For a function f starlike of order $$\alpha $$ , $$0\leqslant \alpha <1$$ non-constant polynomial Q degree n which is non-vanishing in the unit disc $${\mathbb {D}}$$ and $$\beta >0$$ we consider $$F:{\mathbb {D}}\rightarrow {\mathbb {C}}$$ defined by $$F(z)=f(z) (Q(z))^{\beta /n}$$ find largest value $$r\in (0,1]$$ such that $$r^{-1} F(rz)$$ lies various known subclasses functions as class $$\...

We prove the following new characterization of C (Lipschitz) smoothness in Banach spaces. An infinite-dimensional Banach space X has a C smooth (Lipschitz) bump function if and only if it has another C smooth (Lipschitz) bump function f such that f ′(x) 6= 0 for every point x in the interior of the support of f (that is, f does not satisfy Rolle’s theorem). Moreover, the support of this bump ca...

In this paper we establish some results concerning the partial sums of meromorphic p-valent starlike functions and meromorphic p-valent convex functions.

In this paper, we present a new sharp approximation for the gamma function via the tri-gamma function. This approximation is fast in comparison with the recently discovered asymptotic series. We also establish the inequalities related to this approximation. Finally, some numerical computations are provided for demonstrating the superiority of our approximation.

An interesting criterion was given by Tuneski [N. Tuneski, On the quotient of the representations of convexity and starlikeness, Math. Nachr. 248–249 (2003) 200–203] for the analytic functions to be in the class S 1⁄21þAz 1þBz and its subclasses, where 1 6 B < A 6 1. This result is an extension of an earlier result of Silverman [H. Silverman, Convex and starlike criteria, Int. Math. Math. Sci. ...

For analytic functions f(z) in the open unit disk U with f(0) = 0 and f ′(0) = 1, S. S. Miller, P. T. Mocanu and M. O. Reade (Proc. Amer. Math. Soc. 37(1973)) have introduced α-convex functions in U with some condition, and Z. Lewandowski, S. S. Miller and E. Zl /otkiewicz (Ann. Univ. Marie-Curie Skl /odowska 27(1974)) have discussed γ-starlike functions in U with some condition. The object of ...

Let A(ω) be the class of analytic functions of the form: f(z) = (z − ω) + ∞ ∑ k=2 ak(z − ω) defined on the open unit disk U = {z : |z| < 1} normalized with f(ω) = 0, f ′(ω)−1 = 0 and ω is an arbitrary fixed point in U. In this paper, we define a subclass of ω − α − uniform starlike and convex functions by using a more generalized form of Ruschewey derivative operator. Several properties such as...