# Subir Sarkar

Subir Sarkar (12 September 1953, Ichapur, India) is an Indian astroparticle physicist and cosmologist, known for his research demonstrating constraints on the dark sector.

## Education and career

After completing secondary school in 1969, Sarkar studied at IIT Kharagpur, where he graduated with a B.Sc. in 1972 and an M.Sc. in 1974. He then became a graduate student at the Mumbai campus of the Tata Institute of Fundamental Research (TIFR), where he graduated in 1982 with a Ph.D. in physics. From 1979 to 1984 he was a research associate in TIFR's Cosmic Rays Group. In 1983 he was a visiting fellow at the International School for Advanced Studies (Scuola Internazionale Superiore di Studi Avanzati; SISSA) in Trieste. Sarkar was for the academic year 1984–1985 a research associate in CERN's Theory Division and for the academic year 1985–1986 a visiting fellow at the University of Oxford's Department of Astrophysics. For the academic year 1987–1988 he was a research associate in the HEP Theory Group of Rutherford Appleton Laboratory (RAL) in Chilton, Oxfordshire. From 1988 to 1989 he worked in Bhopal for an Indian NGO (Eklavya), specialising in science education and popularisation. In 1990 Sarkar became a staff member of the University of Oxford's Rudolf Peierls Centre for Theoretical Physics. At Wolfson College, Oxford he was a visiting scholar from 1991 to 1993 and a research fellow from 1993 to 1997. At the University of Oxford, he was a departmental lecturer from 1997 to 1998, a tutor in physics at Pembroke College, Oxford from 1997 to 1998. He was promoted to reader in 2000 and professor in 2006, retiring as professor emeritus in 2021. Sarkar headed the University of Oxford's Particle Theory Group from 2011 to 2019. He has also been an adjunct faculty member at TIFR.
Sarkar's research deals with relations between fundamental physics and aspects of astrophysics and cosmology. His research has a wide range, including dark matter, primordial nucleosynthesis, cosmological phase transitions, cosmological inflation, large-scale structure of the universe, and problems with the ΛCDM model. He collaborated with colleagues at the Pierre Auger Observatory, the Big European Bubble Chamber (BEBC), the IceCube Neutrino Observatory, and the Cherenkov Telescope Array in investigations of very high energy cosmic rays and neutrinos. He became a member of the Dark Energy Science Collaboration of the Vera C. Rubin Observatory. He was a founder member of the India Oxford Initiative, which began funding projects in 2019.
The astrophysicist Subir Sarkar should not be confused with the geologist Subir Sarkar, a professor in the Department of Geological Sciences of Jadavpur University.

## Awards and honours

In 2017 Sarkar was awarded the Homi Bhabha Medal and Prize. In 2021 he shared in the Bruno Rossi Prize awarded to Francis Halzen and the IceCube collaboration. From the 11th to the 13th of September 2023, Sarkar's collaborators and former students held a celebration in honour of his career achievements and his 70th birthday.

## Selected publications

* Sarkar, Subir (2003). "New physics from ultrahigh energy cosmic rays". arxiv.org. arXiv:hep-ph/0312223.
* Sarkar, Subir (2002). "Ultra-high energy cosmic rays and new physics". arxiv.org. arXiv:hep-ph/0202013. Bibcode:2002hep.ph....2013S.
* Abel, S.A.; Sarkar, S.; White, P.L. (1995). "On the cosmological domain wall problem for the minimally extended supersymmetric standard model". Nuclear Physics B. 454 (3): 663–681. arXiv:hep-ph/9506359. Bibcode:1995NuPhB.454..663A. doi:10.1016/0550-3213(95)00483-9.
* Sarkar, Subir (1996). "Big bang nucleosynthesis and physics beyond the standard model". Reports on Progress in Physics. 59 (12): 1493–1609. arXiv:hep-ph/9602260. Bibcode:1996RPPh...59.1493S. doi:10.1088/0034-4885/59/12/001.
* Birkel, Michael; Sarkar, Subir (1998). "Extremely high energy cosmic rays from relic particle decays". Astroparticle Physics. 9 (4): 297–309. arXiv:hep-ph/9804285. Bibcode:1998APh.....9..297B. doi:10.1016/S0927-6505(98)00028-0.
* Sarkar, Subir; Toldrà, Ramon (2002). "The high energy cosmic ray spectrum from relic particle decay". Nuclear Physics B. 621 (1–2): 495–520. arXiv:hep-ph/0108098. Bibcode:2002NuPhB.621..495S. doi:10.1016/S0550-3213(01)00565-X.
* Sarkar, Subir (2002). "Possible Astrophysical Probes of Quantum Gravity". Modern Physics Letters A. 17 (15n17): 1025–1035. arXiv:gr-qc/0204092. Bibcode:2002MPLA...17.1025S. doi:10.1142/S0217732302007521.
* Anchordoqui, Luis A.; Goldberg, Haim; Góra, Dariusz; Paul, Thomas; Roth, Markus; Sarkar, Subir; Winders, Lisa Lee (2010). "Using cosmic neutrinos to search for nonperturbative physics at the Pierre Auger Observatory". Physical Review D. 82 (4): 043001. arXiv:1004.3190. Bibcode:2010PhRvD..82d3001A. doi:10.1103/PhysRevD.82.043001.
* Beyer, Konstantin A.; Sarkar, Subir (2023). "Ruling out light axions: The writing is on the wall". SciPost Physics. 15 (1): 003. arXiv:2211.14635. Bibcode:2023ScPP...15....3B. doi:10.21468/SciPostPhys.15.1.003.