Stability of the Electroweak Vacuum in a Scale-Invariant Extension of the SM

We explore the possibility that scale symmetry is a quantum symmetry that is broken only spontaneously in flat space and apply this idea to the Standard Model (SM). The one-loop scalar potential is scale-invariant, since the loop calculations preserve the scale symmetry, with the DR subtraction scale generated spontaneously by the dilaton vacuum expectation value. At the quantum level, the Higgs mass is protected although the theory is non-renormalizable. It is argued that the instability of the effective potential in the Higgs sector that is driven by the quartic coupling running towards negative values becomes worse in the scale-invariant version, since the effective potential becomes unbounded from below.