Author Archives: Adam Day

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About Adam Day

Adam Day is the former publisher of Classical and Quantum Gravity. His background is mostly in publishing, where he thoroughly enjoyed working with the gravitational physics community. He now works as a Data Scientist for SAGE Publishing.

Gravitational lensing by black holes in astrophysics and in Interstellar

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Interstellar's accretion disc, with and without Doppler shift.

Interstellar‘s accretion disc, with and without Doppler shift. Figure 15 a, c from “Gravitational lensing by spinning black holes in astrophysics, and in the movie Interstellar” Oliver James et al 2015 Class. Quantum Grav. 32 065001

New insights into the effects of black holes from the team responsible for the Oscar®-winning visual effects of Interstellar.

Depicting a super-massive black hole in the movie Interstellar presented a new challenge to our visual effects team at Double Negative. Luckily the Executive Producer was theoretical physicist Kip Thorne who ended up working closely with us to create a new computer code, DNGR: Double Negative Gravitational Renderer. This code traces the path of light past a spinning black hole (Kerr metric) whose immense gravity warps space and time in its vicinity. A hot disk of gas orbiting the hole appears to Continue reading →

The spin limit of colliding black holes

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Geoffrey Lovelace

Geoffrey Lovelace is an Assistant Professor of Physics at California State University, Fullerton. As member of Fullerton’s Gravitational-Wave Physics and Astronomy Center and the Simulating eXtreme Spacetimes collaboration, his research interests focus on using computer simulations to model colliding black holes and neutron stars and the gravitational waves they emit.

A single black hole’s size limits its spin. Do colliding black holes obey this limit?

In our recent paper, published in Classical and Quantum Gravity, we take a first look at how supercomputer simulations can help reveal the answer.

A black hole is an object whose gravity is so strong that nothing, even light, can escape from inside its horizon. An isolated, uncharged black hole can be completely described by just two numbers: its spin and its horizon surface area. All of the black hole’s properties then follow from Kerr’s solution of Einstein’s equations.

Kerr’s solution implies that a single black hole can spin no faster than its horizon area times a constant: spinning any faster would destroy the horizon. Astronomers have found evidence that some black holes spin very close to the limit (but still below it). Mathematical relativists have proven that this spin limit is obeyed not only by Continue reading →

Towards 3.5PN accurate polarizations for compact binaries

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Guillame Faye

Guillaume Faye is Chargé de Recherche (researcher)

The gravitational-wave observatory Advanced LIGO is now in its commissioning stage and preparing for its first scientific runs in early 2015. It will be soon followed by the Advanced Virgo detector. Being reasonably optimistic, one can expect the first detections to occur by 2018. The most likely sources to be observed are coalescences of two compact objects. As both detection and
parameter estimation rely on matched filtering techniques, several programs to compute accurate waveform models using various approximation techniques are being pursued. Notably, the post-Newtonian perturbative approach, where all quantities of interest are expanded in powers of Continue reading →

Press release: Interstellar technology throws light on spinning black holes

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Michael Bishop

Michael Bishop is a Senior Press Officer for IOP Publishing

The team responsible for the Oscar-nominated visual effects at the centre of Christopher Nolan’s epic, Interstellar, have turned science fiction into science fact by providing new insights into the powerful effects of black holes. In a paper published today, 13 February, in IOP Publishing’s journal Classical and Quantum Gravity, the team describe the innovative computer code that was used to generate the movie’s iconic images of the wormhole, black hole and various celestial objects, and explain how the code has led them to new science discoveries. Using their code, the Interstellar team, comprising London-based visual effects company Double Negative and Caltech theoretical physicist Kip Thorne, found that when a camera is close up to a rapidly spinning black hole, peculiar surfaces in space, known as caustics, create more than a dozen images of individual stars and of the thin, bright plane of the Continue reading →

Movie review of The Theory of Everything by Eric Poisson

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Eric Poisson

Eric Poisson is a professor of physics at the University of Guelph.

The Theory of Everything directed by James Marsh, starring Eddie Redmayne and Felicity Jones.

We physicists can count ourselves lucky these days. We enjoy an unprecedented presence in popular culture, having central characters in today’s most popular sitcom (The Big Bang Theory) and two recent high-profile movies, Interstellar (previously reviewed for CQG+ by Richard Price) and the subject of this review, The Theory of Everything. Science has become cool. Let’s enjoy this while it lasts!

