查看“︁绞拧数”︁的源代码

'''绞拧数'''（英语：Writhe）是[[纽结理论]]中的一个[[纽结不变量]]。指[[纽结]]在各个方向[[投影图]]的[[拧数]]的[[平均值]]<ref>《绳圈的数学》姜伯驹.大连理工大学出版社.2011年5月第1版.第126页</ref>。一般记作：<math>Wr</math>。

对于[[闭曲线|闭合曲线]]，绞拧数为：
:<math>
Wr=\frac{1}{4\pi}\int_{C}\int_{C}d\mathbf{r}_{1}\times d\mathbf{r}_{2}\cdot\frac{\mathbf{r}_{1}-\mathbf{r}_{2}}{\left|\mathbf{r}_{1}-\mathbf{r}_{2}\right|^{3}}
</math>.

== DNA的应用 ==

* [[DNA超螺旋]]<ref>{{Cite journal|title=Computation of writhe in modeling of supercoiled DNA|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/1097-0282%2820001015%2954%3A5%3C307%3A%3AAID-BIP20%3E3.0.CO%3B2-Y|last=Klenin|first=Konstantin|last2=Langowski|first2=Jörg|date=2000|journal=Biopolymers|issue=5|doi=10.1002/1097-0282(20001015)54:53.0.CO;2-Y|volume=54|pages=307–317|language=en|issn=1097-0282}}</ref><ref>{{Cite book|edition=2nd|chapter=DNA topology|url=https://www.worldcat.org/oclc/56793994|publisher=Oxford University Press|date=2005|location=Oxford|isbn=0-19-856709-X|oclc=56793994|last=Bates, Andrew D.|title=DNA topology|first=|year=|pages=36-37}}</ref><ref>{{Cite journal|title=The Writhing Number of a Space Curve|url=http://www.pnas.org/cgi/doi/10.1073/pnas.68.4.815|last=Fuller|first=F. B.|date=1971-04-01|journal=Proceedings of the National Academy of Sciences|issue=4|doi=10.1073/pnas.68.4.815|volume=68|pages=815–819|language=en|issn=0027-8424|pmc=389050|pmid=5279522}}</ref>

[[File:Simulation of an elastic rod relieving torsional stress by forming coils.ogv|缩略图]]

== 相关条目 ==

* [[环绕数]]
* [[琼斯多项式]]

==参考文献==
{{reflist}}

{{纽结理论}}
[[Category:紐結理論]]
[[Category:纽结不变量]]