The Lifetime of the Universe

TL;DR

The paper investigates bounds on the universe's future lifetime given current observations of dark energy. It analyzes a spatially flat FRW model with dust plus a scalar field with a non-convex potential, deriving the dynamical equations and showing that the present values $\Omega_{m0}$ and $w_0$ constrain the future evolution; it then establishes a lower bound on the future lifetime. Using an anthropic/observation-based argument, it also derives upper bounds on the remaining lifetime under different expansion scenarios, notably $t_{\mathrm{future}} \lesssim e^{10^{50}}$ years for power-law expansion and $t_{\mathrm{future}} \lesssim 10^{60}$ years for exponential expansion. The results have implications for whether dark energy is a true cosmological constant and for the existence and longevity of observer-friendly vacua in the string landscape, thereby informing cosmological futures and fundamental theory constraints. Overall, the work provides concrete, quantitative limits on both the minimum and maximum possible lifetimes of a universe that can support observers.

Abstract

Current observations of the fraction of dark energy and a lower limit on its tension, coupled with an assumption of the non-convexity of the dark energy potential, are used to derive a lower limit of 26 billion years for the future age of the universe. Conversely, our ordered observations, coupled with an assumption that observers are smaller than the universe, are used to argue for an upper limit of about e^10^50 years if the universe eventually undergoes power-law expansion, and an upper limit of only about 10^60 years left for our universe if it continues to expand exponentially at the current rate.