# nLab truncation of a chain complex

### Context

#### Homological algebra

homological algebra

and

nonabelian homological algebra

diagram chasing

# Contents

## Definition

For $C_\bullet$ a chain complex, it truncation $(\tau_{\leq} C)_\bullet$ at some $n \in \mathbb{N}$ is the chain complex defined by

$(\tau_n C)_i = \left\{ \array{ 0 & | i \gt n \\ C_n/B_n & | i = n \\ C_n & | i \lt n } \right. \,,$

where $B_n = im(d_n)$.

For connective chain complexes this is the notion of truncated object in an (infinity,1)-category realized in the (infinity,1)-category of chain complexes.

## References

Created on August 24, 2012 14:13:43 by Urs Schreiber (82.113.106.22)