Enhancement of quark number susceptibility with an alternative pattern of chiral symmetry breaking in dense matter

Understand

We explore a possible phase where chiral $SU(2)_L \times SU(2)_R$ symmetry is spontaneously broken while its center $Z_2$ symmetry remains unbroken and its consequence on thermal quantities.

• In this phase, chiral symmetry breaking is driven by a quartic quark condensate although a bilinear quark condensate vanishes.
• A Ginzburg-Landau free energy leads to a new tricritical point (TCP) between the $Z_2$ broken and unbroken phases.
• Furthermore, a critical point can appear even in the chiral limit where explicit breaking is turned off, instead of a TCP at which restoration of chiral and its center symmetries takes place simultaneously.