There have been longstanding issues with spherical harmonics in SageMath, notably as described in https://groups.google.com/g/sage-support/c/I_d_meMxRbM/m/Esxo5UO2BAAJ In that the latter thread, Eric Gourgoulhon's message of 2019-06-15 gives a simple test case: from sage.functions.special import SphericalHarmonic theta,phi = var('theta phi') spherical_harmonic(1,1, theta,phi) producing the (wrong) result -1/4*sqrt(3)*sqrt(2)*sqrt(-sin(theta)^2)*e^(I*phi)/sqrt(pi) whereas the correct result would be -1/4*sqrt(6)*e^(I*phi)*sin(theta)/sqrt(pi)
Eric also noted that this problem was apparently a consequence of https://trac.sagemath.org/ticket/25034 and suggested a workaround, using the spin-weighted spherical harmonics from the SageMath /kerrgeodesics_gw/ package. An update: * As of 9.3.rc2, SageMath's builting spherical harmonics are still broken (same result as above for Eric's test case). * As of 9.3.rc2, the /kerrgeodesics_gw/ package fails to load (it worked fine for me in 9.2.). I'll report that error to the bhptoolkit.org issue tracker. And a question: Given that the underlying problem https://trac.sagemath.org/ticket/25034 is unlikely to be fixed for 9.3, should we perhaps put a note in the documentation for 9.3 that spherical harmonics are unreliable at present? -- -- "Jonathan Thornburg [remove -animal to reply]" <jthorn4...@gmail.com> Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA currently on the west coast of Canada "There was of course no way of knowing whether you were being watched at any given moment. How often, or on what system, the Thought Police plugged in on any individual wire was guesswork. It was even conceivable that they watched everybody all the time." -- George Orwell, "1984" -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/20210408175352.GA10913%40iron.bkis-orchard.net.
