Harmonically confined particles with long-range repulsive interactions

Abstract

We study an interacting system of $N$ classical particles on a line at thermal equilibrium. The particles are confined by a harmonic trap and repelling each other via pairwise interaction potential that behaves as a power law $\propto {\sum }_{\begin{array}{c}i\ne j\end{array}}^N|x_i-x_j{|}^{-k}$ (with $k>-2$) of their mutual distance. This is a generalization of the well known cases of the one component plasma ($k=-1$), Dyson's log-gas ($k\to 0^{+}$), and the Calogero-Moser model ($k=2$). Due to the competition between harmonic confinement and pairwise repulsion, the particles spread over a finite region of space for all $k>-2$. We compute exactly the average density profile for large $N$ for all $k>-2$ and show that while it is independent of temperature for sufficiently low temperature, it has a rich and nontrivial dependence on $k$ with distinct behavior for $-2<k<1$, $k>1$ and $k=1$.

Main text: 6 pages + 1 Fig., Supp. Mat.: 11 pages + 3 Figs. Accepted for publication in Physical Review Letters