Could anyone explain me what is the interpretation of t^a filed in(adsbygoogle = window.adsbygoogle || []).push({});

Wald's GR book (p.255). It's defined as any (?) field which

fulfills condition [tex] t^a \nabla_a t [/tex], where t is "time function".

What is the difference between [tex]g^{ab}\nabla_b t [/tex]

and t^a. Thanks for answer.

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

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!

# Laps and shift function

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