General affine surface areas

On $L_p$ Affine Surface Area and Curvature Measures

The relationship between $L_p$ affine surface area and curvature measures is investigated. As a result, a new representation of the existing notion of $L_p$ affine surface area depending only on curvature measures is derived. Direct proofs of the equivalence between this new representation and those previously known are provided. The proofs show that the new representation is, in a sense, "polar" to that of Lutwak's and "dual" to that of Schütt & Werner's.

Dual Orlicz-Brunn-Minkowski theory: dual Orlicz $L_ϕ$ affine and geominimal surface areas

This paper aims to develop basic theory for the dual Orlicz $L_ϕ$ affine and geominimal surface areas for star bodies, which belong to the recent dual Orlicz-Brunn-Minkowski theory for star bodies. Basic properties for these new affine invariants will be provided. Moreover, related Orlicz affine isoperimetric inequality, cyclic inequality, Santaló style inequality and Alexander-Fenchel type inequality are established.

Inequalities for mixed $p$-affine surface area

We prove new Alexandrov-Fenchel type inequalities and new affine isoperimetric inequalities for mixed $p$-affine surface areas. We introduce a new class of bodies, the illumination surface bodies, and establish some of their properties. We show, for instance, that they are not necessarily convex. We give geometric interpretations of $L_p$ affine surface areas, mixed $p$-affine surface areas and other functionals via these bodies. The surprising new element is that not necessarily convex bodies provide the tool for these interpretations.

New Orlicz Affine Isoperimetric Inequalities

The Orlicz-Brunn-Minkowski theory receives considerable attention recently, and many results in the $L_p$-Brunn-Minkowski theory have been extended to their Orlicz counterparts. The aim of this paper is to develop Orlicz $L_ϕ$ affine and geominimal surface areas for single convex body as well as for multiple convex bodies, which generalize the $L_p$ (mixed) affine and geominimal surface areas -- fundamental concepts in the $L_p$-Brunn-Minkowski theory. Our extensions are different from the general affine surface areas by Ludwig (in Adv. Math. 224 (2010)). Moreover, our definitions for Orlicz $…

On the monotone properties of general affine surface areas under the Steiner symmetrization

In this paper, we prove that, if functions (concave) $ϕ$ and (convex) $ψ$ satisfy certain conditions, the $L_ϕ$ affine surface area is monotone increasing, while the $L_ψ$ affine surface area is monotone decreasing under the Steiner symmetrization. Consequently, we can prove related affine isoperimetric inequalities, under certain conditions on $ϕ$ and $ψ$, without assuming that the convex body involved has centroid (or the Santaló point) at the origin.

函数情形下的极值仿射表面积

Extremal affine surface areas in a functional setting

本文在函数空间中引入极值仿射表面积，建立其对偶公式，证明其与函数积分幂成正比，从而推广并改进了凸体情形的相关结果。

c-仿射表面积的若干等周型不等式

Some inequalities of isoperimetric type for the c-affine surface area

针对Schütt等人新引入的c-仿射表面积Ω^c，证明球体类中其由半径n/(n+1)的球最大化，建立Santaló型不等式，并得到涉及表面积的更复杂不等式。

关于功能仿射表面积的特征

A Characterization of Functional Affine Surface Areas

本文研究了凸Lipschitz函数空间上估值的特征，证明了此类估值可由常数项、体积和功能仿射表面积线性组合表示，并建立了有限值凸函数的对偶结果。

通过面积交叉比和等距双曲线的仿射角

Affine Angles via Area Cross Ratio and Isoptic Hyperbolas

本文通过面积交叉比定义了仿射角，并证明其在保持选定方向的仿射变换下不变，同时揭示了等距双曲线与双曲幂之间的联系。

$L_p$ geominimal surface areas and their inequalities

In this paper, we introduce the $L_p$ geominimal surface area for all $-n\neq p<1$, which extends the classical geominimal surface area ($p=1$) by Petty and the $L_p$ geominimal surface area by Lutwak ($p>1$). Our extension of the $L_p$ geominimal surface area is motivated by recent work on the extension of the $L_p$ affine surface area -- a fundamental object in (affine) convex geometry. We prove some properties for the $L_p$ geominimal surface area and its related inequalities, such as, the affine isoperimetric inequality and a Santaló style inequality. Cyclic inequalities are established to…

$L_p$积分仿射表面积-变分容量不等式

$L_p$-Integral Affine Surface Area-Variational Capacity Inequalities

针对$n\boldsymbol{\u2265}2$且$1<p<n$的情形，研究$L_p$积分仿射表面积与$L_p$变分容量的不等式问题，否定了Ludwig-Xiao-Zhang提出的两个相关猜想。

A general geometric construction for affine surface area

Let $K$ be a convex body in ${\bf R}^n$ and $B$ be the Euclidean unit ball in ${\bf R}^n$. We show that $$\mbox{lim}_{t\rightarrow 0} \frac{|K| -|K_t|}{|B| - |B_t|}= \frac{as(K)}{as(B)},$$ where $as(K)$ respectively $as(B)$ is the affine surface area of $K$ respectively $B$ and $\{K_t\}_{t\geq 0}$, $\{B_t\}_{t\geq 0}$ are general families of convex bodies constructed from $K$, $B$ satifying certain conditions. As a corollary we get results obtained in [M-W], [Schm],[S-W] and[W].

New $L_p$ Affine Isoperimetric Inequalities

We prove new $L_p$ affine isoperimetric inequalities for all $ p \in [-\infty,1)$. We establish, for all $p\neq -n$, a duality formula which shows that $L_p$ affine surface area of a convex body $K$ equals $L_\frac{n^2}{p}$ affine surface area of the polar body $K^\circ$.

The Orlicz-Petty bodies

This paper is dedicated to the Orlicz-Petty bodies. We first propose the homogeneous Orlicz affine and geominimal surface areas, and establish their basic properties such as homogeneity, affine invariance and affine isoperimetric inequalities. We also prove that the homogeneous geominimal surface areas are continuous, under certain conditions, on the set of convex bodies in terms of the Hausdorff distance. Our proofs rely on the existence of the Orlicz-Petty bodies and the uniform boundedness of the Orlicz-Petty bodies of a convergent sequence of convex bodies. Similar results for the nonhomog…

Random polytopes and affine surface area

Let K be a convex body in $R^d$. A random polytope is the convex hull $[x_1,...,x_n]$ of finitely many points chosen at random in K. $\Bbb E(K,n)$ is the expectation of the volume of a random polytope of n randomly chosen points. I. Bárány showed that we have for convex bodies with $C^3$ boundary and everywhere positive curvature $$ c(d)\lim_{n \to \infty} \frac {vol_d(K)-\Bbb E(K,n)}{(\frac{vol_d(K)}{n})^{\frac{2}{d+1}}} =\int_{\partial K} κ(x)^{\frac{1}{d+1}}dμ(x) $$ where $κ(x)$ denotes the Gauß-Kronecker curvature. We show that the same formula holds for all convex bodies if $κ(x)$ denotes…

Affine isoperimetric inequalities in the functional Orlicz-Brunn-Minkowski theory

In this paper, we develop a basic theory of Orlicz affine and geominimal surface areas for convex and $s$-concave functions. We prove some basic properties for these newly introduced functional affine invariants and establish related functional affine isoperimetric inequalities as well as functional Santaló type inequalities.