What is Asymptotic safety: Definition and 27 Discussions

Asymptotic safety (sometimes also referred to as nonperturbative renormalizability) is a concept in quantum field theory which aims at finding a consistent and predictive quantum theory of the gravitational field. Its key ingredient is a nontrivial fixed point of the theory's renormalization group flow which controls the behavior of the coupling constants in the ultraviolet (UV) regime and renders physical quantities safe from divergences. Although originally proposed by Steven Weinberg to find a theory of quantum gravity, the idea of a nontrivial fixed point providing a possible UV completion can be applied also to other field theories, in particular to perturbatively nonrenormalizable ones. In this respect, it is similar to quantum triviality.
The essence of asymptotic safety is the observation that nontrivial renormalization group fixed points can be used to generalize the procedure of perturbative renormalization. In an asymptotically safe theory the couplings do not need to be small or tend to zero in the high energy limit but rather tend to finite values: they approach a nontrivial UV fixed point. The running of the coupling constants, i.e. their scale dependence described by the renormalization group (RG), is thus special in its UV limit in the sense that all their dimensionless combinations remain finite. This suffices to avoid unphysical divergences, e.g. in scattering amplitudes. The requirement of a UV fixed point restricts the form of the bare action and the values of the bare coupling constants, which become predictions of the asymptotic safety program rather than inputs.
As for gravity, the standard procedure of perturbative renormalization fails since Newton's constant, the relevant expansion parameter, has negative mass dimension rendering general relativity perturbatively nonrenormalizable. This has driven the search for nonperturbative frameworks describing quantum gravity, including asymptotic safety which – in contrast to other approaches – is characterized by its use of quantum field theory methods, without depending on perturbative techniques, however. At the present time, there is accumulating evidence for a fixed point suitable for asymptotic safety, while a rigorous proof of its existence is still lacking.

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  1. M

    A Donoghue's critique of asymptotic safety

    I have not read this paper yet, but Lubos Motl blogs about it here: "A serious critique of the real-world Asymptotic Safety program for quantum gravity". The points I would list in favor of asymptotic safety's significance and viability, may be found in this Physics Stack Exchange...
  2. M

    Can anyone Recommend a good quantum gravity textbook?

    I'm currently doing my thesis in QG and there's a distinct gap between where QFT and GR left off and QG begins, and as I'm sure most of you know, in a thesis you're sort of just thrown right into the deep end. As such, I was hoping someone could recommend a decent textbook that gives a solid...
  3. stevendaryl

    A Asymptotic Safety for Quantum Gravity

    Sabine Hossenfelder recently wrote about an old theory of quantum gravity due to Weinberg: asymptotically safe quantum gravity. Is anyone familiar with this idea? What I couldn't figure out from the article is whether asymptotic safety is an approach to making consistent quantum field theories...
  4. T

    A What is the current status of asymptotic safety?

    Hi everybody, I guess most of you know of the 2009 higgs mass prediction. Nevertheless there has been important changes in the top quark mass estimations. So I wanted to know: 1 if there is any update on that prediction and if it is still in good agreement with the Higgs mass? 2 if there is at...
  5. J

    A Connection between Asymptotic Safety and CDT?

    Are asymptotic safety and causal dynamical triangulation compatible? https://arxiv.org/pdf/1411.7712.pdf As you all know AS has problems with the holographic principle. However, the dimensional reduction obtained in asymptotic safety by using causal dynamical triangulation can make AS compatible...
  6. MrRobotoToo

    I Further Evidence of a 3.5 keV line in Galactic X-Ray Spectra

    That pesky 3.5 keV line just won't go away. The authors note that it's compatible with dark matter composed of 7.02 keV sterile neutrinos. If such is the case, the Majorana mass scale of the seesaw mechanism needn't coincide with the GUT scale (if such a scale even exists).
  7. N

    A Is asymptotic safety linear with respect to the wavefunction

    AS is a local quantum field theory, so I'm assuming that it is? What do you guys think?
  8. N

    A Does supersymmetry rule out asymptotic safety?

    If we find supersymmetry at the LHC, would this prove asymptotic safety in QG wrong? Here's the article https://arxiv.org/pdf/1508.07411v2.pdf
  9. K

    I Asymptotic safety and loop quantum gravity

    this paper https://arxiv.org/abs/1701.02311 Hypercuboidal renormalization in spin foam quantum gravity Benjamin Bahr, Sebastian Steinhaus (Submitted on 9 Jan 2017) In this article we apply background-independent renormalization group methods to spin foam quantum gravity. It is aimed at...
  10. N

    A Can asymptotic safety in quantum gravity be right?

