Why is quantum gravity so difficult (compared to QCD)?

TL;DR

This paper explores the unique challenges of quantizing gravity, highlighting its non-renormalizability and comparing it to other gauge theories to understand why gravity remains difficult to quantize.

Contribution

It provides a conceptual analysis treating gravity as a gauge theory and explains its special difficulties in quantization compared to other gauge theories.

Findings

Gravity's non-renormalizability is a key obstacle.

Gravity differs fundamentally from other gauge theories.

Understanding gravity's uniqueness clarifies quantization challenges.

Abstract

Gravity is difficult to quantize. This is a well-known fact but its reason is given simply by non-renormalizability of the Newton constant and little is discussed why among many quantum gauge theories, gravity is special. In this essay we try to treat the gravity as one of many gauge theories, and discuss how it is special and why it is difficult to quantize.