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Homotopy theory, homological algebra, algebraic treatments of manifolds.

4 votes
0 answers
111 views

The fiber of the alternating map $X^{2n}\to \mathbb{Z}[X]$

Let $X$ be a fibrant connected simplicial set. There is a simplicial map $h_n\colon X^{2n}\to \mathbb{Z}[X]$, defined on points by $(x_1, \ldots x_{2n})\mapsto \sum\limits_{i=1}^{2n}(-1)^ix_i$. Here …
Sergey Sinchuk's user avatar
9 votes

Symplectic K-theory

Matthias has already pointed out that the map $\widetilde{\mathrm{ESp}}_{2n}(R)\rightarrow Sp_{2n}(R)$ need not be surjective. In fact, the same phenomenon arises already for $\mathrm{SL}_n$ (the ima …
Sergey Sinchuk's user avatar