### Model theory for a compact cardinal

by Shelah. [Sh:1019]

We like to develop model theory for T, a complete theory in
{L}_{theta, theta}(tau) when theta is a compact
cardinal. By [Sh:300a] we have bare bones
stability and it seemed we can go
no further. Dealing with ultrapowers (and ultraproducts) we
restrict ourselves to ``D a theta-complete ultrafilter
on I, probably (I, theta)-regular''. The basic theorems work, but
can we generalize deeper parts of model theory?
In particular can we generalize stability enough to
generalize [Sh:c, Ch.VI]? We prove that at least we can
characterize the T 's which are minimal under Keisler's order, i.e.
such that {D:D is a regular ultrafilter on
lambda and M models T => M^lambda /D is
lambda-saturated} .
Further we succeed to connect our investigation with the logic
{L}^1_{< theta} introduced in [Sh:797]: two models are
{L}^1_{< theta}-equivalent iff for some omega-
sequence of theta-complete ultrafilters, the iterated ultra-powers
by it of those two models are isomorphic.
2013.11.14
Doron will read it for a grade, have to finish till 2013.12.31.
Updates 2013.12.27 Have update, revise section 2 strongly now have
both versions of minimality- different characterization;

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