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Dear Paul Halpern,
Twenty years ago, when I heard for the first time of CA, they were used almost like FEM by those who model plasma, heat conduction and the like. Since then I did not get aware of reported convincing benefits. Your essay makes understandable to me chains of more or less speculative hope for foundational insight that might be confirmed in the very far future.
Let me frankly admit that I am ready to accept the big bang as an exiting hypothesis but not yet as proven for good. What about the attribute foundational, I prefer to judge it as did you from experience over centuries. I appreciate that you avoided technicalities that would perhaps anyway not be convincing.
Most appealing to me was your question for upper and lower frequencies of in particular electromagnetic waves. You will certainly not need reading my essay in order to understand that discrete frequencies correspond via cosine transform with continuous functions of temporal or spatial distance and nice versa. Cosine transform differs from Fourier transform in that performing it twice yields the original function. In other words, it is its own inverse.
Not just in CA the notion neighbor plays a role. Hausdorff topology does also consider a neighbor each to the left and to the right. I found out that this is based on a non-Euclidean notion of number and at odds with a lot. For instance, it is to be blame for trouble at zero, for the unwillingness to accept R as sufficient in case of non negative spatial or temporal distance, and even with the usual unilateral attribution of the increment dx to the direction of x.
Regards,
Eckard