Citation for published item:wgeeD wihel nd yhD ree nd interD hle @PHIUA 9niform ongruene ounting for hottky semigroups in vP@AF9D tournl f¤ ur die reine und ngewndte wthemtikF a grelles journlF F Further information on publisher's website:The nal publication is available at www.degruyter.com With an appendix by Jean Bourgain, Alex Kontorovich and Michael Magee.
Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract. Let Γ be a Schottky semigroup in SL2(Z), and for q ∈ N, let Γ(q) := {γ ∈ Γ : γ = e (mod q)} be its congruence subsemigroup of level q. Let δ denote the Hausdorff dimension of the limit set of Γ. We prove the following uniform congruence counting theorem with respect to the family of Euclidean norm balls BR in M2(R) of radius R: for all positive integer q with no small prime factors,as R → ∞ for some cΓ > 0, C > 0, > 0 which are independent of q. Our technique also applies to give a similar counting result for the continued fractions semigroup of SL2(Z), which arises in the study of Zaremba's conjecture on continued fractions.