A very light dilaton

Abstract

We present a completely perturbative model that displays behavior similar to that of walking technicolor. In one phase of the model RG-trajectories run towards an IR-fixed point but approximate scale invariance is spontaneously broken before reaching the fixed point. The trajectories then run away from it and a light dilaton appears in the spectrum.The mass of the dilaton is controlled by the "distance" of the theory to the critical surface, and can be adjusted to be arbitrarily small without turning off the interactions. There is a second phase with no spontaneous symmetry breaking and hence no dilaton, and in which RG trajectories do terminate at the IR-fixed point.

Quantum critical behavior of semisimple gauge theories

“…It is in addition a non-supersymmetric gauge-Yukawa theory that contains spin-0, spin- 1 2 as well as spin-1 particles. Whereas the literature contains investigations of the phase diagram of semi-simple and simple supersymmetric gauge theories [1][2][3], vector-like fermionic gauge theories [4][5][6][7][8][9][10][11][12], chiral gauge theories [13][14][15], Yukawa theories [16][17][18][19][20] and scalar theories [21] only very little has been done concerning the more general class of theories in which the Standard Model falls [22].…”

A bound state model for a light scalar

“…Thus our finding of a light scalar emerging without dilatonic properties, with a form factor closely resembling that of the pion, is consistent with this. Light dilatons do appear in approaches that are more local, such as where there are elementary scalar fields with Yukawa couplings and local potentials with perturbative corrections [20,21]. These local theories that find dilatons are very different from the non-local effective theories that do not find them.…”

Alternatives to an elementary Higgs

“…Assuming that we actually can find theories that spontaneously break conformal symmetry (with a flat-direction since a 0,0 = 0) then we still need to be very careful that any perturbations do not reintroduce a 0,0 = 0. If we add a perturbation λO to the theory then the conditions for a 0,0 to remain small are that the scaling dimension of O is close to, but slightly below, four and the β function for λ is very small all the way from the UV down to the breaking scale f χ (Bellazzini et al, 2013;Chacko and Mishra, 2013;Chacko et al, 2013b;Evans and Tuominen, 2013;Grinstein and Uttayarat, 2011). If these conditions are satisfied a 0,0 will remain small and develop a weak dependence on λ through the running, which will pick out a unique minimum for χ and give the dilaton a small mass.…”