A theorem of J. Hersch (1970) states that for any smooth metric on S, with total area equal to 4π, the first nonzero eigenvalue of the Laplace operator acting on functions is less than or equal to 2 (this being the value for the standard round metric). For metrics invariant under the standard S-action on S, one can restrict the Laplace operator to the subspace of S-invariant functions and consi...

A theorem of J. Hersch (1970) states that for any smooth metric on S2, with total area equal to 4π, the first nonzero eigenvalue of the Laplace operator acting on functions is less than or equal to 2 (this being the value for the standard round metric). For metrics invariant under the standard S1-action on S2, one can restrict the Laplace operator to the subspace of S1-invariant functions and c...

In computational anatomy, one needs to perform statistics on shapes and transformations, and to transport these statistics from one geometry (e.g. a given subject) to another (e.g. the template). The geometric structure that appeared to be the best suited so far was the Riemannian setting. The statistical Riemannian framework was indeed pretty well developped for finite-dimensional manifolds an...

A theorem of J. Hersch (1970) states that for any smooth metric on S, with total area equal to 4π, the first nonzero eigenvalue of the Laplace operator acting on functions is less than or equal to 2 (this being the value for the standard round metric). For metrics invariant under the standard S-action on S, one can restrict the Laplace operator to the subspace of S-invariant functions and consi...

A theorem of J. Hersch (1970) states that for any smooth metric on S, with total area equal to 4π, the first nonzero eigenvalue of the Laplace operator acting on functions is less than or equal to 2 (this being the value for the standard round metric). For metrics invariant under the standard S-action on S, one can restrict the Laplace operator to the subspace of S-invariant functions and consi...

We present some problems related to right(or bi-)invariant metrics d on the symmetric group of permutations S,. Characterizations and constructions of bi-invariant extremal (in the corresponding convex cone) metrics are given, esp. for n 6 5 . We also consider special subspaces of the metric space (S,,, d ) : unit balls, sets with prescribed distances (L-cliques), "hamiltonian" sets. Here we gi...

We provide a new proof of a Frĕıman-type theorem. Specifically, suppose that G is a locally compact abelian group with a Haar measure μG. The δ-ball Bδ of a translation invariant metric is called d-dimensional if μG(B2δ′ ) 6 2 dμG(Bδ′ ) for all δ ′ ∈ (0, δ]. We show that if A is a compact neighborhood with μG(nA) 6 n μG(A) for all n > d log d, then A is contained in a O(d log d)-dimensional bal...

To any metric space it is possible to associate the cardinal invariant corresponding to the least number of rectifiable curves in the space whose union is not meagre. It is shown that this invariant can vary with the metric space considered, even when restricted to the class of convex subspaces of separable Banach spaces. As a corollary it is obtained that it is consistent with set theory that ...

It is known that there is a only one invariant metric, and only one family of invariant affine connections on the the space of probability measures on finite sample spaces. Under certain conditions this may also true for finite measures on finite sample spaces. We extends these results to finite measures on arbitrary sample spaces. It is shown that the generalization of these structures are uni...