ShantanuT01/DACTYL-Pretraining huggingface dataset:
It is explained that the spin scissors and spin-flip are different names of the same physical phenomenon. The relation between WFM and RPA methods is clarified.
Better machine understanding of pedestrian behaviors enables faster progress in modeling interactions between agents such as autonomous vehicles and humans. Pedestrian trajectories are not only influenced by the pedestrian itself but also by interaction with surrounding objects. Previous methods modeled these interactions by using a variety of aggregation methods that integrate different learned pedestrians states. We propose the Social Spatio-Temporal Graph Convolutional Neural Network (Social-STGCNN), which substitutes the need of aggregation methods by modeling the interactions as a graph. Our results show an improvement over the state of art by 20% on the Final Displacement Error (FDE) and an improvement on the Average Displacement Error (ADE) with 8.5 times less parameters and up to 48 times faster inference speed than previously reported methods. In addition, our model is data efficient, and exceeds previous state of the art on the ADE metric with only 20% of the training data. We propose a kernel function to embed the social interactions between pedestrians within the adjacency matrix. Through qualitative analysis, we show that our model inherited social behaviors that can be expected between pedestrians trajectories. Code is available at https://github.com/abduallahmohamed/Social-STGCNN.
We report an experimental investigation of quantum correlations in a two-qutrit spin system in a single nitrogen-vacancy center in diamond at room temperatures. Quantum entanglement between two qutrits was observed at room temperature and the existence of non-classical correlations beyond entanglement in the qutrit case has been revealed. Our work demonstrates the potential of the NV centers as the multi-qutrit system to execute quantum information tasks and provides a powerful experimental platform for studying fundamental physics of high-dimensional quantum systems in future.
The processes leading to the exceptionally hard radio spectra of pulsar-wind nebulae (PWNe) are not yet understood. Radio photon spectral indices among $29$ PWNe from the literature show an approximately normal, $\alpha=0.2\pm0.2$ distribution. We present $\sim 3\sigma$ evidence for a distinct sub-population of PWNe, with a hard spectrum $\alpha=0.01\pm0.06$ near the termination shock and significantly softer elsewhere, possibly due to a recent evacuation of the shock surroundings. Such spectra, especially in the hard sub-population, suggest a Fermi process, such as diffusive shock acceleration, at its extreme, $\alpha=0$ limit. We show that this limit is approached for sufficiently anisotropic small-angle scattering, enhanced on either side of the shock for particles approaching the shock front. In the upstream, the spectral hardening is mostly associated with an enhanced energy gain, possibly driven by the same beamed particles crossing the shock. Downstream, the main effect is a diminished escape probability, but this lowers the acceleration efficiency to $\lesssim25\%$ for $\alpha=0.3$ and $\lesssim1\%$ for $\alpha=0.03$.
We investigate the degree of entanglement between an atom and a driven cavity mode, in the presence of dissipation. Previous work has shown that in the limit of weak driving fields, the steady state entanglement is proportional to the square of the driving intensity. This quadratic dependence is due to the generation of entanglement by the creation of pairs of photons/excitations. In this work we investigate the entanglement between an atom and a cavity in the presence of multiple photons. Nonlinearity of the atomic response is needed to generate entanglement, but as that nonlinearity saturates the entanglement vanishes. We posit that this is due to spontaneous emission, which puts the atom in the ground state and the atom-field state into a direct product state. An intermediate value of the driving field, near the field that saturates the atomic response, optimizes the atom-field entanglement. In a parameter regime for which multiphoton resonances occur, we find that entanglement recurs at those resonances. \cite{Shamailov-10} In this regime, we find that the entanglement decreases with increaing photon number. We also investigate, in the bimodal regime of Alsing et. al.\cite{Alsing-91-DressedState} \cite{Alsing-92-DSS}\cite{Carm-15-X}, the entanglement as a function of atom and/or cavity detuning. Here we find that there is evidence of a phase transition in the entanglement, which occurs at $2\epsilon/g \geq 1$.
