Nuclear mass predictions with anisotropic kernel ridge regression

The anisotropic kernel ridge regression (AKRR) approach in nuclear mass predictions is developed by introducing the anisotropic kernel function into the kernel ridge regression (KRR) approach, without introducing new weight parameter or input in the training. A combination of double two-dimensional Gaussian kernel function is adopted, and the corresponding hyperparameters are tuned carefully through cross-validations to optimize the predictions. The anisotropic kernel shows cross-shape pattern, which highlights the correlations among the isotopes with the same proton number, and those among the isotones with the same neutron number. Significant improvements are achieved by the AKRR approach in both the interpolation and the extrapolation predictions of nuclear masses comparing with the original isotropic KRR approach.