H0 tension: cracks in standard cosmology?

• Deanna Hooper

Local measurements of the Hubble constant are increasingly in tension with the value inferred from a LCDM fit to the cosmic microwave background and baryon acoustic oscillation data. This discrepancy, now at almost 5 sigma, calls for greater scrutiny on all of the measurements involved, and even questions the robustness of our standard cosmological model. In light of this cosmological crisis, many alternatives and extensions to LCDM have been proposed in the literature as a solution to this tension; however, none of the currently proposed solutions are entirely satisfactory. In this talk I will review the early and late time measurements involved in this tension, and discuss possible systematics or problems within these data. I will then present an overview of the different classes of solutions, and the challenges these models face. Finally, I will discuss the properties that a complete solution should have to fully address the Hubble tension, and I will argue that the next decade will make or break LCDM.