B How did quarks appear in the Universe?

[Sphere]

Hello, from what I understood at the very beginning of the universe, the universe was too dense and too hot to allow matter (atoms) to exist, so at the very beginning, the universe was a kind of soup of quarks (components of protons and neutrons). What I was wondering is how quarks appeared in the universe ? How were they created ?

Thank you !

 

[malawi_glenn]

That is the same as asking where the electrons came from. Or photons.

 

[Orodruin]

The whole universe was in a hot dense state.

That effectively means that quarks, photons, electrons, and other elementary particles were continuously produced and annihilated in the hot dense plasma. You may then ask "where did the hot dense state come from?" The answer to that is more elusive and the standard Big Bang model does not address that question.

In inflationary models of the Universe (which are popular but for which there is no real experimental evidence), the hot dense state in essence results after inflation ends and the inflaton field that was responsible for inflation dumps its energy into the standard model sector.

 

[artis]

In inflationary models of the Universe (which are popular but for which there is no real experimental evidence), the hot dense state in essence results after inflation ends and the inflaton field that was responsible for inflation dumps its energy into the standard model sector.

Say even if we find substantial evidence for such field isn't that just "kicking the can down the road" ?
Now instead of not being able to contemplate how and why elementary particles arise we are instead not being able to understand where this mysterious inflation field comes from?

 

[Orodruin]

Say even if we find substantial evidence for such field isn't that just "kicking the can down the road" ?
Now instead of not being able to contemplate how and why elementary particles arise we are instead not being able to understand where this mysterious inflation field comes from?

You can always do that whatever answer you get. Most children happily play that game, but physics is not about finding out some ultimate unquestionable truth. It is about describing what we can infer about how the universe behaves from experimental evidence.

 

[Sphere]

If I understand correctly all the elementary particles that formed the matter that exists today were created from the energy of the inflation field

 

[artis]

You can always do that whatever answer you get. Most children happily play that game, but physics is not about finding out some ultimate unquestionable truth. It is about describing what we can infer about how the universe behaves from experimental evidence.

I am not against good theories based on experimental evidence, what I was trying to say is that I doubt we will ever have good "experimental evidence" for the very beginning of the universe, whatever it was even like. Unless of course we can either replicate the conditions or find the associated fields/particles etc.

As for "unquestionable truth", maybe it's not explicitly said but I think many scientists and layman alike do chase an answer to find out some fundamental truth to nature and reality, it's definitely part of the motivation.

 

[artis]

If I understand correctly all the elementary particles that formed the matter that exists today were created from the energy of the inflation field

https://en.wikipedia.org/wiki/Inflation_(cosmology)

Under "Reheating"

Reheating​

Inflation is a period of supercooled expansion, when the temperature drops by a factor of 100,000 or so. (The exact drop is model-dependent, but in the first models it was typically from 1027 K down to 1022 K.[23]) This relatively low temperature is maintained during the inflationary phase. When inflation ends the temperature returns to the pre-inflationary temperature; this is called reheating or thermalization because the large potential energy of the inflaton field decays into particles and fills the Universe with Standard Model particles, including electromagnetic radiation, starting the radiation dominated phase of the Universe. Because the nature of the inflation is not known, this process is still poorly understood, although it is believed to take place through a parametric resonance.[24][25]

 

[Orodruin]

As for "unquestionable truth", maybe it's not explicitly said but I think many scientists and layman alike do chase an answer to find out some fundamental truth to nature and reality, it's definitely part of the motivation.

Then they chose the wrong carreer. You can dig deeper and deeper but it will always be possible to keep asking ”why?” and eventually you reach a level which simply is not answerable - at least not in finite time.

I would say what drives most scientists is to find out how things work and describe it. That is not the same as requiring a fundamental truth.

 

[malawi_glenn]

Physics is a descriptive science driven by experiments, observations and interplay with mathematical theories. If you want to find THE Truth^TM, you're in the wrong field.
To quote my favorite character in the bible "what is truth?" John 18:38

 

[ohwilleke]

Hello, from what I understood at the very beginning of the universe, the universe was too dense and too hot to allow matter (atoms) to exist, so at the very beginning, the universe was a kind of soup of quarks (components of protons and neutrons). What I was wondering is how quarks appeared in the universe ? How were they created ?

Thank you !

We don't really know.

The earliest point we have good observational confirmation of is Big Bang Nucleosynthesis during which, one protons and neutrons were around, and they formed atoms in roughly the proportions we see today modified by later processes in stars that go supernova and spread around heavier elements. This happens is maybe 15 minutes or an hour (give or take, I'm writing from memory) after the Big Bang in the conventional chronology of the Universe.

Normally, in the Standard Model, when pure energy, such as photons gives rise to photo production of quarks, it creates equal numbers of antiquarks, which would end up annihilating and that leaves you nowhere.

If you just extrapolate the Standard Model as we know it back to the Big Bang, you get a large positive baryon number (baryon number means quarks minus antiquarks, divided by three) for the universe as a whole at the moment of the Big Bang, because the only process that can change the aggregate baryon number of the universe in the Standard Model, which is called a sphaleron process that only takes place at extremely high energies, wouldn't create enough quarks fast enough, from a starting point of zero, to produce the number of quarks that we see today by Big Bang Nucleosynthesis, at which point the quarks had to be there.

