Does Chiral EM Asymmetry Imply Matter-Antimatter Asymmetry?

In summary, a Science Daily report discusses observations of cosmic gamma rays that suggest that magnetic fields in the universe disproportionately have left handed rather than right handed helicity, which could explain matter-antimatter asymmetry in the universe according to a 2001 theory proposed by physicist Vachaspati. This theory, called electroweak baryogenesis, relies on topological solutions to the Yang-Mills equations called sphalerons. These solutions, which are unstable and have a finite lifetime, can mediate baryon and lepton number violating processes during the electroweak phase transition. Vachaspati also proposes that the magnetic field associated with the monopoles involved in the sphaleron process is what leads
  • #1
ohwilleke
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A Science Daily report discusses observations of cosmic gamma rays that suggest that magnetic fields in the universe disproportionately have left handed rather than right handed helicity. It goes on to suggest that under a 2001 theory of another physicist that this could explain matter-antimatter asymmetry in the universe.

http://www.sciencedaily.com/releases/2015/05/150514085655.htm

Is there anything in the Standard Model that would suggest this? (The weak force has chiral asymmetry, but I've never known that there was something similar in electromagnetism.) By what mechanism would one lead to the other?
 
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  • #2
The 2001 paper being referred to is astro-ph/0101261. The proposal there is roughly the following.

One possible explanation of the baryon asymmetry is called electroweak baryogenesis (EWBG). This mechanism relies on topological solutions to the Yang-Mills equations called sphalerons. The idea is that the W and Z fields, along with the Higgs can take topologically nontrivial classical configurations. As a topological configuration, there is an associated topological charge that can be related to baryon number ##B## and lepton number ##L##. In the case of the sphaleron, the configuration is unstable and has some lifetime to decay. The idea of EWBG is that as the temperature of the universe cools through the electroweak scale, we have a phase transition associated with electroweak symmetry breaking. During the phase transition, sphalerons can be produced, which then rapidly decay. These events can mediate baryon and lepton number violating processes that satisfy ##\Delta B = \Delta L## and conserve ##B-L##. For example, an antiquark can be changed into two quarks and 3 antileptons. So these processes open the possibility that antiquarks were converted into quarks, creating a baryon asymmetry resembling what we observe. As I understand it, it is still an open question whether EWBG can explain the observed baryon asymmetry, but there are various technical reasons to be pessimistic.

What Vachaspati notes is that there is another interpretation of the sphaleron as a magnetic monopole connected to an antimonopole connected by something called a Z-string. By a "string" here we mean another kind of topologically classical configuration that has an interpretation as an extended object with a finite energy per unity length. It is called a Z-string because is corresponds to a configuration for the Z field (and the Higgs). In a certain sense, the Weinberg angle is a relationship between the Z field and the EM field. Vachaspati argues that the magnetic field associated with the monopoles is what leads to the generation of a helical magnetic field during the sphaleron decay process. He ties the change in EM helicity to the change in baryon number.

I think the Science Daily article to some degree implies that the magnetic field asymmetry is responsible for the baryon asymmetry in Vachaspati's picture. However, it is the case that the sphaleron process generates both of the asymmetries simultaneously. What is interesting if the claimed observation of magnetic field asymmetry is correct, is that it would hopefully give us a way to estimate the amount of baryon asymmetry due to EWBG. Then we would have a better idea of whether it can explain the total observed baryon asymmetry or if new physics is definitely needed.
 
  • #3
Thanks. That's a really clear explanation.
 

Related to Does Chiral EM Asymmetry Imply Matter-Antimatter Asymmetry?

1. What is chiral EM asymmetry?

Chiral EM asymmetry refers to the difference in the behavior of left-handed and right-handed particles in electromagnetic interactions. This means that the laws of physics are not symmetrical for these two types of particles.

2. How is chiral EM asymmetry related to matter-antimatter asymmetry?

Chiral EM asymmetry is one of the possible explanations for the observed matter-antimatter asymmetry in the universe. It is believed that the initial conditions of the universe were such that there was a slight excess of matter over antimatter, and this asymmetry has been amplified over time through various physical processes.

3. Is chiral EM asymmetry a proven concept?

No, chiral EM asymmetry is currently a theoretical concept and has not been conclusively proven. However, there is ongoing research and experiments being conducted to test its validity.

4. How does chiral EM asymmetry affect our understanding of the universe?

If chiral EM asymmetry is proven to be a valid concept, it would have significant implications for our understanding of the fundamental laws of physics and the origins of the universe. It could also potentially help us solve the mystery of the observed matter-antimatter asymmetry.

5. Can chiral EM asymmetry be observed in everyday life?

Chiral EM asymmetry is a very subtle phenomenon and is not noticeable in everyday life. It can only be observed and studied through advanced experiments and observations in the field of particle physics.

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