ShantanuT01/DACTYL-Pretraining huggingface dataset:
Using the BATSE survey data I find that quite small fraction of GRBs numbering 37 sources seems to emit the radiation similar to thermal bremsstrahlung in the range 20 to 300 keV. I suggest that these bursts may perhaps occur from collision of stars with primordial black holes (PBH). These objects are relic of a hot matter in the early Universe. PBH in the vicinity of stars may be found in consequence of incorporation processes during the formation of stars from interstellar clouds. At present they can form the gravitationally captured haloes around stars like the family of solar comets. The comet paradigm has been used to understand various aspects of PBH. Comet collisions with the Sun and planets are ordinary events in solar system history. On the analogy, one can support the view that PBH collisions with the parent star may be quite frequent events in its history, too. PBHs are the engines driving gamma-ray bursts when collide with the stars. Entering a stellar atmosphere, PBH is supposed to produce the gamma-ray burst due to accretion with duration from a few tenths of second to a few seconds. It can exhibit the main qualitative features of some GRBs. Their masses are estimated in the range from thousandths to hundredths of the solar mass. I found that these burst sources are isotropically distributed on the sky and are seen from a distance up to 50 ps. In this context one may expect that some short GRBs are observable signatures of primordial black holes in the Universe.
We present an investigation of nonlinear interactions between Gravitational Radiation and modified Alfv\'{e}n modes in astrophysical dusty plasmas. Assuming that stationary charged dust grains form neutralizing background in an electron-ion-dust plasma, we obtain the three wave coupling coefficients, and calculate the growth rates for parametrically coupled gravitational radiation and modified Alfv\'{e}n-Rao modes. The threshold value of the gravitational wave amplitude associated with convective stabilization is particularly small if the gravitational frequency is close to twice the modified Alfv\'en wave-frequency. The implication of our results to astrophysical dusty plasmas is discussed.
We report the results of our systematic survey for Galactic 6.7 GHz Class II CH$_3$OH maser emission toward a sample of young stellar objects. The survey was conducted with the Shanghai Tianma Radio Telescope (TMRT). The sample consists of 3348 sources selected from the all-sky \emph{Wide-Field Infrared Survey Explorer (WISE)} point source catalog. We have discussed the selection criteria in detail and the detection results of those at high Galactic latitudes (i.e. $|b|>$ 2$^\circ$) in a previous paper (paper I). Here, we present the results from the survey of those at low Galactic latitudes, i.e. $|b|<2^\circ$. Of 1875 selected \emph{WISE} point sources, 291 positions that were actually associated with 224 sources were detected with CH$_3$OH maser emission. Among them, 32 are newly detected. Majority of the newly detected sources are associated with bright WISE sources. The majority of the detected sources (209/224 = 93.3\%) are quite close to the Galactic Plane ($|b|<1^\circ$) and lie on the inner spiral arms with positive LSR velocities. Detection rate and the color-color distribution of our detection are all matched with our anticipation. Combining with detections from previous surveys, we compile a catalogue of 1085 sources with 6.7 GHz CH$_3$OH maser emission in our Galaxy.
A helix has a wavevector along the z axis with the magnetic moments ferromagnetically-aligned within xy planes with a turn angle kd between the moments in adjacent planes in transverse field Hx = 0. The magnetic structure and x-axis average magnetization per spin of this system in a classical XY anisotropy field HA is studied versus kd, HA, and large Hx at zero temperature. For values of HA below a kd-dependent maximum value, the xy helix phase transitions with increasing Hx into a spin-flop (SF) phase where the ordered moments have x, y, and z components. The moments in the SF phase are taken to be distributed on either one or two xyz spherical ellipses. The minor axes of the ellipses are oriented along the z axis and the major axes along the y axis where the ellipses are flattened along the z axis due to the presence of the XY anisotropy. From energy minimization of the SF spherical ellipse parameters for given values of kd, HA and Hx, four kd-dependent SF phases are found: either one or two xyz spherical ellipses and either one or two xy fans, in addition to the xy helix phase and the paramagnetic (PM) phase with all moments aligned along Hx. The PM phase occurs via second-order transitions from the xy fan and SF phases with increasing Hx. Phase diagrams in the Hx-HA plane are constructed by energy minimization with respect to the SF phases, the xy helix phase, and the xy fan phase for four kd values. One of these four phase diagrams is compared with the magnetic properties found experimentally for the model helical Heisenberg antiferromagnet EuCo2P2 and semiquantitative agreement is found.
