Vector Datasets (VDF)
Collection
7 items • Updated
id stringlengths 36 36 | vector sequence | DOI stringlengths 9 16 | abstract stringlengths 6 4.2k |
|---|---|---|---|
a9251630-70ae-4263-9157-edc65515b33a | [
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0.015447... | astro-ph/9811342 | In a previous paper (Veron et al. 1997) we presented medium resolution (3.4 A
FWHM) spectroscopic observations of 15 "transition objects", selected for
having an ambiguous location in the Veilleux & Osterbrock (1987) diagnostic
diagrams, and showed that most of them were in fact "composite", this being due
to the simultaneous presence on the slit of both a Seyfert or Liner nucleus and
a HII region. Here, we report new spectroscopic observations of 53
emission-line galaxies with a "transition" spectrum, bringing up to 61 the
total number of observed objects in an unbiased sample of 88 "transition
objects". Almost all of the observed galaxies have a "composite" nature,
confirming the finding that true "transition" spectra may not exist at all. By
eliminating "composite objects" from the diagnostic diagrams, a clear
separation between the different classes of nuclear emission-line regions
(Seyfert 2s, Liners and HII regions) becomes apparent; by restricting the
volume occupied by the different line-emitting regions in the 3-dimensional
diagnostic diagrams, we are also restricting the range of possible physical
parameters in these regions. There seems to be no continuity between Seyfert 2s
and Liners, the two classes occupying distinct volumes in the 3-dimensional
space defined by [OIII]5007/Hbeta, [NII]6583/Halpha, and [OI]6300/Halpha.
|
a9251ad6-f3a6-4161-a70a-edf42fa12ba8 | [
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-0.00556253... | 2207.12354 | We consider integrable boundary states in the XXX spin-1/2 spin chain. We
begin by briefly reviewing the algebraic Bethe Ansatz as well as integrable
boundary states in spin chains. Then a recently discovered class of integrable
states known as crosscap states is described and expanded. In these states each
spin is entangled with its antipodal spin. We present a novel proof of the
integrability of both a crosscap state that is known in the literature and one
that has not previously been studied. We then use the machinery of the
algebraic Bethe Ansatz to derive the overlaps between the crosscap states and
off-shell Bethe states.
|
a9251ef6-f6b9-4147-97b2-9b9ed2ce1cba | [
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-0.030295... | 2112.14573 | Modelling the broadband emission of jetted active galactic nuclei (AGN)
constitutes one of the main research topics of extragalactic astrophysics in
the multi-wavelength and multi-messenger domain.
We present agnpy, an open-source python package modelling the radiative
processes of relativistic particles accelerated in the jets of active galactic
nuclei. The package includes classes describing the galaxy components
responsible for line and thermal emission and calculates the absorption due to
$\gamma\gamma$ pair production on several photon fields. agnpy aims at
extending the effort of modelling and interpreting the emission of
extragalactic sources to a wide number of astrophysicists.
We present the package content and illustrate a few examples of applications
of its functionalities. We validate the software by comparing its results
against the literature and against other open-source software.
We illustrate the utility of agnpy in addressing the most common questions
encountered while modelling the emission of jetted active galaxies. When
comparing its results against the literature and other modelling tools adopting
the same physical assumptions, we achieve an agreement within $10-30\%$.
agnpy represents one of the first systematic and validated collection of
established radiative processes for jetted active galaxies in an open-source
python package. We hope it will stand also among the first endeavours providing
reproducible and transparent astrophysical software not only for data reduction
and analysis, but also for modelling and interpretation.
|
a9251f3f-63b9-4f8c-a7c0-bb5c8e210b4d | [
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0.0375... | 1706.02697 | We report high-pressure magnetization and $^{35}$Cl NMR studies on
$\alpha$-RuCl$_3$ with pressure up to 1.5~GPa. At low pressures, the magnetic
ordering is identified by both the magnetization data and the NMR data, where
the $T_N$ shows a concave shape dependence with pressure. These data suggest
stacking rearrangement along the $c$-axis. With increasing pressure, phase
separation appears prominently at $P\ge$~0.45~GPa, and the magnetic volume
fraction is completely suppressed at $P\ge$~1.05~GPa. Meanwhile, a
phase-transition-like behavior emerges at high pressures in the remaining
volume by a sharp drop of magnetization $M(T)$ upon cooling, with the
transition temperature $T_x$ increased to ~250~K at 1~GPa. The $1/^{35}T_1$ is
reduced by over three orders of magnitude when cooled below 100~K. This
characterizes a high-pressure, low-temperature phase with nearly absent static
susceptibility and low-energy spin fluctuations. The nature of the
high-pressure ground state is discussed, where a magnetically disordered state
is proposed as a candidate state.
