Bound on the excess charge for bosonic systems interacting through Coulomb potentials
Rafael D. Benguria, Juan Manuel González-Brantes
TL;DR
The paper proves an improved upper bound on the excess charge $N-Z$ for non-relativistic bosonic atoms with Coulomb interactions, showing $N < 1.4811 Z + 3.1516 Z^{1/3}$ for $Z \ge 12$, refining Lieb's 1984 bound in the bosonic case. The authors adapt Nam's strategy within the Hartree framework, leveraging Virial Theorem relations for the one-particle functional, the Coulomb Uncertainty Principle, and density-based inequalities (Lieb–Oxford, Hoffmann-Ostenhof, GNS) to connect many-body energy to single-particle quantities. The proof proceeds by deriving a lower bound on the $N$-particle energy, bounding the Coulomb and kinetic terms via density functionals, and employing eigenvalue estimates to control the particle number relative to $Z$, culminating in a precise $N/Z$ bound and a computable error term. The result tightens the ionization bound for bosonic atoms and provides a robust, computable threshold applicable to Coulomb-interacting many-body systems.
Abstract
We prove an upper bound on the excess charge for non-relativistic atomic systems, independent of the particle statistics. This result improves Lieb's bound of 1984 for any $Z \ge 12$.
