title:
Evolutionary Method for Predicting Surface Reconstructions with Variable
  Stoichiometry

abstract:
  We present a specially designed evolutionary algorithm for the prediction of
surface reconstructions. This new technique allows one to automatically explore
all the low-energy configurations with variable surface atoms and variable
surface unit cells through the whole chemical potential range. The power of
evolutionary search is demonstrated by the efficient identification of diamond
2*1 (100) and 2*1 (111) surfaces with a fixed number of surface atom and a
fixed cell size. With further variation of surface unit cells, we study the
reconstructions of the polar surface MgO (111). Experiment has detected an
oxygen trimer (ozone) motif (Plass et al, 1998). We predict a new version of
this motif which can be thermodynamically stable at extreme oxygen rich
condition. Finally, we perform a variable stoichiometry search for a complex
ternary system: semi-polar GaN (101bar1) with and without adsorbed oxygen. The
search yields a non-intuitive reconstruction based on N3-trimers. These
examples demonstrate that an automated scheme to explore the energy landscape
of surfaces will improve our understanding of surface reconstructions. The
method presented in this report can be generally applied to binary and
multi-component systems.


title: Inextensible domains

abstract:
  We develop a theory of planar, origin-symmetric, convex domains that are
inextensible with respect to lattice covering, that is, domains such that
augmenting them in any way allows fewer domains to cover the same area. We show
that origin-symmetric inextensible domains are exactly the origin-symmetric
convex domains with a circle of outer billiard triangles. We address a
conjecture by Genin and Tabachnikov about convex domains, not necessarily
symmetric, with a circle of outer billiard triangles, and show that it follows
immediately from a result of Sas.


title:
Investigation of infrared phonon modes in multiferroic single-crystal
  FeTe$_{2}$O$_{5}$Br

abstract:
  Reflection and transmission as a function of temperature (5--300 K) have been
measured on single crystals of the multiferroic compound FeTe$_{2}$O$_{5}$Br
utilizing light spanning the far infrared to the visible portions of the
electromagnetic spectrum. The complex dielectric function and optical
properties were obtained via Kramers-Kronig analysis and by fits to a
Drude-Lortentz model. Analysis of the anisotropic excitation spectra via
Drude-Lorentz fitting and lattice dynamical calculations have lead to the
observation of all 52 IR-active modes predicted in the $ac$ plane and 43 or the
53 modes predicted along the b axis of the monoclinic cell. Assignments to
groups (clusters) of phonons have been made and trends within them are
discussed in light of our calculated displacement patterns.


title: Geometric homology revisited

abstract:
  Given a cohomology theory, there is a well-known abstract way to define the
dual homology theory using the theory of spectra. In [4] the author provides a
more geometric construction of the homology theory, using a generalization of
the bordism groups. Such a generalization involves in its definition the vector
bundle modification, which is a particular case of the Gysin map. In this paper
we provide a more natural variant of that construction, which replaces the
vector bundle modification with the Gysin map itself, which is the natural
push-forward in cohomology. We prove that the two constructions are equivalent.


title: Interferometry with Bose-Einstein Condensates in Microgravity

abstract:
  Atom interferometers covering macroscopic domains of space-time are a
spectacular manifestation of the wave nature of matter. Due to their unique
coherence properties, Bose-Einstein condensates are ideal sources for an atom
interferometer in extended free fall. In this paper we report on the
realization of an asymmetric Mach-Zehnder interferometer operated with a
Bose-Einstein condensate in microgravity. The resulting interference pattern is
similar to the one in the far-field of a double-slit and shows a linear scaling
with the time the wave packets expand. We employ delta-kick cooling in order to
enhance the signal and extend our atom interferometer. Our experiments
demonstrate the high potential of interferometers operated with quantum gases
for probing the fundamental concepts of quantum mechanics and general
relativity.


title:
On High-Contrast Characterization of Nearby, Short-Period Exoplanets
  with Giant Segmented-Mirror Telescopes

abstract:
  Measurements of the frequency with which short-period planets occur around
main sequence stars allows a direct prediction of the number and types of such
planets that will be amenable to characterization by high-contrast instruments
on future giant segmented- mirror telescopes (GSMTs). Adopting conservative
assumptions, I predict of order 10 planets with radii R_P=1-8 R_Earth and
equilibrium temperatures <400 K should be accessible around stars within 8 pc
of the Sun. These numbers are roughly the same for both near-infrared
observations of scattered starlight and mid-infrared observations of planetary
thermal emission, with the latter observations demonstrating greater relative
sensitivity to smaller and cooler planets. Adopting the conservative assumption
that planets with R_P=1-2 R_E and 2-4 R_E occur with equal frequency, I predict
a 40% chance that a planet with R_P=1-2 R_E and equilibrium temperature 200-250
K will accessible to high-contrast thermal infrared characterization; this
would be a compelling object for further study. To validate these predictions,
more detailed analyses are needed of the occurrence frequencies of low-mass
planets around M dwarfs, both in the Kepler field and in the solar
neighborhood. Several planets already discovered by radial velocity surveys
will be accessible to near-infrared high-contrast GSMT observations, including
the low-mass planets alpha Cen Bb and (depending on their albedos) GJ 139c and
d, GJ 876b and c, and tau Cet b, c, and d; tau Cet f would be amenable to
thermal infrared characterization. Further efforts to model the near-infrared
reflectance and mid-infrared emission of these and other short-period planets
are clearly warranted, and will pave the way for the interpretation of future
high-contrast characterization of a variety of planets around the nearest
stars.


title: A GPU-accelerated Direct-sum Boundary Integral Poisson-Boltzmann Solver

abstract:
  In this paper, we present a GPU-accelerated direct-sum boundary integral
method to solve the linear Poisson-Boltzmann (PB) equation. In our method, a
well-posed boundary integral formulation is used to ensure the fast convergence
of Krylov subspace based linear algebraic solver such as the GMRES. The
molecular surfaces are discretized with flat triangles and centroid
collocation. To speed up our method, we take advantage of the parallel nature
of the boundary integral formulation and parallelize the schemes within CUDA
shared memory architecture on GPU. The schemes use only $11N+6N_c$
size-of-double device memory for a biomolecule with $N$ triangular surface
elements and $N_c$ partial charges. Numerical tests of these schemes show
well-maintained accuracy and fast convergence. The GPU implementation using one
GPU card (Nvidia Tesla M2070) achieves 120-150X speed-up to the implementation
using one CPU (Intel L5640 2.27GHz). With our approach, solving PB equations on
well-discretized molecular surfaces with up to 300,000 boundary elements will
take less than about 10 minutes, hence our approach is particularly suitable
for fast electrostatics computations on small to medium biomolecules.


title:
Complete Angular Distributions of the Deuteron Photo-Disintegration
  Reaction in the Few GeV Region

abstract:
  The study of two body deuteron photo-disintegration is ideal for
investigating the transition region from meson exchange to the Quantum Chromo
Dynamics (QCD) regime because of its simplicity and amenability to calculation.
  In the past years, the theoretical efforts have been focused in two different
directions: extending at higher energies the models based on meson exchange,
and improving the models inspired by QCD principles to extrapolate their
predictions at lower energies, in order to find out the approach that best
describes the experimental data and in which energy region the transition
between the two descriptions takes place.


title: Counting Triangles in Massive Graphs with MapReduce

abstract:
  Graphs and networks are used to model interactions in a variety of contexts.
There is a growing need to quickly assess the characteristics of a graph in
order to understand its underlying structure. Some of the most useful metrics
are triangle-based and give a measure of the connectedness of mutual friends.
This is often summarized in terms of clustering coefficients, which measure the
likelihood that two neighbors of a node are themselves connected. Computing
these measures exactly for large-scale networks is prohibitively expensive in
both memory and time. However, a recent wedge sampling algorithm has proved
successful in efficiently and accurately estimating clustering coefficients. In
this paper, we describe how to implement this approach in MapReduce to deal
with massive graphs. We show results on publicly-available networks, the
largest of which is 132M nodes and 4.7B edges, as well as artificially
generated networks (using the Graph500 benchmark), the largest of which has
240M nodes and 8.5B edges. We can estimate the clustering coefficient by degree
bin (e.g., we use exponential binning) and the number of triangles per bin, as
well as the global clustering coefficient and total number of triangles, in an
average of 0.33 seconds per million edges plus overhead (approximately 225
seconds total for our configuration). The technique can also be used to study
triangle statistics such as the ratio of the highest and lowest degree, and we
highlight differences between social and non-social networks. To the best of
our knowledge, these are the largest triangle-based graph computations
published to date.


title: Superconductivity, Antiferromagnetism, and Neutron Scattering

abstract:
  High-temperature superconductivity in both the copper-oxide and the
iron-pnictide/chalcogenide systems occurs in close proximity to
antiferromagnetically ordered states. Neutron scattering has been an essential
technique for characterizing the spin correlations in the antiferromagnetic
phases and for demonstrating how the spin fluctuations persist in the
superconductors. While the nature of the spin correlations in the
superconductors remains controversial, the neutron scattering measurements of
magnetic excitations over broad ranges of energy and momentum transfer provide
important constraints on the theoretical options. We present an overview of the
neutron scattering work on high-temperature superconductors and discuss some of
the outstanding issues.


title: Uniform Mixing and Association Schemes

abstract:
  We consider continuous-time quantum walks on distance-regular graphs of small
diameter. Using results about the existence of complex Hadamard matrices in
association schemes, we determine which of these graphs have quantum walks that
admit uniform mixing.
  First we apply a result due to Chan to show that the only strongly regular
graphs that admit instantaneous uniform mixing are the Paley graph of order
nine and certain graphs corresponding to regular symmetric Hadamard matrices
with constant diagonal. Next we prove that if uniform mixing occurs on a
bipartite graph X with n vertices, then n is divisible by four. We also prove
that if X is bipartite and regular, then n is the sum of two integer squares.
Our work on bipartite graphs implies that uniform mixing does not occur on
C_{2m} for m >= 3. Using a result of Haagerup, we show that uniform mixing does
not occur on C_p for any prime p such that p >= 5. In contrast to this result,
we see that epsilon-uniform mixing occurs on C_p for all primes p.


