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Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2010)

We construct infinitely many Chatelet surfaces, degree 4 del Pezzo surfaces, and Enriques surfaces that are everywhere locally solvable, but have no global rational points. The lack of rational points on these surfaces is explained by an algebraic Brauer-Manin obstruction. The Enriques surfaces arise as quotients of certain K3 surfaces that are ramified double covers of a degree 4 del Pezzo surface with no rational points. We also construct an algebraic family of Chatelet surfaces over an open subscheme of P^1_Q such that exactly 1 Q-fiber has no Q-points. This example is in stark contrast to the philosophy "geometry controls arithmetic".

    Cover page: The algebraic Brauer-Manin obstruction on Chatelet surfaces, degree 4 del Pezzo surfaces, and Enriques surfaces
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2015)
    Using maximal isotropic submodules in a quadratic module over Z_p, we prove the existence of a natural discrete probability distribution on the set of isomorphism classes of short exact sequences of co-finite type Z_p-modules, and then conjecture that as E varies over elliptic curves over a fixed global field k, the distribution of 0 --> E(k) tensor Q_p/Z_p --> Sel_{p^infty} E --> Sha[p^infty] --> 0 is that one. We show that this single conjecture would explain many of the known theorems and conjectures on ranks, Selmer groups, and Shafarevich-Tate groups of elliptic curves. We also prove the existence of a discrete probability distribution of the set of isomorphism classes of finite abelian p-groups equipped with a nondegenerate alternating pairing, defined in terms of the cokernel of a random alternating matrix over Z_p, and we prove that the two probability distributions are compatible with each other and with Delaunay's predicted distribution for Sha. Finally, we prove new theorems on the fppf cohomology of elliptic curves in order to give further evidence for our conjecture.
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