1 2 3 4 5 6 linear combination number 0.1 1.0 eigenvalue all states FIG. 3: SVD spectrum from the overlap of the dominant eigenvectors from USDB and the TBRE. We also compared for contact interactions; we took only two terms, the S = 0 , T = 1 channel and S = 1 , T = 0 channel (there being only the s -wave channel in relative coordinates). These results we summarize in Table 1. TABLE I: Leading eigenvalues from SVD of subspace overlaps of two-term contact interaction Interaction ground states excited states all states USDB 0.60 0.58 0.62 TBRE 0 . 55 ± 0 . 04 0 . 41 ± 0 . 06 0 . 55 ± 0 . 04 For comparison, the leading eigenvalue for the overlaps of USDB versus the six-term monopole is 0.94, while that of the TBRE versus monopole is 0 . 66 ± 0 . 03. There is some- what more sensitivity to the monopole interaction than the contact interaction; however, the reader should keep in mind that is not the whole story. Recall that when fitting an interaction, the linearized equations are cast in the form A ⃗ x = ⃗ B . Our analysis in this paper is entirely with the eigenvalues of A , but in any fit one must also look to ⃗ b (which in practice is the deviation of the theoretical spectra from experiment). For example, in [12] it was found that using a contact interaction brought better agreement than a monopole inter- action. One can understand this in terms of conjugate gradient methods [23]: the direction of local steepest gradient may not in fact point towards the global minimum. By our measures so far, both the TBRE and the empirically-fit USDB look qualitatively similar. Therefore we take a final analysis by comparing the dominant linear combinations of the USDB with those from the TBRE. This is show in Fig. 3, using the same analysis as 6