The formation and development
of the concept of virtual particles
The project investigates the concept of a virtual particle from a historical point of view. This concept is an integral part of modern physics, mainly since it provides a means to interpret and describe complex quantum physical processes in comparatively simple terms. Despite of its wide use, the notion of a virtual particle appears not to be clearly defined. One of the main goals of the project is therefore to trace the origins of the concept and to follow its evolution through time. Since it is of a fundamental quantum physical nature, it is quite clear that the roots of the virtual particle concept are tied to the beginnings of quantum mechanics and quantum field theory. However, the reasons for its introduction, its further development in the context of quantum field theory, S-matrix theory, and Feynman's diagrammatic method have never been the focus of historical research. By taking up these issues, the present project aims to explain the genesis of today's terminological diversity, to bring to the fore the reasons for the apparent inconsistencies, and to further our understanding of concept formation in the physical sciences.