Regge trajectories in meromorphic amplitudes, gravity and polynomial boundedness

05.03.2026 14:00 – 15:00

In this talk I’ll present a theorem regarding meromorphic amplitudes describing the infinite exchange of stable massive higher-spin particles at tree-level. They appear in several context, as weakly coupled UV-complete S-matrices and particularly explicit amplitudes with non-perturbative flavour. For instance they describe large-N gauge theories and weakly-coupled UV completions in gravity.

I will present the results of two papers regarding a no-go theorem showing that such amplitudes must always possess infinitely many Regge trajectories. In our December 2025 paper, we simplified our previous proof by ultimately connecting the tension to causality (polynomial boundedness), and extended it to gravity. The physical interpretation of the results is clear: from a string’s worldsheet perspective, the sub-leading trajectories represent “ripples”, hence our no-go suggests that such UV-completions must always be truly stringy and cannot be frozen to only their leading trajectory.

I’ll start the talk by reviewing basics of S-matrix theory and stringy meromorphic amplitudes. I’ll then present the proof in an elementary manner. I’ll finish by presenting some intriguing numerical results showing that extremal meromorphic amplitudes appear to present the emergence of a mysterious composite “sister” trajectory of slope 1/2 that dominates the amplitude and speculate how this might be related to recent studies in the literature.

Lieu

Bâtiment: Ecole de Physique

Room 234

entrée libre