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Ian Agol
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There are closed hyperbolic 3-manifolds with arbitrarily large algebraic entropy. However, the critical exponent will always be $2$. So there isn't a relation, although there could possibly be an inequality.

Addendum: Sorry, I should have given justification for the statement above. The point is that for any free group $F_k$, there is a closed 3-manifold $N$ such that there is a surjection $\pi_1(N)\to F_k$ (once one has an example for $k=2$, the rest follow by taking finite-index covers of $F_2$ isomorphic to $F_k$, and taking the induced cover of $N$). The growth of $F_k$ with respect to any generating set is at least the growth of $F_k$ with respect to the standard generators (which is $2k-1$), since among any generating set, there must be an independent set of size $k$. Thus, the growth of $\pi_1(N)$ is at least $2k-1$.

There are closed hyperbolic 3-manifolds with arbitrarily large algebraic entropy. However, the critical exponent will always be $2$. So there isn't a relation, although there could possibly be an inequality.

There are closed hyperbolic 3-manifolds with arbitrarily large algebraic entropy. However, the critical exponent will always be $2$. So there isn't a relation, although there could possibly be an inequality.

Addendum: Sorry, I should have given justification for the statement above. The point is that for any free group $F_k$, there is a closed 3-manifold $N$ such that there is a surjection $\pi_1(N)\to F_k$ (once one has an example for $k=2$, the rest follow by taking finite-index covers of $F_2$ isomorphic to $F_k$, and taking the induced cover of $N$). The growth of $F_k$ with respect to any generating set is at least the growth of $F_k$ with respect to the standard generators (which is $2k-1$), since among any generating set, there must be an independent set of size $k$. Thus, the growth of $\pi_1(N)$ is at least $2k-1$.

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Ian Agol
  • 68.9k
  • 3
  • 194
  • 358

There are closed hyperbolic 3-manifolds with arbitrarily large algebraic entropy. However, the critical exponent will always be $2$. So there isn't a relation, although there could possibly be an inequality.