Defect junctions and domain wall dynamics

Abstract

We study a number of domain wall forming models where various types of defect junctions can exist. These illustrate some of the mechanisms that will determine the evolution of defect networks with junctions. Understanding these mechanisms is vital for a proper assessment of a number of cosmological scenarios: we will focus on the issue of whether or not cosmological frustrated domain wall networks can exist at all, but our results are also relevant for the dynamics of cosmic (super)strings, where junctions are expected to be ubiquitous. We also define and discuss the properties that would make up the ideal model in terms of hypothetical frustrated wall networks, and provide an explicit construction for such a model. We carry out a number of numerical simulations of the evolution of these networks, analyze and contrast their results, and discuss their implications for our no-frustration conjecture.

Bifurcation and pattern changing with two real scalar fields

“…We are considering dimensionless variables, that is, we have rescaled both the fields and the space and time coordinates appropriately such that they are now dimensionless quantities. If ε = 0 then the fields, φ and χ, are not coupled and the minima of the potential are at v [11,13] for more details).…”

“…We have also computed τ e by solving the equations of motion for φ and χ numerically (see Ref. [12] for details about the numerical code).…”

“…The evolution of the macroscopic properties of domain wall networks is strongly dependent on whether or not junctions are present and, in the former case, on the dimensionality of the junctions. Although the presence of junctions is not enough to make domain walls a viable dark energy candidate, their impact on the dynamics of the network needs to be taken into account in any quantitative study of cosmological consequences of domain wall evolution [12]. In this paper we perform domain wall network simulations of a new class of one-parameter multi-tension domain wall models, showing that it has a number of interesting properties.…”

“…The outline of this paper is as follows. We start by reviewing the BBL model in Section II, analytically and numerically calculating the domain wall tensions and comparing our results with analytical results, valid for |ε| 1, obtained in [11] (see also [13]). We discuss how bifurcation arises in this model as well as the corresponding implications for the dimensionality of the junctions which may be present when we consider more than one spatial dimension.…”

Cosmic microwave background anisotropies generated by domain wall networks

“…They are, however, often overlooked in cosmology since the energy scale of the phase transition that originates the domain walls is restricted to be smaller than 1 MeV [2]. Nonetheless, there is still room for domain walls to play a relevant role in cosmology: for instance, they have been suggested as a possible significant dark energy contributor [3]-albeit they have since been ruled out as a major dark energy component [4][5][6] -and as a possible explanation for the spatial variations of the fine structure constant hinted at by HIRES/Keck and VLT/UVES data [7][8][9].…”