Detailed Research

Basic question

1. The origin of intergalactic magnetic field. [1]

There are several mechanism to generated primordial magnetic field. There is a general agreement that the observed microGauss magnetic field are the result of weak “seed” fields. (Have to ask, this can’t be a belief among those people, they must based on some facts to deduce such an assumption, so what are they according to? )

Then the question is why there is the initial weak field, where did it come from? what’s the mechanism behind for amplification of “seed” field.

However, these assumptions more or less rely on some unknown physics. There are two main assumption about when the IFMF did occur?

  • During the inflation?
  • Before the inflation?

It effects the approach to determine the constraints on IGMF.

The generation of magnetic fields in the era of pre-recombination [2] has been studied in several literature.Then this paper [1] study magnetogenesis in conventional physics.

It’s about how magnetic fields are generated from nonlinear cosmic inhomogeneities using the tight coupling approximation.

2. What propagation of energetic light can tell us?

The raw gamma ray can be protected(shielded) from interaction with EBL by two factors.

  • Lorentz Invariant Violation
  • Axion Like Particle

3. Propagation of high energy photons

Gamma rays do not traverse the Universe unperturbed. They can interact with background radiation such as the EGBL. The EGBL consists of the starlight emitted over the entire history of the Universe and the starlight that has been absorbed and re-emitted by dust. If a gamma-ray interacts with an EGBL photon, it produces a pair of one electron and its anti-particle, the positron. Just like clouds block the sunlight, the EGBL can partially block gamma rays from reaching us. Using a certain type of galaxies, so called blazers, as cosmic beacons of gamma rays, we can study the EGBL and eventually the formation of stars during the history of the Universe. Much more about the EGBL will be learned with future CTA observations. Check out the article “What the Propagation of Energetic Light Can tell us About the Evolution of Stars, Intergalactic Magnetic Fields and Fundamental Physics” in the CTA newsletter for further information.

Footnotes

[1](1, 2) https://arxiv.org/abs/0805.0169v3
[2]

When the universe was younger than about 300,000 years, the temperature was high enough that all of the hydrogen was ionized, that is the electrons were free and separate from the protons. Because of the presence of the free electrons, photons were scattered around in all directions and could not travel far before changing their direction. Therefore the universe was “opaque”.

When the universe cooled to about 3000 K, the electrons and protons combined to form hydrogen atoms. After “recombination”, photons were able to travel through the universe relatively unimpeded, and the universe became “transparent”.