Faber's Gorenstein conjectures for the rational tails locus

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Let Mg,nrtM_{g,n}^{rt} be the moduli space of stable curves with rational tails, and let R∗(Mg,nrt)R^*(M_{g,n}^{rt}) be its tautological ring. Let Rc∗(Mg,nrt)R^*_c(M_{g,n}^{rt}) denote the compactly supported tautological algebra, consisting of the elements of R∗(M‾g,n)R^*(\overline{M}_{g,n}) that restrict trivially to M‾g,n\Mg,nrt\overline{M}_{g,n} \backslash M_{g,n}^{rt}. The intersection product makes Rc∗(Mg,nrt)R^*_c(M_{g,n}^{rt}) an R∗(Mg,nrt)R^*(M_{g,n}^{rt})-module.

Faber's Gorenstein conjectures. (D) The intersection pairings

Rk(Mg,nrt)×Rc3g−3+n−k(Mg,nrt)→Rc3g−3+n(Mg,nrt)≅QR^k(M_{g,n}^{rt}) \times R^{3g-3+n-k}_c(M_{g,n}^{rt}) \rightarrow R_c^{3g-3+n}(M_{g,n}^{rt}) \cong \mathbb{Q}

are perfect for k≥0k \geq 0. (E) In addition to (D), Rc∗(Mg,nrt)R^*_c(M_{g,n}^{rt}) is a free R∗(Mg,nrt)R^*(M_{g,n}^{rt})-module of rank one.

These assertions generalize the compactly supported tautological-ring conjectures of Hain and Looijenga from MgM_g to the rational tails locus. The source presents them as conjectures, and no resolution status is supplied here.

References

Primary source

Mehdi Tavakol, “The moduli space of curves and its invariants”, arXiv:1610.09589 (2016).

Additional references

6 papers in this index state this conjecture (2000–2016). The statement above is taken from the most recent of them; the others are arXiv:1301.4561, arXiv:1007.3091, arXiv:math/0605488, arXiv:math/0304298, arXiv:math/0002112.

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