A simple 2nd order lower bound to the energy of dilute Bose gases

Abstract

For a dilute system of non-relativistic bosons interacting through a positive, radial potential $v$ with scattering length $a$ we prove that the ground state energy density satisfies the bound $e(\rho )\ge 4\pi a{\rho }^2(1-C\sqrt{\rho a^3})$.

27 pages. Enlarged class of allowed potentials. In particular the "hard core" is now covered