Continuity of symplectically adjoint maps and the algebraic structure of Hadamard vacuum representations for quantum fields on curved spacetime

TL;DR

This paper establishes a connection between symplectic adjoint operators and the topology of one-particle spaces in quantum field theory on curved spacetime, leading to new insights into the structure of local observable algebras in Hadamard states.

Contribution

It introduces a novel method to relate symplectic adjoint operators to scalar product families, impacting the understanding of quantum field representations on curved spacetime.

Findings

The topology of the one-particle space matches that induced by two-point functions of Hadamard states.

Results imply local definiteness, primarity, and Haag-duality of local algebras in these states.

Provides new structural insights into the algebraic quantum field theory on curved spacetime.

Abstract

We derive for a pair of operators on a symplectic space which are adjoints of each other with respect to the symplectic form (that is, they are sympletically adjoint) that, if they are bounded for some scalar product on the symplectic space dominating the symplectic form, then they are bounded with respect to a one-parametric family of scalar products canonically associated with the initially given one, among them being its ``purification''. As a typical example we consider a scalar field on a globally hyperbolic spacetime governed by the Klein-Gordon equation; the classical system is described by a symplectic space and the temporal evolution by symplectomorphisms (which are symplectically adjoint to their inverses). A natural scalar product is that inducing the classical energy norm, and an application of the above result yields that its ``purification'' induces on the one-particle space of the quantized system a topology which coincides with that given by the two-point functions of quasifree Hadamard states. These findings will be shown to lead to new results concerning the structure of the local (von Neumann) observable-algebras in representations of quasifree Hadamard states of the Klein-Gordon field in an arbitrary globally hyperbolic spacetime, such as local definiteness, local primarity and Haag-duality (and also split- and type III_1-properties). A brief review of this circle of notions, as well as of properties of Hadamard states, forms part of the article.