Differences between revisions 13 and 20 (spanning 7 versions)
 ⇤ ← Revision 13 as of 2013-07-11 00:44:46 → Size: 4290 Editor: ursula Comment: ← Revision 20 as of 2013-07-14 18:28:11 → ⇥ Size: 5054 Editor: asalerno Comment: Deletions are marked like this. Additions are marked like this. Line 21: Line 21: * Sperber and Voight, [[http://www.math.dartmouth.edu/~jvoight/articles/sparse-dwork-031913.pdf|"Computing zeta functions of nondegenerate hypersurfaces with few monomials"]] Line 22: Line 23: * Despite the name, this really just does zeta functions for simplices, which correspond to weighted projective spaces. Wong was a student of * Despite the name, this really just does zeta functions for simplices, which correspond to weighted projective spaces. Wong was a student of Daqing Wan.  * Daqing Wan, [[http://www.math.uci.edu/~dwan/mirror.pdf | Mirror Symmetry For Zeta Functions]]   * Mentions Gauss sums=== References on Zeta Functions of K3 Surfaces === * Matthias Schuett, [[http://arxiv.org/abs/1202.1066| Two lectures on the arithmetic of K3 surfaces]]   * Nice reference for facts about K3 surfaces * Scott Ahlgren, Ken Ono and David Penniston, [[http://www.jstor.org/stable/25099117 | Zeta Functions of an Infinite Family of K3 Surfaces]] Line 40: Line 50: == Slides for the introductory talks ==Adriana's slides: [[attachment:sagedaystalk.pdf]]

## Adriana and Ursula's project: Counting points on toric hypersurfaces

### The Plan

We will develop techniques and code for counting points on hypersurfaces in toric varieties over finite fields, with an eye toward arithmetic mirror symmetry.

### Some Background

In string theory, Calabi-Yau varieties describe extra dimensions of the universe, beyond the three spatial and one time dimensions that we move through every day. An interesting conjecture first framed by physicists is that Calabi-Yau varieties should occur in pairs, and that physics in the corresponding paired universes should be indistinguishable. Mathematical interpretations of this conjecture led to the field known as mirror symmetry. In the usual mathematical framework, mirror symmetry constructions require that Calabi-Yau varieties arise in paired or mirror families, and that variations of complex structure in one family correspond to variations of Kaehler structure in the mirror family. When individual pairs of mirror varieties can be identified, mirror symmetry constructions have implications for the arithmetic structure of the varieties.

Suppose we have an algebraic variety X over a finite field K. The congruent zeta function (also known as the Hasse-Weil zeta function) is a generating function for the number of points on X over finite extensions of K. By results of Dwork, the congruent zeta function is rational, and can be written as a ratio of polynomials with integer coefficients with degrees depending on the Betti numbers of X. Mirror symmetry for Calabi-Yau threefold mirror pairs predicts that the Hodge numbers h1,1 and h2,1 are interchanged. The possible implications of this exchange for the arithmetic structure of the varieties were first explored in the physics literature in 2000 by Candelas, de la Ossa, and Rodriguez-Villegas. In particular, because the Hodge numbers control the Betti numbers, it follows that mirror symmetry will be reflected in the congruent zeta functions of mirror pairs.

This arithmetic mirror symmetry phenomenon has been studied extensively for the case where X is a Fermat hypersurface in projective or weighted projective space. We are interested in the case where X is a hypersurface in a toric variety. In this setting, Batyrev showed that the mirror of X can be constructed using the combinatorial information of a reflexive polytope. Sage already incorporates functionality for working with reflexive polytopes and the corresponding toric varieties. We would like to experiment with counting points on hypersurfaces in toric varieties over finite fields, with the goal of comparing congruent zeta functions for mirror families of varieties.

### References on Polytopes and Toric Varieties

• Doran and Whitcher, "From Polytopes to String Theory"

• This popular introduction to the subject appeared in Math Magazine

• Chapter 7 of Vafa and Zaslow, ed.s, Mirror Symmetry

• Cox, Little, and Schenck, Toric Varieties

• A PDF preprint was formerly available on Cox's website
• Cox and Katz, Mirror Symmetry