2020/01/31 by Eugeny Babichev
Physics and Astronomy · #hep-th #gr-qc
paper · pdf · doi:10.1007/jhep07(2020)038
published as JHEP07(2020)038 · 14 pages, 4 figures; v2: clarifications added, matches published version
arxiv created 2020/07/09 · arxiv updated 2020/08/26
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.