Solving Schubert Problems with Littlewood-Richardson Homotopies

Frank Sottile, Ravi Vakil, and Jan Verschelde.
    We present a new numerical homotopy continuation algorithm for finding all solutions to Schubert problems on Grassmannians. This Littlewood-Richardson homotopy is based on Vakil's geometric proof of the Littlewood-Richardson rule. Its start solutions are given by linear equations and they are tracked through a sequence of homotopies encoded by certain checker configurations to find the solutions to a given Schubert problem. For generic Schubert problems the number of paths tracked is optimal. The Littlewood-Richardson homotopy algorithm is implemented using the path trackers of the software package PHCpack.





The manuscript in pdf.
Some pictures illustrating Vakil's geometric Littlewood-Richardson Rule.
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