Fibre Inflation Meets Quintessence: Implications of Perturbative Stabilisation

TL;DR

The paper develops fibre inflation within a perturbative large-volume framework by redefining the base modulus, enabling large-volume stabilization without non-perturbative effects. It demonstrates that four inflationary scenarios, built from base redefinitions and sub-leading perturbative corrections (KK/winding loops, F^4 terms, and log-loop effects), can yield spectral indices and tensor-to-scalar ratios compatible with ACT data, improving upon original fibre-inflation predictions. It also introduces a quintessence sector stabilized by poly-instanton corrections, with an axion from the base modulus acting as dark matter and a lighter fibre axion driving late-time acceleration, yielding a coherent story from inflation to dark energy. Overall, the work shows that perturbative moduli stabilization can underpin a UV-complete cosmological model linking early universe inflation with dynamical dark energy and a small dark-matter component.

Abstract

In this paper, we have discovered a new avenue of fibre inflation in perturbative large volume scenario (pLVS) due to the redefinition of the base modulus. pLVS offers a novel regime where large volume of the internal space is guaranteed without the need of non-perturbative effects. In this setup, we study the possibility where a base redefinition allows to assess different versions of fibre inflation whose spectral index aligns with Atacama Cosmology Telescope (ACT) data and produces tensor-to-scalar ratio in the range $0.008\lesssim r\lesssim 0.01$ in different setups we have considered. The leading order flat direction - which in our case is the fibre modulus - is lifted with the combinations of string loop corrections, leading order $α^{\prime 3}$$R^4$-correction, higher derivative $F^{4}$ corrections as well as our new ingredient redefinition of the modulus. Since recent Dark Energy Spectroscopic Instrument (DESI) results appear to favour a dynamical explanation for late-time acceleration over a simple cosmological constant, exploring quintessence offers a more suitable approach. In this lore, we also examine the quintessence sector to complete our model and account for both early- and late-time cosmic acceleration. In this framework, the poly-instanton correction generates a potential along the axionic directions, and we find that the resulting quintessence behaviour and the subsequent cosmological predictions about dark matter closely resemble the predictions of the original fibre inflation scenario studied earlier.

Figures (8)

• Figure 1: Plot of potential $V(\phi)$ in \ref{['sit1upp']} for varying values of $\alpha$ with minima of $\tau_{f}$ is at $1.03$. For this plot, we set $g_{s}=0.25, \ c_{f}^{KK}=0.0117, \ c^{w}=5, \ |W_{0}|=1$. The minima of $\tau_{f}$ remain essentially unchanged for different values of $\alpha$.
• Figure 2: Slow-roll parameters ($\epsilon$ and $\eta$) vs. $\phi$. For comparative purposes, the same parametric values were considered as in Fig. \ref{['fig:pot1']} with $\alpha=10^{-4}$. This plot illustrates that both parameters become small over the field range relevant for slow-roll inflation.
• Figure 3: The above visualises the trend for $r$ vs. $n_{s}$, computed for various sub-cases at 50-60 e-foldings. The dotted line denoting the original fibre model Cicoli:2008gp and the coloured lines denoting sub-cases from Table \ref{['tab1']}.
• Figure 4: Illustrative plots showing case 2 potential for different values of $\alpha$. Increasing $\alpha$ mainly steepens the large $\phi$ tail.
• Figure 5: $r$ vs. $n_{s}$ plot in similar fashion to Fig. \ref{['fig:3']}. Dotted lines again denote the original fibre model Cicoli:2008gp, with the coloured lines denoting sub-cases from Table \ref{['tab2']}.