Emergence of ghosts in Horndeski theory
arXiv:2001.11784 · doi:10.1007/JHEP07(2020)038
Abstract
We show that starting from initial conditions with stable perturbations, evolution of a galileon scalar field results in the appearance of a ghost later on. To demonstrate this, we consider a theory with k-essence and cubic galileon Lagrangians on a fixed Minkowski background. Explicit analytical solutions of simple waves are constructed, on top of which a healthy scalar degree of freedom is shown to be converted onto a ghost. Such a transformation is smooth and moreover perturbations remain hyperbolic all the time (until a caustic forms). We discuss a relation between the ghost and the appearance of closed causal curves for such solutions.
arXiv comment14 pages, 4 figures; v2: clarifications added, matches published version
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- Gravitational Collapse in Cubic Horndeski Theories
- K-dynamics: well-posed 1+1 evolutions in K-essence
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- Large black-hole scalar charges induced by cosmology in Horndeski theories
- Caustic formation in DBI models: Wave propagation on planar domain walls