I am working with the Physics package in Maple 2018. I have a spacetime with a metric g and the vector field l is the tangent to a null curve. I have two problems:

(1) I want to check in maple that indeed g(l,l)=0. For this I wrote:

SumOverRepeatedIndices(g_[mu,nu]l[~mu]l[~nu])

Firstly, when I try to execute this command, the program keeps on evaluating for a long time. So, I have to `interrupt the current operation', undo this command, save and reopen the file, execute the entire worksheet again and then somehow it works. However, as you can see in step(13) of the attached worksheet, Maple returns an expression for this command but doesn't cancel out terms and show that it is indeed zero. How can I do this?

(2) I wish to find $(\nabla_l l)^\nu$. Is there a way to directly do this? Or should I do something like:

Define(L[mu,~nu]=D_mu l[~nu])

SumOverRepeatedIndices(l[~mu]L[mu,~nu])

Thanks a lot.

Edit: I actually carried out these steps too. First, I defined $L_\mu^\nu$ in step (14). Then, when I ask for the non-zero components of L, I find that the L_\mu,\nu components are given. How can I get the non-zero L_\mu^\nu components? Also, in step (16), I did the `SumOverRepeatedindices' but it returned only a symbolic result without evaluationg.

try2.mw

How I can simplify result? For factor or using rule.

Thanks

Hello,

I am trying to work with the Physics package to calculate Christoffel symbols. I have just started using Maple today and am coming up against a few hurdles.

I want to change the signature of the metric from (+---) to (-+++). I am typing the following in math mode:

Setup( signature = '-+++')

However, this is returning the following error:

"Error, invalid sum/difference" with my command rewritten within a red box together with the last '+" within another red box. Can you please help me out with this?

Thank you.

Hello,

How can write a code for determination of Laplacian in a new form is introduced in maple code (First line).

Thank you.

FOR2
 

Download FOR2

How can plot two  and bipolar figures as attached and extract their data.

Thank You.

with(LinearAlgebra):
assign(seq(U || i = `<,>`(x[i], y[i]), i = 1 .. 3));
U || 4 := U || 1; r := (1/6)*sqrt(3);
assign(seq(V || i = (U || i+U || (i+1))*(1/2)+(`<,>`(`<|>`(0, 1), `<|>`(-1, 0)) . (U || (i+1)-U || i))*r, i = 1 .. 3)); Norm(V || 3-V || 1, 2); is(Norm(V || 3-V || 1, 2) = Norm(V || 3-V || 2, 2)); is(Norm(V || 2-V || 1, 2) = Norm(V || 3-V || 2, 2));

Fsolve produces the correct solution.  solve followed by evalf produces a completely different solution.

What am I doing wrong?

## Ioannes Colla problem: "Divide 10 into three parts such that they
## shall be in continued proportion and that the product of the first
## two shall be 6"
eqs := [a+b+c=10, a/b=b/c, a*b=6];
fsolve(eqs); ## correct solution
evalf(solve(eqs)); ## different

Tom Dean

Would anybody be able to explain to me why I had to rewrite this one baby-procedure that has an if-statement inside my larger procedure, so that I could get a later on if-statement to work? As best I can tell, they mean exactly the same thing.


 

Information that may be pertinent:

 - The entire (overall) procedure worked without throwing any warnings prior to my adding this new if-statement.
 - The if-statement itself worked perfectly fine on another worksheet, though I hadn't tested it inside a procedure.
 - Commenting out the if-statement but retaining the interior commands led to the sheet compiling again, showing that it was in fact the presence of the if-statement causing the issue. 
 - When I commented out the offending baby-procedure that started throwing the warning, the sheet once again compiled.

The added if statement:

if eval_size > 4 then Search(max(seq(eval_cont[i], i = 4 .. eval_size)), eval_cont); evals_pairlist := evals_pairlist[[1 .. 3, %]] fi:

The error I get, and its "positioning": 

Error, invalid expression for inline function

Hello,

How I can remove some problems in my code.

I wrote it before in  software, but in some lines, I have some problems with it.

How I can change it in maple to run well?

Download

Hi freind,

Anybody knows what happen to this coding?

why this error happens? how can i fix it?

thank you!

Please help me for removing an error in my code.

Thank you

Download

Hello,

How I can write a code for the determination of Laplacian in a new form that is introduced in the maple code (First line).

Thank you.

FOR

Maple Worksheet - Error

Failed to load the worksheet //convert/FOR
 

Download FOR

How to do the partition of integer?
If I input:
>Partition(10,2)
then output is:
>[[1, 9], [2, 8], [3, 7], [4, 6],[5,5]]
-------------------------------------------------
"10" is the number that I want to part,and "2" means that there are "two" number's sum = 10
Sorry my Engilsh is not good,but I really need help.
no other restriction!!

Hi everyone

Im new to MaplePrimes aswell as to Maple.

I have a task where i shoud plot the following shape (with a hole in the centre) using the plot3d function:

All i have accomplished in the last hours is the following file A1.0.mw:

As you can see i havent been able to get rid off the surface in the centre nor the spikes on the edge...
 

• In order to fix the issue regarding the centre I assume I have to exclude the range -2..2 from x, but havent been able to do so.
• Regarding the spikes on the edge Im honestly pretty much clueless why they appear in the first place.

After several hours of trying on my own, I really need your help please!

A1.0.mw
 

Download A1.0.mw
 

Please check this code and fix the error. And help me with the below two questions.

1- In the above image, I'm getting the error when I'm to plot my solutions.

2- How to get information from this system?

      The values of x_1 and corresponding y_1 and so on and errors etc

This is a downloadable link to my worksheet [Practice.mw]

Thanks!