ShantanuT01/DACTYL-Pretraining huggingface dataset:
We report the discovery with the Parkes radio telescope of a pulsar associated with the ~ 1700 yr-old oxygen-rich composite supernova remnant G292.0+1.8. PSR J1124-5916 has period 135 ms and period derivative 7.4e-13, implying characteristic age 2900 yr, spin-down luminosity 1.2e37 erg/s, and surface magnetic field strength 1.0e13 G. Association between the pulsar and the synchrotron nebula previously identified with Chandra within this supernova remnant is confirmed by the subsequent detection of X-ray pulsations by Hughes et al. The pulsar's flux density at 1400 MHz is very small, S ~ 0.08 mJy, but the radio luminosity of Sd^2 ~ 2 mJy kpc^2 is not especially so, although it is one order of magnitude smaller than that of the least luminous young pulsar previously known. This discovery suggests that very deep radio searches should be done for pulsations from pulsar wind nebulae in which the central pulsed source is yet to be detected and possibly other more exotic neutron stars.
We use the Herschel Hi-GAL survey data to study the spatial distribution in Galactic longitude and latitude of the interstellar medium and of dense, star-forming clumps in the inner Galaxy. The peak position and width of the latitude distribution of the dust column density as well as of number density of compact sources from the band-merged Hi-GAL photometric catalogues are analysed as a function of longitude. The width of the diffuse dust column density traced by the Hi-GAL 500 micron emission varies across the inner Galaxy, with a mean value of 1{\deg}.2-1{\deg}.3, similar to that of the 250um Hi-GAL sources. 70um Hi-GAL sources define a much thinner disk, with a mean FWHM of 0{\deg}.75, and an average latitude of b=0{\deg}.06, coincident with the results from ATLASGAL. The GLAT distribution as a function of GLON shows modulations, both for the diffuse emission and for the compact sources, with ~0{\deg}.2 displacements mostly toward negative latitudes at l~ +40{\deg}, +12{\deg}, -25{\deg} and -40{\deg}. No such modulations can be found in the MIPSGAL 24 or WISE 22 um data when the entire source samples are considered. The distortions revealed by Herschel are interpreted as large-scale bending modes of the Plane. The lack of similar distortions in tracers of more evolved YSOs or stars rules out gravitational instabilities or satellite-induced perturbations, as they should act on both the diffuse and stellar disk components. We propose that the observed bends are caused by incoming flows of extra-planar gas interacting with the gaseous disk. Stars decouple from the gaseous ISM and relax into the stellar disk potential. The time required for the disappearance of the distortions from the diffuse ISM to the relatively evolved YSO stages are compatible with star-formation timescales.
Global properties of different types of supernovae are overviewed. A special emphasis is made on the issues of interest both for the supernova and cosmic ray physics such as supernova shock waves and neutrino signal.
We show that the $D=11$ Supermembrane theory (M2-brane) compactified on a $M_9 \times T^2$ target space, with constant fluxes $C_{\pm}$ naturally incorporates the geometrical structure of a twisted torus. We extend the M2-brane theory to a formulation on a twisted torus bundle. It is consistently fibered over the world volume of the M2-brane. It can also be interpreted as a torus bundle with a nontrivial $U(1)$ connection associated to the fluxes. The structure group $G$ is the area preserving diffeomorphisms. The torus bundle is defined in terms of the monodromy associated to the isotopy classes of symplectomorphisms with $\pi_{0} (G) = SL(2,Z)$, and classified by the coinvariants of the subgroups of $SL(2,Z)$. The spectrum of the theory is purely discrete since the constant flux induces a central charge on the supersymmetric algebra and a modification on the Hamiltonian which renders the spectrum discrete with finite multiplicity. The theory is invariant under symplectomorphisms connected and non connected to the identity, a result relevant to guaranteed the U-dual invariance of the theory. The Hamiltonian of the theory exhibits interesting new $U(1)$ gauge and global symmetries on the worldvolume induced by the symplectomorphim transformations. We construct explicitly the supersymmetric algebra with nontrivial central charges. We show that the zero modes decouple from the nonzero ones. The nonzero mode algebra corresponds to a massive superalgebra that preserves either $1/2$ or $1/4$ of the original supersymmetry depending on the state considered.
