ShantanuT01/DACTYL-Pretraining huggingface dataset:
Context. Observations of the effect of microlensing in gravitationally lensed quasars could potentially be used to study the structure of the source on distance scales down to the size of the supermassive black hole powering the quasar activity.   Aims. We search for the microlensing effect in the gamma-ray band using the signal from a gravitationally lensed blazar B0218+357.   Methonds. We develop a method of deconvolution of contributions of two images of the source into the gamma-ray band flaring lightcurve. We use this method to study the evolution of the magnification factor ratio between the two images throughout the flaring episodes. We interpret the time variability of the ratio as a signature of the microlensing effect and derive constraints on the physical parameters of the gamma-ray source by comparing the observed variability properties of the magnification factor ratio with those derived from numerical simulations of the microlensing caustics networks.   Results. We find that the magnification factor ratio has experienced a change characteristic for a microlensing caustic crossing event during a 100 d flaring period in 2012. It has further changed between 2012 and a recent flaring episode in 2014. We use the measurement of the maximal magnification and duration of the caustic crossing event to derive an estimate of the projected size of the gamma-ray emission region in B0218+357, $R_\gamma \sim 10^{14}$ cm. This estimate is compatible with a complementary estimate found from the minimal variability time scale. The microlensing / minimal variability time scale measurements of the source size suggest that the gamma-ray emission is produced at the base of the blazar jet, in the direct vicinity of the central supermassive black hole.
We establish in this article spreading properties for the solutions of equations of the type $\partial$ t u -- a(x)$\partial$ xx u -- q(x)$\partial$ x u = f (x, u), where a, q, f are only assumed to be uniformly continuous and bounded in x, the nonlinearity f is of monostable KPP type between two steady states 0 and 1 and the initial datum is compactly sup-ported. Using homogenization techniques, we construct two speeds w $\le$ w such that lim t$\rightarrow$+$\infty$ sup 0$\le$x$\le$wt |u(t, x)--1| = 0 for all w $\in$ (0, w) and lim t$\rightarrow$+$\infty$ sup x$\ge$wt |u(t, x)| = 0 for all w \textgreater{} w. These speeds are characterized in terms of two new notions of generalized principal eigenvalues for linear elliptic operators in unbounded domains. In particu-lar, we derive the exact spreading speed when the coefficients are random stationary ergodic, almost periodic or asymptotically almost periodic (where w = w).
In this paper, we firstly establish the weak laws of large numbers on the canonical space $(\br^\bn,\cb(\br^\bn))$ by traditional truncation method and Chebyshev's inequality as in the classical probability theory. Then we extend them from the canonical space to the general sublinear expectation space. The necessary and sufficient conditions for Peng's law of large numbers are obtained.
We study the impact of cosmological scale modifications to General Relativity on the dynamics of halos within voids by comparing N-body simulations incorporating Hu-Sawicki $f(R)$ gravity, with $|f_{R0}|=10^{-6}$ and $10^{-5}$, to those of $\Lambda$CDM. By examining the radial velocity statistics within voids classified based on their size and density-profile, as "rising" ($R$-type) or "shell" ($S$-type), we find that halo motions in small $R$-type voids, with effective radius $<15 Mpc/h$, reveal distinctive differences between $f(R)$ and $\Lambda$CDM cosmologies.   To understand this observed effect, we study the linear and nonlinear fifth forces, and develop an iterative algorithm to accurately solve the non-linear fifth force equation. We use this to characterize the Chameleon screening mechanism in voids and contrast the behavior with that observed in gravitationally collapsed objects.   The force analysis underscores how smaller $R$-type voids exhibit the highest ratios of fifth force to Newtonian force, which source distinguishable differences in the velocity profiles and thereby provide rich environments in which to constrain gravity.
