ShantanuT01/DACTYL-Pretraining huggingface dataset:
H2 formation is an important process in post-shock regions, since H2 is an active participant in the cooling and shielding of the environment. The onset of H2 formation therefore has a strong effect on the temperature and chemical evolution in the post shock regions. We recently developed a model for H2 formation on a graphite surface in warm conditions. The graphite surface acts as a model system for grains containing large areas of polycyclic aromatic hydrocarbon structures. Here this model is used to obtain a new description of the H2 formation rate as a function of gas temperature that can be implemented in molecular shock models. The H2 formation rate is substantially higher at high gas temperatures as compared to the original implementation of this rate in shock models, because of the introduction of H atoms which are chemically bonded to the grain (chemisorption). Since H2 plays such a key role in the cooling, the increased rate is found to have a substantial effect on the predicted line fluxes of an important coolant in dissociative shocks [O I] at 63.2 and 145.5 micron. With the new model a better agreement between model and observations is obtained. Since one of the goals of Herschel/PACS will be to observe these lines with higher spatial resolution and sensitivity than the former observations by ISO-LWS, this more accurate model is very timely to help with the interpretation of these future results.
Silicon-On-Insulator nanowire transistors of very small dimensions exhibit quantum effects like Coulomb blockade or single-dopant transport at low temperature. The same process also yields excellent field-effect transistors (FETs) for larger dimensions, allowing to design integrated circuits. Using the same process, we have co-integrated a FET-based ring oscillator circuit operating at cryogenic temperature which generates a radio-frequency (RF) signal on the gate of a nanoscale device showing Coulomb oscillations. We observe rectification of the RF signal, in good agreement with modeling.
Using the quark mass density- and temperature dependent model, we have studied the thermodynamical properties and the stability of strangelet at finite temperature. The temperature, charge and strangeness dependences on the stability of strangelet are investigated. We find that the stable strangelets are only occured in the high strangeness and high negative charge region.
After learning a new object category from image-level annotations (with no object bounding boxes), humans are remarkably good at precisely localizing those objects. However, building good object localizers (i.e., detectors) currently requires expensive instance-level annotations. While some work has been done on learning detectors from weakly labeled samples (with only class labels), these detectors do poorly at localization. In this work, we show how to build better object detectors from weakly labeled images of new categories by leveraging knowledge learned from fully labeled base categories. We call this novel learning paradigm cross-supervised object detection. We propose a unified framework that combines a detection head trained from instance-level annotations and a recognition head learned from image-level annotations, together with a spatial correlation module that bridges the gap between detection and recognition. These contributions enable us to better detect novel objects with image-level annotations in complex multi-object scenes such as the COCO dataset.
Information ratchets extract work from heat baths using low entropy information reservoirs. We find that the structure of the reservoirs affects both their performance and phase diagram. By deriving exact probabilities of recurrence in d-dimensional reservoirs we calculate the net extraction of work. Performance is characterised by two critical dimensions (i) For d < 3 driven exploration of the reservoir is essential to extract work (ii) For d > 4 purely diffusive exploration is optimal. This has important consequences for computation where sequential operations constitute a 1D path.
We calculate the polarisation of $\psi$'s and $\Upsilon$'s produced by the fragmentation of heavy quarks. We find that fragmentation to transversely aligned quarkonium is slightly enhanced relative to longitudinally polarised. This net alignment corresponds to a $\sim 5\%$ asymmetry in the angular distribution of leptons produced in the subsequent decay of the quarkonium. We point out that the leading gluon contribution to $\psi$ and $\Upsilon$ production arises from the evolution of the charm quark fragmentation function, rather than from direct gluon fragmentation.
