ShantanuT01/DACTYL-Pretraining huggingface dataset:
We propose a novel approach to few-shot action recognition, finding temporally-corresponding frame tuples between the query and videos in the support set. Distinct from previous few-shot works, we construct class prototypes using the CrossTransformer attention mechanism to observe relevant sub-sequences of all support videos, rather than using class averages or single best matches. Video representations are formed from ordered tuples of varying numbers of frames, which allows sub-sequences of actions at different speeds and temporal offsets to be compared.   Our proposed Temporal-Relational CrossTransformers (TRX) achieve state-of-the-art results on few-shot splits of Kinetics, Something-Something V2 (SSv2), HMDB51 and UCF101. Importantly, our method outperforms prior work on SSv2 by a wide margin (12%) due to the its ability to model temporal relations. A detailed ablation showcases the importance of matching to multiple support set videos and learning higher-order relational CrossTransformers.
Speeded Up Robust Features (SURF) has emerged as one of the more popular feature descriptors and detectors in recent years. Performance and algorithmic details vary widely between implementations due to SURF's complexity and ambiguities found in its description. To resolve these ambiguities, a set of general techniques for feature stability is defined based on the smoothness rule. Additional improvements to SURF are proposed for speed and stability. To illustrate the importance of these implementation details, a performance study of popular SURF implementations is done. By utilizing all the suggested improvements, it is possible to create a SURF implementation that is several times faster and more stable.
We construct a little Higgs model using a simple global symmetry group SU(9) spontaneously broken to SU(8). The electroweak interactions are extended to SU(3)xU(1) and embedded in SU(9). At the electroweak scale, our model is a two Higgs-doublet model. At the TeV scale, there are additional states, which are responsible for the cancellation of one loop quadratic divergences. We compute the effects of heavy states on the precision electroweak observables and find that the lower bounds on the masses of heavy gauge bosons and fermions are between 1 and 2 TeV.
Instance segmentation and classification of nuclei is an important task in computational pathology. We show that StarDist, a deep learning nuclei segmentation method originally developed for fluorescence microscopy, can be extended and successfully applied to histopathology images. This is substantiated by conducting experiments on the Lizard dataset, and through entering the Colon Nuclei Identification and Counting (CoNIC) challenge 2022, where our approach achieved the first spot on the leaderboard for the segmentation and classification task for both the preliminary and final test phase.
We explore the discovery potential of the supersymmetric Higgs bosons through $bg$ channel at Tevatron and LHC. Compared with the process of $qq' \to WH$, this channel is more advantigeous to finding the supersymmetric Higgs bosons at Tevatron if $\tan\beta$ is larger than ten.
The unusually large "dwarf" galaxy Crater II, with its small velocity dispersion, $\simeq 3$ km/s, defies expectations that low mass galaxies should be small and dense. We combine the latest stellar and velocity dispersion profiles finding Crater II has a prominent dark core of radius $\simeq 0.71^{+0.09}_{-0.08}$ kpc, surrounded by a low density halo, with a transition visible between the core and the halo. We show that this profile matches the distinctive core-halo profile predicted by "Wave Dark Matter" as a Bose-Einstein condensate, $\psi$DM, where the ground state soliton core is surrounded by a tenuous halo of interfering waves, with a marked density transition predicted between the core and halo. Similar core-halo structure is seen in most dwarf spheroidal galaxies (dSph), but with smaller cores, $\simeq 0.25$ kpc and higher velocity dispersions, $\simeq 9$km/s, and we argue here that Crater II may have been a typical dSph that has lost most of its halo mass to tidal stripping, so its velocity dispersion is lower by a factor of 3 and the soliton is wider by a factor of 3, following the inverse scaling required by the Uncertainty Principle. This tidal solution for Crater II in the context of $\psi$DM, is supported by its small pericenter of $\simeq 20$ kpc established by Gaia, implying significant tidal stripping of Crater II by the Milky Way is expected.
Paolo Aluffi showed that the Chern--Schwartz--MacPherson class of the complement of a free arrangement agrees with the total Chern class of the sheaf of logarithmic derivations along the arrangement. We describe the defect of equality of the two classes for locally tame arrangements with isolated non-free singular loci.
