From heavy ion and neutron star collisions to the Big Bang

Collaborative Research Centre Transregio 211 to be funded for another four years


The Collaborative Research Centre Transregio “Strongly Interacting Matter under Extreme Conditions”, a joint initiative of the Technical University of Darmstadt, Goethe University Frankfurt and Bielefeld University, has been investigating the most extreme states of matter found in the universe since July 2017. Now the German Research Foundation (DFG) is funding this Transregio (SFB-TRR) 211 for another four years with 8.9 million euros. The new spokesperson is Professor Guy Moore, nuclear physicist at TU Darmstadt. He takes over this function from Professor Dirk Rischke, who researches and teaches at Goethe University Frankfurt. The Transregio also strengthens the cooperation within the Strategic Alliance of Rhine-Main Universities (RMU), which Goethe University Frankfurt, TU Darmstadt, and Johann Gutenberg University Mainz formed in 2015.

The SFB-TR 211 investigates the collision of heavy ions and neutron stars under extreme conditions. The simulation image shows the density of two neutron stars that have merged.

What happens when normal matter is compressed or heated so much that the atomic nuclei overlap and fuse together? Matter then enters a new state whose properties are determined by the “strong interactions,” i.e., the force that binds the protons and neutrons together in the atomic nucleus. This strong interaction also generates the binding between the inner building blocks of the protons and neutrons – the quarks and gluons – and these fundamental building blocks ultimately dominate the properties of matter under extreme conditions.

Such boundary-breaking environmental influences – such as temperatures of more than a trillion degrees and densities of more than one hundred million tonnes per cubic centimetre, which are many orders of magnitude higher than in the centre of the sun – are achieved in heavy ion collisions, which are currently being experimentally investigated at the Relativistic Heavy Ion Collider (RHIC) in New York, at the Large Hadron Collider (LHC) at CERN in Geneva, and in the near future at the FAIR accelerator facility in Darmstadt. Furthermore, such conditions also prevail during the merging of neutron stars, which are among the most powerful astrophysical events and were detected for the first time in 2017 by measuring gravitational waves. Similar conditions also occurred in the first 10 microseconds after the Big Bang and therefore have an impact on the structure and content of the universe today.

Reasons enough, therefore, to investigate the theoretical basis of strongly interacting matter more intensively and to predict its behaviour in experiments, astrophysics, and cosmology. This is the main purpose of the SFB-TRR 211, a collaboration of 24 project leaders and their working groups, with a total of more than 100 researchers involved in 13 subprojects. They explore the theoretical underpinnings of the theory using large-scale numerical investigations on supercomputers using the tools of lattice gauge theory, and also by utilising analytical attempts to probe this fundamental interaction. At the same time, they apply these theoretical advances to make predictions of specific experimental and astrophysical phenomena. The combined expertise of the scientists from the three partner universities is unique worldwide.

The new spokesperson of TRR 211, Professor Guy Moore, says: “We are thrilled that the DFG has recognised our expertise and hard work over the last few years and look forward to continuing our research until mid-2025 – and hopefully in a third funding period in the future.”

TRR 211/feu