Using a generalized self-similar secondary infall model, which accounts for tidal torques acting on the halo, we analyze the velocity profiles of halos in order to gain intuition for N-body simulation results. We analytically calculate the asymptotic behavior of the internal radial and tangential kinetic energy profiles in different radial regimes. We then numerically compute the velocity anisotropy and pseudo-phase-space density profiles and compare them to recent N-body simulations. For cosmological initial conditions, we find both numerically and analytically that the anisotropy profile asymptotes at small radii to a constant set by model parameters. It rises on intermediate scales as the velocity dispersion becomes more radially dominated and then drops off at radii larger than the virial radius where the radial velocity dispersion vanishes in our model. The pseudo-phase-space density is universal on intermediate and large scales. However, its asymptotic slope on small scales depends on the halo mass and on how mass shells are torqued after turnaround. The results largely confirm N-body simulations but show some differences that are likely due to our assumption of a one-dimensional phase space manifold.
We report the discovery of a 4.5 um counterpart to the anomalous X-ray pulsar (magnetar) 1E 2259+586 with the Spitzer Space Telescope. The mid-infrared flux density is 6.3+/-1.0 uJy at 4.5 um and <20 uJy (at 95% confidence) at 8 um, or 0.02% of the 2-10 keV X-ray flux (corrected for extinction). Combining our Spitzer measurements with previously published near-infrared data, we show that the overall infrared emission from 1E 2259+586 is qualitatively similar to that from the magnetar 4U 0142+61. Therefore the passive X-ray-heated dust disk model originally developed for 4U 0142+61 might also apply to 1E 2259+586. However, the IR data from this source can also be fitted by a simple power-law spectrum as might be expected from magnetospheric emission.
Let $E$ be an elliptic curve defined over $\Q$ and with complex multiplication by $\mO_K$, the ring of integers in an imaginary quadratic field $K$. It is known that $E(\F_p)$ has a structure E(\F_p)\simeq \Z/d_p\Z \oplus \Z/e_p\Z. with $d_p|e_p$.   We give an asymptotic formula for the average order of $e_p$, with improved error term, and upper bound estimate for the average of $d_p$.
We discuss a modified gravity model which fits cosmological observations at a level statistically indistinguishable from $\Lambda$CDM and at the same time predicts very large deviations from General Relativity (GR) in the propagation of gravitational waves (GWs) across cosmological distances. The model is a variant of the RT nonlocal model proposed and developed by our group, with initial conditions set during inflation, and predicts a GW luminosity distance that, at the redshifts accessible to LISA or to a third-generation GW detector such as the Einstein Telescope (ET), can differ from that in GR by as much as $60\%$. An effect of this size could be detected with just a single standard siren with counterpart by LISA or ET. At the redshifts accessible to a LIGO/Virgo/Kagra network at target sensitivity the effect is smaller but still potentially detectable. Indeed, for the recently announced LIGO/Virgo NS-BH candidate S190814bv, the RT model predicts that, given the measured GW luminosity distance, the actual luminosity distance, and the redshift of an electromagnetic counterpart, would be smaller by as much as $7\%$ with respect to the value inferred from $\Lambda$CDM.
A precise variational solution to $N$=2--6-body problems is reported. The trial wave functions are chosen to be combinations of correlated Gaussians, which facilitate a fully analytical calculation of the matrix elements. The nonlinear parameters of the trial function are selected by a stochastic method. Fermionic and bosonic few-body systems are investigated for interactions of different type. A comparison of the results with those available in the literature shows that the method is both accurate and efficient.
We prove a product estimate that allows to estimate the quadratic first order nonlinearity of the harmonic map flow in the $L^p$ norm. Then the parabolic analogue of Weyl's lemma for the Lapace operator is established. Both results are applied to prove regularity for the heat flow by parabolic bootstrapping.
In this work we explore the properties of four-dimensional gravity integrands at large loop momenta. This analysis can not be done directly for the full off-shell integrand but only becomes well-defined on cuts that allow us to unambiguously specify labels for the loop variables. The ultraviolet region of scattering amplitudes originates from poles at infinity of the loop integrands and we show that in gravity these integcrands conceal a number of surprising features. In particular, certain poles at infinity are absent which requires a conspiracy between individual Feynman integrals contributing to the amplitude. We suspect that this non-trivial behavior is a consequence of yet-to-be found symmetry or hidden property of gravity amplitudes. We discuss mainly amplitudes in $\mathcal{N}=8$ supergravity but most of the statements are valid for pure gravity as well.
