Hybrid estimation of single exponential sums, exceptional characters and primes in short intervals

We provide a new hybrid estimation of single exponential sums, combining Van der Corput, Huxley and Bourgain’s result. We also focus on primes in short intervals $(x-x^{\alpha },x]$ under the assumption of the existence of exceptional Dirichlet characters and get a small improvement of a 2004 result of Friedlander and Iwaniec. By using our new estimation of exponential sums, we extend the previous admissible range $0.4937⩽\alpha ⩽1$ to $0.4923⩽\alpha ⩽1$.