B. Roy Frieden

Who is B. Roy Frieden?

B. Roy Frieden is an American mathematical physicist.

Frieden obtained a Ph.D. in Optics from The Institute of Optics at the University of Rochester. His doctoral thesis advisor was Robert E. Hopkins. Frieden is now an Emeritus Professor of Optical Sciences at the University of Arizona.

Frieden is best known for his extensive work on Fisher information as a grounding principle for deriving and elaborating physical theory. Such theories take the form of differential equations or probability distribution functions.

Central to Frieden's derivations is the mathematical variational principle of extreme physical information. This principle builds on the well-known idea that the observation of a "source" phenomenon is never completely accurate. That is, information is inevitably lost in transit from source to observation. Furthermore, the random errors that creep in are presumed to define the distribution function of the source phenomenon. As Frieden puts it, "the physics lies in the fluctuations." Finally, the information loss may be shown to be an extreme value. Thus if the observed level of Fisher information in the data has value I, and the level of Fisher information that existed at the source has value J, the EPI principle states that I − J = extremum. In most situations, the extremum is a minimum, meaning that there is a tendency for any observation to faithfully match up with its source.