thresholds are inevitably reached. Volume corrections are no longer exponentially suppressed in asymptotic volumes; they become power law and will likely dwarf any signal. For the extraction of moments and radii of stable particles near zero momentum transfer, however, we are safely away from the multi-particle continuum.

Summary {#summy}
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We have related matrix elements of arbitrary quark bilinear operators that change isospin to isovector combinations of those that do not change isospin. Using flavor twisted boundary conditions on the valence quark fields, form factors of these isovector matrix elements can then be deduced from the lattice at continuous values of the momentum transfer. Isovector moments and radii can thus be determined from simulations at zero lattice momentum. Using twisted boundary conditions on the quark fields dramatically modifies the effect of the finite volume, even away from multi-particle cuts. This systematic effect can be handled with EFTs. The determination of isovector moments and radii without any model-dependent assumptions about the momentum dependence is thus well within reach of current resources.

We thank W. Detmold for discussions, and acknowledge the Institute for Nuclear Theory at the University of Washington for its hospitality and partial support during the course of this investigation. 