For each smooth Fano threefold $X$ with Picard number 1 we consider a weak Landau--Ginzburg model, that is a fibration over $\mathbb C^1$ given by a certain Laurent polynomial. In the spirit of L. Katzarkov's program we prove that the number of irreducible components of the central fiber of its compactification is $h^{1,2}(X)+1$. In particular, it does not depend on the compactification. The question of dependence on the model is open; however we produce examples of different weak Landau--Ginzburg models for the same variety with the same number of components of the central fiber.
Several methods of extrapolating the virial coefficients, including those proposed in this work, are discussed. The methods are demonstrated on predicting higher virial coefficients of one-component hard spheres. Estimated values of the eleventh to fifteenth virial coefficients are suggested. It has been speculated that the virial coefficients, B_n, beyond B_{14} may decrease with increasing n, and may reach negative values at large n. The extrapolation techniques may be utilized in other fields of science where the art of extrapolation plays a role.
We review recent work on various topics related to the modification of kaon properties in nuclei. After a brief exposition of the kaon-nucleon and kaon-nucleus interaction, results from the application to kaonic atoms, renormalization of the f0 and a0 scalar resonances in nuclei and phi decay in the nucleus are shown.
Dwarf galaxies are key objects for small-scale cosmological tests like the abundance problems or the planes-of-satellites problem. It is therefore a crucial task to get accurate information for as many nearby dwarf galaxies as possible. Using extremely deep, ground-based $V$ and $i$-band Subaru Suprime Cam photometry with a completeness of $i=27$ mag, we measure the tip of the red giant branch distance for the dwarf galaxy [TT2009] 25. This dwarf resides in the field around the Milky Way-analog NGC 891. By using a Bayesian approach, we measure a distance of $10.28^{+1.17}_{-1.73}$ Mpc, which is consistent with the distance of NGC 891, thus we confirm it as a member of NGC 891. The dwarf galaxy follows the scaling relations defined by the Local Group dwarfs. We do not find an extended stellar halo around [TT2009] 25. In the small field of view of 100 kpc covered by the survey, only one bright dwarf galaxy and the giant stream are apparent. This is comparable to the Milky Way, where one bright dwarfs reside in the same volume, as well as the Sagittarius stream - excluding satellites which are farther away but would be projected in the line-of-sight. It is thus imperative to survey for additional dwarf galaxies in a larger area around NGC 891 to test the abundance of dwarf galaxies and compare it to the number of satellites around the Milky Way.
We prove derived McKay correspondence in special cases and the decomposition of toric K-equivalence into flops.
The Swampland Distance Conjecture states that at infinite distance in the scalar moduli space an infinite tower of particles become exponentially massless. We study this issue in the context of 4d type IIA and type IIB Calabi-Yau compactifications. We find that for large moduli not only towers of particles but also domain walls and strings become tensionless. We study in detail the case of type IIA and IIB ${\cal N}=1$ CY orientifolds and show how for infinite K\"ahler and/or complex structure moduli towers of domain walls and strings become tensionless, depending on the particular direction in moduli space. For the type IIA case we construct the monodromy orbits of domain walls in detail. We study the structure of mass scales in these limits and find that these towers may occur at the same scale as the fundamental string scale or the KK scale making sometimes difficult an effective field theory description. The structure of IIA and IIB towers are consistent with mirror symmetry, as long as towers of exotic domain walls associated to non-geometric fluxes also appear. We briefly discuss the issue of emergence within this context and the possible implications for 4d vacua.
