JetCalculus[AssignTransformationType] - assign a type (one of projectable, point, contact, differential substitution, generalized differential substitution, generic) to a transformation
Calling Sequences
AssignTransformationType(φ)
Parameters
φ - a transformation
Description
Examples
Let E→ M and F→N be two fiber bundles, and let πk:JkE→ M , πk:JkF→M be the associated bundles of k−jets.
[i] A map φ :E→F which sends the fibers of E to fibers of F (and hence covers a map φ0:M →N) is called a projectable transformation.
[ii] A map φ:E→F is called a point transformation.
[iii] A transformation φ :J1E → J1F is called a contact transformation if the fiber dimensions of E and F are 1 and φ pulls back the contact form on J1F to a multiple of the contact form on J1E.
[iv] If φ:JkE → F and φ covers the identity map M→N ,then φ is called a differential substitution.
[v] A map φ:JkE→F is called a generalized differential substitution.
[vi] A transformation not of one the types [i]--[v] is called generic.
Explicit coordinate formulas for these various types of maps are given in Example 1.
The command AssignTransformationType(φ ) returns the transformation φ, but with internal representation φ of changed to encode its transformation type. The type of a transformation and its prolongation order can be determined by the command DGinfo with the keyword "TransformationType".
Any transformation of type [i]--[v] can be prolonged to higher order jet spaces. See Prolong for further information.
The command AssignTransformationType is part of the DifferentialGeometry:-JetCalculus package. It can be used in the form AssignTransformationType(...) only after executing the commands with(DifferentialGeometry) and with(JetCalculus), but can always be used by executing DifferentialGeometry:-JetCalculus:-AssignTransformationType(...).
with⁡DifferentialGeometry:with⁡JetCalculus:
Example 1.
First initialize various jet spaces of one or two independent variables and one dependent variable and prolong them to order 4.
DGsetup⁡x,y,u,E,4:DGsetup⁡z,v,F,4:DGsetup⁡p,q,w,K,4:
Case 1. Projectable transformations from E to F.
Φ1≔Transformation⁡E,F,z=A⁡x,y,v=B⁡x,y,u
Φ1≔z=A⁡x,y,v=B⁡x,y,u
When a transformation is first defined, it is not given a type.
Tools:-DGinfo⁡Φ1,TransformationType
Now assign the transformation Φ1 a type.
newPhi1≔AssignTransformationType⁡Φ1
newPhi1≔z=A⁡x,y,v=B⁡x,y,u
Tools:-DGinfo⁡newPhi1,TransformationType
projectable,0
This indicates that the transformation is a projectable transformation, the 0 indicates that the transformation has not been prolonged to a jet space.
Case 2. Point transformations:
Φ2≔Transformation⁡E,F,z=A⁡x,y,u,v=B⁡x,y,u
Φ2≔z=A⁡x,y,u,v=B⁡x,y,u
newPhi2≔AssignTransformationType⁡Φ2
newPhi2≔z=A⁡x,y,u,v=B⁡x,y,u
Tools:-DGinfo⁡newPhi2,TransformationType
point,0
Case 3. Contact transformations:
Φ3≔Transformation⁡E,K,p=−u1,q=y,w=−u1⁢x+u,w1=x,w2=u2
Φ3≔p=−u1,q=y,w=−u1⁢x+u,w1=x,w2=u2
newPhi3≔AssignTransformationType⁡Φ3
newPhi3≔p=−u1,q=y,w=−u1⁢x+u,w1=x,w2=u2
Tools:-DGinfo⁡newPhi3,TransformationType
contact,1
By the conventions adopted here, a contact transformation need not be a local diffeomorphism so that, in particular, the dimensions of the bundles E and F need not coincide.
Φ4≔Transformation⁡F,E,x=z,y=1,u=v,u1=v1,u2=0
Φ4≔x=z,y=1,u=v,u1=v1,u2=0
newPhi4≔AssignTransformationType⁡Φ4
newPhi4≔x=z,y=1,u=v,u1=v1,u2=0
Case 4. Differential Substitutions:
vars≔x,y,u,u1,u2,u1,1,u1,2,u2,2
Φ5≔Transformation⁡E,K,p=x,q=y,w=A⁡vars
Φ5≔p=x,q=y,w=A⁡x,y,u,u1,u2,u1,1,u1,2,u2,2
newPhi5≔AssignTransformationType⁡Φ5:
Tools:-DGinfo⁡newPhi5,TransformationType
differentialSubstitution,0
Case 5. Generalized Differential Substitutions:
Φ5≔Transformation⁡E,F,z=A⁡vars,v=B⁡vars
Φ5≔z=A⁡x,y,u,u1,u2,u1,1,u1,2,u2,2,v=B⁡x,y,u,u1,u2,u1,1,u1,2,u2,2
generalizedDifferentialSubstitution,0
Case 6. Generic:
Φ6≔Transformation⁡E,F,z=u1⁢y,v=u2+x⁢u,v1=y
Φ6≔z=u1⁢y,v=x⁢u+u2,v1=y
newPhi6≔AssignTransformationType⁡Φ6
Tools:-DGinfo⁡newPhi6,TransformationType
generic,NA
See Also
DifferentialGeometry
JetCalculus
AssignVectorType
DGinfo
Prolong
Transformation
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