B. Roy Frieden is a mathematical physicist living in Tucson, Arizona (email address: roy.frieden@optics.arizona.edu). He is an Emeritus Professor of Optical Sciences at the University of Arizona. His main work is the use of Fisher information for purposes of deriving and developing physical theories. These theories take the form of known differential equations or probability distribution functions. (Examples are the Schrödinger wave equation of quantum mechanics, and the Maxwell-Boltzmann velocity distribution of statistical mechanics.)

The derivations utilize the mathematical principle of extreme physical information (EPI). 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. That is, "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. The extremum is a minimum in most problems, meaning that there is a tendency for any observation to faithfully match up with its source (which is comforting).

The EPI principle is a variational principle that has been used to derive most fundamental laws of physics, as well as laws of biology, cancer growth, chemistry, and economics. These include new laws and concepts as well. In this way, Fisher information, and in particular its loss I − J during observation, provides a bridge for deriving laws of nature in general.

References

The main reference for the work is the book "Science from Fisher Information, 2nd edition", by B. Roy Frieden (Cambridge University Press, 2004).