EDP Sciences
Free access
Volume 418, Number 3, May II 2004
Page(s) 801 - 811
Section Astrophysical processes
DOI http://dx.doi.org/10.1051/0004-6361:20034516

A&A 418, 801-811 (2004)
DOI: 10.1051/0004-6361:20034516

Numerical experiments in screening theory

G. Shaviv1, 2

1  Institut f $\ddot {\rm u}$r Theoretische Astrophysik Tiergartenstrasse 15, 69121 Heidelberg, Germany
2  On leave from Department of Physics and Asher Space Research Institute, Israel Institute of Technology Haifa, 32000, Israel

(Received 15 October 2003 / Accepted 1 February 2004)

In an attempt to clarify the behavior of the screening phenomenon in N-body systems at thermodynamics equilibrium, under the particular conditions at the core of the Sun, we define the screening energy and summarize the two main types of methods to calculate it: (a) by using classical mean field in Statistical Mechanics and (b) ab initio, by using molecular dynamics and first principles only. We invent a pair interaction with a finite parametrized range and strength, and carry out a numerical experiment which demonstrates the difference between the two aforementioned methods and underlying assumptions as a function of the range of the interaction (or equivalently the number of particles in the interaction zone). We study the effect that fluctuations in the number of particles in the screening/neutralizing cloud have on the screening, and the deviations from mean field results which ensue. We also demonstrate that the classical mean field theory is inaccurate under the conditions prevailing in stellar cores and essentially over estimates the screening. We show how the molecular dynamics results tend to the mean field Statistical Mechanics limits when the number of particles in the neutralizing domain increases.

Key words: methods: N-body simulations -- nuclear reactions, nucleosynthesis, abundances -- plasmas -- Sun: interior

© ESO 2004