Life at the Interface of Particle Physics and String Theory

TL;DR

This paper reviews recent developments at the intersection of particle physics and string theory, emphasizing the role of the multiverse and anthropic reasoning in understanding unresolved questions about the universe.

Contribution

It provides a comprehensive overview of the last decade's progress in connecting string theory, the multiverse, and anthropic principles with particle physics.

Findings

The string landscape offers a vast array of possible universes.

Anthropic reasoning is increasingly used to explain fine-tuning.

Recent developments highlight the importance of environmental factors in fundamental physics.

Abstract

If the results of the first LHC run are not betraying us, many decades of particle physics are culminating in a complete and consistent theory for all non-gravitational physics: the Standard Model. But despite this monumental achievement there is a clear sense of disappointment: many questions remain unanswered. Remarkably, most unanswered questions could just be environmental, and disturbingly (to some) the existence of life may depend on that environment. Meanwhile there has been increasing evidence that the seemingly ideal candidate for answering these questions, String Theory, gives an answer few people initially expected: a huge "landscape" of possibilities, that can be realized in a multiverse and populated by eternal inflation. At the interface of "bottom-up" and "top-down" physics, a discussion of anthropic arguments becomes unavoidable. We review developments in this area, focusing especially on the last decade.