Some new conformal covariants.
Some remarks on metric semisymmetric connections. (Quelques remarques sur les connexions semi-symétriques métriques.)
Some remarks on the physical structure of energy-momentum tensors in general relativity
Sur les symétries des structures géométriques rigides
Nous présentons des résultats de classification pour des variétés lorentziennes de dimension trois avec “beaucoup” de symétries locales.
Symmetry problems 2
Some symmetry problems are formulated and solved. New simple proofs are given for some symmetry problems studied earlier. One of the results is as follows: if a single-layer potential of a surface, homeomorphic to a sphere, with a constant charge density, is equal to c/|x| for all sufficiently large |x|, where c > 0 is a constant, then the surface is a sphere.
Systems of rays in the presence of distribution of hyperplanes
Horizontal systems of rays arise in the study of integral curves of Hamiltonian systems on T*X, which are tangent to a given distribution V of hyperplanes on X. We investigate the local properties of systems of rays for general pairs (H,V) as well as for Hamiltonians H such that the corresponding Hamiltonian vector fields are horizontal with respect to V. As an example we explicitly calculate the space of horizontal geodesics and the corresponding systems of rays for the canonical distribution...