Let K be a p-adic field and let F and G be two formal groups over O_K. We prove that if F and G have infinitely many torsion points in common, then F=G. This follows from a rigidity result: any bounded power series that sends infinitely many torsion points of F to torsion points of F is an endomorphism of F.
The improved quark mass density- dependent model which includes the coupling between the quarks and a non-linear scalar field is presented. Numerical analysis of solutions of the model is performed over a wide range of parameters. The wave functions of ground state and the lowest one-particle excited states with even and odd parity are given. The root-mean squared radius, the magnetic moment and the ratio between the axial-vector and the vector beta-decay coupling constants of the nucleon are calculated. We found that the present model is successful to describe the properties of nucleon.
LAMOST has released more than two million spectra, which provide the opportunity to search for double-peaked narrow emission line (NEL) galaxies and AGNs. The double-peaked narrow-line profiles can be well modeled by two velocity components, respectively blueshifted and redshifted with respect to the systemic recession velocity. This paper presents 20 double-peaked NEL galaxies and AGNs found from LAMOST DR1 using a search method based on multi-gaussian fit of the narrow emission lines. Among them, 10 have already been published by other authors, either listed as genuine double-peaked NEL objects or as asymmetric NEL objects, the remaining 10 being first discoveries. We discuss some possible origins for double-peaked narrow-line features, as interaction between jet and narrow line regions, interaction with companion galaxies and black hole binaries. Spatially resolved optical imaging and/or follow-up observations in other spectral bands are needed to further discuss the physical mechanisms at work.
Transition metal dichalcogenides like MoS$_2$, MoSe$_2$, WS$_2$, and WSe$_2$ have attracted enormous interest during recent years. They are van-der-Waals crystals with highly anisotropic properties, which allows exfoliation of individual layers. Their remarkable physical properties make them promising for applications in optoelectronic, spintronic, and valleytronic devices. Phonons are fundamental to many of the underlying physical processes, like carrier and spin relaxation or exciton dynamics. However, experimental data of the complete phonon dispersion relations in these materials is missing. Here we present the phonon dispersion of bulk MoS$_2$ in the high-symmetry directions of the Brillouin zone, determined by inelastic X-ray scattering. Our results underline the two-dimensional nature of MoS$_2$. Supported by first-principles calculations, we determine the phonon displacement patterns, symmetry properties, and scattering intensities. The results will be the basis for future experimental and theoretical work regarding electron-phonon interactions, intervalley scattering, as well as phonons in related 2D materials.
We present the first results on the spectra of Be/X-ray binary RX J0440.9+4431 obtained with the 2m Ritchey-Cretein-Coude telescope with Cassegrain Multi Mode Spectrograph (CMMS) (with R = 14000) at Terskol observatory. The H-alpha line profile indicates that the new episode of the V/R variability is occuring in the system. The profiles of the H-alpha, H-beta and HeI 7065.71, 6678.15, 5875.97 lines were analyzed and equivalent width were determined. We compared our H-alpha line profile parameters with the previous results from the literature and estimated characteristic time scale for disc changes as about 14 years.
Extrapolations of line-of-sight photospheric field measurements predict radial interplanetary magnetic field (IMF) strengths that are factors of ~2--4 too low. To address this "open flux problem,'' we reanalyze the magnetograph measurements from different observatories, with particular focus on those made in the saturation-prone Fe I 525.0 nm line by the Mount Wilson Observatory (MWO) and the Wilcox Solar Observatory (WSO). The total dipole strengths, which determine the total open flux, generally show large variations among observatories, even when their total photospheric fluxes are in agreement. However, the MWO and WSO dipole strengths, as well as their total fluxes, agree remarkably well with each other, suggesting that the two data sets require the same scaling factor. As shown earlier by Ulrich et al., the saturation correction $\delta^{-1}$ derived by comparing MWO measurements in the 525.0 nm line with those in the nonsaturating Fe I 523.3 nm line depends sensitively on where along the irregularly shaped 523.3 nm line wings the exit slits are placed. If the slits are positioned so that the 523.3 and 525.0 nm signals originate from the same height, $\delta^{-1}$ ~ 4.5 at disk center, falling to ~2 near the limb. When this correction is applied to either the MWO or WSO maps, the derived open fluxes are consistent with the observed IMF magnitude. Other investigators obtained scaling factors only one-half as large because they sampled the 523.3 nm line farther out in the wings, where the shift between the right- and left-circularly polarized components is substantially smaller.