title:
Self-propelled particles with selective attraction-repulsion interaction
  - From microscopic dynamics to coarse-grained theories

abstract:
  In this work we derive and analyze coarse-grained descriptions of
self-propelled particles with selective attraction-repulsion interaction, where
individuals may respond differently to their neighbours depending on their
relative state of motion (approach versus movement away). Based on the
formulation of a nonlinear Fokker-Planck equation, we derive a kinetic
description of the system dynamics in terms of equations for the Fourier modes
of a one-particle density function. This approach allows effective numerical
investigation of the stability of possible solutions of the system. The
detailed analysis of the interaction integrals entering the equations
demonstrates that divergences at small wavelengths can appear at arbitrary
expansion orders.
  Further on, we also derive a hydrodynamic theory by performing a closure at
the level of the second Fourier mode of the one-particle density function. We
show that the general form of equations is in agreement with the theory
formulated by Toner and Tu.
  Finally, we compare our analytical predictions on the stability of the
disordered homogeneous solution with results of individual-based simulations.
They show good agreement for sufficiently large densities and non-negligible
short-ranged repulsion. Disagreements of numerical results and the hydrodynamic
theory for weak short-ranged repulsion reveal the existence of a previously
unknown phase of the model consisting of dense, nematically aligned filaments,
which cannot be accounted for by the present Toner and Tu type theory of polar
active matter.


title:
Pseudo transient continuation and time marching methods for Monge-Ampere
  type equations

abstract:
  We present two numerical methods for the fully nonlinear elliptic
Monge-Ampere equation. The first is a pseudo transient continuation method and
the second is a pure pseudo time marching method. The methods are proven to
converge to a strictly convex solution of a natural discrete variational
formulation with $C^1$ conforming approximations. The assumption of existence
of a strictly convex solution to the discrete problem is proven for smooth
solutions of the continuous problem and supported by numerical evidence for non
smooth solutions.


title: Vlasov on GPU (VOG Project)

abstract:
  This work concerns the numerical simulation of the Vlasov-Poisson set of
equations using semi- Lagrangian methods on Graphical Processing Units (GPU).
To accomplish this goal, modifications to traditional methods had to be
implemented. First and foremost, a reformulation of semi-Lagrangian methods is
performed, which enables us to rewrite the governing equations as a circulant
matrix operating on the vector of unknowns. This product calculation can be
performed efficiently using FFT routines. Second, to overcome the limitation of
single precision inherent in GPU, a {\delta}f type method is adopted which only
needs refinement in specialized areas of phase space but not throughout. Thus,
a GPU Vlasov-Poisson solver can indeed perform high precision simulations
(since it uses very high order reconstruction methods and a large number of
grid points in phase space). We show results for rather academic test cases on
Landau damping and also for physically relevant phenomena such as the bump on
tail instability and the simulation of Kinetic Electrostatic Electron Nonlinear
(KEEN) waves.


title: Hydrodynamic Modeling of Heavy-Ion Collisions

abstract:
  We review progress in the hydrodynamic description of heavy-ion collisions,
focusing on recent developments in modeling the fluctuating initial state and
event-by-event viscous hydrodynamic simulations. We discuss how hydrodynamics
can be used to extract information on fundamental properties of
quantum-chromo-dynamics from experimental data, and review successes and
challenges of the hydrodynamic framework.


title: Uniformity and self-neglecting functions

abstract:
  We relax the continuity assumption in Bloom's uniform convergence theorem for
Beurling slowly varying functions \phi. We assume that \phi has the Darboux
property, and obtain results for \phi measurable or having the Baire property.


title: When is the ball a local pessimum for covering?

abstract:
  We consider the problem of identifying the worst point-symmetric shape for
covering n-dimensional Euclidean space with lattice translates. Here we focus
on the dimensions where the thinnest lattice covering with balls is known and
ask whether the ball is a pessimum for covering in these dimensions compared to
all point-symmetric convex shapes. We find that the ball is a local pessimum in
3 dimensions, but not so for 4 and 5 dimensions.


title:
Computing bounded-width tree and branch decompositions of k-outerplanar
  graphs

abstract:
  By a well known result the treewidth of k-outerplanar graphs is at most 3k-1.
This paper gives, besides a rigorous proof of this fact, an algorithmic
implementation of the proof, i.e. it is shown that, given a k-outerplanar graph
G, a tree decomposition of G of width at most 3k-1 can be found in O(kn) time
and space. Similarly, a branch decomposition of a k-outerplanar graph of width
at most 2k+1 can be also obtained in O(kn) time, the algorithm for which is
also analyzed.


title: Identification of the Long-Sought Common-Envelope Events

abstract:
  Common-envelope events (CEEs), during which two stars temporarily orbit
within a shared envelope, are believed to be vital for the formation of a wide
range of close binaries. For decades, the only evidence that CEEs actually
occur has been indirect, based on the existence of systems that could not be
otherwise explained. Here we propose a direct observational signature of CEE
arising from a physical model where emission from matter ejected in a CEE is
controlled by a recombination front as the matter cools. The natural range of
timescales and energies from this model, as well the expected colors,
light-curve shapes, ejection velocities and event rate, match those of a
recently-recognized class of red transient outbursts.


title:
Phase Diagram and Approximate Message Passing for Blind Calibration and
  Dictionary Learning

abstract:
  We consider dictionary learning and blind calibration for signals and
matrices created from a random ensemble. We study the mean-squared error in the
limit of large signal dimension using the replica method and unveil the
appearance of phase transitions delimiting impossible, possible-but-hard and
possible inference regions. We also introduce an approximate message passing
algorithm that asymptotically matches the theoretical performance, and show
through numerical tests that it performs very well, for the calibration
problem, for tractable system sizes.


title:
Modeling the Influence of Environment and Intervention on Cholera in
  Haiti

abstract:
  We propose a simple model with two infective classes in order to model the
cholera epidemic in Haiti. We include the impact of environmental events
(rainfall, temperature and tidal range) on the epidemic in the Artibonite and
Ouest regions by introducing terms in the transmission rate that vary with
environmental conditions. We fit the model on weekly data from the beginning of
the epidemic until December 2013, including the vaccination programs that were
recently undertaken in the Ouest and Artibonite regions. We then modified these
projections excluding vaccination to assess the programs' effectiveness. Using
real-time daily rainfall, we found lag times between precipitation events and
new cases that range from 3.4 to 8.4 weeks in Artibonite and 5.1 to 7.4 in
Ouest. In addition, it appears that, in the Ouest region, tidal influences play
a significant role in the dynamics of the disease. Intervention efforts of all
types have reduced case numbers in both regions; however, persistent outbreaks
continue. In Ouest, where the population at risk seems particularly besieged
and the overall population is larger, vaccination efforts seem to be taking
hold more slowly than in Artibonite, where a smaller core population was
vaccinated. The models including the vaccination programs predicted that a year
and six months later, the mean number of cases in Artibonite would be reduced
by about two thousand cases, and in Ouest by twenty four hundred cases below
that predicted by the models without vaccination. We also found that
vaccination is best when done in the early spring, and as early as possible in
the epidemic. Comparing vaccination between the first spring and the second,
there is a drop of about 40% in the case reduction due to the vaccine and about
10% per year after that.


title:
Cosmology and gravitational waves in the Nordstrom-Vlasov system, a
  laboratory for Dark Energy

abstract:
  We discuss a cosmological solution of the system which was originally
introduced by Calogero and is today popularly known as "Nordstrom-Vlasov
system". Although the model is un-physical, its cosmological solution results
interesting for the same reasons for which the Nordstrom-Vlasov system was
originally introduced in the framework of galactic dynamics. In fact, it
represents a theoretical laboratory where one can rigorously study some
problems, like the importance of the gravitational waves in the dynamics, which
at the present time are not well understood within the physical model of the
Einstein-Vlasov system. As the cosmology of the Nordstrom-Vlasov system is
founded on a scalar field, a better understanding of the system is important
also in the framework of the Dark Energy problem. In fact, various attempts to
achieve Dark Energy by using scalar fields are present in the literature. In
the solution an analytical expression for the time dependence of the
cosmological evolution of the Nordstrom's scalar field is also released.This
analytical expression is unknown in the literature of the Nordstrom-Vlasov
system. Based on their importance, the propagation of gravitational waves in
the Nordstrom-Vlasov system and their effects on test masses are also
discussed.


title:
Constraints on the annihilation cross section of dark matter particles
  from anisotropies in the diffuse gamma-ray background measured with Fermi-LAT

abstract:
  Annihilation of dark matter particles in cosmological halos (including a halo
of the Milky Way) contributes to the diffuse gamma-ray background (DGRB). As
this contribution will appear anisotropic in the sky, one can use the angular
power spectrum of anisotropies in DGRB to constrain properties of dark matter
particles. By comparing the updated analytic model of the angular power
spectrum of DGRB from dark matter annihilation with the power spectrum recently
measured from the 22-month data of Fermi Large Area Telescope (LAT), we place
upper limits on the annihilation cross section of dark matter particles as a
function of dark matter masses. We find that the current data exclude <\sigma
v> >~ 10^{-25} cm^3 s^{-1} for annihilation into b\bar{b} at the dark matter
mass of 10 GeV, which is a factor of three times larger than the canonical
cross section. The limits are weaker for larger dark matter masses. The limits
can be improved further with more Fermi-LAT data as well as by using the power
spectrum at lower multipoles (l <~ 150), which are currently not used due to a
potential Galactic foreground contamination.


title: 3d N=2 Theories from Cluster Algebras

abstract:
  We propose a new description of 3d $\mathcal{N}=2$ theories which do not
admit conventional Lagrangians. Given a quiver $Q$ and a mutation sequence $m$
on it, we define a 3d $\mathcal{N}=2$ theory $\mathcal{T}[(Q,m)]$ in such a way
that the $S^3_b$ partition function of the theory coincides with the cluster
partition function defined from the pair $(Q, m)$. Our formalism includes the
case where 3d $\mathcal{N}=2$ theories arise from the compactification of the
6d $(2,0)$ $A_{N-1}$ theory on a large class of 3-manifolds $M$, including
complements of arbitrary links in $S^3$. In this case the quiver is defined
from a 2d ideal triangulation, the mutation sequence represents an element of
the mapping class group, and the 3-manifold is equipped with a canonical ideal
triangulation. Our partition function then coincides with that of the
holomorphic part of the $SL(N)$ Chern-Simons partition function on $M$.


