ShantanuT01/DACTYL-Pretraining huggingface dataset:
We have studied the effect of Fe substitution on magnetic and magnetocaloric properties in La0.7Sr0.3Mn1-xFexO3 (x = 0.05, 0.07, 0.10, 0.15, and 0.20) over a wide temperature range (T = 10-400 K). It is shown that substitution by Fe gradually decreases the ferromagnetic Curie temperature (Tc) and saturation magnetization up to x = 0.15 but a dramatic change occurs for x = 0.2. The x = 0.2 sample can be considered as a phase separated compound in which both short-range ordered ferromagnetic and antiferromagnetic phases coexist. The magnetic entropy change (DSm) was estimated from isothermal magnetization curves and it decreases with increase of Fe content from 4.4 J/KgK at 343 K (x = 0.05) to 1.3 J/KgK at 105 K (x = 0.2), under H = 5 T. The La0.7Sr0.3Mn0.93Fe0.07O3 sample shows negligible hysteresis loss, operating temperature over 60 K range around room temperature with refrigerant capacity of 225 J/Kg, and magnetic entropy of 4 J/kgK which will be an interesting compound for application in room temperature refrigeration.
A large single-dish submillimeter-wave telescope equipped with a focal plane array containing ~10^4 bolometers and costing about $120M could locate most protogalaxies in the southern sky within a year of operation.
We study infinite series expansions for the Riemann xi function $\Xi(t)$ in three specific families of orthogonal polynomials: (1) the Hermite polynomials; (2) the symmetric Meixner-Pollaczek polynomials $P_n^{(3/4)}(x;\pi/2)$; and (3) the continuous Hahn polynomials $p_n\left(x; \frac34,\frac34,\frac34,\frac34\right)$. The first expansion was discussed in earlier work by Tur\'an, and the other two expansions are new. For each of the three expansions, we derive formulas for the coefficients, show that they appear with alternating signs, derive formulas for their asymptotic behavior, and derive additional interesting properties and relationships. We also apply some of the same techniques to prove a new asymptotic formula for the Taylor coefficients of the Riemann xi function.   Our results continue and expand the program of research initiated in the 1950s by Tur\'an, who proposed using the Hermite expansion of the Riemann xi function as a tool to gain insight into the location of the Riemann zeta zeros. We also uncover a connection between Tur\'an's ideas and the separate program of research involving the so-called De Bruijn-Newman constant. Most significantly, the phenomena associated with the new expansions in the Meixner-Pollaczek and continuous Hahn polynomial families suggest that those expansions may be even more natural tools than the Hermite expansion for approaching the Riemann hypothesis and related questions.
Using the Livermore X-ray Spectral Synthesizer, which calculates spectral models of highly charged ions based on HULLAC atomic data, we investigate the temperature, density, and photoexcitation dependence of the I(11.92 A)/I(11.77 A) line ratio of Fe XXII. Applied to the Chandra HETG spectrum of the intermediate polar EX Hya, we find that the electron density of its T_e ~ 12 MK plasma is log n_e (cm^-3) = 14.3^{+0.7}_{-0.5}, orders of magnitude greater than that observed in the Sun or other late-type stars.
We study the role of the $\Delta$-isobar current on the response functions for high energy inclusive quasielastic electron scattering from nuclei. We consider a general Lagrangian which is compatible with contact invariance and perform a fully relativistic calculation in first-order perturbation theory for one-particle emission. The dependence of the responses upon off-shell parametrizations is analyzed and found to be mild. A discussion of scaling behaviour and a comparison with various non-relativistic approaches are also presented.
In the Introduction we briefly recall our previous results on stationary electromagnetic fields on black-hole backgrounds and the use of spin-weighted spherical harmonics. We then discuss static electric and magnetic test fields in a Schwarzschild background using some of these results. As sources we do not consider point charges or current loops like in previous works, rather, we analyze spherical shells with smooth electric or magnetic charge distributions as well as electric or magnetic dipole distributions depending on both angular coordinates. Particular attention is paid to the discontinuities of the field, of the 4-potential, and their relation to the source.
