Gravity and Quantum Field Theory
Published on September 12, 2025
Table of Contents
1. Introduction
Gravity, described by Einstein’s General Relativity, governs the large‑scale structure of the universe, while Quantum Field Theory (QFT) provides the framework for the microscopic world of particles and forces. Reconciling these two pillars remains one of the most profound challenges in modern physics.
2. Historical Context
Attempts to quantize gravity began shortly after the development of QFT in the 1930s. Early approaches, such as perturbative quantum gravity, encountered non‑renormalizable divergences, leading physicists to search for alternative formulations.
3. Quantum Fields in Curved Spacetime
One fruitful compromise is to treat matter fields quantum mechanically on a classical curved background. This semiclassical approach predicts phenomena like Hawking radiation and the Unruh effect, showcasing how gravity influences quantum fields.
4. Major Challenges
- Non‑renormalizability: Traditional perturbative techniques break down at high energies.
- Background Independence: Gravity’s dynamical spacetime conflicts with QFT’s fixed background.
- Problem of Time: Time plays different roles in each theory, complicating a unified description.
5. Future Directions
Research avenues include string theory, loop quantum gravity, asymptotic safety, and emergent gravity scenarios. Each offers a distinct perspective on how spacetime might arise from more fundamental quantum constituents.