In this paper we give a financial justification, based on non arbitrage conditions,of the (H) hypothesis in default time modelling. We also show how the (H) hypothesis isaffected by an equivalent change of probability measure.[...]

In this paper, we build a bridge between different reduced-form approaches to pricing defaultable claims. In particular, we showhow the well known formulas by Duffie et al. [12] and by Elliott et al.[14] are related. Moreover, in the spirit of Collin Dufresne et al. [8], wepropose a simple...