# SR for cl. rel. field theories.

1. Jul 18, 2012

### magicfountain

I read basic stuff about relativity (time dilitation etc.) in a HS textbook.
I want to do some relativistic dynamics and go up to Einsteins field equations (GR). For GR I will definitely need tensor analysis. However, what is the math involved in the SR that I need to get to classic relativistic field theories (Electromagnetic),which I want to do before doing GR?

2. Jul 19, 2012

### alialice

For GR you need some basis of differential geometry.
For the second question, I think you refer to Classical Electrodynamics? For it you need vector calculus, and to know something about tensor if you use covariant formalism.

Is this what you were asking?

3. Jul 19, 2012

### magicfountain

As far as my understanding goes, maxwells basic equations describe the EM field without relativistic effects (I have done them already, as well es basic vec. calc. (div. grad. rot.)). I just had a look at some lecture notes from the internet and it had a lot of tensors for relativistic maxwelltheory. not really following it (because I know few about tensors in relativity) i saw langrange densities coming up while going through it.
I know the how to derive lagrange densities in mechanics (they can be nonrelativistic) and thought, there was a way to have maxwell field theory in lagrangian form, but this probably corresponds to relativistic forms only. (is this correct?)
should I start doing tensors and relativity first to get to relativistic maxwelltheory?

4. Jul 19, 2012

### haushofer

Maxwell's equations are inherently relativistic. So why do you say this?

Of course one can take a non-rel. limit, giving "Galilean Maxwell theories", but that's a different cookie.

5. Jul 19, 2012

### magicfountain

Ok, if you mean relative motion (B-field for moving etc.).
Maybe it was wrong, that with relativistic I referred to time dilatation and doing Lorentztransformations.

6. Jul 20, 2012

### alialice

Maxwell theory is relativistic( in the sense of special relativity): it predicts for example that the speed of an electromagnetic wave is c.
What are you looking for, I think it is electrodynamics. You can study the motion of particles in electromagnetic field, and for this you need special relativity and tensors.

7. Jul 20, 2012

### alialice

http://arxiv.org/abs/physics/0311011/
I've just found this notes, try to look at them, even if they are more mathematic than physics.
The standard reference for the subject is a book called Classical Electrodynamics by Jackson.

8. Jul 20, 2012

### magicfountain

Thanks, this helps!
So is this also what the Langrangians are for?

9. Jul 20, 2012

### harrylin

Maxwell's equations relate to a single inertial frame. The change with SR was that the equations are valid for any inertial frame - this doesn't affect the equations at all.

10. Jul 20, 2012

Yes :)