Nonlinear definition of the shadowy mode in higher-order scalar-tensor theories
Antonio De Felice, Shinji Mukohyama, Kazufumi Takahashi
Abstract
Abstract We study U-DHOST theories, i.e., higher-order scalar-tensor theories which are degenerate only in the unitary gauge and yield an apparently unstable extra mode in a generic coordinate system. We show that the extra mode satisfies a three-dimensional elliptic differential equation on a spacelike hypersurface, and hence it does not propagate. We clarify how to treat this “shadowy” mode at both the linear and the nonlinear levels.
Topics & Concepts
HypersurfacePhysicsScalar (mathematics)Degenerate energy levelsTensor (intrinsic definition)Nonlinear systemDifferential geometryGauge theoryUnitary stateMathematical physicsMode (computer interface)Classical mechanicsTheoretical physicsMathematical analysisQuantum mechanicsMathematicsGeometryOperating systemComputer scienceLawPolitical scienceBlack Holes and Theoretical PhysicsPulsars and Gravitational Waves ResearchCosmology and Gravitation Theories