QCD in the heavy dense regime for general Nc: on the existence of quarkyonic matter

Owe Philipsen,Jonas Scheunert

doi:10.1007/jhep11(2019)022

Abstract

Lattice QCD with heavy quarks reduces to a three-dimensional effective theory of Polyakov loops, which is amenable to series expansion methods. We analyse the effective theory in the cold and dense regime for a general number of colours, Nc. In particular, we investigate the transition from a hadron gas to baryon condensation. For any finite lattice spacing, we find the transition to become stronger, i.e. ultimately first-order, as Nc is made large. Moreover, in the baryon condensed regime, we find the pressure to scale as p ∼ Nc through three orders in the hopping expansion. Such a phase differs from a hadron gas with p ∼ {N}_c^0 , or a quark gluon plasma, p ∼ {N}_c^2 , and was termed quarkyonic in the literature, since it shows both baryon-like and quark-like aspects. A lattice filling with baryon number shows a rapid and smooth transition from condensing baryons to a crystal of saturated quark matter, due to the Pauli principle, and is consistent with this picture. For continuum physics, the continuum limit needs to be taken before the large Nc limit, which is not yet possible in practice. However, in the controlled range of lattice spacings and Nc-values, our results are stable when the limits are approached in this order. We discuss possible implications for physical QCD.

Highlights

IntroductionWe consider the effective theory for general colour gauge group SU(Nc), in order to establish contact with another effective approach in the continuum, namely QCD at large Nc. In particular, we analyse thermodynamic functions around the onset transition to baryon matter in the cold and dense regime, for varying and large Nc. In particular, we analyse thermodynamic functions around the onset transition to baryon matter in the cold and dense regime, for varying and large Nc
We have studied the large Nc-behaviour of QCD in the cold and dense regime within an effective lattice theory derived by combined strong coupling and hopping expansions, which is valid for sufficiently heavy quarks
At low temperatures and μB ∼ mB it exhibits a transition to baryon condensation, which is the heavy quark analogue of the nuclear liquid gas transition

Summary

Introduction

We consider the effective theory for general colour gauge group SU(Nc), in order to establish contact with another effective approach in the continuum, namely QCD at large Nc. In particular, we analyse thermodynamic functions around the onset transition to baryon matter in the cold and dense regime, for varying and large Nc. In particular, we analyse thermodynamic functions around the onset transition to baryon matter in the cold and dense regime, for varying and large Nc This allows us to address, by direct calculation, various conjectures made in [9] regarding the phase diagram and the effective degrees of freedom at large Nc. There, the authors argue for the existence of quarkyonic matter, which is characterised by its pressure scaling as p ∼ Nc and has both baryon-like and quark-like aspects. With the spatial links gone, the effective action depends on the temporal links only via Wilson lines closing through the periodic boundary, Nτ

Objectives

Results

Conclusion