A statistical quantity suitable for distinguishing simply-connected RobertsonWalker (RW) universes is introduced, and its explicit expressions for the three possible classes of simply-connected RW universes with an uniform distribution of matter are determined. Graphs of the distinguishing mark for each class of RW universes are presented and analyzed. There sprout from our results an improveme...

We show that any simply connected rectifiable domain Ω can be decomposed into Lipschitz crescents using only crosscuts of the domain and using total length bounded by a multiple of the length of ∂Ω. In particular, this gives a new proof of a theorem of Peter Jones that such a domain can be decomposed into Lipschitz disks. 1991 Mathematics Subject Classification. Primary: 68U05 Secondary: 26B15,...

In 1986 A. Ancona showed, using the Koebe one-quarter Theorem, that for a simply-connected planar domain the constant in the Hardy inequality with the distance to the boundary is greater than or equal to 1/16. In this paper we consider classes of domains for which there is a stronger version of the Koebe Theorem. This implies better estimates for the constant appearing in the Hardy inequality. ...

In this article we construct a new family of simply connected symplectic 4-manifolds with b+2 = 1 and c 2 1 = 2 which are not diffeomorphic to rational surfaces by using rational blow-down technique. As a corollary, we conclude that a rational surface CP ♯7CP 2 admits an exotic smooth structure.