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2019 Volume 41 Issue 2
Article Contents

Yuan ZHOU, Zeng-le ZHANG. Reverse Bonnesen-Style Minkowski Inequalities in the Plane[J]. Journal of Southwest University Natural Science Edition, 2019, 41(2): 70-74. doi: 10.13718/j.cnki.xdzk.2019.02.011
Citation: Yuan ZHOU, Zeng-le ZHANG. Reverse Bonnesen-Style Minkowski Inequalities in the Plane[J]. Journal of Southwest University Natural Science Edition, 2019, 41(2): 70-74. doi: 10.13718/j.cnki.xdzk.2019.02.011

Reverse Bonnesen-Style Minkowski Inequalities in the Plane

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  • Corresponding author: Zeng-le ZHANG
  • Received Date: 11/06/2018
    Available Online: 20/02/2019
  • MSC: O186.5

  • We study in this paper the upper bound of the Minkowski inequality in the plane, i.e. a reverse Bonnesen-style Minkowski inequality, such as AK, L2-AKALUK, L. Let K and L be convex bodies whose areas are AK and AL, respectively, and AK, L is the mixes area of the two convex bodies and UK, L is the geometric invariant related to K and L. We construct a class of convex body by the support function of the given convex bodies. By discussing the geometric properties of the new convex body, we obtain some new stronger reverse Bonnesen-style Minkowski inequalities and some results can be derived from those inequalities.
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  • [1] BANCHOFF T F, POHL W F. A Generalization of the Isoperimetric Inequality[J]. Journal of Differential Geometry, 1971, 6(2):175-192. doi: 10.4310/jdg/1214430403

    CrossRef Google Scholar

    [2] BURAGO Y D, ZALGALLER V A. Geometric Inequalities[M]. Berlin:Springer-Verlag, 1988.

    Google Scholar

    [3] CROKE C B. A Sharp Four Dimensional Isoperimetric Inequality[J]. Commentarii Mathematici Helvetici, 1984, 59(1):187-192. doi: 10.1007/BF02566344

    CrossRef Google Scholar

    [4] ENOMOTO K. A Generalization of the Isoperimetric Inequality on S2 and Flat Tori in S3[J]. Proceedings of the American Mathematical Society, 1994, 120(2):553-558.

    Google Scholar

    [5] GRINBER E L. Isoperimetric Inequalities and Identities for k-Dimensional Cross-Sections of Convex Bodies[J]. Mathematische Annalen, 1991, 291(1):75-86. doi: 10.1007/BF01445191

    CrossRef Google Scholar

    [6] 张增乐, 罗淼, 陈方维.平面上的新凸体与逆Bonnesen-型不等式[J].西南师范大学学报(自然科学版), 2015, 40(4):27-30.

    Google Scholar

    [7] GYSIN L M. The Isoperimetric Inequality for Nonsimple Closed Curves[J]. Proceedings of the American Mathematical Society, 1993, 118(1):197-203. doi: 10.1090/S0002-9939-1993-1079698-X

    CrossRef Google Scholar

    [8] 杨林, 罗淼, 侯林波.逆的对偶Brunn-Minkowski不等式[J].西南大学学报(自然科学版), 2016, 38(4):85-89.

    Google Scholar

    [9] HOWARD R. The Sharp Sobolev Inequality and the Banchoff-Pohl Inequality on Surfaces[J]. Proceedings of the American Mathematical Society, 1998, 126(9):2779-2787. doi: 10.1090/S0002-9939-98-04336-6

    CrossRef Google Scholar

    [10] 曾春娜, 周家足, 岳双珊.两平面凸域的对称混合等周不等式[J].数学学报(中文版), 2012, 55(2):355-362.

    Google Scholar

    [11] 王鹏富, 徐文学, 周家足, 等.平面两凸域的Bonnesen型对称混合不等式[J].中国科学(数学), 2015, 45(3):245-254.

    Google Scholar

    [12] LUO M, XU W X, ZHOU J Z. Translative Containment Measure and Symmetric Mixed Isohomothetic Inequalities[J]. Science China Mathematics, 2015, 58(12):2593-2610. doi: 10.1007/s11425-015-5074-5

    CrossRef Google Scholar

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Reverse Bonnesen-Style Minkowski Inequalities in the Plane

    Corresponding author: Zeng-le ZHANG

Abstract: We study in this paper the upper bound of the Minkowski inequality in the plane, i.e. a reverse Bonnesen-style Minkowski inequality, such as AK, L2-AKALUK, L. Let K and L be convex bodies whose areas are AK and AL, respectively, and AK, L is the mixes area of the two convex bodies and UK, L is the geometric invariant related to K and L. We construct a class of convex body by the support function of the given convex bodies. By discussing the geometric properties of the new convex body, we obtain some new stronger reverse Bonnesen-style Minkowski inequalities and some results can be derived from those inequalities.

  • 对于欧氏平面${{\mathbb{R}}^{2}}$中的点集K,如果对任意xyK,0≤λ≤1,都有λx+(1-λ)yK,则称K为凸集.具有非空内点的紧凸集称为凸体.若凸体K的边界∂K的曲率半径ρ>0,则称凸体K为卵形域.如果K${{\mathbb{R}}^{2}}$中的有界凸集,则以2π为周期的周期函数p(θ)称为K的支持函数. p(θ)是某个卵形域K的支持函数的充要条件是

    凸体K的周长、面积积分公式分别为:

    凸体K, L的面积分别记为AKAL,支持函数分别为pKpL.在Minkowski加法下,凸体K+L的面积表达式为

    其中AK, L表示两凸体的混合面积,其对应表达式为

    等周不等式是著名的几何不等式之一,它是最早用基本几何不变量来刻画平面几何图形的几何不等式.经典等周不等式的几何意义是:平面上周长固定的简单闭曲线中,圆所围成的面积最大.目前,等周不等式已推广到高维欧氏空间、常曲率曲面中,并应用到其他的数学分支(参见文献[1-12]).其中Minkowski不等式是经典等周不等式的推广之一.

