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arXiv · 2605.12414

An Inconsistency in the Null Strings Literature: The Tale of an Overlooked Symmetry

M. M. Sheikh-Jabbari·H. Yavartanoo
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Abstract

Null strings, strings with $2d$ null worldsheets, have about half a century of literature and are relevant in many physically interesting cases, especially when strings probe cosmological or black hole horizons. We observe that the null string action possesses a previously overlooked local symmetry, the consideration of which is necessary for the consistency of null string analyses. By correctly accounting for this symmetry, we show that the number of physical propagating degrees of freedom of null strings in $D$ dimensional target space is $D-3$, in contrast to $D-2$ that one finds in the literature. In other words, null strings probe a codimension-1 null surface on a $D$ dimensional target space. The existence of this overlooked symmetry calls for a thorough revision of results in the null string literature. We briefly mention some of its physical consequences.

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M. M. Sheikh-Jabbari, H. Yavartanoo. 2026-05-12. An Inconsistency in the Null Strings Literature: The Tale of an Overlooked Symmetry. https://arxiv.org/abs/2605.12414

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