(also nonabelian homological algebra)

**Context**

**Basic definitions**

**Stable homotopy theory notions**

**Constructions**

**Lemmas**

**Homology theories**

**Theorems**

**homotopy theory, (∞,1)-category theory, homotopy type theory**

flavors: stable, equivariant, rational, p-adic, proper, geometric, cohesive, directed…

models: topological, simplicial, localic, …

see also **algebraic topology**

**Introductions**

**Definitions**

**Paths and cylinders**

**Homotopy groups**

**Basic facts**

**Theorems**

In a category of chain complexes $Ch_\bullet(\mathcal{A})$, the suspension object of a chain complex $C_\bullet$ is the complex

$\Sigma C_\bullet = C[1]_\bullet$

(or sometimes denoted $C[-1]_\bullet$, depending on an unessential choice of sign convention) obtained by shifting the degrees up by one:

$C[1]_n \coloneqq C_{n-1}$

with the differential the original one but equipped with a sign:

$d^{C[1]}_n \coloneqq - d^C_{n-1}
\,.$

Generally, for $p \in \mathbb{Z}$, $C[p]$ is the chain complex with

$C[p]_n \coloneqq C_{n-p}$

$d^{C[p]}_n \coloneqq (-1)^p d^C_{n-p}
\,.$

Last revised on October 3, 2019 at 13:44:04. See the history of this page for a list of all contributions to it.