ShantanuT01/DACTYL-Pretraining huggingface dataset:
In this paper, we systematically calculate the polarization in soft X-rays emitted from magnetized neutron stars, which are expected to be observed by the next-generation X-ray satellites. Magnetars are one of the targets for these observations. This is because thermal radiation is normally observed in the soft X-ray band, and it is thought to be linearly polarized because of different opacities for two polarization modes of photons in the magnetized atmosphere of neutron stars and the dielectric properties of the vacuum in strong magnetic fields. In their previous study, Taverna et al. illustrated how strong magnetic fields influence the behavior of the polarization observables for radiation propagating in vacuo without addressing a precise, physical emission model. In this paper, we pay attention to the conversion of photon polarization modes that can occur in the presence of an atmospheric layer above the neutron star surface, computing the polarization angle and fraction and systematically changing the magnetic field strength, radii of the emission region, temperature, mass, and radii of the neutron stars. We confirmed that if plasma is present, the effects of mode conversion cannot be neglected when the magnetic field is relatively weak, $B \sim 10^{13} \mathrm{G}$. Our results indicate that strongly magnetized ($B \gtrsim 10^{14} \mathrm{G}$) neutron stars are suitable to detect polarizations, but not-so-strongly magnetized ($B \sim 10^{13} \mathrm{G}$) neutron stars will be the ones to confirm the mode conversion.
We examine the properties of the galaxies and dark matter haloes residing in the cluster infall region surrounding the simulated $\Lambda$CDM galaxy cluster studied by Elahi et al. (2016) at z=0. The $1.1\times10^{15}h^{-1}\text{M}_{\odot}$ galaxy cluster has been simulated with eight different hydrodynamical codes containing a variety of hydrodynamic solvers and subgrid schemes. All models completed a dark-matter only, non-radiative and full-physics run from the same initial conditions. The simulations contain dark matter and gas with mass resolution $m_{\text{DM}}=9.01\times 10^8h^{-1}\text{M}_{\odot}$ and $m_{\text{gas}}=1.9\times 10^8h^{-1}\text{M}_{\odot}$ respectively. We find that the synthetic cluster is surrounded by clear filamentary structures that contain ~60% of haloes in the infall region with mass ~$10^{12.5} - 10^{14} h^{-1}\text{M}_{\odot}$, including 2-3 group-sized haloes ($> 10^{13}h^{-1}\text{M}_{\odot}$). However, we find that only ~10% of objects in the infall region are subhaloes residing in haloes, which may suggest that there is not much ongoing preprocessing occurring in the infall region at z=0. By examining the baryonic content contained within the haloes, we also show that the code-to-code scatter in stellar fraction across all halo masses is typically ~2 orders of magnitude between the two most extreme cases, and this is predominantly due to the differences in subgrid schemes and calibration procedures that each model uses. Models that do not include AGN feedback typically produce too high stellar fractions compared to observations by at least ~1 order of magnitude.
Understanding how the birthplace of stars affects planet-forming discs is important for a comprehensive theory of planet formation. Most stars are born in dense star-forming regions where the external influence of other stars, particularly the most massive stars, will affect the survival and enrichment of their planet-forming discs. Simulations suggest that stellar dynamics play a central role in regulating how external feedback affects discs, but comparing models to observations requires an estimate of the initial stellar density in star-forming regions. Structural analyses constrain the amount of dynamical evolution a star-forming region has experienced; regions that maintain substructure and do not show mass segregation are likely dynamically young, and therefore close to their birth density. In this paper, we present a structural analysis of two clusters in the Carina Nebula, Tr14 and Tr16. We show that neither cluster shows evidence for mass segregation or a centrally concentrated morphology, suggesting that both regions are dynamically young. This allows us to compare to simulations from Nicholson et al. (2019) who predict disc survival rates in star-forming regions of different initial densities. The surviving disc fractions in Tr14 and Tr16 are consistent with their predictions (both are $\sim 10$%), supporting a growing body of evidence that the star-forming environment plays an important role in the survival and enrichment of protoplanetary discs.
