Fat Delta 2: Functorial Subgroups of Topological Abelian Groups
In the predecessor  of this paper the canonical subgroup (Fat Delta) ∆(G) of a compact abelian group G was studied. It is the sum of all closed disconnected subgroups of G and it appeared before in the literature (see ) as td(G), defined for arbitrary topological groups and motivated by completely different considerations. We introduce and compare further functorial subgroups of general topological groups and study their relationships with ∆(G) and td(G).
Dikranjan, D., Lewis, W., Loth, P. & Mader, A. (2023). Fat delta 2: Functorial subgroups of topological abelian groups. Topological Proceedings, 61, 269-304.