I've been reading Wald's book on GR as well as his article "Thermodynamics of Black Holes" in Living Reviews in Relativity about the definitions of mass and energy in GR and the concepts of entropy and temperature of black holes.(adsbygoogle = window.adsbygoogle || []).push({});

I keep coming across the words "bifurcation surface" and "binormal vector", usually when some sort of surface integral is defined to compute the mass, entropy, etc. What exactly do they mean and where can I find a good place that could explain them in an introductory manner?

Thanks!

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# What is a bifurcation surface and a binormal vector?

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