ShantanuT01/DACTYL-Pretraining huggingface dataset:
We modify the method to generate the exact solutions of the Einstein equations basing on the laws of thermodynamics. Firstly, the Komar mass is used to take the place of the Misner-Sharp energy which is used in the original methods, and then several exact solutions of Einstein equations are obtained, including the black hole solution which surrounded by quintessence. Moreover, the geometry surface gravity defined by Komar mass is obtained. Secondly, we use both the Komar mass and the ADM mass to modify such method, and the similar results are obtained. Moreover, with some generalize added to the definition of the ADM mass, our method can be generalized to global monopole sapcetime.
We report results of studying the magnetization, specific heat and thermal expansion of a single crystal with nominal composition Mn 0.85 Fe 0.15 Si . We found no thermodynamic evidences in favor a second order phase transition in the 15 % Fe substituted MnSi. The trajectory corresponding to the present composition of (MnFe)Si is a critical one, i.e. approaching quantum critical point at lowering temperature, but some properties may feel the cloud of helical fluctuations bordering the phase transition line.
We present a method of modeling the radial velocity (RV) measurements which can be useful in searching for planets hosted by chromospherically active stars. We assume that the observed RV signal is induced by the reflex motion of a star as well as by distortions of spectral line profiles, measured by the Bisector Velocity Span (BVS). The RVs are fitted with a common planetary model including RV correction term depending linearly on the BVS, which accounts for the stellar activity. The coefficient of correlation is an additional free parameter of the RV model. That approach differs from correcting the RVs before or after fitting the "pure" planetary model. We test the method on simulated data derived for single-planet systems. The results are compared with the outcomes of algorithms found in the literature.
We classify terminal simplicial reflexive d-polytopes with 3d-1 vertices. They turn out to be smooth Fano d-polytopes. When d is even there is 1 such polytope up to isomorphism, while there are 2 when d is uneven.
We present our implementation of an algorithm which functions as a numerical oracle for the Newton polytope of a hypersurface in the Macaulay2 package NumericalNP.m2. We propose a tropical membership test, relying on this algorithm, for higher codimension varieties based on ideas from Hept and Theobald. To showcase this software, we investigate the Newton polytope of both a hypersurface coming from algebraic vision and the Luroth invariant.
We consider in detail how the quantum-mechanical tunneling phenomenon occurs in a well-behaved octic potential. Our main tool will be the euclidean propagator just evaluated between two minima of the potential at issue. For such a purpose we resort to the standard semiclassical approximation which takes into account the fluctuations over the instantons, i.e. the finite-action solutions of the euclidean equation of motion. As regards the one-instanton approach, the functional determinant associated with the so-called stability equation is analyzed in terms of the asymptotic behaviour of the zero-mode. The conventional ratio of determinants takes as reference the harmonic oscillator whose frequency is the average of the two different frequencies derived from the minima of the potential involved in the computation. The second instanton of the model is studied in a similar way. The physical effects of the multi-instanton configurations are included in this context by means of the alternate dilute-gas approximation where the two instantons participate to provide us with the final expression of the propagator.
We present a proof, which is conditional on the Birch and Swinnerton-Dyer Conjecture for a specific abelian variety, that there do not exist rational numbers x and c such that x has exact period N = 6 under the iteration x |-> x^2 + c. This extends earlier results by Morton for N = 4 and by Flynn, Poonen and Schaefer for N = 5.
The classical trajectory model with stochastic breakup for nuclear collision dynamics of weakly-bound nuclei is further developed. It allows a quantitative study of the importance of incomplete fusion dynamics in the angular distribution of direct alpha-production. Model calculations indicate that the incomplete fusion contribution diminishes with decreasing energy towards the Coulomb barrier, notably separating in angles from the contribution of no-capture breakup events. This should facilitate the experimental disentanglement of these competing reaction processes.
