Gravitational-wave astronomy

Gravitational-wave science holds the potential to address some of the key questions in fundamental physics, astrophysics and cosmology. These include the correctness of the theory of General Relativity and constraining its validity under strong gravity conditions, properties of GWs and the nature of black holes, equation of state of neutron stars, abundance of stellar-mass black holes and the existence of intermediate-mass black holes, merger history of galaxies and supermassive black holes, the central engine of gamma ray bursts, internal processes of supernovae, nature of dark energy, and phase transitions in the early Universe. Read more...

Current status of the field

Gravitational waves distort spacetime and thus change the physical distances between free test masses. The key to gravitational-wave detection is the very precise measurement of small changes (~10^-18 meter) in distance, which can be achieved using laser interferometers. Interferometric GW detectors have been built in the USA (LIGO), Europe (GEO600, Virgo) and Japan (TAMA300). Most of them are Michelson interferometers with Fabry-Perot cavities in each arm of length several hundred meters to several kilometers. The input laser power (and, in some cases, the signal output) is recycled for power build up to achieve strain sensitivity h ~ 10^-22/?Hz for signals in the 40Hz - 1 kHz band. The Japanese project KAGRA, which is in the construction phase, will also feature novel techniques like cryogenic cooling and underground location.

When upgraded over the next five years to their advanced configurations, these detectors will be able to detect coalescence of (optimally-oriented) binary neutron stars at a distance of 500 Mpc and binary black holes at a redshift of z = 2, when the universe was one-third its current size. Advanced ground-based detectors are expected to observe GW signals at monthly or even weekly rates. In addition, the design study for a third generation ground-based interferometer called the Einstein Telescope has completed.

The Indian Initiative in Gravitational-wave Observations

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The localization accuracy for binary neutron stars located at 160 Mpc (oriented face-on with respect to the line of sight) using GW observations. The ellipses contain the 90% localization regions for binaries located at various points in the sky (in geographic coordinate system). Left plot corresponds to the Hanford-Hanford-Livingston-Virgo network and the tight plot to the Hanford-Livingston-Virgo-LIGOIndia network. Red crosses correspond to sky locations where the network would not confidently detect the binary. (Pic: S. Fairhurst)

Because of the inherent limitations of GW detectors (such as limited sky coverage and poor pointing accuracy), and weakness of astrophysical signals, it important to have a worldwide detector network — both from the point of establishing confidence in our first detections; as well as exploring exciting new astrophysics from these sources. Several studies have pointed out that the optimal location for another detector to augment the sensitivity of the current global network is in the Indian Ocean region, with Australia and India as two potential choices. The GW International Committee's (GWIC) Road Map Document strongly supports the GW experimental effort in India.

This presents Indian science an excellent opportunity to launch a major initiative in a promising experimental research frontier well in time before it has obviously blossomed. The IndIGO collaboration has held several meetings of its members and international advisory committee over the past one-year, and has discussed at length a phased strategy for building a large-scale GW detector in the Asia-Pacific region.

Ongoing activities

LIGO-India
The current major IndIGO plans on gravitational-wave astronomy relate to the LIGO-India project. LIGO-India is a proposed advanced gravitational-wave detector to be located in India, whose concept proposal is now under active consideration by the science funding agencies in India and USA. LIGO-India is envisaged as a collaborative project between a consortium of Indian research institutions and the LIGO Laboratory in USA, along with its international partners. Read more

Facilitate international collaborations in GW- physics and astronomy
IndIGO's effort for forging a strong bridge between the Indian scientific community and the International GW community is multifaceted. In addition to spearheading the ambitious proposal to build an advanced advanced GW observatory in the subcontinent, IndIGO is also facilitating the participation of the Indian scientific community in the international effort for the first detection of GWs. A subset of the IndIGO consortium (IndIGO-LSC) is a member group of the LIGO Scientific Collaboration and is involved in analyzing the data collected by the LIGO-Virgo observatories. IndIGO member institutions (IUCAA, TIFR, DU, CMI, IISER-Tvm) in association with the American partners (Caltech and WSU) have set up the Indo-US Center for Gravitational-Wave Physics and Astronomy. This center aims to facilitate collaboration between Indian and US scientists working in GW astronomy, with an eye to consolidating the Indo-US collaboration in GW-theory and data analysis, and extending it for setting up large-scale experimental facilities, and building related technological expertise in India. The center is fully funded by the Indo-US Science and Technology Forum (IUSSTF). IndIGO also has facilitated collaborative projects with GW groups in Japan, Germany and Australia. IUCAA is in the process of building a major high-performance computing infrastructure which will be also used as a Tier-2 data center for GW astronomy.

Initiate a strong experimental GW research program in India
Although the Indian scientific community has made significant contributions to the theory and data-analysis aspects of GW astronomy, the community lacked a major initiative in experimental GW research. IndIGO is committed to fostering experimental GW research in India. The TIFR group is in the process of building a 3-meter scale prototype interferometric GW detector incorporating advanced features like dual recycling, low frequency multi-stage isolators, and eventually, quantum squeezed light and DC read out. This will serve as a research, development and training platform in interferometry research. The sophistication and the cutting-edge technology of the TIFR prototype will attract young researchers and engineers to the experiment. The TIFR group has also developed an original scheme to use the interferometer for measurements of short-range gravity (in the sub-millimeter range) and new measurements of the Casimir force at large separations of 10-100 microns. Such experiments will also provide insight into theories with higher dimensional physics. Other major initiatives undertaken by the Indian groups include design and development of a 1W sub kHz line-width laser for use in a high-resolution length-calibrating interferometer, development of fabrication techniques such as ion beam figuring and liquid jet polishing for fabricating Ultraflat optics for the interferometer, development of metrology techniques for measuring ultra‑flat optics, etc.

Training of students and young scientists
The IndIGO collaboration is organizing several schools and workshops in India aiming to train students and young researchers in various aspects of GW astronomy. The first of such schools was organized in December 2010 at the University of Delhi, with support from the IUCAA Resource Center at the University of Delhi. IndIGO is also coordinating with its international partners in USA and Europe (LIGO, GEO600 and Virgo) in providing short and long-term research opportunities for undergraduate/graduate students and postdocs. For periodic updates, see Events page and resource pages for Students and Researchers. This web page summarizes the summer research projects in the past facilitated by the members and collaborators of the IndIGO consortium.