ShantanuT01/DACTYL-Pretraining huggingface dataset:
In this paper we continue our study of the tree level MHV graviton scattering amplitudes from the point of view of celestial holography. In arXiv:2008.04330 we showed that the celestial OPE of two gravitons in the MHV sector can be written as a linear combination of $\overline{SL(2,\mathbb C)}$ current algebra and supertranslation descendants. In this note we show that the OPE is in fact manifestly invariant under the infinite dimensional Virasoro algebra as is expected for a $2$-D CFT. This is consistent with the conjecture that the holographic dual in $4$-D asymptotically flat space time is a $2$-D CFT. Since we get only one copy of the Virasoro algebra we can conclude that the holographic dual theory which computes the MHV amplitudes is a chiral CFT with a host of other infinite dimensional global symmetries including $\overline{SL(2,\mathbb C)}$ current algebra, supertranslations and subsubleading soft graviton symmetry. We also discuss some puzzles related to the appearance of the Virasoro symmetry.
We study dynamics of nonclassical correlations by exactly solving a model consisting of two atomic qubits with spontaneous emission. We find that the nonclassical correlations defined by different measures give different qualitative characterizations of those correlations. The relative behaviors of those correlation measures are presented explicitly for various quantum states in the two-qubit atomic system. In particular, we find that the robustness of quantum correlations can be greatly enhanced by performing appropriate local unitary operations on the initial state of the system.
We present precise constraints on the normalization of the power spectrum of mass fluctuations in the nearby universe, sigma_8, as a function of the mean local matter density, Omega_m. Using the observed local X-ray luminosity function of galaxy clusters from the extended BCS and REFLEX studies, a mass-luminosity relation determined from Chandra and ROSAT X-ray data and weak gravitational lensing observations, and the mass function predicted by the Hubble Volume simulations of Evrard et al., we obtain sigma_8 = (0.508\pm0.019) Omega_m^-(0.253\pm0.024), with Omega_m < 0.34 at 68 per cent confidence. The degeneracy between sigma_8 and Omega_m can be broken using Chandra measurements of the X-ray gas mass fractions in dynamically relaxed clusters. Using this information and including Gaussian priors on the mean baryon density of the universe and the Hubble constant, we obtain sigma_8=0.695\pm0.042 and Omega_m=0.287\pm0.036, for an assumed flat LambdaCDM cosmology (marginalized 68 per cent confidence limits). Our results are in good agreement with some recent studies based on the local X-ray temperature function of clusters, the redshift evolution of the X-ray luminosity and temperature functions of clusters, early results from the Sloan Digitized Sky Survey, the most recent results from studies of cosmic shear, and combined analyses of the 2dF galaxy redshift survey and cosmic microwave background anisotropies.
In this paper, we give a simple proof of scattering result for the Schr\"odinger equation with combined term $i\pa_tu+\Delta u=|u|^2u-|u|^4u$ in dimension three, that avoids the concentrate compactness method. The main new ingredient is to extend the scattering criterion to energy-critical.
We present a theoretical description of a mechanism for self assembly in binary soft nanoparticle systems of the type which were studied experimentally by Talapin et al [1]. We focus on, in particular, the conditions for formation of dodecagonal phases, and explain why these can be stabilized by the soft shells of the nanoparticles. We describe the different types of phase transition that are possible in terms of an effective free energy derived from n-body depletion potentials. A large variety of crystalline and several quasiperiodic structures are predicted to form, depending on the composition of the binary system and the size ratio of the particles. We show that this theory can qualitatively explain many of the experimentally seen structures, including striped, tetragonal, hexagonal and quasiperiodic phases. We also predict several new square triangle tilings corresponding to different packing fractions and clusters than the one dodecagonal phase that has been observed so far. Our theory can be tested in principle by detailed numerical investigations of the depletion forces in binary systems.
Alpha-decay energies for several chains of super-heavy nuclei are calculated within the self-consistent mean-field approach by using the Fayans functional FaNDF$^0$. They are compared to the experimental data and predictions of two Skyrme functionals, SLy4 and SkM*, and of the macro-micro method as well. The corresponding lifetimes are calculated with the use of the semi-phenomenological formulas by Parkhomenko and Sobiczewski and by Royer and Zhang.
