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Instantons, renormalons and the theta angle in integrable sigma models
by Marcos Marino, Ramon Miravitllas, Tomas Reis
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Submission summary
Authors (as registered SciPost users):  Marcos Mariño · Tomas Reis 
Submission information  

Preprint Link:  https://arxiv.org/abs/2205.04495v3 (pdf) 
Date accepted:  20230927 
Date submitted:  20230828 11:40 
Submitted by:  Reis, Tomas 
Submitted to:  SciPost Physics 
Ontological classification  

Academic field:  Physics 
Specialties: 

Approach:  Theoretical 
Abstract
Some sigma models which admit a theta angle are integrable at both $\vartheta=0$ and $\vartheta=\pi$. This includes the wellknown $O(3)$ sigma model and two families of coset sigma models studied by Fendley. We consider the ground state energy of these models in the presence of a magnetic field, which can be computed with the Bethe ansatz. We obtain explicit results for its nonperturbative corrections and we study the effect of the theta angle on them. We show that imaginary, exponentially small corrections due to renormalons remain unchanged, while instanton corrections change sign, as expected. We find in addition corrections due to renormalons which also change sign as we turn on the theta angle. Based on these results we present an explicit nonperturbative formula for the topological susceptibility of the $O(3)$ sigma model in the presence of a magnetic field, in the weak coupling limit.
Published as SciPost Phys. 15, 184 (2023)
List of changes
1) We clarified the discussion of the deformed "sausage" models to better explain why there are no renormalons in such models. This affects the relevant paragraph in section 1.
2) We added details to the discussion of the nonperturbative effects in the coset sigma models to clarify why some are classified as instantons and other as renormalons, as well as the implications of such distinction. This affects the end of section 4.2 and a little bit of section 5.
3) We updated the references to the convention where Alexei Zamolodchikov is referred as Al. B. Zamolodchikov while Alexander Zamolodchikov is referred as A. B. Zamolodchikov.
Submission & Refereeing History
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