Winner of the 2018 IOP Gravitational Physics Group (GPG) thesis prize: Dr Viraj A A Sanghai

Can you tell us a little bit about the work in your thesis?

One of the challenges of modern cosmology is to interpret observations in a consistent and model-independent way. There are several assumptions in interpreting cosmological/astrophysical data. For example, it is often assumed that Einstein’s theory of gravity is the correct theory of gravity. Furthermore, fundamental to cosmology is the assumption that the universe is homogeneous and isotropic on the largest scales and hence, this is the correct starting point to interpret cosmological data. To test these assumptions, approaches are needed, which work in a model-independent way. Broadly speaking, my thesis addresses these questions.

Thinking back, what was the most interesting thing that happened during your PhD?

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Dr Viraj A A Sanghai is a postdoctoral fellow working on theoretical cosmology at Dalhousie University in Halifax, Canada

The most interesting thing that happened during my PhD was the discovery of gravitational waves by LIGO, due to the merging of two black holes. This opened up a new avenue into testing Einstein’s theory of gravity and started the new field of gravitational wave astronomy. Before this, all our astronomical observations relied on electromagnetic radiation. This discovery is helping us to have a deeper understanding of our Universe. Consequently, the Nobel Prize in Physics was awarded for this discovery. Continue reading

Memories of Professor Stephen Hawking, 1942-2018

by Clifford Will, Editor-in-Chief, Classical and Quantum Gravity


The gravitational physics community, indeed the whole world, mourns the passing on Wednesday 14th March, 2018, of Stephen Hawking at the age of 76. The Editor, Board and staff of CQG offer their heartfelt condolences to Stephen’s family. There are already numerous extended obituaries of Stephen, and I won’t attempt one here (see for example the fine obituaries by Dennis Overbye in the New York Times and by Roger Penrose in the Guardian).

I will, however, offer two personal remembrances of Stephen that I hope will illustrate his humorous side. In 1972, I was a student at the famous Les Houches Summer School on black holes, where Stephen, Brandon Carter and Jim Bardeen lectured and wrote the seminal paper “The Four Laws of Black Hole Mechanics”, that suggested a formal analogy with the laws of thermodynamics. This was soon followed by papers by Jacob Bekenstein and by Stephen that made this more than an analogy. But one of the things I most remember about the school was the awe-struck look on my eight-year-old daughter Betsy’s face watching Stephen in his wheelchair demonstrating how he could wiggle his ears like Dumbo the elephant.

The second remembrance was a visit to Cambridge in 1978, where Stephen had asked me to give a colloquium on tests of GR and invited me and my wife to join him and Jane at “high table” dinner at his college, Gonville and Caius. I showed up in a psychedelic paisley shirt with ridiculously wide collars, baby blue flared jeans, and high-heeled boots (think John Travolta in “Saturday Night Fever”, but with hippie length hair). This was attire totally inappropriate for high table (hey, this was the 70s and was the best I had in my suitcase), but Stephen was delighted to have somebody there who made the stuffy and decorum-obsessed masters of the college more uncomfortable than he did. And when, during the ritual passing of the after-dinner liqueurs along the table, the college master chided me sternly for allowing the port to precede the claret, I thought Stephen was going slide out of his wheelchair, hysterical with laughter.

We have lost a remarkable scientist and a unique human being.


This work is licensed under a Creative Commons Attribution 3.0 Unported License.

 

Surfing a wave to Stockholm

by Clifford M. Will, CQG Editor-in-Chief


What a week for gravitational physics!   

First came the September 27th announcement of another detection of gravitational waves, this time by the three-detector network that included Virgo along with the two LIGO observatories. The source of the gravitational waves was another fairly massive black hole binary merger, with black holes of 30 and 26 solar masses. Once again, about 3 solar masses were converted to energy in a fraction of a second, leaving behind a 53 solar mass black hole spinning at about 70 percent of the maximum allowed. With  Virgo included in the detection, the localization of the source on the sky was improved dramatically over earlier detections by LIGO alone, dropping to a small blob on the sky measuring 60 square degrees, from the large, 1000 square degree banana-shaped regions of earlier detections.

For the first time, a test of gravitational-wave polarizations was carried out.  Because the arms of the two LIGO instruments are roughly parallel, they have very weak sensitivity to different polarization modes of the waves.  But with Virgo’s very different orientation, it was possible to show that the data favor the two spin-2 modes of general relativity over pure spin-0 or pure spin-1 modes.

But then, six days later came the announcement of the Nobel Prize in Physics, awarding one half of the prize to Rainer Weiss of MIT and the other half shared between Kip Thorne and Barry Barish of Caltech, for decisive contributions to the detection of gravitational radiation. CQG congratulates the winners!

Interview with Daniela Saadeh: winner of the IOP Gravitational Physics Group (GPG) thesis prize

Daniela Saadeh

Daniela Saadeh – UCL Astrophysics Group

CQG is proud to sponsor the IOP Gravitational Physics Group (GPG) thesis prize. This year the prize was awarded to Daniela Saadeh, who we have interviewed below. Congratulations Daniela!

Can you tell us a little bit about the work in your thesis?

