Cavity Quantum Electrodynamics Ring Coupled Cluster and the Random Phase Approximation

It is well known that the ground-state correlation energy from the particle-hole channel of the random phase approximation (RPA) is formally equivalent to that from a simplified coupled cluster doubles (CCD) model that includes only ring diagram contraction contributions in the residual equations [{\em J. Chem. Phys.} {\bf 129}, 231101 (2008)]. We generalize this analytic result to the cavity quantum electrodynamics (QED) case and demonstrate the numerical equivalence of QED-RPA and a QED ring-CCD model that accounts for double electron excitations, coupled single electron excitations / single photon creation, and double photon creation.

Source: arXiv:2602.09968v1 - http://arxiv.org/abs/2602.09968v1 PDF: https://arxiv.org/pdf/2602.09968v1 Original Link: http://arxiv.org/abs/2602.09968v1