Observations of young open clusters have revealed a bimodal distribution of fast and slower rotation rates that has proven difficult to explain with predictive models of spin down that depend on rotation rates alone. The Metastable Dynamo Model proposed recently by Brown, employing a stochastic transition probability from slow to more rapid spin down regimes, appears to be more successful but lacks a physical basis for such duality. Using detailed 3D MHD wind models computed for idealized multipole magnetic fields, we show that surface magnetic field complexity can provide this basis. Both mass and angular momentum losses decline sharply with increasing field complexity. Combined with observation evidence for complex field morphologies in magnetically active stars, our results support a picture in which young, rapid rotators lose angular momentum in an inefficient way because of field complexity. During this slow spin-down phase, magnetic complexity is eroded, precipitating a rapid transition from weak to strong wind coupling.
In this paper we present control of infinite-dimensional systems by power shaping methods, which have been used extensively for control of finite dimensional systems. Towards achieving the results we work within the Brayton Moser framework, by using the system of transmission line as an example and derive passivity of the system with respect to the boundary voltages and derivatives of current at the boundary. We then solve the stabilization problem by interconnecting the system through a finite-dimensional controller and generating Casimirs for the closed-loop system. Finally we explore possibility of generating other alternate passive maps.
Molecular-scale manipulation of electronic/ionic charge accumulation in materials is a preeminent challenge, particularly in electrochemical energy storage. Layered van der Waals (vdW) crystals exemplify a diverse family of materials that permit ions to reversibly associate with a host atomic lattice by intercalation into interlamellar gaps. Motivated principally by the search for high-capacity battery anodes, ion intercalation in composite materials is a subject of intense study. Yet the precise role and ability of heterolayers to modify intercalation reactions remains elusive. Previous studies of vdW hybrids represented ensemble measurements at macroscopic films/powders, which do not permit the isolation and investigation of the chemistry at individual 2-dimensional (2D) interfaces. Here, we demonstrate the intercalation of lithium at the level of individual atomic interfaces of dissimilar vdW layers. Electrochemical devices based on vdW heterostructures comprised of deterministically stacked hexagonal boron nitride, graphene (G) and molybdenum dichalcogenide (MoX2; X = S, Se) layers are fabricated, enabling the direct resolution of intermediate stages in the intercalation of discrete heterointerfaces and the extent of charge transfer to individual layers. Operando magnetoresistance and optical spectroscopy coupled with low-temperature quantum magneto-oscillation measurements show that the creation of intimate vdW heterointerfaces between G and MoX2 engenders over 10-fold accumulation of charge in MoX2 compared to MoX2/MoX2 homointerfaces, while enforcing a more negative intercalation potential than that of bulk MoX2 by at least 0.5 V. Beyond energy storage, our new combined experimental and computational methodology to manipulate and characterize the electrochemical behavior of layered systems opens up new pathways to control the charge density in 2D (opto)electronic devices.
We describe the transfer of quantum information and entanglement from three flying (radiation) to three localized (atomic) qubits via cavity modes resonantly coupled to the atoms, in the presence of a common reservoir. Upon addressing the full dynamics of the resulting nine-qubit open system, we find that once the cavities are fed, fidelity and transferred entanglement are optimal, while their peak values exponentially decrease due to dissipative processes. The external radiation is then turned off and quantum correlations oscillate between atomic and cavity qubits. For a class of mixtures of W and GHZ input states we deal with a discontinuous exchange of entanglement among the subsystems, facing the still open problem of entanglement sudden death and birth in a multipartite system.
