From Locality and Unitarity to Cosmological Correlators

Understand

In the standard approach to deriving inflationary predictions, we evolve a vacuum state in time according to the rules of a given model.

• Since the only observables are the future values of correlators and not their time evolution, this brings about a large degeneracy: a vast number of different models are mapped to the same minute number of observables.
• Furthermore, due to the lack of time-translation invariance, even tree-level calculations require an increasing number of nested integrals that quickly become intractable.
• Here we ask how much of the final observables can be "bootstrapped" directly from locality, unitarity and symmetries.