title: Vacuum Stability and the MSSM Higgs Mass

abstract:
  In the Minimal Supersymmetric Standard Model (MSSM), a Higgs boson mass of
125 GeV can be obtained with moderately heavy scalar top superpartners provided
they are highly mixed. The source of this mixing, a soft trilinear
stop-stop-Higgs coupling, can result in the appearance of charge- and
color-breaking minima in the scalar potential of the theory. If such a vacuum
exists and is energetically favorable, the Standard Model-like vacuum can decay
to it via quantum tunnelling. In this work we investigate the conditions under
which such exotic vacua arise, and we compute the tunnelling rates to them. Our
results provide new constraints on the scalar top quarks of the MSSM.


title:
Non-locality of zero-bias anomalies in the topologically-trivial phase
  of Majorana wires

abstract:
  We show that the topologically trivial zero bias peak (ZBP) emerging in
semiconductor Majorana wires due to soft confinement exhibits correlated
splitting oscillations as a function of the applied Zeeman field, similar to
the correlated splitting of the Majorana ZBP. Also, we find that the presence
of a strong impurity can effectively cut the wire in two and destroy the
correlated splitting in both the trivial and the Majorana regimes. We identify
a strong nonlocal effect that operates only in the topologically trivial regime
and demonstrate that the dependence of the ZBP on the confining gate potential
at the opposite end in Majorana wires with two normal metal end-contacts
represents a powerful tool for discriminating between topologically trivial and
nontrivial ZBPs.


title: High redshift signatures in the 21 cm forest due to cosmic string wakes

abstract:
  Cosmic strings induce minihalo formation in the early universe. The resultant
minihalos cluster in string wakes and create a "21 cm forest" against the
cosmic microwave background (CMB) spectrum. Such a 21 cm forest can contribute
to angular fluctuations of redshifted 21 cm signals integrated along the line
of sight. We calculate the root-mean-square amplitude of the 21 cm fluctuations
due to strings and show that these fluctuations can dominate signals from
minihalos due to primordial density fluctuations at high redshift ($z \gtrsim
10$), even if the string tension is below the current upper bound, $G \mu < 1.5
\times 10^{-7}$. Our results also predict that the Square Kilometre Array (SKA)
can potentially detect the 21 cm fluctuations due to strings with $G \mu
\approx 7.5 \times 10^{-8}$ for the single frequency band case and $4.0 \times
10^{-8}$ for the multi-frequency band case.


title:
Direct measurements of dust attenuation in z~1.5 star-forming galaxies
  from 3D-HST: Implications for dust geometry and star formation rates

abstract:
  The nature of dust in distant galaxies is not well understood, and until
recently few direct dust measurements have been possible. We investigate dust
in distant star-forming galaxies using near-infrared grism spectra of the
3D-HST survey combined with archival multi-wavelength photometry. These data
allow us to make a direct comparison between dust around star-forming regions
($A_{V,\mathrm{HII}}$) and the integrated dust content ($A_{V,\mathrm{star}}$).
We select a sample of 163 galaxies between $1.36\le{}z\le1.5$ with H$\alpha$
signal-to-noise ratio $\ge5$ and measure Balmer decrements from stacked spectra
to calculate $A_{V,\mathrm{HII}}$. First, we stack spectra in bins of
$A_{V,\mathrm{star}}$, and find that
$A_{V,\mathrm{HII}}=1.86\,A_{V,\mathrm{star}}$, with a significance of
$\sigma=1.7$. Our result is consistent with the two-component dust model, in
which galaxies contain both diffuse and stellar birth cloud dust. Next, we
stack spectra in bins of specific star formation rate ($\log\,\mathrm{SSFR}$),
star formation rate ($\log\,\mathrm{SFR}$), and stellar mass ($\log{}M_*$). We
find that on average $A_{V,\mathrm{HII}}$ increases with SFR and mass, but
decreases with increasing SSFR. Interestingly, the data hint that the amount of
extra attenuation decreases with increasing SSFR. This trend is expected from
the two-component model, as the extra attenuation will increase once older
stars outside the star-forming regions become more dominant in the galaxy
spectrum. Finally, using Balmer decrements we derive dust-corrected H$\alpha$
SFRs, and find that stellar population modeling produces incorrect SFRs if
rapidly declining star formation histories are included in the explored
parameter space.


title: Which galaxies dominate the neutral gas content of the Universe?

abstract:
  We study the contribution of galaxies with different properties to the global
densities of star formation rate (SFR), atomic (HI) and molecular hydrogen (H2)
as a function of redshift. We use the GALFORM model of galaxy formation, which
is set in the LCDM framework. This model includes a self-consistent calculation
of the SFR, which depends on the H2 content of galaxies. The predicted SFR
density and how much of this is contributed by galaxies with different stellar
masses and infrared luminosities are in agreement with observations. The model
predicts a modest evolution of the HI density at z<3, which is also in
agreement with the observations. The HI density is predicted to be always
dominated by galaxies with SFR<1Msun/yr. This contrasts with the H2 density,
which is predicted to be dominated by galaxies with SFR>10Msun/yr. Current
high-redshift galaxy surveys are limited to detect carbon monoxide in galaxies
with SFR>30Msun/yr, which in our model make up, at most, 20% of the H2 in the
universe. In terms of stellar mass, the predicted H2 density is dominated by
massive galaxies, Mstellar>10^10Msun, while the HI density is dominated by low
mass galaxies, Mstellar<10^9Msun. In the context of upcoming neutral gas
surveys, we suggest that the faint nature of the galaxies dominating the HI
content of the Universe will hamper the identification of optical counterparts,
while for H2, we expect follow up observations of molecular emission lines of
already existing galaxy catalogues to be able to uncover the H2 density of the
Universe.


title:
A New Approach to Detailed Structural Decomposition from the SPLASH and
  PHAT Surveys: Kicked-up Disk Stars in the Andromeda Galaxy?

abstract:
  We characterize the bulge, disk, and halo subcomponents in the Andromeda
galaxy (M31) over the radial range 4 < R_proj < 225 kpc. The cospatial nature
of these subcomponents renders them difficult to disentangle using surface
brightness (SB) information alone, especially interior to ~20 kpc. Our new
decomposition technique combines information from the luminosity function (LF)
of over 1.5 million bright (20 < m_814W < 22) stars from the Panchromatic
Hubble Andromeda Treasury (PHAT) survey, radial velocities of over 5000 red
giant branch stars in the same magnitude range from the Spectroscopic and
Photometric Landscape of Andromeda's Stellar Halo (SPLASH) survey, and
integrated I-band SB profiles from various sources. We use an affine-invariant
Markov chain Monte Carlo algorithm to fit an appropriate toy model to these
three data sets. The bulge, disk, and halo SB profiles are modeled as a Sersic,
exponential, and cored power-law, respectively, and the LFs are modeled as
broken power-laws. We present probability distributions for each of 32
parameters describing the SB profiles and LFs of the three subcomponents. We
find that the number of stars with a disk-like LF is ~5% larger than the the
number with disk-like (dynamically cold) kinematics, suggesting that some stars
born in the disk have been dynamically heated to the point that they are
kinematically indistinguishable from halo members. This is the first
kinematical evidence for a "kicked-up disk" halo population in M31. The
fraction of kicked-up disk stars is consistent with that found in simulations.
We also find evidence for a radially varying disk LF, consistent with a
negative metallicity gradient in the stellar disk.


title: Holographic Charged Renyi Entropies

abstract:
  We construct a new class of entanglement measures by extending the usual
definition of Renyi entropy to include a chemical potential. These charged
Renyi entropies measure the degree of entanglement in different charge sectors
of the theory and are given by Euclidean path integrals with the insertion of a
Wilson line encircling the entangling surface. We compute these entropies for a
spherical entangling surface in CFT's with holographic duals, where they are
related to entropies of charged black holes with hyperbolic horizons. We also
compute charged Renyi entropies in free field theories.


title: On the Magnetohydrodynamics/Gravity Correspondence

abstract:
  The fluid/gravity correspondence relates solutions of the incompressible
Navier-Stokes equation to metrics which solve the Einstein equations. In this
paper we extend this duality to a new magnetohydrodynamics/gravity
correspondence, which translates solutions of the equations of
magnetohydrodynamics (describing charged fluids) into geometries that satisfy
the Einstein-Maxwell equations. We present an explicit example of this new
correspondence in the context of flat Minkowski space. We show that a
perturbative deformation of the Rindler wedge satisfies the Einstein-Maxwell
equations provided that the parameters appearing in the expansion, which we
interpret as fluid fields, satisfy the magnetohydrodynamics equations. As a
byproduct of our analysis we show that in four dimensions, the dual geometry is
algebraically special Petrov type II.


title:
N=2 SUGRA BPS Multi-center solutions, quadratic prepotentials and
  Freudenthal transformations

abstract:
  We present a detailed description of N=2 stationary BPS multicenter black
hole solutions for quadratic prepotentials with an arbitrary number of centers
and scalar fields making a systematic use of the algebraic properties of the
matrix of second derivatives of the prepotential, $\mathcal{S}$, which in this
case is a scalar-independent matrix. In particular we obtain bounds on the
physical parameter of the multicenter solution such as horizon areas and ADM
mass. We discuss the possibility and convenience of setting up a basis of the
symplectic vector space built from charge eigenvectors of the $\ssigma$, the
set of vectors $(\Ppm q_a)$ with $\Ppm$ $\ssigma$-eigenspace proyectors.
  The anti-involution matrix $\mathcal{S}$ can be understood as a Freudenthal
duality $\tilde{x}=\ssigma x$. We show that this duality can be generalized to
"Freudenthal transformations" $$x\to \lambda\exp(\theta \ssigma) x= a
x+b\tilde{x}$$ under which the horizon area, ADM mass and intercenter distances
scale up leaving constant the fix point scalars. In the special case
$\lambda=1$, "$\ssigma$-rotations", the transformations leave invariant the
solution. The standard Freudental duality can be written as
  $\tilde x= \exp(\pi/2 \ssigma) x .$ We argue that these generalized
transformations leave also invariant the general stringy extremal quartic form
$\Delta_4$, $\Delta_4(x)= \Delta_4(\cos\theta x+\sin\theta\tilde{x})$.


