1 For recent reviews, see . 2 In practice, this requires truncation of the quantization condition by assuming that higher partial waves are negligible. Such truncation schemes for the three-particle case have been discussed in Refs. [1,3,11,12,[14][15][16]. We do not consider these further in the present work. 3 In addition the particles were taken to be identical and spinless. Based on experience with the two-particle case, we expect the extensions to multiple channels of non-identical and non-degenerate particles, as well as particles with intrinsic spin, will be relatively straightforward.
arXiv:1810.01429v1 [hep-lat] 2 Oct 2018package The NCAlgebra Suite is used to check the key results by algebraically manipulating matrices of unspecified size as generic non-commuting objects [32].This article is organized as follows. We begin in Sec. II by presenting the final result and defining all of the objects appearing in it. This section is meant to stand alone so that the lattice practitioner does not need to look elsewhere in order to make use of the result. In Sec. III we present the derivation of the quantization condition, with technical details given in Appendix B. The quantization condition is written in terms of the three-body K matrix, which we relate to the physical scattering amplitude in Sec. IV. We summarize, compare to previous work, and give an outlook in Sec. V.The framework presented here relies heavily on two facts: First, that the off-shell version of K 2 has the same poles as its on-shell limit and second, that at the residues of the poles of the off-shell K 2 can be written as a product of functions separately describing the incoming and outgoing two-particle states. In Appendix A we demonstrate these two results using constraints from unitarity and all-orders perturbation theory.
II. SUMMARY OF THE FINAL RESULTThe main result of this article is a quantization condition with solutions equal to the energies of finite-volume three-particle states in a generic, relativistic quantum field theory. In contrast to earlier work, this result also holds for systems with a two-particle resonant subchannel. The particles are assumed to be identical, of physical mass m, and to have a G-parity-like symmetry that restricts interactions to those involving an even number of fields.We assume that K 2 diverges only for a single angular momentum, denoted J, in the energy range of interest, specified below. We further assume that there is only one pole in K (J) 2