ShantanuT01/DACTYL-Pretraining huggingface dataset:
A possible connection between the electromagnetic quantum vacuum and inertia was first published by Haisch, Rueda and Puthoff (1994). If correct, this would imply that mass may be an electromagnetic phenomenon and thus in principle subject to modification, with possible technological implications for propulsion. A multiyear NASA-funded study at the Lockheed Martin Advanced Technology Center further developed this concept, resulting in an independent theoretical validation of the fundamental approach (Rueda and Haisch, 1998ab). Distortion of the quantum vacuum in accelerated reference frames results in a force that appears to account for inertia. We have now shown that the same effect occurs in a region of curved spacetime, thus elucidating the origin of the principle of equivalence (Rueda, Haisch and Tung, 2001). A further connection with general relativity has been drawn by Nickisch and Mollere (2002): zero-point fluctuations give rise to spacetime micro-curvature effects yielding a complementary perspective on the origin of inertia. Numerical simulations of this effect demonstrate the manner in which a massless fundamental particle, e.g. an electron, acquires inertial properties; this also shows the apparent origin of particle spin along lines originally proposed by Schroedinger. Finally, we suggest that the heavier leptons (muon and tau) may be explainable as spatial-harmonic resonances of the (fundamental) electron. They would carry the same overall charge, but with the charge now having spatially lobed structure, each lobe of which would respond to higher frequency components of the electromagnetic quantum vacuum, thereby increasing the inertia and thus manifesting a heavier mass.
After a quarter of a century of gamma-ray burst (GRB) astronomy, the Italian-Dutch satellite BeppoSAX on Feb 28th, 1997 detected a soft X-ray afterglow from GRB 970228 and positioned it accurately. This made possible the successful detection of an optical transient. Two public Hubble Space Telescope (HST) images of the GRB/optical transient region were taken on March 26th and April 7th, 1997. They are analyzed here, with the purpose of understanding the nature of GRB 970228. We find that the position of the faint point-like object V ~ 26 seen at the transient location changed by 0.40 +/-0.10 pixels in 12 days, corresponding to a proper motion of ~ 550 mas/year. By comparison, four adjacent sources in the same field do not show any significant displacement, with astrometric residuals close to zero and average absolute displacements less than 0.09 pixels. If confirmed, this result would strongly support the galactic nature of GRB 970228.
Cosmic reionization is expected to be complex, extended and very inhomogeneous. Existing constraints at z~6 on the volume-averaged neutral hydrogen fraction, <x_HI>, are highly model-dependent and controversial. Constraints at z<6, suggesting that the Universe is highly ionized, are also model-dependent, but more fundamentally are invalid in the context of inhomogeneous reionization. As such, it has recently been pointed out that there is no conclusive evidence that reionization has completed by z~5--6, a fact that has important ramifications on the interpretation of high-redshift observations and theoretical models. We present the first direct upper limits on <x_HI> at z~5--6 using the simple and robust statistic of the covering fraction of dark pixels in the Ly alpha/beta forests of high redshift quasars. With a sample of 13 Keck ESI spectra we constrain <x_HI> < 0.2 at 5 < z < 5.5, rising to <x_HI> < 0.8 at z~6.1. We also find tentative evidence for a break in the redshift evolution of the dark covering fraction at z~5.5. A subsample of two deep spectra provides a more stringent constraint of <x_HI>(z=6.1) < 0.5 when combined with conservative estimates of cosmic variance. This upper limit is comparable to existing results at z~6 but is more robust. The results presented here do not rely on assumptions about the quasar continuum, IGM density, HII morphology or ionizing background fields, and thus are a good starting point for future interpretation of high redshift observations.
In this paper we prove that weak solutions to the Diffusive Wave Approximation of the Shallow Water equations $$ \partial_t u - \nabla\cdot ((u-z)^\alpha|\nabla u|^{\gamma-1}\nabla u) = f $$ are locally bounded. Here, $u$ describes the height of the water, $z$ is a given function that represents the land elevation and $f$ is a source term accounting for evaporation, infiltration or rainfall.
