GRG Editor’s Choice: recent highlight articles

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

Living Reviews in Relativity: “Relativistic dynamics and extreme mass ratio inspirals”

The open-access journal Living Reviews in Relativity has published a new review article on “Relativistic dynamics and extreme mass ratio inspirals” by Pau Amaro-Seoane on 15 May 2018:

Amaro-Seoane, Pau,
“Relativistic dynamics and extreme mass ratio inspirals”,
Living Rev Relativ (2018) 21: 4.
https://doi.org/10.1007/s41114-018-0013-8

ABSTRACT:
It is now well-established that a dark, compact object, very likely a massive black hole (MBH) of around four million solar masses is lurking at the centre of the Milky Way. While a consensus is emerging about the origin and growth of supermassive black holes (with masses larger than a billion solar masses), MBHs with smaller masses, such as the one in our galactic centre, remain understudied and enigmatic. The key to understanding these holes—how some of them grow by orders of magnitude in mass—lies in understanding the dynamics of the stars in the galactic neighbourhood. Stars interact with the central MBH primarily through their gradual inspiral due to the emission of gravitational radiation. Also stars produce gases which will subsequently be accreted by the MBH through collisions and disruptions brought about by the strong central tidal field. Such processes can contribute significantly to the mass of the MBH and progress in understanding them requires theoretical work in preparation for future gravitational radiation millihertz missions and X-ray observatories. In particular, a unique probe of these regions is the gravitational radiation that is emitted by some compact stars very close to the black holes and which could be surveyed by a millihertz gravitational-wave interferometer scrutinizing the range of masses fundamental to understanding the origin and growth of supermassive black holes. By extracting the information carried by the gravitational radiation, we can determine the mass and spin of the central MBH with unprecedented precision and we can determine how the holes “eat” stars that happen to be near them.

Please, visit frequently our relativity channel (http://www.springer.com/livingreviews/relativity) at http://livingreviews.org for other news.

Living Reviews in Relativity: Updated articles from Euclid TWG and KAGRA/LIGO/Virgo

The open-access journal Living Reviews in Relativity has published major updates of two review articles in April 2018:

Abbott, B.P. et al. (KAGRA Collaboration, LIGO Scientific Collaboration and Virgo Collaboration), “Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA”, Living Rev Relativ (2018) 21: 3. https://doi.org/10.1007/s41114-018-0012-9​​​​​​​

Changes:
Major revision, updated and expanded. Several updates to the document have been made. The most significant changes are the inclusion of details regarding KAGRA, and results from O1 and O2, including GW170817, the first detection with an unambiguous multi-messenger counterpart. The key differences are outlined in an appendix.

Amendola, L. et al. (The Euclid Theory Working Group), “Cosmology and fundamental physics with the Euclid satellite”, Living Rev Relativ (2018) 21: 2. https://doi.org/10.1007/s41114-017-0010-3​​​​​​​

Changes:
Major revision, updated and expanded. Seven new figures were added. About 300 new references have been cited. Forecasts are not updated in this version, with respect to 2012.

Please, visit frequently our relativity channel (https://www.springer.com/livingreviews/relativity) at http://livingreviews.org for other news.

Living Reviews in Relativity: “Tests of chameleon gravity”

The open-access journal Living Reviews in Relativity has published a new review article on “Tests of chameleon gravity” by Clare Burrage and Jeremy Sakstein on 16 March 2018:

Burrage, C. and Sakstein, J.,
“Tests of chameleon gravity”,
Living Rev Relativ (2018) 21: 1.
https://doi.org/10.1007/s41114-018-0011-x

