标题： 埃文斯统一场论的评估 II 显示英文标题

标题： An assessment of Evans' unified field theory II

摘要： 埃文斯发展了一种经典的引力和电磁场统一理论，该理论基于满足黎曼-卡坦几何的时空背景。 在附带的一篇论文I中，我们分析了这一理论，并将其概括为九个方程。 我们现在为埃文斯的理论提出一个变分原理，并证明它导出了两个场方程。 第二个场方程在挠率上是代数的，我们可以据此解出挠率。 结果表明，在所有物理情况下，挠率都为零，第一个场方程与埃文斯的统一场理论一起退化为普通的爱因斯坦方程。 显示英文摘要

摘要： 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.