| atlas[`&.`] - tensor product operator Calling Sequence: `&.`(T1, T2, ..., Tn) T1 &. T2 Parameters: T1, T2, ..., Tn - tensors. Description: - The &. procedure calculates the tensor product of given tensors. The main syntax is as follows: Omega &. T i.e.
where and are tensors. To calculate tensor product for tensors use the following `&.`(Omega[1],Omega[2], ...Omega[k]) i.e. ![`&.`(Omega[1],Omega[2],`` .. Omega[k])](prod/atlas/help/images/Prod5.gif) - Tensor product is linear operation with respect to its arguments. Thus if
are 0-forms then: ![`&.`(Omega[1],alpha*Omega[2]+beta*Omega[3]) = alpha*`&.`(Omega[1],Omega[2])+beta*`&.`(Omega[1],Omega[3])](prod/atlas/help/images/Prod7.gif)
Examples: restart: with(atlas): Declare Vectors Vectors(X,Y,Z); 
Declare tensors: Tensors(T=[a,b],Omega=[0,1],Omega[1]=[p,n],Omega[2]=[q,n],Omega[3]=[l,m]); ![{T, Omega[1], Omega[2], Omega[3], Omega}](prod/atlas/help/images/Prod9.gif)
Using &. - procedure: Tensor 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])](prod/atlas/help/images/Prod10.gif)
Some more examples: `&.`(Omega,T,Omega[3],Omega[2],Omega[1]); ![`&.`(Omega,T,Omega[3],Omega[2],Omega[1])](prod/atlas/help/images/Prod11.gif)
And with Lie derivative ( is 1-form): 'L[X]'(Omega&.T)=L[X](Omega&.T); ) = `&.`(iota[X](d(Omega)),T)+`&.`(d(iota[X](Omega)),T)+`&.`(Omega,L[X](T))](prod/atlas/help/images/Prod13.gif)
And again: 'L[X]'(Omega[1]&.Omega[2])=L[X](Omega[1]&.Omega[2]); ) = `&.`(L[X](Omega[1]),Omega[2])+`&.`(Omega[1],L[X](Omega[2]))](prod/atlas/help/images/Prod14.gif)
And finally 'Omega[3]&.(L[Z](Omega)&.T)'=Omega[3]&.(L[Z](Omega)&^T); ![`&.`(Omega[3],`&.`(L[Z](Omega),T)) = (-1)^b*`&.`(Omega[3],`&^`(T,iota[Z](d(Omega))))+(-1)^b*`&.`(Omega[3],`&^`(T,d(iota[Z](Omega))))](prod/atlas/help/images/Prod15.gif)
See Also: atlas , atlas[L] , atlas[Tensors] , atlas[`&^`] , atlas[Forms] . |