Uniform Discreteness of Discrete Orbits of Non-Uniform Lattices in $SL_2(\mathbb{R})$We study the property of uniform discreteness within discrete orbits of non-uniform lattices in $SL_2(\mathbb{R})$, acting on $\mathbb{R}^2$ by linear transformations. We provide a new proof of the conditions under which the orbit of a non-uniform lattice in $SL_2(\mathbb{R})$ is uniformly discrete, by using Diophantine properties. Our results include a detailed analysis of the asymptotic behavior of the error terms. Focusing on a specific group $Γ$ and a discrete orbit of it, $S$, the main result of this paper is that for any $ε>0$, three points in $S$ can be found on a horizontal line within distance $ε$ of each other. This gives a partial result toward a conjecture of Lelièvre. The set $S$ and group $Γ$ are respectively the set of long cylinder holonomy vectors, and Veech group, of the "golden L" translation surface.
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