Carl H. Brans

American mathematical physicist best known for his research into the theoretical underpinnings of gravitation elucidated in his most widely publicized work, the Brans–Dicke theory.

Brans is well known among those engaged in the study of gravity and is noted for his development, with Robert H. Dicke of the Brans–Dicke theory of gravitation in which the gravitational constant varies with time, a leading competitor of Einstein's theory of general relativity. The work of Brans and Dicke actually was closely related to earlier work of Pascual Jordan, but was developed independently. This formulation is often referred to as the Jordan–Brans–Dicke (JBD) scalar–tensor theory of gravity. In this theory, based on speculations of Mach, Eddington, Dirac and others, a universally coupled scalar field, in addition to the metric, is introduced which ultimately results in a theory in which the gravitational constant depends on the distribution of matter in the universe. A number of very accurate measurements made in the late 1970s has indicated that JBD fares no better than the simpler standard Einstein General Relativity, in the solar system context. However, developments in string theory and in inflationary cosmology have renewed interest in scalar field modifications of standard general relativity, although not in the original JBD form.