ShantanuT01/DACTYL-Pretraining huggingface dataset:
Observations of radiative cooling in a synchrotron source offer a possibility to further constrain its properties. Inverse Compton cooling is indicated in the radio spectra during the early phases of SN\,2020oi. It is shown that contrary to previous claims, observations are consistent with equipartition between relativistic electrons and magnetic field as well as a constant mass-loss rate of the progenitor star prior to the supernova explosion. The reason for this difference is the need to include cooling directly in the fitting procedure rather than estimating its effects afterward. It is emphasized that the inferred properties of the supernova ejecta are sensitive to the time evolution of the synchrotron self-absorption frequency; hence, great care should be taken when modeling spectra for which cooling and/or inhomogeneities are indicated. Furthermore, it is noted that the energies of the relativistic electrons in the radio emission regions in supernovae are likely too low for first-order Fermi acceleration to be effective.
We consider categories of rational maps to algebraic groups and study existence and construction of universal objects for such categories, using the duality theory of Laumon 1-motives. In particular, we obtain functorial descriptions of the Albanese of a singular projective variety X over an algebraically closed field of characteristic zero, which is the universal regular quotient of a relative Chow group of points on X, and of its dual.
We consider the two-dimensional Navier-Stokes equations subject to the Dirichlet boundary condition in a half plane for initial vorticity with finite measures. We study local well-posedness of the associated vorticity equations for measures with a small pure point part and global well-posedness for measures with a small total variation. Our construction is based on an $L^{1}$-estimate of a solution operator for the vorticity equations associated with the Stokes equations.
The pd <--> pi+ t process has been calculated in the energy region around the Delta-resonance with elementary production/absorption mechanisms involving one and two nucleons. The isobar degrees of freedom have been explicitly included in the two-nucleon mechanism via pi-- and rho-exchange diagrams. No free parameters have been employed in the analysis since all the parameters have been fixed in previous studies on the simpler pp <--> pi+ d process. The treatment of the few-nucleon dynamics entailed a Faddeev-based calculation of the reaction, with continuum calculations for the initial p-d state and accurate solutions of the three-nucleon bound-state equation. The integral cross-section was found to be quite sensitive to the NN interaction employed while the angular dependence showed less sensitivity. Approximately a 4% effect was found for the one-body mechanism, for the three-nucleon dynamics in the p-d channel, and for the inclusion of a large, possibly converged, number of three-body partial states, indicating that these different aspects are of comparable importance in the calculation of the spin-averaged observables.
We prove the solvability in Sobolev spaces for a class of variational problems related to the TV-model proposed by Rudin, Osher and Fatemi in [1] for the denoising of greyscale images. In contrast to their approach we discuss energy densities with variable growth rates depending on $|\nabla u|$ in a rather general form including functionals of $(1, p)$-growth.
The analysis of the combinatorics resulting from the perturbative expansion of the transition amplitude in quantum field theories, and the relation of this expansion to the Hausdorff series leads naturally to consider an infinite dimensional Lie subalgebra and the corresponding enveloping Hopf algebra, to which the elements of this series are associated. We show that in the context of these structures the power sum symmetric functionals of the perturbative expansion are Hopf primitives and that they are given by linear combinations of Hall polynomials, or diagrammatically by Hall trees. We show that each Hall tree corresponds to sums of Feynman diagrams each with the same number of vertices, external legs and loops. In addition, since the Lie subalgebra admits a derivation endomorphism, we also show that with respect to it these primitives are cyclic vectors generated by the free propagator, and thus provide a recursion relation by means of which the (n+1)-vertex connected Green functions can be derived systematically from the n-vertex ones.
The criterion for an affine primary algebra over the field to be integral, is proven. Using this criterion we give a simple proof that Hilbert scheme of 0-dimensional subschemes of length $l$ of nonsingular $d$-dimensional algebraic variety is reduced for all $d$ and $l$.
We consider one copy of a quantum system prepared in one of two orthogonal pure states, entangled or otherwise, and distributed between any number of parties. We demonstrate that it is possible to identify which of these two states the system is in by means of local operations and classical communication alone. The protocol we outline is both completely reliable and completely general - it will correctly distinguish any two orthogonal states 100% of the time.
Importance sampling is a variance reduction technique for efficient estimation of rare-event probabilities by Monte Carlo. In standard importance sampling schemes, the system is simulated using an a priori fixed change of measure suggested by a large deviation lower bound analysis. Recent work, however, has suggested that such schemes do not work well in many situations. In this paper we consider dynamic importance sampling in the setting of uniformly recurrent Markov chains. By ``dynamic'' we mean that in the course of a single simulation, the change of measure can depend on the outcome of the simulation up till that time. Based on a control-theoretic approach to large deviations, the existence of asymptotically optimal dynamic schemes is demonstrated in great generality. The implementation of the dynamic schemes is carried out with the help of a limiting Bellman equation. Numerical examples are presented to contrast the dynamic and standard schemes.
