For faster navigation, this Iframe is preloading the Wikiwand page for 拉回.

拉回

拉回pullback)是数学中一个基本概念,涉及到两个不同但关联的程序:预复合与纤维积。与之对偶的概念是前推

预复合

[编辑]

和一个函数的预复合也许提供了拉回最基本的概念:简单地说,设 f 是一个变量 y 的函数,这里 y 自身又是另一个变量 x 的函数,那么 f 可以写成 x 的函数,这即 f 被函数 y(x) 拉回。

这样一个基本程序,经常不经意地出现,比如在初等微积分中:有时也称为“忽略拉回”,从流体力学微分几何中随处可见。

但是,不仅只有函数可以在这种意义下“拉回”。拉回可以应用到许多其他对象中去,比如微分形式和它们的上同调类

参见:

纤维积

[编辑]

拉回作为纤维积的概念最终导致了非常广泛的范畴的拉回,但有一些重要的特例:代数几何中的逆像(和拉回)层,以及代数拓扑和微分几何中的拉回丛。

参见:

关系

[编辑]

两种拉回的概念的关系可能最好是用纤维丛的截面来解释:如果 sN 上纤维丛 E 的一个截面,f 是一个从 MN 的映射,那么 s 的由 f 拉回(预复合)M 上的拉回丛(纤维积) f*E 的一个截面。

{{bottomLinkPreText}} {{bottomLinkText}}
拉回
Listen to this article

This browser is not supported by Wikiwand :(
Wikiwand requires a browser with modern capabilities in order to provide you with the best reading experience.
Please download and use one of the following browsers:

This article was just edited, click to reload
This article has been deleted on Wikipedia (Why?)

Back to homepage

Please click Add in the dialog above
Please click Allow in the top-left corner,
then click Install Now in the dialog
Please click Open in the download dialog,
then click Install
Please click the "Downloads" icon in the Safari toolbar, open the first download in the list,
then click Install
{{::$root.activation.text}}

Install Wikiwand

Install on Chrome Install on Firefox
Don't forget to rate us

Tell your friends about Wikiwand!

Gmail Facebook Twitter Link

Enjoying Wikiwand?

Tell your friends and spread the love:
Share on Gmail Share on Facebook Share on Twitter Share on Buffer

Our magic isn't perfect

You can help our automatic cover photo selection by reporting an unsuitable photo.

This photo is visually disturbing This photo is not a good choice

Thank you for helping!


Your input will affect cover photo selection, along with input from other users.

X

Get ready for Wikiwand 2.0 🎉! the new version arrives on September 1st! Don't want to wait?