ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present the results of numerically solving the rate equations for the first 31 rotational states of CS in the ground vibrational state to determine the conditions under which the J=1-0, J=2-1 and J=3-2 transitions are inverted to produce maser emission. The essence of our results is that the CS($v=0$) masers are collisionally pumped and that, depending on the spectral energy distribution, dust emission can suppress the masers. Apart from the J=1-0 and J=2-1 masers the calculations also show that the J=3-2 transition can be inverted to produce maser emission. It is found that beaming is necessary to explain the observed brightness temperatures of the recently discovered CS masers in W51 e2e. The model calculations suggest that a CS abundance of a few times $10^{-5}$ and CS($v=0$) column densities of the order $10^{16}\,\mathrm{cm^{-2}}$ are required for these masers. The rarity of the CS masers in high mass star forming regions might be the result of a required high CS abundance as well as due to attenuation of the maser emission inside as well as outside of the hot core.
We show how to recover the underlying topological space of a quasi-compact quasi-separated scheme from the tensor triangulated structure on its category of perfect complexes.
Among 19 red-giant stars belonging to eclipsing binary systems that have been identified in Kepler data, 15 display solar-like oscillations. We study whether the absence of mode detection in the remaining 4 is an observational bias or possibly evidence of mode damping that originates from tidal interactions. A careful analysis of the corresponding Kepler light curves shows that modes with amplitudes that are usually observed in red giants would have been detected if they were present. We observe that mode depletion is strongly associated with short-period systems, in which stellar radii account for 16-24 % of the semi-major axis, and where red-giant surface activity is detected. We suggest that when the rotational and orbital periods synchronize in close binaries, the red-giant component is spun up, so that a dynamo mechanism starts and generates a magnetic field, leading to observable stellar activity. Pressure modes would then be damped as acoustic waves dissipate in these fields.
This paper deals with some qualitative properties of entropy solutions to hyperbolic conservation laws. In [11] the jump set of entropy solution to conservation laws has been introduced. We find an entropy solution to scalar conservation laws for which the jump set is not closed, in particular, it is dense in a space-time domain. In the later part of this article, we obtain a similar result for the hyperbolic system. We give two different approaches for scalar conservation laws and hyperbolic system to obtain the results. For the scalar case, obtained solutions are more explicitly calculated.
L\'evy flights and L\'evy walks serve as two paradigms of random walks resembling common features but also bearing fundamental differences. One of the main dissimilarities are discontinuity versus continuity of their trajectories and infinite versus finite propagation velocity. In consequence, well developed theory of L\'evy flights is associated with their pathological physical properties, which in turn are resolved by the concept of L\'evy walks. Here, we explore L\'evy flights and L\'evy walks models on bounded domains examining their differences and analogies. We investigate analytically and numerically whether and under which conditions both approaches yield similar results in terms of selected statistical observables characterizing the motion: the survival probability, mean first passage time and stationary PDFs. It is demonstrated that similarity of models is affected by the type of boundary conditions and value of the stability index defining asymptotics of the jump length distribution.
A theory of the anisotropic superexchange and low energy spin excitations in a Mott insulator with t_{2g} orbital degeneracy is presented. We observe that the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the spin Hamiltonian, which invalidate noninteracting spin wave theory. The frustration of classical states is resolved by an order from disorder mechanism, which selects a particular direction of the staggered moment and generates a quantum spin gap. The theory explains well the observed magnon gaps in LaTiO_3. As a test case, a specific prediction is made on the splitting of magnon branches at certain momentum directions.
