Author:

Keywords:

cosmological constant, universe, inflation, Science & Technology, Physical Sciences, Astronomy & Astrophysics, Physics, Particles & Fields, Physics, INFLATION, hep-th, astro-ph, gr-qc, 0201 Astronomical and Space Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 0206 Quantum Physics, Nuclear & Particles Physics, 4902 Mathematical physics, 5101 Astronomical sciences, 5107 Particle and high energy physics

Abstract:

We put forward a framework for cosmology that combines the string landscape with no boundary initial conditions. In this framework, amplitudes for alternative histories for the universe are calculated with final boundary conditions only. This leads to a top-down approach to cosmology, in which the histories of the universe depend on the precise question asked. We study the observational consequences of no boundary initial conditions on the landscape, and outline a scheme to test the theory. This is illustrated in a simple model landscape that admits several alternative inflationary histories for the universe. Only a few of the possible vacua in the landscape will be populated. We also discuss in what respect the top-down approach differs from other approaches to cosmology in the string landscape, like eternal inflation. © 2006 The American Physical Society.