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arxiv_dataset-65001508.03344 | On the phase structure of driven quantum systems
cond-mat.dis-nn cond-mat.str-el
Clean and interacting periodically driven quantum systems are believed to
exhibit a single, trivial "infinite-temperature" Floquet-ergodic phase. In
contrast, here we show that their disordered Floquet many-body localized
counterparts can exhibit distinct ordered phases delineated by sharp
transitions. Some of these are analogs of equilibrium states with broken
symmetries and topological order, while others - genuinely new to the Floquet
problem - are characterized by order and non-trivial periodic dynamics. We
illustrate these ideas in driven spin chains with Ising symmetry.
| arxiv topic:cond-mat.dis-nn cond-mat.str-el |
arxiv_dataset-65011508.03444 | Conformal vector fields on doubly warped product manifolds and
applications
math.DG
In this article, we present a complete study of two disjoint classes of
conformal vector fields on doubly warped product manifolds as well as on doubly
warped space-times. Then we study Ricci solitons on doubly warped product
manifollds admitting these types of conformal vector fields.
| arxiv topic:math.DG |
arxiv_dataset-65021508.03544 | Production cross section estimates for strongly-interacting Electroweak
Symmetry Breaking Sector resonances at particle colliders
hep-ph hep-ex
We are exploring a generic strongly-interacting Electroweak Symmetry Breaking
Sector (EWSBS) with the low-energy effectie field theory for the four
experimentally known particles ($W_L^\pm$, $Z_L$, $h$) and its
dispersion-relation based unitary extension. In this contribution we provide
simple estimates for the production cross section of pairs of the EWSBS bosons
and their resonances at proton-proton colliders as well as in a future $e^-e^+$
(or potentially a $\mu^-\mu^+$) collider with a typical few-TeV energy. We
examine the simplest production mechanisms, tree-level production through a $W$
(dominant when quantum numbers allow) and the simple effective boson
approximation (in which the electroweak bosons are considered as collinear
partons of the colliding fermions). We exemplify with custodial isovector and
isotensor resonances at 2 TeV, the energy currently being discussed because of
a slight excess in the ATLAS 2-jet data. We find it hard, though not
unthinkable, to ascribe this excess to one of these $W_LW_L$ rescattering
resonances. An isovector resonance could be produced at a rate smaller than,
but close to earlier CMS exclusion bounds, depending on the parameters of the
effective theory. The $ZZ$ excess is then problematic and requires additional
physics (such as an additional scalar resonance). The isotensor one (that would
describe all charge combinations) has a smaller cross section.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-65031508.03644 | Self-consistent modelling of line-driven hot-star winds with Monte Carlo
radiation hydrodynamics
astro-ph.SR
Radiative pressure exerted by line interactions is a prominent driver of
outflows in astrophysical systems, being at work in the outflows emerging from
hot stars or from the accretion discs of cataclysmic variables, massive young
stars and active galactic nuclei. In this work, a new radiation hydrodynamical
approach to model line-driven hot-star winds is presented. By coupling a Monte
Carlo radiative transfer scheme with a finite-volume fluid dynamical method,
line-driven mass outflows may be modelled self-consistently, benefiting from
the advantages of Monte Carlo techniques in treating multi-line effects, such
as multiple scatterings, and in dealing with arbitrary multidimensional
configurations. In this work, we introduce our approach in detail by
highlighting the key numerical techniques and verifying their operation in a
number of simplified applications, specifically in a series of self-consistent,
one-dimensional, Sobolev-type, hot-star wind calculations. The utility and
accuracy of our approach is demonstrated by comparing the obtained results with
the predictions of various formulations of the so-called CAK theory and by
confronting the calculations with modern sophisticated techniques of predicting
the wind structure. Using these calculations, we also point out some useful
diagnostic capabilities our approach provides. Finally we discuss some of the
current limitations of our method, some possible extensions and potential
future applications.
| arxiv topic:astro-ph.SR |
arxiv_dataset-65041508.03744 | Adaptive estimation of planar convex sets
math.ST stat.TH
In this paper, we consider adaptive estimation of an unknown planar compact,
convex set from noisy measurements of its support function on a uniform grid.
Both the problem of estimating the support function at a point and that of
estimating the convex set are studied. Data-driven adaptive estimators are
proposed and their optimality properties are established. For pointwise
estimation, it is shown that the estimator optimally adapts to every compact,
convex set instead of a collection of large parameter spaces as in the
conventional minimax theory of nonparametric estimation. For set estimation,
the estimators adaptively achieve the optimal rate of convergence. In both
these problems, our analysis makes no smoothness assumptions on the unknown
sets.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-65051508.03844 | On normed semigroups
math.RA math.GR
The paper begins by exploring the various definitions of norms on semigroups
and then presents a new definition of a normed semigroup. The properties of
normed semigroups in the new sense are investigated. The new definition of the
norm is used to establish a general result on topological regular semigroups
which is then used to prove the surprising result that the semigroup M_n(K) is
not a topological regular semigroup.
| arxiv topic:math.RA math.GR |
arxiv_dataset-65061508.03944 | Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin
films: interplay between correlation, disorder, and spin-orbit coupling
cond-mat.str-el
We investigate the effects of compressive strain on the electrical
resistivity of 5d iridium based perovskite SrIrO3 by depositing epitaxial films
of thickness 35 nm on various substrates such as GdScO3 (110), DyScO3 (110),
and SrTiO3 (001). Surprisingly, we find anomalous transport behaviors in the
tempeature dependent resistivity, where the temperature exponent evolves
continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain.
Furthermore, magnetoresistance always remains positive irrespective of
resistivity upturns at low temperatures. These observations imply that the
delicate interplay between correlation and disorder in the presence of strong
spin-orbit coupling is responsible for the emergence of the non-Fermi liquid
behaviors in 5d perovskite SrIrO3 thin films. We offer a theoretical framework
for the interpretation of the experimental results.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-65071508.04044 | Supporting Developers in Porting Software via Combined Textual and
Structural Analysis of Software Artifacts
cs.SE
This is position paper accepted to the Computational Science & Engineering
Software Sustainability and Productivity Challenges (CSESSP Challenges)
Workshop, sponsored by the Networking and Information Technology Research and
Development (NITRD) Software Design and Productivity (SDP) Coordinating Group,
held October 15th-16th 2015 in Washington DC, USA. It discusses the role
recommendation systems, based on textual and structural information in source
code, and further enhanced by mining related applications, can have in
improving the portability of scientific and engineering software.
| arxiv topic:cs.SE |
arxiv_dataset-65081508.04144 | Moduli induced cogenesis of baryon asymmetry and dark matter
hep-ph hep-th
We study a cogenesis mechanism in which the observed baryon asymmetry of the
universe and the dark matter abundance can be produced simultaneously at low
reheating temperature without violating baryon number in the fundamental
vertex. In particular, we consider a model which could be realized in the
context of type IIB large volume string compactifications. The matter
superfields in this model include additional pairs of color triplet and singlet
superfields in addition to the Minimal Supersymmetric Standard Model (MSSM)
superfields. Assuming that the mass of the additional singlet fermions is
O(GeV) and color triplet fermions is O(TeV), we show that the modulus
dominantly decays into the additional color triplet superfields. After soft
supersymmetry (SUSY) breaking, the lightest eigenstate of scalar component of
color triplet superfield further decays into fermionic component of singlet
superfield and quarks without violating baryon number. Assuming R-parity
conservation, it follows that the singlet superfield will not further decay
into the SM particles and therefore it can be considered as a stable asymmetric
dark matter (ADM) component. We find that the decay of the lightest eigenstate
of scalar component of color triplet superfield gives the observed baryon
asymmetry in the visible sector, an asymmetric dark matter component with the
right abundance and naturally explains cosmic coincidence.
| arxiv topic:hep-ph hep-th |
arxiv_dataset-65091508.04244 | Spin Physics and Transverse Structure
hep-ph
Spin is a welcome complication in the study of partonic structure that has
led to new insights, even if theoretically and experimentally not all dust has
settled, in particular on quark flavor dependence and gluon spin. At the same
time it opened new questions on angular momentum and effects of transverse
structure. In this talk the focus is on the role of the transverse momenta of
partons. Like for collinear parton distribution functions (PDFs), we are also
in the case of transverse momentum dependent (TMD) PDFs, talking about forward
matrix elements. TMD PDFs (or in short TMDs) extend collinear PDFs with only
spin-spin correlations to PDFs that include spin-momentum correlations,
including also time-reversal-odd (T-odd) correlations, relevant for the
description of single spin asymmetries. In this way TMDs open up new ways of
studying the spin structure. Their operator structure within QCD, however, is
more complex leading to various ways of breaking of universality.
| arxiv topic:hep-ph |
arxiv_dataset-65101508.04344 | The ghosts of departed quantities in switches and transitions
math.DS math-ph math.MP
Transitions between steady dynamical regimes in diverse applications are
often modelled using discontinuities, but doing so introduces problems of
uniqueness. No matter how quickly a transition occurs, its inner workings can
affect the dynamics of the system significantly. Here we discuss the way
transitions can be reduced to discontinuities without trivializing them, by
preserving so-called hidden terms. We review the fundamental methodology, its
motivations, and where their study seems to be heading. We derive a prototype
for piecewise smooth models from the asymptotics of systems with rapid
transitions, sharpening Filippov's convex combinations by encoding the tails of
asymptotic series into nonlinear dependence on a switching parameter. We
present a few examples that illustrate the impact of these on our standard
picture of smooth or only piecewise smooth dynamics.
| arxiv topic:math.DS math-ph math.MP |
arxiv_dataset-65111508.04444 | TeV Lepton Number Violation: From Neutrinoless Double Beta Decay to the
LHC
hep-ph nucl-th
We analyze the sensitivity of next-generation tonne-scale neutrinoless double
$\beta$-decay ($0\nu\beta\beta$) experiments and searches for same-sign
di-electrons plus jets at the Large Hadron Collider to TeV scale lepton number
violating interactions. Taking into account previously unaccounted for physics
and detector backgrounds at the LHC, renormalization group evolution, and
long-range contributions to $0\nu\beta\beta$ nuclear matrix elements, we find
that the reach of tonne-scale $0\nu\beta\beta$ generally exceeds that of the
LHC. However, for a range of heavy particle masses near the TeV scale, the high
luminosity LHC and tonne-scale $0\nu\beta\beta$ may provide complementary
probes.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-65121508.04544 | Design and Implementation of Distributed Resource Management for Time
Sensitive Applications
math.OC cs.DC cs.MA
In this paper, we address distributed convergence to fair allocations of CPU
resources for time-sensitive applications. We propose a novel resource
management framework where a centralized objective for fair allocations is
decomposed into a pair of performance-driven recursive processes for updating:
(a) the allocation of computing bandwidth to the applications (resource
adaptation), executed by the resource manager, and (b) the service level of
each application (service-level adaptation), executed by each application
independently. We provide conditions under which the distributed recursive
scheme exhibits convergence to solutions of the centralized objective (i.e.,
fair allocations). Contrary to prior work on centralized optimization schemes,
the proposed framework exhibits adaptivity and robustness to changes both in
the number and nature of applications, while it assumes minimum information
available to both applications and the resource manager. We finally validate
our framework with simulations using the TrueTime toolbox in MATLAB/Simulink.
| arxiv topic:math.OC cs.DC cs.MA |
arxiv_dataset-65131508.04644 | Quantum Max-flow/Min-cut
math.CO cs.IT math.IT quant-ph
The classical max-flow min-cut theorem describes transport through certain
idealized classical networks. We consider the quantum analog for tensor
networks. By associating an integral capacity to each edge and a tensor to each
vertex in a flow network, we can also interpret it as a tensor network, and
more specifically, as a linear map from the input space to the output space.
