Electroweak symmetry breaking as a consequence of compact dimensions

It has been shown recently that the Higgs doublet may be composite, with the left-handed top-bottom doublet and a new right-handed anti-quark as constituents bound by some four-quark operators with non-perturbative coefficients. I show that these operators are naturally induced if there are extra spatial dimensions with a compactification scale in the multi-TeV range. The Higgs compositeness is due mainly to the Kaluza–Klein modes of the gluons, while flavor symmetry breaking may be provided by various fields propagating in the compact dimensions. I comment briefly on the embedding of this scenario in string theory.