In asymptotically safe gravity, radiation-filled Bianchi-I cosmologies show quantum corrections that soften anisotropy, while magnetic fields lead to persistent Kasner anisotropy without Lambda but isotropic de Sitter decay with nonzero Lambda.
Constraints on a primordial magnetic field
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abstract
We derive an upper limit of $B_0<3.4\times 10^{-9}(\Omega_0h_{50}^2)^{1/2}$ Gauss on the present strength of any primordial homogeneous magnetic field. The microwave background anisotropy created by cosmological magnetic fields is calculated in the most general flat and open anisotropic cosmologies containing expansion-rate and 3-curvature anisotropies. Our limit is derived from a statistical analysis of the 4-year Cosmic Background Explorer data for anisotropy patterns characteristic of homogeneous anisotropy averaged over all possible sky orientations with respect to the COBE receiver. The limits we obtain are considerably stronger than those imposed by primordial nucleosynthesis and ensure that other magnetic field effects on the microwave background structure are unobservably small.
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Bianchi-I Cosmology with Radiation in Asymptotically Safe Gravity
In asymptotically safe gravity, radiation-filled Bianchi-I cosmologies show quantum corrections that soften anisotropy, while magnetic fields lead to persistent Kasner anisotropy without Lambda but isotropic de Sitter decay with nonzero Lambda.
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Symbiotic Magnetogenesis during Radiation Domination
A symbiotic axion-dilaton system sources a moderately chiral dark U(1) magnetic field of astrophysically relevant strength during radiation domination through tachyonic amplification without fine-tuning.
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Primordial magnetic fields in the light of upcoming post-EoR Lyman-$\alpha$ and 21-cm observations
Forecasts show DESI-like and SKA1-Mid observations could constrain primordial magnetic field amplitude and spectral index to roughly 10% precision via 21cm auto-spectrum and Lyα-21cm cross-spectrum.
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The Large-Scale Structure of the Universe through the SKA lenses
This review chapter summarizes the cosmic web's theoretical framework, recent radio observations of diffuse gas, and the expected impact of the SKA on detecting baryons in filaments and cluster outskirts.