Cosmological Observables via Non-equilibrium Quantum Dynamics in Non-stationary Spacetimes
In nearly all cases cosmological observables associated with quantum matter fields are computed in a general approximation, via the standard irreducible representations found in the operator formalism of particle physics, where intricacies related to a renormalized stress-energy tensor in a non-stationary spacetime are ignored. Models of the early universe also include a hot, dense environment of quantum fields where far-from-equilibrium interactions manifest expressions for observables with leading terms at higher orders in the coupling. A more rigorous treatment of these cosmological observables may be carried out within the alternative framework of algebraic quantum field theory in curved spacetime, where the field theoretic model of quantum matter is compatible with the classical effects of general relativity. We take the first step towards computing such an observable. We employ the algebraic formalism while considering far-from-equilibrium interactions in a hot, dense environment under the influence of a classical, yet non-stationary, spacetime to derive an expression for the time-dependent energy density as a component of the renormalized stress-energy tensor.