We consider a lcsc group G acting properly on a Borel space S and measurably on an underlying sigma-finite measure space. Our first main result is a transport formula connecting the Palm pairs of jointly stationary random measures on S. A key (and new) technical result is a measurable disintegration of the Haar measure on G along the orbits. The second main result is an intrinsic characterization of the Palm pairs of a G-invariant random measure. We then proceed with deriving a general version of the mass-transport principle for possibly non-transitive and non-unimodular group operations first in a deterministic and then in its full probabilistic form.
Relative BPS state counts for log Calabi-Yau surface pairs were introduced by Gross-Pandharipande-Siebert and conjectured by the authors to be integers. For toric Del Pezzo surfaces, we provide an arithmetic proof of this conjecture, by relating these invariants to the local BPS state counts of the surfaces. The latter were shown to be integers by Peng; and more generally for toric Calabi-Yau threefolds by Konishi.
We present a catalog of all CO (J=4-3 through J=13-12)), [CI], [NII] lines available from extragalactic spectra from the Herschel SPIRE Fourier Transform Spectrometer (FTS) archive combined with observations of the low-J CO lines from the literature and from the Arizona Radio Observatory. This work examines the relationships between LFIR, L'CO, and LCO/LCO(1-0). We also present a new method for estimating probability distribution functions (PDFs) from marginal signal-to-noise ratio Herschel} FTS spectra, which takes into account the instrumental "ringing" and the resulting highly correlated nature of the spectra. The slopes of log(LFIR) vs. log(L'CO) are linear for all mid- to high-J CO lines and slightly sublinear if restricted to (U)LIRGs. The mid- to high-J CO luminosity relative to CO J=1-0 increases with increasing LFIR, indicating higher excitement of the molecular gas, though these ratios do not exceed ~ 180. For a given bin in LFIR, the luminosities relative to CO J=1-0 remain relatively flat from J=6-5 through J=13-12, across three orders of magnitude of LFIR. A single component theoretical photon-dominated region (PDR) model cannot match these flat SLED shapes, though combinations of PDR models with mechanical heating added qualitatively match the shapes, indicating the need for further comprehensive modeling of the excitation processes of warm molecular gas in nearby galaxies.
Terzan 5 is the only Galactic globular cluster that has plausibly been detected in the very-high-energy range. Stacking upper limits by H.E.S.S. on the integral $\gamma$-ray flux of a population of other globular clusters are very constraining for leptonic cluster emission models. We demonstrate that uncertainty in model parameters leads to a large spread in the predicted flux, and there are indeed regions in parameter space for which the stringent stacking upper limits are satisfied. We conduct two more case studies: we study the uncertainties in differential TeV flux for M15, showing that our model can satisfy the stringent MAGIC upper limits for this cluster, for typical cluster parameters. We also calculate the differential flux at TeV energies for $\omega$ Cen, from which five pulsars have recently been detected at radio energies. It is thus important to increase measurement accuracy on key model parameters in order to improve predictions of cluster fluxes so as to better guide the observational strategy of the Cherenkov Telescope Array.
We report on results of finite-size numerical studies of partially filled lowest Landau level at low electron filling factors. We find convincing evidence suggesting that electrons form Wigner Crystals at sufficiently low filling factors, and the critical filling factor is close to 1/7. At nu=1/7 we find the system undergoes a phase transition from Wigner Crystal to the incompressible Laughlin state when the short-range part of the Coulomb interaction is modified slightly. This transition is either continuous or very weakly first order.
We report quadrature observations of an extreme-ultraviolet (EUV) wave event on 2011 January 27 obtained by the Extreme Ultraviolet Imager (EUVI) onboard \emph{Solar Terrestrial Relations Observatory} (\emph{STEREO}), and the Atmospheric Imaging Assembly (AIA) onboard the \emph{Solar Dynamics Observatory} (\emph{SDO}). Two components are revealed in the EUV wave event. A primary front is launched with an initial speed of $\sim$440 km s$^{-1}$. It appears significant emission enhancement in the hotter channel but deep emission reduction in the cooler channel. When the primary front encounters a large coronal loop system and slows down, a secondary much fainter front emanates from the primary front with a relatively higher starting speed of $\sim$550 km s$^{-1}$. Afterwards the two fronts propagate independently with increasing separation. The primary front finally stops at a magnetic separatrix, while the secondary front travels farther before it fades out. In addition, upon the arrival of the secondary front, transverse oscillations of a prominence are triggered. We suggest that the two components are of different natures. The primary front belongs to a non-wave coronal mass ejection (CME) component, which can be reasonably explained with the field-line stretching model. The multi-temperature behavior may be caused by considerable heating due to the nonlinear adiabatic compression on the CME frontal loop. For the secondary front, most probably it is a linear fast-mode magnetohydrodynamic (MHD) wave that propagates through a medium of the typical coronal temperature. X-ray and radio data provide us with complementary evidence in support of the above scenario.
