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atlas™ - modern differential geometry for Maple™

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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));

{z, h, f, g}

Vector fields:
Vectors(E[i],X,Y,Z);

{X, Y, Z, E[i]}

Differential p-forms:
Forms(e[j]=1);

{e[j]}

Coframe 1-forms:
Coframe(e[1]=d(x),e[2]=d(y));

[e[1] = d(x), e[2] = d(y)]

Frame vector fields:
Frame(E[i]);

[E[1] = Diff(``,x), E[2] = Diff(``,y)]

Connection definition:
omega[1,1]:=f*e[2];

omega[1,1] := f*e[2]

omega[1,2]:=0;

omega[1,2] := 0

omega[2,1]:=0;

omega[2,1] := 0

omega[2,2]:=h*e[1];

omega[2,2] := h*e[1]

Connection declaration:
Connection(omega);

omega[i,j]

Curvature calculation:
Curvature(Omega);

Omega[i,j]

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])

Torsion calculation:
Torsion(T);

T[i]

Result:
eval(T);

TABLE([1 = -f*`&^`(e[1],e[2]), 2 = h*`&^`(e[1],e[2])])

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]))

Ricci tensor calculation:
Ricci(r);

r = Diff(f,x)*`&.`(e[1],e[2])+Diff(h,y)*`&.`(e[2],e[1])

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]

cov(E[j],e[2]) = -h*delta[1,j]*e[2]

Lie derivative:
'L[E[1]](E[2])'=L[E[1]](E[2]);

L[E[1]](E[2]) = -f*E[1]+h*E[2]

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])

iota[E[k]](Omega[1,1]) = Diff(f,x)*(delta[1,k]*e[2]-delta[2,k]*e[1])