Generalized Jørgensen trace inequality under displacement hypotheses

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Let Γ=⟨ξ1,ξ2,…,ξn⟩\Gamma=\langle\xi_1,\xi_2,\dots,\xi_n\rangle, and let αn\alpha_n be as described in the generalized Jørgensen conjecture. For i≠1i\ne1, define

Φn=Γ\on−{ξ1,ξ1−1,ξi−1ξ1ξi,ξi−1ξ1−1ξi,ξiξ1ξi−1,ξiξ1−1ξi−1}.\Phi_n=\Gamma_{\o}^n-\{\xi_1,\xi_1^{-1},\xi_i^{-1}\xi_1\xi_i,\xi_i^{-1}\xi_1^{-1}\xi_i,\xi_i\xi_1\xi_i^{-1},\xi_i\xi_1^{-1}\xi_i^{-1}\}.

Let z1z_1 and z2z_2 be the midpoints of the shortest geodesic segments connecting the axes of ξ1\xi_1 to the axes of ξiξ1ξi−1\xi_i\xi_1\xi_i^{-1} and ξi−1ξ1ξi\xi_i^{-1}\xi_1\xi_i, respectively. Assume that there exists an isometry ξi\xi_i, with i≠1i\ne1, such that

dξiξ1ξi−1z2≤dξiξ1ξi−1z1d_{\xi_i\xi_1\xi_i^{-1}}z_2\leq d_{\xi_i\xi_1\xi_i^{-1}}z_1

and

dγz2<12log⁡αnd_\gamma z_2<\tfrac{1}{2}\log\alpha_n

for every isometry γ∈Φn\gamma\in\Phi_n. Generalized Jørgensen trace conjecture. Under these assumptions,

∣trace⁡2(ξ1)−4∣+∣trace⁡(ξ1ξiξ1−1ξi−1)−2∣≥2sinh⁡2(14log⁡αn).|\operatorname{trace}^2(\xi_1)-4|+|\operatorname{trace}(\xi_1\xi_i\xi_1^{-1}\xi_i^{-1})-2|\geq2\sinh^2\left(\tfrac{1}{4}\log\alpha_n\right).

This is presented as a consequence of the preceding conjectural displacement bound and would generalize the corresponding two-generator trace inequality. The source explicitly says that the displacement conjecture and analogous arguments imply this result.

References

Primary source

İlker S. Yüce, “Jorgensen's Inequality and Purely Loxodromic 2-Generator Free Kleinian Groups”, arXiv:1604.02760 (2017).

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