ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present the specific heat, magnetization, optical spectroscopy measurements and the firstprinciple calculations on the Weberite structure Ca2Os2O7 single crystal/polycrystalline sample. The Ca2Os2O7 shows a Curie-Weiss nature at high temperature and goes into a ferrimagnetic insulating state at 327 K on cooling. A \lambda-like peak is observed at 327 K in the specific heat implying a second-order phase transition. The vanishing electronic specific heat at low temperature suggests a full energy gap. At high temperature above the transition, small amount of itinerant carriers with short life time \tau are observed, which is gapped at 20 K with a direct gap of 0:24 eV . Our first principle calculations indicate that the anti-ferromagnetic (AFM) correlation with intermediate Coulomb repulsion U could effectively split Os(4b) t2g bands and push them away from Fermi level(EF). On the other hand, a non-collinear magnetic interaction is needed to push the Os(4c) bands away from EF, which could be induced by Os(4c)-Os(4c) frustration. Therefore, AFM correlation, Coulomb repulsion U and non-collinear interaction all play important roles for the insulating ground state in Ca2Os2O7.
The mechanism of transition from laminar state to turbulent state in Keplerian disks is still unknown. The most popular version today is generation of turbulence due to magnetorotational instability (MRI). However magnetohydrodynamic simulations give the value of Shakura-Sunyaev parameter more then an order of magnitude smaller rather than that found from observations. One way to solve this problem is the existence of an alternative or additional mechanism for generating turbulence. It can be the bypass mechanism, which is responsible for transition to turbulence in Couette and Poiseuille flows. This mechanism is based on the transient growth of linear perturbations in the flow with the subsequent transition to the nonlinear stage. In order to clarify the role of this mechanism in astrophysical disks first of all it is necessary to calculate the maximal possible growth factor of linear perturbations in the flow. In this paper the results of such calculations are presented for perturbations on different scales compared with the disk thickness. Qualitative description of mechanisms responsible for the growth will also be presented. It was found that the most rapidly growing shear harmonics have azimuthal wavelength of the order of the disk thickness. In addition, their initial form is always similar to the vortex perturbations with the same potential vorticity. It was shown that the vortices with azimuthal wavelength more than an order of magnitude in excess of the disc thickness, are still able to grow by dozens of times.
Direct measurements of magnetic fields in low-mass stars of spectral class M have become available during the last years. This contribution summarizes the data available on direct magnetic measurements in M dwarfs from Zeeman analysis in integrated and polarized light. Strong magnetic fields at kilo-Gauss strength are found throughout the whole M spectral range, and so far all field M dwarfs of spectral type M6 and later show strong magnetic fields. Zeeman Doppler images from polarized light find weaker fields, which may carry important information on magnetic field generation in partially and fully convective stars.
Context. Departures from local thermodynamic equilibrium (LTE) distort the calcium abundance derived from stellar spectra in various ways, depending on the lines used and the stellar atmospheric parameters. The collection of atomic data adopted in non-LTE (NLTE) calculations must be sufficiently complete and accurate. Aims. We derive NLTE abundances from high-quality observations and reliable stellar parameters using a model atom built afresh for this work, and check the consistency of our results over a wide wavelength range with transitions of atomic and singly ionised calcium. Methods. We built and tested Ca i and Ca ii model atoms with state-of-the-art radiative and collisional data, and tested their performance deriving the Ca abundance in three benchmark stars: Procyon, the Sun, and Arcturus. We have excellent-quality observations and accurate stellar parameters for these stars. Two methods to derive the LTE / NLTE abundances were used and compared. The LTE / NLTE centre-to-limb variation (CLV) of Ca lines in the Sun was also investigated. Results. The two methods used give similar results in all three stars. Several discrepancies found in LTE do not appear in our NLTE results; in particular the agreement between abundances in the visual and infra-red (IR) and the Ca i and Ca ii ionisation balance is improved overall, although substantial line-to-line scatter remains. The CLV of the calcium lines around 6165 Angs can be partially reproduced. We suspect differences between our modelling and CLV results are due to inhomogeneities in the atmosphere that require 3D modelling.