The quantum max flow is defined to be the maximal rank of this linear map over
all choices of tensors. The quantum min cut is defined to be the minimum
product of the capacities of edges over all cuts of the tensor network. We show
that unlike the classical case, the quantum max-flow=min-cut conjecture is not
true in general. Under certain conditions, e.g., when the capacity on each edge
is some power of a fixed integer, the quantum max-flow is proved to equal the
quantum min-cut. However, concrete examples are also provided where the
equality does not hold.
We also found connections of quantum max-flow/min-cut with entropy of
entanglement and the quantum satisfiability problem. We speculate that the
phenomena revealed may be of interest both in spin systems in condensed matter
and in quantum gravity.
| arxiv topic:math.CO cs.IT math.IT quant-ph |
arxiv_dataset-65141508.04744 | Bath induced coherence and the secular approximation
quant-ph cond-mat.mes-hall
Finding efficient descriptions of how an environment affects a collection of
discrete quantum systems would lead to new insights into many areas of modern
physics. Markovian, or time-local, methods work well for individual systems,
but for groups a question arises: does system-bath or inter-system coupling
dominate the dissipative dynamics? The answer has profound consequences for the
long-time quantum correlations within the system. We consider two bosonic modes
coupled to a bath. By comparing an exact solution to different Markovian master
equations, we find that a smooth crossover of the equations-of-motion between
dominant inter-system and system-bath coupling exists -- but requires a
non-secular master equation. We predict a singular behaviour of the dynamics,
and show that the ultimate failure of non-secular equations of motion is
essentially a failure of the Markov approximation. Our findings justify the use
of time-local theories throughout the crossover between system-bath dominated
and inter-system-coupling dominated dynamics.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-65151508.04844 | Euler Polynomials and Identities for Non-Commutative Operators
math-ph math.MP
Three kinds of identities involving non-commutating operators and Euler and
Bernoulli polynomials are studied. The first identity, as given by Bender and
Bettencourt, expresses the nested commutator of the Hamiltonian and momentum
operators as the commutator of the momentum and the shifted Euler polynomial of
the Hamiltonian. The second one, due to J.-C. Pain, links the commutators and
anti-commutators of the monomials of the position and momentum operators. The
third appears in a work by Figuieira de Morisson and Fring in the context of
non-Hermitian Hamiltonian systems. In each case, we provide several proofs and
extensions of these identities that highlight the role of Euler and Bernoulli
polynomials.
| arxiv topic:math-ph math.MP |
arxiv_dataset-65161508.04944 | Effect of marital status on death rates. Part 2: Transient mortality
spikes
physics.soc-ph stat.AP
We examine what happens in a population when it experiences an abrupt change
in surrounding conditions. Several cases of such "abrupt transitions" for both
physical and living social systems are analyzed from which it can be seen that
all share a common pattern. First, a steep rising death rate followed by a much
slower relaxation process during which the death rate decreases as a power law
(with an exponent close to 0.7). This leads us to propose a general principle
which can be summarized as follows: "ANY abrupt change in living conditions
generates a mortality spike which acts as a kind of selection process." This we
term the Transient Shock conjecture. It provides a qualitative model which
leads to testable predictions. For example, marriage certainly brings about a
major change in environmental and social conditions and according to our
conjecture one would expect a mortality spike in the months following marriage.
At first sight this may seem an unlikely proposition but we demonstrate (by
three different methods) that even here the existence of mortality spikes is
supported by solid empirical evidence.
| arxiv topic:physics.soc-ph stat.AP |
arxiv_dataset-65171508.05044 | Cultures in Community Question Answering
cs.SI cs.CY physics.soc-ph
CQA services are collaborative platforms where users ask and answer
questions. We investigate the influence of national culture on people's online
questioning and answering behavior. For this, we analyzed a sample of 200
thousand users in Yahoo Answers from 67 countries. We measure empirically a set
of cultural metrics defined in Geert Hofstede's cultural dimensions and Robert
Levine's Pace of Life and show that behavioral cultural differences exist in
community question answering platforms. We find that national cultures differ
in Yahoo Answers along a number of dimensions such as temporal predictability
of activities, contribution-related behavioral patterns, privacy concerns, and
power inequality.
| arxiv topic:cs.SI cs.CY physics.soc-ph |
arxiv_dataset-65181508.05144 | Dressed scalar propagator in a non-abelian background from the worldline
formalism
hep-th hep-ph
We study the propagator of a colored scalar particle in the background of a
non-abelian gauge field using the worldline formalism. It is obtained by
considering the open worldline of a scalar particle with extra degrees of
freedom needed to take into account the color charge of the particle, which we
choose to be in the fundamental representation of the gauge group. Specializing
the external gauge field to be given by a sum of plane waves, i.e. a sum of
external gluons, we produce a master formula for the scalar propagator with an
arbitrary number of gluons directly attached to the scalar line, akin to
similar formulas derived in the literature for the case of the scalar particle
performing a loop. Our worldline description produces at the same time the
situation in which the particle has a color charge given by an arbitrarily
chosen symmetric or antisymmetric tensor product of the fundamental.
| arxiv topic:hep-th hep-ph |
arxiv_dataset-65191508.05244 | Fractal percolation, porosity, and dimension
math.PR
We study the porosity properties of fractal percolation sets
$E\subset\mathbb{R}^d$. Among other things, for all $0<\varepsilon<\tfrac12$,
we obtain dimension bounds for the set of exceptional points where the upper
porosity of $E$ is less than $\tfrac12-\varepsilon$, or the lower porosity is
larger than $\varepsilon$. Our method works also for inhomogeneous fractal
percolation and more general random sets whose offspring distribution gives
rise to a Galton-Watson process.
| arxiv topic:math.PR |
arxiv_dataset-65201508.05344 | A Multi-Scale Spatiotemporal Perspective of Connected and Automated
Vehicles: Applications and Wireless Networking
cs.NI
Wireless communication is a basis of the vision of connected and automated
vehicles (CAVs). Given the heterogeneity of both wireless communication
technologies and CAV applications, one question that is critical to technology
road-mapping and policy making is which communication technology is more
suitable for a specific CAV application. Focusing on the technical aspect of
this question, we present a multi-scale spatiotemporal perspective of wireless
communication technologies as well as canonical CAV applications in active
safety, fuel economy and emission control, vehicle automation, and vehicular
infotainment. Our analysis shows that CAV applications in the regime of small
spatiotemporal scale communication requirements are best supported by V2V
communications, applications in the regime of large spatiotemporal scale
communication requirements are better supported by cellular communications, and
applications in the regime of small spatial scale but medium-to-large temporal
scale can be supported by both V2V and cellular communications and provide the
opportunity of leveraging heterogeneous communication resources.
| arxiv topic:cs.NI |
arxiv_dataset-65211508.05444 | Low Temperature metamagnetism and Hall effect anomaly in Kondo compound
CeAgBi2
cond-mat.mtrl-sci cond-mat.str-el
Heavy fermion (HF) materials exhibit a rich array of phenomena due to the
strong Kondo coupling between their localized moments and itinerant electrons.
A central question in their study is to understand the interplay between
magnetic order and charge transport, and its role in stabilizing new quantum
phases of matter. Particularly promising in this regard is a family of
tetragonal intermetallic compounds Ce{$TX$}$_2$ ($T=$ transition metal, $X=$
pnictogen), that includes a variety of HF compounds showing $T$-linear
electronic specific heat $\bf{C_e \sim \gamma T}$, with $\gamma\sim$ 20-500
mJ$\cdot$mol$^{-1}$~K$^{-2}$, reflecting an effective mass enhancement ranging
from small to modest. Here, we study the low-temperature field-tuned phase
diagram of high-quality CeAgBi$_2$ using magnetometry and transport
measurements. We find an antiferromagnetic transition at ${T_{N} = 6.4}$~K with
weak magnetic anisotropy and the easy axis along the $c$-axis, similar to
previous reports (${T_{N} = 6.1}$~K). This scenario, along with the presence of
two anisotropic Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, leads to a
rich field-tuned magnetic phase diagram, consisting of five metamagnetic
transitions of both first and second order. In addition, we unveil an anomalous
Hall contribution for fields $H<54$ kOe which is drastically altered when $H$
is tuned through a trio of transitions at 57, 78, and 84~kOe, suggesting that
the Fermi surface is reconstructed in a subset of the metamagnetic transitions.
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-65221508.05544 | The $m$-$z$ relation for Type Ia supernovae: safety in numbers or safely
without worry?
astro-ph.CO
The $m$-$z$ relation for Type Ia supernovae is compatible with the
cosmological concordance model if one assumes that the Universe is homogeneous,
at least with respect to light propagation. This could be due to the density
along each line of sight being equal to the overall cosmological density, or to
`safety in numbers', with variation in the density along all lines of sight
averaging out if the sample is large enough. Statistical correlations (or lack
thereof) between redshifts, residuals (differences between the observed
distance moduli and those calculated from the best-fitting cosmological model),
and observational uncertainties suggest that the former scenario is the better
description, so that one can use the traditional formula for the luminosity
distance safely without worry.
| arxiv topic:astro-ph.CO |
arxiv_dataset-65231508.05644 | The class number one problem for the real quadratic fields
$\mathbb{Q}\left(\sqrt{(an)^2+4a}\right)$
math.NT
We solve unconditionally the class number one problem for the $2$-parameter
family of real quadratic fields $\mathbb{Q}(\sqrt{d})$ with square-free
discriminant $d=(an)^2+4a$ for positive odd integers $a$ and $n$.
| arxiv topic:math.NT |
arxiv_dataset-65241508.05744 | The Behaviour of the Green Function for the BFKL Pomeron with Running
Coupling
hep-ph
We analyse here in LO the physical properties of the Green function solution
for the BFKL equation. We show that the solution obeys the orthonormality
conditions in the physical region and fulfills the completeness requirements.
The unintegrated gluon density is shown to consists of a set of few poles with
parameters which could be determined by comparison with the DIS data of high
precision.
| arxiv topic:hep-ph |
arxiv_dataset-65251508.05844 | A NuSTAR Observation of the Gamma-Ray-Emitting X-ray Binary and
Transitional Millisecond Pulsar Candidate 1RXS J154439.4-112820
astro-ph.HE
I present a 40 kilosecond Nuclear Spectroscopic Telescope Array (NuSTAR)
observation of the recently identified low-luminosity X-ray binary and
transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4-112820, which
is associated with the high-energy gamma-ray source 3FGL J1544.6--1125. The
system is detected up to ~30 keV with an extension of the same power-law
spectrum and rapid large-amplitude variability between two flux levels observed
in soft X-rays. These findings provide further evidence that 1RXS
J154439.4-112820 belongs to the same class of objects as the nearby bona fide
tMSPs PSR J1023+0038 and XSS J12270-4859 and therefore almost certainly hosts a
millisecond pulsar accreting at low luminosities. I also examine the long-term
accretion history of 1RXS J154439.4-112820 based on archival optical,
ultraviolet, X-ray, and $\gamma$-ray light curves covering the past
$\sim$decade. Throughout this period, the source has maintained similar flux
levels at all wavelengths, which is an indication that it has not experienced
prolonged episodes of a non-accreting radio pulsar state but may spontaneously
undergo such a state transformation in the future.
| arxiv topic:astro-ph.HE |
arxiv_dataset-65261508.05944 | Bijections on m-level Rook Placements
math.CO
Suppose the rows of a board are partitioned into sets of m rows called
levels. An m-level rook placement is a subset of the board where no two squares
are in the same column or the same level. We construct explicit bijections to
prove three theorems about such placements. We start with two bijections
between Ferrers boards having the same number of m-level rook placements. The
first generalizes a map by Foata and Sch\"utzenberger and our proof applies to
any Ferrers board. This bijection also preserves the m-inversion number
statistic of an m-level rook placement, defined by Briggs and Remmel. The
second generalizes work of Loehr and Remmel. This construction only works for a
special class of Ferrers boards, but it yields a formula for calculating the
rook numbers of these boards in terms of elementary symmetric functions.
