完全仿射几何中的极大曲线与热流
The maximal curves and heat flow in fully affine geometry
AI总结:
本文研究完全仿射几何中的极大曲线,通过第二变分公式证明其丰富性,并推广曲线理论,给出热流孤子分类及收敛性结果。
摘要:
在欧几里得几何中,两点之间的最短距离是直线。Chern 在1977年提出猜想:二维欧几里得空间 $\mathbb{R}^2$ 上光滑、局部一致凸函数的仿射极大图必定是抛物面。2000年,Trudinger 和 Wang 完成了该猜想在仿射几何中的证明。(注意:在这些文献中,“仿射几何”指的是“等仿射几何”。)一个自然的问题随之产生:双曲线是否是 $\mathbb{R}^2$ 中的完全仿射极大曲线?本文利用曲线的演化方程,得到了 $\mathbb{R}^2$ 中完全仿射极值曲线的第二变分公式,并证明了 $\mathbb{R}^2$ 中的完全仿射极大曲线远比预想的丰富,其中包括显式曲线 $y=x^\alpha~\left(\alpha\\;\text{为常数且}\\;\alpha\notin\{0,1,\frac{1}{2},2\}\right)$ 和 $y=x\log x$。同时,我们将曲线的基本理论推广到配备 $\text{GA}(n)=\text{GL}(n)\ltimes\mathbb{R}^n$ 的高维情形。此外,在完全仿射平面几何中,我们研究了一个等周不等式,并提供了完全仿射热流的孤子完整分类。我们还研究了该完全仿射热流的局部存在性、唯一性和长期行为。我们证明了闭嵌入曲线在完全仿射热流演化下将收敛于椭圆。
英文摘要:
In Euclidean geometry, the shortest distance between two points is a straight line. Chern made a conjecture in 1977 that an affine maximal graph of a smooth, locally uniformly convex function on two-dimensional Euclidean space $\mathbb{R}^2$ must be a paraboloid. In 2000, Trudinger and Wang completed the proof of this conjecture in affine geometry. (Caution: in these literatures, the term "affine geometry" refers to "equi-affine geometry".) A natural problem arises: Whether the hyperbola is the fully affine maximal curve in $\mathbb{R}^2$? In this paper, by utilizing the evolution equations for curves, we obtain the second variational formula for fully affine extremal curves in $\mathbb{R}^2$, and show the fully affine maximal curves in $\mathbb{R}^2$ are much more abundant and include the explicit curves $y=x^α~\left(α\;\text{is a constant and}\;α\notin\{0,1,\frac{1}{2},2\}\right)$ and $y=x\log x$. At the same time, we generalize the fundamental theory of curves in higher dimensions, equipped with $\text{GA}(n)=\text{GL}(n)\ltimes\mathbb{R}^n$. Moreover, in fully affine plane geometry, an isoperimetric inequality is investigated, and a complete classification of the solitons for fully affine heat flow is provided. We also study the local existence, uniqueness, and long-term behavior of this fully affine heat flow. A closed embedded curve will converge to an ellipse when evolving according to the fully affine heat flow is proved.
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