Solutions with subgroup symmetry for singular equations in bifurcation theory.
We show that asserting the regularity (in the sense of Rund) of a first-order parametric multiple-integral variational problem is equivalent to asserting that the differential of the projection of its Hilbert-Carathéodory form is multisymplectic, and is also equivalent to asserting that Dedecker extremals of the latter -form are holonomic.
In this paper, we characterize a class of biharmonic maps from and between product manifolds in terms of the warping function. Examples are constructed when one of the factors is either Euclidean space or sphere.
We consider the set of all almost Kähler structures (g,J) on a 2n-dimensional compact orientable manifold M and study a critical point of the functional with respect to the scalar curvature τ and the *-scalar curvature τ*. We show that an almost Kähler structure (J,g) is a critical point of if and only if (J,g) is a Kähler structure on M.
We produce new examples of harmonic maps, having as source manifold a space of constant curvature and as target manifold its tangent bundle , equipped with a suitable Riemannian -natural metric. In particular, we determine a family of Riemannian -natural metrics on , with respect to which all conformal gradient vector fields define harmonic maps from into .
This paper describes some recent research on parametric problems in the calculus of variations. It explains the relationship between these problems and the type of problem more usual in physics, where there is a given space of independent variables, and it gives an interpretation of the first variation formula in this context in terms of cohomology.
We discuss the existence of closed geodesic on a Riemannian manifold and the existence of periodic solution of second order Hamiltonian systems.
We present critical groups estimates for a functional defined on the Banach space , bounded domain in , , associated to a quasilinear elliptic equation involving -laplacian. In spite of the lack of an Hilbert structure and of Fredholm property of the second order differential of in each critical point, we compute the critical groups of in each isolated critical point via Morse index.