Shapefinders: A new shape diagnostic for large-scale structure

We construct a set of shapefinders used to determine the shapes of compact surfaces (isodensity surfaces in galaxy surveys or N-body simulations) without fitting them to ellipsoidal configurations, as has been done earlier. The new indicators, based on the Minkowski functionals, arise from simple, geometrical considerations and are derived from the fundamental properties of a surface such as its volume, surface area, integrated mean curvature, and connectivity characterized by the genus. These "shapefinders" could be used to diagnose the presence of filaments, pancakes, and ribbons in large-scale structure. Their lower dimensional generalization may be useful for the study of two-dimensional distributions such as temperature maps of the cosmic microwave background.