Finally we generalize another result of Loehr and Remmel giving a bijection
between boards with the same hit numbers. The second and third bijections
involve the Involution Principle of Garsia and Milne.
| arxiv topic:math.CO |
arxiv_dataset-65271508.06044 | Visualizing NLP annotations for Crowdsourcing
cs.CL
Visualizing NLP annotation is useful for the collection of training data for
the statistical NLP approaches. Existing toolkits either provide limited visual
aid, or introduce comprehensive operators to realize sophisticated linguistic
rules. Workers must be well trained to use them. Their audience thus can hardly
be scaled to large amounts of non-expert crowdsourced workers. In this paper,
we present CROWDANNO, a visualization toolkit to allow crowd-sourced workers to
annotate two general categories of NLP problems: clustering and parsing.
Workers can finish the tasks with simplified operators in an interactive
interface, and fix errors conveniently. User studies show our toolkit is very
friendly to NLP non-experts, and allow them to produce high quality labels for
several sophisticated problems. We release our source code and toolkit to spur
future research.
| arxiv topic:cs.CL |
arxiv_dataset-65281508.06144 | A prestorage method to measure neutron transmission of ultracold neutron
guides
physics.ins-det nucl-ex
There are worldwide efforts to search for physics beyond the Standard Model
of particle physics. Precision experiments using ultracold neutrons (UCN)
require very high intensities of UCN. Efficient transport of UCN from the
production volume to the experiment is therefore of great importance. We have
developed a method using prestored UCN in order to quantify UCN transmission in
tubular guides. This method simulates the final installation at the Paul
Scherrer Institute's UCN source where neutrons are stored in an intermediate
storage vessel serving three experimental ports. This method allowed us to
qualify UCN guides for their intended use and compare their properties.
| arxiv topic:physics.ins-det nucl-ex |
arxiv_dataset-65291508.06244 | Splitting Ward identity
hep-th
Within the background-field framework we present a path integral derivation
of the splitting Ward identity for the one-particle irreducible effective
action in the presence of an infrared regulator, and make connection with
earlier works on the subject. The approach is general in the sense that it does
not rely on how the splitting is performed. This identity is then used to
address the problem of background dependence of the effective action at an
arbitrary energy scale. We next introduce the modified master equation and
emphasize its role in constraining the effective action. Finally, application
to general gauge theories within the geometric approach is discussed.
| arxiv topic:hep-th |
arxiv_dataset-65301508.06344 | From de Sitter to de Sitter: decaying vacuum models as a possible
solution to the main cosmological problems
gr-qc
Decaying vacuum cosmological models evolving smoothly between two extreme
(very early and late time) de Sitter phases are capable to solve or at least to
alleviate some cosmological puzzles, among them: (i) the singularity, (ii)
horizon, (iii) graceful-exit from inflation, and (iv) the baryogenesis problem.
Our basic aim here is to discuss how the coincidence problem based on a large
class of running vacuum cosmologies evolving from de Sitter to de Sitter can
also be mollified. It is also argued that even the cosmological constant
problem become less severe provided that the characteristic scales of the two
limiting de Sitter manifolds are predicted from first principles.
| arxiv topic:gr-qc |
arxiv_dataset-65311508.06444 | HELP : The Herschel Extragalactic Legacy Project & The Coming of Age of
Multi-Wavelength Astrophysics
astro-ph.GA
How did galaxies form and evolve? This is one of the most challenging
questions in astronomy today. Answering it requires a careful combination of
observational and theoretical work to reliably determine the observed
properties of cosmic bodies over large portions of the distant Universe on the
one hand, and accurately model the physical processes driving their evolution
on the other. Most importantly, it requires bringing together disparate
multi-wavelength and multi-resolution spectro-photometric datasets in an
homogeneous and well-characterized manner so that they are suitable for a
rigorous statistical analysis. The Herschel Extragalactic Legacy Project (HELP)
funded by the EC FP7 SPACE program aims to achieve this goal by combining the
expertise of optical, infrared and radio astronomers to provide a
multi-wavelength database for the distant Universe as an accessible value-added
resource for the astronomical community. It will do so by bringing together
multi-wavelength datasets covering the 1000 deg$^2$ mapped by Herschel
extragalactic surveys in an homogeneous and well-characterized manner, creating
a joint lasting legacy from several ambitious sky surveys.
| arxiv topic:astro-ph.GA |
arxiv_dataset-65321508.06544 | A cosmological model of the early universe based on ECG with variable
$\Lambda$-term in Lyra geometry
gr-qc
In this paper, we study interacting extended Chaplygin gas as dark matter and
quintessence scalar field as dark energy with an effective $\Lambda$-term in
Lyra manifold. As we know Chaplygin gas behaves as dark matter at the early
universe while cosmological constant at the late time. Modified field equations
are given and motivation of the phenomenological models discussed in details.
Four different models based on the interaction term are investigated in this
work. Then, we consider other models where Extended Chaplygin gas and
quintessence field play role of dark matter and dark energy respectively with
two different forms of interaction between the extended Chaplygin gas and
quintessence scalar field for both constant and varying $\Lambda$. Concerning
to the mathematical hardness of the problems we discuss results numerically and
graphically. Obtained results give us hope that proposed models can work as
good models for the early universe with later stage of evolution containing
accelerated expansion.
| arxiv topic:gr-qc |
arxiv_dataset-65331508.06644 | Towards a gauge theory interpretation of the real topological string
hep-th
We consider the real topological string on certain non-compact toric
Calabi-Yau three-folds X, in its physical realization describing an orientifold
of type IIA on X with an O4-plane and a single D4-brane stuck on top. The
orientifold can be regarded as a new kind of surface operator on the gauge
theory with 8 supercharges arising from the singular geometry. We use the
M-theory lift of this system to compute the real Gopakumar-Vafa invariants
(describing wrapped M2-brane BPS states) for diverse geometries. We show that
the real topological string amplitudes pick up certain signs across flop
transitions, in a well-defined pattern consistent with continuity of the real
BPS invariants. We further give some preliminary proposals of an intrinsically
gauge theoretical description of the effect of the surface operator in the
gauge theory partition function.
| arxiv topic:hep-th |
arxiv_dataset-65341508.06744 | String Theory at LHC Using Supersymmetry Production From String Balls
hep-ph hep-th
If extra dimensions are found in the second run of LHC in the $pp$ collisions
at $\sqrt{s}$ = 14 TeV then the string scale can be $\sim$ TeV, and we should
produce string balls at LHC. In this paper we study supersymmetry (squark and
gluino) production from string balls at LHC in $pp$ collisions at $\sqrt{s}$ =
14 TeV and compare that with the parton fusion results using pQCD. We find
significant squark and gluino production from string balls at LHC which is
comparable to parton fusion pQCD results. Hence, in the absence of black hole
production at LHC, an enhancement in supersymmetry production can be a
signature of TeV scale string physics at LHC.
| arxiv topic:hep-ph hep-th |
arxiv_dataset-65351508.06844 | Implications of the first AMS-02 antiproton data for dark matter
hep-ph
The implications of the first AMS-02 $\bar p/p$ data for the propagation of
cosmic rays and the properties of dark matter (DM) are discussed. Using various
diffusive re-acceleration (DR) propagation models, one can derive very
conservative upper limits on the DM annihilation cross sections. The limits
turned out to be compatible with that from the Ferm-LAT gamma-ray data on the
dwarf spheroidal satellite galaxies. The flattening of the $\bar p/p$ spectrum
above $\sim 100$~GeV in the current data still leaves some room for TeV scale
DM particles. More antiproton data at high kinetic energies are needed to
constrain the properties of the DM particles.
| arxiv topic:hep-ph |
arxiv_dataset-65361508.06944 | Continuous parameter working memory in a balanced chaotic neural network
cond-mat.dis-nn cs.NE q-bio.NC
It has been proposed that neural noise in the cortex arises from chaotic
dynamics in the balanced state: in this model of cortical dynamics, the
excitatory and inhibitory inputs to each neuron approximately cancel, and
activity is driven by fluctuations of the synaptic inputs around their mean. It
remains unclear whether neural networks in the balanced state can perform tasks
that are highly sensitive to noise, such as storage of continuous parameters in
working memory, while also accounting for the irregular behavior of single
neurons. Here we show that continuous parameter working memory can be
maintained in the balanced state, in a neural circuit with a simple network
architecture. We show analytically that in the limit of an infinite network,
the dynamics generated by this architecture are characterized by a continuous
set of steady balanced states, allowing for the indefinite storage of a
continuous parameter. In finite networks, we show that the chaotic noise drives
diffusive motion along the approximate attractor, which gradually degrades the
stored memory. We analyze the dynamics and show that the slow diffusive motion
induces slowly decaying temporal cross correlations in the activity, which
differ substantially from those previously described in the balanced state. We
calculate the diffusivity, and show that it is inversely proportional to the
system size. For large enough (but realistic) neural population sizes, and with
suitable tuning of the network connections, the proposed balanced network can
sustain continuous parameter values in memory over time scales larger by
several orders of magnitude than the single neuron time scale.
| arxiv topic:cond-mat.dis-nn cs.NE q-bio.NC |
arxiv_dataset-65371508.07044 | The classification problem for operator algebraic varieties and their
multiplier algebras
math.OA math.LO
We study from the perspective of Borel complexity theory the classification
problem for multiplier algebras associated with operator algebraic varieties.
These algebras are precisely the multiplier algebras of irreducible complete
Nevanlinna-Pick spaces. We prove that these algebras are not classifiable up to
algebraic isomorphism using countable structures as invariants. In order to
prove such a result, we develop the theory of turbulence for Polish groupoids,
which generalizes Hjorth's turbulence theory for Polish group actions. We also
prove that the classification problem for multiplier algebras associated with
varieties in a finite dimensional ball up to isometric isomorphism has maximum
complexity among the essentially countable classification problems. In
particular, this shows that Blaschke sequences are not smoothly classifiable up
to conformal equivalence via automorphisms of the disc.
| arxiv topic:math.OA math.LO |
arxiv_dataset-65381508.07144 | Persistence exponent for random walk on directed versions of $Z^2$
math.PR
We study the persistence exponent for random walks in random sceneries (RWRS)
with integer values and for some special random walks in random environment in
$\mathbb Z^2$ including random walks in $\mathbb Z^2$ with random orientations
of the horizontal layers.
| arxiv topic:math.PR |
arxiv_dataset-65391508.07244 | Vaccine escape in 2013-4 and the hydropathic evolution of glycoproteins
of A/H3N2 viruses
q-bio.OT
More virulent strains of influenza virus subtypes H1N1 appeared widely in
2007 and H3N2 in 2011, and especially 2013-4, when the effectiveness of the
H3N2 vaccine decreased nearly to zero. The amino acid differences of
neuraminidase from prior less virulent strains appear to be small (<1%) when
tabulated through sequence alignments and counting site identities and
similarities. Here we show how analyzing fractal hydropathic forces responsible
for neuraminidase globular compaction and modularity quantifies the mutational
origins of increased virulence. It also predicts vaccine escape and specifies
optimized targets for the 2015 H3N2 vaccine different from the WHO target.
