Talk:Direct sum

message: After reading this article I still wonder what a direct sum is. I would like to see an example where the direct sum is calculated for some simple set and where all the steps are included. I'm so tired of mathematicians writing for mathematicians.  —Preceding unsigned comment added by 62.20.172.163 (talk) 08:38, 20 March 2011 (UTC)
replies: text: There's no such thing as a direct sum for sets. Or you could handwave and claim its the same thing as a Cartesian product.  linas (talk) 18:59, 2 September 2012 (UTC)

text: This is due a a failing of the educational system. Some concepts of category theory could be taught in elementary school, and expanded on in high-school and college. Its not any harder to teach than arithmetic. By failing to have an adequate background, the result is that one has to define a direct sum by means of a series of examples, which this article does.  Yes, this article could be improved. But failing to mention category theory up front would be a mistake.  linas (talk) 18:59, 2 September 2012 (UTC)
replies: text: While I do agree that education system sucks and lacks incentive to improve, i almost laughed at your big claim to say category theory should be included in elementary level. --14.198.222.131 (talk) 06:10, 30 September 2013 (UTC)
replies: text: We should manage an initial definition with as little reference to category theory as possible, especially in the lead. The biggest problem that I see here is the use of the term "object" in the lead, which does not define or link it. As far as I can tell, this should be to algebraic structure, as mathematical object is too vague. I'm introducing this link.  — Quondum 12:20, 30 September 2013 (UTC)

text: Good suggestions.  I've taken care of items 1 and 2, will work on 3, 4, and 5.Rick Norwood (talk) 19:23, 20 February 2014 (UTC)
replies: text: 3 above seems to have been taken care of previously.  I've taken care of 5 and, I hope, done something about 4. Rick Norwood (talk) 19:40, 20 February 2014 (UTC)
thread_title:  Confusing 

message: I fixed the lead, but the rest of the article needs work. Ebony Jackson (talk) 05:36, 1 January 2014 (UTC)
replies: text: The new lead makes much sense, but then, now, I don't see a point of having this article separately from direct sum of modules. -- Taku (talk) 14:05, 1 January 2014 (UTC)
thread_title:  Article still needs work 

message: The difference between direct sum and direct product is analogous to the difference between product topology and box topology: both direct sums and product topologies have a cofiniteness condition that direct products and box topologies don't have. GeoffreyT2000 (talk) 00:42, 17 February 2015 (UTC)
replies: text: My impression from reading both articles is that there is no difference. If the two subgroups are both Abelian, "direct product" and "direct sum" are two names for the same thing. If at least one is not Abelian, the term "direct sum" is not used. If this is wrong, it would be really useful to include an example where the direct product of two groups is different from their direct sum. Maproom (talk) 15:22, 11 October 2016 (UTC)
thread_title:  Cofiniteness 

message: Is it time to remove the 'rewrite needed' tag? It was added in August 2012, since when the article pretty much has been rewritten. Mortee (talk) 03:49, 22 January 2017 (UTC)
thread_title:  Remove rewrite tag?