Quenched QCD at finite density

TL;DR

This study investigates quenched QCD at finite chemical potential, revealing a linear decrease in nucleon mass and stable meson spectrum, while highlighting technical challenges and proposing improved simulation methods.

Contribution

It provides new insights into quenched QCD behavior at finite density and discusses technical issues affecting lattice simulations, suggesting ways to overcome them.

Findings

Nucleon screening mass decreases linearly with increasing chemical potential.

Meson spectrum remains unchanged up to half the pion mass.

Identification of technical challenges in lattice simulations at finite density.

Abstract

Simulations of quenched $QCD$ at relatively small but {\it nonzero} chemical potential $\mu$ on $32 \times 16^3$ lattices indicate that the nucleon screening mass decreases linearly as $\mu$ increases predicting a critical chemical potential of one third the nucleon mass, $m_N/3$, by extrapolation. The meson spectrum does not change as $\mu$ increases over the same range, from zero to $m_\pi/2$. Past studies of quenched lattice QCD have suggested that there is phase transition at $\mu = m_\pi/2$. We provide alternative explanations for these results, and find a number of technical reasons why standard lattice simulation techniques suffer from greatly enhanced fluctuations and finite size effects for $\mu$ ranging from $m_\pi/2$ to $m_N/3$. We find evidence for such problems in our simulations, and suggest that they can be surmounted by improved measurement techniques.