From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/3152 Path: news.gmane.org!not-for-mail From: Vaughan Pratt Newsgroups: gmane.science.mathematics.categories Subject: Progressive or linear or ... monoids? Date: Fri, 24 Mar 2006 00:08:15 -0800 Message-ID: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1241019123 7457 80.91.229.2 (29 Apr 2009 15:32:03 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:32:03 +0000 (UTC) To: categories list Original-X-From: rrosebru@mta.ca Sat Mar 25 00:47:19 2006 -0400 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Sat, 25 Mar 2006 00:47:19 -0400 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1FN0Z6-0004sf-5W for categories-list@mta.ca; Sat, 25 Mar 2006 00:39:52 -0400 X-Accept-Language: en-us, en Original-Sender: cat-dist@mta.ca Precedence: bulk X-Keywords: X-UID: 98 Original-Lines: 17 Xref: news.gmane.org gmane.science.mathematics.categories:3152 Archived-At: 1. Is the quasivariety of monoids generated by the groups and the free monoids finitely based? That is, is there a finite set of universal Horn formulas entailing the common universal Horn theory of groups and free monoids? In other words, what do groups and free monoids have in common, besides being monoids? Apart from the (equational) axioms for monoids, the only members of that theory I can think of are xy=x -> y=1 and yx=x -> y=1. 2. How different is the abelian case? More or fewer axioms? Vaughan Pratt