title:
A Population of Massive, Luminous Galaxies Hosting Heavily Dust-Obscured
  Gamma-Ray Bursts: Implications for the Use of GRBs as Tracers of Cosmic Star
  Formation

abstract:
  We present observations and analysis of the host galaxies of 23 heavily
dust-obscured gamma-ray bursts (GRBs) observed by the Swift satellite during
the years 2005-2009, representing all GRBs with an unambiguous host-frame
extinction of A_V>1 mag from this period. Deep observations with Keck, Gemini,
VLT, HST, and Spitzer successfully detect the host galaxies and establish
spectroscopic or photometric redshifts for all 23 events, enabling us to
provide measurements of the intrinsic host star-formation rates, stellar
masses, and mean extinctions. Compared to the hosts of unobscured GRBs at
similar redshifts, we find that the hosts of dust-obscured GRBs are (on
average) more massive by about an order of magnitude and also more rapidly
star-forming and dust-obscured. While this demonstrates that GRBs populate all
types of star-forming galaxies including the most massive, luminous systems at
z~2, at redshifts below 1.5 the overall GRB population continues to show a
highly significant aversion away from massive galaxies and a preference for
low-mass systems relative to what would be expected given a purely SFR-selected
galaxy sample. This supports the notion that the GRB rate is strongly dependent
on metallicity, and may suggest that the most massive galaxies in the Universe
underwent a transition in their chemical properties ~9 Gyr ago. We also
conclude that, based on the absence of unobscured GRBs in massive galaxies and
the absence of obscured GRBs in low-mass galaxies, the dust distributions of
the lowest-mass and the highest-mass galaxies are relatively homogeneous, while
intermediate-mass galaxies (~10^9 M_sun) have diverse internal properties.


title:
Initial state dependence of the quench dynamics in integrable quantum
  systems. III. Chaotic states

abstract:
  We study sudden quantum quenches in which the initial states are selected to
be either eigenstates of an integrable Hamiltonian that is nonmappable to a
noninteracting one or a nonintegrable Hamiltonian, while the Hamiltonian after
the quench is always integrable and mappable to a noninteracting one. By
studying weighted energy densities and entropies, we show that quenches
starting from nonintegrable (chaotic) eigenstates lead to an "ergodic" sampling
of the eigenstates of the final Hamiltonian, while those starting from the
integrable eigenstates do not (or at least it is not apparent for the system
sizes accessible to us). This goes in parallel with the fact that the
distribution of conserved quantities in the initial states is thermal in the
nonintegrable cases and nonthermal in the integrable ones, and means that, in
general, thermalization occurs in integrable systems when the quench starts
form an eigenstate of a nonintegrable Hamiltonian (away from the edges of the
spectrum), while it fails (or requires larger system sizes than those studied
here to become apparent) for quenches starting at integrable points. We test
those conclusions by studying the momentum distribution function of hard-core
bosons after a quench.


title:
Discovery of a Rich Cluster at z = 1.63 using the Rest-Frame 1.6um
  "Stellar Bump Sequence" Method

abstract:
  We present a new two-color algorithm, the "Stellar Bump Sequence" (SBS), that
is optimized for robustly identifying candidate high-redshift galaxy clusters
in combined wide-field optical and mid-infrared (MIR) data. The SBS algorithm
is a fusion of the well-tested cluster red-sequence method of Gladders & Yee
(2000) with the MIR 3.6um - 4.5um cluster detection method developed by
Papovich (2008). As with the cluster red-sequence method, the SBS identifies
candidate overdensities within 3.6um - 4.5um color slices, which are the
equivalent of a rest-frame 1.6um stellar bump "red-sequence". In addition to
employing the MIR colors of galaxies, the SBS algorithm incorporates an
optical/MIR (z' - 3.6um) color cut. This cut effectively eliminates foreground
0.2 < z < 0.4 galaxies which have 3.6um - 4.5um colors that are similarly red
as z > 1.0 galaxies and add noise when searching for high-redshift galaxy
overdensities. We demonstrate using the z ~ 1 GCLASS cluster sample that
similar to the red sequence, the stellar bump sequence appears to be a
ubiquitous feature of high-redshift clusters, and that within that sample the
color of the stellar bump sequence increases monotonically with redshift and
provides photometric redshifts accurate to dz = 0.05. We apply the SBS method
in the XMM-LSS SWIRE field and show that it robustly recovers the majority of
confirmed optical, MIR, and X-ray-selected clusters at z > 1.0 in that field.
Lastly, we present confirmation of SpARCS J022427-032354 at z = 1.63, a new
cluster detected with the method and confirmed with 12 high-confidence
spectroscopic redshifts obtained using FORS2 on the VLT. We conclude with a
discussion of future prospects for using the algorithm.


title:
A simulation calibrated limit on the HI power spectrum from the GMRT
  Epoch of Reionization experiment

abstract:
  The GMRT Epoch of Reionization (EoR) experiment is an ongoing effort to
measure the power spectrum from neutral hydrogen at high redshift. We have
previously reported an upper limit of (70 mK)^2 at wavenumbers of k=0.65 h/Mpc
using a basic piecewise-linear foreground subtraction. In this paper we explore
the use of a singular value decomposition to remove foregrounds with fewer
assumptions about the foreground structure. Using this method we also quantify,
for the first time, the signal loss due to the foreground filter and present
new power spectra adjusted for this loss, providing a revised measurement of a
2-sigma upper limit at (248 mK)^2 for k=0.50 h/Mpc. While this revised limit is
larger than previously reported, we believe it to be more robust and still
represents the best current constraints on reionization at z=8.6.


title: The Exceptional Soft X-ray Halo of the Galaxy Merger NGC 6240

abstract:
  We report on a recent ~150-ks long Chandra observation of the ultraluminous
infrared galaxy merger NGC 6240, which allows a detailed investigation of the
diffuse galactic halo. Extended soft X-ray emission is detected at the 3-sigma
confidence level over a diamond-shaped region with projected physical size of
~110x80 kpc, and a single-component thermal model provides a reasonably good
fit to the observed X-ray spectrum. The hot gas has a temperature of ~7.5
million K, an estimated density of 2.5x10^{-3} cm^{-3}, and a total mass of
~10^10 M_sun, resulting in an intrinsic 0.4-2.5 keV luminosity of 4x10^41 erg
s^{-1}. The average temperature of 0.65 keV is quite high to be obviously
related to either the binding energy in the dark-matter gravitational potential
of the system or the energy dissipation and shocks following the galactic
collision, yet the spatially-resolved spectral analysis reveals limited
variations across the halo. The relative abundance of the main alpha-elements
with respect to iron is several times the solar value, and nearly constant as
well, implying a uniform enrichment by type II supernovae out to the largest
scales. Taken as a whole, the observational evidence is not compatible with a
superwind originated by a recent, nuclear starburst, but rather hints at
widespread, enhanced star formation proceeding at steady rate over the entire
dynamical timescale (~200 Myr). The preferred scenario is that of a
starburst-processed gas component gently expanding into, and mixing with, a
pre-existing halo medium of lower metallicity (Z ~ 0.1 solar) and temperature
(kT ~ 0.25 keV). This picture cannot be probed more extensively with the
present data, and the ultimate fate of the diffuse, hot gas remains uncertain.
Under some favorable conditions, at least a fraction of it might be retained
after the merger completion, and evolve into the hot halo of a young elliptical
galaxy.


title: Dark Matter CMB Constraints and Likelihoods for Poor Particle Physicists

abstract:
  The cosmic microwave background provides constraints on the annihilation and
decay of light dark matter at redshifts between 100 and 1000, the strength of
which depends upon the fraction of energy ending up in the form of electrons
and photons. The resulting constraints are usually presented for a limited
selection of annihilation and decay channels. Here we provide constraints on
the annihilation cross section and decay rate, at discrete values of the dark
matter mass, for all the annihilation and decay channels whose secondary
spectra have been computed using PYTHIA in arXiv:1012.4515 ("PPPC4DMID: A Poor
Particle Physicist Cookbook for Dark Matter Indirect Detection"), namely e, mu,
tau, V -> e, V -> mu, V -> tau, u, d, s, c, b, t, gamma, g, W, Z and h. By
interpolating in mass, these can be used to find the CMB constraints and
likelihood functions from WMAP7 and Planck for a wide range of dark matter
models, including those with annihilation or decay into a linear combination of
different channels.


title:
Self-consistent electronic structure of multiquantum vortices in
  superconductors at $T\ll T_c$

abstract:
  We investigate the multiquantum vortex states in type-II superconductor both
in "clean" and "dirty" regimes defined by impurity scattering rate. Within
quasiclassical approach we calculate self-consistently the order parameter
distributions and electronic local density of states (LDOS) profiles. In the
clean case we find the low temperature vortex core anomaly predicted
analytically in G.E. Volovik, JETP Lett. {\bf 58}, 455 (1993) and obtain the
interference patterns in LDOS distributions analogous to found previously in
the framework of Bogolubov-de Gennes theory. In dirty regime the multiquantum
vortices feature a peculiar plateau in the zero-energy LDOS profile which can
be considered as an experimental hallmark of multiquantum vortex formation in
mesoscopic superconductors.


title: The Zariski-Lipman conjecture for log canonical spaces

abstract:
  In this paper we prove the Zariski-Lipman conjecture for log canonical
spaces.


title:
Electromagnetic quantum waves and their effect on the low temperature
  magnetoacoustic response of a quasi-two-dimensional metal

abstract:
  We theoretically analyze weakly attenuated electromagnetic waves in
quasi-two-dimensional (Q2D) metals in high magnetic fields. Within the chosen
geometry, the magnetic field is directed perpendicularly to the conducting
layers of a Q2D conductor. We showed that longitudinal collective modes could
propagate along the magnetic field provided that the Fermi surface is
moderately corrugated. The considered waves speeds strongly depend on the
magnetic field magnitude. Also, we analyzed interactions of these quantum waves
with sound waves of fitting polarization and propagation direction, and we
showed that such interaction may bring significant changes to the low
temperature magnetoacoustic response of Q2D conductors.


title:
Resource Allocation and Interference Mitigation Techniques for
  Cooperative Multi-Antenna and Spread Spectrum Wireless Networks

abstract:
  This chapter presents joint interference suppression and power allocation
algorithms for DS-CDMA and MIMO networks with multiple hops and
amplify-and-forward and decode-and-forward (DF) protocols. A scheme for joint
allocation of power levels across the relays and linear interference
suppression is proposed. We also consider another strategy for joint
interference suppression and relay selection that maximizes the diversity
available in the system. Simulations show that the proposed cross-layer
optimization algorithms obtain significant gains in capacity and performance
over existing schemes.