In this article, we propose a wellposedness theory for a class of second order backward doubly stochastic differential equation (2BDSDE). We prove existence and uniqueness of the solution under a Lipschitz type assumption on the generator, and we investigate the links between our 2BDSDEs and a class of parabolic fully nonLinear Stochastic PDes. Precisely, we show that the Markovian solution of 2BDSDEs provide a probabilistic interpretation of the classical and stochastic viscosity solution of fully nonlinear SPDEs.
Quantum walks on lattices can give rise to one-particle relativistic wave equations in the long-wavelength limit. In going to multiple particles, quantum cellular automata (QCA) are natural generalizations of quantum walks. In one spatial dimension, the quantum walk can be "promoted" to a QCA that, in the long-wavelength limit, gives rise to the Dirac quantum field theory (QFT) for noninteracting fermions. This QCA/QFT correspondence has both theoretical and practical applications, but there are obstacles to similar constructions in two or more spatial dimensions. Here we show that a method of construction employing distinguishable particles confined to the completely antisymmetric subspace yields a QCA in two spatial dimensions that gives rise to the 2D Dirac QFT. Generalizing to 3D will entail some additional complications, but no conceptual barriers. We examine how this construction evades the "no go" results in earlier work.
We investigate the existence and multiplicity of solutions to the following $p(x)$-Laplacian problem in $\mathbb{R}^{N}$ via critical point theory \begin{equation*} \left\{ \begin{array}{l} -\bigtriangleup _{p(x)}u+V(x)\left\vert u\right\vert ^{p(x)-2}u=f(x,u),\text{ in } \mathbb{R}^{N}, \\ u\in W^{1,p(\cdot )}(\mathbb{R}^{N}). \end{array} \right. \end{equation*} We propose a new set of growth conditions which matches the variable exponent nature of the problem. Under this new set of assumptions, we manage to verify the Cerami compactness condition. Therefore, we succeed in proving the existence of multiple solutions to the above problem without the well-known Ambrosetti--Rabinowitz type growth condition. Meanwhile, we could also characterize the pointwise asymptotic behaviors of these solutions. In our main argument, the idea of localization, decomposition of the domain, regularity of weak solutions and comparison principle are crucial ingredients among others.
We present an aberration corrected scanning transmission electron microscopy (ac-STEM) analysis of the perovskite (LaFeO3) and pyrochlore (Yb2Ti2O7 and Pr2Zr2O7) oxides and demonstrate that both the shape and contrast of visible atomic columns in annular dark-field (ADF) images are sensitive to the presence of nearby atoms of low atomic number (e.g. oxygen). We show that point defects (e.g. oxygen vacancies), which are invisible - or difficult to observe due to limited sensitivity - in X-ray and neutron diffraction measurements, are the origin of the complex magnetic ground state of pyrochlore oxides. In addition, we present, for the first time, a method by which light atoms can be resolved in quantitative ADF-STEM images. Using this method, we resolved oxygen atoms in perovskite and pyrochlore oxides.
We discuss a holographic soft-wall model developed for the description of mesons and baryons with adjustable quantum numbers n, J, L, S. This approach is based on an action which describes hadrons with broken conformal invariance and which incorporates confinement through the presence of a background dilaton field.
We review the string construction of the ``orientifold field theories'' and we show that for these theories the gauge/gravity correspondence is only valid for a large number of colours.
Assuming the existence of a new real scalar singlet $s^0$ coupled to the Standard Model via a scalar quartic portal interaction, we compute the radiative corrections to the decay rates of the heavy scalar mass eigenstate to a couple of gauge bosons $ZZ$ and $W^+W^-(\gamma)$, showing that they can give a contribution as large as ${\cal{O}}$(5\%) and ${\cal{O}}$(7\%), respectively. We also explicitly analyze in detail their dependence on the heavy mass $m_S$ and on the scalar mixing angle $\alpha$, finding that, especially in the large-mass region, these depend on the sign of $\sin\alpha$.
