Reply to ‘Can infrared gravitons screen Λ?’

We reply to the recent criticism by Garriga and Tanaka of our proposal that quantum gravitational loop corrections may lead to a secular screening of the effective cosmological constant. Their argument rests upon a renormalization scheme in which the composite operator (R √−g − 4Λ√−g )ren is defined to be the trace of the renormalized field equations. Although this is a peculiar prescription, we show that it does not preclude secular screening. Other important points are: (1) gauge dependence does not render a Green’s function devoid of physical content; (2) scalar models on a non-dynamical de Sitter background (for which there is no gauge issue) can induce arbitrarily large secular contributions to the stress tensor; (3) the same secular corrections appear in observable quantities in quantum gravity; and (4) the prospects seem good for deriving a simple stochastic formulation of quantum gravity in which the leading secular effects can be summed and for which the expectation values of even complicated, gauge invariant operators can be computed at leading order. PACS numbers: 04.30.Nk, 04.62.+v, 98.80.Cq, 98.80.Hw † e-mail: [email protected] ‡ e-mail: [email protected]