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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A covariant Lagrangian for stable nonsingular bounce
Yong Cai,Yun-Song Piao +1 more
TL;DR: In this article, a covariant effective theory for stable nonsingular bounce was proposed, which has the quadratic order of the second order derivative of the field ϕ but the background set only by P (ϕ, X).
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Primordial gravitational waves in supersolid inflation
TL;DR: In this paper, the tensor-to-scalar ratio depends only on the parameter controlling the breaking of space-reparameterization, and this represents a difference with respect to standard single-field inflationary models.
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Phenomenology of dark energy: exploring the space of theories with future redshift surveys
Federico Piazza,Heinrich Steigerwald,Heinrich Steigerwald,Christian Marinoni,Christian Marinoni,Christian Marinoni +5 more
TL;DR: In this article, the authors use the effective field theory of dark energy to explore the space of modified gravity models which are capable of driving the present cosmic acceleration, and identify five universal functions of cosmic time that are enough to describe a wide range of theories containing a single scalar degree of freedom in addition to the metric.
Journal ArticleDOI
Constraining chameleon models with cosmology
TL;DR: In this article, signatures of chameleon modifications in the nonlinear cosmological structure, comparing different techniques to model them, summarising the current state of observational constraints, and concluding with an outlook on prospective constraints from future observations and applications of the analytic tools developed in the process to more general scalar-tensor theories.
Journal ArticleDOI
Polarizations of gravitational waves in Horndeski theory
Shaoqi Hou,Yungui Gong,Yunqi Liu +2 more
TL;DR: In this paper, the authors analyzed the polarization content of gravitational waves in Horndeski theory and showed that the massless limit of the graviton mass severely constrains the amplitude of the longitudinal polarization, which makes its detection highly unlikely by ground-based or space-borne interferometers in the near future.
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.
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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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