报告题目：Towers and Clubs
Afew years ago Saharon Shelah established an important result that showed that The diamond principle at regular uncountable cardinal often reduces to a (necessary) cardinalarithmetic assumption. We investigate what happens if this assumption is removed. One can expect to obtain a weaker form of diamond (◆) called club. But then among the consequences of diamond, which ones remain valid, especially in terms of almost disjoint stationary sets? This is where (ascending and descending) towers of stationary sets enter the picture.