Starting with a countable transitive model of V=L, we show that by
adding a single Cohen real, c, most intermediate models do no satisfy choice. In
fact, most intermediate models to L[c] are not even definable.
The key part of the proof is the Bristol model, which is intermediate to L[c],
but is not constructible from a set. We will give a broad explanation of the
construction of the Bristol model within the constraints of time.
- Logic Seminar