How Delicate is Brane-Antibrane Inflation?

Abstract

We systematically explore the parameter space of the state-of-the-art brane-antibrane inflation model (Baumann {\it et al}., arXiv:0706.0360, arXiv:0705.3837) which is one of the most rigorously derived from string theory, applying the cosmic background explorer normalization and constraint on the spectral index. We improve on previous treatments of uplifting by antibranes and show that the contributions from noninflationary throats play an important role in achieving a flat inflationary potential. To quantify the degree of fine-tuning needed by the model, we define an effective volume in the part of parameter space which is consistent with experimental constraints, and using Monte Carlo methods to search for a set of optimal parameters, we show that the degree of fine-tuning is alleviated by 8 orders of magnitude relative to a fiducial point which has previously been considered. In fact, close to the optimal parameter values, fine-tuning is no longer needed for any of the parameters. We show that in this natural region of the parameter space, larger values of $n_s$ close to 0.99 (still within 2$\sigma$ of the WMAP5 central value) are favored, giving a new aspect of testability to the model.

33 pages, 12 figures. v2: added discussion of an alternate measure of fine-tuning; published version

References in corpus (18)

• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• de Sitter Vacua in String Theory
• Supergravity and a Confining Gauge Theory: Duality Cascades and $\chi$SB-Resolution of Naked Singularities
• Towards Inflation in String Theory
• Adiabatic and entropy perturbations from inflation
• Tachyon Condensation on the Brane Antibrane System
• On D3-brane Potentials in Compactifications with Fluxes and Wrapped D-branes
• Towards an Explicit Model of D-brane Inflation
• A Delicate Universe
• Holographic Systematics of D-brane Inflation
• Prospects of inflation in delicate D-brane cosmology
• Chasing Brane Inflation in String-Theory
• Multibrane Inflation and Dynamical Flattening of the Inflaton Potential
• Uplifting and Inflation with D3 Branes
• Brane Inflation is Attractive
• Systematics of multi-field effects at the end of warped brane inflation
• Prospects of inflation with perturbed throat geometry

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• Accidental Inflation in the Landscape
• Multi-Field Inflation on the Landscape
• Inflation with improved D3-brane potential and the fine tunings associated with the model
• Brane Inflation and the Overshoot Problem
• Reheating the D-brane universe via instant preheating
• Towards a warped inflationary brane scanning
• DBI Lifshitz Inflation