We propose a general framework governing the intersection properties of extremal rays of irreducible holomorphic symplectic manifolds under the Beauville-Bogomolov form. Our main thesis is that extremal rays associated to Lagrangian projective subspaces control the behavior of the cone of curves. We explore implications of this philosophy for examples like Hilbert schemes of points on K3 surfaces and generalized Kummer varieties. We also collect evidence supporting our conjectures in specific cases.
We conduct numerical simulations of the interacting ejecta from an exploding CO white dwarf (WD) with a He WD donor in the double-detonation scenario for Type Ia supernovae (SNe Ia), and study the possibility of exploding the companion WD. We also study the long time imprint of the collision on the supernova remnant. When the donor He WD has a low mass, M_WD = 0.2Msun, it is at a distance of ~ 0.08Rsun from the explosion, and helium is not ignited. The low mass He WD casts an 'ejecta shadow' behind it. By evolving the ejecta for longer times, we find that the outer parts of the shadowed side are fainter and its boundary with the ambient gas is somewhat flat. More massive He WD donors, M_WD ~ 0.4Msun, must be closer to the CO WD to transfer mass. At a distance of a < 0.045Rsun helium is detonated and the He WD explodes, leading to a triple detonation scenario. In the explosion of the donor WD approximately 0.15Msun of unburned helium is ejected. This might be observed as a peculiar type Ib supernova.
At a distance of 8 kpc, the center of our Galaxy is the nearest galactic nucleus, and has been the subject of numerous key projects undertaken by great observatories such as Chandra, Spitzer, and Herschel. However, there are still no surveys of molecular gas properties in the Galactic center with less than 30" (1 pc) resolution. There is also no sensitive polarization survey of this region, despite numerous nonthermal magnetic features apparently unique to the central 300 parsecs. In this paper, we outline the potential the VLASS has to fill this gap. We assess multiple considerations in observing the Galactic center, and recommend a C-band survey with 10 micro-Jy continuum RMS and sensitive to molecular gas with densities greater than 10^4 cm^{-3}, covering 17 square degrees in both DnC and CnB configurations ( resolution ~5"), totaling 750 hours of observing time. Ultimately, we wish to note that the upgraded VLA is not just optimized for fast continuum surveys, but has a powerful correlator capable of simultaneously observing continuum emission and dozens of molecular and recombination lines. This is an enormous strength that should be fully exploited and highlighted by the VLASS, and which is ideally suited for surveying the center of our Galaxy.
A (3+1)-evolutionary method in the framework of Regge Calculus, essentially a method of approximating manifolds with rigid simplices, makes an excellent tool to probe the evolution of manifolds with non-trivial topology or devoid of symmetry. The "Parallelisable Implicit Evolution Scheme" is one such method. Causality however, is an aspect of this method that has been barely investigated. In this paper, we show how causality can be accounted for in this evolutionary scheme. The revised algorithm is illustrated by a preliminary application to a skeletonised spherical Friedmann-Lema\^itre-Robertson-Walker universe.
We study the three-body radiative decays $B\to \phi(\rho) K\gamma$ induced by a flavor-changing neutral current in the perturbative QCD approach. Pseudoscalar-vector ($PV$) distribution amplitudes (DAs) are introduced for the final-state $\phi K$ ($\rho K$) pair to capture important infrared dynamics in the region with a small $PV$-pair invariant mass. The dependence of these $PV$ DAs on the parton momentum fraction is parametrized in terms of the Gegenbauer polynomials, and the dependence on the meson momentum fraction is derived through their normalizations to time-like $PV$ form factors. In addition to the dominant electromagnetic penguin, the subleading chromomagnetic penguin, quark-loop and annihilation diagrams are also calculated. After determining the $PV$ DAs from relevant branching-ratio data, the direct $CP$ asymmetries and decay spectra in the $PV$-pair invariant mass are predicted for each $B\to \phi(\rho) K\gamma$ mode.