Landauer's principle states that the erasure of information must be a dissipative process. In this paper, we carefully analyze the recording and erasure of information on a physical memory. On the one hand, we show that in order to record some information, the memory has to be driven out of equilibrium. On the other hand, we derive a differential version of Landauer's principle: We link the rate at which entropy is produced at every time of the erasure process to the rate at which information is erased.
We study the Metropolis dynamics of the simplest mean-field spin glass model, the Random Energy Model. We show that this dynamics exhibits aging by showing that the properly rescaled time change process between the Metropolis dynamics and a suitably chosen `fast' Markov chain converges in distribution to a stable subordinator. The rescaling might depend on the realization of the environment, but we show that its exponential growth rate is deterministic.
A static, asymptotically flat, spherically symmetric solutions is investigated in f(R) theories of gravity for a charged black hole. We have studied the weak field limit of f(R) gravity for the some f(R) model such as f(R) = R + epsilon h(R). In particular, weconsider the case lim_{R =0} {h(R)/ dh(R)/dR}=0 and find the space time metric for f(R) = R + {mu}^{4} /R and f(R) = R^{1-epsilon} theories of gravity far away a charged mass point.
We deduce a model relevant for the anomalous metallic state of Sr doped manganites at low temperatures within the ferromagnetic phase. It provides a natural explanation to several anomalous features observed experimentally, such as the vanishing Drude contribution in optical conductivity, the pseudo-gap in the density of states, an the unusual dispersion observed in photoemission.
We build on the evidence provided by our Legacy Survey of Galactic globular clusters (GC) to submit to a crucial test four scenarios currently entertained for the formation of multiple stellar generations in GCs. The observational constraints on multiple generations to be fulfilled are manifold, including GC specificity, ubiquity, variety, predominance, discreteness, supernova avoidance, p-capture processing, helium enrichment and mass budget. We argue that scenarios appealing to supermassive stars, fast rotating massive stars and massive interactive binaries violate in an irreparable fashion two or more among such constraints. Also the scenario appealing to AGB stars as producers of the material for next generation stars encounters severe difficulties, specifically concerning the mass budget problem and the detailed chemical composition of second generation stars. We qualitatively explore ways possibly allowing one to save the AGB scenario, specifically appealing to a possible revision of the cross section of a critical reaction rate destroying sodium, or alternatively by a more extensive exploration of the vast parameter space controlling the evolutionary behavior of AGB stellar models. Still, we cannot ensure success for these efforts and totally new scenarios may have to be invented to understand how GCs formed in the early Universe.
The discovery of changing-look active galactic nuclei (CL AGNs), with appearance and disappearance of broad emission lines and/or with strong variation of line-of-sight column density within a few years, challenges the AGN unification model. We explore the physical mechanisms based on the X-ray spectral evolution for a sample of 15 CL AGNs. We find that the X-ray photon index, $\Gamma$, and Eddington-scaled X-ray luminosity, $L_{\rm 2-10 keV}/L_{\rm Edd}$, follow negative and positive correlations when $L_{\rm 2-10 keV}/L_{\rm Edd}$ is lower and higher than a critical value of $\sim 10^{-3}$. This different X-ray spectral evolution is roughly consistent with the prediction of the accretion-mode transition (e.g., clumpy cold gas or cold disk to advection dominated accretion flow, or vice visa). With quasi-simultaneous X-ray and optical spectrum observations within one year, we find that the CL AGNs observed with and without broad emission lines stay in the positive and negative part of the $\Gamma-L_{\rm 2-10 keV}/L_{\rm Edd}$ correlation respectively. Our result suggest that the change of the accretion mode may be the physical reason for the CL AGNs.
The employ of a noiseless linear amplifier (NLA) has been proven as a useful tool for mitigating imperfections in quantum channels. Its analysis is usually conducted within specific frameworks, for which the set of input states for a given protocol is fixed. Here we obtain a more general description by showing that a noisy and lossy Gaussian channel followed by a NLA has a general description in terms of effective channels. This has the advantage of offering a simpler mathematical description, best suitable for mixed states, both Gaussian and non-Gaussian. We investigate the main properties of this effective system, and illustrate its potential by applying it to loss compensation and reduction of phase uncertainty.