So, either there are new physics at high energies, or particular to the early moments of the universe (in either case, that can't be deducted from the Standard Model), or the quarks we already there at t=0 of the Big Bang.

There are a variety of theories out there to explain where quarks comes from with beyond the Standard Model physics, but while science inspired, they are ultimately just untested speculation.

Previous Physics Forums discussion of the issue can be found here.

For what it is worth, I have a favorite theory (along the lines of this paper), but really there is no more concrete evidence for it than any other theory regarding this question. I like that particular theory because it is minimalist in its need for new physics.

 

[malawi_glenn]

in the Standard Model, when pure energy, such as photons gives rise to photo production of quarks, it creates equal numbers of antiquarks, which would end up annihilating and that leaves you nowhere.

What about CP-violation? Sure it is not enough CP violation in the SM to provide baryogenesis.
Edit: never mind, SM has wrong kind of phase transition...

 

[ohwilleke]

If I understand correctly all the elementary particles that formed the matter that exists today were created from the energy of the inflation field

You shouldn't take that too seriously. There is some evidence for cosmological inflation, although it isn't rock solid. But there is basically no positive evidence for cosmological inflation being the means by which the baryon number of the universe (i.e. quarks minus antiquarks divided by three) came to be. New quarks and new antiquarks get created all the time, but only in ways that conserve net baryon number in the current significantly post-Big Bang temperatures era.

 

[ohwilleke]

What about CP-violation? Sure it is not enough CP violation in the SM to provide baryogenesis.

You need baryon number non-conservation (limited to the sphaleron process in the SM) plus sufficient CP violation in the available amount of time during which temperatures post-Big Bang are still high enough to create sphaleron processes. The conditions are named after the guy who first articulated them.

A sphaleron requires a roughly 9 TeV energy to be concentrated at a density of about 1000 times that of the mass-energy density of a proton (i.e., a radius of about 8.4 * 10^-17 meters; the Schwarzschild radius of a 9 TeV sphaleron is about 2.4 * 10^-50 meters; the Planck length is about 1.6 * 10^-35 meters) citing N.S. Manton "The Inevitability of Sphalerons In Field Theory" (March 27, 2019) ("Based on Lecture at Royal Society Scientific Discussion Meeting: Topological Avatars of New Physics, 4-5 March 2019") at page 7-9 (citation omitted),

It would probably require a collider at least 100 times as powerful as the LHC to create a sphaleron - probably something that the next generation of more powerful particle colliders will not achieve. This would require a mass-energy density more than nine million times greater than either a neutron star, i.e. 10^17 kg/m^3, or the mass-energy density of a minimum sized stellar collapse black hole. There is nothing in Nature that creates the necessary energy-densities post-Big Bang.

Basically, the only SM process known has to finish its job in a fraction of a second before it cools down too much, and needs a lot of CP violation that the SM doesn't provide in sufficient amounts in this process.

 

[malawi_glenn]

limited to the sphaleron process in the SM

Yeah I just realized that SM has wrong kind of phase transition.
I think I wrote about this in my PhD thesis now that I think about it even harder...
have to read that darn book again at some point.
Perhaps I will read it on my little trip instead of my Stephen King book...

 

[ohwilleke]

Yeah I just realized that SM has wrong kind of phase transition.
I think I wrote about this in my PhD thesis now that I think about it even harder...
have to read that darn book again at some point.
Perhaps I will read it on my little trip instead of my Stephen King book...

Less likely to give you nightmares.

 

[Orodruin]

pure energy, such as photons

It needs to be pointed out that there is no such thing as ”pure energy”. This is a common source of misconception here at PF. Photons have energy. They are not energy. Energy is a property, not a substance. There is nothing that makes the energy of photons any more ”pure” than that of other elementary particles.

The conditions are named after the guy who first articulated them.

The Sakharov conditions.
- C and CP violation.
- B violation.
- Out of thermal equilibrium.

wouldn't create enough quarks fast enough, from a starting point of zero

It wouldn’t create any quarks at all starting from zero unless you somehow already have a non-zero B+L. There are different ways to accomplish this.

 

[malawi_glenn]

there is no such thing as ”pure energy”

*drops mic*

 

[Orodruin]

View attachment 304837
*drops mic*

I can’t help but notice that can says ”pure crystal energy”.

 

[malawi_glenn]

I can’t help but notice that can says ”pure crystal energy”.

Don't judge the book by its cover, it is pure energy which you can drink thanks to the crystallization process of quantum black holes

 

[malawi_glenn]

And since you also are in sweden, you can purchase these. It is like having a fusion reactor in powder format

 

[Orodruin]

Don't judge the book by its cover, it is pure energy which you can drink thanks to the crystallization process of quantum black holes

I used to include this in my talks to lighten the mood …

 

[malawi_glenn]

I used to include this in my talks to lighten the mood …

So we have proven the existense of both pure energy and dark matter. Thread closed.

 

[ohwilleke]

It needs to be pointed out that there is no such thing as ”pure energy”.

Fair point.

The Sakharov conditions.
- C and CP violation.
- B violation.
- Out of thermal equilibrium.

Thanks. I was struggling to recall his name and didn't have an easy reference at hand.

It wouldn’t create any quarks at all starting from zero unless you somehow already have a non-zero B+L. There are different ways to accomplish this.

Again, providing yet another reason why we can't answer the question without new physics and/or non-zero initial conditions.

 

[Sphere]

Thank you all for your explanations!