ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present the distributions of elemental abundance ratios using chemodynamical simulations which include four different neutron capture processes: magneto-rotational supernovae, neutron star mergers, neutrino driven winds, and electron capture supernovae. We examine both simple isolated dwarf disc galaxies and cosmological zoom-in simulations of Milky Way-type galaxies, and compare the [Eu/Fe] and [Eu/{\alpha}] evolution with recent observations, including the HERMES-GALAH survey. We find that neither electron-capture supernovae or neutrino-driven winds are able to adequately produce heavy neutron-capture elements such as Eu in quantities to match observations. Both neutron-star mergers and magneto-rotational supernovae are able to produce these elements in sufficient quantities. Additionally, we find that the scatter in [Eu/Fe] and [Eu/{\alpha}] at low metallicity ([Fe/H] < -1) and the [Eu/(Fe, {\alpha})] against [Fe/H] gradient of the data at high metallicity ([Fe/H] > -1) are both potential indicators of the dominant r-process site. Using the distribution in [Eu/(Fe, {\alpha}] - [Fe/H] we predict that neutron star mergers alone are unable to explain the observed Eu abundances, but may be able to together with magneto-rotational supernovae.
The ABC model is a simple diffusive one-dimensional non-equilibrium system which exhibits a phase transition. Here we show that the cumulants of the currents of particles through the system become singular near the phase transition. At the transition, they exhibit an anomalous dependence on the system size (an anomalous Fourier's law). An effective theory for the dynamics of the single mode which becomes unstable at the transition allows one to predict this anomalous scaling.
In frustrated spinel antiferromagnets, dilution with non-magnetic ions can be a powerful strategy for probing unconventional spin states or uncovering interesting phenomena. Here, we present X-ray, neutron scattering and thermodynamic studies of the effects of magnetic dilution of the tetragonally-distorted A-site spinel antiferromagnet, CuRh$_2$O$_4$, with non-magnetic Zn$^{2+}$ ions. Our data confirm the helical spin order recently identified at low-temperatures in this material, and further demonstrate a systematic suppression of the associated N\'eel temperature with increasing site dilution towards a continuous transition with critical doping of $x_{spin} \sim 0.44$. Interestingly, this critical doping is demonstrably distinct from a second structural critical point at $x_{JT} \sim 0.6$, which is consistent with the suppression of orbital order on the A-site through a classical percolative mechanism. This anomalously low value for $x_{spin}$ is confirmed via multiple measurements, and is inconsistent with predictions of classical percolation theory, suggesting that the spin transition in this material is driven by an enhancement of pre-existing spin fluctuations with weak dilution.
This work deals with systems of interacting reinforced stochastic processes, where each process $X^j=(X_{n,j})_n$ is located at a vertex $j$ of a finite weighted direct graph, and it can be interpreted as the sequence of "actions" adopted by an agent $j$ of the network. The interaction among the evolving dynamics of these processes depends on the weighted adjacency matrix $W$ associated to the underlying graph: indeed, the probability that an agent $j$ chooses a certain action depends on its personal "inclination" $Z_{n,j}$ and on the inclinations $Z_{n,h}$, with $h\neq j$, of the other agents according to the elements of $W$.   Asymptotic results for the stochastic processes of the personal inclinations $Z^j=(Z_{n,j})_n$ have been subject of studies in recent papers (e.g. Aletti, Crimaldi, and Ghiglietti [arXiv:1607.08514, Ann. Appl. Probab., 27(6):3787-3844, 2017]; Crimaldi, Dai Pra, Louis, and Minelli [arXiv:1602.06217, Forthcoming in Stochastic Process. Appl.]); while the asymptotic behavior of quantities based on the stochastic processes $X^j$ of the actions has never been studied yet. In this paper, we fill this gap by characterizing the asymptotic behavior of the empirical means $N_{n,j}=\sum_{k=1}^n X_{k,j}/n$, proving their almost sure synchronization and some central limit theorems in the sense of stable convergence. Moreover, we discuss some statistical applications of these convergence results concerning confidence intervals for the random limit toward which all the processes of the system converge and tools to make inference on the matrix $W$.
