Speaker
Description
The origin and evolution of cosmological magnetic fields remain open problems with potential implications for physics beyond the standard cosmological model. In particular, several dark matter scenarios predict non-trivial interactions with primordial magnetic fields, either modifying their initial spectrum or imprinting characteristic signatures during structure formation. Assessing whether such imprints can survive subsequent non-linear evolution requires a detailed understanding of magnetic field amplification mechanisms in realistic cosmological environments.
In this contribution, we present ongoing work aimed at disentangling the physical processes responsible for magnetic field amplification in high-resolution cosmological magnetohydrodynamic simulations performed with the MASCLET code. Our approach is based on a decomposition of the magnetic induction equation formulated in an expanding cosmological background, allowing the magnetic energy evolution to be separated into contributions from compression, stretching, advection, and cosmological expansion. This formalism enables a quantitative assessment of how different environments and dynamical regimes reshape the magnetic field over cosmic time.
A central aspect of this analysis is the distinction between compressive amplification and amplification driven by the small-scale dynamo (SSD). While compressive processes tend to amplify the magnetic field without significantly altering its large-scale topology, the SSD powered by turbulent, rotational motions, efficiently redistributes power across scales and can erase memory of initial configurations. To isolate these effects, we combine the induction-based decomposition with the VORTEX code, which performs a Helmholtz decomposition of the velocity field. This allows us to identify the solenoidal (rotational) component of the stretching term that constitutes the physical signature of the SSD.
This framework provides a physically motivated pathway to evaluate whether primordial magnetic signatures potentially linked to dark matter interactions can survive in specific environments where compressive amplification dominates, or whether they are erased by turbulent dynamo action, exploring the viability of using cosmic magnetism as an indirect probe of dark matter physics.
| Main Contribution topic | Cosmology Dark Matter |
|---|---|
| Secondary contribution topic | Theory / Phenomenology |