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GRG Editor’s Choice: recent highlight articles

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In each volume of the journal General Relativity and Gravitation (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. These recent articles deserve special attention:

Jeremy D. Schnittman
“The collisional Penrose process”
https://doi.org/10.1007/s10714-018-2373-5

Claus Kiefer, David Wichmann
“Semiclassical approximation of the Wheeler–DeWitt equation: arbitrary orders and the question of unitarity”
https://doi.org/10.1007/s10714-018-2390-4

Hideyoshi Arakida
“Light deflection and Gauss–Bonnet theorem: definition of total deflection angle and its applications”
https://doi.org/10.1007/s10714-018-2368-2

Emanuele Berti, Kent Yagi, Nicolas Yunes
“Extreme gravity tests with gravitational waves from compact binary coalescences: (I) inspiral–merger”
https://doi.org/10.1007/s10714-018-2362-8

Please, browse all Editor’s Choice articles at:
https://www.springer.com/gp/livingreviews/relativity/grg-editors-choice

Frank Schulz
Publishing Editor GRG

GRG Editor’s Choice: recent highlight articles

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In each volume of the journal General Relativity and Gravitation (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.

Three recent articles deserve special attention (free-to-read access until April 15, 2018):

Giorgio Sarno, Simone Speziale and Gabriele V. Stagno, 2-vertex Lorentzian spin foam amplitudes for dipole transitions, Gen Relativ Gravit (2018) 50: 43. https://doi.org/10.1007/s10714-018-2360-x

Pedro V. P. Cunha and Carlos A. R. Herdeiro, Shadows and strong gravitational lensing: a brief review, Gen Relativ Gravit (2018) 50: 42. https://doi.org/10.1007/s10714-018-2361-9

Dario Brooks, Paul-Christopher Chavy-Waddy, Alan A. Coley, Adam Forget, Daniele Gregoris, Malcolm A. H. MacCallum and David D. McNutt, Cartan invariants and event horizon detection, Gen Relativ Gravit (2018) 50: 37. https://doi.org/10.1007/s10714-018-2358-4

Frank Schulz
Publishing Editor GRG

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

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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

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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

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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.

Gravitational waves – Publication of a new review paper

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M. Cerdonio, G. Losurdo – Rivista del Nuovo Cimento, 35, 389, 2012

“The purpose of this review is to give an outlook on the initial crop of GW observations, on their impact in fundamental physics, in relativistic astrophysics and in cosmology, and give also an updated view of the methods and technologies, which are making possible the historical achievement of opening the era of GW astronomy.” (From the abstract)

“The review paper “Gravitational waves from discovery to astronomy” by M. Cerdonio and G. Losurdo is a remarkable piece of scientific work (…)
Starting from first principles, the physics and technology involved in the contemporary search for gravitational wave is well described. In particular, some key physics issues, usually overlooked in other reviews, are here nicely analyzed. The perspectives of the field are clearly illustrated.” (From the referee’s report)

Excellent research published online: Newtonian Gravity and the Bargmann Algebra

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Dear Colleagues,

It gives me great pleasure to notify you of the publication of the above article in Classical and Quantum Gravity.

TITLE: Newtonian Gravity and the Bargmann Algebra
AUTHORS: Roel Andringa, Eric Bergshoeff, Sudhakar Panda and Mees de Roo

This article received very positive comments and a high quality rating from its referees. The article is available to download from IOPscience.

Please find below a summary by the authors of the developments made in this article:

‘Newton–Cartan gravity is a geometric formulation of Newtonian gravity, based on the nonrelativistic limit of general relativity. In our paper we confront this traditional view of Newton–Cartan gravity with a different approach that starts from the Bargmann algebra, a centrally extended version of the Galilei algebra. This approach emphasizes the analogy with the formulation of general relativity as a gauge theory of the Poincaré algebra. The algebraic method suggests a number of generalizations, for instance to conformal algebras, and to the Newton–Hooke algebra, which would lead to classical gravity induced by nonrelativistic strings.’

Yours sincerely

Rachel Lawless
Publishing Editor
Classical and Quantum Gravity

High quality article in Classical and Quantum Gravity

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Dear Colleagues,

TITLE: Lost in translation: topological singularities in group field theory
AUTHORS: Razvan Gurau

It gives me great pleasure to notify you of the publication of the above article in Classical and Quantum Gravity. This article received very positive comments and a high quality rating from its referees. The article is available to download here: http://herald.iop.org/link/4107

Please find a summary of the developments made in this article below:

Random matrix models generalize in higher dimensions to Group Field Theories (GFTs) whose Feynman graphs are dual to gluings of simplices. In this paper we prove that the effective behavior of generic GFTs is dominated by singular graphs, not dual to normal simplicial pseudo manifolds. This very serious problem brings into question their viability as quantum field theories. We prove however that, fortunately, the recently introduced “colored” GFT models circumvent this problem, generating only graphs dual to pseudo manifolds. We conclude that they are the correct starting point for the study of GFTs as quantum field theories.

Yours sincerely

Adam Day
Publisher
Classical and Quantum Gravity

Read the Classical and Quantum Gravity Highlights of 2009-2010

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Dear Colleagues,

I am delighted to announce the publication of Classical and Quantum Gravity’s Highlights of 2009-2010. The articles in the list, published between May 2009 and June 2010, were selected by the Editorial Board of Classical and Quantum Gravity (CQG) as a representation of the best recent work in gravitational physics.

http://herald.iop.org/link/4077

The list includes research Papers, Fast Track Communications, review articles and special issue contributions. The selected articles have also proven popular with our readers and have been frequently downloaded.