Let $\mathcal X=\{\mathcal X_t:\, t\geq0,\, \mathcal X_0=0\}$ be a mean zero $\beta$-stable random walk on $\mathbb{Z}$ with inhomogeneous jump rates $\{\tau_i^{-1}: i\in\mathbb{Z}\}$, with $\beta\in(1,2]$ and $\{\tau_i: i\in\mathbb{Z}\}$ a family of independent random variables with common marginal distribution in the basin of attraction of an $\alpha$-stable law, $\alpha\in(0,1)$. In this paper we derive results about the long time behavior of this process, in particular its scaling limit, given by a $\beta$-stable process time-changed by the inverse of another process, involving the local time of the $\beta$-stable process and an independent $\alpha$-stable subordinator; we call the resulting process a quasistable process. Another such result concerns aging. We obtain an (integrated) aging result for $\mathcal X$.
We theoretically investigate the magnetic activation energy of permanent magnets. Practically, it is widely used in a phenomenological form as $\mathcal{F}_\mathrm{B}(H_\mathrm{ext})=\mathcal{F}_\mathrm{B}^0\left(1-H_\mathrm{ext}/H_0\right)^n,$ where $\mathcal{F}_\mathrm{B}^0$ is the activation energy in the absence of an external magnetic field $H_\mathrm{ext}$, $n$ is a real parameter, and $H_0$ is defined by the equation $\mathcal{F}_\mathrm{B}(H_0)=0$. We derive the general and direct expressions for these phenomenological parameters under the restriction of uniform rotation of magnetization and on the basis of the perturbative theory with respect to $H_\mathrm{ext}$. Further,we apply our results to Nd$_2$Fe$_{14}$B magnets and confirm the validity of the proposed method by comparing with the Monte Carlo calculations.
We present Hubble Space Telescope (HST) and ground-based observations of a pair of galaxies at redshift 2.38, which are collectively known as 2142-4420 B1 (Francis et al. 1996). The two galaxies are both luminous extremely red objects (EROs), separated by 0.8 arcsec. They are embedded within a 100 kpc scale diffuse Ly-alpha nebula (or blob) of luminosity ~10^44 erg/s.   The radial profiles and colors of both red objects are most naturally explained if they are young elliptical galaxies: the most distant yet found. It is not, however, possible to rule out a model in which they are abnormally compact, extremely dusty starbursting disk galaxies. If they are elliptical galaxies, their stellar populations have inferred masses of ~10^11 solar masses and ages of ~7x10^8 years. Both galaxies have color gradients: their centers are significantly bluer than their outer regions. The surface brightness of both galaxies is roughly an order of magnitude greater than would be predicted by the Kormendy relation. A chain of diffuse star formation extending 1 arcsec from the galaxies may be evidence that they are interacting or merging.   The Ly-alpha nebula surrounding the galaxies shows apparent velocity substructure of amplitude ~ 700 km/s. We propose that the Ly-alpha emission from this nebula may be produced by fast shocks, powered either by a galactic superwind or by the release of gravitational potential energy.
The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 square degree field of view mounted on the 48-in Oschin Schmidt telescope at Palomar Observatory. One of the key goals of this survey is to conduct high-cadence monitoring of the sky in order to detect optical transient sources shortly after they occur. Here, we describe the real-time capabilities of the PTF and our related rapid multiwavelength follow-up programs, extending from the radio to the gamma-ray bands. We present as a case study observations of the optical transient PTF10vdl (SN 2010id), revealed to be a very young core-collapse (Type II-P) supernova having a remarkably low luminosity. Our results demonstrate that the PTF now provides for optical transients the real-time discovery and rapid-response follow-up capabilities previously reserved only for high-energy transients like gamma-ray bursts.
The electrical conductivity of a pion gas at low temperatures is studied in the framework of Linear Response and Chiral Perturbation Theory. The standard ChPT power counting has to be modified to include pion propagator lines with a nonzero thermal width in order to properly account for collision effects typical of Kinetic Theory. With this modification, we discuss the relevant chiral power counting to be used in the calculation of transport coefficients. The leading order contribution is found and we show that the dominant higher order ladder diagrams can be treated as perturbative corrections at low temperatures. We find that the DC conductivity $\sigma (T)$ is a decreasing function of $T$, behaving for very low $T$ as $\sigma (T)\sim e^2m_\pi\sqrt{m_\pi/T}$, consistently with nonrelativistic Kinetic Theory. When unitarization effects are included, $\sigma(T)$ increases slowly as $T$ approaches the chiral phase transition. We compare with related works and discuss some physical consequences, especially in the context of the low-energy hadronic photon spectrum in Relativistic Heavy Ion Collisions.
