# Exact thresholds and instanton effects in D=3 string theories

Abstract : Three-dimensional string theories with 16 supersymmetries are believed to possess a non-perturbative U-duality symmetry $SO(8,24,\\Zint)$. By covariantizing the heterotic one-loop amplitude under U-duality, we propose an exact expression for the $(\\partial \\phi)^4$ amplitude, that reproduces known perturbative limits. The weak-coupling expansion in either of the heterotic, type II or type I descriptions exhibits the well-known instanton effects, plus new contributions peculiar to three-dimensional theories, including the Kaluza-Klein 5-brane, for which we extract the summation measure. This letter is a post-scriptum to hepth/0001083.
Document type :
Journal articles

https://hal.archives-ouvertes.fr/hal-00016310
Contributor : Boris Pioline Connect in order to contact the contributor
Submitted on : Monday, December 26, 2005 - 4:24:16 PM
Last modification on : Tuesday, November 16, 2021 - 5:00:52 AM

### Citation

N. A. Obers, B. Pioline. Exact thresholds and instanton effects in D=3 string theories. Journal of High Energy Physics, Springer, 2000, 0007, pp.003. ⟨hal-00016310⟩

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