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rtoy / maxima

A Clone of Maxima's repo
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Tetrad.dem does not use the lowered coframe. #3930

Open rtoy opened 1 month ago

rtoy commented 1 month ago

Imported from SourceForge on 2024-07-08 21:19:26 Created by richardgobeli on 2022-09-26 03:50:05 Original: https://sourceforge.net/p/maxima/bugs/4031

It start out using the Macsyma definition of coframe as fri([mu],[a]) as following: fri:matrix( [sqrt(f(r)), 0, 0, 0], [0, sqrt(h(r)), 0, 0], [0, 0, r, 0], [0, 0, 0,r*sin(d)]); The sqrt(f(r)) should be -sqrt(f(r)). It gets the correct result, because the calculation for lg always has an odd number minus signs for a diagonal metric. The calculation for static accelration would get the wrong sign. lg:transpose(lfg.fri).fri,

rtoy commented 1 month ago

Imported from SourceForge on 2024-07-08 21:19:27 Created by vttoth on 2022-09-28 03:58:10 Original: https://sourceforge.net/p/maxima/bugs/4031/#2e60

rtoy commented 1 month ago

Imported from SourceForge on 2024-07-08 21:19:31 Created by richardgobeli on 2022-09-28 21:49:11 Original: https://sourceforge.net/p/maxima/bugs/4031/#1658

It might have been better to call the one Maxima uses a lfri for lowered fri like it is with Reimann and Einstein tensors and the general mixed coframe as fri like the mixed frame is fr. Then fr = transpose(invert(fri)) and not fr = transpose(invert(fri.ufg)) or fr = transpose(invert(lfri.ufg)) = transpose(invert(lfg.fri)).