ShantanuT01/DACTYL-Pretraining huggingface dataset:
Anisotropic magnetoresistance (AMR) is a ubiquitous and versatile probe of magnetic order in contemporary spintronics research. Its origins are usually ascribed to extrinsic effects (i.e. spin-dependent electron scattering), whereas intrinsic (i.e. scattering-independent) contributions are neglected. Here, we measure AMR of polycrystalline thin films of the standard ferromagnets Co, Ni, Ni81Fe19 and Ni50Fe50 over the frequency range from DC to 28 THz. The large bandwidth covers the regimes of both diffusive and ballistic intraband electron transport and, thus, allows us to separate extrinsic and intrinsic AMR components. Analysis of the THz response based on Boltzmann transport theory reveals that the AMR of the Ni, Ni81Fe19 and Ni50Fe50 samples is of predominantly extrinsic nature. However, the Co thin film exhibits a sizeable intrinsic AMR contribution, which is constant up to 28 THz and amounts to more than 2/3 of the DC AMR contrast of 1%. These features are attributed to the hexagonal structure of the Co crystallites. They are interesting for applications in terahertz spintronics and terahertz photonics. Our results show that broadband terahertz electromagnetic pulses provide new and contact-free insights into magneto-transport phenomena of standard magnetic thin films on ultrafast time scales.
We report the spectroscopic confirmation of SPT-CL J0546-5345 at <z> = 1.067. To date this is the most distant cluster to be spectroscopically confirmed from the 2008 South Pole Telescope (SPT) catalog, and indeed the first z > 1 cluster discovered by the Sunyaev-Zel'dovich Effect (SZE). We identify 21 secure spectroscopic members within 0.9 Mpc of the SPT cluster position, 18 of which are quiescent, early-type galaxies. From these quiescent galaxies we obtain a velocity dispersion of 1179^{+232}_{-167} km/s, ranking SPT-CL J0546-5345 as the most dynamically massive cluster yet discovered at z > 1. Assuming that SPT-CL J0546-5345 is virialized, this implies a dynamical mass of M_200 = 1.0^{+0.6}_{-0.4} x 10^{15} Msun, in agreement with the X-ray and SZE mass measurements. Combining masses from several independent measures leads to a best-estimate mass of M_200 = (7.95 +/- 0.92) x 10^{14} Msun. The spectroscopic confirmation of SPT-CL J0546-5345, discovered in the wide-angle, mass-selected SPT cluster survey, marks the onset of the high redshift SZE-selected galaxy cluster era.
We report the results of a comprehensive spectroscopic ellipsometry study of NaCu2O2, a compound composed of chains of edge-sharing Cu2+O4 plaquettes and planes of Cu1+ ions in a O-Cu1+-O dumbbell configuration, in the spectral range 0.75-6.5 eV at temperatures 7 -300 K. The spectra of the dielectric function for light polarized parallel to the Cu1+ planes reveal a strong in-plane anisotropy of the interband excitations. Strong and sharp absorption bands peaked at 3.45 eV (3.7 eV) dominate the spectra for polarization along (perpendicular) to the Cu2+O2 chains. They are superimposed on flat and featureless plateaux above the absorption edges at 2.25 eV (2.5 eV). Based on density-functional calculations, the anomalous absorption peaks can be assigned to transitions between bands formed by Cu1+ 3dxz(dyz) and Cu2+ 3dxy orbitals, strongly hybridized with O pstates. The major contribution to the background response comes from transitions between Cu1+ 3dz2 and 4px(py) bands. This assignment accounts for the measured in-plane anisotropy. The dielectric response along the Cu2+O2 chains develops a weak two-peak structure centered at 2.1 and 2.65 eV upon cooling below 100 K, along with the appearance of spin correlations along the Cu2+O2 chains. These features bear a striking resemblance to those observed in the single-valent Cu2+O2 chain compound LiCuVO4, which were identified as an exciton doublet associated with transitions to the upper Hubbard band that emerges as a consequence of the long-range Coulomb interaction between electrons on neighboring Cu2+ sites along the chains. An analysis of the spectral weights of these features yields the parameters characterizing the on-site and long-range Coulomb interactions.
