Order-separated tensor-network method for QCD in the strong-coupling expansion

TL;DR

This paper presents a novel order-separated tensor network method for QCD in the strong-coupling regime, enabling calculation of thermodynamic properties and extending the applicability near phase transitions.

Contribution

The introduction of the OS-GHOTRG method for QCD in the strong-coupling expansion is a new approach for computing expansion coefficients and thermodynamic observables.

Findings

Successfully computed free energy, particle-number density, and chiral condensate up to third order in inverse coupling.

Extended the method's applicability near phase transitions through fitting transition functions.

Demonstrated the method's effectiveness in two-dimensional QCD models.

Abstract

We introduce the order-separated Grassmann higher-order tensor renormalization group (OS-GHOTRG) method for QCD with staggered quarks in the strong-coupling expansion. The method allows us to determine the expansion coefficients of the partition function, from which we can obtain the strong-coupling expansions of thermodynamical observables. We use the method in two dimensions to compute the free energy, the particle-number density, and the chiral condensate as a function of the chemical potential up to third order in the inverse coupling $\beta$. Although near the phase transition the expansion is only a good approximation to the full theory at small $\beta$, we show that the range of applicability can be greatly extended by fits to judiciously chosen transition functions.