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2
votes
1answer
57 views

Number density of CMB photons?

When we talk about the present-day number density of photons ($n_\gamma\approx 10^8 $ $m^{-3}$) in the universe do we mean the number density of CMB photons? I mean there are other sources of ...
0
votes
0answers
23 views

Asymmetry vs. Simple Statistics WRT Matter / Antimatter Ratios

I'm not clear on why physicists suspect, and are looking for, an asymmetry in nature that favors matter over antimatter. Here's a simple thought experiment to illustrate my confusion: Assume I have ...
2
votes
1answer
35 views

C&CP-Symmetry Violation in Baryogenesis

In cosmology, during the big bang; how does C-Symmetry violation allow for a greater number of baryons to be produced than anti-baryons in Baryogenesis, similarly how does CP-Symmetry tie into this?
0
votes
1answer
20 views

EW phase transition and baryogenesis

There are three Sakharov conditions of baryogenesis: CP symmetry violation. Baryon number conservation violation. Thermodynamical equilibrium violation. In SM the first one is satisfied by CKM ...
3
votes
2answers
84 views

Questions about the strange character of antimatter

Its been a few days and i have just been introduced to the concept of antimatter. Every Speck of matter in the world has its anti form basically that we have antimatter whenever we have matter. But I ...
1
vote
0answers
20 views

Few questions about SM baryogenesis

SM provides baryogenesis via leptogenesis due to anomalies and sphaleron processes. I have a few questions on it. How exactly the anomalies in lepton and baryon currents provide convertation of ...
0
votes
1answer
45 views

Sphaleron interactions erase baryon asymmetry?

The sphaleron interactions in the standard model is $(B-L)$ conserving and $(B+L)$ violating. Each sphaleron transition causes $\Delta B$ and $\Delta L$ to change by the same amount so that ...
0
votes
1answer
30 views

phase transition and effect on leptogenesis

What is the effect on leptogenesis in the standard model if the electroweak phase transition is (i) first order and (ii) second order?
1
vote
0answers
19 views

fate of a hadron in a big rip

As I understand it, if you try to "pull apart" a hadron with sufficient force, you just make more hadrons. Would the same thing happen in a Big Rip? (this answer suggests it would, as long as the ...
2
votes
1answer
243 views

difference between instantons and sphalerons

What is the difference between instantons and sphalerons? If they are different, how do they violate baryon and lepton number in the standard electroweak theory?
1
vote
1answer
68 views

Baryogenesis via Leptogenesis

Baryon number is directly violated through electroweak anomaly and so does the Lepton number, for each transition from one vacuum to another. The two violations are of equal amount $\Delta B=\Delta ...
7
votes
4answers
293 views

temperature of electroweak phase transition

How does one estimate the temperature at which electroweak phase transition (EWPT) occurred? Somewhere I have read it is around 100GeV but the reason was not explained.
1
vote
2answers
65 views

Sakharov condition of departure from equilibrium

I have a doubt with the third Sakharov condition which demands a departure from equilibrium. But why is that necessary when both baryon violating interactions and well as CP violation is present in a ...
2
votes
1answer
88 views

Significance of total divergence anomaly term

What is the significance of the fact that the anomany term (calculated from the triangle diagram) is a total divergence? Or, in other words, what is the significance of $$\partial_\mu j^\mu_A\sim ...
2
votes
2answers
150 views

Why did the big bang need to produce equal amounts of matter and antimatter? [duplicate]

I've tried to find an answer for this but couldn't find one. Whats the problem with matter being created with little or no antimatter
0
votes
3answers
107 views

CPT theorem and annihilation of matter and antimatter after the big bang

Is the hypothesis that antimatter is moving backwards in time compatible with the hypothesis of annihilation of matter and antimatter after the big bang? It is said that the big bang should have ...
1
vote
1answer
147 views

Why is baryon or lepton violation in standard model is a non-perturbative effect?

The baryon number B or lepton number L violation in the standard model arise from triangle anomaly. Right? Triangle diagrams are perturbative diagrams. Then why the B or L violation in Standard model ...
0
votes
1answer
174 views

Matter-antimatter asymmetry problem

As we know that matter-antimatter asymmetry is one of unsolved problems in physics. One possible solution to this problem is given as baryogenesis which produce asymmetry in rate of creation between ...
8
votes
1answer
307 views

Baryogenesis only at the Planck scale, or none at all?

I can think of three general ways of explaining why the universe contains more matter than antimatter: (1) Near the Planck time, the universe had zero baryon asymmetry, but at some later time, ...
4
votes
2answers
182 views

Shouldn't LHC have used $p\bar{p}$ collisions, instead of $pp$ collisions, to study baryogenesis?

Baryogenesis is the physical process(es) that produced baryon antibaryon asymmetry in the early universe. That means, the laws that governed the bigbang was baryon-antibaryon symmetric. On the other ...
6
votes
3answers
755 views

Baryon asymmetry

Baryon asymmetry refers to the observation that apparently there is matter in the Universe but not much antimatter. We don't see galaxies made of antimatter or observe gamma rays that would be ...
13
votes
5answers
583 views

Matter-Antimatter Asymmetry in Experiments?

As I hope is obvious to everyone reading this, the universe contains more matter than antimatter, presumably because of some slight asymmetry in the amounts of the two generated during the Big Bang. ...
23
votes
2answers
542 views

Experimental observation of matter/antimatter in the universe

Ordinary matter and antimatter have the same physical properties when it comes to, for example, spectroscopy. Hydrogen and antihydrogen atoms produce the same spectroscopy when excited, and adsorb the ...