nLab constructive quantum field theory

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Context

Quantum Field Theory

algebraic quantum field theory (perturbative, on curved spacetimes, homotopical)

Introduction

Concepts

field theory:

Lagrangian field theory

quantization

quantum mechanical system, quantum probability

free field quantization

gauge theories

interacting field quantization

renormalization

Theorems

States and observables

Operator algebra

Local QFT

Perturbative QFT

Contents

Idea

In the broad sense of the term, constructive quantum field theory refers to the mathematically rigorous construction of full (i.e. non-perturbative) quantum field theories. More specifically the term has come to be used mainly for attempts to rigorously construct path integral measures for Wick rotated Euclidean field theories on Minkowski spacetime (Jaffe). This approach has led to a construction of scalar field theory in spacetime dimension 3, and Yang-Mills theory in 3 dimensions.

While a mathematically rigorous construction of perturbative quantum field theory is given by causal perturbation theory/perturbative AQFT, construction of non-perturbative quantum field theories has remained by and large elusive, except for toy example of free field theories or low spacetime dimension (e.g. 2d CFTs or scalar field theory in 3d) or topological quantum field theories. In fact the non-perturbative quantization of Yang-Mills theory(QCD) in 4d is listed as one of the open “Millennium Problems” by the Clay Mathematics Institute (see here).

It might be noteworthy that for the established rigorous construction of perturbative QFT via causal perturbation theory/perturbative AQFT a) the path integral or any measures that could go with it plays no role at all (instead the causal additivity of the S-matrix is axiomatized directly) and b) the construction is a formal deformation quantization (Collini 16). This might suggest that rigorous construction of non-perturbative quantum field theory ought to analogously proceed via strict deformation quantization.

References

General

Introduction and review:

On constructive gauge field theory:

See also:

Discussion specifically of constructive path integrals:

Discussion of the problem of quantization of Yang-Mills theory from the point of view of constructive field theory:

See also:

  • Jiasheng Lin: Constructive Quantum Field Theory on Curved Surfaces and Related Topics [arXiv:2507.21655]

Formalization in Lean of the construction of the free scalar quantum field:

For 2D YM theory

For D=2 Yang-Mills theory:

On rigorous construction of path integral measures for 2D Yang-Mills theory (at least for 2D Maxwell theory) invariant under area-preserving diffeomorphisms:

For 3D MCS theory

A construction of what looks like Maxwell-Chern-Simons theory:

For 3D YMCS theory

No rigorous construction of non-abelian 3D Yang-Mills-Chern-Simon theory is currently known.

Comments on what is known and what is not, in comparison to the 2D case:

Last revised on March 18, 2026 at 06:31:21. See the history of this page for a list of all contributions to it.