title: Direct Imaging Detection of Methane in the Atmosphere of GJ 504 b

abstract:
  Most exoplanets detected by direct imaging so far have been characterized by
relatively hot (> ~1000 K) and cloudy atmospheres. A surprising feature in some
of their atmospheres has been a distinct lack of methane, possibly implying
non-equilibrium chemistry. Recently, we reported the discovery of a planetary
companion to the Sun-like star GJ 504 using Subaru/HiCIAO within the SEEDS
survey. The planet is substantially colder (<600 K) than previously imaged
planets, and has indications of fewer clouds, which implies that it represents
a new class of planetary atmospheres with expected similarities to late T-type
brown dwarfs in the same temperature range. If so, one might also expect the
presence of significant methane absorption, which is characteristic of such
objects. Here, we report the detection of deep methane absorption in the
atmosphere of GJ 504 b, using the Spectral Differential Imaging mode of HiCIAO
to distinguish the absorption feature around 1.6 um. We also report updated JHK
photometry based on new Ks-band data and a re-analysis of the existing data.
The results support the notion that GJ 504 b has atmospheric properties
distinct from other imaged exoplanets, and will become a useful reference
object for future planets in the same temperature range.


title:
Measuring cosmic bulk flows with Type Ia Supernovae from the Nearby
  Supernova Factory

abstract:
  Context. Our Local Group of galaxies appears to be moving relative to the
cosmic microwave background with the source of the peculiar motion still
uncertain. While in the past this has been studied mostly using galaxies as
distance indicators, the weight of type Ia supernovae (SNe Ia) has increased
recently with the continuously improving statistics of available low-redshift
supernovae.
  Aims. We measured the bulk flow in the nearby universe ($0.015 < z < 0.1$)
using 117 SNe Ia observed by the Nearby Supernova Factory, as well as the
Union2 compilation of SN Ia data already in the literature.
  Methods. The bulk flow velocity was determined from SN data binned in
redshift shells by including a coherent motion (dipole) in a cosmological fit.
Additionally, a method of spatially smoothing the Hubble residuals was used to
verify the results of the dipole fit. To constrain the location and mass of a
potential mass concentration (e.g., the Shapley supercluster) responsible for
the peculiar motion, we fit a Hubble law modified by adding an additional mass
concentration.
  Results. The analysis shows a bulk flow that is consistent with the direction
of the CMB dipole up to $z \sim 0.06$, thereby doubling the volume over which
conventional distance measures are sensitive to a bulk flow. We see no
significant turnover behind the center of the Shapley supercluster. A simple
attractor model in the proximity of the Shapley supercluster is only marginally
consistent with our data, suggesting the need for another, more distant source.
In the redshift shell $0.06 < z < 0.1$, we constrain the bulk flow velocity to
$< 240~\textrm{km s}^{-1}$ (68% confidence level) for the direction of the CMB
dipole, in contradiction to recent claims of the existence of a large-amplitude
dark flow.


title: Renormalization and redundancy in 2d quantum field theories

abstract:
  We analyze renormalization group (RG) flows in two-dimensional quantum field
theories in the presence of redundant directions. We use the operator picture
in which redundant operators are total derivatives. Our analysis has three
levels of generality. We introduce a redundancy anomaly equation which is
analyzed together with the RG anomaly equation previously considered by
H.Osborn [8] and D.Friedan and A.Konechny [7]. The Wess-Zumino consistency
conditions between these anomalies yield a number of general relations which
should hold to all orders in perturbation theory. We further use conformal
perturbation theory to study field theories in the vicinity of a fixed point
when some of the symmetries of the fixed point are broken by the perturbation.
We relate various anomaly coefficients to OPE coefficients at the fixed point
and analyze which operators become redundant and how they participate in the RG
flow. Finally, we illustrate our findings by three explicit models constructed
as current-current perturbations of SU(2)_k WZW model. At each generality level
we discuss the geometric picture behind redundancy and how one can reduce the
number of couplings by taking a quotient with respect to the redundant
directions. We point to the special role of polar representations for the
redundancy groups.


title: Liquid-solid impacts of yield-stress fluids

abstract:
  This is an entry to the Gallery of Fluid Motion at the 66th annual meeting of
the APS-DFD, held November 2013 in Pittsburgh, PA. In this fluid dynamics video
we demonstrate distinct features of yield-stress fluid droplets impacting
pre-coated surfaces.


title: The non-tempered theta 10 Arthur parameter and Gross-Prasad Conjectures

abstract:
  We provide a construction of local and automorphic non-tempered Arthur
packets of the group SO(3,2) and its inner form SO(4,1) associated with a
certain Arthur's parameter and prove a multiplicity formula.
  We further study the restriction of the representations in these packets to
the subgroup SO(3,1). In particular, we discover that the local Gross-Prasad
conjecture, formulated for generic L-packets, does not generalize naively to a
non-generic A-packet. We also study the non-vanishing of the automorphic
SO(3,1)-period on the group SO(4,1) x SO(3,1) and SO(3,2) x SO(3,1) for the
representations above.
  The main tool is the local and global theta correspondence for unitary
quaternionic similitude dual pairs.


title: Nonuniform Line Coverage from Noisy Scalar Measurements

abstract:
  We study the problem of distributed coverage control in a network of mobile
agents arranged on a line. The goal is to design distributed dynamics for the
agents to achieve optimal coverage positions with respect to a scalar density
field that measures the relative importance of each point on the line. Unlike
previous work, which has implicitly assumed the agents know this density field,
we only assume that each agent can access noisy samples of the field at points
close to its current location. We provide a simple randomized protocol wherein
every agent samples the scalar field at three nearby points at each step and
which guarantees convergence to the optimal positions. We further analyze the
convergence time of this protocol and show that, under suitable assumptions,
the squared distance to the optimal coverage configuration decays as $O(1/t)$
with the number of iterations $t$, where the constant scales polynomially with
the number of agents $n$. We illustrate these results with simulations.


title: Ab initio study of point defects in NiTi-based alloys

abstract:
  Changes in temperature or stress state may induce reversible
B2$\leftrightarrow$(R)$\leftrightarrow$ B19' martensitic transformations and
associated shape memory effects in close-to-stoichiometric nickel-titanium
(NiTi) alloys. Recent experimental studies confirmed a considerable impact of
the hydrogen-rich aging atmosphere on the subsequent B2 austenite
$\leftrightarrow$ B19' martensite transformation path. In this paper, we employ
Density Functional Theory to study properties of Ar, He, and H interstitials in
B2 austenite and B19' martensite phases. We show that H interstitials exhibit
negative formation energies, while Ar and He interstitials yield positive
values. Our theoretical analysis of slightly Ni-rich Ni--Ti alloys with the
austenite B2 structure shows that a slight over-stoichiometry towards Ni-rich
compositions in a range 51--$52\,\text{at.%}$ is energetically favorable. The
same conclusion holds for H-doped NiTi with the H content up to
$\approx6\,\text{at.%}$. In agreement with experimental data we predict H atoms
to have a strong impact on the martensitic phase transformation in NiTi by
altering the mutual thermodynamic stability of the high-temperature cubic B2
and the low-temperature monoclinic B19' phase of NiTi. Hydrogen atoms are
predicted to form stable interstitial defects. As this is not the case for He
and Ar, mixtures of hydrogen and the two inert gases can be used in annealing
experiments to control H partial pressure when studying the martensitic
transformations in NiTi in various atmospheres.


title:
Multi-Longitude Observation Campaign of KV Cancri: an RR Lyrae star with
  irregular Blazhko modulations

abstract:
  We present the results of multi-longitude observations of KV Cancri, an RR
Lyrae star showing an irregular Blazhko effect. With a pulsation period of
0.50208 day, the times of light curve maxima are delayed by 6 minutes per day.
This daily delay regularly leads to long periods of time without maximum light
curve observations for a given site. To cope with this observing time window
problem, we have organized a multi-longitude observation campaign including a
telescope of the AAVSONet. From the observed light curves, 92 pulsation maxima
have been measured covering about six Blazhko periods. The Fourier analysis of
magnitudes at maximum light has revealed a main Blazhko period of 77.6 days and
also a secondary period of 40.5 days. A Fourier analysis of (O-C) values did
not show the secondary Blazhko period. The frequency spectrum of the complete
light curve, from a Fourier analysis and successive pre-whitening with
PERIOD04, has shown triplet structures around the two Blazhko modulation
frequencies but with slightly different periods (77.8 and 42.4 days). The
second Blazhko frequency is statistically not a harmonic of the main Blazhko
frequency. Besides the two Blazhko modulations KV Cnc presents other
particularities like irregularities from Blazhko cycle to cycle and very fast
magnitude variations which can reach a maximum of 2.5 magnitudes per hour over
a period of 15 minutes. This campaign shows that regular observations by
amateur astronomers remain important. Indeed such a detailed characterization
of the Blazhko effect could not be obtained from large-scale surveys, as
cooperative long time-series observations are needed.


title:
A Macroscopic Description of a Generalized Self-Organized Criticality
  System: Astrophysical Applications

abstract:
  We suggest a generalized definition of self-organized criticality (SOC)
systems: SOC is a critical state of a nonlinear energy dissipation system that
is slowly and continuously driven towards a critical value of a system-wide
instability threshold, producing scale-free, fractal-diffusive, and
intermittent avalanches with powerlaw-like size distributions. We develop here
a macroscopic description of SOC systems that provides an equivalent
description of the complex microscopic fine structure, in terms of
fractal-diffusive transport (FD-SOC). Quantitative values for the size
distributions of SOC parameters (length scales $L$, time scales $T$, waiting
times $\Delta t$, fluxes $F$, and energies $E$) are derived from first
principles, using the scale-free probability conjecture, $N(L) dL \propto
L^{-d}$, for Euclidean space dimension $d$. We apply this model to
astrophysical SOC systems, such as lunar craters, the asteroid belt, Saturn
ring particles, magnetospheric substorms, radiation belt electrons, solar
flares, stellar flares, pulsar glitches, soft gamma-ray repeaters, black-hole
objects, blazars, and cosmic rays. The FD-SOC model predicts correctly the size
distributions of 8 out of these 12 astrophysical phenomena, and indicates
non-standard scaling laws and measurement biases for the others.


title:
Microscopically based calculations of the free energy barrier and
  dynamic length scale in supercooled liquids: The comparative role of
  configurational entropy and elasticity

abstract:
  We compute the temperature-dependent barrier for alpha-relaxations in several
liquids, without adjustable parameters, using experimentally determined
elastic, structural, and calorimetric data. We employ the random first order
transition(RFOT) theory, in which relaxation occurs via activated
reconfigurations between distinct, aperiodic minima of the free energy. Two
different approximations for the mismatch penalty between the distinct
aperiodic states are compared, one due to Xia and Wolynes, which scales
universally with temperature as for hard spheres, and one due to Rabochiy and
Lubchenko, which employs measured elastic and structural data for individual
substances. The agreement between the predictions and experiment is
satisfactory, given the uncertainty in the measured experimental inputs. The
explicitly computed barriers are used to calculate the glass transition
temperature for each substance---a kinetic quantity---from the static input
data alone. The temperature dependence of both the elastic and structural
constants enters the temperature dependence of the barrier over an extended
range to a degree that varies from substance to substance. The lowering of the
configurational entropy, however, seems to be the dominant contributor to the
barrier increase near the laboratory glass transition, consistent with previous
experimental tests of the RFOT theory using the XW approximation. In addition,
we compute the temperature dependence of the dynamical correlation length, also
without using adjustable parameters. These agree well with experimental
estimates obtained using the Berthier et al. procedure. Finally, we find the
temperature dependence of the complexity of a rearranging region is consistent
with the picture based on the RFOT theory but is in conflict with the
assumptions of the Adam-Gibbs and "shoving" scenarios for the viscous slowing
down in supercooled liquids.


