Refinements for primes in short arithmetic progressions

Given a zero-free region and an averaged zero-density estimate over all Dirichlet $L$-functions modulo $q\in \mathbb{N}$, we refine the error terms of the prime number theorem in all and almost all short arithmetic progressions. For example, if we assume the Generalized Density Hypothesis, then for any arithmetic progression modulo $q\le {\log }^{\mathrm{\ell }}x$ with $\mathrm{\ell }>0$ and any $\epsilon >0$, the prime number theorem holds in all intervals $(x-\sqrt{x}\exp ({\log }^{\frac{2}{3}+\epsilon }x),x]$ and almost all intervals $(x-\exp ({\log }^{\frac{2}{3}+\epsilon }x),x]$ as $x\to \mathrm{\infty }$. This refines the classic intervals $(x-x^{1\mathrm{/}2+\epsilon },x]$ and $(x-x^{\epsilon },x]$ for any $\epsilon >0$.