We extend non-emtpyness and irreducibility of Hassett divisors to the moduli spaces of $M$-polarizable cubic fourfolds for higher rank lattices $M$, which in turn provides a systematic approach for describing the irreducible components of intersection of Hassett divisors. We show that Fermat cubic fourfold is contained in every Hassett divisor, which yields a new proof of Hassett's existence theorem of special cubic fourfolds. We obtain an algorithm to determine the irreducible components of the intersection of any two Hassett divisors and we give new examples of rational cubic fourfolds. Moreover, we derive a numerical criterion for the algebraic cohomology of a cubic fourfold having an associated K3 surface and answer a question of Laza by realizing infinitely many rank $11$ lattices as the algebraic cohomologies of cubic fourfolds having no associated K3 surfaces.
Killing vectors play a crucial role in characterizing the symmetries of a given spacetime. However, realistic astrophysical systems are in most cases only approximately symmetric. Even in the case of an astrophysical black hole, one might expect Killing symmetries to exist only in an approximate sense due to perturbations from external matter fields. In this work, we consider the generalized notion of Killing vectors provided by the almost Killing equation, and study the perturbations induced by a perturbation of a background spacetime satisfying exact Killing symmetry. To first order, we demonstrate that for nonradiative metric perturbations (that is, metric perturbations with nonvanishing trace) of symmetric vacuum spacetimes, the perturbed almost Killing equation avoids the problem of an unbounded Hamiltonian for hyperbolic parameter choices. For traceless metric perturbations, we obtain similar results for the second-order perturbation of the almost Killing equation, with some additional caveats. Thermodynamical implications are also explored.
For the Dirac particle in the rotational system, the rotation induced inertia effect is analogously treated as the modification of the "spin connection" on the Dirac equation in the flat spacetime, which is determined by the equivalent tetrad. From the point of view of parallelism description of spacetime, the obtained torsion axial-vector is just the rotational angular velocity, which is included in the "spin connection". Furthermore the axial-vector spin coupling induced spin precession is just the rotation-spin(1/2) interaction predicted by Mashhoon. Our derivation treatment is straightforward and simplified in the geometrical meaning and physical conception, however the obtained conclusions are consistent with that of the other previous work.
Using a large sample of 26623 quasars with redshifts in the range $1.5 \le z\le 5.1$ with \civ $\lambda$1549 \AA emission line in Fifth Data Release of the Sloan Digital Sky Survey (SDSS), we investigate the cosmological evolution of the Baldwin Effect, i.e. the relation between the equivalent width (EW) of the \civ emission line and continuum luminosity. We confirm the earlier result that there exists a strong correlation between the \civ EW and the continuum luminosity, and we find that, up to $z\approx 5$, the slope of the Baldwin Effect seems to have no effect of cosmological evolution. A sub-sample of 13960 quasars with broad \civ $\lambda$1549 \AA emission line from SDSS is used to explore the origin of the Baldwin Effect. We find that \civ EW have a strong correlation with the mass of supermassive black hole (SMBH), and a weak correlation with the Eddington ratio, $\lb/\ledd$. This suggests that the SMBH mass is probably the primary drive for the Baldwin Effect.
By using a totally antisymmetric spinor field we generalize Elko theory. We compare our proposed theory with traditional totally antisymmetric spinor field theory based on the Dirac equation. As an application of our formalism we comment about the possibility to link our generalized Elko theory with matroids, qubits and surreal numbers.
