Asymptotic safety of higher derivative quantum gravity non-minimally coupled with a matter system

We review and discuss higher derivative and nonlocal theories of quantum gravity focusing on their UV and unitarity properties. We first consider the general fourth-order gravitational action, then actions containing derivatives up to any given fixed order, and discuss their UV divergences, fixed points and concomitant unitarity issues. This leads to a more general discussion of "asymptotic safety" and unitarity, which motivates the introduction of nonlocal theories containing derivatives to all orders arising from the expansion of entire functions. For such theories good UV behavior is visible at any finite truncation, but unitarity emerges only when derivatives to all orders are included.

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Black holes within asymptotic safety

International Journal of Modern Physics A ◽

10.1142/s0217751x14300117 ◽

2014 ◽

Vol 29 (08) ◽

pp. 1430011 ◽

Cited By ~ 44

Author(s):

Benjamin Koch ◽

Frank Saueressig

Keyword(s):

Black Holes ◽

Black Hole ◽

Quantum Gravity ◽

Space Time ◽

Asymptotic Safety ◽

Angular Momenta ◽

Higher Derivative ◽

The Status ◽

Time Singularities ◽

Characteristic Features

Black holes are probably among the most fascinating objects populating our universe. Their characteristic features found within general relativity, encompassing space–time singularities, event horizons, and black hole thermodynamics, provide a rich testing ground for quantum gravity ideas. We review the status of black holes within a particular proposal for quantum gravity, Weinberg's asymptotic safety program. Starting from a brief survey of the effective average action and scale setting procedures, an improved quantum picture of the black hole is developed. The Schwarzschild black hole and its generalizations including angular momenta, higher-derivative corrections and the implications of extra dimensions are discussed in detail. In addition, the quantum singularity emerging for the inclusion of a cosmological constant is elucidated and linked to the phenomenon of a dynamical dimensional reduction of space–time.

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On the Structure of the Vacuum in Quantum Gravity: A View from the Asymptotic Safety Scenario

Universe ◽

10.3390/universe5080182 ◽

2019 ◽

Vol 5 (8) ◽

pp. 182 ◽

Cited By ~ 3

Author(s):

Alfio Bonanno

Keyword(s):

Quantum Gravity ◽

Degrees Of Freedom ◽

Vacuum State ◽

Critical Surface ◽

Asymptotic Safety ◽

Quantum Chromo Dynamics ◽

Full Theory ◽

Higher Derivative ◽

Quadratic Gravity ◽

Non Gaussian

Although the Asymptotic Safety scenario is one of the most promising approaches to quantum gravity, little attention has been devoted to the issue of the vacuum state. Higher derivative operators often appear on the ultraviolet critical surface around the non-Gaussian fixed point generating additional degrees of freedom which can render the standard vacuum unstable. When this happens, translation and rotational symmetries can be spontaneously broken and a new set of symmetries can show up at the level of the effective action. In this work, it will be argued that a “kinetic condensate” characterizes the vacuum state of asymptotically safe quadratic gravity theories. If this scenario is realized in the full theory, the vacuum state of gravity is the gravitational analogous to the Savvidy vacuum in Quantum Chromo-Dynamics (QCD).

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Gauge invariance and unitarity in higher-derivative quantum gravity

Physical Review D ◽

10.1103/physrevd.33.2756 ◽

1986 ◽

Vol 33 (10) ◽

pp. 2756-2779 ◽

Cited By ~ 139

Author(s):

I. Antoniadis ◽

E. T. Tomboulis

Keyword(s):

Quantum Gravity ◽

Gauge Invariance ◽

Higher Derivative

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ASYMPTOTIC SAFETY IN HIGHER-DERIVATIVE GRAVITY

Modern Physics Letters A ◽

10.1142/s0217732309031521 ◽

2009 ◽

Vol 24 (28) ◽

pp. 2233-2241 ◽

Cited By ~ 201

Author(s):

DARIO BENEDETTI ◽

PEDRO F. MACHADO ◽

FRANK SAUERESSIG

Keyword(s):

Fixed Point ◽

Renormalization Group ◽

Renormalization Group Flow ◽

Functional Renormalization Group ◽

Asymptotic Safety ◽

Higher Derivative ◽

Gravity Theories ◽

Group Flow ◽

Nonperturbative Renormalization

We study the nonperturbative renormalization group flow of higher-derivative gravity employing functional renormalization group techniques. The nonperturbative contributions to the β-functions shift the known perturbative ultraviolet fixed point into a nontrivial fixed point with three UV-attractive and one UV-repulsive eigendirections, consistent with the asymptotic safety conjecture of gravity. The implication of this transition on the unitarity problem, typically haunting higher-derivative gravity theories, is discussed.

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Standard model and graviweak unification with (super)renormalizable gravity. Part I: Visible and invisible sectors of the universe

International Journal of Modern Physics A ◽

10.1142/s0217751x1550044x ◽

2015 ◽

Vol 30 (09) ◽

pp. 1550044 ◽

Cited By ~ 6

Author(s):

L. V. Laperashvili ◽

H. B. Nielsen ◽

A. Tureanu

Keyword(s):

Standard Model ◽

Quantum Gravity ◽

Consistent Theory ◽

Invariant Model ◽

Higher Derivative ◽

Self Consistent ◽

Renormalizable Theory ◽

Theory Of Gravity ◽

Higgs Fields ◽

The Universe

We develop a self-consistent Spin (4, 4)-invariant model of the unification of gravity with weak SU(2) gauge and Higgs fields in the visible and invisible sectors of our universe. We consider a general case of the graviweak unification, including the higher-derivative super-renormalizable theory of gravity, which is a unitary, asymptotically-free and perturbatively consistent theory of the quantum gravity.

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