Regular Article - Theoretical Physics
About apparent superluminal drives in generic gravity theories
Instituto de Matemática Luis Santaló (IMAS), UBA CONICET, Buenos Aires, Argentina
Accepted: 13 April 2022
Published online: 21 April 2022
As is well known, there exists warp drives in GR, such as the Alcubierre bubbles, which achieve an apparent faster than light travel (Alcubierre in Class Quantum Gravity 11:L73, 1994). A result due to Gao and Wald (Class Quantum Gravity 17:4999, 2000) suggests that such a travel is unlikely for GR with matter satisfying both the Null Energy and the Null Generic Conditions. There exists a generalization of this statement due to Galloway, that ensures that the Gao–Wald result is true regardless the underlying gravity model, unless there exists at least one inextendible null geodesic with achronal image in the space time (a null line). The proof of this proposition is based on techniques of causal theories, and has never been released. In the present work an independent proof of this result is presented by use of the Raychaudhuri equation, and avoiding several technical complications described along the text. Some consequences of these affirmations are discussed at last section, in particular their potential use in problems of causality.
© The Author(s) 2022
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Funded by SCOAP3