Li, Tao Rank and genus of 3-manifolds. (English) Zbl 1277.57004 J. Am. Math. Soc. 26, No. 3, 777-829 (2013). In the 1960’s, F. Waldhausen conjectured the equality, for each closed orientable 3-manifold \(M\), between the rank \(r(M)\) of the fundamental group \(\pi_1(M)\) and the Heegaard genus \(g(M)\) of \(M\) [Algebr. geom. Topol., Stanford/Calif. 1976, Proc. Symp. Pure Math., Vol. 32, Part 2, 313–322 (1978; Zbl 0397.57007)]. Various counterexamples may be found in the literature: in particular, B. Boileau and H. Zieschang obtained a Seifert fibered space with \(r(M)=2\) and \(g(M)=3\) [Invent. Math. 76, 455–468 (1984; Zbl 0538.57004)], while J. Schultens and R. Weidman proved the existence of graph manifolds with discrepancy \(g(M) - r(M)\) arbitrarily large [Pac. J. Math. 231 (2), 481–510 (2007; Zbl 1171.57020)].In 2007, the above Conjecture has been re-formulated, by restricting the attention to hyperbolic 3-manifolds: see [P. B. Shalen, in: Gordon, Cameron (ed.) et al., Proceedings of the Technion workshop on Heegaard splittings, Haifa, Israel, summer 2005. Coventry: Geometry & Topology Publications. Geometry and Topology Monographs 12, 335–349 (2007; Zbl 1140.57009)].The present paper gives a negative answer to this “modern version” of the Waldhausen Conjecture. In fact, a closed orientable hyperbolic 3-manifold \(M\) is proved to exist, so that \(g(M) - r(M)\) is arbitrarily large.Actually, the author produces an (atoroidal) 3-manifold with boundary \(\bar M\) with \(r(\bar M) < g(\bar M)\), and the closed counterexample is constructed starting from \(\bar M\), via the so called annulus sum see [the author, Geom. Topol. 14, No. 4, 1871–1919 (2010; Zbl 1207.57031)]. Moreover, every 2-bridge knot exterior is proved to be a JSJ piece of a closed 3-manifold \(M\) with \(r(M) < g(M).\) Reviewer: Maria Rita Casali (Modena) Cited in 23 Documents MSC: 57M05 Fundamental group, presentations, free differential calculus 57M27 Invariants of knots and \(3\)-manifolds (MSC2010) 57M50 General geometric structures on low-dimensional manifolds 57N10 Topology of general \(3\)-manifolds (MSC2010) Keywords:Heegaard genus; rank; hyperbolic 3-manifold; annulus sum Citations:Zbl 0397.57007; Zbl 0538.57004; Zbl 1171.57020; Zbl 1140.57009; Zbl 1207.57031 PDF BibTeX XML Cite \textit{T. Li}, J. Am. Math. Soc. 26, No. 3, 777--829 (2013; Zbl 1277.57004) Full Text: DOI arXiv References: [1] Miklós Abért and Nikolay Nikolov, Rank gradient, cost of groups and the rank versus Heegaard genus problem. arXiv:math/0701361 · Zbl 1271.57046 [2] David Bachman, Saul Schleimer, and Eric Sedgwick, Sweepouts of amalgamated 3-manifolds, Algebr. Geom. 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