GRG Editor’s Choice: Higher curvature gravities cannot be bootstrapped

Deser, S., Higher curvature gravities, unlike GR, cannot be bootstrapped from their (usual) linearizations, Gen Relativ Gravit (2017) 49: 149. https://doi.org/10.1007/s10714-017-2308-6

Editor’s Choice (Research Article)
First Online: 07 November 2017

“This paper extends the author’s original contribution from 1970 to a broad class of theories that modify general relativity. The result is a paper that provides a continuation of the 1970 story. The author’s style and commitment to exposing the structural elements of the procedure make for a very nice article that reads well and serves a useful and illuminating purpose in the ‘extensions of GR’ literature.”

Abstract:
We show that higher curvature order gravities, in particular the propagating quadratic curvature models, cannot be derived by self-coupling from their linear, flat space, forms, except through an unphysical version of linearization; only GR can. Separately, we comment on an early version of the self-coupling bootstrap.

GRG Editor’s Choice:
In each volume of GRG, a few papers are marked as “Editor’s Choice”. The primary criteria is original, high quality research that is of wide interest within the community.

GRG Editor’s Choice: Notable articles in General Relativity & Gravitation

In each volume of the journal General Relativity & Gravitation, a few papers are marked as “Editor’s Choice”. The primary criteria is original, high quality research that is of wide interest within the community.

Tanatarov, I.V. & Zaslavskii, O.B., Collisional super-Penrose process and Wald inequalities, Gen Relativ Gravit (2017) 49: 119. https://doi.org/10.1007/s10714-017-2281-0

Abstract:
We consider collision of two massive particles in the equatorial plane of an axially symmetric stationary spacetime that produces two massless particles afterwards. It is implied that the horizon is absent but there is a naked singularity or another potential barrier that makes possible the head-on collision. The relationship between the energy in the center of mass frame Ec.m. and the Killing energy E measured at infinity is analyzed. It follows immediately from the Wald inequalities that unbounded E is possible for unbounded Ec.m. only. This can be realized if the spacetime is close to the threshold of the horizon formation. Different types of spacetimes (black holes, naked singularities, wormholes) correspond to different possible relations between Ec.m. and E. We develop a general approach that enables us to describe the collision process in the frames of the stationary observer and zero angular momentum observer. The escape cone and escape fraction are derived. A simple explanation of the existence of the bright spot is given. For the particular case of the Kerr metric, our results agree with the previous ones found in Patil et al. (Phys Rev D 93:104015, 2016).

Sakovich, A. & Sormani, C., Almost rigidity of the positive mass theorem for asymptotically hyperbolic manifolds with spherical symmetry, Gen Relativ Gravit (2017) 49: 125. https://doi.org/10.1007/s10714-017-2291-y

Abstract:
We use the notion of intrinsic flat distance to address the almost rigidity of the positive mass theorem for asymptotically hyperbolic manifolds. In particular, we prove that a sequence of spherically symmetric asymptotically hyperbolic manifolds satisfying the conditions of the positive mass theorem converges to hyperbolic space in the intrinsic flat sense, if the limit of the mass along the sequence is zero.

GRG Editor’s Choice: Cosmological solutions with charged black holes

Bibi, R., Clifton, T. and Durk, J., Cosmological solutions with charged black holes, Gen Relativ Gravit (2017) 49: 98. doi:10.1007/s10714-017-2261-4

Open Access | Editor’s Choice (Research Article)
First Online: 30 June 2017

In each volume of the journal General Relativity & Gravitation, a few papers are marked as “Editor’s Choice”. The primary criteria is original, high quality research that is of wide interest within the community.

Abstract:
We consider the problem of constructing cosmological solutions of the Einstein–Maxwell equations that contain multiple charged black holes. By considering the field equations as a set of constraint and evolution equations, we construct exact initial data for N charged black holes on a hypersphere. This corresponds to the maximum of expansion of a cosmological solution, and provides sufficient information for a unique evolution. We then consider the specific example of a universe that contains eight charged black holes, and show that the existence of non-zero electric charge reduces the scale of the cosmological region of the space. These solutions generalize the Majumdar–Papapetrou solutions away from the extremal limit of charged black holes, and provide what we believe to be some of the first relativistic calculations of the effects of electric charge on cosmological backreaction.

The authors:
Jessie Durk is currently a PhD student, researching theoretical cosmology with Dr Timothy Clifton, lecturer at Queen Mary University London. Rashida Bibi is a faculty member of the International Islamic University, Islamabad.

GRG Editor’s Choice articles free to read

On the occasion of the upcoming GR21 conference, selected articles from the journal General Relativity and Gravitation are now free-to-read until July 31, 2016:
http://bit.ly/294Uh4J

In each volume, a few papers are marked as “Editor’s Choice”. The primary criteria is original, high quality research that is of wide interest within the community. We would also like to introduce Springer’s new article interface, optimized for easy reading on mobile devices.

General Relativity and Gravitation is a journal devoted to all aspects of modern gravitational science, and published under the auspices of the ISGRG. The journal publishes research letters and papers, invited review articles on all theoretical and experimental aspects of modern general relativity and gravitation, as well as book reviews and historical articles of special interest.

We welcome your submissions, and see you at GR21!

Topical Collection: The First Century of General Relativity: GR20/Amaldi10

We cordially invite you to read the Topical Collection of articles
The First Century of General Relativity: GR20/Amaldi10
published in the journal General Relativity and Gravitation.

An outstanding collection of 37 articles contributed by prominent international experts, commemorating the First Century of General Relativity!
Guest Editors: Jerzy Lewandowski, Bala Iyer, Sheila Rowan

Visit: http://news.springer.com/re?l=D0In5v6jrI6h42bfsI9
Enjoy your free access to all articles through May 11, 2015!

Message from the Editors-in-Chief:
The discovery of general relativity by Albert Einstein one hundred years ago was quickly recognized as a supreme triumph of the human intellect. To paraphrase Hermann Weyl, “wider expanses and greater depths were suddenly exposed to the searching eye of knowledge, regions of which there was not even an inkling”. To mark this centenary, General Relativity and Gravitation has published a special Topical Collection of articles.

We would like to thank all the contributors, and the guest editors Jerzy Lewandowski, Bala Iyer, Sheila Rowan for their valuable help in bringing this collection together.

A. Ashtekar and R. Maartens
Editors-in-Chief