Fine-tuning criteria for inflation and the search for primordial gravitational waves

Abstract

We revisit arguments that simple models of inflation with a small red tilt in the scalar power spectrum generically yield an observable tensor spectrum. We show that criteria for fine-tuning based upon the algebraic simplicity of the potential depend strongly upon the explicit assumptions they incorporate, particularly regarding the end of inflation. In addition, some models with algebraically simple potentials require carefully tuned initial field configurations, and not all types of fine-tuning are identifiable via the algebraic simplicity of the potential. Conversely, in the absence of a strong prior on the mechanism that ends inflation, we demonstrate the existence of potentials with vanishingly small tensor amplitudes which are natural in terms of both their algebraic form and initial conditions. We thus argue that proposed experiments (CMBPol or BBO) which make highly sensitive measurements of the tensor amplitude cannot definitively rule out the inflationary paradigm.

arXiv comment14 pages, 20 figures, matches version published in PRD; references added

References in corpus (30)

• Hybrid Inflation
• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Inflation
• What would we learn by detecting a gravitational wave signal in the cosmic microwave background anisotropy?
• From Big Crunch to Big Bang
• N-flation
• A limit on the detectability of the energy scale of inflation
• Separation of Gravitational-Wave and Cosmic-Shear Contributions to Cosmic Microwave Background Polarization
• A Microscopic Limit on Gravitational Waves from D-brane Inflation
• Towards an Explicit Model of D-brane Inflation
• The Measure Problem in Cosmology
• A Delicate Universe
• Measures of fine tuning
• Random Matrices and the Spectrum of N-flation
• The cosmic gravitational wave background in a cyclic universe
• Kinematic Constraints to the Key Inflationary Observables
• Considerations in optimizing CMB polarization experiments to constrain inflationary physics
• Inflationary Theory and Alternative Cosmology
• Recovering the Inflationary Potential and Primordial Power Spectrum With a Slow Roll Prior: Methodology and Application to WMAP 3 Year Data
• Inflationary predictions for scalar and tensor fluctuations reconsidered
• Accidental Inflation in String Theory
• Slow Roll Reconstruction: Constraints on Inflation from the 3 Year WMAP Dataset
• Chasing Brane Inflation in String-Theory
• MCMC analysis of WMAP3 and SDSS data points to broken symmetry inflaton potentials and provides a lower bound on the tensor to scalar ratio
• The Lyth Bound and the End of Inflation
• Initial conditions for hybrid inflation
• Detectability of tensor modes in the presence of foregrounds
• The Search For Primordial Tensor Modes
• Brane Inflation is Attractive
• Initial Conditions for Vector Inflation
• The Tensor Desert

Cited by in corpus (13)

• Inflation and the Scale Dependent Spectral Index: Prospects and Strategies
• Bayesian Analysis of Inflation: Parameter Estimation for Single Field Models
• Reconstruction of the primordial power spectrum of curvature perturbations using multiple data sets
• Initial Conditions for Non-Canonical Inflation
• The present and future of the most favoured inflationary models after $Planck$ 2015
• On the Suppression of Parametric Resonance and the Viability of Tachyonic Preheating after Multi-Field Inflation
• The Overshoot Problem in Inflation after Tunneling
• Brane Inflation and the Overshoot Problem
• Initial Energy of a Spatially Flat Universe -- a Hint of its Possible Origin
• Expectations for Inflationary Observables: Simple or Natural?
• Note on initial conditions for small-field inflation
• Scaling behavior of observables as a model characteristic in multifield inflation
• The Einstein Dual Theory of Relativity