Various hints on the neutrino masses namely, ({\em i}) the solar neutrino deficit ({\em ii}) the atmospheric neutrino deficit ({\em iii}) the need for the dark matter and/or ({\em iv}) the non-zero neutrinoless double beta decay collectively imply that all the three neutrinos must be nearlty degenerate. This feature can be understood in the left right symmetric theory. We present a model based on the group $SU(2)_{L}\times SU(2)_R\times U(1)_{B-L}\times SU(2)_H$ which can explain the required departures from degeneracy in neutrino masses and large mixing among them without assuming any of the mixing in the quark or charged lepton sector to be large as would be expected in a typical $SO(10)$ model.
This short paper shows that a projective bundle over a smooth variety with a section can be uniquely recovered from the embedding of the section in its second infinitesimal neighborhood within the bundle.
In this paper we study the growth of ideals in $\mathbb{Z}[t]/(f)$ for a monic cubic polynomial $f$. We also compute the ideal zeta function of $\mathbb{Z}[t]/(t^n)$ for any $n \in \mathbb{N}$.
We describe a simple method to study the dependence of the solar properties on a generic (small) modification the physical inputs adopted in standard solar models calculations.
We investigate the origin and physical properties of OVI absorbers at low redshift (z = 0.25) using a subset of cosmological, hydrodynamical simulations from the OverWhelmingly Large Simulations (OWLS) project. Intervening OVI absorbers are believed to trace shock-heated gas in the Warm-Hot Intergalactic Medium (WHIM) and may thus play a key role in the search for the missing baryons in the present-day Universe. When compared to observations, the predicted distributions of the different OVI line parameters (column density, Doppler parameter, rest equivalent width) from our simulations exhibit a lack of strong OVI absorbers. This suggests that physical processes on sub-grid scales (e.g. turbulence) may strongly influence the observed properties of OVI systems. We find that the intervening OVI absorption arises mainly in highly metal-enriched (0.1 << Z/Z_sun < 1) gas at typical overdensities of 1 << rho/<rho> < 100. One third of the OVI absorbers in our simulation are found to trace gas at temperatures T < 10^5 K, while the rest arises in gas at higher temperatures around T =10^5.3 K. The OVI resides in a similar region of (rho,T)-space as much of the shock-heated baryonic matter, but the vast majority of this gas has a lower metal content and does not give rise to detectable OVI absorption As a consequence of the patchy metal distribution, OVI absorbers in our simulations trace only a very small fraction of the cosmic baryons (<2 percent) and the cosmic metals. Instead, these systems presumably trace previously shock-heated, metal-rich material from galactic winds that is now cooling. The common approach of comparing OVI and HI column densities to estimate the physical conditions in intervening absorbers from QSO observations may be misleading, as most of the HI (and most of the gas mass) is not physically connected with the high-metallicity patches that give rise to the OVI absorption.
We prove a version of Fujita's Conjecture in arbitrary characteristic, generalizing results of K.E. Smith. Our methods use the Frobenius morphism, but avoid tight closure theory. We also obtain versions of Fujita's Conjecture for coherent sheaves with certain ampleness properties.
We investigate entangled photon pair generation in a lossy microring resonator using an input-output formalism based on the work of Raymer and McKinstrie (Phys. Rev. A 88, 043819 (2013)) and Alsing, et al. (Phys. Rev. A 95, 053828 (2017)) that incorporates circulation factors that account for the multiple round trips of the fields within the cavity. We consider the nonlinear processes of spontaneous parametric down conversion and spontaneous four wave mixing, and we compute the generated biphoton signal-idler state from a single bus microring resonator, along with the generation, coincidence-to-accidental, and heralding efficiency rates. We compare these generalized results to those obtained by previous works employing the standard Langevin input-output formalism.
