Nuclear astrophysical plasmas: ion distribution functions and fusion rates

This article illustrates how very small deviations from the Maxwellian exponential tail, while leaving unchanged bulk quantities, can yield dramatic effects on fusion reaction rates and discuss several mechanisms that can cause such deviations.Comment: 9 ReVTex pages including 2 color figure

Dielectronic Recombination Rates In Astrophysical Plasmas

In this work we introduce a new expression of the plasma Dielecronic Recombination (DR) rate as a function of the temperature, derived assuming a small deformation of the Maxwell-Boltzmann distribution and containing corrective factors, in addition to the usual exponential behaviour, caused by non-linear effects in slightly non ideal plasmas. We then compare the calculated DR rates with the experimental DR fits in the low temperature region.Comment: 6 pages, 1 figure, proceedings to the "International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX", 25-30 June 2006, CERN - Genev

Fusion reactions in plasmas as probe of the high-momentum tail of particle distributions

In fusion reactions, the Coulomb barrier selects particles from the high-momentum part of the distribution. Therefore, small variations of the high-momentum tail of the velocity distribution can produce strong effects on fusion rates. In plasmas several potential mechanisms exist that can produce deviations from the standard Maxwell-Boltzmann distribution. Quantum broadening of the energy-momentum dispersion relation of the plasma quasi-particles modifies the high-momentum tail and could explain the fusion-rate enhancement observed in low-energy nuclear reaction experiments.Comment: 9 pages in ReVTeX preprint format, 3 figures, to appear in EPJ

Energy from Negentropy of Non-Cahotic Systems

: Negative contribution of entropy (negentropy) of a non-cahotic system, representing the potential of work, is a source of energy that can be transferred to an internal or inserted subsystem. In this case, the system loses order and its entropy increases. The subsystem increases its energy and can perform processes that otherwise would not happen, like, for instance, the nuclear fusion of inserted deuterons in liquid metal matrix, among many others. The role of positive and negative contributions of free energy and entropy are explored with their constraints. The energy available to an inserted subsystem during a transition from a non-equilibrium to the equilibrium chaotic state, when particle interaction (element of the system) is switched off, is evaluated. A few examples are given concerning some non-ideal systems and a possible application to the nuclear reaction screening problem is mentioned

Negentropy in Many-Body Quantum Systems

Negentropy (negative entropy) is the negative contribution to the total entropy of correlated many-body environments. Negentropy can play a role in transferring its related stored mobilizable energy to colliding nuclei that participate in spontaneous or induced nuclear fusions in solid or liquid metals or in stellar plasmas. This energy transfer mechanism can explain the observed increase of nuclear fusion rates relative to the standard Salpeter screening. The importance of negentropy in these specific many-body quantum systems and its relation to many-body correlation entropy are discussed

Reply to Jay Lawrence. Comments on Piero Quarati et al. Negentropy in Many-Body Quantum Systems. Entropy 2016, 18, 63

The Comments are explicitly related to contents of two published papers: actual [1] and [2].[...

Generalised thermostatistics using hyperensembles

The hyperensembles, introduced by Crooks in a context of non-equilibrium statistical physics, are considered here as a tool for systems in equilibrium. Simple examples like the ideal gas, the mean-field model, and the Ising interaction on small square lattices, are worked out to illustrate the concepts.Comment: Submitted to the Proceedings of CTNEXT07, 6 page

Correlations in superstatistical systems

We review some of the properties of higher-dimensional superstatistical stochastic models. As an example, we analyse the stochastic properties of a superstatistical model of 3-dimensional Lagrangian turbulence, and compare with experimental data. Excellent agreement is obtained for various measured quantities, such as acceleration probability densities, Lagrangian scaling exponents, correlations between acceleration components, and time decay of correlations. We comment on how to proceed from superstatistics to a thermodynamic description.Comment: 8 pages, 4 figures. To appear in the proceedings of CTNEXT07 'Complexity, Metastability and Nonextensivity', Catania 1-5 July 2007, eds. S. Abe, H.J. Herrmann, P. Quarati, A. Rapisarda, C. Tsallis, AIP 200

General properties of nonlinear mean field Fokker-Planck equations

Recently, several authors have tried to extend the usual concepts of thermodynamics and kinetic theory in order to deal with distributions that can be non-Boltzmannian. For dissipative systems described by the canonical ensemble, this leads to the notion of nonlinear Fokker-Planck equation (T.D. Frank, Non Linear Fokker-Planck Equations, Springer, Berlin, 2005). In this paper, we review general properties of nonlinear mean field Fokker-Planck equations, consider the passage from the generalized Kramers to the generalized Smoluchowski equation in the strong friction limit, and provide explicit examples for Boltzmann, Tsallis and Fermi-Dirac entropies.Comment: Paper presented at the international conference CTNEXT07, 1-5 july 2007, Catania, Ital

Combinatorial Entropy for Distinguishable Entities in Indistinguishable States

The combinatorial basis of entropy by Boltzmann can be written $H= {N}^{-1} \ln \mathbb{W}$, where $H$ is the dimensionless entropy of a system, per unit entity, $N$ is the number of entities and $\mathbb{W}$ is the number of ways in which a given realization of the system can occur, known as its statistical weight. Maximizing the entropy (``MaxEnt'') of a system, subject to its constraints, is then equivalent to choosing its most probable (``MaxProb'') realization. For a system of distinguishable entities and states, $\mathbb{W}$ is given by the multinomial weight, and $H$ asymptotically approaches the Shannon entropy. In general, however, $\mathbb{W}$ need not be multinomial, leading to different entropy measures. This work examines the allocation of distinguishable entities to non-degenerate or equally degenerate, indistinguishable states. The non-degenerate form converges to the Shannon entropy in some circumstances, whilst the degenerate case gives a new entropy measure, a function of a multinomial coefficient, coding parameters, and Stirling numbers of the second kind.Comment: Manuscript for CTNEXT07, Catania, draf