ShantanuT01/DACTYL-Pretraining huggingface dataset:
The theory of dark energy stars illustrates how the behavior of matter near to certain kinds of quantum critical phase transitions can be given a geometrical interpretation by regarding the criticality tuning parameter as an extra dimension. In the case of a superfluid with vanishing speed of sound, the implied geometry resembles 5-dimensional anti-de-Sitter. In a dark energy star this geometry applies both inside and outside the horizon radius, so the AdS-CFT correspondence is consistent with the idea that the surface of a compact astrophysical object represents a quantum critical phase transition of space-time. The superfluid transition in a chiron gas, which was originally proposed as a theory of high temperature superconductivity, may provide an exact theory of this transition.
In the case of fully chaotic systems the distribution of the Poincare'recurrence times is an exponential whose decay rate is the Kolmogorov-Sinai(KS) entropy.We address the discussion of the same problem, the connection between dynamics and thermodynamics,in the case of sporadic randomness,using the Manneville map as a prototype of this class of processes. We explore the possibility of relating the distribution of Poincare' recurrence times to `thermodynamics',in the sense of the KS entropy,also in the case of an inverse power law. This is the dynamic property that Zaslavsly [Phys.Today(8), 39(1999)] finds to be responsible for a striking deviation from ordinary statistical mechanics under the form of Maxwell's Demon effect. We show that this way of estabi- lishing a connection between thermodynamics and dynamics is valid only in the case of strong chaos. In the case of sporadic randomness, resulting at long times in the Levy diffusion processes,the sensitivity to initial conditions is initially an inverse pow erlaw,but it becomes exponential in the long-time scale, whereas the distribution of Poincare times keeps its inverse power law forever. We show that a nonextensive thermodynamics would imply the Maxwell's Demon effect to be determined by memory and thus to be temporary,in conflict with the dynamic approach to Levy statistics. The adoption of heuristic arguments indicates that this effect,is possible, as a form of genuine equilibrium,after completion of the process of memory erasure.
The Spitzer Space Telescope First Look Survey Infrared Array Camera (IRAC) near and mid-infrared imaging data partially overlaps the Sloan Digital Sky Survey (SDSS), with 313 visually selected (r<17.6 mag) SDSS Main Sample galaxies in the overlap region. The 3.5 and 7.8 um properties of the galaxies are investigated in the context of their visual properties, where the IRAC [3.5] magnitude primarily measures starlight, and the [7.8] magnitude primarily measures PAH emission from the interstellar medium. As expected, we find a strong inverse correlation between [3.5]-[7.8] and visual color; galaxies red in visual colors (`red galaxies') tend to show very little dust and molecular emission (low `PAH-to-star' ratios), and galaxies blue in visual colors (`blue galaxies,' ie, star-forming galaxies) tend to show large PAH-to-star ratios. Red galaxies with high PAH-to-star ratios tend to be edge-on disks reddened by dust lanes. Simple, visually inferred attenuation corrections bring the visual colors of these galaxies in line with those of face-on disks; ie, PAH emission is closely related to attenuation-corrected, optically inferred star-formation rates. Blue galaxies with anomalously low PAH-to-star ratios are all low-luminosity star-forming galaxies. There is some weak evidence in this sample that the deficiency in PAH emission for these low-luminosity galaxies may be related to emission-line metallicity.
We will give convincing arguments to view transverse spin asymmetries in inclusive reactions, as very exciting observables, although there were considered as irrelevant for a long time. We look forward to new high energy data in the near future.
We formulate sigma-model duality transformations in terms of spin connection. This allows to investigate the symmetry of the string action including higher order $\alpha'$ corrections. An important feature of the new duality transformations is a simple homogeneous transformation rule of the spin connection (with torsion) and specifically adjusted transformation of the Yang-Mills field. We have found that under certain conditions this duality is a symmetry of the full effective string action in the target space, free of $\alpha'$ corrections. We demonstrate how the exact duality generates new fundamental string solutions from supersymmetric string waves.
