A Hamiltonian, post-Born, three-dimensional, on-the-fly ray tracing algorithm for gravitational lensing
arxiv(2024)
摘要
The analyses of the next generation cosmological surveys demand an accurate,
efficient, and differentiable method for simulating the universe and its
observables across cosmological volumes. We present Hamiltonian ray tracing
(HRT) – the first post-Born (accounting for lens-lens coupling and without
relying on the Born approximation), three-dimensional (without assuming the
thin-lens approximation), and on-the-fly (applicable to any structure formation
simulations) ray tracing algorithm based on the Hamiltonian formalism. HRT
performs symplectic integration of the photon geodesics in a weak gravitational
field, and can integrate tightly with any gravity solver, enabling co-evolution
of matter particles and light rays with minimal additional computations. We
implement HRT in the particle-mesh library , leveraging hardware
accelerators such as GPUs and automatic differentiation capabilities based on
. When tested on a point-mass lens, HRT achieves sub-percent
accuracy in deflection angles above the resolution limit across both weak and
moderately strong lensing regimes. We also test HRT in cosmological simulations
on the convergence maps and their power spectra.
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