, i.e. not polynomials or functions of the fields or their derivatives evaluated at a single point in the space of dynamical parameters (e.g. space-time).
The actions appearing in the fundamental theories of physics, such as the Standard Model, are local actions; nonlocal actions play a part in theories that attempt to go beyond the Standard Model and also in some effective field theories.
Nonlocalization of a local action is also an essential aspect of some regularization procedures.
Noncommutative quantum field theory also gives rise to nonlocal actions.
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