The relative second Fox and third dimension subgroup of arbitrary groups

Abstract

Let $I_R(G)$ denote the augmentation ideal of the group algebra $R(G)$ of a group $G$ with coefficients in a commutative ring $R$. We give a complete description of the third relative dimension subgroup $G\cap(1+I_R(K)I_R(G)+I^3_R(G))$ and the second relative Fox subgroup $G\cap(1+I_R(K)I_R(H)+I^2_R(G)I_R(H))$ for any subgroups $K$ and $H$ of $G$.