06/10/2021 at 8:00 AM CEST
New research suggests that the search for dark matter could be mistaking signals from axions, hypothetical fossil particles that carry the information of what happened a second after the Big Bang, the blind spot in the history of the universe, for noise.
The origin of the universe represents one of the greatest mysteries in cosmology. We think that everything started with a great explosion (Big Bang) that gave rise to matter and energy, 13.7 billion years ago.
However, we have never been able to go so far back in our knowledge of the universe: the first news of what happened after the great explosion allowed us to know something of the universe when it was already almost 400,000 years old.
We know nothing about what happened between the Big Bang and those 400,000 years: it represents a blind spot in the history of the universe.
New research from the University of California at Santa Cruz proposes a way to discover what happened in the universe a second after the Big Bang: the key would be to find a mysterious particle called an axion.
Cosmic fossilsAs that particle is still hypothetical, if we confirmed its existence we would not only have discovered a new component of the universe, but it would also allow us to solve the mystery of dark matter, of which we assume it is a part.
Cosmologists are not only convinced of its existence, but also that the axion would have occurred naturally in large quantities just as the universe began its cosmic history.
They also assume that fossil axions continue to exist today: they consider them as a kind of strange photons, because they are attributed the ability to transform into photons (light particles) within electromagnetic fields.
One of the things that scientists are doing to verify that they really exist is trying to create axions in the laboratory using powerful electromagnetic fields. Experiments so far have failed to see them.
Another way to find axions would be to detect them, because cosmologists believe that, if they exist and form part of dark matter, they would be continuously bombarding us: microwave cavities resonant to the mass of the axion in magnetic fields could discover them.
Another technique to detect axions is by means of helioscopes, which try to detect the axions produced inside the Sun.
Related topic: A dark matter particle would be hidden in the X-rays of neutron stars
Twisting axions The new research, published in Physical Review D, complicates the mystery of axions a bit more: it considers that behind the microwave background radiation, a form of electromagnetic radiation that fills the universe completely, there is another radiation that is no less hypothetical and also mysterious.
The microwave background radiation is a consequence of the Big Bang, since cosmologists have found that the early universe was a plasma composed of electrons, photons, and baryons, all of which are well-known and well-proven particles.
That microwave background radiation originated when the universe cooled down enough after the Big Bang to allow protons and electrons to combine into neutral hydrogen.
That combination is the oldest signal we’ve ever recorded in the universe, and it occurred about 400,000 years after the Big Bang – it’s what we call microwave background radiation.
Cosmic axions background
Cosmic axions backgroundThe authors of the new research consider that the axions that arose immediately after the Big Bang form another background radiation, prior to that of microwaves, and that they call the cosmic axion background (CaB).
Although it is only a hypothesis, they point out that there are many reasons to suspect that the axion could exist in our universe as part of that primordial cosmic background.
To find it, one would only have to look better at the experiments currently being carried out to find dark matter.
They indicate that cosmologists may be identifying telltale signals about axions as noise in data from the dark matter search.
Solved mysteriesIf the suspicion that there is information yet to be discovered in the data on dark matter is confirmed, not only the existence of axions would have been verified, the first fossil of what remains of the first seconds after the Big Bang.
In that case, we would have gone back in time like never before to better understand what happened in the blind spot of the history of the universe.
This approach could provide important revelations about dark matter, the temperature of those critical moments, the moment in which the expansion of galaxies began, and if there really were two cosmic phase transitions or symmetry breaks, as explained in a statement .
All these questions that surround the mystery of axions intrigue cosmologists, because solving them would help them better understand the origin of everything we know and experience today.
Cosmic axion background. Jeff A. Dror et al. Phys. Rev. D 103, 115004, 7 June 2021. DOI: https: //doi.org/10.1103/PhysRevD.103.115004
Top photo: Colossal cosmic explosion detected in the Ophiuchus galaxy cluster, some 390 million light-years from Earth. NASA, ESA, ICRAR et al.