The exterior algebra ^V of a linear space V, with basis e1, e2, e3 has a basis consisting of
 
scalar                                                     e0
vectors                                              e1,e2,e3
bivectors                                         e12,e23,e13
trivector                                               e123
 
the multiplication rules are
 
                                                      ei ^ ej = -ej ^ ei
 
together with the associativity and the unity e0. A scalar product on V can be executed to the homogeneous parts ^k V by
 
                                  <Ar, Bs> = det(ai, bj)
 
This scalar valued product can be used to define the contraction ^V * ^V, (u,v) -> u _l v by
 
                                  <u _l v, w> = <v, rev(u) ^ w>  for all w <- ^V  
 
The contraction could also be introduced via the geometric product as
 
                                    u _l v = (u ^ (v e123))/e123
 
Geometrically, for two blades A and B, not orthogonal to each other, the contraction A _l B is the largest subspace of B orthogonal to A.
 
(from P. Lounesto)
 
Elementary functions are available in EVA:
 
sino, coso, tano, asino, acoso, atano, sinho, cosho, tanho, asinho, acosho, atanho, expo, logo, sqrto.
 
Differential operator : nablao(u,x)
    exterior algebra
 

                           
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