What Can the Anthropic Principle Tell Us about the Future of the Dark Energy Universe

Abstract

An anthropic explanation of the evident smallness of the dark energy (DE) density value implies the existence of a time-dependent component of the scalar field, serving, together with a negative-valued cosmological constant, as one of two components to the overall DE density. The observers (i.e. us) might then only evolve in those regions of the universe where the sum of those two components (the positive and a negative ones) is sufficiently close to zero. However, according to Vilenkin and Garriga, the scalar field component has to slowly but surely diminish in time. In about a trillion years, this process will put a cap to the now-observable accelerated expansion of the universe, leading to a subsequent phase of impending collapse. However, the vanishing scalar field might also produce some rather unexpected singularities with a finite nonzero scale factor. We analyze this possibility using a particular example of a Sudden Future Singularities (SFS) and come to a startling conclusion that the time required for an SFS to arise must be “comparable” to the lifetime of the observable universe.