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pro vyhledávání: '"David J. Fernández Bretón"'
Autor:
David J. Fernández Bretón
Publikováno v:
Canadian Journal of Mathematics. 68:44-66
We answer two questions of Hindman, Stepr\=ans and Strauss, namely we prove that every strongly summable ultrafilter on an abelian group is sparse and has the trivial sums property. Moreover we show that in most cases the sparseness of the given ultr
Publikováno v:
Semigroup Forum. 92:242-257
We prove that if S is a commutative semigroup with well founded universal semilattice or a solvable inverse semigroup with well founded semilattice of idempotents, then every strongly productive ultrafilter on S is idempotent. Moreover we show that a