Abstract. We consider the nonlinear eigenvalue problemin Ω, u = 0 on ∂Ω, where Ω is a bounded open set in R N with smooth boundary and p, q are continuous functions on Ω such that 1 < inf Ω q < inf Ω p < sup Ω q, sup Ω p < N, and q(x) < Np(x)/ (N − p(x)) for all x ∈ Ω. The main result of this paper establishes that any λ > 0 sufficiently small is an eigenvalue of the above nonhomogeneous quasilinear problem. The proof relies on simple variational arguments based on Ekeland's variational principle.
Introduction and preliminary resultsA basic result in the elementary theory of linear partial differential equations asserts that the spectrum of the Laplace operator in H In this paper we are concerned with the nonhomogeneous eigenvalue problemwhere Ω ⊂ R N (N ≥ 3) is a bounded domain with smooth boundary, λ > 0 is a real number, and p, q are continuous on Ω.The case p(x) = q(x) was considered by Fan, Zhang and Zhao in [14] who, using the Ljusternik-Schnirelmann critical point theory, established the existence of a sequence of eigenvalues. Denoting by Λ the set of all nonnegative eigenvalues, Fan, Zhang and Zhao showed that sup Λ = +∞, and they pointed out that only under additional assumptions we have inf Λ > 0. We remark that for the p-Laplace operator (corresponding to p(x) ≡ p) we always have inf Λ > 0.In this paper we study problem (1.1) under the basic assumptionOur main result establishes the existence of a continuous family of eigenvalues for problem (1.1) in a neighborhood of the origin. More precisely, we show that there exists λ > 0 such that any λ ∈ (0, λ ) is an eigenvalue for problem (1.1). We start with some preliminary basic results on the theory of Lebesgue-Sobolev spaces with variable exponent. For more details we refer to the book by Musielak [21] and the papers by Edmunds et al. [8,9,10], Kovacik and Rákosník [17], and Samko and Vakulov [24].Assume that p ∈ C(Ω) andFor any h ∈ C + (Ω) we defineFor any p(x) ∈ C + (Ω), we define the variable exponent Lebesgue spaceu is a measurable real-valued function andWe define a norm, the so-called Luxemburg norm, on this space by the formulaLicense or copyright restrictions may apply to redistribution; see http://www.ams.org/journal-terms-of-use
ON A NONHOMOGENEOUS QUASILINEAR EIGENVALUE PROBLEM 2931We remember that the variable exponent Lebesgue spaces are separable and reflexive Banach spaces. If 0 < |Ω| < ∞ and p 1 , p 2 are variable exponent, so that p 1 (x) ≤ p 2 (x) almost everywhere in Ω, then there exists the continuous embeddingWe denote by(Ω) the Hölder type inequalityholds true. An important role in manipulating the generalized Lebesgue-Sobolev spaces is played by the modular of the L p(x) (Ω) space, which is the mapping ρ p(x) :, then the following relations hold true: (Ω), · ) is a separable and reflexive Banach space. We note that if s(x) ∈ C + (Ω) and s(x) < p (x) for all x ∈ Ω, then the embedding W(Ω) is compact and continuous, whereWe refer to Kováčik and Rákosník [17] for more properties of Lebesgue and Sobolev spaces with variable exponen...