Quark number density at imaginary chemical potential and its extrapolation to large real chemical potential by the effective model

TL;DR

This study combines lattice QCD simulations and effective models to analyze quark number densities at imaginary chemical potential, extrapolate to real chemical potential, and investigate neutron star properties and phase transitions.

Contribution

It introduces a method to extrapolate lattice QCD results to large real chemical potentials using an effective two-phase model, linking microscopic calculations to astrophysical phenomena.

Findings

Extrapolated quark densities agree with Taylor expansion results.

The two-phase model reproduces lattice QCD data for order parameters.

Mass-radius relations of neutron stars are consistent with observational constraints.

Abstract

We evaluate quark number densities at imaginary chemical potential by lattice QCD with clover-improved two-flavor Wilson fermion. The quark number densities are extrapolated to the small real chemical potential region by assuming some function forms. The extrapolated quark number densities are consistent with those calculated at real chemical potential with the Taylor expansion method for the reweighting factors. In order to study the large real chemical potential region, we use the two-phase model consisting of the quantum hadrodynamics model for the hadron phase and the entanglement-PNJL model for the quark phase. The quantum hadrodynamics model is constructed to reproduce nuclear saturation properties, while the entanglement-PNJL model reproduces well lattice QCD data for the order parameters such as the Polyakov loop, the thermodynamic quantities and the screening masses. Then, we calculate the mass-radius relation of neutron stars and explore the hadron-quark phase transition with the two-phase model.