ShantanuT01/DACTYL-Pretraining huggingface dataset:
After the termination shock (TS) crossing, the Voyager 2 spacecraft has been observing strong variations of the magnetic field and solar wind parameters in the heliosheath. Anomalous cosmic rays, electrons, and galactic cosmic rays present strong intensity fluctuations. Several works suggested that the fluctuations might be attributed to spatial variations within the heliosheath. Additionally, the variability of the solar wind in this region is caused by different temporal events that occur near the Sun and propagate to the outer heliosphere. To understand the spatial and temporal effects in the heliosheath, it is important to study these effects separately. In this work we explore the role of shocks as one type of temporal effects in the dynamics of the heliosheath. Although currently plasma in the heliosheath is dominated by solar minima conditions, with increasing solar cycle shocks associated with transients will play an important role. We used a 3D MHD multi-fluid model of the interaction between the solar wind and the local interstellar medium to study the propagation of a pair of forward-reverse shocks in the supersonic solar wind, interaction with the TS, and propagation to the heliosheath. We found that in the supersonic solar wind the interaction region between the shocks expands, the shocks weaken and decelerate. The fluctuation amplitudes of the plasma parameters vary with heliocentric distance. The interaction of the pair of shocks with the TS creates a variety of new waves and discontinuities in the heliosheath, which produce a highly variable solar wind flow. The collision of the forward shock with the heliopause causes a reflection of fast magnetosonic waves inside the heliosheath.
Sr I 4607\AA spectral line shows one of the strongest scattering polarization signals in the visible solar spectrum. The amplitudes of these signals are expected to vary at granular spatial scales. This variation can be due to changes in the magnetic field intensity and orientation (Hanle effect) as well as due to spatial and temporal variations in the plasma properties. Measuring the spatial variation of such polarization signal would allow us to study the properties of the magnetic fields at subgranular region. But, the observations are challenging since both high spatial resolution and high spectropolarimetric sensitivity are required at the same time. To the aim of measuring these spatial variations at granular scale, we carried out a spectro-polarimetric measurement with the Zurich IMaging POLarimeter (ZIMPOL), at the GREGOR solar telescope at different limb distances on solar disk. Our results show a spatial variation of scattering linear polarization signals in Sr I 4607\AA line at the granular scale at every $\mu$, starting from 0.2 to 0.8. The correlation between the polarization signal amplitude and the continuum intensity imply statistically that the scattering polarization is higher at the granular regions than in the intergranular lanes.
Currently epsilon near zero materials (ENZ) have become important for controlling the propagation of light and enhancing by several orders of magnitude the Kerr and other nonlinearities. Given this advance it is important to examine the quantum electrodynamic processes and information tasks near ENZ materials. We study the entanglement between two two-level systems near ENZ materials and compare our results with the case where the ENZ material is replaced by a metal. It is shown that with ENZ materials substantial entanglement can be achieved over larger distances than for metal films. We show that this entanglement over large distances is due to the fact that one can not only have large emission rates but also large energy transmission rates at the epsilon-nearzero wavelength. This establishes superiority of ENZ materials for studying processes specifically important for quantum information tasks.
The zeta-function of a complex variety is a power series whose nth coefficient is the nth symmetric power of the variety, viewed as an element in the Grothendieck ring of complex varieties. We prove that the zeta-function of a surface is rational if and only if its Kodaira dimension is negative.
Abundance ratios of carbon, nitrogen and strontium relative to iron, calculated using spectrum synthesis techniques, are given for a sample of main sequence and turnoff stars that belong to the globular cluster omega Centauri. The variations of carbon, nitrogen and/or strontium show several different abundance patterns as a function of [Fe/H]. The source of the enhancements/depletions in carbon, nitrogen and/or strontium may be enrichment from asymptotic giant branch stars of low (1--3 solar masses) and intermediate (3--8 solar masses) mass. Massive rotating stars which produce excess nitrogen without carbon and oxygen overabundances may also play a role. These abundances enable different contributors to be considered and incorporated into the evolutionary picture of omega Cen.
We describe the equivariant cobordism ring of smooth toric varieties. This equivariant description is used to compute the ordinary cobordism ring of such varieties.
