Thanu Padmanabhan

Thanu Padmanabhan (born 10 March 1957) is an Indian theoretical physicist and cosmologist whose research spans a wide variety of topics in Gravitation, Structure formation in the universe and Quantum Gravity. He has published more than 260 papers and reviews in international journals and ten books in these areas. Many of his contributions, especially those related to the analysis and modelling of dark energy in the universe and the interpretation of gravity as an emergent phenomenon, have made significant impact in the field. He is currently a Distinguished Professor at the Inter-University Centre for Astronomy and Astrophysics, (IUCAA) at Pune, India.

Life and career

Born in 1957, Padmanabhan did his schooling in Thiruvananthapuram and earned his B.Sc. (1977) and M.Sc. (1979) in Physics, securing Gold Medals in both for graduating at the top of his class, from the University College, Kerala University. He published his first research paper (on general relativity) when he was still a B.Sc. student, at the age of 20. He joined the Tata Institute of Fundamental Research (TIFR), Mumbai in 1979 for his Ph.D. and became a faculty member there in 1980. 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 toIUCAA 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.

He was the elected President of the Cosmology Commission (2009-2012) of the International Astronomical Union (IAU) and Chairman of the Astrophysics Commission (2011-2014) of the International Union of Pure and Applied Physics (IUPAP). He has also been a Visiting Faculty at many institutes including the California Institute of Technology,Princeton University, and a Sackler in India.

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.

Awards and distinctions

Padmanabhan has received several national and international awards including:

  • Third World Academy of Sciences (TWAS) Prize in Physics (2011
  • Infosys Science Foundation Prize for Physical Sciences (2009)
  • J.C.Bose National Fellowship (DST) (2008)
  • INSA Vainu Bappu Gold Medal (2007)
  • Padma Shri (from the President of India, 2007)
  • Miegunah Fellowship Award (University of Melbourne, Australia, 2004)
  • Homi Bhabha Fellowship (2003)
  • G.D. Birla Award for Scientific Research (2003)
  • Al-Khwarizmi International Award (2002)
  • The Millennium Medal (CSIR, 2000)
  • Shanti Swarup Bhatnagar Award (1996)
  • The Birla Science Prize (1991)
  • Young Scientist Award, (Indian National Science Academy) (1984)

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

Research contributions

Padmanabhan’s work in the last decade, interpreting gravity as an emergent phenomenon, has far-reaching implications both for quantum gravity and for the nature of dark energy, and it has made a deep impact on the subject. He provided a clear interpretation of gravity as an emergent phenomenon and showed that this paradigm extends to a wide class of theories of gravitation including, but not limited to, general relativity. Padmanabhan could also show that several peculiar aspects of classical gravitational theories find natural interpretations in this approach. This approach also provides a novel solution to the cosmological constant problem.He has given two lectures at the Oxford-Cambridge collaborative conference on “Cosmology and the Constants of Nature” about this.[10][11]

Popular descriptions of his work have been published in Scientific American (India), 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 in his home page. Also available is an interview of Padmanabhan by George Musser about his work.

Padmanabhan’s early work was in quantum cosmology, structure formation in the universe and statistical mechanics of gravitating systems. In the 1980s, he provided an interpretation of the Planck length as the `zero-point length’ of the spacetime based on very general considerations. This result, established by theoretical considerations and well-chosen thought experiments, finds an echo in more recent results in several other candidate models for quantum gravity. He has made significant contributions to the study of statistical mechanics of gravitating systems and was a pioneer in the systematic application of these concepts to study the gravitational clustering in an expanding universe.

Pedagogical activities

Padmanabhan has given several lecture courses in India and abroad.

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

Main publications

Technical books

Padmanabhan has authored several advanced level textbooks which are acclaimed as magnificent achievements and used worldwide as standard references.

  • Quantum Field Theory: The Why, What and How, Springer, Heidelberg (2016)
  • Sleeping Beauties in Theoretical Physics: 26 Surprising Insights, Springer, Heidelberg (2015)
  • Gravitation: Foundations and Frontiers, Cambridge University Press, Cambridge, (2010)
  • An Invitation to Astrophysics, World Scientific, Singapore, (2006)
  • Theoretical Astrophysics – Volume III : Galaxies and Cosmology, Cambridge University Press, Cambridge, (2002)
  • Theoretical Astrophysics – Volume II : Stars and Stellar Systems, Cambridge University Press, Cambridge, (2001)
  • Theoretical Astrophysics – Volume I : Astrophysical Processes, Cambridge University Press, Cambridge, (2000) – Review
  • Cosmology and Astrophysics through Problems, Cambridge University Press, Cambridge, (1996) Review
  • Structure Formation in the Universe, Cambridge University Press, Cambridge, (1993) – Review
  • Gravity, Gauge Theories and Quantum Cosmology, (co-authored with J.V. Narlikar), Reidel (1986)

Review articles

  • Emergent Gravity Paradigm: Recent Progress, Mod. Phys. Letters A, 30, 1540007 (2015)
  • Statistical Mechanics of Gravitating Systems, Physics Reports, Vol.188, pp. 285–362 (1990)
  • Cosmological Constant – the Weight of the Vacuum, Physics Reports, Vol. 380, pp. 235–320 (2003)
  • Thermodynamical Aspects of Gravity: New insights, Reports in Progress of Physics, 73, 046901 (2010)
  • Lessons from Classical Gravity about the Quantum Structure of Spacetime, J.Phys.Conf.Ser., 306:012001 (2011)
  • Physical significance of Planck length, Annals of Physics, Vol. 165, pp. 38, (1985)

Science outreach

Apart from his scientific research, Padmanabhan has given many popular science lectures (several of which are available on YouTube) and authored more than a hundred popular science articles published in various national and international journals. He has also authored two popular science books:

  • Quantum Themes: The Charms of the Microworld, World Scientific, Singapore, (2009)
  • After the First Three Minutes – The Story of Our Universe, Cambridge University Press, Cambridge, (1998)

Some of his other contributions are:

  • The Story of Physics, a comic strip serialised in the magazine Science Age, from Sept. 84 to Dec. 86; published in book form by Vigyan Prasar, New Delhi, (2002) and now translated into several Indian regional languages.
  • The IYA Astronomical Diary – 2009, 53 illustrated pages of astronomical information, celebrating the International Year of Astronomy (2009) (with J.V.Narlikar and Samir Dhurde).
  • Dawn of Science – a 24 instalment set of articles on the early history of all branches of science published in the journal ‘Resonance’ in 2010-2012 [based on a set of articles originally published in Science Today from Jan 1990 to April 1992].