A recent study of the X-ray source XMMUJ134736.6+173403 has revealed a strong quasi-periodic modulation of the X-ray flux. The observation of two quasiperiodic oscillations (QPOs) that occur on a daily timescale and exhibit a 3:1 frequency ratio strongly supports the evidence for the presence of an active galactic nucleus black hole (AGN BH). Assuming the orbital origin of QPOs we calculate the upper and lower limit on AGN BH mass M arriving at $M\approx 10^7-10^9M_{\odot}$. Comparing that to mass estimates of other sources, MMUJ134736.6+173403 appears to be the most massive source with commensurable QPO frequencies, and its mass represents the current observational upper limit on AGN BH mass based on QPO observations. We note it will be crucial for the falsification of particular resonance models of QPOs whether only single QPO with frequency that completes the harmonic sequence 3:2:1 is found in this source, or whether there is a new different pair of QPOs with frequencies in the 3:2 ratio. The former case would agree with the prediction of the 3:2 epicyclic resonance model and black hole mass $M\approx(5a^2 + 8a + 8)\times 10^{7}M_{\odot}$, where a is a dimensionless BH spin.
Parametric scaling representations are obtained and studied for the asymptotic behavior of interfacial tensions in the \textit{full} neighborhood of a fluid (or Ising-type) critical endpoint, i.e., as a function \textit{both} of temperature \textit{and} of density/order parameter \textit{or} chemical potential/ordering field. Accurate \textit{nonclassical critical exponents} and reliable estimates for the \textit{universal amplitude ratios} are included naturally on the basis of the ``extended de Gennes-Fisher'' local-functional theory. Serious defects in previous scaling treatments are rectified and complete wetting behavior is represented; however, quantitatively small, but unphysical residual nonanalyticities on the wetting side of the critical isotherm are smoothed out ``manually.'' Comparisons with the limited available observations are presented elsewhere but the theory invites new, searching experiments and simulations, e.g., for the vapor-liquid interfacial tension on the two sides of the critical endpoint isotherm for which an amplitude ratio $-3.25 \pm 0.05$ is predicted.
$^{3}P_{2}$ pairing in neutron matter is investigated using the Bonn potential models. We find pairing energy gaps in pure neutron matter comparable to the results of previous investigators when the attractive tensor coupling is included. However, taking into account that in a neutron star we have matter at $\beta$ equilibrium, we find that the $^{3}P_{2}$-$^{3}F_{2}$ energy gap is reduced considerably.
The spectrum of meson and diquark excitations of dense cold quark matter is investigated in the framework of a Nambu--Jona-Lasinio type model for light quarks of two flavors. It was found out that a first order phase transition occurs when the chemical potential $\mu$ exceeds the critical value $\mu_c=350$ MeV. Above $\mu_c$, the diquark condensate $\vev{qq}$ forms, breaking the color symmetry of strong interaction. The masses of $\pi$- and $\sigma$-mesons are shown to grow with the chemical potential $\mu$ in the color-superconducting phase, but the mesons themselves become almost stable particles due to the Mott effect. Moreover, we have found in this phase an abnormal number of three, instead of five, Nambu--Goldstone bosons, together with a color doublet of light stable diquark modes and a color-singlet heavy diquark resonance with the mass $\sim$ 1100 MeV. In the color symmetric phase, \textit{i.e.} for $\mu <\mu_c$, the splitting between the masses of diquarks and antidiquarks is shown to arise if $\mu\ne 0$, contrary to the case of vanishing chemical potential, $\mu = 0$, where the mass spectrum of antidiquarks and diquarks is degenerate at the value $\sim$ 700 MeV.
Simple argument in favour of unitarity, to all orders, of space-like noncommutative theory is given.
The group of affine transformations with rational coefficients acts naturally on the real line, but also on the $p$-adic fields. The aim of this note is to show that, for random walks whose laws have a finite first moment, all these actions are necessary and sufficient to describe the Poisson boundary, which is in fact the product of all the fields that contract in mean.
We consider a linear chain made of spins of one half in contact with a dissipative environment for which periodic delta-kicks are applied to the qubits of the linear chain in two different configurations: kicks applied to a single qubit and simultaneous kicks applied to two qubits of the linear chain. In both cases the system reaches a non-equilibrium stationary condition in the long time limit. We study the transient to the quasi stationary states and their properties as function of the kick parameters in the single kicked qubit case and report the emergence of stationary entanglement between the kicked qubits when simultaneous kicks are applied. For doing our study we have derived an approximation to a master equation which serves us to analyze the effects of a finite temperature and the zero temperature environment.
