Comments for Annoying Precision
https://qchu.wordpress.com
"A good stock 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 HalmosWed, 19 Oct 2016 19:59:02 +0000hourly1http://wordpress.com/Comment on The categorical exponential formula by Qiaochu Yuan
https://qchu.wordpress.com/2015/11/04/the-categorical-exponential-formula/#comment-6766
Wed, 19 Oct 2016 19:59:02 +0000http://qchu.wordpress.com/?p=19589#comment-6766Thanks for the correction! I intended to say “right multiplication,” and didn’t intend to imply that every element of worked.
]]>Comment on The categorical exponential formula by anon
https://qchu.wordpress.com/2015/11/04/the-categorical-exponential-formula/#comment-6765
Tue, 18 Oct 2016 18:06:49 +0000http://qchu.wordpress.com/?p=19589#comment-6765The G-set automorphisms of G/H are right multiplication by elements of N_G(H)/H, not left multiplication by elements g of G. Also left multiplication by h in H generally does not act trivially on G/H. But the desired conclusion (automorphism fixes H implies acts trivially) still holds.
]]>Comment on The type system of mathematics by Formal vs Functional Series (OR: Generating Function Voodoo Magic) | Power Overwhelming
https://qchu.wordpress.com/2013/05/28/the-type-system-of-mathematics/#comment-6759
Sun, 16 Oct 2016 17:47:19 +0000http://qchu.wordpress.com/?p=12420#comment-6759[…] and “functional series”. They use exactly the same notation but are two different types of objects, and this ends up being the source of lots of errors, because “formal series” do not […]
]]>Comment on Dualizable objects (and morphisms) by Noah Snyder
https://qchu.wordpress.com/2015/10/26/dualizable-objects-and-morphisms/#comment-6757
Sat, 15 Oct 2016 20:53:25 +0000http://qchu.wordpress.com/?p=17492#comment-6757Ah, right, in the presence of projective they’re fp and fg are equivalent. Thanks.
]]>Comment on Dualizable objects (and morphisms) by Qiaochu Yuan
https://qchu.wordpress.com/2015/10/26/dualizable-objects-and-morphisms/#comment-6755
Fri, 14 Oct 2016 04:17:44 +0000http://qchu.wordpress.com/?p=17492#comment-6755I never directly use finitely presented, but only “finitely presented projective” in the form “retract of a finite free module,” which is of course equivalent to “finitely generated projective.”
]]>Comment on Dualizable objects (and morphisms) by Noah Snyder
https://qchu.wordpress.com/2015/10/26/dualizable-objects-and-morphisms/#comment-6754
Thu, 13 Oct 2016 17:44:14 +0000http://qchu.wordpress.com/?p=17492#comment-6754I’m a little confused, I can’t figure out where you used finitely presented rather than just finitely generated in the dual basis lemma.
]]>Comment on Affine varieties and regular maps by Anne
https://qchu.wordpress.com/2009/12/21/affine-varieties-and-regular-maps/#comment-6753
Thu, 13 Oct 2016 13:22:58 +0000http://qchu.wordpress.com/?p=3986#comment-6753What does it mean if pf + qg = 1? (the last proof)
Does that mean f, g dont have common factors and therefore R is UFD.
]]>Comment on What’s a fire, and why does it – what’s the word – burn? by David Jaz Myers
https://qchu.wordpress.com/2016/05/26/whats-a-fire-and-why-does-it-whats-the-word-burn/#comment-6710
Fri, 23 Sep 2016 20:38:03 +0000http://qchu.wordpress.com/?p=25649#comment-6710Bill Hammack (EngineerGuy on YouTube) has done a nice retelling of these lectures, which you can find on his YouTube channel.
]]>Comment on Update, and the combinatorics of quintic equations by Raney’s Lemma | home
https://qchu.wordpress.com/2010/10/08/update-and-the-combinatorics-of-quintic-equations/#comment-6634
Sat, 13 Aug 2016 15:58:57 +0000http://qchu.wordpress.com/?p=5532#comment-6634[…] qchu uses Raney’s Lemma to find the number of -ary trees with nodes, making use of a bijection with -Raney sequences of length . […]
]]>Comment on Boolean rings, ultrafilters, and Stone’s representation theorem by Mahmoud Abdelrazek
https://qchu.wordpress.com/2010/11/22/boolean-rings-ultrafilters-and-stones-representation-theorem/#comment-6566
Fri, 15 Jul 2016 08:46:21 +0000http://qchu.wordpress.com/?p=5999#comment-6566Nice … But wasn’t it enough showing equivalence of and , and as you showed the functors involved in such equivalence are and , they are automatically (contravariantly) adjoint, so you needn’t show this independently … I think I am messing something
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