nLab elliptic chain complex



Index theory

Homological algebra

homological algebra

(also nonabelian homological algebra)



Basic definitions

Stable homotopy theory notions



diagram chasing

Schanuel's lemma

Homology theories




The notion of elliptic chain complex is the generalization of the notion of elliptic operator from single linear maps to chain complexes of linear maps.


For XX a smooth manifold and {E k} k\{E_k\}_{k \in \mathbb{Z}} a collection of vector bundles over XX, a chain complex of differential operators between the spaces of sections of these bundles

Γ(E k+1)P kΓ(E k) \cdots \to \Gamma(E_{k+1}) \stackrel{P_k}{\to} \Gamma(E_k) \to \cdots

is called an elliptic chain complex if the corresponding sequence of symbols

π *E k+1σ(P k)π *E k \cdots \to \pi^* E_{k+1} \stackrel{\sigma(P_k)}{\to} \pi^* E_k \to \cdots

(where π:T *XX\pi \colon T^* X \to X is the cotangent bundle) is an exact sequence.

For instance (Pati, def. 9.4.1).

For a single differential operator PP this says that 0π *E 1σ(P)π *E 000 \to \pi^* E_1 \stackrel{\sigma(P)}{\to} \pi^* E_0 \to 0 is exact, which means that σ(P)\sigma(P) is an isomorphism, hence that PP is an elliptic operator.


Atiyah-Bott lemma

If (,d)(\mathcal{E}, d) is an elliptic complex of smooth sections =Γ X(E)\mathcal{E} = \Gamma_X(E) of a vector bundle EXE \to X overa compact closed manifold XX, then the inclusion

(,d)(¯,d) (\mathcal{E},d) \hookrightarrow (\overline{\mathcal{E}}, d)

into the complex of distributional sections is a quasi-isomorphism, in fact a homotopy equivalence.

This is due to (Atiyah-Bott). A localized refinement (suitable for factorization algebras of local observables) appears as Gwilliam, lemma 5.2.13.


The classical examples of elliptic complexes are discussed also in (Gilkey section 3).

de Rham complex

Let XX be a compact smooth manifold. Then the de Rham complex is an elliptic complex. The corresponding index of an elliptic complex is the Euler characteristic

Ind(Ω (X),d)=χ(X)= p=0 dimX(1) pdimH dR p(X,) Ind(\Omega^\bullet(X),d) = \chi(X) = \sum_{p = 0}^{dim X} (-1)^p dim H_{dR}^p(X, \mathbb{C})

The Yang-Mills complex


The Dolbeault complex

(…) Dolbeault complex

The index of an elliptic complex of the Dolbeault complex is the arithmetic genus

Spin complex

(…) index is A-hat genus (…)


  • V. Pati, Elliptic complexes and index theory (pdf)
  • Michael Atiyah, Raoul Bott, A Lefschetz fixed point formula for elliptic complexes. I, Ann. of Math. (2) 86 (1967),

    374–407. MR 0212836 (35 #3701)

  • Owen Gwilliam, Factorization algebras and free field theories PhD thesis (pdf)

Last revised on March 23, 2020 at 09:44:29. See the history of this page for a list of all contributions to it.