title: Weak values beyond weak measurement

abstract:
  The AAV effect is the well-known phenomenon where a weak measurement followed
by post-selection leads to a pointer shift proportional to the weak value of
the measured observable. The effect is usually derived by considering a
perturbative expansion of the time-evolution operator corresponding to the
measurement. We show that the AAV effect can be instead derived given three
simple conditions on the pointer states. The most important condition is that
the pointer states be approximately indistinguishable. The other two conditions
relate the observables used to characterize the pointer with the measured
system observable. This intuitive approach does not require any model for the
measurement process, but is completely consistent with the usual approach based
on the von Neumann Hamiltonian. Moreover, this approach predicts and explains a
new phenomenon, called weak echo, where the usual weak value behaviour can
re-emerge at high interaction strengths.


title: T-duality revisited

abstract:
  We revisit the transformation rules of the metric and Kalb-Ramond field under
T-duality, and express the corresponding relations in terms of the metric G and
the field strength H=dB. In the course of the derivation, we find an
explanation for potential reductions of the isometry group in the dual
background.
  The formalism employed in this paper is illustrated with examples based on
tori and spheres, where for the latter we construct a new non-geometric
background.


title: Bayesian Low Rank and Sparse Covariance Matrix Decomposition

abstract:
  We consider the problem of estimating high-dimensional covariance matrices of
a particular structure, which is a summation of low rank and sparse matrices.
This covariance structure has a wide range of applications including factor
analysis and random effects models. We propose a Bayesian method of estimating
the covariance matrices by representing the covariance model in the form of a
factor model with unknown number of latent factors. We introduce binary
indicators for factor selection and rank estimation for the low rank component
combined with a Bayesian lasso method for the sparse component estimation.
Simulation studies show that our method can recover the rank as well as the
sparsity of the two components respectively. We further extend our method to a
graphical factor model where the graphical model of the residuals as well as
selecting the number of factors is of interest. We employ a hyper-inverse
Wishart prior for modeling decomposable graphs of the residuals, and a Bayesian
graphical lasso selection method for unrestricted graphs. We show through
simulations that the extended models can recover both the number of latent
factors and the graphical model of the residuals successfully when the sample
size is sufficient relative to the dimension.


title: Subsectors, Dynkin Diagrams and New Generalised Geometries

abstract:
  We examine how generalised geometries can be associated with a labelled
Dynkin diagram built around a gravity line. We present a series of new
generalised geometries based on the groups
$\mathit{Spin}(d,d)\times\mathbb{R}^+$ for which the generalised tangent space
transforms in a spinor representation of the group. In low dimensions these all
appear in subsectors of maximal supergravity theories. The case $d=8$ provides
a geometry for eight-dimensional backgrounds of M theory with only seven-form
flux, which have not been included in any previous geometric construction. This
geometry is also one of a series of "half-exceptional" geometries, which
"geometrise" a six-form gauge field. In the appendix, we consider examples of
other algebras appearing in gravitational theories and give a method to derive
the Dynkin labels for the "section condition" in general. We argue that
generalised geometry can describe restrictions and subsectors of many
gravitational theories.


title: Maximum likelihood geometry in the presence of data zeros

abstract:
  Given a statistical model, the maximum likelihood degree is the number of
complex solutions to the likelihood equations for generic data. We consider
discrete algebraic statistical models and study the solutions to the likelihood
equations when the data contain zeros and are no longer generic. Focusing on
sampling and model zeros, we show that, in these cases, the solutions to the
likelihood equations are contained in a previously studied variety, the
likelihood correspondence. The number of these solutions give a lower bound on
the ML degree, and the problem of finding critical points to the likelihood
function can be partitioned into smaller and computationally easier problems
involving sampling and model zeros. We use this technique to compute a lower
bound on the ML degree for $2 \times 2 \times 2 \times 2$ tensors of border
rank $\leq 2$ and $3 \times n$ tables of rank $\leq 2$ for $n=11, 12, 13, 14$,
the first four values of $n$ for which the ML degree was previously unknown.


title:
Sensitivity of micromechanical actuation on amorphous to crystalline
  phase transformations under the influence of Casimir forces

abstract:
  Amorphous to crystalline phase transitions in phase change materials (PCM)
can have strong influence on the actuation of microelectromechanical systems
under the influence of Casimir forces. Indeed, the bifurcation curves of the
stationary equilibrium points and the corresponding phase portraits of the
actuation dynamics between gold and AIST PCM, where an increase of the Casimir
force of up ~25% has been measured upon crystallization, show strong
sensitivity to changes of the Casimir force as the stiffness of the actuating
component decreases and/or the effective interaction area of the Casimir force
increases, which can also lead to stiction. However, introduction of intrinsic
energy dissipation (associated with a finite quality factor of the actuating
system) can prevent stiction by driving the system to attenuated motion towards
stable equilibrium depending on the PCM state and the system quality factor.


title: Spin Graphs

abstract:
  We show that on any Riemann surface S of genus g>1 any nonsingular even spin
bundle defines e-foloation of S. When a surface is hyperelliptic then all
leaves of this foliation are finite and almost all of them consists of 2g+2
points. Moreover, each leaf carries an additional structure which allows us to
view it as a concrete graph. We find the properties of these spin graphs and we
describe the classification of surfaces which is given by these properties. The
classification is based on a finite genus g>1.number of exceptional graphs
which have to be present on any surface S of


title:
Near-infrared spectroscopic and photometric evolution of Nova V476 Scuti
  -- a nova that formed optically thin dust

abstract:
  We present results of near-infrared (near-IR) $JHK$ (1.07 - 2.5 $\mu$m)
spectroscopic and photometric observations of Nova V476 Scuti (V476 Sct) which
was discovered in outburst in 2005 September. The near-IR observations of the
nova presents the evolution of the post-maxima spectra and near-IR light curve.
The spectra of V476 Sct, observed on 9 different epochs, show prominent lines
due to HI, OI, CI and NI. Based on the IR spectral signatures we independently
identify it as a Fe II type of nova, consistent with the same classification
obtained from optical spectra. A detailed identification of the observed
spectral lines is presented. The near-IR $JHK$ light curve extending for a
period of about 59 days after outburst clearly shows the formation of a
optically thin dust shell, a phenomenon which is not commonly observed in
novae. By fitting black body curves to the spectral energy distributions (SEDs)
the temperatures of the dust shell on different epochs have been estimated.
Dust formation in V476 Sct is consistent with the presence of lines of elements
with low-ionization potential like Na and Mg in the early spectra which had
earlier been suggested by us to be potential indicators of dust formation at a
later phase in a nova's development.


title:
Lyapunov-based Low-thrust Optimal Orbit Transfer: An approach in
  Cartesian coordinates

abstract:
  This paper presents a simple approach to low-thrust optimal-fuel and
optimal-time transfer problems between two elliptic orbits using the Cartesian
coordinates system. In this case, an orbit is described by its specific angular
momentum and Laplace vectors with a free injection point. Trajectory
optimization with the pseudospectral method and nonlinear programming are
supported by the initial guess generated from the Chang-Chichka-Marsden
Lyapunov-based transfer controller. This approach successfully solves several
low-thrust optimal problems. Numerical results show that the Lyapunov-based
initial guess overcomes the difficulty in optimization caused by the strong
oscillation of variables in the Cartesian coordinates system. Furthermore, a
comparison of the results shows that obtaining the optimal transfer solution
through the polynomial approximation by utilizing Cartesian coordinates is
easier than using orbital elements, which normally produce strongly nonlinear
equations of motion. In this paper, the Earth's oblateness and shadow effect
are not taken into account.


title: Probability of Vacuum Stability in Type IIB Multi-K\"ahler Moduli Models

abstract:
  We study the probability that all eigenvalues of the moduli mass matrix at
extremal points are positive in concrete multi-K\"ahler moduli models of type
IIB string theory compactifications in the large volume regime. Our analysis is
motivated by the open question if vacua which are uplifted to de Sitter remain
stable. We derive a simple analytical condition for the mass matrix to be
positive definite, and estimate the corresponding probability in a
supersymmetric moduli stabilization model along the lines of KKLT and a
non-supersymmetric Large Volume Scenario type of model, given a reasonable
range of compactification parameters. Under identical conditions, the
probability for the supersymmetric model is moderately higher than that of the
Large Volume Scenario type model.


title:
Braking down an accreting protostar: disc-locking, disc winds, stellar
  winds, X-winds and Magnetospheric Ejecta

abstract:
  Classical T Tauri stars are low mass young forming stars that are surrounded
by a circumstellar accretion disc from which they gain mass. Despite this
accretion and their own contraction that should both lead to their spin up,
these stars seem to conserve instead an almost constant rotational period as
long as the disc is maintained. Several scenarios have been proposed in the
literature in order to explain this puzzling "disc-locking" situation: either
deposition in the disc of the stellar angular momentum by the stellar
magnetosphere or its ejection through winds, providing thereby an explanation
of jets from Young Stellar Objects.
  In this lecture, these various mechanisms will be critically detailed, from
the physics of the star-disc interaction to the launching of self-confined jets
(disc winds, stellar winds, X-winds, conical winds). It will be shown that no
simple model can account alone for the whole bulk of observational data and
that "disc locking" requires a combination of some of them.


title: A hole-ographic spacetime

abstract:
  We embed spherical Rindler space -- a geometry with a spherical hole in its
center -- in asymptotically AdS spacetime and show that it carries a
gravitational entropy proportional to the area of the hole. Spherical
AdS-Rindler space is holographically dual to an ultraviolet sector of the
boundary field theory given by restriction to a strip of finite duration in
time. Because measurements have finite durations, local observers in the field
theory can only access information about bounded spatial regions. We propose a
notion of Residual Entropy that captures uncertainty about the state of a
system left by the collection of local, finite-time observables. For
two-dimensional conformal field theories we use holography and the strong
subadditivity of entanglement to propose a formula for Residual Entropy and
show that it precisely reproduces the areas of circular holes in AdS3.
Extending the notion to field theories on strips with variable durations in
time, we show more generally that Residual Entropy computes the areas of all
closed, inhomogenous curves on a spatial slice of AdS3. We discuss the
extension to higher dimensional field theories, the relation of Residual
Entropy to entanglement between scales, and some implications for the emergence
of space from the RG flow of entangled field theories.