Even a single point defect in a quantum wire causes a conductance reduction. In this paper we prove (without any approximations) that for any point impurity this conductance reduction in all the sub-bands is exactly 2e^2/h. Moreover, it is shown that in the case of a surface defect, not only is the conductance minimum independent of the defect characteristics, but the transmission matrix also converges to universal (defect-independent) values. We also discuss particle confinement between two arbitrarily weak point defects.
Jellium model achieved great success in predicting stable clusters with closed electronic shells and zero spin. In order to explain the stability of open shell clusters, it is necessary to consider the case of non-degenerate energy levels. In this paper the energy levels in nine low-lying Li$_{19}$ clusters are analysed systematically through superatomic orbital splitting effect. It is found that for originally degenerate orbitals like five 1D orbitals, the more the orbital extends in the direction of the cluster extension, the lower the energy of the orbital becomes. So oblate Li$_{19}$ clusters have the orbital sequence of $1\mathrm{S}^2-1\mathrm{P}_{x/y}^{4}-1\mathrm{P}_{z}^{2}-1\mathrm{D}_{xy/x^2-y^2}^{4}-2\mathrm{S}^2-1\mathrm{D}_{xz/yz}^{4}-1\mathrm{D}_{z^2}^{1}$, while prolate Li$_{19}$ clusters have the sequence of $1\mathrm{S}^2-1\mathrm{P}_{z}^{2}-1\mathrm{P}_{x/y}^{4}-1\mathrm{D}_{z^2}^{2}-1\mathrm{D}_{xz/yz}^{4}-1\mathrm{D}_{xy/x^2-y^2}^{4}-2\mathrm{S}^1$. This electron configuration is applied to predict the shape and magnetic moment of the alkali metal Li$_{n}$ clusters. The stability of the Li$_{14}$ cluster can be successfully interpreted in the framework of orbital splitting effect without resorting to the super valence bond (SVB) model, indicating a non-spherical cluster can achieve good stability without meeting the magic number. It is also proposed that the orbital splitting can be used to predict the shape (prolate, oblate or sphere) and magnetic moment of clusters. 11 out of 16 predicted shapes of Li$_n(n=3-18)$ are consistent with the results obtained by the principle of minimum energy.
Comprehensive calculations of cross sections of photon induced reactions on $^{233-238}$U targets for incident photon energies from 3 up to 30 MeV are undertaken with the statistical model code EMPIRE-3.2 Malta. Results are compared with the experimental data from EXFOR and with the current evaluations. The differences and the similarities between the models and parameters used in calculations of photon- and neutron-induced reactions on the same nuclei are discussed with focus on fission. The role of the extended optical model for fission in improving the description of the measured data and in determining consistent sets of barrier parameters is pointed out.
The mid- and far-infrared view on high-mass star formation, in particular with the results from the Herschel space observatory, has shed light on many aspects of massive star formation. However, these continuum studies lack kinematic information.   We study the kinematics of the molecular gas in high-mass star-forming regions.   We complemented the PACS and SPIRE far-infrared data of 16 high-mass star-forming regions from the Herschel key project EPoS with N2H+ molecular line data from the MOPRA and Nobeyama 45m telescope. Using the full N2H+ hyperfine structure, we produced column density, velocity, and linewidth maps. These were correlated with PACS 70micron images and PACS point sources. In addition, we searched for velocity gradients.   For several regions, the data suggest that the linewidth on the scale of clumps is dominated by outflows or unresolved velocity gradients. IRDC18454 and G11.11 show two velocity components along several lines of sight. We find that all regions with a diameter larger than 1pc show either velocity gradients or fragment into independent structures with distinct velocities. The velocity profiles of three regions with a smooth gradient are consistent with gas flows along the filament, suggesting accretion flows onto the densest regions.   We show that the kinematics of several regions have a significant and complex velocity structure. For three filaments, we suggest that gas flows toward the more massive clumps are present.
