Variations on a theme by Friedman

Ali Enayat

By a remarkable theorem of Friedman (1973), every nonstandard model of arithmetic or set theory has a self-embedding on to a proper initial segment of itself. I will give a brief overview of various refinements of Friedman's result that have been obtained in the past 40 years, including some very recent ones.


Institutional Honorary Doctorate Degree for Prof Dr Harvey M. Friedman