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Asymptotic safety, quantum gravity, and the swampland: a conceptual assessment

Ivano Basile, Benjamin Knorr, Alessia Platania, Marc Schiffer

TL;DR

The paper assesses whether asymptotically safe quantum gravity (ASQG), a field-theoretic approach with a UV fixed point and a finite-dimensional critical surface, can coexist with foundational swampland constraints. It parts the analysis into kinematic and dynamical swampland aspects, focusing on topology change, black-hole thermodynamics, holography, observables, and infinite-distance limits. The main finding is a structural tension: strict ASQG confronts challenges in reconciling topology fluctuations and conventional black-hole entropy with swampland expectations, unless loopholes or non-field-theoretic refinements are invoked. These insights delineate where ASQG can align with swampland ideas and point to avenues such as effective ASQG, IR nonlocality, or matrix/tensor-model realizations as potential resolutions, with further tests via non-perturbative S-matrix bootstrap.

Abstract

We provide a conceptual assessment of some aspects of fundamental quantum field theories of gravity in light of foundational aspects of the swampland program. On the one hand, asymptotically safe quantum gravity may provide a simple and predictive framework, thanks to a finite number of relevant parameters. On the other hand, a (sub-)set of intertwined swampland conjectures on the consistency of quantum gravity can be argued to be universal via effective field theory considerations. We answer whether some foundational features of these frameworks are compatible. This involves revisiting and refining several arguments (and loopholes) concerning the relation between field-theoretic descriptions of gravity and general swampland ideas. We identify the thermodynamics of black holes, spacetime topology change, and holography as the core aspects of this relation. We draw lessons on the features that a field theoretic description of gravity must (not) have to be consistent with fundamental principles underlying the swampland program, and on the universality of the latter.

Asymptotic safety, quantum gravity, and the swampland: a conceptual assessment

TL;DR

The paper assesses whether asymptotically safe quantum gravity (ASQG), a field-theoretic approach with a UV fixed point and a finite-dimensional critical surface, can coexist with foundational swampland constraints. It parts the analysis into kinematic and dynamical swampland aspects, focusing on topology change, black-hole thermodynamics, holography, observables, and infinite-distance limits. The main finding is a structural tension: strict ASQG confronts challenges in reconciling topology fluctuations and conventional black-hole entropy with swampland expectations, unless loopholes or non-field-theoretic refinements are invoked. These insights delineate where ASQG can align with swampland ideas and point to avenues such as effective ASQG, IR nonlocality, or matrix/tensor-model realizations as potential resolutions, with further tests via non-perturbative S-matrix bootstrap.

Abstract

We provide a conceptual assessment of some aspects of fundamental quantum field theories of gravity in light of foundational aspects of the swampland program. On the one hand, asymptotically safe quantum gravity may provide a simple and predictive framework, thanks to a finite number of relevant parameters. On the other hand, a (sub-)set of intertwined swampland conjectures on the consistency of quantum gravity can be argued to be universal via effective field theory considerations. We answer whether some foundational features of these frameworks are compatible. This involves revisiting and refining several arguments (and loopholes) concerning the relation between field-theoretic descriptions of gravity and general swampland ideas. We identify the thermodynamics of black holes, spacetime topology change, and holography as the core aspects of this relation. We draw lessons on the features that a field theoretic description of gravity must (not) have to be consistent with fundamental principles underlying the swampland program, and on the universality of the latter.

Paper Structure

This paper contains 14 sections, 2 equations, 2 figures.

Table of Contents

  1. Introduction
  2. The swampland program and asymptotic safety
  3. The kinematic swampland
  4. Topology change in quantum gravity and field theory
  5. Global symmetries and semiclassical black holes
  6. Consequences of no topology change
  7. Generalizing ASQG beyond QFT
  8. Summary and loopholes
  9. The dynamical swampland
  10. Observables and UV/IR mixing
  11. Infinite-distance limits in theory space
  12. Summary and loopholes
  13. Conclusions
  14. A dictionary for non-stringy readers

Figures (2)

  • Figure 1: A schematic depiction of various logical possibilities regarding the string landscape and asymptotic safety landscapes. In its strict realization, ASQG is fundamental, and its landscape will presumably have a non-trivial intersection with the string landscape. If instead ASQG is a low-energy approximation of string theory, its landscape ought to fall within the string landscape. This paper discusses features of the asymptotic safety landscape from strict ASQG and their interface with a subset of swampland conjectures which are not necessarily tied to string theory, but can be motivated by arguments in EFT and black-hole physics.
  • Figure 2: Various connections between the kinematic aspects of the swampland are shown. The dashed arrow denotes a weaker connection, indicating holography from the Bekenstein-Hawking area law. When specializing to AdSCFT holography, one can prove Harlow:2018jwuHarlow:2018tng completeness and the absence of global symmetries. The blue region in the lower part of the diagram contains connections which persist without summing over spacetime topologies. In \ref{['app:dictionary']} we provide explanations for some of the technical jargon.