2017/03/31 by Hassan Firouzjahi, Mohammad Ali Gorji, Seyed Ali Hosseini Mansoori · 70 citations
Physics and Astronomy · #Action (physics) #Black Holes and Theoretical Physics #Classical mechanics #Cosmological perturbation theory #Cosmology #Cosmology and Gravitation Theories #Derivative (finance) #Galaxies: Formation, Evolution, Phenomena #Geometry #Instability #Kinetic term #Mathematical physics #Mechanics #Newtonian fluid #Perturbation (astronomy) #Physics #Quadratic equation #Quantum electrodynamics #Quantum mechanics #Term (time) #astro-ph.CO #gr-qc #hep-th
paper · pdf · doi:10.1088/1475-7516/2017/07/031
published in Journal of Cosmology and Astroparticle Physics 2017(07), 031 (Institute of Physics) · v2: Discussions improved, references added, JCAP published version
openalex publication_date 2017/07/17 · arxiv created 2017/08/03 · arxiv updated 2017/08/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We study cosmological perturbations in mimetic matter scenario with a general higher derivative function. We calculate the quadratic action and show that both the kinetic term and the gradient term have the wrong sings. We perform the analysis in both comoving and Newtonian gauges and confirm that the Hamiltonians and the associated instabilities are consistent with each other in both gauges. The existence of instabilities is independent of the specific form of higher derivative function which generates gradients for mimetic field perturbations. It is verified that the ghost instability in mimetic perturbations is not associated with the higher derivative instabilities such as the Ostrogradsky ghost.