  In the spirit of the top quark condensation, we propose a model which has a
naturally light composite Higgs boson, "tHiggs", to be identified with the 126
GeV Higgs discovered at the LHC. The tHiggs, a bound state of the top quark and
its flavor (vector-like) partner, emerges as a pseudo Nambu-Goldstone boson
(NGB), "Top-Mode Pseudo", together with the exact NGBs to be absorbed into the
W and Z bosons as well as another (heavier) Top-Mode Pseudo (CP-odd composite
scalar). Those five composite (exact/pseudo) NGBs are dynamically produced
simultaneously by a single supercritical four-fermion interaction having U(3) x
U(1) symmetry which includes the electroweak symmetry, where the vacuum is
aligned by small explicit breaking term so as to break the symmetry down to a
subgroup, U(2) x U(1)', in a way not to retain the electroweak symmetry, in
sharp contrast to the little Higgs models. The explicit breaking term for the
vacuum alignment gives rise to a mass of the tHiggs, which is protected by the
symmetry and hence naturally controlled against radiative corrections.
Realistic top quark mass is easily realized similarly to the top-seesaw
mechanism by introducing an extra (subcritical) four-fermion coupling which
explicitly breaks the residual U(2) x U(1)' symmetry. We present a
phenomenological Lagrangian of the Top-Mode Pseudos along with the standard
model particles, which will be useful for the study of the collider
phenomenology. The coupling property of the tHiggs is shown to be consistent
with the currently available data reported from the LHC. Several
phenomenological consequences and constraints from experiments are also
addressed.