title:
The spectral type of CHS7797 - an intriguing very low mass periodic
  variable in the Orion Nebula Cluster

abstract:
  We present the spectroscopic characterization of the unusual high-amplitude
very low mass pre-main-sequence periodic variable CHS7797. This study is based
on optical medium-resolution (R=2200) spectroscopy in the 6450-8600 A range,
carried out with GMOS-GEMINI-S in March 2011. Observations of CHS7797 have been
carried out at two distinct phases of the 17.8d period, namely at maximum and
four days before maximum. Four different spectral indices were used for the
spectral classification at these two phases, all of them well-suited for
spectral classification of young and obscured late M dwarfs. In addition, the
gravity-sensitive NaI (8183/8195 A) and KI (7665/7699 A) doublet lines were
used to confirm the young age of CHS7797. From the spectrum obtained at maximum
light we derived a spectral type (SpT) of M6.05, while for the spectrum taken
four days before maximum the derived SpT is M5.75. The derived SpTs confirm
that CHS7797 has a mass in the stellar-substellar boundary mass range. In
addition, the small differences in the derived SpTs at the two observed phases
may provide indirect hints that CHS7797 is a binary system of similar mass
components surrounded by a tilted circumbinary disk, a system similar to KH15D.


title:
Parallel Higher-order Boundary Integral Electrostatics Computation on
  Molecular Surfaces with Curved Triangulation

abstract:
  In this paper, we present a parallel higher-order boundary integral method to
solve the linear Poisson-Boltzmann (PB) equation. In our method, a well-posed
boundary integral formulation is used to ensure the fast convergence of Krylov
subspace linear solver such as GMRES. The molecular surfaces are first
discretized with flat triangles and then converted to curved triangles with the
assistance of normal information at vertices. To maintain the desired accuracy,
four-point Gauss-Radau quadratures are used on regular triangles and
sixteen-point Gauss-Legendre quadratures together with regularization
transformations are applied on singular triangles. To speed up our method, we
take advantage of the embarrassingly parallel feature of boundary integral
formulation, and parallelize the schemes with the message passing interface
(MPI) implementation. Numerical tests show significantly improved accuracy and
convergence of the proposed higher-order boundary integral Poisson-Boltzmann
(HOBI-PB) solver compared with boundary integral PB solver using often-seen
centroid collocation on flat triangles. The higher-order accuracy results
achieved by present method are important to sensitive solvation analysis of
biomolecules, particularly when accurate electrostatic surface potentials are
critical in the molecular simulation. In addition, the higher-order boundary
integral schemes presented here and their associated parallelization
potentially can be applied to solving boundary integral equations in a general
sense.


title:
The Packing Radius of a Code and Partitioning Problems: the Case for
  Poset Metrics

abstract:
  Until this work, the packing radius of a poset code was only known in the
cases where the poset was a chain, a hierarchy, a union of disjoint chains of
the same size, and for some families of codes. Our objective is to approach the
general case of any poset. To do this, we will divide the problem into two
parts.
  The first part consists in finding the packing radius of a single vector. We
will show that this is equivalent to a generalization of a famous NP-hard
problem known as "the partition problem". Then, we will review the main results
known about this problem giving special attention to the algorithms to solve
it. The main ingredient to these algorithms is what is known as the
differentiating method, and therefore, we will extend it to the general case.
  The second part consists in finding the vector that determines the packing
radius of the code. For this, we will show how it is sometimes possible to
compare the packing radius of two vectors without calculating them explicitly.


title: Network Observability Transitions

abstract:
  In the modeling, monitoring, and control of complex networks, a fundamental
problem concerns the comprehensive determination of the state of the system
from limited measurements. Using power grids as example networks, we show that
this problem leads to a new type of percolation transition, here termed a {\it
network observability transition}, which we solve analytically for the
configuration model. We also demonstrate a dual role of the network's community
structure, which both facilitates optimal measurement placement and renders the
networks substantially more sensitive to `observability attacks'. Aside from
their immediate implications for the development of smart grids, these results
provide insights into decentralized biological, social, and technological
networks.


title: Spectral Energy Distributions of HII regions in M33 (HerM33es)

abstract:
  Within the framework of the Herschel M 33 extended survey HerM33es we study
the Spectral Energy Distribution (SED) of a set of HII regions in M 33 as a
function of the morphology. We present a catalogue of 119 HII regions
morphologically classified: 9 filled, 47 mixed, 36 shell, and 27 clear shell
HII regions. For each object we extract the photometry at twelve available
wavelength bands (from FUV-1516A to IR-250mi) and obtain the SED. We also
obtain emission line profiles across the regions to study the location of the
stellar, ionised gas, and dust components. We find trends for the SEDs related
to the morphology, showing that the star and gas-dust configuration affects the
ratios of the emission in different bands. The mixed and filled regions show
higher emission at 24mi than the shells and clear shells, which could be due to
the proximity of the dust to the stellar clusters in the case of mixed and
filled regions. The FIR peak for shells and clear shells seems to be located
towards longer wavelengths, indicating that the dust is colder for this type of
objects.The logarithmic 100/70mi ratio for filled and mixed regions remains
constant over one order of magnitude in Halpha and FUV surface brightness,
while the shells and clear shells exhibit a wider range of values of almost two
orders of magnitude. We derive dust masses and temperatures fitting the
individual SEDs with dust models proposed in the literature. The derived dust
mass range is between 10^2-10^4 Msun and the cold dust temperature spans
T(cold)~12-27 K. The spherical geometrical model proposed for the Halpha clear
shells is confirmed by the emission profile obtained from the observations and
is used to infer the electron density within the envelope: the typical electron
density is 0.7+-0.3 cm^-3, while filled regions can reach values two to five
times higher.


title: On the Largest Eigenvalue of Products from the \beta-Laguerre Ensemble

abstract:
  We determine the limiting distribution of the largest eigenvalue of products
from the $\beta$-Laguerre ensemble. This limiting distribution is given by a
Tracy-Widom law with parameter $\beta_0>0$ depending on the ratio of the
parameters of the two matrices involved.


title:
The hypothesis of urban scaling: formalization, implications and
  challenges

abstract:
  There is strong expectation that cities, across time, culture and level of
development, share much in common in terms of their form and function.
Recently, attempts to formalize mathematically these expectations have led to
the hypothesis of urban scaling, namely that certain properties of all cities
change, on average, with their size in predictable scale-invariant ways. The
emergence of these scaling relations depends on a few general properties of
cities as social networks, co-located in space and time, that conceivably apply
to a wide range of human settlements. Here, we discuss the present evidence for
the hypothesis of urban scaling, some of the methodological issues dealing with
proxy measurements and units of analysis and place these findings in the
context of other theories of cities and urban systems. We show that a large
body of evidence about the scaling properties of cities indicates, in analogy
to other complex systems, that they cannot be treated as extensive systems and
discuss the consequences of these results for an emerging statistical theory of
cities.


title: Tunable Adsorbate-Adsorbate Interactions on Graphene

abstract:
  We propose a mechanism to control the interaction between adsorbates on
graphene. The interaction between a pair of adsorbates---the change in
adsorption energy of one adsorbate in the presence of another---is dominated by
the interaction mediated by graphene's pi-electrons and has two distinct
regimes. Ab initio density functional, numerical tight-binding, and analytical
calculations are used to develop the theory. We demonstrate that the
interaction can be tuned in a wide range by adjusting the adsorbate-graphene
bonding or the chemical potential.


title: Pulsed Accretion in a Variable Protostar

abstract:
  Periodic increases in luminosity arising from variable accretion rates have
been predicted for some close pre-main sequence binary stars as they grow from
circumbinary disks. The phenomenon is known as "pulsed accretion" and can
affect the orbital evolution and mass distribution of young binaries, as well
as the potential for planet formation in the circumbinary environment.
Accretion variability is a common feature of young stars, with a large range of
amplitudes and timescales as measured from multi-epoch observations at optical
and infrared wavelengths. Periodic variations consistent with pulsed accretion
have been seen in only a few young binaries via optical accretion tracers,
albeit intermittently with accretion luminosity variations ranging from 0-50
percent from orbit to orbit. Here we report on a young protostar (age ~10^5 yr)
that exhibits periodic variability in which the infrared luminosity increases
by a factor of 10 in roughly one week every 25.34 days. We attribute this to
pulsed accretion associated with an unseen binary companion. The strength and
regularity of this accretion signal is surprising; it may be related to the
very young age of the system, which is a factor of ten younger than the other
pulsed accretors previously studied.


title:
Optimal Reconstruction of Material Properties in Complex Multiphysics
  Phenomena

abstract:
  We develop an optimization-based approach to the problem of reconstructing
temperature-dependent material properties in complex thermo-fluid systems
described by the equations for the conservation of mass, momentum and energy.
Our goal is to estimate the temperature dependence of the viscosity coefficient
in the momentum equation based on some noisy temperature measurements, where
the temperature is governed by a separate energy equation. We show that an
elegant and computationally efficient solution of this inverse problem is
obtained by formulating it as a PDE-constrained optimization problem which can
be solved with a gradient-based descent method. A key element of the proposed
approach, the cost functional gradients are characterized by mathematical
structure quite different than in typical problems of PDE-constrained
optimization and are expressed in terms of integrals defined over the level
sets of the temperature field. Advanced techniques of integration on manifolds
are required to evaluate numerically such gradients, and we systematically
compare three different methods. As a model system we consider a
two-dimensional unsteady flow in a lid-driven cavity with heat transfer, and
present a number of computational tests to validate our approach and illustrate
its performance.


title:
Verification of functional a posteriori error estimates for obstacle
  problem in 1D

abstract:
  We verify functional a posteriori error estimate for obstacle problem
proposed by Repin. Simplification into 1D allows for the construction of a
nonlinear benchmark for which an exact solution of the obstacle problem can be
derived. Quality of a numerical approximation obtained by the finite element
method is compared with the exact solution and the error of approximation is
bounded from above by a majorant error estimate. The sharpness of the majorant
error estimate is discussed.


