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The concept of a nice basis for a Lie algebra was introduced to study the Ricci curvature on nilpotent Lie groups equipped with a left-invariant metric. Despite the many applications in differential geometry, for example in the construction…

Differential Geometry · Mathematics 2026-03-18 Jonas Deré , Jeroen Gantois

A general procedure to find static and axially symmetric, interior solutions to the Einstein equations is presented. All the so obtained solutions, verify the energy conditions for a wide range of values of the parameters, and match…

General Relativity and Quantum Cosmology · Physics 2016-11-07 J. L. Hernandez-Pastora , L. Herrera , J. Martin

We present a classification of all scalar Lie point symmetries of the Standard Model with one or two real gauge-singlet scalars (SM+S and SM+2S). By analyzing the associated field equations, we identify all realizable and inequivalent Lie…

High Energy Physics - Phenomenology · Physics 2026-02-25 M. Aa. Solberg

The coincidence between polynomial neural networks and matrix Lie maps is discussed in the article. The matrix form of Lie transform is an approximation of the general solution of the nonlinear system of ordinary differential equations. It…

Neural and Evolutionary Computing · Computer Science 2019-08-20 Andrei Ivanov , Sergei Andrianov

Aims. Many recent observations of pulsars and magnetars can be interpreted in terms of neutron stars (NS) with multipole electromagnetic fields. As a first approximation, we investigate the multipole magnetic and electric fields in the…

High Energy Astrophysical Phenomena · Physics 2020-07-07 S. Bonazzola , F. Mottez , J. Heyvaerts

Every Lie algebra over a field $E$ gives rise to new Lie algebras over any subfield $F \subseteq E$ by restricting the scalar multiplication. This paper studies the structure of these underlying Lie algebra in relation to the structure of…

Rings and Algebras · Mathematics 2019-01-30 Jonas Deré

Lie symmetries of systems of second-order linear ordinary differential equations with constant coefficients are exhaustively described over both the complex and real fields. The exact lower and upper bounds for the dimensions of the maximal…

Classical Analysis and ODEs · Mathematics 2014-03-25 Vyacheslav M. Boyko , Roman O. Popovych , Nataliya M. Shapoval

We present Hall equilibrium solutions for neutron stars crusts containing toroidal and poloidal magnetic field. Some simple cases are solved analytically while more complicated configurations are found numerically through a Gauss-Seidel…

Solar and Stellar Astrophysics · Physics 2013-05-02 K. N. Gourgouliatos , A. Cumming , M. Lyutikov , A. Reisenegger

We extend two of the methods previously introduced to find discrete symmetries of differential equations to the case of difference and differential-difference equations. As an example of the application of the methods, we construct the…

Mathematical Physics · Physics 2016-08-16 Decio Levi , Miguel A. Rodríguez

The well known nonlinear model for describing the solid tumour growth [Byrne HM., et al. Appl Math Letters 2003;16:567-74] is under study using an approach based on Lie symmetries. It is shown that the model in the two-dimensional (in…

Mathematical Physics · Physics 2021-01-01 Roman Cherniha , Vasyl' Davydovych

Relativistic strongly magnetized plasmas are produced in laboratories thanks to state-of-the-art laser technology but can naturally be found around compact objects such as neutron stars and black holes. Detailed studies of the behaviour of…

Plasma Physics · Physics 2017-05-24 J. Pétri

Static, cylindrically symmetric solutions to nonlinear scalar-Einstein equations are considered. Regularity conditions on the symmetry axis and flat or string asymptotic conditions are formulated in order to select soliton-like solutions.…

General Relativity and Quantum Cosmology · Physics 2011-08-11 K. A. Bronnikov , G. N. Shikin

Magnetic fields inside and around neutron stars are at the heart of pulsar magnetospheric activity. Strong magnetic fields are responsible for quantum effects, an essential ingredient to produce leptonic pairs and the subsequent broadband…

High Energy Astrophysical Phenomena · Physics 2017-11-08 Jérôme Pétri

The polarizability measures how the system responds to an applied electrical field. Computationally, there are many different ways to evaluate this tensorial quantity, some of which rely on the explicit use of the external perturbation and…

Materials Science · Physics 2007-10-16 Micael J. T. Oliveira , Alberto Castro , Miguel A. L. Marques , Angel Rubio

We perform first-principles relativistic particle-in-cell simulations of aligned pulsar magnetosphere. We allow free escape of particles from the surface of a neutron star and continuously populate the magnetosphere with neutral pair plasma…

High Energy Astrophysical Phenomena · Physics 2015-10-08 Alexander Philippov , Anatoly Spitkovsky

We generalize several important results from the perturbation theory of linear operators to the setting of semisimple orthogonal symmetric Lie algebras. These Lie algebras provide a unifying framework for various notions of matrix…

Representation Theory · Mathematics 2023-07-04 Emanuel Malvetti , Gunther Dirr , Frederik vom Ende , Thomas Schulte-Herbrüggen

Equilibria of binary neutron stars in close circular orbits are computed numerically in a waveless formulation: The full Einstein-relativistic-Euler system is solved on an initial hypersurface to obtain an asymptotically flat form of the…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Koji Uryu , Francois Limousin , John L. Friedman , Eric Gourgoulhon , Masaru Shibata

A variational approach is used to develop a robust numerical procedure for solving the nonlinear Poisson-Boltzmann equation. Following Maggs et al., we construct an appropriate constrained free energy functional, such that its…

Soft Condensed Matter · Physics 2020-04-29 M. Baptista , R. Schmitz , B. Duenweg

Finding eigenvalue distributions for a number of sparse random matrix ensembles can be reduced to solving nonlinear integral equations of the Hammerstein type. While a systematic mathematical theory of such equations exists, it has not been…

Disordered Systems and Neural Networks · Physics 2025-01-24 Pawat Akara-pipattana , Oleg Evnin

Following our paper [J. Math. Phys. 50 (2009) 123102], we systematically carry out Lie symmetry analysis for the barotropic vorticity equation on the rotating sphere. All finite-dimensional subalgebras of the corresponding maximal Lie…

Mathematical Physics · Physics 2015-06-03 Alexander Bihlo , Roman O. Popovych