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!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# What is a bifurcation surface and a binormal vector?

**Physics Forums | Science Articles, Homework Help, Discussion**