Speaker: Lucas Lombriser (University of Geneva)
Title: 
Towards a Deeper Understanding of our Cosmos: A Question of Life, the Universe and Everything
Abstract: 
In a first part, I will focus on some persistent gaps in our understanding of the cosmic expansion. The cosmological constant provides a simple explanation of the observed late-time accelerated expansion, but we are confronted with a vacuum energy and coincidence problem. I will first discuss how the measurement of the speed of gravitational waves severely challenges modifications of General Relativity as an alternative explanation of comic acceleration. I will then present a simple solution to both the old and new aspects of the cosmological constant problem with a global Planck mass variation. Finally, I will argue that there is no Hubble tension but rather the discrepant measurements are to be expected from conducting cosmological observations out of a small local void. Accounting for our local underdensity moreover dispenses with the need for an artificially enhanced lensing amplitude in the CMB and brings the current amplitude of matter fluctuations inferred from the CMB and galaxy surveys into agreement. In a second part, I will briefly present some new tools that can be used with forthcoming nonlinear cosmological data in the search for New Physics, which is hoped to provide new hints for establishing a more fundamental understanding of Nature. I will then discuss the Emergence of Life in our Universe as a complementary approach to a deeper understanding of the known physics. I will first revisit the Why Now? problem of the cosmological constant in this context and then examine fine-tuning arguments for the cosmological parameters and fundamental constants and laws of Nature. Finally, I will present a new project for determining the probabilities for the Emergence of Life across the multiverse as a means to establish a better understanding of our own Universe.