English

On the kappa ring of $\overline{M}_{g,n}$

Algebraic Geometry 2013-11-05 v2

Abstract

Let κe(Mg,n)\kappa_e(\overline{M}_{g,n}) denote the kappa ring of Mg,n\overline{M}_{g,n} in codimension ee. For g,e0g,e\geq 0 fixed, as the number nn of the markings grows large we show that the rank of κe(Mg,n)\kappa_e(\overline{M}_{g,n}) is asymptotic to (n+ee)(g+ee)(e+1)!(g+ee)nee!(e+1)!.\frac{{n+e\choose e}{g+e\choose e}}{(e+1)!}\simeq \frac{{g+e\choose e}n^e}{e!(e+1)!}. When g2g\leq 2 we show that a kappa class κ\kappa is trivial if and only if the integral of κ\kappa against all boundary strata is trivial. For g=1g=1 we further show that the rank of κnd(M1,n)\kappa_{n-d}(\overline{M}_{1,n}) is equal to P1(d,nd)|P_1(d,n-d)|, where Pi(d,k)P_i(d,k) denotes the set of partitions p=(p1,...,p)p=(p_1,...,p_\ell) of dd such that at most kk of the numbers p1,...,pp_1,...,p_\ell are greater than ii.

Keywords

Cite

@article{arxiv.1307.2754,
  title  = {On the kappa ring of $\overline{M}_{g,n}$},
  author = {Eaman Eftekhary and Iman Setayesh},
  journal= {arXiv preprint arXiv:1307.2754},
  year   = {2013}
}