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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Generalized multi-Galileons, covariantized new terms, and the no-go theorem for nonsingular cosmologies
Shingo Akama,Tsutomu Kobayashi +1 more
TL;DR: In this article, it was shown that nonsingular cosmological solutions in second-order scalar-tensor theories generically suffer from gradient instabilities, and they extended this no-go result to secondorder gravitational theories with an arbitrary number of interacting scalar fields.
Journal ArticleDOI
On the non-attractive character of gravity in f(R) theories
Franco D. Albareti,Jose A. R. Cembranos,A. de la Cruz-Dombriz,A. de la Cruz-Dombriz,Antonio Dobado +4 more
TL;DR: In this article, the authors derived explicit upper bounds for the contribution of space-time geometry to the Raychaudhuri equation and examined the parameter constraints for some paradigmatic f(R) models in order to ensure a positive contribution to this equation.
Journal ArticleDOI
Testing the equivalence principle on cosmological scales
Camille Bonvin,Pierre Fleury +1 more
TL;DR: In this paper, the relativistic effects in the large-scale structure can be used to directly test whether dark matter satisfies Euler's equation, i.e. whether its free fall is characterised by geodesic motion, just like baryons and light.
Journal ArticleDOI
Scalar-tensor theories of gravity, neutrino physics, and the H0 tension
Mario Ballardini,Matteo Braglia,Matteo Braglia,Fabio Finelli,Daniela Paoletti,Alexei A. Starobinsky,Alexei A. Starobinsky,C. Umilta +7 more
TL;DR: In this paper, the Ricci scalar-tensor model was shown to be robust to changes in the neutrino physics, and the coupling to the scalar was relaxed to 2.3.
Journal ArticleDOI
Conserved cosmological perturbation in Galileon models
TL;DR: In this article, the existence of curvature perturbation on large scales in Galileon-type scalar field models has been proved, based on the conservation of energy-momentum tensor of the Galileon field.
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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