Hey /sci/, what's everyone's opinion...

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Hey /sci/, what's everyone's opinion of the landau course? I'm thinking of taking the time to start from the beginning and read through. Worth the effort or is it a bit of a waste of time?

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ohhh my god those books look sexy, maybe I'll start with the fluids one

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Who wants to go on the journey with me? I'm going to take the plunge and try and read about 2 chapters a week (at least for the beginning). I'll be answering all the problems and would like another anon to answer them with me.

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You need a solid understanding of physics already to even start these books.

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>>7757652

I'm a pretty solid third year

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>>7757648

Some people attempted a reading group last year. Most (everybody) dropped out.

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If you can provide me with links to the books or something I would read these with you.

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>>7757648

Didn't we try this last year? Didn't last.

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>>7757655

Oh well, I'm prepared to try. Good time to start actually beginning of the year. This could be /sci/'s new year resolution. >>7757655

http://people.ds.cam.ac.uk/tdch4/Uploads/Landau%20and%20Lifshitz/LandauLifshitz-Mechanics.pdf

Here's a link for the first volume. I think one chapter a week is a very relaxed pace so should be able to keep that up no matter what really.

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>>7757678

Hell, I'll give it a go. One chapter a week sounds fine, and I'll take the chance to use my new whiteboard.

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>>7757678

There are 10 volumes and each volume has like 7 chapters so it would take 1.5 whole years.

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Ok excellent! We'll see how this goes. Everyone should aim to finish a chapter by the Friday of every week. Obviously questions throughout the week are encourage. Let's see if we can make this place slightly less of a shit dump.

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>>7757631

It would be awesome. It's my third year too.

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I'm in. sounds like a bit of fun.

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one chapter a week should be piss

see you on friday faggots

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>>7757678

Alright. Sign me up. When do we solve the problems?

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Pretty intrigued actually. Might try it out myself.

See you guys on Friday

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Finished the first chapter. There aren't many problems at the end, I skimmed over them cuz I want to try them first. They're pretty interesting tho. Maybe we should get more problems from schaum's Lagrangian Dynamics or Goldstein's book.

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"If all the co-ordinates and velocities are simultaneously specified, it is known from experience that the state of the system is completely determined and that its subsequent motion can, in principle be calculated. Mathematically, this means that, if all the co-ordinate and velocities are given at some instant, the accelerations at that instant are uniquely defined."

Huh? Why can't there be multiple different accelerations for each particle?

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>>7759487

Means net acceleration, not individual components from forces.

Could I have help on this step?

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>>7759487

>>7759496

No, it does mean individual acceleration. It's an observational fact that can't be derived from theory I don't think.

The way in which this related to what was just said is if you imagine a particle in space what determines its acceleration? That's simply the force felt upon it right? So given a specific lagrangian (which determines what the force the particle would feel) the acceleration is uniquely determined. I hope that makes more sense now. Please ask if you need any further clarification.

As for >>7759496 this is a derivation of the Euler Lagrange equations. I'll write up a full derivation when I get back home if you'd like

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What does the small delta before q(t) mean?

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>>7759546

It doesn't mean anything on it's own.

[math] q(t) [/math] and [math] \delta q (t) [/math] are two different unrelated functions.

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>>7759546

It's the variation of q

https://en.wikipedia.org/wiki/Calculus_of_variations

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>>7759598

No, you only take variations of the functionals.

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>>7759624

Why?

It works fine here

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>>7759637

Let's calculate the variations of the functionals [math] J = q [/math] then

[math]\delta J (q; \eta) = \lim_{\varepsilon \to 0} \frac{(q + \varepsilon \eta) - q}{\varepsilon} = \eta [/math].

It is defined but [math] \delta q[/math] is fully independent from [math]q [/math]. Other books simply use [math]\eta [/math] or some other letter in the first place instead of writing the misleading [math] \delta q[/math].

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>>7759660

>J = q

Not a functional since it still depends on time.

[math] \delta q[/math] simply can't be interpreted as variation of q.

