Fakeons, Quantum Gravity and the Correspondence Principle

Anselmi, Damiano

doi:10.1007/978-3-030-38941-3_7

Cited by 3 publications

(2 citation statements)

References 18 publications

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“…is negative, the massive spin-two pole corresponds to an Ostrogradski ghost signalling that the theory is problematic (also see [76][77][78][79] for recent reinterpretations of this degree of freedom as virtual particle leading to the violation of microcausality and [80] for a more detailed discussion on the role of the ghost modes in gravity-mediated scattering amplitudes).…”

Section: Stelle Gravitymentioning

confidence: 99%

Graviton-mediated scattering amplitudes from the quantum effective action

Draper

Knorr

Ripken

et al. 2020

J. High Energ. Phys.

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We employ the curvature expansion of the quantum effective action for gravity-matter systems to construct graviton-mediated scattering amplitudes for non-minimally coupled scalar fields in a Minkowski background. By design, the formalism parameterises all quantum corrections to these processes and is manifestly gauge-invariant. The conditions resulting from UV-finiteness, unitarity, and causality are analysed in detail and it is shown by explicit construction that the quantum effective action provides sufficient room to meet these structural requirements without introducing non-localities or higher-spin degrees of freedom. Our framework provides a bottom-up approach to all quantum gravity programs seeking for the quantisation of gravity within the framework of quantum field theory. Its scope is illustrated by specific examples, including effective field theory, Stelle gravity, infinite derivative gravity, and Asymptotic Safety.

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Section: Stelle Gravitymentioning

confidence: 99%

Graviton-mediated scattering amplitudes from the quantum effective action

Draper

Knorr

Ripken

et al. 2020

J. High Energ. Phys.

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“…Among the different proposals, there are claims that quadratic gravity can be formulated as a unitary theory by bringing back ideas from the Lee-Wick program for higher-derivative theories [54][55][56][57]. For example, Anselmi and Piva introduced a new prescription to define the integration contour around propagator poles in the complex plane, which allows us to remove the higherderivative ghost from the physical spectrum [42][43][44][45][46][47][48]. In this approach, the higher-derivative ghost is interpreted as a fake-particle, or a fakeon.…”

Section: Introductionmentioning

confidence: 99%

Light charged fermions in quantum gravity

2021

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Fakeons, unitarity, massive gravitons, and the cosmological constant

Anselmi

2019

J. High Energ. Phys.

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We give a simple proof of perturbative unitarity in gauge theories and quantum gravity using a special gauge that allows us to separate the physical poles of the free propagators, which are quantized by means of the Feynman prescription, from the poles that belong to the gauge-trivial sector, which are quantized by means of the fakeon prescription. The proof applies to renormalizable theories, including the ultraviolet complete theory of quantum gravity with fakeons formulated recently, as well as low-energy (nonrenormalizable) theories. We clarify a number of subtleties related to the study of scattering processes in the presence of a cosmological constant Λ. The scattering amplitudes, defined by expanding the metric around flat space, obey the optical theorem up to corrections due to Λ, which are negligible for all practical purposes. Problems of interpretation would arise if such corrections became important. In passing, we obtain local, unitary (and "almost" renormalizable) theories of massive gravitons and gauge fields, which violate gauge invariance and general covariance explicitly.

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Fakeons, Quantum Gravity and the Correspondence Principle

Cited by 3 publications

References 18 publications

Graviton-mediated scattering amplitudes from the quantum effective action

Graviton-mediated scattering amplitudes from the quantum effective action

Light charged fermions in quantum gravity

Fakeons, unitarity, massive gravitons, and the cosmological constant

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