We analyzed ionized gas motion and disk orientation parameters for 15 spiral galaxies. Their velocity fields were measured with the H-alpha emission line by using the Fabry-Perot interferometer at the 6m telescope of SAO RAS. Special attention is paid to the problem of estimating the position angle of the major axis (PA_0) and the inclination (i) of a disk, which strongly affect the derived circular rotation velocity. We discuss and compare different methods of obtaining these parameters from kinematic and photometric observations, taking into account the presence of regular velocity (brightness) perturbations caused by spiral density waves. It is shown that the commonly used method of tilted rings may lead to systematic errors in the estimation of orientation parameters (and hence of circular velocity) being applied to galaxies with an ordered spiral structure. Instead we recommend using an assumption of constancy of i and PA_0 along a radius, to estimate these parameters. For each galaxy of our sample we present monochromatic H-alpha- and continuum maps, velocity fields of ionized gas, and the mean rotation curves in the frame of a model of pure circular gas motion. Significant deviations from circular motion with amplitudes of several tens of km/s (or higher) are found in almost all galaxies. The character and possible nature of the non-circular motion are briefly discussed.
The possible Fermi detection of an electromagnetic counterpart to the double black hole merger GW150914 has inspired many theoretical models, some of which propose that the holes spiraled together inside a massive star. However, we show that the heat produced by the dynamical friction on such black hole orbits can exceed the stellar binding energy by a large factor, which means that this heat could destroy the star and thus make it difficult for enough gas to be near the holes at merger to produce detectable photons. These considerations must be taken into account when models are proposed for electromagnetic counterparts to the coalescence of two stellar-mass black holes. We find that only when the two black holes form very close to the center can the star avoid destruction. In that case, dynamical friction can make the black holes coalesce faster than they would in vacuum, which leads to a modification of the gravitational waveform that is potentially observable by advanced LIGO.
We study the time-dependent Ginzburg--Landau equations in a three-dimensional curved polyhedron (possibly nonconvex). Compared with the previous works, we prove existence and uniqueness of a global weak solution based on weaker regularity of the solution in the presence of edges or corners, where the magnetic potential may not be in $L^2(0,T;H^1(\Omega)^3)$.
Let $X$ be a smooth polarized algebraic surface over the compex number field. We discuss the invariants obtained from the moduli stacks of semistable sheaves of arbitrary ranks on $X$. For that purpose, we construct the virtual fundamental classes of some moduli stacks, and we show the transition formula of the integrals over the moduli stacks of the $\delta$-stable Bradlow pairs for the variation of the parameter $\delta$.   Then, we study the relation among the invariants. In the case $p_g>0$, we show that the invariants are independent of the choice of a polarization of $X$. We also show that the invariants can be reduced to the invariants obtained from the moduli of abelian pairs and the Hilbert schemes. In the case $p_g=0$, we obtain the weak wall crossing formula and the weak intersection rounding formula, which describes the dependence of the invariants on the polarization.
This is a sequel to the paper "Large time asymptotics for a cubic nonlinear Schr\"odinger system in one space dimension" by the same authors. We continue to study the Cauchy problem for the two-component system of cubic nonlinear Schr\"odinger equations in one space dimension. We provide criteria for large time decay or non-decay in $L^2$ of the small amplitude solutions in terms of the Fourier transforms of the initial data.
The reduction modulo $p$ of a family of lacunary integer polynomials, associated with the dynamical zeta function $\zeta_{\beta}(z)$ of the $\beta$-shift, for $\beta > 1$ close to one, is investigated. We briefly recall how this family is correlated to the problem of Lehmer. A variety of questions is raised about their numbers of zeroes in $\mathbb{F}_p$ and their factorizations, via Kronecker's Average Value Theorem (viewed as an analog of classical Theorems of Uniform Distribution Theory). These questions are partially answered using results of Schinzel, revisited by Sawin, Shusterman and Stoll, and density theorems (Frobenius, Chebotarev, Serre, Rosen). These questions arise from the search for the existence of integer polynomials of Mahler measure > 1 less than the smallest Salem number 1.176280. Explicit connection with modular forms (or modular representations) of the numbers of zeroes of these polynomials in $\mathbb{F}_p$ is obtained in a few cases. In general it is expected since it must exist according to the Langlands program.
