# A solution to the initial condition problems of inflation : NATON

## TL;DR

This paper proposes that a negative absolute temperature fermion, NATON, can solve the initial condition problem of inflation by providing a pre-inflationary mini inflationary period, ensuring the universe's homogeneity for standard inflation to occur.

## Contribution

It introduces NATON, a negative absolute temperature fermion, as a novel mechanism to address the initial condition problem of inflation through a pre-inflationary phase.

## Key findings

- NATON can induce a mini inflationary period before standard inflation.
- A NATON-dominated era can make the universe sufficiently homogeneous.
- The model aligns with the conditions needed for successful standard inflation.

## Abstract

The recent astonishing realization of the negative absolute temperature (NAT) for motional degrees of freedom \cite{Braun_ea13} inspires its possible application to the early universe. The existence of the upper bound on the energy of the system is the sufficient requirement for a NAT and this might correspond to the Planck scale at the Big Bang model. It has been argued that standard inflation requires an initial patch that is smooth over distance scales a bit larger than the causal horizon at the onset of inflation. We show that this initial condition problem can be solved if the NAT fermion, dubbed ``NATON'', occupies the Universe before the standard inflation is ignited by providing mini inflation prior to the standard one. As long as NATON dominated era lasts until at least ten times older than the Planck time, it makes the Universe homogeneous enough to derive the successful standard inflation.