A new look at Thomas-Fermi theory

In this short note, we argue that Thomas-Fermi theory, the simplest of all density functional theories, although failing to explain features such as molecular binding or stability of negative ions, is surprisingly accurate in estimating sizes of atoms. We give both numerical, experimental and rigorous mathematical evidence for this claim. Motivated by this, we formulate two new mathematical conjectures on the exactness of Thomas-Fermi theory. [GRAPHICS] .