Was the initial condition extremely cold?

[Atlas3]

If all matter was at maximum density, would not the temperature have been extremely cold of the sum of all matter? temperature affects density I think.

 

[Drakkith]

Ignoring the problem with there being a maximum density, no, not necessarily. Compression generally heats a substance up for starters. But if you compress something and then wait a long time, it will equalize with the surrounding environment, taking on whatever temperature the environment has. This might be very cold, but it could also be very hot.

temperature affects density I think.

If the only thing you change is the temperature of something, then yes, density is affected. But I can compress something while I heat it up, or I could cool down a gas while expanding the volume it is contained in (and thus decreasing its density).

 

[PeterDonis]

If all matter was at maximum density

What matter? At what time?

If you are talking about conditions at the Big Bang, the matter was at very high density, but not "maximum" (as @Drakkith points out, there is no such thing), and it was extremely hot, not extremely cold.

temperature affects density I think.

You should not expect your intuition about ordinary matter here on Earth, where yes, cooling something down tends to make it denser (other things being equal), to apply to very different conditions like the early universe.

 

[Atlas3]

@Drakkith @PeterDonis I cannot form a complete paragraph as I have impairments that effect my skills.
What matter? All of it. Dark if it is. I supposed this because if there were an event, what is in our universe has spawned from a consolidated mass. That is just what made sense to me. Then it occurs to me @Drakkith that from what you supposed of compression and heating has an opposite circumstance of cooling and condensing. I like discussion and not arguments so I appreciate your replies. Thanks

 

[PeterDonis]

What matter? All of it.

Ok, then it looks like you are talking about the early universe, so the first part of my post #3 applies.

 

[rootone]

I'm not even sure that 'temperature' has any meaning as a measure of condition in quark-gluon soup

 

[timmdeeg]

I'm not even sure that 'temperature' has any meaning as a measure of condition in quark-gluon soup

I think there is consensus that the "quark-gluon soup" exists at extremely high temperature whereby the analogy of the temperature of a gas due to the kinetic energy of the masses of atoms/molecules doesn't seem applicable.

 

[PeterDonis]

I think there is consensus that the "quark-gluon soup" exists at extremely high temperature

This is correct.

whereby the analogy of the temperature of a gas due to the kinetic energy of the masses of atoms/molecules doesn't seem applicable.

But I'm not sure where you're getting this from; do you have a reference?

 

[timmdeeg]

But I'm not sure where you're getting this from; do you have a reference?

No, I haven't. Regarding kinetic energy I was reasoning in terms of the rest masses of the constituents of a proton. Their contribution to the mass of the proton is tiny. But as I realize now, I can't compare confined quarks with those existing in the Quark soup and hence are not confined.
Could you kindly elaborate a little on the kinetic energy of Quarks in both cases?

 

[PeterDonis]

I can't compare confined quarks with those existing in the Quark soup and hence are not confined.

That's correct. Quarks inside a nucleon are in a different state from quarks in a quark-gluon plasma.

Could you kindly elaborate a little on the kinetic energy of Quarks in both cases?

We don't measure the kinetic energy of quarks directly in either case. But for a quark-gluon plasma, we can make assumptions about the distribution of kinetic energies of the quarks that are similar to what we do for ordinary gases, so we have a statistical model that is similar to the models we use in the kinetic theory of gases.

For quarks inside a nucleon, this sort of model doesn't work. In fact, there isn't a single generally accepted model of a nucleon. So I don't think we have a clear answer about the kinetic energy of quarks inside a nucleon. (For one thing, quarks inside a nucleon are probably not in an eigenstate of the kinetic energy operator, so they don't have a well-defined kinetic energy anyway.)

 

[timmdeeg]

Thanks a lot!