title: Pricing Ad Slots with Consecutive Multi-unit Demand

abstract:
  We consider the optimal pricing problem for a model of the rich media
advertisement market, as well as other related applications. In this market,
there are multiple buyers (advertisers), and items (slots) that are arranged in
a line such as a banner on a website. Each buyer desires a particular number of
{\em consecutive} slots and has a per-unit-quality value $v_i$ (dependent on
the ad only) while each slot $j$ has a quality $q_j$ (dependent on the position
only such as click-through rate in position auctions). Hence, the valuation of
the buyer $i$ for item $j$ is $v_iq_j$. We want to decide the allocations and
the prices in order to maximize the total revenue of the market maker.
  A key difference from the traditional position auction is the advertiser's
requirement of a fixed number of consecutive slots. Consecutive slots may be
needed for a large size rich media ad. We study three major pricing mechanisms,
the Bayesian pricing model, the maximum revenue market equilibrium model and an
envy-free solution model. Under the Bayesian model, we design a polynomial time
computable truthful mechanism which is optimum in revenue. For the market
equilibrium paradigm, we find a polynomial time algorithm to obtain the maximum
revenue market equilibrium solution. In envy-free settings, an optimal solution
is presented when the buyers have the same demand for the number of consecutive
slots. We conduct a simulation that compares the revenues from the above
schemes and gives convincing results.


title:
Imposing system-observer symmetry on the von Neumann description of
  measurement

abstract:
  By imposing system-observer symmetry on the von Neumann description of
measurement, it is shown that the quantum measurement problem is structurally
equivalent to a familiar reverse-engineering problem: that of describing the
behavior of an arbitrary physical device as algorithm instantiation. It is
suggested that this problem can at best be given a relational solution.


title:
Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of
  interface on stability of magnetic properties

abstract:
  A cluster deposition method was used to produce films of loosely aggregated
nanoclusters (NC) of Fe core-Fe3O4 shell or fully oxidized Fe3O4. Films of
these NC on Si(100) or MgO(100)/Fe3O4(100) were irradiated to 10^16 Si2+/cm2
near room temperature using an ion accelerator. Ion irradiation creates
structural change in the NC film with corresponding chemical and magnetic
changes which depend on the initial oxidation state of the cluster. Films were
characterized using magnetometry (hysteresis, first order reversal curves),
microscopy (transmission electron, helium ion), and x-ray diffraction. In all
cases, the particle sizes increased due to ion irradiation, and when a core of
Fe is present, irradiation reduces the oxide shells to lower valent Fe species.
These results show that ion irradiated behavior of the nanocluster films
depends strongly on the initial nanostructure and chemistry, but in general
saturation magnetization decreases slightly.


title:
Efficient Algorithms for Privately Releasing Marginals via Convex
  Relaxations

abstract:
  Consider a database of $n$ people, each represented by a bit-string of length
$d$ corresponding to the setting of $d$ binary attributes. A $k$-way marginal
query is specified by a subset $S$ of $k$ attributes, and a $|S|$-dimensional
binary vector $\beta$ specifying their values. The result for this query is a
count of the number of people in the database whose attribute vector restricted
to $S$ agrees with $\beta$.
  Privately releasing approximate answers to a set of $k$-way marginal queries
is one of the most important and well-motivated problems in differential
privacy. Information theoretically, the error complexity of marginal queries is
well-understood: the per-query additive error is known to be at least
$\Omega(\min\{\sqrt{n},d^{\frac{k}{2}}\})$ and at most
$\tilde{O}(\min\{\sqrt{n} d^{1/4},d^{\frac{k}{2}}\})$. However, no polynomial
time algorithm with error complexity as low as the information theoretic upper
bound is known for small $n$. In this work we present a polynomial time
algorithm that, for any distribution on marginal queries, achieves average
error at most $\tilde{O}(\sqrt{n} d^{\frac{\lceil k/2 \rceil}{4}})$. This error
bound is as good as the best known information theoretic upper bounds for
$k=2$. This bound is an improvement over previous work on efficiently releasing
marginals when $k$ is small and when error $o(n)$ is desirable. Using private
boosting we are also able to give nearly matching worst-case error bounds.
  Our algorithms are based on the geometric techniques of Nikolov, Talwar, and
Zhang. The main new ingredients are convex relaxations and careful use of the
Frank-Wolfe algorithm for constrained convex minimization. To design our
relaxations, we rely on the Grothendieck inequality from functional analysis.


title: C*-algebras associated with endomorphisms of groups

abstract:
  In this work we construct a C*-algebra from an injective endomorphisms of
some group G, allowing the endomorphism to have infinite cokernel. We
generalize results obtained by I. Hirshberg and also by J. Cuntz and A.
Vershik. In good cases we show that the C*-algebra that we study is
classifiable by Kirchberg's classification theorem, with K-groups equal to
K*(C*(G)).


title:
$L^p$-nondegenerate Radon-like operators with vanishing rotational
  curvature

abstract:
  We consider the $L^p \rightarrow L^q$ mapping properties of a model family of
Radon-like operators integrating functions over n-dimensional submanifolds of
${\mathbb R}^{2n}$. It is shown that nonvanishing rotational curvature is never
generic when $n \geq 2$ and is, in fact, impossible for all but finitely many
values of $n$. Nevertheless, operators satisfying the same $L^p \rightarrow
L^q$ estimates as the "nondegenerate" case (modulo the endpoint) are dense in
the model family for all $n$.


title:
Bayesian genome assembly and assessment by Markov Chain Monte Carlo
  sampling

abstract:
  Most genome assemblers construct point estimates, choosing a genome sequence
from among many alternative hypotheses that are supported by the data. We
present a Markov Chain Monte Carlo approach to sequence assembly that instead
generates distributions of assembly hypotheses with posterior probabilities,
providing an explicit statistical framework for evaluating alternative
hypotheses and assessing assembly uncertainty. We implement this approach in a
prototype assembler and illustrate its application to the bacteriophage
PhiX174.


title: Degrees of Freedom for the MIMO Multi-way Relay Channel

abstract:
  This paper investigates the degrees of freedom (DoF) of the L-cluster, K-user
MIMO multi-way relay channel, where users in each cluster wish to exchange
messages within the cluster, and they can only communicate through the relay. A
novel DoF upper bound is derived by providing users with carefully designed
genie information. Achievable DoF is identified using signal space alignment
and multiple-access transmission. For the two-cluster MIMO multi-way relay
channel with two users in each cluster, DoF is established for the general case
when users and the relay have arbitrary number of antennas, and it is shown
that the DoF upper bound can be achieved using signal space alignment or
multiple-access transmission, or a combination of both. The result is then
generalized to the three user case. For the L-cluster K-user MIMO multi-way
relay channel in the symmetric setting, conditions under which the DoF upper
bound can be achieved are established. In addition to being shown to be tight
in a variety of scenarios of interests of the multi-way relay channel, the
newly derived upperbound also establishes the optimality of several previously
established achievable DoF results for multiuser relay channels that are
special cases of the multi-way relay channel.


title:
Photosensor Characterization for the Cherenkov Telescope Array: Silicon
  Photomultiplier versus Multi-Anode Photomultiplier Tube

abstract:
  Photomultiplier tube technology has been the photodetector of choice for the
technique of imaging atmospheric Cherenkov telescopes since its birth more than
50 years ago. Recently, new types of photosensors are being contemplated for
the next generation Cherenkov Telescope Array. It is envisioned that the array
will be partly composed of telescopes using a Schwarzschild-Couder two mirror
design never built before which has significantly improved optics. The camera
of this novel optical design has a small plate scale which enables the use of
compact photosensors. We present an extensive and detailed study of the two
most promising devices being considered for this telescope design: the silicon
photomultiplier and the multi-anode photomultiplier tube. We evaluated their
most critical performance characteristics for imaging gamma-ray showers, and we
present our results in a cohesive manner to clearly evaluate the advantages and
disadvantages that both types of device have to offer in the context of GeV-TeV
gamma-ray astronomy.


title:
Low-Dimensional Reconciliation for Continuous-Variable Quantum Key
  Distribution

abstract:
  We propose an efficient logical layer-based reconciliation method for
continuous-variable quantum key distribution (CVQKD) to extract binary
information from correlated Gaussian variables. We demonstrate that by
operating on the raw-data level, the noise of the quantum channel can be
corrected in the low-dimensional (scalar) space and the reconciliation can be
extended to arbitrary dimensions. The CVQKD systems allow an unconditionally
secret communication over standard telecommunication networks. To exploit the
real potential of CVQKD a robust reconciliation technique is needed. It is
currently unavailable, which makes it impossible to reach the real performance
of the CVQKD protocols. The reconciliation is a post-processing step separated
from the transmission of quantum states, which is aimed to derive the secret
key from the raw data. The reconciliation process of correlated Gaussian
variables is a complex problem that requires either tomography in the physical
layer that is intractable in a practical scenario, or high-cost calculations in
the multidimensional spherical space with strict dimensional limitations. To
avoid these issues we define the low-dimensional reconciliation. We prove that
the error probability of one-dimensional reconciliation is zero in any
practical CVQKD scenario, and provides unconditional security. The results
allow to significantly improve the currently available key rates and
transmission distances of CVQKD.


title: An Inversion Formula for the Gaussian Radon Transform for Banach Spaces

abstract:
  We provide a disintegration theorem for the Gaussian Radon transform Gf on
Banach spaces and use the Segal-Bargmann transform on abstract Wiener spaces to
find a procedure to obtain f from its Gaussian Radon transform Gf.


title:
Frozen-orbital and downfolding calculations with auxiliary-field quantum
  Monte Carlo

abstract:
  We describe the implementation of the frozen-orbital and downfolding
approximations in the auxiliary-field quantum Monte Carlo (AFQMC) method. These
approaches can provide significant computational savings compared to fully
correlating all the electrons. While the many-body wave function is never
explicit in AFQMC, its random walkers are Slater determinants, whose orbitals
may be expressed in terms of any one-particle orbital basis. It is therefore
straightforward to partition the full N-particle Hilbert space into active and
inactive parts to implement the frozen-orbital method. In the frozen-core
approximation, for example, the core electrons can be eliminated in the
correlated part of the calculations, greatly increasing the computational
efficiency, especially for heavy atoms. Scalar relativistic effects are easily
included using the Douglas-Kroll-Hess theory. Using this method, we obtain a
way to effectively eliminate the error due to single-projector, norm-conserving
pseudopotentials in AFQMC. We also illustrate a generalization of the
frozen-orbital approach that downfolds high-energy basis states to a physically
relevant low-energy sector, which allows a systematic approach to produce
realistic model Hamiltonians to further increase efficiency for extended
systems.