We determined the crystal structure of Cs$_2$LiRuCl$_6$, which was synthesized first in this work, and investigated its magnetic properties. Cs$_2$LiRuCl$_6$ has a hexagonal structure composed of linear chains of face-sharing RuCl$_6$ and LiCl$_6$ octahedra. In two-thirds of the structural chains, Ru$^{3+}$ and Li$^+$ sites are almost ordered, while in the other chains their sites are disordered. This situation is analogous to the ground state of the antiferromagnetic Ising model on a triangular lattice. Using electron paramagnetic resonance, we evaluated the $g$ factors of Ru$^{3+}$ with effective spin-1/2 as $g_c\,{=}\,2.72$ and $g_{ab}\,{=}\,1.50$ for magnetic fields $H$ parallel and perpendicular to the $c$ axis, respectively. Magnetization curves for $H\,{\parallel}\,c$ and $H\,{\perp}\,c$ are highly anisotropic. However, these magnetization curves approximately coincide when normalized by the $g$ factors. It was found from the magnetization and specific heat results that Cs$_2$LiRuCl$_6$ can be described as a coupled one-dimensional $S\,{=}\,1/2$ Heisenberg-like antiferromagnet with $J/k_{\rm B}\,{\simeq}\,3.7$ K. Three-dimensional ordering occurs at $T_{\rm N}\,{=}\,0.48$ K. A magnetic phase diagram for $H\,{\parallel}\,c$ is also presented.
The proper parts of face lattices of convex polytopes are shown to satisfy a strong form of the Cohen--Macaulay property, namely that removing from their Hasse diagram all edges in any closed interval results in a Cohen--Macaulay poset of the same rank. A corresponding notion of edgewise Cohen--Macaulay connectivity for partially ordered sets is investigated. Examples and open questions are discussed.
A quantitative model describing large magnetostrain effect observed in several ferromagnetic shape memory alloys such as Ni2MnGa is briefly reported.The paper contains an exact thermodynamic consideration of the mechanical and magnetic properties for a similar type materials. As a result, the basic mechanical state equation including magnetic field effect is directly derived from a general Poisson's rule. It is shown that the magnetic field induced deformation effect is directly connected with the strain dependence of magnetization. A simple model of magnetization and its dependence on the strain is considered and applied to explain the results of experimental study of large magnetostrain effects in Ni2MnGa.
Ram pressure stripping has been proven to be effective in shaping galaxy properties in dense environments at low redshift. The availability of MUSE observations of a sample of distant (z$\sim 0.3-0.5$) clusters has allowed to search for galaxies subject to this phenomenon at significant lookback times. In this paper we describe how we discovered and characterized 13 ram-pressure stripped galaxies in the central regions of two intermediate redshift (z$\sim$0.3-0.4) clusters, A2744 and A370, using the MUSE spectrograph. Emission line properties as well as stellar features have been analyzed to infer the presence of this gas--only stripping mechanism, that produces spectacular ionized gas tails (H$_{\alpha}$ and even more astonishing [OII](3727,3729) departing from the main galaxy body. The inner regions of these two clusters reveal the predominance of such galaxies among blue star-forming cluster members, suggesting that ram-pressure stripping was even more effective at intermediate redshift than in today's Universe. Interestingly, the resolved [OII]/H$_{\alpha}$ line ratio in the stripped tails is exceptionally high compared to that in the disks of these galaxies, (which is comparable to that in normal low-z galaxies), suggesting lower gas densities and/or an interaction with the hot surrounding ICM.
We present the capabilities of our new code for obtaining Doppler maps implementing the maximum likelihood approach. As test data, we used observations of the dwarf nova V2051 Ophiuchi. The system was observed in quiescence at least 16 d before the onset of the next outburst. Using Doppler maps obtained for ten emission lines covering three orbital cycles, we detected spiral structures in the accretion disc of V2051 Oph. However, these structures could be biased as our data sampled the orbital period of the binary at only eight different orbital phases. Our Doppler maps show evolution from a one-arm wave structure in H$\alpha$ to two-armed waves in the other lines. The location of the two-arm structures agrees with simulations showing tidally driven spiral waves in the accretion disc. During consecutive cycles, the qualitative characteristics of the detected structures remained similar but the central absorption increased. For the first time, using the Doppler tomography method, we obtained temperature maps of the accretion disc. However, taking into account all the assumptions involved when using our method to retrieve them, the result should be treated with caution. Our maps present a relatively flat distribution of the temperature over the disc, showing no temperature increase at the location of the spiral arms. Using `ring masking', we have revealed an ionized region located close to the expected location of stream--disc interactions. We found the average temperature of the accretion disc to be 5600 K, which is below the critical limit deduced from the disc instability model.
