ShantanuT01/DACTYL-Pretraining huggingface dataset:
Schemes of switching nanomagnetic memories via the effect of spin torque with various polarizations of injected electrons are studied. Simulations based on macrospin and micromagnetic theories are performed and compared. We demonstrate that switching with perpendicularly polarized current by short pulses and free precession requires smaller time and energy than spin torque switching with collinear in plane spin polarization; it is also found to be superior to other kinds of memories. We study the tolerances of switching to the magnitude of current and pulse duration. An increased Gilbert damping is found to improve tolerances of perpendicular switching without increasing the threshold current, unlike in plane switching.
The supermassive black hole Sgr A* at the center of the Galaxy is surrounded by two misaligned disks of young, massive stars extending from ~0.04 to 0.4 pc. The stellar surface density increases as ~ r^-2 towards Sgr A* but is truncated within 1" (0.04pc). We explore the origin of this annulus using a model in which star formation occurs in a disk of gas created through the partial capture of a gas cloud as it sweeps through the inner few parsecs of the galaxy and temporarily engulfs Sgr A*. We identify the locations within which star formation and/or accretion onto Sgr A* take place. Within 0.04 pc the disk is magnetically active and the associated heating and enhanced pressure prevents the disk from becoming self gravitating. Instead, it forms a magneto-turbulent disk that drains onto Sgr A* within 3 Myr. Meanwhile, fragmentation of the gas beyond the central 0.04 pc hole creates the observed young stellar disk. The two large scale bubbles of gamma-ray emission extending perpendicular to the Galactic plane may be created by a burst of accretion of ~10^5 Msun of gas lying between 0.01 and 0.03 pc. The observed stellar ages imply that this capture event occurred ~10^6.5 yr ago, thus such events occurring over the life time of the Galaxy could have significantly contributed to the current mass of Sgr A* and to the inner few parsec of the nuclear star cluster. We suggest that these events also occur in extragalactic systems.
We present the first wavelet-based all-electron density-functional calculations to include gradient corrections and the first in a solid. Direct comparison shows this approach to be unique in providing systematic ``transparent'' convergence, convergence with a priori prediction of errors, to beyond chemical (millihartree) accuracy. The method is ideal for exploration of materials under novel conditions where there is little experience with how traditional methods perform and for the development and use of chemically accurate density functionals, which demand reliable access to such precision.
We consider the sum of squares function in the ring $\mathbb{Z}_{n}$. We determine formulae in a number of cases when $n$ is a power of a prime.
We have established a relation between the brightest super star cluster magnitude in a galaxy and the host star formation rate (SFR) for the first time in the near infrared (NIR). The data come from a statistical sample of ~ 40 luminous IR galaxies (LIRGs) and starbursts utilizing K-band adaptive optics imaging. While expanding the observed relation to longer wavelengths, less affected by extinction effects, it also pushes to higher SFRs. The relation we find, M_K ~ - 2.6 log SFR, is similar to that derived previously in the optical and at lower SFRs. It does not, however, fit the optical relation with a single optical to NIR color conversion, suggesting systematic extinction and/or age effects. While the relation is broadly consistent with a size-of-sample explanation, we argue physical reasons for the relation are likely as well. In particular, the scatter in the relation is smaller than expected from pure random sampling strongly suggesting physical constraints. We also derive a quantifiable relation tying together cluster-internal effects and host SFR properties to possibly explain the observed brightest SSC magnitude vs. SFR dependency.
Thirteen explosion sites of type II-P and II-L supernovae in nearby galaxies have been observed using integral field spectroscopy, enabling both spatial and spectral study of the explosion sites. We used the properties of the parent stellar population of the coeval supernova progenitor star to derive its metallicity and initial mass (c.f. Paper I). The spectrum of the parent stellar population yields the estimates of metallicity via strong-line method, and age via comparison with simple stellar population (SSP) models. These metallicity and age parameters are adopted for the progenitor star. Age, or lifetime of the star, was used to derive initial (ZAMS) mass of the star by comparing with stellar evolution models. With this technique, we were able to determine metallicity and initial mass of the SN progenitors in our sample. Our result indicates that some type-II supernova progenitors may have been stars with mass comparable to SN Ib/c progenitors.
