Given a 3-holed sphere decomposition of an orientable closed surface, it is shown that each orientation preserving homeomorphism of the surface is isotopic to a composition AB where A is a product of positive Dehn twists and B is a product of negative Dehn twists on the decomposition curves.

We establish the second part of Milnor's conjecture on the volume of simplexes in hyperbolic and spherical spaces. A characterization of the closure of the space of the angle Gram matrices of simplexes is also obtained.

We define a new combinatorial class of triangulations of closed 3manifolds, and study them using twisted squares. As an application, we obtain strong restrictions on the topology of a 3manifold from the existence of non-smooth maxima of the volume function on the space of circle-valued angle structures.

Heegaard diagrams on the boundary of a handlebody are studied from the dynamics systems point of view. A relationship between the strongly irreducible condition of CassonGordan and the Masur's domain of discontinuity for the action of the handlebody group is established.

In this paper, we produce an elementary approach to Thurston's theory of measured laminations on compact surfaces with non-empty boundary. We show that the theory can be derived from a simple inequality for geometric intersection numbers between arcs inside an octagon.