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In this paper we consider a class of second order singular homogeneous differential equations called the Lane-Emden-type with time singularity in the drift coefficient. Lane-Emden equations are singular initial value problems that model…

Dynamical Systems · Mathematics 2024-05-15 Oday Hazaimah

A general class of models is proposed that is able to estimate the whole predictive distribution of a dependent variable $Y$ given a vector of explanatory variables $\xb$. The models exploit that the strength of explanatory variables to…

Methodology · Statistics 2021-03-25 Gerhard Tutz

Although current sensitivity limits are such that true Solar System analogs remain challenging to detect, numerous planetary systems have been discovered that are very different from our own Solar System. The majority of systems harbor a…

Earth and Planetary Astrophysics · Physics 2016-02-03 Niraj K. Inamdar , Hilke E. Schlichting

We obtain two equations (following from two different approaches) for the density profile in a self-gravitating polytropic cylindrically symmetric and rotating turbulent gas disk. The adopted physical picture is appropriate to describe the…

Astrophysics of Galaxies · Physics 2023-12-07 S. Donkov , I. Zh. Stefanov , T. V. Veltchev , R. S. Klessen

In order to simulate rigidly rotating polytropes we have simulated systems of $N$ point particles, with $N$ up to 1800. Two particles at a distance $r$ interact by an attractive potential $-1/r$ and a repulsive potential $1/r^2$. The…

Computational Physics · Physics 2020-07-15 Yngve Hopstad , Jan Myrheim

This article aims to propose a novel analytical model for anisotropic multi-layer elliptical structures incorporating graphene layers. The multi-layer structure is formed of various magnetic materials. An external magnetic bias has been…

We show that density models describing multiple observables with (i) hard boundaries and (ii) dependence on external parameters may be created using an auto-regressive Gaussian mixture model. The model is designed to capture how observable…

Data Analysis, Statistics and Probability · Physics 2022-02-01 Stephen B. Menary , Darren D. Price

Lane Emden differential equation of the polytropic gas sphere could be used to construct simple models of stellar structures, star clusters and many configurations in astrophysics. This differential equation suffers from the singularity at…

Solar and Stellar Astrophysics · Physics 2020-03-25 E. A. -B. Abd-Elsalam , Mohamed I. Nouh

In the mechanics of inviscid conservative fluids, it is classical to generate the equations of dynamics by formulating with adequate variables, that the pressure integral calculated in the time-space domain corresponding to the motion of…

Classical Physics · Physics 2008-07-23 Henri Gouin , Jean-François Debieve

In the present paper we study warm inflationary universe models in the context of a polytropic gas. We derive the characteristics of this model in slow-roll approximation and develop our model in two cases, 1- For a constant dissipative…

General Relativity and Quantum Cosmology · Physics 2015-06-16 M. R. Setare , M. J. S. Houndjo , V. Kamali

Galactic dynamo models have generally relied on input parameters that are very challenging to constrain. We address this problem by developing a model that uses observable quantities as input: the galaxy rotation curve, the surface…

Astrophysics of Galaxies · Physics 2024-04-04 Luke Chamandy , Rion Glenn Nazareth , Gayathri Santhosh

A polytropic process describes the transition of a fluid from one state to another through a specific relationship between the fluid density and temperature. The value of the polytropic index that governs this relationship determines the…

Exploring exoplanets has transformed our understanding of the universe by revealing many planetary systems that defy our current understanding. To study their atmospheres, spectroscopic observations are used to infer essential atmospheric…

Earth and Planetary Astrophysics · Physics 2025-12-19 Flavio Giobergia , Alkis Koudounas , Elena Baralis

Combining isotopic constraints from meteorite data with dynamical models of planet formation proves to be advantageous in identifying the best model for terrestrial planet formation. Prior studies have shown that the probability of…

Earth and Planetary Astrophysics · Physics 2020-09-02 Jingyi Mah , Ramon Brasser

Despite the increase in observational data on exoplanets, the processes that lead to the formation of planets are still not well understood. But thanks to the high number of known exoplanets, it is now possible to look at them as a…

Earth and Planetary Astrophysics · Physics 2015-06-22 C. Mordasini , P. Mollière , K. -M. Dittkrist , S. Jin , Y. Alibert

We present numerical support for the hypothesis that macroscopic observables of dense granular media can be evaluated from averages over typical blocked configurations: we construct the corresponding measure for a class of…

Statistical Mechanics · Physics 2009-10-31 Alain Barrat , Jorge Kurchan , Vittorio Loreto , Mauro Sellitto

In this paper we study anisotropic spherical polytropes within the framework of general relativity. Using the anisotropic Tolman-Oppenheimer-Volkov (TOV) equations, we explore the relativistic anisotropic Lane-Emden equations. We find how…

General Relativity and Quantum Cosmology · Physics 2016-07-20 F. Shojai , M. Kohandel , A. Stepanian

The influence on macroscopic work hardening of small, spherical, elastic particles dispersed within a matrix is studied using an isotropic strain gradient plasticity framework. An analytical solution, based on a recently developed yield…

Materials Science · Physics 2021-10-25 Philip Croné , Peter Gudmundson , Jonas Faleskog

Using a numerical approach based on the coupling of the discrete and finite element methods, we explore the variation of the bulk modulus K of soft particle assemblies undergoing isotropic compression. As the assemblies densify under…

An iterative method is presented for solving the problem of a uniformly rotating, self-gravitating ring without a central body in Newtonian gravity by expanding about the thin ring limit. Using this method, a simple formula relating mass to…

Astrophysics · Physics 2009-11-13 David Petroff , Stefan Horatschek
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