The Cosmological CPT Theorem

In the original CPT theorem one is restricted to flat space and is unable to make converse statements. In this talk I will show how we can reformulate the CPT theorem using a symmetry argument and generalise it to beyond flat space. This in turn allows us to make a non-perturbative statement of unitarity in de Sitter. I will show this applies to the de Sitter wavefunction studied in the cosmology literature and finally comment on the implications for our universe and quantum gravity.