@Carl Love 

Hi Carl, the context for my comment is the last example of the help page for dchange. Take then (17) from that help page and try solving for s using solve and PDEtools:-Solve:

Edgardo S. Cheb-Terrab
Physics, Differential Equations and Mathematical Functions, Maplesoft

@John Fredsted 

It is mentioned in the Updates page: the final update for Maple 17 is Physics-61.1.mla.zip. That happened March 19, after the release of Maple 18. So the fix to the issue you posted is in the update for Maple 18, not for Maple 17. Note that maintaining updates retroactively, for previous releases, is difficult, because not just Physics but the whole library is changing, and Physics depends on these changes; in this case many things changed from Maple 17 to Maple 18. Independent of that, on return I will see if I can prepare a personal fix for you regarding this particular issue. 

Edgardo S. Cheb-Terrab
Physics, Maplesoft

@jakubi 
Indeed, for Maple 16 a complete set of General Relativity tensors got added to Physics, mainly D_, representing the covariant derivative, Christoffel, LeviCivita in curvilinear coordinates etc. With these new commands it is sort of straightforward to tackle tensor calculus problems as the ones mentioned in this post. I show how to do that for the divergence of a stress tensor in polar cylindrical coordinates in an answer appearing further below (or further above ... I never know where is the answer appearing :) )

Edgardo S. Cheb-Terrab
Physics, Differential Equations and Mathematical Functions, Maplesoft

@John Fredsted 

You have a point, and yours is in fact the third MaplePrimes post that asks for the same, a sort of manual for Physics. It is not that command-documentation is missing, I think, but that the amount, and kind, of functionality available is beyond what you can explain in useful ways within traditional help pages for commands.

To fill the gap at some point I added the page ?Physics,Examples, with sections "per area". That is a different concept than "per command". It did help well. Then I added Physics,Conventions, to have all the conventions in one single place - that also helped.

By now however ?Physics,Examples is too large for a single page, even if its approach is still valid, I think, and the conventions would also benefit of a splitting by physics area. The way to go is to add material to fill the gaps in these two pages and organize the whole thing into a mini-manual for Physics, say as an alive computer algebra document, about Vector Analysis, Mechanics, Electrodynamics, Quantum Mechanics, etc. (most of the current sections you see today on ?Physics,Examples and some more), where you could rapidly find computations of the kind that you need to develop. For this manual to be useful it needs to be really very short and with very good examples more than anything else.

I will think about and see how to move this project ahead during this year.

Regarding what you have for documentation today, the help pages ?Physics,Examples, ?Physics,Conventions and ?Updates,MapleXX,Physics, where XX is 16 or 17, plus of course the help pages for the commands themselves, do tell most of the story, even if in fragmentary manner.

Edgardo S. Cheb-Terrab
Physics, Differential Equations and Mathematical Functions, Maplesoft

@juggler 

I personally prefer overwriting the system library folder, because the new library is indeed an updated version, so why would one want to use the old one, but if you want to have both options then installing in a personal directory is the way to go. Or also a third alternative: rename, in the system library folder, Physics.mla to Physics.mla.old, then put the udpated Physics.mla in that directory. In that way you can also go back to the original M17 library if you want by deleting the updated one and renaming back Physics.mla.old -> Physics.mla.

Edgardo S. Cheb-Terrab 
Physics, Differential Equations and Mathematical Functions, Maplesoft

@rashmi 

I suggest you to give values to e and l and use dsolve/numeric and odeplot (see ?dsolve,numeric and ?odeplot). Sometimes of use too, you can combine plots for different values of [e, l] using plots:-display.

Edgardo S. Cheb-Terrab 
Physics, Differential Equations and Mathematical Functions, Maplesoft

@juggler 

No, there are no limitations, as far as I can tell .. but I am not the appropriate person to answer this type of question - perhaps people at support@maplesoft.com can give you a more exact answer.

Edgardo S. Cheb-Terrab 
Physics, Differential Equations and Mathematical Functions, Maplesoft

@Mac Dude 

All ok, just one thing: when testing your example with currrent Maple (17), remember to update Physics with the latest version found at the Maplesoft Physics: Research & Development webpage, where you get not only new developments but also bug fixes to the problems reported.

Edgardo S. Cheb-Terrab 
Physics, DEs and Mathematical Functions, Maplesoft

@John Fredsted 

Hi, yes, for sure. I'll post again here, in this thread.

