Self-adjointness in the Hamiltonians of deparameterized totally constrained theories: a model

TL;DR

This paper investigates the self-adjointness of Hamiltonians in deparameterized constrained theories, demonstrating that well-defined operators can replicate classical physics semiclassically in a simplified model.

Contribution

It introduces a method to construct well-defined operators that preserve semiclassical physics, addressing challenges with square-root Hamiltonians in quantum gravity models.

Findings

Operators can reproduce classical physics semiclassically

The approach applies to a simple model of constrained theory

Addresses self-adjointness issues in quantum Hamiltonians

Abstract

Several proposals to deal with the dynamics of general relativity involve gauge fixings or the introduction matter fields in terms of which the theory is deparameterized. The resulting theories have true Hamiltonians for their evolution that usually involve square roots, and this poses certain challenges for their implementation as self-adjoint quantum operators. We show in the context of a simple model of totally constrained theory that one can introduce related, well defined operators that reproduce semiclassically the same physics as the original ones, at least for states peaked in the regions of phase space where their associated classical quantities are well defined.