Series: Penn State Logic Seminar Date: Tuesday, September 25, 2001 Time: 2:30 - 3:45 PM Place: 306 Boucke Building Speaker: Alwen F. Tiu, Computer Science, Penn State Title: A Logical System That Challenges Sequent Calculus Abstract: In this talk, I will introduce a new framework for presenting logical systems, called the calculus of structures. It is a generalisation of a traditional framework, the one-sided sequent calculus. A certain logical system in the calculus of structures, called System BV, will be presented. System BV is an extension of multiplicative linear logic with a self-dual non-commutative operator. I will show that System BV admits no sequent presentation, under a certain reasonable notion of sequent calculus.