Timeline for Nonnegative smooth function as sum of squares of smooth functions
Current License: CC BY-SA 3.0
4 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Sep 1, 2012 at 20:05 | history | edited | Igor Rivin | CC BY-SA 3.0 |
added info.
|
| Sep 1, 2012 at 8:22 | comment | added | Bazin | Thanks for these references, which I knew. As you point out, Bony's result with $C^m$ functions does not extend obviously to the case $m=+\infty$. Looking at the details of the proof, it is clear that the decomposition is changing drastically when $m$ increases. My problem is that these references to P. Cohen result are not supported by any real article or preprint. So somehow the core of my question is: Does anybody ever put his hand on a P.Cohen preprint tackling that counterexample of a $C^\infty$ nonnegative function which is not a finite sum of squares of $C^\infty$ functions ? | |
| Sep 1, 2012 at 0:45 | history | edited | Igor Rivin | CC BY-SA 3.0 |
fixed typesetting
|
| Aug 31, 2012 at 21:19 | history | answered | Igor Rivin | CC BY-SA 3.0 |