A Statistical Characterization of Regular Simplices
arXiv:math/0612163
Abstract
The positive interpoint distances of n=p+1>1 points in dimension p are equal if and only if their sample covariance matrix is a scalar multiple of the identity.
5 pages, which includes corrections to the published version. Version 2 differs in only small typographical changes: removing an extra sigma squared, and inserting a needed 1/n