title:
Preliminary Design of a Pendulum Experiment for Searching for a
  Lorentz-Violation Signal

abstract:
  This work mainly presents a preliminary design for a pendulum experiment with
both the source mass and the test mass in a striped pattern to amplify the
Lorentz-violation signal, since the signal is sensitive to edge effects.


title: Decoupling and near-optimal restriction estimates for Cantor sets

abstract:
  For any $\alpha\in(0,d)$, we construct Cantor sets in $\mathbb{R}^d$ of
Hausdorff dimension $\alpha$ such that the associated natural measure $\mu$
obeys the restriction estimate $\| \widehat{f d\mu} \|_{p} \leq C_p \| f
\|_{L^2(\mu)}$ for all $p>2d/\alpha$. This range is optimal except for the
endpoint. This extends the earlier work of Chen-Seeger and Shmerkin-Suomala,
where a similar result was obtained by different methods for $\alpha=d/k$ with
$k\in\mathbb{N}$. Our proof is based on the decoupling techniques of
Bourgain-Demeter and a theorem of Bourgain on the existence of $\Lambda(p)$
sets.


title: The intersection of subgroups in free groups and linear programming

abstract:
  We study the intersection of finitely generated subgroups of free groups by
utilizing the method of linear programming. We prove that if $H_1$ is a
finitely generated subgroup of a free group $F$, then the WN-coefficient
$\sigma(H_1)$ of $H_1$ is rational and can be computed in deterministic
exponential time in the size of $H_1$. This coefficient $\sigma(H_1)$ is the
minimal nonnegative real number such that, for every finitely generated
subgroup $H_2$ of $F$, it is true that $\bar {\rm r}(H_1, H_2) \le \sigma(H_1)
\bar {\rm r}(H_1) \bar {\rm r}(H_2)$, where $\bar{ {\rm r}} (H) := \max ( {\rm
r} (H)-1,0)$ is the reduced rank of $H$, ${\rm r} (H)$ is the rank of $H$, and
$\bar {\rm r}(H_1, H_2)$ is the reduced rank of the generalized intersection of
$H_1$ and $H_2$. We also show the existence of a subgroup $H_2^* = H_2^*(H_1)$
of $F$ such that $\bar {\rm r}(H_1, H_2^*) = \sigma(H_1) \bar {\rm r}(H_1) \bar
{\rm r}(H_2^*)$, the Stallings graph $\Gamma(H_2^*)$ of $H_2^*$ has at most
doubly exponential size in the size of $H_1$ and $\Gamma(H_2^*)$ can be
constructed in exponential time in the size of $H_1$.


title:
Non-uniqueness of local stress of three-body potentials in molecular
  simulations

abstract:
  Microscopic stress fields are widely used in molecular simulations to
understand mechanical behavior. Recently, decomposition methods of multibody
forces to central force pairs between the interacting particles have been
proposed. Here, we introduce a force center of a three-body potential and
propose different force decompositions that also satisfy the conservation of
translational and angular momentum. We compare the force decompositions by
stress-distribution magnitude and discuss their difference in the stress
profile of a bilayer membrane using coarse-grained and atomistic molecular
dynamics simulations.


title:
Holographic entanglement entropy in two-order insulator/superconductor
  transitions

abstract:
  We study holographic superconductor model with two scalar fields coupled to
one single Maxwell field in the AdS soliton background away from the probe
limit. We disclose properties of phase transitions mostly from the holographic
topological entanglement entropy approach. With different sets of parameters,
we observe various types of transitions, especially a new first order phase
transition between the condensation of different order parameters in the
insulator/superconductor system. Our results show that the entanglement entropy
is a good probe to critical phase transition points and the order of phase
transitions in the two-order model. We also conclude that the entanglement
entropy is useful to some extent in determining the physically supported
phases. In addition, we investigate properties of the condensation through the
scalar operator and the charge density in the dual theory. As a summary, we
draw the complete phase diagram of the effects of the scalar charge on phase
transitions. At last, we give some qualitative understanding and obtain the
analytical condition for the first order phase transition to occur.


title:
Partial result of Yau's Conjecture of the first eigenvalue in unit
  sphere $\mathbb{S}^{n+1}(1)$

abstract:
  In this paper, we partially solve Yau' Conjecture of the first eigenvalue of
an embedded compact minimal hypersurface of unit sphere $\mathbb{S}^{n+1}(1)$,
i.e., Corollary 1.2. In particular, Corollary 1.3 proves that the condition
$\int_{\Omega_{1}}|\nabla u|^{2}=(n+1)\int_{\Omega_{1}}u^{2}$ is naturally true
and meaningful in Corollary 1.2.


title:
Sparticles in Motion - getting to the line in compressed scenarios with
  the Recursive Jigsaw Reconstruction

abstract:
  The observation of light super-partners from a supersymmetric extension to
the Standard Model is an intensely sought-after experimental outcome, providing
an explanation for the stabilization of the electroweak scale and indicating
the existence of new particles which could be consistent with dark matter
phenomenology. For compressed scenarios, where sparticle spectra
mass-splittings are small and decay products carry low momenta, dedicated
techniques are required in all searches for supersymmetry. In this paper we
suggest an approach for these analyses based on the concept of Recursive Jigsaw
Reconstruction, decomposing each event into a basis of complementary
observables, for cases where strong initial state radiation has sufficient
transverse momentum to elicit the recoil of any final state sparticles. We
introduce a collection of kinematic observables which can be used to probe
compressed scenarios, in particular exploiting the correlation between missing
momentum and that of radiative jets. As an example, we study squark and gluino
production, focusing on mass-splittings between parent super-particles and
their lightest decay products between 25 and 200 GeV, in hadronic final states
where there is an ambiguity in the provenance of reconstructed jets.


title:
Optical analogy to quantum Fourier transform based on pseudorandom phase
  ensemble

abstract:
  In this paper, we introduce an optical analogy to quantum Fourier
tanformation based on a pseudorandom phase ensemble. The optical analogy also
brings about exponential speedup over classical Fourier tanformation. Using the
analogy, we demonstrate three classcial fields to realize Fourier transform
similar to three quantum particles.


title: X(16.7) as the Solution of NuTeV Anomaly

abstract:
  A recent experimental study of excited $^{8}\!Be$ decay to its ground state
reveals an anomaly in the final states angle distribution. This exceptional
result is attributed to a new vector gauge boson X(16.7). We study the
significance of this new boson, especially its effect in anomalies observed in
long-lasting experimental measurements. By comparing the discrepancies between
the standard model predictions and the experimental results, we manage to find
out the values and regions of the couplings of X(16.7) to muon and muon
neutrino. In this work, we find that the newly observed boson X(16.7) may be
the solution of both NuTeV anomaly and the $(g-2)_{\mu}$ puzzle.


title:
Preterm Birth Prediction: Deriving Stable and Interpretable Rules from
  High Dimensional Data

abstract:
  Preterm births occur at an alarming rate of 10-15%. Preemies have a higher
risk of infant mortality, developmental retardation and long-term disabilities.
Predicting preterm birth is difficult, even for the most experienced
clinicians. The most well-designed clinical study thus far reaches a modest
sensitivity of 18.2-24.2% at specificity of 28.6-33.3%. We take a different
approach by exploiting databases of normal hospital operations. We aims are
twofold: (i) to derive an easy-to-use, interpretable prediction rule with
quantified uncertainties, and (ii) to construct accurate classifiers for
preterm birth prediction. Our approach is to automatically generate and select
from hundreds (if not thousands) of possible predictors using stability-aware
techniques. Derived from a large database of 15,814 women, our simplified
prediction rule with only 10 items has sensitivity of 62.3% at specificity of
81.5%.


title: Further improving security of Vector Stream Cipher

abstract:
  Vector Stream Cipher (VSC) is a stream cipher which consists of permutation
polynomial over a ring of modulo $2^w$. The algorithm for generating key stream
is very simple and the encryption is very fast. Some theoretical attacks for
VSC have been reported so far since the invention of VSC in 2004. Then, the
authors proposed some improvements and developed "Vector Stream Cipher 2.0 (VSC
2.0)" to be immune against the theoretical attacks. In this paper, we propose
further improvement of VSC 2.0 to publish as a new chaos cipher "Vector Stream
Cipher 2.1 (VSC2.1)". VSC 2.1 is faster and more secure than VSC 2.0. Our
result suggests that permutation polynomials over a ring of modulo $2^w$ are
useful for cryptography.


title:
On the Tight Chromatic Bounds for a Class of Graphs without Three
  Induced Subgraphs

abstract:
  Here we prove that a graph without some three induced subgraphs has chromatic
number at the most equal to its maximum clique size plus one. Further we show
that the bounds are tight and give examples to show that each of the three
forbidden subgraphs is necessary in the hypothesis.


title: Direct CP Violation in Charmless Three-body Decays of $B$ Mesons

abstract:
  Direct CP violation in charmless three-body hadronic decays of $B$ mesons is
studied within the framework of a simple model based on the factorization
approach. Three-body decays of heavy mesons receive both resonant and
nonresonant contributions. Dominant nonresonant contributions to tree-dominated
and penguin-dominated three-body decays arise from the $b\to u$ tree transition
and $b\to s$ penguin transition, respectively. The former can be evaluated in
the framework of heavy meson chiral perturbation theory with some modification,
while the latter is governed by the matrix element of the scalar density
$\langle M_1M_2|\bar q_1 q_2|0\rangle$. Strong phases in this work reside in
effective Wilson coefficients, propagators of resonances and the matrix element
of scalar density. In order to accommodate the branching fraction and CP
asymmetries observed in $B^-\to K^-\pi^+\pi^-$, the matrix element $\langle
K\pi|\bar sq|0\rangle$ should have an additional strong phase, which might
arise from some sort of power corrections such as final-state interactions. We
calculate inclusive and regional CP asymmetries and find that nonresonant CP
violation is usually much larger than the resonant one and that the
interference effect is generally quite significant. If nonresonant
contributions are turned off in the $K^+K^-K^-$ mode, the predicted CP
asymmetries due to resonances will be wrong in sign when confronted with
experiment. In our study of $B^-\to \pi^-\pi^+\pi^-$, we find that ${\cal
A}_{C\!P}(\rho^0\pi^-)$ should be positive in order to account for CP
asymmetries observed in this decay. However, all theories predict a large and
negative CP violation in $B^-\to \rho^0\pi^-$. Measurements of CP-asymmetry
Dalitz distributions put very stringent constraints on the theoretical models.
We check the magnitude and the sign of violation in some (large) invariant mass
regions to test our model.


title: A New Family of Nonnegative Sine Polynomials

abstract:
  We present a new family of sine polynomials that are nonnegative for all $x$
in $[0,\pi]$.
  We also characterize all nonnegative sine polynomials of degree 3 and all
nonnegative cosine polynomials of degree 2.
  In the latest version, typos in (1.4) and (1.6) are corrected (with >=
replaced by <=).


