高阶Glaeser不等式与实函数根的最优正则性
Higher order Glaeser inequalities and optimal regularity of roots of real functions
摘要:
证明了Glaeser不等式的一个高阶推广,根据该不等式,可以用函数本身及其k阶导数的Holder常数来估计函数的一阶导数.我们应用这些不等式,以获得C^{k}类函数的(k+alpha)次根的导数的逐点估计,其k阶导数是alpha-Holder连续的。由于这样的估计,我们证明了根不仅是绝对连续的,但它的衍生物有一个更高的求和指数。一些例子表明,我们的结果是最优的。
英文摘要:
We prove a higher order generalization of Glaeser inequality, according to which one can estimate the first derivative of a function in terms of the function itself, and the Holder constant of its k-th derivative. We apply these inequalities in order to obtain pointwise estimates on the derivative of the (k+alpha)-th root of a function of class C^{k} whose derivative of order k is alpha-Holder continuous. Thanks to such estimates, we prove that the root is not just absolutely continuous, but its derivative has a higher summability exponent. Some examples show that our results are optimal.
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