Abstract
Regular semisimple Hessenberg varieties are subvarieties of the flag variety Flag(ℂn) arising naturally at the intersection of geometry, representation theory, and combinatorics. Recent results of Abe, Horiguchi, Masuda, Murai, and Sato as well as of Abe, DeDieu, Galetto, and Harada relate the volume polynomials of regular semisimple Hessenberg varieties to the volume polynomial of the Gelfand–Zetlin polytope GZ(λ) for λ = (λ1, λ2, …, λn). In the main results of this paper we use and generalize tools developed by Anderson and Tymoczko, by Kiritchenko, Smirnov, and Timorin, and by Postnikov in order to derive an explicit formula for the volume polynomials of regular semisimple Hessenberg varieties in terms of the volumes of certain faces of the Gelfand–Zetlin polytope, and also exhibit a manifestly positive, combinatorial formula for their coefficients with respect to the basis of monomials in the αi:= λi − λi+1. In addition, motivated by these considerations, we carefully analyze the special case of the permutohedral variety, which is also known as the toric variety associated to Weyl chambers. In this case, we obtain an explicit decomposition of the permutohedron (the moment map image of the permutohedral variety) into combinatorial (n − 1)-cubes, and also give a geometric interpretation of this decomposition by expressing the cohomology class of the permutohedral variety in Flag(ℂn) as a sum of the cohomology classes of a certain set of Richardson varieties.
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References
H. Abe, L. DeDieu, F. Galetto, and M. Harada, “Geometry of Hessenberg varieties with applications to Newton–Okounkov bodies,” Sel. Math., New Ser. 24(3), 2129–2163 (2018).
T. Abe, T. Horiguchi, M. Masuda, S. Murai, and T. Sato, “Hessenberg varieties and hyperplane arrangements,” J. Reine Angew. Math., doi: https://doi.org/10.1515/crelle-2018-0039 (2019); ar**v: 1611.00269 [math.AG].
D. Anderson and J. Tymoczko, “Schubert polynomials and classes of Hessenberg varieties,” J. Algebra 323(10), 2605–2623 (2010).
A. Ayzenberg and M. Masuda, “Volume polynomials and duality algebras of multi-fans,” Arnold Math. J. 2(3), 329–381 (2016).
M. Brion, “Lectures on the geometry of flag varieties,” in Topics in Cohomological Studies of Algebraic Varieties: Impanga Lecture Notes (Birkhäuser, Basel, 2005), Trends Math., pp. 33–85.
P. Brosnan and T. Y. Chow, “Unit interval orders and the dot action on the cohomology of regular semisimple Hessenberg varieties,” Adv. Math. 329, 955–1001 (2018).
F. De Mari, C. Procesi, and M. A. Shayman, “Hessenberg varieties,” Trans. Am. Math. Soc. 332(2), 529–534 (1992).
W. Fulton, Young Tableaux. With Applications to Representation Theory and Geometry (Cambridge Univ. Press, Cambridge, 1997), London Math. Soc. Stud. Texts 35.
M. Guay-Paquet, “A second proof of the Shareshian–Wachs conjecture, by way of a new Hopf algebra,” ar**v: 1601.05498 [math.CO].
M. Harada and M. Precup, “The cohomology of abelian Hessenberg varieties and the Stanley–Stembridge conjecture,” J. Algebr. Comb. (in press); ar**v: 1709.06736 [math.CO].
S. Kaji, “Maple script for equivariant cohomology of flag manifolds,” https://github.com/shizuo-kaji/Maple-flag-cohomology
K. Kaveh, “Crystal bases and Newton–Okounkov bodies,” Duke Math. J. 164(13), 2461–2506 (2015).
K. Kaveh and A. Khovanskii, “Newton–Okounkov bodies, semigroups of integral points, graded algebras and intersection theory,” Ann. Math., Ser. 2, 176(2), 925–978 (2012).
V. Kiritchenko, “Gelfand–Zetlin polytopes and flag varieties,” Int. Math. Res. Not. 2010(13), 2512–2531 (2010).
V. A. Kirichenko, E. Yu. Smirnov, and V. A. Timorin, “Schubert calculus and Gelfand–Zetlin polytopes,” Russ. Math. Surv. 67(4), 685–719 (2012) [transl. from Usp. Mat. Nauk 67 (4), 89–128 (2012)].
M. Kogan, “Schubert geometry of flag varieties and Gelfand–Cetlin theory,” PhD Thesis (Mass. Inst. Technol., Cambridge, 2000).
E. Lee, M. Masuda, and S. Park, “Toric Bruhat interval polytopes,” ar**v: 1904.10187 [math.CO].
M. Masuda and T. E. Panov, “Semifree circle actions, Bott towers and quasitoric manifolds,” Sb. Math. 199(8), 1201–1223 (2008) [transl. from Mat. Sb. 199 (8), 95–122 (2008)].
D. Monk, “The geometry of flag manifolds,” Proc. London Math. Soc., Ser. 3, 9, 253–286 (1959).
A. Postnikov, “Permutohedra, associahedra, and beyond,” Int. Math. Res. Not. 2009(6), 1026–1106 (2009).
J. Shareshian and M. L. Wachs, “Chromatic quasisymmetric functions,” Adv. Math. 295, 497–551 (2016).
G. M. Ziegler, Lectures on Polytopes (Springer, New York, 1995), Grad. Texts Math. 152.
Acknowledgments
We are grateful to Kiumars Kaveh for useful conversations. We are also grateful to Shizuo Kaji for communicating to us the results of his computer computations (see Remark 6.7).
Funding
The first author is supported in part by an NSERC Discovery Grant and a Canada Research Chair (Tier 2) Award. She is also grateful to the Osaka City University Advanced Mathematics Institute for support and hospitality during her fruitful visit in Fall 2017, when much of this work was conducted. The second author is partially supported by JSPS Grant-in-Aid for JSPS Fellows 17J04330. The third author is supported in part by JSPS Grant-in-Aid for Scientific Research 16K05152. The fourth author acknowledges the support of the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (NRF-2018R1A6A3A11047606).
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Dedicated to Professor Victor M. Buchstaber on the occasion of his 75th birthday
Published in Russian in Trudy Matematicheskogo Instituta imeni V.A. Steklova, 2019, Vol. 305, pp. 344–373.
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Harada, M., Horiguchi, T., Masuda, M. et al. The Volume Polynomial of Regular Semisimple Hessenberg Varieties and the Gelfand—Zetlin Polytope. Proc. Steklov Inst. Math. 305, 318–344 (2019). https://doi.org/10.1134/S0081543819030192
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DOI: https://doi.org/10.1134/S0081543819030192