The acceleration of cosmic ray particles and their propagation in the Milky Way and the heliosphere tangle with each other, leading to complexity and degeneracy of the modeling of Galactic cosmic rays (GCRs). The recent measurements of the GCR spectra by Voyager-1 from outside of the heliosphere gave a first direct observation of GCRs in the local interstellar (LIS) environment. Together with the high-precision data near the Earth taken by ACE and AMS-02, we derive the LIS spectra of Helium, Lithium, Beryllium, Boron, Carbon, and Oxygen nuclei from a few MeV/n to TeV/n, using a non-parameterization method. These LIS spectra are helpful in further studying the injection and propagation parameters of GCRs. The nearly 20 years of data recorded by ACE are used to determine the solar modulation parameters over the solar cycles 23 and 24, based on the force-field approximation. We find general agreements of the modulation potential with the results inferred from neutron monitors and other cosmic ray data.
We prove several results from different areas of extremal combinatorics, including complete or partial solutions to a number of open problems. These results, coming mainly from extremal graph theory and Ramsey theory, have been collected together because in each case the relevant proofs are quite short.
In this paper, some properties of multi-qubit states traveling in non-inertial frames are investigated, where we assume that all particles are accelerated. These properties are including fidelities, capacities and entanglement of the accelerated channels for three different states, namely, Greeberger-Horne-Zeilinger (GHZ) state, GHZ-like state and W-state. It is shown here that all these properties are decreased as the accelerations of the moving particles are increased. The obtained results show that the GHZ-state is the most robust one comparing to the others, where the degradation rate is less than that for the other states particularly in the second Rindler region. Also, it is shown here that the entangled property doesn't change in the accelerated frames. Additionally, the paper shows that the degree of entanglement decreases as the accelerations of the particles increase in the first Rindler region. However in the second region, where all subsystems are disconnected at zero acceleration, entangled channels are generated as the acceleration increases. Keywords: Multi-qubit states, Non-inertial frame, Fidelity, Capacity, Entanglement, GHZ state, GHZ-like state, W-state.
The Telescope Array (TA) experiment is designed to observe cosmic-ray-induced air showers at extremely high energies. It is being deployed in a desert of Utah, USA; an array of 3 m^2 scintillation counters will be distributed over 760 km^ and 3 sets of air fluorescence telescopes will be placed in the perimeter of the array. It's primary purpose is to make a decisive measurement of the cosmic ray spectrum in the GZK cutoff region. We expect the first data from the TA in the spring of 2007. As its unique features are included 1) hybrid measurement planned down to 10^17.5 eV, 2) calibration of fluorescence detection by using artificial air showers generated by an electron linac, 3) interaction model calibration by the LHC.
In this paper we consider the field of local times of a discrete-time Markov chain on a general state space, and obtain uniform (in time) upper bounds on the total variation distance between this field and the one of a sequence of $n$ i.i.d. random variables with law given by the invariant measure of that Markov chain. The proof of this result uses a refinement of the soft local time method of [11].
The CO-to-H$_2$ conversion factor ($\alpha_\rm{CO}$) is critical to studying molecular gas and star formation in galaxies. The value of $\alpha_\rm{CO}$ has been found to vary within and between galaxies, but the specific environmental conditions that cause these variations are not fully understood. Previous observations on $\sim$kpc scales revealed low values of $\alpha_\rm{CO}$ in the centers of some barred spiral galaxies, including NGC 3351. We present new ALMA Band 3, 6, and 7 observations of $^{12}$CO, $^{13}$CO, and C$^{18}$O lines on 100 pc scales in the inner $\sim$2 kpc of NGC 3351. Using multi-line radiative transfer modeling and a Bayesian likelihood analysis, we infer the H$_2$ density, kinetic temperature, CO column density per line width, and CO isotopologue abundances on a pixel-by-pixel basis. Our modeling implies the existence of a dominant gas component with a density of $2{-}3\times10^3$ $\rm{cm^{-3}}$ in the central ${\sim}$1 kpc and a high temperature of 30$-$60 K near the nucleus and near the contact points that connect to the bar-driven inflows. Assuming a CO/H$_2$ abundance of $3\times10^{-4}$, our analysis yields $\alpha_\rm{CO}{\sim}0.5{-}2.0$ $\rm{M_\odot\,(K~km~s^{-1}~pc^2)^{-1}}$ with a decreasing trend with galactocentric radius in the central $\sim$1 kpc. The inflows show a substantially lower $\alpha_\rm{CO} < 0.1$ $\rm{M_\odot\,(K~km~s^{-1}~pc^2)^{-1}}$, likely due to lower optical depths caused by turbulence or shear in the inflows. Over the whole region, this gives an intensity-weighted $\alpha_\rm{CO}$ of ${\sim}1.5$ $\rm{M_\odot\,(K~km~s^{-1}~pc^2)^{-1}}$, which is similar to previous dust modeling based results at kpc scales. This suggests that low $\alpha_\rm{CO}$ on kpc scales in the centers of some barred galaxies may be due to the contribution of low optical depth CO emission in bar-driven inflows.
