Waves, stability and exotic black holes

Posted on by

Jake Dunn and Dr Claude Warnick from the Pure Mathematics group at Imperial College, London tell us all about their research using the Klein-Gordon equation to study black holes.

Jake Dunn

Jake Dunn is a PhD student at Imperial College, London.
Claude Warnick is a Lecturer in Pure Mathematics at Imperial College, London.

There is a long standing conjecture in the theory of general relativity that the final state of the gravitational collapse of a star should be a stationary black hole modelled by the Kerr solution. To this date there remains no mathematical proof of this statement, and it seems that we may have to wait a while before this result can be established. Even the simpler problem of black hole stability is a considerable mathematical challenge.

We may think of a stationary black hole as Continue reading →

What does numerical relativity have to do with detecting gravitational waves?

Posted on by

Heather Fong — a PhD candidate in Physics at the University of Toronto, who also loves travelling and gastronomy photography — gives us an insight into her group’s work on using numerical relativity simulations for the detection of gravitational waves.

heatherfong

Heather Fong, a PhD candidate in Physics at the University of Toronto.

Answer: quite a lot! Numerical relativity (NR) provides the most accurate solutions to the binary black hole problem, which is exactly the type of source LIGO wants to detect — and has succeeded at! Most of the time, LIGO’s data streams are overwhelmed with noise, and so we use a technique called matched-filtering to identify gravitational-wave signals. Finding and characterizing signals requires a massive amount of accurate waveforms, and we use semi-analytic waveform models as filters which are built using the results of NR simulations.

Why don’t we use NR alone to identify signals? It certainly would be ideal if the theoretical template waveforms were generated entirely from NR; not only would we be using the most accurate waveforms available, it would also allow us to Continue reading →

Fractals and black hole shadows

Posted on by

Jake Shipley and Dr Sam Dolan work in the Particle Astrophysics and Gravitation group at the University of Sheffield, focusing on general relativity, wave propagation and black hole physics. Here they provide us with an insight into their research. 

Jake Shipley

Jake Shipley is a Ph.D student in the School of Mathematics and Statistics at the University of Sheffield. If Jake were a black hole, you would also see a lensed version of Dr Sam Dolan, standing behind the camera.

This has been a “miracle year” for relativity.

LIGO detected gravitational waves. The LISA Pathfinder mission demonstrated near-perfect freefall in space. And the era of gravitational-wave astronomy began in some style.

A century after black holes and gravitational waves were first predicted, we have learnt something truly mind-boggling: When two black holes collide, they shake the fabric of space-time with more power than is radiated by all the stars in the known universe put together!

The “chirps” from distant black hole collisions will travel for millions of years, at the speed of light, to reach our growing network of gravitational-wave detectors on Earth … and one day, out in space.

Next year, attention will turn to the Event Horizon Telescope (EHT): a global network of radio telescopes linked together to form an Earth-sized virtual telescope, using the technique of Very Long Baseline Interferometry. The EHT will Continue reading →

Highlights of 2015

Posted on by
Clifford Will

Clifford Will is the Editor-in-Chief of Classical and Quantum Gravity

The latest CQG Highlights are now available to view.  These papers represent the most interesting and important work published in CQG in 2015.  They were selected by the CQG Editorial Board and approved at CQG’s recent annual board meeting in London.

This year marks a break from the process used in past years.  CQG Highlights used to be Continue reading →

Focus issue on gravitational waves, now open for submissions

Posted on by

Peter Shawhan and Deirdre Shoemaker invite you to publish your next paper on gravitational waves in CQG’s new open focus issue on the topic.

Peter Shawhan

Peter Shawhan, University of Maryland

Sometimes things come together in unexpected, happy ways. At the CQG editorial board meeting in London last July, we discussed ideas for new focus issues and there was a consensus that the time was right to organize one on the general theme of gravitational waves. We could claim amazing prescience, but honestly we had no idea that Continue reading →

The world we live in – #GR21

Posted on by

This is the second in a series of posts timed to coincide with the GR21 meeting. Keep an eye on CQG+ this week, for more posts on gravitational waves, the CQG Highlights and more.

