Combinatorics, Algebra, & Topology Seminar

AY 2025-2026

All talks are in person unless otherwise specified. 

• Mar

  18
• Costas Arrays

  Kassie Archer

  USNA

  View Abstract

  A Costas array is a collection of points on an n by n grid so that the displacement vector between any two points is unique. They were originally introduced by John Costas to eliminate signals overlapping in frequency-hopping sonar. In this talk, we'll give examples, see how to build them, and discuss what is still unanswered about these arrays.

• Oct

  24
• What is a trace ideal?

  Scott LaLonde

  USNA

  Time: 12:30 PM

  View Abstract

  Given a commutative ring $R$ and an $R$-module $M$, the trace ideal of $M$ is the ideal of $R$ obtained by taking the sum of the images of all homomorphisms from $M$ to $R$. We will discuss properties of the trace ideal and results for various types of commutative rings $R$.