We introduce a method to determine if n-dimensional smooth subvarieties of an ambient space of dimension at most 2n − 2 inherit the Picard group from the ambient space (as it happens when the ambient space is a projective space, according to results of Barth and Larsen). As an application, we give an affirmative answer (up to some mild natural numerical conditions) when the ambient space is a Grassmannian of lines (thus improving results of Barth, Van de Ven and Sommese) or a product of two projective spaces of the same dimension.
This is a short presentation of our talks given at eRHIC Workshop at the BNL. We give here a status report of our attempts to understand how gluon saturation will manifest itself in deep inelastic scattering with nuclei. This summary reflects our current understanding and shows directions of our research rather then a final answer to the question. Nevertheless, we are able to share with our reader our tentative answer to the question:``Why do we need to measure DIS with nuclei and why these data will be complementary to the information obtained from proton DIS".
The behaviour of alkaline carbonates at high pressure is poorly understood. Indeed, theoretical and experimental investigations of general trends of pressure induced structural changes appear in the literature only sporadically. In this article we use a combination of ab-initio calculations and high-pressure experiments in diamond anvil cell to determine crystal structures of high-pressure phases of K2CO3. The comparison with experimental data on Li2CO3 allows to reconstruct the common structural trend, which is consistent with the simple rule that the structure of high-pressure polymorph is the same as the ambient structure of a heavier element compound from the same group of the periodic table. The correctness of the constructed trend is confirmed by the perfect consistency with pressure-induced structural transformations in a wide range of binary A2B compounds.
The emergence of the global COVID-19 pandemic poses new challenges for biometrics. Not only are contactless biometric identification options becoming more important, but face recognition has also recently been confronted with the frequent wearing of masks. These masks affect the performance of previous face recognition systems, as they hide important identity information. In this paper, we propose a mask-invariant face recognition solution (MaskInv) that utilizes template-level knowledge distillation within a training paradigm that aims at producing embeddings of masked faces that are similar to those of non-masked faces of the same identities. In addition to the distilled knowledge, the student network benefits from additional guidance by margin-based identity classification loss, ElasticFace, using masked and non-masked faces. In a step-wise ablation study on two real masked face databases and five mainstream databases with synthetic masks, we prove the rationalization of our MaskInv approach. Our proposed solution outperforms previous state-of-the-art (SOTA) academic solutions in the recent MFRC-21 challenge in both scenarios, masked vs masked and masked vs non-masked, and also outperforms the previous solution on the MFR2 dataset. Furthermore, we demonstrate that the proposed model can still perform well on unmasked faces with only a minor loss in verification performance. The code, the trained models, as well as the evaluation protocol on the synthetically masked data are publicly available: https://github.com/fdbtrs/Masked-Face-Recognition-KD.
We study cluster perturbation theory [Phys. Rev. Lett. \textbf{84}, 522 (2000)] when auxiliary field quantum Monte Carlo method is used for solving the cluster hamiltonian. As a case study, we calculate the spectral functions of the Hubbard model in one and two dimensions and compare our results for the spectral functions to results obtained using exact diagonalization to solve the cluster hamiltonian. The main advantage of using quantum Monte Carlo results as a starting point is that the initial cluster size can be taken to be considerably larger and hence potentially capture more of the relevant physics. The drawback is that quantum Monte Carlo methods yield results at {\it imaginary} times with stochastic errors.