title:
Computational Complexity of the Minimum Cost Homomorphism Problem on
  Three-Element Domains

abstract:
  In this paper we study the computational complexity of the (extended) minimum
cost homomorphism problem (Min-Cost-Hom) as a function of a constraint
language, i.e. a set of constraint relations and cost functions that are
allowed to appear in instances. A wide range of natural combinatorial
optimisation problems can be expressed as Min-Cost-Homs and a classification of
their complexity would be highly desirable, both from a direct, applied point
of view as well as from a theoretical perspective.
  Min-Cost-Hom can be understood either as a flexible optimisation version of
the constraint satisfaction problem (CSP) or a restriction of the
(general-valued) valued constraint satisfaction problem (VCSP). Other
optimisation versions of CSPs such as the minimum solution problem (Min-Sol)
and the minimum ones problem (Min-Ones) are special cases of Min-Cost-Hom.
  The study of VCSPs has recently seen remarkable progress. A complete
classification for the complexity of finite-valued languages on arbitrary
finite domains has been obtained Thapper and Zivny [STOC'13]. However,
understanding the complexity of languages that are not finite-valued appears to
be more difficult. Min-Cost-Hom allows us to study problematic languages of
this type without having to deal with with the full generality of the VCSP. A
recent classification for the complexity of three-element Min-Sol, Uppman
[ICALP'13], takes a step in this direction. In this paper we extend this result
considerably by determining the complexity of three-element Min-Cost-Hom.


title:
Bilayer graphene with parallel magnetic field and twisting: Phases and
  phase transitions in a highly tunable Dirac system

abstract:
  The effective theory for bilayer graphene (BLG), subject to parallel/in-plane
magnetic fields, is derived. With a sizable magnetic field the trigonal warping
becomes irrelevant, and one ends up with two Dirac points in the vicinity of
each valley in the low-energy limit, similar to the twisted BLG. Combining
twisting and parallel field thus gives rise to a Dirac system with tunable
Fermi velocity and cutoff. If the interactions are sufficiently strong, several
fully gapped states can be realized in these systems, in addition to the ones
in a pristine setup. Transformations of the order parameters under various
symmetry operations are analyzed. The quantum critical behavior of various
phase transitions driven by the twisting and the magnetic field is reported.
The effects of an additional perpendicular fields, and possible ways to realize
the new massive phases is highlighted.


title:
Superlattice origin of incommensurable density waves in La_{2-x}Ae_xCuO4
  (Ae = Ba, Sr)

abstract:
  In line with the Coulomb-oscillator model of superconductivity, loop currents
of excited 3s electrons from O^2- ions, passing in the CuO2 plane through
nuclei of nearest-neighbor oxygen quartets, create the antiferromagnetic phase
of undoped copper oxides. Holes, introduced by alkaline-earth doping of
La2CuO4, destroy the loop currents, thereby weakening antiferromagnetism until
it disappears at doping x = 0.02. Further doping of La_2-xAe_xCuO4 gives rise
to incommensurate free-hole density waves whose wavelength is determined by the
spacing of a doping superlattice. Modulating the ordering of the ions' magnetic
moments, the charge-density wave, of incommensurability 2 delta, causes a
magnetic density wave of incommensurability delta. The formula derived for
delta(x) is in excellent agreement with data from X-ray diffraction and neutron
scattering.


title:
Inadequacies of the Fisher Information Matrix in gravitational-wave
  parameter estimation

abstract:
  The Fisher Information Matrix (FIM) has been the standard approximation to
the accuracy of parameter estimation on gravitational-wave signals from merging
compact binaries due to its ease-of-use and rapid computation time. While the
theoretical failings of this method, such as the signal-to-noise ratio (SNR)
limit on the validity of the lowest-order expansion and the difficulty of using
non-Gaussian priors, are well understood, the practical effectiveness compared
to a real parameter estimation technique (e.g. Markov-chain Monte Carlo)
remains an open question. We present a direct comparison between the FIM error
estimates and the Bayesian probability density functions produced by the
parameter estimation code lalinference_mcmc. In addition to the low-SNR issues
usually considered, we find that the FIM can greatly overestimate the
uncertainty in parameter estimation achievable by the MCMC. This was found to
be a systematic effect for systems composed of binary black holes, with the
disagreement increasing with total mass. In some cases, the MCMC search
returned standard deviations on the marginalized posteriors that were smaller
by several orders of magnitude than the FIM estimates. We conclude that the
predictions of the FIM do not represent the capabilities of real
gravitational-wave parameter estimation.


title: On central black holes in ultra-compact dwarf galaxies

abstract:
  CONTEXT: The dynamical mass-to-light (M/L) ratios of massive ultra-compact
dwarf galaxies (UCDs) are about 50% higher than predicted by stellar population
models. AIMS: Here we investigate the possibility that these elevated M/L
ratios are caused by a central black hole (BH), heating up the internal motion
of stars. We focus on a sample of ~50 extragalactic UCDs for which velocity
dispersions and structural parameters have been measured. METHODS: Using
up-to-date distance moduli and a consistent treatment of aperture and seeing
effects, we calculate the ratio Psi=(M/L)_{dyn}/(M/L)_{pop} between the
dynamical and the stellar population M/L of UCDs. For all UCDs with Psi>1 we
estimate the mass of a hypothetical central BH needed to reproduce the observed
integrated velocity dispersion. RESULTS: Massive UCDs (M>10^7 M_*) have an
average Psi = 1.7 +-0.2, implying notable amounts of dark mass in them. We find
that, on average, central BH masses of 10-15% of the UCD mass can explain these
elevated dynamical M/L ratios. The implied BH masses in UCDs range from several
10^5 M_* to several 10^7 M_*. In the M_BH-Luminosity plane, UCDs are offset by
about two orders of magnitude in luminosity from the relation derived for
galaxies. Our findings can be interpreted such that massive UCDs originate from
progenitor galaxies with masses around 10^9 M_*, and that those progenitors
have SMBH occupation fractions of 60-100%. The suggested UCD progenitor masses
agree with predictions from the tidal stripping scenario. Lower-mass UCDs
(M<10^7 M_*) exhibit a bimodal distribution in Psi, suggestive of a coexistence
of massive globular clusters and tidally stripped galaxies in this mass regime.
CONCLUSIONS: Central BHs as relict tracers of tidally stripped progenitor
galaxies are a plausible explanation for the elevated dynamical M/L ratios of
UCDs.


title: The properties of warm dark matter haloes

abstract:
  Well-motivated elementary particle candidates for the dark matter, such as
the sterile neutrino, behave as warm dark matter (WDM).For particle masses of
order a keV, free streaming produces a cutoff in the linear fluctuation power
spectrum at a scale corresponding to dwarf galaxies. We investigate the
abundance and structure of WDM haloes and subhaloes on these scales using high
resolution cosmological N-body simulations of galactic haloes of mass similar
to the Milky Way's. On scales larger than the free-streaming cutoff, the
initial conditions have the same power spectrum and phases as one of the cold
dark matter (CDM) haloes previously simulated by Springel et al as part of the
Virgo consortium Aquarius project. We have simulated four haloes with WDM
particle masses in the range 1.4-2.3keV and, for one case, we have carried out
further simulations at varying resolution. N-body simulations in which the
power spectrum cutoff is resolved are known to undergo artificial fragmentation
in filaments producing spurious clumps which, for small masses (<10^7Msun in
our case) outnumber genuine haloes. We have developed a robust algorithm to
identify these spurious objects and remove them from our halo catalogues. We
find that the WDM subhalo mass function is suppressed by well over an order
magnitude relative to the CDM case for masses <10^9Msun. Requiring that there
should be at least as many subhaloes as there are observed satellites in the
Milky Way leads to a conservative lower limit to the (thermal equivalent) WDM
particle mass of ~1.5\rmn{keV}. WDM haloes and subhaloes have cuspy density
distributions that are well described by NFW or Einasto profiles. Their central
densities are lower for lower WDM particle masses and none of the models we
have considered suffer from the "too big to fail" problem recently highlighted
by Boylan-Kolchin et al.


title: Red-channel (6000-8000 {\AA}) nuclear spectra of 376 local galaxies

abstract:
  We obtained long-slit optical spectra of the nuclear regions of 376 galaxies
in the local Universe using the 1.5m Cassini telescope of Bologna Observatory.
Of these spectra, 164 were either never taken before by the Sloan Digital Sky
Survey (SDSS), or given by the Nasa Extragalactic Database (NED). With these
new spectra, we contribute investigating the occurrence of active galactic
nuclei (AGNs). Nevertheless, we stress that the present sample is by no means
complete, thus, it cannot be used to perform any demographic study. Following
the method presented in Gavazzi et al. (2011), we classify the nuclear spectra
using a six bin scheme: SEY (Seyfert), sAGN (strong AGN), and wAGN (weak AGN)
represent active galactic nuclei of different levels of activity; HII accounts
for star-forming nuclei; RET (retired) and PAS (passive) refer to nuclei with
poor or no star-formation activity. The spectral classification is performed
using the ratio of 6584 {\lambda} [NII] to H{\alpha} lines and the equivalent
width (EW) of H{\alpha} versus [NII]/H{\alpha} (WHAN diagnostic introduced by
Cid Fernandes and collaborators) after correcting H{\alpha} for underlying
absorption. The obtained spectra are made available in machine readable format
via the Strasbourg Astronomical Data Center (CDS) and NED.


title:
Signatures of First Stars in Galaxy Surveys: Multi-Tracer Analysis of
  the Supersonic Relative Velocity Effect and the Constraints from the BOSS
  Power Spectrum Measurements

abstract:
  We study the effect of the supersonic relative velocity between dark matter
and baryons on large-scale galaxy clustering and derive the constraint on the
relative velocity bias parameter from the Baryonic Oscillation Spectroscopic
Survey (BOSS) power spectrum measurements. Recent work has shown that the
relative velocity effect may have a dramatic impact on the star formation at
high redshifts, if first stars are formed in minihalos around z~20, or if the
effect propagates through secondary effects to stars formed at later redshifts.
The relative velocity effect has particularly strong signatures in the large
scale clustering of these sources, including the BAO position. Assuming that a
small fraction of stars in low-redshift massive galaxies retain the memory of
the primordial relative velocity effect, galaxy clustering measurements can be
used to constrain the signatures of the first stars. Luminous red galaxies
contain some of the oldest stars in the Universe and are ideally suited to
search for this effect. Using the BOSS power spectrum measurements from the
Sloan Data Release 9, in combination with Planck, we derive the upper limit on
the fraction of the stars sensitive to relative velocity effect f_star<3.3% at
the 95% confidence level in the CMASS galaxy sample. If additional galaxy
sample not sensitive to the effect is available in a given survey, a joint
multi-tracer analysis can be applied to construct a sample-variance cancelling
combination, providing a model-independent way to verify the presence of the
relative velocity effect in the galaxy power spectrum on large scales. Such a
multi-tracer analysis in future galaxy surveys can greatly improve the current
constraint, achieving a 0.1% level in f_star.


