Astron. Astrophys. 326, 13-22 (1997)

Magnetic fields and large scale structure in a hot universe

I. General equations

E. Battaner , E. Florido and J. Jiménez-Vicente

Departamento de Física Teórica y del Cosmos, Universidad de Granada, E-18071 Granada, Spain

Received 25 September 1996 / Accepted 20 March 1997

Abstract

We consider that no mean magnetic field exists during this epoch, but that there is a mean magnetic energy associated with large-scale magnetic inhomogeneities. We study the evolution of these inhomogeneities and their influence on the large scale density structure, by introducing linear perturbations in Maxwell equations, the conservation of momentum-energy equation, and in Einstein field equations. The primordial magnetic field structure is time independent in the linear approximation, only being diluted by the general expansion, so that is conserved in comoving coordinates. Magnetic fields have a strong influence on the formation of large-scale structure. Firstly, relatively low fields are able to generate density structures even if they were inexistent at earlier times. Second, magnetic fields act anisotropically more recently, modifying the evolution of individual density clouds. Magnetic flux tubes have a tendency to concentrate photons in filamentary patterns.

Key words: Magnetohydrodynamics (MHD) relativity cosmology: large-scale structure of universe

Contents

• 1. Introduction
• 2. The mean magnetic field
• 3. The perturbed quantities
• 4. The perturbed Maxwell equations
• 5. The perturbed equation of motion-energy
• 6. The perturbed Einstein field equations
• 7. Density perturbations
• 8. Conclusions
• Appendix
  • Appendix A: mean magnetic field in the Robertson-Walker metric
  • Appendix B: linear Newtonian evolution of magnetic fields
• References

© European Southern Observatory (ESO) 1997

Online publication: April 20, 1998
helpdesk.link@springer.de