Lagrangian geometry of matroids
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- by Federico Ardila, Graham Denham and June Huh
- J. Amer. Math. Soc. 36 (2023), 727-794
- DOI: https://doi.org/10.1090/jams/1009
- Published electronically: September 9, 2022
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Abstract:
We introduce the conormal fan of a matroid $\operatorname {M}$, which is a Lagrangian analog of the Bergman fan of $\operatorname {M}$. We use the conormal fan to give a Lagrangian interpretation of the Chern–Schwartz–MacPherson cycle of $\operatorname {M}$. This allows us to express the $h$-vector of the broken circuit complex of $\operatorname {M}$ in terms of the intersection theory of the conormal fan of $\operatorname {M}$. We also develop general tools for tropical Hodge theory to prove that the conormal fan satisfies Poincaré duality, the hard Lefschetz theorem, and the Hodge–Riemann relations. The Lagrangian interpretation of the Chern–Schwartz–MacPherson cycle of $\operatorname {M}$, when combined with the Hodge–Riemann relations for the conormal fan of $\operatorname {M}$, implies Brylawski’s and Dawson’s conjectures that the $h$-vectors of the broken circuit complex and the independence complex of $\operatorname {M}$ are log-concave sequences.References
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Bibliographic Information
- Federico Ardila
- Affiliation: Department of Mathematics, San Francisco State University, 1600 Holloway Ave., San Francisco, California 94132; and Departamento de Matemáticas, Universidad de Los Andes, Cra. 1 # 18A - 12, Bogotá, Colombia
- MR Author ID: 725066
- Email: federico@sfsu.edu
- Graham Denham
- Affiliation: Department of Mathematics, University of Western Ontario, 1151 Richmond St., London, Ontario, Canada N6A 5B7
- MR Author ID: 343377
- Email: gdenham@uwo.ca
- June Huh
- Affiliation: Department of Mathematics, Princeton University, Fine Hall, Washington Road, Princeton, New Jersey 08544-100; and Korea Institute for Advanced Study
- MR Author ID: 974745
- Email: huh@princeton.edu
- Received by editor(s): October 29, 2020
- Received by editor(s) in revised form: February 14, 2022
- Published electronically: September 9, 2022
- Additional Notes: The first author’s research was supported by NSF grant DMS-1855610 and Simons Fellowship 613384. The second author’s research was supported by NSERC of Canada. The third author’s research was supported by NSF Grant DMS-1638352 and the Ellentuck Fund
- © Copyright 2022 American Mathematical Society
- Journal: J. Amer. Math. Soc. 36 (2023), 727-794
- MSC (2020): Primary 05B35; Secondary 05E99, 14C25, 14T15, 14T20, 52B05
- DOI: https://doi.org/10.1090/jams/1009
- MathSciNet review: 4583774