Pawan Takhar

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14 years, 298 days

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These are answers submitted by Pawan Takhar

In Maple 15, the Check command for above case does not print any output on the screen. Thus, it remains confusing whether Check is working in this case.  Pawan Takhar

I haven't seen any general documentation about the use of % to make inert forms of functions. Under the help file of new function d_, it is listed that its inert form is %d_. So, I tried using % in front of my function and it worked. Just as Robert has commented, the value command can handle the names beginning with %. Pawan Takhar
Robert and Joe, Thanks for your suggestions. After some trials, I also found one more way that works: If I put "%" sign in front of a function name than it becomes inactive.... dm:=z->diff(z,t)+v[c]*d_[c](z); Next I defined the alias: alias(Dm=%dm): This makes Dm the inert form of dm. Any comments on the use of "%" to make a user-defined function inert? Pawan
Add on to above text. The equation is a simplified form used to denote the point. In real equation, chain rule is being used to expand psi, which is a function of various constitutive variables. Here one can consider that first term has a multiplying scalar variable needed for consistency of units across different terms Pawan
I played further with above. If one does not declare X and Y as tensors, then the check command fails.

> restart;

with(Physics):

Setup(dim=[3,`+`]);

> Define(F,X);

PDEtools:-declare(F[mu,nu](Y),X[mu](Y));

eq:=F[mu,nu](Y)=d_[mu](X[nu](Y),[Y]);

Check(eq);

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#But if X is not declared as a tensor, the Check command will fail.

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In above, unless X and Y are declared as tensors, the Check command fails to match indices on both sides. But, one cannot declare both X and Y as tensors because it gives error in indicial equations. See below:

> restart;

with(Physics):

Setup(dim=[3,`+`]);

> Define(F,X,Y); #Now both X and Y are declared as tensors.

PDEtools:-declare(F[mu,nu](Y),X[mu](Y),Y[mu](X));

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But I obtain the following error.

eq:=F[mu,nu](Y)=d_[mu](X[nu](Y),[Y]);

Error, (in Define) the variables [Y] were already defined as names or indices. You can use Define with the 'clear' or 'redo' options to discard the previous definition.

Maple Equation

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This means that one will not be able to type equations with mixed X and Y terms. When the Check command fails, one cannot use the new "Simplify" command to simplify tensorial equations. I think this is a severe limitation of the current release of Physics package. I hope this is fixed in the near future, unless someone could show me if there is better way to include both X and Y as derivatives in a single equation. Thanks, Pawan Takhar Please replace this text with the link to your file. The link can be found in the File Manager
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