title: Specialized minimal PDFs for optimized LHC calculations

abstract:
  We present a methodology for the construction of parton distribution
functions (PDFs) designed to provide an accurate representation of PDF
uncertainties for specific processes or classes of processes with a minimal
number of PDF error sets: specialized minimal PDF sets, or SM-PDFs. We
construct these SM-PDFs in such a way that sets corresponding to different
input processes can be combined without losing information, specifically on
their correlations, and that they are robust upon smooth variations of the
kinematic cuts. The proposed strategy never discards information, so that the
SM-PDF sets can be enlarged by the addition of new processes, until the prior
PDF set is eventually recovered for a large enough set of processes. We
illustrate the method by producing SM-PDFs tailored to Higgs, top quark pair,
and electroweak gauge boson physics, and determine that, when the PDF4LHC15
combined set is used as the prior, around 11, 4 and 11 Hessian eigenvectors
respectively are enough to fully describe the corresponding processes.


title: New Spectral Features from Bound Dark Matter

abstract:
  We demonstrate that dark matter particles gravitationally bound to the Earth
can induce a characteristic nuclear recoil signal at low energies in direct
detection experiments. The new spectral feature we predict can provide the
ultimate smoking gun for dark matter discovery for experiments with positive
signal but unclear background. The new feature is universal, in that the ratio
of bound over halo dark matter event rates at detectors is independent of the
dark matter-nucleon cross section.


title:
Stellar Velocity Dispersion for a Strongly-Lensed, Intermediate-Mass
  Quiescent Galaxy at z=2.8

abstract:
  Measuring stellar velocity dispersions of quiescent galaxies beyond $z\sim2$
is observationally challenging. Such measurements require near-infrared spectra
with a continuum detection of at least moderate signal-to-noise, often
necessitating long integrations. In this paper, we present deep X-Shooter
spectroscopy of one of only two known gravitationally-lensed massive quiescent
galaxies at $z>2$. This galaxy is quadruply imaged, with the brightest images
magnified by a factor of $\sim5$. The total exposure time of our data is 9.8
hours on-source; however the magnification, and the slit placement encompassing
2 images, provides a total equivalent exposure time of 215 hours. From this
deep spectrum we measure a redshift ($z_{\mathrm{spec}}=2.756\pm0.001$), making
this one of the highest redshift quiescent galaxies that is spectroscopically
confirmed. We simultaneously fit both the spectroscopic and photometric data to
determine stellar population parameters and conclude this galaxy is relatively
young, intermediate-mass, consistent with low dust content, and has quenched
only relatively recently. This recent quenching is confirmed by strong Balmer
absorption, particularly $H\delta$. Remarkably, this proves that at least some
intermediate-mass galaxies have already quenched as early as $z\sim2.8$.
Additionally, we have measured a velocity dispersion
($\sigma=187\pm43~\mathrm{km/s}$), making this the highest-redshift quiescent
galaxy with a dispersion measurement. We confirm that this galaxy falls on the
same mass fundamental plane (MFP) as galaxies at z=2.2, consistent with little
to no evolution in the MFP up to z=2.8. Overall this galaxy is proof of
existence of intermediate-mass quenched galaxies in the distant universe, and
that lensing is a powerful tool for determining their properties with improved
accuracy.


title: New class of quantum error-correcting codes for a bosonic mode

abstract:
  We construct a new class of quantum error-correcting codes for a bosonic mode
which are advantageous for applications in quantum memories, communication, and
scalable computation. These 'binomial quantum codes' are formed from a finite
superposition of Fock states weighted with binomial coefficients. The binomial
codes can exactly correct errors that are polynomial up to a specific degree in
bosonic creation and annihilation operators, including amplitude damping and
displacement noise as well as boson addition and dephasing errors. For
realistic continuous-time dissipative evolution, the codes can perform
approximate quantum error correction to any given order in the timestep between
error detection measurements. We present an explicit approximate quantum error
recovery operation based on projective measurements and unitary operations. The
binomial codes are tailored for detecting boson loss and gain errors by means
of measurements of the generalized number parity. We discuss optimization of
the binomial codes and demonstrate that by relaxing the parity structure, codes
with even lower unrecoverable error rates can be achieved. The binomial codes
are related to existing two-mode bosonic codes but offer the advantage of
requiring only a single bosonic mode to correct amplitude damping as well as
the ability to correct other errors. Our codes are similar in spirit to 'cat
codes' based on superpositions of the coherent states, but offer several
advantages such as smaller mean number, exact rather than approximate
orthonormality of the code words, and an explicit unitary operation for
repumping energy into the bosonic mode. The binomial quantum codes are
realizable with current superconducting circuit technology and they should
prove useful in other quantum technologies, including bosonic quantum memories,
photonic quantum communication, and optical-to-microwave up- and
down-conversion.


title:
The GAPS programme with HARPS-N at TNG XI. Pr~0211 in M~44: the first
  multi-planet system in an open cluster

abstract:
  Open cluster (OC) stars share the same age and metallicity, and, in general,
their age and mass can be estimated with higher precision than for field stars.
For this reason, OCs are considered an important laboratory to study the
relation between the physical properties of the planets and those of their host
stars, and the evolution of planetary systems. We started an observational
campaign within the GAPS collaboration to search for and characterize planets
in OCs We monitored the Praesepe member Pr0211 to improve the eccentricity of
the Hot-Jupiter (HJ) already known to orbit this star and search for additional
planets. An eccentric orbit for the HJ would support a planet-planet scattering
process after its formation. From 2012 to 2015, we collected 70 radial velocity
(RV) measurements with HARPS-N and 36 with TRES of Pr0211. Simultaneous
photometric observations were carried out with the robotic STELLA telescope in
order to characterize the stellar activity. We discovered a long-term trend in
the RV residuals that we show to be due to the presence of a second, massive,
outer planet. Orbital parameters for the two planets are derived by
simultaneously fitting RVs and photometric light curves, with the activity
signal modelled as a series of sinusoids at the rotational period of the star
and its harmonics. We confirm that Pr0211b has a nearly circular orbit ($e =
0.02 \pm 0.01$), with an improvement of a factor two with respect to the
previous determination of its eccentricity, and estimate that Pr0211c has a
mass $M_p\sin i = 7.9 \pm 0.2 M_J$, a period $P>$3500 days and a very eccentric
orbit ($e>$0.60). Such peculiar systems may be typical of open clusters if the
planet-planet scattering phase leading to the formation of HJs is caused by
stellar encounters rather than unstable primordial orbits. Pr0211 is the first
multi-planet system discovered around an OC star. (abridged)


title: Photoinduced Absorption within Single-Walled Carbon Nanotube Systems

abstract:
  We study the photoabsorption properties of photoactive bulk polymer/
fullerene/nanotube heterojunctions in the near-infrared region. By combining
pump-probe spectroscopy and linear response time-dependent density functional
theory within the random phase approximation (TDDFT-RPA) we elucidate the
excited state dynamics of the $E_{11}$ transition within (6,5) and (7,5)
single-walled carbon nanotubes (SWNTs) and combined with
poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C$_{61}$-butyric acid
methyl ester (PCBM) in P3HT/PCBM/SWNT blended samples. We find the presence of
a photoinduced absorption (PA) peak is related mainly to the width of the
photobleach (PB) peak and the charge carrier density of the SWNT system. For
mixed SWNT samples, the PB peak is too broad to observe the PA peak, whereas
within P3HT/PCBM/SWNT blended samples P3HT acts as a hole acceptor, narrowing
the PB peak by exciton delocalization, which reveals a PA peak. Our results
suggest that the PA peak originates from a widening of the band gap in the
presence of excited electrons and holes. These results have important
implications for the development of new organic photovoltaic heterojunctions
including SWNTs.


title:
Type II supernovae as probes of environment metallicity: observations of
  host HII regions

abstract:
  Spectral modelling of SNII atmospheres indicates a clear dependence of metal
line strengths on progenitor metallicity. This motivates further work to
evaluate the accuracy with which these SNe can be used as metallicity
indicators. To assess this accuracy we present a sample of SNII HII-region
spectroscopy, from which environment abundances are derived. These environment
abundances are compared to the observed strength of metal lines in SN spectra.
Combining our sample with measurements from the literature, we present oxygen
abundances of 119 host HII regions, by extracting emission line fluxes and
using abundance diagnostics. Then, following Dessart et al., these abundances
are compared to equivalent widths of Fe 5018 A at various time and colour
epochs. Our distribution of inferred SNII host HII-region abundances has a
range of ~0.6 dex. We confirm the dearth of SNeII exploding at metallicities
lower than those found (on average) in the Large Magellanic Cloud. The
equivalent width of Fe 5018 A at 50 days post explosion shows a statistically
significant correlation with host HII-region oxygen abundance. The strength of
this correlation increases if one excludes abundance measurements derived far
from SN explosion sites. The correlation significance also increases if we only
analyse a 'gold' IIP sample, and if a colour epoch is used in place of time. In
addition, no evidence is found of correlation between progenitor metallicity
and SN light-curve or spectral properties - except for that stated above with
respect to Fe 5018 A equivalent width - suggesting progenitor metallicity is
not a driving factor in producing the diversity observed in our sample. This
study provides observational evidence of the usefulness of SNII as metallicity
indicators. We finish with a discussion of the methodology needed to use SN
spectra as independent metallicity diagnostics throughout the Universe.


title:
The Next Generation Virgo Cluster Survey. VII. The intrinsic shapes of
  low-luminosity galaxies in the core of the Virgo cluster, and a comparison
  with the Local Group

abstract:
  (Abridged) We investigate the intrinsic shapes of low-luminosity galaxies in
the central 300 kpc of the Virgo cluster using deep imaging obtained as part of
the NGVS. We build a sample of nearly 300 red-sequence cluster members in the
yet unexplored $-14 < M_{g} < -8$ magnitude range. The observed distribution of
apparent axis ratios is then fit by families of triaxial models with
normally-distributed intrinsic ellipticities and triaxialities. We develop a
Bayesian framework to explore the posterior distribution of the model
parameters, which allows us to work directly on discrete data, and to account
for individual, surface brightness-dependent axis ratio uncertainties. For this
population we infer a mean intrinsic ellipticity E=0.43, and a mean triaxiality
T=0.16. This implies that faint Virgo galaxies are best described as a family
of thick, nearly oblate spheroids with mean intrinsic axis ratios 1:0.94:0.57.
We additionally attempt a study of the intrinsic shapes of Local Group
satellites of similar luminosities. For the LG population we infer a slightly
larger mean intrinsic ellipticity E=0.51, and the paucity of objects with round
apparent shapes translates into more triaxial mean shapes, 1:0.76:0.49. We
finally compare the intrinsic shapes of NGVS low-mass galaxies with samples of
more massive quiescent systems, and with field, star-forming galaxies of
similar luminosities. We find that the intrinsic flattening in this
low-luminosity regime is almost independent of the environment in which the
galaxy resides--but there is a hint that objects may be slightly rounder in
denser environments. The comparable flattening distributions of low-luminosity
galaxies that have experienced very different degrees of environmental effects
suggests that internal processes are the main drivers of galaxy structure at
low masses--with external mechanisms playing a secondary role.


