English

3-nilpotent obstructions to pi_1 sections for P^1_Q - {0,1,infty}

Algebraic Geometry 2012-08-24 v2

Abstract

We study which rational points of the Jacobian of P^1_K -{0,1,infty} can be lifted to sections of geometrically 3 nilpotent quotients of etale pi_1 over the absolute Galois group. This is equivalent to evaluating certain triple Massey products of elements of H^1(G_K). For K=Q_p or R, we give a complete mod 2 calculation. This permits some mod 2 calculations for K = Q. These are computations of obstructions of Jordan Ellenberg.

Cite

@article{arxiv.1011.0655,
  title  = {3-nilpotent obstructions to pi_1 sections for P^1_Q - {0,1,infty}},
  author = {Kirsten Wickelgren},
  journal= {arXiv preprint arXiv:1011.0655},
  year   = {2012}
}

Comments

49 pages

R2 v1 2026-06-21T16:37:51.579Z