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arXiv · 2509.24703

Aspects of strings without spacetime supersymmetry

Giorgio Leone·Salvatore Raucci
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Abstract

String theory relies on spacetime supersymmetry to guarantee the existence of stable vacua. In this review, we survey two features of non-supersymmetric strings that challenge both aspects: the appearance of tachyons and worldsheet tadpoles. We describe how tachyons arise, how to characterise their presence in closed strings and in their orientifold projections, and how off-shell approaches can be used to tackle them. We then turn to tachyon-free, non-supersymmetric strings. After introducing the simplest ten-dimensional models, we address the additional issues raised by tadpoles and the spacetime consequences of their cancellation. Finally, we discuss recent attempts to explore the non-supersymmetric string landscape.

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Giorgio Leone, Salvatore Raucci. 2025-09-29. Aspects of strings without spacetime supersymmetry. https://doi.org/10.1007/s40766-025-00078-z

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