title: Inverse Function Theorems for Generalized Smooth Functions

abstract:
  Generalized smooth functions are a possible formalization of the original
historical approach followed by Cauchy, Poisson, Kirchhoff, Helmholtz, Kelvin,
Heaviside, and Dirac to deal with generalized functions. They are
set-theoretical functions defined on a natural non-Archimedean ring, and
include Colombeau generalized functions (and hence also Schwartz distributions)
as a particular case. One of their key property is the closure with respect to
composition. We review the theory of generalized smooth functions and prove
both the local and some global inverse function theorems.


title: Hilbert Regularity of Stanley-Reisner Rings

abstract:
  In this note, we characterize the Hilbert regularity of the Stanley-Reisner
ring $K[\bigtriangleup]$ in terms of the $f$-vector and the $h$-vector of a
simplicial complex $\bigtriangleup$. We also compute the Hilbert regularity of
a Gorenstein algebra.


title:
Rate of convergence for the discrete-time approximation of reflected
  BSDEs arising in switching problems

abstract:
  In this paper, we prove new convergence results improving the ones by
Chassagneux, Elie and Kharroubi [Ann. Appl. Probab. 22 (2012) 971--1007] for
the discrete-time approximation of multidimensional obliquely reflected BSDEs.
These BSDEs, arising in the study of switching problems, were considered by Hu
and Tang [Probab. Theory Related Fields 147 (2010) 89--121] and generalized by
Hamad\`ene and Zhang [Stochastic Process. Appl. 120 (2010) 403--426] and
Chassagneux, Elie and Kharroubi [Electron. Commun. Probab. 16 (2011) 120--128].
Our main result is a rate of convergence obtained in the Lipschitz setting and
under the same structural conditions on the generator as the one required for
the existence and uniqueness of a solution to the obliquely reflected BSDE.


title: Numerical RHD simulations of flaring chromosphere with Flarix

abstract:
  Flarix is a radiation-hydrodynamical (RHD) code for modeling of the response
of the chromosphere to a beam bombardment during solar flares. It solves the
set of hydrodynamic conservation equations coupled with non-LTE equations of
radiative transfer. The simulations are driven by high energy electron beams.
We present results of the Flarix simulations of a flaring loop relevant to the
problem of continuum radiation during flares. In particular we focus on
properties of the hydrogen Balmer continuum which was recently detected by
IRIS.


title: Dust interferometers in plasmas

abstract:
  An interferometric imaging technique has been proposed to instantly measure
the diameter of individual spherical dust particles suspended in a gas
discharge plasma. The technique is based on the defocused image analysis of
both spherical particles and their binary agglomerates. Above a critical
diameter, the defocused images of spherical particles contain stationary
interference fringe patterns and the fringe number increases with particle
diameters. Below this critical diameter, the particle size has been measured
using the rotational interference fringe patterns which appear only on the
defocused images of binary agglomerates. In this case, a lower cut-off limit of
particle diameter has been predicted, below which no such rotational fringe
patterns are observed for the binary agglomerates. The method can be useful as
a diagnostics for complex plasma experiments on earth as well as under
microgravity condition.


title:
Superconductivity in a misfit phase combining a topological crystalline
  insulator and a layered transition metal dichalcogenide

abstract:
  We report the characterization of the misfit compound
(Pb1-xSnxSe2)1.16(TiSe2)2, in which a [100] rocksalt bilayer of Pb1-xSnxSe,
which is a topological crystalline insulator in bulk form, alternates with a
double layer of the normally non-superconducting layered transition metal
dichalcogenide TiSe2. The x dependence of Tc displays a weak dome-like shape
with a maximum Tc of 4.5 K at x = 0.2; there is only a subtle change in Tc
corresponding to the expected trivial to topological transition in the
Pb1-xSnxSe bi-layer. We present a more detailed characterization of the
superconductor at x = 0.4, for which the bulk Pb1-xSnxSe phase is in the
topological crystalline insulator regime. For this material, the Sommerfeld
parameter gamma =11.06 mJ mol-1 K-2, the Debye temperature delta D = 161 K, the
normalized specific heat jump value delta C/ gamma Tc = 1.38 and the
electron-phonon constant value lambda ep = 0.72, suggesting that
(Pb0.6Sn0.4Se)1.16(TiSe2)2 is a BCS-type weak coupling superconductor. This
material is of interest for probing the interaction of superconductivity with
the surface states of a topological crystalline insulator.


title: In-Medium Y-Suppression and Feed-down in UU and PbPb Collisions

abstract:
  The suppression of Y mesons in the hot quark-gluon medium (QGP) versus
reduced feed-down is investigated in UU collisions at RHIC energies and PbPb
collisions at LHC energies. Our centrality- and p_T-dependent model encompasses
screening, collisional damping and gluodissociation in the QGP. For Y(1S) it is
in agreement with both STAR and CMS data provided the relativistic Doppler
effect and the reduced feed-down from the Y(nS) and chi_b(nP) states are
properly considered. At both energies, most of the Y(1S) suppression is found
to be due to reduced feed-down, whereas most of the Y(2S) suppression is caused
by the hot-medium effects. The role of the latter increases with energy. The
p_T-dependence is flat due to the relativistic Doppler effect and reduced
feed-down. We predict the Y(1S)-suppression in PbPb at sqrt(s_NN) = 5.02 TeV.


title:
Deep convolutional networks for automated detection of posterior-element
  fractures on spine CT

abstract:
  Injuries of the spine, and its posterior elements in particular, are a common
occurrence in trauma patients, with potentially devastating consequences.
Computer-aided detection (CADe) could assist in the detection and
classification of spine fractures. Furthermore, CAD could help assess the
stability and chronicity of fractures, as well as facilitate research into
optimization of treatment paradigms.
  In this work, we apply deep convolutional networks (ConvNets) for the
automated detection of posterior element fractures of the spine. First, the
vertebra bodies of the spine with its posterior elements are segmented in spine
CT using multi-atlas label fusion. Then, edge maps of the posterior elements
are computed. These edge maps serve as candidate regions for predicting a set
of probabilities for fractures along the image edges using ConvNets in a 2.5D
fashion (three orthogonal patches in axial, coronal and sagittal planes). We
explore three different methods for training the ConvNet using 2.5D patches
along the edge maps of 'positive', i.e. fractured posterior-elements and
'negative', i.e. non-fractured elements.
  An experienced radiologist retrospectively marked the location of 55
displaced posterior-element fractures in 18 trauma patients. We randomly split
the data into training and testing cases. In testing, we achieve an
area-under-the-curve of 0.857. This corresponds to 71% or 81% sensitivities at
5 or 10 false-positives per patient, respectively. Analysis of our set of
trauma patients demonstrates the feasibility of detecting posterior-element
fractures in spine CT images using computer vision techniques such as deep
convolutional networks.


title: Decomposable approximations revisited

abstract:
  Nuclear C*-algebras enjoy a number of approximation properties, most famously
the completely positive approximation property. This was recently sharpened to
arrange for the incoming maps to be sums of order-zero maps. We show that, in
addition, the outgoing maps can be chosen to be asymptotically order-zero.
Further these maps can be chosen to be asymptotically multiplicative if and
only if the C*-algebra and all its traces are quasidiagonal.


title:
Towards modelling X-ray reverberation in AGN: Piecing together the
  extended corona

abstract:
  Models of X-ray reverberation from extended coronae are developed from
general relativistic ray tracing simulations. Reverberation lags between
correlated variability in the directly observed continuum emission and that
reflected from the accretion disc arise due to the additional light travel time
between the corona and reflecting disc. X-ray reverberation is detected from an
increasing sample of Seyfert galaxies and a number of common properties are
observed, including a transition from the characteristic reverberation
signature at high frequencies to a hard lag within the continuum component at
low frequencies, as well a pronounced dip in the reverberation lag at 3keV.
These features are not trivially explained by the reverberation of X-rays
originating from simple point sources. We therefore model reverberation from
coronae extended both over the surface of the disc and vertically. Causal
propagation through its extent for both the simple case of constant velocity
propagation and propagation linked to the viscous timescale in the underlying
accretion disc is included as well as stochastic variability arising due to
turbulence locally on the disc. We find that the observed features of X-ray
reverberation in Seyfert galaxies can be explained if the long timescale
variability is dominated by the viscous propagation of fluctuations through the
corona. The corona extends radially at low height over the surface of the disc
but with a bright central region in which fluctuations propagate up the black
hole rotation axis driven by more rapid variability arising from the innermost
regions of the accretion flow.


title: Optimal Prefix Free Codes With Partial Sorting

abstract:
  We describe an algorithm computing an optimal prefix free code for $n$
unsorted positive weights in time within $O(n(1+\lg \alpha))\subseteq O(n\lg
n)$, where the alternation $\alpha\in[1..n-1]$ measures the amount of sorting
required by the computation. This asymptotical complexity is within a constant
factor of the optimal in the algebraic decision tree computational model, in
the worst case over all instances of size $n$ and alternation $\alpha$. Such
results refine the state of the art complexity of $\Theta(n\lg n)$ in the worst
case over instances of size $n$ in the same computational model, a landmark in
compression and coding since 1952, by the mere combination of van Leeuwen's
algorithm to compute optimal prefix free codes from sorted weights (known since
1976), with Deferred Data Structures to partially sort a multiset depending on
the queries on it (known since 1988).


