Observational Consequences of a Landscape

TL;DR

This paper explores how the landscape paradigm suggests our universe originated from a tunneling event, leading to an open universe with negative curvature, and discusses observational implications and anthropic bounds on inflation.

Contribution

It provides a novel analysis of how the landscape paradigm influences the universe's initial conditions and observable properties, emphasizing the role of tunneling and curvature.

Findings

Our universe likely originated from a tunneling event from a neighboring vacuum.

The universe is probably open with negative spatial curvature.

The number of inflationary efolds may be close to the observational lower bound.

Abstract

In this paper we consider the implications of the "landscape" paradigm for the large scale properties of the universe. The most direct implication of a rich landscape is that our local universe was born in a tunnelling event from a neighboring vacuum. This would imply that we live in an open FRW universe with negative spatial curvature. We argue that the "overshoot" problem, which in other settings would make it difficult to achieve slow roll inflation, actually favors such a cosmology. We consider anthropic bounds on the value of the curvature and on the parameters of inflation. When supplemented by statistical arguments these bounds suggest that the number of inflationary efolds is not very much larger than the observed lower bound. Although not statistically favored, the likelihood that the number of efolds is close to the bound set by observations is not negligible. The possible signatures of such a low number of efolds are briefly described.