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Norbert Ortner

Publications and source records attributed to Norbert Ortner.

8 recordsLinked to original sources
arXiv2024

On the completeness of the space $\mathcal{O}_C$

We give a new proof of the completeness of the space $\mathcal{O}_C$ by applying a criterion of compact regularity for the isomorphic sequence space $\lim_{k\rightarrow} (s\hat \otimes (\ell^\infty)_{-k})$. Along the way we show that the strong dual of any quasinormable Fr\'echet space is a compactly regular $\mathcal{LB}$-space. Finally, we prove that $\lim_{k\rightarrow}(E_k\hat \otimes_\iota F) = (\lim_{k\rightarrow} E_k) \hat \otimes_\iota F$ if the inductive limit $\lim_{k \rightarrow}(E_k \hat \otimes_\iota F)$ is compactly regular.

math.FA↗
arXiv2021

Projective descriptions of spaces of functions and distributions

We present projective descriptions of classical spaces of functions and distributions. More precisely, we provide descriptions of these spaces by semi-norms which are defined by a combination of classical norms and multiplication or convolution with certain functions. These seminorms are simpler than the ones given by a supremum over bounded or compact sets.

math.FA↗
arXiv2017

A simpler description of the $\kappa$-topologies on the spaces $\mathscr{D}_{L^p}$, $L^p$, $\mathscr{M}^1$

The $\kappa$-topologies on the spaces $\mathscr{D}_{L^p}$, $L^p$ and $\mathscr{M}^1$ are defined by a neighbourhood basis consisting of polars of absolutely convex and compact subsets of their (pre-)dual spaces. In many cases it is more convenient to work with a description of the topology by means of a family of semi-norms defined by multiplication and/or convolution with functions and by classical norms. We give such families of semi-norms generating the $\kappa$-topologies on the above spaces of functions and measures defined by integrability properties. In addition, we present a sequence-space representation of the spaces $\mathscr{D}_{L^p}$ equipped with the $\kappa$-topology, which complements a result of J.~Bonet and M.~Maestre. As a byproduct, we give a characterisation of the compact subsets of the spaces $\mathscr{D}'_{L^p}$, $L^p$ and $\mathscr{M}^1$.

math.FA↗
arXiv2016

The space $\dot{\mathcal{B}}'$ of distributions vanishing at infinity - duals of tensor products

Analogous to L.~Schwartz' study of the space $\mathcal{D}'(\mathcal{E})$ of semi-regular distributions we investigate the topological properties of the space $\mathcal{D}'(\dot{\mathcal{B}})$ of semi-regular vanishing distributions and give representations of its dual and of the scalar product with this dual. In order to determine the dual of the space of semi-regular vanishing distributions we generalize and modify a result of A. Grothendieck on the duals of $E \hat\otimes F$ if $E$ and $F$ are quasi-complete and $F$ is not necessarily semi-reflexive.

math.FA↗
arXiv2015

Kernel Identities and Vectorial Regularization

We present the method of "vectorial regularization" to prove kernel identities. This method is applied to derive both known kernel identities, e.g. $\dot{\mathcal{B}}_{xy}=\dot{\mathcal{B}}_x\widehat{\otimes}_\varepsilon\dot{\mathcal{B}}_y$, $\mathcal{D}'_{L^1,xy}=\mathcal{D}'_{L^1,x}\widehat{\otimes}_π\mathcal{D}'_{L^1,y}$, as well as new ones: $\dot{\mathcal{B}}'_{xy}=\dot{\mathcal{B}}'_x\widehat{\otimes}_\varepsilon\dot{\mathcal{B}}'_y$ and $\mathcal{D}_{L^1,xy}=\mathcal{D}_{L^1,x}\widehat{\otimes}_π\mathcal{D}_{L^1,y}$.

math.FA↗