Coating thermal noise research for LIGO-India

Maya Kinley-Hanlon — an undergraduate student in the Department of Physics at the American University in Washington, DC — tells us more about her group’s work on optical coatings for LIGO-India.

Maya Kinley-Hanlon is a PhD candidate in the Department of Physics at the American University in Washington, DC.

Maya Kinley-Hanlon is an undergraduate student in the Department of Physics at the American University in Washington, DC.

Our CQG paper describes measurements of optical coatings on silica glass substrates to determine if storing the LIGO optics for many years before installing them in India will cause any problems.  The coatings are known to be fairly robust in their optical properties, but as is always the case with LIGO optics, no one has any real idea about the thermal noise properties.  Since thermal noise from the coatings is expected to be a limiting noise source in the LIGO detectors, knowing if storing the optics could cause a problem is an important issue.  I worked on this Continue reading

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

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.


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

Focus issue on gravitational waves, now open for submissions

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

How do we know LIGO detected gravitational waves?

The practical challenges of characterizing the Advanced LIGO detectors.


This CQG+ piece is brought to you by experts in the LIGO detector characterisation group (Detchar)
Comics by Nutsinee Kijbunchoo

The Advanced LIGO gravitational wave detectors are extremely sensitive instruments, measuring almost impossibly small changes in length. Their sensitivity is equivalent to measuring a change in distance the thickness of a human hair between Earth and Alpha Centauri, the closest star to Earth. Naturally, such a sensitive measurement picks up background noise in the form of disturbances that pollute the signal. For example, we might expect to see wind gusts, lightning strikes, earthquakes, or four buses full of middle schoolers rolling down the driveway to appear in the data as noise.

How then can we be sure LIGO really detected a Continue reading

TianQin: a space-borne gravitational wave detector

Attendees at the third workshop on the TianQin science mission

Attendees at the third workshop on the TianQin science mission

Gravitational waves can paint a completely new picture of the Universe. Promising advances in technology may make it possible to detect the minute wobbling of spacetime in the next few years. Estimates show that ground-based gravitational wave detectors, such as Advanced LIGO (Laser Interferometer Gravitational-wave Observatory) or Advanced Virgo will probably see several hundred events by 2020. These ground-based instruments will be complemented by space-borne detectors. These are sensitive to a much richer set of sources, including compact binary star systems in our own Milky Way, supermassive black holes consuming stars, and binary supermassive black holes in distant galactic nuclei. Dozens of proposals have been put forward for space-borne gravitational wave detectors, among which the most studied are LISA (Laser Interferometric Space Antenna) and its evolved version, eLISA. The European space agency has picked “Gravitational Universe” as the science theme for its 3rd large science mission L3; if chosen, eLISA might be launched in 2034.

In our paper, we describe the preliminary concept of a newly proposed space-borne gravitational wave detector, TianQin. In old Chinese legend, the lives of the gods in heaven are very similar to the lives of people on the ground (apart from the fact that they can fly, perform other miracles, and are presumably much happier). They also play music using instruments such as a Chinese zither. A zither on the ground is called “Qin”, and one in heaven is “TianQin”. Bearing this name, our experiment is metaphorically seen as Continue reading

Black-hole laboratories in the era of gravitational-wave astronomy

Paolo Pani and Helvi Witek

Helvi and Paolo visiting Toronto during the International Conference on Black Holes at the Fields Institute last year.
Helvi is Research Fellow in the School of Mathematical Sciences at the University of Nottingham. Paolo is Assistant Professor at Sapienza University of Rome and Research Scientist at the Instituto Superior Técnico in Lisbon.

We are proud to present the completed Focus Issue on “Black holes and Fundamental Fieldsone year after its first contribution has been published online.

This issue appears serendipitously at the same time as LIGO’s historic detection of gravitational waves which, simultaneously, provided us with the first direct observational evidence for the existence of black holes (BHs). We wish to take this opportunity to congratulate the LIGO/VIRGO Scientific Collaboration and everyone involved on  their breakthrough discovery!