ABSTRACT:
Theories of modified gravity, where light scalars with non-trivial self-interactions and non-minimal couplings to matter—chameleon and symmetron theories—dynamically suppress deviations from general relativity in the solar system. On other scales, the environmental nature of the screening means that such scalars may be relevant. The highly-nonlinear nature of screening mechanisms means that they evade classical fifth-force searches, and there has been an intense effort towards designing new and novel tests to probe them, both in the laboratory and using astrophysical objects, and by reinterpreting existing datasets. The results of these searches are often presented using different parametrizations, which can make it difficult to compare constraints coming from different probes. The purpose of this review is to summarize the present state-of-the-art searches for screened scalars coupled to matter, and to translate the current bounds into a single parametrization to survey the state of the models. Presently, commonly studied chameleon models are well-constrained but less commonly studied models have large regions of parameter space that are still viable. Symmetron models are constrained well by astrophysical and laboratory tests, but there is a desert separating the two scales where the model is unconstrained. The coupling of chameleons to photons is tightly constrained but the symmetron coupling has yet to be explored. We also summarize the current bounds on f(R) models that exhibit the chameleon mechanism (Hu and Sawicki models). The simplest of these are well constrained by astrophysical probes, but there are currently few reported bounds for theories with higher powers of R. The review ends by discussing the future prospects for constraining screened modified gravity models further using upcoming and planned experiments.

Please, visit frequently our relativity channel (http://www.springer.com/livingreviews/relativity) at http://livingreviews.org for other news.

GRG Editor’s Choice: recent highlight articles

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

Living Reviews in Computational Astrophysics: Higher-order accurate space-time schemes for computational astrophysics

The open-access journal Living Reviews in Computational Astrophysics has published a new review article on 11 December 2017:

Balsara, D.S., Higher-order accurate space-time schemes for computational astrophysics — Part I: finite volume methods, Living Rev Comput Astrophys (2017) 3: 2. https://doi.org/10.1007/s41115-017-0002-8

Abstract:
As computational astrophysics comes under pressure to become a precision science, there is an increasing need to move to high accuracy schemes for computational astrophysics. The algorithmic needs of computational astrophysics are indeed very special. The methods need to be robust and preserve the positivity of density and pressure. Relativistic flows should remain sub-luminal. These requirements place additional pressures on a computational astrophysics code, which are usually not felt by a traditional fluid dynamics code. Hence the need for a specialized review. The focus here is on weighted essentially non-oscillatory (WENO) schemes, discontinuous Galerkin (DG) schemes and PNPM schemes. WENO schemes are higher order extensions of traditional second order finite volume schemes. At third order, they are most similar to piecewise parabolic method schemes, which are also included. DG schemes evolve all the moments of the solution, with the result that they are more accurate than WENO schemes. PNPM schemes occupy a compromise position between WENO and DG schemes. They evolve an Nth order spatial polynomial, while reconstructing higher order terms up to Mth order. As a result, the timestep can be larger. Time-dependent astrophysical codes need to be accurate in space and time with the result that the spatial and temporal accuracies must be matched. This is realized with the help of strong stability preserving Runge–Kutta schemes and ADER (Arbitrary DERivative in space and time) schemes, both of which are also described. The emphasis of this review is on computer-implementable ideas, not necessarily on the underlying theory.

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.

Living Reviews in Relativity: recent publications

The open-access journal Living Reviews in Relativity has published three new review articles in November 2017:

Paschalidis, V. &; Stergioulas, N., “Rotating stars in relativity”, Living Rev Relativ (2017) 20: 7. https://doi.org/10.1007/s41114-017-0008-x

Frolov, V.P., Krtoua, P. &; Kubiznak, D., “Black holes, hidden symmetries, and complete integrability”, Living Rev Relativ (2017) 20: 6. https://doi.org/10.1007/s41114-017-0009-9

Liebling, S.L. &; Palenzuela, C., Dynamical boson stars, Living Rev Relativ (2017) 20: 5. https://doi.org/10.1007/s41114-017-0007-y

Please, visit frequently our relativity channel (http://www.springer.com/livingreviews/relativity) at http://livingreviews.org for other news.

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.

