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arXiv · 2506.05969

Gauge-invariant action for free string field theory with boundary

Carlo Maccaferri·Alberto Ruffino·Jakub Vošmera
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Abstract

We construct fully gauge-invariant kinetic terms for open and closed string field theories on a target space with boundary. This is realized by promoting the gauge parameters at the boundary to extra dynamical modes describing boundary degrees of freedom. Having a gauge-invariant classical action, we also construct the corresponding BV master action and show that the master equation is obeyed thanks to a peculiar nilpotent structure of the BV kinetic operator. From this general construction we explicitly derive free actions for massless and massive modes of open and closed strings propagating on a target with a boundary, including linear-dilaton backgrounds.

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Carlo Maccaferri, Alberto Ruffino, Jakub Vošmera. 2026-02-07. Gauge-invariant action for free string field theory with boundary. https://arxiv.org/abs/2506.05969

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