@DrTonyPadilla @DD_Baumann @REasther So we were working on cosmological correlations, basing it on his seminal paper, where he wrote down a general theorem to calculate in-in correlations using the Baker Campbell Hausdorff formula (Eqn 2 of a 40 page paper!). But we kept getting inconsistent results… @DrTonyPadilla @DD_Baumann @REasther Obviously since it is a Weinberg theorem it must be correct so we thought we were wrong. And so we spent months trying to find out own mistake. But it turns out that there was actually a subtle problem with using the BCH formula for in-in due to vacuum choices…