Astrophysical Applications Research Articles

Novel nonlinear quantum dust acoustic waves for modified variable coefficients Zakharove–Kusnetsov equation in dusty plasma

In this paper, the direct similarity reduction method is used to reduce the modified variable coefficient Zakharove–Kusnetsov equation (vcmZK), which represents the propagation of quantum dust acoustic waves (QDAWs) in an inhomogeneous magnetized dusty plasma field, into a nonlinear ordinary differential equation (NODE). Moreover, the Jacobi elliptic method is used to solve the NODE, where many novel double periodic, kink, and solitary wave solutions are obtained. Additionally, we have chosen to plot periodic, kink, and soliton QDAWs solutions according to some choices for the variable coefficients. According to the a chieved results, we can conclude that the choices of the functional forms of the variable coefficients can control the QDAWs propagation. Finally, the new discovered results may have many important applications in astrophysics, atmospheric science, nanotechnology, and industrial plasma physics.

The inviscid incompressible limit of Kelvin–Helmholtz instability for plasmas

Introduction: The Kelvin–Helmholtz Instability (KHI) is an interface instability that develops between two fluids or plasmas flowing with a common shear layer. KHI occurs in astrophysical jets, solar atmosphere, solar flows, cometary tails, planetary magnetospheres. Two applications of interest, encompassing both space and fusion applications, drive this study: KHI formation at the outer flanks of the Earth’s magnetosphere and KHI growth from non-uniform laser heating in magnetized direct-drive implosion experiments. Here, we study 2D KHI with or without a magnetic field parallel to the flow. We use both the GAMERA code, which solves the compressible Euler equations, and the STRATOSPEC code, which solves the Navier-Stokes equations under the Boussinesq approximation, coupled with the magnetic field dynamics. GAMERA is a global three-dimensional MHD code with high-order reconstruction in arbitrary nonorthogonal curvilinear coordinates, which is developed for a large range of astrophysical applications. STRATOSPEC is a three-dimensional pseudo-spectral code with an accuracy of infinite order (no numerical diffusion). Magnetized KHI is a canonical case for benchmarking hydrocode simulations with extended MHD options.Methods: An objective is to assess whether or not, and under which conditions, the incompressibility hypothesis allows to describe a dynamic compressible system. For comparing both codes, we reach the inviscid incompressible regime, by decreasing the Mach number in GAMERA, and viscosity and diffusion in STRATOSPEC. Here, we specifically investigate both single-mode and multi-mode initial perturbations, either with or without magnetic field parallel to the flow. The method relies on comparisons of the density fields, 1D profiles of physical quantities averaged along the flow direction, and scale-by-scale spectral densities. We also address the triggering, formation and damping of filamentary structures under varying Mach number or Atwood number, with or without a parallel magnetic field.Results: Comparisons show very satisfactory results between the two codes. The vortices dynamics is well reproduced, along with the breaking or damping of small-scale structures. We end with the extraction of growth rates of magnetized KHI from the compressible regime to the incompressible limit in the linear regime assessing the effects of compressibility under increasing magnetic field.Discussion: The observed differences between the two codes are explained either from diffusion or non-Boussinesq effects.

On the detection and precise localization of merging black holes events through strong gravitational lensing

ABSTRACT To unlock the full spectrum of astrophysical and cosmological applications of gravitational-wave detections, it is essential to localize the associated black hole mergers to high precision inside their host galaxies. One possible method to achieve this is to compare the properties of multiple detections of gravitationally lensed binary black hole merger events with the properties of strong gravitational lens systems located in the joint sky localization of the gravitational-wave detections. In this work, we simulate the population of binary black hole mergers lensed by galaxy-scale lenses and detectable by LIGO-Virgo-Kagra in the coming decade and the population of galaxy-scale strong lenses that will be detected by Euclid. We use these simulations to investigate the prospects for localizing strongly lensed binary black hole mergers inside the lensed galaxies of ‘Euclid-like’ galaxy-scale strong lenses. We find that for 20–$50\, \rm \%$ of strongly lensed gravitational-wave events the lens system is detectable with Euclid, if the event falls in its survey footprint. Of these, we expect to correctly identify the strongly lensed host galaxy as likely (with posterior probability) host galaxy – based on Bayesian evidence ranking of candidate hosts – for 34.6–$21.9\,\mathrm{ per\,cent}$ of quadruply lensed gravitational-wave events when given an a priori 1–5 $\deg ^{2}$ gravitational-wave-only sky localization. For triply and doubly lensed gravitational-wave events, this becomes 29.8–$14.9\,\mathrm{ per\,cent}$ and 16.4–$6.6\,\mathrm{ per\,cent}$ respectively. If successfully identified, however, the localization can be better than a fraction of the host-galaxy size, i.e. of order milli-arcseconds. A first detection in the coming decade, however, probably requires dedicated deep and high-resolution follow-ups and continued upgrades in the current and planned gravitational-wave detectors.

