ShantanuT01/DACTYL-Pretraining huggingface dataset:
We propose some variants of Lefschetz fixed point theorem for Fourier-Mukai functors on a smooth projective algebraic variety. Independently we also suggest a similar theorem for endo-functors on the category of perfect modules over a smooth and proper DG algebra.
It has long been assumed that the inversion asymmetry-induced Rashba spin splitting in two-dimensional (2D) systems at zero magnetic field is proportional to the electric field that characterizes the inversion asymmetry of the confining potential. Here we demonstrate, both theoretically and experimentally, that 2D heavy hole systems in accumulation layer-like single heterostructures show the opposite behavior, i.e., a decreasing, but nonzero electric field results in an increasing Rashba coefficient.
Here, we present the theoretical analysis of the structural and electronic degrees of freedom of two different oxide/fluoride perovskite superlattices, KTaO$_3$/KZnF$_3$ and KTaO$_3$/KNiF$_3$. Using first-principles calculations, we found the appearance of a two-dimensional electron, 2DEG, and hole, 2DHG, gases as a function of the number of layers of the different pristine materials. We demonstrate that the phonon-dynamics at the KTO/K$M$F superlattices play a crucial role in the appearance of these effects. Additionally, our results reveal a rather sizeable Rashba-type spin-splitting at these interfaces in comparison to another oxide/oxide counterparts.
Antikink dispersion of the asymmetric $J_1$-$J_2$ sawtooth spin-1/2 anisotropic Heisenberg antiferromagnetic chain has been derived. Value of spin-gap is obtained by estimating the minimum of dispersion relation variationally. The exact doubly-degenerate ground state energy has been derived at the symmetric point, $J_1=J_2$, for the whole anisotropic regime. Analytic form of dispersion relations of three different antikink states is obtained and their validity in the parameter space is discussed. The value of spin-gap, specific heat and susceptibility are estimated numerically by diagonalizing the Hamiltonian for chains of finite length. The inherent frustration of this antiferromagnetic model leads to the appearance of additional peak at low-temperatures in the specific heat.
Cosmological surveys in the far infrared are known to suffer from confusion. The Bayesian de-blending tool, XID+, currently provides one of the best ways to de-confuse deep Herschel SPIRE images, using a flat flux density prior. This work is to demonstrate that existing multi-wavelength data sets can be exploited to improve XID+ by providing an informed prior, resulting in more accurate and precise extracted flux densities. Photometric data for galaxies in the COSMOS field were used to constrain spectral energy distributions (SEDs) using the fitting tool CIGALE. These SEDs were used to create Gaussian prior estimates in the SPIRE bands for XID+. The multi-wavelength photometry and the extracted SPIRE flux densities were run through CIGALE again to allow us to compare the performance of the two priors. Inferred ALMA flux densities (F$^i$), at 870$\mu$m and 1250$\mu$m, from the best fitting SEDs from the second CIGALE run were compared with measured ALMA flux densities (F$^m$) as an independent performance validation. Similar validations were conducted with the SED modelling and fitting tool MAGPHYS and modified black body functions to test for model dependency. We demonstrate a clear improvement in agreement between the flux densities extracted with XID+ and existing data at other wavelengths when using the new informed Gaussian prior over the original uninformed prior. The residuals between F$^m$ and F$^i$ were calculated. For the Gaussian prior, these residuals, expressed as a multiple of the ALMA error ($\sigma$), have a smaller standard deviation, 7.95$\sigma$ for the Gaussian prior compared to 12.21$\sigma$ for the flat prior, reduced mean, 1.83$\sigma$ compared to 3.44$\sigma$, and have reduced skew to positive values, 7.97 compared to 11.50. These results were determined to not be significantly model dependent. This results in statistically more reliable SPIRE flux densities.
