Cosmic structure formation with topological defects

Optical Trapping, Manipulation, and 3D Imaging of Disclinations in Liquid Crystals and Measurement of their Line Tension

“…The study of topological defects is important for understanding defect-mediated phase transitions in condensed matter [1][2][3][4][5]; it is also of a great current interest in cosmology [6][7][8][9]. The nematic liquid crystals (LCs) are convenient model systems for the study of defects and can be useful even for the "cosmology in laboratory" experiments [6][7][8][9].…”

“…The nematic liquid crystals (LCs) are convenient model systems for the study of defects and can be useful even for the "cosmology in laboratory" experiments [6][7][8][9]. Long-range orientational order in nematic LCs is usually described by the director field ) ( ) ( r n r n r r − = representing the average spatial orientation of the LC molecules [1].…”

Symmetry Breaking and Defects

“…The idea that strings alone could seed these density perturbations seems no longer viable, in the light of the data on the cosmic microwave background anisotropy. It is still perfectly possible to fit the data with models incorporating both strings and inflation [16], but a recent analysis concludes that strings probably do not make a significant contribution [17]. They may, however, have had other important cosmological effects, for example in the generation of magnetic fields [18,19,20], high-energy cosmic rays [21,22] and baryogenesis [23,24].…”

Microwave background constraints on decaying defects

“…Note, however, that all cosmic string models with this scale of symmetry breaking are already constrained [15][16][17] by the fact that they would produce observable isocurvature fluctuations in the CMB of amplitude larger than what is compatible with recent CMB anisotropy observations. Consider now strings decaying at a redshift z d larger than z eq (but smaller than 10 6 ).…”

“…Non-conducting cosmic strings will remain in the friction dominated phase in which they strongly interact with the surrounding plasma until the time t x given in (16), which corresponds to the Kibble limit temperature given by…”