The Theory of Everything relates the life of today’s most famous physicist,  Stephen Hawking. The movie focuses mostly on Stephen’s relationship with his first wife, Jane Wilde Hawking, whose book “Travelling to Infinity” provided the basis for Continue reading →

IOP Gravity Thesis Prize 2015

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Timothy_Clifton

Dr Timothy Clifton is the Secretary of the Gravitational Physics Group, at the Institute of Physics

Submissions are now invited for the £500 prize.

The Gravitational Physics Group at the IOP is inviting submissions for their annual thesis prize.  Recent graduates from PhD programs in any area of gravitational physics, or other related areas, are strongly encouraged to apply.  Details are as follows:

Terms of reference, and elligibility
The prize is awarded for excellence in research and communication skills, as demonstrated by the candidate’s thesis.  All members of the IOP Gravitational Physics Group who passed their viva voce exam during the period 1st January 2012 and 31st December 2014 are elligible.

How to enter
Candidates should email an electronic copy of their thesis to Timothy Clifton, and complete the application form.  All sumissions should be made before the 31st of January 2015.

Furthermore, the winner will be invited to submit a paper to Classical and Quantum Gravity based on the winning thesis which, if accepted, will be made a ‘select article’ in CQG.  They will also be given the opportunity to present their work at one of the UK ‘BritGrav’ meetings. Continue reading →

A new algorithm for gravitational wave propagation

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Casey Handmer and Bela Szilagyi

Casey Handmer (graduate student at Caltech) and Bela Szilagyi (senior research fellow at Caltech) discuss the finer points of null cone geometry.

Gravitational wave evolution – spectral style.

Colliding black holes create powerful ripples in spacetime. Of this we are certain. Directly detecting these ripples, or gravitational waves, is one of the hardest unsolved problems in physics. Inferring physical characteristics of black hole binaries and other gravitationally energetic events from their radiation requires accurate numerical simulation for matched filtering.

But gravitational wave simulations are typically plagued by a lack of gauge invariance. Waveform precision and validity is undermined by coordinate choice and movement. Simulations require an extraction methodology to obtain gauge invariant waveforms. These waveforms are Continue reading →

Even a tiny cosmological constant casts a long shadow

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Aruna Kesavan

Aruna Kesavan is a graduate student at the Pennsylvania State University

How safe is it to ignore the cosmological constant in the study of isolated systems and gravitational waves?

Analysis of isolated systems, such as stars, black holes and compact binaries, has dominated gravitational science, spanning diverse areas that include geometric analysis, computational relativity, gravitational waves, relativistic astrophysics and quantum black-holes. For example, over the past four decades, powerful positive energy theorems were proved, a theory of gravitational radiation in exact general relativity was developed, computational simulations were carried out to extract energy-momentum emitted during binary mergers, and evaporation of black holes was analyzed using appropriate Hilbert spaces of asymptotic states.

These advances are based on the Bondi-Penrose framework for zero cosmological constant \Lambda. But by now observations have Continue reading →

Non-CMC solutions to the Einstein constraint equations on asymptotically Euclidean manifolds with apparent horizon boundaries

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Juan A. Valiente Kroon

Juan A. Valiente Kroon works on various aspects of mathematical Relativity and, in particular, on applications of conformal methods to analyse the global properties of spacetimes.

The construction of physically realistic data for the Einstein field equations is one of the great challenges of the Cauchy problem in General Relativity. In this paper C. Meier and M. Holst show how to construct solutions to the constraint equations of General Relativity representing data which will evolve, assuming that a certain form of weak cosmic censorship holds, into a spacetime containing one or more black holes.

The most studied procedure for solving the constraint equations is the so-called conformal method. This approach can be traced back to the pioneering work of Continue reading →

Focus issue: Astrophysics and general relativity of dense stellar systems

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Clifford Will and Pau Amaro-Seoane

Guest Editors: Clifford Will and Pau Amaro-Seoane

We invite you to read the latest CQG focus issue on “Astrophysics and General Relativity of dense stellar systems“, which is available to read now.

Dense stellar systems such as galactic nuclei and stellar clusters are unique laboratories, not only for astrophysics, but also for general relativity. The complexity of these systems is such that, in spite of a huge theoretical, observational and numerical effort there are still a large number of open key questions. This focus issue on the “Astrophysics and General Relativity of Dense Stellar Systems” brings together an array of invited articles on important aspects of these questions.

We hope that you will enjoy reading the articles in the focus issue; all of which are free for a period of time following publication.