On transformations of self-adjoint linear differential systems and their reciprocals
We study polyconvex envelopes of a class of functions related to the function of Kohn and Strang introduced in . We present an example of a function of this class for which the polyconvex envelope may be computed explicitly and we also point out some general features of the problem.
We establish an asymptotic formula for a pair of linearly independent solutions of the subcritical Riemann–Weber type half-linear differential equation. We also complement the results of the author and M. Ünal, Acta Math. Hungar. 120 (2008), 147–163, where the equation was considered in the critical case.
Let , be an -th order differential operator, be its adjoint and be positive functions. It is proved that the self-adjoint equation is nonoscillatory at if and only if the equation is nonoscillatory at . Using this result a new necessary condition for property BD of the self-adjoint differential operators with middle terms is obtained.
Sufficient conditions are given which guarantee that the linear transformation converting a given linear Hamiltonian system into another system of the same form transforms principal (antiprincipal) solutions into principal (antiprincipal) solutions.
In this paper we investigate oscillatory properties of the second order half-linear equation Using the Riccati technique, the variational method and the reciprocity principle we establish new oscillation and nonoscillation criteria for (*). We also offer alternative methods of proofs of some recent oscillation results.
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