Blue straggler stars (BSS) are well studied in globular clusters but their systematic study with secure membership determination is lacking in open clusters. We use Gaia DR2 data to determine accurate stellar membership for four intermediate-age open clusters, Melotte 66, NGC 2158, NGC 2506 and NGC 6819, and three old open clusters, Berkeley 39, NGC 188 and NGC 6791, to subsequently study their BSS populations. The BSS radial distributions of five clusters, Melotte 66, NGC 188, NGC 2158, NGC 2506, and NGC 6791, show bimodal distributions, placing them with Family II globular clusters which are of intermediate dynamical ages. The location of minima, $r_\mathrm{{min}}$, in the bimodal BSS radial distributions, varies from 1.5$r_c$ to 4.0$r_c$, where $r_c$ is the core radius of the clusters. We find a positive correlation between $r_\mathrm{{min}}$ and $N_{\mathrm{relax}}$, the ratio of cluster age to the current central relaxation time of the cluster. We further report that this correlation is consistent in its slope, within the errors, to the slope of the globular cluster correlation between the same quantities, but with a slightly higher intercept. This is the first example in open clusters that shows BSS radial distributions as efficient probes of dynamical age. The BSS radial distributions of the remaining two clusters, Berkeley 39 and NGC 6819, are flat. The estimated $N_{\mathrm{relax}}$ values of these two clusters, however, indicate that they are dynamically evolved. Berkeley 39 especially has its entire BSS population completely segregated to the inner regions of the cluster.
We use high resolution numerical simulations over several hundred of turnover times to study the influence of small scale dissipation onto vortex statistics in 2D decaying turbulence. A self-similar scaling regime is detected when the scaling laws are expressed in units of mean vorticity and integral scale, as predicted by Carnevale et al., and it is observed that viscous effects spoil this scaling regime. This scaling regime shows some trends toward that of the Kirchhoff model, for which a recent theory predicts a decay exponent $\xi=1$. In terms of scaled variables, the vortices have a similar profile close to a Fermi-Dirac distribution.
Cosmic rays are the main agents in controlling the chemical evolution and setting the ambipolar diffusion time of a molecular cloud. We summarise the processes causing the energy degradation of cosmic rays due to their interaction with molecular hydrogen, focusing on the magnetic effects that influence their propagation. Making use of magnetic field configurations generated by numerical simulations, we show that the increase of the field line density in the collapse region results in a reduction of the cosmic-ray ionisation rate. As a consequence the ionisation fraction decreases, facilitating the decoupling between the gas and the magnetic field.
We explore the addition of fundamental matter to the Klebanov-Witten field theory. We add probe D7-branes to the ${\cal N}=1$ theory obtained from placing D3-branes at the tip of the conifold and compute the meson spectrum for the scalar mesons. In the UV limit of massless quarks we find the exact dimensions of the associated operators, which exhibit a simple scaling in the large-charge limit. For the case of massive quarks we compute the spectrum of scalar mesons numerically.
I draw attention to previous work that shows that the observables corresponding to relativistic quantum field modes commonly employed in papers on "relativistic quantum information" cannot be measured by ideal measurements.
The recently discovered sharp peak in the excitation function of the K+/pi+ ratio around 30 A GeV in relativistic heavy-ion collisions is discussed in the framework of the Statistical Model. In this model, the freeze-out of an ideal hadron gas changes from a situation where baryons dominate to one with mainly mesons. This transition occurs at a temperature T = 140 MeV and baryon chemical potential mu(B) = 410 MeV corresponding to an energy of sqrt(s) = 8.2 GeV. The calculated maximum in the K+/pi+ ratio is, however, much less pronounced than the one observed by the NA49 Collaboration. The smooth increase of the K-/pi- ratio with incident energy and the shape of the excitation functions of the Lambda/pi+, Xi-/pi+ and Omega/pi ratios all exhibiting maxima at different incident energies, is consistent with the presently available experimental data. The measured K+/pi+ ratio exceeds the calculated one just at the incident energy when the freeze-out condition is changing.   We speculate that at this point freeze-out might occur in a modified way. We discuss a scenario of an early freeze-out which indeed increases K+/pi+ ratio while most other particle ratios remain essentially unchanged. Such an early freeze-out is supported by results from HBT studies.