Living Reviews and CompAC: new open access articles

The open-access journals Living Reviews in Relativity and Computational Astrophysics and Cosmology have published new articles in May 2017:

Brian D. Metzger, “Kilonovae”, Living Rev. Relativ. (2017) 20:3
https://doi.org/10.1007/s41114-017-0006-z

Douglas Potter, Joachim Stadel and Romain Teyssier, “PKDGRAV3: beyond trillion particle cosmological simulations for the next era of galaxy surveys”, Comput. Astrophys. Cosmol. (2017) 4:2
https://doi.org/10.1186/s40668-017-0021-1

Oliver Porth, Hector Olivares, Yosuke Mizuno, Ziri Younsi, Luciano Rezzolla, Monika Moscibrodzka, Heino Falcke and Michael Kramer, “The black hole accretion code”, Comput. Astrophys. Cosmol. (2017) 4:1
https://doi.org/10.1186/s40668-017-0020-2

Living Reviews are open-access review journals that allow authors to regularly update their articles to include latest developments. Its companion research journals primarily publish original work.

Living Reviews in Relativity: new article and website

The open-access journal Living Reviews in Relativity has published a new review article on 4 April 2017:

Joseph D. Romano and Neil. J. Cornish, Detection methods for stochastic gravitational-wave backgrounds: a unified treatment, Living Rev Relativ (2017) 20:2. doi:10.1007/s41114-017-0004-1

We are also happy to announce that the new Living Reviews community portal (http://www.livingreviews.org) was recently relaunched.

With this common entry point to research and review journals in physics and astronomy, three communities will be able to find associated journals, highlighted articles, and related news ‘just a click away’.

We present Springer’s original research journals along with the Living Reviews open-access series as partner journals serving researchers in relativity, solar physics, and computational astrophysics.

This milestone marks also the completion of the Living Reviews journals’ content transfer from its previous publishing platform to SpringerLink, during which all articles have been retro-digitized and are now also available in standard XML/HTML with embedded MathJax.

Living Reviews in Relativity: new major updates published

The open-access journal Living Reviews in Relativity has recently published two new major updates of review articles:

“The Kerr/CFT correspondence and its extensions” by Geoffrey Compere (http://dx.doi.org/10.1007/s41114-017-0003-2) and “Interferometer techniques for gravitational-wave detection” by Charlotte Bond, Daniel Brown, Andreas Freise and Kenneth A. Strain (http://dx.doi.org/10.1007/s41114-016-0002-8).

Due to a technical error, the latter was published with a wrong article citation ID, which will be corrected as soon as possible. We would also like to apologize to the authors for the tremendous delays caused by workflow adjustments after the journal transfer to Springer.

Recent articles from Computational Astrophysics and Cosmology

I’m writing to let you know about some of the recent articles we’ve published in Computational Astrophysics and Cosmology (CompAC).

With this open-access journal we hope to make the connection between the computational science and the astrophysics communities. In that respect I hope that you will enjoy reading these pioneering papers as much as I have enjoyed them. The following list of publications reflects only a small part of the range in scientific topics we seek for in this journal.

Recent articles:

– “Riemann solvers and Alfven waves in black hole magnetospheres” by B Punsly, D Balsara, J Kim and S Garain
– “In situ and in-transit analysis of cosmological simulations” by B Friesen, A Almgren, Z Lukic, G Weber, D Morozov, V Beckner and M Day
– “Achieving convergence in galaxy formation models by augmenting N-body merger trees” by A J Benson, C Cannella and S Cole
– “Simulations of stripped core-collapse supernovae in close binaries” by A Rimoldi, S Portegies Zwart and E M Rossi

If you are interested in submitting your own work to CompAC, you’ll find all the submission guidelines at the journal’s home page: http://comp-astrophys-cosmol.springeropen.com/

I look forward to reading your work.

