Spectral Representation of Cosmological Correlators

by Denis Werth (Paris Institute of Astrophysics)

Tuesday 22 Oct 2024, 16:30 → 17:30 Europe/Berlin

A.2.25/27 - Atlas (New)

Cosmological correlators are significantly more complex than
their flat-space analogues, such as tree-level scattering amplitudes.
While these amplitudes have rather simple analytic structure and clear
factorisation properties, cosmological correlators often feature branch
cuts and lack neat expressions.

In this talk, after a pedagogical introduction to observational,
phenomenological and theoretical aspects of cosmological correlators
meant for the broad audience, I will present a new off-shell
perturbative method to study and compute cosmological correlators. Using
a spectral representation of massive cosmological propagators that
encodes spontaneous particle production through a suitable prescription,
I will show in detail how such approach not only makes the origin of the
correlator singularity structure and factorisation manifest, but also
renders practical analytical computations more tractable. This approach
explicitly shows that complex correlators are constructed by gluing
lower-point off-shell correlators, and suggests that dispersive methods
hold promise for developing cosmological recursion relations, further
connecting techniques from modern scattering amplitudes to cosmology.

This talk will be mainly based on arXiv:2409.02072.