Unlike some earlier methods based on measuring hemagglutinin antigenic drift
and ferret sera, which take several years, cover only a few candidate strains,
and are ambiguous, the new methods are timely and can be completed, using NCBI
and GISAID amino acid sequences only, in a few days.
| arxiv topic:q-bio.OT |
arxiv_dataset-65401508.07344 | A Spectral Canonical Electrostatic Algorithm
physics.comp-ph physics.plasm-ph
Studying single-particle dynamics over many periods of oscillations is a
well-understood problem solved using symplectic integration. Such integration
schemes derive their update sequence from an approximate Hamiltonian,
guaranteeing that the geometric structure of the underlying problem is
preserved. Simulating a self-consistent system over many oscillations can
introduce numerical artifacts such as grid heating. This unphysical heating
stems from using non-symplectic methods on Hamiltonian systems. With this
guidance, we derive an electrostatic algorithm using a discrete form of
Hamilton's Principle. The resulting algorithm, a gridless spectral
electrostatic macroparticle model, does not exhibit the unphysical heating
typical of most particle-in-cell methods. We present results of this using a
two-body problem as an example of the algorithm's energy- and
momentum-conserving properties.
| arxiv topic:physics.comp-ph physics.plasm-ph |
arxiv_dataset-65411508.07444 | Kinematical Analysis of an Articulated Mechanism
physics.ed-ph physics.comp-ph
The purpose of this work is twofold: to present mathematical expressions for
the kinematics of an articulated mechanism and to perform numerical experiments
with the implemented code. The system of rigid parts is made of two slender
bars and a disk. In the original configuration, a constant counterclockwise
rotation rate is imposed on the disk. In the modified version, this angular
velocity varies linearly with the rotation angle to produce an average rate
that is nearly the same as the constant case. Angles, velocities and
accelerations are analyzed for a 90-degree turn of the disk. The numerical
solutions show the inversion of the linking bar sense of rotation along with
the start of deceleration for both bars. The paper and pencil solution of the
original problem that may lead to a wrong conclusion is explained. Equations
are derived from first principles and the code is placed under version control.
Those in charge of vector dynamics courses may find it useful as a
project-based learning activity.
| arxiv topic:physics.ed-ph physics.comp-ph |
arxiv_dataset-65421508.07544 | Computational Sociolinguistics: A Survey
cs.CL
Language is a social phenomenon and variation is inherent to its social
nature. Recently, there has been a surge of interest within the computational
linguistics (CL) community in the social dimension of language. In this article
we present a survey of the emerging field of "Computational Sociolinguistics"
that reflects this increased interest. We aim to provide a comprehensive
overview of CL research on sociolinguistic themes, featuring topics such as the
relation between language and social identity, language use in social
interaction and multilingual communication. Moreover, we demonstrate the
potential for synergy between the research communities involved, by showing how
the large-scale data-driven methods that are widely used in CL can complement
existing sociolinguistic studies, and how sociolinguistics can inform and
challenge the methods and assumptions employed in CL studies. We hope to convey
the possible benefits of a closer collaboration between the two communities and
conclude with a discussion of open challenges.
| arxiv topic:cs.CL |
arxiv_dataset-65431508.07644 | Singular curves and their compactified Jacobians
math.AG
We survey the theory of the compactified Jacobian associated to a singular
curve. We focus on describing low genus examples using the Abel map.
| arxiv topic:math.AG |
arxiv_dataset-65441508.07744 | Ethnicity sensitive author disambiguation using semi-supervised learning
cs.DL cs.IR stat.ML
Author name disambiguation in bibliographic databases is the problem of
grouping together scientific publications written by the same person,
accounting for potential homonyms and/or synonyms. Among solutions to this
problem, digital libraries are increasingly offering tools for authors to
manually curate their publications and claim those that are theirs. Indirectly,
these tools allow for the inexpensive collection of large annotated training
data, which can be further leveraged to build a complementary automated
disambiguation system capable of inferring patterns for identifying
publications written by the same person. Building on more than 1 million
publicly released crowdsourced annotations, we propose an automated author
disambiguation solution exploiting this data (i) to learn an accurate
classifier for identifying coreferring authors and (ii) to guide the clustering
of scientific publications by distinct authors in a semi-supervised way. To the
best of our knowledge, our analysis is the first to be carried out on data of
this size and coverage. With respect to the state of the art, we validate the
general pipeline used in most existing solutions, and improve by: (i) proposing
phonetic-based blocking strategies, thereby increasing recall; and (ii) adding
strong ethnicity-sensitive features for learning a linkage function, thereby
tailoring disambiguation to non-Western author names whenever necessary.
| arxiv topic:cs.DL cs.IR stat.ML |
arxiv_dataset-65451508.07844 | High-frequency and high-quality silicon carbide optomechanical
microresonators
physics.optics
Silicon carbide (SiC) exhibits excellent material properties attractive for
broad applications. We demonstrate the first SiC optomechanical microresonators
that integrate high mechanical frequency, high mechanical quality, and high
optical quality into a single device. The radial-breathing mechanical mode has
a mechanical frequency up to 1.69 GHz with a mechanical Q around 5500 in
atmosphere, which corresponds to a mechanical f-Q product as high as 9.47x10^12
Hz. The strong optomechanical coupling allows us to efficiently excite and
probe the coherent mechanical oscillation by optical waves. The demonstrated
devices, in combination with the superior thermal property, chemical inertness,
and defect characteristics of SiC, show great potential for applications in
metrology, sensing, and quantum photonics, particularly in harsh environments
that are challenging for other device platforms.
| arxiv topic:physics.optics |
arxiv_dataset-65461508.07944 | Accretion Processes for General Spherically Symmetric Compact Objects
gr-qc astro-ph.SR math.CT
We investigate the accretion process for different spherically symmetric
space-time geometries for a static fluid. We analyse this procedure using the
most general black hole metric ansatz. After that, we examine the accretion
process for specific spherically symmetric metrics obtaining the velocity of
the sound during the process and the critical speed of the flow of the fluid
around the black hole. In addition, we study the behaviour of the rate of
change of the mass for each chosen metric for a barotropic fluid.
| arxiv topic:gr-qc astro-ph.SR math.CT |
arxiv_dataset-65471509.00061 | Value function approximation via low-rank models
cs.LG cs.AI
We propose a novel value function approximation technique for Markov decision
processes. We consider the problem of compactly representing the state-action
value function using a low-rank and sparse matrix model. The problem is to
decompose a matrix that encodes the true value function into low-rank and
sparse components, and we achieve this using Robust Principal Component
Analysis (PCA). Under minimal assumptions, this Robust PCA problem can be
solved exactly via the Principal Component Pursuit convex optimization problem.
We experiment the procedure on several examples and demonstrate that our method
yields approximations essentially identical to the true function.
| arxiv topic:cs.LG cs.AI |
arxiv_dataset-65481509.00161 | Adjacent Pairs Exchange correction to the Random Phase Approximation
cond-mat.mtrl-sci
The Random Phase Approximation (RPA) is a widely employed post Hartree-Fock
or DFT method, capable of capturing van der Waal interactions and other dynamic
correlation effects at relatively low costs of $\mathcal O(N^3)$ in time and
$\mathcal O(N^2)$ in memory, if calculated from imaginary time propagators.
However, since it neglects anti-symmetrization RPA is biased, overestimating
the correlation energy and bond lengths in general. The Second Order Screened
Exchange offers amelioration by anti-symmetrizing one Coulomb interaction but
it comes at considerable costs of $\mathcal O(N^5)$ in time and $\mathcal
O(N^4)$ in memory, since it has to be calculated from the direct ring Coupled
Cluster Doubles (drCCD) amplitudes. We propose a diagrammatic method,
exchanging adjacent pairs in the RPA diagrams - hence its name - offering
similar accuracy but with memory requirement of only $\mathcal O(N^2)$. The
correction is calculated from imaginary time propagators similar to efficient
RPA implementations. It can be calculated in $\mathcal O(N^5)$ steps in
momentum space or $\mathcal O(N^4)$ steps in real space. It improves on SOSEX
in the uniform electron gas for low densities, where correlation effects are
stronger, and first calculations of lattice constants in solids are in
excellent agreement with experiment.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-65491509.00261 | Inter-laboratory comparison of a WDS-EDS quantitative X-ray
microanalysis of a metallic glass
cond-mat.mtrl-sci
We conducted an inter-laboratory study of a metallic glass whose main
component is nickel. Two determinations of the mass fractions of the different
elements present within the sample were asked to the participants: one at an
acceleration voltage of 15 or 20 kV and another one at 5 kV. We compare the
mass fractions obtained from wavelength dispersive (WDS) and energy dispersive
spectrometries (EDS) and also try to find an influence of the kind of EDS
detector and its entrance window, the background subtraction method, the use or
not of standards as well as the quantification method. Both means of WDS and
EDS mass fractions are close to the reference values. The dispersion of the
results was larger at 5 kV than at 15-20 kV owing to the use of the L lines
rather than K lines and to the lowest collected intensities. There is an
exception with the case of boron because at the lowest voltage, the excitation
condition is more favourable for the production of the K line. It appears that
the dispersion of the results is larger with EDS than with WDS but it was not
possible to find a correlation between the large dispersion and one of the
considered experimental parameters and quantification factors. Thus, one can
think that electron microprobes are inherently better for the determination of
mass fractions or that the implementation of quantitative analysis must be
optimized for some cases, especially in SEMs.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-65501509.00361 | Feynman Amplitudes in Mathematics and Physics
math.AG math-ph math.MP
These are notes of lectures given at the CMI conference in August, 2014 at
ICMAT in Madrid. The focus is on some mathematical questions associated to
Feynman amplitudes, including Hodge structures, relations with string theory,
and monodromy (Cutkosky rules).
| arxiv topic:math.AG math-ph math.MP |
arxiv_dataset-65511509.00461 | Freely decaying turbulence in force-free electrodynamics
astro-ph.HE physics.plasm-ph
Freely decaying relativistic force-free turbulence is studied for the first
time. We initiate the magnetic field at a short wavelength and simulate its
relaxation toward equilibrium on two and three dimensional periodic domains, in
both helical and non-helical settings. Force-free turbulent relaxation is found
to exhibit an inverse cascade in all settings, and in 3D to have a magnetic
energy spectrum consistent with the Kolmogorov $5/3$ power law. 3D relaxations
also obey the Taylor hypothesis; they settle promptly into the lowest energy
configuration allowed by conservation of the total magnetic helicity. But in
2D, the relaxed state is a force-free equilibrium whose energy greatly exceeds
the Taylor minimum, and which contains persistent force-free current layers and
isolated flux tubes. We explain this behavior in terms of additional
topological invariants that exist only in two dimensions, namely the helicity
enclosed within each level surface of the magnetic potential function. The
speed and completeness of turbulent magnetic free energy discharge could help
account for rapidly variable gamma-ray emission from the Crab Nebula, gamma-ray
bursts, blazars, and radio galaxies.