The transition from prompt to the afterglow emission is one of the most exciting and least understood phases in gamma-ray bursts (GRBs). Correlations among optical, X-ray and gamma-ray emission in GRBs have been explored, to attempt to answer whether the earliest optical emission comes from internal and/or external shocks. We present optical photometric observations of GRB 180325A collected with the TAROT and RATIR ground-based telescopes. These observations show two strong optical flashes with separate peaks at $\sim50\;$s and $\sim120\;$s, followed by a temporally extended optical emission. We also present X-rays and gamma-ray observations of GRB 180325A, detected by the Burst Alert Telescope (BAT) and X-ray Telescope (XRT), on the Neil Gehrels Swift observatory, which both observed a narrow flash at $\sim80\;$s. We show that the prompt gamma- and X-ray early emission shares similar temporal and spectral features consistent with internal dissipation within the relativistic outflow (e.g. by internal shocks or magnetic reconnection), while the early optical flashes are likely generated by the reverse shock that decelerates the ejecta as it sweeps up the external medium.
We study the effect of disorder on the spacetime supersymmetry that is proposed to emerge at the quantum critical point of pair density wave transition in (2+1)D Dirac semimetals and (3+1)D Weyl semimetals. In the (2+1)D Dirac semimetal, we consider three types of disorder, including random scalar potential, random vector potential and random mass potential, while the random mass disorder is absent in the (3+1)D Weyl semimetal. Via a systematic renormalization group analysis, we find that any type of weak random disorder is irrelevant due to the couplings between the disorder potential and the Yukawa vertex. The emergent supersymmetry is thus stable for weak random potentials. Our work will pave the way for exploration supersymmetry in realistic condensed matter systems.
In view of recent measurements of the mixing angle \theta_{13} a possibility to determine the difference of two CP Majorana phases of the neutrino mixing matrix from the study of neutrinoless double-beta decay is investigated. We show that in the case of the inverted hierarchy of neutrino masses it might be possible if neutrinoless double-beta decay will be observed. The required experimental accuracies and uncertainty in the calculated nuclear matrix elements of the process are discussed.
It is shown that the form factors in the semileptonic decay of ground state heavy mesons to light pseudoscalar mesons are dominated by the vector meson pole at all momentum transfers. First, the general approaches to modeling form factors in terms of quark model, pole dominance, or hybrid shapes are reviewed. It is then shown that in the combined limits of heavy quarks, chiral symmetry, and large~$\Nc$ the form factor is precisely pole-dominated. It is also shown that in a two-dimensional QCD model pole-dominance occurs for any heavy quark mass. Corrections to this limit are discussed and, to illustrate the nature of the approximations, an explicit exact calculation of the approach to the limit in a two-dimensional model is given.
The Gaia mission has provided the largest ever astrometric chart of the Milky Way. Using it to map the Galactic halo is helpful for disentangling its merger history. The identification of halo stars in Gaia DR2 with reliable distance estimates requires special methods because such stars are typically farther away and scarce. We apply the reduced proper motion (RPM) method to identify halo main sequence stars on the basis of Gaia photometry and proper motions. Using the colour-absolute-magnitude relation for this type of stars, we calculate photometric distances. Our selection results in a set of $\sim10^7$ tentative main sequence halo stars with typical distance uncertainties of $7\%$ and with median velocity errors of 20 km/s. The median distance of our sample is $\sim 4.4$ kpc, with the faintest stars located at $\sim 16$ kpc. The spatial distribution of the stars in our sample is centrally concentrated. Visual inspection of the mean velocities of stars on the sky reveals large-scale patterns as well as clear imprints of the GD-1 stream and tentative hints of the Jhelum and Leiptr streams. Incompleteness and selection effects limit our ability to interpret the patterns reliably as well as to identify new substructures. We define a pseudo-velocity space by setting to zero the line-of-sight velocities of our sample stars. In this space, we recover several known structures such as the footprint of Gaia-Enceladus (i.e. the Gaia-Sausage) as well as the Helmi streams and some other retrograde substructures (Sequoia, Thamnos). We show that the two-point velocity correlation function reveals significant clustering on scales smaller than 100 km/s, of similar amplitude as found for the 6D Gaia halo sample. This clustering indicates the presence of nearby streams that are predominantly phase-mixed.
