Title: Quantum origins of the universe: Cosmological open quantum systems

Speaker: Dr. Suddhasattwa Brahma, University of Edinburgh, UK

Abstract: A profound prediction of the standard model of cosmology is that primordial quantum fluctuations are responsible for large-scale structure formation in the universe. However, our knowledge of the early universe is incomplete, and we must treat inflation as an open quantum system and derive, in a systematic manner, quantum corrections to cosmological observables due to interactions with unobservable environments. For instance, the "cosmological horizon" is an example of a spacetime boundary that restricts our observable degrees of freedom while still allowing energy and information to flow across it into hidden sectors. Borrowing techniques from Quantum Optics, Condensed Matter and Quantum Information, I will show how an Open Effective Field Theory formalism can incorporate non-unitary effects in cosmology and describe dissipation and decoherence of primordial fluctuations. I will also highlight new insights this approach provides regarding quantum entanglement in the early universe, and emphasize how the out-of-equilibrium nature of gravitational systems necessarily result in non-Markovian dynamics.