# Towards a novel approach to semi-classical gravity

## TL;DR

This paper proposes a new semi-classical gravity framework using Bohmian mechanics, replacing the expectation value of the energy-momentum tensor with an actual configuration-based tensor, aiming to enhance the traditional approach.

## Contribution

It introduces a Bohmian mechanics-based method for semi-classical gravity, offering an alternative to the standard expectation value approach.

## Key findings

- Potentially more accurate matter source modeling
- Addresses limitations of expectation value approach
- Lays groundwork for further theoretical development

## Abstract

Semi-classical gravity is an approximation to quantum gravity where gravity is treated classically and matter quantum mechanically. Matter is described by quantum field theory on curved space-time, whereas gravity is described by a space-time metric which satisfies Einstein's field equations. In the usual approach to semi-classical gravity, the matter source term in Einstein's field equations is given by the expectation value of the energy-momentum tensor operator. In this paper, we suggest an alternative approach based on Bohmian mechanics. In Bohmian mechanics, a quantum system is described by an actual configuration (e.g., an actual scalar field), which evolves under the influence of the wave function. The idea is to consider the actual energy-momentum tensor corresponding to this configuration as the matter source term in Einstein's field equations. This approach is expected to improve upon the usual approach.