Accelerated Expansion from Negative \Lambda

TL;DR

This paper demonstrates that quantum wave functions with a negative cosmological constant can still predict an accelerating universe, challenging traditional assumptions and broadening the scope of cosmological models consistent with observations.

Contribution

It reveals a universal semiclassical structure in solutions to the Wheeler-DeWitt equation with negative 5, showing such models can predict accelerating universes.

Findings

Wave functions with negative 5 can predict positive effective cosmological constants.

A universal semiclassical asymptotic structure exists for large spatial volumes.

Implications for string cosmology model building are discussed.

Abstract

Wave functions specifying a quantum state of the universe must satisfy the constraints of general relativity, in particular the Wheeler-DeWitt equation (WDWE). We show for a wide class of models with non-zero cosmological constant that solutions of the WDWE exhibit a universal semiclassical asymptotic structure for large spatial volumes. A consequence of this asymptotic structure is that a wave function in a gravitational theory with a negative cosmological constant can predict an ensemble of asymptotically classical histories which expand with a positive effective cosmological constant. This raises the possibility that even fundamental theories with a negative cosmological constant can be consistent with our low-energy observations of a classical, accelerating universe. We illustrate this general framework with the specific example of the no-boundary wave function in its holographic form. The implications of these results for model building in string cosmology are discussed.