title: Anderson localization in metallic nanoparticle arrays

abstract:
  Anderson localization has been observed in various types of waves, such as
matter waves, optical waves and acoustic waves. Here we reveal that the effect
of Anderson localization can be also induced in metallic nonlinear nanoparticle
arrays excited by a random electrically driving field. We find that the
dipole-induced nonlinearity results in ballistic expansion of dipole intensity
during evolution; while the randomness of the external driving field can
suppress such an expansion. Increasing the strength of randomness above the
threshold value, a localized pattern of dipole intensity can be generated in
the metallic nanoparticle arrays. By means of statistics, the mean intensity
distribution of the dipoles reveals the formation of Anderson localization. We
further show that the generated Anderson localization is highly confined, with
its size down to the scale of incident wavelength. The reported results might
facilitate the manipulations of electromagnetic fields in the scale of
wavelength.


title:
Efficient Hyperparameter Optimization of Deep Learning Algorithms Using
  Deterministic RBF Surrogates

abstract:
  Automatically searching for optimal hyperparameter configurations is of
crucial importance for applying deep learning algorithms in practice. Recently,
Bayesian optimization has been proposed for optimizing hyperparameters of
various machine learning algorithms. Those methods adopt probabilistic
surrogate models like Gaussian processes to approximate and minimize the
validation error function of hyperparameter values. However, probabilistic
surrogates require accurate estimates of sufficient statistics (e.g.,
covariance) of the error distribution and thus need many function evaluations
with a sizeable number of hyperparameters. This makes them inefficient for
optimizing hyperparameters of deep learning algorithms, which are highly
expensive to evaluate. In this work, we propose a new deterministic and
efficient hyperparameter optimization method that employs radial basis
functions as error surrogates. The proposed mixed integer algorithm, called
HORD, searches the surrogate for the most promising hyperparameter values
through dynamic coordinate search and requires many fewer function evaluations.
HORD does well in low dimensions but it is exceptionally better in higher
dimensions. Extensive evaluations on MNIST and CIFAR-10 for four deep neural
networks demonstrate HORD significantly outperforms the well-established
Bayesian optimization methods such as GP, SMAC, and TPE. For instance, on
average, HORD is more than 6 times faster than GP-EI in obtaining the best
configuration of 19 hyperparameters.


title: Residue mirror symmetry for Grassmannians

abstract:
  Motivated by recent works on localizations in A-twisted gauged linear sigma
models, we discuss a generalization of toric residue mirror symmetry to
complete intersections in Grassmannians.


title: Evidence accumulation and change rate inference in dynamic environments

abstract:
  In a constantly changing world, animals must account for environmental
volatility when making decisions. To appropriately discount older, irrelevant
information, they need to learn the rate at which the environment changes. We
develop an ideal observer model capable of inferring the present state of the
environment along with its rate of change. Key to this computation is an update
of the posterior probability of all possible changepoint counts. This
computation can be challenging, as the number of possibilities grows rapidly
with time. However, we show how the computations can be simplified in the
continuum limit by a moment closure approximation. The resulting
low-dimensional system can be used to infer the environmental state and change
rate with accuracy comparable to the ideal observer. The approximate
computations can be performed by a neural network model via a rate-correlation
based plasticity rule. We thus show how optimal observers accumulate evidence
in changing environments, and map this computation to reduced models which
perform inference using plausible neural mechanisms.


title: Quotients of Primes in an Algebraic Number Ring

abstract:
  It has been established on many occasions that the set of quotients of prime
numbers is dense in the set of positive real numbers. More recently, it has
been proved that the set of quotients of primes in the Gaussian integers is
dense in the complex plane. In this article, we not only extend this result to
any imaginary quadratic number ring, but also prove that the set of quotients
of primes in any real quadratic number ring is dense in the set of real
numbers. To conclude, we show how to extend these results to an arbitrary
algebraic number ring.


title: Random Permutations Fix a Worst Case for Cyclic Coordinate Descent

abstract:
  Variants of the coordinate descent approach for minimizing a nonlinear
function are distinguished in part by the order in which coordinates are
considered for relaxation. Three common orderings are cyclic (CCD), in which we
cycle through the components of $x$ in order; randomized (RCD), in which the
component to update is selected randomly and independently at each iteration;
and random-permutations cyclic (RPCD), which differs from CCD only in that a
random permutation is applied to the variables at the start of each cycle.
Known convergence guarantees are weaker for CCD and RPCD than for RCD, though
in most practical cases, computational performance is similar among all these
variants. There is a certain type of quadratic function for which CCD is
significantly slower than for RCD; a recent paper by \cite{SunY16a} has
explored the poor behavior of CCD on functions of this type. The RPCD approach
performs well on these functions, even better than RCD in a certain regime.
This paper explains the good behavior of RPCD with a tight analysis.


title:
Phenomenology of two-dimensional stably stratified turbulence under
  large-scale forcing

abstract:
  In this paper we characterize the scaling of energy spectra, and the
interscale transfer of energy and enstrophy, for strongly, moderately and
weakly stably stratified two-dimensional (2D) turbulence under large-scale
random forcing. In the strongly stratified case, a large-scale vertically
sheared horizontal flow (VSHF) co-exists with small scale turbulence. The VSHF
consists of internal gravity waves and the turbulent flow has a kinetic energy
(KE) spectrum that follows an approximate $k^{-3}$ scaling with zero KE flux
and a robust positive enstrophy flux. The spectrum of the turbulent potential
energy (PE) also approximately follows a $k^{-3}$ power-law and its flux is
directed to small scales. For moderate stratification, there is no VSHF and the
KE of the turbulent flow exhibits Bolgiano-Obukhov scaling that transitions
from a shallow $k^{-11/5}$ form at large scales, to a steeper approximate
$k^{-3}$ scaling at small scales. The entire range of scales shows a strong
forward enstrophy flux, and interestingly, large (small) scales show an inverse
(forward) KE flux. The PE flux in this regime is directed to small scales, and
the PE spectrum is characterized by an approximate $k^{-1.64}$ scaling.
Finally, for weak stratification, KE is transferred upscale and its spectrum
closely follows a $k^{-2.5}$ scaling, while PE exhibits a forward transfer and
its spectrum shows an approximate $k^{-1.6}$ power-law. For all stratification
strengths, the total energy always flows from large to small scales and almost
all the spectral indices are well explained by accounting for the scale
dependent nature of the corresponding flux.


title:
Cooperative Repair of Multiple Node Failures in Distributed Storage
  Systems

abstract:
  Cooperative regenerating codes are designed for repairing multiple node
failures in distributed storage systems. In contrast to the original repair
model of regenerating codes, which are for the repair of single node failure,
data exchange among the new nodes is enabled. It is known that further
reduction in repair bandwidth is possible with cooperative repair. Currently in
the literature, we have an explicit construction of exact-repair cooperative
code achieving all parameters corresponding to the minimum-bandwidth point. We
give a slightly generalized and more flexible version of this cooperative
regenerating code in this paper. For minimum-storage regeneration with
cooperation, we present an explicit code construction which can jointly repair
any number of systematic storage nodes.


title: Cavity polaritons with Rydberg blockade and long-range interactions

abstract:
  We study interactions between polaritons, arising when photons strongly
couple to collective excitations in an array of two-level atoms trapped in an
optical lattice inside a cavity. We consider two types of interactions between
atoms: Dipolar forces and atomic saturability, which ranges from hard-core
repulsion to Rydberg blockade. We show that, in spite of the underlying
repulsion in the subsystem of atomic excitations, saturability induces a
broadband bunching of photons for two-polariton scattering states. We interpret
this bunching as a result of interference, and trace it back to the mismatch of
the quantization volumes for atomic excitations and photons. We examine also
bound bipolaritonic states: These include states created by dipolar forces, as
well as a gap bipolariton, which forms solely due to saturability effects in
the atomic transition. Both types of bound states exhibit strong bunching in
the photonic component. We discuss the dependence of bunching on experimentally
relevant parameters.


title:
The radiative efficiency of relativistic jet and wind: A case study of
  GRB 070110

abstract:
  A rapidly spinning, strongly magnetized neutron star is invoked as the
central engine for some Gamma-ray bursts (GRBs), especially, the $"$internal
plateau$"$ feature of X-ray afterglow. However, for these $"$internal
plateau$"$ GRBs, how to produce their prompt emission remains an open question.
Two different physical process have been proposed in the literature, (1) a
new-born neutron star is surrounded by a hyper-accreting and neutrino cooling
disk, the GRB jet can be powered by neutrino annihilation aligning the spin
axis; (2) a differentially rotating millisecond pulsar was formed due to
different angular velocity between the interior core and outer shell parts of
the neutron star, which can power an episodic GRB jet. In this paper, by
analyzing the data of one peculiar GRB 070110 (with internal plateau), we try
to test which model being favored. By deriving the physical parameters of
magnetar with observational data, the parameter regime for initial period
($P_{0\rm }$) and surface polar cap magnetic field ($B_{\rm p}$) of the central
NS are $(0.96\sim 1.2 )~\rm ms$ and $(2.4\sim 3.7)\times 10^{14}~\rm G$,
respectively. The radiative efficiency of prompt emission is about
$\eta_{\gamma} \sim 6\%$. However, the radiative efficiency of internal plateau
($\eta_{\rm X}$) is larger than $31\%$ assuming the $M_{\rm NS}\sim1.4
M_{\odot}$ and $P_{0\rm }\sim1.2 ~\rm ms$. The clear difference between the
radiation efficiencies of prompt emission and internal plateau implies that
they maybe originated from different components (e.g. prompt emission from the
relativistic jet powered by neutrino annihilation, while the internal plateau
from the magnetic outflow wind).


title: VHT: Vertical Hoeffding Tree

abstract:
  IoT Big Data requires new machine learning methods able to scale to large
size of data arriving at high speed. Decision trees are popular machine
learning models since they are very effective, yet easy to interpret and
visualize. In the literature, we can find distributed algorithms for learning
decision trees, and also streaming algorithms, but not algorithms that combine
both features. In this paper we present the Vertical Hoeffding Tree (VHT), the
first distributed streaming algorithm for learning decision trees. It features
a novel way of distributing decision trees via vertical parallelism. The
algorithm is implemented on top of Apache SAMOA, a platform for mining
distributed data streams, and thus able to run on real-world clusters. We run
several experiments to study the accuracy and throughput performance of our new
VHT algorithm, as well as its ability to scale while keeping its superior
performance with respect to non-distributed decision trees.