Kind regards,
Simon Portegies Zwart
Editor-in-Chief
Computational Astrophysics and Cosmology

Living Reviews in Relativity: “Extraction of gravitational waves in numerical relativity”

The open-access journal Living Reviews in Relativity has published a new review article on “Extraction of gravitational waves in numerical relativity” by Nigel T. Bishop and Luciano Rezzolla on 4 October 2016 (metadata correction 10 November 2016):

Bishop, N.T. and Rezzolla, L.,
“Extraction of gravitational waves in numerical relativity”,
Living Rev Relativ (2016) 19: 2.
http://doi.org/10.1007/s41114-016-0001-9

ABSTRACT:
A numerical-relativity calculation yields in general a solution of the Einstein equations including also a radiative part, which is in practice computed in a region of finite extent. Since gravitational radiation is properly defined only at null infinity and in an appropriate coordinate system, the accurate estimation of the emitted gravitational waves represents an old and non-trivial problem in numerical relativity. A number of methods have been developed over the years to “extract” the radiative part of the solution from a numerical simulation and these include: quadrupole formulas, gauge-invariant metric perturbations, Weyl scalars, and characteristic extraction. We review and discuss each method, in terms of both its theoretical background as well as its implementation. Finally, we provide a brief comparison of the various methods in terms of their inherent advantages and disadvantages.

CQG Highlights of 2015 now live

The latest collection of CQG Highlights, selected by the Editorial Board is now available and will be free to read until December 2016. Read the CQG Highlights here: http://iopscience.iop.org/0264-9381/page/highlights

Publish your next paper in CQG for the chance to be selected for next year’s Highlights.
https://mc04.manuscriptcentral.com/cqg-iop

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!

Living Reviews in Relativity: “Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo”

Living Reviews in Relativity has published a new article on “Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo” by the LIGO Scientific Collaboration and the Virgo Collaboration on 8 February 2016.

Please find the abstract and further details below.

————————-
PUB.NO. lrr-2016-1
B. P. Abbott et al. (The LIGO Scientific Collaboration and the Virgo Collaboration)
“Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo”

ACCEPTED: 2016-01-22
PUBLISHED: 2016-02-08

FULL ARTICLE AT:
http://www.livingreviews.org/lrr-2016-1

ABSTRACT:
We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5 deg^2 to 20 deg^2 will require at least three detectors of sensitivity within a factor of ~2 of each other and with a broad frequency bandwidth. Should the third LIGO detector be relocated to India as expected, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

UPCOMING ARTICLES AT:
http://relativity.livingreviews.org/Articles/upcoming.html

English translation of the last and very rare book by A. A. Friedmann (coauthored with V. K. Frederiks)

Vsevolod K. Frederiks, Alexander A. Friedmann, Foundations of the Theory of Relativity: Volume 1 Tensor Calculus (Minkowski Institute Press, Montreal 2015), 182 pages

http://www.minkowskiinstitute.org/mip/books/friedmann3.html

Description:
To mark the 100th anniversary of Einstein’s general relativity the Minkowski Institute Press publishes the first English translation of a very rare book on general relativity (its only Russian publication was in 1924), which turned out to be the last book by A. A. Friedmann (co-authored with V. K. Frederiks). This is the first and the only published volume of a five-volume book project on the foundations of the theory of relativity, brutally terminated by the untimely and tragic death of Friedmann on 16 September 1925. Despite the fact that this book was published in 1924 and despite the presence of some unconventional notions and notations in it, this is still a valuable book, because it is written by two deep thinkers, particularly Friedmann who in 1922 had the deepest understanding of the cosmological implications of Einstein’s general relativity when he first showed that the Universe may expand (which was later discovered by Hubble). What also makes this book valuable is that Frederiks and Friedmann develop the formalism of tensor calculus from a physical point of view by showing why the ideas of general relativity need that formalism. In this sense the book can be even used for self-study.

Living Reviews: “Terrestrial Gravity Fluctuations” / “Grid-based Methods in RHD and RMHD”

Living Reviews in Relativity has published a new review article on “Terrestrial Gravity Fluctuations” by Jan Harms on 2 December 2015.

Living Reviews in Computational Astrophysics has published a new review article on “Grid-based Methods in Relativistic Hydrodynamics and Magnetohydrodynamics” by Jose Maria Marti and Ewald Mueller on 22 December 2015.

