A seesaw mechanism in the Higgs sector

In this paper we revisit the seesaw Higgs mechanism. We show how a seesaw mechanism in a two Higgs doublets model can trigger the electroweak symmetry breaking if at least one of the eigenvalues of the squared-mass matrix is negative. We then consider two special cases of interest. In the decoupling scenario, there is only one scalar degree of freedom in the low-energy regime. In the degenerate scenario, all five degrees of freedom are in the low-energy regime and will lead to observables effects at the LHC. Furthermore, in that scenario, it is possible to impose a discrete symmetry between the doublets that makes the extra neutral degrees of freedom stable. These are thus viable dark-matter candidates. We find an interesting relation between the electroweak-symmetry-breaking mechanism and dark matter.