Using population synthesis, we study a double-degenerate (DD) scenario for SNe Ia, aiming to estimate the maximum possible contribution to the rate of SNe from this scenario and the dependence of the delay-time distribution (DTD) on it. We make an extreme assumption that all mergers of super-Chandrasekhar pairs of CO white dwarfs (WDs) and mergers of CO WDs more massive than 0.47 $M_\odot$ with hybrid or helium WDs more massive than 0.37$M_\odot$ produce SNe Ia. The models are parametrized by the product of the common envelope efficiency and the parameter of binding energy of stellar envelopes $\alpha_{ce}\lambda$, which we vary between 0.25 and 2. The best agreement with observations is obtained for $\alpha_{ce}\lambda$=2. A substantial contribution to the rate of SNe Ia is provided by the pairs with a hybrid WD. The estimated Galactic rate of SNe Ia is $6.5 10^{-3}$ per yr (for the mass of the bulge and thin disk equal to $7.2 10^{10} M_\odot$), which is comparable to the observational estimate $(5.4\pm0.12) 10^{-3}$ per yr. The model DTD for 1 to 8 Gyr range satisfactorily fits DTD for SNe Ia in the field galaxies (Maoz et al. 2012). For this epoch, model DTD is a power low with an index -1.64. At earlier and later epochs our DTD has a deficit of events, as in other studies. Marginal agreement with observational DTD is achieved even if only CO+CO WD with $M_1\geq0.8\,M_\odot$ and $M_2\geq0.6\,M_\odot$ produce SNe Ia. A better agreement of observed and model DTD may be obtained if tidal effects are weaker than assumed and/or metallicity of population is much lower than solar.
This note presents a simple, universal closed form for the powers of any square matrix. A diligent search of the internet gave no indication that the form is known.
Since their discovery twenty years ago, the observed luminosity function of $z\gtrsim6$ quasars has been suspected to be biased by gravitational lensing. Apart from the recent discovery of UHS J0439+1634 at $z\approx6.52$, no other strongly lensed $z\gtrsim6$ quasar has been conclusively identified. The hyperluminous $z\approx6.33$ quasar SDSS J0100+2802, believed to host a supermassive black hole of $\sim10^{10} M_\odot$, has recently been claimed to be lensed by a factor of $\sim450$, which would negate both its extreme luminosity and black hole mass. However, its Ly$\alpha$-transparent proximity zone is the largest known at $z>6$, suggesting an intrinsically extreme ionizing luminosity. Here we show that the lensing hypothesis of $z\gtrsim6$ quasars can be quantitatively constrained by their proximity zones. We first show that our proximity zone analysis can recover the strongly lensed nature of UHS J0439+1634, with an estimated magnification $\mu=28.0^{+18.4}_{-11.7}(^{+44.9}_{-18.3})$ at 68% (95%) credibility that is consistent with previously published lensing models. We then show that the large proximity zone of SDSS J0100+2802 rules out lensing magnifications of $\mu>4.9$ at 95% probability, and conclusively rule out the proposed $\mu>100$ scenario. Future proximity zone analyses of existing $z\gtrsim6$ quasar samples have the potential to identify promising strongly lensed candidates, constrain the distribution of $z\gtrsim6$ quasar lensing, and improve our knowledge of the shape of the intrinsic quasar luminosity function.
We improve on a result by Svetlana Jitomirskaya and Wencai Liu dealing with inhomogeneous Diophantine approximation in the coprime setting.
This paper is a sequel to a paper by the author and Marvin D. Tretkoff (reference [49]), in which we showed the validity of a special case of a conjecture of Green, Griffths and Kerr for certain families of Calabi-Yau manifolds over Hermitian symmetric domains. These results are analogues of a celebrated theorem of Th. Schneider on the transcendence of values of the elliptic modular function, and its generalization to the context of abelian varieties by the author, Shiga and Wolfart. In the present paper, we apply related techniques to many of the examples of families of Calabi-Yau varieties with dense sets of CM fibers in the work of Rohde, and in particular to Borcea-Voisin towers. Our results fit into a broader context of transcendence theory for variations of Hodge structure of higher weight.
