Ioannis D. Platis

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Questions related from Ioannis D. Platis

Which is the best isoperimetric constant in the Heisenberg group?

According to Capogna, Danielli, Tyson & Pauls (An Introduction to the Heisenberg group and the sub Riemannian isoperimetric problem), the isoperimetric best constant in the Heisenberg group is...

01 February 2014 1,224 7 View

In this paper, generalised cross--ratios are defined in all cases of hyperbolic spaces besides the octonionic case.

Is there a publication of a natural definition of octonionic cross--ratios? I have had trouble defining them due to non associativity of octonions. Can this be by--passed?

11 March 2013 333 3 View

A CAT(0) space is Ptolemaean, now Ptolemaean plus what makes a space CAT(0)?

To prove that a CAT(0) space is Ptolemaean is relatively easy, and the converse does not always hold (obviously, e.g. the Heisenberg group with the Koranyi is Ptolemaean). There must be some...

03 March 2013 3,859 2 View