Beyond Lorentz's Lamp-post: Amplitude Techniques for Cosmology
26. March 2021 - 11:30
Scott Melville (University of Cambridge)
Abstract: In recent years, a number of powerful techniques have been developed for scattering amplitudes, exploiting fundamental principles like unitarity and causality to place constraints on our effective field theories. However, most of this progress has been confined to Lorentz-invariant systems, and so cannot be applied to cosmology (in which the expanding spacetime background spontaneously breaks Lorentz symmetry). In this talk, I will describe how we can import these amplitude techniques to systems without Lorentz symmetry, and in particular how they impact the Effective Field of Theory of inflation, identifying a region of parameter space in which unitarity/causality guarantees new physics beyond single-field, weakly coupled inflation.