In this note we give a proof of the Sobolev and Morrey embedding theorems based on the representation of functions in terms of the fundamental solution of suitable partial differential operators. We also prove the compactness of the Sobolev embedding. We first describe this method in the classical setting, where the fundamental solution of the Laplace equation is used, to recover the classical Sobolev and Morrey theorems. We next consider degenerate Kolmogorov equations. In this case, the fundamental solution is invariant with respect to a non-Euclidean translation group and the usual convolution is replaced by an operation that is defined in accordance with this geometry. We recover some known embedding results and we prove the compactness of the Sobolev embedding. We finally apply our regularity results to a kinetic equation.

A Compactness Result for the Sobolev Embedding via Potential Theory / Camellini, Filippo; Eleuteri, Michela; Polidoro, Sergio. - 46:(2021), pp. 61-91. [10.1007/978-3-030-73778-8_4]

### A Compactness Result for the Sobolev Embedding via Potential Theory

#### Abstract

In this note we give a proof of the Sobolev and Morrey embedding theorems based on the representation of functions in terms of the fundamental solution of suitable partial differential operators. We also prove the compactness of the Sobolev embedding. We first describe this method in the classical setting, where the fundamental solution of the Laplace equation is used, to recover the classical Sobolev and Morrey theorems. We next consider degenerate Kolmogorov equations. In this case, the fundamental solution is invariant with respect to a non-Euclidean translation group and the usual convolution is replaced by an operation that is defined in accordance with this geometry. We recover some known embedding results and we prove the compactness of the Sobolev embedding. We finally apply our regularity results to a kinetic equation.
##### Scheda breve Scheda completa Scheda completa (DC)
2021
23-mar-2021
Harnack Inequalities and Nonlinear Operators.
Vespri V., Gianazza U., Monticelli D.D., Punzo F., Andreucci D.
978-3-030-73777-1
978-3-030-73778-8
Springer, Cham
A Compactness Result for the Sobolev Embedding via Potential Theory / Camellini, Filippo; Eleuteri, Michela; Polidoro, Sergio. - 46:(2021), pp. 61-91. [10.1007/978-3-030-73778-8_4]
Camellini, Filippo; Eleuteri, Michela; Polidoro, Sergio
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Utilizza questo identificativo per citare o creare un link a questo documento: `https://hdl.handle.net/11380/1245977`