We calculate $B_{(s)}$, and $D_{(s)}$ to $K^*_0(1430)$ transition form factors, and study semileptonic decays of $B_{(s)}$ and $D_{(s)}\to K_0^*(1430) \bar{\ell}\nu$ based on QCD sum rule. Measuring these semileptonic decays with high statistics will give valuable information on the nature of light scalar mesons.
We show for unit dynamical exponent, $z=1$, the appearance of the Fermi liquid and non-Fermi liquid behavior as we tune the charge density and the magnetic field in 3+1 dimensional field theory using the gauge-gravity duality. There exists an upturn behavior of the resistivity only along the direction perpendicular to the magnetic field. Also, there exists a universal behavior of the resistivity, independent of the dimensionality of the spacetime, in a specific corner of the parameter space, namely, in the large charge density and small magnetic field limit: the longitudinal conductivity goes as $T^{-2/z}$, whereas the Hall conductivity goes as $T^{-4/z}$. It means the Hall coefficient goes as $T^{4/z}$. We compute the diffusion constant from the flow equation of the conductivity.
We present [CII] synthetic observations of smoothed particle hydrodynamics (SPH) simulations of a dwarf galaxy merger. The merging process varies the star-formation rate by more than three orders of magnitude. Several star clusters are formed, the feedback of which disperses and unbinds the dense gas through expanding HII regions and supernova (SN) explosions. For galaxies with properties similar to the modelled ones, we find that the [CII] emission remains optically thin throughout the merging process. We identify the Warm Neutral Medium ($3<\log T_{\rm gas}<4$ with $\chi_{\rm HI}>2\chi_{\rm H2}$) to be the primary source of [CII] emission ($\sim58\%$ contribution), although at stages when the HII regions are young and dense (during star cluster formation or SNe in the form of ionized bubbles) they can contribute $\gtrsim50\%$ to the total [CII] emission. We find that the [CII]/FIR ratio decreases due to thermal saturation of the [CII] emission caused by strong FUV radiation fields emitted by the massive star clusters, leading to a [CII]-deficit medium. We investigate the [CII]-SFR relation and find an approximately linear correlation which agrees well with observations, particularly those from the Dwarf Galaxy Survey. Our simulation reproduces the observed trends of [CII]/FIR versus $\Sigma_{\rm SFR}$ and $\Sigma_{\rm FIR}$, and it agrees well with the Kennicutt relation of SFR-FIR luminosity. We propose that local peaks of [CII] in resolved observations may provide evidence for ongoing massive cluster formation.
In this paper, we introduce constructions of the high-dimensional generalizations of the kagome and diamond crystals. The two-dimensional kagome crystal and its three-dimensional counterpart, the pyrochlore crystal, have been extensively studied in the context of geometric frustration in antiferromagnetic materials. Similarly, the polymorphs of elemental carbon include the diamond crystal and the corresponding two-dimensional honeycomb structure, adopted by graphene. The kagome crystal in d Euclidean dimensions consists of vertex-sharing d-dimensional simplices in which all of the points are topologically equivalent. The d-dimensional generalization of the diamond crystal can then be obtained from the centroids of each of the simplices, and we show that this natural construction of the diamond crystal is distinct from the D_d^+ family of crystals for all dimensions d\neq 3. We analyze the structural properties of these high-dimensional crystals, including the packing densities, coordination numbers, void exclusion probability functions, covering radii, and quantizer errors. Our results demonstrate that the so-called decorrelation principle, which formally states that unconstrained correlations vanish in asymptotically high dimensions, remarkably applies to the case of periodic point patterns with inherent long-range order. We show that the decorrelation principle is already exhibited in periodic crystals in low dimensions via a "smoothed" pair correlation function obtained by convolution with a Gaussian kernel. These observations support the universality of the decorrelation principle for any point pattern in high dimensions, whether disordered or not. This universal property in turn suggests that the best conjectural lower bound on the maximal sphere-packing density in high Euclidean dimensions derived by Torquato and Stillinger [Expt. Math. 15, 307 (2006)] is in fact optimal.
