Abstract
We consider the most general three point function for gravitational waves
produced during a period of exactly de Sitter expansion. The three point
function, or bispectrum, has only three possible shapes, two preserving parity
and one violating parity. The constraint on the shape comes from the de Sitter
isometries and it is valid under very general assumptions. These isometries
imply that these correlation functions should be conformal invariant. One of
the shapes is produced by the ordinary gravity action. The other shapes are
produced by higher derivative corrections and could be as large as the gravity
contribution. We introduce a spinor helicity formalism to describe de Sitter
gravitational waves with circular polarization. These results also apply to
correlation functions in Anti-de Sitter space. They also describe the general
form of stress tensor correlation functions, in momentum space, in a three
dimensional conformal field theory.
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