Path integral measure, cutoffs and the Cosmological Constant

by Carlo Branchina

Wednesday 13 Nov 2024, 14:30 → 15:30 Europe/Rome

Room 281 (Physics and astronomy department)

It has been known for a long time that the calculation of the (euclidean) effective action in quantum gravity gives rise to quartic and quadratic UV-sensitive contributions to the vacuum energy. The comparison of this result to the measured value of the latter, inferred from the observed accelerated expansion of the universe, reveals an extremely severe naturalness problem that represents the strongest facet of the "cosmological constant problem". To get rid of these contributions, a SUSY embedding of the theory is typically invoked. In this talk, I will show that the appearance of these UV-sensitive terms is due to an incorrect treatment of the measure in the gravitational path integral. We will see that, when the measure is carefully treated, these contributions completely disappear and the vacuum energy only presents a mild logarithmic sensitivity to the UV scale. I will then show why usual calculations give rise to quartic and quadratic UV-terms.