ShantanuT01/DACTYL-Pretraining huggingface dataset:
In the coming decades, research in extrasolar planets aims to advance two goals: 1) detecting and characterizing low-mass planets increasingly similar to the Earth, and 2) improving our understanding of planet formation. We present a new planet detection method that is capable of making large advances towards both of these objectives and describe a modest network of telescopes that is able to make the requisite observations. In a system where a known planet transits its host star, a second planet in that system will cause the time between transits to vary. These transit timing variations can be used to infer the orbital elements and mass of the perturbing planet even if it has a mass that is smaller than the mass of the Earth. This detection technique complements other techniques because it is most sensitive in mean-motion resonances where, due to degeneracies, other techniques have reduced sensitivity. Small ground-based observatories have already exceeded the photometric precision necessary to detect sub-Earth mass planets. However, TTV planet searches are currently limited by the relatively small number of high-precision transit data and insufficient observing time on existing telescopes. These issues will be compounded as the number of known transiting planets suitable for TTV study will increase substantially in the near future. A relatively modest investment in a ground-based network of small ($\sim 0.5 {\rm m}$ telescopes could provide the needed coverage and so dramatically increase the effectiveness of transit timing observations.
We numerically investigate the dynamical properties of $\kappa$-type molecular conductors in their antiferromagnetic Mott insulating state. By treating the extended Hubbard model on the two-dimensional $\kappa$-type lattice within the Lanzcos exact diagonalization method, we calculate the one-particle spectral function $A(\boldsymbol{k}, \omega)$ and the optical absorption spectra taking advantage of twisted boundary conditions. We find spin splitting in $A(\boldsymbol{k}, \omega)$ predicted by a previous Hartree-Fock study [M. Naka et al., Nat. Commun. 10, 4305 (2019)]; namely, their up- and down-spin components become different in the general $\boldsymbol{k}$-points of the Brillouin zone, even without the spin-orbit coupling. Furthermore, we demonstrate the variation in the optical properties near the Mott gap by the presence or absence of the antiferromagnetic order, tuned by a small staggered magnetic field.
The most general four-dimensional non-linear sigma-model, having the second-order derivatives only and interacting with a background metric and an antisymmetric tensor field, is constructed. Despite its apparent non-renormalizability, just imposing the one-loop UV-finiteness conditions determines the unique model, which may be finite to all orders of the quantum perturbation theory. This model is known as the four-dimensional Donaldson-Nair-Schiff theory, which is a four-dimensional analogue of the standard two-dimensional Wess-Zumino-Novikov-Witten model, and whose unique finiteness properties and an infinite-dimensional current algebra have long been suspected.
The threshold transverse response functions R_T(q,omega) for 3He and 3H are calculated using the AV18 nucleon-nucleon potential, the UrbanaIX three-body force, and the Coulomb potential. Final states are completely taken into account via the Lorentz integral transform technique. Consistent two-body pi- and rho-meson exchange currents as deduced using the Arenh\"ovel-Schwamb technique are included. The convergence of the method is shown and a comparison of the corresponding MEC contribution is made to that of a consistent MEC for the meson theoretical r-space BonnA potential. The response R_T is calculated in the threshold region at q=174, 324, and 487 MeV/c and compared with available data. The strong MEC contributions in the threshold region are nicely confirmed by the data at q=324 and 487 MeV/c although some differences between theoretical and experimental results remain. A comparison is also made with other calculations, where the same theoretical input is used. The agreement is generally rather good, but leaves also some space for further improvement.
The half metallic properties of Ti\raisebox{-.2ex}{\scriptsize 2}CoSn full-Heusler compound is studied within the framework of the density functional theory with the Perdew Burke Ernzerhof generalized gradient approximation (GGA). Structural optimization was performed and the calculated equilibrium lattice constant is 6.340 A. The spin up band of compound has metallic character and spin down band is semiconducting with an indirect gap of 0.598 eV at equilibrium lattice constant. For the lattice parameter, ranging from 6.193 to 6.884 A the compound presents 100% spin polarization and a total magnetic moment of 3$\mu_{B}$.
Deep learning models have achieved great success in automating skin lesion diagnosis. However, the ethnic disparity in these models' predictions, where lesions on darker skin types are usually underrepresented and have lower diagnosis accuracy, receives little attention. In this paper, we propose FairDisCo, a disentanglement deep learning framework with contrastive learning that utilizes an additional network branch to remove sensitive attributes, i.e. skin-type information from representations for fairness and another contrastive branch to enhance feature extraction. We compare FairDisCo to three fairness methods, namely, resampling, reweighting, and attribute-aware, on two newly released skin lesion datasets with different skin types: Fitzpatrick17k and Diverse Dermatology Images (DDI). We adapt two fairness-based metrics DPM and EOM for our multiple classes and sensitive attributes task, highlighting the skin-type bias in skin lesion classification. Extensive experimental evaluation demonstrates the effectiveness of FairDisCo, with fairer and superior performance on skin lesion classification tasks.
