Herbert Callen

Herbert Bernard Callen (July 1, 1919 – May 22, 1993) was an American physicist specializing in thermodynamics and statistical mechanics. He is considered one of the founders of the modern theory of irreversible thermodynamics, He is also known for developing the fluctuation–dissipation theorem. During World War II, his services were invoked in the theoretical division of the Manhattan Project. Herbert Callen received his bachelor's degree in physics from Temple University in 1941 and his master's degree from the institution the following year. concerns the Kelvin thermoelectric and thermomagnetic relations, and Lars Onsager's reciprocal relations. Upon receiving his PhD, Callen spent a year at the MIT Laboratory for Insulation Research and developed his theory of electrical breakdown for insulators. Specialists consider his most lasting contribution to physics to be the paper co-written with Theodore A. Welton presenting a proof of the fluctuation–dissipation theorem, an extremely general result describing how a system's response to perturbations relates to its behavior at equilibrium.

Retirement and death He retired in 1985. The much revised second edition, published in 1985, became a highly cited reference in the literature In 1984, Callen received the Elliott Cresson Medal from the Franklin Institute. He was made a member of the National Academy of Sciences in 1990.