  The spinless Falicov-Kimball model is one of the simplest models of many-body
physics. While the conduction-electron density of states is temperature
independent in the normal state, the f-electron density of states is strongly
temperature dependent---it has an orthogonality catastrophe singularity in the
metallic phase and is gapped in the insulating phase. The question we address
here is whether the spectral gap is the same for both electron species as T->0.
We find strong evidence to indicate that the answer is affirmative.