The major physical processes responsible for shaping and sculpting pillars in the clouds surrounding massive stars (i.e. the `Pillars of Creation') are now being robustly incorporated into models quantifying the ionizing radiation from massive stars. The detailed gas dynamics within these pillars can now be compared with observations. Our goal is to quantify the gas dynamics in a pillar being sculpted by a nearby massive star. To do this, we use the CO, $^{13}$CO, and C$^{18}$O J=1-0 emission towards a pillar in the Vulpecula Rift. These data are a combination of CARMA and FCRAO observations providing high resolution ($\sim5''$) imaging of large scale pillar structures ($>100''$). We find that this cold ($\sim18$ K), low density material ($8\times10^3$ cm$^{-3}$) material is fragmenting on Jeans scales, has very low velocity dispersions ($\sim0.5$ km s$^{-1}$), and appears to be moving away from the ionizing source. We are able to draw direct comparisons with three models from the literature, and find that those with lower velocity dispersions best fit our data, although the dynamics of any one model do not completely agree with our observations. We do however, find that our observed pillar exhibits many of the characteristics expected from simulations.
Photometric large scale structure (LSS) surveys probe the largest volumes in the Universe, but are inevitably limited by systematic uncertainties. Imperfect photometric calibration leads to biases in our measurements of the density fields of LSS tracers such as galaxies and quasars, and as a result in cosmological parameter estimation. Earlier studies have proposed using cross-correlations between different redshift slices or cross-correlations between different surveys to reduce the effects of such systematics. In this paper we develop a method to characterize unknown systematics. We demonstrate that while we do not have sufficient information to correct for unknown systematics in the data, we can obtain an estimate of their magnitude. We define a parameter to estimate contamination from unknown systematics using cross-correlations between different redshift slices and propose discarding bins in the angular power spectrum that lie outside a certain contamination tolerance level. We show that this method improves estimates of the bias using simulated data and further apply it to photometric luminous red galaxies in the Sloan Digital Sky Survey as a case study.
Natural images contain often curvilinear structures, which might be disconnected, or partly occluded. Recovering the missing connection of disconnected structures is an open issue and needs appropriate geometric reasoning. We propose to find line co-occurrence statistics from the centerlines of blood vessels in retinal images and show its remarkable similarity to a well-known probabilistic model for the connectivity pattern in the primary visual cortex. Furthermore, the probabilistic model is trained from the data via statistics and used for automated grouping of interrupted vessels in a spectral clustering based approach. Several challenging image patches are investigated around junction points, where successful results indicate the perfect match of the trained model to the profiles of blood vessels in retinal images. Also, comparisons among several statistical models obtained from different datasets reveals their high similarity i.e., they are independent of the dataset. On top of that, the best approximation of the statistical model with the symmetrized extension of the probabilistic model on the projective line bundle is found with a least square error smaller than 2%. Apparently, the direction process on the projective line bundle is a good continuation model for vessels in retinal images.
New ultra-hard rhombohedral B2N2 and BC2N - or hexagonal B6N6 and B3C6N3 - are derived from 3R graphite based on crystal chemistry rationale schematizing a mechanism for 2D => 3D transformation. Full unconstrained geometry optimizations leading to ground state energy structures and energy derived quantities as energy-volume equation of states (EOS) were based on computations within the density functional theory (DFT) with generalized gradient approximation (GGA) for exchange-correlation (XC) effects. The new binary and ternary phases are characterized by tetrahedral stacking alike diamond, visualized with charge density representations, and illustrating ion characters. Atom averaged total energies are similar between cubic BN and rh-B2N2 on one hand, and larger stabilization of rhombohedral BC2N versus cubic and orthorhombic forms (in literature assessed from favored C-C and B-N bonding), on the other hand. The electronic band structures are characteristic of insulators with Egap ~ 5 eV. Both phases are characterized by large bulk and shear moduli and very high hardness values i.e. HV(rh-B2N2) = 74 GPa and HV(rh-BC2N) = 87 GPa.
