We derive exact analytical expressions for the spectral density of the Dirac operator at fixed theta-angle in the microscopic domain of one-flavor QCD. These results are obtained by performing the sum over topological sectors using novel identities i
nvolving sums of products of Bessel functions. Because the fermion determinant is not positive definite for negative quark mass, the usual Banks-Casher relation is not valid and has to be replaced by a different mechanism first observed for QCD at nonzero chemical potential. Using the exact results for the spectral density we explain how this mechanism results in a chiral condensate that remains constant when the quark mass changes sign.
