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Constraints on the spectral index for the inflation models in string landscape

Qing-Guo Huang

Abstract

We conjecture that the inflation models with trans-Planckian excursions in the field space should be in the swampland. We check this conjecture in a few examples and investigate the constraints on the spectral index for the slow-roll inflation model in string landscape where the variation of inflaton during the period of inflation is less than the Planck scale $M_p$. A red primordial power spectrum with a lower bound on the spectral index is preferred. Both the tensor-scalar ratio and the running can be ignored.

Constraints on the spectral index for the inflation models in string landscape

Abstract

We conjecture that the inflation models with trans-Planckian excursions in the field space should be in the swampland. We check this conjecture in a few examples and investigate the constraints on the spectral index for the slow-roll inflation model in string landscape where the variation of inflaton during the period of inflation is less than the Planck scale . A red primordial power spectrum with a lower bound on the spectral index is preferred. Both the tensor-scalar ratio and the running can be ignored.

Paper Structure

This paper contains 33 equations, 1 figure.

Figures (1)

  • Figure 1: The lower bounds on $n_s$ and $\alpha_s$ are showed for the single-field inflation model with sub-Planckian excursion in the field space. With a high inflation scale, and radiation and/or matter domination between the end of inflation and nucleosynthesis, $47\leq N\leq 61$. More generally the range has to be $14\leq N\leq 75$Alabidi:2006qa.