Each dot represents an electron experiencing pairwise Coulomb repulsion with every other electron while being confined by an external potential $Q$. The energy of a configuration $z_1, \dots, z_n$ is described by the 2D log-gas Hamiltonian
$$H(z_1,\ldots,z_n) = -\sum_{i \neq j} \log\lvert z_i - z_j \rvert + n\sum_{j=1}^n Q(z_j).$$
The minimum-energy state is a Fekete configuration. For more on the background and context of these systems see my bachelor thesis below.
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