Recently, some hot DA-type white dwarfs have been proposed to plausibly be escaping members of the Hyades. We used hydrogen Balmer lines to measure the radial velocities of seven such stars and confirm that three, and perhaps two others, are/were indeed cluster members and one is not. The other candidate Hyad is strongly magnetic and its membership status remains uncertain. The photospheres of at least one quarter of field white dwarf stars are "polluted" by elements heavier than helium that have been accreted. These stars are orbited by extended planetary systems that contain both debris belts and major planets. We surveyed the seven classical single Hyades white dwarfs and the newly identified (escaping) Hyades white dwarfs and found calcium in the photosphere of LP 475-242 of type DBA (now DBAZ), thus implying the presence of an orbiting planetary system. The spectrum of white dwarf GD 31, which may be, but probably is not, an escaping member of the Hyades, displays calcium absorption lines; these originate either from the interstellar medium or, less likely, from a gaseous circumstellar disk. If GD 31 was once a Hyades member, then it would be the first identified white dwarf Hyad with a cooling age >340 Myr.
For the purpose of deriving the observed nearly tribimaximal neutrino mixing, a possible yukawaon model in the quark sector is investigated. Five observable quantities (2 up-quark mass ratios and 3 neutrino mixing parameters \sin^2 2\theta_{atm}, \tan^2\theta_{solar} and |U_{13}|) are excellently fitted by two parameters (one in the up-quark sector and another one in the right-handed Majorana neutrino sector).
We present a new analysis of the results of the EROS-2, OGLE-II, and OGLE-III microlensing campaigns towards the Small Magellanic Cloud (SMC). Through a statistical analysis we address the issue of the \emph{nature} of the reported microlensing candidate events, whether to be attributed to lenses belonging to known population (the SMC luminous components or the Milky Way disc, to which we broadly refer to as "self lensing") or to the would be population of dark matter compact halo objects (MACHOs). To this purpose, we present profiles of the optical depth and, comparing to the observed quantities, we carry out analyses of the events position and duration. Finally, we evaluate and study the microlensing rate. Overall, we consider five reported microlensing events towards the SMC (one by EROS and four by OGLE). The analysis shows that in terms of number of events the expected self lensing signal may indeed explain the observed rate. However, the characteristics of the events, spatial distribution and duration (and for one event, the projected velocity) rather suggest a non-self lensing origin for a few of them. In particular we evaluate, through a likelihood analysis, the resulting upper limit for the halo mass fraction in form of MACHOs given the expected self-lensing and MACHO lensing signal. At 95% CL, the tighter upper limit, about 10%, is found for MACHO mass of $10^{-2} \mathrm{M}_\odot$, upper limit that reduces to above 20% for $0.5 \mathrm{M}_\odot$ MACHOs.
We consider the Comptonization of an isotropic radiation field by a thermal distribution of electrons with non-vanishing bulk velocity. We include all relativistic effects, including induced scattering and electron recoil, in the derivation of a kinetic equation which is correct to O(theta^2, beta theta^2, beta^2 theta), where beta is the bulk velocity (in units of c) and theta is the ratio of the electron temperature to mass. The result given here manifestly conserves photon number, and easily yields the energy transfer rate between the radiation and electrons. We also confirm recent calculations of the relativistic corrections to the thermal and kinematic Sunyaev-Zel'dovich effect.
We present the study of the linear conductance vs.\ applied gate voltage for an interacting six site ring structure, which is threaded by a flux of $\pi$ and coupled to a left and a right lead. This ring structure is designed to have a vanishing conductance for all gate voltages and temperatures provided interactions are ignored. Therefore this system is an ideal testbed to study the interplay of interaction and interference. First we find a Kondo type resonance for rather large hopping parameter. Second, we find additional resonance peaks which can be explained by a population blocking mechanism. To this end we have to extend the Kubo approach within the Density Matrix Renormalization Group method to handle degenerate states.