We present the discovery of a kinematically-cold stellar population along the SE minor axis of the Andromeda galaxy (M31) that is likely the forward continuation of M31's giant southern stream. This discovery was made in the course of an on-going spectroscopic survey of red giant branch (RGB) stars in M31 using the DEIMOS instrument on the Keck II 10-m telescope. Stellar kinematics are investigated in eight fields located 9-30 kpc from M31's center (in projection). A likelihood method based on photometric and spectroscopic diagnostics is used to isolate confirmed M31 RGB stars from foreground Milky Way dwarf stars: for the first time, this is done without using radial velocity as a selection criterion, allowing an unbiased study of M31's stellar kinematics. The radial velocity distribution of the 1013 M31 RGB stars shows evidence for the presence of two components. The broad (hot) component has a velocity dispersion of 129 km/s and presumably represents M31's virialized spheroid. A significant fraction (19%) of the population is in a narrow (cold) component centered near M31's systemic velocity with a velocity dispersion that decreases with increasing radial distance, from 55.5 km/s at R_proj=12 kpc to 10.6 km/s at R_proj=18 kpc. The spatial and velocity distribution of the cold component matches that of the "Southeast shelf" predicted by the Fardal et al. (2007) orbital model of the progenitor of the giant southern stream. The metallicity distribution of the cold component matches that of the giant southern stream, but is about 0.2 dex more metal rich on average than that of the hot spheroidal component. We discuss the implications of our discovery on the interpretation of the intermediate-age spheroid population found in this region in recent ultra-deep HST imaging studies.
We present a near infrared study focused on the detection and characterization of the youngest stellar component of the NGC 604 giant star-forming region, in the Triangulum galaxy (M 33). By means of color-color diagrams derived from the photometry of JHKs images taken with Gemini-NIRI, we have found 68 candidate massive young stellar objects. The spatial distribution of these sources matches the areas where previous studies suggested that star formation might be taking place, and the high spatial resolution of our deep NIRI imaging allows to pinpoint the star-forming knots. An analysis of the fraction of objects that show infrared excess suggests that the star formation is still active, supporting the presence of a second generation of stars being born, although the evidence for or against sequential star formation does not seem to be conclusive.
In this paper, we discuss the uniqueness for solution to time-fractional diffusion equation $\partial_t^\alpha (u-u_0) + Au=0$ with the homogeneous Dirichlet boundary condition, where an elliptic operator $-A$ is not necessarily symmetric. We prove that the solution is identically zero if its normal derivative with respect to the operator $A$ vanishes on an arbitrary small part of the spatial domain over a time interval. The proof is based on the Laplace transform and the spectral decomposition, and is valid for more general time-fractional partial differential equations, including those involving non symmetric operators.
I derive and discuss a simple semi-analytical model of the evolution of powerful radio galaxies which is not based on assumptions of self-similar growth, but rather implements some insights about the dynamics and energetics of these systems derived from numerical simulations, and can be applied to arbitrary pressure/density profiles of the host environment. The model can qualitatively and quantitatively reproduce the source dynamics and synchrotron light curves derived from numerical modelling. Approximate corrections for radiative and adiabatic losses allow it to predict the evolution of radio spectral index and of inverse-Compton emission both for active sources and for `remnant' sources after the jet has turned off. Code to implement the model is publicly available. Using a standard model with a light relativistic (electron-positron) jet, sub-equipartition magnetic fields, and a range of realistic group/cluster environments, I simulate populations of sources and show that the model can reproduce the range of properties of powerful radio sources as well as observed trends in the relationship between jet power and radio luminosity, and predicts their dependence on redshift and environment. I show that the distribution of source lifetimes has a significant effect on both the source length distribution and the fraction of remnant sources expected in observations, and so can in principle be constrained by observations. The remnant fraction is expected to be low even at low redshift and low observing frequency due to the rapid luminosity evolution of remnants, and to tend rapidly to zero at high redshift due to inverse-Compton losses.
Motivated by the recent development in strong spin-orbit-coupled materials, we consider the dipole-octupole doublets on the triangular lattice. We propose the most general interaction between these unusual local moments. Due to the spin-orbit entanglement and the special form of its wavefunction, the dipole-octupole doublet has a rather peculiar property under the lattice symmetry operation. As a result, the interaction is highly anisotropic in the pseudospin space, but remarkably, is uniform spatially. We analyze the ground state properties of this generic model and emphasize the hidden multipolar orders that emerge from the dipolar and octupolar interactions. We clarify the quantum mutual modulations between the dipolar and octupolar orders. We predict the experimental consequences of the multipolar orders and propose the rare-earth triangular materials as candidate systems for these unusual properties.
