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Initialize a new metric after a change of coordinates

asked 2025-07-06 16:09:04 +0200

Nicola gravatar image

updated 2025-07-07 14:23:08 +0200

Hi to everyone,

I'm new to SageMath and I use it for some General Relativity implementation.

I have a trouble: I cosntructed a metric g on a Manifold M with a coordinate chart like that

X.>t, x, y, z>

Now, I constructed a change of coordinates defining the transition map from X (original) to Y (new one). I don't have any problem with that

Now, I would like to construct a new metric g' on the same Manifold M, that is g in the new coordinates chart Y. I know that i could visualize that using

g.display(Y.frame(), Y)

but I want the new one like a new metric.

Thank you in advance.

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answered 2025-07-08 12:17:27 +0200

eric_g gravatar image

updated 2025-07-08 12:19:32 +0200

Calling the new metric h, you can do

h = M.lorentzian_metric('h')
h[Y.frame(),:,Y] = g[Y.frame(),:,Y]

This will initialize the components of h w.r.t. to chart Y to be identical to those of g in the same chart.

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Thank you!

Nicola gravatar imageNicola ( 2025-07-08 14:27:17 +0200 )edit

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Asked: 2025-07-06 16:09:04 +0200

Seen: 41 times

Last updated: Jul 08