Francesco Nitti, Federico Piazza
We consider the quantum effects of matter fields in scalar-tensor theories
and clarify the role of trace anomaly when switching between conformally
related `frames'. We exploit the property that the couplings between the scalar
and the gauge fields are not frame-invariant and define a `QCD-frame', where
the scalar is not coupled to the gluons. This frame generalizes the `Jordan
frame' in the case of non-metric theories and is particularly convenient for
gravitational phenomenology. Test bodies have trajectories that are as close as
possible to geodesics with respect to such a metric and equivalence principle
violations are directly proportional to the scalar coupling parameters written
in this frame. We show how RG flow and decoupling work in metric and non-metric
theories. RG-running commutes with the operation of switching between frames at
different scales. When only matter loops are considered, our analysis confirms
that metricity is stable under radiative corrections and shows that approximate
metricity is natural in a technical sense.
View original:
http://arxiv.org/abs/1202.2105
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