In this paper, we report our multiwavelength observations of the large-amplitude longitudinal oscillations of a filament on 2015 May 3. Located next to active region 12335, the sigmoidal filament was observed by the ground-based H$\alpha$ telescopes from GONG and by AIA aboard SDO. The filament oscillations were most probably triggered by the magnetic reconnection in the filament channel. The directions of oscillations have angles of 4$^\circ$-36$^\circ$ with respect to the filament axis. The whole filament did not oscillate in phase as a rigid body. Meanwhile, the periods (3100$-$4400 s) of oscillations have a spatial dependence. The values of $R$ are estimated to be 69.4$-$133.9 Mm, and the minimum transverse magnetic field of the dips is estimated to be 15 G. The amplitudes of S5-S8 grew with time, while the amplitudes of S9-S14 damped with time. The amplitudes of oscillations range from a few to ten Mm, and the maximal velocity can reach 30 km s$^{-1}$. Interestingly, the filament experienced mass drainage southwards at a speed of $\sim$27 km s$^{-1}$. The oscillations continued after the mass drainage and lasted for more than 11 hr. After the mass drainage, the phases of oscillations did not change a lot. The periods of S5-S8 decreased, while the periods of S9-S14 increased. The amplitudes of S5$-$S8 damped with time, while the amplitudes of S9-S14 grew. Most of the damping (growing) ratios are between -9 and 14. We propose a schematic cartoon to explain the complex behaviors of oscillations by introducing thread-thread interaction.
Pulsar glitches are sudden spin-ups in pulsar spin frequency ($\nu$). The glitch size, $\Delta\nu/\nu$, is a key parameter in any mechanism puts across towards the understanding of the events.However, the distribution of the glitch sizes has persistently been bimodal.This bimodal nature could be intrinsic or otherwise. In this paper, the glitch size distribution is bisected at $\Delta\nu/\nu = 10^{-7}$ with $\Delta\nu/\nu < 10^{-7}$ being regarded as small size glitches (SSG), while those of $\Delta\nu/\nu > 10^{-7}$ are taken as large size glitches (LSG).The magnitude of SSGis scaled to that of LSG and tested for similarity.In pulsars with mixture of glitch sizes, Lilliefore test is used to identify the distribution pattern of SSGs and LSGs in such pulsars. The result indicates that each half of the size distribution is fundamentally different from one another. LSGs are seen to be normally distributed, while the SSGs are lognormal.
Nontrivial topological structures of non-Abelian gauge fields were discovered in the 1970's. Instanton solutions, describing vacuum tunneling through topological barriers, have fermionic zero modes which are at the origin of $^\prime$t Hooft effective Lagrangian. In the 1980's instanton ensembles have been used to explain chiral symmetry breaking. In the 1990's a large set of numerical simulations were performed deriving Euclidean correlation functions. The special role of scalar diquarks in nucleons, and color superconductivity in dense quark matter have been elucidated.   In these lectures, we discuss further developments of physics related to gauge topology. We show that the instanton-antiinstanton "streamline" configurations describe "sphaleron transitions" in high energy collisions, which result in production of hadronic clusters with nontrivial topological/chiral charges. (They are not yet observed, but discussions of dedicated experiments at LHC and RHIC are ongoing.)   Another new direction is instanton effects in hadronic spectroscopy, both in the rest frame and on the light front. We will discuss their role in central and spin-dependent potentials, formfactors and antiquark nuclear "sea". Finally, we summarize the advances in the semiclassical theory of deconfinement, and chiral phase transitions at finite temperature, in QCD and in some of its "deformed" versions.
By a theorem of Wahl, the canonically embedded curves which are hyperplane section of K3 surfaces are distinguished by the non-surjectivity of their Wahl map. In this paper we address the problem of distinguishing hyperplane sections of abelian surfaces. The somewhat surprising result is that the Wahl map of such curves is (tendentially) surjective, but their second Wahl map has corank at least 2 (in fact a more precise result is proved).
