Strongly interacting quark-gluon plasma and the critical behaviour of QCD at imaginary µ

We study the highly non-perturbative hot region of the QCD phase diagram close to T_c by use of an imaginary chemical potential µ which avoids the sign problem. The number density and the quark number susceptibility are consistent with a critical behaviour associated with the transition line in the negative µ2 halfplane. These results complement and extend the information obtained via the analysis of the susceptibilities evaluated at zero µ, yielding a simple description of the candidate strongly interacting QGP phase.