Series: Penn State Logic Seminar

Date: Tuesday, March 29, 2005

Time: 2:30 - 3:45 PM

Place: 103 Pond Laboratory

Speaker: John Clemens, Penn State, Mathematics

Title: Potential Borel Sets and Stern Absoluteness

Abstract: 

  Stern absoluteness is a principle which says, in effect, that Borel
  sets which can be added by Cohen's method of forcing can be added by
  small forcings.  Using this principle, one can prove many absolute
  theorems about the Borel hierarchy.  I will give an overview of this
  technique and present several applications, including a proof of
  Friedman's theorem about Borel diagonalizers.