Kerr Polarization Transport: Accuracy and Performance in General Relativistic Light Propagation
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866915611764850688 |
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| author | Chowdhury, Shakibul |
| author_facet | Chowdhury, Shakibul |
| contents | We present a compact and reproducible method for general relativistic polarization transport in the Kerr metric that achieves median electric vector position angle (EVPA) residuals of $\langle Δ\mathrm{PA} \rangle \approx 0.09^\circ$, a 95th percentile of $0.31^\circ$, and a worst case $Δ\mathrm{PA} \lesssim 0.32^\circ$ for spins up to $|a/M|=0.9$, while maintaining a fivefold or greater speedup relative to a strict reference integrator. Across the benchmark grid, typical residuals remain at the sub-tenth-degree level, with only modest degradation ($Δ\mathrm{PA} \lesssim 2^\circ$) near the Thorne spin limit. Photon four-momenta $k^μ$ and polarization four-vectors $f^μ$ are advanced using a fourth order Runge-Kutta scheme with cached Christoffel symbols, maintaining the constraints $u\cdot f=0$ and $n\cdot f=0$, where $u^μ$ is the ZAMO four-velocity and $n^μ$ is the disk normal, while keeping $k\cdot f \simeq 0$. A physically motivated gauge is enforced by projecting the polarization into the local zero-angular-momentum observer (ZAMO) screen at every substep, ensuring numerical stability of the orthogonality constraints. Accuracy and performance are benchmarked over a representative grid in spin, inclination, image-plane azimuth, and radius. The method comfortably meets IXPE and NICER polarization tolerances and approaches EHT requirements. The approach provides a practical foundation for future general relativistic polarimetry and simulation pipelines. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_07762 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Kerr Polarization Transport: Accuracy and Performance in General Relativistic Light Propagation Chowdhury, Shakibul High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology We present a compact and reproducible method for general relativistic polarization transport in the Kerr metric that achieves median electric vector position angle (EVPA) residuals of $\langle Δ\mathrm{PA} \rangle \approx 0.09^\circ$, a 95th percentile of $0.31^\circ$, and a worst case $Δ\mathrm{PA} \lesssim 0.32^\circ$ for spins up to $|a/M|=0.9$, while maintaining a fivefold or greater speedup relative to a strict reference integrator. Across the benchmark grid, typical residuals remain at the sub-tenth-degree level, with only modest degradation ($Δ\mathrm{PA} \lesssim 2^\circ$) near the Thorne spin limit. Photon four-momenta $k^μ$ and polarization four-vectors $f^μ$ are advanced using a fourth order Runge-Kutta scheme with cached Christoffel symbols, maintaining the constraints $u\cdot f=0$ and $n\cdot f=0$, where $u^μ$ is the ZAMO four-velocity and $n^μ$ is the disk normal, while keeping $k\cdot f \simeq 0$. A physically motivated gauge is enforced by projecting the polarization into the local zero-angular-momentum observer (ZAMO) screen at every substep, ensuring numerical stability of the orthogonality constraints. Accuracy and performance are benchmarked over a representative grid in spin, inclination, image-plane azimuth, and radius. The method comfortably meets IXPE and NICER polarization tolerances and approaches EHT requirements. The approach provides a practical foundation for future general relativistic polarimetry and simulation pipelines. |
| title | Kerr Polarization Transport: Accuracy and Performance in General Relativistic Light Propagation |
| topic | High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2511.07762 |