Surajit Sen (born November 28, 1960 in Calcutta (modern name Kolkata) in India) is a physicist who works on theoretical and computational problems in non-equilibrium statistical physics and in nonlinear dynamics of many body systems. He holds a Ph.D in physics from The University of Georgia (1990) where he studied with M. Howard Lee. He is also interested in applying physics to study problems of relevance in a societal context. He is a professor of physics at the State University of New York, Buffalo. [1] Much of Sen's recent work can be found in his RUSA lecture at Bharatidasan University. [2]
Sen is credited with developing an exact solution for the Heisenberg equation of motion in a quantum mechanical many body system in 1991. [3] His studies include work on how solitary waves travel in alignments of elastic beads, [4] on how they interact with one another and how these systems [5] [6] [7] tend to reach an equilibrium-like state where equipartitioning of energy is not respected, which he called the quasi-equilibrium state. [8] Suggestion of a similar state was made soon thereafter by Berges et al. [9] Recently, Neyenhuis et al [10] may have found some experimental evidence of this quasi-equilibrium/prethermalization state. Sen's Steel Institute colloquium at the Indian Institute of Technology, Bombay, captures some of his work on strongly nonlinear systems - https://arts-sciences.buffalo.edu/physics/research/non-linear-dynamics-statistical-physics.html.
Recently, his group has also shown how the energy equipartitioned state may in fact be realized in these systems. [11] In 1997, he investigated the possible use of sound bursts in detecting buried small landmines. [12] [13] [14] In 2001, he introduced the tapered granular chain impact dispersion system, [15] which has since been extensively probed. [16] [17] [18] [19] Sen has recently suggested that nonlinear systems may be used to extract mechanical energy from noisy environments and make them into useful energy. [20] Sen's group has used cellular automata based simulations to model land battles between an insurgent army and an intelligent army [21] and used molecular dynamics based simulations to examine the social structure of chimpanzee colonies. [22] He has also been active in modeling partisan elections. [23]
Sen was elected as a Fellow [24] of the American Physical Society [25] in 2008, [26] for the discovery of how solitary waves break and secondary solitary waves form in granular media, for his leadership in organizing forums to represent and recognize the physicists from India and for raising consciousness about the problems and the importance of rural science education in India and the developing world. He was also elected as a Fellow of the American Association for the Advancement of Science in 2012 [27] for pioneering research on solitary waves and their collisions in granular media and for sustained outstanding service and leadership in international physics. [28]
In 2020-2021 he served as a Senior Science Advisor at the United States Agency for International Development while on leave as a Jefferson Science Fellow of the US National Academies. His work is summarized in a JSF Distinguished Lecture presented at the US National Academies https://vimeo.com/566681948. More recently, Sen served as a Distinguished Visiting Professor of Biosciences and Bioengineering at the Indian Institute of Technology Jodhpur, India, where one of his focus areas have been desert ecosystems.
In mathematics and physics, a soliton is a nonlinear, self-reinforcing, localized wave packet that is strongly stable, in that it preserves its shape while propagating freely, at constant velocity, and recovers it even after collisions with other such localized wave packets. Its remarkable stability can be traced to a balanced cancellation of nonlinear and dispersive effects in the medium. Solitons were subsequently found to provide stable solutions of a wide class of weakly nonlinear dispersive partial differential equations describing physical systems.
In physics, an oscillon is a soliton-like phenomenon that occurs in granular and other dissipative media. Oscillons in granular media result from vertically vibrating a plate with a layer of uniform particles placed freely on top. When the sinusoidal vibrations are of the correct amplitude and frequency and the layer of sufficient thickness, a localized wave, referred to as an oscillon, can be formed by locally disturbing the particles. This meta-stable state will remain for a long time in the absence of further perturbation. An oscillon changes form with each collision of the grain layer and the plate, switching between a peak that projects above the grain layer to a crater like depression with a small rim. This self-sustaining state was named by analogy with the soliton, which is a localized wave that maintains its integrity as it moves. Whereas solitons occur as travelling waves in a fluid or as electromagnetic waves in a waveguide, oscillons may be stationary.
A sphaleron is a static (time-independent) solution to the electroweak field equations of the Standard Model of particle physics, and is involved in certain hypothetical processes that violate baryon and lepton numbers. Such processes cannot be represented by perturbative methods such as Feynman diagrams, and are therefore called non-perturbative. Geometrically, a sphaleron is a saddle point of the electroweak potential.
In physics, thermalisation is the process of physical bodies reaching thermal equilibrium through mutual interaction. In general the natural tendency of a system is towards a state of equipartition of energy and uniform temperature that maximizes the system's entropy. Thermalisation, thermal equilibrium, and temperature are therefore important fundamental concepts within statistical physics, statistical mechanics, and thermodynamics; all of which are a basis for many other specific fields of scientific understanding and engineering application.
Harry L. Swinney is an American physicist noted for his contributions to the field of nonlinear dynamics.
Jamming is the physical process by which the viscosity of some mesoscopic materials, such as granular materials, glasses, foams, polymers, emulsions, and other complex fluids, increases with increasing particle density. The jamming transition has been proposed as a new type of phase transition, with similarities to a glass transition but very different from the formation of crystalline solids.