We develop a probabilistic interpretation of two-stage object detection. We show that this probabilistic interpretation motivates a number of common empirical training practices. It also suggests changes to two-stage detection pipelines. Specifically, the first stage should infer proper object-vs-background likelihoods, which should then inform the overall score of the detector. A standard region proposal network (RPN) cannot infer this likelihood sufficiently well, but many one-stage detectors can. We show how to build a probabilistic two-stage detector from any state-of-the-art one-stage detector. The resulting detectors are faster and more accurate than both their one- and two-stage precursors. Our detector achieves 56.4 mAP on COCO test-dev with single-scale testing, outperforming all published results. Using a lightweight backbone, our detector achieves 49.2 mAP on COCO at 33 fps on a Titan Xp, outperforming the popular YOLOv4 model.
We report on results from a 2003 February INTEGRAL observation of the black hole candidate (BHC) 4U 1630-47 and the high energy sources in the Norma Region of the Galaxy and on RXTE and radio observations of 4U 1630-47. To date, there have been 38 new or previously poorly studied sources found by INTEGRAL (the ``IGR'' sources), and 15 of the IGR sources are in the field of view of our observation. We detect 12 of the 15 sources, and we speculate that a subset of the IGR sources may be part of a new population of persistent, hard, intermediate luminosity X-ray sources. During our observations, 4U 1630-47 was in an intermediate state with strong soft and hard components, a power-law photon index of 2.11-2.18, a 4% rms level of timing noise (0.1-10 Hz), and the source was not detected in the radio band. We discuss the evolution of the energy spectrum during the 293 ks INTEGRAL observation, and we report on rapid, high amplitude flaring behavior that has been seen for much of the 2002-2004 outburst.
We present measurements of the electric potential fluctuations on the surface of highly oriented pyrolytic graphite using electrostatic force and atomic force microscopy. Micrometric domain-like potential distributions are observed even when the sample is grounded. Such potential distributions are unexpected given the good metallic conductivity of graphite because the surface should be an equipotential. Our results indicate the coexistence of regions with metallic and insulating behaviors showing large potential fluctuations of the order of 0.25V. We discuss the implications of these measurements in the disorder structure of graphite.
Some recent developments in the study of light and heavy pentaquarks are reviewed, mainly within constituent quark models. Emphasis is made on results obtained in the flavor-spin model where a nearly ideal octet-antidecuplet mixing is obtained. The charmed antisextet is reviewed in the context of an SU(4) classification.
We study the conductance of mesoscopic graphene rings in the presence of a perpendicular magnetic field by means of numerical calculations based on a tight-binding model. First, we consider the magnetoconductance of such rings and observe the Aharonov-Bohm effect. We investigate different regimes of the magnetic flux up to the quantum Hall regime, where the Aharonov-Bohm oscillations are suppressed. Results for both clean (ballistic) and disordered (diffusive) rings are presented. Second, we study rings with smooth mass boundary that are weakly coupled to leads. We show that the valley degeneracy of the eigenstates in closed graphene rings can be lifted by a small magnetic flux, and that this lifting can be observed in the transport properties of the system.
We investigate the stability of ground states to a nonlinear focusing Schr\"odinger equation in presence of a Kirchhoff term. Through a spectral analysis of the linearized operator about ground states, we show a modulation stability estimate of ground states in the spirit of one due to Weinstein [{\it SIAM J. Math. Anal.}, 16(1985),472-491].
The results from the first three years observation in Telescope Array are reviewed. The energy spectrum, mass composition, and anisotropy in arrival directions of ultra-high energy cosmic rays are discussed. The energy spectrum of cosmic rays with energies above $10^{18}$ eV is determined using the data of the fluorescence detectors, surface detectors, and with a hybrid shower reconstruction technique using the both data. The ankle structure is clearly found at $10^{18.7}$ eV. The second bending point is also identified, at which the flux of cosmic rays begins to decrease and the spectral index changes from $E^{-2.68}$ to $E^{-4.2}$. The study of shower development using the fluorescence detector data shows that proton is dominant in cosmic rays above $10^{18.2}$ eV. No apparent anisotropies in the arrival direction of cosmic rays are found. I also present further experimental extensions which are being developed at the Telescope Array site.