We consider the porous medium equation on manifolds with conical singularities and show existence, uniqueness and maximal $L^{p}$-regularity of a short time solution. In particular, we obtain information on the short time asymptotics of the solution near the conical point. Our method is based on bounded imaginary powers results for cone differential operators on Mellin-Sobolev spaces and $R$-sectoriality perturbation techniques.
Establishing strong electron-correlations not only shed lights on overcoming the trade-off limitations for optimizing thermoelectric materials, but can also introduce new functionalities that extend the vision of conventional thermoelectric applications. Here, we demonstrate that the high thermoelectric and thermistor functionalities coexist in lattice distorted SrNbxTi1-xO3 films with electron correlations between carriers and ordering aligned lattice dipoles. As-grown SrNbxTi1-xO3/SrTiO3 with effectively preserved interfacial strains exhibits cross-plane charge ordering and orbital anisotropy, as indicated by the polarization dependent near edge X-ray absorption fine structures. The resultant coulomb-correlations regulate the carrier transport and enhance the Seebeck coefficient more independently via enlarging the system vibration entropy. As-achieved maximum thermoelectric power factor exceeds 100 uWcm-1K-2 measured in the bulk performance of SrNb0.2Ti0.8O3 (2.2 um)/SrTiO3 (100 um), which is comparable to the best thermoelectric materials for low temperature applications. In addition, the strong temperature dependence of the carrier scattering aroused by the lattice dipoles introduces a positive temperature dependent thermistor transportation behavior with large temperature coefficient of resistance ranging from 30 to 300 K, which is rarely seen in conventional thermistors. Combining both functionalities largely extend the horizon in exploring new Joule sensors for detection of temperature and thermal perturbations across a broad temperature range.
Le Borgne et al. (2007) report on the determination of evolutionary changes in the periods of field RR Lyr stars. Thanks to the extension of the GEOS database, we could analyze a sample twice larger than the previous one. We obtained a different picture of the period changes, with a number of stars showing an increasing period greater than that of stars showing a decreasing period.
We re-assess the exclusion limits on the parameters describing the supersymmetric (SUSY) electroweak sector of the MSSM obtained from the search for direct chargino-neutralino production at the LHC. We start from published limits obtained in simplified models, where for the case of heavy sleptons the relevant branching ratio, BR(neu2->neu1 Z), is set to one. We show how the decay mode neu2->neu1 h, which cannot be neglected in any realistic model once kinematically allowed, substantially reduces the excluded parameter region. We analyze the dependence of the excluded regions on the phase of the gaugino soft SUSY-breaking mass parameter, M_1, on the mass of the light scalar tau, on tb as well as on the squark and slepton mass scales. Large reductions in the ranges of parameters excluded can be observed in all scenarios. The branching ratios of charginos and neutralinos are evaluated using a full NLO calculation for the complex MSSM. The size of the effects of the NLO calculation on the exclusion bounds is investigated. We furthermore assess the potential reach of the experimental analyses after collecting 100/fb at the LHC running at 13 TeV.
The centrality dependence of Xi^- and Lambda production in Au+Au interactions at E_lab=6 AGeV is studied within a microscopic transport approach. In line with recent data, a slight enhancement of the Xi^-/(Lambda+Sigma^0) ratio toward central collisions is found. It is demonstrated that the observed production of multiple strange baryons can be traced back to multi-step meson-baryon interactions in the late stages of the collisions. Therefore, the present analysis supports an interpretation of the observed Xi abundance in terms of hadronic re-scattering.
We investigate the spin dynamics of electrons in quantum wells where the Rashba type of spin-orbit coupling is present in the form of random nanosize domains. We study the effect of magnetic field on the spin relaxation in these systems and show that the spatial randomness of spin-orbit coupling limits the minimum relaxation rate and leads to a Gaussian time-decay of spin polarization due to memory effects. In this case the relaxation becomes faster with increase of the magnetic field in contrast to the well known magnetic field suppression of spin relaxation.