Mazur and Tate proposed a conjecture which compares the Mordell-Weil rank of an elliptic curve over $\mathbb{Q}$ with the order of vanishing of Mazur-Tate elements, which are analogues of Stickelberger elements. Under some relatively mild assumptions, we prove this conjecture. Our strategy of the proof is to study divisibility of certain derivatives of Kato's Euler system.
Membership identification is the first step to determine the properties of a star cluster. Low-mass members in particular could be used to trace the dynamical history, such as mass segregation, stellar evaporation, or tidal stripping, of a star cluster in its Galactic environment. We identified member candidates with stellar masses $\sim$0.11--2.4 Msun of the intermediate-age Praesepe cluster (M44), by using Pan-STARRS and 2MASS photometry, and PPMXL proper motions. Within a sky area of 3 deg radius, 1040 candidates are identified, of which 96 are new inclusions. Using the same set of selection criteria on field stars led to an estimate of a false positive rate 16%, suggesting 872 of the candidates being true members. This most complete and reliable membership list allows us to favor the BT-Settl model in comparison with other stellar models. The cluster shows a distinct binary track above the main sequence, with a binary frequency of 20--40%, and a high occurrence rate of similar mass pairs. The mass function is consistent with that of the disk population but shows a deficit of members below 0.3 solar masses. A clear mass segregation is evidenced, with the lowest-mass members in our sample being evaporated from this disintegrating cluster.
We construct an infinite number of new holonomic quasi-local gravitational energy-momentum density pseudotensors with good limits asymptotically and in small regions, both materially and in vacuum. For small vacuum regions they are all a positive multiple of the Bel-Robinson tensor and consequently have positive energy.
The Wide-field Infrared Survey Explorer (WISE) is an extremely capable and efficient black hole finder. We present a simple mid-infrared color criterion, W1-W2 \geq 0.8 (i.e., [3.4]-[4.6] \geq 0.8, Vega), which identifies 61.9 \pm 5.4 AGN candidates per deg2 to a depth of W2 = 15.0. This implies a much larger census of luminous AGN than found by typical wide-area surveys, attributable to the fact that mid-infrared selection identifies both unobscured (type 1) and obscured (type 2) AGN. Optical and soft X-ray surveys alone are highly biased towards only unobscured AGN, while this simple WISE selection likely identifies even heavily obscured, Compton-thick AGN. Using deep, public data in the COSMOS field, we explore the properties of WISE-selected AGN candidates. At the mid-infrared depth considered, 160 uJy at 4.6 microns, this simple criterion identifies 78% of Spitzer mid-infrared AGN candidates according to the criteria of Stern et al. (2005) and the reliability is 95%. We explore the demographics, multiwavelength properties and redshift distribution of WISE-selected AGN candidates in the COSMOS field.
We propose the use of the gyrotropic motion of vortex cores in nanomagnets to produce a magnetic echo, analogous to the spin echo in NMR. This echo occurs when an array of nanomagnets, e.g., nanodisks, is magnetized with an in-plane (xy) field, and after a time \tau a field pulse inverts the core magnetization; the echo is a peak in M_{xy} at t=2\tau. Its relaxation times depend on the inhomogeneity, on the interaction between the nanodots and on the Gilbert damping constant \alpha. Its feasibility is demonstrated using micromagnetic simulation. To illustrate an application of the echoes, we have determined the inhomogeneity and measured the magnetic interaction in an array of nanodisks separated by a distance d, finding a d^{-n} dependence, with n\approx 4.
In this paper, we are interested in the long-time behaviour of stochastic systems of n interacting vortices: the position in R2 of each vortex evolves according to a Brownian motion and a drift summing the influences of the other vortices computed through the Biot and Savart kernel and multiplied by their respective vorticities. For fixed n, we perform the rescalings of time and space used successfully by Gallay and Wayne [5] to study the long-time behaviour of the vorticity formulation of the two dimensional incompressible Navier-Stokes equation, which is the limit as n $\rightarrow$ $\infty$ of the weighted empirical measure of the system under mean-field interaction. When all the vorticities share the same sign, the 2n-dimensional process of the rescaled positions of the vortices is shown to converge exponentially fast as time goes to infinity to some invariant measure which turns out to be Gaussian if all the vorticities are equal. In the particular case n = 2 of two vortices, we prove exponential convergence in law of the 4-dimensional process to an explicit random variable, whatever the choice of the two vorticities. We show that this limit law is not Gaussian when the two vorticities are not equal.