(Abridged) We review abundances of short-lived nuclides in the early solar system (ESS) and the methods used to determine them. We compare them to the inventory for a uniform galactic production model. Within a factor of two, observed abundances of several isotopes are compatible with this model. I-129 is an exception, with an ESS inventory much lower than expected. The isotopes Pd-107, Fe-60, Ca-41, Cl-36, Al-26, and Be-10 require late addition to the solar nebula. Be-10 is the product of particle irradiation of the solar system as probably is Cl-36. Late injection by a supernova (SN) cannot be responsible for most short-lived nuclei without excessively producing Mn-53; it can be the source of Mn-53 and maybe Fe-60. If a late SN is responsible for these two nuclei, it still cannot make Pd-107 and other isotopes. We emphasize an AGB star as a source of nuclei, including Fe-60 and explore this possibility with new stellar models. A dilution factor of about 4e-3 gives reasonable amounts of many nuclei. We discuss the role of irradiation for Al-26, Cl-36 and Ca-41. Conflict between scenarios is emphasized as well as the absence of a global interpretation for the existing data. Abundances of actinides indicate a quiescent interval of about 1e8 years for actinide group production in order to explain the data on Pu-244 and new bounds on Cm-247. This interval is not compatible with Hf-182 data, so a separate type of r-process is needed for at least the actinides, distinct from the two types previously identified. The apparent coincidence of the I-129 and trans-actinide time scales suggests that the last actinide contribution was from an r-process that produced actinides without fission recycling so that the yields at Ba and below were governed by fission.
The study of the Fe abundance in the intra cluster medium (ICM) provides strong constraints on the integrated star formation history and supernova rate of the cluster galaxies, as well as on the ICM enrichment mechanisms. In this Letter, using chemical evolution models for galaxies of different morphological types, we study the evolution of the Fe content of clusters of galaxies. We assume that the ICM Fe enrichment occurs by means of galactic winds arising from elliptical galaxies and from gas stripped from the progenitors of S0 galaxies via external mechanisms, due to the interaction of the inter stellar medium with the ICM. The Fe-rich gas ejected by ellipticals accounts for the X_Fe,ICM values observed at z > 0.5, whereas the gas stripped from the progenitors of the S0 galaxies accounts for the increase of X_Fe,ICM observed at z<0.5. We tested two different scenarios for Type Ia supernova (SN) progenitors and we model the Type Ia SN rate observed in clusters, finding a good agreement between our predictions and the available observations.
We report the detection in space of a new molecular species which has been characterized spectroscopically and fully identified from astrophysical data. The observations were carried out with the 30m IRAM telescope. The molecule is ubiquitous as its $J$=2$\rightarrow$1 transition has been found in cold molecular clouds, prestellar cores, and shocks. However, it is not found in the hot cores of Orion-KL and in the carbon-rich evolved star IRC+10216. Three rotational transitions in perfect harmonic relation J'=2/3/5 have been identified in the prestellar core B1b. The molecule has a 1Sigma electronic ground state and its J=2-1 transition presents the hyperfine structure characteristic of a molecule containing a nucleus with spin 1. A careful analysis of possible carriers shows that the best candidate is NS+. The derived rotational constant agrees within 0.3-0.7 % with ab initio calculations. NS+ was also produced in the laboratory to unambiguously validate the astrophysical assignment. The observed rotational frequencies and determined molecular constants confirm the discovery of the nitrogen sulfide cation in space. The chemistry of NS+ and related nitrogen-bearing species has been analyzed by means of a time-dependent gas phase model. The model reproduces well the observed NS/NS+ abundance ratio, in the range 30-50, and indicates that NS+ is formed by reactions of the neutral atoms N and S with the cations SH+ and NH+, respectively.
We investigate star formation occurring in idealised giant molecular clouds, comparing structures that evolve in isolation versus those undergoing a collision. Two different collision speeds are investigated and the impact of photoionising radiation from the stars is determined. We find that a colliding system leads to more massive star formation both with and without the addition of feedback, raising overall star formation efficiencies (SFE) by a factor of 10 and steepening the high-mass end of the stellar mass function. This rise in SFE is due to increased turbulent compression during the cloud collision. While feedback can both promote and hinder star formation in the isolated system, it increases the SFE by approximately 1.5 times in the colliding case when the thermal speed of the resulting HII regions matches the shock propagation speed in the collision.
