Gauged M-flation, its UV sensitivity and Spectator Species

TL;DR

Gauged M-flation, an inflationary model driven by matrix scalar fields, remains UV safe despite spectator species reducing the cutoff, with the string scale sufficiently high to neglect string effects.

Contribution

This paper demonstrates that gauged M-flation maintains UV safety with a reduced cutoff and clarifies the role of spectator species, extending the understanding of its theoretical consistency.

Findings

Spectator spectrum differs from ungauged case.

UV cutoff is reduced but still above the string scale.

Gauged M-flation remains UV safe with a cutoff of order 0.05-0.1 M_{pl}.

Abstract

In this paper we study gauged M-flation, an inflationary model in which inflation is driven by three NxN scalar field matrices in the adjoint representation of U(N) gauge group. We focus our study on the gauged M-flation model which could be derived from the dynamics of a stack of D3-branes in appropriate background flux. The background inflationary dynamics is unaltered compared to the ungauged case of [arXiv:0903.1481[hep-th]], while the spectrum of "spectator species", the isocurvature modes, differs from the ungauged case. Presence of a large number of spectators, although irrelevant to the slow-roll inflationary dynamics has been argued to lower the effective UV cutoff $\Lambda$ of the theory from the Planck mass, invalidating the main advantage of M-flation in not having super-Planckian field values and unnaturally small couplings. Through a careful analysis of the spectrum of the spectators we argue that, contrary to what happens in N-flation models, M-flation is still UV safe with the modified (reduced) effective UV cutoff $\Lambda$, which we show to be of order (0.5-1)x10^{-1} M_{pl}. Moreover, we argue that the string scale in our gauged M-flation model is larger than $\Lambda$ by a factor of 10 and hence one can also neglect stringy effects. We also comment on the stability of classical inflationary paths in the gauged M-flation.