As endpoints of the hierarchical mass-assembly process, the stellar populations of local early-type galaxies encode the assembly history of galaxies over cosmic time. We use Horizon-AGN, a cosmological hydrodynamical simulation, to study the merger histories of local early-type galaxies and track how the morphological mix of their progenitors evolves over time. We provide a framework for alleviating `progenitor bias' -- the bias that occurs if one uses only early-type galaxies to study the progenitor population. Early-types attain their final morphology at relatively early epochs -- by $z\sim1$, around 60 per cent of today's early-types have had their last significant merger. At all redshifts, the majority of mergers have one late-type progenitor, with late-late mergers dominating at $z>1.5$ and early-early mergers becoming significant only at $z<0.5$. Progenitor bias is severe at all but the lowest redshifts -- e.g. at $z\sim0.6$, less than 50 per cent of the stellar mass in today's early-types is actually in progenitors with early-type morphology, while, at $z\sim2$, studying only early-types misses almost all (80 per cent) of the stellar mass that eventually ends up in local early-type systems. At high redshift, almost all massive late-type galaxies, regardless of their local environment or star-formation rate, are progenitors of local early-type galaxies, as are lower-mass (M$_\star$ $<$ 10$^{10.5}$ M$_{\odot}$) late-types as long as they reside in high density environments. In this new era of large observational surveys (e.g. LSST, JWST), this study provides a framework for studying how today's early-type galaxies have been built up over cosmic time.
We study the Euler-Poincar\'e equations that are the regularized Euler equations derived from the Euler-Poincar\'e framework. It is noteworthy to remark that the Euler-Poincar\'e equations are a generalization of two well-known regularizations, the vortex blob method and the Euler-$\alpha$ equations. We show the global existence of a unique weak solution for the two-dimensional (2D) Euler-Poincar\'e equations with the initial vorticity in the space of Radon measure. This is a remarkable feature of these equations since the existence of weak solutions with the Radon measure initial vorticity has not been established in general for the 2D Euler equations. We also show that weak solutions of the 2D Euler-Poincar\'e equations converge to those of the 2D Euler equations in the limit of the regularization parameter when the initial vorticity belongs to the space of integrable and bounded functions.
In this paper, we recompute contributions to the spectrum of the nonlinear integrated Sachs-Wolfe (iSW)/Rees-Sciama effect in a dark energy cosmology. Focusing on the moderate nonlinear regime, all dynamical fields involved are derived from the density contrast in Eulerian perturbation theory. Shape and amplitude of the resulting angular power spectrum are similar to that derived in previous work. With our purely analytical approach we identify two distinct contributions to the signal of the nonlinear iSW-effect: the change of the gravitational self-energy density of the large scale structure with (conformal) time and gravitational lenses moving with the large scale matter stream. In the latter we recover the Birkinshaw-Gull effect. As the nonlinear iSW-effect itself is inherently hard to detect, observational discrimination between its individual contributions is almost excluded. Our analysis, however, yields valuable insights into the theory of the nonlinear iSW-effect as a post-Newtonian relativistic effect on propagating photons.
We construct a natural measure mu supported on the intersection of a chordal SLE(kappa) curve gamma with the real line R, in the range 4 < kappa < 8. The measure is a function of the SLE path in question. Assuming that boundary measures transform in a ``d-dimensional'' way (where d is the Hausdorff dimension of gamma intersected with R), we show that the measure we construct is (up to multiplicative constant) the unique measure-valued function of the SLE path that satisfies the Domain Markov property.
