Aligned Axion Inflation in String Theory

Abstract: Immense efforts are being applied to search for the imprint of inflationary gravitational waves in CMB B-modes. But most theories that can be excluded by an upper limit r=0.01 are almost completely phenomenological, without a foundation in quantum gravity. I will explain why working in quantum gravity is essential for primordial B-mode science. I will then report on attempts to construct a relatively controllable example of large field inflation in string theory, through axion alignment.