# Simons Collaboration on Arithmetic Geometry, Number Theory, and Computation Annual Meeting 2021

Date & Time

5:00-6:15 PM

• Report on Activities in 2020

In the third year of the project, the scope of our activities and the number of people involved continue to grow. Our monthly meetings involve 25 researchers, 15 of whom are research scientists hired to directly support the goals of the project.

Notable accomplishments include:

• the creation of the site https://researchseminars.org which has become the standard source of information for online mathematical conferences and seminars worldwide — it builds on database expertise cultivated in our core research projects;
• continuing growth in the functionality and scope of the L-functions and Modular Forms Database https://www.lmfdb.org, culminating in the release of version 1.2 in October;
• the online Workshop on Arithmetic Geometry, Number Theory, and Computation at ICERM, focused around nine group projects involving more than 70 researchers both from within the Collaboration and around the world.

Specific results and achievements of PIs include:

• Jennifer Balakrishnan was a featured speaker at the Arizona Winter School, the highest profile number theory event in the US. She offered a mini-course Computational tools for quadratic Chabauty.
• Noam Elkies, with Klagsbrun, contributed New rank records for elliptic curves having rational torsion covering curves over $$\mathbb{Q}$$ with torsion groups $$\mathbb{Z}/n\mathbb{Z}$$ for $$n=2,3,4,6,$$ and $$7$$.
• Bjorn Poonen, with Kedlaya, Kolpakov, and Rubinstein, classified all sets of nonzero vectors in $$\mathbb{R}^3$$ such that the angle formed by each pair is a rational multiple of $$\pi$$. This includes a characterization of tetrahedra with rational dihedral angles, solving a 1976 problem of Conway and Jones. Their preprint, Space vectors forming rational angles, is a tour de force of computational arithmetic, including the solution of a polynomial of degree six with 105 terms in roots of unity.
• Andrew Sutherland, with Booker, found the first integer solution to the equation $$x^3+y^3+z^3 = 42$$ and new integer solutions to $$x^3+y^3+z^3 = 3.$$ This resolves a 1953 question of Mordell and completes a search begun by Miller and Woollett in 1954. Their manuscript, On a question of Mordell, presents a new algorithm to search for representations of positive integers as sums of three cubes, implemented via a massive parallel computation.
• In Counting elliptic curves with an isogeny of degree three with Pizzo and Pomerance and On a probabilistic local-global principle for torsion on elliptic curves with Cullinan and Kenney, John Voight has provided precise asymptotic counts of elliptic curves equipped with extra level structure.

The Collaboration website https://simonscollab.icerm.brown.edu/ lists dozens of preprints written by Collaboration members over this year. We are preparing a volume presenting key algorithms, examples, and foundational results supporting our work, with 21 submissions totaling over 450 pages.

• Public Lecture

Tetrahedra: From Aristotle’s Mistake to Unsolved Problems

Bjorn Poonen, Ph.D.
Massachusetts Institute of Technology

Tetrahedra are three-dimensional shapes with four triangular faces. Which tetrahedra can tile to fill a three-dimensional space? Which tetrahedra have rational dihedral angles (the angle between two intersecting planes)? Which tetrahedra can be sliced and reassembled into a cube? Each of these three problems has been around for at least 45 years, and one of them is over 2300 years old. In this lecture, Bjorn Poonen will discuss the status of these problems and explain how he solved one of them in collaboration with K. Kedlaya, A. Kolpakov, and M. Rubinstein.

Separate registration is required for this free event.