We study the interface dynamics of a discrete model to quantitatively describe electrochemical deposition experiments. Extensive numerical simulations indicate that the interface dynamics is unstable at early times, but asymptotically displays the scaling of the Kardar-Parisi-Zhang universality class. During the time interval in which the surface is unstable, its power spectrum is anomalous; hence the behaviors at length scales smaller than or comparable with the system size are described by different roughness exponents. These results are expected to apply to a wide range of electrochemical deposition experiments.
The invariance property of the mean path length is an astonishing law of Nature governing the motion of particles inside a disordered material. Whatever the strength of the disorder, the property states that the mean path length is exclusively determined by the ratio between the volume and the surface. Till now, the property has been reported as universal and valid in any kind of disordered medium and also beyond diffusion conditions. Nevertheless, we found out that the property fails in anomalous transport and in other kinds of random walk. By means of Monte Carlo simulations of light transport, we show that, in these cases, the invariance property loses its validity and the mean path length becomes dependent on the diffusive characteristics of the medium. The critical issue of such a violation lies in the breaking of isotropy and homogeneity of the radiance in the whole volume. These results are valid for all natural or artificial phenomena where random walkers, whatever their nature, are able to experiment anomalous transport.
We investigate a Mach-Zehnder interferometer fed by two time-dependently driven single-particle sources, one of them placed in front of the interferometer, the other in the center of one of the arms. As long as the two sources are operated independently, the signal at the output of the interferometer shows an interference pattern, which we analyze in the spectral current, in the charge and energy currents, as well as in the charge current noise. The synchronization of the two sources in this specifically designed setup allows for collisions and absorptions of particles at different points of the interferometer, which have a strong impact on the detected signals. It introduces further relevant time-scales and can even lead to a full suppression of the interference in some of the discussed quantities. The complementary interpretations of this phenomenon in terms of spectral properties and tunable two-particle effects (absorptions and quantum exchange effects) are put forward in this article.
Relativistic jets are collimated outflows with speeds close to light speed, which are associated with gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and so on. This article mainly overviews recent developments of polarimetric studies of GRBs and their afterglows in the gamma-ray and optical wavebands as well as the first detections of their radio polarization. Polarimetric observations and theoretical modelings can address the emission mechanism, magnetic field structure, and energetics of GRB jets and related collisionless plasma physics. Some of the discussed key physics are common with AGN jets. Furthermore, we mention that polarimetry of AGN jets and protoplanetary disks may be a novel approach to search for ultra-light axion dark matter.
In this paper, we derive some interesting symmetric properties for the geenralized Euler numbers and polynomials.
In the scattering picture, thermal radiation effects may be associated with the `above barrier' reflection coefficient, which comes into play because of complex turning points. This note contains several general remarks on the application of the above statement to Schwarzschild black hole radiance
The mechanism of f-electron delocalization is investigated within the multi-orbital Anderson lattice model by means of diagrammatic perturbation theory from the atomic limit. The derived equations couple the intra-atomic transition energies, their spectral weights and population numbers of the many-electron states. Its self-consistent solution for praseodymium metal shows that the delocalization can be caused by external pressure via a resonant mixing of f- and conduction electrons in the vicinity of the the Fermi surface. It is also found that: 1. An increase of mixing leads to a decrease of the physical values of the Hubbard interactions, $U^*$, the reduction, however, is small. 2. The initial Hubbard U is split by renormalization into a set of different physical values of $U^*_{i,j}$. 3. The gain in cohesive energy together with the f-sum rule cause a transfer of spectral weight, which is decisive for the delocalization of \f-electrons. 4. The correlated Fermionic quasi particles have their bandwidth slightly reduced compared to the ones obtained by means of the Kohn-Sham equation.
We construct thin shell Lorentzian wormholes in higher dimensional Einstein-Maxwell theory applying the ' Cut and Paste ' technique proposed by Visser. The linearized stability is analyzed under radial perturbations around some assumed higher dimensional spherically symmetric static solution of the Einstein field equations in presence of Electromagnetic field. We determine the total amount of exotic matter, which is concentrated at the wormhole throat.