Given graphs $H$ and $F$, the generalized Tur\'an number $\mathrm{ex}(n,H,F)$ is the largest number of copies of $H$ in $n$-vertex $F$-free graphs. Stability refers to the usual phenomenon that if an $n$-vertex $F$-free graph $G$ contains almost $\mathrm{ex}(n,H,F)$ copies of $H$, than $G$ is in some sense similar to some extremal graph. We obtain new stability results for generalized Tur\'an problems and derive several new exact results.
A search for solar axions has been performed using an axion helioscope which is equipped with a 2.3m-long 4T superconducting magnet, a gas container to hold dispersion-matching gas, PIN-photodiode X-ray detectors, and a telescope mount mechanism to track the sun. A mass region around m_a = 1eV was newly explored.   From the absence of any evidence, analysis sets a limit on axion-photon coupling constant to be g < 5.6-13.4x10^{-10} GeV^{-1} for the axion mass of 0.84<m_a<1.00eV at 95% confidence level. It is the first result to search for the axion in the g-m_a parameter region of the preferred axion models with a magnetic helioscope.
In this letter we introduce the concept of a driven quantum walk. This work is motivated by recent theoretical and experimental progress that combines quantum walks and parametric down- conversion, leading to fundamentally different phenomena. We compare these striking differences by relating the driven quantum walks to the original quantum walk. Next, we illustrate typical dynamics of such systems and show these walks can be controlled by various pump configurations and phase matchings. Finally, we end by proposing an application of this process based on a quantum search algorithm that performs faster than a classical search.
We describe a 4D Eigenvector 1 (4DE1) space that serves as a surrogate H-R diagram for quasars. It provides a context for describing and unifying differences between all broad line AGN. Quasar spectra can be averaged in a non-random way using 4DE1 just as stellar spectra can be averaged non-randomly within the OBAFGKM classification sequence. We find that quasars with FWHM H_beta less than (Population A) and greater than (Population B) 4000 km/s show many significant differences that may point to an actual dichotomy. Broad line profile measures and fits reenforce the idea of a dichotomy because they are fundamentally different: Pop.A - Lorentzian-like and Pop.B - double Gaussian. The differences have implications both for BH mass estimation and for inferences about source structure and kinematics.
The type III observations trace the propagation of energetic electron populations through the Solar Corona which, more often than not, precede or are associated with energy release on the Sun. A sample of Type III bursts in the range 20-650 MHz during the period of extraordinary solar activity (20 October to 4 November 2003) recorded by the ARTEMIS-IV1 radio spectrograph is analysed; its parameters are compared with characteristics of associated flares (Ha and GOES SXR) and CMEs, observed in the same period and reported in the SGR and the LASCO archives respectively. In this report we attempt to establish a correlation between energetic particles and major manifestations of solar activity such as flares and CMEs.
We present timing analysis of the accretion powered pulsar SXP 1062, based on the observations of \textit{Swift}, \textit{XMM-Newton} and \textit{Chandra} satellites covering a time span of about 2 years. We obtain a phase coherent timing solution which shows that SXP 1062 has been steadily spinning down with a rate $-\,4.29(7) \times 10^{-14}$ Hz s$^{-1}$ leading to a surface magnetic field estimate of about $1.5 \times 10^{14}$ G. We also resolve the binary orbital motion of the system from X-ray data which confirms an orbital period of 656(2) days. On MJD 56834.5, a sudden change in pulse frequency occurs with $\Delta\nu = 1.28(5) \times 10^{-6} $ Hz, which indicates a glitch event. The fractional size of the glitch is $\Delta \nu / \nu \! \sim \! 1.37(6) \times 10^{-3}$ and SXP 1062 continues to spin-down with a steady rate after the glitch. A short X-ray outburst 25 days prior to the glitch does not alter the spin-down of the source; therefore the glitch should be associated with the internal structure of the neutron star. While glitch events are common for isolated pulsars, the glitch of SXP 1062 is the first confirmation of the observability of this type of events among accretion powered pulsars. Furthermore, the value of the fractional change of pulse frequency ensures that we discover the largest glitch reported up to now.
