# Search results

1. ### Continuing with physics

I suggest you suplement the feynman lectures, with something else. As entertaining as they are, they aren't a very suitable introduction to physics(buy them anyway though).
2. ### Two body problem in Gr

I'm not exactly sure as to how i can do that. Do i simply write the energy momentum tenosrs for perfect fluids, and apply it to both? It is doesn't sound too difficult actually. One way to make the problem much simpler is to assume you're in a frame such that yuo can ssume one of the bodies is...
3. ### Two body problem in Gr

Not sure exactly what it would look like. We'd have to drop the static assumption obviously. Two body motion is planar so we can drop one of the angles obviously. Now last i checked, the potential for two bodies from the perspective of a one of thebodies depnds solely on its distance from their...
4. ### Two body problem in Gr

How do we formulate the two body problem in Gr. Also if possible how do we solve it, or approximate said solution?
5. ### Buchdal's theorem

Can anyone show me a proof of this theorem? Could someone possibly send me a link?
6. ### Non linear differential equation

yes it is. It may be that. It is possible that I've made a small mistake in my calculations of miswrote someon paper. How do we solve that? Can it be done by inspection? non linearity scares me. could someone help me solve it?
7. ### Non linear differential equation

Yes it is. can you helpme? essentially I determined from G_tt and G_rr that b=-a just like with the ordinary metric. When I plugged it into the G_thetathata equation, it was still fairly ugly, and icouldnt find a solution by inspection. Non linears are annoying.
8. ### Non linear differential equation

I can't type in latex so in this post d^2a is the secpnd derivative of a, while (da)^2 is the square of the derivative. This equation arose from the G_thetatheta compinent of the einstein tensor. Iwas solving tfor the shcwarzchildmetric where where the cosmos constant is nonzero. the...
9. ### Is it necessary to be precocious?

Very well said. It unfortunate that high school is full of people like that!
10. ### Studying Studying a lot, not getting enough sleep

I'm just stressed that i haven't graduated from high school yet(15 years old). I've mastered the curriculum, yet no one bothers to give me the exaqms to get out. Anyway I'm highjacking this thread. I also eat very little.
11. ### Studying Studying a lot, not getting enough sleep

Hard to explain, but simply put, I always feel very sick when I wake up.
12. ### Is it necessary to be precocious?

A child prodigy would do calc before he's eleven, quantum theory and general relativity when he's 13. He is however, rather precocious. Maybe I have very high standards when it comes to mathematical prodigies. Alot of youngsters do calc and such when they're fifteen. Again you probably...
13. ### Studying Studying a lot, not getting enough sleep

I HATE sleeping. Its just the most horrible feeling imaginable. I prefer to use a few red bulls when necessary.
14. ### Is it necessary to be precocious?

:rolleyes: No it really isn't. I'm "precocious" but look at where I've ended up:cry: . Better to have a strong work ethic, combined with somewhat high intelligence. Also precocity is not necessarily synonymous with high intellect, just look at me! Oh and you seem fairly precocious to me anyway!
15. ### Schwarzchild solution with cosmological constant

Question, will i need some knowledge of non linear equations, to generalize it?
16. ### Schwarzchild solution with cosmological constant

How do we solve for it? I still don't know much about non linear equations. Unfortunately, this reduces to R=-4(cosmos constant) which is not a system thus making simplicfication difficult. I'm assuming that we can still use the previous arguments and assume that the metric coompontents Gtt and...
17. ### Calc I: Possible to Self-Teach?

Calculus is a lovely tool used to solve certain fundamental problems. The mian ones are the area beneath an arbitrary curve, and the other is the slope of a tangent line. Let me give you an idea as to how to do this. Say you're driving in your car and you want to know how fast you're going...
18. ### Putnam triangle problem

I drew the corssection along the diagonal like you said i should. I may make logical errors, but i would never make such a gross visual misconception. i really do need to work on thigns that require more computations. I become very intimidated by them and always back down. Though i...
19. ### Putnam triangle problem

Yes to the first part. what was the mistake? I actually know nothing about putnam, some of the problems are fun to solve every now and then, but some problems are annoying.
20. ### Is this professor cool or what?

sorry but what he did was incredibly immature. He should have just sent the kid away for the remainder of the period. I will admit though, it was very funny.
21. ### Putnam triangle problem

I meant side B. no we don't know their exact values the idea is the find which angles(value of the paramtre a) gives the lowest perimeter. The only difference is that ti'll be fully sinosoidal and the root will be eliminmated whihc helps greatly but still. Also how the hell did THIS problem...
22. ### Putnam triangle problem

What other ways are there to compute it(i'm not really interested in this problem but the fact that i don't know the solution is making me upset). i have an other idea as to how but its probably going to turn out ugly anyway.
23. ### Studying A quick question about textbook quality