Please find the abstracts and further details below.

—————-

PUB.NO. lrca-2015-3
Marti, Jose Maria and Mueller, Ewald
“Grid-based Methods in Relativistic Hydrodynamics and Magnetohydrodynamics”

ACCEPTED: 2015-12-01
PUBLISHED: 2015-12-22

FULL ARTICLE AT:
http://www.livingreviews.org/lrca-2015-3

ABSTRACT:
An overview of grid-based numerical methods used in relativistic hydrodynamics (RHD) and magnetohydrodynamics (RMHD) is presented. Special emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods. Results of a set of demanding test bench simulations obtained with different numerical methods are compared in an attempt to assess the present capabilities and limits of the various numerical strategies. Applications to three astrophysical phenomena are briefly discussed to motivate the need for and to demonstrate the success of RHD and RMHD simulations in their understanding. The review further provides FORTRAN programs to compute the exact solution of the Riemann problem in RMHD, and to simulate 1D RMHD flows in Cartesian coordinates.

UPCOMING ARTICLES AT:
http://computastrophys.livingreviews.org/Articles/upcoming.html

—————-

PUB.NO. lrr-2015-3
Harms, Jan
“Terrestrial Gravity Fluctuations”

ACCEPTED: 2015-11-16
PUBLISHED: 2015-12-02

FULL ARTICLE AT:
http://www.livingreviews.org/lrr-2015-3

ABSTRACT:
Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10^-23 Hz^-1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of terrestrial gravity fluctuations will have great impact on the future development of GW detectors and high-precision gravimetry in general, and many open questions need to be answered still as emphasized in this article.

UPCOMING ARTICLES AT:
http://relativity.livingreviews.org/Articles/upcoming.html

New book “Space-time relativity and gravitation” by L. Verozub

Dear hyperspace community,

I would like to announce a new book “Space-time relativity and gravitation”

Abstract
“The book is devoted to the development of Einstein’s theory of gravitation, based on the relativity of space-time and projectively invariant equations of gravitation. It eliminates contradiction of the theory with the modern field theory, because both descriptions of gravity – as a curvature of the Riemannian space-time and as a field in Minkowski space – are not mutually exclusive. On this basis, some of the fundamental problems of the theory and relativistic astrophysics are revised. It is shown, in particular, that the spherically symmetric field does not have a singularity, the energy of the gravitational field of a point mass is finite, and the accelerated expansion of the Universe is a consequence of gravity properties. The book is intended for physicists and astrophysicists. However, it is also apprehensible for senior students”

ISBN: 978-3-659-75511-8

Lambert Acad. Publ., 2015

The book is available at Amazon

Living Reviews in Computational Astrophysics: first articles online

Living Reviews in Computational Astrophysics is a new peer-reviewed open-access journal. Founded and supported by the Max Planck Institute for Astrophysics in Garching, the new member of the pioneering Living Reviews family is published by Springer International.

The journal aims at offering a comprehensive survey of research in computational astrophysics that physicists will know is up-to-date and reliable. Living Reviews is unique in that it only publishes high-quality review articles whose authors commit to update them regularly. This is the meaning of the word “living” in the journal’s title.

Living Reviews in Computational Astrophysics now started publication with its first two review articles: “SPH Methods in the Modelling of Compact Objects” by Stephan Rosswog and “Large Eddy Simulations in Astrophysics” by Wolfram Schmidt.

Please find the abstracts and further details below.

—————
Stephan Rosswog
SPH Methods in the Modelling of Compact Objects

FULL ARTICLE AT:
http://www.livingreviews.org/lrca-2015-1

ABSTRACT:
We review the current status of compact object simulations that are based on the smooth particle hydrodynamics (SPH) method. The first main part of this review is dedicated to SPH as a numerical method. We begin by discussing relevant kernel approximation techniques and discuss the performance of different kernel functions. Subsequently, we review a number of different SPH formulations of Newtonian, special- and general relativistic ideal fluid dynamics. We particularly point out recent developments that increase the accuracy of SPH with respect to commonly used techniques. The second main part of the review is dedicated to the application of SPH in compact object simulations. We discuss encounters between two white dwarfs, between two neutron stars and between a neutron star and a stellar-mass black hole. For each type of system, the main focus is on the more common, gravitational wave-driven binary mergers, but we also discuss dynamical collisions as they occur in dense stellar systems such as cores of globular clusters.

