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A new asymptotic perturbation theory and applications to massless quantum field theories

Hold Date 2013-01-17 16:00~2013-01-17 17:30

Place Seminar Room 7, Faculty of Mathematics building, Ito Campus

Object person  

Speaker ARAI, Asao (Hokkaido University)

The standard analytic or asymptotic perturbation theory considers only perturbations of isolated eigenvalues. In this lecture, we present a new asymptotic perturbation theory which may be valid also for the case where the unperturbed operator has a non-isolated eigenvalue (important examples in which the unperturbed operator has non-isolated eigenvalues appear, e.g., in massless quantum field theories). As an application, we consider a quantum  field model, called the generalized spin-boson model (including the massless case), and, for its ground state energy,  we derive an asymptotic expansion in the coupling constant up to an arbitrary finite order.