The physics of quantum many-body systems have been studied using bulk correlated materials, and recently, moir\'e superlattices formed by atomic bilayers have appeared as a novel platform in which the carrier concentration and the band structures are highly tunable. In this brief review, we introduce an intermediate platform between those systems, namely, a band-filling- and bandwidth-tunable electric double-layer transistor based on a real organic Mott insulator $\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Cl. In the proximity of the bandwidth-control Mott transition at half filling, both electron and hole doping induced superconductivity (with almost identical transition temperatures) in the same sample. The normal state under electric double-layer doping exhibited non-Fermi liquid behaviors as in many correlated materials. The doping levels for the superconductivity and the non-Fermi liquid behaviors were highly doping-asymmetric. Model calculations based on the anisotropic triangular lattice explained many phenomena and the doping asymmetry, implying the importance of the noninteracting band structure (particularly the flat part of the band).
Quasars represent the brightest Active Galactic Nuclei (AGN) in the Universe and are thought to indicate the location of prodigiously growing Black Holes (BHs), with luminosities as high as 10^48 erg/sec. It is often expected though that such an extremely energetic process will take place in the most massive bound structures in the dark matter (DM) distribution. We show that in contrast to this expectation, in a galaxy formation model which includes AGN feedback, quasars are predicted to live in average DM halo environments with typical masses of a few times 10^12 Msun. This fundamental prediction arises from the fact that quasar activity (i.e., BH accretion with luminosity greater than 10^46 erg/sec) is inhibited in DM haloes where AGN feedback operates. The galaxy hosts of quasars in our simulations are identified with over massive (in gas and stars) spheroidal galaxies, in which BH accretion is triggered via a galaxy merger or secular processes. We further show that the z=0 descendants of high redshift (z~6) QSOs span a wide range of morphologies, galaxy and halo masses. The z~6 BHs typically grow only by a modest factor by the present day. Remarkably, high redshift QSOs never inhabit the largest DM haloes at that time and their descendants are very seldom found in the most massive haloes at z=0. We also show that observationally it is very likely to find an enhancement in the abundance of galaxies around quasars at z~5. However, these enhancements are considerably weaker compared to the overdensities expected at the extreme peaks of the DM distribution. Thus, it is very unlikely that a quasar detected in the $z\gtrsim5$ Universe pinpoints the location of the progenitors of superclusters in the local Universe.
Interface states at a boundary between regions with different spin-orbit interactions (SOIs) in two-dimensional (2D) electron systems are investigated within the one-band effective mass method with generalized boundary conditions for envelope functions. We have found that the interface states unexpectedly exist even if the effective interface potential equals zero. Depending on the system parameters, the energy of these states can lie in either or both forbidden and conduction bands of bulk states. The interface states have chiral spin texture similar to that of the edge states in 2D topological insulators. However, their energy spectrum is more sensitive to the interfacial potential, the largest effect being produced by the spin-dependent component of the interfacial potential. We have also studied the size quantization of the interface states in a strip of 2D electron gas with SOI and found an unusual (non-monotonic) dependence of the quantization energy on the strip width.
We present the stellar mass functions (SMFs) of passive and star-forming galaxies with a limiting mass of 10$^{10.1}$ M$_{\odot}$ in four spectroscopically confirmed Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) galaxy clusters at 1.37 $<$ z $<$ 1.63. The clusters have 113 spectroscopically confirmed members combined, with 8-45 confirmed members each. We construct $Ks$-band-selected photometric catalogs for each cluster with an average of 11 photometric bands ranging from $u$ to 8 $\mu$m. We compare our cluster galaxies to a field sample derived from a similar $Ks$-band-selected catalog in the UltraVISTA/COSMOS field. The SMFs resemble those of the field, but with signs of environmental quenching. We find that 30 $\pm$ 20\% of galaxies that would normally be forming stars in the field are quenched in the clusters. The environmental quenching efficiency shows little dependence on projected cluster-centric distance out to $\sim$ 4 Mpc, providing tentative evidence of pre-processing and/or galactic conformity in this redshift range. We also compile the available data on environmental quenching efficiencies from the literature, and find that the quenching efficiency in clusters and in groups appears to decline with increasing redshift in a manner consistent with previous results and expectations based on halo mass growth.
