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Idempotent semigroups and tropical algebraic sets

Zur Izhakian, Eugenii Shustin (2012)

Journal of the European Mathematical Society

The tropical semifield, i.e., the real numbers enhanced by the operations of addition and maximum, serves as a base of tropical mathematics. Addition is an abelian group operation, whereas the maximum defines an idempotent semigroup structure. We address the question of the geometry of idempotent semigroups, in particular, tropical algebraic sets carrying the structure of a commutative idempotent semigroup. We show that commutative idempotent semigroups are contractible, that systems of tropical...

Norms on semirings. I.

Vítězslav Kala, Tomáš Kepka, Petr Němec (2010)

Acta Universitatis Carolinae. Mathematica et Physica

Notes on commutative parasemifields

Vítězslav Kala, Tomáš Kepka, Miroslav Korbelář (2009)

Commentationes Mathematicae Universitatis Carolinae

Parasemifields (i.e., commutative semirings whose multiplicative semigroups are groups) are considered in more detail. We show that if a parasemifield S contains + as a subparasemifield and is generated by + { a } , a S , as a semiring, then S is (as a semiring) not finitely generated.

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