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Fermat-Quartik/Syz (x,y,z)/Charakteristik 3/Semistabil, nicht stark semistabil/Beispiel/en

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Let be the smooth Fermat quartic given by and consider on it the syzygy bundle (which is also the restricted cotangent bundle from the projective plane). This bundle is semistable. Suppose that the characteristic is . Then its Frobenius pull-back is . The curve equation gives a global non-trivial section of this bundle of total degree . But the degree of is negative, hence it can not be semistable anymore.