| arxiv topic:astro-ph.HE physics.plasm-ph |
arxiv_dataset-65521509.00561 | Junction-Less Monolayer MoS2 FETs
cond-mat.mes-hall
This paper introduces monolayer molybdenum disulfide (MoS2) based
junction-less (JL) field-effect transistor (FET) and evaluates its performance
at the smallest foreseeable (5.9 nm) transistor channel length as per the
International Technology Roadmap for Semiconductors (ITRS), by employing
rigorous quantum transport simulations. By comparing with MoS2 based
conventional FETs, it is found that the JL structure naturally lends MoS2 FETs
with superior device electrostatics, and higher ON-current for both
high-performance and low-standby-power applications, especially at high
impurity doping densities. Along with the advantages of the MoS2 JL-FETs, the
effects of impurity scattering induced carrier mobility degradation of JL-FETs
is also highlighted as a key technological issue to be addressed for exploiting
their unique features.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-65531509.00661 | Entropy and approximation numbers of weighted Sobolev spaces via
bracketing
math.FA
We investigate the asymptotic behaviour of entropy and approximation numbers
of the compact embedding $E^m_{p,\sigma}(B)\hookrightarrow L_p(B)$, $1\leq
p<\infty,$ defined on the unit ball $B$ in $\mathbb{R}^n$. Here
$E^m_{p,\sigma}(B)$ denotes a Sobolev space with a power weight perturbed by a
logarithmic function. The weight contains a singularity at the origin. Inspired
by Evans and Harris, we apply a bracketing technique which is an analogue to
that of Dirichlet-Neumann-bracketing used by Triebel if $p=2$.
| arxiv topic:math.FA |
arxiv_dataset-65541509.00761 | Small-scale magnetic and velocity inhomogeneities in a sunspot light
bridge
astro-ph.SR
High resolution spectro-polarimetric observations of a sunspot light bridge
by Hinode, reveal small-scale inhomogeneities in the magnetic field and
velocity. These inhomogeneities arise as a consequence of a weak, secondary
lobe in the Stokes V profile which have a polarity opposite that of the sunspot
and very large (>5 km/s) Doppler velocities of both signs, suggesting two
distinct types of magnetic anomalies. These two sets of inhomogeneities are
highly time-dependent and appear exclusively in the upper half of the light
bridge and only after the light bridge is completely formed. Both sets of
inhomogeneities appear as patches and can be present independent of the other,
next to one another, or spatially separated in a single scan. A two-component
inversion of the corresponding spectral profiles indicate that the
inhomogeneities occupy a very small fraction, amounting to less than 10 %, of
the resolution element. These structures are likely driven by small-scale
magneto-convection where they could further interact with the overlying sunspot
magnetic field to produce reconnection jets in the chromosphere.
| arxiv topic:astro-ph.SR |
arxiv_dataset-65551509.00861 | Dirac Cone Protected by Non-Symmorphic Symmetry and 3D Dirac Line Node
in ZrSiS
cond-mat.mtrl-sci
Materials harboring exotic quasiparticles, such as Dirac and Weyl
fermions\cite{xu2015discovery,borisenko2015time,weng2015weyl,xu2015observation},
have garnered much attention from the physics and material science communities.
These fermions are massless and, in some materials, have shown exceptional
physical properties such as ultrahigh mobility and extremely large
magnetoresistances
\cite{liang2015ultrahigh,ali2014large,du2015unsaturated,shekhar2015large}.
Recently, new materials have been predicted to exist which exhibit line nodes
of Dirac cones
\cite{PhysRevLett.115.036806,xie2015new,burkov2011topological,rhim2015landau}.
Here, we show with angle resolved photoemission studies supported by \textit{ab
initio} calculations that the highly stable, non-toxic and earth-abundant
material, ZrSiS, has an electronic band structure that hosts several Dirac
cones which form a Fermi surface with a diamond-shaped line of Dirac nodes. We
also experimentally show, for the first time, that the square Si lattice in
ZrSiS is an excellent template for realizing the new types of 2D Dirac cones
recently predicted by Young and Kane \cite{young2015dirac} and image an
unforseen surface state that arises close to the 2D Dirac cone. Finally, we
find that the energy range of the linearly dispersed bands is as high as 2\,eV
above and below the Fermi level; much larger than of any known Dirac material
so far. This makes ZrSiS a very promising candidate to study the exotic
behavior of Dirac electrons, or Weyl fermions if a magnetic field is applied,
as well as the properties of lines of Dirac nodes
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-65561509.00961 | A Typology of Authentication Systems
cs.CR
Authentication systems are designed to give the right person access to an
organization's information system and to restrict it from the wrong person.
Such systems are designed by IT professionals to protect an organization's
assets (e.g., the organization's network, database, or other information). Too
often, such systems are designed around technical specifications without regard
for the end user. We argue that doing so may actually compromise a system's
security. This paper examines authentication systems from both the point of
view of the organization and that of the user.
| arxiv topic:cs.CR |
arxiv_dataset-65571509.01061 | Combined analysis of charm-quark fragmentation-fraction measurements
hep-ex hep-ph nucl-ex
A summary of measurements of the fragmentation of charm quarks into a
specific hadron is given. Measurements performed in photoproduction and deep
inelastic scattering in $e^{\pm}p$, $pp$ and $e^+e^-$ collisions are compared,
using up-to-date branching ratios. Within uncertainties, all measurements
agree, supporting the hypothesis that fragmentation is independent of the
specific production process. Averages of the fragmentation fractions over all
measurements are presented. The average has significantly reduced uncertainties
compared to individual measurements.
| arxiv topic:hep-ex hep-ph nucl-ex |
arxiv_dataset-65581509.01161 | Nematicity and magnetism in FeSe and other families of Fe-based
superconductors
cond-mat.str-el cond-mat.supr-con
Nematicity and magnetism are two key features in Fe-based superconductors,
and their interplay is one of the most important unsolved problems. In FeSe,
the magnetic order is absent below the structural transition temperature
$T_{str}=90$K, in stark contrast that the magnetism emerges slightly below
$T_{str}$ in other families. To understand such amazing material dependence, we
investigate the spin-fluctuation-mediated orbital order ($n_{xz}\neq n_{yz}$)
by focusing on the orbital-spin interplay driven by the strong-coupling effect,
called the vertex correction. This orbital-spin interplay is very strong in
FeSe because of the small ratio between the Hund's and Coulomb interactions
($\bar{J}/\bar{U}$) and large $d_{xz},d_{yz}$-orbitals weight at the Fermi
level. For this reason, in the FeSe model, the orbital order is established
irrespective that the spin fluctuations are very weak, so the magnetism is
absent below $T_{str}$. In contrast, in the LaFeAsO model, the magnetic order
appears just below $T_{str}$ both experimentally and theoretically. Thus, the
orbital-spin interplay due to the vertex correction is the key ingredient in
understanding the rich phase diagram with nematicity and magnetism in Fe-based
superconductors in a unified way.
| arxiv topic:cond-mat.str-el cond-mat.supr-con |
arxiv_dataset-65591509.01261 | The spatial clustering of ROSAT All-Sky Survey Active Galactic Nuclei
IV. More massive black holes reside in more massive dark matter halos
astro-ph.GA astro-ph.CO astro-ph.HE
This is the fourth paper in a series that reports on our investigation of the
clustering properties of active galactic nuclei (AGN) identified in the ROSAT
All-Sky Survey (RASS) and Sloan Digital Sky Survey (SDSS). In this paper we
investigate the cause of the X-ray luminosity dependence of the clustering of
broad-line, luminous AGN at 0.16<z<0.36. We fit the H-alpha line profile in the
SDSS spectra for all X-ray and optically-selected broad-line AGN, determine the
mass of the super-massive black hole (SMBH), M_BH, and infer the accretion rate
relative to Eddington (L/L_EDD). Since M_BH and L/L_EDD are correlated, we
create AGN subsamples in one parameter while maintaining the same distribution
in the other parameter. In both the X-ray and optically-selected AGN samples we
detect a weak clustering dependence with M_BH and no statistically significant
dependence on L/L_EDD. We find a difference of up to 2.7sigma when comparing
the objects that belong to the 30% least and 30% most massive M_BH subsamples,
in that luminous broad-line AGN with more massive black holes reside in more
massive parent dark matter halos at these redshifts. These results provide
evidence that higher accretion rates in AGN do not necessarily require dense
galaxy environments in which more galaxy mergers and interactions are expected
to channel large amounts of gas onto the SMBH. We also present semi-analytic
models which predict a positive M_DMH dependence on M_BH, which is most
prominent at M_BH ~ 10^{8-9} M_SUN.
| arxiv topic:astro-ph.GA astro-ph.CO astro-ph.HE |
arxiv_dataset-65601509.01361 | Status of the Medium-Sized Telescope for the Cherenkov Telescope Array
astro-ph.IM
The Cherenkov Telescope Array (CTA), is an international project for the next
generation ground- based observatory for gamma-ray astronomy in the energy
range from 20 GeV to 300 TeV. The sensitivity in the core energy range will be
dominated by up to 40 Medium-Sized Telescopes (MSTs). The MSTs, of
Davies-Cotton type with a 12 m diameter reflector are currently in the
prototype phase. A full-size mechanical telescope structure has been assembled
in Berlin. The telescope is partially equipped with different mirror
prototypes, which are currently being tested and evaluated for performances
characteristics. A report concentrating on the details of the tele- scope
structure, the drive assemblies and the optics of the MST prototype will be
given.
| arxiv topic:astro-ph.IM |
arxiv_dataset-65611509.01461 | Quantum impurities in channel mixing baths
cond-mat.str-el cond-mat.supr-con
We propose a versatile strategy for numerical renormalization group solution
of general channel-mixing Kondo and Anderson models beyond previous reach,
opening the door toward broad applications in protocol non-perturbative
machineries, such as dynamical cluster approximation and cluster dynamical mean
field theory, for strongly correlated electron systems. We illustrate the
strategy by investigating the quantum phase transitions in two quantum impurity
models with cases untouched before.
| arxiv topic:cond-mat.str-el cond-mat.supr-con |
arxiv_dataset-65621509.01561 | Universality of Generalized Bunching and Efficient Assessment of Boson
Sampling
quant-ph cond-mat.other cond-mat.stat-mech
It is found that identical bosons (fermions) show generalized bunching
(antibunching) property in linear networks: The absolute maximum (minimum) of
probability that all $N$ input particles are detected in a subset of
$\mathcal{K}$ output modes of any nontrivial linear $M$-mode network is
attained \textit{only} by completely indistinguishable bosons (fermions). For
fermions $\mathcal{K}$ is arbitrary, for bosons it is either ($i$) arbitrary
for only classically correlated bosons or ($ii$) satisfies $\mathcal{K}\ge N$
(or $\mathcal{K}=1$) for arbitrary input states of $N$ particles. The
generalized bunching allows to certify in a \textit{polynomial} in $N$ number
of runs that a physical device realizing Boson Sampling with \textit{an
arbitrary} network operates in the regime of full quantum coherence compatible
\textit{only} with completely indistinguishable bosons. The protocol needs
\textit{only polynomial} classical computations for the standard Boson
Sampling, whereas an \textit{analytic formula} is available for the scattershot
version.
| arxiv topic:quant-ph cond-mat.other cond-mat.stat-mech |
arxiv_dataset-65631509.01661 | Databases of publications and observations - as a part of the Crimean
Astronomical Virtual Observatory
astro-ph.IM
The paper presents the basic principles of formation of a database (DB) with
information about objects and their physical characteristics from observations
carried out at the Crimean Astrophysical Observatory (CrAO) and published in
"Izvestiya Krymskoi Astrofizicheskoi Observatorii" and other publications. The
emphasis is placed on DBs that are not present in the most complete global
library catalogs and data tables - VizieR (supported by the Strasbourg ADC).
