String theory: from the landscape to the swampland

IAP weekly specialised seminars / 15 March 2024

Mariana Graña (IPhT, CEA Saclay, Gif-sur-Yvette, France)

Despite its uniqueness, string theory has a “landscape” of low-energy solutions with very different observable physics. These solutions are usually found using low-energy effective theories which, in order to satisfy experimental constraints such as the accelerated expansion of the universe, require a number of exotic ingredients whose string theory origin is unclear. The so-called “de Sitter swampland conjecture” speculates that de Sitter space is in the “swampland”, i.e. in the set of seemingly consistent low energy effective theories that cannot be consistently coupled to quantum gravity. After a very brief introduction to string theory, in this colloquium we will review its de Sitter solutions, and try to situate them somewhere on the scenery of string theory.