We report results from a 50 ks XMM-Newton observation of the dust-reddened broad-line quasar FTM 0830+3759 (z=0.413) selected from the FIRST/2MASS Red Quasar survey. For this AGN, a very short 9 ks Chandra exposure had suggested a feature-rich X-ray spectrum and HST images revealed a very disturbed host galaxy morphology. Contrary to classical, optically-selected quasars, the X-ray properties of red (i.e. with J-Ks> 1.7 and R-Ks> 4) broad line quasars are still quite unexplored, although there is a growing consensus that, due to moderate obscuration, these objects can offer a unique view of spectral components typically swamped by the AGN light in normal, blue quasars. The XMM-Newton observation discussed here has definitely confirmed the complexity of the X-ray spectrum revealing the presence of a cold (or mildly-ionized) absorber with Nh ~10^{22} cm^-2 along the line of sight to the nucleus and a Compton reflection component accompanied by an intense Fe K emission line in this quasar with a Lum(2-10) ~5 x 10^{44} erg/s. A soft-excess component is also required by the data. The match between the column density derived by our spectral analysis and that expected on the basis of reddening due to the dust suggests the possibility that both absorptions occur in the same medium. FTM 0830+3759 is characterized by an extinction/absorption-corrected X-ray-to-optical flux ratio alphaox = -2.3, that is steeper than expected on the basis of its UV luminosity. These findings indicate that the X-ray properties of FTM 0830+3759 differs from those typically observed for optically-selected broad line quasars with comparable hard X-ray luminosity.
This paper addresses a major flaw of the cycle consistency loss when used to preserve the input appearance in the face-to-face synthesis domain. In particular, we show that the images generated by a network trained using this loss conceal a noise that hinders their use for further tasks. To overcome this limitation, we propose a ''recurrent cycle consistency loss" which for different sequences of target attributes minimises the distance between the output images, independent of any intermediate step. We empirically validate not only that our loss enables the re-use of generated images, but that it also improves their quality. In addition, we propose the very first network that covers the task of unconstrained landmark-guided face-to-face synthesis. Contrary to previous works, our proposed approach enables the transfer of a particular set of input features to a large span of poses and expressions, whereby the target landmarks become the ground-truth points. We then evaluate the consistency of our proposed approach to synthesise faces at the target landmarks. To the best of our knowledge, we are the first to propose a loss to overcome the limitation of the cycle consistency loss, and the first to propose an ''in-the-wild'' landmark guided synthesis approach. Code and models for this paper can be found in https://github.com/ESanchezLozano/GANnotation
Following on our previous work [S. Delong and B. E. Griffith and E. Vanden-Eijnden and A. Donev, Phys. Rev. E, 87(3):033302, 2013], we develop temporal integrators for solving Langevin stochastic differential equations that arise in fluctuating hydrodynamics. Our simple predictor-corrector schemes add fluctuations to standard second-order deterministic solvers in a way that maintains second-order weak accuracy for linearized fluctuating hydrodynamics. We construct a general class of schemes and recommend two specific schemes: an explicit midpoint method, and an implicit trapezoidal method. We also construct predictor-corrector methods for integrating the overdamped limit of systems of equations with a fast and slow variable in the limit of infinite separation of the fast and slow timescales. We propose using random finite differences to approximate some of the stochastic drift terms that arise because of the kinetic multiplicative noise in the limiting dynamics. We illustrate our integrators on two applications involving the development of giant nonequilibrium concentration fluctuations in diffusively-mixing fluids. We first study the development of giant fluctuations in recent experiments performed in microgravity using an overdamped integrator. We then include the effects of gravity, and find that we also need to include the effects of fluid inertia, which affects the dynamics of the concentration fluctuations greatly at small wavenumbers.
