Abstract. We introduce and develop the Hahn symmetric quantum calculus with applications to the calculus of variations. Namely, we obtain a necessary optimality condition of Euler-Lagrange type and a sufficient optimality condition for variational problems within the context of Hahn's symmetric calculus. Moreover, we show the effectiveness of Leitmann's direct method when applied to Hahn's symmetric variational calculus. Illustrative examples are provided.
1.Introduction. Due to its many applications, quantum operators are recently subject to an increase number of investigations [24][25][26]. The use of quantum differential operators, instead of classical derivatives, is useful because they allow to deal with sets of nondifferentiable functions [4,10]. Applications include several fields of physics, such as cosmic strings and black holes [27], quantum mechanics [12,29], nuclear and high energy physics [18], just to mention a few. In particular, the q-symmetric quantum calculus has applications in quantum mechanics [17].In 1949, Hahn introduced his quantum difference operator [13], which is a generalization of the quantum q-difference operator defined by Jackson [14]. However, only in 2009, Aldwoah [1] defined the inverse of Hahn's difference operator, and short after, Malinowska and Torres [24] introduced and investigated the Hahn quantum variational calculus. For a deep understanding of quantum calculus, we refer the reader to [2,5,6,11,15,16] and references therein.For a fixed q ∈ ]0, 1[ and an ω ≥ 0, we introduce here the Hahn symmetric difference operator of function f at point t = ω 1 − q bỹ