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

If I know the velocity, $\mathbf{v}(\mathbf{r},t)$, everywhere, is it possible to determine the diffusion coefficient, $D(\mathbf{r},t)$ everywhere as well?

Would it be possible from using Fick's Law $$j = -D\cdot\nabla L$$

Or can it be found from the mean-squared displacement with $$\frac{\partial \langle r^2\rangle }{\partial t} = 4D$$ ($6D$ in 3D)

What would be the best way to go about this?

share|cite|improve this question
I've made some significant changes to make the question more understandable/clear. Please edit it if you feel that I have incorrectly modified the question. – Kyle Kanos Mar 20 '14 at 12:51
What is being diffused here? A single gas in ambient? A few different gases in ambient? Something else? – Kyle Kanos Mar 20 '14 at 12:55

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.