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Table of Marks


The table of marks of a finite group G records the numbers of group fixed points for the transitive group actions of G on cosets of its subgroups. Let H_1, H_2, ..., H_r be representatives of the conjugacy classes of subgroups of G. The table of marks is the r×r matrix M=(m_(ij)) with

 m_(ij)=|{H_ig:H_igh=H_ig for every h in H_j}|.

Thus m_(ij) is the number of fixed points of H_j in the transitive action of G on the right cosets of H_i (Burnside 1955).

If the subgroup classes are ordered compatibly with containment up to conjugacy, the table is a lower triangular matrix. Its ith diagonal entry is the subgroup index [N_G(H_i):H_i] of H_i in its normalizer, so the table is a nonsingular matrix. Since every transitive permutation action of G is equivalent to a group action on the cosets of a subgroup, invertibility allows the multiplicities of the transitive constituents of a finite G-set to be recovered from its fixed-point counts. The table also encodes containment information among conjugacy classes of subgroups (GAP).

For example, using the class order 1, C_2, C_3, S_3, the table of marks of the symmetric group S_3 is

 M(S_3)=(6 0 0 0; 3 1 0 0; 2 0 2 0; 1 1 1 1).

Tables of marks were introduced by Burnside and are consequently also called Burnside matrices.


See also

Conjugacy Class, Coset, Finite Group, Group Action, Normalizer, Permutation Group, Subgroup

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References

Burnside, W. Theory of Groups of Finite Order, 2nd ed. New York: Dover, 1955.GAP. "Tables of Marks." Ch. 70 in GAP Reference Manual. https://gap-system.github.io/gap/doc/ref/chap70_mj.html.

Cite this as:

Weisstein, Eric W. "Table of Marks." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/TableofMarks.html

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