Ghosts, instabilities, and superluminal propagation in modified gravity models

2006/04/30 by Antonio De Felice, Mark Hindmarsh, Mark Trodden · 6 citations
Mathematics · Physics and Astronomy · #Advanced Differential Geometry Research #Attractor #Black Holes and Theoretical Physics #Classical mechanics #Cosmology and Gravitation Theories #Curvature #Equivalence (formal languages) #Geometry #Gravitation #Mathematical analysis #Mathematical physics #Mathematics #Physics #Quantum mechanics #Scalar (mathematics) #Scalar field #Superluminal motion #Theoretical physics #astro-ph #gr-qc #hep-th

paper · pdf · doi:10.1088/1475-7516/2006/08/005

published as JCAP 0608 (2006) 005 · 17 pages, 1 figure, uses RevTeX. Added a few comments. Changed the figure

openalex publication_date 2006/08/16 · arxiv created 2006/09/04 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

We consider modified gravity models involving inverse powers of fourth order curvature invariants. Using these models' equivalence to the theory of a scalar field coupled to a linear combination of the invariants, we investigate the properties of the propagating modes. Even in the case for which the fourth derivative terms in the field equations vanish, we find that the second derivative terms can give rise to ghosts, instabilities, and superluminal propagation speeds. We establish the conditions which the theories must satisfy in order to avoid these problems in Friedmann backgrounds, and show that the late time attractor solutions generically exhibit superluminally propagating tensor or scalar modes.

Citations

• Measurements of Ω and Λ from 42 High‐Redshift Supernovae
• Dynamics of k -essence
• Cosmology with a time-variable cosmological 'constant'
• Ghost constraints on modified gravity
• Classification of scalar field potentials with cosmological scaling solutions
• Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
• Is cosmic speed-up due to new gravitational physics?
• Cosmological consequences of a rolling homogeneous scalar field

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• Observational tests of a two parameter power-law class modified gravity in Palatini formalism