Contrary to the common view voids have very complex internal structure and dynamics. Here we show how the hierarchy of structures in the density field inside voids is reflected by a similar hierarchy of structures in the velocity field. Voids defined by dense filaments and clusters can de described as simple expanding domains with coherent flows everywhere except at their boundaries. At scales smaller that the void radius the velocity field breaks into expanding sub-domains corresponding to sub- voids. These sub-domains break into even smaller sub-sub domains at smaller scales resulting in a nesting hierarchy of locally expanding domains. The ratio between the magnitude of the velocity field responsible for the expansion of the void and the velocity field defining the sub voids is approximately one order of magnitude. The small-scale components of the velocity field play a minor role in the shaping of the voids but they define the local dynamics directly affecting the processes of galaxy formation and evolution. The super-Hubble expansion inside voids makes them cosmic magnifiers by stretching their internal primordial density fluctuations allowing us to probe the small scales in the primordial density field. Voids also act like time machines by "freezing" the development of the medium-scale density fluctuations responsible for the formation of the tenuous web of structures seen connecting proto galaxies in computer simulations. As a result of this freezing haloes in voids can remain "connected" to this tenuous web until the present time. This may have an important effect in the formation and evolution of galaxies in voids by providing an efficient gas accretion mechanism via coherent low-velocity streams that can keep a steady inflow of matter for extended periods of time.
Rotation damping and alignment are discussed as prerequisites for polarization power. An expression is derived from first principles, for the damping time of the rotation of a particle in a magnetic field, under the Faraday braking torque, provided its electrical properties are known. This makes it possible to describe mathematically, in great detail, the motion of the particle and determine its ultimate state of motion, if a steady state is possible at all. This work defines, first, the necessary condition for the Faraday braking to be effective: a) the net electronic charge distribution should not be uniform throughout; b) the number of vibration modes should exceed a few tens. Resonance of rotation frequency with any of these modes is not a requirement. For alignment to be possible, the ratio of gyroscopic and conservative magnetic to non-conservative (retarding) magnetic torques must be low. Either dia-, para- or ferro-magnetism can do, and a small susceptibility is enough and even preferable. This opens up a wide spectrum of possible candidates. A few examples are given.
By applying an hyperbolic deformation to the uniformization problem for the infinite strip, we give a method for computing the accessory parameter for the torus with one source as an expansion in the modular parameter q. At O(q^0) we obtain the same equation for the accessory parameter and the same value of the semiclassical action as the one obtained from the b -> 0 limit of the quantum one point function. The procedure can be carried over to the full O(q^2) or even higher order corrections although the procedure becomes somewhat complicated. Here we compute to order q^2 the correction to the weight parameter intervening in the conformal factor and it is shown that the unwanted contribution O(q) to the accessory parameter equation cancel exactly.
In the presence of large extra dimensions, the fundamental scale could be as low as a few TeV. This yields leptogenesis and seesaw at a TeV scale. Phenomenologically two TeV-scale Majorana fermions with a small mass split can realize a resonant leptogenesis whereas a TeV-scale Higgs triplet with a small trilinear coupling to the standard model Higgs doublet can give a verifiable seesaw. We propose an interesting scenario where the small parameters for the resonant leptogenesis and the type-II seesaw can be simultaneously generated by the propagation of lepton number violation from distant branes to our world.
Angular distributions of differential cross sections for the interaction of $K^{+}$ mesons with $^{^{12}}$C nucleus at beam momenta of 635, 715, and 800 MeV/c have been analyzed using 3$\alpha$-particle model of $^{^{12}}$C. Differential cross sections for inelastic transitions to the (2$^{^{+}}$; 4.44 MeV) and (3$^{-}$; 9.64 MeV) states in $^{^{12}}$C are calculated, and deformation lengths $\delta_{2}$ and $\delta_{3}$ are extracted and consistent with other works. Good agreement with experimental data of elastic and inelastic $K^{\pm}$-$^{12}$C scattering is obtained.
Through millennia humans exploited the natural property of metals to get stronger or hardened when mechanically deformed. Ultimately rooted in the motion of dislocations, mechanisms of metal hardening remained in the crosshairs of physical metallurgists for over a century. Here, we performed atomistic simulations at the limits of supercomputing, which are sufficiently large to be statistically representative of macroscopic crystal plasticity yet fully resolved to examine the origins of metal hardening at its most fundamental level of atomic motion. We demonstrate that the notorious staged (inflection) hardening of metals is a direct consequence of crystal rotation under uniaxial straining. At variance with widely divergent and contradictory views in the literature, we observe that basic mechanisms of dislocation behavior are the same across all stages of metal hardening.
