Generalized spin-boson models with non-normalizable form factors

Generalized spin-boson (GSB) models describe the interaction between a quantum mechanical system and structured boson environment, mediated by family of coupling functions known as form factors. We propose an extension class GSB which can accommodate non-normalizable factors, provided that they satisfy weaker growth constraint, thus accounting for rigorous description wider range physical scenarios; we also show such "singular" be rigorously approximated with normalizable Furthermore, discuss in greater detail structure model rotating wave approximation (RWA): this model, result is improved via nonperturbative approach enables us to further extend admissible well compute its resolvent characterize self-adjointness domain.