文摘
We exhibit a finitely generated group G and a sequence of finite index normal subgroups such that for every finite generating subset \({S\subseteq G}\) , the sequence of finite Cayley graphs (G/N n , S) does not coarsely embed into any L p -space for \({1 \leqslant p (moreover, into any uniformly curved Banach space), and yet admits no weakly embedded expander. The reason why our examples do not coarsely embed is a new phenomenon called relative expansion, which we define in terms of Poincaré inequalities.