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atlas™ - modern differential geometry for Maple™

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atlas[`&^`] - exterior product operator

Calling Sequence:

     `&^`(F1,F2, ..., Fn)
     F1 &^ F2

Parameters:

        F1, F2, ..., Fn - forms.

Description:

  •  The &^ procedure calculates the exterior product of given forms. The main syntax is as follows: omega[1]&^omega[2] i.e. `&^`(omega[1],omega[2])  where omega[1]  and omega[2]  are forms. To calculate exterior product for forms omega[1], omega[2] .. omega[k]  use the following `&^`(omega[1],omega[2], ...omega[k]) i.e. `&^`(omega[1],omega[2],`` .. omega[k])
  • Exterior product is linear operation with respect to its arguments. Thus if alpha, beta  are 0-forms then: `&^`(omega[1],alpha*omega[2]+beta*omega[3]) = alpha*`&^`(omega[1],omega[2])+beta*`&^`(omega[1],omega[3])
  • Let omega[1]  be p-form and omega[2]  be q-form then the following formula for exterior product takes place: `&^`(omega[1],omega[2]) = (-1)^(p*q)*`&^`(omega[2],omega[1])  
  • Particularly for 1-forms omega  and sigma  we have: `&^`(omega,sigma) = -`&^`(sigma,omega)

Examples:
restart:
with(atlas):

Declare p-forms:
Forms(sigma=1,omega=1,omega[1]=p,omega[2]=q,omega[3]=l);

{sigma, omega, omega[1], omega[2], omega[3]}

Declare vectors:
Vectors(X,Y,Z);

{X, Y, Z}

Using &^ - procedure:

Exterior product is linear operation with respect to its arguments
'`&^`(omega[1],alpha*omega[2]+beta*omega[3])' = `&^`(omega[1],alpha*omega[2]+beta*omega[3]);

`&^`(omega[1],alpha*omega[2]+beta*omega[3]) = alpha*`&^`(omega[1],omega[2])+beta*`&^`(omega[1],omega[3])

As omega[1]  is p-form and omega[2]  is q-form then under main rule for exterior product we have:
'omega[2]&^omega[1]'=omega[2]&^omega[1];

`&^`(omega[2],omega[1]) = (-1)^(q*p)*`&^`(omega[1],omega[2])

Particularly for 1-forms omega  and sigma  we have:
'sigma&^omega'=sigma&^omega;

`&^`(sigma,omega) = -`&^`(omega,sigma)

Some more examples:
'`&^`(omega,sigma,omega[3],omega[2],omega[1])' = `&^`(omega,sigma,omega[3],omega[2],omega[1]);

`&^`(omega,sigma,omega[3],omega[2],omega[1]) = (-1)^(1+(q+l)*p+l*q)*`&^`(sigma,omega,omega[1],omega[2],omega[3])

And with Lie derivative:
'L[X]'(omega&^sigma)=L[X](omega&^sigma);

L[X](`&^`(omega,sigma)) = -`&^`(sigma,iota[X](d(omega)))-`&^`(sigma,d(iota[X](omega)))+`&^`(omega,iota[X](d(sigma)))+`&^`(omega,d(iota[X](sigma)))

And with exterior derivative:
'd'(omega&^sigma)=d(omega&^sigma);

d(`&^`(omega,sigma)) = `&^`(sigma,d(omega))-`&^`(omega,d(sigma))

And again
'L[X]'(omega[1])=L[X](omega[1]);

L[X](omega[1]) = iota[X](d(omega[1]))+d(iota[X](omega[1]))

And finally
'omega[3]&^(L[Z](omega)&^sigma)'=omega[3]&^(L[Z](omega)&^sigma);

`&^`(omega[3],`&^`(L[Z](omega),sigma)) = -(-1)^l*`&^`(sigma,omega[3],iota[Z](d(omega)))-(-1)^l*`&^`(sigma,omega[3],d(iota[Z](omega)))

See Also:

atlas , atlas[L] , atlas[d] , atlas[`&.`] , atlas[Forms] .