Abstract
We show that the integer cohomology rings of the moduli spaces of stable rational marked curves are Koszul. This answers an open question of Manin. Using the machinery of Koszul spaces developed by Berglund, we compute the rational homotopy Lie algebras of those spaces, and obtain some estimates for Betti numbers of their free loop spaces in case of torsion coefficients. We also prove and conjecture some generalisations of our main result.
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References
Adiprasito, K., Huh, J., Katz, E.: Hodge theory for combinatorial geometries. Ann. Math. (2) 188(2), 381–452 (2018)
Babenko, I.K.: Analytical properties of Poincaré series of a loop space. Math. Notes 27(5), 359–367 (1980)
Berglund, A.: Koszul spaces. Trans. Am. Math. Soc. 366(9), 4551–4569 (2014)
Berglund, A., Börjeson, K.: Free loop space homology of highly connected manifolds. Forum Math. 29(1), 201–228 (2017)
Björner, A.: Shellable and Cohen–Macaulay partially ordered sets. Trans. Am. Math. Soc. 260(1), 159–183 (1980)
Bremner, M., Dotsenko, V.: Algebraic Operads. An Algorithmic Companion. CRC Press, Boca Raton (2016)
Burghelea, D., Fiedorowicz, Z.: Cyclic homology and algebraic \(K\)-theory of spaces II. Topology 25(3), 303–317 (1986)
Cavalieri, R., Hampe, S., Markwig, H., Ranganathan, D.: Moduli spaces of rational weighted stable curves and tropical geometry. Forum Math. Sigma 4, e9 (2016)
Cirici, J., Horel, G.: Étale cohomology, purity and formality with torsion coefficients. ArXiv preprint arXiv:1806.03006
Danilov, V.I.: The geometry of toric varieties. Russ. Math. Surv. 33(2), 97–154 (1978)
De Concini, C., Procesi, C.: Wonderful models of subspace arrangements. Sel. Math. (N.S.) 1(3), 459–494 (1995)
Deligne, P., Griffiths, P., Morgan, J., Sullivan, D.: Real homotopy theory of Kähler manifolds. Invent. Math. 29(3), 245–274 (1975)
Dotsenko, V.: Word operads and admissible orderings. Appl. Category Struct. (2020). https://doi.org/10.1007/s10485-020-09591-0
Dotsenko, V., Khoroshkin, A.: Quillen homology for operads via Gröbner bases. Doc. Math. 18, 707–747 (2013)
Dotsenko, V., Shadrin, S., Vallette, B.: Toric varieties of Loday’s associahedra and noncommutative cohomological field theories. J. Topol. 12, 463–535 (2019)
Etingof, P., Henriques, A., Kamnitzer, J., Rains, E.M.: The cohomology ring of the real locus of the moduli space of stable curves of genus \(0\) with marked points. Ann. Math. (2) 171(2), 731–777 (2010)
Falk, M., Randell, R.: The lower central series of a fiber-type arrangement. Invent. Math. 82(1), 77–88 (1985)
Feichtner, E.M., Yuzvinsky, S.: Chow rings of toric varieties defined by atomic lattices. Invent. Math. 155(3), 515–536 (2004)
Fulton, W.: Introduction to Toric Varieties. Annals of Mathematics Studies. The William H. Roever Lectures in Geometry, vol. 131. Princeton University Press, Princeton (1993)
Gaiffi, G.: Blowups and cohomology bases for De Concini–Procesi models of subspace arrangements. Sel. Math. (N.S.) 3(3), 315–333 (1997)
Gallardo, P., Routis, E.: Wonderful compactifications of the moduli space of points in affine and projective space. Eur. J. Math. 3(3), 520–564 (2017)
Getzler, E.: Operads and moduli spaces of genus \(0\) Riemann surfaces. In: Dijkgraaf, R. H., Faber, C., van der Geer, G. B. M. (eds.) The Moduli Space of Curves (Texel Island, 1994), Progress in Mathematics, vol. 129, pp. 199–230. Birkhäuser, Boston (1995)
Goodwillie, T.: Cyclic homology, derivations, and the free loop space. Topology 24(2), 187–215 (1985)
Halperin, S., Vigué-Poirrier, M.: The homology of a free loop space. Pac. J. Math. 147(2), 311–324 (1991)
Hassett, B.: Moduli spaces of weighted pointed stable curves. Adv. Math. 173(2), 316–352 (2003)
