Solution

ID: past-exam-of-the-lie-algebras-and-representation-theory-of-symmetric-groups-course-of-the-university-of-oxford/2010/b/6/1/solution

There is more than one solution: the trivial representation has character everywhere and the sign representation has character everywhere. Thus
In fact they are the only ones. The full-cycle formula in the preceding discussion forces any candidate to be a hook . For , the standard character is the number of fixed points minus one, so it vanishes on cycle type ; its sign twist does too. For , the hook representation is the exterior square of the standard representation and has character . At cycle type both standard-character values are one, so this character is zero. Its sign twist also vanishes there. Only remain.

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