Tetravalent half-arc-transitive graphs of order
We classify tetravalent -half-arc-transitive graphs of order , where and , are distinct odd primes. This result involves a subclass of tetravalent half-arc-transitive graphs of cube-free order.
We classify tetravalent -half-arc-transitive graphs of order , where and , are distinct odd primes. This result involves a subclass of tetravalent half-arc-transitive graphs of cube-free order.
A singularity is said to be weakly-exceptional if it has a unique purely log terminal blow-up. In dimension 2, V. Shokurov proved that weakly-exceptional quotient singularities are exactly those of types D n, E 6, E 7, E 8. This paper classifies the weakly-exceptional quotient singularities in dimensions 3 and 4.