Let $L$ be a second order uniformly elliptic differential operator in a domain $D$ of $\mathbb{R}^{d}$, $\psi:\mathbb{R}_+\to \mathbb{R}_+$ be a nondecreasing continuous function and let $\xi,g:D\to\mathbb{R}_+$ be locally bounded Borel measurable functions. Under appropriate conditions, we determine a function $\varphi$ with values in $]0,1]$ such that for every nonnegative solution to inequality $-Lu+\xi\psi(u) \geq g$ in $D$ and for every $x\in D$,   $$   u(x)\geq p(x)\,\varphi\left(\frac{G_D(\xi\psi(p))(x)}{p(x)}\right)   $$ where $p=G_Dg$ is the Green function of $g$. The function $\varphi$ is completely determined by $\psi$ and does not depend on $L,D,\xi$ or $g$.
The Milky Way's nuclear stellar disc (NSD) and nuclear star cluster (NSC) are the main features of the Galactic centre. Nevertheless, their observation is hampered by the extreme source crowding and high extinction. Hence, their relation and formation scenario are not fully clear yet. We aim at detecting the stellar populations from the NSC and the NSD along the line-of-sight towards the NSC, and assess whether they have different stellar populations and star formation histories. We analysed the colour-magnitude diagram, $K_s$ vs. $H-K_s$, of a region of $8.2'\times2.8'$ centred on the NSC, and detected two different stellar groups with different extinctions. We studied their red clumps to find the features associated to each of the stellar populations. We obtained that the two groups of stars correspond to the NSD and the NSC, and found that they have significantly different stellar populations and star formation histories. We detected a double red clump for the NSD population, in agreement with previous work, whereas the NSC presents a more complex structure well fitted by three Gaussian features. We created extinction maps to analyse the extinction variation between the detected stellar groups. We found that the high-extinction layer varies on smaller scales (arc-seconds), and that there is a difference of $A_{K_s}\sim0.6$\,mag between both extinction layers. Finally, we obtained that the distance towards each of the stellar populations is compatible with the Galactic centre distance, and found some evidence of a slightly closer distance for the NSD stars ($\sim360\pm200$\,pc).
Kato and Usui developed a theory of partial compactifications for quotients of period domains D by arithmetic groups {\Gamma}, in an attempt to generalize the toroidal compactifications of Ash-Mumford-Rapoport-Tai to non-classical cases. Their partial compactifications, which aim to fully compactify the images of period maps, rely on a choice of fan which is strongly compatible with {\Gamma}. In particular, they conjectured the existence of a complete fan, which would serve to simultaneously compactify all period maps of a given type.   In this paper, we briefly review the theory, and construct a fan which compactifies theimage of a period map arising from a particular two-parameter family of Calabi-Yau threefolds studied by Hosono and Takagi, with Hodge numbers (1,2,2,1). On the other hand, we disprove the existence of complete fans in some general cases, including the (1,2,2,1) case.
We investigate the evolution and number distribution of radio halos in galaxy clusters. Without re-acceleration or regeneration, the relativistic electrons responsible for the diffuse radio emission will lose their energy via inverse-Compton and synchrotron losses in a rather short time, and radio halos will have lifetimes $\sim$ 0.1 Gyr. Radio halos could last for $\sim$ Gyr if a significant level of re-acceleration is involved. The lifetimes of radio halos would be comparable with the cosmological time if the radio-emitting electrons are mainly the secondary electrons generated by pion decay following proton-proton collisions between cosmic-ray protons and the thermal intra-cluster medium within the galaxy clusters. Adopting both observational and theoretical constraints for the formation of radio halos, we calculate the formation rates and the comoving number density of radio halos in the hierarchical clustering scheme. Comparing with observations, we find that the lifetimes of radio halos are $\sim$ Gyr. Our results indicate that a significant level of re-acceleration is necessary for the observed radio halos and the secondary electrons may not be a dominant origin for radio halos.
