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The CID-operator or centralizer-of-involution-domination-operator is an operator that takes as input a subgroup-defining function (which may make sense for all groups or for a more restricted class like finite groups) and outputs a group property as follows. For a subgroup-defining function f, we say that G satisfies the CID of f if for any involution t in G:

f(C_G(t)) \le f(G)

Application to subgroup-defining functions


The CID-operator applied to the 2-layer is the tautology. In other words, the 2-layer of any centralizer of involution is always contained in the 2-layer of the whole group.


It is conjectured that the CID-operator applied to the B-subgroup is also the tautology. This is the famous B-conjecture that has not yet been resolved.

Brauer core

The image of the Brauer core subgroup-defining function under the CID-operator is the group property of being a balanced group.