1:30 pm MCP 201
Bounds on spin-two Kaluza-Klein fields.
I will show that in a broad class of gravity theories, including supergravity in 10 and 11 dimensions, the masses of Kaluza Klein spin-two modes obey several inequalities. This follows from a lower bound on a combination of the Ricci tensor and the warping, which plays an important role in so-called Bakry–Émery geometry and in the theory of optimal transport. The latter framework allows to extend the results to non-smooth spaces, such as those with D-brane singularities. Using a generalization of the so-called Cheeger constant, I will show that, when the internal space consists of small bridges connecting larger manifolds, the KK spectrum contains very light massive spin-two fields. This scenario is realized in explicit string-theory compactifications, which I will describe if time permits.