We revisit the work of Lehn-Lehn-Sorger-van Straten on twisted cubic curves in a cubic fourfold not containing a plane in terms of moduli spaces. We show that the blow-up $Z'$ along the cubic of the irreducible holomorphic symplectic eightfold $Z$, described by the four authors, is isomorphic to an irreducible component of a moduli space of Gieseker stable torsion sheaves or rank three torsion free sheaves. For a very general such cubic fourfold, we show that $Z$ is isomorphic to a connected component of a moduli space of tilt-stable objects in the derived category and to a moduli space of Bridgeland stable objects in the Kuznetsov component. Moreover, the contraction between $Z'$ and $Z$ is realized as a wall-crossing in tilt-stability. Finally, $Z$ is birational to an irreducible component of Gieseker stable aCM bundles of rank six.
We have performed a high-resolution angle resolved Ce 4$d-4f$ resonant photoemission experiment on the heavy fermion superconductor CeIrIn$_5$. We have observed a quasi-particle band which has an energy dispersion of $\sim 30$ meV in the Ce 4$f$ on-resonance spectra. The result suggests that although the 4$f$ spectra are dominated by the localized/correlated character, the small itinerant component is responsible for the superconductivity in this compound.
We present new sets of pion and kaon fragmentation functions obtained in NLO combined analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering with either pions or kaons identified in the final state. At variance with all previous fits, the present analyses take into account data where hadrons of different electrical charge are identified, which allow to discriminate quark from anti-quark fragmentation functions without the need of non trivial flavor symmetry assumptions. The resulting sets are in good agreement with all data analyzed, which cover a much wider kinematical range than in previous fits. An extensive use of the Lagrange multiplier technique is made in order to assess the uncertainties in the extraction of the fragmentation functions and the synergy from the complementary data sets in our global analysis.
Gamma Cas (B0.5IVe) is the noted prototype of a subgroup of classical Be stars exhibiting hard thermal X-ray emission. This paper reports results from a 23-year optical campaign with an Automated Photometric Telescope (APT) on this star. A series of unstable long cycles of length 56--91 days has nearly ceased over the last decade. Herein, we revise the frequency of the dominant coherent signal at 0.82238 cy/d. This signal's amplitude has nearly disappeared in the last 15 years but has somewhat recovered its former strength. We confirm the presence of secondary nonradial pulsation signals found by other authors at frequencies 1.25, 2.48, and 5.03 cy/d. The APT data from intensively monitored nights reveal rapidly variable amplitudes among these frequencies. We show that peculiarities in the 0.82 cy/d waveform exist that can vary even over several days. Although the 0.82 cy/d frequency is near the star's presumed rotation frequency. However, because of its phase slippage with respect to a dip pattern in the star's far-UV light curve it is preferable to consider the latter pattern, not the 0.82 cy/d signal, that carries a rotation signature. We also find hints of the UV dip pattern in periodograms of early-season APT data.
We examine whether existing data in clusters, both old and young, and in the field of the Galactic disk and halo is consistent with a universal slope for the initial mass function (IMF). The most reasonable statement that can be made at the current time is that there is no strong evidence to support a claim of any real variations in this slope. If the IMF slope is universal then this in itself is remarkable implying that variations in metallicity, gas density or other environmental factors in the star formation process play no part in determining the slope of the mass function.
