ShantanuT01/DACTYL-Pretraining huggingface dataset:
Spin-polarized quasiparticles can be easily created during spin-filtering through a ferromagnetic insulator (FI) in contact with a superconductor due to pair breaking effects at the interface. A combination FI-N-FI sandwiched between two superconductors can be used to create and analyze such spin-polarized quasiparticles through their nonequilibrium accumulation in the middle metallic (N) layer. We report spin-polarized quasiparticle regulation in a double spin-filter tunnel junction in the configuration NbN-GdN1-Ti-GdN2-NbN. The middle Ti layer provides magnetic decoupling between two ferromagnetic GdN and a place for nonequilibrium quasiparticle accumulation. The two GdN(1,2) layers were deposited under different conditions to introduce coercive contrast. The quasiparticle tunneling spectra has been measured at different temperatures to understand the tunneling mechanism in these double spin-filter junctions. The conductance spectra were found to be comparable to an asymmetric SINI'S-type tunnel junction. A hysteretic R-H loop with higher resistance for the antiparallel configuration compared to parallel state was observed asserting the spin-polarized nature of quasiparticles. The hysteresis in the R-H loop was found to disappear for sub-gap bias current. This difference can be understood by considering suppression of the interlayer coupling due to nonequilibrium spin-polarized quasiparticle accumulation in the Ti layer.
We supplement (and critically overview) the existing extensive analysis of antiferromagnetic solution for the Hubbard model with a detailed discussion of two specific features, namely (i) the evolution of the magnetic (Slater) gap (here renormalized by the electronic correlations) into the Mott-Hubbard or atomic gap, and (ii) a rather weak renormalization of the effective mass by the correlations in the half-filled-band case, which contrasts with that for the paramagnetic case. The mass remains strongly enhanced in the non-half-filled-band case. We also stress the difference between magnetic and non-magnetic contributions to the gap. These results are discussed within the slave boson approach in the saddle-point approximation, in which there appears a non-linear staggered molecular field due to the electronic correlations that leads to the appearance of the magnetic gap. They reproduce correctly the ground-state energy in the limit of strong correlations. A brief comparison with the solution in the limit of infinite dimensions and the corresponding situation in the doubly-degenerate-band case with one electron per atom is also made.
In this article, we show that a general class of weakly stationary time series can be modeled applying Gaussian subordinated processes. We show that, for any given weakly stationary time series $(z_t)_{z\in\mathbb{N}}$ with given equal one-dimensional marginal distribution, one can always construct a function $f$ and a Gaussian process $(X_t)_{t\in\mathbb{N}}$ such that $\left(f(X_t)\right)_{t\in\mathbb{N}}$ has the same marginal distributions and, asymptotically, the same autocovariance function as $(z_t)_{t\in\mathbb{N}}$. Consequently, we obtain asymptotic distributions for the mean and autocovariance estimators by using the rich theory on limit theorems for Gaussian subordinated processes. This highlights the role of Gaussian subordinated processes in modeling general weakly stationary time series. We compare our approach to standard linear models, and show that our model is more flexible and requires weaker assumptions.
Galaxy clusters exhibit a rich morphology during the early and intermediate stages of mass assembly, especially beyond their boundary. A classification scheme based on shapefinders deduced from the Minkowski functionals is examined to fully account for the morphological diversity of galaxy clusters, including relaxed and merging clusters, clusters fed by filamentary structures, and cluster-pair bridges. These configurations are conveniently treated with idealised geometric models and analytical formulae, some of which are novel. Examples from CLASH and LC$^2$ clusters and observed cluster-pair bridges are discussed.
Parton cascade is a microscopic transport approach for the study of the space-time evolution of the Quark-Gluon Plasma produced in relativistic heavy ion collisions and its experimental manifestations. In the following, parton cascade calculations on elliptic flow and thermalization will be discussed. Dynamical evolution is shown to be important for the production of elliptic flow including the scaling and the breaking of the scaling of elliptic flow. The degree of thermalization is estimated using both an elastic parton cascade and a radiative transport model. A longitudinal to transverse pressure ratio, $P_L/P_T\approx 0.8$, is shown to be expected in the central cell in central collisions. This provides information on viscous corrections to the ideal hydrodynamical approach.
