Characterization of diagonal symmetry: location unknown, and a test based on allied U-processes

For a (possibly multivariate) distribution F, a characterization of (diagonal) symmetry is made with respect to a kernel of degree 2; this is incorporated in the formulation of appropriate U-processes that provide the access to a suitable test statistic for testing the hypothesis of diagonal symmetry when the location is treated as unknown. Asymptotic properties of the test are studied.