We give a non-trivial class of valuation functions for which we give auctions that are efficient, truthful and envy-free. We give interesting classes of valuations for which one can design such auctions. Surprisingly, we also show that minor modifications to these valuations lead to impossibility results, the most surprising of which is that for a natural class of valuations, one cannot achieve...

We re-examine the graceful exit problem in the pre-Big Bang scenario of string cosmology, by considering the most general time-dependent classical correction to the Lagrangian with up to four derivatives. By including possible forms for quantum loop corrections we examine the allowed region of parameter space for the coupling constants which enable our solutions to link smoothly the two asympto...

The notion of a semivaluation has been introduced in [Sch98]. Aside from providing a novel concept generalizing valuations on lattices to the context of semilattices, semivaluations shed new light on the notion of a “partial metric” well known from theoretical computer science (e.g. [Mat94], [Mat95], [O’N97], [BS97] and [BSh97]). As discussed in [Sch98], the characterization of partial metrics ...