Timeline for Function with all but mixed second partial derivatives twice differentiable?
Current License: CC BY-SA 3.0
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| Sep 25, 2012 at 20:50 | comment | added | Michael Renardy | The are well known counterexamples of functions for which $\Delta f$ is continuous, but f is not $C^2$. The question asks what happens under the stronger condition that both $f_{xx}$ and $f_{yy}$ are continuous. | |
| Sep 25, 2012 at 19:38 | history | answered | Delio Mugnolo | CC BY-SA 3.0 |