Novel Signatures of Relativistic Particle Production in Cosmology

• Applicant: Kim Berghaus, Ph.D.
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 548044346

The main objective of my research program is to systematically progress the theoretical understanding of dissipative particle production processes in cosmology, approaching key open questions from various interconnected directions. I will develop open-access tools in the process, enabling detailed studies of dissipative particle production in cosmology in the ongoing era of precision cosmology. My program will make an important contribution to the field of warm inflation, paving the road towards a potential discovery of warm non-gaussianities, a smoking gun prediction of warm inflation, within the next decade. The specific milestones I aim to achieve are to mitigate theoretical uncertainty in key warm inflation observables and modeling. Addressing a discrepant literature by obtaining state-of-the-art predictions for non-gaussianities in warm inflation from two independent methods, I will facilitate a timely search for the warm non-gaussianities in incoming data from the Simons Observatory [9], EUCLID, SPHEREx, and SKA. I will also for the first time obtain results for the warm inflation trispectrum. Furthermore, I will employ numerical lattice simulations to investigate sphaleron heating as a compelling model of warm inflation and evaluate its robustness to initial conditions, and test its dynamics beyond current analytical descriptions. In parallel, my program will explore the undeveloped model landscape of warm inflation via sphaleron heating and its promising connections to the Standard Model, and other open puzzles such as the apparent conservation of charge parity symmetry in QCD, the observed baryon asymmetry, and dark matter, as well as their signatures at future colliders. Making connections to the late universe, my research will identify novel signatures of models with rolling scalar fields that feature non-thermal particle production throughout cosmological history. Going beyond fluid approximations, my group and I will pioneer tools that allow for an accurate description of the full model dynamics, and robustly assess their viability as solutions to the Hubble tension. We will also systematically explore novel predictions for dark energy observables in this class of scalar field models. Making our newly developed tools open-access, we will initiate an effort in which the scientific community can readily confront scalar field models motivated from first principles with precision cosmological data. This work will long-term contribute towards identifying what fundamental theories are viable foundations of the phenomenological ΛCDM model and its extensions.

• DFG Programme: Emmy Noether Independent Junior Research Groups