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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Testing gravity using galaxy clusters: new constraints on beyond Horndeski theories
TL;DR: In this article, a multi-parameter Markov chain Monte Carlo analysis was used to fit the X-ray and lensing profiles of galaxy clusters and obtain new constraints on the parameters governing deviations from Newtons law ϒ1 = -0.11+0.93-0.67 and light bending ϒ2 = −0.22+1.22-1.19.
Journal ArticleDOI
A Simplified Approach to General Scalar-Tensor Theories
TL;DR: In this paper, it was shown that when considering linear perturbations about a Friedmann-Robertson-Walker background, the theory is completely specified by only six functions of time, two of which are constrained by the background evolution.
Journal ArticleDOI
Covariant Horava-like and mimetic Horndeski gravity: cosmological solutions and perturbations
Guido Cognola,Ratbay Myrzakulov,Lorenzo Sebastiani,Sunny Vagnozzi,Sunny Vagnozzi,Sergio Zerbini +5 more
TL;DR: In this article, a modified version of the Horava-Lifshitz model is considered, where diffeomorphism invariance is broken dynamically via a non-standard coupling to a perfect fluid.
Journal ArticleDOI
A no-go theorem for generalized vector Galileons on flat spacetime
TL;DR: For a single copy of U(1) gauge theory, it was shown in this paper that the Galileon-type generalization of electromagnetism on flat spacetime is forbidden.
BookDOI
A Practical Mini-Course on Applied Holography
TL;DR: In this paper, the authors present a collection of notes based on lectures given at IIT Madras in September 2019 and at IFT Madrid in November 2019 on applied holography and especially the analytic and numerical techniques involved.
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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