Obstacles to Constructing de Sitter Space in String Theory

Understand

There have been many attempts to construct de Sitter space-times in string theory.

• While arguably there have been some successes, this has proven challenging, leading to the de Sitter swampland conjecture: quantum theories of gravity do not admit stable or metastable de Sitter space.
• Here we explain that, within controlled approximations, one lacks the tools to construct de Sitter space in string theory.
• Such approximations would require the existence of a set of (arbitrarily) small parameters, subject to severe constraints.