X-ray emission from cool stars is an important tracer for stellar activity. The X-ray luminosity reflects different levels of activity and covers four orders of magnitude in stars of spectral types M-F. Low spectral resolution provided by X-ray observations of stellar coronae in the past allowed the determination of temperature distributions and elemental abundances making use of atomic databases (listing line emissivities and bremsstrahlung continuum for a given temperature structure). The new missions XMM-Newton and Chandra carry X-ray gratings providing sufficient spectral resolution to measure the fluxes of strategic emission lines. I describe the different approaches applicable to low-resolution and high-resolution spectra, especially focusing on the new grating spectra with X-ray lines. From only a few lines it is possible to determine plasma temperatures and associated densities, to check for any effects from resonant scattering, and to identify particular abundance anomalies. Line-based temperature- and density measurements represent only a fraction of the total plasma, but the pressure environment of different fractions can be probed simply by selection of specific lines. Selected results are presented covering all aspects of line-based analyses.
Structure and energetics of rare-earth (RE) defects and luminescence of RE and related defects in zincblende zinc sulfide (ZnS) are investigated using hybrid density-functional defect calculations. We find that europium (Eu) is stable predominantly as the divalent Eu$^{2+}$ ion in bulk ZnS. The trivalent Eu$^{3+}$ is structurally and electronically stable, but energetically unfavorable compared to Eu$^{2+}$ due to the presence of low-energy native defects and Eu$^{2+}$-related defect complexes. Other RE dopants, dysprosium (Dy) and erbium (Er), are stable only as Dy$^{3+}$ and Er$^{3+}$, respectively. These results provide an explanation why it is difficult to realize Eu$^{3+}$ in bulk ZnS. A non-negligible Eu$^{3+}$/Eu$^{2+}$ ratio might be achieved with Li co-doping under S-rich (and probably non-equilibrium) synthesis conditions. Optically, Eu-related defects can act as carrier traps for band-to-defect transitions and emit light in the visible range. To assist with experimental optical characterization of the RE defects, we include band-to-defect luminescence involving native defects (Zn vacancies) and/or non-RE impurities (Cu, Cl, and Al) that may also be present in Eu-doped ZnS samples, and assign luminescence centers often observed in experiments to specific defect configurations.
A novel algorithm for tunable compression to within the precision of reproduction targets, or storage, is proposed. The new algorithm is termed the `Perceptron Algorithm', which utilises simple existing concepts in a novel way, has multiple immediate commercial application aspects as well as it opens up a multitude of fronts in computational science and technology. The aims of this paper are to present the concepts underlying the algorithm, observations by its application to some example cases, and the identification of a multitude of potential areas of applications such as: image compression by orders of magnitude, signal compression including sound as well, image analysis in a multilayered detailed analysis, pattern recognition and matching and rapid database searching (e.g. face recognition), motion analysis, biomedical applications e.g. in MRI and CAT scan image analysis and compression, as well as hints on the link of these ideas to the way how biological memory might work leading to new points of view in neural computation. Commercial applications of immediate interest are the compression of images at the source (e.g. photographic equipment, scanners, satellite imaging systems), DVD film compression, pay-per-view downloads acceleration and many others identified in the present paper at its conclusion and future work section.
In this paper we consider del Pezzo surfaces with only log terminal singularities admitting an action of a finite simple group.
We employ a time-dependent synchrotron-self-Compton code for modeling contemporaneous multiwavelength data of the blazar 1 ES 1218+30.4 The input parameters of the model are used to infer physical parameters of the emitting region. An acceptable fit to the data is obtained by taking into account a stellar emission component in the optical regime due to the host galaxy. The physical parameters inferred from the fit are in line with particle acceleration due to the Fermi mechanism providing s = 2.1 spectra. From the properties of the host galaxy in the optical, we estimate the central black hole mass and thus confirm that the jet power injected into the emission region is in the sub-Eddington regime, as expected for BL Lacertae objects.