Solve third order Lane–Emden–Fowler equation by Adomian decomposition method and quartic trigonometric B-spline method

In this work, we study the Lane–Emden–Fowler equation which has a wide range of applications in astrophysics, classical and quantum mechanics. Firstly, we convert this nonlinear differential equation into an equivalent integral equation. We employ the powerful Adomian decomposition method to derive an analytical solution that will also lead to numerical solutions. Moreover, we exhibit two theorems to ensure the uniqueness of the solution of the problem and to confirm the convergence of the proposed scheme. In addition, we use quartic trigonometric B-spline as a powerful numerical method to achieve numerical solutions. Finally we present a comparison between the proposed methods to show their accuracy performance. Proper graphs are also provided to illustrate the obtained solutions.

Swift : a modern highly parallel gravity and smoothed particle hydrodynamics solver for astrophysical and cosmological applications

ABSTRACT Numerical simulations have become one of the key tools used by theorists in all the fields of astrophysics and cosmology. The development of modern tools that target the largest existing computing systems and exploit state-of-the-art numerical methods and algorithms is thus crucial. In this paper, we introduce the fully open-source highly-parallel, versatile, and modular coupled hydrodynamics, gravity, cosmology, and galaxy-formation code Swift. The software package exploits hybrid shared- and distributed-memory task-based parallelism, asynchronous communications, and domain-decomposition algorithms based on balancing the workload, rather than the data, to efficiently exploit modern high-performance computing cluster architectures. Gravity is solved for using a fast-multipole-method, optionally coupled to a particle mesh solver in Fourier space to handle periodic volumes. For gas evolution, multiple modern flavours of Smoothed Particle Hydrodynamics are implemented. Swift also evolves neutrinos using a state-of-the-art particle-based method. Two complementary networks of sub-grid models for galaxy formation as well as extensions to simulate planetary physics are also released as part of the code. An extensive set of output options, including snapshots, light-cones, power spectra, and a coupling to structure finders are also included. We describe the overall code architecture, summarize the consistency and accuracy tests that were performed, and demonstrate the excellent weak-scaling performance of the code using a representative cosmological hydrodynamical problem with ≈300 billion particles. The code is released to the community alongside extensive documentation for both users and developers, a large selection of example test problems, and a suite of tools to aid in the analysis of large simulations run with Swift.

Unified Framework for Diffusion Generative Models in SO(3): Applications in Computer Vision and Astrophysics

Diffusion-based generative models represent the current state-of-the-art for image generation. However, standard diffusion models are based on Euclidean geometry and do not translate directly to manifold-valued data. In this work, we develop extensions of both score-based generative models (SGMs) and Denoising Diffusion Probabilistic Models (DDPMs) to the Lie group of 3D rotations, SO(3). SO(3) is of particular interest in many disciplines such as robotics, biochemistry and astronomy/cosmology science. Contrary to more general Riemannian manifolds, SO(3) admits a tractable solution to heat diffusion, and allows us to implement efficient training of diffusion models. We apply both SO(3) DDPMs and SGMs to synthetic densities on SO(3) and demonstrate state-of-the-art results. Additionally, we demonstrate the practicality of our model on pose estimation tasks and in predicting correlated galaxy orientations for astrophysics/cosmology.

Analyzing the spatial motion of a rigid body subjected to constant body-fixed torques and gyrostatic moment

This paper aims to explore the rotatory spatial motion of an asymmetric rigid body (RB) under constant body-fixed torques and a nonzero first component gyrostatic moment vector (GM). Euler's equations of motion are used to derive a set of dimensionless equations of motion, which are then proposed for the stability analysis of equilibrium points. Specifically, this study develops 3D phase space trajectories for three distinct scenarios; two of them are applied constant torques that are directed on the minor and major axes, while the third one is the action of applied constant torque on the body’s middle axis. Novel analytical and simulation results for both scenarios of constant torque applied along the minor and middle axes are provided in the context of separatrix surfaces, equilibrium manifolds, periodic or non-periodic solutions, and periodic solutions’ extreme. Concerning the scenario of a directed torque on the major axis, a numerical solution for the problem is presented in addition to a simulation of the graphed results for the angular velocities' trajectories in various regions. Moreover, the influence of GM is examined for each case and a full modeling for the body's stability has been present. The exceptional impact of these results is evident in the development and assessment of systems involving asymmetric RBs, such as satellites and spacecraft. It may serve as a motivating factor to explore different angles within the GM in similar cases, thereby influencing various industries, including engineering and astrophysics applications.