Separately, we consider the formation of a digital archive of observational
data obtained at CrAO - as the interactive DB related to the DB of objects and
publications. Examples of all the above DB as elements integrated into the
Crimean Astronomical Virtual Observatory are presented in the paper. The
operation with CrAO database is illustrated using tools of the International
Virtual Observatory - Aladin, VOPlot, VOSpec jointly with VizieR DB and Simbad.
| arxiv topic:astro-ph.IM |
arxiv_dataset-65641509.01761 | Deep Inelastic Scattering in the Exponentially Small Bjorken Parameter
Regime from the Holographic Softwall Model
hep-th hep-ph
We use the AdS/CFT correspondence and the holographic softwall model to
investigate the Deep Inelastic Scattering (DIS) in the exponentially small $x$
(Bjorken Parameter) regime. We calculate the corresponding structure functions
for scalar fields. Using these results we studied the problem of the saturation
line in the strong interactions. Our results are consistent with those achieved
using other models.
| arxiv topic:hep-th hep-ph |
arxiv_dataset-65651509.01861 | Completely positive entropy actions of sofic groups with $\mathbb{Z}$ in
their center
math.DS
Let $\Gamma$ be a sofic group with a copy of $\mathbb{Z}$ in its center. We
construct an uncountable family of pairwise nonisomorphic measure-preserving
$\Gamma$ actions with completely positive entropy, none of which is a factor of
a Bernoulli shift. Our construction shows that the relation of isomorphism
among completely positive entropy $\Gamma$ actions is not smooth, in contrast
with the relation of isomorphism among Bernoulli shifts.
| arxiv topic:math.DS |
arxiv_dataset-65661509.01961 | Addendum: Electroweak Sudakov effects in W, Z and gamma production at
large transverse momentum
hep-ph hep-ex
In this addendum to Phys. Rev. D 88, no. 1, 013009 (2013), we give results
for the electroweak Sudakov corrections in gauge-boson production at large
transverse momentum p_T at proton colliders. In order for the results to be
easily usable, we provide a simple and accurate parameterization of the
corrections as a function of p_T and the center-of-mass energy \sqrt{s}.
Additionally, we also discuss the dependence of the electroweak corrections on
the rapidity of the produced boson, and comment on the complications that arise
in the photon-production case due to isolation requirements
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-65671509.02061 | Diametral diameter two properties in Banach spaces
math.FA
The aim of this note is to provide several variants of the diameter two
properties for Banach spaces. We study such properties looking for the
abundance of diametral points, which holds in the setting of Banach spaces with
the Daugavet property, for example, and we intro- duce the diametral diameter
two properties in Banach spaces, showing for these new properties stability
results, inheritance to subspaces and characterizations in terms of finite rank
projections.
| arxiv topic:math.FA |
arxiv_dataset-65681509.02161 | Depurated Inversion Method for Orbital-Specific Exchange Potentials
physics.atm-clus physics.chem-ph
This work presents exchange potentials for specific orbitals calculated by
inverting Hartree-Fock wavefunctions. This was achieved by using a Depurated
Inversion Method. The basic idea of the method relies upon the substitution of
Hartree-Fock orbitals and eigenvalues into the Kohn-Sham equation. Through
inversion, the corresponding effective potentials were obtained. Further
treatment of the inverted potential should be carried on. The depuration is a
careful optimization which eliminates the poles and also ensures the
fullfilment of the appropriate boundary conditions. The procedure developed
here is not restricted to the ground state or to a nodeless orbital and is
applicable to all kinds of atoms. As an example, exchange potentials for noble
gases and term-dependent orbitals of the lower configuration of Nitrogen are
calculated. The method allows to reproduce the input energies and wavefunctions
with a remarkable degree of accuracy.
| arxiv topic:physics.atm-clus physics.chem-ph |
arxiv_dataset-65691509.02261 | Misspecification in mixed-model based association analysis
stat.AP
Additive genetic variance in natural populations is commonly estimated using
mixed models, in which the covariance of the genetic effects is modeled by a
genetic similarity matrix derived from a dense set of markers. An important but
usually implicit assumption is that the presence of any non-additive genetic
effect only increases the residual variance, and does not affect estimates of
additive genetic variance. Here we show that this is only true for panels of
unrelated individuals. In case there is genetic relatedness, the combination of
population structure and epistatic interactions can lead to inflated estimates
of additive genetic variance.
| arxiv topic:stat.AP |
arxiv_dataset-65701509.02361 | Characterization of a large CdZnTe coplanar quad-grid semiconductor
detector
physics.ins-det nucl-ex
The COBRA collaboration aims to search for neutrinoless double beta-decay of
$^{116}$Cd. A demonstrator setup with 64 CdZnTe semiconductor detectors, each
with a volume of 1cm$^3$, is currently being operated at the LNGS underground
laboratory in Italy. This paper reports on the characterization of a large (2
$\times$ 2 $\times$ 1.5)cm$^3$ CdZnTe detector with a new coplanar-grid design
for applications in $\gamma$-ray spectroscopy and low-background operation.
Several studies of electric properties as well as of the spectrometric
performance, like energy response and resolution, are conducted. Furthermore,
measurements including investigating the operational stability and a
possibility to identify multiple-scattered photons are presented.
| arxiv topic:physics.ins-det nucl-ex |
arxiv_dataset-65711509.02461 | POLARBEAR Constraints on Cosmic Birefringence and Primordial Magnetic
Fields
astro-ph.CO
We constrain anisotropic cosmic birefringence using four-point correlations
of even-parity $E$-mode and odd-parity $B$-mode polarization in the cosmic
microwave background measurements made by the POLARization of the Background
Radiation (POLARBEAR) experiment in its first season of observations. We find
that the anisotropic cosmic birefringence signal from any parity-violating
processes is consistent with zero. The Faraday rotation from anisotropic cosmic
birefringence can be compared with the equivalent quantity generated by
primordial magnetic fields if they existed. The POLARBEAR nondetection
translates into a 95% confidence level (C.L.) upper limit of 93 nanogauss (nG)
on the amplitude of an equivalent primordial magnetic field inclusive of
systematic uncertainties. This four-point correlation constraint on Faraday
rotation is about 15 times tighter than the upper limit of 1380 nG inferred
from constraining the contribution of Faraday rotation to two-point
correlations of $B$-modes measured by Planck in 2015. Metric perturbations
sourced by primordial magnetic fields would also contribute to the $B$-mode
power spectrum. Using the POLARBEAR measurements of the $B$-mode power spectrum
(two-point correlation), we set a 95% C.L. upper limit of 3.9 nG on primordial
magnetic fields assuming a flat prior on the field amplitude. This limit is
comparable to what was found in the Planck 2015 two-point correlation analysis
with both temperature and polarization. We perform a set of systematic error
tests and find no evidence for contamination. This work marks the first time
that anisotropic cosmic birefringence or primordial magnetic fields have been
constrained from the ground at subdegree scales.
| arxiv topic:astro-ph.CO |
arxiv_dataset-65721509.02561 | Multi-photon entanglement in high dimensions
quant-ph physics.optics
Entanglement lies at the heart of quantum mechanics $-$ as a fundamental tool
for testing its deep rift with classical physics, while also providing a key
resource for quantum technologies such as quantum computation and cryptography.
In 1987 Greenberger, Horne, and Zeilinger realized that the entanglement of
more than two particles implies a non-statistical conflict between local
realism and quantum mechanics. The resulting predictions were experimentally
confirmed by entangling three photons in their polarization. Experimental
efforts since have singularly focused on increasing the number of particles
entangled, while remaining in a two-dimensional space for each particle. Here
we show the experimental generation of the first multi-photon entangled state
where both $-$ the number of particles and the number of dimensions $-$ are
greater than two. Interestingly, our state exhibits an asymmetric entanglement
structure that is only possible when one considers multi-particle entangled
states in high dimensions. Two photons in our state reside in a
three-dimensional space, while the third lives in two dimensions. Our method
relies on combining two pairs of photons, high-dimensionally entangled in their
orbital angular momentum, in such a way that information about their origin is
erased. Additionally, we show how this state enables a new type of "layered"
quantum cryptographic protocol where two parties share an additional layer of
secure information over that already shared by all three parties. In addition
to their application in novel quantum communication protocols, such asymmetric
entangled states serve as a manifestation of the complex dance of correlations
that can exist within quantum mechanics.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-65731509.02661 | Orbital Magnetization of Quantum Spin Hall Insulator Nanoparticles
cond-mat.mes-hall
Both spin and orbital degrees of freedom contribute to the magnetic moment of
isolated atoms. However, when inserted in crystals, atomic orbital moments are
quenched because of the lack of rotational symmetry that protects them when
isolated. Thus, the dominant contribution to the magnetization of magnetic
materials comes from electronic spin. Here we show that nanoislands of quantum
spin Hall insulators can host robust orbital edge magnetism whenever their
highest occupied Kramers doublet is singly occupied, upgrading the spin edge
current into a charge current. The resulting orbital magnetization scales
linearly with size, outweighing the spin contribution for islands of a few nm
in size. This linear scaling is specific of the Dirac edge states and very
different from Schrodinger electrons in quantum rings. Modelling Bi(111)
flakes, whose edge states have been recently observed, we show that orbital
magnetization is robust with respect to disorder, thermal agitation, shape of
the island and crystallographic direction of the edges, reflecting its
topological protection.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-65741509.02761 | $p$-adic heights of Heegner points and Beilinson-Flach elements
math.NT
We give a new proof of Howard's $\Lambda$-adic Gross-Zagier formula, which we
extend to the context of indefinite Shimura curves over $\mathbf{Q}$ attached
to nonsplit quaternion algebras. This formula relates the cyclotomic derivative
of a two-variable $p$-adic $L$-function restricted to the anticyclotomic line
to the cyclotomic $p$-adic heights of Heegner points over the anticyclotomic
tower, and our proof, rather than inspired by the original approaches of
Gross-Zagier and Perrin-Riou, is via Iwasawa theory, based on the connection
between Heegner points, Beilinson-Flach elements, and their explicit
reciprocity laws.
| arxiv topic:math.NT |
arxiv_dataset-65751509.02861 | Preconditioning for continuation model predictive control
math.OC cs.SY
Model predictive control (MPC) anticipates future events to take appropriate
control actions. Nonlinear MPC (NMPC) deals with nonlinear models and/or
constraints. A Continuation/GMRES Method for NMPC, suggested by T. Ohtsuka in
2004, uses the GMRES iterative algorithm to solve a forward difference
approximation $Ax=b$ of the original NMPC equations on every time step. We have
previously proposed accelerating the GMRES and MINRES convergence by
preconditioning the coefficient matrix $A$. We now suggest simplifying the
construction of the preconditioner, by approximately solving a forward
recursion for the state and a backward recursion for the costate, or simply
reusing previously computed solutions.
| arxiv topic:math.OC cs.SY |
arxiv_dataset-65761509.02961 | Strong orientational coupling of block copolymer microdomains to smectic
layering revealed by magnetic field alignment
cond-mat.soft
We elucidate the roles of the isotropic-nematic (I-N) and nematic-smectic A
(N-SmA) transitions in magnetic field directed self-assembly of a liquid
crystalline block copolymer (BCP), using \textit{in situ} x-ray scattering.
Cooling into the nematic from the disordered melt yields poorly ordered and
weakly aligned BCP microdomains. Continued cooling into the SmA however results
in an abrupt increase in BCP orientational order with microdomain alignment
tightly coupled to the translational order parameter of the smectic layers.
