Some extensions of the Open Door Lemma

Authors

  • Ming LI Graduate School of Information Sciences Tohoku University Aobaku, Sendai 980-8579, Japan e-mail: li@ims.is.tohoku.ac.jp
  • Toshiyuki SUGAWA Graduate School of Information Sciences Tohoku University Aobaku, Sendai 980-8579, Japan e-mail: sugawa@math.is.tohoku.ac.jp https://orcid.org/0000-0002-3429-5498

Keywords:

Open door function, subordination.

Abstract

Miller and Mocanu proved in their 1997 paper a greatly useful result which is now known as the Open Door Lemma. It provides a sucient condition for an analytic function on the unit disk to have positive real part. Kuroki and Owa modied the lemma when the initial point is non-real. In the present note, by extending their methods, we give a sucient condition for an analytic function on the unit disk to take its values in a given sector.

Mathematics Subject Classification (2010): 30C45, 30C80.

References

Duren, P.L., Univalent Functions, Springer-Verlag, 1983.

Kuroki, K., Owa, S., Notes on the open door lemma, Rend. Semin. Mat. Univ. Politec. Torino, 70(2012), 423434.

Miller, S.S., Mocanu, P.T., Briot-Bouquet di_erential equations and differential subordinations, Complex Variables Theory Appl., 33(1997), 217-237.

Miller, S.S., Mocanu, P.T., Differential subordinations. Theory and applications, Marcel Dekker, Inc., New York, 2000.

Mocanu, P.T., On strongly-starlike and strongly-convex functions, Studia Univ. Babes-Bolyai Math., 31(1986), 16{21.

Mocanu, P.T., Alpha-convex integral operator and strongly starlike functions, Studia Univ. Babes-Bolyai, Math., 34(1989), 18{24.

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Published

2015-09-30

How to Cite

LI, M., & SUGAWA, T. (2015). Some extensions of the Open Door Lemma. Studia Universitatis Babeș-Bolyai Mathematica, 60(3), 421–430. Retrieved from https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/5793

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