From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/3643 Path: news.gmane.org!not-for-mail From: Marco Grandis Newsgroups: gmane.science.mathematics.categories Subject: Re: terminology: dagger and involution Date: Wed, 28 Feb 2007 09:19:58 +0100 Message-ID: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1241019430 9608 80.91.229.2 (29 Apr 2009 15:37:10 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:37:10 +0000 (UTC) To: categories@mta.ca Original-X-From: rrosebru@mta.ca Wed Feb 28 18:56:14 2007 -0400 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 28 Feb 2007 18:56:14 -0400 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.61) (envelope-from ) id 1HMXbq-0005FL-9u for categories-list@mta.ca; Wed, 28 Feb 2007 18:49:18 -0400 Original-Sender: cat-dist@mta.ca Precedence: bulk X-Keywords: X-UID: 37 Original-Lines: 38 Xref: news.gmane.org gmane.science.mathematics.categories:3643 Archived-At: Dear John, Sooner or later somebody will call them "sharp" categories, or "tilde" categories... What you are saying is a good argument in favour of a sensible, well established name. Also, on a more general ground, should we have a different terminology in, say: - category theory, - category theory applied to computer science, - category theory applied to physics? Funny names, like quark, can be good and typographical names can be useful, when there is no better substitute. Eg, I do not know of any good substitute for "comma category". But I see no reason to replace a sensible name with a meaningless one; or, even worse, many meaningless ones. --------- Dear Jeff, The problem you are mentioning is essentially based on terminology for different dualities in higher categories. I do not think there is a way of finding a coherent terminology for them, which would not clash with some well established, quite sensible use, already existing in some particular case. Therefore, I would not be surprised if the contravariancy of an involution should assume different meanings in different contexts. --------- All the best Marco