Character table-equivalent groups

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This article defines an equivalence relation over the collection of groups. View a complete list of equivalence relations on groups.


Suppose G_1 and G_2 are finite groups and K is a splitting field in characteristic zero for both (we can take K = \mathbb{C} or \overline{\mathbb{Q}}. We say that G_1 and G_2 are character table-equivalent groups if there exists a bijection \alpha between the set of conjugacy classes in G_1 and that of G_2, and a bijection \beta between the set of irreducible characters (up to equivalence) of G_1 and that of G_2, such that under this pair of bijections, the character table of G_1 is identified with that of G_2. In other words, for any character \chi of G_1 and any conjugacy class c of G_1, we have \beta(\chi)(\alpha(c)) = \chi(c).


Character table-equivalent groups share a number of properties and arithmetic function values.

Invariant Why it's the same for character table-equivalent groups
degrees of irreducible representations These can be read off from the character table as the set of values that the character table takes at the identity element's conjugacy class. Note that the identity element's conjugacy class is the unique conjugacy class at which all character values are positive (this can be deduced from the column orthogonality theorem).
order of the whole group Follows from knowledge of degrees of irreducible representations, because sum of squares of degrees of irreducible representations equals order of group
conjugacy class sizes The size of each conjugacy class can be computed using the order and by computing its norm and using the column orthogonality theorem.
order of derived subgroup (or equivalently, its index, which is the order of the abelianization) use number of one-dimensional representations equals order of abelianization
order of center number of conjugacy classes of size 1.
field generated by character values The character table entries are the same, so the field they generate is the same.

On the other hand, the following are not determined: