The structure of correlations of multiplicative functions at almost all
scales, with applications to the Chowla and Elliott conjectures

We study the asymptotic behaviour of higher order correlations $$
\mathbb{E}_{n \leq X/d} g_1(n+ah_1) \cdots g_k(n+ah_k)$$ as a function of the
parameters $a$ and $d$, where $g_1,\dots,g_k$ are bounded multiplicative
functions, $h_1,\dots,h_k$ are integer shifts, and $X$ is large. Our main
structural result asserts, roughly speaking, that such correlations
asymptotically vanish for almost all $X$ if $g_1 \cdots g_k$ does not (weakly)
pretend to be a twisted Dirichlet character $n \mapsto \chi(n)n^{it}$, and
behave asymptotically like a multiple of $d^{-it} \chi(a)$ otherwise. This
extends our earlier work on the structure of logarithmically averaged
correlations, in which the $d$ parameter is averaged out and one can set $t=0$.
Among other things, the result enables us to establish special cases of the
Chowla and Elliott conjectures for (unweighted) averages at almost all scales;
for instance, we establish the $k$-point Chowla conjecture $ \mathbb{E}_{n \leq
X} \lambda(n+h_1) \cdots \lambda(n+h_k)=o(1)$ for $k$ odd or equal to $2$ for
all scales $X$ outside of a set of zero logarithmic density.