# Standard Model - Axion - Seesaw - H portal inflation

## TL;DR

The SMASH model extends the Standard Model with new particles to address multiple fundamental problems in physics and cosmology, providing testable predictions for future experiments and observations.

## Contribution

It introduces a unified framework (SMASH) that links axion physics, neutrino masses, baryogenesis, and inflation within a falsifiable model.

## Key findings

- Predicts a minimum tensor-to-scalar ratio of r ≥ 0.004
- Forecasts a spectral index running α ≥ -8×10^{-4}
- Suggests an axion mass range of 50μeV to 200μeV

## Abstract

Extending the Standard Model with a new complex singlet scalar, right-handed neutrinos and a vector-like quark allows to simultaneously tackle several problems in particle physics and cosmology within a constrained framework that can be falsified by future probes of the cosmic microwave background, as well as by upcoming axion experiments. This Standard Model - Axion - Seesaw - H portal inflation theory (SMASH) provides predictive inflation and $H$ boson stabilization, and can explain baryogenesis, light neutrino masses, dark matter and the strong CP problem. The model contains a unique new mass scale which coincides with the axion decay constant, and also sets the scale for perturbative lepton-number violation processes. Testable predictions include a minimum value of the tensor-to-scalar ratio of $r\gtrsim 0.004$, a running of the spectral index $\alpha\gtrsim-8\times10^{-4}$, a change $\delta N_{\rm eff}\sim 0.03$ in the number of effective relativistic neutrinos, and an axion mass in the range $50\mu eV\leq m_A \leq 200 \mu eV$.