New-born strings are tensionless

Sudip Karan; Bibhas Ranjan Majhi

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arXiv · 2604.05173

New-born strings are tensionless

Sudip Karan·Bibhas Ranjan Majhi

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Abstract

We report a physical origin of tensionless strings, obtained by formulating string dynamics in finite-lifetime settings for the first time. Departing from the conventional paradigm of eternal strings, we construct an inertial worldsheet confined to a finite region of two-dimensional Minkowski spacetime, known as a causal diamond. This reveals a striking result: tensionless strings arise only at the moment of their birth. The ultra-shrinking limit of the diamond worldsheet realizes this birth configuration, thereby uncovering a new tensionless string phase characterized by a global, ultra-local Carrollian structure.

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Sudip Karan, Bibhas Ranjan Majhi. 2026-04-06. New-born strings are tensionless. https://arxiv.org/abs/2604.05173

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