Computably enumerable equivalence relations (ceers) received a lot of attention in the literature. The standard tool to classify ceers is provided by the computable reducibility \(\leqslant _c\). This gives rise to a rich degree structure. In this paper, we lift the study of c-degrees to the \(\Delta ^0_2\) case. In doing so, we rely on the Ershov hierarchy. For any notation a for a non-zero computable ordinal, we prove several algebraic properties of the degree structure induced by \(\leqslant _c\) on the \(\Sigma ^{-1}_{a}\smallsetminus \Pi ^{-1}_a\) equivalence relations. A special focus of our work is on the (non)existence of infima and suprema of c-degrees.

可计算的等价关系（子代）在文献中受到了很多关注。可计算的归约度\（\ leqslant _c \）提供了对cees分类的标准工具。这产生了丰富的学位结构。在本文中，我们将c度的研究提升到\（\ Delta ^ 0_2 \）情况。在此过程中，我们依靠Ershov层次结构。对于非零可计算序数的任何符号a，我们证明了由\（\ Sigma ^ {-1} _ {a} \ smallsetminus \ Pi ^上的\（\ leqslant _c \）诱导的度数结构的若干代数性质。{-1} _a \）等价关系。我们工作的一个特别重点是c的infima和suprema的不存在度。