User talk:RQG

Hello, RQG! Welcome to Wikipedia! Thank you for your contributions to this free encyclopedia. If you decide that you need help, check out Getting Help below, ask me on my talk page, or place {{helpme}} on your talk page and ask your question there. Please remember to sign your name on talk pages by clicking or using four tildes (~~~~); this will automatically produce your username and the date. Finally, please do your best to always fill in the edit summary field. Below are some useful links to facilitate your involvement. Happy editing! 76.66.202.219 (talk) 11:55, 1 December 2009 (UTC) Getting started A tutorial • Our five pillars • Getting mentored How to: edit a page • upload and use images • create your first article Intuitive guide to Wikipedia • Article Creation Wizard Getting help Frequently asked questions • Tips Where to ask questions or make comments Request administrator attention Policies and guidelines Neutral point of view • No original research Verifiability • Reliable sources • Citing sources What Wikipedia is not • Biographies of living persons List of policies • Three-revert rule • Sock puppetry Copyrights • Policy for non-free content • Image use policy External links • Spam • Vandalism • List of guidelines Deletion policy • Conflict of interest • Notability The community Build consensus • Resolve disputes Assume good faith • Civility • Etiquette No personal attacks • No legal threats Community portal • Village pump Signpost • IRC channels • Mailing lists Writing articles Be bold in editing • Develop an article The perfect article • Manual of style Stubs • Categories • Disambiguation Pages needing attention • Peer review Miscellaneous User name • User pages • Talk pages Clean up: General • Spam • Vandalism Join a WikiProject • Translation Useful templates • Tools • User scripts

Your recent edits

Hi there. In case you didn't know, when you add content to talk pages and Wikipedia pages that have open discussion, you should sign your posts by typing four tildes ( ~~~~ ) at the end of your comment. If you can't type the tilde character, you should click on the signature button located above the edit window. This will automatically insert a signature with your name and the time you posted the comment. This information is useful because other editors will be able to tell who said what, and when. Thank you! --SineBot (talk) 22:40, 24 March 2008 (UTC)

Gravitationally aligned rosettes

• Instead of rewriting spiral galaxy to show off a new and untested theory, why didn't you just write a new article at Gravitationally aligned rosette theory or something, and then just link to it from Spiral Galaxy, showing that alternate theories exist?

• No, it would be improper to rewrite density wave theory to showcase the new theory, since the new theory *is not* the topic of the article. If you want an article on the new theory, write a new article.

76.66.202.219 (talk) 11:54, 1 December 2009 (UTC)

affine space

"There have been several complaints about the removed text, which does not respect the mathematical definition of vector space"

The only "complaints" I know of are questions on the article's talk page from people who were clearly confused and whose understanding was deficient. Why don't you go to the talk page an state in details what you find objectionable in the informal description and what you don't understand in it? Michael Hardy (talk) 18:32, 14 July 2014 (UTC)

Of course people are confused by the intuitive "explanation". That is why it should be rewritten, by someone who actually knows what a vector space is in mathematics, and is not still rooted in some crude notion of position vectors as taught by bad high school teachers (since those are the only kind of vector for which one would usually talk of an "origin" RQG (talk) 23:24, 14 July 2014 (UTC).

I am a mathematician and I know what a vector space is. John Baez is a mathematical physicist who is highly respected by mathematicians as an expository writer on abstruse concepts and quite prolific in his writing on such things. In this blog posting you see him saying

"An affine space is like a vector space that has forgotten its origin."

I don't think that your understanding of the matter is superior to mine or to his. Michael Hardy (talk) 20:41, 15 July 2014 (UTC)

surmise

Can you tell me whether I am right or wrong in my surmise that your position on this question of affine spaces comes down to this?:

"(A,V) has more structure than V because the latter has only V and not also A"

As you may or may not have noticed, I publicly guessed that that is what you have in mind in this section. Michael Hardy (talk) 23:45, 17 July 2014 (UTC)

There is more to it than that, but that does summarise why I think the loose description in poor context has caused massive confusion and people not understanding the structure they are dealing with, and why I object to it unless it is made precise. But also, one should not conflate points in A with vectors in V (this is in general a bijection, not an isomorphism), or the origin in A with the zero vector in V. Some people may get away with it some of the time if they are not working at an advanced level of abstraction, but it is not the mathematical structure or the mathematical definition and the article should be mathematically correct. Origins are not mentioned in treatments of vector space. The origin is in A, not in V. The reason for the central position in mathematics of vector space and linear algebra in general is that the abstract structure is applied to situations where an origin is not an appropriate concept. Simply choosing the origin in A is not enough to create a vector space, because the vector space operations also have to be defined. It may be easy to define them, but that is not the point. They are not already defined. In any case there is no need to do this; we already have a vector space V and it just adds confusion to define another one.RQG (talk) 05:51, 18 July 2014 (UTC)