We present results from AstroSat observation of the recent outburst of GRO J2058+42, an X-ray pulsar in a Be-binary system. The source was observed on April 10, 2019 by LAXPC and SXT instruments on AstroSat during its declining phase of the latest giant outburst. Light curves showed a strong pulsation of the pulsar with a period of 194.2201 \pm 0.0016 s, and a spin-up rate of (1.65\pm0.06)\times10^{-11} Hz s^{-1}. Intermittent flaring was detected in light curves between 3--80 keV energy band with increase in intensity by up to 1.8 times its average intensity. Pulse profiles obtained between 3--80 keV energy band of the pulsar showed strong dependence on energy. A broad peak was observed in the power density spectrum of the source consistently during AstroSat observations with its peak oscillation frequency of 0.090 Hz along with its higher harmonics, which may be due to quasi-periodic oscillations, a commonly observed phenomenon in transient X-ray pulsars, during their outburst. AstroSat observation also detected cyclotron absorption features in its spectrum corresponding to (9.7--14.4) keV, (19.3--23.8) keV and (37.8--43.1) keV. The pulse phase resolved spectroscopy of the source showed phase dependent variation in its energy and relative strength of these features. The spectrum was well fitted with an absorbed black-body, a Fermi Dirac cut-off model and alternatively with an absorbed CompTT model. Both these models were combined with a Fe-line and three Gaussian absorption lines to account for observed cyclotron resonance scattering features in the spectrum.
Mathematical population genetics is only one of Kingman's many research interests. Nevertheless, his contribution to this field has been crucial, and moved it in several important new directions. Here we outline some aspects of his work which have had a major influence on population genetics theory.
Embedded clusters like W3 Main are complex and dynamically evolving systems that represent an important phase of the star formation process. We aim at the characterization of the entire stellar content of W3 Main in a statistical sense to identify possible differences in evolutionary phase of the stellar populations and find clues about the formation mechanism of this massive embedded cluster. Methods. Deep JHKs imaging is used to derive the disk fraction, Ks-band luminosity functions and mass functions for several subregions in W3 Main. A two dimensional completeness analysis using artificial star experiments is applied as a crucial ingredient to assess realistic completeness limits for our photometry. We find an overall disk fraction of 7.7 $\pm$ 2.3%, radially varying from 9.4 $\pm$ 3.0 % in the central 1 pc to 5.6 $\pm$ 2.2 % in the outer parts of W3 Main. The mass functions derived for three subregions are consistent with a Kroupa and Chabrier mass function. The mass function of IRSN3 is complete down to 0.14 Msun and shows a break at M $\sim$ 0.5 Msun. We interpret the higher disk fraction in the center as evidence for a younger age of the cluster center. We find that the evolutionary sequence observed in the low-mass stellar population is consistent with the observed age spread among the massive stars. An analysis of the mass function variations does not show evidence for mass segregation. W3 Main is currently still actively forming stars, showing that the ionizing feedback of OB stars is confined to small areas ($\sim$ 0.5 pc). The FUV feedback might be influencing large regions of the cluster as suggested by the low overall disk fraction.
We have fitted low- and medium-energy benchmark datasets employing methods used in the MAID/SAID and dynamical model analyses. Independent fits from the Mainz, RPI, Yerevan, and Kharkov groups have also been performed over the low-energy region. Results for the multipole amplitudes are compared in order to gauge the model-dependence of such fits, given identical data and a single method for error handling.
Upcoming missions, including the James Webb Space Telescope, will soon characterize the atmospheres of terrestrial-type exoplanets in habitable zones around cool K- and M-type stars searching for atmospheric biosignatures. Recent observations suggest that the ionizing radiation and particle environment from active cool planet hosts may be detrimental for exoplanetary habitability. Since no direct information on the radiation field is available, empirical relations between signatures of stellar activity, including the sizes and magnetic fields of starspots, are often used. Here, we revisit the empirical relation between the starspot size and the effective stellar temperature and evaluate its impact on estimates of stellar flare energies, coronal mass ejections, and fluxes of the associated stellar energetic particle events.
