Bregje Pauwels will give the Seminar’s fifth talk in Semester 2 tomorrow afternoon on Zoom. Please find the details below. Anyone desiring to attend the talk or join the mailing list is warmly invited to get in touch: ciappara@maths.usyd.edu.au. Title: Division algebras and parallelizable spheres Abstract: The only finite dimensional division algebras over the real numbers are the real numbers, the complex numbers, the Hamilton quaternions and the Cayley octonions. There are many beautiful proofs of this fact, and one of them uses Bott periodicity and Adams operations. We will discuss this proof, and in the process we will discuss Adams’ theorem on the Hopf invariant. If time permits (probably not), we will also talk about the Leray-Hirsch theorem for K-theory. Time and date: 3 pm Wednesday 16 September Seminar website: https://www.maths.usyd.edu.au/u/ciappara/SAS.html