Thursday, July 4, 2013

1307.0719 (Sigurd K. Næss et al.)

Lensing simulations by Taylor expansion -- not so inefficient after all    [PDF]

Sigurd K. Næss, Thibaut Louis
Cosmic Microwave Background lensing simulation by Taylor expansion has long been considered impractical due to slow convergence, but a recent flat-sky implementation shows that a simple trick eliminates this problem, making Taylor lensing a fast and simple lensing algorithm for the flat sky. Here we generalize the method to the full sky, and study its convergence and performance relative to a commonly used numerical code, Lenspix, with extensive benchmarks of both. Compared to the flat sky case, the method takes a speed hit due to the slow speed of spherical harmonic transforms compared to fast Fourier transforms, resulting in speeds of 1/3 to 2/3 of Lenspix for similar accuracy. However it is much simpler to implement.
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