The origin and heating mechanisms of warm (50<T<200 K) molecular gas in low-mass young stellar objects (YSOs) are strongly debated. Both passive heating of the inner collapsing envelope by the protostellar luminosity as well as active heating by shocks and by UV associated with the outflows or accretion have been proposed. We aim to characterize the warm gas within protosteller objects, and disentangle contributions from the (inner) envelope, bipolar outflows and the quiescent cloud. High-J CO maps (12CO J=6--5 and 7--6) of the immediate surroundings (up to 10,000 AU) of eight low-mass YSOs are obtained with the CHAMP+ 650/850 GHz array receiver mounted on the APEX telescope. In addition, isotopologue observations of the 13CO J=6--5 transition and [C I] 3P_2-3P_1 line were taken. Strong quiescent narrow-line 12CO 6--5 and 7--6 emission is seen toward all protostars. In the case of HH~46 and Ced 110 IRS 4, the on-source emission originates in material heated by UV photons scattered in the outflow cavity and not just by passive heating in the inner envelope. Warm quiescent gas is also present along the outflows, heated by UV photons from shocks. Shock-heated warm gas is only detected for Class 0 flows and the more massive Class I sources such as HH~46. Outflow temperatures, estimated from the CO 6--5 and 3--2 line wings, are ~100 K, close to model predictions, with the exception of the L~1551 IRS 5 and IRAS 12496-7650, for which temperatures <50 K are found. APEX-CHAMP+ is uniquely suited to directly probe a protostar's feedback on its accreting envelope gas in terms of heating, photodissociation, and outflow dispersal by mapping 1'x1' regions in high-J CO and [C I] lines.
The mutually enriching relationship between graphs and matroids has motivated discoveries in both fields. In this paper, we exploit the similar relationship between embedded graphs and delta-matroids. There are well-known connections between geometric duals of plane graphs and duals of matroids. We obtain analogous connections for various types of duality in the literature for graphs in surfaces of higher genus and delta-matroids. Using this interplay, we establish a rough structure theorem for delta-matroids that are twists of matroids, we translate Petrie duality on ribbon graphs to loop complementation on delta-matroids, and we prove that ribbon graph polynomials, such as the Penrose polynomial, the characteristic polynomial, and the transition polynomial, are in fact delta-matroidal. We also express the Penrose polynomial as a sum of characteristic polynomials.
The general stationary cylindrically symmetric solution of Einstein-massless scalar field system with a non-positive cosmological constant is presented. It is shown that the general solution is characterized by four integration constants. Two of these essential parameters have a local meaning and characterize the gravitational field strength. The other two have a topological origin, as they define an improper coordinate transformation that provides the stationary solution from the static one. The Petrov scheme is considered to explore the effects of the scalar field on the algebraic classification of the solutions. In general, these spacetimes are of type I. However, the presence of the scalar field allows us to find a non-vacuum type O solution and a wider family of type D spacetimes, in comparison with the vacuum case. The mass and angular momentum of the solution are computed using the Regge-Teitelboim method in the case of a negative cosmological constant. In absence of a cosmological constant, the curvature singularities in the vacuum solutions can be removed by including a phantom scalar field, yielding non-trivial locally homogeneous spacetimes. These spacetimes are of particular interest, as they have all their curvature invariants constant.
X-ray timing properties of the magnetar SGR 1900+14 were studied, using the data taken with Suzaku in 2009 and NuSTAR in 2016, for a time lapse of 114 ks and 242 ks, respectively. On both occasions, the object exhibited the characteristic two-component spectrum. The soft component, dominant in energies below $\sim 5$ keV, showed a regular pulsation, with a period of $P=5.21006$ s as determined with the Suzaku XIS, and $P=5.22669$ with NuSTAR. However, in $\gtrsim 6$ keV where the hard component dominates, the pulsation became detectable with the Suzaku HXD and NuSTAR, only after the data were corrected for periodic pulse-phase modulation, with a period of $T=40-44$ ks and an amplitude of $\approx 1$ s. Further correcting the two data sets for complex energy dependences in the phase-modulation parameters, the hard X-ray pulsation became fully detectable, in 12-50 keV with the HXD, and 6-60 keV with NuSTAR, using a common value of $T=40.5 \pm 0.8$ ks. Thus, SGR 1900+14 becomes a third example, after 4U 0142+61 and 1E 1547$-$5408, to show the hard X-ray pulse-phase modulation, and a second case of energy dependences in the modulation parameters. The neutron star in this system is inferred to perform free precession, as it is axially deformed by $\approx P/T =1.3 \times 10^{-4}$ presumably due to $\sim 10^{16}$ G toroidal magnetic fields. As a counter example, the Suzaku data of the binary pulsar 4U 1626-67 were analyzed, but no similar effect was found. These results altogether argue against the accretion scenario for magnetars.
