FRIB hosts Nuclear Physics and Dense Matter Equation of State Workshop

FRIB hosted the Nuclear Physics and Dense Matter Equation of State Workshop on 8–12 December. The five-day event brought together researchers in nuclear physics, astrophysics, and gravitational-wave science to examine constraints on the dense matter equation of state, with particular attention to the pressure at twice nuclear saturation density. The workshop was organized as part of the scientific program of the International Research Laboratory on Nuclear Physics and Nuclear Astrophysics (IRL-NPA). 

The program featured presentations from invited experts representing institutions in the United States and Europe, including FRIB, Western Michigan University, Texas A&M University, Florida State University, IP2I Lyon, GANIL Caen, GSI Darmstadt, and INFN Catania. 

Sessions focused on theoretical predictions from energy density functionals and ab-initio calculations, constraints from heavy-ion collisions, data from finite nuclei, and astrophysical observations such as neutron-star mergers and X-ray measurements. Discussions examined sources of uncertainty in each approach and assessed areas where independent predictions overlapped or diverged. Building on these exchanges, participants are preparing a joint research paper that will summarize the workshop and address a central question: how matter behaves under pressures found at densities about two times greater than that of an atomic nucleus—conditions approaching those inside neutron stars.

The workshop is the latest activity undertaken within IRL-NPA, which the French research organization National Centre for Scientific Research (CNRS) and Michigan State University (MSU) established at FRIB in July 2023. IRL-NPA supports joint research in nuclear structure and reactions, nuclear astrophysics, nuclear theory, and experimental instrumentation. During its first years, IRL-NPA has enabled CNRS scientists to participate in several FRIB experiments, including studies of proton capture in aluminum-25, neutron-star crust heating and cooling processes, and electromagnetic radiation. It also facilitated collaborative instrumentation projects such as work on the Advanced Rare Isotope Separator (ARIS) and development efforts related to a superconducting electron cyclotron resonance ion source in coordination with GANIL.

IRL-NPA was built on more than four decades of collaboration between CNRS, FRIB, and FRIB’s predecessor, the National Superconducting Cyclotron Laboratory. Joint efforts include detector development for the Active Target Time Projection Chamber (AT-TPC), theoretical work on fundamental interactions and nuclear modeling, and long-standing student training exchanges with French universities. The partnership also aligns with broader MSU–France collaborations, including research grants, international internships, and exchange programs.

The workshop contributed to ongoing CNRS–MSU efforts to advance shared priorities in nuclear science through coordinated international research.

A major player in basic research worldwide, the National Centre for Scientific Research (CNRS) is the only French organisation active in all scientific fields. Its unique position as a multi-specialist enables it to bring together all of the scientific disciplines in order to shed light on and understand the challenges of today's world, in connection with public and socio-economic stakeholders. Together, the different sciences contribute to sustainable progress that benefits society as a whole.

Michigan State University has been advancing the common good with uncommon will for more than 165 years. One of the world’s leading public research universities, MSU pushes the boundaries of discovery to make a better, safer, healthier world for all while providing life-changing opportunities to a diverse and inclusive academic community through more than 400 programs of study in 17 degree-granting colleges.

Michigan State University (MSU) operates the Facility for Rare Isotope Beams (FRIB) as a user facility for the U.S. Department of Energy Office of Science (DOE-SC), with financial support from and furthering the mission of the DOE-SC Office of Nuclear Physics.

The U.S. Department of Energy Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of today’s most pressing challenges. For more information, visit energy.gov/science.