Higgs-otic Inflation and String Theory

TL;DR

The paper presents Higgs-otic inflation, where a neutral MSSM Higgs doublet acts as the inflaton within a high-scale SUSY-breaking framework. It develops explicit string-theory realizations, notably a Type IIB orientifold with D7-branes, where the inflaton/Higgs is a D7-brane position modulus on a two-torus, with the potential generated by ISD G3 flux via the DBI+CS action. A two-field inflationary scenario emerges, with a field-dependent kinetic term that flattens the potential at large field values, and a no-scale $ n=1$ supergravity description that aligns with the microscopic dynamics. The model yields 50–60 e-folds and tensor-to-scalar ratios around r > 0.07, with the flux parameters constrained by requiring a light SM Higgs at the SUSY-breaking scale; reheating is efficient and the framework elegantly links EWSB and inflation in the same sector. The work also analyzes Planck-suppressed corrections, backreaction, and moduli decoupling, arguing for a consistent, testable large-field inflation scenario within string theory.

Abstract

We propose that inflation is driven by a (complex) neutral Higgs of the MSSM extension of the SM, in a chaotic-like inflation setting. The SUSY breaking soft term masses are of order $10^{12}-10^{13}$ GeV, which is identified with the inflaton mass scale and is just enough to stabilise the SM Higgs potential. The fine-tuned SM Higgs has then a mass around 126 GeV, in agreement with LHC results. We point out that the required large field excursions of chaotic inflation may be realised in string theory with the (complex) inflaton/Higgs identified with a continuous Wilson line or D-brane position. We show specific examples and study in detail a IIB orientifold with D7-branes at singularities, with SM gauge group and MSSM Higgs sector. In this case the inflaton/Higgs fields correspond to D7-brane positions along a two-torus transverse to them. Masses and monodromy are induced by closed string $G_3$ fluxes, and the inflaton potential can be computed directly from the DBI+CS action. We show how this action sums over Planck suppressed corrections, which amount to a field dependent rescaling of the inflaton fields, leading to a linear potential in the large field regime. We study the evolution of the two components of the Higgs/inflaton and compute the slow-roll parameters for purely adiabatic perturbations. For large regions of initial conditions slow roll inflation occurs and 50-60 efolds are obtained with r>0.07, testable in forthcoming experiments. Our scheme is economical in the sense that both EWSB and inflation originate in the same sector of the theory, all inflaton couplings are known and reheating occurs efficiently.

Figures (18)

• Figure 1: Running from $M_c$ down to $M_{SS}$ of the parameters of the Higgs mass matrix (left) and of the mass eigenvalues $m_{H_M}$ and $m_{H_L}$ (right).
• Figure 2: Energy scales in the Higgs-otic Inflation scenario. Below $10^{13}$ GeV the light degrees of freedom in the Higgs sector are given by the $SU(2)$ doublet $H_L$. Above this scale $SU(2)$ is broken and they lie within the neutral components of $h$ and $H$.
• Figure 3: A possible trajectory of the inflaton/Higgs D7-brane cycling around the ${\bf T}^2$ before fluxes are turned on.
• Figure 4: Scalar potential for three different values of $A$, $A=0.1$ (left), $A=0.5$ (centre) and $A=0.9$ (right).
• Figure 5: The required value of A in order to have a massless eigenstate at $M_{SS}$ as a function of the SUSY breaking scale.