Cosmology of Axions and Moduli: A Dynamical Systems Approach

Abstract

This paper is concerned with string cosmology and the dynamics of multiple scalar fields in potentials that can become negative, and their features as (Early) Dark Energy models. Our point of departure is the "String Axiverse", a scenario that motivates the existence of cosmologically light axion fields as a generic consequence of string theory. We couple such an axion to its corresponding modulus. We give a detailed presentation of the rich cosmology of such a model, ranging from the setting of initial conditions on the fields during inflation, to the asymptotic future. We present some simplifying assumptions based on the fixing of the axion decay constant $f_a$, and on the effective field theory when the modulus trajectory is adiabatic, and find the conditions under which these assumptions break down. As a by-product of our analysis, we find that relaxing the assumption of fixed $f_a$ leads to the appearance of a new meta-stable de-Sitter region for the modulus without the need for uplifting by an additional constant. A dynamical systems analysis reveals the existence of many fixed point attractors, repellers and saddle points, which we analyse in detail. We also provide geometric interpretations of the phase space. The fixed points can be used to bound the couplings in the model. A systematic scan of certain regions of parameter space reveals that the future evolution of the universe in this model can be rich, containing multiple epochs of accelerated expansion.

27 pages, 12 figures, comments welcome, v2 minor corrections

References in corpus (30)

• Dynamics of dark energy
• Monodromy in the CMB: Gravity Waves and String Inflation
• String Cosmology: A Review
• An M Theory Solution to the Strong CP Problem and Constraints on the Axiverse
• Ultra-Light Scalar Fields and the Growth of Structure in the Universe
• Dynamical Dark Energy or Simply Cosmic Curvature?
• On the importance of heavy fields during inflation
• Roulette Inflation with Kähler Moduli and their Axions
• Volume Modulus Inflation and the Gravitino Mass Problem
• Axions as Quintessence in String Theory
• The Wasteland of Random Supergravities
• Where in the String Landscape is Quintessence
• Future CMB Constraints on Early, Cold, or Stressed Dark Energy
• Eternal Symmetree
• Poly-instanton Inflation
• String moduli inflation: an overview
• Challenges for String Cosmology
• Compactified String Theories -- Generic Predictions for Particle Physics
• Ultra-light Axions: Degeneracies with Massive Neutrinos and Forecasts for Future Cosmological Observations
• Modulated Reheating and Large Non-Gaussianity in String Cosmology
• Moduli Stabilisation and Applications in IIB String Theory
• Axionic dark energy and a composite QCD axion
• Constraining Variations in the Fine Structure Constant in the presence of Early Dark Energy
• The inflating curvaton
• Dynamics of Generalized Assisted Inflation
• Scale-Dependent Growth from a Transition in Dark Energy Dynamics
• Non-parametric Dark Energy Degeneracies
• Axion-Dilaton Cosmology and Dark Energy
• Moduli-Induced Vacuum Destabilisation
• Black Hole Portal into Hidden Valleys

Cited by in corpus (14)

• Axion Cosmology
• Dynamical systems applied to cosmology: dark energy and modified gravity
• A search for ultra-light axions using precision cosmological data
• Tensor Detection Severely Constrains Axion Dark Matter
• Cosmological signatures of ultralight dark matter with an axionlike potential
• The Spectrum of the Axion Dark Sector
• Quintessence in a quandary: prior dependence in dark energy models
• Axiverse cosmology and the energy scale of inflation
• F-term Stabilization of Odd Axions in LARGE Volume Scenario
• Constraining SUSY with Heavy Scalars -- using the CMB
• Scalar field cosmology in phase space
• How can we tell whether dark energy is composed by multiple fields?
• Jacobi stability analysis of scalar field models with minimal coupling to gravity in a cosmological background
• One-parametric description for scalar field dark matter potentials