In quasi-two-dimensional 1T-TaS2, a charge density wave (CDW) prototype, the transition occurs in two steps, from incommensurate (ICDW) and nearly commensurate (NCCDW) and from NCDW to commensurate (CCDW), locked in the resistivity step-wise behavior. The hysteresis observed in the resistivity across the NCDW-to-CCDW transition has roots to a structural hysteresis, where local distortions of the sqrt(13)a x sqrt(13)a superstructure are revealed by neutron and X-ray diffraction. The structural hysteresis is due to faulty stars of David (SODs) because of Ta displacements away from the perfect trigonal geometry as well as out of plane S distortions. Furthermore, the superstructure exhibits a 3co layer stacking order that weakens on warming and fully disappears in the ICDW state.
We present an investigation of the scaling relations between Supermassive Black Hole (SMBH) masses (Mbh), and their host galaxies' K-band bulge (Lbul) and total (Ltot) luminosities. The wide-field WIRCam imager at the Canada-France-Hawaii-Telescope (CFHT) was used to obtain the deepest and highest resolution near infrared images available for a sample of 35 galaxies with securely measured Mbh, selected irrespective of Hubble type. For each galaxy, we derive bulge and total magnitudes using a two-dimensional image decomposition code that allows us to account, if necessary, for large- and small-scale disks, cores, bars, nuclei, rings, envelopes and spiral arms. We find that the present-day Mbh-Lbul and Mbh-Ltot relations have consistent intrinsic scatter, suggesting that Mbh correlates equally well with bulge and total luminosity of the host. Our analysis provides only mild evidence of a decreased scatter if the fit is restricted to elliptical galaxies. The log-slopes of the Mbh-Lbul and Mbh-Ltot relations are 0.75+/-0.10 and 0.92+/-0.14, respectively. However, while the slope of the Mbh-Lbul relation depends on the detail of the image decomposition, the characterization of Mbh-Ltot does not. Given the difficulties and ambiguities of decomposing galaxy images into separate components, our results indicate that Ltot is more suitable as a tracer of SMBH mass than Lbul, and that the Mbh-Ltot relation should be used when studying the co-evolution of SMBHs and galaxies.
We present time-resolved high energy x-ray diffraction (tr-HEXRD), time-resolved hard x-ray photoelectron spectroscopy (tr-HAXPES) and time-resolved grazing incidence small angle x-ray scattering (tr-GISAXS) data of the reactive molecular beam epitaxy (RMBE) of $\mathrm{Fe_3O_4}$ ultrathin films on various substrates. Reciprocal space maps are recorded during the deposition of $\mathrm{Fe_3O_4}$ on $\mathrm{SrTiO_3(001)}$, MgO(001) and NiO/MgO(001) in order to observe the temporal evolution of Bragg reflections sensitive to the octahedral and tetrahedral sublattices of the inverse spinel structure of $\mathrm{Fe_3O_4}$. A time delay between the appearance of rock salt and spinel-exclusive reflections reveals that first, the iron oxide film grows with $\mathrm{Fe_{1-\delta}O}$ rock salt structure with exclusive occupation of octahedral lattice sites. When this film is 1.1$\,$nm thick, the further growth of the iron oxide film proceeds in the inverse spinel structure, with both octahedral and tetrahedral lattice sites being occupied. In addition, iron oxide on $\mathrm{SrTiO_3(001)}$ initially grows with none of these structures. Here, the formation of the rock salt structure starts when the film is 1.5$\,$nm thick. This is confirmed by tr-HAXPES data obtained during growth of iron oxide on $\mathrm{SrTiO_3(001)}$, which demonstrate an excess of $\mathrm{Fe^{2+}}$ cations in growing films thinner than 3.2$\,$nm. This rock salt phase only appears during growth and vanishes after the supply of the Fe molecular beam is stopped. Thus, it can be concluded the rock salt structure of the interlayer is a property of the dynamic growth process. The tr-GISAXS data link these structural results to an island growth mode of the first 2-3$\,$nm on both MgO(001) and $\mathrm{SrTiO_3(001)}$ substrates.
