Pattern Avoidance and Fiber Bundle Structures on Schubert Varieties
Séminaire lotharingien de combinatoire, 78B (2017)
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We give a permutation pattern avoidance criteria for determining when the projection map from the flag variety to a Grassmannian induces a fiber bundle structure on a Schubert variety. In particular, we show that a Schubert variety has such a fiber bundle structure if and only if the corresponding permutation avoids the split patterns 3|12 and 23|1. We also show that a Schubert variety is an iterated fiber bundle of Grassmannian Schubert varieties if and only if the corresponding permutation avoids (non-split) patterns 3412, 52341, and 635241.
@article{SLC_2017_78B_a6,
author = {Timothy Alland and Edward Richmond},
title = {Pattern {Avoidance} and {Fiber} {Bundle} {Structures} on {Schubert} {Varieties}},
journal = {S\'eminaire lotharingien de combinatoire},
year = {2017},
volume = {78B},
url = {http://geodesic.mathdoc.fr/item/SLC_2017_78B_a6/}
}
Timothy Alland; Edward Richmond. Pattern Avoidance and Fiber Bundle Structures on Schubert Varieties. Séminaire lotharingien de combinatoire, 78B (2017). http://geodesic.mathdoc.fr/item/SLC_2017_78B_a6/