 Kernel of the magnetic X-ray transform in degrees zero and one

For a smooth Anosov magnetic flow on a closed oriented surface, a smooth function plus a smooth one-form can be a smooth flow coboundary only when the function is zero and the one-form is exact. Equivalently their sum has zero integral along every closed orbit precisely in that case, using the smooth Livsic theorem. This is the nontrivial magnetic transform kernel theorem. Exact one-forms give the converse directly, since $F(w\circ \pi )=dw(v)$. The theorem does not require pointwise negative Gaussian curvature.