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Undergraduate Colloquium | Wouter Van Limbeek (UIC)

Wednesday, October 15, 2025 | 5:30 PM - 6:30 PM CT
Lunt Hall, 105, 2033 Sheridan Road, Evanston, IL 60208 map it

Title: The Banach-Tarski paradox, pyramid schemes, and non-amenable groups


Abstract: In 1924, Banach and Tarski proved the following amazing theorem: You can cut up a ball in Euclidean space into some finite number of pieces and reassemble these pieces in such a way that you get two copies of the original ball! We will discuss the proof of this crazy result, what this has to do with a deep notion in group theory called amenability, and why we have not solved the problem of world hunger by doubling and redoubling apples, oranges, potatoes and other spherical foodstuff. No background required except mathematical curiosity.

Audience

  • Faculty/Staff
  • Student
  • Post Docs/Docs
  • Graduate Students

Contact

Reza Gheissari  

gheissari@northwestern.edu

Interest

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