Thomson problem

The objective of the Thomson problem is to determine the minimum electrostatic potential energy configuration of N electrons constrained to the surface of a unit sphere that repel each other with a force given by Coulomb's law. The physicist J. J. Thomson posed the problem in 1904 after proposing an atomic model, later called the plum pudding model, based on his knowledge of the existence of negatively charged electrons within neutrally-charged atoms.

Related problems include the study of the geometry of the minimum energy configuration and the study of the large N behavior of the minimum energy.

The physical system embodied by the Thomson problem is a special case of one of eighteen unsolved mathematics problems proposed by the mathematician Steve Smale — "Distribution of points on the 2-sphere". The solution of each N-electron problem is obtained when the N-electron configuration constrained to the surface of a sphere of unit radius, ${\displaystyle r=1}$, yields a global electrostatic potential energy minimum, ${\displaystyle U(N)}$.

The electrostatic interaction energy occurring between each pair of electrons of equal charges (${\displaystyle e_{i}=e_{j}=e}$, with ${\displaystyle e}$ the elementary charge of an electron) is given by Coulomb's Law,

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