Yoneda Lemma

Yoneda Lemma(Q320577), in Chinese: (米田引理). It is a theorem that embeds a locally small category into a category of functors.

陳述

設${\mathcal {C}}$為一範疇，定義兩個函子範疇如下：

${\mathcal {C}}^{\wedge }:=\mathrm {Fct} ({\mathcal {C}},\mathbf {Set} )$

${\mathcal {C}}^{\vee }:=\mathrm {Fct} ({\mathcal {C}}^{\mathrm {op} },\mathbf {Set} )$