ShantanuT01/DACTYL-Pretraining huggingface dataset:
Spin current injection and spin accumulation near a ferromagnetic insulator (FI)/nonmagnetic metal (NM) bilayer film under a thermal gradient is investigated theoretically. Using the Fermi golden rule and the Boltzmann equations, we find that FI and NM can exchange spins via interfacial electron-magnon scattering because of the imbalance between magnon emission and absorption caused by either non-equilibrium distribution of magnons or non-equilibrium between magnons and electrons. A temperature gradient in FI and/or a temperature difference across the FI/NM interface generates a spin current which carries angular momenta parallel to the magnetization of FI from the hotter side to the colder one. Interestingly, the spin current induced by a temperature gradient in NM is negligibly small due to the nonmagnetic nature of the non-equilibrium electron distributions. The results agree well with all existing experiments.
We suggest the application of nitronylnitroxide substituted with methyl group and 2,2,6,6-tetramethylpiperidin organic radicals as 1/2-spin qubits for self-assembled monolayer quantum devices. We show that the oscillating cantilever driven adiabatic reversals technique can provide the read-out of the spin states. We compute components of the $g$-tensor and dipole-dipole interaction tensor for these radicals. We show that the delocalization of the spin in the radical may significantly influence the dipole-dipole interaction between the spins.
We study a model of weakly ionized, protostellar accretion discs that are threaded by a large-scale, ordered magnetic field and power a centrifugally driven wind. We consider the limiting case where the wind is the main repository of the excess disc angular momentum and generalize the radially localized disc model of Wardle & K\"onigl (1993), which focussed on the ambipolar diffusion regime, to other field diffusivity regimes, notably Hall and Ohm. We present a general formulation of the problem for nearly Keplerian, vertically isothermal discs using both the conductivity-tensor and the multi-fluid approaches and simplify it to a normalized system of ordinary differential equations in the vertical space coordinate. We determine the relevant parameters of the problem and investigate, using the vertical-hydrostatic-equilibrium approximation and other simplifications, the parameter constraints on physically viable solutions for discs in which the neutral particles are dynamically well coupled to the field already at the midplane. When the charged particles constitute a two-component ion--electron plasma one can identify four distinct sub-regimes in the parameter domain where the Hall diffusivity dominates and three sub-regimes in the Ohm-dominated domain. Two of the Hall sub-regimes can be characterized as being ambipolar diffusion-like and two as being Ohm-like. When the two-component plasma consists instead of positively and negatively charged grains of equal mass, the entire Hall domain and one of the Ohm sub-regimes disappear. In all viable solutions the midplane neutral--ion momentum exchange time is shorter than the local orbital time. Vertical magnetic squeezing always dominates over gravitational tidal compression in this model. (Abridged)
In the stable marriage problem N men and N women have to be matched by pairs under the constraint that the resulting matching is stable. We study the statistical properties of stable matchings in the large N limit using both numerical and analytical methods. Generalizations of the model including singles and unequal numbers of men and women are also investigated.
The cosmological sector to the full non-linear topologically massive gravity (TMG) is obtained for localized sources of mass $m$ and spin $\sigma$ besides the asymptotically spinning conical flat sector previously obtained. In a small region near but outside the sources, the metric resembles the spinning conical flat metric, but we find that the mass $m$ creates a negative deficit angle of $3m$ as opposed to $m$. Furthermore, it is not possible to recover the results of pure Einstein gravity in the limit $\mu \to \infty$ unlike the flat sector.
A new Nilsson single-particle structure is proposed for neutron-rich nuclei near $^{132}$Sn. In general, a large reduction in spin-orbit interaction is required and the neutron $N = 82$ gap persists in the new set of parameters. The ground state deformations for several isotopic chains are studied with this set and compared with the results of the standard set and with measured ones. Collective bands in two even-even, neutron-rich nuclei are calculated using the Projected Shell Model with the new set of parameters and improved agreement with existing data is found.
We study proton-gold collisions at RHIC energy $\sqrt{s_{NN}}=200$ GeV within the Parton-Hadron-String Dynamics (PHSD) off-shell transport approach, investigating the influence of the intense electromagnetic fields generated in these small systems. We show the space-time evolution of the magnetic and electric components, emphasizing the huge values of the latter one, in particular the electric field $E_x$ along the impact parameter direction whose magnitude is comparable to the magnetic field $B_y$ perpendicular to the reaction plane. We find a fair agreement of the charged particle pseudorapidity density of the high-multiplicity events with respect to the experimental result of the PHENIX Collaboration. Focusing on the most central collision, we show rapidity distributions and spectra as well as the flow coefficients $v_1$ and $v_2$ and we discuss the impact of the electromagnetic fields on identified particle observables. We compute the directed flow $v_1$ of $\pi^+$, $\pi^-$, $K^+$, $K^-$ for collisions at fixed impact parameter and predict that an electromagnetically-induced splitting in the $v_1$ of positively and negatively charged particles is generated in the Au-going side of p+Au reaction mainly driven by the huge $E_x$ component. We find that this effect is stronger for the strange mesons and increases for increasing impact parameter. Furthermore, we highlight the amount of directed flow generated in the deconfined phase, finding that it constitutes the main contribution in the central rapidity region, especially for kaons. Thus, we support the idea that the directed flow is a promising probe for the electromagnetic fields generated in relativistic nuclear collisions and show that in proton-induced reactions the electric component along the impact parameter axis is the primary origin of a charge-odd $v_1$ of pions and kaons.
