DifferentialGeometry[algebraic operations]
addition, subtraction, scalar multiplication, wedge product, tensor product
Calling Sequence
Parameters
Description
Examples
A &plus B - add two vectors, differential forms or tensors
A &minus B- subtract one vector, differential form or tensor from another
A &mult B - multiply a Maple expression by a vector, differential form or tensor
A &wedge B- form the wedge (or skew) product of a pair of differential forms or multi-vectors
A &tensor B- form the tensor product of a pair of tensors
A &algmult B - multiply two vectors in an algebra
A, B
-
Maple expressions, differential forms or tensors
In the DifferentialGeometry package the wedge product of 1-forms is defined in terms of the tensor product by α⁢∧β⁢=⁢α⁢⊗⁢β⁢−⁢β⁢⊗α.
When using these commands together within a single Maple expression, it is important to use parentheses to insure that the operations are executed in the correct order.
In an interactive Maple session, it is usually more convenient to use the commands evalDG and DGzip to perform these basic algebraic operations.
Here are the precise lists of admissible arguments for these commands.
A &plus B, A &minus B -- A and B: Maple expressions, vectors, differential forms of the same degree, differential biforms of the same bidegree, tensors with the same index type and density weights. A and B must be defined on the same frame.
A &mult B -- A: a Maple expression; B: a Maple expression, vector, differential form, differential biform, tensor. A and B must be defined on the same frame.
A &wedge B -- A and B: Maple expressions or differential forms, differential biforms. If A and B are forms, then the sum of their degrees cannot exceed the dimension of the frame on which they are defined. If A and B are bi-forms, then the sum of their horizontal degrees cannot exceed the dimension of the base manifold on which they are defined. A and B must be defined on the same frame.
A &tensor B -- A and B: Maple expressions, vectors, differential 1-forms, tensors. A and B must be defined on the same frame.
These commands are part of the DifferentialGeometry package, and so can be used in the forms given above only after executing the command with(DifferentialGeometry).
with⁡DifferentialGeometry:with⁡LieAlgebras:
Use DGsetup to define a three-dimensional manifold M with coordinates [x, y, z].
DGsetup⁡x,y,z,M,verbose
The following coordinates have been protected:
x,y,z
The following vector fields have been defined and protected:
D_x,D_y,D_z
The following differential 1-forms have been defined and protected:
dx,dy,dz
frame name: M
Example 1.
Create linear combinations of vector fields and differential 1-forms using &plus and &mult.
X1≔D_x&plusD_z
X1≔D_x+D_z
X2≔3⁢z&multD_x&plus−2⁢y&multD_y
X2≔3⁢z⁢D_x−2⁢y⁢D_y
X3≔X2&minus3⁢z&multX1
X3≔−2⁢y⁢D_y−3⁢z⁢D_z
α1≔sin⁡z&multdx&minuscos⁡y&multdz
α1≔sin⁡z⁢dx−cos⁡y⁢dz
α2≔cos⁡x&multdy&pluscos⁡z&multdz
α2≔cos⁡x⁢dy+cos⁡z⁢dz
Example 2.
Create differential 2-forms using &plus and &mult and &wedge.
α3≔2&multdx&wedgedy&plus5&multdy&wedgedz
α3≔2⁢dx⁢⋀⁢dy+5⁢dy⁢⋀⁢dz
α4≔α1&wedgeα2
α4≔sin⁡z⁢cos⁡x⁢dx⁢⋀⁢dy+sin⁡2⁢z⁢dx2⁢⋀⁢dz+cos⁡y⁢cos⁡x⁢dy⁢⋀⁢dz
α5≔α1&wedgeα2&minusα3
α5≔−2+sin⁡z⁢cos⁡x⁢dx⁢⋀⁢dy+sin⁡2⁢z⁢dx2⁢⋀⁢dz+−5+cos⁡y⁢cos⁡x⁢dy⁢⋀⁢dz
α6≔α1&wedgeα3
α6≔−2⁢cos⁡y−5⁢sin⁡z⁢dx⁢⋀⁢dy⁢⋀⁢dz
Example 3.
Create various tensors using &plus, &mult and &tensor.
T1≔X1&tensorX1
T1≔D_x⁢D_x+D_x⁢D_z+D_z⁢D_x+D_z⁢D_z
T2≔X1&tensorα1
T2≔sin⁡z⁢D_x⁢dx−cos⁡y⁢D_x⁢dz+sin⁡z⁢D_z⁢dx−cos⁡y⁢D_z⁢dz
T3≔1&tensordx&wedgedy
T3≔dx⁢dy−dy⁢dx
T4≔dx&tensordx&tensorD_y&tensorD_z&tensordz
T4≔dx⁢dx⁢D_y⁢D_z⁢dz
T5≔1y2&multdx&tdx+dy&tdy
T5≔dxy2⁢dx+dyy2⁢dy
Example 4.
Create a multi-vector using &plus, &mult and &tensor.
V1≔2&multD_x&wedgeD_y&plus3&multD_y&wedgeD_z
V1≔2⁢D_x⁢⋀⁢D_y+3⁢D_y⁢⋀⁢D_z
Example 5.
Use the command AlgebraLibraryData to retrieve the structure equations for the quaternions.
LA≔AlgebraLibraryData⁡Quaternions,Q
LA≔e12=e1,e1·e2=e2,e1·e3=e3,e1·e4=e4,e2·e1=e2,e22=−e1,e2·e3=e4,e2·e4=−e3,e3·e1=e3,e3·e2=−e4,e32=−e1,e3·e4=e2,e4·e1=e4,e4·e2=e3,e4·e3=−e2,e42=−e1
Initialize.
DGsetup⁡LA,e,i,j,k,θ
algebra name: Q
Calculate some simple sums and products of quaternions.
Q1≔i&algmultj
Q1≔k
Q2≔e&plusi&plusj&plusk&algmulte&minusi&plusj&plusk
Q2≔4⁢e
See Also
DifferentialGeometry
DGzip
evalDG
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