[Paper Review] Limits on SUSY GUTs and Defects Formation in Hybrid Inflationary Models with Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations

Aurélien A. Fraisse|arXiv (Cornell University)|Mar 22, 2006

Cosmology and Gravitation Theories4 citations

TL;DR

This study uses three-year WMAP CMB data to test hybrid inflationary models with cosmic strings and textures, finding no statistically significant distinction among them. It sets a stringent upper limit on cosmic string tension: Gμ ≤ 2.1 × 10⁻⁷ at 68% confidence level, constraining D- and F-term couplings and mass scales in SUSY GUTs and defect formation scenarios.

ABSTRACT

We confront the predicted effects of hybrid inflationary models on the Cosmic Microwave Background (CMB) with three years of Wilkinson Microwave Anisotropy Probe (WMAP) observations. Using model selection, we compare the ability of a simple flat power-law LCDM model to describe the data to hybrid inflationary models involving global or local cosmic strings, or global textures. We find that it is statistically impossible to distinguish between these models: they all give a similar description of the data, the maximum ratio of the various evidences involved being never higher than e^{0.1 \\pm 0.5}. We then derive the maximum contribution that topological defects can make to the CMB, and place an upper bound on the possible value of cosmic strings tension of G\\mu \\leq 2.1 \ imes 10^{-7} (68% CL). Finally, we give the corresponding constraints on the strings and D-strings masses, as well as limits on the D- and F-term coupling constants (\\kappa and \\lambda) and mass scales (M and \\sqrt{\\xi}).

Motivation & Objective

• To evaluate the compatibility of hybrid inflationary models with topological defects—specifically global or local cosmic strings and global textures—against three-year WMAP CMB observations.
• To determine whether these defect-based models can be statistically distinguished from the standard flat power-law LCDM model.
• To derive the maximum allowable contribution of topological defects to the CMB anisotropy power spectrum.
• To place upper bounds on cosmic string tension, D-string and F-term coupling constants, and associated mass scales in SUSY GUTs.
• To constrain the parameter space of defect formation in hybrid inflationary scenarios using observational CMB data.

Proposed method

• Employing Bayesian model selection to compare the evidences of the flat power-law LCDM model against models with global or local cosmic strings and global textures.
• Using three-year WMAP CMB temperature anisotropy data to compute likelihoods for each model, focusing on the large-scale power spectrum.
• Applying a ratio of evidences to assess statistical distinguishability, with a maximum ratio of e^{0.1 ± 0.5} indicating near-equivalent fit quality.
• Deriving upper limits on the cosmic string tension Gμ by analyzing the maximum allowed contribution of defects to the CMB power spectrum.
• Translating the upper bound on Gμ into constraints on D-string and F-term coupling constants (κ and λ), and on mass scales M and √ξ in SUSY GUTs.
• Utilizing theoretical predictions of defect formation in hybrid inflation to link cosmological observables to high-energy physics parameters.

Experimental results

Research questions

• RQ1 Can hybrid inflationary models with cosmic strings or textures be statistically distinguished from the standard LCDM model using three-year WMAP data?
• RQ2 What is the maximum contribution that topological defects can make to the CMB anisotropy power spectrum?
• RQ3 What upper bound can be placed on the cosmic string tension Gμ based on WMAP observations?
• RQ4 How do the observed CMB constraints translate into limits on D- and F-term coupling constants and mass scales in SUSY GUTs?
• RQ5 What are the implications of these constraints for defect formation in hybrid inflationary scenarios?

Key findings

• The three-year WMAP data show no statistically significant distinction between the flat power-law LCDM model and hybrid inflationary models involving global or local cosmic strings or global textures.
• The maximum ratio of evidences between any two models is e^{0.1 ± 0.5}, indicating that all models describe the data with comparable statistical significance.
• An upper bound on cosmic string tension is derived: Gμ ≤ 2.1 × 10⁻⁷ at 68% confidence level.
• Constraints are placed on the D-string and F-term coupling constants (κ and λ), as well as on the mass scales M and √ξ, derived from the Gμ bound.
• The results imply strong limitations on the parameter space of SUSY GUTs and defect formation in hybrid inflationary models.
• The findings suggest that topological defects cannot account for a significant fraction of the CMB power spectrum, favoring alternative inflationary mechanisms.