We outline an approach to prove the two dimensional Jacobian Conjecture using the theory of fractals.
We obtain rates of convergence to stationarity in L^1-Wasserstein distance for a d-dimensional reflected Brownian motion (RBM) in the nonnegative orthant that are explicit in the dimension and the system parameters. The results are then applied to a class of RBMs considered in Blanchet-Chen (2016) and to rank-based diffusions including the Atlas model. In both cases, we obtain explicit rates and bounds on relaxation times. In the first case we improve the relaxation time estimates of O(d^4(log d)^2) obtained in Blanchet-Chen (2016) to O((log d)^2). In the latter case, we give the first results on explicit parameter and dimension dependent rates under the Wasserstein distance. The proofs do not require an explicit form for the stationary measure or reversibility of the process with respect to this measure, and cover settings where these properties are not available. In the special case of the standard Atlas model, we obtain a bound on the relaxation time of O(d^6(log d)^2).
We report observations of molecular oxygen (O$_2$) rotational transitions at 487 GHz, 774 GHz, and 1121 GHz toward Orion Peak A. The O2 lines at 487 GHz and 774 GHz are detected at velocities of 10-12 km/s with line widths 3 km/s; however, the transition at 1121 GHz is not detected. The observed line characteristics, combined with the results of earlier observations, suggest that the region responsible for the O$_2$ emission is 9" (6e16 cm) in size, and is located close to the H2 Peak 1position (where vibrationally-excited H$_2$ emission peaks), and not at Peak A, 23" away. The peak O2 column density is 1.1e18/cm2. The line velocity is close to that of 621 GHz water maser emission found in this portion of the Orion Molecular Cloud, and having a shock with velocity vector lying nearly in the plane of the sky is consistent with producing maximum maser gain along the line-of-sight. The enhanced O$_2$ abundance compared to that generally found in dense interstellar clouds can be explained by passage of a low-velocity C-shock through a clump with preshock density 2e4/cm3, if a reasonable flux of UV radiation is present. The postshock O$_2$ can explain the emission from the source if its line of sight dimension is ~10 times larger than its size on the plane of the sky. The special geometry and conditions required may explain why O$_2$ emission has not been detected in the cores of other massive star-forming molecular clouds.
We investigate the statistics of selected rare events in a (1+1)-dimensional (classical) stochastic growth model which describes the evolution of (quantum) random unitary circuits. In such classical formulation, particles are created and/or annihilated at each step of the evolution process, according to rules which generally favor a growing cluster size. We apply a large-deviation approach based on biased Monte Carlo simulations, with suitable adaptations, to evaluate (a) the probability of ending up with a single particle at a specified final time $t_f$, and (b) the probability of having particles outside the light cone, defined by a "butterfly velocity" $v_B$, at $t_f$. Morphological features of single-particle final configurations are discussed, in connection with whether the location of such particle is inside or outside the light cone; we find that joint occurrence of both events of types (a) and (b) drives significant changes to such features, signalling a second-order phase transition.
Let $E$ be a holomorphic vector bundle on a projective manifold $X$ such that $\det E$ is ample. We introduce three functionals $\Phi_P$ related to Griffiths, Nakano and dual Nakano positivity respectively. They can be used to define new concepts of volume for the vector bundle $E$, by means of generalized Monge-Amp\`ere integrals of $\Phi_P(\Theta_{E,h})$, where $\Theta_{E,h}$ is the Chern curvature tensor of $(E,h)$. These volumes are shown to satisfy optimal Chern class inequalities. We also prove that the functionals $\Phi_P$ give rise in a natural way to elliptic differential systems of Hermitian-Yang-Mills type for the curvature, in such a way that the related $P$-positivity threshold of $E\otimes(\det E)^t$, where $t>-1/{\rm rank} E$, can possibly be investigated by studying the infimum of exponents $t$ for which the Yang-Mills differential system has a solution.