Date: Sun, 2 Jun 1996 23:11:34 -0300 (ADT) Subject: Topos-theoretic classification of Lie groups Date: Sat, 01 Jun 1996 12:14:20 -0400 From: Vladimir Trifonov Those interested in real-world applications of categories are advised considering the following. There is a natural (and strictly defined) sense in which a Heyting algebra is assigned to a Lie group with a family of (proper and/or pseudo)-Riemannian metrics over it (V. Trifonov, Europhysics Letters 32, 7, pp.621-626, 1995): . Initially the result was motivated by the Four-Dimensionality Problem in physics (1.Why does spacetime look four-dimensional?). It turnes out, however, that it gives concise (the paper is letter-sized) and elegant solutions to at least four other difficult problems: 2.Why is the effective metric Lorentzian? 3.Why does it look like there was a big bang? 4.Why are only three matter generations observable? 5.Why does the arrow of time exist? To-date this remains the only solution of the Four-Dimensionality Problem and the Metric Signature Problem (2). For details see recent posts in sci.math.research and sci.physics.research. We need your expertise. Vladimir ______________________________________________________________________ http://www.ed-phys.fr/articles/euro/abs/1995/32/8/ep32801/ep32801.html http://weblab.research.att.com/phoaks/sci/math/research/index.html MAA; Gamma Systems Research Group, Inc.