Why is that i always see and hear people complaining about textbooks? It is true that there are many bad textbooks but why do they buy them? Can't they read reviews or ask around like i do? Also there are many good textbooks and as a self learner I think my opinion counts for something. A...
24. ### Putnam triangle problem

ok this is what i did. First thing I did was , use the sine law to determine side N. I got what you would expect (sin2a/sina)A=B. Now of course B(sina/sin2a) is constant. I will let sin2a/sina equal u i then used the law of cosines to determine the side that is opposite to the obtuse angle. I...
25. ### Putnam triangle problem

how should i go about proving it? Is the solution computation intensive?
26. ### Putnam triangle problem

1. given a triangle with sides A, B and C, where angle a is equal to 2b ,side A is fixed and angle c is obtuse what is the minimum possible perimetre? 2. The cosine law and the sine law are relevant 3.I tried to mkae function of the square of the preimrtre but the computations...
27. ### Topology by munkres

I'm planning on buying this book, but since its so expensive I'm looking for as much information as possible on it. So you're input would be nice. Also if you have some pdf files with a chapter or so, that would really help.
28. ### Question about the weak field approximation

I already do understand this. This is actually the first time I've encountered taylor series(outside of derivation). Its cool. anyway I understand einstein's equation, thus I'm happy it was my original objective. I started studying mathematics last june(conics) and I'm so happy to have finally...
29. ### Question about the weak field approximation

ok the first part makes pefect sense. however i still don't quite understand what you said about the second part. I:E why does the inverse matrix term equal epsilonN^munu rather tahn n^uv +h^uvepsilon i think I understand now, but any extra explanation would be better.
30. ### Question about the weak field approximation

so essentially what we're doing i we are guessing that that certain term is the inverse. and since epsilon is small we can ignore the higher order terms in epsilon without making too much of an error. I still don't think I udnerstand it all that well, but I have a better idea. Still why...
31. ### Question about the weak field approximation

My question is how to do we taylor series expand it. with respect to what ? where do we get that c is equal to -1 and what do you mean by first order? so essentially how do we approximate it?
32. ### Question about the weak field approximation

where do we get the negative sign? and aren't the two matrices multitplied by one another equal to the indeitity map and just that. Where do the higher order terms come from?
33. ### Question about the weak field approximation

my question is how do you derive the inverse from a series expansion(i'm assuming that the term first order means that there is a series expansion). also: http://www.mth.uct.ac.za/omei/gr/chap7/node3.html [Broken] In step 23 they show the formula for the christoffel symbols, but in the...
34. ### Question about the weak field approximation

Wait can you explain how we get the formula for the inverse of the perturbed metric ? I mean derive it via the the expansion(seeing as how you said first order I'm assumign you used one). Please I'm very close and would appreciate it.
35. ### Studying Looking to start studying real mathematics.

no but it would be nice!
36. ### Question about the weak field approximation

How come in the weak field approximation, where the metric is equal to, ds^2=-(1+2phi)dt^2 + dr^2(1-2phi). where of course dr is the three distance. why is phi multiplied by 2? I have two more stupid question regarding a different approach. please just explain it to me as i want to to see...
37. ### Studying Looking to start studying real mathematics.

hi physics forum. As many of you know, I've been studying general relatvity(its going quite well), but I'd like to delve into real rigorous mathematics. so essentially I'm looking for introductiosn to various topics, especially topology abstract algebra and differential geometry. Could someone...
38. ### Question about the energy momentum tensor

why do we define it that way? What properties make it the best possible choice for the gravitational field?
39. ### Einstein hilbert action

So essentially it used because its the simplest, most general(encodes curvature) involves the inverse metric, the ricci tensor, etc.. and such. So essentially its simple and encodes all the information that we may want tin the field equations... This is the first time I've emcountered this...
40. ### Einstein hilbert action

Yes but what is the intuition behind it? What lead hilbert to choose that particular action?
41. ### Einstein hilbert action

Can someone explain to me why this is the appropriate action?It makes some sens that that would be used, but I'd like a detailed explanation from someone familiar with the topic. Why is it the one that yields the proper equations?
42. ### Rate of change

You just multiply the derivative of x with respect to y by 6(chain rule). You can find x as a function of y by solving for it so x=12/y^2.
43. ### Partitions of unity

what are they exactly?
44. ### Discret mathematics problem

Yes its just that and I'd like to know how to prove what combination requires the greatest number of moves.
45. ### Discret mathematics problem

Given n marbles arrayed in a square with n+1 slots(slot n+1 being empty(labelled with numbers from 1 to n+1) you have to bring them all from their orginal positions to a position in whcih bringing them back woudl take the most moves. The rule is to move each marble to the adjacent square...
46. ### Original works

Yes that's what I'm referring too.
47. ### Antisymmetrized tensor product

One is already pretty clear. It always has been.
48. ### Original works

I was trying to find the orginal works of laplace and grassman, but could not find them. Well I found some on amazon but they were permanently out of stock. So I ask you, where in the world can I find them? Also are there any other good texts that you'd liek to recommend(I speak fluent french)?
49. ### Exterior derivative

so where does the other thing come into play?
50. ### Exterior derivative

what i did was (p+dp)^(q+dq) -p^q. i evaluated that and got + p^dq +dp^q +dp^dq what do we do with that? Wher do the other parts come in? Again I'm sorry for my stupidity.