We develop a microscopic theory of a strong electromagnetic field interaction with gated bilayer graphene. Quantum kinetic equations for density matrix are obtained using a tight binding approach within second quantized Hamiltonian in an intense laser field. We show that adiabatically changing the gate potentials with time may produce (at resonant photon energy) a full inversion of the electron population with high density between valence and conduction bands. In the linear regime, excitonic absorption of an electromagnetic radiation in a graphene monolayer with opened energy gap is also studied.
After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion-pion scattering to two-loop accuracy. In the pion-nucleon system, the linear sigma model is contrasted with chiral perturbation theory. The heavy-nucleon expansion is used to construct the effective pion-nucleon Lagrangian to third order in the low-energy expansion, with applications to nucleon Compton scattering.
The effect of realistic metal electronic structure on the lower limit of resistivity in [100] oriented n-Si is investigated using full band Density Functional Theory and Semi-Empirical Tight Binding (TB) calculations. Using simulation unit cells guided by the interface chemistry of epitaxial CoSi2 on [100] oriented Si observed experimentally, it is shown that the 'ideal metal' assumption fails in some situations and consequently underestimates the lower limit of contact resistivity in n-Si by at least an order of magnitude at high doping concentrations. The mismatch in transverse momentum space in the metal and the semiconductor, the so-called 'valley filtering effect', is shown to be dependent on the interface chemistry simulated. The results emphasize the need for explicit inclusion of the metal atomic and electronic structure in the atomistic modeling of transport across metal-semiconductor contacts
High entropy alloys (HEAs) are a series of novel materials that demonstrate many exceptional mechanical properties. To understand the origin of these attractive properties, it is important to investigate the thermodynamics and elucidate the evolution of various chemical phases. In this work, we introduce a data-driven approach to construct the effective Hamiltonian and study the thermodynamics of HEAs through canonical Monte Carlo simulation. The main characteristic of our method is to use pairwise interactions between atoms as features and systematically improve the representativeness of the dataset using samples from Monte Carlo simulation. We find this method produces highly robust and accurate effective Hamiltonians that give less than 0.1 mRy test error for all the three refractory HEAs: MoNbTaW, MoNbTaVW, and MoNbTaTiW. Using replica exchange to speed up the MC simulation, we calculated the specific heats and short-range order parameters in a wide range of temperatures. For all the studied materials, we find there are two major order-disorder transitions occurring respectively at $T_1$ and $T_2$, where $T_1$ is near room temperature but $T_2$ is much higher. We further demonstrate that the transition at $T_1$ is caused by W and Nb while the one at $T_2$ is caused by the other elements. By comparing with experiments, {\color{black} the results provide insight into the role of chemical ordering in the strength and ductility of HEAs.
We investigate the Wigner distributions for $u$ and $d$ quarks in a light-front quark-diquark model of a proton to unravel the spatial and spin structure. The light-front wave functions are modeled from the soft-wall AdS/QCD prediction. We consider the contributions from both the scalar and the axial vector diquarks. The Wigner distributions for unpolarized, longitudinally polarized, and transversely polarized protons are presented in the transverse momentum plane as well as in the transverse impact parameter plane. The Wigner distributions satisfy a Soffer-bound-type inequality. We also evaluate all the leading twist GTMDs and show their scale evolution. The spin-spin correlations between the quark and the proton are investigated
We present the first results of simultaneous INTEGRAL and RXTE observations of the microquasar GRS 1915+105. We focus on the analysis of the unique highly variable observation and show that we might have observed a new class of variability. We then study the energetic dependence of a low frequency QPO from our steady observations.
This paper contains the results of our investigations of BPS instantons and of our work on N=2 supersymmetric gauge theories. The BPS instantons we study appear in type II string theory compactifications on Calabi-Yau threefolds. In the corresponding four-dimensional effective supergravity actions the BPS instantons arise as finite action solutions to the Euclidean equations of motion. For N=2 supersymmetric gauge theories we construct general Lagrangians involving gauge groups with (non-abelian) electric and magnetic (dyonic) charges. In this work a coupling to hypermultiplets is included.
