The Pre-Schwarzian Norm Estimate for Analytic Concave Functions
Let D denote the open unit disk and let S denote the class of normalized univalent functions which are analytic in D. Let Co(α) be the class of concave functions f∈S, which have the condition that the opening angle of f(D) at infinity is less than or equal to πα, α∈(1,2]. In this paper, we find a su...
Saved in:
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2015-01-01
|
| Series: | International Journal of Mathematics and Mathematical Sciences |
| Online Access: | http://dx.doi.org/10.1155/2015/814805 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Let D denote the open unit disk and let S denote the class of normalized univalent functions which are analytic in D. Let Co(α) be the class of concave functions f∈S, which have the condition that the opening angle of f(D) at infinity is less than or equal to πα, α∈(1,2]. In this paper, we find a sufficient condition for the Gaussian hypergeometric functions to be in the class Co(α). And we define a class Co(α,A,B), (-1≤B<A≤1), which is a subclass of Co(α) and we find the set of variabilities for the functional (1-|z|2)(f″(z)/f′(z)) for f∈Co(α,A,B). This gives sharp upper and lower estimates for the pre-Schwarzian norm of functions in Co(α,A,B). We also give a characterization for functions in Co(α,A,B) in terms of Hadamard product. |
|---|---|
| ISSN: | 0161-1712 1687-0425 |