# [SCI] Quantum Field Theory (QED/QCD)

**Quantum Field Theory (QFT)** unifies quantum mechanics with special relativity by describing particles as excitations of quantum fields, explaining the fundamental forces via particle exchange.

## Overview

Quantum Electrodynamics (QED) — the quantum field theory of electromagnetism — was formulated by Feynman, Schwinger, and Tomonaga (1948), who showed how to handle infinities via renormalisation. QED's predictions match experiment to 12 decimal places — the most precisely tested theory in science. The electroweak theory (Glashow, Salam, Weinberg, 1968–1970) unified EM and weak nuclear force. Quantum Chromodynamics (QCD) describes the strong force via coloured quarks and gluons. Together they form the Standard Model.

The concepts of QFT — symmetry groups, spontaneous symmetry breaking, the renormalisation group — spread to condensed matter physics and statistical mechanics, where they describe phase transitions and critical phenomena.

## Key Figures & Recognition

- **Feynman, Schwinger, Tomonaga**: QED. **Nobel Prize 1965**.
- **Glashow, Salam, Weinberg**: Electroweak theory. **Nobel Prize 1979**.
- **Gross, Politzer, Wilczek**: Asymptotic freedom in QCD. **Nobel Prize 2004**.
- **Higgs, Englert**: Higgs mechanism. **Nobel Prize 2013**.

## Seminal Papers

- Feynman, R.P. ["Space-Time Approach to Quantum Electrodynamics." *Phys. Rev.* 76 (1949)](https://doi.org/10.1103/PhysRev.76.769)

## What This Enables
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- **[SCI] Condensed Matter & Topological Physics** — Renormalisation group, effective field theories, and topological field theory are QFT methods now central to condensed matter.
- **[SCI] Quantum Computing Theory** — QFT provides the theoretical substrate for quantum information: qubits are quantum fields, quantum gates are unitary evolutions.
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# Parents

* [SCI] Special Relativity
* [SCI] Special Relativity
* [SCI] General Relativity
* [SCI] Quantum Mechanics