hfalcke, 27 days ago

@franco_vazza So, what is the most likely origin of cosmic magnetic fields and where can I read about it. (Asking for a friend who is writing a book).

franco_vazza, 27 days ago

@hfalcke

Your friend has impeccable taste for crucial questions!

Here a biased list of things:

I start with some "classical" material:

• excellent review by K.Subramanian: https://arxiv.org/pdf/1903.03744

• Widrow+, of some years ago: https://ui.adsabs.harvard.edu/abs/2012SSRv..166...37W/abstract

• Durrer & Neronov https://ui.adsabs.harvard.edu/abs/2013A%26ARv..21...62D/abstract

• this is a well written and high level popular overview of the problem by Quanta Magazine: https://www.quantamagazine.org/the-hidden-magnetic-universe-begins-to-come-into-view-20200702/

next, the latest results and my opinion:

franco_vazza, 27 days ago

@hfalcke

• a friend of mine has recently shared his simulations to help observations probe magnetism :

• https://arxiv.org/abs/2311.04273 : blazar emission & magnetism of voids

• https://arxiv.org/abs/2302.08072: polarised emission from the cosmic web

• https://arxiv.org/abs/2210.06220 : Faraday Rotation from the cosmic web using LOFAR

• https://arxiv.org/abs/2111.09129 status of simulations vs observations in 2021

-https://arxiv.org/abs/2009.01539 test of models allowed by CMB

• https://arxiv.org/abs/1711.02669

next, my summary:

franco_vazza, 27 days ago

@hfalcke

My take:

• B in galaxy clusters (e.g. Coma is very well observed) is explained by both seeding from galaxies or primordial fields;

• the combination of lower limits in voids from blazars, and statistical detections in radio (RM + synchrotron) excludes a purely astroph. origin of cosmic B.

• current modelling of RM in LOTSS prefers primordial models with power on large scales (hence, inflationary).

• extra: this may explain the GW background 🤯 nhttps://arxiv.org/pdf/2009.14174

franco_vazza, 27 days ago

@hfalcke looking forward for the book of your friend, and feel free to discuss this offline if you want

hfalcke, 27 days ago

@franco_vazza that is very interesting and extremely useful. It will take some digesting. The book will be very general, so not all those details can be covered, but the basic question of where the magnetic fields that protect us in our atmosphere come from ultimately is a very interesting one. it could be as complex as the formation of the planet itself, and have the same fundamental origin.