|
a9252d32-d0fd-4141-94f9-dfdec2db9c0d | [
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0.0... | 1606.05165 | We use first-principles calculations based on density functional theory to
investigate the interplay between oxygen vacancies, A-site cation size /
tolerance factor, epitaxial strain, ferroelectricity and magnetism in the
perovskite manganite series, AMnO3 (A=Ca2+, Sr2+, Ba2+). We find that, as
expected, increasing the volume through either chemical pressure or tensile
strain generally lowers the formation energy of neutral oxygen vacancies
consistent with their established tendency to expand the lattice. Increased
volume also favors polar distortions, both because competing rotations of the
oxygen octahedra are suppressed and because coulomb repulsion associated with
cation off-centering is reduced. Interestingly, the presence of ferroelectric
polarization favors ferromagnetic over antiferromagnetic ordering due to
suppressed antiferromagnetic superexchange as the polar distortion bends the
Mn-O-Mn bond angles away from the optimal 180deg. Intriguingly, we find that
polar distortions compete with the formation of oxygen vacancies, which have a
higher formation energy in the polar phases; conversely the presence of oxygen
vacancies suppresses the onset of polarization. In contrast, oxygen vacancy
formation energies are lower for ferromagnetic than antiferromagnetic orderings
of the same structure type. Our findings suggest a rich and complex phase
diagram, in which defect chemistry, polarization, structure and magnetism can
be modified using chemical potential, strain, and electric or magnetic fields.
|
a9253b55-90b0-45e2-be09-8635f49da246 | [
0.006047034,
0.008362125,
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-0.068702206,
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... | 1909.07126 | In this paper, we present a Chebyshev based spectral method for the
computation of the Jost solutions corresponding to complex values of the
spectral parameter in the Zakharov--Shabat scattering problem. The discrete
framework is then used to devise a new algorithm based on a minimum total
variation (MTV) principle for the computation of the norming constants which
comprise the discrete part of the nonlinear Fourier spectrum. The method relies
on the MTV principle to find the points where the expressions for norming
constants are numerically well-conditioned.
|
a9254250-d53b-4e7e-a60d-e71c89182445 | [
-0.009810992,
0.0025540034,
0.046210956,
-0.050384335,
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-0.08244802,
0.0099296775,
-0.007886585,
-0.053567894,
0.041875865,
0.018344097,
-0.05438101,
-0.08048126,
0.025756318,
0.0011059523,
-0.004984349,
-0.02111149,
0.005276086,
0.052401885,
-0.01935... | 2110.03050 | We determine the inner product on the Hilbert space of wavefunctions of the
universe by imposing the Hermiticity of the quantum Hamiltonian in the context
of the minisuperspace model. The corresponding quantum probability density
reproduces successfully the classical probability distribution in the $\hbar
\to 0$ limit, for closed universes filled with a perfect fluid of index $w$.
When $-1/3<w\le 1$, the wavefunction is normalizable and the quantum
probability density becomes vanishingly small at the big bang/big crunch
singularities, at least at the semi-classical level. Quantum expectation values
of physical geometrical quantities, which diverge classically at the
singularities, are shown to be finite.
|
a9254309-d4b9-457b-80a5-35c4dc6186c8 | [
-0.013537947,
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0.006265623,
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-0.030328318,
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0.009841537,
-0.052689333,
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0.037953757,
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0.016687732,
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0.00816... | 2103.09505 | Context: The long-term carbonate-silicate cycle plays an important role in
the evolution of Earth's climate and, therefore, may also be an important
mechanism in the evolution of the climates of Earth-like exoplanets. Aims: We
investigate the effects of radiogenic mantle heating, core size, and planetary
mass on the evolution of the atmospheric partial $CO_2$ pressure, and the
ability of a long-term carbon cycle driven by plate tectonics to control the
atmospheric $CO_2$ pressure. Methods: We developed a box-model which connects
carbon cycling to parametrized mantle convection. The carbon cycle was coupled
to the thermal evolution via the plate speed, which depends on the global
Rayleigh number. Results: We find decreasing atmospheric $CO_2$ pressure with
time, up to an order of magnitude over 10 Gyr. Higher abundances of radioactive
isotopes result in higher $CO_2$ pressures. We find a decreasing Rayleigh
number and plate speed toward planets with larger core mass fractions $f_c$,
which leads to lower atmospheric $CO_2$ pressure. More massive planets may
favor the development of more $CO_2$ rich atmospheres due to hotter interiors.
