AlanTStafford's profile - activity

I have used quaternions a few times perhaps here notebooks could provide some guidance. http://alan.atstafford.co.uk/Pe

What shall we call the SageMath Cotton Tensor convention of -1/2 in four dimensions? This is surely a breakthrough of gr

I was working out transformations between coordinate systems. As a test I transformed and then untransformed so there sh

Thank you, answer accepted. I was nearly there trying restrict but hadn't got to using an intersection. I have the maps

Thank you, answer accepted. I was nearly there trying restrict but hadn't got to using an intersection. I have the maps

Simplification of arctan2(f1,f2) expressions. Why doesn't arctan2(sqrt(a^2 + r^2)*sin(phi)*sin(th), sqrt(a^2 + r^2)*cos(

Simplification of arctan2(f1,f2) expressions. Why doesn't arctan2(sqrt(a^2 + r^2)sin(phi)sin(th), sqrt(a^2 + r^2)cos(phi

Try references for Quadratic forms.

I hope this helps. https://wiki.sagemath.org/quickref?action=AttachFile&do=get&target=quickref-linalg.pdf

Thank you, answer accepted. I was nearly there trying restrict but hadn't got to using an intersection. I have the maps

Thank you, answer accepted. I was nearly there trying restrict but hadn't't got to using an intersection. I have the map

I define a M manifold with three charts, I then define a metric on one of the charts MH. I then want to see the metric components in one of the other charts BL. I have defined differential maps between the charts.

gMann(MH) works and I can display the components but,

gMann(BL) gives the error:

ValueError: the provided domain is not a subset of the field's domain

print(subdomain,self._restrictions) gives 'Open subset MBL of the 4-dimensional Lorentzian manifold M {}' .

How do I make this work please? I will post the code in comments below.

Thank you answer accepted I was nearly there trying restrict but hadn't't got to using an intersection. I have the maps

Link to code at my website. The problem surfaces in cell 6. The function definitions between cell two and six can be ign

Link to code at my website, the function definitions can be ignored. The problem surfaces in cell 6. The function defini

Link to code at my website, the function definitions can be ignored. The problem surfaces in cell 6. The function defini

Link to code at my website, the function definitions can be ignored. The problem surfaces in cell 6. The function defini

First cell: `var('a', domain='real') #Angular momentum as a fraction of rest mass. %display latex # LaTeX rendering t

Problem with Metric Tensor coordinate change. I define a M manifold with three charts, I then define a metric on one of

https://groups.google.com/g/sage-support/c/9JICAs8mgcs/m/KtOSyOiJBAAJ

Not sure but have a look at A.eigenmatrix_left() and eigenmatrix_right() , the eigenvectors are orthogonal and the eigen

I have added some additional tensors to metric.py . _derived_objects = ('_connection', '_ricci_scalar', '_weyl',

I use this code to calculate the cotton tensor. I have tested it against data from maple. I uploaded a test script to th

I use this code to calculate the cotton tensor. I have tested it against data from maple. I uploaded a test script to th

Bach Tensor V. Bach= 1/2 * U + 1/6 * V . def bachV(self, name=None, latex_name=None): if self._bachV is None:

Thanks I have the knack now. I can't accept my answer as I don't have enough karma. I will do so when I do.

Bach Tensor V. Bach= 1/2 * U + 1/6 * V . def bachV(self, name=None, latex_name=None): if self._bachV is None:

Bach Tensor U. Bach= 1/2 * U + 1/6 * V . if self._bachU is None: nabla = self.connection() ricc

if self._bachU is None: nabla = self.connection() ricci = self.ricci() ricci_scalar

Bach Tensor. if self._bach is None: nabla = self.connection() s = self.sch

Bach Tensor. ` if self._bach is None: nabla = self.connection() s = self.sc

Bach Tensor. ` if self._bach is None: nabla = self.connection() s = self.sc

` if self._bach is None: nabla = self.connection() s = self.schouten()

Note. The above bach bachU bachV tensor definitions are only valid for four dimensions. I can work on more general ones

` def bachV(self, name=None, latex_name=None): if self._bachV is None: nabla = self.connection()

` if self._bachU is None: nabla = self.connection() ricci = self.ricci()

` if self._bach is None: nabla = self.connection() s = self.schouten()

I have added some additional tensors to metric.py . _derived_objects = ('_connection', '_ricci_scalar', '_weyl',

I use this code to calculate the cotton tensor. I have tested it against data from maple. I uploaded a test script to th

cot = -(n-2)*nabla(s).antisymmetrize(1,2)

If you check metric.py you will see that the code for the cotton tensor is wrong and not as the explanation above. I ha

Solved, see comments. var('tpar','lpar') tpar = 4 lpar = 4 Parallelism().set('tensor',tpar) Parallelism().set('linbox