Theoretical interpretations of the high-Q^2 events recently observed in deep-inelastic positron-proton scattering at HERA are reviewed. We discuss leptoquarks, squarks with R-parity violating couplings, and contact interactions. Bounds from and implications on other experiments are taken into consideration.
We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z~1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in two hour exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [OIII]/Hb ratio is insufficient as an AGN indicator at z>1. For the four X-ray detected galaxies, the classic diagnostics ([OIII]/Hb vs. [NII]/Ha and [SII]/Ha) remain consistent with X-ray AGN/SF classification. The X-ray data also suggest that "composite" galaxies (with intermediate AGN/SF classification) host bona-fide AGNs. Nearly 2/3 of the z~1.5 emission-line galaxies have nuclear activity detected by either X-rays or the classic diagnostics. Compared to the X-ray and line ratio classifications, the mass-excitation method remains effective at z>1, but we show that the color-excitation method requires a new calibration to successfully identify AGNs at these redshifts.
Batyrev (et. al.) constructed a family of Calabi-Yau varieties using small toric degenerations of the full flag variety G/B. They conjecture this family to be mirror to generic anti-canonical hypersurfaces in G/B. Recently Alexeev and Brion, as a part of their work on toric degenerations of spherical varieties, have constructed many degenerations of G/B. For any such degeneration we construct a family of varieties, which we prove coincides with Batyrev's in the small case. We prove that any two such families are birational, thus proving that mirror families are independent of the choice of degeneration. The birational maps involved are closely related to Berenstein and Zelevinsky's geometric lifting of tropical maps to maps between totally positive varieties.
We report the Fermi Large Area Telescope's detection of extended gamma-ray emission towards the direction of the young massive star cluster NGC 3603. The emission shows a hard spectrum with a photon index of 2.3 from 1 GeV to 250 GeV. The large size and high luminosity of this structure make it unlikely a pulsar wind nebular. On the other hand the spatial correlation with the ionised gas indicate a hadronic origin. The total cosmic ray (CR) protons energy are estimated to be of the order $10^{50} ~\rm erg$ assuming the gamma-ray are produced in the interaction of CRs with ambient gas . The environment and spectral features show significant similarity with the Cygnus cocoon. It reveals that the young star clusters may be a gamma-ray source population and they can potentially accelerate a significant fraction of the Galactic cosmic rays.
In this paper, we analyze some of our real-world deployment of face recognition (FR) systems for various applications and discuss the gaps between expectations of the user and what the system can deliver. We evaluate some of our proposed algorithms with ad-hoc modifications for applications such as FR on wearable devices (like Google Glass), monitoring of elderly people in senior citizens centers, FR of children in child care centers and face matching between a scanned IC/passport face image and a few live webcam images for automatic hotel/resort checkouts. We describe each of these applications, the challenges involved and proposed solutions. Since FR is intuitive in nature and we human beings use it for interactions with the outside world, people have high expectations of its performance in real-world scenarios. However, we analyze and discuss here that it is not the case, machine recognition of faces for each of these applications poses unique challenges and demands specific research components so as to adapt in the actual sites.
Few-shot object detection (FSOD) aims to strengthen the performance of novel object detection with few labeled samples. To alleviate the constraint of few samples, enhancing the generalization ability of learned features for novel objects plays a key role. Thus, the feature learning process of FSOD should focus more on intrinsical object characteristics, which are invariant under different visual changes and therefore are helpful for feature generalization. Unlike previous attempts of the meta-learning paradigm, in this paper, we explore how to enhance object features with intrinsical characteristics that are universal across different object categories. We propose a new prototype, namely universal prototype, that is learned from all object categories. Besides the advantage of characterizing invariant characteristics, the universal prototypes alleviate the impact of unbalanced object categories. After enhancing object features with the universal prototypes, we impose a consistency loss to maximize the agreement between the enhanced features and the original ones, which is beneficial for learning invariant object characteristics. Thus, we develop a new framework of few-shot object detection with universal prototypes ({FSOD}^{up}) that owns the merit of feature generalization towards novel objects. Experimental results on PASCAL VOC and MS COCO show the effectiveness of {FSOD}^{up}. Particularly, for the 1-shot case of VOC Split2, {FSOD}^{up} outperforms the baseline by 6.8% in terms of mAP.