Continuum dislocation dynamics models of mesoscale plasticity consist of dislocation transport-reaction equations coupled with crystal mechanics equations. The coupling between these two sets of equations is such that dislocation transport gives rise to the evolution of plastic distortion (strain), while the evolution of the latter fixes the stress from which the dislocation velocity field is found via a mobility law. Earlier solutions of these equations employed a staggered solution scheme for the two sets of equations in which the plastic distortion was updated via time integration of its rate, as found from Orowan's law. In this work, we show that such a direct time integration scheme can suffer from accumulation of numerical errors. We introduce an alternative scheme based on field dislocation mechanics that ensures consistency between the plastic distortion and the dislocation content in the crystal. The new scheme is based on calculating the compatible and incompatible parts of the plastic distortion separately, and the incompatible part is calculated from the current dislocation density field. Stress field and dislocation transport calculations were implemented within a finite element based discretization of the governing equations, with the crystal mechanics part solved by a conventional Galerkin method and the dislocation transport equations by the least squares method. A simple test is first performed to show the accuracy of the two schemes for updating the plastic distortion, which shows that the solution method based on field dislocation mechanics is more accurate. This method then was used to simulate an austenitic steel crystal under uniaxial loading and multiple slip conditions.
The temperature dependence of the gapped triplet excitations (triplons) in the 2D Shastry-Sutherland quantum magnet SrCu$_2$(BO$_3$)$_2$ is studied by means of inelastic neutron scattering. The excitation amplitude rapidly decreases as a function of temperature while the integrated spectral weight can be explained by an isolated dimer model up to 10~K. Analyzing this anomalous spectral line-shape in terms of damped harmonic oscillators shows that the observed damping is due to a two-component process: one component remains sharp and resolution limited while the second broadens. We explain the underlying mechanism through a simple yet quantitatively accurate model of correlated decay of triplons: an excited triplon is long-lived if no thermally populated triplons are near-by but decays quickly if there are. The phenomenon is a direct consequence of frustration induced triplon localization in the Shastry--Sutherland lattice.
Based on the Fokker-Planck equation we investigate the transport of an overdamped colloidal particle in a static, asymmetric periodic potential supplemented by a time-dependent, delayed feedback force, $F_{\mathrm{fc}}$. For a given time $t$, $F_\mathrm{fc}$ depends on the status of the system at a previous time $t-\tau_\mathrm{D}$, with $\tau_\mathrm{D}$ being a delay time, specifically on the delayed mean particle displacement (relative to some "switching position"). For non-zero delay times $F_{\mathrm{fc}}(t)$ develops nearly regular oscillations generating a net current in the system. Depending on the switching position, this current is nearly as large or even larger than that in a conventional open-loop rocking ratchet. We also investigate thermodynamic properties of the delayed non-equilibrium system and we suggest an underlying Langevin equation which reproduces the Fokker-Planck results.
We study cavitation type equations, $\text{div}(a_{ij}(X) \nabla u) \sim \delta_0(u)$, for bounded, measurable elliptic media $a_{ij}(X)$. De Giorgi-Nash-Moser theory assures that solutions are $\alpha$-H\"older continuous within its set of positivity, $\{u>0\}$, for some exponent $\alpha$ strictly less than one. Notwithstanding, the key, main result proven in this paper provides a sharp Lipschitz regularity estimate for such solutions along their free boundaries, $\partial \{u>0 \}$. Such a sharp estimate implies geometric-measure constrains for the free boundary. In particular, we show that the non-coincidence $\{u>0\}$ set has uniform positive density and that the free boundary has finite $(n- \varsigma )$-Hausdorff measure, for a universal number $0< \varsigma \le 1$.