We apply the BV formalism to non-commutative field theories, introduce BRST symmetry, and gauge-fix the models. Interestingly, we find that treating the full gauge symmetry in non-commutative models can lead to reducible gauge algebras. As one example we apply the formalism to the Connes-Lott two-point model. Finally, we offer a derivation of a superversion of the Harish-Chandra-Itzykson-Zuber integral.
Let $E$ be an elliptic curve defined over $\Q$, and let $G$ be the torsion group $E(K)_{tors}$ for some cubic field $K$ which does not occur over $\Q$. In this paper, we determine over which types of cubic number fields (cyclic cubic, non-Galois totally real cubic, complex cubic or pure cubic) $G$ can occur, and if so, whether it can occur infinitely often or not. Moreover, if it occurs, we provide elliptic curves $E/\Q$ together with cubic fields $K$ so that $G= E(K)_{tors}$.
A maximum jet efficiency line $R\sim 25$ ($R=L_{\rm jet}/L_{\rm bol}$), found in FRII radio galaxies by Fernandes et al., was extended to cover the full range of jet power by Punsly. Recent general relativistic magnetohydrodynamic (GRMHD) simulations on jet formation mainly focused on the enhancement of jet power. In this work, we suggest that the jet efficiency could be very high even for conventional jet power if the radiative efficiency of disk were much smaller. We adopt the model of a thin disk with magnetically driven winds to investigate the observational high efficiency jets in FRII radio galaxies. It is found that the structure of a thin disk can be significantly altered by the feedback of winds. The temperature of disk gradually decreases with increasing magnetic field; the disk density, surface density and pressure also change enormously. The lower temperature and higher surface density in inner disk result in the rapid decrease of radiative efficiency. Thus, the jet efficiency is greatly improved even the jet power is conventional. Our results can explain the observations quite well. A theoretical maximum jet efficiency $R \sim 1000$ suggested by our calculations is large enough to explain all the high jet efficiency in observations even considering the episodic activity of jets.
Using the techniques of Bayer--Macr\`i, we determine the walls in the movable cone of the Mukai system of rank two for a general K3 surface $S$ of genus two. We study the (essentially unique) birational map to $S^{[5]}$ and decompose it into a sequence of flops. We give an interpretation of the exceptional loci in terms of Brill--Noether loci.
Red-shifted components of chromospheric emission lines in the hard X-ray impulsive phase of solar flares have recently been studied through their 30 s evolution with the high resolution of IRIS. Radiative-hydrodynamic flare models show that these redshifts are generally reproduced by electron-beam generated chromospheric condensations. The models produce large ambient electron densities, and the pressure broadening of hydrogen Balmer series should be readily detected in observations. To accurately interpret upcoming spectral data of flares with the DKIST, we incorporate non-ideal, non-adiabatic line broadening profiles of hydrogen into the RADYN code. These improvements allow time-dependent predictions for the extreme Balmer line wing enhancements in solar flares. We study two chromospheric condensation models, which cover a range of electron beam fluxes ($1-5 \times 10^{11}$ erg s$^{-1}$ cm$^{-2}$) and ambient electron densities ($1 - 60 \times 10^{13}$ cm$^{-3}$) in the flare chromosphere. Both models produce broadening and redshift variations within 10 s of the onset of beam heating. In the chromospheric condensations, there is enhanced spectral broadening due to large optical depths at H$\alpha$, H$\beta$, and H$\gamma$, while the much lower optical depth of the Balmer series H12$-$H16 provides a translucent window into the smaller electron densities in the beam-heated layers below the condensation. The wavelength ranges of typical DKIST/ViSP spectra of solar flares will be sufficient to test the predictions of extreme hydrogen wing broadening and accurately constrain large densities in chromospheric condensations.