We study $K^-/K^+$ ratios as a function of centrality (participant nucleon number), transverse mass ($m_t$), and rapidity, in heavy-ion collisions at beam energies between 1A and 2A GeV. We use the relativistic transport model that includes expicitly the strangeness degrees of freedom and consider two scenarios for kaon properties in dense matter, one with and one without medium modifications of their properties. In both scenarios, The $K^-/K^+$ ratio does not change very much with the centrality, while the $K/\pi$ and ${\bar K}/\pi$ ratios increase with increasing centrality. Significant differences are predicted, both in magnitudes and shapes, for the $m_t$ spectra and rapidity distributions of $K^-/K^+$ ratio. Experimental measurement of these ratios, currently under investigation by the FOPI, KaoS, E866, and E895 collaborations, will be useful in revealing the kaon in-medium properties.
In this note we analyse the harmonic functions in $L^2$-sense for an irreducible diffusion on an interval.
We present extensive Monte Carlo simulations on a two-dimensional XY model with a modified form of interaction potential. Thermodynamic quantities other than energy, specific heat etc (such as magnetization, susceptibility, fourth order cumulant of magnetization) are obtained using multiple-histogram reweighting of the data obtained from the simulations. We employ an approach which eliminates the need to construct two-dimensional histograms. This approach makes judicious use of computer memory as well as CPU time. Lee-kosterlitz's method of finite size scaling for a first order transition and analysis using Binder's cumulant method allow us to make an accurate determination of the transition temperature.
We construct nontrivial homomorphisms from the quasi group of some cubic surfaces over $\bbF_{\!p}$ into a group. We show experimentally that the homomorphisms constructed are the only possible ones and that there are no nontrivial homomorphisms in the other cases. Thereby, we follow the classification of cubic surfaces, due to A. Cayley.
The damped and sub-damped Lyman-alpha absorption line systems in quasar spectra are believed to be produced by intervening galaxies. However, the connection of quasar absorbers to galaxies is not well-understood, since attempts to image the absorbing galaxies have often failed. While most DLAs appear to be metal-poor, a population of metal-rich absorbers, mostly sub-DLAs, has been discovered in recent studies. Here we report high-resolution K-band imaging with the Keck Laser Guide Star Adaptive Optics (LGSAO) system of the field of quasar SDSSJ1323-0021 in search of the galaxy producing the z = 0.72 sub-DLA absorber. With a metallicity of 2-4 times the solar level, this absorber is of the most metal-rich systems found to date. Our data show a large bright galaxy with an angular separation of only 1.25" from the quasar, well-resolved from the quasar at the high resolution of our data. The galaxy has a magnitude of K = 17.6-17.9, which corresponds to a luminosity of ~ 3-6 L*. Morphologically, the galaxy is fit with a model with an effective radius, enclosing half the total light, of R_e = 4 kpc and a bulge-to-total ratio of 0.4-1.0, indicating a substantial bulge stellar population. Based on the mass-metallicity relation of nearby galaxies, the absorber galaxy appears to have a stellar mass > 10^{11} M_sun. Given the small impact parameter, this massive galaxy appears to be responsible for the metal-rich sub-DLA. The absorber galaxy is consistent with the metallicity-luminosity relation observed for nearby galaxies, but is near the upper end of metallicity. Our study marks the first application of LGSAO for study of structure of galaxies producing distant quasar absorbers. Finally, this study offers the first example of a massive galaxy with a substantial bulge producing a metal-rich absorber.
The weak $r$-coloring numbers $wcol_r(G)$ of a graph $G$ were introduced by the first two authors as a generalization of the usual coloring number $col(G)$, and have since found interesting theoretical and algorithmic applications. This has motivated researchers to establish strong bounds on these parameters for various classes of graphs.   Let $G^p$ denote the $p$-th power of $G$. We show that, all integers $p >0$ and $\Delta \ge 3$ and graphs $G$ with $\Delta(G) \leq \Delta$ satisfy $col(G^p) \in O(p \cdot wcol_{\lceil p/2\rceil}(G)(\Delta-1)^{\lfloor p/2\rfloor})$; for fixed tree width or fixed genus the ratio between this upper bound and worst case lower bounds is polynomial in $p$. For the square of graphs $G$, we also show that, if the maximum average degree $2k-2 < mad(G) \leq 2k$, then $ col(G^2) \leq (2k-1)\Delta(G)+2k+1$.
