Inflation Driven by Scalar-Neutrino Coupling in a Mass-Varying Neutrino Framework

Abstract

We propose a cosmological framework in which neutrino masses evolve dynamically through coupling with a scalar field that simultaneously drives inflation. The neutrino mass is modeled as a power-law, exponential, or hybrid function of the scalar field, yielding an effective potential that includes neutrino backreaction. Starting from the Einstein-Hilbert action in a flat FLRW background, we derive the modified Friedmann and Klein Gordon equations incorporating this coupling. Using the Fermi-Dirac integrals, we account for the continuous transition of neutrinos from relativistic to non-relativistic regimes. The inflationary dynamics are analyzed via the slow roll parameters derived from the effective potential. Our results show that the scalar neutrino coupling alters the potential slope and curvature, thereby influencing the duration of inflation. The hybrid coupling form provides the most flexible realization, unifying neutrino mass generation with early universe inflation within a single scalar field framework.

Figures (6)

• Figure 1: Comparison of $V(\phi)$ and $V_{\text{eff}}(\phi)$ with $m_\nu=m_0e^{\beta \phi}$ for different values of the coupling parameter $\beta$, with $V_0=1$ and $\alpha=1$.
• Figure 2: Evolution of the first (left panel) and second (right panel) slow-roll parameters, $\epsilon'$ and $\eta$, respectively, for $V_0 = 1$ and $\alpha = 1$. The blue, red, and purple curves correspond to coupling parameters $\beta = 0.01$, $\beta = 0.03$, and $\beta = 0.05$, respectively.
• Figure 3: Comparison of $V(\phi)$ and $V_{\text{eff}}(\phi)$ with $m_\nu=m_0 \phi^n$ for different values of the coupling parameter $n$, with $V_0=1$ and $\alpha=1$.
• Figure 4: Evolution of the first (left panel) and second (right panel) slow-roll parameters, $\epsilon'$ and $\eta$, respectively, for $V_0 = 0.1$ and $\alpha = 1$. The blue, red, and purple curves correspond to the coupling parameters $n = 0.01$, $n = 0.03$, and $n = 0.05$, respectively.
• Figure 5: Comparison of $V(\phi)$ and $V_{\text{eff}}(\phi)$ with $m_\nu=\phi^n e^{\beta \phi}$ for different values of the coupling parameter $\beta$ and $n=0.01$, with $V_0=1$ and $\alpha=1$.