Composite field

{{Short description|Field composed from other elementary fields}}

{{See also|Composite field (mathematics)}}

{{More citations needed|date=June 2025}}

In quantum field theory, a composite field is a field defined in terms of other more "elementary" fields. It might describe a composite particle (bound state) or it might not.

It might be local, or it might be nonlocal. However, "quantum fields do not exist as a point taken in isolation," so "local" does not mean literally a single point.{{cite book|url=https://books.google.com/books?id=lvT1CAAAQBAJ&pg=PA379&dq=%22Composite+field%22+-wikipedia&hl=en&newbks=1&newbks_redir=0&source=|pages=379, 381|title=General Principles of Quantum Field Theory|year=2012|isbn=9789400904910|publisher=Springer Netherlands|access-date=June 12, 2025}}

Composite fields use a very specific kind of statistics, called "duality and arbitrary statistics".{{cite book|pages=175–178|url=https://books.google.com/books?id=fD41DwAAQBAJ&pg=PA176&dq=%22Composite+field%22+-wikipedia&hl=en&newbks=1&newbks_redir=0&source=|title=Quantum Field Theory Approach to Condensed Matter Physics|first=Eduardo C. |last=Marino|year=2017|isbn=9781108508858|publisher=Cambridge University Press |access-date=June 12, 2025}}

Under Noether's theorem, Noether fields are often composite fields,{{cite book|url=https://books.google.com/books?id=MuH0TQvpY5sC&pg=PA430&dq=Composite+field+noether+-wikipedia&hl=en&newbks=1&newbks_redir=0&source=|pages=430–431|title=The Conceptual Framework of Quantum Field Theory|first=Anthony |last=Duncan|year=2012|isbn=9780199573264|publisher=Oxford University Press|access-date=June 12, 2025}} and they are local.

In the generalized LSZ formalism, composite fields, which are usually nonlocal, are used to model asymptotic bound states.{{citation needed|date=June 2025}}