Correlations of the Riemann zeta function

Assuming the Riemann hypothesis, we investigate the shifted moments of the zeta function $$M_{\alpha,{\beta}}(T) = \int_T^{2T} \prod_{k = 1}^m |\zeta(\tfrac{1}{2} + i (t + \alpha_k))|^{2 \beta_k} dt$$ introduced by Chandee, where ${\alpha} = {\alpha}(T) = (\alpha_1, \ldots, \alpha_m)$ and ${\beta} = (\beta_1 \ldots , \beta_m)$ satisfy $|\alpha_k| \leq T/2$ and $\beta_k\geq 0$. We shall prove that $$M_{{\alpha},{\beta}}(T) \ll_{{\beta}} T (\log T)^{\beta_1^2 + \cdots + \beta_m^2} \prod_{1\leq j < k \leq m} |\zeta(1 + i(\alpha_j - \alpha_k) + 1/ \log T )|^{2\beta_j \beta_k}.$$ This improves upon the previous best known bounds due to Chandee and Ng, Shen, and Wong, particularly when the differences $|\alpha_j - \alpha_k|$ are unbounded as $T \rightarrow \infty$. The key insight is to combine work of Heap, Radziwi{\l}{\l}, and Soundararajan and work of the author with the work of Harper on the moments of the zeta function.