In magnetic memory and logic devices, a magnet's magnetization is usually flipped with a spin polarized current delivering a spin transfer torque (STT). This mode of switching consumes too much energy and considerable energy saving can accrue from using a multiferroic nanomagnet switched with a combination of STT and mechanical stress generated with a voltage (VGS). The VGS mode consumes less energy than STT, but cannot rotate magnetization by more than 90?, so that a combination of the two modes is needed for energy-efficient switching.
Ori and Thorne have discussed the duration and observability (with LISA) of the transition from circular, equatorial inspiral to plunge for stellar-mass objects into supermassive ($10^{5}-10^{8}M_{\odot}$) Kerr black holes. We extend their computation to eccentric Kerr equatorial orbits. Even with orbital parameters near-exactly determined, we find that there is no universal length for the transition; rather, the length of the transition depends sensitively -- essentially randomly -- on initial conditions. Still, Ori and Thorne's zero-eccentricity results are essentially an upper bound on the length of eccentric transitions involving similar bodies (e.g., $a$ fixed). Hence the implications for observations are no better: if the massive body is $M=10^{6}M_{\odot}$, the captured body has mass $m$, and the process occurs at distance $d$ from LISA, then $S/N \lesssim (m/10 M_{\odot})(1\text{Gpc}/d)\times O(1)$, with the precise constant depending on the black hole spin. For low-mass bodies ($m \lesssim 7 M_\odot$) for which the event rate is at least vaguely understood, we expect little chance (probably [much] less than 10%, depending strongly on the astrophysical assumptions) of LISA detecting a transition event with $S/N>5$ during its run; however, even a small infusion of higher-mass bodies or a slight improvement in LISA's noise curve could potentially produce $S/N>5$ transition events during LISA's lifetime.
In this letter, we will demonstrate that the breaking of supersymmetry by a non-anticommutative deformation can be used to generate the generalized uncertainty principle. We will analyse the physical reasons for this observation, in the framework of string theory. We also discuss the relation between the generalized uncertainty principle and the Lee-Wick field theories.
Motivated by recent experiments [Vera-Marun et al., arXiv:1109.5969], we formulate a non-linear theory of spin transport in quantum coherent conductors. We show how a mesoscopic constriction with energy-dependent transmission can convert a spin current injected by a spin accumulation into an electric signal, relying neither on magnetic nor exchange fields. When the transmission through the constriction is spin-independent, the spin-charge coupling is non-linear, with an electric signal that is quadratic in the accumulation. We estimate that gated mesoscopic constrictions have a sensitivity that allows to detect accumulations much smaller than a percent of the Fermi energy.
The basic results of optical line broadening and four-wave mixing are deduced from first principles based on time-dependent many-body purturbation theory. The formalism allows us to write all the results in terms of nonequilibrium distribution functions without the need to assume a quasiequilibrium temperature. The connection of these results to the quantum Boltzmann equation is shown, which is also derived from first principles. Last, specific predictions for electron-electron scattering are reviewed.
We construct SO(2,1) x SO(3)-invariant half-BPS solutions in six-dimensional (0,4) supergravity with m tensor multiplets. The space-time manifold of each one of these solutions consists of an AdS_2 x S^2 warped over a Riemann surface Sigma with boundary. The most general local solution is parametrized by one real harmonic function, and m+2 holomorphic functions which are subject to a quadratic constraint and a hermitian inequality, both of which are manifestly SO(2,m) invariant. Imposing suitable conditions on these harmonic and holomorphic functions, we construct globally regular supergravity solutions with N distinct AdS_3 x S^3 asymptotic regions and contractible Sigma. These solutions have an intricate moduli space, whose dimension equals 2(m+1)N -m-2 and matches the counting of three-form charge vectors and un-attracted scalars of the tensor multiplet. Exact explicit formulas for all supergravity fields are obtained in terms of the moduli. Our solutions give the near-horizon geometries for junctions of N self-dual strings in six dimensions, and are holographic duals to CFTs defined on N half-planes which share a common interface line. For m=5, the solutions lift to quarter-BPS solutions for six-dimensional (4,4) supergravity.
