Sharp inequalities for logarithmic coefficients and their applications

Saminathan Ponnusamy, Toshiyuki Sugawa

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


I. M. Milin proposed, in his 1971 paper, a system of inequalities for the logarithmic coefficients of normalized univalent functions on the unit disk of the complex plane. This is known as the Milin conjecture and implies the Robertson conjecture which in turn implies the Bieberbach conjecture. In 1984, Louis de Branges settled the long-standing Bieberbach conjecture by showing the Milin conjecture. Recently, O. Roth proved an interesting sharp inequality for the logarithmic coefficients based on the proof by de Branges. In this paper, following Roth's ideas, we will show more general sharp inequalities with convex sequences as weight functions. By specializing the sequence, we can obtain an abundant number of sharp inequalities on logarithmic coefficients, some of which are provided in Appendix. We also consider the inequality with the help of de Branges system of linear ODE for non-convex sequences where the proof is partly assisted by computer. Also, we apply some of those inequalities to improve previously known results.

Original languageEnglish
Article number102931
JournalBulletin des Sciences Mathematiques
Publication statusPublished - 2021 Feb


  • De Branges theorem
  • Logarithmic coefficient
  • Milin conjecture


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