كيف امتلك الكون مغناطيسية قبل نشوء النجوم الأولى سريع

الملخص الأصلي

كما كتبه المؤلفون، بالإنجليزية arXiv:2606.16680

We derive and compare three mechanisms of cosmological magnetogenesis: the Thomson-scattering velocity-difference mechanism of Takahashi et al.\ (2005), a new density-gradient source identified here for the first time, and the Harrison bulk-flow mechanism of Cembranos et al.\ (2020). Starting from the coupled Maxwell-Boltzmann equations, the complete kinetic theory chain is derived in a single document -- from the BBGKY hierarchy and Thomson collision term, through the generalised Ohm's law, to the second-order magnetic induction equation. The Ohm's law correction terms are each bounded by $$m_e/m_p\approx5.4\times10^{-4}$$, confirming the standard single-fluid approximation to better than $$0.1\%$$. At second order in cosmological perturbations, products of first-order scalar source vorticity, we identify a coupling between the photon density contrast $$\delta_\gamma \equiv \delta\rho^{(1)}_\gamma / \bar\rho_\gamma$$ and the electron-photon velocity difference $$(u_e-u_\gamma)^{(1)}$$ that was implicitly present in previous treatments but never isolated. Numerical evaluation with CAMB~v1.6.6 at $$z=1100$$ shows that this term contributes at $${\approx}0.97\times B_{\rm Tak}$$, giving a scattering-mechanism total $${\approx}1.4\times$$ the Takahashi result. The Harrison mechanism at the Planck bulk-flow limit ($$\beta<8.5\times10^{-4}$$) yields $$B\approx5.7\times10^{-24}$$~G at 1~Mpc today and dominates for $$\beta\gtrsim2\times10^{-3}$$, mildly above the Planck limit. All seed fields exceed the galactic dynamo threshold by many orders of magnitude.