In theoretical physics, topcolor is a model of dynamical electroweak symmetry breaking in which the top quark and anti-top quark form a composite Higgs boson by a new force arising from massive "top gluons." This is analogous to the phenomenon of superconductivity where Cooper pairs are formed by the exchange of phonons. The pairing dynamics and its solution was treated in the Bardeen-Hill-Lindner model. The solution to composite Higgs models was actually anticipated in 1981, and found to be the Infrared fixed point for the top quark mass.
Recently this has been revisited ("Scalar Democracy") in which many composite Higgs bosons may form at very high energies, composed of the known quarks and leptons, perhaps bound by universal force (e.g., gravity, or an extension of topcolor). The standard model Higgs boson is then a top-anti-top boundstate. The theory predicts many new Higgs doublets, starting at the TeV mass scale, with O(1) couplings to the known fermions that may explain their masses and mixing angles. The first sequential new Higgs bosons are accessible to the LHC. 
The original topcolor naturally involved an extension of the standard model color gauge group to a product group SU(3)xSU(3)xSU(3)x... One of the gauge groups contains the top and bottom quarks, and has a sufficiently large coupling constant to cause the condensate to form. The topcolor model anticipates the idea of dimensional deconstruction and extra space dimensions, as well as the large mass of the top quark.
- Christopher T. Hill (1991). "Topcolor: top quark condensation in a gauge extension of the standard model". Physics Letters B. 266 (3–4): 419–424. Bibcode:1991PhLB..266..419H. doi:10.1016/0370-2693(91)91061-Y.
- Christopher T. Hill (1995). "Topcolor assisted technicolor". Physics Letters B. 345 (4): 483–489. arXiv:hep-ph/9411426. Bibcode:1995PhLB..345..483H. doi:10.1016/0370-2693(94)01660-5.
- William A. Bardeen; Christopher T. Hill; Manfred Lindner (1990). "Minimal dynamical symmetry breaking of the standard model". Physical Review D. 41 (5): 1647–1660. Bibcode:1990PhRvD..41.1647B. doi:10.1103/PhysRevD.41.1647.
- Hill, C.T. (1981). "Quark and Lepton masses from Renormalization group fixed points". Phys. Rev. D24: 691. Bibcode:1981PhRvD..24..691H. doi:10.1103/PhysRevD.24.691.
- Christopher Hill; Pedro Machado; Anders Thomsen; Jessica Turner (2019). "Scalar Democracy". Physical Review D. D100 (1): 015015. doi:10.1103/PhysRevD.100.015015.
- Christopher Hill; Pedro Machado; Anders Thomsen; Jessica Turner (2019), Where are the next Higgs Bososns, arXiv:1904.04257