Field theory models for variable cosmological constant - art. no. 063509

Anthropic solutions to the cosmological constant problem require seemingly unnatural scalar field potentials with a very small slope or domain walls ( branes) with a very small coupling to a four-form field. Here we introduce a class of models in which the smallness of the corresponding parameters ca n be attributed to a spontaneously broken discrete symmetry. We also demons trate the equivalence of scalar field and four-form models. Finally, we sho w how our models can be naturally embedded into a left-right symmetric exte nsion of the standard model.