nLab tangent complex




The tangent complex of an algebro-geometric object is meant to behave as the (sheaf of) sections of the tangent bundle.

At least in the generality of derived algebraic stacks XX, the tangent complex is equivalently (up to a shift in degree) the module of sections of the infinitesimal disk bundle of XX (the formal completion of the diagonal Δ X:XX×X\Delta_X \colon X \to X \times X) (Hennion 13, theorem 1).

For AA an ordinary associative algebra, its tangent complex is its module of derivations.

For AA a dg-algebra, its tangent complex is the essentially the value of the derived functor of the derivations-assigning functor on AA. This is closely related to the automorphism ∞-Lie algebra of AA.


The concept goes back to

  • M. Schlessinger, Jim Stasheff, The Lie algebra structure of tangent cohomology and deformation theory, J. Pure Appl. Algebra, 38(1985), 313–322.

The tangent complex of an algebra over an operad in chain complexes is discussed in section 8 of

See also

Last revised on March 21, 2017 at 09:13:09. See the history of this page for a list of all contributions to it.