The QCD phase diagram: recent advances, and its significance in modern physics

Understanding strong interactions in hot and/or dense matter is one of the toughest, but also most interesting, challenges in modern physics. Within the standard model of particle physics, strong interactions are successfully described as gluon-mediated interactions among quarks by Quantum Chromodynamics (QCD). The phase diagram of QCD, in the temperature-baryon density plane, is very rich and includes many different phases, namely the confinement phase, the quark-gluon plasma phase at high temperature, the very dense phases and so on. We delve into recent advancements in our comprehension of this complex phase diagram. Researchers have made significant progress by employing a combination of theoretical tools, including Lattice QCD simulations, Schwinger-Dyson equations, Functional Renormalization Group (FRG) methods, and effective models. We student-friendly review the recent progresses on the QCD phase diagram, focusing on the phase transitions at finite baryon chemical potential, and discuss the relevance of this diagram in several problems of modern physics, that include high energy nuclear collisions, the early universe, and the core of compact stellar objects.

[Image in infographics taken, with permission, from D. Avramescu et al., Phys. Rev. D 107, 114021 (2023)]