We have obtained Spitzer Space Telescope IRS 5.5 - 35 micron spectra of 59 main sequence stars that possess IRAS 60 micron excess. The spectra of five objects possess spectral features that are well-modeled using micron-sized grains and silicates with crystalline mass fractions 0% - 80%, consistent with T-Tauri and Herbig AeBe stars. With the exception of eta Crv, these objects are young with ages <50 Myr. The spectra for the majority of objects are featureless, suggesting that the emitting grains probably have radii a > 10 micron. We have modeled the excess continua using a continuous disk with a uniform surface density distribution, expected if Poynting-Robertson and stellar wind drag are the dominant grain removal processes, and using a single temperature black body, expected if the dust is located in a narrow ring around the star. The IRS spectra of many objects are better modeled with a single temperature black body, suggesting that the disks possess inner holes. The distribution of grain temperatures, based on our black body fits, peaks at Tgr = 110 - 130 K. Since the timescale for ice sublimation of micron-sized grains with Tgr > 110 K is a fraction of a Myr, the lack of warmer material may be explained if the grains are icy. If planets dynamically clear the central portions of debris disks, then the frequency of planets around other stars is probably high. We estimate that the majority of debris disk systems possess parent body masses, MPB < 1 Mearth. The low inferred parent body masses suggest that planet formation is an efficient process. (abridged abstract)
The nature of two-photon interference is a subject that has aroused renewed interest in recent years and is still under debate. In this paper we report the first observation of two-photon interference with independent pseudo-thermal sources in which sub-wavelength interference is observed. The phenomenon may be described in terms of the classical statistical distribution of the two sources and their optical transfer functions.
The relationship between galaxy characteristics and the reionization of the universe remains elusive, mainly due to the observational difficulty in accessing the Lyman continuum (LyC) at these redshifts. It is thus important to identify low-redshift LyC-leaking galaxies that can be used as laboratories to investigate the physical processes that allow LyC photons to escape. The weakness of the [S II] nebular emission lines relative to typical star-forming galaxies has been proposed as a LyC predictor. In this paper, we show that the [S II]-deficiency is an effective method to select LyC-leaking candidates using data from the Low-redshift LyC Survey, which has detected flux below the Lyman edge in 35 out of 66 star-forming galaxies with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope. We show that LyC leakers tend to be more [S II]-deficient and that the fraction of their detections increases as [S II]-deficiency becomes more prominent. Correlational studies suggest that [S II]-deficiency complements other LyC diagnostics (such as strong Lyman-$\alpha$ emission and high [O III]/[O II]). Our results verify an additional technique by which reionization-era galaxies could be studied.
Completely regular tensionful codimension-n brane world solutions are discussed, where the core of the brane is chosen to be a thin codimension-(n-1) shell in an infinite volume flat bulk, and an Einstein-Hilbert term localized on the brane is included (Dvali-Gabadadze-Porrati models). In order to support such localized sources we enrich the vacuum structure of the brane by the inclusion of localized form fields. We find that phenomenological constraints on the size of the internal core seem to impose an upper bound to the brane tension. Finite transverse-volume smooth solutions are also discussed.
Tree-child networks are one of the most prominent network classes for modeling evolutionary processes which contain reticulation events. Several recent studies have addressed counting questions for {\it bicombining tree-child networks} which are tree-child networks with every reticulation node having exactly two parents. In this paper, we extend these studies to {\it $d$-combining tree-child networks} where every reticulation node has now $d\geq 2$ parents. Moreover, we also give results and conjectures on the distributional behavior of the number of reticulation nodes of a network which is drawn uniformly at random from the set of all tree-child networks with the same number of leaves.
A stochastic system under the influence of a stochastic environment is correlated with both present and future states of the environment. Such a system can be seen as implicitly implementing a predictive model of future environmental states. The non-predictive model complexity has been shown to lower-bound the thermodynamic dissipation. Here we explore these statistical and physical quantities at steady state in simple models. We show that under quasi-static driving this model complexity saturates the dissipation. Beyond the quasi-static limit, we demonstrate a lower bound on the ratio of this model complexity to total dissipation, that is realized in the limit of weak driving.