Throughout the past century, the research field of astrophysics has undergone striking changes, widening the detectable electromagnetic spectrum from the lowest energies at radio wavelengths up to the highest gamma-ray energies. In most recent years, other messengers – in particular cosmic rays, neutrinos, and gravitational waves – have provided highly valuable pieces of information on the nonthermal and violent Universe. This type of multimessenger physics is now in transition to a precision science: on the one hand, the detection of elementary particles in astro(particle) physics is identified to significantly improve our knowledge of the nonthermal Universe and its signatures. On the other hand, the interpretation of these data is in need of precision input concerning the basic properties of matter, for once concerning the behavior of the ensemble (plasma physics), but also the interaction and decay properties of baryonic and dark matter (particle, astroparticle, and astrophysics). In this CRC, we will systematically investigate the interplay of matter and energy with special consideration of plasma and particle physics; particular concern will be given to the energy transfer between magnetic fields, cosmic rays, baryonic matter, and dark matter. In doing so, we will decisively investigate the fundamental properties of matter needed to properly model and understand signatures of nonthermal emission in galaxies. By  bridging the gap between multiple different sub-disciplines in physics – astro-, plasma-, astroparticle-, and particle physics – we aim to reach the central goal of creating a unifying view on cosmic interacting matter.

This CRC, {Cosmic Interacting Matters (CIM)}, is organized into two research areas. For various types of galactic systems, Astrophysical signatures of cosmic-ray transport and interaction (A) will provide the basis for a detailed theoretical description of the nonthermal signatures from astrophysical sources, and we will interpret these results in the light of state-of-the-art data taken within CIM. Work within this research area, though, will benefit greatly from investigation into the Fundamental properties of matter (F). Here, fundamental aspects of the plasma (magnetic turbulence, transport, and instabilities), hadronic interactions (hadronic cross sections and decay products at high energies and in forward direction), and dark matter in low-mass galactic systems build the basis for CIM.

In CIM, we will address the following key research questions:

  1. What  are  the  signatures  of  the  interplay between  magnetized,  turbulent astrophysical  plasmas  and cosmic  rays,  and  what  can  they  tell  us  about  the  origin of  cosmic rays?
  2. What are the implications of precision measurements of hadronic interactions at the highest energies for the astrophysical cosmic-ray signatures?
  3. What  are  the  connections  between  the  cosmic signatures  of  baryonic and  dark matter,  moving  down  to  the lowest  halo  masses  and  out  to  large  galactocentric distances?

We will use the unique combination of expertise in plasma-, astro-, astroparticle- and astrophysics present in the research landscape of the Ruhr-Universität Bochum (RUB), joining forces with our local colleagues from Technische Universität Dortmund and Bergische Universität Wuppertal. By combining theoretical endeavors with contributions to key observations, we will take their interplay to a new level, and decisively tackle fundamental physics problems of the 21st century.