Crossover in densities of confined particles with finite range of interaction

Abstract

We study a one-dimensional classical system of $N$ particles confined within a harmonic trap. Interactions among these particles are dictated by a pairwise potential $V(x)$, where $x$ is the separation between two particles. Each particle can interact with a maximum of $d$ neighbouring particles on either side (left or right), if available. By adjusting the parameter $d$, the system can be made nearest neighbour $(d=1)$ to all-to-all $(d=N-1)$ interacting. As suggested by prior studies, the equilibrium density profile of these particles is expected to undergo shape variations as $d$ is changed. In this paper, we investigate this crossover by tuning the parameter $f(=d/N)$ from $1$ to $0$ in the large $N$ limit for two distinct choices of interaction potentials, $V(x) = - |x|$ and $V(x) =- \log(|x|)$ which correspond to 1d one-component plasma and the log-gas model, respectively. For both models, the system size scaling of the density profile for fixed $f$ turns out to be the same as in their respective all-to-all case. However, the scaling function exhibits diverse shapes as $f$ varies. We explicitly compute the average density profile for any $f \in (0,1]$ in the 1d plasma model, while for the log-gas model, we provide approximate calculations for large (close to $1$) and small (close to $0$) $f$. Additionally, we present simulation results to numerically demonstrate the crossover and compare these findings with our theoretical results.