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The order of growth is then the least degree of any such polynomial function p. A nilpotent group G is a group with a lower central series terminating in the identity subgroup. Gromov's theorem states that a finitely generated group has polynomial growth if and only if it has a nilpotent subgroup that is of finite index.
The free abelian group has a polynomial growth rate of order d. The discrete Heisenberg group has a polynomial growth rate of order 4. This fact is a special case of the general theorem of Hyman Bass and Yves Guivarch that is discussed in the article on Gromov's theorem.
See Gromov's theorem on groups of polynomial growth. (Also see D. Edwards for an earlier work.) (Also see D. Edwards for an earlier work.) The key ingredient in the proof was the observation that for the Cayley graph of a group with polynomial growth a sequence of rescalings converges in the pointed Gromov–Hausdorff sense.
The Tits alternative is an important ingredient [2] in the proof of Gromov's theorem on groups of polynomial growth. In fact the alternative essentially establishes the result for linear groups (it reduces it to the case of solvable groups, which can be dealt with by elementary means).
Theorems which use quasi-isometry invariants to prove algebraic results about groups, for example: Gromov's polynomial growth theorem; Stallings' ends theorem; Mostow rigidity theorem. Quasi-isometric rigidity theorems, in which one classifies algebraically all groups that are quasi-isometric to some given group or metric space.
One of Gromov's compactness theorems: Gromov's compactness theorem (geometry) in Riemannian geometry; Gromov's compactness theorem (topology) in symplectic topology; Gromov's Betti number theorem Gromov–Ruh theorem on almost flat manifolds; Gromov's non-squeezing theorem in symplectic geometry; Gromov's theorem on groups of polynomial growth
Fundamental theorem of Galois theory; G. Golod–Shafarevich theorem; Gromov's theorem on groups of polynomial growth;
Another simple example is given by the infinite cyclic group : the Cayley graph of with respect to the generating set {} is a line, so all triangles are line segments and the graph is -hyperbolic. It follows that any group which is virtually cyclic (contains a copy of Z {\displaystyle \mathbb {Z} } of finite index) is also hyperbolic, for ...