[Paper Review] Inflationary cosmology and structure formation

J. A. Peacock|arXiv (Cornell University)|Jan 24, 1996

Cosmology and Gravitation Theories3 references3 citations

TL;DR

This paper presents a comprehensive overview of inflationary cosmology, detailing how primordial density fluctuations arise from quantum fluctuations of scalar fields during inflation. It then traces their evolution in a Friedmann-Robertson-Walker universe, showing how these fluctuations seed large-scale structure, and evaluates the consistency of inflationary models with galaxy clustering and cosmic microwave background data as of 1995.

ABSTRACT

These lectures cover the basics of inflationary models for the early universe, concentrating particularly on the generation of density fluctuations from scalar-field dynamics. The subsequent gravitational dynamics of these fluctuations in dark matter in a Friedmann model are described, leading to a review of the current situation in confronting inflationary models with the latest data on the clustering of galaxies and other measures of large-scale structure.

Motivation & Objective

• To explain the theoretical foundations of inflationary cosmology, particularly the generation of primordial density fluctuations from scalar field quantum fluctuations.
• To describe the gravitational evolution of these fluctuations in a dark matter-dominated Friedmann universe.
• To assess the consistency of inflationary models with observational data on large-scale structure, including galaxy clustering and cosmic microwave background anisotropies.
• To provide a pedagogical framework for understanding how inflationary models predict the observed cosmic structure.
• To evaluate the current status of inflationary models in light of the latest data available in 1995.

Proposed method

• Uses the framework of single-field slow-roll inflation to model the generation of primordial curvature perturbations from vacuum fluctuations of a scalar inflaton field.
• Applies linear perturbation theory in a Friedmann-Robertson-Walker metric to track the growth of density fluctuations in the dark matter component.
• Employs the transfer function formalism to relate initial power spectra to the observed matter power spectrum on large scales.
• Compares theoretical predictions of the matter power spectrum with observational data from galaxy redshift surveys and cosmic microwave background anisotropy measurements.
• Uses the consistency of predicted clustering amplitudes and spectral indices with observations to constrain inflationary parameters.
• Analyzes the role of dark matter in structure formation, assuming cold dark matter as the dominant component.

Experimental results

Research questions

• RQ1 How do quantum fluctuations of the inflaton field generate primordial density perturbations in the early universe?
• RQ2 What is the evolution of these perturbations in a dark matter-dominated Friedmann universe, and how do they lead to large-scale structure?
• RQ3 How well do inflationary models reproduce the observed clustering of galaxies on large scales?
• RQ4 What constraints do cosmic microwave background anisotropy measurements place on inflationary parameters?
• RQ5 What is the current consistency of inflationary models with the observational data available in 1995?

Key findings

• Inflationary models successfully generate a nearly scale-invariant spectrum of primordial curvature perturbations from quantum fluctuations of the inflaton field.
• The observed large-scale structure in galaxy redshift surveys is consistent with predictions from inflationary models assuming a nearly scale-invariant spectrum.
• The amplitude of the matter power spectrum inferred from galaxy clustering data is in good agreement with predictions from inflation, given the observed normalization of the CMB anisotropy.
• The spectral index of the primordial power spectrum is constrained to be close to unity, consistent with the predictions of simple slow-roll inflation.
• The models predict a specific shape for the matter power spectrum that matches the observed clustering on scales of tens to hundreds of megaparsecs.
• The paper concludes that inflationary cosmology provides a robust theoretical framework that is consistent with the large-scale structure data available at the time of publication.