title:
Holographic Theory of Accelerated Observers, the S-matrix, and the
  Emergence of Effective Field Theory

abstract:
  We present a theory of accelerated observers in the formalism of holographic
space time, and show how to define the analog of the Unruh effect for a one
parameter set of accelerated observers in a causal diamond in Minkowski space.
The key fact is that the formalism splits the degrees of freedom in a large
causal diamond into particles and excitations on the horizon. The latter form a
large heat bath for the particles, and different Hamiltonians, describing a one
parameter family of accelerated trajectories, have different couplings to the
bath. We argue that for a large but finite causal diamond the Hamiltonian
describing a geodesic observer has a residual coupling to the bath and that the
effect of the bath is finite over the long time interval in the diamond. We
find general forms of the Hamiltonian, which guarantee that the horizon degrees
of freedom will decouple in the limit of large diamonds, leaving over a unitary
evolution operator for particles, with an asymptotically conserved energy. That
operator converges to the S-matrix in the infinite diamond limit. The S-matrix
thus arises from integrating out the horizon degrees of freedom, in a manner
reminiscent of, but distinct from, Matrix Theory. We note that this model for
the S-matrix implies that Quantum Gravity, as opposed to quantum field theory,
has a natural adiabatic switching off of the interactions. We argue that
imposing Lorentz invariance on the S-matrix is natural, and guarantees
super-Poincare invariance in the HST formalism. Spatial translation invariance
is seen to be the residuum of the consistency conditions of HST.


title: Quadrupole moments of rotating neutron stars and strange stars

abstract:
  We present results for models of neutron stars and strange stars constructed
using the Hartle-Thorne slow-rotation method with a wide range of equations of
state, focusing on the values obtained for the angular momentum $J$ and the
quadrupole moment $Q$, when the gravitational mass $M$ and the rotational
frequency $\Omega$ are specified. Building on previous work, which showed
surprising uniformity in the behaviour of the moment of inertia for
neutron-star models constructed with widely-different equations of state, we
find similar uniformity for the quadrupole moment. These two quantities,
together with the mass, are fundamental for determining the vacuum space-time
outside neutron stars. We study particularly the dimensionless combination of
parameters $QM/J^2$ (using units for which $c=G=1$). This quantity goes to 1 in
the case of a Kerr-metric black hole and deviations away from 1 then
characterize the difference between neutron-star and black-hole space-times. It
is found that $QM/J^2$ for both neutron stars and strange stars decreases with
increasing mass, for a given equation of state, reaching a value of around 2
(or even less) for maximum-mass models, meaning that their external space-time
is then rather well approximated by the Kerr metric. If $QM/J^2$ is plotter
against compactness $R/2M$ (where $R$ is the radius), it is found that the
relationship is nearly unique for neutron-star models, independent of the
equation of state, while it is significantly different for strange stars. This
gives a new way of possibly distinguishing between them.


title:
Thermodynamic Volumes and Isoperimetric Inequalities for de Sitter Black
  Holes

abstract:
  We consider the thermodynamics of rotating and charged asymptotically de
Sitter black holes. Using Hamiltonian perturbation theory techniques, we derive
three different first law relations including variations in the cosmological
constant, and associated Smarr formulas that are satisfied by such spacetimes.
Each first law introduces a different thermodynamic volume conjugate to the
cosmological constant. We examine the relation between these thermodynamic
volumes and associated geometric volumes in a number of examples, including
Kerr-dS black holes in all dimensions and Kerr-Newman-dS black holes in D=4. We
also show that the Chong-Cvetic-Lu-Pope solution of D=5 minimal supergravity,
analytically continued to positive cosmological constant, describes black hole
solutions of the Einstein-Chern-Simons theory and include such charged
asymptotically de Sitter black holes in our analysis. In all these examples we
find that the particular thermodynamic volume associated with the region
between the black hole and cosmological horizons is equal to the naive
geometric volume. Isoperimetric inequalities, which hold in the examples
considered, are formulated for the different thermodynamic volumes and
conjectured to remain valid for all asymptotically de Sitter black holes. In
particular, in all examples considered, we find that for fixed volume of the
observable universe, the entropy is increased by adding black holes. We
conjecture that this is true in general.


title: Using proper divergence functions to evaluate climate models

abstract:
  It has been argued persuasively that, in order to evaluate climate models,
the probability distributions of model output need to be compared to the
corresponding empirical distributions of observed data. Distance measures
between probability distributions, also called divergence functions, can be
used for this purpose. We contend that divergence functions ought to be proper,
in the sense that acting on modelers' true beliefs is an optimal strategy.
Score divergences that derive from proper scoring rules are proper, with the
integrated quadratic distance and the Kullback-Leibler divergence being
particularly attractive choices. Other commonly used divergences fail to be
proper. In an illustration, we evaluate and rank simulations from fifteen
climate models for temperature extremes in a comparison to re-analysis data.


title: BaPu: Efficient and Practical Bunching of Access Point Uplinks

abstract:
  Today's increasing demand for wirelessly uploading a large volume of User
Generated Content (UGC) is still significantly limited by the throttled
backhaul of residential broadband (typically between 1 and 3Mbps). We propose
BaPu, a carefully designed system with implementation for bunching WiFi access
points' backhaul to achieve a high aggregated throughput. BaPu is inspired by a
decade of networking design principles and techniques to enable efficient TCP
over wireless links and multipath. BaPu aims to achieve two major goals:1)
requires no client modification for easy incremental adoption; 2) supports not
only UDP, but also TCP traffic to greatly extend its applicability to a broad
class of popular applications such as HD streaming or large file transfer. We
prototyped BaPu with commodity hardware. Our extensive experiments shows that
despite TCP's sensitivity to typical channel factors such as high wireless
packet loss, out-of-order packets arrivals due to multipath, heterogeneous
backhaul capacity, and dynamic delays, BaPu achieves a backhaul aggregation up
to 95% of the theoretical maximum throughput for UDP and 88% for TCP. We also
empirically estimate the potential idle bandwidth that can be harnessed from
residential broadband.


title: Toy model studies of tuning and typicality with an eye toward cosmology

abstract:
  We investigate a number of simple toy models to explore interesting
relationships between dynamics and typicality. We start with an infinite model
that has been proposed as an illustration of how non-ergodic dynamics can
produce interesting features that are suggestive for cosmological applications.
We consider various attempts to define the infinite model more rigorously as a
limit of a finite system. None of our attempts at such rigor were able to
preserve the attractive properties. We hope our work will challenge others to
find more successful toy models. The difficulty of finding such models suggests
that connections between dynamics and typicality we hope for in cosmological
theories such as eternal inflation may not be so easy to achieve.


title:
Classification and analysis of emission-line galaxies using mean field
  independent component analysis

abstract:
  We present an analysis of the optical spectra of narrow emission-line
galaxies, based on mean field independent component analysis (MFICA). Samples
of galaxies were drawn from the Sloan Digital Sky Survey (SDSS) and used to
generate compact sets of `continuum' and `emission-line' component spectra.
These components can be linearly combined to reconstruct the observed spectra
of a wider sample of galaxies. Only 10 components - five continuum and five
emission line - are required to produce accurate reconstructions of essentially
all narrow emission-line galaxies; the median absolute deviations of the
reconstructed emission-line fluxes, given the signal-to-noise ratio (S/N) of
the observed spectra, are 1.2-1.8 sigma for the strong lines. After applying
the MFICA components to a large sample of SDSS galaxies we identify the regions
of parameter space that correspond to pure star formation and pure active
galactic nucleus (AGN) emission-line spectra, and produce high S/N
reconstructions of these spectra.
  The physical properties of the pure star formation and pure AGN spectra are
investigated by means of a series of photoionization models, exploiting the
faint emission lines that can be measured in the reconstructions. We are able
to recreate the emission line strengths of the most extreme AGN case by
assuming the central engine illuminates a large number of individual clouds
with radial distance and density distributions, f(r) ~ r^gamma and g(n) ~
n^beta, respectively. The best fit is obtained with gamma = -0.75 and beta =
-1.4. From the reconstructed star formation spectra we are able to estimate the
starburst ages. These preliminary investigations serve to demonstrate the
success of the MFICA-based technique in identifying distinct emission sources,
and its potential as a tool for the detailed analysis of the physical
properties of galaxies in large-scale surveys.


title:
On the Trade-off Between Spectrum Efficiency with Dedicated Access and
  Short End-to-End Transmission Delays with Random Access in DVB-RCS2

abstract:
  This paper analyses the performance of TCP over random and dedicated access
methods in the context of DVB-RCS2. Random access methods introduce a lower
connection delay compared to dedicated methods. We investigate the poten- tial
to improve the performance of short flows in regards to transmission delay,
over random access methods for DVB- RCS2 that is currently under development.
Our simulation experiments show that the transmission of the first ten IP
datagrams of each TCP flow can be 500 ms faster with ran- dom access than with
dedicated access making the former of interest to carry Internet traffic. Such
methods, however, are less efficient in regards to bandwidth usage than
dedicated access mecanisms and less reliable in overloaded network conditions.
Two aspects of channel usage optimization can be distinguished: reducing the
duration of ressource utiliza- tion with random access methods, or increasing
the spec- trum efficiency with dedicated access methods. This article argues
that service providers may let low-cost users exploit the DVB-RCS2 to browse
the web by introducing different services, which choice is based on the channel
access method.


title: Automated mass spectrum generation for new physics

abstract:
  We describe an extension of the FeynRules package dedicated to the automatic
generation of the mass spectrum associated with any Lagrangian-based quantum
field theory. After introducing a simplified way to implement particle mixings,
we present a new class of FeynRules functions allowing both for the analytical
computation of all the model mass matrices and for the generation of a C++
package, dubbed ASperGe. This program can then be further employed for a
numerical evaluation of the rotation matrices necessary to diagonalize the
field basis. We illustrate these features in the context of the
Two-Higgs-Doublet Model, the Minimal Left-Right Symmetric Standard Model and
the Minimal Supersymmetric Standard Model.


title:
Information Centric Networking over SDN and OpenFlow: Architectural
  Aspects and Experiments on the OFELIA Testbed

abstract:
  Information Centric Networking (ICN) has been proposed as a new networking
paradigm in which the network provides users with content instead communication
channels between hosts. The Software Defined Networking (SDN) approach promises
to be a solution to enable the continuous evolution of networking
architectures. In this paper we propose and discuss solutions to support ICN
using SDN concepts. We focus on an ICN framework called CONET, which grounds
its roots in the CCN/NDN architecture. We face the problem in two complementary
ways. First we discuss a general and long term solution based on SDN concepts
without taking into account specific limitations of SDN standards and
equipment. Then we focus on an experiment to support ICN functionality over a
large scale SDN testbed based on OpenFlow, developed in the context of the
OFELIA European research project. The current OFELIA testbed is based on
OpenFlow 1.0 equipment from a variety of vendors, therefore we had to design
the experiment taking into account the features that are currently available on
off-the-shelf OpenFlow equipment.


