Criteria for univalence of the Dziok–Srivastava and the Srivastava–Wright operators in the class A

摘要

In the geometric function theory (GFT) much attention is paid to various linear integral operators mapping the class S of the univalent functions and its subclasses into themselves. In [12], [13] Hohlov obtained sufficient conditions that guarantee such mappings for the operator defined by means of Hadamard product with the Gauss hypergeometric function. In our earlier papers as [20], [19], [17], [18], etc., we extended his method to the operators of the generalized fractional calculus (GFC, [16]). These operators have product functions of the forms m+1Fm and m+1Ψm and integral representations by means of the Meijer G- and Fox H-functions. Here we propose sufficient conditions that guarantee mapping of the univalent, respectively of the convex functions, into univalent functions in the case of the celebrated Dziok–Srivastava operator ([8] : J. Dziok, H.M. Srivastava, Classes of analytic functions associated with the generalized hypergeometric function, Appl. Math. Comput. 103, No 1 (1999), pp. 1–13) defined as a Hadamard product with an arbitrary generalized hypergeometric function pFq. Similar conditions are suggested also for its extension involving the Wright pΨq-function and called the Srivastava–Wright operator (Srivastava, [36]). Since the discussed operators include the above-mentioned GFC operators and many their particular cases (operators of the classical FC), from the results proposed here one can derive univalence criteria for many named operators in the GFT, as the operators of Hohlov, Carlson and Shaffer, Saigo, Libera, Bernardi, Erdélyi–Kober, etc., by giving particular values to the orders p ⩽ q + 1 of the generalized hypergeometric functions and to their parameters.