Noninvertibility preservers on Banach algebras
It is proved that a linear surjection , which preserves noninvertibility between semisimple, unital, complex Banach algebras, is automatically injective.
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Bojan Kuzma (2006)
Czechoslovak Mathematical Journal
It is proved that a linear surjection , which preserves noninvertibility between semisimple, unital, complex Banach algebras, is automatically injective.
Béla Bollobás (1974)
Studia Mathematica
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