Vacuum Topology of the Two Higgs Doublet Model

TL;DR

This paper systematically analyzes the vacuum topology and topological defects in the two-Higgs-doublet model using a Majorana scalar-field formalism, identifying various defects and symmetries, and providing analytical solutions for the potential's stability.

Contribution

It introduces a Majorana scalar-field formalism to classify symmetries and topological defects in the two-Higgs-doublet model, extending analysis to more general potentials.

Findings

Identified domain walls, vortices, and monopoles associated with specific symmetries.

Derived conditions for potential stability and convexity.

Provided analytical solutions for vacuum expectation values in the model.

Abstract

We perform a systematic study of generic accidental Higgs-family and CP symmetries that could occur in the two-Higgs-doublet-model potential, based on a Majorana scalar-field formalism which realizes a subgroup of GL(8,C). We derive the general conditions of convexity and stability of the scalar potential and present analytical solutions for two non-zero neutral vacuum expectation values of the Higgs doublets for a typical set of six symmetries, in terms of the gauge-invariant parameters of the theory. By means of a homotopy-group analysis, we identify the topological defects associated with the spontaneous symmetry breaking of each symmetry, as well as the massless Goldstone bosons emerging from the breaking of the continuous symmetries. We find the existence of domain walls from the breaking of Z_2, CP1 and CP2 discrete symmetries, vortices in models with broken U(1)_PQ and CP3 symmetries and a global monopole in the SO(3)_HF-broken model. The spatial profile of the topological defect solutions is studied in detail, as functions of the potential parameters of the two-Higgs doublet model. The application of our Majorana scalar-field formalism in studying more general scalar potentials that are not constrained by the U(1)_Y hypercharge symmetry is discussed. In particular, the same formalism may be used to properly identify seven additional symmetries that may take place in a U(1)_Y-invariant scalar potential.