Thermal RG Flow of AS Quantum Gravity
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arXiv
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2025
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| author | Nyergesy, E. Márián, I. G. Meskhi, E. Turovtsi-Shiutev, Y. Nandori, I. |
| author_facet | Nyergesy, E. Márián, I. G. Meskhi, E. Turovtsi-Shiutev, Y. Nandori, I. |
| contents | We perform the thermal Renormalization Group (RG) study of the Asymptotically Safe (AS) quantum gravity in the Einstein-Hilbert truncation by relating the temperature parameter to the running RG scale as $T \equiv k_T = τk$ (in natural units) in order to determine its thermal evolution in terms of the dimensionless temperature $τ$ which is associated with the temperature of the expanding Universe. Thus, $k_T$ and $k$ are understood as running cutoffs for thermal and quantum fluctuations, respectively. Quantum effects are taken into account by moving along the thermal RG trajectory with fixed value of $τ$ producing the quantum effective action at a given dimensionless temperature. The $τ$-evolution of the dimensionless Newton coupling $g(τ)$ and the dimensionless cosmological constant $λ(τ)$ results in a vanishing $g$-coordinate of the Reuter (i.e., non-Gaussian UV) fixed point in the high temperature limit ($τ\to \infty$) which means that only the symmetric phase of AS gravity survives at $τ= \infty$. Thus, in case of large temperatures the cosmological constant takes on a negative value in the limit $k\to 0$ which was also initially predicted by certain string theories, however, in our approach this is not in disagreement with observations, since during the thermal evolution of the Universe a phase transition occurs and the cosmological constant runs to the expected positive value at low temperatures. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2501_02878 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Thermal RG Flow of AS Quantum Gravity Nyergesy, E. Márián, I. G. Meskhi, E. Turovtsi-Shiutev, Y. Nandori, I. General Relativity and Quantum Cosmology High Energy Physics - Theory We perform the thermal Renormalization Group (RG) study of the Asymptotically Safe (AS) quantum gravity in the Einstein-Hilbert truncation by relating the temperature parameter to the running RG scale as $T \equiv k_T = τk$ (in natural units) in order to determine its thermal evolution in terms of the dimensionless temperature $τ$ which is associated with the temperature of the expanding Universe. Thus, $k_T$ and $k$ are understood as running cutoffs for thermal and quantum fluctuations, respectively. Quantum effects are taken into account by moving along the thermal RG trajectory with fixed value of $τ$ producing the quantum effective action at a given dimensionless temperature. The $τ$-evolution of the dimensionless Newton coupling $g(τ)$ and the dimensionless cosmological constant $λ(τ)$ results in a vanishing $g$-coordinate of the Reuter (i.e., non-Gaussian UV) fixed point in the high temperature limit ($τ\to \infty$) which means that only the symmetric phase of AS gravity survives at $τ= \infty$. Thus, in case of large temperatures the cosmological constant takes on a negative value in the limit $k\to 0$ which was also initially predicted by certain string theories, however, in our approach this is not in disagreement with observations, since during the thermal evolution of the Universe a phase transition occurs and the cosmological constant runs to the expected positive value at low temperatures. |
| title | Thermal RG Flow of AS Quantum Gravity |
| topic | General Relativity and Quantum Cosmology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2501.02878 |