Conformal anomaly and large-scale gravitational coupling

We present a model in which the breakdown of conformal symmetry of a quantu m stress-tenser due to the trace anomaly is related to a cosmological effec t in a gravitational model. This is done by characterizing the traceless pa rt of the quantum stress-tenser in terms of the stress-tensor of a conforma l invariant classical scalar field. We introduce a conformal frame in which the anomalous trace is identified with a cosmological constant. In this co nformal frame we establish the Einstein field equations by connecting the q uantum stress-tenser with the large-scale distribution of matter in the uni verse.