A two Higgs doublet model is employed to study the production of a CP-odd Higgs boson ($A$) associated with a large transverse momentum jet ($j$) at hadron supercolliders. The cross section of $pp \to jA+X$ is evaluated with four subprocesses: $gg \to gA$, $gq \to qA$, $g\bar{q} \to \bar{q}A$ and $q\bar{q} \to gA$. We find that $pp \to jA+X$ is a significant source of CP-odd Higgs bosons at future hadron supercolliders.
The importance of core contributions to the anapole moment in nuclei is examined. A model of the core-polarization correction is presented. The model is based on the coupling of the valence particles to the spin-dipole $J=1^{-}$ giant resonances of the core. A shell-model calculation of this correction is presented. The single-particle moments are calculated with Woods-Saxon and Skyrme Hartree Fock radial wave functions, and the general issues associated with nuclear configuration mixing are discussed.
We analyze the capability of charm production in deep-inelastic ep scattering at HERA to constrain the gluon distribution g(y,\mu^2) of the proton. The dependence of the theoretical predictions for the charm structure function F_2^c on the mass factorization scale \mu and the charm mass is investigated. F_2^c seems to be well suited for a rather clean and local gluon measurement at small momentum fractions y.
We study the conditional preparation of single photons based on parametric downconversion, where the detection of one photon from a given pair heralds the existence of a single photon in the conjugate mode. We derive conditions on the modal characteristics of the photon pairs, which ensure that the conditionally prepared single photons are quantum-mechanically pure. We propose specific experimental techniques that yield photon pairs ideally suited for single-photon conditional preparation.
Line ratios in "fir" triplets of helium-like ions have proven to be a powerful diagnostic of conditions in X-ray emitting gas surrounding massive stars. Recent observations indicate that these ratios can be variable with time.   The possible causes of variation in line ratios are limited: changes in the radiation field or changes in density, and changes in mass-loss or geometry. In this paper, we investigate the ability of changes in the radiation field to induce variability in the ratio R=f/i.   To isolate the radiative effect, we use a heuristic model of temperature and radius changes in variable stars in the B and O range with low-density, steady-state winds. We model the changes in emissivity of X-ray emitting gas close to the star due to differences in level-pumping from available UV photons at the location of the gas.   We find that under these conditions, variability in R is dominated by the stellar temperature. Although the relative amplitude of variability is roughly comparable for most lines at most temperatures, detectable variations are limited to a few lines for each spectral type. We predict that variable values in R due to stellar variability must follow predictable trends found in our simulations.   Our model uses radial pulsations as a mode of stellar variability that maximizes the amplitude of variation in R. This model is robust enough to show which ions will provide the best opportunity for observing variability in the f/i ratio at different stellar temperatures, and the correlation of that variability with other observable parameters. In real systems, the effects would be more complex than in our model, with differences in phase and suppressed amplitude in the presence of non-radial pulsations. This suggests that changes in R across many lines concurrently are not likely to be produced by a variable radiation field.
We study the gravitational fragmentation of circumstellar discs accreting extremely metal-poor ($Z \leq 10^{-3}$ Zsun) gas, performing a suite of three-dimensional hydrodynamic simulations using the adaptive mesh refinement code Enzo. We systematically follow the long-term evolution for 2000 years after the first protostar's birth, for the cases of $Z = 0$, $10^{-5}$, $10^{-4}$, and $10^{-3}$ Zsun. We show that evolution of number of self-gravitating clumps qualitatively changes with $Z$. Vigorous fragmentation induced by dust cooling occurs in the metal-poor cases, temporarily providing about 10 self-gravitating clumps at $Z = 10^{-5}$ and $10^{-4}$ Zsun. However, we also show that the fragmentation is a very sporadic process; after an early episode of the fragmentation, the number of clumps continuously decreases as they merge away in these cases. The vigorous fragmentation tends to occur later with the higher $Z$, reflecting that the dust-induced fragmentation is most efficient at the lower density. At $Z = 10^{-3}$ Zsun, as a result, the clump number stays smallest until the disc fragmentation starts in a late stage. We also show that the clump mass distribution also depends on the metallicity. A single or binary clump substantially more massive than the others appear only at $Z = 10^{-3}$ Zsun, whereas they are more evenly distributed in mass at the lower metallicities. We suggest that the disc fragmentation should provide the stellar multiple systems, but their properties drastically change with a tiny amount of metals.