We prove that only for powers of 2 and 3 could occur counterexamples to the local-global divisibility principle for elliptic curves defined over the rationals. For we refine our previous criterion for the validity of the principle. We also give an example that shows that the assumptions of our criterion are necessary.
In this study, the detailed magnetic field structure of the dense protostellar core Barnard 335 (B335) was revealed based on near-infrared polarimetric observations of background stars to measure dichroically polarized light produced by magnetically aligned dust grains in the core. Magnetic fields pervading B335 were mapped using 24 stars after subtracting unrelated ambient polarization components, for the first time revealing that they have an axisymmetrically distorted hourglass-shaped structure toward the protostellar core. On the basis of simple two- and three-dimensional magnetic field modeling, magnetic inclination angles in the plane-of-sky and line-of-sight directions were determined to be $90^{\circ} \pm 7^{\circ}$ and $50^{\circ} \pm 10^{\circ}$, respectively. The total magnetic field strength of B335 was determined to be $30.2 \pm 17.7$ $\mu {\rm G}$. The critical mass of B335, evaluated using both magnetic and thermal/turbulent support against collapse, was determined to be $M_{\rm cr} = 3.37 \pm 0.94$ ${\rm M}_{\odot}$, which is identical to the observed core mass of $M_{\rm core}=3.67$ M$_{\odot}$. We thus concluded that B335 started its contraction from a condition near equilibrium. We found a linear relationship in the polarization versus extinction diagram, up to $A_V \sim 15$ mag toward the stars with the greatest obscuration, which verified that our observations and analysis provide an accurate depiction of the core.
We investigate heating and evolution of flare loops in a C4.7 two-ribbon flare on 2011 February 13. From SDO/AIA imaging observations, we can identify two sets of loops. Hinode/EIS spectroscopic observations reveal blueshifts at the feet of both sets of loops. The evolution and dynamics of the two sets are quite different. The first set of loops exhibits blueshifts for about 25 minutes followed by redshifts, while the second set shows stronger blueshifts, which are maintained for about one hour. The UV 1600 observation by AIA also shows that the feet of the second set of loops brighten twice. These suggest that continuous heating may be present in the second set of loops. We use spatially resolved UV light curves to infer heating rates in the few tens of individual loops comprising the two loop systems. With these heating rates, we then compute plasma evolution in these loops with the "enthalpy-based thermal evolution of loops" (EBTEL) model. The results show that, for the first set of loops, the synthetic EUV light curves from the model compare favorably with the observed light curves in six AIA channels and eight EIS spectral lines, and the computed mean enthalpy flow velocities also agree with the Doppler shift measurements by EIS. For the second set of loops modeled with twice-heating, there are some discrepancies between modeled and observed EUV light curves in low-temperature bands, and the model does not fully produce the prolonged blueshift signatures as observed. We discuss possible causes for the discrepancies.
We present a comprehensive spectral and temporal study of the black hole X-ray transient MAXI J1820+070 during its outbursts in 2018 using Swift/XRT, NICER, NuSTAR and AstroSat observations. The Swift/XRT and NICER spectral study shows a plateau in the light curve with spectral softening (hardness changes from $\sim$ $2.5$ to $2$) followed by a gradual decline without spectral softening during the first outburst. Also, spectral modelling suggests that the first outburst is in the low/hard state throughout with a truncated disk whereas the thermal disk emission dominates during the second outburst. During the entire outburst, strong reflection signature (reflection fraction varies between $\sim$ $0.38 - 3.8$) is observed in the simultaneous wideband (NICER-NuSTAR, XRT-NuSTAR, AstroSat) data due to the presence of a dynamically evolving corona. The NICER timing analysis shows Quasi-periodic Oscillation (QPO) signatures and the characteristic frequency increases (decreases) in the plateau (decline) phase with time during the first outburst. We understand that the reduction of the electron cooling timescale in the corona due to spectral softening and the resonance oscillation with the local dynamical timescale may explain the above behavior of the source during the outburst. Also, we propose a possible scenario of outburst triggering and the associated accretion geometry of the source.
