lemelinm

1490 Reputation

15 Badges

18 years, 155 days

 

 

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Mario Lemelin
Maple 14.00 Win 7 64 bits
Maple 14.00 Ubuntu 10,04 64 bits
messagerie : mario.lemelin@cgocable.ca téléphone :  (819) 376-0987

MaplePrimes Activity


These are replies submitted by lemelinm

@tomleslie 

Well, I have attached a Maple document and an image inside. All the solutions you gave are wrong from the point of view of a physicist.  If a student was to give me that kind of graph, I would have to give him a 0.  Look at the image and you will see what region is the real solution. And the only simple thing I ask is how to plot the right region.  In the document, the first graph is half of the solution.  I want a command that will show how to have the right region fill with color. And never will I give points to someone that starts the masse M and m at -10.  Maybe I should have stated that I was a physicist.

Wrong_region.mw

@tomleslie 

The mass «m» and «M» cannot be negative.  The plot is wrong of course.  Moreover, we don't see the relation M>2*m

@ecterrab By the way, I do have a problem installing it under windows.  I did the command and I receive this message:

`The "Physics Updates" version "865" is installed but is not active. The active version of Physics is within the library C:\\Program Files\\Maple 2020\\lib\\maple.mla, created 2020, March 4, 20:36 hours`

Then I did Physics:-Version(latest) and after some times, a window opens stating that;

"Connection to the kernel has been lost"

I don't have any firewall installed.

Any ideas?

I am using Maple 2020.1 id 1482634.  What command should I do to find the version of my physics package?

Thank you in advance.

Mario

@acer 

As you will see in the attached document, I don't get the true numbers on the vertical axis but the unit is good. The horizontal axis is OK.  Then equation (4) print OK but why (6) is not?  Do you see what I am doing wrong?  I am using Maple 2020.1

Thank you in advance for your help.

Mario

Quark-Quark_interaction.mw

@acer 

Hello to you.  You have well understood the question.  The use of Units:-UseUnit(MeV) is new to me and I will explore it.  It's a nice trick.  And why I didn't think of this one: combine(pmin, units).

Thank you for your fast response.  I think that it would be nice to have this option in the Physics package: with(Physics, Particles) with the possibility to call a particle (for example Pi+) with the values of I, P, Q, S, C, and B.  Mass in MeV/c^2 and lifetime could be interesting too.  Anyway, this idea came to me while I am reading for the pleasure of the following book: Griffiths, Introduction to Elementary Particles, 2008.

Thank you, Acer.

 

@longrob 

Just to mention that 10 years later, I come accross that simple way to dol it in Maple 2020.  So I was able to do manually the calculation and check with Maple if I was right.  Thank you.

Since I will do 3 courses in Quantum Mechanics (MITx), I am wondering if it would be an added bonus to use the physics package?

 

Thank you again for the fast responses.

@ecterrab 

With you answer, I found out that what I can do is:

> DifferentialGeometry:-Library:-MetricSearch()

And I can find all the metrics as we can see in the book: Stephani - Exact Solutions of Einstein's Field Equations -Cambridge University

That is great.  Thank you!

@Christopher2222 

If I put t := 3 [s], I want to be able to transform it in [m] by using the contextual menu..  But for Maple, this is not possible.  I have to do it manually.  When I load the Physics package, I would like that units take into account that c = 1, etc).

Is this possible or too complex?

@tomleslie 

When you decide that c=1, because the equations are simpler, this make it problematic for an introduction on general relativity.  So I would like to be able to write an equation like this -t^2+x^2+y^2+z^2 and have the result in meter.  That help to check if your calculation is coherent.  This c=1 has an effect everywhere in the theory and I was albe to see in different instances that it complexify the comprehension for the beginners.

@Christopher2222 

Thank you for the reference.

Mario

@John Fredsted 

Here the real commands:

>Setup(metric = Matrix(3, 3, [[1/(-r^2+1), 0, 0], [0, r^2, 0], [0, 0, r^2*sin(theta)^2]], shape = symmetric))

Isn't that fun!  Having done a course on General Relativity, it help to understand what we are doing.

Mario

@John Fredsted 

Thank you again John for your help on this.  Even if I do it in 4D, I only need to put g[0,0]=1.  But your idea help me do that:

restart;
with(Physics); Setup(mathematicalnotation = true, dimension = 3); Coordinates(X = (r, theta, phi)); Setup(metric = Matrix(3, 3, [[Physics:-`^`(1-Physics:-`^`(r, 2), -1), 0, 0], [0, Physics:-`^`(r, 2), 0], [0, 0, Physics:-`*`(Physics:-`^`(r, 2), Physics:-`^`(sin(theta), 2))]], shape = symmetric));

g_[];
Define(A, B);
Setup(differentiationvariables = X);
seq(Christoffel[j, mu, nu, matrix], j = [`~1`, `~2`, `~3`]);
seq(Ricci[mu, nu, matrix], mu = 1 .. 3);
Ricci[scalar];
Einstein[mu, nu, matrix];

I am starting to manage well the physics package.

Mario

 

It would be great to have a book on general relativity with commands, templates for the most used metric and exeamples.  It should take into account that it would need two parts, one for introductory courses and one for advanced users.  I tried to find books like that but with no success.

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