This work is focused on the theory of Gravitoelectromagnetism (GEM). In the first part of this work we present a brief review of gravitoelectromagnetism, we locate and discuss all the problems which appear in this approach. We also try to avoid these problems by proposing new approaches in which we use the additional degrees of freedom of the gravitational field. In the second part of this work, we review our previous work regarding the construction of a tensorial theory, using the formalism of General Relativity, which aims to describe the true electromagnetism. We also extend this theory in order to make it more realistic. Finally in the third part of this work, we investigate the existence of gravitational invariants similar to the electromagnetic ones.
We prove that, for every $n \geq 5$, the Hasse norm principle holds for a degree $n$ extension $K/k$ of number fields with normal closure $F$ such that $\operatorname{Gal}(F/k) \cong A_n$. We also show the validity of weak approximation for the associated norm one tori.
We present an observational study of the vibrationally excited H$_{2}$O line at 658 GHz ($\nu_{2}$=1, 1$_{1, 0}$-1$_{0, 1}$) toward Orion KL using the Atacama Large Millimeter/Submillimeter Array (ALMA). This line is clearly detected at the position of the massive protostar candidate, the Source I. The spatial structure is compact with a size of about 100 AU and is elongated along the northeast-southwest low-velocity (18 km s$^{-1}$) bipolar outflow traced by 22 GHz H$_{2}$O masers, SiO masers, and thermal SiO lines. A velocity gradient can be seen perpendicular to the bipolar outflow. Overall spatial and velocity structure seems analogous to that of the 321 GHz H$_{2}$O maser line previously detected with ALMA and vibrationally excited SiO maser emission. The brightness temperature of the 658 GHz H$_{2}$O line is estimated to be higher than 2$\times$10$^{4}$ K, implying that it is emitted via maser action. Our results suggest that the 658 GHz H$_{2}$O maser line is emitted from the base of the outflow from a rotating and expanding accretion disk as observed for the SiO masers and the 321 GHz H$_{2}$O maser. We also search for two other H$_{2}$O lines at 646 GHz (9$_{7, 3}$-8$_{8, 0}$ and 9$_{7, 2}$-8$_{8, 1}$), but they are not detected in Orion KL.
To reduce the manpower consumption on box-level annotations, many weakly supervised object detection methods which only require image-level annotations, have been proposed recently. The training process in these methods is formulated into two steps. They firstly train a neural network under weak supervision to generate pseudo ground truths (PGTs). Then, these PGTs are used to train another network under full supervision. Compared with fully supervised methods, the training process in weakly supervised methods becomes more complex and time-consuming. Furthermore, overwhelming negative proposals are involved at the first step. This is neglected by most methods, which makes the training network biased towards to negative proposals and thus degrades the quality of the PGTs, limiting the training network performance at the second step. Online proposal sampling is an intuitive solution to these issues. However, lacking of adequate labeling, a simple online proposal sampling may make the training network stuck into local minima. To solve this problem, we propose an Online Active Proposal Set Generation (OPG) algorithm. Our OPG algorithm consists of two parts: Dynamic Proposal Constraint (DPC) and Proposal Partition (PP). DPC is proposed to dynamically determine different proposal sampling strategy according to the current training state. PP is used to score each proposal, part proposals into different sets and generate an active proposal set for the network optimization. Through experiments, our proposed OPG shows consistent and significant improvement on both datasets PASCAL VOC 2007 and 2012, yielding comparable performance to the state-of-the-art results.
We study the spectral geometry of an operator of Laplace type on a manifold with a singular surface. We calculate several first coefficients of the heat kernel expansion. These coefficients are responsible for divergences and conformal anomaly in quantum brane-world scenario.
Recently, the current authors have formulated and extensively explored a rather novel Painleve-Gullstrand variant of the slow-rotation Lense-Thirring spacetime, a variant which has particularly elegant features -- including unit lapse, intrinsically flat spatial 3-slices, and a separable Klein-Gordon equation (wave operator). This spacetime also possesses a non-trivial Killing tensor, implying separability of the Hamilton-Jacobi equation, the existence of a Carter constant, and complete formal integrability of the the geodesic equations. Herein we investigate the geodesics in some detail, in the general situation demonstrating the occurrence of "ultra-elliptic" integrals. Only in certain special cases can the complete geodesic integrability be explicitly cast in terms of elementary functions. The model is potentially of astrophysical interest both in the asymptotic large-distance limit and as an example of a "black hole mimic", a controlled deformation of the Kerr spacetime that can be contrasted with ongoing astronomical observations.
