We study the relationship between algebraic structures and their inverse semigroups of partial automorphisms. We consider a variety of classes of natural structures including equivalence structures, orderings, Boolean algebras, and relatively complemented distributive lattices. For certain subsemigroups of these inverse semigroups, isomorphism (elementary equivalence) of the subsemigroups yield...

For partial automorphisms of C∗-algebras, Takai-Takesaki crossed product duality tends to fail, in proportion to the extent to which the partial automorphism is not an automorphism.

In this paper we propose a general recipe for calculating the automorphism groups of semigroups consisting of partial endomorphisms of relational structures with a single m-ary relation for any m ∈ N over a finite set. We use this recipe to determine the automorphism groups of the following semigroups: the full transformation semigroup, the partial transformation semigroup, and the symmetric in...

1. The automorphism group T(P) of a partial order P is the collection of all order preserving permutations (automorphisms) of P, a subgroup of the symmetric group on P. If P and g are partial orders then P x g becomes a partial order by reverse lexicography: (p, q) < (p', q') if q < q' or q = q' and p < p'. If ƒ is a function whose domain contains the element a, we use af to denote the image of...

In order to count partial orders on a set of n points, it seems necessary to explicitly construct a representative of every isomorphism type. While that is done, one might as well determine their automorphism groups. In this note it is shown how several other types of binary relations can be counted, based on an explicit enumeration of the partial orders and their automorphism groups. A partial...

In this paper we investigate when the generic member of a family of complex K3 surfaces admitting a non–symplectic automorphism of finite order admits also a symplectic automorphism of the same order. We give a complete answer to this question if the order of the automorphism is a prime number and we provide several examples and partial results otherwise. Moreover we prove that, under certain c...