We generalize various existing higher-loop Bethe ansaetze for simple sectors of the integrable long-range dynamic spin chain describing planar N=4 Super Yang-Mills Theory to the full psu(2,2|4) symmetry and, asymptotically, to arbitrary loop order. We perform a large number of tests of our conjectured equations, such as internal consistency, comparison to direct three-loop diagonalization and expected thermodynamic behavior. In the special case of the su(1|2) subsector, corresponding to a long-range t-J model, we are able to derive, up to three loops, the S-matrix and the associated nested Bethe ansatz from the gauge theory dilatation operator. We conjecture novel all-order S-matrices for the su(1|2) and psu(1,1|2) subsectors, and show that they satisfy the Yang-Baxter equation. Furthermore, we muse about the idea that quantum string theory on $AdS_5xS^5$ is also described by a psu(2,2|4) spin chain. We propose asymptotic all-order Bethe equations for this putative “string chain”, which differ in a systematic fashion from the gauge theory equations.

Golm, Germany