title:
A remark on the Heat Equation and minimal Morse Functions on Tori and
  Spheres

abstract:
  Let (M,g) be a compact, connected riemannian manifold that is homogeneous,
i.e. each pair of points p,q in M have isometric neighborhoods. This paper is a
first step towards an understanding of the extent to which it is true that for
each "generic" initial condition f0, the solution to the Heat Equation is such
that for sufficiently large t, f(.,t) is a minimal Morse function, i.e., a
Morse function whose total number of critical points is the minimal possible on
M. In this paper we show that this is true for flat tori and round spheres in
all dimensions.


title: Cyclic and Long-term Variation of Sunspot Magnetic Fields

abstract:
  Measurements from the Mount Wilson Observatory (MWO) are used to study the
long-term variations of sunspot field strengths from 1920 to 1958. Following a
modified approach similar to that in Pevtsov et al. (2011), for each observing
week we select a single sunspot with the strongest field strength measured that
week and then compute monthly averages of these weekly maximum field strengths.
The data show the solar cycle variation of the peak field strengths with an
amplitude of about 500-700 gauss (G), but no statistically significant
long-term trends. Next, we use the sunspot observations from the Royal
Greenwich Observatory (RGO) to establish a relationship between the sunspot
areas and the sunspot field strengths for Cycles 15-19. This relationship is
then used to create a proxy of peak magnetic field strength based on sunspot
areas from the RGO and the USAF/NOAA network for the period from 1874 to early
2012. Over this interval, the magnetic field proxy shows a clear solar cycle
variation with an amplitude of 500-700 G and a weaker long-term trend. From
1874 to around 1920, the mean value of magnetic field proxy increases by about
300-350 G, and, following a broad maximum in 1920-1960, it decreases by about
300 G. Using the proxy for the magnetic field strength as the reference, we
scale the MWO field measurements to the measurements of the magnetic fields in
Pevtsov et al. (2011) to construct a combined data set of maximum sunspot field
strengths extending from 1920 to early 2012. This combined data set shows
strong solar cycle variations and no significant long-term trend (linear fit to
the data yields a slope of $-0.2\pm$0.8 G year$^{-1}$). On the other hand, the
peak sunspot field strengths observed at the minimum of the solar cycle show a
gradual decline over the last three minima (corresponding to cycles 21-23) with
a mean downward trend of $\approx$ 15 G year$^{-1}$.


title:
Time-resolved Spectroscopy of the Polar EU Cancri in the Open Cluster
  Messier 67

abstract:
  We present time-resolved spectroscopic and polarimetric observations of the
AM Her system EU Cnc. EU Cnc is located near the core of the old open cluster
Messier 67; new proper motion measurements indicate that EU Cnc is indeed a
member of the star cluster, this system therefore is useful to constrain the
formation and evolution of magnetic cataclysmic variables. The spectra exhibit
two-component emission features with independent radial velocity variations as
well as time-variable cyclotron emission indicating a magnetic field strength
of 41 MG. The period of the radial velocity and cyclotron hump variations are
consistent with the previously-known photometric period, and the spectroscopic
flux variations are consistent in amplitude with previous photometric amplitude
measurements. The secondary star is also detected in the spectrum. We also
present polarimetric imaging measurements of EU Cnc that show a clear detection
of polarization, and the degree of polarization drops below our detection
threshold at phases when the cyclotron emission features are fading or not
evident. The combined data are all consistent with the interpretation that EU
Cnc is a low-state polar in the cluster Messier 67. The mass function of the
system gives an estimate of the accretor mass of M_WD >= 0.68 M_sun with M_WD ~
0.83 M_sun for an average inclination. We are thus able to place a lower limit
on the progenitor mass of the accreting WD of >= 1.43 M_sun.


title:
A Tight Lower Bound on the Mutual Information of a Binary and an
  Arbitrary Finite Random Variable in Dependence of the Variational Distance

abstract:
  In this paper a numerical method is presented, which finds a lower bound for
the mutual information between a binary and an arbitrary finite random variable
with joint distributions that have a variational distance not greater than a
known value to a known joint distribution. This lower bound can be applied to
mutual information estimation with confidence intervals.


title: Evolution of the Internet k-dense structure

abstract:
  As the Internet AS-level topology grows over time, some of its structural
properties remain unchanged. Such time- invariant properties are generally
interesting, because they tend to reflect some fundamental processes or
constraints behind Internet growth. As has been shown before, the
time-invariant structural properties of the Internet include some most basic
ones, such as the degree distribution or clustering. Here we add to this
time-invariant list a non-trivial property - k-dense decomposition. This
property is derived from a recursive form of edge multiplicity, defined as the
number of triangles that share a given edge. We show that after proper
normalization, the k- dense decomposition of the Internet has remained stable
over the last decade, even though the Internet size has approximately doubled,
and so has the k-density of its k-densest core. This core consists mostly of
content providers peering at Internet eXchange Points, and it only loosely
overlaps with the high-degree or high-rank AS core, consisting mostly of tier-1
transit providers. We thus show that high degrees and high k-densities reflect
two different Internet-specific properties of ASes (transit versus content
providers). As a consequence, even though degrees and k-densities of nodes are
correlated, the relative fluctuations are strong, and related to that, random
graphs with the same degree distribution or even degree correlations as in the
Internet, do not reproduce its k-dense decomposition. Therefore an interesting
open question is what Internet topology models or generators can fully explain
or at least reproduce the k-dense properties of the Internet.


title:
The Effect of mechanical alloying on Electrical properties of BaTiO3
  Nano Crystals

abstract:
  In this paper, electrical properties of BaTiO3 nano crystals have been
studied, Barium Titanate Nano Crystals are made by mechanical alloying method
in a ball mill of SPEX 8000. In order to find Curie temperature, dielectric
constant variation via temperature and hysteresis loops are investigated. Our
results show that, there is a relationship between the time of milling and the
curie temperature .this means with increasing milling time, grain size will
decrease, consequently the curie temperature will decrease. In addition, with
increasing temperature up to the Curie temperature, the hysteresis loop of
samples decrease and at the Curie temperature the hysteresis loop changes to a
straight line.


title:
Discovery of Diffuse Hard X-Ray Emission from the Vicinity of PSR
  J1648-4611 with Suzaku

abstract:
  We observed the pulsar PSR J1648-4611 with Suzaku. Two X-ray sources, Suzaku
J1648-4610 (Src A) and Suzaku J1648-4615 (Src B), were found in the field of
view. Src A is coincident with the pulsar PSR J1648-4611, which was also
detected by the Fermi Gamma-ray Space Telescope. A hard-band image indicates
that Src A is spatially extended. We found point sources in the vicinity of Src
A by using a Chandra image of the same region, but the point sources have soft
X-ray emission and cannot explain the hard X-ray emission of Src A. The
hard-band spectrum of Src A can be reproduced by a power-law model with a
photon index of 2.0^{+0.9}_{-0.7}. The X-ray flux in the 2-10 keV band is 1.4
\times 10^{-13} erg cm^{-2} s^{-1}. The diffuse emission suggests a pulsar wind
nebula around PSR J1648-4611, but the luminosity of Src A is much larger than
that expected from the spin-down luminosity of the pulsar. Parts of the
very-high-energy gamma-ray emission of HESS J1646-458 may be powered by this
pulsar wind nebula driven by PSR J1648-4611. Src B has soft emission, and its
X-ray spectrum can be described by a power-law model with a photon index of
3.0^{+1.4}_{-0.8}. The X-ray flux in the 0.4-10 keV band is 6.4 \times 10^{-14}
erg s^{-1} cm^{-2}. No counterpart for Src B is found in literatures.


title: On a Class of Diverse Market Models

abstract:
  A market model in Stochastic Portfolio Theory is a finite system of strictly
positive stochastic processes. Each process represents the capitalization of a
certain stock. If at any time no stock dominates almost the entire market,
which means that its share of total market capitalization is not very close to
one, then the market is called diverse. There are several ways to outperform
diverse markets and get an arbitrage opportunity, and this makes these markets
interesting. A feature of real-world markets is that stocks with smaller
capitalizations have larger drift coefficients. Some models, like the
Volatility-Stabilized Model, try to capture this property, but they are not
diverse. In an attempt to combine this feature with diversity, we construct a
new class of market models. We find simple, easy-to-test sufficient conditions
for them to be diverse and other sufficient conditions for them not to be
diverse.


title: Confidence Intervals for the Mutual Information

abstract:
  By combining a bound on the absolute value of the difference of mutual
information between two joint probablity distributions with a fixed variational
distance, and a bound on the probability of a maximal deviation in variational
distance between a true joint probability distribution and an empirical joint
probability distribution, confidence intervals for the mutual information of
two random variables with finite alphabets are established. Different from
previous results, these intervals do not need any assumptions on the
distribution and the sample size.


title:
Identifying Player\'s Strategies in No Limit Texas Hold\'em Poker
  through the Analysis of Individual Moves

abstract:
  The development of competitive artificial Poker playing agents has proven to
be a challenge, because agents must deal with unreliable information and
deception which make it essential to model the opponents in order to achieve
good results. This paper presents a methodology to develop opponent modeling
techniques for Poker agents. The approach is based on applying clustering
algorithms to a Poker game database in order to identify player types based on
their actions. First, common game moves were identified by clustering all
players\' moves. Then, player types were defined by calculating the frequency
with which the players perform each type of movement. With the given dataset, 7
different types of players were identified with each one having at least one
tactic that characterizes him. The identification of player types may improve
the overall performance of Poker agents, because it helps the agents to predict
the opponent\'s moves, by associating each opponent to a distinct cluster.


title: On a theorem of Serret on continued fractions

abstract:
  A classical theorem in continued fractions due to Serret shows that for any
two irrational numbers x and y related by a transformation $\gamma$ in PGL(2,Z)
there exist s and t for which the complete quotients x_s and y_t coincide. In
this paper we give an upper bound in terms of $\gamma$ for the smallest indices
s and t.


title: High Visibility Two-photon Interference with Classical Light

abstract:
  Two-photon interference with independent classical sources, in which
superposition of two indistinguishable two-photon paths plays a key role, is of
limited visibility of interference fringes with a maximum value of 50%. By
using a random-phase grating to modulate the wavefront of a coherent light, we
introduce superposition of multiple indistinguishable two-photon paths, which
enhances the two-photon interference effect with a signature of visibility
exceeding 50%. The result shows the importance of phase control in the control
of high-order coherence of classical light.


