Hausdorff dimension
Noun
Meaning
Hausdorff dimension (plural Hausdorff dimensions)
(mathematical analysis) A type of fractal dimension, a real-valued measure of a geometric object that assigns 1 to a line segment, 2 to a square and 3 to a cube. Formally, given a metric space X and a subset of X labeled S, the Hausdorff dimension of S is the infimum of all real-valued d for which the d-dimensional Hausdorff content of S is zero.
If S is nonempty then if the d-dimensional Hausdorff content of S is zero then d is larger than the Hausdorff dimension of S, and if the d-dimensional Hausdorff content of S is infinite then d is smaller or equal to the Hausdorff dimension of S. If the d-dimensional Hausdorff content of S is finite and positive then d is equal to the Hausdorff dimension of S.
Examples
However, 'fractal dimensions' of coastlines and many other natural phenomena are largely heuristic and cannot be regarded rigorously as a Hausdorff dimension.
For example, Shishikura proves that, for a dense set of parameters in the boundary of the Mandelbrot set, the Julia set has Hausdorff dimension two, and then transfers this information to the parameter plane. citation.
For a sufficiently well-behaved X, the Hausdorff dimension is the unique number d such that N(r) grows as 1/r d as r approaches zero.
For shapes that are smooth, or shapes with a small number of corners, the shapes of traditional geometry and science, the Hausdorff dimension is an integer agreeing with the topological dimension.
Hausdorff dimension and Minkowski dimension The Minkowski dimension is similar to, and at least as large as, the Hausdorff dimension, and they are equal in many situations.
If X and Y are non-empty metric spaces, then the Hausdorff dimension of their product satisfies citation : This inequality can be strict.