Posts by franco_vazza@mastodon.social
(DIR) Post #AZMfsAY38Xq5ShQ3ge by franco_vazza@mastodon.social
2023-09-02T12:49:04Z
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Even the simulations which have the most generous feedback, like Illustris TNG, magnetise at most ~20% of the cosmic volume to the level necessary to explain the suppression of secondary emission in blazars.
(DIR) Post #AZMfsCZtaeVJl0IYqG by franco_vazza@mastodon.social
2023-09-02T12:52:50Z
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Here is a simulation I produced, which shows the same effect: magnetisation by an hypothetical primordial seeding on the left, vs magnetisation only from galactic activity on the right. The differences in the volume filling factors are quite striking!
(DIR) Post #AZMfsEIbBvrB5wDm9w by franco_vazza@mastodon.social
2023-09-02T12:53:21Z
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So the necessary conclusion appear to be that something else might have magnetised the Universe on such large scales, and the alternative explanation is that a small level of magnetisation might be produced during Inflation, or high energy phase transitions short after that (like the Electro-Weak phase transition) in which the seeds for nowadays observed magnetic fields have been planted.
(DIR) Post #AZMfsG4UbLlGaldXRw by franco_vazza@mastodon.social
2023-09-02T12:54:16Z
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Last point of discussion, which is also pretty much covered during conferences like this, is to which extent we can trust our current description of the interaction of high energy photons with the intergalactic plasma, on the incredibly low density range of voids. Some indeed proposed that this interaction would lead to instabilities, which would dissipate a fraction of the cascade energy without producing secondary emission, even in the absence of any extragalactic magnetic field.
(DIR) Post #AZMfsHytV8TIVz2608 by franco_vazza@mastodon.social
2023-09-02T12:54:30Z
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If this was the case, then blazar emission cannot be used to constrain cosmic magnetism (bummer).While the modelling of this is quite difficult and there are conflicting view, the consensus leans towards the idea that under real conditions this effect will be too small to explain the absence of the secondary cascade.
(DIR) Post #AZMfsJl8tEey1uc8qO by franco_vazza@mastodon.social
2023-09-02T12:54:46Z
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So, overall (at least in my humble opinion) there is an emerging and reasonably robust view, supported by observations on many different scales and wavelengths, independent modelling techniques and advanced simulations, that the Universe might have produced a tiny seed of magnetism since its beginning, whose relics are still present nowadays in the emptiest regions of the Universe!
(DIR) Post #AZMfsLXkG18DYwMTEu by franco_vazza@mastodon.social
2023-09-02T13:02:00Z
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As a recent follow up of this, the combined analysis of my simulations and new low-redshift radio observations of filaments in the cosmic web seems to have provided a totally independent confirmation of this possibility - even if we are still in the infancy of using low-redshift radio observations to measure cosmic magnetism.
(DIR) Post #AZMfsP7IyGMIe61PaC by franco_vazza@mastodon.social
2023-09-02T13:04:03Z
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In the future, the combination of the Cerenkov Telescope Array (CTA), to continue probing high energies, of the Square Kilometre Array (SKA), to scan the Universe at radio wavelengths, possibly in combination with the Pulsar Timing Array (which might detect the gravitational wave signal also produced by cosmic magnetism) promises to allow us closing on the mystery of the origin of magnetic fields in the Universe.[EoT]
(DIR) Post #AbGkgSbyPONKLoJAMS by franco_vazza@mastodon.social
2023-10-26T12:37:21Z
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Large scale rendering (and zoomed detail) of the evolution of various energy forms in one cosmological volume starting from primordial and tangled magnetic fields.The red colors mark the thermal gas energy, the blue the kinetic gas energy, the green the magnetic energy (relative intensity of colors not to scale).#SimulatedUniverses#astronomy #astrodon
(DIR) Post #Ai3HysVkUnnT4V6hkm by franco_vazza@mastodon.social
2024-05-05T17:04:26Z
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@hannorein "yes, I confirm I am available as a reviewer of this paper"
(DIR) Post #Aknhhtskvc6tICiuTw by franco_vazza@mastodon.social
2024-07-20T09:12:51Z
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Periodic shoutout to this awesome newsletter maintained by @manlius #ComplexityThoughts:https://manlius.substack.com/investigating #complexity and giving updated reviews of interesting papers.It's such a cross-disciplinary field of research, with interesting inputs coming from so many different directions, that a resource like this is unvaluable.#astrodon #academics
(DIR) Post #AlecrSJW50PyIGqycy by franco_vazza@mastodon.social
2024-09-04T08:35:23Z
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@drmambobob absolutely, it has now become super risky to use ChatGpt for this ! can confirm it creates plausible but unrelated functions to what one had in mind.
