Renormalization of Quantum Gravity with Lagrange Multiplier Fields

Abstract

We study the renormalization of Einstein gravity coupled to a scalar field in the Lagrange multiplier (LM) formulation, where a pair of quantum LM fields, $(λ'_{μν},σ')$, is coupled to the gauge-fixed gravitational and scalar equations of motion. Using the fact that in this approach there are no higher loop corrections, we show that renormalizing the two quantum LM fields at one-loop order absorbs, off-shell, five out of the six independent divergent structures. The remaining off-shell counterterm, proportional to $ (\partial_μ\barϕ\,\partial^μ\barϕ)^2, $ is nonzero on shell and cannot be absorbed by any LM field redefinition, since such redefinitions generate only counterterms that vanish on shell. In contrast, in pure gravity (no matter), the LM renormalization absorbs all one-loop divergences and no additional counterterms are required. The LM formulation therefore provides a sharp off-shell separation between equation-of-motion divergences, absorbed into LM field renormalizations, and the single irreducible structure.