18,128 research outputs found
The Pauli Exclusion Principle and SU(2) vs. SO(3) in Loop Quantum Gravity
Recent attempts to resolve the ambiguity in the loop quantum gravity
description of the quantization of area has led to the idea that j=1 edges of
spin-networks dominate in their contribution to black hole areas as opposed to
j=1/2 which would naively be expected. This suggests that the true gauge group
involved might be SO(3) rather than SU(2) with attendant difficulties. We argue
that the assumption that a version of the Pauli principle is present in loop
quantum gravity allows one to maintain SU(2) as the gauge group while still
naturally achieving the desired suppression of spin-1/2 punctures. Areas come
from j=1 punctures rather than j=1/2 punctures for much the same reason that
photons lead to macroscopic classically observable fields while electrons do
not.Comment: This paper received an "honorable mention" in the 2003 Essay
Competition of the Gravity Research Foundation and should be appearing in a
special issue of Int. J. Mod. Phys.
Encountering soviet geography: oral histories of British geographical studies of the USSR and Eastern Europe 1945-1991
This paper considers the history of British geographical studies of the USSR and Eastern Europe 1945-1991, presenting material from a research project which has included thirty-two oral history interviews. Oral history is an especially fruitful research methodology in this context due to the distinct issues of formality and informality involved in researching the Soviet bloc. After discussing the nature of the subdiscipline and the Cold War context, including the role of the British state in shaping the field, the paper considers the role of formal academic meetings and exchanges, and the place of unofficial spaces of encounter in the formation of an intellectual culture. The paper concludes by reflecting on the merits of oral history in studies of the production of geographical knowledge
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