—————
Wolfram Schmidt
“Large Eddy Simulations in Astrophysics””

FULL ARTICLE AT:
http://www.livingreviews.org/lrca-2015-2

ABSTRACT:
In this review, the methodology of large eddy simulations (LES) is introduced and applications in astrophysics are discussed. As theoretical framework, the scale decomposition of the dynamical equations for neutral fluids by means of spatial filtering is explained. For cosmological applications, the filtered equations in comoving coordinates are also presented. To obtain a closed set of equations that can be evolved in LES, several subgrid-scale models for the interactions between numerically resolved and unresolved scales are discussed, in particular the subgrid-scale turbulence energy equation model. It is then shown how model coefficients can be calculated, either by dynamic procedures or, a priori, from high-resolution data. For astrophysical applications, adaptive mesh refinement is often indispensable. It is shown that the subgrid-scale turbulence energy model allows for a particularly elegant and physically well-motivated way of preserving momentum and energy conservation in adaptive mesh refinement (AMR) simulations. Moreover, the notion of shear-improved models for inhomogeneous and non-stationary turbulence is introduced. Finally, applications of LES to turbulent combustion in thermonuclear supernovae, star formation and feedback in galaxies, and cosmological structure formation are reviewed.

UPCOMING ARTICLES AT:
http://computastrophys.livingreviews.org/Articles/upcoming.html

Living Reviews in Relativity resumes publication

Living Reviews in Relativity had been recently acquired by Springer and has now resumed publication with two new review articles: “Exploring New Physics Frontiers Through Numerical Relativity” by Vitor Cardoso et al. and “The Hubble Constant” (major update) by Neal Jackson.

Please find the abstracts and further details below.

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PUB.NO. lrr-2015-1
Vitor Cardoso, Leonardo Gualtieri, Carlos A. R. Herdeiro and Ulrich Sperhake,
“Exploring New Physics Frontiers Through Numerical Relativity”

PUBLISHED: 2015-09-21

FULL ARTICLE AT:
http://www.livingreviews.org/lrr-2015-1

ABSTRACT:
The demand to obtain answers to highly complex problems within strong-field gravity has been met with significant progress in the numerical solution of Einstein’s equations – along with some spectacular results – in various setups. We review techniques for solving Einstein’s equations in generic spacetimes, focusing on fully nonlinear evolutions but also on how to benchmark those results with perturbative approaches. The results address problems in high-energy physics, holography, mathematical physics, fundamental physics, astrophysics and cosmology.

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PUB.NO. lrr-2015-2
Neal Jackson
“The Hubble Constant” (major update)

PUBLISHED: 2015-09-24

FULL ARTICLE AT:
http://www.livingreviews.org/lrr-2015-2

ABSTRACT:
I review the current state of determinations of the Hubble constant, which gives the lengthscale of the Universe by relating the expansion velocity of objects to their distance. There are two broad categories of measurements. The first uses individual astrophysical objects which have some property that allows their intrinsic luminosity or size to be determined, or allows the determination of their distance by geometric means. The second category comprises the use of all-sky cosmic microwave background, or correlations between large samples of galaxies, to determine information about the geometry of the Universe and hence the Hubble constant, typically in a combination with other cosmological parameters. Many, but not all, object-based measurements give H_0 values of around 72 – 74 km s^–1 Mpc^–1, with typical errors of 2 – 3 km s^–1 Mpc^–1. This is in mild discrepancy with CMB-based measurements, in particular those from the Planck satellite, which give values of 67 – 68 km s^–1 Mpc^–1 and typical errors of 1 – 2 km s^–1 Mpc^–1. The size of the remaining systematics indicate that accuracy rather than precision is the remaining problem in a good determination of the Hubble constant. Whether a discrepancy exists, and whether new physics is needed to resolve it, depends on details of the systematics of the object-based methods, and also on the assumptions about other cosmological parameters and which datasets are combined in the case of the all-sky methods.

