%0 Journal Article
%T Relativistic, model-independent, multichannel $2\to2$ transition amplitudes in a finite volume
%A Ra¨²l A. Brice£żo
%A Maxwell T. Hansen
%J Physics
%D 2015
%I arXiv
%X We derive formalism for determining $\textbf{2} + \mathcal J \to \textbf{2}$ infinite-volume transition amplitudes from finite-volume matrix elements. Specifically, we present a relativistic, model-independent relation between finite-volume matrix elements of external currents and the physically observable infinite-volume matrix elements involving two-particle asymptotic states. The result presented holds for states composed of two scalar bosons. These can be identical or non-identical and, in the latter case, can be either degenerate or non-degenerate. We further accommodate any number of strongly-coupled two-scalar channels. This formalism will, for example, allow future lattice QCD calculations of the $\rho$-meson form factor, in which the unstable nature of the $\rho$ is rigorously accommodated.
%U http://arxiv.org/abs/1509.08507v1