title:
Multi-azimuthal-angle effects in self-induced supernova neutrino flavor
  conversions without axial symmetry

abstract:
  The flavor evolution of neutrinos emitted by a supernova (SN) core is
strongly affected by the refractive effects associated with the
neutrino-neutrino interactions in the deepest stellar regions. Till now, all
numerical studies have assumed the axial symmetry for the "multi-angle effects"
associated with the neutrino-neutrino interactions. Recently, it has been
pointed out in \cite{Raffelt:2013rqa} that removing this assumption, a new
multi-azimuthal-angle (MAA) instability would emerge in the flavor evolution of
the dense SN neutrino gas in addition to the one caused by multi-zenith-angle
(MZA) effects. Inspired by this result, for the first time we numerically solve
the non-linear neutrino propagation equations in SN, introducing the azimuthal
angle as angular variable in addition to the usual zenith angle. We consider
simple energy spectra with an excess of \nu_e over anti-\nu_e. In these cases,
we find that even starting with a complete axial symmetric neutrino emission,
the MAA effects would lead to significant flavor conversions in normal mass
hierarchy, in cases otherwise stable under the only MZA effects. The final
outcome of the flavor conversions, triggered by the MAA instability, depends on
the initial asymmetry between \nu_e and anti-\nu_e spectra. If it is
sufficiently large, final spectra would show an ordered behavior with spectral
swaps and splits. Conversely, for small flavor asymmetries flavor decoherence
among angular modes develops, affecting the flavor evolution also in inverted
mass hierarchy.


title:
Comparing galaxy populations in compact and loose groups of galaxies II:
  brightest group galaxies

abstract:
  The properties of the brightest galaxies (BCGs) are studied in both compact
and loose groups of galaxies in order to better understand the physical
mechanisms influencing galaxy evolution in different environments. Samples of
BCGs are selected in the compact groups identified by McConnachie et al.
(2009), and in loose groups taken from Zandivarez & Mart\'inez (2011). The
following physical properties of the BCGs in compact groups and in subsamples
of loose groups are compared, defined by their mass and total luminosity. The
fraction of BCGs classified as red and/or early-type as a function of galaxy
luminosity are studied. The fraction of the group's total luminosity contained
in the BCG and the difference in luminosity between the BCG and the
second-ranked galaxy, are also analysed. Some properties of BCGs in compact and
loose groups are comparable. However, BCGs in compact groups are systematically
more concentrated and have larger surface brightness than their counterparts in
both, high- and low-mass loose groups. The fractions of red and early-type BCGs
in compact groups are consistent with those of high-mass loose groups.
Comparing BCGs in subsamples of compact and loose groups selected for their
similar luminosities, BCGs in compact groups are found to be, on average,
brighter, more massive, larger, redder and more frequently classified as
elliptical. In compact groups, the BCG contains a larger fraction of the
system's total luminosity and differs more in absolute magnitude from the
second-ranked galaxy. BCGs in compact and loose groups are found to be
different. Some mechanisms responsible for transforming late-type galaxies into
early types, such as mergers, may be more effective within compact groups due
to their high densities and small velocity dispersion, which would lead their
BCGs along somewhat different evolutionary paths.


title:
Cosmic Bandits: Exploration versus Exploitation in CMB B-Mode
  Experiments

abstract:
  A preferred method to detect the curl-component, or B-mode, signature of
inflationary gravitational waves (IGWs) in the cosmic microwave background
(CMB) polarization, in the absence of foregrounds and lensing, is a prolonged
integration over a single patch of sky of a few square degrees. In practice,
however, foregrounds abound and the sensitivity to B modes can be improved
considerably by finding the region of sky cleanest of foregrounds. The best
strategy to detect B modes thus involves a tradeoff between exploration (to
find lower-foreground patches) and exploitation (through prolonged
integration). This problem is akin to the multi-armed bandit (MAB) problem in
probability theory, wherein a gambler faces a series of slot machines with
unknown winning odds and must develop a strategy to maximize his/her winnings
with some finite number of pulls. While the optimal MAB strategy remains to be
determined, a number of algorithms have been developed in an effort to maximize
the winnings. Here, based on this resemblance, we tackle the search for IGW B
modes with single frequency experiments in the presence of spatially-varying
foregrounds by developing adaptive survey strategies to optimize the
sensitivity to IGW B modes. We demonstrate, using realistic foreground models
and taking lensing-induced B modes into account, that adaptive experiments can
substantially improve the upper bound on the tensor-to-scalar ratio (by factors
of 2--3 in single frequency experiments, and possibly even more). Similar
techniques can be applied to other surveys, including 21-cm measurements of
signatures of the epoch of reionization, searches for a stochastic primordial
gravitational wave background, deep-field imaging by the James Webb Space
Telescope or various radio interferometers, and transient follow-up searches.


title: Anisotropic Lyman-alpha Emission

abstract:
  As a result of resonant scatterings off hydrogen atoms, Lyman-alpha (Lya)
emission from star-forming galaxies provides a probe of the (hardly isotropic)
neutral gas environment around them. We study the effect of the environmental
anisotropy on the observed Lya emission by performing radiative transfer
calculations for models of neutral hydrogen clouds with prescriptions of
spatial and kinematic anisotropies. The environmental anisotropy leads to
corresponding anisotropy in the Lya flux and spectral properties and induces
correlations among them. The Lya flux (or observed luminosity) depends on the
viewing angle and shows an approximate correlation with the initial Lya optical
depth in the viewing direction relative to those in all other directions. The
distribution of Lya flux from a set of randomly oriented clouds is skewed to
high values, providing a natural contribution to the Lya equivalent width (EW)
distribution seen in observation. A narrower EW distribution is found at a
larger peak offset of the Lya line, similar to the trend suggested in
observation. The peak offset appears to correlate with the line shape (full
width at half maximum and asymmetry), pointing to a possibility of using Lya
line features alone to determine the systemic redshifts of galaxies. The study
suggests that anisotropies in the spatial and kinematic distributions of
neutral hydrogen can be an important ingredient in shaping the observed
properties of Lya emission from star-forming galaxies. We discuss the
implications of using Lya emission to probe the circumgalactic and
intergalactic environments of galaxies.


title: Do group dynamics play a role in the evolution of member galaxies?

abstract:
  We examine galaxy groups from the present epoch to z = 1 to explore the
impact of group dynamics on galaxy evolution. We use group catalagues from the
Sloan Digital Sky Survey (SDSS), the Group Environment and Evolution
Collaboration (GEEC) and the high redshift GEEC2 sample to study how the
observed member properties depend on galaxy stellar mass, group dynamical mass
and dynamical state of the host group. We find a strong correlation between the
fraction of non-star-forming (quiescent) galaxies and galaxy stellar mass, but
do not detect a significant difference in the quiescent fraction with group
dynamical mass, within our sample halo mass range of 10^13-10^14.5 M_sun, or
with dynamical sate. However, at a redshift of approximately 0.4 we do see some
evidence that the quiescent fraction in low mass galaxies (log(M_star/M_sun) <
10.5) is lower in groups with substructure. Additionally, our results show that
the fraction of groups with non-Gaussian velocity distributions increases with
redshift to roughly z = 0.4, while the amount of detected substructure remains
constant to z = 1. Based on these results, we conclude that for massive
galaxies (log(M_star/M_sun_ > 10.5), evolution is most strongly correlated to
the stellar mass of a galaxy with little or no additional effect related to
either the group dynamical mass or dynamical state. For low mass galaxies, we
do see some evidence of a correlation between the quiescent fraction and the
amount of detected substructure, highlighting the need to probe further down
the stellar mass function to elucidate the role of the environment in galaxy
evolution.


title: Quantum phase transitions out of a Z2 x Z2 topological phase

abstract:
  We investigate the low-energy spectral properties and robustness of the
topological phase of color code, which is a quantum spin model for the aim of
fault-tolerant quantum computation, in the presence of a uniform magnetic field
or Ising interactions, using high-order series expansion and exact
diagonalization. In a uniform magnetic field, we find 1st-order phase
transitions in all field directions. In contrast, our results for the Ising
interactions unveil that for strong enough Ising couplings, the Z2 x Z2
topological phase of color code breaks down to symmetry broken phases by 1st-
or 2nd-order phase transitions.


title:
Sterile neutrinos, dark matter, and resonant effects in ultra high
  energy regimes

abstract:
  Interest in light dark matter candidates has recently increased in the
literature; some of these works consider the role of additional neutrinos,
either active or sterile. Furthermore, extragalactic neutrinos have been
detected with energies higher than have ever been reported before. This opens a
new window of opportunities to the study of neutrino properties that were
unreachable up to now. We investigate how an interaction potential between
neutrinos and dark matter might induce a resonant enhancement in the
oscillation probability, an effect that may be tested with future neutrino
data.


title:
Mean age gradient and asymmetry in the star formation history of the
  Small Magellanic Cloud

abstract:
  We derive the star formation history in four regions of the Small Magellanic
Cloud (SMC) using the deepest VI color-magnitude diagrams (CMDs) ever obtained
for this galaxy. The images were obtained with the Advanced Camera for Surveys
onboard the Hubble Space Telescope and are located at projected distances of
0.5-2 degrees from the SMC center, probing the main body and the wing of the
galaxy. We derived the star-formation histories (SFH) of the four fields using
two independent procedures to fit synthetic CMDs to the data. We compare the
SFHs derived here with our earlier results for the SMC bar to create a deep
pencil-beam survey of the global history of the central SMC. We find in all the
six fields observed with HST a slow star formation pace from 13 to 5-7 Gyr ago,
followed by a ~ 2-3 times higher activity. This is remarkable because dynamical
models do not predict a strong influence of either the LMC or the Milky Way
(MW) at that time. The level of the intermediate-age SFR enhancement
systematically increases towards the center, resulting in a gradient in the
mean age of the population, with the bar fields being systematically younger
than the outer ones. Star formation over the most recent 500 Myr is strongly
concentrated in the bar, the only exception being the area of the SMC wing. The
strong current activity of the latter is likely driven by interaction with the
LMC. At a given age, there is no significant difference in metallicity between
the inner and outer fields, implying that metals are well mixed throughout the
SMC. The age-metallicity relations we infer from our best fitting models are
monotonically increasing with time, with no evidence of dips. This may argue
against the major merger scenario proposed by Tsujimoto and Bekki 2009,
although a minor merger cannot be ruled out.