title: Standard and Weierstrass spin groups on hyperelliptic Riemann surfaces

abstract:
  We show that at any standard or Weierstrass point P on a hyperelliptic
Riemann surface S equipped with a nonsingular even spin structure, we may
attach a spin group G(P) in a natural way. All such spin groups are isomorphic
to each other and to the alternating group A(g)<S(g). Moreover, for any two
vertices of the same spin graph we construct a natural, unique isomorphism
between the corresponding, mutually conjugate spin groups.


title:
A continuum of periodic solutions to the four-body problem with various
  choices of masses

abstract:
  In this paper, we apply the variational method with the Structural Prescribed
Boundary Conditions (SPBC) to prove the existence of periodic and
quasi-periodic solutions for planar four-body problem with $m_1=m_3$ and
$m_2=m_4$. A path $q(t)$ in $[0,T]$ satisfies SPBC if the boundaries $q(0)\in
\mathbf{A}$ and $q(T)\in \mathbf{B}$, where $\mathbf{A}$ and $\mathbf{B}$ are
two structural configuration spaces in $(\mathbf{R}^2)^4$ and they depend on a
rotation angle $\theta\in (0,2\pi)$ and the mass ratio $\mu=\frac{m_2}{m_1}\in
\mathbf{R}^+$.
  We show that there is a region $\Omega\subseteq (0,2\pi)\times R^+$ such that
there exists at least one local minimizer of the Lagrangian action functional
on the path space satisfying SPBC $\{q(t)\in H^1([0,T],$ $(\mathbf{R}^2)^4)| $
$q(0)\in $ $\mathbf{A}, q(T)\in $ $\mathbf{B}\}$ for any $(\theta,\mu)\in
\Omega$. The corresponding minimizing path of the minimizer can be extended to
a non-homographic periodic solution if $\theta$ is commensurable with $\pi$ or
a quasi-periodic solution if $\theta$ is not commensurable with $\pi$. In the
variational method with SPBC, we only impose constraints on boundary and we do
not impose any symmetry constraint on solutions. Instead, we prove that our
solutions extended from the initial minimizing pathes have the symmetries.
  The periodic solutions can be further classified as simple choreographic
solutions, double choreographic solutions and non-choreographic solutions.
Among the many stable simple choreographic orbits, the most extraordinary one
is the stable star pentagon choreographic solution when
$(\theta,\mu)=(\frac{4\pi}{5},1)$. Remarkably the unequal-mass variants of the
stable star pentagon are just as stable as the basic equal mass choreography
(See figure 1).


title:
Galaxies with Background QSOs: II. An Automated Search for Multiple
  Galaxy Emission Lines

abstract:
  We have improved upon our previous search technique of systematically
searching QSO spectra for narrow galactic H-alpha emission, which indicates a
foreground galaxy within the Sloan Digital Sky Survey (SDSS) spectral fiber. We
now search for H-alpha plus eight other galactic emission lines in the same
manner. We have scanned the SDSS DR7 QSO catalog spectra searching for these
emission lines. Here we present our sample which focuses on the redshift range
z<0.401 where galactic H-alpha is detectable in the SDSS spectra. This has
revealed 27 unique galaxies on top of QSOs (GOTOQs). We have deblended the QSOs
from the respective galaxies and determined the photometric properties of these
systems. We find upon deblending that most of the galaxies are primarily blue,
late-type galaxies with colors in the range -0.71<(u-r)<2.07. We find a slight
anti-correlation between reddening and impact parameter (E(B-V)_(g-i) vs. b).
The galaxies have average star formation rates of 0.01 to 1 M_sun yr^-1, with
an average of 0.6 M_sun} yr^-1. They range in z from 0 to 0.4 and in stellar
luminosity from about 0.01 L* to 3.0 L*. They are foreground to QSOs of
brightness 17.4 to 20.4 magnitudes (r-band) with impact parameters of 1 to 10
kpc. They represent a fair sample of typical galaxies for which it should be
possible to determine accurately various quantities (e.g. abundances, dust
extinction, Faraday rotation) using follow-up analysis of the background QSOs.
[...]


title: Kepler-like Multi-Plexing for Mass Production of Microlens Parallaxes

abstract:
  We show that a wide-field Kepler-like satellite in Solar orbit could obtain
microlens parallaxes for several thousand events per year that are identified
from the ground, yielding masses and distances for several dozen planetary
events. This is roughly an order of magnitude larger than previously-considered
narrow-angle designs. Such a satellite would, in addition, roughly double the
number of planet detections (and mass/distance determinations). It would also
yield a trove of brown-dwarf binaries with masses, and distances and
(frequently) full orbits, enable new probes of the stellar mass function,
identify isolated black-hole candidates. We show that the actual Kepler
satellite, even with degraded pointing, can demonstrate these capabilities and
make substantial initial inroads into the science potential. We discuss several
"Deltas" to the Kepler satellite aimed at optimizing microlens parallax
capabilities. Most of these would reduce costs. The wide-angle approach
advocated here has only recently become superior to the old narrow-angle
approach, due to the much larger number of ground-based microlensing events now
being discovered.


title:
Doubly Transient Chaos: The Generic Form of Chaos in Autonomous
  Dissipative Systems

abstract:
  Chaos is an inherently dynamical phenomenon traditionally studied for
trajectories that are either permanently erratic or transiently influenced by
permanently erratic ones lying on a set of measure zero. The latter gives rise
to the final state sensitivity observed in connection with fractal basin
boundaries in conservative scattering systems and driven dissipative systems.
Here we focus on the most prevalent case of undriven dissipative systems, whose
transient dynamics fall outside the scope of previous studies since no
time-dependent solutions can exist for asymptotically long times. We show that
such systems can exhibit positive finite-time Lyapunov exponents and
fractal-like basin boundaries which nevertheless have codimension one. In sharp
contrast with its driven and conservative counterparts, the settling rate to
the (fixed-point) attractors grows exponentially in time, meaning that the
fraction of trajectories away from the attractors decays super-exponentially.
While no invariant chaotic sets exist in such cases, the irregular behavior is
governed by transient interactions with transient chaotic saddles, which act as
effective, time-varying chaotic sets.

categories: nlin.CD math.DS nlin.AO physics.class-ph


title: Demystifying Information-Theoretic Clustering

abstract:
  We propose a novel method for clustering data which is grounded in
information-theoretic principles and requires no parametric assumptions.
Previous attempts to use information theory to define clusters in an
assumption-free way are based on maximizing mutual information between data and
cluster labels. We demonstrate that this intuition suffers from a fundamental
conceptual flaw that causes clustering performance to deteriorate as the amount
of data increases. Instead, we return to the axiomatic foundations of
information theory to define a meaningful clustering measure based on the
notion of consistency under coarse-graining for finite data.

categories: cs.LG cs.IT math.IT physics.data-an stat.ML


title: Exceptional Spin groups on hyperelliptic Riemann surfaces

abstract:
  We find all exceptional spin groups attached to the vertices of any
exceptional spin graph on any hyperbolic Riemann surface S of genus g>1. In
particular, we show that when the order r of a graph is r>2 (i.e.the genus of S
must be g>3) then the spin group attached to an exceptional point Q is either
isomorphic to the symmetry group S(r) (when the degree of Q is equal to r) or
to the symmetry group S(r+1)(when the degree of Q is equal to r+1).


title: The Connectedness of Hessenberg Varieties

abstract:
  In this paper we consider certain closed subvarieties of the flag variety,
known as Hessenberg varieties. We give a connectedness criterion for semisimple
Hessenberg varieties generalizing a criterion given by Anderson and Tymoczko.
We show that nilpotent Hessenberg varieties are rationally connected.


title:
Angular analysis of the decay B->K*mumu and studies of mixing and
  CP-violation in the BS0 system with the ATLAS detector

abstract:
  The measurement of B meson decay properties provides an alternative approach
for searches for physics beyond the Standard Model. We present two different
measurements performed with data taken in 2011 with the ATLAS detector at the
Large Hadron collider. The first measurement is based on an angular analysis of
the decay B->K*mumu, and in the second measurement the decay width difference
delta_Gamma_S and the weak phase phi_s of the Bs0 system is determined using
the decay Bs->JPsiPhi. For the second measurement a probability for the flavour
quantum number of the b_quark at production time is determined.


title:
Quantification of the strength of inertial waves in a rotating turbulent
  flow

abstract:
  We quantify the strength of the waves and their impact on the energy cascade
in rotating turbulence by studying the wave number and frequency energy
spectrum, and the time correlation functions of individual Fourier modes in
numerical simulations in three dimensions in periodic boxes. From the spectrum,
we find that a significant fraction of the energy is concentrated in modes with
wave frequency $\omega \approx 0$, even when the external forcing injects no
energy directly into these modes. However, for modes for which the period of
the inertial waves $\tau_\omega$ is faster than the turnover time
$\tau_\textrm{NL}$, a significant fraction of the remaining energy is
concentrated in the modes that satisfy the dispersion relation of the waves. No
evidence of accumulation of energy in the modes with $\tau_\omega =
\tau_\textrm{NL}$ is observed, unlike what critical balance arguments predict.
From the time correlation functions, we find that for modes with $\tau_\omega <
\tau_\textrm{sw}$ (with $\tau_\textrm{sw}$ the sweeping time) the dominant
decorrelation time is the wave period, and that these modes also show a slower
modulation on the timescale $\tau_\textrm{NL}$ as assumed in wave turbulence
theories. The rest of the modes are decorrelated with the sweeping time,
including the very energetic modes modes with $\omega \approx 0$.


title:
Unconditionally stable high-order time integration for moving mesh
  finite difference solution of linear convection-diffusion equations

abstract:
  This paper is concerned with moving mesh finite difference solution of
partial differential equations. It is known that mesh movement introduces an
extra convection term and its numerical treatment has a significant impact on
the stability of numerical schemes. Moreover, many implicit second and higher
order schemes, such as the Crank-Nicolson scheme, will loss their unconditional
stability. A strategy is presented for developing temporally high order,
unconditionally stable finite difference schemes for solving linear
convection-diffusion equations using moving meshes. Numerical results are given
to demonstrate the theoretical findings.