title:
Strains differences in the collective behaviour of zebrafish (Danio
  rerio) in heterogeneous environment

abstract:
  Recent studies show differences in individual motion and shoaling tendency
between strains of the same species. Here, we analyse the collective motion and
the response to visual stimuli in two morphologically different strains (TL and
AB) of zebrafish. For both strains, we observe 10 groups of 5 and 10 zebrafish
swimming freely in a large experimental tank with two identical attractive
landmarks (cylinders or disks) for one hour. We track the positions of the fish
by an automated tracking method and compute several metrics at the group level.
First, the probability of presence shows that both strains avoid free space and
are more likely to swim in the vicinity of the walls of the tank and the
attractive landmarks. Second, the analysis of landmarks occupancy shows that AB
zebrafish are more present in their vicinity than TL zebrafish and that both
strains regularly transit from one landmark to the other with no preference on
the long duration. Finally, TL zebrafish show a higher cohesion than AB
zebrafish. Thus, landmarks and duration of the repicates allow to reveal
collective behavioural variabilities among different strains of zebrafish.
These results provide a new insight into the need to take into account
individual variability of zebrafish strains for studying collective behaviour.


title: Theory of third harmonic generation in graphene: a diagrammatic approach

abstract:
  We present a finite-temperature diagrammatic perturbation theory of third
harmonic generation (THG) in doped graphene. We carry out calculations of the
third-order conductivity in the scalar potential gauge, highlighting a subtle
cancellation between a Fermi surface contribution, which contains only power
laws, and power-law contributions of inter-band nature. Only logarithms survive
in the final result. We conclude by presenting quantitative results for the
up-conversion efficiency at zero and finite temperature. Our results shed light
on the on-going dispute over the dependence of THG on carrier concentration in
graphene.


title:
Giant edge spin accumulation in a symmetric quantum well with two
  subbands

abstract:
  We have studied the edge spin accumulation in a high mobility two-dimensional
electron gas formed in a symmetric well with two subbands. This study is
strongly motivated by the recent experiment of Hernandez et al. [Phys. Rev. B
{\bf 88}, 161305(R) (2013)] who demonstrated the spin accumulation near the
edges of a bilayer symmetric GaAs structure in contrast to no effect in a
single-layer configuration. The intrinsic mechanism of the spin-orbit
interaction we consider arises from the coupling between two subband states of
opposite parities. We obtain a parametrically large magnitude of the edge spin
density for the two-subband sample as compared to the usual single-subband
structure. We show that the presence of a gap in the system, i.e., the energy
separation $\Delta$ between the two subband bottoms, changes drastically the
picture of the edge spin accumulation. Thus one can easily proceed from the
regime of weak spin accumulation to the regime of strong one by varying the
Fermi energy (electron density) and/or $\Delta$. We estimate that by changing
the gap $\Delta$ from zero up to $1\div 2$ K, the magnitude of the effect
changes by three orders of magnitude. This opens up the possibility for the
design of new spintronic devices.


title: Delta-matroids and Vassiliev invariants

abstract:
  Vassiliev (finite type) invariants of knots can be described in terms of
weight systems. These are functions on chord diagrams satisfying so-called
4-term relations. In the study of the sl2 weight system, it was shown that its
value on a chord diagram depends on the intersection graph of the diagram
rather than on the diagram itself. Moreover, it was shown that the value of
this weight system on an intersection graph depends on the cy- cle matroid of
the graph rather than on the graph itself. This result arose the question
whether there is a natural way to introduce a 4-term relation on the space
spanned by matroids, similar to the one for graphs. It happened however that
the answer is negative: there are graphs having isomorphic cycle matroids such
that applying the "second Vassiliev move" to a pair of corresponding vertices
a;b of the graphs we obtain two graphs with nonisomorphic matroids.
  The goal of the present paper is to show that the situation is different for
binary delta-matroids: one can define both the first and the second Vassiliev
moves for binary delta-matroids and introduce a 4-term relation for them in
such a way that the mapping taking a chord diagram to its delta-matroid
respects the corresponding 4-term relations. Moreover, this mapping admits a
natural extension to chord diagrams on several circles, which correspond to
singular links. Delta-matroids were introduced by A. Bouchet for the purpose of
studying embedded graphs, whence their relationship with (multiloop) chord
diagrams is by no means unexpected. Some evidence for the existence of such a
relationship can be found, for example, the Tutte polynomial for embedded
graphs has been introduced. It was shown that this polynomial depends on the
delta-matroid of the embedded graph rather than the graph itself and satises
the Vassilev 4-term relation.


title:
Materials properties of out-of-plane heterostructures of MoS$_2$-WSe$_2$
  and WS$_2$-MoSe$_2$

abstract:
  Based on first-principles calculations, the materials properties (structural,
electronic, vibrational, and optical properties) of out-of-plane
heterostructures formed from the transiti on metal dichalcogenides,
specifically MoS$_2$-WSe$_2$ and WS$_2$-MoSe$_2$ were investigated. The
heterostructures of MoS$_2$-WSe$_2$ and WS$_2$-MoSe$_2$ are found to be direct
and ind irect band gap semiconductors, respectively. However, a direct band gap
in the WS$_2$-MoSe$_2$ heterostructure can be achieved by applying compressive
strain. Furthermore, the excitoni c peaks in both monolayer and bilayer
heterostructures are calculated to understand the optical behavior of these
systems. The suppression of the optical spectrum with respect to the c
orresponding monolayers is due to interlayer charge transfer. The stability of
the systems under study is confirmed by performing phonon spectrum
calculations.


title: Analytical Calculation of Radiative Corrections of a THDM Potential

abstract:
  We obtain a closed form effective potential at the one-loop level of a Two
Higgs Doublet Model. Through the loop expansion we reproduce the expression
presented by Weinberg and Coleman, showing explicitly every step involved in
the calculation. The formalism is then extended to include interaction terms
between two scalar doublets and a final expression of the one-loop level
contributions is presented.


title: Toughness and Strength of Nanocrystalline Graphene

abstract:
  Pristine monocrystalline graphene is claimed to be the strongest material
known with remarkable mechanical and electrical properties. However, graphene
made with scalable fabrication techniques is polycrystalline and contains
inherent nano-scale line and point defects - grain boundaries and
grain-boundary triple junctions - that lead to significant statistical
fluctuations in toughness and strength. These fluctuations become particularly
pronounced for nanocrystalline graphene where the density of defects is high.
Here we use large-scale simulation and continuum modeling to show that the
statistical variation in toughness and strength can be understood with
'weakest-link' statistics. We develop the first statistical theory of toughness
in polycrystalline graphene, and elucidate the nano-scale origins of the
grain-size dependence of its strength and toughness. Our results should lead to
more reliable graphene device design, and provide a framework to interpret
experimental results in a broad class of 2D materials.


title:
Quantum thermal machine acting on a many-body quantum system: role of
  correlations in thermodynamic tasks

abstract:
  We study the functioning of a three-level thermal machine when acting on a
many-qubit system, the entire system being placed in an electromagnetic field
in a stationary out-of-thermal-equilibrium configuration. This realistic setup
stands in between the two so-far explored cases of single-qubit and macroscopic
object targets, providing information on the scaling with system size of purely
quantum properties in thermodynamic contexts. We show that, thanks to the
presence of robust correlations among the qubits induced by the field,
thermodynamic tasks can be delivered by the machine both locally to each qubit
and collectively to the many-qubit system: this allows a task to be delivered
also on systems much bigger than the machine size.


title:
What Can I Do Around Here? Deep Functional Scene Understanding for
  Cognitive Robots

abstract:
  For robots that have the capability to interact with the physical environment
through their end effectors, understanding the surrounding scenes is not merely
a task of image classification or object recognition. To perform actual tasks,
it is critical for the robot to have a functional understanding of the visual
scene. Here, we address the problem of localizing and recognition of functional
areas from an arbitrary indoor scene, formulated as a two-stage deep learning
based detection pipeline. A new scene functionality testing-bed, which is
complied from two publicly available indoor scene datasets, is used for
evaluation. Our method is evaluated quantitatively on the new dataset,
demonstrating the ability to perform efficient recognition of functional areas
from arbitrary indoor scenes. We also demonstrate that our detection model can
be generalized onto novel indoor scenes by cross validating it with the images
from two different datasets.


title: Fast In-Memory SQL Analytics on Graphs

abstract:
  We study a class of graph analytics SQL queries, which we call relationship
queries. Relationship queries are a wide superset of fixed-length graph
reachability queries and of tree pattern queries. Intuitively, it discovers
target entities that are reachable from source entities specified by the query.
It usually also finds aggregated scores, which correspond to the target
entities and are calculated by applying aggregation functions on measure
attributes, which are found on the target entities, the source entities and the
paths from the sources to the targets. We present real-world OLAP scenarios,
where efficient relationship queries are needed. However, row stores, column
stores and graph databases are unacceptably slow in such OLAP scenarios. We
briefly comment on the straightforward extension of relationship queries that
allows accessing arbitrary schemas.
  The GQ-Fast in-memory analytics engine utilizes a bottom-up fully pipelined
query execution model running on a novel data organization that combines
salient features of column-based organization, indexing and compression.
Furthermore, GQ-Fast compiles its query plans into executable C++ source codes.
Besides achieving runtime efficiency, GQ-Fast also reduces main memory
requirements because, unlike column databases, GQ-Fast selectively allows more
dense forms of compression including heavy-weighted compressions, which do not
support random access.
  We used GQ-Fast to accelerate queries for two OLAP dashboards in the
biomedical field. It outperforms Postgres by 2-4 orders of magnitude and
outperforms MonetDB and Neo4j by 1-3 orders of magnitude when all of them are
running on RAM. In addition, it generally saves space due to the appropriate
use of compression methods.


title: Simplicial complexes with lattice structures

abstract:
  If $L$ is a finite lattice, we show that there is a natural topological
lattice structure on the geometric realization of its order complex $\Delta(L)$
(definition recalled). Lattice-theoretically, the resulting object is a
subdirect product of copies of $L$. We note properties of this construction and
of some variants thereof, and pose several questions. For $M_3$ the $5$-element
nondistributive modular lattice, $\Delta(M_3)$ is modular, but its underlying
topological space does not admit a structure of distributive lattice, answering
a question of Walter Taylor.
  We also describe a construction of "stitching together" a family of lattices
along a common chain, and note how $\Delta(M_3)$ can be obtained as a case of
this construction.