We identify the two dimensional AdS subsupergroup $OSp(16/2,R)$ of the M-theory supergroup $OSp(1/32,R)$ which captures the dynamics of $n$ $D0$-branes in the large $n$ limit of Matrix theory. The $Sp(2,R)$ factor in the even subgroup $SO(16) \times Sp(2,R)$ of $OSp(16/2,R)$ corresponds to the AdS extension of the Poincare symmetry of the longitudinal directions. The infinite number of $D0$-branes with ever increasing and quantized values of longitudinal momenta are identified with the Fourier modes of the singleton supermultiplets of $OSp(16/2,R)$,which consist of 128 bosons and 128 fermions. The large $n$ limit of N=16 U(n) Yang-Mills quantum mechanics which describes Matrix theory is a conformally invariant N=16 singleton quantum mechanics living on the boundary of $AdS_{2}$. We also review some of the earlier results on the spectra of Kaluza-Klein supergravity theories in relation to the recent conjecture of Maldacena relating the dynamics of $n$ $Dp$-branes to certain AdS supergravity theories. We point out the remarkable parallel between the conjecture of Maldacena and the construction of the spectra of $11-d$ and type $IIB$ supergravity theories compactified over various spheres in terms of singleton or doubleton supermultiplets of corresponding AdS supergroups.
We present new lower bounds for the size of perfect and separating hash families ensuring their existence. Such new bounds are based on the algorithmic Cluster expansion improved version of the Lov\'asz Local Lemma, which also implies that the Moser-Tardos algorithm finds such hash families in polynomial time.
Coverage of image features play an important role in many vision algorithms since their distribution affect the estimated homography. This paper presents a Genetic Algorithm (GA) in order to select the optimal set of features yielding maximum coverage of the image which is measured by a robust method based on spatial statistics. It is shown with statistical tests on two datasets that the metric yields better coverage and this is also confirmed by an accuracy test on the computed homography for the original set and the newly selected set of features. Results have demonstrated that the new set has similar performance in terms of the accuracy of the computed homography with the original one with an extra benefit of using fewer number of features ultimately reducing the time required for descriptor calculation and matching.
In this note, we study one-dimensional reflected backward doubly stochastic differential equations (RBDSDEs) with one continuous barrier and discontinuous generator (left-or right-continuous). By a comparison theorem establish here for RBDSDEs, we provide a minimal or a maximal solution to RBDSDEs
We further study the unusual trend we found at statistically significant levels in some globular clusters, including NGC 3201: a decreasing iron abundance in red giants towards the cluster centers. We first show that recently published new estimates of iron abundance in the cluster reproduce this trend, in spite of the authors' statement about no metallicity spread due to a low scatter achieved in the [FeII/H] ratio. The mean of [FeII/H] within $R \sim 2'$ from the cluster center is lower, by $\Delta$[FeII/H] = 0.05$\pm$0.02 dex, than in the outer region, in agreement with our original estimate for a much larger sample size within $R \approx 9'$. We found that an older dataset traces the trend to a much larger radial distance, comparable with the cluster tidal radius, at $\Delta$[Fe/H]$\sim$0.2 dex due to higher metallicity of distant stars. We conclude the trend is reproduced by independent datasets and find that it is accompanied with both a notable same-sign trend of oxygen abundance which can vary by up to $\Delta$[O/Fe]$\sim$0.3 dex within $R \approx 9'$, and opposite-sign trend of sodium abundance.
20-component Petras theory of 1/2-spin particle with anomalous magnetic momentum in presence of external electromagnetic and gravitational fields is investigated. The gravitation field is described as space-time curvature. Correctness of the constructed equations in the sense of general relativity and gauge local Lorentz symmetry is proved in detail. Tetrad P-symmetry of the equations is demonstrated. A generally covariant representation of the invariant bilinear form matrix is established and the conserved current of the 20-componen t field is constructed. It is shown that after exclusion of the additional vector-bispinor \Psi_\beta(x) the wave equation for the principal \Psi -bispinor looks as generally covariant Dirac's equation with electromagnetic minimal and Pauli interactions and with an additional gravitational interaction through scalar curvarture R(x)-term. The massless case is analyzed in detail. The conformal non-invariance of the massless equation is demonstrated and new conformally invariant equations for 20-component field are proposed.
Field emission formulae, current-voltage characteristics and energy distribution of emitted electrons, are derived analytically for a nonplanar (hyperboloidal) metallic emitter model. The traditional Fowler-Nordheim formulae, which are derived from a planar emitter model, are modified, and the assumption of the planar emitter in the F-N model is reconsidered. Our analytical calculation also reveals the backgrounds of the previous numerical discussion by He et al. on the effect of the geometry of emitter on field emission. The new formulae contain a parameter which characterizes the sharpness of the hyperboloidal emitter, and experimental data of field emissions from clean tungsten emitters and nanotip emitters are analyzed by making use of this feature.