We studied the large-amplitude SU UMa-type dwarf nova V344 Lyr. A combination of our observations and reports to VSNET has yielded an extensive coverage of outbursts between 1994 July and 2001 June. The analysis of this data showed a mean supercycle length of 109.6 d. This value is one of the smallest among known SU UMa-type dwarf novae (except unusual ER UMa-type dwarf novae). The outburst amplitude of V344 Lyr (~5.5 mag) is found to be much larger than those (3.5 +/- 0.3 mag) of SU UMa-type dwarf novae with similar supercycle lengths. Such a deviation of the amplitude in V344 Lyr is difficult to explain by the inclination effect. The extreme outburst parameters of V344 Lyr would require an additional mechanism to effectively reduce the quiescent luminosity or to increase the outburst frequency.
We use the circularly polarized resonant Rayleigh scattering (RRS) to study the quantum Hall ferromagnet at $\nu$ = 1. At this filling factor we observe a right handed copolarized RRS which probes the Skyrmion spin texture of the electrons in the photoexcited grounds state. The resonant scattering is not present in the left handed copolarization, and this can be related to the correlation between Skymionic effects, screening and spin wave excitations. These results evidence that RRS is a valid method for the study of the spin texture of the quantum Hall states.
We perform calculations of the variation after parity projection with Skyrme interaction for ground and excited states of even-even Mg isotopes. Using the 3D real-space representation, we can take into account any kind of deformation; e.g., cluster structure, gamma-deformation. We also perform the full 3D angular momentum projection to obtained rotational spectra and B(E2). In 24Mg, the ground K^pi=0+ and several odd-parity bands are calculated. In 30,32,34Mg, our calculation reproduces a breaking of the N=20 magic number, so-called "Island of inversion" phenomena. Properties of both the ground and excited states are reasonably reproduced.
We are concerned with the numerical resolution of backward stochastic differential equations. We propose a new numerical scheme based on iterative regressions on function bases, which coefficients are evaluated using Monte Carlo simulations. A full convergence analysis is derived. Numerical experiments about finance are included, in particular, concerning option pricing with differential interest rates.
We present new XMM-Newton observations of the supernova remnant N120 in the LMC, and numerical simulations on the evolution of this supernova remnant which we compare with the X-ray observations. The supernova remnant N120, together with several HII regions, forms a large nebular complex5D (also called N120) whose shape resembles a semicircular ring. From the XMM-Newton data we generate images and spectra of this remnant in the energy band between 0.2 to 2.0 keV. The images show that the X-ray emission is brighter towards the east (i.e., towards the rim of the large nebular complex). The EPIC/MOS1 and MOS2 data reveal a thermal spectrum in soft X-rays. 2D axisymmetric numerical simulations with the Yguaz\'u-a code were carried out assuming that the remnant is expanding into an inhomogeneous ISM with an exponential density gradient and showing that thermal conduction effects are negligible. Simulated X-ray emission maps were obtained from the numerical simulations in order to compare them with the observations. We find good agreement between the XMM-Newton data, previous optical kinematic data, and the numerical simulations; the simulations reproduce the observed X-ray luminosity and surface brightness distribution. We have also detected more extended diffuse X-ray emission probably due to the N120 large HII complex or superbubble.
When searching for Calabi.Yau differential equations, often different formulas for the coefficients give the same differential equation. The coefficients are usually sums (simple, double or triple) of products of binomial coefficients. This results in numerous binomial identities.
The Fibonacci sequence has been generalized in many ways. One of them is defined by the relation $t_n=at_{n-1}+t_{n-2}$ if $n$ is even, $t_n=bt_{n-1}+t_{n-2}$ if $n$ is odd, with initial values $t_0=0$ and $t_1=1$, where $a$ and $b$ are positive integers. This sequence is called biperiodic Fibonacci sequence. In this paper, we introduce a $q$-analogue of this sequence. We prove several identities of $q$-analogues of the Fibonacci sequence. We give algebraic and combinatorial proofs.
