Domains of variability of Laurent coefficients and the convex hull for the family of concave univalent functions
Bhowmik, Bappaditya ; Ponnusamy, Saminathan ; Wirths, Karl-Joachim
Kodai Math. J., Tome 30 (2007) no. 1, p. 385-393 / Harvested from Project Euclid
Let D denote the open unit disc and let p $\in$ (0,1). We consider the family Co(p) of functions f : D → $\overline{{\mathbf C}}$ that satisfy the following conditions: ¶ (i) f is meromorphic in D and has a simple pole at the point p. ¶ (ii) f(0) = f′(0) – 1 = 0. ¶ (iii) f maps D conformally onto a set whose complement with respect to $\overline{{\mathbf C}}$ is convex. ¶ We determine the exact domains of variability of some coefficients an (f) of the Laurent expansion ¶ $f(z)=\sum_{n=-1}^{\infty} a_n(f)(z-p)^n,$ |z – p|<1 – p, ¶ for f $\in$ Co(p) and certain values of p. Knowledge on these Laurent coefficients is used to disprove a conjecture of the third author on the closed convex hull of Co(p) for certain values of p.
Publié le : 2007-10-14
Classification: 
@article{1193924942,
     author = {Bhowmik, Bappaditya and Ponnusamy, Saminathan and Wirths, Karl-Joachim},
     title = {Domains of variability of Laurent coefficients and the convex hull for the family of concave univalent functions},
     journal = {Kodai Math. J.},
     volume = {30},
     number = {1},
     year = {2007},
     pages = { 385-393},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1193924942}
}
Bhowmik, Bappaditya; Ponnusamy, Saminathan; Wirths, Karl-Joachim. Domains of variability of Laurent coefficients and the convex hull for the family of concave univalent functions. Kodai Math. J., Tome 30 (2007) no. 1, pp.  385-393. http://gdmltest.u-ga.fr/item/1193924942/