In this paper we consider a nonlocal energy $I_\alpha$ whose kernel is obtained by adding to the Coulomb potential an anisotropic term weighted by a parameter $\alpha\in \R$. The case $\alpha=0$ corresponds to purely logarithmic interactions, minimised by the celebrated circle law for a quadratic confinement; $\alpha=1$ corresponds to the energy of interacting dislocations, minimised by the semi-circle law. We show that for $\alpha\in (0,1)$ the minimiser can be computed explicitly and is the normalised characteristic function of the domain enclosed by an \emph{ellipse}. To prove our result we borrow techniques from fluid dynamics, in particular those related to Kirchhoff's celebrated result that domains enclosed by ellipses are rotating vortex patches, called \emph{Kirchhoff ellipses}. Therefore we show a surprising connection between vortices and dislocations.
Utilizing multiwavelength observations and magnetic field data from SDO/AIA, SDO/HMI, GOES and RHESSI, we investigate a large-scale ejective solar eruption of 2014 December 18 from active region NOAA 12241. This event produced a distinctive three-ribbon flare, having two parallel ribbons corresponding to the ribbons of a standard two-ribbon flare, and a larger-scale third quasi-circular ribbon offset from the other two ribbons. There are two components to this eruptive event. First, a flux rope forms above a strong-field polarity-inversion line and erupts and grows as the parallel ribbons turn on, grow, and spread part from that polarity-inversion line; this evolution is consistent with the tether-cutting-reconnection mechanism for eruptions. Second, the eruption of the arcade that has the erupting flux rope in its core under goes magnetic reconnection at the null point of a fan dome that envelops the erupting arcade, resulting in formation of the quasi-circular ribbon; this is consistent with the breakout reconnection mechanism for eruptions. We find that the parallel ribbons begin well before (12 min) circular ribbon onset, indicating that tether-cutting reconnection (or a non-ideal MHD instability) initiated this event, rather than breakout reconnection. The overall setup for this large-scale (circular-ribbon diameter 100000 km) eruption is analogous to that of coronal jets (base size 10000 km), many of which, according to recent findings, result from eruptions of small-scale minifilaments. Thus these findings confirm that eruptions of sheared-core magnetic arcades seated in fan-spine null-point magnetic topology happen on a wide range of size scales on the Sun.
It is shown that, if inclusive lepton scattering off nuclei at high momentum transfer is analyzed in terms of proper scaling variables, useful information on Nucleon-Nucleon short range correlations in nuclei can be obtained. The traditional approach to Y-scaling is critically analyzed and a novel approach to Y-scaling, which incorporates the effects from two- and three-nucleon correlations in nuclei, is illustrated.
We found that the actual computational time-cost of the QFT is O(n 2^n) for large n in a quantum computer using nuclear spins. The computational cost of a quantum algorithm has usually been estimated as the sum of the universal gates required in such ideal mathematical models as the Quantum Turing Machine(QTM) and the quantum circuit. This cost is proportional to an actual time-cost in the physical implementation where all quantum operations can be achieved in the same time. However, if the implementation takes a different time for each quantum gate, there is a possibility that the actual time-cost will have a different behavior from the ideal cost. So we estimated the actual time-cost of the QFT in these implementations by considering the gating time. The actual time-cost is drastically different from O(n^2) estimated by complexity analysis.
A method is developed for calculating effective sums of divergent series. This approach is a variant of the self-similar approximation theory. The novelty here is in using an algebraic transformation with a power providing the maximal stability of the self-similar renormalization procedure. The latter is to be repeated as many times as it is necessary in order to convert into closed self-similar expressions all sums from the series considered. This multiple and complete renormalization is called self-similar bootstrap. The method is illustrated by several examples from statistical physics.
The energy dependence of chirally expanded pi N isoscalar and isovector amplitudes b_0(E) and b_1(E) respectively, for zero-momentum off shell pions near threshold, is used to impose the minimal substitution requirement E -> E - V_c on the properly constructed pion optical potential within a large-scale fit to 100 pionic-atom data across the periodic table which also include the recently established `deeply bound' pionic atoms of Pb and Sn. This fit cannot be reconciled with the well known free-space values of the pi N threshold amplitudes. In contrast, introducing the empirically known energy dependence for on-shell pions leads to a better fit and to satisfactory values for the pi N threshold amplitudes. The difference between these two approaches is briefly discussed.
