Zusammenfassung
The effect of the complex phase of the fermion determinant is a key question
related to the sign problem in finite-density QCD. Recently it has been shown
that ignoring the complex phase -- the phase quenching -- does not change the
expectation values of a class of observables in a certain region of the phase
diagram when a number of colors N_c is large. In this paper we study the effect
of the phase quenching within the frameworks of effective models and
holographic models. We show, in a unified manner, that the phase quenching
gives exact results for a class of fermionic observables (e.g., chiral
condensate) in the mean-field approximation and for gauge-invariant gluonic
observables (e.g., Polyakov loop) up to one-meson-loop corrections beyond mean
field. We also discuss implications for the lattice simulations and confirm
good quantitative agreement between our prediction and existing lattice QCD
results. Therefore the phase quenching provides rather accurate answer already
at N_c=3 with small 1/N_c corrections which can be taken into account by the
phase reweighting.
Nutzer