Targeted optimization in small-scale atomic structure calculations: application to Au I

The lack of reliable atomic data can be a severe limitation in astrophysical modelling, in particular of events such as kilonovae that require information on all neutron-capture elements across a wide range of ionization stages. Notably, the presence of non-orthonormalities between electron orbitals representing configurations that are close in energy can introduce significant inaccuracies in computed energies and transition probabilities. Here, we propose an explicit targeted optimization (TO) method that can effectively circumvent this concern while retaining an orthonormal orbital basis set. We illustrate this method within the framework of small-scale atomic structure models of Au I, using the Grasp2018 multiconfigurational Dirac–Hartree–Fock atomic structure code. By comparing to conventional optimization schemes we show how a TO approach improves the energy level positioning and ordering. TO also leads to better agreement with experimental data for the strongest E1 transitions. This illustrates how small-scale models can be significantly improved with minor computational costs if orbital non-orthonormalities are considered carefully. These results should prove useful to multi-element atomic structure calculations in, for example, astrophysical opacity applications involving neutron-capture elements.

FORKLENS: Accurate weak-lensing shear measurement with deep learning

Context. Weak gravitational lensing is one of the most important probes of the nature of dark matter and dark energy. In order to extract cosmological information from next-generation weak lensing surveys (e.g., Euclid, Roman, LSST, and CSST) as much as possible, accurate measurements of weak lensing shear are required. Aims. There are existing algorithms to measure the weak lensing shear on imaging data, which have been successfully applied in previous surveys. In the meantime, machine learning (ML) has been widely recognized in various astrophysics applications in modeling and observations. In this work, we present a fully deep-learning-based approach to measuring weak lensing shear accurately. Methods. Our approach comprises two modules. The first one contains a convolutional neural network (CNN) with two branches for taking galaxy images and point spread function (PSF) simultaneously, and the output of this module includes the galaxy’s magnitude, size, and shape. The second module includes a multiple-layer neural network (NN) to calibrate weak-lensing shear measurements. We name the program FORKLENS and make it publicly available online. Results. Applying FORKLENS to CSST-like mock images, we achieve consistent accuracy with traditional approaches (such as moment-based measurement and forward model fitting) on the sources with high signal-to-noise ratios (S/N > 20). For the sources with S/N < 10, FORKLENS exhibits an ~36% higher Pearson coefficient on galaxy ellipticity measurements. Conclusions. After adopting galaxy weighting, the shear measurements with FORKLENS deliver accuracy levels to 0.2%. The whole procedure of FORKLENS is automated and costs about 0.7 milliseconds per galaxy, which is appropriate for adequately taking advantage of the sky coverage and depth of the upcoming weak lensing surveys.

Theories of Relativistic Dissipative Fluid Dynamics.

Relativistic dissipative fluid dynamics finds widespread applications in high-energy nuclear physics and astrophysics. However, formulating a causal and stable theory of relativistic dissipative fluid dynamics is far from trivial; efforts to accomplish this reach back more than 50 years. In this review, we give an overview of the field and attempt a comparative assessment of (at least most of) the theories for relativistic dissipative fluid dynamics proposed until today and used in applications.

Calculations of energy levels, transition rates, lifetimes and Landé g factors for silicon-like Kr XXIII

The multiconfiguration Dirac–Hartree–Fock (MCDHF) method is employed to calculate excitation energies, transition rates, lifetimes and Landé g factors for the lowest 700 levels belonging to the 22 configurations 3s23p{3l,4l′}, 3s3p2{3l,4l′}, 3s23d{3d,4s,4p}, 3s{3p3d2,3d3}, 3p{3p3,3p23d,3p3d2,3d3}, 3d4 with l = 1, 2 and l′ = 0, 1, 2, 3 in Kr XXIII. The present excitation energies are compared with available experimental and theoretical values. The mean relative difference between our results and the values provided by the National Institute of Standards and Technology (NIST) is only 0.05%, which suggests a good agreement. The uncertainties of the transition rates are estimated based on quantitative and qualitative evaluation method which analyzes the dependencies of the line strength S on the gauge parameter G. It is observed that 49.6% of E1 S values have uncertainties of ≤ 1% (AA) and over 82% have uncertainties of ≤ 3% (A). The present wavelengths and transition rates are compared with the experimental values and generally good agreements have been achieved. For lifetime, the present MCDHF values fall well within the range of experimental error. Comparison of the computed Landé g factors is also made with the Landé g factors in pure LS-coupling. These accurate data can be useful for fusion plasma research and astrophysical applications.

