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arXiv · 2610.30093

Extended vs. thin screen approximation in astrophysical settings

Manuel Adlberger·Tobias Kramer
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Abstract

Context: In the context of radio wave propagation through plasma concentrations and for gravitational lensing, the thin screen approximation often provides a suitable approximation for scattering and deflections caused by three-dimensional spatial structures. For scattering of electromagnetic waves from an extended medium, stochastic theories provide analytical bounds on ensemble averaged quantities, such as the scintillation index. If neither the conditions for a stochastic treatment nor the thin screen approximation are fulfilled, fully numerical methods are required. Aims: For an extended structure, the applicability of the thin screen approximation needs to be verified by comparing it with the fully three-dimensional scattering solution. We discuss various exact solutions to simple lensing geometries and provide numerical results for the propagation in the branched-flow regime, which is also of relevance in astrophysical applications. Methods: We transfer several analytical results obtained in quantum mechanical scattering theory to astrophysical settings and complement them with different numerical methods to quantify the deviations of thin screen theories from an extended medium results. Results: We provide the analytical results for spherical waves scattered by a point source and show the emergence of branchef flow in the intermediate regime between thin screen physics and stochastic media results.

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Manuel Adlberger, Tobias Kramer. 2026-10-21. Extended vs. thin screen approximation in astrophysical settings. https://arxiv.org/abs/2610.30093

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