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A congruence modulo four for real Schubert calculus with isotropic flags. (English) Zbl 1368.14065

Summary: We previously obtained a congruence modulo four for the number of real solutions to many Schubert problems on a square Grassmannian given by osculating flags [N. Hein et al., J. Reine Angew. Math. 714, 151–174 (2016; Zbl 1403.14088)]. Here, we consider Schubert problems given by more general isotropic flags, and prove this congruence modulo four for the largest class of Schubert problems that could be expected to exhibit this congruence.

MSC:

14N15 Classical problems, Schubert calculus
14P10 Semialgebraic sets and related spaces

Citations:

Zbl 1403.14088
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