title:
Realization and modeling of rf superconducting quantum interference
  device metamaterials

abstract:
  We have prepared meta-atoms based on radio frequency superconducting quantum
interference devices (RF SQUIDs) and examined their tunability with dc magnetic
field, rf current, and temperature. RF SQUIDs are superconducting split ring
resonators in which the usual capacitance is supplemented with a Josephson
junction, which introduces strong nonlinearity in the rf properties. We find
excellent agreement between the data and a model which regards the Josephson
junction as the resistively and capacitively-shunted junction. A magnetic field
tunability of 80 THz/Gauss at 12 GHz is observed, a total tunability of 56$%$
is achieved, and a unique electromagnetically-induced transparency feature at
intermediate excitation powers is demonstrated for the first time. An RF SQUID
metamaterial is shown to have qualitatively the same behavior as a single RF
SQUID with regards to DC flux and temperature tuning.


title:
Innermost collimation structure of the M87 jet down to ~ten
  Schwarzschild radii

abstract:
  We investigated the detailed inner jet structure of M87 using the Very Long
Baseline Array data at 2, 5, 8.4, 15, 23.8, 43, and 86 GHz, especially focusing
on the multi-frequency properties of the radio core at the jet base. First, we
measured a size of the core region transverse to the jet axis, defined as
$W_{\rm c}$, at each frequency \nu, and found a relation between $W_{\rm c}$
and $\nu$ as $W_{\rm c}(\nu) \propto \nu^{-0.71\pm0.05}$. Then, by combining
$W_{\rm c}(\nu)$ and the frequency dependence of the core position $r_{\rm
c}(\nu)$, which was obtained by our previous study, we have constructed a
collimation profile of the innermost jet $W_{\rm c}(r)$ down to ~10
Schwarzschild radii ($R_{\rm s}$) from the central black hole. We found that
$W_{\rm c}(r)$ smoothly connects with the width profile of the outer
edge-brightened, parabolic jet, and then follows a similar radial dependence
down to several tens of $R_{\rm s}$. Closer to the black hole, the measured
radial profile suggests a possible change of the jet collimation shape from the
outer parabolic one, in which the jet shape tends to become more
radially-oriented. This could be related to a magnetic collimation process
or/and interaction with surrounding materials at the jet base. The present
results shed light on the importance of higher-sensitivity/resolution imaging
studies for M87 at 86, 43 and also 22 GHz, and should be examined more
rigorously.


title: Flat bundles with complex analytic holonomy

abstract:
  Let G be a connected complex Lie group. We show that any flat principal
G-bundle over any finite CW-complex pulls back to a trivial bundle over some
finite covering space of the base space if and only if each real characteristic
class of positive degree of G vanishes. A third equivalent condition is that
the derived group of the radical of G is simply connected. As a corollary, the
same conditions are equivalent if G is a connected amenable Lie group. In
particular, if G is a connected compact Lie group then any flat principal
G-bundle over any finite CW-complex pulls back to a trivial bundle over some
finite covering space of the base space.


title: Super-renormalizable or finite completion of the Starobinsky theory

abstract:
  The recent Planck data of Cosmic Microwave Background (CMB) temperature
anisotropies support the Starobinsky theory in which the quadratic Ricci scalar
drives cosmic inflation. We build up a multi-dimensional quantum consisted
ultraviolet completion of the model in a phenomenological "bottom-up approach".
We present the maximal class of theories compatible with unitarity and
(super-)renormalizability or finiteness which reduces to the Starobinsky theory
in the low-energy limit. The outcome is a maximal extension of the
Krasnikov-Tomboulis-Modesto theory including an extra scalar degree of freedom
besides the graviton field. The original theory was afterwards independently
discovered by Biswas-Gerwick-Koivisto-Mazumdar starting from first principles.
We explicitly show power counting super-renormalizability or finiteness (in odd
dimensions) and unitarity (no ghosts) of the theory. Any further extension of
the theory is non-unitary confirming the existence of at most one single extra
degree of freedom, the scalaron. A mechanism to achieve the Starobinsky theory
in string (field) theory is also investigated at the end of the paper.


title: An introduction to HKR character theory

abstract:
  The generalized character theory of Hopkins, Kuhn, and Ravenel is an
important tool in the study of Morava E-theory and higher height phenomena in
chromatic homotopy theory. In this paper, we provide an introduction to HKR
character theory with many examples, applications, and alternative points of
view.


title:
A quantum polylog algorithm for non-normal maximal cyclic hidden
  subgroups in the affine group of a finite field

abstract:
  We give an algorithm to solve the quantum hidden subgroup problem for maximal
cyclic non-normal subgroups of the affine group of a finite field (if the field
has order $q$ then the group has order $q(q-1)$) with probability
$1-\varepsilon$ with (polylog) complexity $O(\log(q)^{R}\log(\varepsilon)^{2})$
where $R<\infty.$


title:
Tensor force effects and high-momentum components in the nuclear
  symmetry energy

abstract:
  We analyze microscopic many-body calculations of the nuclear symmetry energy
and its density dependence. The calculations are performed in the framework of
the Brueckner-Hartree-Fock and the Self-Consistent Green's Functions methods.
Within Brueckner-Hartree-Fock, the Hellmann-Feynman theorem gives access to the
kinetic energy contribution as well as the contributions of the different
components of the nucleon-nucleon interaction. The tensor component gives the
largest contribution to the symmetry energy. The decomposition of the symmetry
energy in a kinetic part and a potential energy part provides physical insight
on the correlated nature of the system, indicating that neutron matter is less
correlated than symmetric nuclear matter. Within the Self-Consistent Green's
Function approach, we compute the momentum distributions and we identify the
effects of the high momentum components in the symmetry energy. The results are
obtained for the realistic interaction Argonne V18 potential, supplemented by
the Urbana IX three-body force in the Brueckner-Hartree-Fock calculations.


title:
A Reynolds-averaged turbulence modeling approach to the maintenance of
  the Venus superrotation

abstract:
  A maintenance mechanism of an approximately linear velocity profile of the
Venus zonal flow or superrotation is explored, with the aid of a
Reynolds-averaged turbulence modeling approach. The basic framework is similar
to that of Gierasch (1975) in the sense that the mechanism is examined under a
given meridional circulation. The profile mimicking the observations of the
flow is initially assumed, and its maintenance mechanism in the presence of
turbulence effects is investigated from a viewpoint of the suppression of
energy cascade. In the present work, the turbulent viscosity is regarded as an
indicator of the intensity of the cascade. A novelty of this formalism is the
use of the isotropic turbulent viscosity based on a nonlocal time scale linked
to a large-scale flow structure. The mechanism is first discussed
qualitatively. On the basis of these discussions, the two-dimensional numerical
simulation of the proposed model is performed, with an initially assumed
superrotation, and the fast zonal flow is shown to be maintained, compared with
the turbulent viscosity lacking the nonlocal time scale. The relationship of
the present model with the current general-circulation-model simulation is
discussed in light of a crucial role of the vertical viscosity.


title: A Latent Social Approach to YouTube Popularity Prediction

abstract:
  Current works on Information Centric Networking assume the spectrum of
caching strategies under the Least Recently/ Frequently Used (LRFU) scheme as
the de-facto standard, due to the ease of implementation and easier analysis of
such strategies. In this paper we predict the popularity distribution of
YouTube videos within a campus network. We explore two broad approaches in
predicting the popularity of videos in the network: consensus approaches based
on aggregate behavior in the network, and social approaches based on the
information diffusion over an implicit network. We measure the performance of
our approaches under a simple caching framework by picking the k most popular
videos according to our predicted distribution and calculating the hit rate on
the cache. We develop our approach by first incorporating video inter-arrival
time (based on the power-law distribution governing the transmission time
between two receivers of the same message in scale-free networks) to the
baseline (LRFU), then combining with an information diffusion model over the
inferred latent social graph that governs diffusion of videos in the network.
We apply techniques from latent social network inference to learn the sharing
probabilities between users in the network and apply a virus propagation model
borrowed from mathematical epidemiology to estimate the number of times a video
will be accessed in the future. Our approach gives rise to a 14% hit rate
improvement over the baseline.


title: Improving the GPU space of computation under triangular domain problems

abstract:
  There is a stage in the GPU computing pipeline where a grid of thread-blocks
is mapped to the problem domain. Normally, this grid is a k-dimensional
bounding box that covers a k-dimensional problem no matter its shape. Threads
that fall inside the problem domain perform computations, otherwise they are
discarded at runtime. For problems with non-square geometry, this is not always
the best idea because part of the space of computation is executed without any
practical use. Two- dimensional triangular domain problems, alias td-problems,
are a particular case of interest. Problems such as the Euclidean distance map,
LU decomposition, collision detection and simula- tions over triangular tiled
domains are all td-problems and they appear frequently in many areas of
science. In this work, we propose an improved GPU mapping function g(lambda),
that maps any lambda block to a unique location (i, j) in the triangular
domain. The mapping is based on the properties of the lower triangular matrix
and it works at a block level, thus not compromising thread organization within
a block. The theoretical improvement from using g(lambda) is upper bounded as I
< 2 and the number of wasted blocks is reduced from O(n^2) to O(n). We compare
our strategy with other proposed methods; the upper-triangular mapping (UTM),
the rectangular box (RB) and the recursive partition (REC). Our experimental
results on Nvidias Kepler GPU architecture show that g(lambda) is between 12%
and 15% faster than the bounding box (BB) strategy. When compared to the other
strategies, our mapping runs significantly faster than UTM and it is as fast as
RB in practical use, with the advantage that thread organization is not
compromised, as in RB. This work also contributes at presenting, for the first
time, a fair comparison of all existing strategies running the same experiments
under the same hardware.


title: On the velocity-strengthening behavior of dry friction

abstract:
  The onset of frictional instabilities, e.g. earthquakes nucleation, is
intimately related to velocity-weakening friction, in which the frictional
resistance of interfaces decreases with increasing slip velocity. While this
frictional response has been studied extensively, less attention has been given
to steady-state velocity-strengthening friction, in spite of its potential
importance for various aspects of frictional phenomena such as the propagation
speed of interfacial rupture fronts and the amount of stored energy released by
them. In this note we suggest that a crossover from steady-state
velocity-weakening friction at small slip velocities to steady-state
velocity-strengthening friction at higher velocities might be a generic feature
of dry friction. We further argue that while thermally activated rheology
naturally gives rise to logarithmic steady-state velocity-strengthening
friction, a crossover to stronger-than-logarithmic strengthening might take
place at higher slip velocities, possibly accompanied by a change in the
dominant dissipation mechanism. We sketch a few physical mechanisms that may
account for the crossover to stronger-than-logarithmic steady-state
velocity-strengthening and compile a rather extensive set of experimental data
available in the literature, lending support to these ideas.


