Polynomial maps over finite fields and residual finiteness of mapping tori of group endomorphisms
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- Borisov, A. & Sapir, M. Invent. math. (2005) 160: 341. doi:10.1007/s00222-004-0411-2
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We prove that every mapping torus of any free group endomorphism is residually finite. We show how to use a not yet published result of E. Hrushovski to extend our result to arbitrary linear groups. The proof uses algebraic self-maps of affine spaces over finite fields. In particular, we prove that when such a map is dominant, the set of its fixed closed scheme points is Zariski dense in the affine space.