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Subir Sarkar (12 September 1953, Ichapur, India) is an Indian astroparticle physicist and cosmologist, known for his research demonstrating constraints on the dark sector.
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. [1] From 1988 to 1989 he worked in Bhopal for an Indian NGO (Eklavya), specialising in science education and popularisation. [2] 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. [1]
Sarkar's research deals with relations between fundamental physics and aspects of astrophysics and cosmology. [2] His research has a wide range, including dark matter, primordial nucleosynthesis, [3] cosmological phase transitions, cosmological inflation, large-scale structure of the universe, [2] and problems with the ΛCDM model. [4] 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. [2] He became a member of the Dark Energy Science Collaboration of the Vera C. Rubin Observatory. [5] He was a founder member of the India Oxford Initiative, [6] which began funding projects in 2019. [7]
The astrophysicist Subir Sarkar should not be confused with the geologist Subir Sarkar, a professor in the Department of Geological Sciences of Jadavpur University. [8]
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. [1] 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. [9]
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate. Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed those physical laws to be understood.
In astronomy, dark matter is a hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravitational effects which cannot be explained by general relativity unless more matter is present than can be observed. Such effects occur in the context of formation and evolution of galaxies, gravitational lensing, the observable universe's current structure, mass position in galactic collisions, the motion of galaxies within galaxy clusters, and cosmic microwave background anisotropies.
A neutrino is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. The rest mass of the neutrino is much smaller than that of the other known elementary particles. The weak force has a very short range, the gravitational interaction is extremely weak due to the very small mass of the neutrino, and neutrinos do not participate in the electromagnetic interaction or the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected.
Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter.
In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equally throughout the universe on a large scale, and should, therefore, produce no observable inequalities in the large-scale structuring over the course of evolution of the matter field that was initially laid down by the Big Bang.
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray particles.
An acceleron is a hypothetical subatomic particle postulated to relate the mass of the neutrino to the dark energy conjectured to be responsible for the accelerating expansion of the universe. The acceleron was postulated by researchers at the University of Washington in 2004.
A strongly interacting massive particle (SIMP) is a hypothetical particle that interacts strongly between themselves and weakly with ordinary matter, but could form the inferred dark matter despite this.
In physical cosmology, leptogenesis is the generic term for hypothetical physical processes that produced an asymmetry between leptons and antileptons in the very early universe, resulting in the present-day dominance of leptons over antileptons. In the currently accepted Standard Model, lepton number is nearly conserved at temperatures below the TeV scale, but tunneling processes can change this number; at higher temperature it may change through interactions with sphalerons, particle-like entities. In both cases, the process involved is related to the weak nuclear force, and is an example of chiral anomaly.
The cosmic neutrino background is the universe's background particle radiation composed of neutrinos. They are sometimes known as relic neutrinos.
Astroparticle physics, also called particle astrophysics, is a branch of particle physics that studies elementary particles of astrophysical origin and their relation to astrophysics and cosmology. It is a relatively new field of research emerging at the intersection of particle physics, astronomy, astrophysics, detector physics, relativity, solid state physics, and cosmology. Partly motivated by the discovery of neutrino oscillation, the field has undergone rapid development, both theoretically and experimentally, since the early 2000s.
Extragalactic cosmic rays are very-high-energy particles that flow into the Solar System from beyond the Milky Way galaxy. While at low energies, the majority of cosmic rays originate within the Galaxy (such as from supernova remnants), at high energies the cosmic ray spectrum is dominated by these extragalactic cosmic rays. The exact energy at which the transition from galactic to extragalactic cosmic rays occurs is not clear, but it is in the range 1017 to 1018 eV.
The Kolar Gold Fields (KGF), located in the Kolar district of the state of Karnataka, India, are a set of defunct gold mines known for the neutrino particle experiments and unusual observations that took place there starting in 1960. The experiments ended with the closing of the mine in 1992.
Probir Roy is an Indian particle physicist and a former professor at Tata Institute of Fundamental Research. He is also a senior scientist of the Indian National Science Academy at Bose Institute and a former Raja Ramanna fellow of Department of Atomic Energy at Saha Institute of Nuclear Physics.
Céline Bœhm is a professor of Particle Physics at the University of Sydney. She works on astroparticle physics and dark matter.
Angela Villela Olinto is an American astroparticle physicist who is the provost of Columbia University. Previously, she served as the Albert A. Michelson Distinguished Service Professor at the University of Chicago as well as the dean of the Physical Sciences Division. Her current work is focused on understanding the origin of high-energy cosmic rays, gamma rays, and neutrinos.
Francis Louis Halzen is a Belgian particle physicist. He is the Hilldale and Gregory Breit Distinguished Professor at the University of Wisconsin–Madison and Director of its Institute for Elementary Particle Physics. Halzen is the Principal Investigator of the IceCube Neutrino Observatory at the Amundsen–Scott South Pole Station in Antarctica, the world's largest neutrino detector which has been operational since 2010.
Dharam Vir Ahluwalia was an Indian-born American theoretical physicist who made significant contributions to physics of neutrino oscillations, gravitationally induced phases, interface of the gravitational and quantum realms, and mass dimension one fermions. In 2019 he published Mass Dimension One Fermions.
Nikolaos Emmanuel Mavromatos is a Greek theoretical physicist, specialising in string theory, particle physics, and cosmology. He has an international reputation for his research on quantum spacetimes, uncertainty relations in string theory, and ideas for tests of possible violations of Lorentz invariance and CPT invariance.
Thomas Korff Gaisser was a particle physicist, cosmic ray researcher, and a pioneer of astroparticle physics. He is known for his book Cosmic Rays and Particle Physics and the Gaisser–Hillas function.
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