Wednesday, October 1, 20144:50 pmModels of PAGC 6300

# Elementary end extensions and the pentagon lattice

## Roman Kossak

### The City University of New York

By a theorem of Wilkie, every countable model M of PA has an elementary end extension N such that interstructure lattice Lt(N/N) is isomorphic to the pentagon lattice. I will explain why the theorem does not generalize to uncountable models.

Roman Kossak is professor of mathematics at The City University of New York, at Bronx Community College and also at the CUNY Graduate Center. He conducts research in mathematical logic, especially in model theory of Peano Arithmetic.