title: Quasimaps to GIT fiber bundles and applications

abstract:
  Brown proved that the I-function of a toric fibration lies on the overruled
Lagrangian cone of its genus zero Gromov-Witten theory, introduced by Coates
and Givental. In this paper, we prove the theorem for partial flag variety
fibrations. To do so, we will construct new moduli spaces generalising the idea
of Ciocan-Fontanine, Kim and Maulik.


title: Chiral observables and S-duality in N = 2* U(N) gauge theories

abstract:
  We study N = 2* theories with gauge group U(N) and use equivariant
localization to calculate the quantum expectation values of the simplest chiral
ring elements. These are expressed as an expansion in the mass of the adjoint
hypermultiplet, with coefficients given by quasi-modular forms of the S-duality
group. Under the action of this group, we construct combinations of chiral ring
elements that transform as modular forms of definite weight. As an independent
check, we confirm these results by comparing the spectral curves of the
associated Hitchin system and the elliptic Calogero-Moser system. We also
propose an exact and compact expression for the 1-instanton contribution to the
expectation value of the chiral ring elements.


title: Zeros in the magic neutrino mass matrix

abstract:
  We study the phenomenological implications of the presence of two zeros in a
magic neutrino mass matrix. We find that only two such patterns of the neutrino
mass matrix are experimentally acceptable. We express all the neutrino
observables as functions of one unknown phase $\phi$ and two known parameters
$\Delta m^{2}_{12}$, $r=\Delta m^{2}_{12}/\Delta m^{2}_{23}$. In particular, we
find $\sin^2 \theta_{13}=(2/3)r/(1+r)$. We also present a mass model for the
allowed textures based upon the group $A_{4}$ using type I+II see-saw
mechanism.


title: Robust Contextual Outlier Detection: Where Context Meets Sparsity

abstract:
  Outlier detection is a fundamental data science task with applications
ranging from data cleaning to network security. Given the fundamental nature of
the task, this has been the subject of much research. Recently, a new class of
outlier detection algorithms has emerged, called {\it contextual outlier
detection}, and has shown improved performance when studying anomalous behavior
in a specific context. However, as we point out in this article, such
approaches have limited applicability in situations where the context is sparse
(i.e. lacking a suitable frame of reference). Moreover, approaches developed to
date do not scale to large datasets. To address these problems, here we propose
a novel and robust approach alternative to the state-of-the-art called RObust
Contextual Outlier Detection (ROCOD). We utilize a local and global behavioral
model based on the relevant contexts, which is then integrated in a natural and
robust fashion. We also present several optimizations to improve the
scalability of the approach. We run ROCOD on both synthetic and real-world
datasets and demonstrate that it outperforms other competitive baselines on the
axes of efficacy and efficiency (40X speedup compared to modern contextual
outlier detection methods). We also drill down and perform a fine-grained
analysis to shed light on the rationale for the performance gains of ROCOD and
reveal its effectiveness when handling objects with sparse contexts.


title:
Higher AGT Correspondences, W-algebras, and Higher Quantum Geometric
  Langlands Duality from M-Theory

abstract:
  We further explore the implications of our framework in [arXiv:1301.1977,
arXiv:1309.4775], and physically derive, from the principle that the spacetime
BPS spectra of string-dual M-theory compactifications ought to be equivalent,
(i) a 5d AGT correspondence for any compact Lie group, (ii) a 5d and 6d AGT
correspondence on ALE space of type ADE, and (iii) identities between the
ordinary, q-deformed and elliptic affine W-algebras associated with the 4d, 5d
and 6d AGT correspondence, respectively, which also define a quantum geometric
Langlands duality and its higher analogs formulated by
Feigin-Frenkel-Reshetikhin in [3,4]. As an offshoot, we are led to the
sought-after connection between the gauge-theoretic realization of the
geometric Langlands correspondence by Kapustin-Witten [5,6] and its algebraic
CFT formulation by Beilinson-Drinfeld [7], where one can also understand Wilson
and 't Hooft-Hecke line operators in 4d gauge theory as monodromy loop
operators in 2d CFT, for example. In turn, this will allow us to argue that the
higher 5d/6d analog of the geometric Langlands correspondence for simply-laced
Lie (Kac-Moody) groups G (G_k), ought to relate the quantization of circle
(elliptic)-valued G Hitchin systems to circle/elliptic-valued ^LG
(^LG_k)-bundles over a complex curve on one hand, and the transfer matrices of
a G (G_k)-type XXZ/XYZ spin chain on the other, where ^LG is the Langlands dual
of G. Incidentally, the latter relation also serves as an M-theoretic
realization of Nekrasov-Pestun-Shatashvili's recent result in [8], which
relates the moduli space of 5d/6d supersymmetric G (G_k)-quiver SU(K_i) gauge
theories to the representation theory of quantum/elliptic affine (toroidal)
G-algebras.


title: Study of CPO resonances on the intercombination line in $^{173}$Yb

abstract:
  We study coherent population oscillations (CPO) in an odd isotope of the
two-electron atom Yb. The experiments are done using magnetic sublevels of the
$ F_g = 5/2 \rightarrow F_e = 3/2 $ hyperfine transition in $^{173}$Yb of the $
{\rm {^1S_0} \rightarrow {^3P_1}} $ intercombination line. The experiments are
done both with and without an appied magnetic field. In the absence of an
applied field, the complicated sublevel structure along with the saturated
fluorescence effect causes the linewidth to be larger than the 190 kHz natural
linewidth of the transition. In the presence of a field (of magnitude 330 mG),
a well-defined quantization axis is present which results in the formation of
two M-type systems. The total fluorescence is then limited by spin coherence
among the ground sublevels. In addition, the pump beam gets detuned from
resonance which results in a reduced scattering rate from the $ {\rm ^3P_1} $
state. Both of these effects result in a reduction of the linewidth to a
subnatural value of about 100 kHz.


title:
Physical-constraints-preserving central discontinuous Galerkin methods
  for special relativistic hydrodynamics with a general equation of state

abstract:
  The ideal gas equation of state (EOS) with a constant adiabatic index is a
poor approximation for most relativistic astrophysical flows, although it is
commonly used in relativistic hydrodynamics. The paper develops high-order
accurate physical-constraints-preserving (PCP) central discontinuous Galerkin
(DG) methods for the one- and two-dimensional special relativistic hydrodynamic
(RHD) equations with a general EOS. It is built on the theoretical analysis of
the admissible states for the RHD and the PCP limiting procedure enforcing the
admissibility of central DG solutions. The convexity, scaling and orthogonal
invariance, and Lax-Friedrichs splitting property of the admissible state set
are first proved with the aid of its equivalent form, and then the high-order
central DG methods with the PCP limiting procedure and strong stability
preserving time discretization are proved to preserve the positivity of the
density, pressure, and specific internal energy, and the bound of the fluid
velocity, maintain the high-order accuracy, and be $L^1$-stable. The accuracy,
robustness, and effectiveness of the proposed methods are demonstrated by
several 1D and 2D numerical examples involving large Lorentz factor, strong
discontinuities, or low density or pressure etc.


title: Gravitational surface Hamiltonian and entropy quantization

abstract:
  The surface Hamiltonian corresponding to the surface part of a gravitational
action has $xp$ structure where $p$ is conjugate momentum of $x$. Moreover, it
leads to $TS$ on the horizon of a black hole. Here $T$ and $S$ are temperature
and entropy of the horizon. Imposing the hermiticity condition we quantize this
Hamiltonian. This leads to an equidistant spectrum of its eigenvalues. Using
this we show that the entropy of the horizon is quantized. This analysis holds
for any order of Lanczos-Lovelock gravity. For general relativity, the area
spectrum is consistent with Bekenstein's observation. This provides a more
robust confirmation of this earlier result as the calculation is based on the
direct quantization of the Hamiltonian in the sense of usual quantum mechanics.


title:
Suzaku and XMM-Newton Observations of the North Polar Spur: Charge
  Exchange or ISM Absorption?

abstract:
  By revisiting the Suzaku and XMM-Newton data of the North Polar Spur, we
discovered that the spectra are inconsistent with the traditional model
consisting of pure thermal emission and neutral absorption. The most prominent
discrepancies are the enhanced O VII and Ne IX forbidden-to-resonance ratios,
and a high O VIII Ly$\beta$ line relative to other Lyman series. A
collisionally ionized absorption model can naturally explain both features,
while a charge exchange component can only account for the former. By including
the additional ionized absorption, the plasma in the North Polar Spur can be
described by a single-phase CIE component with temperature of 0.25 keV, and
nitrogen, oxygen, neon, magnesium, and iron abundances of $0.4-0.8$ solar. The
abundance pattern of the North Polar Spur is well in line with those of the
Galactic halo stars. The high nitrogen-to-oxygen ratio reported in previous
studies can be migrated to the large transmission of the O VIII Ly$\alpha$
line. The ionized absorber is characterized by a balance temperature of
$0.17-0.20$ keV and a column density of $3-5 \times 10^{19}$ cm$^{-2}$. Based
on the derived abundances and absorption, we speculate that the North Polar
Spur is a structure in the Galactic halo, so that the emission is mostly
absorbed by Galactic ISM in the line of sight.


title: Reverse Data-Processing Theorems and Computational Second Laws

abstract:
  Drawing on an analogy with the second law of thermodynamics for adiabatically
isolated systems, Cover argued that data-processing inequalities may be seen as
second laws for "computationally isolated systems," namely, systems evolving
without an external memory. Here we develop Cover's idea in two ways: on the
one hand, we clarify its meaning and formulate it in a general framework able
to describe both classical and quantum systems. On the other hand, we prove
that also the reverse holds: the validity of data-processing inequalities is
not only necessary, but also sufficient to conclude that a system is
computationally isolated. This constitutes an information-theoretic analogue of
Lieb's and Yngvason's entropy principle. We finally speculate about the
possibility of employing Maxwell's demon to show that adiabaticity and
memorylessness are in fact connected in a deeper way than what the formal
analogy proposed here prima facie seems to suggest.

categories: quant-ph cond-mat.stat-mech cs.IT math.IT


title: Model-mapped RPA for determining the effective Coulomb interaction

abstract:
  We present a new method to obtain interaction part of a model Hamiltonian
from the result of the first-principles calculation. The effective interaction
contained in the model is determined based on the random phase approximation
(RPA). In contrast to previous methods such as projected RPA or constrained
RPA, the new method takes into account the long-range part of the polarization
effect when determining the interaction in the model. After we discuss problems
in previous RPA methods, we will give the formulation of the new method, and
show how it works for the single-band Hubbard model of HgBa$_2$CuO$_4$.


