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We report on a revision of our previous computation of the renormalizedexpectation value of the stress-energy tensor of a massless, minimally coupledscalar with a quartic self-interaction on a locally de Sitter background. Thismodel is important because it demonstrates that quantum effects can lead toviolations of the weak energy condition on cosmological scales - on average,not just in fluctuations - although the effect in this particular model is fartoo small to be observed. The revision consists of modifying the propagator sothat dimensional regularization can be used when the dimension of therenormalized theory is not four. Although the finite part of the stress-energytensor does not change (in D=4) from our previous result, the counterterms do.We also speculate that a certain, finite and separately conserved part of thestress tensor can be subsumed into a natural correction of the initial statefrom free Bunch-Davies vacuum.Comment: 9 pages, references adde

physical review. d. particles, fields, gravitation, and cosmology/physical review. d, particles, fields, gravitation, and cosmology

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Quantum effects can renderw<−1on cosmological scales