Some interesting features of new massive gravity

TL;DR

This paper proves that the BHT new massive gravity model is uniquely unitary at tree level among 3D gravity theories with curvature-squared terms and explores its distinctive properties like time dilation and delay.

Contribution

It establishes the uniqueness of the BHT model as the only unitary 3D gravity with curvature-squared modifications at tree level.

Findings

BHT model is the only unitary 3D gravity with curvature-squared terms at tree level.

The model exhibits time dilation and time delay effects absent in Einstein 3D gravity.

Analysis of these properties highlights the model's distinctive gravitational features.

Abstract

A proof that new massive gravity - the massive 3D gravity model proposed by Bergshoeff, Hohm and Townsend (BHT) - is the only unitary system at the tree level that can be constructed by augmenting planar gravity through the curvature-squared terms, is presented. Two interesting gravitational properties of the BHT model, namely, time dilation and time delay, which have no counterpart in the usual Einstein 3D gravity, are analyzed as well.