de Sitter Vacua in the String Landscape

Understand

The late-time behavior of our universe is one of accelerated expansion, or that of a de Sitter space, and therefore motivates us to look for time-dependent backgrounds.

• Finding such backgrounds in string theory has always been a challenging problem.
• An even harder problem is to find time-dependent backgrounds that allow positive dark energies.
• As a first step to handle such scenarios, we study a time-dependent background in type IIB theory, with four-dimensional de Sitter isometries, by uplifting it to M-theory and then realizing it as a coherent, or squeezed-coherent, state over an appropriate solitonic configuration.