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Starlikeness and convexity of a class of analytic functions. (English) Zbl 1120.30018

Summary: Let \({\mathcal A}\) be the class of analytic functions in the unit disk that are normalized with \(f(0)=f'(0)-1=0\) and let \(-1\leq B<A\leq 1\). In this paper we study the class \(G_{\lambda,\alpha}=\{f\in{\mathcal A}:|(1-\alpha +azf''(z)/f'(z)) /zf'(z)/f(z)-(1-\alpha)|<\lambda\), \(z\in{\mathcal U}\}\), \(0\leq \alpha\leq 1\), and give sharp sufficient conditions that embed it into the classes \(S^*[A,B]=\{f\in{\mathcal A}:zf'(z)/f(z)\prec(1+Az)/(1+Bz)\}\) and \(K(\delta)=\{f\in{\mathcal A}:1+zf''(z)/f' (z)\prec(1-\delta)(1+z)/(1-z)+ \delta\}\), where “\(\prec\)” denotes the usual subordination. Also, sharp upper bound of \(|a_2|\) and of the Fekete-Szegö functional \(|a_3-\mu a^2_2|\) is given for the class \(G_{\lambda,\alpha}\).

MSC:

30C45 Special classes of univalent and multivalent functions of one complex variable (starlike, convex, bounded rotation, etc.)

References:

[1] Bulboacă, T.; Tuneski, N., New criteria for starlikeness and strongly starlikeness, Mathematica (Cluj), 43(66), 1, 11-22 (2003) (2001) · Zbl 1097.30503
[2] Duren, P. L., Univalent Functions. Univalent Functions, Fundamental Principles of Mathematical Sciences, 259, xiv+382 (1983), New York: Springer, New York · Zbl 0514.30001
[3] Miller, S. S.; Mocanu, P. T., Differential subordinations and univalent functions, The Michigan Mathematical Journal, 28, 2, 157-172 (1981) · Zbl 0439.30015 · doi:10.1307/mmj/1029002507
[4] Miller, S. S.; Mocanu, P. T., On some classes of first-order differential subordinations, The Michigan Mathematical Journal, 32, 2, 185-195 (1985) · Zbl 0575.30019 · doi:10.1307/mmj/1029003185
[5] Miller, S. S.; Mocanu, P. T., Differential Subordinations. Theory and Applications. Differential Subordinations. Theory and Applications, Monographs and Textbooks in Pure and Applied Mathematics, 225, xii+459 (2000), New York: Marcel Dekker, New York · Zbl 0954.34003
[6] Obradowič, M.; Tuneski, N., On the starlike criteria defined by Silverman, Zeszyty Naukowe Politechniki Rzeszowskiej. Matematyka, 181, 24, 59-64 (2001) (2000) · Zbl 0999.30016
[7] Ravichandran, V.; Darus, M.; Seenivasagan, N., On a criteria for strong starlikeness, The Australian Journal of Mathematical Analysis and Applications, 2, 1, article 6, 12 (2005) · Zbl 1083.30015
[8] Silverman, H., Convex and starlike criteria, International Journal of Mathematics and Mathematical Sciences, 22, 1, 75-79 (1999) · Zbl 0921.30009 · doi:10.1155/S0161171299220753
[9] Singh, V., On some criteria for univalence and starlikeness, Indian Journal of Pure and Applied Mathematics, 34, 4, 569-577 (2003) · Zbl 1114.30015
[10] Singh, V.; Tuneski, N., On criteria for starlikeness and convexity of analytic functions, Acta Mathematica Scientia. Series B, 24, 4, 597-602 (2004) · Zbl 1087.30016
[11] Tuneski, N., On certain sufficient conditions for starlikeness, International Journal of Mathematics and Mathematical Sciences, 23, 8, 521-527 (2000) · Zbl 0954.30003 · doi:10.1155/S0161171200003574
[12] Tuneski, N., On a criteria for starlikeness of analytic functions, Integral Transforms and Special Functions, 14, 3, 263-270 (2003) · Zbl 1052.30019 · doi:10.1080/1065246031000074399
[13] Tuneski, N., On the quotient of the representations of convexity and starlikeness, Mathematische Nachrichten, 248/249, 1, 200-203 (2003) · Zbl 1017.30009 · doi:10.1002/mana.200310015
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