Key points are not available for this paper at this time.
representation for the canonical variables used in conventional theory, but its utilization of "state" as defined by its expectation value form, rather than as a vector in a Hilbert space, means that, a priori, the energy of a state is a somewhat vague mathematical object. The problem is thus that of dealing, in a fashion which is effective from a quite broad point of view, with the vacuum for free fields, the ultimate aim being to arrive at a simple characteri- zation which may be adapted with a reasonable degree of confidence to the case of interacting fields.
I. E. Segal (Sat,) studied this question.