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arXiv 1702.05925gr-qchep-thnlin.SI
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具有阿贝尔等距群$\mathcal{G}_2$的Einstein-Maxwell方程的可积和不可积结构

Integrable and non-integrable structures in Einstein - Maxwell equations with Abelian isometry group $\mathcal{G}_2$

George A. Alekseev

摘要:

本文研究了具有非零轨道的阿贝尔二维等距群$\mathcal{G}_2$与电磁场具有相同对称性的一类电真空Einstein-Maxwell场(具有宇宙常数).对于这些领域,我们描述的结构,所谓的"非动力学自由度"的存在,以及存在的宇宙学常数的变化(在一个惊人的相似的方式)的动力学方程和破坏其已知的可积结构。对已知的爱因斯坦-麦克斯韦方程组的简化形式--恩斯特方程组和自对偶Kinnersley方程组在非动力学自由度的存在下进行了修正,并考虑了具有非动力学自由度的场的子类:(I)具有宇宙学常数的真空度规,(II)具有等距群$\mathcal{G}_2$且轨道不允许正交2-曲面的真空时空(非正交传递等距群)和(III)电真空场更一般的电磁场结构比已知的可积的情况下。对于这些类,在对角度量的情况下,场方程可以被简化为唯一的四阶非线性方程的一个实函数$α(x^1,x^2)$的特征面积元素上的等距群$\mathcal{G}_2$的轨道。这些类的解决方案的简单例子。本文指出,如果对于四维或更高维的爱因斯坦场方程的某些二维约化,函数$α(x^1,x^2)$具有"调和"结构,而不是(与其他场变量一起)某些非线性方程的解,这可能表明这些约化的动力学方程对于所有非动力学自由度为零的场可能是完全可积的。

英文摘要:

The classes of electrovacuum Einstein - Maxwell fields (with a cosmological constant), which metrics admit an Abelian two-dimensional isometry group $\mathcal{G}_2$ with non-null orbits and electromagnetic fields possess the same symmetry, are considered. For these fields we describe the structures of so called "nondynamical degrees of freedom" which presence as well as the presence of a cosmological constant change (in a strikingly similar ways) the dynamical equations and destroy their known integrable structures. Modifications of the known reduced forms of Einstein - Maxwell equations -- the Ernst equations and self-dual Kinnersley equations in the presence of non-dynamical degrees of freedom are found and subclasses of fields with non-dynamical degrees of freedom are considered for : (I) vacuum metrics with cosmological constant, (II) vacuum space-times with isometry groups $\mathcal{G}_2$ which orbits do not admit the orthogonal 2-surfaces (none-orthogonally-transitive isometry groups) and (III) electrovacuum fields with more general structures of electromagnetic fields than in the known integrable cases. For these classes, in the case of diagonal metrics, the field equations can be reduced to the only nonlinear equation of the fourth order for one real function $α(x^1,x^2)$ which characterises the element of area on the orbits of the isometry group $\mathcal{G}_2$ . Simple examples of solutions for each of these classes are presented. It is pointed out that if for some two-dimensional reduction of Einstein's field equations in four or higher dimensions, the function $α(x^1,x^2)$ possess a "harmonic" structure, instead of being (together with other field variables) a solution of some nonlinear equations, this can be an indication of possible complete integrability of these reduced dynamical equations for the fields with vanishing of all non-dynamical degrees of freedom.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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