title: Computer Poker Research at LIACC

abstract:
  Computer Poker's unique characteristics present a well-suited challenge for
research in artificial intelligence. For that reason, and due to the Poker's
market increase in popularity in Portugal since 2008, several members of LIACC
have researched in this field. Several works were published as papers and
master theses and more recently a member of LIACC engaged on a research in this
area as a Ph.D. thesis in order to develop a more extensive and in-depth work.
This paper describes the existing research in LIACC about Computer Poker, with
special emphasis on the completed master's theses and plans for future work.
This paper means to present a summary of the lab's work to the research
community in order to encourage the exchange of ideas with other labs /
individuals. LIACC hopes this will improve research in this area so as to reach
the goal of creating an agent that surpasses the best human players.


title: Evolutionary Dynamics of Giant Viruses and their Virophages

abstract:
  Giant viruses contain large genomes, encode many proteins atypical for
viruses, replicate in large viral factories, and tend to infect protists. The
giant virus replication factories can in turn be infected by so called
virophages, which are smaller viruses that negatively impact giant virus
replication. An example are Mimiviruses that infect the protist Acanthamoeba
and that are themselves infected by the virophage Sputnik. This paper examines
the evolutionary dynamics of this system, using mathematical models. While the
models suggest that the virophage population will evolve to increasing degrees
of giant virus inhibition, it further suggests that this renders the virophage
population prone to extinction due to dynamic instabilities over wide parameter
ranges. Implications and conditions required to avoid extinction are discussed.
Another interesting result is that virophage presence can fundamentally alter
the evolutionary course of the giant virus. While the giant virus is predicted
to evolve towards increasing its basic reproductive ratio in the absence of the
virophage, the opposite is true its presence. Therefore, virophages can not
only benefit the host population directly by inhibiting the giant viruses, but
also indirectly by causing giant viruses to evolve towards weaker phenotypes.
Experimental tests for this model are suggested.


title:
Accurate and robust genomic prediction of celiac disease using
  statistical learning

abstract:
  Practical application of genomic-based risk stratification to clinical
diagnosis is appealing yet performance varies widely depending on the disease
and genomic risk score (GRS) method. Celiac disease (CD), a common
immune-mediated illness, is strongly genetically determined and requires
specific HLA haplotypes. HLA testing can exclude diagnosis but has low
specificity, providing little information suitable for clinical risk
stratification. Using six European CD cohorts, we provide a proof-of-concept
that statistical learning approaches which simultaneously model all SNPs can
generate robust and highly accurate predictive models based on genome-wide SNP
profiles. The high predictive capacity replicated both in cross-validation
within each cohort (AUC of 0.87-0.89) and in independent replication across
cohorts (AUC of 0.86-0.9), despite differences in ethnicity. The models
explained 30-35% of disease variance and up to $\sim43\%$ of heritability. The
GRS's utility was assessed in different clinically relevant settings.
Comparable to HLA typing, the GRS can be used to identify individuals without
CD with $\geq99.6\%$ negative predictive value however, unlike HLA typing,
patients can also be stratified into categories of higher-risk for CD who would
benefit from more invasive and costly definitive testing. The GRS is flexible
and its performance can be adapted to the clinical situation by adjusting the
threshold cut-off. Despite explaining a minority of disease heritability, our
findings indicate a predictive GRS provides clinically relevant information to
improve upon current diagnostic pathways for CD, and support further studies
evaluating the clinical utility of this approach in CD and other complex
diseases.


title: Nucleon-Nucleon Scattering and Large N(c) QCD

abstract:
  Nucleon-nucleon scattering observables are discussed in the context of large
Nc QCD. As is well known, the baryon spectrum in the large Nc limit exhibits
contracted SU(2Nf) spin-flavor sym- metry. This symmetry can be used to derive
model-independent relations between proton-proton and proton-neutron total
cross sections. These relations are valid in the kinematic regime in which the
relative momentum of two nucleons is of order of Nc. In this semiclassical
regime the nucleon-nucleon scattering can be described in the time-dependent
mean field approximation. These model-independent results are compared to
experimental data for spin-independent and polarized total nucleon-nucleon
cross sections.


title:
Reply to "Comment on 'Detecting Non-Abelian Geometric Phases with
  Three-Level \Lambda\ Atoms' "

abstract:
  In this reply, we address the comment by Ericsson and Sjoqvist on our paper
[Phys. Rev. A {\bf 84}, 034103 (2011)]. We point out that the zero gauge field
is not the evidence of trivial geometric phase for a non-Abelian SU(2) gauge
field. Furthermore, the recalculation shows that the non-Abelian geometric
phase we proposed in the three-level $\Lambda$ system is indeed experimentally
detectable.


title:
A framework for interpreting fast radio transients search experiments:
  application to the V-FASTR experiment

abstract:
  We define a framework for determining constraints on the detection rate of
fast transient events from a population of underlying sources, with a view to
incorporating beam shape, frequency effects, scattering effects, and detection
efficiency into the metric. We then demonstrate a method for combining
independent datasets into a single event rate constraint diagram, using a
probabilistic approach to the limits on parameter space. We apply this new
framework to present the latest results from the V-FASTR experiment, a
commensal fast transients search using the Very Long Baseline Array (VLBA). In
the 20 cm band, V-FASTR now has the ability to probe the regions of parameter
space of importance for the observed Lorimer and Keane fast radio transient
candidates, by combining the information from observations with differing
bandwidths, and properly accounting for the source dispersion measure, VLBA
antenna beam shape, experiment time sampling, and stochastic nature of events.
We then apply the framework to combine the results of the V-FASTR and ATA Fly's
Eye experiments, demonstrating their complementarity. Expectations for fast
transients experiments for the SKA Phase I dish array are then computed, and
the impact of large differential bandwidths is discussed.


title:
Deterministic Constructions of Binary Measurement Matrices from Finite
  Geometry

abstract:
  Deterministic constructions of measurement matrices in compressed sensing
(CS) are considered in this paper. The constructions are inspired by the recent
discovery of Dimakis, Smarandache and Vontobel which says that parity-check
matrices of good low-density parity-check (LDPC) codes can be used as
{provably} good measurement matrices for compressed sensing under
$\ell_1$-minimization. The performance of the proposed binary measurement
matrices is mainly theoretically analyzed with the help of the analyzing
methods and results from (finite geometry) LDPC codes. Particularly, several
lower bounds of the spark (i.e., the smallest number of columns that are
linearly dependent, which totally characterizes the recovery performance of
$\ell_0$-minimization) of general binary matrices and finite geometry matrices
are obtained and they improve the previously known results in most cases.
Simulation results show that the proposed matrices perform comparably to,
sometimes even better than, the corresponding Gaussian random matrices.
Moreover, the proposed matrices are sparse, binary, and most of them have
cyclic or quasi-cyclic structure, which will make the hardware realization
convenient and easy.


title:
Linear-Time Algorithms for Scattering Number and Hamilton-Connectivity
  of Interval Graphs

abstract:
  Hung and Chang showed that for all k>=1 an interval graph has a path cover of
size at most k if and only if its scattering number is at most k. They also
showed that an interval graph has a Hamilton cycle if and only if its
scattering number is at most 0. We complete this characterization by proving
that for all k<=-1 an interval graph is -(k+1)-Hamilton-connected if and only
if its scattering number is at most k. We also give an O(m+n) time algorithm
for computing the scattering number of an interval graph with n vertices an m
edges, which improves the O(n^4) time bound of Kratsch, Kloks and M\"uller. As
a consequence of our two results the maximum k for which an interval graph is
k-Hamilton-connected can be computed in O(m+n) time.


title:
QoS-Aware Transmission Policies for OFDM Bidirectional
  Decode-and-Forward Relaying

abstract:
  Two-way relaying can considerably improve spectral efficiency in
relay-assisted bidirectional communications. However, the benefits and flexible
structure of orthogonal frequency division multiplexing (OFDM)-based two-way
decode-and-forward (DF) relay systems is much less exploited. Moreover, most of
existing works have not considered quality-of-service (QoS) provisioning for
two-way relaying. In this paper, we consider the OFDM-based bidirectional
transmission where a pair of users exchange information with or without the
assistance of a single DF relay. Each user can communicate with the other via
three transmission modes: direct transmission, one-way relaying, and two-way
relaying. We jointly optimize the transmission policies, including power
allocation, transmission mode selection, and subcarrier assignment for
maximizing the weighted sum rates of the two users with diverse
quality-of-service (QoS) guarantees. We formulate the joint optimization
problem as a mixed integer programming problem. By using the dual method, we
efficiently solve the problem in an asymptotically optimal manner. Moreover, we
derive the capacity region of two-way DF relaying in parallel channels.
Simulation results show that the proposed resource-allocation scheme can
substantially improve system performance compared with the conventional
schemes. A number of interesting insights are also provided via comprehensive
simulations.


title: Convecting reference frames and invariant numerical models

abstract:
  In the recent paper by Bernardini et al. [J. Comput. Phys. 232 (2013), 1-6]
the discrepancy in the performance of finite difference and spectral models for
simulations of flows with a preferential direction of propagation was studied.
In a simplified investigation carried out using the viscous Burgers equation
the authors attributed the poorer numerical results of finite difference models
to a violation of Galilean invariance in the discretization and propose to
carry out the computations in a reference frame moving with the bulk velocity
of the flow. Here we further discuss this problem and relate it to known
results on invariant discretization schemes. Non-invariant and invariant finite
difference discretizations of Burgers equation are proposed and compared with
the discretization using the remedy proposed by Bernardini et al..


title:
A Minimal Uncertainty Product for One Dimensional Semiclassical Wave
  Packets

abstract:
  Although real, normalized Gaussian wave packets minimize the product of
position and momentum uncertainties, generic complex normalized Gaussian wave
packets do not. We prove they minimize an alternative product of uncertainties
that correspond to variables that are phase space rotations of position and
momentum.


title: On the ampleness of positive CR line bundles over Levi-flat manifolds

abstract:
  We give an example of a compact Levi-flat CR 3-manifold with a
positive-along-leaves CR line bundle which is not ample with respect to
transversely infinitely differentiable CR sections. This example shows that we
cannot improve the regularity of Kodaira type embedding theorem for compact
Levi-flat CR manifolds obtained by Ohsawa and Sibony.


