Time:  3:30pm  4:30 pm 
Room: 
Wean Hall 8220

Speaker: 
James Cummings Department of Mathematical Sciences CMU 
Title: 
Definable subsets of singular cardinals

Abstract: 
Shelah proved the surprising result that if μ is a singular strong limit cardinal of uncountable cofinality, then there is a subset X of μ such that all subsets of μ are ordinaldefinable from X. We will give a proof and discuss some complementary consistency results. 