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Abstract
摘要 |
Assuming perturbative (tree-level) unitarization of the S-matrix imposes strong constraints on the spectrum of the theory's UV completion. The famous example being upper bound for the Higgs mass. In this talk we will show that when applied to theories with massless three-point interactions, violations of unitarity inevitably appear at the scale of the newly introduced particle. This forces the theory to include an infinite tower of massive particles. Assuming factorized form of the S-matrix forces integer spacing of m^2. For gravity this leads to two solutions for the four-point scattering. For non-renormalizable scalar theories without a three-point massless interaction, we will show that only DBI action can be unitarized. This rules out perturbative completion for a large class of effective theories with Galilean symmetry, including the DGP model. |
