ljp's profile - activity

MM = Manifold(4, 'MM', latex_name=r'\mathcal{M}', start_index=0)  
chartt.<t,x,y,z> = MM.chart()

gg = MM.lorentzian_metric('gg')
gg[0,0] = -1
gg[1,1] = 1
gg[2,2] = 1
gg[3,3] = 1

some_tensor = MM.tensor_field(1,1)
christoffel = gg.christoffel_symbols()
some_contraction = some_tensor['^i_j'] * christoffel['^j_kl']

The above code doesn't work and crashes with the following error:
ValueError: wrong number of indices: 3 expected, while 4 are provided

I know that the Christoffels are only a CompWithSym and not a real tensor, but shouldn't one still be able to generate some contracted quantities?

I wonder if there is any way to access tensor elements by a slicing operation, so that parts of the tensor can be set by another tensor or the other way around. Another useful thing would be the ability to display only the slice of interest of a tensor.
At the moment I'm just looping over the components using the irange of the Manifold.