Auxiliary field

In physics, and especially quantum field theory, an auxiliary field is one whose equations of motion admit a single solution. Therefore, the Lagrangian describing such a field A {displaystyle A} contains an algebraic quadratic term and an arbitrary linear term, while it contains no kinetic terms (derivatives of the field): In physics, and especially quantum field theory, an auxiliary field is one whose equations of motion admit a single solution. Therefore, the Lagrangian describing such a field A {displaystyle A} contains an algebraic quadratic term and an arbitrary linear term, while it contains no kinetic terms (derivatives of the field): The equation of motion for A {displaystyle A} is