title: Efficient Algorithms for Constructing Very Sparse Spanners and Emulators

abstract:
  Miller et al. \cite{MPVX15} devised a distributed\footnote{They actually
showed a PRAM algorithm. The distributed algorithm with these properties is
implicit in \cite{MPVX15}.} algorithm in the CONGEST model, that given a
parameter $k = 1,2,\ldots$, constructs an $O(k)$-spanner of an input unweighted
$n$-vertex graph with $O(n^{1+1/k})$ expected edges in $O(k)$ rounds of
communication. In this paper we improve the result of \cite{MPVX15}, by showing
a $k$-round distributed algorithm in the same model, that constructs a
$(2k-1)$-spanner with $O(n^{1+1/k}/\epsilon)$ edges, with probability $1-
\epsilon$, for any $\epsilon>0$. Moreover, when $k = \omega(\log n)$, our
algorithm produces (still in $k$ rounds) {\em ultra-sparse} spanners, i.e.,
spanners of size $n(1+ o(1))$, with probability $1- o(1)$. To our knowledge,
this is the first distributed algorithm in the CONGEST or in the PRAM models
that constructs spanners or skeletons (i.e., connected spanning subgraphs) that
sparse. Our algorithm can also be implemented in linear time in the standard
centralized model, and for large $k$, it provides spanners that are sparser
than any other spanner given by a known (near-)linear time algorithm.
  We also devise improved bounds (and algorithms realizing these bounds) for
$(1+\epsilon,\beta)$-spanners and emulators. In particular, we show that for
any unweighted $n$-vertex graph and any $\epsilon > 0$, there exists a $(1+
\epsilon, ({{\log\log n} \over \epsilon})^{\log\log n})$-emulator with $O(n)$
edges. All previous constructions of $(1+\epsilon,\beta)$-spanners and
emulators employ a superlinear number of edges, for all choices of parameters.
  Finally, we provide some applications of our results to approximate shortest
paths' computation in unweighted graphs.


title: Improvable Knapsack Problems

abstract:
  We consider a variant of the knapsack problem, where items are available with
different possible weights. Using a separate budget for these item
improvements, the question is: Which items should be improved to which degree
such that the resulting classic knapsack problem yields maximum profit?
  We present a detailed analysis for several cases of improvable knapsack
problems, presenting constant factor approximation algorithms and two PTAS.


title: Damping of the Milky Way bar by manifold-driven spirals

abstract:
  We describe a new phenomenon of `bar damping' that may have played an
important role in shaping the Milky Way bar and bulge as well as its spiral
structure. We use a collisionless N-body simulation of a Milky Way-like galaxy
initially composed of a dark matter halo and an exponential disk with Toomre
parameter slightly above unity. In this configuration, dominated by the disk in
the center, a bar forms relatively quickly, after 1 Gyr of evolution. This is
immediately followed by the formation of two manifold-driven spiral arms and
the outflow of stars that modifies the potential in the vicinity of the bar,
apparently shifting the position of the L_1/L_2 Lagrange points. This
modification leads to the shortening of the bar and the creation of a next
generation of manifold-driven spiral arms at a smaller radius. The process
repeats itself a few times over the next 0.5 Gyr resulting in further
substantial weakening and shortening of the bar. The time when the damping
comes to an end coincides with the first buckling episode in the bar which
rebuilds the orbital structure so that no more new spiral arms are formed. The
morphology of the bar and the spiral structure at this time show remarkable
similarity to the present properties of the Milky Way. Later on, the bar starts
to grow rather steadily again, weakened only by subsequent buckling episodes
occurring at more distant parts of the disk.


title:
Entire solutions of superlinear problems with indefinite weights and
  Hardy potentials

abstract:
  We provide the structure of regular/singular fast/slow decay radially
symmetric solutions for a class of superlinear elliptic equations with an in-
definite weight on the nonlinearity f (u, r). In particular we are interested
in the case where f is positive in a ball and negative outside, or in the re-
versed situation. We extend the approach to elliptic equations in presence of
Hardy potentials. By the use of Fowler transformation we study the
corresponding dynamical systems, presenting the construction of invariant
manifolds when the global existence of solutions is not ensured.


title: Anomalous Dynamical Responses in a Driven System

abstract:
  The interplay between structure and dynamics in non-equilibrium steady-state
is far from understood. We address this interplay by tracking Brownian Dynamics
trajectories of particles in a binary colloid of opposite charges in an
external electric field, undergoing cross-over from homogeneous to lane state,
a prototype of heterogeneous structure formation in non-equilibrium systems. We
show that the length scale of structural correlations controls heterogeneity in
diffusion and consequent anomalous dynamic responses, like the exponential tail
in probability distributions of particle displacements and stretched
exponential structural relaxation. We generalise our observations using
equations for steady state density which may aid to understand microscopic
basis of heterogeneous diffusion in condensed matter systems.

categories: cond-mat.soft cond-mat.mes-hall cond-mat.stat-mech physics.comp-ph physics.data-an


title:
A New Lightweight Algorithm to compute the BWT and the LCP array of a
  Set of Strings

abstract:
  Indexing of very large collections of strings such as those produced by the
widespread sequencing technologies, heavily relies on multi-string
generalizations of the Burrows-Wheeler Transform (BWT), and for this problem
various in-memory algorithms have been proposed. The rapid growing of data that
are processed routinely, such as in bioinformatics, requires a large amount of
main memory, and this fact has motivated the development of algorithms, to
compute the BWT, that work almost entirely in external memory. On the other
hand, the related problem of computing the Longest Common Prefix (LCP) array is
often instrumental in several algorithms on collection of strings, such as
those that compute the suffix-prefix overlap among strings, which is an
essential step for many genome assembly algorithms. The best current
lightweight approach to compute BWT and LCP array on a set of $m$ strings, each
one $k$ characters long, has I/O complexity that is $O(mk^2 \log |\Sigma|)$
(where $|\Sigma|$ is the size of the alphabet), thus it is not optimal. In this
paper we propose a novel approach to build BWT and LCP array (simultaneously)
with $O(kmL(\log k +\log \sigma))$ I/O complexity, where $L$ is the length of
longest substring that appears at least twice in the input strings.


title: On the Rotation of Sunspots and Their Magnetic Polarity

abstract:
  The rotation of sunspots of 2 yr in two different solar cycles is studied
with the data from the Helioseismic and Magnetic Imager on board the \it Solar
Dynamics Observatory \rm and the Michelson Doppler Imager instrument on board
the \it Solar and Heliospheric Observataory.\rm We choose the $\alpha$ sunspot
groups and the relatively large and stable sunspots of complex active regions
in our sample. In the year of 2003, the $\alpha$ sunspot groups and the
preceding sunspots tend to rotate counterclockwise and have positive magnetic
polarity in the northern hemisphere. In the southern hemisphere, the magnetic
polarity and rotational tendency of the $\alpha$ sunspot groups and the
preceding sunspots are opposite to the northern hemisphere. The average
rotational speed of these sunspots in 2003 is about $0^{\circ}.65 \rm \
hr^{-1}$. From 2014 January to 2015 February, the $\alpha$ sunspot groups and
the preceding sunspots tend to rotate clockwise and have negative magnetic
polarity in the northern hemisphere. The patterns of rotation and magnetic
polarity of the southern hemisphere are also opposite to those of the northern
hemisphere. The average rotational speed of these sunspots in 2014/2015 is
about $1^{\circ}.49 \rm \ hr^{-1}$. The rotation of the relatively large and
stable preceding sunspots and that of the $\alpha$ sunspot groups located in
the same hemisphere have opposite rotational direction in 2003 and 2014/2015.


title:
AUGURY: A time-series based application for the analysis and forecasting
  of system and network performance metrics

abstract:
  This paper presents AUGURY, an application for the analysis of monitoring
data from computers, servers or cloud infrastructures. The analysis is based on
the extraction of patterns and trends from historical data, using elements of
time-series analysis. The purpose of AUGURY is to aid a server administrator by
forecasting the behaviour and resource usage of specific applications and in
presenting a status report in a concise manner. AUGURY provides tools for
identifying network traffic congestion and peak usage times, and for making
memory usage projections. The application data processing specialises in two
tasks: the parametrisation of the memory usage of individual applications and
the extraction of the seasonal component from network traffic data. AUGURY uses
a different underlying assumption for each of these two tasks. With respect to
the memory usage, a limited number of single-valued parameters are assumed to
be sufficient to parameterize any application being hosted on the server.
Regarding the network traffic data, long-term patterns, such as hourly or daily
exist and are being induced by work-time schedules and automatised
administrative jobs. In this paper, the implementation of each of the two tasks
is presented, tested using locally-generated data, and applied to data from
weather forecasting applications hosted on a web server. This data is used to
demonstrate the insight that AUGURY can add to the monitoring of server and
cloud infrastructures.


title: Partial regularity of Solutions of Navier-Stokes equations

abstract:
  In this paper, we study the singular set of 3-dimensional Navier-Stokes
equations. Under the
condition$\frac{1}{R^{\frac{3s}{q}+2-s}}\int^{R^{2}}_{0}(\int_{B_{R}}|u|^{q}dx)^{\frac{s}{q}}ds
<C,$ for $(q,s)\in\{(2,5),(5,2)\},$ we use the backward uniqueness of parabolic
equations to show that the Hausdorff dimension of the singular set is less than
1.


title:
Convection-driven kinematic dynamos at low Rossby and magnetic Prandtl
  numbers

abstract:
  Most large-scale planetary magnetic fields are thought to be driven by low
Rossby number convection of a low magnetic Prandtl number fluid. Here kinematic
dynamo action is investigated with an asymptotic, rapidly rotating dynamo model
for the plane layer geometry that is intrinsically low magnetic Prandtl number.
The thermal Prandtl number and Rayleigh number are varied to illustrate
fundamental changes in flow regime, ranging from laminar cellular convection to
geostrophic turbulence in which an inverse energy cascade is present. A
decrease in the efficiency of the convection to generate a dynamo, as
determined by an increase in the critical magnetic Reynolds number, is observed
as the buoyancy forcing is increased. This decreased efficiency may result from
both the loss of correlations associated with the increasingly disordered
states of flow that are generated, and boundary layer behavior that enhances
magnetic diffusion locally. We find that the spatial characteristics of
$\alpha$, and thus the large-scale magnetic field, is dependent only weakly on
changes in flow behavior. However, our results are limited to the linear,
kinematic dynamo regime, and future simulations including the Lorentz force are
therefore necessary to assess the robustness of this result. In contrast to the
large-scale magnetic field, the behavior of the small-scale magnetic field is
directly dependent on, and therefore shows significant variations with, the
small-scale convective flow field.


title:
Kinematic sensitivity to the Fierz term of $\beta$-decay differential
  spectra

abstract:
  The current most stringent constraints on exotic scalar or tensor couplings
in neutron and nuclear $\beta$ decay, involving left-handed neutrinos, are
obtained from the Fierz interference term. The sensitivity to this term in a
correlation coefficient is usually driven by an energy-averaged kinematic
factor that increases monotonically toward smaller values of the $\beta$
endpoint energies. We first point out here that this property does not hold for
certain differential observables that are directly sensitive to the Fierz term,
such as the $\beta$ or the recoil energy spectrum. This observation is relevant
for the selection of sensitive transitions in searches for exotic couplings
through spectrum shape measurements. We then point out previous errors in the
exploitation of measurements of the $\beta-\nu$ angular correlation coefficient
and discuss their impact on the extraction of constraints on exotic couplings.