Let $M=Q(i\sqrt{d})$ be any imaginary quadratic field with a positive square-free $d$. Consider the polynomial \[ f(x)=x^3-ax^2-(a+3)x-1, \] with a parameter $a\in Z$. Let $K=M(\alpha)$, where $\alpha$ is a root of $f$. This is an infinite parametric family of sextic fields depending on two parameters, $a$ and $d$. Applying relative Thue equations we determine the relative power integral bases of these sextic fields over their quadratic subfields. Using these results we also determine generators of (absolute) power integral bases of the sextic fields.
The theory of cold, relativistic, magnetohydrodynamic outflows is generalized by the inclusion of an intense radiation source. In some contexts, such the breakout of a gamma-ray burst jet from a star, the outflow is heated to a high temperature at a large optical depth. Eventually it becomes transparent and is pushed to a higher Lorentz factor by a combination of the Lorentz force and radiation pressure. We obtain its profile, both inside and outside the fast magnetosonic critical point, when the poloidal magnetic field is radial and monopolar. Most of the energy flux is carried by the radiation field and the toroidal magnetic field that is wound up close to the rapidly rotating engine. Although the entrained matter carries little energy, it couples the radiation field to the magnetic field. Then the fast critical point is pushed inward from infinity and, above a critical radiation intensity, the outflow is accelerated mainly by radiation pressure. We identify a distinct observational signature of this hybrid outflow: a hardening of the radiation spectrum above the peak of the seed photon distribution, driven by bulk Compton scattering. The non-thermal spectrum -- obtained by a Monte Carlo method -- is most extended when the Lorentz force dominates the acceleration, and the seed photon beam is wider than the Lorentz cone of the MHD fluid. This effect is a generic feature of hot, magnetized outflows interacting with slower relativistic material. It may explain why some GRB spectra appear to peak at photon energies above the original Amati et al. scaling. A companion paper addresses the case of jet breakout, where diverging magnetic flux surfaces yield strong MHD acceleration over a wider range of Lorentz factor.
The existence of an acoustic plasmon in extrinsic (doped or gated) monolayer graphene was found recently in an {\it ab initio} calculation with the frozen lattice [M. Pisarra {\it et al.}, arXiv:1306.6273, 2013]. By the {\em fully dynamic} density-functional perturbation theory approach, we demonstrate a strong coupling of the acoustic plasmonic mode to lattice vibrations. Thereby, the acoustic plasmon in graphene does not exist as an isolated excitation, but it is rather bound into a combined plasmon-phonon mode. We show that the coupling provides a mechanism for the {\em bidirectional} energy exchange between the electronic and the ionic subsystems with fundamentally, as well as practically, important implications for the lattice cooling and heating by electrons in graphene.
In this paper, we prove the Effective Bogomolov's Conjecture for hyperelliptic curves defined over function fields.
Massive young stellar objects are known to undergo an evolutionary phase in which high mass accretion rates drive strong outflows. A class of objects believed to trace this phase accurately is the GLIMPSE Extended Green Object (EGO) sample, so named for the presence of extended 4.5 $\mu$m emission on sizescales of $\sim$0.1 pc in \textit{Spitzer} images. We have been conducting a multi-wavelength examination of a sample of 12 EGOs with distances of 1 to 5 kpc. In this paper, we present mid-infrared images and photometry of these EGOs obtained with the SOFIA telescope, and subsequently construct SEDs for these sources from the near-IR to sub-millimeter regimes using additional archival data. We compare the results from greybody models and several publicly-available software packages which produce model SEDs in the context of a single massive protostar. The models yield typical \rstar\/$\sim$10 \rsun, \tstar\/$\sim$10$^3$ to 10$^4$ K, and \lstar\/$\sim$1~$-$~40~$\times$~10$^3$ \lsun; the median $L/M$ for our sample is 24.7 \lsun/\msun. Model results rarely converge for \rstar\/ and \tstar, but do for \lstar, which we take to be an indication of the multiplicity and inherently clustered nature of these sources even though, typically, only a single source dominates in the mid-infrared. The median $L/M$ value for the sample suggests that these objects may be in a transitional stage between the commonly described ``IR-quiet'' and ``IR-bright'' stages of MYSO evolution. The median $T_{dust}$ for the sample is less conclusive, but suggests that these objects are either in this transitional stage or occupy the cooler (and presumably younger) part of the IR-bright stage.
