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Download fileGreen’s relations in finite transformation semigroups
conference contribution
posted on 2018-02-22, 13:48 authored by Lukas Fleischer, Manfred Kufleitner© Springer International Publishing AG 2017. We consider the complexity of Green’s relations when the semigroup is given by transformations on a finite set. Green’s relations can be defined by reachability in the (right/left/two-sided) Cayley graph. The equivalence classes then correspond to the strongly connected com-ponents. It is not difficult to show that, in the worst case, the number of equivalence classes is in the same order of magnitude as the number of elements. Another important parameter is the maximal length of a chain of components. Our main contribution is an exponential lower bound for this parameter. There is a simple construction for an arbitrary set of generators. However, the proof for constant alphabet is rather involved. Our results also apply to automata and their syntactic semigroups.
Funding
This work was supported by the DFG grants DI 435/5-2 and KU 2716/1-1.
History
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- Science
Department
- Computer Science