Interactive Quadratic Gravity

TL;DR

This paper develops a self-consistent quadratic gravity theory incorporating quantum scalar fields, introducing a novel interaction term that modifies the gravitational field equations and quantum field behavior in higher-dimensional curved spacetime.

Contribution

It proposes a new coupling between R^2 and quantum fields in quadratic gravity, leading to simplified equations and a method for solving quantum modes in six-dimensional anisotropic backgrounds.

Findings

Derived a renormalizable energy-momentum tensor for quadratic gravity.

Introduced a geometric source term in the quantum wave equation.

Developed a method to obtain quantum mode solutions using Green's functions.

Abstract

A quadratic semiclassical theory, regarding the interaction of gravity with a massive scalar quantum field, is considered in view of the renormalizable energy-momentum tensor in a multi-dimensional curved spacetime. According to it, a self-consistent coupling between the square curvature term R^{2} and the quantum field \Phi should be introduced in order to yield the "correct" renormalizable energy-momentum tensor in quadratic gravity theories. The subsequent interaction discards any higher-order derivative terms from the gravitational field equations, but, in the expence, it introduces a geometric source term in the wave equation for the quantum field. Unlike the conformal coupling case (R\Phi ^{2}), this term does not represent an additional "mass" and, therefore, the quantum field interacts with gravity not only through its mass (or energy) content (~\Phi ^{2}), but also, in a more generic way (R^{2}\Phi). Within this context, we propose a general method to obtain mode-solutions for the quantum field, by means of the associated Green's function in an anisotropic six-dimensional background.