title: On Geometry of Schmidt Legendre Transformation

abstract:
  A geometrization of Schmidt-Legendre transformation of the second order
Lagrangians is proposed by building a proper Tulczyjew's triplet. The
symplectic relation between Ostrogradsky-Legendre and Schmidt-Legendre
transformations is obtained. Several examples are presented.


title:
Amplitude determination for MM -> MM, M= pi, K and cross-sections for
  gamma gamma -> pi^+pi^-, pi^0 pi^0 in a chiral model

abstract:
  Recently Dai and Pennington have performed a comprehensive analysis of
essentially all pion and kaon pair production data from two-photon collisions
below 1.5 GeV, including all high statistics results from Belle, as well as the
older data from Mark II at SLAC, CELLO at DESY, and Crystal Ball at SLAC.
Imposing the basic constraints required by analyticity, unitarity, and crossing
symmetry and making use of Low's low energy theorem for QED, they are able to
extract the final-state strong-interaction scattering amplitudes for the
intermediate pi pi->pi pi and pi pi-> K\bar K reactions in a model-independent
fashion. In addition, they provide good fits to the respective gamma gamma-> pi
pi cross-sections that are known in the low-energy sector in the restricted
angular range, | cos theta|< 0.6-0.8. Using the parameters obtained in this
fashion, these authors contruct the \gamma\gamma->pi pi cross-sections
integrated over the full angular range. In this work, we use a version of
chiral perturbation theory developed by Oller and Oset to evaluate the
final-state strong-interaction amplitudes directly theoretically and we compare
our thus obtained low-energy QCD-based results directly with the amplitudes
extracted by Dai and Pennington. We also calculate the gamma gamma -> pi pi
cross-sections (integrated over the full angular range) and compare these with
those obtained by Dai and Pennington. This calculation thus gives a more
detailed insight into the fit of chiral perturbation theory, not just to the
measured gamma gamma-> pi pi cross-sections, as is usually presented, but
rather to a higher level of detail through the available analysis of the
experimental data for the underlying final-state strong-interaction meson-meson
scattering amplitudes pi pi-> pi pi and pi pi-> K\bar K themselves. The fits
appear to be reasonable over the energy range considered.


title: Dual-support Smoothed Particle Hydrodynamics

abstract:
  In this paper we develop a dual-support smoothed particle hydrodynamics
(DS-SPH) that naturally satisfies the conservation of momentum, angular
momentum and energy when the varying smoothing length is utilized. The DS-SPH
is based on the concept of dual-support, which is introduced to consider the
unbalanced interactions between the particles with different smoothing lengths.
Our DS-SPH formulation can be implemented in traditional SPH with little
changes and improve the computational efficiency. Several numerical examples
are presented to demonstrate the capability of the method.


title: Laser-guide-stars used for cophasing broad capture ranges

abstract:
  Segmented primary mirrors are indispensable to master the steady increase in
spatial resolution. Phasing optics systems must reduce segment misalignments to
guarantee the high optical quality required for astronomical science programs.
Modern telescopes routinely use adaptive optics systems to compensate for the
atmosphere and use laser-guide-stars to create artificial stars as bright
references in the field of observation. Because multiple laser-guide-star
adaptive optics are being implemented in all major observatories, we propose to
use man-made stars not only for adaptive optics, but for phasing optics. We
propose a method called the doublet-wavelength coherence technique (DWCT),
exploiting the D lines of sodium in the mesosphere using laser guide-stars. The
signal coherence properties are then used. The DWCT capture range exceeds
current abilities by a factor of 100. It represents a change in paradigm by
improving the phasing optics capture range from micrometric to millimetric. It
thereby potentially eliminates the need of a man-made mechanical pre-phasing
step. Extremely large telescopes require hundreds of segments, several of which
need to be substituted on a daily basis to be recoated. The DWCT relaxes
mechanical integration requirements and speeds up integration and
re-integration process.


title: Reaching Majority Agreement in a Disconnected Network

abstract:
  We investigate the problem of reaching majority agreement in a disconnected
network. We obtain conditions under which such an agreement is certainly
possible/impossible, and observe that these coincide in the ternary case.


title: Self-compensation due to point defects in Mg-doped GaN

abstract:
  Using hybrid density functional theory, we address point defects susceptible
to cause charge compensation upon Mg doping of GaN. We determine the free
energy of formation of the nitrogen vacancy and of several Mg-related defects.
The entropic contribution as a function of temperature is determined within the
quasiharmonic approximation. We find that the Mg interstitial shows a
noticeably lower free energy of formation than the Mg substitutional to Ga in
p-type conditions. Therefore, the Mg impurity is amphoteric behaving like an
acceptor when substitutional to Ga and like a double donor when accommodated in
an interstitial position. The hybrid-functional results are then linked to
experimental observations by solving the charge neutrality equations for
semiconductor dominated by impurities. We show that a thermodynamic equilibrium
model is unable to account for the experimental hole concentration as a
function of Mg doping density, due to nitrogen vacancies and Mg interstitials
acting as compensating donors. To explain the experimental result, which
includes a dropoff of the hole concentration at high Mg densities, we thus
resort to nonequilibrium models. We show that either nitrogen vacancies or Mg
interstitials could be at the origin of the self-compensation mechanism.
However, only the model based on interstitial Mg donors provides a natural
mechanism to account for the sudden appearance of self-compensation. Indeed,
the amphoteric nature of the Mg impurity leads to Fermi-level pinning and
accounts for the observed dropoff of the hole concentration of GaN samples at
high Mg doping. Our work suggests that current limitations in p-type doping of
GaN could be overcome by extrinsically controlling the Fermi energy during
growth.


title:
Optical quenching and recovery of photoconductivity in single-crystal
  diamond

abstract:
  We study the photocurrent induced by pulsed-light illumination (pulse
duration is several nanoseconds) of single-crystal diamond containing nitrogen
impurities. Application of additional continuous-wave light of the same
wavelength quenches pulsed photocurrent. Characterization of the optically
quenched photocurrent and its recovery is important for the development of
diamond based electronics and sensing.


title: Canonical free-energy barrier of particle and polymer cluster formation

abstract:
  A common approach to study nucleation rates is the estimation of free-energy
barriers. This usually requires knowledge about the shape of the forming
droplet, a task that becomes notoriously difficult in macromolecular setups
starting with a proper definition of the cluster boundary. Here, we demonstrate
a shape-free determination of the free energy for temperature-driven cluster
formation in particle as well as polymer systems. Combined with rigorous
results on equilibrium droplet formation, this allows for a well-defined
finite-size scaling analysis of the effective interfacial free energy at fixed
density. We first verify the theoretical predictions for the formation of a
liquid droplet in a supersaturated particle gas by generalized-ensemble Monte
Carlo simulations of a Lennard-Jones system. Going one step further, we then
generalize this approach to cluster formation in a dilute polymer solution. Our
results suggest an analogy with particle condensation, when the macromolecules
are interpreted as extended particles.


title:
Quantum correlation effects on two successive measurements that are
  presented by non-commuting operators

abstract:
  Two measurements of $A$ and $B$ are carried out one after the other. The
measurements of $A$ are controlled by the parameter $\lambda_A$ in the Kraus
operator, where the measurements of $B$ are controlled by the parameter
$\lambda_B$. Strong measurements imply that the parameters in the Kraus
operators approach infinite large values while weak measurements are carried
out when the parameters approach zero. Here we prove that by repeating on the
two successive measurements of $A$ and $B$ then: (1) Average over all
measurements of $A$ is invariant of the measurement strength parameters
$\lambda_A$ and $\lambda_B$. It implies that all surprising results obtained in
weak measurements of $A$ are washed out when the average is taken. (2) If the
operators $\hat A$ and $\hat B$ commute then the mean value of $B$ as obtained
by taking the average of the results for $B$ over all measurements is invariant
of $\lambda_A$ and $\lambda_B$. Moreover it is exactly equal to the expectation
value of $\hat B$ as expected for strong measurements of $B$. (3) If $\hat A$
and $\hat B$ do not commute \textit{and} another condition given in this paper
is satisfied then the mean value of the results obtained for $B$ depends on the
value of $\lambda_A$ and not on the value of $\lambda_B$. An illustrative
possible experiment to show the effect of the strength of the measurements of A
on the results obtained for the measurements of B is given.


title:
Mixing Properties for Hom-Shifts and the Distance between Walks on
  Associated Graphs

abstract:
  Let $\mathcal H$ be a finite connected undirected graph and $\mathcal
H_{walk}$ be the graph of bi-infinite walks on $\mathcal H$; two such walks
$\{x_i\}_{i\in \mathbb Z}$ and $\{y_i\}_{i \in \mathbb Z}$ are said to be
adjacent if $x_i$ is adjacent to $y_i$ for all $i \in \mathbb Z$. We consider
the question: Given a graph $\mathcal H$ when is the diameter (with respect to
the graph metric) of $\mathcal H_{walk}$ finite? Such questions arise while
studying mixing properties of hom-shifts (shift spaces which arise as the space
of graph homomorphisms from the Cayley graph of $\mathbb Z^d$ with respect to
the standard generators to $\mathcal H$) and are the subject of this paper.


title: On Shearing Fluids with Homogeneous Densities

abstract:
  In this paper, we study shearing spherically symmetric homogeneous density
fluids in comoving coordinates. It is found that the expansion of the
four-velocity of a perfect fluid is homogeneous, whereas its shear is generated
by an arbitrary function of time M(t), related to the mass function of the
distribution. This function is found to bear a functional relationship with
density. The field equations are reduced to two coupled first order ordinary
differential equations for the metric coefficients, g 11 and g 22. We have
explored a class of solutions assuming that M is a linear function of the
density. This class embodies, as a subcase, the complete class of shear-free
solutions. We have discussed the off quoted work of Kustaanheimo (1947) and
have noted that it deals with shear-free fluids having anisotropic pressure. It
is shown that the anisotropy of the fluid is characterized by an arbitrary
function of time. We have discussed some issues of historical priorities and
credentials related to shear-free solutions. Recent controversial claims by
Mitra (2011, 2012) have also been addressed. We found that the singularity and
the shearing motion of the fluid are closely related. Hence, there is a need
for fresh look to the solutions obtained earlier in comoving coordinates.
Keywords (separated by '-') Shearing solution - Perfect fluids - Homogeneous
density


title:
The closure constraint for the hyperbolic tetrahedron as a Bianchi
  identity

abstract:
  The closure constraint is a central piece of the mathematics of loop quantum
gravity. It encodes the gauge invariance of the spin network states of quantum
geometry and provides them with a geometrical interpretation: each decorated
vertex of a spin network is dual to a quantized polyhedron in $\mathbb{R}^{3}$.
For instance, a 4-valent vertex is interpreted as a tetrahedron determined by
the four normal vectors of its faces. We develop a framework where the closure
constraint is re-interpreted as a Bianchi identity, with the normals defined as
holonomies around the polyhedron faces of a connection (constructed from the
spinning geometry interpretation of twisted geometries). This allows us to
define closure constraints for hyperbolic tetrahedra (living in the
3-hyperboloid of unit future-oriented spacelike vectors in $\mathbb{R}^{3,1}$)
in terms of normals living all in $SU(2)$ or in $SB(2,\mathbb{C})$. The latter
fits perfectly with the classical phase space developed for $q$-deformed loop
quantum gravity supposed to account for a non-vanishing cosmological constant
$\Lambda>0$. This is the first step towards interpreting $q$-deformed twisted
geometries as actual discrete hyperbolic triangulations.


