Year: 2011
Type: article
Abstract: We study the cosmology of a generalized Galileon field $\ensuremath{\phi}$ with five covariant Lagrangians in which $\ensuremath{\phi}$ is replaced by general scalar functions ${f}_{i}(\ensuremath{\phi})$ ($i=1,\dots{},5$). For these theories, the equations of motion remain at second order in time derivatives. We constrain the forms of the functions ${f}_{i}(\ensuremath{\phi})$ from the requirement to possess de Sitter solutions responsible for dark energy. There are two possible choices for power-law functions ${f}_{i}(\ensuremath{\phi})$, depending on whether the coupling $F(\ensuremath{\phi})$ with the Ricci scalar $R$ is independent of $\ensuremath{\phi}$ or depends on $\ensuremath{\phi}$. The former corresponds to the covariant Galileon theory that respects the Galilean symmetry in the Minkowski space-time. For generalized Galileon theories we derive the conditions for the avoidance of ghosts and Laplacian instabilities associated with scalar and tensor perturbations as well as the condition for the stability of de Sitter solutions. We also carry out a detailed analytic and numerical study for the cosmological dynamics in those theories.
Authors: Antonio De Felice, Shinji Tsujikawa
Institution: Tokyo University of Science
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Award: G5473262123
OpenAlex ID: W2011362317