We combine different techniques to extract information about the logarithmic contributions to the two-body conservative dynamics within the post-Newtonian (PN) approximation of General Relativity. The logarithms come from the conservative part of non linear gravitational-wave tails and their iterations. Explicit, original expressions are found for conservative dynamics logarithmic tail terms up to 6PN order by adopting both traditional PN calculations and effective field theory (EFT) methods. We also determine all logarithmic terms at 7PN order, fixing a sub-leading logarithm from a tail-of-tail-of-tail process by comparison with self-force (SF) results. Moreover, we use renormalization group techniques to obtain the leading logarithmic terms to generic power n, appearing at (3n + 1)PN order, and we resum the infinite series in a closed form. Half-integer PN orders enter the conservative dynamics starting at 5.5PN, but they do not generate logarithmic contributions up to next-to-next-to-leading order included. We nevertheless present their contribution at leading order in the small mass ratio limit.
I. MOTIVATIONS AND OVERVIEWThe post-Newtonian (PN) approximation to General Relativity (GR) has been a largely successful framework to perturbatively solve Einstein's equations, widely adopted and approached with a variety of methods, see Refs. [1][2][3][4][5] for recent reviews. Among the most important methods we mention the ADM Hamiltonian approach [6-8], the Multipolar-post-Minkowskian framework with PN matching (MPM-PN) [9,10], the direct integration of the relaxed field equations (DIRE) [11], the surface-integral approach [12] and the Effective Field Theory (EFT) approach pioneered by Ref. [13]. In particular we want to highlight here the great synergies existing today between the EFT approach and more traditional PN methods.Within the two-body dynamics, we focus in the present work on tail processes, which arise from the back-scattering of gravitational waves (GW) off the quasi-static curvature sourced by the total mass of the binary system. Tail effects are known from a long time (see e.g. [14,15]) but were first identified and investigated in the present context in [16][17][18]. They are present in both the conservative and dissipative sectors of the theory. The conservative tail effect at 4PN order [19,20] has been recently fully incorporated into the 4PN equations of motion using the ADM Hamiltonian method [21][22][23][24], the Fokker Lagrangian in harmonic coordinates [25][26][27][28] and the EFT approach [29][30][31][32]. Moreover the leading and next-to-leading logarithmic tail terms in the energy function of compact binaries on circular orbits have been derived [33][34][35][36].Tails present themselves with a characteristic logarithmic and hereditary nature, i.e., which depends of the entire history of the source rather than its state at the retarded time, corresponding to wave propagation inside the retarded light-cone. We focus our investigation in the present work to such tail logarithmic contributio...