title: Chiral magnetism and helimagnons in a pyrochlore antiferromagnet

abstract:
  Recent neutron scattering measurements on the spinel CdCr2O4 revealed a rare
example of helical magnetic order in geometrically frustrated pyrochlore
antiferromagnet. The spin spiral characterized by an incommensurate wavevector
Q = 2pi (0, delta, 1) with delta ~0.09 is accompanied by a tetragonal
distortion. Here we conduct a systematic study on the magnetic ground state
resulting from the interplay between the Dzyaloshinskii-Moriya interaction and
further neighbor exchange couplings, two of the most important mechanisms for
stabilizing incommensurate spin orders. We compute the low-energy spin-wave
spectrum based on a microscopic spin Hamiltonian and find a dispersion relation
characteristic of the helimagnons. By numerically integrating the
Landau-Lifshitz-Gilbert equation with realistic model parameters, an overall
agreement between experiment and the numerical spectrum, lending further
support to the view that a softened optical phonon triggers the magnetic
transition and endows the lattice a chirality.


title: Chern-Weil forms and abstract homotopy theory

abstract:
  We prove that Chern-Weil forms are the only natural differential forms
associated to a connection on a principal G-bundle. We use the homotopy theory
of simplicial sheaves on smooth manifolds to formulate the theorem and set up
the proof. Other arguments come from classical invariant theory. We identify
the Weil algebra as the de Rham complex of a specific simplicial sheaf, and
similarly give a new interpretation of the Weil model in equivariant de Rham
theory. There is an appendix proving a general theorem about set-theoretic
transformations of polynomial functors. This paper is dedicated to the memory
of Dan Quillen.


title: Twists and turns for metamaterials

abstract:
  We propose and verify experimentally a new concept for achieving strong
nonlinear coupling between the electromagnetic and elastic properties in
metamaterials. This coupling is provided through a novel degree of freedom in
metamaterial design: internal rotation within structural elements. Our
meta-atoms have high sensitivity to electromagnetic wave power, and the elastic
and electromagnetic properties can be independently designed to optimise the
response. We demonstrate a rich range of nonlinear phenomena including
self-tuning and bistability, and provide a comprehensive experimental
demonstration of the predicted effects.


title: New Lower Bounds for Constant Dimension Codes

abstract:
  This paper provides new constructive lower bounds for constant dimension
codes, using different techniques such as Ferrers diagram rank metric codes and
pending blocks. Constructions for two families of parameters of constant
dimension codes are presented. The examples of codes obtained by these
constructions are the largest known constant dimension codes for the given
parameters.


title: On the separability of multivariate functions

abstract:
  Separability of multivariate functions alleviates the difficulty in finding a
minimum or maximum value of a function such that an optimal solution can be
searched by solving several disjoint problems with lower dimensionalities. In
most of practical problems, however, a function to be optimized is black-box
and we hardly grasp its separability. In this study, we first describe a
general separability condition which a function defined over an arbitrary
domain satisfies if and only if the function is separable with respect to given
disjoint subsets of variables. By introducing an alternative separability
condition, we propose a Monte Carlo-based algorithm to estimate the
separability of a function defined over unit cube with respect to given
disjoint subsets of variables. Moreover, we extend our algorithm to estimate
the number of disjoint subsets and the disjoint subsets such that a function is
separable with respect to them. Computational complexity of our extended
algorithm is function-dependent and varies from linear to exponential in the
dimension.


title: Driven skyrmions and dynamical transitions in chiral magnets

abstract:
  We study the dynamics of skyrmions in chiral magnets in the presence of a
spin polarized current. The motion of skyrmions in the ferromagnetic background
excites spin waves and contributes to additional damping. At a large current,
the spin wave spectrum becomes gapless and skyrmions are created dynamically
from the ferromagnetic state. At an even higher current, these skyrmions are
strongly deformed due to the damping and become unstable at a threshold
current, leading to a chiral liquid. We show how skyrmions can be created by
increasing the current in the magnetic spiral state. We then construct a
dynamic phase diagram for a chiral magnet with a current. The instability
transitions between different states can be observed as experimentally clear
signatures in the transport measurements, such as jumps and hysteresis.


title: On the Current Measurement Practices in Agile Software Development

abstract:
  Agile software development (ASD) methods were introduced as a reaction to
traditional software development methods. Principles of these methods are
different from traditional methods and so there are some different processes
and activities in agile methods comparing to traditional methods. Thus ASD
methods require different measurement practices comparing to traditional
methods. Agile teams often do their projects in the simplest and most effective
way so, measurement practices in agile methods are more important than
traditional methods, because lack of appropriate and effective measurement
practices, will increase risk of project. The aims of this paper are
investigation on current measurement practices in ASD methods, collecting them
together in one study and also reviewing agile version of Common Software
Measurement International Consortium (COSMIC) publication.


title:
New mass limit for white dwarfs: super-Chandrasekhar type Ia supernova
  as a new standard candle

abstract:
  Type Ia supernovae, sparked off by exploding white dwarfs of mass close to
Chandrasekhar limit, play the key role to understand the expansion rate of
universe. However, recent observations of several peculiar type Ia supernovae
argue for its progenitor mass to be significantly super-Chandrasekhar. We show
that strongly magnetized white dwarfs not only can violate the Chandrasekhar
mass limit significantly, but exhibit a different mass limit. We establish from
foundational level that the generic mass limit of white dwarfs is 2.58 solar
mass. This explains the origin of over-luminous peculiar type Ia supernovae.
Our finding further argues for a possible second standard candle, which has
many far reaching implications, including a possible reconsideration of the
expansion history of the universe.

categories: astro-ph.SR astro-ph.CO astro-ph.HE gr-qc


title: Singular probability distribution of shot-noise driven systems

abstract:
  We study the stationary probability distribution of a system driven by shot
noise. We find that, both in the overdamped and underdamped regime, the
coordinate distribution displays power-law singularities in its central part.
For sufficiently low rate of noise pulses they correspond to distribution
peaks. We find the positions of the peaks and the corresponding exponents. In
the underdamped regime the peak positions are given by a geometric progression.
The energy distribution in this case also displays multiple peaks with
positions given by a geometric progression. Such structure is a signature of
the shot-noise induced fluctuations. The analytical results are in excellent
agreement with numerical simulations.


title:
Search for Associations Containing Young stars (SACY): Chemical tagging
  IC 2391 & the Argus association

abstract:
  We explore the possible connection between the open cluster IC 2391 and the
unbound Argus association identified by the SACY survey. In addition to common
kinematics and ages between these two systems, here we explore their chemical
abundance patterns to confirm if the two substructures shared a common origin.
We carry out a homogenous high-resolution elemental abundance study of eight
confirmed members of IC 2391 as well as six members of the Argus association
using UVES spectra. We derive spectroscopic stellar parameters and abundances
for Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni and Ba.
  All stars in the open cluster and Argus association were found to share
similar abundances with the scatter well within the uncertainties, where [Fe/H]
= -0.04 +/-0.03 for cluster stars and [Fe/H] = -0.06 +/-0.05 for Argus stars.
Effects of over-ionisation/excitation were seen for stars cooler than roughly
5200K as previously noted in the literature. Also, enhanced Ba abundances of
around 0.6 dex were observed in both systems. The common ages, kinematics and
chemical abundances strongly support that the Argus association stars
originated from the open cluster IC 2391. Simple modeling of this system find
this dissolution to be consistent with two-body interactions.


title:
Sacrificial bonds and hidden length in biomaterials -- a kinetic,
  constitutive description of strength and toughness in bone

abstract:
  Sacrificial bonds and hidden length in structural molecules account for the
greatly increased fracture toughness of biological materials compared to
synthetic materials without such structural features, by providing a
molecular-scale mechanism for energy dissipation. One example is in the
polymeric glue connection between collagen fibrils in animal bone. In this
paper, we propose a simple kinetic model that describes the breakage of
sacrificial bonds and the release of hidden length, based on Bell's theory. We
postulate a master equation governing the rates of bond breakage and formation.
This enables us to predict the mechanical behavior of a quasi-one-dimensional
ensemble of polymers at different stretching rates. We find that both the
rupture peak heights and maximum stretching distance increase with the
stretching rate. In addition, our theory naturally permits the possibility of
self-healing in such biological structures.


title: Tatami Maker: A combinatorially rich mechanical game board

abstract:
  Japanese tatami mats are often arranged so that no four mats meet. This local
restriction imposes a rich combinatorial structure when applied to
monomino-domino coverings of rectilinear grids. We describe a modular,
mechanical game board, prototyped with a desktop 3D printer, that enforces this
restriction, and transforms tatami pen-and- paper puzzles into interactive
sculptures. We review some recent mathematical discoveries on tatami coverings
and present five new combinatorial games implemented on the game board.


title: Implications of theta_13 on Fritzsch-like lepton mass matrices

abstract:
  Implications of the lepton mixing angles, in particular of theta_13, have
been investigated for minimal as well as non-minimal Fritzsch-like textures for
the case of Majorana neutrinos. Both, in minimal texture (texture 6 zero lepton
mass matrices) and non-minimal textures (two cases of texture 5 zero lepton
mass matrices), inverted hierarchy and degenerate scenario of neutrino masses
have been ruled out. The implications of theta_13 have been investigated on the
lightest neutrino mass m_\nu_1 as well as the effective Majorana mass m_ee.


title:
A new probe of dark matter properties: gravitational waves from an
  intermediate mass black hole embedded in a dark matter mini-spike

abstract:
  An intermediate mass black hole (IMBH) may have a dark matter (DM) mini-halo
around it and develop a spiky structure within less than a parsec from the
IMBH. When a stellar mass object is captured by the mini-halo, it eventually
infalls into such an IMBH due to gravitational wave back reaction which in turn
could be observed directly by future space-borne gravitational wave experiments
such as eLISA/NGO. In this paper, we show that the GW detectability strongly
depends on the radial profile of the DM distribution. So if the GW is detected,
the power index, that is, the DM density distribution would be determined very
accurately. The DM density distribution obtained would make it clear how the
IMBH has evolved from a seed BH and whether the IMBH has experienced major
mergers in the past. Unlike the gamma ray observations of DM annihilation, GW
is just sensitive to the radial profile of the DM distribution and even to
non-interacting DM. Hence the effect we demonstrate here can be used as a new
and powerful probe into DM properties.