Speaker
Description
The violation of the conformal limit for the speed of sound, $c_s^2=1/3$, has emerged as a critical feature of dense strongly interacting matter. Astrophysical observations — including gravitational-wave data from LIGO/Virgo and precise neutron-star radius measurements from NICER — indicate that the equation of state must undergo a rapid stiffening at intermediate baryon densities. This behavior is commonly associated with the emergence of a peak in the speed of sound and may signal the onset of a phase transition in the dense QCD regime.
Direct lattice QCD simulations at finite baryon density are severely hindered by the sign problem. Nevertheless, effective QCD models, as well as lattice-accessible theories such as two-color QCD and QCD at finite isospin chemical potential, provide valuable insight into the nonperturbative dynamics of dense quark matter. These approaches consistently support the existence of a peak in $c_s^2$, in qualitative agreement with astrophysical expectations.
We present and analyze recent analytical and numerical results obtained within effective models of QCD, with particular emphasis on the behavior of the equation of state and its stiffening at intermediate densities. These results help establish a concrete connection between effective theoretical descriptions of dense QCD matter and phenomenological constraints derived from astrophysical observations.
