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We study the relation between the Jordan-Einstein frame transition and thepossible description of the crossing of singularities in flat Friedmannuniverses, using the fact that the regular evolution in one frame cancorrespond to crossing singularities in the other frame. We show that someinteresting effects arise in simple models such as one with a massless scalarfield or another wherein the potential is constant in the Einstein frame. Thedynamics in these models and in their conformally coupled counterparts aredescribed in detail, and a method for the continuation of such cosmologicalevolutions beyond the singularity is developed. We compare our approach withsome other, recently developed, approaches to the problem of the crossing ofsingularities.

Transformations between Jordan and Einstein frames: Bounces, antigravity, and crossing singularities