Combinatoric explosion of renormalization tamed by Hopf algebra: 30-loop Pade-Borel resummation

It is easy to sum chain-free self-energy rainbows, to obtain contributions to anomalous dimensions. It is also easy to resum rainbow-free self-energy chains. Taming the combinatoric explosion of all possible nestings and chainings of a primitive self-energy divergence is a much more demanding problem. We solve it in terms of the coproduct Delta, antipode S, and grading operator Y of the Hopf algebra of undecorated rooted trees. The vital operator is S star Y, with a star product effected by Delta. We perform 30-loop Pade-Borel resummation of 463 020 146 037 416 130 934 BPHZ subtractions in Yukawa theory, at spacetime dimension d = 4, and in a trivalent scalar theory, at d = 6, encountering residues of S star Y that involve primes with up to 60 digits. Even with a very large Yukawa coupling, g = 30, the precision of resummation is remarkable, a 31-loop calculation suggests that it is of order 10(-8). (C) 2000 Elsevier Science B.V. All rights reserved.