On the exit out of the Gakhov set controlled by the subordination conditions

A. V. Kazantsev

Učënye zapiski Kazanskogo universiteta. Seriâ Fiziko-matematičeskie nauki, Uchenye Zapiski Kazanskogo Universiteta. Seriya Fiziko-Matematicheskie Nauki, Tome 156 (2014) no. 1, pp. 31-43

Résumé

A Gakhov set $\mathcal G$ is the class of all holomorphic and locally univalent functions in the unit disk, which have no more than one root of the Gakhov equation. For the series of the well-known subclasses of univalent functions having the zero root of the Gakhov equation, an effective desription is given for the set of all trajectories of the exit out of $\mathcal G$; such an exit takes place when the parameter value corresponds to the sharp constant in the appropriate uniqueness condition of the root. It is shown that the exit out of $\mathcal G$ may occur due to the bifurcations of the two following types only: 1) the maximum at zero splits into two maxima and the saddle; 2) the non-zero semisaddle appears and then divides into the maximum and the saddle.

Détail

Keywords: hyperbolic derivative, conformal (inner mapping) radius, bifurcations of critical points, Gakhov set, class of starlike functions
Mots-clés : subordination conditions.

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