# 組合せ論セミナー

## 第29回 2012年11月5日 16:00〜17:30

Gary Greaves（東北大学）「Cyclotomic graphs and matrices」

Certain classes of algebraic integers can be studied fruitfully by associating them to combinatorial objects. For example, recently, progress has been made on a couple of conjectures concerned with algebraic integers whose conjugates have small absolute value. These results have relied on the classification of cyclotomic graphs (graphs whose eigenvalues are contained in the interval [-2,2]) and their generalisations. This talk will describe some of these results with an emphasis on combinatorics rather than number theory.