title: Photoacoustic Tomography in a Rectangular Reflecting Cavity

abstract:
  Almost all known image reconstruction algorithms for photoacoustic and
thermoacoustic tomography assume that the acoustic waves leave the region of
interest after a finite time. This assumption is reasonable if the reflections
from the detectors and surrounding surfaces can be neglected or filtered out
(for example, by time-gating). However, when the object is surrounded by
acoustically hard detector arrays, and/or by additional acoustic mirrors, the
acoustic waves will undergo multiple reflections. (In the absence of absorption
they would bounce around in such a reverberant cavity forever). This disallows
the use of the existing free-space reconstruction techniques. This paper
proposes a fast iterative reconstruction algorithm for measurements made at the
walls of a rectangular reverberant cavity. We prove the convergence of the
iterations under a certain sufficient condition, and demonstrate the
effectiveness and efficiency of the algorithm in numerical simulations.


title:
Domain wall trajectory determined by its fractional topological edge
  defects

abstract:
  A domain wall (DW) in a ferromagnetic nanowire is composed of elementary
topological bulk and edge defects with integer and fractional winding numbers,
respectively, whose relative spatial arrangement determines the chirality of
the DW. Here we show how we can understand and control the trajectory of DWs in
magnetic branched networks, composed of connected nanowires, by considering
their fractional elementary topological defects and how they interact with
those innate to the network. We first develop a highly reliable mechanism for
the injection of a DW of a given chirality into a nanowire and show that its
chirality determines which branch the DW follows at a symmetric Y-shaped
magnetic junction - the fundamental building block of the network. Using these
concepts, we unravel the origin of the one-dimensional nature of magnetization
reversal of connected artificial spin ice systems that have been observed in
the form of Dirac strings.


abstract:
  We prove Strichartz estimates for gravity water waves, in arbitrary dimension
and in fluid domains with general bottoms. We consider rough solutions such
that, initially, the first order derivatives of the velocity field are not
controlled in $L^\infty$-norm, or the initial free surface has a curvature not
controlled in $L^2$-norm.


title: Generalised Dicke non-equilibrium dynamics in trapped ions

abstract:
  We explore trapped ions as a setting to investigate non-equilibrium phases in
a generalised Dicke model of dissipative spins coupled to phonon modes. We find
a rich dynamical phase diagram including superradiant-like regimes, dynamical
phase-coexistence and phonon-lasing behaviour. A particular advantage of
trapped ions is that these phases and transitions among them can be probed in
situ through fluorescence. We demonstrate that the main physical insights are
captured by a minimal model and consider an experimental realisation with Ca+
ions trapped in a linear Paul trap.


title: Microwave control of the interaction between two optical photons

abstract:
  A microwave field is used to control the interaction between pairs of optical
photons stored in highly excited collective states (Rydberg polaritons). We
show that strong dipole-dipole interactions induced by the microwave field
destroy the coherence of polariton modes with more than one Rydberg excitation.
Consequently single-polariton modes, which correspond to single stored photons,
are preferentially retrieved from the sample. Measurements of the photon
statistics of the retrieved light field also reveal non-trivial propagation
dynamics of the interacting polaritons.


title: Likely Dominance of WIMP Annihilation to Fermion Pair + W/Z

abstract:
  Arguably, the most popular candidate for Dark Matter (DM) is a massive,
stable, Majorana fermion. However, annihilation of Majorana DM to two fermions
features a helicity-suppressed s-wave rate. The process radiating a gauge boson
via electroweak (EW) and electromagnetic (EM) bremsstrahlung removes this
s-wave suppression, and is likely to be the dominant modes of gauge-singlet
Majorana DM annihilation. Given their enhanced annihilation rate with radiatedW
and Z gauge bosons, and the subsequent dominant W/Z decays via hadronic
channels, Majorana DM tends to produce more antiprotons than positrons. This
result contrasts with observations, thereby presenting a challenge to model
building with Majorana DM.


title:
Regions of Stability for a Linear Differential Equation with Two
  Rationally Dependent Delays

abstract:
  Stability analysis is performed for a linear differential equation with two
delays. Geometric arguments show that when the two delays are rationally
dependent, then the region of stability increases. When the ratio has the form
1/n, this study finds the asymptotic shape and size of the stability region.
For example, a delay ration of 1/3 asymptotically produces a stability region
44.3% larger than any nearby delay ratios, showing extreme sensitivity in the
delays. The study provides a systematic and geometric approach to finding the
eigenvalues on the boundary of stability for this delay differential equation.
A nonlinear model with two delays illustrates how our methods can be applied.


title: First measurement of time-dependent CP violation in Bs -> K+K- decays

abstract:
  Direct and mixing-induced CP-violating asymmetries in Bs -> K+K- decays are
measured for the first time using a data sample of pp collisions, corresponding
to an integrated luminosity of 1.0 fb^{-1}, collected with the LHCb detector at
a centre-of-mass energy of 7 TeV. The results are C_{KK} = 0.14 \pm 0.11 \pm
0.03 and S_{KK} = 0.30 \pm 0.12 \pm 0.04, where the first uncertainties are
statistical and the second systematic. The corresponding quantities are also
determined for B0 -> pi+pi- decays to be C_{pipi} = -0.38 \pm 0.15 \pm 0.02 and
S_{pipi} = -0.71 \pm 0.13 \pm 0.02, in good agreement with existing
measurements.


title: Subtraction method and stability condition in the extended RPA theories

abstract:
  The extended RPA theories are analyzed from the point of view of the problem
of stability of their solutions. Three kinds of such theories are considered:
the second RPA and two versions of the quasiparticle-phonon coupling model
within the time-blocking approximation: the model including 1p1h*phonon
configurations and the two-phonon model. It is shown that stability is ensured
by making use of the subtraction method proposed previously to solve double
counting problem in these theories. This enables one to generalize the famous
Thouless theorem proved in the case of the RPA. These results are illustrated
by an example of schematic model.


title: Electroweak Corrections at High Energies

abstract:
  We present a survey of the most abundant processes at the LHC for sensitivity
to electroweak corrections at \sqrt{s} = 8, 14, 33, and 100 TeV proton-proton
collision energies. The processes studied are pp -> dijet, inclusive W and Z,
W/Z+jets, and WW. In each case we compare the experimental uncertainty in the
highest kinematic regions of interest with the relative magnitude of
electroweak corrections and fixed-order \alpha_S calculations.


title:
Realizing the Harper Hamiltonian with Laser-Assisted Tunneling in
  Optical Lattices

abstract:
  We experimentally implement the Harper Hamiltonian for neutral particles in
optical lattices using laser-assisted tunneling and a potential energy gradient
provided by gravity or magnetic field gradients. This Hamiltonian describes the
motion of charged particles in strong magnetic fields. Laser-assisted tunneling
processes are characterized by studying the expansion of the atoms in the
lattice. The band structure of this Hamiltonian should display Hofstadter's
butterfly. For fermions, this scheme should realize the quantum Hall effect and
chiral edge states.


title: Spin Hall torque magnetometry of Dzyaloshinskii domain walls

abstract:
  Current-induced domain wall motion in the presence of the
Dzyaloshinskii-Moriya interaction (DMI) is experimentally and theoretically
investigated in heavy-metal/ferromagnet bilayers. The angular dependence of the
current-induced torque and the magnetization structure of Dzyaloshinskii domain
walls are described and quantified simultaneously in the presence of in-plane
fields. We show that the DMI strength depends strongly on the heavy metal,
varying by a factor of 20 between Ta and Pa, and that strong DMI leads to wall
distortions not seen in conventional materials. These findings provide
essential insights for understanding and exploiting chiral magnetism for
emerging spintronics applications.


title:
Visualizing Spacetime Curvature via Gradient Flows III: The Kerr Metric
  and the Transitional Values of the Spin Parameter

abstract:
  The Kerr metric is one of the most important solutions to Einstein's field
equations, describing the gravitational field outside a rotating black hole. We
thoroughly analyze the curvature scalar invariants to study the Kerr spacetime
by examining and visualizing their covariant gradient fields. We discover that
the part of the Kerr geometry outside the black hole horizon changes
qualitatively depending on the spin parameter, a fact previously unknown. The
number of observable critical points of the curvature invariants' gradient
fields along the axis of rotation changes at several transitional values of the
spin parameter. These transitional values are a fundamental property of the
Kerr metric. They are physically important since in general relativity these
curvature invariants represent the cumulative tidal and frame-dragging effects
of rotating black holes in an observer-independent way.


title: Modules over categories and Betti posets of monomial ideals

abstract:
  We introduce to the context of multigraded modules the methods of modules
over categories from algebraic topology and homotopy theory. We develop the
basic theory quite generally, with a view toward future applications to a wide
class of graded modules over graded rings. The main application in this paper
is to study the Betti poset B=B(I,k) of a monomial ideal I in the polynomial
ring R=k[x_1,...,x_m] over a field k, which consists of all degrees in Z^m of
the homogeneous basis elements of the free modules in the minimal free
Z^m-graded resolution of I over R. We show that the order simplicial complex of
B supports a free resolution of I over R. We give a formula for the Betti
numbers of I in terms of Betti numbers of open intervals of B, and we show that
the isomorphism class of B completely determines the structure of the minimal
free resolution of I, thus generalizing with new proofs results of Gasharov,
Peeva, and Welker. We also characterize the finite posets that are Betti posets
of a monomial ideal.


title:
Possible multiparticle ridge-like correlations in very high multiplicity
  proton-proton collisions

abstract:
  The CMS collaboration at the LHC has reported a remarkable and unexpected
phenomenon in very high-multiplicity high energy proton-proton collisions: a
positive correlation between two particles produced at similar azimuthal
angles, spanning a large range in rapidity. We suggest that this "ridge"-like
correlation may be a reflection of the rare events generated by the collision
of aligned flux tubes connecting the valence quarks in the wave functions of
the colliding protons. The "spray" of particles resulting from the approximate
line source produced in such inelastic collisions then gives rise to events
with a strong correlation between particles produced over a large range of both
positive and negative rapidity. We suggest an additional variable that is
sensitive to such a line source which is related to a commonly used measure,
ellipticity.


