A bstract We study two-dimensional string theory on a time-dependent background, whose worldsheet description consists of Liouville at central charge c = 1 and 25, together with the conformal ghosts. compute tree-level three-point four-point components cosmological wavefunction in perturbation theory. The latter is evaluated numerically by decomposing correlation functions into Virasoro blocks ...

Positive vacuum energy together with extra dimensions of space imply that our fourdimensional Universe is unstable, generically to decompactification of the extra dimensions. Either quantum tunneling or thermal fluctuations carry one past a barrier into the decompactifying regime. We give an overview of this process, and examine the subsequent expansion into the higher-dimensional geometry. Thi...

We explore cosmology of intersecting braneworlds with induced gravity on the branes. We find the cosmological equations that control the evolution of a moving codimension one brane and a codimension two brane that sits at the intersection. We study the Friedmann equation at the intersection, finding new contributions from the six dimensional bulk. These higher dimensional contributions allow us...

The study of topological quantum field theories increasingly relies upon concepts from higher-dimensional algebra such as n-categories and n-vector spaces. We review progress towards a definition of n-category suited for this purpose, and outline a program in which n-dimensional TQFTs are to be described as n-category representations. First we describe a ‘suspension’ operation on ncategories, a...

We describe extended inflation and its typical problems. We then briefly review essential features of Kaluza-Klein theory, and show that it leads to a scenario of inflationary cosmology in four dimensions. The problem of stable compactification of extra spatial dimensions is discussed. The requirements for successful exetended inflation lead to constraints on the parameters of higher dimensiona...