Fluid nature constrains Horndeski gravity

Abstract

The elusive physical nature of Horndeski gravity is elucidated in a new approach depicting this class of theories as a dissipative effective fluid. Requiring the constitutive equations of the latter to be those of a Newtonian fluid restricts the theory to only two disconnected subclasses of "viable" Horndeski gravity. Therefore, a stress-energy tensor of Horndeski effective fluid, linear in the first derivatives of the fluid's 4-velocity, is a sufficient condition for gravitational waves to propagate at light speed. All other Horndeski theories correspond to exotic non-Newtonian effective fluids.

arXiv comment28 pages, 2 tables. Matches published version in General Relativity and Gravitation

References in corpus (23)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• Thermodynamics of Spacetime: The Einstein Equation of State
• Curvature Quintessence
• Strong constraints on cosmological gravity from GW170817 and GRB 170817A
• Dark Energy after GW170817 and GRB170817A
• Horndeski theory and beyond: a review
• Non-equilibrium Thermodynamics of Spacetime
• First-order relativistic hydrodynamics is stable
• Causality and existence of solutions of relativistic viscous fluid dynamics with gravity
• Cuscuton: A Causal Field Theory with an Infinite Speed of Sound
• Nonlinear causality of general first-order relativistic viscous hydrodynamics
• Speed of Gravitational Waves and the Fate of Scalar-Tensor Gravity
• Stable and causal relativistic Navier-Stokes equations
• Extended Cuscuton: Formulation
• Spontaneous scalarization in generalised scalar-tensor theory
• Imperfect fluid description of modified gravities
• First-order thermodynamics of Horndeski gravity
• Thermodynamics of scalar-tensor gravity
• Reversible and Irreversible Spacetime Thermodynamics for General Brans-Dicke Theories
• First-order thermodynamics of scalar-tensor cosmology
• Equivalence between Horndeski and beyond Horndeski theories and imperfect fluids
• Generalized McVittie geometry in Horndeski gravity with matter

Cited by in corpus (10)

• Ghost and Laplacian Instabilities in the Teleparallel Horndeski Gravity
• Past-directed scalar field gradients and scalar-tensor thermodynamics
• First-order thermodynamics of Horndeski cosmology
• First-order thermodynamics of scalar-tensor gravity
• Alternative formulations of the thermodynamics of scalar-tensor theories
• Cuscuton Bounce Beyond the Linear Regime: Bispectrum and Strong Coupling Constraints
• General analysis of Noether symmetries in Horndeski gravity
• Eckart heat-flux applicability in $F(\Phi ,X)R$ theories and the existence of temperature gradients
• Thermal channels of scalar and tensor waves in Jordan-frame scalar--tensor gravity
• Covariant single-field formulation of effective cosmological bounces