A novel language for spinning (A)dS correlators

Although the Universe appears homogeneous and isotropic on large scales, its late-time structure exhibits striking inhomogeneities, such as galaxies clustering in filaments around vast voids. These features can be traced back to the initial conditions in the early Universe, seeded by quantum fluctuations during cosmic inflation—a period of rapid expansion before the hot Big Bang. These initial conditions are encoded in the correlators of quantum fields defined on the future boundary of the inflationary spacetime. The cosmological bootstrap approach aims to derive these boundary correlators directly using physical principles—such as symmetries, locality, unitarity and causality—rather than relying on complex calculations within quantum field theory.
In this thesis, we address a long-standing challenge in the cosmological bootstrap related to spinning massless particles (such as gluons and gravitons) corresponding to conserved currents on the boundary. Inspired by the success of spinor-helicity variables for flat space amplitudes, we develop twistors as the natural variables that simplify the boundary correlators of these currents in both de Sitter (dS) space—which approximates the inflationary spacetime—and Anti-de Sitter (AdS) space. We show that, remarkably, twistors trivialize the constraints of current conservation and conformal symmetry simultaneously. This enables compact, elegant expressions for spinning two- and three-point correlators, revealing their hidden simplicity. The thesis concludes by highlighting the potential of twistors to also simplify higher-point correlators and further advance the cosmological bootstrap program.