zbMATH — the first resource for mathematics

Examples
 Geometry Search for the term Geometry in any field. Queries are case-independent. Funct* Wildcard queries are specified by * (e.g. functions, functorial, etc.). Otherwise the search is exact. "Topological group" Phrases (multi-words) should be set in "straight quotation marks". au: Bourbaki & ti: Algebra Search for author and title. The and-operator & is default and can be omitted. Chebyshev | Tschebyscheff The or-operator | allows to search for Chebyshev or Tschebyscheff. "Quasi* map*" py: 1989 The resulting documents have publication year 1989. so: Eur* J* Mat* Soc* cc: 14 Search for publications in a particular source with a Mathematics Subject Classification code (cc) in 14. "Partial diff* eq*" ! elliptic The not-operator ! eliminates all results containing the word elliptic. dt: b & au: Hilbert The document type is set to books; alternatively: j for journal articles, a for book articles. py: 2000-2015 cc: (94A | 11T) Number ranges are accepted. Terms can be grouped within (parentheses). la: chinese Find documents in a given language. ISO 639-1 language codes can also be used.

Operators
 a & b logic and a | b logic or !ab logic not abc* right wildcard "ab c" phrase (ab c) parentheses
Fields
 any anywhere an internal document identifier au author, editor ai internal author identifier ti title la language so source ab review, abstract py publication year rv reviewer cc MSC code ut uncontrolled term dt document type (j: journal article; b: book; a: book article)
On the “three-space” problem for locally quasi-convex topological groups. (English) Zbl 0955.22006
The main result of this paper is the analogue for topological groups of a theorem due to S. Dierolf which states that there exists a nonlocally convex twisted sum of the locally convex spaces $X$ and $Y$ if and only if there exists a nonlocally convex twisted sum of $X$ and $ℝ$. It reads as follows: Given two abelian locally quasi-convex groups $H$ and $G$ there exists a nonlocally quasi-convex extension of $H$ and $G$ if and only if there exists a nonlocally quasi-convex extension of the circle group ${S}^{1}$ and $G$. The proof relies on methods of homological algebra.
MSC:
 22B05 General properties and structure of LCA groups 46B20 Geometry and structure of normed linear spaces 46B28 Spaces of operators; tensor products; approximation properties 46B08 Ultraproduct techniques in Banach space theory