Abstract:
Since the 1990s, a multitude of observations has hinted at an accelerated expansion of the universe, giving Einstein's Cosmological Constant a new role in today's concordance cosmology.
Yet, what is the physical origin of this mysterious form of ``dark energy'' with negative pressure? In this talk, I will introduce observations in the late-time, local universe that can contribute to shed further light into 69% of the cosmic dark sector.
Binary systems in our local neighbourhood can constrain dark energy unbiased of any astronomical foregrounds. With increasing measurement precision and accurate calibration by simulations the weaker dependence on the cosmological background is overcome and complementary bounds to the ones from CMB observations can be attained [1]. This will enable further test of the Cosmological Principle and insights into the nature of dark energy from a new, additional viewpoint.
Could dark energy consist of (primordial) black holes and their impact on astrophysics in their environment? One possibility could be to attribute cosmic expansion to mutually repelling black holes coarse-grained to a background density. The second part of the talk will pursue the question if such super-extremal charged black holes could exist. Contrary to first intuition, the extreme nature of such objects will be shown to have a weak impact on our local universe and observables to select candidate objects will be introduced [2].
Based on
[1] https://arxiv.org/abs/2310.11488
[2] https://arxiv.org/abs/2301.13210
