Conformal Anomalies and Gravitational Waves

Abstract

We argue that the presence of conformal anomalies in gravitational theories can lead to observable modifications to Einstein's equations via the induced anomalous effective actions, whose non-localities can overwhelm the smallness of the Planck scale. The fact that no such effects have been seen in recent cosmological or gravitational wave observations therefore imposes strong restrictions on the field content of possible extensions of Einstein's theory: all viable theories should have vanishing conformal anomalies. We then show that a complete cancellation of conformal anomalies in D=4 for both the $C^2$ invariant and the Euler (Gauss-Bonnet) invariant can only be achieved for N-extended supergravities with $N\ge 5$, as well as for M theory compactified to four dimensions.

4 pages

References in corpus (2)

• Enhanced Ultraviolet Cancellations in N = 5 Supergravity at Four Loop
• Spontaneous Breaking of Conformal Invariance and Trace Anomaly Matching

Cited by in corpus (14)

• TTT in CFT: Trace Identities and the Conformal Anomaly Effective Action
• Absence of U(1) Anomalous Superamplitudes in $\mathcal{N}\ge 5$ Supergravities
• Conformal Anomaly for Non-Conformal Scalar Fields
• Universal definition of the non-conformal trace anomaly
• Finite Action Principle and Horava-Lifshitz Gravity: early universe, black holes and wormholes
• Nonlinear (Super)Symmetries and Amplitudes
• The Action with Manifest E7 Type Symmetry
• Supersymmetry constraints on U-duality invariant deformations of $N\ge 5$ Supergravity
• A rederivation of the conformal anomaly for spin-1/2
• Conformal Anomaly and Off-Shell Extensions of Gravity
• Cancelling the vacuum energy and Weyl anomaly in the standard model with dimension-zero scalar fields
• Test-field limit of metric nonlinear gravity theories
• Asymptotic safety and quantum gravity amplitudes
• Signatures of supermassive charged gravitinos in liquid scintillator detectors