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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Gravitational Wave Polarizations in $f(R)$ Gravity and Scalar-Tensor Theory
Yungui Gong,Shaoqi Hou +1 more
TL;DR: In this paper, the authors investigate the polarizations of gravitational waves in $f(R)$ gravity and Horndeski theory, both containing scalar modes, and find that in addition to the familiar $+$ and $\times$ polarizations, there are transverse breathing and longitudinal polarizations excited by the massive scalar mode and the new polarization is a single mixed state.
Journal ArticleDOI
G-Warm inflation
TL;DR: In this paper, a warm inflationary universe in the context of the G-model is studied under a general formalism and the inflationary dynamics and the cosmological perturbations considering a coupling of the form G(,X)=g() X.
Journal ArticleDOI
Generalized Galilean Genesis
Sakine Nishi,Tsutomu Kobayashi +1 more
TL;DR: In this paper, a unified description of the Galilean genesis scenario in terms of the Horndeski theory with second-order field equations is given, which results in controlling the evolution of the Hubble rate.
Journal ArticleDOI
Beyond δ : Tailoring marked statistics to reveal modified gravity
Georgios Valogiannis,Rachel Bean +1 more
TL;DR: In this paper, the authors assess the performance of a new ''marked'' transformation and perform a systematic comparison with the clipping and logarithmic transformations, in the context of modified gravity models.
Journal ArticleDOI
Constraining the interaction between dark sectors with future HI intensity mapping observations
TL;DR: In this article, a model of interacting dark matter and dark energy, in which the two components are coupled, was studied and the predictions for the 21-cm intensity mapping power spectra were calculated for future single-dish intensity mapping surveys (BINGO, FAST and SKA-I).
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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