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Résumé |
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
2512.17828, we simplified our 2024 proof by ultimately connecting the tension to
causality (polynomial boundedness), and extended it to graviton scattering in d=4.
The physical interpretation of the results is clear: from a string’s worldsheet
perspective, the sub-leading trajectories represent ripples on the worldsheet,
hence our no-go suggests that such meromorphic UV-completions must always be
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. This trajectory dominates the amplitude and I’ll
speculate how this might be related to recent studies in the literature that found
single-trajectory like objects in large-N gauge theories and gravity, in apparent
tension with the no-go. |
