Topological defects: A problem for cyclic universes?

Abstract

We study the behaviour of cosmic string networks in contracting universes, and discuss some of their possible consequences. We note that there is a fundamental time asymmetry between defect network evolution for an expanding universe and a contracting universe. A string network with negligible loop production and small-scale structure will asymptotically behave during the collapse phase as a radiation fluid. In realistic networks these two effects are important, making this solution only approximate. We derive new scaling solutions describing this effect, and test them against high-resolution numerical simulations. A string network in a contracting universe, together with the gravitational radiation background it has generated, can significantly affect the dynamics of the universe both locally and globally. The network can be an important source of radiation, entropy and inhomogeneity. We discuss the possible implications of these findings for bouncing and cyclic cosmological models.

11 RevTeX 4 pages, 6 figures; version to appear in Phys. Rev. D

References in corpus (13)

• The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang
• Cosmic Evolution in a Cyclic Universe
• From Big Crunch to Big Bang
• On the Evolution of Abelian-Higgs String Networks
• Primordial perturbations in a non singular bouncing universe model
• On the Spectrum of Fluctuations in an Effective Field Theory of the Ekpyrotic Universe
• Passing through the bounce in the ekpyrotic models
• The Impact of an Extra Background of Relativistic Particles on the Cosmological Parameters derived from Microwave Background Anisotropies
• The failure of cosmological perturbation theory in the new ekpyrotic and cyclic ekpyrotic scenarios
• Recycling the universe using scalar fields
• Comment on "Density perturbations in the ekpyrotic scenario"
• Has the Universe always expanded ?
• Topological Defects in Contracting Universes

Cited by in corpus (6)

• Frustrated Expectations: Defect Networks and Dark Energy
• Domain wall network evolution in (N+1)-dimensional FRW universes
• Cosmic (super)strings with a time-varying tension
• p-brane dynamics in N+1-dimensional FRW universes
• Physical and invariant models for defect network evolution
• Adiabatic fluctuations from cosmic strings in a contracting universe