We measure the orbital properties of halo stars using 7-dimensional information provided by Gaia and the Sloan Digital Sky Survey. A metal-rich population of stars, present in both local main sequence stars and more distant blue horizontal branch stars, have very radial orbits (eccentricity ~ 0.9) and apocenters that coincide with the stellar halo "break radius" at galactocentric distance r ~ 20 kpc. Previous work has shown that the stellar halo density falls off much more rapidly beyond this break radius. We argue that the correspondence between the apocenters of high metallicity, high eccentricity stars and the broken density profile is caused by the build-up of stars at the apocenter of a common dwarf progenitor. Although the radially biased stars are likely present down to metallicities of [Fe/H] ~ -2 the increasing dominance at higher metallicities suggests a massive dwarf progenitor, which is at least as massive as the Fornax and Sagittarius dwarf galaxies, and is likely the dominant progenitor of the inner stellar halo.
In 1975 Pippenger and Golumbic proved that any graph on $n$ vertices admits at most $2e(n/k)^k$ induced $k$-cycles. This bound is larger by a multiplicative factor of $2e$ than the simple lower bound obtained by a blow-up construction. Pippenger and Golumbic conjectured that the latter lower bound is essentially tight. In the present paper we establish a better upper bound of $(128e/81) \cdot (n/k)^k$. This constitutes the first progress towards proving the aforementioned conjecture since it was posed.
We compute the exclusive electroproduction, $\gamma^* p \rightarrow V p$, of heavy quarkonia $V$ to NLO in the collinear factorisation scheme, which has been formally proven for this process. The inclusion of an off-shell virtuality $Q^2$ carried by the photon extends the photoproduction phase space of the exclusive heavy quarkonia observable to electroproduction kinematics. This process is relevant for diffractive scattering at HERA and the upcoming EIC, as well as at the proposed LHeC and FCC.
We fix an error in the bound obtained in [13] for the crossing number of wrapped butterflies. The new bound finer than the one provided earlier.
A new lattice Boltzmann method for simulating multiphase flows is developed theoretically. The method is adjusted such that its continuum limit is the Navier-Stokes equation, with a driving force derived from the Cahn-Hilliard free energy. In contrast to previous work, however, the bulk and interface terms are decoupled, the former being incorporated into the model through the local equilibrium populations, and the latter through a forcing term. We focus on gas-liquid phase equilibria with the possibility to implement an arbitrary equation of state. The most novel aspect of our approach is a systematic Chapman-Enskog expansion up to the third order. Due to the third-order gradient in the interface forcing term, this is needed for full consistency with both hydrodynamics and thermodynamics. Our construction of a model that satisfies all conditions is based upon previous work by Chen, Goldhirsch, and Orszag (J. Sci. Comp. 34, 87 (2008)), and implies 59 and 21 velocities in three and two dimensions, respectively. Applying the conditions of positivity of weights, existence of a two-phase region in the phase diagram, and positivity of the bulk viscosity, we find substantial restrictions on the permitted equation of state, which can only be lifted by an even more refined model. Moreover, it turns out that it is necessary to solve a self-consistent equation for the hydrodynamic flow velocity, in order to enforce the identity of momentum density and mass current on the lattice. The analysis completely identifies all spurious terms in the Navier-Stokes equation, and thus shows how to systematically eliminate each of them, by constructing a suitable collision operator. (continued - see article PDF)
Free energies as a function of a selected set of collective variables are commonly computed in molecular simulation and of significant value in understanding and engineering molecular behavior. These free energy surfaces are most commonly estimated using variants of histogramming techniques, but such approaches obscure two important facets of these functions. First, the empirical observations along the collective variable are defined by an ensemble of discrete observations and the coarsening of these observations into a histogram bins incurs unnecessary loss of information. Second, the free energy surface is itself almost always a continuous function, and its representation by a histogram introduces inherent approximations due to the discretization. In this study, we relate the observed discrete observations from biased simulations to the inferred underlying continuous probability distribution over the collective variables and derive histogram-free techniques for estimating this free energy surface. We reformulate free energy surface estimation as minimization of a Kullback-Leibler divergence between a continuous trial function and the discrete empirical distribution and show that this is equivalent to likelihood maximization of a trial function given a set of sampled data. We then present a fully Bayesian treatment of this formalism, which enables the incorporation of powerful Bayesian tools such as the inclusion of regularizing priors, uncertainty quantification, and model selection techniques. We demonstrate this new formalism in the analysis of umbrella sampling simulations for the $\chi$ torsion of a valine sidechain in the L99A mutant of T4 lysozyme with benzene bound in the cavity.