title: The Parabolic Jet Structure in M87 as a Magnetohydrodynamic Nozzle

abstract:
  The structure and dynamics of the M87 jet from sub-milli-arcsec to arcsecond
scales are continuously examined. We analysed the VLBA archival data taken at
43 and 86 GHz to measure the size of VLBI cores. Millimeter/sub-mm VLBI cores
are considered as innermost jet emissions, which has been originally suggested
by Blandford & K\"onigl. Those components fairly follow an extrapolated
parabolic streamline in our previous study so that the jet has a single
power-law structure with nearly five orders of magnitude in the distance
starting from the vicinity of the supermassive black hole (SMBH), less than 10
Schwarzschild radius ($r_{\rm s}$). We further inspect the jet parabolic
structure as a counterpart of the magnetohydrodynamic (MHD) nozzle in order to
identify the property of a bulk acceleration. We interpret that the parabolic
jet consists of Poynting-flux dominated flows, powered by large amplitude,
nonlinear torsional Alfv\'en waves. We examine the non-relativistic MHD nozzle
equation in a parabolic shape. The nature of trans-fast magnetosonic flow is
similar to the one of transonic solution of Parker's hydrodynamic solar wind;
the jet becomes super-escape as well as super-fast magnetosonic at around $\sim
10^{3}\,r_{\rm s}$, while the upstream trans-Alfv\'enic flow speed increases
linearly as a function of the distance at $\sim 10^{2}$ - $10^{3}\, r_{\rm s}$.
We here point out that this is the first evidence to identify these features in
astrophysical jets. We propose that the M87 jet is magnetically accelerated,
but thermally confined by the stratified ISM inside the sphere of gravitational
influence of the SMBH potential, which may be a norm in AGN jets.


title: The contribution of spin to jet-disk coupling in black holes

abstract:
  The spin of supermassive black holes could power jets from active galactic
nuclei (AGN), although direct observational evidence for this conjecture is
sparse. The accretion disk luminosity and jet power, on the other hand, have
long been observed to follow a linear correlation. If jet power is coupled to
black hole spin, deviations from the jet-disk correlation for a sample of AGN
can be used to probe the dispersion of the spin parameter within this sample.
To exploit this idea, we matched double-lobed radio sources from the FIRST
survey to spectroscopically confirmed quasars from SDSS. We obtain 763 FR-II
quasars with a median redshift of z=1.2 A tight correlation between the optical
luminosity of the accretion disk and the lobe radio luminosity is observed. We
estimate that 5-20% of the bolometric disk luminosity is converted to jet
power. Most of the scatter to the optical-radio correlation is due to
environment; deviations from jet-disk coupling due to internal factors (e.g.,
spin) contribute at most 0.2 dex. Under the assumption that the
Blandford-Znajek mechanism operates in AGN, we obtain an upper limit of 0.1 dex
to the dispersion of the product of the spin and the magnetic flux threading
the horizon. If black hole spin determines the AGN jet efficiency, then our
observations imply that all FR-II quasars have very similar spin. In addition,
the quasar spin distribution needs to have a wide gap to explain the
radio-quiet population. The alternative, and perhaps more likely,
interpretation of the tight jet-disk correlation is that black hole spin is not
relevant for powering AGN jets.


title:
Profiling hot and dense nuclear medium with high transverse momentum
  hadrons produced in d+Au and Au+Au collisions by the PHENIX experiment at
  RHIC

abstract:
  PHENIX measurements of high transverse momentum ($p_T$) identified hadrons in
$d$+Au and Au+Au collisions are presented. The nuclear modification factors
($R_{d{\rm A}}$ and $R_{\rm AA}$) for $\pi^0$ and $\eta$ are found to be very
consistent in both collision systems, respectively. Using large amount of $p+p$
and Au+Au datasets, the fractional momentum loss ($S_{\rm loss}$) and the
path-length dependent yield of $\pi^0$ in Au+Au collisions are obtained. The
hadron spectra in the most central $d$+Au and the most peripheral Au+Au
collisions are studied. The spectra shapes are found to be similar in both
systems, but the yield is suppressed in the most peripheral Au+Au collisions.


title: BPS Black Hole Horizons in N=2 Gauged Supergravity

abstract:
  We study static BPS black hole horizons in four dimensional N=2 gauged
supergravity coupled to $n_v$-vector multiplets and with an arbitrary cubic
prepotential. We work in a symplectically covariant formalism which allows for
both electric and magnetic gauging parameters as well as dyonic background
charges and obtain the general solution to the BPS equations for horizons of
the form $AdS_2\times \Sigma_g$. In particular this means we solve for the
scalar fields as well as the metric of these black holes as a function of the
gauging parameters and background charges. When the special Kahler manifold is
a symmetric space, our solution is completely explicit and the entropy is
related to the familiar quartic invariant. For more general models our solution
is implicit up to a set of holomorphic quadratic equations. For particular
models which have known embeddings in M-theory, we derive new horizon
geometries with dyonic charges and numerically construct black hole solutions.
These correspond to M2-branes wrapped on a Riemann surface in a local
Calabi-Yau five-fold with internal spin.


title: Graywulf: A platform for federated scientific databases and services

abstract:
  Many fields of science rely on relational database management systems to
analyze, publish and share data. Since RDBMS are originally designed for, and
their development directions are primarily driven by, business use cases they
often lack features very important for scientific applications. Horizontal
scalability is probably the most important missing feature which makes it
challenging to adapt traditional relational database systems to the ever
growing data sizes. Due to the limited support of array data types and metadata
management, successful application of RDBMS in science usually requires the
development of custom extensions. While some of these extensions are specific
to the field of science, the majority of them could easily be generalized and
reused in other disciplines. With the Graywulf project we intend to target
several goals. We are building a generic platform that offers reusable
components for efficient storage, transformation, statistical analysis and
presentation of scientific data stored in Microsoft SQL Server. Graywulf also
addresses the distributed computational issues arising from current RDBMS
technologies. The current version supports load balancing of simple queries and
parallel execution of partitioned queries over a set of mirrored databases.
Uniform user access to the data is provided through a web based query interface
and a data surface for software clients. Queries are formulated in a slightly
modified syntax of SQL that offers a transparent view of the distributed data.
The software library consists of several components that can be reused to
develop complex scientific data warehouses: a system registry, administration
tools to manage entire database server clusters, a sophisticated workflow
execution framework, and a SQL parser library.


title: Loop Liquid in an Ising-Spin Kondo Lattice Model on a Kagome Lattice

abstract:
  Phase diagram of an Ising-spin Kondo lattice model on a kagome lattice is
investigated by a Monte Carlo simulation. We find that the system exhibits a
peculiar ferrimagnetic state at a finite temperature, in which each triangle is
in a two-up one-down spin configuration but the spin correlation does not
develop any superstructure. We call this state the loop liquid, as it is
characterized by the emergent degree of freedom, self-avoiding up-spin loops.
We elucidate that the system shows phase transitions from the loop liquid to
ferrimagnetically ordered states and a crossover to a partially ferromagnetic
state by changing the electron density and temperature. These can be viewed as
crystallization and cohesion of the loops, respectively. We demonstrate that
the loop formation is observed in the optical conductivity as a characteristic
resonant peak.


title:
New families of integrable two-dimensional systems with quartic second
  integrals

abstract:
  The method introduced in (Yehia H M 2006 J. Phys. A: Math. Gen. 39 5807-5824)
and (Yehia H M 2012 J. Phys. A: Math. Gen. 45 395209) is extended to construct
new families of several-parameter integrable systems, which admit a
complementary integral quartic in the velocities. A total of 12 new systems are
obtained, with a number of parameters ranging from 7 up to 16 parameters.


title: Category of asynchronous systems and polygonal morphisms

abstract:
  A weak asynchronous system is a trace monoid with a partial action on a set.
A polygonal morphism between weak asynchronous systems commutes with the
actions and preserves the independence of events. We prove that the category of
weak asynchronous systems and polygonal morphisms has all limits and colimits.


title: Increasing stability for optical tomography

abstract:
  We study the phenomenon of increasing stability in the diffuse optical
tomography (DOT). It is well-known that the DOT inverse problem is
exponentially ill-posed. In this paper, we show that the ill-posedness
decreases when we increase the frequency.


title:
Smallness of \theta_{13} and the size of the Solar Mass Splitting: Are
  they related?

abstract:
  Compared to the other neutrino mixing angles \theta_{13} is small. The solar
mass splitting is about two orders smaller than the atmospheric splitting. We
show that it is possible that both are perturbative effects on a more symmetric
structure. The perturbation also affects the solar mixing angle and can make
alternate mixing patterns such as tribimaximal, bimaximal, or other variants
equally viable. For real perturbations this can be accomplished only for normal
mass ordering and with the lightest neutrino mass less than 10^{-2} eV. Both
mass orderings can be accommodated by going over to complex perturbations
provided the lightest neutrino is heavier. The CP-phase in the lepton sector
that emerges distinguishes between different mixing models.


title: Coevolutionary immune system dynamics driving pathogen speciation

abstract:
  We introduce and analyze a within-host dynamical model of the coevolution
between rapidly mutating pathogens and the adaptive immune response. Pathogen
mutation and a homeostatic constraint on lymphocytes both play a role in
allowing the development of chronic infection, rather than quick pathogen
clearance. The dynamics of these chronic infections display emergent structure,
including branching patterns corresponding to asexual pathogen speciation,
which is fundamentally driven by the coevolutionary interaction. Over time,
continued branching creates an increasingly fragile immune system, and leads to
the eventual catastrophic loss of immune control.


title: Possible violation of the optical theorem in LHC experiments

abstract:
  The optical theorem allowing the determination of the total cross section for
a hadron-hadron scattering from the imaginary part of the forward elastic
scattering amplitude is believed to be an unavoidable consequence of the
conservation of probability and of the unitary S matrix. This is a fundamental
theorem which contains not directly measurable imaginary part of the forward
elastic scattering amplitude. The impossibility of scattering phenomena without
the elastic channel is considered to be a part of the quantum magic. However if
one takes seriously the idea that the hadrons are extended particles one may
define a unitary S matrix such that one cannot prove the optical theorem.
Moreover data violating the optical theorem do exist but they are not
conclusive due to the uncertainties related to the extrapolation of the
differential elastic cross-section to the forward direction. These results were
published several years ago but they were forgotten. In this paper we will
recall these results in an understandable way and we will give the additional
arguments why the optical theorem can be violated in high energy strong
interaction scattering and why it should be tested and not simply used as a
tool in LHC experiments.


title:
Spherically symmetric vacuum solutions arising from trace dynamics
  modifications to gravitation

abstract:
  We derive the equations governing static, spherically symmetric vacuum
solutions to the Einstein equations, as modified by the frame-dependent
effective action arising from trace dynamics. We give analytic and numerical
results for the solutions of these equations, first in polar coordinates, and
then in isotropic coordinates. General features of the static case are that (i)
there is no horizon, since $g_{00}$ is non-vanishing for finite values of the
polar radius, and only vanishes (in isotropic coordinates) at the internal
singularity, (ii) the Ricci scalar $R$ vanishes identically, and (iii) there is
a physical singularity at cosmological distances. The large distance
singularity may be an artifact of the static restriction, since we find that
the behavior at large distances is altered in a time-dependent solution using
the Mc Vittie Ansatz.

