Thermal RG Flow of AS Quantum Gravity

Abstract

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 $T\equiv k_T=\tau k$ (in natural units) in order to determine its thermal evolution in terms of the dimensionless temperature $\tau$ 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 $\tau$ producing the quantum effective action at a given dimensionless temperature. The $\tau$-evolution of the dimensionless Newton coupling $g(\tau )$ and the dimensionless cosmological constant $\lambda (\tau )$ results in a vanishing $g$-coordinate of the Reuter (i.e., non-Gaussian UV) fixed point in the high temperature limit ($\tau \to \infty$) which means that only the symmetric phase of AS gravity survives at $\tau =\infty$. 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.

7 pages, 5 figures, final version, published in Phys. Lett. B

References in corpus (10)

• Exact evolution equation for the effective potential
• Asymptotically Safe Lorentzian Gravity
• Background Independence and Asymptotic Safety in Conformally Reduced Gravity
• Conformal sector of Quantum Einstein Gravity in the local potential approximation: non-Gaussian fixed point and a phase of unbroken diffeomorphism invariance
• Higgs Criticality beyond the Standard Model
• Dimensional regularization, Wilsonian RG, and the Naturalness/Hierarchy problem
• Physical Tuning and Naturalness
• On the ultraviolet behavior of conformally reduced quadratic gravity
• Time Evolution and Thermal Renormalization Group Flow in Cosmology
• On the Lorentz symmetry in conformally reduced Quantum Gravity

Cited by in corpus (1)

• From negative to positive cosmological constant through decreasing temperature of the Universe: connection with string theory and spacetime foliation results