将电磁场视为基本场，而度规仅视为辅助场
To consider the electromagnetic field as fundamental, and the metric only as a subsidiary field
摘要：
根据Asher Peres（1962）的旧建议，我们认为电磁场是基本场，度规是辅助场。在遵循这一思想的过程中，我们以一种非同态不变量和度量无关的方式来表述麦克斯韦理论。然后，根据激励$H=(H,D)$和场强$F=(E,B)$给出电磁场。此外，在$H$和$F$之间，即$H \sim κF$，具有本构张量$κ$，假定了局部和线性的“时空关系”。本文用阿达玛方法研究了电磁波波前（不连续面）的传播。我们发现一个广义菲涅耳方程，是四次的波的波前的波向量。我们讨论了在什么条件下波沿光锥传播。因此，我们通过纯粹的电磁方法推导出时空的度规，直到共形因子。
英文摘要：
In accordance with an old suggestion of Asher Peres (1962), we consider the electromagnetic field as fundamental and the metric as a subsidiary field. In following up this thought, we formulate Maxwell's theory in a diffeomorphism invariant and metric-independent way. The electromagnetic field is then given in terms of the excitation $H=(H,D)$ and the field strength $F=(E,B)$. Additionally, a local and linear ``spacetime relation'' is assumed between $H$ and $F$, namely $H \sim κF$, with the constitutive tensor $κ$. The propagation is studied of electromagnetic wave fronts (surfaces of discontinuity) with a method of Hadamard. We find a generalized Fresnel equation that is quartic in the wave covector of the wave front. We discuss under which conditions the waves propagate along the light cone. Thereby we derive the metric of spacetime, up to a conformal factor, by purely electromagnetic methods.
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