Timeline for Does hypoellipticity imply the existence of a parametrix?
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| Jun 26, 2021 at 15:38 | comment | added | Bazin | @Bob Yuncken If you take a look at the "lifting" procedure due to Rothschild \& Stein to prove the optimal hypoellipticity of the second operator, you will see that this is very far from the explicit construction of a parametrix. Also if you look at Chapter 27 on Subellipticity in L. Hörmander's ALPDO volume IV, you will check that the subellipticity of $D_x+i x^2(D_y+ c\vert D_z\vert)$ requires the full strength of the whole chapter which does not lead to a parametrix construction. | |
| Jun 25, 2021 at 5:49 | comment | added | Bob Yuncken | This is fascinating. What are you basing your comments on? Why shouldn't we expect a nice parametrix for the second operator, for instance? Any references or hints would be appreciated. | |
| Apr 23, 2021 at 12:01 | history | answered | Bazin | CC BY-SA 4.0 |