We find generators for the algebra of rational differential invariants for general and degenerate Kundt spacetimes and relate this to other approaches to the equivalence problem for Lorentzian metrics. Special attention is given to dimensions three and four.

中文翻译：

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昆特时空的微分不变量

我们为一般和退化昆特时空的有理微分不变量的代数找到生成器，并将其与洛伦兹度量的等价问题的其他方法联系起来。特别注意维度三和四。