Fast Analytic Computation of Cosmic String Power Spectra

Abstract

We present analytic expressions for the cosmic string unequal time correlator (UETC) in the context of the Unconnected Segment Model (USM). This eliminates the need to simulate the many thousands of network realisations needed to estimate the UETC numerically. With our approach we can compute the UETC very accurately, over all scales of interest, in the order of ~20-30 seconds on a single CPU. Our formalism facilitates an efficient approach to computing Cosmic Microwave Background (CMB) anisotropies for cosmic strings. Discretising the UETC and performing an eigen-decomposition to act as sources in the CAMB CMB code, the power spectrum can be calculated by summing over a finite number of eigenmodes. A much smaller number of eigenmodes are required compared to the conventional approach of averaging power spectra over a finite number of realisations of the string network. With the additional efficiency and performance improvements offered by the OpenMP CAMB code, the time required to compute string power spectra is significantly reduced compared to the standard serial CMBACT code. The latter takes ~30 hours on a modern single threaded CPU for 2000 network realisations. Similar percent level accuracy can be achieved with our approach on a moderately threaded CPU (8 threads) in only ~15 minutes. If accuracy is only required at the 10 percent level and the CPU is more highly threaded, cosmic string power spectra are now possible in ~2-3 minutes. This makes exploration of the string parameter space now possible for Markov-Chain-Monte-Carlo (MCMC) analysis.

13 pages, 3 figures, minor corrections and improvements, matches published version

References in corpus (48)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Efficient Computation of CMB anisotropies in closed FRW models
• Cosmological parameters from CMB and other data: a Monte-Carlo approach
• A Line of Sight Approach to Cosmic Microwave Background Anisotropies
• Cosmic strings
• Hybrid Inflation
• Towards Inflation in String Theory
• False Vacuum Inflation with Einstein Gravity
• Brane Inflation
• Large Scale Structure and Supersymmetric Inflation without Fine Tuning
• Cosmic String Production Towards the End of Brane Inflation
• Cosmic F- and D-strings
• The Inflationary Brane-Antibrane Universe
• CMB Anisotropies: Total Angular Momentum Method
• How generic is cosmic string formation in SUSY GUTs
• Formation and evolution of cosmic D-strings
• Quantitative String Evolution
• Cosmological evolution of cosmic string loops
• Extending the Velocity-dependent One-scale String Evolution Model
• Large parallel cosmic string simulations: New results on loop production
• Power Spectra in Global Defect Theories of Cosmic Structure Formation
• Cosmic Strings and Superstrings
• CMB power spectrum contribution from cosmic strings using field-evolution simulations of the Abelian Higgs model
• Towards an Explicit Model of D-brane Inflation
• Collisions of Cosmic F- and D-strings
• Fractal Properties and Small-scale Structure of Cosmic String Networks
• Numerical simulations of string networks in the Abelian-Higgs model
• On the Evolution of Abelian-Higgs String Networks
• Evolution of cosmic string configurations
• Cosmic microwave background anisotropy from wiggly strings
• Scaling of Multi-Tension Cosmic Superstring Networks
• Abelian Higgs Cosmic Strings: Small Scale Structure and Loops
• Updated constraints on the cosmic string tension
• Signals of Inflationary Models with Cosmic Strings
• Seeking String Theory in the Cosmos
• Cosmic String constraints from WMAP and the South Pole Telescope
• A detail study of defect models for cosmic structure formation
• B-modes from Cosmic Strings
• Cosmic strings and their induced non-Gaussianities in the cosmic microwave background
• Structure formation by cosmic strings with a cosmological constant
• The Scalar, Vector and Tensor Contributions to CMB anisotropies from Cosmic Defects
• Cosmic string parameter constraints and model analysis using small scale Cosmic Microwave Background data
• Velocity-Dependent Models for Non-Abelian/Entangled String Networks
• Transonic Elastic Model for Wiggly Goto-Nambu String
• Constraints on the fundamental string coupling from B-mode experiments
• The effect of kinematic constraints on multi-tension string network evolution
• Cosmic string evolution with a conserved charge

Cited by in corpus (16)

• CMB constraints on cosmic strings and superstrings
• Scaling from gauge and scalar radiation in Abelian Higgs string networks
• Gravitational Waves from Global Cosmic Strings and Cosmic Archaeology
• Did BICEP2 see vector modes? First B-mode constraints on cosmic defects
• Constraints on the Nambu-Goto cosmic string contribution to the CMB power spectrum in light of new temperature and polarisation data
• Constraining topological defects with temperature and polarization anisotropies
• Energy-momentum correlations for Abelian Higgs cosmic strings
• CMB power spectrum of Nambu-Goto cosmic strings
• Multi-Scale Pipeline for the Search of String-Induced CMB Anisotropies
• Semianalytic calculation of cosmic microwave background anisotropies from wiggly and superconducting cosmic strings
• Highly Excited Strings I: Generating Function
• CMB anisotropies generated by cosmic string loops
• The bispectrum of matter perturbations from cosmic strings
• The bispectrum of cosmic string temperature fluctuations including recombination effects
• Weak lensing from self-ordering scalar fields
• Primordial magnetic fields from the string network