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)
Matrices over semirings. (English) Zbl 0884.15010
Let R be a commutative semiring with multiplicative identity 10 (for example, the nonnegative integers), and let M n (R) denote the semiring of n×n matrices over R. Because the condition of invertibility in M n (R) is rather restrictive in this situation, the author introduces the concept of “semi-invertibility”: AM n (R) is semi-invertible if there exist A 1 ,A 2 M n (R) such that I+AA 1 =AA 2 and I+A 1 A=A 2 A. Some more or less straightforward generalizations of criteria for invertibility when R is a ring are made to give criteria for semi-invertibility in the semiring case.
MSC:
15A33Matrices over special rings
16Y60Semirings