Theoretical Constraints on Additional Higgs Bosons in Light of the 126   GeV Higgs
  We present a sum rule for Higgs fields in general representations under $SU(2)_L \times U(1)_Y$ that follows from the connection between the Higgs couplings and the mechanism that gives the electroweak bosons their masses, and at the same time restricts these couplings. Sum rules that follow from perturbative unitarity will require us to include singly and doubly charged Higgses in our analysis. We examine the consequences of these sum rules for Higgs phenomenology in both model independent and model specific ways. The relation between our sum rules and other works, based on dispersion relations, is also clarified. 
Benjam\'in Grinstein, Christopher W. Murphy, David Pirtskhalava and   Patipan Uttayarat
hep-ph