We investigate the role of conflicts in pedestrian traffic, i.e. situations where two or more people try to enter the same space. Therefore a recently introduced cellular automaton model for pedestrian dynamics is extended by a friction parameter $\mu$. This parameter controls the probability that the movement of all particles involved in a conflict is denied at one time step. It is shown that these conflicts are not an undesirable artefact of the parallel update scheme, but are important for a correct description of the dynamics. The friction parameter $\mu$ can be interpreted as a kind of internal local pressure between the pedestrians which becomes important in regions of high density, ocurring e.g. in panic situations. We present simulations of the evacuation of a large room with one door. It is found that friction has not only quantitative effects, but can also lead to qualitative changes, e.g. of the dependence of the evacuation time on the system parameters. We also observe similarities to the flow of granular materials, e.g. arching effects.
We derive a semiclassical scheme for the conductance through a rectangular cavity. The transmission amplitudes are expressed as a sum over families of trajectories rather than a sum over isolated trajectories. The contributing families are obtained from the evaluation of a finite number of continued fractions. We find that, contrary to the chaotic case, the conductance fluctuations increase with the incoming energy and the correlation function exhibits a singularity at the origin.
Spin-torque oscillators are strong candidates as nano-scale microwave generators and detectors. However, because of large amplitude-phase coupling (non-linearity), phase noise is enhanced over other linear auto-oscillators. One way to reduce nonlinearity is to use ferromagnetic layers as a resonator and excite them at localized spots, making a resonator-excitor pair. We investigated the excitation of oscillations in dipole-coupled ferromagnetic layers, driven by localized current at ferromagnetic nano-contacts. Oscillations possessed properties of optical-mode spin-waves and at low field ($\approx$200 Oe) had high frequency (15 GHz), a moderate precession amplitude (2--3$^\circ$), and a narrow spectral linewidth ($<$3 MHz) due to localized excitation at nano-contacts. Micromagnetic simulation showed emission of resonator's characteristic optical-mode spin-waves from disturbances generated by domain-wall oscillations at nano-contacts.
Let $M$ be a compact complex manifold equipped with a Gauduchon metric. If $TM$ is holomorphically trivial, and (V, \theta) is a stable SL(r,{\mathbb C})-Higgs bundle on $M$, then we show that $\theta= 0$. We show that the correspondence between Higgs bundles and representations of the fundamental group for a compact Kaehler manifold does not extend to compact Gauduchon manifolds. This is done by applying the above result to G/\Gamma, where $\Gamma$ is a discrete torsionfree cocompact subgroup of a complex semisimple group $G$.
We present CO(1-0) and HI(21-cm) observations of the central region of the wet merger remnant NGC 34. The Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations detect a regularly rotating disk in CO with a diameter of 2.1 kpc and a total molecular hydrogen mass of ($2.1 \pm 0.2) \times10^9~M_\odot$. The rotation curve of this gas disk rises steeply, reaching maximum velocities at 1" (410 pc) from the center. Interestingly, HI observations done with the Karl G. Jansky Very Large Array show that the absorption against the central continuum has the exact same velocity range as the CO in emission. This strongly suggests that the absorbing HI also lies within 1" from the center, is mixed in and corotates with the molecular gas. A comparison of HI absorption profiles taken at different resolutions (5"-45") shows that the spectra at lower resolutions are less deep at the systemic velocity. This provides evidence for HI emission in the larger beams, covering the region from 1 kpc to 9 kpc from the center. The central rapidly rotating disk was likely formed either during the merger or from fall-back material. Lastly, the radio continuum flux of the central source at mm wavelengths ($5.4\pm1.8$ mJy) is significantly higher than expected from an extrapolation of the synchrotron spectrum, indicating the contribution of thermal free-free emission from the central starburst.