Is There A String Theory Landscape

TL;DR

The paper critically evaluates the proposed string theory landscape, arguing that AdS flux vacua are plausible while meta-stable de Sitter states face fundamental issues due to the breakdown of long-distance EFT and potential instabilities requiring a full quantum gravity description. It contrasts two explanatory modes—datums-based grounding and anthropic reasoning—concluding that anthropics alone do not deliver robust predictions for low-energy physics and often conflict with experiment. Through RG arguments and detailed phenomenological considerations, the authors contend that the discretuum’s predictive power is severely limited unless additional structure (e.g., discrete symmetries addressing the strong CP problem) is found. They ultimately argue that a deeper, principled framework for quantum gravity is needed to connect flux vacua to observable physics, as the current landscape picture risks inconsistency with experimental data and lacks reliable calculational control.

Abstract

We examine recent claims of a large set of flux compactification solutions of string theory. We conclude that the arguments for AdS solutions are plausible. The analysis of meta-stable dS solutions inevitably leads to situations where long distance effective field theory breaks down. We then examine whether these solutions are likely to lead to a description of the real world. We conclude that one must invoke a strong version of the anthropic principle. We explain why it is likely that this leads to a prediction of low energy supersymmetry breaking, but that many features of anthropically selected flux compactifications are likely to disagree with experiment.