Improving and Maximal Inequalities for Primes in Progressions

Abstract: Assume that $ y < N$ are integers, and that $ (b,y) =1$. Define an average along the primes in a progression of diameter $ y$, given by integer $ (b,y)=1 $. \begin{align*} A_{N,y,b} := \frac{\phi (y)}{N} \sum {\substack{n <N\\n\equiv b\pmod{y}}} \Lambda (n) f(x-n) \end{align*} Above, $\Lambda $ is the von Mangoldt function and $\phi $ is the totient function. We establish improving and maximal inequalities for these averages. These bounds are uniform in the choice of progression. For instance, for $ 1< r < \infty $ there is an integer $N _{y, r}$ so that \begin{align*} \lVert \sup _{N>N _{y,r}} \lvert A{N,y,b} f \rvert \rVert_{r}\ll \lVert f\rVert_{r}. \end{align*} The implied constant is only a function of $ r$. The uniformity over progressions imposes several novel elements on the proof.