Measurement Analysis and Quantum Gravity

TL;DR

This paper examines whether measurement theory logically necessitates the quantization of gravity, analyzing thought experiments and models to argue that empirical evidence is essential for such a conclusion.

Contribution

It applies DeWitt-type measurement analysis to gravitational interactions and reviews existing arguments, challenging the notion that logical consistency alone mandates quantum gravity.

Findings

Logical arguments do not conclusively prove gravity must be quantized.

Empirical tests are necessary to justify a quantum theory of gravity.

Gedanken experiments alone are insufficient for this conclusion.

Abstract

We consider the question of whether consistency arguments based on measurement theory show that the gravitational field must be quantized. Motivated by the argument of Eppley and Hannah, we apply a DeWitt-type measurement analysis to a coupled system that consists of a gravitational wave interacting with a mass cube. We also review the arguments of Eppley and Hannah and of DeWitt, and investigate a second model in which a gravitational wave interacts with a quantized scalar field. We argue that one cannot conclude from the existing gedanken experiments that gravity has to be quantized. Despite the many physical arguments which speak in favor of a quantum theory of gravity, it appears that the justification for such a theory must be based on empirical tests and does not follow from logical arguments alone.