Dante's Inferno

TL;DR

The paper tackles the UV sensitivity of high-scale inflation by proposing Dante's Inferno, a two-field inflation model with two axions whose fundamental field ranges remain sub-Planckian. By adiabatically eliminating the heavy direction, the model yields an effective quadratic potential for φ_eff with a suppressed mass m_eff, reproducing chaotic-inflation-like predictions while easing the η-problem. It embeds this construction in Type IIB string theory as a two-axion generalization of axion monodromy, using ED1 instantons and NS5-brane monodromy to generate the necessary cosine and monodromy terms, with a hierarchical decay-constant ratio f_r/f_θ controlling backreaction. The results show that large tensor modes can be achieved within a controlled UV-complete framework, expanding the viable parameter space for stringy inflation and illustrating how multi-field monodromy can reconcile high-scale inflation with subplanckian microphysics.

Abstract

We present a simple two-field model of inflation and show how to embed it in string theory as a straightforward generalization of axion monodromy models. Phenomenologically, the predictions are equivalent to those of chaotic inflation, and in particular include observably large tensor modes. The whole high-scale large-field inflationary dynamics takes place within a region of field space that is parametrically subplanckian in diameter, hence improving our ability to control quantum corrections and achieve slow-roll inflation.

Figures (4)

• Figure 1: The potential in \ref{['V']} (for $W(r)=\frac{1}{2} m^2 r^2$) in Cartesian coordinates, which faithfully represent the metric on field space.
• Figure 2: The potential in \ref{['V']} for $W(r)=\frac{1}{2} m^2 r^2$ in cylindrical coordinates, which do not faithfully reproduce the field-space metric as given in \ref{['L']}, contrary to Cartesian coordinates in figure \ref{['fig2']}. On the other hand, in polar coordinates, the periodicity in ${\theta}$ is apparent and the similarity with Inferno as described by Dante Dante becomes evident.
• Figure 3: The field-space contour plot of the potential. Brighter red shading corresponds to higher energy and vice versa. Both rotated and un-rotated coordinates are shown together with $\phi_{\mathrm{eff}}$ which is always tangent to the inflationary trajectory. Upon the use of the ${\theta}$ shift-symmetry, the whole inflationary trajectory can be contained into a region of subplanckian diameter, indicated by the dotted box.
• Figure 4: A cartoon of the ingredients required to embed Dante's Inferno in string theory.