We present new observations made with the IRAM 30m telescope of the J=1-0 and 3-2 lines of HCN and HCO^+ used to probe the dense molecular gas content in a sample of 17 local luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). These observations have allowed us to derive an updated version of the power law describing the correlation between the FIR luminosity (L_FIR) and the HCN(1-0) luminosity (L'_HCN(1-0)) of local and high-redshift galaxies. We present the first clear observational evidence that the star formation efficiency of the dense gas (SFE_dense), measured as the L_FIR/L'_HCN(1-0) ratio, is significantly higher in LIRGs and ULIRGs than in normal galaxies, a result that has also been found recently in high-redshift galaxies. This may imply a statistically significant turn upward in the Kennicutt-Schmidt law derived for the dense gas at L_FIR >= 10^11 L_sun. We have used a one-phase Large Velocity Gradient (LVG) radiative transfer code to fit the three independent line ratios derived from our observations. The results of this analysis indicate that the [HCN]/[HCO^+] abundance ratios could be up to one order of magnitude higher than normal in a significant number of LIRGs and ULIRGs of our sample. An overabundance of HCN at high L_FIR implies that the reported trend in the L_FIR/L'_HCN ratio as a function of L_FIR would be underestimating a potentially more dramatic change of the SFE_dense. Results obtained with two-phase LVG models corroborate that the L'_HCN(1-0)-to-M_dense conversion factor must be lowered at high L_FIR. We discuss the implications of these findings for the use of HCN as a tracer of the dense molecular gas in local and high-redshift luminous infrared galaxies.
Taylor's power law states that the variance function decays as a power law. It is observed for population densities of species in ecology. For random networks another power law, that is, the power law degree distribution is widely studied. In this paper the original Taylor's power law is considered for random networks. A precise mathematical proof is presented that Taylor's power law is asymptotically true for the $N$-stars network evolution model.
This paper is a sequel of \cite{CD:2012}. We show how to establish a functional Edgeworth expansion of any order thanks to the Stein method. We apply the procedure to the Brownian approximation of compensated Poisson process and to the linear interpolation of the Brownian motion. It is then apparent that these two expansions are of rather different form.
In this paper we give a meaning to the nonlinear characteristic Cauchy problem for the Wave Equation in base form by replacing it by a family of non-characteristic problems in an appropriate algebra of generalized functions. We prove existence of a solution and we precise how it depends on the choice made. We also check that in the classical case (non-characteristic) our new solution coincides with the classical one.
In this paper we study the positivity of the cotangent bundle of projective manifolds. We conjecture that the cotangent bundle is pseudoeffective if and only the manifold has non-zero symmetric differentials. We confirm this conjecture for most projective surfaces that are not of general type.
Despite being the most prominent emission line in the solar spectrum, there has been a notable lack of studies devoted to variations in Ly$\alpha$ emission during solar flares in recent years. However, the few examples that do exist have shown Ly$\alpha$ emission to be a substantial radiator of the total energy budget of solar flares (on the order of 10%). It is also a known driver of fluctuations in earth's ionosphere. The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory now provides broadband, photometric Ly$\alpha$ data at 10 s cadence with its Multiple EUV Grating Spectrograph-Photometer (MEGS-P) component, and has observed scores of solar flares in the 5 years since it was launched. However, the MEGS-P time profiles appear to display a rise time of tens of minutes around the time of the flare onset. This is in stark contrast to the rapid, impulsive increase observed in other intrinsically chromospheric features (H$\alpha$, Ly$\beta$, LyC, C III, etc.). Furthermore, the emission detected by MEGS-P peaks around the time of the peak of thermal soft X-ray emission, rather than during the impulsive phase when energy deposition in the chromosphere - often assumed to be in the form of nonthermal electrons - is greatest. Given that spectrally-resolved Ly$\alpha$ observations during flares from SORCE/SOLSTICE peak during the impulsive phase as expected, this suggests that the atypical behaviour of MEGS-P data is a manifestation of the broadband nature of the observations. This could imply that other lines and/or continuum emission that becomes enhanced during flares could be contributing to the passband. Users are hereby urged to exercise caution when interpreting broadband Ly$\alpha$ observations of solar flares. Comparisons have also been made with other broadband Ly$\alpha$ photometers such as PROBA2/LYRA and GOES/EUVS-E.
An N=1, d=4 supersymmetric compactification of the perturbative heterotic string is described by a d=2 (0,2) superconformal field theory. The first-order marginal deformations of the internal (0,2) SCFT are in 1 to 1 correspondence with massless gauge-neutral scalars in the spacetime theory. Working at tree-level in the alpha' expansion, we describe these first order deformations for SCFTs with a (0,2) non-linear sigma model description. Our results clarify the structure of deformations of heterotic Calabi-Yau compactifications and more general heterotic flux vacua.
Phases of the spherical harmonic analysis of full-sky cosmic microwave background (CMB) temperature data contain useful information complementary to the ubiquitous angular power spectrum. In this letter we present a new method of phase analysis on incomplete sky maps. It is based on Fourier phases of equal-latitude pixel rings of the map, which are related to the mean angle of the trigonometric moments from the full-sky phases. They have an advantage for probing regions of interest without tapping polluted Galactic plane area, and can localize non-Gaussian features and departure from statistical isotropy in the CMB.