categories: gr-qc astro-ph.CO hep-th math-ph math.MP quant-ph


title:
How biochemical resources determine fundamental limits in cellular
  sensing

abstract:
  Living cells deploy many resources to sense their environments, including
receptors, downstream signaling molecules, time and fuel. However, it is not
known which resources fundamentally limit the precision of sensing, like weak
links in a chain, and which can compensate each other, leading to trade-offs
between them. We show by modeling that in equilibrium systems the precision is
limited by the number of receptors; the downstream network can never increase
precision. This limit arises from a trade-off between the removal of extrinsic
noise in the receptor and intrinsic noise in the downstream network.
Non-equilibrium systems can lift this trade-off by storing the receptor state
over time in chemical modification states of downstream molecules. As we
quantify for a push-pull network, this requires i) time and receptors; ii)
downstream molecules; iii) energy (fuel turnover) to drive modification. These
three resource classes cannot compensate each other, and it is the limiting
class which sets the fundamental sensing limit. Within each class, trade-offs
are possible. Energy allows a power-speed trade-off, while time can be traded
against receptors.


title: On numerical modelling of contact lines in fluid flows

abstract:
  We study numerically a reduced model proposed by Benilov and Vynnycky (J.
Fluid Mech. {\bf 718} (2013), 481), who examined the behavior of a contact line
with a $180^{\circ}$ contact angle between liquid and a moving plate, in the
context of a two-dimensional Couette flow. The model is given by a linear
fourth-order advection-diffusion equation with an unknown velocity, which is to
be determined dynamically from an additional boundary condition at the contact
line.
  The main claim of Benilov and Vynnycky is that for any physically relevant
initial condition, there is a finite positive time at which the velocity of the
contact line tends to negative infinity, whereas the profile of the fluid flow
remains regular. Additionally, it is claimed that the velocity behaves as the
logarithmic function of time near the blow-up time.
  Compared to the previous computations based on COMSOL built-on algorithms, we
use MATLAB software package and develop a direct finite-difference method to
study dynamics of the reduced model under different initial conditions. We
confirm the first claim but also show that the blow-up behavior is better
approximated by a power function, compared with the logarithmic function. This
numerical result suggests a simple explanation of the blow-up behavior of
contact lines.


title:
A novel test for selection on cis-regulatory elements reveals positive
  and negative selection acting on mammalian transcriptional enhancers

abstract:
  Measuring natural selection on genomic elements involved in the
cis-regulation of gene expression -- such as transcriptional enhancers and
promoters -- is critical for understanding the evolution of genomes, yet it
remains a major challenge. Many studies have attempted to detect positive or
negative selection in these noncoding elements by searching for those with the
fastest or slowest rates of evolution, but this can be problematic. Here we
introduce a new approach to this issue, and demonstrate its utility on three
mammalian transcriptional enhancers. Using results from saturation mutagenesis
studies of these enhancers, we classified all possible point mutations as
up-regulating, down-regulating, or silent, and determined which of these
mutations have occurred on each branch of a phylogeny. Applying a framework
analogous to Ka/Ks in protein-coding genes, we measured the strength of
selection on up-regulating and down-regulating mutations, in specific branches
as well as entire phylogenies. We discovered distinct modes of selection acting
on different enhancers: while all three have experienced negative selection
against down-regulating mutations, the selection pressures on up-regulating
mutations vary. In one case we detected positive selection for up-regulation,
while the other two had no detectable selection on up-regulating mutations. Our
methodology is applicable to the growing number of saturation mutagenesis data
sets, and provides a detailed picture of the mode and strength of natural
selection acting on cis-regulatory elements.


title: Surface tension and curvature energy of quark matter in the NJL model

abstract:
  In this paper we study the surface tension and the curvature energy of
three-flavor quark matter in equilibrium under weak interactions within the
Nambu-Jona-Lasinio model. We include the effect of color superconductivity and
describe finite size effects within the multiple reflection expansion (MRE)
framework. Our calculations result in large values of the surface tension which
disfavor the formation of mixed phases at the hadron-quark inter-phase inside a
hybrid star.


title: The molecular mechanism of a cis-regulatory adaptation in yeast

abstract:
  Despite recent advances in our ability to detect adaptive evolution involving
the cis-regulation of gene expression, our knowledge of the molecular
mechanisms underlying these adaptations has lagged far behind. Across all model
organisms the causal mutations have been discovered for only a handful of gene
expression adaptations, and even for these, mechanistic details (e.g. the
trans-regulatory factors involved) have not been determined. We previously
reported a polygenic gene expression adaptation involving down-regulation of
the ergosterol biosynthesis pathway in the budding yeast Saccharomyces
cerevisiae. Here we investigate the molecular mechanism of a cis-acting
mutation affecting a member of this pathway, ERG28. We show that the causal
mutation is a two-base deletion in the promoter of ERG28 that strongly reduces
the binding of two transcription factors, Sok2 and Mot3, thus abolishing their
regulation of ERG28. This down-regulation increases resistance to a widely used
antifungal drug targeting ergosterol, similar to mutations disrupting this
pathway in clinical yeast isolates. The identification of the causal genetic
variant revealed that the selection likely occurred after the deletion was
already present at high frequency in the population, rather than when it was a
new mutation. These results provide a detailed view of the molecular mechanism
of a cis-regulatory adaptation, and underscore the importance of this view to
our understanding of evolution at the molecular level.


title: Sampling-based learning control of inhomogeneous quantum ensembles

abstract:
  Compensation for parameter dispersion is a significant challenge for control
of inhomogeneous quantum ensembles. In this paper, we present a systematic
methodology of sampling-based learning control (SLC) for simultaneously
steering the members of inhomogeneous quantum ensembles to the same desired
state. The SLC method is employed for optimal control of the state-to-state
transition probability for inhomogeneous quantum ensembles of spins as well as
$\Lambda$ type atomic systems. The procedure involves the steps of (i) training
and (ii) testing. In the training step, a generalized system is constructed by
sampling members according to the distribution of inhomogeneous parameters
drawn from the ensemble. A gradient flow based learning and optimization
algorithm is adopted to find the control for the generalized system. In the
process of testing, a number of additional ensemble members are randomly
selected to evaluate the control performance. Numerical results are presented
showing the success of the SLC method.


title: Instability of Schwarzschild-AdS black hole in Einstein-Weyl gravity

abstract:
  We investigate the classical stability of Schwarzschild-AdS black hole in a
massive theory of the Einstein-Weyl gravity. It turns out that the linearized
Einstein tensor perturbations exhibit unstable modes featuring the
Gregory-Laflamme instability of five-dimensional AdS black string, in contrast
to the stable Schwarzschild-AdS black hole in the Einstein-Weyl gravity. We
confirm that the instability of the black hole in the Einstein-Weyl gravity
arises from the massiveness but not a feature of fourth-order derivative theory
giving ghost states.


title: Character sums over shifted primes

abstract:
  For integer $q$, let $\chi$ be a primitive multiplicative character$\pmod q.$
For integer $a$ coprime to $q$, we obtain a new bound for the sums $$\sum_{n\le
N}\Lambda(n)\chi(n+a),$$ where $\Lambda(n)$ is the von Mangoldt function. This
bound improves and extends the range of a result of Friedlander, Gong and
Shparlinski


title:
Estimates of anisotropic Sobolev spaces with mixed norms for the Stokes
  system in a half-space

abstract:
  We are concerned with the non-stationary Stokes system with non-homogeneous
external force and non-zero initial data in ${\mathbb R}^n_+ \times (0,T)$. We
obtain new estimates of solutions including pressure in terms of mixed
anisotropic Sobolev spaces. As an application, some anisotropic Sobolev
estimates are presented for weak solutions of the Navier-Stokes equations in a
half-space in dimension three.


title: Quasi-maximum modulus principle for the Stokes equations

abstract:
  In this paper, we extend the maximum modulus estimate of the solutions of the
nonstationary Stokes equations in the bounded $C^2$ cylinders for the space
variables in \cite{CC} to time estimate. We show that if the boundary data is
$L^\infty$ and the normal part of the boundary data has log-Dini continuity
with respect to time, then the velocity is bounded. We emphasize that there is
no continuity assumption on space variables in the new maximum modulus
estimate. This completes the maximum modulus estimate.


title: Exact form factors of the O(N) $\sigma$-model

abstract:
  A general form factor formula for the $O(N)\sigma$-model is constructed and
applied to several operators. The large N limits of these form factors are
computed and compared with the 1/N expansion of the $O(N)\sigma$-model in terms
of Feynman graphs and full agreement is found. In particular, O(3) and O(4)
form factors are discussed. For the $O(3)\sigma$-model several low particle
form factors are calculated explicitly.


title: Morse Theory, Higgs fields and Yang-Mills-Higgs functionals

abstract:
  In this paper we give an overview of different Morse-theoretic methods used
to study the topology of moduli spaces of Higgs bundles.


title: Simplified SUSY at the ILC

abstract:
  At the ILC, one has the possibility to search for SUSY in an
model-independent way: The corner-stone of SUSY is that sparticles couple as
particles. This is independent of the mechanism responsible for SUSY breaking.
Any model will have one Lightest SUSY Particle (LSP), and one Next to Lightest
SUSY Particle (NLSP). In models with conserved R-parity, the NLSP must decay
solely to the LSP and the SM partner of the NLSP. Therefore, studying NLSP
production and decay can be regarded as a "simplified model without
simplification": Any SUSY model will have such a process.
  The NLSP could be any sparticle: a slepton, an electroweak-ino, or even a
squark. However, since there are only a finite number of sparticles, one can
systematically search for signals of all possible NLSP:s. This way, the entire
space of models that have a kinematicall y reachable NLSP can be covered. For
any NLSP, the "worst case" can be determined, since the SUSY principle allows
to calculate the cross-section once the NLSP nature and mass are given. The
region in the LSP-NLSP mass-plane where the "worst case" could be discovered or
excluded experimentally can be found by estimating background and efficiency at
each point in the plane. From experience at LEP, it is expected that the lower
signal-to background ratio will indeed be found for models with conserved
R-parity.
  In this document, we show that at the ILC, such a program is possible, as it
was at LEP. No loop-holes are left, even for difficult or non-standard cases:
whatever the NLSP is it will be detectable.


