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arXiv · 2601.08973

On string loops in Calabi-Yau orientifolds in large volume

Manki Kim
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Abstract

We explain and illustrate how to compute string-loop amplitudes in Calabi-Yau orientifold compactification in the large volume limit with the help of the patch-by-patch description of string field theory. We compute the one-loop partition function of the D1-instanton in type IIB string theory compactified on an O9 orientifold of a Calabi-Yau threefold to the first order in the large volume expansion. We show that the unphysical divergence arising from a naive choice of PCOs is canceled by vertical integration. The corollaries of this result, including the universal part of the normalization of the D-instanton superpotential and the one-loop renormalization of K\"ahler moduli, will be presented elsewhere.

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Manki Kim. 2026-01-13. On string loops in Calabi-Yau orientifolds in large volume. https://arxiv.org/abs/2601.08973

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