1. Hořava, P.: Quantum gravity at a Lifshitz point. Phys. Rev. D. 79, 084008 (2009)
2. In effect, the Epstein-Glaser approach [3] avoids the infrared problem by multiplying the interaction by a test function g(x), which vanishes rapidly for | x | → ∞ $|x| \to \infty $ . In this case, the long range part of the interaction is cut-off. Infrared problem arises in the adiabatic limit g(x)→1. Performing the adiabatic limit is a delicate task, since the limit has to be taken s.t. observable quantities (cross sections) remain finite. Blanchard-Seneor [4] showed that the adiabatic limit exists (in the distributional sense) for the QED and λ: ϕ 2n : Theories.
3. Epstein, H., Glaser, V.: The role of locality in perturbation theory,. Ann. Inst. Henri Poincaré 19, 211 (1973)
4. Blanchard, P., Seneor, R.: Green’s functions for theories with massless particles (in perturbation theory). Ann. Inst. Henri Poincaré 23, 147 (1975)
5. Scharf, G.: Finite Quantum Eletrodynamics: the Causal Approach, 2nd edn.Springer (1995)