The interpretation of stellar apparent fundamental parameters must be treated consistently with the characteristics of their surface rotation law. We develop a model to determine the distribution of the effective temperature and gravity, which depend on the surface differential rotation law and on the stellar external geometry. The basic assumptions are: a) the atmosphric layers are in radiative equilibrium; b) the bolometric flux is anti-parallel with the effective gravity; c) the angular velocity in the surface is Omega=Omega(theta,alpha,k)] where (alpha,k) are free parameters. The effective temperature varies with co-latitude `theta' and on the differential-rotation law through the effective gravity and the gravity-darkening function (GDF). Although the derived expressions can be treated numerically, for some low integer values of k, analytical forms of the `integral ofcharacteristic curves', on which the determination of the GDF relies, are obtained. The effects of the quantities (eta,alpha,k) (eta=ratio between centrifugal and gravitational accelerations at the equator) on the determination of the Vsini parameter and on the `gravity-darkening exponent' are studied. Depending on the values of (eta,alpha,k) the velocity V in the derived Vsini may strongly deviate from the equatorial rotational velocity. It is shown that the von Zeipel's-like gravity-darkening exponent $\beta_1$ depends on all parameters $(\eta,\alpha,k)$ and that its value also depends on the viewing-angle i. Hence, there no unique interpretation of this exponent determined empirically in terms of (i,alpha). The data on rotating stars should be analyzed by taking into account the rotational effects through the GDF, by assuming k=2 as a first approximation. Instead of the classical pair (eta,beta1), it would be more useful to determine the quantities (eta,alpha,i) to characterize stellar rotation.
We give examples of families of Frobenius type structures on the punctured plane and we study their limits at the boundary. We then discuss the existence of a limit Frobenius manifold. We also give an example of a logarithmic Frobenius manifold.
We define a covariance-type operator on Wiener space: for F and G two random variables in the Gross-Sobolev space $D^{1,2}$ of random variables with a square-integrable Malliavin derivative, we let $Gamma_{F,G}=$ where $D$ is the Malliavin derivative operator and $L^{-1}$ is the pseudo-inverse of the generator of the Ornstein-Uhlenbeck semigroup. We use $\Gamma$ to extend the notion of covariance and canonical metric for vectors and random fields on Wiener space, and prove corresponding non-Gaussian comparison inequalities on Wiener space, which extend the Sudakov-Fernique result on comparison of expected suprema of Gaussian fields, and the Slepian inequality for functionals of Gaussian vectors. These results are proved using a so-called smart-path method on Wiener space, and are illustrated via various examples. We also illustrate the use of the same method by proving a Sherrington-Kirkpatrick universality result for spin systems in correlated and non-stationary non-Gaussian random media.
Supervised deep neural networks are the-state-of-the-art for many tasks in the remote sensing domain, against the fact that such techniques require the dataset consisting of pairs of input and label, which are rare and expensive to collect in term of both manpower and resources. On the other hand, there are abundance of raw satellite images available both for commercial and academic purposes. Hence, in this work, we tackle the insufficient labeled data problem in satellite image classification task by introducing the process based on the self-supervised learning technique to create the synthetic labels for satellite image patches. These synthetic labels can be used as the training dataset for the existing supervised learning techniques. In our experiments, we show that the models trained on the synthetic labels give similar performance to the models trained on the real labels. And in the process of creating the synthetic labels, we also obtain the visual representation vectors that are versatile and knowledge transferable.