title:
Geminal embedding scheme for optimal atomic basis set construction in
  correlated calculations

abstract:
  We introduce an efficient method to construct optimal and system adaptive
basis sets for use in electronic structure and quantum Monte Carlo
calculations. The method is based on an embedding scheme in which a reference
atom is singled out from its environment, while the entire system (atom and
environment) is described by a Slater determinant or its antisymmetrized
geminal power (AGP) extension. The embedding procedure described here allows
for the systematic and consistent contraction of the primitive basis set into
geminal embedded orbitals (GEOs), with a dramatic reduction of the number of
variational parameters necessary to represent the many-body wave function, for
a chosen target accuracy. Within the variational Monte Carlo method, the Slater
or AGP part is determined by a variational minimization of the energy of the
whole system in presence of a flexible and accurate Jastrow factor,
representing most of the dynamical electronic correlation. The resulting GEO
basis set opens the way for a fully controlled optimization of many-body wave
functions in electronic structure calculation of bulk materials, namely,
containing a large number of electrons and atoms. We present applications on
the water molecule, the volume collapse transition in cerium, and the
high-pressure liquid hydrogen.


title:
On the Automorphism Groups of the Z2Z4-Linear 1-Perfect and
  Preparata-Like Codes

abstract:
  We consider the symmetry group of a $Z_2Z_4$-linear code with parameters of a
$1$-perfect, extended $1$-perfect, or Preparata-like code. We show that,
provided the code length is greater than $16$, this group consists only of
symmetries that preserve the $Z_2Z_4$ structure. We find the orders of the
symmetry groups of the $Z_2Z_4$-linear (extended) $1$-perfect codes. Keywords:
additive codes, $Z_2Z_4$-linear codes, $1$-perfect codes, Preparata-like codes,
automorphism group, symmetry group.


title:
Error Propagation Dynamics of PIV-based Pressure Field Calculations: How
  well does the pressure Poisson solver perform inherently?

abstract:
  Obtaining pressure field data from particle image velocimetry (PIV) is an
attractive technique in fluid dynamics due to its noninvasive nature. The
application of this technique generally involves integrating the pressure
gradient or solving the pressure Poisson equation using a velocity field
measured with PIV. However, very little research has been done to investigate
the dynamics of error propagation from PIV-based velocity measurements to the
pressure field calculation. Rather than measure the error through experiment,
we investigate the dynamics of the error propagation by examining the Poisson
equation directly. We analytically quantify the error bound in the pressure
field, and are able to illustrate the mathematical roots of why and how the
Poisson equation based pressure calculation propagates error from the PIV data.
The results show that the error depends on the shape and type of boundary
conditions, the dimensions of the flow domain, and the flow type.


title:
A Helioseismic Survey of Near-surface Flows Around Active Regions and
  their Association with Flares

abstract:
  We use helioseismic holography to study the association of shallow flows with
solar flare activity in about 250 large sunspot groups observed between 2010
and 2014 with the Helioseismic and Magnetic Imager on the Solar Dynamics
Observatory. Four basic flow parameters: horizontal speed, horizontal component
of divergence, vertical component of vorticity, and a vertical kinetic helicity
proxy, are mapped for each active region during its passage across the solar
disk. Flow indices are derived representing the mean and standard deviation of
these parameters over magnetic masks and compared with contemporary measures of
flare X-ray flux. A correlation exists for several of the flow indices,
especially those based on the speed and the standard deviation of all flow
parameters. However, their correlation with X-ray flux is similar to that
observed with the mean unsigned magnetic flux density over the same masks. The
temporal variation of the flow indices are studied, and a superposed epoch
analysis with respect to the occurrence to 70 M and X-class flares is made.
While flows evolve with the passage of the active regions across the disk, no
discernible precursors or other temporal changes specifically associated with
flares are detected.


title: Experimental Searches for the Axion and Axion-like Particles

abstract:
  Four decades after its prediction, the axion remains the most compelling
solution to the Strong-CP problem and a well-motivated dark matter candidate,
inspiring a host of elegant and ultrasensitive experiments based on
axion-photon mixing. This report reviews the experimental situation on several
fronts. The microwave cavity experiment is making excellent progress in the
search for dark matter axions in the microelectronvolt range and may be
plausibly extended up to 100 mu eV. Within the past several years however, it
has been realized that axions are pervasive throughout string theories, but
with masses that fall naturally in the nanoelectronvolt range, for which a
NMR-based search is under development. Searches for axions emitted from the
Sun's burning core, and purely laboratory experiments based on photon
regeneration have both made great strides in recent years, with ambitious
projects proposed for the coming decade. Each of these campaigns has pushed the
state of the art in technology, enabling large gains in sensitivity and mass
reach. Furthermore each modality has also been exploited to search for more
generalized axion-like particles, that will also be discussed in this report.
We are hopeful, even optimistic, that the next review of the subject will
concern the discovery of the axion, its properties, and its exploitation as a
probe of early universe cosmology and structure formation.


title:
Finite element approximation of a time-fractional diffusion problem in a
  non-convex polygonal domain

abstract:
  An initial-boundary value problem for the time-fractional diffusion equation
is discretized in space using continuous piecewise-linear finite elements on a
polygonal domain with a re-entrant corner. Known error bounds for the case of a
convex polygon break down because the associated Poisson equation is no longer
$H^2$-regular. In particular, the method is no longer second-order accurate if
quasi-uniform triangulations are used. We prove that a suitable local mesh
refinement about the re-entrant corner restores second-order convergence. In
this way, we generalize known results for the classical heat equation due to
Chatzipantelidis, Lazarov, Thom\'ee and Wahlbin.


title: Violation of the Leggett-Garg Inequality in Neutrino Oscillations

abstract:
  The Leggett-Garg inequality, an analogue of Bell's inequality involving
correlations of measurements on a system at different times, stands as one of
the hallmark tests of quantum mechanics against classical predictions. The
phenomenon of neutrino oscillations should adhere to quantum-mechanical
predictions and provide an observable violation of the Leggett-Garg inequality.
We demonstrate how oscillation phenomena can be used to test for violations of
the classical bound by performing measurements on an ensemble of neutrinos at
distinct energies, as opposed to a single neutrino at distinct times. A study
of the MINOS experiment's data shows a greater than $6{\sigma}$ violation over
a distance of 735 km, representing the longest distance over which either the
Leggett-Garg inequality or Bell's inequality has been tested.


title:
Continuous Data Assimilation for a 2D B\'enard Convection System through
  Horizontal Velocity Measurements Alone

abstract:
  In this paper we propose a continuous data assimilation (downscaling)
algorithm for a two-dimensional B\'enard convection problem. Specifically we
consider the two-dimensional Boussinesq system of a layer of incompressible
fluid between two solid horizontal walls, with no-normal flow and stress free
boundary condition on the walls, and fluid is heated from the bottom and cooled
from the top. In this algorithm, we incorporate the observables as a feedback
(nudging) term in the evolution equation of the horizontal velocity. We show
that under an appropriate choice of the nudging parameter and the size of the
spatial coarse mesh observables, and under the assumption that the observed
data is error free, the solution of the proposed algorithm converges at an
exponential rate, asymptotically in time, to the unique exact unknown reference
solution of the original system, associated with the observed data on the
horizontal component of the velocity. Moreover, we note that in the case where
the observational measurements are not error free, one can estimate the error
between the solution of the algorithm and the exact reference solution of the
system in terms of the error in the measurements.


title:
On the Symmetries and the Capacity Achieving Input Covariance Matrices
  of Multiantenna Channels

abstract:
  In this paper we study the capacity achieving input covariance matrices of a
single user multiantenna channel based solely on the group of symmetries of its
matrix of propagation coefficients. Our main result, which unifies and improves
the techniques used in a variety of classical capacity theorems, uses the Haar
(uniform) measure on the group of symmetries to establish the existence of a
capacity achieving input covariance matrix in a very particular subset of the
covariance matrices. This result allows us to provide simple proofs for old and
new capacity theorems. Among other results, we show that for channels with two
or more standard symmetries, the isotropic input is optimal. Overall, this
paper provides a precise explanation of why the capacity achieving input
covariance matrices of a channel depend more on the symmetries of the matrix of
propagation coefficients than any other distributional assumption.


title: Bounds for Extreme Zeros of Quasi-orthogonal Ultraspherical Polynomials

abstract:
  We discuss and compare upper and lower bounds obtained by two different
methods for the positive zero of the ultraspherical polynomial
$C_{n}^{(\lambda)}$ that is greater than $1$ when $-3/2 < \lambda < -1/2.$ Our
first approach uses mixed three term recurrence relations and interlacing of
zeros while the second approach uses a method going back to Euler and Rayleigh
and already applied to Bessel functions and Laguerre and $q$-Laguerre
polynomials. We use the bounds obtained by the second method to simplify the
proof of the interlacing of the zeros of $(1-x^2)C_{n}^{(\lambda)}$ and
$C_{n+1}^{(\lambda)}$, for $-3/2 < \lambda < \infty$.


title: Bifurcation of space periodic solutions in symmetric reversible FDEs

abstract:
  In this paper, we propose an equivariant degree based method to study
bifurcation of periodic solutions (of constant period) in symmetric networks of
reversible FDEs. Such a bifurcation occurs when eigenvalues of linearization
move along the imaginary axis (without change of stability of the trivial
solution and possibly without $1:k$ resonance). Physical examples motivating
considered settings are related to stationary solutions to PDEs with non-local
interaction: reversible mixed delay differential equations (MDDEs) and
integro-differential equations (IDEs). In the case of $S_4$-symmetric networks
of MDDEs and IDEs, we present exact computations of full equivariant
bifurcation invariants. Algorithms and computational procedures used in this
paper are also included.


title:
Possibility of triple magic trapping of clock and Rydberg states of
  divalent atoms in optical lattices

abstract:
  We predict the possibility of "triply-magic" optical lattice trapping of
neutral divalent atoms. In such a lattice, the ${^1}\!S_{0}$ and ${^3}\!P_{0}$
clock states and an additional Rydberg state experience identical optical
potentials, fully mitigating detrimental effects of the motional decoherence.
In particular, we show that this triply magic trapping condition can be
satisfied for Yb atom at optical wavelengths and for various other divalent
systems (Ca, Mg, Hg and Sr) in the UV region. We assess the quality of triple
magic trapping conditions by estimating the probability of excitation out of
the motional ground state as a result of the excitations between the clock and
the Rydberg states. We also calculate trapping laser-induced photoionization
rates of divalent Rydberg atoms at magic frequencies. We find that such rates
are below the radiative spontaneous-emission rates, due to the presence of
Cooper minima in photoionization cross-sections.


