General Relativity

William Fish's picture

Special Relativity has been around for ~100 years, General Relativity for ~90 years.  I'm hoping that with the assistance of Maple and Mapleprimes I may be able to do some tensor calculus to better understand Einstein.  Perhaps the twin paradox is within my reach.  Perhaps even the orbit of Mercury.

I have read A Journey Into Gravity and Spacetime by John Archibald Wheeler.  I'm looking for another book and Introduction to Tensor Calculus, Relativity and Cosmology by D. F. Lawden looks like it might do the trick.  The website Einstein's Equations looks like it will be helpful.

I would like your advice and of course, I'm looking for the golden road.

So the question is, how do I get there from where I am?

 

Comments

gkokovidis's picture

GRTensorII

Start with the link below and work through the examples to get a feeling for the package. There are further links and documentation as well.

grtensor.phy.queensu.ca/

 

Regards,
Georgios Kokovidis
Dräger Medical


William Fish's picture

GRTensorII

Thank you.  I'm reading it.

Gravitation

Have you already looked at John Fredsted's Maple  package, "Gravitation"?  I think it's available at Maplesofts website (Applications Center).

v/r,

William Fish's picture

Gravitation

No, I did not have Gravitation but I do now.  Thank you.

John Fredsted's picture

General relativity

Maybe the wikipedia page General relativity may also have your interest. As to the golden road towards general relativity, I am not sure. I think that it depends on ones background, for instance, whether you are a mathematician or a physicist, or something third.

Back in the late eighties I struggled for three years on my own [at that time no formal course was available at my university, believe it or not] before I understood general relativity. The difficulty was, along side understanding the intimidating machinary of tensor calculus, to give up my physical notion that coordinates matter - they don't: coordinates are only the work of man. The coordinate covariance of the equations of general relativity embodies that notion.

So, to me there seems to be two things to understand: the tensor calculus of Riemannian manifolds, and the physical reason for using it in the description of gravitation. Doing the former without the latter gives a very valuable insight into the beautiful concepts of Riemannian geometry [geodesics, connection, curvature, etc.], but does not necessarily give one an understanding of gravitation and the true genius of Einstein.

Critics wanted! no rewards sorry ^_=

Is it the Gravitation circle here? I guess, so no better  place where to get attracted non earth  strings  attached, ops I almost dismissed the other … holy strings the supadupa strings of the unifying Theory  Quest ….
No joking to much, I hope.
The subject:

1) the Newtonian gravitation law supposes a intertial absolute frame, plus Cavendish experiment s and so on gave an experimental verification of F= k*(M*m)/(R^2) not too faar from human touch and normal sight …. 2) This is the ontic side of the issue, lets go at the ontological side:a) why interacting mass do not add up, but multiply their action? b) isn’t it possible hat the Newtonian law contains already enough  information aiming to quanto-gravitational theories?

The questions are linked, in my mind, of course, by a series of neural strings connecting: the product of masses to a statistical sight (probability of independent but related events – the coins & Binomial – multiply, 2a) by equating M to m --> m^2 woul be a perfect square of a probable mass operator”, c) where to disguised the hidden wave function? The best place were to look is a the Gravitational field, calculating the potential U= - k* (Mm/R).

The results requiring heavy critics and suggestions:

1) since equating the masses, in the sense of considering a single mass and its "virtual" double, is improper in Newtonian theory frame, could be that labeling somehow the equated mass by “I” the imaginary unity would have help. So I had done it.

U= - (k im*m)/R  -> (U/m) = -(k i m)/R. -> (U/m) + (k i m)/R =?.

Here is the critical point, peraphs since I deliberatly I tought that what =0 for real values, could = z in the complex frame i’m trying to get out  of / or fit in (?) the classic formula. I then equated  the upper right side to a possibly mock complex variable Z,  followed by rising the formula as a pover of “e”-> e^Z=e^(U/m) * e^(k I m)/R,
Recalling that Z=a+iB is equivalent to e^Z=e^a *(cos(b) +I sin(b)) (cfr Wunsh, Complex Variables p 96.97)
I proceeded conformably  

e^Z=e^(U/m) * (cos((km)/R) + I  sin ((km)/R)

The equation identify clearly a real and an imaginary component of the potential energy, and what most intrigues is the wave form of both:

                       Re                                           Img
e^Z = e^(U/m) * (cos((km)/R) + I e^(U/m)* sin ((km)/R)

Reonsidering the initial condition Z=0 the equation becomes
 

(e^-(U/m))= (cos((km)/R) + I e^(U/m)* sin ((km)/R)

Practically we are facing two orthogonal waves, the cos Real valued wave, and rotate of 90° by I multiplication sin wave, with a difference in period  of Pi/2.
The waves are mainly concentrated within the unit disk. It's there the maximal density and wide change in period spectra, because of R at denominator at the cos and sin arguments.

Though very clumsy, and bound to a thin hope about the legitimacy of introducing I when equating masses, guess the scenario offered at the end, is rather fascinating. Somehow it relates to the inner behavior of the mass its-self, and possibly with its peculiar way of originating as “a double vitual-real”. In my view m^2 instead of M*m, is the Unitarian subject of the gravitational law. though it must be intended analogically because of the dynamic double). The orthogonal waves, (vector  basis of a possible mass field?), oscillating asynchronously must show further consequences in terms of gravitational energy /mass distribution and mass motion and interaction: as a “particle” &/or as a “2 waves packets”.

Hope finding many critics to all this, and some help  to get things done properly.
Thanks for your attention.
Federiclet
 

just a list of possible intersting books

hello

here a list of few books which might peraphs tur to be usefull to you:

George GAMOW, Gravity, Doubleday Anchor, Science & Study Series, (N. 8, 22)

George GAMOW, Mr. Thomkins in Paperback, Cambridge Univ Press (1993)

Peter G. BERGMANN, The riddle of gravitation, Dover (New York, 1992)

Einstein, Lorentz, Weyl, Minkowski,The principle of relativity, A collection of original papers on the special and general Theory of Relativity, notes by Sommerfeld, Dover (New York) re-edition of 1952 Collected papers.

Einstein's miraculous year. Five papers that change the face of physics, Princeton Univ Press, 1998

Hans REICHENBACH, The philosophy of space & time, introductory remarks by Rudoilf CARNAP, Dover (New York) new english translation of the first edition 1957 in English, of H. R. Philosophie der Raum-Zeit-Lehre(original dating 1953).

It is a great book whith a rich bibliography up to date and of historical and prosographycal meaning.

 

Ciao

Take care

Federiclet

 

 

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