#paperday Want to start the week with a fresh paper which clearly thinks outside of the box?

Here you go

https://arxiv.org/abs/2504.08461

"Astrophysical constraints on the simulation hypothesis for this Universe: why it is (nearly) impossible that we live in a simulation"

Will do a paper explainer in the near future...

Nice rendering of the growing mass distribution in a simulated cluster of galaxies, and of the shocks driven by the same process, by former PhD student Matteo Angelinelli, using Julia over ENZO simulations.

Revolving around one axis of a 3D simulation of baryons in a massive cluster of galaxies (ENZO simulation, movie with SAO's DS9).

VIsualisation of the central turmoil of gas temperature, around a simulated Active Galactic Nuclei in a Persus-like cluster of galaxies.
Simulations by PhD student Stefano Sotira using ENZO

#astrodon #astronomy #science
#SimulatedUniverses

Backwards structure formation is cool too
#SimulatedUniverses #astronomy #astrodon #science

I got reminded at a talk at a recent conference that I produced this nice RGB rendering of two alternative scenarios for the generation of magnetic fields in the Universe - I entirely forgot about it, the papers was about Fast Radio Burst (https://arxiv.org/pdf/1805.11113, not really my thing) so it went forgotten...why not resurrect it.

Evolution of a simulated small group of galaxies, with several key quantities integrated along the line of sight on display.

Prepared for a lecture but nice to show.

Some movie of the evolution of cosmic ray electrons released into the cosmic web by different simulated processes (all in the same run, but tracked with different fluid species).

1) relativistic electrons injected by shocks, via diffusive shock acceleration.

#SimulatedUniverses #astronomy #astrodon #science

For the curious, the related very recent paper is here:
https://ui.adsabs.harvard.edu/abs/2025arXiv250119041V/abstract

Turmoiling evolution of the magnetic fields expelled by galaxies into the network of the cosmic web, in a small cosmological simulations with ENZO and animated gif assembled with SAO's DS9.

Simulated accretion of gas matter (right) and compression and amplification of magnetic field (left) in a cluster of galaxies with a final mass of 6e14 solar masses.

When you are done reading about aliens and #Ufos, here is a nice technical overview of implementations, results and problems of feedback models in cosmological simulations, by Valentini & Dolag https://arxiv.org/2502.06954

Bottom line: all models tend to produce different results - but all are perfect

Evolution of the magnetic field amplitude for a large cosmic volume, from z=50 to z=0, under the assumption of an initial stochastic magnetic field (initial spectrum P(k) \propto k^1), simulated wit the ENZO code.

The information of the initial seed field is lost within the turbulent cluster of galaxies at the centre, but is somewhat preserved in cosmic voids and partially in filaments.

A tale of three simulated clusters of galaxies, evolving in parallel in three different #SimulatedUniverses (but all with same cosmological parameters).

Somewhat soothing, although their collisions are believed to be the most energetic events in the Universe (but happens on billions of years timescales...)

Did I inject too many particle tracers in the simulation?
naa....

#SimulatedUniverses
#astronomy
#science

Some more "raw footage" generated for the paper I described yesterday:

https://mastodon.social/@franco_vazza/113938850759071077

This one shows the effect of only galaxy feedback on magnetic fields and cosmic ray electrons (while the contribution from shocks is not shown here)

Final evolution of a newly simulated cluster, from z=0.6 to z=0 (i.e. about 5 billion years) showing all quantities which are relevant to predict its radio emission over time.

Sad grid artefacts at the boundary of expanding shocks, due to adaptive mesh refinement, but the central regions where radio emission may form are well sampled.

Fun

Simulation done with ENZO on CINECA, map making with @julialang , movie done with SAO-DS9.

I'm waiting editorial final acceptance to post about long accepted paper of mine,
anyway, this is a view of the possible integrated activity of active galactic nuclei, residing at the centre of all galaxies in this simulation, which enriched the intergalactic medium with cosmic rays and magnetic fields.
The colors on the left go from dark to pale depending on the "age" of cosmic rays in the cells! (dark=young).
The right map shows dark matter.