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Résumé |
Non-Lorentzian geometries arise when the relativistic light-cone structure of general relativity is deformed or contracted. Examples include Newton-Cartan geometry, relevant for non-relativistic limits, and Carrollian geometry, relevant for ultra-local limits. I will begin by briefly reviewing how such structures emerge for particles in general relativity, and then explain how they can be generalized to extended objects, such as strings and p-branes.I will subsequently focus on how non-Lorentzian geometry appears in string theory. In particular, near-BPS and decoupling limits of string/M-theory often isolate protected sectors in which the underlying spacetime geometry becomes non-Lorentzian. This provides a geometric language for non-relativistic strings, matrix-theory-type limits and AdS/CFT, as well as extensions of holography beyond the standard AdS/CFT setting. A central aim is to highlight a conceptual bridge: non-Lorentzian geometry offers a systematic way to take singular limits of spacetime, while string theory supplies microscopic settings in which these limits acquire dynamical and holographic meaning. |
