Naturalness in Cosmological Initial Conditions

Abstract

We propose a novel approach to the problem of constraining cosmological initial conditions. Within the framework of effective field theory, we classify initial conditions in terms of boundary terms added to the effective action describing the cosmological evolution below Planckian energies. These boundary terms can be thought of as spacelike branes which may support extra instantaneous degrees of freedom and extra operators. Interactions and renormalization of these boundary terms allow us to apply to the boundary terms the field-theoretical requirement of naturalness, i.e. stability under radiative corrections. We apply this requirement to slow-roll inflation with non-adiabatic initial conditions, and to cyclic cosmology. This allows us to define in a precise sense when some of these models are fine-tuned. We also describe how to parametrize in a model-independent way non-Gaussian initial conditions; we show that in some cases they are both potentially observable and pass our naturalness requirement.

35 pages, 8 figures

References in corpus (22)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Preliminary Maps and Basic Results
• Non-Gaussian features of primordial fluctuations in single field inflationary models
• The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang
• Non-Gaussianity from Inflation: Theory and Observations
• The Pre-Big Bang Scenario in String Cosmology
• Cosmic Evolution in a Cyclic Universe
• Second-Order Cosmological Perturbations from Inflation
• Density Perturbations in the Ekpyrotic Scenario
• Signatures of Short Distance Physics in the Cosmic Microwave Background
• Are Inflationary Predictions Sensitive to Very High Energy Physics?
• Initial Conditions for Inflation
• Perturbations in bouncing cosmologies: dynamical attractor vs scale invariance
• Effective Field Theories and Inflation
• Decoupling in an expanding universe: boundary RG-flow affects initial conditions for inflation
• Decoupling in an expanding universe: backreaction barely constrains short distance effects in the CMB
• Inflation and de Sitter Holography
• Bounds on Generic High-Energy Physics Modifications to the Primordial Power Spectrum from Back-Reaction on the Metric
• Scalar perturbations in regular two-component bouncing cosmologies
• Holography, Diffeomorphisms, and Scaling Violations in the CMB
• A Cosmological Window on Trans-Planckian Physics
• Effective Field Theory Approach to Cosmological Initial Conditions: Self-Consistency Bounds and Non-Gaussianities
• Decoupling, Trans-Planckia and Inflation

Cited by in corpus (13)

• Observational Signatures and Non-Gaussianities of General Single Field Inflation
• On the one loop corrections to inflation and the CMB anisotropies
• Large non-Gaussian Halo Bias from Single Field Inflation
• Fossilized Gravitational Wave Relic and Primordial Clocks
• Scale-dependent power spectrum from initial excited-de Sitter modes
• The renormalization of the energy-momentum tensor for an effective initial state
• Quantum Cosmic No-Hair Theorem and Inflation
• Cosmological matching conditions
• String Propagation through a Big Crunch/Big Bang Transition
• Primordial non-Gaussianities in single field inflationary models with non-trivial initial states
• Trans-Planckian enhancements of the primordial non-Gaussianities
• Aspects of Dirichlet S-branes
• Inflation in Non-de Sitter Background with Coherent States