Gluon propagator in two-color dense QCD: Massive Yang-Mills approach at one loop

Abstract

We study the Landau gauge gluon propagators in dense two-color QCD at quark chemical potential, µq, in the range from 0.5 to 1.0 GeV not reachable by the perturbative method at weak coupling. In order to take into account the non-perturbative effects, at tree level we use a massive Yang-Mills model for the Yang-Mills theory (or the Curci-Ferrari model) which has successfully described the lattice results of the gluon and ghost propagators in the Landau gauge. We couple quarks to this theory and compute the one-loop polarization effects in medium. The presence of the gluon mass significantly tempers the medium effects and uncertainties associated with the strong coupling constant αs. The diquark condensate in two-color QCD is color-singlet, for which neither electric nor magnetic screening masses should appear at the scale less than the diquark gap. The presence of the gap helps to explain the lattice results which are not very sensitive to the quark density. Meanwhile we also found the limitation of the one-loop estimate as well as the lack of some physics in perturbative medium corrections. *

Dense two-color QCD towards continuum and chiral limits

“…Although these theories all have qualitative features which distinguish them from real QCD at nonzero baryon chemical potential -notably a gauge-invariant Bose-Einstein condensate (BEC) above an onset chemical potential µ o -they share salient features such as spontaneous chiral symmetry breaking and confinement at T = µ = 0, and may be used as laboratories for strongly interacting theories at high density. Lattice results from these theories may also be used as a check on the approximations made in other approaches which do not suffer from the sign problem, including Polyakov-loop extended Nambu-Jona-Lasinio models [11], massive perturbation theory [12,13], quark-meson(-diquark) coupling models [14], the functional renormalisation group [15] or Dyson-Schwinger equations [16,17].…”

Dense two-color QCD from Dyson-Schwinger equations

“…Lattice calculations were performed for this theory [51][52][53][54][55][56][57][58][59] and we will compare results for the gluon propagator, the quark number density and the chiral condensate. QC 2 D was also investigated with various continuum methods, e.g., [60][61][62][63][64][65][66][67][68]. Furthermore, it has attracted attention [69][70][71][72][73][74][75] as a potential theory for a composite Higgs in the context of technicolor [76].…”

QCD equations of state and speed of sound in neutron stars

“…If we accept the BCS relation T s 0.57 with being the size of the gap, then 180 MeV. This would suggest that gluons remain non-perturbative, and the studies of gluon propagators seem consistent with this point of view [91,92].…”