# Some remarks on a new exotic spacetime for time travel by free fall

## TL;DR

This paper reviews a new, topologically trivial spacetime model with closed causal curves, analyzing its causal structure, physical effects, and energy conditions, contributing to the understanding of potential time travel geometries.

## Contribution

It provides a comprehensive review of a recently proposed exotic spacetime, including its causal properties, physical effects, and classification of its stress-energy tensor.

## Key findings

- Spacetime has closed causal curves without curvature singularities.
- Redshift and blueshift effects are analyzed within this model.
- The stress-energy tensor is classified using Hawking-Ellis criteria.

## Abstract

This work is essentially a review of a new spacetime model with closed causal curves, recently presented in another paper (Class. Quantum Grav. \textbf{35}(16) (2018), 165003). The spacetime at issue is topologically trivial, free of curvature singularities, and even time and space orientable. Besides summarizing previous results on causal geodesics, tidal accelerations and violations of the energy conditions, here redshift/blueshift effects and the Hawking-Ellis classification of the stress-energy tensor are examined.