Most Heisenberg-like spin chains flow to a universal free-fermion fixed point near the magnetic-field induced saturation point. Here we show that an exotic fixed point, characterized by two species of low-energy excitations with mutual anyonic statistics, may also emerge in such spin chains if the dispersion relation has two minima. By using bosonization, two-magnon exact calculations, and numerical density-matrix-renormalization-group, we demonstrate the existence of this anyonic-liquid fixed point in an XXZ spin chain with up to second neighbor interactions. We also identify a range of microscopic parameters, which support this phase.
The parametrized system called ``ideal clock'' is turned into an ordinary gauge system and quantized by means of a path integral in which canonical gauges are admissible. Then the possibility of applying the results to obtain the transition amplitude for empty minisuperspaces, and the restrictions arising from the topology of the constraint surface, are studied by matching the models with the ideal clock. A generalization to minisuperspaces with true degrees of freedom is also discussed.
Temporal analysis of INTEGRAL/IBIS data has revealed a 5.7195\pm0.0007 day periodicity in the supergiant fast X-ray transient (SFXT) source AX J1845.0-0433, which we interpret as the orbital period of the system. The new-found knowledge of the orbital period is utilised to investigate the geometry of the system by means of estimating an upper limit for the size of the supergiant (<27 R_{\sun}) as well as the eccentricity of the orbit (\epsilon<0.37).
Annealing has been extensively used to control crystal growth and physical properties of materials with unfortunately unclear mechanism and quantitative correlations. Here we present the "annealing temperature - grain size - band gap" correlation for ZnO nanocrystals with experimental evidence. Findings revealed that the annealing condition determines the critical size by equating the thermal and the cohesive energy of the undercoordinated atoms in the surface skin, which in turn induce local strain and quantum entrapment, perturbing the Hamiltonian and hence the band gap. The formulation provides a general guideline for controlling crystal growth and performance of materials, and makes predictive design and fabrication of functional nanomaterials into reality.
A numerical method for computation of heteroepitaxial growth in the presence of strain is presented. The model used is based on a solid-on-solid model with a cubic lattice. Elastic effects are incorporated using a ball and spring type model. The growing film is evolved using Kinetic Monte Carlo (KMC) and it is assumed that the film is in mechanical equilibrium. The strain field in the substrate is computed by an exact solution which is efficiently evaluated using the fast Fourier transform. The strain field in the growing film is computed directly. The resulting coupled system is solved iteratively using the conjugate gradient method. Finally we introduce various approximations in the implementation of KMC to improve the computation speed. Numerical results show that layer-by-layer growth is unstable if the misfit is large enough resulting in the formation of three dimensional islands.
SWIFT bursts appear to be more distant than previous bursts. We present the Boer & Gendre relation that link redshift and afterglow luminosities. Taking advantage of the XMM-Newton, Chandra and BeppoSAX catalogs, and using this relation, we have investigated the redshift distribution of GRBs. We find that XMM burst sources with unknown redshift appear to be more distant than those with a known redshift. We propose that this effect may be due to a selection effect of pre-SWIFT optical observations.
In this paper, we formally introduce the notion of Ap{\'e}ry-like sums and we show that every multiple zeta values can be expressed as a $\bf Z$-linear combination of them. We even describe a canonical way to do so. This allows us to put in a new theoretical context several identities scattered in the literature, as well as to discover many new interesting ones. We give in this paper new integral formulas for multiple zeta values and Ap\'ery-like sums. They enable us to give a short direct proof of Zagier's formulas for $\zeta(2,\ldots,2,3,2,\ldots,2)$ as well as of similar ones in the context of Ap{\'e}ry-like sums. The relations between Ap\'ery-like sums themselves still remain rather mysterious, but we get significant results and state some conjectures about their pattern.
Inertial effects in non-inertial reference frames are compared with quantum properties of tests objects. The real space-time and perfect inertial reference frame can be compared accurate to the uncertainty relation. Complexities if describing micro-object in non-inertial reference-frames are avoidable using Ostrogradski's Canonical Formalism.