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From: Osher Doctorow on 8 Aug 2010 14:22 From Osher Doctorow Superstring Theory regards 3 of its 10 Dimensions as being 3 Spatial Dimensions, which in Dimensional Analysis would be symbolized for example as Lx, Ly, Lz, where the subscripts x, y, z are ideally in orthogonal directions usually. That leaves only 5 Dimensions to be added to Dimensional Analysis' current 5 typical Fundamental Dimensions of M (mass), L (length), T (time), Q ((Electric) Charge), theta (temperature, if we use Superstring Theory's Lx, Ly, Lz - but then we no longer have 5 Fundamental Dimensions of Dimensional Analysis, since L changes to Lx, Ly, Lz. Something is wrong with this picture. In Dimensional Analysis applications, unless 2 or more directions like x and y or x and y and z are all relevant to the particular problem and have DIFFERENT TYPES OF INFLUENCE on the problem, L is used as the Fundamental Dimension. Lx, Ly, Lz are SUBTYPES OF L, not replacements for L. Otherwise, we could claim that different types of Mass corresponding to different Fundamental or other important particles are different Fundamental dimensions, yielding dimensions of Mp (mass of proton), Me (mass of electron), and on and on. Theoretical Physics uses both viewpoints, and quite often problems are simplified by choosing their setting in one spatial direction like x and then generalizing if necessdary. So how many Fundamental Dimensions do we need in Dimensional Analysis to correspond to the 10 dimensions of Superstring Theory or the 11 of Supersymmetry? Collapsing the 3 Superstring dimensions of space into one Fundamental Dimension L yields only two spacetime observable dimensions correspond to L, T (time), instead of 4 (x, y, z, t), so we only need 3 more Fundamental Dimensions in addition to M, L, T, Q, theta to reach 8 Fundamental Dimensions with L, T added. The 3 subtypes Lx, Ly, Lz of L if they were to replace L among these 8 (which is analogously done in Superstring Theory but without declaring them Fundamental Dimensions) would yield 2 additional dimensions to yield 10 Dimensional Analysis "Fundamental Dimensions". The 3 Fundamental Dimensions that we need in addition to M, L, T, Q, theta, can still be built from the Repulsive vs Attractive or Expansive vs Contractive or the Probabilistic dimensions discussed in the last few sections and subsections. One might prefer distinguishing between attractive "length" L1 and repulsive length L2, attractive mass M1 and repulsive mass M2, and attractive charge Q1 and repulsive charge Q2. Or one might prefer the Probabilistic types such as P(A-->B), P(B|A), P(A) for example. Osher Doctorow
From: Osher Doctorow on 8 Aug 2010 14:37
From Osher Doctorow If we do use the Probability route mentioned, then P(A-->B), P ' (A-- >B), and either P(A)P(B) or P(A<-->B) would seem to be better than P(B| A) and P(A). In fact, it is easy to show that P(A ' --> A) = P(A), P(universe --> A) = P(A), etc. In physical language, we would be introducing the dimensions of Probable Causation/Influence (P(A-->B)), Internality-Externality (P(A-- >B) vs P ' (A-->B) above), and Dependence-Independence (P(A)P(B) vs the others), or if we use the last quantity P(A<-->B) we would have Probable Correlation. Notice that Internality-Externality has the nice topological quality of being important in that field and in geometry as well. Causation, Influence and Probability are certainly important in a very large variety of physical problems, and similarly for Independence vs Dependence. Osher Doctorow |