Surface area and other measures of ellipsoids

We begin by studying the surface area of an ellipsoid in En as the function of the lengths of the semi-axes. We give an explicit formula as an integral over Sn−1, use this formula to derive convexity properties of the surface area, to give sharp estimates for the surface area of a large-dimensional ellipsoid, to produce asymptotic formulas for the surface area and the isoperimetric ratio of an ellipsoid in large dimensions, and to give an expression for the surface in terms of the Lauricella hypergeometric function. We then write down general formulas for the volumes of projections of ellipsoids, and use them to extend the above-mentioned results to give explicit and approximate formulas for the higher integral mean curvatures of ellipsoids. Some of our results can be expressed as isoperimetric results for higher mean curvatures.