This brief set of notes presents a modest introduction to the basic features entering the construction of supersymmetric quantum field theories in four-dimensional Minkowski spacetime, building a bridge from similar lectures presented at a previous Workshop of this series, and reaching only at the doorstep of the full edifice of such theories.
Using the LHC and Tevatron data, we set upper and lower limits on the total width of the Higgs-like boson. The upper limit is based on the well-motivated assumption that the Higgs coupling to a W or Z pair is not much larger than in the Standard Model. These width limits allow us to convert the rate measurements into ranges for the Higgs couplings to various particles. A corollary of the upper limit on the total width is an upper limit on the branching fraction of exotic Higgs decays. Currently, this limit is 47% at the 95% CL if the electroweak symmetry is broken only by doublets.
Extragalactic foregrounds in temperature maps of the Cosmic Microwave Background (CMB) severely limit the ability of standard estimators to reconstruct the weak lensing potential. These foregrounds are not fully removable by multi-frequency cleaning or masking and can lead to large biases if not properly accounted for. For foregrounds made of a number of unclustered point sources, an estimator for the source amplitude can be derived and deprojected, removing any bias to the lensing reconstruction. We show with simulations that all of the extragalactic foregrounds in temperature can be approximated by a collection of sources with identical profiles, and that a simple bias hardening technique is effective at reducing any bias to lensing, at a minimal noise cost. We compare the performance and bias to other methods such as "shear-only" reconstruction, and discuss how to jointly deproject any arbitrary number of foregrounds, each with an arbitrary profile. In particular, for a Simons Observatory-like experiment foreground-hardened estimators allow us to extend the maximum multipole used in the reconstruction, increasing the overall statistical power by $\sim 50\%$ over the standard quadratic estimator, both in auto and cross-correlation. We conclude that source hardening outperforms the standard lensing quadratic estimator both in auto and cross-correlation, and in terms of lensing signal-to-noise and foreground bias.
The decoration of graphene samples with adatoms or nanoparticles leads to the enhancement of spin-orbit interactions as well as to the introduction of symmetry-breaking effects that could have drastic effects on spin and electronic transport phenomena. We present an analysis based on symmetry considerations and examine the impact on the scattering matrix for graphene systems containing defects that enhance spin-orbit interactions, while conserving the electronic total angular momentum. We show that the appearance and dominance of skew scattering, and the related observation of valley and/or spin Hall effect in decorated graphene samples, suggests the set of symmetries that adatom perturbations should satisfy. We further show that detailed measurements of the transport and elastic times as a function of carrier concentration make it possible to not only extract the strength of the spin-orbit interaction, as suggested before, but also obtain the amplitude of the symmetry-breaking terms introduced. To examine how different terms would affect measurements, we also present calculations for typical random distributions of impurities with different perturbations, illustrating the detailed energy dependence of different observables
We report on the analysis of 13 gamma-ray pulsars discovered in the Einstein@Home blind search survey using Fermi Large Area Telescope (LAT) Pass 8 data. The 13 new gamma-ray pulsars were discovered by searching 118 unassociated LAT sources from the third LAT source catalog (3FGL), selected using the Gaussian Mixture Model (GMM) machine learning algorithm on the basis of their gamma-ray emission properties being suggestive of pulsar magnetospheric emission. The new gamma-ray pulsars have pulse profiles and spectral properties similar to those of previously-detected young gamma-ray pulsars. Follow-up radio observations have revealed faint radio pulsations from two of the newly-discovered pulsars, and enabled us to derive upper limits on the radio emission from the others, demonstrating that they are likely radio-quiet gamma-ray pulsars. We also present results from modeling the gamma-ray pulse profiles and radio profiles, if available, using different geometric emission models of pulsars. The high discovery rate of this survey, despite the increasing difficulty of blind pulsar searches in gamma rays, suggests that new systematic surveys such as presented in this article should be continued when new LAT source catalogs become available.
