Dear all,
I am using stress-energy tensor to derive equation of state of photon gas (assuming it as a perfect fluid).
I completed all the steps except one:
average value of [cos(θ)]^2 over unit sphere = 1/3.
I have no idea how this is so. (θ is polar angle).
I tried integrating over...
All the derivation of the equation of line on complex plane uses the fact that (x,y) \in R^2 can be identified with x+iy \in C.
Thus, they begin with ax+by+c = 0 then re-write x = (z+\bar{z})/2 and y = (z-\bar{z})/(2i), and substitute it into real plane line equation to get it in complex...
I am having a trouble finding relationship between 'a' and 't' by integrating friedmann equation in a multi-component universe.
It would be very helpful if you can help me with just
matter-curvature only universe and matter-lambda only universe.
The two integrals looks like following...
thank you so much for taking your time to give your response!
I would definitely be willing to invest those time.
My summer plan is just study math and physics (which I really have been keeping past one month by going to library almost every day!)
Do you have any recommendation on...
Thank you so much for the helpful link!
I am definitely interested in derivation! I feel like I truly understand only when I really understand the derivation. It would really be wonderful if I can get hold of text that explains the derivation.
Otherwise, understanding how it is used, and...
Hello everyone.
This is more of statistical / probability question.
I need to understand Maxwell-Boltzmann distribution, but I find wikipedia article way out of my league.. I really can't understand lot of what they are saying.
Is there a good reading material that I can introduce myself...
Thank you for reminding me everyone, it has been long since I took my mechanics class.
Right, the escape velocity can be computed by
potential energy + kinetic energy = 0
which makes
v = sqrt(2GM/r).
But, what causes the difference between hyperbola and parabola?
When comet is...
Hello.
I read from a calculus book (Larson) that
shape of comet's orbit is determined by its velocity in following way.
Ellipse if v < sqrt(2GM/p)
Parabola if v = sqrt(2GM/p)
Hyperbola if v > sqrt(2GM/p)
where p is the distance between one vertex and one focus of the comet's orbit...
Hello,
I just have a quick question about CMB.
Why is it from 380,000 years after big bang? Why not before?
Will you please tell me if my explantion is right?
Before 380,000 years, the universe was too dense to have any neutral atoms (free electrons and protons / plasma). And...
Thank you so much for all your help everyone! and Naty1, thank you for such a strong enthusiasm. I will sure read that article and ask you more if you do not mind!
Sincerely
Question:
With the assumption that Hubble parameter 'H_0' from v=(H_0)*r is constant,
I would like to ask you a question.
Will there be more and more objects that will not be visible as time goes by?
I ask this because, if some object is initially
some 'x' light years away, say...
Question:
Please correct me if I am wrong:
the oldest light that we just begin to receive is around 14 billion light years old.
This light originated from a lightsource that was about
30 million light years away (380,000 years after big bang.)
So although the lightsource was 30 million...
Thank you so much for your help.
I only have finished Halliday Resnick Walker's Fundamentals of Physics.
I am not sure if that is enough for the prereq? I sure have never seen
the energy density expression in HRW though..
so do you mean if I integrate the element "ε(f) df" over all the...
Okay... probably no one knows both of the university.
They are both extremely small school.
But please read this post, and I think anyone can help me out here.
Before I describe my situation, I thank you for your help.
Like many of you here, I am a physics enthusiast.
When I first took...