Galaxies and cosmology

The formation and evolution of galaxies critically depends on the cosmological boundary conditions which are currently subject to much discussion. The reason why the standard LCDM model of cosmology is under discussion is due, last not least, to the highly significant findings that unexpectedly-massive galaxies formed at redshifts larger than 10, that the local measurements of the expansion rate of the Universe differ from the global ones (the „Hubble tension“), that the tests for the existence of dark matter particles using Chandrasekhar dynamical friction show dark matter particles to be non-existent, as well as many other major failures. Depending on the detailed interests of the PhD student, this project will involve dark-matter-free numerical simulations with star formation of interacting galaxies in compact groups, of the formation and evolution of galaxies of different masses, and can also involve studies of the stellar populations in galaxies based on a physically-varying stellar initial mass function. The project might also include simulations of structure formation in a non-LCDM cosmology. The methods will rely on using suitable simulations codes as already used in the research group (based on the RAMSES code) and the IGIMF theory. This work will be conducted in collaboration with scientists in Prague and in China (Dr. Eda Gjergo, Dr. Zhiqiang Yan), Canada (Dr. Nikolaos Samaras), the University of Bonn (Dr. Ingo Thies, Dr. Jan Pflamm-Altenburg and others), Masaryk University (Dr. Tereza Jerabkova) and may involve a collaboration with an Australian team. Interested students are expected to have a documented track record of activities related to the astrophysics of galaxies and/or computer simulations and to be particularly interested in exploring the problems without dark matter. The student will be funded through Charles University and the Astronomical Institute.

Examples of recent research papers:

„Dynamical Friction Constraints on the Dark Matter Hypothesis Across Astronomical Scales“ (Hernandez & Kroupa, 2025arXiv251103776H)
„On the initial conditions of the νHDM cosmological model“ (Samaras et al., 2025MNRAS.541..784S)
„The impact of early massive galaxy formation on the cosmic microwave background“ (Gjergo & Kroupa, 2025NuPhB101716931G)
„Massive Star Formation at Supersolar Metallicities: Constraints on the Initial Mass Function“ (Gjergo et al., 2025arXiv250920440G)
„The many tensions with dark-matter based models and implications on the nature of the Universe“ (Kroupa, Gjergo et al., 2023eppg.confE.231K)
„Has JWST Already Falsified Dark-matter-driven Galaxy Formation?“ (Haslbauer et al., 2022ApJ…939L..31H)
„Star formation triggered by galaxy interactions in modified gravity“ (Renaud et al., 2016MNRAS.463.3637R)