Abstract
We describe the second cohomology of a regular semisimple Hessenberg variety by generators and relations explicitly in terms of GKM theory. The cohomology of a regular semisimple Hessenberg variety becomes a module of a symmetric group \(\mathfrak{S}_n\) by the dot action introduced by Tymoczko. As an application of our explicit description, we give a formula describing the isomorphism class of the second cohomology as an \(\mathfrak{S}_n\)-module. Our formula is not exactly the same as the known formula by Chow or Cho, Hong, and Lee, but they are equivalent. We also discuss its higher degree generalization.
Similar content being viewed by others
Notes
A. Ayzenberg, M. Masuda, and T. Sato, “Regular semisimple Hessenberg varieties with cohomology generated in degree two” (in preparation).
References
H. Abe, M. Harada, T. Horiguchi, and M. Masuda, “The cohomology rings of regular nilpotent Hessenberg varieties in Lie type A,” Int. Math. Res. Not. 2019 (17), 5316–5388 (2019).
H. Abe and T. Horiguchi, “A survey of recent developments on Hessenberg varieties,” in Schubert Calculus and Its Applications in Combinatorics and Representation Theory (Springer, Singapore, 2020), Springer Proc. Math. Stat. 332, pp. 251–279.
H. Abe, T. Horiguchi, and M. Masuda, “The cohomology rings of regular semisimple Hessenberg varieties for \(h=(h(1),n,\dots ,n)\),” J. Comb. 10 (1), 27–59 (2019).
A. Białynicki-Birula, J. B. Carrell, and W. M. McGovern, Algebraic Quotients. Torus Actions and Cohomology. The Adjoint Representation and the Adjoint Action (Springer, Berlin, 2002), Encycl. Math. Sci. 131.
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).
S. Cho, J. Hong, and E. Lee, “Permutation module decomposition of the second cohomology of a regular semisimple Hessenberg variety,” arXiv: 2107.00863 [math.AG].
T. Chow, “\(e\)-Positivity of the coefficient of \(t\) in \(X_G(t)\),” E-print (2015), http://timothychow.net/h2.pdf.
S. Dahlberg and S. van Willigenburg, “Lollipop and lariat symmetric functions,” SIAM J. Discrete Math. 32 (2), 1029–1039 (2018).
F. De Mari, C. Procesi, and M. A. Shayman, “Hessenberg varieties,” Trans. Am. Math. Soc. 332 (2), 529–534 (1992).
Y. Fukukawa, H. Ishida, and M. Masuda, “The cohomology ring of the GKM graph of a flag manifold of classical type,” Kyoto J. Math. 54 (3), 653–677 (2014).
W. Fulton, Young Tableaux. With Applications to Representation Theory and Geometry (Cambridge Univ. Press, Cambridge, 1997), LMS Stud. Texts 35.
M. Goresky, R. Kottwitz, and R. MacPherson, “Equivariant cohomology, Koszul duality, and the localization theorem,” Invent. Math. 131 (1), 25–83 (1998).
M. Guay-Paquet, “A modular law for the chromatic symmetric functions of \((3+1)\)-free posets,” arXiv: 1306.2400v1 [math.CO].
J. Huh, S.-Y. Nam, and M. Yoo, “Melting lollipop chromatic quasisymmetric functions and Schur expansion of unicellular LLT polynomials,” Discrete Math. 343 (3), 111728 (2020).
J. Shareshian and M. L. Wachs, “Chromatic quasisymmetric functions,” Adv. Math. 295, 497–551 (2016).
E. H. Spanier, Algebraic Topology (McGraw-Hill, New York, 1966).
N. Teff, “Representations on Hessenberg varieties and Young’s rule,” in Proc. 23rd Int. Conf. on Formal Power Series and Algebraic Combinatorics (FPSAC 2011), Reykjavik, 2011 (Assoc. Discrete Math. Theor. Comput. Sci., Nancy, 2011), Discrete Math. Theor. Comput. Sci., Proc., pp. 903–914.
J. S. Tymoczko, “Permutation actions on equivariant cohomology of flag varieties,” in Toric Topology (Am. Math. Soc., Providence, RI, 2008), Contemp. Math. 460, pp. 365–384.
Funding
The work of the first and second authors was performed within the framework of the HSE University Basic Research Program.
Author information
Authors and Affiliations
Corresponding author
Additional information
Published in Russian in Trudy Matematicheskogo Instituta imeni V.A. Steklova, 2022, Vol. 317, pp. 5–26 https://doi.org/10.4213/tm4289.
Rights and permissions
About this article
Cite this article
Ayzenberg, A.A., Masuda, M. & Sato, T. The Second Cohomology of Regular Semisimple Hessenberg Varieties from GKM Theory. Proc. Steklov Inst. Math. 317, 1–20 (2022). https://doi.org/10.1134/S0081543822020018
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1134/S0081543822020018