Introducing the concept of the Widom line in the QCD phase diagram

Abstract

Critical phenomena emerging from the critical end point of a first-order transition are ubiquitous in nature. Here we bring the concept of a supercritical crossover, the Widom line, initially developed in the context of fluids, into the interacting matter described by quantum chromodynamics (QCD). We show that the existence of the putative critical end point between hadron gas and quark-gluon plasma in the temperature versus chemical potential of the QCD phase diagram implies the existence of a Widom line emerging from it in the supercritical region. We survey the thermodynamic anomalies already identified in simplified theoretical models of QCD exhibiting a critical end point, to show that they can be interpreted in terms of a Widom line. Then we suggest possible directions where the Widom line concept could provide new light on the QCD phase diagram.

arXiv comment8 pages, 5 figures; accepted version

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• Towards a unified hadron-quark equation of state for neutron stars within the relativistic mean-field model
• Higgs Phases and Boundary Criticality
• Ambipolar doping of a charge-transfer insulator in the Emery model
• Many-body critical phase in a quasiperiodic chain and dynamical Widom lines in Fock space properties
• Supercritical-subcritical correspondence, asymmetric effects and antisymmetric corrections near a critical point
• Quantum Supercritical Crossover with Dynamical Singularity
• The Widom line in the Ising model on a decorated bilayer lattice
• The Frenkel line and the pseudogap: an analogy between classical and electronic fluids