Conclusions: The dependence of plate tectonics on mantle cooling has a
significant effect on the long-term evolution of the atmospheric $CO_2$
pressure. Carbon cycling mediated by plate tectonics is efficient in regulating
planetary climates for a wide range of mantle radioactive isotope abundances,
planet masses and core sizes. More efficient carbon cycling on planets with a
high mantle abundance of thorium or uranium highlights the importance of
mapping the abundances of these elements in host stars of potentially habitable
exoplanets. Inefficient carbon recycling on planets with a large core mass
fraction ($f_c\gtrsim 0.8$) emphasizes the importance of precise mass-radius
measurements of Earth-sized exoplanets.
|
a9254862-aeab-4083-b5ff-402572fbb7a6 | [
0.0070519187,
0.0010746267,
0.0058063166,
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0.0043434026,
-0.012303197,
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... | 1509.01494 | In this paper, we study the existence of positive entire large and bounded
radial positive solutions for a nonlinear system. Our results give an answer of
the question raised in [11].
|
a92548cd-8762-4325-8433-0bcb7162cf81 | [
-0.012867475,
-0.018348586,
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0.0008329371,
0.05324856,
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0.031755045,
-0.030... | 2012.05220 | Stellar distances constitute a foundational pillar of astrophysics. The
publication of 1.47 billion stellar parallaxes from Gaia is a major
contribution to this. Yet despite Gaia's precision, the majority of these stars
are so distant or faint that their fractional parallax uncertainties are large,
thereby precluding a simple inversion of parallax to provide a distance. Here
we take a probabilistic approach to estimating stellar distances that uses a
prior constructed from a three-dimensional model of our Galaxy. This model
includes interstellar extinction and Gaia's variable magnitude limit. We infer
two types of distance. The first, geometric, uses the parallax together with a
direction-dependent prior on distance. The second, photogeometric, additionally
uses the colour and apparent magnitude of a star, by exploiting the fact that
stars of a given colour have a restricted range of probable absolute magnitudes
(plus extinction). Tests on simulated data and external validations show that
the photogeometric estimates generally have higher accuracy and precision for
stars with poor parallaxes. We provide a catalogue of 1.47 billion geometric
and 1.35 billion photogeometric distances together with asymmetric uncertainty
measures. Our estimates are quantiles of a posterior probability distribution,
so they transform invariably and can therefore also be used directly in the
distance modulus (5log10(r)-5). The catalogue may be downloaded or queried
using ADQL at various sites (see
http://www.mpia.de/homes/calj/gedr3_distances.html) where it can also be
cross-matched with the Gaia catalogue.
|
a9255b5c-8908-4bcf-a942-dad263368f3a | [
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0.039279398,
0.001... | 1202.2563 | The Fokker-Planck equations describe time evolution of probability densities
of stochastic dynamical systems and are thus widely used to quantify random
phenomena such as uncertainty propagation. For dynamical systems driven by
non-Gaussian L\'evy processes, however, it is difficult to obtain explicit
forms of Fokker-Planck equations because the adjoint operators of the
associated infinitesimal generators usually do not have exact formulation. In
the present paper, Fokker- Planck equations are derived in terms of infinite
series for nonlinear stochastic differential equations with non-Gaussian L\'evy
processes. A few examples are presented to illustrate the method.
|
a92562ad-13ec-4c3c-b857-1771b9f3b65b | [
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-0.0... | 1911.03070 | Cross-lingual word embeddings transfer knowledge between languages: models
trained on high-resource languages can predict in low-resource languages. We
introduce CLIME, an interactive system to quickly refine cross-lingual word
embeddings for a given classification problem. First, CLIME ranks words by
their salience to the downstream task. Then, users mark similarity between
keywords and their nearest neighbors in the embedding space. Finally, CLIME
updates the embeddings using the annotations. We evaluate CLIME on identifying
health-related text in four low-resource languages: Ilocano, Sinhalese,
Tigrinya, and Uyghur. Embeddings refined by CLIME capture more nuanced word
semantics and have higher test accuracy than the original embeddings. CLIME
often improves accuracy faster than an active learning baseline and can be
easily combined with active learning to improve results.
|
a9256359-5063-41a8-8d01-2202037a22a8 | [
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0.0032820934... | 2108.05311 | We use the infinite volume reconstruction method to calculate the
charged/neutral pion mass difference. The hadronic tensor is calculated on
lattice QCD and then combined with an analytic photon propagator, and the mass
splitting is calculated with exponentially-suppressed finite volume errors. The
calculation is performed using six gauge ensembles generated with $2+1$-flavor
domain wall fermions, and five ensembles are at the physical pion mass. Both
Feynman and Coulomb gauge are adopted in the calculation and result in a good
agreement when the lattice spacing approaches zero. After performing the
continuum extrapolation and examining the residual finite-volume effects, we
obtain the pion mass splitting $\Delta m_\pi = 4.534(42)(43)~\mathrm{MeV}$,
which agrees well with experimental measurements.
