What does inflation say about dark energy given the swampland conjectures?

Chien-I Chiang,Jacob M Leedom,Hitoshi Murayama

doi:10.1103/physrevd.100.043505

Abstract

We discuss the relations between swampland conjectures and observational constraints on both inflation and dark energy. Using the requirement $|\nabla V|\geq c V$, with $c$ as a universal constant whose value can be derived from inflation, there may be no observable distinction between constant and non-constant models of dark energy. However, the latest modification of the above conjecture, which utilizes the second derivative of the potential, opens up the opportunity for observations to determine if the dark energy equation of state deviates from that of a cosmological constant. We also comment on the observability of tensor fluctuations despite the conjecture that field excursions are smaller than the Planck scale.

Highlights

The discovery of the accelerating expansion of the Universe [1,2] was a huge surprise to the community
The latest modification of the above conjecture, which utilizes the second derivative of the potential, opens up the opportunity for observations to determine if the dark energy equation of state deviates from that of a cosmological constant
Motivated by the obstructions encountered in various attempts, the de Sitter swampland conjecture was proposed [66], which states that the scalar potential of a low-energy limit of quantum gravity must satisfy

Summary

INTRODUCTION

The discovery of the accelerating expansion of the Universe [1,2] was a huge surprise to the community. Motivated by the obstructions encountered in various attempts, the de Sitter swampland conjecture was proposed [66], which states that the scalar potential of a low-energy limit of quantum gravity must satisfy. The current accelerating expansion must involve a quintessence field Q whose potential VQ must satisfy þ w This does not exclude observable quintessence, given the fact that so far almost all observations are consistent with a cosmological constant, such a small lower bound on a possible deviation of w from −1 makes it questionable if it is worthwhile to push the sensitivity of the observations further. The refined de Sitter swampland conjecture was proposed [101,128], which states that the scalar potential of a lowenergy theory that can be consistently coupled to quantum gravity should satisfy either. See [129] for a recent discussion on w considering the refined dS conjecture

SINGLE-FIELD SLOW-ROLL INFLATION MODELS

MULTIFIELD SLOW-ROLL INFLATION MODELS

IMPLICATIONS FOR DARK ENERGY

CONCLUSIONS