“…In this sense, the model under consideration is similar to the EinsteinCartan theory that also reduces to Einstein's general relativity in absence of the sources with spin, see [5,13].…”
Evans developed a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. In an accompanying paper I, we analyzed this theory and summarized it in nine equations. We now propose a variational principle for Evans' theory and show that it yields two field equations. The second field equation is algebraic in the torsion and we can resolve it with respect to the torsion. It turns out that for all physical cases the torsion vanishes and the first field equation, together with Evans' unified field theory, collapses to an ordinary Einstein equation.
“…In this sense, the model under consideration is similar to the EinsteinCartan theory that also reduces to Einstein's general relativity in absence of the sources with spin, see [5,13].…”
Evans developed a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. In an accompanying paper I, we analyzed this theory and summarized it in nine equations. We now propose a variational principle for Evans' theory and show that it yields two field equations. The second field equation is algebraic in the torsion and we can resolve it with respect to the torsion. It turns out that for all physical cases the torsion vanishes and the first field equation, together with Evans' unified field theory, collapses to an ordinary Einstein equation.
“…If we relax the former constraint, T α = 0, we arrive at the Riemann-Cartan (RC) spacetime of the viable EinsteinCartan theory of gravity, see [9,27,52,75]. Since still Q αβ = 0, such a RC-spacetime carries a metric-compatible connection and, accordingly, a length is invariant under parallel displacement.…”
Section: Metric-affine Geometry Of Spacetimementioning
We show that the Einstein-aether theory of Jacobson and Mattingly (J&M) can be understood in the framework of the metric-affine (gauge theory of) gravity (MAG).We achieve this by relating the aether vector field of J&M to certain post-Riemannian nonmetricity pieces contained in an independent linear connection of spacetime.Then, for the aether, a corresponding geometrical curvature-square Lagrangian with a massive piece can be formulated straightforwardly. We find an exact spherically symmetric solution of our model.
“…Within the EC-theory, the energy-momentum law reads, see Sciama, Kibble, and others [36,38,51,57,66,71,72],…”
Section: Energy-momentum and Angular Momentum Lawsmentioning
confidence: 99%
“…Incidentally, in four dimensions, RC-geometry was first applied in the viable Einstein-Cartan(-Sciama-Kibble) theory of gravity, for short EC-theory [35,36,51,66,67,71,72].…”
Section: Defining Rc-geometrymentioning
confidence: 99%
“…In fact, in the same papers [15], he linked, within a consistent theoretical framework, torsion to the spin of matter. He laid the groundwork to what we call nowadays the EC-theory of gravity [2,36,72]. This excludes the mentioned identification of a piece of the torsion with the electromagnetic potential.…”
Evans developed a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. This geometry can be characterized by an orthonormal coframe ϑ α and a (metric compatible) Lorentz connection Γ αβ . These two potentials yield the field strengths torsion T α and curvature R αβ . Evans tried to infuse electromagnetic properties into this geometrical framework by putting the coframe ϑ α to be proportional to four extended electromagnetic potentials A α ; these are assumed to encompass the conventional Maxwellian potential A in a suitable limit. The viable Einstein-Cartan(-Sciama-Kibble) theory of gravity was adopted by Evans to describe the gravitational sector of his theory. Including also the results of an accompanying paper by Obukhov and the author, we show that Evans' ansatz for electromagnetism is untenable beyond repair both from a geometrical as well as from a physical point of view. As a consequence, his unified theory is obsolete.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.