Talk:Generalized quadrangle
Add topicLatest comment: 8 years ago by Wcherowi in topic Wrong letter
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What is absolute lines?
[edit]Non-classical examples : What is absolute lines? Where I may read about it? Jumpow (talk) 19:56, 5 September 2017 (UTC)
- Yeah, this should really be improved. The space is equipped with a polarity (a mapping of points to lines of order two which preserves incidence). Under the polarity a point could lie on its image (which is a line), but doesn't have to. A point is absolute if it lies on its image and a line is absolute if it passes through its image (which is a point). I haven't checked recently, but you might be able to find more information at Pole and polar. --Bill Cherowitzo (talk) 20:28, 5 September 2017 (UTC)
Wrong letter
[edit]Definition:
- with P = {1,2,3,4,5,6,7,8,9} and L = {123, 456, 789, 147, 258, 369}
I think, must be "and B = " Jumpow (talk) 16:23, 6 September 2017 (UTC)
- Yep. Fixed it. This is a common error. In general incidence theory one speaks of points and blocks (hence the B), but if you come to the subject with more of a geometric slant it is more common to refer to points and lines (with the line set often denoted by a capital script L). It's fairly easy to forget which symbols are being used and get them mixed up. --Bill Cherowitzo (talk) 17:02, 6 September 2017 (UTC)