Journal ArticleDOI
Second-order scalar-tensor field equations in a four-dimensional space
TLDR
In this article, the second-order Euler-Lagrange tensors are derived from a Lagrangian which is at most of second order in the derivatives of the field functions.Abstract:
Lagrange scalar densities which are concomitants of a pseudo-Riemannian metric-tensor, a scalar field and their derivatives of arbitrary order are considered. The most general second-order Euler-Lagrange tensors derivable from such a Lagrangian in a four-dimensional space are constructed, and it is shown that these Euler-Lagrange tensors may be obtained from a Lagrangian which is at most of second order in the derivatives of the field functions.read more
Citations
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Who You Gonna Call? Runaway Ghosts, Higher Derivatives and Time-Dependence in EFTs
TL;DR: In this paper, the authors review the formulation of effective field theories (EFTs) in time-dependent situations, with particular attention paid to their domain of validity, and show by explicit calculation that the low-energy action obtained from a sensible UV completion need not take the restrictive form required to obtain only second-order field equations.
Journal ArticleDOI
Finding Horndeski theories with Einstein gravity limits
TL;DR: In this article, a scaling method was proposed to identify dominant terms in the equations of motion by considering formal limits of the couplings that enter through the new terms in a modified Horndeski action.
Journal ArticleDOI
Caustics for spherical waves
Claudia de Rham,Hayato Motohashi +1 more
TL;DR: In this article, the development of caustics in shift-symmetric scalar field theories was studied by focusing on simple waves with an arbitrary number of space dimensions, and it was shown that the pure Galileon, the DBI-Galileon, and the extreme-relativistic Galileon naturally emerge as the unique set of CAUSIC-free theories.
Journal ArticleDOI
A note on a mimetic scalar-tensor cosmological model
TL;DR: In this article, a specific Horndeski scalar-gravity mimetic model is investigated within a FLWR space-time, and the mimetic scalar field is implemented via a Lagrangian multiplier.
Journal ArticleDOI
Compact objects in scalar-tensor theories after GW170817
TL;DR: In this paper, a scalar-tensor set-up with horizons is considered and the physics of locally asymptotically flat black holes and relativistic stars are numerically investigated.
References
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Journal ArticleDOI
Mach's principle and a relativistic theory of gravitation
Carl H. Brans,R. H. Dicke +1 more
TL;DR: In this paper, the role of Mach's principle in physics is discussed in relation to the equivalence principle and the difficulties encountered in attempting to incorporate Mach's principles into general relativity are discussed.
Journal ArticleDOI
The Einstein Tensor and Its Generalizations
TL;DR: In this paper, the number of independent tensors of this type depends crucially on the dimension of the space, and, in the four dimensional case, the only tensors with these properties are the metric and the Einstein tensors.
Journal ArticleDOI
Comments on the scalar-tensor theory
TL;DR: In this article, the ponderomotive laws of a scalar-tensor theory are constructed free of approximations in the form of integral laws, and the integrals are extended over two-and three-dimensional domains that lie entirely in empty space but surround the regions containing matter.
Journal ArticleDOI
The uniqueness of the einstein field equations in a four-dimensional space.
TL;DR: In this article, the Euler-Lagrange equations corresponding to a Lagrange density which is a function of g ≥ 2 and its first two derivatives are investigated and necessary and sufficient conditions for these equations to be of second order are obtained and it is shown that in a four-dimensional space the Einstein field equations (with cosmological term) are the only permissible second order Euler Lagrange equations.
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