We present the H-alpha flux measurements for 44 nearby dwarf galaxies, derived from the observations at the 6-m BTA telescope. H-alpha fluxes were used to determine the rate of integral star formation of galaxies, SFR. For the observed galaxies the value of log SFR lies in the range from 0 to -8 M_sun/yr. The specific star formation rate for all the sample galaxies does not exceed the limit of log SSFR=-9.2 yr^{-1}. A burst of star formation was detected in the center of a nearby dwarf galaxy UGC 2172.
In this study, using Moller and Tolman prescriptions we calculate energy and momentum densities for the general cylindrically symmetric spacetime metric. We find that results are finite and well defined in these complexes. We also give the results for some cylindrically symmetric spacetime models.
Materials which can undergo slow diffusive transformations as well as fast displacive transformations are studied using the phase-field method. The model captures the essential features of the time-temperature-transformation (TTT) diagrams, continuous cooling transformation (CCT) diagrams, and microstructure formation of these alloys. In some materials systems there can exist an intrinsic volume change associated with these transformations. We show that these coherency strains can stabilize mixed microstructures (such as retained austenite-martensite and pearlite-martensite mixtures) by an interplay between diffusive and displacive mechanisms, which can alter TTT and CCT diagrams. Depending on the conditions there can be competitive or cooperative nucleation of the two kinds of phases. The model also shows that small differences in volume changes can have noticeable effects on the early stages of martensite formation and on the resulting microstructures.   -- Long version of cond-mat/0605577   -- Keywords: Ginzburg-Landau, martensite, pearlite, spinodal decomposition, shape memory, microstructures, TTT diagram, CCT diagram, elastic compatibility
We use simple analytic reasoning to identify physical processes that drive the evolution of the cosmic star formation density in cold dark matter universes. Based on our analysis, we formulate a model to characterise the redshift dependence of the star formation history and compare it to results obtained from a set of hydrodynamic simulations which include star formation and feedback. At early times, densities are sufficiently high and cooling times sufficiently short that abundant quantities of star-forming gas are present in all dark matter halos that can cool by atomic processes. Consequently, the star formation density generically rises exponentially as z decreases, independent of the details of the physical model for star formation, but dependent on the normalisation and shape of the cosmological power spectrum. This part of the evolution is dominated by gravitationally driven growth of the halo mass function. At low redshifts, densities decline as the universe expands to the point that cooling is inhibited, limiting the amount of star-forming gas available. We find that in this regime the star formation rate scales approximately in proportion to the cooling rate within halos. We derive analytic expressions for the full star formation history and show that they match our simulation results to better than ~10%. Using various approximations, we reduce the expressions to a simple analytic fitting function that can be used to compute global cosmological quantities that are directly related to the star formation history. As examples, we consider the integrated stellar density, the supernova and gamma-ray burst rates observable on Earth, the metal enrichment history of the Universe, and the density of compact objects. (abridged)
The effective interaction GXPF1 for shell-model calculations in the full $pf$ shell is tested in detail from various viewpoints such as binding energies, electro-magnetic moments and transitions, and excitation spectra. The semi-magic structure is successfully described for $N$ or Z=28 nuclei, $^{53}$Mn, $^{54}$Fe, $^{55}$Co and $^{56,57,58,59}$Ni, suggesting the existence of significant core-excitations in low-lying non-yrast states as well as in high-spin yrast states. The results of $N=Z$ odd-odd nuclei, $^{54}$Co and $^{58}$Cu, also confirm the reliability of GXPF1 interaction in the isospin dependent properties. Studies of shape coexistence suggest an advantage of Monte Carlo Shell Model over conventional calculations in cases where full-space calculations still remain too large to be practical.
