Conditions for the custodial symmetry in multi-Higgs-doublet models

Abstract

We derive basis-independent, necessary and sufficient conditions for the custodial symmetry in N-Higgs-doublet models (NHDM) for N > 2, and apply them on some 3HDM examples.

Comments: 37 pages, 1 figure. A section on spontaneous breaking of the custodial SO(4) symmetry is added, in addition to a section on the Ivanov-Silva model and a discussion of theorem 1 in the case N=2. Equivalent to the version published in JHEP