Recently, the ANITA collaboration reported on two upward-going extensive air shower events consistent with a primary particle that emerges from the surface of the ice. These events may be of $\nu_\tau$ origin, in which the neutrino interacts within the Earth to produce a $\tau$ lepton that emerges from the Earth, decays in the atmosphere, and initiates an extensive air shower. In this paper we estimate an upper bound on the ANITA acceptance to a diffuse $\nu_\tau$ flux detected via $\tau$-lepton-induced air showers within the bounds of Standard Model (SM) uncertainties. By comparing this estimate with the acceptance of Pierre Auger Observatory and IceCube and assuming SM interactions, we conclude that a $\nu_\tau$ origin of these events would imply a neutrino flux at least two orders of magnitude above current bounds.
Centaurus A is the closest radio-loud active galaxy. Very Long Baseline Interferometry (VLBI) enables us to study the jet-counterjet system on milliarcsecond (mas) scales, providing essential information for jet emission and propagation models. We study the evolution of the central parsec jet structure of Cen A over 3.5 years. The proper motion analysis of individual jet components allows us to constrain jet formation and propagation and to test the proposed correlation of increased high energy flux with jet ejection events. Cen A is an exceptional laboratory for such detailed study as its proximity translates to unrivaled linear resolution, where 1 mas corresponds to 0.018 pc. The first 7 epochs of high-resolution TANAMI VLBI observations at 8 GHz of Cen A are presented, resolving the jet on (sub-)mas scales. They show a differential motion of the sub-pc scale jet with significantly higher component speeds further downstream where the jet becomes optically thin. We determined apparent component speeds within a range of 0.1c to 0.3c, as well as identified long-term stable features. In combination with the jet-to-counterjet ratio we can constrain the angle to the line of sight to ~12{\deg} to 45{\deg}. The high resolution kinematics are best explained by a spine-sheath structure supported by the downstream acceleration occurring where the jet becomes optically thin. On top of the underlying, continuous flow, TANAMI observations clearly resolve individual jet features. The flow appears to be interrupted by an obstacle causing a local decrease in surface brightness and a circumfluent jet behavior. We propose a jet-star interaction scenario to explain this appearance. The comparison of jet ejection times with high X-ray flux phases yields a partial overlap of the onset of the X-ray emission and increasing jet activity, but the limited data do not support a robust correlation.
We investigate the emergence and consequences of odd-frequency spin-triplet s-wave pairing in superconducting hybrid junctions at the edge of a two-dimensional topological insulator without any magnetism. More specifically, we consider several different normal-superconductor hybrid systems at the topological insulator edge, where spin-singlet s-wave superconducting pairing is proximity-induced from an external conventional superconductor. We perform fully analytical calculations and show that odd-frequency mixed spin-triplet s-wave pairing arises due to the unique spin-momentum locking in the topological insulator edge state and the naturally non-constant pairing potential profile in hybrid systems. Importantly, we establish a one-to-one correspondence between the local density of states (LDOS) at low energies and the odd-frequency spin-triplet pairing in NS, NSN and SNS junctions along the topological insulator edge; at interfaces the enhancement in the LDOS can directly be attributed to the contribution of odd-frequency pairing. Furthermore, in SNS junctions we show that the emergence of the zero-energy LDOS peak at the superconducting phase $\phi=\pi$ is associated purely with odd-frequency pairing in the middle of the junction.
The electronic properties of armchair graphene nanoribbons (AGNRs) can be significantly modified from semiconducting to metallic states, by applying a uniform perpendicular magnetic field (B-field). Here, we theoretically study the bandgap modulation induced by a perpendicular B-field. The applied B-field causes the lowest conduction subband and the top-most valence subband to move closer to one another to form the n=0 Landau level. We exploit this effect to realize a device relevant MR modulation. Unlike in conventional spin-valves, this intrinsic MR effect is realized without the use of any ferromagnetic leads. The AGNRs with number of dimers, Na=3p+1 [p=1,2,3,...] show the most promising behavior for MR applications, with large conductance modulation and hence, high MR ratio at the optimal source-drain bias. However, the MR is suppressed at higher temperature due to the spread of the Fermi function distribution. We also investigate the importance of the source-drain bias in optimizing the MR. Lastly, we show that edge roughness of AGNRs has the unexpected effect of improving the magnetic sensitivity of the device and thus increasing the MR ratio.
