In the early Universe, magnetic fields may have been billions of times weaker than a typical fridge magnet, resembling the magnetism created by neurons in our brains. Yet, these faint fields have left quantifiable traces in the cosmic web, the vast structure connecting galaxies across space. This insight comes from a study that harnessed around a quarter of a million computer simulations, led by researchers from SISSA (the International School for Advanced Studies in Trieste) alongside the Universities of Hertfordshire, Cambridge, Nottingham, Stanford, and Potsdam. The team’s findings, recently published in Physical Review Letters, outline both possible and maximum strengths of these primordial magnetic fields, enhancing our understanding of the early Universe and the emergence of the first stars and galaxies.
A Magnetic Cosmic Web
“The cosmic web is a complex, filamentary structure that connects galaxies throughout the Universe, yet many mysteries remain. One puzzle is why it is magnetized, especially in remote areas that are not densely populated, where magnetism is less expected,” explains Mak Pavičević, a SISSA PhD student and lead author. Matteo Viel, his supervisor and co-author, adds, “We theorized that this magnetism could trace back to events during the Universe’s infancy, possibly related to processes from the primordial era. For instance, the filaments may have become magnetized during the inflation phase before the ‘Big Bang’ or through later events known as phase transitions. Our research aimed to validate these ideas while quantifying the strengths of these primordial magnetic fields.”
Exploring the Universe’s Origins with Simulations
The international team conducted over 250,000 simulations to analyze the cosmic web and understand the role of primordial magnetic fields. Vid Iršič from the University of Hertfordshire, a co-author of the study, states, “These simulations are the most advanced and extensive attempts to assess the impact of primordial magnetic fields on the intergalactic cosmic web.” Pavičević and Viel further explain, “By comparing our simulations with observational data, we confirmed our hypotheses. Including primordial magnetic fields changed the cosmic web’s appearance, aligning it more closely with observational data. Notably, a standard Universe model featuring a very weak magnetic field of approximately 0.2 nano-gauss fits experimental data significantly better.”
New Upper Limits on Primordial Magnetic Fields
The researchers established a particularly low maximum value for the strength of primordial magnetic fields, which is several times lower than previous estimates. Pavičević and Viel conclude, “Our findings impose strict limits on magnetic field intensity from the early Universe and align with recent independent data from cosmic microwave background studies. They explain, “This evidence will enhance our understanding of early cosmic events, as these magnetic fields likely increased the cosmic web’s density, accelerating star and galaxy formation. Further validation of our results could come from observations by the James Webb Space Telescope.” Vid Iršič adds, “These new limits will not only clarify the influence of primordial magnetic fields on cosmic evolution but also have significant implications for other theoretical models that explore how structures formed.”
Summary: A recent study involving over 250,000 simulations has shed light on primordial magnetic fields in the universe, suggesting they were incredibly weak yet left traces in the cosmic web. Researchers have set new upper limits on these fields, enhancing our understanding of cosmic evolution and the formation of early stars and galaxies.
