High-harmonic cosmic strings and gravitational waves
arXiv:2108.08242
Abstract
In this thesis we describe high-harmonic cosmic string loops in a general relativistic context, and study the implications of high-harmonic content for the predicted gravitational wave signal from cosmic string networks. Initially, we introduce the variational principle, spacetime concepts and other mathematical tools that we will need for the calculations in the following chapters. We introduce the FLRW universe and the universe. We then describe the Nambu-Goto cosmic string in a curved spacetime, its equations of motion and its energy-momentum tensor. Fixing the spacetime to be flat, and fixing the gauge, we find the motion of the cosmic string and we present and discuss special solutions. Using the odd-harmonic family of cosmic string loops, we calculate the number of cusps per period and the values of the second derivatives of the left- and right-moving harmonic modes at the cusp, and study their dependence on the harmonic order. We then develop a toy model that calculates the stable daughter loops produced from a parent loop using a statistical approach based on a binary tree description of the loop chopping. We also use the toy model to calculate the average number of cusps produced from a system of loops that self intersect over their course of existence. We derive the gravitational waveform emitted from a cusp as observed away from the cusp, in any direction of observation. We then propagate this result in an FLRW spacetime to reach an expression of its amplitude on Earth. Assuming two different cosmic string network models, we implement our above mentioned high-harmonic results to find the amplitude of the signal and the rate at which these signals reach an observer on Earth.
arXiv commentPhD thesis, School of Physics and Astronomy, Faculty of Science, University of Nottingham, October 2020
References in corpus (38)
- The Cosmological Constant and Dark Energy
- Modified Gravity and Cosmology
- Cosmic strings
- Towards Inflation in String Theory
- False Vacuum Inflation with Einstein Gravity
- Brane Inflation
- Cosmic F- and D-strings
- The Inflationary Brane-Antibrane Universe
- CMB Anisotropies: Total Angular Momentum Method
- Gravitational wave bursts from cosmic strings
- Gravitational wave bursts from cusps and kinks on cosmic strings
- How generic is cosmic string formation in SUSY GUTs
- The number of cosmic string loops
- Stochastic gravitational wave background from smoothed cosmic string loops
- Power Spectra in Global Defect Theories of Cosmic Structure Formation
- Cosmic Strings and Superstrings
- New limits on cosmic strings from gravitational wave observation
- Fractal Properties and Small-scale Structure of Cosmic String Networks
- Scaling of cosmic string loops
- Gravitational wave bursts from cosmic (super)strings: Quantitative analysis and constraints
- CMB constraints on cosmic strings and superstrings
- The case against scaling defect models of cosmic structure formation
- Abelian Higgs Cosmic Strings: Small Scale Structure and Loops
- Inflation and String Theory
- Scaling from gauge and scalar radiation in Abelian Higgs string networks
- On CCC-predicted concentric low-variance circles in the CMB sky
- A detail study of defect models for cosmic structure formation
- Cosmic Strings and Cosmic Superstrings
- Cosmic string loop shapes
- Gravitational Wave Bursts from Cosmic Superstrings with Y-junctions
- Gravitational wave signatures from kink proliferation on cosmic (super-) strings
- Observational constraints on light cosmic strings from photometry and pulsar timing
- Energy-conservation constraints on cosmic string loop production and distribution functions
- Gravitational smoothing of kinks on cosmic string loops
- Gravitational back-reaction near cosmic string kinks and cusps
- Gravitational Wave Bursts from Cosmic String Cusps and Pseudocusps
- Shape of Cosmic String Loops
- Closed Strings with Low Harmonics and Kinks