General relativity Definition and 999 Threads

Homework Statement I have been trying to understand the actual applications and mathematics behind Einstein's Field Equations. I have watched a two hour long lecture on how they were derived and have pretty much understood it, however I still don't know how to actually "use" Einstein's Field...

The CMB used to be gamma rays, right? And now it's microwaves - more redder energy: so where did the rest of the energy go?

I'll begin by admitting that I did not scroll through the entire list of threads to see if there was already a post similar to the one I am beginning. I do apologize if I've broken any rules but I gave up searching after 6 pages and noticed there were at least a hundred more. My question...

Hi, everybody. I have some problem with Wald's statement shown in the picture. This is from the last paragraph in Page 178. He claimed that there are only solutions with two of the p_{\alpha} positive and one negative. But it's easy to find out that if two of the p_{\alpha} are negative while...

I am wondering as to how many metrics have been discovered that obey all the laws of General Relativity? I am posting the ones that I have briefly studied, please post more if you have knowledge of them. Schwarzschild metric: c^2 {d \tau}^{2} =\left(1 - \frac{r_s}{r} \right) c^2 dt^2 -...

This is a question on the nitty-gritty bits of general relativity. Would anybody mind teaching me how to work these indices? **Definitions**: Throughout the following, repeated indices are to be summed over. Hodge dual of a p-form X: (*X)_{a_1...a_{n-p}}\equiv...

Hi guys, I was reading some stuff about general relativity and the first impression is that isn't completely the follow-up to SR. In what I've read it has a different assumption about inertial frames, that they are only significant only locally. What does this really mean and what are the...

Hello. For all those to whom the concepts of general relativity, big bang and universal expansion are not clear, I just updated my page of cosmology. There I presented a rather simple proof of the Friedmann equations, that are the particular case of the Einstein's equation of General Relativity...

General Relativity -- Motion in Newtonian Limit Homework Statement Assume that the metric of space-time in a weak gravitational field, \frac{\phi}{c^2} << 1 is ds^2 = (1 + \frac{2\phi}{c^2})c^2 dt^2 - (dx^1)^2 - (dx^2)^2 - (dx^3)^2 for some arbitrary scalar function phi. Use the...

Hello, I was working out of a text for my own knowledge and I ran into a slight snag which has become bothersome. First I was asked to find the condition on a linear transformation for which the dot product u \cdot u= u_0^2 - u_1^2{} is preserved. Easily I found that for u' = \Lambda u our...

Suppose a photon with speed |\vec{v}(t)|=c. With its frequency f(t) it has the momentum h/c^2 f(t)\vec{v}(t). Further suppose a (classical) gravitational field \vec{g}(x,y,z)\in R^3. Putting the photon at position s(t)\in R^3 into the field and equating a) the force as the product of...

I am trying to understand the implications of the Birkhoff theorem as it applies to a cavity within a spherically symmetric, stationary thin shell. Is the region of space-time within the cavity described by the actual Minkowski metric diag{1,-1,-1,-1}, or is it some other metric with constant...

Consider a man standing inside lift which is free from all external influences (gravitational or otherwise). Suddenly someone begins to pull the lift with some acceleration. Now if the man releases a ball he sees it falls onto the floor. Since he sees the lift at rest he concludes that there is...

I have used GRTensorII and Cadabra for some time. And I think Cadabra have great potential for GR. But the current vision of Cadabra only deals with abstract tensor analysis, not with writing out of explicit components. So ,(eq :)when I try to check my final tensor expressions of solutions of...

I'm currently in my last year as an undergrad B.S. Physics and am looking for graduate schools that would be suitable for me to study GR. I know that many schools are lacking in this department, i.e. my own school, so I'd like to find one that would allow me to study the area of General...

Homework Statement Hello, I have a little problem with this figure, this is not an assignment or something else I just don't understand how we can find that d∅=gocos3(α)/c² *dz Homework Equations go=G*M/R² with R the sun's radius The Attempt at a Solution I wrote all what I can deduce...

The question is pretty simple, why would we even want to combine the two big theories to create a unified theory of everything? Is it not better to simply say that the laws of physics behave differently at these scales and that a theory of one doesn't necessarily have to work with another...

hello, i want to know if there an experience that shows how can we verify the quantum physics that studies everything that is subatomic up to quark ,and thank u again

I am a high school student. I looked up Special relativity and grasped it pretty easily, without needing to learn any new math. But when I tried to read about general relativity, I was immediately confused by all the math, equations and notation. My problem is that I have no idea where to...

I'm currently doing a course on general relativity, and I'm struggling with the following exercise - I would greatly appreciate the help anyone might offer. Whilst not technically homework (not assessed or in a tutorial set) it is from a collection of difficult questions from a recommended...

This is from an older thread: If that's true, how does the electron's spin cause it to behave like a small bar magnet? Why does relativity demand an electron have a magnetic field? Thanks!

If I am traveling in a spaceship in a speed close to the speed of light the time will delay right? However I am in space where there is low gravity which means that time will speed up. What will exactly happens to time will it speed up because of low gravity or delay because of the speed...

Hi. I saw this: http://physics.stackexchange.com/questions/35431/is-the-law-of-conservation-of-energy-still-valid Now, if that's the case, then I wonder about a related question: can general relativity be used to create perpetual motion machines? If not, then why not (i.e. how does energy...

In special relativity clocks are used to record events and proper time gives the time in an inertial frame so two times are used. In general relativity I only see proper time being used. Is there an implicit understanding about clocks?

Author: Bernard Schutz Title: A First Course in General Relativity Amazon Link: https://www.amazon.com/dp/0521887054/?tag=pfamazon01-20 Prerequisities: Better part of a undergraduate (BS) physics program Contents: Undergraduate, upper level; Graduate, introductory Table of Contents...

