Abstract
We show that constraints on scalar field potentials and towers of light massive states in asymptotic limits of scalar field space (as posited by the de Sitter Conjecture and the Swampland Distance Conjecture, respectively) are correlated with the prospects for defining asymptotic observables in expanding FRW cosmologies. The observations of a "census taker" in an eternally inflating cosmology are further related to the question of whether certain domain walls satisfy a version of the Weak Gravity Conjecture. This suggests that answers to fundamental questions about asymptotic observables in cosmology could help shed light on the Swampland program, and vice versa.
Highlights
The past few years have seen significant advances in our understanding of the physics of black holes
From the discussion in the previous section, we see that the strong de Sitter conjecture (dSC) may be motivated by a more physical principle: the existence of asymptotic hat regions, which may be necessary for the existence of well-defined observables in spacetimes with positive vacuum energy, requires that V → 0 limits exist in scalar field space and that these limits occur in regions with decelerating expansion
We have seen that a strong version of the dSC in asymptotic regions of scalar field space— previously distinguished by dimensional reduction—would offer the best prospects for defining asymptotic observables in eternal inflation, as it implies the existence of hat regions and rules out the possibility of terminal quintessence vacua in asymptotic regions of scalar field space
Summary
The past few years have seen significant advances in our understanding of the physics of black holes. Strong evidence has been provided for the absence of global symmetries in quantum gravity [8,9,10,11,12,13,14] and the weak gravity conjecture (WGC) [15,16,17,18,19]—two conjectures motivated by demanding consistent black hole decay—as well as the swampland distance conjecture (SDC) [20,21,22,23,24,25,26]. We will argue that older studies on the difficulties of defining asymptotic observables in an expanding universe may shed light on recent studies of scalar field potentials in string theory, and in turn, recent progress on the weak gravity conjecture and black hole complementarity may shed light on asymptotic observables in de Sitter space.
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