Hugh Everett III was an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 physicist

Physicist

A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

 who first proposed the many-worlds interpretation

Many-worlds interpretation

The many-worlds interpretation is an interpretation of quantum mechanics that asserts the objective reality of the universal wavefunction, but denies the actuality of wavefunction collapse. Many-worlds implies that all possible alternative histories and futures are real, each representing an...

 (MWI) of quantum physics, which he termed his "relative state" formulation.

Discouraged by the scorn of other physicists for MWI, Everett ended his physics career after completing his Ph.D. Afterwards, he developed the use of generalized Lagrange multipliers

Lagrange multipliers

In mathematical optimization, the method of Lagrange multipliers provides a strategy for finding the maxima and minima of a function subject to constraints.For instance , consider the optimization problem...

 for operations research

Operations research

Operations research is an interdisciplinary mathematical science that focuses on the effective use of technology by organizations...

 and applied this commercially as a defense analyst and a consultant

Consultant

A consultant is a professional who provides professional or expert advice in a particular area such as management, accountancy, the environment, entertainment, technology, law , human resources, marketing, emergency management, food production, medicine, finance, life management, economics, public...

. He was married to Nancy Everett née Gore.