The Chromatic Fourier Transform

Abstract

Abstract We develop a general theory of higher semiadditive Fourier transforms that includes both the classical discrete Fourier transform for finite abelian groups at height $n=0$ , as well as a certain duality for the $E_n$ -(co)homology of $\pi $ -finite spectra, established by Hopkins and Lurie, at heights $n\ge 1$ . We use this theory to generalize said duality in three different directions. First, we extend it from $\mathbb {Z}$ -module spectra to all (suitably finite) spectra and use it to compute the discrepancy spectrum of $E_n$ . Second, we lift it to the telescopic setting by replacing $E_n$ with $T(n)$ -local higher cyclotomic extensions, from which we deduce various results on affineness, Eilenberg–Moore formulas and Galois extensions in the telescopic setting. Third, we categorify their result into an equivalence of two symmetric monoidal $\infty $ -categories of local systems of $K(n)$ -local $E_n$ -modules [-12pc] and relate it to (semiadditive) redshift phenomena. The Great Wave off Kanagawa, Katsushika Hokusai.