# rigid

## Primary tabs

Synonym:
rigidity result, rigidity theorem, rigidity
Type of Math Object:
Definition
Major Section:
Reference
Groups audience:

## Mathematics Subject Classification

### Rigid

I don't quite understand this definition. To me, it is not clear what a "degree of freedom" is, or what does it mean to be determined by a 'limited' number of them. Limited in what sense? (assuming we know what a degree of freedom is)

### Re: Rigid

I think the intent of the entry is to give a feel for what the notion of rigidity should be, and how it's used in mathematical conversation, rather than a definition of the term itself.

While somewhat nonstandard, I do think entries like this have a place in the encyclopedia...being able to communicate ideas of imprecisely-defined notions is something that mathematicians do. This notion or "rigidity" is yet another piece of vocabulary at their disposal.

So my suggestion for matte is that he make it more clear that this is not a formal definition (actually, I think the first sentence of Version 1 of this entry was pretty good)...how about something like

"The term 'rigid' is used in mathematics to describe a collection of objects in which each object is completely determined by fewer parameters than expected."

Hope this helps,

Cam