On Composite Two Higgs Doublet Models
  We investigate composite two Higgs doublet models realized as pseudo Goldstone modes, generated through the spontaneous breaking of a global symmetry due to strong dynamic at the TeV scale. A detailed comparative survey of two possible symmetry breaking patterns, SU(5) -> SU(4) x U(1) and SU(5) x SU(4), is made. We point out choices for the Standard Model fermion representations that can alleviate some phenomenological constraints, with emphasis towards a simultaneous solution of anomalous Zb\bar{b} coupling and Higgs mediated Flavor Changing Neutral Currents. We also write down the kinetic lagrangian for several models leading to Two Higgs Doublets and identify the anomalous contributions to the T parameter. Moreover, we describe a model based on the breaking $SO(9)/SO(8)$ in which there is no tree-level breaking of custodial symmetry, discussing also the possible embeddings for the fermion fields. 
Enrico Bertuzzo, Tirtha Sankar Ray, Hiroshi de Sandes and Carlos A.   Savoy
hep-ph