title: Fingerprinting Internet DNS Amplification DDoS Activities

abstract:
  This work proposes a novel approach to infer and characterize Internet-scale
DNS amplification DDoS attacks by leveraging the darknet space. Complementary
to the pioneer work on inferring Distributed Denial of Service (DDoS)
activities using darknet, this work shows that we can extract DDoS activities
without relying on backscattered analysis. The aim of this work is to extract
cyber security intelligence related to DNS Amplification DDoS activities such
as detection period, attack duration, intensity, packet size, rate and
geo-location in addition to various network-layer and flow-based insights. To
achieve this task, the proposed approach exploits certain DDoS parameters to
detect the attacks. We empirically evaluate the proposed approach using 720 GB
of real darknet data collected from a /13 address space during a recent three
months period. Our analysis reveals that the approach was successful in
inferring significant DNS amplification DDoS activities including the recent
prominent attack that targeted one of the largest anti-spam organizations.
Moreover, the analysis disclosed the mechanism of such DNS amplification DDoS
attacks. Further, the results uncover high-speed and stealthy attempts that
were never previously documented. The case study of the largest DDoS attack in
history lead to a better understanding of the nature and scale of this threat
and can generate inferences that could contribute in detecting, preventing,
assessing, mitigating and even attributing of DNS amplification DDoS
activities.


title: Optimal Sensor Placement and Enhanced Sparsity for Classification

abstract:
  The goal of compressive sensing is efficient reconstruction of data from few
measurements, sometimes leading to a categorical decision. If only
classification is required, reconstruction can be circumvented and the
measurements needed are orders-of-magnitude sparser still. We define enhanced
sparsity as the reduction in number of measurements required for classification
over reconstruction. In this work, we exploit enhanced sparsity and learn
spatial sensor locations that optimally inform a categorical decision. The
algorithm solves an l1-minimization to find the fewest entries of the full
measurement vector that exactly reconstruct the discriminant vector in feature
space. Once the sensor locations have been identified from the training data,
subsequent test samples are classified with remarkable efficiency, achieving
performance comparable to that obtained by discrimination using the full image.
Sensor locations may be learned from full images, or from a random subsample of
pixels. For classification between more than two categories, we introduce a
coupling parameter whose value tunes the number of sensors selected, trading
accuracy for economy. We demonstrate the algorithm on example datasets from
image recognition using PCA for feature extraction and LDA for discrimination;
however, the method can be broadly applied to non-image data and adapted to
work with other methods for feature extraction and discrimination.


title: Dynamic Load Balancing in GPU-Based Systems - Early Experiments

abstract:
  The dynamic load-balancing framework in Charm++/AMPI, developed at the
University of Illinois, is based on using processor virtualization to allow
thread migration across processors. This framework has been successfully
applied to many scientific applications in the past, such as BRAMS, NAMD,
ChaNGa, and others. Most of these applications use only CPUs to perform their
operations. However, the use of GPUs to improve computational performance is
quickly getting massively disseminated in the high-performance computing
community. This paper aims to investigate how the same Charm++/AMPI framework
can be extended to balance load in a synthetic application inspired by the
BRAMS numerical forecast model, running mostly on GPUs rather than on CPUs.
Many major questions involving the use of GPUs with AMPI where handled in this
work, including: how to measure the GPU's load, how to use and share GPUs among
user-level threads, and what results are obtained when applying the mandatory
over-decomposition technique to a GPU-accelerated program.


title:
A mathematical model for distinguishing bias from sensitivity effects in
  multialternative detection tasks

abstract:
  Studies investigating the neural bases of cognitive phenomena such as
perception, attention and decision-making increasingly employ multialternative
task designs. It is essential in such designs to distinguish the neural
correlates of behavioral choices arising from changes in perceptual factors,
such as enhanced sensitivity to sensory information, from those arising from
changes in decisional factors, such as a stronger bias for a particular
response or choice (choice bias). To date such a distinction is not possible
with established approaches. Thus, there is a critical need for a theoretical
approach that distinguishes the effects of changes in sensitivity from those of
changes in choice bias in multialternative tasks. Here, we introduce a
mathematical model that decouples choice bias from perceptual sensitivity
effects in multialternative detection tasks: multialternative tasks that
incorporate catch trials to measure the ability to detect one among multiple
(potential) stimuli or stimulus features. By formulating the perceptual
decision in a novel, multidimensional signal detection framework, our model
identifies the distinct effects of bias and sensitivity on behavioral choices.
With a combination of analytical and numerical approaches, we demonstrate that
model parameters (sensitivity, bias) are estimated reliably and uniquely, even
in tasks involving arbitrarily large numbers of alternatives. Model simulations
revealed that ignoring choice bias or performance during catch trials produced
systematically inaccurate estimates of perceptual sensitivity, a finding that
has important implications for interpreting behavioral data in multialternative
detection and cued attention tasks. The model will find important application
in identifying the effects of neural perturbations (stimulation or
inactivation) on an animal's perception in multialternative attention and
decision-making tasks.


title:
Three maximally entangled states can require two-way LOCC for local
  discrimination

abstract:
  We show that there exist sets of three mutually orthogonal $d$-dimensional
maximally entangled states which cannot be perfectly distinguished using
one-way local operations and classical communication (LOCC) for arbitrarily
large values of $d$. This contrasts with several well-known families of
maximally entangled states, for which any three states can be perfectly
distinguished. We then show that two-way LOCC is sufficient to distinguish
these examples. We also show that any three mutually orthogonal $d$-dimensional
maximally entangled states can be perfectly distinguished using measurements
with a positive partial transpose (PPT) and can be distinguished with one-way
LOCC with high probability. These results circle around the question of whether
there exist three maximally entangled states which cannot be distinguished
using the full power of LOCC; we discuss possible approaches to answer this
question.


title: Flow of Navier-Stokes Fluids in Converging-Diverging Distensible Tubes

abstract:
  We use a method based on the lubrication approximation in conjunction with a
residual-based mass-continuity iterative solution scheme to compute the flow
rate and pressure field in distensible converging-diverging tubes for
Navier-Stokes fluids. We employ an analytical formula derived from a
one-dimensional version of the Navier-Stokes equations to describe the
underlying flow model that provides the residual function. This formula
correlates the flow rate to the boundary pressures in straight cylindrical
elastic tubes with constant-radius. We validate our findings by the convergence
toward a final solution with fine discretization as well as by comparison to
the Poiseuille-type flow in its convergence toward analytic solutions found
earlier in rigid converging-diverging tubes. We also tested the method on
limiting special cases of cylindrical elastic tubes with constant-radius where
the numerical solutions converged to the expected analytical solutions. The
distensible model has also been endorsed by its convergence toward the rigid
Poiseuille-type model with increasing the tube wall stiffness.
Lubrication-based one-dimensional finite element method was also used for
verification. In this investigation five converging-diverging geometries are
used for demonstration, validation and as prototypes for modeling
converging-diverging geometries in general.


title:
Nanoscale Spin Seebeck Rectifier: Controlling Thermal Spin Transport
  across Insulating Magnetic Junctions with Localized Spin

abstract:
  The spin Seebeck effect is studied across a charge insulating magnetic
junction, in which thermal-spin conjugate transport is assisted by the exchange
interactions between the localized spin in the center and electrons in metallic
leads. We show that, in contrast with bulk spin Seebeck effect, the figure of
merit of such nanoscale thermal-spin conversion can be infinite, leading to the
ideal Carnot efficiency in the linear response regime. We also find that in the
nonlinear spin Seebeck transport regime, the device possesses the asymmetric
and negative differential spin Seebeck effects. In the last, the situations
with leaking electron tunneling are also discussed. This nanoscale thermal spin
rectifier, by tuning the junction parameters, can act as a spin Seebeck diode,
spin Seebeck transistor and spin Seebeck switch, which could have substantial
implications for flexible thermal and information control in molecular spin
caloritronics.


title: Exact Learning of RNA Energy Parameters From Structure

abstract:
  We consider the problem of exact learning of parameters of a linear RNA
energy model from secondary structure data. A necessary and sufficient
condition for learnability of parameters is derived, which is based on
computing the convex hull of union of translated Newton polytopes of input
sequences. The set of learned energy parameters is characterized as the convex
cone generated by the normal vectors to those facets of the resulting polytope
that are incident to the origin. In practice, the sufficient condition may not
be satisfied by the entire training data set; hence, computing a maximal subset
of training data for which the sufficient condition is satisfied is often
desired. We show that problem is NP-hard in general for an arbitrary
dimensional feature space. Using a randomized greedy algorithm, we select a
subset of RNA STRAND v2.0 database that satisfies the sufficient condition for
separate A-U, C-G, G-U base pair counting model. The set of learned energy
parameters includes experimentally measured energies of A-U, C-G, and G-U
pairs; hence, our parameter set is in agreement with the Turner parameters.


title: Localization phase diagram of two-dimensional quantum percolation

abstract:
  We examine quantum percolation on a square lattice with random dilution up to
$q=38%$ and energy $0.001 \le E \le 1.6$ (measured in units of the hopping
matrix element), using numerical calculations of the transmission coefficient
at a much larger scale than previously. Our results confirm the previous
finding that the two dimensional quantum percolation model exhibits
localization-delocalization transitions, where the localized region splits into
an exponentially localized region and a power-law localization region. We
determine a fuller phase diagram confirming all three regions for energies as
low as $E=0.1$, and the delocalized and exponentially localized regions for
energies down to $E=0.001$. We also examine the scaling behavior of the
residual transmission coefficient in the delocalized region, the power law
exponent in the power-law localized region, and the localization length in the
exponentially localized region. Our results suggest that the residual
transmission at the delocalized to power-law localized phase boundary may be
discontinuous, and that the localization length is likely not to diverge with a
power-law at the exponentially localized to power-law localized phase boundary.
However, further work is needed to definitively assess the characters of the
two phase transitions as well as the nature of the intermediate power-law
regime.


title: Magnetic properties of two-dimensional charged spin-1 Bose gases

abstract:
  Within the mean-field theory, we investigate the magnetic properties of a
charged spin-1 Bose gas in two dimension. In this system the diamagnetism
competes with paramagnetism, where Lande-factor $g$ is introduced to describe
the strength of the paramagnetic effect. The system presents a crossover from
diamagnetism to paramagnetism with the increasing of Lande-factor. The critical
value of the Lande-factor, $g_{c}$, is discussed as a function of the
temperature and magnetic field. We get the same value of $g_{c}$ both in the
low temperature and strong magnetic field limit. Our results also show that in
very weak magnetic field no condensation happens in the two dimensional charged
spin-1 Bose gas.


