Conveners
Real Universe Runs Imaginary: All-Loop Renormalisation and the Phase of the de Sitter Wavefunction
- Xi Tong
Description
The late-time wavefunction provides a natural framework for understanding cosmological observables in the primordial universe. For shift-symmetric scalars in de Sitter space, the wavefunction starts out purely real at tree level. Quantum corrections complicate this simple picture: the renormalisation of UV divergences produces an anomalous imaginary part. In this talk, I will show that this phase is not arbitrary. Under the assumptions of unitarity, locality, dilation, and a Bunch–Davies vacuum, it is fixed entirely by the renormalisation-scale dependence of the wavefunction at every loop order. This result packages the effects of unitary renormalization into a compact all-loop relation that echoes the dilation property of flat-space form factors. We further show that this relation implies an infinitely family of identities connecting correlators of massless fields and their conjugate momenta. I will explain the general argument and demonstrate the resulting relations at one loop.