  Caron-Huot has recently given an interesting formula that determines OPE data
in a conformal field theory in terms of a weighted integral of the four-point
function over a Lorentzian region of cross-ratio space. We give a new
derivation of this formula based on Wick rotation in spacetime rather than
cross-ratio space. The derivation is simple in two dimensions but more involved
in higher dimensions. We also derive a Lorentzian inversion formula in one
dimension that sheds light on previous observations about the chaos regime in
the SYK model.
