Speaker
Description
One of the most important open questions in cosmology is the so-called Hubble tension, which is an apparent disagreement between local universe measurements of the present-time Hubble parameter and measurements inferred from early-universe observations under the assumption of the $\Lambda$CDM model, which supplements general relativity (GR) with a cosmological constant $\Lambda$ and cold dark matter (CDM). Numerous modified theories have been studied in order to address this open question. While a large class of these models describes gravity as the curvature of spacetime, as it is the case in general relativity, an alternative class of theories employ a different mathematical background based on torsion and / or nonmetricity, while curvature is absent. In my talk I give an overview of such models and their cosmological dynamics. In particular, I will focus on quadratic teleparallel theories, which are motivated by their similarity to Yang-Mills theories, and thus share some common features with theories encountered in particle physics. To discuss the qualitative phenomenological features, I make use of the method of dynamical systems, which allows in particular studying the late-time behavior of the solutions. I will present several current results on cosmological attractor solutions.