The sensitivity of superconducting qubits allows for spectroscopy and coherence measurements on individual two-level systems present in the disordered tunnel barrier of an $\mathrm{Al/AlO_x/Al}$ Josephson junction. We report experimental evidence for the decoherence of two-level systems by Bogoliubov quasiparticles leaking into the insulating $\mathrm{AlO_x}$ barrier. We control the density of quasiparticles in the junction electrodes either by the sample temperature or by injecting them using an on-chip dc-SQUID driven to its resistive state. The decoherence rates were measured by observing the two-level system's quantum state evolving under application of resonant microwave pulses and were found to increase linearly with quasiparticle density, in agreement with theory. This interaction with electronic states provides a noise and decoherence mechanism that is relevant for various microfabricated devices such as qubits, single-electron transistors, and field-effect transistors. The presented experiments also offer a possibility to determine the location of the probed two-level systems across the tunnel barrier, providing clues about the fabrication step in which they emerge.
This paper has been withdrawn by the author due to a crucial error
We study the nucleon-nucleon interaction in a chiral constituent quark model by using the resonating group method, convenient for treating the interaction between composite particles. The calculated phase shifts for the 3S1 and 1S0 channels show the presence of a strong repulsive core due to the combined effect of the quark interchange and the spin-flavour structure of the effective quark-quark interaction. Such a symmetry structure stems from the pseudoscalar meson exchange between the quarks and is a consequence of the spontaneous breaking of the chiral symmetry. We perform single and coupled channel calculations and show the role of coupling of the $\Delta\Delta$ and hidden color CC channels on the behaviour of the phase shifts.
The Smith high velocity cloud (V(LSR) = 98 kms) has been observed at two locations in the emission lines [OIII]5007, [NII]6548 and H-alpha. Both the [NII] and H-alpha profiles show bright cores due to the Reynolds layer, and red wings with emission extending to V(LSR) = 130 kms. This is the first simultaneous detection of two emission lines towards a high velocity cloud, allowing us to form the ratio of these line profiles as a function of LSR velocity. At both cloud positions, we see a clear distinction between emission at the cloud velocity, and the Reynolds layer emission (V(LSR) = 0). The [NII]/H-alpha ratio (=0.25) for the Reynolds layer is typical of the warm ionised medium. At the cloud velocity, this ratio is enhanced by a factor of 3-4 compared to emission at rest with respect to the LSR. A moderately deep upper limit at [OIII] (0.12R at 3-sigma) was derived from our data. If the emission arises from dilute photoionisation from hot young stars, the highly enhanced [NII]/H-alpha ratio, the [OIII] non-detection and weak H-alpha emission (0.24-0.30R) suggest that the Smith Cloud is 26+/-4 kpc from the Sun, at a Galactocentric radius of 20+/-4 kpc. This value assumes that the emission arises from an optically thick slab, with a covering fraction of unity as seen by the ionizing photons, whose orientation is either (a) parallel to the Galactic disk, or (b) such as to maximize the received flux from the disk. The estimated mass and size of the cloud are 4x10^6 Msun and 6 kpc. We discuss a possible association with the much larger Sgr dwarf, at a galactocentric radius of 16+/-2 kpc, which lies within 35 degrees (~12 kpc) of the Smith Cloud.
We study the emergence of glassy states after a sudden cooling in lattice models with short range interactions and without any a priori quenched disorder. The glassy state emerges whenever the equilibrium model possesses a sufficient number of coexisting crystalline phases at low temperatures, provided the thermodynamic limit be taken before the infinite time limit. This result is obtained through simulations of the time relaxation of the standard Potts model and some exclusion models equipped with a local stochastic dynamics on a square lattice.
The theorem of Greenberg-Kazhdan-Drinfeld describes the formal neighborhood of a closed arc. After giving a complete proof with examples, two possible versions for the relative case of the theorem are discussed. Each one is shown to hold for some classes of morphisms, including smooth morphisms and closed embeddings in smooth variety.