TRR 211:  Strong-Interaction Matter under Extreme Conditions

Subject Area Physics
Term since 2017
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 315477589
 

Project Description

In the first instants of the Big Bang and during neutron-star mergers (NSMs), matter exhibits extremes of temperature and density, which are of great observational and theoretical importance and where matter is dominated by the strong interaction. A major experimental effort is underway at laboratories around the world to reproduce and study these conditions through heavy-ion collisions (HICs). The CRC-TR 211 ``Strong-interaction Matter under Extreme Conditions'' seeks to provide the matching theoretical effort to describe these experiments and observations by applying the theory of the strong interaction, QCD, to these environments. The work is carried out under subprojects, which are divided thematically into two groups. One set of projects works to improve our understanding of the properties and behavior of strong-interaction matter under extreme conditions, using techniques grounded in QCD. The other set applies these results to make predictions and interpret data in HICs, early-Universe cosmology, and NSMs.The main challenge to predicting the behavior of strong-interaction matter under extreme conditions is that it involves QCD in a regime where the interactions between constituents are strong and the behavior is relativistic. The most reliable tool in this regime simulates the constituent fields of QCD, the quark and gluon fields, numerically in discretized space-time: lattice QCD. We use this approach extensively to study thermodynamical properties across many regimes, some of them little studied in the lattice community. This methodology encounters problems when treating large chemical potentials or when studying real-time phenomena, so we extend our theoretical reach by including effective theories, by using analytical continuation techniques, and by using systematically improvable approximation schemes such as the Functional Renormalization Group. These methodologies are tested against lattice methods and then used to extend our theoretical range. This allows an exploration of the phase structure, thermodynamical potential, and dynamical-response coefficients of strong-interaction matter in a wide range of extreme conditions.In applying these results to HICs, the early Universe, and NSMs, we take advantage of the fact that strong-interaction matter shows strong collective behavior. This enables theoretical descriptions built around hydrodynamic response, which we use to predict the behavior of HICs and NSMs, and which we extend by developing an understanding of the role of spin in relativistic hydrodynamics. We also apply our understanding of QCD to predict the behavior of heavy quarks, high-energy particles (jets), and electromagnetic signals in HICs, and weak-interaction phenomena in NSMs. And we study how the strong interaction may play a role in Dark-Matter formation and in primordial gravitational waves.
DFG Programme CRC/Transregios

Current projects

Completed projects

Applicant Institution Technische Universität Darmstadt
Co-Applicant Institution Goethe-Universität Frankfurt am Main; Universität Bielefeld
Spokespersons Professor Dr. Guy Moore, from 7/2021 until 6/2025; Professor Dr. Dirk H. Rischke, until 6/2021; Professor Dr. Sören Schlichting, since 7/2025