skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Search for: All records

Creators/Authors contains: "Martin, Daniel E"

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Abstract In 2021, Chen proved that the size of any connected component of the Markoff mod$$p$$ p graph is divisible by$$p$$ p . In combination with the work of Bourgain, Gamburd, and Sarnak, Chen’s result resolves a conjecture of Baragar for all but finitely many primes: the Markoff mod$$p$$ p graph is connected. In particular, strong approximation for Markoff triples holds for all but finitely many primes. We provide an alternative proof of Chen’s theorem. 
    more » « less
    Free, publicly-accessible full text available August 1, 2026
  2. Abstract For π“ž an imaginary quadratic ring, we compute a fundamental polyhedron in hyperbolic 3-space for the action of PE2(π“ž), the projective elementary subgroup of PSL2(π“ž). This allows for new, simplified proofs of theorems of Cohn, Nica, Fine, and Frohman. Namely, we obtain a presentation for PE2(π“ž), show that it has infinite index and is its own normalizer in PSL2(π“ž), and split PSL2(π“ž) into a free product with amalgamation that has PE2(π“ž) as one of its factors. 
    more » « less