On the combinatorial cuspidalization of hyperbolic curves
Mochizuki, Shinichi
Osaka J. Math., Tome 47 (2010) no. 1, p. 651-715 / Harvested from Project Euclid
In this paper, we continue our study of the pro-$\Sigma$ fundamental groups of configuration spaces associated to a hyperbolic curve, where $\Sigma$ is either the set of all prime numbers or a set consisting of a single prime number, begun in an earlier paper. Our main result may be regarded either as a combinatorial, partially bijective generalization of an injectivity theorem due to Matsumoto or as a generalization to arbitrary hyperbolic curves of injectivity and bijectivity results for genus zero curves due to Nakamura and Harbater--Schneps. More precisely, we show that if one restricts one's attention to outer automorphisms of such a pro-$\Sigma$ fundamental group of the configuration space associated to a(n) affine (respectively, proper) hyperbolic curve which are compatible with certain ``fiber subgroups'' (i.e., groups that arise as kernels of the various natural projections of a configuration space to lower-dimensional configuration spaces) as well as with certain cuspidal inertia subgroups, then, as one lowers the dimension of the configuration space under consideration from $n+1$ to $n \ge 1$ (respectively, $n \ge 2$), there is a natural injection between the resulting groups of such outer automorphisms, which is a bijection if $n \ge 4$. The key tool in the proof is a combinatorial version of the Grothendieck conjecture proven in an earlier paper by the author, which we apply to construct certain canonical sections.
Publié le : 2010-09-15
Classification:  14H30,  14H10
@article{1285334471,
     author = {Mochizuki, Shinichi},
     title = {On the combinatorial cuspidalization of hyperbolic curves},
     journal = {Osaka J. Math.},
     volume = {47},
     number = {1},
     year = {2010},
     pages = { 651-715},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1285334471}
}
Mochizuki, Shinichi. On the combinatorial cuspidalization of hyperbolic curves. Osaka J. Math., Tome 47 (2010) no. 1, pp.  651-715. http://gdmltest.u-ga.fr/item/1285334471/