We performed a search for eclipsing and dipping sources in the archive of the EXTraS project - a systematic characterization of the temporal behaviour of XMM-Newton point sources. We discovered dips in the X-ray light curve of 3XMM J004232.1+411314, which has been recently associated with the hard X-ray source dominating the emission of M31. A systematic analysis of XMM-Newton observations revealed 13 dips in 40 observations (total exposure time $\sim$0.8 Ms). Among them, four observations show two dips, separated by $\sim$4.01 hr. Dip depths and durations are variable. The dips occur only during low-luminosity states (L$_{0.2-12}<1\times10^{38}$ erg s$^{-1}$), while the source reaches L$_{0.2-12}\sim2.8\times10^{38}$ erg s$^{-1}$. We propose this system to be a new dipping Low-Mass X-ray Binary in M31 seen at high inclination (60$^{\circ}$-80$^{\circ}$), the observed dipping periodicity is the orbital period of the system. A blue HST source within the Chandra error circle is the most likely optical counterpart of the accretion disk. The high luminosity of the system makes it the most luminous dipper known to date.
The new bismuth chalcogenide La0.92Bi1.08S3 crystallizes in the monoclinic space group C2/m with a = 28.0447(19) {\AA}, b = 4.0722(2) {\AA}, c = 14.7350(9) {\AA}, and $\beta$ = 118.493(5){\deg}. The structure of La0.92Bi1.08S3 is built up of NaCl-type Bi2S5 blocks, and BiS4 and LaS5 infinitely long chains forming a compact three-dimensional framework with parallel tunnels. Optical spectroscopy and resistivity measurements reveal a semiconducting behavior with a band gap of ~ 1 eV and activation energy for transport of 0.36(1) eV. Thermopower measurements suggest the majority carriers of La0.92Bi1.08S3 are electrons. Heat capacity measurements indicate no phase transitions from 2 to 300 K. Band structure calculations at the density functional theory level confirm the semiconducting nature and the indirect gap of La0.92Bi1.08S3.
The real Ginibre ensemble consists of random $N \times N$ matrices formed from i.i.d. standard Gaussian entries. By using the method of skew orthogonal polynomials, the general $n$-point correlations for the real eigenvalues, and for the complex eigenvalues, are given as $n \times n$ Pfaffians with explicit entries. A computationally tractable formula for the cumulative probability density of the largest real eigenvalue is presented. This is relevant to May's stability analysis of biological webs.
CaCO3 crystals' physical properties, such as polymorphism and hence the reflectivity and stability, are critical factors of their qualities in industrial applications. Factors such as additives and substrates that influence CaCO3 polymorphism have been intensively studied. However, the effects of ionic strength created by varying additives are seldom paid attention to. This study is analyzing how ionic strength of the growth solution influences the crystalline structure of CaCO3, by applying growth solutions containing different types of cations of varying concentrations, K+, Na+, and NH4+. This study reveals that the ionic strength plays a significant role in polymorph selection in the way that the percentage of vaterite among the precipitates increases with the concentration of ionic strength.
Sgr A* is currently being fed by winds from a cluster of gravitationally bound young mass-loosing stars. Using observational constraints on the orbits, mass loss rates and wind velocities of these stars, we numerically model the distribution of gas in the ~ 0.1--10'' region around Sgr A*. We find that radiative cooling of recently discovered slow winds leads to the formation of many cool filaments and blobs, and to a thin and rather light accretion disc of about an arcsecond scale. The disc however does not extend all the way to our inner boundary. Instead, hot X-ray emitting gas dominates the inner arcsecond. In our simulations, cool streams of gas frequently enter this region on low angular momentum orbits, and are then disrupted and heated up to the ambient hot gas temperature. The accreting gas around Sgr A* is thus two-phase, with a hot component, observable at X-ray wavelengths, and a cool component, which may be responsible for the majority of time variability of Sgr A* emission on hundred and thousand years time-scales. We obtain an accretion rate of a few times 10^-6 msun/year, consistent with Chandra estimates, but variable on time-scales even shorter than hundred years. These results strongly depend on the chosen stellar orbits and wind parameters. Further observational input is thus key to a better modelling of Sgr A* wind accretion.
We carried out visual and parametric searches for dwarf galaxies in five loose groups of galaxies. Follow-up spectroscopy with the HET has shown a 50% success rate of morphological selection. The evolutionary status of the studied groups differs: while the NGC 6962 group has a partially relaxed core, surrounded by an infall region, the NGC 5005/5033 group and the IC 65 group, which consist only of late-type galaxies, are probably still assembling.
Superfluidity is a generic feature of various quantum systems at low temperatures and it is in particular important for the description of dynamics of low energy nuclear reactions. The time-dependent density functional theory (TDDFT) is, to date, the only microscopic method which takes into account in a consistent way far from equilibrium dynamics of pairing field and single-particle degrees of freedom. The local version of TDDFT, so called TDSLDA, is particularly useful for the description of nuclear reactions and is well suited for leadership class computers of hybrid (CPU+GPU) architecture. The preliminary results obtained for collisions involving both medium-mass and heavy nuclei at the energies around the Coulomb barrier are presented.