2008/03/31 by Mattia Mecchia, Mecchia, Mattia, Bruno Zimmermann +1
Mathematics · #57M60 #57S17 #57S25 #FOS: Mathematics #Finite Group Theory Research #Geometric Topology (math.GT) #Geometric and Algebraic Topology #Homotopy and Cohomology in Algebraic Topology
paper · pdf · doi:10.48550/arxiv.0803.4454
openalex publication_date 2008/03/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We show that the only finite nonabelian simple groups which admit a locally linear, homologically trivial action on a closed simply connected 4-manifold M (or on a 4-manifold with trivial first homology) are the alternating groups A5, A6 and the linear fractional group PSL(2,7) (we note that for homologically nontrivial actions all finite groups occur). The situation depends strongly on the second Betti number b2(M) of M and has been known before if b2(M) is different from two, so the main new result of the paper concerns the case b2(M)=2. We prove that the only simple group that occurs in this case is A5, and then give a short list of finite nonsolvable groups which contains all candidates for actions of such groups.