We describe a recent full-polarization radio continuum survey, performed using the Westerbork Synthesis Radio Telescope (WSRT), of several nearby galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The WSRT-SINGS survey has been utilized to study the polarized emission and Faraday rotation measures (RMs) in the targets, and reveals an important new observational trend. The azimuthal distribution of polarized flux seems to be intimately related to the kinematic orientation of galaxies, such that in face-on galaxies the lowest level of polarized flux is detected along the kinematic major axis. In highly inclined galaxies, the polarized flux is minimized on both ends of the major axis, and peaks near the minor axis. Using models of various three-dimensional magnetic field geometries, and including the effects of turbulent depolarization in the midplane, we are able to reproduce the qualitative distribution of polarized flux in the target galaxies, its variation with inclination, and the distribution of RMs, thereby constraining the global magnetic field structure in galaxies. Future radio telescope facilities, now being planned and constructed, will have properties making them extremely well-suited to perform vastly larger surveys of this type, and are thereby poised to significantly increase our understanding of the global structure of galactic magnetic fields. We discuss progress that can be made using surveys which will be realized with these new facilities, focusing in particular on the Aperture Tile in Focus (APERTIF) and Australian Square Kilometre Array Pathfinder (ASKAP) telescopes, both based on Focal Plane Array (FPA) designs, which are expected to be particularly useful for wide-field polarization applications.
Electronic structures for InxGa1-xAs nanowires with [100], [110], and [111] orientations and critical dimensions of approximately 2 nm are treated within the framework of density functional theory. Explicit band structures are calculated and properties relevant to nanoelectronic design are extracted including band gaps, effective masses, and density of states. The properties of these III-V nanowires are compared to silicon nanowires of comparable dimensions as a reference system. In nonpolar semiconductors, quantum confinement and surface chemistry are known to play a key role in the determination of nanowire electronic structure. InxGa1-xAs nanowires have in addition effects due to alloy stoichiometry on the cation sublattice and due to the polar nature of the cleaved nanowire surfaces. The impact of these additional factors on the electronic structure for these polar semiconductor nanowires is shown to be significant and necessary for accurate treatment of electronic structure properties.
We explore the effects of the resummation of large logarithmic perturbative corrections to double-longitudinal spin asymmetries for inclusive and semi-inclusive deep inelastic scattering in fixed-target experiments. We find that the asymmetries are overall rather robust with respect to the inclusion of the resummed higher-order terms. Significant effects are observed at fairly high values of x, where resummation tends to decrease the spin asymmetries. This effect turns out to be more pronounced for semi-inclusive scattering. We also investigate the potential impact of resummation on the extraction of polarized valence quark distributions in dedicated high-x experiments.
A generalization of the classical statistics ``maj'' and ``inv'' (the major index and number of inversions) on words is introduced, parameterized by arbitrary graphs on the underlying alphabet. The question of characterizing those graphs that lead to equi-distributed "inv" and "maj" is posed and answered.
A healthy lifestyle is the key to better health and happiness and has a considerable effect on quality of life and disease prevention. Current lifelogging/egocentric datasets are not suitable for lifestyle analysis; consequently, there is no research on lifestyle analysis in the field of computer vision. In this work, we investigate the problem of lifestyle analysis and build a visual lifelogging dataset for lifestyle analysis (VLDLA). The VLDLA contains images captured by a wearable camera every 3 seconds from 8:00 am to 6:00 pm for seven days. In contrast to current lifelogging/egocentric datasets, our dataset is suitable for lifestyle analysis as images are taken with short intervals to capture activities of short duration; moreover, images are taken continuously from morning to evening to record all the activities performed by a user. Based on our dataset, we classify the user activities in each frame and use three latent fluents of the user, which change over time and are associated with activities, to measure the healthy degree of the user's lifestyle. The scores for the three latent fluents are computed based on recognized activities, and the healthy degree of the lifestyle for the day is determined based on the scores for the latent fluents. Experimental results show that our method can be used to analyze the healthiness of users' lifestyles.
We study a nonlocal regularisation of a scalar conservation law given by a fractional derivative of order between one and two. The nonlocal operator is of Riesz-Feller type with skewness two minus its order. This equation describes the internal structure of hydraulic jumps in a shallow water model. The main purpose of the paper is the study of the vanishing viscosity limit of the Cauchy problem for this equation. First, we study the properties of the solution of the regularised problem and then we show that solutions converge to the entropy solution of the scalar conservation law in this limit in $C([0,T];L^1_{loc}(\mathbb{R}))$ for initial data in $L^\infty(\mathbb{R})$, and in $C([0,T];L^1(\mathbb{R}))$ for initial data in $ L^\infty(\mathbb{R})\cap BV(\mathbb{R})$. In order to prove these results we use weak entropy inequalities and the double scale technique of Kruzhkov. Such techniques also allow to show the $L^1(\mathbb{R})$ contraction of the regularised problem. For completeness, we study the behaviour in the tail of travelling wave solutions for genuinely nonlinear fluxes. These waves converge to shock waves in the vanishing viscosity limit, but decay algebraically as $x-ct \to \infty$, rather than exponentially, the latter being a behaviour that they exhibit as $x-ct \to- \infty$, however. Finally, we generalise the results concerning the vanishing viscosity limit to Riesz-Feller operators.