NGC6240 is a well-studied nearby galaxy system in the process of merging. Based on optical, X-ray, and radio observations, it is thought to harbor two active nuclei We carried out a detailed optical 3D spectroscopic study to investigate the inner region of this system in connection with existing MERLIN and VLBA data. We observed NGC6240 with very high spatial resolution using the MUSE instrument in the Narrow-Field Mode with the four-laser GALACSI adaptive optics system on the ESO VLT under seeing conditions of 0.49 arcsec. Our 3D spectra cover the wavelength range from 4725 to 9350 AA at a spatial resolution of ~75 mas. We report the discovery of three nuclei in the final state of merging within a region of only 1 kpc in the NGC6240 system.Thanks to MUSE we are able to show that the formerly unresolved southern component actually consists of two distinct nuclei separated by only 198 pc. In combination with Gaia data we reach an absolute positional accuracy of only 30 mas that is essential to compare optical spectra with MERLIN and VLBA radio positions. The verification and detailed study of a system with three nuclei, two of which are active and each with a mass in excess of $9\times10^{7} M_{\odot}$, is of great importance for the understanding of hierarchical galaxy formation via merging processes since multiple mergers lead to a faster evolution of massive galaxies in comparison to binary mergers. So far it has been suggested that the formation of galactic nuclei with multiple supermassive black holes (SMBHs) is expected to be rare in the local universe.Triple massive black hole systems might be of fundamental importance for the coalescence of massive black hole binaries in less than a Hubble time leading to the loudest sources of gravitational waves in the millihertz regime.
In this paper we show that the l^n-torsion part of the cohomological Brauer groups of certain schemes associated to symmetric powers of a projective smooth curve over a separably closed field k are isomorphic, when `l is invertible in k. The schemes considered are the Symmetric powers themselves, then the corresponding Picard schemes and also certain Quot-schemes. We also obtain similar results for Prym varieties associated to certain finite covers of such curves: we prove such results only for curves defined over the field of complex numbers.
Unconventional quasiparticle excitations in condensed matter systems have become one of the most important research frontiers. Beyond two- and fourfold degenerate Weyl and Dirac fermions, three-, six- and eightfold symmetry protected degeneracies have been predicted however remain challenging to realize in solid state materials. Here, charge density wave compound TaTe4 is proposed to hold eightfold fermionic excitation and Dirac point in energy bands. High quality TaTe4 single crystals are prepared, where the charge density wave is revealed by directly imaging the atomic structure and a pseudogap of about 45 meV on the surface. Shubnikov de-Haas oscillations of TaTe4 are consistent with band structure calculation. Scanning tunneling microscopy reveals atomic step edge states on the surface of TaTe4. This work uncovers that charge density wave is able to induce new topological phases and sheds new light on the novel excitations in condensed matter materials.
We study the stability of the normal bundle of canonical genus $8$ curves and prove that on a general curve the bundle is stable. The proof rests on Mukai's description of these curves as linear sections of a Grassmannian $\mathrm{G}(2,6)$. This is the next case of a conjecture by M. Aprodu, G. Farkas, and A. Ortega: the general canonical curve of every genus $g \geq 7$ should have stable normal bundle. We also give some more evidence for this conjecture in higher genus.
