Where is tree-level string theory?

• Published in: The journal of high energy physics Vol. 2025; no. 2; pp. 157 - 50
• Main Authors: Albert, Jan, Knop, Waltraut, Rastelli, Leonardo
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 25.02.2025; Springer Nature B.V; SpringerOpen
• Subjects: Classical and Quantum Gravitation; Effective Field Theories; Elementary Particles; Gravity; High energy physics; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Regular Article - Theoretical Physics; Relativity Theory; Scattering; Scattering Amplitudes; String Theory; Supergravity Models; Supersymmetric Gauge Theory; Supergravity Models; Effective Field Theories; Scattering Amplitudes; Supersymmetric Gauge Theory
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP02(2025)157

A bstract We investigate the space of consistent tree-level extensions of the maximal supergravities in ten dimensions. We parametrize theory space by the first few EFT coefficients and by the on-shell coupling of the lightest massive state, and impose on these data the constraints that follow from 2 → 2 supergraviton scattering. While Type II string theory lives strictly inside the allowed region, we uncover a novel extremal solution of the bootstrap problem, which appears to contain a single linear Regge trajectory, with the same slope as string theory. We repeat a similar analysis for supergluon scattering, where we find instead a continuous family of extremal solutions with a single Regge trajectory of varying slope.