New acetylene line list near 3.8-μm - Part III - 12C13CH2 and 12C2HD

The intensities of minor acetylene isotopologues 12C13CH2 and 12C2HD have been studied from Fourier transform spectra of acetylene in natural abundance using high optical path length. This study completes the work performed in the two first paper of the series (JQSRT 2023;295:108,413 and JQSRT 2023;311:108,771) where 71 bands of 12C2H2 were studied in the ΔP = 4 spectral region (∼2400–2900 cm−1). In this work, 692 measured line intensities allowed to derive vibrational transition dipole moment squared (and sometimes Herman-Wallis coefficients) for 11 bands of 12C13CH2 and 6 bands of 12C2HD. Using line positions and broadening parameters from literature, a line list has been generated for atmospheric and astrophysical applications.

A hybrid approach to generating diatomic line lists for high resolution studies of exoplanets and other hot astronomical objects: updates to ExoMol MgO, TiO, and VO line lists

ABSTRACT The best molecular line lists for astrophysical applications today require both high accuracy of line positions for strong lines as well as high overall completeness. The former is required to enable, for example, molecular detection in high-resolution cross-correlation observations of exoplanets, while completeness is required for accurate spectroscopic and radiative properties over broad temperature and spectral ranges. The use of empirical energies generated with the marvel procedure is a standard way to improve accuracy; here we explore methods of extending the use of these levels using predicted shifts and isotopologue extrapolation, as well as augmenting the levels from other sources such as effective Hamiltonian studies. These methods are used to update ExoMol line lists for the main $^{24}$Mg$^{16}$O and $^{48}$Ti$^{16}$O isotopologues, as well as for $^{24}$Mg$^{17}$O, $^{24}$Mg$^{18}$O, $^{25}$Mg$^{16}$O, $^{26}$Mg$^{16}$O, $^{46}$Ti$^{16}$O, $^{47}$Ti$^{16}$O, $^{49}$Ti$^{16}$O, and $^{50}$Ti$^{16}$O; new marvel results for $^{51}$V$^{16}$O are also presented.

Dusty Plasma: A Comprehensive Review

Dusty plasmas, characterized by the presence of micron or submicron-sized particles (dust) within a plasma of ions, electrons, and neutral species, represent a complex and intriguing state of matter. This review article provides a comprehensive overview of dusty plasmas, covering their formation mechanisms, fundamental properties, theoretical models, experimental techniques, and diverse applications. Dusty plasmas occur naturally in environments such as space, planetary atmospheres, and industrial processes, where they are formed through various mechanisms including micrometeorite impacts, volcanic eruptions, and cometary outgassing. In laboratory settings, they are generated in controlled discharge chambers using radio frequency or direct current sources, facilitating studies on their dynamic interactions and behavior. The physical characteristics and behavior of dusty plasmas are influenced by a range of forces including electrostatic, ion drag, gravitational, thermophoretic, and magnetic forces. These interactions give rise to collective phenomena such as dust acoustic waves, ion-dust interactions, and the formation of ordered structures like Coulomb crystals. Understanding these phenomena is essential for applications in astrophysics, materials science, semiconductor manufacturing, and environmental research. Theoretical approaches, including fluid dynamics, kinetic theories, and Particle-in-Cell (PIC) simulations, provide insights into the complex dynamics of dusty plasmas. Experimental methods such as Langmuir probes, laser scattering, and high-speed imaging are employed to characterize their properties and behaviors. Applications of dusty plasmas span diverse fields, from studying planetary formation processes to enhancing semiconductor device fabrication and environmental monitoring. Despite significant advancements, challenges remain in accurately modeling plasma dynamics and controlling dust particles in industrial applications. Future research directions include advancing diagnostic techniques, refining theoretical models, and exploring novel applications in materials science and technology. The interdisciplinary nature of dusty plasma research ensures continued exploration and innovation in understanding and utilizing this unique state of matter.

