394 research outputs found
BCS as Foundation and Inspiration: The Transmutation of Symmetry
The BCS theory injected two powerful ideas into the collective consciousness
of theoretical physics: pairing and spontaneous symmetry breaking. In the 50
years since the seminal work of Bardeen, Cooper, and Schrieffer, those ideas
have found important use in areas quite remote from the stem application to
metallic superconductivity. This is a brief and eclectic sketch of some
highlights, emphasizing relatively recent developments in QCD and in the theory
of quantum statistics, and including a few thoughts about future directions. A
common theme is the importance of symmetry {\it transmutation}, as opposed to
the simple {\it breaking} of electromagnetic symmetry in classic
metallic superconductors.Comment: 25 pages, 4 figures. Contribution to "Fifty Years of Bardeen, Cooper,
and Schrieffer'', to be published by World Scientific. Also to appear in
IJMP
Radical Conservatism and Nucleon Decay
Unification of couplings, observation of neutrino masses in the expected
range, and several other considerations confirm central implications of
straightforward gauge unification based on SO(10) or a close relative and
incorporating low-energy supersymmetry. The remaining outstanding consequence
of this circle of ideas, yet to be observed, is nucleon instability. Clearly,
we should aspire to be as specific as possible regarding the rate and form of
such instability. I argue that not only esthetics, but also the observed
precision of unification of couplings, favors an economical symmetry-breaking
(Higgs) structure. Assuming this, one can exploit its constraints to build
reasonably economical, overconstrained yet phenomenologically viable models of
quark and lepton masses. Putting it all together, one arrives at reasonably
concrete, hopeful expectations regarding nucleon decay. These expectations are
neither ruled out by existing experiments, nor hopelessly inaccessible.Comment: LaTeX, 14 pages, 4 figures; moved reference, corrected typo, improved
two figure
Unification of Force and Substance
Maxwell's mature presentation of his equations emphasized the unity of
electromagnetism and mechanics, subsuming both as "dynamical systems". That
intuition of unity has proved both fruitful, as a source of pregnant concepts,
and broadly inspiring. A deep aspect of Maxwell's work is its use of redundant
potentials, and the associated requirement of gauge symmetry. Those concepts
have become central to our present understanding of fundamental physics, but
they can appear to be rather formal and esoteric. Here I discuss two things:
The physical significance of gauge invariance, in broad terms; and some
tantalizing prospects for further unification, building on that concept, that
are visible on the horizon today. If those prospects are realized, Maxwell's
vision of the unity of field and substance will be brought to a new level.Comment: Talk at Royal Society Symposium, "Unifying Physics and Technology in
the Light of Maxwell's Equations", November 2015. 26 pages, no figure
From "Not Wrong" to (Maybe) Right
This is a short, light spirited account of how some possibly important
science actually happened. It very much conflicts with Popper's contention that
the key to scientific progress is falsification.Comment: This is, in essence, a solicited "Turning Points" feature written for
Nature. It appeared, in a slightly abbreviated form, in the March 18 issu
Multiversality
Valid ideas that physical reality is vastly larger than human perception of
it, and that the perceived part may not be representative of the whole, exist
on many levels and have a long history. After a brief general inventory of
those ideas and their implications, I consider the cosmological "multiverse"
much discussed in recent scientific literature. I review its theoretical and
(broadly) empirical motivations, and its disruptive implications for the
traditional program of fundamental physics. I discuss the inflationary axion
cosmology, which provides an example where firmly rooted, plausible ideas from
microphysics lead to a well-characterized "mini-multiverse" scenario, with
testable phenomenological consequences.Comment: 23 pages. Solicited review for Classical and Quantum Gravit
Opportunities, Challenges, and Fantasies in Lattice QCD
Some important problems in quantitative QCD will certainly yield to hard work
and adequate investment of resources, others appear difficult but may be
accessible, and still others will require essentially new ideas. Here I
identify several examples in each class.Comment: 10 pages, 2 figures; Keynote talk at Lattice 2002, Boston, June 2002.
(Text unchanged; figure formatting corrected.) Email correspondence to
[email protected]
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