We present an analysis of the relationship between the orientation of magnetic fields and filaments that form in 3D magnetohydrodynamic simulations of cluster-forming, turbulent molecular cloud clumps. We examine simulated cloud clumps with size scales of L ~ 2-4 pc and densities of n ~ 400-1000 cm^-3 with Alfven Mach numbers near unity. We simulated two cloud clumps of different masses, one in virial equilibrium, the other strongly gravitationally bound, but with the same initial turbulent velocity field and similar mass-to-flux ratio. We apply various techniques to analyze the filamentary and magnetic structure of the resulting cloud, including the DisPerSE filament-finding algorithm in 3D. The largest structure that forms is a 1-2 parsec-long filament, with smaller connecting sub-filaments. We find that our simulated clouds, wherein magnetic forces and turbulence are comparable, coherent orientation of the magnetic field depends on the virial parameter. Subvirial clumps undergo strong gravitational collapse and magnetic field lines are dragged with the accretion flow. We see evidence of filament-aligned flow and accretion flow onto the filament in the subvirial cloud. Magnetic fields oriented more parallel in the subvirial cloud and more perpendicular in the denser, marginally bound cloud. Radiative feedback from a 16 Msun star forming in a cluster in one of our simulations ultimately results in the destruction of the main filament, the formation of an HII region, and the sweeping up of magnetic fields within an expanding shell at the edges of the HII region.
We answer a question of T.Shioda and show that, for any positive integer $m$ prime to 6, the Picard group of the Fermat surface $\Phi_m$ is generated by the classes of lines contained in $\Phi_m$.
We present photometric and spectroscopic observations of the type Ibn supernova (SN) 2019uo, the second ever SN Ibn with flash ionization (He II, C III, N III) features in its early spectra. SN 2019uo displays a rapid post-peak luminosity decline of 0.1 mag d$^{-1}$ similar to most of the SNe Ibn, but is fainter ($M^V_{max} = -18.30 \pm 0.24$ mag) than a typical SN Ibn and shows a color evolution that places it between SNe Ib and the most extreme SNe Ibn. SN 2019uo shows P-cygni He I features in the early spectra which gradually evolves and becomes emission dominated post peak. It also shows faster evolution in line velocities as compared to most other members of the type Ibn subclass. The bolometric light curve is fairly described by a $^{56}$Ni + circumstellar interaction model.
The optical light that is generated simultaneously with the x-rays and gamma-rays during a gamma-ray burst (GRB) provides clues about the nature of the explosions that occur as massive stars collapse to form black holes. We report on the bright optical flash and fading afterglow from the powerful burst GRB 130427A and present a comparison with the properties of the gamma-ray emission that show correlation of the optical and >100 MeV photon flux light curves during the first 7,000 seconds. We attribute this correlation to co-generation in an external shock. The simultaneous, multi-color, optical observations are best explained at early times by reverse shock emission generated in the relativistic burst ejecta as it collides with surrounding material and at late times by a forward shock traversing the circumburst environment. The link between optical afterglow and >100 MeV emission suggests that nearby early peaked afterglows will be the best candidates for studying GRB emission at GeV/TeV energies.
The medical image is characterized by the inter-class indistinction, high variability, and noise, where the recognition of pixels is challenging. Unlike previous self-attention based methods that capture context information from one level, we reformulate the self-attention mechanism from the view of the high-order graph and propose a novel method, namely Hierarchical Attention Network (HANet), to address the problem of medical image segmentation. Concretely, an HA module embedded in the HANet captures context information from neighbors of multiple levels, where these neighbors are extracted from the high-order graph. In the high-order graph, there will be an edge between two nodes only if the correlation between them is high enough, which naturally reduces the noisy attention information caused by the inter-class indistinction. The proposed HA module is robust to the variance of input and can be flexibly inserted into the existing convolution neural networks. We conduct experiments on three medical image segmentation tasks including optic disc/cup segmentation, blood vessel segmentation, and lung segmentation. Extensive results show our method is more effective and robust than the existing state-of-the-art methods.