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>>7757678

>http://people.ds.cam.ac.uk/tdch4/Uploads/Landau%20and%20Lifshitz/LandauLifshitz-Mechanics.pdf

Wait, you're telling me it's available for free? The fuck, how did I not know, thanks Anon.

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>>7757690

>10 volumes

What's the tenth volume?

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Are all the volumes self contained? Or do I need to go through them in order for notion etc?

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>>7757655

Yeah, I tried the exact same thing last year.

I could make about half a dozend interests at first, collected two, three skype names and put some effort into moderating it.

This was my first post to spark discussion

http://pastebin.com/gmaZM378

I did it for 3 weeks, the added a checklist link in one post to see how many people were actually reading the thread and it was only 2 people.

Most people will say they are interested (because they are) "but... I have a lot to do right now" so they become lurkers at best.

Sad but true, but if you have the time, I'd say give it a try.

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>>7759867

http://www.amazon.com/Course-Theoretical-Physics-All-Volumes/lm/RMVH4G2YKW3NH

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>>7757631

The QED volume is too old to be worthwhile, and Part 2 of Statistical Physics might be getting a bit dated. The rest are good.

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>>7757631

Those are pretty hard, but there's a ton of information. My uni finally started getting them. Unfortunately we only have 3 of them.

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>>7759496

Here is a more detailed derivation of the Euler-Lagrange Equations.

Landau skips many steps.

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>>7760105

What book is this from?

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Is there an error in the first problem? Lev says kinetic energy is [math] T = \frac{1}{2}(l_{1}\phi_{1})^{1} [/math] however when I do it I get that it's proportional to the derivative of Phi, not Phi itself. Thoughts?

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>>7760160

Forgot mass of particle 1 in the equation, anyways my question stands the same.

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>>7760160

Without knowing the problem, check the units and see if it makes sense.

Energy is

[math] kg^1·m^2·s^{-2} [/math]

in conventional units

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>>7760160

Aren't l_1 and phi_1 squared (you have a power of 1)?

Also, doesn't it just follow from T = (1/2)*m*v^2 where v = l_1*phi_1?

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>>7760160

I believe there is a dot over the phi. It is just that the dot is so closely written to the phi that it looks like it were a part of it.

Stuff like that always happens in old textbooks without proper LaTeX.

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>>7760178

The position vector is in terms the of the angle Phi which is a function over time(the angle changes as the particle sways) , so when you derivate said vector and find its magnitude you'll end up derivating the angle. I can't upload pic with calculations because my phone's connection got slowed down

>>7760174

The units check out.

>>7760184

KEK there it is. Mystery solved, thanks anon.

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>>7760178

And yes, my bad, it's supposed to be a power of 2. Typing on a phone isn't a very trivial task.

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>>7760105

Cool, thanks a lot man.

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Problem 3: why are y components substracted on the position vector of the mass? Shouldn't they be added?

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Final year math major. I've always had an interest in classical physics and I've always wanted to work through this series. I don't know anything about physics, however, so I'm not sure this would be the best first look at the concepts.

I'm also not sure if these books are rigorous or outdated at this point.

My background includes virtually all of undergrad math though, without any sort of physical intuition. If you're still here after the summer, OP, j will have graduated. And since I'll have nothing to do for a while before graduate school starts, I will gladly give you my Skype name and we can work through this series together.

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I'd love to join you guys but my physics skills suck. Any way I can do something similiar to you guys but easier? Or should I just attempt to do this?

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>>7761129

What's your mathematical and physical background?

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>>7761136

ODE/PDE, some linear, Calculus, a bit of compex analysis, some stats. I'm just gonna say that my physics is, for lack of a better word, sloppy but I have exposure to mechanics, EM, and quantum

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>>7761152

Similar boat to me, then. I don't have any physical intuition either. You could always try studying the current standard books in those areas.

You could also try Mechanics by Michael Spivak. Absolutely amazing book about physics for mathematicians.

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>>7761390

But the problems in the book already come with the solutions.

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How's everyone doing? Curious just to get a rough idea of numbers

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>>7763242 as i said above, for pure reader count you can post a strawpoll between you sentences to check how many see it

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