title:
A Scalable Blocked Gibbs Sampling Algorithm For Gaussian And Poisson
  Regression Models

abstract:
  Markov Chain Monte Carlo (MCMC) methods are a popular technique in Bayesian
statistical modeling. They have long been used to obtain samples from posterior
distributions, but recent research has focused on the scalability of these
techniques for large problems. We do not develop new sampling methods but
instead describe a blocked Gibbs sampler which is sufficiently scalable to
accomodate many interesting problems. The sampler we describe applies to a
restricted subset of the Generalized Linear Mixed-effects Models (GLMM's); this
subset includes Poisson and Gaussian regression models. The blocked Gibbs
sampling steps jointly update a prior variance parameter along with all of the
random effects underneath it. We also discuss extensions such as flexible prior
distributions.


title:
Distributed Subgradient-based Multi-agent Optimization with More General
  Step Sizes

abstract:
  A wider selection of step sizes is explored for the distributed subgradient
algorithm for multi-agent optimization problems, for both time-invariant and
time-varying communication topologies. The square summable requirement of the
step sizes commonly adopted in the literature is removed. The step sizes are
only required to be positive, vanishing and non-summable. It is proved that in
both unconstrained and constrained optimization problems, the agents' estimates
reach consensus and converge to the optimal solution with the more general
choice of step sizes. The idea is to show that a weighted average of the
agents' estimates approaches the optimal solution, but with different
approaches. In the unconstrained case, the optimal convergence of the weighted
average of the agents' estimates is proved by analyzing the distance change
from the weighted average to the optimal solution and showing that the weighted
average is arbitrarily close to the optimal solution. In the constrained case,
this is achieved by analyzing the distance change from the agents' estimates to
the optimal solution and utilizing the boundedness of the constraints. Then the
optimal convergence of the agents' estimates follows because consensus is
reached in both cases. These results are valid for both a strongly connected
time-invariant graph and time-varying balanced graphs that are jointly strongly
connected.


title: Three-Dimensional All-Dielectric Photonic Topological Insulator

abstract:
  The discovery of two-dimensional topological photonic systems has transformed
our views on electromagnetic propagation and scattering of classical waves, and
a quest for similar states in three dimensions, known to exist in condensed
matter systems, has been put forward. Here we demonstrate that symmetry
protected three-dimensional topological states can be engineered in an
all-dielectric platform with the electromagnetic duality between electric and
magnetic fields ensured by the structure design. Magneto-electric coupling
playing the role of a synthetic gauge field leads to a topological transition
to an insulating regime with a complete three-dimensional photonic bandgap. An
emergence of surface states with conical Dirac dispersion and spin-locking is
unimpeded. Robust propagation of surface states along two-dimensional domain
walls defined by the reversal of magneto-electric coupling is confirmed
numerically by first principle studies. It is shown that the proposed system
represents a table-top platform for emulating relativistic physics of massive
Dirac fermions and the surface states revealed can be interpreted as
Jackiw-Rebbi states confined to the interface between two domains with opposite
particle masses.


title:
Physically feasible three-level transitionless quantum driving with
  multiple Schr\"{o}dinger dynamics

abstract:
  Three-level quantum systems, which possess some unique characteristics beyond
two-level ones, such as electromagnetically induced transparency, coherent
trapping, and Raman scatting, play important roles in solid-state quantum
information processing. Here, we introduce an approach to implement the
physically feasible three-level transitionless quantum driving with multiple
Schr\"{o}dinger dynamics (MSDs). It can be used to control accurately
population transfer and entanglement generation for three-level quantum systems
in a nonadiabatic way. Moreover, we propose an experimentally realizable hybrid
architecture, based on two nitrogen-vacancy-center ensembles coupled to a
transmission line resonator, to realize our transitionless scheme which
requires fewer physical resources and simple procedures, and it is more robust
against environmental noises and control parameter variations than conventional
adiabatic passage techniques. All these features inspire the further
application of MSDs on robust quantum information processing in experiment.


title:
Full statistics of erasure processes: Isothermal adiabatic theory and a
  statistical Landauer principle

abstract:
  We study driven finite quantum systems in contact with a thermal reservoir in
the regime in which the system changes slowly in comparison to the
equilibration time. The associated isothermal adiabatic theorem allows us to
control the full statistics of energy transfers in quasi-static processes.
Within this approach, we extend Landauer's Principle on the energetic cost of
erasure processes to the level of the full statistics and elucidate the nature
of the fluctuations breaking Landauer's bound.

categories: math-ph cond-mat.stat-mech math.MP quant-ph


title:
Unidirectional transport of wave packets through tilted discrete
  breathers in nonlinear lattices with asymmetric defects

abstract:
  We consider the transfer of lattice wave packets through a tilted discrete
breather (TDB) in opposite directions in the discrete nonlinear Schr\"{o}dinger
model with asymmetric defects, which may be realized as a Bose-Einstein
condensate trapped in a deep optical lattice, or as optical beams in a
waveguide array. A unidirectional transport mode is found, in which the
incident wave packets, whose energy belongs to a certain interval between full
reflection and full passage regions, pass the TDB only in one direction, while,
in the absence of the TDB, the same lattice admits bi-directional propagation.
The operation of this mode is accurately explained by an analytical
consideration of the respective energy barriers. The results suggest that the
TDB may emulate the unidirectional propagation of atomic and optical beams in
various settings. In the case of the passage of the incident wave packet, the
scattering TDB typically shifts by one lattice unit in the direction from which
the wave packet arrives, which is an example of the tractor-beam effect,
provided by the same system, in addition to the rectification of incident
waves.


title: Obliquity Variability of a Potentially Habitable Early Venus

abstract:
  Venus currently rotates slowly, with its spin controlled by solid-body and
atmospheric thermal tides. However, conditions may have been far different 4
billion years ago, when the Sun was fainter and most of the carbon within Venus
could have been in solid form, implying a low-mass atmosphere. We investigate
how the obliquity would have varied for a hypothetical rapidly rotating Early
Venus. The obliquity variation structure of an ensemble of hypothetical Early
Venuses is simpler than that Earth would have if it lacked its large Moon
(Lissauer et al., 2012), having just one primary chaotic regime at high
prograde obliquities. We note an unexpected long-term variability of up to
$\pm7^\circ$ for retrograde Venuses. Low-obliquity Venuses show very low total
obliquity variability over billion-year timescales -- comparable to that of the
real Moon-influenced Earth.


title:
Heralded quantum repeater based on the scattering of photons off single
  emitters in weak-coupling regime

abstract:
  We propose a heralded quantum repeater based on the scattering of photons off
single emitters in one-dimensional waveguides. We show the details by
implementing nonlocal entanglement generation, entanglement swapping, and
entanglement purification modules with atoms in waveguides, and discuss the
feasibility of the repeater with currently achievable technology. In our
scheme, the faulty events can be discarded by detecting the polarization of the
photons. That is, our protocols are accomplished with fidelity of 100% in
principle, which is advantageous for implementing realistic long-distance
quantum communication. Moreover, additional atomic qubits are not required, but
only a single-photon medium. Our scheme is scalable and attractive since it can
be realized in solid-state quantum systems. With the great progress on
controlling atom-waveguide systems, the repeater may be very useful in quantum
information processing in the future.


title: Modified Dark Matter

abstract:
  Modified dark matter (MDM, formerly known as MoNDian dark matter) is a
phenomenological model of dark matter, inspired by quantum gravity. We review
the construction of MDM by generalizing entropic gravity to de-Sitter space as
is appropriate for an accelerating universe (in accordance with the Lambda-CDM
model). Unlike cold dark matter models, the MDM mass profile depends on the
baryonic mass. We successfully fit the rotation curves to a sample of 30 local
spiral galaxies with a single free parameter (viz., the mass-to-light ratio for
each galaxy). We show that dynamical and observed masses agree in a sample of
93 galactic clusters. We also comment on strong gravitational lensing in the
context of MDM.


title: Fast Muon Simulation in the JUNO Central Detector

abstract:
  The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose
neutrino experiment designed to measure the neutrino mass hierarchy using a
central detector (CD), which contains 20 kton liquid scintillator (LS)
surrounded by about 17,000 photomultiplier tubes (PMTs). Due to the large
fiducial volume and huge number of PMTs, the simulation of a muon particle
passing through the CD with the Geant4 toolkit becomes an extremely
computation-intensive task. This paper presents a fast simulation
implementation using a so-called voxel method: for scintillation photons
generated in a certain LS voxel, the PMT's response is produced beforehand with
Geant4 and then introduced into the simulation at runtime. This
parameterisation method successfully speeds up the most CPU consuming process,
the optical photon's propagation in the LS, by a factor of 50. In the paper,
the comparison of physics performance between fast and full simulation is also
given.


title:
Separation of Signals Consisting of Amplitude and Instantaneous
  Frequency RRC Pulses Using SNR Uniform Training

abstract:
  This work presents sample mean and sample variance based features that
distinguish continuous phase FSK from QAM and PSK modulations. Root raised
cosine pulses are used for signal generation. Support vector machines are
employed for signals separation. They are trained for only one value of SNR and
used to classify the signals from a wide range of SNR. A priori information
about carrier amplitude, carrier phase, carrier offset, roll-off factor and
initial symbol phase is relaxed. Effectiveness of the method is tested by
observing the joint effects of AWGN, carrier offset, lack of symbol and
sampling synchronization, and fast fading.


title:
The chemical composition of red giants in 47 Tucanae. II. Magnesium
  isotopes and pollution scenarios

abstract:
  The phenomenon of multiple populations in globular clusters is still far from
understood, with several proposed mechanisms to explain the observed behaviour.
The study of elemental and isotopic abundance patterns are crucial for
investigating the differences among candidate pollution mechanisms. We derive
magnesium isotopic ratios for 13 stars in the globular cluster 47 Tucanae (NGC
104) to provide new, detailed information about the nucleosynthesis that has
occurred within the cluster. For the first time, the impact of 3D model stellar
atmospheres on the derived Mg isotopic ratios is investigated. Using both
tailored 1D atmospheric models and 3D hydrodynamical models, we derive
magnesium isotopic ratios from four features of MgH near 5135{\AA} in 13 giants
near the tip of the RGB, using high signal-to-noise, high-resolution spectra.
We derive the magnesium isotopic ratios for all stars and find no significant
offset of the isotopic distribution between the pristine and the polluted
populations. Furthermore, we do not detect any statistically significant
differences in the spread in the Mg isotopes in either population. No trends
were found between the Mg isotopes and [Al/Fe]. The inclusion of 3D atmospheres
has a significant impact on the derived 25Mg/24Mg ratio, increasing it by a
factor of up to 2.5, compared to 1D. The 26Mg/24Mg ratio, on the other hand,
essentially remains unchanged. We confirm the results seen from other globular
clusters, where no strong variation in the isotopic ratios is observed between
stellar populations, for observed ranges in [Al/Fe]. We see no evidence for any
significant activation of the Mg-Al burning chain. The use of 3D atmospheres
causes an increase of a factor of up to 2.5 in the fraction of 25Mg, resolving
part of the discrepancy between the observed isotopic fraction and the
predictions from pollution models.