These results underscore the significance of the N-SmA transition in generating
highly aligned states under magnetic fields in these hierarchically ordered
materials.
| arxiv topic:cond-mat.soft |
arxiv_dataset-65771509.03061 | Stochastic modeling and performance monitoring of wind farm power
production
physics.data-an physics.flu-dyn
We present a new stochastic approach to describe and remodel the conversion
process of a wind farm at a sampling frequency of 1Hz. When conditioning on
various wind direction sectors, the dynamics of the conversion process appear
as a fluctuating trajectory around an average IEC-like power curve, see section
II. Our approach is to consider the wind farm as a dynamical system that can be
described as a stochastic drift/diffusion model, where a drift coefficient
describes the attraction towards the power curve and a diffusion coefficient
quantifies additional turbulent fluctuations. These stochastic coefficients are
inserted into a Langevin equation that, once properly adapted to our particular
system, models a synthetic signal of power output for any given wind
speed/direction signals, see section III. When combined with a pre-model for
turbulent wind fluctuations, the stochastic approach models the power output of
the wind farm at a sampling frequency of 1Hz using only ten-minute average
values of wind speed and directions. The stochastic signals generated are
compared to the measured signal, and show a good statistical agreement,
including a proper reproduction of the intermittent, gusty features measured.
In parallel, a second application for performance monitoring is introduced in
section IV. The drift coefficient can be used as a sensitive measure of the
global wind farm performance. When monitoring the wind farm as a whole, the
drift coefficient registers some significant deviation from normal operation if
one of twelve wind turbines is shut down during less than 4% of the time. Also,
intermittent anomalies can be detected more rapidly than when using ten-minute
averaging methods. Finally, a probabilistic description of the conversion
process is proposed and modeled in appendix A, that can in turn be used to
further improve the estimation of the stochastic coefficients.
| arxiv topic:physics.data-an physics.flu-dyn |
arxiv_dataset-65781509.03161 | OCR extensions - local identifiers, labeled GUIDs, file IO, and data
block partitioning
cs.DC
We present several proposals for extending the Open Community Runtime (OCR)
specification. The extension are identifiers with local validity, which use the
concept of futures to provide OCR implementations more optimization
opportunities, labeled GUIDs with creator functions, which are based on the
local identifiers and allow the developer to create arrays of OCR objects that
are safe from race conditions in case of concurrent creation of objects, a
simple file IO interface, which builds on top of the existing data block
concepts, and finally data block partitioning, which allows better control and
flexibility in situations where multiple tasks want to access disjoint parts of
a data block.
| arxiv topic:cs.DC |
arxiv_dataset-65791509.03261 | Maximum Likelihood Estimation for Single Particle, Passive Microrheology
Data with Drift
cond-mat.soft stat.ME
Volume limitations and low yield thresholds of biological fluids have led to
widespread use of passive microparticle rheology. The mean-squared-displacement
(MSD) statistics of bead position time series (bead paths) are either applied
directly to determine the creep compliance [Xu et al (1998)] or transformed to
determine dynamic storage and loss moduli [Mason & Weitz (1995)]. A prevalent
hurdle arises when there is a non-diffusive experimental drift in the data.
Commensurate with the magnitude of drift relative to diffusive mobility,
quantified by a P\'eclet number, the MSD statistics are distorted, and thus the
path data must be "corrected" for drift. The standard approach is to estimate
and subtract the drift from particle paths, and then calculate MSD statistics.
We present an alternative, parametric approach using maximum likelihood
estimation that simultaneously fits drift and diffusive model parameters from
the path data; the MSD statistics (and consequently the compliance and dynamic
moduli) then follow directly from the best-fit model. We illustrate and compare
both methods on simulated path data over a range of P\'eclet numbers, where
exact answers are known. We choose fractional Brownian motion as the numerical
model because it affords tunable, sub-diffusive MSD statistics consistent with
typical 30 second long, experimental observations of microbeads in several
biological fluids. Finally, we apply and compare both methods on data from
human bronchial epithelial cell culture mucus.
| arxiv topic:cond-mat.soft stat.ME |
arxiv_dataset-65801509.03361 | Physical Observations of (196256) 2003 EH$_{1}$, Presumed Parent of the
Quadrantid Meteoroid Stream
astro-ph.EP
The near-Earth asteroid (196256) 2003 EH1 has been suggested to have a
dynamical association with the Quadrantid meteoroid stream. We present
photometric observations taken to investigate the physical character of this
body and to explore its possible relation to the stream. We find no evidence
for on-going mass-loss. A model fitted to the point-like surface brightness
profile at 2.1 AU limits the fractional contribution to the integrated
brightness by near-nucleus coma to $\leq$ 2.5 %. Assuming an albedo equal to
those typical of cometary nuclei ($\it p_{\rm R}$=0.04), we find that the
effective nucleus radius is $r_e$ = 2.0$\pm$0.2 km. Time-resolved ${\it
R}$-band photometry can be fitted by a two-peaked lightcurve having a
rotational period of 12.650$\pm$0.033 hr. The range of the lightcurve, $\Delta
m_{\rm R}$= 0.44 $\pm$ 0 .01 mag, is indicative of an elongated shape having an
axis ratio $\sim$1.5 projected into the plane of the sky. The asteroid shows
colors slightly redder than the Sun, being comparable with those of C-type
asteroids. The limit to the mass loss rate set by the absence of resolved coma
is $\lesssim$ 2.5$\times$ 10$^{-2}$ kg ${\rm s^{-1}}$, corresponding to an
upper limit on the fraction of the surface that could be sublimating water ice
$f_A$ $\lesssim$ 10$^{-4}$. Even if sustained over the 200-500 yr dynamical age
of the Quadrantid stream, the total mass loss from 2003 EH1 would be too small
to supply the reported stream mass ($10^{13}$ kg), implying either that the
stream has another parent or that mass loss from 2003 EH1 is episodic.
| arxiv topic:astro-ph.EP |
arxiv_dataset-65811509.03461 | A comprehensive investigation on the slowing down of cosmic acceleration
astro-ph.CO
Shafieloo ea al. firstly proposed the possibility that the current cosmic
acceleration (CA) is slowing down. However, this is rather counterintuitive
because a slowing down CA cannot be accommodated in most mainstream
cosmological models. In this work, by exploring the evolutionary trajectories
of dark energy equation of state $w(z)$ and deceleration parameter $q(z)$, we
present a comprehensive investigation on the slowing down of CA from both the
theoretical and the observational sides. For the theoretical side, we study the
impact of different $w(z)$ by using six parametrization models, and then
discuss the effects of spatial curvature. For the observational side, we
investigate the effects of different type Ia supernovae (SNe Ia), different
baryon acoustic oscillation (BAO), and different cosmic microwave background
(CMB) data, respectively. We find that (1) The evolution of CA are insensitive
to the specific form of $w(z)$; in contrast, a non-flat Universe more favors a
slowing down CA than a flat Universe. (2) SNLS3 SNe Ia datasets favor a slowing
down CA at 1$\sigma$ confidence level, while JLA SNe Ia samples prefer an
eternal CA; in contrast, the effects of different BAO data are negligible. (3)
Compared with CMB distance prior data, full CMB data more favor a slowing down
CA. (4) Due to the low significance, the slowing down of CA is still a
theoretical possibility that cannot be confirmed by the current observations.
| arxiv topic:astro-ph.CO |
arxiv_dataset-65821509.03561 | Regain Control of Growing Dependencies in OMNeT++ Simulations
cs.SE
When designing simulation models, it is favourable to reuse existing models
as far as possible to reduce the effort from the first idea to simulation
results. Thanks to the OMNeT++ community, there are several toolboxes available
covering a wide range of network communication protocols. However, it can be
quite a daunting task to handle the build process when multiple existing
simulation models need to be combined with custom sources. Project references
provided by the OMNeT++ Integrated Development Environment (IDE) are just
partly up to the task because it can be barely automated. For this reason, a
new approach is presented to build complex simulation models with the help of
CMake, which is a wide-spread build tool for C and C++ projects. The resulting
toolchain allows to handle dependencies conveniently without need for any
changes in upstream projects and also takes special care of OMNeT++-specific
aspects.
| arxiv topic:cs.SE |
arxiv_dataset-65831509.03661 | Global Architecture of Planetary Systems (GAPS), a project for the whole
Italian Community
astro-ph.EP astro-ph.IM astro-ph.SR
The GAPS project is running since 2012 with the goal to optimize the science
return of the HARPS-N instrument mounted at Telescopio Nazionale Galileo. A
large number of astronomers is working together to allow the Italian community
to gain an international position adequate to the HARPS-N capabilities in the
exoplanetary researches. Relevant scientific results are being obtained on both
the main guidelines of the collaboration, i.e., the discovery surveys and the
characterization studies. The planetary system discovered around the southern
component of the binary XO-2 and its characterization together with that of the
system orbiting the northern component are a good example of the completeness
of the topics matched by the GAPS project. The dynamics of some planetary
systems are investigated by studying the Rossiter-McLaughlin effect, while host
stars are characterized by means of asteroseismology and star-planet
interaction.
| arxiv topic:astro-ph.EP astro-ph.IM astro-ph.SR |
arxiv_dataset-65841509.03761 | Haar bases on quasi-metric measure spaces, and dyadic structure theorems
for function spaces on product spaces of homogeneous type
math.CA math.FA
We give an explicit construction of Haar functions associated to a system of
dyadic cubes in a geometrically doubling quasi-metric space equipped with a
positive Borel measure, and show that these Haar functions form a basis for
$L^p$. Next we focus on spaces $X$ of homogeneous type in the sense of Coifman
and Weiss, where we use these Haar functions to define a discrete square
function, and hence to define dyadic versions of the function spaces $H^1(X)$
and ${\rm BMO}(X)$. In the setting of product spaces $\widetilde{X} = X_1
\times \cdots \times X_n$ of homogeneous type, we show that the space ${\rm
BMO}(\widetilde{X})$ of functions of bounded mean oscillation on
$\widetilde{X}$ can be written as the intersection of finitely many dyadic
${\rm BMO}$ spaces on $\widetilde{X}$, and similarly for $A_p(\widetilde{X})$,
reverse-H\"older weights on $\widetilde{X}$, and doubling weights on
$\widetilde{X}$. We also establish that the Hardy space $H^1(\widetilde{X})$ is
a sum of finitely many dyadic Hardy spaces on $\widetilde{X}$, and that the
strong maximal function on $\widetilde{X}$ is pointwise comparable to the sum
of finitely many dyadic strong maximal functions. These dyadic structure
theorems generalize, to product spaces of homogeneous type, the earlier
Euclidean analogues for ${\rm BMO}$ and $H^1$ due to Mei and to Li, Pipher and
Ward.