Using class field theory, we prove a restriction on the intersection of the maximal abelian extensions associated with different number fields. This restriction is then used to improve a result of Rosen and Silverman about the linear independence of Heegner points. In addition, it yields effective restrictions for the special points lying on an algebraic subvariety in a product of modular curves. The latter application is related to the Andr\'e-Oort conjecture.
Smooth primitively polarized $\mathrm{K3}$ surfaces of genus 36 are studied. It is proved that all such surfaces $S$, for which there exists an embedding $\mathrm{R} \hookrightarrow \mathrm{Pic}(S)$ of some special lattice $\mathrm{R}$ of rank 2, are parameterized up to an isomorphism by some 18-dimensional unirational algebraic variety. More precisely, it is shown that a general $S$ is an anticanonical section of a (unique) Fano 3-fold with canonical Gorenstein singularities.
Let ${\cal{C}}_1$ be the set of fundamental cycles of breadth-first-search trees in a graph $G$ and ${\cal{C}}_2$ the set of the sums of two cycles in ${\cal{C}}_1$. Then we show that $(1) {\cal{C}}={\cal{C}}_1\bigcup{\cal{C}}_2$ contains a shortest $\Pi$-twosided cycle in a $\Pi$-embedded graph $G$;$(2)$ $\cal{C}$ contains all the possible shortest even cycles in a graph $G$;$(3)$ If a shortest cycle in a graph $G$ is an odd cycle, then $\cal{C}$ contains all the shortest odd cycles in $G$. This implies the existence of a polynomially bounded algorithm to find a shortest $\Pi-$twosided cycle in an embedded graph and thus solves an open problem of B.Mohar and C.Thomassen[2,pp112]
We report the discovery of 1.97 ms period gamma-ray pulsations from the 75 minute orbital-period binary pulsar now named PSR J1653-0158. The associated Fermi Large Area Telescope gamma-ray source 4FGL J1653.6-0158 has long been expected to harbor a binary millisecond pulsar. Despite the pulsar-like gamma-ray spectrum and candidate optical/X-ray associations -- whose periodic brightness modulations suggested an orbit -- no radio pulsations had been found in many searches. The pulsar was discovered by directly searching the gamma-ray data using the GPU-accelerated Einstein@Home distributed volunteer computing system. The multi-dimensional parameter space was bounded by positional and orbital constraints obtained from the optical counterpart. More sensitive analyses of archival and new radio data using knowledge of the pulsar timing solution yield very stringent upper limits on radio emission. Any radio emission is thus either exceptionally weak, or eclipsed for a large fraction of the time. The pulsar has one of the three lowest inferred surface magnetic-field strengths of any known pulsar with $B_{\rm surf} \approx 4 \times 10^{7}\,$G. The resulting mass function, combined with models of the companion star's optical light curve and spectra, suggests a pulsar mass $\gtrsim 2\,M_{\odot}$. The companion is light-weight with mass $\sim 0.01\,M_{\odot}$, and the orbital period is the shortest known for any rotation-powered binary pulsar. This discovery demonstrates the Fermi Large Area Telescope's potential to discover extreme pulsars that would otherwise remain undetected.
The constrained local model (CLM) proposes a paradigm that the locations of a set of local landmark detectors are constrained to lie in a subspace, spanned by a shape point distribution model (PDM). Fitting the model to an object involves two steps. A response map, which represents the likelihood of the location of a landmark, is first computed for each landmark using local-texture detectors. Then, an optimal PDM is determined by jointly maximizing all the response maps simultaneously, with a global shape constraint. This global optimization can be considered as a Bayesian inference problem, where the posterior distribution of the shape parameters, as well as the pose parameters, can be inferred using maximum a posteriori (MAP). In this paper, we present a cascaded face-alignment approach, which employs random-forest regressors to estimate the positions of each landmark, as a likelihood term, efficiently in the CLM model. Interpretation from CLM framework, this algorithm is named as an efficient likelihood Bayesian constrained local model (elBCLM). Furthermore, in each stage of the regressors, the PDM non-rigid parameters of previous stage can work as shape clues for training each stage regressors. Experimental results on benchmarks show our approach achieve about 3 to 5 times speed-up compared with CLM models and improve around 10% on fitting quality compare with the same setting regression models.