title:
A singular one-parameter family of solutions in cubic superstring field
  theory

abstract:
  Performing a gauge transformation of a simple identity-like solution of
superstring field theory, we construct a one-parameter family of solutions, and
by evaluating the energy associated to this family, we show that for most of
the values of the parameter the solution represents the tachyon vacuum, except
for two isolated singular points where the solution becomes the perturbative
vacuum and the half brane solution.


title: Non-Markovian discrete qubit dynamics

abstract:
  The study of open quantum systems is important for fundamental issues of
quantum physics as well as for technological applications such as quantum
information processing. The interaction of a quantum system with it's
environment is usually detrimental for the quantum properties of the system and
leads to decoherence. However, sometimes a coherent partial exchange of
information takes place between the system and the environment and the dynamics
of the open system becomes non-Markovian. In this article we study discrete
open quantum system dynamics where single evolution step consist of local
unitary transformation on the open system followed by a coupling unitary
between the system and the environment. We implement experimentally a local
control protocol for controlling the transition from Markovian to non-Markovian
dynamics.


title: Spectrum Estimation from Samples

abstract:
  We consider the problem of approximating the set of eigenvalues of the
covariance matrix of a multivariate distribution (equivalently, the problem of
approximating the "population spectrum"), given access to samples drawn from
the distribution. The eigenvalues of the covariance of a distribution contain
basic information about the distribution, including the presence or lack of
structure in the distribution, the effective dimensionality of the
distribution, and the applicability of higher-level machine learning and
multivariate statistical tools. We consider this fundamental recovery problem
in the regime where the number of samples is comparable, or even sublinear in
the dimensionality of the distribution in question. First, we propose a
theoretically optimal and computationally efficient algorithm for recovering
the moments of the eigenvalues of the population covariance matrix. We then
leverage this accurate moment recovery, via a Wasserstein distance argument, to
show that the vector of eigenvalues can be accurately recovered. We provide
finite--sample bounds on the expected error of the recovered eigenvalues, which
imply that our estimator is asymptotically consistent as the dimensionality of
the distribution and sample size tend towards infinity, even in the sublinear
sample regime where the ratio of the sample size to the dimensionality tends to
zero. In addition to our theoretical results, we show that our approach
performs well in practice for a broad range of distributions and sample sizes.


title:
Continuum study on QCD phase diagram through an OPE-modified gluon
  propagator

abstract:
  Within the Dyson-Schwinger equations (DSEs) framework, a gluon propagator
model incorporating quark's feedback through operator product expansion (OPE)
is introduced to investigate the QCD phase diagram in the
temperature--chemical-potential ($T-\mu$) plane. Partial restoration of chiral
symmetry at zero temperature and finite temperature are both studied,
suggesting a first order phase transition point on the $\mu$ axis and a
critical end point at $(T_E,\mu_E)/T_c = (0.85,1.11)$, where $T_c$ is the
pseudo-critical temperature. In addition, we find the pseudo-critical line can
be well parameterized with the curvature parameter $\kappa$ and a consistent
decrease in $\kappa$ with more of gluon propagator distributed to quark's
feedback.


title:
Towards Quantum Simulation of Chemical Dynamics with Prethreshold
  Superconducting Qubits

abstract:
  The single excitation subspace (SES) method for universal quantum simulation
is investigated for a number of diatomic molecular collision complexes.
Assuming a system of $n$ tunably-coupled, and fully-connected superconducting
qubits, computations are performed in the $n$-dimensional SES which maps
directly to an $n$-channel collision problem within a diabatic molecular wave
function representation. Here we outline the approach on a classical computer
to solve the time-dependent Schr\"odinger equation in an $n$-dimensional
molecular basis - the so-called semiclassical molecular-orbital close-coupling
(SCMOCC) method - and extend the treatment beyond the straight-line,
constant-velocity approximation which is restricted to large kinetic energies
($\gtrsim 0.1$ keV/u). We explore various multichannel potential averaging
schemes and an Ehrenfest symmetrization approach to allow for the application
of the SCMOCC method to much lower collision energies (approaching 1 eV/u). In
addition, a computational efficiency study for various propagators is performed
to speed-up the calculations on classical computers. These computations are
repeated for the simulation of the SES approach assuming typical parameters for
realistic pretheshold superconducting quantum computing hardware. The
feasibility of applying future SES processors to the quantum dynamics of large
molecular collision systems is briefly discussed.


title: Particle Transport in a 3D duct by adding and doubling

abstract:
  Particle transport through a duct by Lambertian reflection from duct walls is
again considered. This popular transport example has been solved by most
numerical transport methods except notably one- the method of doubling. We
shall show that the method of doubling provides every bit as, or more, accurate
reflectances and transmittances as the numerical discrete ordinates (NDO) and
analytical discrete ordinates (ADO) methods with less mathematical and
numerical effort.


title:
Limit theorems for critical first-passage percolation on the triangular
  lattice

abstract:
  Consider (independent) first-passage percolation on the sites of the
triangular lattice $\mathbb{T}$. Denote the passage time of the site $v$ in
$\mathbb{T}$ by $t(v)$, and assume that $P(t(v)=0)=P(t(v)=1)=1/2$. Denote by
$b_{0,n}$ the passage time from 0 to the halfplane
$\{v\in\mathbb{T}:\mbox{Re}(v)\geq n\}$, and by $T(0,nu)$ the passage time from
0 to the nearest site to $nu$, where $|u|=1$. We prove that as
$n\rightarrow\infty$, $b_{0,n}/\log n\rightarrow 1/(2\sqrt{3}\pi)$ a.s.,
$E[b_{0,n}]/\log n\rightarrow 1/(2\sqrt{3}\pi)$ and Var$[b_{0,n}]/\log
n\rightarrow 2/(3\sqrt{3}\pi)-1/(2\pi^2)$; $T(0,nu)/\log n\rightarrow
1/(\sqrt{3}\pi)$ in probability but not a.s., $E[T(0,nu)]/\log n\rightarrow
1/(\sqrt{3}\pi)$ and Var$[T(0,nu)]/\log n\rightarrow 4/(3\sqrt{3}\pi)-1/\pi^2$.
This answers a question of Kesten and Zhang (1997) and improves our previous
work (2014). From this result, we derive an explicit form of the central limit
theorem for $b_{0,n}$ and $T(0,nu)$. A key ingredient for the proof is the
moment generating function of the conformal radii for conformal loop ensemble
CLE$_6$, given by Schramm, Sheffield and Wilson (2009).


title:
Skolem Sequence Based Self-adaptive Broadcast Protocol in Cognitive
  Radio Networks

abstract:
  The base station (BS) in a multi-channel cognitive radio (CR) network has to
broadcast to secondary (or unlicensed) receivers/users on more than one
broadcast channels via channel hopping (CH), because a single broadcast channel
can be reclaimed by the primary (or licensed) user, leading to broadcast
failures. Meanwhile, a secondary receiver needs to synchronize its clock with
the BS's clock to avoid broadcast failures caused by the possible clock drift
between the CH sequences of the secondary receiver and the BS. In this paper,
we propose a CH-based broadcast protocol called SASS, which enables a BS to
successfully broadcast to secondary receivers over multiple broadcast channels
via channel hopping. Specifically, the CH sequences are constructed on basis of
a mathematical construct---the Self-Adaptive Skolem sequence. Moreover, each
secondary receiver under SASS is able to adaptively synchronize its clock with
that of the BS without any information exchanges, regardless of any amount of
clock drift.


title: A Framework to Prevent QR Code Based Phishing Attacks

abstract:
  Though the rapid development and spread of Information and Communication
Technology (ICT) making people's life much more easier, on the other hand it
causing some serious threats to the society. Phishing is one of the most common
cyber threat, that most users falls in. This research investigate on QR code
based phishing attacks which is a newly adopted intrusive method and how to
enhance the awareness and avoidance behavior of QR based phishing attacks
through the user centric security education approaches using game based
learning.


title: Impurity entropy of junctions of multiple quantum wires

abstract:
  We calculate the zero-temperature impurity entropy of a junction of multiple
quantum wires of interacting spinless fermions. Starting from a given
single-particle S-matrix representing a fixed point of the renormalization
group (RG) flows, we carry out fermionic perturbation theory in the bulk
interactions, with the perturbation series summed in the random phase
approximation (RPA). The results agree completely with boundary conformal field
theory (BCFT) predictions of the ground state degeneracy, and also with known
RG flows through the g-theorem.


title:
Consensus conditions of continuous-time multi-agent systems with
  time-delays and measurement noises

abstract:
  This work is concerned with stochastic consensus conditions of multi-agent
systems with both time-delays and measurement noises. For the case of additive
noises, we develop some necessary conditions and sufficient conditions for
stochastic weak consensus by estimating the differential resolvent function for
delay equations. By the martingale convergence theorem, we obtain necessary
conditions and sufficient conditions for stochastic strong consensus. For the
case of multiplicative noises, we consider two kinds of time-delays, appeared
in the measurement term and the noise term, respectively. We first show that
stochastic weak consensus with the exponential convergence rate implies
stochastic strong consensus. Then by constructing degenerate Lyapunov
functional, we find the sufficient consensus conditions and show that
stochastic consensus can be achieved by carefully choosing the control gain
according to the noise intensities and the time-delay in the measurement term.


abstract:
  Identifying a set of influential spreaders in complex networks plays a
crucial role in effective information spreading. A simple strategy is to choose
top-$r$ ranked nodes as spreaders according to influence ranking method such as
PageRank, ClusterRank and $k$-shell decomposition. Besides, some heuristic
methods such as hill-climbing, SPIN, degree discount and independent set based
are also proposed. However, these approaches suffer from a possibility that
some spreaders are so close together that they overlap sphere of influence or
time consuming. In this report, we present a simply yet effectively iterative
method named VoteRank to identify a set of decentralized spreaders with the
best spreading ability. In this approach, all nodes vote in a spreader in each
turn, and the voting ability of neighbors of elected spreader will be decreased
in subsequent turn. Experimental results on four real networks show that under
Susceptible-Infected-Recovered (SIR) model, VoteRank outperforms the
traditional benchmark methods on both spreading speed and final affected scale.
What's more, VoteRank is also superior to other group-spreader identifying
methods on computational time.


