One-loop four-graviton string amplitude at finite $\alpha'$
Abstract
We evaluate the one-loop four-graviton scattering amplitude in type-II superstring theory exactly in \alpha' α ′ . This result is achieved by combining physical insights into the i\varepsilon i ε prescription in string theory with a new technical application of the Rademacher expansion of modular integrals. We provide an implementation of our formula in \texttt{C++} 𝙲++ and use it to study the behavior of the amplitude at finite \alpha' α ′ and in different kinematic regimes. Our analysis reveals a tension between explicit computations and the saddle point analysis of Gross and Mende in the high-energy limit and suggests the presence of additional saddle points.
Fields of Study & Subjects
Black Holes and Theoretical Physics
Quantum Chromodynamics and Particle Interactions
Algebraic structures and combinatorial models
Publication details
- Journal / source
- SciPost Physics
- Publisher
- Stichting SciPost
- Volume
- 20
- Issue
- 2
- Publication date
- 23 February 2026
- Language
- EN