Quillen plus construction

The *Quillen plus construction* is a method for simplifying the fundamental group of the homotopy type of a topological space without changing its ordinary homology and ordinary cohomology groups.

It was introduced by Kervaire (1969), but was crucially used by Daniel Quillen to define the algebraic K-theory groups by applying it to the classifying space of the stable general linear group, $GL(A)$, of a ring $A$.

The plus construction doesn’t change the homology of the space but ‘kills’ a perfect normal subgroup of $G$ within the classifying space $BG$. For algebraic K-theory, that subgroup is the stable elementary linear group?, $E(A)$ within $GL(A)$.

- M. Kervaire,_Smooth homology spheres and their fundamental groups_, Trans. Amer. Math. Soc., 144 (1969) pp. 67–72

See section IV.1 of

- Charles Weibel,
*The K-Book: An introduction to algebraic K-theory*(web)

See also

- Dustin Clausen,
*Plus construction considerations*, MO/121351/2503.

Relation to the group completion theorem:

- Thomas Nikolaus,
*The group completion theorem via localizations of ring spectra*, 2017 (pdf)

Last revised on October 11, 2019 at 02:38:47. See the history of this page for a list of all contributions to it.