title: Tempered Fractional Feynman-Kac Equation

abstract:
  Functionals of Brownian/non-Brownian motions have diverse applications and
attracted a lot of interest of scientists. This paper focuses on deriving the
forward and backward fractional Feynman-Kac equations describing the
distribution of the functionals of the space and time tempered anomalous
diffusion, belonging to the continuous time random walk class. Several examples
of the functionals are explicitly treated, including the occupation time in
half-space, the first passage time, the maximal displacement, the fluctuations
of the occupation fraction, and the fluctuations of the time-averaged position.


title: Four-junction superconducting circuit

abstract:
  We develop a theory for the quantum circuit consisting of a superconducting
loop interrupted by four Josephson junctions and pierced by a magnetic flux
(either static or time-dependent). In addition to the similarity with the
typical three-junction flux qubit in the double-well regime, we demonstrate the
difference of the four-junction circuit from its three-junction analogue,
including its advantages over the latter. Moreover, the four-junction circuit
in the single-well regime is also investigated. Our theory provides a tool to
explore the physical properties of this four-junction superconducting circuit.


title: Finite volume HWENO schemes for nonconvex conservation laws

abstract:
  We illustrate that numerical solutions of high order finite volume Hermite
weighted essentially non-oscillatory (HWENO) scheme for some nonconvex
conservation laws perform poorly or converge to the entropy solution in a slow
speed. The modified finite volume HWENO schemes based either on first order
monotone schemes or a second order entropic projection following the work of
Qiu and Shu [SIAM J. Sci. Comput., 31 (2008), 584-607] are proposed and
compared for solving one-dimensional scalar problems. We extend the modified
finite volume HWENO based on first order monotone schemes for one-dimensional
systems and two-dimensional scalar conservation laws. Numerical tests for
several representative examples will be reported.


title: A conservative semi-Lagrangian HWENO method for the Vlasov equation

abstract:
  In this paper, we present a high order conservative semi-Lagrangian (SL)
Hermite weighted essentially non-oscillatory (HWENO) method for the Vlasov
equation based on dimensional splitting [Cheng and Knorr, Journal of
Computational Physics, 22(1976)]. The major advantage of HWENO reconstruction,
compared with the original WENO reconstruction, is compact. For the split
one-dimensional equation, to ensure local mass conservation, we propose a high
order SL HWENO scheme in a conservative flux-difference form, following the
work in [J.-M. Qiu and A. Christlieb, Journal of Computational Physics,
v229(2010)]. Besides performing dimensional splitting for the original 2D
problem, we design a proper splitting for equations of derivatives to ensure
local mass conservation of the proposed HWENO scheme. The proposed fifth order
SL HWENO scheme with the Eulerian CFL condition has been tested to work well in
capturing filamentation structures without introducing oscillations. We
introduce WENO limiters to control oscillations when the time stepping size is
larger than the Eulerian CFL restriction. We perform classical numerical tests
on rigid body rotation problem, and demonstrate the performance of our scheme
via the Landau damping and two-stream instabilities when solving the
Vlasov-Poisson system.


title: On the sensitivities dependence in non-autonomous dynamical systems

abstract:
  For discrete autonomous dynamical systems (ADS) $(X, d, f)$, it was found
that in the three conditions defining Devaney chaos, topological transitivity
and dense periodic points together imply sensitive dependence on initial
condition(Banks, Brooks, Cairns, Davis and Stacey, 1992). In this paper, the
result of Banks et al. is generalized to a class of the non-autonomous
dynamical systems (NADS) $(X,f_{1,\infty})$. Also, by the studying of NADS over
their iterated systems $(X,f_{1,\infty}^{[k]})$, we know that for two sensitive
NADS, the one which preserve sensitive in its any times iterated systems is
more sensitive than the one not. In this case, several sufficient conditions
ensuring two kinds of sensitivities are preserved under the arbitrary number of
iterations of certain NADS are given.


title: Two Photon Decays of $\eta_c$ from Lattice QCD

abstract:
  We present an exploratory lattice study for the two-photon decay of $\eta_c$
using $N_f=2$ twisted mass lattice QCD gauge configurations generated by the
European Twisted Mass Collaboration. Two different lattice spacings of
$a=0.067$fm and $a=0.085$fm are used in the study, both of which are of
physical size of 2$fm$. The decay widths are found to be $1.025(5)$KeV for the
coarser lattice and $1.062(5)$KeV for the finer lattice respectively where the
errors are purely statistical. A naive extrapolation towards the continuum
limit yields $\Gamma\simeq 1.122(14)$KeV which is smaller than the previous
quenched result and most of the current experimental results. Possible reasons
are discussed.


title:
Breather-to-soliton and rogue wave-to-soliton transitions in a resonant
  erbium-doped fiber system with higher-order effects

abstract:
  Under investigation in this paper is the higherorder nonlinear Schrodinger
and Maxwell-Bloch (HNLSMB) system which describes the wave propagation in an
erbium-doped nonlinear fiber with higher-order effects including the
fourth-order dispersion and quintic nonKerr nonlinearity. The breather and
rogue wave (RW) solutions are shown that they can be converted into various
soliton solutions including the multipeak soliton, periodic wave, antidark
soliton, M-shaped soliton, and W-shaped soliton. In addition, under different
values of higher-order effect, the locus of the eigenvalues on the complex
plane which converts breathers or RWs into solitons is calculated.


title:
Latent common manifold learning with alternating diffusion: analysis and
  applications

abstract:
  The analysis of data sets arising from multiple sensors has drawn significant
research attention over the years. Traditional methods, including kernel-based
methods, are typically incapable of capturing nonlinear geometric structures.
We introduce a latent common manifold model underlying multiple sensor
observations for the purpose of multimodal data fusion. A method based on
alternating diffusion is presented and analyzed; we provide theoretical
analysis of the method under the latent common manifold model. To exemplify the
power of the proposed framework, experimental results in several applications
are reported.


title: Unit Commitment with N-1 Security and Wind Uncertainty

abstract:
  As renewable wind energy penetration rates continue to increase, one of the
major challenges facing grid operators is the question of how to control
transmission grids in a reliable and a cost-efficient manner. The stochastic
nature of wind forces an alteration of traditional methods for solving
day-ahead and look-ahead unit commitment and dispatch. In particular,
uncontrollable wind generation increases the risk of random component failures.
To address these questions, we present an N-1 Security and Chance-Constrained
Unit Commitment (SCCUC) that includes the modeling of generation reserves that
respond to wind fluctuations and tertiary reserves to account for single
component outages. The basic formulation is reformulated as a mixed-integer
second-order cone problem to limit the probability of failure. We develop three
different algorithms to solve the problem to optimality and present a detailed
case study on the IEEE RTS-96 single area system. The case study assesses the
economic impacts due to contingencies and various degrees of wind power
penetration into the system and also corroborates the effectiveness of the
algorithms.


title:
Non-robustly intermingled basins for perturbations of time-one map of
  Anosov flows

abstract:
  Perturbations of time-one maps of transitive Anosov flows are studied. We
show that most perturbations have no intermingled basins of hyperbolic physical
measures.


title: Active Particles in Complex and Crowded Environments

abstract:
  Differently from passive Brownian particles, active particles, also known as
self-propelled Brownian particles or microswimmers and nanoswimmers, are
capable of taking up energy from their environment and converting it into
directed motion. Because of this constant flow of energy, their behavior can
only be explained and understood within the framework of nonequilibrium
physics. In the biological realm, many cells perform directed motion, for
example, as a way to browse for nutrients or to avoid toxins. Inspired by these
motile microorganisms, researchers have been developing artificial particles
that feature similar swimming behaviors based on different mechanisms; these
manmade micro- and nanomachines hold a great potential as autonomous agents for
healthcare, sustainability, and security applications. With a focus on the
basic physical features of the interactions of self-propelled Brownian
particles with a crowded and complex environment, this comprehensive review
will put the reader at the very forefront of the field, providing a guided tour
through its basic principles, the development of artificial self-propelling
micro- and nanoparticles, and their application to the study of nonequilibrium
phenomena, as well as the open challenges that the field is currently facing.


title: Strongly-coupled nanotube electromechanical resonators

abstract:
  Coupling an electromechanical resonator with carbon-nanotube quantum dots is
a significant method to control both the electronic charge and the spin quantum
states. By exploiting a novel micro-transfer technique, we fabricate two
strongly-coupled and electrically-tunable mechanical resonators on a single
carbon nanotube for the first time. The frequency of the two resonators can be
individually tuned by the bottom gates, and strong coupling is observed between
the electron charge and phonon modes of each resonator. Furthermore, the
conductance of either resonator can be nonlocally modulated by the phonon modes
in the other resonator. Strong coupling is observed between the phonon modes of
the two resonators, which provides an effective long distance electron-electron
interaction. The generation of phonon-mediated-spin entanglement is also
theoretically analyzed for the two resonators. This strongly-coupled nanotube
electromechanical resonator array provides an experimental platform for future
studies of the coherent electron-phonon interaction, the phonon mediated
long-distance electron interaction, and entanglement state generation.


title:
First look at the PYTHIA8 hadronization program for neutrino interaction
  generators

abstract:
  Current and future neutrino oscillation experiments utilize information of
hadronic final states to improve sensitivities on oscillation parameters
measurements. Among the physics of hadronic systems in neutrino interactions,
the hadronization model controls multiplicities and kinematics of final state
hadrons from the primary interaction vertex. For relatively high invariant mass
events, neutrino interaction generators rely on the PYTHIA6 hadronization
program. Here, we show a possible improvement of this process in neutrino event
generators, by utilizing expertise from the HERMES experiment. Next, we discuss
the possibility to implement the PYTHIA8 program in neutrino interaction
generators, including GENIE and NEUT. Finally, we show preliminary comparisons
of PYTHIA8 predictions with neutrino hadron multiplicity data from bubble
chamber experiments within the GENIE hadronization validation tool.


title: A Search for Neutral Current Single Gamma with ND280 at T2K

abstract:
  The methodology and preliminary results for the search of single photons
initiated by Neutral Current neutrino interactions with the ND280 detector at
the T2K experiment are presented. This measurement aims to set the first limit
on single-photon neutrino production below 1~GeV. Neutrino production of single
photon is a subdominant process in neutrino interactions. Because photons and
electrons have very similar signatures in neutrino detectors, careful
estimations need to be made not to bias the \nue appearance oscillation results
of accelerator neutrino experiments. The single photons are created by a
nuclear resonance (typically $\Delta$(1232)) after interaction of the neutrino.
The cross section is expected to be of the order of $10^{-42} cm^{2}$. The main
background is composed of $\pi^{0}$ decaying into two photons, where only one
photon is detected, and $\pi^{0}$ events creating photons from outside of the
fiducial volume.


