Abstract
A genuine dilaton σ allows scales to exist even in the limit of exact conformal invariance. In gauge theories, these may occur at an infrared fixed point (IRFP) α IR through dimensional transmutation. These large scales at α IR can be separated from small scales produced by θ μ μ , the trace of the energy-momentum tensor. For quantum chromodynamics (QCD), the conformal limit can be combined with chiral S U ( 3 ) × S U ( 3 ) symmetry to produce chiral-scale perturbation theory χ PT σ , with f 0 ( 500 ) as the dilaton. The technicolor (TC) analogue of this is crawling TC: at low energies, the gauge coupling α goes directly to (but does not walk past) α IR , and the massless dilaton at α IR corresponds to a light Higgs boson at α ≲ α IR . It is suggested that the W ± and Z 0 bosons set the scale of the Higgs boson mass. Unlike crawling TC, in walking TC, θ μ μ produces all scales, large and small, so it is hard to argue that its “dilatonic” candidate for the Higgs boson is not heavy.
Highlights
It is surprising how far the notion of a “dilaton” has strayed from the original version of 1968–1970. it can be any of the following: I
This is being interpreted as a type-III dilaton for walking TC, but it is more likely to be a genuine dilaton, and evidence for an infrared fixed point (IRFP) just outside the conformal window
Crawling TC [1] is the most recent application of the idea of an NG mode at the IRFP of a gauge theory. It adopts the standard TC viewpoint [57,58,59] that the Higgs mechanism is the dynamical effect of a gauge theory which resembles quantum chromodynamics (QCD), with a TC coupling α which is nonperturbative at scales of a few TeV
Summary
It is surprising how far the notion of a “dilaton” has strayed from the original version of 1968–1970. For values of α just below α IR , θμ appears as a small perturbation which produces small scales, such as the mass acquired by the type-I dilaton: a light Higgs boson. A light scalar boson has been observed in lattice data for SU (3) gauge theory with N f = 8 triplet fermions [24,25,26,27] and two sextet fermions [28,29] In each case, this is being interpreted as a type-III dilaton for walking TC, but it is more likely to be a genuine dilaton, and evidence for an IRFP just outside the conformal window
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
