Timeline for Does the generalised directional derivative satisfy any version of the chain rule?
Current License: CC BY-SA 4.0
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| Mar 27, 2020 at 22:48 | comment | added | Bazin | Well the chain rule is about finding the derivative of $F\circ u$. My remark above is highlighting the fact that when you have a limited amount of regularity, say when the function $u$ is not better than $L^\infty$, if you have the weak information that $Xu$ belongs to $L^1$, you can still apply the chain rule and this is the core argument for the DiPerna-Lions theory for first-order linear equations with $W^{1,1}$ coefficients. | |
| Mar 26, 2020 at 4:21 | comment | added | Willie Wong | I fail to see how this addresses the question in the OP. Can you give more details? | |
| Mar 25, 2020 at 16:36 | history | answered | Bazin | CC BY-SA 4.0 |