Trans-Planckian Issues for Inflationary Cosmology

TL;DR

This paper reviews the trans-Planckian problem in inflationary cosmology, questioning the robustness of inflation predictions and the potential observability of Planck-scale physics effects on current cosmological data.

Contribution

It provides a comprehensive review of the trans-Planckian issues in inflationary cosmology and discusses the implications for the robustness of inflationary predictions.

Findings

Highlights the potential influence of trans-Planckian physics on observable cosmological fluctuations

Discusses the theoretical uncertainties in inflation predictions due to unknown physics at Planck scales

Reviews possible observational signatures of Planck-scale effects in cosmological data

Abstract

The accelerated expansion of space during the period of cosmological inflation leads to trans-Planckian issues which need to be addressed. Most importantly, the physical wavelength of fluctuations which are studied at the present time by means of cosmological observations may well originate with a wavelength smaller than the Planck length at the beginning of the inflationary phase. Thus, questions arise as to whether the usual predictions of inflationary cosmology are robust considering our ignorance of physics on trans-Planckian scales, and whether the imprints of Planck-scale physics are at the present time observable. These and other related questions are reviewed in this article.