Abstract
The algebraic monoid structure of an incidence algebra is investigated. We show that the multiplicative structure alone determines the algebra automorphisms of the incidence algebra. We present a formula that expresses the complexity of the incidence monoid with respect to the two sided action of its maximal torus in terms of the zeta polynomial of the poset. In addition, we characterize the finite (connected) posets whose incidence monoids have complexity \(\le 1\). Finally, we determine the covering relations of the adherence order on the incidence monoid of a star poset.
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Communicated by Benjamin Steinberg.
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Can, M.B. Incidence monoids: automorphisms and complexity. Semigroup Forum 103, 414–438 (2021). https://doi.org/10.1007/s00233-021-10199-6
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DOI: https://doi.org/10.1007/s00233-021-10199-6
Keywords
- Incidence algebras
- Regular monoids
- Completely regular monoids
- Complexity
- Group of semigroup automorphism
- Adherence order