UPCOMING ARTICLES AT:
http://relativity.livingreviews.org/Articles/upcoming.html

New book: “Superradiance” by R. Brito, V. Cardoso and P. Pani

Dear hyperspace community,

We would like to announce the publication of a new book on the physics of superradiance, co-authored by R. Brito, V. Cardoso and P. Pani, Springer Lecture Notes in Physics vol. 906 (2015).

Details of the book are available at
http://link.springer.com/book/10.1007%2F978-3-319-19000-6

or in Amazon

http://www.amazon.com/Superradiance-Extraction-Black-Hole-Implications-Astrophysics/dp/3319189999

This volume gives a unified picture of the multifaceted subject of superradiance, with a focus on recent developments in the field, ranging from fundamental physics to astrophysics. The book covers all our current understanding on the physics of the amplification of waves by a medium, including classical effects such as the Cherenkov effect. The main body of the book deals with superradiance in black hole physics, with important applications in astrophysics and particle physics. Each chapter ends with a list of outstanding open problems and future directions.

Best wishes to all,

Richard Brito, Vitor Cardoso, Paolo Pani

New book: “Cosmological and Black Hole Apparent Horizons” by V. Faraoni

Dear hyperspace community,

I would like to announce the publication of a new book which may be of interest to some of you: “Cosmological and Black Hole Apparent Horizons” by V. Faraoni, 199 pages, 8 figures,
Springer Lecture Notes in Physics vol. 907 (2015)
ISBN:978-3-319-19239-0 (Print) 978-3-319-19240-6 (Online)
Details of the book are available at
http://link.springer.com/book/10.1007/978-3-319-19240-6

Best wishes to all,

Valerio Faraoni
Physics Department
Bishop’s University
Sherbrooke, Quebec, Canada

New Book: “Einstein’s Apple : Homogeneous Einstein Fields” by Engelbert L. Schucking and Eugene J. Surowitz

After 15 years of effort to grow this apple tree, it has finally dropped its first fruit, namely our volume “Einstein’s Apple” which is now available in hardcover and e-book formats from World Scientific via

http://www.worldscientific.com/worldscibooks/10.1142/9333

The work provides an accessible introduction to concepts such as teleparallelism and torsion that are slighted in many courses; historical introduction sections include the early uses of these concepts and Einstein’s own early insights.

Cheers, Eugene Surowitz

New book: “Introduction to General Relativity, Black Holes and Cosmology”, by Y. Choquet-Bruhat

Dear Colleagues in General Relativity

To please the kind staff of Oxford University Press, and myself, I send you as propaganda for my last book “Introduction to General Relativity, Black Holes and Cosmology”, whose details can also be found at this website: http://ukcatalogue.oup.com/product/9780199666454.do

With best wishes to all

Yvonne Choquet-Bruhat

New Book: “Differential Forms and The Geometry of General Relativity” by Tevian Dray

I am pleased to announce the publication of my book: “Differential Forms and The Geometry of General Relativity”, by Tevian Dray, 321 pages; 85 figures.
A K Peters/CRC Press, 2015.

Publication details are available at:
http://www.crcpress.com/product/isbn/9781466510005
This book emphasizes the use of differential forms to describe general relativity.

Online versions of the two parts of the book also exist in both wiki and PDF formats, and are available at:
http://www.physics.oregonstate.edu/coursewikis/GDF
http://www.physics.oregonstate.edu/coursewikis/GGR

Please note that the online versions do not contain all of the editorial changes in the print edition.

Tevian Dray
Professor of Mathematics
Oregon State University
http://www.math.oregonstate.edu/~tevian