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• CommentRowNumber1.
• CommentAuthorUrs
• CommentTimeMay 5th 2010

at signature we should eventually think about some disambiguation. There are many things in math called “signature”- For instance the signature of a permutation.

• CommentRowNumber2.
• CommentAuthorTodd_Trimble
• CommentTimeMay 5th 2010
• (edited May 5th 2010)
I just added a disambiguation to signature, and wrote signature (disambigation) (stub).
• CommentRowNumber3.
• CommentAuthorUrs
• CommentTimeMay 5th 2010

thanks, Todd. For the moment I just added a link at the disambiguation page also to your signature-page.

• CommentRowNumber4.
• CommentAuthorIan_Durham
• CommentTimeMay 5th 2010

Not to resurrect a sore subject, but we tend to also use the word signature in describing metrics. Not sure how that fits in with what is already there.

• CommentRowNumber5.
• CommentAuthorTodd_Trimble
• CommentTimeMay 5th 2010
True, Ian, and that's a special case of signature of a quadratic form (as mentioned at signature (disambiguation)), which is to be written.
• CommentRowNumber6.
• CommentAuthorUrs
• CommentTimeMay 5th 2010

another major signature-topic would be the signature-genus. Also to be written…

• CommentRowNumber7.
• CommentAuthorUrs
• CommentTimeMay 5th 2010

right, I see we are in trouble already: elliptic cohomology had a link to signature, but meant is the signature genus. Now it points to signature in logic.

Todd, if you don’t mind, I am now going to name the disambiguation page just “signature”, so that in case of doubt people see the disambiguation page, and then I will rename your signature enttry into something more specific. What would be a good choice. Maybe “signature (in logic)” ?

• CommentRowNumber8.
• CommentAuthorTodd_Trimble
• CommentTimeMay 6th 2010
Of course I don't mind -- thanks, Urs.

I've been writing a section on the language of the signature which ought to eventually include the classical syntactic account (with variables, terms, atomic formulas, and all that), but really I'm writing a slightly experimental description of the categorical way of viewing the language. The idea is basically to tie in with first-order Boolean-valued hyperdoctrines and describe the language of a signature as an initial hyperdoctrine in an appropriate sense. I jotted down what I am driving at at signature.
• CommentRowNumber9.
• CommentAuthorDavidRoberts
• CommentTimeMay 6th 2010

Cache bug is messing up the signature, signature (in logic) and signature (disambiguation) pages. I can’t get to the last one, as it redirects to signature, which for me is what is now signature (in logic).

• CommentRowNumber10.
• CommentAuthorUrs
• CommentTimeMay 6th 2010
• (edited May 6th 2010)

Todd,

there was probably a misunderstanding. While you write

Of course I don’t mind

you then reverted my changes when you

jotted down what I am driving at at signature.

I have now re-reverted it. Let’s see if we can agree on this:

• the page signature (in logic) contains the material that a few hours back you typed into signature;

• the page signature is what was originally your “signature (disambiguation)”. I think if there is need for a disambiguation page, then that disambiguation page must have just the ambiguous keyword as its title. Otherwise it won’t serve the desired purpose. Previous pages of this kind include for instance homotopy.

• CommentRowNumber11.
• CommentAuthorEric
• CommentTimeMay 6th 2010

FWIW, I like Urs suggested way to handle disambiguation, i.e. a page with simply the ambiguous name as title with a list of links to the various uses of that word. Maybe a few words thrown in to explain what’s going on as in signature.

• CommentRowNumber12.
• CommentAuthorTodd_Trimble
• CommentTimeMay 6th 2010
> you then reverted my changes

I did? How did that happen? Sorry about that. I was trying to be reasonably careful and *not* do that sort of thing!
• CommentRowNumber13.
• CommentAuthorUrs
• CommentTimeMay 6th 2010

Probably the cache bug interfering. It keeps surprising me what that bug can do.

But never mind, at least I could revert everything. sometimes it happens that the cache bug messes up things and then even prevents us from fixing them. Anyway, it’s all good now.

• CommentRowNumber14.
• CommentAuthorzskoda
• CommentTimeMay 6th 2010

My first association is Hirzebruch signature, regarding that the topology is the main topic in nlab so far…

• CommentRowNumber15.
• CommentAuthorTodd_Trimble
• CommentTimeNov 25th 2012

Slightly expanded signature of a permutation.

• CommentRowNumber16.
• CommentAuthorTodd_Trimble
• CommentTimeSep 28th 2015

Added the observation to signature of a permutation that computing the parity of the number of even-length cycles gives a perfectly respectable definition of the group homomorphism to $\{1, -1\}$.