Scattering amplitudes of massive spin-2 particles generically grow with energy and lead to violations of perturbative unitarity. One way to partially soften such amplitudes is with the infinite towers of particles present in Kaluza-Klein theories. In this talk I will discuss in detail this mechanism of unitarization for general dimensional reductions of pure gravity and show that it leads to some interesting constraints on the eigenfunctions and eigenvalues of the scalar Laplacian on closed manifolds. A consequence of these constraints is that there exists an upper bound on the gaps between Kaluza-Klein excitations of the graviton in Calabi-Yau compactifications of string theory.

James Bonifacio is a theoretical physicist who received his DPhil from the University of Oxford in 2017 and is currently working as a postdoctoral researcher at Case Western Reserve University. His research involves the use of effective field theories to study gravity and cosmology. He is especially interested in using symmetries and scattering amplitudes as theoretical tools to classify and constrain quantum field theories.