title: Chaotic instantons in scalar field theory

abstract:
  We consider a new class of instantons in context of quantum field theory of a
scalar field coupled with a chaotic background source field. We show how the
instanton associated to the quantum tunneling from a metastable false to the
true vacuum will be corrected by an exponential enhancement factor. Possible
implications are discussed.


title: Hamiltonian Analysis of Mixed Derivative Horava-Lifshitz Gravity

abstract:
  This short note is devoted to the canonical analysis of the Horava-Lifshitz
gravity with mixed derivative terms that was proposed in arXiv:1604.04215. We
determine the algebra of constraints and we show that there is one additional
scalar degree of freedom with respect to the non-projectable Horava-Lifshitz
gravity.


title: Incremental Noising and its Fractal Behavior

abstract:
  This manuscript is about further elucidating the concept of noising. The
concept of noising first appeared in \cite{CVPR14}, in the context of curvature
estimation and vertex localization on planar shapes. There are indications that
noising can play for global methods the role smoothing plays for local methods
in this task. This manuscript is about investigating this claim by introducing
incremental noising, in a recursive deterministic manner, analogous to how
smoothing is extended to progressive smoothing in similar tasks. As
investigating the properties and behavior of incremental noising is the purpose
of this manuscript, a surprising connection between incremental noising and
progressive smoothing is revealed by the experiments. To explain this
phenomenon, the fractal and the space filling properties of the two methods
respectively, are considered in a unifying context.


title: Automata for Specifying and Orchestrating Service Contracts

abstract:
  An approach to the formal description of service contracts is presented in
terms of automata. We focus on the basic property of guaranteeing that in the
multi-party composition of principals each of them gets his requests satisfied,
so that the overall composition reaches its goal. Depending on whether requests
are satisfied synchronously or asynchronously, we construct an orchestrator
that at static time either yields composed services enjoying the required
properties or detects the principals responsible for possible violations. To do
that in the asynchronous case we resort to Linear Programming techniques. We
also relate our automata with two logically based methods for specifying
contracts.


title:
The Milky Way Hot Baryons and their Peculiar Density Distribution: a
  Relic of Nuclear Activity

abstract:
  We know that our Galaxy is permeated by tenuous, hot, metal-rich gas. However
much remains unknown about its origin, the portion of the Galaxy that it
permeates, its total mass, as any role it may play in regulating activity in
the Galaxy. In a Letter currently in the press with the ApJ, we show that this
hot gas permeates both the disk of the Galaxy and a large spherical volume,
centered on the Galactic nucleus, and extending out to distances of at least
60-200 kpc from the center. This gas displays a peculiar density distribution
that peaks about 6 kpc from the Galaxy's center, likely witnessing a period of
strong activity of the central super-massive black hole of the Milky Way that
occurred 6 Myrs ago. With our study we are also able to update the total
baryonic mass of the Galaxy to Mb = (0.8-4)x1e11 Solar Masses, sufficient to
close the Galaxy's baryon census.


title:
Multiple positive solutions of a Sturm-Liouville boundary value problem
  with conflicting nonlinearities

abstract:
  We study the second order nonlinear differential equation \begin{equation*}
u"+ \sum_{i=1}^{m} \alpha_{i} a_{i}(x)g_{i}(u) - \sum_{j=0}^{m+1} \beta_{j}
b_{j}(x)k_{j}(u) = 0, \end{equation*} where $\alpha_{i},\beta_{j}>0$,
$a_{i}(x), b_{j}(x)$ are non-negative Lebesgue integrable functions defined in
$\mathopen{[}0,L\mathclose{]}$, and the nonlinearities $g_{i}(s), k_{j}(s)$ are
continuous, positive and satisfy suitable growth conditions, as to cover the
classical superlinear equation $u"+a(x)u^{p}=0$, with $p>1$. When the positive
parameters $\beta_{j}$ are sufficiently large, we prove the existence of at
least $2^{m}-1$ positive solutions for the Sturm-Liouville boundary value
problems associated with the equation. The proof is based on the Leray-Schauder
topological degree for locally compact operators on open and possibly unbounded
sets. Finally, we deal with radially symmetric positive solutions for the
Dirichlet problems associated with elliptic PDEs.


title: 25 years of CNNs: Can we compare to human abstraction capabilities?

abstract:
  We try to determine the progress made by convolutional neural networks over
the past 25 years in classifying images into abstractc lasses. For this purpose
we compare the performance of LeNet to that of GoogLeNet at classifying
randomly generated images which are differentiated by an abstract property
(e.g., one class contains two objects of the same size, the other class two
objects of different sizes). Our results show that there is still work to do in
order to solve vision problems humans are able to solve without much
difficulty.


title:
A posteriori analysis for dynamic model adaptation in convection
  dominated problems

abstract:
  In this work we present an a posteriori error indicator for approximation
schemes of Runge-Kutta-discontinuous-Galerkin type arising in applications of
compressible fluid flows. The purpose of this indicator is not only for mesh
adaptivity, we also make use of this to drive model adaptivity. This is where a
perhaps costly complex model and a cheaper simple model are solved over
different parts of the domain. The a posteriori bound we derive indicates the
regions where the complex model can be relatively well approximated with the
cheaper one. One such example which we choose to highlight is that of the
Navier-Stokes-Fourier equations approximated by Euler's equations.


title:
Local Feature Detectors, Descriptors, and Image Representations: A
  Survey

abstract:
  With the advances in both stable interest region detectors and robust and
distinctive descriptors, local feature-based image or object retrieval has
become a popular research topic. %All of the local feature-based image
retrieval system involves two important processes: local feature extraction and
image representation. The other key technology for image retrieval systems is
image representation such as the bag-of-visual words (BoVW), Fisher vector, or
Vector of Locally Aggregated Descriptors (VLAD) framework. In this paper, we
review local features and image representations for image retrieval. Because
many and many methods are proposed in this area, these methods are grouped into
several classes and summarized. In addition, recent deep learning-based
approaches for image retrieval are briefly reviewed.


title: Probabilistic logic of quantum observations

abstract:
  A probabilistic propositional logic, endowed with an epistemic component for
asserting (non-)compatibility of diagonizable and bounded observables, is
presented and illustrated for reasoning about the random results of projective
measurements made on a given quantum state. Simultaneous measurements are
assumed to imply that the underlying observables are compatible. A sound and
weakly complete axiomatization is provided relying on the decidable first-order
theory of real closed ordered fields. The proposed logic is proved to be a
conservative extension of classical propositional logic.


title:
Growing complex network of citations of scientific papers --
  measurements and modeling

abstract:
  To quantify the mechanism of a complex network growth we focus on the network
of citations of scientific papers and use a combination of the theoretical and
experimental tools to uncover microscopic details of this network growth.
Namely, we develop a stochastic model of citation dynamics based on
copying/redirection/triadic closure mechanism. In a complementary and coherent
way, the model accounts both for statistics of references of scientific papers
and for their citation dynamics. Originating in empirical measurements, the
model is cast in such a way that it can be verified quantitatively in every
aspect. Such verification is performed by measuring citation dynamics of
Physics papers. The measurements revealed nonlinear citation dynamics, the
nonlinearity being intricately related to network topology. The nonlinearity
has far-reaching consequences including non-stationary citation distributions,
diverging citation trajectory of similar papers, runaways or "immortal papers"
with infinite citation lifetime etc. Thus, our most important finding is
nonlinearity in complex network growth. In a more specific context, our results
can be a basis for quantitative probabilistic prediction of citation dynamics
of individual papers and of the journal impact factor.


title:
Towards MRI-Based Autonomous Robotic US Acquisitions: A First
  Feasibility Study

abstract:
  Robotic ultrasound has the potential to assist and guide physicians during
interventions. In this work, we present a set of methods and a workflow to
enable autonomous MRI-guided ultrasound acquisitions. Our approach uses a
structured-light 3D scanner for patient-to-robot and image-to-patient
calibration, which in turn is used to plan 3D ultrasound trajectories. These
MRI-based trajectories are followed autonomously by the robot and are further
refined online using automatic MRI/US registration. Despite the low spatial
resolution of structured light scanners, the initial planned acquisition path
can be followed with an accuracy of 2.46 +/- 0.96 mm. This leads to a good
initialization of the MRI/US registration: the 3D-scan-based alignment for
planning and acquisition shows an accuracy (distance between planned ultrasound
and MRI) of 4.47 mm, and 0.97 mm after an online-update of the calibration
based on a closed loop registration.


title: Half-tapering strategy for conditional simulation with large datasets

abstract:
  Gaussian conditional realizations are routinely used for risk assessment and
planning in a variety of Earth sciences applications. Conditional realizations
can be obtained by first creating unconditional realizations that are then
post-conditioned by kriging. Many efficient algorithms are available for the
first step, so the bottleneck resides in the second step. Instead of doing the
conditional simulations with the desired covariance (F approach) or with a
tapered covariance (T approach), we propose to use the taper covariance only in
the conditioning step (Half-Taper or HT approach). This enables to speed up the
computations and to reduce memory requirements for the conditioning step but
also to keep the right short scale variations in the realizations. A criterion
based on mean square error of the simulation is derived to help anticipate the
similarity of HT to F. Moreover, an index is used to predict the sparsity of
the kriging matrix for the conditioning step. Some guides for the choice of the
taper function are discussed. The distributions of a series of 1D, 2D and 3D
scalar response functions are compared for F, T and HT approaches. The
distributions obtained indicate a much better similarity to F with HT than with
T.


