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Dear Mrs. Forum,

Jacob Hirbawi sent you a bug report today.

gap> data := CharTable("SL",2,13);; gap> rep := data.irreducibles[14];; gap> Eigenvalues(data,rep,6); [ 7/13, -7/13, 7/13, 6/13, 7/13, -7/13, 7/13, -7/13, 7/13, 6/13, 7/13, 6/13, -6/13, 6/13, 7/13, 6/13, 7/13, -7/13, 7/13, -7/13, 7/13, 6/13, 7/13, -7/13, 7/13, 6/13 ]#this one has the problem; shouldn't the result be integers?

Of course the multiplicities of eigenvalues should be integers.

The problem here is a bug in the generic table of 'SL(2,q)' for odd 'q'.

This will be fixed in the next version of GAP.

For 'q' not too big, the tables of 'SL(2,q)' are also available as

library tables (in ATLAS format), for example 'CharTable( "2.L2(13)" )'

is the (correct) table of 'SL(2,13)'.

Kind regards, and thanks to Jacob Hirbawi.

Thomas Breuer

(sam@math.rwth-aachen.de)

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