Kleinian Schottky groups, Patterson-Sullivan measures, and Fourier decay

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Wenyu Pan, Penn State University

Let Γ be a Zariski dense Kleinian Schottky subgroup of PSL2(C). Let Λ(Γ)C be its limit set, endowed with a Patterson-Sullivan measure μ supported on Λ(Γ). We show that the Fourier transform ˆμ(ξ) enjoys polynomial decay as |ξ| goes to infinity. This is a PSL2(C) version of the result of Bourgain-Dyatlov, and uses the decay of exponential sums based on Bourgain-Gamburd sum-product estimate on C. These bounds on exponential sums require a delicate non-concentration hypothesis which is proved using some representation theory and regularity estimates for stationary measures of random walks on SL2(C). This is a work on progress with Frédéric Naud and Jialun Li.