Look out for the CQG Highlights Brochure in 2011, which will be available at gravitational physics meetings. The brochure summarises the highlighted papers and will tell you more about the journal’s ongoing activities including prize sponsorships and forthcoming special issues.

I invite you to submit your work to CQG and look forward to seeing it promoted as a CQG Highlight in the future.

Yours sincerely

Adam Day
Publisher
Classical and Quantum Gravity

Excellent research published online: Combining gravity with the forces of the standard model on a cosmological scale

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Dear Colleagues,

TITLE: Combining gravity with the forces of the standard model on a cosmological scale
AUTHORS: Claus Gerhardt

It gives me great pleasure to notify you of the publication of the above article in Classical and Quantum Gravity.

This article received very positive comments and a high quality rating from its referees. The article is available to download here:

http://herald.iop.org/branding/m19/rzl/$CONTACT_ID/link/3780

Please find a summary of the developments made in this article written by the authors below:

We prove the existence of a spectral resolution of the Wheeler-DeWitt equation when the underlying spacetime is a Friedman universe with flat spatial slices and where the matter fields are comprised of the strong interaction, with SU(3) replaced by a general SU(n), n >= 2, and the electro-weak interaction.

The wave functions are maps from R[4n+10] to a subspace of the antisymmetric Fock space, and one noteworthy result is that, whenever the electro-weak interaction is involved, the image of an eigenfunction is in general not one dimensional, i.e., in general it makes no sense specifying a fermion and looking for an eigenfunction the range of which is contained in the one dimensional vector space spanned by the fermion

Yours sincerely

Adam Day
Publisher
Classical and Quantum Gravity

Excellent research published online: Accurate light-time correction due to a gravitating mass

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Dear Colleagues,

TITLE: Accurate light-time correction due to a gravitating mass
AUTHORS: Neil Ashby, Bruno Bertotti

It gives me great pleasure to notify you of the publication of the above article in Classical and Quantum Gravity.

This article received very positive comments and a high quality rating from its referees. Please find a summary of the developments made in this article below:

The time delay and deflection of light passing between two points near a spherical mass of gravitational radius m, are expressed to second order in m in terms of endpoint positions and angle subtended at the source by the endpoints, instead of unknown quantities such as the closest approach distance b. We minimize Fermat’s action functional and solve the eikonal equation for a null geodesic. In a close superior conjunction the second-order correction contains an enhanced part of order m2R/b2, where R is of the order of the endpoint distances from the sun. We compare these results to previous calculations, in particular with the second-order terms introduced in NASA’s Orbit Determination Program. We use asymptotic series to determine which higher-order terms are important.

The results are significant for understanding the results of the Cassini light-time experiment, and for future missions whose purpose may include measuring the PPN parameter gamma.

Yours sincerely

Adam Day
Publisher
Classical and Quantum Gravity

Excellent research published online: Reduced Hamiltonian for next-to-leading order Spin-Squared Dynamics of General Compact Binaries

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Dear Colleagues,

TITLE: Reduced Hamiltonian for next-to-leading order Spin-Squared Dynamics of General Compact Binaries
AUTHORS: Steven Hergt, Jan Steinhoff and Gerhard Schaefer

It gives me great pleasure to notify you of the publication of the above article in Classical and Quantum Gravity.

This article received very positive comments and a high quality rating from its referees.

Please find a summary of the developments made in this article below:

Fully reduced Hamiltonians belong to the most compact and elegant dynamical devices in physics. This particularly applies to spinning compact binaries in general relativity where approximate Hamiltonians are now available including spin-orbit, spin(1)spin(2), and spin-squared terms, all through next-to-leading order (NLO) in relativistic coupling counted in powers of the inverse of speed-of-light squared, called post-Newtonian expansion. The most complicated terms are the spin-squared ones which include information about the rotational deformation of black holes and, depending on a specific model, of neutron stars. For both a fully reduced NLO spin-squared Hamiltonian is derived and compared with former results from the Effective Field Theory approach where a nonreduced effective potential was obtained which is cast into Hamilton form under variable transformation applicable to all NLO spin terms. The result should have impact on the description of inspiralling binaries in gravitational wave astronomy.

Yours sincerely

Adam Day
Publisher
Classical and Quantum Gravity

Iopscience.org/cqg

GW Notes: New issue and highlight on EMRI waveforms

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It is a pleasure for us to announce the third issue of GW Notes. This issue’s invited article by Nicolas Yunes is focussing on “Gravitational Wave Modelling of Extreme Mass Ratio Inspirals and the Effective-One-Body Approach”.

The electronic journal “GW Notes” <http://brownbag.lisascience.org/lisa-gw-notes/> and its blog “The LISA Brownbag” <http://brownbag.lisascience.org/> , both produced by the AEI, propose to offer scientists of the Gravitational Wave community the opportunity to more easily follow advances in the areas of astrophysics, general relativity and data analysis. We hope to achieve this by selecting the most significant e-prints and listing them in abstract form with a link to the full paper in both a single e-journal (GW Notes) and a blog (The LISA Brownbag).

Of course, this also implies that the paper will have increased impact, since it will reach a broader public, and so we encourage you to not forget submitting your own work.

Best regards,

Bernard Schutz and Pau Amaro-Seoane