• Title/Summary/Keyword: lemma

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THE IDEMPOTENT RELATION AND THE PROOF OF URYSOHN'S LEMMA

  • Kim, Seungwook
    • Korean Journal of Mathematics
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    • v.17 no.4
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    • pp.411-417
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    • 2009
  • The Urysohn's lemma which is crucial tool for the study of the metrization problem is proved in the sense of set-theoretic concept, namely, by the idempotent relation defined on a given topology.

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Applications of the Schwarz Lemma and Jack's Lemma for the Holomorphic Functions

  • Ornek, Bulent Nafi;Catal, Batuhan
    • Kyungpook Mathematical Journal
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    • v.60 no.3
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    • pp.507-518
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    • 2020
  • We consider a boundary version of the Schwarz Lemma on a certain class of functions which is denoted by 𝒩. For the function f(z) = z + a2z2 + a3z3 + … which is defined in the unit disc D such that the function f(z) belongs to the class 𝒩, we estimate from below the modulus of the angular derivative of the function ${\frac{f{^{\prime}^{\prime}}(z)}{f(z)}}$ at the boundary point c with f'(c) = 0. The sharpness of these inequalities is also proved.

AN IMPROVED LOWER BOUND FOR SCHWARZ LEMMA AT THE BOUNDARY

  • ORNEK, BULENT NAFI;AKYEL, TUGBA
    • The Pure and Applied Mathematics
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    • v.23 no.1
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    • pp.61-72
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    • 2016
  • In this paper, a boundary version of the Schwarz lemma for the holom- rophic function satisfying f(a) = b, |a| < 1, b ∈ ℂ and ℜf(z) > α, 0 ≤ α < |b| for |z| < 1 is invetigated. Also, we estimate a modulus of the angular derivative of f(z) function at the boundary point c with ℜf(c) = a. The sharpness of these inequalities is also proved.

A SHARP SCHWARZ AND CARATHÉODORY INEQUALITY ON THE BOUNDARY

  • Ornek, Bulent Nafi
    • Communications of the Korean Mathematical Society
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    • v.29 no.1
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    • pp.75-81
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    • 2014
  • In this paper, a boundary version of the Schwarz and Carath$\acute{e}$odory inequality are investigated. New inequalities of the Carath$\acute{e}$odory's inequality and Schwarz lemma at boundary are obtained by taking into account zeros of f(z) function which are different from zero. The sharpness of these inequalities is also proved.

THE CONDITIONAL BOREL-CANTELLI LEMMA AND APPLICATIONS

  • Chen, Qianmin;Liu, Jicheng
    • Journal of the Korean Mathematical Society
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    • v.54 no.2
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    • pp.441-460
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    • 2017
  • In this paper, we establish some conditional versions of the first part of the Borel-Cantelli lemma. As its applications, we study strong limit results of $\mathfrak{F}$-independent random variables sequences, the convergence of sums of $\mathfrak{F}$-independent random variables and the conditional version of strong limit results of the concomitants of order statistics.