Modified quark-meson coupling model for nuclear matter

Abstract

The quark-meson coupling model for nuclear matter, which describes nuclear matter as non-overlapping MIT bags bound by the self-consistent exchange of scalar and vector mesons, is modified by introducing medium modification of the bag constant. We model the density dependence of the bag constant in two different ways: one invokes a direct coupling of the bag constant to the scalar meson field, and the other relates the bag constant to the in-medium nucleon mass. Both models feature a decreasing bag constant with increasing density. We find that when the bag constant is significantly reduced in nuclear medium with respect to its free-space value, large canceling isoscalar Lorentz scalar and vector potentials for the nucleon in nuclear matter emerge naturally. Such potentials are comparable to those suggested by relativistic nuclear phenomenology and finite-density QCD sum rules. This suggests that the reduction of bag constant in nuclear medium may play an important role in low-and medium-energy nuclear physics.

Change of MIT bag constant in nuclear medium and implication for the EMC effect

“…B/B 0 ∼ 35 − 40% at the nuclear matter saturation density, the predictions for the rescaling parameter are in good agreement with those required to explain the depletion of the structure function observed in a range of nuclei. Such a large reduction of the bag constant, as shown in previous works [11,12], also implies large and canceling Lorentz scalar and vector potentials for the nucleon in nuclear matter which are comparable to those suggested by the relativistic nuclear phenomenology and finite-density QCD sum rules. This indicates that the reduction of bag constant and hence the increase of confinement size in nuclei may play important role in low-and medium-energy nuclear physics and the modified QMC model provides a useful framework to accommodate both the change of confinement size and the quark structure of the nucleon in describing nuclear phenomena.…”

“…The reader is referred to Refs. [11][12][13] for further details and motivations for introducing the medium modification of the bag constant.…”

“…[11][12][13]. This modification can lead to the recovery of relativistic nuclear phenomenology, in particular the large canceling isoscalar Lorentz scalar and vector potentials and hence the strong spin-orbit force for the nucleon in nuclear matter.…”

The nuclear matter stability in a non-local chiral quark model

“…We obtained the nucleon wave function from the Faddeev equation and showed that the nucleon size significantly increases in the medium. This implies a swollen nucleon in nuclear matter which has many attendant consequences [38,39,40,41]. Our estimation of in-medium nucleon size should be taken more qualitatively since the quark density function given in Eq.…”

Neutron Stars with Bose-Einstein Condensation of Antikaons as MIT Bags

“…The model has been further developed by several authors [17][18][19][20][21]. An important revision of the model was made in Ref.…”