Cosmological Perturbations seeded by Topological Defects: Setting the Initial Conditions

Abstract

We consider a perfectly homogeneous and isotropic universe which undergoes a sudden phase transition. If the transition produces topological defects, which we assume, perturbations in the geometry and the cosmic fluid also suddenly appear. We apply the standard general relativistic junction conditions to match the pre- and post- transition eras and thus set the initial conditions for the perturbations. We solve their evolution equations analytically in the case when the defects act as a coherent source and their density scales like the background density. We show that isocurvature as well as adiabatic perturbations are created, in a ratio which is independent of the detailed properties of the defects. We compare our result to the initial conditions currently used in the literature and show how the cosmic fluid naturally "compensates" for the presence of the defects.

26 pages, TeX, no figure, published in Phys. Rev. D; correction of the isocurvature perturbation and of a few typos

References in corpus (4)

• Power Spectra in Global Defect Theories of Cosmic Structure Formation
• CMB Anisotropy Induced by Cosmic Strings on Angular Scales $>15^{\prime }$
• Microwave Background Anisotropies from Scaling Seed Perturbations
• Painless causality in defect calculations

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• Constraints on scalar and tensor perturbations in phenomenological and two-field inflation models: Bayesian evidences for primordial isocurvature and tensor modes
• CMB temperature anisotropy at large scales induced by a causal primordial magnetic field
• Topological Defects and CMB anisotropies : Are the predictions reliable ?
• Probing early-universe phase transitions with CMB spectral distortions
• Note on Structure Formation from Cosmic String Wakes
• Causal perturbation theory in general FRW cosmologies I: energy momentum conservation and matching conditions
• Cosmic microwave background anisotropies seeded by incoherent sources
• The No-defect Conjecture: Cosmological Implications
• Global Textures and The Formation of Self-Bound Gravitational Systems