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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Journal ArticleDOI
Effective Description of Higher-Order Scalar-Tensor Theories
TL;DR: In this paper, the dispersion relations for the linear perturbations around Minkowski and a cosmological background were derived for the Degenerate Higher-Order Scalar-Tensor (DHOST) theories.
Journal ArticleDOI
Extended mimetic gravity: Hamiltonian analysis and gradient instabilities
TL;DR: In this article, a class of degenerate higher-order scalar-tensor theories is proposed as an extension of mimetic gravity, which can generate a large class of theories with at most three physical degrees of freedom.
Journal ArticleDOI
Nonlinear structure formation in the Cubic Galileon gravity model
TL;DR: In this article, the authors model the growth of large scale structure in the Cubic Galileon gravity model, by running a suite of N-body cosmological simulations using the ECOSMOG code.
Journal ArticleDOI
UV-protected (Natural) Inflation: Primordial Fluctuations and non-Gaussian Features
Cristiano Germani,Yuki Watanabe +1 more
TL;DR: In this article, the UV-protected inflation model was considered and it was shown that the curvature perturbations in the local form are completely dominated by the nonlinear gauge transformation from the spatially flat to uniform-field gauge and/or by parity violating interactions of the inflaton and gauge bosons.
Journal ArticleDOI
Effects of modified gravity on B-mode polarization
TL;DR: In this article, the authors explore the impact of modified gravity on $B$-modes, identifying two main separate effects: lensing and propagation of tensor modes, and obtain that the gravitational wave speed is compatible with the speed of light and constrained to within about 10%.
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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