אירועים והרצאות בפקולטה למדעי המחשב ע"ש הנרי ומרילין טאוב

I will describe several old and new applications of topological and algebraic methods in the derivation of combinatorial results. In all of them the proofs provide no efficient procedures for solving the corresponding algorithmic questions. The problem of finding such procedures (or convincing reasons indicating that they are unlikely to exist) is an intriguing challenge.