A four-derivative UV-complete QFT is shown to have consistent perturbative scattering by quantizing on a Krein space with an embedded two-field O(1,1) theory that enforces ghost parity and positive probabilities.
No-ghost theorem for the fourth-order derivative Pais-Uhlenbeck oscillator model
8 Pith papers cite this work. Polarity classification is still indexing.
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abstract
Contrary to common belief, it is shown that theories whose field equations are higher than second order in derivatives need not be stricken with ghosts. In particular, the prototypical fourth-order derivative Pais-Uhlenbeck oscillator model is shown to be free of states of negative energy or negative norm. When correctly formulated (as a $\cP\cT$ symmetric theory), the theory determines its own Hilbert space and associated positive-definite inner product. In this Hilbert space the model is found to be a fully acceptable quantum-mechanical theory that exhibits unitary time evolution.
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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.
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.
Ghostly quantum systems can have discrete non-dense energy spectra under classical stability conditions, providing counterexamples to spectral denseness.
A quantum ghost coupled polynomially to a harmonic oscillator has unitary evolution and a stable vacuum because a conserved quantity possesses a positive discrete spectrum.
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.
Apparent exponential growth of metric perturbations in the Newtonian gauge for quadratic-gravity inflation is gauge-dependent and non-generic; other gauges remain well-behaved.
Review of spectral noncommutative geometry applied to the Standard Model, including bosonic and fermionic actions, Euclidean vs Lorentz issues, and going beyond the SM.
citing papers explorer
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Escape from Ostrogradsky via Hidden Ghost Parity
A four-derivative UV-complete QFT is shown to have consistent perturbative scattering by quantizing on a Krein space with an embedded two-field O(1,1) theory that enforces ghost parity and positive probabilities.
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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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Quantum mechanics with a ghost: Counterexamples to spectral denseness
Ghostly quantum systems can have discrete non-dense energy spectra under classical stability conditions, providing counterexamples to spectral denseness.
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Unitary Time Evolution and Vacuum for a Quantum Stable Ghost
A quantum ghost coupled polynomially to a harmonic oscillator has unitary evolution and a stable vacuum because a conserved quantity possesses a positive discrete spectrum.
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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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Gauge-independent approach to inflation in quadratic gravity
Apparent exponential growth of metric perturbations in the Newtonian gauge for quadratic-gravity inflation is gauge-dependent and non-generic; other gauges remain well-behaved.
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Spectral Noncommutative Geometry, Standard Model and all that
Review of spectral noncommutative geometry applied to the Standard Model, including bosonic and fermionic actions, Euclidean vs Lorentz issues, and going beyond the SM.