Lattice QC2D at High Baryon Density

Abstract

It is proposed to study QCD with two colours (rather than the physical three) at non-zero baryon density. The results should help our understanding of the ultradense states of matter (with densities exceeding 10⁶ tonnes/cm³) thought to be at the cores of astrophysical objects such as neutron stars. In particular, we will study the transition from confined ’nuclear matter’, consisting of well-defined diquark bound states, to deconfined ’quark matter’, which is expected to be degenerate and exhibit similar properties to electrons in a metal as well as exotic new phenomena such as ’colour superconductivity’. The project will employ finer lattice spacings (0.1fm) and larger volumes (3fm³) than any previous study, and in addition to establishing basic thermodynamic information in this under-explored regime, hopes to furnish new results on the excitations and transport properties of dense baryonic matter. In reality, there are three quark colours. However, current simulation techniques all require on probabilistic methods where the action must be real. This is true for three colours in a vacuum, but not true at finite particle density (ie chemical potential μ ≠ 0) where it becomes complex. Having just two colours gives the theory a real action making orthodox four-dimensional lattice QCD Monte Carlo simulation methods applicable. This investigation is an essential first step towards understanding the physics of the full theory at non-zero μ.