We carried out detailed studies of the magnetic structure, magnetoelastic coupling, and thermal properties of EuCrO$_3$ nano-powders from room temperature to liquid helium temperature. Our neutron powder diffraction and X-ray powder diffraction measurements provide precise atomic positions of all atoms in the cell, especially for the light oxygen atoms. The low-temperature neutron powder diffraction data revealed extra Bragg peaks of magnetic origin which can be attributed to a $G_x$ antiferromagnetic structure with an ordered moment of $\sim$ 2.4 $\mu_{\rm B}$ consistent with the $3d^3$ electronic configuration of the Cr$^{3+}$ cations. Apart from previously reported antiferromagnetic and ferromagnetic transitions in EuCrO$_3$ at low temperatures, we also observed an anomaly at about 100 K. This anomaly was observed in temperature dependence of sample's, lattice parameters, thermal expansion, Raman spectroscopy, permittivity and conductance measurements. This anomaly is attributed to the magnetoelastic distortion in the EuCrO$_3$ crystal.
The magnetic chemically peculiar (mCP) stars of the upper main sequence exhibit strong, globally-organised magnetic fields which are inclined to the rotational axis and facilitate the development of surface abundance inhomogeneities resulting in photometric and spectroscopic variability. Therefore, mCP stars are perfectly suited for a direct measurement of the rotational period without the need for any additional calibrations. We have investigated the rotational properties of mCP stars based on an unprecedentedly large sample consisting of more than 500 objects with known rotational periods. Using precise parallaxes from the Hipparcos and Gaia satellite missions, well-established photometric calibrations and state-of-the-art evolutionary models, we have determined the location of our sample stars in the Hertzsprung-Russell diagram and derived astrophysical parameters such as stellar masses, effective temperature, radii, inclinations and critical rotational velocities. We have confirmed the conservation of angular momentum during the main sequence evolution; no signs of additional magnetic braking were found. The inclination angles of the rotational axes are randomly distributed, although an apparent excess of fast rotators with comparable inclination angles has been observed. We have found a rotation rate of $\upsilon/\upsilon_{\rm crit} \geq 0.5$ for several stars, whose characteristics cannot be explained by current models. For the first time, we have derived the relationship between mass and rotation rate of mCP stars, and provide an analysis that links mass and rotation with magnetic field strength. Our sample is unique and offers crucial input for forthcoming evolutionary models that include the effects of magnetic fields for upper main sequence stars.
This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of gamma-ray bursts. For a summary, we refer to the paper.
Recent observations of molecular clouds show that dense filaments are the sites of present-day star formation. Thus, it is necessary to understand the filament formation process because these filaments provide the initial condition for star formation. Theoretical research suggests that shock waves in molecular clouds trigger filament formation. Since several different mechanisms have been proposed for filament formation, the formation mechanism of the observed star-forming filaments requires clarification. In the present study, we perform a series of isothermal magnetohydrodynamics simulations of filament formation. We focus on the influences of shock velocity and turbulence on the formation mechanism and identified three different mechanisms for the filament formation. The results indicate that when the shock is fast, at shock velocity v_sh = 7 km/s, the gas flows driven by the curved shock wave create filaments irrespective of the presence of turbulence and self-gravity. However, at a slow shock velocity v_sh = 2.5 km/s, the compressive flow component involved in the initial turbulence induces filament formation. When both the shock velocities and turbulence are low, the self-gravity in the shock-compressed sheet becomes important for filament formation. Moreover, we analyzed the line-mass distribution of the filaments and showed that strong shock waves can naturally create high-line-mass filaments such as those observed in the massive star-forming regions in a short time. We conclude that the dominant filament formation mode changes with the velocity of the shock wave triggering the filament formation.
We present a quasilocal formalism, based on the one proposed by Brown and York, for dilaton gravity with Yang-Mills fields. For solutions possessing sufficient symmetry, we define conserved quantities such as mass, angular momentum, and charge. We also present a micro-canonical action and use it to arrive at a quasilocal version of the first law of thermodynamics for static systems containing a black hole.