We propose an architecture for realizing quantum information transfer (QIT). In this architecture, a LC circuit is used to induce the necessary interaction between flux qubits, each magnetically coupling to a nitrogen-vacancy center ensemble (NVCE). We explicitly show that for resonant interaction and large detuning cases, high-fidelity QIT between two spatially-separated NVCEs can be implemented. Our proposal can be extended to achieve QIT between any two selected NVCEs in a large hybrid system by adjusting system parameters, which is important in large scale quantum information processing.
We show that the gauge singlet scalar boson in low-energy supersymmetric model may behave as the standard model (SM) Higgs boson if the singlet couples to (heavy) vector-like colored particles. In this case, the SM-Higgs-like signal at the LHC can be mimicked by the singlet production process for wide range of the singlet mass.
Hardware-aware neural architecture designs have been predominantly focusing on optimizing model performance on single hardware and model development complexity, where another important factor, model deployment complexity, has been largely ignored. In this paper, we argue that, for applications that may be deployed on multiple hardware, having different single-hardware models across the deployed hardware makes it hard to guarantee consistent outputs across hardware and duplicates engineering work for debugging and fixing. To minimize such deployment cost, we propose an alternative solution, multi-hardware models, where a single architecture is developed for multiple hardware. With thoughtful search space design and incorporating the proposed multi-hardware metrics in neural architecture search, we discover multi-hardware models that give state-of-the-art (SoTA) performance across multiple hardware in both average and worse case scenarios. For performance on individual hardware, the single multi-hardware model yields similar or better results than SoTA performance on accelerators like GPU, DSP and EdgeTPU which was achieved by different models, while having similar performance with MobilenetV3 Large Minimalistic model on mobile CPU.
We show the effect of composition on structural and magnetic characteristics of pure phase polycrystalline Ga<2-x>Fe<x>O<3> (GFO) for compositions between 0.8 <= x <= 1.3. X-ray analysis reveals that lattice parameters of GFO exhibit a linear dependence on Fe content in single phase region indicating manifestation of Vegard's law. Increasing Fe content of the samples also leads to stretching of bonds as indicated by the Raman peak shifts. Further, low temperature magnetic measurements show that the coercivity of the samples is maximum for Ga:Fe ratio of 1:1 driven by a competition between decreasing crystallite size and increasing magnetic anisotropy.
Motivated by recent observations of the star formation rate density function out to z~7, we describe a simple model for the star formation rate density function at high redshift based on the extended Press-Schechter formalism. This model postulates a starburst following each major merger, lasting for a time t_SF and converting at most f_star of galactic gas into stars. We include a simple physical prescription for supernovae feedback that suppresses star formation in low mass galaxies. Constraining t_SF and f_star to describe the observed star formation rate density at high redshifts, we find that individual starbursts were terminated after a time t_SF~10^7 years. This is comparable to the main-sequence lifetimes of supernova progenitors, indicating that high redshift starbursts are quenched once supernovae feedback had time to develop. High redshift galaxies convert ~10% of their mass into stars for galaxies with star formation rates above ~1 solar mass per year, but a smaller fraction for lower luminosity galaxies. Our best fit model successfully predicts the observed relation between star formation rate and stellar mass at z>~4, while our deduced relation between stellar mass and halo mass is also consistent with data on the dwarf satellites of the Milky Way. We find that supernovae feedback lowers the efficiency of star formation in the lowest mass galaxies and makes their contribution to reionization small. As a result, photo-ionization feedback on low mass galaxy formation does not significantly affect the reionization history. Using a semi-analytic model for the reionization history, we infer that approximately half of the ionizing photons needed to complete reionization have already been observed in star-forming galaxies.
The one dimensional symmetric simple exclusion process (SSEP) is one of the very few exactly soluble models of non-equilibrium statistical physics. It describes a system of particles which diffuse with hard core repulsion on a one dimensional lattice in contact with two reservoirs of particles at unequal densities. The goal of this note is to review the two main approaches which lead to the exact expression of the large deviation functional of the density of the SSEP in its steady state: a microscopic approach (based on the matrix product ansatz and an additivity property) and a macroscopic approach (based on the macroscopic fluctuation theory of Bertini, De Sole, Gabrielli, Jona-Lasinio and Landim).