Moritz Müller:
Partially definable forcing and weak arithmetics
Time and place
Wednesday, 4.2.15, 16:30-17:30, Raum 404, Eckerstr. 1
Abstract
Given a nonstandard model M of arithmetic we want to expand it\nby interpreting a binary relation symbol R such that R^M does something\nprohibitive, e.g. violates the pigeonhole principle in the sense that R^M\nis a bijection from n+1 onto n for some (nonstandard) n in M. The goal is\nto do so saving as much as possible from ordinary arithmetic. More\nprecisely, we want the expansion to satisfy the least number principle for\na class of formulas as large as possible. We describe a forcing method to\nproduce such expansions and revisit the most important results in the\narea.\n