The description of the baryon spectrum is performed using the hypercentral Consituent Quark Model (hCQM), mainly in comparison with the harmonic oscillator (h.o.). Recentlly many new states, at various levels of confidence have been observed, leading to a softening of the missing resonance problem in the case of positive parity states. However, the number of negative states is higher that predicted by the commonly used h.o. scheme and therefore one is forced to take into account also the higher energy shells, which contain an overall number of states much greater than the observed one. It is shown that, thanks to the peculiar level scheme of the hCQM, the recently observed negative parity states can be considered as belonging to the lower shells, keeping the missing resonance problem within more acceptable limits.
We investigate the spatial distribution of star formation (SF) within bars of nearby disk galaxies (inclination $< 65^{\circ}$) from the S$^4$G survey. We use archival GALEX far- and near-UV imaging for 772 barred galaxies. We also assemble a compilation of continuum-subtracted H$\alpha$ images for 433 barred galaxies, of which 70 are produced by ourselves from ancillary photometry and MUSE/CALIFA IFU data cubes. We employ two complementary approaches: i) the analysis of bar/disk stacks built from co-added UV images of hundreds of galaxies; and ii) the classification of the morphology of ionised regions in galaxies into three main SF classes: A) only circumnuclear SF, B) SF at the bar ends, but not along the bar, and C) SF along the bar. Lenticular galaxies typically belong to SF class A: this is probably related to bar-induced SF quenching. The distribution of SF class B peaks for early- and intermediate-type spirals: this most likely results from the interplay of gas flow, shocks, and enhanced shear in centrally concentrated galaxies with large bar amplitudes. Late-type galaxies are mainly assigned to SF class C: we argue that this is a consequence of low shear. In bar stacks of spirals, the UV emission traces the stellar bars and dominates on their leading side, as witnessed in simulations. For early-types, the central UV emission is $\sim$0.5 mag brighter in strongly barred galaxies, relative to their weakly barred counterparts: this is related to the efficiency of strong bars sweeping the disk gas and triggering central starbursts. We also show that the distributions of SF in inner ringed galaxies are broadly the same in barred and non-barred galaxies, including a UV/H$\alpha$ deficit in the middle part of the bar: this hints at the effect of resonance rings trapping gas. Distinct distributions of SF within bars are reported in galaxies of different morphological types (Abridged).
We determine the homological dimension of various isogeny categories of commutative algebraic groups over a field $k$, in terms of the cohomological dimension of $k$ at certain primes. This generalizes results of Serre, Oort and Milne, by an alternative approach.
We systematically study the coherent transport (Josephson tunneling and counterflow current) and its breakdown which leads to incoherent charge flow in in the excitonic BCS condensate formed in GaAs bilayers at $\nu_{tot}=1/2+1/2$. The Josephson currents in samples with three different interlayer distances vary by four orders of magnitude. In contrast, the breakdown thresholds for the $\nu_{tot}=1$ quantum Hall state are comparable. Furthermore, Coulomb drag in a Corbino ring reveals that the coherent counterflow current coexists with the dissipative charge transport.
We demonstrate preferential orientation of nitrogen-vacancy (NV) color centers along two of four possible crystallographic axes in diamonds grown by chemical vapor deposition on the {100} face. We identify the relevant growth regime and present a possible explanation of this effect. We show that preferential orientation provides increased optical read-out contrast for NV multi-spin measurements, including enhanced AC magnetic field sensitivity, thus providing an important step towards high fidelity multi-spin-qubit quantum information processing, sensing and metrology.
We introduce a scalable photonic platform that enables efficient generation of entangled photon pairs from a semiconductor quantum dot. Our system, which is based on a self-aligned quantum dot-micro-cavity structure, erases the need for complex steps of lithography and nanofabrication. We experimentally show collection efficiency of 0.17 combined with a Purcell enhancement of up to 1.7 in the pair emission process. We harness the potential of our device to generate photon pairs entangled in time bin, reaching a fidelity of 0.84(5) with the maximally entangled state. The achieved pair collection efficiency is 4 times larger than the state-of-the art. The device, which theoretically supports pair extraction efficiencies of nearly 0.5 is a promising candidate for the implementation of bright sources of time-bin, polarization- and hyper entangled photon pairs in a straightforward manner.
