Dark matter could help us discover their origin

Mini-haloes of dark matter scattered throughout the cosmos could function as highly sensitive probes of primordial magnetic fields. This is what emerges from a theoretical study carried out by SISSA and published in Physical Examination Letters.

Present on immense scales, magnetic fields are found everywhere in the universe. However, their origin still remains a subject of debate among researchers. One intriguing possibility is that magnetic fields arose close to the birth of the universe itself; that is, they are primordial magnetic fields.

In this study, the researcher showed that if magnetic fields are indeed primordial, then they could cause an increase in small-scale dark matter density disturbances. The ultimate effect of this process would be the formation of mini dark matter halos which, if detected, would hint at the primordial nature of magnetic fields. Thus, in an apparent paradox, the invisible part of our universe could be useful in resolving the nature of a component of the visible part.

Shedding light on the formation of magnetic fields

“Magnetic fields are omnipresent in the cosmos,” explains Pranjal Ralegankar of SISSA, the author of the research. “A possible theory regarding their formation suggests that those observed so far could be produced in the early stages of our universe.”

“However, this proposal lacks an explanation in the standard model of physics. To shed light on this aspect and find a way to detect ‘primordial’ magnetic fields, we propose with this work a method that we could define as ‘primordial’ magnetic fields. indirect’. Our approach is based on a question: what is the influence of magnetic fields on dark matter?” We know that there is no direct interaction. However, as Ralegankar explains, “there is has an indirect one that occurs through gravity.”

Straight from the primordial universe

Primordial magnetic fields can increase electron and proton density disturbances in the early universe. When these become too important, they themselves influence the magnetic fields. The consequence is the suppression of small-scale fluctuations.

Ralegankar explains: “In the study, we show something unexpected. The growth of baryon density gravitationally induces the growth of dark matter disturbances without the possibility of subsequent cancellation. This would cause them to collapse on a small scale, producing mini-haloes of dark matter. “. The consequence, continues the author, is that, although the density fluctuations of baryonic matter are canceled, they would leave traces through the mini-haloes, all only by gravitational interactions.

“These theoretical findings,” concludes Pranjal Ralegankar, “also suggest that the abundance of mini-halos is not determined by the current presence of primordial magnetic fields but rather by their strength in the early universe. Thus, a detection of mini-haloes of dark matter The halos would strengthen the hypothesis that magnetic fields formed very early, even within a second after the Big Bang.”