[Revised entry by Meinard Kuhlmann on September 9, 2026.
Changes to: Main text, Bibliography]
Quantum Field Theory (QFT) is the mathematical and conceptual framework for contemporary high-energy physics, or “particle physics” (but see the discussion of the problematic particle interpretation below). It is also a framework used in other areas of theoretical physics, such as condensed matter physics and statistical mechanics. In a rather informal sense QFT is the extension of quantum mechanics (QM), dealing with particles, over to fields, i.e., systems with an infinite number of degrees of freedom. (See the entry on…

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