A fundamental assumption of the standard model of cosmology is that the large-scale Universe is isotropic – i.e. that its properties are independent of direction. Historically, this concept stemmed from the Copernican Principle, the philosophical statement that we do not occupy a ‘special’ place in the Universe. In physical terms, this idea is converted into the assumption that all positions and directions in the Universe are equivalent, so that no observer is ‘privileged’.

However, assumptions must be tested, especially foundational ones. General relativity – our standard theory of gravity – allows for many ways in which spacetime could be anisotropic: directional symmetry is not fundamentally required. If the Universe were indeed to be anisotropic, we would actually need to carefully revise our understanding (for instance, calculations about its history or content). Making this health check is very important! Continue reading

So long, and thanks for all the manuscripts

Adam Day

Adam Day is the Publisher of Classical and Quantum Gravity

Years ago, I sat, somewhat nervously, in a small, dimly lit room in an old office block. I’d applied for a dream job and I was expecting to learn the outcome of that application. A senior member of staff tactfully began the meeting with some friendly small-talk that did absolutely nothing to calm my nerves.

I’d heard of CQG – even before I’d seen the job advert. Reputed for its high standards of peer-review, it also held the distinction of being the first physics journal on the web. Clearly, this was a journal for brilliant pioneers and innovators (submit here) and I wanted to be part of that. Furthermore, I’d enjoyed studying relativity as an undergraduate and had hoped to become a gravitational-wave researcher, so the science of CQG was already close to my heart.  I can’t even remember the colour of the walls in that old office, but I can still hear the words “I’d like to offer you the job” very clearly.

Looking back Continue reading

Highlights of 2016 now free to read 

By Clifford Will.


Clifford Will

Clifford Will is the Editor-in-Chief of Classical and Quantum Gravity, Distinguished Professor of Physics at the University of Florida, Chercheur Associé at the Institut d’Astrophysique de Paris, and James McDonnell Professor of Space Sciences Emeritus at Washington University in St. Louis.

I am delighted to present the CQG Highlights of 2016 which are now free to read.  This prestigious annual collection is selected by the editorial board and includes notable papers on gravitational waves, black holes, general relativity, cosmology, quantum gravity and more.

As well as being free to read on the web, each paper is promoted by the journal in a number of campaigns.  Watch for the CQG Highlights brochure at your next conference.

CQG Highlights remains one of CQG’s most popular promotions.  Don’t miss your chance to be included in CQG Highlights of 2017 by publishing your next great paper in CQG.

 

 

Continue reading

Happy new year!

By Clifford Will.


Clifford Will

Clifford Will is the Editor-in-Chief of Classical and Quantum Gravity, Distinguished Professor of Physics at the University of Florida, Chercheur Associé at the Institut d’Astrophysique de Paris, and James McDonnell Professor of Space Sciences Emeritus at Washington University in St. Louis.

What a year for gravitational physics!  In February, the LIGO and Virgo Collaborations (LVC) announced the first detection of gravitational waves.  The MICROSCOPE satellite test of the equivalence principle took to the skies in April and, in June, LISA Pathfinder surpassed all expectations in demonstrating the key technologies required to detect gravitational waves in space.  As if all that wasn’t enough, the LVC announced a second detection of a binary black hole merger later that month.  By September, NASA revealed that it would rejoin ESA in funding the LISA mission with a view to launching a 3-armed space interferometer by 2030.  Could we have wished for more?

CQG launched a focus issue on the topic of gravitational waves in 2016 edited by Peter Shawhan and Deirdre Shoemaker.  You can submit your next great paper on gravitational waves to the issue which is currently open to submissions and will be promoted in a number of channels throughout 2017.  All submissions will be subject to CQG’s usual high standard of peer review.

To keep track of the latest CQG publications and news in 2017, you can follow the CQG+ blog or follow the journal on social media (Twitter, Facebook).

I want to express my appreciation to all CQG authors, referees and readers who supported the journal in 2016.  I particularly wish to thank the journal’s Editorial Board Members and Advisory Panel Members who assist in directing the strategy of the journal and who oversee CQG’s peer review.  I also welcome new Board and Panel members to CQG. I look forward to working with all of you in the coming year.

With the LIGO detectors’ second observation run underway, I am certain that we have more to look forward to in 2017. Continue reading

LIGO’s gravitational wave detection is Physics World 2016 Breakthrough of the Year

by Clifford M Will.


Physics World breakthrough of the year prize

The Physics World 2016 Breakthrough of the Year goes to the LIGO Scientific Collaboration for their revolutionary, first ever direct observations of gravitational waves.

Long awaited direct detection of Einstein’s gravitational-waves tops Physics World’s list of the 10 key breakthroughs in physics in 2016

It give me great pleasure to report that the LIGO Scientific Collaboration are to receive Physics World’s Breakthrough of the year award.  At the end of every year, the Physics World editorial team reveals what it believes to be the top 10 research breakthroughs for the past year and one of these is selected to be the Physics World Breakthrough of the year.

In recognition of this achievement, the Physics World team have created a short documentary movie with the assistance of members of the LIGO collaboration from Cardiff University.

The video features Samantha Usman, who recently wrote an excellent CQG+ entry about the discovery.
Continue reading

Highlights of 2015

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

The world we live in – #GR21

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