scholarly journals Quantum Gravity: A Fluctuating Point of View

2021 ◽  
Vol 8 ◽  
Author(s):  
Jan M. Pawlowski ◽  
Manuel Reichert
Keyword(s):  
Fixed Point ◽  
Quantum Gravity ◽  
Point Of View ◽  
Group Approach ◽  
Functional Renormalization Group ◽  
Renormalization Group Approach ◽  
Pure Gravity ◽  
Classical Gravity ◽  
Curvature Dependence ◽  
Metric Fluctuations

In this contribution, we discuss the asymptotic safety scenario for quantum gravity with a functional renormalization group approach that disentangles dynamical metric fluctuations from the background metric. We review the state of the art in pure gravity and general gravity–matter systems. This includes the discussion of results on the existence and properties of the asymptotically safe ultraviolet fixed point, full ultraviolet-infrared trajectories with classical gravity in the infrared, and the curvature dependence of couplings also in gravity–matter systems. The results in gravity–matter systems concern the ultraviolet stability of the fixed point and the dominance of gravity fluctuations in minimally coupled gravity–matter systems. Furthermore, we discuss important physics properties such as locality of the theory, diffeomorphism invariance, background independence, unitarity, and access to observables, as well as open challenges.

Crossover scaling: A renormalization group approach

1994 ◽  
Vol 444 (1921) ◽  
pp. 287-296 ◽  
Keyword(s):  
Fixed Point ◽  
Renormalization Group ◽  
Correlation Length ◽  
Degrees Of Freedom ◽  
Scaling Laws ◽  
Anisotropy Parameter ◽  
Corrections To Scaling ◽  
Group Approach ◽  
Scaling Exponents ◽  
Renormalization Group Approach

We derive a theory of crossover scaling based on a scaling variable g ξ g , where g is the anisotropy parameter inducing the crossover and ξ g is the correlation length in the presence of g . Our considerations are field theoretic and based on a renormalization group with a g dependent differential generator that interpolates between qualitatively different degrees of freedom. ξ g is a nonlinear scaling field for this renormalization group and interpolates between ( T – T c ( g )) – v 0 and ( T – T c ( g )) – v ∞ ( v 0 and v ∞ being the isotropic and anisotropic exponents respectively). By expanding about a ‘floating’ fixed point we can make corrections to scaling small throughout the crossover. In this formulation effective scaling exponents obey standard scaling laws, e. g. γ eff = v eff (2 – ɳ eff ). We discuss its advantages giving for various crossovers explicit supporting perturbative calculations of the susceptibility, which is found to conform to the general form derived from the g dependent renormalization group.

scholarly journals Improved Reissner–Nordström–(A)dS black hole in asymptotic safety

2016 ◽  
Vol 31 (26) ◽  
pp. 1650141 ◽  
Author(s):  
Cristopher González ◽  
Benjamin Koch
Keyword(s):  
Black Hole ◽  
Einstein Gravity ◽  
Cosmic Censorship ◽  
Black Hole Mass ◽  
Crucial Point ◽  
Group Approach ◽  
Functional Renormalization Group ◽  
Charged Black Holes ◽  
Renormalization Group Approach ◽  
Cosmic Censorship Hypothesis

This paper studies the quantum modifications of the Reissner–Nordström–(A)dS black hole within Quantum Einstein Gravity, coupled to an electromagnetic sector. Quantum effects are introduced on the level of the improvements of the classical solution, where the originally constant couplings ([Formula: see text], [Formula: see text] and [Formula: see text]) are promoted to scale dependent quantities ([Formula: see text], [Formula: see text] and [Formula: see text]). Those running couplings are calculated in the functional renormalization group approach. A crucial point of this so-called “improving solutions” procedure is the scale setting where the arbitrary scale [Formula: see text] acquires physical meaning due to a relation to the coordinate scale [Formula: see text]. It is proposed to use such scale settings which are stable after iterative improvements. Using this method one finds that for those improved solutions, there is no stable remnant and due to the appearance of a new internal horizon, there is also no necessity to impose a minimal black hole mass for charged black holes, in order to avoid the cosmic censorship hypothesis.

Sign in / Sign up

Export Citation Format

Share Document