title: The Colored Hadwiger Transversal Theorem in $\mathbb R^d$

abstract:
  Hadwiger's transversal theorem gives necessary and sufficient conditions for
a family of convex sets in the plane to have a line transversal. A higher
dimensional version was obtained by Goodman, Pollack and Wenger, and recently a
colorful version appeared due to Arocha, Bracho and Montejano. We show that it
is possible to combine both results to obtain a colored version of Hadwiger's
theorem in higher dimensions. The proofs differ from the previous ones and use
a variant of the Borsuk-Ulam theorem. To be precise, we prove the following.
Let $F$ be a family of convex sets in $\mathbb R^d$ in bijection with a family
$P$ of points in $\mathbb R^{d-1}$. Assume that there is a coloring of $F$ with
sufficiently many colors such that any colorful Radon partition of points in
$P$ corresponds to a colorful Radon partition of sets in $F$. Then some
monochromatic subfamily of $F$ has a hyperplane transversal.


title: On Measure Concentration of Random Maximum A-Posteriori Perturbations

abstract:
  The maximum a-posteriori (MAP) perturbation framework has emerged as a useful
approach for inference and learning in high dimensional complex models. By
maximizing a randomly perturbed potential function, MAP perturbations generate
unbiased samples from the Gibbs distribution. Unfortunately, the computational
cost of generating so many high-dimensional random variables can be
prohibitive. More efficient algorithms use sequential sampling strategies based
on the expected value of low dimensional MAP perturbations. This paper develops
new measure concentration inequalities that bound the number of samples needed
to estimate such expected values. Applying the general result to MAP
perturbations can yield a more efficient algorithm to approximate sampling from
the Gibbs distribution. The measure concentration result is of general interest
and may be applicable to other areas involving expected estimations.


title: Luminescence of cadmium fluoride doped with rare-earth ions

abstract:
  Absorption, excitation and emission spectra of cadmium fluoride crystals
doped with rare-earth ions were investigated. In contrast to alkaline-earth
fluorides the absorption spectra due to 4f - 5d transitions of Ce$^{3+}$,
Pr$^{3+}$ and Tb$^{3+}$ ions are broadened. No 5d-4f emissions were observed.
These prove that 5d(e$_g$) levels of rare earth ions lie in conduction band of
CdF$_2$ crystal. Emission spectra of Tb$^{3+}$ show the group of 4f-4f
$^5$D$_4$-$^7$F$_j$ lines in contrast to other alkaline-earth fluorides where
emission due to $^5$D$_3$-$^7$F$_j$ transitions is also observed. The absence
of the emission is due to position of $^5$D$_3$ level within condution band.
  Among the all measured crystals doped with impurity ions (Pr, Nd, Eu, Ho, Tb,
Tm, Yb, Ga, In or Mn), the CdF$_2$ doped with Pr$^{3+}$, Tb$^{3+}$, or
Mn$^{2+}$ ions have the highest light outputs under x-ray excitation.


title: Constructing a class of topological solitons in magnetohydrodynamics

abstract:
  We present a class of topological plasma configurations characterized by
their toroidal and poloidal winding numbers, $n_t$ and $n_p$ respectively. The
special case of $n_t=1$ and $n_p=1$ corresponds to the Kamchatnov-Hopf soliton,
a magnetic field configuration everywhere tangent to the fibers of a Hopf
fibration so that the field lines are circular, linked exactly once, and form
the surfaces of nested tori. We show that for $n_t \in \mathbb{Z}^+$ and
$n_p=1$ these configurations represent stable, localized solutions to the
magnetohydrodynamic equations for an ideal incompressible fluid with infinite
conductivity. Furthermore, we extend our stability analysis by considering a
plasma with finite conductivity and estimate the soliton lifetime in such a
medium as a function of the toroidal winding number.


title: About the global magnetic fields of stars

abstract:
  We present a review of observations of the stellar longitudinal (effective)
magnetic field ($B_e$) and its properties. This paper also discusses
contemporary views on the origin, evolution and structure of $B_e$.


title:
Dynamic cache reconfiguration based techniques for improving cache
  energy efficiency

abstract:
  Modern multicore processors are employing large last-level caches, for
example Intel's E7-8800 processor uses 24MB L3 cache. Further, with each CMOS
technology generation, leakage energy has been dramatically increasing and
hence, leakage energy is expected to become a major source of energy
dissipation, especially in last-level caches (LLCs). The conventional schemes
of cache energy saving either aim at saving dynamic energy or are based on
properties specific to first-level caches, and thus these schemes have limited
utility for last-level caches. Further, several other techniques require
offline profiling or per-application tuning and hence are not suitable for
product systems. In this research, we propose novel cache leakage energy saving
schemes for single-core and multicore systems; desktop, QoS, real-time and
server systems. We propose software-controlled, hardware-assisted techniques
which use dynamic cache reconfiguration to configure the cache to the most
energy efficient configuration while keeping the performance loss bounded. To
profile and test a large number of potential configurations, we utilize
low-overhead, micro-architecture components, which can be easily integrated
into modern processor chips. We adopt a system-wide approach to save energy to
ensure that cache reconfiguration does not increase energy consumption of other
components of the processor. We have compared our techniques with the
state-of-art techniques and have found that our techniques outperform them in
their energy efficiency. This research has important applications in improving
energy-efficiency of higher-end embedded, desktop, server processors and
multitasking systems. We have also proposed performance estimation approach for
efficient design space exploration and have implemented time-sampling based
simulation acceleration approach for full-system architectural simulators.


title:
Critical phenomena and noise-induced phase transitions in neuronal
  networks

abstract:
  We study numerically and analytically first- and second-order phase
transitions in neuronal networks stimulated by shot noise (a flow of random
spikes bombarding neurons). Using an exactly solvable cortical model of
neuronal networks on classical random networks, we find critical phenomena
accompanying the transitions and their dependence on the shot noise intensity.
We show that a pattern of spontaneous neuronal activity near a critical point
of a phase transition is a characteristic property that can be used to identify
the bifurcation mechanism of the transition. We demonstrate that bursts and
avalanches are precursors of a first-order phase transition, paroxysmal-like
spikes of activity precede a second-order phase transition caused by a
saddle-node bifurcation, while irregular spindle oscillations represent
spontaneous activity near a second-order phase transition caused by a
supercritical Hopf bifurcation. Our most interesting result is the observation
of the paroxysmal-like spikes. We show that a paroxysmal-like spike is a single
nonlinear event that appears instantly from a low background activity with a
rapid onset, reaches a large amplitude, and ends up with an abrupt return to
lower activity. These spikes are similar to single paroxysmal spikes and sharp
waves observed in EEG measurements. Our analysis shows that above the
saddle-node bifurcation, sustained network oscillations appear with a large
amplitude but a small frequency in contrast to network oscillations near the
Hopf bifurcation that have a small amplitude but a large frequency. We discuss
an amazing similarity between excitability of the cortical model stimulated by
shot noise and excitability of the Morris-Lecar neuron stimulated by an applied
current.


title: The surface density of states of layered {\it f}-electron materials

abstract:
  We theoretically analyze the surface density of states of heavy fermion
materials such as CeCoIn$_5$. Recent experimental progress made it possible to
locally probe the formation of heavy quasi-particles in these systems via
scanning tunneling microscopy, in which strongly temperature-dependent
resonances at the Fermi energy have been observed. The shape of these
resonances varies depending on the surface layer, i.e. if Cerium or Cobalt
terminates the sample. We clarify the microscopic origin of this difference by
taking into account the layered structure of the material. Our simple model
explains all the characteristic properties observed experimentally, such as a
layer-dependent shape of the resonance at the Fermi energy, displaying a
hybridization gap for the Cerium-layer and a peak or dip structure for the
other layers. Our proposal resolves the seemingly unphysical assumptions in the
preceding analysis based on the two-channel cotunneling model.


title: Capillary fracture of soft gels

abstract:
  A liquid droplet resting on a soft gel substrate can deform that substrate to
the point of material failure, whereby fractures develop on the gel surface
that propagate outwards from the contact-line in a starburst pattern. In this
paper, we characterize i) the initiation process in which the number of arms in
the starburst is controlled by the ratio of surface tension contrast to the
gel's elastic modulus and ii) the propagation dynamics showing that once
fractures are initiated they propagate with a universal power law $L\propto
t^{3/4}$. We develop a model for crack initiation by treating the gel as a
linear elastic solid and computing the deformations within the substrate from
the liquid/solid wetting forces. The elastic solution shows that both the
location and magnitude of the wetting forces are critical in providing a
quantitative prediction for the number of fractures and, hence, an
interpretation of the initiation of capillary fractures. This solution also
reveals that the depth of the gel is an important factor in the fracture
process, as it can help mitigate large surface tractions; this finding is
confirmed with experiments. We then develop a model for crack propagation by
considering the transport of an inviscid fluid into the fracture tip of an
incompressible material, and find that a simple energy-conservation argument
can explain the observed material-independent power law. We compare predictions
for both linear elastic and neo-Hookean solids finding that the latter better
explains the observed exponent.


title:
Collision Dynamics of Particle Clusters in a Two-dimensional Granular
  Gas

abstract:
  In a granular gas, inelastic collisions produce an instability in which the
constituent particles cluster heterogeneously. These clusters then interact
with each other, further decreasing their kinetic energy. We report experiments
of the free collisions of dense clusters of particles in a two-dimensional
geometry. The particles are composed of solid CO$_{2}$, which float nearly
frictionlessly on a hot surface due to sublimated vapor. After two dense
clusters of $\approx$ 100 particles collide, there are two distinct stages of
evolution. First, the translational kinetic energy rapidly decreases by over
90% as a "jamming front" sweeps across each cluster. Subsequently, the kinetic
energy decreases more slowly as the particles approach the container
boundaries. In this regime, the measured velocity distributions are
non-Gaussian with long tails. Finally, we compare our experiments to computer
simulations of colliding, two-dimensional, granular clusters composed of
circular, viscoelastic particles with friction.


title:
Discovery of the recombining plasma in the south of the Galactic center;
  a relic of the past Galactic center activity?