The true excitement around this discovery arises from the fact that it marks the beginning of the long-sought-for era of gravitational-wave astronomy. As Kip Thorne recently put it, “Recording a gravitational wave […] has never been a big motivation for LIGO, the motivation has always been to open a new window to the Universe”. The outstanding observation of a BH binary coalescence — and the expectation of Continue reading

Gravitational waves detected. Einstein was right … again

Clifford Will

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

As if celebrating the 100th birthday of general relativity weren’t enough, the LIGO-Virgo collaboration has provided “the icing on the cake” with today’s announcement of the first direct detection of gravitational waves. At press conferences in the USA and Europe, and in a paper in Physical Review Letters published afterward, the team announced the detection of a signal from a system of two merging black holes.

The signal arrived on 14 September, 2015 (its official designation is GW150914), and was detected by both the Hanford and Livingston advanced detectors of the LIGO observatory (the advanced Virgo instrument in Italy is not yet online). It was detected first by Continue reading

Classifying noise transients in advanced gravitational-wave detectors

Read the full article in Classical and Quantum Gravity (Open Access):
Classification methods for noise transients in advanced gravitational-wave detectors   Jade Powell, Daniele Trifirò, Elena Cuoco, Ik Siong Heng and Marco Cavaglià 2015 Class. Quantum Grav. 32 215012


Jade Powell

Jade Powell is a PhD student at the University of Glasgow

A careful analysis of detector noise is necessary to determine whether a real gravitational-wave signal exists in the data of Advanced LIGO and Virgo. Instrumental and environmental disturbances can produce non-astrophysical triggers in science data, so called “glitches”. These glitches may reduce the duty cycle of the interferometers, and they could lead to a false detection if they occur simultaneously in multiple detectors. In the initial science runs of LIGO and Virgo a glitch could be classified by looking at an image of its time series waveform or spectrogram. This proved to be a slow and inefficient method for characterising a large number of glitches. To solve this problem the detector characterization team proposed a challenge for the fast automatic classification of Continue reading

Spontaneous Scalarization: Dead or Alive?

Read the full article for free* in Classical and Quantum Gravity:
Slowly rotating anisotropic neutron stars in general relativity and scalar-tensor theory
Hector O Silva, Caio F B Macedo, Emanuele Berti and Luís C B Crispino 2015 Class. Quantum Grav. 32 145008

*until 21/10/15

Emanuele Berti and Hector Okada da Silva

Hector O. Silva (right) is a graduate student of Professor Emanuele Berti (left) in the gravity group at the University of Mississippi (USA).

This is a time for celebration for anyone with even a passing interest in gravity. Einstein’s general theory of relativity is turning 100, Advanced LIGO started the first observing run on September 18, and LISA Pathfinder is scheduled to launch in the Fall. While we celebrate the centenary of general relativity, we should also remember that there are many good reasons why the theory may well require modifications. Cosmological observations indicate that most of the Continue reading

Designing the future of gravitational wave astronomy: Choosing the best sites for the next generation of gravitational wave detectors

Fig 1

A new view of the world map, with the black areas indicating allowable sites for building future generation gravitational wave detectors. The other coloured areas are excluded for various reasons.

Imagine you could time travel to decades after the first detections of gravitational waves by ground-based interferometers: someone has already had the call from Stockholm, a series of amazing gravitational wave discoveries have been reported and the watching world is going wild about gravitational wave astronomy.  Such momentous events would certainly trigger the demand for even more sensitive and powerful gravitational wave detectors to drive forward this exciting new field of observational astronomy. But the immediate question would be: where to put these multi-billion dollar instruments?  Future generations of gravitational wave detectors, like the proposed European Einstein Telescope, would be very expensive to build, so choosing the most favourable sites in which to build them will be a crucial issue. Our work, published in Classical and Quantum Gravity, explores the question of Continue reading