to default correlation.