Unimodular time in JT gravity: a holographic clock
Fuente:
arXiv
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| Autori principali: | , |
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| Natura: | Preprint |
| Pubblicazione: |
2026
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| _version_ | 1866918285740605440 |
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| author | Etkin, Altay Rassouli, Farbod-Sayyed |
| author_facet | Etkin, Altay Rassouli, Farbod-Sayyed |
| contents | How is a ''bulk clock'' encoded holographically? We address this in Jackiw-Teitelboim (JT) gravity, where a natural physical clock emerges by promoting the vacuum energy to a dynamical variable: the vacuum cosmological constant becomes a top form degree of freedom conjugate to spacetime volume, thereby defining a notion of bulk physical time. This construction is naturally formulated in the Henneaux-Teitelboim (HT) framework. We show that the boundary dynamics is the Schwarzian mode coupled to a free particle on $U(1)$, matching the universal low-energy effective action of the complex SYK model. By further clarifying the role of the vacuum cosmological constant as a top form, we establish the equivalence between JT gravity coupled to two-dimensional Maxwell theory and 2d HT gravity via an explicit field redefinition. The initial question is addressed: we show that the resulting boundary theory can itself be rewritten as an observer action, equivalently a $(0+1)$-dimensional HT theory. This yields a direct identification of the boundary clock with the $U(1)$ phase mode, and makes its relation to the bulk clock explicit. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_07911 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Unimodular time in JT gravity: a holographic clock Etkin, Altay Rassouli, Farbod-Sayyed High Energy Physics - Theory General Relativity and Quantum Cosmology How is a ''bulk clock'' encoded holographically? We address this in Jackiw-Teitelboim (JT) gravity, where a natural physical clock emerges by promoting the vacuum energy to a dynamical variable: the vacuum cosmological constant becomes a top form degree of freedom conjugate to spacetime volume, thereby defining a notion of bulk physical time. This construction is naturally formulated in the Henneaux-Teitelboim (HT) framework. We show that the boundary dynamics is the Schwarzian mode coupled to a free particle on $U(1)$, matching the universal low-energy effective action of the complex SYK model. By further clarifying the role of the vacuum cosmological constant as a top form, we establish the equivalence between JT gravity coupled to two-dimensional Maxwell theory and 2d HT gravity via an explicit field redefinition. The initial question is addressed: we show that the resulting boundary theory can itself be rewritten as an observer action, equivalently a $(0+1)$-dimensional HT theory. This yields a direct identification of the boundary clock with the $U(1)$ phase mode, and makes its relation to the bulk clock explicit. |
| title | Unimodular time in JT gravity: a holographic clock |
| topic | High Energy Physics - Theory General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2601.07911 |