| Connection with torsion Copyright © 2004-2008 by DigiArea Group . All rights reserved. Problem: For given connection calculate the following : - curvature 2-forms
- torsion 2-forms
- Riemannian tensor
- Ricci tensor
restart: with(atlas): Function declaration: Functions(f=f(x,y),h=h(x,y),g=g(x,y),z=z(x,y)); 
Vector fields: Vectors(E[i],X,Y,Z); ![{X, Y, Z, E[i]}](prod/atlas/Templates/images/conntor2.gif)
Differential p-forms: Forms(e[j]=1); ![{e[j]}](prod/atlas/Templates/images/conntor3.gif)
Coframe 1-forms: Coframe(e[1]=d(x),e[2]=d(y)); ![[e[1] = d(x), e[2] = d(y)]](prod/atlas/Templates/images/conntor4.gif)
Frame vector fields: Frame(E[i]); ![[E[1] = Diff(``,x), E[2] = Diff(``,y)]](prod/atlas/Templates/images/conntor5.gif)
Connection definition: omega[1,1]:=f*e[2]; ![omega[1,1] := f*e[2]](prod/atlas/Templates/images/conntor6.gif)
omega[1,2]:=0; ![omega[1,2] := 0](prod/atlas/Templates/images/conntor7.gif)
omega[2,1]:=0; ![omega[2,1] := 0](prod/atlas/Templates/images/conntor8.gif)
omega[2,2]:=h*e[1]; ![omega[2,2] := h*e[1]](prod/atlas/Templates/images/conntor9.gif)
Connection declaration: Connection(omega); ![omega[i,j]](prod/atlas/Templates/images/conntor10.gif)
Curvature calculation: Curvature(Omega); ![Omega[i,j]](prod/atlas/Templates/images/conntor11.gif)
Result: eval(Omega); ![TABLE([(1, 2) = 0, (1, 1) = Diff(f,x)*`&^`(e[1],e[2]), (2, 2) = -Diff(h,y)*`&^`(e[1],e[2]), (2, 1) = 0])](prod/atlas/Templates/images/conntor12.gif)
Torsion calculation: Torsion(T); ![T[i]](prod/atlas/Templates/images/conntor13.gif)
Result: eval(T); ![TABLE([1 = -f*`&^`(e[1],e[2]), 2 = h*`&^`(e[1],e[2])])](prod/atlas/Templates/images/conntor14.gif)
Curvature tensor calculation: Riemann(R); ![R = 1/2*Diff(f,x)*`&.`(E[1],e[1],`&^`(e[1],e[2]))-1/2*Diff(h,y)*`&.`(E[2],e[2],`&^`(e[1],e[2]))](prod/atlas/Templates/images/conntor15.gif)
Ricci tensor calculation: Ricci(r); ![r = Diff(f,x)*`&.`(e[1],e[2])+Diff(h,y)*`&.`(e[2],e[1])](prod/atlas/Templates/images/conntor16.gif)
Some more simple calculations: Covariant derivatives: 'cov(E[j],e[1])'=cov(E[j],e[1]); 'cov(E[j],e[2])'=cov(E[j],e[2]); ![cov(E[j],e[1]) = -f*delta[2,j]*e[1]](prod/atlas/Templates/images/conntor17.gif)
![cov(E[j],e[2]) = -h*delta[1,j]*e[2]](prod/atlas/Templates/images/conntor18.gif)
Lie derivative: 'L[E[1]](E[2])'=L[E[1]](E[2]); ![L[E[1]](E[2]) = -f*E[1]+h*E[2]](prod/atlas/Templates/images/conntor19.gif)
Interior products: 'iota[E[k]](T[1])'=iota[E[k]](T[1]); 'iota[E[k]](Omega[1,1])'=iota[E[k]](Omega[1,1]); ![iota[E[k]](T[1]) = -f*(delta[1,k]*e[2]-delta[2,k]*e[1])](prod/atlas/Templates/images/conntor20.gif)
![iota[E[k]](Omega[1,1]) = Diff(f,x)*(delta[1,k]*e[2]-delta[2,k]*e[1])](prod/atlas/Templates/images/conntor21.gif)
|