(DIR) Post #AodbVgK8uFzetcJZXE by franco_vazza@mastodon.social
2024-12-02T14:21:44Z
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@futurebird I sort of get your being annoyed, although I study all of that every day, and I do mostly get the "fun" part. The fact that these structures are so big and far also means they could not care less about all our daily miseries and tragedies ...The annoying part for me really is that they also evolve on hundreds of million years timescales....so whatever nice simulation or theory I come up with...not only I won't ever see if it's true, but not even humankind will... 🙄
(DIR) Post #AodocH0ciut9oZesFM by franco_vazza@mastodon.social
2024-12-02T16:48:38Z
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@futurebird Indeed, with magnetic sauce on top
(DIR) Post #AuxG9s9TuK0uPTidjk by franco_vazza@mastodon.social
2025-06-09T13:09:17Z
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@stux this is genius!
(DIR) Post #AxE1GEL2DTy7pMsCum by franco_vazza@mastodon.social
2025-08-16T10:45:15Z
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#SimulatedUniverses A 100 Megaparsec cubic simulated volume getting progressively filled by cosmic web structures, one layer of baryonic matter at a time ( here using 64 layers of depth 1.56 Megaparsec each).Rendering done using #Julialang in parallel using 16 cores on my MAC - the input simulation has 1024^3 cells.The tiniest detail of the cosmic network tend to get lost as the entire distribution of matter gets added along the line of sight! #science #astronomy #physics
(DIR) Post #Ayq0PB08GyTbaBGuqO by franco_vazza@mastodon.social
2025-10-03T09:49:48Z
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Another massive #strike in #Bologna and in #Italy today. Called only yesterday, it has unclear objectives, it combines many themes and is also against this government.It is more emotional then rational, it mixes so much discontents and it's a reaction to the feeling of helplessness about what governments allow to happen before our eyes.That's why I 100% felt like participating, and for the first time I did together with my 11yr old son. 🫠#scioperogenerale #Flottilla #sciopero
(DIR) Post #Ayq0PFLu5yGh4rUMKm by franco_vazza@mastodon.social
2025-10-03T09:59:32Z
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An impressive view from the top via Corriere della Sera https://video.corrieredibologna.corriere.it/il-video-della-marea-umana-per-la-palestina-a-bologna-piazza-maggioe-piazza-nettuno-e-il-centro-pieni-con-/5627d2d0-4003-4cc3-a418-9ee7799cdxlk
(DIR) Post #Ayq0PFkibi7MJp6B0q by franco_vazza@mastodon.social
2025-10-03T09:54:53Z
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What I mean by "unclear objectives" is that it is not realistic to think that what we do here can change what happens in #Gaza now, or that the government will change tomorrow, or else.But it's about creating ripples, as large as possible to overlap with other ripples, to change the course of events in the near or remote future. For me it was also fundamental to show my son how many people care about the same stuff his parents talk about - there's a larger world there than in social media.
(DIR) Post #Ayq0PKDvz1reBanZ6e by franco_vazza@mastodon.social
2025-10-03T09:57:58Z
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(all this said, I still don't understand the point of a tiny fraction of people smashing stuff or blocking trains and highways, since the main goal to show participation and make it a huge national event is obtained already. But it's me, I'm old...)