The dense-matter equation of state from QCD and effective theories with parity doubling

• Applicant: Dr. Jürgen Eser
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565402889

The research project investigates the equation of state of dense neutron-rich matter. It concerns matter in the range of medium to large baryon densities and moderate temperature, as found in the inner cores of neutron stars, in neutron-star mergers, as well as in matter produced in relativistic heavy-ion collisions. Our current knowledge of the properties of matter under such conditions, where lattice calculations and perturbative techniques fail, is still very limited. The aim of the project is to foster our understanding of the phase structure of dense neutron-rich matter based on an effective nucleonic theory, which is commonly referred to as the parity-doublet model. This effective theory and its parameters will be derived from the fundamental interactions of Quantum Chromodynamics using the non-perturbative functional renormalization group approach and dynamical hadronization. In contrast to many similar relativistic models, the parity-doublet model accommodates a nucleon mass that is compatible with the chiral symmetry of Quantum Chromodynamics. The model has also received support from lattice calculations. The chiral-invariant nucleon mass is expected to have a large impact on the phase structure at large baryon density, which makes the model particularly interesting. Furthermore, we will look for indications of quark and diquark degrees of freedom as the density increases, and eventually confront the equation of state with observations of neutron stars.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Professor Dr. Jean-Paul Blaizot