Is there a list of all the general relativity lecture videos somewhere? Most of the videos I find do not have very good resolution of the black boards.

Homework Statement Show that Ui \frac{dU^i}{d\tau} = 0 Homework Equations Raising Indices: Ui = gkiUi = Ui where gk is a dummy index The Attempt at a Solution I'm interpreting this question to mean a scalar multiplying each component of a four vector = 0. Also, since the same...

Hello (a) The universe U is a topological space whose elements are called events and as each event has a neighborhood homeomorphic to R^4. (b) A local coordinate system is a homeomorphism between an open subset of U and a bounded subset of R. (c) A world line segment is a continuous...

Author: Bernard Schutz Title: A First Course in General Relativity Amazon Link: https://www.amazon.com/dp/0521887054/?tag=pfamazon01-20 Prerequisities:

Author: L.P. Hughston and K.P. Tod Title: An Introduction to General Relativity Amazon Link: https://www.amazon.com/dp/052133943X/?tag=pfamazon01-20

Author: Sean M. Carroll Title: Spacetime and Geometry: An Introduction to General Relativity Amazon Link: https://www.amazon.com/dp/0805387323/?tag=pfamazon01-20 Download Link: http://ned.ipac.caltech.edu/level5/March01/Carroll3/Carroll_contents.html Prerequisities: Contents: Contents: 1...

Author: Robert M. Wald Title: General Relativity Amazon Link: https://www.amazon.com/dp/0226870332/?tag=pfamazon01-20 Prerequisities: Contents:

Hi all, I'm having a discussion with someone who believes they understand GR, here is their understanding of how gravity works... "The time and space at your feet are different from the time and space at your head. This has been experimentally verified, especially in terms of the time...

What is the best software for GR calculations ? GRTensor ?

can you explain me please the difference between the special and general relativity i did some research and only what i found and what i understand and i ' m not sure is that te SR is applied only in inertial frame and the GR is applied in the noninertial frame correct me please if i ' m...

I'm in the United States, taking undergraduate courses, and I believe I had what was an introduction to special relativity in Modern Physics class (Lorenz transformations, time dilation, the relativistic doppler effect, time dilation, length contraction, etc.). I just wonder what class general...

I have a broader question on this - is mass at all properly defined in GR context, including rest mass or so-called invariant mass? Leaving aside concept of mass gain, I have been under the impression that mass itself is defined in different ways in different situations in GR, with caveats...

So this is purely for self-study purposes. Say I'm very keen on understanding GR well, but I don't even have the prerequisites done for even starting to grasp GR. Would anyone be able to give an outline of the skills necessary in understanding GR? An outline would look something like this...

Hello, Can anybody tell me what is meant by exact solution to General Relativity or exact solution to Einstein's field equation. -- Shounak

Hi, I have some questions about general relativity. I'd appreciate if somebody could enlighten me :) I heard that according to Einstein, objects do not accelerate in a gravitational field, it is just spacetime that is warped around them. So what exactly does this mean? Is it that due to...

Hello everybody, I was watching a documentary about black holes the other day and I noticed something odd. General Relativity is said to break down when you apply the mathematics on a singularity. In this case, the center of the black hole. The radius of a singularity would be 0. Now there...

I am unable to find any source describing at any lengths transformations of the type x \rightarrow -x beyond the case of static spacetime (and even in the case of static spacetime, it is rarely the fundamental definition, which tends to be more along the lign of orthogonality with an...

People seem to be seriously looking for "Lorentz violating" neutrino oscillations - meaning direct violation of special relativity. What is a short name for the symmetry that distinguishes general relativity from special (the symmetry between acceleration and gravity)?

I think I read once that length does not exist in general relativity, though I'm not sure if I got that hopelessly muddled or if there are subtleties that I am missing. I have a vague understanding of length contraction, but I thought that what I was reading said that there simply is no length...

In f(R) gravity as http://en.wikipedia.org/wiki/F%28R%29_gravity , i have problem with the term [ g_ab □ - ∇_a ∇_b ] F(R) , well actually is [ ∇_b ∇_a - ∇_a ∇_b ] F(R) , but F is a function of Ricci Factor and Ricci Factor is expressed as a(t) ( scale factor ) . for the a = b = 0 i say this...

Homework Statement The gravitational redshift tends to decrease the frequency of light as it travels upwards a distance h,\frac{\Delta{f}}{f_{0}}=\frac{-gh}{c^2} integrate both sides of this equation (from the surface of the gravitation body out to infinity) to derive the expression for the...

I would like to know if there are exact solutions using General Relativity to determine: 1) time dilation from velocity, and 2) velocity from redshift (arising from kinematic movement). I understand that Special Relativity can handle both of these questions, but the implementation of SR is...

I know little to nothing about G.R. but it is interesting to look up knowledge,especially physics, so please correct me if I am wrong.. It is easy to picture how one giant mass distorts spacetime on 2D scale, but what if there is multiple bodies of masses present and would this turn into a...

Homework Statement I have derived the metric in for 2D Rindler space in a previous problem and it is explicitly given again here: ds^2 = dx^2 - (dx^0)^2 = dw^2 - (1+gw/c^2)^2(dw^0)^2 , where (x^0, x) are Minkowski coordinates in an intertial system I and (w^0,w) the Rindler coordinates of a...

On 2 October, 5 days from now, Derek Wise will give an online international seminar talk which will be a followup to his June 2012 paper with Stefen Gielen---as I recall a lot of us found that paper very interesting and it topped the second quarter MIP poll. So I want to review that paper, the...