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The Strange World of the Hausdorff Metric Geometry


X. Hausdorff Segments


We have seen that if A and B are single point sets in H(Rn), then there is always a point at each location between A and B. A reasonable question to ask is if this is true in general. This question was answered in [6]. In particular, if A and B are elements of H(Rn) and r = h(A, B), then the set


M(s) = (A)s (B)r-s


satisfies AM(s)B with h(A, M(s)) = s for any s in [0, r].


To illustrate, the next applet shows how the intersections M(s) (gray shaded regions) of the sets (A)s and (B)r-s vary as s varies from 0 to h(A, B). The values of s are represented by the position of the black point on the slider at the top of the screen. Here s represents a specific location on the Hausdorff segment between A and B. The values of s can be altered by moving the black point on the slider. In this case, A is represented by the red disk (think of A as the sun) and B by the blue crescent (think of B as a new moon). The picture is not to scale. As the value of s changes, the intersections of the dilations seem to “morph” the sun into the moon, and vice-versa. I call this example the Unification Morph or, alternatively, the Sun – Young Moon morph (see for information regarding the nomenclature).




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