In the context of scalar quantum field theory, we introduce a class of generically nonlinear quantum-background splits for which the splitting Ward identity, encoding the single-field dependence in the effective action, can be solved exactly. We show that this can be used to construct an effective action which is both covariant and dependent on the background and fluctuation fields only through a single total field in a way independent from the dynamics. Moreover, we discuss the criteria under which the ultraviolet symmetries are inherited by the quantum effective action. The approach is demonstrated through some examples, including the $O(N)$ effective field theory, which might be of interest for the Higgs sector of the Standard Model or its extensions.

• Received 20 July 2017

DOI:https://doi.org/10.1103/PhysRevD.96.085001