title:
Neutral atomic hydrogen (HI) gas evolution in field galaxies at z ~ 0.1
  and 0.2

abstract:
  We measure the neutral atomic hydrogen (HI) gas content of field galaxies at
intermediate redshifts of z ~ 0.1 and z ~ 0.2 using hydrogen 21-cm emission
lines observed with the Westerbork Synthesis Radio Telescope (WSRT). In order
to make high signal-to-noise ratio detections, an HI signal stacking technique
is applied: HI emission spectra from multiple galaxies, optically selected by
the CNOC2 redshift survey project, are co-added to measure the average HI mass
of galaxies in the two redshift bins. We calculate the cosmic HI gas densities
({\Omega}_{HI}) at the two redshift regimes and compare those with measurements
at other redshifts to investigate the global evolution of the HI gas density
over cosmic time. From a total of 59 galaxies at z ~ 0.1 we find {\Omega}_{HI}
= (0.33 $\pm$ 0.05) ~ $\times$ 10$^{-3}$, and at z ~ 0.2 we find {\Omega}_{HI}
= (0.34 $\pm$ 0.09) ~ $\times$ 10$^{-3}$, based on 96 galaxies. These
measurements help bridge the gap between high-z damped Lyman-$\alpha$
observations and blind 21-cm surveys at $z=$ 0. We find that our measurements
of {\Omega}_{HI} at z ~ 0.1 and 0.2 are consistent with the HI gas density at z
~ 0 and that all measurements of {\Omega}_{HI} from 21-cm emission observations
at $z \la$ ~ 0.2 are in agreement with no evolution of the HI gas content in
galaxies during the last 2.4 Gyr.


title:
The computational power of matchgates and the XY interaction on
  arbitrary graphs

abstract:
  Matchgates are a restricted set of two-qubit gates known to be classically
simulable when acting on nearest-neighbor qubits on a path, but universal for
quantum computation when the qubits are arranged on certain other graphs. Here
we characterize the power of matchgates acting on arbitrary graphs.
Specifically, we show that they are universal on any connected graph other than
a path or a cycle, and that they are classically simulable on a cycle. We also
prove the same dichotomy for the XY interaction, a proper subset of matchgates
related to some implementations of quantum computing.


title:
ManyClaw: Slicing and dicing Riemann solvers for next generation highly
  parallel architectures

abstract:
  Next generation computer architectures will include order of magnitude more
intra-node parallelism; however, many application programmers have a difficult
time keeping their codes current with the state-of-the-art machines. In this
context, we analyze Hyperbolic PDE solvers, which are used in the solution of
many important applications in science and engineering. We present ManyClaw, a
project intended to explore the exploitation of intra-node parallelism in
hyperbolic PDE solvers via the Clawpack software package for solving hyperbolic
PDEs. Our goal is to separate the low level parallelism and the physical
equations thus providing users the capability to leverage intra-node
parallelism without explicitly writing code to take advantage of newer
architectures.


title:
The Association of Solar Flares with Coronal Mass Ejections During the
  Extended Solar Minimum

abstract:
  We study the association of solar flares with coronal mass ejections (CMEs)
during the deep, extended solar minimum of 2007-2009, using extreme-ultraviolet
(EUV) and white-light (coronagraph) images from the {\it Solar Terrestrial
Relations Observatory} (STEREO). Although all of the fast (v $>$ 900 km
s$^{-1}$) {\it and} wide ($\theta >$ 100$\arcdeg$) CMEs are associated with a
flare that is at least identified in GOES soft X-ray light curves, a majority
of flares with relatively high X-ray intensity for the deep solar minimum (e.g.
$\gtrsim$1 \times 10^{-6}$ W m$^{-2}$ or C1) are not associated with CMEs.
Intense flares tend to occur in active regions with strong and complex
photospheric magnetic field, but the active regions that produce CME-associated
flares tend to be small, including those that have no sunspots and therefore no
NOAA active-region numbers. Other factors on scales comparable to and larger
than active regions seem to exist that contribute to the association of flares
with CMEs. We find the possible low coronal signatures of CMEs, namely
eruptions, dimmings, EUV waves, and Type III bursts, in 91%, 74%, 57%, and 74%,
respectively, of the 35 flares that we associate with CMEs. None of these
observables can fully replace direct observations of CMEs by coronagraphs.


title:
Interference Reduction in High Density WLAN Deployments using antenna
  Selection

abstract:
  In this work, we present a novel, robust scheme for high density WLAN
deployments. This scheme uses well known selection diversity at the
transmitter. We show that our scheme increases the number of simultaneous
transmissions at any given time without excessive overhead (compared to other
schemes such as Multi-user MIMO). Furthermore, this scheme can be easily
implemented using existing standards.


title:
Assessment of Cowling approximation in computing ellipticity of a
  magnetized non-barotropic star

abstract:
  A deformation of a neutron star due to its own magnetic field is an important
issue in gravitational wave astronomy, since a misaligned rotator with small
ellipticity may emit continuous gravitational wave that may be observed by
ground-based detectors. Recently Mastrano et al. (2011,2013) evaluated
deformations induced by both poloidal and toroidal magnetic field in
non-barotropic model stars by neglecting the gravitational field perturbation
(Cowling approximation). Following their treatment in non-barotropic fluid and
magnetic configurations, we here assess the effect of gravitational
perturbation that they neglected. We show that the ellipticity computed with
gravitational perturbation is roughly twice as large as that obtained by
Cowling approximation. We should allow this amount of error in using the neat
analytic treatment proposed by them.


title: Reflection factorizations of Singer cycles

abstract:
  The number of shortest factorizations into reflections for a Singer cycle in
GL_n(F_q) is shown to be (q^n-1)^(n - 1). Formulas counting factorizations of
any length, and counting those with reflections of fixed conjugacy classes are
also given. The method is a standard character-theory technique, requiring the
compilation of irreducible character values for Singer cycles, semisimple
reflections, and transvections. The results suggest several open problems and
questions, which are discussed at the end.


title: Further refinement of strong multiplicity one for GL(2)

abstract:
  We obtain a sharp refinement of the strong multiplicity one theorem for the
case of unitary non-dihedral cuspidal automorphic representations for GL(2).
Given two unitary cuspidal automorphic representations for GL(2) that are not
twist-equivalent, we also find sharp lower bounds for the number of places
where the Hecke eigenvalues are not equal, for both the general and
non-dihedral cases. We then construct examples to demonstrate that these
results are sharp.


title:
On the size of Satake parameters for unitary cuspidal automorphic
  representations for GL(4)

abstract:
  Let \Pi\ be a cuspidal automorphic representation for GL(4) over a number
field F. We obtain unconditional lower bounds on the number of places at which
the Satake parameters are not "too large". In the case of self-dual \Pi\ with
non-trivial central character, our results imply that the set of places at
which \Pi\ is tempered has an explicit positive lower Dirichlet density. Our
methods extend those of Ramakrishnan by careful analysis of the hypothetical
possibilities for the structure of the Langlands conjugacy classes, as well as
their behaviour under functorial lifts. We then discuss the analogous problem
in GL(3).


title:
Application of Inventory Management Principles for Efficient Data
  Placement in Storage Networks

abstract:
  The principles and strategies found in material management are comparable and
analogue with the data management. This paper concentrates on the conversion of
product inventory management principles into data inventory management
principles. Efforts were made to enumerate various impacting parameters that
would be appropriate to consider if any data inventory model could be plotted.


title:
ForestClaw: Hybrid forest-of-octrees AMR for hyperbolic conservation
  laws

abstract:
  We present a new hybrid paradigm for parallel adaptive mesh refinement (AMR)
that combines the scalability and lightweight architecture of tree-based AMR
with the computational efficiency of patch-based solvers for hyperbolic
conservation laws. The key idea is to interpret each leaf of the AMR hierarchy
as one uniform compute patch in $\sR^d$ with $m^d$ degrees of freedom, where
$m$ is customarily between 8 and 32. Thus, computation on each patch can be
optimized for speed, while we inherit the flexibility of adaptive meshes. In
our work we choose to integrate with the p4est AMR library since it allows us
to compose the mesh from multiple mapped octrees and enables the cubed sphere
and other nontrivial multiblock geometries. We describe aspects of the parallel
implementation and close with scalings for both MPI-only and OpenMP/MPI hybrid
runs, where the largest MPI run executes on 16,384 CPU cores.


title:
The electronic specific heat of Ba1-xKxFe2As2 (x=0 to 1.0) from 2K to
  380K

abstract:
  Using a high-resolution differential technique we have determined the
electronic specific heat coefficient gamma(T) of Ba1-xKxFe2As2 with x=0 to 1.0,
at temperatures (T) from 2K to 380K and in magnetic fields H=0 to 13T. In the
normal state gamma_n(x,T) increases strongly with x at low temperature,
compatible with a mass renormalisation ~12 at x=1, and decreases weakly with x
at high temperature. A superconducting transition is seen in all samples from
x=0.2 to 1, with transition temperatures and condensation energies peaking
sharply at x=0.4. Superconducting coherence lengths xi_{ab}~20{\AA} and
xi_c~3{\AA} are estimated from an analysis of Gaussian fluctuations. For many
dopings we see features in the H and T-dependences of gamma_s(T,H) in the
superconducting state that suggest superconducting gaps in three distinct
bands. A broad "knee" and a sharp mean-field-like peak are typical of two
coupled gaps. However, several samples show a shoulder above the sharp peak
with an abrupt onset at T_{c,s} and a T-dependence
gamma_s(T)\propto\sqrt{1-T/T_{c,s}}. We provide strong evidence that the
shoulder is not due to doping inhomogeneity and suggest it is a distinct gap
with an unconventional T-dependence Delta_s(T)\propto(1-T/T_{c,s})^{0.75} near
T_{c,s}. We estimate band fractions and T=0 gaps from 3-band alpha-model fits
to our data and compare the x-dependences of the band fractions with
spectroscopic studies of the Fermi surface.


title: The Mid-Infrared Extinction Law in the Large Magellanic Cloud

abstract:
  Based on the photometric data from the Spitzer/SAGE survey and with red
giants as the extinction tracers, the mid-infrared (MIR) extinction laws in the
Large Magellanic Cloud (LMC) are derived for the first time in the form of
A_\lambda/A_Ks, the extinction in the four IRAC bands (i.e., [3.6], [4.5],
[5.8] and [8.0]um) relative to the 2MASS Ks band at 2.16um. We obtain the
near-infrared (NIR) extinction coefficient to be E(J-H)/E(H-Ks)=1.29\pm0.04 and
E(J-Ks)/E(H-Ks)=1.94\pm0.04. The wavelength dependence of the MIR extinction
A_\lambda/A_Ks in the LMC varies from one sightline to another. The overall
mean MIR extinction is A_[3.6]/A_Ks=0.72\pm0.03, A_[4.5]/A_Ks=0.94\pm0.03,
A_[5.8]/A_Ks=0.58\pm0.04, and A_[8.0]/A_Ks=0.62\pm0.05. Except for the
extinction in the IRAC [4.5] band which may be contaminated by the 4.6um CO gas
absorption of red giants (which are used to trace the LMC extinction), the
extinction in the other three IRAC bands show a flat curve, close to the Milky
Way Rv = 5.5 model extinction curve (where Rv is the optical total-to-selective
extinction ratio). The possible systematic bias caused by the correlated
uncertainties of Ks-\lambda and J-Ks is explored in terms of Monte-Carlo
simulations. It is found that this could lead to an overestimation of
A_lambda/A_Ks in the MIR.