Julian Schwinger was one of the leading theoretical physicists of the twentieth century. His contributions are as important, and as pervasive, as those of Richard Feynman, with whom he shared the 1965 Nobel Prize for Physics. Yet, while Feynman is universally recognized as a cultural icon, Schwinger is little known even to many within the physics community. In his youth, Julian Schwinger was a nuclear physicist, turning to classical electrodynamics after World War II. In the years after the war, he (...) was the first to renormalize quantum electrodynamics. Subsequently, he presented the most complete formulation of quantum field theory and laid the foundations for the electroweak synthesis of Glashow, Weinberg, and Salam, and he made fundamental contributions to the theory of nuclear magnetic resonance, to many-body theory, and to quantum optics. He developed a unique approach to quantum mechanics, measurement algebra, and a general quantum action principle. His discoveries include 'Feynman's' parameters and 'Glauber's' coherent states; in later years he also developed an alternative to operator field theory which he called Source Theory, reflecting his profound phenomenological bent. His late work on the Thomas-Fermi model of atoms and on the Casimir effect continues to be an inspiration to a new generation of physicists. This biography describes the many strands of his research life, while tracing the personal life of this private and gentle genius. (shrink)

Environmentalists often argue that, in order to address fundamentally the harmful impact of their activities on the environment, western industrial societies need to change their attitude to nature. Specifically, they need to see nature as sacred, and to acknowledge that humanity is a part of nature rather than separate from it. In this paper, I seek to show that these tow ideas are incompatible in the context of western culture. Drawing particularly on ideas expressed by western conservationists, I argue that (...) nature is already seen as sacred, and that its sacredness depends on it being seen as separate from humanity, an idea which effectively contradicts the scientific knowledge on which many conservationists base their actions. Goodin's green theory of value is used as a source of ideas about why non-human nature is experienced as sacred, and can be extended to suggest that other values, such as 'development' and progress', are also seen as sacred. (shrink)

Recently, there has been renewed interest in the search for low-mass magnetic monopoles. At the University of Oklahoma we are performing an experiment (Fermilab E882) using material from the old D0 and CDF detectors to set limits on the existence of Dirac monopoles of masses of the order of 500 GeV. To set such limits, estimates must be made of the production rate of such monopoles at the Tevatron collider, and of the binding strength of any such produced monopoles to (...) matter. Here we sketch the still primitive theory of such interactions, and indicate why we believe a credible limit may still be obtained. On the other hand, there have been proposals that the classic Euler–Heisenberg Lagrangian together with duality could be employed to set limits on magnetic monopoles having masses less than 1 TeV, based on virtual, rather than real processes. The D0 collaboration at Fermilab has used such a proposal to set mass limits based on the nonobservation of pairs of photons each with high transverse momentum. We critique the underlying theory, by showing that the cross section violates unitarity at the quoted limits and is unstable with respect to radiative corrections. We therefore believe that no significant limit can be obtained from the current experiments, based on virtual monopole processes. (shrink)

In this series of articles the early life and work of the young Julian Schwinger are explored. In the present article, we discuss Schwinger's winding up his work at the MIT Radiation Laboratory, being offered a tenured professorship at Harvard University, getting married, and settling down into a highly productive teaching and research career.

In this series of articles the early life and work of the young Julian Schwinger is explored. After a brilliant beginning at Columbia University, where he received his Ph.D., Schwinger went to work with J. Robert Oppenheimer in Berkeley. His stay, work, and interactions with Oppenheimer are discussed.

In this series of articles the early life and work of the young Julian Schwinger are explored. In this first article, Schwinger's childhood, growing-up, and early education are discussed.

In this series of articles the early life and work of the young Julian Schwinger are explored. In the present article, Schwinger's work at the MIT Radiation Laboratory during the Second World War is described.

In this series of articles the life and work of the young Julian Schwinger are explored. In this second article in the series, Schwinger's work at Columbia University, up to the completion of his doctorate and a little after, is discussed. Schwinger soon matured into a brilliant theoretical physicist.

Starting from the earlier notions of stationary action principles, these tutorial notes shows how Schwinger's Quantum Action Principle descended from Dirac's formulation, which independently led Feynman to his path-integral formulation of quantum mechanics. Part I brings out in more detail the connection between the two formulations, and applications are discussed. Then, the Keldysh-Schwinger time-cycle method of extracting matrix elements is described. Part II will discuss the variational formulation of quantum electrodynamics and the development of source theory.