Weyl Anomalies and Cosmology (Quantum Spacetime Seminar series)

I'll  discuss effects of Weyl anomalies arising from renormalization of  composite operators in a cosmological context. I’ll first describe a  two-dimensional model of gravity in which the nonlocal  contributions to the quantum effective action arising from such Weyl anomalies  slow down exponential de Sitter expansion to quasi de Sitter power law expansion and  lead to  a slow dilution of vacuum energy.  I’ll describe methods to systematically compute similar nonlocal effects for general actions in four dimensions for cosmological spacetimes using local renormalization group and compare them with the Barvinsky-Vilkovisky expansion. I’ll conclude by discussing possible implications for primordial magnetogenesis and quantum stability of (anti) de Sitter spacetimes.