Thursday, October 20, 2016 - 12:00
427 Thackeray Hall
Abstract or Additional Information
For a finite group, the order of group and the orders are two most important basic concepts. Let G be a finite group and πe(G) be the set of element orders in G. In 1987, we posed the following conjecture. Let G be a group and M a finite simple group. Then G≅M if and only if (a) πe(G)=πe(M), and (b) |G|=|M|. That is, for all finite simple groups we may characterize them using only their orders and the sets of their element orders. Now the above conjecture has became a theorem after a series of proofs by Chinese and Russian mathematicians (1987-2009). In this talk, we will discuss the above characterization and related topics. Especially, some unsolved problems depending on number theory and Diophantine equations will be discussed.