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We review some recent developments in the conformal gravity theory that has been advanced as a candidate alternative to standard Einstein gravity. As a quantum theory the conformal theory is both renormalizable and unitary, with unitarity…

High Energy Physics - Theory · Physics 2015-05-27 Philip D. Mannheim

The Maxwell extension of the conformal algebra is presented. With the help of gauging the Maxwell-conformal group, a conformally invariant theory of gravity is constructed. In contrast to the conventional conformally invariant actions, our…

High Energy Physics - Theory · Physics 2020-02-21 Salih Kibaroğlu , Oktay Cebecioğlu

We couple a conformal scalar field in (2+1) dimensions to Einstein gravity with torsion. The field equations are obtained by a variational principle. We could not solve the Einstein and Cartan equations analytically. These equations are…

General Relativity and Quantum Cosmology · Physics 2018-06-06 H. T. Özçelik , R. Kaya , M. Hortaçsu

The four-dimensional gauge group of general relativity corresponds to arbitrary coordinate transformations on a four-manifold. Theories of gravity with a dynamical structure remarkably like Einstein's theory can be obtained on the basis of…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Julian Barbour , Niall O Murchadha

We present a streamlined proof that any Einstein-AdS space is a solution of the Lu, Pang and Pope conformal gravity theory in six dimensions. The reduction of conformal gravity into Einstein theory manifestly shows that the action of the…

High Energy Physics - Theory · Physics 2023-11-13 Giorgos Anastasiou , Ignacio J. Araya , Cristobal Corral , Rodrigo Olea

We derive rigorous bounds on corrections to Einstein gravity using unitarity and analyticity of graviton scattering amplitudes. In $D\geq 4$ spacetime dimensions, these consistency conditions mandate positive coefficients for certain…

High Energy Physics - Theory · Physics 2016-04-06 Brando Bellazzini , Clifford Cheung , Grant N. Remmen

Einstein-Hilbert action with a determinantal invariant has been considered. The obtained field equation contains the \texttt{inverse Ricci tensor}, $\Re_{\alpha\beta}$. The linearized solution of invariant has been examined, and constant…

General Relativity and Quantum Cosmology · Physics 2016-02-16 Nurettin Pirinccioglu

It has been recently shown that there is a particular combination of conformal invariants in six dimensions which accepts a generic Einstein space as a solution. The Lagrangian of this Conformal Gravity theory -- originally found by Lu,…

High Energy Physics - Theory · Physics 2021-08-04 Giorgos Anastasiou , Ignacio J. Araya , Cristobal Corral , Rodrigo Olea

The Janis-Newman-Winicour metric is a solution of Einstein's gravity minimally coupled to a real massless scalar field. The $\gamma$-metric is instead a vacuum solution of Einstein's gravity. These spacetimes have no horizon and possess a…

General Relativity and Quantum Cosmology · Physics 2018-03-08 Hrishikesh Chakrabarty , Carlos A. Benavides-Gallego , Cosimo Bambi , Leonardo Modesto

The theory described by the sum of the Einstein-Hilbert action and the action of conformal scalar field possesses the duality symmetry which includes some special conformal transformation of the metric, and also inversion of scalar field…

High Energy Physics - Theory · Physics 2009-10-30 I. L. Shapiro

We present a global conformal invariant on closed six-manifolds which obstructs the existence of a conformally Einstein metric. We show that this obstruction is nontrivial and, up to multiplication by a constant, is the unique such…

Differential Geometry · Mathematics 2022-07-06 Jeffrey S. Case

We study the three dimensional Einstein gravity conformally coupled to a scalar field. Solutions of this theory are geometries with vanishing scalar curvature. We consider solutions with a constant scalar field which corresponds to an…

High Energy Physics - Theory · Physics 2012-11-08 M. Hasanpour , F. Loran , H. Razaghian

We construct polynomial conformal invariants, the vanishing of which is necessary and sufficient for an $n$-dimensional suitably generic (pseudo-)Riemannian manifold to be conformal to an Einstein manifold. We also construct invariants…

Differential Geometry · Mathematics 2007-05-23 A. Rod Gover , Pawel Nurowski

We construct explicitly deformations of Einstein's theory of gravity that are consistent and phenomenologically viable since they respect, in particular, cosmological backgrounds. We show that these deformations have unique symmetries in…

High Energy Physics - Theory · Physics 2013-05-30 Felix Berkhahn , Dennis Dietrich , Stefan Hofmann , Florian Kühnel , Parvin Moyassari

We review the current status and prospects for the conformal invariant fourth order theory of gravity which has recently been advanced by Mannheim and Kazanas as a candidate alternative to the standard second order Einstein theory. We…

General Relativity and Quantum Cosmology · Physics 2009-09-25 Philip D. Mannheim

We construct higher-dimensional generalizations of the Eguchi-Hanson gravitational instanton in the presence of higher-curvature deformations of general relativity. These spaces are solutions to Einstein gravity supplemented with the…

High Energy Physics - Theory · Physics 2022-11-03 Cristóbal Corral , Daniel Flores-Alfonso , Gastón Giribet , Julio Oliva

A relation between gravity on Poisson manifolds proposed in arXiv:1508.05706 and Einstein gravity is investigated. The compatibility of the Poisson and Riemann structures defines a unique connection, the contravariant Levi-Civita…

High Energy Physics - Theory · Physics 2017-05-19 Yukio Kaneko , Hisayoshi Muraki , Satoshi Watamura

We study the cosmology of a quadratic metric-compatible torsionful gravity theory in the presence of a perfect hyperfluid. The gravitational action is an extension of the Einstein-Cartan theory given by the usual Einstein-Hilbert…

General Relativity and Quantum Cosmology · Physics 2021-10-07 Damianos Iosifidis , Lucrezia Ravera

Starting from the original Einstein action, sometimes called the Gamma squared action, we propose a new setup to formulate modified theories of gravity. This can yield a theory with second order field equations similar to those found in…

General Relativity and Quantum Cosmology · Physics 2021-07-14 Christian G. Boehmer , Erik Jensko

We show that the action of Einstein's gravity with a scalar field coupled in a generic way to spacetime curvature is invariant under a particular set of conformal transformations. These transformations relate dual theories for which the…

General Relativity and Quantum Cosmology · Physics 2009-11-10 L. R. Abramo , L. Brenig , E. Gunzig , A. Saa