We evaluate the strangeness production from equilibrating and transversely expanding quark gluon plasma which may be created in the wake of relativistic heavy ion collisions. We consider boost invariant longitudinal and cylindrically symmetric transverse expansion of a gluon dominated partonic plasma, which is in local thermal equilibrium. Initial conditions obtained from the self screened parton cascade model are used. We empirically find that the final extent of the partonic equilibration rises almost linearly with the square of the initial energy density. This along with the corresponding variation with the number of participants may help us distinguish between various models of parton production.
We analyze the spectral asymmetry of Stokes V (circularly polarized) profiles of an individual network patch in the quiet Sun observed by Sunrise/IMaX. At a spatial resolution of 0.15"-0.18", the network elements contain substructure which is revealed by the spatial distribution of Stokes V asymmetries. The area asymmetry between the red and blue lobes of Stokes V increases from nearly zero at the core of the structure to values close to unity at its edges (one-lobed profiles). Such a distribution of the area asymmetry is consistent with magnetic fields expanding with height, i.e., an expanding magnetic canopy (which is required to fulfill pressure balance and flux conservation in the solar atmosphere). Inversion of the Stokes I and V profiles of the patch confirms this picture, revealing a decreasing field strength and increasing height of the canopy base from the core to the periphery of the network patch. However, the non-roundish shape of the structure and the presence of negative area and amplitude asymmetries reveal that the scenario is more complex than a canonical flux tube expanding with height surrounded by downflows.
It turns out that all instances of the diophantine Frobenius problem for three coprime a_i have a common geometric structure which is independent of arithmetic coincidences among the a_i. By exploiting this structure we easily obtain Johnson's formula for the largest non-representable z, as well as a formula for the number of such z. A procedure is described which computes these quantities in O(log(max a_i)) steps.
We use improved truncated Operator Product Expansion (OPE) for the Adler function, involving two types of terms with dimension $D=6$, in the double-pinched Borel-Laplace Sum Rules and Finite Energy Sum Rules for the V+A channel strangeless semihadronic $\tau$ decays. The generation of the higher order perturbative QCD terms of the $D=0$ part of the Adler function is carried out using a renormalon-motivated ansatz incorporating the leading UV renormalon and the first two leading IR renormalons. The trunacted $D=0$ part of the Sum Rules is evaluated by two variants of the fixed-order perturbation theory (FO), by Principal Value of the Borel resummation (PV), and by contour-improved perturbation theory (CI). For the experimental V+A channel spectral function we use the ALEPH $\tau$-decay data. We point out that the truncated FO and PV evaluation methods account correctly for the renormalon structure of the Sum Rules, while this is not the case for the truncated CI evaluation. We extract the value of the ${\overline {\rm MS}}$ coupling $\alpha_s(m_{\tau}^2) = 0.3235^{+0.0138}_{-0.0126}$ [$\alpha_s(M_Z^2)=0.1191 \pm 0.0016$] for the average of the two FO methods and the PV method, which we consider as our main result. If we included in the average also CI extraction, the value would be $\alpha_s(m_{\tau}^2) = 0.3299^{+0.0232}_{-0.0225}$ [$\alpha_s(M_Z^2)=0.1199^{+0.0026}_{-0.0028}$]. This work is an extension and improvement of our previous work [Eur.Phys.J.C81 (2021) 10, 930] where we used for the truncated OPE a more naive (and widely used) form and where the extracted values for $\alpha_s(M_Z^2)$ were somewhat lower.