Recent HST determinations of the expansion's rate of the Universe (the Hubble constant, H_0) assumed that the Cepheid Period-Luminosity relation at V and I are independent of metallicity (Freedman, et al., 1996, Saha et al., 1996, Tanvir et al., 1995). The three groups obtain different vales for H_0. We note that most of this discrepancy stems from the asumption (by both groups) that the Period-Luminosity relation is independent of metallicity. We come to this conclusion as a result of our study of the Period-Luminosity relation of 481 Cepheids with 3 millions two colour measurements in the Large Magellanic Cloud and the Small Magellanic Cloud obtained as a by-product of the EROS microlensing survey. We find that the derived interstellar absorption corrections are particularly sensitive to the metallicity and when our result is applied to recent estimates based on HST Cepheids observations it makes the low-H_0 values higher and the high-H_0 value lower, bringing those discrepant estimates into agrement around $H_0 \approx 70 km/s Mpc^{-1}$.
The deviation of primordial Helium production due to a variation on the difference between the rest masses of the nucleons is presented. It is found an upper bound $\delta (M_{_n} - M_{_p}) \alt 0.129$ MeV, between the present and nucleosynthesis epochs. This bound is used to analyze Wesson's theory of gravitation; as a result, it is ruled out by observation.
We report the results of multifrequency-VLBI observations of GHz-Peaked-Spectrum (GPS) radio sources. The VLBI structure and component spectra of some GPS sources are presented. Our VLBI results show that about 80% of the GPS galaxies exhibit a compact double or CSO-like structure, while the GPS quasars tend to show a core-jet. The component spectra of the GPS galaxies are often steep/convex, and the core has a flat spectrum but it is usually hidden or weak. In addition, we studied the variability of GPS sources by comparing new flux density measures, acquired with the Urumqi 25m telescope at 4.85 GHz, with previous 87GB data. The results show that 44% of the GPS quasars varied higher than 10% in passed 20 years, while the fraction is only 12% for the GPS galaxies meaning that the GPS quasars are much more variable than GPS galaxies. In total, 25% of GPS sources show >10% variability at 4.85 GHz in our sample.
We partially answer, in terms of monodromy, Murty and Patankar's question: Given an absolutely simple abelian variety over a number field, does it have simple specializations at a set of places of positive Dirichlet density?   The answer is based on the classification of pairs (G,V) consisting of a semi-simple algebraic group G over a non-archimedean local field and an absolutely irreducible representation V of G such that G admits a maximal torus acting irreducibly on V.
Let $K$ be an algebraic number field with ring of integers $\Cal{O}_{K}$, $p>2$ be a rational prime and $G$ be the cyclic group of order $p $. Let $\Lambda$ denote the order $\Cal{O}_{K}[G].$ Let $Cl(\Lambda)$ denote the locally free class group of $\Lambda$ and $D(\Lambda)$ the kernel group, the subgroup of $Cl(\Lambda)$ consisting of classes that become trivial upon extension of scalars to the maximal order. If $p$ is unramified in $K$, then $D(\Lambda) = T(\Lambda)$, where $T(\Lambda)$ is the Swan subgroup of $Cl(\Lambda).$ This yields upper and lower bounds for $D(\Lambda)$. Let $R(\Lambda)$ denote the subgroup of $Cl(\Lambda)$ consisting of those classes realizable as rings of integers, $\Cal{O}_{L},$ where $L/K$ is a tame Galois extension with Galois group $Gal(L/K) \cong G.$ We show under the hypotheses above that $T(\Lambda)^{(p-1)/2} \subseteq R(\Lambda) \cap D(\Lambda) \subseteq T(\Lambda)$, which yields conditions for when $T(\Lambda)=R(\Lambda) \cap D(\Lambda)$ and bounds on $R(\Lambda) \cap D(\Lambda)$. We carry out the computation for $K=\Bbb{Q}(\sqrt{-d}), d>0, d \neq 1$ or $3.$ In this way we exhibit primes $p$ for which these fields have tame Galois field extensions of degree $p$ with nontrivial Galois module structure.
The complete family of exact solutions representing accelerating and rotating black holes with possible electromagnetic charges and a NUT parameter is known in terms of a modified Plebanski-Demianski metric. This demonstrates the singularity and horizon structure of the sources but not that the complete space-time describes two causally separated black holes. To demonstrate this property, the metric is first cast in the Weyl-Lewis-Papapetrou form. After extending this up to the acceleration horizon, it is then transformed to the boost-rotation-symmetric form in which the global properties of the solution are manifest. The physical interpretation of these solutions is thus clarified.