Fine-tuning and the Second Law of Thermodynamics from the perspective of de Sitter quantum gravity

Abstract

In this essay, we discuss the fine-tuning problems of the Higgs mass and the cosmological constant. We argue that these are indeed legitimate problems, as opposed to some other "problems" that are sometimes described using similar vocabulary. We then notice, following Tom Banks, that the problems become less compelling once we recognize that the Universe contains quantum gravity, and thus isn't fundamentally described by bulk QFT. Embracing this "solution" requires a reversal of the standard arrows UV->IR and past->future. The first reversal is familiar from AdS/CFT. The second reversal refers more specifically to our Universe's cosmology, and is clearly in potential conflict with the Second Law of Thermodynamics. In the final part of the essay, we attempt to defuse this conflict, suggesting that the Second Law can arise naturally from de Sitter boundary conditions at future infinity.