Pre-big bang model has Planck problem

TL;DR

The paper critiques the pre-big bang model's inflation mechanism, highlighting that it leads to a Planck problem where the Planck length grows faster than the universe's scale, requiring unnatural constants for explanation.

Contribution

It identifies a fundamental flaw in the pre-big bang model's inflationary mechanism, demonstrating its inability to naturally explain the large universe without unnatural constants.

Findings

The Planck length grows faster than the scale factor in the model.

The model requires unnatural constants similar to non-inflationary big bang models.

The pre-big bang mechanism does not adequately solve the horizon and flatness problems.

Abstract

The pre-big bang's kinetic driven inflationary mechanism is not an adequate form of inflation: the Planck length grows more rapidly than the scale factor. In order to explain our large universe, the resulting post-big bang universe requires the same unnatural constants (Planck problem) as those of any other non-inflationary big bang model.