The Wave Function Of The Universe And The Stringy Landscape

The singularity theorems of Hawking and Penrose imply that the universe must have a singularity in its past - representing the 'birth' of the universe. General Relativity fails in explaining the dynamics of the universe close to the singularity. One expects the quantum theory of gravity to successfully explain the birth and the subsequent evolution of the universe. The wavefunction of the universe purports to explain precisely this in an energy regime where one can trust a semiclassical theory of quantum gravity. The wavefunction is particularly interesting in the light of the recent developments in String Theory. An entire landscape of stringy vacua - deSitter, anti-deSitter, and supersymmetric - has emerged and the number of vacua seems to be infinite. In the lack of a unique vacuum, attempts are being made to construct a set of selection principles. The wavefunction is a natural choice for a cosmological selection mechanism. There have been various proposals for the wavefunction in the last two decades and a debate exists as to which is the correct one for describing the spontaneous creation of the universe. We present calculations that shed some light on a possible resolution of the debate, and suggest a cure to the nonnormalizability of the wavefunction using a well known concept of decoherence in quantum measurements and condensed matter physics. Further, this 'improved wavefunction' is shown to predict a class of vacua as favorable for the creation of the universe whose energy scale lies in the range of the inflationary energy scale. We also mention some recent advances made in toy model wavefunctions using string theory calculations