Recent content by Dr. Strange

This scenario is disturbing to me. The general idea here is that a hypothetical field which creates negative energy densities is somehow able to decompose into a overdensities of a hypothetical particle that isn't part of the standard model. Let's assume we can continue from here without ever...

I am far from an expert, but if you're suggesting that dark matter pre-dates the inflation field then you're back at the original problem: inflation removed all inhomogeneities in whatever came before. I would assume that includes any dark matter overdensities.

I'm trying to understand the mechanisms of the anisotropies in the CMB. The general idea is that there are fluctuations in some field (e.g. inflation) and the baryonic and dark matter rush into the space compressing the fluid. The photon energy pushes back on just the baryonic matter while the...

Yes. I am basically asking how much energy a box full of CMB light would contain. In other words, if you knew what the total cubic volume of the universe was, could you use the temperature of space to calculate the total energy of the universe?

In the graph below, the blue line represents FLRW without Λ, which was our 'expected' value before 1998. After the discovery that SNe Ia did not follow this relation, we added "Einstein's Greatest Blunder" back into the metric and got the red line. While you are technically right, practically...

If I have a 1 km cube of empty space at a constant temperature of 2.7 K, how much energy do I have? That is, if I know the total volume of space in the universe and I know what the average temperature of that space is, can I computer to total energy of the universe?

Deceleration has nothing to do with it. The 'expected' value was based on the FLRW metric, which is a linear relation. People suspected the universe was decelerating, but there was no 'law' to my knowledge that created an expected value.

Getting back to the original question, is the 'Optical Depth', the tau, τ, of the ΛCDM parameters, the depth of the CMB 'surface'? If t1 = 380,000 years and t2 = 487,000, is the optical depth then 107,000 years (or the equivalent in z)?

Yes, that was very helpful. Is there any relation between the first peak of the BAO spectrum and one of these z values (for example, the 1090 value quoted in the Plank final results).

How does that happen if the regions are not causally connected?

Sorry, I didn't follow all of that. In layman's terms, which value represents the red-shift where the electrons traveled freely through the universe. Also, if it isn't asking too much, could you also give a layman's description of optical depth, τ. I see it's a parameter to ΛCDM and if you...

Were all parts of the universe in causal contact before inflation?

I'm trying to visualize this, but something is giving me trouble. At the end of inflation, were all the points of space in causal contact with each other?

Wikipedia gives the redshift of recombination at z = 1500 (roughly 4,000 K). The Plank report list a 'redshift for which the optical length equals unity' and gives a value of 1090. What is the difference between the two?

Yes, thank you. I'm trying to zero in on what problems, exactly, are solved by Inflation. That's why I needed the clarification. So let me try it again. You seem to be saying that tiny fluctuations in a normal quantum field would grow into densities that we see in the CMB (with much larger...