Iyudu, N.: On Koszulity in homology of moduli spaces of stable \(n\)-pointed curves of genus zero. ArXiv preprint arXiv:1304.6343
Jöllenbeck, M., Welker, V.: Minimal Resolutions via Algebraic Discrete Morse Theory. Memoirs of the American Mathematical Society, vol. 923. American Mathematical Society, Providence (2009)
Keel, S.: Intersection theory of moduli space of stable \(n\)-pointed curves of genus zero. Trans. Am. Math. Soc. 330(2), 545–574 (1992)
Khoroshkin, A., Willwacher, T.: Real moduli space of stable rational curves revisted. ArXiv preprint arXiv:1905.04499
Knudsen, F.: The projectivity of the moduli space of stable curves. II. The stacks \(M_{g, n}\). Math. Scand. 52(2), 161–199 (1983)
Kohno, T.: Série de Poincaré-Koszul associée aux groupes de tresses pures. Invent. Math. 82(1), 57–75 (1985)
Kontsevich, M., Manin, Y.: Quantum cohomology of a product. With an appendix by R. Kaufmann. Invent. Math. 124(1–3), 313–339 (1996)
Lambrechts, P.: On the Betti numbers of the free loop space of a coformal space. J. Pure Appl. Algebra 161(1–2), 177–192 (2001)
Loday, J.-L., Vallette, B.: Algebraic Operads. Grundlehren der mathematischen Wissenschaften, vol. 346. Springer, Heidelberg (2012)
Losev, A., Manin, Y.: Extended modular operad. In: Hertling, K., Marcolli, M. (eds.) Frobenius Manifolds, Aspects of Mathematics, vol. E36, pp. 181–211. Friedr. Vieweg, Wiesbaden (2004)
Losev, A., Manin, Y.: New moduli spaces of pointed curves and pencils of flat connections. Mich. Math. J. 48, 443–472 (2000)
Manin, Y.: Higher structures, quantum groups, and genus zero modular operad. ArXiv preprint arXiv:1802.04072
Manin, Y.: Moduli stacks \({\overline{L}}_{g, S}\). Mosc. Math. J. 4(1), 181–198 (2004)
Manin, Y., Vallette, B.: Monoidal structures on the categories of quadratic data. ArXiv preprint arXiv:1902.03778
McCleary, J.: On the mod \(p\) Betti numbers of loop spaces. Invent. Math. 87(3), 643–654 (1987)
Milnor, J.W., Moore, J.C.: On the structure of Hopf algebras. Ann. Math. (2) 81(2), 211–264 (1965)
Petersen, D.: Koszulness of the cohomology ring of moduli of stable genus zero curves, MathOverflow question. https://mathoverflow.net/q/99613, 2012-06-15
Polishchuk, A., Positselski, L.: Quadratic Algebras. University Lecture Series, vol. 37. American Mathematical Society, Providence (2005)
Procesi, C.: The toric variety associated to Weyl chambers. In: Lothaire, M. (ed.) Mots, Lang. Raison. Calc., pp. 153–161. Hermés, Paris (1990)
Readdy, M.A.: The pre-WDVV ring of physics and its topology. Ramanujan J. 10(2), 269–281 (2005)
Singh, D.: The moduli space of stable \(N\)-pointed curves of genus zero. Ph.D. Thesis, University of Sheffield (2004)
Ufnarovskij, V.A.: Combinatorial and asymptotic methods in algebra. In: Kostrikin, A. I., Shafarevich, I. R. (eds.)Algebra, VI, Encyclopedia of Mathematics Sciences, vol. 57, pp. 1–196. Springer, Berlin (1995)
Willwacher, T.: M. Kontsevich’s graph complex and the Grothendieck–Teichmüller Lie algebra. Invent. Math. 200(3), 671–760 (2015)
Yuzvinsky, S.: Cohomology bases for the De Concini–Procesi models of hyperplane arrangements and sums over trees. Invent. Math. 127(2), 319–335 (1997)
Acknowledgements
I am grateful to Yuri Ivanovich Manin for encouragement. I also wish to thank Greg Arone, Alexander Berglund, Alex Fink, Vincent Gélinas, Anton Khoroshkin, Natalia Iyudu, Vic Reiner, Pedro Tamaroff, and Bruno Vallette for useful discussions. The paper benefited from extraordinarily thorough peer review process, and I wish to offer my deep gratitude to the anonymous referee whose queries made me spell out the proof in great detail, leaving no stone unturned. Special thanks are due to Neil Strickland for providing a copy of [46], and to Geoffroy Horel for a discussion of results of [9].
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