| arxiv topic:math.CA math.FA |
arxiv_dataset-65851509.03861 | Cavity-enhanced simultaneous dressing of quantum dot exciton and
biexciton states
quant-ph cond-mat.mes-hall
We demonstrate the simultaneous dressing of both vacuum-to-exciton and
exciton-to-biexciton transitions of a single semiconductor quantum dot in a
high-Q micropillar cavity, using photoluminescence spectroscopy. Resonant
two-photon excitation of the biexciton is achieved by spectrally tuning the
quantum dot emission with respect to the cavity mode. The cavity couples to
both transitions and amplifies the Rabi-frequency of the likewise resonant cw
laser, driving the transitions. We observe strong-field splitting of the
emission lines, which depend on the driving Rabi field amplitude and the
cavity-laser detuning. A dressed state theory of a driven 4-level atom
correctly predicts the distinct spectral transitions observed in the emission
spectrum, and a detailed description of the emission spectra is further
provided through a polaron master equation approach which accounts for cavity
coupling and acoustic phonon interactions of the semiconductor medium.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-65861509.03961 | Coherent manipulation of Andreev states in superconducting atomic
contacts
cond-mat.mes-hall cond-mat.supr-con
Coherent control of quantum states has been demonstrated in a variety of
superconducting devices. In all these devices, the variables that are
manipulated are collective electromagnetic degrees of freedom: charge,
superconducting phase, or flux. Here, we demonstrate the coherent manipulation
of a quantum system based on Andreev bound states, which are microscopic
quasiparticle states inherent to superconducting weak links. Using a circuit
quantum electrodynamics setup we perform single-shot readout of this "Andreev
qubit". We determine its excited state lifetime and coherence time to be in the
microsecond range. Quantum jumps and parity switchings are observed in
continuous measurements. In addition to possible quantum information
applications, such Andreev qubits are a testbed for the physics of single
elementary excitations in superconductors.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con |
arxiv_dataset-65871509.04061 | Geometry and Dynamics of a Coupled 4D-2D Quantum Field Theory
hep-th
Geometric and dynamical aspects of a coupled 4D-2D interacting quantum field
theory - the gauged nonAbelian vortex - are investigated. The fluctuations of
the internal 2D nonAbelian vortex zeromodes excite the massless 4D Yang-Mills
modes and in general give rise to divergent energies. This means that the
well-known 2D CP(N-1) zeromodes associated with a nonAbelian vortex become
nonnormalizable. Moreover, all sorts of global, topological 4D effects such as
the nonAbelian Aharonov-Bohm effect come into play. These topological global
features and the dynamical properties associated with the fluctuation of the 2D
vortex moduli modes are intimately correlated, as shown concretely here in a
U(1) x SU(N) x SU(N) model with scalar fields in a bifundamental representation
of the two SU(N) factor gauge groups.
| arxiv topic:hep-th |
arxiv_dataset-65881509.04161 | Gradient flows of time-dependent functionals in metric spaces and
applications for PDEs
math.AP
We develop a gradient-flow theory for time-dependent functionals defined in
abstract metric spaces. Global well-posedness and asymptotic behavior of
solutions are provided. Conditions on functionals and metric spaces allow to
consider the Wasserstein space $\mathscr{P}_{2}(\mathbb{R}^{d})$ and apply the
results for a large class of PDEs with time- dependent coefficients like
confinement and interaction potentials and diffusion. Our results can be seen
as an extension of those in Ambrosio-Gigli-Savar\'e (2005)[2] to the case of
time-dependent functionals. For that matter, we need to consider some residual
terms, time-versions of concepts like $\lambda$-convexity,
time-differentiability of minimizers for Moreau-Yosida approximations, and a
priori estimates with explicit time-dependence for De Giorgi interpolation.
Here, functionals can be unbounded from below and satisfy a type of
$\lambda$-convexity that changes as the time evolves.
| arxiv topic:math.AP |
arxiv_dataset-65891509.04261 | Search for pair production of a new heavy quark that decays into a $W$
boson and a light quark in $pp$ collisions at $\sqrt{s} = 8$ TeV with the
ATLAS detector
hep-ex
A search is presented for pair production of a new heavy quark ($Q$) that
decays into a $W$ boson and a light quark ($q$) in the final state where one
$W$ boson decays leptonically (to an electron or muon plus a neutrino) and the
other $W$ boson decays hadronically. The analysis is performed using an
integrated luminosity of 20.3 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 8$
TeV collected by the ATLAS detector at the LHC. No evidence of $Q\bar{Q}$
production is observed. New chiral quarks with masses below 690 GeV are
excluded at 95% confidence level, assuming BR$(Q\to Wq)=1$. Results are also
interpreted in the context of vectorlike quark models, resulting in the limits
on the mass of a vectorlike quark in the two-dimensional plane of BR$(Q\to Wq)$
versus BR$(Q\to Hq)$.
| arxiv topic:hep-ex |
arxiv_dataset-65901509.04361 | Magnetization reversal of giant perpendicular magnetic anisotropy at the
magnetic-phase transition in FeRh films on MgO
cond-mat.mtrl-sci
Phenomena originated from spin-orbit interaction, such as magnetic anisotropy
(MA), Rashba-type interactions, or topological insulators, have drawn huge
attention for its intriguing physics. In particular, the search for a novel
antiferromagnetic material, with potentially large perpendicular MA (PMA), has
been becoming very intensive for next-generation high density memory
applications. Here, we propose that substitutions of transition metals Ru and
Ir, neighboring and same group elements in the periodic table, for the Rh site
in the vicinity of surface can induce a substantially large PMA, up to an order
of magnitude of 20 erg/cm2, in FeRh films on MgO. The main driving mechanism
for this huge PMA is the interplay between the dxy and dx2-y2 states of strong
spin-orbit 4d and 5d orbitals. Further investigations demonstrate that
magnetization direction of PMA undergoes a transition into an in-plane
magnetization at the antiferromagnetic-to-ferromagnetic phase transition, which
provides a viable route for achieving large and switchable PMA associated with
the magnetic-phase transition in antiferromagnetic spintronics.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-65911509.04461 | On the nonvanishing of abstract Cauchy-Riemann cohomology groups
math.CV math.AP math.DG
In this paper, we prove the infinite dimensionality of some local and global
cohomology groups on abstract Cauchy-Riemann manifolds.
| arxiv topic:math.CV math.AP math.DG |
arxiv_dataset-65921509.04561 | A variational approach to the Yau-Tian-Donaldson conjecture
math.DG math.AG
We give a variational proof of a version of the Yau-Tian-Donaldson conjecture
for twisted K\"ahler-Einstein currents, and use this to express the greatest
(twisted) Ricci lower bound in terms of a purely algebro-geometric stability
threshold. Our approach does not involve the continuity method or
Cheeger-Colding-Tian theory, and uses instead pluripotential theory and
valuations. Along the way, we study the relationship between geodesic rays and
non-Archimedean metrics.
| arxiv topic:math.DG math.AG |
arxiv_dataset-65931509.04661 | Reheating of the Universe as holographic thermalization
hep-th gr-qc hep-ph
Assuming gauge/gravity correspondence we study reheating of the Universe
using its holographic dual. Inflaton decay and thermalisation of the decay
products correspond to collapse of a spherical shell and formation of a
blackhole in the dual anti-de Sitter (AdS) spacetime. The reheating temperature
is computed as the Hawking temperature of the developed blackhole probed by a
dynamical boundary, and is determined by the inflaton energy density and the
AdS radius, with corrections from the dynamics of the shell collapse. For given
initial energy density of the inflaton field the holographic model gives
significantly lower reheating temperature than the instant reheating scenario,
while it is shown to be safely within phenomenological bounds.
| arxiv topic:hep-th gr-qc hep-ph |
arxiv_dataset-65941509.04761 | Robustness via Diffractal Architectures
physics.optics
When plane waves diffract through fractal-patterned apertures, the resulting
far-field profiles or diffractals also exhibit iterated, self-similar features.
Here we show that this specific architecture enables robust signal processing
and spatial multiplexing: arbitrary parts of a diffractal contain sufficient
information to recreate the entire original sparse signal.
| arxiv topic:physics.optics |
arxiv_dataset-65951509.04861 | Effect of Delta potential on the pion-/pion+ ratio in heavy-ion
collisions at intermediate energies
nucl-th nucl-ex
Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU) transport
model, effects of $\Delta$ resonance potential on the free n/p and
$\pi^-/\pi^+$ ratios in the central collision of $^{197}Au+^{197}Au$ at beam
energies of 200 and 400 MeV/A are studied. It is found that the effect of
$\Delta$ potential on the ratio of pre-equilibrium free $n/p$ is invisible. The
effect of $\Delta$ isovector potential on the kinetic energy integrating ratio
of $\pi^-/\pi^+$ may be observable only at lower incident beam energies and
with stiffer symmetry energy. The strength of the $\Delta$ isoscalar potential
affects the height of the $\pi^-/\pi^+$ ratio around the Coulomb peak but does
not affect the kinetic energy integrating ratio of $\pi^-/\pi^+$. In heavy-ion
collisions at intermediate energies, relating to the question of
non-conservation of energy on $\Delta$ or $\pi$ productions, one can replace
the $\Delta$ potential by nucleon isoscalar potential especially a soft
symmetry energy is employed.
| arxiv topic:nucl-th nucl-ex |
arxiv_dataset-65961509.04961 | Hamiltonian Relative Equilibria with Continuous Isotropy
math.DS
In symmetric Hamiltonian systems, relative equilibria usually arise in
continuous families. The geometry of these families in the setting of free
actions of the symmetry group is well-understood. Here we consider the question
for non-free actions. Some results are already known in this direction, and we
use the so called bundle equations to provide a systematic treatment of this
question which both consolidates the known results, extending the scope of the
results to deal with non-compact symmetry groups, as well as producing new
results. Specifically we address questions about the stability, persistence and
bifurcations of these relative equilibria.
| arxiv topic:math.DS |
arxiv_dataset-65971509.05061 | Microwave excitation of spin wave beams in thin ferromagnetic films
cond-mat.mes-hall
We present an approach enabling generation of narrow spin wave beams in thin
homogeneous ferromagnetic films. The main idea is to match the wave vector of
the spin wave with that corresponding to the spectral maximum of the exciting
microwave magnetic field only locally, in the region of space from which the
beam should be launched. We show that this can be achieved with the aid of a
properly designed coplanar waveguide transducer generating a nonuniform
microwave magnetic field. The resulting two-dimensional spin wave beams
obtained in micromagnetic simulations propagate over distances of several
micrometers. The proposed approach requires neither inhomogeneity of the
ferromagnetic film nor nonuniformity of the biasing magnetic field, and it can
be generalized to yield multiple spin wave beams of different width at the same
frequency. Other possible excitation scenarios and applications of spin wave
beam magnonics are also discussed.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-65981509.05161 | The role of water in the behavior of wood
cond-mat.mtrl-sci cond-mat.soft
Wood, due to its biological origin, has the capacity to interact with water.
Sorption/desorption of moisture is accompanied with swelling/shrinkage and
softening/hardening of its stiffness. The correct prediction of the behavior of
wood components undergoing environmental loading requires that the moisture
behavior and mechanical behavior of wood are considered in a coupled manner. We
propose a comprehensive framework using a fully coupled poromechanical
approach, where its multiscale implementation provides the capacity to take
into account, directly, the exact geometry of the wood cellular structure,
using computational homogenization. A hierarchical model is used to take into
account the subcellular composite-like organization of the material. Such
advanced modeling requires high resolution experimental data for the
appropriate determination of inputs and for its validation. High-resolution
x-ray tomography, digital image correlation, and neutron imaging are presented
as valuable methods to provide the required information.
| arxiv topic:cond-mat.mtrl-sci cond-mat.soft |
arxiv_dataset-65991509.05261 | Conductance of graphene flakes contacted at their corners
cond-mat.mes-hall
Linear conductance of junctions formed by graphene flakes with order of
nanometer-thick electrodes attached at the corners of the flakes is studied.
The explored structures have sizes up to 20000 atoms and the conductance is
studied as a function of applied gate voltage varied around the Fermi level.
The finding, obtained computationally, is that junctions formed by
armchair-edge flakes with the electrodes connected at the acute-angle corners
block the electron transport while only junctions with such electrodes at the
obtuse-angle corners tend to provide the high electrical conductance typical
for metallic GNRs. The finding in case of zig-zag edges is similar with an
exception of a relatively narrow gate voltage interval in which each studied
junction is highly conductive as mediated by the edge states. The contrast
between the conductive and insulating setups is typically several orders of
magnitude in terms of ratio of their conductances. Main results of the paper
remain to a large extent valid also in the presence of edge disorder.
| arxiv topic:cond-mat.mes-hall |
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