Comments for Annoying Precision
https://qchu.wordpress.com
"A good stack of examples, as large as possible, is indispensable for a thorough understanding of any concept, and when I want to learn something new, I make it my first job to build one." - Paul HalmosSun, 26 Apr 2015 04:36:36 +0000hourly1http://wordpress.com/Comment on Projective objects by Compact objects | Annoying Precision
https://qchu.wordpress.com/2015/03/28/projective-objects/#comment-5069
Sun, 26 Apr 2015 04:36:36 +0000http://qchu.wordpress.com/?p=17224#comment-5069[…] « Projective objects […]
]]>Comment on Operations, pro-objects, and Grothendieck’s Galois theory by Compact objects | Annoying Precision
https://qchu.wordpress.com/2013/06/23/operations-pro-objects-and-grothendiecks-galois-theory/#comment-5068
Sun, 26 Apr 2015 04:36:33 +0000http://qchu.wordpress.com/?p=12927#comment-5068[…] they represent the finite powers of the forgetful functor , which preserve filtered colimits (see this previous post). And every object is the colimit of the canonical diagram of finitely generated free objects […]
]]>Comment on The free cocompletion I by Compact objects | Annoying Precision
https://qchu.wordpress.com/2014/04/01/the-free-cocompletion-i/#comment-5067
Sun, 26 Apr 2015 04:36:30 +0000http://qchu.wordpress.com/?p=14685#comment-5067[…] are computed pointwise preserves not only filtered colimits but all colimits. And by the universal property of the Yoneda embedding, every presheaf is a colimit of representable […]
]]>Comment on Constructing Poisson algebras by ebrahim
https://qchu.wordpress.com/2011/08/27/constructing-poisson-algebras/#comment-5053
Tue, 14 Apr 2015 19:06:32 +0000http://qchu.wordpress.com/?p=8387#comment-5053Great post. Can you recommend any references for this material?
]]>Comment on SO(3) and SU(2) by Qiaochu Yuan
https://qchu.wordpress.com/2011/02/05/so3-and-su2/#comment-5040
Wed, 01 Apr 2015 08:06:08 +0000http://qchu.wordpress.com/?p=6642#comment-5040I didn’t draw it! I stole it from Wikipedia.
]]>Comment on SO(3) and SU(2) by Rod Vance
https://qchu.wordpress.com/2011/02/05/so3-and-su2/#comment-5038
Wed, 01 Apr 2015 00:44:29 +0000http://qchu.wordpress.com/?p=6642#comment-5038Dear Qiachou Yuan: love your site and also your keen and pithy insights on Math Overflow and Math SE. Very simple question: what did you use to draw that beautiful stereographic projection. I’ve seen the same software used a great deal on Wikipedia math entries (perhaps by you).
]]>Comment on Split epimorphisms and split monomorphisms by Projective objects | Annoying Precision
https://qchu.wordpress.com/2012/10/01/split-epimorphisms-and-split-monomorphisms/#comment-5037
Sun, 29 Mar 2015 01:11:24 +0000http://qchu.wordpress.com/?p=10955#comment-5037[…] all projective modules. Next we need the following observation. Recall that an object is a retract of an object if there are maps such that (so is a split epimorphism and is a split […]
]]>Comment on Monomorphisms and epimorphisms by Projective objects | Annoying Precision
https://qchu.wordpress.com/2012/09/29/monomorphisms-and-epimorphisms/#comment-5036
Sun, 29 Mar 2015 01:11:21 +0000http://qchu.wordpress.com/?p=10844#comment-5036[…] : Recall that a morphism is an epimorphism if and only if its cokernel pair is trivial, or explicitly if […]
]]>Comment on A meditation on semiadditive categories by Projective objects | Annoying Precision
https://qchu.wordpress.com/2012/09/14/a-meditation-on-semiadditive-categories/#comment-5035
Sun, 29 Mar 2015 01:11:19 +0000http://qchu.wordpress.com/?p=10590#comment-5035[…] a linear functor automatically preserves finite coproducts, is right exact iff it preserves […]
]]>Comment on Ultrafilters in topology by Ultrafilters – Interlude: the Stone topology on general Tychonoff spaces | the capacity to be alone
https://qchu.wordpress.com/2010/12/09/ultrafilters-in-topology/#comment-5032
Thu, 26 Mar 2015 19:48:35 +0000http://qchu.wordpress.com/?p=6216#comment-5032[…] can say more: given any nonprincipal ultrafilter $mathcal{F}$, it of course converges to a single point $xin X$, by compact Hausdorffness. Hence its image under any continuous $f:Xto Y$ into a compact […]
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