The monotone conjecture for arbitrary Schubert problems on flag manifolds

Let α={α1<<αk}\alpha=\{\alpha_1<\dotsb<\alpha_k\} with αk<n\alpha_k<n, and let (w1,,wm)(w_1,\dotsc,w_m) be a Schubert problem for F(α;n)\mathbb{F}\ell(\alpha;n). For each permutation wiw_i, let δ(wi)\delta(w_i) be its set of descents. A list (t1,,tm)(RP1)m(t_1,\dotsc,t_m)\in(\mathbb{R}\mathbb{P}^1)^m is monotone with respect to (w1,,wm)(w_1,\dotsc,w_m) when the map tiδ(wi)t_i\mapsto\delta(w_i) is monotone for an ordering compatible with some orientation of RP1\mathbb{R}\mathbb{P}^1. General monotone conjecture. The intersection

Xw1(t1)Xw2(t2)Xwm(tm)X_{w_1}(t_1)\cap X_{w_2}(t_2)\cap\dotsb\cap X_{w_m}(t_m)

is transverse and all its points of intersection are real whenever the points are monotone with respect to (w1,,wm)(w_1,\dotsc,w_m). The conjecture extends the Grassmannian formulation to arbitrary Schubert problems; the source notes examples with no monotone points and reports computational evidence, but the general assertion remains open.

Sources & referencesView supporting material

Primary source

James Ruffo, Yuval Sivan, Evgenia Soprunova and Frank Sottile, “Experimentation and conjectures in the real Schubert calculus for flag manifolds”, arXiv:math/0507377 (2005).

Additional references

2 papers in this index state this conjecture (2005). The statement above is taken from the most recent of them; the others are arXiv:math/0502040.

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