abstract:
  We report Suzaku results for soft X-ray emission to the south of the Galactic
center (GC). The emission (hereafter "GC South") has an angular size of ~42' x
16' centered at (l, b) ~ (0.0, -1.4), and is located in the largely extended
Galactic ridge X-ray emission (GRXE). The X-ray spectrum of GC South exhibits
emission lines from highly ionized atoms. Although the X-ray spectrum of the
GRXE can be well fitted with a plasma in collisional ionization equilibrium
(CIE), that of GC South cannot be fitted with a plasma in CIE, leaving
hump-like residuals at ~2.5 and 3.5 keV, which are attributable to the
radiative recombination continua of the K-shells of Si and S, respectively. In
fact, GC South spectrum is well fitted with a recombination-dominant plasma
model; the electron temperature is 0.46 keV while atoms are highly ionized (kT
= 1.6 keV) in the initial epoch, and the plasma is now in a recombining phase
at a relaxation scale (plasma density x elapsed time) of 5.3 x 10^11 s cm^-3.
The absorption column density of GC South is consistent with that toward the GC
region. Thus GC South is likely to be located in the GC region (~8 kpc
distance). The size of the plasma, the mean density, and the thermal energy are
estimated to be 97 pc x 37 pc, 0.16 cm^-3, and 1.6 x 10^51 erg, respectively.
We discuss possible origins of the recombination-dominant plasma as a relic of
past activity in the GC region.


abstract:
  We show how to construct Darmon points on elliptic curves over totally real
fields.


title: Non-Linear Spin Dynamics Of The Electron Liquid In Nanosystems

abstract:
  We investigate the dynamics of spin-nonequilibrium electron systems in the
hydrodynamic flow regime, when the normal scattering processes, which conserve
the total quasi-momentum of the system of electrons and quasi-particles that
interact with them, dominate over other scattering processes. We obtain a set
of spin-hydrodynamic equations for the case of an arbitrary electron spectrum
that varies slowly with the coordinates. Solving the one-dimensional non-linear
problem we found the exact solutions both for the electrical potential in the
open-ends circuit and for the spin-electrical oscillation in an inhomogeneous
conducting ring. As we demonstrate, the oscillation characteristics are
different in the cases of a magnetic ring and a non-magnetic ring to which the
spin polarization was injected. We found also that a voltage between the ends
of the open circuit may reveal the presence of an inhomogeneous spin
polarization of the electron density.


title: Picosecond Dynamics of Internal Exciton Transitions in CdSe Nanorods

abstract:
  The picosecond dynamics of excitons in colloidal CdSe nanorods are directly
measured via their 1s to 2p-like internal transitions by ultra-broadband
terahertz spectroscopy. Broadened absorption peaks from both the longitudinal
and transverse states are observed at 8.5 and 11 THz, respectively. The onset
of exciton-LO phonon coupling appears as a bleach in the optical conductivity
spectra at the LO phonon energy for times > 1 ps after excitation. Simulations
show a suppressed exciton temperature due to thermally excited hole states
being rapidly captured onto ligands or unpassivated surface states. The
relaxation kinetics are manipulated and the longitudinal transition is quenched
by surface ligand exchange with hole capturing pyridine.


title:
Detection of a single fundamental charge with nanoscale resolution in
  ambient conditions using the NV$^-$ center in diamond

abstract:
  Single charge detection with nanoscale spatial resolution in ambient
conditions is a current frontier in metrology that has diverse
interdisciplinary applications. Here, such single charge detection is
demonstrated using two nitrogen-vacancy (NV) centers in diamond. One NV center
is employed as a sensitive electrometer to detect the change in electric field
created by the displacement of a single electron resulting from the optical
switching of the other NV center between its neutral (NV$^0$) and negative
(NV$^-$) charge states. As a consequence, our measurements also provide direct
insight into the charge dynamics inside the material.


title:
A generalized Debye source approach to electromagnetic scattering in
  layered media

abstract:
  The standard solution to time-harmonic electromagnetic scattering problems in
homogeneous layered media relies on the use of the electric field dyadic
Green's function. However, for small values of the governing angular frequency
$\omega$, evaluation of the electric field using this Green's function exhibits
numerical instability. In this short note, we provide an alternative approach
which is immune from this low-frequency breakdown as $\omega \to 0$. Our
approach is based on the generalized Debye source representation of Maxwell
fields. Using this formulation, the electric and magnetic fields gracefully
decouple in the static limit, a behavior similar to that of the classical
Lorenz-Debye-Mie representation of Maxwell fields in spherical geometries. We
derive extensions of both the generalized Deybe source and Lorenz-Debye-Mie
representations to planar geometries, as well as provide equations for the
solution of scattering from a perfectly conducting half-space and in layered
media using a Sommerfeld-like approach. These formulas are stable as $\omega$
tends to zero, and offer alternatives to the electric field dyadic Green's
function.

categories: physics.class-ph math-ph math.MP math.NA


title:
Implicit solvation model for density-functional study of nanocrystal
  surfaces and reaction pathways

abstract:
  Solid-liquid interfaces are at the heart of many modern-day technologies and
provide a challenge to many materials simulation methods. A realistic
first-principles computational study of such systems entails the inclusion of
solvent effects. In this work we implement an implicit solvation model that has
a firm theoretical foundation into the widely used density-functional code
VASP. The implicit solvation model follows the framework of joint density
functional theory. We describe the framework, our algorithm and implementation,
and benchmarks for small molecular systems. We apply the solvation model to
study the surface energies of different facets of semiconducting and metallic
nanocrystals and the S$_{\text{N}} 2$ reaction pathway. We find that solvation
reduces the surface energies of the nanocrystals, especially for the
semiconducting ones and increases the energy barrier of the S$_{\text{N}} 2$
reaction.


title:
The monodromy representation and twisted period relations for Appell's
  hypergeometric function F_4

abstract:
  We consider the system $\mathcal{F}_4(a,b,c)$ of differential equations
annihilating Appell's hypergeometric series $F_4(a,b,c;x)$. We find the
integral representations for four linearly independent solutions expressed by
the hypergeometric series $F_4$. By using the intersection forms of twisted
(co)homology groups associated with them, we provide the monodromy
representation of $\mathcal{F}_4(a,b,c)$ and the twisted period relations for
the fundamental systems of solutions of $\mathcal{F}_4$.


title:
Progenitor Type Identification for Supernova Remnant N103B in the Large
  Magellanic Cloud by Suzaku and Chandra Observations

abstract:
  This paper presents a detailed analysis of supernova remnant (SNR) N103B
located in the Large Magellanic Cloud (LMC), based on Suzaku and Chandra
observations. The spectrum of the entire SNR was reproduced using 3 ISM
components with the kT of 0.32, 0.56, and 0.92keV and one ejecta component of
3.96keV, based on spectral analysis of the Suzaku/XIS data. The ejecta was
overabundant in heavy elements, such as Mg, Si, S, Ca, Fe, and Ni. The
unprecedentedly high quality of data obtained by XIS, allowed us to correctly
distinguish between the emissions from the ISM and the ejecta for the first
time. Combining XIS spectral analysis with Chandra/ACIS image analysis, we
verified that the ejecta distributions for elements from Si to Fe-K were
similar to one another, although Fe-K emission was located slightly inward
compared with that of lighter elements such as Si, S, Ar, and Ca. The
onion-like structure of the ejecta was maintained after the SN. In addition,
the ISM emission represented by O and Fe-L was located inside the ejecta
emission. We compared hydrogen-rich ejecta plasma, which is indicative of Type
II SNRs, with plasma rich in heavy elements and poor in hydrogen, which is
mainly observed in Type Ia. In the case of N103B, we could not determine
whether the origin of the continuum emission in the 4.0-6.0keV band was from
ejecta or high-temperature ISM only based on the spectral modeling of XIS data.
High-energy continuum images in the 5.2-6.0keV band obtained by ACIS were
extremely similar to those of ejecta, implying that the origin of the
high-energy continuum might indeed be the ejecta. By combining spectral
analysis with high-energy continuum images, we found some indications for
H-dominated plasma, and as a result, that the progenitor of N103B might have
been a Type II. The progenitor mass was estimated to be 13 Msun based on the
abundance patterns of Mg, Fe, and Ni relative to Si.


title: Galois branched covers with fixed ramification locus

abstract:
  We examine conditions under which there exists a non-constant family of
Galois branched covers of curves over an algebraically closed field $k$ of
fixed degree and fixed ramification locus, under a notion of equivalence
derived from considering linear series on a fixed smooth proper source curve
$X$. We show such a family exists precisely when the following conditions are
satisfied: $\operatorname{char}(k)=p>0$, $X$ is isomorphic to $\mathbb{P}^1_k$,
there is a unique ramification point, and the Galois group is
$(\mathbb{Z}/p\mathbb{Z})^m$ for some integer $m>0$.


title: Index theory of the de Rham complex on manifolds with periodic ends

abstract:
  We study the de Rham complex on a smooth manifold with a periodic end modeled
on an infinite cyclic cover X' \to X. The completion of this complex in
exponentially weighted L^2-norms is Fredholm for all but finitely many
exceptional weights determined by the eigenvalues of the covering translation
map H_*(X') \to H_*(X'). We calculate the index of this weighted de Rham
complex for all weights away from the exceptional ones.


title: Scattering by a long-range potential

abstract:
  The phenomenon of wave tails has attracted much attention over the years from
both physicists and mathematicians. However, our understanding of this
fascinating phenomenon is not complete yet. In particular, most former studies
of the tail phenomenon have focused on scattering potentials which approach
zero asymptotically ($x\to\infty$) faster than $x^{-2}$. It is well-known that
for these (rapidly decaying) scattering potentials the late-time tails are
determined by the first Born approximation and are therefore {\it linear} in
the amplitudes of the scattering potentials (there are, however, some
exceptional cases in which the first Born approximation vanishes and one has to
consider higher orders of the scattering problem). In the present study we
analyze in detail the late-time dynamics of the Klein-Gordon wave equation with
a ({\it slowly} decaying) Coulomb-like scattering potential:
$V(x\to\infty)=\alpha/x$. In particular, we write down an explicit solution
(that is, an exact analytic solution which is not based on the first Born
approximation) for this scattering problem. It is found that the asymptotic
($t\to\infty$) late-time behavior of the fields depends {\it non}-linearly on
the amplitude $\alpha$ of the scattering potential. This non-linear dependence
on the amplitude of the scattering potential reflects the fact that the
late-time dynamics associated with this slowly decaying scattering potential is
dominated by {\it multiple} scattering from asymptotically far regions.


title:
Trapped-ion decay spectroscopy towards the determination of ground-state
  components of double-beta decay matrix elements

abstract:
  A new technique has been developed at TRIUMF's TITAN facility to perform
in-trap decay spectroscopy. The aim of this technique is to eventually measure
weak electron capture branching ratios (ECBRs) and by this to consequently
determine GT matrix elements of $\beta\beta$ decaying nuclei. These branching
ratios provide important input to the theoretical description of these decays.
The feasibility and power of the technique is demonstrated by measuring the
ECBR of $^{124}$Cs.


