Observation of deconfinement in a cold dense quark medium

V G Bornyakov,E.-M Ilgenfritz,A V Molochkov,A Yu Kotov,A A Nikolaev,V V Braguta

doi:10.1007/jhep03(2018)161

Abstract

In this paper we study the confinement/deconfinement transition in lattice SU(2) QCD at finite quark density and zero temperature. The simulations are performed on an 324 lattice with rooted staggered fermions at a lattice spacing a = 0.044 fm. This small lattice spacing allowed us to reach very large baryon density (up to quark chemical potential μq > 2000 MeV) avoiding strong lattice artifacts. In the region μq ∼ 1000 MeV we observe for the first time the confinement/deconfinement transition which manifests itself in rising of the Polyakov loop and vanishing of the string tension σ. After the deconfinement is achieved at μq > 1000 MeV, we observe a monotonous decrease of the spatial string tension σs which ends up with σs vanishing at μq > 2000 MeV. From this observation we draw the conclusion that the confinement/deconfinement transition at finite density and zero temperature is quite different from that at finite temperature and zero density. Our results indicate that in very dense matter the quark-gluon plasma is in essence a weakly interacting gas of quarks and gluons without a magnetic screening mass in the system, sharply different from a quark-gluon plasma at large temperature.

Highlights

JHEP03(2018)161 mechanism of the fermion mass generation in a dense medium and even the formula for the fermion mass gap is the same in both theories [9]
In the region μq ∼ 1000 MeV we observe for the first time the confinement/deconfinement transition which manifests itself in rising of the Polyakov loop and vanishing of the string tension σ
Our results indicate that in very dense matter the quark-gluon plasma is in essence a weakly interacting gas of quarks and gluons without a magnetic screening mass in the system, sharply different from a quark-gluon plasma at large temperature

Summary

Lattice set-up

In the present paper we continue our study of two-color QCD in the region of very large baryon (quark) density. In addition to the bulk of simulations at finite μq, simulations for calibration at √ In this case our string tension at μq = 0 amounts to σ0 = 476(5) MeV at a = 0.044 fm, whereas in our previous study [14] the lattice spacing was almost three times larger, a = 0.112 fm. In the present paper we reach the region of baryon density corresponding to a quark chemical potential μq > 2000 MeV which is the largest value ever reached in lattice simulations of SU(2) QCD. Numerical simulations in the region of large baryon density require considerable computer resources For this reason, for the present paper we conducted our study at a pion mass of mπ = 740(40) MeV, a value which is larger than that used in [14]. For the calculation of the Polyakov loop one step of HYP smearing with the same parameters was employed

Numerical results and discussion

Conclusion