Nonextensive statistical mechanics: Some links with astronomical phenomena

Jan, 2003
23 pages
Published in:
  • Astrophys.Space Sci. 290 (2004) 259-274
e-Print:

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Abstract: (arXiv)
A variety of astronomical phenomena appear to not satisfy the ergodic hypothesis in the relevant stationary state, if any. As such, there is no reason for expecting the applicability of Boltzmann-Gibbs (BG) statistical mechanics. Some of these phenomena appear to follow, instead, nonextensive statistical mechanics. In the same manner that the BG formalism is based on the entropy SBG=kipilnpiS_{BG}=-k \sum_i p_i \ln p_i, the nonextensive one is based on the form Sq=k(1ipiq)/(q1)S_q=k(1-\sum_ip_i^q)/(q-1) (with S1=SBGS_1=S_{BG}). The stationary states of the former are characterized by an {\it exponential} dependence on the energy, whereas those of the latter are characterized by an (asymptotic) {\it power-law}. A brief review of this theory is given here, as well as of some of its applications, such as the solar neutrino problem, polytropic self-gravitating systems, galactic peculiar velocities, cosmic rays and some cosmological aspects. In addition to these, an analogy with the Keplerian elliptic orbits {\it versus} the Ptolemaic epicycles is developed, where we show that optimizing SqS_q with a few constraints is equivalent to optimizing SBGS_{BG} with an infinite number of constraints.