Recent content by Discman

Dear kimbyd, thank you for your clarification. Still some questions A perturbation longer than the horizon scale means that a part of it, let's say, the middle part, is lying sub horizontally. Doesn't that part also not oscillate? Are there very small perturbations, so the latest generated...

I don't still understand what happens before the re-entry, especially in radiation period? The period of acoustic waves is always measured right from end of inflation. During inflation the Hubble horizon is indeed the point till where gravitation acts. But I understand from your answer that...

Still I don't understand the meaning of the re-entry of perturbations in the horizon. OK, I understand the shortening of the Hubble radius opposite the length scales during inflation and the extension of the horizon after inflation. But what happened in the time after inflation till the...

Thank you very much. By coincidence I was just beginning to think into that direction when your answer arrived.

With these numbers I am pointing of course at the cosmic standard ruler which is used in the BAO. Speed fundamental tone of acoustic waves 0,6 c, time to sound horizon 380.000 yrs And the calculated standard ruler is the radius of the sound horizon shell (not the diamater) So, again, why 2 times...

What I'm doing wrong? speed X time = distance 0,6 c X 380000 jr = 228000 ly times expansion of 1000 gives 228.000.000 ly This is equal to about 72 Mpc Why is the standard ruler 2 times as long: about 150 Mpc What is wrong, or do I forget in my calculation?

Yes, the more I'm thinking about my last remark: as a co-mover I see it in the same way as Wayne Hu and as a steady observer on Earth I see according to bapowell? Right?

I'm getting more and more confused. On all the figures of Wayne Hu I see oscillating sound waves originating right after end of inflation. Now you are telling me that they start oscillating after re-entering. Also on calculating the wavelength of the fundamental mode they take the full 380.000...

Not totally. Why is the late re-entry always specified. Does this mean that all we see on the last scattering surface derives from the period between that re-entry and the sound-horizon. What I also not understand is the correlation right after the end of inflation between the Hubble sphere...

After much reading I still don't understand your answer that there are already perturbations right after end of inflation. From this kind of figures they reappear late in the baryon-photon period. Do I make wrong conclusions from this and other figures? A

Thank you all, but bapowell catches my problem very well. Before I can react I have to study the interesting paper he quoted for me what will take some time.

I don't understand the difference between the Jeans Mass and the fundamental mode. Both are reaching till the horizon but according to me is the Jeans mass not oscillating. So what is the relation between a Jeans mass and the fundamental mode of the acoustic waves?

Thank you. From your answer I now understand that perturbations were re-entering all the time, also before the beginning of the matter era.

Sorry, I'm not very clear. I am talking now about the subhorizon fluctuations and my question is what happens to them when perturbations re-enter the horizon. Does a great photon concentration from the radiation era now fall together with the baryons in a potential well of the re-entering...

Then still there is the problem that the length of the basic tone is calculated right from the end of inflation till the sound horizon and not calculated from the re-entering till the sound horizon. Is the fluctuation in the radiation era a part of the total wavelength?