Shell stars, in particular the cooler ones, often do not show conspicuous Balmer-line emission and may consequently be missed in surveys that specifically search for emission signatures in the Halpha line. The present work is aimed at identifying stars with shell-signatures via a search for strong FeII multiplet 42 lines at 4924, 5018, 5169A in archival LAMOST spectra. Candidates were selected by probing the FeII 42 lines in the spectra of a sample of colour-preselected early-type stars using a modified version of the MKCLASS code and then categorised by visual inspection of their spectra. We identified 75 stars showing conspicuous shell features, 43 Am/CP1 stars, 12 Ap/CP2 stars, and three objects with composite spectra. Spectral types and equivalent width measurements of the FeII 42 lines are presented for the sample of shell stars. Except for three objects, all shell stars appear significantly removed from the ZAMS in the colour-magnitude diagram, which is likely due to extinction by circumstellar material. We find a correlation between the equivalent width of the 5169A line and the distance to the locus of the main-sequence stars (the larger the IR-excess, the stronger the 5169A line) and studied the variability of the shell star sample using TESS data, identifying a very high proportion of double stars. All but 14 shell stars are new discoveries, which highlights the efficiency of the here presented novel approach to identify stars with subtle shell features. This study may be used as a blueprint for discovering these objects in massive spectral databases.
Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their solar system's counterparts are the asteroid and Edgeworth-Kuiper belts. The DUNES survey aims at detecting extra-solar analogues to the Edgeworth-Kuiper belt around solar-type stars, putting in this way the solar system into context. The survey allows us to address some questions related to the prevalence and properties of planetesimal systems. We used {\it Herschel}/PACS to observe a sample of nearby FGK stars. Data at 100 and 160 $\mu$m were obtained, complemented in some cases with observations at 70 $\mu$m, and at 250, 350 and 500 $\mu$m using SPIRE. The observing strategy was to integrate as deep as possible at 100 $\mu$m to detect the stellar photosphere. Debris discs have been detected at a fractional luminosity level down to several times that of the Edgeworth-Kuiper belt. The incidence rate of discs around the DUNES stars is increased from a rate of $\sim$ 12.1% $\pm$ 5% before \emph{Herschel} to $\sim$ 20.2% $\pm$ 2%. A significant fraction ($\sim$ 52%) of the discs are resolved, which represents an enormous step ahead from the previously known resolved discs. Some stars are associated with faint far-IR excesses attributed to a new class of cold discs. Although it cannot be excluded that these excesses are produced by coincidental alignment of background galaxies, statistical arguments suggest that at least some of them are true debris discs. Some discs display peculiar SEDs with spectral indexes in the 70-160$\mu$m range steeper than the Rayleigh-Jeans one. An analysis of the debris disc parameters suggests that a decrease might exist of the mean black body radius from the F-type to the K-type stars. In addition, a weak trend is suggested for a correlation of disc sizes and an anticorrelation of disc temperatures with the stellar age.
We present a new framework to treat the dissipation and fluctuation dynamics associated with nucleon-nucleon scattering in heavy-ion collisions. The two-body collision processes are effectively described in terms of the diffusion of nucleons in viscous nuclear media, governed by a set of Langevin equations in momentum space. The new framework combined with the usual mean field dynamics can be used to simulate heavy-ion collisions at intermediate energies. As a proof of principle, we simulate Au + Au reactions and obtain results consistent with other existing codes under the same constrained conditions. We also study the formation of fragments in Sn + Sn reactions at 50 MeV/nucleon, and results are discussed and compared with two other models commonly employed for collisions.
We prove a sharp H\"older estimate for solutions of linear two-dimensional, divergence form elliptic equations with measurable coefficients, such that the matrix of the coefficients is symmetric and has {\em unit determinant}. Our result extends some previous work by Piccinini and Spagnolo. The proof relies on a sharp Wirtinger type inequality.
We present central velocity dispersions and Mg$_2$ line indices for an all-sky sample of $\sim$ 1178 elliptical and S0 galaxies, of which 984 had no previous measures. This sample contains the largest set of homogeneous spectroscopic data for a uniform sample of elliptical galaxies in the nearby universe. These galaxies were observed as part of the ENEAR project, designed to study the peculiar motions and internal properties of the local early-type galaxies. Using 523 repeated observations of 317 galaxies obtained during different runs, the data are brought to a common zero-point. These multiple observations, taken during the many runs and different instrumental setups employed for this project, are used to derive statistical corrections to the data and are found to be relatively small, typically $\lsim$ 5% of the velocity dispersion and 0.01 mag in the \mg line-strength. Typical errors are about 8% in velocity dispersion and 0.01 mag in \mg, in good agreement with values published elsewhere.