Quantum Chromodynamics (QCD) exhibits striking emergent phenomena when matter is driven to extreme temperatures and densities. Extreme temperatures can be achieved experimentally by colliding heavy nuclei at relativistic energies, producing a short-lived droplet of quark–gluon plasma (QGP), the state of matter that filled the early universe a microsecond after the Big Bang. By contrast, relatively cold but extremely dense QCD matter resides in the interiors of neutron stars. This talk will explore the efforts to map complementary regions of the QCD phase diagram by integrating insights from collider experiments and astrophysical observations.
I will show how observables from heavy-ion collisions reveal key QCD features—such as deconfinement and approximate chiral symmetry restoration—and how recent advances in theoretical modeling, combined with Bayesian inference, are constraining fundamental properties of QCD matter. I will discuss how collisions at varying energies are being used to map the QCD phase diagram, including searches for a critical point and a first-order phase transition. Finally, I will highlight how tools developed for heavy-ion phenomenology can be repurposed to probe even denser regimes relevant to neutron stars and neutron star mergers, deepening our understanding of the emergent properties of QCD matter across different regions of the phase diagram.