Let $G$ be a finitely presented group. Can we find a finite simplicial complex $X$ such that $\pi_1(X)=G$ and $\pi_2(X)=0$?
I know the conclusion is true if we only require $X$ to be a CW-complex.
Let $G$ be a finitely presented group. Can we find a finite simplicial complex $X$ such that $\pi_1(X)=G$ and $\pi_2(X)=0$?
I know the conclusion is true if we only require $X$ to be a CW-complex.
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Yes, Hatcher constructs an infinite simplicial complex BG which is aspherical and has $\pi_1 BG = G$ in the appendices to Chapter 1 of his algebraic topology book.
Now given a simplicial complex $X$ with k-skeleton $X_k$, the map $i: X_k \to X$ induces an isomorphism on $\pi_i$ with $i < k$ and a surjection on $\pi_k$. This follows quickly from the cellular approximation theorem and its relative version, and holds for the k-skeleton of any CW complex; a simplicial complex is a special case.
So take the 3-skeleton $(BG)_3$. This has approximately $|G|^3$ simplices.