This paper deals with the existence of global weak solutions for a wide class of (multiple species) cross-diffusions systems. The existence is based on two different ingredients: an entropy estimate giving some gradient control and a duality estimate that gives naturally L^2 control. The proof relies on a semi-implicit scheme tailored for cross-diffusion systems firstly defined by the two authors and collaborators. These results are applied to models having an entropy relying on the detailed balance condition recently exhibited by Chen et. al.
Cassiopeia A was observed using the Low-Band Antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon-alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of > 5 from two independent LOFAR datasets. The derived line velocities (v_LSR ~ -50 km/s) and integrated optical depths (~ 13 s^-1) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR dataset and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 %) integrated optical depths, indicating that there is small-scale angular structure on the order of ~1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 x 10^-4 on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band.
In this paper we find different types of black holes for the Born-Infeld extended new massive gravity. Our solutions include (un)charged warped (A)dS black holes for four and six derivative expanded action. We also look at the black holes in unexpanded BI action. In each case we calculate the entropy, angular momentum and mass of the black holes. We also find the central charges for the CFT duals.
The remarkable properties of graphene stem from its two-dimensional (2D) structure, with a linear dispersion of the electronic states at the corners of the Brillouin zone (BZ) forming a Dirac cone. Since then, other 2D materials have been suggested based on boron, silicon, germanium, phosphorus, tin, and metal di-chalcogenides. Here, we present an experimental investigation of a single silicon layer on Au(111) using low energy electron diffraction (LEED), high resolution angle-resolved photoemission spectroscopy (HR-ARPES), and scanning tunneling microscopy (STM). The HR-ARPES data show compelling evidence that the silicon based 2D overlayer is responsible for the observed linear dispersed feature in the valence band, with a Fermi velocity of v_F ~10^(+6) m.s^(-1) comparable to that of graphene. The STM images show extended and homogeneous domains, offering a viable route to the fabrication of silicene-based opto-electronic devices.
We derive an estimate for the distance, measured in lattice spacings, inside two-dimensional critical percolation clusters from the origin to the boundary of the box of side length $2n$, conditioned on the existence of an open connection. The estimate we obtain is the radial analogue of the one found in the work of Damron, Hanson, and Sosoe. In the present case, however, there is no lowest crossing in the box to compare to, so we construct a path $\gamma$ from the origin to distance $n$ that consists of "three-arm" points, and whose volume can thus be estimated by $O(n^2\pi_3(n))$. Here, $\pi_3(n)$ is the "three-arm probability" that the origin is connected to distance $n$ by three arms, two open and one dual-closed. We then develop estimates for the existence of shortcuts around an edge $e$ in the box, conditional on $\{e\in \gamma\}$, to obtain a bound of the form $O(n^{2-\delta}\pi_3(n))$ for some $\delta>0$.
We present a halo model prediction of the image separation distribution of strong lenses. Our model takes account of the subhalo population, which has been ignored in previous studies, as well as the conventional halo population. Halos and subhalos are linked to central and satellite galaxies by adopting an universal scaling relation between masses of (sub-)halos and luminosities of galaxies. Our model predicts that 10%-20% of lenses should be caused by the subhalo population. The fraction of lensing by satellite galaxies (subhalos) peaks at ~1'' and decreases rapidly with increasing image separations. We compute fractions of lenses which lie in groups and clusters, and find them to be ~14% and ~4%, respectively: Nearly half of such lenses are expected to be produced by satellite galaxies, rather than central parts of halos. We also study mass distributions of lensing halos and find that even at image separations of ~3'' the deviation of lens mass distributions from isothermal profiles is large: At or beyond ~3'' image separations are enhanced significantly by surrounding halos. Our model prediction agrees reasonably well with observed image separation distributions from galaxy to cluster scales.