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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Scalar-tensor theories and modified gravity in the wake of GW170817
TL;DR: In this paper, a degenerate higher-order scalar-tensor (DHOST) theory is presented, which can lead to a deviation from standard gravity inside matter, parametrized by three coefficients which satisfy a consistency relation.
Journal ArticleDOI
A unifying description of dark energy
TL;DR: The approach provides a unified treatment of the linear cosmological perturbations about a FLRW universe, obtained by a systematic expansion of the general action up to quadratic order, and shows that the behaviour of these linear perturbation is generically characterized by five time-dependent functions.
Journal ArticleDOI
Effective field theory approach to quasi-single field inflation and effects of heavy fields
TL;DR: In this article, the authors apply the effective field theory approach to quasi-single field inflation, which contains an additional scalar field with Hubble scale mass other than inflaton, based on the time-dependent spatial diffeomorphism, which is not broken by the timedependent background evolution.
Journal ArticleDOI
Essential Building Blocks of Dark Energy
TL;DR: In this article, a minimal description of single field dark energy/modified gravity within the effective field theory formalism for cosmological perturbations is proposed, which encompasses most existing models.
Journal ArticleDOI
Towards a Nonsingular Bouncing Cosmology
TL;DR: In this article, a nonsingular bouncing cosmology using single scalar field matter with non-trivial potential and non-standard kinetic term is presented, where the potential sources a dynamical attractor solution with Ekpyrotic contraction which washes out small amplitude anisotropies.
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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