Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have a very basic question. What exactly is meant by "regular" initial data in general relativity? Does it mean smooth? at least $C^{2}$?

All literature on the subject just uses this term without exact explanation, so it seems that it's something very trivial, but I just wanted to know for sure.

share|cite|improve this question
With Bianchi identities it seems better than the metric tensor would be, at least, 3 times differentiable, but I think that the standard is infinitely differentiable, so $C^{\infty}$. – Trimok Jun 10 '13 at 9:46
Could you include an example of where the term is being used so that we can have some context. The answer to this could very well be context-dependent after all. – joshphysics Jun 10 '13 at 16:30
@joshphysics well,it's used literally in every book/paper. Some examples: link, on page 2 talks about "sufficiently regular" without explanation what it is, or another example link – ConciseAndClear Jun 11 '13 at 7:32

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.