Eberhard Schruefer

Excalc: Correct a problem with calculating the commutator containing frame vectors. Fix a typo in the manual. Add the display of a defined frame when calling the statement displayframe.

Hi Daniel, Maybe you can help with testing? The two following procedures should fix the problem with the commutator and would add printing of the frame when present. Please read them in right after you loaded excalc. symbolic procedure frame u; begin scalar y; putform(list(car u,nil),-1); flag(list car u,'covariant); basisvectorl!* := for each j in indxl!* collect !*a2k list(car u,lowerind j); if null dbaseform2base2form then return; commutator!-of!-framevectors := for each j in pickupwedges dbaseform2base2form...

Hi Daniel, Thank you very much for your report. Those are very welcome. Indeed there is a typo in the documentation. I agree that there should be the possibility to display a 'frame' definition if present. I will add a statement for that. And finally, the result for the commutator is a bug that sneaked in over time. Hopefully, I find some time during next week to correct this. Eberhard

Hi Daniel, This is more of a question than a bug. If you are looking for the equation of geodesics, you could do it like in the snippet below. There it is for a Schwarzschild like geometry. Eberhard load excalc; % Define the velocity and acceleration components. Those should bear % contravariant indices. pform {u(k), a(k)}=0; remflag('(u a),'covariant); factor u; % definition of a coframe for Schwarzschild: coframe e t = sqrt(1 - 2*m/r)*d t, e r = 1/sqrt(1 - 2*m/r)*d r, e ph = r*sin(th)*d ph, e th...

It seems to take no end - other missing files.

It seems to take no end - other missing files.

It seems to take no end - other missing files.