We consider the interacting system of D=4 N=1 supergravity and the Brink-Schwarz massless superparticle as described by the sum of their superfield actions, and derive the complete set of superfield equations of motion for the coupled dynamical system. These include source terms given by derivatives of a vector superfield current density with support on the worldline. This current density is constructed from the spin 3/2 and spin 2 current density `prepotentials'. We analyze the gauge symmetry of the coupled action and show that it is possible to fix the gauge in such a way that the equations of motion reduce to those of the supergravity-bosonic particle coupled system.
We combine new Wide Field Camera~3 IR Channel (WFC3/IR) F160W (H) imaging data for NGC1399, the central galaxy in the Fornax cluster, with archival F475W (g), F606W (V), F814W (I), and F850LP (z) optical data from the Advanced Camera for Surveys (ACS). The purely optical g-I, V-I, and g-z colors of NGC1399's rich globular cluster (GC) system exhibit clear bimodality, at least for magnitudes $I_814 > 21.5$. The optical-IR I-H color distribution appears unimodal, and this impression is confirmed by mixture modeling analysis. The V-H colors show marginal evidence for bimodality, consistent with bimodality in V-I and unimodality in I-H. If bimodality is imposed for I-H with a double Gaussian model, the preferred blue/red split differs from that for optical colors; these "differing bimodalities" mean that the optical and optical-IR colors cannot both be linearly proportional to metallicity. Consistent with the differing color distributions, the dependence of I-H on g-I for the matched GC sample is significantly nonlinear, with an inflection point near the trough in the g-I color distribution; the result is similar for the I-H dependence on g-z colors taken from the ACS Fornax Cluster Survey. These g-z colors have been calibrated empirically against metallicity; applying this calibration yields a continuous, skewed, but single-peaked metallicity distribution. Taken together, these results indicate that nonlinear color-metallicity relations play an important role in shaping the observed bimodal distributions of optical colors in extragalactic GC systems.
Chandra ACIS observed the field of the extended TeV source HESS J1834-087 for 47 ks. A previous XMM-Newton EPIC observation of the same field revealed a point-like source (XMMU J183435.3-084443) and an offset region of faint extended emission. In the low-resolution, binned EPIC images the two appear to be connected. However, the high-resolution Chandra ACIS images do not support the alleged connection. Instead, in these images XMMU J183435.3-084443 is resolved into a point source, CXOU~J183434.9--084443 (L=2.5 x 10e33 ergs/s, for a distance of 4 kpc; photon index 1.1), and a compact (~20'') nebula with an isotropic morphology and a softer spectrum (L=4.2 x10e33 ergs/s, photon index 2.7). The nature of the nebula is uncertain. We discuss a dust scattering halo and a pulsar-wind nebula as possible interpretations. Based on our analysis of the X-ray data, we re-evaluate the previously suggested interpretations of HESS J1834-087 and discuss a possible connection to the Fermi LAT source 1FGL J1834.3-0842c. We also obtained an upper limit of 3 x 10e-14 ergs/s cm^2 on the unabsorbed flux of the SGR J1833--0832 (in quiescence), which happened to be in the ACIS field of view.
The packing chromatic number $\chi_{\rho}(G)$ of a graph $G$ is the smallest integer $k$ such that the vertex set of $G$ can be partitioned into sets $\Pi_1,\ldots,\Pi_k$, where $\Pi_i$, $i\in [k]$, is an $i$-packing. The following conjecture is posed and studied: if $G$ is a subcubic graph, then $\chi_{\rho}(S(G))\le 5$, where $S(G)$ is the subdivision of $G$. The conjecture is proved for all generalized prisms of cycles. To get this result it is proved that if $G$ is a generalized prism of a cycle, then $G$ is $(1,1,2,2)$-colorable if and only if $G$ is not the Petersen graph. The validity of the conjecture is further proved for graphs that can be obtained from generalized prisms in such a way that one of the two $n$-cycles in the edge set of a generalized prism is replaced by a union of cycles among which at most one is a 5-cycle. The packing chromatic number of graphs obtained by subdividing each of its edges a fixed number of times is also considered.