Based on density functional theory calculations, the structural and electronic properties of polythiophene in periodic and oligomer forms have been investigated. In particular, the effects of Li or Cl adsorption onto a monolayer and Li or Cl-intercalation into bulk or bilayer polythiophene are addressed using periodic calculations. The binding energy of Li or Cl adsorbed bulk or bilayer polythiophene is significantly larger than for the monolayer. The trends in the binding energy as a function of adsorbent remain the same for both the periodic and molecular cases. The band gap or HOMO-LUMO gap and charge transfer are analysed. In addition, for the bulk or bilayer, different kinds of stacking have been considered. It is found that the parallel bulk or bilayer structure is energetically favorable compared to flipping the second layer by 180$^\circ$. This has been considered for both the periodic and oligomer forms. Moreover, for Li adsorption, polarons are found to be more stable than bipolarons, while the situation is opposite for Cl adsorption. The detailed analysis of the present study will be useful for understanding the structural properties and the tuneability of the electronic states, which is an important step to construct polythiophene based electronic devices.
Le & Dermer developed a gamma-ray burst (GRB) model to fit the redshift and the jet opening angle distributions measured with pre-Swift and Swift missions and showed that GRBs do not follow the star formation rate. Their fitted results were obtained without the opening angle distribution from Swift with an incomplete Swift sample, and that the calculated jet opening angle distribution was obtained by assuming a flat $\nu F_\nu$ spectrum. In this paper, we revisit the work done by Le & Dermer with an assumed broken power law GRB spectrum. Utilizing more than 100 GRBs in the Swift sample that include both the observed estimated redshifts and jet opening angles, we obtain a GRB burst rate functional form that gives acceptable fits to the pre-Swift and Swift redshift and jet opening angle distributions with an indication that an excess of GRBs exists at low redshift below $z \approx 2$. The mean redshifts and jet opening angles for pre-Swift~(Swift) are $\langle z \rangle \sim 1.3$ ($1.7$) and $\langle \theta_{\rm j} \rangle \sim 7^o$ ($11^o$), respectively. Assuming a GRB rate density (SFR9), similar to the Hopkins & Beacom star formation history and as extended by Li, the fraction of high-redshift GRBs is estimated to be below 10% and 5% at $z \geq 4$ and $z\geq 5$, respectively, and below 10% at $z \leq 1$.
By using Fourier-transform scanning tunneling spectroscopy we measure the interference patterns produced by the impurity scattering of confined Dirac quasiparticles in epitaxial graphene nanoflakes. Upon comparison of the experimental results with tight-binding calculations of realistic model flakes, we show that the characteristic features observed in the Fourier-transformed local density of states are related to scattering between different transverse modes (sub-bands) of a graphene nanoflake and allow direct insight into the electronic spectrum of graphene. We also observe a strong reduction of quasiparticle lifetime which is attributed to the interaction with the underlying substrate. In addition, we show that the distribution of the onsite energies at flower defects leads to an effectively broken pseudospin selection rule, where intravalley back-scattering is allowed.
In this paper, we first introduce geometric operations for linear categories, and as a consequence generalize Orlov's blow up formula [O04] to possibly singular local complete intersection centres. Second, we introduce refined blowing up of linear category along base--locus, and show that this operation is dual to taking linear section. Finally, as an application we produce examples of Calabi--Yau manifolds which admits Calabi--Yau categories fibrations over projective spaces.
We predict a novel quantum interference based on the negative refraction across a semiconductor P-N junction: with a local pump on one side of the junction, the response of a local probe on the other side behaves as if the disturbance emanates not from the pump but instead from its mirror image about the junction. This phenomenon is guaranteed by translational invariance of the system and matching of Fermi surfaces of the constituent materials, thus it is robust against other details of the junction (e.g., junction width, potential profile, and even disorder). The recently fabricated P-N junctions in 2D semiconductors provide ideal platforms to explore this phenomenon and its applications to dramatically enhance charge and spin transport as well as carrier-mediated long-range correlation.