Disturbing Implications of a Cosmological Constant

TL;DR

Dyson, Kleban, and Susskind explore the implications of a cosmological constant through horizon complementarity and causal-patch holography, arguing that a finite, unitary description yields inevitable Poincaré recurrences and deep paradoxes about initial conditions and the arrow of time. Using AdS black hole analogies and an observocentric gauge, they show horizon degrees of freedom exchange with bulk energy yet recognize tensions with standard cosmology and speculative dS/CFT ideas. Their analysis suggests that, if a true cosmological constant exists, most livable histories arise from rare fluctuations rather than conventional inflation, making our universe extraordinarily atypical unless additional structure or weighting is imposed. Consequently, either the cosmological constant must be reconciled with new physics or the recurrence-dominated picture must be revised to explain our observed cosmos.

Abstract

In this paper we consider the implications of a cosmological constant for the evolution of the universe, under a set of assumptions motivated by the holographic and horizon complementarity principles. We discuss the ``causal patch" description of spacetime required by this framework, and present some simple examples of cosmologies described this way. We argue that these assumptions inevitably lead to very deep paradoxes, which seem to require major revisions of our usual assumptions.

Figures (7)

• Figure 1: An eternal AdS Schwarzshild black hole, or de Sitter space. The horizontal boundaries are space-like singularities in the case of the AdS black hole, and the infinitely inflated past and future in the case of de Sitter.
• Figure 2: The causal patch for an observer at the boundary of an AdS Schwarzschild black hole, or in de Sitter space.
• Figure 3: An AdS black hole created by an infalling shell of energy originating at the boundary.
• Figure 4: The causal patch for two types of global time transitions from one de Sitter space to another.
• Figure 5: A transition from a de Sitter space with a small radius of curvature to a matter dominated phase, followed by a transition to a large de Sitter. In this example, the horizon is pushed all the way around to the south pole of the sphere, and vanishes for intermediate times.