Inflation Assisted by Heterotic Axions

• Published in: arXiv.org 2007-04
• Main Author: Olsson, Martin E
• Format: Article
• Language: English
• Subjects: Spectra; String theory; Tensors; Variations
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0702109

We explore the possibility of obtaining inflation in weakly coupled heterotic string theory, where the model dependent axions are responsible for driving inflation. This model can be considered as a certain extrapolation of \(m^{2}\phi^{2}\)-inflation, and is an attempt to explicitly realize the so called N-flation proposal in string theory. The instanton generated potential for the axions essentially has two parameters; a natural mass scale \(M\) and the string coupling \(g_{s}\). For isotropic compactifications leading to of order \(\mathcal{O} (10^4)\) axions in the four dimensional spectrum we find that with \((M, g_{s})\simeq(M_{GUT}, 0.5)\) the observed temperature fluctuations in the CMB are correctly reproduced. We assume an initially random distribution for the vevs of the axions. The spectral index, \(n_{s}\), is generically more red than for \(m^{2}\phi^{2}\)-inflation. The greater the vevs, the more red the spectral index becomes. Allowing for a wide range of vevs 55 \(e\)-foldings from the end of inflation, we find \(0.946\lesssim n_{s} \lesssim 0.962\). The tensor-to-scalar ratio, \(r\), is more sensitive to the vevs, but typically smaller than in \(m^{2}\phi^{2}\)-inflation. Furthermore, in the regime where the leading order theory is valid, \(r\) is bounded by \(r < 0.10\). The spectral index and the tensor-to-scalar ratio are correlated. For example, \(n_{s}\simeq 0.951\) corresponds to \(r\simeq 0.036\).