Journal of Mathematics and Statistics 6 (3): 253-260, 2010
ISSN 1549-3644
© 2010 Science Publications
253
On Parametric p-Valent Meromorphic Functions
Poonam Sharma
Department of Mathematics and Astronomy,
University of Lucknow Lucknow, 226007, India
Abstract: Problem statement: In this research, we studied parametric p-valent meromorphic
functions P
α
f by considering two classes
p
M()
α
β and
p
M ( ,A)
α
λ . Approach: With the help of Jack’s
Lemma an inclusion relation for the class
p
M
α
was obtained and it is shown that this class is closed by
an integral operator I
c
. Results: A subordination result for the class
p
M ( ,A)
α
λ was proved.
Consequences of main results with the results for special values of the parameter α were discussed.
Conclusion/Recommendations: Our results certainly generalized several results obtained earlier as
well as generate new results.
Key words: Meromorphic functions, starlike functions, convolution, generalized hypergeometrc
functions
INTRODUCTION
Let M
p
denotes a class of functions of the form:
p k p
k p
k 1
f (z) z a z ,p N {1, 2,3,...}
∞
- -
-
=
= + ∈ =
∑
(1a)
which are analytic and p-valent in the punctured unit
disk U
*
= {z: 0<|z|<1} = U\{0}. We say that a function
f(z) ∈ M
p
is in the class M
*
p
(β) if f(z) ≠ 0 and:
zf '(z)
Re ,0 p,z U
f (z)
< -β ≤β< ∈
Functions in the class M
*
p
(β) are called p-valent
meromorphic starlike of order β.
Let g
α
(z) ∈M
p
be of the form:
[ ] ( 29
p k p
k p
k 1
g (z) z b z
∞
- -
α -
=
= + α
∑
(1b)
whose coefficient b
k-p
([α]) has a parameter α which is
either -p or a positive real and it satisfies the relation:
[ ] ( 29 [ ] ( 29
k p k p
k
b 1 b
- -
α+
α+ = α
α
(1c)
For g
α
(z) given by (1b), a parametric convolution
operator P
α
: M
p
→M
p
, on the function f(z) of the form
(1a) is defined by:
( 29 [ ] ( 29
( 29
p k p
k p k p
k 1
P f(z)
f g (z) z a b z
g f (z)
α
∞
- -
α - -
=
α
= * = + α
= *
∑
(1d)
where, ‘*’ stands for convolution or Hadamard product.
We have:
[ ] ( 29
1 p k p
k p k p
k 1
k
P f(z) z a b z
∞
α+ - -
- -
=
α+
= + α
α
∑
1
z(P f(z))'
For p, P f(z)
p
α
α+
α=- ≡-
Using (1c) and (1d), we can easily obtain the
identity related to parametric p-valent meromorphic
functions:
1
z(P f(z))' P f(z) ( p)P f(z)
α α+ α
=α - α+ (1e)
Several subclasses of p-valent meromorphic
functions involving various convolution operators have
been defined and studied in (Aouf, 2008; Liu and
Srivastava, 2001; 2004; Raina and Srivastava, 2006;
Srivastava and Patel, 2006; Srivastava et al., 2008;
Wang et al., 2009; Yang, 2001). The purpose of this
study is to unify the results obtained earlier and to give
some new results. Motivated with these earlier works
especially the work of Cho (Srivastava and Owa, 1992;