|
a92565f7-b211-4b74-b2d4-b07bb8dff4c4 | [
0.039336357,
0.02498257,
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-0.051142875,
-0.062172662,
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-0.050221562,
-0.041580364,
0.047644954,
0.07366763,
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-0.02... | 1912.04943 | We present SKD, a novel keypoint detector that uses saliency to determine the
best candidates from a point cloud for tasks such as registration and
reconstruction. The approach can be applied to any differentiable deep learning
descriptor by using the gradients of that descriptor with respect to the 3D
position of the input points as a measure of their saliency. The saliency is
combined with the original descriptor and context information in a neural
network, which is trained to learn robust keypoint candidates. The key
intuition behind this approach is that keypoints are not extracted solely as a
result of the geometry surrounding a point, but also take into account the
descriptor's response. The approach was evaluated on two large LIDAR datasets -
the Oxford RobotCar dataset and the KITTI dataset, where we obtain up to 50%
improvement over the state-of-the-art in both matchability and repeatability.
When performing sparse matching with the keypoints computed by our method we
achieve a higher inlier ratio and faster convergence.
|
a92566ec-ca47-4bff-8856-b13c22639608 | [
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0.0638019,
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0.0014449899,
0.033006985,... | 1707.02845 | We investigate the dependence of transmission losses on the choice of a slack
bus in high voltage AC transmission networks. We formulate a transmission loss
minimization problem in terms of slack variables representing the additional
power injection that each generator provides to compensate the transmission
losses. We show analytically that for transmission lines having small,
homogeneous resistance over reactance ratios ${r/x\ll1}$, transmission losses
are generically minimal in the case of a unique \textit{slack bus} instead of a
distributed slack bus. For the unique slack bus scenario, to lowest order in
${r/x}$, transmission losses depend linearly on a resistance distance based
indicator measuring the separation of the slack bus candidate from the rest of
the network. We confirm these results numerically for several IEEE and Pegase
testcases, and show that our predictions qualitatively hold also in the case of
lines having inhomogeneous ${r/x}$ ratios, with optimal slack bus choices
reducing transmission losses by ${10}\%$ typically.
|
a9257564-2d5f-41f4-854e-6e52fa13b5fd | [
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0.024864355,
-0.0... | 2204.00733 | We consider the Clarkson-McLeod solutions of the fourth Painlev\'e equation.
This family of solutions behave like $\kappa
D_{\alpha-\frac{1}{2}}^2(\sqrt{2}x)$ as $x\rightarrow +\infty$, where $\kappa $
is an arbitrary real constant and $D_{\alpha-\frac{1}{2}}(x)$ is the parabolic
cylinder function. Using the Deift-Zhou nonlinear steepest descent method, we
obtain the singular asymptotics of the solutions as $x\to-\infty$ when $\kappa
\left( \kappa -\kappa ^*\right )>0$ for some real constant $\kappa ^*$. The
connection formulas are also explicitly evaluated. This proves and extends
Clarkson and McLeod's conjecture that when the parameter $\kappa >\kappa ^*>0$,
the Clarkson-McLeod solutions have infinitely many simple poles on the negative
real axis.
|
a92578a6-0b67-4b50-848d-9bb210a38582 | [
0.012906182,
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-0.01413107... | 2102.01390 | Special point defects in semiconductors have been envisioned as suitable
components for quantum-information technology. The identification of new deep
centers in silicon that can be easily activated and controlled is a main target
of the research in the field. Vacancy-related complexes are suitable to provide
deep electronic levels but they are hard to control spatially. With the spirit
of investigating solid state devices with intentional vacancy-related defects
at controlled position, here we report on the functionalization of silicon
vacancies by implanting Ge atoms through single-ion implantation, producing
Ge-vacancy (GeV) complexes. We investigate the quantum transport through an
array of GeV complexes in a silicon-based transistor. By exploiting a model
based on an extended Hubbard Hamiltonian derived from ab-initio results we find
anomalous activation energy values of the thermally activated conductance of
both quasi-localized and delocalized many-body states, compared to conventional
dopants. We identify such states, forming the upper Hubbard band, as
responsible of the experimental sub-threshold transport across the transistor.
The combination of our model with the single-ion implantation method enables
future research for the engineering of GeV complexes towards the creation of
spatially controllable individual defects in silicon for applications in
quantum information technologies.
|
a92579b5-6507-43bb-8cce-69e4cbbc23d0 | [
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-0.102292284,
0.0070120203,
-0.022637924,
-0.013395558,
-0.023490353,
-0.0035450847,
0.012734516,
-0.013200... | 2201.01231 | The method of characteristics is extended to set-valued Hamilton-Jacobi
equations. This problems arises from a calculus of variations' problem with a
multicriteria Lagrangian function: through an embedding into a set-valued
framework, a set-valued Hamilton-Jacobi equation is derived, where the
Hamiltonian function is the Fenchel conjugate of the Lagrangian function. In
this paper a method of characteristics is described and some results are given
for the Fenchel conjugate.
|
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