Talk:Exalcomm

Todo

 * define morphisms between them
 * give examples of morphisms and non-isomorphic extensions
 * show module structure for exal
 * define exal for schemes
 * add explanation of composition of exal groups with the module formed by a direct sum of dual numbers, giving $$H^1(X,T_X)\oplus H^1(X,T_X)$$

Confusion in section "Relation with the cotangent complex"
I think there is a mistake here. The correct statement should be

$$Exalcom_{A}(B, M) \cong Ext^1_{B}(L_{B / A}, M)$$.

Illusie, in [1], uses $$Exal$$ instead of Grothendieck's $$Exalcom$$.

None of the original French texts use $$Exalcomm$$, they write $$Exalcom$$ (EGA IV) or $$Exal$$ (Illusie).

Amyekut (talk) 10:32, 11 March 2023 (UTC)