IR-fixed Euclidean vacuum for linearized gravity on de Sitter space

Understand

We consider the Euclidean vacuum for linearized gravity on the global de Sitter space, obtained from the Euclidean Green's function on the 4-sphere.

• We use the notion of Calder\'on projectors to recover a quantum state for the Lorentzian theory on de Sitter space.
• We show that while the state is gauge invariant and Hadamard, it is not positive on the whole of the phase space.
• We show however that a suitable modification at low energies yields a well-defined Hadamard state on global de Sitter space.