title: Mapping the stereotyped behaviour of freely-moving fruit flies

abstract:
  Most animals possess the ability to actuate a vast diversity of movements,
ostensibly constrained only by morphology and physics. In practice, however, a
frequent assumption in behavioral science is that most of an animal's
activities can be described in terms of a small set of stereotyped motifs. Here
we introduce a method for mapping the behavioral space of organisms, relying
only upon the underlying structure of postural movement data to organize and
classify behaviors. We find that six different drosophilid species each perform
a mix of non-stereotyped actions and over one hundred hierarchically-organized,
stereotyped behaviors. Moreover, we use this approach to compare these species'
behavioral spaces, systematically identifying subtle behavioral differences
between closely-related species.


title:
Imaging of the solar atmosphere by the Siberian Solar Radio Telescope at
  5.7 GHz with an enhanced dynamic range

abstract:
  The Siberian Solar Radio Telescope (SSRT) is a solar-dedicated
directly-imaging interferometer observing the Sun at 5.7 GHz. The SSRT operates
in the two-dimensional mode since 1996. The imaging principle of the SSRT
restricts its opportunities in observations of very bright flare sources, while
it is possible to use `dirty' images in studies of low brightness features,
which do not overlap with side lobes from bright sources. The interactive CLEAN
technique routinely used for the SSRT data provides imaging of active regions
but consumes much time and efforts and does not reveal low-brightness features
below the CLEAN threshold. The newly developed technique combines the CLEAN
routine with the directly imaging capability of the SSRT and provides clean
images with an enhanced dynamic range automatically. These elaborations
considerably extend the range of tasks, which can be solved with the SSRT. We
show some examples of the present opportunities of the SSRT and compare its
data with the images produced by the Nobeyama Radioheliograph at 17 GHz as well
as observations in different spectral ranges.


title:
High-Order Discontinuous Galerkin Finite Element Methods with Globally
  Divergence-Free Constrained Transport for Ideal MHD

abstract:
  The modification of the celebrated Yee scheme from Maxwell equations to
magnetohydrodynamics is often referred to as the constrained transport
approach. Constrained transport can be viewed as a sort of predictor-corrector
method for updating the magnetic field, where a magnetic field value is first
predicted by a method that does not preserve the divergence-free condition on
the magnetic field, followed by a correction step that aims to control these
divergence errors. This strategy has been successfully used in conjunction with
a variety of shock-capturing methods including WENO, central, and wave
propagation schemes. In this work we show how to extend the basic CT framework
to the discontinuous Galerkin finite element method on both 2D and 3D Cartesian
grids. We first review the entropy-stability theory for semi-discrete DG
discretizations of ideal MHD, which rigorously establishes the need for a
magnetic field that satisfies the following conditions: (1) the divergence of
the magnetic field is zero on each element, and (2) the normal components of
the magnetic field are continuous across element edges/faces. In order to
achieve such a globally divergence-free magnetic field, we introduce a novel CT
scheme that is based on two ingredients: (1) we introduce an element-centered
magnetic vector potential that is updated via a discontinuous Galerkin scheme
on the induction equation; and (2) we define a mapping that takes
element-centered magnetic field values and element-centered magnetic vector
potential values and creates on each edge /face a representation of the normal
component of the magnetic field; this representation is then mapped back to the
elements to create a globally divergence-free element-centered representation
of the magnetic field. For problems with shock waves, we make use of so-called
moment-based limiters to control oscillations in the conserved quantities.


title: Multilabel Consensus Classification

abstract:
  In the era of big data, a large amount of noisy and incomplete data can be
collected from multiple sources for prediction tasks. Combining multiple models
or data sources helps to counteract the effects of low data quality and the
bias of any single model or data source, and thus can improve the robustness
and the performance of predictive models. Out of privacy, storage and bandwidth
considerations, in certain circumstances one has to combine the predictions
from multiple models or data sources to obtain the final predictions without
accessing the raw data. Consensus-based prediction combination algorithms are
effective for such situations. However, current research on prediction
combination focuses on the single label setting, where an instance can have one
and only one label. Nonetheless, data nowadays are usually multilabeled, such
that more than one label have to be predicted at the same time. Direct
applications of existing prediction combination methods to multilabel settings
can lead to degenerated performance. In this paper, we address the challenges
of combining predictions from multiple multilabel classifiers and propose two
novel algorithms, MLCM-r (MultiLabel Consensus Maximization for ranking) and
MLCM-a (MLCM for microAUC). These algorithms can capture label correlations
that are common in multilabel classifications, and optimize corresponding
performance metrics. Experimental results on popular multilabel classification
tasks verify the theoretical analysis and effectiveness of the proposed
methods.


title: Applying Gaussian quantum discord to quantum key distribution

abstract:
  In this paper, we theoretically prove that the Gaussian quantum discord state
of optical field can be used to complete continuous variable (CV) quantum key
distribution (QKD). The calculation shows that secret key can be distilled with
a Gaussian quantum discord state against entangling cloner attack. Secret key
rate is increased with the increasing of quantum discord for CV QKD with the
Gaussian quantum discord state. Although the calculated results point out that
secret key rate using the Gaussian quantum discord state is lower than that
using squeezed state and coherent state at the same energy level, we
demonstrate that the Gaussian quantum discord, which only involving quantum
correlation without the existence of entanglement, may provide a new resource
for realizing CV QKD.


title: Multivariate time-space harmonic polynomials: a symbolic approach

abstract:
  By means of a symbolic method, in this paper we introduce a new family of
multivariate polynomials such that multivariate L\'evy processes can be dealt
with as they were martingales. In the univariate case, this family of
polynomials is known as time-space harmonic polynomials. Then, simple
closed-form expressions of some multivariate classical families of polynomials
are given. The main advantage of this symbolic representation is the plainness
of the setting which reduces to few fundamental statements but also of its
implementation in any symbolic software. The role played by cumulants is
emphasized within the generalized Hermite polynomials. The new class of
multivariate L\'evy-Sheffer systems is introduced.


title:
Dynamics of skyrmions in chiral magnets: dynamic phase transitions and
  equation of motion

abstract:
  We study the dynamics of skyrmions in a metallic chiral magnet. First we show
that skyrmions can be created dynamically by destabilizing the ferromagnetic
background state through a spin polarized current. We then treat skyrmions as
rigid particles and derive the corresponding equation of motion. The dynamics
of skyrmions is dominated by the Magnus force, which accounts for the weak
pinning of skyrmions observed in experiments. Finally we discuss the quantum
motion of skyrmions.


title: Fe K lines in the nuclear region of M82

abstract:
  We study the spatial distribution of the Fe 6.4 and 6.7 keV lines in the
nuclear region of M82 using the Chandra archival data with a total exposure
time of 500 ks. The deep exposure provides a significant detection of the Fe
6.4 keV line. Both the Fe 6.4 and 6.7 keV lines are diffuse emissions with
similar spatial extent, but their morphology do not exactly follow each other.
Assuming a thermal collisional-ionization-equilibrium model, the fitted
temperatures are around 5-6 keV and the Fe abundances are about 0.4-0.6 solar
value. We also report the spectrum of a point source, which shows a strong Fe
6.7 keV line and is likely a supernova remnant or a superbubble. The fitted Fe
abundance of the point source is 1.7 solar value. It implies that part of the
iron may be depleted from the X-ray emitting gases as the predicted abundance
is about 5 solar value assuming complete mixing. If this is a representative
case of the Fe enrichment, a mild mass-loading of a factor of 3 will make the
Fe abundance of the point source in agreement with that of the hot gas, which
then implies that most of the hard X-ray continuum (2-8 keV) of M82 has a
thermal origin. In addition, the Fe 6.4 keV line is consistent with the
fluorescence emission irradiated by the hard photons from nuclear point
sources.


title: The (S,{2})-Iwasawa theory

abstract:
  Iwasawa made the fundamental discovery that there is a close connection
between the ideal class groups of $\mathbb{Z}_{p}$-extensions of cyclotomic
fields and the $p$-adic analogue of Riemann's zeta functions
$$\zeta(s)=\sum_{n=1}^{\infty}\frac{1}{n^{s}}.$$
  In this paper, we show that there may also exist a parallel Iwasawa's theory
corresponding to the $p$-adic analogue of Euler's deformation of zeta functions
$$\phi(s)=\sum_{n=1}^{\infty}\frac{(-1)^{n-1}}{n^{s}}.$$


title:
Scientifically unacceptable concept of the Epoch of Malthusian
  Stagnation

abstract:
  In order to control the growth of human population it is helpful to
understand correctly the mechanism of growth, and the first essential step is
to investigate current interpretations and reject any unscientific
explanations. One of such popular but questionable interpretations is the
concept of the Epoch of Malthusian Stagnation. We discuss its origin, narrative
and claims. We explain why this concept is scientifically unacceptable. This
investigation questions also the closely-related Demographic Transition Theory,
whose essential component is the assumed mechanism of Malthusian stagnation for
the first stage of growth.


title: Range-Renewal Structure of I.I.D. Samplings

abstract:
  In this note the range-renewal structure of general independent and
identically distributed samplings is discussed, which is a natural extension of
the result in Chen et al (arXiv:1305.1829).


title: A Switch for Artificial Resistivity and Other Dissipation Terms

abstract:
  We describe a new switch to reduce dissipation from artificial resistivity in
Smoothed Particle Magnetohydrodynamics simulations. The switch utilises the
gradient of the magnetic field to detect shocks, setting alpha_B = h |gradB| /
|B|. This measures the relative degree of discontinuity, and the switch is not
dependent on the absolute field strength. We present results comparing the new
resistivity switch to the switch of Price & Monaghan (2005), showing that it is
more robust in capturing shocks (especially in weak fields), while leading to
less overall dissipation. The design of this switch is generalised to create
similar switches for artificial viscosity and thermal conduction, with proof of
concept tests conducted on a Sod shock tube and Kelvin-Helmholtz instabilities.


title:
An Online Algorithm for Separating Sparse and Low-dimensional Signal
  Sequences from their Sum

abstract:
  This paper designs and evaluates a practical algorithm, called practical
recursive projected compressive sensing (Prac-ReProCS), for recovering a time
sequence of sparse vectors $S_t$ and a time sequence of dense vectors $L_t$
from their sum, $M_t:= S_t + L_t$, when any subsequence of the $L_t$'s lies in
a slowly changing low-dimensional subspace. A key application where this
problem occurs is in video layering where the goal is to separate a video
sequence into a slowly changing background sequence and a sparse foreground
sequence that consists of one or more moving regions/objects. Prac-ReProCS is a
practical modification of its theoretical counterpart which was analyzed in our
recent work. Experimental comparisons demonstrating the advantage of the
approach for both simulated and real videos are shown. Extension to the
undersampled case is also developed.