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arXiv · 2112.14609

Flat JT Gravity and the BMS-Schwarzian

Hamid Afshar·Blagoje Oblak
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Abstract

We consider Minkowskian Jackiw-Teitelboim (JT) gravity in Bondi gauge at finite temperature, with non-zero vacuum energy. Its asymptotic symmetries span an extension of the warped Virasoro group, dubbed "BMS$_2$", which we investigate in detail. In particular, we show that this extension has a single coadjoint orbit when central charges are real and non-zero. The ensuing BMS-Schwarzian action has no saddle points, and only coincides with the boundary action functional of flat JT gravity up to a crucial dilatonic zero-mode that ensures the existence of a well-defined bulk variational principle. We evaluate the corresponding gravitational partition function, which turns out to be one-loop exact precisely thanks to the presence of such a zero-mode.

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Hamid Afshar, Blagoje Oblak. 2021-12-29. Flat JT Gravity and the BMS-Schwarzian. https://doi.org/10.1007/jhep11(2022)172

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