Correlations among discontinuities in QCD phase diagram

Understand

We show, in general, that when a discontinuity of either zeroth-order or first-order takes place in an order parameter such as the chiral condensate, discontinuities of the same order emerge in other order parameters such as the Polyakov loop.

• A condition for the coexistence theorem to be valid is clarified.
• Consequently, only when the condition breaks down, zeroth-order and first-order discontinuities can coexist on a phase boundary.
• We show with the Polyakov-loop extended Nambu--Jona-Lasinio model that such a type of coexistence is realized in the imaginary chemical potential region of the QCD phase diagram.