    Asymptotic safety in quantum gravity is a local QFT. According to many people, local quantum field theories cannot be correct in terms of being a quantum gravity theory. Lubos Motl outlines 4 reasons why they can't be right. "Quantum gravity cannot be described as a local field theory in the...
  11. K

    I Recent paper Asymptotic safety in quantum gravity

    http://arxiv.org/abs/1609.04813 Quantum gravity on foliated spacetime - asymptotically safe and sound Jorn Biemans, Alessia Platania, Frank Saueressig (Submitted on 15 Sep 2016) Asymptotic Safety provides a mechanism for constructing a consistent and predictive quantum theory of gravity valid on...
  12. K

    I Can Loop Quntuam gravity be merged with Asymptotic safety

    can Loop Quntuam gravity be merged with Asymptotic safety scenario in gravity into a single theory of QG, one that has both concepts ? i.e if you start with Loop Quntuam gravity in 4D, can you show that it is also implies Asymptotic safety scenario in gravity in 4D? are there any papers...
  13. K

    Asymptotic Safety Scenario in QG vs LQG

    the paper Asymptotic safety of gravity and the Higgs boson mass Mikhail Shaposhnikova, , , Christof Wetterichb predicts the Higgs mass. it also forms the framework of the neutrino minimal standard model. any research papers comparing Asymptotic Safety Scenario in QG vs LQG? does anyone here...
  14. E

    Color Kinematics Duality and Asymptotic Safety

    So, you'll have to forgive me, but I am an engineer, not a physicist, but I take an interest in quantum gravity. My understanding is primarily conceptual, not mathematical. So if my question is dumb, I apologize. Ok, here goes: I'm aware of Zwi Bern's conjectured color-kinematics duality...
  15. tom.stoer

    Asymptotic safety and the "no boundary" proposal

    Does anybody know papers in which the asymptotic safety approach has been applied to the "no boundary" proposal?
  16. M

    Asymptotic safety and local gauge invariance

    Hi folks -- does anyone know of a good survey article on the topic of whether local gauge invariance is a requirement of a fundamental theory within QFT -- hence of an asymptotically safe theory? I only have a few scattered remarks to this effect (by F. Wilczek mostly), so any good...
  17. atyy

    Limit cycles in asymptotic safety?

    Litim and Satz have just addressed a question I've long wondered about. http://arxiv.org/abs/1205.4218 Limit cycles and quantum gravity Daniel Litim, Alejandro Satz We study renormalization group equations of quantum gravity in four dimensions. We find an ultraviolet fixed point in accordance...
  18. M

    Light fermions and ~125 GeV Higgs from asymptotic safety

    From http://arxiv.org/abs/1112.2415, "Planck scale Boundary Conditions and the Higgs Mass", I learn of http://arxiv.org/abs/0912.0208, "Asymptotic safety of gravity and the Higgs boson mass", which predicts a Higgs mass of 127 GeV as a consequence of the vanishing of the Higgs self-interaction...
  19. atyy

    Asymptotic safety on the lattice

    Interesting posts from Georg von Hippel at http://latticeqcd.blogspot.com/ Monday, July 11, 2011 Lattice 2011, Day One "Next was a talk by Jack Laiho on Asymptotic Safety and Quantum Gravity. The concept of asymptotic safety as introduced by Weinberg states that a perturbatively...
  20. marcus

    Asymptotic safety and black holes (new Mattingly paper)

    Dave Mattingly has been a frequent collaborator with Ted Jacobson (his thesis advisor). You know of Jacobson if, for example, you followed the recent discussion of "gravity as entropic force" by Erik Verlinde and others. In 1995 Jacobson derived the Einstein field equation from thermodynamics...
  21. marcus

    Krasnov framework for asymptotic safety in QG (Perimeter video)

    http://pirsa.org/10050002/ Deformations of General Relativity Kirill Krasnov 2010-05-05 "I will describe a very special (infinite-parameter) family of gravity theories that all describe, exactly like General Relativity, just two propagating degrees of freedom. The theories are obtained by...
  22. Physics Monkey

    Some confusion about asymptotic safety

    I'm trying to understand why asymptotic safety is a reasonable approach to quantum gravity. Here is my present understanding: 1. Asymptotic safety is roughly the statement that perturbative gravity (by which i mean a spin 2 field) has a UV fixed point where it becomes like any other conformal...
  23. marcus

    Videos for Asymptotic Safety conference are online

    We already have videos for 5 of the talks. Steven Weinberg http://pirsa.org/09110039/ Martin Reuter http://pirsa.org/09110040/ Jean Zinn-Justin http://pirsa.org/09110041/ Holger Gies http://pirsa.org/09110042/ Benjamin Ward http://pirsa.org/09110043/ Here's the schedule...
  24. marcus

    Asymptotic Safety paper thanks Jacques Distler

    "We thank J. Distler and R. Percacci for animated discussions which triggered this investigation. Furthermore, we are grateful to J.P. Blaizot, A. Codello, R. Loll, E. Manrique, and M. Reuter for useful conversations..." It's interesting to contemplate the different ways that progress in...
  25. marcus

    More evidence for asymptotic safety (Saueressig, Machado, Benedetti)

    http://arxiv.org/abs/0901.2984 Asymptotic safety in higher-derivative gravity Dario Benedetti, Pedro F. Machado, Frank Saueressig 4 pages (Submitted on 20 Jan 2009) "We study the non-perturbative renormalization group flow of higher-derivative gravity employing functional renormalization...
  26. marcus

    Percacci's home page (brief explanations of asymptotic safety and unification)

    (here's more on SISSA if you want) Here's Percacci's page: http://people.sissa.it/~percacci/ Here's a sample: ==exerpt== ASYMPTOTIC SAFETY A quantum field theory that is perturbatively renormalizable and asymptotically free can be regarded as a fundamental theory, because it makes sense up to...
  27. S

    The Asymptotic Safety Scenario in QG

    I want to recommend the following paper to anyone who wants the spec up on Renormalization Group flows, fixed points, or asymptotic safety. The author is interested in reviving the functinal integral approach to QG, which was aboandoned when 't Hooft and Veltzman showed GR was nonrenomalizable...