We show that a purely algebraic structure, a two-dimensional scattering diagram, describes a large part of the wall-crossing behavior of moduli spaces of Bridgeland semistable objects in the derived category of coherent sheaves on P 2 . This gives a new algorithm computing the Hodge numbers of the intersection cohomology of the classical moduli spaces of Gieseker semistable sheaves on P 2 .
Contents0. Introduction 0.1. Description of S(D in u,v ) and D P 2 u,v 0.2. Structure of the proof of Theorem 0.1 0.3. Applications to moduli spaces of Gieseker semistable sheaves 0.4. Relations with previous and future works 0.5. Plan of the paper 0.6. Acknowledgments 1. The scattering diagram S(D in u,v ) 1.1. Local scattering diagrams 1.2. Scattering diagrams 1.3. The scattering diagrams S(D in ) 1.4. The scattering diagrams S(D in u,v ), S(D in q ± ) and S(D in cl ± ) 1.5. Action of ψ(1) on scattering diagrams 2. The scattering diagram D P 2 u,v 2.1. Coherent sheaves on P 2 2.2. Stability conditions 2.3. Moduli spaces and walls 2.4. Intersection cohomology invariants 2.5. Scattering diagrams from stability conditions 2.6. Action of ψ(1) on D P 2 u,v 3. Consistency of D P 2 u,v 3.1. Statement of Theorem 3.1 3.2. Local structure near a wall 3.3. Numerical invariants from mixed Hodge theory 3.4. Donaldson-Thomas formalism 3.5. Wall-crossing formula 3.6. End of the proof of Theorem 3.1