We derive analytic formulae for the energy average (including the energy average of the fluctuation contribution) and variance of the intraband decay intensity of a superdeformed band. Our results may be expressed in terms of three dimensionless variables: $\Gamma^{\downarrow}/\Gamma_S$, $\Gamma_N/d$, and $\Gamma_N/(\Gamma_S+\Gamma^{\downarrow})$. Here $\Gamma^{\downarrow}$ is the spreading width for the mixing of a superdeformed (SD) state $|0>$ with the normally deformed (ND) states $|Q>$ whose spin is the same as $|0>$'s. The $|Q>$ have mean level spacing $d$ and mean electromagnetic decay width $\Gamma_N$ whilst $|0>$ has electromagnetic decay width $\Gamma_S$.   The average decay intensity may be expressed solely in terms of the variables $\Gamma^{\downarrow}/\Gamma_S$ and $\Gamma_N/d$ or, analogously to statistical nuclear reaction theory, in terms of the transmission coefficients $T_0(E)$ and $T_N$ describing transmission from the $|Q>$ to the SD band via $|0\angle$ and to lower ND states.   The variance of the decay intensity, in analogy with Ericson's theory of cross section fluctuations depends on an additional variable, the correlation length $\Gamma_N/(\Gamma_S+\Gamma^{\downarrow})=\frac{d}{2\pi}T_N/(\Gamma_S+\Gamma^{\d ownarrow})$. This suggests that analysis of an experimentally obtained variance could yield the mean level spacing $d$ as does analysis of the cross section autocorrelation function in compound nuclear reactions.   We compare our results with those of Gu and Weidenm\"uller.
Hundreds of Type 2 quasars have been identified in Sloan Digital Sky Survey (SDSS) data, and there is substantial evidence that they are generally galaxies with highly obscured central engines, in accord with unified models for active galactic nuclei (AGNs). A straightforward expectation of unified models is that highly obscured Type 2 AGNs should show little or no optical variability on timescales of days to years. As a test of this prediction, we have carried out a search for variability in Type 2 quasars in SDSS Stripe 82 using difference-imaging photometry. Starting with the Type 2 AGN catalogs of Zakamska et al. (2003) and Reyes et al. (2008), we find evidence of significant g-band variability in 17 out of 173 objects for which light curves could be measured from the Stripe 82 data. To determine the nature of this variability, we obtained new Keck spectropolarimetry observations for seven of these variable AGNs. The Keck data show that these objects have low continuum polarizations (p<~1% in most cases) and all seven have broad H-alpha and/or MgII emission lines in their total (unpolarized) spectra, indicating that they should actually be classified as Type 1 AGNs. We conclude that the primary reason variability is found in the SDSS-selected Type 2 AGN samples is that these samples contain a small fraction of Type 1 AGNs as contaminants, and it is not necessary to invoke more exotic possible explanations such as a population of "naked" or unobscured Type 2 quasars. Aside from misclassified Type 1 objects, the Type 2 quasars do not generally show detectable optical variability over the duration of the Stripe 82 survey.
The characteristics of the type II bursts with herringbone structure observed both by ground based radio telescopes (UTR-2, URAN-2) and spaceborn spectrometers (STEREO A-B) are discussed. The burst was recorded on 7 June, 2011 in the frequency band 3--33~MHz. It was characterized by extremely rich fine structure. The statistical analysis of more than 300 herringbone sub-bursts constituting the burst was performed separately for the positively (reverse) and negatively (forward) drifting sub-bursts. The sense and the degree of circular polarization of the herringbone sub-bursts were measured in the respectively wide frequency band (16--32~MHz). A second order fine frequency structure of the herringbone sub-bursts was firstly observed and processed. Using STEREO COR1 (A,B) and SOHO LASCO C2 images the direction and radial speed of the CME responsible for the studied type II burst were determined. The possible location of the type II burst source on the flank of the shock was found.
We show that if a sequence of dense graphs has the property that for every fixed graph F, the density of copies of F in these graphs tends to a limit, then there is a natural ``limit object'', namely a symmetric measurable 2-variable function on [0,1]. This limit object determines all the limits of subgraph densities. We also show that the graph parameters obtained as limits of subgraph densities can be characterized by ``reflection positivity'', semidefiniteness of an associated matrix. Conversely, every such function arises as a limit object. Along the lines we introduce a rather general model of random graphs, which seems to be interesting on its own right.