Abstract Details
| Name: Chandranathan Anandavijayan Affiliation: International Centre for Theoretical Sciences (ICTS),Tata Institute of Fundamental Research, Bengaluru, India Conference ID: ASI2025_296 Title : Spectral evolution in decaying MHD turbulence: Implications for early-universe magnetic fields Authors and Co-Authors : Pallavi Bhat 1, Chandranathan Anandavijayan 1 Abstract Type : Poster Abstract Category : High Energy Phenomena, Fundamental Physics and Astronomy Abstract : Magnetic fields are pervasive across the universe, existing even in cosmic voids. Observations of TeV blazar spectra in these voids indicate the presence of a magnetic field of approximately $10^{-15} G$, likely of primordial origin. Such primordial magnetic fields can significantly influence the evolution of cosmic plasma, impacting processes such as Big Bang nucleosynthesis and recombination. In the early universe, magnetic fields may have been generated during inflation or phase transitions. Their subsequent non-linear decay is characterized by a decay timescale and is constrained by a conserved quantity. It is currently agreed that this decay proceeds via magnetic reconnection. In ideal magnetohydrodynamics (MHD), magnetic helicity is conserved; however, in the absence of magnetic helicity, it cannot constrain the decay, even though it remains conserved. This has led to debate regarding the relevant conserved quantity in this scenario. It was proposed that conservation of magnetic helicity fluctuations is relevant, but our prior work critically analyzed this claim and demonstrated that conservation of anastrophy (square of the vector potential) is the true constraint. In this study, we analytically calculate the evolution of the magnetic spectrum using piecewise power laws. To validate our results, we perform numerical simulations with the pseudo-spectral solver DEDALUS. The resulting scaling relations confirm the true conserved quantity. This finding is significant not only for advancing our understanding of decaying MHD turbulence but also for early-universe physics. |