Edgardo S. Cheb-Terrab
Physics, DEs and Mathematical Functions, Maplesoft

@Alejandro Jakubi 

Not sure what you mean. In Physics you can set the metric to whatever you want, including arbitrary. The same in DifferentialGeometry. But it is current Maple, not Maple 12.

Edgardo S. Cheb-Terrab 
Physics, DEs and Mathematical Functions, Maplesoft

@John Fredsted 

There seems to be a bug in assume: after you assume(theta1(t,x,y,z),scalar): and assume(theta2(t,x,y,z),scalar): I would expect getassumptions(theta1(t,x,y,z)) to return {(theta1(t, x, y, z))::scalar} but instead it returns {(theta2(t, x, y, z))::scalar}. From that output, Dagger cannot conclude about theta1(t,x,y,z) and so it returns with dagger instead of conjugate.

The solution to all this is to have one more option in Setup, as said, to indicate that something is scalar, even an algebraic expression perhaps more general than a function. One of the advantages of this approach, as the one already in place to indicate that something is real, is that it does not change the object into something else and therefore you can reuse expressions involving the assumed objects that were entered before the assumption got placed. Likely, you can remove the assumption at any point and reuse expressions entered while the assumptions were holding. All this because when you Setup(real = {a,b,c}) there is no change to a, b or c. 

Have in mind however that I'm somewhat overloaded with activity related to the upcomming Maple release - will probably only be able to implement this new setting in February ...

Edgardo S. Cheb-Terrab
Physics, DEs and Mathematical Functions, Maplesoft

@Carl Love 

In the previous reply I meant this could be done taking the standard `print/diff` (the one there when you restart) as template, but you can also change the one installed by `PDEtools/declare` instead - in fact it is probably easier, despite that the routine is much bigger. So in that case look right after line 92 as shown by showstat: the local variable called tty_ans is the f[x,x,x,y,y] object; insert a couple of lines there to convert to tty_ans := f[3x, 2y]. Note however that if it is a function of only one variable and that variable happens to be the prime variable tty_ans is not an indexed object. To workaround that situation, search for things like ... if dx = prime_variable ... and replace that equation that involves 'prime_variable' by the word false.

Edgardo S. Cheb-Terrab 
Physics, DEs and Mathematical Functions, Maplesoft

@Carl Love 

Take as template the `print/diff` of Maple 17: right after line 20 as shown by showstat(`print/diff`) starts a loop that does most of what you need - a small alteration in the conditional that starts at line 24 would suffice.

Having said that, note that `print/diff` is changed on background by a number of packages in order to display things according to the increased functionality they provide; this is the case when you use PDEtools:-declare and also Physics.  Next, have in mind that the display is one thing, the copy & paste is another one, and if you want the latter to work you need to use something else, e.g. Typesetting:-mcomplete. Finally, print/diff is an internal routine, it changes frequently (e.g. its size for Maple 18 multiplied by two) in order to accomodate new functionality, so just be aware that what you write and works in one release may be conflictive with the print/diff of the next release ... as said these are internal routines, that is the way it is for them.

Edgardo S. Cheb-Terrab 
Physics, DEs and Mathematical Functions, Maplesoft

@peter137

Thank you for your comments. There is a vision behind this project and it's coming along nicely. And yes, updates for the Physics package are being posted around the clock, serveral times a week. Our goal is to accelerate the development with rapid ping-pong-like feedback - with the results available for download right away, and mainly to move the focus into what people are actually doing with the package today. Things like what you see in the two previous posts on Quantum Mechanics (here and here, the third one comes next week) illustrate not only what we can do today with this package but also how constructive this new developmental approach of presenting updates around the clock is.

I wrote a first draft of a book on the use of Physics a long time ago, when this was a University project. It was rather popular among students. I considered updating and completing it many times, but have not had the time. Hopefully, I'll be able to complete it during 2014.

Edgardo S. Cheb-Terrab
Physics, Maplesoft

@Sergio Parreiras 

Hola, :) I'd need the actual Maple input for dsys; you could either paste it in 1D or attach a mw with the 2D input. Advancing: it is not possible to set an independent variable as arbitrary, but there may be ways to achieve the same thing -I need to give a look and with a concrete example to think about is simpler. Also the error interruption is not appropriate, that requires a fix. Y gracias por el feedback Sergio! :)

Best

Edgardo S. Cheb-Terrab
Physics, DEs and Mathematical Functions, Maplesoft