Several major open problems in cosmology involve spacetime-filling media with unknown microphysics, and can only be probed through their gravitational effects. This observation motivates a systematic open-system approach, in which gravity evolves in the presence of a generic, unobservable environment.
After a brief review of the Schwinger–Keldysh path integral formalism for open systems, I...
Cosmological systems involve unknown microphysics with which gravity interacts. To circumvent the lack of a precise description of all cosmic constituents, it is necessary to adopt an open-system approach, in which interactions between the fields of interest and an unspecified environment are modelled through dissipation and stochastic noise. Within this framework, the concept of physical...
We develop a twistor-space framework to compute boundary correlators via a boundary limit of nested Penrose transforms in (A)dS$_4$. Starting from correlators of (anti-)self-dual bulk fields, the boundary limit reproduces the correlators of the dual conserved currents; we demonstrate this explicitly for two- and three-point functions. The two-point correlator is rendered finite by working in...
There are two major descriptions of massive spinning fields during inflation, coined as cosmological collider (CC) physics and cosmological condensed matter (CCM) physics. We will go through each description, how it couples to the inflaton, and compare the cosmological signatures each description can produce. If time allows, we will also go into corrections to Feynman rules of the CC...
