Effective mass (solid-state physics) from both sides gives where is the th element of , is the th element of , and are the th and th elements of , respectively, and is the total energy of the particle according to the Planck–Einstein relation. The index is contracted by the use of Einstein notation (there is an implicit summation over ). Since Newton's second law uses the inertial mass (not the gravitational mass), we can identify the inverse of this mass in the equation above as the tensor This tensor expresses the change in group velocity due to a change in crystal momentum. Its
N. S. Satya Murthy Indian Academy of Sciences elected Murthy as a fellow in 1975. The Council of Scientific and Industrial Research awarded him the Shanti Swarup Bhatnagar Prize, one of the highest Indian science awards in 1979. He became an elected fellow of the Indian National Science Academy in 1981. He was also a life member of the Magnetics Society of India. The Indian Physics Association has instituted an annual award, "N. S. Satya Murthy Memorial Award" for recognizing research excellence in physical sciences among young scientists. N. S. Satya Murthy Nivrathi Suryanarayanashastry Satya Murthy (5 February 1936 – 8 October 1984) was