Susceptibility of neural networks to adversarial attack prompts serious safety concerns for lane detection efforts, a domain where such models have been widely applied. Recent work on adversarial road patches have successfully induced perception of lane lines with arbitrary form, presenting an avenue for rogue control of vehicle behavior. In this paper, we propose a modular lane verification system that can catch such threats before the autonomous driving system is misled while remaining agnostic to the particular lane detection model. Our experiments show that implementing the system with a simple convolutional neural network (CNN) can defend against a wide gamut of attacks on lane detection models. With a 10% impact to inference time, we can detect 96% of bounded non-adaptive attacks, 90% of bounded adaptive attacks, and 98% of patch attacks while preserving accurate identification at least 95% of true lanes, indicating that our proposed verification system is effective at mitigating lane detection security risks with minimal overhead.
The effective field theory (EFT) for triaxially deformed even-even nuclei is generalized to include the vibrational degrees of freedom. The pertinent Hamiltonian is constructed up to next-to-leading order. The leading order part describes the vibrational motion, and the NLO part couples rotations to vibrations. The applicability of the EFT Hamiltonian is examined through the description of the energy spectra of the ground state bands, $\gamma$-bands, and $K=4$ bands in the $^{108, 110, 112}$Ru isotopes. It is found that by taking into account the vibrational degrees of freedom, the deviations for high-spin states in the $\gamma$-band observed in the EFT with only rotational degrees of freedom disappear. This supports the importance of including vibrational degrees of freedom in the EFT formulation for the collective motion of triaxially deformed nuclei.
The existence of travelling waves for a coupled system of hyperbolic/ parabolic equations is established in the case of a finite number of velocities in the kinetic equation. This finds application in collective motion of chemotactic bacteria. The analysis builds on the previous work by the first author (arXiv:1607.00429) in the case of a continuum of velocities. Here, the proof is specific to the discrete setting, based on the decomposition of the population density in special Case's modes. Some counter-intuitive results are discussed numerically, including the coexistence of several travelling waves for some sets of parameters, as well as the possible non-existence of travelling waves.
We present a study of the distribution and kinematics of the neutral gas in the low-inclination Scd galaxy NGC 6946. The galaxy has been observed for 192 hours at 21-cm with the Westerbork Synthesis Radio Telescope. These are among the deepest observations ever obtained for a nearby galaxy. We detect widespread high-velocity HI (up to about 100 km/s) and find 121 HI holes, most of which are located in the inner regions where the gas density and the star formation rate are higher. Much of the high-velocity gas appears to be related to star formation and to be, in some cases, associated with HI holes. The overall kinematics of the high-velocity gas is characterized by a slower rotation as compared with the regular disk rotation. We conclude that the high-velocity gas in NGC 6946 is extra-planar and has the same properties as the gaseous halos observed in other spiral galaxies including the Milky Way. Stellar feedback (galactic fountain) is probably at the origin of most of the high-velocity gas and of the HI holes. There are also indications, especially in the outer regions, -an extended HI plume, velocity anomalies, sharp edges, and large-scale asymmmetries- pointing to tidal encounters and recent gas accretion.
A large set of high precision full-Stokes spectropolarimetric observations of prominences in He-D3, Halpha and Hbeta lines has been recorded with the ZIMPOL polarimeter at the Gregory-Coude Telescope in Locarno. The observational technique allows us to obtain measurements free from seeing induced spurious effects. The instrumental polarization is well under control and taken into account in the data analysis. We present our observational results for each of the above-mentioned lines. Of particular interest is that most of our Halpha measurements show anti-symmetric V profiles that are a characteristic signature of the Zeeman effect in the prominence plasma. A Stokes inversion technique based on the quantum theory of the Hanle and Zeeman effects is being applied on observed Stokes profiles in the He-D3 line in order to obtain information on the magnetic field vector that confines the prominence plasma.