Increasing observational evidence supports a picture for a close link among AGN phenomenum, star-formation processes and galaxy formation. Since the physical phenomena related to the onset of both AGN and star formation are very likely characterized by a strong far infrared (FIR) emission it becomes mandatory to investigate the FIR energy domain. However, because of their faintness in the FIR energy range, very little is known about the FIR properties of type 1 AGN, and type 2 AGN, which are supposed to be missed in classical searches, still lack definition and samples. Our aim is to investigate the FIR properties of optically selected type 1 AGN, compare them to Ultraluminous Infrared Galaxies (ULIRGs) and derive some general characteristics of the population. Expectations for future surveys are also presented.
We report the structure and magnetic properties of a new iridate compound, SrxLa11-xIr4O24, where the d-electron count of Ir and therefore its number of unpaired electrons can be tuned continuously from 5d5 Ir4+ to 5d4 Ir5+, i.e. from SrLa10Ir4O24 to Sr5La6Ir4O24. The IrO6 octahedra in SrxLa11-xIr4O24 are isolated from each other and from other transition elements, minimizing band effects, and the doping is on the framework sites, not the Ir sites, minimizing the effects of disorder. Measurements of the temperature dependent magnetic susceptibility are employed to determine the evolution of the Ir magnetic moment on progressing from 5d5 Ir4+ to 5d4 Ir5+, and are clearly best described by a transition from a J=1/2 to a J=0 Ir magnetic state; that is, the evolution of the magnetic susceptibility shows the dominance of spin-orbit coupling in determining the magnetic properties of a material with highly isolated IrO6 octahedra.
We present a method for calculating explicit expressions of the shear three-point function for various cosmological models. The method is applied here to the one-halo model in case of power law density profiles for which results are detailed. The three-point functions are found to reproduce to a large extent patterns in the shear correlations obtained in numerical simulations and may serve as a guideline to implement optimized methods for detecting the shear three-point function. In principle, the general method presented here can also be applied for other models of matter correlation.
Carried out in this study is an improved analysis of the measurements of the three pion-nucleon ($\pi N$) reactions, which can be subjected to experimental investigation at low energy (pion laboratory kinetic energy $T \leq 100$ MeV), i.e., of the two elastic-scattering (ES) processes $\pi^\pm p \to \pi^\pm p$ and of the $\pi^- p$ charge-exchange (CX) reaction $\pi^- p \to \pi^0 n$. After the application of the four steps of the first phase of the new analysis procedure, $52$ entries - of the $1150$ degrees of freedom of the new initial database (DB) of this project - were identified as outliers and were removed from the input. In this manner, three `clean' (devoid of outliers) DBs were obtained, which were submitted to further analysis using the ETH model. The phase-shift analysis (PSA) of the ES measurements comprises the results of one hundred joint fits to the data, each fit being carried out at one value (randomly generated, in normal distribution, according to a recent result) of the model parameter $m_\sigma$, which is associated with the effective range of the scalar-isoscalar part of the $\pi N$ interaction. The result of the PSA of the ES data for the (square of the) charged-pion coupling constant $f_c$ is: $f_c^2=0.0764(15)$. An exclusive fit of the ETH model to the low-energy $\pi^- p$ CX DB was also performed, for the first time in the recent years, after suppressing the contributions to the partial-wave amplitudes of the ETH model which originate from the scalar-isoscalar $t$-channel Feynman diagram. The predictions, obtained from these two types of fits (PSA of the ES data and exclusive fit of the ETH model to the $\pi^- p$ CX DB) for the (popular) symmetrised relative difference $R_2$ were compared in the entire low-energy region, separately for the $s$ wave, as well as for the no-spin-flip and spin-flip $p$-wave parts of the $\pi N$ scattering amplitude.