Let $G$ be a finite cyclic group. Every sequence $S$ over $G$ can be written in the form $S=(n_1g)\cdot\ldots\cdot(n_lg)$ where $g\in G$ and $n_1, \ldots, n_l\in[1, \ord(g)]$, and the index $\ind(S)$ of $S$ is defined to be the minimum of $(n_1+\cdots+n_l)/\ord(g)$ over all possible $g\in G$ such that $\langle g \rangle =G$.   A conjecture on the index of length four sequences says that every minimal zero-sum sequence of length 4 over a finite cyclic group $G$ with $\gcd(|G|, 6)=1$ has index 1. The conjecture was confirmed recently for the case when $|G|$ is a product of at most two prime powers. However, the general case is still open. In this paper, we make some progress towards solving the general case. Based on earlier work on this problem, we show that if $G=\langle g\rangle$ is a finite cyclic group of order $|G|=n$ such that $\gcd(n,6)=1$ and $S=(x_1g)(x_2g)(x_3g)(x_4g)$ is a minimal zero-sum sequence over $G$ such that $x_1,\cdots,x_4\in[1,n-1]$ with $\gcd(n,x_1,x_2,x_3,x_4)=1$, and $\gcd(n,x_i)>1$ for some $i\in[1,4]$, then $\ind(S)=1$.   By using an innovative method developed in this paper, we are able to give a new (and much shorter) proof to the index conjecture for the case when $|G|$ is a product of two prime powers.
In order to clear up the sensitivity of the nucleus-nucleus scattering to the nuclear matter distributions of exotic halo nuclei, we have calculated differential cross sections for elastic scattering of the $^6$He and $^{11}$Li nuclei on several nuclear targets at the energy of 0.8 GeV/nucleon with different assumed nuclear density distributions in $^6$He and $^{11}$Li.
We present the results of the systematic study of all magnetar outbursts observed to date, through a reanalysis of data acquired in about 1100 X-ray observations. We track the temporal evolution of the outbursts soft X-ray spectral properties and the luminosities of the single spectral components as well as of the total emission. We model empirically all outburst light curves, and estimate the characteristic decay time-scales as well as the energetics involved. We investigate the link between different parameters (e.g. the luminosity at the peak of the outburst and in quiescence, the maximum luminosity increase, the decay time-scale and energy of the outburst, the neutron star surface dipolar magnetic field and characteristic age, etc.), and unveil several correlations among these quantities. We discuss our results in the context of the internal crustal heating and twisted bundle models for magnetar outbursts. This study is complemented by the Magnetar Outburst Online Catalogue (http://magnetars.ice.csic.es), an interactive data base where the user can plot any combination of the parameters derived in this work, and download all data.
In anticipation of the upcoming deployment of the James Webb Space Telescope (JWST), we present high-redshift predictions by the well-established Santa Cruz semi-analytic model. We update the models by re-calibrating them after adopting cosmological parameters consistent with recent constraints from Planck. We provide predictions for rest-frame UV luminosity functions for galaxy populations over a wide range of $M_\text{UV}$ from $\sim-6$ to $\sim-24$ between $z = 4 - 10$. In addition, we present the corresponding predictions for observed-frame galaxy number counts in different redshift bins in the full set of NIRCam filters. We provide predictions of the quantitative effect on these observables of varying the physical recipes implemented in the models, such as the molecular gas depletion time (star formation efficiency) scalings or the scalings of outflow rates driven by stars and supernovae with galaxy circular velocity. Based on these results, we discuss what may be learned about the physical processes that shape galaxy formation from JWST observations of galaxy number densities at different intrinsic luminosities. All data tables for the results presented in this work are available at https://www.simonsfoundation.org/semi-analytic-forecasts-for-jwst/.