Surprises on the way to the QCD phase diagram

Lattice results over the last few years are reviewed, which have produced some unexpected insights into the QCD phase structure. The chiral phase transition in the limit of massless quarks is likely of second order for all Nf=2-6, and remains second order independent of the value of an imaginary chemical potential for baryon number. On the other hand, for physical quark masses and zero density an approximate SU (4) chiral spin symmetry is observed to emerge in a temperature range above the chiral crossover Tch, which reduces to the expected chiral symmetry at a second crossover 3Tch. Spectral functions for pseudoscalar mesons, which successfully reproduce both spatial and temporal lattice correlators, show resonance-like peaks above the chiral crossover Tch, suggesting the presence of chirally symmetric, hadron-like thermoparticles in this regime. Implications for the QCD phase diagram are discussed.