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);

#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));

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.

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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