We successfully synthesize single crystals of the verdazyl radical $\alpha$-2,3,5-Cl$_3$-V. $Ab$ $initio$ molecular orbital calculations indicate that the two dominant antiferromagnetic interactions, $J_{\rm{1}}$ and $J_{\rm{2}}$ ($\alpha =J_{\rm{2}}/J_{\rm{1}}\simeq 0.56$), form an $S$ = 1/2 distorted square lattice. We explain the magnetic properties based on the $S$ = 1/2 square lattice Heisenberg antiferromagnet using the quantum Monte Carlo method, and examine the effects of the lattice distortion and the interplane interaction contribution. In the low-temperature regions below 6.4 K, we observe anisotropic magnetic behavior accompanied by a phase transition to a magnetically ordered state. The electron spin resonance signals exhibit anisotropic behavior in the temperature dependence of the resonance field and the linewidth. We explain the frequency dependence of the resonance fields in the ordered phase using a mean-field approximation with out-of-plane easy-axis anisotropy, which causes a spin-flop phase transition at approximately 0.4 T for the field perpendicular to the plane. Furthermore, the anisotropic dipole field provides supporting information regarding the presence of the easy-axis anisotropy. These results demonstrate that the lattice distortion, anisotropy, and interplane interaction of this model are sufficiently small that they do not affect the intrinsic behavior of the $S$ = 1 / 2 square lattice Heisenberg antiferromagnet.
High pressure behavior of potassium chlorate (KClO$_3$) has been investigated from 0-10 GPa by means of first principles density functional theory (DFT) calculations. The calculated ground state parameters, transition pressure and phonon frequencies using semiempirical dispersion correction scheme are in excellent agreement with experiment. It is found that KClO$_3$ undergoes a pressure induced first order phase transition with an associated volume collapse of 6.4$\%$ from monoclinic (\emph{P2$_1$/m}) $\rightarrow$ rhombohedral (\emph{R3m}) structure at 2.26 GPa, which is in good accord with experimental observation. However, the transition pressure was found to underestimate (0.11 GPa) and overestimate (3.57 GPa) using LDA and GGA functionals, respectively. Mechanical stability of both the phases are explained from the calculated single crystal elastic constants. In addition, the zone center phonon frequencies have been calculated using density functional perturbation theory at ambient as well as at high pressure and the lattice modes are found to soften under pressure between 0.6 to 1.2 GPa. The present study reveals that the observed structural phase transition leads to changes in the decomposition mechanism of KClO$_3$ which corroborates with the experimental results.
Using science verification observations obtained with ESPRESSO at the Very Large Telescope (VLT) in 4UT mode, we report the first bound on the carbon isotope ratio 12C/13C of a quiescent, near-pristine damped Ly-alpha (DLA) system at z=2.34. We recover a limit log10(12C/13C) > +0.37 (2 sigma). We use the abundance pattern of this DLA, combined with a stochastic chemical enrichment model, to infer the properties of the enriching stars, finding the total gas mass of this system to be log10(M_gas/M_sun)=6.3+1.4-0.9 and the total stellar mass to be log10(M_*/M_sun)=4.8+/-1.3. The current observations disfavour enrichment by metal-poor Asymptotic Giant Branch (AGB) stars with masses <2.4 Msun, limiting the epoch at which this DLA formed most of its enriching stars. Our modelling suggests that this DLA formed very few stars until >1 Gyr after the cosmic reionization of hydrogen and, despite its very low metallicity (~1/1000 of solar), this DLA appears to have formed most of its stars in the past few hundred Myr. Combining the inferred star formation history with evidence that some of the most metal-poor DLAs display an elevated [C/O] ratio at redshift z<3, we suggest that very metal-poor DLAs may have been affected by reionization quenching. Finally, given the simplicity and quiescence of the absorption features associated with the DLA studied here, we use these ESPRESSO data to place a bound on the possible variability of the fine-structure constant, Delta alpha/alpha=(-1.2 +/- 1.1)x10^-5.
We describe human-subject laboratory experiments on probabilistic auctions based on previously proposed auction protocols involving the simulated manipulation and communication of quantum states. These auctions are probabilistic in determining which bidder wins, or having no winner, rather than always having the highest bidder win. Comparing two quantum protocols in the context of first-price sealed bid auctions, we find the one predicted to be superior by game theory also performs better experimentally. We also compare with a conventional first price auction, which gives higher performance. Thus to provide benefits, the quantum protocol requires more complex economic scenarios such as maintaining privacy of bids over a series of related auctions or involving allocative externalities.