Harnessing the Power of Quantum: Applications in Astrophysics and Cosmology

Harnessing the Power of Quantum: Applications in Astrophysics and Cosmology

Nuclear astrophysics studies with the Trojan Horse Method

Our understanding of how stars evolve relies on two critical factors: energy production and chemical evolution. These factors are influenced by thermonuclear reactions. However, directly measuring these reactions in a laboratory setting can be challenging due to small reaction cross sections or the need for radioactive targets that are impractical to handle. To overcome these challenges, scientists have developed indirect techniques. One such method is the Trojan Horse Method (THM), which utilizes transfer reactions to determine cross sections of reactions relevant to stellar burning processes. In this paper, we will delve into the features of the Trojan Horse Method, its application in nuclear astrophysics, and provide examples of THM measurements.

A quintic B-spline technique for a system of Lane-Emden equations arising in theoretical physical applications

<abstract> <p>In the present study, we introduce a collocation approach utilizing quintic B-spline functions as bases for solving systems of Lane Emden equations which have various applications in theoretical physics and astrophysics. The method derives a solution for the provided system by converting it into a set of algebraic equations with unknown coefficients, which can be easily solved to determine these coefficients. Examining the convergence theory of the proposed method reveals that it yields a fourth-order convergent approximation. It is confirmed that the outcomes are consistent with the theoretical investigation. Tables and graphs illustrate the proficiency and consistency of the proposed method. Findings validate that the newly employed method is more accurate and effective than other approaches found in the literature. All calculations have been performed using Mathematica software.</p> </abstract>

Scalable stellar evolution forecasting

Many astrophysical applications require efficient yet reliable forecasts of stellar evolution tracks. One example is population synthesis, which generates forward predictions of models for comparison with observations. The majority of state-of-the-art rapid population synthesis methods are based on analytic fitting formulae to stellar evolution tracks that are computationally cheap to sample statistically over a continuous parameter range. The computational costs of running detailed stellar evolution codes, such as MESA, over wide and densely sampled parameter grids are prohibitive, while stellar-age based interpolation in-between sparsely sampled grid points leads to intolerably large systematic prediction errors. In this work, we provide two solutions for automated interpolation methods that offer satisfactory trade-off points between cost-efficiency and accuracy. We construct a timescale-adapted evolutionary coordinate and use it in a two-step interpolation scheme that traces the evolution of stars from zero age main sequence all the way to the end of core helium burning while covering a mass range from 0.65 to 300 M⊙. The feedforward neural network regression model (first solution) that we train to predict stellar surface variables can make millions of predictions, sufficiently accurate over the entire parameter space, within tens of seconds on a 4-core CPU. The hierarchical nearest-neighbor interpolation algorithm (second solution) that we hard-code to the same end achieves even higher predictive accuracy, the same algorithm remains applicable to all stellar variables evolved over time, but it is two orders of magnitude slower. Our methodological framework is demonstrated to work on the MESA ISOCHRONES AND STELLAR TRACKS (Choi et al. 2016) data set, but is independent of the input stellar catalog. Finally, we discuss the prospective applications of these methods and provide guidelines for generalizing them to higher dimensional parameter spaces.

Mechanics of geodesics in information geometry and black hole thermodynamics

In this paper, we shall discuss the theory of geodesics in information geometry, and an application in astrophysics. We will study how gradient flows in information geometry describe geodesics, explore the related mechanics by introducing a constraint, and apply our theory to Gaussian model and black hole thermodynamics. Thus, we demonstrate how deformation of gradient flows leads to more general Randers–Finsler metrics, describe Hamiltonian mechanics that derive from a constraint, and prove duality via canonical transformation. We also verified our theories for a deformation of the Gaussian model, and described dynamical evolution of flat metrics for Kerr and Reissner–Nordström black holes.

Investigation of the valence-shell excitations of molecular carbon disulfide by high-energy electron scattering

Absolute generalized oscillator strengths of the valence-shell excitations of carbon disulfide have been determined by a joint investigation of a fast electron impact experiment and equation of motion coupled cluster with singles and doubles (EOM-CCSD) calculations. Based on the present experimental and theoretical results, the transition nature of the excitations are elucidated, and some controversies about the transition assignments are resolved. By extrapolating the generalized oscillator strengths to zero momentum transfer, the corresponding optical oscillator strengths were determined, which provide a cross-check to the previous experimental and theoretical results. Moreover, the integral cross sections of the valence-shell excitations from their excitation thresholds to 5000 eV have been obtained by means of the BE-scaling method. The oscillator strengths and integral cross-sections complement the fundamental data of carbon disulfide and supply important applications in astrophysics and atmospheric physics.