title: Notes on entanglement entropy for excites holographic states in 2d

abstract:
  In this work we revisit the problem of contributions of excited holographic
states to the entanglement entropy in two-dimensional conformal field theories.
Using the results of replica trick method we find three expressions for these
contributions. First, we express the contribution of the excited states in
terms of Aharonov invariants. It is shown that beside the Schwarzian, the
one-point functions of descendants of energy-momentum also contribute. Given
Schwarz-Christoffel map, the contributions to any order can be easily computed.
The second expression relates the entanglement entropy of excited states to
Faber polynomials and Grunsky coefficients. Based on the relation of Grunsky
coefficiens to tau-funcion of dispersionless Toda hierarchy, we find the third
expression for contributions of excited holographic states to the entanglement
entropy.


title:
Precision Measurements in Electron-Positron Annihilation: Theory and
  Experiment

abstract:
  Theory results on precision measurements in electron-positron annihilation at
low and high energies are collected. These cover pure QCD calculations as well
as mixed electroweak and QCD results, involving light and heavy quarks. The
impact of QCD corrections on the $W$-boson mass is discussed and, last not
least, the status and the perspectives for the Higgs boson decay rate into
$b\bar b$, $c\bar c$ and into two gluons.


title:
The two-loop electroweak bosonic corrections to $\sin^2\theta_{\rm
  eff}^{\rm b}$

abstract:
  The prediction of the effective electroweak mixing angle $\sin^2\theta_{\rm
eff}^{\rm b}$ in the Standard Model at two-loop accuracy has now been completed
by the first calculation of the bosonic two-loop corrections to the $Z{\bar
b}b$ vertex. Numerical predictions are presented in the form of a fitting
formula as function of $M_Z, M_W, M_H, m_t$ and $\Delta{\alpha}$, ${\alpha_{\rm
s}}$. For central input values, we obtain a relative correction of
$\Delta\kappa_{\rm b}^{(\alpha^2,\rm bos)} = -0.9855 \times 10^{-4}$, amounting
to about a quarter of the fermionic corrections, and corresponding to
$\sin^2\theta_{\rm eff}^{\rm b} = 0.232704$. The integration of the
corresponding two-loop vertex Feynman integrals with up to three dimensionless
parameters in Minkowskian kinematics has been performed with two approaches:
(i) Sector decomposition, implemented in the packages FIESTA 3 and SecDec 3,
and (ii) Mellin-Barnes representations, implemented in AMBRE 3/MB and the new
package MBnumerics.


title: System theory and orthogonal multi-wavelets

abstract:
  In this paper we provide a complete and unifying characterization of
compactly supported univariate scalar orthogonal wavelets and vector-valued or
matrix-valued orthogonal multi-wavelets. This characterization is based on
classical results from system theory and basic linear algebra. In particular,
we show that the corresponding wavelet and multi-wavelet masks are identified
with a transfer function $$
  F(z)=A+B z (I-Dz)^{-1} \, C, \quad z \in \mathbb{D}=\{z \in \mathbb{C} \ : \
|z| < 1\}, $$ of a conservative linear system. The complex matrices $A,\ B, \
C, \ D$ define a block circulant unitary matrix. Our results show that there
are no intrinsic differences between the elegant wavelet construction by
Daubechies or any other construction of vector-valued or matrix-valued
multi-wavelets. The structure of the unitary matrix defined by $A,\ B, \ C, \
D$ allows us to parametrize in a systematic way all classes of possible wavelet
and multi-wavelet masks together with the masks of the corresponding refinable
functions.


title:
Isobaric first-principles molecular dynamics of liquid water with
  nonlocal van der Waals interactions

abstract:
  We investigate the structural properties of liquid water at near ambient
conditions using first-principles molecular dynamics simulations based on a
semilocal density functional augmented with nonlocal van der Waals
interactions. The adopted scheme offers the advantage of simulating liquid
water at essentially the same computational cost of standard semilocal
functionals. Applied to the water dimer and to ice Ih, we find that the
hydrogen-bond energy is only slightly enhanced compared to a standard semilocal
functional. We simulate liquid water through molecular dynamics in the NpH
statistical ensemble allowing for fluctuations of the system density. The
structure of the liquid departs from that found with a semilocal functional
leading to more compact structural arrangements. This indicates that the
directionality of the hydrogen-bond interaction has a diminished role as
compared to the overall attractions, as expected when dispersion interactions
are accounted for. This is substantiated through a detailed analysis comprising
the study of the partial radial distribution functions, various local order
indices, the hydrogen-bond network, and the selfdiffusion coefficient. The
explicit treatment of the van der Waals interactions leads to an overall
improved description of liquid water.


title:
Gated Siamese Convolutional Neural Network Architecture for Human
  Re-Identification

abstract:
  Matching pedestrians across multiple camera views, known as human
re-identification, is a challenging research problem that has numerous
applications in visual surveillance. With the resurgence of Convolutional
Neural Networks (CNNs), several end-to-end deep Siamese CNN architectures have
been proposed for human re-identification with the objective of projecting the
images of similar pairs (i.e. same identity) to be closer to each other and
those of dissimilar pairs to be distant from each other. However, current
networks extract fixed representations for each image regardless of other
images which are paired with it and the comparison with other images is done
only at the final level. In this setting, the network is at risk of failing to
extract finer local patterns that may be essential to distinguish positive
pairs from hard negative pairs. In this paper, we propose a gating function to
selectively emphasize such fine common local patterns by comparing the
mid-level features across pairs of images. This produces flexible
representations for the same image according to the images they are paired
with. We conduct experiments on the CUHK03, Market-1501 and VIPeR datasets and
demonstrate improved performance compared to a baseline Siamese CNN
architecture.


title:
Variational perturbation and extended Plefka approaches to dynamics on
  random networks: the case of the kinetic Ising model

abstract:
  We describe and analyze some novel approaches for studying the dynamics of
Ising spin glass models. We first briefly consider the variational approach
based on minimizing the Kullback-Leibler divergence between independent
trajectories and the real ones and note that this approach only coincides with
the mean field equations from the saddle point approximation to the generating
functional when the dynamics is defined through a logistic link function, which
is the case for the kinetic Ising model with parallel update. We then spend the
rest of the paper developing two ways of going beyond the saddle point
approximation to the generating functional. In the first one, we develop a
variational perturbative approximation to the generating functional by
expanding the action around a quadratic function of the local fields and
conjugate local fields whose parameters are optimized. We derive analytical
expressions for the optimal parameters and show that when the optimization is
suitably restricted, we recover the mean field equations that are exact for the
fully asymmetric random couplings (M\'ezard and Sakellariou, 2011). However,
without this restriction the results are different. We also describe an
extended Plefka expansion in which in addition to the magnetization, we also
fix the correlation and response functions. Finally, we numerically study the
performance of these approximations for Sherrington-Kirkpatrick type couplings
for various coupling strengths, degrees of coupling symmetry and external
fields. We show that the dynamical equations derived from the extended Plefka
expansion outperform the others in all regimes, although it is computationally
more demanding. The unconstrained variational approach does not perform well in
the small coupling regime, while it approaches dynamical TAP equations of
(Roudi and Hertz, 2011) for strong couplings.


title:
Landau modeling of dynamical nucleation of martensite at grain
  boundaries under local stress

abstract:
  The dynamical nucleation of martensite in polycrystals is simulated by means
of Lagrange-Rayleigh dynamics with Landau energetics, which is capable of
obtaining the local stress as a result of the interplay of the potential of
transformation and external loadings. By monitoring the patio-temporal
distribution of the strain in response to the local stress, we demonstrate that
the postcursors, high angle grain boundaries and triple junctions act as
favorable heterogeneous nucleation sites corresponding to different loading and
cooling conditions, and predict the phase diagram of the nucleation mode of
martensite.


title:
A Siamese Long Short-Term Memory Architecture for Human
  Re-Identification

abstract:
  Matching pedestrians across multiple camera views known as human
re-identification (re-identification) is a challenging problem in visual
surveillance. In the existing works concentrating on feature extraction,
representations are formed locally and independent of other regions. We present
a novel siamese Long Short-Term Memory (LSTM) architecture that can process
image regions sequentially and enhance the discriminative capability of local
feature representation by leveraging contextual information. The feedback
connections and internal gating mechanism of the LSTM cells enable our model to
memorize the spatial dependencies and selectively propagate relevant contextual
information through the network. We demonstrate improved performance compared
to the baseline algorithm with no LSTM units and promising results compared to
state-of-the-art methods on Market-1501, CUHK03 and VIPeR datasets.
Visualization of the internal mechanism of LSTM cells shows meaningful patterns
can be learned by our method.


title:
Coherent forward scattering as a signature of Anderson metal-insulator
  transitions

abstract:
  We show that the coherent forward scattering (CFS) interference peak
amplitude sharply jumps from zero to a finite value upon crossing a
metal-insulator transition. Extensive numerical simulations reveal that the CFS
peak contrast obeys the one-parameter scaling hypothesis and gives access to
the critical exponents of the transition. We also discover that the critical
CFS peak directly controls the spectral compressibility at the transition where
eigenfunctions are multifractal, and we demonstrate the universality of this
property with respect to various types of disorder.


title: Symmetric noncommutative birational transformations

abstract:
  In a previous paper (arXiv:1410.5207) certain birational transformations were
constructed between the noncommutative schemes associated to quadratic and
cubic three dimensional Sklyanin algebras. In the current paper we consider the
inverse birational transformations and show that they are of the same type.
Moreover we extend everything to the $\mathbb{Z}$-algebras context, which
allows us to incorporate the noncommutative quadrics introduced by Van den
Bergh.


title: Formation Mechanisms of IMBH in Globular Clusters

abstract:
  We very briefly discuss proposed in the literature possible scenarios for
intermediate mass black holes (IMBH) formation in globular clusters. We also
discuss the results of the MOCCA simulations of about 2000 models (BigSurvey)
regarding the distribution of events connected with electromagnetic and
gravitational radiations, namely: mass transfer on IMBH, collisions and mergers
with IMBH and mergers with IMBH due to gravitational radiation. The rates of
these events are very small, so their observation is very improbable.


