Hamiltonian formulation of curvature squared action

TL;DR

This paper refines the Hamiltonian formulation of curvature squared actions in quantum cosmology by adding a boundary term, enabling a consistent quantum interpretation of higher order gravity models.

Contribution

It introduces a boundary term to the $R^2$ action, facilitating proper Hamiltonian formulation and quantum analysis of higher order curvature invariant models.

Findings

Boundary term ensures correct Hamiltonian formulation.

Method confirmed in homogeneous and anisotropic models.

Supports quantum interpretation of higher order gravity.

Abstract

It has been observed earlier that, in principle, it is possible to obtain a quantum mechanical interpretation of higher order quantum cosmological models in the spatially homogeneous and isotropic background, if auxiliary variable required for the Hamiltonian formulation of the theory is chosen properly. It was suggested that for such a choice, it is required to get rid of all the total derivative terms from the action containing higher order curvature invariant terms, prior to the introduction of auxiliary variable. Here, the earlier work has been modified and it is shown that the action, $A=\beta\int \sqrt{-g} R^2 d^4 x$ should be supplemented by a boundary term in the form $\sigma=4\beta\int ^{3}R K \sqrt{h} d^{3}x$, where, $^3 R$, $K$ and $h$ are the Ricci scalar for three-space, trace of the extrinsic curvature and determinant of the metric on the three space respectively. The result has been tested in the background of homogeneous and anisotropic models and thus confirmed.