Active matter is matter composed of large numbers of active "agents", each of which consumes energy in order to move or to exert mechanical forces. Such systems are intrinsically out of thermal equilibrium. Unlike thermal systems relaxing towards equilibrium and systems with boundary conditions imposing steady currents, active matter systems break time reversal symmetry because energy is being continually dissipated by the individual constituents. Most examples of active matter are biological in origin and span all the scales of the living, from bacteria and self-organising bio-polymers such as microtubules and actin, to schools of fish and flocks of birds. However, a great deal of current experimental work is devoted to synthetic systems such as artificial self-propelled particles. Active matter is a relatively new material classification in soft matter: the most extensively studied model, the Vicsek model, dates from 1995.
Robert William Boyd is an American physicist noted for his work in optical physics and especially in nonlinear optics. He is currently the Canada Excellence Research Chair Laureate in Quantum Nonlinear Optics based at the University of Ottawa, professor of physics cross-appointed to the school of electrical engineering and computer science at the University of Ottawa, and professor of optics and professor of physics at the University of Rochester.
In condensed matter physics, a time crystal is a quantum system of particles whose lowest-energy state is one in which the particles are in repetitive motion. The system cannot lose energy to the environment and come to rest because it is already in its quantum ground state. Because of this, the motion of the particles does not really represent kinetic energy like other motion; it has "motion without energy". Time crystals were first proposed theoretically by Frank Wilczek in 2012 as a time-based analogue to common crystals – whereas the atoms in crystals are arranged periodically in space, the atoms in a time crystal are arranged periodically in both space and time. Several different groups have demonstrated matter with stable periodic evolution in systems that are periodically driven. In terms of practical use, time crystals may one day be used as quantum computer memory.
Sergej Flach is a theoretical physicist whose research has spanned a number of scientific fields in his career. With about 240 publications to his name, his research has been cited over 16,000 times giving him an h-index of 58 and i10-index of 174. He is a member of the American Physical Society, German Physical Society, Korean Physical Society, and New Zealand Institute of Physics. He is an editorial board member of Chaos (2016-) and was an editorial board member of Physical Review E (2009-2011).
Bernstein–Greene–Kruskal modes are nonlinear electrostatic waves that propagate in an unmagnetized, collisionless plasma. They are nonlinear solutions to the Vlasov–Poisson equation in plasma physics, and are named after physicists Ira B. Bernstein, John M. Greene, and Martin D. Kruskal, who solved and published the exact solution for the one-dimensional case in 1957.
Maria Cristina Marchetti is an Italian-born, American theoretical physicist specializing in statistical physics and condensed matter physics. In 2019, she received the Leo P. Kadanoff Prize of the American Physical Society. She held the William R. Kenan, Jr. Distinguished Professorship of Physics at Syracuse University, where she was the director of the Soft and Living Matter program, and chaired the department 2007–2010. She is currently Professor of Physics at the University of California, Santa Barbara.
Bulbul Chakraborty is the Enid and Nate Ancell Professor of Physics at Brandeis University. She is recognized for her contributions to soft condensed matter theory studying systems far from equilibrium, such as granular materials, amorphous systems, and statistical physics. She is an elected American Physical Society and American Association for the Advancement of Science fellow.
John Holmes Malmberg was an American plasma physicist and a professor at the University of California, San Diego. He was known for making the first experimental measurements of Landau damping of plasma waves in 1964, as well as for his research on non-neutral plasmas and the development of the Penning–Malmberg trap.
Douglas J. Durian is Professor of Physics and Astronomy at the University of Pennsylvania. He is known for his research contributions to the field of experimental soft matter, particularly in the areas of foams and granular flows. He has held multiple visiting professorships and leaderships positions in the soft matter physics community. He is a Fellow of the American Physical Society.
In statistical mechanics and condensed matter physics, the Kovacs effect is a kind of memory effect in glassy systems below the glass-transition temperature. A.J. Kovacs observed that a system’s state out of equilibrium is defined not only by its macro thermodynamical variables, but also by the inner parameters of the system. In the original effect, in response to a temperature change, under constant pressure, the isobaric volume and free energy of the system experienced a recovery characterized by non-monotonic departure from equilibrium, whereas all other thermodynamical variables were in their equilibrium values. It is considered a memory effect since the relaxation dynamics of the system depend on its thermal and mechanical history.
Dov I. Levine is an American-Israeli physicist, known for his research on quasicrystals, soft condensed matter physics, and statistical mechanics out of equilibrium.
Robert Everett Ecke is an American experimental physicist who is a laboratory fellow and director emeritus of the Center for Nonlinear Studies (CNLS) at Los Alamos National Laboratory and Affiliate Professor of Physics at the University of Washington. His research has included chaotic nonlinear dynamics, pattern formation, rotating Rayleigh-Bénard convection, two-dimensional turbulence, granular materials, and stratified flows. He is a Fellow of the American Physical Society (APS) and of the American Association for the Advancement of Science (AAAS), was chair of the APS Topical Group on Statistical and Nonlinear Physics, served in numerous roles in the APS Division of Fluid Dynamics, and was the Secretary of the Physics Section of the AAAS.
Elbio Rubén Dagotto is an Argentinian-American theoretical physicist and academic. He is a distinguished professor in the department of physics and astronomy at the University of Tennessee, Knoxville, and Distinguished Scientist in the Materials Science and Technology Division at the Oak Ridge National Laboratory.
Germán Sierra is a Spanish theoretical physicist, author, and academic. He is Professor of Research at the Institute of Theoretical Physics Autonomous University of Madrid-Spanish National Research Council.