Toeplitz determinants with a one-cut regular potential and Fisher–Hartwig singularities I. Equilibrium measure supported on the unit circle

We consider Toeplitz determinants whose symbol has: (i) a one-cut regular potential V , (ii) Fisher–Hartwig singularities and (iii) a smooth function in the background. The potential V is associated with an equilibrium measure that is assumed to be supported on the whole unit circle. For constant potentials V , the equilibrium measure is the uniform measure on the unit circle and our formulas reduce to well-known results for Toeplitz determinants with Fisher–Hartwig singularities. For non-constant V , our results appear to be new even in the case of no Fisher–Hartwig singularities. As applications of our results, we derive various statistical properties of a determinantal point process which generalizes the circular unitary ensemble.