Thanu Padmanabhan

Padmanabhan did his schooling in Thiruvananthapuram and earned his B.Sc. (1977) and M.Sc. (1979) in Physics, from the University College, Kerala University.[4] He published his first research paper (on general relativity) when he was still a B.Sc. student, at the age of 20.[5] He joined the Tata Institute of Fundamental Research (TIFR), Mumbai in 1979 for his Ph.D. and became a faculty member there in 1980.[6] He held various faculty positions at TIFR during 1980-1992 and also spent a year (in 1986-87) at the Institute of Astronomy, Cambridge. He moved to IUCAA in 1992 and served as its Dean, Core Academic Programmes, for 18 years (1997-2015).

Padmanabhan has also served as Adjunct Faculty of the Tata Institute of Fundamental Research (Mumbai), the Harish-Chandra Research Institute (Allahabad), the Raman Research Institute (Bangalore) and the Indian Institute of Science, Education and Research (IISER, Pune) at different periods in his career. He is currently adjunct faculty of IISER, Mohali.

Padmanabhan served as the Chairman (2006–09) of the Time Allocation Committee[7] of the Giant Meterwave Radio Telescope of NCRA. He was the Chairman (2008–11) of the Indian National Science Academy's National Committee [8] which interfaces with the activities of the International Astronomical Union. In addition to advising the Government on policy issues, this also required him to coordinate the International Year of Astronomy 2009 activities in the country.

He was elected as the President of the Cosmology Commission (2009-2012) of the International Astronomical Union (IAU) and was providing advice to IAU activities in this field. He was elected in 2011 as the Chairman of the Astrophysics Commission (2011-2014) of the International Union of Pure and Applied Physics (IUPAP) [9] and co-ordinated the activities of IUPAP in this area. He has also been a Visiting Faculty at many institutes including the California Institute of Technology, Princeton University, and a Sackler Distinguished Astronomer of the Institute of Astronomy, Cambridge. He is an elected fellow of The World Academy of Sciences and of all the three National Academies of Science in India (the Indian National Science Academy, Indian Academy of Sciences, and the National Academy of Sciences, India).

Padmanabhan is an excellent teacher and has served as an active guide and mentor to several young researchers. Links to many of his innovative courses, which are available in YouTube, can also be accessed through his Facebook page.[10]

In addition to his scientific research, Padmanabhan works actively to popularize science and has given over 300 popular science lectures and has authored more than 100 popular science articles. He did a comic strip serial "The Story of Physics"[11] intended for school children. Published by Vigyan Prasar (New Delhi), it was translated into half a dozen regional Indian languages and made available at an affordable price at Indian schools. To commemorate the International Year of Astronomy (IYA) 2009, he published (with J.V.Narlikar and Samir Dhurde) the IYA Astronomical Diary 2009,[12] which comprises 53 illustrated pages of astronomical information. In 2019, he co-authored with Vasanthi Padmanabhan the "Dawn of Science" (published by Springer[13]). This is a lucid and captivating book which takes the reader back to the early history of all the sciences, starting from antiquity and ending roughly at the time of Newton. Each of the 24 chapters focuses on a particular and significant development in the evolution of science, and is connected in a coherent way to the others to yield a smooth, continuous storyline.

He is married to Vasanthi Padmanabhan, who has a Ph.D. in astrophysics from TIFR, Mumbai and has one daughter, Hamsa Padmanabhan, who has a Ph.D. in astrophysics from IUCAA, Pune.

Padmanabhan has received several national and international awards including:

His research work has won prizes nine times (in 1984, 2002, 2003, 2006, 2008, 2012, 2014, 2018 and 2020) including the First Prize in 2008 from the Gravity Research Foundation, USA.[23]

A Stanford study in 2020, listing top scientists in different fields, has ranked Padmanabhan as 24th in world in his research area.[24][25]

Padmanabhan's original research contributions have made a significant impact on the subjects of gravitation and cosmology. His work in the last decade has far-reaching implications both for quantum gravity and for the nature of dark energy.[26][27] During 2002–2015, he provided a clear interpretation of gravity as an emergent phenomenon (like elasticity or fluid dynamics) and showed that this paradigm extends to a wide class of theories of gravitation including, but not limited to, general relativity.[28][29] Padmanabhan could show that several peculiar aspects of classical gravitational theories find natural interpretations in this approach.[30] Such an interpretation also provides a novel solution to the cosmological constant problem.[31] He has given two lectures at the Oxford-Cambridge collaborative conference on "Cosmology and the Constants of Nature" about this.[32][33]

Popular (non-technical) descriptions of Padmanabhan's research have been published in Scientific American (India),[34] and a more technical description is available in an article from the Gravity Research Foundation in 2008, that describes his First Prize work. Another popular article about his work which appeared in a German science magazine along with the English translation is available on his home page. An interview of Padmanabhan by George Musser about his work can be found here.

In the earlier part of Padmanabhan's career (1980-2001), he made important contributions to quantum cosmology, structure formation in the universe and statistical mechanics of gravitating systems. In the 1980s, he came up with an interpretation of the Planck length as the `zero-point length' of the spacetime based on very general considerations.[35] This result, established by theoretical considerations and well-chosen thought experiments,[36] finds an echo in more recent results in several other candidate models for quantum gravity. He developed the complex path method (in 1998 [37]) to study black hole thermodynamics which was a precursor to the `tunneling paradigm' that became quite popular later on. He is a recognized authority in the subject of the statistical mechanics of gravitating systems[38] and was a pioneer in the systematic application of these concepts to study the gravitational clustering in an expanding universe.[39] He has been invited to lecture twice at the Les Houches Schools (in 2002 and 2008) to a broader community about this subject.

In November 2016, Padmanabhan published research studies advocating a new paradigm shift in understanding gravity.[40][41] A key question in quantum gravity lies in understanding the primordial, pre-geometric phase of the universe, from which the classical, geometric phase described by Einstein's equations emerges along with the notions of space and time themselves. Padmanabhan introduced the notion of Cosmic Information (called 'CosmIn') which allows to connect these two phases in a fascinating manner. CosmIn, which is a conserved quantity, measures the total information transferred from the quantum gravitational phase to the classical phase of the universe. Quantum gravitational considerations advocate an astonishingly simple value for CosmIn: 4π, the number of information 'bits' on the surface of a sphere of unit radius. Using these considerations, CosmIn was able to relate the numerical value of the cosmological constant - possibly the deepest unsolved problem in theoretical physics today - to the energy scale at which the universe made the quantum-to-classical transition.[42] This is the first time that a model with no adjustable parameters is able to provide a holistic explanation for both these observations, which has far-reaching implications for the quantum structure of spacetime. A non-technical account covering this latest development in Padmanabhan's research was recently published in the magazine 'Nautilus'.[43]

• A 50-hour course by Padmanabhan on Quantum Field Theory, (available on YouTube).
• A one-semester course of lectures on General Relativity by Padmanabhan.
• Another set of lectures (15 hours) by Padmanabhan on Advanced Topics in General relativity at the 'troisieme cycle de la physique en suisse romande' course (Geneva, Switzerland).
• Thanu Padmanabhan's Home page