6 papers
Constructing strongly equivalent nonisomorphic models for unsuperstable theories, Part A
Tapani Hyttinen, Saharon Shelah
We study how equivalent nonisomorphic models an unsuperstable theory can have. We measure the equivalence by Ehrenfeucht-Fraisse games.
Interpreting groups and fields in some nonelementary classes
Tapani Hyttinen, Olivier Lessmann, Saharon Shelah
This paper is concerned with extensions of geometric stability theory to some nonelementary classes. We prove the following theorem: Theorem: Let C be a large homogeneous model of…
More on the Ehrenfencht-Fraisse game of length omega_1
Tapani Hyttinen, Saharon Shelah, Jouko Väänänen
Let A and B be two first order structures of the same relational vocabulary L. The Ehrenfeucht-Fraisse-game of length gamma of A and B denoted by EFG_gamma(A,B) is defined as follo…
Potential isomorphism and semi-proper trees
Alex Hellsten, Tapani Hyttinen, Saharon Shelah
We study a notion of potential isomorphism, where two structures are said to be potentially isomorphic if they are isomorphic in some generic extension that preserves stationary se…
Forcing a Boolean Algebra with predesigned automorphism group
Tapani Hyttinen, Saharon Shelah
For suitable groups G we will show that one can add a Boolean algebra B by forcing in such a way that Aut(B) is almost isomorphic to G. In particular, we will give a positive answe…
Strong splitting in stable homogeneous models
Tapani Hyttinen, Saharon Shelah
We study elementary submodels of a stable homogeneous structure. We improve the independence relation defined in [T. Hyttinen, On nonstructure of elementary submodels of a stable h…