title:
Slippery but tough - the rapid fracture of lubricated frictional
  interfaces

abstract:
  We study the onset of friction for rough contacting blocks whose interface is
coated with a thin lubrication layer. High speed measurements of the real
contact area and stress fields near the interface reveal that propagating shear
cracks mediate lubricated frictional motion. While lubricants reduce interface
resistances, surprisingly, they significantly increase energy dissipated,
$\Gamma$, during rupture. Moreover, lubricant viscosity affects the onset of
friction but has no effect on $\Gamma$. Fracture mechanics provide a new way to
view the otherwise hidden complex dynamics of the lubrication layer.


title:
Magneto centrifugal winds from accretion discs around black hole
  binaries

abstract:
  We want to test if self-similar magneto-hydrodynamic (MHD) accretion-ejection
models can explain the observational results for accretion disk winds in BHBs.
In our models, the density at the base of the outflow, from the accretion disk,
is not a free parameter, but is determined by solving the full set of dynamical
MHD equations without neglecting any physical term. Different MHD solutions
were generated for different values of (a) the disk aspect ratio
($\varepsilon$) and (b) the ejection efficiency ($p$). We generated two kinds
of MHD solutions depending on the absence (cold solution) or presence (warm
solution) of heating at the disk surface. The cold MHD solutions are found to
be inadequate to account for winds due to their low ejection efficiency. The
warm solutions can have sufficiently high values of $p (\gtrsim 0.1)$ which is
required to explain the observed physical quantities in the wind. The heating
(required at the disk surface for the warm solutions) could be due to the
illumination which would be more efficient in the Soft state. We found that in
the Hard state a range of ionisation parameter is thermodynamically unstable,
which makes it impossible to have any wind at all, in the Hard state. Our
results would suggest that a thermo-magnetic process is required to explain
winds in BHBs.


title:
Geometric properties of solutions to the total variation denoising
  problem

abstract:
  This article studies the denoising performance of total variation (TV) image
regularization. More precisely, we study geometrical properties of the solution
to the so-called Rudin-Osher-Fatemi total variation denoising method. The first
contribution of this paper is a precise mathematical definition of the
"extended support" (associated to the noise-free image) of TV denoising. It is
intuitively the region which is unstable and will suffer from the staircasing
effect. We highlight in several practical cases, such as the indicator of
convex sets, that this region can be determined explicitly. Our second and main
contribution is a proof that the TV denoising method indeed restores an image
which is exactly constant outside a small tube surrounding the extended
support. The radius of this tube shrinks toward zero as the noise level
vanishes, and are able to determine, in some cases, an upper bound on the
convergence rate. For indicators of so-called "calibrable" sets (such as disks
or properly eroded squares), this extended support matches the edges, so that
discontinuities produced by TV denoising cluster tightly around the edges. In
contrast, for indicators of more general shapes or for complicated images, this
extended support can be larger. Beside these main results, our paper also
proves several intermediate results about fine properties of TV regularization,
in particular for indicators of calibrable and convex sets, which are of
independent interest.


title:
Special transitions in an O($n$) loop model with an Ising-like
  constraint

abstract:
  We investigate the O($n$) nonintersecting loop model on the square lattice
under the constraint that the loops consist of ninety-degree bends only. The
model is governed by the loop weight $n$, a weight $x$ for each vertex of the
lattice visited once by a loop, and a weight $z$ for each vertex visited twice
by a loop. We explore the $(x,z)$ phase diagram for some values of $n$. For
$0<n<1$, the diagram has the same topology as the generic O($n$) phase diagram
with $n<2$, with a first-order line when $z$ starts to dominate, and an
O($n$)-like transition when $x$ starts to dominate. Both lines meet in an
exactly solved higher critical point. For $n>1$, the O($n$)-like transition
line appears to be absent. Thus, for $z=0$, the $(n,x)$ phase diagram displays
a line of phase transitions for $n\le 1$. The line ends at $n=1$ in an
infinite-order transition. We determine the conformal anomaly and the critical
exponents along this line. These results agree accurately with a recent
proposal for the universal classification of this type of model, at least in
most of the range $-1 \leq n \leq 1$. We also determine the exponent describing
crossover to the generic O($n$) universality class, by introducing topological
defects associated with the introduction of `straight' vertices violating the
ninety-degree-bend rule. These results are obtained by means of transfer-matrix
calculations and finite-size scaling.


title:
Casimir energy between two parallel plates and projective representation
  of Poincar\'e group

abstract:
  The Casimir effect is a physical manifestation of zero point energy of
quantum vacuum. In a relativistic quantum field theory, Poincar\'e symmetry of
the theory seems, at first sight, to imply that non-zero vacuum energy is
inconsistent with translational invariance of the vacuum. In the setting of two
uniform boundary plates at rest, quantum fields outside the plates have
(1+2)-dimensional Poincar\'e symmtry. Taking a massless scalar field as an
example, we have examined the consistency between the Poincar\'e symmetry and
the existence of the vacuum enegy. We note that, in quantum theory, symmetries
are represented projectively in general and show that the Casimir energy is
connected to central charges appearing in the algebra of generators in the
projective representations.


title:
A Simple extension of Dematerialization Theory: Incorporation of
  Technical Progress and the Rebound Effect

abstract:
  Dematerialization is the reduction in the quantity of materials needed to
produce something useful over time. Dematerialization fundamentally derives
from ongoing increases in technical performance but it can be counteracted by
demand rebound - increases in usage because of increased value (or decreased
cost) that also results from increasing technical performance. A major question
then is to what extent technological performance improvement can offset and is
offsetting continuously increasing economic consumption. This paper contributes
to answering this question by offering some simple quantitative extensions to
the theory of dematerialization. The paper then empirically examines the
materials consumption trends as well as cost trends for a large set of
materials and a few modern artifacts over the past decades. In each of 57 cases
examined, the particular combinations of demand elasticity and technical
performance rate improvement are not consistent with dematerialization.
Overall, the theory extension and empirical examination indicate that there is
no dematerialization occurring even for cases of information technology with
rapid technical progress. Thus, a fully passive policy stance that relies on
unfettered technological change is not supported by our results.


title:
Constraints on Axions and Axionlike Particles from Fermi Large Area
  Telescope Observations of Neutron Stars

abstract:
  We present constraints on the nature of axions and axionlike particles (ALPs)
by analyzing gamma--ray data from neutron stars using the Fermi Large Area
Telescope. In addition to axions solving the strong CP problem of particle
physics, axions and ALPs are also possible dark matter candidates. We
investigate axions and ALPs produced by nucleon--nucleon bremsstrahlung within
neutron stars. We derive a phenomenological model for the gamma--ray spectrum
arising from subsequent axion decays. By analyzing 5 years of gamma-ray data
(between 60 MeV and 200 MeV) for a sample of 4 nearby neutron stars, we do not
find evidence for an axion or ALP signal, thus we obtain a combined 95\%
confidence level upper limit on the axion mass of 7.9$\times 10^{-2}$ eV, which
corresponds to a lower limit for the Peccei-Quinn scale $f_a$ of 7.6$\times
10^7$ GeV. Our constraints are more stringent than previous results probing the
same physical process, and are competitive with results probing axions and ALPs
by different mechanisms.


title:
On the absence of Volterra correct restrictions and extensions of the
  Laplace operator

abstract:
  At the beginning of the last century J. Hadamard constructed the well-known
example illustrating the incorrectness of the Cauchy problem for elliptic-type
equations. If the Cauchy problem for some differential equation is correct,
then it is usually a Volterra problem, i.e., the inverse operator is a Volterra
operator. At present, not a single Volterra correct restriction or extension
for elliptic-type equations is known. In the present paper, we prove the
absence of Volterra correct restrictions of the maximal operator $\widehat{L}$
and Volterra correct extensions of the minimal operator $L_0$ generated by the
Laplace operator in $L_2(\Omega)$, where $\Omega$ is the unit disk.


title: Network nestedness as generalized core-periphery structures

abstract:
  The concept of nestedness, in particular for ecological and economical
networks, has been introduced as a structural characteristic of real
interacting systems. We suggest that the nestedness is in fact another way to
express a mesoscale network property called the core-periphery structure. With
real ecological mutualistic networks and synthetic model networks, we reveal
the strong correlation between the nestedness and core-periphery-ness (likeness
to the core-periphery structure), by defining the network-level measures for
nestedness and core-periphery-ness in the case of weighted and bipartite
networks. However, at the same time, via more sophisticated null-model
analysis, we also discover that the degree (the number of connected neighbors
of a node) distribution poses quite severe restrictions on the possible
nestedness and core-periphery parameter space. Therefore, there must exist
structurally interwoven properties in more fundamental levels of network
formation, behind this seemingly obvious relation between nestedness and
core-periphery structures.


title: CoCos under short-term uncertainty

abstract:
  In this paper we analyze an extension of the Jeanblanc and Valchev (2005)
model by considering a short-term uncertainty model with two noises. It is a
combination of the ideas of Duffie and Lando (2001) and Jeanblanc and Valchev
(2005): share quotations of the firm are available at the financial market, and
these can be seen as noisy information about the fundamental value, or the
firm's asset, from which a low level produces the credit event. We assume there
are also reports of the firm, release times, where this short-term uncertainty
disappears. This credit event model is used to describe conversion and default
in a CoCo bond.


title: Walsh Sampling with Incomplete Noisy Signals

abstract:
  With the advent of massive data outputs at a regular rate, admittedly, signal
processing technology plays an increasingly key role. Nowadays, signals are not
merely restricted to physical sources, they have been extended to digital
sources as well.
  Under the general assumption of discrete statistical signal sources, we
propose a practical problem of sampling incomplete noisy signals for which we
do not know a priori and the sampling size is bounded. We approach this
sampling problem by Shannon's channel coding theorem. Our main results
demonstrate that it is the large Walsh coefficient(s) that characterize(s)
discrete statistical signals, regardless of the signal sources. By the
connection of Shannon's theorem, we establish the necessary and sufficient
condition for our generic sampling problem for the first time. Our generic
sampling results find practical and powerful applications in not only
statistical cryptanalysis, but software system performance optimization.