The error thrown in your line of code is because you are trying to calculate the cross product of two 1-dimensional tensors in dim4.
However, even if you fix it by using torch.cross(m1, m2, 0), you’ll get the following error:
RuntimeError: dimension 0 does not have size 3

I’m not a mathematician, but as far as I know the cross product only exists in 3- and 7-dimensional Euclidean space. W. S. Massey wrote a paper 2 about it.
Would the cos formula for the angle calculation work for you or are you somehow bound to the sin formula?
angle = torch.acos(torch.dot(m1, m2) / (m1.norm() * m2.norm()))