A relativistic distorted-wave impulse-approximation model is applied to quasi-elastic neutrino-nucleus scattering. The bound state is obtained in the framework of the relativistic mean field theory and the final state interaction is taken into account in the scattering state. Results for the charged- and neutral-current neutrino (antineutrino) reactions on $^{12}$C target nucleus are presented and the sensitivity of various quantities to the strange quark content of the nucleon weak current is discussed.
The solutions of the Wigner-transformed time-dependent Hartree--Fock--Bogoliubov equations are studied in the constant-$\Delta$ approximation. This approximation is known to violate particle-number conservation. As a consequence, the density fluctuation and the longitudinal response function given by this approximation contain spurious contributions. A simple prescription for restoring both local and global particle-number conservation is proposed. Explicit expressions for the eigenfrequencies of the correlated systems and for the density response function are derived and it is shown that the semiclassical analogous of the quantum single--particle spectrum has an excitation gap of $2\Delta$, in agreement with the quantum result. The collective response is studied for a simplified form of the residual interaction.
The interlayer spin correlations in the magnetic/non-magnetic semiconductor superlattices are reviewed. The experimental evidences of interlayer exchange coupling in different all-semiconductor structures, based on neutronographic and magnetic studies, are presented. A tight-binding model is used to explain interaction transfer across the non-magnetic block without the assistance of carriers in ferromagnetic EuS/PbS and antiferromagnetic EuTe/PbTe systems.
Convolutional Networks (ConvNets) have recently improved image recognition performance thanks to end-to-end learning of deep feed-forward models from raw pixels. Deep learning is a marked departure from the previous state of the art, the Fisher Vector (FV), which relied on gradient-based encoding of local hand-crafted features. In this paper, we discuss a novel connection between these two approaches. First, we show that one can derive gradient representations from ConvNets in a similar fashion to the FV. Second, we show that this gradient representation actually corresponds to a structured matrix that allows for efficient similarity computation. We experimentally study the benefits of transferring this representation over the outputs of ConvNet layers, and find consistent improvements on the Pascal VOC 2007 and 2012 datasets.
Let $\sE$ be an ample rank $r$ bundle on a smooth toric projective surface, $S$, whose topological Euler characteristic is $e(S)$. In this article, we prove a number of surprisingly strong lower bounds for $c_1(\sE)^2$ and $c_2(\sE)$. We also enumerate the exceptions to either the inequality $c_1(\sE)^2\ge 4e(S)$ or the inequality $c_2(\sE)\ge e(S)$ holding.
We have carried out a search for new R Coronae Borealis (RCB) variables using the publicly accessible data from various photometric sky surveys and-whenever available-AAVSO visual data. Candidates were selected from Tisserand`s "Catalogue enriched with R CrB stars" and by a visual inspection of light curves from the ASAS-3, MACHO, NSVS and OGLE surveys. We have identified two new RCB stars, four RCB candidates, and one DY Persei (DYPer) star candidate. Our identification was based mainly on photometric variability, color-color diagrams, and further information drawn from various catalogue sources; spectroscopic classifications were also reported in our analysis whenever available. Additionally, we present a sample of interesting stars which-although showing similar photometric variability-can be ruled out as RCB and DYPer stars or have been rejected as such on spectroscopic grounds in recent studies. Although not useful in the investigation of the aforementioned groups of variables, these objects defy an easy classification and might be interesting targets for follow-up studies which we encourage for all stars presented in this paper.