Appears in collection : 2018 - T1 - WS1 - Model theory and combinatorics

The wonderful theory of stability and ranks developed for many notions in first order model theory implies that many model theoretic constructions are absolute, since they can be expressed in terms of internal properties measurable by the existence of certain formulas. However, it is not at all the case that all natural model-theoretic notions are absolute. Our talk will survey some known results about absoluteness and ask some new questions.