Extra spin-2 in quadratic gravity is a dual inverted harmonic oscillator with vanishing Källén–Lehmann density, fixing a principal-value propagator and preserving unitarity with renormalizability.
Quantum Gravity, Fakeons And Microcausality
4 Pith papers cite this work. Polarity classification is still indexing.
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abstract
We investigate the properties of fakeons in quantum gravity at one loop. The theory is described by a graviton multiplet, which contains the fluctuation $h_{\mu \nu }$ of the metric, a massive scalar $\phi $ and the spin-2 fakeon $\chi _{\mu \nu }$. The fields $\phi $ and $\chi _{\mu \nu }$ are introduced explicitly at the level of the Lagrangian by means of standard procedures. We consider two options, where $\phi $ is quantized as a physical particle or a fakeon, and compute the absorptive part of the self-energy of the graviton multiplet. The width of $\chi _{\mu \nu }$, which is negative, shows that the theory predicts the violation of causality at energies larger than the fakeon mass. We address this issue and compare the results with those of the Stelle theory, where $\chi _{\mu \nu }$ is a ghost instead of a fakeon.
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UNVERDICTED 4representative citing papers
Complex poles in the ghost propagator induce persistent interactions at asymptotic times, rendering negative-norm ghost states indistinguishable from superpositions of positive-norm multi-particle states and eliminating free asymptotic ghost particles.
Ghosts lack asymptotic particle interpretation due to interference and different Riemann-sheet pole structures compared to decaying unstable particles, with finite-time effects producing narrower resonances and higher peaks.
Causality is a misleading metaphysical concept that should be abandoned in fundamental physics, making renouncing microcausality acceptable for consistent quantum gravity theories such as those using fakeons.
citing papers explorer
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Unitary Quadratic Quantum Gravity in 4D
Extra spin-2 in quadratic gravity is a dual inverted harmonic oscillator with vanishing Källén–Lehmann density, fixing a principal-value propagator and preserving unitarity with renormalizability.
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Asymptotic Quantum Dynamics of Ghost Fields
Complex poles in the ghost propagator induce persistent interactions at asymptotic times, rendering negative-norm ghost states indistinguishable from superpositions of positive-norm multi-particle states and eliminating free asymptotic ghost particles.
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Ghosts versus Unstable Particles in Quantum Field Theory
Ghosts lack asymptotic particle interpretation due to interference and different Riemann-sheet pole structures compared to decaying unstable particles, with finite-time effects producing narrower resonances and higher peaks.
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On Causality and Predictivity
Causality is a misleading metaphysical concept that should be abandoned in fundamental physics, making renouncing microcausality acceptable for consistent quantum gravity theories such as those using fakeons.