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. Krishnan dialogues and expressed them in his drama and films so that the message came across, but the subject was not offended. He acted in nearly 150 Tamil films and the matinee-duo of N. S. Krishnan and T. A. Madhuram (later his wife) was very popular in his day; he also did roles along with leading stage and cine artists such as T. S. Durairaj, "Pulimootai" Ramasamy, C.S. Pandian and writers such as Udumalai Narayana Kavi and Subbu Armugham and gave a number of hits. He was a talented singer and his hits include "Sivakavi", "Raja Rani", and "Manamagal". Though he