Meet Bala Iyer, theoretical physicist leading advanced gravitational-wave project for India

Bala Iyer, among the project leads for LIGO-India, says India could be a world leader in astrophysics 20 years from now.

Theoretical physicist Bala Iyer | International Centre for Theoretical Sciences website (https://www.icts.res.in/)

Bengaluru: Few people outside the world of astrophysics might have heard of Bala Iyer, but he is no less than a rockstar within the community. 

Bala Iyer is one of the project leads for LIGO-India, the planned advanced gravitational-wave observatory to be based in the country, and the chair for IndIGO, the consortium of physicists that proposed the project. 

He specialises in the study of inspiraling compact binaries (ICB), where neutron stars and/or black holes spiral into each other and eventually collide. All gravitational waves detected so far have been from colliding black holes or neutron stars.

His computations with physicists Luc Blanchet and Thibault Damour are among those that formed a crucial base for the construction of templates for interferometric gravitational-wave detectors, such as LIGO in the US — which is credited with the Nobel-winning feat of pulling off the first-ever detection of gravitational waves — and Virgo in Italy.

Bala Iyer has been elected as a fellow of American Physical Society (2012) and the International Society of General Relativity and Gravitation (2013). And he is currently a faculty member at the International Centre for Theoretical Sciences (ICTS), which recently held a week-long conference on gravitational waves nicknamed ‘Bala-fest’ in his honour. 

Childhood and inspiration

Iyer was born on 28 December 1952 at Parli in Kerala, but grew up in Kalyan on the outskirts of Mumbai. 

“In school, I read, in a magazine called Science Today, an article by [the astronomer] Jayant Narlikar titled The Arrows of Time,” he told ThePrint in an interview. “It was about how the concept of time has different meanings in physics.”

The idea of questioning something as fundamental as the meaning of time enamoured Iyer, and this was what first pushed him towards physics. 

“I realised that those are the kinds of questions I wanted to answer,” he said.

In 1973, he got a BSc in physics from Ramnarain Ruia College in Mumbai. While at college, he formed a physics study group where students explored topics beyond their subjects with the help of professional physicists. 

This is what formed his “mental makeup” to pursue research in physics, he said. He went on to obtain an MSc in Physics in 1976 from the then-newly-formed department of physics at Bombay University. 

Iyer also completed his PhD from the university in 1980 under the guidance of Arvind Kumar, a leading expert in quantum field theory who has been conferred with the Padma Shri. With him, Iyer worked on ‘quantum field theory in curved spacetime’ — a subject that was all the rage at the time because two of the greatest minds in science, Stephen Hawking and Subrahmanyan Chandrasekhar, were involved in an associated sphere, the study of black holes. 

His work attempted to reconcile relativity’s curved spacetime with quantum mechanics. “A paper that Kumar and I wrote was even cited in Chandrasekhar’s groundbreaking Mathematical Theory of Black Holes book,” Iyer said. 

Work and contribution

In 1980, Iyer moved to Bengaluru as a postdoc at the Raman Research Institute (RRI) under the famous scientist C.V. Vishveshwara, who was best known for proving, mathematically, the stability of a black hole. 

Here, he worked on classical relativity and the problems within it, such as perturbations in spacetime created by black holes. Gravitational waves were not mainstream yet, and relativity was the topic of the day. 

The duo worked out the theory of what we know today as ‘ultra compact objects’, a phrase that was coined by them. 

Compact objects themselves are stellar remnants left over after a star dies: White dwarfs, neutron stars, and black holes. Ultra compact objects are theorised to be more compact than neutron stars but not as much as black holes. (Compactness is defined mathematically as mass/radius, density is mass/volume.)

His work led to the mathematical class of problems that explains black holes using ‘String Theory’, and if black holes are present in higher dimensions. “The research is now moving from finding applications of relativity to solving problems posed by relativity,” said Iyer.

Foray into gravitational-wave physics

In the late 1980s, gravitational waves began to emerge as an area of research, and Iyer switched his focus to understanding these ripples in spacetime that are created by compact objects moving around in the fabric of the universe. 

“Chandrashekhar would always say that researchers should change their fields every 10 years to keep up with emerging areas,” said Iyer. “My 10 years had elapsed and gravitational waves looked promising.”

In 1989-90, Iyer went to France on a sabbatical from the RRI to work with Thibault Damour, a theoretical physicist at Institut des Hautes Études Scientifiques (IHÉS) and a leading expert in general relativity. 

Damour worked on binary black holes, a subject that Iyer was immediately drawn to as well. 

“From the start of my collaboration with Bala Iyer in 1990, I appreciated his rare talents — his sharp mind, the depth of his thinking, his extreme carefulness for going through complicated reasonings and computations,” Damour told ThePrint. 

“His theoretical brightness was always accompanied by an exceptional modesty and human warmth.”

Iyer wrote two papers with Damour before moving back to the RRI in the early 1990s, just when talks began in the international community about the construction of interferometers to detect gravitational waves. Iyer’s research progressed to understanding what the results could be like. 

“I became involved in mathematical computations of gravitational waves from colliding or spiralling neutron stars and black holes,” said Iyer.

His work was a part of the foundation on which the detectors were built, and the first gravitational waves detected in 2015 matched perfectly with what was expected. 

“He has made world-class contributions to the theoretical description of coalescing binary black holes that have played a key role in the detection and interpretation of gravitational wave signals by the LIGO-Virgo collaboration,” said Damour. 

LIGO-India

In 2007, during the International Conference on Gravitation and Cosmology (ICGC) at the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, the idea of having a LIGO observatory in India was first proposed by physicist Rana Adhikari (now with CalTech). 

Two years later, at IUCAA’s 20-year anniversary, discussions began on how to take gravitational-wave research in India “to the next level”. 

“Thus the IndIGO consortium was formed in 2009,” said Iyer. “And I became the chair and Sanjeev Dhurandhar (and later Tarun Souradeep) the spokesperson of the council.”

Today, the consortium has over 120 Indian physicists from nine institutions as members. However, the interferometer, expected to come up in the Hingoli district of Maharashtra, is wrought with technical complications.

In 2010, the American LIGO detectors were shut down and upgraded to ‘Advanced LIGO’, which helped quickly detect gravitational waves in rapid succession. This year, it was announced that LIGO is expected to be in the ‘Advanced LIGO Plus’ mode by 2024. 

With every such improvement and upgrade to existing LIGO technology, LIGO-India’s design becomes more complicated. 

“LIGO-India is a moving target,” said Iyer. “It is a challenge for us but we’re currently building the expertise and strategy to keep up with it.”

This makes it absolutely clear that a completely new type of astronomy is shaping up, Iyer said. And he is at the forefront of it all, building the foundation and training gravitational-wave physicists of the future. 

“In the next 20 years, we could potentially become a world leader in the field,” he added.