A new version of Fisher’s discriminant analysis (FDA) is introduced in this paper. Our algorithm searches also for a reduced space in which patterns can be discriminated. However, no intermediate class separability criterion (such as Fisher’s mean distance divided by variance) is used whatsoever. Classification performance is optimized directly. Since no statistical hypothesis are made, the met...

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The usual deenition of hyperbolicity of a group G demands that all geodesic triangles in the Cayley graph of G should be thin. Using the theorem that a subquadratic isoperimetric inequality implies a linear one, we show that it is in fact only necessary for all triangles from a given combing to be thin, thus giving a new criterion for hyperbolicity of nitely presented groups. Given a group G th...