    本文主要研究平面上的逆Bonnesen-型Minkowski不等式,形如

    其中UK, L是与K, L有关的非负几何不变量.设K, L为欧氏平面${{\mathbb{R}}^{2}}$中的卵形域,其支持函数分别为pKpL.通过利用KL的支持函数,构造了一类新凸体Mt,其支持函数为:

    其中C为与K, L相关的几何不变量,tC取值的不同而改变其取值范围的参数.当t=0时,Mt为凸体K;当C=1,t=1时,Mt为凸体L.设:

    $C=-{{\vartheta }_{m}}\left(K, L \right), ~0 < t\le \frac{1}{2}$时,和当$C=-{{\vartheta }_{M}}\left(K, L \right), \text{ }\frac{1}{2}\le t < 1$时,我们确定新凸体Mt,通过讨论凸体Mt的几何性质,我们得到一些新的逆Bonnesen-型Minkowski不等式,并且加强了文献[12]中定理4.6的结果,同时也给出了等号成立条件.

    引理1  设K, L为欧氏平面${{\mathbb{R}}^{2}}$中的卵形域,则

     ρm(K, L)和ρM(K, L)的定义[12]可分别等价于:

    ${{\vartheta }_{m}}$(K, L)与${{\vartheta }_{M}}$(K, L)的定义((3)式),不等式(4)显然成立.

    利用引理1,我们得到以下结果.

    定理1  设K, L为欧氏平面${{\mathbb{R}}^{2}}$中的卵形域,则:

    不等式(5)等号成立当且仅当KL位似.

     取(2)式中$C=-{{\vartheta }_{m}}\left(K, L \right)$,我们有

    $0 < t\le \frac{1}{2}$时,由ρ的定义和引理1,得到

    因此${{p}_{{{M}_{t}}}}=\left(1-t \right){{p}_{K}}-t{{\vartheta }_{m}}\left(K, L \right){{p}_{L}}$是一类凸集Mt的支持函数,Mt的面积At

    特别地,当$t=\frac{1}{2}$时,有

    将(6)式改写成两种形式:

    代入不等式(1)中,我们分别得到如下新的逆Bonnesen-型Minkowski不等式:

    不等式(5)等号成立的条件是${{M}_{t=\frac{1}{2}}}$的面积为0.此时${{M}_{t=\frac{1}{2}}}$只能是一条线段或一个点.如果${{M}_{t=\frac{1}{2}}}$是一条线段,则由(2)式可知,K的支持函数为

    这与K为卵形域矛盾,因此${{M}_{t=\frac{1}{2}}}$只能为一个点,即等号成立当且仅当KL位似.

    由定理1,我们得到以下逆Bonnesen-型Minkowski不等式:

    推论1  设K, L为欧氏平面${{\mathbb{R}}^{2}}$中的卵形域,则:

     注意到,定理1中(5)式不等号右边括号内几何量是非负的,即:

    由引理1,可证得

    两边同时积分,我们有

    因此,不等式(8)的第一个不等式成立.同理,可证得(8)式第二个不等式成立.由不等式(4)和(8),我们有:

    再由定理1可推出不等式(7).

    在文献[12]中,利用Blaschke滚动定理也得到了(7)式.由上述证明,可发现(5)式强于(7)式,因此我们加强了文献[12]中的结果.

    定理2  设K, L为欧氏平面${{\mathbb{R}}^{2}}$中的卵形域,则:

    不等式(9)等号成立当且仅当KL位似.

     用类似于定理1的讨论,取(2)式中$C=-{{\vartheta }_{M}}\left(K, L \right)$.当$\frac{1}{2}\le t < 1$时,我们得到一类凸集Mt,其支持函数为

    则其面积为

    特别地,当$t=\frac{1}{2}$时,有

    (10) 式可改写为:

    代入不等式(1)中,得到不等式(9).同理,等号成立时,${{M}_{t=\frac{1}{2}}}$只能为一个点,即KL位似.

    类似推论1的证明,由定理2,可得以下较弱的逆Bonnesen-型Minkowski不等式.

    推论2  设K, L为欧氏平面${{\mathbb{R}}^{2}}$中的卵形域,则:

    由定理1和定理2,我们可得如下新的逆Bonnesen-型Minkowski不等式:

    定理3  设K, L为欧氏平面${{\mathbb{R}}^{2}}$中的卵形域,则

    等号成立当且仅当KL位似.

     将不等式(5),(9)中的第一个不等式,两边同时开根号,分别得到:

    不等式两边分别相加再平方,得到不等式(12).

    下面,我们将给出文献[12]中定理4.6等号成立条件.

    定理4  设K, L为欧氏平面${{\mathbb{R}}^{2}}$中的卵形域,则

    等号成立当且仅当KL为圆盘.

     由引理1和定理3,有

    下面证明(13)式等号成立.若K, L为圆盘,显然(13)式等号成立.反之,假设(13)式等号成立,则必有(14)式中第一个不等式等号成立,此时KL位似,从而

    ρL不是常数,则有

    由于

    这与(15)式矛盾,故ρL是常数.再由(15)式,有

    ρK是常数.综上所述,等号成立当且仅当KL均为圆盘.

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