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Phys. Rev. E 74, 021110 (2006) [21 pages]

Force distribution in a randomly perturbed lattice of identical particles with 1/r2 pair interaction

Andrea Gabrielli
Istituto dei Sistemi Complessi–CNR, Via dei Taurini 19, 00185 Rome, Italy and SMC-INFM, Physics Department, University "La Sapienza" of Rome, 00185 Rome, Italy

Thierry Baertschiger
Dipartimento di Fisica, Università "La Sapienza," 00185 Rome, Italy and Istituto dei Sistemi Complessi–CNR, Via dei Taurini 19, 00185 Rome, Italy

Michael Joyce
Laboratoire de Phyisique Nucléaire et Hautes Energies, Université Pierre et Marie Curie–Paris 6, UMR 7585, F-75005 Paris, France

Bruno Marcos
Dipartimento di Fisica, Università "La Sapienza," 00185 Rome, Italy, and Istituto dei Sistemi Complessi–CNR, Via dei Taurini 19, 00185 Rome, Italy

Francesco Sylos Labini
E. Fermi Center, Via Panisperna 89 A, Compendio del Viminale, 00184 Rome, Italy and Istituto dei Sistemi Complessi–CNR, Via dei Taurini 19, 00185 Rome, Italy
Received 6 March 2006; revised 22 June 2006; published 9 August 2006

We study the statistics of the force felt by a particle in the class of a spatially correlated distribution of identical pointlike particles, interacting via a 1/r2 pair force (i.e., gravitational or Coulomb), and obtained by randomly perturbing an infinite perfect lattice. We specify the conditions under which the force on a particle is a well-defined stochastic quantity. We then study the small displacements approximation, giving both the limitations of its validity and, when it is valid, an expression for the force variance. The method introduced by Chandrasekhar to find the force probability density function for the homogeneous Poisson particle distribution is extended to shuffled lattices of particles. In this way, we can derive an approximate expression for the probability distribution of the force over the full range of perturbations of the lattice, i.e., from very small (compared to the lattice spacing) to very large where the Poisson limit is recovered. We show in particular the qualitative change in the large-force tail of the force distribution between these two limits. Excellent accuracy of our analytic results is found on detailed comparison with results from numerical simulations. These results provide basic statistical information about the fluctuations of the interactions (i) of the masses in self-gravitating systems like those encountered in the context of cosmological N-body simulations, and (ii) of the charges in the ordered phase of the one-component plasma, the so-called Coulomb or Wigner crystal.

©2006 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevE.74.021110
DOI: 10.1103/PhysRevE.74.021110
PACS: 02.50.-r; 05.40.-a; 61.43.-j
  • 02.50.-r
    Probability theory, stochastic processes, and statistics
  • 05.40.-a
    Fluctuation phenomena, random processes, noise, and Brownian motion
  • 61.43.-j
    Structure of disordered solids
  • YEAR: 2006
KEYWORDS: lattice theory, gravitation, electromagnetism, Poisson distribution

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