Adam Day and the NYT building

Adam Day admiring the view from the top of the Rockefeller Center in NYC

I once had the experience of trying to find journal articles in an old bricks and mortar library. I spent a whole afternoon scouring a few thousand journal copies (and never did find what I was looking for). Information was scarce in those days and there were few ways to get it.

Watching scholarly communication develop since then has been interesting. In many ways, it’s now much easier to find papers – especially when you know exactly what you want to read. However, readers increasingly now find Continue reading →

CQG’s guide to Twitter at conferences – #GR21

Posted on by
Adam Day

Adam Day, Executive Editor of Classical and Quantum Gravity in New York City for #GR21

The first time I heard of Twitter, I thought “why would anyone use this?” It seemed to have such limited utility – another passing internet fad that we would all grow tired of soon. Out of curiosity, I joined Twitter back in 2009 and it was clear at that point that gravitational physicists shared my first impressions. There were very few CQG authors signed up to the service and fewer who were visibly using it.

Over time, however, that picture changed and my mind with it. There is now Continue reading →

What makes a CQG Paper different?

Posted on by
Adam Day

Adam Day is the Executive Editor of Classical and Quantum Gravity

CQG is known for its high standard of peer review. We’re extremely grateful to everyone in the gravitational physics community who has helped to build and maintain this standard over the years. Detailing everything that goes into this would go beyond the scope of a single blog post. Nevertheless, I thought it might be helpful to you if I say a few words about what we are looking for in referees’ reports here at the CQG editorial office.

If you have refereed for CQG lately, you will have seen Continue reading →

Why is our universe about to decay?

Posted on by
Dr Kin-ya Oda (left, Osaka university) and Dr Masatoshi Yamada (right, Kyoto university).

Dr Kin-ya Oda (left, Osaka university) and Dr Masatoshi Yamada (right, Kyoto university).

It has been revealed that we are living on the edge of vacuum instability by the discovery of Higgs particle at the Large Hadron Collider since 2012. The determination of Higgs mass finally provides the last-missed parameter, the Higgs self coupling, to be 0.12 in the Standard Model of particle physics after nearly half century of its foundation. This value completes the initial conditions for a set of differential equations, called renormalization group (RG) equations, which govern how particles interact at very high energy scales. It turns out that the self coupling can vanish or even become negative at the Planck scale, where the quantum gravity effects become significant. We note for later reference that the Yukawa coupling between the Higgs and top quark plays a crucial role to reduce the Higgs self coupling in its RG evolution. The Higgs potential is about to become Continue reading →

Book review: Covariant Loop Quantum Gravity, an elementary introduction to quantum gravity and spinfoam theory

Posted on by
Rodolfo Gambini is Professor of Physics at Universidad de la República, Montevideo Uruguay

Rodolfo Gambini is Professor of Physics at Universidad de la República, Montevideo Uruguay

Review of “Covariant Loop Quantum Gravity, an elementary introduction to quantum gravity and spinfoam theory” by Carlo Rovelli and Francesca Vidotto

One of the central problems of contemporary physics is finding a theory that allows for describing the quantum behavior of the gravitational field. This book is a remarkable update on one of the most promising approaches for the treatment of this problem: loop quantum gravity. It places special emphasis on the covariant techniques, which provide with a definition of the path integral, an approach known as spin foams. It is a field that has undergone quite a bit of development in the last two decades. The book gives an overview of this area, discussing a series of results that are presented with great clarity. Both students and established researchers will benefit from the book, which provides a dependable introduction and reference material for further studies. Only a basic knowledge of general relativity, quantum mechanics and quantum field theory is assumed. The conceptual aspects and key ideas are discussed in the main body of the book and Continue reading →