We investigate whether the equivalence theorem in f(R)-type gravity is valid also in quantum theory. It is shown that, if the canonical quantization is assumed, equivalence does not hold in quantum theory.
The four-dimensional Einstein-Gauss-Bonnet (4DEGB) gravity is proposed as a singular limit of the higher-dimensional EGB gravity with a rescaled coupling constant. Follow-up work indicates that the 4DEGB gravity may be equivalent to a special Horndeski gravity. However, the full equivalence of the two theories has not been proven. In this paper, we test the possible equivalence for Bianchi type I metric. We consider two symmetry choices of the extra dimensions in the 4DEGB gravity and obtain the explicit cosmological evolution equations of the theories. Our result shows that, for one symmetry …
Humboldt-Universität zu Berlin(柏林洪堡大学);Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut)(马克斯·普朗克引力物理研究所(爱因斯坦研究所));Universidad Complutense de Madrid(马德里康普顿斯大学);Dublin Institute for Advanced Studies(都柏林高等研究院);Charles University(查理大学)
We review the possible violation of the Equivalence Principle at finite temperature T in the framework of curvature based Extended Theories of Gravity. Specifically, we first show how it is possible to derive Equivalence Principle violation from Quantum Field Theory at non-vanishing T. Subsequently, we exhibit how this result can be precisely recovered by following an alternative path that envisages the employment of generalized Einstein equations with a temperature-dependent energy-momentum tensor. Finally, we adopt the latter formalism in the context of some Extended Gravity models to quanti…
We give a general overview of various flavors of the equivalence principle in classical and quantum physics, with special emphasis on the so-called weak equivalence principle, and contrast its validity in mechanics versus field theory. We also discuss its generalisation to a theory of quantum gravity. Our analysis suggests that only the strong equivalence principle can be considered fundamental enough to be generalised to a quantum gravity context, since all other flavors of equivalence principle hold only approximately already at the classical level.
Rastall gravity is a modified gravity proposal that incorporates a non-conserved energy momentum tensor (EMT). We study the equivalence between Rastall gravity and general relativity, analyzing its consequences for an EMT of dark matter and dark energy. We find that the translation between the Rastall and Einstein interpretations modifies the equation of state for each component. For instance, cold dark matter can translate into warm dark matter. If the EMT components are allowed to interact, the translation also changes the type of interaction between the components.
Equivalence of scalar-tensor theories and scale-dependent gravity
Technische Universität Wien(维也纳工业大学);Pontificia Universidad Católica de Chile(智利天主教 Pontificia 大学);Radboud University(拉德堡德大学);Silesian University in Opava(奥帕瓦西里西亚大学);Universitat Politècnica de València(巴伦西亚理工大学)
We construct phase-space structure of a typical higher-order theory of gravity, in the background of anisotropic Bianchi-1 mini-superspace, following `Modified Horowitz Formalism' as well as applying `Dirac Algorithm' (after taking care of the divergent terms), and establish equivalence. Canonical quantization, and semiclassical approximation are performed to expatiate the fact that such a quantum theory transits successfully to a classical de-Sitter universe. Inflation has thereafter been studied. The numerical values of the inflationary parameters show excellent agreement with the latest rel…
We present a novel derivation of Einstein equations from the balance between Clausius entropy crossing the boundary of a local causal diamond and entanglement entropy associated with its horizon. Comparing this derivation with the entanglement equilibrium approach developed by Jacobson, we are able to argue for the equivalence of matter entanglement and Clausius entropy in the semiclassical regime. We also provide a direct comparison of both entropies for conformal matter, showing their equivalence without appealing to gravitational dynamics. Furthermore, we determine that gravitational dynami…
In this Chapter we illustrate the close connection between the violation of the weak equivalence principle typical of gravitational interactions at finite temperature, and similar violations induced by a breaking of the local Lorentz symmetry. We also discuss the physical implications of the effective repulsive forces possibly arising in such a generalized gravitational context, by considering, for an illustrative purpose, a quasi-Riemannian model of gravity with rotational symmetry as the local gauge group in tangent space.
Permanent Underdetermination from Approximate Empirical Equivalence in Field Theory: Massless and Massive Scalar Gravity, Neutrino, Electromagnetic, Yang-Mills and Gravitational Theories
Off-shell equivalence in quantum field theory and gravity
Universidade Federal do Paraná(巴拉那联邦大学);SISSA(的里雅斯特高等研究学校);INFN, Sezione di Trieste(意大利国家核物理研究所的里雅斯特分部);IFPU – Institute for Fundamental Physics of the Universe(宇宙基础物理研究所)