Frerick, Leonhard; Jorda Mora, Enrique; Wengenroth, Jochen(Springer-Verlag, 2020-08)
[EN] We introduce sufficient as well as necessary conditions for a compact set K such that there is a continuous linear extension operator from the space of restrictions C-infinity (K) = {F vertical bar(K) : F is an element ...
Frerick, Leonhard; Jorda Mora, Enrique; Kalmes, Thomas; Wengenroth, Jochen(Elsevier, 2014-04-01)
We prove that for a strongly continuous semigroup T on the Frechet space omega of all scalar sequences, its generator is a continuous linear operator A is an element of L(omega) and that, for all x is an element of omega ...
Frerick, Leonhard; Jorda Mora, Enrique; Wengenroth, Jochen(Elsevier, 2011-08-01)
For a compact set K subset of R(d) we present a rather easy construction of a linear extension operator E : epsilon (K) -> C(infinity) for the space of Whitney jets epsilon (K) which satisfies linear tame continuity estimates ...
Frerick, Leonhard; Arne Jakobs; Jorda Mora, Enrique; Wengenroth, Jochen(Elsevier, 2020-09-01)
[EN] For a compact set K subset of R-d we characterize the existence of a linear extension operator E: E(K) -> C-infinity (R-d) for the space of Whitney jets E(K) with a certain loss of derivatives sigma, that is, the ...
Frerick, Leonhard; Jorda Mora, Enrique; Wengenroth, Jochen(European Mathematical Society, 2016)
[EN] For a compact set K subset of R-d we characterize the existence of a linear extension operator E: E (K) -> C-infinity(R-d) for the space of Whitney jets E (K) without loss of derivatives, that is, it satisfies the ...