We study the process of spinning up black holes by accretion from slim disks in a wide range of accretion rates. We show that for super-Eddington accretion rates and low values of the viscosity parameter alpha (\lesssim 0.01) the limiting value of the dimensionless spin parameter a_* can reach values higher than a_*=0.9978 inferred by Thorne (1974) in his seminal study. For \mdot=10\mdot_{Edd} and alpha=0.01 spin equilibrium is reached at a_*=0.9994. We show that the equilibrium spin value depends strongly on the assumed value of alpha. We also prove that for high accretion rates the impact of captured radiation on spin evolution is negligible.
We report the discovery of a compact supercluster structure at z=0.9. The structure comprises three optically-selected clusters, all of which are detected in X-rays and spectroscopically confirmed to lie at the same redshift. The Chandra X-ray temperatures imply individual masses of ~5x10^14 Msun. The X-ray masses are consistent with those inferred from optical--X-ray scaling relations established at lower redshift. A strongly-lensed z~4 Lyman break galaxy behind one of the clusters allows a strong-lensing mass to be estimated for this cluster, which is in good agreement with the X-ray measurement. Optical spectroscopy of this cluster gives a dynamical mass in good agreement with the other independent mass estimates. The three components of the RCS2319+00 supercluster are separated from their nearest neighbor by a mere <3 Mpc in the plane of the sky and likely <10 Mpc along the line-of-sight, and we interpret this structure as the high-redshift antecedent of massive (~10^15 Msun) z~0.5 clusters such as MS0451.5-0305.
The interstellar medium of the Milky Way and nearby disk galaxies harbours large-scale coherent magnetic fields of Microgauss strength, that can be explained via the action of a mean-field dynamo. As in our previous work, we aim to quantify dynamo effects that are self-consistently emerging in realistic direct magnetohydrodynamic simulations, but we generalise our approach to the case of a non-local (non-instantaneous) closure relation, described by a convolution integral in space (time). To this end, we leverage our comprehensive simulation framework for the supernova-regulated turbulent multi-phase interstellar medium. By introducing spatially (temporally) modulated mean fields, we extend the previously used test-field method to the spectral realm -- providing the Fourier representation of the convolution kernels. The resulting spectra of the dynamo mean-field coefficients that we obtain broadly match expectations and allow to rigorously constrain the degree of scale separation in the Galactic dynamo. A surprising result is found for the diamagnetic pumping term, which increases in amplitude when going to smaller scales. Our results amount to the most comprehensive description of dynamo mean-field effects in the Galactic context to date. Surveying the relevant parameter space and quenching behaviour, this will ultimately enable the development of assumption-free sub-grid prescriptions for otherwise unresolved global galaxy simulations.
It is commonly thought that stars are responsible for reionizing the Universe. However, deep searches for star-forming galaxies during the epoch of reionization have not yet found sufficient galaxies to provide the necessary ionising flux. Fast accretion shocks associated with gravitational infall of baryons during the formation of galaxies have recently been proposed as an alternative method of generating the required ionising photons. In this Letter we assess the contribution to hydrogen reionization from shocked gas associated with gravitational infall. We find that shocks can ionize no more than a few percent of the cosmic hydrogen by z~6. However, the small fraction of ionizing radiation produced by fast accretion shocks would be significantly more biased than that associated with stars, leading to a modification of the luminosity weighted source clustering by ~10%. This modification of the bias may be measurable with future precision experiments utilising the redshifted 21cm line to study the distribution of hydrogen during the reionization era.
Molecular electronics on silicon has distinct advantages over its metallic counterpart. We describe a theoretical formalism for transport through semiconductor-molecule heterostructures, combining a semi-empirical treatment of the bulk silicon bandstructure with a first-principles description of the molecular chemistry and its bonding with silicon. Using this method, we demonstrate that the presence of a semiconducting band-edge can lead to a novel molecular resonant tunneling diode (RTD) that shows negative differential resistance (NDR) when the molecular levels are driven by an STM potential into the semiconducting band-gap. The peaks appear for positive bias on a p-doped and negative for an n-doped substrate. Charging in these devices is compromised by the RTD action, allowing possible identification of several molecular highest occupied (HOMO) and lowest unoccupied (LUMO) levels. Recent experiments by Hersam et al. [1] support our theoretical predictions.