  Our purpose in this paper is to discuss criteria for the existence of a
precise dual description of a cosmology. A number of exact descriptions exist
for flat and anti de Sitter backgrounds and possibly for open FRW universes
that nucleate in an eternally inflating background. In addition duals have been
proposed for de Sitter space, and for crunching FRW bubbles with negative
cosmological constant. In the latter cases there is reason to think the
dualities are at best approximate. One of our primary purposes is to analyze
the quality of these descriptions, i.e., how exact they can be made.
Maldacena's recent discussion of dualities involving crunching FRW cosmologies
provides an opportunity for exploring some of these question.
