Advances in Mathematics ( IF 1.5 ) Pub Date : 2021-05-07 , DOI: 10.1016/j.aim.2021.107777 Edward Bierstone , Jean-Baptiste Campesato , Pierre D. Milman
We address the question of whether geometric conditions on the given data can be preserved by a solution in (1) the Whitney extension problem, and (2) the Brenner-Fefferman-Hochster-Kollár problem, both for functions. Our results involve a certain loss of differentiability.
Problem (2) concerns the solution of a system of linear equations , where A is a matrix of functions on , and are vector-valued functions. Suppose the entries of are semialgebraic (or, more generally, definable in a suitable o-minimal structure). Then we find such that, if is definable and the system admits a solution , then there is a definable solution. Likewise in problem (1), given a closed definable subset X of , we find such that if is definable and extends to a function on , then there is a definable extension.
中文翻译:
半代数或可定义方程的解
我们解决以下问题:是否可以通过(1)惠特尼扩展问题和(2)Brenner-Fefferman-Hochster-Kollár问题中的解来保留给定数据上的几何条件 职能。我们的结果包括一定程度的可微性损失。
问题(2)涉及线性方程组的解 ,其中A是以下函数的矩阵, 和 是向量值函数。假设是半代数的(或更普遍地,可以以合适的o-最小结构定义)。然后我们发现 这样,如果 是可定义的,系统允许 解决方案 ,然后有一个 可定义的解决方案。同样地,在问题(1),给定的封闭可定义子集X的, 我们发现 这样,如果 是可定义的,并延伸到 功能开启 ,然后有一个 可定义的扩展名。