16 [45] Actually, in [29], another notation v ( p $^{2}$) has been used instead of w ( p $^{2}$), the relation being w ( p $^{2}$) = p $^{2}$v ( p $^{2}$) . [46] The author of [8] came to the conclusion that a straight- forward implementation of the horizon condition leads to G (0) = 3, rather than G (0) = ∞ . [47] In particular, since we will always assume the use of a mass independent renormalization scheme, we may com- pute a 3 with all external mass scales (= sources) equal to zero. Said otherwise, a 3 is completely determined by the dynamics of the original Yang-Mills action, in which case it is known to vanish to all orders [41]. [40] N. Maggiore and M. Schaden, Phys. Rev. D 50 (1994) 6616. [41] O. Piguet and S. P. Sorella, Lect. Notes Phys. M28 (1995) 1. [42] However, let us mention that no unanimous consensus on this matter has yet been reached, see e.g. [16–20] for possible other opinions on the infrared behavior of the ghost propagator. [43] See also [32]. [44] We recall here that in order to consistently discuss com- posite operators at the quantum level, they need to be introduced into the theory by means of suitable sources.