Existence of minimizers for generalized Lagrangian functionals and a necessary optimality condition --- Application to fractional variational problems

Abstract

We study dynamic minimization problems of the calculus of variations with generalized Lagrangian functionals that depend on a general linear operator $K$ and defined on bounded-time intervals. Under assumptions of regularity, convexity and coercivity, we derive sufficient conditions ensuring the existence of a minimizer. Finally, we obtain necessary optimality conditions of Euler-Lagrange type. Main results are illustrated with special cases, when $K$ is a general kernel operator and, in particular, with $K$ the fractional integral of Riemann-Liouville and Hadamard. The application of our results to the recent fractional calculus of variations gives answer to an open question posed in [Abstr. Appl. Anal. 2012, Art. ID 871912; doi:10.1155/2012/871912].

This is a preprint of a paper whose final and definite form will appear in Differential and Integral Equations, ISSN 0893-4983 (See http://www.aftabi.com/DIE.html). Submitted 19/July/2013; Accepted 16/March/2014