Critical line from imaginary to real baryonic chemical potentials in two-color QCD

The method of analytic continuation from imaginary to real chemical potentials $\mu$ is one of the few available techniques to study QCD at finite temperature and baryon density. One of its most appealing applications is the determination of the critical line for small $\mu$: we perform a direct test of the validity of the method in this case by studying two-color QCD, where the sign problem is absent. The (pseudo)critical line is found to be analytic around ${\mu }^2=0$, but a very large precision would be needed at imaginary $\mu$ to correctly predict the location of the critical line at real $\mu$.