Spacelike fluctuations of the stress tensor for de Sitter vacuum

The two-point function characterizing the stress tensor fluctuations of a m assless, minimally coupled field for an invariant vacuum state in de Sitter spacetime is discussed. This two-point function is explicitly computed for spacelike-separated points which are geodesically connected. We show that these fluctuations are as important as the expectation value of the stress tensor itself. These quantum field fluctuations will induce fluctuations in the geometry of de Sitter spacetime. This paper is a first step toward the computation of such metric fluctuations, which may be of interest for larg e-scale structure formation in cosmology. The relevance of our results in t his context is briefly discussed.