We present, for the first time, an optical spectroscopic data cube of the giant star-forming region 30 Doradus, obtained with the GIRAFFE on the VLT at Paranal Observatory. The main emission lines present in this data cube correspond to H{\alpha}, [NII] 6548 {\AA} and [NII] 6584 {\AA}. By using this data set, we found that H{\alpha} presents from simple to multiple profiles, which suggests that different physical mechanisms act in different ways on the excited gas in 30 Doradus. We found, at least, three unclassified large expanding structures. These structures correlate with peaks in the X-ray distribution. Given the excellent signal-to-noise ratio and the large spatial coverage of this data cube, we have studied in detail the kinematics of 30 Doradus, showing the importance of the small scale phenomena on the integrated properties of 30 Doradus.
The size of the horizon at the matter-radiation equality is a key scale of the Big Bang cosmology that is directly related to the energy-matter content of the Universe. In this letter, we argue that this scale can be accurately measured from the observed clustering of galaxies in new large scale surveys. We demonstrate that the zero-crossing, r_c, of the 2-point galaxy correlation function is closely related to the horizon size at matter-radiation equality for a large variety of flat LCDM models. Using large-volume cosmological simulations, we also show that the pristine zero-crossing is unaltered by non-linear evolution of density fluctuations, redshift distortions and galaxy biases. This makes r_c a very powerful standard ruler that can be accurately measured, at a percent level, in upcoming experiments that will collect redshifts of millions of galaxies and quasars.
We present new tests to identify stationary position-dependent additive shear biases in weak gravitational lensing data sets. These tests are important diagnostics for currently ongoing and planned cosmic shear surveys, as such biases induce coherent shear patterns that can mimic and potentially bias the cosmic shear signal. The central idea of these tests is to determine the average ellipticity of all galaxies with shape measurements in a grid in the pixel plane. The distribution of the absolute values of these averaged ellipticities can be compared to randomized catalogues; a difference points to systematics in the data. In addition, we introduce a method to quantify the spatial correlation of the additive bias, which suppresses the contribution from cosmic shear and therefore eases the identification of a position-dependent additive shear bias in the data. We apply these tests to the publicly available shear catalogues from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) and the Kilo Degree Survey (KiDS) and find evidence for a small but non-negligible residual additive bias at small scales. As this residual bias is smaller than the error on the shear correlation signal at those scales, it is highly unlikely that it causes a significant bias in the published cosmic shear results of CFHTLenS. In CFHTLenS, the amplitude of this systematic signal is consistent with zero in fields where the number of stars used to model the PSF is higher than average, suggesting that the position-dependent additive shear bias originates from undersampled PSF variations across the image.
The long-tail distribution of the visual world poses great challenges for deep learning based classification models on how to handle the class imbalance problem. Existing solutions usually involve class-balancing strategies, e.g., by loss re-weighting, data re-sampling, or transfer learning from head- to tail-classes, but most of them adhere to the scheme of jointly learning representations and classifiers. In this work, we decouple the learning procedure into representation learning and classification, and systematically explore how different balancing strategies affect them for long-tailed recognition. The findings are surprising: (1) data imbalance might not be an issue in learning high-quality representations; (2) with representations learned with the simplest instance-balanced (natural) sampling, it is also possible to achieve strong long-tailed recognition ability by adjusting only the classifier. We conduct extensive experiments and set new state-of-the-art performance on common long-tailed benchmarks like ImageNet-LT, Places-LT and iNaturalist, showing that it is possible to outperform carefully designed losses, sampling strategies, even complex modules with memory, by using a straightforward approach that decouples representation and classification. Our code is available at https://github.com/facebookresearch/classifier-balancing.
The processes of open and hidden charm production in $NN$ collisions and of open charm production in $\gamma N$ collisions are studied. The near-threshold cross section is predicted and polarization phenomena are calculated in frame of an effective Lagrangian approach.
We study the large time behavior of solutions of first-order convex Hamilton-Jacobi Equations of Eikonal type set in the whole space. We assume that the solutions may have arbitrary growth. A complete study of the structure of solutions of the ergodic problem is provided : contrarily to the periodic setting, the ergodic constant is not anymore unique, leading to different large time behavior for the solutions. We establish the ergodic behavior of the solutions of the Cauchy problem (i) when starting with a bounded from below initial condition and (ii) for some particular unbounded from below initial condition, two cases for which we have different ergodic constants which play a role. When the solution is not bounded from below, an example showing that the convergence may fail in general is provided.