The saturation effect refers to the phenomenon that the kernel ridge regression (KRR) fails to achieve the information theoretical lower bound when the smoothness of the underground truth function exceeds certain level. The saturation effect has been widely observed in practices and a saturation lower bound of KRR has been conjectured for decades. In this paper, we provide a proof of this long-standing conjecture.

翻译：饱和效应是指当真实函数的平滑度超过一定水平时，核岭回归（KRR）无法达到信息论下界的现象。饱和效应已在实践中被广泛观测到，且相关下界猜想已有数十年历史。本文给出了这一长期猜想的一个证明。