1. Ordered spaces
Risking semantic incoherence, we propose in this paper to use the term ordered
space to mean any totally ordered set X equipped with a topology
[Tscr ], while retaining
the term linearly ordered space for its usual role of denoting the special case in
which [Tscr ] is the order topology: the topology generated by the
order-open initial and final segments of X.
The categories that we shall consider are full subcategories of the category
OrdTop of ordered spaces and order-preserving continuous maps.
It is easy to see
that — in contrast to the situation in the full subcategory LinOrdTop
of linearly
ordered spaces — every inverse spectrum in OrdTop has a limit and
that OrdTop
admits subspaces and quotient spaces. These limits, subspaces and quotient spaces
are all constructed precisely as in the category Top and are given
their naturally
induced orderings: where, however, we note that, for the ordered space
X to induce
an ordering on a quotient space, the quotient space (construed as a decomposition)
must partition X into intervals rather than into arbitrary subsets.
(In the terminology of [1], these constructions define
subspaces and quotient spaces in OrdTop as,
respectively, the domains and codomains of extremal monomorphisms and
epimorphisms.) The purpose of the paper is to identify the closures of
LinOrdTop under these constructions.