4 papers
Subset expansions of monoids
Victoria Gould, Marianne Johnson
We initiate the study of the expansion of a monoid obtained via the semidirect product of acting naturally on the left of its power set (regarded as a semi…
A new approach to the grammic monoid
Marianne Johnson, António Malheiro
We give an alternative description of the grammic monoid in terms of weakly increasing subsequences. Specifically, we show that words in the generators dete…
Free inverse monoids are co-context-free
Tara Macalister Brough, Marianne Johnson, Mark Kambites +1
We prove (using grammars) that the free inverse monoid of every finite rank has co-context-free word problem. Equivalently, the co-word problem of the free inverse monoid of every…
Forbidden configurations for coherency
Victoria Gould, Marianne Johnson
Right (and left) coherency and right (and left) weak coherency are natural finitary conditions for monoids. Determining whether or not a given monoid has any of these properties is…