title:
Electrical conductivity of a monolayer produced by random sequential
  adsorption of linear $k$-mers onto a square lattice

abstract:
  The electrical conductivity of a monolayer produced by the random sequential
adsorption (RSA) of linear $k$-mers onto a square lattice was studied by means
of computer simulation. Overlapping with pre-deposited $k$-mers and detachment
from the surface were forbidden. The RSA continued until the saturation jamming
limit, $p_j$. The isotropic and anisotropic depositions for two different
models: of an insulating substrate and conducting $k$-mers (C-model) and of a
conducting substrate and insulating $k$-mers (I-model) were examined. The
Frank-Lobb algorithm was applied to calculate the electrical conductivity in
both the $x$ and $y$ directions for different lengths ($k=1$ -- $128 $) and
concentrations ($p=0$ -- $p_j$) of the $k$-mers. The `intrinsic electrical
conductivity' and concentration dependence of the relative electrical
conductivity $\Sigma (p)$ ($\Sigma=\sigma/ \sigma_m$ for the C-model and
$\Sigma=\sigma_m /\sigma$ for the I-model, where $\sigma_m$ is the electrical
conductivity of substrate) in different directions were analyzed. At large
values of $k$ the $\Sigma (p)$ curves became very similar and they almost
coincided at $k=128$. Moreover, for both models the greater the length of the
$k$-mers the smoother the functions $\Sigma_{xy}(p)$, $\Sigma_{x}(p)$ and
$\Sigma_{y}(p)$. For the C-model, the other interesting findings are: for large
values of $k$ ($k=64, 128$), the values of $\Sigma_{xy}$ and $\Sigma_{y}$
increase rapidly with the initial increase of $p$ from 0 to 0.1; for $k \geq
16$, all the $\Sigma_{xy}(p)$ and $\Sigma_{x}(p)$ curves intersect with each
other at the same iso-conductivity points; for anisotropic deposition, the
percolation concentrations are the same in the $x$ and $y$ directions, whereas,
at the percolation point the greater the length of the $k$-mers the larger the
anisotropy of the electrical conductivity, i.e., the ratio $\sigma_y/\sigma_x$
($>1$).


title: The far-ultraviolet spectra of two hot PG1159 stars

abstract:
  PG1159 stars are hot, hydrogen-deficient (pre-) white dwarfs with atmospheres
mainly composed of helium, carbon, and oxygen. The unusual surface chemistry is
the result of a late helium-shell flash. Observed element abundances enable us
to test stellar evolution models quantitatively with respect to their
nucleosynthesis products formed near the helium-burning shell of the progenitor
asymptotic giant branch stars. Because of the high effective temperatures
(Teff), abundance determinations require ultraviolet spectroscopy and non-local
thermodynamic equilibrium model atmosphere analyses. Up to now, we have
presented results for the prototype of this spectral class and two cooler
members (Teff in the range 85,000-140,000 K). Here we report on the results for
two even hotter stars (PG1520+525 and PG1144+005, both with Teff = 150,000 K)
which are the only two objects in this temperature-gravity region for which
useful far-ultraviolet spectra are available, and revisit the prototype star.
Previous results on the abundances of some species are confirmed, while results
on others (Si, P, S) are revised. In particular, a solar abundance of sulphur
is measured in contrast to earlier claims of a strong S deficiency that
contradicted stellar evolution models. For the first time, we assess the
abundances of Na, Al, and Cl with newly constructed non-LTE model atoms.
Besides the main constituents (He, C, O), we determine the abundances (or upper
limits) of N, F, Ne, Na, Al, Si, P, S, Cl, Ar, and Fe. Generally, good
agreement with stellar models is found.


title:
Detection of forbidden line components of lithium-like carbon in stellar
  spectra

abstract:
  We report the first identification of forbidden line components from an
element heavier than helium in the spectrum of astrophysical plasmas. As yet,
these components were identified only in laboratory plasmas and not in
astrophysical objects. Forbidden components are well known for neutral helium
lines in hot stars, particularly in helium-rich post-AGB stars and white
dwarfs. We discovered that two hitherto unidentified lines in the ultraviolet
spectra of hot hydrogen-deficient (pre-) white dwarfs can be identified as
forbidden line components of triply ionized carbon (C IV). The forbidden
components (3p-4f and 3d-4d) appear in the blue and red wings of the strong,
Stark broadened 3p-4d and 3d-4f lines at 1108 Angstroem and 1169 Angstroem,
respectively. They are visible over a wide effective temperature range
(60,000-200,000 K) in helium-rich (DO) white dwarfs and PG1159 stars that have
strongly oversolar carbon abundances.


title:
The Design and Implementation of a Rekeying-aware Encrypted
  Deduplication Storage System

abstract:
  Rekeying refers to an operation of replacing an existing key with a new key
for encryption. It renews security protection, so as to protect against key
compromise and enable dynamic access control in cryptographic storage. However,
it is non-trivial to realize efficient rekeying in encrypted deduplication
storage systems, which use deterministic content-derived encryption keys to
allow deduplication on ciphertexts. We design and implement REED, a
rekeying-aware encrypted deduplication storage system. REED builds on a
deterministic version of all-or-nothing transform (AONT), such that it enables
secure and lightweight rekeying, while preserving the deduplication capability.
We propose two REED encryption schemes that trade between performance and
security, and extend REED for dynamic access control. We implement a REED
prototype with various performance optimization techniques and demonstrate how
we can exploit similarity to mitigate key generation overhead. Our trace-driven
testbed evaluation shows that our REED prototype maintains high performance and
storage efficiency.


title:
Spin excitations in systems with hopping electron transport and strong
  position disorder in a large magnetic field

abstract:
  We discuss the spin excitations in systems with hopping electron conduction
and strong position disorder. We focus on the problem in a strong magnetic
field when the spin Hamiltonian can be reduced to the effective single-particle
Hamiltonian and treated with conventional numerical technics. It is shown that
in a 3D system with Heisenberg exchange interaction the spin excitations have a
delocalized part of the spectrum even in the limit of strong disorder, thus
leading to the possibility of the coherent spin transport. The spin transport
provided by the delocalized excitations can be described by a diffusion
coefficient. Non-homogenous magnetic fields lead to the Anderson localization
of spin excitations while anisotropy of the exchange interaction results in the
Lifshitz localization of excitations. We discuss the possible effect of the
additional exchange-driven spin diffusion on the organic spin-valve devices.


title:
On the solvability of third-order three point systems of differential
  equations with dependence on the first derivative

abstract:
  This paper presents sufficient conditions for the solvability of the third
order three point boundary value problem \begin{equation*} \left\{
\begin{array}{c} -u^{\prime \prime \prime }(t)=f(t,\,v(t),\,v^{\prime }(t)) \\
-v^{\prime \prime \prime }(t)=h(t,\,u(t),\,u^{\prime }(t)) \\ u(0)=u^{\prime
}(0)=0,u^{\prime }(1)=\alpha u^{\prime }(\eta ) \\ v(0)=v^{\prime
}(0)=0,v^{\prime }(1)=\alpha v^{\prime }(\eta ).
  \end{array}
  \right. \end{equation*} The arguments apply Green's function associated to
the linear problem and the Guo--Krasnosel'ski\u{\i} theorem of
compression-expansion cones. The dependence on the first derivatives is
overcome by the construction of an adequate cone and suitable conditions of
superlinearity/sublinearity near $0$ and $+\infty .$ Last section contains an
example to illustrate the applicability of the theorem.


title: Self-similar space-filling sphere packings in three and four dimensions

abstract:
  Inversive geometry can be used to generate exactly self-similar space-filling
sphere packings. We present a construction method in two dimensions and
generalize it to search for packings in higher dimensions. We newly discover 29
three-dimensional and 13 four-dimensional topologies of which 10 and 5,
respectively, are bearings. To distinguish and characterize the packing
topologies, we numerically estimate their fractal dimensions and we analyze
their contact networks.


title: Synthesable differentiation-invariant subspaces

abstract:
  We describe differentiation-invariant subspaces of $C^\infty(a,b)$ which
admit spectral synthesis. This gives a complete answer to a question posed by
A.~Aleman and B.~Korenblum. It turns out that this problem is related to a
classical problem of approximation by polynomials on the real line. We will
depict an intriguing connection between these problems and the theory of de
Branges spaces.


title:
Investigation of the tunnel magnetoresistance in junctions with a
  strontium stannate barrier

abstract:
  We experimentally investigate the structural, magnetic and electrical
transport properties of La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ based magnetic tunnel
junctions with a SrSnO$_3$ barrier. Our results show that despite the large
number of defects in the strontium stannate barrier, due to the large lattice
mismatch, the observed tunnel magnetoresistance is comparable to tunnel
junctions with a better lattice matched STiO$_3$ barrier, reaching values of up
to 350% at T=5 K. Further analysis of the current-voltage characteristics of
the junction and the bias voltage dependence of the observed tunnel
magnetoresistance show a decrease of the TMR with increasing bias voltage. In
addition, the observed TMR vanishes for T>200 K. Our results suggest that by
employing a better lattice matched ferromagnetic electrode and thus reducing
the structural defects in the strontium stannate barrier even larger TMR ratios
might be possible in the future.


title:
On Stable Throughput of Cognitive Radio Networks With Cooperating
  Secondary Users

abstract:
  In this paper, we study cooperative cognitive radio networks consisting of a
primary user and multiple secondary users. Secondary users transmit only when
primary user is sensed as silent and may interfere with primary transmission
due to imperfect sensing. When primary activity is sensed correctly, secondary
users cooperate with primary user by assisting retransmission of failed packets
of primary user. We analyze packet throughput of primary and secondary users
for three variations of proposed cooperation method. Signal flow graph (SFG)
based approach is employed to obtain closed form expressions of packet
throughput. The analysis is done for two cases; individual sensing and
cooperative sensing. Further, we characterize optimal transmission probability
of secondary users that maximizes individual secondary packet throughput
keeping all queues in the system stable. Results present a comparison of
throughput performance of proposed cooperation methods under different
scenarios and show their benefits for both primary as well as secondary user
throughput.


title: The moving plane method for singular semilinear elliptic problems

abstract:
  We consider positive solutions to semilinear elliptic problems with singular
nonlinearities, under zero Dirichlet boundary condition. We exploit a refined
version of the moving plane method to prove symmetry and monotonicity
properties of the solutions, under general assumptions on the nonlinearity.


title: Exponential Patterns in Arithmetic Ramsey Theory

abstract:
  We show that for every finite colouring of the natural numbers there exists
$a,b >1$ such that the triple $\{a,b,a^b\}$ is monochromatic. We go on to show
the partition regularity of a much richer class of patterns involving
exponentiation. For example, as a corollary to our main theorem, we show that
for every $n \in \mathbb{N}$ and for every finite colouring of the natural
numbers, we may find a monochromatic set including the integers $x_1,\ldots,x_n
>1$; all products of distinct $x_i$; and all "exponential compositions" of
distinct $x_i$ which respect the order $x_1,\ldots,x_n$. In particular, for
every finite colouring of the natural numbers one can find a monochromatic
quadruple of the form $\{ a,b,ab,a^b \}$, where $a,b>1$.


title:
Analysis of DIS structure functions of the nucleon within truncated
  Mellin moments approach

abstract:
  We present generalized evolution equations and factorization in terms of the
truncated Mellin moments (TMM) of the parton distributions and structure
functions. We illustrate the $x$ and $Q^2$ dependence of TMM in the polarized
case. Using the TMM approach we compare the integrals of $g_1$ with HERMES and
COMPASS data from the limited $x$-ranges.