On November 2, 2021, at a seminar as part of the iTHEMS-phys seminar series, Dr. Katsuki Aoki (YITP, Kyoto University) delivered a talk on the topic of consistency conditions on the Standard Model of particle physics imposed from the requirements of a more fundamental ultraviolet (UV) theory. Underlying assumptions on UV completion can impose constraints on its low-energy effective field theories (EFTs). The swampland program aims to clarify consistent and inconsistent EFTs with quantum gravity and aims to understand quantum gravity from low-energy physics and vice versa. One of the most well-established constraints is called positivity bounds, provided that general assumptions such as Poincare invariance and unitarity are satisfied at all scales. Dr. Aoki first explained how these consistency conditions arise especially in the presence of gravity. He then showed that the positivity bound is violated if the Standard Model coupled to General Relativity is extrapolated up to 10^16 GeV, requiring new physics there or below. The precise value of the cutoff is determined by hadronic physic while it is insensitive from non-gravitational physics beyond the Standard Model. This is a signal from established physics for the necessity of quantum gravity below 10^16 GeV.

Reported by Ryo Namba