The interacting electron and hole in transition-metal dichalcogenides is considered. For investigation of the interaction between electron and hole we obtain the Bethe-Salpeter equation for two interacting Dirac particles. The dependence of a few lowest binding energies of electron and hole on the interaction constant for different potentials is found. We demonstrate that the behavior of the potential at small distances significantly affects on the values of the binding energies. For small interaction constant we have developed the perturbative method of the binding energy calculation. For the largre interaction constant the binding energies are found numerically. The critical values of the interaction constant for the Coulomb potential and exponential potential are found.
The charmonium dissociation by mesons in relativistic heavy-ion reactions is analyzed within the Regge approach. It is shown that the inclusion of the initial and final state interactions in the dissociation of J/Psi to bar{D}* D* close to threshold increases the cross section significantly and can not be neglected in comparison to the total dissociation rate. This is due to resonant bar{D}*-D* interactions in sqrt{s} close to the masses of the Psi(4.04) and Psi(4.16) mesons. We also investigate thermal effects of the (c bar{c}) width for such processes in the medium. All these effects change both the magnitude and the shape of the cross section as a function of sqrt{s}. The results obtained should be applied in the analysis of open and hidden charm production in heavy-ion collisions.
We introduce the notion of inverse effect of magnetostriction for magnetostrictive/piezoelectric heterostructures and study this effect theoretically and experimentally. It is shown that the inverse effect of magnetostriction may crucially contribute to the mechanism of magnetoelectric coupling. It is shown that the studied effect essentially modifies the saturation magnetostriction of the whole structure as compared to its magnetic phase bulk and also induces an additional magnetic anisotropy. Our consideration provides useful insight into the fundamental issue of strain-mediated magnetoelectric coupling. Understanding this effect may lead to its utilization in original experimental concepts and the improvement of the ME coupling.
In this paper we present a hybrid system composed by a neural network based estimator system and genetic algorithms. It uses an unsupervised Hebbian nonlinear neural algorithm to extract the principal components which, in turn, are used by the MUSIC frequency estimator algorithm to extract the frequencies. We generalize this method to avoid an interpolation preprocessing step and to improve the performance by using a new stop criterion to avoid overfitting. Furthermore, genetic algorithms are used to optimize the neural net weight initialization. The experimental results are obtained comparing our methodology with the others known in literature on a Cepheid star light curve.
We investigate the effect that the intrinsic spin-orbit and the inter- and intra-layer Rashba interactions have on the energy spectrum of either an unbiased or a biased graphene bilayer. We find that under certain conditions, a Dirac cone is formed out of a parabolic band and that it is possible to create a "Mexican hat"-like energy dispersion in an unbiased bilayer. In addition, in the presence of only an intralayer Rashba interaction, the K (K') point splits into four distinct ones, contrarily to the case in single-layer graphene, where the splitting also takes place, but the low-energy dispersion at these points remains identical.
We have mapped from the quantum to the classical limit the spin excitation spectrum of the antiferromagnetic spin-1 Heisenberg chain system CsNiCl3 in its paramagnetic phase from T=5 to 200K. Neutron scattering shows that the excitations are resonant and dispersive up to at least T=70K, but broaden considerably with increasing temperature. The dispersion flattens out with increasing temperature as the resonance energy Delta at the antiferromagnetic wave-vector increases and the maximum in the dispersion decreases. The correlation length xi between T=12 and 50K is in agreement with quantum Monte Carlo calculations. xi is also consistent with the single mode approximation, suggesting that the excitations are short-lived single particle excitations. Below T=12K where three-dimensional spin correlations are important, xi is shorter than predicted and the experiment is not consistent with the random phase approximation for coupled quantum chains. At T=200K, the structure factor and second energy moment of the excitation spectrum are in excellent agreement with the high-temperature series expansion.
We show that every k-dichromatic vertex-critical digraph on at most 2k-2 vertices has a disconnected complement. This answers a question of Bang-Jensen et al., and generalises a classical theorem of Gallai on undirected vertex-critical graphs.