# Through the Big Bang in inflationary cosmology

## TL;DR

This paper extends previous work showing that certain singularities in inflationary cosmology can be mathematically continued through, using multiple scalar fields with controlled potentials, advancing the understanding of the early universe.

## Contribution

It generalizes earlier results by demonstrating that singularities can be extended through in models with multiple scalar fields and realistic inflationary potentials.

## Key findings

- Singularity extension is possible with multiple scalar fields.
- Results apply to inflationary potentials like Starobinsky's.
- The approach advances towards realistic cosmological models.

## Abstract

Singularities in General Relativity are regions where the description of spacetime in terms of a pseudo-Riemannian geometry breaks down. The theory seems unable to predict the evolution of the physical degrees of freedom around and beyond such regions. In a recent paper, the author and collaborators challenged this view by providing an example of a singularity at which Einstein's equations can be rewritten in a form that satisfies an existence and uniqueness theorem, thereby predicting that each solution can be continued uniquely through the singularity. This result was obtained under the assumption of homogeneity (but not isotropy), and requires the presence of a massless free scalar field. This paper extends the result to N scalar fields with a potential, the only requirement being that it does not grow too fast. In particular, the result is compatible with inflationary potentials, e.g. Starobinsky's. This brings us one step closer to the goal of extending the original result to realistic cosmologies.