11/08/2023
By Brenden Bowen
The Kennedy College of Sciences, Department of Physics and Applied Physics, invites you to attend a Master's thesis defense by Brenden Bowen on "Open system dynamics in interacting quantum field theories."
Candidate Name: Brenden Bowen
Defense Date: Wednesday, Nov. 22, 2023
Time: 3 p.m.
Location: TBD
Thesis Title: Open system dynamics in interacting quantum field theories
Advisor:
Nishant Agarwal, Physics and Applied Physics, UMass Lowell
Committee:
- Archana Kamal, Physics and Applied Physics, UMass Lowell
- Hugo Ribeiro, Physics and Applied Physics, UMass Lowell
Abstract:
A quantum system that interacts with an environment generally undergoes non-unitary evolution described by a non-Markovian or Markovian master equation. In this paper, we construct the non-Markovian Redfield master equation for a quantum scalar field that interacts with a second field through a bilinear or nonlinear interaction on a Minkowski background. We use the resulting master equation to set up coupled differential equations that can be solved to obtain the equal-time two-point function of the system field. We show how the equations simplify under various approximations including the Markovian limit, and argue that the Redfield equation-based solution provides a perturbative resummation to the standard second order Dyson series result. For the bilinear interaction, we explicitly show that the Redfield solution is closer to the exact solution than the perturbation theory-based one. Further, the environment correlation function is oscillatory and non-decaying in this case, making the Markovian master equation a poor approximation. For the nonlinear interaction, on the other hand, the environment correlation function is sharply peaked and the Redfield solution matches that obtained using a Markovian master equation in the late-time limit.