We study the electronic transport properties of a monolayer graphene with a one-dimensional modulated height profile caused, for instance, by substrate ondulations. We show that the combined effect of the resulting strain fields induce modulated scalar and vector potentials that give rise to Weiss oscillations in the magnetoconductivity. We also find that similar effects can be obtained by applying a parallel magnetic field to the graphene-substrate interface. The parameters of an experimental set-up for a physical realization of these findings in graphene systems are discussed.
We introduce a variational theory for processes adapted to the multi-dimensional Brownian motion filtration. The theory provides a differential structure which describes the infinitesimal evolution of Wiener functionals at very small scales. The Markov property is replaced by a finite-dimensional approximation procedure based on controlled inter-arrival times and jumps of approximating martingales. The theory reveals that a large class of adapted processes follow a differential rule which is similar in nature to a fundamental theorem of calculus in the context of Wiener functionals. Null stochastic derivative term turns out to be a non-Markovian version of the classical second order parabolic operator and connections with theory of local-times and $(p,q)$-variation regularity are established. The framework extends the pathwise functional calculus and it opens the way to obtain variational principles for processes. Applications to semi-linear variational equations and stochastic variational inequalities are presented. In particular, we provide a feasible dynamic programming principle for fully non-Markovian/non-semimartingale optimal stopping problems.
Aims. The process of pitch-angle isotropization is important for many applications ranging from diffusive shock acceleration to large-scale cosmic-ray transport. Here, the basic analytical description is revisited on the basis of recent simulation results. Methods. Both an analytical and a numerical investigation were undertaken of the Fokker-Planck equation for pitch-angle scattering. Additional test-particle simulations obtained with the help of a Monte-Carlo code were used to verify the conclusions. Results. It is shown that the usual definition of the pitch-angle Fokker-Planck coefficient via the mean-square displacement is flawed. The reason can be traced back to the assumption of homogeneity in time which does not hold for pitch-angle scattering. Conclusions. Calculating the mean free path via the Fokker-Planck coefficient has often proven to give an accurate description. For numerical purposes, accordingly, it is the definition that has to be exchanged in favor of the pitch-angle correlation function.
We analyze Hubble Space Telescope observations of scattering regions in 20 luminous obscured quasars at $0.24<z<0.65$ (11 new observations and 9 archival ones) observed at rest-frame $\sim 3000$\AA. We find spectacular $5-10$ kpc-scale scattering regions in almost all cases. The median scattering efficiency at this wavelength (the ratio of observed to estimated intrinsic flux) is 2.3\%, and 73\% of the observed flux at this wavelength is due to scattered light, which if unaccounted for may strongly bias estimates of quasar hosts' star formation rates. Modeling these regions as illuminated dusty cones, we estimate the radial density distributions of the interstellar medium as well as the geometric properties of circumnuclear quasar obscuration -- inclinations and covering factors. Small derived opening angles (median half-angle and standard deviation 27\dg$\pm$9\dg) are inconsistent with a 1:1 type 1 / type 2 ratio. We suggest that quasar obscuration is patchy and that the observer has a $\sim 40\%$ chance of seeing a type 1 source even through the obscuration. We estimate median density profile of the scattering medium to be $n_{\rm H}=0.04-0.5$ $(1{\rm kpc}/r)^2$ cm$^{-3}$, depending on the method. Quasars in our sample likely exhibit galaxy-wide winds, but if these consist of optically thick clouds then only a small fraction of the wind mass ($\la 10\%$) contributes to scattering.
We demonstrate that secure communication using coherent states is possible. The optimal eavesdropping strategy for an M-ry ciphering scheme shows that the minimum probability of error in a measurement for bit determination can be made arbitrarily close to the pure guessing value P_e=1/2. This ciphering scheme can be optically amplified without degrading the security level. New avenues are open to secure communications at high speeds in fiber-optic or free-space channels.