Type: Incollection

Linear stability of coherent systems and applications to Butler´s conjecture

Castorena, A.; Hitching, G. H.; Luna, E.;

Book Title: Moduli, motives and bundles: new trends in algebraic geometry

Editor: Pedro L. del Ángel R.; Frank Neumann and Alexander H. W. Schmitt

Abstract:

The notion of linear stability of a variety in projective space was introduced by Mumford in the context of GIT. It has subsequently been applied by Mistretta and others to Butler's conjecture on stability of the dual span bundle (DSB) M-V,M- E of a general generated coherent system (E, V). We survey recent progress in this direction on rank one coherent systems, prove a new result for hyperelliptic curves, and state some open questions. We then extend the definition of linear stability to generated coherent systems of higher rank. We show that various coherent systems with unstable DSB studied in [7] are also linearly unstable. We show that linearly stable coherent systems of type (2, d, 4) for low enough d have stable DSB, and use this to prove a particular case of Butler's conjecture. We then exhibit a linearly stable generated coherent system with unstable DSB, confirming that linear stability of (E, V) in general remains weaker than semistability of MV, E in higher rank. We end with a list of open questions on the higher rank case.